JPS6017433B2 - How to purify magnetic ink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying magnetic ink in a recording method using magnetic fluid.

Conventionally, commercially available magnetic fluids have a particle size of 100
It is a liquid in which A-sized magnetic fine particles are colloidally suspended in dispersed soot together with a surfactant, and is essentially a liquid that is stable for a long period of time and does not cause sedimentation or aggregation.

Magnetite (Fe304) is generally used as magnetic fine particles.
In addition, composite ferrites such as manganese ferrite and zinc ferrite are used, exhibiting a black color, and are applied to image recording devices as black ink, and various recording methods have been proposed that take advantage of their magnetic properties. Dispersants for this magnetic fluid include paraffin, water, ester oil, silicone oil, etc., and surfactants include carboxylic acids such as oleic acid and linoleic acid, as well as cationic activators and/or ionic activators. be done. The magnetic properties of this magnetic fluid are said to exhibit superparamagnetism. The two main methods used to produce this magnetic fluid are the '11 fine particle wet synthesis method and the '21 pulverization method, in which large particles are removed by centrifugation after synthesizing and dispersing magnetic fine particles. This is done to create a stable colloidal solution. Centrifugal separation is performed at a centrifugal force of about 200,002 to 40,000 degrees (ta: gravitational acceleration) to produce a magnetic fluid. When these magnetic fluids are used as magnetic inks, they may also contain dyes and coloring pigments. The inventors of the present invention have conducted a detailed study for the purpose of using a magnetic fluid as a recording ink, and have found that when magnetic ink is left in a magnetic field for a long time, the magnetic particles in the magnetic ink become concentrated in the magnetic field, especially when the magnetic field is concentrated. A phenomenon occurred in which the particles aggregated and precipitated at points and did not immediately redisperse after the magnetic field was removed.

This is to prevent damage to the original properties of a magnetic fluid, and when we investigated the cause, we found that some magnetic particles, which were thought to be large particles or unstable particles in the magnetic ink, precipitated. It was something that was done. This magnetic sedimentation occurs when the ink is left for a long time in a place where the magnetic field is concentrated, or rather, where the lines of magnetic force diverge significantly. In this case, no magnetic precipitation occurred regardless of the magnetic strength. Sedimentation at locations where this magnetic field was concentrated depended on the strength of the concentrated magnetic field and also on the concentrated envelope of the magnetic field. These are based on the magnetic particles as impurities in the magnetic ink mentioned above, and it has been found that this magnetic field purification can be purified most efficiently rather than centrifugation. This phenomenon of magnetic precipitation of impurities causes various problems when using magnetic inks. That is, when magnetic ink is left in a magnetic field, the sedimentary particles therein begin to gradually settle and deposit in areas where the magnetic field is concentrated. If the ink is gradually flowing, the sedimentary magnetic particles in the ink will gradually accumulate and form a precipitate, causing the ink to completely lose its fluid behavior at that point. In particular, in a recording device using this ink, this magnetic sedimentation occurs at an important part of the head tip where a magnetic field is applied, and becomes a cause of inhibiting image recording. Therefore, the present invention provides a method using a concentrated magnetic field as a method for purifying magnetic ink, and provides a magnetic ink that does not undergo magnetic field sedimentation.

Below, the state of magnetic precipitation will be explained in detail, and a specific method for purifying magnetic ink using a concentrated magnetic field will be described. The magnetic fine particles in the magnetic ink are usually stably dispersed in a colloidal form and do not cause any sedimentation for a long period of time.

When this magnetic ink 3 is adsorbed to a permanent magnet 1 via a magnetic plate 2 as shown in FIG. 1, a precipitate 4 is formed on the edge of the magnet 1 after being left for a long time. In other words, magnetic sedimentation in the present invention is not sedimentation that occurs instantaneously due to a magnetic field, but
A substance that forms precipitates in areas where the magnetic field is concentrated due to being left in a magnetic field for a long time. - When the magnet shown in Fig. 1 is removed from the magnetic plate 2 and the mirror is opened, no magnetic force acts on the magnetic slope, so the magnetic ink 3 flows away and only the precipitate 4 remains.
The precipitation abundance depends on the magnetic field strength and also on the degree of magnetic field concentration. The magnetic field concentration here refers to the divergence of magnetic field lines,
It refers to the containment of Shuto, and when there is a parallel magnetic field, this magnetic field neutrality is defined as zero. Therefore, the magnetic field is most likely to be concentrated at the pole tip, and magnetic sedimentation is most likely to occur here. The concentrated magnetic field in the present invention means a magnetic field with high magnetic field concentration and magnetic strength, and it is effective to perform magnetic refining with a concentrated magnetic field higher than the practical magnetic field in which magnetic ink is actually used for recording. Next, as specific methods for magnetic refining, there are two methods: a 0-notch method and a continuous method.The batch method is a more efficient refining method, and although it has better refining efficiency, it does not require long-term counterfeiting. Therefore, it is inefficient, and the continuous method after that point is easier to implement as an apparatus.

In this continuous method, the ink is flowed as slowly as possible, but the purification efficiency is high. However, in any case, providing several stages or more of concentrated magnetic fields increases the purification rate and improves the purity of the magnetic ink. Next, the configuration will be specifically explained.

Example 1 A purified magnetic material 3 (saturation magnetization: 0 Gauss, specific gravity: 1,39, viscosity: 2 centipoise (2 centipoise)) using paraffin as a base oil was heated to a thickness of 0.5 centipoise (2 centipoise) as shown in Fig. 2.
Place it in an iron plate container 5 with 25 ribs, and place 20 cylindrical alnico magnets 6 with 3 bars, 3 heights, and a maximum surface magnetization of 1000 Gauss in a row, as shown in the figure, and place the bottom of the iron plate container. was adsorbed.

The magnet was removed once every day to gradually remove the precipitate 4, and then set again, and magnetic purification was repeated for 7 days. The amount of sediment decreased sequentially from total evening → 10 evening → 8 evening → 7 evening → 3 evening → 1 evening,
After 7 days, we were able to obtain ink with a measurement accuracy of 1 evening (1.5 evenings on Saturdays). When the physical properties of this magnetic ink were measured, the saturation magnetization was 374 Gauss, and the specific gravity was 1.351.
Although the viscosity was 22.5 centivoids (20° C.), which was slightly different from the initial physical properties, no further sedimentation was observed in a practical magnetic field of 1000 Gauss or less. Example 2 The same unpurified magnetic fluid 3 as in Example 1 was continuously purified using the apparatus shown in FIG.

The same number of magnets as in Example 1 were used. Note that the flow rate is 3
It was supplied at cc/min. Obtained magnetic ink 3' 1
When its physical properties were measured, it had a saturation magnetization of 375 Gauss, a specific gravity of 1.352, and a viscosity of 1.5 Gauss. It was 7 centipoise (20°C). The value is very similar to the purified ink of Example 1,
Similarly, no sedimentation was observed in a practical magnetic field. Example 3 Magnetic ink 3 is raised at a position of 300 m from the tip of a multi-stylus 7 in which coated iron wires with a diameter of 60 mm are arranged in a line of 128 wires at a density of 8 wires/willow as shown in Fig. 4. A magnet 8 was glued, and then an ink supply V supply approximately 9 made of a magnet was glued thereto.

A sub-tank 10 was provided below, and the supply passageway 9 was immersed therein. The sub-tank and the ink tank 11 were connected, and an ink magnetic purification section 12 was provided in the middle. When the same unpurified magnetic fluid as in Example 1 was supplied from the ink tank, the ink that passed through the magnetic refining section 12 was further purified, and the sedimentation of the magnetic particles in the ink on the raised magnet at the tip of the head was extremely small. Improvement was seen. The stylus 7 of the multi-stylus head of this device is used as the (10) electrode, and with the configuration shown in FIG. Recording body 1 with a thickness of 60 peaks on the electrode
4 were placed next to each other.

And set the height of the ink ridge at the tip of the stylus to 20.
After adjusting to Buddha m, the stylus 7 and back electrode 13
A DC bias power supply 15 and pulse power supplies 16 and 17 were connected in series to cause the magnetic ink to fly between the two. Using this device, the bias voltage IKV and the pulse voltage were each 40
When a recording experiment was conducted at 0 V, the ink flew away from the tip of the ridge, and a clear image was obtained. Furthermore, when we conducted continuous recording experiments using this device, we found that conventional devices, which could not record after about two hours due to magnetic sedimentation of the ink, were able to record continuously for several days, producing stable and clear images. was gotten. As described above, the magnetic ink purification method of the present invention removes unstablely dispersed magnetic fine particles by applying a concentrated magnetic field to the magnetic ink.
It has become possible to dramatically improve the practicality of magnetic ink.

Furthermore, this purification method can be widely used in the manufacturing process of magnetic ink, and can also be applied to magnetic inks containing other dyes and pigments, making it extremely versatile. Further, as explained in the embodiments, it can be combined with various recording apparatuses, and has an excellent effect that greatly contributes to improving the performance of the recording apparatus.

[Brief explanation of the drawing]

Figures 1a and b are side views for explaining the sedimentation of magnetic ink due to a magnetic field, Figure 2 is a block diagram of an apparatus for realizing one embodiment of the purification method of the present invention, and Figure 3 is another embodiment. FIG. 4 is a block diagram of a main part of a recording apparatus to which the method of the present invention is applied, and FIG. 5 is a side view of a main part of the recording apparatus. 2...Magnetic plate, 3...Magnetic ink, 4...
...Sediment, 5...Iron plate container, 6...
···magnet. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. Applying a concentrated magnetic field to a magnetic ink consisting of magnetic fine particles colloidally dispersed in a dispersion medium by a surfactant to precipitate and remove the unstablely dispersed magnetic fine particles. A method for purifying magnetic ink, characterized by removing the magnetic ink. 2. The magnetic ink refining method according to claim 1, wherein the concentrated magnetic field is applied by a permanent magnet installed outside the magnetic ink container. 3. A method for refining magnetic ink according to claim 1, characterized in that a concentrated magnetic field is applied from the bottom of the magnetic plate using a large number of permanent magnets, and the magnetic plate is tilted to cause the magnetic ink to flow down thereon.