Positive vs Negative Mode: Which Works Better for LCD Screens

Liquid crystal display, short for LCD, is widely used in all kinds of daily electronic devices. It refers to liquid crystal display technology as a whole. Based on driving principles, LCD products are categorized into static drive, simple matrix drive and active matrix drive.

Different rotating angles of internal liquid crystal molecules create varied working modes, which lead to obvious differences in screen display performance.

TN twisted nematic liquid crystal was developed later than DSM type material, and it has laid solid groundwork for the mainstream development of modern LCD industry. Subsequent HTN, STN, FSTN and DFSTN all derive from TN technology. These variants differ mainly in liquid crystal arrangement structure, twist angle and internal circuit design.

Standard TN screen features a 90-degree liquid crystal twist angle. HTN ranges from 90 degrees to 120 degrees. STN adopts 180 to 270 degrees torsion design. FSTN and DFSTN are upgraded STN products, adjusted by modifying twist angles and polarizer matching ways. STN display can present yellow-green, blue and gray visual effects, while TN type is divided into positive and negative display styles. FSTN and DFSTN show classic black and white pictures. FSTN adds compensation film on original STN basis, and DFSTN applies double-layer FSTN structure to achieve steady black-white display effect.

VA liquid crystal owns distinctive structural characteristics. Its internal liquid crystal molecules stand vertically against glass base plate, maintaining vertical arrangement status when no voltage is supplied.

We analyze diverse LCD types comprehensively from display effect, viewing angle, cost positioning, applicable fields, driving channels as well as strengths and weaknesses.

Common TN screen delivers gray and yellow-green display tone, with viewing angle between 30 to 50 degrees. It boasts low cost and is mostly made into segment display screens, matching 1/8 driving channel. This type enjoys low mold opening expense and unit price, consumes little power. It can cooperate with TFT component to form active matrix display, featuring quick response and low technical entry threshold. Yet it fails to generate high-frequency signals, accompanied by narrow viewing angle, ordinary contrast and unnatural color restoration.

Negative TN screen presents black background display, sharing the same viewing angle range and low cost level. It is widely applied to segment panels, electronic watches, calculators and portable game consoles. It retains cost and power saving advantages, but cannot support high-pass signal output, with limited visual angle and contrast, and only fixed black background available.

HTN shows yellow-green and gray pictures, with viewing angle expanded to 60 to 70 degrees. Its cost sits between TN and STN products with balanced cost performance. It fits conventional segment screens and general measuring instruments, equipped with 1/8 driving channel. Compared with TN screen, it gains wider viewing range, easy production process and extensive application coverage. Its drawbacks lie in insufficient contrast and average display quality, not suitable for high-drive LCD production.

STN screen displays gray and yellow-green background, supporting maximum 150-degree viewing angle with medium pricing. Yellow-green and blue film versions cost equally, while gray film type is priced higher. It can be manufactured into segment and dot matrix screens, serving high-grade meters, welding machines and portable note devices, configured with 1/240 driving channel. It has strong driving capacity, abundant display content, diverse display styles and broad usability. Nevertheless, it sets strict standards for production equipment and raw materials, resulting in low finished product yield and relatively high overall cost.

Negative STN takes dark blue as background with light colored fonts, keeping identical viewing angle, price level and driving channel parameter. It possesses reliable driving performance, while facing the same strict production requirements and high material cost.

FSTN can display gray white, colorful background with black characters, reaching 150 degrees viewing angle and slightly higher selling price. It is versatile dot matrix screen material with 1/240 driving channel. It owns uniform background color, wide viewing angle and semi-transflective property, remaining visible clearly under sunlight. It adapts to high-density dot matrix and various graphic display. Defects include impure background tone, slow response speed and color shift under high temperature. It consumes more power and only applies to passive matrix structure, unable to combine with TFT module.

Negative DFSTN realizes pure black background display, with font color consistent with backlight tone. It reaches 150-degree viewing angle and higher production cost, mainly used for dot matrix display. Optimized compensation film effectively offsets color deviation caused by temperature change, keeping stable high contrast effect all the time. The downside is only single black background available and expensive manufacturing cost.

VA screen shows white fonts against black background, with viewing angle of 100 degrees and high market price. It is commonly made into segment code display modules, matching 1/8 or 1/16 driving channel for character dot matrix use. It achieves pure black background and outstanding contrast ratio, restores vivid color and fixes the insufficient black tone and viewing angle flaws of traditional TN screens, only with higher production expenditure.

Viewing angle performance ranks from small to large: TN＜HTN＜VA＜STN, FSTN and Negative DFSTN

Screen response speed ranks from fast to slow: TN＞HTN＞STN＞FSTN＞VA

Display contrast level ranks from high to low: VA＞FSTN and Negative DFSTN＞STN＞HTN＞TN

Two mainstream display modes have distinct traits. Positive mode adopts semi-transflective structure, working normally without backlight support. It runs under low voltage with low power consumption, and can be viewed clearly under all light environments.

Negative mode applies full transparent polarizer design, which needs matched backlight to work normally. To guarantee clear visibility under strong sunlight, screen brightness needs to reach over 800 nits.

All above analysis and comparison are provided for practical reference.

Hot Display has focused on LCD screen research, development and manufacturing for twenty years, supplying full-range products covering all above types.