JP2000225788A - Manufacture of thermomagnetic recording medium and thermomagnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce surface roughness of a surface of a recording medium by first providing an at least thermomagnetic recording layer on a temporary support, and thereafter transferring the layer on a true support. SOLUTION: The thermomagnetic recording medium 1 is obtained by coating a temporary support with microcapsules 15 together with a binder 16 to form an at least thermomagnetic recording layer 12, and thereafter transferring at least the layer 12 to a true support 11. As the temporary support and the true support 11, a polyvinyl chloride, a polyester or the like is solely or compositely used. Thus, a side of the support when coating with the recording layer becomes a front surface side of a final product after transferring, and a front surface when coating the layer having rough surface roughness caused by particle size of the capsules becomes the support side after transferring, and hence a surface having relatively small protrusion and recess unevenness can be obtained as a final recording medium. Thus, an unevenness or a partial omission can be prevented in the case of printing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermomagnetic recording medium for displaying an image by heating with a thermal head or the like while applying magnetism, and in particular, is excellent in resolution and image printing stability, and has repeated printing durability. High reversibility thermomagnetic recording medium.

[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 an image formation, it takes a long time to attract the magnetic particles, resulting in a magnetic recording medium having low 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), a magnetic recording medium in which light-absorbing magnetic particles and light-reflective non-magnetic particles are encapsulated in microcapsules is known.

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, the magnetic recording medium obtained in this manner has a very low resolution compared to other recording methods using heat or light because the magnetic force is applied over a wide range. 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.

On the other hand, the present inventors disclose in a recording layer a microcapsule containing at least flake-like magnetic powder and a dispersion medium which is in a solid state at room temperature and dispersed in a recording layer. A recording medium was proposed (Japanese Unexamined Patent Application Publication No.
-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. Further, even if unexpected heat is applied by a heater in winter or inside a car in summer, the magnetic powder does not move by heat alone, so that the image stability against heat is good.

As a recording method of the thermomagnetic recording medium, for example, (1) a method using an optical head capable of converting heat such as laser light and a magnetic field forming means capable of applying a uniform magnetic field;
(2) a method using a thermal head and a magnetic field forming means capable of applying a uniform magnetic field, (3) a method using a magnetic head and a heat applying means capable of applying a uniform heat, and (4) a line for both heat and a magnetic field. And the like.

[0015]

Among the above recording methods, (2) a method of recording using a thermal head and a uniform magnetic field is as follows.
Compared to the case of using a magnetic head, an image with a higher resolution can be recorded.However, since a heat applying means such as a thermal head is generally of a contact type and receives pressure simultaneously with heat, it is necessary to repeatedly record and erase. During use, the protective layer and the recording layer were sometimes damaged. In addition, since microcapsules containing magnetic powder have a relatively large particle size of about 10 to 150 μm, the surface tends to be rough when a thermomagnetic recording layer is applied normally, Even if a protective layer is provided, it is difficult to completely solve the problem. If the surface roughness of the recording medium surface is rough as described above, a gap is generated between the head and the recording medium, and the heat transfer becomes non-uniform. The present invention aims to solve this problem.

[0016]

Means for Solving the Problems The present invention has been made to achieve the above object, and the invention according to claim 1 is to disperse and arrange at least microcapsules containing magnetic powder in a binder. In a thermomagnetic recording medium having a thermomagnetic recording layer and a protective layer, it is necessary to first provide at least a thermomagnetic recording layer on a temporary support, and then transfer the thermomagnetic recording layer to a true support. This is a method of manufacturing a thermomagnetic recording medium, which is a feature. The invention according to claim 2 is a thermomagnetic recording medium having a thermomagnetic recording layer and a protective layer in which microcapsules containing at least magnetic powder are dispersed in a binder, wherein at least the protective layer is provided on a temporary support. And a thermomagnetic recording layer, and then transferring a protective layer, a thermomagnetic recording layer, and a coloring layer on a true support. According to a third aspect of the present invention, in the method of manufacturing a thermomagnetic recording medium according to the first or second aspect, the center line average roughness Ra of the surface of the temporary support on the coating surface side is provided.
Is 5 μm or less. Claim 4
The invention relates to a thermomagnetic recording medium having a thermomagnetic recording layer and a protective layer on a support, in which at least microcapsules containing magnetic powder are dispersed in a binder, and a center line average roughness of the surface of the protective layer. A thermomagnetic recording medium, wherein Ra is 5 μm or less. The invention of claim 5 is
A thermomagnetic recording material manufactured by the method for manufacturing a thermomagnetic recording material according to claim 3. According to a sixth aspect of the present invention, there is provided a thermomagnetic recording medium according to the fourth aspect, manufactured by the method for manufacturing a thermomagnetic recording medium according to the third aspect.

<Operation> In the thermomagnetic recording medium manufactured by the method of manufacturing a thermomagnetic recording medium of the present invention, the thermomagnetic recording layer of the capsule is once applied to a temporary support, It is provided by transferring to a support. In this method, the temporary support-side surface of the recording layer becomes the surface side after the transfer, and the recording layer surface having a rough surface roughness due to the particle size of the capsule becomes the support side after the transfer. As a surface of a simple recording medium, a surface with relatively few irregularities is obtained, and the repetitive printing / erasing resistance is improved. In particular, when a temporary support having a surface roughness of 5 μm or less is used, the final surface roughness of the recording medium surface is also 5 μm or less, and it is unlikely that unevenness or partial peeling will occur in printing. In addition, even if a true support is used whose thickness is extremely thinner than the thickness of the thermomagnetic recording layer, paper, or the like, which has a rough surface, even if the temporary support has a sufficient thickness and surface With good properties, a thermomagnetic recording material having good surface properties can be obtained without wrinkling when the thermomagnetic recording layer is applied and dried.

[0018]

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 thermomagnetic recording body produced by the method of the present invention, and FIG. 2 is a cross-sectional view showing one embodiment of a microcapsule used for a thermomagnetic recording layer in the present invention. 3 and 4 are explanatory views showing a method of manufacturing the thermomagnetic recording medium of the present invention, FIG. 5 is an explanatory view showing a state of manufacturing the thermomagnetic recording medium of the present invention, and FIG. FIG. 7 is an explanatory view showing a state in which the flake-like magnetic powder is oriented in parallel to the thermomagnetic recording layer of the thermomagnetic recording medium produced by the method of FIG. 1, and FIG. 7 shows the thermomagnetic recording produced by the method of the present invention. FIG. 4 is an explanatory view showing a state in which flake-shaped magnetic powder is partially oriented in a direction perpendicular to the thermomagnetic recording layer of the body.

FIG. 1 shows the structure of a thermomagnetic recording medium 1 produced by the production method of the present invention.
A thermomagnetic recording layer 12 and a protective layer 14 on which a coating material obtained by dispersing microcapsules 15 containing flake-like magnetic powder or the like in a binder 16 are sequentially laminated.

FIG. 2 is a sectional view showing an embodiment of the microcapsule 15 used for the thermomagnetic recording layer 12 in the present invention. The microcapsule 15 is formed by dispersing a core material 21 mainly composed of a suspension in which a flake-shaped magnetic powder 22 is dispersed in a dispersion medium (for example, an organic compound such as wax) 23 in a solid state at normal temperature, by using a shell material made of a polymer or the like. This is a configuration encapsulated by 24.

The flake-like magnetic powder 22 is obtained by, for example, using iron, nickel, iron / nickel, iron / nickel / chromium, etc., stainless steel, cobalt, cobalt / aluminum, samarium / cobalt alloy, etc., with an atomizer or hammer mill. Flakes can be used. In particular, in order to enhance the affinity of the magnetic powder with an organic solvent, etc., higher ester treatment, silane coupling treatment,
It is preferable to perform titanate coupling treatment or the like.
The size of the flake-like magnetic powder 22 in the present invention is 5 μm to 30 μm and the thickness is 0 μm in consideration of the ease of rotation in the microcapsule due to the application of magnetism, the image contrast of the thermomagnetic recording layer 12 and the like. It is preferably between 1 μm and 3 μm. The flake-like magnetic powder 22
A colored layer may be provided on the surface of the substrate.

As the dispersion medium 23, room temperature (about 10 to 35
C.) and a solid (showing a solid phase state) and a fluid state when heated to a temperature higher than room temperature (about 40 to 80 ° C.). Commonly known materials 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 can be used alone or in combination as appropriate. In addition, you may color in the range which does not obstruct light transmittance.

The above-mentioned flaky magnetic powder 22, dispersion medium 2
A core material 21 mainly composed of 3 or the like is covered with a shell material 24 such as a polymer, and is microencapsulated. This shell material 24
The resin used as, for example, commonly used resins, for example, acrylic resin, methacrylic resin, polystyrene, polyester resin, polyurethane resin, polyurea resin, polyamide resin, epoxy resin, natural resin and the like, and these may be used alone. , Or a mixture of two or more kinds.

Microcapsule 1 having the above 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, the particles are produced by an in-situ polymerization method in which monomers are supplied from the outer phase of a suspension in which flake-like magnetic powders 22 as the core substance 21 are uniformly dispersed in a dispersion medium 24, or a phase separation method. Microcapsules 15 having a uniform diameter and easy movement of the flake-shaped magnetic powder 22 can be manufactured. The polymerizable monomer used here is acrylic acid ester, methacrylic acid ester, styrene and its derivatives, isocyanate,
Various amines, compounds having an epoxy group, and the like are suitable.

The particle size of the microcapsules 15 is 10
It is preferably about μm to 200 μm. When the particle diameter 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 effect is weakened and the contrast is lowered. When the particle size is 200 μm or more, the dispersion medium 23 which shows a solid phase state at room temperature in the capsule is relatively large and the thickness increases, so that it is difficult to sufficiently dissolve the instantaneous heat of the thermal head. And the recording density may be insufficient or recording may not be possible.

In the thermomagnetic recording medium 1 manufactured by the manufacturing method of the present invention, the microcapsules 15 having the above-described structure are applied on a temporary support 10 together with a binder 16 to form at least a thermomagnetic recording layer 12. , True support 1
1 is obtained by transferring at least the thermomagnetic recording layer 12. At this time, the layer transferred from the temporary support,
At least a thermomagnetic recording layer only needs to be included. As shown in FIG. 4, after a protective layer or a coloring layer (or an adhesive layer or the like) is simultaneously provided on the temporary support in addition to the thermomagnetic recording layer,
The layers may be transferred onto a true support.

The temporary support 10 may be made of a synthetic resin such as polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate, polystyrene, polyethylene terephthalate, natural resin, paper, synthetic paper, metal, ceramics, glass, or the like. It can be used as a combined complex. The shape may be any shape such as a card shape, a sheet shape, a film shape, a plate shape, and a three-dimensional shape as long as it has a relatively smooth surface partially. In particular, when the surface roughness is 5 μm,
With the following smooth surface, a better thermomagnetic recording medium can be produced.

A water-based binder, a solvent-based binder, an emulsion-based binder, or the like is used as a binder 16 when the microcapsules 15 having the above-described structure are coated on the temporary support 10 to form a thermomagnetic recording layer. However, it is preferable to use a curable resin since the friction resistance and the repeated print erasure resistance of the recording medium are improved. Examples of the curable resin include a UV-curable resin, a photo-curable resin such as an EB-curable resin, a thermosetting resin having an isocyanate group, a melamine group, an epoxy group, and the like, and a moisture-curable resin. Can be

The protective layer 14 needs to protect the microcapsules 15 in the thermomagnetic recording layer and have a light transmitting property so that the flake-like magnetic powder 22 in the microcapsules 15 can be seen from the outside. Such a protective layer 14
Various known resins such as various polymer resins and films can be used as long as they are transparent. For example, epoxy resin, tetrafluoroethylene,
Synthetic resins such as polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate, polystyrene, etc.
Films of natural resin, nylon, polyethylene terephthalate, polyimide and the like can be used.

As described above, the protective layer 14 is formed by transferring the thermomagnetic recording layer from the temporary support 10 to the true support 11,
It may be provided on the thermomagnetic recording layer, or may be provided by first providing a protective layer on a temporary support, providing a thermomagnetic recording layer thereon, and transferring the protective layer and the thermomagnetic recording layer together. good. Also,
At this time, if the adhesion between the thermomagnetic recording layer and the protective layer is poor, an adhesive layer may be provided between the two layers.

The protective layer 14 may be colored in a range that does not affect the reading and reading of the lower thermomagnetic recording layer, or may be provided with a colored layer (not shown) having a light transmitting property. For the coloring of the protective layer, a pigment or a dye is mixed,
When a coloring layer (not shown) is provided, a pigment or dye dispersed or dissolved in a binder or the like is formed on the thermomagnetic recording layer 12 by coating. As the pigment or dye, 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 are generally known titanium dioxide, zinc sulfide, lead titanate, zirconium oxide, lead white, cadmium red, inorganic pigments such as cadmium yellow, fine particles of organic pigments such as phthalocyanine pigments, and dyes are azo dyes. Various known pigments and dyes such as quinoline dyes and phthalocyanine dyes are used. 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.

The true support 11 is made of polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate,
It can be used as a composite of single or combined synthetic resins such as polystyrene and polyethylene terephthalate, natural resins, paper, synthetic paper, metal, ceramics and the like. In addition, the shape can also be selected according to the application such as a card shape or a sheet shape, a film shape, a plate shape, and in addition, physical properties required according to the application, for example, strength, rigidity, concealment, light opacity, etc. It can be appropriately selected from the above materials.

The true support 11 may be colored for the purpose of improving the contrast. Alternatively, the same effect can be obtained by using a true support 11 provided with a colored layer. Alternatively, the same applies if a thermomagnetic recording layer is provided on a temporary support and then a colored layer is provided thereon. The coloring layer is formed by dispersing or dissolving a pigment or dye in a binder or the like. Various known pigments and dyes can be used according to the intended display color. For example, a carbon black is suitable for monochrome printing.

The thermomagnetic recording layer 12, the protective layer 14,
For example, a known printing method such as an offset printing method, a gravure printing method, a silk screen printing method, or a coating method such as a roll coating method or a knife edge method, or an ink mixed with the microcapsules 15 described above may be used. Can be prepared by a forming method such as an ink jet method in which the ink is sprayed onto a base material, and can be appropriately selected from the above-described methods according to the use and quantity of the information recording medium to be prepared.

Next, a method of forming a display image on the thermomagnetic recording medium of the present invention will be described. Fig. 5 shows flake magnetic powder 2
FIG. 2 is an explanatory view showing an enlarged cross-sectional view of a part of the thermomagnetic recording medium 1 of the present invention in which a microcapsule 15 containing a suspension dispersed in an organic solvent as a dispersion medium 23 is coated on a support 11. . Initially, the flake-like magnetic powder 22 is fixed in the dispersion medium 23 in a state of being uniformly dispersed in the microcapsule 15.

FIG. 6 is an explanatory view showing a state in which the flake-like magnetic powder 22 in the microcapsule 15 is oriented in parallel to the thermomagnetic recording layer 12. This thermomagnetic recording layer 1
When 2 is heated by the thermal head 30 while applying a uniform magnetic field, the dispersion medium 23 in the microcapsule is in a molten state, and the flake-like magnetic powder 22 can be oriented or moved (rotated). Then, the orientation state becomes the same as the magnetic application direction. Therefore, in the figure, the flake-like magnetic powder 22 in the microcapsule 15 is oriented parallel to the thermomagnetic recording layer 12 by the magnetism applied uniformly to the thermomagnetic recording layer 12 in the direction parallel to the support. . As a result, the surface of the thermomagnetic recording medium has a uniform color tone in which most of the incident light is reflected by the flake-like magnetic powder 22.

FIG. 7 shows the thermomagnetic recording layer 1 of the thermomagnetic recording medium 1.
At the same time as applying a uniform magnetic field in the direction perpendicular to 2, it is partially heated by the thermal head to melt the dispersion medium 23 in the microcapsule and move (rotate) the flake-like magnetic powder 22. And the orientation state is the same as the magnetic application direction. Accordingly, the flake-like magnetic powder 22 in the microcapsules 15 of the thermomagnetic recording layer 12 is oriented in the direction perpendicular to the thermomagnetic recording layer 12 in the drawing.
As a result, the incident light is hardly reflected (or absorbed) by the flake magnetic powder 22, so that the flake magnetic powder 2 oriented in a direction parallel to the thermomagnetic recording layer 12.
A difference in reflection between the flake-shaped magnetic powder 22 and the flake-shaped magnetic powder 22 oriented in the vertical direction, that is, a contrast is obtained, and thereby, visible display information can be recorded.

This image formation is simple due to magnetism and heat of low energy enough to lower the viscosity of the dispersion medium, so that recording is easy, and by controlling the particle size of the microcapsules, the resolution can be improved. High image formation is possible. In addition, since the image formed by the thermal / magnetic head is in a fixed state at the same time when the dispersion medium returns to normal temperature, its recording stability is good, and since it is not possible to form an image only with magnetism except in a molten state, No fogging is caused by touching the magnet. The magnetic recording medium according to the present invention is provided with both the mobility at the time of recording of the flake-like magnetic powder contained therein, that is, both the good recording reactivity and the stability of the recorded image. The information can be recorded by setting the orientation of the flake-shaped magnetic powder to the magnetic recording layer based on one of the parallel direction and the perpendicular direction and partially setting the other to the other direction. Based on the fact that the orientation state of the flake-like magnetic powder is in the vertical direction, the visible state information may be recorded by partially changing the orientation state in the parallel direction.

Further, by setting the applied energy and pulse width to the thermal head to smaller appropriate conditions, the flake-like magnetic powder is moved (rotated from the horizontal state to the vertical state (or from the vertical state to the horizontal state)). ), Printing can be stopped during the movement (rotation). This state has an intermediate visible density between the case where the flake-like magnetic powder is in the horizontal state and the case where the flake-like magnetic powder is in the vertical state. That is, according to this method, gradation expression can be performed by changing the printing conditions of the thermal head. Of course, as a method of setting such a flake-like magnetic powder in a state between a horizontal state and a vertical state, printing may be performed with a thermal head by setting the direction of a magnetic field in a direction between a horizontal direction and a vertical direction.

[0041]

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

<Example 1><Preparation of coating liquid for reversible thermosensitive magnetic recording layer> 80 parts by weight of paraffin wax, which was heated at 60 ° C. and melted by heating 60 parts by weight of flaky nickel powder subjected to silane coupling treatment. And the dispersion was heated to 60 ° C.
It was dispersed in 200 parts by weight of a 0% gelatin aqueous solution for about 5 minutes using a homogenizer so that the average particle diameter was 75 μm at a rotation speed of 2000 rpm. 10 to the resulting dispersion
A 200% by weight aqueous solution of gum arabic was mixed, and 1000 parts by weight of water was further added. The mixture was maintained at 40 ° C., and a 10% aqueous solution of acetic acid was added dropwise to adjust the pH to 4. After that, the liquid temperature was set to 5
The mixture was cooled to ℃, 10 parts by weight of a 30% aqueous formalin solution was added, and a 10% aqueous sodium hydroxide solution was added dropwise to adjust the pH to 9, thereby preparing microcapsules having a gelatin-arabic gum wall. The microcapsules were dispersed in an aqueous emulsion-type UV-curable resin liquid to obtain a reversible thermosensitive magnetic recording layer coating liquid.

<Preparation of Reversible Recording Medium> On a 100 μm polyethylene film, the reversible thermosensitive magnetic recording layer coating solution was applied and dried, and UV irradiation was performed to form a thermomagnetic recording layer having a thickness of 90 μm. Next, a urethane-based laminate adhesive layer was provided on 188 μm black polyethylene terephthalate (PET) with a dry film thickness of 5 μm. The recording layer side of the polyethylene film provided with the above thermomagnetic recording layer and black PET
The adhesive layer side was adhered and laminated, and then the polyethylene film was peeled off to transfer the thermomagnetic recording layer to black PET. Further, a UV-curable resin (containing a lubricant filler) was applied on the thermomagnetic recording layer, and then cured by UV irradiation to form a protective layer having a thickness of 10 μm.

<Recording of Image> The entire thermomagnetic recording medium was heated to 100 ° C., and a magnetic field was applied horizontally to the layer to bring the entire surface into an erased state. Next, with a magnetic field applied perpendicularly to the layer, printing is performed with a thermal head according to the pattern of visible display information to be recorded, and the magnetic powder in the microcapsules in the pattern part is vertically oriented and the recording state is established. did.

<Example 2><Preparation of coating liquid for reversible thermosensitive magnetic recording layer> Flake-shaped cobalt aluminum alloy 60 treated with oleic acid
Parts by weight were uniformly dispersed in 80 parts by weight of a mixed solvent of paraffin wax and dibutyl phthalate which was heated to 50 ° C. in which 2 parts by weight of a yellow dye was dissolved, and the dispersion was heated to 50 ° C. in 5% polyvinyl alcohol. Using a homogenizer, dispersion was carried out in 200 parts by weight at a rotation speed of 2500 rpm for an average particle size of 40 μm for about 5 minutes. Melamine-formalin prepolymer aqueous solution 10 was added to the resulting dispersion.
0 parts by weight were added, and a 20% aqueous acetic acid solution was added dropwise to adjust the pH to 6. Thereafter, the temperature of the solution was raised to 65 ° C., and a 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 prepare a reversible thermosensitive magnetic recording layer coating liquid.

<Preparation of reversible recording medium> Center line average roughness
On a copper plate with Ra <2 μm, a UV-curable resin (containing a lubricant and a filler) having a thickness of 10 μm was provided as a protective layer. Further, a urethane resin was provided thereon as an adhesive layer with a dry film thickness of 1 μm. Furthermore,
The reversible thermosensitive magnetic recording layer coating solution was applied thereon, dried, and then heat-cured at 120 ° C. for 10 minutes to obtain a 50 μm thermosensitive magnetic recording layer. Further, a mixed solution of a phthalocyanine-based pigment and an aqueous acrylic emulsion was applied thereon as a cyan colored layer to form a colored layer with a dry film thickness of 10 μm. Next, a urethane resin of 10 μm was provided as an adhesive layer on a 200 μm coated paper. Then, after thermal lamination such that the colored layer on the copper plate and the adhesive layer of the coated paper are in contact with each other, the protective layer, the thermomagnetic recording layer, and the colored layer are coated by peeling off at the interface between the protective layer and the copper plate. It was transferred to paper to obtain a thermomagnetic recording medium.

<Recording of Image> The recording medium was heated to 100 ° C., and a magnetic field was applied horizontally to the layer to bring the entire surface into an erased state. Next, with a magnetic field applied perpendicularly to the layer, printing is performed with a thermal head according to the pattern of visible display information to be recorded, and the magnetic powder in the microcapsules in the pattern part is vertically oriented and the recording state is established. did.

<Comparative Example 1> An adhesive layer was formed on 188 μm black PET without transferring the thermomagnetic recording layer in Example 1.
A thermomagnetic recording layer was prepared by providing a thermomagnetic recording layer and a UV-curable resin (containing a lubricant filler) in the same order as in Example 1.

<Comparative Example 2> In Example 2, without using a copper plate,
An adhesive layer, a thermomagnetic recording layer, an adhesive layer, and a protective layer were provided in this order on a 100 μm coated paper in the same thickness as in Example 2 to produce a thermomagnetic recording medium.

Comparative Example 3 A thermomagnetic recording medium was produced in the same manner as in Example 2 except that a film having a center line average roughness Ra of about 5 μm was used instead of the copper plate.

Table 1 shows the results obtained by examining the densities at the time of decoloration and the print densities of each sample, the presence or absence of an image defect, the repetitive print resistance, and the surface roughness. In the examples according to the production method of the present invention, since the surface was smoother than the comparative example, there was no image dropout and the repeated printing resistance was high. Further, in Comparative Example 3, a slight drop was observed.

[0052]

[Table 1]

[0053]

According to the thermomagnetic recording medium manufactured by the method of manufacturing a thermomagnetic recording medium of the present invention, the thermomagnetic recording layer of the capsule is once applied to a temporary support, and then the true support is obtained. Since this is a method in which the recording layer is transferred, the surface on the temporary support side when the recording layer is coated will be the surface side of the final product after transfer, and the recording layer with a rough surface due to the particle size of the capsule will be coated. Since the surface at the time is on the support side after the transfer, a surface with relatively few irregularities can be obtained as the surface of the final recording medium, and the repeated printing / erasing resistance is improved. In particular, when a temporary support having a center line average roughness Ra of 5 μm or less is used, the final center line average roughness Ra of the surface of the recording medium becomes 5 μm or less, and unevenness or partial It is less likely that nicking will occur. In addition, even if a true support is used whose thickness is extremely thinner than the thickness of the thermomagnetic recording layer, paper, or the like, which has a rough surface, even if the temporary support has a sufficient thickness and surface With good properties, a thermomagnetic recording material having good surface properties can be obtained without wrinkling when the thermomagnetic recording layer is applied and dried.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a thermomagnetic recording medium manufactured by a method of the present invention.

FIG. 2 is a sectional view showing one embodiment of a microcapsule used for a thermomagnetic recording layer in the present invention.

FIG. 3 is an explanatory view showing a method for producing a thermomagnetic recording medium of the present invention.

FIG. 4 is an explanatory view showing a method for producing a thermomagnetic recording medium of the present invention.

FIG. 5 is an explanatory view showing a state at the time of manufacturing a thermomagnetic recording medium of the present invention.

FIG. 6 is an explanatory view showing a state in which flake-shaped magnetic powder is oriented in parallel to a thermomagnetic recording layer of a thermomagnetic recording medium produced by the method of the present invention.

FIG. 7 is an explanatory view showing a state in which flake-like magnetic powder is partially oriented in a direction perpendicular to a thermomagnetic recording layer of a thermomagnetic recording body produced by the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Thermomagnetic recording body 11 ... Support 12 ... Thermomagnetic recording layer 14 ... Protective layer 15 ... Microcapsule 16 ... Binder 21 ... Core substance 22 ... Flake Magnetic powder 23 ・ ・ ・ Dispersion medium 24 ・ ・ ・ Shell substance

Claims (6)

[Claims] 1. A method for producing a thermomagnetic recording medium having a thermomagnetic recording layer in which at least microcapsules encapsulating magnetic powder are dispersed in a binder and a protective layer on a support. Forming a thermomagnetic recording layer on the support, and then transferring the thermomagnetic recording layer onto the true support. 2. A method for producing a thermomagnetic recording medium having a thermomagnetic recording layer and a protective layer each having at least microcapsules enclosing magnetic powder dispersed in a binder on a support. A method for producing a thermomagnetic recording medium, comprising: providing at least a protective layer and a thermomagnetic recording layer on a support of (1), and thereafter transferring the protective layer and the thermomagnetic recording layer on a true support. 3. The thermomagnetic recording medium according to claim 1, wherein a center line average roughness Ra of the surface of the temporary support on the coating surface side is 5 μm or less. Production method. 4. A thermomagnetic recording medium having at least a thermomagnetic recording layer in which microcapsules containing at least magnetic powder are dispersed in a binder and a protective layer on a support, the center line average roughness of the surface of the protective layer. A thermomagnetic recording medium, wherein Ra is 5 μm or less. 5. A thermomagnetic recording material manufactured by the method for manufacturing a thermomagnetic recording material according to claim 3. 6. A thermomagnetic recording medium according to claim 4, manufactured by the method for manufacturing a thermomagnetic recording medium according to claim 3.