JP5649272B2 - Reflective display device - Google Patents

Description

  The present invention relates to a reflective display device, and more particularly to a reflective display device using electroplating for dimming, which has an electrode in contact with an electrolyte solution, and an electroplating film is formed on the electrode.

As a display device with high visibility and low power consumption, electronic paper has been actively developed. An example in which a color filter is combined with a display device using electroplating is described in Patent Document 1. In Patent Document 1, a silver salt solution is disposed between the working electrode and the counter electrode, and a color filter is disposed on the light incident side of the working electrode (on the side opposite to the silver salt solution arrangement side of the working electrode). This is a structure in which a white background plate is arranged on the upper side (on the opposite side of the silver salt solution arrangement side). When silver is deposited on the working electrode, the light incident through the color filter is absorbed by the deposited silver. On the other hand, when silver is not deposited on the working electrode, the light incident through the color filter is transmitted through the working electrode, is reflected from the white background plate, is transmitted through the working electrode and the color filter, and performs color display.
Japanese Patent Laid-Open No. 11-101994

  In Patent Document 1, incident light has a structure that passes through a color filter before being reflected by a reflective layer. In order to display white in this structure, pixels for three primary colors are required. Each pixel reflects only a single color, and the non-reflected color component of incident light is absorbed by the color filter of each pixel. For example, blue and green components are absorbed in pixels that reflect red, red and green components are absorbed in pixels that reflect blue, and blue and red components are absorbed in pixels that reflect green. Therefore, when displaying white, the red component is absorbed by the blue and green pixels, the blue component is absorbed by the red and green pixels, and the green component is absorbed by the red and blue pixels. In other words, the area that reflects red is 1/3 of the display device area. The same applies to green and blue. As described above, since each color is reflected only in an area of ３, the overall reflectance during white display is only １ ／ even if only the effective reflection area ratio of each color is seen. Improvement of the rate is desired.

  An object of the present invention is to provide a reflective display device capable of performing two-color display using an electroplated film, and has a particularly high reflectivity during white display and can perform good black display. A reflective display device will be provided.

  Another object of the present invention is to provide a reflective display device that can display white with high reflectivity and can be applied to better color display.

The reflective display device according to the present invention includes a first electrode, a second electrode disposed to face the first electrode, and at least one of the first electrode and the second electrode. A third electrode disposed opposite to the other electrode and adjacent to the other electrode, at least the first electrode, the second electrode, and the electrolyte solution disposed between the third electrode , and at least the Control means for setting a direction of a current flowing between the first electrode, the second electrode, and the third electrode, and a current flowing between the first electrode and the second electrode . An electroplating film is formed on one of the first electrode and the second electrode by setting the direction, and a reflective display device using electroplating for dimming,
A first surface in contact with the first electrode of the electroplating film formed on the front Symbol first electrode, a second which is not in contact with the second electrode of the electroplating film formed on the second electrode And at least one of the reflectance and the absorptance is different,
The control means includes: a first mode in which a first electroplating film that forms the first surface in contact with the first electrode is formed on the first electrode; and Forming a second electroplating film that forms the second surface that is not in contact with the second electrode, and setting the first electrode without the first electroplating film; and Providing a third mode in which an electroplating film is formed on the third electrode, and the first and second electrodes are absent from the first and second electroplating films;
When the electroplating film is formed on the first electrode, the reflected light from the first surface is used for display, and when the electroplating film is formed on the second electrode, the second surface is used. The reflected light is used for display.

  According to the present invention, it is possible to obtain a reflective display device that can perform two-color display using an electroplated film, has a high reflectance particularly during white display, and can perform good black display.

  In addition, according to the present invention, it is possible to obtain a reflective display device capable of displaying white with high reflectivity and capable of color display.

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

(First embodiment)
FIG. 1 is a cross-sectional view showing a schematic configuration of a first embodiment of a reflective display device of the present invention. The pixel 40 in FIG. 1 shows a case where the electroplating film 10 is formed on the first electrode 2. The pixel 41 in FIG. 1 shows a case where the electroplating film 10 is formed on the first electrode 4.

  In FIG. 1, the first electrode 2 having light transmittance is formed on a substrate 1 having light transmittance (which becomes the first substrate), and the second electrode 4 having light transmittance is light transmissive. It is formed on a substrate 6 having a property (to be a second substrate). The first electrode 2 and the second electrode 4 are disposed to face each other with the electrolyte solution 3 interposed therebetween. Although the 2nd electrode 4 may have a light transmittance, it may be formed with the metal which does not have a light transmittance. The substrate 6 on which the second electrode 4 is provided does not have to be light transmissive. The electrolyte solution 3 contains a metal element that becomes two or more kinds of metal ions. The light-transmitting electrode may be substantially light-transmitting and may not be formed of a transparent electrode such as ITO, and a metal thin film, a metal net structure, or a comb-tooth structure is used. (The same applies to the embodiments described later).

  When a current is passed using the first electrode 2 as a cathode and the second electrode 4 as an anode, metal ions contained in the electrolyte solution 3 are reduced and deposited on the surface of the first electrode 2, as shown in the pixel 40. A metal is electroplated on the first electrode 2 to form an electroplated film 10. At this time, the color of the deposited electroplating film is affected by the composition of the electrolyte solution 3. For example, when the electrolyte solution 3 contains silver and copper, the interface between the first electrode 2 and the electroplating film 10 (the first surface of the electroplating film) is a non-colored mirror surface and reflects incident light. When viewed from the side of the first electrode 2, white as the first color is visually recognized.

  On the other hand, when a current is passed using the second electrode 4 as a cathode and the first electrode 2 as an anode, metal ions contained in the electrolyte solution 3 are reduced and deposited on the surface of the second electrode 4, as shown in the pixel 41. The second electrode 4 is electroplated with metal to form the electroplated film 10. When the electroplating film 10 is viewed from the first electrode 2 side, the surface of the electroplating film 10 that is not in contact with the second electrode 4 (second surface of the electroplating film) is visually recognized. At this time, the color of the deposited electroplating film is affected by the composition of the electrolyte solution 3. For example, when the electrolyte solution 3 contains silver and copper, the surface has a rough uneven shape and absorbs incident light, so that the second color, black, is visually recognized.

  In order to form electroplated films having different colors on the front and back surfaces, the electrolyte solution contains a metal element that becomes two or more kinds of metal ions, like the electrolyte solution 3 containing silver and copper exemplified in this embodiment. Yes. The electrolyte solution contains at least a first metal element as a plating seed and a second metal element having a redox potential close to that of the first metal element as two or more metal elements. In this embodiment, silver is used as the first metal element, and copper is used as the second metal element.

  Here, the second metal element is assumed to have a redox potential close to that of the first metal element, which will be described below. As a main component in the electrolyte solution, a first substance having a higher redox potential than the first metal element and a second substance having a higher redox potential than the first metal element as the main component in the solution. Material. For example, when a dimethylformamide solution is used as the electrolyte solution, the first substance corresponds to bromine and the second substance corresponds to hydrogen. When the redox potentials of the first substance and the second substance are the first potential and the second potential, the redox potential of the second metal element in the electrolyte solution is more than the first potential. Low and higher than the second potential. According to the previous example, assuming that the redox potential of silver as the first metal element is a reference (0V), the redox potential (first potential) of bromine (first substance) is higher than the redox potential of silver. High (+0.2 V), the redox potential (second potential) of hydrogen (second substance) is lower than the redox potential of silver (−0.8 V). The redox potential of copper, which is the second metal element, is located between the first potential and the second potential (−0.3 V). The second metal element in such a state is defined as a second metal element that is “close to the first metal element in oxidation-reduction potential”.

  Usually, in electroplating used for dimming, an electrolyte solution is designed so that unintended oxidation / reduction of an unintended substance does not occur within a range where the potential of the electrode changes. That is, the electrolyte solution does not contain a substance having a near redox potential so that a substance other than the metal to be plated is not reduced on the electrode. This is because when a plurality of metals are oxidized and reduced on the same electrode, disturbance occurs and a clean electroplated film is not deposited. However, in this embodiment, disturbance is intentionally caused by putting two kinds of metal elements having an oxidation-reduction potential in the electrolyte solution in a range where the potential of the electrode changes. Due to this disturbance, the deposited electroplating film grows into a large uneven shape, resulting in a greatly different color of the electroplating film on the front and back.

  In the pixel 40, when a current is passed with the second electrode 4 as a cathode and the first electrode 2 as an anode in a state where an electroplating film is formed on the first electrode 2, an electric current is applied on the second electrode 4. As the plating film is formed, the electroplating film formed on the first electrode 2 is dissolved. Therefore, by changing the direction in which current flows between the first electrode 2 and the second electrode 4, electroplating is performed on any of the first electrode 2 and the second electrode 4 in the same pixel. A film can be formed.

  If a reflective display device is configured using such a principle, it is possible to switch between black and white two-color display. Further, gradation display is also possible by controlling the film thickness of the electroplating film.

  In the reflective display device of this embodiment, the second electrode 4 is made light transmissive and the substrate 6 is made light transmissive, so that two colors having different colors on the front surface and the back surface as shown in FIG. Display can also be performed. That is, when the electroplating film 10 is formed on the first electrode 2, as shown in FIG. 2, for example, when the electrolyte solution 3 contains silver and copper, the electroplating film 10 is formed from the first electrode 2 side. When viewed, the first color, white, is visible. On the other hand, when viewed from the second electrode 4 side, the second color, black, is visually recognized. In this way, two-color display with different colors on the front and back surfaces is possible. Further, when the electroplating film 10 is formed on the second electrode 4, when the electroplating film 10 is viewed from the first electrode 2 side, the second color black is visually recognized. On the other hand, when viewed from the second electrode 4 side, white as the first color is visually recognized. In this way, two-color display with different colors on the front and back surfaces is possible. In FIG. 2, the substrate 1 and the substrate 6 are omitted for simplification.

  One of the first electrode 2 or the second electrode 4 may be composed of a metal wire such as a platinum wire. In this case, since the platinum wire is hardly visually recognized, a reflection type display device as shown in FIG. 2 can be configured.

  In addition, the two-color display of different colors on the front and back surfaces performed using the electroplating film formed on the first electrode 2 and the table performed using the electroplating film formed on the second electrode 4 described above. Two-color display with different colors on the back side can be combined. By doing so, it is also possible to realize a reflective display device that can perform two-color display on the front surface and the back surface.

(Second Embodiment)
FIG. 3 is a cross-sectional view showing a schematic configuration of a second embodiment of the reflective display device of the present invention. FIG. 3 shows three pixels 101, 102, and 103. The reflective display device includes a first substrate 1 that protects the surface, a first electrode 2, a colored second electrode 4 that faces the first electrode 2 with the electrolyte solution 3 interposed therebetween, and a first electrode The third electrode 5 in contact with the same electrolyte solution as the electrode 2 and the second electrode 4 and the second substrate 6 are laminated. The first electrode 2 and the first substrate 1 are light transmissive. The electrolyte solution 3 contains two or more kinds of metal ions. The area of the third electrode 5 is made smaller than the area of the second electrode 4. Even if the 2nd board | substrate 6 has a light transmittance, it does not need to have a light transmittance. In FIG. 3, the pixel 101 forms the electroplating film 10 on the second electrode 4, the pixel 102 forms the electroplating film 10 on the first electrode 2, and the pixel 103 forms the electroplating film on the third electrode 5. The case where is formed is shown.

  When a current is passed using the first electrode 2 as a cathode and the second electrode 4 and the third electrode 5 as an anode, metal ions contained in the electrolyte solution 3 are exposed to the surface of the first electrode 2 as in the pixel 102. Then, the metal is electroplated. At this time, the color of the deposited metal film is affected by the composition of the electrolyte solution 3. For example, when the plating solution contains silver and copper, the interface between the first electrode 2 and the electroplating film (the first surface of the electroplating film) becomes a mirror surface having no color and reflects incident light. When viewed from one side, the first color, white, is visible.

  When a current is passed using the second electrode 4 as a cathode and the first electrode 2 and the third electrode 5 as an anode, a plating film is electrodeposited on the surface of the second electrode 4 as in the pixel 101. . At this time, when viewed from the substrate 1 side, the surface of the electroplating film that does not contact the electrode (second surface of the electroplating film) is visually recognized from the surface, but the surface has a rough uneven shape, In order to absorb incident light, the second color, black, is visible.

  Further, when a current is passed using the third electrode 5 as a cathode and the first electrode 2 and the second electrode 4 as an anode, metal ions contained in the electrolyte solution 3 are added to the third electrode 5 as in the pixel 103. The metal is electroplated by reduction deposition on the surface. At this time, all of the metal deposited on the surfaces of the first electrode 2 and the second electrode 4 is also dissolved, so that the second electrode 4 of the second electrode 4 is transmitted from the surface through the first electrode 2 having optical transparency. The color is visible.

  The second electrode 4 may use the color of the material itself, or may use selective reflection by a laminated structure. For example, when the second electrode 4 is formed with a laminated structure of TiN and AlCu, the reflection color can be adjusted by the film thickness of TiN due to interference.

  Further, the same effect can be obtained even if the second electrode 4 is made of a light-transmitting material and a colored substance is arranged on the support substrate 6.

  If a reflective display device is configured using such a principle, it is possible to switch three-color display.

  The electroplating film formed / disappeared on the surface of the first electrode 2 and the electroplating film formed / disappeared on the surface of the second electrode 4 can adjust the light transmittance by adjusting the film thickness of the plating. Or the reflectance can be adjusted.

(Third embodiment)
FIG. 4A is a cross-sectional view showing a schematic configuration of a third embodiment of the reflective display device of the present invention. The present embodiment relates to an apparatus for displaying a full color by arranging a plurality of pixels in a matrix. The configuration of the present embodiment is the same as the configuration of the second embodiment, and the second electrode 4 and the substrate 6 are made light-transmitting, and the reflected wavelength band is red under the second electrode 4 and the third electrode 5, respectively. , Blue and green reflectors 17, 18, and 19 are arranged. In the pixels 101 and 102, the same display as in FIG. 3 is performed, but in the pixel 103, the second electrode 4 and the substrate 6 transmit light and are reflected by the reflecting plate 19, and the color of the reflecting plate 19 is visible.

  In this embodiment, a reflector is used as the reflector. However, the reflector can be formed by forming a reflective layer that reflects a specific color for each pixel on the substrate 6 by printing or the like. The reflector may be configured by forming a color filter and disposing a reflective plate thereon. 4A shows an example in which the electrodes 4 and 5 are formed on one surface of the substrate 6 and a reflector as a reflector is formed on the opposite surface, but the reflector such as the reflector is an electrolyte. As long as the electrodes 4 and 5 can be formed on the substrate without any problem even if they are in contact with the solution, they may be provided between the substrate 6 and the electrodes 4 and 5.

  Hereinafter, the principle of performing full-color display will be described with reference to FIGS. 4B and 4C. FIG. 4B is a cross-sectional view for explaining the operating principle of the full color display of the third embodiment of the reflective display device of the present invention. FIG. 4C is a configuration diagram showing a conceptual configuration of the full-color display of FIG. In FIG. 4B, the electroplating film formed on the surface of the second electrode 4 of each of the pixels 101, 102, 103 is black, and the light absorption rate is adjusted in the range of 0 to 100%. Are shown as the light control layers 11, 13, and 15. The light absorption rate of 0 is a state where an electroplating film is not formed or is so thin that light absorption is not recognized. Further, the electroplating film formed on the surface of the first electrode 2 of each of the pixels 101, 102, and 103 is white, and the second light control layer 12 that adjusts the light reflectance in the range of 0 to 100%. , 14 and 16. The light reflectance of 0 is a state in which no electroplating film is formed or is so thin that no light reflection is observed.

  In the reflective display device of this embodiment, it is not always necessary to control the absorptance and reflectance in the range of 0% to 100%. For example, the range of about 30% to 70% can be used. In the following, 0%, 100%, and the like are conceptually expressed, but these values are not essential requirements of the present embodiment.

Further, the transmittance of the first light control layers ₁₁ , ₁₃ , and ₁₅ is T ₁ , the reflectance is R ₁ , and the absorption rate is A _1. Assuming that the absorption rate is T ₂ , R ₂ , A ₂ , the following formulas 1 and 2 are established, respectively.

T ₁ = 1−A ₁ −R ₁ (Formula 1)
_{T 2 = 1-A 2 -R} 2 ( formula 2)

The first dimmer layer the reflectivity R ₁ since it is composed of electroplated film black 0, the second dimmer layer is composed of a white electroplating film, considered absorptivity A ₂ 0 Therefore, Equations 1 and 2 are approximated by Equations 3 and 4.

T ₁ = 1−A ₁ (Formula 3)
T ₂ = 1-R ₂ (Formula 4)

FIG. 5 is a schematic cross-sectional view showing reflection, transmission, and absorption of light incident on a pixel. The incident light intensity is 1, and the reflectance at the reflector is Rc. On the surface 23 of the second light control layer, the light having the light intensity R ₂ of the incident light is reflected and the light having the light intensity T ₂ is transmitted. Transmitted light intensity T ₂ are, in the surface 24 of the first dimmer layer, R ₁ times the light intensity T ₂ is reflected, T ₁ times the light intensity T ₂ is transmitted. The T ₁ · T ₂ light transmitted through the first dimming layer is reflected by the reflector at Rc times, that is, T ₁ · T ₂ · Rc times of light incident from the outermost surface, and the first dimming layer is reflected again. Incident on the optical layer. The surface 24 of the first light control layer transmits T ₁ times the incident light, that is, T ₁ ² · T ₂ · Rc times the light incident from the outermost surface. The transmitted light again passes through the surface 23 of the second light control layer, and T ₂ times is transmitted. Therefore, the transmitted light is T ₁ ² · T ₂ ² · Rc times the light intensity of the light incident from the outermost surface. Become. Further, when the light of the light intensity R ₂ reflected by the surface 23 of the second light control layer is also added, the light intensity of the reflected light is (R ₂ + (T ₁ ² · T ₂ ² · Rc) times. Therefore, the reflected light intensity I follows Formula 5.

I = R ₂ + T ₁ ²・ T ₂ ²・ Rc
= R ₂ + (1-A ₁ ) ² · (1-R ₂ ) ² · Rc (Formula 5)

It will be sequentially described below that the display device can perform color display, black display, and white display with high reflectance.
First, when displaying a specific color, for example, red, both the first dimming layer 11 and the second dimming layer 12 on the reflection plate 17 that reflects the red wavelength band are set in a transmissive state. That is, T ₁ = T ₂ = 1, and the first light control layers 13 and 15 on the reflection plates 18 and 19 that reflect the blue and green wavelength bands are in an absorption state. The second light control layers 14 and 16 may be in a reflective state or a transmissive state, but here are in a transmissive state. These are summarized in Table 1 with Rc = 0.33. Table 1 is calculated by the absorption rate of the first dimming layer, the reflectance of the second dimming layer, and Equation 5 for each pixel having the red, green, and blue reflectors 17, 18, and 19. 3 is a table summarizing reflected light intensity I. In addition, although the notation such as “reflectance 1”, “absorption rate 1”, “reflectance 0”, and “absorption rate 0” is conceptually shown here, this is an ideal state and is not necessarily complete reflection. Complete absorption is not essential. The same applies to the following expressions.

  Incident light is transmitted through the light control layers 11 and 12 on the reflection plate 17 that reflects the red wavelength band, and the reflection plate 17 reflects red. Since the light control layers 13 and 15 absorb incident light and neither reflect nor transmit light, the blue and green pixels are black. As a result, only the red color is reflected and displayed in red.

  Similarly, the light control layer states when displaying white are summarized in Table 2. Since all incident light is reflected by the light control layer during white display, white display is obtained. That is, according to the present embodiment, during white display, incident light is not absorbed by a color filter or the like and is totally reflected, so that a white display with high reflectance can be realized. Similarly, Table 3 summarizes the configuration for expressing black.

Similarly, gradation display from white to black is also possible. It is possible to express white with reflectance n (0 <n <1), that is, gray by adjusting as shown in Table 4.

  By the combination as described above, it is possible to realize color display and display with high reflectivity during white display. In addition, said combination is an example and is not necessarily limited to this, Furthermore, various combinations can be performed.

  The reflective display device of each embodiment described above can be realized as a passive matrix drive display device or an active matrix drive display device. A spacer is provided between the substrate 1 and the substrate 6 in order to keep the distance between the substrates constant although it depends on the size of the display device. The spacer is formed in an arbitrary shape including a cylinder, a sphere, and a quadrangular column.

  In the following description, the passive matrix drive type reflective display device and the active matrix drive type reflective display device will be described by taking the configuration of the second embodiment shown in FIG. 3 as an example. The same configuration can be adopted in the embodiment. In the first embodiment, the third electrode 5 is excluded.

  In FIG. 9, the colored second electrode 4 is arranged on the substrate 6 in a plurality of lines in one direction (X direction). The third electrode 5 is arranged on the substrate 6 in a plurality of lines in parallel with the second electrode 4. Here, the third electrode 5 does not contribute to display, and thus is formed by a thin line having a width smaller than that of the second electrode 4. However, the third electrode 5 can contribute to the display by forming the same electroplating film when the electroplating film is formed on the second electrode 4.

  The first electrode 2 having light transmittance is a second line arranged in a plurality of lines on the substrate 1 having light transmittance in a plurality of lines in a direction perpendicular to the X direction (Y direction). The electrode 4 is arranged so as to cross the electrode 4.

  The shape of the second electrode 4 and the third electrode 5 is not limited to the shape shown in FIG. 9, and the electrode 4 is enclosed in a “U” shape as shown in the plan view of FIG. Thus, the line-shaped electrode 5 having a “−”-shaped (line-shaped) protruding portion (on one side in the Y direction) can be provided. Further, as shown in the plan view of FIG. 10C, the line-shaped electrode 5 having “−”-shaped (line-shaped) protruding portions on both sides (both sides in the Y direction) so as to surround the electrode 4 from both sides. Can be provided. FIG. 10A is a plan view of the electrode 4 and the electrode 5 shown in FIG. The scanning of the electrode 5 can be selected for each line and a current can be passed. However, it is also possible to select two lines at the same time and pass a current to shift each line. In this operation, for example, when a current is passed from the electrode 4 to the electrode 5, a current can be passed from the electrode 4 to the two lines of electrodes 5 provided on both sides.

  A configuration in which the electrode 5 is provided along one side of the electrode 4 as shown in FIG. 10A, a configuration in which the electrode 4 is surrounded by the electrode 5 in a “U” shape as shown in FIG. 10B, and FIG. The configuration in which the periphery of the electrode 4 is surrounded by the electrode 5 as described above can be applied to an active matrix drive type. However, in the case of the active matrix drive type, the electrode 4 and the electrode 5 are provided for each pixel.

  In the case of an active matrix drive type reflective display device, as shown in FIG. 11, the electrode 4 and the electrode 5 are arranged for each pixel, and each of the electrode 4 and the electrode 5 is a first switch T1 such as a thin film transistor, a third switch. Connected to the switch T3. The electrode 2 is a common electrode. A second switch T2 and a fourth switch T4 such as a thin film transistor control the conduction of the first switch T1 and the third switch T3, respectively. The second switch T2 and the fourth switch T4 are respectively connected to the control terminals of the first switch T1 and the third switch T3 (when the switch is a field effect transistor, it becomes a gate). The control terminals of the second switch T2 and the fourth switch T4 (when the switch is a field effect transistor, the gate) are respectively connected to the scanning lines (when the switch is a field effect transistor, the gate line) 28 is connected. Is done. By the on / off control of the second switch T2 and the fourth switch T4, the data signal is applied from the data line 29 to the control terminal of the first switch T1 and the capacitor C1, the third switch T3 and the capacitor C2, respectively, and the capacitor C1. , C2 stores data signals. The first to fourth switches are provided for each pixel. Due to the on / off control of the first and third switches T1, T3, a current having a set current density flows through the first and third switches. Reference numeral 31 denotes a ground (GND) line.

  In the above-described passive matrix drive type reflection type display device and active matrix drive type reflection type display device, by using the control signal circuit (being a control means) shown in FIG. 12, FIG. 13 (a), (b), Two kinds of voltages are switched and applied to the electrode 2, the electrode 4 and the electrode 5. The control signal circuit controls the direction (direction) in which current flows between the three electrodes 2, 4, and 5 shown in FIGS. 12, 13 (a), and (b). That is, when the electrode 2 is used as a cathode and the electrode 4 and the electrode 5 are used as an anode, the electrode 2 is set to GND, and the electrodes 4 and 5 are set to the voltage V. When the electrode 4 is used as a cathode and the current is supplied using the electrodes 2 and 5 as an anode, the electrode 4 is set to GND, and the electrodes 2 and 5 are set to a voltage V. In addition, when the electrode 5 is used as a cathode and the electrode 2 and the electrode 4 are used as currents, the electrode 5 is set to GND, and the electrodes 2 and 4 are set to a voltage V.

  In this way, the control signal circuit includes the first mode in which the first electroplating film that forms the first surface in contact with the first electrode 2 is formed on the first electrode 2, and the second mode A second mode in which a second electroplating film that forms a second surface not in contact with the second electrode 4 is formed on the electrode 4, and the first electroplating film is not present on the first electrode 2. And a third mode in which an electroplating film is formed on the third electrode 5 and the first and second electrodes 2 and 4 have no first and second electroplating films.

  The pixel size of the reflective display device of this embodiment is not particularly limited and is appropriately set according to the application. For example, the pixel size can be set from about 10 μm to several tens of mm.

  In the present embodiment, a barrier for separating pixels is not provided, but such a barrier may be provided as necessary. However, if the voltage applied between the pixels is not more than a certain critical voltage, the electroplating does not occur, and it can be set so as not to be affected by the adjacent pixels. This is also described in, for example, Japanese Patent Application Laid-Open No. 2004-170850.

  When the reflection type display device of this embodiment is used, the film formed by plating has different reflectance and absorptivity between the first surface and the second surface. Specifically, in the plating film, the surface in contact with the electrode (first surface) has the same level of smoothness as that of the electrode and becomes a mirror surface, so the film color (first color) is plated. It will be the color of the metal itself. For example, if the metal is silver, the first color is white. The surface not in contact with the electrode (second surface), that is, the surface in contact with the liquid is a very rough and uneven surface, and the incident light is absorbed while being repeatedly reflected in the rough surface. The film color (second color) is a dark color such as black or brown.

  In contrast to the configuration of the electrodes, when the first electrode arranged on the surface side is plated, the color of the first surface (first color) is visually recognized and arranged on the back side with the plating solution interposed therebetween. When the second electrode is plated, the color of the second surface (second color) is visually recognized.

  The color density increases as the thickness of the plating film increases. That is, the greater the film thickness, the higher the reflectivity of the first surface and the higher the absorptance of the second surface. On either side, the smaller the film thickness, the higher the transmittance and the closer to transparency. The plating film thickness is substantially proportional to the plating time and current density and can be controlled.

  Furthermore, the third color can be expressed by the state in which neither the first electrode nor the second electrode is realized by using the third electrode. The third color is the color of the second electrode itself when the second electrode is a substance that reflects light in a specific wavelength band, and the third color is the third color when the second electrode is a transparent substance. The color becomes transparent. When the third color is transparent, a specific color can be displayed by stacking a reflective plate that reflects a specific wavelength band under the reflective display device.

  As a more specific example, a reflective display device in which the first color is white, the second color is black, the second electrode is transparent, and the third color is determined by the reflector can be realized. . In a state where the first electrode is plated with white, which is the first color, incident light is reflected without being subjected to wavelength selection, so that reflection with high reflectance is possible. In particular, compared to the conventional example, incident light is reflected over the entire wavelength band without being absorbed by a color filter or the like, so that a white display with a high reflectance can be obtained. Similarly, the second color, black, and the third color by the reflector can be displayed. By combining the above states, it is possible to realize a reflective display device capable of displaying white with high reflectivity and capable of color display.

Example 1
A specific apparatus configuration of the first embodiment of the present invention will be described with reference to FIG. For the substrate 1, glass having a thickness of 0.7 mm was used, and for the first electrode 2, ITO having a thickness of 150 nm formed by a sputtering method was used. As the electrolyte solution 3, a solution containing dimethylformamide (DMF) as a solvent, silver chloride 300 mmol / L, and copper sulfate pentahydrate 100 mmol / L as a plating seed was used. Moreover, this solution contains 1 mol / L of tetrabutylammonium bromide (TBAB) as a supporting electrolyte and a solution containing a brightener. The pixel size was 0.7 mm × 0.7 mm, and the thickness of the electrolyte layer 3 was 0.1 millimeter. As the second electrode 4, the same ITO film as that of the first electrode 2 was used. Silver was used as the third electrode 5. Glass was used for the support substrate 6. Reflecting plates 17, 18, and 19 for reflecting light in a specific wavelength band are provided on the back surface of the glass.

When a potential of 1.5 V is applied using the first electrode 2 as a cathode and the second electrode 4 and the third electrode 5 as an anode, a current of 10 mA / cm ² flows and the plating film is formed on the surface of the first electrode. Since it was formed, white was visually recognized from the surface. When a potential of 1.5 V is applied with the second electrode 4 as a cathode and the first electrode 2 and the third electrode 5 as an anode, a current of 10 mA / cm ² flows, and a plating film is formed on the electrode 4. As a result, black was visually recognized from the surface.

In addition, when a potential of 1.5 V is applied with the third electrode 5 as the cathode and the first electrode 2 and the second electrode 4 as the anode, a current of 10 mA / cm ² flows, and the surfaces of the electrodes 2 and 4 are plated. The film dissolved and disappeared. The incident light is transmitted through the electrode 2 and the electrode 4, then reflected by the reflectors 17, 18, and 19 and again through the electrode 2 and the electrode 4, so that the color of the wavelength band reflected by the reflector is visible from the surface. It was done. Although this embodiment uses a reflector as a reflector, the reflector can be formed on the substrate 6 by forming a reflective layer that reflects a specific color for each pixel by printing or the like. The reflector may be configured by forming a color filter and disposing a reflective plate thereon.

  In this embodiment, the light-transmitting substrate 1 for protecting the surface can be made of a light-transmitting solid such as a resin other than glass. For the first electrode 2 and the second electrode 4, in addition to ITO, IZO (Indium-Zinc-Oxide), zinc oxide, titanium oxide, and other conductive transparent materials can be used as transparent electrodes. . Moreover, if it has a light transmittance, a metal thin film, a metal net structure, and a comb-tooth structure can also be used. For the third electrode 5, platinum, carbon, gold or the like can be used as long as it is a conductor of the same type as the metal to be plated, or a stable conductor that does not change by the plating reaction, and a transparent material such as ITO is used. It can also be used. Further, when the electrode 4 is colored and has a property of reflecting a specific wavelength band, the reflection plates 17, 18 and 19 of the pixel can be omitted. The reflection plates 17, 18, and 19 are formed by disposing colored paper on a glass substrate having a thickness of 0.1 mm, and the reflection plates are laminated on the substrate 6 so that the paper contacts the substrate 6.

The reflective plates 17, 18 and 19 of the reflective display device according to the present embodiment are made of three colors of red, green and blue, and are arranged in a matrix with a Bayer arrangement, thereby forming a reflective display device capable of color display. . The pixels are driven by active matrix driving using transistors. Note that the color arrangement of the reflector is not limited to the Bayer arrangement. The color arrangement is not limited to the above, and may be cyan, magenta, or yellow. The driving may be passive matrix driving using crossed electrodes.
(Example 2)
FIG. 6 is a cross-sectional view of a pixel of a reflective display device according to the second embodiment of the present invention. 6 shows a configuration in which a diffusion sheet 26 is further added to the configuration of FIG. 3 or FIG. The diffusion sheet 26 has a wider viewing angle than the reflective display device of FIG. 3 or FIG. 4, and enables display that is closer to paper and easier to see.

The position where the diffusion sheet 26 is disposed is not limited to the outermost surface, but may be anywhere on the surface side of the “metal film reflecting light” formed by the plating. Further, the material is not limited to the diffusion sheet, and other members may also serve as a diffusion function. For example, the support substrate 1 or the first electrode 2 may have a structure having a light diffusion effect.
Example 3
FIG. 7 is a cross-sectional view of a pixel of a reflective display device according to a third embodiment of the present invention. In order to obtain the same effect as in Example 2, a 0.05 mm pitch uneven pattern is formed on the surface of the transparent electrode 2 in FIG. 3 or 4 in contact with the electrolyte solution 3 by a photo process and wet etching. Other configurations are the same as those in FIG. When the transparent electrode 2 having the unevenness is plated with a metal film that reflects light, the light is scattered by the unevenness, so that a high-quality white display close to paper becomes possible. Needless to say, the concavo-convex pattern has only to have a function of scattering light, and the pitch size, arrangement, electrode material, and the like are not limited to the above values.
Example 4
FIG. 8 is a cross-sectional view of a pixel of a reflective display device according to a fourth embodiment of the present invention. 8 has the same configuration as that of FIG. 3 or FIG. 4, but the second electrode 4 is formed of a transparent material so as to reflect a specific wavelength band between the support substrate 6 and the second electrode 4. A multilayer film 27 as a reflector is arranged. Good by laminating films with different refractive indexes with a thickness of n · d = m · λ / 2 (n is the refractive index, d is the film thickness, and m is an integer) with respect to the wavelength λ to be reflected Selective reflection is possible.

  As an example, in order to reflect blue light having a wavelength of 450 nm, it can be favorably reflected by alternately stacking three layers of 308 nm thick silica (refractive index 1.46) and 180 nm thick titania (refractive index 2.5).

  Green having a wavelength of 550 nm can be reflected by stacking three layers of 377 nm silica and 220 nm titania. Moreover, red with a wavelength of 700 nm can be reflected by stacking three layers of 479 nm silica and 280 nm titania. In order to give a desired pixel a desired reflection characteristic, photolithography and etching can be used. Of course, the material and thickness of the multilayer film are not limited to this, and can be selected in accordance with a necessary band.

  INDUSTRIAL APPLICABILITY The present invention can be used for a reflective display device that has a high reflectance during white display and can perform good black display, and a reflective display device that requires color display in addition to the white and black displays. . For example, it can be used for an image display device, a message board, electronic paper, etc. for displaying a photograph such as an advertising device or a digital camera. Further, it can be used for a segment type reflective display device such as a watch.

It is sectional drawing which shows schematic structure of 1st Embodiment of the reflective display apparatus of this invention. It is a schematic sectional drawing which shows the other display method of the reflection type display apparatus of 1st Embodiment. It is sectional drawing which shows schematic structure of 2nd Embodiment of the reflection type display apparatus of this invention. (A) is sectional drawing which shows schematic structure of 3rd Embodiment of the reflection type display apparatus of this invention, (b) is the operation | movement principle of the full color display of 3rd Embodiment of the reflection type display apparatus of this invention. FIG. 6C is a configuration diagram illustrating a conceptual configuration of the full-color display in FIG. 5. It is a cross-sectional schematic diagram which shows reflection, permeation | transmission, and absorption of the light which injected into the pixel. It is pixel sectional drawing of the reflection type display apparatus of the 2nd Example of this invention. It is pixel sectional drawing of the reflection type display apparatus of the 3rd Example of this invention. It is pixel sectional drawing of the reflection type display apparatus of the 4th Example of this invention. It is a figure which shows the perspective view of the reflection type display apparatus in the case of performing passive matrix drive. It is a top view which shows the structural example of the electrodes 4 and 5 of this embodiment. It is a circuit block diagram in the case of carrying out the active matrix drive of the reflection type display apparatus by this embodiment. It is a circuit diagram which shows the control circuit which controls the direction through which an electric current flows. It is a circuit diagram which shows the control circuit which controls the direction through which an electric current flows.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 1st electrode 3 Electrolyte solution 4 2nd electrode 5 3rd electrode 6 2nd board | substrate 11 Light control layer 12 which absorbs light 12 Light control layer which reflects light 13 Light control which absorbs light Light layer 14 Light control layer 15 that reflects light 15 Light control layer that absorbs light 16 Light control layer that reflects light 17 Reflector that reflects red 18 Reflector that reflects green 19 Reflector that reflects blue 23 Second Surface of the light control layer 24 Surface of the first light control layer 25 Surface of the reflector 26 Diffusion sheet 27 Dielectric multilayer film

Claims (8)

A first electrode; a second electrode disposed opposite the first electrode; and at least one electrode of the first electrode and the second electrode, and adjacent to the other electrode A third electrode, an electrolyte solution disposed between at least the first electrode, the second electrode, and the third electrode, and at least the first electrode and the second electrode And a control means for setting a direction of a current flowing between the first electrode and the third electrode, and setting the direction of the current flowing between the first electrode and the second electrode by setting the direction of the first An electroplating film is formed on one of the electrode and the second electrode, and a reflective display device using electroplating for dimming,
A first surface of the electroplating film formed on the first electrode that contacts the first electrode, and a second surface of the electroplating film formed on the second electrode that does not contact the second electrode The surface has at least one of reflectance and absorptivity,
The control means includes: a first mode in which a first electroplating film that forms the first surface in contact with the first electrode is formed on the first electrode; and Forming a second electroplating film that forms the second surface that is not in contact with the second electrode, and setting the first electrode without the first electroplating film; and Providing a third mode in which an electroplating film is formed on the third electrode, and the first and second electrodes are absent from the first and second electroplating films;
When the electroplating film is formed on the first electrode, the reflected light from the first surface is used for display, and when the electroplating film is formed on the second electrode, the second surface is used. A reflection type display device using the reflected light of the display for display.   The electrolyte solution includes a first metal element and a second metal element as plating seeds, wherein the first metal element is silver and the second metal element is copper. The reflective display device according to claim 1. The second electrode is light transmissive, and a reflector that reflects a specific wavelength band is provided on a side of the second electrode opposite to the side facing the first electrode. The reflective display device according to claim 1 or 2 . It said second electrode is a reflective display device according to any one of claims 1-3 made from a material which reflects a specific wavelength band. The said 1st electrode is distribute | arranged to the 1st board | substrate which has a light transmittance, The said 2nd electrode is distribute | arranged to the 2nd board | substrate, The any one of Claim 1 to 4 characterized by the above-mentioned. The reflective display device described. The second electrode is arranged in one direction in a plurality of lines, and the first electrode is perpendicular to the one direction in a plurality of lines so as to intersect the second electrode arranged in a plurality of lines. reflective display device according to any one of claims 1-5 comprising arranged in a direction. Wherein the side opposite to the opposing sides of the second electrode of the first electrode, the reflection type display device according to any one of claims 1 to 6 having a layer for diffusing light. Reflective display device according to any one of claims 1 to 7 wherein the first electrode having an uneven shape to diffuse the light.