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--- screen_manufacturing [2026/05/29 17:53] – [4. Over coat layer] sophie
+++ screen_manufacturing [2026/05/29 19:06] (current) – [Transistor technology] 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).
 s
-## 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
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+------------
 ## LCD screen manufacturing
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 Light from the LEDs enters a Light Guide Plate (LGP) designed to distribute it evenly across the screen area. The LGP uses internal reflection and surface patterns to direct light forward[( 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]])]. Multiple optical films, including diffuser sheets and prism films, are stacked on top of the LGP. Diffusers scatter the light to hide LGP patterns, while prism films collimate the light toward the viewer to enhance brightness. A reflector film is placed underneath the LGP to recycle escaping light. These components are securely held within a plastic module frame.
-#### Frame Assembly
-The completed LCD panel and backlight unit are integrated into a protective frame assembly. A plastic frame maintains the alignment of the optical films and the light guide. A metal bezel is then attached to provide structural strength and house the control electronics. Screws, adhesives, and clips are used to permanently join the module components. This housing protects the sensitive panel and circuits from external moisture and mechanical impacts[( 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]])]. Once assembled, the display is a complete module ready for final quality assurance.
-#### Final Testing
-The assembled module undergoes electrical and visual inspections before being shipped. Automated Optical Inspection (AOI) identifies dot pixel defects, line faults, and luminance non-uniformity. "Aging" is a common step where modules are operated in a high-temperature environment to ensure early-stage reliability[( 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]])]. Functional patterns (White, Black, Red, Green, Blue) are displayed to verify chromaticity and switching response. Modules with cosmetic flaws, such as scratches or cracks, are identified and sorted for repair or scrap. Only modules that pass all performance and safety standards are packaged for final shipment.
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 {{ :capture_d_ecran_2026-04-16_160810.png?direct&400 |}}
 ### 5. pixel fabrication
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 The cathode is mostly made of Al or Ag [(OLED_fundamentals > [[https://ia801606.us.archive.org/35/items/ebooks_201907/Daniel%20J.%20Gaspar%2C%20Evgueni%20Polikarpov%20-%20OLED%20Fundamentals_%20Materials%2C%20Devices%2C%20and%20Processing%20of%20Organic%20Light-Emitting%20Diodes-CRC%20Press%20%282015%29.pdf | Daniel J. Gaspar, Evgueni Polikarpov - OLED Fundamentals_ Materials, Devices, and Processing of Organic Light-Emitting Diodes-CRC Press (2015)]])] for bottom-emission (it needs to be reflective), and and Mg:Ag [(OLED_fundamentals)] for top-emission (semi-transparent).
-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
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 This method can be used for flexible screens.
 Sources : ([https://www.wiley.com/en-es/Flat+Panel+Display+Manufacturing-p-9781119161363|Flat Panel Display Manufacturing]
-)
-### 7. Assembly
+---------------
+## 7. Frame Assembly
+The completed panel unit is integrated into a protective frame assembly. A plastic frame maintains the alignment of the optical films and the light guide. A metal bezel is then attached to provide structural strength and house the control electronics. Screws, adhesives, and clips are used to permanently join the module components. This housing protects the sensitive panel and circuits from external moisture and mechanical impacts[( 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]])]. Once assembled, the display is a complete module ready for final quality assurance.
 ----
-### 8. Testings
+## 8. Testings
+The assembled module undergoes electrical and visual inspections before being shipped. Automated Optical Inspection (AOI) identifies dot pixel defects, line faults, and luminance non-uniformity. "Aging" is a common step where modules are operated in a high-temperature environment to ensure early-stage reliability[( 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]])]. Functional patterns (White, Black, Red, Green, Blue) are displayed to verify chromaticity and switching response. Modules with cosmetic flaws, such as scratches or cracks, are identified and sorted for repair or scrap. Only modules that pass all performance and safety standards are packaged for final shipment.
 ----
+## References