Thermal transfer imaging process

The present invention provides a method for reproducing continuous tone images by means of a thermal head. The method involves the image-wise heat transfer of a reducing agent from a donor element to a receiving layer of a receiving element. The receiving element contains a thermoreducible silver source such as e.g. silver behenate. The process of the present invention provides high density images with multiple intermediate density levels.

We claim:

1. A thermal imaging process comprising in order, the steps of:

a) bringing a donor layer of a donor element into face to face relationship with a receiving layer of a receiving element to obtain an assemblage,

b) image-wise heating the assemblage by means of a thermal head, thereby causing image-wise transfer of an amount of a thermotransferable reducing agent to said receiving element in accordance with the amount of heat supplied by said thermal head,

c) separately said donor element from said receiving element, and

d) overall heating said receiving element, wherein

(i) said donor element comprises said donor layer on a support, wherein said donor layer comprises both a binder and a thermotransferable reducing agent which is capable of reducing a silver source to metallic silver upon heating, and

(ii) said receiving element comprises said receiving layer on a support, said receiving layer comprising a silver source which is capable of being reduced by means of a heat in the presence of a reducing agent.

2. A thermal imaging process according to claim 1, wherein said thermally reducible source of silver is an organic silver salt.

3. A thermal imaging process according to claim 2, wherein said organic silver salt is silver behenate.

4. A thermal imaging process according to claim 1, wherein said receiving layer of said receiving element containing said silver source further comprises a toning agent.

5. A thermal imaging process according to claim 1, wherein said receiving element further comprises a release agent in said receiving layer or in a separate layer on top thereof.

6. A thermal imaging process according to claim 5, wherein said release agent is a silicone compound.

7. A thermal imaging process according to claim 1 wherein the average printing power applied by means of the thermal head during said image-wise heating is not more than 10 Watt/mm.sup.2.

8. A thermal imaging process according to claim 1, wherein said image-wise heating is carried out line by line and wherein the time for printing a single line with said thermal head is at most 45 ms.

9. A thermal imaging process according to claim 1, wherein said overall heating is performed by means of a heated roller.