Study On Ultrafast Laser Processing Technology Of K9 Glass Microstructures

With the popularity of mobile phones,tablet personal computers,televisions and other consumer electronic products,people have higher requirements for the display quality and product thickness of liquid crystal display(LCD).In order to further reduce the thickness of LCD,the concept of glass light guide plate was proposed in the display industry in 2015,but the laser processing technology of glass light guide plate scattering microstructures is still less studied.Due to the advantages of high transmittance and less internal impurities,K9 glass is an ideal material for glass light guide plate.Under the circumstances,this paper studies the ultrafast laser processing technology of K9 glass microstructure: femtosecond laser serial processing technology,femtosecond/picosecond laser parallel processing technology based on static/dynamic hologram.The research contents are as follows:In the research of femtosecond laser serial processing technology,the laser processing mechanism,morphology and profile of K9 glass and PMMA were compared.Firstly,by means of pulse percussion,the damage threshold and incubation effect of K9 glass and PMMA were calculated.K9 glass was found to have a higher threshold energy,better chemical stability,and less recast layer of the processed surface.Then,by means of laser concentric circle rotary cutting,micro-holes with a diameter of about 200 μm were processed on the surface of K9 glass and PMMA using different processing speeds.It was found that with the increase of spot overlap rate,the greater the laser energy acting on the material surface,the greater the etching depth of microstructures.In terms of processing morphologies,there was no obvious sputtering on the surface of K9 glass microstructure,and the profile was smooth.Finally,the K9 glass light guide plate backlight module is simulated by Light Tools optical software,and it is found that its luminance uniformity can reach 90.2%,which is higher than that of the PMMA light guide plate backlight module(87.0%),which meets the display requirements.In the research of femtosecond laser parallel processing technology based on static hologram,three microchannels were processed with three parallel laser beams.Firstly,a hologram containing three laser beams was generated by GSW algorithm.The hologram was loaded into the liquid crystal spatial light modulator,and the incident laser light was modulated into three laser beams after passing through the modulator window.In the process of machining,the output power of laser was changed,and three microchannels were processed by modulated three parallel laser beams.Through the observation of the processing results,it was found that the width of the three microchannels increases significantly with the increase of laser power,but the uniformity remains above 90%.This indicates that the laser power has little effect on the energy uniformity of the split-beam laser.Due to the small scale of the microchannels,the recasting layer and glass slags had a great impact on the observation.In this paper,the post-treatment of the processing results was carried out through ultrasonic cleaning and KOH solution corrosion.It was found that ultrasonic cleaning can only remove the glass slags which attached to the processing area,while KOH solution can well remove the recast layer on both sides of the microchannels.For the microchannels processed with high laser power,the uniformity of width and depth is still high after soaking in KOH solution.In the research of picosecond laser parallel processing technology based on dynamic hologram,the micro-holes array structure was processed by multi beam laser and multiple holograms.When the laser was directly split into twenty-five beams,the complete micro-holes array cannot be etched because the incident laser power is too low.It is a good way to used five symmetrically distributed five laser beam holograms and four randomly distributed six laser beam holograms in parallel processing.Loaded all the holograms into the liquid crystal spatial light modulator,and set the interval at which the spatial light modulator reads the hologram.By observing the processing results,without systematic error and zero order light interference,the average diameter of the prepared micro holes array was 3.213 μm and 2.706 μm respectively,and the uniformity reached 91 %.In this paper,it is found that the error of the processing system and the interference of zero-order light had a great influence on the uniformity of the diameter,while the influence of the number of split beams and the arrangement of the target beam is not obvious.The above research will provide technical guidance for the laser processing technology of the glass light guide plate scattering microstructures,provide a new reference for the ultrafast laser processing technology,and promote the wider application of K9 glass in the optoelectronics industry.