Patent Application
20110109582
The present invention relates to display devices.
In recent years, along with the improvement in the speed of operation of personal computers, spreading of network infrastructure, data storage coming to have large capacities, and reduction in price, opportunities are increasing more and more for obtaining and viewing documents and images, etc., that were conventionally provided in the form of paper printed matter, as simple electronic information.
As a display device for viewing such electronic information, the conventional liquid crystal displays or CRTs, or in recent years, light emitting types such as organic EL displays, etc., are being used. In particular, when the electronic information is document information, while it is necessary to watch the display device intently for relatively long periods of time, as a drawback of the conventional display devices, it has been generally known that the eyes get strained due to flickering.
Reflection type displays using external light have been known as the display devices for correcting this drawback.
As a display method for realizing such a reflection type display, the electrodeposition method has been known that uses the precipitation from solutions of metals or salt of metal (this method is hereinafter abbreviated as the ED method). The ED method has various advantages such as, possible to be driven at a relatively low voltage, having a simple cell structure, excellent in the contrast between black and white and the black quality, etc. (see Patent Document 1 and Patent Document 2).
However, in a display device of the ED method, since a certain amount of time is required for the precipitation or dissolution of metal, when an attempt is made to display the handwritten information input from a touch panel simultaneously with the inputting of the information, there is the problem that the display speed cannot keep up with the handwriting speed. In a conventional liquid crystal panel, etc., the handwritten input information from the touch panel is stored in a memory, and the screen is scanned based on this information from the memory, and then the handwritten information is displayed. In a case like liquid crystal display panel, since the response speed is fast, there was no problem even in this method of display. However, in a case of display device of the ED method, if this display method is used as it is, the display cannot keep up with the writing speed, and the handwritten information is displayed after a delay, which leads to poor operational performance.
In order to solve such a problem, in Patent Document 3 a method of writing in a short time corresponding to the position of the pen by applying voltages to the X and Y electrode terminals of the display device directly from the location information (X, Y) at each instant of time that is generated by the pen for handwriting has been proposed.
In Patent Document 3, at the time of writing corresponding to the position of the pen, high speed display driving has been made possible by applying for a short time a voltage exceeding the threshold voltage at which crystals start precipitating and forming crystals that become the nuclei. Further, since the display density of the handwritten part is insufficient with only the formation of crystals that become the nuclei, the display density is supplemented by additional writing.
However, in the method disclosed in Patent Document 3, if a new handwriting input is made while the additional writing is being done to supplement the display density, there is a problem that until the additional writing is completed it is not possible to display the image of the new handwriting input that has been made. In addition, when an overlapping handwriting input is made in the same location, since a voltage exceeding the threshold voltage is applied to the electrochemical display element several times, the amount of precipitation of metal becomes excessive, and the problem occurs that the displayed image becomes difficult to be erased even if an erasing voltage is applied.
The present invention was developed considering the above problem, and the purpose is to provide a reflection type display device capable to display the information input by handwriting at a practical speed without losing the characteristics of the electrochemical display element.
The purpose of the present invention can be achieved by the following structures.
1. A display device having a display screen constituted by matrix-arranged electrochemical display elements and displaying an image by applying writing electric currents corresponding to the display densities to be displayed to said respective electrochemical display elements, wherein the display device comprises;
a first memory for storing display density values X to be displayed next respectively in each electrochemical display element;
a second memory for storing display density values Y being currently displayed respectively in each electrochemical display element;
an input section for inputting location information on the display screen;
a first updating section for updating the display density value X stored in said first memory corresponding to the location information which has been input from the input section based on the location information;
a comparison section which compares the display density value X stored in said first memory with the display density value Y stored in said second memory corresponding to the display density value X;
a driver for applying a writing current to each electrochemical display element based on the result of comparison by said comparison section; and,
a second updating section that updates the display density value Y which is being stored in said second memory along with the application of the writing current by said driver.
2. The display device described in Structure 1 above, wherein the driver applies a writing current to the electrochemical display element for which said comparison section has determined that X>Y.
3. The display device described in Structures 1 or 2 above, wherein said control section is further provided with a third storage section for storing the display density values X of a plurality of pages to be stored in said first memory.
4. The display device described in any one of Structures 1 to 3 above, wherein said first memory is a FIFO memory, and the updating of the display density value X being stored in said first memory by said first updating section and the comparison of the display density value X and the display density value Y by said comparison section are performed asynchronously.
5. The display device described in any one of Structures 1 to 4 above, wherein said input section is a touch panel provided in the top layer of said display screen.
According to the present invention, in a display device using electrochemical display elements, it is possible to display the information input by handwriting at a practicable speed.
Some embodiments of the present invention will be explained in the following based on the drawings.
The display device 100 is, for example, an electronic book, and displays the data such as images, text characters, etc., stored in the storage section 10 (see
Further, the top layer of the display screen 50 is a touch panel 40 as an input section for inputting the location information on the screen. A user switches a mode to the handwriting mode by making input operations to the touch panel 40, and carries out handwriting input by specifying the position or the region on the screen. The input operation to the touch panel 40 can be made using a stylus pen 55 (see
The electrochemical display element 1 holds an electrolyte 31 between a transparent ITO electrode 32 and a silver electrode 30. A current source 33 is connected to the ITO electrode 32 and the silver electrode 30. When a current “i” is applied flour the current source 33 to the silver electrode 30 in the direction of the arrow in the figure, a reduction reaction of silver ions in the electrolyte 31 takes place and silver is precipitated. Since the precipitated silver absorbs light, the density of the electrochemical element 1 as seen from the side of the ITO electrode 32 becomes high.
On the other hand, when a current “i” is applied from the current source 33 to the silver electrode 30 in a direction opposite to that of the arrow in the figure, an oxidization reaction takes place at the ITO electrode 32, and the precipitated silver becomes silver ion and dissolves into the electrolyte 31. If the current “i” is applied for a specific interval of time in a direction opposite to that of the arrow in the figure, the density of the electrochemical display element 1 as seen from the ITO electrode 32 side becomes white in color which is its initial state. Here, VED is the voltage between the ITO electrode 32 and the silver electrode 30 when the current “i” is applied.
The electrolyte 31 can be prepared, for example by inverting the phase of silver from an aqueous silver salt solution to a non-aqueous silver salt solution. This aqueous silver salt solution can be prepared by dissolving a publicly known silver salt in water.
Each pixel includes an electrochemical display element 1, a driving transistor 2, a supplementary capacitor 3 and a switching transistor 4. In
The symbols 5a, 5b, and 5c denote scanning lines, which connect the gates of the switching transistors 4 of the pixels in the row direction are with each other, and they are connected to the gate driver 12. The symbols 8a, 8b, and 8c denote signal lines, which connect the sources of the switching transistors 4 along the column direction with each other, and they are connected to the source driver 14.
The gate driver 12 makes ON-OFF control of the switching transistors 4, by outputting the output voltages G1, G2, and G3 to the scanning lines 5a, 5b, and 5c, and selects the row to which the control voltage is to be applied.
The source driver 14 has driver circuits for each of the signal lines 8a, 8b, and 8c, and outputs the output voltages S1, S2, and S3 to the signal lines 8a, 8b, and/or 8c connected on the output side based on the control, of the display controller 11. The driver circuits of the source driver 14 are binary drivers having the values of ON and OFF, and outputs either the control voltage Vs input to the source driver 14 or the OFF voltage which is 0V based on the ON-OFF signals for each of the signal lines 8a, 8b, and 8c transmitted from the display controller 11.
The display controller 11 which includes a clock generator circuit and logic circuits, etc., controls the source driver 14, the gate driver 12, and the bus power supply 13, etc., at a prescribed frequency, and functions as a driver that applies current to the prescribed electrochemical display element 1.
The CPU 71 functions as a control section that controls the entire display device based on the programs stored in the storage section 10. The storage section 10 includes a recording medium such a ROM (Read Only Memory) or a flash memory, etc., and stores various types of programs and data that control the display device 100. The CPU 71 is provided with a comparison section 70 that successively compares the values of the display densities of the first frame memory 60 and the second frame memory 61, and suitably updates the values of the display densities stored respectively in the first frame memory 60 and the second frame memory 61.
The first frame memory 60 and the second frame memory 61 are frame memories of one screen respectively having storage areas corresponding to the number of pixels of the display screen 50. The first frame memory 60 stores the display density values X that have to be displayed next in the display screen 50 by the electrochemical display elements 1 (each pixel). The second frame memory 61 stores the display density values Y that are currently being displayed in the display screen 50 by the electrochemical display elements 1 (each pixel). The comparison section 70 reads the display density value X and the display density value Y of the corresponding pixel respectively from the first frame memory 60 and the second frame memory 61, and compares the two values.
The display controller 11 transmits the interrupt signal INT3 to the CPU 71 at the prescribed timing, and receives the result data of comparison carried out by the comparing section 70.
The third frame memory 62 has the capacity to store the image data (the display density values X) of a plurality of pages, and is configured so that the display density values X of the page specified by the operation section 42 is stored in the first frame memory 60. Further, in the figure, the first frame memory 60, the second frame memory 61, and the third frame memory 62 are indicated as FM1, FM2, and FM3, respectively.
A touch panel 40 is connected to a touch panel controller 41. The touch panel controller 41 successively scans the input regions of the touch panel 40, and when there is an input to the touch panel 40, it sends the interrupt signal INT1 to the CPU 71, and also transmits the information of the location where the input was made to the CPU 71.
When the next button 43 or the back button 44 constituted by mechanical switches is operated, the operation section 42 sends the interrupt signal INT2 to the CPU 71, and also transmits the information to the CPU 71 which button was operated.
The display controller 11, the CPU 71, the storage section 10, the first frame memory 60, the second frame memory 61, the third frame memory 62, and the touch panel controller 41, etc., are connected to the bus line B1 that includes the address bus and the data bus, and each connected element exchanges data via the bus line B1.
Since the circuit configurations of the respective pixels on the display screen 50 are the same, hereinafter, the pixel of the first row and first column will be explained as an example, using
The drain of the driving transistor 2 is connected to the bus line 6, the source is connected to the silver electrode 30 of the electrochemical display element 1 (ED11). The supplementary capacitor 3 is connected between the source and the gate of the driving transistor 2 and retains the control voltage Vs applied between the source and the gate. The bus line 6 is connected to the bus power supply 13, and supplies the bus voltage VB to the driving transistor 2. The driving transistor 2 applies a constant current to the electrochemical display element 1 according to the bus voltage VB and the control voltage Vs applied between the gate and source.
The source of the switching transistor 4 is connected to the signal line 8a, the drain is connected to the supplementary capacitor 3 and the gate of the driving transistor 2, and the gate is connected to the gate driver 12. When the output voltage G1 of the gate driver 12 becomes ‘H’, the switching transistor 4 turns ON, and the output voltage S1 of the source driver 14 is applied to the gate and the supplementary capacitor 3 of the driving transistor 2.
The common electrode 7 is connected to the ITO electrodes 32 of the electrochemical display elements 1 of the respective pixels, and it is connected to GND at one end.
The writing operation of the display device of the present embodiment is explained below using
The horizontal axis Tx of
Next, the time chart of
T1 in
F1 indicates the frame duration of the first frame and F2 indicates the frame duration of the second frame. The explanations are given starting from the program interval T1 of the first frame of
During T1, VB and VC are 0V, and the currents i11 to i33 of the respective electrochemical display elements 1 are 0.
The display controller 11 transmits the interrupt signal INT3 to the CPU 71 at the timing of t11, the beginning of the first frame, and requests the result data of comparison that the comparison section 70 has read out from the first frame memory 60 and the second frame memory 61 the display density value X and the display density values Y, respectively, of the pixels of the first row and compares them.
When the CPU 71 receives the interrupt signal INT3, it carries out interrupt processing, described in detail later, and transmits the result data of comparison of the first row compared by the comparison section 70 to the display controller 11. The display controller 11 controls the source driver 14, turns ON the signal lines 8 corresponding to the pixels for which the comparing section 70 determined as X>Y, and turns OFF the signal lines 8 corresponding to all other pixels.
The example in
The output voltages S1, S2, and S3 of the source driver 14 are Vs, and the voltage between the gate and the source of the driving transistors 2 connected to ED11, ED12, and ED13 of the first row is set to Vs which is retained by the supplementary capacitor 3.
Next, the display controller 11 sends the interrupt signal INT3 to the CPU 71 at the timing t12 and requests the result data of comparison of the second row from the comparing section 70. The display controller 11 similarly controls the source driver 14, and turns ON the signal lines 8 corresponding to the pixels for which the comparing section 70 determined that X>Y, and turns OFF the signal lines 8 corresponding to all other pixels.
The example in
The output voltages S1, S2, and S3 of the source driver 14 are Vs, and the voltage between the gate and source of the driving transistors 2 connected to ED21, ED22, and ED23 of the second row is set to Vs which is retained by the supplementary capacitor 3.
Next, the display controller 11 sends the interrupt signal INT3 to the CPU 71 at the timing t13 and requests the result data of comparison of the third row from the comparing section 70. The display controller 11 similarly controls the source driver 14, turns ON the signal lines 8 corresponding to the pixels for which the comparing section 70 determined that X>Y, and turns OFF the signal lines 8 corresponding to all other pixels.
The example in
Therefore, the output voltages S1 and S2 of the source driver 14 is Vs and the voltages between the gate and source of the driving transistors 2 connected to ED31 and ED32 in the third row are set to Vs which is retained by the supplementary capacitors 3. Further, during this period, the output voltage S3 is 0, and the voltage between the gate and the source of the driving transistor 2 connected to ED33 is set to 0V that is retained by the supplementary capacitor 3.
During the next T2 writing interval, the display controller 11 changes the output voltage VB of the bus power supply 13 from 0 to VBh. When the output voltage VB becomes VBh, the driving transistor 2 applies a constant current to the electrochemical display elements 1 according to the voltage between the gate and the source of the driving transistor 2, and said voltage is being retained by the supplementary capacitor 3.
In the example shown in
Similarly, even during the program interval T1 of the second frame F2, the display controller 11 transmits the interrupt signal INT3 to the CPU 71 at the timing t21, and requests the result of comparison in the first row carried out by the comparing section 70. Similarly, the display controller 11 controls the source driver 14, and turns ON the signal line 8 corresponding to the pixels for which the comparing section 70 determined that X>Y, and turns OFF the signal lines 8 of all other pixels.
The example in
Therefore, the output voltages S1 and S2 of the source driver 14 is Vs, and the voltages between the gate and the source of the driving transistors 2 connected to ED11 and ED12 are set to Vs that are retained by the supplementary capacitors 3. Further, during this period, the output voltage S3 is 0, and the voltage between the gate and source of the driving transistor 2 connected to ED13 is set to 0V that is retained by the supplementary capacitor 3.
Thereafter, the display controller 11 transmits the interrupt signal INT3 to the CPU 71 at the timing t22 and the timing t23, and similar processing is made.
During the writing interval T2, a constant current is applied to the electrochemical display elements 1 according to the voltage between the gate and the source of the driving transistors 2 which was retained by the supplementary capacitors 3 during the interval T1. The example in
When a current with a current value of “ia” is applied to the electrochemical display element 1 during the interval T2, the display density D of the electrochemical display element increases by 1. For example, when writing for one frame is carried out to an electrochemical display element 1, which display density is 0, the display density becomes 1.
In
Further, since the display density D changes according to the integrated value of the writing current, it is not necessary to carry out the writing by successive frames. In addition, while the 11-step gradation from 0 to 10 is used in the present embodiment, it is also possible to use still more steps, or to use fewer steps of gradation by suitably setting the value of the writing current “ia” and the writing interval.
Next, the control procedure of the display device 100 in the present embodiment will be explained using the flow charts of
The flow chart of
When an input is made using a stylus pen 55, etc., on the touch panel 40, an interrupt signal INT1 is transmitted from the touch panel controller 41 to the CPU 71, and the handwriting input interrupt servicing routine shown in
The Step S10 is executed in the handwriting input interrupt servicing routine.
S10: This is the step in which the CPU 71 updates the display density value X of the first frame memory 60 corresponding to the handwriting input.
The CPU 71 updates the display density value X stored in the first frame memory 60 based on the location information detected by the touch panel controller 41. In the present embodiment, the CPU 71 updates the display density value X stored in the first frame memory 60 at the address corresponding to the location information detected by the touch panel controller 41 to the maximum display density 10.
When the interrupt servicing ends, the processing by the CPU 71 returns to the source routine.
That is all of the explanation regarding the handwriting input interrupt servicing routine.
Next, the flow chart of
When the operator presses the next button 43 or the back button 44 of the operation section 42, the interrupt signal INT2 is transmitted from the operation section 42 to the CPU 71, and the CPU 71 starts the operation button interrupt servicing routine shown in
In the operation button interrupt servicing routine, the Step S20 is executed.
S20: When the operation of either the next button 43 or the back button 44 is detected, the CPU 71 reads out the image data of the corresponding page from the third frame memory 62 as well as initializing the display screen, and writes the display density values X of that page in the first frame memory 60.
For example, when the operator presses the next button 43 in the operation section 42 in the state that the first page is being displayed, the CPU 71 reads out the image data of the second page from the third frame memory 62 and writes the image data (the display density values X) in the first frame memory 60.
When the interrupt servicing ends, the processing by the CPU returns to the source routine.
The above is the explanation of the operation button interrupt servicing routine.
Next, the flow chart of
The interrupt signal INT3 is transmitted from the display controller 11 at the rising edge of Gn of each frame as explained in
S101: This is the step of comparing the values of the display densities of the first frame memory 60 and the second frame memory 61 for the nth line.
The comparison section 70 successively reads and compares the display density values X stored in the first frame memory 60 and the display density values Y stored in the second frame memory 61 along the row direction for the nth row, and determines the result as ‘H’ when Xnm>Ynm, and determines the result as ‘L’ when Xnm≦Ynm. The comparison section 70 temporarily stores the determined results in the storage section 10.
For example, in the case of the first column of the first row, if it is considered that X11 is 10 and Y11 is 0, the determined result is ‘H’, and this result is temporarily stored in the storage section 10.
S102: This is the step of outputting to the display controller 11 the result of comparison made in Step S101.
The CPU 71 outputs the result of comparison made in Step S101 and temporarily stored in the storage section 10 to the display controller 11. The display controller 11 turns ON the driver circuit of the source driver 14 for which the result was determined as ‘H’, and turns OFF the driver circuit of the source driver 14 for which the result was determined as ‘L’.
S103: This is the step of updating the display density values Y of the nth row in the second frame memory 61.
The display controller 11 increases the display density values Y of the pixels of the nth row in the second frame memory 61 corresponding to the writing current. For example, if the display density value is 0, the display density value Y11 will be updated to 1.
S104: This is the step of comparing n and
The CPU 71 compares n with the final row, of the display device.
When n≠nmax (NO in Step S104), the processing proceeds to Step S105.
S105: This is the step of making n=n+1.
The value of n is incremented to n+1 if the comparison has not been completed up to the final row nmax, and the processing returns to the source routine.
For example, if n is 1, n is updated to 2, and when the interrupt signal INT3 is transmitted from the display controller 11 next, the display density of the second row will be compared in this routine.
When n=nmax (YES in Step S104), the processing proceeds to Step S106.
S106: This is the step of making n=1.
Since the comparison was done up to the final row, n is set to n=1 and the processing returns to the source routine.
When the interrupt signal INT3 is transmitted from the display controller 11 next, the processing of the next frame is to be done, and the comparison of the display density is started from the first row in this routine.
The above is the explanation of the display controller interrupt servicing routine.
Next, the processings of the display device explained so far will be detailed based on a concrete example using
a shows the position of the stylus pen 55 at the time immediately after starting to write a horizontal line by handwriting input, and
The lines shown in
The F0 to F17 shown along the time axis in
Further, t1 is the timing that the first frame starts, and the program interval T1 described in
80
a, 80b, 80c, and 80c1 in
Further, 90a, 90b, 90c, 90d, 90; and 90g in
The explanations will be given sequentially along the time axis of
At the timing ts1, the interrupt signal INT1 is transmitted from the touch panel controller 41 to the CPU 71, and the handwriting input interrupt servicing routine shown in
80
a shows the display density value X of the first frame memory 60 at the instant of time t1 In other words, as shown in
Further, the display density values Y of the display density of the second frame memory 61 at the instant of time t1 are all 0 although they are not shown in the figure.
In the first frame that starts from the timing t1, the interrupt signal INT3 is transmitted to the CPU 71 periodically at every rising edge of Gn from the display controller 11 during the program interval T1, and the CPU 71 executes the display controller interrupt servicing routine.
In the display controller interrupt servicing routine, as explained in
The electrochemical element 1, to which a writing current was applied, gradually increases the density, and when the writing interval T2 ends, a horizontal line with a display density value 1 is displayed at positions corresponding to the pixel indicated as Pa and the pixel to its right on the display screen 50.
Further, in the Step S103 of the display controller interrupt servicing routine, the CPU 71 increases the display density values Y to 1 in the second frame memory 61 at positions corresponding to the pixel indicated by Pa and the pixel to its right, and at the timing t2, the state will be as shown in
On the other hand, at the timing t2, the writing of the horizontal line by the stylus pen 55 has been completed, and the display density values X stored in the first frame memory 60 have become 10 corresponding to the position from the pixel indicated by Pa to the 10th pixels to the right as shown in
Similar to the first frame, even during the second frame the CPU 71 executes the display controller interrupt servicing routine, and the display controller 11 applies a writing current to the electrochemical display elements 1 corresponding to the pixels for which X>Y.
Going through a processing similar to the first frame, the display density values Y of the second frame memory 61 corresponding to the pixels where writing current was applied have increased at the timing t3 as shown in
In the succeeding frames, writing current is applied to the corresponding electrochemical display elements 1 until X becomes equal to Y and the display density of such portion will gradually increase the density on the display screen 50. For example, at the timing t9, the display density has become high as shown in
In this manner, in the present embodiment, since the information of the handwriting is displayed lightly immediately after the handwriting input, and the display density is gradually increased, thus handwriting input can be displayed at a practicable speed.
Similarly, when a vertical line is written at the timing of ts3, the interrupt signal INT1 is transmitted from the touch panel controller 41 to the CPU 71, the handwriting input interrupt servicing routine shown in
80
c shows the display density value X of the first frame memory 60 at the instant of time t9. In other words, the display density value X is 10 at the pixels where the horizontal line has been written and from the pixel indicated by Pb to the position that two pixels below as shown in
Similar to the explanations given so far, in the ninth frame the CPU 71 executes the display controller interrupt servicing routine, and applies writing currents to the electrochemical display elements 1 corresponding to the pixels with X>Y.
By a similar processing, the pixels of the second frame memory 61 will be shown in
In the succeeding frames, writing currents are applied to the corresponding electrochemical display elements 1 until X becomes equal to Y and the written image gradually increases the display density on the display screen. For example, at the timing t11, the display density is as shown in
In this manner, writing currents are added in the pixels for which X>Y at every frame the display density value Y of the pixels of the horizontal line and the vertical line become 10 as shown in
Further, in the present embodiment, although an example was explained here in which the part where the handwriting input was displayed in black color with the maximum display density 10, it is also possible to display in white color with the minimum display density of 0. (When the background is black, it is desirable to display in white color.) To reduce the display density of the electrochemical display element 1, it is sufficient to reverse the polarities of the common voltage Vc and the control voltage Vs so that the current in the electrochemical display element 1 flows in a direction opposite to that shown in
Next, a display device according to a second preferred embodiment will be explained.
The biggest difference between the first embodiment and the second embodiment is that a FIFO memory is used for the first frame memory 60. In the present embodiment, two bus lines are provided i.e. the bus line B2 to which the display controller 11 and the second frame memory 61 are connected, and the bus line B3 to which the CPU 71 and the third frame memory 62, the touch panel controller 41, the storage section 10, etc., are connected. The input port IP of the first frame memory 60 is connected to the bus line B3, and its output port OP is connected to the bus line B2. The image data of one row input by the CPU 71 through the input port IP is read out successively from the output port OP by the display controller 11 via the bus line B2.
In the present embodiment, the data input from the CPU 71 and the data read out by the display controller 11 are made asynchronously, and it is not necessary to adjust the timing by the interrupt signal INT3 as in the first embodiment.
By having this type of configuration, since the writing to and the reading from the first frame memory 60 are carried out using different bus lines respectively, there is no bus line contention, and the display controller 11 can read out the image data from the first frame memory 60 at the prescribed timings without any delay.
The display controller 11 of the present embodiment has, for example, a clock generator circuit, a CPU, memory, and logic circuits, etc., and has a comparison section 70.
Other configuration and the configuration elements are similar to the first embodiment, and the same reference numbers are denoted to the respective configuration elements and their explanations are omitted here.
Next, the control carried out by the display controller 11 in the present embodiment will be explained.
In the second embodiment, the display controller 11 executes the procedure according to the flow chart shown in
S201: This is the step of setting n=1.
The display controller 11 initializes n to n=1.
S202: This is the step of comparing the display density values of the first frame memory 60 and the second frame memory 61 as to the nth row.
The comparison section 70 successively reads and compares the display density values X stored in the first frame memory 60 and the display density values Y stored in the second frame memory 61, respectively, of the nth row in the row direction, and determines the result as ‘H’ when Xnm>Ynm and as ‘L’ when Xnm≦Ynm. The comparison section 70 temporarily stores the result of determination in the memory of the display controller 11.
For example, in the case of the first column of the first row, if it is considered that X11 is 10 and Y11 is 0, the determined result will be ‘H’, and a writing electric current is applied to the electrochemical display element 1 of the first column of the first row in the subsequent processing.
S203: This is the step of outputting the result of comparison made in Step S101 to the source driver 14.
The CPU 71 outputs to the source driver 14 the result of comparison made in Step S102 and stored temporarily in the memory of the display controller 11. The display controller 11 turns ON the driver circuit of the source driver 14 for which the determination of ‘H’ has been made, and turns OFF the driver circuit of the source driver 14 for which the determination of ‘L’ has been made.
S204: This is the step of updating the display density values Y of the nth line of the second frame memory 61.
The display controller 11 updates the display density values Y corresponding to the pixels of the nth row of the second frame memory 61. For example, if the display density value Y11 of the first column of the first row was 0, it is updated to 1.
S205: This is the step of comparing n and nmax.
The display controller 11 compares the value n with the value of the final row nmax of the display device.
When n≠nmax (NO in Step S205), the processing proceeds to Step S207.
S207: This is the step of making n=n+1.
The value of n is incremented to n+1 since the comparison is not completed up to the final row nmax, and the processing returns to Step S202.
When n=nmax (YES in Step S205), the processing proceeds to Step S206.
S206: This is the step of applying writing current.
The display controller 11 instructs the bus power supply 13 to output VBh, and after waiting for the duration of T2, the processing returns to Step S201.
In this manner, the writing to the electrochemical display element 1 is repeated at a constant frequency.
The above is the explanation of the control routine of the display controller 11.
Although an example using software control was explained in the present embodiment, it is also possible to configure the display controller 11 using only hardware logic so that a similar procedure will be realized
Further, in the present embodiment, although an ED type was used for the electrochemical display elements 1, it is also possible to use other types such as the electro-chromic type, etc., as long as it is a display element having memory characteristics which display density changes with the application of an electric current.
In addition, in the present embodiment, although a touch panel 40 was used as the input section for inputting the location information on the top layer of the display screen 50, it is also possible to use other configurations such as, for example, identifying the location information on the display screen 50 by taking an image of a stylus pen 55 optically, etc.
In the above manner, according to the present invention, it is possible to provide a reflection type display device that can carry out handwriting display at a practicable speed irrespective of the timing of the handwriting input and without losing the display characteristics of the electrochemical display elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-185866 | Jul 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/061735 | 6/26/2009 | WO | 00 | 1/11/2011 |
