JP2004077876A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device capable of preventing uneven distribution of particles in image writing by an external electrode. <P>SOLUTION: In an image display medium 12, a part between a display substrate 14 and a rear substrate 16 is divided by partition members 20 into a plurality of cells 18 and particles 22 are encapsulated into respective cells 18. Synchronization marks 30 corresponding to respective cells 18 are formed on the display substrate 14 along the direction of an arrow A. A voltage applying means 28 moves an electrode head 24 on the display substrate 14 in the direction of the arrow A and applies voltage according to image information between an electrode 25 and a rear electrode when the synchronization mark 30 is detected in synchronism with the passage of the partition member 20 by a detecting sensor 27. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image display device that can be repeatedly rewritten, and more particularly to an image display device that displays an image by applying a voltage while moving an externally provided electrode on an image display medium.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a so-called electronic paper, an image display technology having a memory property capable of repeatedly rewriting, such as rotation of colored particles (twisting ball display), electrophoresis, thermal rewritable, liquid crystal having memory properties, electrochromy, and the like. It has been known.
[0003]
Among such technologies, as an image display medium for displaying using colored particles (toner), air is used as a medium between a display substrate and a non-display substrate, in which conductive colored particles and white particles are opposed to each other. Then, there is an image display medium in which a charge transport layer and an electrode are formed inside both substrates (Japanese Hardcopy L99 Transactions p249-p251, Japan Hardcopy L99fall Preprints p10-p13). In such an image display medium, charges are injected into the conductive colored particles through the charge transport layer, and the charged injected conductive colored particles move by an electric field between the substrates formed according to the image by the electrodes. Attaches to display substrate. Thereby, an image is displayed on the display substrate side as a contrast between the conductive colored particles and the white particles.
[0004]
Japanese Patent Application Laid-Open No. 2001-215909 discloses a device in which particles are sealed in a cell, an electrostatic latent image is written on a display substrate by a movable multi-stylus electrode, and the particles are moved to perform display. I have.
[0005]
Japanese Patent Application Laid-Open No. 2002-14380 discloses that a plurality of particles having different colors and charging characteristics are sealed between a display substrate and a non-display substrate, and an electric field is applied from outside the display substrate to an electrode provided in an image writing unit. An apparatus for displaying an image by applying particles and moving the particles is disclosed.
[0006]
In the case of such a configuration in which an image is displayed by the movable electrode provided outside the substrate, it is not necessary to provide an electrode in the substrate, the apparatus can be simplified, and the cost of the image display medium alone can be reduced. it can.
[0007]
In addition, since the electrodes need only be driven by one line (or a plurality of lines in which the electrodes are arranged in a staggered pattern), the driving circuit can be simplified and the cost can be simplified as compared with the case where the driving elements are provided on the entire surface of the image display medium Can be cheaper.
[0008]
Further, since it is not necessary to arrange a transparent electrode (for example, an ITO electrode) on the image display medium, the transmittance of the display substrate can be increased, and the image display medium can be brightly recognized.
[0009]
[Problems to be solved by the invention]
As shown in FIG. 10, the image display medium using the above-described colored particles has a space in which particles 106 move by a partition member 104 provided between the display substrate 100 and the back substrate 102. The space is filled with gas or liquid. The particles 106 are preliminarily triboelectrically charged or have a predetermined amount of charge by applying a charge, and are provided with a moving electrode 108 provided on the display substrate 100 side and a back electrode provided on the back substrate 102 side. The substrate moves between the substrates by an electric field formed by a voltage applied by the voltage application unit 112 between the substrates. In order for the particles 106 to move by receiving a force from the electric field, the packing density of the particles 106 is preferably low, and usually has a sufficient moving space for the particle volume.
[0010]
When a voltage is applied to the moving electrode 108, as shown in FIG. 10, the electric field generated at the center of the moving electrode 108 is only an electric field component in a direction orthogonal to the substrate surface. There is a gradient in the electric field on the side of the edge of, and there is an electric field component in a direction parallel to the substrate.
[0011]
Since the charged particles receive a force along the direction of the electric field, particles near the outside of the end of the moving electrode 108 having a gradient of the electric field may move under the force toward the center of the moving electrode 108. is there. In particular, when the moving electrode 108 moves in the direction of the arrow while an electric field is applied, the moving electrode 108 is dragged by the moving electrode 108 to cause the particles 106 to be biased, which may cause a defect in a display image.
[0012]
In this case, even if the substrate is partitioned into a plurality of cells by the partition member 104, if the moving electrode is moved while the electric field is applied in the cell, the particles are biased in the cell.
[0013]
In particular, in order to increase the amount of the particles 106 moving to the display substrate 100 side, by applying an alternating electric field which alternately applies electric fields having different polarities, the particles 106 which are stuck to the substrate in the early stage of the electric field application and hard to move are reduced. When the particles 106 are peeled off from the substrate by the energy of collision between the particles and moved to a predetermined substrate side to contribute to display, the particles move in the moving direction of the moving electrode 108, so that a display image becomes uneven. In some cases.
[0014]
The present invention has been made in view of the above-described circumstances, and has as its object to provide an image display device that can prevent uneven distribution of particles in image writing by an external electrode.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1, wherein at least one of the pair of substrates has a light-transmitting property, and the pair of substrates can move between the substrates movably according to an electric field formed by a voltage applied between the pair of substrates. An image display medium provided with at least one kind of particle group enclosed in, and a partition member for partitioning the substrates into a plurality of cells, and an electrode moving in a predetermined direction on one of the pair of substrates in a predetermined direction A head, a back electrode provided on the other substrate side of the pair of substrates, and a voltage corresponding to image information at a predetermined timing synchronized with passage of the partition member while moving the electrode head in the predetermined direction. Voltage applying means for applying a voltage between the electrode head and the back electrode.
[0016]
According to the invention, the image display device includes the image display medium and the voltage applying unit.
[0017]
The image display medium includes a pair of substrates, a group of particles, and a partition member. At least one of the pair of substrates has a light-transmitting property. The light-transmitting substrate serves as a display substrate, and the other substrate serves as a rear substrate.
[0018]
Particle groups are sealed between the pair of substrates. The particle group is movably enclosed between the substrates according to an electric field formed by an applied voltage. In addition, as described in claim 5, the particle group can be a plurality of particle groups having different charging characteristics and colors as described in claim 5. Thereby, various colors can be displayed. The substrate is partitioned into a plurality of cells by a partition member.
[0019]
The voltage applying means moves the electrode head moving in a predetermined direction on one of the pair of substrates in a predetermined direction while applying a voltage corresponding to the image information at a predetermined timing synchronized with the passage of the partition member. The voltage is applied between the head and the back electrode provided on the other substrate side of the pair of substrates. Note that the back electrode may be provided outside the other substrate, may be provided inside the other substrate, or may be provided inside the other substrate, that is, on the surface on the one substrate side.
[0020]
The electrode head includes, for example, an electrode having a width in a predetermined direction in which the electrode head moves is substantially the same as or larger than the width of the cell in the predetermined direction. The same number as the number is provided. In this case, the back electrode is a uniform electrode that covers the entire surface of the other substrate, for example. That is, in this case, so-called active matrix driving is employed, and the voltage applying unit applies a voltage to the electrode of the cell (pixel) at the image writing position while moving the electrode head in a predetermined direction. Further, the electrodes of the electrode head may be arranged in a line in a direction orthogonal to the predetermined direction, or may be arranged in a plurality of lines. Further, they may be arranged in a staggered arrangement.
[0021]
In addition, the electrode of the electrode head is a long electrode whose longitudinal direction is a direction perpendicular to the predetermined direction, and the back electrode is a plurality of long electrodes whose longitudinal direction is the predetermined direction in a direction perpendicular to the predetermined direction. It may be arranged side by side. That is, in this case, a so-called simple matrix drive is adopted, and the voltage applying means applies a voltage between the electrode of the electrode head and the electrode corresponding to the image writing position of the back electrode while moving the electrode head.
[0022]
The voltage applying unit applies a voltage between the electrode head and the back electrode, that is, between the pair of substrates, in synchronization with the passage of the partition member. That is, the voltage applying unit does not continuously apply a voltage while the electrode head is moving, for example, but moves the particles in the cell when the electrode head is positioned on the cell to which the image is written. The voltage is applied only for the minimum necessary time. Thus, it is possible to prevent the particles of the cell after the cell to which the image is to be written, that is, the particles of the cell for which the image has already been written from being dragged in the moving direction of the electrode head and unevenly distributed. Therefore, a high quality image can be displayed without unevenness in the display image.
[0023]
The invention according to claim 2, wherein the voltage applying means applies a voltage corresponding to image information between the electrode head and the back electrode when a rear end of the electrode head in the predetermined direction passes through the partition member. Is applied.
[0024]
According to the present invention, when the rear end of the electrode head in the predetermined direction passes through the partition member, a voltage corresponding to the image information is applied between the electrode head and the back electrode, so that the width of the electrode head in the predetermined direction is reduced. Even when the width of the cell is larger than the width of the cell in the predetermined direction, it is possible to prevent the particles of the cell for which the image writing has already been completed from being dragged in the moving direction of the electrode head and unevenly distributed.
[0025]
The invention according to claim 3, wherein the one substrate includes a synchronization mark arranged corresponding to the cell along the predetermined direction, and the electrode head includes detection means for detecting the synchronization mark, The voltage applying means applies a voltage corresponding to the image information between the moving electrode and the back electrode when the synchronization mark is detected.
[0026]
According to the present invention, a synchronization mark is provided on one of the substrates along a predetermined direction, that is, for example, by printing or the like, corresponding to each column of cells along the moving direction of the electrode head. This synchronization mark is detected by detection means provided on the electrode head.For example, when the rear end of the electrode head in a predetermined direction passes through the partition member, a voltage corresponding to image information is applied to the electrode head and the back electrode. Is arranged at the position where the voltage is applied.
[0027]
The detecting means can optically read the synchronization mark, for example. Alternatively, the synchronization mark may be formed of a conductive member, and the presence or absence of the synchronization mark may be detected by detecting conduction with the mark.
[0028]
Further, the voltage applying means may set the predetermined timing based on a length of the cell and the partition member in the predetermined direction and a moving speed of the electrode head. .
[0029]
That is, for example, when the rear end of the electrode head in a predetermined direction passes through the partition member, a predetermined timing for applying the voltage, that is, the voltage, so that a voltage corresponding to the image information is applied between the electrode head and the back electrode. Set the application interval. This eliminates the need to provide a synchronization mark on the substrate and eliminates the need for detecting means, so that the apparatus can be configured at low cost.
[0030]
Further, as described in claim 5, the particle group may be a plurality of particle groups having different charging characteristics and colors.
[0031]
In that case, an image display device with clearer contrast can be obtained by moving and displaying different types of particles by an electric field.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0033]
FIG. 1B shows a schematic configuration of an image display device 10 according to the present invention. As shown in FIG. 1B, the image display device 10 includes an image display medium 12.
[0034]
The image display medium 12 maintains a constant distance between the transparent display substrate 14 on the side on which an image is displayed and a rear substrate 16 facing the transparent display substrate 14 with a small gap, and separates a plurality of substrates from each other. A partition member 20 for partitioning the cells 18 is provided, and particles 22 are sealed in each cell 18.
[0035]
1A and 1B, the image display device 10 applies a voltage corresponding to image information to the display substrate 14 while moving on the display substrate 14 in the direction of arrow A in the figure. The electrode head 24, the back electrode 26 provided on the back substrate 16 side, and the voltage applying means 28 for applying a voltage according to image information to the electrode head 24 and the back electrode 26 while moving the electrode head 24 in the direction of arrow A. Have.
[0036]
Further, on the display substrate 14, as shown in FIG. 1A, synchronization marks 30 are formed corresponding to each cell 18 along the moving direction of the electrode head 24. The voltage applying unit 28 applies a voltage at the timing when the synchronization mark 30 is detected.
[0037]
The display substrate 14 of the image display medium 12 is transparent and has an insulating property in a direction parallel to the substrate surface. ⁸ Ω or more and 10 ¹⁰ It is preferably Ω or more. This can prevent the electric field at the time of writing an image from being equal in a direction parallel to the substrate surface, and does not cause a defect such as blurred image. Further, the display substrate 14 may have conductivity in a direction where a region corresponding to the cell 18 is orthogonal to the substrate surface, that is, in a thickness direction of the substrate. In this case, it is necessary that the cells 18 be insulated.
[0038]
The back substrate 16 may be insulative or conductive, and its thickness is designed to obtain sufficient strength according to the structure and area. By providing the back electrode 26 provided on the back substrate 16 as close to the electrode head 24 as possible, an electric field actually acting between the substrates with respect to a voltage applied between the electrode head 24 and the back electrode 26 is provided. This is preferable because the strength of the driving power can be increased and the driving power supply can be reduced in power. When insulating particles are used as the particles 22, it is preferable that the surface of the rear substrate 16, that is, the surface on the display substrate side, be insulative because the charge of the particles 22 is not released. Note that, instead of providing electrodes outside the rear substrate 16, electrodes such as metal and ITO electrodes may be provided on the rear substrate 16.
[0039]
The substrates are separated by a partition member 20 having a height enough to move the particles 22. The distance between the substrates depends on the particle size of the particles 22, but is preferably about 5 to 100 times the particle size of the particles 22. Although it depends on the filling amount of the particles 22, which will be described later, if the distance between the substrates is too small relative to the particle diameter, the particles 22 may aggregate between the substrates, which may cause image defects. On the other hand, if the distance between the substrates is too large, it is necessary to increase the applied voltage, and the driving power increases, which is not preferable.
[0040]
The space between the substrates may be filled with a gas, a liquid, or may be in a state close to a vacuum. In the case of a gas, in order to keep the chargeability of the particles 22 good, it is preferable that the humidity is low, the relative humidity is preferably 60% or less, and more preferably 40% or less. In the case of a liquid, it is necessary that the liquid be an insulating liquid such as an isopar in order to hold the charge of the particles 22.
[0041]
Although not shown in FIG. 1, the display substrate 14 and the rear substrate 16 are fixed by sealing the outer edge of the substrate with a seal portion for sealing the particles 22 and the enclosed gas and liquid. ing. For the seal portion, an adhesive, a thermosetting or UV curable resin, or the like is used.
[0042]
The partition member 20 keeps the distance between the substrates constant, joins the substrates, and divides the inside of the substrate into a subdivided cell structure. The partition member 20 preferably has a width that is inconspicuous when viewed from the display substrate 14 side. The width of the tip of the partition member 20 viewed from the display substrate side of the cell 18 and the width of one side (cell pitch) Is preferably 1/10 or less, since the aperture ratio effective for display (the ratio of the area sum of the cells 18 to the total effective display area) becomes about 80% or more, and the display contrast can be improved.
[0043]
The partition member 20 may be manufactured by using a photolithography method or screen printing on any of the substrates, or may sandwich a stitch-shaped resin molded product manufactured by, for example, injection molding, hot pressing, or embossing.
[0044]
The particles 22 that can be charged between the substrates are particles that can hold a charge, for example, insulating particles. One type of particle group may be used, or a plurality of types of particle groups may be used. When a plurality of types of particle groups are used, the charge polarity and color of each particle group are differently combined. In particular, by using, for example, white particles and particles colored in other colors that are charged with opposite polarities, a clear image can be displayed as if the image were printed on paper.
[0045]
In the case of using insulating particles of opposite polarities, each particle group is in a mixed state by Coulomb force between the substrates immediately after enclosing, and by applying an electric field of Coulomb force or more between these particles, Particles charged with opposite polarities are separated from each other, move in the directions of electric fields of opposite polarities, and adhere to the substrate surface. Even when the electric field is cut off, the particles adhere to and are held near the substrate surface on the side to which they have been moved by the mirror image force and the van der Waals force. In addition, each particle group is deposited on each substrate side, and in practice, the applied voltage at the time of rewriting only needs to apply an external force equal to or greater than the image force and the van der Waals force.
[0046]
Note that “movable between substrates” means that particles existing on one substrate side can move to the other substrate side by an electric field formed by applying a voltage, and a certain electric field causes all particles to move. In addition to the case where the particles move at the same time, the case where the particles of a certain particle group do not move depending on a certain electric field strength, but can move when the electric field strength is increased. That is, if the particles are encapsulated in such a state, the movement of the particles is not substantially hindered by the presence of other types of particle groups.
[0047]
Further, in order for each type of particles to be able to move between the substrates, the packing ratio of the particles between the substrates, the fluidity between the particles, the particle shape, the particle diameter, the material of the particles, and the inner surface of the substrate (the particles and the electrodes are in direct contact with each other) In this case, it depends on how to set the electrode surface, etc., but it is particularly preferable to set as follows.
[0048]
First, as for the filling amount, an image can be displayed if the filling ratio of all particles contained between the substrates is 0.1% or more and 50% by volume or less, but if it is 40% or less, particularly 25% or less. This is preferable because the contrast of the image can be improved. If it exceeds 50%, the particles rapidly become dense and their movement begins to be hindered, and the proportion of particles that stop on one substrate side increases, which causes a decrease in contrast. If it is 50% or less, each particle can move between the substrates.
[0049]
The higher the fluidity, the better, and the shape of the particles is preferably a curved surface. A spherical shape such as an elliptical sphere is more preferable, and a true sphere is more preferable. To increase the fluidity, an external additive for reducing the frictional force may be added to the particles.
[0050]
The particle size may be any as long as it can be moved by an applied electric field. However, when a gas is sealed between the substrates or when the substrate is used in a state close to a vacuum, the average particle size is preferably 1 μm or more. In the case of 1 μm or less, the bonding force between particles or between particles and substrate is dominated by van der Waals force rather than Coulomb force, making it difficult to separate particles of opposite polarity by an electric field. Would. However, if the particles can be separated by combining a force other than an electric field such as ultrasonic vibration, it may be possible to use even particles smaller than 1 μm. In particular, when it is required to enhance the memory property of the image, it is preferable that the thickness be smaller than 1 μm. When it is required to simplify the image rewriting device or to perform high-speed rewriting, the thickness is 1 μm or more. It is preferred that
[0051]
When particles are moved in a liquid, they are easily moved even if they are 1 μm or less. Therefore, they have the characteristic that they are inferior in memory to those in gas, and have the characteristic that the display density can be controlled stepwise by electric field strength and application time. .
[0052]
As for the combination of the particle and the part that comes into contact with the particle such as the substrate material or the electrode, it is easier to move the particle between the substrates by selecting one that has a smaller adhesive force. preferable. The substrate surface may be flat or a scattering surface (particularly, the back substrate 16 on the display substrate 14 side).
[0053]
As a method for charging each particle, besides a method of charging the particles by an electric field after enclosing the particles, a plurality of types of particle groups may be preliminarily charged by friction by mixing and stirring, and then the particles may be charged between substrates. Further, in the case of insulating particles, the image display medium itself can be vibrated after the particles are enclosed, and the particles can be charged to opposite polarities by stirring and frictionally charging the particles.
[0054]
Further, the average charge amount (fC / particle) of the particles is approximately proportional to the square of the average particle diameter 2r of the particles, and the smaller the average particle diameter, the smaller the average charge amount (fC / particle). The preferred range of the average charge amount is also different. That is, the average charge amount of each particle is ± 5 × (r ² / 10 ² ) (FC / piece) or more, ± 150 × (r ² / 10 ² ) (FC / piece) or less. The average charge amount is 5 × (r ² / 10 ² ) (FC / particle), the particles separate and move between the substrates in different directions, but do not show a sufficient display density. Also, 150 × (r ² / 10 ² If it is larger than fC / particles, the particles do not separate, move as aggregates in the same direction, and the display density contrast decreases. The charging characteristics of the particles can be controlled by the material constituting the particles, the external and internal additives added to the particles, the layer structure of the particles, the shape of the particles, and the like.
[0055]
For example, TiO (OH) on the surface ₂ Particles to which an additive containing a titanium compound obtained by a reaction between the compound and a silane compound may be used. As a result, an appropriate amount of charge is obtained, the charge retention is stabilized, and the flowability is improved, so that the electric field applied between the substrates allows the particles to smoothly adhere between the substrates without firmly adhering to the inner surface of the substrate. In addition, it can move stably and can display an image with high contrast.
[0056]
Such an image display medium 12 can display an image by applying a voltage corresponding to the image information, whereby the particles move between the substrates according to the image. Further, even if the electric field formed between the substrates disappears, the particles that have moved onto the substrates remain in place due to the image force and the adhesive force, and can maintain an image. Thereafter, when an electric field is applied again, the particles can move again. In this way, an image can be repeatedly displayed by applying an electric field from outside according to the image information.
Note that at least one of the particle groups may be magnetic particles. In this case, the particles can be moved by the magnetic force.
[0057]
Further, spacer particles having a larger diameter than the particles may be sealed between the substrates. Thereby, the distance between the substrates can be kept substantially constant.
[0058]
Further, multicolor display can be performed by enclosing particles having different colors or particles having different combinations in each cell. For example, color display can be performed by arranging three types of particles of red, green, and blue in the same arrangement for each cell. Alternatively, when two types of particles are sealed in each cell, yellow particles and white particles, magenta particles and white particles, and cyan particles and white particles may be sealed. Then, a color image can be formed by generating an electric field for each color.
[0059]
In the electrode head 24, electrodes 25 having substantially the same shape and size as the cell 18, for example, are formed in a row in a direction orthogonal to the arrow A direction on the surface in contact with the display substrate 14. The contact surface with the display substrate 14 is preferably provided with an insulating layer in order to prevent electric shock due to accidental contact or short circuit due to conductive dust.
[0060]
1A, the shape and size of the electrode 25 are substantially the same as those of the cell 18; however, the present invention is not limited to this, and the shape and size of the cell 18 may include a plurality of electrodes 25. Or, conversely, the electrode 25 may have a shape and a size that include the plurality of cells 18.
[0061]
Although the number of the electrodes 25 is three in FIG. 1A for simplicity of description, the number of the electrodes 25 depends on the size of the image display medium 12, the area of the image display medium, the content of the image, the resolution of the written image, and the like. As described above, the number is about 10 to 600 per inch (25.4 mm). If elements are arranged so that the electrodes 25 do not overlap in the direction perpendicular to the direction of movement of the electrode head 24, the efficiency of image writing is improved.
[0062]
The back electrode 26 is provided on the back substrate 16 side, and is a uniform solid electrode having substantially the same area as the back substrate 16. The back electrode 26 may be arranged inside the back substrate 16. Further, instead of the solid electrode, an electrode having substantially the same shape and size as the cell 18 may be used similarly to the electrode provided on the electrode head 24. Further, an electrode head similar to the electrode head 24 may be provided on the rear substrate 16 side, and both the electrode heads 24 may be moved synchronously. Thus, leakage of the electric field applied between the substrates can be reduced, and the displayed image can be sharpened.
[0063]
The electrode head 24 may be provided on the back substrate 16 side, and the back electrode 16 may be provided on the display substrate 14 side. However, when the electrode head 24 is provided on the display substrate 14 side, the electric field for moving the particles 22 can be narrowed. This is preferable because the image can be sharpened. When the electrode head 24 is provided on the rear substrate 16 side, although the displayed image is slightly inferior to the case where the electrode head 24 is provided on the display substrate 14 side, the appearance is good because the electrode head 24 itself is not located on the observer side. can do.
[0064]
The electrode head 24 is driven in the direction of arrow A in FIG. This moving means includes, for example, a guide rail provided on one or both sides of the image display medium 12 along the direction of arrow A and a drive motor for moving the electrode head 24 along the guide rail. One end or both ends of the electrode head 24 in a direction orthogonal to the arrow A direction is connected to a guide rail movably in the arrow A direction, and is driven in the arrow A direction by a drive motor.
[0065]
An elastic member such as a spring for pressing the electrode head 24 against the display substrate 14 from above is provided in order to improve the contact property of the image display medium 12 with the display substrate 14 and reliably apply voltage. You may.
[0066]
In addition, as shown in FIG. 1A, the electrode head 24 includes a detection sensor 27 for optically reading, for example, a synchronization mark 30 formed on the display substrate 14. The synchronization mark 30 is formed on the display substrate 14 so that the detection sensor 27 detects the synchronization mark 30 when the electrode head 24 passes through the partition member 20, that is, when the electrode head 24 is located almost directly above the cell 18. Is done.
[0067]
The voltage applying unit 28 applies a voltage according to the image information to the electrode 25. The voltage to be applied is, for example, several tens of volts to several hundred volts, depending on the charge amount of the particles 22 and the distance between the electrode 25 and the back electrode 26. The electric field formed by the applied voltage is appropriately set depending on the charge amount of the particles 22 and the adhesion to the substrate surface. ⁶ V / m-10 × 10 ⁶ V / m. The voltage application time t is set according to the response speed of the particles 22 (movement speed between the substrates), and is about several milliseconds to 100 milliseconds in the case of particle movement in gas, and several tens of milliseconds in liquid. From milliseconds to a few seconds.
[0068]
The moving speed v of the electrode head 24 is determined by the relationship between the voltage application time t and the width L of the cell 18 in the direction of arrow A, and is set so that v <(L / t). It is possible to reduce that the particles 22 are dragged in the inside 18 and the particles 22 are unevenly distributed. Further, it is preferable that v is set to about 1/10 of (L / t), because the particles 22 can be further prevented from being dragged inside the cell 18.
[0069]
Further, an alternating electric field that alternately applies electric fields having different polarities may be applied during the voltage application time t. In this case, the particles moved in the initial stage of the electric field application are reciprocated between the substrates in accordance with the direction of the electric field, and the particles which are hardly moved by being attached to the substrate in the initial stage are peeled off from the substrate by the energy of the collision between the particles, and the predetermined movement is performed. It can be moved to the substrate side. If the electric field direction at the end of the voltage application time t is set to the direction in which the particles are moved and the voltage application is terminated, the amount of the particles that contribute to the display can be increased, and the effect of improving the contrast of the displayed image can be obtained. .
[0070]
Next, the timing of voltage application by the voltage application unit 28 will be described.
[0071]
The voltage applying means 28 moves the electrode head 24 in the direction of arrow A in the figure, as shown in FIG. Then, when the synchronization mark 30 is detected by the detection sensor 27, that is, when the electrode head 24 passes through the partition member 20 and the electrode head 24 is located directly above the cell 18, the voltage is applied for the voltage application time t. Thereby, the particles 22 in the cell 18 move, and an image is displayed.
[0072]
As described above, the voltage applying unit 28 does not continuously apply the voltage, and applies the voltage in a pulsed manner for the voltage application time t in synchronization with the passage of the electrode head 24 through the partition member 20 of the electrode head 24. As a result, the particles 22 in the cell 18 to which the image is to be written or the upstream cell 18 in which the image has already been written are not dragged in the moving direction of the electrode head 24 and unevenly distributed. As a result, it is possible to prevent the image quality of the display image from deteriorating.
[0073]
It is preferable that the line in the direction orthogonal to the direction of arrow A of the partition member 20 and the line at the rear end of the electrode head 24 are substantially parallel to each other. The crosstalk of the particles 22 between the cells 18, that is, the movement interference of the particles 22 between the electrodes 25, is set to be equal to or an integral multiple of the arrangement interval of the cells 18 in the orthogonal direction. It is preferable because it can be prevented.
[0074]
Further, since the electric field gradient generated from the rear end side in the moving direction of the electrode head 24 causes image deterioration as described above, as shown in FIGS. It is preferable to arrange the synchronization mark 30 so that the detection sensor 27 detects the synchronization mark 30 immediately after passing through the partition member 20 and a voltage is applied. Thereby, a voltage can be applied when the electrode head 24 has reliably passed through the partition member 20, and the particles 22 in the upstream cell 18 for which image writing has already been completed are dragged in the moving direction of the electrode head 24. Can be prevented.
[0075]
Also, as shown in FIGS. 3 and 4, even when the width of the electrode 25 in the direction of arrow A in the figure is larger than the width of the cell 18 in the same direction, the voltage is applied after the electrode 25 has passed through the partition member 20 without fail. Further, it is possible to prevent the particles 22 in the cell 18a (the cell on the left side of the electrode head 24 in FIG. 3) immediately before the image writing has been completed from being dragged in the moving direction of the electrode head 24. In this case, the particles 22 in the cell 18b (the cell on the right side of the electrode head 24 in FIG. 3) downstream of the cell 18 to which the image is to be written may move. Is applied and the image writing is performed, so that the particles move to the predetermined position again and the bias is eliminated, so that there is no particular problem.
[0076]
In the present embodiment, the detection sensor 27 detects the synchronization mark 30 optically. However, the present invention is not limited to this. The synchronization mark 30 is formed of a conductive member, and the conduction with the synchronization mark 30 is detected. Thus, the synchronization mark 30 may be detected.
[0077]
Further, the timing of voltage application may be set based on the length of the cell 18 and the partition member 20 in the moving direction of the electrode head 24 and the moving speed v of the electrode head without providing the synchronization mark 30 and the detection sensor 27. .
[0078]
That is, as shown in FIG. 4A, for example, the arrangement interval of the cells 18 determined by the length of the cell 18 and the partition member 20 in the moving direction of the electrode head 24 is p, and the arrangement interval p and the From the moving speed v, the voltage application interval s is set as s = p / v. Thus, a voltage is applied every s time at the timing when the rear end of the electrode head 24 passes through the partition member 20. As described above, since the voltage is applied by setting the voltage application interval s based on the arrangement interval p of the cells 18 and the moving speed v of the electrode head 24, it is not necessary to provide the synchronization mark 30 on the display substrate 14 in advance. Since there is no need to provide the detection sensor 27, the apparatus can be configured at low cost. This is particularly effective in a configuration in which the resolution of image display is 50 pixels or less per inch and an error is relatively unlikely to occur.
[0079]
In this embodiment, the case where one kind of particles 22 is used has been described. However, as shown in FIG. 5B, a structure using particles 23 having different charging characteristics and colors from the particles 22 may be used. . For example, when a group of white and black particles with different charging polarities is used, the white portion of the image can be represented by bright white with high reflectivity, and if characters and figures are displayed with black particles, the contrast becomes clearer. A simple image display device can be obtained. Also, by enclosing particles of different colors for each image display medium, or by using a combination of different colors in the plane of the image display medium (for example, in a region where white and black particles are enclosed in the image display medium, The area where the white and red particles are enclosed is separated and arranged by a partition member, etc., and the particles are moved according to the color of the image), to attract the observer's attention and to ensure the recognition of information. Various expressions, such as making things, are possible, and convenience can be improved. Thus, various colors and images can be displayed by using a plurality of types of particles.
[0080]
Further, in the present embodiment, the case where the electrodes 25 are arranged in one line on the electrode head 24 has been described. However, when it is difficult to arrange the electrodes 25 in one line at equal intervals, FIG. As described above, the electrodes 25 may be arranged in a staggered manner.
[0081]
In the example of FIG. 6, four electrode rows including three electrodes 25 arranged at intervals of three pixels in a direction orthogonal to the moving direction of the electrode head 24 are arranged in four rows in the moving direction of the electrode head 24. Are located. Each electrode row is shifted by one pixel in a direction orthogonal to the direction of movement of the electrode head 24.
[0082]
When the electrodes 25 are arranged in a staggered manner in this manner, when the electrodes 25 in the first column come on the cells 18 in the first column as shown in FIG. 6B from the state of FIG. Then, the detection sensor 27 detects the synchronization mark 30 corresponding to the cell 18 in the first column, and a voltage is applied to the electrode 25 (the electrode indicated by oblique lines) by the voltage applying means 28. Next, when the electrode 25 in the first column comes over the cell 18 in the second column, the detection sensor 27 detects the synchronization mark 30 corresponding to the cell 18 in the second column, and the voltage applying means 28 applies the voltage to the first column. A voltage according to the image information is applied to the electrode 25, and a voltage according to the image information is applied to the second column of electrodes (electrodes indicated by oblique lines) as shown in FIG. As a result, an image is written to the cells 18 in the second column and an image is written to the cells 18 in the first column.
[0083]
Similarly, as shown in FIGS. 6 (D) to 6 (F), a voltage is applied to the electrodes 25 in the third and fourth columns by the voltage applying means 28 to write an image in the cells 18 in the first column. finish. That is, in this case, the image is written into the cells 18 for one column in four divided steps. In the state of FIG. 6F, the image writing to the cell 18 in the first column has been completed, but the image writing in the fourth column has also been performed to the cell 18 in the second column. Since 3/4 of the entire image has already been written to the cells 18 in the second column, even if the image is written to the cells 18 in one column by dividing it four times, the entire image is written. The image writing time does not increase so much, and there is no particular problem.
[0084]
Further, in the present embodiment, the case where the electrode head 24 is provided with the plurality of individual electrodes 25 corresponding to the cells 18 and the image is displayed by the active matrix driving has been described. Display may be performed. That is, as shown in FIG. 7, the electrode 25 is a long electrode whose longitudinal direction is a direction orthogonal to the direction of the arrow A, which is the moving direction of the electrode head 24, and the back electrode 26 is the longitudinal direction of the arrow A. And a plurality of divided electrodes. In this case, the voltage applying unit 28 selectively applies a voltage to the divided electrode corresponding to the position where the image is to be written, according to the image information. As a result, only the particles 22 at the positions where the divided electrodes to which the voltage is applied intersect with the electrodes 25 of the electrode head 24 move between the substrates.
[0085]
Further, the electrode head 24 may be a pen-type electrode provided with only one electrode. In this case, the image writing may be performed by moving the electrode head two-dimensionally according to the image information.
[0086]
(Example)
Next, examples of the present invention will be described.
[0087]
First, the image display medium 12 will be described. As the display substrate 14, a 100 × 100 × 0.5 mm glass substrate was used. The surface of the glass substrate in contact with the particles is coated with a polycarbonate resin (PC-Z) at a thickness of 5 μm. The back substrate 16 was prepared by forming a grid-like partition at a pitch of 1 mm on a 100 × 100 × 0.6 mm single-sided copper-clad glass epoxy substrate by photolithography. The height of the partition member 20 was 150 μm, and the width of the partition was 100 μm. The surface of the back electrode 26 on the back substrate 16 side was coated with a polycarbonate resin (PC-Z) to a thickness of 5 μm to be insulated. The back electrode 26 was joined to one end of the voltage applying means 28.
[0088]
Spherical fine particles of titanium oxide-containing crosslinked polymethyl methacrylate having a volume average particle diameter of 20 μm obtained by mixing fine powder of titania treated with isopropyltrimethoxysilane at a weight ratio of 100: 0.4 (Techpolymer manufactured by Sekisui Plastics Co., Ltd.) MBX-20-White is classified) and spherical particles of carbon-containing cross-linked polymethyl methacrylate having a volume average particle diameter of 20 μm (Techpolymer MBX-20-Black manufactured by Sekisui Chemical Co., Ltd. are classified) at a weight ratio of 2 to 2 After mixing at a ratio of 1 and shaking off through a screen, and applying a UV-curable adhesive to both substrates, the substrates were joined in an environment of dry air at a relative humidity of 20%, and were pressurized and cured.
[0089]
On the display substrate 14, the synchronization mark 30 was formed by transferring the carbon paste by screen printing at the same interval as the arrangement interval of the cells 18 so as to form a square having a side of 0.5 mm, followed by drying and curing. The electrode 25 is a copper electrode having a cross section of 0.9 × 0.9 mm arranged in an epoxy resin at a pitch of 1 mm, and after polishing the end, is protected with a 50 μm thick PTFE resin film to prevent short-circuit and abrasion. Protected. At the portion of the electrode 25 facing the synchronization mark 30, a copper electrode having a tip diameter of 200 μm and having a diameter of 200 μm is arranged at an interval of 100 μm, and a trigger signal is generated when both electrodes simultaneously contact the synchronization mark 30. And the detection sensor 27 was constructed.
[0090]
The voltage applying unit 28 applied a DC voltage of −800 V between the back electrode 26 and the electrode 25 for 10 ms after the trigger signal was generated. The electrode head 24 was moved at a moving speed of 10 mm / s. In the initial state, white particles were displayed on the entire surface of the display substrate 14 and image writing was performed under the above conditions. As a result, a part of the positively charged black particles on the rear substrate 16 side showed the effect of the electric field. As a result, the liquid crystal was moved to the display substrate 14 side, and the display density of the written cell 18 was almost saturated. At this time, the particles were not dragged by the movement of the electrode head 24.
[0091]
Next, another embodiment of the present invention will be described.
[0092]
First, the image display medium 12 will be described. The display substrate 14 has a size of 210 × 300 × 0.12 mm and a resistance value of 10 ¹² An Ω resin (PET) film was used. The rear substrate 16 used a glass epoxy substrate of 210 × 300 × 1.0 mm. As shown in FIG. 8, a copper electrode provided in the back substrate 16 was used as the back electrode 26.
[0093]
Then, after laminating and adhering four 50 μm-thick dry film resist films on the rear substrate 16, by photolithography, an opening ratio of 81% at which the width between the cells 18 is 1 μm and the interval between the cells 18 is 1 mm is 100 μm. The partition member 20 was created. The number of cells 18 is 180 × 270.
[0094]
After forming the partition member 20, the back substrate 16 was dip-coated using a solution of polycarbonate PC-Z) dissolved in a solvent. Thereafter, the coating was dried at 70 ° C. for 1 hour to form a coating of 5 μm. Thereby, it was insulated from the back electrode 26.
[0095]
The black particles 22 were prepared by treating silica (A-130 manufactured by Aerozil Corporation) with aminopropyltrimethoxysilane, and then stirring and mixing a fine powder at a weight ratio of 100 to 0.8 to obtain a volume average particle diameter. Black spherical particles of 10 μm carbon-containing crosslinked polymethyl methacrylate were used.
[0096]
As the white particles 23, white spherical particles of titanium oxide-containing crosslinked polymethyl methacrylate having a volume average particle diameter of 10 μm obtained by stirring and mixing fine powder of titania treated with isobutyltrimethoxysilane at a weight ratio of 100 to 0.4 were used. . The black spherical particles and the self-colored spherical particles were mixed at a weight ratio of 3: 4, whereby the white particles were negatively charged and the black particles were positively charged.
[0097]
The back substrate 26 is fixed on a flat plate, the partition member 20 is covered with a 50 μm-thick metal mask having an opening corresponding to the cell 18, and the mixed particles are sieved on the back substrate 16 through a stainless mesh screen. The metal mask was removed and only the cells 18 were uniformly filled with particles. The amount of encapsulated particles averaged 5.2 mg / cm per area ² And the volume filling ratio between the substrates was about 17%. A thermosetting epoxy resin was applied on the periphery of the substrate and on the partition member 20, and the surface substrate (film) 14 was bonded to produce the image display medium 12.
[0098]
The electrode head 24 has a structure as shown in FIG. 9, and has a width of 1.5 mm on the side in contact with the image display medium 12 and a length of 250 mm in a direction perpendicular to the moving direction of the electrode head 24. Then, a flexible electrode in which 180 flat copper electrodes having an electrode width of 0.9 mm are arranged at a pitch of 1 mm on a polyimide film is fixed on an ABS resin having a thickness of 1 mm, and the flexible electrode is fixed to the image display medium 12 of the electrode head 24. The copper electrode was exposed to a length of about 1 mm at the contacting portion. Each electrode is connected to a voltage applying means 28 and applies a voltage for writing an image between the electrodes and the back electrode 26.
[0099]
The movement of the electrode head 24 was performed as follows. The image display medium 12 is fixed on a stage that moves on one axis with a ball screw, and the ball screw is driven by a motor while the electrode head 24 is pressed against the surface of the display substrate 14 of the image display medium 12 with a load of 50 g. The image display medium 12 and the electrode head 24 were relatively moved along the surface of the display substrate 14 at a speed of 5 mm / sec. The electrode head 24 is mounted so as to be adjustable in the width direction of the image display medium 12 (a direction orthogonal to the direction of arrow A). After the image display medium 12 is fixed on the stage, the center of the cell 18 and the center of the electrode 25 are aligned. Adjust accordingly.
[0100]
A voltage of 250 V was applied between each electrode 25 at the tip of the electrode head 24 and the back electrode 26 by voltage applying means 28 connected to the electrode head 24. The electric field formed by the applied voltage is about 0.8 × 10 ⁶ V / m. When a voltage was applied so that the display substrate 14 side became positive, the negatively charged white particles moved to the display substrate 14 side to display white. Conversely, when a voltage was applied such that the display substrate 14 side became negative, the black particles moved to the display substrate 14 side and black was displayed. The voltage application time t was 15 milliseconds. Since the moving speed v of the electrode head 24 is 5 mm / sec and the width L of the cell 18 is 0.9 mm, L / t = 60 mm / sec, and the moving speed v is set to 1/10 or less of L / t. Was. By setting the voltage application cycle to 0.2 seconds from the moving speed of the electrode head 24 and the pitch of the cells 18, it is possible to synchronize the cycle of the passage of the partition member 20. Further, the movement start point of the electrode head 24 was adjusted so that the writing voltage was reached when the electrode head 24 reached the cell 18 to be written first, so that the image writing and the passage through the partition member 20 were synchronized.
[0101]
Display was performed by operating the image display device 10 under the above conditions. First, in order to uniformly display white, the electrode head 24 is relatively moved, and a positive voltage is applied to all the electrodes 25 of the electrode head 24 while synchronizing with the passage of the partition member 20. Became white display (0.30 in optical density of reflection densitometer).
[0102]
Conversely, when a negative voltage was applied to all the electrodes 25, the entire surface of the image display medium 12 displayed black (1.40 as the optical density of the reflection densitometer). At this time, the black particles moved to the rear substrate 16 side and could not be visually recognized from the display substrate 14 side. Next, according to the image data, a negative voltage was applied only to the electrode 25 corresponding to the portion where an image was to be displayed in black display, and the other electrodes 25 were written at the same potential as the rear substrate 16 to perform image writing. An image was displayed according to the relative movement of the electrode head 24. When the displayed cell 18 is observed, the black particles move to the display substrate 14 side, and at the same time, the white particles move to the back substrate 16 side, and are concealed by the black particles on the display substrate 14 side, so that they can be visually observed. could not. In addition, when the vicinity of the partition member 20 was magnified and examined, the white display and the black display were close to the partition member 20 of the cell 18 adjacent to the cell 18, and the particles were not properly concealed due to the bias or omission of the particles on the rear substrate 16 (ie, No black line or black noise was observed in the case of a white display cell), and a clear display was obtained as a whole.
[0103]
On the other hand, when the moving speed of the electrode head 24 was set to 5.5 mm / sec, and the image display apparatus was driven under the same conditions as those in the above embodiment, writing was performed on the partition member 20 of the electrode head 24. There was noticeable noise that was observed as black streaks in the cells, partially synchronized with the passage. As a result of enlarged observation, in some cells, the particles were deviated by about 50 μm in the moving direction of the electrode head 24, and the particles were partially dragged.
[0104]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it has the effect that the uneven distribution of particles can be prevented and the unevenness in a displayed image can be prevented.
[Brief description of the drawings]
FIG. 1A is a plan view of an image display device, and FIG. 1B is a side view of the image display device.
FIG. 2 is a diagram illustrating a side view of the image display device and a voltage application timing.
FIG. 3 is a diagram illustrating a side view of the image display device and a voltage application timing.
4A is a plan view of the image display device, and FIG. 4B is a side view of the image display device.
5A is a plan view of the image display device, and FIG. 5B is a side view of the image display device.
FIGS. 6A to 6F are diagrams for explaining the timing of voltage application by the electrode head 24. FIGS.
FIG. 7 is a diagram showing another embodiment of the driving method of the image display device.
FIG. 8 is a sectional view of an image display medium.
FIG. 9 is a perspective view of the image display device.
FIG. 10 is a side view of a conventional image display device.
[Explanation of symbols]
10. Image display device
12 Image display media
14 Display board
16 back substrate
18 cells
20 Partition members
22, 23 particles
24 Electrode head
25 electrodes
26 Back electrode
27 detection sensor (detection means)
28 Voltage application means
30 Sync mark

Claims (5)

A pair of substrates at least one of which has a light-transmitting property, at least one kind of particle group that is movably sealed between the substrates according to an electric field formed by a voltage applied between the pair of substrates, and the substrate An image display medium provided with a partition member for partitioning the space into a plurality of cells,
An electrode head that moves in a predetermined direction on one of the pair of substrates,
A back electrode provided on the other substrate side of the pair of substrates,
While moving the electrode head in the predetermined direction, voltage applying means for applying a voltage corresponding to image information at a predetermined timing synchronized with the passage of the partition member between the electrode head and the back electrode,
An image display device comprising: The voltage applying unit may apply a voltage according to image information between the electrode head and the back electrode when a rear end of the electrode head in the predetermined direction passes through the partition member. The image display device according to claim 1. The one substrate includes a synchronization mark arranged corresponding to the cell along the predetermined direction, the electrode head includes a detection unit that detects the synchronization mark, and the voltage applying unit includes the synchronization mark. The image display device according to claim 1, wherein a voltage corresponding to the image information is applied between the moving electrode and the back electrode when the image is detected. 3. The image according to claim 1, wherein the voltage applying unit sets the predetermined timing based on a length of the cell and the partition member in the predetermined direction and a moving speed of the electrode head. 4. Display device. The image display device according to claim 1, wherein the particle group is a plurality of particle groups having different charging characteristics and colors.

Images