JPH0725156A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material forming a developed color image excellent in oil resistance, humidity resistance and heat resistance by providing a thermal color forming layer containing a dye precursor and a specific coupler reacting with the precursor to form a color on a sheet like substrate. CONSTITUTION:A specific amt. of a coupler represented by general formula (wherein R is a non-substituted aromatic group or an aromatic group substituted with one member selected from a lower alkyl group, a lower alkoxy group and a halogen atom, A is a divalent or more group and n is an integer of 2 or more) and a specific amt. of a triphenylmenthane or fluorane type leuco dye are mixed in a water-soluble binder such as polyvinyl alcohol under stirring to prepare a coating soln. for a thermal color forming layer. This coating soln. is applied to a sheet like substrate such as paper, synthetic paper or a plastic film and dried to laminate the thermal color forming layer to obtain a thermal recording material. A coating layer such as a protective layer or a printing layer can be further formed on the thermal color forming layer.

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, that is, a heat-sensitive recording material which forms a color image by heating, and more particularly to a heat-sensitive recording material which does not lose a once-colored image and is excellent in storage stability of recording. is there. More specifically, the present invention provides good long-term storage stability of recorded images,
At the same time, the present invention relates to an image recording body having excellent moisture resistance of a recorded image, environment resistance such as heat resistance, and oil resistance. INDUSTRIAL APPLICABILITY The thermosensitive recording medium of the present invention is useful for facsimile paper, cash dispenser paper, tickets, commuter passes, labels such as POS labels, cards such as prepaid cards and pass tickets.

[0002]

2. Description of the Related Art A heat-sensitive recording material is generally composed of a sheet-like substrate such as paper, synthetic paper, or plastic film, on which a color-forming substance composed of an electron-donating leuco dye and an electron-accepting phenolic compound or organic acid. A heat-sensitive color-developing layer containing, as a main component, a color-developing substance composed of the organic acidic substance described above is provided, and a recorded image can be obtained by reacting the color-developing components with thermal energy. Such thermal recording materials are disclosed in, for example, Japanese Patent Publication No. 43-4160 and Japanese Patent Publication No. 45-14.
It is disclosed in Japanese Unexamined Patent Publication No. 039 and Japanese Unexamined Patent Publication No. 48-27736, and is widely put into practical use.

The above-mentioned thermal recording medium has the advantages that the recording apparatus is compact, inexpensive, and easy to maintain. Utilizing this advantage, the output of a computer, facsimile, automatic Widely used in ticket vending machines, printers for scientific measuring instruments, and printers for CRT medical measurement. However, in a conventional so-called dye-type thermosensitive recording medium in which a thermosensitive coloring layer containing a color-developing dye substance, a color-developing substance and a binder as an active ingredient is coated on a support, the coloring reaction is reversible. Therefore, there is a known defect that a color image disappears over time. This erasing phenomenon is accelerated by exposure to light, high humidity and high temperature atmosphere, and further progresses rapidly due to contact with oil or the like, and the image is erased to an unreadable level.

In the case of using a color-forming system containing a dye precursor mainly containing a colorless or light-colored lactone ring compound, many techniques have been disclosed in order to suppress the above-mentioned decoloring phenomenon. For example, (1) JP-A-60-78782, JP-A-59-167292, JP-A-59-114096,
And a compound containing a phenolic antioxidant as described in JP-A-59-93387 in the thermosensitive color-developing layer, and (2) a hydrophobic polymer compound emulsion as disclosed in JP-A-56-146796. (3) A water-soluble polymer compound or a hydrophobic polymer compound emulsion is provided as an intermediate layer on the thermosensitive color-developing layer as shown in JP-A-58-199189. (4) JP-A-62-16457, in which a surface layer of an oil-based paint containing a hydrophobic polymer compound as a resin component is provided.
There are known those containing an epoxy compound as shown in JP-A No. 9 and (5) those using a metal salt of a specific salicylic acid derivative found in JP-A No. 62-169681 as a developer.

When the above-mentioned phenolic antioxidant is blended in the heat-sensitive color-developing layer, the environment resistance is slightly improved as compared with the image in the case where it is not included, but the oil resistance (for example, salad oil is used as the coloring surface). No improvement is observed in the storage ratio of the image density after a certain period of time when it was brought into contact with.
On the other hand, in the thermal recording material provided with the protective layer and the surface layer,
Although environmental resistance is slightly improved, decolorization is unavoidable in long-term tests, and oil resistance also improves image storability immediately after contact with oil. Disappears almost completely and is not an essential solution to the above problems.

Further, in the case of containing an epoxy compound, a relatively long time is required from the heating color development operation to the stabilization of the color image, and for example, salad oil is added to the color image immediately after color development. When applied, a large part of the colored image is erased. Further, in the case of using a specific salicylic acid metal salt, although oil resistance is improved, color development of the white paper part is seen in the heat resistance test, and the chemical structure of an effective specific salicylic acid is complicated and expensive. Have.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves these problems of the prior art and provides a heat-sensitive recording material which is excellent in oil resistance, moisture resistance, heat resistance, etc. of a color image, and is therefore excellent in long-term storage stability. It is the one we are trying to provide. That is, the present invention can be used not only as a heat-sensitive recording type ticket for an automatic ticket vending machine, but also for use on a coupon ticket, a commuter ticket, etc., which require preservation, and in contact with oils and fats. POS to be attached to the packaging surface of food wrapped in vinyl film
Not only suitable as a label for a barcode system, but also for long-term storage such as facsimile paper and word processing paper,
Another object of the present invention is to provide a thermal recording material that can be used as an image printer paper for CRT.

[0008]

DISCLOSURE OF THE INVENTION The present inventors have investigated a thermosensitive color developing layer in which the effect of improving the storage stability of a color image is developed within a short time after the formation of the color image, and as a result, Two or more arylamidosulfonyl groups represented by the formula (II) per molecule:

[Chemical 2] (In the formula (II), R is a member selected from an unsubstituted aromatic group and an aromatic group substituted with at least one member selected from a lower alkyl group, a lower alkoxy group and a halogen atom. Represents an aromatic compound having
The present invention has been completed by discovering that a color image having not only excellent color developing ability but also high oil resistance and thus having an excellent long-term storage stabilizing effect can be formed.

The thermosensitive recording medium of the present invention comprises a sheet-like substrate,
Formed on at least one surface of the sheet-like substrate, and
A colorless or light-colored dye precursor, and a heat-sensitive color-developing layer containing a color-developing agent that reacts with this dye precursor under heating to develop a color, and the color-developing agent has the following general formula (I):

[Chemical 3] (However, in the formula (I), R is an unsubstituted aromatic group, and a member selected from a lower alkyl group, a lower alkoxy group, and an aromatic group substituted with at least one member selected from a halogen atom. And A represents a divalent or higher valent group).

[0010]

The thermosensitive recording material of the present invention is characterized in that the developer contained in the thermosensitive coloring layer contains the compound of the formula (I). In the compound of the formula (I), the group represented by A is not particularly limited as long as it is a group having a valence of 2 or more, particularly an organic group, but the following groups a to g are preferable. it can. Among these, particularly preferred are the aromatic groups of groups e to g.

Group a: Divalent or higher valent organic group derived from aliphatic hydrocarbon Group b: Divalent or higher valent organic group derived from aliphatic hydrocarbon containing at least one hetero atom in the main chain c: a divalent or higher organic group derived from an aliphatic hydrocarbon containing at least one substituted or unsubstituted aromatic hydrocarbon in the main chain group d: at least one substituted or unsubstituted in the main chain A divalent or higher valent organic group derived from an aliphatic hydrocarbon containing a heteroaromatic ring of group e: a divalent or higher valent organic group derived from a substituted or unsubstituted aromatic hydrocarbon group f: a substituted or unsubstituted Divalent or higher valent organic group derived from heteroaromatic ring group g: two or more aromatic hydrocarbon groups and heteroaromatic ring groups are organic groups of the above groups a to c, carbonyl group, thiocarbonyl group, and Sulfonyl Divalent or higher organic group derived from a compound having a bond structure by functional group such as

Typical examples of the organic groups belonging to the above groups a to g are shown below.

[Chemical 4]

[0013]

[Chemical 5]

The compound of formula (I) used in the present invention acts as a developer for the dye precursor. That is, the compound of formula (I) does not have an acidic functional group such as a phenolic hydroxyl group or a carboxyl group, but exhibits a strong color developing ability to a dye precursor such as a basic leuco dye. Is. It is understood that the color developing performance of the compound of formula (I) is that the amide group in the compound of formula (I) is activated by the sulfonyl group adjacent to it. Further, it is contained in the molecule that the image formed by the reaction of the compound of formula (I) and the dye precursor shows high storage stability under various environments.
It is understood to be due to the synergistic effect of one or more arylamidosulfonyl groups (Formula II).

In the compound of formula (I) of the present invention, the aromatic group represented by R is, for example, p-toluene group,
It can be selected from o-toluene group, 1-naphthalene group, p-chlorobenzene group, p-anisole group and the like.

Specific examples of the compound of formula (I) useful in the present invention are as follows. N, N'-bis (p-
Toluoyl) -1,2-ethanedisulfonamide, N,
N'-bis (p-toluoyl) -m-phenylenedisulfonamide, N, N'-bis (p-toluoyl) -p-
Phenylenedisulfonamide, N, N'-bis (p-toluoyl) -o-phenylenedisulfonamide, N,
N'-bis (benzoyl) -m-phenylenedisulfonamide, N, N'-bis (p-chlorobenzoyl) -m
-Phenylenedisulfonamide, N, N'-bis (p-
Anisoyl) -m-phenylenedisulfonamide, N,
N'-bis (o-toluoyl) -m-phenylenedisulfonamide, N, N'-bis (1-naphthoyl) -m-
Phenylenedisulfonamide, N, N'-bis (2-naphthoyl) -m-phenylenedisulfonamide, N,
N'-bis (p-toluoyl) -2,4-toluene disulfonamide, N, N'-bis (p-toluoyl)-
4,4'-diphenylmethanedisulfonamide, N,
N'-bis (o-toluoyl) -4,4'-diphenylmethanedisulfonamide, N, N'-bis (benzoyl) -4,4'-diphenylmethanedisulfonamide,
N, N'-bis (p-toluoyl) -4,4'-diphenylsulfone disulfonamide, N, N'-bis (p-
Toluoyl) -3,3'-diphenylsulfone disulfonamide, N, N'-bis (p-toluoyl) -4,
4'-diphenyl ether disulfonamide, N, N '
-Bis (p-toluoyl) -2,5-furandisulfonamide, N, N'-bis (p-toluoyl) -1,5-
Naphthalenedisulfonamide, N, N'-bis (p-toluoyl) -1,5-naphthalenedisulfonamide,
N, N'-bis (o-toluoyl) -1,6-naphthalenedisulfonamide, N, N'-bis (o-anisoyl) -2,6-naphthalenedisulfonamide, N, N '
-Bis (o-chlorobenzoyl) -2,7-naphthalenedisulfonamide, N, N'-bis (p-toluoyl)
-4,4'-diphenyldisulfonamide, N, N'-
Bis (o-toluoyl) -4,4'-diphenyldisulfonamide, N, N'-bis (p-anisoyl) -4,
4'-diphenyldisulfonamide, N, N'-bis (p-toluoyl) -2,4'-diphenyldisulfonamide, N, N'-bis (p-toluoyl) -4,4 '
-Diphenyl sulfide disulfonamide, N, N'-
Bis (o-toluoyl) -4,4'-diphenylsulfide disulfonamide These compounds may be used alone or in combination of two or more thereof.

The compound of formula (I) as described above can be synthesized, for example, by the following reaction.

[Chemical 6]

In the present invention, the leuco dye used as the dye precursor can be selected from conventionally known compounds such as triphenylmethane type compounds, fluorane type compounds and diphenylmethane type compounds. As such a dye precursor,
For example, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-3
-Yl) -4-azaphthalide, crystal violet lactone, 3- (N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinoflu Oran, 3
-Diethylamino-6-methyl-7- (o, p-dimethylanilino) fluorane, 3- (N-ethyl-Np-
Toluidino) -6-methyl-7-anilinofluorane,
3-pyrrolidino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7- Anilinofluorane, 3-diethylamino-7- (o-chloroanilino) fluorane,
3-diethylamino-7- (m-trifluoromethylanilino) fluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6-methylfluorane, and 3-cyclohexylamino-6.
One or more selected from -chlorofluorane, 3- (N-ethyl-N-hexylamino) -6-methyl-7- (p-chloroanilino) fluorane and the like can be used.

Further, in the heat-sensitive color developing layer of the present invention, a conventionally known developer compound consisting of a phenol or an organic acid is contained in combination with the compound of the formula (I) within a range not inhibiting the desired effect. May be. These conventional developer compounds are
For example, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis (1-methyl-1- (4 ′ -Hydroxyphenyl) ethyl) benzene, 1,3-bis (1-methyl-1- (4 ′)
-Hydroxyphenyl) ethyl) benzene, dihydroxydiphenyl ether (JP-A-1-180382),
Benzyl p-hydroxybenzoate (JP-A-52-140)
483), bisphenol S, 4-hydroxy-4 '
-Isopropyloxydiphenyl sulfone (JP-A-60
-13852), 1,1-di (4-hydroxyphenyl) cyclohexane, 1,7-di (4-hydroxyphenylthio) -3,5-dioxaheptane (JP-A-59-59).
52,694), 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone (JP-A-60-20828).
No. 6) etc. can be selected.

Further, it is preferable that the heat-sensitive coloring layer of the present invention contains a heat-fusible substance (so-called sensitizer) in combination. As the sensitizer, a heat-fusible organic compound having a melting point of 50 to 150 ° C. is used.
7-191089), p-benzylbiphenyl (JP-A-60-82382), benzylnaphthyl ether (JP-A-58-87094), dibenzyl terephthalate (JP-A-58-98285), p-benzyloxy. Benzyl benzoate (JP-A-57-201691),
Diphenyl carbonate, ditolyl carbonate (JP-A-58-1364)
89), m-terphenyl (JP-A-57-89994).
No.), 1,2-bis (m-tolyloxy) ethane (JP-A-60-56588), 1,5-bis (p-methoxyphenoxy) -3-oxapentane (JP-A-62-18).
1183), oxalic acid diesters (JP-A-64-1)
583), 1,4-bis (p-tolyloxy) benzene (JP-A-2-153787), and the like.

The thermosensitive coloring layer of the present invention may further contain a hindered phenol compound or an ultraviolet absorber. They are disclosed, for example, in JP-A-57-151394.
No. 58-160191 and 58-690.
96, JP-A-59-2884, JP-A-59-951
90, JP-A-60-22288, and JP-A-60-25.
5485, JP-A 61-44686, JP-A 62-
169683, JP-A-63-17081, JP-A-1
-249385 and compounds disclosed in JP-A-2-266645 and the like, and specifically, for example,
1,1,3-tris (3'-cyclohexyl-4'-hydroxyphenyl) butane, 1,1,3-tris (2-
Methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4′-thiobis (3-methyl-6-t
ert-butylphenol), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 2,2'-dihydroxy-4,4'-. Dimethoxybenzophenone, p-
Octylphenyl salicylate, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, ethyl-2-cyano-3,3'-diphenylacrylate,
It can be selected from tetra (2,2,6,6, -tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboate and the like.

The thermosensitive coloring layer of the present invention comprises a dye precursor mainly consisting of a leuco dye, a compound of the above formula (I) of the present invention, and optionally a sensitizer. Further, the thermosensitive coloring layer may optionally contain a conventionally known phenol type or organic acid type developer, antioxidant, ultraviolet absorber, or wax, and an organic or inorganic pigment. It is preferable to include the class.
Further, the heat-sensitive color forming layer contains a binder for fixing these components to the sheet-shaped substrate.

In the present invention, the content of the dye precursor in the thermosensitive coloring layer is preferably 5 to 20% by weight based on the dry weight of the thermosensitive coloring layer.
The content of the color developer of the formula (I) of the present invention is generally 10 to 50.
It is preferably in the weight%. When the content of the color developing agent compound of the formula (I) is less than 10% by weight, the obtained thermosensitive color developing layer exhibits insufficient color developing ability, and even when the content exceeds 50% by weight, the color developing ability is saturated. However, no particular improvement is seen, which may be economically disadvantageous.

When the thermosensitive coloring layer contains an antioxidant or an ultraviolet absorber, its content is preferably 1 to 10% by weight. When a conventionally known phenol-based or organic acid-based developer is contained, its content is 5 to 40% by weight.
Is preferable, and when the sensitizer is contained, its content is preferably 10 to 40% by weight. Waxes,
When the white pigment is contained in the thermosensitive coloring layer, its content is preferably 5 to 20% by weight and 10 to 50% by weight, respectively, and the content of the binder is generally 5 to 20% by weight.

Examples of the above-mentioned organic or inorganic pigments include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, calcined clay, talc, and surface-treated calcium carbonate. Inorganic fine powder such as silica and silica, urea-formalin resin, styrene / methacrylic acid copolymer,
And organic fine powder such as polystyrene resin.

As the waxes, known waxes such as paraffin, amide wax, bisimide wax, and metal salt of higher fatty acid can be used.

Examples of the binder include polyvinyl alcohols having various molecular weights, starch and its derivatives, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose and ethylcellulose,
Sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, alginic acid Water-soluble polymer materials such as soda, gelatin, and casein, as well as polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate , Ethylene / vinyl acetate copolymer, and styrene /
Each latex such as butadiene / acrylic copolymer can be used.

The sheet-like substrate used in the thermosensitive recording medium of the present invention is paper, coated paper having a surface coated with a pigment and / or latex, laminated paper, synthetic paper made of polyolefin resin, plastic film. You can choose from

On at least one surface of such a sheet-like substrate, a coating solution containing a mixture of the above-mentioned required components is applied and dried to form a thermosensitive coloring layer to produce a thermosensitive recording material. The coating amount of the thermosensitive coloring layer is 1 to 1 when the coating liquid layer is dried.
It is preferably 5 g / m ² and particularly preferably ² to 10 g / m ² . In the heat-sensitive recording material of the present invention, a coating layer such as a protective layer or a printing layer can be further formed on the heat-sensitive color developing layer.

[0030]

EXAMPLES The present invention will be specifically described with reference to the following examples. Unless otherwise specified, "part" and "%" represent "part by weight" and "% by weight", respectively.

Synthesis Example 1 [N, N'-bis (p-toluoy)
Synthesis of m) -m-phenylenedisulfonamide] In a three-necked flask equipped with a dropping funnel and a thermometer,
11.8 g of m-phenylenedisulfonamide and 10
g of pyridine were added and these were dissolved in 200 ml of dichloromethane. While vigorously stirring this solution with a magnetic stirrer, 15.5 g of p was added from the dropping funnel.
-Toluoyl chloride was added dropwise to the above solution. In this reaction, an exothermic reaction occurred at the same time as the dropping, so the dropping operation was performed while cooling the reaction solution from the outside so that the temperature did not exceed 20 ° C. After the addition was complete, the reaction mixture was stirred at room temperature for a further 1 hour, after which it was heated to reflux for 1 hour. After the solvent was distilled off from this reaction mixture, the obtained solid was dispersed and washed with an aqueous hydrochloric acid solution, and a crude product was obtained by filtration. When this was recrystallized using a mixed solvent of ethanol and water, 18.2 g of pale yellow crystals were obtained.

The melting point of the obtained crystal product is 252 to 25.
It was 4 ° C. In addition, NMR measurement, mass spectrometry and IR
By measurement, the obtained crystal product was identified as the target compound. The results of NMR measurement (in heavy DMSO) are as follows. δ = 2.35 (s, 6H), 7.28 (d,
4H), 7.73 (d, 4H), 7.94 (t, 1
H), 8.32 (d, 2H), 8.61 (s, 1H),
Other peaks that are considered to be attributed to NH are δ = 12.
Appeared near 4. In addition, the following characteristic absorption was confirmed by IR measurement (KBr tablet method). 1698 cm ^-1 (derived from carbonyl group) 1159 cm ^-1 (derived from sulfonyl group)

Synthesis Example 2 [N, N'-bis (p-toluoy)
1) Synthesis of 4,4′-diphenyldisulfonamide] In a three-necked flask equipped with a dropping funnel and a thermometer, 1
5.6 g of 4,4'-diphenyldisulfonamide was added and this was dissolved in 100 g of pyridine. While stirring this solution with a magnetic stirrer,
5.5 g of p-toluoyl chloride was added dropwise from the dropping funnel. Since an exothermic reaction occurred at the same time as the dropping, the dropping was performed while cooling from the outside so that the temperature of the reaction solution did not exceed 20 ° C. After the addition was completed, the reaction mixture was stirred at room temperature for another hour, and then heated at 70 ° C. for 1 hour. After cooling the obtained reaction liquid, this was poured into a large amount of hydrochloric acid acidic aqueous solution to precipitate a solid, and a crude product was separated by filtration. This was recrystallized from acetonitrile and 2
1.4 g of white crystals were obtained.

The melting point of the obtained crystalline product is 290-29.
It was 2 ° C. In addition, NMR measurement, mass spectrometry and IR
It was identified that the crystal product obtained by the measurement was the target compound. The results of NMR measurement (in heavy DMSO) are as follows. δ = 2.35 (s, 6H), 7.30 (d, 4)
H), 7.80 (d, 4H), 8.02 (d, 4H),
8.16 (d, 4H) and other peaks that are thought to be due to N-H appeared around δ = 12.5. In addition, the following characteristic absorption was confirmed by IR measurement (KBr tablet method). 1671cm ^-1 (derived from a carbonyl group) 1165 cm ^-1 (derived from sulfonyl group)

Example 1 A thermosensitive recording paper was prepared by the following procedure . 20 7-anilinofluoran polyvinyl alcohol 10% solution 10 Water 70 The composition - (1) Preparation of Dispersion Liquid Ingredients Amount of A (parts) 3- (N-isopentyl -N- ethylamino) -6-methyl Using a sand grinder, the average particle size is 1
It was pulverized until it became less than μm.

[0036] (2) Preparation of Dispersion Liquid Ingredients Amount of B (parts) N, N'-bis (p- toluoyl)-m-phenylene 10 disulfonamide oxalic di p- methylbenzyl ester 10 polyvinyl alcohol 10% solution 10 Water 70 The above composition is used in a sand grinder to give an average particle size of 1
It was pulverized until it became less than μm.

(3) Preparation of Pigmented Undercoat Paper 85 parts of calcined clay (trademark: Ansilex, manufactured by Engelhard) was dispersed in 320 parts of water to obtain a dispersion,
Styrene-butadiene copolymer emulsion (solid content 5
A coating solution was prepared by mixing 40 parts of 0%) and 50 parts of a 10% aqueous solution of oxidized starch. This coating solution is applied to a basis weight of 48
The coating amount after drying on one side of the g / m ² base paper is 7.0 g.
/ M ² and then dried to prepare a pigment-undercoated paper.

(4) Formation of thermosensitive coloring layer 30 parts of calcium carbonate pigment, 20 parts of 25% zinc stearate dispersion, in 50 parts of solution A and 200 parts of solution B,
A coating liquid was prepared by mixing 15 parts of a 30% stearic acid amide dispersion liquid, 15 parts of a 30% paraffin dispersion liquid, and 100 parts of a 10% polyvinyl alcohol aqueous solution, and stirring the mixture. This coating solution was applied to one surface of the pigment-undercoated paper so as to have a coating amount after drying of 5.0 g / m ² and dried to form a thermosensitive color-developing layer to prepare a thermosensitive recording paper.

The thermal recording paper obtained as described above was treated with a super calender, and the Bekk smoothness of the surface was adjusted to 600 to 1000 seconds.

The sample thus obtained was subjected to a color development test with an applied energy of 0.49 mj / dot by using a dynamic color development tester which was a commercial thermal facsimile machine manufactured by Hitachi, Ltd. The obtained color density is Macbeth reflection densitometer R
It was measured by D-914 (this is referred to as original concentration). Then, a test piece was prepared from the color-developed sample, and within 30 minutes after the color development, salad oil was applied to the test piece and allowed to stand at room temperature for 3 hours, and then excess oil was wiped off to obtain a residual image density on the test piece. Was measured with a Macbeth reflection densitometer, and the image preservation ratio was calculated according to the following formula. Image preservation ratio (%) = (residual image density / original density) × 100 Test results are shown in Table 1.

Example 2 In the same manner as in Example 1, a thermosensitive recording paper was prepared. However,
In preparing Dispersion B, instead of N, N′-bis (p-toluoyl) -m-phenylenedisulfonamide,
N, N'-bis (p-toluoyl) -p-phenylenedisulfonamide was used. The test results are shown in Table 1.

Example 3 In the same manner as in Example 1, a thermal recording paper was prepared. However,
In preparing Dispersion B, instead of N, N′-bis (p-toluoyl) -m-phenylenedisulfonamide,
N, N'-bis (benzoyl) -m-phenylenedisulfonamide was used. The test results are shown in Table 1.

Example 4 A thermal recording paper was prepared in the same manner as in Example 1. However, instead of N, N′-bis (p-toluoyl) -m-phenylenedisulfonamide in the preparation of Dispersion B,
N, N'-bis (p-chlorobenzoyl) -m-phenylenedisulfonamide was used. The test results are shown in Table 1.

Example 5 A thermal recording paper was prepared in the same manner as in Example 1. However, instead of N, N′-bis (p-toluoyl) -m-phenylenedisulfonamide in the preparation of Dispersion B,
N, N'-bis (p-toluoyl) -4,4'-diphenyldisulfonamide was used and diphenylsulfone was used instead of oxalic acid di-p-methylbenzyl ester. The test results are shown in Table 1.

Example 6 A thermal recording paper was prepared in the same manner as in Example 5. However, instead of N, N′-bis (p-toluoyl) -m-phenylenedisulfonamide in the preparation of Dispersion B,
N, N'-bis (p-toluoyl) -4,4'-diphenylsulfide disulfonamide was used. The test results are shown in Table 1.

Example 7 A thermosensitive recording paper was prepared in the same manner as in Example 1. However, in the formation of the thermosensitive coloring layer, 40 parts of solution A, and B
Liquid part 120 parts to calcium carbonate pigment 40 parts, 25% zinc stearate dispersion liquid 20 parts, 30% paraffin dispersion liquid 15
Parts, 10% polyvinyl alcohol aqueous solution 120 parts, and wetting aid (trademark: Dapro U99, manufactured by San Nopco) 3
The parts were mixed and stirred to prepare a coating liquid. This coating solution
On one side of synthetic paper (trademark: YUPO FPG-80, manufactured by Oji Synthetic Paper Co., Ltd.), a thermosensitive coloring layer is formed by coating and drying so that the coating amount after drying is 8.5 g / m ^2, and a thermosensitive coloring layer is formed. Was produced. The test results are shown in Table 1.

Example 8 A thermosensitive recording paper was prepared in the same manner as in Example 1. However, in the preparation of Dispersion A, 3- (N-isopentyl-N-
Instead of ethylamino) -6-methyl-7-anilinofluorane, 3- (N, N-dibutylamino) -6-methyl-7-anilinofluorane was used. The test results are shown in Table 1.

Comparative Example 1 A thermosensitive recording paper was prepared in the same manner as in Example 1. However, instead of N, N′-bis (p-toluoyl) -m-phenylenedisulfonamide in the preparation of Dispersion B,
2,2-bis (4-hydroxyphenyl) propane (ie bisphenol A) was used. Table 1 shows the test results
Shown in.

[0049]

[Table 1]

As is clear from Table 1 above, the color-developed image obtained using the novel developer compound of the present invention shows a color image which is higher than that obtained when bisphenol A, which is a typical developer, is used.
The oil resistance was remarkably excellent.

[0051]

The heat-sensitive recording material of the present invention contains a compound having two or more N-arylamidosulfonyl groups in one molecule as a developer in the heat-sensitive color developing layer. The color image formed on the color layer exhibits excellent oil resistance immediately after color development. Therefore, the thermosensitive recording medium of the present invention is useful for forming a record for long-term storage.

Claims (1)

[Claims] 1. A sheet-like substrate, a colorless or light-colored dye precursor which is formed on at least one surface of the sheet-like substrate, and a developer which reacts with the dye precursor under heating to develop a color thereof. And a heat-sensitive color developing layer containing, wherein the developer is represented by the following general formula (I): (However, in the formula (I), R is an unsubstituted aromatic group, and a member selected from a lower alkyl group, a lower alkoxy group, and an aromatic group substituted with at least one member selected from a halogen atom. And A represents a divalent or higher valent group, and n represents an integer of 2 or more.).