Recording material

A recording material containing as a color forming system (a) a colorless or light-colored dye precursor, and (b) an isocyanate compound having aromaticity, and if necessary (c) a color developer is excellent in image retention rates in terms of light resistance and plasticizer resistance and has a large degree of freedom of hues.

BACKGROUND OF THE INVENTION 
This invention relates to a recording material containing a special color 
forming system excellent in image storability. 
Heretofore, a number of chemical color forming systems using recording 
energy such as heat, pressure, light, electric current, etc. have been 
known. Among them, a color forming system of two components, that is, an 
ordinary colorless or light-colored dye precursor and a color developer 
which forms a color in contact with the dye precursor, has long been known 
and widely used in recording materials. For example, there are used 
heat-sensitive recording materials using heat energy, pressure-sensitive 
recording materials using pressure energy, light-sensitive recording 
materials using light energy and electrical current-passing heat-sensitive 
recording materials using electrical energy. Among them, the 
pressure-sensitive recording materials are most generally used due to the 
use of plain paper. 
In general, the pressure-sensitive recording materials are prepared by 
forming an emulsion of a dye precursor using a suitable solvent in several 
microns, microcapsulizing the emulsion, coating the resulting 
microcapsules on a support to form a top sheet, and preparing a bottom 
sheet by coating a color developer on a support. Image recording can be 
obtained by facing the microcapsul coated plane and the color developer 
coated plane oppositely, applying a writing or hitting pressure thereon to 
rupture microcapsuls and to release the contents including the dye 
precursor, and contacting the contents with a color developer in the color 
developer layer to bring about a color forming reaction. 
On the other hand, heat-sensitive materials are widely used recently. Since 
the heat-sensitive recording method using a thermal head has many 
advantages in that no noise takes place at the time of recording due to 
non-impact, development and fixing are not necessary, maintenance of 
apparatus is easy, and the like, it is widely used in outputs of 
computers, printers for table-type computers, recorders for medical 
measuring apparatus, low-speed and high-speed facsimile machines, 
automatic ticket vending machines, heat-sensitive copying machines, etc. 
Heat-sensitive recording materials generally comprises a support and formed 
thereon a heat-sensitive layer comprising a finely ground dye precursor, a 
finely ground color developer and the like, and a binder. By heating with 
a thermal head, a thermal pen, laser, etc., the color developer and the 
dye precursor are melted and contacted to bring about a color forming 
reaction for obtaining image recording. 
As the dye precursor, electron-donating compounds are used, and as the 
color developer, electron-accepting compounds are used, in general. This 
is because the dye precursor which is an electron-donating compound is 
highly reactive and instantly gives a colored image with a high density 
when contacted with the dye precursor which is an electron-accepting 
compound. There are other advantages in that there can be obtained an 
appearance near a white color, there can be obtained various kinds of 
developed hues such as a red color, an orange color, a yellow color, a 
green color, a blue color, a black color, etc. But there are disadvantages 
in that the obtained image is low in light resistance and weather 
resistance, the obtained image is inferior in storability of recording, 
e.g., it is easily discolored when exposed to light such as sunbeams. Due 
to such disadvantages, the utility of heat-sensitive recording materials 
is limited to some extent. Improvement of the heat-sensitive recording 
materials is strongly desired. 
In order to improve the above-mentioned disadvantages, U.S. Pat. No. 
4,521,793 discloses a recording material comprising a color forming agent 
system comprising an isocyanate compound having aromaticity formed on the 
same substrate or different substrates. This color forming agent system 
forms a carboxamide series azomethine colored product by the catalytic 
reaction of the two components. The colored product is excellent in 
chemical resistance and light resistance. The hue of the colored product 
can widely be changed by properly selecting the imino compounds and 
isocyanate compounds to be used. Most obtained colors are red, orange and 
yellow. For example, as to a black color which is required in many cases 
for recording, there is mostly obtained black tinted with red. It is 
relatively difficult to obtain a black color tinted with blue. 
In order to improve the disadvantages of U.S. Pat. No. 4,521,793, Japanese 
Patent Unexamined Publication No. 59-135186 discloses a recording sheet 
comprising a support and formed thereon a color forming layer comprising 
(i) a known color forming agent system of a well-known leuco dye and an 
acidic substance and (ii) a color forming agent system of the imino 
compound and the isocyanate compound mentioned above, said recording sheet 
satisfying the storage stability of recording and the degree of freedom of 
hues which are developable. But said recording sheet is still insufficient 
in selecting proper hues and image storability such as plasticizer 
resistance. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a recording material excellent 
in image storability by using a color forming system different from known 
color forming systems. 
This invention provides a recording material comprising a two-component 
color forming system comprising (a) a colorless or light-colored dye 
precursor and (b) an isocyanate compound having aromaticity, said color 
forming system being carried on a substrate or at least two different 
substrates. 
This invention also provides a recording material comprising a 
three-component color forming system comprising (a) a colorless or 
light-colored dye precursor, (b) an isocyanate compound having 
aromaticity, and (c) a color developer which can form a color by 
contacting with the dye precursor, said color forming system being carried 
on a substrate or at least two different substrates.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The color forming system used in this invention fundamentally comprises (a) 
a colorless or light-colored dye precursor and (b) an isocyanate compound 
having aromaticity. It is a very surprising thing that a color forming 
system compring (b) an isocyanate compound having aromaticity which is one 
component of the color forming system of U.S. Pat. No. 4,521,793, and (a) 
a colorless or light-colored dye precursor which is also one component in 
a known color forming system disclosed in Japanese Patent Unexamined 
Publication No. 59-135186, can form a color which is excellent in image 
storability such as light resistance, plasticizer resistance, etc. 
When the dye precursor (a) contacts with the isocyanate compound having 
aromaticity (b) via outer energy such as heat, a colored reaction product 
is formed by the reaction of the two components. Since this reaction is 
irreversible, the obtained reaction product cannot be changed to the 
colorless or light-colored dye precursor again. As a result, the obtained 
colored reaction product constitutes an image excellent in image 
storability. According to prior art, since the reaction between the dye 
precursor and a conventional color developer is a reversible color forming 
reaction, the resulting image is inferior in image storability such as 
light resistance, plasticizer resistance, etc. But, according to this 
invention, since the dye precursor is reacted with a reactant which can 
bring about an irreversible reaction, that is, the isocyanate compound 
having aromaticity, the image storability is unexpectedly improved. 
Further, the color forming system used in this invention is also improved 
in the degree of freedom for hues, that is, desired hues can be obtained 
freely by properly selecting dye precursors from a wide range of various 
dye precursors. This is also improved compared with U.S. Pat. No. 
4,521,793. Particularly, the formation of a black color is effective in 
this invention. 
The isocyanate compound having aromaticity (b) includes colorless or pale 
color aromatic isocyanates and heterocyclic isocyanates which are solid at 
room temperature. 
Examples of the isocyanate compounds are 2,6-dichlorophenyl isocyanate, 
p-chlorophenyl isocyanate, 1,3-phenylene diisocyanate, 1,3-dimethylbenzene 
4,6-diisocyanate, 1,4-dimethylbenzene 2,5-diisocyanate, 1-methoxybenzene 
2,4-diisocyanate, 1-methoxybenzene 2,5-diisocyanate, 1-ethoxybenzene 
2,4-diisocyanate, 2,5-dimethoxybenzene 1,4-diisocyanate, 
2,5-diethoxybenzene 1,4-diisocyanate, 2,5-dimethoxybenzene 
1,4-diisocyanate, azobenzene 4,4'-diisocyanate, diphenylether 
4,4'-diisocyanate, naphthalene 1,4-diisocyanate, naphthalene 
1,5-diisocyanate, naphthalene 1,6-diisocyanate, naphthalene 
2,6-diisocyanate, naphthalene 2,7-diisocyanate, 3,3'-dimethyl-biphenyl 
4,4'-diisocyanate, 3,3'-dimethoxybiphenyl 4,4'-diisocyanate, 
diphenylmethane 4,4'-diisocyanate, diphenyldimethylmethane 
4,4'-diisocyanate, benzophenone 3,3'-diisocyanate, fluorene 
2,7-diisocyanate, anthraquinone 2,6-diisocycnate, 9-ethylcarbazole 
3,6-diisocyanate, pyrene 3,8-diisocyanate, naphthalene 
1,3,7-triisocyanate, biphenyl 2,4,4'-triisocyanate, 
4,4',4"-triisocyanate-2,5-dimethoxytriphenylamine, p-dimethylaminophenyl 
isocyanate, tris(4-phenyl isocyanate)thiophosphate, etc. These isocyanate 
compounds can be used alone or as a mixture thereof. 
As the dye precursor (a), there can be used triphenylmethanes, fluorans, 
diphenylmethanes, thiazines, and spiropyrans. 
Examples of the dye precursors are 
3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4- 
diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide 
, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7-chlorofluoran, 
3-(N-cyclohexylamino)-7-methylfluoran, 3-diethylamino-7-methylfluoran, 
3-diethylamino-6-chloro-7-methylfluoran, 3-diethylamino-7-anilinofluoran, 
3-diethylamino-6-methyl-7-dibenzylaminofluoran, 
3-(N-ethyl-N-p-toluidino)-7-anilinofluoran, 
3-diethylamino-7-(O-chloroanilino)fluoran, 
3-dibutylamino-7-(O-chloroanilino)fluoran, 
3-diethylamino-6-methyl-7-anilinofluoran, 
3-(N-ethyl-N-p-toluidino)-6-methyl-7-anilinofluoran, 
3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluoran, 
3-piperidino-6-methyl-7-anilinofluoran, 
3-pyrrolidino-6-methyl-7-anilinofluoran, 
3-diethylamino-7-(m-trifluoromethylanilino)fluoran, 
3-(N-ethyl-N-isopentylamino)-6-methyl-7-anilinofluoran, 
3-diethylamino-6-methyl-7-(p-phenetidino)fluoran, 
3-dibutylamino-7-(O-fluoroanilino)fluoran, etc. These dye precursors can 
be used alone or as a mixture thereof. 
The isocyanate compound (b) is used in an amount of 0.1 to 10 parts by 
weight, preferably 0.25 to 5 parts by weight, more preferably 0.5 to 3 
parts by weight per part by weight of the dye precursor (a). When the 
amount of the isocyanate compound is less than 0.1 part by weight, the 
color formation of the dye precursor becomes insufficient and the 
developed color density becomes low. On the other hand, when the amount of 
the isocyanate compound is more than 10 parts by weight, unreacted 
isocyanate compound remains uneconomically. 
In the case of three-component color forming system comprising (a) a 
colorless or light-colored dye precursor, (b) an isocyanate compound 
having aromaticity, and (c) a color developer which can form a color by 
contacting with the dye precursor, a higher image density than the case of 
the two-component color forming system comprising (a) the dye precursor 
and (b) the isocyanate compound can be obtained in addition to higher 
image storability such as light resistance and plasticizer resistance, 
etc. 
In the three-component color forming system, the isocyanate compound is 
used in an amount of 0.1 to 10 part by weight, preferably 0.25 to 5 parts 
by weight, more preferably 0.5 to 3 parts by weight, per part by weight of 
the dye precursor. When the amount of the isocyanate compound is less than 
0.001 part by weight, sufficient image storability cannot be obtained. On 
the other hand, there is no upper limit of the amount of the isocyanate 
compound, but when the amount is more than 5 parts by weight, an 
economically unpreferable case often takes place. The color developer is 
used in an amount of 0.1 to 20 parts by weight, preferably 0.25 to 10 
parts by weight, more preferably 0.5 to 5 parts by weight, per part by 
weight of the dye precursor. 
As the color developer, there can be used acidic substances, that is, 
electron-accepting compounds conventionally used in this art. These 
electron-accepting compounds can be selected properly depending on kinds 
of recording materials, for example, pressure-sensitive recording 
materials, heat-sensitive recording materials, electric current-passing 
heat-sensitive recording materials, heat-transfer recording materials, 
static recording materials, laser recording materials, etc. 
For example, in the case of heat-sensitive recording materials, phenol 
derivatives and aromatic carboxylic acid derivatives are mainly used as 
the color developer. Among phenol derivatives, those having at least one 
phenolic hydroxyl group are preferable, and those having no substituent at 
one or both of phenolic hydroxyl groups positioned at the ortho positions 
are more preferable. 
Examples of the phenol derivatives are phenol, p-t-butylphenol, 
p-phenylphenol, 1-naphthol, 2-naphthol, p-hydroxyacetophenone, 
2,2'-dihydroxybiphenyl, 4,4'-isopropylidenediphenol, 4,4'-isopropylidene 
diphenol, 4,4'-isopropylidenebis(2-t-butylphenol), 
4,4'-isopropylidenebis(2-chlorophenol), 4,4'-cyclohexylidenediphenol, 
2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)pentane, 
2,2-bis(4-hydroxyphenyl)hexane, methyl diphenolacetate, 
bis(4-hydroxyphenyl)sulfone, C bis(3-allyl-4-hydroxyphenyl)sulfone, 
4-hydroxy-4'-methyldiphenylsulfone-4-hydroxy-4'-isopropyloxydiphenylsulfon 
e, bis(4-hydroxyphenyl)sulfide, 4,4'-thiobis(2-t-butyl-5-methyl)phenol, 
1,7-bis(4-hydroxyphenylthio)-3,5-dioxyheptane, novolac type phenol resins, 
etc. 
Examples of the aromatic carboxylic acid derivatives are benzoic acid, 
p-t-butyl benzoate, p-hydroxybenzoic acid, methyl p-hydroxybenzoate, 
isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, lauryl gallate, 
stearyl gallate, salicylanilide, 5-chlorosalicylanilide, a metal (e.g. Zn) 
salt of 5-t-butyl salicylate, a metal (e.g. Zn) salt of hydroxynaphthoic 
acid, etc. 
In the case of the pressure-sensitive recording materials, there can be 
used as the color developer inorganic compounds such as acid clay, active 
clay, attapulgite, bentonite, zeolite, colloidal silica, magnesium 
silicate, talc, aluminum silicate, etc.; phenol derivatives such as 
phenol, cresol, butylphenol, octylphenol, phenylphenol, chlorophenol, 
salicylic acid, and aldehyde condensed novolac resins derived from these 
compounds and metal salts thereof; salicylic acid derivatives such as 
3-isopropyl salicylate, 3-phenyl salicylate, 3-cyclohexyl salicylate, 
3,5-di-t-butyl salicylate, 3,5-di(.alpha.-methylbenzyl)salicylate, 
3,5-di-t-octyl salicylate, 3-methyl-5-benzyl salicylate, 
3,5-di(.alpha.,.alpha.-dimethylbenzyl)salicylate, 
3-phenyl-5-(.alpha.,.alpha.-dimethylbenzyl)salicylate, etc. and metal 
salts thereof. 
In the case of the light-sensitive recording materials, there can be used 
as the color developer compounds which produce hydrogen halides, 
carboxylic acids, sulfonic acids, phenols, etc., by light. Examples of 
these compounds are organic halogen compounds such as carbon tetrabromide, 
iodoform, trichloromethylsulfonylbenzene, etc.; o-quinoneazide 
derivatives; phenol esters of sulfonic acid, etc. 
Recording materials using the two-component color-forming system comprising 
(a) the dye precursor and (b) the isocyanate compound having aromaticity, 
or the three-component color-forming system comprising (a) the dye 
precursor, (b) the isocyanate compound having aromaticity, and (c) the 
color developer, can be prepared as follows. 
As disclosed in Japanese Patent Examined Publication Nos. 43-4160, 44-3680 
and 45-14039, the color-forming components, that is, the dye precursor, 
the isocyanate compound, and if necessary the color developer, in 
dispersed state of very fine powder are coated on a support together with 
a binder to form a color-forming layer. The color-forming layer may be a 
single layer or a plurality of layers. The color-forming components may be 
contained in the same layer or in different layers. In the case of 
multi-layers, one or more intermediate layers may be interposed among 
individual layers. Further, a protective layer may be formed on a 
color-forming layer, or an undercoating layer may be previously formed on 
the support. The isocyanate compound having aromaticity is used in a 
dispersed form of very fine powder like other color-forming component(s) 
in neighbor thereof. The object of this invention can be attained even if 
the isocyanate compound is added to any color-forming layers. 
The color-forming layer or layers may contain one or more pigments such as 
diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, 
magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum 
hydroxide, urea-formaldehyde resin, etc.; metal salts of higher fatty 
acids such as zinc stearate, calcium stearate, etc. or waxes such as 
paraffins, oxidized paraffin wax, polyethylene, oxidized polyethylene, 
stearamide, castor wax, etc. for preventing wear of heads or sticking of 
heads; dispersing agents such as sodium dioctyl sulfosuccinate, etc.; 
ultraviolet absorbers such as benzophenones, benzotriazoles, etc.; surface 
active agents, fluorescent dyes, etc. 
In the case of using as pressure-sensitive recording materials, there can 
be used techniques disclosed in U.S. Pat. Nos. 2,505,470; 2,712,507; 
2,730,456; 2,730,457 and 3,418,250. For example, the dye precursor alone 
or admixed is dissolved in a solvent of synthetic oil such as alkylated 
naphthalene, alkylated diphenyl, alkylated diphenylmethane, alkylated 
diarylethane, chlorinated paraffin, or the like, or a vegetable oil, 
animal oil, or mineral oil, alone or as a mixture thereof. The resulting 
solution is dispersed in a binder and coated on a support, or the 
dispersion contained in microcapsules is coated on a support together with 
a binder, to prepare a top sheet. On the other hand, the isocyanate 
compound alone or mixed with the color developer is dispersed in a binder, 
and if necessary mixed with one or more pigments and the like additives, 
and coated on a support to prepare a bottom sheet. The coated surfaces of 
the top sheet and the bottom sheet are faced oppositely and used for 
recording images. It is also possible to use intermediate sheets obtained 
by coating the dispersion of the isocyanate compound on one side of a 
support and coating the dispersion containing the dye precursor on the 
other side of the support. In the case of self-contained type, the 
dispersion of the isocyanate compound and the dispersion of the dye 
precursor are coated on the same side of a support in admixture or 
multilayers. Various other conventional types of recording materials can 
also be applied to this invention. 
Microcapsules can be produced by the coacervation method disclosed, for 
example, in U.S. Pat. Nos. 2,800,457 and 2,800,458; by the interfacial 
polymerization method disclosed, for example, in Japanese Patent Examined 
Publication Nos. 38-19574, 42-446, and 42-771; by the in-situ method 
disclosed, for example, in Japanese Patent Examined Publication No. 
36-9168 and Japanese Patent Unexamined Publication No. 51-9079; by the 
melt dispersion cooling method disclosed, for example, in British Patent 
Nos. 952,807 and 965,074; by the spray drying method disclosed, for 
example, in U.S. Pat. No. 3,111,407 and British Patent No. 930,422. 
According to the interfacial polymerization method, an oil-soluble monomer 
and a water-soluble monomer are used and a film is formed at the 
interface. For example, a polyamide film is formed at the interface by 
using a polybasic acid chloride in the oil phase and a polyvalent amine in 
the water phase; a polyester film is formed at the interface by using a 
polybasic acid chloride in the oil phase and a polyhydric hydroxy compound 
in the water phase; a polyurethane film is formed at the interface by 
using a polyvalent isocyanate in the oil phase and a polyhydric alcohol or 
phenol in the water phase; or a polyurea film is formed at the interface 
by using a polyvalent isocyanate in the oil phase and a polyvalent amine 
in the water phase. 
As mentioned above, an isocyanate compound can be used as one reactive 
monomer for forming a film according to the interfacial polymerization 
method for producing microcapsules. But in this case, the isocyanate 
compound is consumed to form films of microcapsules, and not used as a 
color-forming component. Further, the use of the water-soluble monomer 
together with the isocyanate compound is essential. Therefore, the use of 
isocyanate compound in the microcapsule production technique is clearly 
distinguished from the use of the isocyanate compound as a color-forming 
component in this invention. 
The electric current-passing heat-sensitive recording material can be 
prepared, for example, according to Japanese Patent Unexamined Publication 
No. 49-11344 and 50-48930. For example, an electroconducting agent such as 
copper iodide, zinc oxide, or the like, a dye precursor and an isocyanate 
compound having aromaticity, and if necessary a color developer, are 
dispersed together with a binder and coated on a support. Alternatively, 
an electroconducting agent is previously coated on a support or vapor 
deposited on a support to form an electroconducting layer, on which a 
dispersion of a dye precursor, an isocyanate compound having aromaticity, 
and if necessary a color developer, and a binder is coated on a support. 
As the support used in the recording material of this invention, there can 
be used paper, various kinds of non-woven fabrics, synthetic resin films, 
laminate paper, synthetic paper, metal foils, etc. It is possible to use a 
composite sheet obtained by combining these support materials depending on 
purposes. 
As the binder, there can be used water-soluble binders such as starchs, 
hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, 
gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, 
styrenemaleic anhydride copolymer, ethylene-maleic anhydride copolymer, 
etc.; latex type water-insoluble binders such as styrene-butadiene 
copolymer, acrylonitrile-butadiene copolymer, methyl acrylate-butadiene 
copolymer, etc. 
This invention is explained in detail referring to Examples, in which all 
parts and percents are by weight unless otherwise specified. 
EXAMPLE 1 
3-(N-Ethyl-N-isopentylamino)-6-methyl-7-anilinofluoran in an amount of 10 g 
and 30 g of a 2% aqueous solution of polyvinyl alcohol were ball milled 
for 24 hours to give a dispersion. On the other hand, 10 g of 
4,4',4"-triisocyanate-2,5-dimethoxyphenylamine and 30 g of a 2% aqueous 
polyvinyl alcohol were balled milled for 24 hours to give a dispersion. 
After mixing the resulting dispersions, 100 g of a 40% dispersion of 
calcium carbonate, 25 g of a 20% dispersion of zinc stearate, 25 g of a 
20% dispersion of stearamide and 140 g of a 10% aqueous solution of 
polyvinyl alcohol were added to the resulting mixture and stirred 
sufficiently to give a coating liquid. 
The coating liquid was coated on a base sheet having a basis weight of 55 
g/m.sup.2 so as to make the coating amount 7.0 g/m.sup.2 in solids content 
using a Mayer bar and dried, followed by treatment with a super calender 
to provide a heat-sensitive recording material. 
EXAMPLE 2 
The process of Example 1 was repeated except for using 
4,4',4"-triisocyanate-triphenylamine in place of 
4,4',4"-triisocyanate-2,5-dimethoxytriphenylamine to provide a 
heat-sensitive recording material. 
EXAMPLE 3 
The process of Example 1 was repeated except for using 
3,6-diisocyanate-N-ethylcarbazole in place of 
4,4',4"-isocyanate-2,5-dimethoxytriphenylamine to provide a heat-sensitive 
recording material. 
EXAMPLE 4 
The process of Example 1 was repeated except for using 
1,4-diisocyanate-2,5-diethoxybenzene in place of 
4,4',4"-triisocyanate-2,5-dimethoxytriphenylamine to provide a 
heat-sensitive recording material. 
COMATIVE EXAMPLE 1 
The process of Example 1 was repeated except for using 
2,2-bis(p-hydroxyphenyl)propane in place of 
4,4',4"-triisocyanate-2,5-dimethoxytriphenylamine to provide a 
heat-sensitive recording material. 
COMATIVE EXAMPLE 2 
4,4',4"-Triisocyanate-2,5-dimethoxytriphenylamine in an amount of 10 g and 
30 g of a 2% aqueous solution of polyvinyl alcohol were ball milled for 24 
hours for dispersing. On the other hand, 10 g of 
1,3-diimino-4,5,6,7-tetrachloroindoline and 30 g of 2% aqueous solution of 
polyvinyl alcohol were ball milled for 24 hours for dispersing. After 
mixing the resulting dispersions, 100 g of a 40% dispersion of calcium 
carbonate, 25 g of a 20% dispersion of zinc stearate, 25 g of a 20% 
dispersion of stearamide and 140 g of a 10% aqueous solution of polyvinyl 
alcohol were added to the resulting mixture and stirred sufficiently to 
give a coating liquid. 
A heat-sensitive recording material was obtained in the same manner as 
described in Example 1. 
EVALUATION 1 
The heat-sensitive recording materials obtained in Examples 1 to 4 and 
Comparative Examples 1 and 2 were subjected to printing using a 
heat-sensitive paper printing tester (mfd. by Matsushita Denshi Buhin 
K.K.) under conditions of applied pulse of 3.0 millisec. and applied 
voltage of 16.00 volts. The density of obtained colored images was 
measured by using a Macbeth densitometer RD918 and shown in Table 1. 
EVALUATION 2 
The colored image obtained in Evaluation 1 was exposed to sunbeams inside a 
window glass at south side for 12 days. The densities before and after the 
test were measured in the same manner as described in Evaluation 1. The 
image retention rate in terms of light resistance was obtained by the 
following equation and shown in Table 1. 
##EQU1## 
EVALUATION 3-1 
A mending tape (Scotch 810, a trade name, mfd. by Minnesota Mining and 
Manufacturing Co.) was adhered to the colored image portion obtained in 
Evaluation 1 and stored at room temperature for 7 days. The densities 
before and after the test were measured in the same manner as described in 
Evaluation 1. The image retention rate in terms of plasticizer resistance 
was obtained by the following equation and shown in Table 1. 
##EQU2## 
EVALUATION 3-2 
The densities of initial textures of the heat-sensitive recording materials 
obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were measured 
by using the Macbeth densitometer RD918. A mending tape was adhered to a 
texture portion in the same manner as described in Evaluation 3-1 and the 
density of color at the texture portion with the lapse of time (texture 
density after contacted with plasticizer) was measured by using the 
Macbeth densitometer RD918. The results are shown in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Evaluation 2 
Evaluation 3-1 
Evaluation 3-2 
Evaluation 1 
Image retention 
Image retention 
Texture 
Developed 
rate in terms 
rate in terms 
Initial 
density after 
color of light 
of plasticizer 
density 
contacted with 
density 
resistance (%) 
resistance (%) 
of texture 
plasticizer 
__________________________________________________________________________ 
Example 1 
1.02 98.0 102.9 0.07 0.15 
Example 2 
0.97 97.9 101.1 0.05 0.14 
Example 3 
1.04 96.2 98.1 0.06 0.16 
Example 4 
1.10 98.2 101.8 0.08 0.18 
Comparative 
1.19 72.5 21.5 0.06 0.05 
Example 1 
Comparative 
0.72 87.6 116.6 0.06 0.37 
Example 2 
__________________________________________________________________________ 
Note: 
1 In Evaluation 31, the image retention rate of more than 100% means that 
the developed color density increases with the lapse of time. 
2 In Evaluation 32, the texture density with the lapse of time being 
higher than the initial value means that the plasticizer in the mending 
tape influences the texture density. 
As is clear from Table 1, the image retention rates in terms of both light 
resistance and plasticizer resistance are high in Examples 1 to 4. In 
Comparative Example 1, the developed color density is high, but the image 
retention rate in terms of light resistance is low and particularly the 
image retention rate in terms of plasticizer resistance is extremely as 
low as 21.5%. In Comparative Example 2 wherein the imino compound and 
isocyanate compound are used as the color forming system, the developed 
color density is low and there is an undesirable tendency to develop a 
color from the initial texture density with the lapse of time when 
contacted with the plasticizer as shown in Evaluation 3-2. 
EXAMPLE 5 
3-(N-Ethyl-N-isopentylamino)-6-methyl-7-anilinofluoran in an amount of 10 g 
and 30 g of a 2% aqueous solution of polyvinyl alcohol were ball milled 
for 24 hours to give a dispersion. On the other hand, 25 g of 
2,2-bis(p-hydroxyphenyl)propane and 75 g of a 2% aqueous solution of 
polyvinyl alcohol were balled milled for 24 hours to give a second 
dispersion. A third dispersion was prepared by ball milling 10 g of 
4,4',4"-triisocyanate-2,5-dimethoxytriphenylamine and 30 g of a 2% aqueous 
solution of polyvinyl alcohol for 24 hours. After mixing three 
dispersions, 80 g of a 50% dispersion of calcium carbonate, 25 g of a 20% 
dispersion of zinc stearate, and 200 g of a 10% aqueous solution of 
polyvinyl alcohol were added thereto and stirred sufficiently to give a 
coating liquid. 
A heat-sensitive recording material was obtained by coating the coating 
liquid on a base sheet having a basis weight of 55 g/m.sup.2 so as to make 
the coating amount 5.0 g/m.sup.2 in solids content, and dried, followed by 
treatment with a super calender. 
EXAMPLE 6 
The process of Example 5 was repeated except for using 
4,4',4"-triisocyanate-triphenylamine in place of 
4,4',4"-triisocyanate-2,5-dimethoxytriphenylamine to give a heat-sensitive 
recording material. 
EXAMPLE 7 
The process of Example 5 was repeated except for using 
3,6-diisocyanate-N-ethylcarbazole in place of 
4,4',4"-isocyanate-2,5-dimethoxytriphenylamine to give a heat-sensitive 
recording material. 
EXAMPLE 8 
The process of Example 5 was repeated except for using 
1,4-diisocyanate-2,5-diethoxybenzene in place of 
4,4',4"-triisocyante-2,5-dimethoxytriphenylamine to give a heat-sensitive 
recording material. 
EXAMPLE 9 
The process of Example 5 was repeated except for using benzyl 
4-hydroxybenzoate in place of 2,2-bis(p-hydroxyphenyl)propane to give a 
heat-sensitive recording material. 
COMATIVE EXAMPLE 3 
The process of Example 5 was repeated except for not using 
4,4',4"-triisocyanate-2,5-dimethoxytriphenylamine to give a heat-sensitive 
recording material. 
COMATIVE EXAMPLE 4 
The process of Example 9 was repeated except for not using 
4,4',4"-triisocyanate-2,5-dimethoxytriphenylamine to give a heat-sensitive 
recording material. 
Using the heat-sensitive recording materials obtained in Examples 5 to 9 
and Comparative Examples 3 and 4, evaluations were made using Evaluations 
1 and 2 mentioned above. The results are shown in Table 2. 
TABLE 2 
______________________________________ 
Evaluation 1 
Evaluation 2 
Developed Image retention 
color density 
rate (%) 
______________________________________ 
Example 5 1.14 97.3 
Example 6 1.10 98.2 
Example 7 1.15 95.8 
Example 8 1.20 91.6 
Example 9 1.09 89.1 
Comparative 1.19 72.5 
Example 3 
Comparative 1.13 36.1 
Example 4 
______________________________________ 
As is clear from Table 2, the image retention rates are high in Examples 5 
to 9. On the other hand, in Comparative Examples 3 and 4, although the 
developed color densities are the same as those of Examples 5 to 9, the 
image retention rates are low. 
EXAMPLE 10 
(1) Production of Top Sheet 
In 100 parts of a 5% aqueous solution of pH 4.0 obtained by dissolving 
styrene-maleic anhydride copolymer and a small amount of sodium hydroxide, 
80 parts of an oil Nisseki Hisol N-296 (a trade name mfd. by Nippon 
Petrochemicals Co., Ltd.) dissolving 2.5 parts of 
3-diethylamino-7-chlorofluofluoran was emulsified. A melamine-formaldehyde 
precondensate was prepared by mixing 10 parts of melamine, 25 parts of a 
37% formalin solution and 65 parts of water, making the pH of the mixture 
9.0 with sodium hydroxide, and heating the mixture at 60.degree. C. for 15 
minutes to make transparent. The precondensate was added to the 
above-mentioned emulsion and stirred for 4 hours while maintaining at 
60.degree. C., followed by cooling to room temperature. The resulting 
microcapsule dispersion had a solids content of 45%. 
A top sheet was produced by coating the thus obtained microcapsule 
dispersion on paper and dried. 
(2) Production of Bottom Sheet 
4,4',4"-Triisocyanate-2,5-dimethoxytriphenylamine in an amount of 10 g and 
30 g of a 2% aqueous solution of polyvinyl alcohol were ball milled for 24 
hours to give a dispersion. To this dispersion, 125 g of a 40% dispersion 
of calcium carbonate and 120 g of a 10% polyvinyl alcohol aqueous solution 
were added and stirred sufficiently. The resulting coating liquid was 
coated on a base sheet having a basis weight of 40 g/m.sup.2 using a mayer 
bar to give a bottom sheet. 
EVALUATION 4 
The top sheet and the bottom sheet obtained in Example 10 were laminated so 
as to face the coated sides oppositely and pressed to give a colored image 
on the bottom sheet. For comparison, using a commercially available bottom 
sheet not treated with the isocyanate compound having aromaticity, a 
colored image was obtained as mentioned about. Densities of individual 
colored images were measured by using the Macbeth densitometer RD918. The 
results are shown in Table 3. 
EVALUATION 5 
The colored image obtained in Evaluation 4 was exposed to sunbeams inside a 
window glass at south side for 2 days. The image retention rate in terms 
of light resistance was obtained in the same manner as described in 
Evaluation 2. The results are shown in Table 3. 
EVALUATION 6 
A mending tape (Scotch 810, a trade name, mfd. by Minnesota Mining and 
Manufacturing Co.) was adhered to the colored image portion obtained in 
Evaluation 4 and stored at room temperature for 7 days. The densities 
before and after the test were measured in the same manner as described in 
Evaluation 4 to obtain the image retention rate in terms of plasticizer 
resistance. The results are shown in Table 3. 
TABLE 3 
______________________________________ 
Evaluation 5 
Evaluation 6* 
Image retention 
Image retention 
Evaluation 4 
rate in rate in 
Developed terms of light 
terms of light 
color density 
resistance (%) 
resistance (%) 
______________________________________ 
Example 10 
0.57 96.5 107.0 
Comparision 
0.61 87.0 40.5 
______________________________________ 
Note: 
*In Evaluation 6, the image retention rate of more than 100% means that 
the developed color image increases with the lapse of time. 
As is clear from Table 3, the image retention rates in terms of both light 
resistance and plasticizer resistance are high in Example 10. On the other 
hand, in comparison, the image retention rate is low and that in terms of 
plasticizer resistance is extremely low. 
EXAMPLE 11 
(1) Production of Top Sheet 
A top sheet was produced in the same manner as described in Example 10 (1). 
(2) Production of Bottom Sheet 
4,4',4"-Triisocyanate-2,5-dimethoxytriphenylamine in an amount of 10 g and 
30 g of a 2% aqueous solution of polyvinyl alcohol were balled milled for 
24 hours to prepare a dispersion. The resulting dispersion was coated on a 
bottom sheet commercially available for common pressure-sensitive paper, 
and dried to give a bottom sheet. 
Using the top sheet and the bottom sheet, Evaluations 4 and 5 were carried 
out. 
For comparison, a bottom sheet commercially available and not treated with 
the isocyanate compound having aromaticity was used and evaluated in the 
same manner as mentioned above. The results are shown in Table 4. 
TABLE 4 
______________________________________ 
Evaluation 4 
Evaluation 5 
Developed Image retention 
color density 
rate (%) Hue 
______________________________________ 
Example 11 
0.66 100 Black color 
was maintained 
without change. 
Comparison 
0.61 87 Changed to red. 
______________________________________ 
As is clear from Table 4, the image retention rate is 100% (without any 
change) and the hue is not changed. In contrast, in comparison, the image 
retention rate is decreased to 87% and the hue is changed from black to 
red. 
The fundamental two-component color forming system used in the recording 
material of this invention is clearly different from known two-component 
color forming system comprising a dye precursor and a color developer, or 
an imino compound and an isocyanate compound having aromaticity, and is 
superior to the known two-component color forming system in the image 
retention rates in terms of light resistance and plasticizer resistance, 
causes no hue change when exposed to light and has a large degree of 
freedom for hues. Thus, the recording material of this invention is 
remarkably useful industrially.