Isoindoline pigments

1. An isoindoline pigment of the general formula I

in which the variables are defined as follows:

R 1 is C 1 -C 4 -alkyl;

R 2 is hydrogen or C 1 -C 4 -alkyl,

whose value expressing ease of dispersion in LDPE is 10 and which require a reduction ratio of ≧5 to obtain ⅓ of standard depth of shade.

2. The isoindoline pigment of formula I according to claim 1 , in which R 1 is methyl and R 2 is hydrogen.

3. A process for the preparation of isoindoline pigments according to claim 1 , which comprises subjecting the crude pigment produced during pigment synthesis to heat treatment for from 1 to 60 hours at a temperature T in the range from 90 to 180° C. in aqueous suspension, to which organic solvents from the group of alcohols, ether alcohols, ethers, ketones, carboxamides, and carboxylic esters may have been added, and then isolating the material conventionally, where the temperature T [° C.] is to be calculated from the treatment time t [h] by the following formula using the selected treatment time:

T [° C.]=[148−14.4 ln( t )]±10.

4. The process according to claim 3 , wherein the suspension produced during aqueous pigment synthesis is subjected to the heat treatment.

5. A process for making colored plastics, comprising:

incorporating the isoindoline pigments of the formula I according to claim 1 into high-molecular-weight organic materials of natural and synthetic origin.

6. The process according to claim 5 , wherein the high-molecular-weight materials are plastics, powder coatings, inks, toners, and color filters.

7. The process according to claim 5 , wherein the high-molecular-weight materials are plastics.

8. A plastic, colored with isoindoline pigments according to claim 1 .

9. The process according to claim 3 , wherein the organic solvents have been added.