Fabrication of thin-film encapsulation layer for light emitting device
An ink jet process is used to deposit a material layer to a desired thickness. Layout data is converted to per-cell grayscale values, each representing ink volume to be locally delivered. The grayscale values are used to generate a halftone pattern to deliver variable ink volume (and thickness) to the substrate. The halftoning provides for a relatively continuous layer (e.g., without unintended gaps or holes) while providing for variable volume and, thus, contributes to variable ink/material buildup to achieve desired thickness. The ink is jetted as liquid or aerosol that suspends material used to form the material layer, for example, an organic material used to form an encapsulation layer for a flat panel device. The deposited layer is then cured or otherwise finished to complete the process.
1. An apparatus for fabricating a layer for an electronic device having one or more light emitting elements, the layer to have a desired thickness, the apparatus comprising:
an ink jet printer to receive a substrate, the one or more light emitting elements formed on the substrate, and to print droplets of an organic material onto the substrate, in a manner so as to form a liquid coat over the one or more light emitting elements;
circuitry to control the volume of the liquid printed per unit area of the substrate in dependence on the desired thickness by causing the ink jet printer to vary at least one of a droplet area density or a size of the droplets, in a manner such that a thicker liquid coat is formed by a greater droplet area density or size and a thinner liquid coat is formed by a lesser droplet area density or size, and in a manner where at least one value dependent on the desired thickness is received by the circuitry and used by the circuitry to specify thickness of the liquid coat as deposited; and
a processing mechanism to process the liquid coat once deposited to form the layer from the liquid coat so as to have the desired thickness.
2. The apparatus of claim 1 , wherein said apparatus is to produce the layer for each substrate of a series of substrates, and wherein:
each respective substrate comprises an active region, an exposed region and a buffer region between the active region and the exposed region, the active region to receive the layer at a uniform thickness corresponding to the desired thickness, the exposed region not to receive the layer, the buffer region to provide a transition between the active region and the exposed region; and
the buffer region is to receive the layer according to a second volume of the liquid deposited per unit area, relative to the active region.
3. The apparatus of claim 2 , wherein the circuitry is to cause the ink jet printer to vary an electronic drive signal supplied to nozzles of a printhead of the ink jet printer, to vary size of the droplets in the buffer region relative to the active region, so as to deposit the second volume of the liquid per unit area.
4. The apparatus of claim 2 , wherein the circuitry is to cause the ink jet printer to vary droplet area density provided by droplets ejected from nozzles of a printhead of the ink jet printer, to vary a number of the droplets per unit area in the buffer region relative to the active region, so as to deposit the second volume of the liquid per unit area.
5. The apparatus of claim 4 , wherein the circuitry is to cause the ink jet printer to vary the droplet area density by depositing droplets at fewer nodes of a print grid, so as to reduce a spatial frequency at which droplets are deposited in the buffer region relative to the active region.
6. The apparatus of claim 4 , wherein the circuitry is to cause the ink jet printer to vary the droplet area density by varying time-dependent frequency of a trigger signal supplied in common to the nozzles of the ink jet printer, so as to vary spatial frequency of the deposition of the droplets in the buffer region relative to the active region.
7. The apparatus of claim 4 , wherein the circuitry is to cause the ink jet printer to vary the droplet area density by varying time-dependent frequency of a trigger signal supplied to a first one of the nozzles of the ink jet printer relative to a second one of the nozzles of the ink jet printer, so as to vary spatial frequency of droplets provided by the first one in the buffer region relative to spatial frequency of droplets provided by the second one in the buffer region.
8. The apparatus of claim 2 , wherein:
the second volume is to be selected according to a calibration process performed on a test substrate, the calibration process to measure deviation between a lip of a deposited layer and the uniform thickness; and
the second volume of the liquid per unit area is selected so as to reduce the deviation.
9. The apparatus of claim 1 , wherein:
the volume of the liquid printed per the unit area comprises a first volume per the unit area;
the one or more electronic elements are to be part of an electronic display panel, the electronic display panel comprising an active region which encompasses a pixelated portion of the electronic display panel, an exposed region and a buffer region between the active region and the exposed region, the active region to receive the layer at a uniform thickness corresponding to the desired thickness, the exposed region not to receive the layer, the buffer region to provide a transition between the active region and the exposed region; and
the buffer region is to receive the layer according to a second volume of the liquid deposited per unit area, relative to the active region, the second volume selected so as to reduce deviation between a lip of the layer and the uniform thickness.
10. The apparatus of claim 1 , wherein the organic material comprises a monomer and wherein the processing mechanism comprises a source to expose the liquid coat to radiation to convert the monomer to a polymer.
11. The apparatus of claim 10 , wherein the radiation is ultraviolet radiation.
12. The apparatus of claim 1 , wherein the organic material comprises a first material and wherein the processing mechanism comprises a source to expose the liquid coat to radiation to convert the first material into a second material, wherein the second material is to be in a solid state following said conversion.
13. The apparatus of claim 1 , wherein the one or more light emitting elements comprises at least two independently-controllable light emitting elements, and wherein the layer is to span the at least two independently-controllable light emitting elements.
14. The apparatus of claim 1 , wherein said apparatus is to produce the layer for each substrate of a series of substrates, and wherein the ink jet printer is to print the liquid according to a common scan pattern and a common nozzle firing pattern for each of the respective substrates.
15. The apparatus of claim 1 , wherein the layer is a thin film layer comprising at least one of an encapsulation layer, or a planarization layer, or a barrier layer.