JPH0486785A - Electrophoretic display panel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophoretic display panel used in an electrophoretic display device.

[Conventional technology]

An electrophoretic display device consists of an electrophoretic display panel that is sealed and filled with an electrophoretic display liquid whose display state changes when an electric field is applied, and a means for applying an electric field to the electrophoretic display panel. something is proposed.

An electrophoretic display liquid consists of a dispersion medium such as an organic solvent, electrophoretic fine particles such as titanium oxide (hereinafter referred to as fine particles), a dye for the dispersion medium to provide color contrast with the fine particles, a dispersion stabilizer, a charge imparting agent, etc. It consists of stabilizers, etc. Furthermore, in an electrophoretic display panel, a transparent substrate on which transparent electrodes are formed and a back insulating substrate are placed 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. It has a similar configuration. 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. 2 shows the configuration of this type of electrophoretic display device. 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. Its 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.

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 as shown in FIG. An electrostatic image 4 is formed.

Conversely, if the control power source 8 is applied with the opposite polarity as shown in FIG. 3(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. 3(a), a voltage opposite to that in FIG. 3(a) is applied to the corona wire 1 to generate negative corona ions, and the control power source 8,
If a voltage opposite to that shown in FIG. 3(a) is applied to the bias power supply 9, negative corona ions will pass through the control circuit, reach the electrostatic image 4 (positive corona ions), and the electrostatic image 4 will be erased. .

FIG. 4 is a perspective view of the electrophoretic display device, and a driving method will be explained. Reference numeral 1o 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', etc. are made, and around the through holes, the upper control electrode and the lower control electrode explained in FIG. 3 form a pair, and the adjacent electrode are formed independently from each other (not shown), and a large number of pairs of electrode groups constitute a control electrode array. Ion flow control section 1o
is moved up and down at a constant pitch (for example, 1 mm) (
scanning). In the case of Figure 4, the direction of the control electrode array (horizontal direction)
are rows, vertical control electrode columns generated by vertical movement of the ion flow control unit 1o are columns, and intersections between rows and columns are pixels. 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. 4, 11 is a fine particle and 12 is a light beam. Although FIG. 4 shows a method in which the ion flow control section 1o is arranged horizontally and scans up and down, a method in which the ion flow control section 1o is arranged vertically and is caused to scan left and right is also possible.

In this case, the electrophoretic display liquid has a problem in that particles settle as it is used, resulting in a decrease in display uniformity and contrast, resulting in deterioration in display quality. Conventionally, in order to solve this problem, a method has been proposed in which the display liquid is confined in an area that is smaller than the pixel. That is, this is a method in which an electrophoresis cell is divided into minute regions using a photolithography technique or is microencapsulated.

[Problem to be solved by the invention]

However, with these methods, injection of the display liquid and microencapsulation processing are difficult, which is a problem especially in the case of large cells.

The present invention provides an electrophoretic display panel that confines a display liquid in a minute area and allows easy injection of the display liquid.

[Means to solve the problem]

The present invention provides an electrophoretic display in which a transparent substrate on which a transparent electrode is formed and a back insulating substrate 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. The panel is characterized by forming a number of approximately spherical cavities that communicate with each other within a sealed space.

〔Example〕

The present invention will be explained with specific examples.

First, solvent-soluble, approximately spherical beads with diameters of approximately 100 μ and 2 to 5 μ are prepared. Although commercially available products may be used, they may also be produced as follows. 10 g of aromatic resin (trade name Unirange #700, manufactured by Nippon Petrochemical ■) was dissolved in 100 cc of acetone, and an ionic surfactant (sodium dioctyl sulfosuccinate, manufactured by Wako Pure Chemical Industries, Ltd., reagent) was dissolved in this. Mix it with 1000 cc of water to prepare an emulsion. This is heated to 70° C. to evaporate acetone to prepare a Uniresin bead suspension, which is then filtered to obtain beads. The particle size of the beads can be adjusted by the amount of surfactant added. With 6 µm of sodium dioctyl sulfosuccinate, beads with a diameter of about 1'OOμ were obtained, and with 200 µm beads with a diameter of 2-5 µm were obtained. 50g of 100μ beads prepared in this way, 3g of 2-5μ beads
0g was prepared and dispersed in 1000cc of 2% polyvinyl alcohol.

This was applied to a thickness of 1 mm on a transparent electrode (ITO) formed on a 1 m square glass substrate (transparent substrate). 6
It was dried at 0°C to obtain a polyvinyl alcohol film containing Uniresin beads. FIG. 1 is an end view of the central longitudinal section of this film. 10 through 2-5μ beads 22
It has a structure in which beads 21 of 0μ are connected continuously and held by polyvinyl alcohol. A second substrate (for example, a 100 μm polyester film) is laminated thereon as a back insulating substrate 6a via a spacer 6b (for example, an adhesive-coated polyester film, 100 μm thick) to form an electrophoretic cell 6 (for example, a 1° thick layer). 0 μm).

Next, acetone is injected into the cell, and the Uniresin beads are dissolved and removed as follows. First, beads 22 of 2 to 5μ are dissolved, and acetone enters through the dissolved portion to dissolve the Uniresin beads 21 of 10μ.

At this time, if ultrasonic waves are used, acetone can easily enter. After forming substantially spherical cavities that communicate with each other in this manner, the acetone is removed and the display liquid is injected. In this case, since the cavities communicate with each other, the injection operation can be easily performed using a normal injection method. Furthermore, once injected, since the communicating portion is as small as 2 to 5 microns, the purpose of confining and retaining the display liquid in a minute area can be fully achieved.

Diameter 50 as a particle size dog bead forming a cavity
~300μ beads are used in appropriate combination with beads having a diameter of 1~10μ as small beads forming the communicating portion.

〔Effect of the invention〕

The electrophoretic display panel of the present invention confines the display liquid in a minute area, so particles are less likely to settle, and at the same time, the display liquid can be easily injected.

[Brief explanation of drawings]

FIG. 1 is a central longitudinal cross-sectional end view of a bead-containing polyvinyl alcohol film, FIG. 2 is a sectional view of an electrophoretic display device, FIGS. 3(a) and 3(b) are circuit diagrams explaining the formation of an electrostatic image, and FIG. The figure is a perspective view of an electrophoretic display device. Explanation of symbols 21 100 μ beads 222 ~ 5 μ beads Diagram factor

Claims (1)

[Claims] 1. An electrophoretic 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 gap between them to form a sealed space, and this sealed space is filled with an electrophoretic display liquid. An electrophoretic display panel characterized in that a number of substantially spherical cavities communicating with each other are formed in a sealed space.