JP2000122102A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device of a high contrast ratio capable of displaying white with higher whiteness. SOLUTION: This display device 20 has a plurality of two-color balls 23 consisting of a pair of hemispherical parts 23a, 23b varying in colors or reflectivity and electrostatic charge characteristics and fluid bodies 24 rotatably enclosing these two-color balls 23. The one hemispherical parts of the two-color balls 23 are white. The fluid bodies 24 enclosing the two-color balls 23 exhibit white.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention provides a two-color ball in which one half is white and the other half is black, and the two-color ball rotates according to the polarity to exhibit white or black. The present invention relates to a display device that performs various displays.

[0002]

2. Description of the Related Art In recent years, CRTs and liquid crystal displays have become mainstream display devices. However, it is said that a light-emitting display such as a CRT is not suitable for reading a document or the like because it tires eyes. On the other hand, liquid crystal displays, which use a backlight, are said to be as tiring to the eyes as CRTs, and those without a backlight have poor contrast. There was a drawback of forcing. Further, these displays generally do not have a memory property, and there is a disadvantage that an image disappears when the power is turned off.

[0003] Against this background, displays of portable information devices such as PDAs, notebook computers, and e-book players, which are expected to become more widespread in the future,
It is considered essential to be easy on the eyes, low in power consumption, and having image memory properties.

Conventionally, electrophoretic display devices and two-color ball display devices have been known as displays that satisfy these requirements to some extent. The electrophoretic display device is configured based on the principle that electrophoretic particles composed of charged fine particles migrate and collect on an electrode having a polarity opposite to the charge of the electrophoretic particles by the action of an electric field. is there.

That is, as shown in FIG. 4, a transparent substrate 2 provided with a transparent electrode 1 such as ITO
And a substrate 4 provided with an electrode 3 that does not require transparency is opposed at a predetermined interval, and electrophoretic particles 5 made of, for example, white charged particles and dispersed between the substrates 2 and 4. And the dispersion medium 6 thus formed. Here, the electrophoretic particles 5 are made of, for example, a white pigment such as titanium dioxide, and the dispersion medium 6 is, for example, colored black.

In such an electrophoretic display device, when a positive voltage is applied to the transparent electrode 1 and a negative voltage is applied to the other electrode 3 as shown in FIG. If 5 is negatively charged,
The electrophoretic particles 5 electrophores toward the positive transparent electrode 1 by Coulomb force and adhere to the transparent electrode 1. When the electrophoretic display device in such a state is observed from the eye position E shown in FIG. 4, the portion where the white charged particles (electrophoretic particles 5) adhere appears to be white through the transparent electrode 1 and the transparent substrate 2. become.

On the other hand, when the polarity of the applied voltage is reversed, the white charged particles (electrophoretic particles 5) electrophoretically migrate toward the rear electrode 3 as shown in FIG. It will be hidden behind the black dispersion medium 6. Therefore, when observed from the eye position E, this portion appears black. Further, in this electrophoretic display device, once the white charged particles (electrophoretic particles 5) adhere to the electrode 1 (or 3), the display state can be maintained for a while without applying a voltage. .

However, in the electrophoretic display device according to such a method, either the color of the electrophoretic particles 5 or the color of the dispersion medium 6 is displayed. When the color is white and the color of the dispersion medium 6 is black, the black dispersion medium 6 remains between the white particles 5 gathered by electrophoresis, so that a clear white color could not be obtained. When the color of the electrophoretic particles is black and the color of the dispersion medium is white, white can be obtained by increasing the concentration of white in the dispersion medium, but in that case, when displaying black, The dark white dispersion medium remains between the black particles (electrophoretic particles), so dark black cannot be produced.
As a result, a high contrast ratio could not be obtained.

The two-color ball display device comprises a hemisphere half of which is white and the other half of which has a color such as black. The zeta of these white halves, ie, a white hemisphere and a colored hemisphere of black or the like, is formed. It is composed of a large number of two-color balls having different potentials, and utilizes the principle that these two-color balls rotate by the action of an electric field.

That is, in this two-color ball display device, as shown in FIG. 5, a transparent substrate 11 provided with a transparent electrode 10 such as ITO and a substrate 13 provided with an electrode 12 which does not require transparency are provided at a predetermined distance. Are filled with a large number of two-color balls 14 and a liquid flow body 15 rotatably surrounding the two-color balls 14. Note that, in the example shown in FIG.
a is positively charged, and the hemispherical portion 14b, which is a colored portion such as black, is negatively charged.

In such a two-color ball display device, a voltage is applied between the electrodes 10 and 12 disposed on the inner surfaces of the substrates 11 and 13 which hold the two-color balls 14... When the applied electric field is applied, the two-color ball 14 rotates according to the polarity, and the colored hemispherical portion as shown in the portion A in FIG. 5 corresponding to the polarity of the voltage applied to the transparent electrode 10 or the electrode 12, respectively. 14b faces the transparent substrate 11 side, or the white hemispherical portion 14a faces the substrate 13 side as shown in a part B in FIG. The behavior of the two-color balls 14 makes it possible to display white or black. Further, in the two-color ball display device, even if the application of the voltage is stopped, the display state is maintained for a while.

[0012]

However, it has been difficult to obtain a high contrast ratio even in a two-color ball display device which performs display based on such a method. Because the two-color ball 14 itself is in each hemisphere portion 14a, 14b
Is clear, but a gap is required between the two-color balls 14 to allow the fluid 15 to enter, so that the two-color balls 14 can be rotated. Because it cannot be filled into

In order to solve such a drawback, as shown in FIG. 6, two-color balls 14 are arranged in multiple layers (multi-layers), and a part where a gap is generated in one layer is supplemented by a second layer. Has also been proposed. However, even in this case, the white of the second layer is affected by the black of the first layer, and the white of the first layer is one.
Since it is darker than the white of the layer, a sufficient effect has not yet been obtained for displaying white more white. Also,
Since the distance between the electrodes 10 and 12 becomes longer,
There is also a problem that a higher voltage is required for driving.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a display device having a high contrast ratio capable of displaying white more white.

[0015]

According to the display device of the present invention,
A two-color ball comprising a pair of hemispherical portions having different colors or reflectivity and charging characteristics, and a fluid body rotatably surrounding the two-color ball, wherein one hemisphere of the two-color ball is provided. The portion is white, and the fluid surrounding the two-color ball is white, which is a means for solving the problem.

According to this display device, one hemispherical portion of the two-color ball is white, and the fluid surrounding the two-color ball is
Since the white color is assumed, when performing white display, the two-color ball and the fluid complement each other,
White is displayed more white.

Further, the fluid body is formed by white electrophoretic particles electrophoresing in the same direction as the white side of the two-color ball when an electric field is applied, and a transparent electrophoretic particle for dispersing the electrophoretic particles. When formed with a dispersion medium, when displaying white, not only the white side of the two-color ball faces the display surface, but also the white electrophoretic particles move to the display surface side. It is possible to display whiter. Further, when displaying black, the white electrophoretic particles move to the electrode side opposite to the display surface, thereby preventing the white electrophoretic particles from remaining on the display surface side to make blackish whitish.

Furthermore, if each two-color ball and the fluid body are encapsulated in a microcapsule and these are encapsulated in the microcapsule, contact between the two-color balls can be avoided, and the display device can be prevented. Can be simplified. When the fluid is formed by the electrophoretic particles and the dispersion medium, uneven distribution of the electrophoretic particles can be suppressed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a display device of the present invention will be described in detail with reference to embodiments. FIG. 1 is a view showing an embodiment of a display device according to the present invention. In FIG. 1, reference numeral 20 denotes a display device. In this display device 20, a transparent (translucent) transparent substrate (transparent substrate) 21 made of a glass plate or a plastic film and a counter substrate (substrate) 22 also made of a glass plate or a plastic film have a predetermined gap. The two-color ball 23 and the fluid 2
4 and a number of microcapsules 25 ...
These are configured by enclosing them.

On the inner surface of the transparent substrate 21, stripe-shaped transparent electrodes 26 made of ITO are formed in parallel, and on the inner surface of the counter substrate 22, a stripe-shaped transparent electrode 26 made of ITO, aluminum or the like is formed. The counter electrodes 27 are formed in parallel. These transparent electrodes 26 ...
And the opposing electrodes 27 are arranged orthogonal to each other, thereby enabling matrix driving. (Note that, in FIG. 1, for convenience of explanation, the transparent substrate 21 is rotated by 90 ° C. for convenience, so that the transparent electrodes 26... And the counter electrodes 27. Yes.)

The microcapsules 25 are arranged on the transparent substrate 21.
Between the substrates 21 and 22, which are ideally placed in a close-packed state, and are fixed between the substrates 21 and 22 by a fixing agent 28 made of a UV adhesive or the like. The layer 29 is formed. These microcapsules 25 are formed from a transparent capsule 25a having a diameter of about several tens of μm, a two-color ball 23 and a fluid body 24 contained in the capsule 25a. Here, such microcapsules 25 are
It is manufactured by a conventionally known technique, and particularly has various functions such as barrier properties by being formed by a chemical manufacturing method.

Two-color ball 2 encapsulated in capsule 25a
Reference numeral 3 denotes a pair of hemispherical portions having different colors or reflectances and different charging characteristics. In this example, a white hemispherical portion 23a serving as a positively charged white display portion and a negatively charged black display portion are provided. It comprises a black hemispherical portion 23b.
Here, in order to produce the two-color ball 23 having such a configuration, for example, a glass ball filled with titanium dioxide so as to appear white is produced, and the glass ball is placed in a vacuum deposition chamber, and a half thereof is placed in the vacuum deposition chamber. For example, a black material, for example, a mixture of antimony sulfide and magnesium fluoride is coated.

The two-color ball 23 and the fluid body 24 obtained in this manner are both dielectric materials and are macroscopically electrically neutral, but microscopically, the two-color ball 23.
The electric double layer is formed around. The zeta potential is known as a measurable aspect of the electric double layer, and this zeta potential has a function of the ball surface material for a given liquid. Therefore, a zeta potential having different characteristics is generated due to a difference in color or a property of a substance which causes a difference between the reflectance and the charging characteristics between the white hemisphere portion 23a and the black hemisphere portion 23b in the two-color ball 23. Therefore, when an electric field is applied between the transparent electrode 26 and the counter electrode 27, the two-color ball 23 flows through the fluid 24 as described later due to the difference in zeta potential between the white hemisphere 23a and the black hemisphere 23b. It rotates until the dipole moment matches the direction of the electric field.

The white hemispherical portion 23a and the black hemispherical portion 23
If a difference is previously made between the charge amounts of b and b,
The two-color ball 23 also generates a monopole charge in addition to the dipole charge, whereby the two-color ball 23 moves in the direction of the electric field when an electric field is applied between the transparent electrode 26 and the counter electrode 27. It comes into contact with the inner wall of the capsule 25a. When the two-color ball 23 comes into contact with the inner wall of the capsule 25a in this manner, the two-color ball 23 is separated by the frictional force with the inner wall until the two-color ball 23 separates again from the inner wall of the capsule 25a by the action of the monopole charge. 23 is prevented from rotating. Therefore, even if the electric field is cut off, the two-color ball 23 stays at that position for a while, so that the display image is held and the memory property is obtained.

A fluid 24 which is encapsulated in a capsule 25a together with a two-color ball 23 to form a microcapsule 25
Is a rotatable two-color ball 23 that surrounds and holds the ball 23. In this example, the ball 23 is formed by white electrophoretic particles 30 and a transparent dispersion medium 31 that disperses the white electrophoretic particles 30. The white electrophoretic particles 30 are formed by mixing titanium dioxide into a polyethylene resin or the like, and electrophoreses in the same direction as the white hemispherical portion 23a of the two-color ball 23 faces when an electric field is applied. Like
It is charged.

The transparent dispersion medium 31 is made of a non-volatile oil such as alkylnaphthalene, diallylethane, alkylbiphenyl, triallyldimethane, low-viscosity silicone oil, vegetable or animal oil, and the like. Further, in the dispersion medium 31, a charge control agent, a dispersant, a lubricant, a stabilizer, and the like are added as necessary.

Next, the display device 2 having such a configuration will be described.
The operation of 0 will be described. As described above, the two-color ball 23 has a white hemispherical portion 23a charged positively, a black hemispherical portion 23b negatively charged, and the charged amount of the black hemispherical portion 23b is smaller than the charged amount of the white hemispherical portion 23a. It is assumed that the white electrophoretic particles 30 are positively charged.

Under such a configuration, when a positive electric field is applied to the transparent electrode 26 side and a negative electric field is applied to the counter electrode 27 side as shown in the part A in FIG. 1, the two-color ball 23 becomes the black hemispherical part 23b. Rotate so as to face the transparent electrode 26 side. Further, at this time, the two-color ball 23 is negatively charged as a whole because the charge amount of the black hemispherical portion 23b is larger than the charge amount of the white hemispherical portion 23a, and therefore moves to the positive side transparent electrode 26. . Further, the white electrophoretic particles 30
Moves to the counter electrode 27 side.

As a result, from the eye position E in FIG.
Looking at the portion, the black hemispherical portion 23b is mainly seen, and this portion looks black. Therefore, when the set of states like the part A is viewed from the eye position E in FIG.
As shown in (a), a black hemispherical portion 23b is seen at a substantially central position of the microcapsule 25, and the periphery thereof looks grayish as shown by hatching in the figure, so that the portion looks black as a whole. A black display is obtained.

On the other hand, as shown in part B in FIG.
When a negative electric field is applied to the side 6 and a positive electric field is applied to the side of the counter electrode 27, the two-color ball 23 rotates so that the black hemisphere 23b faces the counter electrode 27 and the white hemisphere 23a faces the transparent electrode 26. At this time, since the two-color ball 23 is negatively charged as a whole, the positive electrode 2
Move to 7. Further, the white electrophoretic particles 30 move to the transparent electrode 26 side.

As a result, from the eye position E in FIG.
Looking at the portion, the white electrophoretic particles 30 are seen, and the white hemisphere portion 23a of the two-color ball 23 is seen through the gap, so that this portion looks white. Therefore, this B
When a set of states like a part is viewed from an eye position E in FIG. 1, as shown in FIG.
Although the area 25 is slightly grayish as shown by hatching in the figure, the white electrophoretic particles 30 and the white hemispherical portion 23 a of the two-color ball 23 are contained in the microcapsule 25.
Is visible as a whole as a whole, and this portion forms a white display.

Note that the conventional two-color ball display device in which the fluid body 24 does not exhibit white color and therefore does not have the white electrophoretic particles 30 is shown in FIG. 2A when displaying black. Although it looks the same as the state, when white is displayed, it looks only as shown in FIG. 2C, and sufficient white was not obtained. That is, in the conventional display device, although the white hemisphere portion 23a of the two-color ball 23 can be seen at the center in the capsule 25a, the periphery of the two-color ball 23,
Since the capsules 25a and 25a appear grayish as indicated by hatching in the figure, the capsules 25a and 25a did not appear sufficiently white as a whole, and the whiteness was significantly lower than that of the display device 20 of the present invention.

Also, in the conventional electrophoretic display device as shown in FIG. 4, when expressing white, it looks like FIG. 2B, but it is actually visible on the surface. There was a black dispersion medium between the white electrophoretic particles, and thus the black dispersion medium was visible from the gaps between the white electrophoretic particles, resulting in insufficient whiteness. On the other hand, in the display device 20 of the present example, since the black dispersion medium is not used, the black dispersion medium does not exist between the white electrophoretic particles 30a seen on the surface as described above, and the white electrophoresis is not performed. Particle 30a
Since the white hemispherical portion 23a of the two-color ball 23 can be seen from the gap, there is no disadvantage that the white display is blurred as in the conventional electrophoretic display device.

In the display device 20 described above, the fluid 24 surrounding the two-color ball 23 is formed by the white electrophoretic particles 30 and the transparent dispersion medium 31 so as to exhibit a white color. When the display is performed, the white electrophoretic particles 30
Are visible, and the white hemispherical portion 23a of the two-color ball 23 is visible from the gap. Therefore, white can be displayed more white by the two-color ball 23 and the fluid body 24 complementing each other in this way.

The individual two-color balls 23 and the fluid bodies 24
Are encapsulated in the capsule 25a and these are encapsulated in the microcapsule 25, so that it is possible to prevent the two-color balls 23 from contacting each other and hindering the rotation,
Further, the manufacture of the display device can be simplified, and the uneven distribution of the white electrophoretic particles 30 can be suppressed.

Although the microcapsules 25 are used in the above embodiment, each pixel may have a cell structure and be divided. In the display medium 20 of the embodiment, the transparent electrode 26 is provided on the transparent substrate 21.
Further, the counter electrodes 27 are provided on the counter substrate 22, respectively.
The present invention is not limited to this. For example, FIG.
As shown in FIG. 3, a structure without electrodes may be used. Further, as shown in FIG. 3 (b), a structure without one substrate (substrate), and as shown in FIG. ) May be omitted. Even when no electrodes are provided, 2
If an electric field is externally applied to the display medium composed of the color balls 23 and the fluid body 24, a display according to the electric field can be performed.

[0037]

As described above, in the display device of the present invention, one hemispherical portion of the two-color ball is made white and the fluid surrounding the two-color ball is made white, so that the white display is performed. When performing the above, the two-color ball and the fluid body complement each other, so that white can be displayed more white. Therefore, a display device that is easy on the eyes, has low power consumption, has memory properties, and is whiter and more excellent in contrast. In addition, if this display device is configured without electrodes, the cost of the display device itself can be reduced, the flexibility can be improved, and the display of the display due to the surface reflection of the transparent electrode can be further improved. It is also possible to prevent invisibility.

Further, the fluid body is formed by white electrophoretic particles electrophoresing in the same direction as the white side of the two-color ball when an electric field is applied, and a transparent electrophoretic particle for dispersing the electrophoretic particles. When formed with a dispersion medium, when displaying white, not only the white side of the two-color ball faces the display surface, but also the white electrophoretic particles move to the display surface side. It can be displayed whiter, and when displaying black, the white electrophoretic particles move to the electrode side opposite to the display surface, so that the white electrophoretic particles remain on the display surface side and make blackish whitish Can be prevented.

Furthermore, if these two-color balls and the fluid body are encapsulated in microcapsules and these are individually encapsulated in the microcapsules, the two-color balls come into contact with each other and their rotation is hindered, resulting in malfunction. In addition, the manufacturing of the display device can be simplified, for example, the workability in forming a sheet or a panel can be improved, and the uneven distribution of the electrophoretic particles can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional side view of a main part showing a schematic configuration of an embodiment of a display device according to the present invention.

2A is an explanatory diagram of a black display state of the display device shown in FIG. 1, FIG. 2B is an explanatory diagram of a white display state of the display device shown in FIG. 1, and FIG. FIG. 4 is an explanatory diagram of a white display state of the display device.

FIGS. 3A to 3C are cross-sectional views of a main part showing a modification of the display device of the present invention.

FIG. 4 is a side sectional view showing a main part of an example of an electrophoretic display device.

FIG. 5 is a side sectional view showing a main part of an example of a conventional two-color ball display device.

FIG. 6 is a side sectional view showing a main part of another example of a conventional two-color ball display device.

[Explanation of symbols]

20 display device, 21 transparent substrate, 22 counter substrate, 2
3 ... two-color ball, 23a ... white hemisphere part, 23b ... black hemisphere part, 24 ... fluid, 25 ... microcapsule, 25a
... capsule, 26 ... transparent electrode, 27 ... counter electrode, 30 ...
White electrophoretic particles, 31 ... dispersion medium

Claims (5)

[Claims] 1. A display device comprising: a plurality of two-color balls composed of a pair of hemispherical portions having different colors or reflectances and different charging characteristics; and a fluid body rotatably surrounding the two-color balls. A display device, wherein one hemispherical portion of the two-color ball is white, and the fluid surrounding the two-color ball is white. 2. The electrophoretic device according to claim 1, wherein the fluid body is configured such that, when an electric field is applied, white electrophoretic particles that electrophorese in the same direction as the white side of the two-color ball faces, and a transparent electrophoretic particle that disperses the electrophoretic particles. The display device according to claim 1, wherein the display device is formed of a dispersion medium. 3. The two-color ball and the fluid body are disposed between a pair of base materials facing each other, and at least one of the pair of base materials is formed of a light-transmitting transparent base material. The display device according to claim 1, wherein: 4. The display device according to claim 3, wherein an electrode is provided on each of the pair of base materials, and the electrodes provided on the transparent base material are transparent electrodes made of a transparent conductive material. . 5. The display device according to claim 1, wherein the two-color ball is individually enclosed in a microcapsule together with the fluid body.