Agfa-gevaert Ag

Agfa-gevaert Aktiengesellshcaft

Walter Patzold

Helmut Kampfer

Franz Moll

Bruno Mucke

Heinrich Odenwalder

Klaus Wagner

Anita Von Konig

Lothar Rosenhahn

Hans Ohlschlager

Harald Von Rintelen

Friedhelm Sommer

Helmut Reuss

Gunther Mahlberg

Karl Czernik

Werner Verburg

Karl Steinbeck

A quick-developing highly sensitive silver halide emulsion distinguished by steep gradation, a minimal increase in fog during storage, improved threshold gradation and low sensitivity to below-threshold pre-exposure is obtained by the addition of a diindoyl disulfide during preparation of the emulsion.

Photographic silver halide emulsion

A gradation-variable BW paper comprising only one silver halide emulsion layer, in which re-sensitization is avoided, is obtained with a mixture of at least two photosensitive silver halide emulsions, of which one has its absorption maximum in the range from 480 to 580 while the other has its absorption maximum below 480 nm, providing the emulsion which has its absorption maximum below 480 nm contains a compound corresponding to the following formula ##STR1## in which X represents the remaining members of an optionally benzo- or naphtho-condensed heterocycle optionally containing further substituents.

Gradation-variable black-and-white paper

The sensitivity/fog ratio can be improved by using photographic silver halide emulsions containing gelatine which has a cysteine content of less than 10 ppm and a gold number of .gtoreq.23 .mu.mol/g.

Photographic silver halide emulsion containing gelatine

A gradation variable black-and-white paper containing only one light sensitive silver halide emulsion layer in which transfer of sensitization is prevented may be obtained by sensitization with at least one compound corresponding to the following formula ##STR1## in which at least one of the groups R.sub.1, R.sub.5 or R.sub.6 is halogen.

Gradation variable black- and -white paper

Compounds corresponding to the formula: ##STR1## wherein R.sub.1 and R.sub.2 denote alkyl groups with 1 to 8 carbon atoms, an optionally substituted alkenyl group with 2 to 5 carbon atoms, an optionally substituted cycloalkyl group with 5 or 6 carbon atoms or an optionally substituted aryl group or R.sub.1 and R.sub.2 together represent the ring members required to form a 5- or 6-membered cycloalkyl or cycloalkenyl group, are suitable for use as antifoggants in photographic recording materials.

Photographic recording material

The tamper-proof document consists of a photographic material as information carrier comprising front- and back gelatine layers, the outer of the gelatine layers of which contain particles of a homo- or copolymer of an acrylic and/or methacrylic acid ester. The information carrier is laminated on one or both sides to a transparent foil by means of a hardenable adhesive. The document is remarkably safe against falsification.

Tamper-proof document

An improved photographic material is provided comprising a mixture of individual emulsions having the same narrow particle size distribution but which are desensitized in a differring degree.

Emulsion mixture for color reversal (reflection viewing) material

Process for the preparation of silver images by imagewise exposure of a photographic material comprising at least one light-sensitive silver halide emulsion layer and treatment of the material with a developer composition, wherein the improvement comprises the development is carried out in the presence of 3-mercapto-5-(2-furyl)-1,2,4-triazole. The 3-mercapto-5-(2-furyl)-1,2,4-triazole decreases the fog during development, and when this is the first development in a black-and-white or color reversal process, increases the reversal silver or color density.

Growing community of inventors

Leverkusen, Germany

Walter Patzold