Chemistry and the Apple TV

Such may not be the case today but formerly at MIT two terms of calculus, or the equivalent, was required for any degree, even what passes for liberal arts there. Engineers had to take a 3rd term. Chemical engineers and materials science folk took 18.03 “differential equations”, EEs took 18.031, also differential equations but with a greater emphasis on linear systems. The difference in the math embodied much of the difference between those branches of engineering, EE’s general deal with linear systems, chemistry is decidedly non-linear.

In practice, what this frequently means is that product development is very different for chemicals and materials than for electronics. In electronics, in linear systems, you can generally reduce the product risk and speed the time to market by testing the subsystems independently. In chemical systems even if different chemistries only touch each other rather than are mixed, the interface itself is a new system that must be tested and examined. Ions can migrate across boundaries or even re-arrange themselves within a monolithic material changing or defeating the product performance. In the display industry, when displays were actually made in the US, much of the industry was composed of chemical and materials folk. Today, as displays are all purchased from Asia, the domestic industry is largely EEs that design end product and develop display specifications.

Motorola spent close to a billion dollars building a fab and developing a process to make Field Emissions Displays (FEDs). In the end, they discovered tramp elements were migrating from their substrate into the FED structure. Using a different substrate, a different glass, meant starting over completely in process development. The investment was written off. A CRT glass plant once had to throw away several full days (the plant ran 24/7) of production during a product shortage due to parts per billion of fluorine in the glass. Fluorine outgasses from the glass in CRTs and is a powerful phosphor poison as is copper. Westinghouse, the inventor of the active matrix LCD, was put out of the TV business by a parts per billion copper problem in their plant water reclamation system. TV tubes would go dark about 6 months after consumers took them home.

Reportedly, Apple recently hired the OLED expert from LG prompting speculation that the much rumored Apple branded TV set will be an OLED. In the recent release of the iPhone 5 Apple had issues with the anodized aluminum coating on the case and with the sapphire lens cover. The lens cover was an optics issue but one that would have been expected if the company had truly comprehended the difference between a glass which it is familiar with and a transparent ceramic as is sapphire, fundamentally not the same thing. Two of the iPhone 5 product issues stemmed from predictable issues due to the nature of the materials they were using. Motorola's FED problem could have been anticipated as well. After Corning sold its consumer products business, the cookware industry is now rediscovering the difference between tempered flint glass and aluminum-borosilicate which was formerly synonymous with the term Pyrex.

OLED technology has had a long gestation period due to stability issues with the material. I would not expect Apple to venture so far into new materials technology. On a LinkedIn thread regarding LCD stability and suitability as outdoor digital signage, one of the posters commented that OLEDs might provide a better solution. If any stability issues remain with OLEDs, 24/7 operation and the heat and light of an outdoor installation will certainly bring those to light more so than use as a consumer TV. I would expect a proving period in TVs, as well as a cost reduction period, before OLEDs start finding their way into outdoor signage. I don’t expect that proving period to involve an Apple branded OLED TV. If Apple comes to market with a TV, I expect it to be an LCD, a very good LCD, but an LCD none-the-less. I also expect that the Apple magic will be in how its used rather than just a good looking screen. When Tim Cook said, “When I go into my living room and turn on the TV, I feel like I have gone backwards in time by 20 to 30 years", he wasn't referring to the picture quality.

The Other part of SpectraVue

As I mentioned in the original blog posting, there were actually two parts to the SpectraVue invention, The viewing film and the channel waveguide. Although the viewing film died a quick death after AlliedSignal folded the venture, the industry was mightily impressed with the channel waveguide and the design was widely adopted both in backlights for LCD as well as general lighting. The channel waveguide is something of the reverse of the viewing film, using a cons structure to columnate light rather than disperse it. The channel waveguide was rather problematic at the time as it did such a good job columnating light that you could see each individual channel element shining right through the display. The solution that was most obvious, giving the beams from each element some distance to integrate ran contrary to the trend of thinner displays. There was no appreciable LCD monitor business at the time; everything was notebooks. Finer structures and applications that could tolerate some thickness lead to a revival of the technique and AlliedSignal, after buying then changing its name to Honeywell, had a good time suing those that had adopted the idea.

Assuming the channel waveguide structure could be mad fine enough, there is an application for it on the front of some displays as well as in the backlight. If the optical pathway is run in reverse, you have a very efficient structure for capturing all off axis light and dumping it into the wavegude at sub TIR angles. This would give a display with extremely narrow viewing angle, virtually head on only, but the captured ambient light could be redirected to the LCDs own backlight or otherwise used to power the display.

A 12K Display

In other locations, I discuss some benefits of leaving out the color filter from LCD designs for signage: lower thermal radiation absorption, no cf fading, a brighter image. There is, of course a 4th benefit to removing the color filter in that you automatically get 3X more addressable pixels. That could give you a 3K display if applied to what would otherwise be an HDTV resolution screen or a 12K display if applied to the new 4K format.

Corning used to supply the glass for a 19” 12K monochrome CRT in the 1980’s. The customer used Corning’s standard 19” CRT glass to build the display although only about ½ of the glass supplied actually was within their spec. The 12K benchmark was important to the customer as it was a replacement for medical X-ray film. Because of liability concerns, the electronic replacement had to have at least the resolution of what it was replacing. I am unsure what X-ray film resolution is, but my understanding is that standard portrait film is the equivalent of 8K. With the transition to flat panel technology and the requirement of multi- billion dollar fabs, the opportunity to build such displays went away, replaced in part by the ability to pinch and zoom.

With the widespread availability of imagers well in excess of 12K, the market for 12K devices might extend well beyond the medical device market. Again, “digital signage “ is a possibility but there are a variety of other workstations where people look at images where 12K could be useful. … certainly defense as well. I would expect that whether they be field sequential color or monochrome, the product orders for 12K displays will start showing up.

Unbundling the Optical Stack for Better Environmental Performance

LCDs used outdoors as digital signage must be protected from the environment. Typically, they will have a cover glass to protect them from being poked and prodded. They may also have air-conditioning to protect the LCD from reaching its thermal clearing temperature or otherwise suffering thermal damage. Objects in direct sun can reach temperatures as much as 185⁰ F, and more than 70⁰ F above the ambient air temperature. The cover glass may be plate glass or chemically strengthened glass. Chemically strengthened glass has the advantage of being thinner and lighter. Plate glass has an advantage in that if it does fracture, it typically cracks rather than shattering, a feature known as "frangibility". This is especially true if a laminated solution is used. For public spaces, especially confined spaces such as in transportation applications, management of the broken glass hazard may be critical.

However, the cover glass may also be part of the thermal solution. The polarizers of an LCD, by definition, absorb about 50% of the light that hits them. They are agnostic as to which direction the light comes from absorbing 50% of inbound sunlight as well. Removing the outer polarizer from the LCD and laminating it between the layers of the cover glass puts a few millimeters of glass and an air gap between the absorbed thermal energy and the liquid crystal. This would cut the solar radiation load on the LCD by 50% and also provide the opportunity for passive, chimney, cooling rather than a powered air conditioner. Here, I discus removing the color filter as well. In addition to the brightness benefit, removing the color filter would have some solar radiation benefits as well. Certainly it will obviate any issues with solarization or fading of the color filter.