KR100872157B1 - Electrophoretic display device and method for eliminating afterimage - Google Patents

Abstract

An electrophoretic display device and a method for eliminating an afterimage are provided to implement a natural image and remove the afterimage by suppressing sudden brightness change while reducing power consumption. A vertical data line defines a matrix type pixel by crossing a horizontal scan line. A switching element is mounted in each pixel on and off by a scan signal for a frame. A data signal of a data signal section for gradation of a display image is applied to an electronic ink cell. The data signal of an inverted data signal section for inverse gradation of a display image is applied to the electronic ink cell.

Description

Electrophoretic display device and method for eliminating afterimage}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophoretic display device, and more particularly, to an electrophoretic display device for displaying an image by electrophoresis caused by a data signal containing grayscale information of a display image for each frame, and its electrophoretic display device. It relates to an afterimage removal method.

In recent years, as the society enters the era of full-fledged informatization, the display field for processing and displaying a large amount of data has been rapidly developed. In response, various flat display devices having excellent characteristics such as thinning and lightening have been developed. (flat panel display device) is introduced to quickly replace the existing cathode ray tube display (CRT).

Representative examples of flat panel displays currently used include liquid crystal display devices (LCDs), plasma display panel devices (PDPs), field emission display devices (FEDs), and electroluminescent displays. Electro luminescence Display device (ELD) etc. are mentioned. However, since they all represent an emissive type that transmits and displays light generated from a separate light source, light emission or phosphor, it is pointed out that there is much room for improvement in terms of power consumption because of low bistableness and high power dependence. It is becoming.

As a result, the display image can be preserved for a long time even in the state of high bi-stability, that is, the voltage is removed, so the power consumption is extremely low, and it is a thin, light, and flexible reflective display device. Electrophoretic display devices called (Electronic Paper: E-papre) have attracted attention.

The electrophoretic display device has not been clearly defined yet, but it is a generic display device that realizes the unique characteristics of paper, which is thin, light, flexible, and not easily torn, and has excellent visibility in electronic products regardless of the viewing angle. According to the mechanism, particles, liquid crystals, fluids, and MEMS are classified as shown in Table 1 below.

TABLE 1

However, the electrophoretic display generally refers to a case of electrophoretic phenomena of charged particles, and the method is a twist ball method using a hemispherical twist ball charged with electrostatic charges again. And a microparticle system that uses electrophoresis of charged particles, and a microcapsule method that is similar to the microparticle method but encapsulates charged particles together with a predetermined fluid in a predetermined unit.

1 is a schematic diagram of a general microcapsule type electrophoretic display device.

As shown, the microcapsule type electrophoretic display device has a form in which the electron ink layer 30 is interposed between the first and second electrodes 10 and 20 facing in parallel.

In this case, under the premise that the electrophoretic display device is a front display type, the first electrode 10 on the front surface exposed to the user is made of a transparent electrode, and the electron ink layer 30 is a binder in which the electron ink capsules 40 are dispersed. (binder) shows the form of a film 32, at least one kind of fine particles are encapsulated in the electronic ink capsule 40 together with a predetermined fluid. For convenience, when the at least one kind of the fine particles is a positively charged white first fine particle 42 and a negatively charged black fine particle 44, the first and second electrodes 10, It is possible to freely express black, gray and white gradations by changing the distribution state of the first and second fine particles 42 and 44 according to the type and intensity of the voltage applied to 20).

On the other hand, a general electrophoretic display device is mainly used an active matrix type having a high contrast ratio and advantageous for displaying a video, and an electrophoretic panel for image display is essential. It is included in cattle.

In this case, a plurality of horizontal scan lines and vertical data lines intersect each other in the electrophoretic panel to define pixels in a matrix form, and each pixel includes scan and data lines. A switching element that is connected to and turned on / off by a scan signal of a scan line, and an electronic ink cell that is connected to the switching element one-to-one and selectively driven by a data signal of a data line This intervenes. The electron ink cell includes first and second electrodes (see 10 and 20 of FIG. 1) and an electron ink layer (see 30 of FIG. 1) interposed therebetween, and is scanned by scanning in a scan line. When the switching element selected for each scan line is turned on by the voltage, the data signal of the data line is applied to the electronic ink cell connected to the switching element, and the gray level change appears through the electrophoresis of the electronic ink cell. The image is displayed.

In other words, a general electrophoretic display device displays an image using a scan signal containing on / off information of switching elements of each scan line and a data signal containing grayscale information of a desired display image, and the scan signal is 1 on the scan line. Images are displayed in units of frames input.

As a result, if the charges charged in the electron ink cells for the display image of the previous frame are not sufficiently discharged, an image sticking or afterimage appears on the display image of the frame. That is, a general electrophoretic display device displays an image by electrophoretic phenomenon of an electronic ink cell by a data signal containing gray scale information for a frame-by-frame display image. Therefore, when the fine particles previously aligned by the data signal for the display image of the previous frame cannot be rearranged quickly by the data signal for the display image of the frame, an afterimage in which the previous frame image is superimposed on the frame image appears. This is directly related to serious image quality deterioration.

Accordingly, at present, a method of inserting a black or white reset screen over the entire surface of the electrophoretic panel by applying a separate reset signal between display images for each frame of the electrophoretic display device is mainly performed. Although used, this is a method of resetting all pixels irrespective of the display image of the frame to be displayed, and the sudden change in luminance due to the black or white reset screen as well as additional power wastage for the reset signal. It causes user fatigue and discomfort, and afterimage removal effect is also insufficient.

Accordingly, an object of the present invention is to solve the above disadvantages, and to provide a concrete method for more effectively removing an afterimage of an electrophoretic display device. Specifically, an object of the present invention is to provide an electrophoretic display device and an afterimage removal method thereof capable of effectively eliminating an afterimage while embodying a natural image by suppressing a sudden change in brightness while preventing additional power wastage.

In order to achieve the above object, the present invention provides an electrophoretic display device for displaying an image by electrophoresis by a data signal containing grayscale information of a display image for each frame, wherein the data signals for each frame are respectively displayed in the display image. The present invention provides an electrophoretic display device including a data signal section including gradation information and an inversion data signal section including inversion gradation information for the inversion gradation image of the display image.

The present invention also provides an electrophoretic display for displaying an image in a frame-by-frame display image, comprising: a horizontal scan line and a vertical data line defining pixels in a matrix form intersecting with the horizontal scan line; A switching element mounted on each pixel and turned on / off by the scan signal for each frame; An electronic ink cell connected to the switching element in a one-to-one correspondence and mounted on each pixel and expressing a gray level through electrophoresis by the data signal for each frame; A scan driver connected to the scan line and scanning the scan signal for each frame to the scan line; The data signal for each frame including the data line connected to the data line, the data signal section including the grayscale information of the display image, and the at least one inverted data signal section including the inverted grayscale information for the inverted grayscale image of the display image; An electrophoretic display device including a data driver applied to a data line is provided.

In this case, the inversion data signal section is characterized by polarity inversion of the data signal section, wherein the data signal section, the first data signal section before the inversion data signal section and the second after the inversion data signal section The data signal for each frame is divided into a data signal section, wherein the first data signal section, the inverted data signal section, and the second data signal section appear in this order. When the duration of the data signal section is T1, the duration of the inverted data signal section is T2, and the duration of the second data signal section is T3, the relationship T1, T2 < T3 is shown. In particular, the T1, T2 is characterized in that each of the response time of the electronic ink cell more than zero.

In addition, the present invention is an afterimage removal method of an electrophoretic display device for displaying a display image for each frame by changing the gray level caused by the electrophoresis of the electrophoretic cell, wherein each frame is (a) the display image on the electronic ink cell Applying a data signal of a data signal section for gradation of the display signal; and (b) applying a data signal of an inversion data signal section for inverting gradation of the display image to the electronic ink cell at least once. Provides a method for removing afterimages of a display device.

In this frame, step (a) is performed for T1 time, step (b) is for T2 time, step (a) is for T3 time in each frame, and T1, T2, and T3 are T1, T2 < It is characterized in that the relationship between the T3, T1, T2 is characterized in that each of the response time of the electronic ink cell more than zero.

As described above, the present invention removes afterimages by using a data signal for a display image of the frame, thereby eliminating a reset screen by a separate reset signal and at the same time removing the afterimage relatively simply and efficiently. This can prevent additional power consumption and sudden brightness changes.

Particularly, the present invention removes an afterimage by using a data signal section including at least one data signal section including grayscale information for a display image of the frame and an inverted data signal section including inversion grayscale information of the display image. While the display image of the unit is smoothly switched, the image after which the afterimage is completely removed can be displayed.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a schematic plan view of the electrophoretic display device according to the present invention, and is supplied to the electrophoretic panel 50 by processing an electrophoretic panel 50 in which a direct image is displayed, and processing various signals necessary for displaying the image thereof. The driving circuit unit 60 is included.

First, in the electrophoretic panel 50, a plurality of horizontal scan lines 52 and vertical data lines 54 intersect to define a pixel P in a matrix form, and scan and data are defined in each pixel P. FIG. A switching device (not shown) connected to the lines 52 and 54, and an electronic ink cell 56 connected to the switching device and a one-to-one correspondence are mounted.

In this case, a thin film transistor (TFT) may be used as the switching element. In this case, the gate electrode of the thin film transistor is in the scan line 52, the drain electrode is in the data line 54, and the source electrode is electron. Respectively connected to the ink cells 56. In addition, the electron ink cell 56 may have a form in which an electron ink layer is interposed between the first and second electrodes in parallel, and on the premise that the electrophoretic panel 50 is a front display type, a first front surface facing the user. The electrode is made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), and a common voltage is applied, while the second electrode has a high work function such as a transparent conductive material or aluminum (Al). It is made of a metal material and is connected to the source electrode of the thin film transistor. In addition, the electron ink layer may represent a film form of a binder in which the electron ink capsules are dispersed, and at least one kind of fine particles are encapsulated in the electronic ink capsule together with a predetermined fluid, and the fine particles are white fine particles having a positive charge. And negatively charged black fine particles (see FIG. 1).

Next, the driving circuit unit 60 generates an on / off control signal of the switching element and scans the scan line 52 to each scan line 52 and the display image of each frame. A data driver (64) for generating a data signal containing grayscale information and applying it to the data line 54, and processing a video signal transmitted from the outside to scan control signals and data for each frame scan signal and data signal. And an image controller 66 for generating a control signal.

At this time, although not separately shown in the drawing, the image controller 66 includes an interface for relaying an external video signal, an image and an input control signal in the video signal, for example, a vertical synchronizing signal (Vsync). ) And a signal control unit for generating a scan control signal and a data control signal based on a horizontal synchronizing signal (Hsync), a main clock (MCLK), a data enable signal (DE), and the like. A power supply voltage generator that generates a turn on / off and a turn off voltage and a common voltage of the switching element, and a gray voltage generator that generates a plurality of gray voltages associated with the grayscales of the display image for each frame. It may include.

Accordingly, the scan driver 62 sequentially enables the scan line 52 by one horizontal synchronizing time in each frame based on the scan control signal of the signal controller to turn on / off the switching elements of the scan lines 52. In addition, the data driver 64 selects a reference voltage for each frame in response to the data control signal of the signal controller to generate a data signal containing grayscale information of the display image, and to synchronize the timing with the scan signal for each scan line 52. Transfer to data line 54.

As a result, the electrophoretic panel 50 of the electrophoretic display device according to the present invention displays an image in a frame-by-frame display image, the display image of each frame control on / off of the selected switching signal for each scan line 52 It is implemented by a data signal containing a scan signal for and a gray scale information for gray scale implementation of a corresponding frame display image. When the data signal is applied to the electronic ink cell 56 of the selected pixel P, the gray scale according to the electrophoresis phenomenon A change is accompanied, and a display image in units of frames is displayed through the gradation combination of these pixels P. FIG.

In this case, the data signal for each frame of the electrophoretic display device according to the present invention includes a data signal section for implementing the gray scale of the frame display image, and a gray scale opposite to the display image of the frame, i.e., inverted data for gray scale implementation of the inverted image. The signal section is included at least once, thereby effectively eliminating afterimages that may appear in the display image of the frame due to the display image of the previous frame.

3 is a waveform diagram of a data signal applied to the electrophoretic panel 50 in an arbitrary frame such that a desired image is displayed from the electrophoretic display device according to the present invention. Referring to FIG. As shown in the data signal for the display image for each frame, data signal sections t1 and t3 containing the gray scale information for gray scale implementation of the frame display image, as well as inverted data for inverting the gray scale opposite to the frame display image. It can be seen that the signal section t2 is included at least once.

In this case, the data signal sections t1 and t3 are obtained through the data driver 64 including the signal controller and the gray voltage generator of the image controller 66 according to the general description, while the inverted data signal sections t2 are the data drivers. (64), or the like, or separately generate an inverted data signal opposite to the display image gradation of the frame through the gradation voltage generation unit of the image controller 66 based on the video signal or the polarity inversion of the data signal section. It can also be obtained by combining this with the data signal.

Further, the data signal sections t1 and t3 respectively distinguish the first data signal section t1 before the inversion data signal section t2 and the second data signal section t3 after the inversion data signal section t2. Meanwhile, the first data signal section t1, the inverted data signal section t2, and the second data signal section t3 may appear sequentially in the data signal for each frame. In particular, the first data signal section ( When the duration of t1) is T1, the duration of the inversion data call section is T2, and the duration of the second data signal section t3 is T2, it is preferable that the relationship T1, T2 &lt; T3 is shown. In addition, as long as the above relationship is satisfied, T1 may be T2, and T1 and T2 may be appropriately selected from the response rate level of zero or more particles.

For reference, the response time of the fine particles under the premise that the data signal voltage level (Vt to -Vt) of the electrophoretic display device is -15V to 15V is expressed by Equation 1 below.

<Equation 1> τ to d2 / μV

(d: diameter (moving distance) of microcapsules, μ: electrophoretic mobility of particles, V: applied voltage)

Therefore, when the approximate value is substituted into Equation 1, τ is about 150 to 200 ms, which means the minimum time for the electrophoresis of the fine particles. Each frame display image of the electrophoretic display device according to the present invention is The first data signal section t1 and the inverted signal data section t2 may be appropriately included in the data signal for the range of 0 to 200 ms, respectively. If the voltage level of the data signal section is within the range of -15V to 15V, the voltage level of the inverted data signal section t2 is within the range of 15 to 15V according to the assumptions above, and the second and second data signal sections t1 and t3. It may be appropriately selected to indicate a value different from.

On the other hand, Figure 4 is a flow chart showing the display image of the frame unit displayed through the electrophoretic panel 50 according to the present invention, referring to FIG. 2 and 3 above, the electrophoretic panel 50 according to the present invention A first gradation image corresponding to the gradation of the frame display image for each frame, an inverted gradation image opposite to the gradation of the frame display image, and a second gradation image corresponding to the gradation of the frame display image in the same manner as the first gradation image Although two gradation images are displayed sequentially, the user recognizes the target display image as the first and second gradation images, and more as the second gradation image according to the relationship of T1, T2 &lt; T3.

More specifically, Figure 5 is a waveform diagram of the scan signal (SS1, SS2, SS3 ... SSn) and the data signal (DS) for displaying an arbitrary frame display image through the electrophoretic display device according to the present invention 2 to 4, the electrophoretic display device according to the present invention synchronizes the data signal DS in synchronization with the scan signals SS1, SS2, SS3... ) Are input to the data signal DS, and a first data signal section t1, an inverted data signal section t2, and a second data signal section t3 are sequentially displayed in the data signal DS.

Accordingly, the display image actually displayed on the electrophoretic panel 50 is the same as that of FIG. 6, and on the assumption that the display image to be displayed on the frame is displayed on the white background with a black "T", the previous frame A black " T " of white color is displayed on the electrophoretic panel 50 at the same time as the display image T by the first data signal section t1, as desired, from the display image to the frame display image. Then, a white "T" of black color is displayed as the inverted gradation image Tc by the inversion data signal section t2, and then the same display image as the target as the display image by the second data signal section t3. The white background black "T", which is T), is displayed and remains until the end of the corresponding frame.

At this time, since the first data signal section t1 and the inverted data signal section t2 are extremely short instants of less than the response time of the electrophoretic cell greater than 0, the user cannot recognize the actual screen change, but the first data signal section t1 ) And the inversion data signal section t2, the particles of the electrophoretic cell 56 can be sufficiently rearranged, and then the second data signal section t2 is used as a display image that the user can actually recognize. The displayed image is displayed so that the afterimage is effectively removed.

For reference, FIG. 7 is a photograph showing a part of the screen displayed through the actual electrophoretic panel according to the afterimage removing method of the present invention. Although an afterimage may appear, a display image from which the afterimage has been completely removed is displayed from the display screen by the second data signal section.

1 is a schematic cross-sectional view of a general electrophoretic display device.

2 is a schematic plan view of an electrophoretic display device according to the present invention;

3 is a waveform diagram of a data signal of an electrophoretic display device according to the present invention;

Figure 4 is a flow chart for the afterimage removal method of the electrophoretic display device according to the present invention.

5 is a scan and data signal waveform diagram of the electrophoretic display device according to the present invention.

7 is a screen picture according to the afterimage removal method of the electrophoretic display device according to the present invention.

<Description of the symbols for the main parts of the drawings>

50: electrophoretic panel 52: scan line

54: data line 56: electronic ink cell

60: drive circuit 62: scan driver

64: data driver 66: image control unit

P: Pixel

Claims (9)

delete delete delete delete An electrophoretic display device displaying an image in a frame-by-frame display image, A horizontal scan line and a vertical data line crossing the horizontal scan line and defining a pixel in a matrix form; A switching element mounted on each pixel and turned on / off by the scan signal for each frame; An electronic ink cell connected to the switching element in a one-to-one correspondence and mounted on each pixel and expressing a gray level through electrophoresis by the data signal for each frame; A scan driver connected to the scan line and scanning the scan signal for each frame to the scan line; The data signal for each frame including the data line connected to the data line, the data signal section including the grayscale information of the display image, and the at least one inverted data signal section including the inverted grayscale information for the inverted grayscale image of the display image; A data driver applied to the data line, The inversion data signal section is a polarity inversion of the data signal section. The data signal section is divided into a first data signal section before the inversion data signal section and a second data signal section after the inversion data signal section. The data signal for each frame is divided into the first data signal section and the inversion. A data signal section and the second data signal section appear in sequence; The data signal for each frame includes T1, T2 &lt; T3 when the duration of the first data signal section is T1, the duration of the inverted data signal section is T2, and the duration of the second data signal section is T3. Electrophoretic display showing relationship. The method of claim 5, And T1 and T2 are each equal to or greater than 0 and less than or equal to the response time of the electronic ink cell. delete As an afterimage removing method of an electrophoretic display device displaying a display image for each frame by changing the gradation caused by the electrophoresis of an electronic ink cell, Each frame includes (a) applying a data signal of a data signal section for gradation of the display image to the electronic ink cell, and (b) inverted data for inverting gradation of the display image to the electronic ink cell. At least one step of applying a data signal of the signal section, In each frame, step (a) is performed for T1 time, step (b) is performed for T2 time, step (a) is performed for T3 time, and T1, T2, and T3 are T1, T2 &lt; Method of removing afterimage of electrophoretic display device showing relationship. The method of claim 8, And T1 and T2 are each equal to or greater than zero and equal to or less than a response time of the electronic ink cell.

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