JPH09277715A - Reversible heat-sensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high contrast between a generation part and an extinction part and obtain superior preservation properties for image by using in a heat- sensitive recording layer, a dye precursor and a sulfonyl urea compound including a non-phenol long-chain alkyl group as a developer. SOLUTION: The reversible heat-sensitive recording body has on a sheet-like supporting body a heat-sensitive recording layer including a dye precursor and a developer which makes the dye precursor reversibly generate and extinguish color. The developer includes at least one aromatic compound expressed by the formula in one molecule. The recording layer generates and extinguishes color only when a sulfonyl urea compound having a long-chain alkyl group of 11 or more carbons is used as the developer. The color is generated at a heating temperature of 80-180 deg.C, and extinguished at 50-120 deg.C not higher than the heating temperature. The color-generated and extinguished state is maintained even when the recording body is cooled at room temperatures.

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 medium capable of coloring and decoloring by controlling heating conditions and maintaining the colored and decolored states at room temperature. To elaborate further,
The present invention relates to a reversible thermosensitive recording medium that forms a colored image on a white background, has high contrast, and is excellent in image storability.

[0002]

2. Description of the Related Art Conventionally, thermal recording media are compact, inexpensive, and easy to maintain, so computers, measuring instruments, registers, CD / ATMs, facsimiles, vending machines, handy terminals, etc. However, recently it is also used as a magnetic heat sensitive card such as a prepaid card or a point card due to its combination with magnetic recording. In these magnetic thermosensitive cards, magnetic information is rewritten each time it is used, whereas thermosensitively recorded images cannot be rewritten. Therefore, new information such as the residual count is additionally written in a portion where no image is recorded. However, since the area of the recordable portion is limited, it is unavoidable that the amount of information to be heat-sensitively recorded is reduced or the card is remade when the recording area is exhausted. As a means for solving such a problem, it has been strongly desired to develop a reversible thermosensitive recording medium which can be rewritten many times.

Against the background of the problems of dust and deforestation, which have been actively discussed in recent years, it is desired to recycle thermal recording paper. There are various possible methods for reproducing heat-sensitive recording paper. Among them, as a versatile method that does not require a large device such as a deinking device, the development of a rewritable heat-sensitive recording medium that can be rewritten many times Is desired. Further, the reversible thermosensitive recording medium has been attracting attention as a recording material for a simple display as disclosed in JP-A-3-233490 and JP-A-5-42762, and is suitable for these devices. The development of reversible thermosensitive recording media is also strongly desired.

Against this background, various reversible thermosensitive recording media have been proposed. For example, JP-A-63-107
584, JP-A-4-78573 and 4-
Japanese Patent No. 358878 discloses a polymer type reversible thermosensitive recording medium that utilizes the change in transparency depending on heating conditions. However, because it is a recording method that uses transparency-white turbidity due to the phase change of the polymer, sufficient transparency or sufficient opacity cannot be easily obtained, and the contrast between the coloring part and the erasing part becomes low, resulting in darkness. It has a problem of poor visibility in the place. Further, in general, a white image is recorded on a colored background, and it is difficult to obtain a so-called paper-like recording material that records a colored image on a white background.

As a method for solving these problems, a dye-type reversible thermosensitive recording medium has been proposed which enables reversible recording while using a dye used in a conventional thermosensitive recording medium. The dye-type reversible thermosensitive recording medium makes it easy to record a colored image on a white background, and is a recording system that utilizes the change in absorption wavelength due to heating conditions.
A relatively high contrast is obtained. As a dye type reversible thermosensitive recording medium, for example, the following methods are known.

JP-A-58-191190 and JP-A-60-193691 disclose methods using gallic acid and phloroglucinol as color developers. However, because it requires water or water vapor to erase,
It has a drawback that the erasing device becomes large. JP-A-60-264285 and JP-A-62-1408
Japanese Patent No. 81 discloses a thermochromic material having hysteresis. However, the image holding temperature range is
Since it is limited in both the upper and lower limits, it has the drawbacks that the device becomes complicated and the ambient temperature for use is limited. Japanese Patent Laid-Open No. 63-173684 discloses a method of using an ascorbic acid derivative as a color developer. However, it has a drawback that the color is not sufficiently erased at the time of erasing.

JP-A-2-188293 and JP-A-2-188294 disclose a method using a salt of a specific organic acid such as gallic acid and a higher aliphatic amine as a developer. . However, since the color forming reaction and the color erasing reaction are competitive reactions, it is difficult to control so that either reaction selectively proceeds, and there is a drawback that it is difficult to obtain high contrast. JP-A-5-1243
No. 60 and JP-A-6-210954,
A method of using an organic phosphoric acid compound having a long-chain alkyl group or a phenolic compound as a developer is disclosed. However, there are drawbacks in that the color may not be sufficiently erased at the time of erasing and the storability of the color image may be insufficient. As described above, many techniques have been disclosed for the reversible thermosensitive recording medium, but each has various drawbacks, and no one having sufficiently satisfactory performance in practical use has yet been obtained.

[0008]

SUMMARY OF THE INVENTION The present invention is capable of forming a color image on a white background using a small-sized device, performing color development and color erasure only by a difference in heating conditions, and having high contrast. An object of the present invention is to provide a reversible thermosensitive recording medium having excellent image storability.

[0009]

DISCLOSURE OF THE INVENTION The inventors of the present invention can perform color development and color erasure only by heating, and have a high contrast between the color development part and the color erasure part. In order to obtain a thermal recording material, focusing on a dye-type reversible thermosensitive recording method that utilizes the reaction between a dye and a color developing agent, as a result of intensive research, a sulfonylurea compound having a non-phenolic long-chain alkyl group as a color developing agent It has been found that a desired reversible thermosensitive recording medium can be obtained by utilizing the above, and the present invention has been completed.

The reversible thermosensitive recording medium of the present invention comprises a sheet-shaped support, a colorless or light-colored dye precursor formed on the sheet-shaped support, and a developer for reversibly developing and erasing the color. A thermosensitive recording layer containing a colorant, and as the color developer, the following general formula (I) is included in one molecule:

Embedded image (However, R ₁ represents a member selected from an alkyl group having 1 to 8 carbon atoms, a halogen atom and an aralkyl group, and Y is
The following chemical formula:

Embedded image Represents a member selected from a divalent group represented by
Represents an integer of 10 to 29. ) It is characterized by containing at least one kind of aromatic compound represented by.

The reversible thermochromic coloring and erasing method of the reversible thermosensitive recording material according to the present invention comprises heating the thermosensitive coloring layer of the above recording material to record an image by color development, and after use of this recording,
The heat-sensitive color-developing layer is heated at a temperature lower than the color-developing heating temperature to erase the color-developed image.

In the general formula (I), R ₁ has ₁ carbon atom.
The alkyl groups, halogen atoms and aralkyl groups of 8 to 8 are shown below, and the following groups are preferred.

Embedded image

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the reversible thermosensitive recording medium of the present invention, a thermosensitive recording layer containing a dye precursor and a color developer rapidly develops a color upon heating, and the color development state is maintained at room temperature by quenching. To be done. On the other hand, the color-developed image portion held at room temperature can be erased by heating it to a temperature not higher than the color-developing temperature, and the decolored state is held even when cooled to room temperature. Although the mechanism of color development and decolorization is not clear, the urea group in the sulfonylurea group represented by the formula (I) in the color developer is activated by the sulfonyl group adjacent thereto, so that a basic leuco group is present. Color development occurs with a strong color development ability to the dye, while when the color development body is heated below the color development temperature, the long chain alkyl groups in the color development agent are oriented and induce crystallization of the color development agent. , It is considered that the dye and the developer separate and disappear. Generally, the heating temperature for color development is 80 to 180 ° C, and the temperature range where decolorization occurs is 5
The temperature is 0 to 120 ° C. and lower than the color heating temperature.
Generally, color development is performed by a thermal head or the like, which can be rapidly cooled after heating, but decolorization is performed by keeping the temperature below the color development heating temperature to control the heating / cooling rate. No need. The temperature retention time during decoloring is preferably 0.1 seconds or more. The process of recording and erasing this color image will be described with reference to FIG.

In FIG. 1, when an unrecorded recording medium in the state A is heated, the color density abruptly increases above the temperature T2 via the state B, and further via the state C.
When the coloring reaction is completed, the state D is reached and the highest coloring density is exhibited. When state D is rapidly cooled to room temperature, state F is reached via state E. The state F is a state in which the color development is maintained at room temperature, and the recording of the image is completed. When this recorded image is heated and held in the temperature range T1, the color density is gradually reduced, and the state A'is passed through the state G to completely erase the color. When it is cooled to room temperature, state A is reached.
State A is a state in which the decolored state is maintained at room temperature,
This completes the image deletion. The color-decoloring reversible cycle described above can be repeated.

Specific examples of the aromatic compound used as a color developer in the reversible thermosensitive recording medium of the present invention are preferably compounds represented by the following chemical formula. These compounds may be used alone or as a mixture of two or more thereof.

[0016]

[Chemical 6]

[0017]

Embedded image

Further, the length of the long-chain alkyl group of the color developer according to the present invention must be 11 or more, and 30
The following is preferred. Even in that area, 14-21
Is more preferable. If the number of carbon atoms is less than 11, the decoloring ability may not reach a practical level, and if it exceeds 30, the color developing ability may be lowered. In the heat-sensitive recording layer of the reversible heat-sensitive recording material of the present invention, examples of the compound used as the dye precursor include triphenylmethane-based compounds, fluoran-based compounds and diphenylmethane-based compounds, which can be selected from conventionally known 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-anilinofluorane, 3-diethylamino-6-methyl-
7-anilinofluorane, 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) fluoran, 3-
Diethylamino-6-methyl-7-chlorofluorane,
These are 3-diethylamino-6-methylfluorane and 3-cyclohexylamino-6-chlorofluorane.

Furthermore, 3- (N-ethyl-N-cyclohexyl) -6-methyl-7- (p-chloroanilino)
Fluoran, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3- [N- (3-ethoxypropyl) -N-ethylamino] -6-methyl-7-
Anilinofluorane, 3- (N-n-hexyl-N-ethylamino) -7- (o-chloroanilino) fluorane, 3- (N-ethyl-N-2-tetrahydrofurfurylamino) -6-methyl- 7-anilinofluoran, 3
-(N-ethyl-N-isopentylamino) -6-methyl-7-anilinofluorane, 2,2-bis {4-
[6 '-(N-cyclohexyl-N-methylamino)-
3'-methylspiro [phthalide-3,9'-xanthene] -2'-ylamino] phenyl} propane and 3
One or more selected from -dibutylamino-7- (o-chloroanilino) fluorane and the like can be used.

Further, in the present invention, a conventionally known developer comprising phenols or organic acids and a sulfonyl (thio) urea aromatic compound having no long-chain alkyl group within a range that does not inhibit the desired effect. Can be used in combination with the sulfonylurea type developer having a long chain alkyl group according to the present invention.

These conventional color developers 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-52-140483), bisphenol S, 4-hydroxy-4'-isopropyloxydiphenyl sulfone (JP-A-60-13)
852), 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-60-208)
No. 286).

Further, N- (p-toluenesulfonyl) -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'-benzylurea (above, JP-A-5-3
2061), 4,4'-bis (p-toluenesulfonylaminocarbonylamino) -diphenylmethane,
4,4'-bis (o-toluenesulfonylaminocarbonylamino) -diphenylmethane, 4,4'-bis (benzenesulfonylaminocarbonylamino) -diphenylmethane, 1,2-bis [4 '-(p-toluenesulfonylaminocarbonyl) Amino) phenyloxy] ethane, 4,4′-bis (p-toluenesulfonylaminocarbonylamino) diphenyl ether and 3,3′-
Bis (p-toluenesulfonylaminocarbonylamino) diphenylsulfone (above, JP-A-5-14735)
7 gazette).

The reversible thermosensitive recording medium of the present invention can contain a heat-fusible substance generally known as a sensitizer in the thermosensitive recording layer. Examples thereof include oxalic acid diesters (JP-A-64-1583), di (4-methylbenzyl) oxalate (JP-B-5-62597), 1,
2-bis (m-tolyloxy) ethane (JP-A-60-5
6588), diphenyl sulfone (JP-A-60-
No. 15667) and p-benzylbiphenyl (JP-A-60-82382), these compounds have the ability to develop high density color development of a reversible thermosensitive recording medium by relatively low applied energy. It also has the ability to accelerate the decolorization reaction and improve reversibility.

The heat-sensitive recording layer of the present invention may further contain waxes and pigments as long as the effects of the present invention are not impaired, and usually a binder. As the waxes, known waxes such as paraffin, amide wax, bisimide wax, and higher fatty acid metal salt can be used.

Examples of the pigment include silica, clay, calcined clay, talc, calcium carbonate, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, and inorganic fine particles such as surface-treated calcium carbonate and silica. In addition to the powder, an organic fine powder such as a urea-formalin resin, a styrene / methacrylic acid copolymer, and a polystyrene resin can be used. The binder, polyvinyl alcohol of various molecular weight,
Starch and its derivatives, methoxycellulose, carboxymethylcellulose, methylcellulose, cellulose derivatives such as 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, sodium alginate, gelatin, and Water-soluble polymer materials such as casein, polyvinyl acetate, polyurethane,
Latex such as styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, and styrene / butadiene / acrylic copolymer Can be used.

In the heat-sensitive recording layer of the reversible heat-sensitive recording material of the present invention, the content of the dye precursor is generally preferably from 5 to 40% by weight based on the dry weight of the heat-sensitive recording layer, and the content of the color developing agent. Is generally preferably 5 to 50% by weight based on the dry weight of the heat-sensitive recording layer. Content of developer is 5% by weight
When the amount is less than 1, the developing ability becomes insufficient, and even when it is used in a large amount exceeding 50% by weight, the developing ability is saturated and no remarkable improvement in the contrast between the coloring density and the erasing density is observed. , May be economically disadvantageous. Further, the content of the decolorization accelerator is generally preferably 5 to 50% by weight based on the dry weight of the heat-sensitive recording layer. When the content of the decolorization accelerator is less than 5% by weight, the decolorization promoting effect is insufficient,
If a large amount is used in excess of weight%, the color density may be insufficient.

Further, the heat-sensitive recording layer has a sulfonyl (thio) group containing no phenols, organic acids, or long-chain alkyl groups.
When a conventionally known color developer composed of a urea-based aromatic compound is contained, the content thereof is preferably 10% by weight or less based on the weight of the heat-sensitive recording layer. Phenols, organic acids,
Alternatively, if the content of the conventionally known color developer composed of a sulfonyl (thio) urea-based aromatic compound having no long-chain alkyl group is more than 10% by weight, the color erasing reaction is inhibited and the color-developing portion and the color-erasing portion are blocked. There may be a case where the contrast is deteriorated.

When waxes and pigments are contained in the thermosensitive recording layer, their contents are 5 to 20% by weight and 1 respectively.
It is preferably from 0 to 50% by weight, and the binder content is generally from 5 to 20% by weight.

Supports used in the reversible thermosensitive recording medium of the present invention
The holder is paper (acidic paper) that has been used for conventional thermal recording media.
(Including paper and neutral paper), paint the surface with pigment, latex, etc.
Engineered coated paper, laminated paper, polyolefin-based
Synthetic paper made from resin, polyolefin, polyester
In addition to plastic films such as polyester and polyimide, glass
You can choose from plates, conductive rubber sheets, etc.
You. On at least one side of such a support, the required
Apply a coating solution containing a mixture of ingredients and dry to apply a reversible feeling.
A thermal recording material is manufactured. The coating amount is as if the coating liquid layer had dried.
1 to 15 g / m ^TwoIs preferred and 2 to 10 g / m^TwoBut special
Preferred.

In the present invention, an undercoat layer may be provided below the reversible thermosensitive coloring layer. Further, the back surface of the reversible thermosensitive recording medium can be provided with a back layer for preventing blocking at the time of contact between the front and back surfaces, suppressing permeation of water or oil from the back surface, and curling control. Further, in order to improve heat resistance, light resistance, printability, and repeated durability of coloring and decoloring, a protective layer, a printing layer, or the like may be formed on the reversible thermosensitive coloring layer. it can. Light resistance can be improved by containing an ultraviolet absorber in the protective layer. Further, by using a surface resin coating and curing layer containing an unsaturated organic compound that can be cured by electron beam irradiation as a main component for the protective layer, it is possible to dramatically improve the durability against repeated coloring and decoloring.

In the present invention, the reversible thermosensitive recording medium can be further processed to increase the added value of the reversible thermosensitive recording medium to give a reversible thermosensitive recording medium having a higher function. For example, reversible heat-sensitive reversible thermosensitive recording that can be magnetically recorded by applying pressure sensitive adhesive, rewetting adhesive, or delayed tack type adhesive to the back surface to make adhesive paper, rewetting adhesive paper, delayed tack paper, or magnetically processing. It can be a recording body. Further, the back side can be used to have a function as a thermal transfer paper, an inkjet paper, a carbonless paper, an electrostatic recording paper, or a xerographic paper, so that the recording paper can be recorded on both sides. Of course, a double-sided reversible thermosensitive recording medium can also be used. The device for recording (coloring) and erasing (erasing) an image can be selected from a thermal head, a constant temperature bath, a heating roller, a heating pen, a sheet heating element, a laser beam, an infrared ray, etc. depending on the purpose of use. It is not particularly limited to these.

[0032]

The present invention will be specifically described below with reference to examples. Unless otherwise specified, "part" and "%" represent "part by weight" and "% by weight", respectively. Example 1 A reversible thermosensitive recording medium was prepared by the following operation. (1) Preparation of Dispersion Liquid Ingredients Amount of A (parts) 3-dibutylamino-6-methyl-7-20 anilinofluoran polyvinyl alcohol - using a sand grinder Le 10% solution 10 Water 70 The composition, average Particle size is 1
It was pulverized until it became less than μm.

[0033] (2) Preparation Ingredients Amount of Dispersion B (parts) N-(methanesulfonyl) -N '- [4- (n- octadeca Noiruamino) phenyl] urea (Compound No.1 However, n = 17) 20 Polyvinyl alcohol 10% liquid 10 Water 70 The composition described above was used with a sand grinder to give an average particle size of 1
It was pulverized until it became less than μm. (3) Preparation Ingredients Amount of Dispersion C (parts) of oxalic acid - using a sand grinder di -p- methylbenzyl ester 20 polyvinyl alcohol 10% solution 10 Water 70 The composition, average particle size of 1
It was pulverized until it became less than μm.

(4) Formation of reversible thermosensitive recording layer 75 parts of solution A, 150 parts of solution B, 75 parts of solution C, 30 parts of calcined clay, 25% paraffin wax emulsion 2
Parts and 100% 10% polyvinyl alcohol aqueous solution
The parts were mixed and stirred to obtain a coating liquid. This coating solution was applied to one surface of a polyester film having a thickness of 75 μm so that the coating amount after drying would be 5.0 g / m ^2, and dried to form a reversible thermosensitive recording layer. (5) Supercalender treatment The heat-sensitive sheet obtained as described above was treated with a supercalender, and the surface smoothness of the heat-sensitive coloring layer was adjusted to 3000 to 5000 seconds to obtain a reversible thermosensitive recording medium.

(6) Coloring and Decoloring Test The reversible thermosensitive recording medium thus obtained was subjected to a printing voltage of 21.% using a thermosensitive coloring tester THPMD manufactured by Okura Electric.
Printing was performed under the conditions of 7 v and a print pulse of 1.0 ms. The print color density was measured with a Macbeth reflection densitometer RD-914. Further, this color-developed sample was heated under the conditions of heating temperature of 100 ° C., pressure of 1 kg / cm ² and heating time of 1 second using a thermal gradient tester manufactured by Toyo Seiki Co., Ltd., and then the decolorization density was measured by Macbeth reflection densitometer RD-914. It was measured at. Table 1 shows the test results. (7) Preservation test After the print color density was measured in the same manner as in the color test of the above item 8, the color samples obtained were allowed to stand at 40 ° C for 7 days, and the color density was measured in the same manner. The image storability at this time was evaluated by the image storage ratio: (color density after leaving at 40 ° C. for 7 days / color density immediately after printing) × 100 (%). Table 1 shows the test results.

Example 2 (1) Formation of reversible thermosensitive coloring layer 70 parts of solution A, 140 parts of solution B and 14 parts of solution C described in Example 1
8 parts of calcined clay, 2 parts of 25% paraffin wax emulsion, and 170 parts of 10% aqueous polyvinyl alcohol solution were mixed with 0 part and stirred to prepare a coating solution. This coating liquid was applied to a polyester film having a thickness of 75 μm so that the coating amount after drying would be 5.0 g / m ^2, and dried to form a reversible thermosensitive recording layer. (2) Formation of overcoat layer Kaolinite clay dispersion liquid (solid content concentration 60%) 50
Parts, 350 parts of 10% modified polyvinyl alcohol aqueous solution,
220% 10% casein solution, 2 parts 25% paraffin wax emulsion, dimethylol urea crosslinking agent 10
And 35 parts of water were mixed and stirred to prepare a coating liquid for the overcoat layer. This coating solution was coated on the reversible thermosensitive recording layer so that the coating amount after drying was 1.5 g / m ^2, and dried to form an overcoat layer. The surface was smoothed by supercalendering and adjusted to 3000 to 5000 seconds to obtain a reversible thermosensitive recording medium. The above reversible thermosensitive recording medium was subjected to the same test as in Example 1. Table 1 shows the test results.

Example 3 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 2. However, in the preparation of the dispersion liquid B, N- (methanesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No. 1 where n = 1
Instead of 7) N- (benzylsulfonyl) -N '-[4
-(N-eicosanoylamino) phenyl] urea (Compound No. 5 with n = 19) was used. The test results are shown in Table 1. Example 4 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 2. However, in the preparation of the dispersion liquid B, N- (methanesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No. 1 where n = 1
7) instead of N- (n-octanesulfonyl) -N'-
[4- (n-octadecanoylamino) phenyl] urea (Compound No. 6 with n = 17) was used. The test results are shown in Table 1.

Example 5 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 2. However, in the preparation of the dispersion liquid B, N- (methanesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No. 1 where n = 1
7) instead of N- (methanesulfonyl) -N '-[4-
(n-Octadecyloxycarbonylamino) phenyl] urea (Compound No. 11 with n = 18) was used. Table 1 shows the test results. Example 6 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 2. However, in the preparation of the dispersion liquid B, N- (methanesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No. 1 where n = 1
7) instead of N- (methanesulfonyl) -N '-[4-
(n-pentadecylthiocarbonylamino) phenyl]
Urea (Compound No. 13, where n = 15) was used.
Table 1 shows the test results. Example 7 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 2. However, in the preparation of Dispersion A, 3-dibutylamino-7- (o-chloroanilino) fluorane was used instead of 3-dibutylamino-6-methyl-7-anilinofluorane. The test results are shown in Table 1.

Comparative Example 1 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 2. However, in the preparation of the dispersion liquid B, N- (methanesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No. 1 where n = 1
7) instead of N- (methanesulfonyl) -N '-[4-
(n-Pentanoylamino) phenyl] urea was used. Table 1 shows the test results. Comparative Example 2 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 2. However, in the preparation of the dispersion liquid B, N- (methanesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No. 1 where n = 1
7) instead of N- (methanesulfonyl) -N '-[4-
(n-Decanoylamino) phenyl] urea was used.
Table 1 shows the test results.

Comparative Example 3 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 2. However, in the preparation of the dispersion liquid B, N- (methanesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No. 1 where n = 1
7) instead of N- (4-hydroxyphenyl) -N'-
n-octadecyl urea was used. The test results are shown in Table 1. Comparative Example 4 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 2. However, in the preparation of the dispersion liquid B, N- (methanesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No. 1 where n = 1
Gallic acid was used instead of 7). Table 1 shows the test results. Comparative Example 5 A reversible thermosensitive recording medium was prepared and tested in the same manner as in Example 2. However, in the preparation of the dispersion liquid B, N- (methanesulfonyl) -N '-[4- (n-octadecanoylamino) phenyl] urea (Compound No. 1 where n = 1
Ascorbic acid was used instead of 7). Table 1 shows the test results.

[0041]

[Table 1]

As is clear from comparison between Examples 1 to 7 and Comparative Examples 3 to 5, the reversible thermosensitive recording medium of the present invention showed a color development of a phenol compound having a long alkyl chain, gallic acid, ascorbic acid and the like. It has a higher contrast than the compound using the agent and has excellent storage stability. In addition, Example 1
As is clear from comparison between Comparative Examples 1 to 7 and Comparative Examples 1 and 2, the reversible thermosensitive recording medium of the present invention uses a sulfonylurea compound having a long chain alkyl group having a total carbon number of 11 or more as a developer. It can be seen that the coloring and decoloring effects are exhibited only when.

[0043]

The reversible thermosensitive recording medium of the present invention forms a colored image on a white background, has a high contrast and is excellent in image storability. Therefore, the reversible thermosensitive recording medium of the present invention has extremely high practical value.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between temperature and color density in the color developing and erasing cycles of the reversible thermosensitive recording medium of the present invention.

Claims (1)

[Claims] 1. A heat-sensitive recording layer comprising a sheet-shaped support, a colorless or light-colored dye precursor formed on the sheet-shaped support, and a color developer that reversibly develops and decolors the dye precursor. Further, as a color developer, the following general formula (I): (However, R ₁ represents a member selected from an alkyl group having 1 to 8 carbon atoms, a halogen atom and an aralkyl group, and Y is
The following chemical formula: Represents a member selected from a divalent group represented by
Represents an integer of 10 to 29. ) A reversible thermosensitive recording medium comprising at least one aromatic compound represented by