Small and medium-sized LCD touch solutions

A resistive lcd touch screen is a display device that uses pressure sensing to achieve touch control. Its core structure consists of two layers of ITO conductive film and spacer points. When a force of 10-50 grams is applied, the upper and lower conductive layers come into contact, forming a voltage divider circuit. The controller calculates the touch coordinates through analog-to-digital conversion. It can be operated with any object and is adaptable to harsh environments such as dust and oil. It is commonly used in cost-sensitive or complex environments, such as industrial remote controls and machine tool operation terminals.

Different LCD touch technologies have their own unique principles and technical characteristics. Resistive touch technology, a long-standing solution, has a core structure consisting of an ITO (indium tin oxide) conductive film, a PET substrate, and isolation points. When a force of 10-50 grams is applied, the upper and lower conductive layers come into contact, forming a voltage divider circuit. The controller then calculates the touch coordinates through analog-to-digital conversion. This technology's advantage lies in its ability to be touched by any object. It still finds application in industrial remote controls (2-3 inch screens) and machine tool operating terminals in dusty environments. However, its 85% light transmittance and limited lifespan of 2 million touches have led to its gradual elimination from the consumer electronics market.

A lcd capacitive touchscreen is a display device that uses human body current sensing to achieve touch control. Its core is a matrix of ITO electrodes etched onto a glass surface. When a finger approaches, the capacitance between the electrodes changes (typically in the range of 0.5-2pF). The controller determines the touch location through self-capacitance or mutual capacitance detection. It has high light transmittance, supports multi-touch and high-precision operation (up to 2mm touch accuracy), and has a fast response speed. It can meet the fast operation requirements of 120Hz refresh rates in scenarios such as 7-12-inch medical diagnostic equipment, making it one of the mainstream touch technologies in the current market.

Projected capacitive touch (PCT) technology has become mainstream in the market. It involves etching a matrix of ITO electrodes onto a glass surface. When a finger approaches, the capacitance between the electrodes changes (typically in the 0.5-2pF range). Touch location is determined through self-capacitance or mutual capacitance detection. Currently, high-end solutions utilize 1920×1080 resolution panels with a 16:9 aspect ratio, supporting 10-point touch and 2mm touch accuracy. In 7-12-inch medical diagnostic equipment, response speeds can reach 120Hz refresh rates, meeting the needs of doctors for rapid image switching.

An in-cell LCD touch screen integrates the touch sensing layer directly into the LCD display, eliminating the need for a separate touch panel attached to the screen surface (as in traditional external GFF or GG touch screens).

The key feature of this technology is that the touch sensor is embedded between the LCD's liquid crystal pixel layer and color filter, or directly fabricated on the display panel's glass substrate, allowing the touch and display functions to share some structural layers.

In-Cell lcd touch technology represents a cutting-edge advancement in the industry. It integrates touch sensors directly into the LCD's pixel structure, eliminating the glass layer required for traditional external touch panels. This reduces screen thickness by 0.3mm and increases light transmittance to 92%. By embedding the touch electrodes within the color filter of the liquid crystal cell, the device achieves waterproof and dustproof design (IP67 rating). However, this technology suffers from low yield rates and is currently primarily used in high-end 5- to 8-inch smart home control panels.

The core principle of in-cell touch technology is to integrate touch sensors directly into the LCD's pixel structure, eliminating the separate glass touch layer used in traditional external touch solutions. This technology involves etching ITO touch electrodes on the color filter side or array substrate side of the LCD cell, allowing the touch and display functions to share the same panel space. When a finger touches the screen, the capacitance between the electrodes changes. The touch detection module integrated into the panel driver IC captures this signal and uses an algorithm to determine the touch coordinates. This design achieves a deep fusion of display and touch, reducing screen thickness while improving light transmittance. However, it requires extremely high process precision and a balance between interference between pixel display and touch signals.