JP2000118134A - Heat-sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a heat-sensitive recording material having improved coloring sensitivity without deteriorating the storage stability (moisture resistance and plasticizer resistance) of a recorded image. SOLUTION: A heat-sensitive recording material with a heat-sensitive layer containing a leuco dye which is colorless or of light color at the normal temperature and a developer to be colored by reacting with the leuco dye and formed on a substrate, and at least one kind of compound represented by a general formula is contained as a sensitivity improver in the heat-sensitive coloring layer. In the formula, R represents alkyl, alkoxyl, aryl, nitro group or halogen atom, and in the case (n) is 2 or more, they can be different, and (n) represents 0-5 integer. X represents single bond or -Cm. H2m-, Y represents a bivalent aliphatic group or a bivalent unsaturated aliphatic group and (m) represents 1-5 integer.

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 material, and more particularly to a heat-sensitive recording material having improved color sensitivity without deteriorating the storage stability (moisture resistance and plasticizer resistance) of a recorded image. .

[0002]

2. Description of the Related Art In recent years, the amount of information has increased along with the diversification of information. In the field of information recording for recording such information, various recording methods and recording materials have been studied and put to practical use. I have. Among them, the thermal recording method is 1) inexpensive and compact in hardware, 2) a recorded image can be obtained by simply heating a thermal recording material, and does not require a complicated developing step. 3) Thermal recording The production and preservation of the material are easier and cheaper than other recording materials. 4) Inexpensive paper is often used as a support for the heat-sensitive recording material. It has the advantage that the recording material feels like that of plain paper, and is used in many fields such as computer output, printers such as calculators, recorders for various measuring instruments, facsimile machines, automatic ticketing machines, thermocopiers, and labels. ing.

In particular, recently, heat-sensitive recording materials have been used for labels, cards, receipts, and the like, and high functions different from conventional functions have been demanded. Conventionally, phenol compounds, for example, bisphenol A, bisphenol S derivatives, hydroxybenzoic acid esters, and the like have been widely used as color developers for developing leuco dyes. When a heat-sensitive recording material using these developers is used for a label or a receipt in a POS system or the like, a label or a receipt particularly used in a food counter or the like is made of water,
It often comes in contact with wrap films and oils, and has the drawback that recorded images are significantly discolored.

[0004] In order to solve such a problem in the conventional heat-sensitive recording material, Japanese Patent Publication No. Sho 63
JP-A-46067, JP-A-63-176181 and JP-B-3-39474 disclose a method of incorporating a diphenylsulfone derivative having a phenol skeleton as a color developing agent. Kaihei 7
JP-A-96667 discloses a method in which a benzoic acid derivative is contained as a developer, and JP-A-62-82070 and JP-A-2-122977 describe a method in which a salicylic acid derivative is contained as a developer. JP-A-5-32061, JP-A-5-147357, JP-A-5-14
No. 8220 discloses a method of incorporating a sulfonylaminocarbonylamino derivative as a color developing agent.
JP-A-164579 discloses a method in which an epoxy compound is used in combination with a phenolic developer. JP-A-59-73990, JP-A-61-160292, and JP-A-4-3.
No. 7589 proposes stabilizing storage by a method of including a sulfonic acid ester derivative as a sensitivity improver. However, heat-sensitive recording materials having high storage stability have to use relatively special coloring materials and additives, so that they often have a drawback of relatively low sensitivity, and have not been satisfactory.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of such a viewpoint.
An object of the present invention is to provide a heat-sensitive recording material having improved coloring sensitivity without deteriorating the storage stability (moisture resistance, plasticizer resistance) of a recorded image.

[0006]

That is, the present invention provides a heat-sensitive coloring layer containing a colorless or light-colored leuco dye at room temperature, and a developer which, when heated, reacts with the leuco dye to form a color. A heat-sensitive recording material provided on a body, wherein at least one compound represented by the following general formula (1) is contained in the heat-sensitive coloring layer as a sensitivity improver.

Embedded image (Wherein R is an alkyl group, an alkoxy group, an aryl group,
It represents a nitro group or a halogen atom, and when n is 2 or more, they may be different, and n represents an integer of 0 to 5.
X represents a single bond or -C _m H _2m -, Y represents represents a divalent saturated aliphatic group or a divalent unsaturated aliphatic group, m represents an integer of 1 to 5. )

In the present invention, the leuco dye used as a color former is a substance that is colorless or pale at room temperature and reacts with a developer under heating to form a color.
Triallylmethane dyes such as 3′-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide;
Diphenylmethane dyes such as 4,4'-bisdimethylaminobenzhydridobenzyl ether, thiazine dyes such as benzoylleucomethylene blue, spiro dyes such as 3-methylspirodinaphthopyran, fluorane dyes, and other leuco dyes Auramine, indoline,
Indigo dyes and the like can be mentioned. When using these color formers, one or more selected ones can be used.

In the present invention, the sensitivity enhancer used for the purpose of improving the color sensitivity and the storage stability of the color image is at least one compound represented by the general formula (1), and is preferably Is a compound having a melting point of 60 to 160 ° C. Compounds having a melting point lower than 60 ° C. may cause defects such as causing a coloring reaction during the production of the heat-sensitive recording material and decreasing the stability of the whiteness of the background of the heat-sensitive recording material. Further, a compound having a melting point exceeding 160 ° C. makes it difficult to obtain a highly sensitive thermosensitive recording material.

In the general formula (1), R which gives a preferable compound is a methyl group, an ethyl group, a methoxy group,
An ethoxy group, a phenyl group, a nitro group, a halogen atom, and the like, n is 0 or 1 to 2, X is a single bond, -C
H ₂ - such that, -C 2 or 3 carbon atoms as _{Y 2 H 4 -, - C} 3 H
_{6 -, - C 2 H 2} - , etc. or cyclohexyl.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION [Compound 1]
To [Compound 6] are preferred examples of the sensitivity improver, but the present invention is not limited thereto.

[Compound 1] (melting point: 99-100 ° C.)

Embedded image [Compound 2] (melting point: 114-115 ° C)

Embedded image [Compound 3] (melting point: 123-124 ° C)

Embedded image [Compound 4] (melting point: 80-84 ° C)

Embedded image [Compound 5] (melting point: 102-103 ° C)

Embedded image [Compound 6] (melting point: 116-117 ° C)

Embedded image

The compound represented by the general formula (1) can be obtained by reacting an aniline derivative or an aralkylamine derivative with an acid anhydride in various solvents to obtain an amic acid, followed by dehydration imidization. it can. For example,
In a dimethylacetamide solution in which succinic anhydride is dissolved,
After dropping o-toluidine to make an amic acid, [Compound 1] can be obtained by adding a dehydration catalyst such as sulfuric acid and heating and stirring.

The compound represented by the general formula (1) is
One kind may be used alone, or a mixture with another sensitivity improver may be used in combination. As such a sensitivity improver,
For example, stearic acid amide, palmitic acid amide, oleic acid amide, capric acid amide, linoleic acid amide,
Nitrogen-containing compounds such as atearic acid anilide, benzyl 4-hydroxybenzoate, benzyl 4-benzyloxybenzoate, phenyl 2-naphthoate, benzyl 2-naphthoate, phenyl 1-hydroxy-2-naphthoate Ester compounds such as ester, dibenzyl oxalate, di (4-methylbenzyl) oxalate, dibenzyl terephthalate, n-butyl isophthalate, phenyl p-toluenesulfonate, and 4-benzylbiphenyl , M-terphenyl, fluorene, fluoranthene, 2,6-diisopropylnaphthalene, 3-benzylacenaphthene, 1,2-bis (3,4-dimethylphenyl) ethane, 1,2-bis (2,4-dimethylphenyl) ) Ethane, 1,2- Aromatic hydrocarbon compounds such as bis (2,4,5-trimethylphenyl) ethane, 2-benzyloxynaphthalene, 1,4-diethoxynaphthalene, 1,2-diphenoxyethane, 1,2-bis (3 '
-Methylphenoxy) ethane, 1,2-diphenoxybenzene, 1,4-diphenoxybenzene, 4- (4'-
Methylphenoxy) biphenyl, diphenylsulfone,
4,4′-diisopropoxydiphenyl sulfone, 4,
Examples thereof include ether compounds such as 4′-diphenoxydiphenylthioether and benzyl-4-methylthiophenylether, and sulfur-containing compounds.

In the present invention, the developer used together with the leuco dye is a substance which comes into contact with the leuco dye by heating to develop the leuco dye. Examples of such a developer include phenol derivatives such as 4-tert-butylphenol and 4-phenylphenol, naphthol derivatives such as 1-naphthol and 2-naphthol, and 2,2 ′
-Dihydroxybiphenyl, 2,2-bis (4'-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, 2,4'-dihydroxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl)
Sulfone, 4-hydroxy-4′-isopropoxydiphenylsulfone, bis (4-hydroxyphenyl) sulfoxide, bis (3-allyl-4-hydroxyphenyl) sulfoxide, 4-hydroxy-4′-isopropoxydiphenylsulfoxide, Bis (4-hydroxyphenyl) sulfide, bis (3-allyl-4-hydroxyphenyl) sulfide, bis (3-methyl-4-
Hydroxyphenyl) sulfide, 4-hydroxy-
4'-isopropoxydiphenyl sulfide, 1,7-
Bisphenol derivatives such as bis (4-hydroxyphenylthio) -3,5-dioxaheptane; hydroxybenzoic acid ester derivatives such as 4-hydroxybenzoic acid benzyl ester and 4-hydroxyphenethyl ester;
Salicylic acid derivatives such as salicylic acid, 3-isopropylsalicylic acid, 3,5-di-tert-butylsalicylic acid or metal salts thereof, benzoic acid, benzyl 2-carboxy-benzoate, benzyl 4-carboxy-benzoate, 4-nitrobenzoate Acid, a benzoic acid derivative such as 4-chlorobenzoic acid or a metal salt thereof, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane,
Organic developers such as sulfonylurea derivatives such as 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenyl ether and urea derivatives such as diphenylurea and diphenylthiourea are exemplified. Further, an inorganic color developer such as acid clay, activated clay, aluminum chloride, zinc chloride, and zinc bromide can be used.

In addition to these, additives such as an epoxy compound, an epoxy resin, zinc stearate, iron stearate, and zinc salicylate may be used in combination in order to improve the storage stability of the colored portion.

Further, various additives can be added to the heat-sensitive recording material of the present invention according to the use and the like. Such additives include, for example, polyvinyl alcohol, latex, methylcellulose, carboxymethylcellulose, polyacrylic acid casein, gelatin, starch, or the like, which fix the leuco dye and the electron-accepting substance dispersed on the fine particles in a state of being isolated from each other. Examples include binders such as these derivatives, and white pigments such as calcium carbonate, silica, kaolin, clay, talc, and titanium oxide added for the purpose of whiteness of the heat-sensitive coloring layer, slipperiness of a writing instrument, and sticking. These additives are mixed or separately applied to a support such as paper or film to form a thermosensitive coloring layer. In addition, this thermosensitive coloring layer is a heat insulating layer,
It may have another layer such as a protective layer.

In the heat-sensitive recording material of the present invention, the compound represented by the general formula (1) contained in the heat-sensitive coloring layer has a high thermal response and dissolves the dye and the developer when melted. It is conceivable that the easiness of the coloring enhances the coloring sensitivity and improves the robustness of the printed image.

[0018]

The present invention will be specifically described below based on examples and comparative examples. Example 1 (1) Preparation of Solution A [Compound 1] 11.5 parts by weight, 2,2-bis (4'-hydroxyphenyl) propane (hereinafter referred to as BPA) 1
1.5 parts by weight, 10 wt% aqueous solution of polyvinyl alcohol 4
6 parts by weight and 46 parts by weight of water were pulverized, mixed and dispersed by using a sand mill to prepare a liquid A having an average particle diameter of about 0.6 μm. (2) Preparation of solution B 5.5 parts by weight of 7'-anilino-3 '-(dibutylamino) -6'-methylfluorane and 49.5 parts by weight of a 10 wt% aqueous polyvinyl alcohol solution were pulverized and mixed using a paint shaker. And dispersed to prepare a liquid B having an average particle diameter of 0.8 μm. (3) Preparation of thermal recording paper 20 parts by weight of liquid A, 10 parts by weight of liquid B, 1 part by weight of paraffin wax emulsion (manufactured by Chukyo Yushi: Hydrin Z-7), paraffin wax emulsion (manufactured by Chukyo Yushi: Hydrin P-7) 4 parts by weight, 10 parts by weight of a 50% calcium carbonate dispersion and 11.5 parts by weight of a 10% by weight aqueous solution of polyvinyl alcohol were mixed to prepare a coating solution, and the coating solution was applied on a base paper, dried, and dried. A thermal recording paper having a coating amount of 6 g / m ² was prepared. (4) Color Test A dynamic color test is performed on the heat-sensitive recording paper prepared as described above using a printing tester (manufactured by Okura Electric Co., Ltd.). Printing was performed, and printing was performed at 27 V and 1.9 ms for a plasticizer resistance test. Simultaneously, the color density of the background was measured. The results are shown in Table 1. The color density was measured using a Macbeth reflection densitometer RD-9.
14 were used. (5) Humidity resistance test Thermal recording paper printed under the above conditions (24 V, 1.0 ms)
Is stored in a thermo-hygrostat (40 ° C., relative humidity 90%) for 10 hours, and then the color density of the printed portion is measured with a Macbeth reflection densitometer R.
The measurement was performed using D-914, and the results are shown in Table 1.
Shown in (6) Plasticizer resistance test Thermal recording paper printed under the above conditions (27 V, 1.9 ms)
Then, a vinyl chloride wrap is brought into close contact with the entire printing surface, stored in a dryer (50 ° C.) for 10 hours, and then the color density of the printed portion is measured using a Macbeth reflection densitometer RD-914. It is shown in Table 1.

Example 2 A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that [Compound 5] was used instead of [Compound 1] in the preparation of Solution A of Example 1. A color test, a humidity resistance test, and a plasticizer resistance test were performed in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 1 A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that the liquid A in Example 1 was prepared without using a sensitivity enhancer. A color development test, a humidity resistance test and a plasticizer resistance test were carried out. Table 1 shows the results.

Example 3 In preparing the solution A of Example 1, bis (4) was used in place of BPA.
-Hydroxyphenyl) sulfone (hereinafter referred to as BPS) was used to prepare a thermosensitive recording paper in exactly the same manner as in Example 1, and a color development test, a humidity resistance test and a plasticizer resistance were performed in the same manner as in Example 1. The test was performed. Table 1 shows the results.

Example 4 Example 1 was prepared in the same manner as in Example 1, except that [Compound 3] was used instead of [Compound 1] and BPS was used instead of BPA. To prepare a thermal recording paper,
A color test, a humidity resistance test, and a plasticizer resistance test were performed in the same manner as in Example 1. Table 1 shows the results.

Example 5 The procedure of Example 1 was repeated, except that [Compound 5] was used in place of [Compound 1] and BPS was used in place of BPA when preparing the solution A of Example 1. To prepare a thermal recording paper,
A color test, a humidity resistance test, and a plasticizer resistance test were performed in the same manner as in Example 1. Table 1 shows the results.

Example 6 In the same manner as in Example 1 except that [Compound 6] was used in place of [Compound 1] and BPS was used in place of BPA in preparing the solution A of Example 1. To prepare a thermal recording paper,
A color test, a humidity resistance test, and a plasticizer resistance test were performed in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 In the preparation of the solution A of Example 1, B was used without using a sensitivity enhancer.
A heat-sensitive recording paper was prepared in exactly the same manner as in Example 1 except that BPS was used in place of PA, and a color development test, a humidity resistance test and a plasticizer resistance test were performed as in Example 1. Table 1 shows the results.

Comparative Example 3 In the preparation of Solution A of Example 1, except that para-benzylbiphenyl (hereinafter referred to as p-BBP) was used instead of [Compound 1] and BPS was used instead of BPA. A thermosensitive recording paper was prepared in exactly the same manner as in Example 1, and a color test, a humidity resistance test and a plasticizer resistance test were performed in the same manner as in Example 1.
Table 1 shows the results.

Example 7 In preparing the solution A of Example 1, 4,4 'was used instead of BPA.
-(P-toluenesulfonylaminocarbonylamino)
A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that diphenylmethane (hereinafter, referred to as p-TSADM) was used, and a color development test, a humidity resistance test, and a plasticizer resistance test were performed in the same manner as in Example 1. went. Table 1 shows the results.

Example 8 The procedure of Example 1 was repeated except that [Compound 2] was used in place of [Compound 1] and p-TSADM was used in place of BPA when preparing the solution A of Example 1. In the same manner, a thermosensitive recording paper was prepared, and a color development test, a humidity resistance test, and a plasticizer resistance test were performed in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 4 In preparing the solution A of Example 1, p was used instead of [Compound 1].
A thermosensitive recording paper was prepared in exactly the same manner as in Example 1 except that BBP was used and p-TSADM was used instead of BPA, and a color development test, a humidity resistance test, and a plasticizer were prepared in the same manner as in Example 1. A sex test was performed. Table 1 shows the results.

[0030]

[Table 1]

[0031]

According to the present invention, a heat-sensitive recording material containing at least one compound represented by the general formula (1) as a sensitivity improver in a heat-sensitive coloring layer has a storage stability of a recorded image (moisture resistance). (Plasticizer resistance) without deteriorating the color sensitivity.

Claims (1)

[Claims] 1. A thermosensitive recording material comprising a support having thereon a thermosensitive coloring layer containing a colorless or pale-colored leuco dye at room temperature and a color developer which reacts with the leuco dye by heating to form a color. A heat-sensitive recording material comprising at least one compound represented by the following general formula (1) as a sensitivity improver in the heat-sensitive coloring layer. Embedded image (Wherein R is an alkyl group, an alkoxy group, an aryl group,
It represents a nitro group or a halogen atom, and when n is 2 or more, they may be different, and n represents an integer of 0 to 5.
X represents a single bond or -C _m H _2m -, Y represents represents a divalent saturated aliphatic group or a divalent unsaturated aliphatic group, m represents an integer of 1 to 5. )