JP4836613B2 - Novel phenolic compounds - Google Patents

Description

  The present invention relates to a novel phenol compound, and more specifically, a novel phenol which is an electron-accepting compound useful as a developer for a reversible thermosensitive recording medium capable of forming and erasing a color image by controlling thermal energy. Relates to compounds.

  2. Description of the Related Art Conventionally, heat-sensitive recording media using a color developing reaction between an electron donating color developing compound (hereinafter also referred to as a color former or a leuco dye) and an electron accepting compound (hereinafter also referred to as a developer) are widely known. With the progress of OA, it is widely used as an output sheet for facsimiles, word processors, scientific measuring instruments, etc., and recently as a magnetic thermal card such as prepaid cards and point cards. However, these conventional recording media that have been put to practical use are being reviewed for recycling and reduced usage due to environmental problems. However, since they are irreversible colors, once recorded images are erased. It cannot be used repeatedly, and the area of the recordable part is limited because new information is added to the part where no image is recorded. Therefore, the actual situation is that the amount of information to be recorded is reduced or the card is remade when the recording area runs out. Therefore, it has been desired to develop a reversible thermosensitive recording medium that can be rewritten any number of times, against the background of the dust problem and forest destruction problem that have been actively discussed in recent years.

  By the way, various reversible thermosensitive recording media have been proposed from these requirements. For example, polymer-type reversible thermosensitive recording media using physical changes such as transparency and cloudiness are disclosed (see Patent Documents 1 and 2). In addition, a dye-type reversible thermosensitive recording medium utilizing a chemical change has been newly proposed. Specifically, those using a combination of gallic acid and phloroglucinol as a developer (for example, see Patent Document 3), those using a compound such as phenolphthalein or thymolphthalein as a developer (for example, patents) Reference 4), a recording layer containing a homogeneous solution of color former, developer, and carboxylic acid ester (see, for example, Patent Documents 5, 6, and 7), and an ascorbic acid derivative used as the developer (For example, refer to Patent Document 8), and those using a salt of bis (hydroxyphenyl) acetic acid or gallic acid and a higher aliphatic amine as a developer (for example, refer to Patent Documents 9 and 10).

  Furthermore, the present inventors previously used an organic phosphate compound, aliphatic carboxylic acid compound or phenol compound having a long-chain aliphatic hydrocarbon group as a developer in Patent Document 11, and this and a leuco dye which is a color former. In combination, the color development and decoloring can be easily performed under heating and cooling conditions, and the color development state and the color erasure state can be stably maintained at room temperature, and the color development and color erasure are repeated. A reversible thermosensitive coloring composition and a reversible thermosensitive recording medium using the same for a recording layer have been proposed. Thereafter, it has been proposed to use a phenolic compound having a long chain aliphatic hydrocarbon group having a specific structure (see, for example, Patent Documents 12 and 13).

However, the recording medium using such a material has problems such as a slow erasing speed and a long time for rewriting, insufficient erasing, or low thermal stability of a color image.
Therefore, the present inventors further proposed a recording medium having a high contrast between color development and decoloration, capable of high-speed erasing, and excellent in color stability of the image area by using the phenol compound described in Patent Document 14. . The recording medium using this phenolic compound can be erased by a heating member such as a hot stamp, a heat roller, or a ceramic heater, and has excellent practicality.

However, many of the compounds described in Patent Document 14 have a high melting point, and it is necessary to heat to a high temperature during color development and decoloration, and application of high energy is necessary.
To apply high energy, it is necessary to apply a pulse for a long time during recording, so the writing speed is slow, and since the temperature is high, damage to the recording medium is large and dents are easily generated. There has been a problem that the power source of the apparatus becomes large and the rewriting apparatus becomes large.

  On the other hand, phenol compounds having a relatively low melting point have been proposed as the phenol compounds described in Patent Document 12. However, recording media using these compounds have good color development sensitivity but poor image storage stability and practicality. Was low.

JP 63-107584 A JP-A-4-78573 Japanese Patent Laid-Open No. 60-193691 Japanese Patent Laid-Open No. Sho 61-237684 JP-A-62-138556 JP-A-62-138568 JP-A-62-140881 Japanese Patent Laid-Open No. 63-173684 JP-A-2-188293 JP-A-2-188294 JP-A-5-124360 Japanese Patent Laid-Open No. 6-210954 JP-A-10-95175 JP-A-10-67177

  An object of the present invention is to provide a novel phenol compound having high color development sensitivity, stable color development and erasability, and excellent storage stability when used as a developer for a reversible thermosensitive recording medium. Is to provide.

  In the reversible coloring and decoloring phenomenon of such a color former and developer composition, the present inventors have shown that the ability of the developer having a long-chain aliphatic group to develop color and intermolecular aggregation. We thought that balance of force was important, and designed, synthesized, and studied compounds with various structures. As a result, it has been found that the above problem can be solved by using a phenol compound having a specific structure as a developer.

  That is, the said subject is solved by the phenolic compound represented by following formula (1) of this invention.

（式中、ｎは２３から２９の整数を表わす）

(Where n represents an integer from 23 to 29)

  The phenolic compound of the present invention is a novel compound. Furthermore, a reversible thermosensitive recording medium using the compound of the present invention as a developer can provide reproducible recording with excellent color development sensitivity and color density and excellent image storage stability and high practicality. Thus, a highly practical rewritable recording medium can be obtained.

  The present invention relates to a novel phenol compound represented by the following formula (1).

（式中、ｎは２３から２９の整数を表わす）

(Where n represents an integer from 23 to 29)

  Such a novel phenol compound is obtained, for example, by a coupling reaction with p-aminophenol via a long-chain aliphatic isocyanate derived from a long-chain aliphatic amine, or from a long-chain fatty acid or a fatty acid ester. It is obtained by coupling reaction with p-aminophenol via acid chloride, then azidation and isocyanate. Usually, after completion of the coupling reaction with p-aminophenol, the solution is returned to room temperature or further cooled, a hydrophilic organic solvent solution of acid such as hydrochloric acid is added, the precipitate is filtered, washed and dried, and then an appropriate solvent. Recrystallize using When both the hydroxyl group and the amino group are present, the urethane bond formation reaction and the coupling reaction become competitive, but in the case of p-aminophenol, the electron donating property of the hydroxyl group is reduced due to the resonance structure of the benzene ring. Therefore, the condensation reaction proceeds predominantly, and the phenol compound can be obtained with high selectivity. The phenol compound used in the present invention is not limited to this synthesis method.

  The reversible thermosensitive recording medium using the developer, which is the phenol compound of the present invention, can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. This basic coloring / decoloring phenomenon will be described.

FIG. 1 shows the relationship between the color density of this recording medium and the temperature. Introduction gradually heated the recording medium in the decolored state (A), leuco dye and the developer are mixed melt at temperatures T ₁ begins to melt, coloring occurs a molten color developed state (B). When rapidly cooled from the melt color state (B), the color state can be lowered to room temperature and a fixed color state (C) is obtained. Whether or not this color development state is obtained depends on the rate of temperature decrease from the molten state, and in slow cooling, the color disappears during the temperature decrease, and the same color disappearance state (A) or rapid color development state (C ) A relatively low concentration state is formed. On the other hand, rapidly cooled colored state (C) is again raised gradually and discoloring occurs at a lower temperature T ₂ than the coloring temperature (E from D), returns the beginning when the temperature decreases from here to the same decolored state (A). The actual color developing temperature and color erasing temperature vary depending on the combination of the developer and color former used, and can be selected according to the purpose. Further, the density of the melt coloring state and the coloring density when rapidly cooled are not necessarily the same and may be different.

  In the recording medium using the developer of the present invention, the colored state (C) obtained by quenching from the melted state is a state in which the developer and the color former are mixed in a state where they can contact each other between molecules, This often forms a solid state. This state is a state where the developer and the color former are aggregated to maintain the color development, and it is considered that the color development is stabilized by the formation of this aggregated structure. On the other hand, the decolored state is a state in which both phases are separated. This state is a state in which molecules of at least one compound aggregate to form a domain or crystallize, and the color former and developer are separated and stabilized by aggregation or crystallization. It is done. In the compound of the present invention, complete decolorization occurs when both of them are phase-separated and the developer is crystallized. In both the decoloring by slow cooling from the molten state and the decoloring by raising the temperature from the colored state shown in FIG. 1, the aggregation structure changes at this temperature, and phase separation and crystallization of the developer occur.

  The developer is composed of a phenol group that is a color development site, a hydrogen bonding associative group that controls the structure, and a long-chain aliphatic hydrocarbon group as an important basic skeleton that imparts color developability and color erasability. So far, efforts have been focused on the balance between the phenolic group that is the coloring site and the hydrogen-bonding associative group that is dominant in the structure. The reason is that it has been considered that the stability of the color development state becomes more stable as the aggregation structure of the developer and color former is more stable. Therefore, it has been studied so far to introduce one or more hydrogen bonding associative groups into the developer molecular structure. However, the problem is that the developer molecules have a high melting point due to the strong hydrogen bonds of the developer molecules and the increase in the number of hydrogen bonds, and the color development start temperature increases and the sensitivity characteristics of the recording medium deteriorate. Occurred. For this reason, the present inventors focused on a long-chain aliphatic hydrocarbon group that has been considered to dominate another structure, and a phenol group and an aliphatic group at both ends of the urea group, which are excellent in color developability and erasability, respectively. We focused on investigating the balance of the length of the aliphatic hydrocarbons of the developers with modified aromatic hydrocarbon groups. However, no research has been conducted so far to increase the number of carbon atoms of the aliphatic hydrocarbon group at the end of the developer. This was nothing but a synthesis problem. An aliphatic hydrocarbon group having 18 or less carbon atoms is commercially available as an isocyanate derivative, and a developer can be easily obtained from a condensation reaction of the isocyanate and an amine derivative. For those having up to 22 carbon atoms, a fatty acid amine can be used to synthesize a derivative from an aliphatic amine by isocyanate conversion using phosgene.

However, this method could not synthesize a developer having 23 or more carbon atoms. As a result of intensive studies, the present inventors have found a new synthesis method and succeeded in producing a novel developer represented by the chemical formula (1) of the present invention from 23 or more fatty acids. As a result, it was found that the stability of the colored state is remarkably improved by increasing the number of carbon atoms of the alkyl group as the long-chain aliphatic hydrocarbon group. In particular, in contrast to image storability at 60 ° C. required for this type of recording medium, when the carbon number of the alkyl group is 22 or less, the stability of the colored state is poor and the storability of the image area is fatal. However, the color development state at 60 ° C. was remarkably improved by setting it to 23 or more, and a high image retention rate could be obtained.
This is because the decolorization start temperature from the colored state depends on the chain length of the alkyl group, and in the case of 22 carbon atoms, the decolorization start temperature is 60 ° C. or less, but by setting it to 23 or more, the decoloration start temperature Is 60 ° C. or higher, and a dramatic change appears in the image storage stability at 60 ° C.
Further, it was revealed that even when the alkyl chain length is increased, the melting point of the compound is almost constant and does not increase, and the melting point is not increased to cause a decrease in color development sensitivity.
Furthermore, these developer compounds having an alkyl group having 23 or more carbon atoms are sufficiently decolored by heating in a short time at the decoloring temperature in spite of the stable color development state, and high-speed erasability. It is also excellent.

  The color former used together with the present invention exhibits an electron donating property and can be used alone or in combination. The color former itself is a colorless or light-colored dye precursor, and is not particularly limited. For example, the color former is a known dye precursor such as a phthalide compound, an azaphthalide compound, or a fluorane compound.

Specific examples of the leuco dye used together with the present invention include the following, but the leuco dye is not limited thereto.
2-anilino-3-methyl-6-diethylaminofluorane,
2-anilino-3-methyl-6-di (n-butylamino) fluorane,
2-anilino-3-methyl-6- (Nn-propyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (N-isopropyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (N-isobutyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (Nn-amyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (N-sec-butyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (Nn-amyl-N-ethylamino) fluorane,
2-anilino-3-methyl-6- (N-iso-amyl-N-ethylamino) fluorane,
2-anilino-3-methyl-6- (Nn-propyl-N-isopropylamino) fluorane,
2-anilino-3-methyl-6- (N-cyclohexyl-N-methylamino) fluorane,
2-anilino-3-methyl-6- (N-ethyl-p-toluidino) fluorane,
2-anilino-3-methyl-6- (N-methyl-p-toluidino) fluorane,
2- (m-trichloromethylanilino) -3-methyl-6-diethylaminofluorane,
2- (m-trifluoromethylanilino) -3-methyl-6-diethylaminofluorane,
2- (m-trichloromethylanilino) -3-methyl-6- (N-cyclohexyl-N-methylamino) fluorane,
2- (2,4-dimethylanilino) -3-methyl-6-diethylaminofluorane,
2- (N-ethyl-p-toluidino) -3-methyl-6- (N-ethylanilino) fluorane,
2- (N-ethyl-p-toluidino) -3-methyl-6- (N-propyl-p-toluidino) fluorane,
2-anilino-6- (Nn-hexyl-N-ethylamino) fluorane,
2- (o-chloroanilino) -6-diethylaminofluorane,
2- (o-chloroanilino) -6-dibutylaminofluorane,
2- (m-trifluoromethylanilino) -6-diethylaminofluorane,
2,3-dimethyl-6-dimethylaminofluorane,
3-methyl-6- (N-ethyl-p-toluidino) fluorane,
2-chloro-6-diethylaminofluorane,
2-bromo-6-diethylaminofluorane,
2-chloro-6-dipropylaminofluorane,
3-chloro-6-cyclohexylaminofluorane,
3-bromo-6-cyclohexylaminofluorane,
2-chloro-6- (N-ethyl-N-isoamylamino) fluorane,
2-chloro-3-methyl-6-diethylaminofluorane,
2-anilino-3-chloro-6-diethylaminofluorane,
2- (o-chloroanilino) -3-chloro-6-cyclohexylaminofluorane,
2- (m-trifluoromethylanilino) -3-chloro-6-diethylaminofluorane,
2- (2,3-dichloroanilino) -3-chloro-6-diethylaminofluorane,
1,2-benzo-6-diethylaminofluorane,
3-diethylamino-6- (m-trifluoromethylanilino) fluorane,
3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide,
3- (1-octyl-2-methylindol-3-yl) -3- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (2-methyl-4-diethylaminophenyl) -7-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (4-diethylaminophenyl) -4-azaphthalide,
3- (1-ethyl-2-methylindol-3-yl) -3- (4-Nn-amyl-N-methylaminophenyl) -4-azaphthalide,
3- (1-methyl-2-methylindol-3-yl) -3- (2-hexyloxy-4-diethylaminophenyl) -4-azaphthalide,
3,3-bis (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide,
3,3-bis (2-ethoxy-4-diethylaminophenyl) -7-azaphthalide and the like.

  The ratio of the developer and the color former, which is the compound of the present invention, varies in an appropriate range depending on the combination of the compounds used, but the molar ratio of the compound of the present invention is 0.1 to 20 with respect to the color former 1. Range, preferably in the range of 0.2 to 10. If the amount of the developer is less or more than this range, the density of the colored state is lowered, which causes a problem. In addition, the color former and the developer can be used in a microcapsule.

  In the recording medium using the developer which is the compound of the present invention, the binder resin used for forming the reversible thermosensitive recording layer together with the leuco dye and the developer is, for example, polyvinyl chloride, polyvinyl acetate, vinyl chloride acetic acid. Vinyl copolymer, ethyl cellulose, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, polycarbonate, polyacrylate ester, polymethacrylate ester, acrylic acid copolymer, maleic acid copolymer There are coalesced, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, starches and the like. The role of these binder resins is to keep the materials of the composition uniformly dispersed without being displaced by the application of heat for recording and erasing. Therefore, it is preferable to use a resin having high heat resistance as the binder resin. For example, the binder resin may be crosslinked with heat, ultraviolet light, electron beam, or the like.

  Specific examples of the crosslinked resin used in the recording medium using the developer which is the compound of the present invention include acrylic polyol resin, polyester polyol resin, polyurethane polyol resin, phenoxy resin, polyvinyl butyral resin, and cellulose acetate. Resin having a group that reacts with a crosslinking agent such as propionate and cellulose acetate butyrate, or a resin copolymerized with a monomer having a group that reacts with a crosslinking agent and other monomers, but is limited to these materials Is not to be done.

  Further, preferably, a resin having a hydroxyl value of 70 (KOHmg / g) or more is contained (initially used). As the resin having a hydroxyl value of 70 (KOHmg / g) or more, acrylic polyol resin, polyester polyol resin, polyurethane A polyol resin or the like is used. When the compound of the present invention is used, an acrylic polyol resin is preferably used because of good color development stability and good decoloring properties. The hydroxyl value is 70 (KOHmg / g) or more, particularly preferably 90 (KOHmg / g) or more. The magnitude of the hydroxyl value affects the crosslink density and thus affects the chemical resistance and physical properties of the coating film. The present inventors have found that durability, coating film surface hardness, and crack resistance are improved when the hydroxyl value is 70 (KOHmg / g) or more. Whether or not it is a reversible thermosensitive recording medium using a resin having a hydroxyl value of 70 (KOHmg / g) or more can be confirmed by analyzing the amount of residual hydroxyl groups and the amount of ether bonds.

  In addition, acrylic polyol resins have different characteristics depending on the structure. Hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA), 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl methacrylate ( HPMA), 2-hydroxybutyl monoacrylate (2-HBA), 1,4-hydroxybutyl monoacrylate (1-HBA), etc. are used, but it is particularly preferable to use a monomer having a primary hydroxyl group. Since the crack resistance and durability are good, 2-hydroxyethyl methacrylate is preferably used.

  Examples of the curing agent include conventionally known isocyanates, amines, phenols, epoxy compounds and the like. Of these, isocyanate curing agents are preferably used. The isocyanate compound used here is selected from known modified urethane monomers, allophanate-modified, isocyanurate-modified, burette-modified, carbodiimide-modified, blocked isocyanate and the like. The isocyanate monomer that forms the modified product includes tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), naphthylene diisocyanate (NDI), paraphenylene diisocyanate ( PPDI), tetramethylxylylene diisocyanate (TMXDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), lysine diisocyanate (LDI), isopropylidenebis (4-cyclohexylisocyanate) (IPC) ), Cyclohexyl diisocyanate (CHDI), tolidine diisocyanate (TODI), and the like. The present invention is not limited to.

  Furthermore, you may use the catalyst used for this kind of reaction as a crosslinking accelerator. Examples of the crosslinking accelerator include tertiary amines such as 1,4-diaza-bicyclo [2,2,2] octane, and metal compounds such as organic tin compounds. Further, the total amount of the curing agent may or may not undergo a crosslinking reaction. That is, an unreacted curing agent may be present. Since this type of crosslinking reaction proceeds over time, the presence of an unreacted curing agent does not indicate that the crosslinking reaction has progressed at all, but an unreacted curing agent is detected. However, this does not mean that there is no resin in a crosslinked state. Further, as a method for distinguishing whether the polymer in the present invention is in a crosslinked state or in a non-crosslinked state, it can be distinguished by immersing the coating film in a highly soluble solvent. That is, since the polymer in the non-crosslinked state dissolves in the solvent and does not remain in the solute, the presence or absence of the polymer structure of the solute may be analyzed.

  Furthermore, according to the present invention, the recording layer contains a color development / decoloration control agent having a linear hydrocarbon group, a hydrogen bond group such as an amide group or a urea group, and the like together with the developer and the leuco dye. As a result, the storage stability of the color image is good, and the erasability at the time of erasing is also improved to obtain good erasability.

  Further, a protective layer containing a resin in a crosslinked state can be provided on the reversible thermosensitive recording layer. As the resin used for the protective layer, the same thermosetting resin, ultraviolet curable resin, and electron beam curable resin as those used for the recording layer are used.

  As the resin used in the protective layer, an ultraviolet absorbing polymer having an ultraviolet absorbing group in the molecular structure is particularly preferably used.

  As the ultraviolet absorbing polymer, a monomer having an ultraviolet absorbing group and a polymer having a monomer having a crosslinkable functional group are preferably used. As the monomer having an ultraviolet absorbing group, (2 '-Hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-ω-butyl- A monomer having a benzotriazole skeleton such as 5′-methylphenyl) -5-chlorobenzotriazole is particularly preferably used.

  Examples of the monomer containing a functional group include 2-isopropenyl-2-oxazoline, 2-aziridinylethyl (meth) acrylate, methacrylic acid, glycidyl (meth) acrylate, hydroxylethyl (meth) acrylate, hydroxyl Examples include propyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, and tetrahydrofurfuryl (meth) acrylate, among which hydroxylethyl (meth) ) Acrylate, hydroxylpropyl (meth) acrylate and the like are particularly preferably used.

  Furthermore, in order to increase the strength of the coating film and improve heat resistance, the following monomers may be copolymerized with a copolymer of a monomer containing an ultraviolet absorbing group and a monomer containing a functional group. For example, monomer groups such as styrene, styrene-butadiene, styrene-isobutylene, ethylene vinyl acetate, vinyl acetate, methacrylonitrile, vinyl alcohol, vinyl pyrrolidone, acrylonitrile, methacrylonitrile; acrylic acid, methyl (meth) acrylate, ethyl (meth ) Acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, ethylhexyl (meth) acrylate, octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) ) Acrylate, lauryl tridecyl (meth) acrylate, tridecyl (meth) acrylate, cetyl stearyl (meth) acrylate, stearyl (meth) acrylate (Meth) acrylic acid ester groups not containing functional groups such as cyclohexyl (meth) acrylate and benzyl (meth) acrylate; ethylene di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene Glycol di (meth) acrylate, decaethylene glycol di (meth) acrylate, pentacontahector ethylene glycol (meth) acrylate, butylene di (meth) acrylate, pentaerythritol tetra (meth) acrylate, trimethylolpropane tri (meth) acrylate, penta Decaethylene glycol di (meth) acrylate, phthalic acid diethylene glycol di (meth) acrylate, etc. have two or more polymerizable double bonds in one molecule Although it is mentioned from a monomer group etc., it is not particularly limited, among them, styrene, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, Particularly preferred is t-butyl (meth) acrylate. Moreover, 2 or more types can also be used together as needed.

  From the above, specific preferred examples of the polymer having an ultraviolet absorption structure in the reversible thermosensitive recording medium using the compound of the present invention include 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H. -Copolymer consisting of benzotriazole, 2-hydroxyethyl methacrylate and styrene, Copolymer consisting of 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2-hydroxypropyl methacrylate and methyl methacrylate Examples include coalescence, but are not particularly limited.

Furthermore, the protective layer can contain inorganic fine particles having ultraviolet absorbing ability.
The inorganic pigment used in the recording medium using the developer which is the compound of the present invention is optional as long as it has a mean particle diameter of 0.1 μm or less. Examples of such inorganic pigments include zinc oxide, indium oxide, alumina, silica, zirconium oxide, tin oxide, cerium oxide, iron oxide, antimony oxide, barium oxide, calcium oxide, bismuth oxide, nickel oxide, magnesium oxide, chromium oxide, Manganese oxide, tantalum oxide, niobium oxide, thorium oxide, hafnium oxide, molybdenum oxide, iron ferrite, nickel ferrite, cobalt ferrite, barium titanate, metal oxides such as potassium titanate and complex oxides thereof, zinc sulfide, Metal sulfides such as barium sulfate or sulfate compounds, titanium carbide, silicon carbide, molybdenum carbide, tungsten carbide, metal carbides such as tantalum carbide, aluminum nitride, silicon nitride, boron nitride, nitride Rukoniumu, vanadium nitride, titanium nitride, niobium nitride, and metal nitrides such as gallium nitride.

Among these, a pigment having an absorption edge in a wavelength region of 400 nm or less is particularly preferable.
Such a pigment includes a pigment (A) having an absorption edge in the ultraviolet UV-A region, that is, an ultraviolet UV-A region having a wavelength of 320 to 400 nm, and an inorganic pigment having an absorption edge on the shorter wavelength side than the ultraviolet UV-A region ( B) can be classified into two groups. The inorganic pigment (A) or the inorganic pigment (B) can be used alone, but the effect becomes more remarkable by using the inorganic pigment (A) and the inorganic pigment (B) in combination. When the inorganic pigment (A) or the inorganic pigment (B) is used alone, these pigments can be contained in either the intermediate layer or the protective layer. In the case where the inorganic pigment (A) and the inorganic pigment (B) are used in combination, these pigments can be simultaneously contained in the intermediate layer or the protective layer, but the inorganic pigment (A) and the inorganic pigment (B) are included in the intermediate layer. And can be contained separately in the protective layer. In this case, by incorporating the inorganic pigment (A) in the intermediate layer and the inorganic pigment (B) in the protective layer, the effect of ultraviolet absorbing ability is more remarkably exhibited.

Specific examples of the inorganic pigment (A) include zinc sulfide, titanium oxide, indium oxide, cerium oxide, tin oxide, molybdenum oxide, zinc oxide, and gallium nitride.
Specific examples of the inorganic pigment (B) include silica, alumina, silica-alumina, antimony oxide, magnesium oxide, zirconium oxide, barium oxide, calcium oxide, strontium oxide, silicon nitride, aluminum nitride, boron nitride, and barium sulfate. Can be mentioned.

  Furthermore, inorganic / organic fillers, lubricants and the like used for this type of recording medium may be used in the protective layer of the recording medium using the developer which is the compound of the present invention.

The support of the recording medium using the developer that is the compound of the present invention is paper, resin film, PET film, synthetic paper, metal foil, glass, or a composite thereof, and the like, and can hold a heat-sensitive recording layer. Anything is acceptable. Moreover, the thing of the thickness as needed can be used individually or by bonding. That is, it is preferably 60 to 150 μm, and a support having an arbitrary thickness from about several μm to about several mm is used.
Moreover, when providing the said under layer on these support bodies, crack generation | occurrence | production prevention and generation | occurrence | production of a burr | flash are improved by providing through an contact bonding layer.
The adhesive layer can be formed by the same coating method as that for each of the above layers.

The present invention will be specifically described by the following examples.
Example 1 (Synthesis 1 of the phenolic compound of the present invention)

反応容器にトルエン２００ｍＬとリグノセリン酸１３．３ｇを加え、さらに塩化チオニルを８．６ｇ加え、８時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン１００ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム３．５ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに２時間攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール３．５ｇを加え、１時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量１５．２ｇ、収率は８９％であった。融点は１４５℃であった。Ｐｈｉ社製ＴＲＩＦＴ IIIを用いて、ＴＯＦ−ＳＩＭＳ（飛行時間型二次イオン質量分析装置）により質量分析を行ない、目的物の分子量に相当するピークを得た。その結果を表１に示す。また、観測された正ピーク及び負ピークをそれぞれ図２及び図３に示す。また、生成物の赤外吸収スペクトル（ＫＢｒ法）は図４に示した。これらの結果から目的の構造であることが確認された。

To the reaction vessel, 200 mL of toluene and 13.3 g of lignoceric acid were added, 8.6 g of thionyl chloride was further added, and the mixture was heated to reflux for 8 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. To the resulting acid chloride compound, 100 mL of acetone was added and stirred with ice cooling. An aqueous solution in which 3.5 g of sodium azide was dissolved was gradually added so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 2 hours. The obtained reaction solution was extracted with toluene and washed, then the reaction solution was dried over magnesium sulfate, transferred to the reaction solution, and then heated at an internal temperature of 80 ° C. After confirming that generation of nitrogen was completed and an isocyanate compound was formed, 3.5 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 1 hour, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 15.2 g, and the yield was 89%. The melting point was 145 ° C. Mass spectrometry was performed by TOF-SIMS (time-of-flight secondary ion mass spectrometer) using TRIFT III manufactured by Phi, and a peak corresponding to the molecular weight of the target product was obtained. The results are shown in Table 1. The observed positive and negative peaks are shown in FIGS. 2 and 3, respectively. The infrared absorption spectrum (KBr method) of the product is shown in FIG. From these results, the target structure was confirmed.

Example 2 (Synthesis 2 of the phenolic compound of the present invention)

反応容器にトルエン１００ｍＬとペンタコサン酸５．４ｇを加え、さらに塩化チオニルを３．４ｇ加え、６時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン１５０ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム１．４ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに１時間攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール１．５ｇを加え、１時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量５．８ｇ、収率は８４％であった。融点は１４６℃であった。Ｐｈｉ社製ＴＲＩＦＴ IIIを用いて、ＴＯＦ−ＳＩＭＳ（飛行時間型二次イオン質量分析装置）により質量分析を行ない、目的物の分子量に相当するピークを得た。その結果を表１に示す。また、観測された正ピーク及び負ピークをそれぞれ図２及び図３に示す。また、生成物の赤外吸収スペクトル（ＫＢｒ法）は図５に示した。これらの結果から目的の構造であることが確認された。

To the reaction vessel, 100 mL of toluene and 5.4 g of pentacosanoic acid were added, 3.4 g of thionyl chloride was further added, and the mixture was heated to reflux for 6 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. To the resulting acid chloride compound, 150 mL of acetone was added and stirred with ice cooling. An aqueous solution in which 1.4 g of sodium azide was dissolved was gradually added so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 1 hour. The obtained reaction solution was extracted with toluene and washed, then the reaction solution was dried over magnesium sulfate, transferred to the reaction solution, and then heated at an internal temperature of 80 ° C. After confirming that the generation of nitrogen was completed and an isocyanate compound was formed, 1.5 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 1 hour, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 5.8 g, and the yield was 84%. The melting point was 146 ° C. Mass spectrometry was performed by TOF-SIMS (time-of-flight secondary ion mass spectrometer) using TRIFT III manufactured by Phi, and a peak corresponding to the molecular weight of the target product was obtained. The results are shown in Table 1. The observed positive and negative peaks are shown in FIGS. 2 and 3, respectively. The infrared absorption spectrum (KBr method) of the product is shown in FIG. From these results, the target structure was confirmed.

Example 3 (Synthesis 3 of a phenolic compound of the present invention)

反応容器にトルエン２５０ｍＬとセロチン酸１２．０ｇを加え、さらに塩化チオニルを７．２ｇ加え、さらに数滴のＤＭＦを加え、８時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン１００ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム２．９ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに３時間攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール３．３ｇを加え、１時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量１１．４ｇ、収率は７５％であった。融点は１４３℃であった。Ｐｈｉ社製ＴＲＩＦＴ IIIを用いて、ＴＯＦ−ＳＩＭＳ（飛行時間型二次イオン質量分析装置）により質量分析を行ない、目的物の分子量に相当するピークを得た。その結果を表１に示す。また、観測された正ピーク及び負ピークをそれぞれ図２及び図３に示す。また、生成物の赤外吸収スペクトル（ＫＢｒ法）は図６に示した。これらの結果から目的の構造であることが確認された。

To the reaction vessel, 250 mL of toluene and 12.0 g of serotic acid were added, 7.2 g of thionyl chloride was further added, a few drops of DMF were added, and the mixture was heated to reflux for 8 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. To the resulting acid chloride compound, 100 mL of acetone was added and stirred with ice cooling. An aqueous solution in which 2.9 g of sodium azide was dissolved was gradually added so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 3 hours. The obtained reaction solution was extracted with toluene and washed, then the reaction solution was dried over magnesium sulfate, transferred to the reaction solution, and then heated at an internal temperature of 80 ° C. After confirming that the generation of nitrogen was completed and an isocyanate compound was formed, 3.3 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 1 hour, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 11.4 g, and the yield was 75%. The melting point was 143 ° C. Mass spectrometry was performed by TOF-SIMS (time-of-flight secondary ion mass spectrometer) using TRIFT III manufactured by Phi, and a peak corresponding to the molecular weight of the target product was obtained. The results are shown in Table 1. The observed positive and negative peaks are shown in FIGS. 2 and 3, respectively. The infrared absorption spectrum (KBr method) of the product is shown in FIG. From these results, the target structure was confirmed.

Example 4 (Synthesis 4 of the phenolic compound of the present invention)

反応容器にトルエン３５０ｍＬとモンタン酸１０．５ｇを加え、さらに塩化チオニルを５．９ｇ加え、さらに数滴のＤＭＦを加え、５時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン３００ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム２．４ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに１時間攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール２．７ｇを加え、１時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量１１．９ｇ、収率は９１％であった。融点は１４３℃であった。Ｐｈｉ社製ＴＲＩＦＴ IIIを用いて、ＴＯＦ−ＳＩＭＳ（飛行時間型二次イオン質量分析装置）により質量分析を行ない、目的物の分子量に相当するピークを得た。その結果を表１に示す。また、観測された正ピーク及び負ピークをそれぞれ図２及び図３に示す。また、生成物の赤外吸収スペクトル（ＫＢｒ法）は図７に示した。これらの結果から目的の構造であることが確認された。

To the reaction vessel, 350 mL of toluene and 10.5 g of montanic acid were added, 5.9 g of thionyl chloride was further added, and a few drops of DMF were added, and the mixture was heated to reflux for 5 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. To the resulting acid chloride compound, 300 mL of acetone was added and stirred with ice cooling. Thereto was gradually added an aqueous solution in which 2.4 g of sodium azide was dissolved so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 1 hour. The obtained reaction solution was extracted with toluene and washed, then the reaction solution was dried over magnesium sulfate, transferred to the reaction solution, and then heated at an internal temperature of 80 ° C. After confirming that the generation of nitrogen was completed and an isocyanate compound was formed, 2.7 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 1 hour, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 11.9 g and the yield was 91%. The melting point was 143 ° C. Mass spectrometry was performed by TOF-SIMS (time-of-flight secondary ion mass spectrometer) using TRIFT III manufactured by Phi, and a peak corresponding to the molecular weight of the target product was obtained. The results are shown in Table 1. The observed positive and negative peaks are shown in FIGS. 2 and 3, respectively. The infrared absorption spectrum (KBr method) of the product is shown in FIG. From these results, the target structure was confirmed.

Example 5 (Synthesis 5 of the phenolic compound of the present invention)

反応容器にトルエン５０ｍＬとメリシン酸２．０ｇを加え、さらに塩化チオニルを１．１ｇ加え、さらに数滴のＤＭＦを加え、３時間加熱還流した。それをエバポレーターにより溶媒および塩化チオニルを減圧留去した。得られた酸クロリド化合物にアセトン１０ｍＬを加え、氷冷で攪拌した。そこにアジ化ナトリウム０．４３ｇを溶かした水溶液を温度が１０℃を超えないように徐々に加え、さらに１時間半攪拌した。得られた反応溶液をトルエンで抽出し洗浄したのち、反応溶液を硫酸マグネシウムで乾燥させ、反応溶液に移し変えたのち、内温８０℃で加熱した。窒素の発生が完結しイソシアネート化合物が生成したことを確認した後、反応溶液に、ｐ−アミノフェノール０．４８ｇを加え、１時間加熱攪拌を行なった後、室温に戻し、析出物をろ別し、アセトンで洗浄した。乾燥後、テトラヒドロフランを用いて再結晶することにより化合物を得た。収量２．３５ｇ、収率は９５％であった。融点は１４４℃であった。Ｐｈｉ社製ＴＲＩＦＴ IIIを用いて、ＴＯＦ−ＳＩＭＳ（飛行時間型二次イオン質量分析装置）により質量分析を行ない、目的物の分子量に相当するピークを得た。その結果を表１に示す。また、観測された正ピーク及び負ピークをそれぞれ図２及び図３に示す。また、生成物の赤外吸収スペクトル（ＫＢｒ法）は図８に示した。これらの結果から目的の構造であることが確認された。

To the reaction vessel, 50 mL of toluene and 2.0 g of mellic acid were added, 1.1 g of thionyl chloride was further added, a few drops of DMF were added, and the mixture was heated to reflux for 3 hours. The solvent and thionyl chloride were distilled off under reduced pressure using an evaporator. To the resulting acid chloride compound, 10 mL of acetone was added and stirred with ice cooling. Thereto was gradually added an aqueous solution in which 0.43 g of sodium azide was dissolved so that the temperature did not exceed 10 ° C., and the mixture was further stirred for 1.5 hours. The obtained reaction solution was extracted with toluene and washed, then the reaction solution was dried over magnesium sulfate, transferred to the reaction solution, and then heated at an internal temperature of 80 ° C. After confirming that the generation of nitrogen was completed and an isocyanate compound was formed, 0.48 g of p-aminophenol was added to the reaction solution, and the mixture was heated and stirred for 1 hour, then returned to room temperature, and the precipitate was filtered off. And washed with acetone. After drying, the compound was obtained by recrystallization using tetrahydrofuran. The yield was 2.35 g, and the yield was 95%. The melting point was 144 ° C. Mass spectrometry was performed by TOF-SIMS (time-of-flight secondary ion mass spectrometer) using TRIFT III manufactured by Phi, and a peak corresponding to the molecular weight of the target product was obtained. The results are shown in Table 1. The observed positive and negative peaks are shown in FIGS. 2 and 3, respectively. The infrared absorption spectrum (KBr method) of the product is shown in FIG. From these results, the target structure was confirmed.

Application Example 1 (Example of making a reversible thermosensitive recording medium)
[Creation of thermal recording layer]
4 parts of the phenolic compound of Example 1

アクリルポリオール樹脂
（三菱レイヨン社製ＬＲ５０３ 固形分濃度５０％溶液） ９部
メチルエチルケトン ７０部
上記組成物をボールミルを用いて平均粒径約１μｍまで粉砕分散した。得られた分散液に２−アニリノ−３−メチル−６−ジブチルアミノフルオラン１．５部、日本ポリウレタン社製コロネートＨＬ（アダクト型ヘキサメチレンジイソシアネート７５％酢酸エチル溶液）２部を加え、良く攪拌し感熱記録層塗布液を調製した。
上記組成の感熱記録層塗布液を、厚さ１８８μｍの白ＰＥＴにワイヤーバーを用い塗布し、１００℃２分で乾燥した後、６０℃２４時間加熱して、膜厚約１１．０μｍの記録層を設けた。

Acrylic polyol resin (LR503 manufactured by Mitsubishi Rayon Co., Ltd., 50% solid content solution) 9 parts Methyl ethyl ketone 70 parts The above composition was pulverized and dispersed to an average particle size of about 1 µm using a ball mill. To the obtained dispersion, 1.5 parts of 2-anilino-3-methyl-6-dibutylaminofluorane and 2 parts of Coronate HL (adduct type hexamethylene diisocyanate 75% ethyl acetate solution) manufactured by Nippon Polyurethane Co., Ltd. are added and stirred well. A thermal recording layer coating solution was prepared.
The thermal recording layer coating solution having the above composition was applied to white PET having a thickness of 188 μm using a wire bar, dried at 100 ° C. for 2 minutes, and then heated at 60 ° C. for 24 hours to form a recording layer having a thickness of about 11.0 μm. Was provided.

[Create protection layer]
40% solution of UV-absorbing polymer (UV-G300 manufactured by Nippon Shokubai Co., Ltd.) 10 parts Isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., Coronate HX) 1.4 parts Silicone-based acrylic resin (GS-1015 manufactured by Toagosei Co., Ltd.) 0 .5 parts Methyl ethyl ketone 10 parts The above composition was well stirred to prepare a protective layer coating solution.
A protective layer coating solution having the above composition is applied onto the recording layer using a wire bar, dried at 100 ° C. for 2 minutes, and then heated at 60 ° C. for 24 hours to provide a protective layer having a thickness of about 3.5 μm. The reversible thermosensitive recording medium of the invention was produced.

Application example 2
A reversible thermosensitive recording medium was produced in the same manner as in Application Example 1 except that the compound of Example 2 was used instead of the developer used in Application Example 1.

Application example 3
A reversible thermosensitive recording medium was prepared in the same manner as in Application Example 1 except that the compound of Example 3 was used instead of the developer used in Application Example 1.

Application example 4
A reversible thermosensitive recording medium was prepared in the same manner as in Application Example 1 except that the compound of Example 4 was used instead of the developer used in Application Example 1.

Application example 5
A reversible thermosensitive recording medium was prepared in the same manner as in Application Example 1 except that the compound of Example 5 was used instead of the developer used in Application Example 1.

Comparative Example 1
A reversible thermosensitive recording medium was produced in the same manner as in Application Example 1 except that the following compound (melting point: 145 ° C.) was used instead of the developer used in Application Example 1.

Comparative Example 2
A reversible thermosensitive recording medium was produced in the same manner as in Application Example 1 except that the following compound (melting point: 145 ° C.) was used instead of the developer used in Application Example 1.

Comparative Example 3
A reversible thermosensitive recording medium was prepared in the same manner as in Application Example 1 except that the following compound (melting point: 171 ° C.) was used instead of the developer used in Application Example 1.

The reversible thermosensitive recording medium produced as described above was tested as follows.
Test 1: Color development characteristics Printing was performed at the voltage shown in Table 1 under the condition of a pulse width of 2 msec using a thermal printing simulator manufactured by BCOM. The color density and background density were measured using a Macbeth densitometer RD914. The results are shown in Table 2.

Test 2: Decoloring characteristics After printing at the voltage shown in the table using a thermal printing apparatus manufactured by B.COM as in Test 1, the printed part was subjected to the condition of a pulse width of 2 msec using the same printing simulator. Erasing was performed by gradation printing while changing the voltage. At that time, the most erased site was defined as the erase concentration, and the erase rate was calculated by the following formula. The results are shown in Table 3.
Erase rate (%) = (1− (erase density−background density) / (color density−background density)) × 100
Appropriate conditions were selected for the printing voltage and the voltage used for erasing depending on the color development sensitivity and decoloring characteristics of the recording medium.

Test 3: Image storability The printed image obtained in Test 2 was stored under dry conditions at 60 ° C for 24 hours. After measuring the density before and after storage in the same manner as in Test 1, the image retention rate was calculated by the following formula. The results are shown in Table 4.
Image retention (%) = (image density after storage−background density after storage) / (image density before storage−background density before storage) × 100

表２で示すように実施例は融点の高い比較例３と比べて、１６Ｖで濃度が高く発色感度に顕著な差が現れている。表３で示すように、実施例は高い発色特性と消去特性を有していることがわかる。表４で示すように、比較例１，２，３では、６０℃乾燥条件での画像保持率が低下しているのに対して、実施例では高い保持率を示した。つまり、本発明を用いた可逆性感熱記録媒体は、発色感度、消色性が高く、さらに高い耐熱保存性を有しているのがわかる。

As shown in Table 2, the Example has a high concentration at 16 V and a remarkable difference in color development sensitivity as compared with Comparative Example 3 having a high melting point. As shown in Table 3, it can be seen that the examples have high coloring characteristics and erasing characteristics. As shown in Table 4, in Comparative Examples 1, 2, and 3, the image retention rate under the 60 ° C. drying condition was lowered, whereas in the Examples, a high retention rate was exhibited. That is, it can be seen that the reversible thermosensitive recording medium using the present invention has high color development sensitivity and decoloring property, and further has high heat-resistant storage stability.

It is a figure which shows the color development and decoloring characteristic of the reversible thermosensitive coloring composition of this invention. It is a positive ion peak profile of the phenol compound of this invention using the time-of-flight type secondary ion mass spectrometer. It is a positive ion peak profile of the phenol compound of this invention using the time-of-flight type secondary ion mass spectrometer. 2 is an infrared absorption spectrum of the compound of the present invention synthesized in Example 1. 2 is an infrared absorption spectrum of the compound of the present invention synthesized in Example 2. 2 is an infrared absorption spectrum of the compound of the present invention synthesized in Example 3. 4 is an infrared absorption spectrum of the compound of the present invention synthesized in Example 4. 2 is an infrared absorption spectrum of the compound of the present invention synthesized in Example 5.

Claims (1)

A phenol compound represented by the following formula (1).

(Where n represents an integer from 23 to 29)

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