JP2000203162A - Heat-sensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat-sensitive recording medium adapted to a use of a coupon ticket, a commuter pass or the like having higher sensitivity than a conventional heat-sensitive recording medium and simultaneously excellent oil resistance, plasticizer resistance and hence excellent long term preservation such as, for example, necessity of a long preservation and adapted as a label for a bar code system. SOLUTION: In the heat-sensitive recording medium comprising a heat- sensitive color developing layer containing a dye precursor and a developer, the developing layer further contains at least one type of phenoxyacetoxy compound represented by the formula (wherein n is an integer of 2 or above, R, R are each a hydrogen atom or one member selected from a lower alkyl group and an alkoxy group). A developer having two or more sulfonyl urea group in one molecule is used together to make the high sensitivity and preservation compatible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium which forms a color image by heating, and more particularly to a thermosensitive recording medium having high recording sensitivity. In addition, the present invention provides image recording paper, cash dispenser paper, tickets, commuter passes, POS
Good for long-term storage of recorded images, suitable for labels such as labels, cards such as prepaid cards and toll tickets,
At the same time, it relates to a heat-sensitive recording medium having excellent water resistance, oil resistance, and plasticizer resistance of a recorded image.

[0002]

2. Description of the Related Art In general, a heat-sensitive recording material is formed on a support such as paper, synthetic paper, plastic film or the like by using a color-forming substance such as an electron-donating leuco dye and an organic acidic substance such as an electron-accepting phenolic compound. It is provided with a heat-sensitive coloring layer having a color-developing substance, and a recording image can be obtained by causing a coloring reaction of these coloring components by thermal energy. Such a heat-sensitive recording medium is disclosed in JP-B-43-4160, JP-B-45-14039, and JP-B-48-14039.
No. 27736, etc., and are widely used.

[0003] The thermal recording medium having the above configuration has a compact recording device, is inexpensive, and is easy to maintain. Therefore, the output of an electronic computer, a facsimile, an automatic ticket vending machine, a printer of a scientific measuring instrument, or a printer of a scientific measuring instrument. It is used for a wide range of applications such as printers for CRT medical measurement. A so-called high-sensitivity thermosensitive recording medium capable of obtaining a sufficient recording density with less energy has been demanded as the size of the apparatus is reduced and energy saving is advanced. Many methods have been proposed to achieve this sensitivity enhancement. Among them, the most prominent one has an aromatic structure and a melting point of 60.
This is a method in which a heat-fusible substance at about 120 ° C. to 120 ° C. is added to the thermosensitive coloring layer. These examples are described in JP-A-57-19108.
No. 9, JP-A-60-82382, JP-A-58
-98285, JP-A-57-89994, and the like. However, development of a new substance has been desired in order to further increase the sensitivity.

On the other hand, there is another demand for a thermosensitive recording medium. That is, there is a demand for a heat-sensitive recording medium that enhances the stability of a print formed by heating and makes it difficult for the print once formed to be easily erased. A chromogenic dye substance on a support,
In a conventional dye-type thermosensitive recording medium formed by applying a heat-sensitive coloring layer containing a color-developing substance and a binder as active ingredients, the coloring image is not reversible because the coloring reaction is reversible. It is known that the color will disappear. This decoloration is light exposure, high humidity,
And accelerated in a high-temperature atmosphere, and further accelerated by being left in water for a long time, contacting with an oil such as salad oil, or a plasticizer, and eventually the image is erased to an unreadable level.

[0005] In a color-forming system using a dye mainly containing a colorless or pale-colored lactone ring compound, various techniques have been disclosed for suppressing this decoloring phenomenon. For example, JP-A-60-78782, JP-A-59-16729
No. 2, Japanese Unexamined Patent Publication No. Sho 59-114096,
As disclosed in JP-A-9-93387, a compound in which a phenolic antioxidant is blended in a heat-sensitive coloring layer, and as disclosed in JP-A-56-146796, a hydrophobic polymer compound emulsion or the like is used. Examples include those used for the protective layer.

As disclosed in JP-A-58-199189, a water-soluble polymer compound or a hydrophobic polymer compound emulsion is provided as an intermediate layer on a thermosensitive coloring layer, and a hydrophobic polymer compound is coated thereon. Japanese Patent Application Laid-Open No. 62-1645, provided with a surface layer of an oil-based paint as a resin component
As disclosed in Japanese Patent Application Laid-Open No. 79-1679, a phenolic developer is used in combination with an epoxy compound.
As disclosed in Japanese Patent Application Publication No. 9681, there is known one using a metal salt of a specific salicylic acid derivative as a color developer.

The color image obtained in the thermosensitive coloring layer containing the above-mentioned phenolic antioxidant has a higher oil resistance (for example, a constant value when the salad oil is brought into contact with the coloring surface) than the color image without the compound. No improvement in the image density storage rate after a period of time) and the plasticizer resistance (preservation rate of the image density after a certain period of time when a wrap film or the like containing a plasticizer is brought into contact with a coloring surface) are not observed. .

In the case of a thermosensitive recording medium provided with a protective layer and a surface layer, the decoloration of an image is suppressed in a short-time contact with an oil or a plasticizer, but the decoloration in a long-time contact is prevented. Is inevitable,
It is not an essential solution to the above problem. In the case of using a phenolic compound and an epoxy compound in combination, a relatively long time is required from the time when the heating and coloring operation is performed to the time when the coloring image is stabilized, for example, by applying salad oil to the coloring image immediately after coloring. When a colored image is brought into contact with a plasticizer or a plasticizer, a considerable portion of the color image is erased.

Further, those using a specific metal salt of salicylic acid have improved image storability, but the coloring of a white paper portion is observed in a heat resistance test, and the chemical structure of an effective specific salicylic acid is complicated and expensive. There is a disadvantage that there is. Furthermore, in general, heat-sensitive recording materials having high preservability have to add additives or use a somewhat special coloring material,
It often has the disadvantage of relatively low sensitivity.

[0010]

Therefore, in the present invention,
It is an object to obtain a thermosensitive recording medium having higher sensitivity than a conventional thermosensitive recording medium. Another object of the present invention is to provide a heat-sensitive recording medium which has high sensitivity and excellent oil resistance and plasticizer resistance, and thus has excellent long-term storage properties.
More specifically, for example, it can be used not only as a thermal recording type ticket for an automatic ticket vending machine, but also suitable for use on coupons and commuter passes that require long-term storage, such as a plasticizer and oil and fat. It is suitable as a label for POS barcode systems to be attached to the packaging surface of food wrapped with a polyvinyl chloride film where contact is inevitable, and requires long-term storage facsimile paper and word processing paper that require high sensitivity, and CRT It is an object of the present invention to provide a thermosensitive recording medium that can be used as an image printer paper.

[0011]

In order to solve the above problems, the present invention employs the following constitution. That is, the present invention relates to a sheet-like substrate, a colorless or light-colored dye precursor formed on at least one surface of the sheet-like substrate, and a developing color that reacts with the dye precursor under heating to develop a color. A thermosensitive coloring layer containing an agent, wherein said thermosensitive coloring layer further comprises the following general formula (I):

Embedded image (However, in the formula (I), n represents an integer of 2 or more;
R ¹ and R ² represent at least one phenoxyacetoxy compound represented by a hydrogen atom or a member selected from a lower alkyl group and an alkoxy group).

In a preferred embodiment of the present invention, the phenoxyacetoxy compound is 1,4-bis (phenoxyacetoxy) butane.

Further, another invention of the present invention provides a thermosensitive recording medium of the present invention, wherein the developer is represented by the following general formula (II):

Embedded image (Wherein, in the formula (II), R ³ is an unsubstituted aromatic group, and
A represents a member selected from a lower alkyl group or an aromatic group substituted by a halogen atom, A represents a divalent or higher valent organic group or an inorganic group, and n represents an integer of 2 or more. ), Which comprises at least one compound represented by the formula (1):

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the compound represented by the general formula (I) contained in the heat-sensitive coloring layer is a so-called sensitizer and contributes to the improvement of the color-forming sensitivity of the heat-sensitive coloring layer. Specific examples of the compound represented by formula (I) are as follows. 1,2-bis (phenoxyacetoxy) ethane, 1,2
-Bis (o-tolyloxyacetoxy) ethane, 1,2
-Bis (m-tolyloxyacetoxy) ethane, 1,2
-Bis (p-tolyloxyacetoxy) ethane, 1,3
-Bis (phenoxyacetoxy) propane, 1,3-bis (o-tolyloxyacetoxy) propane, 1,3-
Bis (m-tolyloxyacetoxy) propane, 1,3
-Bis (p-tolyloxyacetoxy) propane, 1,
4-bis (phenoxyacetoxy) butane, 1,4-bis (o-tolyloxyacetoxy) butane, 1,4-bis (m-tolyloxyacetoxy) butane, 1,4-bis (p-tolyloxyacetoxy) butane 1,5-bis (phenoxyacetoxy) pentane, 1,5-bis (o-tolyloxyacetoxy) pentane, 1,5-bis (m-tolyloxyacetoxy) pentane, 1,5-
Bis (p-tolyloxyacetoxy) pentane, 1,6
-Bis (phenoxyacetoxy) hexane, 1,6-bis (o-tolyloxyacetoxy) hexane, 1,6-
Bis (m-tolyloxyacetoxy) hexane, 1,6
-Bis (p-tolyloxyacetoxy) hexane, 1,
8-bis (phenoxyacetoxy) octane, 1,8-
Bis (o-tolyloxyacetoxy) octane, 1,8
-Bis (m-tolyloxyacetoxy) octane, 1,
8-bis (p-tolyloxyacetoxy) octane and the like.

These compounds may be used alone or as a mixture of two or more. Among the above, 1,4-bis (phenoxyacetoxy) butane exhibits a particularly good sensitizing effect.

Further, one of the factors that contributes to the improvement of the color development sensitivity of the thermosensitive coloring layer using the developer compound represented by the general formula (II) is that the melting point of the compound represented by the general formula (I) is as follows. The fact that the compound represented by the general formula (I) alone has a particularly high sensitizing effect as compared with other heat-fusible organic compounds, which is suitable for a sensitizing effect is explained. Can not. Although the other reasons have not been elucidated clearly, the solubility of the compound represented by the general formula (I) in a moderate amount when the compound represented by the general formula (I) is melted by heating has a great effect. It is presumed to have given.

The developer used in the present invention is a conventionally known developer composed of phenols or organic acids, or a developer having two or more sulfonylurea groups in one molecule. It is as follows. For example, as phenols, 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-1-1
No. 80382) benzyl p-hydroxybenzoate (Japanese Patent Application Laid-Open No. 52-140483), bisphenol S, 4-hydroxy-4′-isopropyloxydiphenyl sulfone (Japanese Patent Application Laid-Open No. 60-13852),
1-di (4-hydroxyphenyl) cyclohexane,
1,7-di (4-hydroxyphenylthio) -3,5-
Dioxaheptane (JP-A-59-52694),
3,3′-diallyl-4,4′-dihydroxydiphenylsulfone (JP-A-60-208286),
4-bis (phenylsulfonyl) phenol (Japanese Unexamined Patent Application Publication No.
-269000) and the like. Further, as a developer other than phenol, N- (p-toluenesulfonyl)-disclosed in JP-A-5-3261 is disclosed.
N'-phenylurea, N- (p-toluenesulfonyl)
-N '-(p-methoxyphenyl) urea, N- (p-toluenesulfonyl) -N'-(o-tolyl) urea, N-
(P-toluenesulfonyl) -N '-(m-tolyl) urea, N- (p-toluenesulfonyl) -N'-(p-tolyl) urea, N- (p-toluenesulfonyl) -N'-
(O-chlorophenyl) urea, N- (benzenesulfonyl) -N'-phenylurea, N- (p-chlorobenzenesulfonyl) -N'-phenylurea and the like can be mentioned. These compounds may be used alone,
Alternatively, two or more kinds may be mixed.

The most preferred color developer in the present invention is represented by the following general formula (II):

Embedded image (Wherein, in the formula (II), R ³ is an unsubstituted aromatic group, and
A represents a member selected from a lower alkyl group or an aromatic group substituted by a halogen atom, A represents a divalent or higher valent organic group or an inorganic group, and n represents an integer of 2 or more. And a developer containing at least one compound represented by formula (1).

That is, examples of R ³ include an unsubstituted aromatic group such as a phenyl group and a naphthyl group.
R ³ is a lower alkyl group or an aromatic group substituted with a halogen atom, and may be substituted with both a lower alkyl group and a halogen atom. Preferred lower alkyl groups include methyl, ethyl, and propyl. Preferred halogen atoms are chlorin and fluorin atoms. Specifically, R ³ is a p-tolyl group, an o-tolyl group,
Examples thereof include a p-chlorophenyl group.

In the above formula (II) representing the most preferred developer compound, n represents an integer of 2 or more, and n is 2
It is preferred that In the above formula, A is n
Represents an organic group or an inorganic group having a valence equal to The type of the organic or inorganic group represented by A is not limited, but generally it is desirable to be selected from the following groups.

(A) carbonyl group, thiocarbonyl group,
Functional groups such as sulfonyl groups (b) divalent or higher organic groups derived from aliphatic hydrocarbons (c) divalent or higher organic groups derived from aliphatic hydrocarbons containing one or more hetero atoms in the main chain (D) at least one carbonyl group, thiocarbonyl group, imide group, imino group, sulfonyl group, divalent or higher organic group derived from an aliphatic hydrocarbon containing an ester bond in the main chain

(E) 2 derived from an aliphatic hydrocarbon containing at least one substituted or unsubstituted aromatic hydrocarbon in the main chain
(G) divalent or higher organic group derived from an aliphatic hydrocarbon containing at least one substituted or unsubstituted heteroaromatic ring in the main chain (g) substituted or unsubstituted aromatic carbon Divalent or more organic group derived from hydrogen (h) 2 derived from a substituted or unsubstituted heteroaromatic ring
Organic group having a valency of 2 or more (i) a divalent or higher valent organic group derived from a compound in which two or more of an aromatic hydrocarbon and a heteroaromatic ring are bonded by the above polyvalent groups (a) to (d) .

The compound of the general formula (II) used in the present invention acts as a color developer. That is, the compound of the general formula (II) does not have an acidic functional group such as a phenolic hydroxyl group or a carboxyl group, but exhibits a strong color developing ability with respect to a leuco basic dye. This strong color developing ability is understood to be because the urea group in the compound of the general formula (II) is activated by the sulfonyl group adjacent thereto.

The following are examples of compounds of the general formula (II). Bis (p-toluenesulfonylaminocarbonylamino) ketone, 1,2-bis (p-toluenesulfonylaminocarbonylamino) ethane, 1,1,6,6-tetra (p-toluenesulfonylaminocarbonylamino) amino
Heptane, 1,5-bis (p-toluenesulfonylaminocarbonylamino) -3-oxapentane, 1,3-
Bis (p-toluenesulfonylaminocarbonylaminomethyl) -benzene, 1,4-bis (p-toluenesulfonylaminocarbonylaminomethyl) -benzene,
4,4'-bis (p-toluenesulfonylaminocarbonylamino) -diphenylmethane, 4,4'-bis (o
-Toluenesulfonylaminocarbonylamino) -diphenylmethane, 4,4'-bis (benzenesulfonylaminocarbonylamino) -diphenylmethane, 4,4 '
-Bis (1-naphthalenesulfonylaminocarbonylamino) -diphenylmethane, 2,2-bis (4 ',
4 ″-(p-toluenesulfonylaminocarbonylamino) phenyl) propane, 1,2-bis (4 ′-(p
-Toluenesulfonylaminocarbonylamino) phenyloxy) ethane, 1,3-bis (p-toluenesulfonylaminocarbonylamino) benzene, 1,4-bis (p-toluenesulfonylaminocarbonylamino) benzene, 1,5-bis ( p-toluenesulfonylaminocarbonylamino) naphthalene, 1,8-bis (p-toluenesulfonylaminocarbonylamino) naphthalene, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenyl ether, 3,3′-bis ( p-toluenesulfonylaminocarbonylamino) diphenylsulfone, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylsulfone.
These compounds may be used alone or as a mixture of two or more.

In the present invention, the leuco dye used as the dye precursor can be selected from conventionally known ones such as triphenylmethane type, fluoran type and diphenylmethane type compounds. For example, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, crystal violet lactone, 3- (N-ethyl-N-
Isopentylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-
(O, p-dimethylanilino) fluoran, 3- (N-
Ethyl-Np-toluidino) -6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-
7-anilinofluoran, 3- (N-cyclohexyl-
N-methylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-dibutylamino-7-
(M-trifluoromethylanilino) fluoran, 3-
Diethylamino-6-methyl-7-chlorofluoran,
3-diethylamino-6-methylfluoran, and 3
-Cyclohexylamino-6-chlorofluoran, 3-
(N-ethyl-N-hexylamino) -6-methyl-7
One or more selected from-(p-chloroanilino) fluoran and the like can be used.

In the heat-sensitive coloring layer of the present invention, a conventionally known heat-fusible substance (sensitizer) can be used in combination within a range not to impair the desired effect. Representative examples thereof include 1-hydroxy-2-naphthoic acid phenyl ester (JP-A-57-19089), p-benzylbiphenyl (JP-A-60-82382), and benzylnaphthyl ether (JP-A-60-82382). 58-87094), dibenzyl terephthalate (JP-A-58-98285), p-
Benzyl benzyl benzoate (JP-A-57-201)
No. 691), diphenyl carbonate, ditolyl carbonate (JP-A-5
8-136489), m-terphenyl (JP-A-57 / 1979)
-89994), 1,2-bis (m-tolyloxy)
Ethane (JP-A-60-56588), 1,5-bis (p-methoxyphenoxy) -3-oxapentane (JP-A-62-181183), oxalic acid diesters (JP-A-64-1583), 1,4-bis (p-tolyloxy) benzene (JP-A-2-153783) and the like.

The thermosensitive coloring layer of the thermosensitive recording medium of the present invention may further contain waxes, and preferably contains organic or inorganic pigments. The thermosensitive coloring layer further contains a binder for fixing these components to the support.

The content of the dye precursor in the heat-sensitive coloring layer is generally preferably 5 to 20% by weight of the dry weight of the heat-sensitive coloring layer, and the content of the developer compound is generally 5% by weight of the heat-sensitive coloring layer. Preferably, it is about 50% by weight.
If the content is less than 5% by weight, the color developing ability may be insufficient. If the content is more than 50% by weight, the color developing ability is saturated and no particular improvement is observed, which is economically disadvantageous. It may be. The compound of the formula (I) preferably accounts for 5 to 50% by weight based on the weight of the thermosensitive coloring layer.
If the addition is less than 5% by weight, the sensitizing effect may be insufficient, and if the addition exceeds 50% by weight, the sensitizing effect may be saturated, and a further increase in sensitivity may not be expected.

When a conventional sensitizer other than the general formula (I) is contained, its content is preferably from 10 to 40% by weight.
When waxes and white pigments are contained in the heat-sensitive coloring layer, the content is preferably 2 to 20% by weight and 2 to 50% by weight, respectively, and the content of the binder is generally 5 to 20% by weight. . The above contents are also values based on the dry weight of the thermosensitive coloring layer.

Examples of the above 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. And inorganic fine powders such as silica and urea-formalin resin, styrene / methacrylic acid copolymer,
And organic fine powders such as polystyrene resin. Examples of the waxes include, for example, paraffin, amide wax, bisimide wax,
Known materials such as metal salts of higher fatty acids can be used.

As the binder, polyvinyl alcohols having various molecular weights, starch and derivatives thereof, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic amide / acrylic ester can be used. Water-soluble polymer materials such as polymers, acrylamide / acrylate / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein;
Polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylate,
Latexes such as vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, and styrene / butadiene / acrylic copolymer can be used.

The sheet-like substrate used in the thermosensitive recording medium of the present invention includes paper (including acidic paper and neutral paper), coated paper having a surface coated with a pigment or latex, laminated paper,
It can be selected from synthetic paper, plastic film, etc. made from polyolefin resin. A coating solution containing a mixture of the above-mentioned required components is applied on at least one surface of such a sheet-like substrate, and dried to produce a thermosensitive recording medium. The amount of coating is from 1 to 15 g /
m ² is preferred, and ² to 10 g / m ² is more preferred.

In the thermosensitive recording medium of the present invention, a coating layer such as a protective layer or a printing layer can be further formed on the thermosensitive coloring layer. Also, a pigment is provided between the support and the coating layer.
An undercoat layer containing (preferably an oil-absorbing pigment) and an adhesive may be provided.

In the present invention, the thermal recording medium can be further processed in order to increase the added value of the thermal recording medium, and can be provided with a higher function. For example, adhesive paper, re-wet adhesive paper, delayed tack paper can be processed by applying adhesive, rewet adhesive, delayed tack type adhesive to the back surface, or heat-sensitive recording that can be magnetically recorded on the back surface by magnetic processing It can be a material. In addition, thermal transfer paper, inkjet paper, carbonless paper,
Adds functions as electrostatic recording paper and xerographic paper,
It is also possible to use recording paper capable of recording on both sides. Of course, a double-sided thermosensitive recording medium can also be used.

[0035]

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

<Synthesis Example 1> Synthesis of 1,4-bis (phenoxyacetoxy) butane In a three-necked flask equipped with a thermometer, a reflux tube and a dropping funnel, 9.1 g of phenoxyacetic acid and 100 ml of N, N-dimethylformamide were added. And 8.3 g of potassium carbonate are added to the solution. While stirring this mixture with a magnetic stirrer, 6.5 g of a dropping funnel was added at room temperature.
1,4-dibromobutane was added. The reaction suspension was stirred at room temperature, heated under reflux at 110 ° C. for 1 hour, cooled to room temperature, added to 200 ml of water, and stirred vigorously to precipitate a white solid. This white solid is filtered,
Purification was performed by a recrystallization method, and 8.55 g of white crystals were obtained. By NMR measurement, the obtained compound was identified as the target compound.

The results of NMR measurement (CDCl 3) are as follows. δ = 1.65 (s, 4H), 4.19 (s, 4H), 4.
62 (s, 4H), 6.78 (d, 4H), 6.98
The (t, 2H), 7.27 (d, 4H) crystals were analyzed by DSC (differential scanning calorimetry) and found to have an endothermic peak at 90 ° C., presumably due to the melting point of the compound.

<Synthesis Example 2> Synthesis of 1,2-bis (phenoxyacetoxy) ethane The same operation as in Synthesis Example 1 was performed. However, instead of 6.5 g of 1,4-dibromobutane, 5.64 g of 1,2
-Dibromoethane was used. As a result, 6.41 g of white crystals were obtained. The melting point of this compound was 89 ° C., and the obtained compound was identified as the target product by NMR measurement.

The results of NMR measurement (CDCl 3) are as follows. δ = 4.40 (s, 4H), 4.61 (s, 4H), 6.
92 (d, 4H), 7.00 (t, 2H), 7.28
(T, 4H)

<Synthesis Example 3> Synthesis of 1,2-bis (m-tolyloxyacetoxy) ethane The same operation as in Synthesis Example 1 was performed. However, 9.95 g of 3-methylphenoxyacetic acid was used in place of 9.1 g of phenoxyacetic acid, and 5.65 g of 1,2-dibromoethane was used in place of 6.5 g of 1,4-dibromobutane. . As a result, 8.0 g of white crystals were obtained. The melting point of this compound was 71 ° C., and it was identified by NMR measurement that the obtained compound was the target compound.

The results of NMR measurement (CDCl 3) are as follows. δ = 2.28 (s, 6H), 4.39 (s, 4H), 4.
61 (s, 4H), 6.68 (d, 2H), 6.69
(S, 2H), 6.80 (d, 2H), 7.24 (t, 2
H)

<Synthesis Example 4> Synthesis of 1,2-bis (p-tolyloxyacetoxy) ethane The same operation as in Synthesis Example 1 was performed. However, 9.95 g of 4-methylphenoxyacetic acid was used instead of 9.1 g of phenoxyacetic acid, and 5.65 g of 1,2-dibromoethane was used instead of 6.5 g of 1,4-dibromobutane. . As a result, 5.50 g of a white solid was obtained. The melting point of this compound was 52 ° C., and the compound obtained by NMR measurement was identified as the desired product.

The results of NMR measurement (CDCl 3) are as follows. δ = 2.32 (s, 6H), 4.42 (s, 4H), 4.
57 (s, 4H), 6.81 (d, 4H), 7.18
(D, 4H)

<Synthesis Example 5> Synthesis of 1,2-bis (o-tolyloxyacetoxy) ethane The same operation as in Synthesis Example 1 was performed. However, 9.95 g of 2-methylphenoxyacetic acid was used in place of 9.1 g of phenoxyacetic acid, and 5.65 g of 1,2-dibromoethane was used in place of 6.5 g of 1,4-dibromobutane. As a result, 7.9 g of white crystals were obtained. The melting point of this compound was 56 ° C., and the compound obtained by NMR measurement was identified as the desired product.

The results of NMR measurement (CDCl 3) are as follows. δ = 2.29 (s, 6H), 4.45 (s, 4H), 4.
59 (s, 4H), 6.67 (d, 4H), 6.89
(T, 2H), 7.23 (overlap of t and d, 4H)

Example 1 A heat-sensitive recording paper was prepared by the following operation. (1) Preparation of pigment-coated paper 85 parts of calcined clay (trade name: Ansilex) were mixed with 320 parts of water.
In a dispersion obtained by dispersing styrene / butadiene copolymer emulsion (solid content: 50%), 40 parts, 10%
By mixing the aqueous solution of oxidized starch and 50 parts by adjusting the coating solution, coating the coating solution as the top of the base paper basis weight 48 g / m ^2, the coating amount after drying is 7.0 g / m ² As a result, a pigment-coated paper was prepared.

[0047] (2) Preparation Ingredients Amount of Dispersion A (parts) 3- (N, N-dibutylamino) -6-methyl-7-anilinofluoran 20 polyvinyl alcohol - le 10 solution 10 Water 70 The above composition Using a sand grinder, the average particle size is 1
It was pulverized until it became not more than μm.

Le 10% aqueous solution 10 Water 70 The composition - [0048] (3) Preparation Ingredients Amount of Dispersion B (parts) of 4,4'-bis (p- toluenesulfonyl-amino - carbonylamino) - diphenylmethane 20 Polyvinyl alcohol Using a sand grinder, pulverization was performed until the average particle size became 1 μm or less.

[0049] (4) Dispersion Preparation Ingredients Amount of C (parts) 1,4-bis (phenoxy acetoxy) butane 20 Polyvinyl alcohol - using a sand grinder Le 10% aqueous solution 10 Water 70 The composition, average particle size Was reduced to 1 μm or less.

(5) Formation of heat-sensitive coloring layer 60 parts of solution A, 120 parts of solution B, 120 parts of solution C, 23 parts of HG clay (Kaolinite pigment manufactured by Huber), 20 parts of a 25% zinc stearate dispersion, 15 parts of 30% paraffin dispersion and 12% aqueous solution of polyvinyl alcohol 12
0 parts were mixed and stirred to obtain a coating solution. This coating solution was applied on one side of a pigment-coated paper at a coating amount of 5.0 g / m ² after drying.
To form a heat-sensitive coloring layer, and a heat-sensitive recording paper was prepared.

(6) Test of Thermal Paper The sample obtained as described above was subjected to a dynamic thermal coloring simulator THPMD manufactured by Okura Electric (printing voltage: 21.7 V).
The sample was colored in a checkered pattern under the printing conditions of an applied pulse width of 0.5 ms and 0.7 ms. The color density was measured with a Macbeth reflection densitometer RD-914 black filter, and this measured value was used as a value representative of the recording sensitivity. Further, dioctyl terephthalate (a typical plasticizer) was applied to the sample that had been colored with the applied pulse width of 0.7 ms within 30 minutes after the color development, left at room temperature for 3 hours, and then the oil or plasticizer on the surface was wiped off. The residual image density was measured with a Macbeth reflection densitometer, and the image storage rate was calculated according to the following equation. Image preservation ratio (%) = (color density after immersion of plasticizer) / (color density before immersion of plasticizer) × 100 The test results are shown in Table 1.

Example 2 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing dispersion C, 1,2-bis (phenoxyacetoxy) ethane was used instead of 1,4-bis (phenoxyacetoxy) butane, and the dispersion was measured with a Macbeth reflection densitometer RD-914 black filter. Table 1 shows the test results.

Example 3 A thermosensitive recording paper was produced and tested in the same manner as in Example 1. However, in preparing dispersion C, 1,2-bis (m-tolyloxyacetoxy) ethane was used in place of 1,4-bis (phenoxyacetoxy) butane, and the dispersion was measured with a Macbeth reflection densitometer RD-914 black filter. . Table 1 shows the test results.

Example 4 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing Dispersion C, 1,4-bis (m-tolyloxyacetoxy) butane was used instead of 1,4-bis (phenoxyacetoxy) butane, and measured with a Macbeth reflection densitometer RD-914 black filter. . Table 1 shows the test results.

<Comparative Example 1> A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing Dispersion C, p-benzylbiphenyl (melting point 87 ° C.) was used instead of 1,4-bis (phenoxyacetoxy) butane. Table 1 shows the test results.

Comparative Example 2 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing Dispersion C, dibenzyl terephthalate (melting point 94 ° C.) was used instead of 1,4-bis (phenoxyacetoxy) butane.
Was used. Table 1 shows the test results.

[0057]

[Table 1]

Example 5 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing Dispersion B, 4-hydroxy-4'-isopropyloxydiphenyl sulfone was used instead of 4,4'-bis (p-toluenesulfonylaminocarbonylamino) -diphenylmethane. Table 2 shows the test results.

Example 6 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing Dispersion B, 3,3′-diallyl-4,4′-dihydroxydiphenyl sulfone was used instead of 4,4′-bis (p-toluenesulfonylaminocarbonylamino) -diphenylmethane. Table 2 shows the test results.

Comparative Example 3 A thermosensitive recording paper was prepared and tested in the same manner as in Example 1. However, in preparing Dispersion B, 3,3′-diallyl-4,4′-dihydroxydiphenylsulfone was used instead of 4,4′-bis (p-toluenesulfonylaminocarbonylamino) -diphenylmethane, In preparing the dispersion C, p-benzylbiphenyl (melting point 87 ° C.) was used instead of 1,4-bis (phenoxyacetoxy) butane. Table 2 shows the test results.

[0061]

[Table 2]

From Table 1, it is confirmed that the sensitizer of the general formula (I) of the present invention has high image storability and high sensitivity when used in combination with a developer having high storability. Also, from Table 2, it is confirmed that the sensitivity is greatly improved when the sensitizer of the general formula (I) of the present invention is used in combination with a known color developer whose storage stability is not particularly high.

[0063]

As described above, according to the present invention, it is possible to obtain a thermosensitive recording medium having higher sensitivity than the conventional thermosensitive recording medium. Further, by the combination of the sensitizer of the present invention and a specific color developer, a heat-sensitive recording medium having high sensitivity and excellent oil resistance and plasticizer resistance, and thus excellent long-term storage properties can be obtained. For example, a thermal recording medium suitable for use in a thermal recording type ticket for an automatic ticket vending machine, a coupon, a commuter pass, or the like can be obtained. In addition, the heat-sensitive recording material of the present invention is suitable as a label for a POS barcode system, which is attached to the packaging surface of a food packaged with a polyvinyl chloride film, which is inevitably in contact with a plasticizer and fats and oils. It can also be used as required facsimile paper for long-term storage, word processing paper, and CRT image printer paper.

Claims (3)

[Claims] 1. A sheet-like substrate, a colorless or light-colored dye precursor formed on at least one surface of the sheet-like substrate, and a developer which reacts with the dye precursor under heating to form a color. Wherein the thermosensitive coloring layer further comprises the following general formula (I): (However, in the formula (I), n represents an integer of 2 or more;
R ¹ and R ² represent at least one phenoxyacetoxy compound represented by a hydrogen atom or a member selected from a lower alkyl group and an alkoxy group). 2. The method according to claim 1, wherein the phenoxyacetoxy compound is 1,2.
The heat-sensitive recording material according to claim 1, wherein the heat-sensitive recording material is 4-bis (phenoxyacetoxy) butane. 3. The developing agent of the following general formula (II): (Wherein, in the formula (II), R ³ is an unsubstituted aromatic group, and
A represents a member selected from a lower alkyl group or an aromatic group substituted by a halogen atom, A represents a divalent or higher valent organic group or an inorganic group, and n represents an integer of 2 or more. The thermosensitive recording medium according to claim 1, comprising at least one compound represented by the formula: