JP2011232525A - Method of driving electrophoresis display device, electrophoresis display device and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform embedding and reading of secret data by a simple and easy method in an electrophoresis display device.SOLUTION: There is provided a method of driving of an electrophoresis display device that includes a first pixel electrode (21a), a second pixel electrode (21b), a common electrode (22) and an electrophoresis element (23) containing first particles (83) and second particles (84). The method of driving of the electrophoresis display device comprises a first displaying step of displaying a first color by attracting the first particles (83) to the common electrode (22), a second displaying step of displaying a second color by attracting the second particles (84) to the common electrode (22), a third displaying step of displaying a third color by attracting the first particles (83) to the first pixel electrode (21a) while attracting the second particles (84) to the second pixel electrode (21b) and a fourth displaying step of displaying the third color by attracting the second particles (84) to the first pixel electrode (21a) while attracting the first particles (83) to the second pixel electrode (21b). Here, in particular, pixels displaying the third color through the fourth displaying step are embedded with invisible and secret data.

Description

  The present invention relates to an electrophoretic display device driving method, an electrophoretic display device, and a technical field of an electronic apparatus including the electrophoretic display device.

  In this type of electrophoretic display device, an image is generated by moving the electrophoretic particles by applying a potential difference between the pixel electrode and the common electrode provided on each of the pair of substrates sandwiching the electrophoretic element including the electrophoretic particles. Is displayed. The electrophoretic element includes, for example, black particles and white particles, and each of these two types of particles is attracted to the common electrode side, whereby two gradations of black or white are displayed. Furthermore, a technique has been proposed that can display gradations of three or more colors by using electrophoretic particles of colors other than black and white (for example, red and blue), a colored solvent, and the like. (For example, see Patent Documents 1 to 3).

  On the other hand, the electrophoretic display device as described above has a characteristic that it keeps an image once displayed. For this reason, security measures are required for electronic data stored in a memory or the like, and security measures are also required for displayed image data. As a security measure, for example, a technique of embedding a digital watermark in data has been proposed (see, for example, Patent Document 4).

JP 2005-31345 A Japanese translation of PCT publication No. 2005-500571 JP 2009-9092 A JP-A-9-191394

  However, the technique according to Patent Document 4 requires an information processing device having a high-performance and complicated arithmetic processing function such as spatial frequency analysis in order to create and read watermark data. This will increase the cost of introduction. On the other hand, in order to avoid such an increase in cost, the calculation performance must be reduced, but it is insufficient because it is not possible to meet the demand of easily creating a watermark or quickly reading a watermark.

  In particular, in an electrophoretic display device, when the embedded watermark data is read from an image, it is first required to obtain in which part the watermark data is embedded. Therefore, it takes time to obtain and read out another means such as an encryption method. In addition, there is a risk of increasing the cost when the reading device is introduced.

  As described above, the security measures in the electrophoretic display device have technical problems that have various practical disadvantages.

  The present invention has been made in view of the above-described problems, for example, and a method for driving an electrophoretic display device capable of embedding and reading watermark data by an extremely simple method, as well as an electrophoretic display device and an electronic apparatus. It is an issue to provide.

  In order to solve the above problems, the driving method of the electrophoretic display device of the present invention faces the first pixel electrode and the second pixel electrode provided for each pixel, and the first pixel electrode and the second pixel electrode. And a first electrode corresponding to a first color and an electrophoretic element including a second particle corresponding to a second color, the driving method of the electrophoretic display device comprising: the first electrode corresponding to the first color; A first display step of attracting the second particles to the pixel electrode and the second pixel electrode and displaying the first color by attracting the first particles to the common electrode; and the first pixel electrode and the second pixel electrode A second display step of attracting the first particles to the two pixel electrodes and displaying the second color by attracting the second particles to the common electrode; and attracting the first particles to the first pixel electrodes , The second pixel A third display step of displaying the first color and a third color different from the second color by attracting the second particles, and attracting the second particles to the first pixel electrode; A fourth display step for displaying the third color by attracting the first particles to the second pixel electrode, and the pixel for displaying the third color by the fourth display step includes: Unlike the pixels that display the third color in three display steps, hidden data that cannot be seen is embedded.

  According to the driving method of the electrophoretic display device of the present invention, for example, an electrophoretic element is provided between an element substrate provided with a first pixel electrode and a second pixel electrode for each pixel and a counter substrate provided with a common electrode. The electrophoretic display device in which is held is driven. The electrophoretic element has first particles corresponding to the first color and second particles corresponding to the second color, and each particle is attracted to the common electrode side, whereby the first color and the first color. Two colors can be displayed. In addition, the first particle and the second particle are attracted to the first pixel electrode and the second pixel electrode, respectively, so that a third color different from the first color and the second color can be displayed. Yes.

  In the pixel that should display the first color, the first color is displayed by attracting the second particles to the first pixel electrode and the second pixel electrode and attracting the first particles to the common electrode. More specifically, the first particles and the second particles are charged with different polarities, and the first pixel electrode and the second pixel electrode are supplied with a potential having a polarity that attracts the second particles, and the common electrode Is supplied with a polar potential that attracts the first particles. Thereby, the first particles corresponding to the first color can be viewed from the common electrode side, and the first color is displayed in the pixel.

  In the pixel that should display the second color, the first color is attracted to the first pixel electrode and the second pixel electrode, and the second color is displayed by attracting the second particle to the common electrode. More specifically, a potential having a polarity that attracts the first particles is supplied to the first pixel electrode and the second pixel electrode, and a potential having a polarity that attracts the second particles is supplied to the common electrode. Thereby, the second particles corresponding to the second color can be viewed from the common electrode side, and the second color is displayed in the pixel.

  In the pixel that should display the third color, there are two types of pixels, unlike the pixel that should display the first color and the second color. Specifically, in the third display step, the first color is attracted to the first pixel electrode, and the third color is displayed by attracting the second particle to the second pixel electrode. In other words, the first pixel electrode is supplied with a potential having a polarity that attracts the first particles, and the second pixel electrode is supplied with a potential having a polarity that attracts the second particles. As a result, both the first particles corresponding to the first color and the second particles corresponding to the second color cannot be seen from the common electrode side. For example, the third color which is a color of other particles, a solvent, etc. Displayed in pixels.

  On the other hand, in the fourth display step, the second color is attracted to the first pixel electrode, and the third color is displayed by attracting the first particle to the second pixel electrode. That is, a potential having a polarity that attracts the second particles is supplied to the first pixel electrode, and a potential having a polarity that attracts the first particles is supplied to the second pixel electrode. As a result, both the first particle corresponding to the first color and the second particle corresponding to the second color cannot be seen from the common electrode side, and the third color is displayed in the pixel as in the third display step. The

  Particularly in the present invention, there are two types of pixels as described above even if the pixels display the same third color. That is, there are pixels that display the third color in the third display step, and pixels that display the third color in the fourth display step. These pixels differ only in whether the first particles and the second particles are attracted to the first pixel electrode or the second pixel electrode, and are indistinguishable when viewed from the common electrode side. Therefore, by using these two types of pixels properly, it is possible to embed secret data that cannot be visually recognized in the display image.

  Specifically, the pixel in which the confidential data is not embedded is in a state in which the first particles are attracted to the first pixel electrode and the second particles are attracted to the second pixel electrode by the third display process. On the other hand, the pixel in which the confidential data is embedded is brought into a state in which the second particles are attracted to the first pixel electrode and the first particles are attracted to the second pixel electrode by the fourth display process. In this way, although each pixel displays the third color, it surely becomes a pixel having a different particle state. Therefore, a viewer who browses an image in which secret data is embedded by the data creator cannot visually determine the presence or absence of the secret data or where the secret data exists.

  When the embedded confidential data is read from the display image, for example, the pixel in which the confidential data is embedded (that is, the second particles are attracted to the first pixel electrode by the fourth display step, and the second pixel electrode is It is only necessary to supply a potential that changes the color displayed only in the pixel in which the first particles are attracted. In this way, only the color of the pixel in which the confidential data is embedded is changed without changing the color of the pixel in which the confidential data is not embedded. Thus, the viewer can visually determine the confidential data.

  As described above, according to the driving method of the electrophoretic display device of the present invention, it is possible to embed secret data and read secret data by a very simple method.

  In one aspect of the driving method of the electrophoretic display device of the present invention, in the pixel in which the third color is displayed by the third display step and the fourth display step, a predetermined potential is applied to the first pixel electrode. , By supplying the second particle attracted to the first pixel electrode by the fourth display step to the common electrode side, thereby providing a secret data reading step that makes the second particle visible.

  According to this aspect, when a viewer who browses an image tries to read confidential data embedded in the image, a predetermined potential is supplied to the first pixel electrode. Here, the “predetermined potential” is a potential having a polarity opposite to the polarity with which the second particles are charged. Therefore, when a predetermined potential is supplied to the first pixel electrode, the pixel in which the secret data is embedded (that is, the second particle is attracted to the first pixel electrode, and the first particle is attracted to the second pixel electrode). In the state pixel), a force that pushes out the second particle acts on the first pixel electrode. In other words, the second particles that have been attracted to the first pixel electrode are attracted toward the common electrode or the second pixel electrode. Therefore, the viewer can see the second particles from the common electrode side.

  On the other hand, in a pixel in which confidential data is not embedded (that is, a pixel in which the first particles are attracted to the first pixel electrode and the first particles are attracted to the second pixel electrode), the first pixel electrode Even if a force that pushes out two particles works, since the second particles are not attracted to the first pixel electrode, the particle state does not change. In other words, neither the first particles attracted to the first pixel electrode nor the second particles attracted to the second pixel electrode move. Therefore, when viewed from the viewer, the pixels in which the confidential data is not embedded do not change.

  As described above, in this aspect, since the color can be changed only in the pixel in which the confidential data is embedded, it is possible to reliably read the confidential data that cannot be visually recognized. Further, since it is sufficient to supply a predetermined potential to all the pixels displaying the third color, the viewer can easily read the confidential data without knowing in which part the confidential data is embedded. be able to.

  In order to solve the above problems, an electrophoretic display device according to the present invention is arranged so that a first pixel electrode and a second pixel electrode provided for each pixel are opposed to the first pixel electrode and the second pixel electrode. A common electrode, an electrophoretic element including a first particle corresponding to a first color and a second particle corresponding to a second color, the first pixel electrode and the second pixel electrode, and the common electrode A control unit that controls to display an image by supplying a potential to each of the first and second pixel electrodes. The control unit attracts the second particles to the first pixel electrode and the second pixel electrode, and First display means for displaying a first color by attracting the first particles to the electrode; attracting the first particles to the first pixel electrode and the second pixel electrode; and Second color by attracting particles Different from the first color and the second color by attracting the first particles to the first pixel electrode and attracting the second particles to the second pixel electrode, the second display means for displaying Third display means for displaying a third color, and a second color for attracting the second particles to the first pixel electrode and for displaying the third color by attracting the first particles to the second pixel electrode. The pixel that displays the third color by the fourth display means is different from the pixel that displays the third color by the third display means and cannot be visually recognized. Confidential data is embedded.

  In the electrophoretic display device of the present invention, for example, an electrophoretic element is sandwiched between an element substrate provided with a first pixel electrode and a second pixel electrode for each pixel and a counter substrate provided with a common electrode. . The electrophoretic element has first particles corresponding to the first color and second particles corresponding to the second color, and each particle is attracted to the common electrode side, whereby the first color and the first color. Two colors can be displayed. In addition, the first particle and the second particle are attracted to the first pixel electrode and the second pixel electrode, respectively, so that a third color different from the first color and the second color can be displayed. Yes.

  In the present invention, the control unit drives the pixels described above. For example, the control unit is provided as an integrated circuit on a flexible substrate electrically connected to a pair of substrates, and controls the entire operation of the apparatus. In particular, the control unit performs the same operation as each step in the driving method of the electrophoretic display device of the present invention described above. Therefore, as in the case of the driving method of the electrophoretic display device of the present invention, it is possible to embed secret data and read secret data by a very simple method.

  In addition, the control unit of the present invention may be configured to include a secret data reading unit that performs an operation corresponding to the secret data reading process which is an aspect of the driving method of the electrophoretic display device of the present invention described above. In this case, the viewer of the image can read out the confidential data more reliably and easily.

  In one aspect of the electrophoretic display device of the present invention, the electrophoretic element includes uncharged third particles corresponding to the third color.

  According to this aspect, since the electrophoretic element includes the uncharged third particles corresponding to the third color, the first particles and the second particles are attracted to the first pixel electrode and the second pixel electrode, respectively. If it is, the third color corresponding to the third particle that is not attracted to any electrode is displayed on the common electrode side. Accordingly, it is possible to reliably display three types of colors with a relatively simple device configuration.

  In another aspect of the electrophoretic display device of the present invention, the electrophoretic element includes a solvent corresponding to the third color.

  According to this aspect, since the electrophoretic element includes the solvent corresponding to the third color, when the first particles and the second particles are attracted to the first pixel electrode and the second pixel electrode, respectively. The third color which is the color of the solvent is displayed on the common electrode side. Accordingly, it is possible to reliably display three types of colors with a relatively simple device configuration.

  In another aspect of the electrophoretic display device of the present invention, the first pixel electrode and the second pixel electrode have translucency.

  According to this aspect, since the first pixel electrode and the second pixel electrode have translucency, the first pixel electrode and the second pixel electrode are not seen from the first pixel electrode and the second pixel electrode side. , You can see which color particles are attracted. That is, the embedded confidential data can be confirmed from a different side than usual.

  In the above configuration, if only the data creator side can see the back side (that is, the first pixel electrode and the second pixel electrode side), only the data creator can check the secret data using the back side. Can be configured. Alternatively, if only the viewer who wants to browse the secret data can see the back side, the confirmation from the back side can be used as the secret data reading means.

  In another aspect of the electrophoretic display device of the present invention, the first pixel electrode and the second pixel electrode have light shielding properties.

  According to this aspect, since the first pixel electrode and the second pixel electrode have a light shielding property, the first pixel electrode and the second pixel electrode have a light shielding property, as viewed from the first pixel electrode and the second pixel electrode side. It is not possible to see which colored particles are attracted. In other words, the embedded confidential data cannot be confirmed from a different side. Therefore, it is possible to increase the security of confidential data.

  Even if the first pixel electrode and the second pixel electrode are not light-shielding, any member existing on the first pixel electrode and second pixel electrode side as viewed from the electrophoretic element has light-shielding properties. If it does, the same effect can be acquired. From the viewpoint of improving security, it is preferable that not only the first pixel electrode and the second pixel electrode but also many members existing on the first pixel electrode and second pixel electrode side have a light shielding property. .

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

  According to the electronic apparatus of the present invention, since the electro-optical device according to the present invention described above is provided, watermark data can be embedded and read out by a simple method, for example, wristwatch, electronic paper, electronic notebook, mobile phone Various electronic devices such as portable audio devices 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 plan view showing an overall configuration of an electrophoretic display device according to an embodiment. 3 is an equivalent circuit diagram illustrating an electrical configuration of a pixel in the electrophoretic display device according to the embodiment. FIG. It is a fragmentary sectional view of the display part of the electrophoretic display device concerning an embodiment. It is a conceptual diagram which shows the electrophoretic particle at the time of writing of the pixel which performs black display. It is a conceptual diagram which shows the electrophoretic particle at the time of writing of the pixel which performs red display. It is a conceptual diagram (the 1) which shows the electrophoretic particle at the time of writing of the pixel which performs a white display. It is a conceptual diagram (the 2) which shows the electrophoretic particle at the time of writing of the pixel which performs a white display. It is a conceptual diagram which shows the electrophoretic particle at the time of secret data reading of the pixel which performs black display. It is a conceptual diagram which shows the electrophoretic particle at the time of secret data reading of the pixel which performs red display. It is a conceptual diagram (the 1) which shows the electrophoretic particle at the time of secret data reading of the pixel which performs white display. It is a conceptual diagram (the 2) which shows the electrophoretic particle at the time of secret data reading of the pixel which performs white display. It is a matrix figure which shows the written data according to a kind. It is a matrix figure which shows the display color at the time of writing according to a kind. It is a matrix figure which shows the display color at the time of secret data reading according to a kind. It is a top view which shows the electronic paper lottery at the time of distribution. It is a top view which shows the electronic paper lot at the time of data reading.

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

<Electrophoretic display device and driving method thereof>
An electrophoretic display device and a driving method thereof according to the present embodiment will be described with reference to FIGS. In the following embodiments, a TFT active matrix driving type electrophoretic display device will be described as an example of the electrophoretic display device of the present invention.

  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 block diagram showing the overall configuration of the electrophoretic display device according to this embodiment.

  In FIG. 1, the electrophoretic display device 1 according to the present embodiment includes a display unit 3, a controller 10, a scanning line driving circuit 60, a data line driving circuit 70, and a common potential supply circuit 220.

  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 first data lines 50 (that is, data lines X1, X2,..., Xn). And n second data lines 200 (that is, data lines K1, K2,..., Kn) are 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 first data lines 50 and the second data lines 200 are in the column direction (that is, the Y direction). It extends to. Pixels 20 are arranged corresponding to the intersections of the m scanning lines 40 and the n first data lines 50 and the second data lines 200.

  The controller 10 controls operations of the scanning line driving circuit 60, the data line driving circuit 70, and the common potential supply circuit 220. For example, the controller 10 supplies timing signals such as a clock signal and a start pulse to each circuit.

  Based on the timing signal supplied from the controller 10, the scanning line driving circuit 60 sequentially supplies a scanning signal in a pulse manner to each of the scanning lines Y1, Y2,.

  The data line driving circuit 70 supplies image signals to the first data lines X1, X2,..., Xn and the second data lines K1, K2,. The image signal takes a binary potential of a high potential VH (for example, 15 V) or a low potential VL (for example, 0 V).

  The common potential supply circuit 220 supplies the common potential Vcom to the common potential line 93. Note that the common potential Vcom may be a constant potential, or may vary depending on, for example, the gradation to be written.

  In the present embodiment, as will be described later, the pixel 20 is supplied with the same potential as the common potential Vcom. This may be realized, for example, by setting the common potential Vcom output from the common potential supply circuit 220 to the same potential as the high potential VH or the low potential VL, or from the data line driving circuit 70 to the high potential VH and In addition to the low potential VL, another potential that is the same as the common potential Vcom may be supplied.

  Various signals are input / output to / from the controller 10, the scanning line driving circuit 60, the data line driving circuit 70, and the common potential supply circuit 220. However, those not particularly related to the present embodiment are not described here. .

  FIG. 2 is an equivalent circuit diagram illustrating the electrical configuration of the pixel.

  In FIG. 2, the pixel 20 includes a first transistor 24a and a second transistor 24b, a first pixel electrode 21a and a second pixel electrode 21b, a common electrode 22, an electrophoretic element 23, a first storage capacitor 27a and a second storage capacitor 27a. And a storage capacitor 27b.

  The first transistor 24a and the second transistor 24b are composed of, for example, N-type transistors.

  The first transistor 24a has its gate electrically connected to the scanning line 40, its source electrically connected to the data line 50, and its drain being the first pixel electrode 21a and the first storage capacitor 27a. Is electrically connected. The first transistor 24a pulses an image signal supplied from the data line driving circuit 70 (see FIG. 1) via the first data line 50 via the scanning line 40 from the scanning line driving circuit 60 (see FIG. 1). Is output at a timing corresponding to the scanning signal supplied.

  The second transistor 24b has its gate electrically connected to the scanning line 40, its source electrically connected to the second data line 200, and its drain being the second pixel electrode 21b and the second holding line. The capacitor 27b is electrically connected. The second transistor 24b corresponds to an image signal supplied from the data line driving circuit 70 via the second data line 200 in accordance with a scanning signal supplied in a pulse form from the scanning line driving circuit 60 via the scanning line 40. Output at timing.

  The first pixel electrode 21 a and the second pixel electrode 21 b are arranged to face the common electrode 22 with the electrophoretic element 23 interposed therebetween. An image signal is supplied to the first pixel electrode 21a from the data line driving circuit 70 via the first data line 50 and the first transistor 24a. An image signal is supplied from the data line driving circuit 70 to the second pixel electrode 21b via the second data line 200 and the second transistor 24b.

  The common 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 cells each containing electrophoretic particles.

  The first storage capacitor 27a and the second storage capacitor 27b are composed of a pair of electrodes arranged to face each other with a dielectric film interposed therebetween. One electrode of the first storage capacitor 27 a is electrically connected to the first transistor 24 a and the first pixel electrode 21 a, and the other electrode is electrically connected to the common potential line 93. The second storage capacitor 27 b has one electrode electrically connected to the second transistor 24 b and the first pixel electrode 21 b and the other electrode electrically connected to the common potential line 93. According to the first storage capacitor 27a and the second storage capacitor 27b, the image signal can be maintained for a certain period.

  Next, a specific configuration of the display unit of the electrophoretic display device according to the present embodiment will be described with reference to FIG.

  FIG. 3 is a partial cross-sectional view of the display unit of the electrophoretic display device according to this embodiment.

  In FIG. 3, the display unit 3 is configured such that an 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 substrate made of, for example, glass or plastic. Although not shown here on the element substrate 28, the first transistor 24a and the second transistor 24b, the first storage capacitor 27a and the second storage capacitor 27b, which are described above with reference to FIG. A stacked structure in which the first data line 50, the second data line 200, the common potential line 93, and the like are formed is formed. A plurality of first pixel electrodes 21a and second pixel electrodes 21b are provided in a matrix on the upper layer side of the stacked structure.

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

  A partition wall 88 for partitioning pixels is formed between the element substrate 28 and the counter substrate 29. In a region surrounded by the element substrate 28, the counter substrate 29, and the partition wall 88 (hereinafter also referred to as “cell”), a dispersion medium 81, a plurality of white particles 82 dispersed in the dispersion medium 81, and a plurality of black particles 83 and a plurality of red particles 84 are enclosed. That is, the electrophoretic element 23 includes a dispersion medium 81, white particles 82, black particles 83, and red particles 84.

  The electrophoretic element 23 may be configured to have one microcapsule for each pixel. In this case, the dispersion medium 81, white particles 82, black particles 83, and red particles 84 are enclosed in the microcapsules. The microcapsules are fixed between the element substrate 28 and the counter substrate 29 by a binder and an adhesive layer made of, for example, resin.

  The dispersion medium 81 is a medium in which the white particles 82, the black particles 83, and the red particles 84 are dispersed in the cell. 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, cycloaliphatic 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 particle 82 is an example of the “third particle” in the present invention, and is a particle (polymer or colloid) made of a white pigment such as titanium dioxide, zinc white (zinc oxide), antimony trioxide, or the like. The white particles 82 are not charged, for example.

  The black particles 83 are an example of the “first particles” in the present invention, and are particles (polymer or colloid) made of a black pigment such as aniline black or carbon black. The black particles 83 are negatively charged, for example.

  The red particle 84 is an example of the “second particle” in the present invention, and is a particle made of a red pigment such as quinacridone red or cadmium red. The red particles 84 are positively charged, for example.

  According to the configuration described above, the black particles 83 and the red particles 84 move in the dispersion medium 81 by the electric field generated by the potential difference between the first pixel electrode 21 a and the second pixel electrode 21 b and the common electrode 22. Can do. On the other hand, the uncharged white particles 82 move in the dispersion medium 81 relatively uniformly regardless of the electric field.

  In addition, these particles include a charge control agent composed of particles of electrolyte, surfactant, metal soap, resin, rubber, oil, varnish, compound, etc., titanium coupling agent, aluminum coupling agent as necessary. A dispersant such as a silane coupling agent, a lubricant, a stabilizer, and the like can be added.

  Moreover, green, blue, etc. can be displayed by replacing the pigment used for the white particle 82, the black particle 83, and the red particle 84 with pigments, such as green and blue, for example. Further, instead of the white particles 82, a dispersion medium 81 colored in white can be used.

  Next, a driving method of the electrophoretic display device according to the present embodiment will be described with reference to FIGS. In the following, only the steps unique to the present embodiment will be described in detail, and description of other steps will be omitted as appropriate.

  First, the display data writing operation will be described with reference to FIGS.

  FIG. 4 is a conceptual diagram showing electrophoretic particles at the time of writing in a pixel that performs black display.

  In FIG. 4, when black is written in the pixel 20, a voltage is applied so that the potentials of the first pixel electrode 21 a and the second pixel electrode 21 b are relatively lower than the potential of the common electrode 22. Thereby, positively charged red particles 84 are attracted to the first pixel electrode 21a and the second pixel electrode 21b. On the other hand, negatively charged black particles 83 are attracted to the common electrode 22. As a result, the black particles 83 gather on the display surface side (that is, the common electrode 22 side) in the cell, and the color of the black particles 83 (that is, black) is displayed on the display surface of the display unit 3. Will be.

  FIG. 5 is a conceptual diagram showing electrophoretic particles at the time of writing in a pixel that performs red display.

  In FIG. 5, when red is written in the pixel 20, a voltage is applied so that the potentials of the first pixel electrode 21 a and the second pixel electrode 21 b are relatively higher than the potential of the common electrode 22. Thereby, negatively charged black particles 83 are attracted to the first pixel electrode 21a and the second pixel electrode 21b. On the other hand, the positively charged red particles 84 are attracted to the common electrode 22. As a result, the red particles 84 gather on the display surface side (that is, the common electrode 22 side) in the cell, and the color of the red particles 84 (that is, red) is displayed on the display surface of the display unit 3. Will be.

  FIG. 6 is a conceptual diagram (part 1) illustrating electrophoretic particles at the time of writing in a pixel that performs white display.

  In FIG. 6, when white is written in the pixel 20, a voltage is applied so that the potential of the first pixel electrode 21a is relatively higher than the potential of the second pixel electrode 21b. As a result, the negatively charged black particles 83 are attracted to the first pixel electrode 21a. On the other hand, the positively charged red particles 84 are attracted to the second pixel electrode 21b. Further, the common electrode 22 is not supplied with a potential. As a result, the white particles 82 which are uncharged particles gather relatively on the display surface side (that is, the common electrode 22 side) in the cell, and the white particles 82 are collected on the display surface of the display unit 3. A color (that is, white) will be displayed.

  FIG. 7 is a conceptual diagram (part 2) illustrating electrophoretic particles at the time of writing in a pixel that performs white display.

  In FIG. 7, when white is written in the pixel 20, it is possible to display white by a method different from the method shown in FIG. Specifically, the voltage is applied so that the potential of the first pixel electrode 21a is relatively lower than the potential of the second pixel electrode 21b. As a result, the positively charged red particles 84 are attracted to the first pixel electrode 21a. On the other hand, negatively charged black particles 83 are attracted to the second pixel electrode 21b. Further, the common electrode 22 is not supplied with a potential. As a result, the white particles 82 which are uncharged particles gather relatively on the display surface side (that is, the common electrode 22 side) in the cell, and the white particles 82 are collected on the display surface of the display unit 3. A color (that is, white) will be displayed.

  In this embodiment, as described above, there are two methods even when displaying the same white color. That is, there is a method for displaying white by the method shown in FIG. 6 and a method for displaying white by the method shown in FIG. The pixels 20 displaying white by these methods differ only in whether the black particles 83 and the red particles 84 are attracted to the first pixel electrode 21a or the second pixel electrode 21b. It is indistinguishable from what you see. Therefore, by using these two types of pixels 20 properly, it is possible to embed secret data that cannot be visually recognized in the display image.

  Specifically, in the pixel 20 in which the confidential data is not embedded, the black particles 83 are attracted to the first pixel electrode 21a and the red particles 84 are attracted to the second pixel electrode 21b by the method illustrated in FIG. It is said. On the other hand, the pixel 20 in which the confidential data is embedded is in a state in which the red particles 84 are attracted to the first pixel electrode 21a and the black particles 83 are attracted to the second pixel electrode 21b by the method shown in FIG. . In this way, each pixel is surely a pixel having a different particle state even though both pixels display white. Accordingly, it is possible to reliably embed the confidential data so that the image viewer cannot visually determine whether the confidential data exists or where the confidential data exists.

  Next, with reference to FIG. 8 to FIG. 11, the read operation of the embedded secret data will be described.

  FIG. 8 is a conceptual diagram showing electrophoretic particles at the time of reading secret data of pixels performing black display.

  In FIG. 8, when the secret data is read by the pixel 20 displaying black, a positive potential is supplied to the first pixel electrode 21a. On the other hand, no potential is supplied to the second pixel electrode 21 b and the common electrode 22. However, the switches for switching on and off the supply of potential to the first pixel electrode 21a and the second pixel electrode 21b are both turned off, and the potential of each electrode does not change. Therefore, each particle does not move and the display remains black.

  FIG. 9 is a conceptual diagram showing the electrophoretic particles at the time of reading the secret data of the pixel performing red display.

  In FIG. 9, when the secret data is read by the pixel 20 displaying red, a positive potential is supplied to the first pixel electrode 21a. On the other hand, no potential is supplied to the second pixel electrode 21 b and the common electrode 22. However, the switches for switching on and off the supply of potential to the first pixel electrode 21a and the second pixel electrode 21b are both turned off, and the potential of each electrode does not change. Therefore, each particle does not move and the display remains red.

  FIG. 10 is a conceptual diagram (No. 1) showing electrophoretic particles at the time of reading secret data of pixels that perform white display.

  In FIG. 10, in the pixel 20 that displays white in which the confidential data is not embedded, a positive potential is supplied to the first pixel electrode 21 a when the confidential data is read. On the other hand, no potential is supplied to the second pixel electrode 21 b and the common electrode 22. Here, in particular, since the black particles 83 that are already negatively charged at the time of writing are attracted to the first pixel electrode 21a (see FIG. 6), each particle does not move. Therefore, the display remains white.

  FIG. 11 is a conceptual diagram (No. 2) showing the electrophoretic particles at the time of reading the secret data of the pixel that performs white display.

  In FIG. 11, in the pixel 20 displaying the white color in which the confidential data is embedded, a positive potential is supplied to the first pixel electrode 21a when the confidential data is read. On the other hand, no potential is supplied to the second pixel electrode 21 b and the common electrode 22. As a result, the potential of the first pixel electrode 21a is relatively higher than the potentials of the second pixel electrode 21b and the common electrode 22, so that negatively charged black particles 83 are attracted to the first pixel electrode 21a. Further, the red particles 84 attracted to the first pixel electrode 21a at the time of writing move to the second pixel electrode 21b and the common electrode 22 side having a low potential. Therefore, the color displayed on the display unit 3 is a color obtained by mixing the white particles 83 with the red particles 84 (pinkish white).

  As described above, when the secret data is read, regardless of how many colors are displayed in the pixel 20, if a positive potential is supplied to the first pixel electrode 21a, the pixel in which the secret data is embedded is used. Only the displayed color changes. Therefore, it is possible to read secret data very easily and reliably.

  The above-described pixels 20 (ie, black display, red display, white display without confidential data, and white display with confidential data) are summarized as follows.

  FIG. 12 is a matrix diagram showing data to be written by type.

  In FIG. 12, in the electrophoretic display device according to the present embodiment, data displayed on each pixel 20 is black, red, white A (that is, white that does not have confidential data) and white B (that is, confidential data). And white). In each pixel 20, as shown in FIGS. 4 to 7, potentials corresponding to the first pixel electrode 21a, the second pixel electrode 21b, and the common electrode 22 are supplied.

  FIG. 13 is a matrix diagram showing the display colors at the time of writing for each type.

  In FIG. 13, the colors displayed in each pixel 20 to which writing has been performed are three types of black, red, and white. That is, white that does not have confidential data (that is, white A) and white that has confidential data (that is, white B) are visually distinct from each other, although the state of each particle is different. Can not.

  FIG. 14 is a matrix diagram showing display colors by type when secret data is read.

  In FIG. 14, the colors displayed on each pixel 20 at the time of reading secret data are four types of black, red, dull white, and white. That is, the color changes only in white (that is, white B) pixels 20 having secret data. Therefore, it is possible to suitably read confidential data.

  In the electrophoretic display device according to the present embodiment, whether or not the data has confidential data cannot be determined from the common electrode 22 as described above, but from the first pixel electrode 21a and the second pixel electrode 21b. It can be determined. That is, it can be seen by looking at which of the first pixel electrode 21a and the second pixel electrode 21b the black particles 83 and the red particles 84 are attracted.

  On the other hand, in order to prevent the secret data from being confirmed from the first pixel electrode 21a and the second pixel electrode 21b side, the first pixel electrode 21a and the second pixel electrode 21b are made of a light-shielding member. Good. On the other hand, in order to be able to confirm the secret data from the first pixel electrode 21a and the second pixel electrode 21b side intentionally, the first pixel electrode 21a and the second pixel electrode 21b are made of a translucent member. What is necessary is just to comprise.

  As described above, according to the driving method of the electrophoretic display device according to the present embodiment, it is possible to embed and read secret data by a very simple method.

<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 is taken as an example.

  FIG. 15 is a plan view showing an electronic paper lottery at the time of distribution.

  As shown in FIG. 15, in the electronic paper lottery 1000, a region 1000 b located in the central portion surrounded by the region 1000 a includes the electrophoretic display device according to the above-described embodiment as a display unit that displays an image. . The electronic paper lottery 1000 has flexibility, and is composed of a rewritable sheet having the same texture and flexibility as conventional paper.

  Here, in the electronic paper lottery area 1000b, only white is displayed at the time of distribution. That is, although white A that does not have confidential data and white B that has confidential data are mixed, their presence and position cannot be visually discriminated.

  FIG. 16 is a plan view showing an electronic paper lot when secret data is read.

  As shown in FIG. 16, when a predetermined voltage is applied in the electromagnetic paper lot, the color of the pixel in which the confidential data is embedded changes, and characters that have not been displayed until then appear. The secret data can be read out only by applying a predetermined voltage regardless of the secret data. For example, only one inexpensive and simple read-only machine is required. Therefore, the introduction cost of equipment can be suppressed. The used electronic paper lottery 1000 can be collected and reused.

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

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and an electrophoretic display with such a change. An apparatus driving method, an electrophoretic display device, and an electronic apparatus are also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 3 ... Display part, 10 ... Controller, 20 ... Pixel, 21a ... 1st pixel electrode, 21b ... 2nd pixel electrode, 22 ... Common electrode, 23 ... Electrophoretic element, 24a ... 1st transistor, 24b ... 2nd transistor, 27a ... first holding capacitor, 27b ... second holding capacitor, 28 ... element substrate, 29 ... counter substrate, 40 ... scan line, 50 ... data line, 60 ... scan line drive circuit, 70 ... data line drive circuit, 82 ... White particles 83 ... Black particles 84 ... Red particles 88 ... Partition walls 93 ... Common potential lines 200 ... Second data lines 220 ... Common potential supply circuits

Claims (8)

A first pixel electrode and a second pixel electrode provided for each pixel; a common electrode disposed to face the first pixel electrode and the second pixel electrode; and a first particle corresponding to the first color; A method for driving an electrophoretic display device including an electrophoretic element including second particles corresponding to a second color,
A first display step of drawing the second particles to the first pixel electrode and the second pixel electrode and displaying the first color by drawing the first particles to the common electrode;
A second display step of drawing the first particles to the first pixel electrode and the second pixel electrode and displaying the second color by drawing the second particles to the common electrode;
The first particles are attracted to the first pixel electrode, and the second particles are attracted to the second pixel electrode to display the first color and a third color different from the second color. 3 display processes;
A fourth display step of drawing the second particles to the first pixel electrode and displaying the third color by drawing the first particles to the second pixel electrode;
Unlike the pixel displaying the third color in the third display step, the pixel displaying the third color in the fourth display step is embedded with invisible confidential data. Driving method of electrophoretic display device.   In the pixel in which the third color is displayed by the third display step and the fourth display step, a predetermined potential is supplied to the first pixel electrode, whereby the first display step is performed by the fourth display step. 2. The driving of an electrophoretic display device according to claim 1, further comprising: a secret data reading step for extruding the second particles attracted to the pixel electrode toward the common electrode to make the second particles visible. Method. A first pixel electrode and a second pixel electrode provided for each pixel;
A common electrode disposed to face the first pixel electrode and the second pixel electrode;
An electrophoretic element comprising first particles corresponding to a first color and second particles corresponding to a second color;
A control unit that controls to display an image by supplying a potential to each of the first pixel electrode, the second pixel electrode, and the common electrode;
The controller is
First display means for attracting the second particles to the first pixel electrode and the second pixel electrode and displaying the first color by attracting the first particles to the common electrode;
Second display means for displaying the second color by attracting the first particles to the first pixel electrode and the second pixel electrode and attracting the second particles to the common electrode;
The first particles are attracted to the first pixel electrode, and the second particles are attracted to the second pixel electrode to display the first color and a third color different from the second color. 3 display means;
And a fourth display means for displaying the third color by attracting the second particles to the first pixel electrode and attracting the first particles to the second pixel electrode,
Unlike the pixel displaying the third color by the third display unit, the pixel displaying the third color by the fourth display unit is embedded with invisible confidential data. Electrophoretic display device.   The electro-optical device according to claim 3, wherein the electrophoretic element includes uncharged third particles corresponding to the third color.   The electro-optical device according to claim 3, wherein the electrophoretic element includes a solvent corresponding to the third color.   The electro-optical device according to claim 3, wherein the first pixel electrode and the second pixel electrode have translucency.   The electro-optical device according to claim 3, wherein the first pixel electrode and the second pixel electrode have a light shielding property.   An electronic apparatus comprising the electrophoretic display device according to claim 3.

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