JP5846543B2 - Electrophoretic display device - Google Patents

Description

  The present invention relates to a display device that operates when fine particles charged by electrophoresis move.

  In recent years, in electrophoretic display technology, a display device has been developed in which a number of microcapsules enclosing an electrophoretic dispersion liquid containing a liquid phase dispersion medium and electrophoretic particles are sandwiched between two resin films having electrodes. Has been. By encapsulating the electrophoretic dispersion liquid in the microcapsules, there are advantages that the dispersion liquid can be prevented from flowing out and the sedimentation and aggregation of the electrophoretic particles can be reduced in the manufacturing process of the display device. In addition, this electrophoretic display device can be reduced in cost and thickness because it does not require a backlight. In addition to having a wide field of view and high contrast, the display has a memory property, so the next generation. As a display device, various proposals have been made (for example, see Patent Document 1).

  In the manufacture of an electrophoretic display device, an image display layer that operates by electrophoresis in which a large number of microcapsules are spread in an adhesive layer is laminated on a transparent electrode of a transparent substrate having a transparent electrode to form a sheet. What is called an electronic ink sheet is used. The electronic ink sheet is cut into a desired size and bonded onto a drive substrate having a pixel electrode as a drive electrode, whereby a display device body can be formed. A material such as plastic is used for the substrate of this display device from the viewpoints of flexibility, difficulty in cracking, and weight reduction.

  On the other hand, in an electrophoretic display device having such a microcapsule, particularly when a pixel electrode is employed as a drive electrode, wiring for driving the pixel electrode is formed on the back surface of the drive substrate on which the pixel electrode is formed. It is common to form with a foil pattern. That is, the pixel electrode is driven by conducting a wiring made of a copper foil pattern formed on the back surface of the drive substrate to the pixel electrode through the through hole.

  Hereinafter, an electrophoretic display device using a flexible circuit board as a driving substrate will be described. 10 is a plan view showing a conventional electrophoretic display device, and FIG. 11 is a cross-sectional view taken along line AA of FIG. As shown in FIGS. 10 and 11, the electrophoretic display device 100 is a display device except for a tip portion 111 of a flexible circuit board (hereinafter abbreviated as FPC) 110 in which the display device body 101 is a second substrate. The main body 101 is enclosed by an upper surface protective film 131 that covers the viewing side surface and a lower surface protective film 132 that covers the rear surface. End portions of the upper surface protective film 131 and the lower surface protective film 132 are formed with a sealing portion 133 that is pressure-bonded via a thermoplastic adhesive as shown by the hatched portion in FIG. The display device body 101 is electrophoresed between the transparent substrate 124 which is the first substrate including the transparent electrode 123, the FPC 110 including the pixel electrode 114 made of copper foil, and the transparent electrode 123 and the pixel electrode 114. And an image display unit 120 that operates. The image display unit 120 is formed by spreading a large number of microcapsules 122 in an adhesive layer 121.

The FPC 110 uses a polyimide film having a thickness of 25 μm and a copper foil having a thickness of 10 μm stretched on both sides of the substrate. A plurality of 7-segment pixel electrodes 114 are formed on the surface. On the back surface, a wiring electrode 113 that connects the output electrode 118 and the pixel electrode 114, an input electrode 117 that is disposed so as to face the output electrode 118, and a connector electrode 116 that is connected to the input electrode 117. Is formed. Each of the above-described electrodes is subjected to nickel plating with a thickness of 3 μm and gold plating with a thickness of 0.05 μm. The wiring electrode 113 is electrically connected to the pixel electrode 114 through a through-hole electrode 114 h provided in the opening of the FPC 110. In addition, an IC 140 that is a driving circuit is connected to the input electrode 117 and the output electrode 118 through a protruding electrode. Here, the IC 140 is shown as an example of the driving circuit, but an FPC connected to an external circuit may be connected to the output power 118.

  The back surface of the FPC 110 is covered with a protective layer 115 made of a photosensitive acrylic resin having a thickness of 25 μm and a polyimide film for protecting the wiring electrode 113 except for the connector electrode 116, the input electrode 117 and the output electrode 118. ing.

  The display device main body 101 has an adhesive layer 121 on the transparent electrode 123 side of a flexible transparent substrate 124 made of PET (polyethylene terephthalate) resin having a thickness of 100 μm and having a transparent electrode 123 made of ITO having a thickness of 0.05 μm. The image display unit 120 having a configuration in which a large number of microcapsules 122 having a diameter of 30 to 50 μm are laid is laminated on the pixel electrode 114 of the FPC 110 by laminating an adhesive sheet 119.

  The operation of the display device main body 101 is generally known (see, for example, Patent Document 2), and will be described with reference to FIG. FIG. 12 is an enlarged cross-sectional view of the main part of the display device main body 101, and shows the display operation of the microcapsule 122 with respect to the applied voltage. That is, in the microcapsule 122, white particles 122x made of titanium oxide or the like as charged particles and black particles 122y made of carbon black or the like are dispersed in a transparent dispersion medium having high viscosity such as silicone oil. It is enclosed in the state.

  Among the electrodes arranged so as to sandwich the image display layer 120, the transparent electrode 123 that is a common electrode is grounded, and the portions 114a, 114b, and 114c in which a negative voltage is applied to the pixel electrode 114 are subjected to the microcapsule 122 by the electric field. The negatively charged white particles 122x move to the display side, that is, the transparent electrode 123 side, and the positively charged black particles 122y move to the non-display side, that is, the pixel electrode 114 side. As a result, when viewed from the display side, the pixel electrode portion is displayed white by reflection of the white particles 122x.

  On the other hand, in the portions 114d, 114e, and 114f where a positive voltage is applied to the pixel electrode 114, the white particles 122x negatively charged in the microcapsule 122 by the electric field move to the non-display side and the black particles 122y positively charged. Moves to the display side. As a result, when viewed from the display side, the pixel electrode portion is displayed black as light is absorbed by the black particles 122y. Note that the left half of the central microcapsule 122b is white when a negative electric field is applied by the pixel electrode 114c, and the right half is black when a positive electric field is applied by the pixel electrode 114d. As described above, the microcapsule 122 does not necessarily correspond to one pixel electrode 114, and the pixel electrodes 114 c and 114 d on both sides like the microcapsule 122 b arranged across the two pixel electrodes 114. The display can be divided by receiving different electric fields.

  As described above, the display state of the microcapsule 122 can be changed to white or black depending on the polarity of the voltage applied between the transparent electrode 123 and the pixel electrode 114. At this time, the white particles 122x and the black particles 122y move in the dispersion medium by electrophoresis. However, even after the voltage is applied and the display state is changed, the application of the voltage is stopped. It has a memory property that retains its display state due to the force. Accordingly, since the electrophoretic display device 100 only needs to apply a driving voltage when changing the display, a display device with extremely low power consumption can be realized.

JP 2010-181768 (pages 1, 2 and 4) JP 2010-8473 A (FIG. 4, pages 6-7)

  However, it has been found that the applicant has the following problems when the electrophoretic display device 100 is manufactured. The problem will be described below with reference to FIGS. FIG. 13 is a cross-sectional view illustrating a state in which the image display unit 120 is started to press against the pixel electrode 114 of the FPC 110 using the press roller 150 in the display device main body 101. FIG. 14 shows a state in which the pressure contact is completed by the roller 150. In the electrode gap 170 without the pixel electrode of the FPC 110, the electrode gap 170 is formed by the transparent substrate 124 having the transparent electrode 123 being pushed and bent by the pressure of the roller 150. The microcapsule 122h corresponding to the position is pushed down, and the conductive adhesive sheet 119 is deformed.

  15 and 16 are cross-sectional views showing problems due to deformation of the adhesive sheet 119. FIG. For easy understanding, the white particles and the black particles in the microcapsule 122h in FIGS. 15 and 16 are not shown. FIG. 15 is a cross-sectional view when the wiring electrode 113 does not exist on the back side of the electrode gap 170 in the FPC 110. Since the transparent substrate 124 is deformed by the thickness of the surface pixel electrode 114 with respect to the pressure of the roller 150 illustrated in FIG. 15, the deformation of the conductive adhesive sheet 119 is small. Therefore, after the pressure of the roller 150 disappears as shown in FIG. 15, the deformation of the pressure-sensitive adhesive sheet 119 is restored to some extent, and a small air layer 160a is formed. However, as shown by solid arrows, both ends of the electrode gap 170 are formed. The electric field from the pixel electrode 114 can be controlled, and the microcapsule 122h can operate normally.

  FIG. 16 is a cross-sectional view when the wiring electrode 113 exists on the back side of the electrode gap 170 in the FPC 110. The wiring electrode 113 provided on the back surface is transparent to the pressure of the roller 150 shown in FIG. Since the substrate 124 is greatly deformed, the deformation of the adhesive sheet 119 is large as shown in FIG. 16, and in some cases, the substrate 124 may be cut as illustrated. Therefore, after the pressure of the roller 150 is lost, the deformation of the adhesive sheet 119 is large and cannot be restored. Accordingly, in this case, a large air layer 160b is formed, and electric field control from the pixel electrodes 114 at both ends of the electrode gap 170 becomes impossible as indicated by a dotted arrow, and the microcapsule 122h cannot operate normally and is displayed in black. There is a problem that a white spot phenomenon occurs in which a portion to be whitened becomes white.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to minimize the problem that the electric field control of the gap between the electrodes in which the pixel electrodes are not arranged cannot operate normally. It is an object of the present invention to provide an electrophoretic display device that can be prevented.

The means of the present invention for achieving the above-described object includes a first substrate having a transparent electrode, a second substrate having a pixel electrode, and an image display operated by electrophoresis between the transparent electrode and the pixel electrode. A pixel electrode for forming an image display portion and a background electrode are provided on the upper surface of the second substrate, and an electric signal is applied to the pixel electrode and the background electrode on the back surface side of the second substrate. In the electrophoretic display device having a wiring electrode, all the wiring electrodes are orthogonal to the electrode gap between the pixel electrodes forming the image display unit or the electrode gap between the pixel electrode and the background electrode. The electrode width of the wiring electrode at the portion that is drawn in the direction and intersects the electrode gap between the pixel electrodes or the electrode gap between the pixel electrode and the background electrode is narrower than the electrode width of the portion that does not intersect the electrode gap. And

In addition, the pixel electrode forming the image display unit is preferably an image display unit having a seven-segment configuration.

  According to the present invention, even if a phenomenon in which electric field control cannot be normally performed at a location where no electrode is present between the electrodes, the white area phenomenon in the display of the electrophoretic display device can be achieved by reducing the area. Can be reduced and display quality can be improved.

It is a top view which shows the image display part in the electrophoresis type display apparatus of this invention. It is a principal part top view which shows one character of the image display part shown in FIG. It is a principal part top view which shows the back surface of FPC corresponding to the image display part in 1st Embodiment of this invention. It is a principal part top view which shows the upper surface of FPC corresponding to the image display part shown in FIG. It is a principal part top view which shows the back surface of FPC of a reference example. It is a principal part top view which shows the upper surface of FPC of a reference example. It is a principal part top view which shows the upper surface of FPC of a reference example. It is a top view which shows the back surface of FPC corresponding to the image display part in 2nd Embodiment of this invention. It is a top view which shows the back surface of FPC corresponding to the image display part in 3rd Embodiment of this invention. It is a top view of the conventional electrophoretic display device of the present invention. It is AA sectional drawing of the electrophoresis type display apparatus shown in FIG. It is a principal part expanded sectional view of a display apparatus main body. It is principal part sectional drawing which shows the adhesion state of an image display part. It is principal part sectional drawing which shows the adhesion state of an image display part. It is principal part sectional drawing which shows the adhesion state of an image display part. It is principal part sectional drawing which shows the adhesion state of an image display part.

  Hereinafter, an electrophoretic display device which is the best embodiment of the present invention will be described in detail with reference to the drawings. The configuration and operation of the electrophoretic display device of the present invention are basically the same as the configuration of the conventional electrophoretic display device shown in FIGS. The configuration of the image display unit 120 including the FPC, which is a characteristic part of the present invention, is different from the conventional electrophoretic display device. The same members as those in the electrophoretic display device shown in FIGS.

  FIG. 1 is a plan view of an image display unit 10 (120 in FIG. 11) including an FPC in an electrophoretic display device of the present invention, and three 7-segment pixel electrodes and a background electrode are formed on the upper surface side of the FPC 110. Explain the case. FIG. 2 is a detailed plan view showing a part of the image display unit 10 shown in FIG. 1 and a pixel electrode for one character having a 7-segment structure surrounded by a one-dot chain line in FIG. It is composed of seven pixel electrodes 11a to 11g indicated by hatching and three background electrodes 12a, 12b and 12c indicated by cross hatching. An oblique straight electrode gap 13 is formed between the pixel electrodes 11a to 11g having a 7-segment structure, and an oblique straight electrode gap 14a and an electrode parallel to the straight line are provided between the pixel electrode 11 and the background electrode 12. A gap 14b is formed.

(First embodiment)
3 and 4 show the image display unit 10 according to the first embodiment of the present invention, and FIG. 3 is a back view of the FPC 110 corresponding to the image display unit 10, from the pixel electrode 11 a on the upper surface side of the FPC 110 indicated by a dotted line. The wiring electrode 15 for supplying an electrical signal to 11g and the background electrodes 12a to 12c is drawn to the output electrode side 110s of the FPC 110. That is, all the wiring electrodes 15 are all orthogonal to the electrode gaps 14 a and 14 b between the pixel electrode 11 and the background electrode 12 by the through-hole electrodes 16 connected to the pixel electrode 11 and the background electrode 12 on the upper surface of the FPC 110. It is pulled out in the direction and guided to the output electrode side 110s. FIG. 4 shows the display state of the pixel electrode 11 formed on the image display unit 10 on the upper surface of the FPC 110, and all the seven segments are lit black, but the electrodes between the pixel electrodes 11 where no pixel electrode exists. The gap 13 is also lit in black by driving the pixel electrodes 11 on both sides of the electrode gap 13 as described with reference to FIG. 12, and a continuous 8-character is displayed. Actually, even if all the wiring electrodes 15 are pulled out in the direction orthogonal to the electrode gaps 13, 14a, 14b, a region that slightly overlaps occurs. For this reason, the white spot phenomenon described with reference to FIG. 16 occurs in this portion. However, since the size of the area is not large enough to be recognized by human eyes, even if a white spot phenomenon occurs, it is hardly noticeable.

  FIGS. 5 and 6 are reference views shown for comparison with the first embodiment of the present invention shown in FIGS. 3 and 4, and are plan views of the FPC 110 corresponding to the image display unit 40, and FIG. FIG. 6 shows the top surface. The basic configuration of FIGS. 5 and 6 is the same as that of the image display unit 10 of the first embodiment shown in FIGS. 3 and 4, and the same reference numerals are given to the same elements, and duplicate descriptions are omitted.

  That is, the wiring electrode 15 of the FPC 110 shown in FIG. 5 differs from the wiring electrode 15 of the FPC 110 shown in FIG. 3 in that the background electrode 12a and the background in the wiring electrode 15 connecting the three background electrodes 12a, 12b, and 12c. The wiring electrode 15k connected to the electrode 12b is overlapped with the electrode gap 13k between the pixel electrode 11a and the pixel electrode 11b (this portion is indicated by a one-dot chain line frame K). As a result, as shown in FIG. 16, the microcapsules 122 arranged in the wiring electrode 15k are in a state in which electric field control is impossible. Therefore, the 8-character display of the pixel electrode shown in FIG. It can be seen that the microcapsule 122 corresponding to the electrode gap 13k inside K is in a white-out state and in an incomplete display state.

  Further, as a display state, the background is displayed in black, and the 7-segment pixel is displayed in white. In that case, the background electrode is displayed in black, and a part of the pixel electrode is changed to white display. In the initial state, the entire image display unit is displayed in black. However, as shown in FIG. 5, when the wiring electrode 15k overlaps the electrode gap 13k between the pixel electrode 11a and the pixel electrode 11b, as shown in FIG. When black display is performed, only the portion of the electrode gap 13k is in a white-out state P3, which becomes conspicuous, and display quality is significantly deteriorated.

  As described above, compared with the reference examples of FIGS. 5, 6, and 7, in the present invention of FIGS. 3 and 4, the wiring electrodes are arranged so as not to overlap with the electrode gap as much as possible, and a large blank state is generated. I try not to. That is, there is a difference in pixel electrode display between the present invention in which all the wiring electrodes are arranged perpendicular to the electrode gap 14 and the reference example in which the wiring electrodes are arranged in parallel with a part of the electrode gaps 13 and 14. You can see that it happens.

(Second Embodiment)
FIG. 8 is a back view of the FPC 110 corresponding to the image display unit 20 in the second embodiment of the present invention, and corresponds to the back view of the FPC 110 of the image display unit 10 in the first embodiment shown in FIG. Accordingly, the basic configuration is the same, the same elements are denoted by the same reference numerals, and a duplicate description is omitted.

The image display unit 20 in the second embodiment differs from the image display unit 10 in the first embodiment in the shape of the wiring electrodes on the back surface of the FPC 110, and all the wiring electrodes 15 in the pixel display unit 10 have the same line width. On the other hand, the wiring electrode 15 of the image display unit 20 has the electrode width of the wiring electrode 15a in the region where the pixel electrode forming the image display unit 20 is arranged, and the pixel electrode forming the image display unit 20 is arranged. That is, the line width is narrower than the electrode width of the wiring electrode 15b outside the region. This is preferable because the wiring electrode 15 has a wider line width from the viewpoint of electrical characteristics, since the electric resistance is smaller. However, when viewed as a display device, the wiring line 15 is whiter when the line width across the electrode gap 14 is narrower. This is desirable because the size of the missing portion is small. Accordingly, in the image display unit 20, the wiring electrode 15a from which the pixel electrode part involved in white spots is drawn has a narrower line width in consideration of the effect as a display device, and the wiring electrode 15b outside the pixel electrode part is electrically connected. The line width is increased in consideration of the effects of the effects.

(Third embodiment)
FIG. 9 is a rear view of the FPC 110 corresponding to the image display unit 30 in the third embodiment of the present invention, and corresponds to the rear view of the FPC 110 of the image display unit 20 in the second embodiment shown in FIG. Accordingly, the basic configuration is the same, the same elements are denoted by the same reference numerals, and a duplicate description is omitted.

  The difference between the image display unit 30 in the third embodiment and the image display unit 20 in the second embodiment is the shape of the wiring electrode 15 on the back surface of the FPC 110, and the wiring electrode 15 of the image display unit 20 uses the image display unit 20. Although all the electrode widths of the wiring electrodes 15a in the pixel electrode arrangement region to be formed are narrower than the electrode widths of the wiring electrodes 15b outside the pixel electrode region forming the image display unit 20, image display is performed. The wiring electrode 15 of the part 30 is divided into two kinds of electrode widths of the wiring electrode 15 from which the pixel electrode part forming the image display part 30 is drawn, and the wiring of only the part passing through the electrode gap 14 (14a, 14b) The electrode width of the electrode 15a is narrow, and the other portion of the wiring electrode 15c is wider than the wiring electrode 15a in the same manner as the wiring electrode 15b outside the pixel electrode portion. That. According to the above configuration, since only the electrode width of the wiring electrode 15a only in the portion that passes through the electrode gap 14 is narrowed, the size of the white portion can be reduced, and at the same time, the electrode width of the wiring electrode 15c in the other portion. There is a merit to lower the electrical resistance by the amount of widening.

  In the embodiment of the present invention described above, the wiring electrode is drawn out in a direction orthogonal to the electrode gap 14 between the pixel electrode and the background electrode, but with respect to the electrode gap 13 between the pixel electrodes. May be drawn in a direction orthogonal to each other. Further, although the wiring electrodes for one character of 7 segments have been described as the pixel electrodes of the image display unit, the same wiring is performed for the plurality of 7 segment characters of the image display unit shown in FIG.

10, 20, 30, 40, 120 Image display unit 11 (a to g), 114 Pixel electrode 12 (ac) Background electrode 13, 14 (a, b), 170 Electrode gap 15 (ac), 113 Wiring electrode 16, 114h Through hole
DESCRIPTION OF SYMBOLS 100 Electrophoretic display apparatus 101 Display apparatus main body 110 Flexible printed circuit board (FPC)
116 Connector electrode 117 Input electrode 118 Output electrode 119 Conductive adhesive sheet 121 Adhesive layer 122 Microcapsule 122x White particles 122y Black particles 123 Transparent electrode 124 Transparent substrate 131 Upper surface protective film 132 Lower surface protective film 133 Sealing portion 140 IC
150 Roller 160a, 160b Air layer

Claims (2)

A first substrate including a transparent electrode; a second substrate including a pixel electrode; and an image display unit that operates by electrophoresis between the transparent electrode and the pixel electrode.
The upper surface of the second substrate includes a pixel electrode and a background electrode that form the image display unit,
In the electrophoretic display device having a wiring electrode for applying an electrical signal to the pixel electrode and the background electrode on the back surface side of the second substrate,
All the wiring electrodes are drawn out in a direction orthogonal to the electrode gap between the pixel electrodes forming the image display unit, or the electrode gap between the pixel electrode and the background electrode ,
An electrode width of the wiring electrode in a portion intersecting with an electrode gap between the pixel electrodes or an electrode gap between the pixel electrode and the background electrode is narrower than an electrode width of a portion not intersecting with the electrode gap. An electrophoretic display device.   2. The electrophoretic display device according to claim 1, wherein the pixel electrode forming the image display unit has a 7-segment configuration.

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