Note: this is an excerpt from a six-part series from Focus Display Solutions of Chandler, Ariz. The series will provide non-technical insights into why products such as cell phones use a color display, and other instruments, such as a blood pressure monitor, use 20-year-old non-color monochrome technology. This series will cover terms such as half-life, power budget, NRE, transflective, and others, and address the different LCD module options available when selecting a display for your product by being broken down into the following parts:
- Which color LCD technology is best for your application?
- What is the best monochrome (non-color) LCD for my application?
- Do I need a backlight and what type?
- What temperatures will this display operate in?
- Do I want a standard off-the-shelf display or a custom?
- What LCD module to use if I have limited power for my display?
- What is the Best Color LCD for My Application?
- The first question to ask when designing a new product with an LCD is 'Do I want a color or a monochrome display?
Part 6: What is the Best Color LCD for My Application
When choosing between a color LCD display and a monochrome display, there are several variables to consider. These include cost, EOL (end-of-life), power consumption, ability to customize, and appearance or perception of your product.
End of life is when the product is no longer manufactured. Once a product is discontinued it then becomes Legacy. The world is in color so why don't all new products use color displays? After all, nobody watches black and white TV anymore. Users have come to expect color displays in all of the products they purchase because the appearance of a color display sets certain products apart from those which use the old monochrome technology.
Three of the mainstream color LCD technologies currently in use are TFT, OLED and FSC. My goal is to help the OEMs understand and decide which display is best for their product and will appeal the most to their end customer.
TFT vs. OLED
The best way to introduce these two types of displays is to compare them side-by-side and discuss their advantages and disadvantages. Please keep in mind that what is cutting edge today may be obsolete tomorrow, some of the comparisons below are guaranteed to change in the next few years.
TFTs (thin-film transistor) have been around for several years and control a large percentage of the color LCD market. Although this is the most popular color technology in use today, OLEDs (organic light-emitting diodes) looks like they will surpass TFT technology in the next few years.
TFTs and OLEDs can be seen in applications such as cell phones, laptop computers, and digital cameras. Video and high-resolution photos are also possible on both types.
Below are questions to ask yourself when choosing the display for your product.
What temperature range do I need the display to work in?
Winner: OLEDs. OLEDs operate at temperatures as low as -40ºC (-40ºF) and as high as 85ºC (185ºF). TFTs perform poorly below -20ºC (-4ºF) and above +70ºC (158ºF).
Which Technology offers the largest variety of sizes?
Winner: TFT. The current size of TFTs range from 0.9 inches up to, and exceeding 19.2 inches, whereas OLEDs range from 0.5 inches to 7.7 inches (Samsung Galaxy Tab 7.7). It is important to note that these sizes are not absolute. There are TFT and OLED displays that are larger than the sizes listed above, but they are not in mass production at this time.
When choosing the size of your display, keep in mind two major factors: the popularity of the size and the number of suppliers that manufacture that size. Popular displays are LCDs that are manufactured in large quantities. The greater the popularity of the display, the less likely it will be discontinued in the near future, thus the lower the cost. The greater the number of manufactures for a particular size, the lower the cost, an the easier to second source.
Which display is the brightest?
Winner: OLEDs. A picture is worth a thousand words.
Which display offers the longest half-life?
Winner: TFTs. Half-life is a measurement of how many hours of use before a display becomes half-as-bright as when it was first turned on. The blue in the OLED has a half-life of 14,000 hours. This does not mean the display will burn out at that point, but will only be half-as-bright as when it was first turned on. There is much research in progress to increase the number of hours.
Keep in mind that not all products require the display to be on 24/7. Many products that require batteries, such as cell phones and digital cameras, only make use of the LCD for one to two hours a day. Many of these devices will be obsolete before the display reaches 14,000 hours.
Which display has the lowest power consumption?
Winner: OLEDs (most of the time). The exception to this is that the power consumption on an OLED for a white background is higher than a TFT.
Which offers the faster response time?
Winner: OLEDs. OLEDs are estimated to be less than 0.01 mS (milliseconds). TFT is in the neighborhood of 15 mS. That's milliseconds. The human eye blinks every 300 to 400 milliseconds. There are 86,400,000 milliseconds in one day. The eye can barely consciously detect a difference of 15 mS but the brain can tell there's something up.
Which display is thinner?
Winner: OLEDs. OLEDs are not only thinner but in the near future will be flexible.
Which display is more economical?
Winner: TFTs. TFTs cost less at this time, but the price difference continues to erode.
Summary
TFTs have been around longer then OLEDs. This head start has allowed TFT manufacturers more time to dominate the market, offer more sizes and lower the cost. The OLED has a few technical set backs at this time, but as technology improves, many or all of these issues may go away.
Focus Display Solutions invites consumers who have any questions concerning LCD displays to send them to displaytalk@focuslcd.com
