JPH04113387A - Electrophoresis display device - Google Patents

Abstract

PURPOSE:To obtain a sharp image regardless of a time elapse by composing an electrophoresis display of a filmy migration body which contains particulates and liquid which differs in color from the particulates and providing the filmy migration body with a viscoelasticity characteristic where the migration body migrates with electrostatic charges of larger than a specific value. CONSTITUTION:Liquid 103 obtained by mixing titanium dioxide 102 as particulates, an acryl monomer as ultraviolet-ray setting resin, and hydroxacetphenon as an optical initiator with a solvent is injected into an electrophoresis cell formed by arranging a transparent substrate 105 where a transparent electrode 104 of ITO, etc., is formed and a back insulating substrate 108 of a polyester film, etc., opposite each other across spacers 101; and the substrates are held horizontally for 12 hours and the particles 102 settle and are deposited on the substrate 105. The cell is irradiated with ultraviolet rays from below to form the filmy migration body, which has the viscoelasticity characteristic of migration with electrostatic charges of >=0.5nC/cm<2>. Then only the liquid 103 is taken out, the cell is cleaned three times with a petroleum-based solvent, and liquid 107 obtained by mixing an ion surface active agent with this solvent is injected and charged hermetically. This panel does not decrease in contrast even when left for six months.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an electrophoretic display device.

(Prior Art) An electrophoretic display device consists of an electrophoretic display panel that is hermetically packed with an electrophoretic display system whose display state changes by applying an electric field, and means for applying an electric field to the electrophoretic display panel. , various methods have been proposed so far.

An electrophoretic display system consists of a dispersion medium such as an organic solvent, electrophoretic fine particles such as titanium oxide (referred to as fine particles in the present invention), a dye for the dispersion medium to provide color contrast with the fine particles, and a dispersion stabilizer. It consists of stabilizers such as charge imparting agents. In addition, an electrophoretic display panel has a transparent substrate on which transparent electrodes are formed and a back insulating substrate that are arranged facing each other with a required gap between them via a spacer to form a sealed space, and this sealed space is filled with an electrophoretic display liquid. Configuring.

By applying an electric field to this electrophoretic display liquid, the fine particles of the electrophoretic display liquid migrate toward the transparent substrate, and the color of the fine particles appears on the display surface. By applying an electric field in the opposite direction, the fine particles migrate toward the back insulating substrate, and the color of the colored dispersion medium appears on the display surface. In this way, the electrophoretic display device can obtain a desired display by controlling the direction of the electric field, and since the display also has memory properties, it is possible to reduce power consumption and obtain a high-contrast display.

In a device that uses charging of corona ions as disclosed in Japanese Patent Application Laid-Open No. 62-34187 as a means of applying an electric field to an electrophoretic display panel, there is a problem of crosstalk between areas where display is to be performed and areas where display is not to be performed. Since there is no space, large-area, large-capacity displays are possible, and it is expected to be used as a large-sized electronic display.

FIG. 3 shows the structure of an electrophoretic display panel. In the electrophoretic display panel 6, a transparent substrate (display surface) 6d on which a transparent electrode 6c is formed and a back insulating substrate 6a are arranged facing each other with a required gap between them via a spacer 6b to form a sealed space. An electrophoretic display liquid 7 is filled.

Application of an electric field to an electrophoretic display panel utilizes an electrostatic image created by charging corona ions. The operation will be explained with reference to FIG. Gold-plated tungsten wire (corona wire) 1,
Corona ions are generated by applying a positive or negative voltage. 2 is a discharge frame. The passage of these ions through the control circuit board is controlled by the control circuit board 3. The control circuit board 3 is configured such that an upper control electrode 3a and a lower control electrode 3b are arranged at a predetermined interval, and a corona ion flow can pass through a through hole provided in the center. Figure 4 (a
) When the control power source 8 is applied so that the upper control electrode 3a is positive and the lower control electrode 3b is negative, the electric field becomes forward, and the corona ions pass through and form an electrostatic image 4 on the back insulating substrate 6a. Form. Conversely, if the control power source 8 is applied with the opposite polarity as shown in FIG. 4(b), corona ions cannot pass through.

Note that 9 is a bias power supply. The electrostatic image 4 that has passed through the control circuit board and is charged on the back insulating substrate 6a of the electrophoretic display panel is erased using corona ions of opposite polarity. That is, in FIG. 4(a), the corona wire 1 has a fourth
Applying a voltage opposite to that in Figure 4(a) generates negative corona ions, and applying voltages opposite to those in Figure 4(a) to the control power source 8 and bias power source 9 generates negative corona ions in the control circuit. It passes through the hole, reaches the electrostatic image 4 (positive corona ions), and the electrostatic image 4 is erased.

FIG. 5 is a perspective view of an electrophoretic display device, and a driving method will be explained. Reference numeral 10 denotes an ion flow control section, which is composed of a corona wire 1, a discharge frame 2, and a control circuit board 3. The control circuit board 3 has a fixed pitch (for example, 1 mm).
), a large number of through holes 5', 5', . . . are opened, and the upper control electrode and the lower control electrode explained in FIG. The electrodes are formed independently from each other (not shown), and this large number of pairs of electrodes constitutes a control electrode array. The ion flow control unit 10 moves the ion flow up and down at a constant pitch (for example, 1 mm) (scanning). In the case of FIG. 5, the direction of the control electrode array (horizontal direction) is the row, the vertical control electrode array generated by the vertical movement of the ion flow control unit 10 is the column, and the intersection of the row and column is the pixel. . The driving is performed by moving the ion flow control unit 10 at a constant pitch (scanning) and selectively charging pixels at the intersections of rows and columns with corona ions to form an electrostatic image 4.

In FIG. 5, 11 is a fine particle and 12 is a light beam. Although FIG. 5 shows a method in which the ion flow control section 10 is arranged horizontally and scans up and down, a method in which the ion flow control section 10 is arranged vertically and is caused to scan left and right is also possible.

(Problems to be Solved by the Invention) Electrophoretic display liquids have a problem in that, as they are used, fine particles settle, aggregate, etc., resulting in decreased display uniformity and contrast, resulting in deterioration of display quality.

There is also the problem that the ion charge leaks to the periphery of the pixel, reducing the clarity of the image.

That is, the amount of charge of each pixel is normally 1 to 5 nC/Cm2, but in the pixel portion, subsequent ions are diffused by the electric field of the charged ions, and the amount of ion charge is distributed so as to decrease continuously around the pixel. Since the amount of migrating fine particles is proportional to the amount of ion charge, fine particles proportional to the amount of ion charge also migrate around the pixel, reducing the clarity of the image.

The present invention provides an electrophoretic display device whose display quality does not deteriorate over time and whose images are clear.

(Means for Solving the Problems) The present invention provides a method for forming a sealed space by arranging a transparent substrate on which a transparent electrode is formed and a back insulating substrate facing each other with a required distance between them via a spacer, and electrically connecting the sealed space. In an electrophoretic display device equipped with a display panel encapsulating a electrophoretic display system and an electric field applying means for applying an electric field to the display panel by charging corona ions, the electrophoretic display system is connected to a film-like electrophoretic body containing fine particles. It is characterized in that it is composed of fine particles and liquids of different colors, and has viscoelastic properties such that the film-like migration material migrates due to an electrical charge of 0.5 nC/cm2 or more.

FIGS. 1(a), (b), and (C) show a first embodiment of the present invention. ITO (Indium Tin Oxide) via a 100 μm thick spacer 101
Titanium dioxide was added as fine particles to a solvent in an electrophoresis cell formed by arranging a transparent substrate 105 such as a 3 mm thick glass plate or the like on which a transparent electrode 104 was formed and a back insulating substrate 108 such as a 100 μm thick polyester film, etc., facing each other. 102
(Product name: Tybake R6701 manufactured by Ishihara Sangyo ■), an acrylic monomer (Product name: Kayarad HX-620, manufactured by Nippon Kayaku ■) as an ultraviolet curing resin, and hydroxyacetophenone (Product name: Grocure 1173, manufactured by Merck) as a photoinitiator are mixed. The substrate was held horizontally by injecting the liquid 103 (FIG. 1(a)). If you hold this state for 12 hours,
The titanium dioxide particles 102 are precipitated and deposited on a transparent substrate 105 made of a glass substrate with a transparent electrode 104 attached thereto. Ultraviolet rays are irradiated from the lower side of the transparent substrate 105 by an ultraviolet irradiator 106 (FIG. 1(b)). As a result, the ultraviolet curing resin is cured, and a film-like migration body containing titanium dioxide is formed. That is, the ultraviolet curable resin is cured to form a two-dimensional polymer network, and a film-like electrophoretic body in which titanium dioxide particles are fixed to this two-dimensional polymer network is obtained.

This film-like migration material containing titanium dioxide has a fixed distance between titanium dioxide particles by the resin, so there is no risk of particles settling or agglomeration, and the polymer network has a mesh shape, so the film-like migration material Electrophoresis (movement)
At this time, the dispersion medium can freely pass through the film-like electrophoretic body.

Next, only the liquid 103 was taken out while leaving the film-like migration material of the electrophoresis cell, and washed three times with a petroleum-based solvent (trade name: Isopar G1 manufactured by Exxon Chemical Co., Ltd.). Liquid 10 mixed with agent (sodium dioctyl sulfosuccinate, manufactured by Tokyo Kasei ■)
7 was injected into an electrophoresis cell and sealed to prepare an electrophoresis display panel (FIG. 1(C)).

This electrophoretic display panel showed no decrease in contrast even after being rewritten with -Gallo or left unused for six months.

FIGS. 2(a), (b), and (C) show a second embodiment of the present invention. Titanium dioxide 102 (trade name: Tybake R670, manufactured by Ishiya Sangyo ■) was placed on a transparent substrate 105 consisting of a glass substrate with a transparent electrode 104 coated with paraffin 109 (manufactured by Wako Pure Chemical Industries, Ltd., reagent, melting point 43°C) to a thickness of 3 μm. ) and polyvinyl alcohol (manufactured by Wako Pure Chemical Industries, Ltd.)
Aqueous solution 1 containing a mixture of (Special reagent grade) and an ionic surfactant (sodium dioctyl sulfosuccinate, manufactured by Tokyo Kasei)
10 was added dropwise (FIG. 2(a)). Next, water was evaporated to obtain a film-like electrophoretic body containing fine particles in which titanium dioxide was fixed to a two-dimensional network structure made of polyvinyl alcohol (FIG. 2(b)).

Transparent substrates 108 made of polyester film are placed facing each other with a spacer (not shown) interposed therebetween, and a solution 10 of a mixture of petroleum solvent and ionic surfactant used in the first embodiment is used.
7 was injected and sealed. The entire electrophoresis cell was then heated for 50
The paraffin 109 was melted by heating to .degree. C. and dissolved in a petroleum solvent to liberate a film-like electrophoretic body containing titanium dioxide, forming an electrophoretic display panel (FIG. 2(c)).

This electrophoretic display panel showed no decrease in contrast even after being rewritten for one gallon or left unused for six months.

(Function) When an electric field is applied to the electrophoretic display panel obtained in the present invention, the part of the film-like migration body containing fine particles to which the electric field is applied moves, for example, to the lower transparent substrate side, and the fine particles appear on the surface of the transparent substrate. By applying an electric field in the opposite direction to this color, the film-like electrophoretic material at that location moves toward the upper back insulating substrate, and the color of the liquid, which is different from that of the fine particles, appears on the surface of the transparent substrate.

In the present invention, when a film-like electrophoretic body migrates, it means that when a certain electric field is applied, the film-like electrophoretic body at the place where the electric field is applied moves toward the lower transparent substrate, and when it moves in the opposite direction. This means that by applying an electric field, the film-like electrophoretic body at that location moves toward the upper back insulating substrate.

In the film-like migration medium containing fine particles of the present invention, since the distance between the fine particles is fixed, sedimentation and aggregation of the fine particles can be prevented even during long-term storage.

Further, the film-like electrophoretic body of the present invention has a 0.5nC/cm2
Because it has a viscoelastic property that migrates due to the above-mentioned electrical charge, the film-like migration material migrates only in areas charged with 0.5 nC/cm2 or more, and the film-like migration material migrates in areas with a charge amount of less than 0.5 nC/cm2. Does not migrate. Around each pixel, the ion charge amount is distributed so as to decrease continuously, that is, it becomes an analog charge amount distribution, but in the electrophoretic display device of the present invention, such an analog charge amount distribution is converted into a digital one. Because it can be converted to a standard display state, a clear screen can be obtained.

(Effects of the Invention) The electrophoretic display device of the present invention shows no deterioration in display quality over time and provides clear images.

[Brief explanation of drawings]

Figure 1 (a), (b), (C), Figure 2 (a), (b)
, (C) are sectional views showing the manufacturing process of the electrophoretic display panel of the present invention, FIG. 3 is a sectional view showing the structure of the electrophoretic display panel, and FIGS. 4(a) and (b) are electrostatic images. FIG. 5 is a perspective view of the electrophoresis device. Explanation of symbols 101 Spacer 102 Titanium dioxide 105 Transparent substrate 108 Back insulating substrate 1'11 Film-like electrophoretic body containing fine particles ■ ■ Fig.

Claims (1)

[Claims] 1. A display panel in which a transparent substrate on which a transparent electrode is formed and a back insulating substrate are placed facing each other with a required interval between them to form a sealed space, and an electrophoretic display system is enclosed in the sealed space, and a corona In an electrophoretic display device equipped with an electric field applying means for applying an electric field to a display panel by charging ions, the electrophoretic display system is composed of a film-like electrophoretic body containing fine particles, a liquid having a different color from the fine particles, and a film 1. An electrophoretic display device characterized in that the electrophoretic body has viscoelastic properties such that it migrates due to an electric charge of 0.5 nC/cm^2 or more.