Photosensitive, image-forming composition containing a leuco 2,3-disubstituted-1-indanone and a photooxidant

Leuco dye compositions containing a compound of the formula: ##STR1## wherein m = 0 or 1: Ar is an arylene or lower alkyl substituted arylene radical; PA1 R.sub.1 and R.sub.2, which may be the same or different, are lower alkyl or hydroxyalkyl groups, or ##STR2## R.sub.3 is H, lower alkyl, benzyl, R.sub.4, or ##STR3## R.sub.5 is H, a C.sub.3 -C.sub.6 alkyl group, an aryl group, ##STR4## wherein n=2-6; and R.sub.6 is a lower alkyl group or an aryl group. Where m = 1, the formula represents a colorless leuco compound; where m = 0, the formula represents the yellow dye derivative of the leuco. These compounds are particularly useful in photosensitive compositions.

BACKGROUND OF THE INVENTION 
This invention relates to new leuco compounds and the intense yellow dyes 
obtained therefrom by oxidation. Providing improved new dyes, particularly 
a new primary (yellow, red and blue) color, is continually an important 
objective of industrial research. Moreover, the properties required are 
frequently complicated by the utility envisaged. A particularly 
challenging task is presented by the demanding set of properties required 
for colors and color formers to be used in photoimaging systems. 
Accordingly, it is an objective of the present invention to provide new 
compounds which are capable of forming intense yellow images upon 
oxidation. A further objective is to provide the above compounds which are 
particularly useful in photosensitive systems. Another objective is to 
attain superior neutral (gray-to-black) shades, by combining the above 
novel leuco with selected leuco triarylmethanes which can be oxidized to 
purple dyes, particularly for use in photoimaging systems. 
The invention comprises compounds of the formula: 
##STR5## 
wherein m = 0 or 1; Ar is an arylene or lower alkyl substituted arylene 
radical; 
R.sub.1 and R.sub.2, which may be the same or different, are lower alkyl or 
hydroxyalkyl groups, or 
##STR6## 
R.sub.3 is H, lower alkyl, benzyl, R.sub.4, or 
##STR7## 
R.sub.5 is H, a C.sub.3 -C.sub.6 alkyl group, an aryl group, 
##STR8## 
wherein n = 2-6; and R.sub.6 is a lower alkyl group or an aryl group. 
Compounds of the formula, wherein m = 1, represent essentially colorless 
leuco dyes; they may be oxidized to their corresponding yellow dye forms, 
which are represented by the formula, wherein m = 0. The leuco dyes of 
formula 1 may be used in photosensitive image forming compositions 
containing a photooxidant capable of oxidizing the leuco dye, such as 
hexaarylbiimidazoles and N-halolophines. These leuco dyes may also be used 
in combination with other leucos, such as the preferred leuco 
triarylmethane of the following general formula: 
##STR9## 
wherein R.sub.7, R.sub.8, R.sub.9, and R.sub.10, which may be the same or 
different, are lower alkyl groups. A mixture of leuco dyes of formulas 1 
and 2 yields an intense black color on oxidation. Such image-forming 
compositions may be used to coat paper or film, as hereinafter 
exemplified, and may contain other ingredients appropriate for such 
utility, for example, solvents, plasticizers, and binders. 
The leuco dyes of formula 1 and their corresponding oxidized dye forms, 
mixtures thereof with other leuco dyes and their corresponding oxidized 
dye forms, compositions containing said leuco dyes, oxidized dyes and 
mixtures thereof, and substrates coated with said compositions, are within 
the scope of this invention. 
DETAILED DESCRIPTION 
The leuco dyes of this invention represented by formula 1 wherein m = 1, 
may be oxidized to yellow dyes represented by formula 1 wherein m = 0, as 
exemplified by the conversion of 
2-(p-diethylaminophenylmethyl)-3-hydroxy-1-indanone: 
##STR10## 
to 2-(p-diethylaminophenylmethylidene)-3-hydroxy-1-indanone: 
##STR11## 
As may be seen from the leuco of formula 2 and the corresponding dye form 
of formula 4, the carbon atom which connects the indanone and the 
disubstituted aminoaryl group is bonded to the 2-position of the indanone 
with a single bond in the leuco and with a double bond in the 
corresponding dye. This difference is brought about upon oxidation of the 
leuco, during which two hydrogens are removed from the leuco compound, 
represented by the general formula 1, wherein m = 1, thus forming the 
double bond and yielding the bright yellow dyes, represented by general 
formula 1, wherein m = 0. The leuco of formula 3 and the dye of formula 4 
are preferred species of the compounds of this invention. 
Other species include the following compounds and their corresponding dye 
forms: 
2(p-diethylaminophenylmethyl)-3-methoxy-1-indanone, 
2(p-dimethylaminophenylmethyl)-3-n-butoxy-1-indanone, 
2(p-diethylaminophenylmethyl)-3-n-octyloxy-1-indanone, 
2(p-diethylaminophenylmethyl)-3-benzyloxy-1-indanone, 
2(p-diethylaminophenylmethyl)-3-nitrobenzyloxy-1-indanone, 
2(p-diethylaminophenylmethyl)-1-indanone-3-carbamate, 
2(p-diethylaminophenylmethyl)-1-indanone-3-N-n-propylcarbamate, 
2(p-diethylaminophenylmethyl)-1-indanone-3-N-phenylcarbamate, 
2(p-diethylaminophenylmethyl)-1-indanone-3-N-p-nitrophenylcarbamate, 
the diurethane of 2(p-diethylaminophenylmethyl)-3-hydroxy-1-indanone and 
1,6-diisocyanatohexane, the diurethane of 
2(p-diethylaminophenylmethyl)-3-hydroxy-1-indanone and 
tolylene-2,4-diisocyanate, 
di[2(p-diethylaminophenylmethyl)-3-indanyl-1-one] ether, 
2(p-di-2'-hydroxyethylaminophenylmethyl)-3-hydroxy-1-indanone, 
2(p-di-2'-acetoxyethylaminophenylmethyl)-3-hydroxy-1-indanone, 
2(p-di-2'-benzoyloxyethylaminophenylmethyl)-3-hydroxy-1-indanone. 
The disubstituted aminoaryl groups of the compounds of the invention are 
preferably diethylaminoaryl such as p-diethylaminophenyl and 
p-diethylamino-o-tolyl; others operable include p-dimethylaminophenyl, 
p-N-methyl-N-ethylaminophenyl, p-N-methyl-N-iso-propylaminophenyl, 
p-N-methyl-N-tert-butylaminophenyl, and p-N,N-di-n-butyl-o-tolyl. 
The term "lower alkyl" is employed herein to denote an alkyl group having 
from 1 to 8 carbon atoms. As stated in formula 1, Ar is an arylene radical 
which may have lower alkyl substituents. Preferably, Ar is an arylene 
radical having 6 aromatic carbon atoms. The preferred lower alkyl 
substituent is methyl. 
The leuco dyes of this invention may be prepared by condensing 
1,3-indandione and the appropriate dialkylaminoarylaldehyde and reducing 
the intermediate thus formed. Two synthesis methods, leading to a typical 
leuco of this invention, 
trans-3-hydroxy-2-(p-diethylaminophenylmethyl)-1-indanone, are outlined 
below. The first method is most direct in terms of using a minimum number 
of steps. 
##STR12## 
The first reaction of Method A, a condensation, is executed with ease. The 
second step involves reduction of one ketone group to an alcohol, and 
saturation of an alkene linkage. Although the desired product is obtained, 
it may be contaminated with deeply red by-product, thereby requiring a 
fairly extensive purification procedure giving rise to low yields of 
product. 
A preferred preparative route, of only slightly greater complexity, is 
outlined below. Using this route, the products of all steps are obtained 
in sufficient purity to be used without further purification. Moreover, 
the products of steps 2 and 3 precipitate as readily filterable, easily 
washable solids; the product of step 1 is not isolated. Finally, the use 
of aromatic solvents, e.g., benzene, in each step of this preferred route 
is especially advantageous for obtaining leuco dye in high purity and 
yield. 
##STR13## 
The other leuco compounds of this invention are prepared by an analogous 
process on substituting the appropriate 
N,N-disubstitutedaminoarylaldehyde. In addition, urethane leuco dyes may 
be readily prepared by reacting aryl or alkyl isocyanates with the 
(secondary) alcohol functional group of the 3-hydroxy-1-indanone leucos by 
well-known procedures. Thus, the preparation of the urethane derivatives 
of this invention is readily carried out by reacting the 
3-hydroxy-1-indanones with an appropriate aryl or alkyl isocyanate in a 
suitable inert solvent as, for example, octane or benzene, in the presence 
of a small amount of a basic catalyst, e.g., pyridine, as shown in Example 
8. This synthesis, thus, merely involves dissolving the above reactants in 
the solvent, heating the reaction mixture for 1-2 hours at 
80.degree.-100.degree. C., and then cooling. On cooling, the urethane 
derivative precipitates in crystalline, easily filtered, readily workable 
form; the product is isolated in high yield and purity. Further 
purification may be readily effected by recrystallization; acetonitrile is 
an effective solvent for recrystallization. 
Useful aryl or alkyl isocyanates may vary widely in the number of 
substituents permissable on the aromatic ring, as well as their position. 
Preferred aryl isocyanates include phenyl and .alpha.-naphthyl 
isocyanates, o, m-, and p-nitrophenyl isocyanates. Other operable 
substituents include lower alkyl, lower alkoxy, halo-, and cyano groups. 
These leuco urethanes yield, when formulated in photosensitive 
compositions, yellow photoimages of high optical density as shown in 
Example 8. 
The compounds described in this invention are particularly useful in 
photoimaging applications, wherein the compounds are used in combination 
with a photooxidant capable of oxidizing the leuco dye so as to form a 
differently colored compound. The oxidation may be readily effected by 
photodissociated hexarrylbiimidazoles, as disclosed in U.S. Pat. No. 
3,390,994 to Cescon, U.S. Pat. No. 3,390,996 to MacLachlan, and U.S. Pat. 
No. 3,445,234 to Cescon and Dessauer, whose disclosures are incorporated 
herein by reference. That is, photolysis of hexaarylbiimidazole 
compositions containing the above leuco dyes leads to intense yellow 
images in the exposed area; with a given amount of leuco dye, the density 
of the color is proportional to the amount of radiation. 
Another class of photooxidants useful in photosensitive formulations 
containing the leuco dyes of this invention, since they are dissociable 
into the corresponding triarylimidazolyl and halogen radicals, are the 
N-halotriarylimidazoles (N-halolophines), defined as follows: 
##STR14## 
wherein X is Cl or Br; and A, B, and D are aryl groups, which may be the 
same or different, carbocyclic or heterocyclic, substituent-free or 
bearing substituents that do not interfere with the dissociation step and 
the subsequent oxidation of the oxidizable substrate. 
The aryl groups include one- and two-ring aryls, such as phenyl, biphenyl, 
naphthyl, pyridyl, furyl and thienyl. Suitable inert substituents on the 
aryl groups have Hammett sigma (para) values in the -0.5 to 0.8 range and 
are other than hydroxyl, sulfhydryl, amino, alkylamino or dialkylamino. 
Preferably, these inert substituents are free of Zerewitinoff hydrogen, 
i.e., have no hydrogens reactive towards methyl magnesium iodide. 
Representative substituents and their sigma values, (relative to H = 
0.00), as given by Jaffe, Chem., Rev. 53, 219-233 (1953) arc: methyl 
(-0.17), ethyl (-0.15), t-butyl (-0.20), phenyl (0.001), butoxy (-0.32), 
phenoxy (-0.03), fluoro (0.06), chloro (0.23), bromo (0.23), iodo (0.28), 
methylthio (-0.05), nitro (0.78), ethoxycarbonyl (0.52), and cyano (0.63). 
The foregoing substituents are preferred; however, other substituents 
which may be employed include trifluoromethyl (0.55), chloromethyl (0.18), 
carboxyl (0.27), cyanomethyl (0.01), 2-carboxyethyl (-0.07), and 
methylsulfonyl (0.73). Thus, the substituents may be halogen, cyano, lower 
hydrocarbyl (including alkyl, halo alkyl, cyanoalkyl, and aryl), lower 
alkoxy, aryloxy, lower alkylthio, arylthio, sulfo, alkylsulfonyl, 
arylsulfonyl, and nitro, and lower alkylcarbonyl. In the foregoing list, 
alkyl groups referred to there are preferably of 1-6 carbon atoms; while 
aryl groups referred to therein are preferably of 6-10 carbon atoms. 
Preferably the aryl radicals are carbocyclic, particularly phenyl, and the 
substituents have Hammett sigma values in the range -0.4 to +0.4, 
particularly lower alkyl, lower alkoxy, chloro, fluoro, bromo and benzo 
groups. 
In a preferred class, the 2 aryl group is a phenyl ring bearing an ortho 
substituent having a Hammett sigma value in the -0.4 to +0.4 range. 
Preferred ortho substituents are fluorine, chlorine, bromine, methyl and 
methoxy groups; especially chloro. Such derivatives tend less than others 
to form color when the light-sensitive compositions are applied to and 
dried on substrates at somewhat elevated temperatures, e.g., in the range 
70.degree.-100.degree. C. 
These N-halotriarylimidazoles are readily prepared by halogenating 
triarylimidazoles, preferably with N-chlorosuccinimide or 
N-bromosuccinimide; preparation of triarylimidazoles is old in the art, 
e.g., see Assignee's U.S. Pat. No. 3,445,234. A convenient preparation 
involves heating the N-halosuccinimide and triarylimidazole in carbon 
tetrachloride to reflux temperature for 1-2 hours. Upon cooling to ice 
bath temperature, succinimide precipitates and is removed by filtration. 
The desired product (N-halotriarylimidazole) is isolated from the filtrate 
by removing the solvent; this process may yield an oily residue of 
product, from which pure, crystalline N-halotriarylimidazole is obtained 
by recyrstallization from a suitable solvent, e.g., 1-chlorobutane. This 
general reaction may be depicted as follows: 
##STR15## 
These novel N-halotriarylimidazoles are effective photooxidants for leuco 
dyes, as described in this invention, since they are photo-dissociable to 
yield oxidizing agents, presumably as depicted by the following equation: 
##STR16## 
That is, photodissociation of N-halotriarylimidazoles yields both haogen 
and triarylimidazolyl radicals, both of which are known to oxidize leuco 
dyes in photosensitive formulations (e.g., U.S. Pat. No. 3,042,515 to 
Wainer and U.S. Pat. No. 3,445,234). 
Preferred N-halotriarylimidazoles include 
N-chloro-2-(2'-chlorophenyl)-4,5-diphenyl imidazole and 
N-chloro-2-(2',6'-dichlorophenyl)-4,5-diphenyl imidazole. 
Obtaining yellow images, as described herein, with the compounds of this 
invention is useful in its own right. However, an additional important 
embodiment of this invention is the combination of the leuco dyes of 
formula 1, wherein m = 1, with selected leuco dyes oxidizable to purple 
dyes. When oxidized in the preferred hexaarylbiimidazole system, this 
combination yields very intense (gray-to-black) neutral shades. The 
preferred companion leuco dyes have a generic structure according to 
formula 2. A particularly preferred companion leuco dye is 
3-methoxy-4-n-octanamidophenyl-bis-(4'-diethylamino-2'-methylphenyl)methan 
e having the following structure: 
##STR17## 
Upon oxidation, this leuco is converted to a triarylmethane dye of 
formula: 
##STR18## 
wherein X.sup.- is the anion of a strong acid. 
The compound of formula 7 is, of course, merely a preferred species of the 
dyes that can be formed by oxidation of the leucos of formula 2. These 
dyes ae more generally described by the formula: 
##STR19## 
wherein X.sup.- is the anion of a strong acid, and R.sub.7, R.sub.8, 
R.sub.9, and R.sub.10, which may be the same or different, are lower alkyl 
groups. 
Several synthetic routes are available leading to the leuco 
triarylmethanes. The following equations illustrate a convenient route to 
a preferred, complementary leuco triarylmethane especially useful for 
obtaining black photoimages: 
##STR20## 
Obviously, related leuco triarylmethanes may be prepared by using different 
components. For example, the components of steps (1) and (3) may contain 
the same or different alternate alkyl groups on the nitrogen. The acyl 
halide of step (2), clearly, could also be varied in chain length or 
stereochemistry. 
In the operation of this embodiment of the invention, i.e., obtaining black 
images, the above leuco triarylmethanes are also oxidized by 
photoactivated hexaarylbiimidazoles or N-halophines; the corresponding dye 
then exists as a cationic triarylmethane having a structure according to 
formula B. The above X.sup.- results from the addition to the 
photosensitive formulation of a strong acid (as described in U.S. Pat. No. 
3,445,234, Col. 13, lines 13-37). Alkylbenzenesulfonic acids, wherein the 
alkyl group has from 6 to 16 carbon atoms, are preferred. 
Dodecylbenzenesulfonic acid is particularly preferred.

The following examples provide details regarding preparation and utility of 
the compounds of the invention. 
EXAMPLE 1 
A. Preparation of 3-Hydroxy-1-Indanone 
A mixture of 73.25 g. (0.5 mole) of 1,3-indandione, 10.0 g. of 10% Pd on 
charcoal and 800 ml. of 2B-ethanol was added on the 1 liter flask of a 
Brown Hydrogenator, and hydrogen equivalent to 125 ml. of 1M sodium 
borohydride solution was added at room temperature and atmospheric 
pressure (0.5 mole H.sub.2). The solution was filtered through a bed of 
Celite Filter Aid, and the bed washed with ethanol. The ethanol solution 
was concentrated, and from the concentrate, a small amount of white solid 
separated, 1,3-indanediol, 1,6 g., m.p. 182.degree.-187.degree.. This 
by-product was filtered off and discarded. Evaporation of the filtrate 
gave 70.2 g. of nearly colorless oil (yield &gt; 95%) which can be used 
directly in the aldehyde condensation. The IR spectrum of the product 
showed typical hydroxyl and carbonyl absorption. 
B. The Preparation of 
3-Hydroxy-2-(p-Diethylaminophenyl-methylidene)-1-Indanone 
A mixture of 56.6 g.(0.32 mole) of p-diethylaminobenzaldehyde, 47.36 g. 
(0.32 mole) of 3-hydroxy-1-indanone and 7 ml. of piperidine was then 
heated with magnetic stirring to 80.degree.-100.degree. C. for 1.5 hours 
(the mixture is a melt at the reaction temperature). The mixture was 
cooled in ice water, 90 ml. of 1-chlorobutane and seed was added. The 
product tended to come out as a gum; the solution was therefore heated, 
cooled (seeded) and muddy brown solid separated. The product was collected 
by filtration and the brown solid washed until bright orange; 43.62 g. 44% 
yield, m.p. 139.degree.-141.degree., m.p. recrystallized material 
(1-chlorobutane) 142.degree.-143.degree. C. An extra 11% yield was 
obtained through concentration and refiltration of the filtrate; the 
latter fraction washed up as cleanly as the first. The IR spectrum and 
elemental analysis are those expected of the titled merocyanine 
derivative. 
C. Systhesis of Leuco Dye Trans-3-Hydroxy-2-(p-Diethylaminophenyl Methyl) 
Indanone 
A mixture of 3.7 g. (0.012 mole) of the recrystallized (m.p. 
142.degree.-143.degree.) merocyanine derivative of Part B, 1.0 g. of 10% 
Pd on charcoal and 200 ml. of absolute ethanol was then added to the 
hydrogenation flask of a Brown Hydrogenator, and hydrogen equivalent to 
15.0 ml. of a 0.2M sodium borohydride solution (0.012 mole of H.sub.2) was 
added at room temperature and atmospheric pressure. At this point, the 
supernatant solution of the hydrogenation mixture was still colored, and 
to attain a colorless solution, an additional 4 ml. of borohydride 
solution was added. The solution was filtered through a bed of Celite, the 
filtrate was evaporated, and a minimum amount of carbon tetrachloride was 
added to attain solution at reflux temperature. The solution was cooled in 
an ice bath and seeded, and an almost colorless solid separated. The solid 
was collected by filtration and washed with carbon tetrachloride; 1.8 g. 
(48.5% yield) of pale yellow product was thereby collected, m.p. 
113.degree.-115.degree.. The filtrate contained additional product as 
shown by TLC (Thin Layer Chromatography) analysis; a second solid fraction 
was crystallized from the filtrate, 0.82 g., m.p. 95.degree.-98.degree.. 
The latter material would have to be recrystallized before use. The first 
fraction was of excellent quality and useful without recrystallization. 
The melting point of the sample recrystallized from methanol, ethanol and 
acetonitrile was 115.degree.-118.degree. C. The IR spectrum and elemental 
analyses are those expected of the leuco dye of the invention. 
Anal. Calc'd. for C.sub.20 H.sub.23 NO.sub.2 : C, 77.64; H, 7.49; N, 
4.53Found: C, 77.59; H, 7.45; N, 4.55 
The product, depicted below, is assigned the trans-structure as shown on 
the basis that the nmr absorption of H.sub.A is split into a doublet (in 
CDCl.sub.3 containing D.sub.2 O) with J.sub.AB = 3.0 cps. The latter small 
coupling constant is appropriate for only the trans H.sub.A -- H.sub.B 
configuration. 
##STR21## 
Repeating the above, but using benzene as solvent to the three steps, leads 
to improved yields. Because H.sub.A is tautomerically labile, and the 
2-position to which H.sub.A is attached is a chiral center, cis and trans 
isomers may exist in equilibrium mixtures, especially in the photoimaging 
systems described hereinafter. 
EXAMPLE 2 
Another species of the dye of the invention, 
2-(4'-diethylamino-2'-methylphenylmethylidene)-3-hydroxy-1-indanone, gave 
results similar to the dye of Example 1. This dye has a melting point of 
160.degree.-161.5.degree. C. and has the formula: 
##STR22## 
The dye was prepared in 22% yield by condensation of 3-hydroxy-1-indanone 
with 2-methyl-4-diethylaminobenzaldehyde in the presence of piperidine. 
The corresponding leuco dye has a melting point of 112.degree.-114.degree. 
C. and has the structure: 
##STR23## 
It was prepared from the above dye from in 77% yield by hydrogenation in 
benzene over Pd on charcoal catalyst. 
EXAMPLES 3-5 
A coating composition is prepared from the following ingredients: 
______________________________________ 
Acetone 60 ml. 
2,2'-Bis(o-chlorophenyl)-4,4',5,5'-tetrakis 
(m-methoxyphenyl)biimidazole 
0.4180 g. 
Leuco dye 1.8 .times. 10.sup.-4 mole 
p-Toluenesulfonic acid monohydrate 
0.400 g. 
Trimethyl 3,3',3"-nitrilotripropionate 
1.0 ml. 
9,10-Phenanthrenequinone 
0.054 g. 
Cellulose acetate butyrate (Eastman EAB 
171-40) 6.0 g. 
Polyethyleneoxide adduct of o-phenylphenol 
average formula 
C.sub.6 H.sub.5 --C.sub.6 H.sub.4 --O(CH.sub.2 CH.sub.2 O).sub.2.25 
3.0 g. 
______________________________________ 
A high holdout, calendered, bleached, sulfite paper is coated with about 3 
milliliters of the above composition per 1000 square centimeters and dried 
in the air. 
Color formation is obtained using a contact printer with Sylvania 
Blacklight blue fluorescent lamps. Irradiance is 2.75 milliwatts per 
square centimeter as measured with a YSI Radiometer, Model 65, with probe, 
Model 6551 in its protective plastic container, against the glass surface 
of the printer. (The indicated reading, 2.75 mw/cm.sup.2, is estimated to 
be about 60% of that actually existing at the surface of the glass.) 
Samples are exposed for 30 seconds through a .sqroot.2 or a .sqroot.2 
stepwedge. The .sqroot.2 stepwedge is vacuum deposited Inconel-X on quartz 
made by Mufoletto Optical Co. The .sqroot.2 stepwedge is a special 
stepwedge made by Eastman Kodak Co. 
Deactivation is obtained using a printer as above with Sylvania fluorescent 
lamps containing a special phosphor, PER-105. Irradiance is 5.0 milliwatts 
per square centimeter measured with the YSI Radiometer as above. The same 
stepwedges are used as for color formation. Deactivation exposures of 60 
seconds through stepwedges are followed by color formation exposure of 30 
seconds without stepwedge to determine how much deactivation has occurred. 
Three photoimageable/photodeactivatable papers were prepared as above, 
varying the leuco dyes. One portion of each paper was subjected to imaging 
irradiation, and another to deactivation irradiation, also as described 
above. The following table gives the contrast obtainable, using three 
leuco dyes, between the photoimaged and photodeactivated portions. The 
contrast is reported as optical density (OD) units, as measured on a 
MacBeth RD-100 reflecting densitometer. The value .DELTA.OD is the imaged 
OD minus the deactivated OD. The maximum OD is the visual diffuse optical 
density obtained on a sample by color formation exposure through step No. 
1 (clear area) of the stepwedge. 
TABLE I 
______________________________________ 
CONTRAST DATA- 
YELLOW-IMAGED/DEACTIVATED PAPERS 
OD 
Ex. OD-Imaged Deac- 
No. Leuco Dye & Deactivated 
tivated 
.DELTA.OD 
______________________________________ 
3 Dye of Example 1 
0.70 0.1 0.60 
4 Dye of Example 2 
0.62 0.1 0.52 
5 2-(p-Diethyl- 0.40 0.1 0.30 
aminophenylmethyl 
1-indanone 
______________________________________ 
Clearly, as evidenced by the data in Table I, the leuco dyes of Examples 1 
and 2 are superior (yield more intense yellow images) to the closely 
related art (Ex. No. 5 ) under the conditions of these examples. Indeed, 
nearly a two-fold increase in intensity is obtained with the color formers 
of this invention. The behavior of the above compounds may, of course, 
vary in different systems, and no representation is made as to them. 
Substantially identical results may be obtained on substituting equivalent 
weights of the reductant (hydrogen donor) N,N-dibenzylethanolamine acetate 
for the reductant trimethylnitrilotripropionate. This new reductant is 
readily prepared by acetylating, N,N-dibenzylethanolamine, which is 
commercially available, with acetic anhydride in acetic acid as solvent; 
the preparative details are as follows: 
N,N-dibenzylethanolamine, 62.5 g., 0.26 mole, and an equal weight of 
glacial acetic acid were stirred at room temperature until solution was 
complete. Following cooling to 10.degree. C., acetic anhydride (53 g., 
0.52 mole) was added to effect acetylation. Since acetylation is an 
exothermic reaction, slow addition and a cooling bath were used to 
maintain the mixture's temperature at 25.degree..+-. 5.degree. C. The 
reaction mixture was further stirred for 1.5 hours at room temperature 
upon completing the anhydride addition. 
Isolating the product involved first removing the acetic acid solvent by 
distillation under reduced pressure, while maintaining the pot temperature 
below 80.degree. C. The pot residue was then neutralized with aqueous 
sodium carbonate, and extracted with benzene. The benzene phase containing 
the desired product was washed three times with water and then dried. The 
benzene was then removed by reduced pressure distillation, maintaining the 
pot temperature below 60.degree. C. The pot residue gave 
N,N-dibenzylethanolamine acetate [(C.sub.6 H.sub.5 --CH.sub.2)--.sub.2 
N-CH.sub.2 CH.sub.2 OCOCH.sub.3, 67 g., 92% yield b.p. 
334.degree.-336.degree. C., with decomposition] in high yield and 
sufficient purity to be used as reductant in dual response, photosensitive 
formulations without further purification. The purity of the product was 
also confirmed by chromatographic analysis; the infrared and nuclear 
magnetic resonance spectra were consistent with the structure assigned. 
EXAMPLE 6 
Preparation of a Preferred Leuco Triarylmethane, 
3-Methoxy-4-octanamidophenyl-bis-(4'-diethylamino-2'-methylphenyl) methane 
A preferred three-step route has been outlined above. The first two steps 
of the scheme are accomplished with relative ease. Two processes are 
described for the more difficult step 3; the formic acid condensation 
method is favored for its ability to yield clean product. The yield in 
step 3 i.e. the formic acid procedure has been found to depend upon the 
molar excess of N,N-diethyl-m-toluidine used in the reaction, and 
therefore three examples of reactions run with varying ratios of reactants 
are given. 
Step 1: 
The Preparation of 
(2-Methyl-4-diethylaminophenyl)-(3'-methoxy-4'-aminophenyl) Methyl Urea 
A mixture of 96.9 g. (0.792 mole) of o-anisidine, 168.0 g. of urea, 180 ml 
of water, and 264 g. of conc. sulfuric acid is prepared, with stirring, by 
addition of the components in rapid succession (in the order given), and 
150.3 g (0.792 mole) of 4-diethylamino-o-tolualdehyde (distilled) was 
added last. The temperature rose without additional heat to reflux 
temperature (15-20 min.), and, without subsequent heating, the mixture was 
stirred for a total of 1 hour. The mixture was poured, with mechanical 
stirring, into a mixture of ice and water (1000 ml), 400 ml of conc. 
ammonium hydroxide and 800 ml of ether. The resulting heterogeneous 
mixture was stirred for one-half hour (beaker in ice), the mixture 
filtered and the cake washed with 1000 ml of water and three times with 
ether (600 ml each). The crude product, as isolated above, takes the form 
of irregular size pearls, pale yellow, 280.0 g (96.5% theor.) m.p. 
110.degree.-115.degree.. The infrared spectrum is characteristic of the 
amino urea product. 
Step 2: 
Acylation of the Amino Urea 
To a stirred mixture of 182.7 g (0.5 mole) of amino urea and 1000 ml of 
acetonitrile was added, at one time, 81.3 g (0.5 mole) of n-octanoyl 
chloride. The mixture was stirred for 1 hour at room temperature, 2000 ml 
of water was added to the yellow solution, and 390 ml of 10% sodium 
carbonate solution was added slowly to allow for gas evolution and crystal 
formation (the final solution was basic, pH=8). The mixture was filtered, 
the cake washed with water (3000 ml) and the solid was washed four times 
with acetonitrile (1300 ml) to give a colorless product, 193.3 g (yield 
80% theor.), m.p. 160.degree.-165.degree. C. The infrared spectrum is 
characteristic of the acylated urea product. 
Step 3: 
Formation and Separation of the Leuco Dye by the Cellosolve Method 
A mixture of 9.65 g (0.02 mole) of the acylated urea product, 3.26 g (0.02 
mole) of N,N-diethyl-m-toluidine, 50 ml of Cellosolve and 3 ml of conc. 
sulfuric acid was mixed in the order noted, and a solid separated after a 
3-4 min. period which dissolved upon heating to reflux temperature 
(134.degree. C.). The stirred mixture was heated at reflux temperature for 
40 min., and 50 ml of isopropanol was added. The addition of sodium 
carbonate solution (to pH=9) caused a dispersed tan gum to separate; the 
addition of 25 ml of methanol, with stirring of the neutralized mixture in 
an ice bath, gave a filterable solid. The latter was collected by 
filtration and washed with isopropanol, water, and 2B-ethanol, yielding 
5.9 g of leuco dye, m.p. 85.degree.-87.degree. C. The infrared spectrum is 
characteristic of 
3-methoxy-4-octanamidophenyl-bis-(4'-diethylamino-2'-methylphenyl)methane. 
A second fraction (1.0 g. ) was collected from the filtrate for a total 
collected yield of 53%. The melting point of the sample recrystallized 
from methanol was 86.degree.-89.degree. C. 
Anal. Calc'd. for C.sub.38 H.sub.55 N.sub.3 O.sub.2 : C, 77.90; H, 9.46; N, 
7.17. 
Found: C, 77.87; H, 9.67; N, 7.68. 
Alternative Step 3: 
Condensation in Formic Acid 
A mixture of 9.65 g. (0.02 mole) of the acylated urea product, 9.78 g (0.06 
mole) of N,N-diethyl-m-toluidine and 25 ml of formic acid was heated at 
reflux temperature for one-half hour, cooled and poured in 50 ml of conc. 
ammonium hydroxide solution and ice water. The oil which separated was 
separated from the aqueous phase with methylene chloride, and both 
methylene chloride and some excess toluidine were removed by distillation 
of 500 ml of added water on a rotary evaporator. The water insoluble 
residue was triturated with ethanol to give a colorless solid, m.p. 
88.degree.-90.degree., 5.00 g of leuco dye. The filtrates from above were 
treated by conventional steam distillation techniques (because of 
remaining toluidine), and water insoluble residue, when treated as above, 
yielded 3.2 g of colorless leuco dye. The latter fraction possessed a 
minor leuco dye contaminant (as determined by TLC), yet the two fractions 
possessed identical infrared spectra (total yield, 71%). The infrared 
spectrum is characteristic of 
3-methoxy-4-octanamidophenyl-bis-(4'-diethylamino-2'-methylphenyl) 
methane. 
The reaction of 0.02 mole of acylated urea and 0.04 mole of 
N,N-diethyl-m-toluidine, when treated as above, gave a 65% yield of leuco 
dye. 
A third example of the formic acid condensation is as follows: 
A mixture of 38.60 g (0.08 mole) of the acylated urea, 13.04 g (0.08 mole) 
of N,N-diethyl-m-toluidine and 100 ml of formic acid was heated at reflux 
temperature for 150 min., cooled, and poured into a mixture of 100 ml of 
isopropanol, 100 ml of water, 230 ml of conc. ammonium hydroxide solution, 
and 8.0 g of the leuco dye used as seed. A mixture of brown gum and solid 
separated in one lump, the aqueous phase was decanted, and a mixture of 
100 ml of methanol and 75 ml of isopropanol was added to the residue. 
Heating nearly dissolved the solid phase, and cooling gave a thick 
crystalline slurry; the product was collected by filtration and washed to 
a colorless state with isopropanol; 28.9 g leuco dye was collected, yield 
corrected for seed, 20.90 g (45% yield). 
EXAMPLE 7 
A Black, Photoimageable/Photodeactivatable-Proof Paper 
A coating composition is prepared from the following ingredients: 
______________________________________ 
Wt. 
Weight Per- 
Moles (Grams) cent Constituent 
______________________________________ 
237 g 80.37 Acetone 
(300 ml) 
3.2.times.10.sup.-3 
2.50 0.85 2,2-(o-chlorophenyl)- 
4,4',5'-tetrakis 
(m-methoxyphenyl)- 
biimidazole 
1.35.times.10.sup.-2 
4.20 1.42 Richonic Acid B 
(Richardson Co. 
tradename for 
dodecylbenzene- 
sulfonic acid) 
8.times.10.sup.-3 
2.2 0.74 triethanolamine tri- 
acetate 
1.2.times.10.sup.-2 
3.3 1.12 trimethyl 3,3',3"- 
nitrilotriprop- 
ionate 
1.17.times.10.sup.-3 
0.2430 0.082 9,10-phenanthrane- 
quinone 
30.0 10.16 cellulose acetate 
butyrate (thermo- 
plastic binder, 
Eastman EAB 272-20) 
6.5.times.10.sup.-5 
0.015 0.005 pyrenequinone (a 1:1 
mixture of 1,6- and 
1,8-isomers) 
6.50 2.20 Santicizer-3 (N-ethyl- 
p-toluenesulfonamide, 
Monsanto Chemical 
Company) 
5.70 1.93 polyethyleneoxide 
adduct of o-phenyl- 
phenol prepared from 
2.25 moles of 
ethylene oxide per 
mole of the phenol 
and having the 
average formula 
C.sub.6 H.sub.5 --C.sub.6 H.sub.4 --O(CH.sub.2 
CH.sub.2).sub.2.25 H 
2.0 0.68 "Syloid" 63 - a 9 micron 
synthetic silica 
produced by Grace- 
Davidson Chemical Co. 
0.25 0.085 mixed fluorocarbon 
esters of formula 
F(CF.sub.2 CF.sub.2).sub.n CH.sub.2 CH.sub.2 
OCO 
--(CH.sub.2).sub.16 CH.sub.3 where 
n = 3 and 4 
1.08.times.10.sup.-3 
0.330 0.11 trans-3-hydroxy-2- 
(p-diethylaminophenyl- 
methyl)-1-indanone 
1.08.times.10.sup.-3 
0.6320 0.21 3-methoxy-4-n-octanamido- 
phenyl-bis-(4'-diethyl- 
amino-2'-methylphenyl) 
methane 
______________________________________ 
The above formulation was coated on regular HG paper, a commercial product 
of the P. J. Schweitzer Co. Following drying, to evaporate the volatile 
solvent, the coating weight of the dried coating was 11 lbs./3000 square 
feet. This coated paper, upon irradiation with ultraviolet light, gave a 
black photoimage with good contrast as described in the following table: 
______________________________________ 
SENSITOMETRY RESULTS 
Initial 
2 weeks 4 weeks 
______________________________________ 
Optical Density 1.03 1.02 1.02 
(Imaging) 
Background Optical Density 
0.13 0.12 0.12 
(Deactivation) 
______________________________________ 
The imaging and deactivation light sources were the same as described for 
Examples 3-5. 
EXAMPLE 8 
Urethane Derivatives 
Urethane derivatives of the leuco dye prepared in Example 1 were prepared 
according to the following general equation: 
##STR24## 
The derivatives prepared had the following structures: 
##STR25## 
Preparation of I 
The leuco yellow dye of Example 1 (1 g., 0.03 mole), phenyl isocyanate (0.5 
g.) and octane (5 ml.) was heated to reflux. When the temperature reached 
100.degree. C., pyridine (3 drops) was added. The solids immediately went 
into solution; after 1.5 hours at 100.degree. C., thin layer 
chromatographic (tlc) analysis showed that all the original yellow color 
former (of Example 1) had reacted and a new yellow color former was 
produced. On cooling, the product (I) which precipitated was collected by 
filtration. After recrystallization from acetonitrile, the m.p. was 
170.degree.-171.5.degree. C. 
Anal. Calc'd. for C.sub.27 H.sub.28 N.sub.2 O.sub.3 (Formula I): C, 75.67; 
H, 6.57; O, 11.20; N, 6.54. Found: C, 75.56; H, 6.64; O, 11.28; N, 6.44. 
Products II-V were prepared similarly; the results are reported in the 
following table: 
TABLE 
__________________________________________________________________________ 
Amount Aryl Melting Point 
Urethane 
Leuco of Isocyanate 
Solvent 
Reaction 
of 
Derivative 
Example 1 
and (amount) 
and (amount) 
Time (hrs.) 
Derivative 
__________________________________________________________________________ 
II 2 g. .alpha.-naphthyliso- 
octane 1.5 hrs. 
128-129.degree. C. 
(0.0065 mole) 
cyanate (20 ml.) 
at 100.degree. C. 
(1.1 g., 0.0065 
mole) 
III " p-nitrophenyl 
benzene 
1 hr. at 
169-170.degree. C. 
isocyanate 
(20 ml.) 
reflux 
(1.1 g., 0.0065 
mole) 
IV " m-nitrophenyl 
" 2 hrs. at 
164-166.degree. C. 
isocyanate reflux 
(1.1 g., 0.0065 
mole) 
V " o-nitrophenyl 
" " 135-136.degree. C. 
isocyanate 
(1.1 g., 0.0065 
mole) 
__________________________________________________________________________ 
Photooxidation Using Urethane Derivatives I, III-V Color Formers 
A coating composition is prepared from the following ingredients: 
______________________________________ 
Acetone 60 ml. 
2,2'-Bis(o-chlorophenyl)-4,4',5,5'- 
tetrakis (m-methoxyphenyl)biimidazole 
0.64 g. 
Leuco dye 6 .times. 10.sup.-4 mole 
p-Toluenesulfonic acid monohydrate 
0.2283 g. 
Cellulose acetate butyrate (Eastman 
6.0 g. 
EAB 531-1) 
Polyethyleneoxide adduct of o-phenyl- 
4.0 g. 
phenol average formula 
C.sub.6 H.sub.5 --C.sub.6 H.sub.4 --O(CH.sub.2 CH.sub.2 O).sub.2.25 
______________________________________ 
The above formulations were applied to Mylar.RTM. polyester film (7 .times. 
8 inches) to yield a dry coating weight (after drying to remove the 
volatile solvent) of approximately 0.6 g./56 in..sup.2. The dry, coated 
films were imaged by exposing the films for 30 seconds, as described in 
Examples 3-5, to Sylvania Blacklight Blue fluorescent lamps. Using the 
Cary spectrophotometer, the .mu.max, and optical densities of the imaged 
samples were measured (Table II). The data collected from this experiment 
showed that two of the four compounds have optical densities, after 
imaging for 30 seconds, that are greater by a factor of at least 1.6 when 
compared to Example 1. Compound I has an optical density that is greater 
by a factor of 2 (1.50 compared to 0.76) and compound V has an optical 
density that is greater by a factor 1.6 (1.22 compared to 0.76). The data 
are summarized in Table II below: 
TABLE II 
______________________________________ 
OD after 
Amount Color Former Imaging for 30 sec. 
______________________________________ 
0.185 g. Example 1 0.76 
0.257 g. Compound I 1.50 
0.284 g. Compound III 0.88 
0.284 g. Compound IV 0.79 
0.284 g. Compound V 1.22 
______________________________________ 
The imaging was performed as in Examples 3-5, and optical density was 
measured with a Cary spectrophotometer at .mu.max., which was determined 
to be 445 nm. The optical density of the background (unimaged formulation) 
was in all cases less than 0.08. 
EXAMPLE 9 
Preparation of N-Halotriarvlimidazoles 
A. N-Chloro-2-(2'-chlorophenyl)-4,5-diphenylimidazole 
The preparation of 2-(o-chlorophenyl)-4,5-diphenylimidazole 
(o-chlorolophine) is described in British patent specification No. 
997,396, Example 1. 
A mixture of 14.24 g. of 2-(o-chlorophenyl)-4,5-diphenylimidazole (0.04 
mole), 5.34 g. of N-chlorosuccinimide (0.04 mole), and 500 ml. of carbon 
tetrachloride was heated at reflux temperature for 1 hour, cooled to 
0.degree. C., and the precipitated residue was separated by filtration. 
The solvent of the filtrate was evaporated under vacuum at 35.degree. C. 
1-Chlorobutane was added in minimal amount to the oily residue to induce 
crystallization. The solid that formed was collected by filtration; 5.88 
g., m.p. 105.degree.-107.degree. C. An additional fraction was collected 
from the filtrate, 5.45 g. 
Anal. Calc'd. for C.sub.21 H.sub.14 N.sub.2 Cl.sub.2 : C, 69.06; H, 3.86; 
N, 7.67; Cl, 19.41. Found: C, 68.66; H, 3.68; N, 7.74 Cl, 19.39. 
Infrared and nuclear magnetic resonance spectra are consistent with the 
tilted compound's structure. 
B. N-Bromo-2-(2'-chlorophenyl)-4,5-diphenylimidazole 
A mixture of 6.62 g. (0.02 mole) of o-chlorolophine 3.56 g. (0.02 mole) of 
N-bromosuccinimide, and 200 ml. of carbon tetrachloride was heated at 
reflux temperature for 1 hour. During this time the solution became pale 
orange. The solution was cooled to 0.degree. C., filtered, and the 
succinimide washed with carbon tetrachloride; weight, 2.16 g. The filtrate 
was concentrated to oil under vacuum at 35.degree. C. The orange residue 
was diluted with 15 ml. of 1-chlorobutane and stirred magnetically. The 
stirring induced crystal formation. A tan-orange solid separated, was 
filtered, washed with cold 1-chlorobutane, and collected by filtration; 
5.192 g.; the IR spectrum was almost identical with that of the chloro 
derivative A; m.p. 103.degree.-105.degree. C. 
Anal. Calc'd. for C.sub.22 H.sub.14 N.sub.2 ClBr: C, 61.56; H, 3.44; N, 
6.84. Found: C, 61.73; H, 3.53; N, 6.88. 
The infrared and nuclear magnetic resonance spectra were also consistent 
with a structure corresponding to the tilted compound. 
C. N-Chloro-2-(2',6'-dichlorophenyl)-4,5-diphenylimidazole 
2-(2',6'-Dichlorophenyl)-4,5-diphenylimidazole was prepared in a manner 
identical with Example II of Brit. patent specification No. 997,396, but 
substituting 2,6-dichlorobenzaldehyde for the 2,4-dichlorobenzaldehyde of 
the Example. 
A mixture of 14.60 g. (0.04 mole) of the 
2-(2',6'-dichlorophenyl)-4,5-diphenylimidazole, 5.34 g. (0.04 mole) of 
N-chlorosuccinimide, and 400 ml of carbon tetrachloride was heated at 
reflux temperature for 2 hours. The solution was cooled, filtered, and the 
filtrate concentrated under vacuum. The resulting solid-oil mixture was 
triturated with 1-chlorobutane to give a residue of 16.68 g., m.p. 
120.degree.-140.degree. C. (broad). The compound proved difficult to 
recrystallize from common solvent and only acetonitrile and nitromethane 
afforded resonable recovery of crystals; from the latter solvents the 
crystals formed as large chunky aggregates. The best fraction 0.7664 g. 
has m.p. 125.degree.-127.degree. C.; an IR spectrum showed no NH 
absorption and a very strong 1620 cm.sup.-1 band. 
Anal. Calc'd. for C.sub.22 H.sub.13 N.sub.2 Cl.sub.3 : C, 63.10; H, 3.28; 
N, 7.01; Cl, 26.61. Found: C, 63.32; H, 3.37; N, 7.38; Cl, 26.20. 
The infrared and nuclear magnetic resonance spectra were all consistent 
with the structure of the tilted compound. 
Use of N-Halotriarylimidazoles as Photooxidants for Leuco Dyes 
Two solutions were prepared. Solution A contained the leuco dye of Example 
1 (0.5 g.) in benzene (100 ml.); solution B contained N-chlorolophine as 
prepared in Example 9, Part A, (0.01 g.) in benzene (2 ml.). A 1.00 ml. 
aliquot of solutions A and B were mixed, and the resulting solution 
applied totally to 64 cm..sup.2 of Whatman No. 1 filter paper. The paper 
was dried in an air stream and then a portion was irradiated with a Xenon 
(HiCo) flash lamp to give a strong yellow image over a nearly colorless 
background. 
Substantially identical results may be obtained with N-bromolophine of Part 
B and N-chlorolophine of Part C. 
EXAMPLE 10 
Leuco Yellow Imaging, Photopolymerization Fixing 
Through exposure control, e.g., by altering the intensity and time of 
exposure, as more fully described in Cescon, Cohen & Dessauer, U.S. 
application Ser. No. 740,130, filed June 26, 1968, and assigned to the 
assignee herein, color-forming and polymerization reactions can be 
controlled so as to produce substantially colored or uncolored 
compositions. Thus polymerization fixed images can be produced in imaging 
applications by sequentially applied exposures that substantially 
completely polymerize the composition while controlling the amount of 
color produced in adjacent areas. 
The leuco dyes of this invention are also useful in this type of 
photosensitive formulation, as detailed below. 
A coating composition was prepared as follows: 
______________________________________ 
Acetone 45.6 ml. 
Cellulose acetate butyrate (EAB-272-20) 
3.96 g. 
Triethyleneglycol dimethacrylate 
3.96 g. 
2,2'-Bis(o-chlorophenyl)-4,4',5,5'-tetrakis- 
(m-methoxyphenyl)biimidazole 
0.471 g. 
2,2'-Bis(o-chlorophenyl)4,4',5,5'-tetra- 
0.471 g. 
phenylbiimidazole 
Leuco dye of Example 1 0.309 g. 
p-Toluenesulfonic acid 0.375 g. 
2-Mercaptobenzoxazole 0.014 g. 
______________________________________ 
These formulations were coated on 3 mil Mylar.RTM. polyester film, dried 
and laminated with a 1.42 mil Mylar.RTM. polyester film. The dried coating 
weight was equivalent to 0.36 lb./100 ft..sup.2 ; the dried coating 
thickness was approximately 0.6 mil. 
The above coated film was imagewise deactivated (by irradiation through a 
stencil or master) by a 12-second exposure (0.9 mw/cm..sup.2) to low 
intensity radiation from a high pressure mercury-vapor lamp (HBO-200), 
which had been passed through a water, a Corning I-69, and a Schott UG-11 
filter combination; this filter combination transmits light principally in 
the near ultraviolet range. 
The resulting deactivated film was then thoroughly dried by storage in a 
desiccator (over "Drierite") for 3.5 hours. The resultant, deactivated 
(photopolymerized), dry film was then imaged by exposure to 5 flashes 
(high intensity) from a Xenon flashtube (Model K, HiCo Corporation, 
Watertown, Mass.). 
The sensitometry results obtained are reported below. The numbers are the 
optical densities obtained in the yellow region of the spectrum, as 
measured by a Cary spectrophotometer at 443 nm. 
______________________________________ 
OPTICAL DENSITIES 
Imaged and Deactivated 
Deactivated Only .DELTA.O.D. 
______________________________________ 
2.00 0.20 1.80 
______________________________________