OLED Display Panel Planarization for Inkjet Printing Uniformity

The planarization layer is divided into two distinct parts: a first planarization part with uneven surface corresponding to the light-emitting area, and a second planarization part with thicker structure corresponding to the defining area. This segmentation allows each part to serve different functional requirements - the first part maintains the underlying step differences while the second part provides the necessary planarization for inkjet printing.

Different regions of the planarization layer are given different thicknesses and surface characteristics. The first planarization part has an uneven surface that preserves the step differences, while the second planarization part has a thicker, more uniform structure that provides planarization. This local differentiation resolves the contradiction by providing planarization only where needed without compromising the overall structure.

The pixel area is segmented into a light-emitting area and a defining area, with each area having different planarization characteristics. The first planarization part corresponds to the light-emitting area and maintains larger step differences, while the second planarization part corresponds to the defining area and provides better flatness for uniform ink spreadability.

The dual-structure planarization layer acts as an intermediary between the substrate with large step differences and the inkjet printing process. It provides a transition zone that gradually reduces the step differences in the defining area while preserving them in the light-emitting area, thereby enabling uniform ink spreadability without requiring complete elimination of substrate irregularities.

The planarization layer implements local quality by providing different thicknesses in different regions. The second planarization part has greater thickness to provide planarization, while the first planarization part has lesser thickness to avoid the trace climbing and breaking issues associated with uniformly thick PLN structures. This localized approach maintains reliability while achieving the necessary flatness.

By segmenting the planarization layer into two parts with different thicknesses, the invention avoids creating a uniformly thick structure that would cause trace climbing and breaking during film deposition. The segmented structure allows the planarization function to be performed where needed without creating the reliability issues associated with uniformly thick PLN layers.