U.S. patent number 3,923,524 [Application Number 05/410,948] was granted by the patent office on 1975-12-02 for fogged direct positive silver halide emulsions containing photographic sensitizing dyes derived from substituted salicylaldehydes.
This patent grant is currently assigned to Eastman Kodak Company. Invention is credited to Jan Raymond Haase.
United States Patent |
3,923,524 |
Haase |
December 2, 1975 |
Fogged direct positive silver halide emulsions containing
photographic sensitizing dyes derived from substituted
salicylaldehydes
Abstract
Cyanine and merocyanine photographic sensitizing dyes derived
from substituted salicylaldehydes and light sensitive silver halide
emulsions containing such dyes are disclosed. Also disclosed are
certain reversible spiropyranmerocyanine dye systems, the
stabilization of a dye in either the spiropyran form or the
merocyanine form and observations of these photochromic materials
when coated in polymeric matrices.
Inventors: |
Haase; Jan Raymond (Rochester,
NY) |
Assignee: |
Eastman Kodak Company
(Rochester, NY)
|
Family
ID: |
23626925 |
Appl.
No.: |
05/410,948 |
Filed: |
October 29, 1973 |
Current U.S.
Class: |
430/592; 430/83;
430/606; 430/591 |
Current CPC
Class: |
G03C
1/12 (20130101); G03C 1/22 (20130101); G03C
1/685 (20130101) |
Current International
Class: |
G03C
1/22 (20060101); G03C 1/685 (20060101); G03C
1/12 (20060101); G03C 001/22 () |
Field of
Search: |
;96/139,140,90 PC:1.6/
;96/101 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Brown; J. Travis
Attorney, Agent or Firm: Chipaloski; M. R.
Claims
I claim:
1. A fogged direct positive photographic silver halide emulsion
containing at least one photographic silver halide sensitizing dye
selected from those having the formulas: ##SPC14##
and ##SPC15##
wherein a is 0 or 1; Z represents a heterocyclic nucleus selected
from the group consisting of thiazoles, benzothiazoles,
naphthothiazoles, thieno-[1,2-a]benzothiazoles, oxazoles,
benzoxazoles, naphthoxazoles, selenazoles, benzoselenazoles,
naphthoselenazoles, thiazolines, 2-quinolines, 4-quinolines,
3,3-dialkylindolenines, 2-pyridines, 4-pyridines, imidazoles,
benzimidazoles, naphthimidazoles, and lepidines; R represents a
lower alkyl group or an aryl group; and R.sub.1 and R.sub.2 each
represents hydrogen, a nitro group, a halo group, a lower alkoxy
group or a lower alkyl group, provided that at least one of the
groups R.sub.1 and R.sub.2 is a nitro group or a halo group.
2. A fogged direct positive photographic silver halide emulsion
containing a photographic silver halide sensitizing dye of the
formula: ##SPC16## wherein a is 0 or 1; Z represents a heterocyclic
nucleus selected from the group consisting of thiazoles,
benzothiazoles, naphthothiazoles, thieno-[1,2-a]benzothiazoles,
oxazoles, benzoxazoles, naphthoxazoles, selenazoles,
benzoselenazoles, naphthoselenazoles, thiazolines, 2-quinolines,
4-quinolines, 3,3-dialkylindolenines, 2-pyridines, 4-pyridines,
imidazoles, benzimidazoles, naphthimidazoles, and lepidines; R
represents a lower alkyl group or an aryl group; R.sub.1 and
R.sub.2 each represents hydrogen, a nitro group, a halo group, a
lower alkoxy group or a lower alkyl group, provided that at least
one of the groups R.sub.1 and R.sub.2 is a nitro group or a halo
group.
3. A fogged direct positive photographic silver halide emulsion
containing a photographic silver halide sensitizing dye of the
formula: ##SPC17##
wherein a is 0 or 1; Z represents a heterocyclic nucleus selected
from the group consisting of thiazoles, benzothiazoles, oxazoles,
benzoxazoles, naphthoxazoles, selenazoles, benzoselenazoles,
naphthoselenazoles, thiazolines, 2-quinolines, 4-quinolines,
3,3-dialkylindolenines, 2-pyridines, 4-pyridines, imidazoles,
benzimidazoles, naphthimidazoles, and lepidines; R represents a
lower alkyl group or an aryl group; and R.sub.1 and R.sub.2 each
represents hydrogen, a nitro group, a halo group, a lower alkoxy
group or a lower alkyl group, provided that at least one of the
groups, R.sub.1 and R.sub.2 is a nitro group or a halo group.
4. A photographic silver halide emulsion as defined in claim 1
wherein said sensitizing dye is
1',3'-diethyl-2',3'-dihydro-6-nitrospiro(2H)-1-benzopyran-2,2'-1H-imidazo[
4,5-b]quinoxaline.
5. A photographic silver halide emulsion as defined in claim 1
wherein said sensitizing dye is
6-[(1-methylnaphtho-[1,2-d]thiazolin-2-ylidene)ethylidene]-4-nitro-2,4-cyc
lohexadienone.
6. A photographic silver halide emulsion as defined in claim 1
wherein said sensitizing dye is
6[(3-ethylbenzoselenazolinylidene)ethylidene]-4-nitro-2,4-cyclohexadienone
7. A photographic silver halide emulsion as defined in claim 1
wherein said sensitizing dye is
6-[(1-ethylnaphtho-[2,3-d]thiazolin-2-ylidene)ethylidene]-4-nitro-2,4-cycl
ohexadienone.
8. A photographic silver halide emulsion as defined in claim 1
wherein said sensitizing dye is
6-[(3-ethyl-2-benzothiazolinylidene)ethylidene]-4-nitro-2,4-cyclohexadieno
ne.
9. A photographic silver halide emulsion as defined in claim 1
wherein said sensitizing dye is selected from the group consisting
of
6-[(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)ethylidene]-4-nitro-2,4-cycloh
exadienone;
6-nitro-2',3'-dihydro-1',3',3'-trimethylspiro(2H)-1-benzopyran2,2'-(1H)-pyr
rolo[2,3-b]pyridine;
6-[(1,3-diethyl-2-benzimidazolinylidene)ethylidene]-4-nitro2,4-cyclohexadie
none;
6-[(1-ethyl-4-(1H)-quinolylidene)ethylidene]-4-nitro-2,4-cyclohexadienone;
6-[(5,6-dichloro-1,3-diethyl-2-benzimidazolinylidene)ethylidene]-4-nitro-2,
4-cyclohexadienone; and
6-[(3,4-diphenyl-4-thiazolin-2-ylidene)ethylidene]-4-nitro2,4-cyclohexadien
one.
10. A fogged direct positive photographic element comprising a
support having thereon at least one layer of a photographic silver
halide emulsion containing at least one photographic sensitizing
dye selected from those having the formulas: ##SPC18##
and ##SPC19##
wherein a is 0 or 1; Z represents a heterocyclic nucleus selected
from the group consisting of thiazoles, benzothiazoles,
naphthothiazoles, thieno-[1,2-a]benzothiazoles, oxazoles,
benzoxazoles, naphthoxazoles, selenazoles, benzoselenazoles,
naphthoselenazoles, thiazolines, 2-quinolines, 4-quinolines,
3,3-dialkylindolenines, 2-pyridines, 4-pyridines, imidazoles,
benzimidazoles, naphthimidazoles, and lepidines; R represents a
lower alkyl group or an aryl group; and R.sub.1 and R.sub.2 each
represents hydrogen, a nitro group, a halo group, a lower alkoxy
group or a lower alkyl group, provided that at least one of the
groups R.sub.1 and R.sub.2 is a nitro group or a halo group.
11. A fogged direct positive photographic element comprising a
support having thereon at least one layer of a photographic silver
halide emulsion containing at least one photographic sensitizing
dye of the formula: ##SPC20## wherein a is 0 or 1; Z represents a
heterocyclic nucleus selected from the group consisting of
thiazoles, benzothiazoles, naphthothiazoles, thieno-[1,2-a]
benzothiazoles, oxazoles, benzoxazoles, naphthoxazoles,
selenazoles, benzoselenazoles, naphthoselenazoles, thiazolines,
2-quinolines, 4-quinolines, 3,3-dialkylindolenines, 2-pyridines,
4-pyridines, imidazoles, benzimidazoles, naphthimidazoles, and
lepidines; R represents a lower alkyl group or an aryl group; and
R.sub.1 and R.sub.2 is a nitro group or a halo group.
12. A fogged direct positive photographic element comprising a
support having thereon at least one layer of a photographic silver
halide emulsion containing at least one photographic sensitizing
dye of the formula: ##SPC21## wherein a is 0 or 1; Z represents a
heterocyclic nucleus; selected from the group consisting of
thiazoles, benzothiazoles, naphthothiazoles, thieno-[1,2-a]
benzothiazoles, oxazoles, benzoxazoles, naphthoxazoles,
selenazoles, benzoselenazoles, naphthoselenazoles, thiazolines,
2-quinolines, 4-quinolines, 3,3-dialkylindolenines, 2-pyridines,
4-pyridines, imidazoles, benzimidazoles, naphthimidazoles, and
lepidines; R represents a lower alkyl group or an aryl group; and
R.sub.1 and R.sub.2 each represents hydrogen, a nitro group, a halo
group, a lower alkoxy group or a lower alkyl group, provided that
at least one of the groups R.sub.1 and R.sub.2 is a nitro group or
a halo group.
Description
This invention relates to photographic silver halide emulsions
containing sensitizing dyes derived from substituted
salicylaldehydes.
In accordance with this invention there are provided photographic
silver halide emulsions containing a sensitizing dye represented by
the following general formulas: ##SPC1##
And ##SPC2##
Wherein a is 0 or 1; R preferably represents a lower alkyl group
having 1 to 8 carbon atoms such as methyl, ethyl, propyl, butyl,
etc., and including substituted lower alkyl groups such as a
carboxyalkyl group (e.g., carboxymethyl, carboxyethyl,
carboxypropyl, carboxybutyl, etc.), an alkoxycarbonyl alkyl group
(e.g., methoxycarbonylmethyl, ethoxycarbonylethyl,
propoxycarbonylethyl, propoxycarbonylbutyl, etc.), a sulfoalkyl
group (e.g., sulfomethyl, sulfoethyl, sulfopropyl, sulfobutyl,
etc.), a hydroxyalkyl group (e.g., hydroxymethyl, hydroxyethyl,
hydroxypropyl, hydroxybutyl, etc.), an alkoxyalkyl group (e.g.,
methoxyethyl, methoxypropyl, ethoxyethyl, ethoxypropyl, etc.), a
sulfoalkoxyalkyl group, as well as an aryl group such as phenyl,
4-methylphenyl, 4-chlorophenyl, etc.; R.sub.1 and R.sub.2 may be
the same or different groups and each represents hydrogen, a nitro
group, a halo group such as chloro, bromo, fluoro, or iodo, a lower
alkoxy group such as methoxy, ethoxy, propoxy, etc., or a lower
alkyl group such as previously defined for R provided that at least
one of the groups R.sub.1 and R.sub.2 must be a nitro group or a
halo group; and Z represents the nonmetallic atoms necessary to
complete a heterocyclic nucleus containing from 5 to 6 atoms in the
heterocyclic ring, such as a heterocyclic nucleus of the thiazole
series (e.g., thiazole, 4-methylthiazole, 5-methylthiazole,
4-phenylthiazole, 5-phenylthiazole, 4,5-dimethylthiazole,
4,5-diphenylthiazole, 4-(2-thienyl)thiazole, etc.), those of the
benzothiazloe series (e.g., benzothiazole, 4-chlorobenzothiazole,
5-chlorobenzothiazole, 6-chlorobenzothiazole,
7-chlorobenzothiazole, 4-methylbenzothiazole,
5-methylbenzothiazole, 6-methylbenzothiazole, 5-bromobenzothiazole,
6-bromobenzothiazole, 4-phenylbenzothiazole, 5-phenylbenzothiazole,
4-methoxybenzothiazole, 5-methoxybenzothiazole,
6-methoxybenzothiazole, 5-iodobenzothiazole, 6-iodobenzothiazole,
4-ethoxybenzothiazole, 5-ethoxybenzothiazole,
tetrahydrobenzothiazole, 5,6-dimethoxybenzothiazole,
5,6-dihydroxymethylenebenzothiazole, 5-hydroxybenzothiazole, etc.),
those of the naphthothiazole series (e.g., naphtho[2,1-d]thiazole,
naphtho[1,2-d]thiazol, 5-methoxynaphtho[1,2-d]thiazole,
5-ethoxynaphtho[1,2-d]thiazole, 7-methoxynaphtho[1,2-d]thiazole,
8-methoxynaphtho[1,2-d]thiazole, etc.), those of the
thieno[1,2-a]benzothiazole series (e.g.,
5-methoxythieno[1,2-a]benzothiazole etc.), those of the oxazole
series (e.g., 4-methyloxazole, 5-methyloxazole, 4-phenyloxazole,
4,5-diphenyloxazole, 4-ethyloxazole, 4,5-dimethyloxazole,
5-phenyloxazole, etc.), those of the benzoxazole series (e.g.,
benzoxazole, 5-chlorobenzoxazole, 5-phenylbenzoxazole,
5-methylbenzoxazole, 6-methylbenzoxazole, 5,6-dimethylbenzoxazole,
4,6-dimethylbenzoxazole, 5-methoxybenzoxazole, 5-ethoxybenzoxazole,
6-chlorobenzoxazole, 5-hydroxybenzoxazole, 6-hydroxybenzoxazole,
etc.), those of the naphthoxazole series (e.g.,
naphth[2,1-d]oxazole, naphth[1,2-d]-oxazole, etc.), those of the
selenazole series (e.g., 4-methylselenazole, 4-phenylselenazole,
etc.), those of the benzoselenazole series (e.g., benzoselenazole,
5-chlorobenzoselenazole, 5-methoxybenzoselenazole,
5-hydroxybenzoselenazole, tetrahydrobenzoselenazole, etc.), those
of the naphthoselenazole series (e.g., naphtho[2,1-d]selenazole,
naphtho[1,2-d]selenazole, etc.), those of the thiazoline series
(e.g., thiazoline, 4-methylthiazoline, etc.), those of the
2-quinoline series (e.g., quinoline, 3-methylquinoline,
5-methylquinoline, 7-methylquinoline, 8-methylquinoline,
6-chloroquinoline, 8-chloroquinoline, 6-methoxyquinoline,
6-ethoxyquinoline, 6-hydroxyquinoline, 8-hydroxyquinoline, etc.),
those of the 4-quinoline series (e.g., quinoline,
6-methoxyquinoline, 7-methylquinoline, 8-methylquinoline, etc.),
those of the 1-isoquinoline series (e.g., isoquinoline,
3,4-dihydroisoquinoline, etc.) those of the 3,3-dialkylindolenine
series (e.g., 3,3-dimethylindolenine, 3,3,5-trimethylindolenine,
3,3,7-trimethylindolenine, etc.), those of the 2-pyridine series
(e.g., pyridine, 3-methylpyridine, 4-methylpyridine,
5-methylpyridine, 6-methylpyridine, 3,4-dimethylpyridine,
3,5-dimethylpyridine, 3,6-dimethylpyridine, 4,5-dimethylpyridine,
4,6-dimethylpyridine, 4-chloropyridine, 5-chloropyridine,
6-chloropyridine, 3-hydroxypyridine, 4-hydroxypyridine,
5-hydroxypyridine, 6-hydroxypyridine, 3-phenylpyridine,
4-phenylpyridine, 6-phenylpyridine, etc.), those of the 4 pyridine
series (e.g., 2-methylpyridine, 3-methylpyridine, 2-chloropyridine,
3-chloropyridine, 2,3-dimethylpyridine, 2,5-dimethylpyridine,
2,6-dimethylpyridine, 2-hydroxypyridine, 3-hydroxypyridine, etc.),
those of the imidazole series (e.g., imidazole, 4-methylimidazole,
5-ethylimidazole, 4-chloroimidazole, 4,5-dichloroimidazole,
4-methoxyimidazole, 5-phenylimidazole, etc.), those of the
benzimidazole series (e.g., benzimidazole, 4-methylbenzimidazole,
5-methylbenzimidazole, 6-methylbenzimidazole,
5,6-dichlorobenzimidazole, 5-chlorobenzimidazole,
5-phenylbenzimidazole, 6-phenylbenzimidazole, etc.), those of the
naphthimidazole series (e.g., naphth[1,2-d]imidazole,
naphth[2,1-d]imidazole, etc.), those of the lepidine series (e.g.,
lepidine, 7-chlorolepidine, 7-methyllepidine, etc.).
The alkyl groups or moieties referred to herein typically have 1 to
20 carbon atoms, lower alkyl radicals or moieties have 1 to 8
carbon atoms and aryl groups or moieties typically have 6 to 20
carbon atoms.
The dye compounds defined by Formulas I and II are prepared by
heating a mixture of a substituted salicylaldehyde having the
formula ##SPC3##
wherein R.sub.1 and R.sub.2 are as previously defined with a
nitrogen-containing heterocyclic compound containing a reactive
methyl group or a methylene group represented by the general
formulas ##EQU1## wherein R, Z and a are as previously defined and
A represents an anionic group such as chloride, bromide, iodide,
p-toluenesulfonate, thiocyanate, perchlorate, acetate,
methylsulfate, ethylsulfate, etc. The reaction is preferably
conducted in an inert solvent such as tetrahydrofuran, pyridine,
quinoline, isoquinoline, ethanol, propanol, butanol, etc., and in
the presence of a basic condensing agent such as the trialkyl
amines (e.g., triethylamine, tri-n-propylamine, tri-n-butylamine
etc.), piperidine, N-methylpiperidine, N-ethylpiperidine, N,
N-dimethylaniline, etc.
The following examples disclose the preparation of some of the dyes
of Formulas I and II:
EXAMPLE 1
1',3'-Diethyl-2',3'-dihydro-6-nitrospiro(2H)-1-benzopyran-2,2'-1H-imidazo[4
,5-b]quinoxaline ##SPC4##
A solution of 1,3-diethyl-2-methylimidazo[4,5-b]quinoxolium
p-toluenesulfonate (4.12 g., .01 mole), 5-nitrosalicylaldehyde
(1.67 g., .01 mole) and piperidine (1.0 g.) in ethanol (30 ml.) is
heated to reflux for 10 minutes. During this period a dye
crystallizes as green crystals and is collected upon cooling. The
yield of dye after washing with ethanol and ether and drying is 2.4
g. (62% yield). The dye is refluxed in ethanol (130 ml.) containing
3 drops of triethylamine for 24 hours. The volume is then reduced
to 40 ml. After cooling, 1.75 g. (45% yield) of a pale green solid
is obtained, having a melting point of 215.degree.-217.degree.C.
Photocolorization occurs when a solution of this compound is
irradiated with UV light.
Analysis: Calculated: C, 64.8%; H, 49.0%; N 18.0%. Found: C, 64.7%;
H, 5.1%; N 18.2%.
EXAMPLE 2
6-[(1-Methylnaphtho[1,2-d]thiazolin-2-ylidene)ethylidene]-4-nitro-2,4-cyclo
hexadienone ##SPC5##
A mixture of 1,2-dimethylnaphtho[1,2-d]thiazolium
p-toluenesulfonate (3.85 g., 0.01 mole), 5-nitrosalicylaldehyde
(1.67 g., 0.01 mole) and piperidine (0.87 g., 0.01 mole) is
refluxed for 10 minutes in ethanol (25 ml.). The dye precipitates
upon cooling and is collected and washed with ethanol to give 3.35
g. of product. A sample of 1.5g. of this crude product is digested
in dimethylformamide containing a small amount of ethanol. The dye
is collected and dried. The yield of dye is 1.4 g. (85% yield)
having a melting point of 243.degree.-245.degree.C. The dye can be
reversibly bleached with visible light.
Analysis: Calculated: C, 65.9%; H, 4.2%; N, 7.7%. Found: C, 66.2%;
H, 4.2%; N, 7.7%.
EXAMPLE 3
6-[(1-Ethylnaphtho[1,2,-d]thiazolin-2-ylidene)ethylidene]-4-nitro-2,4-cyclo
hexadienone ##SPC6##
A solution of 1-ethyl-2-methylnaphtho[1,2-d]thiazolium
p-toluenesulfonate (3.99 g., 0.01 mole) and 5-nitrosalicylaldehyde
(1.67 g., 0.01 mole) in ethanol (50 ml.) is prepared and filtered
at room temperature. Piperidine (1.0 g.) is added and the reaction
mixture is heated for 10 minutes. A precipitate is formed and
collected upon cooling and then washed with ethanol. The yield of
dye is 2.83 g. (75% yield) having a melting point of
230.degree.C.
Analysis: Calculated: C, 67.0%; A, 4.3%; N 7.4%. Found: C, 66.9%;
H, 4.4%; N 6.9%.
EXAMPLE 4
6[(3-Ethyl-2-benzoselenazolinylidene)ethylidene]4-nitro-2,4-cyclohexadienon
e ##SPC7##
A solution of 3-ethyl-2-methylbenzoselenazolium p-toluenesulfonate
(3.49 g., 0.01 mole) and 5-nitrosalicyladehyde (1.67 g., 0.01 mole)
is prepared in ethanol (45 ml.) and filtered at room temperature.
Piperidine (0.87 g., 0.01 mole) is added and the reaction mixture
is heated for 10 minutes. A solid precipitates and is collected and
washed with ethanol. The yield of dye after drying is 2.78 g. (75%
yield) having a melting point of 239.degree.C. The dye can be
reversibly bleached with visible light.
Analysis: Calculated: C 54.7%; H 3.8%; N 7.5% Found: C 54.4%; H
3.8%; N 7.3%
EXAMPLE 5
6-[(1-Ethylnaphtho[2,3-d]thiazolin-2-ylidene)ethylidene]-4-nitro-2,4-cycloh
exadienone ##SPC8##
A solution of 1-ethyl-2-methylnaphtho[2,3-d]thiazolium
p-toluenesulfonate (4.0 g., 0.01 mole) and 5-nitrosalicyladehyde
(1.67 g., 0.01 mole) in ethanol (100 ml.) is prepared and filtered
at room temperature. Piperidine (0.87 g., 0.01 mole) is added to
the solution and the reaction mixture is refluxed for 15 minutes.
After cooling, the dye is collected and washed with ethanol. This
provides 2.5 g. of product. This material is dissolved in m-cresol
with slight warming and filtered hot. Boiling methanol is then
added until the dye begins to crystallize. After cooling, the dye
is collected, washed and dried. The yield of dye is 0.9 g. (24%
yield) having a melting point of 207.degree.-209.degree.C.
Analysis: Calculated: C, 67.0%; H, 4.3%. Found: C, 67.0%; H,
4.6%.
EXAMPLE 6
6-Nitro-2',3'-dihydro-1',3',3'-trimethylspiro(2H)-1-benzopyran-2,2'(1H)pyrr
olo[2,3-b]pyridine ##SPC9##
A solution of 2-methylene-1,3,3-trimethyl-3H-pyrrolo[2,3-b]pyridine
(3.2 g., 0.02 mole) and 5-nitrosalicylaldehyde (3.34 g., 0.02 mole)
is refluxed for 1 hour in ethanol (50 ml.) containing a drop of
piperidine. Upon cooling, a solid crystallizes from the reaction
mixture. The solid is recrystallized from ethanol-methylcyclohexane
to obtain 1.7 g. (26% yield) of a colorless solid having a melting
point of 163.degree.-164.degree.C. Photocoloration is observed when
solutions of this compound are irradiated with UV light.
EXAMPLE 7
6-[(1,3-Diethyl-2-benzimidazolinylidene)ethylidene]4-nitro-2,4-cyclohexadie
none ##SPC10##
A solution of 1,3-diethyl-2-methylbenzimidazolium iodide (3.16 g.,
0.01 mole), 5-nitrosalicylaldehyde (1.67 g., 0.01 mole) and
piperidine (0.87 g.) is refluxed in ethanol (15 ml.) for one hour.
Upon cooling, the dye precipitates and is collected, washed with
ethanol and dried. This provides 2.86 g. of dye. The material is
recrystallized once from dimethylformamide to obtain 1.0 g. of dye
having a melting point of 271.degree.C. (dec.). Color changes are
observed when solutions of this dye are irradiated.
Analysis: Calculated: C, 67.6%; H, 5.7%; N 12.5%. Found: C, 67.5%;
H, 6.0%; N 12.4%.
EXAMPLE 8
6-[(3-Ethyl-2-benzoxazolinylidene)ethylidene]-4-nitro-2,4-cyclohexadieneone
##SPC11##
A mixture of 3-ethyl-2-methylbenzoxazolium iodide (2.89 g., 0.01
mole), 5-nitrosalicylaldehyde (1.67 g., 0.01 mole) and piperidine
(1.0 g.) is refluxed in tetrahydrofuran (75 ml.) for 20 minutes.
The dye precipitates and after cooling is collected, washed with
tetrahydrofuran and dried. This provides 2.4 g. of dye. This
material is digested in water, collected and dried. This solid is
then recrystallized from m-cresol-methanol to obtain 1.87 g. (60%
yield) of dye having a melting point of 228.degree.-230.degree.C.
Solutions of the dye can be reversibly photobleached with visible
light.
EXAMPLE 9
6-[(1-Ethyl-4(1H)-quinolylidene)ethylidene]-4-nitro2,4-cyclohexadienone
This dye is prepared by the procedure described in Example 3 in an
88% yield. The product has a melting point of
260.degree.-262.degree.C.
Analysis: Calculated: C, 71.2%; H, 5.0%. Found: C, 71.0%; H,
5.1%.
EXAMPLE 10
6-[(3-Ethylnaphtho[2,1-d]thiazolin-2-ylidine)ethylidene]-4-nitro-2,4-cycloh
exadienone
This dye is prepared by the procedure described in Example 5 in a
75% yield. The product has a melting point of
239.degree.-240.degree.C. and is photoactive.
EXAMPLE 11
6-[(5,6-Dichloro-1,3-diethyl-2-benzimidazolinylidene)ethylidene]-4-nitro-2,
4-cyclohexadienone
This dye is prepared by the procedure described in Example 3 in an
86% yield. The product has a melting point of
292.degree.-294.degree.C. (dec.) and is photoactive.
Analysis: Calculated: C, 58.8%; H, 4.4%. Found: C, 58.6%; H,
4.4%.
EXAMPLE 12
6-[(3,4-Diphenyl-4-thiazolin-2-ylidene)ethylidene]4-nitro-2,4-cyclohexadien
one
This dye is prepared by the procedure described in Example 7 except
that the product is recrystallized from ethanol. The product is
obtained in a 19% yield, has a melting point of
192.degree.-197.degree.C. and is photoactive.
EXAMPLE 13
6-[(1-Methyl-2(1H)-quinolylidene)ethylidene]-4nitro-2,4-cyclohexadienone
This dye is prepared by the procedure described in Example 3 in an
82% yield. The product has a melting point of
250.degree.-253.degree.C.
Analysis: Calculated: C, 70.6%; H, 4.6%. Found: C, 70.5%; H,
4.6%.
EXAMPLE 14
6-[(3-Ethyl-2-benzothiazolinylidene)ethylidene]-4nitro-2,4-cyclohexadienone
This dye is prepared by the procedure desribed in Example 3 in a
72.5% yield. The product has a melting point of
235.degree.-240.degree.C. and is photoactive.
Analysis: Calculated: C, 62.6%; H, 4.3%. Found: C, 62.7%; H,
4.4%.
EXAMPLE 15
6-[(1,3-Diethyl-1H-imidazo-[4,5-b]quinoxalin-2(3H)ylidene)ethylidene]-2-met
hoxy-4-nitro-2,4-cyclohexadienone
This dye is prepared by the procedure described in Example 5 in a
25% yield. The product has a melting point of 241.degree.C. and is
photoactive.
Analysis: Calculated: C, 63.0%; H, 5.0%. Found: C, 62.6%; H,
5.2%.
EXAMPLE 16
6-[(3-Ethyl-2-benzothiazolinylidene)ethylidene]-2-methoxy-4-nitro-2,4-cyclo
hexadienone
This dye is prepared by the procedure described in Example 3 in a
50% yield. The product has a melting point of
242.degree.-244.degree.C.
Analysis: Calculated: C, 60.7%; H, 4.5%. Found: C, 61.0%; H,
4.7%.
EXAMPLE 17
6-[(1-Methylnaphtho[1,2-d]-thiazolin-2-ylidene)ethylidene]-2-nitro-2,4-cycl
ohexadienone
This dye is prepared by the procedure described in Example 3 in an
85% yield. The product has a melting point of
202.degree.-206.degree.C. and is photoactive.
Analysis: Calculated: C, 66.3%; H, 3.9%. Found: C, 66.0%; H,
4.0%.
EXAMPLE 18
6-[(3-Ethyl-2-benzothiazolinylidene)ethylidene]-2-nitro-2,4-cyclohexadienon
e
This dye is prepared by the procedure described in Example 7 except
that the product is recrystallized in ethanol. The product is
obtained in a 16% yield, has a melting point of
191.degree.-193.degree.C. (dec.), and is photoactive.
Analysis: Calculated: C, 62.6%; H, 4.3%. Found: C, 62.6%; H,
4.3%.
EXAMPLE 19
3,5-Dibromo-6-[(3-ethyl-2-benzothiazolinylidene)ethylidene]-2,4-cyclohexadi
enone
This dye is prepared by the procedure described in Example 3 in an
85% yield. The product has a melting point of
194.degree.-196.degree.C.
Analysis: Calculated: C, 48.2%; H, 3.1%. Found: C, 47.9%; H,
3.3%.
EXAMPLE 20
6-[(1,3-Diethyl-1H-imidazo[4,5-b]quinoxalin
-2(3H)-ylidene)ethylidene]2,4-dinitro-2,4-cyclohexadienone
This dye is prepared by the procedure described in Example 3 in a
56% yield. The product has a melting point of 274.degree.C. (dec.)
and is photoactive.
Analysis: Calculated: C, 58.1%; H, 4.2%. Found: C, 57.9%; H,
4.5%.
EXAMPLE 21
6-[(1-Methylnaphtho[1,2-d]thiazolin-2-ylidene)ethylidene]-2,4-dinitro-2,4-c
yclohexadienone
This dye is prepared by the procedure described in Example 5 in a
36% yield. The product has a melting point of 303.degree.C. (dec.)
and is photoactive.
Analysis: Calculated: C, 59.0%; H, 3.2%. Found: C, 59.1%; H,
3.3%.
EXAMPLE 22
6-[(5,6-Dichloro-1,3-diethyl-2-benzimidazolinylidene)ethylidene]-2,4-dinitr
o-2,4-cyclohexadienone
This dye is prepared by the procedure described in Example 5 in a
6% yield. The product has a melting point of 325.degree.C. (dec.)
and is photoactive.
Analysis: Calculated: C, 50.6%; H, 3.6%. Found: C, 50.9%; H,
3.7%.
EXAMPLE 23
4-Nitro-6-[(4,5,6,7-tetrachloro-1,3-diethyl-2-benzimidazolinylidene)ethylid
ene]-2,4-cyclohexadienone
This dye is prepared by the procedure described in Example 3 in a
50% yield. The product has a melting point of 250.degree.C. (dec.)
and is photoactive.
Analysis: Calculated: C, 48.0%; H, 3.2%. Found: C, 48.2%; H,
3.5%.
EXAMPLE 24
6-[(3-Ethyl-4-phenyl-4-thiazolin-2-ylidene)ethylidene]-4-nitro-2,4-cyclohex
adienone
This dye is prepared by the procedure described in Example 3 in a
90% yield. The product has a melting point of
221.degree.-222.degree.C. (dec.) and is photoactive.
Analysis: Calculated: C, 64.8%; H, 4.6%. Found: C, 64.7%; H,
4.5%.
EXAMPLE 25
6-[(1,2-Dihydropyrrolo[2,1-b]benzothiazol-3-yl)methylene]-4-nitro-2,4-cyclo
hexadienone
This dye is prepared by the procedure described in Example 3 in a
65% yield. The product has a melting point of
254.degree.-255.degree.C.
Analysis: Calculated: C, 62.9%; H, 3.7%. Found: C, 62.6%; H,
3.7%.
EXAMPLE 26
6-[(2,3-Dihydro-1H-pyrido[2,1-b]benzothiazol-4-yl)methylene]-4-nitro-2,4-cy
clohexadienone
This dye is prepared by the procedure described in Example 3 in a
54% yield and is digested in ethanol. The product has a melting
point of 234.degree.-239.degree.C. (dec.).
EXAMPLE 27
6-[(1-Ethylnaphtho[1,2-d]thiazolin-2-ylidene)ethylidene]-2,4-dinitro-2,4-cy
clohexadienone
This dye is prepared by the procedure described in Example 3 in a
39% yield. The product has a melting point of
308.degree.-309.degree.C. and is photoactive.
EXAMPLE 28
2,4-Dibromo-6-[(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)ethylidene]-2,4-cy
clohexadienone
This dye is prepared by the procedure described in Example 5 in a
75% yield. The product has a melting point of 190.degree.C. and is
photoactive.
EXAMPLE 29
3,5-Dichloro-6-[(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)ethylidene]-2,4-c
yclohexadienone
This dye is prepared by the procedure described in Example 3 in a
53% yield. The product is recrystallized from a mixture of dimethyl
formamide, methanol and hexane. The product has a melting point of
215.degree.-217.degree.C. and is photoactive.
EXAMPLE 30
3,5-Dichloro-6-[(3-ethylnaphtho[2,1-d]thiazolin-2-ylidene)ethylidene]-2,4-c
yclohexadienone
This dye is prepared by the procedure described in Example 30 in a
50% yield. The product has a melting point of 217.degree.C. and is
photoactive.
EXAMPLE 31
3,5-Dichloro-6-[(3-ethyl-2-benzothiazolinylidene)ethylidene]-2,4-cyclohexad
ienone
This dye is prepared by the procedure described in Example 5 in a
58% yield. The product has a melting point of
142.degree.-148.degree.C. and is photoactive.
EXAMPLE 32
3,5-Dichloro-6-[(3-methyl-2-benzothiazolinylidene)ethylidene]-2,4-cyclohexa
dienone
This dye is prepared by the procedure described in Example 11 in a
42% yield. The product has a melting point of
216.degree.-217.degree.C. and is photoactive.
EXAMPLE 33
6,8-Dibromo-1',3'-diethyl-2',3'-dihydrospiro[2H]-1-benzopyran-2,2'-(1H)-imi
dazo[4,5-b]quinoxaline
This dye is prepared by the procedure described in Example 3 in a
36% yield. The product is recrystallized from methylene chloride,
has a melting point of 136.degree.-137.degree.C. and is
photoactive.
EXAMPLE 34
6-[(1-Ethylnaphtho[1,2-d]thiazolin-2-ylidene)ethylidene]-2-methoxy-5-nitro-
2,4-cyclohexadienone
This dye is prepared by the procedure described in Example 3 in a
40% yield. The product is recrystallized from a mixture of dimethyl
formamide and ethanol. The product has a melting point of
240.degree.-241.degree.C. and is photoactive.
EXAMPLE 35
6-[(3-Ethylnaphtho[2,1-d]thiazolin-2-ylidene)ethylidene]-2-methoxy-5-nitro-
2,4-cyclohexadienone
This dye is prepared by the procedure described in Example 11 in a
59% yield. The product has a melting point of 239.degree.C. and is
photoactive.
EXAMPLE 36
2-Methoxy-6-[(1-methyl-naphtho[1,2-d]thiazolin-2ylidene)]-4-nitro-2,4-cyclo
hexadienone
This dye is prepared by the procedure described in Example 3 in a
97% yield. The product has a melting point of
251.degree.-254.degree.C.
Analysis: Calculated: C, 64.3%; H 4.1%. Found: C, 64.5%; H
4.3l%.
Depending upon the nature of the nitrogen-containing heterocyclic
nucleus, i.e., the group ##EQU2## the dyes at ambient temperatures
exist in either the merocyanine open colored form of Formula I or
the closed colorless spiropyran form of Formula II. Regardless of
which form they are in at ambient temperatures, they generally may
be converted to the other form. Thus, these dyes exhibit extremely
efficient photochromic behavior. By control of the dye structure
and the exciting wavelength, the dyes may be used in either
negative or positive silver halide photographic systems. The dyes
of Formula I are particularly useful as spectral sensitizers for
direct positive silver halide photographic systems and for organic
photoconductors.
Photographic silver halide emulsions which can be spectrally
sensitized by the dyes of this invention can comprise, for example,
silver chloride, silver bromide, silver bromoiodide, silver
chlorobromide, silver chloroiodide, silver chlorobromoiodide
crystals or mixtures thereof. Suitable emulsions are described in
Product Licensing Index, Volume 92, December 1971, Publication
9232, page 107, Paragraph I.
The silver halide emulsions can be unwashed or washed to remove
soluble salts after precipitation of the silver halide as described
in the aforementioned Product Licensing Index reference at page
107, Paragraph II.
The dyes of this invention are advantageously incorporated in the
washed, finished emulsion and should be uniformly distributed
throughout the emulsion. The dyes can be added from solutions in
appropriate solvents which are compatible with the emulsion and
which are substantially free from deleterious effects on the light
sensitive materials.
The types of silver halide emulsions that can be sensitized with
the new dyes of this invention include those prepared with
hydrophilic colloids that are known to be satisfactory vehicles for
dispersed silver halides as described in the aforementioned Product
Licensing Index reference at Paragraph VIII.
The concentration of the new dyes in the emulsion can vary widely,
e.g., from about 5 to 100 mg. per liter of flowable emulsion
containing, for example, 50 g. of silver bromide per liter. The
specific concentration will vary according to the type of
light-sensitive material in the emulsion and the effects desired.
The suitable and most economical concentration for a given emulsion
will be apparent to those skilled in the art upon making the tests
and observations customarily used in the art of emulsion
making.
To prepare a gelatin-silver halide emulsion sensitized with one of
the dyes of this invention, the following procedure is
satisfactory. A quantity of the dye is dissolved in a suitable
solvent and a volume of this solution containing from 5 to 100 mg.
of dye is slowly added to one liter of a gelatin-silver halide
emulsion. With most of the dyes, 10 to 20 mg. of dye per liter of
emulsion suffices to produce the maximim sensitizing effect with
the ordinary gelatin-silver bromide (including bromoiodide and
chlorobromide) emulsions. With fine grain emulsions, which include
most of the ordinarily employed gelatin-silver chloride emulsions,
somewhat larger concentrations of dye may be necessary to obtain
the optimum sensitizing effect. While this procedure has dealt with
emulsions comprising gelatin, it will be appreciated that these
remarks apply generally to any emulsion wherein all or part of the
gelatin is substituted by another suitable hydrophilic colloid as
mentioned above.
Photographic silver halide emulsions containing the sensitizing
dyes of this invention can also contain other addenda such as
chemical sensitizers, e.g., reducing agents; sulfur, selenium or
tellurium compounds; gold, platinum or palladium compounds; or
combinations of these. Procedures for chemically sensitizing silver
halide emulsions are described in Sheppard et al. U.S. Pat. No.
1,623,499 issued Apr. 5, 1927; Waller et al. U.S. Pat. No.
2,399,083 issued Apr. 23, 1946; McVeigh U.S. Pat. No. 3,297,477
issued Jan. 10, 1967 and Dunn U.S. Pat. No. 3,297,446 issued Jan.
10, 1967. The emulsions can contain development modifiers that
function as speed increasing compounds such as polyalkylene
glycols, cationic surface active agents and thioethers or
combinations of these as described in Piper U.S. Pat. No. 2,886,437
issued May 12, 1959; Dann et al U.S. Pat. No. 3,046,900 issued July
12, 1960 and Goffe U.S. Pat. No. 3,294,540 issued Dec. 27,
1966.
The silver halide emulsions can be protected against the production
of fog and can be stabilized against loss of sensitivity during
keeping. Useful antifoggants and stabilizers are listed in the
aforementioned Product Licensing Index reference at Paragraph
V.
The photographic silver halide emulsions of this invention can be
coated on a wide variety of supports. Typical supports include
cellulose nitrate film, cellulose acetate film, poly(vinyl acetal)
film, polystyrene film, poly(ethylene terephthalate) film,
polycarbonate film and related films or resinous materials, as well
as glass, paper, metal and the like. Typically, a flexible support
is employed, especially a paper support, which can be partially
acetylated or coated with baryta and/or an alpha-olefin polymer,
particularly a polymer of an alpha-olefin containing 2 to 10 carbon
atoms such as polyethylene, polypropylene, ethylenebutene
copolymers and the like.
Photographic elements having silver halide emulsions coated thereon
can contain developing agents such as those listed in the
aforementioned Product Licensing Index reference at Paragraph VI.
The emulsions layers can be hardened by various organic or
inorganic hardeners, alone or in combination, such as those
disclosed in the aforementioned Product Licensing Index reference
at Paragraph VII.
The photographic layers of this invention may also include other
addenda known to be beneficial in photographic emulsions such as
those listed in the Product Licensing Index reference at Paragraphs
IV, XI, XII and XIII.
EXAMPLE 37
The sensitizing effects of several of the dyes described above are
illustrated in the following tabulation where the sensitizing range
and sensitizing minimum values are shown for these dyes. The dyes
are tested in a bromoiodide direct positive emulsion containing 2.5
mole percent iodide and having an average grain size of 0.2 micron
as described in Berriman U.S. Pat. No. 3,367,778. The dyes,
dissolved in suitable solvents are added to separate portions of
the emulsion at the concentrations indicated. The emulsions are
chemically fogged and are coated at a coverage of 100 mg. of silver
per square foot on a cellulose acetate film support. A sample of
each coating is exposed on an Eastman 1B Sensitometer, processed
for 6 minutes in an Elon-hydroquinone developer, fixed, washed and
dried. The photographic results from these tests are set forth in
Table I.
TABLE I ______________________________________ Dye Concentration
(mg/mole of silver Sensitizing Sensitizing Example halide) Range
(nm) Maximum (nm) ______________________________________ 1 400 to
590 550 2 200 to 580 550 3 200 to 550 630 4 200 to 580 550 5 400 to
600 550 7 200 to 470 -- 9 200 to 470 -- 10 400 to 560 530 11 200 to
470 -- 12 200 to 470 -- 14 400 to 575 535
______________________________________
EXAMPLE 38
The dyes of Examples 1 to 7, 9 to 12 and 14 are tested in a silver
bromoiodide emulsion containing 2.5 mole percent iodide and having
an average particle size of 0.2 micron. The dyes, dissolved in
suitable solvents, are added to separate portions of the emulsion
at the concentrations indicated in Table II. The emulsions are
digested at 40.degree.C. for 10 minutes and coated at a coverage of
100 mg. of silver per square foot on a cellulose aacetate film
support. A sample of each coating is then exposed to a mercury
vapor lamp for a 365 nm emission on a spectrophotometer to obtain
the sensitizing range. The coatings are processed to 6 minutes in
an Elon-hydroquinone developer, fixed, washed and dried. The
photographic results from these tests are set forth in Table
II.
TABLE II ______________________________________ Dye Concentration
Sensi- (mg/mole of silver tizing Desensitization Example halide)
Range (nm) in Log E Units ______________________________________ 1
100 to 484 -.27 2 100 to 480 -.40 3 200 to 470 -.75 4 100 to 465
-1.02 5 100 to 460 -1.37 6 100 to 485 -.01 7 100 to 500 +.07 sens.
9 100 to 485 -.28 10 100 to 485 -.30 11 100 to 510 -.03 12 100 to
490 -.05 14 100 to 485 -.35
______________________________________
EXAMPLE 39
As previously noted, the merocyanine dyes of Formula I and the
spiropyran compounds of Formula II exhibit photochromic behavior.
To illustrate this effect, various tests are conducted on the
compounds shown in Table III. The tests are carried out in test
tubes at room temperature using a 200 watt Xenon flash lamp. In
most cases, photobleaching is more efficient when an ultraviolet
filter is placed between the lamp and the sample. Table III sets
forth the photochromic properties of the dyes tested in various
solvents. The notation "decolorized" indicates that the dye is
photobleached. For most of the dyes, the values for
.lambda..sub.max and E .times. 10.sup.4 are determined at the time
the solution is prepared and again after 24 hours. In the last 4
columns of Table III, the numbers in parentheses are the values for
E .times. 10.sup.4 and the numbers which are not in parentheses are
the values of .lambda..sub.max. The notation "s" following a value
for .lambda..sub.max indicates the presence of a shoulder on a
larger absorption band.
In all cases the 24 hour reading represents the position of
thermodynamic equilbrum. In many cases while the dye form was
isolated the solution equilibra involves some spiropyran
(colorless) form.
TABLE III
__________________________________________________________________________
.lambda..sub.max (E .times. 10.sup.4) 10% M-Cresol- Photoactivity
Pyridine 90% Ethyl Alcohol Dye of Example Number Methanol Pyridine
Initial After 24 hrs. Initial After 24 hrs.
__________________________________________________________________________
1 color color spiropyran 525 (0.23) forms forms stable 2 decolor-
decolor- 570 not soluble 510 (2.95) 510 (2.83) ized ized dye stable
3 decolor- decolor- 570 (5.13) 570 (4.95) 513 (3.08) 513 (2.47)
ized ized dye stable dye stable 4 decolor- decolor- 570 (3.69) 570
(2.91) 522 (2.91) 522 (1.94) ized ized mostly dye some dye 14
decolor- decolor- 565 (4.24) 563 (1.45) 511 (3.08) 511 (3.02) ized
ized mostly spiropyran mostly dye at equilibrum 5 decolor- decolor-
582 (2.84) 582 (0.08) 533 (3.69) 533 (3.09) ized ized all
spiropyran all dye at equilibrum 10 decolor- decolor- 575 (3.44)
575 (3.10) 518 (2.03) 518 (1.85) ized ized mostly dye mostly dye 12
no decolor- 553 (3.40) 553 (3.29) 502 (1.54) 502 (1.37) change ized
all dye all dye 9 no no 605 (3.84) 605 (3.71) 529 (2.30) 529 (2.24)
change change all dye all dye 10 no no 541 (3.69) 541 (3.69) 480
(2.31) 480 (2.27) change change all dye all dye 13 no no 573 (4.75)
572 (2.46) 508 (2.88) 508 (2.77) change change some spiropyran all
dye 12 no no 518 (3.46) 518 (3.14) 457 (2.08) 457 (1.84) change
change all dye mostly dye 11 color color 496 (2.09) 510s(0.82) 426
(2.25) 415 (2.25) change change 445 (2.25) 438 (2.56) 409 (2.13)
undergoes cis-trans isomerism 7 color color 441 (2.61) 438 (2.81)
427 (1.67) 417 (1.60) change change change in 395s(1.55) curve
shape undergoes cis-trans isomerism 37 no no change change 592
(3.51) 592 (3.45) 541 (2.53) 541 all dye 15 color color 609 (0.14)
561 (2.98) 561 (0.84) generated generated all spiropyran all
spiropyran 16 no no 589 (4.51) 589 (4.21) 541 (3.31) 541 change
change all dye 18 decolor- ized 19 no no 605 (3.83) 605 (3.51) 552
(2.50) 552 change change mostly dye 20 color decolor- 544 (4.81)
544 (0.65) 492 (1.56) 492 (1.17) change ized mostly spiropyran
mostly dye 21 not decolor- 535 (3.66) 535 (3.18) 491 (2.63)
491s(0.98) soluble ized mostly dye mostly spiropyran or
decomposition
__________________________________________________________________________
Dye Numbers 7 and 11 are not decolorized but definite changes in
color are observed. Dye Number 15 gives an initially weak colored
solution, the color being intensified by flashing in the absence of
an ultraviolet filter. The failure of photobleaching to occur in
Dye Numbers 15, 16 and 37 may be caused by a very rapid thermal
return in these systems. The 2-methoxy group appears to be
responsible for this effect. The most efficient compounds in the
photobleaching reactions are those derived from
5-nitrosalicylaldehyde and which contain 5-member heterocyclic
nuclei. The data in Table III indicates that the dye form is
generally more stable when the heterocyclic nuclei become more
basic.
The following examples illustrate the behavior of dyes in polymers
of varying polarity and the effect of metal ions and metal
chelates, particularly of the rare earth series, on stabilizing the
dye in either the merocyanine or the spiropyran form:
EXAMPLE 40
This example employs Dye Number 1 of Table III which in most
polymers and solutions exists as the closed (colorless) spiropyran
and forms the intensely colored merocyanine (blue-purple) when
exposed to light with a wavelength of less than 400 nm. The colored
form is rapidly bleached by light of wavelength greater than 400
nm. A solution of the dye, dissolved in pyridine, is added to a 10%
solution of a 50% butyl acrylate-50% styrene copolymer in ethyl
acetate, so as to give a 10.sup.-.sup.5 M concentration of the dye
in the polymer solution. The resulting highly colored solution
fades to colorless shortly after mixing. The solution is
hand-coated on a conductive polyethylene terephthalate film base at
a knife setting of 0.008 inches under red safelights, then air
dried. A portion of this coating is exposed to an ultraviolet lamp
(140 watts) for 15 seconds through a resolving-power chart (etched
chrome plated quartz glass). The exposed area of the coating
becomes a deep purple, giving an excellent color negative. This
negative image can be bleached immediately to give the colorless
spiropyran by exposure to light from a photoflood lamp (150 watts)
of a wavelength greater than 400 nm or by exposure for 15 minutes
under conditions of normal lighting (about 100 ft. cdls.). The
re-exposure of the resulting colorless film to ultraviolet light
intensifies the previously unexposed areas with the background
considerably less colored. This image appears as a positive and
indicates some dye fatigue after the first exposure to ultraviolet
light. This latent image positive can be repeatedly intensified
after bleaching by exposure to ultraviolet light. When the
colorless, previously unexposed, film is intensified in a
non-imagewise manner by exposure to ultraviolet light and then
imagewise exposed to light of wavelength greater than 400 nm, the
resulting positive can be bleached with visible light, then
re-intensified with ultra-violet light, and imagewise exposed with
visible light without a trace of the first exposure (i.e., no
latent image). This procedure may also be repeated many times. It
is thus seen that fatigue occurs during exposure to ultraviolet
light (but either not at all or to a much lesser extent) during
exposure to visible light (less than 400 nm). The coating is also
thermally sensitive, and by subjecting the coating to heat, the
photochromic system will revert to the colorless spiropyran in
seconds.
EXAMPLE 41
Dye Number 1 of Table III and Dye Number 23 having the formula
##SPC12##
are dissolved in pyridine and mixed with a solution of a polymer as
described in Example 40. The mixture of Dye Number 1 in solution is
initially colored and changes to colorless when coated or upon
standing. Both the solution and coating of Dye Number 23 are pink.
The coating containing Dye Number 23 slowly turns dark brown at
which point the coating is relatively stable. Exposure of this
coating to ultraviolet light gives little intensification and the
coating does not bleach to light of wavelength greater than 400 n.
If exposures are made shortly after coating, the image is stable
for several days to light of wavelength greater than 400 nm, and is
stable for several weeks if kept in the dark.
The following example illustrates the stabilization of a
photochromic system in either its merocyanine form or the
spiropyran form by forming an insoluble metal salt or complex of
the available oxygen or sulfur on the nucleus of the merocyanine
dye or by complexing the closed spiropyran.
EXAMPLE 42
A mixture of 3 .times. 10.sup.-.sup.5 mole of Dye Number 1 and 1
.times. 10.sup.-.sup.5 mole of a europium chelate salt having the
formula ##SPC13##
in a butylacrylate-styrene polymer is dissolved in a mixture of
pyridine and ethyl acetate. Before the addition of the europium
chelate salt, the polymer solution containing Dye Number 1 is
purple. The solution immediately turns magenta upon the addition of
the europium chelate salt. The mixture turns colorless when coated
on a substrate and then turns red after several days if kept in the
dark. When this coating is exposed imagewise to an ultraviolet
light source of 140 watts, the exposed area becomes magenta. This
material is faster to form an image that the corresponding polymer
solution in the absence of the europium chelate salt and is fairly
stable to tungsten light. Under conditions of normal lighting, the
dye-image fades within 2-3 hours. The coating containing the metal
chelate retains its image for many weeks if kept in the dark
whereas the same coating without the metal chelate fades in 15
minutes. The coating containing the metal chelate turns red upon
heating and cannot be photobleached whereas the same coating which
does not contain the metal chelate rapidly turns colorless when
heated.
EXAMPLE 43
Example 42 is repeated substituting Dye Number 23 for Number 1.
Separate coatings are made containing cadmium, cobalt, mercury,
silver and zinc ions instead of the europium chelates used in
Example 42. These coatings have an excellent image to background
density after imagewise exposure to ultraviolet light. The dye
image is stable up to one week when viewed periodically under
tungsten light and the remainder of the time stored in a
refrigerator in the dark. At equilibrium, the dye exists in the
merocyanine form, and after a week's time becomes colored and
blends with the image. At this point, the coatings are stable to
tungsten, ultraviolet light and heat. The color of the coating
containing the dye alone, i.e., containing no metal ions, is brown,
the color of the coating containing cadmium ions is brown, the
color of the coating containing cobalt ions is tan, the color of
the coating containing silver ions is yellow and the color of the
coating containing zinc ions is brown.
As used in the structural formulas herein, "C.sub.2 H.sub.5 " is an
ethyl group and "C.sub.6 H.sub.5 " is a phenyl group.
The invention has been described in detail with reference to
particular embodiments thereof, but it will be understood that
variations and modifications can be effected within the spirit and
scope of the invention as described hereinabove and as defined in
the appended claims.
* * * * *