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screen_manufacturing [2026/05/29 18:01] – [7. Frame Assembly] sophiescreen_manufacturing [2026/06/01 01:17] (current) – [5. pixel fabrication] sophie
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 Once the glass substrates are ready, the next step depends on the kind of thin film transistor (TFT) backplane technology that is being employed. The TFT backplane is the electronic controller for the display and controls individual pixels within the display. There are several types of TFT backplanes such as amorphous silicon (a-Si), indium gallium zinc oxide (IGZO), low temperature polysilicon (LTPS), and low temperature polyoxide (LTPO). Once the glass substrates are ready, the next step depends on the kind of thin film transistor (TFT) backplane technology that is being employed. The TFT backplane is the electronic controller for the display and controls individual pixels within the display. There are several types of TFT backplanes such as amorphous silicon (a-Si), indium gallium zinc oxide (IGZO), low temperature polysilicon (LTPS), and low temperature polyoxide (LTPO).
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-## Transistor technology 
  
-#### Amorphous silicon (a-Si) 
  
-Amorphous silicon (a-Si) is the most mature and widely used backplane technology due to its straightforward manufacturing and scalability to massive substrate sizes. It involves depositing an unorganized silicon film via plasma-enhanced chemical vapor deposition (PECVD), which is highly cost-effective. While it is excellent for general applications, a-Si has low electron mobility (around 0.5 to 1.0 cm²/Vs), limiting its use in ultra-high-resolution or high-refresh-rate displays [( Flay_Panel_Display_Manufacturing>[[https://www.wiley.com/en-es/Flat+Panel+Display+Manufacturing-p-9781119161363|Flat Panel Display Manufacturing, Jun Souk, Shinji Morozumi, Fang-Chen Luo, Ion Bita, 2018]]). Additionally, it lacks the bias stability required for current-driven devices like OLEDs. Despite these limitations, a-Si remains the benchmark for mainstream TVs, budget notebooks, and desktop monitors. Recent efforts have focused on reducing mask counts (to 4 or 5) to further lower production costs  
-[( Flay_Panel_Display_Manufacturing>[[https://www.wiley.com/en-es/Flat+Panel+Display+Manufacturing-p-9781119161363|Flat Panel Display Manufacturing, Jun Souk, Shinji Morozumi, Fang-Chen Luo, Ion Bita, 2018]])]. 
  
-#### Indium-galium-zinc oxide (IGZO) +--- 
- +-
-IGZO, being a metal oxide semiconductor, represents a major leap in performance over a-Si. It offers 10 to 20 times higher mobility [(Flay_Panel_Display_Manufacturing>[[https://www.wiley.com/en-es/Flat+Panel+Display+Manufacturing-p-9781119161363|Flat Panel Display Manufacturing, Jun Souk, Shinji Morozumi, Fang-Chen Luo, Ion Bita, 2018]])], enabling smaller transistors that increase pixel aperture ratios and allow for higher resolutions. One of IGZO's most unique properties is its extremely low off-state leakage current, which permits low-refresh-rate driving (as low as 1Hz) to save power during static images [([[https://www.tandfonline.com/doi/full/10.1080/15980316.2023.2281224|Recent progress in liquid crystal devices and materials of TFT-LCDs]], Jung, Junho, et al. Journal of Information Display 25.1 (2024): 121-142)]. It is highly compatible with existing a-Si manufacturing lines, making it a scalable solution for large 8K TVs and high-end monitors. While it is more sensitive to moisture and oxygen, leading to the need for advanced passivation layers [([[https://www.tandfonline.com/doi/full/10.1080/15980316.2020.1818641|Recent progress in the development of backplane thin film transistors for information displays]], Ji, Dongseob, et al. Journal of Information Display 22.1 (2021): 1-11)], it is currently a leading backplane for both LCDs and large OLED TVs. +
- +
- +
-#### Low-temperature polycrystalline silicon (LTPS) +
- +
-Low-temperature polycrystalline silicon (LTPS) is a high-performance backplane technology mainly used in premium smartphones and mobile devices. It is produced by using excimer laser annealing (ELA) to transform amorphous silicon into a highly organized crystalline structure. This results in very high electron mobility (often >100 cm²/Vs), allowing for much smaller transistors and the integration of complex circuits directly on the glass [( Flay_Panel_Display_Manufacturing>[[https://www.wiley.com/en-es/Flat+Panel+Display+Manufacturing-p-9781119161363|Flat Panel Display Manufacturing, Jun Souk, Shinji Morozumi, Fang-Chen Luo, Ion Bita, 2018]])]. This technology, called system on glass (SOG), helps manufacturers create ultra-thin bezels in modern smartphones. However, the laser process is expensive, complex, and difficult to scale to large TV-sized substrates with uniform quality [( Flay_Panel_Display_Manufacturing>[[https://www.wiley.com/en-es/Flat+Panel+Display+Manufacturing-p-9781119161363|Flat Panel Display Manufacturing, Jun Souk, Shinji Morozumi, Fang-Chen Luo, Ion Bita, 2018]])]. +
- +
- +
-#### Low-temperature polycrystalline oxide (LTPO) +
- +
-Low-temperature polycrystalline oxide (LTPO) is an advanced hybrid backplane technology that combines LTPS and oxide TFT technologies on the same substrate. LTPS transistors handle fast switching and processing tasks, while oxide transistors are used for pixel driving because they consume very little power. This combination allows displays to adjust refresh rates dynamically, switching from very high refresh rates for gaming to extremely low refresh rates, such as 1 Hz, for power saving [([[https://www.tandfonline.com/doi/full/10.1080/15980316.2020.1818641|Recent progress in the development of backplane thin film transistors for information displays]], Ji, Dongseob, et al. Journal of Information Display 22.1 (2021): 1-11)]. As a result, LTPO displays can significantly improve battery life. The manufacturing process is more complicated and expensive because it requires more photolithography steps and precise temperature control [([[https://www.tandfonline.com/doi/full/10.1080/15980316.2020.1818641|Recent progress in the development of backplane thin film transistors for information displays]], Ji, Dongseob, et al. Journal of Information Display 22.1 (2021): 1-11)]. Currently, LTPO is used in flagship smartphones and smartwatches, where energy efficiency and display performance are especially important. +
- +
-### Manufacturers +
- +
-- Samsung Display and LG Display are the dominant global producers of LTPS backplanes for high-resolution mobile devices and flexible OLEDs +
-- Sharp Corporation is famous for the commercialization of IGZO (Oxide TFTs), applying it to their high-resolution LCDs and specialized handheld panels +
-- BOE Technology Group mass-produces large panels using both Oxide TFTs for 8K televisions and LTPS for advanced mobile applications +
-- AU Optronics (AUO) has established production lines for both technologies to compete in premium monitor and notebook segments +
-- Sony and Panasonic have historically developed Oxide backplanes for large OLED TV prototypes and high-transmittance IPS monitors +
-- For LTPO technology, Samsung and LG are currently the primary suppliers for high-end consumer electronics manufacturers +
- +
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 ## 0. Glass substrate fabrication ## 0. Glass substrate fabrication
  
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 ## LCD screen manufacturing ## LCD screen manufacturing
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 #### anode fabrication #### anode fabrication
  
 +The anode is formed on the substrate and the pixel control circuit. In the case of bottom-emission, the anode must be transparent to allow light to pass through it. Conversely, if the OLED is configured for top-emission, the anode must be reflective. The light passes through the cathode, and the reflective properties of the anode serve primarily to increase the light output efficiency. {{ref>anodefab}} illustrates the deposition of the anode (coloured in yellow) onto a TFT substrate of a white OLED. 
 +
 +<figure center|anodefab>
 {{ :capture_d_ecran_2026-04-16_160913.png?direct&400 |}} {{ :capture_d_ecran_2026-04-16_160913.png?direct&400 |}}
 +<caption> anode fabrication one the substrate </caption>
 +</figure>
  
 #### bank fabrication #### bank fabrication
 +
 An organic insulator film is used to set apart different colors with a blank layer, and to prevent short circuit between the electrodes. The organic insulator film should be selected among those materials that would not absorb moisture and that show minimum outgassing [([[https://doi.org/10.1002/j.2168-0159.2012.tb06108.x|Transmissive Low Outgassing Organic Insulator Suitable for Various OLED Displays]], Hiroaki Shindo, Takashi Tsutsumi, Takaaki Sakurai, Masahiro Hanmura, Akira Honma, 2012)].  An organic insulator film is used to set apart different colors with a blank layer, and to prevent short circuit between the electrodes. The organic insulator film should be selected among those materials that would not absorb moisture and that show minimum outgassing [([[https://doi.org/10.1002/j.2168-0159.2012.tb06108.x|Transmissive Low Outgassing Organic Insulator Suitable for Various OLED Displays]], Hiroaki Shindo, Takashi Tsutsumi, Takaaki Sakurai, Masahiro Hanmura, Akira Honma, 2012)]. 
  
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 The processes used for deposition of the cathode are either **vacuum thermal evaporation combined with an FMM** (Fine Metal Mask)[([[https://advanced.onlinelibrary.wiley.com/doi/epdf/10.1002/aelm.202500555|Vacuum Thermal Evaporation for OLEDs: Fundamentals, Optimization, and Implications for Perovskite LEDs]])] for small displays, or **vacuum thermal evaporation with open mask** for large displays. The processes used for deposition of the cathode are either **vacuum thermal evaporation combined with an FMM** (Fine Metal Mask)[([[https://advanced.onlinelibrary.wiley.com/doi/epdf/10.1002/aelm.202500555|Vacuum Thermal Evaporation for OLEDs: Fundamentals, Optimization, and Implications for Perovskite LEDs]])] for small displays, or **vacuum thermal evaporation with open mask** for large displays.
  
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 ### 6. Encapsulation ### 6. Encapsulation
  
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-cc+
  
 ## 7. Frame Assembly ## 7. Frame Assembly