JP2009230060A - Electrophoresis device and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophoresis device capable of providing quality of display close to that of paper. <P>SOLUTION: The electrophoresis device includes a first substrate 10, an insulating layer 12 provided on an upper side of the first substrate, a plurality of individual electrodes 14 provided on an upper side of the insulating layer, electrophoretic layers 16 provided on upper sides of a plurality of individual electrodes, respectively, a common electrode 22 formed with a transparent electric conductive membrane, provided on an upper side of the electrophoretic layer, and opposing to each of a plurality of individual electrodes, and a second transparent substrate 24 for supporting the common electrode. Each of a plurality of individual electrodes is constituted of an electric conductive membrane having high reflectance of bright color such as white color, light gray color or the like. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrophoresis apparatus used for display applications and the like, and an electronic apparatus including the electrophoresis apparatus.

  Conventionally, much attention has not been paid to the material of the pixel electrode (individual electrode) in the electrophoresis apparatus used for display applications. For example, in Japanese Patent Application Laid-Open No. 2006-189780 (Patent Document 1), the pixel electrode of the electrophoretic display device is described as “consisting of a transparent conductive material such as IZO or ITO or a conductive material having reflectivity”. Has been. However, in order to obtain a high reflectance in the electrophoretic device, it is desirable that the reflectance of the back surface of the electrophoretic material (electrophoretic layer) be higher. If the back surface reflectance is low, it is difficult to increase the reflectance during visual recognition. In order to obtain display quality close to that of paper, a high reflectance (particularly white reflectance) is indispensable.

JP 2006-189780 A

  A specific aspect of the present invention is to provide an electrophoretic device capable of realizing a high reflectance.

  The electrophoresis apparatus according to the present invention includes (a) a first substrate, (b) an insulating layer provided on the upper side of the first substrate, and (c) a plurality of individual electrodes provided on the upper side of the insulating layer. (D) an electrophoretic layer provided on the upper side of the plurality of individual electrodes, and (e) a transparent conductive film, which is provided on the upper side of the electrophoretic layer and faces each of the plurality of individual electrodes. An electrophoretic device comprising: a common electrode; and (f) a transparent second substrate that supports the common electrode, wherein each of the plurality of individual electrodes is made of a light conductive film.

  According to such a configuration, each pixel electrode disposed on the back surface of the electrophoretic layer is configured to have a light color such as white or light color, thereby allowing the reflectance when viewed from the second substrate side (that is, macroscopic). High reflectance) and display quality close to that of paper can be obtained.

  Preferably, each of the plurality of individual electrodes is white. Thereby, since the reflectance of each pixel electrode is further improved, the reflectance during visual recognition can be further increased.

  Each of the plurality of individual electrodes described above is preferably made of, for example, an aluminum thin film. Thereby, an individual electrode having a high reflectance (for example, 80% or less) is obtained.

  It is also preferable that the insulating layer is made of a light insulating film such as white or light color. As a result, the reflectance of the underlying insulating layer seen from the gaps between the individual electrodes is improved, so that the reflectance at the time of visual recognition can be further increased.

  The light-colored insulating film described above is realized by a film containing an aluminum oxide sintered body, for example. Thereby, an insulating film with high reflectivity is obtained.

  The electrophoretic layer described above includes, for example, a plurality of microcapsules. By applying the present invention to such a microcapsule type electrophoresis apparatus, the reflectance of the gap between the microcapsules can be improved, and an electrophoresis apparatus having a high reflectance during visual recognition can be obtained.

  Preferably, the width of at least one direction of each of the plurality of individual electrodes is set larger than the width of each of the plurality of microcapsules. More preferably, the width in the other direction of each individual electrode is set larger than the width of each microcapsule. As a result, the ratio of the gaps between the microcapsules covered by the low-reflectance pixel electrodes is increased, the reflectance of the gaps described above is more reliably increased, and the reflectance during viewing is improved. Can do.

  An electronic apparatus according to the present invention includes the above-described electrophoresis apparatus as a display unit. Here, the “electronic device” includes all devices including a display unit that uses display by an electrophoretic material, and includes a display device, a television device, electronic paper, a clock, a calculator, a mobile phone, a portable information terminal, and the like. Including. Also, things that deviate from the concept of “equipment”, for example, flexible paper / film-like objects, belonging to real estate such as wall surfaces to which these objects are attached, moving objects such as vehicles, flying objects, ships, etc. Including those belonging to. By providing the electrophoretic device according to the present invention as a display unit, an electronic apparatus including a display unit with excellent reflectivity during viewing can be obtained.

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

  FIG. 1 is a schematic cross-sectional view showing the configuration of an electrophoresis apparatus according to an embodiment to which the present invention is applied. An electrophoretic device 1 shown in FIG. 1 is an active matrix type display device configured by arranging a plurality of pixels in a matrix, and includes a first substrate 10, an insulating layer 12, a plurality of pixel electrodes (individual electrodes). ) 14, the electrophoretic layer 16, the common electrode 22, and the second substrate 24. As illustrated, the electrophoretic layer 16 in the present embodiment is configured by arranging a plurality of microcapsules each containing a large number of electrophoretic particles 18 and 20. For convenience of explanation, circuit portions (switching elements, wirings, etc.) for supplying drive signals to the pixel electrodes 14 and the common electrode 22 are not shown.

  The first substrate 10 is made of an insulating substrate such as a glass substrate or a plastic substrate. The thickness of the first substrate 10 is preferably 25 μm or more from the viewpoint of physical strength of the substrate when forming a thin film circuit, and is 200 μm or less from the viewpoint of ensuring the flexibility of the substrate. Although it is desirable, it is not limited to these numerical values.

The insulating layer 12 is provided on the first substrate 10. As this insulating layer 12, for example, an inorganic insulating film such as a silicon oxide film (SiO _x ) or a silicon nitride film (SiN) can be used. In addition, as the insulating film 12, it is also preferable to use an insulating film made of a bright (typically white) insulating material such as a film containing an aluminum oxide sintered body. This is because the reflectance on the back surface of the display area of the electrophoretic device 1 can be increased and the reflectance during visual recognition can be improved. The insulating film 12 made of a film containing an aluminum oxide sintered body is, for example, a material obtained by sintering a raw material powder such as aluminum oxide, silica, magnesia, calcia, etc., is dispersed in an organic solvent. A film can be formed by a method such as a coating method and then dried.

  Each of the pixel electrodes 14 is provided on the insulating layer 12 and is spaced apart from each other. In the present embodiment, each pixel electrode 14 is formed using a light color (typically white), that is, a material having high reflectivity. Specifically, each pixel electrode 14 is obtained, for example, by depositing an aluminum (Al) thin film on the insulating layer 12 on the first substrate 10 using a sputtering method and patterning the aluminum (Al) thin film. Such a pixel electrode 14 has a very high reflectance of about 90% over the entire visible light range. Thereby, the reflectance of the display area back surface of the electrophoresis apparatus 1 can be increased, and the reflectance during visual recognition can be improved.

  The electrophoretic layer 16 is disposed between the first substrate 10 and the second substrate 24, more specifically, between each pixel electrode 14 and the common electrode 22. The electrophoretic layer 16 in this embodiment includes a large number of microcapsules fixed by a binder. Each microcapsule contains an electrophoretic dispersion medium and electrophoretic particles. The electrophoretic particles have a property of moving in the electrophoretic dispersion medium according to an applied voltage, and one type (one color) or more of electrophoretic particles are used. In the present embodiment, the first particles 18 that are positively charged and the second particles 20 that are negatively charged are contained in each microcapsule. The thickness of the electrophoretic layer 16 is, for example, about 30 μm to 75 μm.

  The common electrode 22 is formed over substantially the entire surface of the second substrate 24 and is disposed so as to face each pixel electrode 14. In the present embodiment, since it is assumed that the second electrode 24 is visible, the common electrode 22 is configured using a transparent conductive film. Examples of the transparent conductive film constituting the common electrode 22 include a tin-doped indium oxide film (ITO film), a fluorine-doped tin oxide film (FTO film), an antimony-doped zinc oxide film, and indium. A zinc oxide film doped with aluminum, a zinc oxide film doped with aluminum, or the like can be used. These transparent conductive films can be formed by a film forming technique such as sputtering, electron beam, ion plating, vacuum deposition, or chemical vapor deposition (CVD).

  The second substrate 24 is made of, for example, a transparent thin film (transparent insulating synthetic resin base material), and is provided so as to cover the electrophoretic layer 16. The thickness of the second substrate 24 is, for example, about 10 to 200 μm. In addition, the 2nd board | substrate 24 is not limited only to a film-form board | substrate, A glass substrate, a plastic substrate, etc. may be sufficient.

  The electrophoretic device 1 of the present embodiment has such a configuration. Next, a configuration for improving the reflectance during visual recognition will be described in more detail.

  FIG. 2 is a schematic plan view showing an arrangement state of each microcapsule constituting the electrophoretic layer. Note that a plurality of circles shown in the drawing schematically show the microcapsules. As shown in the figure, when each microcapsule is provided on each pixel electrode 14, it is assumed that each microcapsule maintains a spherical shape without being crushed at all. The visual coverage is about 90.7% at the maximum (when each microcapsule can be coated most closely as shown). At this time, there is always a region (gap) that is not covered by the microcapsules between the microcapsules. In the figure, the above-mentioned numerical value of 90.7% is the result of calculating the ratio of the area of the portion covered by each microcapsule indicated by a circle to the area of the region surrounded by the solid square. . FIG. 2 shows an ideal case in which the entire surface of each pixel electrode 14 can be covered with microcapsules without any defects. In practice, however, it is considered that the coverage is further reduced to 90% or less. . Below, the case where each microcapsule could be applied ideally is considered.

  3 and 4 are graphs showing the results of estimating the reflectance and contrast ratio of the electrophoresis apparatus of this embodiment. 3 and 4, the horizontal axis represents the reflectance of the portion (gap) not covered with the capsule, the left vertical axis represents the contrast ratio, and the right vertical axis represents the reflectance. When the electric field is applied to each microcapsule to control the distribution of the first particles 18 and the second particles in the microcapsule so that the visual state from the second substrate 24 side becomes “black display” It is assumed that the reflectance of the single microcapsule is 5%, and the reflectance of the single microcapsule is 60% when the viewing state from the second substrate 24 side is “white display”. The values of the black reflectance 5% and the white reflectance 60% of the microcapsule alone assumed here are realistic and appropriate values in consideration of the reflection and absorption of the capsule material, binder, transparent electrode, protective film, etc. It is. At this time, when the reflectance of the entire region of the electrophoretic device 1 and the contrast are calculated by changing the reflectance of the region not covered by the microcapsule (gap region; see FIG. 2), the result shown in FIG. 3 is obtained. From this graph, it can be seen that when the reflectance of the gap region (gap reflectance) decreases, the white reflectance significantly decreases. In general, it is considered that a white reflectance of 60% or more is necessary to obtain display quality close to that of paper. Here, even if it is assumed that the white reflectance of the microcapsule alone is increased to 80% by using a material that absorbs very little, the tendency is the same. FIG. 4 shows the gap reflectance dependency of the reflectance and contrast ratio at that time. In order to obtain a high reflectance, it is necessary to increase the gap reflectance. From such consideration, in order to increase the gap reflectance, it is important to improve the reflectance of each pixel electrode 14 as described above. In addition, since the pixel electrodes 14 need to be separated from each other, it is desirable that the gap between the pixel electrodes 14 is also highly reflective. Therefore, as described above, the insulating layer 12 below each pixel electrode 14 is also desired to have a high reflectance.

  FIG. 5 is a schematic plan view for explaining the relative size relationship between the size of each microcapsule and each pixel electrode. A plurality of circles shown in the drawing schematically show each microcapsule of the electrophoretic layer 16, and a rectangle shown by a dotted line schematically shows the pixel electrode 14. As shown in the figure, when each microcapsule is provided on each pixel electrode 14, it is assumed that each microcapsule is kept in a spherical shape without being crushed and is arranged in a close-packed state. As shown in FIG. 5, each pixel electrode 14 preferably has a width D1 in at least one direction larger than a width (corresponding to the capsule diameter) D3 of each microcapsule in plan view. In the illustrated example, D1 is three times or more than D3. It is more desirable that each pixel electrode 14 has a width D2 in one other direction larger than a width (corresponding to the capsule diameter) D3 of each microcapsule in plan view. In the illustrated example, D2 is also three times as large as D3. Thereby, the ratio that the gaps between the microcapsules are covered by the high-reflectance pixel electrodes 14 is further increased, and the gap reflectance described above can be more reliably increased.

  FIG. 6 is a perspective view illustrating a specific example of an electronic apparatus to which the electrophoresis apparatus is applied. FIG. 6A is a perspective view illustrating an electronic book which is an example of the electronic apparatus. The electronic book 1000 includes a book-shaped frame 1001, a cover 1002 provided to be rotatable (openable and closable) with respect to the frame 1001, an operation unit 1003, and the electrophoresis apparatus according to the present embodiment. The display unit 1004 is provided. FIG. 6B is a perspective view illustrating a wrist watch which is an example of an electronic apparatus. The wrist watch 1100 includes a display unit 1101 configured by the electrophoresis apparatus according to the present embodiment. FIG. 6C is a perspective view illustrating electronic paper which is an example of the electronic apparatus. The electronic paper 1200 includes a main body unit 1201 configured by a rewritable sheet having the same texture and flexibility as paper, and a display unit 1202 configured by the electrophoresis apparatus according to the present embodiment. The range of electronic devices to which the electrophoretic device can be applied is not limited to this, and includes a wide range of devices that utilize changes in visual color tone accompanying the movement of charged particles. For example, in addition to the above-described devices, those belonging to real estate such as wall surfaces to which an electrophoretic film is bonded, and those belonging to moving bodies such as vehicles, flying objects, and ships are also applicable.

  According to the present embodiment as described above, each pixel electrode 14 disposed on the back surface of the electrophoretic layer 16 is configured to have a light color such as white, whereby the reflectance when viewed from the second substrate 24 side. It is possible to increase (macroscopic reflectance). This effect becomes remarkable by making the width of each pixel electrode 14 larger than the width of each microcapsule as described above. In addition, the insulating layer 14 is also configured to have a light color such as white, whereby the reflectance at the time of visual recognition can be further increased.

  In addition, this invention is not limited to the content of embodiment mentioned above, In the range of the summary of this invention, it can change and implement variously.

  For example, in the above-described embodiment, an example in which microcapsules are used as an example of the electrophoretic layer is illustrated, but the configuration of the electrophoretic layer is not limited thereto. For example, the present invention can be applied even to an electrophoretic layer having a structure 26 called a cell structure, a rib structure or a partition structure as shown in FIG. In that case, if the structure 26 shown in FIG. 6 is disposed on the pixel electrode 14, electrophoretic particles are disposed in each cell partitioned by the partition walls, and the common electrode 22 is disposed above the partition walls. Good (see FIG. 1). In this case, the total reflectance can be increased by forming the structure 26 with a material having a high reflectance. For example, when the area occupied by the partition walls of the structure 26 in the plan view is 9.3%, the same result as the above-described graph (see FIGS. 3 and 4) is obtained.

  In the above-described embodiment, an active matrix display device is shown as an example of the electrophoresis device according to the present invention, but the scope of the present invention is not limited to this. The present invention can also be applied to an electrophoresis apparatus which is a so-called segment type display device. Further, the electrophoretic apparatus to which the present invention is applied is not limited to display applications.

It is a schematic cross section which shows the structure of the electrophoresis apparatus of one Embodiment. It is a schematic plan view which shows the arrangement | positioning state of each microcapsule which comprises an electrophoresis layer. It is a graph which shows the result of having estimated the reflectance and contrast ratio of the electrophoresis apparatus. It is a graph which shows the result of having estimated the reflectance and contrast ratio of the electrophoresis apparatus. It is a schematic plan view for demonstrating the relative magnitude relationship of the size of each microcapsule and each pixel electrode. It is a perspective view explaining the specific example of the electronic device to which the electrophoresis apparatus is applied. 1 is a schematic perspective view illustrating a so-called cell structure or the like.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrophoresis apparatus, 10 ... 1st board | substrate, 12 ... Insulating layer, 14 ... Pixel electrode (individual electrode), 16 ... Electrophoresis layer, 18 ... 1st particle | grains, 20 ... 2nd particle | grains, 22 ... Common electrode, 24 ... Second substrate, 26 ... Structure

Claims (8)

A first substrate;
An insulating layer provided on an upper side of the first substrate;
A plurality of individual electrodes provided on the upper side of the insulating layer;
An electrophoretic layer provided on an upper side of the plurality of individual electrodes;
A common electrode made of a transparent conductive film, provided on the electrophoretic layer and facing each of the plurality of individual electrodes;
A transparent second substrate supporting the common electrode;
Each of the plurality of individual electrodes is made of a light-colored conductive film,
Electrophoresis device.   The electrophoresis apparatus according to claim 1, wherein each of the plurality of individual electrodes is white.   The electrophoresis apparatus according to claim 1, wherein each of the plurality of individual electrodes is made of an aluminum thin film.   The electrophoretic device according to claim 1, wherein the insulating layer is made of a light-colored insulating film.   The electrophoresis device according to claim 4, wherein the insulating film is a film containing an aluminum oxide sintered body.   The electrophoresis device according to claim 1, wherein the electrophoresis layer includes a plurality of microcapsules.   The electrophoresis apparatus according to claim 6, wherein a width of at least one direction of each of the plurality of individual electrodes is set to be larger than a width of each of the plurality of microcapsules.   An electronic apparatus comprising the electrophoresis device according to any one of claims 1 to 7.

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