A reflective film is an optical component used within a display’s backlight assembly to recycle light and increase brightness/efficiency, whereas a plastic backlight is a type of complete backlighting unit structure, often utilizing an edge-lit design with light guide plates and various films, including a reflective film as its bottom layer.

The Optical Reflective Film for Liquid Crystal Display (LCD) market refers to a specialized segment in the electronics and display technology industries, driven by the growing demand for high-quality visual experiences. Optical reflective films are primarily used in LCD panels to improve their brightness and contrast by reflecting and optimizing light. These films contribute to enhancing the clarity, color accuracy, and overall display performance of devices like televisions, smartphones, tablets, and monitors. The global demand for such technology has surged in recent years, as consumers and businesses alike seek displays with superior image quality and energy efficiency.

Traditional Module Structure

• LCD Glass
• Backlight Optical Stack
• Backlight Reflector Sheet
• Plastic Frame / Plastic Housing
• Metal Back Plate

Functional separation

• Optical function: Backlight reflector
• Structural function: Plastic frame
• Encapsulation function: Frame + back shell

 

Reflective Film Bottom Design (Intergraded Structure)

• LCD Glass
• Backlight Optical Stack
• Reflective Film (Structural + Optical)
• Integrated Sealing Layer (No Plastic Frame)

Integrated Functionality

• Optical Reflection
• Bottom Packaging
• Structural Support
• Module Fixing
• Thickness Control

In order to achieve below Engineering Objectives

• Module thinning design
• Lightweight structure
• Simplified BOM structure
• Optimized cost structure
• Automation-friendly assembly
• Integrated module design

Overall, compared with a conventional plastic backlight housing, the reflective-film bottom design achieves a thinner profile and lower weight, while the plastic backlight structure provides higher mechanical robustness.

 

 

Q&A for Reflective Film Bottom design

Question 1:  Are the Reflective film bottom design meets structural strength and aging resistance requirements?

Answer: It meets the requirements. The structural strength must not only be provided by the LCD module itself, but the overall structure of the complete device housing must also protect the LCD module. In terms of aging test, it is no different from products with plastic frame bottom sealing.

Question 2: Is it able to meet the compatibility of thermal expansion and contraction?

Answer:  Yes, Orient Display factory able to meet this requirement.

Question 3:  Is the Reliability testing (vibration, drop, thermal cycling), will also be performed for reflective film bottom design LCD?

Answer: Yes, Orient factory able to perform the same Reliability test accordingly.

Question 4: Is the reflectivity able meet the backlight luminous efficacy requirements?

Answer:  Yes, we can meet this requirement.

Question 5: Is the bottom sealing structure able to meet IP protection design requirements?

Answer: There is no problem with dust protection. However, the waterproof performance of an individual product is slightly worse than that of a product with a sealed bottom frame. If the entire machine is properly protected, the performance is the same.

 

If you have any questions, please contact our engineering.

Types of Barcodes

The types of barcodes can be divided into two main categories:

1. One-Dimensional Barcodes (1D Barcode)

Features:

Encodes data only in the horizontal direction, suitable for short sequences of numbers or letters. Commonly used in retail, logistics, and industrial systems.

Barcode Type	Features	Common Uses
EAN-13 / EAN-8	Numeric only (0–9), includes a check digit; international standard for retail barcodes	Supermarkets, retail products
UPC-A / UPC-E	North American standard, similar to EAN	Retail packaging
Code 39	Supports letters, numbers, and some symbols; variable bar width	Industry, warehousing, military
Code 128	High density, supports full ASCII; encodes long strings	Logistics, healthcare, tickets
Interleaved 2 of 5 (ITF-25)	Numeric only; interleaved structure	Carton codes, shipping packages
Codabar	Numbers + specific start/stop characters (A–D)	Libraries, blood banks, legacy systems
MSI / Plessey	Numeric, older format	Internal retail systems

 

Common selection recommendations:

• For retail products → use EAN-13 / UPC-A
• For internal codes, warehousing, or custom text → use Code 128 (most versatile)

 

2. Two-Dimensional Barcodes (2D Barcode)

Features:

Encodes information in both horizontal and vertical directions, allowing much more data storage. Most can be scanned by smartphones.

Barcode Type	Features	Common Uses
QR Code	Most widely used; supports numbers, letters, Chinese characters, and binary; built-in error correction	Payments, URLs, product traceability
Data Matrix	Compact size, high error correction, easily recognized by industrial cameras	Chips, electronic components, medical devices
PDF417	Stacked linear format, can encode long text	Boarding passes, ID cards, logistics labels
Aztec Code	No need for an external quiet zone, suitable for small areas	Tickets, mobile interfaces
MaxiCode	Developed by UPS for logistics	International parcel sorting systems

 

Common selection recommendations:

• For smartphone scanning → QR Code
• For factory, metal, or small component marking → Data Matrix

 

3. How to Choose

Application	Recommended Barcode Type
Retail sales (recognized by POS systems)	EAN-13 / UPC-A
Internal asset or workstation labeling	Code 128
Mobile scanning (URLs, info display)	QR Code
High-density, small-size, industrial scanning	Data Matrix
Very limited printing space but still scannable	Aztec

 

Barcode Display Resolution Requirements

1. Concept of PPI

PPI (Pixels Per Inch) refers to the number of pixels contained in one inch (25.4 mm) of display length.
It indicates the pixel density or level of detail of the screen — the higher the PPI, the denser the pixels, and the smoother and sharper the images and text will appear.

Formula:

Alternatively, for one direction (horizontal or vertical):

 Example: Orient Display E-Paper AES200200A00-1.54ENRS

• Active Area (AA): 27 mm × 27 mm (≈ 1.063 in × 1.063 in)
• Resolution: 200 × 200 pixels
• Pixel Pitch: 0.135 × 0.135 mm

Or equivalently, using pixel pitch:

Quick Reference Table

Pixel Pitch	Equivalent PPI
10 mil (0.254 mm)	100 ppi
7.5 mil (0.191 mm)	133 ppi
6.5 mil (0.165 mm)	154 ppi
5 mil (0.127 mm)	200 ppi
2.5 mil (0.064 mm)	400 ppi

 

2. Resolution Requirements for Common 1D Barcodes

a. EAN-13 / EAN-8 / UPC-A / UPC-E (Retail Codes)

• Typical X dimension: 0.33 mm (13 mil)
• Recommendation: Minimum 2 pixels per narrow bar
• Required PPI:

• Practical Recommendation:
  ≥ 150 ppi usable, ≥ 200 ppi preferred
  • At 27 mm active area:
    • 150 ppi → ~160×160 px
    • 200 ppi → ~213×213 px

 

b. Code 128 (Logistics / Internal Encoding, Very Common)

• Typical X dimension: 0.25 mm (10 mil)
• Required PPI:

• Recommendation:
  ≥ 200 ppi preferred, especially for longer codes.
  At ~150 ppi, the barcode must be enlarged and simplified to avoid crowding.

 

c. Code 39, ITF-25, Codabar, MSI, etc.

• Lower density, mostly for internal management.
• Typical X dimension: 0.33–0.5 mm
• Recommended PPI: ≥ 120–150 ppi
• Practical Note:
  150 ppi is generally sufficient; less demanding than Code 128.

 

3. Resolution Requirements for 2D Barcodes

2D barcodes rely on module size (the smallest square unit). Each module should ideally be represented by at least 2 pixels.

a. QR Code

• Typical module width: 0.3–0.5 mm

For 0.3 mm modules:

• Recommendation:
  Minimum ~170 ppi, recommended ≥ 200 ppi
  • On a 27 mm, 200 ppi display → ~213×213 px — sufficient for medium-size QR codes.

 

b. Data Matrix

• Used for small components and chips; modules can be very small (0.2–0.3 mm).
• For 0.2 mm modules:

• Recommendation:
  ≥ 250 ppi suitable, 300 ppi preferred for industrial use.
  If the screen is only 200 ppi, enlarge the Data Matrix (module ≥ 0.25–0.3 mm).

 

c. PDF417 / Aztec Code

• High-density symbologies; require higher pixel density.
  • PDF417: ≥ 200–250 ppi recommended
  • Aztec: ≥ 200 ppi minimum; 300 ppi preferred when space is limited

 

4. Summary for 27 mm × 27 mm E-Paper Displays

Barcode Type	Minimum Usable PPI	Recommended PPI	Recommended Pixels (27 mm area)
EAN / UPC	≥150 ppi	200 ppi	≈ 213×213
Code 39 / ITF-25	≥150 ppi	200 ppi	≈ 213×213
Code 128	≥200 ppi	250–300 ppi	213×213 / 320×320
QR Code	≥170 ppi	200–300 ppi	213×213 / 320×320
Data Matrix	≥250 ppi	300 ppi	≈ 320×320
PDF417 / Aztec	≥200 ppi	250–300 ppi	≥ 213×213

If you have any questions, please contact our engineering.

What is a backlight

LCDs themselves do not emit light, so they require an external planar light source system to enable image display. This system is called a backlight (Backlight).

Types of backlights

Based on the light emission method, backlights can be divided into direct-lit (direct-type) and edge-lit (side-lit) types. Among them, edge-lit backlights are widely used in small- and medium-sized applications, such as mobile phones, tablets, and computers.

Working principle

The working principle of a backlight is to convert a point light source into a uniform surface (area) light source, providing the external illumination required for LCD display.

Composition of an edge-lit backlight

An edge-lit backlight mainly consists of a light bar (LED + FPC), light guide plate (LGP), reflector sheet (R), diffuser film (D), and brightness enhancement film (prism film, BEF), among other components.

1. LED (Light Emitting Diode)

An LED is the light source of the backlight module. Together with the FPC, it forms what is commonly referred to as the light bar (Light Bar).
The light-emission principle of an LED is as follows:

An LED emits light through electroluminescence. When a forward voltage is applied, electrons and holes recombine in the PN junction, releasing energy in the form of photons, thereby producing visible light.

2. Light Guide Plate (LGP)

A linear light source array composed of LEDs injects light into the light guide plate from one side. The light propagates inside the LGP and strikes the micro-dot patterns on the plate, where scattering occurs. As a result, the light exits from the surface of the LGP without dot patterns, forming a uniform surface light source.

3. Reflector

The reflector reflects the light that leaks from the bottom of the LGP back into the light guide plate for reuse, thereby increasing light utilization efficiency.

4. Diffuser

The diffuser uniformizes the light passing through it by refraction and scattering caused by acrylic beads, rough surfaces, or diffusing particles within the film. This process effectively evens out the light distribution and helps mask luminance non-uniformities and defects.

5. Brightness Enhancement Film (BEF)

BEF, also known as a prism film, has a light-concentrating function that increases display brightness. As shown below, among the three commonly used film-stack configurations, the high-brightness solution is clearly 2 BEF + 1 DBEF. BEF works by using micro-prism structures to redirect scattered light into the viewing direction, thereby improving on-axis luminance. DBEF (Dual Brightness Enhancement Film) further enhances efficiency by recycling polarized light, resulting in a noticeable brightness gain when combined with BEF.

6. Dimming methods

There are two mainstream backlight dimming methods: DC dimming and PWM dimming. In addition to these, MIX dimming is also a commonly used dimming mode today.

If you have any questions, please contact our engineering.

For more information about backlight, please visit our Knowledge Base.

Most Common Mounting Methods (Consumer Displays / Laptops)

1. Front Bezel Snap-Fit

Principle

• The panel is inserted from the front
• A plastic front bezel uses snap-fit clips to hold the panel around its perimeter
• The rear cover is then assembled as a whole

Pros

• Low cost and fast assembly
• No screws required (or very few)

Cons

• Moderate impact resistance
• Snap clips are prone to damage after repeated disassembly

Commonly Used In

• Laptop computers
• Low-cost monitors
• All-in-one PC front housings

 

2. Screw + Bracket Mounting (Most Secure)

Principle

• The four corners and/or edges of the panel have VESA or M2/M3 mounting holes
• The panel is fastened to the rear housing using PCB, metal, or plastic brackets
• The front bezel is used only for decoration and dust protection

Pros

• High structural strength
• Controlled load on the panel (prevents glass damage)
• Easy to service and repair

Cons

• Slightly higher cost
• More assembly steps

Commonly Used In

• Desktop monitors
• Industrial displays
• Medical / commercial equipment

 

Thin and Bezel-Less Display Solutions

3. Double-Sided Tape / OCA Adhesive Bonding

Principle

• High-strength double-sided tape (such as 3M VHB) or high-strength adhesives are applied along the panel edges
• The panel is bonded directly to the mid-frame or metal backplate

Pros

• Ultra-thin and minimalist design
• Excellent appearance (narrow bezels)

Cons

• Difficult to repair or rework
• High requirements for assembly precision
• Thermal expansion and contraction must be carefully considered

Commonly Used In

• Ultra-thin displays
• OLED displays
• Tablets / high-end all-in-one PCs

 

4. Metal Mid-Frame Clamping (High-End Approach)

Principle

• The panel is placed into a CNC-machined metal mid-frame
• Slight clamping lips are formed around the perimeter
• Screws secure the backplate, creating an overall clamping structure

Pros

• Extremely high rigidity
• Even stress distribution on the panel
• Good thermal dissipation

Cons

• High cost
• Complex mechanical design

Commonly Used In

• High-end professional monitors
• Industrial control displays
• High-brightness outdoor displays

 

Industrial / Automotive / Vibration-Resistant Applications

5. Backplate Tray + Shock-Absorbing Pads

Principle

• The panel is placed on a metal tray
• Silicone or foam shock-absorbing pads are added around the perimeter
• Screws are used to secure the assembly without directly pressing on the panel

Characteristics

• Excellent vibration and impact resistance
• Prevents stress concentration on the glass
• Long service life

Cons

• Thicker overall structure

Commonly Used In

• Automotive displays
• Military / industrial equipment
• Outdoor devices

 

A Typical “Combined Structure” of a Display

• Front Bezel (snap-fit / decorative)
• Panel (LCD / OLED)
• Foam / Double-Sided Tape / Brackets
• Metal Mid-Frame / Plastic Frame
• Main PCB + Backplate

In real products, multiple methods are almost always combined, for example:

• Snap-fit + screws
• Adhesive bonding + mid-frame
• Tray + shock-absorbing pads + screws

 

Common Design Pitfalls (Very Important)

1. Never press directly on the glass with screws

• Brackets or pressure plates must be used

2. Leave clearance at the edges for thermal expansion

• LCD panels can deform under temperature changes

3. Avoid localized stress

• Otherwise, “Newton rings / mura / dark spots” may appear

4. Provide strain relief for flex cables

• FPCs must have sufficient bend radius

 

If you have any questions, please contact our engineering.

A High Transparent LCD Display without using polarizer has been development. Its name is Polymer Nematic Liquid Crystal Display (PNLC).  A PNLC is a nematic liquid crystal system lightly cross-linked with a polymer network formed by in-situ photopolymerization so that the Liquid Crystal will present off and on states in the electrified state. This puts PNLC between:  Conventional nematic LCDs (TN / IPS / VA) and Polymer-dispersed systems (PDLC).

How PNLC Works (Step-by-Step)

1. Material Structure

• Nematic LC host (high birefringence is common)
• ~1–5 wt% polymerizable monomer
• UV curing forms a continuous but sparse polymer network

2. Optical States

OFF state (no field):

• LC director is distorted by polymer anchoring
• Produces:
  • Controlled scattering, or
  • Randomized birefringence

ON state (electric field applied):

• LC aligns with the field
• Polymer network limits flow but allows reorientation
• Optical state becomes uniform

 

Key Features

• Transparent with transmission rate: ~90% (without polarizer used)
• Fast response: ~20ms at 10V, ~120ms at 5V
• Contrast Rate (CR): ~3.
• Vop: 3.3-10V
• Current consumption: 1mA/3.3V
• Interface: Parallel, SPI or I2C
• Temperature range: Storage: -30℃~80℃, Operating: -20℃~70℃
• Dyes can be added to produce different high transparent color displays.

Applications

Vehicular Head Up Display

 

Smart Home

 

Aviation

 

Wearable

 

For more information about our PNLC capabilities, please checkout our newsletter.

If you have any questions, please contact our engineering.

Brief Introduction to the Polarization (Dark Edge) Phenomenon

Previously, we encountered a phenomenon where, before the LCD fully powers on, a noticeable dark or black border appears around the edges of the screen.

We generally refer to this as a polarization phenomenon. It appears similar to the illustration below.

Characteristics of This Phenomenon

• Occurs only during initial power-on or cold start
• Most noticeable under full white or light-colored backgrounds
• Gradually disappears as the panel temperature rises during operation
• Does not affect display functionality
• Does not affect touch performance
• Does not impact panel lifetime

The dark border typically fades within a few seconds to several tens of seconds.

This is a normal optical characteristic of LCD panels, not a defect and not a quality issue.

 

Root Causes of the Dark Edge Phenomenon

When the LCD is first powered on, the liquid crystal molecules, voltage driving system, and backlight system have not yet reached a stable operating state. This causes slightly reduced brightness in edge areas, forming a visible dark border.

1. Initial Polarization of Liquid Crystal

At power-on:

• Liquid crystal molecular alignment is not fully established
• Vcom (common voltage) waveform is not yet fully stabilized
• Positive/negative polarity switching has not fully entered steady-state

The edge area is more sensitive to voltage variations due to:

• Seal glue (frame seal)
• Black Matrix (BM) limitations

Under a white background, the edges therefore appear darker than the center.

2. Low Temperature Effects

When the LCD temperature is low:

• Liquid crystal viscosity is higher
• Response time is slower

Edge areas warm up more slowly due to structural shielding, so brightness recovery is delayed — making the dark border more visible.

 

3. Backlight Startup Instability

At initial startup:

• Backlight LED brightness has not fully stabilized
• Light guide plate edge illumination is not yet uniform

This results in lower brightness at the edges compared to the center.

 

4. Structural Light Absorption

LCD edges inherently include several unavoidable structures:

• Seal glue (Seal)
• FPC circuit area
• Black Matrix masking area (BM)
• Backlight frame edges

These structures absorb more light during startup, amplifying the dark edge effect.

 

Solutions / Mitigation Methods

1. Software Optimization (Highly Recommended)

• Avoid displaying high-gray or pure white images during the first few seconds after power-on
• Use dark backgrounds (black / dark blue / dark gray) during startup
  → This almost completely hides the phenomenon
• Delay full-white display by 1–3 seconds
• Apply gradual backlight ramp-up (soft start) to improve cold-start edge uniformity

2. Hardware Optimization (If Further Improvement Is Required)

• Improve panel preheating strategy
  For example, briefly drive low gray levels at startup to accelerate stabilization
• Fine-tune Vcom voltage (must be verified per panel specification)
  Helps reduce initial polarization deviation
• Optimize backlight startup curve
  Allows the light guide plate to reach uniform brightness more quickly

 

3. Usage Recommendations

• Avoid displaying pure white high-brightness images immediately under very low temperature conditions
• At low temperatures, liquid crystal viscosity increases, making dark edges more noticeable

 

USB-C Sample White Screen Issue – Analysis & Improvement

 

1. Observed White Screen Condition

During testing, another issue was observed:

After testing, the display remained connected to the computer. The computer was powered off, but the power supply remained connected. Under this condition, the display panel turned completely white.

The factory initially suggested this was a polarization phenomenon. However, we believe it is more likely related to power supply, backlight control, or display driver logic.

When the laptop lid is closed, the system may enter sleep or standby mode. Although power remains connected, there is theoretically no video signal. In this condition:

• The display should go dark
• The backlight should turn off

 

2. First Improvement Verification

To resolve the issue, the engineer routed out a video signal detection pin to determine whether a valid video signal was present.

The logic implemented:

• When video signal is detected → turn on display power
• When no signal → cut off display power

Testing showed this method was effective:

• When the video signal was removed, the white screen did not appear
• However, during signal restoration, a brief white transition was visible

Since this was only a functional verification, further optimization will be implemented via software:

• When signal is detected, apply a short delay before powering on the display
• This avoids the visible white transition

 

3. Second Improvement Verification

Based on the first solution, further hardware and software optimizations were implemented.

An external MCU was used to control:

• Signal arrival detection
• Display power enable
• Backlight enable

Only after confirming valid signal arrival does the MCU power on the display and backlight.

Results:

• When the computer is shut down, the display shows no image
• The backlight is fully turned off
• The white screen issue is completely resolved

 

4. Minor Startup Backlight Flash Issue

Another minor issue was observed:

When the computer boots up and USB-C first supplies power to the display, the display circuitry is still in reset state. During this moment, the backlight briefly flashes.

Solution:

• Add a delay circuit stage
• Stagger the power timing between system reset and backlight enable

This eliminates the brief backlight flash.

The adjusted startup time is approximately 1–2 seconds.

 

If you have any questions, please contact our engineering.