JP5509953B2 - Display device - Google Patents

Description

  The present invention relates to a display device.

  In recent years, with the increase in the operating speed of personal computers, the spread of network infrastructure, the increase in capacity and price of data storage, information such as documents and images provided on printed paper on paper has become easier to use electronic information. The opportunity to obtain and browse the electronic information is increasing more and more.

  In order to browse such electronic information, conventional liquid crystal displays and CRTs, and in recent years, light-emitting displays such as organic EL displays are mainly used. However, especially when the electronic information is document information, it is necessary to keep an eye on the document information for a relatively long time. As a disadvantage of a general light-emitting display, eyes flicker due to flickering, inconvenient to carry, and reading It is known that the posture is limited and the power consumption increases when reading for a long time.

  An electrochemical display method is known as a display method for solving these drawbacks, and as an example, an electrodeposition method (hereinafter abbreviated as ED method) using dissolution precipitation of a metal or a metal salt is known. Yes. (For example, refer to Patent Documents 1 and 2.)

  The ED display element can be driven at a low voltage of 3V or less, can be realized with a simple cell configuration, and has excellent display quality (bright paper-like white and firm black). Yes.

  When driving an electrochemical display element such as an ED system, a constant voltage equal to or higher than a threshold value is applied to both ends of the electrochemical display element for a certain period of time. The display state can be controlled by voltage or time.

  On the other hand, even in a display device using such an electrochemical display element, there are many requests for displaying a color image. However, when a color filter is provided in a reflective element such as an electrochemical display element, there is a problem that the reflectance of each pixel is lowered and the display screen becomes dark.

  As a method of colorizing without reducing the brightness as much as possible, a pixel of four colors is obtained by adding W (white) to the three primary colors of R (red), G (green), and B (blue). Is known (see, for example, Patent Document 3).

Japanese Patent No. 3428603 JP 2003-241227 A JP 2001-147666 A

  Display devices using these electrochemical display elements are often battery-driven, and power saving is an important issue in order to enable long-term use.

  However, when an image is displayed in units of four sub-pixels of RGBW as one pixel unit, the number of pixels to which a voltage is applied for image rewriting is significantly increased as compared with the case of monochrome display, so that the power consumption of the display device increases.

  The present invention has been made in view of the above problems, and an object thereof is to provide a display device capable of displaying a bright color image while suppressing power consumption.

  The object of the present invention can be achieved by the following constitution.

1. A plurality of display elements that display white, display elements that display red, display elements that display green, and display elements that display blue are arranged as one pixel unit, and power is supplied to each of the display elements. A display device capable of displaying a color image when applied,
When displaying an image by the one pixel unit from the first image data corresponding to the power applied to each display element when displaying an image by three display elements that display red, green, and blue, respectively A data conversion unit for converting into second image data corresponding to the power applied to the display element;
The data converter is
Based on the first image data, the data according to the power applied to the display element that displays white, and the sum of the display density of the display elements constituting the one pixel unit,
A predetermined value is subtracted from the first image data to obtain second image data of a display element that displays red, green, and blue, and a white display element is formed so as to be equal to the calculated sum of the display densities. A display device characterized in that data corresponding to applied power is calculated and used as second image data.

2. The data converter is
2. The display device according to 1 above, wherein the first image data of a display element that applies the least amount of power among display elements that display red, green, and blue is the predetermined value.

  3. 3. The display according to item 1 or 2, further comprising a table showing a relationship between the power applied to the display element and the display density of the display element for the display element that displays red, green, blue, and white. apparatus.

  4). 4. The display device according to any one of 1 to 3, wherein the display element is an electrochemical display element.

  The display device according to the present invention has white, red, green, and blue display elements as one pixel unit from the first image data corresponding to a case where an image is displayed by three display elements that display red, green, and blue. As a second image data corresponding to the case where an image is displayed.

  The data conversion unit calculates data corresponding to the power applied to the display element that displays white based on the first image data and the sum of the display densities by one pixel unit. A value obtained by subtracting a predetermined value from each of the first image data is used as second image data, and data corresponding to the power applied to the white display element is calculated so as to be equal to the calculated sum of display densities. Image data.

  Therefore, it is possible to provide a display device that can display a bright color image while suppressing power consumption.

It is a figure which shows the general view of the display apparatus 100 which concerns on embodiment of the display apparatus of this invention. 1 is a schematic cross-sectional view showing a basic configuration of an ED type electrochemical display element 1 used in a display device 100 in the present embodiment. 3 is a diagram for explaining a relationship between a time during which a writing voltage is applied to the electrochemical display element 1 and a display density D. FIG. It is a figure which shows the electrical constitution of the display apparatus 100 in this embodiment. It is a figure which shows the arrangement | sequence of the color filter of this embodiment. 3 is a time chart showing a change in voltage of each part when an image is displayed on the electrochemical display element 1. It is a graph which shows an example of the relationship between the display density of a color image and frame number N in this embodiment. 3 is a diagram for explaining an internal configuration of a control unit 11. FIG. It is a flowchart explaining the procedure of displaying the color image of this embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an external view showing an example of a display device according to an embodiment of the present invention.

  The display device 100 is, for example, a tablet PC, an electronic book, or a PDA, and displays data such as images and characters stored in the memory 10 (see FIG. 4) on the display screen 50. The display screen 50 uses an electrochemical display element 1 (see FIG. 2) which is a memory-type display element capable of gradation display. The operation unit 42 is provided with a forward button 43 and a reverse button 44 which are mechanical switches. For example, when the user presses the forward button 43, the data on the next page of the data displayed on the display screen 50 is read from the memory 10 and displayed. Similarly, when the user presses the reverse button 44, the data of the page before the data displayed on the display screen 50 is read from the memory 10 and displayed.

  FIG. 2 is a schematic cross-sectional view showing a basic configuration of an ED type electrochemical display element 1 used in the display device 100. 2A shows a state in which black is displayed by the electrochemical display element 1, and FIG. 2B shows a state in which white is displayed.

  The ED electrochemical display element 1 shown in FIG. 2 holds an electrolyte 31 between a transparent ITO (tin-doped indium oxide) electrode 32 and a silver electrode 30. A power source 34 is connected to the ITO electrode 32 and the silver electrode 30. The user observes the electrochemical display element 1 from the ITO electrode 32 side.

  As shown in FIG. 2A, when a negative voltage is applied to the ITO electrode 32 from the power source 34 to the silver electrode 30, a current flows in the direction of the arrow in the figure, and silver contained in the electrolyte 31 is deposited on the ITO electrode 32 side. A reaction occurs. Hereinafter, the negative voltage applied to the ITO electrode 32 is referred to as a write voltage.

  35 is precipitated silver, and the precipitated silver 35 absorbs light, so that the concentration of the electrochemical display element 1 viewed from the ITO electrode 32 side is increased. Reference numeral 36 schematically shows dissolved silver. On the silver electrode 30 side, a phenomenon occurs in which the precipitated silver is dissolved in the electrolyte 31.

  When a positive voltage is applied to the ITO electrode 32 from the power source 34 to the silver electrode 30 as shown in FIG. 2B, a current flows in the direction of the arrow in the figure, and silver dissolution reaction occurs on the ITO electrode 32 side. Hereinafter, the positive voltage applied to the ITO electrode 32 is referred to as an erasing voltage. In the state of FIG. 2A, silver deposited on the ITO electrode 32 side dissolves in the electrolyte 31, and when an erasing voltage is applied for a certain period of time, a light diffusing substance (for example, titanium oxide particles) mixed in the electrolyte 31. As a result, the electrochemical display element 1 viewed from the ITO electrode 32 side becomes white in the initial state.

  The electrolyte 31 contained in the electrochemical display element 1 can be prepared by, for example, phase inversion of silver from a silver salt aqueous solution to a non-aqueous silver salt solution. Such an aqueous silver salt solution can be prepared by dissolving a known silver salt in water.

  FIG. 3 is a view for explaining the relationship between the time for applying the write voltage to the electrochemical display element 1 and the display density D. In FIG.

  In FIG. 3, the horizontal axis represents Tx, the time for applying the writing voltage, and 0 to 24 on the vertical axis represent the display density value D. 0 is the minimum display density (white) of the electrochemical display element 1, 24 is the maximum display density (black) of the electrochemical display element 1, and this figure is an example of displaying 25 gradation levels from 0 to 24. is there. As shown in FIG. 3, in the electrochemical display element 1 of this embodiment, when a predetermined write voltage is applied, the display density D increases according to the write time Tx.

  FIG. 4 is a diagram illustrating a configuration of a display device according to the present embodiment, and FIG. 5 is a diagram illustrating an arrangement of color filters according to the present embodiment. Although FIG. 4 shows the configuration of only 3 rows × 3 columns of pixels for simplification of description, in order to display an image on the display screen 50, more n rows × m columns of pixels are used. For example, if the XGA display screen 50 is configured, the number of pixels is 1024 × 768. Further, since the color filter array is 2 rows × 2 columns as shown in FIG. 5, the number of pixels in the rows and columns is preferably a multiple of two.

  In FIG. 4, each pixel includes an electrochemical display element 1, a drive transistor 2, and a switching transistor 4. In FIG. 4, each of the electrochemical display elements 1 of the pixels of n rows × m columns is denoted as Pnm. For example, the electrochemical display element 1 of the pixel in the first row and first column is expressed in order as P11, and the electrochemical display element 1 of the pixel in the second row and second column is expressed as P12.

  FIG. 5 shows an arrangement of color filters provided in pixels of 4 rows × 4 columns.

  G (green) color filter material is applied to P11, R (red) color filter material is applied to P12, and B (blue) color filter material is applied to P21. Since P22 is not coated with a color filter material, it is written as W, which means a white pixel. Four pixels of R, G, B pixels and W pixels are sub-pixels constituting one pixel unit of the color image. Similarly, the four pixels P13, P14, P23, and P24, the four pixels P31, P32, P41, and P42, and the four pixels P33, P34, P43, and P44 constitute one pixel unit.

  Reference numerals 5a, 5b, and 5c denote scanning lines that connect the gates of the switching transistors 4 and the gate drivers 12 of the pixels arranged in the row direction to each other. Reference numerals 8a, 8b, and 8c denote signal lines that connect the sources of the switching transistors 4 of the pixels arranged in the column direction and the source driver 14 to each other. The gate driver 12 controls on / off of the switching transistor 4 by selectively outputting the output voltages G1, G2, and G3 to the scanning lines 5a, 5b, and 5c based on the control of the display control unit 11. The row to which the control voltage is applied to the driving transistor 2 is selected. The drain of the driving transistor 2 is connected to the silver electrode 30 of the electrochemical display element 1 of each pixel, and the source is grounded by the GND bus 6.

  The source driver 14 has a driver circuit for each of the signal lines 8a, 8b, and 8c, and outputs output voltages S1, S2, and S3 to the signal lines 8a, 8b, and 8c based on the control of the display control unit 11. The driver circuit of the source driver 14 is an on / off binary driver, and outputs a control voltage Vs input to the source driver 14 or 0V which is an off voltage based on the control of the display control unit 11.

  The control voltage power supply 15 outputs the control voltage Vs based on the control of the display control unit 11 and supplies it to the source driver 14.

The bus lines 7a, 7b, and 7c are connected to the ITO electrode 32 of the electrochemical display element 1 of each pixel for each row, and one end thereof is connected to the common power supply 13. Common power supply 13 outputs a common voltage V _C is positive or negative voltage by a command of the display control unit 11.

  When the output voltages S1, S2, and S3 of the source driver 14 are Vs, which is an on-voltage, when the switching transistor 4 is turned on, Vs is applied to the gate of the driving transistor 2, and the driving transistor 2 is turned on and the electrochemical display element. 1 is applied with a common voltage Vc. After that, even when the switching transistor 4 is turned off, the driving transistor 2 is kept on by the stray capacitance of the gate.

  When the output voltages S1, S2, and S3 of the source driver 14 are 0V that is an off voltage, when the switching transistor 4 is turned on, 0V is applied to the gate of the drive transistor 2, and the drive transistor 2 is turned off.

  The memory 10 includes a recording medium such as a ROM (Read Only Memory) or a flash memory.

The first frame memory 60 and the second frame memory 61 are frame memories for one screen each having a storage area corresponding to the number of pixels of the display screen 50. The first frame memory 60 calculates frame number values N _R , N _G , corresponding to the display density of the pixels displaying R, G, B, W calculated based on the first image data read from the memory 10. N _B and N _W are stored.

The second frame memory 61 has a display density of pixels that display R, G, B, and W converted by the data converter 80 as second image data to be displayed on the display screen 50 next time by the electrochemical display element 1. The corresponding frame number values M _R , M _G , M _B and M _W are stored. In the drawing, the first frame memory 60 and the second frame memory 61 are denoted as FM1 and FM2, respectively.

  The control part 11 is comprised from CPU etc. and controls the display apparatus 100 whole based on a program.

  Next, control when displaying an image on the display device 100 of the present invention will be described with reference to FIG.

  FIG. 6 is a time chart showing a change in voltage of each part when an image is displayed on the electrochemical display element 1. FIG. 6 illustrates a page feed mode in which writing is performed after an erase voltage is applied to the electrochemical display element 1 to erase images of all the electrochemical display elements 1.

First, the voltages V _P11 , V _P21 , and V _P31 applied to P11, P21, and P31 in the first column will be described using the time chart of FIG. The horizontal axis of the time chart of FIG. 6 is a time axis, and F _W 1 to F _W 5 represent the first to fifth frames. N expressed as F _W N is a frame number, and represents the number of frame periods from the start of writing. In the page feed mode, the common voltage V _C is V _cb as shown in FIG.

T _{0 to} t ₅ are the start timings of the first to sixth frames.

In the time chart of FIG. 6, only F _W 5 is displayed to simplify the drawing.

First, the output voltages G1, G2, and G3 of the gate driver 12 in each frame _FW will be described.

When the output voltage G1 in the first row of the gate driver 12 becomes “H” during ΔT, the switching transistor 4 in the first row is turned on. Then, the gate voltages of the drive transistors 2 connected to P11, P12, and P13 in the first row are set to the outputs S1, S2, and S3 of the source driver 14, respectively, and are held in stray capacitances (not shown). Therefore, when the switching transistor 4 is turned on when the output of the source driver 14 is V _S1 , the driving transistor 2 is turned on. Next, when the output of the source driver 14 is 0 V, the driving transistor 2 is turned on until the switching transistor 4 is turned on. Keeps the on state.

  Next, the output voltage G2 of the second row of the gate driver 12 becomes “H” during ΔT, and the gate voltages of the driving transistors 2 connected to P21, P22, and P23 of the second row are respectively those of the source driver 14. The outputs S1, S2, and S3 are set and held in a stray capacitance (not shown). Similarly, the gate voltages of the drive transistors 2 connected to the P31, P32, and P33 in the third row are also set to the outputs S1, S2, and S3 of the source driver 14, respectively, and held in stray capacitances (not shown).

  Outputs S1, S2, and S3 of the source driver 14 are set according to a display density value X that is a density of an image displayed on the electrochemical display element 1.

  The operation of the example of FIG. 6 will be described.

In the frame _{F W 1~F W 5, P11,} P21, P31 driving transistor 2 is connected to is turned on sequentially, P11, P21, P31 to _{V cb} is applied.

  In addition, although the electrochemical display element 1 in the first column has been described, a voltage is similarly applied to the electrochemical display elements 1 in other columns.

  In this way, the electrochemical display element 1 is sequentially scanned, and a voltage corresponding to the display image X is applied for a predetermined frame period.

FIG. 7 is a graph showing an example of the relationship between the display density of the color image and the frame number N. In the drawing, D _R , D _G , D _B , and D _W are the display density of the R pixel, the display density of the G pixel, the display density of the B pixel, and the display density of the W pixel, respectively.

In the example of FIG. 7, in the all white state in which erases all the images of the electrochemical display element 1 of N = 0, _{D W} is _{0, D R, D G,} D B are both 16. This is an electrochemical display device provided with color filters, the minimum display density transmittance is lowered because of the color filters is because the increases, D _R, D G for simplicity of explanation in this _embodiment, D _B Is 16 in all cases.

Further, when the frame number is 8, that is, when frame writing is performed 8 times, all of D _R , D _G , D _B , and D _W become the maximum display density, and the value is 24.

The display density _DW of the electrochemical display element not provided with the color filter has a low minimum display density, and the electrochemical display elements D _R , D _G , and D _B provided with the color filter in one frame writing as shown in FIG. It is assumed that the display density increases three times.

  A conversion table showing the relationship of FIG. 7 is stored in the ROM 96.

Hereinafter, when the number of frame periods from the start of writing to the R, G, B, and W sub-pixels is distinguished, they are denoted as N _R , N _G , N _B , and N _W.

  Next, a procedure for displaying a color image in the present embodiment will be described with reference to FIGS.

  FIG. 8 is a diagram for explaining the internal configuration of the control unit 11, and the internal configuration of the display screen 50 is omitted.

  The control unit 11 includes a CPU 98 (central processing unit), a RAM 97 (Random Access Memory), a ROM 96 (Read Only Memory), and the like, and reads a program stored in the ROM 96 which is a nonvolatile storage unit to the RAM 97. Each part of the display device 100 is centrally controlled according to the program.

  The data conversion unit 80 generates a second image corresponding to a case where an image is displayed with R, G, B, and W pixels from a first image data corresponding to an image displayed with R, G, and B pixels. Convert to image data.

  The voltage application control unit 83 controls the drive transistor 2 to apply an erase voltage or a write voltage to each electrochemical display element 1 based on the frame number.

  FIG. 9 is a flowchart illustrating a procedure for displaying a color image according to the present embodiment.

  Hereinafter, description will be made along the flowchart of FIG. 9 with reference to the characteristics of FIG.

Note that image writing is performed in units of frame periods, and power (voltage) is applied to the electrochemical display element 1 according to the frame number during the frame period. In this embodiment, the frame period is represented by F _W N (N is a frame number).

  When the operator presses the forward button 43 or the reverse button 44 of the operation unit 42, an interrupt signal is transmitted from the operation unit 42 to the display control unit 11, and the display control unit 11 starts an operation button interrupt processing routine shown in FIG. Is done.

  S101: This is a step of erasing the entire screen.

  The display control unit 11 erases the entire screen and initializes it. The display density of all the electrochemical display elements 1 is the lowest display density.

  S102: This is a step of designating a page from which the first image data is read from the memory 10 and writing the image data of the page into the first frame memory 60.

  The CPU 98 designates a page from which the first image data is read from the memory 10 and writes the image data of the page in the first frame memory 60.

For example, when the operator presses the forward button 43 of the operation unit 42, the CPU 98 updates the page designation read from the memory 10 from the first page to the second page, and changes R, G, and B stored in the second page. First image data (frame numbers N _R , N _G , N _B ) of the pixel to be displayed is written in the first frame memory 60.

S103: This is a step of calculating the frame number N _W of the pixel displaying white.

The data converter 80 calculates the frame number N _W from the image data (frame numbers N _R , N _G , N _B ) of the pixels displaying R, G, B.

In the present embodiment, N _W is calculated by the following equation.

_{N W = (N R + N} G + N B) / 3
For example, when N _R , N _G , and N _B are 2, 8, and 8, N _W = 6. Hereinafter, an example in which N _R , N _G , and N _B are 2, 8, and 8 will be described.

_S104: N _R, N _G, find the minimum value C of _{N B.}

Data converting unit 80 _obtains the minimum value C of _{N R, N G, N B} .

If N _R , N _G , and N _B are 2, 8, and 8, the minimum value C is 2 of N _R.

Incidentally, N _R, in the case of _N G, any two is smaller than the other one with the same value _of the N _B, the same value as the minimum value C. _Further, N _R, if N G, is _{N B} equivalence, the minimum value C to zero.

S105: frame number _{N R, N G,} is a step of converting the _{N B.}

Data conversion section _80, N _R, subtracts the N G, respectively, from _{N B} C, frame number _M R after data _conversion, M G, and calculates the _{M B.}

M _R = N _R -C
M _G = N _G -C
M _B = N _B -C
When N _R , N _G , and N _B are 2, 8, and 8, C = 2, so that M _R , M _G , and M _B are 0, 6, and 6.

S106: The display density D (M _W ) after data conversion is calculated so that the sum of display densities before and after data conversion is the same.

The data conversion unit 80 calculates the sum of display densities before data conversion of one pixel unit, and the display density D (M _W ) after data conversion in which the sum of display densities after data conversion becomes the same as before data conversion. Is calculated.

The data conversion unit 80 obtains D _W (M _W ) by the following equation.

D _W (M _W ) = (D _R (N _R ) + D _G (N _G ) + D _B (N _B ) + D _W (N _W )) − (D _R (M _R ) + D _G (M _G ) + D _B ( M _B ))
In this embodiment,
D _W (M _W ) = (18 + 24 + 24 + 18) − (16 + 22 + 22) = 24
It is. Since the display density of the R, G, and B subpixels after data conversion is lower (brighter) than before data conversion, the display density of the W subpixel is increased (darker) and the sum of the display densities in units of one pixel. Is not changing.

S107: a step of obtaining the image data _{M W} after conversion.

Data conversion unit 80 calculates the M _W by equation display density D and the frame number M _W.

In this embodiment,
M _W = D _W (M _W ) / 3 = 24/3 = 8.

Data conversion section 80, the calculated _{M R, M G, M B} , and stores the image data _{M W} in the second frame memory 61.

  S108: This is a step of displaying an image.

  The voltage application control unit 83 writes an image by applying a voltage to a predetermined electrochemical display element 1 based on the image data in the second frame memory 61 in the procedure for writing the image described in FIG.

  The flowchart of FIG. 9 has been described above.

In this way, the frame numbers N _R , N _G , N _B , and N _W before data conversion by the data conversion unit 80 are 2, 8, 8, and 6, and are necessary for rewriting the four subpixels. While the total number was 24, the frame numbers M _R , M _G , M _B , and M _W after data conversion are 0, 6, 6, and 8, and the total number of necessary frame numbers is 20. Since the frame number represents the number of times power is applied to the electrochemical display element 1 for a predetermined time for writing, the electrochemical display element 1 having a smaller frame number consumes less power.

  In this embodiment, since the sum of the frame numbers is reduced without changing the display density sum of one pixel unit after the data conversion, it is possible to reduce the power consumption before the data conversion without changing the brightness of the color display.

  Since the display density of the W sub-pixel is 24 in the embodiment, when the minimum value C obtained in step S104 becomes a large value, the display density of the W sub-pixel is increased (darkened) to increase the display unit by pixel. It becomes impossible to prevent the total display density from changing. In such a case, the data conversion unit 80 may be configured not to perform data conversion.

  Further, in this embodiment, an example in which an image is written from the entire white state using the reflective display element has been described. However, even when an image is written from the transmissive display element or the entire black state. Applicable.

  As described above, according to this embodiment, it is possible to provide a display device that can display a bright color image while suppressing power consumption.

DESCRIPTION OF SYMBOLS 1 Electrochemical display element 2 Drive transistor 4 Switching transistor 5a, 5b, 5c Scan line 7a, 7b, 7c Bus line 8a, 8b, 8c Signal line 10 Memory 11 Display control part 12 Gate driver 13 Common power supply 14 Source driver 30 Silver electrode DESCRIPTION OF SYMBOLS 31 Electrolyte 32 ITO electrode 34 Power supply 80 Data conversion part 81 Current prediction part 83 Voltage application control part 100 Display apparatus

Claims (3)

And electrochemical display element for displaying white, a plurality of sequences electrochemical display element for displaying red, a electrochemical display device for displaying green, and electrochemical display element for displaying a blue color, as one pixel unit, A display device capable of displaying a color image by applying power to each of the electrochemical display elements,
When an image is displayed by three electrochemical display elements that display red, green, and blue, the image is displayed by the one pixel unit from the first image data corresponding to the power applied to each electrochemical display element. A data conversion unit for converting into second image data corresponding to the power applied to each electrochemical display element when
The data converter is
Calculating the data according to the power applied to the electrochemical display element that displays white color based on the first image data, and the sum of the display densities of the electrochemical display elements constituting the one pixel unit;
The second image data of the electrochemical display element that displays red, green, and blue by subtracting predetermined values from the first image data, respectively, and the second display data of red is calculated from the calculated sum of the display densities. Data corresponding to the power applied to the white electrochemical display element from the display density of the image data, the display density of the second image data of green, and the display density obtained by subtracting the display density of the second image data of blue Is calculated and used as second image data. The data converter is
2. The display according to claim 1, wherein the first image data of an electrochemical display element that applies the least amount of electric power among the electrochemical display elements that display red, green, and blue is the predetermined value. apparatus. Red, green, blue, and the electrochemical display element for displaying white, claims, characterized in that it has a power to be applied to the electrochemical display devices, a table representing a relationship between the display density of the electrochemical display device 3. The display device according to 1 or 2 .

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