Transparent Display Technology

The technology for making a transparent display is not secret. Basically, TFT electrons and TFT pixels are transparent. However, the color filter is not transparent because the RGB color pixels and black matrix are arrayed on the color filter sheet. The backlight unit is also not transparent because of the many optical films (such as brightness enhancement films, prism sheet, diffuser, and reflectors) and the LED light sources. The trick to making a transparent display is basically to remove the backlight unit and transform the color filter structure.

A transparent display is similar to an LCD module without a backlight assembly. The RGB color pixels and the black matrix array in the color filter are reduced to the minimum size for transparency. Therefore, the resolution and color gamut cannot be high. In many cases, panel makers remove the color filter, making the transparent display monochrome. However, the emphasis is on transparency, so sacrificing resolution or color saturation is not a problem. In other words, the transparent display can be considered a value-added open cell panel with a frame bezel because panel makers don’t need to assemble the backlight unit.

TFT LCD makers have been developing transparent displays since pioneers like Samsung and LG Display started making them, as the following table shows:

Table 1-  Panel Makers’ Transparent Display Products

Panel Maker

Size

Resolution

Color Gamut

AUO

65”

FHD (1920 × 1080)

72%

Innolux Corp

55”

FHD (1920 × 1080)

72%

LG Display

26”

HD (1366 × 768)

68%

32”

FHD (1920 × 1080)

68%

37”

FHD (1920 × 1080)

68%

42”

FHD (1920 × 1080)

72%

47”

FHD (1920 × 1080)

72%

Samsung

22”

WSXGA (1680 × 1050)

5%

46”

HD (1366 × 768)

72%

55”

FHD (1920 × 1080)

72%

Examples of Transparent Display

What are the applications for a TFT LCD panel that is transparent?

  • Shop windows: A transparent LCD panel could show the latest store information while simultaneously allowing consumers to see products through the display. We have also seen some interesting cases in small demo boxes.
  • Games, pachinko, and slot machines: Transparent displays can be eye-catching.
  • Vending machines: This may be the largest potential market for transparent displays because they allow for digital signage without loss of customer-facing area on the vending machine.
  • Refrigerator: On commercial refrigerators, a transparent display in the door can function as digital signage while letting consumers see the products. On home-based refrigerators, the display can show menus, recipes, health information, or ordering information.

We have seen several interesting applications of transparent displays.

RS Transparent Display Products

The first is from a Japanese company called RS (http://www.rs2006.co.jp/), which demonstrated a series of transparent display products at the 2012 FPD International Exhibit in Japan, as shown in the following figure. The four products had 10.2”, 22”, 32”, and 42” transparent displays. The 10.2” and 22” displays were for the front glass of a demonstration box, and the 32” and 42” displays were used on vending machines.

Figure 1-  RS: Transparent Display

Source: Quarterly Large-Area TFT LCD Product Roadmap Report

Planar’s LookThru Box

Another interesting case is Planar’s LookThru box, as shown in the following figure. The Planar LookThru display box uses a 32” display that provides interactive information with a transparent LCD surface glass, allowing consumers to see the product within. The transparent LCD front surface can deliver a variety of messages while featuring the actual product inside the box, in portrait or landscape orientation. The technology balances transparency with vibrant colors.

Applications include retail merchandizing, corporate displays, museum exhibits, award or trophy cases, education or corporate settings, tradeshow exhibits, and a wide range of architectural applications.

Figure 2-  Planar’s LookThru Box

Source: http://www.planardigitalsignage.com/products/transparent-displays/home

Planar offers very detailed specs for their 32” transparent display, as shown below:

Table 2-  Specifications of Planar’s LookThru Box Display

Source: http://www.planardigitalsignage.com/products/transparent-displays/home

Smart Cafeteria

Panel maker AUO has proposed another interesting application. It’s a smart cafeteria for a food court or restaurant. Like the transparent digital signage on a vending machine, this display shows menus and pricing, takes orders, provides health information, and so on. Data collected via the transparent display can be used to manage menu items, and users can provide feedback and see rankings from other diners.

Figure 3-  Smart Cafeteria

Source: AUO

Vending Machines

With the touch panel integrated in the transparent LCD on the vending machine surface, consumers can get additional information via QR (quick response) codes or pay using NFC (near-field communication). The transparent LCD on the vending machine is important in facilitating QR code and NFC use.

Vending machine owners can use these methods to collect consumer information as well. A transparent LCD panel with a camera could be a good tool for collecting end-user information (such as gender and age). Of course, this has to comply with laws and regulations, which are restrictive in many countries.

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