High Bright Display Technologies & The Advantages

of VBOND

Large LCD displays for Dynamic Signage

• Retail digital signage is a great market.

• And now you want to take large LCDs outside.

• It should be easy, right?

Large LCD displays for Dynamic Signage

• New displays are 500 nits +• New displays are 2000+ : 1

contrast• They should be perfect, right?

What is a nit?

1 meter

1 meter

1 meter

A nit is a unit of projected light energy from one candle, measured from its source,measured one meter away, measured over a one meter square area. A footlambert is the same light measured one foot away, over a one foot square area. 1 ft lambert is the same as 3.426 nits

Contrast ratios: two methods, two results

350nits

Intrinsic Contrast RatioOn the surface, the display, may read a 300:1 contrast ratio. This does not take into account ambient lighting. In addition, the light meter is measuring total flux regardless of angular distribution

Extrinsic Contrast RatioA reading from a distance, taking into account ambient light and reflections. A good extrinsic contrast ratio is 10 :1.

How LCDs work

Liquid Crystal Display• Liquid = Fluid• Crystal = Organized Molecular Structure

When placed onto an alignment layer, the molecules will track in the general

direction of the grooves.

How LCDs work

Rear Polarizer

Alignment Layer

Cell Gap

Color filter on front glass

Front Polarizer

Transistors on rear glass

Light from the backlight is polarized and then twists 90 degrees through the LC material allowing it to

pass through the front polarizer.

How LCDs work

The transistor applies an electrical field across the cell. The LCD molecules align to the direction of the flow. This

prevents the LCD from twisting. No twist, no light transmission

Luminance vs. Illuminance

1000-1500 nits

1500 nits

• 1500 nits is read only on “white”

• Black level can go as high as 100-150 nits

• This is only 10-15:1 contrast

Effects of illuminance

1500 nits

10,000 ft Candles

5% reflection adds to the “white” level but also to the “black” level, lowering the contrast ratio, washing out the display

5% reflectionAmbient light is “illuminance”

Brightness versus Contrast

• “Brightness” lightens or darkens the image. “Contrast” changes the distinction between the light and dark areas.

• Humans can “perceive” roughly 100 levels of brightness.

• Humans can “see” roughly 1 billions levels of contrast.• The human eye eventually becomes saturated with

brightness and becomes more responsive to contrast. • Contrast ratio is much more significant than brightness

in high ambient illumination environments.• The human visual system amplifies the difference in

contrast: lateral inhibition

Contrast Example

This is a test

This is a test

High contrast, easy to read

Very low contrast but it is readable

Two types of display enhancements

Display enhancement has two approaches: Brightness and Contrast. Outdoor LCD displays require both in order to make them readable in high ambient light.

Brightness:• Active- Adding more lights • Passive- Collects and focuses the

available lightContrast: • Direct Bonding AR glass• Air gap AR film and windows

For outdoor viewability, one must increase both!

Passive Brightness Enhancement

50% of the backlight light never gets out the front

50% of the light will transmit in either of

these orientation

No light will get through at this

orientation

Reflective Polarizer

Passive Brightness Enhancement

Reflective Polarizer transmits all light in its orientation direction but will reflect back any light not in alignment. Additionally, the light is rotated slightly, to be reflected off the rear reflector.

Reflective Polarizer-

Passive Brightness Enhancements

Horizontally aligned BEF- Collects light going up or down

and channels it forward

BEF- Brightness Enhancement –

Vertically aligned BEF- Collects light going left and right and

directs it to the front

Passive Brightness Enhancements

Transflective Film- Mirror film

Light from the outside comes in, and is reflected off the rear wall

Passive Brightness Enhancement

ELG- Enhanced Light Guide

Light from the CCFLs is non-directed and bounces in all directions. Some light never makes out the front.

Passive Brightness Enhancement

ELG- Enhanced Light Guide

Micro-prisms internal to light guide

ELG with the Reflective Polarizer is very effective in converting non-collimated light to collimated light

Light returning from reflective polarizer

Light from CCFT

Active Brightness EnhancementDual tubes Multiple edge-lit

tubesMultiple rear-lit tubes

Contrast Enhancement with Anti-reflecting technology

Whether a film or glass bond, AR coatings eliminate reflective loss

Challenges of enhancing large LCDs

• DBEF- Factories already use it• BEFs- Steals light from the sides, not good• ELGs- Works with edge lighting, not rear

lighting.• Transflective film, hmmm maybe.• Backlighting- Displays already have high

bright back lights• AR film- Not big enough and very expensive

More challenges with large LCDs

• Large LCDs are designed for TV, with fast response and wide viewing angles.

• Their structure lowers light transmission from backlights by 50% (more lights, heat and power with lower results).

• Their fast responding LC material causes problems.

Challenges of enhancing large LCDs

• Have we mentioned HEAT?!?!?

Lots of heat from the CCFLs

50% of the heat load is Infrared radiation

Air gaps traps heat and allows it to go higher

Heat is a big issue

A display will go “isotropic” or

“clear” at as low as 50o C

Isotropic is the point where the LCD molecules go random (instead of organized, causing the

display to go black

Formulas

Luminance + ReflectionReflection

= Contrast Ratio

Reflection = 5% x # of surfaces x ambient light

Even with high bright backlights, contrast may be

low

Reflection = 10K ftC x 15% R= 1500 nits

5%5%

5%1500 + 1500

1500= 1.85 :1 Contrast

VBOND eliminates reflective loss and increases contrast

5%5%

5%

VBOND eliminates the two internal points of reflection. With AR coatings on the front, overall reflections drops to less than 2%

Reflection = 10K ftC x 2% R= 50 nits

1500*0.85 + 5050

= 26 :1 Contrast1500 nits

VBOND Benefits• Low reflective loss means higher

contrast in high bright environments• Display are daylight readable at 500 nits,

sunlight readable at 800 nits• Backlight power can be lowered to reduce

overall power draw and less heat production

• No air gap eliminates “greenhouse” effect heat rise. • Solid bond will conduct heat out of the

display• Cooler displays will not “clear”or go

isotropic as quickly.• No air gap prevents moisture from

forming under the window.

Benefits of VBOND for Outdoor Signage

• VBOND is not size dependent. Large size LCDs are no problem.

• Glass thicknesses and other features such as chemical strengthening or tempering is offered.

• Glass can be developed to reflect infrared radiation, lowering the heat load.

VBOND Benefits

• Reworkable through production process• Reworkable in post-production• Low toxicity, environmentally friendly

materials.• Excellent UV resistance• Excellent optical properties• Excellent mechanical properties• Low glass transition temperature