JPH0322041B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in magnetic fluids, and more particularly to improvements in the hue of magnetic fluids. A magnetic fluid is a liquid in which magnetic particles with a particle size of approximately 50 to 200 Å are suspended in a dispersion medium together with a surfactant, and is stable for a long period of time and has the property of not causing sedimentation or condensation. The above-mentioned magnetic particles include, for example, magnetic fine particles containing ferrites such as magnetite, manga ferrite, nickel ferrite, cobalt ferrite, iron-zinc ferrite, manganese-zinc ferrite, nickel-zinc ferrite, and barium ferrite. As the surfactant, for example, carboxylic acids such as oleic acid and linoleic acid, cationic surfactants, nonionic surfactants, etc. are used alone or in combination. Examples of the dispersion medium include paraffin, ester oil, ether, and fluorinated hydrocarbon. In addition, magnetic fluids are widely used in the mechanical field such as sealants and lubricants, in the separation field such as specific gravity separation and oil/water separation, in the printing and recording field such as magnetic or electrostatic latent image developers and inkjet, and in toys. . The magnetic fluid of the present invention can be used for the above-mentioned magnetic fluid applications, and is especially effective in the field of printing and recording. Therefore, in order to facilitate understanding of the magnetic fluid of the present invention, the magnetic fluid recording method will be explained below, but this is not intended to impose unnecessary limitations on the present invention. The magnetic fluid recording method is a method of recording by using the above-mentioned magnetic fluid as a recording ink and making it fly, migrate, or deflect by pressure, magnetic force, Coulomb force, or the like. Conventionally, the magnetic fluids used in recording methods in this field include (1) using the magnetic fluid as it is or diluting it with a dispersion medium, (2) using a dye soluble in the dispersion medium dissolved in the magnetic fluid, ( 3) Three methods have been proposed: using pigments dispersed in magnetic fluid. Although magnetic fluid is normally black or dark brown,
When it forms a thin layer on the recording medium or penetrates into the recording medium, it becomes reddish, and the hue of the image formed on the recording medium becomes dark brown or brown. Therefore, when the above-mentioned magnetic fluid (1) was used, there was a drawback that a black image could not be obtained. Furthermore, using the magnetic fluid (1) had the disadvantage that it could only record the color of the magnetic particles. In order to overcome the above drawbacks of the magnetic fluid (1), magnetic fluids (2) and (3) have been proposed. However, in the magnetic fluid (2), when a recording medium that permeates liquid, such as paper or cloth, is used, the permeation speed differs due to the difference in particle size between the magnetic particles and the dye. Therefore, for example, the dye penetrates into the back surface of the recording medium, causing color separation, and the hue of the image becomes browner than the hue of the magnetic fluid (2). In the magnetic fluid (3), the drawbacks of the magnetic fluid (2) were overcome by making the particle sizes of the magnetic particles and the pigment almost the same. However, it is generally difficult to finely disperse pigments to a size of several hundred angstroms, and it also has the drawback that fine dispersion of pigments requires a long time. The present invention aims to overcome these conventional drawbacks and provide a magnetic fluid with rich hues. It is an object of the present invention to provide a magnetic fluid having excellent properties, particularly in the field of application of magnetic fluid where hue is a problem. The magnetic fluid of the present invention is characterized in that colorant-containing liquid particles are dispersed in the magnetic fluid. That is, it is characterized in that a colorant-containing liquid is dispersed in a magnetic fluid in the form of a colloid (hereinafter referred to as a colored colloid). It is also an effective means to use a surfactant to more stably disperse the colored colloid.
The following two items are mainly requested here. (a) Colored colloids are stably dispersed in the magnetic fluid. (b) The colored colloid does not affect the dispersion stability of the magnetic particles. Now, in order to satisfy the above two requirements, it is necessary that the colored colloid has no influence on the surfactant of the magnetic particles. Further, when the colored colloid is dispersed using a surfactant, it is necessary that the surfactant of the colored colloid does not interact with the surfactant of the magnetic particles. In other words, it is sufficient to prevent the surfactant of the colored colloid from becoming excessive. Next, materials used in the present invention will be explained. However, the materials described below are just examples, and of course do not limit the present invention. First, liquid components forming colored colloids include water, alcohol, cellosolve, acetone, and the like. As a colorant, as a dye, CI
Direct dyes such as Direct Violet 1, 7, 9, CI Direct Blue 2, 6, 15, acid dyes such as CI Acid Orange 8, 10, 19, CI Acid Green 7, 9, 41, CI Basic Blue 1, 3, 5, CI basic green 1, 4,
Basic dyes such as 6, CI Disperse Violet 18, 23, 26, CI Disperse Blue 5
Examples include disperse dyes such as 5, 56, 58, and the like. Furthermore, organic pigments and inorganic pigments that are stably dispersed in water, alcohol, cellosolve, acetone, etc. are also provided.
As the surfactant for the colored colloid, nonionic surfactants such as sorbitan monolaurate, sorbitan monooleate, and polyoxyethylene nonylphenol ether, and anionic surfactants such as sodium dialkyl sulfosuccinate are used. Next, as a method for dispersing the colored colloid, a conventional method may be used in which a liquid containing a magnetic fluid and a coloring agent and a surfactant of the colored colloid are stirred and dispersed using a mixer, a colloid mill, a homogenizer, or the like. Specific examples will be described below. First, Table 1 shows Matsumoto Yushi Pharmaceutical Co., Ltd. used in the examples.
The magnetic fluids and their compositions are shown in the manufactured magnetic fluids. The dispersion medium of the magnetic fluid used here was kerosene, and the concentration of magnetic particles was 20 vol%.
Further, the composition of the magnetic particles is an analysis value at the time of particle production. For comparison, Table 1 also shows hues recorded using only magnetic fluid.

【table】

[Table] Magnetic fluids A to C were dispersed using the method described in Table 2. In addition, in the colorant liquid column in the table, the name of the colorant and the concentration of the colorant with respect to the medium are written. The magnetic fluid produced as described above was used as ink, and the magnetic fluid recording device shown in the figure was used to fly it onto recording paper. The hue at this time is also listed in Table 2.

[Table] Here is a brief explanation of the magnetic fluid recording device.
The main part of the stylus 1 is such that one end of the stylus 1 is brought into contact with a magnet 2, and the other end of the stylus 1 is opposed to an electrode 4 with a recording paper 3 interposed therebetween. At this time, due to the magnetic field of the magnet 2, the ink 5 is raised along the stylus 1 to its tip. Next, a voltage 6 (recording voltage) corresponding to the image signal is applied between the stylus 1 and the electrode 4.
When the ink 5 is applied, the ink 5 flies from the tip of the above-mentioned bump 7 due to Coulomb force. In the manner described above, recording can be performed on the recording paper 3 according to the image signal. When the above-mentioned magnetic fluid was left for several months and examined, no separation, condensation, or precipitation of magnetic particles or colored colloids was observed. Further, after being left for several months, an experiment was conducted in which recording was performed using a magnetic fluid recording device in the same manner as described above, but there was no change in the hue of the recorded image. Although the embodiments of the magnetic fluid of the present invention have been described above, they are merely examples, and needless to say, they do not impose unnecessary limitations on the present invention. Furthermore, similar effects can be obtained with magnetic fluids using ester-based, ether-based, or fluorinated hydrocarbon-based dispersion media. Further, the recording method is not limited to the embodiments, and for example, it can be used as ink for ink jets, ballpoint pens, and the like. Furthermore, it goes without saying that it can be used in all fields of application of magnetic fluids. As explained above, the magnetic fluid of the present invention is
By dispersing it in a magnetic fluid using water, alcohol, cellosolve, etc. as a medium, it is possible to provide a magnetic fluid exhibiting various hues. In addition, the means for dispersing it as a colored colloid may be any ordinary means;
It also has the effect of stably dispersing in a short time. When the magnetic fluid of the present invention is used as an ink for printing and recording, it is recorded together with magnetic particles in a colored colloidal state, so even if it is recorded on a permeable recording medium such as recording paper, the magnetic particles will be colored on the recording medium. does not separate from the agent. Therefore, it is possible to record with the hue at the time when the magnetic fluid was adjusted, and there is an effect that resolution does not deteriorate due to penetration. At the same time, it has the effect of not choosing a recording medium. Furthermore, since the magnetic particles of the present invention have basic physical properties such as electrical properties and viscosity that are almost unchanged from those of conventional magnetic fluids, they can be used in fields of application of magnetic fluids without any change from conventional magnetic fluids. Furthermore, in the magnetic fluid of the present invention, the same effect can be obtained even when colorant-containing oil particles are dispersed in a magnetic fluid using water as a dispersion medium.

[Brief explanation of drawings]

The drawings are diagrams showing the principle of the magnetic fluid recording device used in the examples. 1... Stylus, 2... Magnet, 3... Recording paper, 4... Electrode, 5... Ink, 6... Recording voltage, 7... Uplift.

Claims (1)

[Scope of Claims] 1 Magnetic particles and liquid particles that are a liquid different from the dispersion medium and that contain a colorant are dispersed in a dispersion medium selected from the group consisting of hydrocarbons, ethers, esters, and fluorinated hydrocarbons. magnetic fluid. 2. The magnetic fluid according to claim 1, wherein the magnetic particles include ferrite. 3. The magnetic fluid according to claim 1, wherein the colorant-containing liquid particles are dispersed with a surfactant.