JPH04344287A - Reversible thermal color developing composition and reversible thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a reversible thermal color developing composition which thermally develops a color and discharges a color when kept at room temperature by mixing an electron-donative dye precursor, specific organic phosphoric acid compound and/or specific organic acid, discoloration temperature adjusting agent and a low volatile solvent. CONSTITUTION:A thermal color developing composition uses a color development reaction between am electron-donative color developing compound and an electron-receptive compound. An organic phosphoric acid compound expressed by formula I (R1 is a higher alkyl group, etc.) and/or an organic acid having a hydroxyl group as carbon at alpha-position expressed by formula II (R2 is a higher alkenyl group, etc.). Further, a discoloration temperature adjusting agent and a low volatile solvent are added to the composition to obtain a reversible thermal color developing composition. This thermal color developing composition develops a color due to heating and the composition in a color development state discharges the color, if left alone in an atmosphere.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermochromic composition and a reversible thermosensitive recording material 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 decolored state at high temperatures, and can maintain its colored or decolored 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 thermally colored in a specific temperature range and decolored by heating at a higher temperature, but since the color developing and color reducing 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

Problem to be Solved by the Invention The present invention provides a reversible thermochromic composition and a reversible thermosensitive recording material that utilize the reaction between a color former and a color developer, and solves the above-mentioned problems found in the prior art. To provide a reversible thermochromic composition and a reversible thermosensitive recording material which can easily erase a colored image by leaving it at room temperature and form a colored image again on the traces of erasing. The task is to do so.

[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.

That is, according to the present invention, in a thermochromic composition that utilizes a color-forming reaction between an electron-donating color-forming compound and an electron-accepting compound, as the electron-accepting compound,
Organic phosphoric acid compounds represented by the general formula R1-PO(OH)2 (wherein R1 represents a higher alkyl group or alkenyl group) and/or the general formula R2-
An organic acid having a hydroxyl group at the α-position carbon represented by CH(OH)COOH (wherein R2 represents a higher alkyl group or alkenyl group) is used, and the composition also contains a discoloration temperature regulator and a low volatile solvent. Provided are a reversible thermochromic composition characterized by containing the following, and a reversible heat recording material comprising this composition supported on a support.

The composition of the present invention can be colored by heating, and the colored composition can be decolored by being left at room temperature. The decolored composition can be colored again by heating it. The thermochromic composition of the present invention is capable of repeating such coloring and decoloring.

[0008] 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, and is not particularly limited. fluoran-based compounds, phenothiazine-based compounds, leuco-auramine-based compounds, rhodamine-lactam-based compounds, spiropyran-based compounds, indolinophthalide-based compounds, and the like. In the present invention, it is particularly preferable to use a compound containing a halogen and/or a compound represented by the following general formula [Formula 1].

[0009]

[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)

[0010] 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,

0012
]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.

[0013] As the coloring agent represented by the above 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, etc.

[0022] The discoloration temperature regulator used in the present invention is as follows:
A meltable substance that is liquid or solid at room temperature and has a melting point of 30° C. or higher and is solid at room temperature is used. These polar organic compounds include alcohols, esters, acid amides, carboxylic acids, ethers and ketones,
For example, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol, stearyl myristate, propyl palmitate, ethyl stearate, butyl stearate, glycerin tristearate, glycerin trimyristate,
Examples include propylene glycol distearate, glycerin monocetyl ether, myristic acid, palmitic acid, lauric acid, didecyl ether, didodecyl ether, stearic acid amide, and the like. This discoloration temperature regulator is
It shows the effect of changing the coloring temperature and coloring temperature of the composition.

As the low volatility solvent used in the present invention, a hydrocarbon solvent whose boiling point at normal pressure is 100° C. or higher is used. Such solvents can be selected from those commonly used as pressure-sensitive oils, such as alkylnaphthalene compounds, diarylalkane compounds, alkylbiphenyl compounds, terphenyl compounds, triarylmethane compounds, etc. Included. For example, dimethylnaphthalene, diethylnaphthalene, diisopropylnaphthalene, 1-methyl-1-dimethylphenyl-
Examples include 1-phenylmethane, 1-methyl-1-ethylphenyl-1-phenylmethane, dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl, hydrogenated terphenyl, and tritolylmethane. This low volatility solvent improves the thermal responsiveness and color density of the composition.

In the composition of the present invention, the appropriate proportion of the color developer used is in the range of 1 to 10 parts by weight per 1 part by weight of the color former. The appropriate proportion of the discoloration temperature regulator used is 100 to 500 parts by weight, preferably 300 to 400 parts by weight, based on 100 parts by weight of the total amount of color forming agent and color developer. The appropriate amount of the low-volatile solvent is 10 to 100 parts by weight, preferably 30 to 80 parts by weight, per 100 parts by weight of the discoloration temperature regulator.

The heat-sensitive recording material of the present invention can be obtained by supporting the above-mentioned thermochromic composition on a support. That is, the above-mentioned color forming agent and color developer are used as they are or encapsulated in microcapsules, and are uniformly dispersed or dissolved in water or an organic solvent together with a discoloration temperature regulator, a low volatility solvent, and a binder, and then applied to a support. It can be obtained by applying it on top. As the support, paper, synthetic paper, plastic film, paper/plastic film composite, etc. are used. This support is usually white, but may be lightly colored for identification purposes. 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 color formers and color developers is
This can be carried out 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 heat-sensitive 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 heating means for forming a recorded image is not particularly limited, and may include a thermal pen, a thermal head, laser heating, and the like.

[0029]

Effects of the Invention The thermochromic composition of the present invention develops color when heated, and the color-developed composition disappears by being left as it is. That is, when a colored composition is left to stand naturally, the color density gradually decreases over time. In the color-forming composition of the present invention, the color disappears to its original state in about several hours to 12 hours, and
The color density sufficient for image reading is maintained for about 1 minute to 1 hour. Therefore, since the heat-sensitive recording material obtained using the composition of the present invention has a temporary memory function as described above, it can be used as a recording material for checking the contents of the printed record in a printing device such as a word processor. It is suitable. That is, when printing on thermal recording paper using a thermal recording device such as a word processor, in order to check the recorded content that has been input, print it out once on the thermal recording paper, look at the resulting print, The text and layout are revised, typos are corrected, etc., but in this case, the paper whose recorded contents have been checked is disposed of as waste and is not used effectively. When the heat-sensitive recording material of the present invention is used, the printed content of the checked paper will disappear naturally by being left alone, and it will return to a printable state again, so there is no need to dispose of it as waste.
Can be used repeatedly. After checking the recorded content using the thermal recording material of the present invention and correcting the recorded content in the device, the modified archival print is produced by printing out on a conventional thermal recording material having a permanent memory function. Obtainable.

[0030]

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 3-N-methyl-N-isopropylamino-6-methyl-7-anilinofluorane

1 part octadecylphosphonic acid
Part 3 Stearyl alcohol

15 parts Diisopropylnaphthalene (manufactured by Kureha Chemical Co., Ltd., KMC-113) A material consisting of 10 parts is uniformly dissolved at about 100°C. 30 parts of the above dissolved material was added dropwise to 60 parts of a 3% aqueous solution of styrene-maleic anhydride copolymer whose pH was adjusted to 4.5 and heated to 80°C, and a microscopic particle of 2 to 10 μm was added using a mixer. Emulsify and disperse into droplets. Next, while stirring the obtained emulsion, 7.0 parts of melamine-formalin prepolymer (manufactured by Sanwa Chemical Co., Ltd., Nikalac MX-54) was added and reacted at 70°C for 3 hours to form microcapsules with an average particle size of 3.2 μm. A dispersion was obtained. Next, the obtained dispersion 30
A coating solution was prepared by adding 30 parts of 10% polyvinyl alcohol to the coating solution, and the coating solution was applied to thin orange-colored high-quality paper with a basis weight of 66 g/m2 so that the amount of adhesion was 10 g/m2 when dry. When the thus obtained thermal recording paper was printed using a word processor (Ricoh My Report N-11), a black image with a print density of 1.21 was obtained. The density of this image decreased to 1.00 after 10 minutes, but there was no problem in reading it. After 10 hours of standing, the print disappeared and returned to its original state, and there was almost no deterioration in functionality due to repeated use.

Example 2 3-diethylamino-5-methyl-7-dibenzylaminofluorane 1 part α-hydroxyoctadecanoic acid
3 parts myristyl alcohol

7 parts stearyl alcohol

8 parts diphenylmethane solvent (manufactured by Nippon Petrochemical Co., Ltd., SAS-296)
The 5 parts of the material are uniformly dissolved at approximately 100°C. P
A 3% aqueous gelatin solution of a styrene-maleic anhydride copolymer with H adjusted to 4.5. 25 parts of the above solution was added dropwise to 50 parts of an aqueous gelatin solution heated to 80°C, and mixed using a mixer.
Emulsify and disperse to form microdroplets of ~8 μm. Next, while stirring the obtained emulsion, urea-formalin prepolymer (manufactured by Mitsui Toatsu Chemical Co., Ltd., Euramin P-1500) 1
Add 1.0 part and react at 70°C for 3 hours to reduce the average particle size to 3.
．． A 5 μm microcapsule dispersion was obtained. Next, 30 parts of the obtained dispersion was added with 30 parts of 10% polyvinyl alcohol.
A coating solution was prepared by adding 50% of the solution, and the coating solution was applied to a high-quality paper with a basis weight of 66 g/m 2 so that the amount of adhesion after drying was 10 g/m 2 . When the thermal recording paper thus obtained was printed using a word processor (Ricoh My Report NL-1), a green image with a print density of 1.23 was obtained. The density of this image decreased to 1.01 after 10 minutes, but there was no problem in reading it. After 10 hours of standing, the print disappeared and returned to its original state with no afterimage, and no deterioration in functionality was observed due to repeated use.

Claims (3)

[Claims] Claim 1. A thermochromic composition that utilizes a color-forming reaction between an electron-donating color-forming compound and an electron-accepting compound, in which the electron-accepting compound has 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-
An organic acid having a hydroxyl group at the α-position carbon represented by CH(OH)COOH (wherein R2 represents a higher alkyl group or alkenyl group) is used, and the composition also contains a discoloration temperature regulator and a low volatile solvent. 1. A reversible thermochromic composition comprising: 2. The reversible thermochromic compound according to claim 1, wherein the electron-donating color-forming compound is a halogen-containing electron-donating color-forming compound and/or a compound represented by the following general formula: [Claim 1] 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 (represents an integer of 2) 3. A reversible heat-sensitive recording material comprising the composition of claim 1 or 2 supported on a support.