JPH08476B2 - Reversible thermosensitive recording material - Google Patents

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 capable of repeatedly forming an image and erasing the image,
In particular, the present invention relates to a reversible thermosensitive recording material which has a high contrast, can be easily visually discriminated, and can form and erase an image only by controlling thermal energy.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for the reuse of paper from the viewpoint of measures against the rapid increase of urban garbage and global environmental protection. Thermal recording paper is widely used in office automation equipment such as word processors and facsimiles and continues to be consumed in large amounts, which is one of the causes of the above problems. However, thermal recording paper cannot be used as recycled paper for technical and economic reasons, and at present,
It is in a state of being discarded. To solve such a problem, the use of a reversible thermosensitive recording material capable of thermosensitive printing capable of repeating image formation and erasing thereof can be a solution.

Reversible thermosensitive recording materials have hitherto been disclosed in JP-A-63-39377, JP-A-63-41186 and JP-A-2-
566, JP 2-1363, JP 2-80289, JP 2
-81672, JP-A-2-86491, JP-A-58-191190,
JP-A-60-193691, JP-A-60-255482, JP-A-4-1
4482, International Publication WO 90/11898, JP-A-4-46986, JP-A-4-50289, JP-A-4-50290, and Japanese Patent Application No. 3-255.
The invention is disclosed in Japanese Patent Application No. 401, Japanese Patent Application No. 4-054625, Japanese Patent Application No. 4-062740 and the like.

Among these, the contents described in the former 7 are:
Dispersing an organic low molecular weight substance in an organic polymer binder,
The content is to reversibly crystallize and polycrystallize the organic low molecular weight substance by thermal energy. However, since the image formation in this case utilizes white turbidity due to polycrystallization, it has a drawback that the contrast is low and it is difficult to visually determine.

The contents described in the following three parties are composed of a color former, a developer and an organic polymer binder. Printing can be done by heat, but the erasing must be done by water or steam. There's a problem.

Further, the contents described in Japanese Patent Laid-Open No. 14482/1992 are for erasing the printed image naturally, and cannot intentionally control the printing and erasing.

Further, the contents described in the remaining 7 persons consist of a leuco compound, a color-developing / reducing agent which reacts with the leuco compound thermally to cause coloring and decoloring, and an organic polymer-based binder,
Coloring and erasing are performed by controlling heat energy. However, in the case where the developer and the color-reducing agent are a complex or a salt consisting of phenolcarboxylic acid and one kind of amine, those having a relatively high color density are difficult to be decolored, and those which are easy to decolor have a comparative color density. There was a problem that it was low.

[0008]

As described above, in the prior art, a reversible thermosensitive recording material capable of thermosensitive printing capable of repeating image formation and erasing has been obtained which has sufficiently satisfactory characteristics. There wasn't. .

An object of the present invention is to solve the problems of the above-mentioned prior art, have high contrast, can be easily visually discriminated, and perform image formation and erasure only by controlling thermal energy. It is an object of the present invention to provide a reversible thermosensitive recording material which is capable of high color density and has a good decoloring property and which can repeatedly perform image formation and erasing.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that an organic polymer binder contains a leuco dye and a substance that reacts with the leuco dye to develop and decolorize. In the reversible heat-sensitive recording material, the substance which develops and decolorizes by reacting with a leuco dye is phenolcarboxylic acid, one kind of alkoxypropylamine having 4 to 23 carbon atoms, and 8 carbon atoms. To a charge transfer complex consisting of one of alkylamines from 18 to 18, the image formation is thermosensitive color development caused by instantaneous heating, and the decolorization is caused by heating over time as compared with the thermosensitive color development. It has been found that the above object can be achieved by using a reversible thermosensitive recording material characterized by being colored.

[0011]

The function of repeating coloring and decoloring of the material of the present invention is as described below. When the leuco dye is heated with an acidic substance called a developer, both or the developer melt, and the leuco dye is affected by the acidity of the developer to open the lactone ring in the leuco dye, What was initially colorless develops color. On the contrary, when a basic substance is brought into contact with the colored leuco dye, the opened lactone ring is closed to return to a colorless state. Therefore, the lactone ring can be opened or closed by using the color-developing / reducing agent which is a complex or salt of phenolcarboxylic acid and amine. This is because the above-mentioned color developing and decoloring agent that develops and decolorizes by reacting with a leuco dye is a substance having both an acidic substance, a phenolcarboxylic acid, and a basic amine, so that both acidic and basic are Equipped
In addition, the acidity and the basicity can be controlled by the heating mode. That is, in the case of instantaneous heating such as in a thermal printer, the acidity of the phenolcarboxylic acid works to develop the color, and in the slow heating, the basicity of the amine works to erase the color. The process of coloring and erasing can be repeated many times. In addition, the color-developed or decolored material in this manner retains the color-developed state or the decolorized state unless the color-developed material is decolored or the decolored material is colored. There is.

The conventional color-developing / reducing agent uses a complex or salt composed of phenolcarboxylic acid and one kind of amine. As described above, those having a relatively high color density are difficult to be erased, However, the developer / color-reducing agent of the present invention contains phenolcarboxylic acid, one of alkoxypropylamines having 4 to 23 carbon atoms, and 8 carbon atoms. A reversible thermosensitive recording material with high color density and good decolorization can be obtained because it consists of three components, one of up to 18 alkylamines, and these form a charge transfer complex. it can. That is, the electron acceptor phenolcarboxylic acid and the electron donor alkoxypropylamine form a charge transfer complex. On the other hand, phenolcarboxylic acid which is an electron acceptor and alkylamine which is an electron donor also form a charge transfer complex. Each of these charge transfer complexes reacts with a leuco dye to produce coloring and decoloring due to the difference in the heating form as described above, and this can be repeated, but in the former case, the coloring density is lower than that in the latter. It is relatively expensive but difficult to erase. This is because the endothermic effect for color development occurs at a lower temperature than the latter, so that the color density is high, and the change from acidic to basic for color erasing proceeds relatively slowly, which makes it difficult to erase color. On the other hand, in the latter case, the endothermic effect for color development occurs earlier than in the former, so the color density is lower, and the change from acidic to basic for decolorization occurs at a higher temperature. Easy to color. From these, materials used for the former and latter charge transfer complexes, namely, phenolcarboxylic acid and one of alkoxypropylamines having 4 to 23 carbon atoms, and alkylamines having 8 to 8 carbon atoms When a charge-transfer complex consisting of three types, one of which is up to 18, is used as the developer and color-reducing agent, the advantages of both the former and the latter appear. It is possible to obtain a reversible thermosensitive material having good chromaticity.

Of the three types of materials that make up the developer and color reducer,
Specific examples of phenolcarboxylic acids include gallic acid, salicylic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, and 2,6-dihydroxybenzoic acid. Acid, 3,5-dihydroxybenzoic acid, gentisic acid, protocatechuic acid,
2,3,4-trihydroxybenzoic acid, 2,4,6-trihydroxybenzoic acid, 2-hydroxy -m-toluic acid, hydroxy-o-toluic acid, hydroxy-p-toluic acid, 3,5
-Di-t-butylsalicylic acid, 3,5-di-tert-amylsalicylic acid, hydroxyisophthalic acid, hydroxyphthalic acid, 4-chlorosalicylic acid, 4-bromo-α-resorcinic acid, 5-methoxysalicylic acid, caffeic acid, umbell Acid, hydroxyphenylacetic acid, 3- (p-hydroxyphene
Examples thereof include nyl) propionic acid and hydroferulic acid.

Specific examples of the alkoxypropylamine having 4 to 23 carbon atoms include 3-methoxypropylamine, 3-ethoxypropylamine, 3-propoxypropylamine, 3-butyloxypropylamine and 3-pentyloxy. Propylamine, 3-hexyloxypropylamine, 3-heptyloxypropylamine, 3-octyloxypropylamine, 3-nonyloxypropylamine, 3-decyloxypropylamine, 3-undecyloxypropylamine, 3-dodecyloxy Propylamine, 3-tridecyloxypropylamine, 3-tetradecyloxypropylamine, 3-pentadecyloxypropylamine, 3-hexadecyloxypropylamine, 3-heptadecyloxypropylamine, 3-octadecyloxypropylamine , 3-nonadecyl propyl amine, 3-eicosyloxy propylamine, can be mentioned 3- (2-ethylhexyl) propyl amine.

Specific examples of the alkylamine having 8 to 18 carbon atoms include octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine and hexadecylamine. , Heptadecylamine, octadecylamine and the like.

Specific examples of leuco dyes that can be used in the reversible thermosensitive recording material of the present invention include crystal violet lactone, 2- (2-chloroanilino) -6-diethylaminofluorane and 2-anilino-3-methyl- 6-dibutylaminofluorane, 2- (2-chloroanilino) -6
-Dibutylaminofluorane, 1,3-dimethyl-6-diethylaminofluorane, 2-N, N-dibenzylamino-6
-Diethylaminofluorane, 3-indolino-3-p-
Dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluorane, 2- (2
-Fluorophenylamino) -6-diethylaminofluorane, 2- (2-fluorophenylamino) -6-di-n-butylaminofluorane, 3-diethylamino-7-cyclohexylaminofluorane, 3-diethylamino-5- Methyl-7-t-butylfluorane, 3-diethylamino-6
-Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-p-butylanilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2-anilino-3-methyl-6- ( N-ethyl-p-toluidino) -fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-N-methylcyclohexylamino-6-methyl-7 -Anilinofluorane, 3-N-ethylpentylamino-6-methyl-7-anilinofluorane, 3-cyclohexylmethylamino-6-methyl-7-anilinofluorane, 3-ethylisobutylamino-6- Methyl-7-anilinofluorane, 3-propylmethylamino-6-methyl-7-anilinofluorane and the like can be mentioned.

Further, as the organic polymer binder in the present invention, an organic polymer material which is soluble in water or an organic solvent can be used. As specific examples, polyvinyl alcohol, ethyl cellulose, cellulose acetate, polystyrene, polyvinyl chloride, acrylic resin, polyurethane, polyvinyl butyral, nitrocellulose and the like can be used.

As a method for providing a heat-sensitive recording layer on a support, a leuco dye, a color-developing agent and an organic polymer binder are uniformly dispersed or dissolved in water or an organic solvent, and if necessary, sensitized. A liquid obtained by adding an improving agent such as an agent or white pigment is applied to a support such as paper or plastic film by a method such as bar coating, blade coating, air knife coating, gravure coating, doctor coating, etc. Coated,
The recording layer can be obtained by drying.

Image formation on the recording layer produced as described above can be performed by instantaneous heating as in a thermal printer. Further, the formed image can be erased by heat energy different from heat-sensitive image formation, that is, by heating for a long time. Erasure by heat energy can be performed using a device such as a thermal gradient tester, a heat roll, a drier, an incubator, and a hot plate.

[0020]

EXAMPLES The reversible thermosensitive recording material of the present invention will be specifically described below with reference to examples. The "parts" used in the examples mean parts by weight.

[0021]

Example 1 Liquid A Crystal violet lactone 4 parts Polyvinyl alcohol 1 part Water 31 parts Liquid B Liquid charge transfer complex consisting of gallic acid, 3-methoxypropylamine and octylamine 16.2 parts Polyvinyl alcohol 3 parts Water 121 parts Solution A above , Solution B was crushed by ball milling for 20 hours each, and then the dispersion obtained by mixing Solution A and Solution B was applied by bar coating to 80 μm thick fine paper and dried at 60 ° C for 20 minutes. Thus, a reversible thermosensitive paper having an image forming layer thickness of 5 μm was produced. In addition, gallic acid and 3-methoxypropylamine
The molar ratio with is 1: 1, and the molar ratio of gallic acid and octylamine is
The ratio is 1: 1.

[0022]

[Comparative Example 1] A reversible thermosensitive paper was prepared in the same manner as in Example 1 except that the charge transfer complex in the solution B of Example 1 was replaced with a charge transfer complex consisting of gallic acid and 3-methoxypropylamine. A sample was prepared.

[0023]

[Comparative Example 2] A reversible thermosensitive paper sample was prepared in the same manner as in Example 1 except that the charge transfer complex in the solution B of Example 1 was replaced with a charge transfer complex composed of gallic acid and octylamine. did.

[0024]

Example 2 Liquid A 2- (2-chloroanilino) -6-diethylaminofluorane 4 parts Acrylic resin (Mitsubishi Rayon Acrypet MF) 2 parts Toluene 30 parts B liquid 2-hydroxy -m-toluic acid and 3- Charge transfer complex consisting of decyloxypropyl amine and tetradecyl amine 22.5 parts Calcium carbonate 20 parts Acrylic resin (Acrypet MF made by Mitsubishi Rayon) 6 parts Toluene 118 parts After crushing each of solutions A and B by sand milling for 1 hour , The dispersion obtained by mixing Solution A and Solution B was applied on a film made of polyethylene terephthalate with a thickness of 50 μm by air knife coating, and then dried at 60 ° C for 10 minutes to obtain the image forming layer thickness. A 5 μm reversible thermosensitive sheet was prepared. In addition, 2-hydroxy-m-toluic acid and 3-decyl
The molar ratio with oxypropylamine is 1: 1, 2-hydro
Molar ratio of xy-m-toluic acid to tetradecylamine.
Is 1: 1.

[0025]

[Comparative Example 3] The same procedure as in Example 2 was repeated except that the charge transfer complex in the liquid B formulation of Example 2 was replaced with a charge transfer complex consisting of hydroxy-m-toluic acid and 3-decyloxypropylamine. A reversible heat-sensitive sheet sample was prepared.

[0026]

[Comparative Example 4] Reversible thermosensitivity was carried out in the same manner as in Example 2 except that the charge transfer complex in the liquid B formulation of Example 2 was replaced with a charge transfer complex consisting of hydroxy-m-toluic acid and tetradecylamine. A sheet sample was prepared.

[0027]

Example 3 Liquid A 2-anilino-3-methyl-6-dibutylaminofluorane 4 parts Polyvinyl butyral (degree of polymerization = 700) 2 parts Toluene 15 parts Isopropyl alcohol 15 parts Liquid B 3- (p-hydroxyphenyl) Charge transfer complex consisting of propionic acid, 3- (2-ethylhexyloxy) propylamine and octadecylamine 22.4 parts Zinc stearate 6 parts Calcium carbonate 20 parts Polyvinyl butyral (degree of polymerization = 700) 6 parts Toluene 59 parts Isopropyl alcohol 59 parts After the liquid A and liquid B were pulverized in a ball mill for 20 hours each, the dispersion liquid obtained by mixing liquid A and liquid B was applied by blade coating to a 80 μm-thick quality paper and then
It was dried at ℃ for 15 minutes to prepare a reversible thermosensitive paper having an image forming layer thickness of 5 μm. In addition, 3- (p-hydroxyphenyl)
Ropionic acid and 3- (2-ethylhexyloxy) propyl
The molar ratio with amine is 1: 1, 3- (p-hydroxyphene)
The molar ratio of (nyl) propionic acid to octadecylamine is
It is 1: 1.

[0028]

[Comparative Example 5] The charge transfer complex in the liquid B formulation of Example 3 was
A reversible thermosensitive paper sample was prepared in the same manner as in Example 3 except that the charge transfer complex consisting of 3- (hydroxyphenyl) propionic acid and 3- (2-ethylhexyloxy) propylamine was used.

[0029]

[Comparative Example 6] The charge transfer complex in the liquid B of Example 3 was mixed.
A reversible thermosensitive paper sample was prepared in the same manner as in Example 3 except that the charge transfer complex consisting of 3- (hydroxyphenyl) propionic acid and octadecylamine was replaced.

Each sample of the example and the comparative example produced as described above was printed with a thermal printer and then placed on a hot plate at 110 ° C. to be erased. The time required for the measurement was measured. The results are shown in Table 1. The print density is a value measured using a Macbeth reflection densitometer.

[0031]

[Table 1]

From the results in Table 1, Example 1 and Comparative Example 1,
2, Example 2 and Comparative Examples 3 and 4, Example 3 and Comparative Examples 5 and 6
In comparison with the above, it can be seen that in any case, the samples of the examples have higher print density and can achieve decoloring in a relatively short time.

[0033]

As described above, by using the reversible thermosensitive recording material as the recording material of the present invention, the problems of the prior art can be solved, the contrast is high, and the visual discrimination is possible. Reversible that can be easily performed and that image formation and erasing can be performed only by controlling thermal energy, that the color density is high and the decoloring property is good, and that this image forming and erasing can be repeated. A heat-sensitive recording material could be provided.

Claims (1)

[Claims] 1. A leuco dye in an organic polymer binder,
In a reversible thermosensitive recording material comprising a substance that reacts with the leuco dye to develop and decolor, the substance that reacts with the leuco dye to develop and decolor is a phenolcarboxylic acid and from 4 to 4 carbon atoms. A charge transfer complex consisting of one of the alkoxypropylamines up to 23 and one of the alkylamines having 8 to 18 carbon atoms, wherein the image formation is a thermosensitive color development caused by instantaneous heating. The reversible thermosensitive recording material is characterized in that the decoloring is the decoloring caused by heating over time as compared with the thermosensitive coloring.