CA1075065A

CA1075065A - Light sensitive heat developable dry silver sheet material containing an organic sensitizing amide

Info

Publication number: CA1075065A
Application number: CA227,042A
Authority: CA
Inventors: Jack E. Reece
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1974-06-05
Filing date: 1975-05-15
Publication date: 1980-04-08
Also published as: DE2524823C2; FR2274068B1; DE2524823A1; GB1499596A; FR2274068A1; JPS5433847B2; JPS517914A

Abstract

SENSITIZING OF DRY SILVER

Abstract of the Disclosure Photosensitive heat-developable dry silver sheet materials, containing organic silver salt and reducing agent and in which a minor portion of the silver salt has been halidized, are given an orders-of-magnitude increase in photographic speed by incorporating an organic sensitizing amide prior to halidizing.

Description

~075065 Thls lnvention relates to llght-3ensltlve heat-developable dry sllver coatingQ and sheet materlals and thelr preparatlon. In partlcular the lnventlon relates to lmprove-ments ln the photographlc speed of dry sllver coatlngs as 5 achleved by controlled additlon of deflned amlde sensltlzing materials.
U. S. Patent No. 3,457,075 describes the preparation of dry sllver coatlng compositions containing light-stable organlc silver salt, reducing agent, and photosensitive silver -10 halide, the silver halide being formed by halidization of a minor portion of the organic silver salt. Varlous modifications have been described, see for example U. S. Patents Nos.
3,589,903, 3,635,719 and 3,667,959; but have resulted ln no - -substantial improvement ln photographic sensltivlty.
It has now been found possible to achieve substantial increase in photographic speed or sensitivity of dry silver coatings prepared as above described, by incorporating organic 7 sensitizing amides. Surprisingly, a substantial increase in ~' sensitivity is obtained only when the amide is added to the 20 organic silver salt prior to halidization. In a preferred procedure the amide and a small amount of binder are added to the silver salt, well dispersed in a volatile liquid vehicle, followed by addition of the halidizing agent, the last-named ~ and subsequent steps being performed under darkroom conditions.
25 By following this procedure, the speed of the resulting light-sensitive sheet has been increased by as much as two orders .;
¦of magnitude. More specifically, a sheet has been made as ;described having a relative speed of approximately 100-150, compared to a sheet made identically except for omission of 30 the amide and having a relative speed of unity.
:' 1.

~P

1075~ 5 The speed of the light-sensitive coating is determined as the reciprocal of the exposure required to generate a density of 0.6 greater than base plus fog. Exposure and density are obtained by customary sensitometric procedures. Relative speed is then the ratio of the speed of the sample to ; that of a control sample.
The effectiveness of various amides differs widely but may easily be determined by a simple test procedure as will be detailed under Example 1 hereinafter. Those amides which in such test show a speed of at least about two relative to a control speed of unity are to be considered as practical sensitizing amides for the purposes of this invention.
Surprisingly, compounds of otherwise similar structure but devoid of the amide function, and which have previously been suggested as useful in enhancing the maximum image density in heat-developable photosensitive coatings, are found to contribute essentially no increase in speed when sub-stituted for the sensitizing amide in the processes of this invention.
Accordingly, therefore, the invention provides in the process of making a light-sensitive heat-developable dry silver sheet material con-taining (a) photosensitive silver halide catalyst-forming means and ~b) heat-sensitive reactant image-forming means including an organic silver salt ', 20 oxidizing agent and a reducing agent for silver ion, the oxidation reduction reaction of which, to produce a visible charge, is accelerated by said catalyst, the improvement comprising: mixing with the organic silver salt, prior to halidization thereof, a spectrally inert sensitizing amide, and thereafter halidizing a minor proportion of said organic silver salt, where-in said sensitizing amide sensitizes the sheet material so that the photo-graphic speed of the material is increased to at least two compared to an otherwise identical sheet material free of said amide whose speed is taken as unity speed being measured by sensitometric exposure to a 6100K light source and heat development for 30 seconds at 260F, said sensitizing amide being a monomeric amide having the structure:

D

~0750f~S

RlcoNR2R3~RlR2NcoNR3R4 or (RlR2 )3 wherein one of the R groups represents hydrogen or a group with from one to eight carbon atoms and no more than one heteroatom selected from the group consisting of N, S and O for each two carbon atoms and the remaining R groups represent groups with from one to eight carbon atoms and no more than one heteroatom selected from the group consisting of N, S and 0 for each two carbon atoms, and groups forming rings with the amide nitrogen included, with the proviso that none of Rl, R2, R3 and R4 in the formula RlR2NCONR3R4 lU may be hydrogen.
The sensitizing amides fall within the structural formulas RlCONR2R3, RlR2NCONR3R4, or ~RlR2N)3P0 wherein the R radicals may be hydrogen or hydrocarbon. The hydrocarbon radical may contain oxygen, nitrogen, or sulfur atoms in such minor proportion as to be substantially the equivalent of hydrocarbon. Two of the R radicals may together represent a divalent hydrocarbon radical. Substituted hydrocarbon radicals wherein the substituent groups are inert with respect to the dry photographic system are likewise be included. The term hydrocarbon as used in the practice of the present invention describing Rl, R2, R3 and R4 refers to groups (straight, branched or cyclic) with no more than eight carbon atoms in any substituent group (i.e.
Rl, R-2, R3 and R4), and having no more than 1 heteroatom selected from the group of N~ S and 0 for each two carbon atoms. The groups may form rings with the amide nitrogen included (e.g., morpholine, l-alkyl-pyridone, capro-lactam, piperidone, and pyrrolidinone). The total number of carbon atoms in all of the substituent hydrocarbon groups (i.e. Rl, R2, R3 and R4) should not exceed 16. Preferred are saturated acyclic moieties with no more than four carbon atoms and no skeletal heteroatoms. With such preferred groups, it is further preferred that the total number of carbon atoms in all the substituent R groups not exceed eight.
The use of certain specific amide containing materials as ~D ~ 3 _ sensitizers is shown in United States Patent 3,819,382 wherein polymer~
for~ed of polyethylene oxtdes and al~phatic amides are used, the polymer~
havinq molecular weights of at least 1700. These materials were not specifically used in the examples of th~t patent and no suggestion of use prior to halidization in the patent.
The amides used in the practice of the invention are spectrally inert amide sensitizers. When added in the conventional manner, after halid-; ization, speed incxeases to relative speeds of 1.6 and 2.2 have been found.
However, it has not been possible to achieve relative speeds of 5.0 by the addition of monomeric amides excePt by the practice of the present invention.
Transparent photosensitive coatings applied to transparent film backings are preferred in performing the sensitometric tests herein des-cribed, but translucent or opague substrates, such as, for exa~ple, paper, and non--:`
~' n - 3a -.: ~

transparent subcoatings and photoqensltlve coatlngs are llke-wlse useful. The photosensltlve sllver hallde component may be sllver bromlde, chlorlde, lodlde or a mlxture of two or more. Spectrally senqltlzlng dyes, antlfoggants, tonlng agents, and other additlves and modlflers may be lncorporated.
In the followlng illustrative but non-limitlng Examples, proportions are glven in parts by weight unless otherwise indicated.

Example 1 A mixture containing 12.5 g. of silver behenate, 6.6 g.
of methyl isobutyl ketone, 21.0 g. of toluene, and 60 g. of methyl ethyl ketone is charged to a stlrred reaction vessel.
Whlle thls mixture ls stirred, an amount of the amide com-pound equimolar to the amount of silver present is added, followed in about five minutes by 1.0 weight per cent (based on the total mixture) of polyvinyl butyral resin.
After an additional five minutes' stirring, 5.6 ml.
of a solution prepared by mixing 10 ml. of 48~ hydrobromic acid ~ith 78.2 ml. of methanol is added during about one minute. After 30 minutes, 0.6 ml. of solution containing `; 18 g. of mercuric bromide in methanol to 100 ml. is added with stirring followed within five minutes by 7.3 g. of poly-~ vinyl butyral resin.
After a final five minutes' stirring, the mixture so obtained is coated on polyester film and dried at 70-90 C.
- for 4-7 minutes. The dry coating weight is 1.3-1.4 g./sq. ft.
The dried film is then overcoated with a solution containing 5.8 g. of methyl ethyl ketone, 1.1 g. of methanol, 0.4 g. of ~075065 polyvinyl acetate polyvinyl chloride copolymer, 0.6 g. of a hindered phenol developer (l,l-bis(2-hydroxy-3,5-dimethylphenyl)-3,5,5-trimethylhexane) and 0.12 g. of toner (phthalazinone) and again dried, the added dry coating weight being 0.35 g.~sq. ft. The film is exposed sensitometrically using a 6100 K. light source and developed by heating for 30 seconds at 260 F.
A summary of the relative speeds of films prepared in this manner with a variety of different amides is given in the following table. Some of the films prepared are not in accordance with the invention defined above in respect to the amide and are presented for purposes of comparison.
Table 1 Amide Rel. Speed none (control sample) N,N'-diacetyl-2-aminophenyl disulfide 0.6 succinimide 0.7 N,N-dimethyl chloroacetamide 0.8 polyvinylpyrrolidone 0.8 N-methyl maleimide 0.8 cyclohexanone 1.0 N-ethylsuccinimide 1.0 butyrolactone 1.0 N,N-diethylurethane 1.0 p-nitrobenzamide 1.3 formamide 1.3 N,N-diphenylacbtamide 2.0 N,N,N',N'-tetramethyl phthalamide 2.0 5-methyl-2-pyrrolidinone 2.1 l-vinyl-2-pyrrolidinone 2.1 benzamide 2.6 acetamide 2.9 D 5 _ ~075065 Amlde Rel. Speed poly-N,N'-dlmethylacrylamide 3.0 p-methoxybenzamlde 5.6 p-chlorobenzamide 6.5 N,N-dimethylacrylamide 6.5 N,N-dimethyl lactamide 6.8 N,N-dimethyl ~ormamide 6.8 hexamethyl phosphonamide 7.1 N,N'-diacetylpiperazine 7.4 N-methylacetamide 9.1 - --N,N'-dimethylethyleneurea 12 N-methylpropionamide 12 ~ 2-pyrrolidinone 13 N,N-dimethylbenzamide 17 ~ 15 hexamethylene formamide 26 caprolactam 26 N,N-dimethylacetamide 40 N,N,N'N'-tetramethylurea 49 N-acetyl morpholine 55 1-methyl-2-pyrrolidinone 59*
N,N-dimethylnicotinamide 60 l-methyl-2-piperidone 66 l-methyl-2-pyridone 90 l-benzyl-2-pyrrolidinone 132 *The value reported for l-methyl-2-pyrrolid~none is an average of several trials showing a range of relative ~.;
speeds of 44 to 72.

. .

~0750~;5 It may be observed that of the compounds tested, the first nine resulted in no lmprovement in relative speed as compared with the control sample. The succinimides in parti-cular caused appreciable fog formation and such materials are undesirable. Speeds of about 1.3 to 1.5 relative to a control speed of unity are readily observable; at relative speeds of five to ten, the effect is highly significant; at relative speeds greater than ten, particularly those greater than 50, the products are commercially useful in operations previously inaccessible to the dry silver sheet materials.

Example 2 This example illustrates the effect on sensitivity of adding the sensitizing amide at different times in the pre-paration sequence. The components and amounts of each are as set forth in Example 1, the sole difference being in the step of adding the sensitizer. In each case the amide is l-methyl-

2-pyrrolidinone.
A. The amide is added to the silver soap dispersion just prior to halidization. The relative speed is 72.
B. The amide is added in a final step following addition of the halidizing agents and additional binder resin and shortly prior to coating. The relative speed is 1.6.
C. The amide is added to the silver soap dispersion prior to adding the one per cent of polyvinyl butyral resin.
The relative speed is 50.
D. The amide and the one per cent of polyvinyl - butyral resin are added simultaneously. The relative speed (for a single test) is 69, i.e., very similar to A and slightly greater than C.

~o75065 In the foregoing Examples the amide ls present in equlmolar amount based on the silver soap. Useful results in terms of signlficantly increased relative speeds are obtained with between one-hundreth and two moles of sensitizing amide per mole of silver soap. Example 3 illustrates the effect of amide concentration on speed, using l-methyl-2-pyrrolidinone in all cases.

Example 3 An iodobromide emulsion similar to that in Example l is prepared as follows. To 178 g. portions of a mixture of silver behenate in the solvent system described previously are added mixtures each containing a different amount of the amide and sufficient methyl ethyl ketone to make lO grams. After 5 minutes' mixing, l gram of polyvinyl butyral resin ls added and stirring continued. Under safelight conditions the mixture is treated with a mixture containing hydrobromic acid and cadmium iodide prepared immediately before use by combining 5 ml. of a solution containing 5 ml. of 48% hydrobromic acid in 87 ml. of methanol with 1.5 ml. of a solution containing ; 20 1.83 g. of cadmium iodide in lO0 ml. of methanol.
, Stirring is continued 30 minutes after which 0.5 ml.
of the mercuric bromide solution described previously is added followed by 12.5 g. of polyvinyl butyral resin. Coatings are prepared as in Example l and are overcoated as described pre-viously. Table 2 summarizes the effects of variations in the amount of the amide added initially on the photographic speed of the finished film relative to that of a control film con-taining none of the amide.

;

~075065 Table 2 Amount of Amlde Mole Ratlo Added, g. Amlde/Ag Relatlve Speed ---- 1.0 0.015 .003 1.8 0.036 .007 2.3 0.053 .01 1.5 0.107 .02 1.5 0.30 .o6 5.2 10 0.51 .10 4.8 1.0 .2 3.9

3.0 .6 9.8 5.0 1.0 14.1 Many of the sensitizing amide materials are per se volatile and might be expected to be removed from the coatlng during the step of solvent removal. Apparently a considerable proportion, at least of the more volatile materials, is indeed lost. However, it has been found possible to detect at least trace amounts of l-methyl-2-pyrrolidinone in sheets made with : 20 this material even after prolonged heating, using such so-phisticated methods of analysis as gas chromatography on a chloroform extract of the coating.
Somewhat comparable sensitizing effects may also be obtained with dimethyl sulfoxide. Thus, addition of this material subsequent to halidization, as in Example 2B, results in a sheet having a relative speed of only 2.2; whereas a relative speed of 52 is achieved by introducing the ~imethyl sulfoxide prior to halidization, i.e., as in Example 1. How-ever, this substance decomposes on heating, is moderately - _ 9 _ .~ .

: . ., ~ .
: ' ' , ' . ' ' ~ 0750~;5 hazardous, and i~ to be avolded ln the practlce of the ln-ventlon.
Spectral sensltlzatlon of the composltlons and coatlngs of thls inventlon may be accompllshed in known manner, l.e., through the lncorporatlon of spectral sensltlzing dyes, of whlch a number of examples have been glven ln U. S. Patent No. 3,457,075 previously referred to. The sensltlzlng amldes of the present inventlon are colorless and do not affect the spectra; response of the sllver hallde other than to increase lts apparent natlve llght sensltlvlty.
Halidlzatlon with other sources of halide ions, to -- -produce other photosensltive silver halides or mixtures for specific purposes, is likewise taught in the prior art and may be employed in the practice of this invention; greatest speed is ordinarily obtalned with dry silver compositions wherein the photosensitive silver halide catalyst-forming means is a mixture of silver bromide and a minor proportion of silver lodide.
Other variations include, for example, incorporating all components in a single coating, or adding the hindered phenol reducing agent to the first rather than the second coating. In all cases it is essential that the sensitizing amide be added to the silver soap prior to conversion of a portion of the silver content to the photosensitive silver halide.

Claims

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

1. In the process of making a light-sensitive heat-developable dry silver sheet material containing (a) photosensitive silver halide catalyst-forming means and (b) heat-sensitive reactant image-forming means including an organic silver salt oxidizing agent and a reducing agent for silver ion, the oxidation reduction reaction of which, to produce a visible charge, is accelerated by said catalyst, the improvement comprising: mixing with the organic silver salt, prior to halidization thereof, a spectrally inert sensi-tizing amide, and thereafter halidizing a minor proportion of said organic silver salt, wherein said sensitizing amide sensitizes the sheet material so that the photographic speed of the material is increased to at least two compared to an otherwise identical sheet material free of said amide whose speed is taken as unity, speed being measured by sensitometric exposure to a 6100°K light source and heat development for 30 seconds at 260°F, said sensitizing amide being a monomeric amide having the structure:
R1CONR2R3, R1R2NCONR3R4 or (R1R2N)3PO

wherein one of the R groups represents hydrogen or a group with from one to eight carbon atoms and no more than one heteroatom selected from the group consisting of N, S and O for each two carbon atoms and the remaining R groups represent groups with from one to eight carbon atoms and no more than one heteroatom selected from the group consisting of N, S and O for each two carbon atoms, and groups forming rings with the amide nitrogen included, with the proviso that none of R1, R2, R3 and R4 in the formula may be hydrogen.

2. Process of claim 1 wherein said amide is a 2-pyrrolidinone.

3. Process of claim 1 wherein said amide is a 1-alkyl-2-pyridone.

4. Process of claim 1 wherein said amide is a 2-piperidone.

5. Process of claim 1 wherein said amide is a substituted urea of the formula wherein R1 - R4 are as defined above.

6. Process of claim 1 wherein said amide is a tertiary amide.

7. Process of claim 1 wherein the molar ratio of said amide to said salt is between one-hundredth and two.

8. Process of claim 7 wherein said molar ratio is approximately unity.

9. A light-sensitive heat developable dry silver sheet material comprising (a) photosensitive silver halide catalyst forming means and (b) heat-sensitive reactant image-forming means including an organic silver salt oxidizing agent and a reducing agent for silver ion, further comprising a monomeric spectrally inert organic sensitizing amide added prior to hali-dization of said organic silver salt and having a photographic speed of at least 5 compared to an otherwise identical sheet material free of said amide and wherein the speed is taken as unity, speed being measured by sensito-metric exposure to a 6100°K light source and heat development for 30 seconds at 260°F, said sensitizing amide being represented by the formula:
R1CONR2R3, R1R2NCONR3R4 or (R1R2N)3PO

wherein one of the R groups represents hydrogen or a group with no more than eight carbon atoms and no more than one heteroatom selected from the group consisting of N, S and 0 for each two carbon atoms and the remaining R groups represent groups with no more than eight carbon atoms and no more than one heteroatom selected from the group consisting of N, S and 0 for each two carbon atoms, and groups forming fused rings with the amide nitrogen included, with the proviso that none of R1, R2, R3 and R4 in the formula may be hydrogen.

10. The process of claim 2 wherein said amide is a 1-alkyl or 1-benzyl pyrrolidinone.

11. The process of claim 4 wherein said amide is a 1-alkyl piperidone.

12. The process of claim 10 wherein said amide is a 1-alkyl pyrroli-dinone wherein said 1-alkyl group has 1 to 4 carbon atoms.

12. The process of claim 11 wherein said amide is a 1-alkyl piperi-done wherein said 1-alkyl group has 1 to 4 carbon atoms.

14. The process of claim 1 wherein said amide is selected from the group consisting of N,N-dimethylacrylamide, N,N-dimethyl lactamide, N,N-di-methyl formamide, hexamethyl phosphonamide, N,N-diacetylpiperazine, N-methyl-acetamide, N,N-dimethylethyleneurea, N-methylpropionamide, 2-pyrrolidinone, N,N-dimethylbenzamide, hexamethylene formamide, caprolactam, N,N-dimethyl-acetamide, N,N,N',N'-tetramethylurea, N-acetyl morpholine, 1-methyl-2-pyrrolidinone, N,N-dimethylnicotinamide, 1-methyl-2-piperidone, 1-methyl-2-pyridone, and 1-benzyl-2-pyrrolidinone.

15. The process of claim 1 wherein R1, R2, R3, and R4 are saturated acyclic moieties with no more than four carbon atoms.

16. The process of claim 15 wherein R1, R2, R3 and R4 are alkyl groups.

17. The process of claim 15 wherein R1, R2, R3 and R4 are alkoxy groups.

18. The process of claim 15 wherein R1, R2, R3 and R4 contain no skeletal hetero atoms.