Abstract: A thermosensitive recording material comprising a thermosensitive layer provided on a substrate, and the thermosensitive layer comprises as main ingredients a leuco dye and a developer to make colored state of said leuco dye when heated, wherein the developer is an oligomer composition obtained from the reaction of a polyvalent isocyanate compound represented by following Formula (I) with an aromatic amine represented by following Formula (II); 1

Abstract: A heat-sensitive recording material including, on a support, a heat-sensitive color-developable layer containing an electron-donating colorless dye and an electron-accepting compound, wherein the electron-accepting compound contains a compound represented by R1—Ph—SO2R2, and an adhesive strength when an adhesive sheet such as a revenue stamp is affixed to a recording face of a heat-sensitive recording paper made of the heat-sensitive recording material is larger than a given value, and a center line average roughness Ra75 of the heat-sensitive recording face is 2.0 &mgr;m or less.

Abstract: A heat sensitive recording material comprising a recording layer formed on a substrate and containing at least one colourless or light-coloured colour former and at least one colour developer, the material being characterised in that the recording material gives a blue image, and the colour developer being at least one compound represented by the formula (1) wherein R1 is unsubstituted or substituted phenyl, naphthyl or C1-C20alkyl, X is a group of the formula (a), (b), or (c), A is unsubstituted or substituted phenylene, naphthylene or C1-C12alkylene, or is an unsubstituted or substituted heterocyclic group, B is a linking group of formula: —O—SO2—, —SO2—O—, —NH—SO2—, —SO2—NH—, —S—SO2—, —O—CO—, —O—CO—NH—, —NH—CO—, —NH—CO—O—, —S—CO—NH—, —S—CS—NH—, —CO—NH—SO2—, —

Abstract: The present invention is to provide a reversible two-color heat-sensitive recording material which uses an electron-donative dye precursor which is usually colorless or a pale color and an electron-accepting compound, and a reversible heat-sensitive color-forming composition which is capable of forming a color-formation state and decolorization state relatively due to difference in heating temperature and/or cooling rate after heating is formed on a support, wherein the reversible heat-sensitive color-forming composition comprises at least two kinds of compositions having different color tones to be formed and the compositions are each present separately and in an independent state, and crystallization rates of the electron-donative compounds at the time of changing from the color-formation state to the decolorization state are different from each other.

Abstract: A heat-sensitive recording material in which a heat-sensitive color-developing layer containing at least an electron-donating colorless dye, an electron-accepting compound, a sensitizer and preferably an image stabilizer is disposed on a support, the heat-sensitive color-developing layer containing (1) 4-hydroxybenzenesulfonanilide as the electron-accepting compound and (2) 2-benzyloxynaphthalene and ethylenebisstearic acid amide or methylolstearic acid amide as the sensitizer, and (3) the 2-benzyloxynaphthalene (x) to ethylenebisstearic acid amide or methylolstearic acid amide (y) mass ratio (x/y) being within 95/5 to 40/60 range.

Abstract: A thermosensitive recording composition includes a leuco dye, a color developer containing 4,4′-bisphenol S, and a sensitizer containing 4-acetylbiphenyl. A thermosensitive recording material has a support and a thermosensitive recording layer which is provided on the support and contains the above-mentioned thermosensitive recording composition.

Abstract: A thermographic recording element having at least one image forming layer contains an organic silver salt, a reducing agent, and optionally, a photosensitive silver halide. The element further contains a substituted alkene derivative of specific structure and preferably a specific hydrazine derivative. The element can be processed in a fully dry basis to produce images having high Dmax and gradation and free of black pepper.

Abstract: A thermally sensitive recording medium that contains a compound represented by general formula (1) as a color developer, and a compound represented by general formula (2) or general formula (3) as a sensitizer. The said thermally sensitive recording medium has sufficient color developing sensitivity with lower impressive energy, and has good image preservability of recorded part, good resistance to humid and heat resistance of background white paper part. In the formulae, R1 represents a hydrogen atom, a methyl group or a chlorine atom, R2 and R3 represents a methyl group, an alkoxy group or an allyloxy group, m and n represents an integer of 1-5, R4 represents an alkyl group, an alkoxy group of carbon number 1-6 or an electron withdrawing group and o represents an integer of 0-2.

Abstract: A heat-sensitive recording material includes a support having disposed thereon a heat-sensitive color-forming layer that includes an electron-donating leuco-dye, an electron-receiving compound and an UV absorbent, wherein the layer contains 4-hydroxybenzenesulfonanilide as the electron-receiving compound. Because the layer includes 4-hydroxybenzenesulfonanilide, the heat-sensitive recording material has high sensitivity and improved image preservability, chemical resistance and sticking resistance.

Abstract: A multi chromatic thermally sensitive recording medium comprising, a higher temperature color developing layer containing dye precursor and an organic color developer that reacts with said dye precursor and develops color by heating, and at least one lower temperature color developing layer that develops different color from that of said higher temperature color developing layer and develops color by lower temperature than the color developing temperature of said higher temperature color developing layer laminated in order on a substrate, wherein an organic color developer contained in said higher temperature color developing layer contains said diphenylsulfone bridgeable type compound represented by general formula (1) and/or said 3-{[(phenylamine)carbonyl]amino}benzenesulfoneamide compound represented by general formula (2), wherein, X and Y can be different and indicates a saturate or an unsaturated liner or grafted hydrocarbon group of carbon number 1 to 12 which can

Abstract: The invention is a novel developer composition which comprises one or more phenol derivative of sulfonamide structure represented by the formula (1) and one or more constituents selected from a polyvalent metal compound, antioxidant and reducing agent and provides dispersion having excellent preservation stability on atomization in water. The heat sensitive recording material comprising the developer composition has high color density in developed image and is also excellent in whiteness degree before recording. wherein X1 is a hydrogen or halogen atom, an alkyl, alkoxy or hydroxyl group, Z1 is a hydrogen atom or alkyl group, and R1 is an unsubstituted or substituted alkyl or aryl group.

Abstract: A heat-sensitive recording material includes a support having successively disposed thereon: a heat-sensitive color-forming layer containing an electron-donating colorless dye and an electron-accepting compound; and a protective layer; wherein the heat-sensitive color-forming layer contains a water-soluble polymer and 4-hydroxybenzenesulfonanilide as the electron-accepting compound, and the protective layer contains at least one inorganic pigment selected from aluminum hydroxide, kaolin and amorphous silica. The electron-donating colorless dye is preferably at least one selected from 2-anilino-3-methyl-6-di-n-butylaminofluoran, 2-anilino-3-methyl-6-di-n-amylaminofluoran and 2-anilino-3-methyl-6-(N-ethyl-N-p-benzyl)aminofluoran.

Abstract: A light-permeable thermosensitive recording material having a light permeable support and a thermosensitive recording layer formed thereon and including a leuco dye, a color developer for the leuco dye, and a binder resin, wherein the developer is a compound represented by the following formula (1): 1

Abstract: An imaging medium comprises a color change layer containing a leuco dye. An acidic developing layer comprising a polyhydroxystyrene reacts with said color change layer to produce a color upon the application of heat. The polyhydroxystyrene may be used alone or in combination with traditional leuco dye developers.

Abstract: Disclosed is a thermosensitive recording material comprising a sheet-shaped support and a thermosensitive recording layer which is formed on at least one surface of the support and comprises a colorless or light-colored dye precursor and a color developer capable of reacting with the dye precursor and inducing color formation therein upon application of heat thereto, the color developer comprising a compound represented by the following formula (I) or analog thereof: 1

Abstract: Disclosed is a heat-sensitive recording material comprising a support and a heat-sensitive recording layer formed on the support and containing a leuco dye, a developer and a binder, wherein the heat-sensitive recording material uses as the developer at least two hydroxy-diphenylsulfone compounds such as 4-hydroxy-4′-isopropoxy-diphenylsulfone, 2,4′-dihydroxy-diphenylsulfone and the like, and uses as the leuco dye a black-color-forming leuco dye such as 3-di(n-butyl)amino-6-methyl-7-anilinofluoran or the like and 0.5 to 3.5 wt. %, relative to the black-color-forming leuco dye, of a red-color-forming leuco dye such as 3-diethylamino-7-chlorofluoran or the like.

Abstract: A thermally imageable element can be imaged using heat alone without the need for photosensitivity or post-imaging processing. The element contains image-forming chemistry that comprises i) image precursor chemistry and ii) a catalyst or a catalyst precursor that upon imagewise heating is capable of promoting thermally induced image formation with the image precursor chemistry. The image-forming chemistry i) and ii) components are in reactive association and uniformly dispersed or dissolved within a binder in one or more layers of the element. Thus, the element is capable of being thermally addressed to provide a visible image as a result of thermally induced catalytic transformation of the image-forming chemistry.

Abstract: A thermosensitive recording material having high whiteness and resistance to color formation under high temperature, high humidity conditions has a thermosensitive colored image-forming layer formed on a substrate sheet and includes a dye precursor, a binder and a color developing agent including a compound of the formula (I) and optionally a compound of the formula (V). R1, R3=unsubstituted or methyl or chlorine-substituted aryl group, R2=at least C3 divalent organic group, R4=at least C3 alkyl, aralkyl or aryloxyalkyl group.

Abstract: The invention relates to an imaging member comprising at least one light insensitive layer comprising an oxidant and a multifunctional dye-forming coupler. It further relates to a method of imaging comprising providing an imaging member comprising at least one light insensitive layer comprising a catalytic center and multifunctional dye-forming coupler, imagewise applying a first developer solution that will react with said multifunctional dye-forming coupler, imagewise applying a second developer solution that will react with multifunctional dye-forming coupler, wherein said first developer solution and said second developer solution produce different colors.

Abstract: The present invention provides a heat sensitive recording material which has high sensitivity and high degree of color formation, excellent storage stability in image portions and non-image portions (i.e., background portions), high whiteness in background portions, and can stably maintain a high contrast image for a long period of time. The heat sensitive recording material has, on a support, a heat sensitive color-forming layer having an electron donating colorless dye and an electron accepting compound. At least one type of the electron accepting compound is 2,4-bis(phenylsulfonyl) phenol, and the heat sensitive color-forming layer further has 2-naphthylbenzyl ether and an amide compound as thermally fusible substances.

Abstract: Disclosed is a heat-sensitive recording material comprising a support and a heat-sensitive recording layer formed on the support and containing a leuco dye and a developer,

Abstract: A thermally printable thermoplastic media includes a thermoplastic material having a thermally activated composition incorporated therein. The thermally activated composition includes a leuco-dye, a color developer, and a reaction promoter. The printable media preferably has a thickness of from about 0.5 to about 1.5 mils to provide a roll with a longer length than a conventional paper roll, thereby increasing the amount of printable media which can be contained on a roll. The thermally printable thermoplastic media is manufactured by combining a thermoplastic material and a thermally activated composition, melting the combined thermoplastic material and thermally activated composition and forming a film from the combined thermoplastic material and thermally activated composition, typically by extrusion. To prevent pre-imaging or initiation of a thermo-chromogenic reaction from the heat involved in extrusion, the extrusion is preferably carried out in an oxygen-free environment.

Abstract: A thermal recording sheet which is satisfactory in sensitivity in color development, background heat resistance, and background color, is free from powdering, and has excellent image retention. The sheet comprises supporting and formed thereon a thermal color development layer containing as main components a colorless or light-colored basic dye and an organic color developer, and is characterized in that the thermal color development layer contains at least one dihydroxydiphenyl sulfone compound represented by general formula (1) as the organic color developer, and further contains either at least one saturated fatty acid monoamide represented by general formula (2) in an amount of 1.5 to 5 parts per part of the organic color developer or a combination of at least one saturated fatty acid monoamide represented by general formula (2) and at least one diphenyl sulfone derivative represented by the general formula (3).

Abstract: A thermosensitive recording material having high whiteness and resistance to color formation under high temperature, high humidity conditions has a thermosensitive colored image-forming layer formed on a substrate sheet and includes a dye precursor, a binder and a color developing agent including a compound of the formula (I) and optionally a compound of the formula (V).

Abstract: A heat-sensitive recording material formed of a support having disposed thereon a heat-sensitive color-forming layer that includes an electron-donating leuco-dye and an electron-receiving compound, with the heat-sensitive color-forming layer including, N-(4-hydroxyphenyl)-p-toluenesulfonamide as the electron-donating leuco-dye. The heat-sensitive color-forming layer may include 2-benzyloxynaphthalene or a combination of 2-benzyloxynaphthalene and methylolstearic acid amide as a sensitizer, calcite-type precipitated calcium carbonate light and/or aluminium hydroxide as an inorganic pigment, polyvinyl alcohol having a degree of saponification of 85 to 99 mol % and a degree of polymerization of from 200 to 2000 as an adhesive, and 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane and/or 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane as an image stabilizer.

Abstract: A composition includes at least two aromatic carboxylic acid compounds selected from the group consisting of aromatic carboxylic acid compounds of formulas (I), (II) and (III) as specified in the specification. A thermosensitive recording material has a support, and a thermosensitive coloring layer formed thereon which contains a leuco dye and a color developer capable of inducing color formation in the leuco dye upon application of heat thereto, with the color developer comprising the aforementioned composition of the aromatic carboxylic acid compounds.

Abstract: Disclosed is a heat-sensitive recording material comprising a support and a heat-sensitive recording layer which is formed on the support and contains a leuco dye, a developer, a sensitizer and a binder, the heat-sensitive recording material using, as the developer, at least one member selected from the group consisting of N-(p-toluenesulfonyl)-m-aminophenol and N-(p-toluenesulfonyl)-p-aminophenol, and as the sensitizer, (a) at least one member selected from the group consisting of 1,2-diphenoxyethane, 1,2-di(3-methylphenoxy)ethane, 2-naphthyl benzyl ether and di-p-methylbenzyl oxalate and (b) a higher fatty acid amide such as stearic acid amide.

Abstract: A photoimaging material which comprises a support and a photoimaging layer formed on the support. The photoimaging layer comprises microcapsules and a reducing agent present outside the microcapsules. The microcapsules contain a leuco dye capable of oxidative color formation, a photooxidizing agent and an organosulfur antioxidant. The reducing agent is 2,2′-methylenebis(4-methyl-6-t-butylphenol) or 2,2′-methylenebis(4-ethyl-6-t-butylphenol). The photoimaging material is capable of thermal image fixing based on a method of forming color by radical oxidation of various leuco dyes to the corresponding dyes with a photooxidizing agent. The photoimaging material is not prone to background coloring (fogging) during storage under dark or light conditions after image fixing, and does not foul the inside of the apparatus during thermal image fixing.

Abstract: A color developer composition comprising (A) a color developer containing a polyvalent metal salt of a salicylic acid derivative, and (B) a polyester polyol having in the molecule skeleton at least one carbonate bond or ester bond, and a derivative thereof, an aqueous dispersion and a color developing ink using this color developer composition, and a recording sheet having a layer containing this color developer composition on a base material.

Abstract: A heat-sensitive recording sheet comprises an electron donative leuco dye, an acidic developer for developing the dye, and a sensitizer. The acidic developer has a main component of a phenolic compound that contains a sulfonyl group in a molecule. The sensitizer comprises an amide compound, N-(4-tolyl) -phenylacetic amide. An amide compound to be mixed with the N-(4-tolyl)-phenylacetic amide for use in the sensitizer is at least one compound selected from the group consisting of N -cyclohexylphenylacetic amide, N-phenylphenylacetic amide, N-(2-tolyl)phenylacetic amide, N-phenylphenoxyacetic amide, N-(4-tolyl)phenoxyacetic amide, N-phenyl-(4-tolyloxy)acetic amide and N-(4-tolyl)-(4-tolyloxy)acetic amide.

Abstract: A thermosensitive recording medium including; a support; and a thermosensitive recording layer formed overlying the support and including a leuco dye, a color developer and a sensitizer, wherein the color developer includes a compound selected from the group consisting of compounds having one of the following formulae (1), (2) and (3): 1

Abstract: Disclosed is a heat-sensitive recording material comprising a support and a heat-sensitive coloring layer formed on the support, wherein

Abstract: The present invention relates to a thermosensitive recording material of heat fixing type. The thermosensitive recording material comprises, on a sheet substrate, a subbing layer and a thermosensitive color image-forming layer in this order, the thermosensitive color image-forming layer comprising a colorless or light-colored dye precursor and a color-developer which reacts with the dye precursor to color the precursor when the color-developer is heated, the color-developer being selected such that the color image formed has a high solvent resistance after the coloring, and the subbing layer comprising a color developability reducing substance capable of reducing the color-developing function of the color-developer and having a melting point of 40° C. or higher. According to the present invention, a thermosensitive recording material is provided, which has a good fixing property and particularly an excellent legibility of colored images even after accidental heating.

Abstract: A decolorable material contains a color former, a developer, a matrix material, and a decolorant capable of physically or chemically adsorbing the developer, the developer having a molecular weight of 120 to 210. The material is capable of forming a clear image, and the image formed from the material can be decolored well, even when the amount of the decolorant used is small.

Abstract: A thermosensitive recording medium capable of forming a visible image thereon when subjected to thermal printing, which has a transparent support, a thermosensitive recording layer provided on the transparent support, containing a dye and a color developer capable of inducing a color in the dye upon the application of heat thereto in the course of the thermal printing, and a mat layer, containing a granular thermosensitive recording layer, containing a granular filler and a binder resin, the mat layer having a surface smoothness of 100 to 2000 sec before subjected to the thermal printing, and a portion of the mat layer subjected to the thermal printing having a surface smoothness of 5,000 sec or less at most.

Abstract: The invention is a novel developer composition which comprises one or more phenol derivative of sulfonamide structure represented by the formula (1) and one or more constituents selected from a polyvalent metal compound, antioxidant and reducing agent and provides dispersion having excellent preservation stability on atomization in water. The heat sensitive recording material comprising the developer composition has high color density in developed image and is also excellent in whiteness degree before recording.

Abstract: A thermally sensitive recording medium which has thermally sensitive recording layer containing colorless or pale colored basic leuco dye and organic color developer as main components on a substrate, wherein said thermally sensitive recording layer contains diphenylsulfone bridgeable type compound represented by general formula (1) and at least one compound represented by general formula (1). In general formula (2), X and Y can be different and indicates a saturated or an unsaturated liner or grafted hydrocarbon group of carbon number 1-12 which can possess ether bond, or indicates wherein R indicates a methylene group or an ethylene group, T indicates a hydrogen atom or an alkyl group of carbon number 1-4, and R1-R6 independently indicate a halogen atom, an alkyl group of carbon number 1-6, or an alkenyl group, further, m, n, p, q, r, t indicate an integer number of 0-4 and when are bigger than 2, R1-R6 can be different, and a is an integer of 0-10.

Abstract: Disclosed is a reversible heat-sensitive recording material which is excellent in light resistance and is remarkably free from discoloration caused by exposure to light and erasing failure and which shows a high layer strength and has durability against repeated printing and erasing, the reversible heat-sensitive recording material having a support, a reversible heat-sensitive recording layer formed on the support and at least one protective layer formed thereon, the reversible heat-sensitive recording layer containing a normally colorless or slightly colored dye precursor and a reversible color developer capable of causing a reversible change in color density of the dye precursor on the basis of a difference in cooling rate after heating, wherein at least one of the said layers contains an isocyanate compound and an ultraviolet absorbent capable of reacting with the isocyanate compound to undergo crosslinking.

Abstract: The thermally sensitive recording medium having sufficient color developing density and develops sepia color or light brown color. The color difference a* value of developed image of said thermally sensitive recording medium regulated by JIS-Z-8729 is within the region of 0˜40 and b* value is within the region of 0˜55.

Abstract: A reversible thermosensitive coloring composition including an electron donating coloring agent and an electron accepting color developer, wherein the composition achieves a colored state when heated at a temperature not lower than a coloring temperature and then cooled at a cooling speed (a), and the composition in the colored state achieves a non-colored state when heated at a temperature lower than the coloring temperature and not lower than an erasing temperature, or when heated at a temperature not lower than the coloring temperature and then cooled relatively slowly compared to the cooling speed (a), and wherein the electron accepting color developer includes a phenolic compound having the following formula (1): wherein n is an integer of from 1 to 3; m is an integer of from 1 to 20; r is 0 or an integer of from 1 to 3; X and Y independently represent a divalent group including a hetero atom; R1 represents a hydrocarbon group having from 1 to 20 carbon atoms; and R2 represents a hydroc

Abstract: A magnetic recording medium, and methods of making and reading the same, including on at least a portion of a substrate an irreversible recording layer which contains an irreversible recording material undergoing an irreversible change of saturation magnetization upon heating. The invention involves the steps of previously heating the irreversible recording layer to form an initial heated region in which a plurality of heated bars whose saturation magnetization has been irreversibly changed are arrayed in a bar code pattern, and converting unheated bars disposed between the heated bars into a heated state for changing the array pattern of heated bars, thereby recording the information.

Abstract: A thermosensitive recording material including a transparent substrate; a thermosensitive recording layer which is formed overlying the substrate and which includes an electron donating coloring agent, an electron accepting color developer and a binder resin; and an overcoat layer which is formed overlying the recording layer and which includes a binder resin which has substantially the same refractive index as the recording material, wherein at least one of the recording layer and a layer adjacent to the recording layer includes a light-heat converting agent and the recording material has transmittance not less than about 10% in a range of from 360 to 420 nm in wavelength. The recording material on which images are recorded is useful for a block copy for flexography, gravure printing, offset printing and screen printing.

Abstract: There is provided a coupler giving a magenta pigment excellent in hue using a diazonium salt compound which can be fixed at a wavelength around 420 nm.

Abstract: Disclosed is a reversible heat-sensitive recording material comprising a support and a reversible heat-sensitive recording layer containing a dye precursor which is usually colorless or a pale color and a reversible color developing agent capable of causing a reversible change in color density of the dye precursor due to the difference in cooling rate after heating, and the reversible color developing agent is a compound represented by the following formula (I): wherein R1 and R2 may be the same or different from each other and each represent a C1-18 divalent hydrocarbon group; R3 represents a C1-24 hydrocarbon group; X1 represents a divalent connecting group having at least one —CONH— bonding; X2 represents an oxygen atom or a sulfur atom; n is an integer of 1 to 3; and m is 0 or 1.

Abstract: A thermosensitive recording material has a support and a thermosensitive coloring layer formed thereon containing a leuco dye and a color developer capable of inducing color formation in the leuco dye upon application of heat thereto, with the color developer including at least one compound (A) having in a molecule thereof at least two aromatic ring moieties with specific structures, selected from the group consisting of an aromatic ring moiety having at least one carboxyl group and electron-attracting functional group, an aromatic ring moiety having at least one carboxyl group and electron-donating functional group, and an aromatic ring moiety having at least one carboxyl group, free of the electron-attracting and electron-donating functional groups. An aromatic carboxylic acid compound serving as the above-mentioned compound (A) and the producing method thereof are also disclosed.

Abstract: The invention relates to an imaging member comprising at least one layer comprising catalytic centers and an aqueous permeable matrix wherein said imaging member is substantially free of photosensitive silver halide. It further relates to a method of imaging comprising supplying an oxidant and imagewise applying at least one soluble dye forming coupler in developer solution to such an imaging member.

Abstract: The present invention provides a recording material comprising a substrate, a heat-sensitive layer formed on the substrate by a coating liquid containing (1) microcapsules containing a colorless or light-colored electron-donative dye precursor and (2) a dispersion of solids comprising color developers, and a protective layer formed on the heat-sensitive layer, wherein the dispersion of solids comprising color developers is a dispersion prepared by co-dispersing at least three color developers including at least one solid color developer, preferably a water-soluble color developer, in the form of solid particles and at least one amorphous color developer together with a water-soluble polymer, and wherein the solid particles of the color developers contained in the dispersion have particle diameters in the range of from 0.3 to 0.5 .mu.m and the haze of the heat-sensitive recording material is 55% or less.

Abstract: A heat-sensitive recording material in which a heat-sensitive color-developing layer comprising, as the main components, a usually colorless or light-colored color former and a developer capable of developing the color former upon heating on a support, characterized by comprising, as the developer, crystals of 3,3'-diallyl-4,4'-dihydroxy-diphenyl sulfone which have DSC (Te) of at least 149.degree. C. and which are of a crystal form characterized by an X-ray diffraction pattern having peaks at least at diffraction angles (2.theta.) [.degree.] of 7.2 and 22.0, obtained by an X-ray powder diffractometry using Cu--K.alpha. rays. This heat-sensitive recording material is high in sensitivity, little in Discoloration of the ground in heat and moisture and excellent in image durability.

Abstract: The present invention is directed to recording materials characterized in that the recording materials comprise at least one of diphenyl sulfone derivatives represented by the following general formula (I); ##STR1## wherein Y represents a linear or branched (un)-saturated C.sub.1 -C.sub.12 hydrocarbon group, a C.sub.1 -C.sub.8 hydrocarbon group having an ether linkage, or a group represented by a general formula; ##STR2## wherein R represents methylene or ethylene; R.sup.1, R.sup.2, R.sup.3 and R.sup.4 represent each independently lower alkyl or lower alkenyl; m represents 0 or an integer of 1 or 2,; and n, p, q and r represent each independently 0 or an integer of 1 to 4, provided when n, p, q and r are each 2 or above, the substituents represented by R.sup.1, R.sup.2, R.sup.3 and R.sup.4 may be each different from one another.

Abstract: A thermal sensitive recording medium which has a feature to change the color of recorded pattern slowly and spontaneously after development, and the recorded pattern which has several days passed can be easily distinguished from that of just after development. Said thermal sensitive recording medium contains 4-hydroxybenzoic acid ester represented by general formula (I) as a color developer and uses triphenylmethane-based leuco dye and reddish color developing leuco dye whose maximum absorption wave length is 450.about.560 nm as a dye precursor. ##STR1## In this formula, R represents unsubstituted or substituted lower alkyl group of carbon number 1-7 or benzyl group.