Backlight Module Research Articles

An LED light propagation cavity with staggered light bars for eliminating the Hot Spot

The light source of traditional edge-lit backlight modules typically consists of LED bars which composed of multiple LED chips. However, the spacing between the chips can create distinct bright and dark spots (Hot Spot) on the input surface of the light guide plate (LGP), thereby affecting the optical performance of the backlight module. In this paper, we proposed an edge-lit backlight module with staggered light bars, incorporating a light propagation cavity design to enhance light receiving efficiency and eliminate Hot Spot. Firstly, we designed the structure of the staggered light bars and the light propagation cavity. Secondly, the advantages of the new backlight module design in eliminating Hot Spot were verified through TracePro simulations. The simulation results showed that the maximum irradiance of the backlight module reached 81,010 W/m2, and the luminance uniformity peaked at 75.142 %. Compared to the traditional backlight modules, the light receiving efficiency was increased by 6.62 %, and the luminance uniformity was improved by 1.34 times, which effectively mitigated the Hot Spot. Finally, we discussed the impact of the improved backlight module in reducing the thickness of the LGP and decreasing the number of LED chips, achieved superior optical performance. This study demonstrates the significant advantages of the light propagation cavity in eliminating Hot Spot within backlight modules.

Development of single-sided structure collimation film for direct-lit collimated backlight module

In this paper, we proposed an optical structure to enhance the collimation and uniformity of 405 nm LED backlight modules. The structure is called a single-sided structure collimation film (SSSCF), which consists of a lenticular lens array, slit apertures, and a highly reflective coating surface. A lenticular lens array with slit apertures converts the angle of diffusive incident light into collimated light. The high-reflective coating of the collimation film can reflect back the light that does not enter the slit aperture to the backlight module for energy recycling. Finally, we have developed a direct-lit backlight module with optimized collimation properties (FWHM = ±3.4°, gain = 2.3%, NSR = 0) and great uniformity (uniformity > 83.5%). We also demonstrated good consistency between our simulation results with optical measurement. The collimated backlight module developed in this study has great potential for future applications, including high-precision 3D printing objects, liquid crystal displays with high contrast ratio or narrow viewing angles, and telecentric illumination devices used in precision machine vision systems.

Advancing LED technology: the FDCSP element’s breakthrough in mini and micro-LED packaging and backlight module enhancement

In this research, we introduce an advanced methodology for the calculation of bulk light sources tailored for free-form surface design, focusing on the principle of energy conservation. This method is especially relevant for the evolving needs of micro-LED packaging, highlighting its potential in this burgeoning field. Our work includes the development of an algorithm for creating freeform-designed chip-scale package (FDCSP) components. These components seamlessly integrate LEDs and lenses, underscoring our commitment to advancing free-form surface design in chip-level packaging. By adhering to the principle of energy conservation, our approach facilitates a meticulous comparison of simulation outcomes with predefined target functions. This enables the iterative correction of discrepancies, employing layering techniques to refine the design until the simulated results closely align with our goals, as demonstrated by an appropriate difference curve. The practical application of these simulations leads to the innovative design of FDCSP devices. Notably, these devices are not just suitable for traditional applications in backlight modules but are explicitly optimized for the emerging sector of micro-LED packaging. Our successful demonstration of these FDCSP devices within backlight modules represents a significant achievement. It underscores the effectiveness of our design strategy and its expansive potential to transform micro-LED packaging solutions. This research not only contributes to the theoretical understanding of energy conservation in lighting design but also paves the way for groundbreaking applications in micro-LED and backlight module technologies.

A Robust Texture-Less Gray-Scale Surface Matching Method Applied to a Liquid Crystal Display TV Diffuser Plate Assembly System

In most liquid crystal display (LCD) backlight modules (BLMs), diffuser plates (DPs) play the essential role in blurring the backlight. A common BLM consists of multiple superimposed optical films. In a vision-based automated assembly system, to ensure sufficient accuracy, each of the multiple cameras usually shoots a local corner of the DP and jointly estimates the target pose, guiding the robot to assemble the DP on the BLM. In general, DPs are typical of texture-less objects with simple shapes. Due to the image background of superimposed multilayer optical films, the robustness of the most common detection methods must be improved to meet industrial needs. To solve the above problem, a texture-less surface matching method based on gray-scale images was proposed. An augmented and normalized gray-scale vector represents the texture-less gray-scale surface in a low-dimensional space. The cosine distance is then used to calculate the similarity between the template and matching vectors, combined with shape-based matching (SBM); the proposed method can obtain high robustness when detecting DPs. An image database from actual production lines was used in the experiment. In comparative tests with the NCC, SBM, YOLOv5s, and YOLOv5x methods, our proposed method had the best precision at all confidence thresholds. Although recall was slightly inferior to SBM, the comprehensive evaluation F1-Score reached 0.826, significantly outperforming the other methods. Regarding localizing accuracy, our algorithm also performed best, reaching 5.7 pixels. Although the time consumption of a single prediction is about 0.6 s, it can still meet industrial needs. These experimental results show that the proposed method has high robustness in detecting DPs and is especially suitable for vision-based automatic assembly tasks in BLM.

Wide heart-shaped mini-LEDs without a second lens as a large area, ultra-high luminance, and flat light source.

In recent years, the demand for outdoor advertising and industrial display applications has been steadily increasing. Outdoor environments require higher brightness levels, thus requiring a reduction in the thermal resistance of the light source package. However, using secondary optical lenses to decrease the number of light sources is not a suitable solution because it may lead to the issue of lens detachment. Therefore, this paper proposes a packaging structure for wide heart-shaped angular light distribution mini-light emitting diodes (WHS mini-LEDs) with a primary optical design to enhance the light-emitting angle. The chips are directly bonded to an aluminum substrate using the metal eutectic process to minimize thermal resistance in the packaging. The experimental results indicated that the WHS mini-LED package had a total thermal resistance of 6.7 K/W. In a 55-inch backlight module (BLM), only 448 WHS mini-LEDs coupled with a quantum dot (QD) film and a brightness enhancement film (BEF) were required. Each lamp board was operated at 20.5 V and 5.5 A. The average luminance of the liquid crystal module (LCM) can reach 2234.2 cd/m2 with a uniformity of 90% and an NTSC value of 119.3%. This design offers a competitive advantage for outdoor advertising displays and industrial displays that require large areas, high brightness, and high color saturation.

One-step fast fabrication of multi-layer quantum dot diffusion plate for stable display and ultra-long life, a novel quantum dot packaging strategy

Quantum dots (QDs), renowned for their distinctive optical and physical attributes, are extensively employed in diverse fields such as lighting, displays, electronics, sensors, and solar cells. Nonetheless, the susceptibility to light, oxygen, and moisture is a major obstacle to the development of QDs. Achieving simple, efficient, and universal modification or encapsulation for enhanced stability remains a challenge. Herein, a one-step fast fabrication of multi-layer quantum dot diffusion plate (QD-DP) with excellent barrier and optical properties was proposed, which is alternately stacked by MS-EVOH and MS-QDs layers. The barrier phase morphology undergoes a fiber-flake transition induced by the bidirectional tensile force field during multiplication, and layer-by-layer encapsulation synergistically enhances the barrier performance, photo-oxygen stability, thermal-oxygen stability, and fluorescence lifetime of QD-DP in backlight applications. Under high-power UV irradiation, the fluorescence intensity ofMS/MS-QD 128L dropped to 90 % (T90) in only about 10 minutes, while the T90 of MS-E/MS-QD 128L was close to 216 hours, improved more than 1200 times. Concurrently, the quantum dot diffusion plate (QD-DP), characterized by an alternating multi-layer structure, demonstrated an elevated backlight color gamut value of ∼ 120 % NTSC, outperforming conventional quantum dot light emitting diodes (QLED). Compared with existing QDs backlight modules, a simpler structure, more efficient preparation process, and longer fluorescence lifetime of QD-DP were achieved.Moreover, unlike prevalent modification or packaging technologies that only target specific QD types, our alternating multilayer coextrusion packaging technology is applicable to all kinds of QDs and is simple, efficient, and universal.It was believed that this work could provide new opportunities for all kinds of QDs encapsulation and application in many fields and will be the dawn of large-scale commercialization of QDs.

Foldable low-cost point-of-care device for testing blood coagulation using smartphones

Cardiovascular diseases (CVDs) caused by thrombotic events are a significant global health concern, affecting millions of people worldwide. The international normalized ratio (INR) is the most widely used measure of coagulation status, and frequent testing is required to adjust blood-thinning drug dosage, requiring hospital visits and experts to perform the test. Here we present a low-cost and portable smartphone-based device for screening INR levels from whole blood samples at the point of care. Our device uses a 3D printed platform and light-emitting diode backlight modules to create a uniform optical environment, and its foldable design allows for easy transport. Our device also features an algorithm that allows users to acquire and process video of sample flow in a microfluidic channel on their smartphone, providing a cost-effective and convenient option for blood coagulation monitoring at the point of care. We tested the performance of our smartphone-based INR device using both commercially available control samples and clinical human blood samples, demonstrating high accuracy and reliability. Our device has the potential to improve patient outcomes by enabling more frequent monitoring and, as appropriate, dosage adjustments of blood-thinning drugs, providing an affordable and portable option for screening INR levels at the point of care.

Optimized Design with Artificial Intelligence Quantum Dot White Mini LED Backlight Module Development

This study delves into the innovation of mini light-emitting diode (mini-LED) backlight module designs, a significant advancement in display technology. The module comprises a substrate, a receiving plane, and an LED structure, which uses a blue light with specific spectral characteristics. When combined with a red-green quantum dot (QD) film, it produces white light. For improved illumination uniformity, the Mini-LED structure was optimized with a focus on the thickness and concentration of layers, especially the TiO2 diffusion layer. A comprehensive design methodology using LightTools (8.6.0) optical simulation software was employed, linked with MATLAB (R2022a) for varied parameters and using the double deep Q-network (DDQN) algorithm via Python as a reinforcement learning agent. This approach facilitated optimal architecture design based on illumination uniformity. Also, the bidirectional scattering distribution function (BSDF) was employed to calculate the scattering properties of the backlight module’s surface, providing accurate simulation results. The DDQN algorithm enhanced the learning design, reducing simulation runs by 76.7% compared to traditional methods. The optimized solution achieved an impressive illumination uniformity of 83.8%, underscoring the benefits of integrating advanced algorithms into display technology optimization.

Design and fabrication of large area vat photopolymerization 3D printing system using a 32-inch quasi-collimated visible backlight module with local dimming control

In this paper, we accomplished the first 32-inch liquid crystal display (LCD) type vat photopolymerization 3D printing system based on the quasi-collimated visible backlight module with local dimming control. The large building area (40x70cm) of the 3D printing system can greatly increase the size of printing objects and the production rate. We focused on the design of quasi-collimated backlights and analyzed their optical properties and the appearance of 3D printing objects fabricated by them. The optical performances of the quasi-collimated backlight using stacks of optical films feature no large angle leakage light, 86% intensity uniformity, and less than ±15° angular distribution of emitting light. After the optimization process by combining a variety of optical films, the uniformity, and collimation of the backlight module are greatly improved. Moreover, combining a local dimming algorithm with 3D printing technology can completely suppress unexpected photopolymerization residues, increase resin utilization rate, save energy, and greatly improve the probability of success in the 3D printing process, especially in large printing objects.

Preview the Products on Display at Display Week 2023

Preview the Products on Display at Display Week 2023

P‐12.5: Optical film microstructure design for ultra‐thin MiniLED backlight modules

The backlight module is a key component for providing a light source for a Liquid Crystal Display (LCD), and its thickness has a direct impact on the thickness of the display. In order to reduce the thickness of the display product, it can be realized by reducing the thickness of the backlight module. In order to solve this problem, this paper proposes a design method for the microstructure of the optical film applied to the mini LED backlight module. The microstructured optical film designed in this paper can effectively improve the uniformity of brightness and realize the ultra‐thinning of the backlight module. Based on the principle of total reflection, the optical film microstructure is designed for the miniLED Lambertian light source. Under the assumption that the point light source is established, the extended light source is discretized into point light sources, and then the light energy that can be used for circulation is calculated for each point light source, and all point light sources The cyclic energy of is accumulated as the cyclic energy corresponding to the extended light source, and when its value is the largest, the best shape of the microstructure is obtained. The simulation results show that after adding the microstructured optical film, the illumination uniformity of the backlight module reaches 91.2%, which meets the uniformity requirements of the backlight module. The method of designing microstructured optical film proposed in this paper can effectively realize the ultra‐thinness of the backlight module and has strong practicability.

P‐4.1: Analysis and Application of the Peel Strength of the Foam Tape on Display Panel

In order to solve the problem of peel between display panel and backlight module in new display products such as four-sided borderless display and curved display, in this paper, the peel strength of foam tape was studied through experiment and simulation, and the peel stress strength of the foam tape was established to guide product design. Firstly, the peel stress of foam tape was obtained by peel strength experiment of foam tape samples. Then, the simulation model was established by using finite element software, and the load weight corresponding to the tilt experiment of the 27-inch four-sided borderless display was calculated. Finally, the accuracy of the simulation model was verified by the tilt experiment of 27-inch display, and the peel stress strength of the foam tape was established. The peel stress was about 1.94×10 -2 MPa. Based on the peel stress strength, the minimum width of foam tape for 23.8-inch four-sided borderless display was 1.5 mm. The display passed the 60 ℃/90% RH HTHHS 500 hours experiment, meeting the product quality requirements. This method can guide the size design of foam tape for new display products such as four-sided borderless display and curved display, and enhance the ultimate design competitiveness of products.

13.1: The design and preparation of flexible MiniLED plate with nano‐Ag paste

The development and preparation process of a flexible MiniLED line subgrade board on a white reflective sheet was carried out in this paper using silk‐printing nanoscale silver paste assisted bonding technology. The design of the line conductivity parameter ‐ nanoscale silver paste parameter model, printing plate selection, and process verification were systematically completed, as well as the preparation and reliability confirmation of flexible MiniLED lamp board. The flexible MiniLED lamp board with disposable sintered nano silver slurry lines was successfully prepared, and the 65" backlight module was constructed.

Ultrastable and highly efficient CsPbBr3 composites achieved by dual‐matrix encapsulation for display devices

AbstractPerovskite nanocrystals (NCs) with high stabilities and excellent optical performances are crucial for display applications. However, to date, perovskite emitters with both high photoluminescence (PL) quantum yield (PLQY) and high stabilities under harsh synergistic humidity–heat–light aging conditions have not been reported. The promising high‐temperature solid‐state sintering with single oxide matrices cannot ensure high PLQY and synergistic aging stabilities of perovskites. Herein, both the PLQY and overall (thermal, moisture, and photo) stabilities of all‐inorganic perovskite (CsPbBr3) NCs are improved by dual‐matrix encapsulation, which is accomplished by in situ crystallization of CsPbBr3@Cs4PbBr6 nanocomposites in silica molecular sieve (MS) templates via advanced solid‐state synthesis a using precisely controlled molar ratio of precursor components and cooling rates. The Cs4PbBr6 matrix effectively passivates the surfaces of CsPbBr3 NCs, and the MS matrix insulates CsPbBr3@Cs4PbBr6 from the external environment. The resulting CsPbBr3@Cs4PbBr6/MS composites exhibit the highest PLQY (>90%) among those of the solid‐state perovskite NCs and significant stabilities against water, heat, and blue light irradiation, maintaining more than 80% of their initial PL intensities after being aged for 1000 h under synergistic high‐humidity (85%), high‐temperature (85°C), and strong blue light irradiation (350 mW cm−2) conditions. To the best of our knowledge, these CsPbBr3@Cs4PbBr6/MS composites represent the most stable perovskite emitters under synergistic humidity–heat–light aging conditions. The liquid crystal display backlight module fabricated using these stable composites demonstrates a wide color gamut of 131% of the National Television Standards Committee standard. We speculate that this dual‐matrix encapsulation can be used for industrial mass production.image

Zero-Optical-Distance Mini-LED Backlight with Cone-Shaped Light Coupling Microstructures

This paper presents a zero-optical-distance mini-LED backlight with cone-shaped light coupling microstructures to achieve an ultra-thin backlight architecture (~0.1 mm thickness) by combining the characteristics of direct-lit and edge-lit backlights. There is no gap between the light guide plate (LGP) and the reflector, as well as between the LGP and the mini-LED embedded in the reflector. The illuminance uniformity and light extraction efficiency (LEE) of the whole structure reach 91.47% and 77.09%, respectively. Nine sub-modules are spliced together to realize 2D local dimming with 0.29% crosstalk. The structure shows high optical performance while reducing the thickness of the backlight module, which is of great significance for the development of mini-LED backlights.

P‐3.18: Design of Microstructure Optical Film for Ultra‐thin MiniLED Backlight Module

P‐3.18: Design of Microstructure Optical Film for Ultra‐thin MiniLED Backlight Module

27.4: Design of Double Freeform Lens for Mini‐LED Backlight Modules

Mini light‐emitting diodes (Mini‐LEDs) have been considered as promising light sources for direct‐lit backlight modules (BLU). To achieve uniform illumination, double freeform lenses are usually employed to redistribute rays from Mini‐LEDs. The traditional design method of a single lens under the point light source can achieve high uniformity on the observation plane. However, in the array configuration, especially when the horizontal distance between Mini‐LEDs is not equal to the vertical distance, the uniformity decreases when it is applied under the extended light source. To solve this problem, a lens design method is proposed in this paper to satisfy the requirement on uniformity. Firstly, the illuminance value is numerically calculated based on array configuration and illuminance superposition method. Then we optimize the illuminance distribution curve with the feedback method. A double freeform lens is designed based on the optimized illuminance curve. On the target plane, the simulation results show that compared with the traditional method of lens design, the uniformity improves from 77.69% to 88.03%. The design method is simple, effective, and easy to implement.

P‐16.11: The Scheme Study and Halo Test of Vehicle Glass Based Mini LED Module

A 12.3-inch Mini LED Module has been developed to realize highlight, high contrast and Local Dimming, Which is different from the ordinary side-in backlight module, and the light-emitting surface is directly below the module. The luminance is 1800nit and the contrast is more than 1,000,000:1. The module has passed the reliability of vehicle regulation. In the last the paper introduces the halo performance of the module.

P‐12.3: A Viewing Angle Switchable Liquid Crystal Display Panel with Area Control

We propose a switchable LCD panel with “sandwich” mode, which can realize the view partition control.LCD including normal FFS mode and dimmers CP‐1 and CP‐2 for light reception. The dimmer is provided with a positive liquid crystal layer, a planar viewing angle control electrode and a comb pixel electrode. The dimmer is used to narrow the outgoing light from the required area of the backlight module. This architecture can realize the wide and narrow viewing angle switching of 45 ° anti peeping effect and regional anti peeping display. Therefore, switching the information disclosure and regional information privacy mode will become a new partition free switching anti peeping technology.

Locally controllable 2D/3D mixed display and image generation method.

In this paper, a locally controllable two-dimensional (2D)/ three-dimensional (3D) mixed display system and corresponding image generation method are proposed. The proposed system is mainly composed of a collimating backlight module (CBM) and a light control module (LCM). The CBM provides collimating polarized light. The LCM modulates a part of the collimating polarized light to form point light sources for 3D display and the other part to form scattered light sources for 2D display. The 2D and 3D display states can be locally controlled by using a pixelated mask loaded on a polarization switching layer. In addition, a corresponding image generation method is proposed. According to observer's demand, the parallax image is divided into target image area and residual image area by using deep learning matting algorithm, and a 2D/3D mixed light field image with full parallax 3D target image and high-resolution 2D residual image is generated. We developed a prototype based on the proposed locally controllable 2D/3D mixed display structure and generated two sets of 2D/3D mixed light field image with different target objects and residual objects from the same parallax images. The experimental results demonstrated the effectiveness of our proposed system and the corresponding image generation method. High-resolution 2D image and full parallax 3D image were displayed and locally switched in the experimental system.