JPH04229294A - Thermal transfer dye donating material - Google Patents

Abstract

PURPOSE:To obtain a sharp color image superior in fastness to light by incorporating a pyrazoloazole azomathine dye having a specific atom group in a dye donating layer on a substrate. CONSTITUTION:A pyrazoloazole azomathine dye containing at least one of groups having the structure of an ultraviolet absorber shown by a general formula I or II in a molecular is incorporated in a dye donating layer. In the formula, R<11>-R<19> independently represent hydrogen atom or nonmetallic substituent. With the use of the dye, a fastness to light is remarkably improved in comparison with the pyrazoloazole azomathine dye when the ultraviolet absorber is added to an image receiving layer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer dye-providing material using a thermally transferable dye. More specifically, the present invention relates to a thermal transfer dye-providing material containing a pyrazoloazole azomethine dye that does not easily fade.

0002

BACKGROUND OF THE INVENTION At present, thermal transfer methods, electrophotographic methods, ink jet methods, and the like are being actively studied as technologies related to color hard copies. The thermal transfer method has many advantages over other methods because the equipment is easy to maintain and operate, and the equipment and consumables are inexpensive. Thermal transfer methods include a method in which a thermal transfer material in which a heat-melting ink layer is formed on a base film is heated by a thermal head to melt the ink and recorded on a thermal transfer image-receiving material, and a method in which a heat-transferable dye is formed on a base film. There is a method in which a thermal transfer dye-providing material containing a coloring material layer is heated by a thermal head to thermally transfer the dye onto a thermal transfer image-receiving material. By changing the amount, the amount of dye transferred can be changed, which facilitates gradation recording, which is particularly advantageous for high-quality full-color recording. However, there are various restrictions on the heat-transferable dyes used in this method, and there are very few that satisfy all the required performances. Required performances include, for example, having favorable spectral characteristics for color reproduction, being easily transferable to heat, being resistant to light and heat, being resistant to various chemicals, being resistant to loss of sharpness, and having good image quality. It is difficult to retransfer, and it is easy to make a thermal transfer dye-providing material.

Among these, the absorption characteristics of dyes are particularly important. Regarding this absorption property, among the three colors yellow, magenta, and cyan, magenta pigment in particular has
Since it is necessary to be sharp on both the short wavelength side and the long wavelength side, there are few dyes that have satisfactory absorption characteristics. Among magenta dyes, the pyrazoloazole azomethine dye disclosed in JP-A-64-63194 has excellent absorption as a magenta dye. Furthermore, there are few cyan dyes that have sharp absorption, and it has been desired to develop a cyan dye that has sharp absorption. Among cyan dyes, JP-A-64-48863 and JP-A-6
The pyrazoloazole azomethine dyes disclosed in No. 4-48862 and JP-A No. 63-145281 have the required sharp absorption.

0004

However, the above-mentioned pyrazoloazole azomethine dyes also had the drawback of low light fastness. Therefore, the present inventor conducted a detailed study on the relationship between the structure of pyrazoloazole azomethine dyes and light fastness. As a result, we found that pyrazoloazole azomethine dyes that have a specific atomic group in the molecule that has the effect of suppressing fading have significantly higher light fastness than pyrazoloazole azomethine dyes that do not. This led to the invention. Here, we will touch on conventional knowledge. JP-A-62-260152 and JP-A-63-145089 disclose a technique for improving the light fastness of dyes by adding an ultraviolet absorber to an image-receiving layer. The specific atomic group, which is a feature of the dye of the present invention, has the same structure as the ultraviolet absorber. However, these two techniques are completely different. This is because, according to studies conducted by the present inventors, the light fastness of pyrazoloazole azomethine dyes improves only slightly when an ultraviolet absorber is added to the image-receiving layer.
Or not at all. In contrast, the light fastness of the pyrazoloazole azomethine dye in which an atomic group with a specific structure is introduced into the molecule as in the present invention is significantly improved. This cannot be expected at all from the above-mentioned prior art.

[0005]

[Means for Solving the Problems] The above problems have been solved by the following configuration. A thermal transfer dye-providing material comprising a dye-providing layer containing a heat-transferable dye on a support, characterized in that the dye-providing layer contains a heat-transferable dye represented by general formula (I). Thermal transfer dye-donor material. General formula (
I)

[0006]

[C4]

In the formula, R1 and R2 each independently represent an alkyl group, an aryl group, a hydrogen atom or a heterocyclic group. R3, R4, R5, R6 and R7
each independently represents a hydrogen atom or a nonmetallic substituent. Za, Zb and Zc each independently represent -C(R8
)= or -N=. R8 represents a hydrogen atom or a nonmetallic substituent. R3 and R4, and/or R
4 and R1, and/or R1 and R2, and/
or R2 and R5 and/or R5 and R6 are
They may be bonded to each other to form a ring structure. However, R
1, R2, R3, R4, R5, R6, R7
, R8 is represented by the following general formula (II)
or (III). General formula (II)

[0008]

[C5] General formula (III)

[0009]

[C6]

In the formulas (II) and (III), R11, R1
2, R13, R14, R15, R16, R17, R18
, R19 each independently represent a hydrogen atom or a nonmetallic substituent.

Among the dyes represented by the general formula (I),
Those represented by the following general formulas (IV), (V), (VI), and (VII) are preferred.

0012

[C7]

[0013]

[Chemical formula 8]

[0014]

[Chemical formula 9]

[0015]

[Chemical formula 10]

R7 represents a hydrogen atom or a nonmetallic substituent, among which hydrogen atom, halogen atom, alkyl group, cycloalkyl group, alkoxy group, aryl group, acylamino group, alkoxycarbonylamino group,
A fluoronylamino group, ureido group, alkylthio group, arylthio group, alkoxycarbonyl group, carbamoyl group, sulfamoyl group, sulfonyl group, acyl group, amino group, and anilino group are preferred.

[0017] This will be explained in more detail below. R7 is
Hydrogen atoms, halogen atoms (chlorine atoms, bromine atoms, etc.), alkyl groups (1 to 12 carbon atoms, such as methyl, ethyl, butyl, isopropyl, t-butyl, hydroxyethyl,
methoxyethyl, cyanoethyl, trifluoromethyl)
, cycloalkyl groups (e.g. cyclopentyl, cyclohexyl), alkoxy groups (1 to 12 carbon atoms, e.g. methoxy, ethoxy, isopropoxy, methoxyethoxy, hydroxyethoxy), aryl groups (e.g. phenyl, p-tolyl, p-methoxy) phenyl, p-chlorophenyl, o-methoxyphenyl), aryloxy group (
For example, phenoxy, p-methylphenoxy, p-methoxyphenoxy, o-methoxyphenoxy), aralkyl groups (e.g. benzyl, 2-phenethyl), cyano groups, acylamino groups (e.g. acetylamino, propionylamino, isobutyroylamino). ), alkoxycarbonylamino groups (e.g. methoxycarbonylamino,
ethoxycarbonylamino, isopropoxycarbonylamino), sulfonylamino groups (e.g. methanesulfonylamino), benzenesulfonylamino, trifluoromethanesulfonylamino), ureido groups (3-methylureido, 3,3-dimethylureido, 1,3- dimethylureido), alkylthio groups (e.g. methylthio,
butylthio), arylthio groups (e.g. phenylthio, p-tolylthio), alkoxycarbonyl groups (e.g. methoxycarbonyl, ethoxycarbonyl), carbamoyl groups (e.g. methylcarbamoyl, dimethylcarbamoyl), sulfamoyl groups (e.g. dimethylsulfamoyl, diethylsulfamoyl), sulfonyl groups (e.g. methanesulfonyl, butanesulfonyl, benzenesulfonyl), acyl groups (e.g. acetyl, butyroyl), amino groups (e.g. methylamino, dimethylamino), anilino groups (e.g. anilino groups). ). R8 and R8' represent a hydrogen atom or a nonmetallic substituent, and among them, a hydrogen atom, an alkyl group, a cycloalkyl group, an aralkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group, an alkoxycarbonyl group. is preferred. Specific examples of these substituents are R7
The following can be mentioned.

R3, R4, R5 and R6 are
Each independently represents a hydrogen atom or a nonmetallic substituent, and the nonmetallic substituent is an alkyl group (preferably having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, butyl)
, alkoxy group (preferably 1 to 12 carbon atoms, e.g. methoxy, ethoxy, methoxyethoxy, isopropoxy), halogen atom (bromine, fluorine, chlorine), acylamino group [preferably an alkylcarbonylamino group having 1 to 12 carbon atoms ( For example, formylamino, acetylamino, propionylamino, cyanoacetylamino), preferably an arylcarbonylamino group having 7 to 15 carbon atoms (for example, benzoylamino, p-tolylamino, pentafluorobenzoylamino, m-methoxybenzoylamino), Alkoxycarbonyl group (preferably 2 or more carbon atoms)
13, e.g. methoxycarbonyl, ethoxycarbonyl), cyano group, sulfonylamino group (preferably 1 to 10 carbon atoms, e.g. methanesulfonylamino, ethanesulfonylamino, N-methylmethanesulfonylamino),
Carbamoyl group [preferably an alkylcarbamoyl group having 2 to 12 carbon atoms (for example, methylcarbamoyl, dimethylcarbamoyl, butylcarbamoyl, isopropylcarbamoyl, t-butylcarbamoyl, cyclopentylcarbamoyl, cyclohexylcarbamoyl, methoxyethylcarbamoyl, chloroethylcarbamoyl, cyanoethylcarbamoyl, Ethylcyanoethylcarbamoyl, benzylcarbamoyl, ethoxycarbonylmethylcarbamoyl, furfurylerbamoyl, tetrahydrofurfurylcarbamoyl, phenoxymethylcarbamoyl, allylcarbamoyl, crotylcarbamoyl, prenylcarbamoyl, 2,3-dimethyl-2-butenylcarbamoyl, homoallylcarbamoyl, homocrotylcarbamoyl, homoprenylcarbamoyl), preferably an arylcarbamoyl group having 7 to 15 carbon atoms (e.g. phenylcarbamoyl, p-tolylcarbamoyl, m-methoxyphenylcarbamoyl, 4,5-dichlorophenylcarbamoyl, p-cyanophenylcarbamoyl, p −
acetylaminophenylcarbamoyl, p-methoxycarbonylphenylcarbamoyl, m-trifluoromethylphenylcarbamoyl, o-fluorophenylcarbamoyl, 1-naphthylcarbamoyl), preferably a C4-C12 heterylcarbamoyl group (e.g. 2-pyridylcarbamoyl, 3-pyridylcarbamoyl, 4-pyridylcarbamoyl, 2-benzthiazolylcarbamoyl, 2-benzidazolylcarbamoyl, 2-(4-methyl)1,3,4-thiadiazolylcarbamoyl)],
Sulfamoyl group (preferably 0 to 12 carbon atoms, e.g. methylsulfamoyl, dimethylsulfamoyl), aminocarbonylamino group (preferably 1 to 10 carbon atoms,
For example, methylaminoerbonylamino, dimethylaminocarbonylamino), alkoxycarbonylamino groups (
Preferably, it has 2 to 10 carbon atoms, such as methoxycarbonylamino and ethoxycarbonylamino. R
Preferred among 4, R5 and R6 is a hydrogen atom. Preferred among R3 are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms,
Halogen atoms (fluorine, chlorine, bromine), acylamino groups having 1 to 4 carbon atoms, sulfonylamino groups having 1 to 4 carbon atoms,
Aminocarbonylamino group having 1 to 4 carbon atoms, 2 to 4 carbon atoms
4 is an alkoxycarbonylamino group. Among these, R3 is most preferably a hydrogen atom.

R1 and R2 each independently represent a hydrogen atom, an alkyl group (preferably 1 to 20 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, 2
-methoxyethyl, 3-methoxypropyl, ethoxyethyl, 2-phenylethyl, 2-cyanoethyl, cyanomethyl, 2-chloroethyl, 3-bromopropyl, 2-
Methoxycarbonylethyl, 3-ethoxycarbonylpropyl, 2-(N-methylaminocarbonyl)ethyl,
3-(N,N-dimethylaminocarbonyl)propyl,
2-acetylaminoethyl, 3-(ethylcarbonylamino)propyl, 2-acetyloxyethyl), aryl group (preferably 6 to 14 carbon atoms, e.g. phenyl, p
-Tolyl, p-methoxyphenyl, 2,4-dichlorophenyl, p-nitrophenyl, 2,4-dicyanophenyl, 2-naphthyl), heterocyclic groups (including those with substituents. 3 to 12 carbon atoms, e.g. 2-oxypiperidin-3-yl, 2-oxytetrahydropyran-3-yl) are preferred. Preferred R1 and R2 are optionally substituted alkyl groups having 1 to 20 carbon atoms (e.g., methyl, ethyl, propyl, 2-cyanoethyl, 2-acetyloxyethyl, 2-ethoxycarbonylethyl,
-methoxyethyl).

R9, R9', R9'', and R9
′′′ represents a hydrogen atom or a nonmetallic substituent. Specific examples thereof include those described for R3, R4, R5, and R6. R9, R9', R9
'', and R9''' are preferably hydrogen atoms. Among the structures represented by formulas (IV), (V), (VI), and (VII), the structures of formulas (IV) and (V) are preferable. Preferably.

Formulas (II) and (III) will be explained in detail. R11, R12, R13, R14, R15
, R16, R17, R18, and R19 each independently represent a hydrogen atom or a nonmetallic substituent. A specific example is R
Mention may be made of those mentioned under 3, R4, R5 and R6. Specific examples of the atomic group represented by formula (II) are shown below, but the present invention is not limited thereto.

[0022]

[Chemical formula 11]

[0023]

[Chemical formula 12]

[0024]

[Chemical formula 13]

[0025]

[Chemical formula 14]

Specific examples of the compounds used in the present invention will be described below. The present invention is not limited to these compounds.

[0027]

[Chemical formula 15]

[0028]

[Chemical formula 16]

[0029]

[Chemical formula 17]

[0030]

[Chemical formula 18]

[0031]

[Chemical formula 19]

[0032]

[C20]

[0033]

[C21]

[0034]

[C22]

[0035]

[C23]

[0036] Below, examples of synthesis of the pyrazoloazole azomethine dye used in the present invention will be shown, and the present invention will be explained in more detail. Synthesis example 1

[0037]

[C24]

Step - 10 g of compound A, 12.7 g of p-toluenesulfonic acid chloride, and 50 ml of acetonitrile were stirred under ice cooling, and 10 g of pyridine was added dropwise. After reacting for 10 minutes, water 20
The mixture was poured into 0 ml and extracted with ethyl acetate. The organic layer was washed twice with water, dried over magnesium sulfate, and filtered to obtain an ethyl acetate solution of Intermediate B. Step-■ The entire ethyl acetate solution of Intermediate B obtained in Step-■ was reacted with 8.0 g of Compound C, 6.5 g of sodium carbonate, and 100 ml of dimethylacetamide at 60°C for 1 hour. Then, the reaction solution was poured into water, extracted with ethyl acetate,
After washing with water, drying, and filtration, the solvent was distilled off. The crude product was purified using silica gel column chromatography to obtain 11.0 g of Intermediate D. (Yield 50.3%). Step-■ Intermediate D 10.0g, water 50ml, concentrated hydrochloric acid 10
ml was stirred under ice-cooling, and 5.7 g of sodium nitrite was slowly added. Furthermore, 10 ml of concentrated hydrochloric acid
The mixture was added and reacted at room temperature for 1 hour. Thereafter, the reaction solution was poured into water, neutralized with sodium carbonate, and extracted with ethyl acetate. The solvent was distilled off to give 10.1 g of Intermediate E. Ta. (Yield 95.0%). Step - 3.0 g of Intermediate E, 2.0 g of Compound F, 200 ml of ethanol, and 0.83 ml of acetic anhydride were reacted at 60° C. for 30 minutes. Compound 1 was obtained by distilling off the solvent of the reaction solution.
A crude product was obtained. The crude product was purified by silica gel column chromatography (ethyl acetate; hexane = 1:4 to 1:1).
) to obtain 1.2 g of Compound 1. (Yield 24.7
%) mp. Amorphous with no clear melting point λmax
; 539 nm (in ethyl acetate) εmax ; 5.33×
104 l·mol-1, cm-1 Synthesis Example 2 (Compound 2
synthesis)

[0039]

[C25]

Step-■ Intermediate E 10g, iron powder 1
4 g of ammonium chloride, 0.7 g of ammonium chloride, 100 ml of isopropanol, and 20 ml of water were refluxed for 1 hour. Thereafter, suction filtration was performed using Celite, and the iron powder was thoroughly washed with isopropanol. After adding 8.9 g of 1,5-naphthalenedisulfonic acid tetrahydrate to the filtrate, the solvent was distilled off to obtain 18 g of Intermediate F. (quantitative). Step-■ 0.88 g of compound G, 20 ml of ethyl acetate, 20 ml of ethanol, 50 ml of methylene chloride, 50 ml of water, and 2.46 g of sodium carbonate are stirred, and 1.4 g of sodium persulfate and 1.8 g of intermediate F are added. were added slowly over 15 minutes alternately. After that, the mixture was reacted for 30 minutes, water was added, and extraction was performed with ethyl acetate. Separation drying and filtration were performed, and the solvent was distilled off. The crude product was purified using silica gel column chromatography to obtain 0.4 g of Compound 2. (Yield 21.3%
) mp. Amorphous with no clear melting point λmax; 526 nm (in ethyl acetate) εmax;
5.24×104 l・mol−1, cm−1

004
1] The dye of the present invention can have various hues such as magenta, purple, blue, and cyan depending on the selection of substituents. Preferably, magenta color or cyan color can be used. Among these, it is most preferable to use magenta.

The heat-transferable dye of the present invention is incorporated into a coloring material layer on a support, used as a heat-transfer dye-providing material, and used for image formation by a heat-transfer system. Next, the case where the heat-transferable dye of the present invention is used for image formation by thermal transfer method will be described in detail below. Normally, to construct a full-color image, three color pigments of yellow, magenta, and cyan are required. Therefore, one color dye, magenta or cyan, can be selected from among the heat-transferable dyes of the present invention, and the other two colors can be selected from conventionally known dyes. Alternatively, two colors, magenta and cyan, can be selected from the dyes of the present invention, and the yellow dye can be selected from conventionally known dyes. For the same color, the dye of the present invention and a conventionally known dye may be mixed and used. Furthermore, two or more types of the dyes of the present invention may be used in a mixture of the same color.

The method of using the thermal transfer dye of the present invention will be described. Thermal transfer dye-providing materials can be used in sheet form or in continuous roll or ribbon form. The yellow, magenta and cyan dyes of the present invention are usually arranged on a support so as to form independent areas. For example, a yellow dye area, a magenta dye area, and a cyan dye area are arranged on one support in a plane-sequential or line-sequential manner. Also,
It is also possible to prepare three types of thermal transfer dye-providing materials in which the yellow dye, magenta dye, and cyan dye described above are provided on separate supports, and then thermally transfer the dyes from these to one thermal transfer image-receiving material in sequence. The dyes of the present invention can be dissolved or dispersed together with a binder resin in a suitable solvent and coated on a support, or can be printed on a support by a printing method such as a gravure method. The thickness of the dye-donating layer containing these dyes is usually about 0.2 to 5 in terms of dry film thickness.
It is preferable to set the thickness to .mu.m, particularly in the range of 0.4 to 2 .mu.m. As the binder resin used with the above dyes,
Any conventionally known binder resin can be used for this purpose, and one is usually selected that has high heat resistance and does not hinder dye migration when heated. For example, polyamide resins, polyester resins, epoxy resins, polyurethane resins, polyacrylic resins (e.g. polymethyl methacrylate, polyacrylamide, polystyrene-2-acrylonitrile), vinyl resins including polyvinylpyrrolidone, polychlorinated resins, etc. Vinyl resin (e.g. vinyl chloride-vinyl acetate copolymer)
, polycarbonate resin, polystyrene, polyphenylene oxide, cellulose resin (e.g. methylcellulose, ethylcellulose, carboxymethylcellulose, cellulose acetate hydrogen phthalate, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose triacetate)
, polyvinyl alcohol resins (e.g. partially saponified polyvinyl alcohols such as polyvinyl alcohol, polyvinyl acetal, polyvinyl butyral), petroleum resins, rosin derivatives, coumaron-indene resins, terpene resins, polyolefin resins (e.g. polyethylene,
Polypropylene) etc. are used. In the present invention, such a binder resin is preferably used in an amount of about 80 to 600 parts by weight per 100 parts by weight of the dye. In the present invention, any conventionally known ink solvent can be used as the ink solvent for dissolving or dispersing the above pigment and binder resin.

As the support for the thermal transfer dye-providing material, any conventionally known support can be used. Examples include polyethylene terephthalate; polyamide; polycarbonate; glassine paper; condenser paper; cellulose ester; fluorine polymer; polyether; polyacetal; polyolefin; polyimide; polyphenylene sulfide; polypropylene; polysulfone; cellophane. The thickness of the support of the thermal transfer dye-providing material is generally 2 to 3 mm.
It is 0 μm. An undercoat layer may be provided if necessary. Further, a dye diffusion preventing layer made of a hydrophilic polymer may be provided between the support and the dye-donating layer. This further improves the transfer density. As the hydrophilic polymer, the water-soluble polymers described above can be used. A slipping layer may also be provided to prevent the thermal head from sticking to the dye-donating material. This slipping layer is composed of lubricating substances, such as surfactants, solid or liquid lubricants or mixtures thereof, with or without polymeric binders. In order to prevent sticking due to the heat of the thermal head and improve slippage when printing from the back side of the dye-donating material, it is preferable to apply an anti-sticking treatment to the side of the support on which the dye-donating layer is not provided. For example, ■ reaction products of polyvinyl butyral resin and isocyanate, ■ alkali metal salts or alkaline earth metal salts of phosphoric acid esters, and ■
It is preferable to provide a heat-resistant slip layer mainly composed of a filler. Polyvinyl butyral resin has a molecular weight of 60,000 to 20
with a glass transition point of 80 to 110°C,
Further, from the viewpoint of having a large number of reaction sites with isocyanate, it is preferable that the weight percentage of the vinyl butyral portion is 15 to 40%. As the alkali metal salt or alkaline earth metal salt of phosphoric acid ester, Gafac RD720 manufactured by Toho Chemical Co., Ltd. is used, and it has a concentration of 1 to 5 with respect to povinyl butyral resin.
It is good to use about 0% by weight, preferably about 10 to 40% by weight. The heat-resistant slip layer preferably has a heat-resistant lower layer, and is made of a combination of a synthetic resin that can be cured by heating and its curing agent, such as polyvinyl butyral and polyvalent isocyanate, acrylic polyol and polyvalent isocyanate, cellulose acetate and titanium chelating agent, Alternatively, a combination of polyester and an organic titanium compound may be applied by coating.

The dye-donor element may also be provided with a hydrophilic barrier layer to prevent diffusion of the dye towards the support. Hydrophilic dye barrier layers contain hydrophilic materials useful for their intended purpose. Generally excellent results have been obtained using gelatin, poly(acrylamide), poly(isopropylacrylamide), butyl methacrylate grafted gelatin, ethyl methacrylate grafted gelatin, cellulose monoacetate, methylcellulose, poly(vinyl alcohol), poly(ethyleneimine), poly( acrylic acid), a mixture of poly(vinyl alcohol) and poly(vinyl acetate), a mixture of poly(vinyl alcohol) and poly(acrylic acid), or a mixture of cellulose monoacetate and poly(acrylic acid). can get. Particularly preferred are poly(acrylic acid), cellulose monoacetate or poly(vinyl alcohol). The dye-providing material may be provided with a subbing layer. In the present invention, any undercoat layer may be used as long as it has the desired effect, but preferred specific examples include (acrylonitrile-vinylidene chloride-acrylic acid) copolymer (weight ratio 14:80:6), (butyl acrylate) copolymer -2-aminoethyl methacrylate-2-hydroxyethyl methacrylate) copolymer (weight ratio 30:20)
:50), linear/saturated polyesters such as Bostik 7650 (Emhart, Bostik Chemical Group) or chlorinated high density poly(ethylene-trichloroethylene) resins. There is no particular limit to the amount of the undercoat layer applied, but it is usually used in an amount of 0.1 to 2.0 g/m2.

In the present invention, the thermal transfer dye-providing material is superimposed on the thermal transfer image-receiving material, and heat is applied in accordance with the image information from either side, preferably from the back side of the thermal transfer dye-providing material, using a heating means such as a thermal head. By applying energy, the dye in the dye-donating layer can be transferred to the thermal transfer image-receiving material according to the magnitude of the heating energy, and a color image with excellent clarity and resolution and gradation can be obtained. Further, an anti-fading agent can also be transferred in the same manner. Heating means are not limited to thermal heads, but also laser light (
For example, known devices such as a semiconductor laser), an infrared flash, and a thermal pen can be used. In the present invention, the thermal transfer dye-providing material can be combined with a thermal transfer image-receiving material to print images using various thermal printing printers, facsimiles, magnetic recording systems, optical recording systems, etc., to print images on televisions, CRTs, etc. It can be used to create prints from the screen. For details of the thermal transfer recording method, reference can be made to the description in JP-A-60-34895.

The thermal transfer image-receiving material used in combination with the thermal transfer dye-providing material of the present invention is one in which an image-receiving layer for receiving the dye transferred from the dye-providing material is provided on a support. This image-receiving layer accepts the heat-transferable dye that migrates from the thermal transfer dye-providing material during printing, and contains a single substance capable of receiving the heat-transferable dye that has the function of dyeing the heat-transferable dye. It is preferable to have a film with a thickness of about 0.5 to 50 μm containing the binder material or other binder substances. Typical examples of polymers that can accept heat-transferable dyes include the following resins. (b) Those having an ester bond Dicarboxylic acid components such as terephthalic acid, isophthalic acid, and succinic acid (these dicarboxylic acid components may be substituted with sulfo groups, carboxyl groups, etc.), ethylene glycol, diethylene glycol, Polyester resin obtained by condensation of propylene glycol, neopentyl glycol, bisphenol A, etc.: Polyacrylic acid ester resin or polymethacrylic acid ester resin such as polymethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polybutyl acrylate: Polycarbonate resin: Polyvinyl acetate resin: Styrene acrylate resin: Vinyltoluene acrylate resin, etc. Specifically, JP-A No. 59-101395, JP-A No. 63-7971, JP-A No. 6
No. 3-7972, No. 63-7973, No. 60-294
Examples include those described in No. 862. In addition, commercially available products include Toyobo's Byron 290 and Byron 20.
0, Byron 280, Byron 300, Byron 103
, Byron GK-140, Byron GK-130, Kao ATR-2009, ATR-2010, etc. can be used. (b) Products with urethane bonds, such as polyurethane resins. (c) Polyamide resins having amide bonds, etc. (d) Things with urea bonds, such as urea resins. (e) Things with sulfone bonds, such as polysulfone resins. (f) Others having highly polar bonds, such as polycaprolactone resin, styrene-maleic anhydride resin, polyacrylonitrile resin, etc. In addition to the synthetic resins mentioned above, mixtures or copolymers thereof can also be used.

The thermal transfer image-receiving material, particularly the image-receiving layer, may contain a high-boiling organic solvent or a thermal solvent as a substance capable of receiving heat-transferable dyes or as a dye-diffusing agent. Specific examples of high boiling point organic solvents and thermal solvents include JP-A-62-174754 and JP-A-62-245253.
No. 61-209444, No. 61-200538, No. 62-8145, No. 62-9348, No. 62-
Examples include compounds described in No. 30247 and No. 62-136646. The image-receiving layer of the thermal transfer image-receiving material of the present invention may have a structure in which a substance capable of receiving a heat-transferable dye is dispersed and carried in a water-soluble binder. As the water-soluble binder used in this case, various known water-soluble polymers can be used, but a water-soluble polymer having a group capable of crosslinking with a hardening agent is preferred. The image receiving layer may be composed of two or more layers. In that case, a synthetic resin with a low glass transition point is used for the layer closer to the support, or a high-boiling point organic solvent or a hot solvent is used to improve dyeing properties, and the outermost layer is made of a synthetic resin with a low glass transition point. Avoid surface stickiness by using synthetic resins with higher points, or by minimizing or not using high boiling point organic solvents or hot solvents.
It is desirable to have a structure that prevents failures such as adhesion with other substances, retransfer to other substances after transfer, and blocking with the thermal transfer dye-providing material. The total thickness of the image receiving layer is 0.5
A range of 50 μm, particularly 3 to 30 μm is preferred. In the case of a two-layer structure, the outermost layer has a thickness of 0.1 to 2 μm, especially 0.2 to 1 μm.
It is preferable to set it in the range of m.

The thermal transfer image-receiving material of the present invention may have an intermediate layer between the support and the image-receiving layer. The intermediate layer is a cushion layer, a porous layer, a dye diffusion prevention layer, or a layer having two or more of these functions, depending on the constituent material.
In some cases, it also serves as an adhesive. The dye diffusion-preventing layer plays a role, in particular, in preventing the heat-transferable dye from diffusing into the support. The binder constituting this diffusion prevention layer may be water-soluble or organic solvent-soluble, but a water-soluble binder is preferred, and examples thereof include the water-soluble binders mentioned above as the binder for the image-receiving layer, particularly gelatin. The porous layer is a layer that prevents the heat applied during thermal transfer from diffusing from the image-receiving layer to the support and effectively utilizes the applied heat. The image receiving layer, cushion layer, porous layer, diffusion prevention layer, adhesive layer, etc. that constitute the thermal transfer image receiving material of the present invention include silica, clay, talc, diatomaceous earth, calcium carbonate, calcium sulfate, barium sulfate, aluminum silicate, Fine powders of synthetic zeolite, zinc oxide, litovone, titanium oxide, alumina, etc. may also be included. The support used in the thermal transfer image-receiving material of the present invention can withstand the transfer temperature and satisfies the requirements in terms of smoothness, whiteness, slipperiness, friction, antistatic property, denting after transfer, etc. You can use anything. For example, synthetic paper (polyolefin-based, polystyrene-based, etc.), high-quality paper, art paper,
Coated paper, cast coated paper, wallpaper, backing paper, synthetic resin or emulsion impregnated paper, synthetic rubber latex impregnated paper, synthetic resin internalized paper, paperboard, cellulose fiber paper, polyolefin coated paper (especially paper coated on both sides with polyethylene) Paper supports such as, various plastic films or sheets such as polyolefin, polyvinyl chloride, polyethylene terephthalate, polystyrene, methacrylate, polycarbonate, etc., and films or sheets treated to give white reflective properties to this plastic, and any combination of the above. A laminate according to the above can also be used.

A fluorescent brightener may be used in the thermal transfer image-receiving material. An example is K. Vevnkatarama
Volume n “The Chemistry of Synt”
"Hetic Dyes" Volume 5 Chapter 8, Japanese Patent Publication No. 1983-
Examples include compounds described in No. 143752 and the like. More specifically, stilbene compounds, coumarin compounds, biphenyl compounds, benzoxazolyl compounds, naphthalimide compounds, pyrazoline compounds, carbostyril compounds, 2,5-dibenzoxazolethiophene compounds, etc. Can be mentioned. Optical brighteners can be used in combination with antifade agents. In the present invention, in order to improve the releasability of the thermal transfer dye-providing material and the thermal transfer image-receiving material, among the layers constituting the dye-providing material and/or the image-receiving material, particularly preferably the outermost layer is the surface where both materials come into contact. It is preferable that a mold release agent be included in the mold release agent. Examples of mold release agents include solid or waxy substances such as polyethylene wax, amide wax, and Teflon powder; surfactants such as fluorine-based and phosphate esters; and conventionally known oils such as paraffin-based, silicone-based, and fluorine-based oils. Although any of the above mold release agents can be used, silicone oil is particularly preferred. As the silicone oil, in addition to unmodified silicone oil, modified silicone oils such as carboxy-modified, amino-modified, and epoxy-modified silicone oils can be used. An example of this is the “
Examples include various modified silicone oils described on pages 6 to 18B of the "Modified Silicone Oil" technical data. When used in an organic solvent-based binder, amino-modified silicone oil having a group that can react with the crosslinking agent of this binder (for example, a group that can react with isocyanate) is also emulsified and dispersed in a water-soluble binder. For example, carboxy-modified silicone oil (for example, manufactured by Shin-Etsu Silicone Co., Ltd.: trade name X-22-3710) is effective.

The layers constituting the thermal transfer dye-providing material and the thermal transfer image-receiving material used in the present invention may be hardened with a hardening agent. When curing organic solvent-based polymers, JP-A-61-199997 and JP-A-58-21539 are used.
Hardeners described in No. 8 etc. can be used. For polyester resins, it is particularly preferable to use isocyanate-based hardeners. For curing water-soluble polymers, see U.S. Pat. No. 4,678,739, column 41;
No. 55, No. 62-245261, No. 61-18942
The hardening agents described in No. 1, etc. are suitable for use. More specifically, aldehyde hardeners (such as formaldehyde), aziridine hardeners, epoxy hardeners, and vinylsulfone hardeners (N,N'-ethylene-bis(vinylsulfonylacetamide)). ethane, etc.), N-methylol hardeners (dimethylol urea, etc.), and polymer hardeners (compounds described in JP-A-62-234157, etc.).

An anti-fading agent may be used in the thermal transfer dye-providing material and the thermal transfer image-receiving material. Antifading agents include, for example, antioxidants, ultraviolet absorbers, or certain metal complexes. Examples of antioxidants include chroman compounds, coumaran compounds, phenol compounds, phenol compounds (for example, hindered phenols), hydroquinone derivatives, hindered amine derivatives, and spiroindane compounds. Also, JP-A-61-159644
Compounds described in the above are also effective. As a UV absorber,
Benzotriazole compounds (U.S. Pat. No. 3,533,
794, etc.), 4-thiazolidone compounds (U.S. Patent No. 3,352,681, etc.), benzophenone compounds (Japanese Patent Application Laid-open No. 56-2784, etc.), and others.
-48535, 62-136641, 61-8
There are compounds described in No. 8256 and the like. Also, JP-A-62
The ultraviolet absorbing polymer described in Japanese Patent No. 260152 is also effective. As a metal complex, US Pat. No. 4,241,15
No. 5, No. 4,245,018, columns 3 to 36, No. 4 of the same
, No. 254, No. 195, columns 3 to 8, JP-A-62-1747
No. 41, No. 61-88256, pages (27) to (29),
There are compounds described in Japanese Patent Application No. 62-234103, Japanese Patent Application No. 62-311096, Japanese Patent Application No. 62-230596, etc. An example of a useful anti-fading agent is JP-A-62-215
No. 272, pages (125) to (137). An anti-fading agent for preventing fading of the dye transferred to the image-receiving material may be included in the image-receiving material in advance, or it may be supplied to the image-receiving material from the outside by a method such as transfer from a dye-donating material. It's okay. The above antioxidants, ultraviolet absorbers, and metal complexes may be used in combination.

Various surfactants can be used in the constituent layers of the thermal transfer dye-providing material and the thermal transfer image-receiving material for the purposes of coating aids, improving releasability, improving slipperiness, preventing electrification, accelerating development, and the like. For example, saponins (steroids), alkylene oxide derivatives (e.g. polyethylene glycol, polyethylene glycol alkyl ethers, polyethylene glycol alkyl aryl ethers, polyethylene glycol esters, polyethylene glycol sorbitan esters, polyalkylene glycol alkyl amines or amides, silicones nonionic surfactants such as polyethylene oxide adducts), glycidol derivatives (e.g. alkenylsuccinic acid polyglycerides, alkylphenol polyglycerides), fatty acid esters of polyhydric alcohols, alkyl esters of sugars: alkyl carboxylates, Alkyl sulfonates, alkylnaphthalene sulfonates, alkyl sulfates, alkyl phosphates, N-acyl-N-alkyl taurines, sulfosuccinates, sulfoalkyl polyethylene alkylphenyl ethers, polyoxyethylene alkyl phosphorus Anionic surfactants containing acidic groups such as carboxy groups, sulfo groups, phospho groups, sulfate ester groups, phosphate ester groups such as acid esters: amino acids, aminoalkyl sulfonic acids, aminoalkyl sulfates or phosphate esters, Double-sided surfactants such as alkyl betaines and amine oxides: Alkyl amine salts, aliphatic or aromatic quaternary ammonium salts, polycyclic quaternary ammonium salts such as pyridinium and imidazolium, and aliphatic or aromatic quaternary ammonium salts; Cationic surfactants such as phosphonime or sulfonium salts containing cationic surfactants can be used. Specific examples of these are described in JP-A-62-173463 and JP-A-62-183457. In addition, when dispersing substances that can accept heat-transferable dyes, mold release agents, anti-fading agents, ultraviolet absorbers, optical brighteners, and other hydrophobic compounds in a water-soluble binder, the interface is used as a dispersion aid. Preferably, an activator is used. For this purpose, in addition to the above-mentioned surfactants, surfactants described on pages 37-38 of JP-A-59-157636 are particularly preferably used.

[0054] The constituent layers of the thermal transfer dye-providing material and the thermal transfer image-receiving material may contain an organic fluoro compound for the purpose of improving slipperiness, preventing electrification, improving releasability, and the like. Representative examples of organic fluoro compounds include JP-B No. 57-9053, columns 8 to 17, JP-A No. 61-20944, JP-A No. 62-13.
Examples thereof include fluorine-based surfactants described in No. 5826, etc., and hydrophobic fluorine-containing compounds such as oily fluorine-based compounds such as fluorine oil, or solid fluorine compound resins such as tetrafluoroethylene resin. A matting agent can be used in the thermal transfer dye-providing material and the thermal transfer image-receiving material. As matting agents, in addition to the compounds described in JP-A-61-88256 (page 29) such as silicon dioxide, polyolefin or polymethacrylate, benzoguanamine resin beads, polycarbonate resin beads, AS resin beads, etc. No. 62-1100
There is a compound described in No. 65.

[0055]

EXAMPLES The following Examples and Comparative Examples show the production of a thermal transfer dye-providing material and a thermal transfer image-receiving material, printing using both materials, and testing of a thermal transfer image-receiving material.

Example-1 (Thermal transfer dye-providing material (1-1)
) Preparation) Using a 6 μm thick polyethylene terephthalate film (manufactured by Teijin) with heat-resistant slipping treatment on the back side as a support, a coating composition for a thermal transfer dye-donating layer having the following composition was applied on the surface of the film. A thermal transfer dye-providing material (1-1) was prepared by applying wire bar coating to a dry thickness of 1.5 μm. Coating composition for thermal transfer dye-donating layer Dye 1

10 mmol Polyvinyl butyral resin (Denka Kagaku Denka Butyral 5
000-A)

3g toluene

40ml methyl ethyl ketone

40 ml polyisocyanate (Takenate D110N, manufactured by Takeda Pharmaceutical) 0.2 ml Next, the same procedure as above was carried out except that the above dye 1 was changed to other dyes listed in Table 1. The thermal transfer dye-providing material of the present invention and the comparative thermal transfer dye Donor materials (1-2) to (1-14) were prepared, respectively.

(Preparation of thermal transfer image-receiving material A) Synthetic paper with a thickness of 150 μm (manufactured by Oji Yuka Co., Ltd., YUPO-FPG) was used as a base material.
-150), and coated the surface with a coating composition for an image-receiving layer having the following composition with a wire bar to a dry thickness of 8.
A thermal transfer image-receiving material was formed by coating in a thickness of .mu.m. Drying was performed for 30 minutes in an oven at a temperature of 100° C. after temporary drying with a hair dryer. Image-receiving layer coating composition A Polyester resin (Toyobo Vylon-280)
22g polyisocyanate (KP-90: Dainippon Ink Chemical)
4g Amino-modified silicone oil (KP-857 manufactured by Shin-Etsu Silicone) 0.5g Methyl ethyl ketone
8
5ml toluene

85ml cyclohexanone
15m
l

The thermal transfer dye-providing materials (1-1) to (1-14) obtained as described above and the thermal transfer image-receiving material are superimposed so that the thermal transfer dye-providing layer and the image-receiving layer are in contact with each other, and the thermal transfer Printing was performed from the support side of the donor layer using a thermal head under the conditions of a thermal head output of 0.25 W/dot, a pulse width of 0.15 to 15 m Sec, and a dot density of 6 dots/mm to the image receiving layer of the image receiving material. When the magenta dye was dyed imagewise, a clear image recording with no transfer unevenness was obtained. Next, each of the recorded thermal transfer materials obtained as described above was transferred for 7 days to 17,000
The stability of the color image was examined by irradiating it with a lux fluorescent lamp. Status A reflection density was measured before and after irradiation, and the stability was evaluated based on the ratio. The results are shown in Table 1.

Table 1 No. Pigment
Maximum concentration Lightfastness
Remarks 1-1 1
2.0 90
Present invention 1-2
5 1.5
92 〃
1-3a
2.1 79
Comparative example 1-4 2
1.7 9
0 Present invention 1-5
6 1.4
92 〃
1-6b
1.8 70
Comparative example 1-7
3 1.9
91 Present invention 1-
8 4 1.4
95
〃 1-9 10
1.7 89
〃 1-10
12 1.8
90〃
1-11 14
1.5 94
〃 1-12
19 1.5
86 〃
1-13 24 1
．． 9 90
〃 1-14 c
2.3 4
5 Comparative Example Comparative dye

[0060]

[C26]

[0061]No. From the comparison of 1-1, 1-2, and 1-3, dyes 1 and 5 of the present invention having a specific atomic group in the molecule are better than comparative dye a from which the corresponding specific atomic group is removed.
It can be seen that the light fastness is significantly higher. (more than double the dye decomposition rate). Furthermore, No. 1-4, 1-5, 1-6
The same can be said from the comparison. (In this case, there is a difference of more than 3 times in the dye decomposition rate.) Also, 1-7 to 1-13
As can be seen from Figures 1 and 1-14, all of the dyes of the present invention have high light fastness.

Example 2 A specific atomic group structure having the effect of suppressing fading of the dye used in the present invention is a structure of a so-called ultraviolet absorber. However, the effect is fundamentally different and significantly different from the method of using an ultraviolet absorber in the image-receiving layer. Using image-receiving layer coating composition B having the same composition except that 7 g of the following ultraviolet absorber was added to the image-receiving layer coating composition used in Example-1, Example-
Thermal transfer image-receiving material B was prepared in accordance with Example 1.

Using the obtained thermal transfer image-receiving material, the thermal transfer image-receiving material of Example-1, and the thermal transfer dye-providing materials 1-1, 1-3, 1-2, and 1-6 used in Example-1, Transfer was performed according to Example-1. The light fastness was then tested under the conditions of Example-1.

[0064]

[C27]

Table 2 No. Thermal transfer dye Pigment Thermal transfer dye Maximum density Light fastness Notes
Donor material Receiving paper 2-1 1-1 1
A 2.0 90
Present invention 2-2 1-1
1 B 1.9
91 〃 2-3 1-
3 a A
2.1 79 Comparative example 2-
4 1-3 a B
2.0 80
〃 2-5 1-4 2
A 1.7
90 Present invention 2-6 1-4
2 B 1.7
91 〃 2-7
1-6 bA
1.8 70 Comparative example
2-8 1-6 b
B 1.7 72
〃

[0066] Table 2 No. 2-1 and 2-
2, 2-3 and 2-4, 2-5 and 2-6, 2-7 and 2-8
, it can be seen from the comparison that adding an ultraviolet absorber to the image-receiving layer increases light fastness, but the extent of this increase is very small. On the other hand, 2-1 and 2-3, 2-2 and 2-4, 2-5 and 2
A comparison of -7, 2-6, and 2-8 shows that the effect of introducing an atomic group with a specific structure into the molecule is very large.

Example 3 Thermal transfer dye-providing material (3-1) was prepared by using the resin and dye shown in Table 3 in place of the polyvinyl butyral resin and dye in the thermal transfer dye-providing layer coating composition of Example-1. , (3-2), and (3-3) were created. When printing was carried out using the same image-receiving material as in Example 1, a clear image recording without transfer unevenness was obtained as shown in Table 3. It also had excellent light fastness.

Table 3 Dye-providing material resin
Pigment Maximum concentration Remaining rate (%)
3-1 Ethylcellulose
1 1.9
91 3-2 Cellulose acetate butyrate
2 1.7
90 3-3 Polysulfone
5 1.4
91

Examples of combinations of other thermal transfer image-receiving materials and the above thermal transfer dye-providing material of the present invention are shown below. Example 4 (Preparation of thermal transfer image-receiving material) Synthetic paper with a thickness of 150 μm (manufactured by Oji Yuka: YUPO-FPG-) was used as a support.
150), and wire bar coated the image-receiving layer coating composition C with the following composition on the surface to a dry thickness of 1.
A thermal transfer image-receiving material was prepared by applying the film to a thickness of 0 μm. Drying was performed for 30 minutes in an oven at a temperature of 100° C. after temporary drying with a hair dryer.

Image-receiving layer coating composition C Polyester resin No. 1*

2.0g Amino-modified silicone oil (KF-
857: Shin-Etsu Silicone) 0.5g Epoxy modified silicone oil (KF-100T: Shin-Etsu Silicone)

0.5g methyl ethyl ketone
85m
l Toluene

85ml cyclohexanone
30ml
*Polyester resin No. 1

[0071]

[C28]

When printing was carried out in combination with the thermal transfer dye-providing materials of Examples 1 and 2, clear image recording was obtained. Moreover, the light fastness was also excellent.

Example-5 (Preparation of thermal transfer image-receiving material) 20
Prepare a resin-coated paper in which polyethylene is laminated to a thickness of 15 μm and 25 μm on both sides of a 0 μm paper, respectively, and coat the 15 μm thick laminated surface with a coating composition for an image receiving layer having the following composition by wire bar coating to a dry thickness of 10 μm. A thermal transfer image-receiving material was prepared by coating and drying. Coating composition for image-receiving layer Polyester resin No. 1

25g Amino-modified silicone oil (K
F-857: Shin-Etsu Silicone) 0.8g Polyisocyanate (KP-90: Dainippon Ink)
4g methyl ethyl ketone

100ml toluene

When 100 ml was printed in the same manner as in Example 4, a clear and high-density image record was obtained. Moreover, the light fastness was also excellent.

Example 6 (Preparation of thermal transfer image-receiving material) An organic solvent solution of a dye-receiving polymer having the composition (B') was emulsified and dispersed in an aqueous gelatin solution having the composition (A') below using a homogenizer to obtain a dye-receiving material. A gelatin dispersion of the material was prepared. (A') Gelatin aqueous solution Gelatin

2.3g Sodium dodecylbenzenesulfonate (5% aqueous solution)
20ml water

80ml (B'
) Dye-receptive polymer solution Polyester resin (manufactured by Toyobo: Vylon 300)
7.0g Carboxy-modified silicone oil (manufactured by Shin-Etsu Silicone:
X-22-3710)
0.
7g methyl ethyl ketone

20ml toluene

10ml
triphenyl phosphate
1
．． 5 g of the dispersion thus prepared was added with a fluorosurfactant (a) C3F7SO2N(C3F7)CH2COO
0.5g of K in a mixed solvent of water/methanol (1:1) 1
A solution dissolved in 0 ml was added to prepare a coating composition for an image-receiving layer. This coating composition was corona discharged onto the surface to a thickness of 1
50 μm synthetic paper (manufactured by Oji Yuka: YUPO-SGG-1
50) A thermal transfer image-receiving material was obtained by applying a wet film thickness of 75 μm onto the film by wire bar coating and drying. Images were recorded in the same manner as in Example 1 using the thermal transfer dye-providing materials and thermal transfer image-receiving materials obtained in Examples 1 and 2. The images obtained had high density, clarity, and high fastness.

[0075]

As described above, when transferring to an image receiving material using the thermal transfer dye-providing material of the present invention, a clear color image with excellent fastness can be obtained.

Claims (1)

[Claims] Claim 1: A thermal transfer dye-providing material comprising a dye-providing layer containing a heat-transferable dye on a support, wherein the dye-providing layer contains a heat-transferable dye represented by general formula (I). A thermal transfer dye-providing material characterized by: General formula (I
) [Image Omitted] In the formula, R1 and R2 each independently represent an alkyl group, an aryl group, a hydrogen atom or a heterocyclic group. R
3 , R4 , R5 , R6 and R7 each independently represent a hydrogen atom or a nonmetallic substituent. Za, Z
b and Zc are each independently -C(R8)= or -N
= represents. R8 represents a hydrogen atom or a nonmetallic substituent. R3 and R4, and/or R4 and R1
, and/or R1 and R2, and/or R2 and R
5 and/or R5 and R6 may be bonded to each other to form a ring structure. However, R1, R2, R
At least one of 3, R4, R5, R6, R7, and R8 is represented by the following general formula (II) or (III)
It is bonded to the atomic group represented by. General formula (II) [
[Chemical formula 2] General formula (III) [Chemical formula 3] In the formulas (II) and (III), R11, R12, R13,
R14, R15, R16, R17, R18, R19 are
Each independently represents a hydrogen atom or a nonmetallic substituent.