JP2002250944A - Electrophoresis display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophoresis display device which has a high contrast and a long service life. SOLUTION: In the electrophoresis display device, a dispersed system which has electrophoresis particles dispersed in a dispersion medium is enclosed in a microcapsule, and the microcapsule is arranged between electrode plates. When the diameter of the microcapsule during manufacturing is expressed as 2r, or the volume of one microcapsule is expressed as V and the distance between the electrode plates is expressed as d, the relation of (4/3)π(d/2)<3> <V<(4/3)π(d/0.4)<3> and d/2<r<d/0.4 are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device using electrophoretic particles, and more particularly, to a display device in which microcapsules each individually enclosing a dispersion system in which electrophoretic particles are dispersed in a dispersion medium are arranged between electrode plates. And an electrophoretic display device.

[0002]

2. Description of the Related Art An electrophoretic display device utilizing an electrophoretic phenomenon is known. The electrophoretic display device is, for example, shown in FIG.
As shown in (1), a substrate 31 at least one of which is transparent and an electrode plate 32 formed on the surface thereof are opposed to each other, and electrophoretic particles are placed in a liquid dispersion medium in a cell divided by a porous spacer 36 between the electrode plates. This is a structure in which the dispersed dispersion system 34 is enclosed. In the electrophoretic display device having this porous spacer, by controlling the polarity of the electrode plate, an electric field is applied to the electrophoretic particles to cause the electrophoretic particles to adsorb or separate from the transparent electrode plate side, thereby displaying a desired character, symbol or figure. be able to. However, in this electrophoretic display device, since the electrode plate and the dispersion system are in direct contact with each other, there is a problem that the dispersion system is easily deteriorated and it is difficult to uniformly form the dispersion system on the electrode substrate. Was.

[0003] To solve this problem, Patent No. 255
No. 1783, a dispersion system containing electrophoretic particles is sealed between a pair of transparent electrode plates, at least one of which is transparent, and electrophoresis in the dispersion system is performed under the action of a display control voltage applied between the electrode plates. In an electrophoretic display device in which a required display operation is performed by changing an optical reflection characteristic by changing a distribution state of particles, at least one kind of a dispersion medium having different optical characteristics from the dispersion medium in a colored dispersion medium. There has been disclosed an electrophoretic display device in which a large number of microcapsules enclosing a dispersion system in which electrophoretic particles are dispersed are formed, and these microcapsules are arranged between the electrode plates.

In this electrophoretic display device, as shown in FIG. 4, at least one of a transparent substrate 41 and an electrode plate 42 formed on the surface thereof are opposed to each other, and a dispersion system in which electrophoretic particles are dispersed in a dispersion medium. This is a structure in which a microcapsule 45 in which 44 are individually sealed and a binder material 43 are arranged between electrode plates.

[0005]

However, in the conventionally known microcapsule type electrophoretic display device shown in FIG. 4, the microcapsules are spherical, the diameter is 2r ', and the distance between the electrode plates is small. When d, d> 2r ′. For this reason, when the microcapsules are arranged between the electrode plates, many gaps are generated between the electrode plates, and there is a problem that the contrast is lower than that of the conventional electrophoretic display device shown in FIG. Furthermore, since the microcapsules are locally in contact with the electrode plate, the electric field cannot be applied uniformly to the electrophoretic particles dispersed in the microcapsules, and the electrophoretic particles are only applied to the portion in contact with the electrode plate and its surroundings. Moves, and optical reflection does not appear in other places, so that the contrast is reduced. In addition, since a large amount of current flows only where the electrode plate is in contact, convection of the electrophoretic particles in the microcapsules and local deterioration of the microcapsules and the contents are caused, thereby causing a problem of shortening the product life.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an excellent electrophoretic display device which can obtain high contrast and does not deteriorate even in long-term use. is there.

[0007]

The above-mentioned problems can be solved by the present invention according to any one of the following (1) to (5). (1) An electrophoretic display device in which a dispersion system in which electrophoretic particles are dispersed in a dispersion medium is encapsulated in microcapsules, and the microcapsules are arranged between electrode plates.
When the volume of the microcapsule is V and the distance between the electrode plates is d, (4/3) π (d / 2) ³ <V <
(4/3) π (d / 0.4) ³ , wherein the electrophoretic display device is characterized in that: (2) An electrophoretic display device in which a dispersion system in which electrophoretic particles are dispersed in a dispersion medium is encapsulated in microcapsules, and the microcapsules are disposed between electrode plates.
When the volume of the microcapsules is V and the distance between the electrode plates is d, (4/3) π (d / 1.6) ³ <V
<(4/3) π (d / 0.6) ^{3. An} electrophoretic display device. (3) The electrophoretic display device according to (1) or (2), wherein the microcapsules are spherical when manufactured. (4) An electrophoretic display device in which a dispersion system in which electrophoretic particles are dispersed in a dispersion medium is encapsulated in microcapsules, and the microcapsules are disposed between electrode plates.
When the diameter at the time of manufacturing the microcapsules is 2r and the distance between the electrode plates is d, d / 2 <r <d / 0.4.
An electrophoretic display device comprising: (5) An electrophoretic display device in which a dispersion system in which electrophoretic particles are dispersed in a dispersion medium is encapsulated in microcapsules, and the microcapsules are disposed between electrode plates.
When the diameter at the time of manufacturing the microcapsules is 2r and the distance between the electrode plates is d, d / 1.6 <r <d /
An electrophoretic display device having a ratio of 0.6. (6) The electrophoretic display device according to any one of (1) to (5), wherein a distance d between the electrode plates is 1 μm <d <200 μm.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electrophoretic display device according to the present invention is shown in FIG.
As shown in the figure, a microcapsule 15 in which a transparent substrate 11 at least one of which is opposed to an electrode plate 12 formed on the surface thereof and a dispersion system 14 in which electrophoretic particles are dispersed in a dispersion medium are individually encapsulated, and a binder material 13 is provided between the electrode plates.

As the substrate, glass or plastic can be used, and particularly when used as electronic paper, a flexible plastic film having a thickness of 300 μm or less is preferable. In the case of such a plastic film, it is preferable to provide a gas barrier layer in order to prevent gas and water vapor from permeating.

When the volume of the microcapsule is V and the distance between the electrode plates is d, (4/3) π (d / 2) ³
<V <(4/3) π (d / 0.4) ³ is satisfied. If the volume of the microcapsules is larger than the above range, the microcapsules will be broken, and if the volume is smaller than the above range, the effect of improving the contrast cannot be sufficiently obtained. Also,
Preferably (4/3) π (d / 1.6) ³ <V <(4 /
3) The relationship of π (d / 0.6) ³ is satisfied. Within this range, a high contrast can be obtained and a long life without deterioration even during long-term use can be achieved.

In addition, microcapsules are produced at the time of manufacture.
Is spherical, and the present invention has a diameter of 2 as shown in FIG.
The relationship of d / 2 <r <d / 0.4 is satisfied as r.
You. The diameter during the production of the microcapsules is
Above the range, the microcapsules will be destroyed,
Below the above range, the effect of improving contrast is sufficient.
I can't get it. Preferably, d / 1.6 <r <d /
The relationship 0.6 is satisfied. In this range, high
Provides trust and degrades over long periods of use
, And a long service life without any occurrence of the problem can be achieved. What
The microcapsules were placed between the substrates and the production was completed
In the state of the display device, the microcapsules are
It is not a spherical shape, but a shape compressed by the upper and lower substrates.
You. In other words, in this state, the microcapsule
Let V = (4/3) πr ^Three, Between the electrode plates
Where d is the distance of (4/3) π (d / 2)^Three<
V <(4/3) π (d / 0.4)^ThreeAnd preferably
(4/3) π (d / 1.6)^Three<V <(4/3) π (d
/0.6)^ThreeSatisfy the relationship In other words,
The electrophoretic display device of the present invention has a distance d between electrodes and a microcapsule.
The ratio d / r of the radius r of the pusher is 0.4 <d / r <2.
Preferably, the relationship of 0.6 <d / r <1.6 is satisfied.
Add

More preferably, 1 μm <d <200 μm
It is. When the distance between the electrode plates is less than the above range, a short circuit between the electrode plates is likely to occur. When the distance is more than the above range, the particles in the dispersed microcapsules aggregate and the contrast tends to decrease. Furthermore, since the moving speed of the electrophoretic particles is proportional to the distance between the electrodes and the square of d, by reducing d, the response of the display device can be sped up.

When microcapsules are mass-produced by the current manufacturing technology, their diameters are not exactly the same,
It has a certain particle size distribution. The microcapsules used in the present invention are classified so that the ratio of the minimum particle size to the maximum particle size is 2 or less, more preferably 1.5 or less. Of course, depending on the accuracy of the classification, it is unavoidable that slightly large particles or extremely small particles are mixed in an industrial production process. In the present invention, the diameter 2r at the time of manufacturing the microcapsules uses the average value of the classified microcapsules.

The dispersed electrophoretic particles to be encapsulated in the microcapsules include titanium oxide, carbon black, navy blue or phthalocyanine green, well-known colloid particles, various organic / inorganic pigments, dyes, and metal powders. Alternatively, fine powder such as glass or resin can be used as appropriate. For example, as the pigment, an inorganic pigment or an organic pigment is used, and as the inorganic pigment particles, lead white, zinc white, lithopone,
Titanium dioxide, zinc sulfide, antimony oxide, calcium carbonate, kaolin, mica, barium sulfate, gloss white, alumina white, talc, silica, calcium silicate, cadmium yellow, cadmium liptone yellow, yellow iron oxide, titanium yellow, titanium barium Yellow, Cadmium Orange, Cadmium Lipton Orange, Molybdate Orange, Bengala, Lead Tan, Silver Vermilion, Cadmium Red, Cadmium Lipton Red, Amber, Brown Iron Oxide, Chrome Zinc Brown, Chrome Green, Chromium Oxide, Viridian, Cobalt Green , Cobalt chrome green, titanium cobalt green, dark blue,
Cobalt blue, ultramarine, Cerulean blue, cobalt aluminum chrome blue, cobalt violet, mineral violet, carbon black, iron black, manganese ferrite black, cobalt ferrite black, copper chrome black, copper chromium manganese black, titanium black, aluminum powder, copper powder , Lead powder, tin powder, zinc powder and the like. Organic pigment particles include Fast Yellow, Disazo Yellow, Condensed Azo Yellow, Anthrapyrimidine Yellow, Isoindoline Yellow, Copper Azomethine Yellow, Quinophthaloin Yellow, Benzimidazolone Yellow, Nickel Dioxime Yellow, Monoazo Yellow Lake, and Dinitroaniline Orange , Pyrazolone orange, perinone orange, naphthol red,
Toluidine Red, Permanent Carmine, Brilliant Fast Carlet, Pyrazolone Red, Rhodamine 6G Lake, Permanent Red, Risor Red, Bon Lake Red, Lake Red, Brilliant Carmine, Bordeaux 10B, Naphthol Red, Quinacridone Magenta, Condensed Azo Red, Naphthol Carmine, Perylene Scarred.

It is also possible to enclose white particles and black particles charged with different charges in positive and negative directions in one microcapsule. Further, by coloring several types of particles having different electrophoretic velocities (different in zeta potential), it is possible to colorize by driving voltage.

The dispersion medium of the dispersion system includes, in addition to water, alcohols, hydrocarbons, halogenated hydrocarbons, etc., various natural or synthetic oils, alcohol solvents, various esters, aliphatic hydrocarbons, and the like. An alicyclic hydrocarbon, an aromatic hydrocarbon, a halogenated hydrocarbon, or a mixture of various other oils alone or in an appropriate mixture can be used. In such a dispersion system, if necessary, in addition to a charge control agent composed of particles such as an electrolyte and a surfactant, a metallic soap, a resin, a rubber, an oil, a varnish, and a compound, a dispersant, a lubricant, a stable An agent can be added.

In the present invention, the microcapsules can be prepared by an ordinary method for preparing microcapsules. The method for preparing the microcapsules used at that time can be prepared by an in-situ method, an interfacial polymerization method, a coacervation method, or the like. At that time, polyurethane, polyurea, Polyurea-polyurethane, urea-formaldehyde resin, melamine-formaldehyde resin, polyamide,
Polyester, polysulfonamide, polycarbonate, polysulfinate, epoxy, acrylate, methacrylate, vinyl acetate, gelatin,
Gum arabic and the like.

In the display device of the present invention, when a matrix element is used, a conventionally known simple matrix drive or an active matrix drive such as a TFT or MIM can be used.

[0019]

Next, the present invention will be described specifically with reference to examples. These are only one aspect of the present invention, and the scope of the present invention is not limited thereto.

As a dispersion system to be encapsulated in the microcapsules, 12 parts of titanium oxide, CR50 (manufactured by Ishihara Sangyo),
A mixture of 1.5 parts of oleic acid, 0.5 part of a titanium-based coupling agent, 1 part of a blue anthraquinone-based dye, and 85 parts of hexylbenzene mixed by ultrasonic dispersion, is used as a gum arabic gelatin-based. The microcapsules were adjusted by the composite coacervation method described above to have an average diameter of 50 microns. An emulsion of a silicone compound was used as a binder material. Further, 1,4-butanediol was used as a dielectric constant adjuster, and only 8 parts were mixed with the binder material.

The binder material and the microcapsules are:
The mixture was mixed at a weight ratio of 2 to prepare a slurry containing about 50% by weight of water to obtain a display liquid for electrophoretic display.

As a transparent substrate, a 0.15 mm-thick flexible transparent plastic film formed by simultaneously sputtering silicon oxide on both surfaces is used, and a polyvinyl alcohol layer (gas barrier layer) and a transparent conductive film (ITO film) are formed on one surface thereof. After applying the above-mentioned display liquid for electrophoretic display to the substrate on which was formed. An electrophoretic display panel was manufactured by disposing the upper substrates facing each other with nylon beads serving as spacers and sealing both transparent substrates with an epoxy resin adhesive.

Various types of electrophoretic display devices shown in Table 1 were manufactured with different diameters of nylon beads. When these electrophoretic display cells were connected to a bipolar power supply and a voltage was applied while reversing the positive and negative voltages, blue and white displays were obtained. The reflectance was measured by illuminating each display color at 45 degrees and receiving vertically, and the contrast was determined from the ratio of the reflectance of both display colors. The time required for the contrast measured by applying a DC voltage to reach 90% of the contrast was defined as the inversion time. Further, the contrast after 100,000 times and 500,000 times of reversal was evaluated with the reversal of positive / negative applied every second. FIG. 5 shows the relationship between d / r and contrast in Examples and Comparative Examples.

[0024]

[Table 1]

Samples 1 to 5 of the present invention satisfying the relationship of 2 <d / r <0.4 all provided a practically satisfactory contrast. However, d / r = 0.5 (= 0.48)
In Sample 5, a defective product in which part of the microcapsules was destroyed in almost half of the samples manufactured under the same conditions, and Sample 7 of Comparative Example with d / r = 0.4 was manufactured under the same conditions. In all samples, defective products were found in which microcapsules were destroyed, and evaluation was not possible. In particular, it was confirmed that Samples 2 and 3 satisfying the relationship of 1.6 <d / r <0.6 have high contrast and do not deteriorate even after 500,000 inversions.

The diameter 2r of the microcapsules is 30
An electrophoretic display device having a thickness of 0 μm was separately prepared, and an electrophoretic display device which was disposed so as to face the opposite side via a 150 μm nylon bead was prepared.
The initial contrast was 13, but decreased to 6 after 100,000 inversion tests of positive and negative application. As a result of the analysis, it was confirmed that the particles were aggregated and enlarged in the microcapsules.

[0027]

From the above results, the effects of the present invention are clear. The electrophoretic display device according to the present invention can achieve a high contrast and a long life without deterioration even during long-term use.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of an electrophoretic display device of the present invention.

FIG. 2 is a view showing a microcapsule at the time of manufacture used for the electrophoretic display device of the present invention.

FIG. 3 is a cross-sectional configuration diagram of a conventional electrophoretic display device having a porous spacer.

FIG. 4 is a cross-sectional configuration diagram of a conventional electrophoretic display device including a microcapsule for enclosing a dispersion system.

FIG. 5 is a diagram showing a relationship between d / r and contrast in Examples and Comparative Examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 12 Electrode plate 13 Binder material 14 Dispersion system 15 Microcapsule 31 Substrate 32 Electrode plate 34 Dispersion system 36 Porous spacer 41 Substrate 42 Electrode plate 43 Binder material 44 Dispersion system 45 Microcapsule

Claims (6)

[Claims] 1. An electrophoretic display device in which a dispersion system in which electrophoretic particles are dispersed in a dispersion medium is encapsulated in microcapsules, and the microcapsules are disposed between electrode plates. (4/3) π (d / 2) ³ where V is the volume and d is the distance between the electrode plates.
An electrophoretic display device wherein <V <(4/3) π (d / 0.4) ³ . 2. An electrophoretic display device wherein a dispersion system in which electrophoretic particles are dispersed in a dispersion medium is encapsulated in microcapsules, and the microcapsules are arranged between electrode plates. Is V and the distance between the electrode plates is d, (4/3) π (d / 1.
6) An electrophoretic display device, wherein ³ <V <(4/3) π (d / 0.6) ³ . 3. The electrophoretic display device according to claim 1, wherein the microcapsules have a spherical shape when manufactured. 4. An electrophoretic display device in which a dispersion system in which electrophoretic particles are dispersed in a dispersion medium is encapsulated in microcapsules, and the microcapsules are arranged between electrode plates. The diameter at the time of production of 2r,
When the distance between the electrode plates is d, d / 2 <r <d
/0.4, the electrophoretic display device. 5. An electrophoretic display device, wherein a dispersion system in which electrophoretic particles are dispersed in a dispersion medium is encapsulated in microcapsules, and the microcapsules are arranged between electrode plates. The diameter at the time of production of 2r,
When the distance between the electrode plates is d, d / 1.6 <r
<D / 0.6. An electrophoretic display device. 6. The distance d between the electrode plates is 1 μm <d <2.
The electrophoretic display device according to claim 1, wherein the thickness of the electrophoretic display device is 00 μm.