JP2004240310A - Display device and its driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that in a display device using an EA fluid consisting of an insulating liquid and particles as a display medium, response speed is slow and high contrast display can not be obtained because of existence of particles stuck to and remaining on a substrate. <P>SOLUTION: EA particles 4a are enclosed in an air layer 4c formed by cell gap regulating members 6 having 20 μm height between upper and lower substrates 2 and 3. In the case of white display, the EA particles 4a are arranged between first and second electrodes 13a and 13b by applying positive voltage to the first electrode 13a on the upper substrate 2 and negative voltage to the second electrode 13b on the lower substrate 3 opposed to the upper substrate 2 to form an electric field in the direction vertical to the substrates. The EA particles 4a are arranged between first and second electrodes 13c and 13d by applying positive voltage and negative voltage to the first and the second electrodes 13c and 13d, respectively. A reflection plate 8 or insulating particles 4b are observed at a part except the parts at which the first electrodes 13a and 13c and the second electrodes 13b and 13d are formed to form white display. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a display device, particularly to a foldable display such as electronic paper.
[0002]
[Prior art]
Japanese Patent Application Laid-Open No. 9-230803 discloses a display device capable of changing display contents easily and at high speed by using electric field alignment particles (hereinafter, referred to as EA particles).
[0003]
FIG. 5 is a diagram showing a configuration of a display device proposed in Japanese Patent Application Laid-Open No. 9-230803.
[0004]
A voltage is applied between the first plurality of linear electrodes 65a, 65b,..., 65n and the second plurality of linear electrodes 67a, 67b,. When the EA particles 59 are applied, the EA particles 59 are arranged by the electric field arrangement effect, the transparent glass plates 51 and 53 become transparent and display is possible, and the EA particles 59 are applied to only one of the first and second plural linear electrodes, for example, the second , 67n are alternately applied to the plurality of linear electrodes 67a, 67b,..., 67n only, the EA particles 59 move toward the second plurality of linear electrodes 67a, 67b,. The transparent glass plates 51 and 53 are opaque and the display is erased, and the display contents can be easily and quickly changed.
[0005]
[Patent Document 1]
JP-A-9-230803
[Problems to be solved by the invention]
However, in the case of a display device using the EA fluid as a display medium as described above, the following problems remain.
[0007]
That is,
(1) An EA fluid composed of an insulating liquid and particles has a low response speed because the particles move in the liquid.
[0008]
(2) Since the EA particles aggregated in a chain between the electrodes strongly adhere to the substrate, a high voltage is required to return to the original state. Further, even if a voltage necessary for driving is applied, particles remaining on the substrate remain, so that sufficient white display or black display cannot be performed. Therefore, a high-contrast display cannot be obtained.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the display device and the driving method of the present application have the following configurations.
[0010]
That is, in the display device of the present application and the driving method thereof,
(1) A pair of substrates, at least one of which is transparent, and a plurality of particle groups sealed in a gas phase between the substrates, and an image is displayed by moving the particle groups by an applied electric field. A display panel is provided, and the plurality of particle groups are two or more particle groups having different dielectric constant differences, and are configured to include a particle group having an electric field arrangement effect and a particle group having no electric field arrangement effect.
[0011]
(2) The plurality of particle groups have a configuration including two or more particle groups having different specific gravities.
[0012]
(3) The diameter of the primary particles constituting the particle group having no electric field arrangement effect is fine particles having a diameter of 50 nm or less.
[0013]
(4) The electric field is a horizontal electric field formed by a common electrode formed on the one substrate and a pixel electrode formed on the substrate on which the common electrode is formed and opposed to the common electrode. And
[0014]
(5) A configuration including a vibration unit provided on the display panel is provided.
[0015]
(6) The vibration means is a piezoelectric element.
[0016]
(7) The vibrating means is an electrode provided on the display panel.
[0017]
(8) A configuration is provided that includes a synchronization circuit that synchronizes the timing for operating the vibration means with the timing for driving the display panel.
[0018]
(9) A pair of substrates, at least one of which is transparent, and a plurality of particle groups sealed in a gas phase between the substrates, and an image is displayed by moving the particle groups by an applied electric field. A method for driving a display device, comprising: a display panel; and a vibration unit provided on the display panel, wherein the driving of the display device synchronizes a timing of operating the vibration unit with a timing of driving the display panel. Method.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0020]
(Embodiment 1)
FIG. 2 is an overall view showing the configuration of the display device according to the first embodiment of the present invention. In FIG. 2, 1 is a display panel, 2 is an upper substrate, 3 is a lower substrate, 4 is an electric field aligning fluid (EA fluid), 5 is a partition for pixel configuration, 6 is a cell gap regulating member, 7 is a vibration member, 8 is a reflection layer, 9 is a vibrating means, 10 is a panel drive circuit, 11 is a vibration circuit, and 12 is a synchronous circuit.
[0021]
FIG. 3 is a block diagram illustrating a configuration of the display device according to the first embodiment of the present invention. In FIG. 3, 13 is a pixel, 14 is a first electrode driver, and 15 is a second electrode driver.
[0022]
FIG. 1 is a diagram showing a pixel portion of a display device at the time of white display according to the first embodiment of the present invention. FIG. 1A is a plan view of the pixel portion, and FIG. It is sectional drawing of a pixel part.
[0023]
4A and 4B are diagrams showing a pixel portion of the display device at the time of black display according to the first embodiment of the present invention. FIG. 4A is a plan view of the pixel portion, and FIG. FIG. 3 is an enlarged cross-sectional view of a pixel unit.
[0024]
1 and 4, reference numeral 4a denotes electric field arranging particles (EA particles), 4b denotes insulating fine particles, 4c denotes an air layer, 13a and 13c denote first electrodes, 13b and 13d denote second electrodes.
[0025]
Each pixel 13 includes first electrodes 13a and 13c and second electrodes 13b and 13d. These first and second electrodes are driven by a first electrode driver 14 and a second electrode driver 15, respectively. The operations of the first electrode driver 14 and the second electrode driver 15 are configured to be controlled by the panel drive circuit 10, and the gate signals G 1, G 2,. , Gn, and source signals S1, S2,..., Sn through the second electrode driver 15.
[0026]
In the first embodiment, the upper substrate 2 on the observation side is a transparent resin film having a thickness of 0.1 mm to 0.2 mm, and the lower substrate 3 is a similar transparent resin film. The reflection layer 8 is a white layer formed on the inner surface of the lower substrate 3 with TiO ₂ (titania), Al ₂ O ₃ (alumina) or the like. The first electrodes 13a and 13c and the second electrodes 13b and 13d are conductors formed of ITO, Al, or the like.
[0027]
Further, the EA particles 4a are spherical black particles having a diameter of about 1 to 10 μm synthesized from acrylic particles, black carbon, or the like, and the insulating fine particles 4b are made of SiO ₂ (silica) or TiO ₂ having a dielectric constant that is significantly different from that of the EA particles 4a. (Titania), acrylic or the like, and a spherical particle having a diameter of 10 nm to 100 nm, desirably having a primary fine particle of 50 nm or less, a low specific gravity and excellent fluidity is preferable. With such a combination, when an electric field is formed near the EA particles 4a, the EA particles 4a can be arranged according to the electric field.
[0028]
Here, it is desirable that the EA particles 4a have low specific gravity and excellent fluidity similarly to the insulating fine particles 4b. As a specific structure therefor, spherical silica fine particles having a diameter of 30 nm were immobilized on the entire surface layer of spherical acrylic particles having a diameter of 5 μm by a method such as mechanochemical. In order to further reduce the specific gravity, the acrylic particles are more preferably hollow or porous. With such a structure, the fluidity of the particles is improved, the frictional resistance when the particles move is reduced, and the kinetic energy required for the movement of the particles is reduced. Can be driven.
[0029]
Hereinafter, each configuration and its operation will be described in detail.
[0030]
As shown in FIGS. 1 and 2, the display panel 1 has an EA particle 4a encapsulated in an air layer 4c formed by an upper substrate 2 and a lower substrate 3 and maintaining a predetermined gap. Configuration. Here, the gap of the air layer 4c is maintained at 20 μm by the cell gap regulating member 6, and the filling rate of the EA particles 4a is about 10% to 30% by weight of the EA particles 4a in terms of volume of the air layer 4c. . After the filling of the EA particles 4a, the peripheral edges of the upper substrate 2 and the lower substrate 3 are hermetically sealed with an epoxy adhesive or the like.
[0031]
The white display is realized by the configuration as shown in FIG. That is, a positive voltage is applied to the first electrode 13a formed on the upper substrate 2, and a second electrode 13b formed on the lower substrate 3 and opposed to the first electrode 13a and the substrate in the vertical direction (Z direction). Is applied with a negative voltage. Due to this potential difference, an electric field is formed in the vertical direction (Z direction) on the substrate, and the EA particles 4a are arranged between the first electrode 13a and the second electrode 13b along the electric field distribution. Similarly, by applying a positive voltage to the first electrode 13c and a negative voltage to the second electrode 13d, the EA particles 4a are arranged between the first electrode 13c and the second electrode 13d. Therefore, the reflection plate 8 or the insulating fine particles 4b are observed in places other than where the first electrodes 13a and 13c and the second electrodes 13b and 13d are formed, and white display is performed.
[0032]
On the other hand, black display is realized by the configuration as shown in FIG. That is, a positive voltage is applied to the first electrode 13a formed on the upper substrate 2, and a negative voltage is applied to the first electrode 13c similarly formed on the upper substrate 2 and opposed in the horizontal direction (X direction). I do. Due to this potential difference, an electric field is formed in the horizontal direction (X direction) on the substrate, and the EA particles 4a are arranged between the first electrodes 13a and 13c along the electric field distribution. Therefore, since the EA particles 4a colored black are observed, black is displayed.
[0033]
Here, when the fluidity and dispersibility of the particles are not good, the problem is that the EA particles 4a once arranged by the electric field arrangement effect are fixed to the upper substrate 2 due to aggregation, and particles which cause display defects are generated. there were.
[0034]
In the first embodiment, the vibration means 9 is provided on the panel 1 to solve the problem that the particles are fixed.
[0035]
Hereinafter, a method for preventing the particles from sticking in the first embodiment will be described with reference to FIG.
[0036]
The vibration means 9 is made of a piezoelectric element or the like, and is fixed to the surface of the upper substrate 2. The vibrating circuit 11 causes the vibrating means 9 to vibrate at a high frequency of about 1 kHz to 3 kHz, and the entire upper substrate 2 vibrates, thereby separating particles attached to the upper substrate 2. Here, when the fixed pattern is displayed for a certain period of time, the particles fixed to the upper substrate 2 become very strong, and the voltage required for applying the vibration is 100 V to 200 V.
[0037]
By synchronizing the panel driving circuit 10 and the vibration circuit 11 using the synchronization circuit 12, vibration can be given in accordance with the timing of switching from black display to white display, and particles can be smoothly separated. Thus, high-speed response can be achieved without deteriorating display characteristics such as contrast. In this case, the voltage required for applying the vibration may be about 20 V to 50 V.
[0038]
In the first embodiment, the vibration unit 9 is provided separately from the display panel 1. However, the same effect can be obtained by using the first electrode and the second electrode itself. .
[0039]
【The invention's effect】
As described above, the display device and the method of driving the display device according to the present invention can provide the following operational effects. That is,
(1) Since no liquid is used as the EA fluid, the response speed is high, and an image suitable for displaying a moving image can be obtained.
[0040]
(2) Since there are almost no particles remaining on the substrate, good white display or black display can be achieved, and a high-contrast display can be obtained.
[0041]
From the above, it is possible to provide an electronic paper which can be bent, has high contrast, and is suitable for displaying a moving image, and therefore has an extremely large industrial value.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a pixel unit of a display device during white display according to a first embodiment of the present invention. FIG. 1 (a) is a plan view of the pixel unit. FIG. 1 (b) is a cross-sectional view of the pixel unit along line AA. FIG. 3 is an overall view showing the configuration of the display device according to the first embodiment of the present invention. FIG. 3 is a block diagram showing the configuration of the display device according to the first embodiment of the present invention. (A) Plan view of the pixel unit in black display in (a) Plan view of the pixel unit (b) Cross-sectional view of the pixel unit along line BB [FIG. 5] Diagram showing the configuration of the display device in the conventional example Description]
DESCRIPTION OF SYMBOLS 1 Display panel 2 Upper substrate 3 Lower substrate 4 Electric field arrangement fluid (EA fluid)
4a Electric field alignment particles (EA particles)
4b Insulating fine particles 4c Air layer 5 Pixel configuration partition 6 Cell gap regulating member 7 Vibration member 8 Reflective layer 9 Vibration means 10 Panel drive circuit 11 Vibration circuit 12 Synchronous circuit 13 Pixels 13a, 13c First electrodes 13b, 13d Second electrode 14 First electrode driver 15 Second electrode driver 51, 53 Transparent glass plate 55 EA fluid 57 Electrically insulating medium 59 EA particles 61, 63 Seal member 65n First plurality of linear electrodes 67n Second plurality Striatal electrode 69 Chain

Claims (9)

A pair of substrates at least one of which is transparent,
A plurality of particle groups sealed in a gas phase between the substrates, comprising a display panel for displaying an image by moving the particle group by an applied electric field,
The display device, wherein the plurality of particle groups are two or more particle groups having different dielectric constants, and include a particle group having an electric field arrangement effect and a particle group having no electric field arrangement effect. The display device according to claim 1, wherein the plurality of particle groups include two or more particle groups having different specific gravities. The display device according to claim 1, wherein the diameter of the primary particles constituting the particle group having no electric field arrangement effect is a fine particle having a diameter of 50 nm or less. The electric field is a horizontal electric field formed by a common electrode formed on the one substrate and a pixel electrode formed on the substrate on which the common electrode is formed and provided opposite to the common electrode. The display device according to claim 1, wherein The display device according to claim 1, further comprising a vibration unit provided on the display panel. The display device according to claim 5, wherein the vibrating means is a piezoelectric element. The display device according to claim 5, wherein the vibrating means is an electrode provided on the display panel. 6. The display device according to claim 5, further comprising a synchronization circuit that synchronizes a timing at which the vibration unit is operated and a timing at which the display panel is driven. A pair of substrates at least one of which is transparent,
A display panel comprising a plurality of particle groups sealed in a gas phase between the substrates, and displaying an image by moving the particle groups by an applied electric field,
A driving method of a display device comprising: a vibration unit provided in the display panel,
A method of driving a display device, comprising: synchronizing a timing for operating the vibrating means with a timing for driving the display panel.

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