英文原文
Types of LCD Products -Glassor Modules
The most fundamental decision to make iswhether the displaywi l lhave the drive circuitry attached (module),or not (glass only).There areadvantages and disadvantagesto each approach.
When purchasing a Custom LCD Module, thebasic electronic designworkwi l l be done bythe manufacturer.This obviously saves design timeand reduces the manpower needed to bring a product to market.Youcan benefit from the experience we have gained during our previousdesigns to shorten the design cycle and del iver an optimized product.The major decisions you need to make are the interface type,withstandard serial or paral lel interfaces being the most common, and thetype of integrated backl ighting desired.The temperature range,viewingangle,viewing mode,and contrastwi l l need to be considered,but thosedecisions are common to both approaches.
Aglassonlydesign putsthedesign burden ontheenduser.Youwi l lneed to learn a greatdeal about LCD's in order to completeyourdesign.Lucki ly,our website provides Appl ication Information and Web Links toassist you in the search for the information you may need.
The main reasonsto buyjust the LCD glassareto reduce costs,andprovide design flexibi l ity.The total cost of the components necessarytobui ld the drive circuitry is typical ly less than the cost of a pre-bui lt
module, and as long as you have space on your existing PC board,youwon't have to payforan extra PC board on which to mount the display,and have access to cost effective assembly and test. By doing a l ittlehomework,yourdesign wi l lworkjustaswel l asa module, andwi l l al lowthe flexibi l ity most designers need to adapt their design to everchangingdemands.
Types of LCD Images
The LCD can contain character icons, segments,graphic dot arrays,oranycombination.
Icons: By making a custom LCD,you can place images on the glassthat specifical ly complement your produce, these are cal led "Icons".These si lhouettes can take the shape of any image you may need andcountasone pixel ordoton the LCD.
Segments: Segments on an LCD display make upa larger character,such as a segment in a seven segment numeric character (displays 0-9),or a segment in a 14 segment alpha-numeric character (displays 0-9&A-Z).
Dot Arrays:These dot arrays can be made in almost anysize and dotcount. Exampleswould be character displaysthat use a series of 5x7 dotarrays to create a string of alphanumeric characters,or the larger 320 x240 graphic arrays that make images along with variable sizealpha-numeric characters.
Types of Liquid and Technology
The type of technology used is determined by the specificperformance requirementsyou set for thedisplaythat you are designing.Since several variations wi l l do a finejob, the ultimate consideration iscost.So here is a quick breakdown of the technologies we offer.
TN: Low production and NRE costs, poor viewing angle, averagecontrast.Coloration:Blackon Gray.Static preferred,butoperates wel l upto a 32:1 Multiplex rate. LCD Glass favorite.
STN:Medium production and NRE costs, average viewing angle,average contrast. Coloration Black on Green, or Dark Blue on Gray.Works wel l at high Multiplex rates. LCD Module favorite,high end LCDglasschoice.
FSTN:Medium high production and NRE costs.Good viewing angle,excel lent contrast. Coloration Black on White.Works wel l at highMultiplex rates.Higher end LCD Module favorite.
Negative Image: This is an effect that reverses the image on thedisplayand is onlyoffered with transmissive displays.The visual effect isto al low the backl ight to define the pixels turned "on" (transparent),whi le the "off" pixels remain opaque.This configuration works best inmoderate to low l ight conditions.
Viewing Mode and Polarizers
Theviewing mode is control led bythe rear polarizer,and how much
it does or does not reflect l ight.We offer three modes.
Reflective: This type of polarizer gives the display the brightestappearance in high to moderate ambient l ight conditions,with thehighestcontrast ratio possible.Unfortunately, itwi l l be difficultto read atnightorunderchanging l ightningconditions (thinkGame Boy).
Transflective: (Favorite solution) If your display must be readableunder a wide range of l ighting conditions, you wi l l general ly want atransflective display so that it wi l l look very good in the bright sunl ight,butwi l l also be back-l ightableat twi l ightand at night.Thetradeoff witha transflective display is that it wi l l not look as good as a reflectivedisplay during the day, and it wi l l not look as good as a transmissivedisplay at night. It wi l l however enable you to have an acceptablecompromise between the two, and provides a very acceptableappearance.
Transmissive:This display needsto have a working backl ight, unlessit gets its l ight from being a "window" type of device where the areabehind the LCD has a l ight source room ambient l ight.Where it is in acontained display, the backl ight may have a problem overpowering highambient l ight.Thistype of displaylooksgreat foran indoorappl ication,but is not very good in appl ications where power consumption is aproblem and it needs a strong backl ight. Remember, this choice ofpolarizerwi l l not operate unlessthere is an active backl ight.
The polarizers are also affected bytemperature,and a qual ity grademust be specified when choosing a polarizer.Afteryou have determinedyour environmental temperature requirements,you then need to choosethe polarizer grade.Here are your typical choices.
Commercial Grade Polarizers: Displays which wi l l be indoors, ormostly indoors, can use commercial grade polarizers.These polarizerswi l l hold up very wel l when used in most instrumentation, office andhome products, and other appl ications where the products wi l l beprotected from high temperature, sunl ight,and humidity.
Industrial Grade Polarizers: For harsh environments, a polarizerspecifical lydesigned for outdoor,extremely humid conditions should beused.We cal l these polarizers industrial grade.
Viewing Direction
The viewing direction of a LCD part is defined as the angles above,below, left, and right of the point-of-view that is perpendicular to thecenterof the display.
6:00 viewing direction has optimum contrast from below theperpendicularviewing plane(most popular).
12:00 viewing direction has optimum contrast from above theperpendicularviewing plane.
9:00 viewing direction has optimum contrast to the left side of theperpendicularviewing plane(uncommon).
3:00 viewing direction has optimum contrast to right side of theperpendicularviewing plane(uncommon).
Please keep in mind that viewing direction is less important for adirect drive display.As a general rule, the higher the multiplex rate, themore important the viewing direction becomes.Also, if your display isgoing to be viewed bya person wearing polarized sunglasses,you mustspecify this in the comment section to ensure that the display wi l l notlookblanktoan observerwearing polarized sunglasses.Howeverkeep inmind that for quoting purposes, the price of thedisplaywi l l not changemuch (usual ly only a few cents) if you change your mind for the finalviewing direction of the display.
Environmental Considerations -Temperature Range
The operating and storage temperature range of an LCD areimportant considerations, since operating outside of those ranges wi l lresult in a display that is not readable (outside operational range) orpermanentlydamagethe LCD(outside storage range).The combinationof the LCD fluid, polarizers, operational voltage, and multiplex ratedetermine the temperature range of the part. So instead of goingthrough the different combinations of these parameters, here are somegeneral guidel ines you can use when specifying the temperature rangeof your LCD, and manufacturer can then assist you in the process ofselecting the correct fluid, polarizers, and voltage for your appl ication.
These values are typical operating temperature ranges.
LCD TN Glass/Static or Low Multiplex Rates:Standard Temp Range:-10¡ãC to +60¡ãC,Wide Temp Range: -40¡ãC to +80¡ãC, Special izedTemp range:down to-55¡ãC,or upto+110¡ãC
LCD TN Modules /Multiplexed: Standard Temp Range: -0¡ãC to+50¡ãC,Wide Temp Range: -20¡ãC to +70¡ãC, Special ized Temp range:-40¡ãC to+90¡ãC
LCD STN&FSTN Modules /Multiplexed: Standard Temp Range:0¡ãC to+50¡ãC,Wide Temp Range: -20¡ãC to+70¡ãC, Special ized Temprange: -40¡ãC to+80¡ãC
Another note to remember is the LCD Glass and Polarizers are notthe only l imiting factors in thetemperature range of the LCDs.You alsoneed to take into consideration the temperature l imitations of thebackl ightand control ler ICsthat maybe presentalong with the LCD.LCD Module Backl ighting
When developing an LCD Module, a backl ightcan beaddedto l ightthe LCD and there are several options avai lable to backl ight a LCDmodule. The considerations in backl ighting a display are the l ightingintensity, l ife of thebackl ight,and thepower it consumes.Here is a quickcomparison of the backl ights avai lable.
LED:Offered in both edge and array l it, this technology is preferreddue to its variety of colors, intensity, long l ife (>100K Hrs), wide
temperature range, and low voltage requirements. The downsides arethe power consumption of some configurations (large sizes), and theuniformityof the l ighting for those same configurations.
EL Panel : This backl ight is very low power, but it requires a highvoltage(120VAC@400Hz Typical ly)and it has a relatively short l ife(halfintensity l ife\<4K Hrs),and medium temperature range.
Cold Cathode Florescent Lamp:This backl ight has a lot of intensityfor the power consumed, and has its appl ications for the larger LCDdisplays.The downsides are a short l ife span (\<20K Hrs),vibration wi l lreducethe l ifespan of thetube, l imited temperature range,and the highvoltage it needs to operate(>300VAC@30-80KHz).
LCD Glare Fi lter
It is possible to put an anti-reflective fi lter over the frontof a displayto improve viewabi l ity in harsh l ighting conditions.This fi lter is bondeddirectly to the front polarizer of the display and its front surface eitherphysical lyorchemical lyroughened.This surface re-directthe l ightwavesso that they continue travel ing forward instead of reflecting backtowardthe observer.New anti-reflective materials can reduce the front surfacereflectionsto lessthan 0.3%or less.
Physical Size
In general, the larger the display, the higher the price. The mostexpensive part of the Glass or Module LCD in most cases is the glass.
Manufacturersusual ly usea master laminate(Sheetof glass)which is 14"x 16".We can produce a single displaythat size,or we can partition thearrayinto hundreds of smal ler displays .Ourstrategyisto maximizethenumber of individual displayswhich we can get onto this laminate.Wetherefore recommend display sizes that give our customers maximumglass uti l ization.
First LEDSummary
LED (Light Emitting Diode), l ight-emitting diode, is a sol id statesemiconductor devices,which can be directly converted into electricityto l ight. LED isthe heartof a semiconductorchip, thechip isattached tooneendof a stent, isthe negativeside, theotherendof the powerof thecathode, the entire chip packageto be epoxy resin.Semiconductor chipis composed of two parts,partof the P-type semiconductor, it inside thehole-dominated, the other side is the N-type semiconductor, here ismainly electronic. But l inking the two semiconductors, among them theformation of a"PNjunction."When the currentthrough thewires role inthis chip, wi l l be pushing e-P, P zone in the hole with electroniccomposite,and then to be issued in theform of photon energy,and thisis the principle of LED luminescence.Thewavelength of l ight that is thecolor of l ight, is formed by the PN junction of the decisions of thematerial .
Second LED history and development
