JP2000185489A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a lightness even when a color of a colored layer of a lower layer of a magnetic recording layer is except black by incorporating the recording layer containing a microcapsule for enclosing a magnetic powder having a specific color dispersively disposed in a binder on an upper layer of the colored layer on a support made of a nonmagnetic material. SOLUTION: A colored layer 17 is formed on a support 11, a magnetic recording layer 12 coated with a microcapsule 15 for enclosing a magnetic powder having a specific color together with a binder 16 on the layer 17, and a protective layer 14 is further laminated. When the powder is oriented in a parallel direction by a magnetism applied in a parallel direction to the layer 12, the powder reflects an incident light so that the surface becomes the specific color. When the powder is oriented in a vertical direction by magnets 30 disposed above and below in the vertical direction, the powder does not reflect an incident light. Thus, a contrast of a difference of reflections of the powder oriented in a horizontal direction and the powder oriented in the vertical direction is obtained, thereby recording visible display information.

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 for displaying images by orienting magnetic powder by applying magnetism.
In particular, the present invention relates to a magnetic recording medium having good whiteness in an unprinted portion, excellent image stability, and suitable for color display by selectively using magnetic powder fine particles having a specific color.

[0002]

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

[0003] However, in such a magnetic recording medium, when the suspension is sealed between two substrates and a character and a pattern are drawn from one of the substrates with a magnetic pen to actuate magnetism, the magnetic particles of the suspension are attracted. As a result, the same characters and patterns can be obtained, but the specific gravity of the magnetic particles is much larger than that of the dispersing medium, and the attracted magnetic particles have a drawback that the characters and patterns cannot be retained for a long time because they settle with time. .

[0004] Further, since all the magnetic particles that have been magnetized by the magnetic pen are attracted to the magnetic pen, the magnetic particles that are present away from the magnetic pen are also attracted, so that only unclear characters or patterns can be obtained. It also had disadvantages. In order to prevent sedimentation of the 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 is approximated to that of the dispersion medium, the magnetic force acting on the magnetic particles can be reduced. Since the force becomes extremely small, it becomes difficult to be sucked by the magnetic pen, and a defect occurs in that a high-density, clear character or pattern cannot be obtained.

Further, if the apparent specific gravity of the magnetic particles is approximated to that of the dispersion medium, it is difficult for the magnetic particles to be attracted to the opposite side of the substrate even when erasing a character or a pattern. Repeating it turned black overall, which was not practical.

As a form for solving these drawbacks, for example, Japanese Patent Publication No. 57-27463 and Japanese Patent Application Laid-Open No. 62-53
As described in JP-A-359, as a dispersion medium,
By using a liquid with a yield value equal to or higher than a certain value or a thickener, clear and high-contrast characters and images without blur can be displayed, the display can be maintained stably for a long time, and complete erasure can be performed. 2. Description of the Related Art A magnetic recording medium that can be neatly cleaned is known.

However, this magnetic recording medium is formed so that honeycomb-shaped cells each having a side and a depth of about 2 mm are provided on the entire surface of the transparent plastic sheet, and the magnetic particles and the white pigment are contained in the cells. Was injected into a dispersion medium, and the suspension was sealed with a transparent sheet, and had the following disadvantages. That is, since the image is formed by moving the magnetic particles from the back surface to the front surface in the honeycomb-shaped cells, it is impossible to make the resolution of the image smaller than that of the honeycomb-shaped cells. In addition, it is difficult to form the honeycomb-shaped cells, to enlarge or extremely reduce the size of the honeycomb-shaped cells, and to inject a suspension into the honeycomb-shaped cells.

As another mode, for example, Japanese Patent Laid-Open No. 2-14
No. 6082 and JP-A-4-233581, unlike a magnetic recording medium in which magnetic particles and a pigment are sealed in a honeycomb cell as described above, magnetic particles are encapsulated in microcapsules. A magnetic recording medium obtained by applying this on a support is known. According to this method, the resolution can be increased by controlling the particle diameter of the microcapsules, and the manufacturing process is easy. In addition, various films and the like can be selected for the substrate on which the microcapsules are applied, and the shape and size can be freely selected.

However, the image formation shown here is performed by the following method. First, the permanent magnet attracts the light-absorbing magnetic particles in the microcapsule to the back side of the magnetic recording medium, and the light-reflecting non-magnetic particles remain on the surface of the magnetic recording medium. The color of the non-magnetic particles becomes the erased state. Next, by applying and recording magnetism from the surface of the magnetic recording medium with a permanent magnet, light-absorbing magnetic particles are attracted to the surface by the magnetism, and desired characters and images are formed. Therefore, in such image formation, it takes time to exchange the non-magnetic particles with the magnetic particles, resulting in a magnetic recording medium having poor sensitivity.

Further, as another form using microcapsules, for example, Japanese Patent Application Laid-Open No. 1-145637,
JP-A-63-153197, JP-B-4-7518
JP, JP-A-6-79986, JP-A-6-92
068 or EyneS. Truble
P. S. & E. As described in U.S. Pat. No. 7,213 (1963), there is known a magnetic recording medium in which flake-shaped light-reflective magnetic particles are encapsulated in microcapsules.

In the image forming method of this embodiment, first, at the time of manufacturing a magnetic recording medium, the incident light is totally reflected by making the magnetic particles in the coated capsules parallel to the plane of the magnetic recording medium in advance to make the capsule appear bright. Next, by performing magnetic recording, the magnetic particles rotate and scatter the incident light,
As a result, contrast is generated and a black image is formed.

However, in the magnetic recording medium thus obtained, when there is no colored layer under the recording layer, the contrast between the printed portion and the unprinted portion is not so large and is not practically sufficient. Even when a colored layer other than black was provided, the color became dark, and only a color with low lightness could be expressed. Furthermore, since the magnetic recording medium can be easily printed and erased by the magnetic force, the image can be easily read or erased by touching the magnet so that the unprinted portion is fogged or the image is erased. It has the disadvantage of poor stability.

[0013]

On the other hand, the inventors have developed a microcapsule containing at least flake-like magnetic powder and a dispersion medium in which the flake-like magnetic powder is dispersed and has a solid phase state at room temperature. A magnetic recording medium dispersed therein has been proposed (JP-A-8-175059). According to this method, since the dispersion medium in the microcapsules is solid at room temperature, fogging occurs in the unprinted portion or the image is erased just by touching the magnet as described above. And the image stability against magnetic force is good. Also,
Even if unexpected heat is applied to a heater in the winter or a car in the summer, the magnetic powder does not move by the heat alone, so that the image stability against the heat is good. However, even in this case, since the magnetic powder has a black or metallic luster color, if the color of the colored layer below the recording layer is other than black, the color becomes dark and only a color with low brightness can be sufficiently expressed. I could not do it.

[0014]

Means for Solving the Problems The present invention has been made to achieve the above-mentioned object, and the invention according to claim 1 is to provide at least a colored layer on a support made of a non-magnetic material. And, further, in a magnetic recording medium having a magnetic recording layer in which a microcapsule encapsulating magnetic powder is dispersed in a binder as an upper layer, wherein the magnetic powder is a magnetic powder having a specific color. Magnetic recording medium.

A second aspect of the present invention is the magnetic recording medium according to the first aspect, wherein the magnetic powder having the specific color is a white magnetic powder.

According to a third aspect of the present invention, there is provided the magnetic recording medium according to any one of the first and second aspects, wherein the magnetic powder having a specific color or the white magnetic powder has an average particle size of 5 μm to 4 μm.
It is characterized by being between 0 μm.

According to a fourth aspect of the present invention, in the magnetic recording medium according to any one of the first to third aspects, the dispersion medium of the magnetic powder in the microcapsules is a substance which shows a solid phase state at normal temperature. Features.

<Operation> Since the magnetic recording medium of the present invention uses white magnetic powder as the magnetic powder in the capsule, when the magnetic powder is oriented in the capsule in the horizontal direction and connected, The incident light is scattered, and the whiteness becomes higher than before. Further, when the magnetic powders are vertically aligned and connected, the color of the lower colored layer is not darkened, and a color with high lightness can be expressed. Further, when a magnetic powder having a specific color is used instead of the white magnetic powder, for example, it is possible to display red on a blue background, yellow on a green background, and the like. In addition, by making the dispersion medium of the magnetic powder in the microcapsules a material that shows a solid phase state at room temperature, it becomes a heat / magnetic recording medium that can be recorded with heat and magnetism. No fogging or deletion of the image is caused, and the stability of the image is improved.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing one embodiment of a magnetic recording medium of the present invention, FIG. 2 is a cross-sectional view showing one embodiment of a microcapsule used for a magnetic recording layer in the present invention, and FIG. FIG. 4 is an explanatory view showing a state when the magnetic recording medium is manufactured. FIG. 4 shows a state in which white magnetic powder (or magnetic powder having a specific color) is oriented in parallel to the magnetic recording layer of the magnetic recording medium of the present invention. FIG. 5 is an explanatory view showing a state in which white magnetic powder (or magnetic powder having a specific color) is oriented in a direction perpendicular to the magnetic recording layer of the magnetic recording medium of the present invention. It is explanatory drawing which shows the state formed.

FIG. 1 shows the structure of a magnetic recording medium 1 of the present invention. A microcapsule 15 containing a support 11, a colored layer 17, a white magnetic powder (or a magnetic powder having a specific color) and the like is used as a binder 16. A magnetic recording layer 12 to which a dispersed coating material is applied and a protective layer 14 are sequentially laminated.

FIG. 2 shows a white magnetic powder (or a magnetic powder having a specific color) used for the magnetic recording layer 12 in the present invention.
FIG. 3 is a cross-sectional view showing one embodiment of a microcapsule 15 including

The white magnetic powder 22 may be any material as long as it contains a magnetic material partially and looks fine as white. For example, stainless steel such as iron, nickel, iron / nickel, iron / nickel / chrome, etc. Particles such as cobalt, cobalt-aluminum, samarium-cobalt alloy, etc., which have been made into powdery or flake-like fine particles by an atomizer or a hammer mill, can be used after whitening. The whitening treatment may be performed by coating the magnetic powder fine particles with a metal, a metal oxide, a white inorganic compound, a white crystalline organic compound, or the like by a wet or dry method known in the art. For example, a plating method, a spray drying method, a vapor deposition method and the like can be mentioned. Further, these white magnetic powders may be subjected to a higher ester treatment, a silane coupling treatment, a titanate coupling treatment or the like in order to increase the affinity with an organic solvent or the like. The size of the white magnetic powder 22 in the present invention is determined by the thickness of the concealing layer capable of concealing the magnetic powder in white, the ease of movement of the magnetic powder in the microcapsule by applying a magnetic field, and the image contrast of the magnetic recording layer 12. In consideration of the above, the particle size is preferably 5 μm to 40 μm. The magnetic powder having a specific color is the same as the white magnetic powder except that the color is not limited to white. The specific color can be any color, such as red, green, and yellow.

As the dispersion medium 23, a hydrophobic solvent or the like is preferable, but a high-boiling solvent having low volatility at room temperature is particularly preferable. When a thermal / magnetic recording medium is used, it is solid at normal temperature (in the range of about 10 to 35 ° C.) (shows a solid state) and heated to a temperature equal to or higher than normal temperature (in the range of about 40 to 80 ° C.). Use a material that is in a fluid state when it is used.
For example, generally known organic compounds satisfying the above conditions, such as natural or synthetic waxes such as paraffin wax and carnauba wax, natural or synthetic resins, and carboxylic acid esters, alone or in combination with a solvent or the like may be used as appropriate. Can be. In addition, you may color in the range which does not obstruct light transmittance.

The above-mentioned core material 21 mainly composed of the white magnetic powder (or magnetic powder having a specific color) 22 and the dispersion medium 23 is covered with a shell material 24 such as a polymer to be microencapsulated. Examples of the resin used as the shell material 24 include commonly used resins such as acrylic resin, methacrylic resin, polystyrene, polyester resin, polyurethane resin, polyurea resin, polyamide resin, epoxy resin, and natural resin. These can be used alone or in combination of two or more.

Microcapsule 1 having the above-mentioned shell material
Examples of the production method 5 include a phase separation method in which a polymer rich phase is separated around a core substance dispersed in a polymer solution, and a liquid in which a polymer is cured around a core substance in a polymer solution with a polymer curing test agent or the like. Medium-curing coating method, in-situ polymerization method in which a monomer or a polymerization catalyst is supplied from one of the emulsions in which the core substance is dispersed, or the external phase is supplied, and the surface of the core substance is covered with a polymer, and the emulsion in which the core substance is dispersed. Microencapsulation techniques such as interfacial polymerization, in which monomers are supplied from both the internal and external phases, are preferred, but not limited to these methods.

In particular, an in situ polymerization method in which a white magnetic powder (or a magnetic powder having a specific color) 22 as a core substance 21 is uniformly dispersed in a dispersion medium 24 and monomers are supplied from an external phase of a suspension, or a phase separation method The microcapsules 15 having a uniform particle size and easy movement of the white magnetic powder (or magnetic powder having a specific color) 22 can be manufactured. As the polymerizable monomer used here, acrylates, methacrylates, styrene and its derivatives, isocyanates, various amines, compounds having an epoxy group, and the like are preferable.

The particle size of the microcapsules 15 is 10
It is preferably about μm to 300 μm. If the particle size is 10 μm or less, the size of the magnetic powder contained in the capsule becomes small, and the content is relatively small, so that the concealing curing is weakened and the contrast is lowered. On the other hand, if the particle size is 300 μm or more, the thickness is too large, and it takes time to move the magnetic powder.

In the magnetic recording medium 1 of the present invention, a colored layer is formed on a support 11, a microcapsule 15 having the above-described structure is applied together with a binder 16 to form a magnetic recording layer 12, and a protective layer 14 is formed. Are laminated.

The support 11 is a composite of a synthetic resin such as polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate, polystyrene, polyethylene terephthalate, natural resin, paper, synthetic paper, metal, ceramics, etc., alone or in combination. Can be used. In addition, the shape can be selected according to the application such as a card shape or a sheet shape, a film shape, and further, in consideration of physical properties required according to the application, for example, strength, rigidity, concealing property, light opacity, etc., from the above materials, It can be selected as appropriate.

As a coloring component of the coloring layer 17, a pigment alone, a mixture of several kinds of pigments, a mixture of a pigment and a polymer, a dye alone, a mixture of several kinds of dyes and the like can be used. For example, pigments commonly known as titanium dioxide, zinc sulfide, lead titanate, zirconium oxide, lead white,
Fine particles of inorganic pigments such as cadmium red and cadmium yellow, organic pigments such as phthalocyanine pigments, and various known pigments and dyes such as azo dyes, quinoline dyes, and phthalocyanine dyes are used as the dyes. When a pigment or a mixture of a pigment and a polymer is used, the above-described pigment or the pigment and the polymer are kneaded and then pulverized, or the pigment or the pigment-dispersed monomer is subjected to emulsion polymerization, suspension polymerization, or dispersion polymerization. A method such as polymerization is used. In this case, the polymer is preferably crosslinkable. As a binder for dispersing and dissolving these pigments or dyes, an aqueous binder, a solvent binder, an emulsion binder and the like are used. It is also possible to select a plurality of colors to be printed and express them simultaneously by patterning these colors.

The microcapsules 15 in the magnetic recording layer 12
As the binder 16 for dispersing, an aqueous binder,
A solvent-based binder, an emulsion-based binder, or the like is used as appropriate, but it is particularly preferable to use a curable resin because the friction resistance of the recording medium and the resistance to repeated printing and erasure are improved. As the curable resin, for example, a UV curable resin, EB
In addition to a photo-curable resin such as a curable resin, a thermosetting resin having an isocyanate group, a melamine group, an epoxy group, and the like, a moisture-curable resin and the like can be given.

The protective layer 14 protects the microcapsules 15 formed on the support 11 and also allows the white magnetic powder (or magnetic powder having a specific color) 22 in the microcapsules 15 to be seen from the outside. It is necessary to have transparency. As such a protective layer 14, various known materials such as various polymer resins and films can be used as long as they are transparent. For example, synthetic resins such as epoxy resin, tetrafluoroethylene, polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate, and polystyrene; natural resins; and films such as nylon, polyethylene terephthalate, and polyimide can be used. Particularly, a polyethylene terephthalate film, a polyethylene naphthalate film, or the like is preferable.

The magnetic recording layer 12, the protective layer 14, and the colored layer 17 may be formed by a known printing method such as an offset printing method, a gravure printing method, a silk screen printing method, a roll coating method, or a knife edge method. A transfer method using a transfer sheet having a transfer layer mixed with the microcapsules 15 described above, an ink jet method in which ink mixed with the microcapsules 15 is sprayed onto a base material, a support 11 and a protective layer 14. In the meantime, it can be formed by a forming method such as a method of filling a solution mixed with the microcapsules 15 described above, and the method can be appropriately selected from the above methods according to the use and quantity of the information recording medium to be formed.

Next, a method of forming a display image on the magnetic recording medium of the present invention will be described. FIG. 3 shows a magnetic recording medium of the present invention in which a microcapsule 15 containing a suspension in which a white magnetic powder (or a magnetic powder having a specific color) 22 is dispersed in an organic solvent serving as a dispersion medium 23 is coated on a support 11. FIG. 2 is an explanatory diagram showing a cross-sectional view in which a part of 1 is enlarged. Initially, white magnetic powder (or magnetic powder having a specific color) 22 is uniformly dispersed in the microcapsule 15.

FIG. 4 is an explanatory view showing a state where white magnetic powder (or magnetic powder having a specific color) 22 in the microcapsule 15 is connected and oriented in a direction parallel to the magnetic recording layer 12. is there. Due to the magnetism uniformly applied to the magnetic recording layer 12 in the direction parallel to the support, the white magnetic powder (or magnetic powder having a specific color) 22 in the microcapsule 15 is oriented so as to be continuous, The surface of the recording medium has a uniform white tone in which most of the incident light is reflected by white magnetic powder (or magnetic powder having a specific color) 22 (in the case of a magnetic powder having a specific color, the specific magnetic powder has a specific color). Color.)
Here, in order to efficiently orient the white magnetic powder (or a magnetic powder having a specific color) so as to be continuous in a plane, for example, a method of arranging a magnet on all side surfaces of the magnetic recording medium, a method of mounting a magnet on the side surface of the magnetic recording medium Method of rotating the magnetic recording medium after placing the
There is a method of rotating a magnet around the side surface of the magnetic recording medium.

FIG. 5 is an explanatory view showing a state in which white magnetic powder (or magnetic powder having a specific color) 22 is connected and oriented perpendicularly to the magnetic recording layer 12 of the magnetic recording medium 1. is there. For example, by arranging magnets vertically in the vertical direction, the white magnetic powder (or magnetic powder having a specific color) 22 in the microcapsules 15 of the magnetic recording layer 12 is oriented so as to be continuous with the magnetic recording layer 12 in the vertical direction. You. Thus, the incident light is hardly reflected in the incident direction by the white magnetic powder (or the magnetic powder having a specific color) 22, and thus the white magnetic powder (or the specific magnetic powder) oriented in the direction parallel to the magnetic recording layer 12. The difference in reflection between the magnetic powder 22 having a color and the white magnetic powder 22 (or a magnetic powder having a specific color) oriented in the vertical direction, that is, a contrast is obtained, and thus, it is possible to record visible display information. it can.
The state of the magnetic powder in these capsules can be created by a magnetic head, a magnetic pen, or the like.

Since this image formation utilizes magnetism, recording is easy, and an image with high resolution can be formed by controlling the particle size of the microcapsules. In particular, when a white magnetic powder is used, whiteness is excellent when horizontally oriented and the contrast is good. Also,
A bright color can be expressed without darkening the color of the underlying colored layer during vertical alignment.

Information is recorded by setting the orientation state of the white magnetic powder (or magnetic powder of a specific color) to the magnetic recording layer based on one of the parallel direction and the perpendicular direction and partially setting the other. In contrast to the above, based on the fact that the orientation state of the white magnetic powder (or the magnetic powder having a specific color) is in the vertical direction, the orientation state is partially changed in the parallel direction and the visual display is performed. Information may be recorded.

The microcapsules used here can be formed into a coating film by mixing with a binder and applied, so that they can be applied to various supports and processed into various shapes. Since it is possible and the manufacturing process is simple, the range of application can be expanded. In particular, when applied on paper, it can be used as information recording paper for household faxes and the like, and printing and erasing can be easily and reversibly performed by applying heat and magnetism, so that it can be used as recycled paper.

[0040]

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

<Example 1> [Preparation of coating liquid for reversible magnetic recording layer] Titanium dioxide particles having an average particle size of 1.5 µm around magnetic powder particles (iron-nickel alloy) having an average particle size of 15 µm using a hybridizer. To produce a white magnetic powder.

Next, this white magnetic powder was subjected to a silane coupling treatment. 30 parts of these white fine particles and 70 parts of dodecylbenzene are mixed well, and this is mixed with 10% gelatin aqueous solution 4
2,000 parts by weight, using a homogenizer, rotating speed 2
The dispersion was performed for about 5 minutes so that the average particle size became 75 μm at 000 rpm. To the obtained dispersion, 400 parts by weight of a 10% aqueous solution of gum arabic was mixed, and 1000 parts by weight of water was further added.
Was adjusted to 4. Thereafter, the liquid temperature was cooled to 5 ° C.
10 parts by weight of a formalin aqueous solution was added, and a 10% aqueous solution of sodium hydroxide was added dropwise to adjust the pH to 9, thereby preparing microcapsules having a gelatin-arabic gum wall.

After filtering the microcapsules, the microcapsules were dispersed in an aqueous emulsion-type UV-curable resin liquid to obtain a reversible heat-sensitive /
A magnetic recording layer coating liquid was obtained.

[Preparation of Reversible Recording Medium] Thickness 100 μm
A black layer made of carbon black and urethane resin was provided as a colored layer on the biaxially stretched polyethylene terephthalate (PET) sheet. The reversible thermosensitive / magnetic recording layer coating solution was applied thereto, dried, and irradiated with UV to form a magnetic recording layer having a thickness of 90 μm. Furthermore, after applying a UV-curable resin (containing a lubricant filler), the resin was cured by UV irradiation to form a protective layer having a thickness of 20 μm.

[Recording of Image] The entire thermal / magnetic recording medium was erased by applying a magnetic field horizontally to the layer.
Next, printing was performed by applying a magnetic field partially vertically to the layer, and the magnetic powder in the microcapsules in the pattern portion was vertically oriented to obtain a recording state. The density of the recording part was measured with an optical reflection density system.

<Example 2> [Preparation of coating liquid for reversible thermosensitive / magnetic recording layer]
Silver was sputtered on 60 parts by weight of the nickel alloy to obtain white magnetic powder, which was subjected to oleic acid treatment. Next, this was uniformly dispersed in 100 parts by weight of a mixed solvent of paraffin wax and dibutyl phthalate, which was heated to 50 ° C. and melted,
This dispersion was placed in 300 parts by weight of 5% polyvinyl alcohol heated to 50 ° C. using a homogenizer at a rotational speed of 2%.
The dispersion was carried out for about 5 minutes so that the average particle size became 100 μm at 500 rpm. To the resulting dispersion was added 100 parts by weight of a melamine-formalin prepolymer aqueous solution, and a 20% acetic acid aqueous solution was added dropwise to adjust the pH to 6. Thereafter, the liquid temperature was reduced to 65.
C. and the polymerization reaction was carried out for 30 minutes to produce microcapsules having a melamine-formalin wall. This capsule was mixed with an acrylic emulsion resin and an epoxy curing agent to obtain a reversible heat-sensitive / magnetic recording layer coating liquid.

[Preparation of reversible recording medium]
As a cyan colored layer, a mixture of a phthalocyanine pigment and an aqueous acrylic emulsion was applied and provided. next,
After applying the reversible thermosensitive / magnetic recording layer coating solution and drying,
Thermal curing was performed at 0 ° C. for 10 minutes to obtain a 50 μm heat-sensitive / magnetic recording layer. Next, a urethane-based laminating adhesive was applied on 50 μm of the slippery PET and dried, and then the applied 50 μm PET and the coated paper were bonded and laminated so that each coated layer was on the inside. Thus, a thermal / magnetic recording medium was obtained.

[Recording of Image] The above recording medium was heated to 80 ° C., and a magnetic field was applied horizontally to the layer so that the white magnetic powder was horizontally aligned in a plane and aligned, and the entire surface was erased. And Next, with a magnetic field applied perpendicular to the layers,
Printing was performed by a thermal head in accordance with the pattern of the visible display information to be recorded, and the magnetic powder in the microcapsules in the pattern portion was vertically connected and oriented to obtain a recording state.

Comparative Examples 1 and 2 Reversible thermosensitive recording media were prepared and evaluated in the same manner as in Examples 1 and 2, except that the magnetic powder particles were not subjected to whitening treatment.

Table 1 shows a comparison of printability between Examples 1 and 2 and Comparative Examples 1 and 2.

[0051]

[Table 1]

In Examples 1 and 2, the whiteness in the decolored portion, that is, in the horizontal alignment state, was higher than that in Comparative Examples 1 and 2, and the contrast was large. Further, the color tone of the cyan printing portion of Example 2 was brighter and easier to see than that of Comparative Example 2.

[0053]

The magnetic recording medium of the present invention uses white magnetic powder as the magnetic powder in the capsule. Therefore, when the magnetic powder is aligned in the capsule in the horizontal direction and connected to the capsule, the magnetic recording medium is incident. Light is scattered and the whiteness becomes higher than before. Further, when the magnetic powders are vertically aligned and connected, the color of the lower colored layer is not darkened, and a color with high lightness can be expressed. Also, by making the dispersion medium of the magnetic powder in the microcapsules a material that shows a solid phase state at normal temperature, it becomes a heat / magnetic recording body that can be recorded by heat and magnetism, and can be printed with a thermal head and a magnetic field. Also,
The fogging of the unprinted portion or the erasure of the image is not caused just by touching the magnet, and the stability of the image is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a magnetic recording medium of the present invention.

FIG. 2 is a cross-sectional view showing one embodiment of a microcapsule used for a magnetic recording layer of the magnetic recording medium of the present invention.

FIG. 3 is an explanatory view showing a state when a magnetic recording medium of the present invention is manufactured.

FIG. 4 is an explanatory view showing a state in which white magnetic powder (or a magnetic powder having a specific color) is oriented parallel to the magnetic recording layer of the magnetic recording medium of the present invention.

FIG. 5 is an explanatory view showing a state in which white magnetic powder (or magnetic powder having a specific color) is oriented in a direction perpendicular to the magnetic recording layer of the magnetic recording medium of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic recording body 11 ... Support 12 ... Magnetic recording layer 14 ... Protective layer 15 ... Microcapsule 16 ... Binder 17 ... Colored layer 21 ... Core substance 22 ... White magnetic powder (or magnetic powder having a specific color) 23 ... Dispersion medium 24 ... Shell material 30 ... Thermal / magnetic head

Claims (4)

[Claims] 1. A magnetic recording apparatus comprising: a support made of a nonmagnetic material; and a magnetic recording layer comprising at least a colored layer and a microcapsule containing magnetic powder dispersed in a binder. A magnetic recording medium, wherein the magnetic powder is magnetic powder fine particles having a specific color. 2. The magnetic recording medium according to claim 1, wherein the magnetic powder particles having the specific color are white magnetic powder particles. 3. The magnetic recording medium according to claim 1, wherein the average particle size of the magnetic powder particles having the specific color is between 5 μm and 40 μm. 4. The magnetic recording medium according to claim 1, wherein the dispersion medium of the magnetic powder in the microcapsules is a substance showing a solid phase state at normal temperature.