JPH04308790A - Reversible thermal recording material and reversible thermal color-forming composition - Google Patents

Abstract

PURPOSE:To easily produce and erase a color only by heating by a method wherein a halogen-containing electron donative color developing compound or the like is used as an electron donative color developing compound in a recording layer, and a specific organic acid or the like is used as an electron accepting compound in the recording layer. CONSTITUTION:In a reversible thermal recording material, a recording layer mainly composed of an electron donative color developing compound, an electron accepting compound, and a binder is provided on a substrate. As the electron donative color developing compound, a halogen-containing electron donative color developing compound and/or a compound shown by a right general formula is used. As the electron donative color developing compound, an organic phosphoric compound shown by a general formula R1-PO(OH)2 and/or an organic acid having hydroxyl group bonded to an alpha-carbon atom shown by a general formula R2-CH(OH)COOH is used. In the formulas, R1 and R2 represent alkyl or alkenyl. In addition, a crystallizing nucleator for accelerating the crystallization of the electron accepting compound exists in the recording layer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording material and a reversible thermochromic composition that utilize a coloring reaction between an electron-donating color-forming compound and an electron-accepting compound.

0002

[Prior art and its problems] Conventionally, thermal recording utilizes a color reaction between an electron-donating color-forming compound (hereinafter also referred to as a color former) and an electron-accepting compound (hereinafter also referred to as a color developer). The materials are widely known, including the output of electronic computers, facsimile machines, automatic ticket vending machines, printers for scientific measuring machines, and C.
It is widely applied to RT medical measurement printers, etc. However, in all conventional products, the coloring is irreversible, and coloring and decoloring cannot be repeated alternately.

On the other hand, according to patent publications, some heat-sensitive recording materials that utilize a color-forming reaction between a color-forming agent and a color-developing agent have been proposed in which coloring and decoloring are performed reversibly. For example, according to Japanese Patent Application Laid-Open No. 60-193691,
A combination of gallic acid and phloroglucinol is shown to be used as a color developer. The colored material obtained by thermally coloring this product is one that can be decolored with water or steam. However, in the case of this heat-sensitive recording material, it is difficult to make it water resistant, there are problems in recording storage stability, and there are further problems in that the color erasing device for erasing the coloring body becomes large. JP-A-61-237684 discloses a rewritable optical recording material using compounds such as phenolphthalene, thymolphthalene, and bisphenol as color developers. This product forms a colored body by heating and slowly cooling it, and can be decolored by heating the colored body once to a temperature higher than the coloring density and then rapidly cooling it. However, in the case of this recording material, the process of coloring and erasing is complicated, and the coloring body obtained by erasing the coloring body still has some coloring, which makes it difficult to obtain colored images with good contrast. I can't. Japanese Patent Publication No. 62-140881
No., JP-A-62-138568 and JP-A-62-13
No. 8556 discloses a homogeneous compatible solution of a color former, a color developer, and a carboxylic acid ester. This product exhibits a completely colored state at low temperatures, a completely discolored state at high temperatures, and can maintain its colored or discolored state at intermediate temperatures.
By printing on this material with a thermal head, white characters (colorless body) can be recorded on a colored background (colorable body). Therefore, in the case of this recording material, since the recorded image is a negative image, its uses are limited, and in addition, in order to preserve the recorded image, it is necessary to maintain the image within a specific temperature range. JP-A 2-188294 and JP-A 2-188293 disclose salts of gallic acid and higher aliphatic amines and bis(hydroxyphenyl), which reversibly develop and reduce color, and bis(hydroxyphenyl) as color developers. The use of a salt of acetic acid or butyric acid with a higher aliphatic amine is shown. This product can be heated to develop color in a specific temperature range and decolored by heating at a higher temperature, but since the color development and color reduction effects occur competitively, these effects cannot be reversed thermally. It is difficult to control and it is difficult to obtain good image contrast. As described above, conventional reversible heat-sensitive recording materials that utilize the reaction between a color former and a color developer have various problems and are still unsatisfactory.

0004

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems found in the prior art in reversible thermosensitive recording materials and thermochromic compositions that utilize the reaction between a color former and a color developer. The coloring and decoloring can be easily performed by heating alone, and the coloring and decoloring states can be maintained at room temperature, and the decoloring temperature is lower than the coloring temperature, and furthermore, the coloring and decoloring states can be maintained at room temperature. The object of the present invention is to provide a reversible thermosensitive recording material and a thermochromic composition that have a high density contrast between a state and a decolorized state.

[0005]

[Means for Solving the Problems] The present inventors have conducted extensive research to solve the above problems, and as a result, have completed the present invention.

[0006] In a reversible thermosensitive recording material in which a recording layer containing an electron-donating color-forming compound, an electron-accepting compound, and a binder as main components is provided on a support, as the electron-donating color-forming compound, Using a halogen-containing electron-donating color-forming compound and/or a compound represented by the following general formula [Formula 1], as the electron-accepting compound, the general formula R1-PO
(OH)2 (wherein R1 represents a higher alkyl group or alkenyl group) and/or an organic phosphoric acid compound represented by the general formula R2-CH(OH)COOH (wherein R2 represents a higher alkyl group or alkenyl group) ) is used, and the recording layer contains a crystallization nucleating agent that promotes crystallization of the electron-accepting compound. Heat-sensitive recording material.

[Formula 1] (However, R1 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R2 is a hydrogen atom or an optionally substituted amino group,
X is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenylamino group, m is an integer of 1 or 2, Y is an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 2 carbon atoms, n is 1 or (representing an integer of 2) is provided. Further, according to the present invention, in a thermochromic composition containing an electron-donating color-forming compound and an electron-accepting compound as main components, the electron-donating color-forming compound contains an electron-donating compound containing a halogen. Using a color-forming compound and/or a compound represented by the following general formula [Chemical formula 1], as the electron-accepting compound, the general formula R1-PO
(OH)2 (wherein R1 represents a higher alkyl group or alkenyl group) and/or an organic phosphoric acid compound represented by the general formula R2-CH(OH)COOH (wherein R2 represents a higher alkyl group or alkenyl group) ) is used, and the composition contains a crystallization nucleating agent that promotes crystallization of the electron-accepting compound. Thermochromic composition.

[Formula 1] (However, R1 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R2 is a hydrogen atom or an optionally substituted amino group,
X is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenylamino group, m is an integer of 1 or 2, Y is an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 2 carbon atoms, n is 1 or (representing an integer of 2) is provided.

The heat-sensitive recording material and thermochromic composition of the present invention develop color instantly when heated, and the color-forming state remains stable even at room temperature.On the other hand, the composition in the color-forming state The color disappears instantly when heated below temperature, and the erased state remains stable even at room temperature.Such reversible, unique coloring and fading behavior is a new and surprising phenomenon that has never been seen before. It is.

Taking the heat-sensitive recording material of the present invention as an example, the principle of color development and color erasure, that is, image formation and image erasure, will be explained below with reference to the graph shown in FIG. The vertical axis of the graph represents color density, and the horizontal axis represents temperature. Solid line 1 represents the image forming process by heating, and broken line 3 represents the image erasing process by heating. A is the density in the completely erased state, B is the density in the fully colored state when heated to a temperature of T1 or higher, C is the density in the fully colored state at a temperature of T0 or lower, and D is the density between T0 and T1. It shows the concentration when heated and erased at a temperature of .

The heat-sensitive recording material of the present invention is in a colorless state (A) at temperatures below T0. To perform recording, the recording material is heated to a temperature of T1 or higher using a thermal head or the like to develop color (B) and form a recorded image. Even if this recorded image is returned to a temperature below T0 according to solid line 2, it remains in the same state (C) and the memorability of recording is not lost.

Next, in order to erase the recorded image, the formed recorded image is heated to a temperature between T0 and T1, which is lower than the coloring temperature, so that it becomes colorless (D). In this state, even if the temperature is returned to below T0, the colorless state (A) is maintained. That is, the process of forming a recorded image reaches C along the path of solid line ABC, and the recording is maintained. Next, the process of erasing the recorded image reaches A along the path indicated by the broken line CDA, and the erased state is maintained. This behavioral characteristic of forming and erasing a recorded image is reversible and can be repeated many times.

FIG. 2 is an explanatory diagram showing an example of image formation and image erasing, in which 1 is a support and 2 is a reversible thermosensitive recording layer. The image forming steps (A)→(B) are achieved by performing recording printing at a temperature of T1 or higher in FIG. 1 using an image forming heat source, for example, the thermal head 4. Next, the image erasing step (B)→(A) is accomplished by heating the image to a temperature between T0 and T1 using an image erasing heat source, for example, the heating roller 5. In FIG. 2, 3 indicates a colored image.

The heat-sensitive recording material and thermochromic composition of the present invention contain a color former and a color developer as essential components. A colored state is formed by heating and melting the color forming agent and color developing agent, while the colored state is erased by heating at a temperature lower than the coloring temperature, and the colored state and the colorless state stably exist at room temperature. It is. The mechanism of color development and color erasure in the heat-sensitive recording material and thermochromic composition of the present invention is such that when the color former and the color developer are heated and melted and mixed at the color development temperature, the composition consisting of the color former and the color developer becomes amorphous and forms a colored state, while when heated at a temperature lower than the coloring temperature, the color developer of the colored composition crystallizes and forms a colored erased state. It is based on

[0013] A composition comprising a conventional color forming agent and a color developing agent, for example, a leuco compound having a lactone ring, which is a dye precursor widely used in conventional thermal recording paper, and a phenolic compound exhibiting a color developing effect. When these are melted and mixed by heating, a color develops due to ring opening of the lactone ring of the leuco compound. This colored state exhibits an amorphous state in which both are compatible. This colored amorphous state exists stably at room temperature, but crystallization does not occur even when heated again, and because there is no separation of the phenolic compound from the leuco compound, the lactone ring does not close and the color disappears. I don't.

On the other hand, when the composition of the present invention consisting of a color forming agent and a color developer is melted and mixed by heating, it becomes a colored state, exhibits an amorphous state as in the conventional case, and is stable at room temperature. exist. However, in the case of the present invention, when this colored amorphous composition is heated below the color development temperature, that is, at a temperature that does not reach a molten state, the color developer crystallizes and becomes compatible with the color former. The bond due to the state can no longer be maintained, and the color developer separates from the color former. It is thought that due to the separation of the color developer from the color former due to crystallization, the color developer cannot accept electrons from the color former, and the color former loses its color.

The above-mentioned unique color developing/disappearing behavior observed in the composition of the present invention is due to the compatibility between the color forming agent and the color developer by heating and melting, the strength of the action of both in the color developing state, and the color developing agent. It is related to the solubility of the agent in the color former, the crystallinity of the color developer, etc.
Since the decoloring is caused by separation of the color developer from the color former due to crystallization, the selection of the color former and developer is important in order to obtain an excellent decolorizing effect.

The coloring agent used in the present invention is a compound exhibiting electron-donating properties, and is itself a colorless or light-colored dye precursor. 1] is used.

[0017] Examples of color formers containing halogen as a substituent used in the present invention include the following. 3,3-bis(p-dimethylaminophenyl)
-6-chlorphthalide, 3-cyclohexylamino-6
-Chlorfluorane, 3-cyclohexylamino-6-
Bromofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-bromofluorane, 3-dipropylamino-7-chlorofluorane,

0
3-Diethylamino-6-chloro-7-phenylamino-fluorane, 3-pyrrolidino-6-chloro-
7-phenylamino-fluorane, 3-diethylamino-6-chloro-7-(m-trifluoromethylphenyl)
Amino-fluorane, 3-cyclohexylamino-6-
Chlor-7-(o-chlorophenyl)amino-fluorane, 3-diethylamino-6-chloro-7-(2',3
'dichlorophenyl)amino-fluorane,

0019
]3-diethylamino-6-methyl-7-chlorofluoran, 3-dibutylamino-6-chloro-7-ethoxyethylamino-fluoran, 3-diethylamino-7-
(o-chlorophenyl)amino-fluorane, 3-diethylamino-7-(o-bromophenyl)amino-fluorane, 3-diethylamino-7-(o-chlorphenyl)amino-fluorane, 3-dibutylamino-7-(
o-fluorophenyl)amino-fluorane, 6'-bromo-3'-methoxybenzoindolino-pyrylospirane, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chlor-5'
-chlorphenyl) phthalide, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorphenyl) phthalide, 2-{3,6
-bis(diethylamino)}-9-(o-chlorophenyl)amino-xantylbenzoic acid lactam, etc.

[0020] As the coloring agent represented by the general formula [Formula 1] used in the present invention, the following are exemplified.

3-(N-methyl-N-phenylamino)
-7-amino-fluorane, 3-(N-ethyl-N-phenylamino)-7-amino-fluorane, 3-(N-
Propyl-N-phenylamino)-7-amino-fluorane, 3-{N-methyl-N-(p-methylphenyl)
amino}-7-amino-fluorane, 3-{N-ethyl-N-(p-methylphenyl)amino}-7-amino-
Fluoran, 3-{N-propyl-N-(p-methylphenyl)amino}-7-amino-fluoran, 3-{N
-Methyl-N-(p-ethylphenyl)amino}-7-
Amino-fluoran, 3-{N-ethyl-N-(p-ethylphenyl)amino}-7-amino-fluoran, 3
-{N-propyl-N-(p-ethylphenyl)amino}-7-amino-fluorane,

3-{N-methyl-N-(2',4'-dimethylphenyl)amino}-7-amino-fluorane,
3-{N-ethyl-N-(2',4'-dimethylphenyl)amino}-7-amino-fluorane, 3-{N-propyl-N-(2',4'-dimethylphenyl)amino}- 7-amino-fluorane, 3-{N-methyl-N-
(p-chlorophenyl)amino}-7-amino-fluorane, 3-{N-ethyl-N-(p-chlorophenyl)
amino}-7-amino-fluorane, 3-{N-propyl-N-(p-chlorophenyl)amino}-7-amino-fluorane,

3-(N-methyl-N-phenylamino)
-7-methylamino-fluorane, 3-(N-ethyl-
N-phenylamino)-7-methylamino-fluorane, 3-(N-propyl-N-phenylamino)-7-methylamino-fluorane, 3-{N-methyl-N-(p
-methylphenyl)amino}-7-ethylamino-fluoran, 3-{N-ethyl-N-(p-methylphenyl)amino}-7-benzylamino-fluoran, 3-{
N-Methyl-N-(2',4'-dimethylphenyl)amino}-7-methylamino-fluorane, 3-{N-ethyl-N-(2',4'-dimethylphenyl)amino}
-7-ethylamino-fluoran, 3-{N-methyl-
N-(2',4'-dimethylphenyl)amino}-7-
benzylamino-fluorane,

3-{N-ethyl-N-(2',4'-dimethylphenyl)amino}-7-benzylamino-fluorane, 3-(N-methyl-N-phenylamino)-7
-dimethylamino-fluorane, 3-(N-ethyl-N
-phenylamino)-7-dimethylamino-fluorane, 3-{N-methyl-N-(p-methylphenyl)amino}-7-diethylamino-fluorane, 3-{N-ethyl-N-(p-methylphenyl) ) amino}-7-diethylamino-fluorane, 3-(N-methyl-N-phenylamino)-7-dipropylaminofluorane, 3-
(N-ethyl-N-phenylamino)-7-dipropylaminofluorane, 3-{N-methyl-N-(p-methylphenyl)amino}-7-dibenzylamino-fluorane,

3-{N-ethyl-N-(p-methylphenyl)amino}-7-dibenzylamino-fluorane, 3-{N-ethyl-N-(p-methylphenyl)
amino}-7-di(p-methylbenzyl)amino-fluorane, 3-{N-methyl-N-(p-methylphenyl)amino}-7-acetylamino-fluorane, 3-{
N-ethyl-N-(p-methylphenyl)amino}-7
-benzoylamino-fluorane, 3-{N-methyl-
N-(p-methylphenyl)amino}-7-(o-methoxybenzoyl)amino-fluorane, 3-{N-ethyl-N-(p-methylphenyl)amino}-6-methyl-7-phenylamino- Fluoran, 3-{N-methyl-N-(p-methylphenyl)amino}-6-methyl-
7-phenylamino-fluorane,

3-{N-methyl-N-(p-methylphenyl)amino}-6-tert-butyl-7-(p-methylphenyl)amino-fluorane, 3-(N-ethyl-N-phenylamino) )-6-methyl-7-(N-ethyl-N-(p-methylphenyl)amino-fluorane,
3-{N-propyl-N-(p-methylphenyl)amino}-6-methyl-7-{N-methyl-N-(p-methylphenyl)amino}-fluorane, 3-{N-ethyl-N -(p-methylphenyl)amino}-5-methyl-
7-benzylamino-fluorane, 3-{N-ethyl-
N-(p-methylphenyl)amino}-5-chloro-7
-dibenzylamino-fluorane, 3-{N-methyl-
N-(p-methylphenyl)amino}-5-methoxy-
7-dibenzylamino-fluorane, 3-{N-ethyl-N-(p-methylphenyl)amino}-6-methyl-
fluoran, 3-{N-ethyl-N-(p-methylphenyl)amino}-5-methoxy-fluoran, and the like.

In the present invention, the following are used as color developers. (1) Organic phosphoric acid compound represented by the following general formula (1)
R1-PO(OH)2
(
1) However, R1 is a linear or branched higher alkyl group or alkenyl group, and usually has 8 to 30 carbon atoms. Specific examples of this organic phosphoric acid compound include the following. Octylphosphonic acid, nonylphosphonic acid, decylphosphonic acid, dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid.

(2) An organic acid having a hydroxyl group at the α-position carbon represented by the following general formula (2). R2-CH(OH)COOH
(2) However, R2 is a linear or branched higher alkyl group or alkenyl group, and usually has 6 to 28 carbon atoms. Specific examples of the organic acid having a hydroxyl group at the α-position carbon include the following. α-hydroxyoctanoic acid, α-hydroxydodecanoic acid,
α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, α-hydroxypentadecanoic acid, α-hydroxyeicosanoic acid, α-hydroxydocosanoic acid acids etc.

In the present invention, a crystallization nucleating agent that promotes crystallization of the color developer is added to a thermochromic composition containing a color former and a color developer. This crystallization nucleating agent promotes the crystallization of the color developer during cooling and improves the color erasing speed and color erasing density.It reduces the degree of supercooling of crystallization and increases the number of crystal nuclei. It has the role of making the crystals finer and accelerating the crystallization rate, and as a result, the thermal response is improved and a colorless state without residual color can be obtained. As the crystalline nucleating agent, any substance can be used as long as it promotes crystallization of the color developer, such as dibenzylidene sorbitol, p-methyldibenzylidene sorbitol, dimethyldibenzylidene sorbitol, p-ethyldibenzylidene sorbitol, etc. Examples include sorbitols, condensates of D-sorbitol and benzaldehyde, and higher fatty acid amides.

[0030] The proportions of each component used in the thermochromic composition are as follows:
Although it is necessary to select an appropriate ratio depending on the physical properties of the components used, it can actually be selected within a fairly wide range. The ratio of color former and color developer is 1:1 to 1 by weight.
A range of 0 is appropriate, preferably 1:( ) to (
) is within the range. The amount of the crystallization nucleating agent added is suitably 0.5 to 20% by weight based on the total amount of the color former, color developer, and crystallization nucleating agent. If the amount of the crystallization nucleating agent added is less than the above range, the effect of the crystallization nucleating agent will decrease, while if it is too large, the color of the crystallization nucleating agent (usually white) will cause a decrease in color density. This causes the inconvenience of causing

The heat-sensitive recording material of the present invention can be prepared by applying a coloring agent, a color developer, and a crystallization nucleating agent as they are or encapsulating them in microcapsules together with a binder on a suitable support such as paper, synthetic paper, or plastic film. It can be obtained by uniformly dispersing or dissolving it in water or an organic solvent and coating it on a support. The coating liquid can be prepared by dispersing each component using a dispersing machine such as a ball mill, attritor, or sand mill. In this case, the color former and color developer can be dispersed together.

As the binder, various conventional binders can be used as appropriate, such as polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, methoxy cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, cellulose acetate, gelatin, casein, starch, and polyacrylic. Acid soda, povinylpyrrolidone, polyacrylamide,
Maleic acid copolymer, acrylic acid copolymer, polystyrene, polyvinyl chloride, polyvinyl acetate, polyacrylic esters, polymethacrylic esters, vinyl chloride/vinyl acetate copolymer, styrene copolymer, polyester, There are polyurethane, etc. The usage rate of binder is
A suitable proportion is 0.5 to 10 parts by weight per 1 part by weight of the color former. Microencapsulation of the composition components can be performed by a known method such as a coacervation method, an interfacial polymerization method, or an in-situ polymerization method.

In the present invention, various additives used in ordinary thermal recording paper, such as dispersants, surfactants, fillers,
Color image stabilizers, antioxidants, light stabilizers, lubricants, etc. can also be added.

Furthermore, a protective layer may be provided for the purpose of protecting the recording layer, improving durability, preventing sticking of the thermal head, and improving other performance. The main components of the protective layer include various water-soluble resins, latex, thermoplastic resins,
Alternatively, a thermosetting resin, a photocurable resin, etc. may be used. The recording image can be formed by using a thermal pen, a thermal head, laser heating, etc., depending on the purpose of use, and is not particularly limited. Similarly, erasing of recorded images is not particularly limited as long as the temperature conditions for erasing can be provided, such as a heating roller, a planar heating element, a constant temperature bath, hot air, or a thermal head. It is also possible to perform so-called overwriting, in which a recorded image is erased by a thermal head set at an erasing temperature, and at the same time a recorded image is formed by another thermal head set at a recording temperature.

[0035]

EXAMPLES The present invention will now be explained in more detail by way of examples. Note that all parts and percentages below are based on weight.

Example 1 A coating solution was prepared by stirring and dissolving the following composition. 3-diethylamino-7-(o-chlorophenyl)
Amino-fluorane 10 parts Octadecylphosphonic acid
30 copies
(Gelol MD manufactured by Shin Nihon Rika) Vinyl chloride-vinyl acetate copolymer
30 parts (VYHH manufactured by Union Carbide) Tetrahydrofuran

250 parts isopropyl alcohol
50 parts or more of the coating solution prepared as above was coated onto a 100 μm thick polyester film using a wire bar to a thickness of approximately 1.5 μm.
A reversible thermosensitive recording sheet was obtained by coating and drying to a thickness of μm. The reversible thermosensitive recording sheet thus prepared was tested at a pressure of 2
As a result of printing under the conditions of Kg/m2 and 2 seconds and measuring the color development temperature range and color density (Magbeth Densitometer D-918), a high density black image with a density of 1.35 was obtained at 100℃ or higher. Obtained. Next, when this printed reversible thermosensitive recording sheet was placed in a constant temperature bath at 70° C. for 8 seconds, the image was completely erased and the sheet returned to its original state. This reversible behavior of coloring and decoloring was reproducible, and although this test was repeated 10 times, no deterioration in function was observed, confirming that it is extremely excellent as a reversible thermosensitive recording material.

Example 2 A coating solution was prepared by stirring and dissolving the following composition. 3-{N-ethyl-N-(p-methylphenyl)amino} 10 parts -6-methyl-
7-phenylamino-fluorane α-hydroxyoctadecanoic acid
30 parts Condensate of D-sorbitol and benzaldehyde
4 parts (Nippon Rika Gelol D) Vinyl chloride-vinyl acetate copolymer

30 copies (VYHH manufactured by Union Carbide)
Tetrahydrofuran

250 parts isopropyl alcohol

At least 50 parts of the coating solution prepared as described above was coated onto a 100 μm thick polyester film using a wire bar to a coating thickness of about 1.5 μm and dried to obtain a reversible thermosensitive recording sheet. When the same test as in Example 1 was conducted on this reversible thermosensitive recording sheet, 9.
It developed a black color with a density of 1.28 at temperatures above 5°C, and was completely erased under erasing conditions of 75°C. Moreover, the same repeatability characteristics as in Example 1 were exhibited. When this sheet was printed with a word processor (Ricoh My Report N-11) using a thermal head, clear black print with a color density of 1.25 was obtained. This printed recording sheet is stable under normal usage conditions, and is erased by passing it through a heated roll machine set at 75°C, returning to its original transparent state.
No functional decline was observed due to repeated use.

Example 3 [Liquid A], [Liquid B] and [Liquid C] were prepared by pulverizing and dispersing the following compositions in a ball mill to a particle size of 1 to 4 μm. [Liquid A] 3-diethylamino-7-(o-chlorophenyl)
Amino 10 parts - Fluorane 10% polyvinyl alcohol aqueous solution
Part 10 Water

30 parts [Liquid B] Hexadecylphosphonic acid

10 parts Octadecanoic acid amine

2 parts 10% polyvinyl alcohol aqueous solution
Part 10 Water

30 copies [
C liquid] carbon calcium

10 parts 5% methylcellulose aqueous solution

Part 10 Water

3
0 parts or more 10 parts of [Liquid], 30 parts of [B] and 30 parts of [C] were mixed to prepare a coating liquid, and this was dried on high-quality paper with a basis weight of 48 g/m2. Adhesion amount is 5g/m
2, and after drying, calendering was performed. When the reversible thermosensitive recording sheet prepared as described above was subjected to the same test as in Example 1, it developed a black color with a density of 1.32 at temperatures above 110°C, and a density of 0.07 under erasing conditions at 70°C. It was deleted. The repeatability characteristics were also reproduced.

Example 4 [Liquid A], [Liquid B] and [Liquid C] were prepared by pulverizing and dispersing the following compositions in a ball mill to a particle size of 1 to 4 μm. [Liquid A] 3-{N-ethyl-N-(p-methylphenyl)amino} 10 parts -7-phenylamino-fluoran 10% polyvinyl alcohol aqueous solution
Part 10 Water

30 copies [
B solution] α-hydroxyhexadecanoic acid
10 copies
Octadecylbenzamide

2 parts 10% polyvinyl alcohol aqueous solution

Part 10 Water

30 parts [Liquid C] Carbon calcium

10 parts 5% methylcellulose aqueous solution

Part 10 Water

3
0 parts or more 10 parts of [Liquid], 30 parts of [B] and 30 parts of [C] were mixed to prepare a coating liquid, and this was dried on high-quality paper with a basis weight of 48 g/m2. Adhesion amount is 5g/m
2, and after drying, calendering was performed. This reversible thermosensitive recording sheet gave a black image with a developed color density of 1.28 under the same conditions as in Example 1, and its erased density was 0.08. This reversible test of color development and decolorization was repeated 10 times, but no deterioration in function was observed.

Composition consisting of 7 parts of 3-{N-(P-phenylaminophenyl)amino}-6-methyl-7-phenylamino-fluorane, 21 parts of docosylphosphonic acid, and 3 parts of octadecanoic acid amine Uniformly dissolve at about 100°C. The above melt was added dropwise into 80 parts of a 3% aqueous solution of styrene-maleic anhydride copolymer whose pH was adjusted to 4.5 and heated to 80°C, and mixed with a mixer for 2 to 10 minutes.
Emulsify and disperse to form micro droplets of μm size. Next, melamine-formalin prepolymer (manufactured by Sanwa Chemical Co., Ltd., Nikalac MX-54) was added while stirring the resulting emulsion7.
Add 0g and react at 80℃ for 3 hours to obtain an average particle size of 3.2.
A microcapsule dispersion of μm size was obtained. A coating solution was prepared by adding 30 parts of 10% polyvinyl alcohol to 30 parts of the obtained dispersion, and the coating solution was applied to a high-quality paper having a basis weight of 66 g/m2 so that the amount of adhesion upon drying was 5 g/m2. When the thus prepared reversible thermosensitive recording sheet was printed using a word processor (Ricoh My Report NL-1), the printing density was 1.31 in blue-black. The print was stable at room temperature and was erased by passing it through a heated roll machine set at 75° C. in the same manner as in Example 2, and showed similar repeatability.

Comparative Example 1 Recording sheets were prepared in the same manner as in Examples 1 to 5 except that the respective nucleating agents were removed, and the same test was conducted. Both erasing time was inferior to the system containing a nucleating agent as in the example. Furthermore, it was confirmed that when the amount of the crystallization nucleating agent added exceeds 20% by weight based on the total amount of the color former, color developer, and crystallization nucleating agent, the color image density decreases significantly. .

[0042]

Effects of the Invention As explained above, the reversible thermosensitive recording material and thermochromic composition according to the present invention can easily develop and erase color by controlling thermal energy, and can produce high-contrast images with memory properties. It has high stability, excellent erasability, no deterioration due to repeated use, and the hue can be freely selected, so it can be used as a rewritable recording medium and in many other applications.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the color density and temperature of the reversible thermosensitive recording material of the present invention, and is an explanatory diagram of the principle of color development and color erasure. The solid line (A→B→C) represents the image forming process, and the broken line (C
→D→A) shows the image erasing process.

FIG. 2 shows an explanatory diagram of an image forming process and an image erasing process.

[Explanation of symbols]

1 Support 2 Reversible recording layer 3 Colored image 4 Thermal head 5 Heating roller

Claims (2)

[Claims] Claim 1. A reversible thermosensitive recording material comprising a recording layer comprising an electron-donating color-forming compound, an electron-accepting compound, and a binder as main components on a support, wherein the electron-donating color-forming compound As the electron-accepting compound, an electron-donating color-forming compound containing a halogen and/or a compound represented by the following general formula [Formula 1] is used, and as the electron-accepting compound, a compound represented by the general formula R1-
An organic phosphoric acid compound represented by PO(OH)2 (where R1 represents a higher alkyl group or alkenyl group) and/or the general formula R2-CH(OH)COOH (wherein R2 represents a higher alkyl group or alkenyl group) A reversible method characterized in that an organic acid having a hydroxyl group at the α-position carbon represented by heat-sensitive recording material. [Formula 1] (However, R1 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R2 is a hydrogen atom or an optionally substituted amino group,
X is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenylamino group, m is an integer of 1 or 2, Y is an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 2 carbon atoms, n is 1 or (represents an integer of 2) 2. A thermochromic composition containing an electron-donating color-forming compound and an electron-accepting compound as main components, wherein the electron-donating color-forming compound contains a halogen. Using a compound and/or a compound represented by the following general formula [Chemical formula 1], the electron-accepting compound is represented by the general formula R1-PO(OH)2 (wherein R1 represents a higher alkyl group or an alkenyl group). and/or an organic acid having a hydroxyl group at the α-position carbon represented by the general formula R2-CH(OH)COOH (wherein R2 represents a higher alkyl group or alkenyl group), and the composition 1. A reversible thermochromic composition, characterized in that the composition contains a crystallization nucleating agent that promotes crystallization of the electron-accepting compound. [Formula 1] (However, R1 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R2 is a hydrogen atom or an optionally substituted amino group,
X is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenylamino group, m is an integer of 1 or 2, Y is an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 2 carbon atoms, n is 1 or (represents an integer of 2)