JP4925090B2 - Display device - Google Patents

Description

  The present invention relates to a display device, and more particularly to a display device using an electrorheological fluid.

  An electrorheological fluid (hereinafter referred to as “ER fluid”) is a fluid whose rheological properties such as viscosity and stress change in response to an external electric field, such as a clutch, a valve, a damper, an actuator, etc. Application to various devices is expected.

  A typical configuration of the ER fluid is a configuration in which insulating solid particles are dispersed in an insulating liquid. When an electric field is applied to the ER fluid, a chain structure of solid particles (hereinafter referred to as “bridge”) is applied along this direction. ”) Is formed, and rheological properties such as fluid viscosity change due to the attractive force between the bridges. Although the mechanism by which this bridge is formed has not been fully elucidated, the ion dissociation groups on the surface of the solid particles are dissociated by the influence of moisture present in the liquid to form an electric double layer. On the other hand, it is considered that when the electric double layer is distorted by an electric field, the solid particles are electrically attracted to each other, and the rheological properties are changed.

  By the way, the use of ER fluid in a display device is also actively proposed. For example, in Non-Patent Document 1 below, an ER fluid is sandwiched between a pair of electrodes, and an electric field is applied or removed between the pair of electrodes. Thus, there is disclosed a technique for dimming light by causing a difference in light transmittance. Patent Document 1 below discloses a technique using a display material sheet in which a microencapsulated ER fluid is sandwiched between a pair of electrodes. Patent Document 2 below discloses a technique related to a display device in which a reference electrode and an adjacent electrode are nested in one of a pair of opposing substrates, and a counter electrode is formed on the entire surface of the other substrate. ing.

Journal of colloid and InterfaceScience, 1996, 177, 250-256. JP 2004-54165 A JP-A-8-129184

  However, in any of the above techniques, when the electric field is applied to the non-applied state, the solid particles are dispersed using the Brownian motion of the solid particles. There is a problem that it takes a certain amount of time to disperse. Further, if a bridge is formed by applying an electric field, solid particles are solidified, and there is a problem that dispersion is extremely difficult only by Brownian motion or the like.

  Accordingly, an object of the present invention is to solve the above-described problems and provide a display device having excellent response characteristics.

  As a result of intensive studies on the above problems, the present inventors can realize excellent response characteristics by writing and erasing images by generating a plurality of electric field directions in the pixel region of the display device. The present invention has been completed.

  That is, a display device according to one means of the present invention includes a first substrate and a second substrate that are arranged to face each other, a spacer that is sandwiched between the first substrate and the second substrate, and an electrorheology. A first pixel electrode and a second pixel electrically independent of the first pixel electrode on a surface of the first substrate facing the second substrate. The electrode is formed, and the third pixel electrode and the fourth pixel electrode electrically independent from the third pixel electrode are formed on the surface facing the first base of the second substrate. Features.

  Further, in this means, the first substrate is provided with a first switching element capable of electrically connecting the first pixel electrode and the second pixel electrode, and the second substrate is provided with the first substrate. It is also desirable that a second switching element that can electrically connect the third pixel electrode and the fourth pixel electrode is formed.

  Further, in this means, the third switching element that enables the first pixel electrode and the third pixel electrode to be electrically connected, and the second pixel electrode and the fourth pixel electrode can be electrically connected. It is also desirable to have a driver circuit in which a fourth switching element is formed.

  In this means, it is desirable that the first electrode and the second electrode are arranged substantially in parallel, and further, the third electrode and the fourth electrode are also arranged substantially in parallel.

  Further, in this means, the first pixel electrode and the third pixel electrode, and the second pixel electrode and the fourth pixel electrode are arranged so as to overlap when the first substrate is viewed from the vertical direction. It is also desirable that

  As described above, according to the present invention, a display device having excellent response characteristics can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Needless to say, the present invention can be implemented in many different forms and is not limited to the following embodiments and examples.

  FIG. 1 is a diagram showing an outline of a configuration of a display device according to the present embodiment (hereinafter referred to as “the present display device”). The display device 1 includes a first substrate 2 and a second substrate 3 that are disposed to face each other (hereinafter, the first substrate 2 and the second substrate 3 are also referred to as a “pair of substrates”). And a spacer 4 and an electrorheological fluid layer 5 sandwiched between the pair of substrates.

  Further, the colored layer 7 is disposed on the surface of the second substrate 3 of the present display device opposite to the surface facing the first substrate, and the observer of the display device can select the second substrate 2 of the first substrate 2. The image displayed on the display device 1 can be visually recognized by observing the display device 1 from the surface opposite to the surface facing the substrate 3. The color of the colored layer 7 is white or a reflective material (insulating solid particles are light-transmitting in monochrome display) so that the color can be seen by an observer when a display device described later is in a transmissive state. Or a material that does not reflect light (when insulating solid particles scatter light), and is colored in red, green, or green, for example, for color display. It is desirable that

  The first substrate 2 and the second substrate 3 according to the present embodiment are not particularly limited as long as they are transparent, and as a material, for example, a transparent plastic such as glass, polycarbonate resin, or acrylic resin is used. It can be suitably employed. In addition, when a pair of substrates is a so-called transmissive display device, it is desirable that both of them are transparent. However, when a reflective display device is used, at least one of the substrates may be transparent.

The spacer 4 is for keeping the distance between the pair of substrates at a desired thickness. In this embodiment, the spacer 4 has a plate shape in which a plurality of rectangular cutouts 41 are formed. Is filled with ER fluid. As a material of the spacer 4, it is desirable to have an insulating property so as not to weaken an electric field applied to the ER fluid. For example, organic materials such as polyethylene and polystyrene can be used, and SiO ₂ and SiN can be used. Inorganic materials can also be used. The shape of the spacer 4 is not particularly limited as long as the distance between the pair of substrates can be maintained at a desired thickness, and may be, for example, a spherical spacer or a columnar spacer. The thickness of the spacer 4 can be appropriately adjusted depending on the applied voltage or the like, but is preferably about 100 μm to 5 mm.

  The electrorheological fluid layer (hereinafter referred to as “ER fluid layer”) 5 includes an ER fluid, and is not particularly limited as long as the rheological properties can be changed by applying an electric field. An insulating liquid in which particles are dispersed is preferable.

  Insulating solid particles are particles that can move in response to an electric field in an insulating liquid. Details will be described later, but light and darkness can be achieved as a display device by scattering or absorption of light. is there. The insulating solid particles are not limited as long as they are movable particles. For example, silica, cellulose, starch, titanium oxide, titanium dioxide, titanium hydroxide, and the like can be suitably used. For example, inorganic / organic composite particles described in “Industrial Materials (1994, Vol. 142, No. 3, pp. 104-106)” can also be used. The size of the solid particles can be appropriately adjusted and is not particularly limited, but is preferably in the range of about 6 μm to 20 μm.

  Further, as the insulating liquid, it is preferable to have a light transmitting property, and is not limited to the following, for example, fluorine-based inert liquid, aliphatic saturated hydrocarbon, silicone oil, Liquid paraffin or the like can be suitably used. Further, the insulating liquid may be mixed with a colorant such as a dye or a pigment as long as the light transmittance is not hindered.

  Further, in the display device according to the present embodiment, a region corresponding to the cutout portion 41 of the spacer 4 is a pixel region, and in this pixel region, a surface of the first substrate 2 facing the second substrate 3 is A first pixel electrode 61 and a second pixel electrode 62 electrically independent of the first pixel electrode 61 are formed, and a surface of the second substrate 3 facing the first substrate 2 is formed on the first substrate electrode 61. A third pixel electrode 63 and a fourth pixel electrode 64 electrically independent of the third pixel electrode are formed. FIG. 2 is a partial perspective view of the spacer 4 in the vicinity of one cutout portion 41, and FIG. 3 is a partial cross-sectional view (after display device assembly). Here, the pixel electrode is a wiring different from a scanning wiring and a signal wiring, which will be described later, and applies an electric field to the ER fluid layer 5 to move solid particles. The first to fourth pixel electrodes can be appropriately selected to generate electric fields in a plurality of directions. The shape of the pixel electrode is not particularly limited, but for example, each pixel electrode shape is a linear shape, and the first and second pixel electrodes, the third and fourth pixel electrodes are arranged in parallel, The first to fourth pixel electrodes are desirable in that a good image can be obtained when they are overlapped (arranged) with the pixel electrodes of the opposite substrate when viewed from the substrate vertical direction (this embodiment). In FIG. 1, the first pixel electrode and the third pixel electrode, and the second pixel electrode and the fourth pixel electrode are overlapped with each other). The material of the first to fourth pixel electrodes is not particularly limited as long as an electric field can be generated. For example, a transparent electrode such as ITO or IZO, a metal electrode such as aluminum or copper, or the like can be used. It can be used suitably. In the case of a metal electrode, when the solid particles are light scattering, there is an advantage that it is not necessary to dispose a black matrix.

  Other electrode wirings and the like of the display device according to the present embodiment are not particularly limited as long as a voltage can be applied to the ER fluid layer 5 through the first to fourth pixel electrodes. For example, FIG. As shown in (A) and (B), in each of a pair of substrates, a plurality of scanning wirings 65 and a plurality of signal wirings 66 are provided on a surface facing the other substrate, and each of the scanning wirings and the signal wirings intersects with each other. And a plurality of transistors 67 and 68 formed corresponding to each of the pixel electrodes, and at least a storage capacitor 69 for holding a voltage during a display period. This can be realized by connecting to any one of the first to fourth pixel electrodes. 4A is a diagram showing an equivalent circuit of the wiring structure on the first substrate 2, and FIG. 4B is a diagram showing an equivalent circuit of the wiring structure on the second substrate 3. The plurality of scanning wirings and the plurality of signal wirings can be controlled by being connected to a peripheral circuit formed in the peripheral portion of the substrate, a driver circuit disposed on another tape substrate, or the like.

  Next, the actual operation of the display device will be described with reference to FIG. FIG. 5 is a diagram showing an outline of one section of the display device according to the embodiment, as in FIG. 3.

  First, FIG. 5A shows that the first pixel electrode and the second pixel electrode, the third pixel electrode and the fourth pixel electrode are equipotential, respectively, and the first electrode 61 and the third electrode. 63 is a diagram when the voltage V1 is applied between the second electrode 62 and the fourth electrode 64. Thus, by applying a voltage between the first electrode and the third electrode, and between the second electrode 62 and the fourth electrode 64, the insulating solid particles 51 in the ER fluid layer 5 are It is polarized, and is bridged and unevenly distributed along the electric field generated between the first electrode 61 and the third electrode 63 and between the second electrode 62 and the fourth electrode 64. As a result, in other regions (regions between the first electrode and the second electrode), the density of the insulating solid particles 51 decreases, and the observer can visually recognize the color of the colored layer 7. (This state is referred to as a “transmission state”) and can function as a display device.

  On the other hand, FIG. 5B shows that the first pixel electrode and the third pixel electrode, the second pixel electrode and the fourth pixel electrode are equipotential, and the first electrode 61 and the second electrode. 6 is a diagram when the voltage V2 is applied between the third electrode 63 and the fourth electrode 64. By doing so, a bridge can be formed between the first pixel electrode and the second pixel electrode, and between the third pixel electrode and the fourth pixel electrode. As a result, the light incident on the region between the pixel electrodes is scattered by the insulating solid particles 51, and white display can be performed (this state is referred to as “scattering state”). Note that V1 and V2 can be appropriately adjusted according to the electric field applied to the insulating solid particles and the distance between the pixel electrodes, and are not necessarily the same.

  FIG. 6 shows an example of the electrical connection relationship of the pixel electrodes for generating the electric field. As described above, in the display device, the first pixel electrode and the second pixel electrode, the third electrode and the fourth pixel electrode are equipotential in the transmission state, and the first pixel electrode and the third pixel electrode are in the scattering state. The first switching element that enables connection between the first pixel electrode and the second pixel electrode so that the second pixel electrode and the second pixel electrode can be equipotential. 81, a second switching element 82 enabling connection between the third electrode and the fourth pixel electrode, and a third switching enabling connection between the first pixel electrode and the third pixel electrode. It is desirable to have at least a fourth switching element 84 for enabling connection between the element 83 and the second pixel electrode and the fourth pixel electrode. The first and second switching elements can be provided on each of the pair of substrates, for example, in a driver circuit connected to the outside of the pair of substrates. The third and fourth switching elements are desirably provided in a driver circuit connected to the outside of the pair of substrates because the potentials of the pixel electrodes on different substrates need to be equal.

  As described above, according to the present embodiment, by arranging four electrically independent pixel electrodes in the pixel region, a plurality of directional electric fields can be generated between the respective pixel electrodes, and the scattering state is changed from the transmission state. In this case, since an electric field can be generated in any case from the scattering state to the transmission state, a display device with high speed and excellent responsiveness can be obtained without depending on diffusion due to Brownian motion. Moreover, solidification of solid particles can be prevented by using application of an electric field even when the transmission state is changed to the scattering state or when the scattering state is changed to the transmission state.

  In this embodiment, an electric field is applied to the first pixel electrode and the second pixel electrode, and the third pixel electrode and the fourth pixel electrode in the scattering state. A mode in which an electric field is generated only between the pixel electrode and the second pixel electrode is also possible. A cross-sectional view of the scattering state in this embodiment is shown in FIG.

  Note that the display device according to the present embodiment can be manufactured by various methods as long as the above configuration is adopted, but can be manufactured by the following method.

  Examples of the above embodiment will be specifically described below. In this example, a display device with one pixel region was created and evaluated for easy understanding.

  First, a 10 mm × 10 mm glass substrate (thickness 1 mm) is used as a substrate, a 3 mm thick silicone rubber spacer having a 5 mm × 5 mm rectangular cut is sandwiched, and ER fluid is poured into the cut and these are inserted. Bonded together and sealed. As the ER fluid, 50.1 g of silicone oil (TSF451-10 (registered trademark), manufactured by GE Toshiba Silicone) was used as an insulating liquid, and TiO (OH) 2 particles were used as insulating solid particles. In addition, 0.288 g of a surfactant (TSF4700 (registered trademark), manufactured by GE Toshiba Silicone) was added to the ER fluid as an additive, and the mixture was previously dispersed for 10 minutes with an ultrasonic disperser. Note that pixel electrodes made of first to fourth ITO were formed on a pair of glass substrates, and each of them was a rectangle having a width of 1 mm and a length of 5 mm. In addition, the first pixel electrode, the second pixel electrode, the third electrode, and the fourth electrode were spaced apart by 3 mm and arranged in parallel. Note that the first to fourth pixel electrodes were each connected to an external power source via wiring separately formed on the substrate.

  Here, a voltage was applied to the display device to generate an electric field, and the transmission state and the scattering state were repeated. Then, the transmittance (%) was measured (using TD932 manufactured by Macbeth) in the transmission state and the scattering state, and the number of writings was plotted on the horizontal axis. The result is shown in FIG. The transmittance in each state was defined as the ratio of the intensity of light incident on the display device and the light transmitted by the display device. In addition, the voltage applied between the first pixel electrode and the third pixel electrode in the transmissive state, and between the second pixel electrode and the fourth pixel electrode is 1 kV. The voltage applied between the second pixel electrode, the third pixel electrode, and the fourth pixel electrode was 1 kV.

  As a result, as is clear from the figure, it was confirmed that the change in transmittance was small even when writing and erasing were repeated, and the transmission state and the scattering state were repeated, and the writing durability was excellent.

  Note that when the transmission state is changed to the scattering state (when a voltage is applied between the first pixel electrode and the second pixel electrode, and between the third pixel electrode and the fourth pixel electrode), the scattering state is changed to the transmission state. Of the transmittance change of the display device in each of the above cases (when a voltage is applied between the first pixel electrode and the third pixel electrode, and between the second pixel electrode and the fourth pixel electrode) Also confirmed. As a result, it was confirmed that not only the response from the scattering state to the transmission state but also the response from the transmission state to the scattering state was as fast as possible. This was much faster and more reliable than when using Brownian diffusion. In this configuration, it is possible to increase the speed by adjusting the applied voltage, the width and length of the electrode, the configuration of the ER fluid layer to be sandwiched, and the like. In particular, if the distance between the electrodes is shortened, it will lead to a high definition, and further effects will be exhibited.

  As described above, it was confirmed that the display device according to the present example has sufficiently excellent response characteristics.

  The present invention can be applied to various display devices, and is not limited thereto. For example, the present invention can be applied to a display device such as a personal computer, a mobile phone, and a mobile terminal, and electronic paper.

1 is a diagram showing an outline of a configuration of a display device according to an embodiment. 1 is a schematic perspective view of the vicinity of one cutout portion of a display device according to an embodiment. FIG. 3 is a schematic cross-sectional view in the vicinity of one cutout portion of the display device according to the embodiment. The figure explaining the outlines, such as electrode wiring of the display apparatus which concerns on embodiment. The figure for demonstrating the actual operation | movement of the display apparatus which concerns on embodiment. 4A and 4B are diagrams for explaining an electrical connection relationship of pixel electrodes in a display device according to an embodiment. FIG. 6 is a diagram for explaining another operation of the display device of the display device according to the embodiment. The figure which shows the measurement result about the response speed of the display apparatus which concerns on an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Display apparatus, 2 ... 1st board | substrate, 3 ... 2nd board | substrate, 4 ... Spacer, 5 ... ER fluid layer, 7 ... Colored plate, 41 ... Cutout part, 51 ... Solid particle, 52 ... Liquid, 61 ... First pixel electrode, 62 ... second pixel electrode, 63 ... third pixel electrode, 64 ... fourth pixel electrode, 81 ... first switching element, 82 ... second switching element, 83 ... third Switching element, 84... Fourth switching element

Claims (2)

A first substrate and a second substrate disposed opposite to each other;
An electrorheological fluid layer including an insulating liquid in which spacers and insulating solid particles sandwiched between the first substrate and the second substrate are dispersed;
A first pixel electrode formed on a surface of the first substrate facing the second substrate;
Formed on a surface of the first substrate facing the second substrate, disposed adjacent to the first pixel electrode and substantially parallel to the first pixel electrode; An electrically independent second pixel electrode;
A third pixel electrode formed on a surface of the second substrate facing the first substrate and disposed facing the first pixel electrode;
Formed on a surface of the second substrate facing the first substrate, adjacent to the third pixel electrode, substantially parallel to the third pixel electrode and opposed to the second pixel electrode; A fourth pixel electrode disposed and electrically independent of the third pixel electrode;
An on state in which the first pixel electrode and the second pixel electrode are electrically connected and a first potential is supplied to the first pixel electrode and the second pixel electrode; A first switching element that controls an off state in which the first pixel electrode and the second pixel electrode are electrically disconnected;
The third pixel electrode and the fourth pixel electrode are electrically connected, and a second potential different from the first potential is applied to the third pixel electrode and the fourth pixel electrode. A second switching element that controls an on state to be supplied and an off state in which the third pixel electrode and the fourth pixel electrode are electrically disconnected;
An ON state in which the first pixel electrode and the third pixel electrode are electrically connected, and a third potential is supplied to the first pixel electrode and the third pixel electrode; A third switching element for controlling an off state in which the first pixel electrode and the third pixel electrode are electrically disconnected;
The second pixel electrode and the fourth pixel electrode are electrically connected, and a fourth potential different from the third potential is applied to the second pixel electrode and the fourth pixel electrode. A fourth switching element that controls an on state to be supplied and an off state in which the second pixel electrode and the fourth pixel electrode are electrically disconnected from each other;
In the first state, the first switching element and the second switching element are turned on, and the third switching element and the fourth switching element are turned off.
In the second state, the first switching element and the second switching element are turned off, and the third switching element and the fourth switching element are turned on. . The display device according to claim 1, wherein the first state is a transmission state, and the second state is a scattering state.

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