JP2005199441A - Laser recording-type thermal recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser recording-type thermal recording material which is also equipped with excellent resistance to natural light during the storage of paper before use, which has a proper contrast excellent in laser recordability, such as optical recording sensitivity, and scanner readability of a recording image, and which is excellent in the property of prevention of counterfeit such as tampering, disabling the additional recording of a high-resolution character or image, peculiar to laser recording. <P>SOLUTION: In this laser recording-type thermal recording material, a thermal recording layer, which mainly includes a light absorbing material for absorbing at least laser light so as to convert it into heat and a colorless or light-colored basic colorless dye and an organic developer, is provided on a substrate; and a compound, which is expressed by formula (I), and an ultraviolet absorber are contained as a light absorbing agent. In formula (I), n represents an integer of 1-4, and the structural formulae of Xn, Yn and Zn<SP>-</SP>are indicated in Table 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laser-recording type thermal recording material on which an image is recorded by laser light irradiation.

Among direct recording methods that do not require development or fixing, thermal recording paper materials that use electron-donating leuco dyes and electron-accepting developers as color formers are excellent in operability and maintainability, so Widely used in printers. However, in this method, since the thermal head and the heat generating IC pen are directly brought into contact with the heat-sensitive recording medium and recording is performed, the colored molten material adheres to the thermal head and the heat generating IC pen, thereby causing troubles such as sticking and sticking. This causes problems such as recording failures and recording quality. In particular, when the line is continuously written in the recording flow direction as in a plotter printer, it is practically impossible to perform continuous printing without causing the problem of residue adhesion. In addition, it is difficult to increase the image resolution to 8 lines / mm or more with the recording method using a thermal head.
Therefore, as a method for solving problems such as sticking and sticking and further improving the resolution, a non-contact recording method using a laser beam having a wavelength in the vicinity of the near infrared region disclosed in Patent Document 1 and Patent Document 2 is proposed. Has been.

However, in the above method, a near-infrared absorber is directly added to the heat-sensitive color developing layer coating, and it is applied and dried to obtain a light-absorbing heat-sensitive color developing layer. It is necessary to increase the amount of the near-infrared absorber that absorbs the laser beam and converts it into heat, and since each of the absorbers is considerably colored, the ground color is deteriorated. In addition, when the addition amount is decreased to reduce the background coloration, a sufficient color density cannot be obtained. As a countermeasure, it has been proposed that a near-infrared absorber is contained in a layer different from the heat-sensitive color developing layer and used by being laminated, but it is disadvantageous in operation to have a multilayer structure.
In addition, in recent newspaper plate making systems, it is necessary to work in the development process, waste liquid, waste gas, and dark place in order to create a PS plate (Pre-Sensitized plate) for printing newspapers. Therefore, the conventional photographic paper (silver salt film) system is shifting to a dry film system capable of recording with a laser. If an error is found by proofreading in the process of creating the PS plate, dry film-correction by cutting and pasting-scanner reading-electronic information-dry film, and many steps must be repeated until reaching the PS plate Don't be. As the dry film, for example, a laser recording type thermal proof described in Patent Document 3 containing a dye and a color developing material that absorbs laser light and performs photothermal conversion in the thermal layer can be used.

However, as described above, in the case of the conventional recording medium, since the near-infrared absorber is often colored, even if the recorded image can be read by human eyes, It is difficult to obtain high accuracy in the case of optical reading such as a scanner because the contrast between the image area (background) and the image area is inferior, and sufficient practicality is still obtained as a dry film substitute for photographic paper in plate making systems. Absent.
In Patent Document 4, in order to reduce the coloring of the background, the radical can be converted by irradiating a dye capable of converting laser light into heat energy and becoming colorless by reacting with the radical and ultraviolet light having a wavelength of 400 nm or less. It describes that a photo radical generator to be generated is contained in a heat-sensitive recording layer, and after recording with a laser beam, it is colorless to make the background white or colorless.
On the other hand, there are increasing opportunities for the use of thermal recording paper for gold vouchers such as lotteries, horse races, and boat races. In these applications, there is a possibility that one heat-sensitive recording paper may become a high-priced cash voucher, and therefore, establishment of a forgery prevention technique that makes it impossible to falsify by appending or the like is desired.

However, in general, a thermal recording paper is a write-once recording medium that can be recorded later on an unrecorded portion, and therefore has a problem that other data can be easily recorded. Further, particularly in the case of a laser recording type thermal recording medium, since recording with high-definition characters or images that cannot be reproduced by a conventional thermal head is possible, there is a concern that even if tampered, it is difficult to notice with the naked eye.
Therefore, for example, in Patent Document 5, after recording an image in an optical recording medium containing a coloring material capable of converting laser light into thermal energy and a coloring material in a thermal recording layer, light having a specific wavelength is recorded. It is described that, by decomposing the dye by irradiating, the photothermal conversion ability is deactivated and the additional recording becomes difficult.
JP 58-209594 A JP 58-94494 A JP 2000-238436 A JP-A-5-278330 Japanese Patent Laid-Open No. 7-172054

As described in Patent Documents 4 and 5, it is known that the light absorbing material is deactivated to erase the color or prevent additional recording. However, in either case, the color development performance and the resolution of the dye are not sufficient, and high recording is performed. In order to obtain sensitivity, a considerable amount of light-absorbing material is required, and there are disadvantages in terms of operation such as ultraviolet irradiation.
In addition, these light-absorbing materials lack stability to light, so they are gradually decomposed when left exposed to natural light (indoor light such as fluorescent lamps and sunlight), deactivating photothermal conversion ability. As a result, there is a practical problem such as insufficient colorability when printed.
From the above circumstances, the present invention has excellent light resistance against natural light during storage of paper before use, has good contrast excellent in laser recording suitability such as optical recording sensitivity and scanner readability of recorded images, and laser recording It is an object of the present invention to provide a laser-recording type thermal recording material that makes it impossible to make additional writing with specific high-definition characters or images and has excellent anti-counterfeiting properties such as tampering.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a light-absorbing material that absorbs at least laser light and converts it into heat, a colorless to light-colored electron-donating leuco dye, and electron-accepting on the support. In a thermosensitive recording medium provided with a thermosensitive recording layer containing a color developing agent as a main component, the following formula (I) and an ultraviolet absorber or an ultraviolet absorber and a hindered amine light stabilizer as a light absorber: The present inventors have found that it is a recording material and have reached the present invention.

(Wherein, Xn, Yn and Zn ^- structural formula are shown in the following Table 1)

In the present invention, it has excellent light resistance to natural light during storage of paper before use, has high recording sensitivity, decomposes the light-absorbing material by light irradiation of a specific wavelength, and deactivates the photothermal conversion capability, thereby performing laser recording. A special high-resolution image cannot be added, and the absorption of the light-absorbing material in the visible light region is eliminated. A laser recording type thermosensitive recording medium having contrast can be obtained.
Furthermore, the following general formula (II) as a decoloring agent:

(Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently an alkyl group, aryl group, allyl group, aralkyl group, alkenyl group, alkynyl group, silyl group, heterocyclic group, substituted alkyl group, A substituted aryl group, a substituted allyl group, a substituted aralkyl group, a substituted alkenyl group, a substituted alkynyl group or a substituted silyl group, wherein at least one of R ₁ , R ₂ , R ₃ and R ₄ is alkyl having 1 to 12 carbon atoms; Group; R ₅ , R ₆ , R ₇ and R ₈ are each independently a hydrogen atom, alkyl group, aryl group, allyl group, aralkyl group, alkenyl group, alkynyl group, heterocyclic group, substituted alkyl group, substituted aryl group Represents a substituted allyl group, a substituted aralkyl group, a substituted alkenyl group or a substituted alkynyl group.)
By containing the compound represented by the formula (I), the decomposition of the compound represented by the formula (I) by light is greatly accelerated, the postscript / falsification prevention by the deactivation of the photothermal conversion ability is easily performed, and the good contrast by the decolorization is obtained. A heat-sensitive recording material can be obtained.
Among the compounds represented by the general formula (II), the following formula (III):

(Wherein, m represents an integer of 1 to 3, Zm ^- structural formula are shown in the following Table 2)

Is more preferable because it has a good decoloring ability.

As described above, since the laser recording type thermosensitive recording material of the present invention has a high recording density and a small amount of the light absorbing material may be used, the background coloration can be suppressed. Furthermore, since the ground color can be made white or colorless by deactivation of the light-absorbing material due to light irradiation, it has a good contrast with excellent scanner readability. In addition, since it has excellent light resistance against natural light, a laser-recording type thermal recording material having a stable photothermal conversion ability over a long period of time without decomposing the light-absorbing material during storage of paper before use is obtained. be able to.
Therefore, it can be used as a recording body of a new system that replaces the use of photographic paper in newspaper making and the like, which is very useful. Furthermore, since additional recording with a laser is impossible, it has excellent characteristics for preventing counterfeiting such as tampering, and can be expected to be applied to a voucher.

The present invention will be specifically described below.
The light absorbing material used in the present invention is a substance that absorbs light from a recording source, converts the absorbed light into heat, and releases the heat to the outside. Therefore, the light of the recording source can be absorbed and converted into heat as widely as possible, and the absorption of light having a wavelength in the infrared region that is equal to or close to the laser oscillation wavelength region (about 760 to 1100 nm) is particularly high. Is preferable in terms of heat conversion efficiency and the amount of heat generated.
In the present invention, in particular, four kinds of compounds represented by the above formula (I) (hereinafter sometimes referred to as compound (I)) are used as the light absorbing material. Since compound (I) has a very strong light absorption capability and can efficiently perform photothermal conversion even when the amount used is small, it is considered that a heat-sensitive recording material with high contrast can be obtained while suppressing the background color. In addition, since the compound (I) has the property of being decomposed by light irradiation, the photothermal conversion ability is deactivated to make additional writing impossible, or since the absorption in the visible light region is lost, the ground color becomes white or light, A heat-sensitive recording material having further excellent contrast can be obtained.

As the light that deactivates the compound (I), energy that does not cause the thermosensitive recording layer to develop color and that in the laser wavelength region or visible light wavelength region used for recording is preferably used. Slightly inactive at wavelengths in the ultraviolet region. If the light to be deactivated is the same as the recording wavelength, it is considered advantageous to simplify the equipment installation. In addition, when the heat-sensitive recording layer is heated to the extent that it does not develop color at the same time as light irradiation (about 50 ° C. or less), decomposition is further promoted and effective.
Further, in order to realize high-precision scanner readability, the difference in reflectance between the image portion and the ground color portion when irradiated with light having a wavelength of 600 nm or more is 60% or more, and further 70% or more. Preferably, the heat-sensitive recording material of the present invention has a good contrast between the image portion and the ground color portion, with a large difference in absorption intensity at the reading main wavelength of the scanner.

The decolorizer used in the present invention is one that decomposes and generates radicals when irradiated with light. The generated radicals are considered to act effectively on the compound (I) which is a light absorbing material, and play a role of promoting the deactivation and decoloring of the photothermal conversion ability.
Specifically, it is represented by the compound represented by the above general formula (II), and among them, particularly when three compounds represented by the above compound (III) are used with the compound (I), a good decoloring ability. This is more preferable.
The ultraviolet absorber used in the present invention is gradually decomposed when a light-absorbing material such as compound (I) is left exposed to natural light (indoor light such as a fluorescent lamp or sunlight). It has an action to prevent. That is, the light-absorbing material is used in a role of preventing practical problems such as inability to obtain a sufficient color forming ability when printing is performed due to inactivation of the photothermal conversion ability.

  Specific examples of ultraviolet absorbers include, for example, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2 ′. Benzophenone ultraviolet absorbers such as dihydroxy-4-methoxybenzophenone and 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, salicylic acid systems such as phenyl salicylate, pt-butylphenyl salicylate and p-octylphenyl salicylate UV absorber, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-5′-t-butylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′) , 5'-Di-t-butyl Enyl) benzotriazole, 2- (2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole <Tomisorb 600>, 2- (2′-hydroxy-3 ′, 5 ′) -Di-t-butylphenyl) -5-chlorobenzotriazole, 2 '-[2'-hydroxy-3'-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5 '-Methylphenyl] benzotriazole, 2,2-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol] <ADK STAB LA-31> Benzotriazole-based ultraviolet absorbers such as those described in JP-A-2001-150810, and aqueous emulsion type polymer ultraviolet absorbers and benzoxazinones It includes such external absorbents, used alone or as a mixture of two or more thereof.

The reason why the ultraviolet absorber used in the present invention exhibits such a fading prevention effect is not clear, but a light absorbing material such as compound (I) is poor in stability against natural light, and therefore absorbs ultraviolet rays in the vicinity thereof. It is thought that fading, that is, deterioration of the light absorbing material is prevented by adding an agent and significantly reducing the integrated amount of light irradiated to the light absorbing material itself.
In general, electron-donating leuco dyes turn yellow when exposed to the same natural light. Therefore, when the light-absorbing material is decolored and the ground color portion of the paper is made colorless, the yellowing occurs. The appearance was deteriorated and the image was damaged. However, by adding the ultraviolet absorber, yellowing of the leuco dye can be significantly suppressed for the same reason as the fading prevention effect of the light absorbing material, and a good contrast can be obtained.
Among these ultraviolet absorbers, those having a benzotriazole structure are more preferable because of their high ultraviolet absorption ability and excellent anti-fading properties.
The compounding quantity of a ultraviolet absorber is 1-500 weight part with respect to 1 weight part of light absorption materials used, Preferably about 1-300 weight part is used. If the amount is too small, the anti-fading property cannot be sufficiently exhibited. If the amount is too large, the improvement in the anti-fading property can hardly be expected, and the cost tends to increase.

The hindered amine light stabilizer used in the present invention has the role of remarkably suppressing deterioration of the light absorbing material and yellowing of the leuco dye by inhibiting the activity of extra radicals generated when exposed to natural light. In particular, combined use with an ultraviolet absorber is effective. Although the above reason is not clear, the UV absorber absorbs light in the ultraviolet region included in natural light, and the activity of radicals generated by light in a different region or UV region that could not be absorbed is hindered amine light stabilization It is considered that the agent acts effectively to prevent the fading of the light absorbing material and the yellowing of the leuco dye by inhibiting the agent.
Specific examples of the hindered amine light stabilizer include, for example, 1,6-bis (2,2,6,6-tetramethyl-4-piperidylamino) hexane / dibromoethane polycondensate, 1,6-bis (2 , 2,6,6-tetramethyl-4-piperidylamino) hexane / 2,4-dichloro-6-morpholino-s-triazine polycondensate, 1,6-bis (2,2,6,6-tetramethyl -4-piperidylamino) hexane / 2,4-dichloro-6-tert-octylamino-s-triazine polycondensate, 1,5,8,12-tetrakis [2,4-bis (N-butyl-N- (2,2,6,6-tetramethyl-4-piperidyl) amino) -s-triazin-6-yl] -1,5,8,12-tetraazadodecane, 1,5,8,12-tetrakis [ 2,4-bis (N-butyl N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino) -s-triazin-6-yl] -1,5,8,12-tetraazadodecane, 1,6,11-tris [2,4-bis (N-butyl-N- (2,2,6,6-tetramethyl-4-piperidyl) amino) -s-triazin-6-ylaminoundecane, 1,6,11-tris [ Examples include hindered amine compounds such as 2,4-bis (N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino) -s-triazin-6-ylaminoundecane. Or a mixture of two or more. In particular, (2,2,6,6-tetramethyl-4-piperidyl / tridecyl) -1,2,3,4-butanetetracarboxylate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl ) -1,2,3,4-butanetetracarboxylate is preferred.

The amount of the hindered amine light stabilizer used is 1 to 500 parts by weight, preferably about 1 to 300 parts by weight, based on 1 part by weight of the light absorbing material used. Further, it is used in an amount of about 0.1 to 50 parts by weight, preferably about 0.1 to 10 parts by weight with respect to 1 part by weight of the ultraviolet absorber. If the amount is too small, the anti-fading property cannot be sufficiently expressed, and if the amount is too large, color development may be inhibited.
Various known compounds can be used as the electron-donating leuco dye used in the present invention. These can be used alone or in combination of two or more, and are appropriately selected depending on the application and required quality characteristics. Specific examples include the following compounds, but are not limited thereto.

(1) Triarylmethane compound 3,3′-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide <trade name: crystal violet lactone, CVL>, 3- (4-dimethylamino-2-methylphenyl) ) -3- (4-Dimethylaminophenyl) phthalide, 3,3′-bis (2- (4-dimethylaminophenyl) -2- (4-methoxyphenyl) ethenyl) -4,5,6,7-tetra Chlorophthalide <NIR-Black>, 3,3′-bis (4-dimethylaminophenyl) phthalide <MGL>, 3- (4-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) ) Phthalide, 3- (4-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3′-bis (4-ethylcarba) 3-yl) -3-dimethylaminophthalide, 3,3′-bis (1-ethyl-2-methylindol-3-yl) phthalide <Indolyl Red>, 3,3′-bis (2 -Phenylindol-3-yl) -5-dimethylaminophthalide, tris (4-dimethylaminophenyl) methane <LCV> and the like.
(2) Diphenylmethane compounds 4,4-bis (dimethylamino) benzhydrin benzyl ether, N-halophenyl-leucooramine, N-2,4,5-trichlorophenylleucooramine and the like.

(3) Xanthene compounds Rhodamine B-anilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-butylaminofluorane, 3-diethylamino-7-anilinofluorane <Green-2 >, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-dibutylamino-7- (2-chloroanilino) fluorane <TH-107>, 3-diethylamino-7- (3-trifluoromethylanilino) fluorane <Black-100>, 3-diethylamino-6-methyl-7-anilinofluorane <ODB>, 3-dibutylamino-6-methyl-7-anilinofluorane <ODB-2>, 3-piperidino-6 -Methyl-7-anilinofluorane, 3- (N-isoamyl-N-ethylamino) C) -6-methyl-7-anilinofluorane <S-205>, 3- (N-ethyl-N-tolylamino) -6-methyl-7-anilinofluorane, 3- (N-cyclohexyl-N) -Methylamino) -6-methyl-7-anilinofluorane <PSD-150>, 3-diethylamino-6-chloro-7- (β-ethoxyethylamino) fluorane, 3-diethylamino-6-chloro-7- (Γ-chloropropylamino) fluorane, 3-cyclohexylamino-6-chlorofluorane <OR-55>, 3-diethylamino-6-chloro-7-anilinofluorane, 3- (N-cyclohexyl-N-methyl) Amino) -6-methyl-7-anilinofluorane, 3-diethylamino-7-phenylfluorane and the like.
(4) Thiazine compounds benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, and the like.

(5) Spiro compounds 3-Methylspirodinaphthopyran, 3-ethylspirodinaphthopyrans, 3-benzylspirodinaphthopyrans, 3-methylnaphtho- (6′-methoxybenzo) spiropyrans and the like can be mentioned.
(6) Pentadiene compound 1,1,5,5-tetrakis (4-dimethylaminophenyl) -3-methoxy-1,4-pentadiene, 1,1,5,5-tetrakis (4-dimethylaminophenyl) -1 , 4-pentadiene and the like.

  Most of the above leuco dyes absorb light in the visible light region and mainly absorb light having a wavelength of 600 nm or less. In the present invention, in addition to the above leuco dye, the use of a leuco dye having a main wavelength of absorption at a wavelength of 600 nm or more, particularly 600 to 700 nm, improves the scanner readability and is effective. As such a leuco dye, it is preferable to use a fluoran leuco dye and / or a phthalide leuco dye. As the fluorane leuco dye, 3- (Np-tolyl-N-ethylamino)-(1′-N-ethyl-2 ′, 2 ′, 4′-trimethylpyridyl)-[a] -fluorane <H -1046>. Examples of the phthalide leuco dye include 3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide <GN-2>, 3,6,6′-tris (dimethylamino) spiro [fluorene-9. , 3′-phthalide] <Green-118>, 3,3′-bis (2- (4-dimethylaminophenyl) -2- (4-methoxyphenyl) ethenyl) -4,5,6,7-tetrachloro An example is phthalide <NIR-Black>.

  Next, as an electron-accepting developer used in the present invention, an active acidic clay, attapulgite, colloidal silica, aluminum silicate and other inorganic acidic substances, benzyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, 4- 4-hydroxybenzoic acid esters such as normal propyl hydroxybenzoate, isopropyl 4-hydroxybenzoate, butyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, diisopropyl 4-hydroxyphthalate, dibenzyl 4-hydroxyphthalate, 4-hydroxyphthalic acid diesters such as 4-hydroxyphthalic acid dihexyl, phthalic acid monobenzyl ester, phthalic acid monocyclohexyl ester, phthalic acid monophenyl ester, phthalic acid monomethylphenyl ester, etc. Bis (4-hydroxy-3-tert-butyl-6-methylphenyl) sulfide, bis (4-hydroxy-2,5-dimethylphenyl) sulfide, bis (4-hydroxy-5-ethyl-2-methyl) Bishydroxyphenyl sulfides such as phenyl) sulfide, 3,4-bisphenol A, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane <bisphenol A>, bis ( 4-hydroxyphenyl) methane <bisphenol F>, 2,2-bis (4-hydroxyphenyl) hexane, tetramethylbisphenol A, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4- Bis (2- (4-hydroxyphenyl) propyl) benzene, 1,3-bis (2- (4 -Hydroxyphenyl) propyl) benzene, 1,4-bis (4-hydroxyphenyl) cyclohexane, 2,2'-bis- (4-hydroxy-3-isopropylphenyl) propane, 1,4-bis (1- (4 Bisphenols such as-(2- (4-hydroxyphenyl) -2-propyl) phenyl) ethyl) benzene, 4-hydroxy-4'-isopropoxydiphenylsulfone <D-8>, 4-hydroxy-4'-methoxy 4-hydroxyphenyl aryl sulfones such as diphenyl sulfone, 4-hydroxy-4′-normal propoxydiphenyl sulfone, bis (4-hydroxyphenyl) sulfone <bisphenol S>, tetramethylbisphenol S, bis (3-ethyl-4- Hydroxyphenyl) sulfone, bis (3-pro 4-hydroxyphenyl) sulfone, bis (3-isopropyl-4-hydroxyphenyl) sulfone, bis (3-tert-butyl-4-hydroxy-6-methylphenyl) sulfone, bis (3-chloro-4-hydroxy) Bishydroxyphenyl sulfones such as phenyl) sulfone, bis (3-bromo-4-hydroxyphenyl) sulfone, 2-hydroxyphenyl-4′-hydroxyphenylsulfone,

Diphenylsulfone bridged compound described in International Publication WO97 / 16420, compound described in International Publication WO02 / 081229 or JP2002-301873, 4-hydroxybenzenesulfonate, 4-hydroxyphenyl-p-tolylsulfonate, 4-hydroxyphenylarylsulfonates such as 4-hydroxyphenyl-p-chlorobenzenesulfonate, benzyl 4-hydroxybenzoyloxybenzoate, ethyl 4-hydroxybenzoyloxybenzoate, normal propyl 4-hydroxybenzoyloxybenzoate, 4 4-hydroxybenzoyloxybenzoates such as isopropyl hydroxybenzoyloxybenzoate and butyl 4-hydroxybenzoyloxybenzoate, 2,4-dihydroxy Benzophenones such as nzophenone, α, α′-bis- (3-methyl-4-hydroxyphenyl) -m-diisopropylbenzophenone, 2,3,4,4′-tetrahydroxybenzophenone, N-stearyl-p-aminophenol 4-hydroxysalicylanilide, 4,4′-dihydroxydiphenyl ether, n-butylbis (hydroxyphenyl) acetate, α, α ′, α ″ -tris (4-hydroxyphenyl) -1,3,5-triisopropylbenzene, Stearyl gallate, 4,4′-thiobis (6-tert-butyl-m-cresol), 2,2-bis (3-allyl-4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfide, bis ( 4-hydroxy-3-methylphenyl) sulfide, p-tert- Phenolic compounds such as tilphenol, p-phenylphenol, p-benzylphenol, 1-naphthol, 2-naphthol, thiourea compounds such as N, N′-di-m-chlorophenylthiourea, benzoic acid, p-tert- Butylbenzoic acid, trichlorobenzoic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, terephthalic acid, salicylic acid, 3-isopropyl Salicylic acid, 3-tert-butylsalicylic acid, 4- (2- (p-methoxyphenoxy) ethyloxy) salicylic acid, 4- (3- (p-tolylsulfonyl) propyloxy) salicylic acid, 5- (p- (2- (p -Aromatic carboxylic acids such as -methoxyphenoxy) ethoxy) cumyl) salicylic acid, and Salts of these aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel, as well as antipyrine complexes of zinc thiocyanate, terephthalaldehyde acid and other aromatic carboxylic acids And organic acid substances such as composite zinc salts. Two or more of these may be mixed. Of these, bishydroxyphenylsulfones such as bis (4-hydroxyphenyl) sulfone <bisphenol S> and 4-hydroxyphenylarylsulfones such as 4-hydroxy-4'-isopropoxydiphenylsulfone are particularly preferable.

In a normal heat-sensitive recording material, a sensitizer is used for the purpose of improving sensitivity. Also in the heat-sensitive recording material of the present invention, a sensitizer can be added to the heat-sensitive recording layer depending on the purpose. Although the specific example is shown below, this invention is not limited to these, Moreover, you may use these in mixture of 2 or more types.
Stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoyl stearic acid amide, N-eicosanoic acid amide, ethylene bis stearic acid amide, behenic acid amide, methylene bis stearic acid amide, methylol amide, N-methylol stearic acid Amides, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di -P-chlorobenzyl, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, 1,2-bis (phenoxymethyl) benzene <PMB-2>, tolylbiphenyl ether, di (p-methoxy) Enoxyethyl) ether, 1,2-di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4 -Chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, Examples include p-acetoluidide, p-acetophenetide, N-acetoacetyl-p-toluidine, di (-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, etc. Is done. These sensitizers are usually used in an amount of 0.1 to 10 parts by weight with respect to 1 part by weight of the electron donating leuco dye.

  In the heat-sensitive recording material of the present invention, a storage stabilizer can be used for stabilization during storage. Specific examples of the storage stabilizer include 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane and 1,1,3-tris (2-methyl-4-hydroxy). -5-cyclohexylphenyl) butane, 4,4'-butylidenebis (2-tert-butyl-5-methylphenol), 4,4'-thiobis (2-tert-butyl-5-methylphenol), 2,2'-thiobis Hindered phenol compounds such as (6-tert-butyl-4-methylphenol) and 2,2′-methylenebis (6-tert-butyl-4-methylphenol), 4-benzyloxy-4 ′-(2-methylglycidyl) Oxy) diphenylsulfone, sodium, 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate, etc., and these storage stabilizers 0.1 to 10 parts by weight per normal electron donating leuco dye 1 part by weight is used.

  Specific examples of the binder used in the heat-sensitive recording material of the present invention include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and acetoacetyl group-modified polyvinyl alcohol. , Silicon-modified polyvinyl alcohol, isobutylene-maleic anhydride copolymer alkali salt, styrene-maleic anhydride copolymer alkali salt, ethylene-maleic anhydride copolymer alkali salt, styrene-acrylic acid copolymer alkali salt, etc. Latex such as water-soluble binder, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-butadiene copolymer, urea resin, melamine resin, De resins, and water dispersible binder such as a polyurethane resin. At least one of these binders is used in the range of 5 to 80% by weight based on the total solid content of the heat-sensitive recording layer, overcoat layer, intermediate layer, undercoat layer, or backcoat layer.

In addition, as filler, inorganic filler such as activated clay, clay, calcined clay, diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, barium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, Organic fillers such as urea-formalin resin, polystyrene resin, and phenol resin are used.
Further, a dispersant such as sodium dioctylsulfosuccinate, a surfactant, an antifoaming agent, a fluorescent brightening agent, a water-resistant agent, a lubricant, an ultraviolet absorber, an antioxidant and the like are used as desired.
As the support in the heat-sensitive recording material of the present invention, paper such as high-quality paper, medium-quality paper, recycled paper, and coated paper is mainly used, but various nonwoven fabrics, plastic films, synthetic paper, metal foil, etc. A combined composite sheet or the like is arbitrarily used.

In addition, an overcoat layer such as a polymer material is provided on the heat-sensitive recording layer for the purpose of enhancing the storage stability, or an undercoat layer such as a polymer material containing a filler is provided under the heat-sensitive recording layer for the purpose of increasing the color development sensitivity. You can also. An intermediate layer may be provided between the thermosensitive recording layer and the overcoat layer.
The heat-sensitive recording material of the present invention can be produced by a conventionally known method using various materials as described above. The method for preparing the coating solution for each layer of the heat-sensitive recording material is not particularly limited. Generally, water is used as a dispersion medium, and a light-absorbing material, an electron-donating leuco dye, and an electron-accepting developer, as well as a binder and necessary It is prepared by mixing and stirring fillers, lubricants and the like that are added according to the conditions. For the leuco dye and developer, pulverize and disperse each separately in an aqueous system using a sand grinder, attritor, ball mill, etc., and then mix them to obtain an aqueous paint, or use either the leuco dye or the developer. A method of obtaining a water-based paint after microencapsulation is known. The use ratio of the leuco dye and the developer is appropriately selected according to the type of the leuco dye and the developer to be used and is not particularly limited, but is 0.1 to 50 parts by weight with respect to 1 part by weight of the leuco dye. Preferably, about 0.1 to 10 parts by weight of the developer is used.

In the present invention, the light-absorbing material can obtain excellent color development performance even with an extremely small amount of use such as 0.1 parts by weight or less with respect to 1 part by weight of the leuco dye. In particular, about 0.01 to 0.08 part by weight is preferable. The total solid content of the heat-sensitive recording layer is about 0.05 to 5% by weight, more preferably 0.05 to 3% by weight. The decoloring agent is used in an amount of 0.01 to 25 parts by weight, preferably 0.05 to 10 parts by weight with respect to 1 part by weight of the light absorbing material. In the present invention, the light-absorbing material is effectively dispersed with a sensitizer, dissolved or melt-mixed in advance, and thus the light-absorbing ability is enhanced. Further, it is more preferable to atomize to an average particle size of 3 μm or less after dispersion or mixing in a sensitizer. As the sensitizer, the same one as the heat-sensitive recording layer can be used.
It is more preferable to atomize the near-infrared absorber, decolorizer, and coloring material (leuco dye, developer, sensitizer) so as not to exceed an average particle diameter of 3 μm. The reason for this is that as long as the material is atomized, the dot diameter of the colored printed part is almost the same as the spot diameter of the laser beam, which is the light source, and the dot diameter is uniform, resulting in high-quality, clear printing and line drawing. This is because it is considered that

The method for forming each layer of the thermal recording material is not particularly limited, and air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating, die coating, etc. can be appropriately selected. For example, the heat-sensitive recording layer coating liquid is applied on the support and dried, and then the overcoat layer coating liquid is further applied on the heat-sensitive recording layer and dried. The coating amount of the heat-sensitive recording layer coating composition is 2~12g / m ² approximately by dry weight, preferably 3 to 10 g / m ² approximately, the undercoat layer, the coating amount of the intermediate layer or an overcoat layer coating liquid by dry weight, 0.1 to 15 g / ^{m 2} approximately, it is preferably adjusted in the range of about 0.5 to 10 g / ^{m 2.}
The thermosensitive recording material of the present invention can be provided with a backcoat layer on the back side of the support, if necessary, to further improve the storage stability. Further, after each layer is formed, a smoothing process such as supercalendering can be performed.
Further, as a condition for the color erasing step, the entire surface is irradiated with light after image recording. The wavelength of irradiation light at this time is preferably 600 nm visible light or 800 nm near infrared light. Further, it is more preferable to perform heat treatment at the same time that the heat-sensitive recording layer does not develop color, since decolorization is promoted.

Hereinafter, the present invention will be described in detail with reference to specific examples. However, the present invention is not limited to this embodiment. “Parts” and “%” represent “parts by weight” and “% by weight”, respectively, unless otherwise specified.
[Evaluation test]
Laser recording was performed on the laser recording type thermosensitive recording bodies obtained from Examples 1 to 18 and Comparative Examples 1 to 3 below using a dry plotter GX-3700 (wavelength: 830 nm) manufactured by Matsushita Electric Printing Co., Ltd. The density of the color part was measured with a Macbeth densitometer RD-19.
Thereafter, the entire surface was irradiated with a 600 nm visible light lamp to deactivate the light absorbing material to make it colorless (decolored), and the density of the ground color portion was measured with a Macbeth densitometer RD-19.
In addition, the readability when read with a scanner (reading wavelength 630 nm) was expressed as ◯: good reading, x: poor accuracy (or inability to read).
Furthermore, the ability to prevent forgery when recording with a laser again on the laser-recording type thermosensitive recording medium after being colorless (excellent recording ability is excellent): ◯: no color development and additional recording impossible, Δ: slight X: Color was developed and additional writing was possible.

  Next, in order to evaluate the light stability during storage of paper when left exposed to natural light (indoor light such as fluorescent lamps or sunlight), it was left under a fluorescent lamp of 5000 lux for 24 hours. Laser recording was performed on the laser-recording type thermal recording materials obtained from Examples 1 to 18 and Comparative Examples 1 to 3 using a dry plotter GX-3700 (wavelength 830 nm) manufactured by Matsushita Dentsu Graphic Printing. The density of the image area was measured with a Macbeth densitometer RD-19, and the light resistance stability by exposure to natural light was evaluated as follows: ◎: good color development without fading of the ground color part, ○: ground color part slightly faded It has a good color developing ability, Δ: slightly colored, x: no color developed and not usable.

[Example 1]
Liquid A (developer dispersion)
4-Hydroxy-4′-isopropoxydiphenylsulfone <D-8>
6.0 parts 10% aqueous polyvinyl alcohol solution 20.0 parts water 10.0 parts The mixture of the above composition was ground to a mean particle size of 1 micron with a sand grinder.
Liquid B (light absorbing material dispersion)

<Showa Denko IR2MF>
0.3 parts 1,2-bis (phenoxymethyl) benzene <PMB-2> 5.0 parts 10% polyvinyl alcohol aqueous solution 10.0 parts water 6.0 parts Mixture liquid of the above composition was averaged by a sand grinder Grind to 1 micron diameter.
Liquid C (Discolorant dispersion)

<P3B made by Showa Denko>
0.3 parts 1,2-bis (phenoxymethyl) benzene <PMB-2> 5.0 parts 10% polyvinyl alcohol aqueous solution 10.0 parts water 6.0 parts Mixture liquid of the above composition was averaged by a sand grinder Grind to 1 micron diameter.

D liquid (dye dispersion)
3-Dibutylamino-6-methyl-7-anilinofluorane <ODB-2>
3.0 parts 10% aqueous polyvinyl alcohol solution 5.0 parts water 2.0 parts The mixture of the above composition was ground to a mean particle size of 1 micron with a sand grinder.
Liquid E (UV absorber dispersion)
2,2-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol] <ADK STAB LA-31> 3.0 parts 10% polyvinyl alcohol Aqueous solution 6.0 parts Water 6.0 parts The mixture of the above composition was ground to a mean particle size of 1 micron with a sand grinder.
Liquid F (Hindered amine light stabilizer dispersion)

<ADK STAB LA-52>
3.0 parts 10% polyvinyl alcohol aqueous solution 6.0 parts water 6.0 parts

The mixture of the above composition was ground to a mean particle size of 1 micron with a sand grinder. Next, the dispersion was mixed at the following ratio to obtain a coating solution.
A liquid 40.0 parts B liquid 5.0 parts C liquid 10.0 parts D liquid 10.0 parts E liquid 10.0 parts F liquid 10.0 parts silica 30% dispersion 30.0 parts 60 g of the above coating liquid A laser-recording type thermal recording material was prepared by coating and drying on one side of a sheet of / m ^{2 so} that the coating amount was 7.0 g / m ² . (In the heat-sensitive recording layer, the amount of the light absorbing material used is about 0.02 part with respect to 1 part of the leuco dye.)

[Example 2]
The decolorizer of Example 1 is represented by the following structural formula

<Showa Denko BP3B>
In addition, the ultraviolet absorber is changed to 2- (2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole <Tomisorb 600>, and without using a hindered amine light stabilizer. Other than that, a laser recording type thermosensitive recording material was prepared in exactly the same manner as in Example 1.

[Example 3]
The decolorizer of Example 2 is represented by the following structural formula

<N3B from Showa Denko>
In addition, the laser recording type thermosensitive material was exactly the same as in Example 2 except that the ultraviolet absorbent dispersion was changed to the aqueous emulsion type polymeric ultraviolet absorbent (30%) described in the preparation examples of JP-A-2001-150810. A record was created.

[Example 4]
The procedure was carried out except that the liquid C (decolorant) of Example 2 was not used and the ultraviolet absorber was changed to 2,2′-p-phenylenebis (4H-3,1-benzoxazin-4-one). A laser recording type thermal recording material was prepared in the same manner as in Example 2.

[Example 5]
The light absorbing material of Example 1 has the following structural formula

<Showa Denko IR13F>
In addition, the ultraviolet absorber was changed to 2,2′-p-phenylenebis (4H-3,1-benzoxazin-4-one), and a hindered amine light stabilizer was not used. A laser recording type thermal recording material was prepared in exactly the same manner.

[Example 6]
The light absorbing material of Example 2 was IR13F manufactured by Showa Denko, and the ultraviolet absorber was 2,2-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazole-2- I) Phenol] <Adeka Stab LA-31> and a hindered amine light stabilizer of F solution

<ADK STAB LA-57>
A laser recording type thermosensitive recording material was prepared in the same manner as in Example 2, except that 10 parts were added instead of the above.

[Example 7]
The light absorbing material of Example 3 was IR13F manufactured by Showa Denko, and the ultraviolet absorber was 2- (2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole <Tomisorb 600> A laser recording type thermosensitive recording material was prepared in the same manner as in Example 3 except that the dispersion liquid was used.

[Example 8]
Except for changing the light absorbing material of Example 4 to IR13F manufactured by Showa Denko, and changing the ultraviolet absorbent dispersion to the aqueous emulsion type polymeric ultraviolet absorbent (30%) described in the preparation examples of JP-A No. 2001-150810, A laser recording type thermosensitive recording material was prepared in exactly the same manner as in Example 4.

[Example 9]
The light absorbing material of Example 1 has the following structural formula

<Showa Denko IRB>
In addition, the ultraviolet absorber dispersion was used as an aqueous emulsion type polymer ultraviolet absorber (30%) described in Preparation Examples of JP-A No. 2001-150810, and a hindered amine light stabilizer was not used. In the same manner as in No. 1, a laser recording type thermal recording material was prepared.

[Example 10]
Example 2 except that the light absorbing material of Example 2 was changed to IRB made by Showa Denko, and the ultraviolet absorber was changed to 2,2′-p-phenylenebis (4H-3,1-benzoxazin-4-one). In the same manner as in No. 2, a laser recording type thermosensitive recording material was prepared.

[Example 11]
The light absorbing material of Example 3 was IRB manufactured by Showa Denko, and the ultraviolet absorber was 2,2-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazole-2- I) Phenol] <Adeka Stab LA-31> dispersion, and F liquid hindered amine light stabilizer

<ADK STAB LA-67>
A laser-recording type thermosensitive recording material was prepared in the same manner as in Example 3 except that 10 parts were added instead.

[Example 12]
The light absorbing material of Example 4 is IRB manufactured by Showa Denko, and the ultraviolet absorber is 2- (2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole <Tomisorb 600> A laser-recording type thermosensitive recording material was prepared in exactly the same manner as in Example 4 except that the above was changed.

[Example 13]
The light absorbing material of Example 1 has the following structural formula

<Showa Denko IRT>
In addition, the ultraviolet absorber is changed to 2- (2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole <Tomisorb 600>, and without using a hindered amine light stabilizer. Other than that, a laser recording type thermosensitive recording material was prepared in exactly the same manner as in Example 1.

[Example 14]
Except for changing the light-absorbing material of Example 2 to IRT made by Showa Denko, and changing the ultraviolet absorbent dispersion to the aqueous emulsion type polymeric ultraviolet absorbent (30%) described in the preparation examples of JP-A No. 2001-150810, A laser recording type thermosensitive recording material was prepared in exactly the same manner as in Example 2.

[Example 15]
Except that the light absorbing material of Example 3 was changed to IRT made by Showa Denko, and the ultraviolet absorber was changed to 2,2′-p-phenylenebis (4H-3,1-benzoxazin-4-one) dispersion, A laser recording type thermosensitive recording material was prepared in exactly the same manner as in Example 3.

[Example 16]
The light absorbing material of Example 4 is IRT manufactured by Showa Denko, and the ultraviolet absorber is 2,2-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazole-2- I) Phenol] A laser-recording thermosensitive recording material was prepared in the same manner as in Example 4 except that 10 parts of the hindered amine light stabilizer of liquid F was added to <Adeka Stab LA-31>.

[Example 17]
In addition to the A, B, C, D, E, and F solutions of Example 1, the G solution was prepared.
Liquid G (leuco dye dispersion that absorbs light of 600 to 700 nm)
3,3-bis (4-diethylamino-2-ethoxyphenyl) -4-azaphthalide <GN-2> 1.0 part 10% aqueous polyvinyl alcohol solution 5.0 parts water 2.0 parts A mixed solution of the above composition Grind to an average particle size of 1 micron with a sand grinder. Next, the dispersion was mixed at the following ratio to obtain a coating solution.
Liquid A 40.0 parts B liquid 5.0 parts C liquid 10.0 parts D liquid 10.0 parts E liquid 10.0 parts F liquid 10.0 parts G liquid 10.0 parts Silica 30% dispersion 30.0 Part The above coating solution was applied and dried on one side of 60 g / m ² of paper so as to have a coating amount of 7.0 g / m ² to prepare a laser recording type thermal recording material.

[Example 18]
The test was performed in exactly the same manner as in Example 1 except that laser recording was performed on the laser-recording type thermosensitive recording material obtained in Example 1 and an ultraviolet lamp having a wavelength of 360 nm was used for the colorless recording.

[Comparative Example 1]
A laser recording type thermosensitive recording material was prepared in exactly the same manner as in Example 1 except that the light absorbing material of Example 1 was changed to Nippon Kayaku CY-20 (cyanine light absorbing material).

[Comparative Example 2]
A laser recording type thermosensitive recording material was prepared in exactly the same manner as in Example 1 except that the light absorbing material of Example 1 was changed to NK-6288 (cyanine light absorbing material) manufactured by Hayashibara Biochemical Laboratories.

[Comparative Example 3]
A laser recording type thermosensitive recording material was prepared in the same manner as in Example 1 except that the E solution (ultraviolet absorber) and the F solution (hindered amine light stabilizer) of Example 1 were not used.
Table 3 shows the light absorbing materials, decolorizers, ultraviolet absorbers, and hindered amine light stabilizers used in the examples and comparative examples, and Table 4 shows the evaluation results.

UVA1: Aqueous emulsion type polymer ultraviolet absorber described in Preparation Examples of JP-A-2001-150810
UVA2: 2,2'-p-phenylenebis (4H-3,1-benzoxazin-4-one)

Claims (5)

A heat-sensitive recording layer comprising a light-absorbing material that absorbs at least laser light and converts it into heat, a colorless to light-colored electron-donating leuco dye, and an electron-accepting developer as main components on a support. A laser-recording type heat-sensitive recording material characterized in that the recording material contains a compound represented by the following formula (I) as a light absorber and an ultraviolet absorber.

(In the formula, n represents an integer of 1 to 4, and the structural formulas of Xn, Yn and Zn ⁻ are shown in Table 1 below)

  2. A laser recording type thermal recording material according to claim 1, wherein the ultraviolet absorber is a benzotriazole type.   3. The heat-sensitive recording material according to claim 1, further comprising a hindered amine light stabilizer as an antioxidant. In the heat-sensitive recording material according to any one of claims 1, 2, and 3, the following general formula (II):

(Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently an alkyl group, aryl group, allyl group, aralkyl group, alkenyl group, alkynyl group, silyl group, heterocyclic group, substituted alkyl group, A substituted aryl group, a substituted allyl group, a substituted aralkyl group, a substituted alkenyl group, a substituted alkynyl group or a substituted silyl group, wherein at least one of R ₁ , R ₂ , R ₃ and R ₄ is alkyl having 1 to 12 carbon atoms; Group; R ₅ , R ₆ , R ₇ and R ₈ are each independently a hydrogen atom, alkyl group, aryl group, allyl group, aralkyl group, alkenyl group, alkynyl group, heterocyclic group, substituted alkyl group, substituted aryl group Represents a substituted allyl group, a substituted aralkyl group, a substituted alkenyl group or a substituted alkynyl group.)
A laser recording type heat-sensitive recording material comprising a compound represented by the formula: The decolorizer according to claim 4 is represented by the following formula (III):

(Wherein, m represents an integer of 1 to 3, Zm ^- structural formula are shown in the following Table 2)

A laser-recording type thermal recording material, characterized by being a compound represented by the formula: