Understanding LCD, OLED, Mini LED, and Micro LED Display Technologies

As autonomous driving technology develops and the intelligence of automobiles accelerates, there is an increasing amount of information that needs to be displayed in vehicles, leading to a growing number of displays. Looking at the new cars released today, large screens and multiple screens in cars are an inevitable development trend.

SAIC Feifan R710: 25-inch mini instrument screen, 15.05-inch OLED, 12.3-inch mini co-pilot screen

According to the characteristics of these screens, they can be roughly classified into four types: LCD, OLED, Mini LED, and Micro LED. Among these four types, Mini LED has captured everyone’s attention in the past two years. In this article, we will briefly introduce these four display technologies.

1. Backlight and Direct Display

A display image is composed of multiple pixels, and the technologies mentioned above (LCD, OLED, Mini LED, Micro LED) can be divided into two categories based on the light-emitting principles of these pixels: direct display and backlight. Each pixel emits light directly, which we commonly refer to as direct display; while light generated from a refracted source is reflected to the human eye to form this pixel, it is called backlight. Below, we will deepen this understanding through typical solutions of backlight and direct display using Mini LED.

1. What is Mini LED?

First, let’s briefly review what Mini LED is. Mini LED, also known as “sub-millimeter light-emitting diodes,” are LED devices with chip sizes between 50-200μm, situated between small-pitch LED and MicroLED, representing a further refinement of small-pitch LED technology. Mini/MicroLED is a product of the fine development of LED displays, and as the technological path gradually becomes clearer, it will become a new blue ocean for LED display applications.

Hawei Technology’s official introduction to Mini LED backlight panels

Compared to the mainstream display technology LCD, Mini LED has superior display effects, a significant improvement in response speed, a lighter and thinner screen, and a substantial reduction in power consumption, which can extend battery life.

In comparison with OLED displays, Mini LED maintains excellent display effects and flexibility while achieving faster response speeds and higher temperature reliability. The key feature of Mini LED compared to small-pitch LED is its depackaging, primarily targeting the high-end small-pitch LED market, allowing for higher resolution and display effects.

2. Differentiating Backlight and Direct Display from Different Mini LED Solutions

Using Mini LED for backlight is essentially still LCD, while direct display uses Mini LED to directly display images. The direction of the liquid crystal molecules is controlled by the LCD panel circuit to allow the backlight (of different colors) to shine on the display screen.

Mini LED backlight (blue layer)

Mini direct display combines three colors of Mini RGB chips, while Mini backlight consists of Mini blue light chips + QD, converting to white light, used behind the LCD as backlight.

Tianma’s Mini LED direct display screen

Introduction to Tianma’s direct display screen:

Based on LTPS glass substrate using Mini-LED direct display technology, it can achieve high resolution, high reliability, and high contrast excellent display effects; at the same time, the AM driving scheme saves ICs, has high circuit integration, and obvious cost advantages.

Using 6pcs of individual units, seamlessly spliced into an 18.1-inch product, with an LED pitch of less than 0.50mm, it can easily enhance resolution compared to traditional small-pitch displays; and the contrast far exceeds that of current market traditional LCD displays, reaching million-level contrast.

2. Comparison of Four Display Technologies

Currently, the aforementioned four display technologies each have their own advantages and disadvantages. Overall, the next generation of displays should theoretically be self-emitting and capable of flexible display shapes, with Micro LED/OLED development. However, as the two technologies mentioned above still have some issues in mass production, Mini LED backlight technology has become a hot solution today. Below is a simple comparative introduction to these four solutions.

1. LCD

The structure of an LCD panel is relatively complex. In addition to the glass substrate, it also includes a liquid crystal layer, color filters, polarizers, light guides, and backlight modules, among other components. LCD refers to the liquid crystal layer, which is used to control the direction of light; it does not emit light by itself and requires LED backlight as a light source. Moreover, LCD does not display images directly; it needs to use color filters to create images. The color filter is composed of many pixel points, each of which contains red (R), green (G), and blue (B) sub-pixels. According to the basic concept of color science, the three primary colors RGB can be combined into various colors in reality based on different brightness ratios, and different colored pixel points combine to form the colored images we see.

The LCD backlight layer usually consists of dozens to hundreds of LED beads larger than 200μm. These LED beads are either all on or all off; they cannot be controlled individually. All pixels on the LCD screen share a large backlight layer.

Side profile of an LCD pixel point

LCD display panels are cost-effective, lightweight, energy-efficient, and have relatively mature technology with low failure rates.

2. OLED

QLED (Quantum Light Emitting Diode) has unique optical properties, and when powered, it can display different colors based on particle size, while also having long lifespan, wide color gamut, high brightness, and pure colors.

Compared to LCD, OLED screens have advantages such as displaying pure black, no light leakage, near-infinite contrast, short response time, flexibility, and low power consumption. However, OLED screens also have disadvantages such as shorter lifespan, screen flickering, and lower pixel density.

3. Mini LED

Mini LED miniaturizes the LED beads in the LCD backlight layer, with each LED bead measuring approximately 50-200μm, allowing more backlight beads to fit, enhancing brightness and uniformity. Mini LED divides the backlight layer into smaller segments, allowing for zone dimming through LED chips, thus improving the long-criticized black and white contrast issues of LCDs, achieving display effects close to OLED while avoiding lifespan issues.

4. Micro LED

Micro LED integrates all the advantages of LCD and OLED, featuring high picture quality, low energy consumption, and long lifespan, but it has high manufacturing difficulty and production costs.

Side profile of a Micro LED pixel point

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3. Mini LED Backlight Process Flow

The Mini LED process flow is roughly illustrated below: sorting, printing, testing, solid crystal, testing, rework, and testing.

-end-

Aibang has created a vehicle display communication group, currently including companies such as FAW, SAIC, Geely, Great Wall, Changan, Harman, Marelli, Huayang, Desay SV, Hangsheng Electronics, Tianma, BOE, TPK, Changxin Technology, Xinli, Laibo, Lens, Bern, Teiyi, Shengli Precision, Star Technology, TDK, Wacker, 3M, Tongli Optoelectronics, Corning, Schott, Asahi Glass, Dongxu, Niebling, Sumitomo, Saibel, and other upstream and downstream enterprises in the industry chain. Friends are welcome to scan the code to join the group.

Event Recommendation 1: The 4th Vehicle Display New Technology Industry Forum (August 17, Shanghai)

No.	Topic	Invited Guests
1	Development and Demand of In-Vehicle Innovative Products Brought by the New Four Modernizations of Automobiles	FAW Hongqi
2	Application Cases of Innovative Display Technology in Automotive Cockpits	Huayang
3	Feasibility Study on Sub-surface Display and Transparent Display Products in Automotive Applications	Qishi Xunrui (Suzhou) Technology Co., Ltd.
4	Prospects and Current Status of MicroLED Applications in New Automotive Displays	Tianma
5	Prospects for the Application of Glassless 3D Technology in Automobiles	Holographic Information Technology
6	Application of Mini LED Backlight Technology in Automotive Displays	Handamei
7	Discussion on Automotive Mini LED Backlight Driver Chip Solutions	Lumissil
8	Application and Challenges of Plasma Technology in MiniLED Processes	Shengding Precision
9	Introduction to Innovative Display Vehicle Optical Bonding Solutions	Paili Ma
10	Detection Technology Solutions for Mini/MicroLED Products	Yuanfang
11	Application of Local Dimming Products in Automotive Intelligent Surfaces and Ambient Light Products	ams OSRAM
12	Application Cases of OLED Products in Automotive Lighting Products	Yiguang
13	Technical Challenges of Automotive Display Cover Plates and Optical Bonding in Innovative Display Products	Corning
14	Introduction to Projection Technology in Innovative Display Technology	Ma Honghu
15	Application of High Durability Functional Films in Automotive Display Products	3M
16	Introduction to Air Non-contact Technology in Automotive Displays	Dongchao Technology
17	Roundtable: Guest and Topic Planning on Market Opportunities and Challenges for New Display Products such as Mini/Micro LED in Automotive; Progress of Domestic Chips in the Industry Chain for New Display Products such as Mini/Micro LED; Technical Paths for Cost Reduction and Efficiency Increase of New Display Products such as Mini/Micro LED; Current Technical and Yield Challenges of New Display Products such as Mini/Micro LED;	OEMs, first-tier suppliers, and experts from the complete industry chain such as material or equipment suppliers

Event Recommendation 2: The 5th Automotive Head-Up Display HUD Technology Forum (August 16, Shanghai)

No.	Topic	Invited Guests
1	Market Analysis and Technology Trends of HUD under the Trend of Automotive Intelligence	S&P Global/ Zuo Si
2	Preparation Progress and Standard Interpretation of Automotive Head-Up Display HUD Group	Group Standard Technical Experts
3	The Role Evolution of HUD in the Development of Autonomous Driving Technology	OEMs
4	Introduction to the Hardware and Software of Huayang AR HUD	Huayang
5	Introduction to Innovative Applications of Harman Head-Up Display HUD	Harman
6	Introduction to the Development and Application of Coating Technology for Head-Up Displays HUD	Huicheng Vacuum
7	Application of High-Performance Adhesives in HUDs	tesa
8	AID&HUD Space Fusion Application: Creating a Digitized Future Mobility Smart Cabin	Prism Holography
9	Innovative Solutions for Large Area Small Volume AR HUD	Zhi Yun Valley
10	Introduction to the Application of COC Materials in HUD Product Structures	Tuoxian Technology
11	Breakthroughs and Applications of LCOS Technology in AR-HUD	Shenzhen Hantong Automotive Electronics
12	Introduction to DLP Digital Optical Processing Technology in Head-Up Displays HUD	TI
13	High Definition Automotive Micro Displays: LCOS Helps Large-Scale Application of AR-HUD	OmniVision
14	Revolutionary Technology in HUD: Holographic Waveguide	Longjing Optoelectronics
15	Curved Mirror Technology Solutions for Automotive Head-Up Displays HUD	Changxin
16	Software Algorithm Introduction for Automotive Head-Up Displays HUD	Rainbow Soft eSoft
17	HUD Optical Testing Solution Corresponding to SAE Standards	Yuanfang
18	Rapidly Increasing Penetration Rate: Opportunities and Challenges for AR-HUD	Ruiwei Vision
19	Roundtable: (Under Planning)	Key Guests from the Industry Chain

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