JP2012220820A - Electro-optic device and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electro-optic device with a display having flexibility that can perform display of high quality regardless of a curved degree of the display.SOLUTION: The electro-optic device includes: a pixel electrode (21) provided for each pixel (20) in a display (3); a pixel circuit (24) which is provided for each pixel (20) in the display (3) and is electrically connected to the pixel electrode (21); drive sections (60, 70) for driving the pixel circuit (24); a detection section (300) for detecting a curved degree of the display (3); and a control section (10) for controlling the drive sections (60, 70) to compensate a change in an electrical characteristic of the pixel circuit (24) due to the curve of the display (3) according to the detected curved degree.

Description

  The present invention relates to a technical field of an electro-optical device such as an electrophoretic display device and an electronic apparatus such as electronic paper provided with the electro-optical device.

  As an example of this type of electro-optical device, there is an electrophoretic display (EPD) having flexibility (that is, flexibility) used for a flexible display such as electronic paper. In such an electrophoretic display device, for example, a pixel electrode and a data signal (or data voltage) supplied to the pixel electrode are controlled on a display portion of a flexible substrate such as a plastic film for each pixel. The pixel circuit is formed.

  For example, in Patent Document 1, a displacement caused by flexibility in a display input device including a flexible display unit is detected as a change in electrical characteristics, and input data is determined corresponding to the detected displacement. Technology is disclosed.

JP 2004-46792 A

  In the electrophoretic display device having flexibility as described above, when the display image is rewritten in a state where the electrophoretic display device is bent, the electrical characteristics of the pixel circuit are bending stress (that is, bending stress). There is a technical problem in that there is a risk of rewriting the display image, for example, an afterimage is generated or the display image is not rewritten.

  The present invention has been made in view of the above-described problems, for example, and is, for example, an electro-optical device used in a flexible display, which can perform high-quality display regardless of the bending state of the display unit. It is an object to provide an electro-optical device and an electronic apparatus including such an electro-optical device.

  In order to solve the above problems, an electro-optical device according to the present invention is an electro-optical device that includes a plurality of pixels and includes a flexible display unit, and is provided in the display unit for each pixel. A pixel electrode; a pixel circuit provided in the display unit for each pixel; and electrically connected to the pixel electrode; a drive unit that drives the pixel circuit; and a detection unit that detects a degree of bending of the display unit And a control unit that controls the driving unit so as to compensate for a change in electrical characteristics of the pixel circuit due to the bending of the display unit in accordance with the detected degree of bending.

  The electro-optical device according to the present invention includes a flexible display unit, and is used for a flexible display such as electronic paper. The electro-optical device according to the present invention includes, for example, a flexible substrate such as a plastic film, and a pixel electrode and a pixel circuit are provided for each pixel on the flexible substrate. The pixel circuit includes, for example, a pixel transistor electrically connected to the pixel electrode. According to the electro-optical device of the present invention, during operation, a data voltage corresponding to an image to be displayed, for example, by a driving unit such as a data line driving circuit or a scanning line driving circuit is applied to the pixel electrode of each pixel. The image can be displayed on the display unit. Note that typically, the display portion is provided with a plurality of scanning lines and a plurality of data lines so as to cross each other, and the source of the pixel transistor of the pixel circuit is electrically connected to the data line. The gate electrode of the pixel transistor is electrically connected to the scanning line, and the drain of the pixel transistor is electrically connected to the pixel electrode. During operation of the electro-optical device according to the present invention, a scanning signal is supplied to the gate of the pixel transistor via the scanning line, and a data voltage is supplied to the source of the pixel transistor via the data line, so that the on-state A data voltage is supplied to the pixel electrode through the pixel transistor. By changing the state of the electro-optical material according to the data voltage supplied to the pixel electrode in each pixel, an image can be displayed on the display unit.

  In the present invention, in particular, the degree of bending of the display unit is detected by the detection unit, and the control unit compensates for a change in the electrical characteristics of the pixel circuit due to the bending of the display unit according to the degree of bending detected by the detection unit. In addition, the drive unit is controlled. The detection unit is a bending sensor, for example, and is configured to be able to detect the bending state (for example, curvature) of the display unit. The control unit controls the drive unit in accordance with the degree of bending detected by the detection unit so as to compensate for a change in the electrical characteristics of the pixel circuit due to the bending of the display unit. Therefore, high-quality display can be performed regardless of the bending state of the display unit.

  Here, when the display portion is bent, a bending stress (that is, bending stress) is generated in the pixel circuit, which may change the electrical characteristics of the pixel circuit. Therefore, if no measures are taken and the driving unit drives the pixel circuit regardless of the bending state of the display unit, the data voltage is applied to the pixel electrode via the pixel circuit with the display unit being bent. May not be applied properly, and there may be a problem in rewriting the display image, for example, when an afterimage is generated or the display image is not rewritten when the display image is rewritten on the display unit.

  However, according to the present invention, as described above, the control unit controls the drive unit so as to compensate for the change in the electrical characteristics of the pixel circuit due to the bending of the display unit according to the bending state detected by the detection unit. Since the control is performed, the data voltage can be appropriately applied to the pixel electrode through the pixel circuit even when the display portion is bent. Therefore, for example, it is possible to reduce or prevent the occurrence of problems in rewriting the display image. Therefore, high-quality display can be performed regardless of the bending state of the display unit.

  As described above, according to the electro-optical device according to the present invention, high-quality display can be performed regardless of the bending state of the display unit.

  In one aspect of the electro-optical device according to the present invention, the control unit includes a lookup table in which the bending state and the electrical characteristics of the pixel circuit are associated with each other.

  According to this aspect, the control unit can reliably control the drive unit according to the detected bending condition by referring to the lookup table.

  In another aspect of the electro-optical device according to the aspect of the invention, the pixel circuit includes a pixel transistor, and the control unit compensates for a change in electrical characteristics of the pixel transistor due to bending of the display unit. Control the drive.

  According to this aspect, during the operation of the electro-optical device, the driving unit supplies the scanning signal to the gate of the pixel transistor via the scanning line, and supplies the data voltage to the source of the pixel transistor via the data line. As a result, the data voltage is supplied to the pixel electrode through the pixel transistor turned on. By changing the state of the electro-optical material according to the data voltage supplied to the pixel electrode in each pixel, an image can be displayed on the display unit.

  According to this aspect, the control unit controls the drive unit so as to compensate for a change in the electrical characteristics of the pixel transistor due to the bending of the display unit. Specifically, the control unit controls the drive unit so as to change the time during which the pixel transistor is turned on and the gate voltage or the source voltage of the pixel transistor in accordance with the detected bending state. Therefore, high-quality display can be performed regardless of the bending state of the display unit.

  In the aspect in which the pixel circuit includes a pixel transistor, the control unit may control the driving unit so as to change a time for which the pixel transistor is turned on according to the detected bending state. Good.

  In this case, high-quality display can be more reliably performed regardless of the degree of bending of the display unit.

  In the aspect in which the pixel circuit includes a pixel transistor, the control unit may control the driving unit so as to change a gate voltage of the pixel transistor according to the detected bending state.

  In this case, high-quality display can be more reliably performed regardless of the degree of bending of the display unit.

  In the aspect in which the pixel circuit includes a pixel transistor, the control unit may control the driving unit so as to change a source voltage of the pixel transistor according to the detected bending state.

  In this case, high-quality display can be more reliably performed regardless of the degree of bending of the display unit.

  In another aspect of the electro-optical device according to the invention, the electro-optical device includes a substrate having a flexible region and a non-flexible region, the display unit is formed in the flexible region, and the detection unit includes a differential transistor pair. And a first transistor formed in the flexible region and a second transistor formed in the non-flexible region.

  According to this aspect, the degree of bending of the display unit can be detected with high accuracy by the detection unit. Therefore, the control unit can control the pixel circuit with high accuracy in accordance with the degree of bending detected by the detection unit. Therefore, high-quality display can be more reliably performed regardless of the bending state of the display unit.

  In the aspect in which the detection unit includes the first and second transistors forming a differential transistor pair, the first transistor is provided in each of the plurality of pixels, and is formed in the same process as the pixel transistor. Also good.

  In this case, the degree of bending of the display unit can be detected with higher accuracy by the detection unit. Therefore, the control unit can control the pixel circuit with higher accuracy according to the degree of bending detected by the detection unit.

  In order to solve the above-described problems, an electronic apparatus according to the present invention includes the above-described electro-optical device according to the present invention (including various aspects thereof).

  According to the electronic device of the present invention, the electro-optical device according to the present invention described above is provided, so that high-quality display can be performed, for example, wristwatch, electronic paper, electronic notebook, mobile phone, portable audio device. Various electronic devices such as can be realized.

  The effect | action and other gain of this invention are clarified from the form for implementing invention demonstrated below.

1 is a perspective view illustrating a schematic configuration of an electrophoretic display device according to a first embodiment. It is a block diagram which shows the electric constitution of the principal part of the electrophoretic display device which concerns on 1st Embodiment. FIG. 3 is an equivalent circuit diagram illustrating an electrical configuration of a pixel according to the first embodiment. It is a fragmentary sectional view of the display part of the electrophoretic display device concerning a 1st embodiment. It is a schematic diagram which shows the structure of the microcapsule which concerns on 1st Embodiment. It is a table | surface which shows notionally the lookup table used for the control according to the bending condition of the display part based on 1st Embodiment. It is a figure which shows an example of a mode that the thin-film transistor formed in the plastic film changes an electrical property according to the curvature of a film. It is a perspective appearance figure showing the bending sensor concerning a 1st embodiment typically. It is a figure explaining the circuit of the bending sensor which concerns on 1st Embodiment. It is a figure explaining the timing chart which drives a circuit, when measuring a bending condition with the bending sensor which concerns on 1st Embodiment. It is a perspective view which shows the structure of the electronic paper which is an example of the electronic device to which the electro-optical device is applied. It is a perspective view which shows the structure of the electronic notebook which is an example of the electronic device to which the electro-optical apparatus is applied.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, an electrophoretic display device, which is an example of an electro-optical device according to the invention, is taken as an example.

<First Embodiment>
The electrophoretic display device according to the first embodiment will be described with reference to FIGS.

  First, the overall configuration of the electrophoretic display device according to the present embodiment will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a perspective view illustrating a schematic configuration of the electrophoretic display device according to the present embodiment.

  In FIG. 1, an electrophoretic display device 1 according to the present embodiment is a flexible electrophoretic display device used for a flexible display such as electronic paper, and is configured to be able to perform display on the display unit 3. Has been. The electrophoretic display device 1 includes a flexible region 322 having flexibility and a non-flexible region 321 having no flexibility. The display unit 3 is formed in the flexible region 322.

  FIG. 2 is a block diagram showing an electrical configuration of the main part of the electrophoretic display device 1.

  In FIG. 2, the electrophoretic display device 1 includes a display unit 3, a controller 10, a scanning line driving circuit 60, a data line driving circuit 70, a common potential supply circuit 220, and a bending sensor 300.

  In the display unit 3, m rows × n columns of pixels 20 are arranged in a matrix (in a two-dimensional plane). The display unit 3 includes m scanning lines 40 (that is, scanning lines Y1, Y2,..., Ym) and n data lines 50 (that is, data lines X1, X2,..., Xn). It is provided so as to cross each other. Specifically, the m scanning lines 40 extend in the row direction (that is, the X direction), and the n data lines 50 extend in the column direction (that is, the Y direction). The pixels 20 are arranged corresponding to the intersections of the m scanning lines 40 and the n data lines 50. As will be described in detail later, the display unit 3 is also provided with a detection circuit 310 (see FIGS. 8 and 9) constituting the bending sensor 300.

  The controller 10 controls operations of the scanning line driving circuit 60, the data line driving circuit 70, the common potential supply circuit 220, and the like. The controller 10 is an example of the “control unit” according to the present invention, and controls the scanning line driving circuit 60 and the data line driving circuit 70 in accordance with the bending state of the display unit 3 detected by the bending sensor 300 described later. . The scanning line driving circuit 60 and the data line driving circuit 70 constitute an example of the “driving unit” according to the present invention.

  The scanning line driving circuit 60 sequentially supplies a scanning signal in a pulse manner to each of the scanning lines Y1, Y2,..., Ym under the control of the controller 10.

  The data line driving circuit 70 supplies data signals to the data lines X1, X2,..., Xn under the control of the controller 10. The data signal basically takes one of a reference potential GND (for example, 0 V), a high potential VH (for example, +15 V), or a low potential VL (for example, −15 V). In the present embodiment, basically, a data signal having a low potential VL is supplied to the pixel 20 that should display black, and a data signal having a high potential VH to the pixel 20 that should display white. Is supplied.

  The common potential supply circuit 220 supplies a common potential Vcom (in this embodiment, the same potential as the reference potential GND) to the common potential line 93.

  Note that various signals are input to and output from the controller 10, the scanning line driving circuit 60, the data line driving circuit 70, and the common potential supply circuit 220, but descriptions of those that are not particularly related to the present embodiment are omitted. .

  The bending sensor 300 is a bending sensor configured to be able to detect the bending state (that is, the curvature) of the display unit 300. The bending sensor 300 outputs the detected degree of bending to the controller 10. The specific configuration of the bending sensor 300 will be described later in detail with reference to FIGS.

  FIG. 3 is an equivalent circuit diagram showing an electrical configuration of the pixel 20.

  In FIG. 3, the pixel 20 includes a pixel transistor 24, a pixel electrode 21, a counter electrode 22, an electrophoretic element 23, and a storage capacitor 27. The pixel transistor 24 and the storage capacitor 27 constitute an example of the “pixel circuit” according to the present invention.

  The pixel transistor 24 is configured by an N-type thin film transistor (TFT). The pixel transistor 24 has a gate electrically connected to the scanning line 40, a source electrically connected to the data line 50, and a drain electrically connected to the pixel electrode 21 and the storage capacitor 27. Has been. The pixel transistor 24 supplies a data signal supplied from the data line driving circuit 70 (see FIG. 1) via the data line 50 in a pulse manner from the scanning line driving circuit 60 (see FIG. 1) via the scanning line 40. It outputs to the pixel electrode 21 and the storage capacitor 27 at a timing according to the scanning signal.

  A data signal is supplied to the pixel electrode 21 from the data line driving circuit 70 via the data line 50 and the pixel transistor 24. The pixel electrode 21 is disposed so as to face the counter electrode 22 via the electrophoretic element 23.

  The counter electrode 22 is electrically connected to a common potential line 93 to which a common potential Vcom is supplied.

  The electrophoretic element 23 is composed of a plurality of microcapsules each containing electrophoretic particles.

  The storage capacitor 27 is composed of a pair of electrodes opposed to each other via a dielectric film, one electrode is electrically connected to the pixel electrode 21 and the pixel transistor 24, and the other electrode is electrically connected to the common potential line 93. Connected. The data signal can be maintained for a certain period by the storage capacitor 27.

  Next, a specific configuration of the display unit 3 of the electrophoretic display device 1 will be described with reference to FIGS. 4 and 5.

  FIG. 4 is a partial cross-sectional view of the display unit 3 of the electrophoretic display device 1.

  In FIG. 4, the display unit 3 is configured such that the electrophoretic element 23 is sandwiched between an element substrate 28 and a counter substrate 29. In the present embodiment, description will be made on the assumption that an image is displayed on the counter substrate 29 side.

  The element substrate 28 is a flexible substrate such as a plastic film. On the element substrate 28, although not shown here, a stack in which the pixel transistor 24, the storage capacitor 27, the scanning line 40, the data line 50, the common potential line 93, and the like described above with reference to FIG. 3 are formed. A structure is formed. A plurality of pixel electrodes 21 are provided in a matrix on the upper layer side of the stacked structure. The element substrate 28 may be a flexible substrate made of glass or the like.

  The counter substrate 29 is a transparent flexible substrate made of, for example, a plastic film. On the surface of the counter substrate 29 facing the element substrate 28, the counter electrode 22 is formed in a solid shape so as to face the plurality of pixel electrodes 9a. The counter electrode 22 is made of a transparent conductive material such as magnesium silver (MgAg), indium / tin oxide (ITO), indium / zinc oxide (IZO). The counter substrate 29 may be a flexible substrate made of glass or the like.

  The electrophoretic element 23 is an example of an electro-optical material, and includes a plurality of microcapsules 80 each including electrophoretic particles. The electrophoretic element 23 is opposed to the element substrate 28 by a binder 30 and an adhesive layer 31 made of, for example, resin. It is fixed between the substrates 29. In the electrophoretic display device 1 according to this embodiment, in the manufacturing process, an electrophoretic sheet in which the electrophoretic element 23 is previously fixed to the counter substrate 29 side by the binder 30 is separately manufactured, such as the pixel electrode 21. It is constituted by being bonded by an adhesive layer 31 to the element substrate 28 side on which is formed.

  One or a plurality of microcapsules 80 are sandwiched between the pixel electrode 21 and the counter electrode 22, and are arranged in one pixel 20 (in other words, with respect to one pixel electrode 21).

  FIG. 5 is a schematic diagram showing the configuration of the microcapsule 80. In FIG. 5, a cross section of the microcapsule 80 is schematically shown.

  In FIG. 5, the microcapsule 80 is formed by enclosing a dispersion medium 81, a plurality of white particles 82, and a plurality of black particles 83 inside a coating 85. The microcapsule 80 is formed in a spherical shape having a particle size of about 50 μm, for example.

  The coating 85 functions as an outer shell of the microcapsule 80 and is formed of a translucent polymer resin such as acrylic resin such as polymethyl methacrylate and polyethyl methacrylate, urea resin, gum arabic, and gelatin. .

  The dispersion medium 81 is a medium for dispersing the white particles 82 and the black particles 83 in the microcapsules 80 (in other words, in the coating 85). Examples of the dispersion medium 81 include water, alcohol solvents such as methanol, ethanol, isopropanol, butanol, octanol, and methyl cellosolve, various esters such as ethyl acetate and butyl acetate, and ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. , Aliphatic hydrocarbons such as pentane, hexane and octane, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, benzene, toluene, xylene, hexylbenzene, hebutylbenzene, octylbenzene, nonylbenzene, decylbenzene, undecyl Aromatic hydrocarbons such as benzenes with long chain alkyl groups such as benzene, dodecylbenzene, tridecylbenzene, tetradecylbenzene, etc., halo such as methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, etc. Emissions of hydrocarbons, carboxylate or other oils may be used singly or as a mixture. In addition, a surfactant may be added to the dispersion medium 81.

  The white particles 82 are particles (polymer or colloid) made of a white pigment such as titanium dioxide, zinc white (zinc oxide), and antimony trioxide, and are negatively charged, for example.

  The black particles 83 are particles (polymer or colloid) made of a black pigment such as aniline black or carbon black, and are positively charged, for example.

  For this reason, the white particles 82 and the black particles 83 can move in the dispersion medium 81 by the electric field generated by the potential difference between the pixel electrode 21 and the counter electrode 22.

  These pigments include electrolytes, surfactants, metal soaps, resins, rubbers, oils, varnishes, charge control agents composed of particles such as compounds, titanium-based coupling agents, aluminum-based coupling agents, silanes as necessary. A dispersant such as a system coupling agent, a lubricant, a stabilizer, and the like can be added.

  4 and 5, when a voltage is applied between the pixel electrode 21 and the counter electrode 22 so that the potential of the counter electrode 22 is relatively high, the positively charged black particles 83 are While being attracted to the pixel electrode 21 side in the microcapsule 80 by the Coulomb force, the negatively charged white particles 82 are attracted to the counter electrode 22 side in the microcapsule 80 by the Coulomb force. As a result, the white particles 82 gather on the display surface side (that is, the counter electrode 22 side) in the microcapsule 80, and the color of the white particles 82 (that is, white) is displayed on the display surface of the display unit 3. Will be displayed. Conversely, when a voltage is applied between the pixel electrode 21 and the counter electrode 22 so that the potential of the pixel electrode 21 becomes relatively high, the negatively charged white particles 82 are generated by the Coulomb force. While attracted to the electrode 21 side, the positively charged black particles 83 are attracted to the counter electrode 22 side by Coulomb force. As a result, the black particles 83 are collected on the display surface side of the microcapsule 80, and the color of the black particles 83 (that is, black) is displayed on the display surface of the display unit 3.

  In addition, red, green, blue, etc. can be displayed by replacing the pigment used for the white particle 82 and the black particle 83 with pigments, such as red, green, and blue, for example.

  Next, with reference to FIGS. 6 and 7 in addition to FIGS. 1 to 4, the control according to the bending state of the display unit 3, which is a characteristic control of the electrophoretic display device 1 according to the present embodiment. explain.

  1 to 4, in this embodiment, in particular, the bending state of the display unit 3 (see FIG. 1) is detected by the bending sensor 300 (see FIG. 2), and the controller 10 (see FIG. 2) is detected by the bending sensor 300. The scanning line driving circuit 60 and the data line driving circuit 70 (hereinafter referred to as scanning) so as to compensate for the change in the electrical characteristics of the pixel transistor 24 (see FIG. 3) due to the bending of the display unit 3 according to the detected bending state. The line driving circuit 60 and the data line driving circuit 70 are collectively referred to as a “driving unit” as appropriate. Specifically, the controller 10 has a look-up table 900 as shown in FIG. 6. By referring to the look-up table 900, the bending state of the display unit 3 detected by the bending sensor 300 can be determined. Accordingly, the time for turning on the pixel transistor 24 (that is, the writing time for writing the data signal to the pixel electrode 21, in other words, the pulse width of the scanning signal, hereinafter referred to as “writing time” as appropriate), The gate voltage (that is, the voltage of the scanning signal that turns on the pixel transistor 24) and the source voltage of the pixel transistor 24 (that is, the voltage of the data signal) are controlled.

  FIG. 6 is a table conceptually showing a look-up table 900 used for control according to the degree of bending of the display unit 3.

  In FIG. 6, the look-up table 900 shows that the writing time (that is, the time during which the pixel transistor 24 is turned on), the gate voltage of the pixel transistor 24, and the source voltage of the pixel transistor 24 depend on the bending state of the display unit 3. Stored in advance. More specifically, in the lookup table 900, the writing time when the display unit 3 is bent into a convex shape is the time when the display unit 3 is flat (that is, when the curvature is 0 (zero)). The writing time is set to be shorter than the writing time, and the writing time when the display unit 3 is bent in a concave shape is set to be longer than the writing time when the display unit 3 is flat. In the lookup table 900, the gate voltage when the display unit 3 is bent in a convex shape is set to be lower than the gate voltage when the display unit 3 is flat, and the display unit 3 is concave. The gate voltage when it is bent is set to be higher than the gate voltage when the display unit 3 is flat. In the lookup table 900, the source voltage when the display unit 3 is bent in a convex shape is set to be lower than the source voltage when the display unit 3 is flat, and the display unit 3 is concave. The source voltage when bent to be higher than the source voltage when the display unit 3 is flat is set. Furthermore, in the look-up table 900, the writing time when the display unit 3 is bent into a convex shape is set to be shorter as the magnitude of the curvature is larger, and the display unit 3 is bent into a concave shape. The writing time is set so as to increase as the curvature increases. In the look-up table 900, the gate voltage when the display unit 3 is bent into a convex shape is set to be lower as the curvature increases, and the display unit 3 is bent into a concave shape. The gate voltage is set so as to increase as the curvature increases. In the look-up table 900, the source voltage when the display unit 3 is bent into a convex shape is set so as to decrease as the magnitude of the curvature increases, and the display unit 3 is bent into a concave shape. The source voltage is set so as to increase as the curvature increases.

Note that “the display unit 3 is bent into a convex shape” means that the surface of the element substrate 28 (that is, the surface on the side of the element substrate 28 where the pixel transistors 24 and the like are formed) is convex. Means that the display unit 3 is bent so that the surface of the element substrate 28 is concave.
Here, when the display unit 3 is bent, a bending stress (that is, a bending stress) is generated in the pixel transistor 24, so that the electrical characteristics of the pixel transistor 24 may be changed.

  FIG. 7 is a diagram illustrating an example of a state in which a thin film transistor formed on a plastic film changes electrical characteristics in accordance with the curvature of the film.

  In FIG. 7, the strain applied to the thin film transistor is shown on the x-axis, and the rate of change of on-current at that time is shown on the y-axis. A triangular solid line indicates a characteristic change of the N-type thin film transistor, and a square broken line indicates a characteristic change of the P-type thin film transistor.

  In FIG. 7, the thin film transistor is formed on the film surface. When the film surface is curved so as to have a convex shape with respect to the source / drain direction of the thin film transistor, the thin film transistor is subjected to tensile stress in the source / drain direction and suffers from an elongation strain. On the other hand, when the film surface is curved so as to be concave, the thin film transistor is subjected to compressive stress in the source / drain direction and suffers from shrinkage. The on-characteristics of the transistor change depending on the strain applied. In this embodiment, the pixel transistor 24 is composed of an N-type thin film transistor. Therefore, when the pixel transistor 24 is bent into a convex shape, the on-current increases as the curvature increases, and the pixel transistor 24 is bent into a concave shape. In some cases, the on-current decreases as the curvature increases.

  Therefore, if no measures are taken and the driving unit drives the pixel transistor 24 regardless of the bending state of the display unit 3, the pixel transistor 24 is connected to the pixel electrode 21 with the display unit 3 bent. The data signal cannot be properly supplied via the display, and when the display image is rewritten on the display unit 3, for example, an afterimage is generated or the display image is not rewritten. May occur.

  However, according to the present embodiment, as described above, the bending state of the display unit 3 is detected by the bending sensor 300, and the controller 10 depends on the bending of the display unit 3 according to the bending state detected by the bending sensor 300. The drive unit is controlled so as to compensate for a change in the electrical characteristics of the pixel transistor 24.

  More specifically, in the present embodiment, in particular, the controller 10 refers to the look-up table 900 so that when the display unit 3 is bent into a convex shape, the larger the curvature is, the larger the pixel transistor is. 24 is set to a shorter value, the gate voltage of the pixel transistor 24 is set to a lower value, and the source voltage of the pixel transistor 24 is set to a lower value. Therefore, when the pixel transistor 24 is bent together with the display unit 3, it is possible to reduce or prevent the on-current of the pixel transistor 24 from becoming larger than when the display unit 3 is flat. Therefore, excessive writing of data signals to the pixel electrode 21 can be reduced or prevented. Thereby, a high-quality display becomes possible. In addition, it is possible to reduce or prevent an excessive voltage from being applied to the electrophoretic element 23 and to suppress or prevent deterioration of the electrophoretic element 23. As a result, the reliability of the electrophoretic display device 1 can be improved.

  Further, particularly in the present embodiment, the controller 10 refers to the look-up table 900 so that when the display unit 3 is bent in a concave shape, the writing time of the pixel transistor 24 increases as the curvature increases. A longer value is set, a gate voltage of the pixel transistor 24 is set to a higher value, and a source voltage of the pixel transistor 24 is set to a higher value.

  Therefore, when the pixel transistor 24 is bent together with the display unit 3, it is possible to reduce or prevent the on-current of the pixel transistor 24 from becoming smaller than when the display unit 3 is flat. Therefore, it is possible to reduce or prevent the data signal from being sufficiently written to the pixel electrode 21 (that is, the insufficient writing of the data signal to the pixel electrode 21 occurs). Thereby, a high-quality display becomes possible.

  As described above, according to the electrophoretic display device 1 according to the present embodiment, high-quality display can be performed regardless of the bending state of the display unit 3.

  Next, a specific configuration of the bending sensor 300 according to the present embodiment will be described in detail with reference to FIGS. In the following drawings, the scales are different for each layer and each member so that each layer and each member can be recognized in the drawing.

"Bending sensor overview"
FIG. 8 is a perspective external view schematically showing the bending sensor 300 according to the present embodiment.

  In FIG. 8, the bending sensor 300 according to the present embodiment is formed on an element substrate 28 which is a flexible substrate such as a soft plastic film. The element substrate 28 has a non-flexible region 321 and a flexible region 322. The flexible region 322 has flexibility as the name indicates, and the element substrate 28 having flexibility is used as it is. The non-flexible region 321 does not have flexibility and usually has a fixed shape. In the present embodiment, a hard fixing plate 307 is fixed to a part of the back surface of the element substrate 28, and the element substrate 28 is not bent at that portion to form a non-flexible region 321. In the flexible region 322, a plurality of N-type first thin film transistors TN1 (i, j) (see FIG. 9) are arranged in a matrix to form a detection circuit 310. More specifically, the first thin film transistor TN1 (i, j) is arranged for each pixel 20 one by one. On the other hand, the non-flexible region 321 is provided with an N-type second thin film transistor TN2 (see FIG. 9) and constitutes a part of the output circuit 304. The first thin film transistor TN1 (i, j) and the second thin film transistor TN2 form a differential transistor pair. The second thin film transistor TN2 operates as a reference transistor, and compares the electrical characteristics of the first thin film transistor TN1 (i, j) with the electrical characteristics of the second thin film transistor TN2, thereby comparing the first thin film transistor TN1 (i, j). The bending state of the part (namely, the display part 3) where is arranged is detected. The first thin film transistor TN1 is an example of the “first transistor” according to the present invention, and the second thin film transistor TN2 is an example of the “second transistor” according to the present invention.

  The plurality of first thin film transistors TN1 (i, j) arranged in the detection circuit 310 are sequentially selected by the first selection circuit 351 and the second selection circuit 361 arranged on the outer periphery of the detection circuit 310. One side of the element substrate 28 is defined as a first direction (a direction parallel to the x axis and a row direction), and another direction intersecting (substantially orthogonal to) the first direction is defined as a second direction (on the y axis). The first selection circuit 351 and the first processing circuit 352 are formed along the first direction outside the detection circuit 310, and the second selection circuit 361 and the first processing circuit 352 are formed in parallel. The dual processing circuit 362 is formed along the second direction outside the detection circuit 310. A plurality of first thin film transistors TN1 (i, j) are formed along the first direction and selected by the first selection circuit 351 in the first direction. Similarly, a plurality of first thin film transistors TN1 (i, j) are formed along the second direction and selected by the second selection circuit 361 in the second direction. The first thin film transistors TN1 (i, j) arranged in a matrix are sequentially selected in this way, and their electrical characteristics are compared with the electrical characteristics of the second thin film transistor TN2 each time, thereby measuring the surface distribution related to the bending state. Is done.

"Measurement Principle"
Next, the principle of measuring the degree of bending will be described with reference to FIG. 7 again.

  In FIG. 7, as described above, when the film surface is curved so as to have a convex shape with respect to the source / drain direction of the thin film transistor, the thin film transistor receives a tensile stress in the source / drain direction and suffers an elongation strain. On the other hand, when the film surface is curved so as to be concave, the thin film transistor is subjected to compressive stress in the source / drain direction and suffers from shrinkage. The on-characteristics of the transistor change depending on the strain applied.

In an N-type thin film transistor, the on-current increases when the thin-film transistor receives a tensile stress in the source / drain direction, and the on-current decreases when the thin-film transistor receives a compressive stress. In contrast, in a P-type thin film transistor, the on-current decreases when the thin film transistor is subjected to a tensile stress in the source / drain direction, and the on-current increases when it receives a compressive stress. The increase / decrease amount of the on-current has a linear relationship with the distortion amount. Therefore, if the amount of change in the on-current is detected when the film is bent, the amount of strain ε _T that the thin film transistor covers at that time can be known. On the other hand, the following relational expression holds between the amount of strain ε _T covered by the thin film transistor and the curvature radius R _F of the curved film.

Here, the d _T thickness of the thin film transistor layer, the d _F film thickness, Y _T is the Young's modulus of the thin film transistor layer, Y _F is the Young's modulus of the film. Using Equation 1, if the amount of distortion ε _T is known, the radius of curvature R _F of the film in the field can be determined. By examining the on-current of the first thin film transistor TN1 (i, j) distributed in a planar manner in this way, the surface distribution of the bending state can be measured. Specifically, the radius of curvature R _{Fij at} each point where the first thin film transistor TN1 (i, j) is disposed is determined.

  As shown in FIG. 7, since the amount of change with respect to the on-current distortion is small, in this embodiment, the reference transistor (second thin film transistor TN2) and the first thin film transistor TN1 (i, j) that do not receive bending stress. The difference between the two is differentially amplified, and the amount of bending (the radius of curvature Rij) is measured.

"circuit"
Next, the circuit of the bending sensor 300 will be described with reference to FIG.

  FIG. 9 is a diagram illustrating a circuit of the bending sensor 300 according to the present embodiment.

  As shown in FIG. 8, the bending sensor 300 includes a detection circuit 310, an output circuit 304, a first selection circuit 351, a first processing circuit 352, a second selection circuit 361, and a second processing circuit 362. In the detection circuit 310, first thin film transistors TN1 (i, j) are arranged in a matrix of m rows and n columns. m and n are integers of 1 or more (1 ≦ i ≦ m, 1 ≦ j ≦ n). The first selection circuit 351 selects one specific row line from m row lines R (i) in the first direction. Therefore, the first selection circuit 351 is also a row selection circuit. A shift register or a decoder is used for the first selection circuit 351. The first processing circuit 352 processes the selection signal from the first selection circuit 351 so as to be suitable for measurement. Specifically, a level shifter for converting the selection potential and a buffer for selecting a row line stably at high speed are provided. The second selection circuit 361 selects one specific column line from the n column lines C (j) in the second direction. Therefore, the second selection circuit 361 is also a column selection circuit. A shift register or a decoder is used for the second selection circuit 361. The second processing circuit 362 processes the selection signal from the second selection circuit 361 so as to be suitable for measurement. Specifically, a level shifter for converting the selection potential and a buffer for selecting the column line stably at high speed are provided.

  Returning to FIG.

  In addition, the second processing circuit 362 includes column selection transistors TN3 (j) and TN4 (j). The output circuit 304 amplifies the electrical state of the first thin film transistor TN1 (i, j) and outputs it as LDOUT and XLDOUT. Among these circuits, the detection circuit 310, the output circuit 304, and the column selection transistors TN3 (j) and TN4 (j) in the second processing circuit 362 are formed by thin film transistors. In this embodiment, in addition to these, the first selection circuit 351, the first processing circuit 352, and the second selection circuit 361 are also formed of thin film transistors (N-type and P-type) having a CMOS configuration. Circuits other than the column selection transistors TN3 (j) and TN4 (j) in the circuit 351, the first processing circuit 352, the second selection circuit 361, and the second processing circuit 362 are formed by an external silicon IC chip. Also good.

The first thin film transistor TN1 (i, j) and the second thin film transistor TN2 positioned in the i row and j column form a differential transistor pair and are arranged symmetrically with each other. That is, the drains of both transistors are connected to the first power source and are arranged in parallel with the power source. The first power supply is a positive power supply _Vdd . In addition, as for the source and drain of the N-type thin film transistor, the higher the potential becomes the drain, and the lower the potential becomes the source. In FIG. 9, the source and drain of each thin film transistor are indicated by s and d, respectively. Note that the gate of the first thin film transistor TN1 (i, j) is connected to the row line R (i) of the i-th row, and a selection signal or a non-selection signal is supplied. The reference signal V _ref is supplied to the gate of the second thin film transistor TN2.

The bending sensor 300 further includes a fifth thin film transistor TN5 and a sixth thin film transistor TN6, and the fifth thin film transistor TN5 and the sixth thin film transistor TN6 form a current mirror pair. In the current mirror pair, the sources of both transistors are connected in common, and the same potential is applied to the gate, so that the drain potential of both transistors is slightly increased during saturation operation (V _ds > V _gs −V _th > 0). Even though they are different, they are transistor pairs that carry the same current.

The bending sensor 300 further includes a seventh thin film transistor TN7. The seventh thin film transistor TN7 is a current source transistor. A current source transistor is a transistor that performs a saturation operation and always supplies a constant current even if the drain potential slightly varies. The source of the fifth thin film transistor TN5 and the source of the sixth thin film transistor TN6 are connected to the drain of the seventh thin film transistor TN7, and the source of the seventh thin film transistor TN7 is connected to the second power source. The second power source is a negative power supply _{V ss.} The first control signal Cnt1 is supplied to the gate of the seventh thin film transistor TN7. Since the fifth thin film transistor TN5 and the sixth thin film transistor TN6 always pass the same current and the seventh thin film transistor TN7 supplies a constant current, the fifth thin film transistor TN5 and the sixth thin film transistor TN6 always have the same current (the seventh Half of the current through the thin film transistor TN7).

  The third thin film transistor TN3 (j) and the fourth thin film transistor TN4 (j) located in the jth column are column selection transistors. That is, the third thin film transistor TN3 (j) is disposed between the first thin film transistor TN1 (i, j) and the fifth thin film transistor TN5, and the first thin film transistor TN1 (i, j) and the fifth thin film transistor TN5. Can be electrically connected. The source of the third thin film transistor TN3 (j) is connected to the drain of the fifth thin film transistor TN5, and the drain of the third thin film transistor TN3 (j) is connected to the source of the first thin film transistor TN1 (i, j). As a result, when a selection signal (high potential signal) enters the j-th column line C (j), the first thin film transistor TN1 (i, j) and the fifth thin film transistor TN5 are electrically connected. Conversely, when a non-selection signal (low potential signal) enters the column line C (j), the first thin film transistor TN1 (i, j) and the fifth thin film transistor TN5 are electrically insulated. Similarly, the fourth thin film transistor TN4 (j) is disposed between the second thin film transistor TN2 and the sixth thin film transistor TN6, and can electrically connect the second thin film transistor TN2 and the sixth thin film transistor TN6. . The source of the fourth thin film transistor TN4 (j) is connected to the drain of the sixth thin film transistor TN6, and the drain of the fourth thin film transistor TN4 (j) is connected to the source of the second thin film transistor TN2. As a result, when the selection signal (high potential signal) is input to the column line C (j), the second thin film transistor TN2 and the sixth thin film transistor TN6 are electrically connected. Further, when a non-selection signal (low potential signal) enters the column line C (j), the second thin film transistor TN2 and the sixth thin film transistor TN6 are electrically insulated. The selection signal or non-selection signal supplied to the column line C (j) level-shifts the output from the second selection circuit 361 as necessary, and the output from the level shifter is reinforced by a buffer. That is, the third thin film transistor TN3 and the fourth thin film transistor TN4 are controlled by the second selection circuit 361.

Detection result from the output circuit 304, the drain potential _{V 6} of the sixth thin film transistor TN6 is output as LDOUT, drain potential _{V 5} of the fifth thin film transistor TN5 is output as XLDOUT.

"Measurement method"
Next, a measurement method using the bending sensor 300 will be described with reference to FIG.

  FIG. 10 is a diagram for explaining a timing chart for driving a circuit when the bending state is measured by the bending sensor 300 according to the present embodiment.

In FIG. 10, first, prior to measurement, the potential value of V _ref at the time of measurement is determined. As described above, the bending sensor 300 includes the electrical characteristics of the second thin film transistor TN2 that is located in the non-flexible portion and serves as the reference transistor, and the electrical characteristics of the plurality of first thin film transistors TN1 (i, j) located in the flexible portion. By comparing the characteristics with each other, the degree of bending of the portion where the first thin film transistor TN1 (i, j) is located is detected. On the other hand, a thin film transistor generally has slightly different electrical characteristics for each transistor. In order to correct this, the value of V _ref is determined in order to cancel the variation of each transistor arranged in the detection circuit 310. Specifically, the bending sensor 300 is installed on a flat surface so that the detection circuit 310 is flat. Each first TFT TN1 (i, j) in this state to select (as a row line R (i) a selection signal potential _{H 1,} column line C a (j) and the selection signal potential _{H 2),} LDOUT Output And the value of V _ref for each first thin film transistor TN1 (i, j) are determined so that the output of XLDOUT becomes equal to the output of XLDOUT (V ₅ = V ₆ ). V _ref is a value close to the selection signal potential H ₁ supplied to the row line R (i). When the selection potential to be taken by V _ref when selecting the first thin film transistor TN1 (i, j) is H _rij , this is expressed by the following equation.

Upon detection circuit 310 is flat, provided set all of the first TFT _{TN1 (i, j) V 5} = V 6 become like the _{H rij} against (or theta _ij), which is first to an external controller Store it in non-volatile memory. Thereafter, the detection circuit 310 is aligned with the surface of the object, and the degree of bending of the surface is measured.

  At the time of measurement, the external controller supplies appropriate signals and power to the first selection circuit 351, the first processing circuit 352, the second selection circuit 361, the second processing circuit 362, etc., and as a result, each row line, column line, output The following signals shown in FIG. 10 are supplied to the circuit 304.

Row lines R (1) to R (M) are alternately selected one by one. Normally, selection is made in order from the first row line R (1) to the Mth row line R (M) of the last row. The row line is supplied with the selection signal potential (high potential) H ₁ to the selected lifting, the non-selection signal voltage at the time of non-selection (low potential) L is supplied. The non-selection signal potential L is a potential close to the negative power supply potential V _ss or V _ss and is clearly lower than the high potential. For example, L = V _ss = 0V (ground potential). The selection signal potential is, for example, H ₁ = 5.4V.

In a period in which one row line is selected, column lines (C (1) to C (N)) are alternately selected one by one. Normally, the selection is made in order from the first column line C (1) to the Nth column line C (N) of the last column. The column line is supplied with the selection signal potential (high potential) H ₂ to select lifting, the non-selection signal voltage at the time of non-selection (low potential) L is supplied. The non-selection signal potential L is a potential close to the negative power supply potential V _ss or V _ss and is clearly lower than the high potential. For example, L = V _ss = 0V (ground potential). The selection signal potential is, for example, H ₂ = 7.0V.

In this way, a specific one is selected from the plurality of first thin film transistors TN1 (i, j). At that time, a selection potential H _rij suitable for the selected first thin film transistor TN1 (i, j) is read from the nonvolatile memory and set to V _ref . The selection potential H _rij is set so that the output voltage is V ₅ = V ₆ if the first thin film transistor TN1 (i, j) is flat. Therefore, when the value of V ₅ to V ₆ is read, the selection potential H _rij is selected. It can be seen how the first thin film transistor TN1 (i, j) is bent. For example, if the selected portion is bent in a convex shape, the potential of LDOUT (V ₆ ) is lowered and the potential of XLDOUT (V ₅ ) is raised, so the value of V ₅ -V ₆ is positive. On the other hand, when the selected portion is bent in a concave shape, the potential of LDOUT (V ₆ ) becomes high and the potential of XLDOUT (V ₅ ) becomes low, so the value of V ₅ -V ₆ becomes negative.

"how to use"
When using the bending sensor 300, a preparation period and a measurement period may be provided. The preparation period is a period in which measurement is repeated at a low frequency in preparation for the measurement period. During the measurement period, the bending sensor 300 repeats the measurement with high frequency. In this embodiment, the image storage period is a preparation period, and the measurement period is immediately before the image rewriting period.

  During the preparation period and the measurement period, the bending sensor performs the measurement operation according to the method described in the “Measurement Method” section above, but the measurement frequency is different. In the preparation period, the number of measurements performed within a unit time is small, and this is large in the measurement period. A period for selecting and measuring all the measurement cells arranged in m rows and n columns (TN1 (i, j) is arranged in the measurement cell in i row and j column) is defined as one frame. When the time from one period to the next frame period is the standby period, the measurement frequency is the reciprocal of the sum of the frame period and the standby period (1 / (frame period + standby period)). That is, the measurement frequency in the measurement period is made larger than the measurement frequency in the preparation period. As an example, in the measurement period, the standby period is set to zero, and the frame frequency (reciprocal of the frame period) and the measurement frequency are matched. On the other hand, the standby period in the preparation period is a relatively long time of several milliseconds or more (for example, 1 second), and the measurement frequency in the preparation period is made to substantially coincide with the reciprocal of the standby period.

  By providing such a preparation period and a measurement period, power consumption can be reduced during the preparation period, and time resolution can be maximized during the measurement period. Here, the frame period is the same in both the preparation period and the measurement period, and the standby period is changed. However, the present invention is not limited to this, and the frame period may be changed between the preparation period and the measurement period. That is, the measurement frequency in the measurement period may be increased by setting the clock frequency in the measurement period higher than the clock frequency in the preparation period.

"Transistor size and driving conditions"
Next, with reference to FIG. 9, conditions for realizing high-sensitivity and high-performance measurement will be described. Hereinafter, the first thin film transistor TN1 (i, j) is abbreviated as TN1. Similarly, the second thin film transistor TN2 to the seventh thin film transistor TN7 are also abbreviated. H _rij and θ _ij are also abbreviated as H _r and θ. Note that represents a drain potential of TN3 at _{V 3,} represented by _{7, V} the drain potential of _V 4, TN7 the drain potential of TN4.

Since TN1 and TN2 are differential input pairs, nonlinear operation such as saturation operation is desirable. TN3 and TN4 are column selection transistors, and linear operation is desirable from the viewpoint of widening the output potential range. Thus, for the TN3 and _{TN4, V ds} unless small, _{V 3} ≒ _{V 5} and _{V 4} become ≒ _{V 6} desirably possible. TN5 and TN6 must be in saturation with the current mirror pair. Further, since TN7 is a current source transistor, it must be operated in an arrow-saturated manner.

  First, the symbol of Equation 3 is used to express the current equation of the transistor.

Here, W is the width of the transistor channel formation region, L is the length of the transistor channel formation region, C _ox is the gate insulating film capacitance per unit area, and μ is the mobility. Then, the approximate expression of the saturation characteristic is expressed by Expression 4.

  Further, the approximate expression of the linear characteristic is expressed by Expression 5.

In this embodiment, the threshold voltage of the thin film transistor is represented by _Vth , and it is approximated that the _Vth variation between the thin film transistors is slight. That is, it is approximated that V _{th of} TN1 to TN7 are all equal. Further, it is assumed that _Vth is positive and the entire current (current of TN7) is 2I. First, represent the Z from TN1 TN7 from _{Z 1} in _{Z 7,} these are the relationship in Equation 6.

When Expression 6 is satisfied, when a change in the current of TN1 due to bending is regarded as a change in the gate potential, the difference between the assumed gate potential of TN1 and _Vref is linearly amplified and output. Hereinafter, driving conditions required for each transistor will be examined.

  (1) TN1 is preferably saturated. Therefore, it is desirable that the saturation conditions represented by Expression 7 and Expression 8 are satisfied.

  As a result, the drain current of TN1 is given by

  (2) Saturation operation is desirable for TN2. Therefore, it is desirable that the saturation condition represented by Expression 10 and Expression 11 is satisfied.

  As a result, the drain current of TN2 is as follows.

  (3) TN3 is preferably linear. Therefore, it is desirable that the linear condition expressed by Equation 13 is satisfied.

  As a result, the drain current of TN3 is as follows.

  (4) TN4 is preferably linear. Therefore, it is desirable that the linear condition expressed by Equation 15 is satisfied.

  As a result, the drain current of TN4 is given by

  (5) It is desirable that TN5 operates in saturation. Therefore, it is desirable that the saturation condition expressed by Equation 17 is satisfied.

  As a result, the drain current of TN5 is as follows.

  (6) It is desirable that TN6 operates in saturation. Therefore, it is desirable that the saturation condition expressed by Equation 19 and Equation 20 is satisfied.

  As a result, the drain current of TN6 is as follows.

  (7) It is desirable for TN7 to perform a saturation operation. Therefore, it is desirable that the saturation condition expressed by Equation 22 be satisfied.

  As a result, the drain current of TN7 is as follows.

  Here, in order to satisfy Expression 22, Expression 24 is used.

  For example, δ is about 0.1 V, and ideally less than about 1 V in order to easily satisfy the saturation condition.

  Next, in order to satisfy Expressions 13 and 15, Expression 25 is used.

  As a result, at least Expressions 26 and 27 are satisfied.

  From Equation 23 relating to TN7 and Equation 16 relating to TN4, the following equation is obtained.

  Applying Equation 24 and Equation 25 to Equation 28 yields the following.

  For the right side of Equation 29, Equation 30 is considered.

  Here, Equation 31 is used.

  In this way, Expression 32 is obtained.

That is, TN4 operates linearly when the gate voltage is V _th +1 V or higher. Furthermore, in order to reliably reduce the potential drop at TN4 to less than 0.1 V and to operate TN4 in a linear manner, the following expression should be satisfied.

  Equation 33 is transformed to Equation 34.

  In this case, the relationship of Formula 35 is obtained.

  That is, the linear condition (Formula 15) is clearly satisfied.

  Next, the configuration is determined to satisfy all desirable conditions. Equation (36) is obtained with respect to Equation (23) relating to TN7 and Equation (21) relating to TN6.

  In this way, Expression 37 is obtained from Expression 21 and Expression 23.

  Next, Equation 38 is given to Equation 9 relating to TN1 and Equation 18 relating to TN5.

  In this way, Equation 39 is obtained.

  Based on the discussion of TN7 and TN4 (discussions from Equation 28 to Equation 35), the relationship is expressed by Equation 40 and Equation 41.

  By substituting Equation 41 into Equation 39 and simultaneously with Equation 37, the solutions of Equation 42 and Equation 43 are obtained.

  From Equation 12 regarding TN2 and Equation 21 regarding TN6, Equation 44 is obtained.

  Substituting Equation 37 and Equation 40 into Equation 44 yields Equation 45.

  The following shows how to satisfy each of the conditions that should be satisfied in order to realize high-sensitivity and high-performance measurement.

  Equation 7 as a preferred condition: Equation 7 is obtained from Equation 41 and Equation 42.

  Formula 10 as a suitable condition: Formula 10 is expressed by Formula 46 from Formula 40 and Formula 44.

Formula 8 as a preferred condition: Formula V is positively satisfied if Formula 47 holds because V _th is positive.

Formula 11 as a preferred condition: Formula V is positively satisfied if Formula 48 holds because V _th is positive.

  Formula 13 and Formula 15 as preferred conditions: Formula 13 and Formula 15 are satisfied by Formula 24 and Formula 34.

  Formula 17 as a preferred condition: Formula 17 is expressed by Formula 46 from Formula 42 and Formula 43.

  Formula 19 as a preferred condition: Formula 19 is expressed by Formula 49 from Formula 42 and Formula 45.

  Here, Formula 50 is assumed.

In this way, Equation 19 as the preferred condition is rewritten as Equation 51.

  Formula 22 as a preferred condition: Formula 24 to Formula 22 are expressed as Formula 52.

  When Formula 43 is applied to this, Formula 22 becomes Formula 53.

  By equation 24 this means equation 54.

  Now, the relationship of Equation 55 is assumed.

  Then, the mathematical formula 56 is obtained from the mathematical formula 43 and the mathematical formula 42.

  That is, substantially equal drain voltages are applied to TN1, TN5, and TN7. Similarly, substantially equal drain voltages are applied to TN2, TN6, and TN7. At this time, the relation of Expression 57 is established by Expression 24 and Expression 55.

In summary, the potential relationship is such that the formula 55, the formula 24, the formula 25, the formula 57, the formula 50, and the formula 51 are satisfied. As an example, V _th = 1.5 V, δ = 0.3 V, γ = 0.1 V, V _dd = 5.4 V, H ₁ = 5.4 V, H ₂ = 7 V, H ₃ = 1.8 V , H _r = 5.4 ± θV, 0 ≦ θ <1.5V.

  Regarding the transistor size, Expression 6 and Expression 34, Expression 36, Expression 38 to Expression 58 are used.

  By adopting such electrical relationship and transistor size, highly sensitive and accurate measurement is realized.

  As described above, according to the bending sensor 300, the degree of bending of the display unit 3 can be detected with high accuracy. Therefore, the controller 10 can control the drive unit with high accuracy in accordance with the degree of bending detected by the bending sensor 300. Therefore, according to the electrophoretic display device 1 according to the present embodiment, high-quality display can be more reliably performed regardless of the bending state of the display unit 3.

  In the present embodiment, in particular, the first thin film transistor TN1 (i, j) is provided in each of the plurality of pixels 20 and is formed in the same process as the pixel transistor 24. Therefore, the first thin film transistor TN1 (i, j) and the pixel transistor 24 have almost or completely the same electrical characteristics. Therefore, the bending sensor 300 can detect the degree of bending of the display unit 3 with higher accuracy. As a result, high-quality display can be more reliably performed regardless of the degree of bending of the display unit 3.

<Electronic equipment>
Next, electronic devices to which the above-described electrophoretic display device is applied will be described with reference to FIGS. Below, the case where the electrophoretic display device described above is applied to electronic paper and electronic notebook is taken as an example.

  FIG. 11 is a perspective view illustrating a configuration of the electronic paper 1400.

  As shown in FIG. 11, the electronic paper 1400 includes the electrophoretic display device according to the above-described embodiment as a display unit 1401. The electronic paper 1400 has flexibility, and includes a main body 1402 formed of a rewritable sheet having the same texture and flexibility as conventional paper.

  FIG. 12 is a perspective view illustrating a configuration of the electronic notebook 1500.

  As shown in FIG. 12, an electronic notebook 1500 is one in which a plurality of electronic papers 1400 shown in FIG. 11 are bundled and sandwiched between covers 1501. The cover 1501 includes display data input means (not shown) for inputting display data sent from an external device, for example. Thereby, according to the display data, the display content can be changed or updated while the electronic paper is bundled.

  Since the electronic paper 1400 and the electronic notebook 1500 described above include the electrophoretic display device according to the above-described embodiment, low power consumption and high-quality image display can be performed.

  In addition to these, the electrophoretic display device according to the present embodiment described above can be applied to a display unit of an electronic device such as a wristwatch, a mobile phone, or a portable audio device.

  In addition to the electrophoretic display device, the present invention can also be applied to a display device using an electronic powder fluid.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and an electro-optical device with such a change. In addition, electronic devices are also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 3 ... Display part, 10 ... Controller, 20 ... Pixel, 21 ... Pixel electrode, 22 ... Counter electrode, 24 ... Pixel transistor, 28 ... Element substrate, 29 ... Counter substrate, 40 ... Scanning line, 50 ... Data line, 60 ... Scanning line driving circuit, 70 ... Data line driving circuit, 82 ... White particles, 83 ... Black particles, 220 ... Common potential supply circuit, 300 ... Bending sensor, 310 ... Detection circuit, 321 ... Non-flexible region, 322 ... Flexible Region, TN1 ... first thin film transistor, TN2 ... second thin film transistor, 900 ... lookup table.

Claims (9)

An electro-optical device comprising a plurality of pixels and a flexible display unit,
A pixel electrode provided for each of the pixels in the display unit;
A pixel circuit provided in the display unit for each pixel and electrically connected to the pixel electrode;
A drive unit for driving the pixel circuit;
A detection unit for detecting the degree of bending of the display unit;
An electro-optical device comprising: a control unit that controls the driving unit so as to compensate for a change in electrical characteristics of the pixel circuit due to the bending of the display unit according to the detected bending state. .   The electro-optical device according to claim 1, wherein the control unit includes a look-up table in which the bending state and the electrical characteristics of the pixel circuit are associated with each other. The pixel circuit includes a pixel transistor,
The electro-optical device according to claim 1, wherein the control unit controls the driving unit so as to compensate for a change in electrical characteristics of the pixel transistor due to bending of the display unit.   The electro-optical device according to claim 3, wherein the control unit controls the driving unit so as to change a time for which the pixel transistor is turned on according to the detected bending state. .   5. The electro-optical device according to claim 3, wherein the control unit controls the driving unit so as to change a gate voltage of the pixel transistor according to the detected degree of bending.   6. The control unit according to claim 3, wherein the control unit controls the driving unit to change a source voltage of the pixel transistor according to the detected degree of bending. Electro-optic device. Comprising a substrate having a flexible region and a non-flexible region;
The display unit is formed in the flexible region,
The detection unit includes a first transistor formed in the flexible region and a second transistor formed in the non-flexible region, which form a differential transistor pair. The electro-optical device according to any one of the above.   The electro-optical device according to claim 7, wherein the first transistor is provided for each of the pixels and is formed in the same process as the pixel transistor.   An electronic apparatus comprising the electro-optical device according to claim 1.

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