| Liquid crystal display(LCD)has many advantages such as low radiation,low energy consumption and good picture quality,which has been widely used in the field of computers,culture and entertainment,advertising media and industrial control.LCD is mainly composed of liquid crystal panel and backlight module(BLM).Among them,the BLM provides the light source for the LCD.The core component of the BLM is the light guide plate(LGP).The LGP has an important influence on the display quality of the LCD,and it usually relies on the surface microstructures to improve the luminance and uniformity of the entire LCD.Therefore,it is of great significance to conduct in-depth research on the design and manufacture of the LGP microstructure.In order to improve luminance and uniformity of LGP,this paper proposes a pyramid-shaped microstructure for the bottom surface arrangement of LGP,and conducts research on the femtosecond laser processing technology of the microstructures and the optical performance of LGP.The main tasks are as follows:The first part mainly introduces the interaction mechanism between femtosecond laser and LGP,the basic working principle and the common detection method of LGP,deduces the microstructures distribution law of unilateral incoming light.Combining the above theories and methods,the optical performance of the proposed pyramid-shaped microstructure and the commonly used hemispherical microstructure were compared by establishing a BLM model.The simulation shows that under the same microstructure bottom area,the luminance of the pyramid-shaped microstructure LGP is always higher than that of the hemispherical microstructure LGP.The second part was mainly the experimental research on the pyramid-shaped microstructures of the LGP processed by femtosecond laser.Firstly,the femtosecond laser precision manufacturing system is utilized to explore the influence of multiple process parameters on the microstructure morphology.When the repetition frequency is 50k Hz,the pulse energy is 3.17J/cm~2,the spot overlap rate is 60%,the processing times is 1 time,the microstructure filling pitch is 16μm,the feed times is 3 times and the feed distance is0.01mm,high-quality processing of pyramid-shaped microstructures with different depths can be achieved by superimposing multiple layers in CAD and setting the size and focal position of each layer.Finally,according to the microstructure distribution law and the test method of LGP,the proposed pyramid-shaped microstructures and the commonly used hemispherical microstructures are processed on the bare surface of LGP in a large area and optically tested.The test shows that the average luminance of the pyramid-shaped microstructure LGP is 1660.3cd/m~2,and the average luminance of the hemispherical microstructure LGP is 1465.3cd/m~2,which verifies the simulation results.The third part mainly studied the influence mechanism of light extraction efficiency of pyramid-shaped microstructure LGP.It is found that the scattering area of the microstructures plays a decisive role in the light extraction efficiency of LGP.Within a certain range,the light extraction efficiency increases rapidly with the increase of the scattering area of the microstructures.The number and coverage of microstructures also have a certain impact on the light extraction efficiency of LGP,but the impact is limited.Finally,the experiment is designed to convert a single 400μm pyramid-shaped microstructure into four small 200μm pyramid-shaped microstructures for large-area processing on the bare surface of LGP.The optical test shows that the average luminance of LGP after conversion increased from 1165.5cd/m~2 to 1614.3cd/m~2.It is due to the increase in the total scattering area,number and coverage of the microstructures after conversion.The fourth part focuses on the optimization of the luminance uniformity of pyramid-shaped microstructure LGP.Three methods are adopted separately to improve the luminance uniformity of LGP:adjusting the microstructure size parameters,adjusting the microstructure density by area,and adjusting the bottom side length distribution of the microstructures by polynomial.The simulation results indicate that the luminance uniformity of the LGP optimized by the three methods can reach more than 80%.After comparative analysis,the large-area pyramid-shaped microstructures optimized by the polynomial are selected for femtosecond laser processing.The optical test shows that the luminance uniformity of the processed LGP is 84.08%,which meets national standards and industrial application requirements.The above research provides a new reference for the design and processing of microstructures and the optical performance optimization of the LGP,which is beneficial to improve the processing quality of the microstructure and enhance the optical performance of the LGP. |
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