The Digital Signage Expo (DSE) is in full swing at the Las Vegas Convention Center, and there are a lot of things here to interest display people. I’m going to focus on just one of them.
But first, there’s an important point to be made about the digital signage world: Display technology is what people think about last and least. What’s worse is that they’re right. Obviously, you can pick the wrong display for an application, but a successful digital signage deployment also depends on content creation; media players; network design and hardware; software for sequencing, layering, and updating; sign placement; and successfully identifying the network’s audience, purpose, and business model. So, if your display company wants to establish a niche in the signage ecosystem, you have to realize you’re a flea on the tail of the signage dog. You have to listen, you have to be responsive, and you have to be humble. And that’s not always easy. (Personally, I have trouble with humble.)
With that painful subject out of the way, let’s talk about the black spot. At LG Display’s booth the company showed two displays, both which had hot, bright spotlights shining on them. One display (the competitor’s display, of course) had a large black spot where the spotlight was aimed.
What was happening is not new in the display world. The display was becoming hot enough to exceed the liquid crystal’s clearing temperature. That is, it was exceeding the temperature in which the liquid crystal material is in the nematic state needed for the display to operate, and was entering the temperature range where the material becomes an isotropic liquid. This maximum operating temperature, said Jun Joon, LG Display Vice President for the Public Display Department, is typically 75 degrees C.
Until recently, this phenomenon has not been a major issue outside of some aerospace applications. But now that LCDs are increasingly being used for outdoor signage, clearing temperature is becoming important in a wider range of displays.
LGD has worked with its LC suppliers Merck and Chisso to modify the LC material and raise its clearing temperature to 110 degrees C, which is why the LGD panel in the photo does not show a blackened spot.
Joon says LGD has a competitive advantage here because with the company’s in-plane switching (IPS) cell technology the clearing temperature can be raised without any serious trade-offs in other characteristics. According to Joon, this is not true for competitors who use some version of vertical alignment (VA) technology, because raising the clearing temperature for the LC molecules that are used in VA displays seriously impacts the response time. (I invite makers of VA, MVA, and PVA displays to email me with their opinions.)
Without taking sides, I can say that LGD is not alone in thinking this is a significant issue. Hyundai was also showing a high-temperature display for signage. And Planar, which is accelerating its activity in outdoor signage - particularly in drive-through menu signs for fast-food restaurants - takes the issue seriously.
There was much more going on at DSE. My colleagues and I will write more about that in forthcoming Display Dailies and, in greater depth, in the coming issue of Large Display Report.