CA1133905A - Thermolabile acutance dyes - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Images produced in photothermographic emulsions wing silver halide as a llght-sensitive material therein n sufferer from light scattering effects on the silver halide.
Acutance dyes are disclosed which can absorb scattered light and which are blenched at the development temperature of the photothermograpbic composition.

Description

FN gl5,235 ~339g~5 THERMOL~BILE ACUTANCE DYES
-This invention relates to cornpounds suitable for use as acutance dyes in photosensitive compositions, to the preparation of such compounds and to photosensitive compositions containing the compounds. The invention is particularly concerned with photothermographic compositions of the type known as "dry silver" compositions.
Dry silver photosensitive compositions comprise an intimate mixture of a light-sensitive silver halide~
a reducing agent for silver ions, and another silver compound such as a silver salt of an organic acid, e.g., silver behenate or silver saccharine or a complexed silver salt. The organic silver salt or complex is substantially light-insensitive and, upon reduction, gives a visible change. Such a mixture is usually prepared in suspension and the resulting dispersion spread as a layer on a suitable substrate. When dry, the layer is exposed to a light image and thereafter a reproduction of the image can be developed by heating the layer in the presence of the reducing agent for silver ions such as hydroquinone or certain substituted phenols.
It is because the exposure and development of the layer occur without using an externally applied developer solution, such as conventional aqueous solu-tions, that these materials are often referred to as dry silver light-sensitive materials. Such materials in which minor amounts of a photosensitive sllver halide catalyst-progenitor (the catalyst being photoinduced silver) are associated in catalytic proximity with ma;or . , ~ ; , ~ ~: , ; . . .

" 1~339U5

2-amounts of a heat sensitive oxidation-reduction image forming reaction mixture which reacts more rapidly in the presence of the catalyst resulting upon exposure of the silver halide are well known in the art. Examples of such materials are described in British Patent No.
1,110,046 and in U.S. Patent Nos. 3,839,049 and 3,LI57,o75.
We believe that whenthe mixture is exposed to light a latent image of silver is formed in the silver halide. Thereafter, the organic silver compound can be reduced by heating in the presence of the reducing agent, this reduction being catalyzed image-wise by the light exposed silver halide. By a suitable choice of temperature, the reduction of the silver compound can be catalyzed in the light exposed areas to give a visible darkening while any slight reduction which occurs in the non-light exposed areas is lnsufficient to give a marked change.
Because the silver halide acts as a catalyst-progenitor, very small amounts of it can suffice, e.g., 0.1 to 10%
by weight of the mixture. However, large amounts, e.g., ~0 up to 15 or even 20%~ may be desirable in some circum-stances.
To improve the sharpness or definition of photographic images~ a dye known as an acutance dye is often incorporated into photosensitive compositions. To be effective, the acutance dye will absorb at wavelengths at which the photosensitive composition is sensitive.
The longer the path length of the light in the layer of light sensitive composition~the greater the attenuation.
Therefore, scattered light is at-enuated or absorbed to a - ~ . ,. . ~ . : :

- - . : .: . : : : ::
~ .. ~. . . :. . . : - :

~339~5 larger extent than light which impinges directly on a light sensitive crystal. As a result, although the overall speed of the composition is reduced slightly, scattered light and other light rays which are liable to produce a blurred image are preferen~ially absorbed. The overall definition and sharpness of images produced in the layer thus are increased.
An acutance dye for use in a dry silver composi-tion is preferably heat labile, that is to say, it is decomposed or converted by the heat development of the dry silver composition to one or more compounds which are colorless.
It is therefore an ob~ect of this invention to provide dry silver compositions with acutance dyes which absorb light at at least some of those wavelengths to which the composition is sensitive and which are rendered essentially colorless upon heat development of the dry silver composition.
According to this invention there is provided a light-sensitive composition comprising an intimate mixture of a substantially light-insensitive silver compound which upon reduction gives a visible change, silver halide to provide a catalyst for this reduction, a reducing agent for silver ions, and, as an acutance dye, a compound in accordance with that part of the invention hereinafter described.
According to the invention there is also provided a compound having the general formula:

: : :, : , . :: :. :.. , - , .. .
, ~ -, : : ., : : . ;
. :;,: ,. ~,, ,: :: , :
- , : :

1~339(~

k / ~CH-CH~

~ =CH
R Rl R8 wherehl Rlisanla~lkyl~grOùp of from 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms and more preferably 1 to 4 carbon atoms, R2 is the group z ~ X wherein X, Y and Z are independently selected from the group of H, N02 and CN, wi*h the proviso that at least one of X, Y, and Z
is N02. Preferably neither X nor Y is H. Preferably X, Y and Z are combina-tions of N02 and CN or both are N02. R3, R4 and R5 are independently selected from the group consisting of H, halogen, alkyl or alkoxy of 1 to 4 carbon atoms, alkenyl of 2 to 4 carbon atoms, ~CH23 COOH wherein P is 0, 1, 2 or

3, -N02, -NH2, or -NHCOCH3, or any two of the adjacent groups are the atoms necessary to form a fused on benzene ring~D represents -CH=CH-, o,-~NR7, ~ C(CH3)2, -S- -Se- or NR7, R7 represents an alkyl group of 1 to 4 carbon atoms or CH3CO-I n is 1 when k is O and k is 1 when n is 0, and m is 0, 1, 2 or 3.
The more preferred dyes of the invention are represented by the formula:

.

., ;, :: : ~ ,, . , ~ . , : ,: : " .. , :.; , ~339~S

R8 z R6 N~C~ X (II) 2 s~ Y
rt Rl wherein X, Y and Z are selected from the group o~ H, NO2, CN, perfluoroalkyl of l to 4 carbon atoms, and halogen, with the proviso that at least one of X, Y and Z is NO2. Preferably neither X nor Y is H, and most preferably X
and Y are NO2 or CN, especially the oase where both X and Y are NO2~
R6 is alkyl of l to 12 carbon atoms, pre~erably l to 8~carbon atoms, and most `
preferably l to 4 carbon~atoms, 7 - ~:
R is any qulnoline; dye s~ubstltuent, preferably alkyl, alkoxy:, halogen, NO2, or -aryl, and most preferably alkyl or alkoxy:of l to 4 carbon atoms. There;may be more than~

one R7 group:on~the quinoline~nucleus,~and 8~
~ R is H, or~alkyl or alkoxy of l~ to~ B
carbon atoms, most preferably H or alkyl or :
alkoxy~of l~to~3 carbon:atoms.
The substitution~of the quinoline portion of the dyes o~ the present~:invent~lon~;is~known~in the art as shown in DT:(W. German)~2,:2:42,761.
The~substituents R3,~R4, and~R5:~(and~R7)~may be the same as or different from one another and each ~L~3391t~S

represents a substituent which can be present in a cyanine dye type neterocyclic nucleus. Such substituents are known in the art and include hydrogen or halogen, e.g., chlorine, bromine or iodine, an alkyl or alkoxy group containing 1 to 4 carbon atoms, an alkenyl group containing 2 to 4 carbon atoms, -(CH2)pCOOH where p is 0, 1, 2 or 3, -NO2, -NH2, or -NHCOCH3, or any two ad~acent groups of R3 to R5 together represent the carbon atoms needed to complete a fused on benzene ring. Preferably at least one, more preferably at least two, of the substituents R3 to R5 represent hydrogen atoms. The most preferred substituents to be represented by each of R3 to R5 are hydrogen, chlorine or bromine atoms, or methyl, ethyl, methoxy or ethoxy groups.
It is found that dry silver compositions con-taining one of the above noted acutance dyes can give excellent sharp images and that the acutance dye will be rendered essentially colorless by the heating required to develop the composition. This is unexpected in view of the fact that many of these dyes are found not to be decomposed to a colorless state when they are heated on their own to the temperature at which the dry silver compositions are heated for development.
The acutance dyes may be incorporated into the dry silver compositions of the invention in an amount from 5 x 10 to 0.1 mole of acutance dye per kilogram of total dry solids in the composition. Preferably, however, the dyes are incorporated in an amount of from 2 x 10 3 t~o 3 x 10 mole of acutance dye per kilogram of dry .

- . :~ : : : : :
: : ,. , solids in the composition.
The light-sensitive compositions of the invention will normally be spread for use on a support, suitable supports including, for example, paper, polymeric materials such as polyester or polyamide ~ilm bases, and glass. The composition will normally be prepared as a solution or suspension which is spread as a layer on the support and then the solvent or vehicle is evaporated to leave a dry photosensitive layer. If desired, a coating aid or binder such as polyvinyl butyral7 polymethyl methacrylate, cellulose acetate~ polyvinyl acetate~ cellulose acetate-propionate and cellulose acetate butyrate, can be incorporated in the light-sensitive mixture.
The substantially light-insensitive silver compound is suitably a silver salt of an organic acid or a complexed silver salt. The organic acid may be a C12 to C29 aliphatic acid and is preferably a C16 to C~5 aliphatic acid. Examples~include silver behenate, silver laurate, silver myristate, s31~er palmitate, and silver stearate. Other sil~er salts of organic acids include sil~er arachidate and silver saccharine.
The reducing agent for this substantially light-insensitive silver compound can normally be quite mild. Suitable examples include hydroquinone and substituted phenols such as 1-methyl-4-hydroxy-naphthalene, methyl gallate, catechol, phenylene diamine, p-amino-phenol and l-phenyl-3-pyrazolidone. The reducing agent can be incorporated into the light-sensitive composition. Alternatively, the composition :

- ~ :, :: .. : :, ; .- . . . .

~339~5 can be placed in contact with the reducing agent after exposure to light. For example r a light-sensitive coating can be e~posed to a light image, placed in contact with a layer containing the reducing agent and the image then developed by heating. Preferably, however, the reducing agent is incorporated in the light-sensitive composition before this is spread on the support. Then the storage stability of the composition can be improved by incor-porating in the composition a small amount of a stabilizer such as an acid stabilizer, e.g., succinic acid, benzoic acid or salicyclic acid.
The silver halide can be present in amounts of up to 20~ by weight of the mixture of silver compounds or can be present in small amounts, e.g., 0.1 to 10% by weight of the mixture of silver compounds. It can be added as such to the substantially light-insensitive compound or formed in s-itu by adding a soluble halide, e.g., a mercury or sodium halide, to the substantially light-insensitive silver compound. The silver halide can, for example, ~y chloride, bromide or a mixture of them and/or other silver halide.
The light-sensitive compositions o~ the invention can include one ox more sensitizing dyes to improve their sensitivity to parts of the spectrum other than the shorter wavelengths. Thus dye sensitized dry silver compositions of the present invention can contain an additional acutance dye such as one of those described in U.S. Patent Specification Serial No. 4,153,463 (72~Q5~Q8).

, : :
- - : ,, i ."~ ,: , . .
. i .: ~ : . ., .:; ~ : , ;

3L~339~5 _9_ The dyes of the present invention may all be made according to the following reaction scheme:

R5~3 Rl N 7k ~ ~
C~CH-CH~mCH+F ~ X
~CH=CH ~ N2 ~
y R5 ~ R3 t-amine~ H~ + ~ ~ z Rl N 7k ~
\~ ~C fCH-CH}mC ~X + ~-amine HF

This method is performed in the presence of a strong tertiary amlne such as a diisopropy1ethylamine.: For 15 example, in forming ~1,4-dihydro-4-(2,4-dinitrophenyl)-nitromethylene-l-methylquinoline (which may be also named 1,4-dihydro-1-methyl-4-(~,2,4-trinitrobenzylidene)quino-line), one wouId react 4-nitromethyIene-l-methyl 1,4-dihydroquinoline with 2,4-dinitrofluorobenzene in diisopropylethylamine. Referring to the preferred structural formula II, the~fol1owing compounds were prepared by this method.

:

~ ~ 339~5 Melt. P. (C) Ex. 6 8 (Decomposition No. R R7 R X Y Temperature) 1C2H5 H H No2 No2 228-30 3 7 H H N02 No2 215 3C2H5 H H CN No2 232-4

4 CX3 H CH3 No2 No2 237-9 5C2X5 H H N02(Z) N2 230 6 CH3oCH3(4) H No2 No2 205--06 7 CH3 QCH3 H CN No2 229-31 In the table, the numbers in parentheses indicate the position of attachment for particular substituents.
Infrared analysis and nucleus magnetic resonance analysis confirmed the structure of each of these dyes.
Example 8 Four hundred grams of a dispersion containing - 13 parts by weight of silver behenate in 87 parts of a solvent composed of 67 parts by weight methylethylketone, 26 parts by welght toluene, and 7 parts by weight methyl-isobutylketone was charged to a temperature-controlled stirred reaction vessel at 15C. Dark room conditions -were maintained during all subsequent work.
The following materials were added sequentially with 20-30 minutes of stirring between separate additions.

A. 2 g of 1-methyl-2-pyrrolidinone in 6 g of polyvinylbutyral, B, 8 ml of 2M HBr (in ethanol) and 3.2 ml ~ of O.lM HI (in ethanol)~

C. 10 g of a copolymer derived from 91% by weight vinylchIoride, 3% vinylacetate, and 6% by weight vinyl alcohol polymerized to a molecular~weight of about 23,000, and 24 g of polyvinyl butyral, ~339~5 Do 1.8 ml of 0.5M HgBr2 tin ethanol) was added with 5 minutes of stirring, E 5.2 g of phthalazinone and 7.8 g of 2,6-bis-(2'-hydroxy-3~-t-butyl-5~-methylbenzyl)-4-methylphenol, F. 2.8 ml of a sensitizer solution having

5 mg/ml of the sensitizer in N-methyl pyrrolidone, the sensitizer having the formula:

= CH-CH ~

C2H5 0 >~=\

10 mg of each candidate acutance dye was welghed into separate vessels with 3 ml of methylethyl-ketone to dissolve or disperse the dye. 50 gram portions of the light-sensitive dispersion formed above were com-bined with the dye solut~ions and~to portions of methyl-ethylketone alone as a control. All materials were stirred for three minutes. The portions were then allowed to stand at room temperature for 30~mlnutes, then they were knife coated at 85 microns thickness on polyester and dried for four minutes at 85C. Each ~
sample was topcoated with a 50 micron knife coating of a vinylchlorlde/vinylacetate copolymer as a 5%~by weight solution in methylethylketone.
The produced film samples were exposed at the wavelengths indicated below through a 0.25 mm aperture mask overlaid with a continuous denslty wedge in a vacuum frame. This permitted an easy comparison of image flare at equlvalent~optlcal densities after :

-.. . . . :: ,:

S

development for 15 seconds at 12'7C in an inert fluoro-carbon chemical bath. All dye samples had markedly less flare than the control samples, particularly at an optical density of 2Ø Except for the dye of Example ~, no samples left significant visible stain after processing.
The dye of Example 8 left a magenta stain which faded within an hour under room light. The dyes used in the examples were as follows:
Example 8 ~ (560 nm) 10~ ~ N02 CH -N ~ C~ CN

Example 9 ~ (500 nm), ~,~ N2 ~\ ~
~ 7 ~ N02 Example lO~ the dye of Example 1 (500 nm), Example ll, the dye of Example 2 (500 nm), Example 12, the dye of Example~ 5 (500 nm).

,:

,. .. .

Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A dye of the formula wherein R1 is an alkyl group of from 1 to 12 carbon atoms, R2 is the group wherein X, Y, and Z are independently selected from the class consisting of H, NO2 and CN, with the proviso that at least one of X, Y and Z is NO2, R3, R4 and R5 are independently selected from the group consisting of H, halogen, alkyl or alkoxy of 1 to 4 carbon atoms, alkenyl of 2 to 4 carbon atoms, ?CH2?p COOH wherein p is 0, 1, 2 or 3, -NO2, -NH2, or -NHCOCH3, or any two of the adjacent groups are the atoms necessary to form a fused on benene ring, D represents -HC-CH-, 0, , -S-, -Se-. or , R7 represents an alkyl group of 1 to 4 carbon atoms or CH3CO-R 8 is selected from the group consisting of H, alkyl of 1 to 8 carbon atoms and alkoxy of 1 to 8 carbon atoms, n is 1 when k is 0 and k is 1 when n is 0, and is 0, 1, 2, or 3.

2. A photothermographic emulsion comprising a silver salt of an organic acid, silver halide in catalytic proximity to said silver salt, a binder for said silver salt and silver halide, and a reducing agent for silver ions, said emulsion being characterized by containing a dye of claim 1 therein.

3. A dye according to claim 1 having the formula:

wherein R6 is alkyl of 1 to 8 carbon atoms, R4 is selected from the group consisting of alkyl, alkoxy, halogen, and N02, R8 is selected from the group consisting of H, alkyl of 1 to 8 carbon atoms and alkoxy of 1 to 8 carbon atoms, and X, Y and Z are selected from the group consisting of H, N02, CN, halogen, and perfluoroalkyl of 1 to 4 carbon atoms with the proviso that at least one of X, Y and Z is N02.

4. The dye of claim 3 wherein R6 is alkyl of 1 to 4 carbon atoms, R8 is H, and X and Y are selected from the group consisting of N02 and CN, and Z is selected from the group consisting of H, N02, and CN.