Process for the preparation of high chloride tabular grain emulsions

• US 5,061,617 A
• Filed: 12/07/1990
• Issued: 10/29/1991
• Est. Priority Date: 12/07/1990
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Maskasky, Joe E.
• Primary Examiner(s): Bowers, Jr., Charles L.
• Assistant Examiner(s): Baxter, Janet C.
• Application Number:
  US07/623,839
• Time in Patent Office: 326 Days
• Field of Search: 430/567, 430/569
• US Class Current: 430/569
• CPC Class Codes: G03C 1/0053 with high content of silver chloride
• CPC Class Codes: G03C 1/015 Apparatus or processes for the preparation of emulsions coating, drying G03C1/74 ; G03C1/07 takes precedence; special processes for tabular grains G03C1/0051
• CPC Class Codes: G03C 1/07 Substances influencing grain growth during silver salt formation
• CPC Class Codes: G03C 2001/0055 Aspect ratio of tabular grains in general; High aspect ratio; Intermediate aspect ratio; Low aspect ratio
• CPC Class Codes: G03C 2001/03511 Bromide content
• CPC Class Codes: G03C 2001/03517 Chloride content
• CPC Class Codes: G03C 2200/03 111 crystal face
• CPC Class Codes: G03C 2200/43 Process

Abstract

An improved process is disclosed of preparing a high chloride tabular grain emulsion. The concentration of thiocyanate ion in the dispersing medium at nucleation and during grain growth is relied upon a favor the formation of {111} crystal faces. The concentration of chloride ion in the thiocyanate ion containing dispersing medium is relied upon to produce the grain twinning necessary for tabular grain formation.

Claims

1. A process of preparing a photographic emulsion comprised of a dispersing medium and radiation sensitive silver halide grains wherein at least 35 percent of the total grain projected area is accounted for by tabular grains having parallel {111} major crystal faces and containing at least 50 mole percent chloride, based on total silver, said emulsion being prepared by introducing silver ion into a dispersing medium containing chloride ion,

CHARACTERIZED IN THAT

grain nucleation is controlled to favor the formation of {111} crystal faces by providing thiocyanate ions in a concentration range of from 2 to 30 millimoles per liter in the dispersing medium prior to introducing silver ion,

parallel twin planes are introduced in the grains by maintaining in the presence of thiocyanate ions a chloride ion concentration of at least 0.5 molar in the dispersing medium, and

grain growth is controlled to favor the formation of the tabular grains having parallel {111} major crystal faces by maintaining a concentration of thiocyanate ions in the dispersing medium in the range of from 0.2 to 10 mole percent, based on total silver introduced.

2. A process according to claim 1 further characterized in that the radiation sensitive silver halide grains contain at least 80 percent chloride.

3. A process according to claim 2 further characterized in that the halide ions in the radiation sensitive silver halide grains consist essentially of silver chloride.

4. A process according to any one of claims 1, 2 or 3 further characterized in that the dispersing medium contains a 0.5 to 4.0 molar concentration of chloride ion.

5. A process according to claim 4 further characterized in that the dispersing medium contains a 0.5 to 2.5 molar concentration of chloride ion.

6. A process according to claim 1, 2 or 3 further characterized in that halide ion is added to the dispersing medium concurrently with the silver ion.

7. A process according to claim 6 further characterized in that chloride ion is added to the dispersing medium concurrently with the silver ion.

8. A process according to claim 1 or 2 further characterized in that bromide ion is added to dispersing medium concurrently with the silver ion.

9. A process according to claim 1 or 2 further characterized in that iodide ion is added to the dispersing medium concurrently with the silver ion.

10. A process according to claim 1 or 2 further characterized in that iodide ion is incorporated in the emulsion in a concentration of less 1 mole percent, based on total silver.

11. A process according to claim 1, 2 or 3 further characterized in that the concentration of thiocyanate ions in the dispersing medium is in the range of from 5 to 20 millimoles per liter prior to introducing the silver ion.

12. A process according to claim 1, 2 or 3 further characterized in that grain growth is controlled to favor the formation of the tabular grains having parallel {111} major crystal faces by maintaining a concentration of thiocyanate ions in the dispersing medium in the range of from 1.5 to 5 mole percent, based on total silver introduced.

13. A process according to claim 1, 2 or 3 further characterized in that the tabular grains account for greater than 50 percent of the total grain projected area.

14. A process according to claim 1, 2 or 3 further characterized in that the tabular grains exhibit a tabularity of greater than 20.

15. A process according to claim 14 further characterized in that the tabular grains exhibit a tabularity in the range of from greater than 25 to 100.

16. A process according to claim 15 further characterized in that the tabular grains exhibit a tabularity in the range of from 30 to 50.

17. A process according to claim 1, 2 or 3 further characterized in that the dispersing medium contains a gelatino peptizer.