JPH115367A - Reversible thermosensitive magnetic recording medium and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reversible thermosensitive magnetic recording medium capable of improving the durability of repeated printing and erasing, and a method for manufacturing the same. SOLUTION: On a base material 11, at least a magnetic recording layer 9 for performing magnetic recording, a concealing layer 7 for concealing coloring of the magnetic recording layer 9, a leuco dye, a color-reducing agent and a resin as main components. Thermosensitive recording layer 3 and protective layer 1 contained as
In the reversible thermosensitive magnetic recording medium in which are sequentially laminated, the concealing layer 7 contains a light-opaque pigment and a resin having active hydrogen as main components, and between the concealing layer 7 and the reversible thermosensitive recording layer 3, A heat-resistant layer 5 containing an ultraviolet-curable resin and a crosslinking agent as main components was formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reversible thermosensitive recording layer comprising a leuco dye, a color reducing agent and a resin as main components, wherein the magnetic recording layer and the reversible thermosensitive recording layer are on the same surface of a substrate. The present invention relates to a reversible thermosensitive magnetic recording medium located on the side and a method for manufacturing the same.

[0002]

2. Description of the Related Art In various cards such as ID cards and prepaid cards, heat-sensitive recording is performed for displaying a balance and the like in addition to, for example, magnetic recording. This thermosensitive recording is widely used because it does not require development, has high color density and is inexpensive. For example, a thermosensitive magnetic recording medium is an application of such a thermosensitive recording technique.

As a conventional thermosensitive magnetic recording medium, a "thermosensitive magnetic recording medium" disclosed in Japanese Patent Application Laid-Open No. 8-318690 will be described with reference to FIG. FIG. 2 shows a schematic sectional view of the thermosensitive magnetic recording medium.

[0004] The thermosensitive magnetic recording medium shown in FIG.
A base 29; a magnetic recording layer 27 formed on the base 29 for performing magnetic recording; and an aluminum powder and a nitro powder formed on the magnetic recording layer 27 for concealing the coloring of the magnetic recording layer 27. A concealing layer 25 containing a cellulose resin; a leuco dye formed on the concealing layer 25 and substantially insoluble in an aromatic hydrocarbon solvent for performing thermal recording; The thermosensitive recording layer 23 contains a soluble resin and a protective layer 21 formed on the thermosensitive recording layer 23.

[0005] Magnetic recording is performed on the magnetic recording layer 27, and the heat-sensitive recording layer 23 is heated so that the heat-sensitive recording layer 23 is colored to display desired characters and the like.

As described above, in the thermosensitive magnetic recording medium shown in FIG. 2, the leuco dye contained in the thermosensitive recording layer 23 is substantially insoluble in the aromatic hydrocarbon solvent, and the concealing layer using the nitrocellulose resin is used. Since a resin soluble in the aromatic hydrocarbon solvent contained in 27 is used as a binder,
It is stated that the recording characteristics can be improved and the resistance to the environment can be improved.

[0007]

However, Japanese Patent Application Laid-open No.
The "thermosensitive magnetic recording medium" disclosed in JP-318690A aims to sufficiently improve the durability when the number of times of use is one, and when the printing and erasing are repeatedly performed several tens of times. If the thermosensitive recording layer is a reversible thermosensitive recording layer capable of reversible display of visible information, the hardness of the concealing layer is insufficient and the print erasure is not performed. Since the repetition durability is not high enough to withstand the heating and pressurization during printing and erasing, there is a problem that the coating film is destroyed or delamination occurs after performing printing and erasing many times. doing.

In order to improve the durability of the reversible thermosensitive magnetic recording medium for repeated printing and erasure, it is conceivable to add an ultraviolet-curable resin to the concealing layer to increase the hardness of the concealing layer to form a hard film. However, the opaque layer contains a light-opaque pigment such as aluminum (Al) powder or titanium oxide (TiO ₂ ) powder in order to conceal the coloring of the magnetic recording layer. When the ultraviolet rays are blocked, the ultraviolet-curable resin cannot be sufficiently cured by the irradiation of the ultraviolet rays, so that the durability of the repeated printing and erasing cannot be improved.

[0009] In addition, by using a heat-crosslinkable resin for the hiding layer,
If the concealing layer is a hard film, the adhesion between the cured concealing layer and the reversible thermosensitive recording layer cannot be improved. In addition, the durability of repeated printing and erasing cannot be improved.

Here, in order to improve the adhesion between the concealing layer and the reversible thermosensitive recording layer, a resin having a functional group having good adhesiveness may be contained in the concealing layer. Although the adhesion between the concealing layer and the reversible thermosensitive recording layer is improved, this functional group acts on the leuco dye contained in the reversible thermosensitive recording layer, so-called fog occurs, and the reversible thermosensitive recording layer is formed. In addition, unnecessary coloring occurs, and the visibility of the display of the reversible thermosensitive recording layer is reduced.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a reversible thermosensitive magnetic recording medium capable of improving the durability of repeated printing and erasing, and a method of manufacturing the same.

[0012]

According to the first aspect of the present invention,
On a substrate, at least a magnetic recording layer for performing magnetic recording, a concealing layer for concealing the coloring of the magnetic recording layer, a reversible thermosensitive recording containing a leuco dye, a color-reducing agent and a resin as main components. Layer, and a reversible thermosensitive magnetic recording medium in which a protective layer is sequentially laminated, wherein the concealing layer contains a resin having a light-impermeable pigment and active hydrogen as a main component, and the concealing layer and the reversible thermosensitive recording layer A heat-resistant layer containing at least an ultraviolet curable resin and a crosslinking agent as main components.

Therefore, according to the present invention, since the coating material for the heat-resistant layer impregnates the concealing layer when the heat-resistant layer is formed, the crosslinking agent contained in the heat-resistant layer as a main component is contained in the concealing layer. The resin containing hydrogen is cured, the hardness of the concealing layer is increased, and the adhesion between the heat-resistant layer and the concealing layer is improved, and the ultraviolet-curable resin contained as a main component in the heat-resistant layer is irradiated with ultraviolet rays. Irradiation can increase the hardness of the heat-resistant layer, so that the durability against heating and pressurizing during printing and erasing can be improved, and the printing and erasing durability of reversible thermosensitive magnetic recording media can be improved. Performance can be improved.

According to a second aspect of the present invention, in the first aspect of the present invention, the resin having active hydrogen is a vinyl chloride / vinyl acetate / maleic anhydride copolymer,
It is a vinyl acetate / vinyl alcohol copolymer or nitrocellulose.

Therefore, according to the present invention, the effect of the first aspect of the present invention is obtained, and the resin having active hydrogen contained as a main component in the concealing layer is made of vinyl chloride / vinyl acetate / maleic anhydride. Since it is any of a polymer, a vinyl chloride / vinyl acetate / vinyl alcohol copolymer, or nitrocellulose, these can be appropriately cured by a crosslinking agent contained as a main component in the heat-resistant layer.

According to a third aspect of the present invention, in the first or second aspect, the ultraviolet curable resin has an acid value of 5 KOHmg / g or less.

Therefore, according to the present invention, the effect of the invention described in claim 1 or 2 is obtained, and the acid value of the ultraviolet curable resin contained as a main component in the heat resistant layer is 5 KOH.
mg / g or less, the reaction between the ultraviolet curable resin and the leuco dye contained as a main component in the reversible thermosensitive recording layer can be suppressed, so that unnecessary coloring of the reversible thermosensitive recording layer can be suppressed. Can be suppressed.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the thickness of the heat-resistant layer is:
It is characterized by being in the range of 0.1 to 10 μm.

Therefore, according to the present invention, the effect according to any one of the first to third aspects can be obtained, and the thickness of the heat-resistant layer is in the range of 0.1 to 10 μm. This makes it possible to follow the bending of the thermosensitive magnetic recording medium and to prevent the occurrence of cracks.

According to a fifth aspect of the present invention, there is provided a magnetic recording layer forming step of forming a magnetic recording layer for performing magnetic recording on a substrate, and a step of forming a light impermeable pigment and active hydrogen on the magnetic recording layer. Applying a paint containing a resin having as a main component,
A concealing layer forming step of drying to form a concealing layer, and a coating containing a UV curable resin and a crosslinking agent as main components is applied on the concealing layer, dried, and cured by irradiating ultraviolet rays, A heat-resistant layer forming step of forming a heat-resistant layer, an aging step of performing aging after forming the heat-resistant layer, and a reversible step of forming a reversible thermosensitive recording layer on the heat-resistant layer after performing the aging. And a protective layer forming step of forming a protective layer on the reversible thermosensitive recording layer.

Therefore, according to the present invention, since the magnetic recording layer, the concealing layer, and the heat-resistant layer are sequentially laminated on the base material, the aging step of performing aging is provided.
The crosslinking agent contained as a main component in the heat-resistant layer hardens the concealing layer sufficiently, so that the hardness of the concealing layer can be sufficiently hardened and the adhesion between the concealing layer and the heat-resistant layer is improved. Can be done.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of a reversible thermosensitive magnetic recording medium according to the present invention and a method for manufacturing the same will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of one embodiment of the reversible thermosensitive magnetic recording medium according to the present invention.

Referring to FIG. 1, a reversible thermosensitive magnetic recording medium according to this embodiment has a magnetic recording layer 9 for performing magnetic recording, a light-impermeable pigment and active hydrogen on a substrate 11. A concealing layer 7 containing a resin as a main component, a heat-resistant layer 5 containing a UV-curable resin and a crosslinking agent as a main component, and a leuco dye, a color-reducing agent and a resin for performing reversible thermosensitive recording. , And a protective layer 1 for protecting the surface of the reversible thermosensitive recording layer 3 is sequentially laminated.

First, the substrate 11 shown in FIG. 1 will be described. The substrate 11 is made of, for example, polyethylene terephthalate (PET), polyacetate, polystyrene (P
S), an epoxy resin, a synthetic resin sheet such as polyvinyl chloride (PVC) and polycarbonate (PC) or a synthetic paper can be used. The thickness of the substrate 11 is usually 1
It is about 00 to 300 μm.

The magnetic recording layer 9 may be a layer generally used as a magnetic recording layer in this type of magnetic recording medium.

For example, as a magnetic material, Ba-ferrite having a particle size of 10 μm or less, preferably 0.01 to 5 μm, Sr
Ferrite, Co-coated γ-Fe ₂ O ₃ , γ-Fe ₂ O ₃ ,
Using needle-like iron powder, CrO ₂ , polyester resin, alkyd resin generally used as binder resin,
A vinyl resin, a polyurethane resin, or a mixed resin thereof can be used.

The mixing ratio between the binder resin and the magnetic material is appropriately set in consideration of the adhesion to the substrate 11, the strength of the coating film, the voltage detected by the magnetic head, and the like. Usually, the former / the latter are in the range of 1/1 to 1/10 by weight ratio, preferably 1/2 to 1/10.
1/8 is appropriate.

The thickness of the magnetic recording layer 9 is usually 5 to 20.
It is about μm.

The concealing layer 7 has such a color as to visually conceal the color of the magnetic recording layer 9 and to give a sufficient contrast to the color of the reversible thermosensitive recording layer 3 described later. Therefore, the opaque layer 7 contains, as a main component, a non-magnetic metal such as aluminum powder or a light-opaque pigment such as a non-magnetic metal oxide such as titanium oxide powder.

The properties to be provided by the material used to form the concealing layer 7 are such that the material is sufficiently cured by a crosslinking agent contained as a main component in the heat-resistant layer 5 described below, and
This is a property of improving the adhesion between the heat-resistant layer 5 and the concealing layer 7.

Therefore, a resin having active hydrogen such as a hydroxyl group or a carboxyl group is essential as a resin to be contained in the concealing layer 7 as a main component, and specific examples of the resin having active hydrogen include vinyl chloride / vinyl acetate. / Vinyl maleic anhydride copolymer, vinyl chloride / vinyl acetate / vinyl alcohol copolymer, or nitrocellulose, and two or more of them may be used in combination. The thickness of the concealing layer 7 is, for example, 0.05 to 3 μm.
m.

The heat-resistant layer 5 is made of a UV-curable resin in order to improve the durability of the reversible thermosensitive magnetic recording medium shown in FIG. A crosslinking agent is contained as a main component.

As the ultraviolet-curable resin, for example, the physical strength of the concealing layer 7 can be maintained from the heat shear stress when printing and erasing by a thermal head, and
In order to suppress the reaction with the leuco dye contained in the reversible thermosensitive recording layer 3, it is preferable to use an ultraviolet curable resin having an acid value of 5 KOHmg / g or less. Specifically, for example, a urethane acrylate resin, an epoxy acrylate resin Resin or a mixed resin thereof can be used.

The cross-linking agent may be any one that cures the resin having active hydrogen in the concealing layer 7 when the coating for the heat-resistant layer is impregnated into the concealing layer 7 at the time of forming the heat-resistant layer. For example, an isocyanate-based curing agent, carbodiimide A system curing agent or the like can be used.

The thickness of the heat-resistant layer 5 may be such that the concealing layer 7 is impregnated when the heat-resistant layer is formed and a thin film is formed on the surface, and specifically 0.1 to 10 μm. When the thickness is larger than this thickness, it is impossible to follow the bending of the reversible thermosensitive magnetic recording medium, and a crack may be generated.

Therefore, by irradiating the heat-resistant layer 5 with ultraviolet light, the hardness of the heat-resistant layer 5 becomes sufficiently high to withstand heating and pressure during printing and erasing. Thereby, the resin having active hydrogen contained as a main component in the concealing layer 7 is cured, and the hardness of the concealing layer 7 is increased, and the adhesion between the heat-resistant layer 5 and the concealing layer 7 is improved. It is possible to improve the durability of the reversible thermosensitive magnetic recording medium for repeated printing and erasing.

The reversible thermosensitive recording layer 3 is a layer composed of, for example, a leuco dye, a color reducing agent and a binder resin, and reversibly repeats coloring / decoloring by heat. Leuco dyes are generally referred to as colorless or pale color electron-donating dye precursors. Further, the color-reducing agent is called an electron-accepting compound, which causes a reversible color change in the dye precursor due to a difference in cooling rate after heating, and is an aliphatic hydrocarbon group having 6 or more carbon atoms. A phenolic compound or a phthalic acid compound having at least one or an acidic compound having a phenolic hydroxyl group and an amino group is used.

Next, the color-reducing agent according to the present invention comprises 4,
4'-isopropylidenephenol, benzyl-p-hydroxybenzoate, 4,4'-dihydroxy-3,
5'-diallyldiphenylsulfone, methyl-bis (hydroxyphenyl) acetate, gallic ester, p-phenylphenol and the like. Examples of the leuco dye include crystal violet lactone, 3-indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluoran, and 2- (2-chlorophenylamine) -diethylaminofluoran. 2- (2-fluorophenylamino) -6-diethylaminofluoran, 2- (2-fluorophenylamino) -6-di-n-butylaminofluoran, 3-diethylamino-7-cyclohexylaminofluoran, 3 -Diethylamino-5-methyl-7-
t-butylfluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6
-Methyl-7-p-butylanilinofluoran, 3-cyclohexylamino-6-chlorofluoran, 2-anilino-3-methyl-6- (N-ethyl-p-toluidino) -fluoran, 3-pyrrolidino- 6-methyl-7-
Anilinofluoran, 3-pyrrolidino-7-cyclohexylaminofluoran, 3-N-methylcyclohexylamino-6-methyl-7-anilinofluoran, 3-N
-Ethylpentylamino-6-methyl-7-anilinofluoran and the like.

The above usually colorless or pale-color electron-donating dye precursors may be used alone or in combination of two or more.

Examples of the binder resin include starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylamide / acrylate copolymer, acrylamide / Water-soluble polymers such as acrylate / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacryl Latexes such as acid esters, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer and the like can be mentioned.

In the reversible thermosensitive recording material, it is sufficient that rapid cooling occurs after heating in order to perform color development, and it is sufficient that the cooling rate after heating is slow in order to perform color erasing. For example, when heating with a suitable heat source (thermal head, laser light, heat roll, heat stamp, high frequency heating, radiant heat from an electric heater, hot air, etc.) for a relatively long time, not only the recording layer but also the support is heated. As a result, the cooling rate is low, resulting in a phase separation state (decoloring state). On the other hand, after heating by an appropriate method,
By rapidly cooling by pressing a low-temperature metal block or the like, a color-developed state can be developed.
In addition, when heating is performed for a very short time using a thermal head, laser light, or the like, cooling (solidification) starts immediately after the completion of heating, so that a colored state can be developed.
Therefore, even if the same heating temperature and / or the same heat source is used, the color development state and the decoloration state can be arbitrarily developed by controlling the cooling rate.

Here, the reversible thermosensitive recording layer 3 has a thickness of 3 to 10 μm.
m.

The protective layer 1 contains an ultraviolet curable resin in order to make the hardness sufficient. In addition, in order to form appropriate irregularities on the surface of the protective layer 1 to prevent glare on the surface of the protective layer, prevent scratches on the surface of the protective layer, and impart self-cleaning properties of the thermal head,
It is preferable that the protective layer 1 contains silica.

Therefore, according to the embodiment of the reversible thermosensitive magnetic recording medium according to the present invention shown in FIG. 1, the opaque layer 7 contains a light-opaque pigment and a resin having active hydrogen as main components. Since the heat-resistant layer 5 contains an ultraviolet curable resin and a cross-linking agent as main components, it is possible to prevent the color of the magnetic recording layer 9 from being visually recognized by the concealing layer 7 and to form the heat-resistant layer at the time of forming the heat-resistant layer. Paint for impregnating the hiding layer,
The cross-linking agent contained as a main component in the heat-resistant layer 5 is
By reacting with a resin having active hydrogen contained as a main component in the concealing layer 7, the resin having active hydrogen contained as a main component in the concealing layer 7 is hardened, and the hardness of the concealing layer 7 is increased. The adhesiveness between the heat-resistant layer 5 and the heat-resistant layer 5 is improved, and further, the ultraviolet-curable resin contained as a main component in the heat-resistant layer 5 by irradiating the heat-resistant layer 5 with ultraviolet light is used for heating during printing and erasing. Since the resin is cured to the extent that it can sufficiently withstand pressure, the durability of the reversible thermosensitive magnetic recording medium for repeated printing and erasing can be improved.

Next, a method for manufacturing the reversible thermosensitive magnetic recording medium shown in FIG. 1 will be described. First, after forming the magnetic recording layer 9 on the base material 11, a coating containing a light-opaque pigment and a resin having active hydrogen as a main component is applied to the magnetic recording layer 9 and dried to form the concealing layer 7. To form

Thereafter, a coating containing an ultraviolet-curable resin and a crosslinking agent as main components is applied onto the concealing layer 7, dried, and cured by irradiating ultraviolet rays to form the heat-resistant layer 5.

After the heat-resistant layer 5 is formed, aging is performed immediately without forming the reversible thermosensitive recording layer 3. This aging is performed, for example, by heating to 60 ° C. for 24 hours, and the aging is performed so that the cross-linking agent contained as a main component in the heat-resistant layer 5 sufficiently cures the concealing layer 7. Therefore, the aging for which the curing is sufficient is not particularly limited to the aging under these conditions.

After the aging, a reversible thermosensitive recording layer 3 containing a leuco dye, a color-reducing agent and a resin as main components is formed.
A protective layer 1 is formed thereon.

Therefore, according to this method of manufacturing a reversible thermosensitive magnetic recording medium, when manufacturing a reversible thermosensitive magnetic recording medium having the structure shown in FIG. 1, aging is performed after forming the heat-resistant layer 5. Therefore, the cross-linking agent contained in the heat-resistant layer 5 sufficiently cures the concealing layer 7, and accordingly, the concealing layer 7
Can be made sufficiently hard, and the adhesion between the concealing layer 7 and the heat-resistant layer 5 can be improved.

[0050]

EXAMPLES Next, specific examples of the reversible thermosensitive recording medium according to the present invention will be described in comparison with comparative examples in terms of composition and evaluation of physical properties.

Examples 1 to 6 and Comparative Examples 1 to 6 described below
Reference numeral 4 denotes a structure in which a substrate, a magnetic recording layer, a concealing layer, a heat-resistant layer, a reversible thermosensitive recording layer, and a protective layer are sequentially laminated as shown in FIG. Whether or not to form the layer is changed, and further, the composition of the layer is changed.

However, in all of Examples 1 to 6 and Comparative Examples 1 to 4, only the concealing layer and the heat-resistant layer were used to change the presence or absence or the composition thereof.

Therefore, in all of Examples 1 to 6 and Comparative Examples 1 to 4, the substrate, the magnetic recording layer, the reversible thermosensitive recording layer and the protective layer are the same.

Therefore, the composition of the base material, the magnetic recording layer, the concealing layer, the heat-resistant layer, the reversible thermosensitive recording layer and the protective layer will be described below with reference to Examples 1 to 6, and Examples 2 to 6 and Comparative Example 1 will be described. With respect to Nos. 4 to 4, only the changes or changes in the concealing layer and the heat-resistant layer with respect to Example 1 will be described.

Example 1 Base Material White polyethylene terephthalate (P) having a thickness of 188 μm
ET) was used.

Magnetic Recording Layer A material having the following composition was dispersed in a ball mill for 8 hours to prepare a coating material. To this coating material, 3 parts by weight of an isocyanate-based curing agent (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added. , Coating with a wire bar, performing magnetic field alignment treatment,
Dry (100 ° C, 2 minutes) and aging (60 °
C, 96 hours) to form a dry film thickness of 10 μm.・ Barium ferrite (made by Toda Kogyo Co., Ltd., trade name MC)
-127) 100 parts by weight ・ Carbon black (manufactured by Mitsubishi Chemical Corporation, trade name MA1)
00) 2 parts by weight ・ Polyester resin (manufactured by Toyobo Co., Ltd., trade name: Byron 200) 20 parts by weight ・ Polyester resin (manufactured by Toyobo Co., Ltd., trade name: Byron 500) 5 parts by weight ・ Solvent (MEK: toluene: MIBK = 1: 2: 1 mixture) 130 parts by weight

Hiding layer A material having the following composition was stirred with a stirrer for 30 minutes to obtain a coating, coated with a wire bar, and dried (100 ° C, 1 ° C).
Min) and a dry film thickness of 2 μm was formed. 45 parts by weight of aluminum paste (trade name MH8803, manufactured by Asahi Kasei Kogyo Co., Ltd.) 55 parts by weight of nitrocellulose resin (trade name: BT-SL, manufactured by Asahi Kasei Kogyo Co., Ltd.) Solvent (MEK: toluene = 1: 1 mixture) 200 parts by weight

Heat-resistant layer A paint having the following composition was applied with a wire bar, dried (100 ° C., 1 minute), and irradiated with ultraviolet rays (160 W / cm).
Aging (60 °) after 3 lamps, 30 m / min)
C, 24 hours) to form a dry film thickness of 1 μm.・ Ultraviolet curable resin (Dainippon Ink & Chemicals, Inc.)
Product name Unidick 17-806, urethane acrylate resin, acid value, below the measurement limit) 50 parts by weight-Photopolymerization initiator (trade name Irgacure 184, manufactured by Ciba Geigy Co., Ltd.)-2 parts by weight-Isocyanate-based crosslinking agent (Japan) Polyurethane Industry Co., Ltd., trade name Coronate L) 10 parts by weight Solvent (MEK: toluene = 1: 1 mixture) 200 parts by weight

Reversible thermosensitive recording layer A material having the following composition was dispersed in a paint shaker for 1 hour to obtain a paint, coated with a wire bar, and dried (80 ° C).
C, 1 minute) to form a dry film thickness of 6 μm. -Leuco dye (3-diethylamino-6-methyl-7-
Anilino Fluoran, manufactured by Yamamoto Kasei Co., Ltd., trade name OD
B) 1 part by weight ・ Sensitive color reducing agent (N- (4-hydroxyphenyl) -N′-
n-octadecyl urea, JP-A-6-210954) 3
Parts by weight-Acrylic resin (Mitsubishi Rayon Co., Ltd., trade name BR-
83) 4 parts by weight Solvent (MEK: toluene = 1: 1 mixture) 50 parts by weight

Protective Layer A material having the following composition was dispersed in a paint shaker for 10 minutes to obtain a paint, which was then coated with a wire bar and dried (80).
° C, 1 minute), UV irradiation (160W / cm3 lamp, 3
(0 m / min), and then formed into a dry film thickness of 1 μm.・ Ultraviolet curable paint (Dainippon Ink and Chemicals Co., Ltd.)
Brand name C3-374) 100 parts by weight ・ Silica (P-603, manufactured by Mizusawa Chemical Co., Ltd.) 5
Parts by weight solvent (MEK: toluene = 1: 1 mixed solvent) 150
Parts by weight

Next, the second embodiment is different from the first embodiment.
The changes or changes in Comparative Examples 1 to 6 and Comparative Examples 1 to 4 will be described below.

Example 2 In Example 1, the nitrocellulose resin used as the coating material for the concealing layer was changed to a polyester resin (manufactured by Toyobo Co., Ltd., trade name: Byron 200). Otherwise, it is the same.

Example 3 In Example 1, the amount of the isocyanate-based crosslinking agent in the paint used for the heat-resistant layer was changed from 10 parts by weight to 2 parts by weight. Other than that is the same.

Example 4 In Example 1, the amount of the isocyanate-based crosslinking agent in the paint used for the heat-resistant layer was changed from 10 parts by weight to 50 parts by weight. Other than that is the same.

(Example 5) In Example 1, an ultraviolet-curable resin used for the heat-resistant layer (Dainippon Ink Chemical Industry Co., Ltd.)
(Trade name: Unidick 17-806, urethane acrylate resin, acid value, below the measurement limit), UV curable resin (Dainippon Ink & Chemicals, Inc., trade name: Unidick V-5502, epoxy acrylate) Resin, acid value, 3KOHmg / g or less)
The weight was changed from 40 parts by weight to 40 parts by weight. Other than that is the same.

Example 6 In Example 1, an isocyanate-based crosslinking agent used for the heat-resistant layer was replaced with a carbodiimide-based crosslinking agent (Carbodilite V-0, manufactured by Nisshinbo Industries, Inc.).
1), and the weight part was changed from 10 parts by weight to 8 parts by weight. Other than that is the same.

Comparative Example 1 In Example 1, the heat-resistant layer was omitted. Other than that is the same.

Comparative Example 2 In Example 1, except for the heat-resistant layer, 10 parts by weight of an isocyanate-based curing agent (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to the coating material used for the hiding layer. . Other than that is the same.

(Comparative Example 3) In Example 1, the isocyanate-based crosslinking agent was removed from the paint used for the heat-resistant layer. Other than that is the same.

(Comparative Example 4) In Example 1, an isocyanate-based crosslinking agent (Nippon Polyurethane Industry Co., Ltd.)
Was added to the heat-resistant layer to remove the isocyanate-based crosslinking agent. Other than that is the same.

With respect to the reversible thermosensitive magnetic recording media of Examples 1 to 6 and Comparative Examples 1 to 4 formed as described above, the results of comparison of the background density, print density, and erase density in the initial state were as follows. And 5 using a thermal head
Table 1 shows the comparison results of the background density, the print density, the erase density, and the state of the print erase portion after printing and erasing 0 times.

[0072]

[Table 1]

Here, using a thermal head having a dot density of 8 dots / mm, a printing energy of 0.50 mJ / d
ot and erasing energy were set to 0.25 mJ / dot. For the density measurement, a reflection densitometer Macbeth RD-918 was used.

Table 1 shows the initial state and the state after printing and erasing have been performed 50 times. In addition, the display in the evaluation column indicates the overall evaluation of the background density, the print density, the erase density, and the state of the print erase portion after performing printing and erasing 50 times. Indicates, ○
Indicates good, and x indicates bad. First, the comparison result of the initial state will be described.

In the initial state, there was no significant difference in the background density, print density and erase density in each of Examples 1 to 6 and Comparative Examples 1 to 4.

Next, the state after printing and erasing are repeated 50 times will be described. First, there was no remarkable difference in the background density in Examples 1 to 6 and Comparative Examples 1 to 4.

Regarding the print density, in Examples 1 to 6 and Comparative Example 4, no remarkable difference occurred, but in Comparative Examples 1 to 3, the print density decreased. this is,
In Examples 1 to 6 and Comparative Example 4, the hardness of the concealing layer was sufficient, indicating that the coating film did not deteriorate even after printing and erasing were repeated 50 times. 1 to
In No. 3, there was no heat-resistant layer, the concealing layer was not cured at all (Comparative Example 1), the concealing layer was cured but there was no heat-resistant layer (Comparative Example 2), or the heat-resistant layer contained a crosslinking agent. No (Comparative Example 3) indicates that after printing and erasing were repeated 50 times, the coating film deteriorated, and that proper printing was not performed.

As for the erase density, there is no significant difference in Examples 1 to 6 and Comparative Example 4 in the same manner as in the above-described print density comparison results. An increase in concentration has occurred. This is the same as Example 1
6, and in Comparative Example 4, the hardness of the concealing layer was sufficient, indicating that no deterioration of the coating film occurred even after repeating printing and erasing 50 times. In Comparative Examples 1 to 3, No heat-resistant layer, no concealment layer cured (Comparative Example 1), concealment layer cured, but no heat-resistant layer (Comparative Example 2), or no heat-resistant layer containing cross-linking agent (Comparative Example 2) Comparative Example 3) Therefore, after printing and erasing were repeated 50 times, the coating film deteriorated, indicating that proper erasing was not performed.

The state of the print erased portion is described in Example 1.
In Nos. To 6, there is no abnormality, but in Comparative Examples 1 to 4, the coating film destruction occurs in Comparative Examples 1 and 2, the coating film deviates in Comparative Example 3, and the concealing layer in Comparative Example 4 Delamination has occurred between the heat-resistant layer and the heat-resistant layer.

This is because in Examples 1 to 3 where no abnormality occurred.
No. 6 indicates that the hardness of the concealing layer is sufficient, and that the adhesion between the concealing layer and the heat-resistant layer is also sufficient.

In Comparative Example 1, since the concealing layer was not cured at all, the hardness of the concealing layer was insufficient, and the coating film was broken by heat and shearing force generated by the thermal head.

In Comparative Example 2, although the concealing layer was cured, the heat-resistant layer for protecting the concealing layer was removed, so that the concealing layer was durable enough to withstand 50 times of repeated printing and erasing. No destruction of the coating film, such as displacement of the concealing layer and cracks as a whole, occurred.

In Comparative Example 3, the UV-curable resin in the heat-resistant layer absorbed by the concealing layer was not completely cured, and thus the concealing layer was not sufficiently cured, resulting in displacement of the coating film.

In Comparative Example 4, since the concealing layer was cured by adding a crosslinking agent and the heat-resistant layer was an ultraviolet-curable resin, the concealing layer and the heat-resistant layer had sufficient hardness, but the concealing layer was hardened. Since the heat-resistant layer was formed after being completely cured, the adhesion between the concealing layer and the heat-resistant layer was insufficient, and delamination between the heat-resistant layer and the concealing layer occurred.

Accordingly, from the comparison results shown in Table 1, the heat-resistant layer contains an ultraviolet-curable resin and an isocyanate-based cross-linking agent or a carbodiimide-based cross-linking agent as a cross-linking agent as main components, and the heat-resistant layer has a heat-resistant layer. By including a resin having active hydrogen that reacts with a crosslinking agent contained as a main component in the layer, the hardness of the concealing layer and the heat-resistant layer is increased, and the adhesion between the concealing layer and the heat-resistant layer is improved. It can be seen that good results can be obtained after printing and erasing are repeated many times.

[0086]

As apparent from the above description, according to the present invention, at least a magnetic recording layer for performing magnetic recording, a concealing layer for concealing coloring of the magnetic recording layer, In a reversible thermosensitive magnetic recording medium in which a reversible thermosensitive recording layer and a protective layer each containing a leuco dye, a color-developing agent and a resin as main components are sequentially laminated, a resin having a light-opaque pigment and active hydrogen in a hiding layer is used. By containing a heat-resistant layer containing a UV-curable resin and a cross-linking agent as a main component between the concealing layer and the reversible thermosensitive recording layer, the concealing layer allows the magnetic recording layer to be visually colored. When the heat-resistant layer paint is impregnated into the heat-resistant layer when the heat-resistant layer is formed, the cross-linking agent contained as a main component in the heat-resistant layer reacts with the active hydrogen-containing resin contained as the main component in the mask layer. Conceal The hardness of the heat-resistant layer can be increased by irradiating ultraviolet rays to the heat-resistant layer, while increasing the hardness of the heat-resistant layer and the concealing layer. Can be provided.

Further, when the resin having active hydrogen is any of vinyl chloride / vinyl acetate / maleic anhydride copolymer, vinyl chloride / vinyl acetate / vinyl alcohol copolymer or nitrocellulose, the heat-resistant layer A reversible thermosensitive magnetic recording medium capable of increasing the hardness of the concealing layer by appropriately reacting a crosslinking agent contained as a main component with the resin having active hydrogen can be provided.

Since the ultraviolet curable resin contained as a main component in the heat-resistant layer has an acid value of 5 KOHmg / g or less, the dye contained as a main component in the reversible thermosensitive recording layer and the dye contained as a main component in the heat-resistant layer are used. It is possible to provide a reversible thermosensitive magnetic recording medium capable of suppressing unnecessary reaction with the ultraviolet curable resin.

The thickness of the heat-resistant layer is 0.1 to 10 μm
Therefore, it is possible to provide a reversible thermosensitive magnetic recording medium that can follow the bending of the reversible thermosensitive magnetic recording medium and can prevent the occurrence of cracks.

Furthermore, after the step of sequentially laminating the magnetic recording layer, the concealing layer, and the heat-resistant layer on the base material, an aging step of performing aging is provided.
Since the cross-linking agent contained as a main component in the heat-resistant layer sufficiently cures the concealing layer, and the reaction with the resin having active hydrogen contained as a main component in the concealing layer can be appropriately advanced, the concealing layer It is possible to provide a method for producing a reversible thermosensitive magnetic recording medium, which can harden and make the adhesion between the heat-resistant layer and the concealing layer sufficient.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of a reversible thermosensitive magnetic recording medium according to the present invention.

FIG. 2 is a schematic sectional view of a conventional thermosensitive magnetic recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Protective layer 3 Reversible thermosensitive recording layer 5 Heat resistant layer 7 Concealment layer 9 Magnetic recording layer 11 Substrate

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B41M 5/18 BZ 101F (72) Inventor Minoru Fujita 4--12-12 Koishikawa, Bunkyo-ku, Tokyo Kyodo Printing Co., Ltd.

Claims (5)

[Claims] 1. A base material comprising at least a magnetic recording layer for performing magnetic recording, a concealing layer for concealing coloring of the magnetic recording layer, a leuco dye, a color-reducing agent and a resin as main components. The reversible thermosensitive recording layer, and a reversible thermosensitive magnetic recording medium in which a protective layer is sequentially laminated, wherein the concealing layer contains a resin having a light-opaque pigment and active hydrogen as main components, and the concealing layer and the reversible A reversible thermosensitive magnetic recording medium, wherein a heat-resistant layer containing at least an ultraviolet-curable resin and a crosslinking agent as main components is formed between the thermosensitive recording layer and the thermosensitive recording layer. 2. The resin having active hydrogen is one of a vinyl chloride / vinyl acetate / maleic anhydride copolymer, a vinyl chloride / vinyl acetate / vinyl alcohol copolymer, and nitrocellulose. The reversible thermosensitive magnetic recording medium according to claim 1. 3. The ultraviolet-curable resin has an acid value of 5 KO.
Hmg / g or less.
4. The reversible thermosensitive magnetic recording medium according to 1. 4. The heat-resistant layer has a thickness of 0.1 to 10 μm.
The reversible thermosensitive magnetic recording medium according to any one of claims 1 to 3, wherein 5. A magnetic recording layer forming step of forming a magnetic recording layer for performing magnetic recording on a base material; and a resin having a light-impermeable pigment and active hydrogen on the magnetic recording layer. A concealing layer forming step of forming a concealing layer by applying a paint containing as a coating, and applying a paint containing a UV curable resin and a cross-linking agent as main components on the concealing layer, drying, and drying. Irradiating and curing, heat-resistant layer forming step of forming a heat-resistant layer, After forming the heat-resistant layer, aging execution step of performing aging, After performing the aging, on the heat-resistant layer, reversible Manufacturing a reversible thermosensitive magnetic recording medium, comprising: a reversible thermosensitive recording layer forming step of forming a reversible thermosensitive recording layer; and a protective layer forming step of forming a protective layer on the reversible thermosensitive recording layer. Method.