JPH07129104A - Magnetic recording body - Google Patents

Abstract

(57) [Abstract] [Purpose] The part to which magnetism is applied has a distinct brightness and darkness different from the part to which no magnetism is applied, has high resolution, is clear, and has excellent image stability, reversible display, and A magnetic recording body capable of color display is provided. [Structure] The magnetic recording medium 1 is a dispersion of colored magnetic particles 22 and a pigment or dye 23, and has a viscosity at room temperature of 200 cp.
It has a magnetic display layer 12 containing microcapsules 14 encapsulating an organic solvent 24 having a viscosity of 100 s or more and a viscosity of 100 cps or less when heated, and the surface of the magnetic recording medium is usually a uniform color tone due to the color of a pigment or a dye. When recording, the magnetic particles in the portion of the dispersion medium that is in a fluidized state due to heat move to the magnetic application side, and an image of the color of the colored magnetic particles 22 is formed.
In the erasing, the colored magnetic particles 22 move to the magnetic application side with heating and the surface becomes the color of the pigment or dye again, and the image is erased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium which displays an image magnetically upon heating, and more particularly to a magnetic recording medium which is excellent in resolution and image stability, is capable of reversible display and is capable of color display. .

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium utilizing magnetism, a magnetic field is applied to a suspension in which magnetic particles are dispersed in a coloring dispersion medium, as described in, for example, JP-A-48-56393. By doing so, a method is known in which the magnetic particles are moved to change the color of the colored dispersion medium and display is performed.

However, in such a magnetic recording medium, when the suspension is sealed between two substrates and one of the substrates draws characters and patterns with a magnetic pen to apply magnetism, the magnetic particles of the suspension are attracted. Although the characters and patterns are obtained as they are, since the specific gravity of the magnetic particles is much larger than that of the dispersion medium, the attracted magnetic particles have the drawback that the characters and patterns cannot be retained for a long time because they settle with time. .

Further, since all the magnetic particles magnetized by the magnetic pen are attracted to the magnetic pen, the magnetic particles existing apart from the magnetic pen are also attracted, so that only unclear characters and patterns are obtained. It also had drawbacks. In order to prevent sedimentation of magnetic particles, for example, if the magnetic particles are made finer or the magnetic particles are coated with a polymer having a low specific gravity, and the apparent specific gravity of the magnetic particles approximates that of the dispersion medium, the magnetic particles Since the force becomes extremely small, it becomes difficult to be sucked by the magnetic pen, which causes a defect that it is not possible to obtain a clear character or pattern with high density.

Further, if the apparent specific gravity of the magnetic particles is approximated to that of the dispersion medium, the magnetic particles are difficult to be attracted to the opposite side of the substrate even when characters and patterns are erased, and the particles cannot be completely erased. Repeatedly, it turned black overall, which was not practical.

As a mode for solving these drawbacks, for example, Japanese Examined Patent Publication No. 57-27463 and Japanese Unexamined Patent Publication No. 62-53359.
As described in the publication, as a dispersion medium, a liquid having a yield value of a certain value or more, or by using a thickener, it is possible to display clear, high-contrast characters and images without blurring, There is known a magnetic recording medium which can stably hold a display for a long time and can be completely erased.

However, this magnetic recording medium is formed by forming honeycomb cells each having a side and a depth of about 2 mm on the entire surface of a transparent plastic sheet, and the magnetic particles and the white pigment are contained in the cells. The suspension was injected into a dispersion medium, and the suspension was sealed with a transparent sheet, which had the following drawbacks. That is, since the image is formed by moving the magnetic particles from the back surface to the front surface in the honeycomb-shaped cell, it is impossible to make the resolution of the image smaller than that of the honeycomb-shaped cell. Further, it is difficult to form honeycomb cells, to make the honeycomb cells large or very small, and to inject a suspension into the honeycomb cells.

As another mode, for example, Japanese Patent Laid-Open No. 1-14
5637 or Eyne S. et al. Trumb
le P.L. S. & E. 7 213 (1963), unlike a magnetic recording medium in which magnetic particles and a pigment are sealed in a honeycomb-shaped cell as described above, the magnetic particles are encapsulated in a microcapsule, which is then placed on a support. There is known a magnetic recording medium coated on the. According to this method, the resolution can be increased by controlling the particle size of the microcapsules, and the manufacturing process is easy. Further, various films and the like can be selected as the substrate on which the microcapsules are applied, and the shape and size can be freely selected.

However, in the image forming method shown here, at the time of manufacturing a magnetic recording body, first, the magnetic particles in the coated capsules are oriented in parallel to the plane of the magnetic recording body in advance so that all the incident light is reflected to make it appear bright. Keep it. Next, by magnetically recording, the magnetic particles rotate to scatter and absorb the incident light, and a contrast is produced, so that a black image is formed. That is, the magnetic particles used here are generally limited to flat particles such as nickel, iron and barium-ferrite, and the principle of image formation is based on the orientation of the magnetic particles. It is necessary to always orient the flat surface of the grain parallel to the plane of the magnetic recording medium, but it is difficult to orient it uniformly and completely in this way, and it is not perfectly oriented. The magnetic particles produce an image in which light and dark are not clearly defined.

Further, as another form using the microcapsules, for example, as disclosed in JP-A Nos. 2-146082 and 4-233581, light-absorbing magnetic particles and light-reflecting particles are used. A magnetic recording body in which non-magnetic particles are enclosed in microcapsules is known.

In the image formation of this form, first, the permanent magnet attracts the light-absorbing magnetic particles in the microcapsules to the back surface side of the magnetic recording medium, and accordingly, the light-reflecting non-magnetic particles become magnetic recording medium. By remaining on the surface of the non-magnetic particles, the surface becomes the color of the non-magnetic particles and is in the erased state. Then, by applying and recording magnetism from the surface of the magnetic recording medium by a permanent magnet, the light-absorbing magnetic particles are magnetically attracted to the surface, and desired characters and images are formed.

However, the magnetic recording material thus obtained has a magnetic force over a wide range, and therefore has a resolution extremely inferior to that of recording by other heat or light. Furthermore, since the magnetic recording medium can be easily printed and erased by magnetic force, the image may be fogged in the unprinted portion or the image may be erased by just touching the magnet. It has the drawback of poor stability.

Further, as a magnetic recording medium capable of color display, for example, the N and S poles of the magnetic particles described in JP-A-1-63991 are colored in different colors, and the magnetic particles are rotated by applying a magnetic force. A magnetic recording body for color display, and magnetic particles having different magnetic properties described in JP-A-4-175196 are colored in different colors,
2. Description of the Related Art There is known a magnetic recording body that controls a magnetic field strength to perform color display.

However, in the case of the above magnetic recording body for color display, it is difficult for the former to color the fine magnetic particles when coloring the N pole and the S pole of the magnetic particles in different colors.
The color coding of each pole is incomplete, and the latter has a drawback that it is difficult to control the magnetic field strength at the time of display and both of them cannot perform clear color display due to the ambiguity of the control of the magnetic field.

[0015]

A conventional magnetic recording medium using a magnetic material as a display means cannot display an image with a high resolution, and a part of the displayed image is affected by an external magnetic field. Alternatively, the image is erased in an unreadable state or fog occurs in the unprinted portion, so that stable recording cannot be performed and further clear color display cannot be performed. Further, there has been no magnetic recording material having mobility of the magnetic particles contained therein, that is, good recording reactivity and stability of recorded image.

Therefore, in the present invention, the portion to which magnetism is applied is
An object of the present invention is to provide a magnetic recording medium which has a clear contrast from the non-applied portion, has high resolution, is clear, has excellent image stability, is capable of reversible display, and is capable of color display. .

[0017]

The present invention has been made to achieve the above object, and at least one of the magnetic recording bodies according to the invention of claim 1 is made of a nonmagnetic material having transparency. Microcapsules containing magnetic particles and a pigment or dye coated with a colored layer, and an organic solvent having a viscosity of 200 cps or more at room temperature and a viscosity of 100 cps or less at the time of heating, which are dispersed between the supports. It is characterized in that a magnetic display layer is formed by dispersing and disposing the above in a binder.

A magnetic recording medium according to a second aspect of the present invention is a magnetic recording medium characterized in that the colored layer coating the magnetic particles comprises a coating film containing a pigment as a main component.

A magnetic recording medium according to a third aspect of the present invention is characterized in that a concealing layer is provided between the surface of the magnetic particles and the coloring layer.

The magnetic recording medium according to a fourth aspect of the present invention is a magnetic recording medium characterized in that the concealing layer is made of an inorganic powder or a metal thin film dispersed in an organic polymer.

[0021]

The magnetic recording material of the present invention comprises a magnetic particle and a pigment or dye coated with a colored layer, and an organic solvent having a viscosity of 200 cps or more at room temperature and a viscosity of 100 cps or less when heated. It has a magnetic display layer containing microcapsules containing and, usually, the magnetic particles are attracted to the back side, which is one side of the magnetic recording medium, that is, below the microcapsules, and the other side. The surface of the magnetic recording medium has a uniform color tone due to the color of the pigment or dye.

The recording on the magnetic recording medium of the present invention is performed by scanning from the surface side of the magnetic recording medium with a magnetism generating means having a heating means, and the magnetic property of the portion of the dispersion medium in which the viscosity is lowered by heat to become a fluid state. The particles magnetically move to the upper side of the microcapsule, that is, to the surface on the side of the magnetic generation means, and a color image is formed by the magnetic particles coated with the coloring layer. By applying magnetism to the entire surface from the back surface or by scanning the back surface with a magnetism generating means having a heating means, the magnetic particles are attracted to the magnetism generating means side below the microcapsules, and the surface of the magnetic recording medium is re-established. It becomes the color of the pigment or dye and the image is erased.

[0023]

The present invention will be described in detail below with reference to the drawings.
FIG. 1 is a sectional view showing an embodiment of a magnetic recording body of the present invention, FIG. 2 is a sectional view showing an embodiment of a microcapsule used in the magnetic recording body of the present invention, and FIG. It is a cross-sectional view showing an example of magnetic particles coated with a layer,
FIG. 4 is a cross-sectional view showing an embodiment of the magnetic particles coated with a hiding layer and a coloring layer, FIG. 5 is a cross-sectional view showing the state of the magnetic recording medium of the present invention during production, and FIG. FIG. 8 is an explanatory diagram showing a state in which the magnetic recording medium of the present invention has not been recorded by an erasing operation, and FIG. 7 is an explanatory diagram showing a state of the magnetic recording medium of the present invention during recording.

The magnetic recording medium 1 shown in FIG.
1. A magnetic display layer 1 coated with a coating material in which microcapsules 14 containing magnetic particles are dispersed in a binder 15.
2. Further, the protective support 13 is sequentially laminated. The microcapsules 14 used in the magnetic display layer 12 shown in FIG. 2 are the colored magnetic particles 22 or the colored magnetic particles 2.
2 ', and the pigment or dye 23 has a viscosity of 20 at room temperature.
0 cps or more, and viscosity when heated is 100 cps
A core substance 20 having a suspension as a main component dispersed in an organic solvent 24 described below is sequentially laminated with a shell substance 27 made of a polymer to be encapsulated. In particular, the shell substance 27 is preferably transparent or translucent so that the inside of the microcapsule 14 can be seen. As shown in FIG. 3, the colored magnetic particles 22 constituting the core substance 20 are formed by forming a colored layer 25 made of, for example, a coating film containing a pigment as a main component on the surface of the magnetic particles 21.

Further, as shown in FIG. 4, colored magnetic particles 22 '
A concealing layer 26 may be provided between the surface of the magnetic particles 21 and the colored layer 25. According to this, since the color of the magnetic particles is concealed, the color layer 25 is not affected by the color of the magnetic particles being seen through as compared with the case where the color layer 25 formed on the outer surface is formed alone. Can be made thinner. The hiding layer 26 is formed of an inorganic powder or a metal thin film dispersed in an organic polymer.

Colored magnetic particles 22 constituting the core material 20,
As the magnetic fine particles 21 of 22 ', it is possible to use magnetic particles alone, a mixture of several kinds of magnetic particles, or a mixture of magnetic particles and a polymer. For example, magnetite, ferrite and other iron, cobalt, nickel, and other ferromagnets, alloys containing these elements, or compound fine particles are used. In this case, the magnetic particles may be subjected to a surface treatment such as a silane coupling treatment in order to enhance the affinity with the organic solvent or the like. When a mixture of magnetic particles and a polymer is used, the above-mentioned magnetic particles and a polymer are kneaded and then pulverized, or a monomer in which the magnetic particles are dispersed is subjected to a method such as emulsion polymerization, suspension polymerization, or dispersion polymerization. And the like are used for the polymerization. In this case, the polymer is preferably crosslinkable. The size of the magnetic particles is 0.1 μm to 10 μm, considering the ease of movement due to magnetism and the image density.
Is preferred.

A colored layer 25 covering the magnetic particles 21 is also provided.
Can be a pigment as a main component and a pigment alone or a mixture of several pigments, or a mixture of a pigment and a polymer. For example, fine particles of inorganic pigments such as titanium dioxide, zinc sulfide, lead titanate, cadmium red and cadmium yellow, and organic pigments such as phthalocyanine pigments are used. The coloring layer 25 is adjusted by a phase separation method in which a concentrated phase of a polymer in which a pigment is dispersed is separated around magnetic particles 21 formed by dispersing a polymer solution in which a pigment is dispersed, and a dispersed in a polymer solution in which a pigment is dispersed. The magnetic particles 21 are prepared by curing the polymer around the magnetic particles 21 by a curing agent such as a polymer curing test agent, and supplying a suspension of the magnetic particles 21 with a pigment-dispersed monomer or a polymerization catalyst. Dispersion polymerization method in which the surface of the pigment is covered with a polymer in which a pigment is dispersed, an impact method in an air stream in which the surface of magnetic particles is directly mixed and milled with a pigment, or a suspension in which magnetic particles are dispersed in a polymer solution in which a pigment is dispersed is sprayed. Microencapsulation techniques such as spray drying to dry are preferred. Another method is to form a pigment layer composed of a metal oxide by immersing magnetic particles in an organometallic compound solution, pulling it up and drying it, and then firing it to decompose the organometallic compound, or diluting a metal salt. Examples include a method in which magnetic particles are suspended in an acidic solution, a metal salt is hydrolyzed to precipitate a hydrated metal oxide on the surface thereof, and the pigment is baked to form a pigment layer made of a metal compound. The method of adjusting the colored layer 25 is not limited to these methods.

The concealing layer 26 is the colored layer 25 as described above.
It is possible to reduce the effect that the color of the magnetic particles can be seen through, and it is particularly effective when the colored layer is a light color such as yellow. Specifically, it is composed of an inorganic polymer dispersed in an organic polymer or a metal thin film. The adjustment method is a phase separation method in which the concentrated phase of the polymer solution in which the inorganic powder is dispersed is separated around the magnetic particles formed by dispersing the inorganic powder in the polymer solution, and the magnetic property in which the pigment is dispersed in the polymer solution is separated. A liquid curing coating method in which a polymer is cured around a particle 21 with a curing agent such as a polymer curing test agent, a suspension of the magnetic particles 21 in which a monomer in which a pigment is dispersed and a polymerization catalyst are supplied to clean the surface of the magnetic particles 21. Dispersion polymerization method in which the pigment is dispersed in a polymer, magnetic particle surface is directly mixed and milled with the pigment in an air stream, or a suspension in which magnetic particles are dispersed in a polymer solution in which a pigment is dispersed is sprayed and dried. Microencapsulation techniques such as the drying method are preferred. The adjustment method is not limited to these methods. The above-mentioned inorganic powder preferably has a high refractive index and a large hiding power, and for example, titanium dioxide, zinc sulfide, lead titanate, zirconium oxide and the like are preferable, but the inorganic powder is not particularly limited thereto. The method for adjusting the concealing layer 26 using a metal thin film is mainly a method using electroless plating,
There is a method of decomposing the organometallic compound after chemically or physically adsorbing the organometallic compound on the surface of the magnetic particles.
It is preferable that the metal used has almost no magnetic properties and does not affect the color tone of the colored layer, such as aluminum, silver, zinc or tin.

As the pigment or dye 23, a pigment alone,
A mixture of several pigments, a mixture of pigments and polymers,
A single dye or a mixture of several dyes can be used. For example, pigments are the commonly known titanium dioxide,
Fine particles of inorganic pigments such as zinc sulfide, lead titanate, zirconium oxide, lead white, cadmium red, and cadmium yellow, organic pigments such as phthalocyanine pigments, and dyes such as azo dyes, quinoline dyes, and phthalocyanine dyes are used.
In this case, the pigment or the pigment may be subjected to surface treatment such as silane coupling treatment in order to enhance the affinity with the organic solvent and the like. When a pigment or a mixture of a pigment and a polymer is used, the above pigment or the pigment and the polymer are kneaded and then pulverized, or the pigment or the monomer in which the pigment is dispersed is subjected to emulsion polymerization, suspension polymerization, dispersion polymerization. A method of polymerizing using such a method is used. In this case, the polymer is preferably crosslinkable. The pigment or the size of the pigment is preferably 0.01 μm to 10 μm in consideration of hiding the magnetic particles.

The organic solvent 24 may be at room temperature (about 10-4).
Viscosity of 200 cps or more in the range of 0 ° C. and 100 c when heated (in the range of about 40 to 80 ° C.)
Any generally known one such as liquid paraffin, natural fats and oils, and synthetic fats and oils can be used as appropriate as long as it is not more than ps.

The core material 20 containing the above-mentioned colored magnetic particles 22, 22 ', the pigment or dye 23, the organic solvent 24, etc. as a main component is covered with a shell material 27 such as a polymer to be microencapsulated. Examples of the resin used as the shell substance 27 include commonly used resins such as acrylic resin, methacrylic resin, polystyrene, polyester resin, polyurethane resin, polyurea resin, polyamide resin, epoxy resin and natural resin. It is also possible to use these alone or in combination of two or more.

The method for producing the microcapsules having the above-mentioned shell material includes a phase separation method in which a concentrated phase of the polymer is separated around the core material dispersed in the polymer solution, and a method of separating the polymer around the core material in the polymer solution. In-liquid coating method in which a polymer is cured with a curing test agent, etc., an in-situ weight that coats the surface of the core substance with the polymer by supplying a monomer or a polymerization catalyst from either one of the emulsion in which the core substance is dispersed or the external phase. Suitable methods include, but are not limited to, microencapsulation techniques such as interfacial polymerization in which a monomer is supplied from both the internal phase and the external phase of the emulsion in which the core substance is dispersed.

Particularly, the colored magnetic particles as the core substance and the pigment are uniformly dispersed in a solvent to produce a monomer from the outer phase of the suspension, or the phase separation method is used to produce a uniform particle size. In addition, it is possible to manufacture microcapsules in which colored magnetic particles and pigments can easily move. The polymerizable monomer used here is preferably acrylic acid ester, methacrylic acid ester, styrene and its derivatives, isocyanate, various amines, compounds having an epoxy group, and the like.

In the magnetic recording material of the present invention, the microcapsules 14 having the above-mentioned structure are provided on the support 11 in the binder 1.
The magnetic display layer 12 is formed by coating with No. 5, and the protective support 13 is further laminated.

The support 11 is a composite of synthetic resins such as polyvinyl chloride, polyester, polycarbonate, polymethylmethacrylate, polystyrene and polyethylene terephthalate, natural resin, paper, synthetic paper, metal, ceramics, etc., alone or in combination. Can be used. In addition, its shape can be selected according to the application such as a card shape or a sheet shape, a film shape, and further considering the physical properties required according to the application, for example, strength, rigidity, hiding power, light opacity, etc. It can be appropriately selected.

As the binder 15 in which the microcapsules 14 are dispersed, a water-based binder, a solvent-based binder, an emulsion-based binder or the like is appropriately used.
Further, as the protective support 13, epoxy resin, tetrafluoroethylene, etc., or polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate,
It is possible to use synthetic resins such as polystyrene and polyethylene terephthalate, and natural resins. This protective support 13
Is required to hold the microcapsules 14 formed on the support 11 and be transparent so that the microcapsules 14 can be seen from the outside. be able to.

These forming methods include well-known printing methods such as an offset printing method, a gravure printing method and a silk screen printing method, a coating method such as a roll coating method and a knife edge method, and the microcapsules 14 described above. A transfer method using a transfer sheet in a transfer layer, an ink jet method in which ink containing the above-mentioned microcapsules 14 is sprayed onto a base material, and a solution containing the above-mentioned microcapsules 14 between a support 11 and a protective support 13. Can be prepared by a forming method such as a filling method, and can be appropriately selected from the above-mentioned methods depending on the use and quantity of the information recording medium to be prepared.

Next, an image forming method for the magnetic recording medium of the present invention will be described. FIG. 5 shows colored magnetic particles 22, 22 ′,
FIG. 3 is an explanatory view showing an enlarged cross section of a part of the magnetic recording medium of the present invention in which the microcapsules 14 containing the suspension in which the pigment or the dye 23 is dispersed in the organic solvent 24 are coated on the support 11. Initially, the colored magnetic particles 22 and the pigments or dyes 23 are fixed in the organic solvent 24 in the microcapsules 14 in a uniformly dispersed state.

FIG. 6 is an explanatory view showing a state when a normal image is erased, that is, when no image is recorded. The entire surface of the magnetic recording body is uniformly heated, the viscosity of the organic solvent 24 in the microcapsules is lowered, and the fluidity is increased. The colored magnetic particles 22 and 22 'are attracted below the microcapsules, and the surface of the magnetic recording medium has a uniform color tone due to the color of the pigment or dye 23.

FIG. 7 is an explanatory view showing a state in which recording is performed by applying magnetism from a magnetic generating means having a heating function from above the magnetic recording body. The organic solvent 24 in the microcapsules in the portion heated by the heat / magnetic head device 28, which is a magnetism generating means with a heating function, such as liquid paraffin, has increased fluidity, and the colored magnetic particles 22 in the microcapsules are magnetized by magnetism. 22 'is attracted above the microcapsules. On the other hand, in the portion that is not heated by the thermal / magnetic head device 28, the colored magnetic particles 22 and 22 'do not move inside the microcapsule, and the pigment or dye 23 exists above the microcapsule. Therefore, by heating and magnetically applying the recording portion in accordance with the recording information, an image of the color of the colored magnetic particles of the recorded portion can be obtained in the pigment color of the unrecorded portion. . The thermal / magnetic head device 28 is an ordinary magnetic head to which a heating unit such as a heater is added, and the heating unit may have a heating capacity enough to reduce the viscosity of the organic solvent 24.

Since this image formation is simple due to heat of low energy that lowers the magnetism and the viscosity of the organic solvent, recording is easy, and the resolution can be improved by controlling the particle size of the microcapsules. High image formation is possible. Further, when the colored magnetic particles are attracted to the back surface of the magnetic recording medium, the color of the magnetic particles is hidden by the pigment or dye 23. Further, the image formed by the thermal / magnetic head device 28 having a heating function has good recording stability and fluidity because the viscosity increases and the fluidity decreases and becomes fixed at the same time when the organic solvent returns to room temperature. Since it is not possible to form an image only by magnetism except in the state, touch the external magnetic field such as a magnet,
There is no fog on the image. The magnetic recording medium according to the present invention has the mobility of the colored magnetic particles contained therein at the time of recording, that is, both good recording reactivity and stability of the recorded image. The color can be any color. Also, by heating,
Since the colored magnetic particles can move only in the portion of the organic solvent that is in a fluidized state, an image with high resolution can be obtained.

Furthermore, since the microcapsules can be made into a coating liquid by mixing with a binder, they can be applied to various supports and can be processed into various shapes, and the manufacturing process is simple. Therefore, the range of applications can be expanded. In particular, when applied on paper, it can be used as information recording paper for household faxes and the like, and can be used as recycled paper because printing and erasing can be performed easily and reversibly by applying heat and magnetism.

The present invention will be described below with reference to specific examples.
The details will be described.

Example 1 [Formation of colored magnetic particles] Magnetic particles 15 having an average particle size of 1 μm
Parts by weight, 30 parts by weight of Watching Red, 60 parts by weight of polyurethane resin, and 15 parts by weight of 2,4-toluidine isocyanate as a cross-linking agent 600 parts by weight of methyl ethyl ketone in a solution Using an ultra-high speed homogenizer, a rotation speed of 500
It was dispersed at 0 rpm, and the resulting solution was added with n-hexane 15
0 parts by weight was dropped, and a polyurethane resin layer containing Watching Red was phase-separated around the magnetic particles to form a colored layer to obtain colored magnetic particles.

[Microencapsulation] 15 parts by weight of magnetic particles (colored magnetic particles) coated with the above colored layer, 30 parts by weight of titanium dioxide having an average particle size of 0.5 μm and subjected to silane coupling treatment, and liquid paraffin 80 Dispersed evenly in parts by weight. This dispersion was added to 300 parts by weight of a 10% gelatin aqueous solution using a homogenizer to rotate at a rotation speed of 2000 r.
The particles were dispersed for about 10 minutes so that the average particle size was 100 μm in pm. 300 parts by weight of a 10% aqueous solution of gum arabic at 40 ° C. was mixed with the obtained dispersion, and water at 40 ° C. was added.
00 parts by weight was added, the temperature was kept at 40 ° C., and a 10% aqueous acetic acid solution was added dropwise to adjust the pH to 4. Then, the liquid temperature was cooled to 5 ° C., 10 parts by weight of 30% formalin aqueous solution was added, and
% Aqueous sodium hydroxide solution was added dropwise to adjust the pH to 9. Further, the liquid temperature was raised to 50 ° C. to obtain gelatin-arabic gum microcapsules.

A magnetic display layer using the above-mentioned microcapsules is provided on plain paper, and a protective layer made of acrylic resin is further provided. Then, the entire surface of the magnetic recording medium is heated, and a magnetic force is applied from below to obtain a white color. A magnetic recording paper was obtained. By recording with a magnetic head equipped with a heating function, a clear and clear image of red light and dark was obtained on a white background.

Example 2 Formation of Concealing Layer 15 parts by weight of magnetic particles having an average particle size of 1 μm, 30 parts by weight of titanium dioxide and 60 parts by weight of polystyrene were rotated in a solution of 600 parts by weight of methyl ethyl ketone using an ultrahigh speed homogenizer. Disperse at several 5000 rpm,
150 parts by weight of ethanol was added dropwise to the obtained solution, and polystyrene containing titanium dioxide was phase-separated around the magnetic particles to form a hiding layer.

[Formation of Colored Magnetic Particles] 15 parts by weight of magnetic particles coated with the above-mentioned concealing layer, 30 parts by weight of cadmium yellow,
60 parts by weight of polyurethane resin and 15 parts by weight of 2,4-toluidine isocyanate as a cross-linking agent were dispersed in 600 parts by weight of methyl ethyl ketone in a solution using an ultrahigh speed homogenizer at a rotation speed of 5000 rpm, and n- was added to the resulting solution.
150 parts by weight of hexane was dropped, and a polyurethane resin layer containing cadmium yellow was phase-separated around the magnetic particles, and a colored layer was formed on the concealing layer to obtain colored magnetic particles.

[Microencapsulation] 15 parts by weight of magnetic particles (colored magnetic particles) coated with a colored layer and 35 parts by weight of phthalocyanine blue having an average particle diameter of 0.5 μm, which has been subjected to silane coupling treatment, are added to liquid paraffin. Evenly dispersed in 80 parts by weight. This dispersion was dispersed in 200 parts by weight of a 5% aqueous polyvinyl alcohol solution using a homogenizer at a rotation speed of 2000 rpm for about 10 minutes so that the average particle diameter was 100 μm. 100 parts by weight of a melamine-formalin prepolymer aqueous solution was added to the obtained dispersion, and a 20% acetic acid aqueous solution was added dropwise to adjust the pH to 6.
Then, the liquid temperature was raised to 65 ° C. and a polymerization reaction was carried out for 30 minutes to obtain melamine-formalin resin microcapsules.

A magnetic display layer using the above-mentioned microcapsules is provided on plain paper, and a protective layer made of acrylic resin is further provided. Then, the entire surface of the magnetic recording medium is heated, and magnetism is exerted from below, whereby blue color is obtained. A magnetic recording paper was obtained. Recording with a magnetic head equipped with a heating function gave a clear image with a bright and dark yellow tone on a blue background.

Example 3 [Formation of Hiding Layer] A hiding layer made of a tin thin film was formed on the surface of magnetic particles having an average particle diameter of 1 μm by electroless plating.

[Formation of colored magnetic particles] 15 parts by weight of magnetic particles coated with the above-mentioned concealing layer, 30 parts by weight of titanium dioxide,
60 parts by weight of polystyrene was added to 600 parts by weight of methyl ethyl ketone in a solution using an ultra-high speed homogenizer to rotate at 50 rpm.
Disperse at 00 rpm and add ethanol 15 to the resulting solution.
0 part by weight was dropped, and polystyrene containing titanium dioxide was phase-separated around the magnetic particles to form a colored layer on the concealing layer to obtain colored magnetic particles.

[Microencapsulation] 15 parts by weight of magnetic particles (colored magnetic particles) coated with a colored layer and 30 parts by weight of chromium hydroxide having a silane coupling treatment and an average particle size of 0.5 μm are flowed. It was uniformly dispersed in 80 parts by weight of paraffin. This dispersion was dispersed in 200 parts by weight of a 5% aqueous solution of polyvinyl alcohol using a homogenizer at a rotation speed of 2000 rpm for about 5 minutes so that the average particle diameter was 100 μm. A 10% aqueous sodium carbonate solution was added dropwise to adjust the pH to 8-9. The liquid temperature was adjusted to 25 ° C., and a 20% urea-formalin prepolymer aqueous solution 200 was added.
Part by weight was added, and acetic acid was further added dropwise to adjust the pH to 4. Then, the reaction was carried out at 30 ° C. for 3 hours and at 50 ° C. for 2 hours to obtain urea-formalin resin microcapsules.

A magnetic display layer using the above-mentioned microcapsules is provided on plain paper, and a protective layer made of acrylic resin is further provided. Then, the entire surface of the magnetic recording medium is heated and a magnetic force is applied from below to obtain a green color. A magnetic recording paper was obtained. By recording with a magnetic head with a heating function, a clear image of bright and dark green and white was obtained.

[0055]

INDUSTRIAL APPLICABILITY The magnetic recording medium of the present invention includes an organic solvent in which magnetic particles coated with a colored layer and a pigment or dye are dispersed, and the viscosity at room temperature is 200 cps or more and the viscosity when heated is 100 cps or less. In the non-recorded state, the colored magnetic particles are attracted to the back side, which is one side of the magnetic recording body, and the surface of the magnetic recording body, which is the other side, is not covered with pigment. It shows a uniform color tone by color, and the recording state is scanned from the surface side of the magnetic recording body with a thermal / magnetic head device having a heating means, and colored magnetic particles are applied to the surface side of the magnetic recording body by heating and application of magnetism. An image of a color is formed by the magnetic particles (colored magnetic particles) that move and are covered with the colored layer. For erasing, the colored magnetic particles are attracted below the microcapsules by heating the entire surface and applying magnetism to the entire surface from the back surface of the magnetic recording material, or by scanning the back surface of the magnetic recording material with heating and application of magnetism. The surface of the recording medium becomes the color of the pigment or dye again, and the image can be erased.

That is, in the magnetic recording medium of the present invention, since the portion to which magnetism is applied is different from the portion to which no magnetism is applied, the contrast is clear, the resolution is high, the image is sharp, and the image stability is excellent. Since the color of the particles can be arbitrarily set, it has an excellent effect such that color display is possible.

Further, according to the present invention, since image formation can be easily performed by heating at a low temperature and applying magnetism, the energy consumption is low, and by using the microcapsules for the recording layer, the particle size of the microcapsules can be reduced. The resolution can be increased by controlling.

Moreover, since the magnetic particles, pigments or dyes are dispersed in the organic solvent having a viscosity of 200 cps or more at room temperature and a viscosity of 100 cps or less at the time of heating in the microcapsules, the viscosity is high except during recording. Since the fluidity is low, stable recording can be obtained without causing magnetic particles in the microcapsules to move even when magnetism such as a magnet is applied from the outside after information recording. In addition, since the area affected by magnetism does not expand by encapsulating microcapsules, the movement of magnetic particles can be almost limited only to the part where heating and magnetism are applied, so an organic solvent that has high resolution and low fluidity at room temperature By using, the image stability is also excellent.

Further, since the coating liquid containing the microcapsules can be applied, there is an effect that the manufacturing process of the magnetic recording material can be simplified.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a magnetic recording body of the present invention.

FIG. 2 is a cross-sectional view showing an example of microencapsulated magnetic particles used for a recording layer in the present invention.

FIG. 3 is a cross-sectional view showing an example of magnetic particles coated with a colored layer used as a core substance in the present invention.

FIG. 4 is a cross-sectional view showing an example of magnetic particles coated with a hiding layer and a coloring layer used as a core substance in the present invention.

FIG. 5 is a cross-sectional view showing a state during manufacturing of the magnetic recording body of the present invention.

FIG. 6 is an explanatory diagram showing a non-recorded state by the erasing operation of the magnetic recording body of the present invention.

FIG. 7 is an explanatory diagram showing a recording state of the magnetic recording medium of the present invention.

[Explanation of symbols]

1 Magnetic Recording Material 11 Support 12 Magnetic Display Layer 13 Protective Support 14 Microcapsule 15 Binder 20 Core Material 21 Magnetic Particle 22 Colored Magnetic Particle 23 Pigment or Dye 24 Viscosity at Normal Temperature is 200 cps or More and Viscosity at Heating is 100 cps or Less Organic solvent 25 Coloring layer 26 Hiding layer 27 Shell substance 28 Thermal / magnetic head device

Claims (4)

[Claims] 1. A magnetic particle and a pigment or dye coated with a colored layer between a support made of a non-magnetic material, at least one of which has transparency, and a viscosity of 200 cps or more at room temperature formed by dispersing these. A magnetic recording material comprising: a magnetic display layer formed by dispersing and arranging microcapsules containing an organic solvent having a viscosity of 100 cps or less when heated in a binder. 2. The colored layer for coating the magnetic particles comprises a coating film containing a pigment as a main component.
The magnetic recording material described. 3. The magnetic recording medium according to claim 1, wherein a concealing layer is provided between the surface of the magnetic particles and the colored layer. 4. The magnetic recording medium according to claim 3, wherein the concealing layer is made of an inorganic powder or a metal thin film dispersed in an organic polymer.