JP2002036721A - Heat sensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording medium which has no problem of corrosion being caused by sweat, etc., and whose face can be matted, and moreover, which does no need an underlayer to smooth the surface of a magnetic recording layer even when a heat sensitive recording layer is to be formed on the magnetic recording layer. SOLUTION: The heat sensitive recording medium is characterized by that a heat sensitive recording layer is formed on at least one face of a non-magnetic base. The heat sensitive recording layer contains organic micro hollow particles and resin. Each of the hollow particles has an outer diameter of 0.2 to 1 μm and a ratio between an inner diameter and outer diameter of 0.4 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording medium, and more particularly to a heat-destructible heat-sensitive recording medium.

[0002]

2. Description of the Related Art In general, a write-once thermosensitive magnetic recording medium has a magnetic recording layer and a thermosensitive recording layer made of a nonmagnetic metal thin film formed on at least one surface of a nonmagnetic substrate. Magnetic recording can be performed in the same manner as a normal magnetic card, and visual information such as characters can be thermally recorded using a thermal recording layer.

[0003] Here, the above-described thermal recording is performed by heating the thermal recording layer in the pattern area when heated by a pattern such as a character shape by a thermal head or a laser beam. By the nonmagnetic metal that constitutes melting and aggregating into granules,
A break is formed in the metal thin film, and the base color is exposed to the outside through the break to produce a visual difference from the metallic luster of the thin film portion.

[0004]

However, in these known heat-sensitive recording media, the heat-sensitive recording layer for recording the above-mentioned visual information has a low melting point non-magnetic metal thin film, for example, Sn.
Or, since it is composed of a thin film of Sn alloy or the like, usually a vapor-deposited film formed by a vacuum vapor deposition method, even when an appropriate protective layer made of a resin film is formed on this thin film, the heat-sensitive recording by the above-described method causes a break. There was a problem of corrosion due to sweat etc. through the boundary of the part. There was also a problem that a matte surface having no metallic luster cannot be obtained. Further, when a heat-sensitive recording layer made of a metal thin film is formed on a magnetic recording layer like a heat-sensitive magnetic recording medium, it is necessary to provide an underlayer for smoothing the surface of the magnetic recording layer.

According to the present invention, in view of such circumstances, the heat-sensitive recording layer has no problem of corrosion due to sweat or the like, and can have a matte surface. Further, the heat-sensitive recording layer is formed on the magnetic recording layer. It is an object of the present invention to provide a thermosensitive recording medium that does not require an underlayer for smoothing the surface of a magnetic recording layer even when formed.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies on the above object and as a result, when the heat-sensitive recording layer is constituted by a layer in which organic hollow fine particles are dispersed and bound in a resin, this layer is Under normal conditions, it has an opaque white color, but when partially heated with a thermal head or the like, the organic hollow microspheres in this part are deformed or dissolved to become transparent, and develop a color such as a colored layer on the base. Desired printing becomes possible,
With this printing method, there is no problem of corrosion due to sweat or the like as in the past, and it is also possible to use a matte surface, and even if a heat-sensitive recording layer is formed on the magnetic recording layer, the surface of the magnetic recording layer It was found that there was no need to provide an underlayer for smoothing the image, and the present invention was completed.

That is, the present invention relates to a heat-sensitive recording medium characterized in that a heat-sensitive recording layer containing organic hollow microspheres and a resin is formed on at least one surface of a nonmagnetic substrate. The outer diameter of the sphere is 0.2-1μ
m, the thermosensitive recording medium having a ratio of inner diameter to outer diameter of 0.4 or more, the thermosensitive recording medium comprising a colored layer formed between the nonmagnetic substrate and the thermosensitive recording layer, the nonmagnetic The heat-sensitive recording medium in which the substrate is transparent and a heat-sensitive recording layer is formed on one surface of the transparent substrate and a colored layer is formed on the other surface, and the heat-sensitive medium between the non-magnetic substrate and the heat-sensitive recording layer, or On the surface opposite to the surface on which the recording layer is formed, a magnetic recording layer is formed on the heat-sensitive recording medium, the magnetic recording layer is also provided with a colored layer, the heat-sensitive recording medium is further protected on the heat-sensitive recording layer. The present invention relates to the thermosensitive recording medium having a layer.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The non-magnetic substrate in the present invention is a non-magnetic soft synthetic resin film having a thickness of usually about 150 to 250 μm, for example, a polyester film,
For example, a polyvinyl chloride film is used. In the present invention, a heat-sensitive recording layer containing organic hollow microspheres and a resin is formed on at least one surface of the nonmagnetic substrate. The formation method is not particularly limited, but usually, a heat-sensitive paint containing organic hollow microspheres and a resin is prepared, applied to a non-magnetic substrate, and dried.

The hollow organic microspheres may be hollow microspheres made of an organic material such as an organic polymer, and the material composition is not particularly limited. A preferred material is polystyrene seed. Then, methyl methacrylate and a polyfunctional monomer such as divinyl benzene are dissolved, and this is subjected to emulsion polymerization using a water-soluble polymerization initiator, so that methyl methacrylate and divinyl benzene are dissolved. Organic hollow microspheres obtained by copolymerization can be exemplified.

The outer diameter (particle diameter) and the ratio of the inner diameter to the outer diameter of the organic hollow microspheres are preferably such that the outer diameter is 0.2 to 1 μm and the ratio of the inner diameter to the outer diameter is 0.4 or more. More preferably, the outer diameter is 0.3 to 0.7 μm, and the ratio of the inner diameter to the outer diameter is 0.5 or more. The outer diameter is 0.3-0.5μ
m, the ratio of the inner diameter to the outer diameter is more preferably 0.6 or more. When the outer diameter is less than 0.2 μm, the whiteness decreases. When the outer diameter exceeds 1 μm, a large amount of organic hollow microspheres is required to obtain the same whiteness. Also, even in the range of the above outer diameter,
When the ratio between the inner diameter and the outer diameter is less than 0.4, the whiteness decreases. The production of organic hollow microspheres having a ratio of inner diameter to outer diameter of more than 0.8 becomes difficult, and the upper limit of the ratio of inner diameter to outer diameter of organic hollow microspheres that can be practically used is 0.8.

[0011] Commercially available organic hollow microspheres include JSR
“SX866 (A)”, “SX864 (B)”,
"SX865 (B)" and "OP42" and "OP62" manufactured by Rom & Haas. These organic hollow microspheres have an outer diameter of 0.2 to 1 μm and a ratio of the inner diameter to the outer diameter of 0.4 or more. Among these, “SX866 (A)”, “SX864 (B)”, “SX
865 (B) "has a high melting temperature, and is suitable as a heat-sensitive recording medium for applications requiring heat resistance, such as highway cards. Further, "OP42" and "OP62" manufactured by Rom & Haas Co., Ltd. have a relatively low melting temperature, and are suitable for use as a heat-sensitive recording medium such as a prepaid card used in a normal environment. .

The amount of the organic hollow microspheres used in the heat-sensitive paint is
It is preferably from 10 to 35% by weight, more preferably from 20 to 35% by weight, even more preferably from 20 to 30% by weight. If the amount is less than 10% by weight, the whiteness of the heat-sensitive recording layer decreases,
If it exceeds 35% by weight, the viscosity becomes too high, and it becomes difficult to form a heat-sensitive recording layer having a predetermined thickness, and the adhesion strength of the heat-sensitive recording layer to a non-magnetic substrate decreases.

The resin for dispersing and binding the organic hollow microspheres includes:
Depending on the solvent used, a resin soluble in this solvent is used. Specifically, urethane resin, α-olefin-maleic acid copolymer resin, acrylic resin, styrene-acrylic copolymer resin, rosin resin, vinyl acetate resin, polyvinyl butyral resin, vinyl chloride resin, polyamide There are a resin and an epoxy resin. Among these, as a resin having high solubility in a ketone / alcohol mixed solvent,
Urethane resin, α-olefin-maleic acid copolymer resin, acrylic resin, styrene-acrylic copolymer resin,
Vinyl acetate resin, polyvinyl butyral resin and the like are preferably used.

[0014] Commercial products of such resins include, for example,
Mitsubishi Rayon “PB121”, “PB383”,
“PB122”, “PB123”, “PB204”,
Acrylic resin such as “PB2008” (acid value 10 mg KO
H / g has good dispersibility), and “G7” manufactured by Kyoei Chemical Co., Ltd.
Α-olefin-maleic anhydride copolymer partial ester such as “00” (effective for improving flexibility), “E700”, “E755”, “E920”, “E” manufactured by Takeda Pharmaceutical Company Limited.
Urethane resin such as “790” and “E760” (adhesiveness,
Effective for improving whiteness).

The amount of the resin used is preferably 2 to 20% by weight, more preferably 3 to 15% by weight,
13% by weight is more preferred. If it is less than 2% by weight, the adhesion to the underlying colored layer or the like will be poor, and if it exceeds 20% by weight, the whiteness of the heat-sensitive recording layer will be reduced or the viscosity will be too high to make application difficult.

In the heat-sensitive paint, the solvent used is an organic hollow microsphere “SX866” manufactured by JSR Corporation.
(A) "," SX864 (B) "," SX865 "
(B) ", methyl ethyl ketone,
A ketone solvent such as methyl isobutyl ketone, an alcohol solvent such as ethyl alcohol and isopropyl alcohol, and an aromatic hydrocarbon solvent such as toluene are used alone or as a mixture. As organic hollow microspheres, “OP42” and “OP6” manufactured by Rom & Haas Co., Ltd.
When using “2”, etc., since these are easily soluble in ketone solvents and aromatic hydrocarbon solvents, water or alcohol solvents such as ethyl alcohol and isopropyl alcohol may be used alone or as a mixture. To use. For thermal paint,
In addition to the above components, various additives can be blended if necessary.

The heat-sensitive recording layer formed on the non-magnetic substrate as described above diffusely reflects incident light by replacing the solvent permeating the hollow portions of the organic hollow microspheres with air during the coating and drying steps. To give an opaque white color. When the organic hollow microspheres are heated and printed at a temperature higher than the softening or melting temperature of the organic hollow microspheres with a thermal head or the like, the organic hollow microspheres are deformed or melted, and the printed portion becomes transparent and develops a color such as a colored layer on the base. At this time, the printing (heating) energy can be selected according to the type of the organic hollow microspheres.
"SX866 (A)", "SX864" manufactured by R company
(B) "," SX865 (B) "or the like having a high melting temperature, high energy printing is performed. On the other hand, Rom &Haas" OP42 "," OP62 "or the like having a low melting temperature. Good printing quality can be obtained by selecting low energy printing.

In order to better exhibit such color printing performance, the amount of the organic hollow microspheres in the heat-sensitive recording layer is 20
-80% by weight is preferable, 25-75% by weight is more preferable, 35-75% by weight is further preferable, and 45-75% by weight is preferable.
% Is most preferred. If it is less than 20% by weight, the whiteness is insufficient, and if it exceeds 80% by weight, the strength of the heat-sensitive recording layer becomes insufficient. The thickness of the heat-sensitive recording layer is 0.5 to 30 μm.
Is preferable, 1 to 20 μm is more preferable, and 1 to 15 μm
m is more preferred, and 1 to 10 μm is most preferred.
If it is less than 0.5 μm, the whiteness is insufficient, and if it exceeds 30 μm, the energy required for printing becomes too large, and the life of the thermal head or the like becomes short.

The underlayer of the heat-sensitive recording layer must be colored. Therefore, a colored substrate is used as the non-magnetic substrate, or more preferably, a colored layer is formed between the non-magnetic substrate and the heat-sensitive recording layer. Alternatively, when the nonmagnetic substrate is transparent, it is desirable to form a heat-sensitive recording layer on one surface of the transparent substrate and form a colored layer on the opposite surface. The colored layer is formed of one or more resins selected from polyurethane resins, butyral resins, vinyl chloride resins, polyester resins, acrylic resins, etc., and black pigments such as carbon black. It is formed by applying a color paint obtained by mixing color pigments such as cyan, mageenda, yellow and the like, followed by drying.

Although the thickness of the colored layer is not particularly limited, it is usually 0.1 mm in order to better exhibit the original effect of the colored layer.
The thickness is preferably 5 μm or more. In particular, when a magnetic recording layer described later is formed between the nonmagnetic substrate and the heat-sensitive recording layer, the thickness is preferably 0.5 to 4 μm, and more preferably 1 to 2 μm. If it exceeds 4 μm, the total thickness of the heat-sensitive recording layer and the protective layer described later becomes too large, and the signal from the magnetic recording layer may be weak. For the same reason, the total thickness of the heat-sensitive recording layer and the protective layer is preferably 3 to 10 μm.

In the present invention, at least one magnetic recording layer is formed between the non-magnetic substrate and the heat-sensitive recording layer or on the surface of the non-magnetic substrate opposite to the surface on which the heat-sensitive recording layer is formed. A thermosensitive recording medium capable of performing magnetic recording in addition to thermosensitive recording using a layer may be used. The magnetic recording layer comprises a magnetic powder,
Even a magnetic coating film having a thickness of usually about 10 to 20 μm formed by applying and drying a magnetic paint containing a binder and various additives as necessary is formed by a thin film forming means such as a vacuum evaporation method or a sputtering method. The thickness to be formed is 0.1-0.
It may be a magnetic metal thin film of about 3 μm.

The magnetic powder for forming the magnetic coating film includes B
a, Sr, Ca, Pb ferrite, γ-Fe ₂ O ₃ , F
O ₃ -based magnetic powder composed of e ₃ O ₄ , CrO ₂ , γ-Fe ₂ O ₃ containing Co, Fe, Co, Cr, Ni, alloys of these, and a small amount of other metal or non-metal elements A metal magnetic powder made of an alloy or the like is used. As the material for forming the magnetic metal thin film, the same metal or alloy as the constituents of the metal magnetic powder is used. As a binder for forming the magnetic coating film, a polyurethane resin, a butyral resin, a vinyl chloride resin, a polyester resin, an acrylic resin, etc. may be used alone or in combination.
It is used by mixing more than one kind.

The magnetic recording layer usually functions as a colored layer. However, in order to further enhance the function as a colored layer, the magnetic recording layer is colored black by, for example, including a black pigment such as carbon black in the magnetic coating film. This may enhance the function as a colored layer. Of course, even when the colored magnetic recording layer is formed, the colored layer may be formed separately from the magnetic recording layer. When a colored magnetic recording layer or an uncolored magnetic recording layer is formed, the positional relationship between the magnetic recording layer and the colored layer with respect to the nonmagnetic substrate can be arbitrarily selected according to the purpose of the formation.

In the present invention, a protective layer can be formed on the heat-sensitive recording layer in order to improve the durability of the heat-sensitive recording layer. This protective layer is made of a material having transparency and heat resistance such as silicone, acrylic, fluorine, epoxy, etc. An organic thin film of 5 μm, preferably 0.5 to 3 μm is used. In addition, Si
It is made of a material such as O ₂ , SiO, TiO ₂ , Al ₂ O ₃ and has a thickness of 0.2 to 1.5 μm, preferably 0.5 to 1 μm.
A μm inorganic thin film is also used. A similar protective layer can be formed on the exposed magnetic recording layer provided on the opposite side of the nonmagnetic substrate.

In the present invention, in addition to the above-mentioned layers, if necessary, for the purpose of improving adhesiveness and recording performance,
A suitable intermediate layer having a thickness of 0.1 to 5 μm, preferably 0.5 to 3 μm may be provided between any of the above layers.
As a material for forming such an intermediate layer, one or more resins such as a polyurethane resin, a butyral resin, a vinyl chloride resin, a polyester resin, and an acrylic resin are used.

Further, in the present invention, by dissolving or dispersing additives such as a fluorescent dye, yellow magenta, a cyan dye and a pigment in the heat-sensitive paint, and forming a heat-sensitive recording layer from the heat-sensitive paint, By giving a unique color-forming function by the above-mentioned additive contained in the heat-sensitive recording layer,
Various modifications can be made.

[0027]

The present invention will now be described more specifically with reference to examples. However, the present invention is not limited only to the following examples. In the following, “parts” means “parts by weight”.

Example 1 Ba ferrite magnetic powder (average particle diameter 0.8 μm) 80
Part, polyurethane resin (“Pandex T5201” manufactured by Dainippon Ink and Chemicals, Inc.), 17 parts, trifunctional polyisoiane
Compound ("Coronate L" manufactured by Nippon Polyurethane)
3 parts, carbon black 4 parts, toluene 260 parts and cyclohexanone 260 parts were uniformly mixed and dispersed to prepare a magnetic paint.

Separately, organic hollow microspheres (J
“SX866 (A)” manufactured by SR Company, outer diameter 0.36 μm,
100 parts of an acrylic resin ("Dianal PB121" manufactured by Mitsubishi Rayon Co., Ltd., acid value 180 mg KOH / g) 40 parts of an acrylic resin (ratio of inner diameter to outer diameter 0.67), urethane resin solution (manufactured by Takeda Pharmaceutical Co., Ltd.) 20 parts of Taketake E920), 300 parts of methyl isobutyl ketone and 300 parts of ethyl alcohol were mixed and dispersed in a ball mill for 3 hours to prepare a heat-sensitive paint.

As the non-magnetic substrate, a polyethylene terephthalate film having a thickness of 188 μm was used. On the non-magnetic substrate, the above-mentioned magnetic paint is applied by a gravure coating method, and dried to form a colored magnetic recording layer having a thickness of 15 μm. It was applied and dried to form a heat-sensitive recording layer having a thickness of 2 μm. On this heat-sensitive recording layer, a protective coating made of an ultraviolet-curable acrylic-modified epoxy resin is applied and dried to form a protective layer having a thickness of 2 μm. Was prepared.

Example 2 As an organic hollow microsphere, "SX866" manufactured by JSR Corporation was used.
"SX864 (B)" manufactured by JSR in place of "(A)"
(Outer diameter 0.55 μm, ratio of inner diameter to outer diameter 0.50) 10
A thermosensitive recording medium capable of thermosensitive recording and magnetic recording was produced in the same manner as in Example 1 except that 0 part was used.

Example 3 As an organic hollow microsphere, "SX866" manufactured by JSR Corporation was used.
"SX865 (B)" made by JSR in place of (A) "
(Outer diameter 0.55 μm, ratio of inner diameter to outer diameter 0.40) 10
A thermosensitive recording medium capable of thermosensitive recording and magnetic recording was produced in the same manner as in Example 1 except that 0 part was used.

Example 4 While stirring 156 parts of water and 20 parts of isopropanol,
12 parts of ammonia water (28% by weight of ammonia), 60 parts of styrene-acrylic copolymer resin solution ("Jillon Creel 52" manufactured by Jillson & Jillson, solid content 60% by weight), 12 parts of carbitol, organic 140 parts of a hollow microsphere dispersion liquid (“Ropeg OP42” manufactured by Rom Hass, solid content 40% by weight, outer diameter of organic hollow microspheres 0.42 μm, ratio of inner diameter to outer diameter about 0.6) Were sequentially added little by little to prepare a heat-sensitive paint. A heat-sensitive recording medium capable of heat-sensitive recording and magnetic recording was produced in the same manner as in Example 1 except that this heat-sensitive paint was used.

Comparative Example 1 A magnetic recording layer having a thickness of 15 μm was formed on a polyethylene terephthalate film having a thickness of 188 μm as a nonmagnetic substrate in the same manner as in Example 1. On this magnetic recording layer, a modified acrylic resin (“VH311” manufactured by Washin Chemical Co., Ltd.)
(Clear B)), 100 parts of an isocyanate compound ("VH311 Clear A" manufactured by Wasin Chemical Co.) and 300 parts of methyl ethyl ketone,
After drying, an underlayer having a thickness of 2 μm was formed. On this underlayer, a thermosensitive recording layer composed of a Sn thin film having a thickness of 50 nm was formed by a vacuum evaporation method.

Next, a polyurethane resin ("Pandex T520" manufactured by Dai Nippon Ink Co., Ltd.) was formed on the heat-sensitive recording layer.
1)) 5 parts, 1 part of a trifunctional polyisoyanate compound ("Coronate L" manufactured by Nippon Polyurethane Co., Ltd.), 45 parts of ethyl acetate and 45 parts of toluene
After drying, an intermediate layer having a thickness of 2 μm was formed. Finally,
A protective coating composed of an ultraviolet-curable acrylic-modified epoxy resin was applied thereon and dried to form a protective layer having a thickness of 2 μm, thereby producing a thermosensitive recording medium.

With respect to each of the heat-sensitive recording media of Examples 1 to 4 and Comparative Example 1, the quality of printing by heating printing was examined. In Examples 1 to 3 and Comparative Example 1, printing was performed by heating with a high energy of 25 kJ / m ² (25 mJ / mm ² ) using a thick film printer. In the fourth embodiment, 15 k
Heat printing was performed at a low energy of J / m ² (15 mJ / mm ² ). The quality of the print quality was evaluated by the following four grades. ◎: Very good printing was possible ○: Almost good printing was possible △: Printing was somewhat unclear ×: Almost no printing was possible

After the evaluation of the printing quality, the printed matter was immersed in an artificial sweat solution and examined for corrosion after standing for 24 hours.
Further, it was determined whether or not each of the heat-sensitive recording layers could be made a matte surface. The results are shown in Table 1.

[0038]

As is clear from the results in Table 1 above, in the heat-sensitive recording media of Examples 1 to 4 of the present invention, high energy printing (Examples 1 to 4) was performed according to the type of the organic hollow microsphere used. 3) and low energy printing (Example 4)
Good printing quality was obtained, there was no problem of corrosion by artificial sweat liquid after printing, and a matte surface could be obtained. On the other hand, in the conventional thermosensitive recording medium using a metal thin film as the thermosensitive recording layer, good printing quality was obtained by high energy printing, but corroded by artificial sweat liquid after printing.
Further, it has a metallic luster and cannot be used as a matte surface.

The thermal recording media of Examples 1 to 4
Since the magnetic recording layer is colored substantially black including carbon black, which is a black pigment, it functions as a base coloring layer of the heat-sensitive recording layer, and the above-described good heating printing was performed. Due to the presence of the recording layer, magnetic recording utilizing this was also successfully performed.

[0041]

As described above, according to the present invention, the heat-sensitive recording layer containing the organic hollow microspheres and the resin is formed on at least one surface of the non-magnetic substrate. There is no problem of corrosion due to, for example, it is possible to have a matte surface, and even when a heat-sensitive recording layer is formed on the magnetic recording layer, an underlayer for smoothing the surface of the magnetic recording layer is provided. An unnecessary thermosensitive recording medium can be provided.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Seiji Watani 1-88 Ushitora, Ibaraki-shi, Osaka F-term in Hitachi Maxell Co., Ltd. (Reference) 2C005 HA06 HA09 HA10 JA01 JC03 KA27 2H111 HA07 HA18 HA35

Claims (7)

[Claims] 1. A heat-sensitive recording medium characterized in that a heat-sensitive recording layer containing organic hollow microspheres and a resin is formed on at least one surface of a nonmagnetic substrate. 2. An organic hollow microsphere having an outer diameter of 0.2 to 1 μm.
2. The heat-sensitive recording medium according to claim 1, wherein the ratio between m and the inner diameter and the outer diameter is 0.4 or more. 3. The thermosensitive recording medium according to claim 1, wherein a colored layer is formed between the nonmagnetic substrate and the thermosensitive recording layer. 4. The heat-sensitive recording medium according to claim 1, wherein the non-magnetic substrate is transparent, and a heat-sensitive recording layer is formed on one surface of the transparent substrate and a colored layer is formed on the other surface. 5. The magnetic recording layer according to claim 1, wherein a magnetic recording layer is formed between the non-magnetic substrate and the heat-sensitive recording layer or on a surface of the non-magnetic substrate opposite to the surface on which the heat-sensitive recording layer is formed. The heat-sensitive recording medium according to the above. 6. The magnetic recording layer also serves as a colored layer.
2. The heat-sensitive recording medium according to item 1. 7. The method according to claim 1, wherein a protective layer is provided on the heat-sensitive recording layer.
7. The heat-sensitive recording medium according to any one of items 1 to 6,