Modular Display History P14

Flexible /?fleks?b(?)l / adjective

• It bends. To bend. Bendy. Bendable. Floppy. Twisty. Curvy. Swooping. Droopy.

What does “flexible display” mean? Did anyone ever ask for a flexible CRT or a flexible Jumbotron? If not was it because they were afraid of being laughed out of the room? Do people assume heavy things are inherently not flexible? What about other technologies? It is a fact that an LCD panel is flexible right up until it isn’t. LG has made some very interesting flexible OLED products but they are wisely not selling the roll up version delivered in a tube so customers can just velcro it to the wall. Have you ever checked to see if any of the walls of your house are plumb? Do people know that the large format LG OLED displays used in televisions and the smaller OLED panels in phones are built on a completely different display stack?

If you have to bend all the fibers to get them into the display is the display flexible? How many people mean “stretchable” when they say “flexible”? I have a lot of questions.

I am going to divide flexible displays into the following categories: Bendable, Segmented, Fabrics (soft meshes), and Mechanical. There are some gaps here that I will address later in the article. It is also worth noting that some of these break my earlier categorization of displays into boxes, space frames, and shells (monocoque) and this is because I excluded tensioned displays.

BENDABLE - This is a solid two-dimensional plane that can be deformed to create 2D and some limited 3D curves. A thin FR4 based PCB would meet this criteria as would variable flexible PCB options.

SEGMENTED - This is a single unit formed of nominally uniform subsections that are held together by an adjustable frame or shell that allows for the curvature of the segments to be controlled and fixed at a desired point.

FABRICS - These can be fabric based meshes or nets. The key factor will be that the connection from pixel to pixel or module to module can move independently from the connections to other points in the array such that the display can be "draped" in a non-2D manner.

MECHANICAL - A very large screen that can change its shape might be considered flexible in some manner. Flexible joints that allow a screen to change the physical relationships between display modules for example.

We can add to this classification a timeline that indicates that designers and tinkerers wanted flexible displays almost as soon as companies even started imagining full color LED video displays. This statement from 1993 "Further, the color display device according to the present invention includes a color display device having a display portion which can be rolled" and through the use of "three light emission diodes of three colors, for example, red, yellowish green, and blue". The interest in less rigid displays also drives this statement about LCD panels from 1994 "With the technology thus limited, it is a general aim of the present invention to provide an electronic display which is readily configured in a curved or flexible (hereinafter non-planar) configuration, and is thus suitable for applications not readily served by the current flat panel liquid crystal displays."

I first encountered the illustration on the right below (Zhang) when I was researching a patent that Element Labs was considering filing in March of 2006.

The appearance of full color LED displays was followed almost immediately by simple mesh screens such as the LEC screen in Japan and the initial fabric design concepts for the backdrop of the U2 PopMart tour happened right a the beginning of the modern LED display industry. This rapid iteration was driven by the accessibility of the modular components that go together to make a screen. Once there are "intelligent LED clusters" you could make strings of LED pixels meaning that the design and functionality of the electronics and the mechanical system can be separated in such a way that one set of electronics (and string of LEDs) could be integrated into a variety of different configurations. This is a critical point that ties into several of the earlier articles and was the focus of Modular History Part Ten. An LED display is an arbitrary arrangement of components to the degree that the driver is separate from the light emitting components is separate from the mechanical and packaging systems. So in theory I could take 192 LED dice (64 x r, g, b ) and some driver components and make a nice animation where we bounce through a series of assembled and exploded views where each finished design is immediately stripped back out to its raw components and then reconstituted as a completed different screen. As Michael Hao noted last week, you can put the red, green, and blue LED dies in three discrete LED packages or you can integrate all three colors into a single package. A wide range of designs were possible with off the shelf components and if you are willing to move beyond what is available off the shelf and you have a modest budget you could get custom LED packages or custom drivers and you can make something new at a fraction of the cost of other display systems. This is not possible with an LCD display because LCD display production is driven by process engineering costs and the optimization of a flow of display glass through a fab. An LCD display manufacturer might want guarantee 100,000 units a month volume when they look at producing a custom panel. At lower volume the costs are eye watering. OLED displays are the same. Making a custom CRT was probably just as bad. This massive variation in display topology is unique to LED.

BENDABLE - I like the phrasing in the quote above. A bendable display delivers a "non-planar" screen surface. This is possible by altering the materials used or by simply making the materials so thin that they can be bent to a certain degree.This is what is happening with large format flexible OLED and also what happens when you try an pick up any modern LCD glass over about 40" diagonal. The glass is so thin that if you lift one corner the panel will become ... non-planar. The Shinoda Plasma tubes should probably be categorized as a bendable display in spite of the fact that the each display was composed of many tubes. And there is another non-planar plasma display option using plasma spheres. This work was performed by Carol Wedding at Imaging Systems Technology.

In the case of LED display modules this can be achieved by using a very thin standard fiberglass (FR4) PCB or by using polyimide or another flexible PCB material. Nanolumens obviously factor into any discussion of this particularly because their particular journey started with a ground up rethink of how to drive an LED display. And while they eventually adopted a more traditional LED display topology it is the belief in the initial concept that drove their commitment to flexibility (link to photo).

Another early advocate of flexible LED tiles was Digiled who introduced the digiFLEX product in 2008. The digiFLEX module integrated a silicone rear housing with magnetic physical connections that work with any ferrous material an integrator might use. This means a laser cut sheet metal armature can be applied to a form allowing for a large continuous surface for the magnets. This can be viewed, from a certain angle, as an adaptation of the MiPix clip system.

You can see in both displays above the ability to deform off axis from the orientation of the display matrix which is interesting but limited by the need to join the edges of modules and the inability of these products to offer a true 3D curve without the use of trapezoidal modules.

SEGMENTED - A segmented display is composed of a series of LED modules that are connected to a structure that maintains the physical relationship between the modules as the curvature of the frame is adjusted. The are multiple ways to do this but I think the Winvision panel below is a good example.

It is easy to see the functional blocks of this frame. The low profile strips connected to a flexible lateral rib that can be tensioned by adjusting the arm. The degree of the adjustment is clearly visible in the center spine.

This "family" of flexible displays can extend into lower resolution displays like the ROE Linx, Revolution Display FlexMesh (VER), and other earlier displays. It is possible within this definition to extend the term Segmented to any assembly composed of multiple modules connected in an adjustable linkage. By this definition an Element Labs Stealth panel would not be a Segmented display but a touring rig of Element Labs Stealth panels shipped on a set cart or case and connected to a curved header would be a Segmented display. This inconsistency is because I am making all of this up as I go. Happy to hear your rules in the comments.

The LED segments in the display can be scaled to deliver a full display (rather than a mesh) and depending on the rigidity of the segments the finished display could be segmented or curved. In the Gtek display below you can see clear vertical lines dividing the segments. The picture of the GS2.9TC on the left shows the edge of the PCB.

FABRICS - A Fabric display will almost always be composed of LED strings because as noted earlier the electrical requirements and the mechanical design may not ... mesh. [Thank you. You read this far and I dropped that on you.] The demo screen for PopMart is a good example. If you can drape the screen across a car and the result is even vaguely car shaped then it is probably a fabric.The Soft-LED product from Main Light is a good example. Color Kinetics light strings integrated into a drape.

Element Labs introduced a product called Helix H75, that was developed by a small UK company. H75 was a cargo net like mesh. Each module had four pixels but the intra-module connections were all flexible.

The one area of flexibility that we do not cover above is the flexibility of LED screens and pixelated LED tape. The question I would ask mirrors the contraction in the Stealth panels. A single panel is not flexible but when used in an array connected by flexible hinges the product could be considered as a Segmented flexible display. If you took a single piece of pixelated Cotco LED tape is that a flexible video display? What if you integrate multiple pieces of LED string into a backing material like the Main Light Soft-LED product?

The illustration below relates to this video - Secret Video

The nice thing about LED string and LED tape is that you can meet a lot of unusual design requirements by bending LED string or LED tape into all types of contorted arrangements.

I think both of the projects above were handled by XL Video. The Beastie Boys project on the left always reminded me of an Alexander Calder mobile although I have no idea if that was the intent [Additional information]. If you want more of the same you can check out the Marco Borsato show here.

MECHANICAL SCREENS - A screen where the flexibility is defined by the ability to vary the position of one module relative to other modules in the system.

I remember Tait and Nocturne making a Venetian blind screen for a tour. The LAADtech screen is conceptually if not mechanically similar. The link to the PDF document is well worth following in spite of the streak of "the condescension of hindsight" that is apparent in a document from 2013 covering a screen designed in 2005. [Yes, he beats up on Stealth a bit]

And the Barco FLX was conceived of as a much more ambitious hybrid of string and structure. The FLX 24 was at the core of the U2 360 screen. The one ring to bind them all. A flexible and modular string product designed to give designers total freedom.

It is obvious that you can approach “Flexibility” from a number of different angles. I have laid out a few but there is something consistent here which is that the goals of the designer and the requirements of the application drive the design just the same as any creative display. There is an approach that says “I can do everything with LED tape” and a reality that a more carefully considered design will yield a more robust system.