DE1547748B1 - Process for preparing a light developable silver halide photographic emulsion - Google Patents

Description

lation-sensitive photographic recording 40 has a large density difference between image areas and

Have non-image areas, which remain in place even after prolonged storage, and which are used for production of records with archive quality are chemically developable.

It has now been found that this object is achieved in a surprisingly simple manner can be used to prepare the light developable silver halide photographic emulsion Silver halide grains used in counter

used materials belonging to the class of so-called developable recording materials. In order to produce permanent, visible images, these recording materials - like the name says - be subjected to chemical development and fixation after exposure.

About this subsequent chemical development
to save, one has so-called copy-out
Developed photographic recording materials which upon exposure directly provide a visible wart of both an organic thioether and an image and do not have to be developed. of a thiocyanate, optionally in the presence of these copying-out recording materials lead salts.

but have the disadvantage that the invention generally provides a method for

are much less sensitive than the fully developed. ■ Making a photodevelopable photographic one Recording materials and that the silver halide emulsion thereof, their silver halide produced Images are fickle and only form nid in an acidic environment in the presence of a have a short lifespan.

For the rapid recording of light rays, for example in oscilloscopes and so-called light recorders, a third type of photographic recording material has recently been used, which are referred to as so-called light-developable recording materials. On the one hand, these recording materials are more sensitive than those that can be copied out Recording materials and, on the other hand, do not require chemical development like that developable recording materials. They have a using a hydrophilic Thioethers of the general formula

H0 (—R — S—) _r R0H
(HO — R — S — R — O — R ² -) ₂

R'-O-R-S-R CNH-R ²

(R'- O-R- S-R-) ₂ S

\ R'-NHC RSRJ ₂ O
or

(RO) ₅ -R

S S

(RO) ₅ -R

where means

R is an alkylene radical with 1 to 5 carbon atoms, R 'is an alkyl radical with 1 to 5 carbon atoms, R ^{2 is} an alkylene radical with 1 to 5 carbon atoms, r is the number 1, 2 or 3 and

s is the number 1 or 2,

preferably in amounts of 1 to 10 g per mole of silver halide, preferably in the further presence a water-soluble lead salt, which is characterized in that the silver halide formation in the presence of a water-soluble thiocyanate in amounts of 1 to 10 g per mole of silver halide a pH value below 5 takes place.

The preferred thiocyanate used in the process of the invention is sodium or potassium cyanate and as thioether a thioether of the general formulas

HO (- CH _{2 CH 2} - S -) _r - CH ₂ CH ₂ OH

(CH ₂ CH ₂ - O) ₅ -CH ₂ CH ₂

(CH ₂ CH ₂ - O) ₅ - CH ₂ CH ₂

where r is the number 1, 2 or 3 and s is the number 1 or 2 or

1, 10-dithia-4,7,13,16-tetraoxycyclooctadecane,
l, 17-di- (N-ethylcarbamyl) -6,12-dithia-9-oxa-

heptadecane,

3,15-dioxa-6,9,12-trithiaheptadecane,
10.13-diaza-3,20-dioxa-9,14-dioxo-6,17-dithia-

docosan,

6,9-dioxa-3,12-dithiatetradecane-1,14-diol,
3,6,9-trithiaundecane-1,11-diol,
4,10-dioxa-1,7-dithiacyclododecane or
1,8-dihydroxy-3,6-dithiaoctane.

According to a preferred embodiment, a silver halide is used which is at least 50 mol percent consists of bromide and less than 10 mole percent iodide.

According to a further preferred embodiment, the lead salt used is lead nitrate in an amount of 0.85 g per mole of silver halide.

The light developable photographic silver halide emulsions obtainable by the process of the invention represent a new class of light developable photographic emulsions which are particularly suitable for use in oscilloscope recorders, in which a light beam is reflected from a galvanometer mirror, for recording very rapid events, for example rocket launches , suitable. With the most varied of exposure intensities and transport speeds of the recording material within the recording device, they provide high-contrast and permanent recordings with a low background density. A light developable photographic recording material produced therewith has balanced sensitivity properties, the minimum image density D _mi "being just as low as when using thioethers alone, while the maximum image density D _{max is} just as great as when using thiocyanate alone. As can be seen from the comparative example below, the photodevelopable silver halide photographic emulsion prepared according to the present invention has a synergistic increase in sensitivity with short exposure times and a balanced increase in sensitivity with long exposure times, so that excellent photographic images can be produced therewith under a wide variety of recording conditions.

That for preparing the light developable silver halide photographic emulsion by the process Thioethers suitable for the invention are, for example, from the French patent 1,368,647 and US Pat. No. 3,271,157. They are in aqueous solution in concentrations from about 0.1 to 50, preferably from 1 to 10 g of thioether per mole of silver halide are used. Apart from the above-mentioned specific preparation of the silver halide grains, starting materials known for preparing the silver halide emulsions by the process of the invention and manufacturing techniques used in the manufacture of light developable photographic Silver halide emulsions can usually be used. This means that as silver halides for example silver chloride, silver bromide, silicon bromide iodide, silver chloride iodide and silver chloride bromide iodide can be used. Preferably, the silver halide is at least 50 mole percent silver bromide and less than 10 mole percent from silver iodide. Particularly suitable emulsions are described, for example, in the USA patent 2,592,250 and in the book by G1 a f k i d e s, "Photographic Chemistry", Vol. 1, pp. 31-32.

The process of the invention is particularly suitable for the preparation of so-called internal image emulsions, that is to say emulsions with silver halide grains which have predominantly internal sensitivity. Such emulsions are those which are coated on a transparent substrate, through a light intensity scale between 1 χ 10 ~ ⁶ and a second exposed, at 18.3 ° C for 5 minutes in a 0.3% potassium ferricyanide solution and bleached for 5 minutes in a Type B developer of the composition given below - have a sensitivity which, measured at a density of 0.1 above fog, is greater than the sensitivity of an identical test specimen exposed in the same way and for 6 minutes at 20 ° C has been developed in a developer A of the composition given below.

The developer B is a so-called "inner grain" developer, the developer A is a so-called "surface" developer.

Developer A

N-methyl-p-aminophenol sulfate .... 0.31 g

Sodium sulfite anhydrous 39.6 g

Hydroquinone 6.0 g

Sodium carbonate anhydrous .... 18.7 g

Potassium bromide 0.86 g

Citric acid 0.68 g

Potassium metabisulphite 1.5 g

Made up to 11 with water.

Developer B

N-methyl-p-aminophenol sulfate 2.0 g

Anhydrous sodium sulfite 90.0 g

Hydroquinone 8.0 g

Sodium carbonate monohydrate 52.5 g

Potassium bromide 5.0 g

Sodium thiosulfate 10.0 g

Made up to 11 with water.

The preparation of the silver halide photographic emulsion by the process of the invention takes place in such a way that a water-soluble silver salt and a water-soluble halide in one acidic medium are reacted with each other with precipitation of the corresponding silver halide. Of the The pH of the medium is below 5. To acidify the reaction medium, for example Acids such as phosphoric acid, trifluoroacetic acid, hydrobromic acid, hydrochloric acid, sulfuric acid and nitric acid can be used. Preferably, an excess of water-soluble Halide used. The pAg value during the silver halide precipitation is expediently 8 until 10.

The water-soluble thiocyanate and the thioether can be used in the colloid solution and / or in the reaction be added with the aqueous silver salt solution certain aqueous halide solution. Preferably the silver halide grains should have an average grain size of about 0.1 to 10 microns, particularly from about 0.5 to 2 microns. It has proven advantageous to use the silver halide emulsion after the precipitation of the silver halide, but before the application of the emulsion to a layer support, additionally a water-soluble one To add halide, preferably an iodide. It has proven to be useful when adding one additional water-soluble halide 0.1 to 50 mol percent, preferably 1 to 10 mol percent, of the water-soluble halide, based on the silver halide, to be added. Particularly advantageous water-soluble halides for this purpose are, for example, the ammonium, calcium, lithium, Magnesium, potassium and sodium salts.

If the silver halide emulsions are prepared in the presence of a water-soluble lead salt, this is expediently added to the water-soluble halide together with the water-soluble silver salt. Lead-silver halides precipitate. When using a lead salt, the concentration of the same is expediently 0.01 to 5 mol percent, based on the silver bromide as a constituent of the silver halide. The use of lead ions in the formation of the silver halide causes the background density (D _min ) to decrease while the image density _{(D max} ) is increased.
The formation of images using the photographic material thus obtained is carried out under the conditions normally used in the exposure and development of light-developable photographic material. This means that the photographic recording material of the invention is first exposed to the action of an electromagnetic radiation source of high intensity, the action of the radiation being relatively brief, after which the exposed material is exposed to a radiation source of lower intensity. The first exposure is preferably carried out with at least 1.076 lux seconds at an intensity of more than 1076 lux. Light sources of high intensity suitable for the first exposure are known and are used, for example, in oscillographs. For example, radiation sources such as those described in US Pat. No. 2,580,427 are suitable. Radiation sources that emit visible light of high intensity or X-rays are also suitable. The following may be mentioned, for example mercury vapor lamps with a strong blue and ultraviolet emission, xenon lamps, light g of a composition emit that approaches the daily ™ light, and tungsten lamps with high red-light emission. This first exposure initially creates a latent image in the emulsion layer.

The formed latent image is then developed light by the emulsion layer to ver Erstbelichtung ₇ applies a radiation source of lower intensity than it was exposed.

At least 0.0011 lux seconds are expediently used for this second exposure. as Radiation source, the usual known radiation sources come into question, the fluorescent light emit, e.g. conventional incandescent lamps or daylight lamps. It is also suitable for a second exposure Daylight.

In general, the latent image formed in the emulsion layer during the first exposure is not visible and only becomes visible after the development of light. If desired, the photographic material during development of the light heated ^ are. Thus, the photographic recording \ material can for example be heated to a temperature of 90 to 200 ° C long after Erstbelichtung 1 to 30 seconds.

Optionally, the photographic recording material after the first exposure latent image has been created, or after the second exposure to produce archival quality images, developed and fixed in a known manner in aqueous developer solutions and fixing solutions will.

The following examples are intended to illustrate the invention in more detail.

example 1

By slowly adding an aqueous solution of silver nitrate containing 0.85 g of lead nitrate per mole of silver nitrate and a solution of potassium bromide and sodium chloride to one in vigorous motion held 1.1% aqueous gelatin solution at a temperature of 60 ° C with a pH value of about 2.0 adjusted by nitric acid became various light developable gelatin-silver chlorobromide emulsions with 5 mole percent chloride

and 95 mole percent bromide. The precipitation of the silver halide took place in the presence of the additives given in Table A below. The concentrations given in the table below mean g / per mole of silver halide.

Table A.

emulsion

additions

A *)!, S-dihydroxy ^ o-dithiaoctane (2.6 g)

+ Sodium thiocyanate (2.2 g)

B sodium thiocyanate (2.2 g)

C sodium thiocyanate (4.8 g)

D 1,8-dihydroxy-3,6-dithiaoctane (2.6 g)

E l.S-Dihydroxy-S ^ -dithiaoctane (4.8 g)

F 1,8-dihydroxy-3,6-dithiaoctane (2.6 g)

+ Sodium thiosulfate (2.2 g)
*) Photographic emulsion according to the invention.

To each of the emulsions was added 0.4 mole percent, based on the silver halide, of imidazole-2-thiol added and about 2 mole percent, based on the silver halide, of potassium iodide. The different Emulsions were then made with 5 - [(1-ethylnaphtho- (1,2-d) thiazolin-2-ylidene) -ethylidene] -3-η-heptyl-phenyl-2-thiohydantoin spectrally sensitized.

The emulsions obtained in this way were applied to photographic paper supports in such a way that 2.8 g of silver and 5.16 g of gelatin were obtained ^{on a support area of 1 m 2.} The photographic papers obtained were then exposed in a conventional sensitometer for 10 ~ ⁴ seconds through a step wedge with neutral density levels of 0.15 log E. The latent images obtained were developed by exposing the photographic materials to 377 lux of fluorescent daylight for 5 minutes.

Then the maximum and the minimum density and the number of visible 0.15 log E levels were measured. The maximum densities (D _max ) corresponded to the densities of the exposed areas, and the minimum densities (jD, ",") corresponded to the densities in the background areas or non-image areas. The number of visible 0.15 log Ε steps served as a guide for the sensitivity of the emulsion layers in question. The light-developed recording materials obtained were exposed for 63 hours to fluorescent daylight lamps of 753 lux, whereupon the D _max values,! »,«, »Values and the density levels were determined again. The results obtained are shown in Table B below.

Table B.

emulsion Difference D _max - D _mi "
after the light
development Loss of visible
0.15 log Ε steps
the development of light A. 0.23 no loss B. 0.10 Minus 1 level C. 0.15 Minus 1 level D. 0.17 Minus 1 level E. 0.20 Minus 1 level F. no noticeable difference after the
Light development

The data given in Table B above show that the use of a water-soluble thiocyanate together with an organic thioether (emulsion A according to the invention) leads to a light-developable silver halide emulsion whose difference D _max - D _{min is} particularly large.

Example 2

This example shows that a photographic material prepared according to the invention can be further chemically developed even after the imagewise exposure and light development can if archival quality images are to be produced.

A photographic recording material with an emulsion corresponding to emulsion A of Example 1 was, as described in Example 1, exposed and light-developed. The light-developed photographic material thus obtained was then developed in a developer of the above composition A for 60 seconds at a temperature of 21 ° C. It was then fixed, washed and dried in the usual way. The original D _mO3c zones of the light-developed recording material were not chemically developed, while the original D _mi - "zones were developed to a high density. In this way a reverse image was obtained. A value of 0.64 was measured for the difference D _max - D _min.

Example 3

Further photographic recording materials of the construction described in Example 1 were produced with an emulsion of the type of emulsion A, but this time the silver halide in Presence of 2.2 g of potassium thiocyanate instead of sodium thiocyanate and 2.0 g of l, 10-dithia-4,7,13,16-tetraoxacyclooctadecane, 4,10-Dioxa- 1,7-dithiacyclododecane,!, N-DiCN-äthylcarbamyty-ojn-dithia ^ -oxaheptadecane, 3.15 - Dioxa - 6.9.12 - trithiaheptadecane, 10.13 - Diaza - 3.20 - dioxa - 9.14 - dioxo - 6.17 - dithiadocosane, 3,6,9-trithiaunde'can ~ l, ll-diol or 6,9-dioxa-3,12-dithiatetradecane-1,14-diol instead of 1,8-dihydroxy-3,6-dithiaoctane was prepared. The concentrations used are again expressed in grams per mole of silver halide in the emulsion.

The emulsions obtained were, as described in Examples 1 and 2, exposed and light-developed. In all cases, the same favorable results as in Examples 1 and 2 were obtained.

Example 4 (comparative example)

Comparative tests were carried out to demonstrate the technical progress that can be achieved according to the invention carried out using light developable photographic materials having a silver halide emulsion layer were prepared whose silicon superhalide grains were once in the presence of a thiocyanate alone (sample 1), once in the presence of a thioether alone (sample 2) and once in the presence both a thioether and a thiocyanate were precipitated at pH below 5 (sample 3). The recording materials obtained in this way were subjected to customary sensitometric tests.

109553/355

In the process, those given in Table C below were given Get results.

a) Production of the light-developable photographic recording materials

Following the procedure given in Example 1, three silver halide emulsions were prepared: the precipitation of the silver halide grains in the presence of the thioether indicated below and / or thiocyanate was carried out in the specified amounts:

Sample 1: 2.2 grams of sodium thiocyanate per mole

Silver halide,
Sample 2: 2.2 g of 2,2 '- (ethylenedithiodiethanol) per

Moles of silver halide, sample 3: 2.2 g sodium thiocyanate + 2.6 g

2,2 '- (ethylene dithiodiethanol) per mole

Silver halide.

Each emulsion was 5 - [(l-ethylnaphtho (l, 2-d) -thiazolin - 2 - ylidene) ethylidene] - 3 - η - heptyl -1 - phenyl-2-thiohydantoin, Potassium iodide, 2-imidazolinethione, a surface-active agent and a hardener were added. The photosensitive layer thus obtained was applied to a paper support in the usual manner. The three light developable photographic materials thus obtained were tested as indicated below.

b) Investigation of the sensitometric properties

The recording material samples produced as described under a) were exposed sensitometrically through a continuous gray wedge with a density distance of 0.3. The short exposure lasted 34 microseconds (an unfiltered xenon light flash with an intensity by a factor of 750 ± 50 higher than the long exposure), the long exposure lasted ₅ seconds with simulated xenon light. The following results were obtained:

Table C.

Relative sensitivity

(compared to a density of 0.05

above D _m! ")

short exposure *)

long exposure **)

Background coloring

Sample 1
Sample 2

Sample 3

87 97

100

160

73

100 dark blue greyish cream colored light cream colored

*) 34 microseconds, xenon light.
**). V ₅ seconds, xenon light.

In all cases, the image was exposed to a cold white daylight lamp for 30 seconds light developed at 53.8 lux for a long time and 538 lux for 5 minutes.

From the test results given above, it can be seen that when used at the same time a thioether and a thiocyanate to precipitate the silver halide grains in the silver halide emulsion a light developable photographic material was obtained whose sensitivity at short exposure times was improved in a synergistic manner and that a balanced increase in sensitivity at long Exposure times so that it was used to make photographic direct copies under changing Copying conditions was more suitable than the previously known recording materials.

Claims (6)

Claims: 40-45 or (R'- O-R- S-R-) 2 S \ R'-NHC-R-S -R-J2 O (R-O) x -R S S (R-O) 5-R where means 55 1. Method of making a photodevelopable photographic silver halide emulsion whose silver halide formation in an acidic medium in Presence of a thioether of the general formula HO (—R — S—) _r RAW (HO — R— S —R— O — R ² -) ₂ R'-O-R-S-R CNH-R ² -J R is an alkylene radical with 1 to 5 carbon atoms, R 'is an alkyl radical with 1 to 5 carbon atoms, R ^{2 is} an alkylene radical with 1 to 5 carbon atoms, r is the number 1, 2 or 3 and s is the number 1 or 2 preferably in amounts of 1 to 10 g per mole of silver halide, preferably more Presence of a water-soluble lead salt, characterized in that the Silver halide formation in the presence of a water-soluble thiocyanate in amounts of 1 to 10 g takes place per mole of silver halide at a pH below 5. 2. The method according to claim 1, characterized in that that sodium or potassium thiocyanate is used. 3. The method according to claims 1 and 2, characterized in that a thioether of the general Formulas is used HO (-CH ₂ CH ₂ - S -) _r - CH ₂ CH ₂ OH (CH ₂ CH ₂ - O) ₅ -CH ₂ CH ₂ S - S (CH ₂ CH ₂ - 0) _s - CH ₂ CH ₂ where r is the number 1, 2 or 3 and s is the number 1 or 2. 4. The method according to claim 3, characterized in that the thioether 1, 10-dithia-4,7,13,16-tetraoxycyclooctadecane, 1,17-Di (N-ethylcarbamyl) -6,12-dithia-9-oxa- heptadecane, 3,15-dioxa-6,9,12-trithiaheptadecane,
10,13-diaza-3,20-dioxa-9,14-dioxo- 6,17-dithiadocosane, ö ^ -Dioxa ^ lI-dithiatetradecane-l ^ -diol,
3,6,9-trithiaundecane-1,11-diol,
4,10-Dioxa-1 J-dithiacyclododecane or
1,8-dihydroxy-3,6-dithiaoctane is used. 5. Process according to claims 1 to 4, characterized in that the silver halide to consists of at least 50 mole percent bromide and less than 10 mole percent iodide. 6. The method according to claims 1 to 5, characterized in that 0.85 g of lead nitrate per Moles of silver halide can be used.