How 4K x 2K LCD TVs affect display panel manufacturing, yields

This article was published in the DisplaySearch Monitor, June 2012, and authored by David Hsieh.

July 2, 2012 — Liquid crystal display (LCD) panel makers have added new display features — high color gamut, 3D, LED backlight, slim type, ultra-slim bezel, 120 Hz/240 Hz/480 Hz frame rate driving, fast response time, high brightness — with varying success in driving TV demand.

Consumers will not pay a price premium for a new feature that cannot be proven valuable. For example, high color gamut was panned because broadcasting systems regulate the color gamut of content, and preferences for color saturation vary widely.

Instead of “spec up,” more and more end users are looking to “spec down” for budgetary reasons. Lower but acceptable panel brightness now prevails, as it helps to reduce backlight cost. Meanwhile, as analyzed in the May 09, 2012 DisplaySearch Monitor article “Direct LED TV Selling Better than Edge LED TV,” the cost effective direct type LED-backlight LCD TV is doing well in sell-through results. While its form factor is not slim, some end users care more about how an ultra-slim bezel looks from the front.

For all these reasons, LCD TV panel and set makers are wondering what new features will add value for end users and motivate another replacement cycle.

 

Higher resolution: The next added value?

Many people believe that ultra-high 3840 × 2160 definition (UHD or UD), also known as 4K×2K, will be a meaningful value-added feature on next-generation TV displays. 4K×2K has 4x as many pixels as full high definition (FHD, 1920 × 1080), which is the current prevailing resolution for LCD TV panels.

Smart phones and tablet PCs prove that the higher the resolution, the better for end users. These very high definition devices set consumer expectations for televisions. Because LCD TVs are still mainly used for watching rather than interaction or content creation, consumers will perceive very high resolution as a direct benefit to viewing, unlike other new features (such as smart, connected, or 3D TV and LED backlights).

The best quality video is recognized as vivid with no difference between reality and screen, and the higher the resolution, the more vivid the content. 3D technology halves resolution on LCD TVs. On 4K×2K LCD TVs, the impact of the downgrade in resolution when watching 3D content is not as severe. With 4K×2K, even after the 3D downgrade, the resolution is full HD, falling from 3840 × 2160 to 1920 × 1080.

For ultra-large LCD TVs, such as 60-80”, pixels are so big that they are visible in FHD. Therefore 4K×2K is recognized as necessary on very large TVs.

 

4K × 2K manufacturing options

Most panel makers have been working on 55”+ panels for 4K×2K. This is because panel makers target high-end and very large screen markets.

Most panel makers are implementing oxide thin-film transistor (TFT) manufacturing for 4K×2K resolution. Because of the higher electron mobility of oxide, it’s easier to design with a smaller pixel; therefore more pixels can be implanted onto the glass substrate. However, the oxide TFT process requires a 6-8 photomask process, compared to the 4-5 photomask process for amorphous silicon (a-Si) TFT. This will affect fab capacity. Chimei Innolux is planning to use a-Si TFT, rather than oxide TFT. In theory, this is workable and Chimei Innolux can save lots of surplus cost for new photomasks and maintain a better yield rate.

4K×2K LCD TV panels are a big challenge for TFT LCD process yield rate and stability. In the current TFT LCD process, the yield rate and reliability of HD and FHD do differ much. However, when the pixel count quadruples, the yield rate will fall significantly. Meanwhile, the higher resolution means panel transmittance will be reduced because there are more pixels on the substrate. As analyzed in the TFT LCD Process Roadmap Report, there are many new technologies needed for this kind of ultra-high definition:

  • High resolution photo lithography (high resolution patterning)
  • SHA (super high aperture) ratio
  • High mobility backplanes (such as oxide TFT or microcrystalline silicon)
  • Copper (Cu) metallization
  • BM (black matrix) width reduction
  • The EE (electronics engineering) panel design: data/scan driving, input format compatibility, and value-added features including 4K up-conversion, 3D, and local dimming backlight.

 

Panel makers developing 4K×2K

The market outlook for 4K×2K is still unclear due to TV broadcasting bandwidth limitations. Despite this, LCD TV panel makers have developed many 4K×2K panels.

Table. 4K×2K Ultra High Definition LCD TV Panel Development. Source: DisplaySearch China Smart TV & Smart Display Conference.

Maker

Size

Native
Resolution

Panel
Technology

3D

3D Technology

MP (Estimate)

AUO

65”

3840×2160

Oxide TFT

Yes

Lenticular lens

Q2’12
(LGD, Vizio)

55”

3840×2160

A-Si TFT

Yes

Lenticular lens (naked eye)

Now
(Toshiba)

LG Display

84”

3840×2160

Oxide TFT

Yes

FPR (film pattern retarder)

Q1’12-
Q2’12

Samsung

70”

3840×2160

Oxide TFT

 

 

Q2’12

70”

3840×2160

Oxide TFT

Yes

240 Hz, Shutter glass

Q2’12

82”

3840×2160

 

 

 

 

Sharp

64”

4096×2160

 

 

 

EOL

60”

3840×2160

Oxide TFT,
Photo alignment

 

 

2012

Chimei
Innolux

56”

3840×2160

 

No

 

Now
(Medical)

50”

3840×2160

A-Si TFT

120 Hz

 

Q4’12

65”

3840×2160

A-Si TFT

120 Hz

 

Q4’12

AUO is currently the only panel maker that has commercialized a 4K×2K product. The product is a 55” 4K×2K LCD TV with glasses-free 3D and a powerful video driving engine (Toshiba’s REGZA), shown below.

Figure 1. Toshiba’s 55” 4K×2K LCD TV with AUO’s Panel. Source: Toshiba.

There’s also a face tracking feature, which should assist users who choose to video chat in high resolution. It’s said that LGE and Vizio are also interested in launching a 4K×2K LCD TV in the North America market later this year.

Sharp is focusing on 4K×2K and calling it Super Hi-Vision, as analyzed in the May 10, 2012 DisplaySearch Monitor article “Sharp’s Leading TV Panel Technologies.”

4K×2K Ecosystem

The biggest concern for 4K×2K remains the ecosystem. Currently the TV ecosystem relies on the bandwidth of broadcasting and transmission. For content providers, it will be harder to achieve UD as the cost of production, post-production, storage, and data transmission will be very high.

Content is also an issue for 4K×2K TVs. At the DisplaySearch China Smart TV & Smart Display Conference, Chimei Innolux used a slide to illustrate the current 4K×2K ecosystem status (shown below).

Figure 2. 4K×2K Ecosystem status. Source: Chimei Innolux.
  • Camera: Commercial cameras are available, and some are already reaching 8K×4K. These professional cameras are very expensive, but some camera companies such as Sony or JVC plan to introduce a 4K×2K camera for general consumers.
  • Content: For content providers, the high cost of post-production is a concern. A 4K×2K program is estimated to cost 5-6 times more than HD.
  • Broadcasting: NHK and BBC plan to use 4K×2K or even 8K×4K broadcasting for the 2012 Olympics in London. This experiment will explore the challenges to the growth of 4K×2K broadcasting.
  • Coding/De-Coding Standard: H264 seems to be sufficient for 4K×2K. The new generation H265 will be ready by 2013. At the same time, enhancing compression will further reduce the bottleneck of 4K×2K signal transmission. Also, there are some up-scaling solutions to convert HD and FHD signals to 4K, such as QDEO.
  • BD Capacity: With the enormous amount of data for 4K×2K, storage and transmission are big challenges. For storage, dual-layer Blu-ray DVDs can provide 50 GB capacity, and some can even be 200 GB with current compression technology. DVD makers are studying how to increase compression ratio.
  • BD Player: Blu-ray disc players also need to support 4K×2K.
  • HDMI: The HDMI 1.4a standard supports 4K×2K, but HEVC (High Efficient Video Coding) will be better.
  • Bandwidth: ADSL and fiber have achieved 100 Mbps per second. However, it’s still time consuming to transmit 4K×2K data. For example, a 3-hour 4K×2K movie equals 3 terabytes of data, which requires 200 Blu-ray discs.

With all of these opportunities and challenges, the DisplaySearch Quarterly Global TV Shipment and Forecast Report is forecasting that 4K×2K TV will account for 22% of all 50”+ FPD TVs in 2017.

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