JP2913197B2 - Method for developing magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to magnetic recording used for optically observing the recording trajectory of a magnetic recording medium such as an audio tape, a video tape, a computer tape, and a magnetic disk. The present invention relates to a method for developing a medium.

<Conventional technology> Conventionally, as a method of developing a magnetic recording medium, a phenomenon is used in which a ferromagnetic powder is sprinkled on a magnetic recording medium, and a magnetic substance powder that is sucked forms a gray image according to the strength of magnetization of a recording portion. There was a way to do that.

In addition, a surface treated with a fatty acid such as oleic acid
磁性 A magnetic fluid in which ferrite fine particles such as magnetite are dispersed in a hydrocarbon-based solvent or water is applied to a magnetic recording medium, and then washed away with a solvent, and left after being sucked according to the strength of the magnetization of the recording portion. A method of observing a light and shade image formed by fine particles has been widely practiced and adopted.

Further, Japanese Patent Publication No. 61-26130 also discloses a developing solution for video tape and a developing method using the same, and a magnetite powder surface-treated with oleic acid is mixed with an aliphatic acid having a weight ratio of about 0.5 to 1.5 times. Colloidal stock solution dispersed in hydrocarbons, 50-300 times the volume ratio of this stock solution
The developer is adjusted by diluting with 1,1,2-trichloro-1,2,2-trifluoroethane, a video tape is immersed in the developer obtained in this way, and then pulled up from the solution many times. The development was performed by repeating the process twice.

<Problems to be Solved by the Invention> However, the method using the conventional ferromagnetic powder as described above cannot cope with the recent rapid development of magnetic material manufacturing technology for magnetic recording. In other words, the recording density of magnetic recording has become extremely high, and the recording wavelength has become extremely small. Conversely, if magnetic recording is to be developed and optically accurate observation is to be performed, the ferromagnetic property is sufficiently smaller than the recording wavelength. Although it is necessary to use body particles, even if fine ferromagnetic particles are used, a few fine particles to several tens of particles, and in some cases even more particles aggregate to form a single large particle In order to show the behavior, it was impossible to observe an accurate recording locus in a region where the recording wavelength was small.

In addition, the developing method in which a magnetic fluid is applied to a magnetic recording medium and then washed, the sharpness and uniformity of development are affected by slight differences in working conditions, and the use of a large amount of washing solvent is uneconomical. There was a disadvantage that it was.

On the other hand, the developer using 1,1,2-trichloro-1,2,2-trifluoroethane described above enables clear and uniform development, and can simplify the development work.
It is more effective than the above two examples. However, on the other hand, since many magnetite particles are aggregated and settled with time in the course of dilution, magnetite actually involved in development is only a part of the used amount, and the efficiency is poor. Therefore, in order to obtain a clear image, it has been necessary to take measures such as repeated development and development over a long period of time.

Further, this developing solution has a drawback that ferrite particles are sedimented with time and thus cannot be stored for a long period of time, and the diluent must be adjusted each time it is used.

Furthermore, 1,1,2-trichloro-1,2,2-trifluoroethane used in this developer is a fluorocarbon (fluorocarbon) solvent, and the reduction and total elimination of its use are currently demanded. It is.

The above-mentioned CFC solvent is a liquid having a low boiling point, has characteristics such as low toxicity, non-flammability, heat stability, and chemical stability, and has a property of dissolving fats and oils well without corroding metals. Used in a wide variety of fields such as detergents, sprays, and foaming agents.In recent years, CFCs released into the atmosphere hardly decompose in the troposphere and reach the stratosphere, where they are decomposed by ultraviolet rays and release chlorine. And destruction of the ozone layer in the stratosphere. As a result, the amount of solar ultraviolet (UV-B), which has harmful effects on living organisms, reaches the surface, and in the troposphere, exhibits a greenhouse effect similar to that of carbon dioxide, adverse effects on ecosystems and abnormal weather on a global scale. It has become clear that it causes environmental problems such as the above, and it is necessary to protect the ozone layer by reducing the use of the above-mentioned fluorocarbon solvent and completely eliminating it during this century.

Therefore, a clear and homogeneous development can be performed without using a chlorofluorocarbon solvent, and the development operation can be performed easily and in a short time. Examination was expected.

<Means for Solving the Problems> The present invention has been proposed in view of the above, and in a method of observing the recording trajectory of a magnetic recording medium using a developer in which a ferromagnetic powder is dispersed, a diluent or The present invention relates to a method for developing a magnetic recording medium, wherein a solvent containing a low-viscosity silicone oil as an active ingredient is used as a cleaning liquid.

More specifically, a solution obtained by diluting a stock solution obtained by dispersing ferromagnetic powder with a diluent containing low-viscosity silicone oil as an active ingredient was brought into contact with a magnetic recording medium, or the stock solution was brought into contact with a magnetic recording medium. Thereafter, the recording locus of the magnetic recording medium is optically observed by washing away with the diluent.

As the ferromagnetic powder used in the present invention described above, carbon iron powder, metal magnetic powder such as Sendust powder,
Ferrite fine particles represented by (MeO) _m · (Fe ₂ O ₃ ) _n may be used, or those obtained by surface-treating them with a fatty acid may be used.

As an example of the method for producing the above-mentioned strong fine particles, for example, Fe ²⁺
And an acidic solution containing Fe3 ^{+ at} a weight ratio of 1: 2 to an alkaline solution to adjust the pH to 9 or more, and ripening at an appropriate temperature, followed by inclined washing until the pH becomes 8 or less, and magnetite having a diameter of about 50 to 200 mm. Fine particles can be obtained.

When the above-mentioned metal (Me) is replaced by one or more of other divalent metal ions, for example, Mn ²⁺ , Ni ²⁺ , Co ²⁺ , Zn ²⁺ , various ferromagnetic ferrite fine particles can be obtained. It can be used by controlling the particle size to 150 mm or less in diameter.

Further, an example of a method for producing a ferrite magnetic powder in which ferrite fine particles are surface-treated with a fatty acid is shown. When dewatered after stirring, magnetite magnetic powder in which magnetite fine particles are surface-treated with oleic acid can be obtained.

The fatty acid used for the surface treatment of the ferrite fine particles is not limited to oleic acid, but may be one of various unsaturated fatty acids such as linoleic acid, linoleic acid and erucic acid.
Species or two or more can be used.

The above-mentioned ferromagnetic powder is dispersed in about 2 to 5 times the amount of a dispersion solvent composed of, for example, a hydrocarbon solvent or the like to obtain a developing solution. Then, a solvent containing a low-viscosity silicone oil as an active ingredient is mixed with the above-mentioned undiluted developing solution to obtain a developer.

Examples of the low-viscosity silicone oil used as the diluent include a silicone oil having a viscosity at 25 ° C. of about 1 cs or less, and include hexamethyldisiloxane, and octmethyltrisiloxane.
These silicone oils, which can be used alone or as a mixture, have low viscosity and relatively good volatility, and are suitable for the development of the present invention.

The low-viscosity silicone oil can stably disperse the ferrite magnetic powder without agglomeration or sedimentation, has low toxicity, has excellent developing characteristics, and also has an evaporation rate suitable for a developing operation at room temperature. .

In this case, the mixing ratio of the diluent mixed with the developing solution is
Although not particularly limited, the ferromagnetic powder in the developer at the time of development needs to be 0.2 to 5 g / 100 ml. If the amount is 0.2 g / 100 ml or less, development of the recording locus cannot be obtained, and if the amount is 5 g / 100 ml or more, a clear recording locus cannot be observed.

The diluent can be used by mixing the low-viscosity silicone oil with a saturated hydrocarbon having 6 or more carbon atoms.

That is, a mixture of a saturated hydrocarbon such as hexane, heptane, octane, nonane, and decane, and a low-viscosity silicone oil can be used as a diluent of a stock solution for developing a ferrite magnetic powder. When a system alcohol solvent is used, a phenomenon that the video tape bends after development occurs.

In addition, the mixing ratio of the saturated hydrocarbon and the low-viscosity silicone oil in the above-mentioned diluent slightly varies depending on the type of the saturated hydrocarbon used, but the weight ratio is 1: 1 to 9: 1.
It is. The diluent in this range disperses the ferrite magnetic powder stably over a long period of time and shows excellent developing characteristics. When the content of the saturated hydrocarbon is larger than the above range, the magnetic medium to be developed is developed. Is fogged, and clear development cannot be obtained. When the amount of the low-viscosity silicone oil is large, the dispersibility is poor, so that the ferrite magnetic powder is liable to settle out, whereby clear development cannot be obtained.

The present invention is to use the diluted solution as described above, as a low-viscosity developer by mixing it with a developing stock solution in which the above-described ferromagnetic powder is dispersed, and immerse a recording medium and pull it up for sharp development. It can be performed.

The diluent of the present invention described above uses a low-viscosity silicone oil represented by hexamethyldisiloxane or octomethyltrisiloxane to improve the sharpness and uniformity of an image formed by development, and to reduce the conventional fluorocarbon solvent. Alternatively, it is possible to adjust a developer exhibiting more excellent developing characteristics than a developer using a hydrocarbon solvent.

Further, the developer prepared by using the diluent of the present invention can be stably dispersed and stored without aggregating or settling the ferromagnetic powder, so that the developing operation can be continuously performed.

Furthermore, when a developer prepared by using the diluent of the present invention is used, the immersion time required for development may be as short as 1 to 3 minutes as in the case of a conventional fluorocarbon solvent, and in particular, high immersion time such as metal tape In the case of a magnetized high coercive force medium, the recording density is high in addition to the magnetization strength, and conventionally, clear development was difficult, but a very clear image can be obtained by immersion for several seconds to several tens of seconds. .

The present invention proposes a developing method using a diluent containing a low-viscosity silicone oil as an active ingredient as a cleaning liquid.

In this case, the ferromagnetic powder is sprayed directly on the recording medium surface, or the developing solution is applied to the recording medium, and then washed with a diluent containing low-viscosity silicone oil as an active ingredient, and the magnetization of the recording portion is measured. The recording trajectory can be optically observed based on the grayscale image formed by the fine particles remaining after being sucked according to the strength.

<Effects of the Invention> As described above, according to the present invention, by using a solvent containing a low-viscosity silicone oil such as hexamethyldisiloxane or octmethyltrisiloxane as an active ingredient as a diluting liquid or a washing liquid, development is achieved. In terms of sharpness and uniformity of the formed image, it is superior to a conventional developer using a chlorofluorocarbon solvent or a hydrocarbon-based solvent and its developing method. Since the particles are stably dispersed without causing the development, excellent development characteristics are exhibited, and the development operation can be continuously performed for a long time.

Furthermore, with the above-mentioned developer, development can be performed in a short immersion time. In particular, a high-magnetization high-coercivity medium, such as a metal tape, which has conventionally been difficult to develop sharply, also obtains a very clear image. be able to.

Therefore, the present invention has high practical value as a developing method excellent in dispersibility, storage stability and developing characteristics without using a chlorofluorocarbon solvent.

<Examples> Examples of the present invention will be described below.

Example 1 100 ml of a 1 mol / ferrous sulfate aqueous solution and 100 ml of a 1 mol / ferric sulfate aqueous solution were mixed, and an aqueous sodium hydroxide solution was added thereto with stirring until the pH reached 9.5 to precipitate magnetite crystals. Stirring was further continued for 30 minutes, and after aging, gradient washing was performed until the pH reached 8.0 to remove the electrolyte.

Next, 100 ml of a 10% by weight aqueous solution of sodium oleate
Was added and the mixture was heated and stirred at 80 to 90 ° C. for 30 minutes. After cooling,
Separation and dehydration of magnetite whose surface is covered with oleic acid by absorption filtration and drying at a low temperature of 40-70 ° C.
g of dry powder was obtained.

10 g of this dry powder was added to 10 ml of n-octane and stirred at 100 ° C. for a minute to obtain a dispersion. The dispersion was collected in a centrifuge at 20,000 G for 1 hour, and the supernatant was used as a stock solution for development. The concentration of magnetite was measured to be 350% by weight. 2 ml of this undiluted developing solution was mixed with 120 ml of n-octane and 80 ml of hexamethylenedisiloxane to prepare a 200 ml diluent.
And stirred.

After standing overnight, 150 ml of the supernatant was collected, a small piece of videotape was immersed and slowly pulled up 2 minutes later, dried, and observed with a microscope. As a result, a very clear recording locus was observed.

Example 2 To 5 ml of the undiluted developing solution obtained in the same manner as in Example 1, n-
Octane 25 ml was added and mixed. A small piece of video tape was immersed in this solution for 2 minutes, immediately immersed in 50 ml of a washing solution comprising a mixed solution of 25 ml of n-octane, 20 ml of methylenedisiloxane, and 5 ml of octmethyltrisiloxane for 10 seconds to rinse off.
After slowly pulling up and drying, observation with a microscope revealed a very clear recording locus.

Claims (1)

(57) [Claims] In a method for observing a recording locus of a magnetic recording medium using a developer in which a ferromagnetic powder is dispersed, a solvent containing a low-viscosity silicone oil as an active ingredient is used as a diluting liquid or a cleaning liquid. A method for developing a magnetic recording medium, comprising: