JP2015184358A - Display device, control method, and control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine a drive parameter according to individual variation in characteristic between display elements, while suppressing an influence on display.SOLUTION: A display device includes: an electro-optical layer; a pixel electrode; a measurement electrode; an adhesion layer that is formed between the electro-optical layer and the pixel electrode and the measurement electrode; a measuring part that measures, when the pixel electrode and the measurement electrode are made to have a different potential from each other, a current flowing through the measurement electrode; and a drive control part that controls a drive voltage to be applied to the electro-optical layer on the basis of a result of the measurement by the measuring part.

Description

  The present invention relates to a technique for determining a drive parameter in a display device.

  A display device including a memory display element such as an EPD is known. A memory-type display element has an advantage that display can be maintained without supplying power, but has a problem that display characteristics greatly change according to environmental factors such as temperature.

  Techniques for compensating for temperature characteristics of display elements are known (for example, Patent Documents 1 to 4). Patent Document 1 discloses a technology in which a temperature sensor is provided in an apparatus, and drive parameters are determined according to the temperature measured by the temperature sensor. Patent Document 2 discloses a technique for changing the applied voltage depending on the temperature in order to reduce the response delay of the display element at a low temperature. Patent Document 3 discloses a technique for changing a selection period in order to reduce a response delay of a display element at a low temperature. Patent Document 4 discloses a technique for estimating a temperature using a current flowing through an electrophoretic element and correcting a drive voltage according to the estimated temperature.

Japanese Patent No. 4615860 JP 2011-242569 A JP 2011-242567 A JP2011-76000A

  In the techniques described in Patent Documents 1 to 3, it is difficult to cope with individual variations in characteristics of display elements. In the technique described in Patent Literature 4, since the current flowing through the electrophoretic element is measured, the temperature measurement sometimes affects the display.

  On the other hand, the present invention provides a technique for determining drive parameters in response to individual variations in characteristics of display elements while suppressing the influence on display.

The present invention provides an electro-optic layer, a pixel electrode, a measurement electrode, the electro-optic layer, an adhesive layer formed between the pixel electrode and the measurement electrode, the pixel electrode, and the measurement electrode. A measurement unit that measures the current flowing through the measurement electrode when the electrodes are at different potentials, and a drive control that controls the drive voltage applied to the electro-optic layer based on the measurement result of the measurement unit A display device.
According to this display device, it is possible to determine the drive parameter in accordance with the individual variation in the characteristics of the display element while suppressing the influence on the display.

The measurement unit applies a reverse voltage having a polarity opposite to that of the potential difference generated between the first electrode and the second electrode for the same time as the measurement in order to measure the current. You may control to.
According to this display device, DC balance can be maintained.

The measurement unit may measure a current when the measurement unit is applying the reverse voltage.
According to this display device, the parameter can be determined using a more accurate measurement result.

The display device includes a power source used for writing data to the electro-optic layer, and a power source control unit that changes the power source from one of an operating state and a stopped state to the other, and the measuring unit includes the power source The measurement may be performed when the control unit changes the power source from the stopped state to the operating state.
According to this display device, the timing at which the parameter is changed can be limited.

The drive control unit includes at least one of a voltage applied to the electro-optical layer, a frequency that is a reciprocal of a cycle for supplying a voltage to the pixel circuit for applying a voltage to the electro-optical layer, and an application time of the voltage May be determined based on the measurement result of the measurement unit.
According to this display device, at least one of the voltage applied to the electro-optical layer, the voltage switching frequency, and the voltage application time can be changed according to the measurement result.

The drive control unit sets the voltage applied to the electro-optic layer to a positive first voltage, a negative second voltage, and a third voltage that is zero voltage, or a positive or negative first voltage. Switching from one of the one voltage and the second voltage that is a zero voltage to the other may be determined based on the measurement result of the measurement unit.
According to this display device, the bipolar drive and the unipolar drive can be changed according to the measurement result.

The display device may include a housing that houses the electro-optic layer, and at least a part of the measurement electrode may be hidden by the housing.
According to this display device, it is possible to reduce the influence on the display as compared with the case where the current is measured using the electrode that is not hidden in the housing.

According to another aspect of the invention, there is provided a control for a display device including an electro-optic layer, a pixel electrode, a measurement electrode, the electro-optic layer, and an adhesive layer formed between the pixel electrode and the measurement electrode. A method of measuring a current flowing through the measurement electrode when the pixel electrode and the measurement electrode are at different potentials; and applying to the electro-optic layer based on the measurement result A control method comprising controlling a driving voltage applied.
According to this control method, it is possible to determine the drive parameter corresponding to the individual variation in the characteristics of the display element while suppressing the influence on the display.

Furthermore, the present invention controls a display device having an electro-optic layer, a pixel electrode, a measurement electrode, the electro-optic layer, and an adhesive layer formed between the pixel electrode and the measurement electrode. A control device that performs the measurement when the electro-optic layer, the adhesive layer formed between the pixel electrode and the measurement electrode, and the pixel electrode and the measurement electrode have different potentials. There is provided a control device including a measurement unit that measures a current flowing through an electrode for use, and a drive control unit that controls a drive voltage applied to the electro-optic layer based on a measurement result of the measurement unit.
According to this control device, it is possible to determine the drive parameter in accordance with individual variations in the characteristics of the display element while suppressing the influence on the display.

1 is a diagram showing a configuration of an electronic apparatus 1000 according to an embodiment. FIG. 3 is a diagram illustrating a cross-sectional structure of the electro-optical panel 10. FIG. 6 illustrates a cross-sectional structure of a circuit layer 113. 2 is a diagram illustrating a planar structure of the electro-optical panel 10. FIG. The figure which shows the shape of the common electrode 131. The figure which illustrates the positional relationship of a pixel area | region and the housing | casing B. FIG. FIG. 5 is a diagram showing an equivalent circuit of the pixel 23. The figure which illustrates a drive waveform table. The figure which illustrates the circuit structure of the protection circuits 291-293. 10 is a flowchart showing the operation of the electronic apparatus 1000. The figure explaining leakage current. The figure which illustrates LUT. FIG. 6 is a diagram illustrating another example of the planar structure of the electro-optical panel 10.

1. Configuration FIG. 1 is a diagram illustrating a configuration of an electronic apparatus 1000 according to an embodiment. The electronic device 1000 is a tablet computer, for example. The electronic apparatus 1000 includes the electro-optical device 1 and the host device 3. The electro-optical device 1 is a display device that displays at least one of characters and images. In this example, the electro-optical device 1 includes an electro-optical panel 10 and a display controller 20. The electro-optical panel 10 is an electro-optical element, more specifically, a device using a memory-type display element that can maintain a display without supplying electric power, specifically, an EPD (Electrophoretic Display).

  The host device 3 includes a CPU 31, a RAM 32, a storage device 33, an input / output IF 34, a sensor 35, a high voltage power source 36, a low voltage power source (not shown), and a power source control unit 37. The CPU 31 is a device that controls another hardware configuration of the electronic device 1000. The RAM 32 is a storage device that functions as a work area when the CPU 31 executes a program. The storage device 33 is a non-volatile storage device that stores data and programs. The input / output IF 34 is an interface through which the host device 3 inputs / outputs data or signals with other devices. In this example, the input / output IF 34 supplies a signal to the display controller 20. The sensor 35 measures a predetermined physical state (for example, tilt, acceleration, temperature, humidity, brightness, etc.) and outputs a signal indicating the measurement result.

  The high-voltage power source 36 is a power source used for updating the display in the electro-optical panel 10 and is a power source for supplying a predetermined writing voltage (for example, + 15V, −15V). The low-voltage power supply is a power supply that consumes less power than the high-voltage power supply 36 and supplies a voltage (for example, 3V to 5V) for operating the logic circuit. The power supply control unit 37 performs control to change the state of the high-voltage power supply 36 from one of a stopped state (off) and an operating state (on) to the other. For example, when a predetermined time elapses after the display is updated on the electro-optical panel 10, the power control unit 37 causes the high-voltage power source 36 to transition to a stopped state. For example, when the CPU 31 instructs the display to be updated, the power supply control unit 37 causes the high-voltage power supply 36 to transition to the operating state. Even when the high-voltage power supply 36 is in a stopped state, the power supply control unit 37 can hold various data by maintaining the low-voltage power supply in an operating state.

  In addition, the electronic device 1000 includes an input device (for example, a touch screen, a keypad, etc.) and a communication device (for example, a wireless communication device) (all not shown).

  The display controller 20 is a control device (drive control unit) that controls the electro-optical panel 10. The display controller 20 has a VRAM (Video RAM, not shown) that stores image data before update and image data after update. When the display controller 20 receives an image update instruction from the host device 3, the display controller 20 controls the electro-optical panel 10 to display an image indicated in the updated image data.

  FIG. 2 is a diagram illustrating a cross-sectional structure of the electro-optical panel 10. The electro-optical panel 10 includes a first substrate 11, an electrophoretic layer 12, and a second substrate 13. The first substrate 11 and the second substrate 13 are substrates for sandwiching the electrophoretic layer 12.

  The first substrate 11 includes a substrate 111, an adhesive layer 112, and a circuit layer 113. The substrate 111 is made of an insulating material such as glass. In another example, the substrate 111 may be formed of a material having flexibility in addition to insulation, such as polycarbonate. The adhesive layer 112 is a layer that adheres the circuit layer 113 and the electrophoretic layer 12. The circuit layer 113 is a layer in which a circuit for driving the electrophoretic layer 12 is formed. Although details of the circuit layer 113 will be described later, the circuit layer 113 includes a pixel electrode 114.

  The electrophoretic layer 12 is an example of an electro-optical layer, and includes microcapsules 121 and a binder 122. The microcapsule 121 is fixed by a binder 122. As the binder 122, a material having good affinity with the microcapsule 121, excellent adhesion with the electrode, and insulating properties is used. The microcapsule 121 is a capsule in which a dispersion medium and electrophoretic particles are stored. The microcapsule 121 is made of a flexible material such as an Arabic gum / gelatin compound or a urethane compound.

  Electrophoretic particles are particles (polymer or colloid) having the property of moving by an electric field in a dispersion medium. In the present embodiment, white electrophoretic particles and black electrophoretic particles are stored in the microcapsule 121. The black electrophoretic particles are particles containing a black pigment such as aniline black or carbon black, and are positively charged in this embodiment. The white electrophoretic particles are particles containing a white pigment such as titanium dioxide or aluminum oxide, and are negatively charged in this embodiment.

  The second substrate 13 includes a common electrode 131, a film 132, and a substrate 133. The film 132 serves to seal and protect the electrophoretic layer 12. The film 132 is formed of a transparent and insulating material such as polyethylene terephthalate. The common electrode 131 is formed of a transparent and conductive material, for example, indium tin oxide (ITO). As the transparent and conductive material, for example, a zinc oxide transparent electrode (ZnO added with In, Ga, or Al) may be used in addition to ITO. Here, the term “transparent” means that at least visible light is transmitted. The substrate 133 is formed of a material such as glass or polycarbonate, like the substrate 111.

  In the microcapsule 121, the electrophoretic particles move according to the voltage applied to the electrophoretic layer 12. The gradation is expressed by the position of the electrophoretic particle after movement. When the potential of the pixel electrode 114 is positive (for example, +15 V) with respect to the potential EPcom of the common electrode 131, the negatively charged white electrophoretic particles move to the pixel electrode 114 side and are positively charged. Black electrophoretic particles move to the common electrode 131 side. At this time, when the electro-optical panel 10 is viewed from the second substrate 13 side, the pixels appear black. When the potential of the pixel electrode 114 is negative (for example, −15 V) with respect to the potential EPcom of the common electrode 131, the positively charged black electrophoretic particles move to the pixel electrode 114 side and are negatively charged. The white electrophoretic particles moving to the common electrode 131 side. At this time, the pixel appears white. Hereinafter, the voltage applied to the pixel electrode 114 is expressed using the potential EPcom as a reference.

FIG. 3 is a diagram illustrating a cross-sectional structure of the circuit layer 113. The circuit layer 113 includes a gate electrode layer 1131, an insulating layer 1132, a semiconductor layer 1133, a source / drain electrode layer 1134, an insulating layer 1135, and a pixel electrode layer 1136 in this order from the substrate 111 side. The gate electrode layer 1131 is a conductive layer including a gate electrode of a transistor to be described later, and is formed of, for example, p-Si (polycrystalline silicon). Note that in this example, the gate electrode layer 1131 also forms part of the capacitor. The semiconductor layer 1133 includes a semiconductor film that becomes a channel of the transistor, and is formed of, for example, a-Si (amorphous silicon). The source / drain electrode layer 1134 includes the source electrode and the drain electrode of the TFT 231 and is made of, for example, Al. The pixel electrode layer 1136 is a conductive layer including the pixel electrode 114, and is formed of a transparent and conductive material (for example, ITO). The insulating layer 1132 and the insulating layer 1135 are layers for insulating the conductive layers, and are formed of, for example, a silicon nitride film (Si ₃ N ₄ ). The insulating layer 1132 and the insulating layer 1135 may be formed of a material other than a silicon nitride film, for example, a silicon oxide film (SiO ₂ ) or a silicon oxynitride film (SiNO).

  FIG. 4 is a diagram illustrating a planar structure of the electro-optical panel 10. FIG. 4 shows a planar structure of the electro-optical panel 10 as viewed from the front, that is, from the normal direction of the surface of the electro-optical panel 10. FIG. 4 does not show the appearance of the electro-optical panel 10, but merely shows the positions of the pixels and electrodes.

  In this example, the electro-optical panel 10 includes a dot matrix type display element. The electro-optical panel 10 includes m scanning lines 21, n data lines 22, (m × n) pixels 23, a scanning line driving circuit 24, and a data line driving circuit 25. The scanning line driving circuit 24 and the data line driving circuit 25 are controlled by the display controller 20.

  The scanning line 21 is disposed along the row direction (x direction) and transmits a scanning signal. The scanning signal is a signal for sequentially and exclusively selecting one scanning line 21 from the m scanning lines 21. The data line 22 is arranged along the column direction (y direction) and supplies a data voltage to the pixel 23. The scanning line 21 and the data line 22 are insulated. The pixel 23 is provided corresponding to the intersection of the scanning line 21 and the data line 22. In addition, when it is necessary to distinguish one scanning line 21 from the other among the plurality of scanning lines 21, they are referred to as the first row, the second row,. The same applies to the data line 22. When it is necessary to distinguish one pixel 23 among the plurality of pixels 23 from the other pixels 23, the pixel 23 in the i-th row and j-th column is referred to as a pixel (j, i).

  The scanning line driving circuit 24 outputs a scanning signal Y for sequentially and exclusively selecting one scanning line 21 from the m scanning lines 21. The scanning signal Y is, for example, a signal that sequentially becomes a high level exclusively. The data line driving circuit 25 outputs a data signal X. The data signal X is a signal for supplying a data potential for changing the gradation of the pixel. The data line driving circuit 25 outputs a data signal indicating a data voltage corresponding to the pixel in the row selected by the scanning signal.

  In FIG. 4, the wiring formed by the gate electrode layer 1131 is indicated by a solid line, and the wiring formed by the source / drain electrode layer 1134 is indicated by a broken line. That is, the scanning line 21 is formed by the gate electrode layer 1131, and the data line 22 is formed by the source / drain electrode layer 1134. Each pixel 23 has a unique pixel electrode 114. Further, the electro-optical panel 10 includes a parting electrode (peripheral electrode) 26 around the (m × n) pixels 23. The parting electrode 26 is provided in a portion other than the pixel region (outside the region where pixels that can be individually controlled are formed), and a region for displaying the same gradation (region for displaying a predetermined gradation) This is an electrode for forming a so-called parting. The parting electrode 26 is provided in a frame shape around the pixel region so as to surround the pixel region. In this example, the parting is a so-called electric parting out and has the same structure as the pixel 23 electrically. That is, in the region where the pixel 23 and the parting electrode are provided, an electrode is provided so as to sandwich the electrophoretic layer 12 and the adhesive layer 112, and a voltage is applied between the parting electrode 26 and the common electrode 131. The optical state of the electrophoretic layer 12 can be controlled to be white or black and its halftone. Note that the pixel electrode 114 and the parting electrode 26 are formed by the pixel electrode layer 1136. In FIG. 4, the electrode formed by the pixel electrode layer 1136 is indicated by a hatched region.

  In addition, the electro-optical panel 10 includes protection circuits 291 to 293. The protection circuits 291 to 293 are circuits for preventing a short circuit between the electrodes.

  FIG. 5 is a diagram illustrating the planar structure of the electro-optical panel 10, particularly the shape of the common electrode 131. In this example, the common electrode 131 is divided into two regions, a rectangular region corresponding to the pixel region, a frame-like region corresponding to the parting-off. Note that the common electrode 131 may extend from the pixel region to a region overlapping the parting electrode 26.

  In addition, at least a part of the electro-optical panel 10 other than the pixel region is covered with a housing. That is, at least a part of the parting electrode 26 is in a state where it is hidden behind the casing and cannot be seen. For example, the inner edge of the housing is disposed so as to overlap the parting electrode in plan view. In other words, the casing is provided so as to cover the outer edge of the parting electrode 26 when viewed from the display surface side, and the inner edge of the parting electrode 26 is not covered by the casing.

  6 is a diagram illustrating the positional relationship between the pixel region and the housing B in the plan view of FIG. The housing B has a frame shape so as to surround the pixel region.

  FIG. 7 is a diagram illustrating an equivalent circuit of the pixel 23. The pixel 23 includes a TFT 231, a capacitor 232, and an electrophoretic element 233. The electrophoretic element 233 includes the pixel electrode 114, the electrophoretic layer 12, and the common electrode 131. The TFT 231 is an example of a switching element that controls data writing to the pixel electrode 114, and is, for example, an n-channel TFT. The gate, source, and drain of the TFT 231 are electrically connected to the scanning line 21, the data line 22, and the pixel electrode 114, respectively. When a low level scanning signal (non-selection signal) is input to the gate, the source and drain of the TFT 231 are in a high impedance state. When a high-level scanning signal (selection signal) is input to the gate, the source and drain of the TFT 231 are in a low impedance state, and a data voltage is written to the pixel electrode 114. In addition, one electrode of the capacitor 232 is connected to the drain of the TFT 231, and the other electrode of the capacitor 232 is electrically connected to the wiring 27 set to the reference potential Vcom. The capacitor 232 holds a charge corresponding to the data voltage. One pixel electrode 114 is provided for each pixel 23 and faces the common electrode 131. The common electrode 131 is common to all the pixels 23 (the common electrode is continuously provided so as to face the pixel electrodes 114 of all the pixels 23), and the potential EPcom is applied through the wiring 28. The electrophoretic layer 12 is sandwiched between the pixel electrode 114 and the common electrode 131. An electrophoretic element 233 is formed by the pixel electrode 114, the electrophoretic layer 12, and the common electrode 131. A voltage corresponding to the potential difference between the pixel electrode 114 and the common electrode 131 is applied to the electrophoretic layer 12. Hereinafter, the voltage applied to the electrophoretic layer 12, that is, the voltage applied to the pixel 23 is expressed with reference to the common electrode 131.

  In the following description, a unit period from when the scanning line driving circuit 24 selects the first scanning line 21 to when the selection of the m-th scanning line 21 is completed is referred to as “frame”. Each scanning line 21 is selected once per frame, and a data signal is supplied to each pixel 23 once per frame.

  Next, an outline of a method for driving the electro-optical panel 10 will be described. In this example, the time length of one frame is shorter than the response time of the electrophoretic layer 12. The response time of the electrophoretic layer 12 refers to the optical state (for example, relative brightness) of the electrophoretic layer 12 when a predetermined voltage (for example, +15 V) is applied to another reference value (for example, 90%). %) Is the time until the transition. That is, the gradation cannot be changed from the lowest gradation to the highest gradation by applying a voltage for only one frame. Therefore, voltage application is performed over a plurality of frames in order to transition from the current gradation to a desired gradation. The applied voltage in the pixel 23 is any one of a positive voltage (for example, +15 V), a negative voltage (for example, −15 V), and a zero voltage. There are many sequences of combinations (approximately mathematically permutations) of applied voltages in each frame to transition from the current gray level to the desired gray level. It can be said that the voltage application sequence indicates a change with time of the applied voltage. In this sense, this is hereinafter referred to as a “drive waveform”.

  FIG. 8 is a diagram illustrating a drive waveform table. The drive waveform table describes information on applied voltages in a plurality of frames when the display of a pixel is changed from the current gradation to the next gradation. In FIG. 8, “+”, “−”, and “0” indicate a positive voltage, a negative voltage, and a zero voltage, respectively. The drive waveform table shown in FIG. 8 is for the case where all gradation transitions are performed by applying a voltage of 4 frames. The longer of the number of frames required for the transition from the lowest gradation to the highest gradation and the number of frames required for the transition from the highest gradation to the lowest gradation is referred to as “basic frame number”. In the example of FIG. 8, the number of basic frames is four. Note that after the fourth frame, 0 V is applied to discharge the charge held in the capacitor 232.

  FIG. 8 shows one drive waveform table, but in the embodiment according to the present invention, a plurality of different drive waveform tables are used for driving the electro-optical panel. Each of the plurality of drive waveform tables is designed for different purposes such as increasing the rewriting speed and reducing the afterimage. In the following description, one or a plurality of drive waveform tables may be referred to as a drive waveform group. In the following description, a drive waveform group designed for a certain purpose is referred to as a “mode”. For example, a driving waveform for high-speed rewriting is referred to as a first mode driving waveform, and a low afterimage driving waveform is referred to as a second mode driving waveform.

  Since driving of the electro-optic panel 10 is affected by environmental factors (for example, temperature), there are a plurality of driving waveform tables corresponding to a plurality of environmental factors in each mode. For example, one drive waveform table selected from the plurality of drive waveform tables is used according to the use scene and environmental factors. FIG. 8 shows a drive waveform table corresponding to one environmental factor of one mode selected in this way.

  From the applied voltage information recorded in one drive waveform table selected according to the drive waveform mode and environmental factors, the applied voltage information according to the current gradation, the next gradation, and the frame number is obtained. Used. For example, in FIG. 8, when the current gray level and the next gray level are dark gray (DG) and light gray (LG), the negative voltage is output as the data voltage in the second frame. That is, in this example, it can be said that the voltage applied in each frame is determined by the five parameters of the drive waveform mode, environmental factor (temperature), current gradation, next gradation, and frame number. In the following, for the sake of simplicity, an example in which a common drive waveform is used regardless of environmental factors will be described.

  The drive waveform is defined by various parameters in addition to the voltage application sequence (FIG. 8). Hereinafter, these parameters are referred to as driving parameters. The driving parameters include, for example, the following.

(I) Voltage value The voltage value here is the value (absolute value) of the positive voltage and the negative voltage. For example, when + 15V is used as the positive voltage and −15V is used as the negative voltage, 15V is the voltage value. Note that the driving method of the pixel 23 includes a bipolar drive and a unipolar drive. Bipolar driving refers to a driving method in which a pixel to which a positive voltage is applied, a pixel to which a negative voltage is applied, and a pixel to which a zero voltage is applied can be mixed in the same frame. Unipolar driving refers to a driving method in which only one of positive polarity voltage and zero voltage or only one of negative polarity voltage and zero voltage is applied to all pixels in a single frame. The applied voltage of a single frame in the unipolar drive is, for example, 0V and + 30V. The driving parameter may include information indicating whether unipolar driving or bipolar driving is applied.
(Ii) Frequency The frequency here is the frame frequency, that is, the reciprocal of the frame period.
(Iii) Voltage application time The voltage application time here is the length of the drive waveform. In the example of FIG. 8, the length of the drive waveform corresponds to 4 frames.

  FIG. 9 is a diagram illustrating a circuit configuration of the protection circuits 291 to 293. In this example, the circuits shown in FIGS. 9A to 9C are used as the protection circuits 291 to 293, respectively. Note that the circuit shown here is merely an example, and the protection circuits 291 to 293 are not limited thereto.

2. Operation FIG. 10 is a flowchart showing the operation of the electronic apparatus 1000. The flow in FIG. 10 is executed periodically, for example. Alternatively, the flow of FIG. 10 is started when a predetermined event occurs. This event is, for example, an instruction to update the display from the host device 3, or the electronic device 1000 has transitioned from the sleep state to the normal state. The sleep state refers to a part of the electronic device 1000, for example, a state where the high-voltage power supply 36 is off, or a state where the electronic device 1000 consumes less power than a normal state. Even in the sleep state, the low-voltage power supply is kept on, and the drive parameters used in the display update before entering the sleep state and the image data of each of the plurality of pixels representing the current gradation are held. In this way, by limiting the event that triggers the measurement of the leakage current described below, it is possible to reduce the influence on the display.

  In step S100, the CPU 31 of the host apparatus 3 instructs the display controller 20 to update the image. Specifically, the CPU 31 writes the updated image data in the VRAM of the display controller 20 and instructs the display controller 20 to update the image.

  In step S101, the display controller 20 deletes the display. The erasure of display means that all the pixels 23 have a predetermined gradation value. As the predetermined gradation value, for example, a maximum gradation value (for example, white) or a minimum gradation value (for example, black) is used. For erasing the display in step S101, the previous drive parameters and image data held in the logic circuit are used. The previous drive parameter is the drive parameter used when the image displayed on the electro-optical panel 10 was written in step S101. Here, the DC balance can be achieved by erasing the display using the conventional drive parameters. The DC balance is a value obtained by integrating the applied voltage with the voltage application time in each pixel. DC balance means that the integral value is almost zero.

  In step S102, the display controller 20 measures the leak current.

  FIG. 11 is a diagram illustrating the leakage current. Here, the leakage current mainly refers to a current flowing through the adhesive layer 112. Here, the current between the pixel electrode 114 of the pixel 23 located on the outermost periphery in the display area and the parting electrode 26 is measured. The display controller 20 has a current measurement circuit 261 for measuring the current flowing into the parting electrode 26.

  An equivalent circuit of the electrophoretic layer 12 and the adhesive layer 112 is shown on the right side of FIG. An equivalent circuit of the electrophoretic layer 12 and the adhesive layer 112 is connected in series. An equivalent circuit of the electrophoretic layer 12 is represented by a parallel circuit of a resistor RE and a capacitor CE. An equivalent circuit of the adhesive layer 112 is represented by a parallel circuit of a resistor RAD and a capacitor CAD.

  The characteristics of the adhesive layer 112 have temperature dependency, and this temperature dependency affects the display in the electrophoretic layer 12. For example, when the temperature is relatively low, the resistance RAD of the adhesive layer 112 increases, and the effective voltage applied to the electrophoretic layer 12 decreases. Further, when the temperature is relatively high, the resistance of the adhesive layer 112 decreases, and thus the lateral leakage current increases. When the leakage current in the horizontal direction increases, the potential of the adjacent pixel electrode also changes, the display of the adjacent pixel 23 also changes, and the gradation is different and blurring occurs in the display of the adjacent pixel. There is.

  In step S102, the display controller 20 controls to apply a predetermined voltage (first potential, for example, positive voltage) to the pixel electrodes of all the pixels 23 for a predetermined time. Simultaneously with the application of the voltage to the pixel 23, the display controller 20 applies a voltage (second potential lower than the first potential, for example, zero V, or negative voltage) different from that of the pixel 23 to the parting electrode 26. Control. Furthermore, the display controller 20 controls the common electrode 131 to be in a high impedance state. During this time, the current measurement circuit 261 measures the current flowing into the parting electrode 26.

  Refer to FIG. 10 again. In step S103, the display controller 20 compensates the measurement current. That is, the voltage applied to the pixel electrode 114 and the parting electrode 26 is controlled so that a voltage having the same magnitude as that applied in step S102 and a reverse polarity is applied. The DC balance can be maintained by compensating the measurement current.

  In step S104, the display controller 20 calculates a leak resistance, that is, a resistance value of the adhesive layer 112 from the current value measured in step S102. In the calculation of the resistance value, in addition to the measured current value, the voltage applied to the pixel 23 and the flow length of the leak current (distance between the pixel electrode 114 and the parting electrode 26) are used.

  In step S105, the display controller 20 determines a driving parameter to be used next. In this example, the display controller 20 has an LUT that associates a leak resistance with a drive parameter, and determines the drive parameter using this LUT.

  FIG. 12 is a diagram illustrating an LUT. In this example, voltage, frequency, and voltage application time are recorded as LUTs as drive parameters. When the leakage resistance is R1, the corresponding drive parameters are voltage V1, frequency F1, and voltage application time T1. When the calculated leakage resistance value is not recorded in the LUT (for example, when the leakage resistance RL is R1 <RL <R2), the display controller 20 calculates the leakage resistance recorded in the LUT. The drive parameter corresponding to the leak resistance closest to the leaked resistance RL is used. Alternatively, the display controller 20 may determine the drive parameter by linear interpolation.

  As the frequency recorded in the LUT, for example, a value is recorded such that the higher the temperature, the lower the frequency, and the lower the temperature. Thus, by using an appropriate frequency according to the temperature of the adhesive layer, it is possible to obtain an effect of preventing bleeding at a high temperature and an effect of low power consumption at a low temperature.

  In another example, the LUT stores information specifying that bipolar driving is performed when the temperature is higher than the threshold temperature and single driving is performed when the temperature is lower than the threshold temperature. In addition, as a drive waveform at the time of bipolar drive, a drive waveform for writing an updated image after writing an inverted gradation of the image before the update is used. Thereby, the effect of preventing bleeding can be obtained. Further, by using unipolar driving at low temperatures, it becomes possible to apply a higher voltage to the electrophoretic material than in bipolar driving, so that the response delay of the display element can be reduced.

  In yet another example, the display controller 20 may select the drive waveform itself according to the leak resistance instead of or in addition to changing the drive parameter. It can be said that the drive waveform itself is also included in the “drive parameter”.

  Refer to FIG. 10 again. In step S106, the display controller 20 determines whether the new drive parameter determined in step S105 is different from the previous drive parameter. When there are a plurality of drive parameters, if any one of them is different from the previous value, it is determined that the drive parameters are different. When it is determined that the new drive parameter is different from the previous drive parameter (S106: YES), the display controller 20 moves the process to step S107. When it is determined that the new drive parameter is the same as the previous drive parameter (S106: NO), the display controller 20 moves the process to step S108.

  In step S107, the display controller 20 updates the drive parameter. That is, at the time of the subsequent display update, the display controller 20 uses the drive parameter determined in step S105. When the drive parameter is updated, the display controller 20 moves the process to step S108.

  In step S108, the display controller 20 updates the display. That is, the display controller 20 controls the scanning line driving circuit 24 and the data line driving circuit 25 so as to update the gradation of the pixel 23 according to the image data. Note that the determination in step S106 may be omitted, and the drive parameters may be overwritten in all cases.

  As described above, according to the present embodiment, the drive parameter is adjusted using the result of measuring the resistance of the material (adhesive layer 112) constituting the electro-optical panel 10. The drive parameters can be adjusted according to the characteristics. In addition, according to the present embodiment, it is not necessary to provide a temperature sensor in the electro-optical panel 10, so that the electro-optical panel 10 can be further reduced in weight. Furthermore, since the drive parameter is determined using the leakage current measured in a period different from the display update, the influence on the display can be reduced. The leakage current is at least partially performed using the parting electrode 26 hidden behind the casing, and the influence on the display can be reduced as compared with the case where the electrode not hidden behind the casing is used. Further, when an external temperature sensor is used, the temperature sensor can measure the temperature of the casing or the ambient environmental temperature. However, according to this embodiment, the temperature of the element itself can be measured. For example, even when there is a temperature difference between the housing and the electro-optical panel 10, according to the present embodiment, appropriate driving can be performed.

3. Modifications The present invention is not limited to the above-described embodiments, and various modifications can be made. Hereinafter, some modifications will be described. Two or more of the following modifications may be used in combination.

3-1. Modification 1
The flow path for measuring the leakage current is not limited to that described in the embodiment. For example, the display controller 20 may measure a leakage current between a certain pixel 23 and another pixel 23. For example, the pixels connected to adjacent data lines may be set to different voltages, and the leakage current may be measured via the inspection circuit. Alternatively, the electro-optical panel 10 may have two electrodes dedicated to leak current measurement that do not perform gradation display. In this case, the display controller 20 measures the leakage current between these two measurement electrodes. When an electrode dedicated to measuring leakage current is used, the leakage current can be measured at an arbitrary timing independent of the display update in the pixel 23.

3-2. Modification 2
When the reverse voltage is applied (step S103), the display controller 20 may measure the current (reverse current) flowing out from the parting electrode 26. Thereby, the display controller 20 can calculate the leakage resistance when the reverse voltage is applied. In this case, the display controller 20 may determine the drive parameter using the leak resistance measured in step S102 and step S103 (for example, using the average value of both). By measuring the leak resistance twice, a more accurate result can be obtained as compared with the case of measuring only once.

  In step S103, the display controller 20 does not apply a reverse voltage, but flows to the parting electrode 26 so that a current having the same magnitude and a direction opposite to the leakage current (hereinafter referred to as “reverse current”) flows. The voltage to be applied may be controlled. Further, in this case, the display controller 20 may measure the voltage applied to the pixel 23 and the parting electrode 26 and calculate the leakage resistance from the measured voltage value.

  The voltage applied to the parting electrode 26 may be a voltage that becomes the potential EPcom applied to the common electrode 131 at the time of display update S108. In this case, the voltage applied to the pixel 23 is a driving voltage in bipolar driving. In step S102, + 15V is applied to the pixel 23 and EPcom is applied to the parting electrode 26. In step S103, -15V is applied to the pixel 23 and EPcom is applied to the parting electrode 26. In the TFT 231, field through (push-down, punch-through) that lowers the voltage of the drain electrode, that is, the pixel electrode 114 occurs at the moment of turning off from on, but the potential difference between the parting electrode 26 and the pixel electrode 114 in steps S 102 and S 103. Since the (absolute value) is almost the same, the DC balance can be maintained.

3-3. Modification 3
The method for determining the drive parameter is not limited to the method using the LUT. The display controller 20 may determine the drive parameter by using a mathematical expression indicating the leakage resistance dependency (that is, temperature dependency) of the drive parameter. In this case, the display controller 20 stores this mathematical formula, and determines the drive parameter using the calculated leak resistance and this mathematical formula.

3-4. Modification 4
FIG. 13 is a diagram illustrating another example of the planar structure of the electro-optical panel 10. The structure of the electro-optical panel 10 is not limited to that illustrated in FIGS. 4 and 5. FIG. 13A shows the arrangement of the scanning lines 21, the data lines 22, and the TFTs 231. FIG. 13B illustrates the arrangement of the pixel electrode layer 1136 with respect to FIG. Of the TFTs 231 shown in FIG. 13A, the outermost TFT 231 belongs to a pixel that does not function as the pixel 23 (does not contribute to display of an image according to image data), that is, a dummy pixel. As shown in FIG. 13B, for the dummy pixel, the pixel electrode layer 1136 has a continuous continuous shape, and forms a parting electrode (peripheral electrode) 26. For the portion of the pixel structure in FIG. 13A excluding the outermost pixel structure, that is, the pixels in the display region, the pixel electrode layer 1136 has an independent shape for each pixel. Is forming. 4 and 5, the TFT 231 is not provided below the parting electrode 26 (no dummy pixel is provided).

3-5. Other Modifications The flow for determining the drive parameters is not limited to that shown in FIG. For example, the display controller 20 may not delete the display (step S101) before measuring the leakage current. Further, the display controller 20 may not perform compensation of the measurement current (step S103) after the leakage current is measured.

  The voltage applied to the pixel 23 when measuring the leakage current is not limited to that described in the embodiment. At the time of measuring the leakage current, the same voltage (leakage current measurement voltage) may not be applied to the pixel electrodes 114 of all the pixels 23. The voltage for leak current measurement may be applied only to a part of the pixels 23 in the pixel region, for example, the pixel electrode 114 of the pixel 23 located on the outermost periphery of the pixel region.

  Further, at the time of measuring the leakage current, a voltage for measuring the leakage current may be applied only to the pixel electrode 114 of at least the pixels in the first row and the m-th row. That is, by supplying a voltage for current measurement to all the data lines and selecting only the first scanning line and the m-th scanning line, pixels of the pixels connected to the first scanning line and the m-th scanning line are selected. A voltage for current measurement is supplied to the pixel electrode 114.

  The display element used for the electro-optical panel 10 is not limited to an electrophoretic display element using microcapsules. Other memory display elements such as a partition type (microcup) electrophoresis system, an electro-powder fluid, a cholesteric liquid crystal, and an electrochromic may be used.

DESCRIPTION OF SYMBOLS 1 ... Electro-optical apparatus, 3 ... Host apparatus, 10 ... Electro-optical panel, 11 ... 1st board | substrate, 12 ... Electrophoresis layer, 13 ... 2nd board | substrate, 20 ... Display controller, 21 ... Scan line, 22 ... Data line, DESCRIPTION OF SYMBOLS 23 ... Pixel, 24 ... Scanning line drive circuit, 25 ... Data line drive circuit, 26 ... Parting electrode, 27 ... Wiring, 28 ... Wiring, 31 ... CPU, 32 ... RAM, 33 ... Storage device, 34 ... Input / output IF, 35 ... sensor, 36 ... high voltage power supply, 37 ... power supply control unit, 111 ... substrate, 112 ... adhesive layer, 113 ... circuit layer, 114 ... pixel electrode, 121 ... microcapsule, 122 ... binder, 131 ... common electrode, 132 ... Film, 133 ... substrate, 231 ... TFT, 232 ... capacitance, 233 ... electrophoretic element, 261 ... current measurement circuit, 291 ... protection circuit, 1000 ... electronic equipment, 1131, ... Gate electrode layer, 1132 ... insulating layer, 1133 ... semiconductor layer, 1134 ... source-drain electrode layer, 1135 ... insulating layer, 1136 ... pixel electrode layer

Claims (9)

An electro-optic layer;
A pixel electrode;
A measuring electrode;
An adhesive layer formed between the electro-optic layer and the pixel electrode and the measurement electrode;
A measurement unit for measuring a current flowing through the measurement electrode when the pixel electrode and the measurement electrode have different potentials;
And a drive control unit that controls a drive voltage applied to the electro-optic layer based on a measurement result of the measurement unit. The measurement unit controls to apply a reverse voltage having a reverse polarity and a potential difference generated between the first electrode and the second electrode for the same time as the measurement in order to measure the current. The display device according to claim 1. The display device according to claim 2, wherein the measurement unit measures a current when the reverse voltage is applied. A power source used to write data to the electro-optic layer;
A power supply control unit for causing the power supply to transition from one of an operating state and a stopped state to the other,
The display according to any one of claims 1 to 3, wherein the measurement unit performs the measurement when the power supply control unit changes the power supply from the stopped state to the operating state. apparatus. The drive control unit includes at least one of a voltage applied to the electro-optical layer, a frequency that is a reciprocal of a cycle for supplying a voltage to the pixel circuit for applying a voltage to the electro-optical layer, and an application time of the voltage The display device according to claim 1, wherein the display device is determined based on an immediate result of the measurement unit. The drive control unit sets the voltage applied to the electro-optic layer to a positive first voltage, a negative second voltage, and a third voltage that is zero voltage, or a positive or negative first voltage. The display device according to claim 5, wherein switching from one of the one voltage and the second voltage, which is zero voltage, to the other is determined based on a measurement result of the measurement unit. A housing for housing the electro-optic layer;
The display device according to claim 1, wherein at least a part of the measurement electrode is hidden in the housing. A control method for a display device comprising an electro-optic layer, a pixel electrode, a measurement electrode, the electro-optic layer, and an adhesive layer formed between the pixel electrode and the measurement electrode,
Measuring the current flowing through the measurement electrode when the pixel electrode and the measurement electrode have different potentials;
Controlling the drive voltage applied to the electro-optic layer based on the measurement result. A control device for controlling a display device having an electro-optic layer, a pixel electrode, a measurement electrode, the electro-optic layer, and an adhesive layer formed between the pixel electrode and the measurement electrode. ,
An adhesive layer formed between the electro-optic layer and the pixel electrode and the measurement electrode;
A measurement unit for measuring a current flowing through the measurement electrode when the pixel electrode and the measurement electrode have different potentials;
And a drive control unit that controls a drive voltage applied to the electro-optic layer based on a measurement result of the measurement unit.

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