Patents by Inventor David G. Leppard

David G. Leppard has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 4518688
    Abstract: Compounds of the formula I ##STR1## in which X is a group ##STR2## and R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are monovalent organic radicals, at least one of which contains a sterically hindered phenol group and at least one of which contains a polyalkylpiperidine group, are outstanding light stabilizers for color-photographic recording materials. They also have a stabilizing action on the photo dyes and their precursors when stored in the dark.
    Type: Grant
    Filed: November 25, 1983
    Date of Patent: May 21, 1985
    Assignee: Ciba-Geigy AG
    Inventors: David G. Leppard, Jean Rody
  • Patent number: 4518679
    Abstract: A color-photographic recording material which, in at least one light-sensitive silver halide emulsion layer, one intermediate layer and/or one protective layer, contains, as a stabilizer, at least one polyalkylpiperidine compound of the formula I or II ##STR1## in which m is the numbers 1 or 2 and, if m=1, A is a group of the formula ##STR2## and, if m=2, A is a group of the formula ##STR3## Color images which are obtained by image-wise exposure and development of this color-photographic recording material, display good stability towards the action of visible and ultraviolet light.Reference is made to the description in respect of the meanings of the substituents and symbols in the formulae I and II.
    Type: Grant
    Filed: December 2, 1983
    Date of Patent: May 21, 1985
    Assignee: Ciba-Geigy AG
    Inventors: David G. Leppard, Jean Rody
  • Patent number: 4517283
    Abstract: A color-photographic recording material which, in at least one light-sensitive silver halide emulsion layer, an interlayer and/or a protective layer, contains a stabilizer mixture comprising(i) a compound with at least one group of the formula ##STR1## or a polymer with recurring structural units of the formula I, and (ii) a phenolic antioxidant.Color images obtained by imagewise exposure and development of this color-photographic recording material show good stability to the action of visible and ultraviolet light.With respect to the definitions of the substituents in formula I, reference is made to the description.
    Type: Grant
    Filed: December 15, 1983
    Date of Patent: May 14, 1985
    Assignee: Ciba-Geigy AG
    Inventors: David G. Leppard, Jean Rody
  • Patent number: 4496649
    Abstract: A color-photographic recording material which, in at least one light-sensitive silver halide emulsion layer, an interlayer and/or a protective layer, contains at least one polyalkylpiperidine compound of the formula I ##STR1## in which R is an OH group and R.sub.1 is a group of the formula II ##STR2## or of the formula ##STR3## and X is a group of the formula ##STR4## or of the formula ##STR5## Color images obtained by imagewise exposure and development of this color-photographic recording material show good stability to the action of visible and ultraviolet light.With respect to the definitions of the substituents and symbols in the formulae, reference is made to the description.
    Type: Grant
    Filed: December 15, 1983
    Date of Patent: January 29, 1985
    Assignee: Ciba-Geigy AG
    Inventors: David G. Leppard, Jean Rody
  • Patent number: 4465757
    Abstract: Compounds of the formula I ##STR1## in which A, R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are as defined in claim 1, are effective optical stabilizers for photographic dyes and their precursors. They are added to the colorphotographic recording materials as the latter are being prepared, and, as a result, the developed images have a longer optical stability.
    Type: Grant
    Filed: September 16, 1983
    Date of Patent: August 14, 1984
    Assignee: Ciba-Geigy A.G.
    Inventors: David G. Leppard, Jean Rody
  • Patent number: 4465765
    Abstract: Compounds of the formula I ##STR1## in which A is a direct bond or a substituted or unsubstituted alkylene radical, X is --O-- or --N(R.sup.16)--, R.sup.2 is a monovalent radical, R.sup.5 or R.sup.3 is hydroxyl, and R.sup.1, R.sup.4, R.sup.6, R.sup.7 and R.sup.8 are hydrogen or monovalent radicals, are effective stabilizers for photographic dyes and precursors thereof. In particular, they increase the light fastness of the developed color images.
    Type: Grant
    Filed: August 16, 1983
    Date of Patent: August 14, 1984
    Assignee: Ciba-Geigy A.G.
    Inventors: David G. Leppard, Jean Rody
  • Patent number: 4452884
    Abstract: A color-photographic recording material which, in at least one light-sensitive silver halide emulsion layer, an interlayer and/or a protective layer, contains at least one polyalkylpiperidine compound of the formula I ##STR1## as a light stabilizer. Color images obtained by imagewise exposure and development of this color-photographic recording material display good stability to the action of visible and ultra-violet light.With respect to the definitions of the substituents and symbols in formula I, reference is made to the specification.
    Type: Grant
    Filed: December 17, 1982
    Date of Patent: June 5, 1984
    Assignee: Ciba-Geigy AG
    Inventor: David G. Leppard
  • Patent number: 4430425
    Abstract: Color photographic silver halide material which contains in at least one coupler containing silver halide emulsion layer or in a layer adjacent thereto(a) a hydroquinone of the formula ##STR1## wherein p is 1 or 2 and q is 0 or 1, provided that p+q is 1 or 2, R is a radical of the formula ##STR2## wherein Q is selected from the residues (1) --COZR.sub.4, wherein Z is O or NR.sub.5, and R.sub.4 is hydrogen, alkyl optionally interrupted by oxygen, cycloalkyl, alkenyl, aryl, aralkyl or a heterocyclic ring, and R.sub.5 is hydrogen or alkyl or together with R.sub.4 and the nitrogen atom to which they are bonded form a heterocyclic ring,(2) --OX, wherein X is R.sub.5 or --COR.sub.7, wherein R.sub.7 is hydrogen, alkyl cycloalkyl, alkenyl, aryl or aralkyl,(3) --NR.sub.8 R.sub.9, wherein R.sub.8 is hydrogen or alkyl, and R.sub.9 is hydrogen, alkyl or --COR.sub.7, or R.sub.8 and R.sub.9 together with the nitrogen atom to which they are bonded form a ring,(4) --P(O)(OR.sub.10 ')([O].sub.x R.sub.
    Type: Grant
    Filed: June 18, 1982
    Date of Patent: February 7, 1984
    Assignee: Ciba-Geigy AG
    Inventor: David G. Leppard
  • Patent number: 4407935
    Abstract: The compounds of the formula ##STR1## in which R is amino, cyclic amino, aryloxy or a group of the formula ##STR2## in which L is a radical of the formula .dbd.N-Z, with Z being alkyl or cycloalkyl, or is a heterocyclic radical, aryleneoxy or oxyaryleneoxy and R' and R" are hydrogen, alkyl or halogen, and x and y are 0, 1, 2 or 3, are suitable development accelerators for the development of exposed photographic materials containing silver halide. They accelerate the reduction of the exposed silver salt to silver and thus enhance the sensitivity of the photographic material.
    Type: Grant
    Filed: January 15, 1982
    Date of Patent: October 4, 1983
    Assignee: Ciba-Geigy AG
    Inventors: Mario Fryberg, David G. Leppard
  • Patent number: 4268593
    Abstract: Recording material, for color photography, which contains at least one piperidine compound containing one or more alkyl-substituted phenol groups, as the light stabilizer, in at least one light-sensitive silver halide emulsion layer, one interlayer and/or one protective layer. Colored images which are obtained by image-wise exposure and development of this recording material for color photography display good stability towards the action of visible and ultraviolet light.
    Type: Grant
    Filed: November 5, 1979
    Date of Patent: May 19, 1981
    Assignee: Ciba-Geigy AG
    Inventors: David G. Leppard, Michael Rasberger
  • Patent number: 4229577
    Abstract: Color photographic material is provided which contains at least one silver halide emulsion layer containing a yellow color coupler of the formula ##STR1## wherein G is the radical of a yellow coupler which is bonded to the heterocyclic ring by means of the active methylene group, Z is --CO-- or --SO.sub.2 --, M is hydrogen if Z is --CO--, or a substituent and R is hydrogen or a substituent.The new two-equivalent yellow couplers lead due to their improved reactivity (high maximum density), minimal fog and high fastness to light and outstanding spectral properties of the dyestuffs formed therefrom to a color photographic material of advantageous properties.
    Type: Grant
    Filed: April 27, 1978
    Date of Patent: October 21, 1980
    Assignee: Ciba-Geigy AG
    Inventors: Graham Evans, Mario Fryberg, Thomas Stauner, Paul Tschopp, David G. Leppard
  • Patent number: 4115121
    Abstract: Color photographic material is provided which contains at least one silver halide emulsion layer containing a yellow color coupler of the formula ##STR1## wherein G is the radical of a yellow coupler which is bonded to the heterocyclic ring by means of the active methylene group, Z is --CO-- or --SO.sub.2 --, M is hydrogen if Z is --CO--; or a substituent and R is hydrogen or a substituent.
    Type: Grant
    Filed: March 30, 1977
    Date of Patent: September 19, 1978
    Assignee: Ciba-Geigy AG
    Inventors: Graham Evans, Mario Fryberg, Thomas Stauner, Paul Tschopp, David G. Leppard