| Photoresist is a photosensitive material that is sensitive to light and reacts after light or other radiation to form different solubility.Color photoresist is the most important raw material of flat panel display,which determines the color effect of display color.With the emergence of new display technology,the requirement of screen resolution is getting higher and higher.The improvement of screen resolution means that the size of the display pixel is reduced,which requires that the color photoresist prepared for the pixel has high resolution(small size).In this paper,the preparation process of patterned color photoresist and the composition of color photoresist were explored to study its influence on the resolution of color photoresist.The main research contents and results are as follows :1.The effects of different lithography process parameters,including spin coating process,vacuum degree of vacuum drying,pre-drying temperature and time,exposure amount and distance,development time,and secondary baking temperature and time,on the resolution of color photoresist were studied.It is found that the film thickness uniformity can be improved by increasing the uniform spin coating time.Reducing vacuum drying pressure,increasing pre-drying temperature,increasing pre-drying time,increasing exposure energy and reducing exposure distance can improve the resolution of color photoresist;there is the best high resolution development interval in the development time,and the color photoresist with high resolution can be obtained when the development time is controlled at about 2×B.T.2.The composition of color photoresist was studied,mainly including the molecular weight and acid value of polyacrylate resin,the addition of epoxy resin or bisphenol fluorene resin,the functionality of acrylate monomer,the type of photoinitiator,the dispersion of color paste and the addition of silane coupling agent,etc.,which affected the resolution of color photoresist.The results showed that : 1)When the molecular weight of polyacrylate resin is 11000 g/mol,the acid value is79 mg KOH/g ～ 100 mg KOH/g,the resolution of color photoresist is the highest.2)A small amount of epoxy resin or bisphenol fluorene resin mixed with polyacrylate resin,and the addition of silane coupling agent can make the color photoresist still show good resolution at low curing temperature.3)The crosslinking degree of acrylate monomers with low functionality is low during curing,which cannot effectively reduce the solubility of photoresist in the development solution in the exposure area and is prone to development stripping.With the increase of acrylate monomer functionality,the crosslinking degree of the film increased,and the solubility of the film in the development solution decreased,which was beneficial to the improvement of the resolution of the color photoresist.4)Different types of initiators have different curing effect.The photoinitiator with long wavelength absorption tends to solidify inside,and the resolution is slightly higher,but it will bring rough surface and water MURA.The photoinitiator with short wavelength absorption tends to solidify the surface and has a slightly lower resolution,but the surface roughness is good and the water MURA is good.The combination of long wavelength absorption photoinitiator and short wavelength absorption photoinitiator has the best comprehensive performance.5)The decrease of pigment particle size in the color paste is conducive to improving the resolution of photoresist.3.The comprehensive performance of the optimized composition of color photoresist was studied.It was found that the resolution of the optimized color photoresist could reach 2.5 μm,and the resolution could still reach 2.5 μm when the pre-drying temperature dropped to 70 °C.In addition,it has excellent surface morphology and weather resistance,meeting the application requirements. |
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