The “electronic paper” that does not hurt the eyes, what is the mystery and opportunity behind the electronic paper, can it replace the traditional LCD? How does e-paper produce color? Five development directions and thinking prospects of future electronic paper
What is electronic paper, and can it replace traditional LCD?
In this era of information explosion, people need to read books, documents and instant messages extensively every day, but the traditional liquid crystal display (LCD) is not suitable for long-term reading, which prompted the invention of electronic paper (ePaper).
The ideal electronic paper has the characteristics of light and easy to carry, low energy consumption, easy to curl, etc., and also has the characteristics of retaining images after turning off the power. The current electronic paper on the market is based on electrophoretic display. Charged dye particles can move above or below the electrophoretic display film and display color according to the direction and intensity of the applied electric field. In addition to being used in readers, mobile phones and wearable devices, e-paper can also be used in shelf labels in hypermarkets and instant message billboards in bus stations, taking into account energy saving and low-carbon goals.
What is electronic paper, and can it replace traditional LCD?
The ideal e-paper is light and easy to carry, low energy consumption, easy to curl and other characteristics, and these are the lack of LCD characteristics, so e-paper is expected to become one of the most important displays of the next generation.
In addition, because the electronic paper has the characteristics of being able to retain the image after the power is turned off, and it can display the image purely with dye through a reflective non-luminous way, which has the advantage of protecting the human eye, such as books, labels, posters, bulletin boards, etc., electronic paper can be used.
Over the past 50 years, various e-paper technologies have been proposed to achieve this goal, such as: quick responseliquid powder display, cholesteric liquid crystal display and other displays.
However, based on the system integration practice considerations such as the display quality of images, the design complexity of electronic drive system, and the stability of mass production, electrophoretic display (EPD) is still the mainstream at present.
Now the mainstream electronic paper products on the market, basically most of the electrophoretic material as the display medium, with thin film transistor substrate to form a display matrix panel. Because the electrophoretic material film itself is soft, if it can be combined with the soft TFT substrate, the soft e-paper can achieve the goal of free curling.
How does e-paper produce color?
The e-paper material of EPD is composed of charged dye particles suspended on a colored or transparent solution. Its basic principle is to move the charged particles to the top or bottom of the electrophoretic display film according to the direction and intensity of the applied electric field. In the steady state, electrophoresis displays no power consumption and has the power saving function of stopping the dye particles to maintain the image.
In order to achieve an even distribution of particles in the electrophoretic material, two main technologies have been developed: microcaps and microcups, which also have their own characteristics and corresponding and suitable applications.
Internal structure of microcup black-and-white electrophoretic display
In the case of a black-and-white microcup electrophoretic display (above), each microcup contains positively charged white titanium dioxide (TiO2) particles and a black fluid solution. The top of the microcup is a transparent soft substrate and the bottom is an electrode. When the electrode changes, the charged particles will move up or down according to the positive or negative of the electrode, making the pixel display white particles or black solution. Then, it is combined with a colloid with a high viscosity coefficient, so that the dye particles are not easy to move in the medium, and the characteristics of the original display screen can be maintained when the power is off.
Structure diagram of microcup color electrophoresis display
As for colored electronic paper, the microcup is placed with more than two kinds of colored particles. Take the micro-cup color electrophoresis display as an example, put white (W), cyan (C), magenta (M), yellow (Y) four particles in the micro-cup, with white particles to form the upper reflective surface, when the display of blue will be pushed to the top of the panel, so that the white particles form a reflective surface, the light reflected by the two particles C and M becomes blue; The order M, Y, W, C, will show red.
By stacking a variety of colored particles, using the additive and subtractive characteristics of colored particles, different colors can be reflected. The colors that may be displayed include charged particles in white, black (K), red (R), green (G), blue (B), cyan, magenta, and yellow.
TFT Active matrix drive e-paper
The above displays are paired with the TFT active matrix-driven e-paper system architecture, in which the EPD film is attached to a flexible or rigid TFT backplane that provides the circuitry required for the electrodes. Since the typical driving voltage of the electrophoretic display is ±15 volts (V), the new generation of multi-particle color e-paper requires more different voltages, so the color e-paper is then converted to other different voltages through power circuits.
In addition, the flash memory in the system is used to store the drive waveform mapping table and image, which will be loaded into random access memory (RAM) when the system is turned on. And through the display controller (display controller) simultaneously access the control table and image to generate the control signal of the driver chip, and send the signal to the driver chip (driver chip) to display the image.
Five development directions and thinking prospects of future electronic paper
The technology of black and white electronic paper has been very mature, and the recent development of electronic paper technology can be explained from the core technical side and the application technical side. The core technology development direction of electronic paper includes the following five items:
Soft color electronic paper
Commercially available matrix electronic paper must be equipped with TFT array backplane, and mature TFT backplane mostly uses glass substrate. If it can be paired with a soft TFT backplane, the goal of soft e-paper can be achieved. There are already experimental products on the market, and the reliability and electrical characteristics of the soft backplane will continue to be improved in the future.
Image processing system of color electronic paper and corresponding chip design
The driving method and color performance of multi-particle color electronic paper are completely different from the old color electronic paper. For example, each pixel of old color electronic paper can only be selected in a limited number of colors, and it is not easy to have multi-color level performance, so it is completely different in the topic of color processing; The image processing algorithm and chip design of the new generation of multi-particle color e-paper still need to be continuously studied by academia and industry.
A new generation of video playback chip design
When electronic paper is used in the context of reading documents, it can already have a good user experience, but now many new types of reading materials are also paired with movies or animations, so the function of electronic paper to play movies is becoming increasingly important. Over the past few years, with real-time video processing technology, black and white electronic paper has been able to bring users a very good video playback experience. However, due to the different display principles of the next generation of color electronic paper, image updating, color conversion, and driving methods are also different, so it is still necessary to continue to improve its computing efficiency.
Design of front light control algorithm for color electronic paper
In order to further increase the color performance of colored e-paper, a new generation of colored e-paper panels has added red, green, blue, and white four-color front light sources to assist. However, the influence of the front light on the panel color is comprehensive, select the current ratio of the four colors in the front light module for the input screen, and allow the panel pixels to adjust the selection of the front light to a certain extent, and finally improve the overall color performance of the screen.
Although this issue is similar to the backlight control of LCD, the extended issue of the next generation of multi-particle color electronic paper with different colors of the front light is still to be discussed, and the technology of real-time color processing chips needs to be developed.
Next generation electronic paper driver chip design
In the multi-particle color e-paper driver mode, each output stage requires multiple possible output voltages, which will result in a multi-voltage selector for each output stage circuit in the driver chip. However, the more voltages available, the more complex the chip will be, so the drive system and the corresponding chip suitable for the next generation of multi-particle color e-paper are still under continuous development.
The development direction of application technology can include the following three technologies:
Design of man-machine interface control chip for color electronic paper
When general users read paper documents, they often use a pen on the document to add reading experience and emphasis, so e-paper has also developed a handwriting prediction algorithm suitable for black and white e-paper. By improving the algorithm architecture, the human-machine interface control chip can be applied to the next generation of color e-paper systems, and then the probability statistical model can be modified to accurately predict the future handwriting may appear, and the e-paper panel can be driven in advance to further reduce the handwriting delay, and develop an accelerated design chip.
Non-power electronic paper with near field communication
near field communication (NFC) allows contactless point-to-point data transmission between electronic devices, as well as short range and high frequency wireless communication. Its operating principle is to use the sensor to emit radio waves, touch a certain range of induction coils, and then generate current through electromagnetic induction, supply the chip to operate and emit electromagnetic wave response sensors.
If the driving energy source is different, it can be divided into active and passive ⸺ the active electronic paper system has a built-in battery, which can actively transmit signals for the sensor to read; The passive device itself has no battery, and the required current is generated by the radio wave electromagnetic induction of the sensor, so it will only respond passively to the sensor when it receives the signal sent by the sensor. By integrating this technology with the basic characteristics of the power supply needed to change the display content using e-paper, a power-free e-paper system can be developed.
New types of electronic paper applications
In addition to being used in readers, mobile phones, and other wearable devices, e-paper has also been widely used in shelf labels in hypermarkets. The real-time information and prices displayed on these price tags can be updated in real time through wireless communication technology, reducing the burden of manpower requirements. On the other hand, electronic paper is very suitable for use in the bus station instant message billboards, especially in many remote areas of the wiring project is very difficult, if you can by electronic paper extreme power-saving characteristics, combined with solar energy storage system and wireless communication system, you can be directly installed, directly used.
In addition, electronic paper has been successfully used in luggage boarding bar codes, instant password for credit cards and other applications. In the future, the application level can be extended to all kinds of advertising signs again, so that the content displayed on the sign is more diversified and rich, and it will not waste energy. It can even be combined with artificial intelligence (AI) systems to apply electronic paper to areas such as smart homes and smart cities, so that the display of instant messages can be everywhere, and also take into account energy saving goals.
The invention of electronic paper is not to completely replace the existing display, its basic goal is to provide human enjoyment of reading vehicles, used to replace printers and paper. If people gradually change their reading habits from paper to electronic paper, we will have the opportunity to create a paperless world and achieve the goal of energy saving, carbon reduction and sustainable planet.
The “electronic paper” that does not hurt the eyes, behind the mystery and opportunity
The “electronic paper” that does not hurt the eyes, what is the mystery and opportunity behind the electronic paper, can it replace the traditional LCD? How does e-paper produce color? Five development directions and thinking prospects of future electronic paper
What is electronic paper, and can it replace traditional LCD?
In this era of information explosion, people need to read books, documents and instant messages extensively every day, but the traditional liquid crystal display (LCD) is not suitable for long-term reading, which prompted the invention of electronic paper (ePaper).
The ideal electronic paper has the characteristics of light and easy to carry, low energy consumption, easy to curl, etc., and also has the characteristics of retaining images after turning off the power.
The current electronic paper on the market is based on electrophoretic display. Charged dye particles can move above or below the electrophoretic display film and display color according to the direction and intensity of the applied electric field.
In addition to being used in readers, mobile phones and wearable devices, e-paper can also be used in shelf labels in hypermarkets and instant message billboards in bus stations, taking into account energy saving and low-carbon goals.
What is electronic paper, and can it replace traditional LCD?
The ideal e-paper is light and easy to carry, low energy consumption, easy to curl and other characteristics, and these are the lack of LCD characteristics, so e-paper is expected to become one of the most important displays of the next generation.
In addition, because the electronic paper has the characteristics of being able to retain the image after the power is turned off, and it can display the image purely with dye through a reflective non-luminous way, which has the advantage of protecting the human eye, such as books, labels, posters, bulletin boards, etc., electronic paper can be used.
Over the past 50 years, various e-paper technologies have been proposed to achieve this goal, such as: quick responseliquid powder display, cholesteric liquid crystal display and other displays.
However, based on the system integration practice considerations such as the display quality of images, the design complexity of electronic drive system, and the stability of mass production, electrophoretic display (EPD) is still the mainstream at present.
Now the mainstream electronic paper products on the market, basically most of the electrophoretic material as the display medium, with thin film transistor substrate to form a display matrix panel. Because the electrophoretic material film itself is soft, if it can be combined with the soft TFT substrate, the soft e-paper can achieve the goal of free curling.
How does e-paper produce color?
The e-paper material of EPD is composed of charged dye particles suspended on a colored or transparent solution. Its basic principle is to move the charged particles to the top or bottom of the electrophoretic display film according to the direction and intensity of the applied electric field. In the steady state, electrophoresis displays no power consumption and has the power saving function of stopping the dye particles to maintain the image.
In order to achieve an even distribution of particles in the electrophoretic material, two main technologies have been developed: microcaps and microcups, which also have their own characteristics and corresponding and suitable applications.
Internal structure of microcup black-and-white electrophoretic display
In the case of a black-and-white microcup electrophoretic display (above), each microcup contains positively charged white titanium dioxide (TiO2) particles and a black fluid solution. The top of the microcup is a transparent soft substrate and the bottom is an electrode. When the electrode changes, the charged particles will move up or down according to the positive or negative of the electrode, making the pixel display white particles or black solution. Then, it is combined with a colloid with a high viscosity coefficient, so that the dye particles are not easy to move in the medium, and the characteristics of the original display screen can be maintained when the power is off.
Structure diagram of microcup color electrophoresis display
As for colored electronic paper, the microcup is placed with more than two kinds of colored particles. Take the micro-cup color electrophoresis display as an example, put white (W), cyan (C), magenta (M), yellow (Y) four particles in the micro-cup, with white particles to form the upper reflective surface, when the display of blue will be pushed to the top of the panel, so that the white particles form a reflective surface, the light reflected by the two particles C and M becomes blue; The order M, Y, W, C, will show red.
By stacking a variety of colored particles, using the additive and subtractive characteristics of colored particles, different colors can be reflected. The colors that may be displayed include charged particles in white, black (K), red (R), green (G), blue (B), cyan, magenta, and yellow.
TFT Active matrix drive e-paper
The above displays are paired with the TFT active matrix-driven e-paper system architecture, in which the EPD film is attached to a flexible or rigid TFT backplane that provides the circuitry required for the electrodes. Since the typical driving voltage of the electrophoretic display is ±15 volts (V), the new generation of multi-particle color e-paper requires more different voltages, so the color e-paper is then converted to other different voltages through power circuits.
In addition, the flash memory in the system is used to store the drive waveform mapping table and image, which will be loaded into random access memory (RAM) when the system is turned on. And through the display controller (display controller) simultaneously access the control table and image to generate the control signal of the driver chip, and send the signal to the driver chip (driver chip) to display the image.
Five development directions and thinking prospects of future electronic paper
The technology of black and white electronic paper has been very mature, and the recent development of electronic paper technology can be explained from the core technical side and the application technical side. The core technology development direction of electronic paper includes the following five items:
Commercially available matrix electronic paper must be equipped with TFT array backplane, and mature TFT backplane mostly uses glass substrate. If it can be paired with a soft TFT backplane, the goal of soft e-paper can be achieved. There are already experimental products on the market, and the reliability and electrical characteristics of the soft backplane will continue to be improved in the future.
The driving method and color performance of multi-particle color electronic paper are completely different from the old color electronic paper. For example, each pixel of old color electronic paper can only be selected in a limited number of colors, and it is not easy to have multi-color level performance, so it is completely different in the topic of color processing; The image processing algorithm and chip design of the new generation of multi-particle color e-paper still need to be continuously studied by academia and industry.
When electronic paper is used in the context of reading documents, it can already have a good user experience, but now many new types of reading materials are also paired with movies or animations, so the function of electronic paper to play movies is becoming increasingly important. Over the past few years, with real-time video processing technology, black and white electronic paper has been able to bring users a very good video playback experience. However, due to the different display principles of the next generation of color electronic paper, image updating, color conversion, and driving methods are also different, so it is still necessary to continue to improve its computing efficiency.
In order to further increase the color performance of colored e-paper, a new generation of colored e-paper panels has added red, green, blue, and white four-color front light sources to assist. However, the influence of the front light on the panel color is comprehensive, select the current ratio of the four colors in the front light module for the input screen, and allow the panel pixels to adjust the selection of the front light to a certain extent, and finally improve the overall color performance of the screen.
Although this issue is similar to the backlight control of LCD, the extended issue of the next generation of multi-particle color electronic paper with different colors of the front light is still to be discussed, and the technology of real-time color processing chips needs to be developed.
In the multi-particle color e-paper driver mode, each output stage requires multiple possible output voltages, which will result in a multi-voltage selector for each output stage circuit in the driver chip. However, the more voltages available, the more complex the chip will be, so the drive system and the corresponding chip suitable for the next generation of multi-particle color e-paper are still under continuous development.
The development direction of application technology can include the following three technologies:
When general users read paper documents, they often use a pen on the document to add reading experience and emphasis, so e-paper has also developed a handwriting prediction algorithm suitable for black and white e-paper. By improving the algorithm architecture, the human-machine interface control chip can be applied to the next generation of color e-paper systems, and then the probability statistical model can be modified to accurately predict the future handwriting may appear, and the e-paper panel can be driven in advance to further reduce the handwriting delay, and develop an accelerated design chip.
near field communication (NFC) allows contactless point-to-point data transmission between electronic devices, as well as short range and high frequency wireless communication. Its operating principle is to use the sensor to emit radio waves, touch a certain range of induction coils, and then generate current through electromagnetic induction, supply the chip to operate and emit electromagnetic wave response sensors.
If the driving energy source is different, it can be divided into active and passive ⸺ the active electronic paper system has a built-in battery, which can actively transmit signals for the sensor to read; The passive device itself has no battery, and the required current is generated by the radio wave electromagnetic induction of the sensor, so it will only respond passively to the sensor when it receives the signal sent by the sensor. By integrating this technology with the basic characteristics of the power supply needed to change the display content using e-paper, a power-free e-paper system can be developed.
In addition to being used in readers, mobile phones, and other wearable devices, e-paper has also been widely used in shelf labels in hypermarkets. The real-time information and prices displayed on these price tags can be updated in real time through wireless communication technology, reducing the burden of manpower requirements. On the other hand, electronic paper is very suitable for use in the bus station instant message billboards, especially in many remote areas of the wiring project is very difficult, if you can by electronic paper extreme power-saving characteristics, combined with solar energy storage system and wireless communication system, you can be directly installed, directly used.
In addition, electronic paper has been successfully used in luggage boarding bar codes, instant password for credit cards and other applications. In the future, the application level can be extended to all kinds of advertising signs again, so that the content displayed on the sign is more diversified and rich, and it will not waste energy. It can even be combined with artificial intelligence (AI) systems to apply electronic paper to areas such as smart homes and smart cities, so that the display of instant messages can be everywhere, and also take into account energy saving goals.
The invention of electronic paper is not to completely replace the existing display, its basic goal is to provide human enjoyment of reading vehicles, used to replace printers and paper. If people gradually change their reading habits from paper to electronic paper, we will have the opportunity to create a paperless world and achieve the goal of energy saving, carbon reduction and sustainable planet.