JP2000066249A - Electrophoretic display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophoretic display device which is improved in display performance by putting a technique including a dispersion system into microcapsules into practicability. SOLUTION: This electrophoretic device is constituted by inclosing the microcapsules including the dispersion media wlored by dyestuffs and the electrophoretic particles dispersed therein into a spacing between a transparent substrate and a counter substrate arranged to face the same and executes display action by the electrophoretic effect of the electrophoretic particles by the presence or absence of the voltage impression between the transparent substrate and the counter substrate. In such a case, the wall materials of the microcapsules are formed by including at least one kind among the fluorine compd, monomers expressed by the following formulas (1) to (7) as their components. In the formulas, R denotes a hydrogen atom or halogen atom or methyl group and (n) denotes an integer from 2 to 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophoretic display device utilizing the electrophoretic phenomenon of electrophoretic particles dispersed in a dispersion medium.

[0002]

2. Description of the Related Art In the electrophoresis phenomenon, certain particles are electrically charged when suspended in a medium (dispersion medium). When an electric field is applied in this state, the charged particles pass through the dispersion medium. And move (migrate) to the side of the electrode having the opposite charge.

As an electrophoretic image display (Electrophoretic image display, EPID) utilizing such a phenomenon, for example, a device having a structure shown in FIG. 5 is conventionally known. The electrophoretic display device 1 shown in FIG. 5 includes electrophoretic particles (hereinafter abbreviated as “electrophoretic particles”) 5 in a liquid dispersion medium 4 in a gap between a transparent substrate 2 and an opposing substrate 3 opposed thereto.
That is, the transparent electrode 6 is provided by enclosing a state in which the colloidal particles are suspended. The transparent electrode 6 is provided on the inner surface of the transparent substrate 2, and the counter electrode 7 is provided on the inner surface of the counter substrate 3. .

However, in such a display device 1, if there is no partition between pixels, particles move between pixels. If this movement occurs repeatedly, the migrating particles 5 are unevenly distributed for each pixel, which causes a decrease in display performance. In view of the above, a technique of forming pixels into a cell structure in order to provide a partition is disclosed in Japanese Patent Application Laid-Open Nos. 49-32038, 59-34518, and 59-1.
No. 71930.

[0005]

However, such a technique for forming a pixel into a cell structure has problems such as difficulty in assembling and difficulty in injecting a dispersion system comprising a dispersant and migrating particles. Practical application is difficult. As a solution to such a problem, a technique of encapsulating a dispersion system in microcapsules (JP2551783) has been proposed. According to this technique, non-uniformity of the migrating particles and irreversible adsorption to the electrode do not occur, which is advantageous in terms of handling. However, with this disclosed technology,
There is no description about the material and size of the microcapsules, and therefore, this technology has not yet been fully commercialized.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrophoretic display device in which the technology of encapsulating a dispersion system in microcapsules is used to improve the display performance. It is in.

[0007]

According to the electrophoretic display device of the present invention, a dispersion medium colored with a dye and dispersed in the gap are provided between a transparent substrate and an opposing substrate disposed opposite thereto. An electrophoretic display device, in which a microcapsule containing electrophoretic particles is encapsulated, and a display operation is performed by an electrophoretic action of the electrophoretic particles depending on whether or not a voltage is applied between the transparent substrate and the counter substrate, The wall material of the microcapsule has the following general formula (1) to
The means for solving the above-mentioned problem is that at least one of the fluorine compound monomers represented by (7) is formed as a component thereof.

Embedded image

According to this electrophoretic display device, the wall material of the microcapsule is made of at least one of the fluorine compound monomers represented by the above general formulas (1) to (7):
Since it is formed by including as a component thereof, the affinity of the fluorine compound monomer for the dispersion medium is low, and therefore, even within the microcapsule, the affinity between the wall material of the microcapsule and the dispersion medium is reduced. I have. Therefore, when the electrophoretic particles are electrophoresed on the light incident side of the microcapsule and the incident light is reflected and scattered by the electrophoretic particles, the amount of the colored dispersion medium remaining in a state of being attached to the inner surface of the microcapsule wall decreases, Thereby, absorption of incident light by the dispersion medium near the inner surface of the microcapsule wall is suppressed. In addition, since the adsorption of the electrophoretic particles to the inner surface of the microcapsule wall is also suppressed, the deterioration of the image quality due to the adsorption is also suppressed.

Since the electrophoretic particles and the dispersion medium are contained in each of a large number of microcapsules, large movement of the electrophoretic particles can be suppressed.
Further, the particle size of such microcapsules is 1 μm.
It is preferable that the thickness be not less than m and not more than 100 μm. 100 μm
When the size exceeds 1 μm, the size of the microcapsules themselves becomes visible, causing a sense of incongruity when viewed. For example, when the size is less than 1 μm, the number of encapsulated electrophoretic particles decreases. This is because the reflection efficiency of the incident light decreases.

The particle size of the electrophoretic particles is 10 μm.
m, and when it exceeds 10 μm, the number of microcapsules decreases, and the above-mentioned reflection effect at the interface between the electrophoretic particles cannot be sufficiently obtained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electrophoretic display device of the present invention will be described in detail with reference to embodiments. FIG. 1 is a diagram showing an embodiment of the electrophoretic display device of the present invention.
Reference numeral 10 denotes an electrophoretic display device. The electrophoretic display device 10 has a transparent (translucent) transparent substrate 11 made of a glass plate and a transparent counter substrate 1 also made of a glass plate.
2 are opposed to each other via a predetermined gap.
A large number of microcapsules 15 containing a dispersion medium 13 and electrophoretic particles 14 are arranged, and these are encapsulated.

On the inner surface of the transparent substrate 11, stripe-shaped transparent electrodes 16 made of ITO are formed in parallel, and on the inner surface of the counter substrate 12, the stripe-shaped opposing electrodes 17 made of ITO are also formed. Are formed side by side. The transparent electrode 16 and the counter electrode 17.
Are arranged orthogonally to each other, thereby enabling matrix driving. Transparent substrate 11
The scattering film 18 is stuck on the outer surface of. The scattering film 18 is made of IDS-21 ([trade name]; manufactured by Dai Nippon Printing Co., Ltd.) which is also used for a reflection type liquid crystal display and the like, and causes scattering when light passes through the film. This makes the white display clearer.

The dispersion medium 13 encapsulated in the microcapsules 15 is a non-volatile oil having a specific gravity of about 0.9 to 1.2, such as alkyl naphthalene, diallyl ethane, alkyl biphenyl, triallyl dimethane, or a low viscosity oil. Silicone oils, vegetable oils, animal oils, and the like can be used, and are used after being colored to an appropriate color by a coloring agent. In addition, as such a dispersion medium 13, a dispersion medium whose specific gravity is increased by fluorination (WO9533085) may be used. As for the coloring, it is preferable to mix three or four kinds of coloring agents of different colors to color black. In the present embodiment, a silicone oil (manufactured by Toray Dow Corning Silicone Co., Ltd.) colored blue with an azo-based dye (manufactured by Japan Photographic Dye Laboratories) is used.

The electrophoretic particles 14 are made of positively or negatively charged resin dielectric particles. In this embodiment, a toner made of silicone (trade name: Tospearl (manufactured by Toshiba Silicone Co., Ltd.)) is used.

The dispersion medium 13 and the electrophoretic particles 14 are contained in the microcapsules 15 in a state where the electrophoresis particles 14 are dispersed in the dispersion medium 13 as described above. The microcapsules 15 are laid in a single layer in the gap between the transparent electrode 16 of the transparent substrate 11 and the counter electrode 17 of the counter substrate 12 by close-packing, and are transparently bonded so as not to move in the gap. It is fixed between the substrates 11 and 12 by a layer 19.

Here, such a microcapsule 15
Is a material in which at least one of the fluorine compound monomers represented by the aforementioned general formulas (1) to (7) is
It is formed by including it as a component and has a particle size of 50μ.
It is classified into about m. Such a microcapsule 15 can be manufactured by a known method, but the barrier property of the capsule to the dispersion medium 13 must be sufficiently ensured.

Specifically, as the encapsulation method, the monomers represented by the general formulas (1) to (7) and a polymerizable monomer such as a methacrylic acid derivative or a methyl methacrylate derivative are mixed with an organic solvent, silicone oil, The polymer is dissolved in a water-insoluble dispersion medium such as oil in the presence of a polymerization initiator, and this is suspended and dispersed in a water-alcohol-based medium using a homogenizer or the like. The electrophoretic particles 14 are added and dispersed and emulsified.
Then, the dispersion medium 13, the electrophoretic particles 14,... Are taken into the raw materials such as the methacrylic acid derivative and the methyl methacrylate derivative. Then, under these conditions, the monomers represented by the general formulas (1) to (7) and the polymerizable monomer are heated and polymerized by a known in situ polymerization method, whereby the dispersion medium 13 is formed. , The microcapsules 15 containing the electrophoretic particles 14.
Is produced.

Specific examples of the polymerizable monomer include lauryl methacrylate, lauryl acrylate, stearyl methacrylate, stearyl acrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, dodecyl methacrylate, dodecyl acrylate, hexyl methacrylate, hexyl acrylate, octyl methacrylate, Octyl acrylate,
Vinyl laurate, vinyl stearate and the like. Specific examples of the polymerization initiator include benzoyl peroxide, t-butyl perbenzoate, diamyl peroxide, lauryl oxide, and azobisisobutyronitrile.

In this example, azoisobutyronitonyl was used as a polymerization initiator, and methacrylic acid,
Methyl methacrylate, n-propyl methacrylic acid, n-
Butyl methacrylic acid and 2,2 represented by the above general formula (5)
These are dissolved in a dispersion medium using 2,2-trifluoroethyl methacrylic acid, and dispersed and emulsified in a water-alcohol-based solution together with the dispersion medium 13 and the electrophoretic particles 14, by a known in situ polymerization method. Microcapsules 15 were prepared by polymerization, and sieved to classify to 50 μm.

The microcapsules 15 thus obtained have a low affinity for the dispersion medium 13 of the fluorine compound monomer represented by the general formulas (1) to (7). Capsule 1
5, the affinity between the wall material and the dispersion medium 13 is small.

In order to spread the microcapsules 15 thus obtained in a single layer on the counter substrate 12, a counter electrode (not shown in FIG. 2) on the inner surface of the counter substrate 12 as shown in FIG. ), An adhesive 20 before curing (or a semi-cured state) is applied in advance, and in this state, a doctor blade 21 and an adjusting plate 22 disposed on the front side of the doctor blade 21 are disposed thereon. The doctor blade 21 is disposed so that the gap between the bottom surface 21 a and the surface of the adhesive 20 is substantially equal to the particle size of the microcapsule 15, and the adjustment plate 22 is located between the bottom surface 21 a and the front surface of the doctor blade 21. The microcapsules 15 are arranged at regular intervals so that the microcapsules 15 can enter between them.
The microcapsules 15 are arranged so that the gap between them is smaller than the particle size of the microcapsules 15.

The microcapsules 15 are filled and supplied between the doctor blade 21 and the adjusting plate 22 arranged as described above, and the doctor blade 21 and the adjusting plate 22 are further moved in the direction of the arrow in FIG. Are spread over the counter substrate 12 in one layer. At this time, by applying the adhesive 20 in advance, the movement of the microcapsules 15 spread over this is regulated, so that the spread state is maintained.

When the microcapsules 15 are laid in one layer on the opposing substrate 12 in this manner, the transparent substrate 11 is placed with the microcapsules 15 interposed therebetween, and the transparent substrate 11 and the opposing substrate 12 are A transparent adhesive is filled in between and cured to form a transparent adhesive layer 19.
Here, the adhesive for forming the transparent adhesive layer 19 is not particularly limited as long as it is transparent, and various adhesives such as methacrylic acid-based adhesives can be used. It is preferable to use an ultraviolet irradiation-curable type since it has little adverse effect on the ink. An adhesive 20 for holding the microcapsules 15 in a spread state.
May function as a binder or the like, and examples thereof include vinyl chloride, vinyl acetate, and polyurethane.

In the electrophoretic display device 1 having such a configuration, for example, a voltage is applied between the transparent electrode 16 and the opposing electrode 17 so that the electrophoretic particles 14.
As shown on the left side of the middle, when the light is shifted to the transparent substrate 11 side, the incident light that enters from the outside and reaches the microcapsule 15 after passing through the scattering film 18, the transparent substrate 11, and the transparent electrode 16 is indicated by an arrow in FIG. Are reflected by the electrophoretic particles 14 and again, the scattering film 18, the transparent substrate 1
1. The reflected light transmitted through the transparent electrode 16 is emitted to the outside, and a white display is formed.

At this time, since the microcapsules 15 have a low affinity between the wall material and the dispersion medium 13, the microcapsules 15 remain attached to the inner surfaces of the microcapsules 15 as shown in FIG. The amount of the dispersion medium 13 is reduced, whereby absorption of incident light by the dispersion medium 13 between the inner surface of the microcapsule 15 and the electrophoretic particles 14 near the inner surface of the wall of the microcapsule 15 is suppressed. That is, in the case of a conventional microcapsule, the affinity with the dispersion medium 13 is not small unlike the present invention, but is usually large, and therefore, as shown in FIG.
The space between the inner surface of the electrophoretic particles 5 and the electrophoretic particles 14 is filled with the dispersion medium 13. Therefore, although the incident light is absorbed by the dispersion medium 13, in this example, the absorption of the incident light is suppressed as described above.

On the other hand, in order to display a dark color (color by the colorant in the dispersion medium 13), for example, the transparent electrode 16 and the counter electrode 1 are used.
When the electrophoretic particles 14 are biased toward the opposing substrate 12 as shown on the right side in FIG. 1 by applying a voltage between them, only the colored dispersion medium 13 exists on the transparent substrate 11 side. Become like Therefore, the incident light that enters from the outside, reaches the microcapsule 15 through the scattering film 18, the transparent substrate 11, and the transparent electrode 16,
It is absorbed by the coloring dye therein and forms a dark color display colored by the coloring dye.

As described above, according to the electrophoretic display device 10 of the present embodiment, the wall material of the microcapsules 15 is formed using 2,2,2-trifluoroethyl methacrylic acid which is a fluorine compound monomer. Since the affinity between the wall material of the microcapsules 15 and the dispersion medium is small, the electrophoretic particles 14 migrate to the light incident side of the microcapsules 15, and the incident light is reflected and scattered by the electrophoretic particles 14. At this time, the amount of the dispersion medium 13 remaining in a state of being attached to the inner surface of the wall of the microcapsule 15 can be reduced, whereby absorption of incident light by the dispersion medium 13 near the inner surface of the wall of the microcapsule 15 is suppressed, and the reflection efficiency Can be increased.

Further, since the affinity between the wall material of the microcapsules 15 and the dispersion medium 13 is reduced, the adsorption of the electrophoretic particles 14 on the inner surfaces of the walls of the microcapsules 15 can be suppressed. When the electrophoretic particles 14 are electrophoresed on the side opposite to the light incident side, the electrophoretic particles 14 remain adsorbed on the inner surface of the wall of the microcapsule 15 and white is slightly mixed with the original dark display. It is also possible to suppress inconvenience such as deterioration of image quality.

In the above example, a silicone toner (trade name: Tospearl (manufactured by Toshiba Silicone Co., Ltd.)) was used as the electrophoretic particles 14. However, the present invention is not limited to this. It may be formed of a composite material obtained by apparently compounding a material and a low-molecular resin material.

In order to prepare electrophoretic particles comprising such a composite material, for example, first, a vinyl chloride-vinyl acetate copolymer containing a secondary hydroxyl group, behenic acid and an isocyanate curing agent for curing are mixed with methyl ethyl ketone. , Cyclohexane and toluene. The isocyanate curing agent is added for crosslinking and curing so that the electrophoretic particles obtained by complexing here do not dissolve during the formation of microcapsules. Next, the solution is atomized by a spraying method, and the particles are dried by heating at 60 ° C. for 2 hours. Thereafter, curing is performed by heating at 80 ° C. for 4 hours under reduced pressure, and the obtained particles are further sieved to a particle diameter of 2 to 2.
Classify into 3 μm particles. Then, the particles after the classification are heated to 90 ° C. and further rapidly cooled.

Then, at the time of curing, the low-molecular-weight resin material enters a state in which the low-molecular-weight resin material enters, and the low-molecular-weight material that has entered further shrinks due to cooling to form voids inside the high-molecular-weight resin material. Since the layer becomes a layer, scattering occurs at the interface due to a difference in refractive index between the air layer and the resin material, and the obtained electrophoretic particles become cloudy. The turbidity of the electrophoretic particles increases the reflection efficiency of the electrophoretic particles, thereby increasing the efficiency of reflection and scattering of incident light as compared with conventional electrophoretic particles.

Therefore, when the electrophoretic particles made of such a composite material are used, the electrophoretic particles are clouded and the reflection efficiency is increased. The efficiency of reflection / scattering of the incident light is higher than that in the case of using the conventional electrophoretic particles, so that the contrast ratio is increased and the display performance is improved.

In the present invention, the electrophoretic particles 1
As shown in FIG. 4, a metal dielectric film 14b formed by coating a metal on the surface of the resin dielectric particles 14a as shown in FIG. 4 may be used. In such electrophoretic particles 14, it is desirable that the resin dielectric particles 14a have a small specific gravity and a uniform particle size. For example, the resin dielectric particles 14a are formed by a polymerization method used as a developer (toner) in an electrophotographic process. Spherical toner is preferably used. The toner produced by this polymerization method preferably has a particle size of several μm and a uniform particle size. In addition to such toners, resin spheres used as spacers in liquid crystal displays have very uniform particle diameters, and are suitable for use as resin dielectric particles 14a.

The metal film 14b is made of a metal having a high reflectance to visible light, such as aluminum (Al) or silver (Ag). If the film thickness is less than 20 nm, the particle surface cannot be sufficiently coated, and if it exceeds 100 nm, the specific gravity of the whole electrophoretic particles becomes large.
In particular, it is desirable to adjust the film thickness so that the specific gravity is equal to the specific gravity of the dispersion medium 13.

For the coating of the resin dielectric particles 14a with the metal film 14b, known methods such as an electroless plating method, a sputtering method, and a CVD method can be adopted. A so-called common agent having a metal film on the surface of micro-order fine particles is used in a liquid crystal display. Such a material can be used as the electrophoretic particles 14. As the electrophoretic particles 14 provided with such a metal film, specifically, those obtained by coating a silicone resin (Tospearl [trade name]; manufactured by Toshiba Silicone Co., Ltd.) with a particle diameter of 3 μm with silver by electroless plating are used. Used.

When such electrophoretic particles 14 are used,
Since the reflection by the electrophoretic particles 14 is substantially performed by the metal film 14b, the resin dielectric particles 14
The reflectance is much higher than that reflected at a, and the resulting display has a much higher contrast ratio, thereby improving its display performance.

In the above example, the transparent electrode 16 and the counter electrode 17 are provided on the inner surfaces of the transparent substrate 11 and the counter substrate 12, respectively. However, the present invention is not limited to this. If an electric field can be applied between the substrates 11 and 12 from the outside or the like, the transparent electrodes 16 and
It is not always necessary to provide the counter electrode 17. Further, in the above example, a glass plate is used as the transparent substrate 11 and the counter substrate 12, but the present invention is not limited to this, and a flexible plastic film can be used. As the adhesive to be used, an adhesive having a glass transition temperature of 0 ° C. or less after curing is used so as not to impair flexibility. When a flexible plastic film is used as the transparent substrate, the scattering film 18 having a transparent electrode formed on the inner surface thereof may be used as it is.

The transparent substrate 11 may be coated with an AR coat or an AG coat in order to prevent the reflection or the like from occurring due to surface reflection of incident light. By doing
Higher image quality can be obtained by suppressing reflection. In addition, the opposite substrate 12 and the opposite electrode 17 may be formed of a non-transparent material because incident light from the transparent substrate 11 does not pass through them.

[0039]

As described above, in the electrophoretic display device of the present invention, the wall material of the microcapsule is made of at least one of the fluorine compound monomers represented by the general formulas (1) to (7). Is contained as a component thereof, so that the affinity between the wall material of the microcapsule and the dispersion medium is reduced even in the microcapsule due to the low affinity of the fluorine compound monomer for the dispersion medium. Can be. Therefore, when the electrophoretic particles are migrated to the light incident side of the microcapsule and the incident light is reflected and scattered by the electrophoretic particles, the amount of the coloring dispersion medium remaining in a state of being attached to the inner surface of the microcapsule wall is reduced. Thereby, absorption of incident light by the dispersion medium near the inner surface of the microcapsule wall can be suppressed, the reflection efficiency can be increased, and the display performance can be improved.

Also, since the adsorption of the electrophoretic particles to the inner surface of the microcapsule wall can be suppressed, for example, when the electrophoretic particles are electrophoresed on the side opposite to the light incident side in order to form a dark display, It is also possible to suppress the inconvenience that the image is still adsorbed on the inner surface of the microcapsule wall and white is slightly mixed with the original dark color display, thereby deteriorating the image quality.

The electrophoretic display device of the present invention has a very simple structure and is lightweight, thin, and has low power consumption, so that it can be used as a display of a portable terminal or the like.
Further, the present invention is also applicable to electronic books and electronic notebooks. If a communication function or the like is provided, it can be used as a portable information terminal. In addition, if a flexible plastic plate is used as the transparent substrate or the counter substrate, the electrophoretic display device can be manufactured into a flexible display sheet close to current paper, and in this case, a rewritable paper can be used. Can be used as print media. Furthermore, since it can be manufactured in a thin sheet shape, a plurality of sheets can be collectively used like a book without using each sheet.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining a method of spreading microcapsules.

3A and 3B are diagrams for explaining a state of a dispersion medium near the inner surface of a wall of a microcapsule, where FIG. 3A is a sectional side view of a main part for explaining an example of the present invention, and FIG. It is a principal part sectional view for demonstrating.

FIG. 4 is an enlarged cross-sectional view illustrating a configuration of an electrophoretic particle.

FIG. 5 is a side sectional view showing a schematic configuration of an example of a conventional electrophoretic display device.

[Explanation of symbols]

Reference Signs List 10: electrophoretic display device, 11: transparent substrate, 12: counter substrate, 13: dispersion medium, 14: electrophoretic particles, 15: microcapsule

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C094 AA02 AA03 AA06 AA11 AA15 AA22 AA43 AA45 AA54 AA55 BA75 BA76 CA14 DA06 DA15 EA00 EA05 EA06 EB04 ED02 ED13 FA01 FA02 FB01 FB16 GB01 HA08 JA08

Claims (6)

[Claims] A microcapsule enclosing a dispersion medium colored by a dye and electrophoretic particles dispersed therein is enclosed in a gap between a transparent substrate and an opposing substrate disposed opposite to the transparent substrate. In the electrophoretic display device which performs a display operation by an electrophoretic action of the electrophoretic particles depending on whether or not a voltage is applied between the transparent substrate and the counter substrate, the wall material of the microcapsule has the following general formula ( 1) ~
It is formed by including at least one of the fluorine compound monomers represented by (7) as a component thereof. An electrophoretic display device comprising: 2. The electrophoretic display device according to claim 1, wherein the electrophoretic particles are a composite material composed of a vinyl chloride-vinyl acetate copolymer and a higher fatty acid. 3. The electrophoretic display device according to claim 1, wherein the electrophoretic particles are formed by coating a surface of a resin dielectric particle with a metal. 4. The microcapsule having a particle size of 1 to 1
2. The electrophoretic display device according to claim 1, wherein the thickness is 00 μm. 5. The electrophoretic display device according to claim 1, wherein the particle diameter of the electrophoretic particles is 10 μm or less. 6. The electrophoretic display device according to claim 1, wherein a scattering film is provided on the light incident side of the transparent substrate, or the transparent substrate is made of a scattering film.