JPH04232941A - Layer for forming thermal developing photosensitive image containing dye which can undergo photo-bleach - Google Patents

Abstract

PURPOSE: To provide a negative effect thermal photographic image forming system which produces a sharp and stable image by avoiding such disadvantages of conventional techniques that (1) sensitization of a UV-sensitive photoinitiator is necessary and (2) an image is unstable (for a printout product) due to thermal interaction of the UV-sensitive photoinitiator and leuco dyes. CONSTITUTION: By this method, an image forming layer containing nitrate, leuco dye and a dye which can be photobleached. The compsn. is usually supported by a binder such as a polymer binder. The binder also may contain an org. acid.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to photosensitive imaging layers, and more particularly to photographic imaging layers containing nitrate salts, leuco dyes, photobleachable dyes, binders, and optionally added organic acids. Ultraviolet radiation sensitive initiators sensitized by the photobleachable dyes described above may also be present.

0002

BACKGROUND OF THE INVENTION Many methods and compositions using leuco dyes to provide optical density are known in the imaging art. For example, U.S. Patent No. 4,017,313
No. 1, a photographically sensitizing leuco dye, a photosensitizer for the dye, an aromatic aldehyde, and a secondary or tertiary amine are used in combination. Other photographic sensitizing systems using leuco dyes are U.S. Pat. No. 3,390,997;
No. 4,326, and No. 2,772,284. The mechanism of these latter two patents is “Aromatic aldehyde-leuco dye photooxidation (Aromatic
Aldehyde-Leuco Dye Photo
oxidation)”, H. D. Hartzler
zler), Pure Appl. Chem. , 197
9, Vol. 49, pp. 353-356.

``Light-Sensing System''
tive Systems)”, Koser, J. (
Kosar, J. ), John Wiley and Sons, New York, 1965, No. 3
On page 69, there is a printout (
A print-out photosensitive system is described. Since these are printout types, thermal amplification (thermal
amplification) does not exist.

Photocuring of polymerizable materials (eg, negative-action printing plates), photolysis of materials (eg, positive-action printing plates), photoinitiated diazonium salt coupling reactions (
A large number of photosensitive materials have been used in the past in different imaging processes using various photoinitiated phenomena, such as diazonium microfilms, etc. Equivalents of other photoinitiators in certain ethylenically unsaturated printing plate compositions (e.g., U.S. Pat. No. 3,741,769) include cationic and epoxy polymerization (e.g., U.S. Pat. No. 4,026, No. 705, No. 3,981
A class of indonium photoinitiators has also been proposed (1997).

Thermographic imaging systems are well known in the art. A thermographic system is defined as a photosensitive imaging system that is thermally developed. Thermographic systems are typically 80-2
Requires a development temperature in the range of 00°C. Many imaging systems use photosensitive compounds, leuco or bleachable dyes, and nitrate salts to produce color images.

An imaging system sensitive to ultraviolet (UV) light containing a leuco or bleachable dye, a nitrate ion, and a diazonium salt in a binder is disclosed in US Pat. No. 4,730,401. has been done. In such cases where leuco dyes are used, a negative working imaging system thermographic material is provided. That is, a final image is obtained in which the exposed areas have a higher optical density than the unexposed areas. Conversely, if bleachable dyes are used, a positive working thermographic imaging system is provided. That is, the optical density of unexposed areas in the final image is denser than that of exposed areas. The bleachable dyes used in this case do not play the role of sensitizers or photoinitiators.

A related imaging composition containing a diazonium salt and a leuco dye in a binder is described in US Pat. No. 4,394,433. These non-amplified compositions are positive-action thermographic compositions and are fundamentally different from the compositions of the present invention, which are amplified by the action of nitrate salts.

Other photosensitive thermally developable imaging systems are known. No. 4,460,677 describes a thermally developable imaging system containing a leuco dye, a nitrate ion, and a spectrally sensitized organic compound having a photodegradable halogen atom. Similarly, U.S. Pat. No. 4,386,154 describes leuco dyes, nitrate ions, and (1) aromatic iodonium salts and (2)
A thermally developable imaging system is described containing a spectrally sensitizing compound selected from photodegradable halogen atom-containing compounds. Both of these compositions act as negative imaging systems and thermally develop very good image density in the exposed areas. This latent image is formed by exposure to visible light, and an image is formed by thermal development. The color fidelity and contrast of both these systems is reduced by the presence of the sensitizer stain. This sensitizer stain is a color due to unreacted sensitizer in unexposed areas and colored by-products derived from the reacted sensitizer in exposed areas. This sensitizer stain reduces the aesthetic value of the image. Furthermore, the presence of (1) aromatic iodonium salts or (2) compounds containing photodegradable halogen atoms generally results in image printouts lasting from minutes to days under ambient conditions. .

Heat-developable photosensitive imaging systems are also described in several Japanese patents.

Japanese Patent No. 77,025,330 discloses that oxazine or phenothiazine leuco dye (BLM
Two-component UV light-sensitive positive-working imaging compositions are described consisting of B) (mono- or di-substituted or partitioned with dialkylamino groups), and an oxidizing agent such as a nitrate ion.

Japanese Patent No. 77,004,180 describes the use of triplet sensitizers for BLMB. Suitable sensitizers are aromatic carbonyl compounds and aromatic nitro compounds. This patent describes a negative system and a positive system, and Japanese Patent No. 77,02
Corresponds to No. 5,330. The compositions described herein are UV light sensitive. However, the compositions of this invention are sensitive over the visible spectrum from 400 to 700 nm. The compounds described in this patent are not the same as the compounds used in the present invention.

Japanese Patent No. 76,035,847 describes a photosensitive heat-fixable recording material containing a free radical-generating organohalogen compound, a leuco dye and a base. This is a negative-acting system that does not contain oxidizing agents.

Japanese Patent No. 77,025,088 discloses that acid-sensitive leuco dyes (eg naphthospiropyran), organic halides (eg C
BR4), a photochemical acid generator, is described.

Japanese Patent No. 79,001,453 discloses an oxidizing agent, a compound that changes color or develops color by reacting with the oxidizing agent, and a compound that deactivates the color developer in exposed or unexposed areas. The containing thermographic materials are described. The images may be positive or negative and do not use sensitizers or diaryliodonium salts or organic compounds with photodegradable halogen atoms, which are components of the present invention that activate rather than deactivate the color developer. The photosensitive material used is a colorless or nearly colorless arylquinone, and an ultraviolet light source is used. Furthermore, the photosensitive materials used here are not photobleachable.

A decolorizable imaging system containing a binder, a nitrate salt, an acid, and a dye is described in US Pat.
No. 36,323 and No. 4,373,020. These systems are particularly useful as antifogging layers in thermographic systems where the dye is bleached by the development temperature.

It is known in the art to use photobleachable dyes containing o-nitroarylidenes as antifogging or arcutance dyes. For example, U.S. Patent Nos. 4,111,699 and 4,271
, No. 263, No. 4,088,497, No. 4,03
No. 3,948, No. 4,028,113, No. 3,9
No. 88,156, No. 3,988,154, No. 3,
No. 984,248 and RE No. 3,615,432 (RE No. 28,225). This use of photobleachable dyes has no bearing on the functionality of this invention. Additionally, o-nitroarylidene dyes have been found to desensitize silver halide imaging systems.

Spectral sensitization of silver-containing thermographic compositions is described in US Pat. No. 4,461,828.

No. 4,713,312 describes background sensitization in imaging systems based on photosensitive microcapsules by using photobleachable sensitizers in the 390-500 nm range for free radical polymerization. It is described that it reduces stains. This patent states that 500 to 700 nm is necessary for full color reproduction.
Complete removal of residual sensitizer stain is not provided because the sensitizer used over the m range is not photobleachable. Therefore, stain is added to the background in unexposed areas.

[0019]

SUMMARY OF THE INVENTION Briefly stated, the present invention provides nitrate salts,
A thermographic imaging layer containing a leuco dye, a photobleachable dye, a binder, and optionally an organic acid is provided.

The present invention provides an imaging layer comprising a nitrate salt, a leuco dye, and a photobleachable dye. These compositions are usually supported by binders, such as polymeric binders, and these binders may also contain organic acids.

The image forming layer of the present invention comprises exposed areas of the composition,
and, if necessary, subsequent development followed by blanket irradiation.
It also reduces residual sensitizer stain in both unexposed areas. Additionally, exposing the blanket irradiated imaging layer to ammonia vapor thermally stabilizes (fixes) the layer.

With the composition of the present invention, lower than 5×104 ergs/cm2 and
Sensitivity to visible light (the exposure required to produce an image) of even less than The generation of amplification is then clearly demonstrated.

The present invention solves the drawbacks of the conventional technology (1) U
By overcoming the drawbacks of the need to sensitize the V-sensitive photoinitiator and (2) image instability (printout) caused by thermal interaction of the UV-sensitive photoinitiator with the leuco dye. A negative action thermographic imaging system is provided that produces clear and stable images.

According to the present invention, a binder, a leuco dye,
A novel thermographic imaging layer containing nitrate ions, a photobleachable dye, and optionally an organic acid is achieved. After exposing the system, the application of heat oxidizes the leuco dye in the exposed or unexposed areas more rapidly, thereby forming an image corresponding to the negative-positive image used. This image results depending on the differential rate at which oxidation occurs in exposed and unexposed areas. A latent image is formed by exposure to visible light, followed by thermal development to form a stable image, and optionally exposure to blanket light;
Then exposed to ammonia vapor. No solution treatment step is required.

[0025]

DESCRIPTION OF THE INVENTION There are at least four types of components in the image forming layer of the present invention. The four components are (1) a photobleachable dye, (2) a nitrate salt, (3) a leuco dye, and (
4) Polymer resin (binder). Acidic materials constitute a preferred fifth component.

Photobleachable Dyes The term photobleachable refers to dyes from about 350 to about 1100 nm.
This means that the dye is converted into a colorless or nearly colorless form (ie the molar absorbance is reduced by at least a factor of 5) by actinic radiation during m. Photobleachable sensitizers useful in the present invention are bleached by at least 10%, preferably at least 25% and more preferably at least 50% when exposed to the conditions set forth below. 0.1 to 0.6 by coating polyethylene terephthalate (4 mils thick) with this sensitizer.
Forms a colored film upon absorption of . The tinted film is then placed on the Fresnel lens of a 3M brand model 213 overhead projector and exposed for 5 minutes.

The photobleachable sensitizer is bleached at a given percentage when this layer contains a sensitizer that reduces the absorption (absorption intensity) at the longest wavelength absorption band maximum by the given percentage. It is said that This absorption is measured by measuring the percent reduction in optical density provided by the sensitizer or the percent of radiation actually absorbed.

[0028] This overhead projector has 3
General Electric 82V with a color temperature of 3300°K
Using an ENX 360W single projection bulb. The light intensity at the mage stage is 0.46 W/cm2±0.05 W/cm2.

Compounds useful as photobleachable dyes of the present invention include, but are not limited to, o-nitro-substituted arylidene dyes and arylnitrone dyes. As used herein, the term "arylidene" refers to a group formed from an aryl group and a methine linking group (eg, benzylidene, cinnamylidene, etc.). o-Nitro-substituted arylidene dyes typically contain nitrogen,
o-nitro- linked through a methine chain linking group to a basic heterocyclic nucleus containing an electron-donating atom such as oxygen or sulfur
It has a substituted aryl group. The number of atoms bonding the electron donating atom and the aryl group is an even number or an odd number.

In a preferred embodiment, the o-nitro-
The substituted aryl group is bonded to a 5- or 6-membered basic cyanine-type heterocyclic nucleus through an acyclic methine chain having an even or odd number of methine groups. The heterocyclic nuclei can further have carbocycles and heterocycles fused thereto. The o-nitro-substituted aryl group may have a phenyl or heterocyclic nucleus. Alternatively, the o-nitro-substituted aryl group can have a core formed by a fused aromatic or heteroaromatic ring, such as naphthyl. U.S. Patent No. 3,984,248
No. 3,988,154, No. 3,988,15
No. 6 and No. 4,271,263 describe several o-nitroarylidene dyes as arcutance dyes in heat-developable photographic sensitizing compositions. U.S. Pat. No. 4,095,981 describes several o-nitroarylidene dyes as energy-sensitive dyes in silver-based photographic or thermographic materials.

In a particularly preferred embodiment of the invention, the o-nitro-substituted dye has three formulas. Formula (I)
is shown below.

embedded image where k is 0 or 1, m is 0 or 1,
L is a substituted methine group (e.g. -CH=, -C(CH3)
is a methine group that includes oxygen (-O-, etc.), and A is oxygen (-O-
), sulfur (-S-), or an electron-donating moiety such as >N-R1.

R1 is (1) an alkyl group having 1 to 18 carbon atoms, preferably a lower alkyl group having 1 to 4 carbon atoms (for example, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, isobutyl, tert
-butyl); a sulfoalkyl group, preferably a sulfo-lower alkyl group having 1 to 4 carbon atoms in the alkyl moiety (e.g., β-sulfoethyl, γ-sulfopropyl, γ-sulfobutyl, etc.); a carboxyalkyl group,
Carboxy lower alkyl groups, preferably having 1 to 4 carbon atoms in the alkyl moiety (e.g. β-carboxyethyl, γ-carboxypropyl, δ-carboxybutyl, etc.); sulfoalkyl groups, preferably having 1 to 4 carbon atoms in the alkyl moiety sulfato lower alkyl groups (e.g. β-sulfatoethyl, γ-sulfatopropyl, δ-sulfatobutyl, etc.); alkoxyalkyl groups, preferably lower having 1 to 4 carbon atoms in both the alkoxy and alkyl moieties Alkoxy lower alkyl groups (e.g. β-methoxyethyl, γ-
methoxypropyl, δ-propoxybutyl, etc.); acyloxyalkyl groups, preferably acyloxy lower alkyl groups having 1 to 4 carbon atoms in the alkyl moiety (
acetyloxyethyl, propanoyloxyethyl, butanoyloxybutyl, benzoyloxyethyl, tolyloxypropyl, etc.); alkoxycarbonylalkyl groups, preferably lower alkoxycarbonyl having 1 to 4 carbon atoms in both the alkoxy and alkyl moieties Lower alkyl groups (e.g. β-methoxycarbonylethyl, δ-ethoxycarbonylbutyl,
β-butoxycarbonylethyl, etc.); dialkylaminoalkylene groups, preferably di-lower alkylamino-lower alkylene groups having 1 to 4 carbon atoms in the alkylene and alkyl moieties (e.g. dimethylaminoethylene, diethylaminopropylene, diethylaminobutylene, etc.); cyclo Aminoalkylene groups, preferably cycloamino lower alkyl groups having 4 to 6 atoms in the cycloamino moiety and 1 to 4 atoms in the alkyl moiety (e.g. pyrrolidinylethylene, morpholinopropylene, piperidinebutylene, pyrrolidinylmethylene (2) alkenyl groups (including substituted alkenyl groups), preferably lower alkenyl groups containing 2 to 4 carbon atoms (e.g., ethyl, allyl, 1-propenyl, 1-butenyl, 2-butenyl, etc.); or (3) aryl groups (including substituted aryl groups), such as phenyl, naphthyl, tolyl, xylyl, halophenyl (e.g. p-
chlorophenyl, p-bromophenyl, etc.), alkoxyphenyl (e.g. methoxyphenyl, 2,4-dichlorophenyl, etc.), and alkyl groups, preferably aryl lower alkyl groups having 1 to 4 carbon atoms in the alkyl moiety (e.g. benzyl, β-phenethyl, o
-fenbutyl, etc.); or (4) hydrogen.

Y is an atom that necessarily completes an aryl (preferably a phenyl or naphthyl ring). The aryl ring is o-nitro-substituted, preferably p-substituted with nitro or other electron-withdrawing groups, and it may have other substituents and other fused carbocycles fused to it, e.g. , 2-nitrophenyl, 2,4-dinitrophenyl, 2,6-dinitrophenyl, 2,4,6-trinitrophenyl, 2-nitronaphthyl, 2,4-dinitronaphthyl, 2-nitro-4-cyanophenyl , 2-
nitro-4-ethoxycarbonylphenyl, 2-nitro-4-trifluoromethylphenyl, etc.).

Z is a nonmetallic atom that necessarily completes a heterocyclic nucleus of the type used in cyanine dyes having 5 or 6 atoms in the electron-donating heterocycle of this formula. The heterocycle may have a second heteroatom such as oxygen, nitrogen, selenium or sulfur. This preferred heterocyclic nucleus is
Thiazole nuclei having substituted and unsubstituted benzothiazole and naphthothiazole nuclei (e.g., 0-thiazole, 4-methylthiazole, 4-phenylthiazole, 4,5-diphenylthiazole, 4-(2-thienyl)thiazole, benzothiazole) , 4-chlorobenzothiazole, 4-methylbenzothiazole, 4-methoxybenzothiazole, 4-ethoxybenzothiazole, 4
-Phenylbenzothiazole, 5-chlorobenzothiazole, 5-bromobenzothiazole, 5-methylbenzophenylbenzothiazole, 5-methoxybenzothiazole, 5-ethoxybenzothiazole, 6-chlorobenzothiazole, 6-ethoxybenzothiazole, 5 -methoxynaphtha[2,3-d]thiazole, 5-nitrobenzothiazole, 6-nitrobenzothiazole, 5-chloro-6-nitrobenzothiazole, etc.); Oxazole nucleus having substituted and unsubstituted benzoxazole and naphthoxazole nuclei etc. (e.g., oxazole, 4-phenyloxazole, benzoxazole, 5-phenyloxazole,
-chlorobenzoxazole, 5-methylbenzoxazole, 5-bromobenzoxazole, 5-methoxybenzoxazole, 5-ethoxybenzoxazole, 5-phenylbenzoxazole, 5-nitrobenzoxazole, 6-nitrobenzoxazole, 5-chloro -6-nitrobenzoxazole, etc.); substituted or unsubstituted benzoselenazole and selenazole core containing naphthoselenazole core, etc. (for example, selenazole, 4-methylselenazole, 4-nitroselenazole,
4-phenylselenazole, benzoselenazole, 5-
Chlorobenzoselenazole, 6-chlorobenzoselenazole, naphtho[2,1-l]selenazole, 5-nitrobenzoselenazole, 6-nitrobenzoselenazole,
5-chloro-6-nitrobenzoselenazole, nitro group-substituted naphthoselenazole, etc.); thiazoline nucleus (e.g., thiazoline, 4-methylthiazoline, 4-nitrothiazoline, etc.); 2-pyridine nucleus (e.g., 2-pyridine, 5-methyl-2-pyridine, etc.); 4-pyridine nucleus (e.g., 4-pyridine, 3-methyl-4-pyridine, nitro-substituted pyridine, etc.); 3,3-dialkylindolenine nucleus (e.g., 3,3 -dimethylindolenine, 3,3-diethyl-5- or 6-cyanoindolenine, 3,3-diethyl-5- or 6-nitroindolenine, 3,3-dimethyl-5- or 6-nitroindolenine, etc. ); imidazole nuclei (e.g., imidazole, 1-alkylimidazole, benzimidazole, 1,3-dialkyl, 1,3-diaryl, or 1-alkyl-3-arylimidazole and benzimidazole (e.g., 5-chloro-1, 3-Dialkylbenzimidazole, 5-chloro-1,3-diarylbenzimidazole, 5-methoxy-1,3-dialkylbenzimidazole, 5-methoxy-1,3-diarylbenzimidazole, 5-cyano-1,3- dialkylbenzimidazole, 5-cyano-1,3-diarylbenzimidazole, 1,3-dialkylnaphtho[1,2-d]imidazole, 1,3-diarylnaphtho[1,2-d]imidazole, etc.); quinoline nucleus (
For example, quinoline, 6-methylquinoline, 6-methoxyquinoline, 6-ethoxyquinoline, 6-ethoxyquinoline, 6-chloroquinoline, 4-methoxyquinoline, 4-
methylquinoline, 8-methoxyquinoline, 2-methylquinoline, 4-chloroquinoline, 6-nitroquinoline, etc.); imidazo[4,5-b]quinoxaline core (e.g. imidazo[4,5-b]quinoxaline, 1, 1,3-dialkylimidazo[4,5-b] such as 3-diethylimidazo[4,5-b]quinoxaline, 6-chloro-1,3-diethylimidazo[4,5-b]quinoxaline
1,3-diallylimidazo[4,5
-b]quinoxaline, 1,3-dialkenylimidazo[4,5-b]quinoxaline such as 6-chloro-1,3-diallylimidazo[4,5-b]quinoxaline, etc.
1,3-diphenylimidazo[4,5-b]quinoxaline, 6-chloro-1,3-diphenylimidazo[4,5
1,3-diarylimidazo[4,5-b]quinoxalines such as -b]quinoxalines); ,3-b]pyridine, 3,3-diethyl-3H-pyrrolo[2,3-b]pyridine.
, 3-dialkyl-3H-pyrrolo[2,3-b]pyridine, 1,3,3-triethyl-3H-pyrrolo[2,3-
b] 1,3,3-trialkyl-3H such as pyridine
-pyrrolo[2,3-b]pyridine, etc.); and from the group consisting of thiazolo[4,5-b]quinoline nuclei, pyrylium (including benzopyrylium, thiapyrylium, and benzothiapyryllium) nuclei, and dithiolinium nuclei. selected. Formula (II) is shown below.

embedded image Here, R2 is hydrogen, an alkyl group of 1 to 18 carbon atoms, or an aryl group of 6 to 10 carbon atoms, optionally a halogen, an alkoxy group of 1 to 6 carbon atoms, or an alkoxy group of 6 to 10 carbon atoms. an alkyl or aryl group substituted by an aryl group, and R2 is preferably hydrogen, and R3 and R4 are each independently hydrogen, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms, or a halogen and R5 is halogen, nitro, cyano, 1-6
It is a carbalkoxy group of a carbon atom or a halogen, and R6 and R7 together constitute a benzo group. Formula (I
II) is shown below.

embedded image where R2 to R7 are as defined above and R8 is hydrogen, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms, or a halogen.

In another preferred embodiment, the spectrally sensitized initiator is an arylnitrone of formula (IV).

embedded image where k is as defined above, R9 is an aryl or substituted aryl group (e.g., phenyl, tolyl, naphthyl, anthracenyl, etc.), and R10 and R11
each independently represents an electron-rich substituted aryl or heterocyclic group (e.g., p-dimethylaminophenyl, 4-methoxy-1-naphthyl, 2-furanyl, N-methylpyrrol-2-yl, thiophen-2-yl, etc.) ), and hydrogen. However, R10
and R11 are both not hydrogen.

The photobleachable dye should be present at least 0.05% by weight of the dry imaging layer, with a maximum of 1.5% by weight or more. Preferably they are present at 0.075-1.25%, more preferably 0.1-1.0% by weight of this layer.

Binders Any natural or synthetic water-insoluble polymer binder can be used in the present invention. Organic polymeric resins (generally thermoplastic resins, although thermosetting ones may also be used) are preferred. If speed is important, water-insoluble, water-impermeable, water-resistant polymers should be used, and acids may need to be added to the system to increase the rate of coloration (i.e., leuco dye oxidation). be. Resins such as phenoxy resins, polyesters, polyvinyl resins, polycarbonates, polyamides, polyvinyl acetals, polyvinylidene chloride, polyacrylates, cellulose esters, copolymers and mixtures of such classes of resins are preferably used. If the proportion and activity of leuco dyes and nitrate ions require specific development times and temperatures,
The resin must be resistant to such conditions. Generally, this polymer has a temperature of 3 at 200°F (93°C).
It does not decompose or lose its structural integrity at 0 seconds, more preferably at 260°F (127°C). Preferred polymers include polyvinylidene chloride resins (e.g., Saran™, supplied by Dow Chemical Co., Midland, MI), phenoxy resins (e.g., Hackensack, NJ). , PKHHTM and PAHJTM from Union Carbide) and polyvinyl formals (e.g. MO, St. Louis (
St. Louis), Monsanto Chemical (Mons
Formvar™ provided by Anto Chemical Co., Ltd.

[0038] Since the performance requirements are not so great, there is no criticality regarding the selection of binder. In practice, transparency and translucency are also not essential conditions. However, it is desirable that it be transparent or translucent.

[0039] This binder plays a number of additional important roles in the construction of the invention. The imageable material is protected from ambient conditions such as moisture. The consistency of the coating and the quality of this image are improved. Also, the durability of the final image is significantly improved. The binder should be present in the layer at least about 25% by weight of the ingredients, preferably 50 or 70%, and more preferably at least about 80% by weight of the dry ingredients (i.e. excluding solvent in this layer). It must exist in A generally useful range is 30 to 98 weight percent binder, with 75 to 95 weight percent preferred.

Nitrate Salts Nitrate salts themselves are well known. They can be supplied as various chemical compounds. However, it is preferably provided as a metal salt, more preferably as a metal hydride salt. Other ions that are common good oxidizing ions such as nitrite, chlorate, iodate, perchlorate, periodate, and persulfate do not provide satisfactory results. Extremely active oxidizing agents such as iodates do not perform as well as nitrate ionic compositions even when used in relatively small amounts to prevent complete oxidation and immediate oxidation or coloration of the dye. Interestingly, nitrate exhibits superior performance compared to other ions in implementing the present invention.

[0041] Most methods of providing the nitrate salt in the composition can be used in the present invention, such as:
Organic salts, metal salts, acid salts, mixtures of acids and salts and other means of providing this ion are useful. For example, zinc,
Cadmium, potassium, calcium, zirconyl (Zr
O2), nickel, aluminum, chromium, iron, copper, magnesium, lithium, lead and cobalt, ammonium nitrate, cerium (III) ammonium nitrate, and combinations thereof.

[0042] The nitrate salt component of the present invention is prepared by heating the image forming layer to a temperature not exceeding 200°C for 60 seconds, preferably at 16°C.
60 seconds or most preferably 30 seconds at a temperature not exceeding 0°C.
Sufficient amount of HNO to oxidize when heated for seconds
3, NO, NO2, or N2O4 is preferably present in an amount sufficient to form the layer. This is accomplished by many different types of salts, such as organic and inorganic salts, and a variety of different configurations.

The most preferred method of providing such a thermal oxidant-providing nitrate salt is to provide a hydrated nitrate such as hexahydrated magnesium nitrate (Mg)NO3)2x6H2O.

In addition to hydrated nitrate salts, non-hydrated salts such as ammonium nitrate, pyridinium nitrate, and guanidium nitrate under acidic environments also provide the oxidizing capacity required to practice this invention. provide.

In addition to the inorganic types of salts generally described above, organic salts in non-alkaline environments are also useful in the practice of this invention. In particular, nitrated quaternary ammonium salts such as guanidium nitrate perform very well in acid environments. However, this does not provide useful images in basic environments.

Any oxidants released from the nitrate salt (eg HNO3, NO, NO2 and/or N
2O4) is neutralized by an alkaline environment, which is thought to inhibit the oxidation of leuco dyes. Therefore, an acidic environment is preferred for nitrate salts. Another consideration should be made in the selection of nitrate salts. That is, the cation in the salt must be non-reactive with the dye. Non-reactive salts, as defined in the practice of this invention, are those having cations that do not spontaneously oxidize the dyes present with them at room temperature. This can be measured in many ways. For example, the dye and the non-nitrate (preferably halide) salt of the cation can be co-dissolved in solution. If this salt spontaneously oxidizes the dye (within 2 minutes) at room temperature,
This is a reactive salt. While cerium (IV) nitrate is reactive, hydrated cerium (III) nitrate is not.

Preferred salts are nickel nitrate hexahydrate, magnesium nitrate hexahydrate, aluminum nitrate 9hydrate, iron(III) nitrate 9hydrate, copper(II) nitrate trihydrate, zinc nitrate hexahydrate. , tetrahydrate cadmium nitrate, pentahydrate bismuth nitrate, tetrahydrate thorium nitrate, hexahydrate cobalt nitrate, 9
Hydrated metal salts such as hydrated gadolinium or lanthanum nitrate, mixtures of these hydrated nitrates. The nonahydrate (eg lithium nitrate) or organic nitrate can be mixed together.

Organic nitrates are also very useful in the practice of this invention. These nitrates are usually
Quaternary nitrogen forms include compounds such as guanidium nitrate, pyridinium nitrate, and the like. Preferably, it has at least 1.10 moles of nitrate ions per mole of leuco dye. More preferably at least 0.30 or 0.50 moles per mole of dye. Typically, the nitrate will constitute from 0.005 to 10%, preferably from 0.1 to 10%, more preferably from 0.5 to 8% by weight of the imaging layer.

Leuco Dyes Leuco dyes are well known. These are colorless compounds;
Forms colored dyes upon oxidation. Such leuco dyes are well described in the art (e.g., U.S. Pat. No. 3,974,147; Mace, C.
．． E. K. (Mees, C.E.K.), James, R. (James, R.), Theory of Photographic Processes (T.
he theory of photography
Process), 3rd edition, MacMillan
llan), New York, No. 283-284, 39
pp. 0-391; and Koser, J. (Kosar,
J. ), photosensitive system (Light-Sensitive
Systems), Joan Wiley & Sons, New York, 1965, No. 367, 370
~380, 406 pages). Only such leuco dyes that can be converted to colored dyes by oxidation are useful in the practice of this invention. Preferred such leuco dyes are acylated leucodiazine, phenoxazine, and phenothiazine dyes, examples of which are described in U.S. Pat.
No. 677, No. 4,647,525, and British Patent No. 1,271,289.

Acid- or base-sensitive dyes such as phenolphthalein and other indicator dyes are not useful in this invention. The indicator dye only forms a temporary image;
They are too sensitive to changes in the environment.

The leuco dye is present in an amount of at least about 0.3% by weight, preferably at least 1% by weight of the total weight of the photosensitive layer. More preferably, it is present in an amount of at least 2 to 10% or more (eg, 15%) by weight of the dry weight of the imaging layer. About 10 mol% nitrate/leuco dye is the minimum proportion used, preferably 20-80 mol%, 35-65 mol%
is even more preferable. Nitrate/dye mole percent ratios greater than 100% are certainly useful. The leuco dye is usually 0.5 to 15% by weight of the imaging layer, preferably 2% by weight of the imaging layer.
It accounts for ~8% by weight.

Initiator The term "initiator" as used herein refers to either a diaryliodonium salt or a photodegradable organohalogen compound. Each of these two types of initiators are known in the art.

The diaryliodonium salt of the present invention is represented by the following formula.

embedded image wherein R5 and R6 are each selected from aromatic groups. Such aromatic groups may have 4 to 20 carbon atoms with substantially all substituents (e.g., substituted or unsubstituted phenyl, naphthyl, thienyl, and furanyl).
, W is a carbon-carbon bond, oxygen, sulfur,

embedded image where R7 is aryl (e.g. 6-2
0 carbon atoms) or acyl (e.g., 2 to 20 carbon atoms), or R8-C-R9, where R8 and R9 are hydrogen, an alkyl group of 1 to 4 carbon atoms, and an alkyl group of 2 to 4 carbon atoms. atomic alkenyl group, p is 0 or 1
and Q- is any anion.

Here, the term "group" refers to a substituent, for example, an ether group (eg, CH3
-CH2-CH2-O-CH2-), haloalkyl, nitroalkyl, carboxyalkyl, hydroxyalkyl, and the like. On the other hand, the term "alkyl" refers only to hydrocarbons. Substituents that react with the active ingredient, such as very strongly reducing or oxidizing substituents, are not sensitometrically inert or non-hazardous and are therefore naturally excluded.

When a photodegradable organic halogen compound is irradiated, one or more carbon-halogen bonds are cleaved to form free radicals. The carbon-halogen bond cleavage energy should be between 40 and 70 kcal/mol. This is reflected in U.S. Patent No. 3,515,5.
No. 52, and No. 3,536,481. Preferred halogen compounds are not gases at room temperature and have polarographic half-wave reduction potentials greater than about -0.9V. This is discussed in U.S. Pat. Nos. 3,640,718, 3,617,288, and 3,779
It is described in No. 778.

Examples of diaryliodonium cations useful in the practice of this invention include diphenyliodonium, di(4-chlorophenyl)iodonium, 4-trifluoromethylphenylphenyliodonium, 4-
Examples include ethylphenylphenyliodonium, di(4-acetylphenyl)iodonium, tolylphenyliodonium, anisylphenyliodonium, 4-butoxyphenylphenyliodonium, di(4-phenylphenyl)iodonium, di(carbomethoxyphenyl)iodonium, etc. . Examples of this iodonium cation are U.S. Pat. Nos. 3,729,313 and 4,076.
, No. 705, and No. 4,386,154. Bis-type forms of such initiators may also be used.

Examples of photodegradable organic halogen compounds include:
Hexabromoethane, α, α, α', α'-tetrabromoxylene, carbon tetrabromide, m-nitro(tribromoacetyl)benzene, α, α, α-trichloroacetanilide, trichloromethylsulfonylbenzene, tribromoquinal Zine, bis(pentachlorocyclopentadiene)
, tribromomethyldinoxaline (tribromo
methylduinoxaline), α,α-dibromo-p-nitrotoluene, α, α, α, α', α',
α'-Hexachloro-p-xylene, dibromotetrachloroethane, pentabromoethane, dibromodibenzoylmethane, carbon tetraiodide, 2,4-bis(trichloromethyl)-6-methyl-s-triazine, 2,4,6 -tris(trichloromethyl)-s-triazine, and 2
, 4-bis(trichloromethyl)-6-(p-methoxystyryl)-s-triazine.
Examples include triazine. Such compounds are described in U.S. Pat. No. 3,515,552, U.S. Pat. No. 3,536,489, U.S. Pat.
No. 4,386,154 and No. 3,779,
No. 778.

Acidic Materials The speed can be increased by adding acidic materials to the photosensitive layer. Acids used in the present invention are generally known by those skilled in the art. Organic acids are preferred. However, inorganic acids (generally at relatively low concentrations) are also useful. Most preferred are organic acids having carboxyl groups. The acid should be present at least about 0.1% by weight of the total weight of the photosensitive layer. More preferably the acid is present in an amount of 0.2 to 2.0 times the amount of nitrate ions. For example, the acid may be 0.05 to 10% by weight, preferably 0.05% to 10% by weight.
It may be present in an amount of 1 to 7% by weight, more preferably 0.5 to 5% by weight. Generally, high molecular weight acids are used in high concentrations and low molecular weight acids are used in low concentrations. Anhydrides such as phthalic anhydride, maleic anhydride, succinic anhydride, acetic anhydride, and the like may also be used.

In forming or coating the imaging layer on the substrate, the temperatures used during the process should not be such that the layer becomes colored or the photobleachable dyes decompose. Several color reactions are resistant to selected initial leuco dye concentrations that vary predictably. However, it is preferred that no or very little leuco dye be oxidized during this formation and coating. A more stabilized layer is thereby formed. Depending on the expected development temperature, the coating or forming temperature can vary. Therefore, if the expected development temperature is, for example, 220
If the temperature is 104°F (104°C), this drying temperature is 140°C.
°F (60°C). In this case, therefore, this layer hardly increases in optical density if left at this drying temperature for less than 6 to 7 minutes. A suitable developing temperature range is 160-350°F (71-177°C).
), and the preferred standing time is between 3 seconds and 2 minutes,
5-60 between 175-250°F (79-121°C)
Seconds are preferred. Longer, lower development times are also commonly used.

The image-forming layer of the present invention requires reactive association under certain conditions in the active ingredient in order to be imageable. That is, the individual components may or may not be separated in layers by impermeable barriers (ie, do not dissolve, break or fragment during use). Generally, the active ingredients are intimately mixed (eg, molecularly mixed) into the layer. They are individually maintained in a thermoplastic binder. The thermoplastic binder is dispersed or mixed into the layer. This thermoplastic binder is softened by heating, allowing the components to move. However, such heating requires a longer period of time than the development time. These components are incorporated into a binder medium and their microparticles are then incorporated into a second layer binder medium according to U.S. Pat.
No. 708,928.

The imaging layer of the present invention may contain various materials in combination with the essential components of the present invention. For example, plasticizers, coating aids, antioxidants (e.g. ascorbic acid, hindered phenols, phenidone, etc., which are used in amounts to prevent oxidation of the dye when heated), surfactants, antistatic agents, etc. In addition to agents, waxes, UV absorbers, nitrates, weak oxidizing agents, and brighteners may be used in the practice of this invention without adverse effect.

What is not taught by the prior art, and which is revealed by the present invention, is that photobleachable photosensitive photoinitiators can be used in combination with nitrate salts and leuco dyes, thereby increasing the photosensitive A thermally developable imaging system is provided. Visible light sensitive systems are desirable to reproduce all natural colors; ultraviolet light or blue sensitive photoinitiators are not desirable.

Additionally, by eliminating the need for iodonium salts or organohalogen-containing compounds, the compositions of the present invention increase the stability of images developed by reductive printout.

When using photobleachable dyes with observable absorption in the visible spectrum, residual dye stain in the exposed areas is reduced after development. A further blanket exposure may remove the dye stain in the unexposed areas. It is then fixed by treatment with ammonia vapor. This improves the contrast, color fidelity, and light fastness of the developed imaging system across the visible spectrum.

[0065]

EXAMPLES Other aspects of the invention, such as its advantages over the prior art, are illustrated in the following non-limiting examples.

Unless otherwise indicated, materials used in the following examples were purchased from Aldrich Chemical, Milwaukee, WI.
It was purchased from Al). The novel materials prepared in the following examples were identified using one or more of the analytical methods listed below. Infrared absorption spectrum, ultraviolet absorption spectrum, 1H nuclear magnetic resonance spectrum, and mass spectrum. We also used the abbreviations listed below. Tetrahydrofuran (THF), methanol (MeOH), ethanol (EtOH), tris(trichloromethyl)-1,
3,5-triazine (TTT), diphenyliodonium hexafluorophosphate (Ph2I), melting point (m
p), boiling point (bp).

The terms "Dmax and Dmin" refer to the maximum and minimum values of optical density, respectively, measured in the layer in which this image was developed. The optical density is
MacBeth (MacBet) using Status A Red or Green filters as required.
h) TD504 densitometer (Newburgh, NY, Kollmo
rgen Corp)). basic·
Basic Blue 3-benzoyl leuco is Pergascript Turquoise from Ciba-Geigy (Ardsley, New York).
Purchased under the trademark of uoise) TM. The structures of the dyes used in the examples of the present invention are shown at the end as Formulas 1 to 52.

[0068]

EXAMPLE 1 O-nitroarylidene dyes of the type shown in Table 1 were prepared according to the procedure described in U.S. Pat. No. 3,988,154.

[Table 1]

[0069]

Example 2 O-nitroarylidene dyes of the type shown in Table 2 below were prepared according to the procedure described in U.S. Pat. No. 4,271,263.

[Table 2]

[0070]

[Example 3] 2-(2-nitrobenzylidene)-1,3
-diethyl-1,2-dihydroimidazo[4,5-b]
Preparation of Quinoxaline 36. 2.06 g (5 mmol) of 2-methylene-1,3- in 20 ml of butyronitrile
Diethyl-1,2-dihydroimidazo[4,5-b]quinoxalinium p-toluenesulfonate, 0.70g
(5 mmol) o-fluoronitrobenzene, 1.3
A solution containing 0 g (10 mmol) diisopropylethylamine was heated to reflux for 6 days. The solvent was removed under reduced pressure and the crude solid was washed twice with 25 ml of hexane. This product was added in 25 ml batches of hot hexane (total 20
A brown-orange solid with a mp of 160-162°C was obtained by extraction with 0ml).

[0071]

Example 4 Preparation of dye 37. A violet-brown solid (mp 264-267°C) was obtained according to the procedure described in US Pat. No. 3,988,154 using 4-fluoro-5-nitrophenylsulfone (Aldrich).

[0072]

Example 5 Preparation of Dye 38. U.S. Patent No. 3,988,
154, 4-fluoro-5
A dark brown solid (mp 156-159°C) was obtained from -nitrophenyl sulfone (Aldrich). 3ml THF
A solution containing 4 mg of Dye 39 was photobleached to an 86% colorless product after 5 minutes in a 3M Model 213 overhead projector.

[0073]

Example 6 This example shows that a system containing o-nitroarylidene dye 1 can effectively form photographic images with visible light. 10 mg o-nitroarylidene dye 1, 80 mg Basic Blue 3 benzoylleuco, 940 mg solution (MeOH 9 g, Mg(NO3
) 2x6H2O 0.2g, and tartaric acid 0.14g), and 7.5g 20% PK in THF
A coating solution was prepared by mixing HHTM. The solution was placed on a shaking table for 15 minutes at room temperature in the dark. Under suitable safe light, pour this solution into a 4 mil thick layer (
0.1 mm) clear polyethylene film to a wet thickness of 4 mils (0.1 mm), air dried for 15 minutes, and dried at 50° C. for 5 minutes. This dry film development temperature was determined using a 3M brand "179" Contact Printer Processor with a white tungsten light source.
1/8 inch x 2 inch side using
2 in the longitudinal direction with 32 exposure settings (approximately 8.5 x 105 microwatts/cm2 as determined by a radiometric filter).
Determined by exposure for 0 seconds. This small piece was sent to Reichert Heizbank.
nk) equipment (Austria, Kofler-Reichert (K
(Texp) in the exposed areas and the thermal limit (Texp) in the unexposed areas for 20 seconds.
Tunexp) was measured. Cyan color is 72℃ each.
and developed at 85°C. A 10 second exposure through the template after thermal development at 90° C. for 20 seconds produced a bright cyan transmission image as a negative of the original template. This image had a transmission optical density of Dmax=2.15 and Dmin=0.09 optical density units (measured with a Status A red filter on a Macbeth TD504 densitometer). Imaged and processed 8" x 2" (20.3 cm x 5.
1 cm) half of the strip was exposed for 5 minutes on a 3M brand model 213 overhead projector. The unexposed half of the UV spectrum was obtained. The λmax of Dye 1 was measured. Then, the optical density at λmax of the remaining exposed half was measured. The red background stain due to Dye 1 in the film was photobleached by 94% (i.e., reduced by 94% at λmax of the film);
This resulted in a virtually colorless background.

[0074]

Example 7 In this example, a system using o-nitroarylidene dye 1 provides superior photographic imaging in visible light and improved image stability compared to conventional halogenated compound configurations. Explain that it will be provided. An 8 inch by 2 inch (20 inch) dry film of Example 6
．． 3cm x 5.1cm) small piece with 3M brand “179”
Stouffer √2, 21 stage tablet (IN, South Bend) at 32 exposure settings with contact printer processor
nd), Stofel Graphic Arts (Sto
(Graphic Arts) for 10 seconds in the vertical direction. The pieces were processed on a drum processor at 90° C. with a dwell time of 20 seconds. This resulted in a negative of the original image with an 8 step cyan image with a transmission optical density greater than 1.0. Also, this cyan image has Dmin+0.6 (here, Dmax=2
．． (Macbeth TD50
4 densitometer with a Status A red filter). Processed samples were exposed for 2 hours on a 3M brand model 213 overhead projector. Dmin was increased by below 0.06 and Dmax was increased by 0.05 optical density units.

60 mg of 2 as described in Example 6
,4,6-tris(trichloromethyl)-1,3,5-
A control film containing triazine was prepared. This dry film measures 8 inches x 2 inches (2.3 cm x 5.1 cm).
cm) The strips were exposed vertically for 10 seconds through a Stoffel √2, 21 step tablet at a 32 exposure setting on a 3M brand "179" contact printer processor. The pieces were processed in a drum processor at 89° C. with a standing time of 20 seconds. This allows Dmin
An 8-level negative of the original image of a cyan image with an optical density of +0.6 was obtained. This treated sample was
Exposure was carried out for 2 hours using a 13-inch overhead projector. Dmin increased by 1.30 and Dmax increased by 0.50 optical density units (measured with a Status A red filter on a Macbeth TD504 densitometer).
.

[0076]

Examples 8-11 These examples demonstrate that systems containing o-nitroarylidene dye 1 alone provide improved image stability compared to conventional halide or iodonium compound configurations. show. A film was prepared in the same manner as in Example 6, except that 60 mg of the ingredients were added as needed. An 8 inch x 2 inch (20.3 cm x 5.1 cm) piece of each of these films was placed on the Reichart-Heitzbank apparatus for 20 seconds and
Exposures were made for 30 minutes on an M brand model 213 overhead projector. Dm on cyan background
The increase in in was determined on a Macbeth TD504 densitometer using a Status A red filter.

[0077]

[Table 3]

[0078]

Example 12 This example shows that the thermal development process is time and temperature dependent and therefore the development time or temperature range can be adjusted. Other films were prepared in a similar manner using the formulation of Example 6. This dry film measures 8 inches x 2 inches (20.3 cm x 5.1 cm).
) Stoffel small pieces at 32 exposure settings on a 3M brand "179" contact printer processor √2,2
Expose vertically for 10 seconds through a 1-stage tablet,
Heat developed for the times indicated to achieve similar Dmin levels. The development times and corresponding required temperatures are shown in Table 4.

[Table 4]

[0079]

Examples 13-18 These examples describe other negative working imaging systems. the indicated amount of o
- Nitroarylidene dye, 80 mg Basic Blue 3 benzoylleuco, 940 mg solution (MeO
H 9g, Mg(NO3)2×6H2O 0.26
g, and 0.14 g of succinic acid), 7.
A film was prepared according to the method described in Example 6 by using a coating solution containing 5 g of 20% PKHHTM in THF. The developing temperature of each dry film was set to 3.
Maximum exposure setting (approximately 2.4 x 106 microwatts/
cm2) for 20 seconds in the longitudinal direction of half an 8 inch by 2 inch piece. Place each piece on the Reichardt-Heitzbank apparatus for 20 seconds to determine the thermal limit of the exposed area (Texp) and the thermal limit of the unexposed area (Texp).
Tunexp) was measured. The sensitivity of each of this dry negative action film was adjusted to 1 at maximum exposure setting on a 3M brand "179" contact printer processor.
0 seconds Stoffel √ 2, 21 steps 8 inches x 2 inches (20.3 cm x 5.1 c) vertically through the tablet
m) Measured by exposing half of the piece to light. Each piece was processed on a drum processor with a dwell time of 20 seconds at the temperature that produced the Dmin level. The speed of each small piece (in number of stages) is determined by the transmission optical density Dm
in+0.6 optical density units (measured with a Macbeth TD504 densitometer with a Status A red filter) at one point. The amount of photobleaching of each film was measured as described in Example 6. The results for each film are shown in Table 5. and shows the common uses of various o-nitroarylidene dyes.

[0080]

[Table 5]

[0081]

Examples 19-26 These examples illustrate positive working imaging systems. Example 1 except that the velocity (in plate numbers) of each positive acting strip was measured at a point where the density was Dmax - 0.6 optical density units.
Films were prepared and evaluated in the same manner as in Examples 3 to 18. Table 6 shows the results for each film. The results also indicate general use for o-nitroarylidene dyes. Some are clearly more effective than others;
Both positive and negative images can be generated. It is important to note that the phenomena caused by imaging are not understood.

[0082]

[Table 6]

[0083]

Examples 27-28 Evaluations similar to those described in US Pat. No. 4,386,154 and US Pat. No. 4,460,677 were performed. A standard evaluation solution was prepared with the following composition. Polyvinyl butyral (molecular weight 45,00
0-55,000, hydroxyl content 9.0-13.
0%, Monsanto Chem.
．． Co. ) products with the trademark “Butvar-
50 g of 5% (wt/vol) methyl ethyl ketone solution of "B76", 0 trimethylolpropane trimethacrylate
．． 3 g, and 0.03 g of 2-methyl-4,6-bis(trichloromethyl)-1,3,5-triazine.

0.02 g of indicator dye was added to this solution. This solution was deposited on a 2.0 mil (0.05 mm) clear polyethylene terephthalate film.
The knife was coated using a knife orifice of mm). The coating was then air dried for 30 minutes. The other 2 mils (
A transparent polyethylene terephthalate film (0.05 mm) was carefully placed over the dried film. This dry film coating had minimal air entrainment and was a flexible, sticky coating. The laminate was then exposed to a 3M Model 70 light source (650 Watt tungsten lamp) for 15 seconds through a template with clear and opaque areas. The dyes of Examples 27 and 28 were substantially photobleached in the exposed areas. After exposure, the cover film was removed and the coating was treated with a finely divided black toner powder of the type commonly used in xerography. If the evaluation material was the sensitizer described in U.S. Pat. Bis(trichloromethyl)-1,3,5-triazine)-derived photogenerated free radicals. Since this polymerized area is substantially non-tacky, the black toner powder adheres selectively to the tacky, unexposed areas of the coating. Thereby, a visible image corresponding to the template is provided. The results shown in Table 7 are a comparison with a conventional sensitizing agent (5,10-diethoxy-16,17-dimethoxyviolanthrene). These examples are described in U.S. Patent No. 4,386.
, 154 and 4,460,677.

[0085]

[Table 7]

[0086]

Example 29 This example shows the process of preparing a transparent image. 20mg o-nitroarylidene dye 1, 160m
g basic blue 3 benzoyl leuco, 1.8
8g solution (27g MeOH, Mg(NO3) 2x6H
0.78 g of 2O, and 0.42 g of succinic acid), and 15 g of 20% PKHHT in THF
A film was prepared as in Example 6 using a coating solution containing M. The dried film was exposed through a color negative on a 3M brand "179" contact printer processor for 20 seconds at a 64 exposure setting and then heat developed at 82° C. with a dwell time of 20 seconds on a drum processor. This created a bright cyan transparent image on a red background as a negative of the original image. The image was exposed for 2-5 minutes on a 3M brand Model 213 overhead projector. The final image has the red background removed.

[0087]

Example 30 This example illustrates that sensitivity can be increased as the exposure temperature is increased. A film was prepared using the same formulation as in Example 6 and in a similar manner, except that the acid solution contained 0.14 g of succinic acid instead of tartaric acid. The dried film was stored in a dark bag at room temperature for two weeks. This dry film was passed through a Stoffel√2, 21-step tablet on a hot plate.
3 from film with 50 watt tungsten reflector
Exposure was made at a 0 inch point. This film was then thermally developed in a drum processor at 95°C for a standing time of 25 seconds. This created a bright cyan transparent image as a negative of the original image. This table shows Dmin+0.6
The number of developed cyan color steps in transmitted optical density (measured with a Status A red filter on a Macbeth TD504 densitometer) is shown. The number of cyan color steps with a transmitted optical density of 1.0 optical density or higher and Dmax for this exposure temperature are shown.

[0088]

[Table 8]

[0089]

Example 31 A film was produced in the same manner as in Example 30. Calibrate this dry film at room temperature (
calibrated visible light at 536 nm with a bandwidth of 20 nm in a densitometer through a Stoffel √2, 21 step tablet. This film was left on the drum processor for 25 minutes.
Thermal development was carried out at 91° C. for 2 seconds. This film is Dmin+0
．． 2000 ergs/ to produce a transmission optical density of 6
cm2 of light energy and an optical density of 1.0 (
A light energy of 2600 ergs/cm 2 was required to produce a Macbeth TD504 densitometer (measured with a Status A red filter).

[0090]

Example 32 A 4 mil filled opaque polyethylene terephthalate film was prepared as in Example 30. This dry film was exposed through a Stoffel √2, 21 stage tablet at a 32 exposure setting for 5 seconds on a 3M brand "179" contact printer processor and then exposed on a drum processor for a dwell time of 25 seconds 9.
Heat development was performed at 1°C. This image is 3M brand "No. 213"
The image was exposed for 5 minutes using an overhead projector. This produced a bright cyan image as a reflective print without any red background stain. At that time, the Dmax reflected optical density is 3.0 optical density units (Macbeth TR527
) as measured by a densitometer with a Status A red filter. Furthermore, nine levels of cyan color were produced with reflective optical densities greater than 1.0.

[0091]

Example 33 A film was produced in the same manner as in Example 30. This dry film is 8 inches by 2 inches (20.
3cm x 5.1cm)
79'' contact printer processor for 10 seconds at the 32 exposure setting and stored in the dark for the specified time. Each piece was placed in the Reichardt-Heitzbank apparatus for 20 seconds. Table 9 shows the time between exposure and thermal development and the difference in image temperature between exposed and unexposed areas (
ΔT°C).

[Table 9]

[0092]

Example 34 20 mg o-nitroarylidene dye 24, 80 mg benzoylleuco of Basic Blue 3, 0.94 g solution (MeOH 27 g, Mg(
NO3)2×6H2O0.78g and succinic acid 0.4
20 in THF), and 7.5 g in THF.
A film was prepared as in Example 6 using a coating solution containing % PKHHTM. The dried film was exposed through a Stoffel √2, 21 stage tablet on a 3M brand "179" contact printer processor for 10 seconds at a 32 exposure setting. This film was thermally developed in a drum processor at 88° C. for a standing time of 20 seconds. This gives us 2.8 optical density units (Macbeth TD5
Dmax in units of transmitted optical density (measured with a Status A red filter by a 0.04 densitometer), 0.
A bright cyan transparent image was formed as a negative of the original image with a Dmin of 12 optical density units and an image optical density of 6 steps greater than or equal to 1.0 optical density units.

[0093]

Example 35 10 mg o-nitroarylidene dye 1, 120 mg diazine magenta leuco 46, 0.9
4g solution (27g MeOH, 2x Mg(NO3)
(prepared from 0.78 g 6H2O and 0.42 g succinic acid) and 7.5 g 20% PKH in THF.
A film was prepared in the same manner as in Example 6 using a coating solution containing HTM. This dry film is passed through the Stoffel√2, 21-step tablet to the 3M brand "1".
79'' contact printer processor for 10 seconds at 32 exposure setting. The film was thermally developed using a drum processor at 80° C. with a dwell time of 20 seconds and exposed for 5 minutes using a 3M brand model 213 overhead projector. Due to this, 1.7
Dmax in optical density units of 0 optical density units (Status A green filter), Dm in optical density units of 0.22
In, and a bright cyan transparent image as a negative of the original image was formed with a five step number of image optical density of 1.0 optical density units or greater.

[0094]

Example 36 A solution of 10 mg o-nitroarylidene dye 1, 60 mg 2,4,6-tris(trichloromethyl)-1,3,5-triazine, 120 mg diazine magenta leuco 23, 0.94 g (MeOH2
7g, prepared from 0.78g Mg(NO3)2x6H2O and 0.42g succinic acid), and 7.5
A film was prepared as in Example 6 using a coating solution containing 20% PKHHTM in THF. The dried film was exposed through a Stoffel √2, 21 stage tablet on a 3M brand "179" contact printer processor for 10 seconds at a 32 exposure setting. Leave this film in a drum processor for 20 seconds88
Heat developed at ℃. This film is 3M brand No. 213
Exposure was performed for 5 minutes using an overhead projector. By this, the transmission optical density Dmax of 2.10 optical density units (Status A green filter),
A bright cyan transparent image was formed as a negative of the original image with a Dmin of 0.12 optical density units.

This sample and the sample of Example 35 with transmission optical density Dmax 2.0 and Dmin 0.07 optical density units were exposed for 30 minutes on a 3M brand Model 213 overhead projector. The increase in Dmax and Dmin is shown in Table 10.

[Table 10]

[0096]

Examples 37-42 This example shows that a variety of different leuco dyes can be used in construction. All configurations are
It was produced in the same manner as in Example 6 except that a different leuco dye was used instead of the leuco dye in Example 6. The development temperature for this dry film was 8 inches by 2 inches (20.
3cm x 5.1cm)
79'' was determined by vertical exposure on a contact printer processor for 20 seconds at a 32 exposure setting. Place these small pieces into the Reichert-Heitzbank device for 20 minutes.
The developing temperature was determined. The size of each film is 8 inches x 2 inches (20.3 cm x 5.1 cm)
) was exposed vertically through a Stoffel √2, 21-step tablet on a 3M brand "179" contact printer processor for 10 seconds at a 32 exposure setting;
It was then thermally developed for 20 seconds on a drum processor at an appropriate development temperature. The red stain from o-nitroarylidene dye 1 was removed by exposing the sample for 5 minutes on a 3M brand Model 213 overhead projector. Preferred development temperature for this example, average Dm
Table 11 shows the in average Dmax and the average number of stages of transmission optical density of Dmin+0.6. A Status A red filter was used for densitometer readings of the blue and cyanthiazine and oxazine samples. A Status A green filter was used for reading the magentadiazine sample.

[0097]

[Table 11]

[0098]

Example 43 10 mg o-nitroarylidene dye 1, 80 mg methylene blue thiazine benzoyl leuco, 0.94 g solution (MeOH 9 g, Mg(N
O3) 2x6H2O 0.26g and 1,3,5-
prepared from 0.16 g of benzenetricarboxylic acid),
A film was made as in Example 6 using a coating solution containing 20% PKHHTM and 7.5 g of THF. The dried film was exposed through a Stoffel √2, 21 stage tablet on a 3M brand "179" contact printer processor for 10 seconds at a 32 exposure setting. This film was thermally developed in a drum processor at 89° C. for a standing time of 20 seconds. The film was exposed for 5 minutes using a 3M brand model 213 overhead projector. This results in a transmission optical density D of 1.76 optical density units (status A red filter).
max, Dmin in 0.09 optical density units, and 1.
A bright cyan transparent image was formed as a negative of the original image with 6 steps of image optical density greater than or equal to 0 optical density units.

0099

Example 44 This example illustrates that one or more leuco dyes can be used in the present imaging system. 5 mg o-nitroarylidene dye 1, 40 mg Basic Blue 3 benzoyl leuco, 58 mg diazine magenta leuco 46, 470 mg solution (9 g MeOH, Mg(
NO3)2×6H2O 0.26g, and tartaric acid 0
．． A film was prepared as in Example 6 using 14 g of 20% PKHHTM in THF) and 7.5 g of 20% PKHHTM in THF. Adjust the development temperature of this dry film to half of an 8 inch x 2 inch (20.3 cm x 5.1 cm) strip using a 3M brand "179" contact printer.
Determined by vertical exposure using the processor at 32 exposure settings for 20 seconds. The strip was placed on a Reichardt-Heitzbank apparatus for 20 seconds and the development temperature was determined. 102℃ in non-exposed areas,
In the exposed area, a mixed purple color was produced and developed at 88° C. due to the development of both leuco dyes.

[0100]

Examples 45-48 These examples illustrate various nitrate salts that can be used in the present construction. Example 6 except using 0.94 g of a solution prepared from 9 g of methanol, 0.14 g of succinic acid, and a given amount of nitrate salt.
A film was prepared in the same manner. The development temperature for each dry film was adjusted to 8 inches x 2 inches (20.3 cm).
3M brand “179”
3 for 20 seconds using a contact printer processor
Determined by vertical exposure in 2 exposure settings. Each piece was placed on the Reichardt-Heitzbank apparatus for 20 seconds to determine the thermal limits of the exposed areas (Texp) and the thermal limits of the unexposed areas (Tunexp). Place half of the 8 inch x 2 inch (20.3 cm x 5.1 cm) strip lengthwise through a Stoffel√2, 21-tier tablet into a 3M brand "179" contact printer.
The sensitivity of each negative working film was determined by exposing the processor for 10 seconds at 32 exposure settings. Each piece was processed using a drum processor for a dwell time of 20 seconds at the temperature that produced the Dmin level. This produced a bright cyan transparent image as the original negative. The velocity (in stages) of each strip was determined at the point where the transmitted optical density was Dmin+0.6 optical density units. Development temperature of this example, Dmin,
Table 12 shows the number of stages of image optical density of Dmax and Dmin+0.6. A Status A red filter was used for densitometer readings. When silver nitrate was added to this formulation, undesirable oxidation of the coating formulation occurred within 1 minute. This unacceptable film has a very high background Dm when dried at room temperature.
It had in. Therefore, silver nitrate is not a useful oxidizing agent in the present invention.

[0101]

[Table 12]

[0102]

Examples 49-52 These examples illustrate the desirability of acidic materials in this configuration. A solution of 10 mg o-nitroarylidene dye 1, 120 mg magentadiazine leuco 46, 940 mg (prepared from 9 g MeOH, a given amount of acid, and a given amount of nitrate salt)
, and 7.5 g of 20% PKHHTM in THF. The development temperature for each dry film was adjusted to 8 inches x 2 inches (2
0.3 cm x 5.1 cm) by vertical exposure using a 3M brand "179" contact printer processor at a 32 exposure setting for 20 seconds. Place each piece on the Reichardt-Heitzbank apparatus for 20 seconds to determine the thermal limits of the exposed area (Tex
p) and the thermal limit (Tunexp) of the unexposed area was determined. 8 inches x 2 inches (20.3 cm x 5.1 cm)
) vertically through the Stoffel√2, 21-tier tablet and 3M brand "179" contact
The sensitivity of each negative working film was determined by exposing for 10 seconds at 32 exposure settings using a printer processor. Each piece was processed using a drum processor for a dwell time of 20 seconds at the temperature that produced the Dmin level. This produced a bright cyan transparent image as the original negative. The velocity (in stages) of each strip was determined at the point where the transmitted optical density was Dmin+0.6 optical density units. Development temperature in this example,
Table 13 shows the number of stages of image optical density of Dmin, Dmax, and Dmin+0.6. A Status A green filter was used for densitometer readings.

[0103]

[Table 13] *Positive image

[0104]

Examples 53-55 These examples demonstrate other binders useful in the present invention. 10 mg o-nitroarylidene dye 1, 80 mg Basic Blue 3 benzoylleuco, 940 mg solution (9 g MeOH, 0.14 g succinic acid, and Mg(NO3) 2 x 6H2O
A film was prepared as in Example 6 using 0.26 g of the binder in THF or methyl ethyl ketone for Saran F-310™. The development temperature of each dry film was adjusted by exposing half of an 8 inch x 2 inch (20.3 cm x 5.1 cm) strip lengthwise for 20 seconds at a 32 exposure setting using a 3M brand "179" contact printer processor. It was measured by Place each piece in the Reichardt-Heitzbank apparatus for 20 seconds to determine the thermal limit of the exposed area (Texp) and the thermal limit of the unexposed area (Texp).
Tunexp) was determined. 8 inches x 2 inches (20
．． 3cm x 5.1cm) Stoffel√2,2
Determined by vertical exposure through a 1-stage tablet using a 3M brand "179" contact printer processor for 10 seconds at 32 exposure settings. Leave each piece in a drum processor for 2 hours.
The treatment was carried out for 0 seconds at the temperature at which the Dmin level occurred. A bright cyan transparent image resulted as the original negative. The speed of each piece (in number of stages) is the transmitted optical density Dm
It was determined at a point that is in+0.6 optical density units. Development temperature, Dmin, Dmax and Dmi in this example
Table 14 shows the number of stages of image optical density of n+0.6. A Status A red filter was used for densitometer readings.

[0105]

[Table 14] *Not measured

[0106]

Examples 56-57 A solution of 10 mg of the given o-nitroarylidene dye, 80 mg of benzoylleuco 3 of Basic Blue 3, 470 mg of MeOH (27 g of MeOH and 0.78 g of Mg(NO3)2×6H2O, and 0 succinic acid) .42g), and 7.5
A film was prepared as in Example 6 using 20% PKHHTM in THF. The developing temperature of each dry film was adjusted to 8 inches x 2 inches (20.3 cm x 5
．． Measurements were made by exposing half of a 1 cm) strip lengthwise for 20 seconds at maximum exposure setting using a 3M brand "179" contact printer processor. Place each piece on the Reichardt-Heitzbank device 2
After 0 seconds, the thermal limit (Texp) of the exposed area and the thermal limit (Tunexp) of the non-exposed area were measured. This positive image was placed on a 3M brand model 213 overhead projector for 5 minutes. The results are shown in Table 15.

[Table 15]

[0107]

Examples 58-59 10 mg of a given o-nitroarylidene dye, 80 mg of methylene blue benzoyl leuco, 470 mg of a solution (27 g of MeOH and Mg
(NO3)2x6H2O 0.78g, and succinic acid 0.42g), and 7.5g TH
A film was prepared as in Example 6 using 20% PKHHTM in F. The development temperature of each dry film was set to 8 inches x 2 inches (20.3 cm x 5.1 cm).
) with half of the small piece of 3M brand "179" contact
Measurements were made using a printer processor with a 20 second vertical exposure at maximum exposure setting. Each piece was placed on the Reichardt-Heitzbank apparatus for 20 seconds and the thermal limit of the exposed area (Texp) and the thermal limit of the unexposed area (Tunexp) were measured. This positive image was placed on a 3M brand model 213 overhead projector for 5 minutes. The results are shown in Table 16.

[Table 16]

[0108]

Examples 60-61 10 mg of a given o-nitroarylidene dye, 80 mg of diazine magenta leuco 46
, 470 mg of solution (27 g of MeOH and Mg(NO
3) 0.78g of 2x6H2O and 0.78g of succinic acid.
prepared from 42 g), and 7.5 g of 2 in THF.
A film was prepared as in Example 6 using 0% PKHHTM. The developing temperature of each dry film is
Measurements were taken by exposing half of an 8 inch x 2 inch (20.3 cm x 5.1 cm) strip lengthwise using a 3M brand "179" contact printer processor for 20 seconds at maximum exposure setting. Each piece was placed on the Reichardt-Heitzbank apparatus for 20 seconds and the thermal limit of the exposed area (Texp) and the thermal limit of the unexposed area (Tunexp) were measured. This positive image 3
Placed on an M Brand Model 213 overhead projector for 5 minutes. The results are shown in Table 17.

[Table 17]

[0109]

Examples 62-63 A solution of 10 mg of a given o-nitroarylidene dye, 80 mg of Leuco 53, 470 mg of MeOH (27 g of MeOH and Mg(NO3) 2×6H2O
0.78 g and 0.42 g of succinic acid), and 7.5 g of 20% PKHHTM in THF.
A film was prepared in the same manner as in Example 6 using The development temperature of each dry film was adjusted by half of an 8 inch x 2 inch (20.3 cm x 5.1 cm) strip lengthwise for 20 seconds at maximum exposure setting using a 3M brand "179" contact printer processor. It was measured by exposing it to light. Place each piece on the Reichardt-Heitzbank apparatus for 20 seconds until the thermal limit of the exposed area (
Texp) and thermal limit of unexposed area (Tunexp)
was measured. This positive image is the 3M brand 21st
It was placed on a Type 3 overhead projector for 5 minutes. The results are shown in Table 18.

[Table 18]

[0110]

Examples 64-70 These examples demonstrate that arylidene dyes containing an aryl group in addition to the o-nitrophenyl moiety produce negative working imaging systems. Amounts of o-nitroarylidene dye, 80 mg of Basic Blue 3 benzoylleuco, 940 mg of solution (9 g of MeOH and Mg(NO3) 2 x 6H2O
A film was prepared as in Example 6 using 0.26 g of 20% PKHHTM in THF) and 7.5 g of 20% PKHHTM in THF. The development temperature of each dry film was adjusted by half of an 8 inch x 2 inch (20.3 cm x 5.1 cm) strip lengthwise for 20 seconds at maximum exposure setting using a 3M brand "179" contact printer processor. It was measured by exposing it to light. Place each piece on the Reichardt-Heitzbank apparatus for 20 seconds until the thermal limit (T
exp) and the thermal limit (Tunexp) of the unexposed area were measured. This positive image is the 3M brand No. 213
The model was placed on an overhead projector for 5 minutes. The results are shown in Table 19.

[0111]

[Table 19]

[0112]

Example 71 This example shows that the imaging layer of the present invention can be thermally stabilized by exposure to ammonia vapor. 7.50g 20% PKHHTM in THF, 0.1
2g magenta leuco 46, 0.01g 1, and 0
．． A solution was prepared from 94 g of solution (9 g of MeOH, 0.26 g of hexahydrate magnesium nitrate, and 0.14 g of tartaric acid). Add this solution to 4 mil clear polyester (P
ET) The substrate was coated to a wet thickness of 4 mils and dried for 15 minutes at room temperature and 5 minutes at 50°C. The film was cut into strips and placed in a Reichart-Heitzbank thermal gradient machine for 20 seconds. The thermally developed strip was then placed in a chamber containing ammonia vapor from concentrated ammonium hydroxide at room temperature. Exposure times were 0, 0.5, 1, 5, 10 and 15 minutes.

This strip was then measured using a Macbeth TR527 densitometer (Status A red filter) using a 3M brand model 213 overhead projector to measure the optical density increase in the background area Dmin below the temperature at which the dye was thermally developed. was also measured as a function of time at a temperature 5°C lower. The graph in FIG. 1 shows that the color formation in the background area (printout) was reduced with increasing exposure to ammonia vapor. A significant reduction in printout occurred with 1-5 minutes of ammonia exposure.

Control experiments using water vapor instead of ammonia vapor showed no dependence of printout rate on contact time.

[0115]

[Example 72] By condensing o-phenylhydroxylamine and the corresponding aldehyde (3,3-(4'-dimethylaminophenyl) propenal or 3-(4'-dimethylaminophenyl) propenal), Nitron dyes 47 and 48 were prepared in EtOH by Wess, P.R.
t,P. R. ), Davis, G. C. (Davis, G.
．． C. ), Griffing, B. F. (Griffing
,B. F. ), J. Imag. Sci. , 1986,
This was carried out according to the method described in Vol. 30, p. 65. Compound 47 was recrystallized from EtOH (mp 243-9, depending on heating rate, λmax=428 nm). Compound 4
8 was recrystallized from toluene (mp247-9, λma
x=417nm). Upon continuous irradiation in THF solution, 24 and 25 showed 98% and 100% photobleaching to a colorless product, respectively.

[0116]

Examples 73-74 This example shows that o-nitroarylidene dye 1 activates oxidation by nitrate upon exposure to light. Solution A was prepared by mixing 26.25 g of 20% PKHHTM in tetrahydrofuran, 0.28 g of Basic Blue 3 benzoyl leuco, and 0.04 g of Dye 1. 26.25 g of 20% PKHHTM in tetrahydrofuran, and 0.25 g of 20% PKHHTM in tetrahydrofuran.
Solution B was prepared by mixing 28 g of Basic Blue 3 benzoyl leuco. 9 g methanol, 0.26 g Mg(NO3)2×6H2O, and 0
．． Solution C was prepared by mixing 14 g of succinic acid. Solutions D and E were prepared by mixing 7.5 g of solution A or solution B and 0.94 g of solution C, respectively. A coating was prepared by the procedure of Example 6.

0117] 20.3cm x 5.1cm (8 inches x 2
The thermal limit reading (the lower temperature limit at which dye development occurs) was determined as the average of multiple samples. The results obtained are shown in Table 20.

[Table 20]

Strips of film coated with Solution D were imagewise exposed for 10 seconds at an exposure setting of 32 in a 3M Brand Model 179 Contact Printer Processor. The thermal limit of this exposed sample was measured as described above to obtain an average value of 86°C.

[0119]

Example 75 This example shows that a fixed image with reduced background dye stain, improved color and improved thermal stability was obtained by (1) imagewise exposure, (2) thermal development, (3)
It is shown to be prepared by the steps of blanket exposure and (4) fixation by exposure to ammonia vapor. The film construction of Example 74 was imagewise exposed as in Examples 74-75 and heat treated at 85° C. for 20 seconds to produce a blue-cyan original negative with magenta stain over the exposed and unexposed areas. An image arose. Measure transmission densitometer readings (status A green filter, magenta color indication, and status A filter, cyan color indication) in both the Dmax (exposed) and Dmin (unexposed) regions using a Macbeth TR527 densitometer. did.

[0120] This imaged and heat-treated sample was
Blanket illumination was performed for 1 minute using an M brand model 213 overhead projector to obtain a bright cyan image with reduced background stain. Dmin and D again
The max reading was recorded. The results shown in Table 21 demonstrate that exposure photobleaching provides improvements in Dmin and color purity.

[Table 21] a) Before blanket irradiation exposure b) After blanket irradiation exposure

The unexposed areas of this imaged, heat treated, and blanket exposed sample were cut into two strips. Both strips were not initially exposed to an imaging light source, so they were necessarily colorless. Place one strip in an ammonia vapor chamber (30%
(equilibrium concentration of aqueous ammonium hydroxide), and the other did not undergo this operation. Both strips were then placed on a Reichart-Heitzbank thermal gradient apparatus for 20 seconds and the thermal limit was measured. Also, 75 to 85 of this Reichert-Heitzbank thermal gradient device.
A Status A red densitometer reading (image - indicating dye fog) was determined in the area touched by the °C area. The results are shown in Table 22.

[0122]

[Table 22]

[0123]

Examples 76-81 This example discloses the preparation of o-nitroarylidene dyes useful as photobleachable dyes useful in the present invention. The o-nitroarylidene dyes shown in Table 23 were prepared according to the procedure described in U.S. Pat. No. 3,988,154.

Table 23 a) PKHH is a phenoxy resin obtained from Union Carbide Co., Hackensack, NJ.

[0124]

[Examples 82-93] These examples are Examples 76-8
The photobleachable sensitizer No. 1 is shown to be useful in the present invention.

A coating solution was prepared with the following ingredients. 7.5 g of 20% PKHHTM in THF, 80 mg of Basic Blue 3 benzoyl leuco (Argascript Turquoise™, Ciba-Geigy, Ardsley, NY), 4-9 mg of sensitizer, 940 mg of solution (M
eOH9g, Mg(NO3)2×6H2O 0.26
g, prepared from 0.14 g of succinic acid) and 60 m
g of 2,4,6-tris(trichloromethyl)-1,3
, 5-triazine (TTT), or diphenyliodonium hexafluorophosphate (Ph2I).

The solution was placed on a shaking table in the dark at room temperature for 15 minutes. 4 times this solution under suitable safe light.
Knife coated onto mil (0.1 mm) clear polyethylene terephthalate film at a wet thickness of 4 mil (0.1 mm). Then, it was left at 66°C for 3.25 minutes. Several similar strips from this film (approximately 8 inches x 2 inches)
was cut and evaluated as follows.

[0127] The developing temperature of each dry film was set to 8
Half of a 2 inch x 2 inch (20.3 cm x 5.1 cm) strip was printed using a 3M brand "179" contact printer processor for 20 seconds at 32 exposure settings (approximately 8.5
x 105 microwatts/cm2). Each piece was heated for 20 minutes on a Reichardt-Heitzbank thermal gradient apparatus (Cambridge Instruments, Buffalo, NY).
Wait for a second, then set the thermal limit (temperature at which development occurs) of the exposed area (T
exp) and the thermal limit of the unexposed area (Tunexp) were determined. The results are shown in Table 24.

[0128]

[Table 24]

[0129]

Examples 94-105 Similar strips of Examples 82-93 were evaluated as follows.

The amount of photobleaching was determined by the following procedure. Half of the strips were exposed for 5 minutes using a 3M brand model 213 overhead projector. The UV spectrum of the unexposed film was measured, the λmax was measured, and the optical density of the exposed strip was measured at this λmax. This thermophotographic speed was determined by the following procedure. Stoffel√2, 21 steps (I
3M brand "179" through Stoffel Graphic Arts Equipment, South Bend, N.
” 32 exposure settings for 10 seconds using a contact printer processor (approximately 1.4 for 450-900 nm)
x 104 erg seconds/cm2) in the longitudinal direction. This strip was inserted between Tunxep and Texp at locations where a background density of <0.2 was measured (Example 8).
2 to 93) for 20 seconds. This speed in plate number was determined at the point where the density was 0.6+fog. The results are shown in Table 25.

[0131]

[Table 25]

[0132]

EXAMPLE 106 The following example shows that the photobleachable dyes of this invention differ from the thermographic systems of US Pat. No. 4,386,154 and US Pat. No. 4,460,677. U.S. Patent Nos. 4,386,145 and 4,460
An evaluation similar to the sensitizing agent evaluation described in , No. 677 was conducted. A standard evaluation solution was prepared with the composition shown below. 5.0
g of polyvinyl butyral (molecular weight 45,000-55
, 000, hydroxyl content 9.0-13.0%, Butval TM-B76, Monsanto Chemical Co., St. Louis, MO) in 5% (wt/vol) methyl ethyl ketone solution, 0.3 g trimethylolpropane trimethacrylate. , and 0.03 g of 2-methyl-4,6-bis(
trichloromethyl)-1,3,5-triazine.

0.02 g of the specified dye was added to this solution. This solution was knife coated onto a 2 mil (0.05 mm) clear polyethylene terephthalate film using a 2.0 mil knife orifice and the coating was air dried for 30 minutes. . Another 2 mil (0.05 mm) clear polyethylene terephthalate film was carefully placed over this minimal air entrapment dry soft adhesive coating. This laminate is 3M
A Type 70 light source (650 Watt tungsten lamp) was exposed through the template with transparent and opaque areas. This operation will cause dyes 1 and 3 to appear in the exposed area.
was essentially photobleached. After exposure, the protective film was removed and the coating was treated with black toner powder of the type normally used for xerography. If the evaluation material is a sensitizer such as that described in U.S. Pat. 2-methyl-4
, 6-bis(trichloromethyl)-1,3,5-triazine). Since the polymerized areas are substantially non-tacky, the black toner powder selectively adheres to the tacky unexposed areas of the coating. This provides a visible image according to the template. The results are shown below. Then, a comparison was made with the conventional sensitizing agent (5,10-diethoxy-16,17-dimethoxyviolanthrene). Based on the results shown in Table 26, the present invention was applied to U.S. Pat.
460,677.

[0134]

[Table 26]

[0135]

Examples 107-116 These examples illustrate several o-nitropyridyl-2-ydene and o,p-dinitropyridyl-2-ydene dyes useful as photobleachable sensitizers in the embodiments of this invention. Preparation is shown. This o-
A general method for preparing nitropyridyl-2-ydene and o,p-dinitropyridyl-2-ydene dyes 7-26 is shown in Table 27 below. 2.5 mmol of the appropriate 2- or 4-alkyl quaternary salt (as described in U.S. Pat. No. 4,111,699), 2.5 mol of 2-chloro-3-
To a refluxing solution of nitropyridine or 2-chloro-3,5-dinitropyridine and 30 ml of dry acetonitrile (distilled from calcium hydride) 5 ml of diisopropylethylamine was added dropwise over 5 minutes. The reaction mixture was refluxed for an additional 5 hours. The resulting black mixture was cooled and left overnight. The precipitate was filtered, washed with acetonitrile, and dried to obtain a product.

[0136]

[Table 27]

[0137]

[Examples 117-134] This example is Examples 107-1
16 photobleachable sensitizers are shown to be useful in the present invention. Coated film samples were prepared according to the procedures of Examples 82-87. The results are shown in Table 28.

[0138]

[Table 28]

[0139]

Examples 135-142 These examples demonstrate the preparation of several o-nitropyrimidyl-4-idene dyes as photobleachable sensitizers useful in the practice of the present examples.

o-Nitropyrimidyl-4-ydene dye 1
General operations for 7-24. 5.2 mmol of the appropriate 2- or 4-alkyl quaternary salt (U.S. Pat. No. 4,11
1,699), 5.2 mmol of 4
, 6-dichloro-5-nitropyrimidine and 30 ml
5 ml of diisopropylethylamine was added dropwise over 5 minutes to a refluxing solution of dry acetonitrile (distilled from calcium hydride). The reaction mixture was refluxed for an additional 5 hours. The resulting dark mixture was cooled and left overnight. The precipitate was filtered off, washed with acetonitrile and dried to give the products listed in Table 29.

[Table 29]

[0141]

[Examples 141-152] These examples are Example 13
Photobleachable sensitizers between 5 and 140 are shown to be useful in the present invention. Coated film samples were prepared according to the procedures of Examples 82-87. The results are shown in Table 30.

[Table 30]

The invention has been described in detail in specific embodiments. However, it should be understood that various changes and modifications may be made within the scope of the invention.

[0143]

[Chemical formula 11]

[0144]

[Chemical formula 12]

[0145]

[Chemical formula 13]

[0146]

[Chemical formula 14]

[0147]

[Chemical formula 15]

[0148]

[Chemical formula 16]

[0149]

[Chemical formula 17]

[0150]

[Chemical formula 18]

[Brief explanation of the drawing]

FIG. 1 is a graph showing that color formation in the background area (printout) was reduced with increasing exposure to ammonia vapor.

Claims (10)

[Claims] 1. An imaging layer consisting essentially of a binder, at least one leuco dye, at least one compound that is a source of nitrate ions, and at least one photobleachable dye. 2. The imaging layer of claim 1 further comprising an ultraviolet radiation sensitive initiator sensitized by the photobleachable dye. 3. An imaging layer consisting essentially of a binder, at least one leuco dye, at least one compound that is a source of nitrate ions, at least one photobleachable dye, and at least one acidic compound. . 4. The imaging layer of claim 3 further comprising an ultraviolet radiation sensitive initiator sensitized by the photobleachable dye. 5. The image-forming layer according to claim 1, wherein the photobleachable dye is of the following formula (I), formula (II), or formula (III):
] where a) k is 0 or 1, b) m is 0 or 1, c) L is a methine group each including a substituted methine group, and d) A is an electron donating moiety, sulfur, or >N-R1, e) R1 is an alkyl group, an aralkyl group, a sulfoalkyl group, a sulfatoalkyl group, an alkoxycarbonylalkyl group, an alkoxyalkyl group, an acyloxyalkyl group, an acyloxyalkyl group, a dialkylaminoalkylene group, a cyclo an aminoalkylene group, an alkenyl group or an aryl group; f) Z is a nonmetallic atom that necessarily completes a cyanine dye-type heterocyclic nucleus having 5 or 6 atoms in the heterocycle containing A; , a second heteroatom selected from the group consisting of , nitrogen, selenium, or sulfur atoms, and g) Y is the atom that necessarily completes the aryl or heteroaromatic group; In the formula, R2 is hydrogen, an alkyl group of 1 to 24 carbon atoms or an aryl group of 6 to 10 carbon atoms, optionally a halogen, an alkoxy group of 1 to 6 carbon atoms, or an aryl group of 6 to 10 carbon atoms. is an alkyl or aryl group substituted with a group, R3 and R4 are each independently hydrogen, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms, or a halogen, and R5 is hydrogen, nitro , cyano, a carbalkoxy group of 1 to 6 carbon atoms, or halogen, and R6 and R7 together constitute a benzo group; embedded image where R2 to R6 are as defined above, R8 is each independently a halogen, an alkyl group having 1 to 6 carbon atoms,
It is an alkoxy group of 1 to 6 carbon atoms, or a halogen. 6. Claims 1 and 2, wherein the photobleachable dye is an arylnitrone represented by the following formula (IV).
The image forming layer according to any one of 3 and 3: embedded image where k is 0 or 1, R9 is aryl or a substituted aryl group, and R10 and R11 are R10
and R11 are each independently selected from an electron-rich substituted aryl or heterocyclic group and hydrogen, with the proviso that R11 are both not hydrogen. 7. At least 0.0% by weight of the layer.
Any of claims 1, 2 or 3, containing 5% leuco dye, at least 0.005% photobleachable dye and containing at least 0.10 mole nitrate ion per mole leuco dye. The image forming layer described in . 8. An imaging layer according to claim 1, wherein the nitrate ion is present in the form of a metal salt of nitrate. 9. The nitrate ion is present in the layer as a metal nitrate salt, the leuco dye is present in at least 2% by weight of the layer, and the o-nitroarylidene dye is present in 0.005 to 8% by weight of the layer. 8. The imaging layer of claim 5, wherein the binder is present in an amount of at least 80% by weight of the layer. 10. Exposing the layer of claim 1 to light,
An image forming method comprising the steps of: generating a visible image by heating the exposed layer; and reducing background stain by exposing the entire image.