JP4168556B2 - Electrophoretic display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophoretic display device that displays characters, symbols, graphics, and the like by utilizing the movement of electrophoretic particles in a medium by applying a voltage.
[0002]
[Prior art]
The electrophoretic display device exhibits an electrophoretic phenomenon in which colored particles such as organic pigments and / or inorganic pigments introduced between electrodes arranged opposite to each other move a polymer or colloidal particles due to a potential difference in a solution. This is a display device that displays information by applying a voltage between opposing electrodes to change the distribution state of the electrophoretic particles in the dispersing agent to change the optical reflection characteristics.
[0003]
  Various methods for improving the performance of electrophoretic display devices have been proposed so far.
  As an electrophoretic display device, two flat transparent electrodes are initially arranged to face each other, and are partitioned by a porous spacer between them, and the spacers are separated by electrophoretic particles and dispersion media between the opposed electrodes. , Dyes andDispersantThere has been proposed a spacer type electrophoretic display device in which a dispersion solution composed of the above is introduced and a voltage is applied between the electrodes.
[0004]
  On the other hand, the applicant of the present application has proposed a microcapsule type electrophoretic display device described in, for example, Japanese Patent No. 2551783 in order to improve display performance. The microcapsule-type electrophoretic display device includes an electrophoretic particle, a dispersion medium, a dye, and the like in the spacer-type electrophoretic display device.DispersantDispersion solution consisting of (these(Also referred to as a dispersion system) is housed (encapsulated) in a microcapsule, and the spacer is excluded. When such a microcapsule is used, the composition of the microencapsulated dispersion system is maintained uniformly, and a uniform and stable display operation can be realized (display unevenness is eliminated), and the display color is made different for each microcapsule. Therefore, it is possible to display various colors in one electrophoretic display device, and since it is housed in a microcapsule, it is necessary to provide a spacer that makes it easy to enclose the dispersion solution, which was a difficult task. Since there is no effect, the structure is simplified and the effective area of display is increased.
[0005]
Although the above-described electrophoretic display device using the microcapsules sufficiently achieves the display purpose, depending on the use of the electrophoretic display device, display retention (memory) characteristics for a long period, that is, displayed characters, symbols and figures Such information is required to be held for a long time without applying a voltage.
[0006]
In order to achieve such a requirement, a method (means) such as solidifying a dispersion solution itself composed of electrophoretic particles, a dispersion medium, a dye and a dispersant in a display holding state is required. A technique using such means is disclosed in, for example, Japanese Patent Publication No. 50-15115.
An overview of the method disclosed in this publication is given below. As the dispersion medium, a material that is solid at room temperature but softens to liquid when heated, or softens to liquid when a solvent is applied is used. Examples of such materials include resin, rubber, beeswax, plant wax, waxes such as mineral wax (paraffin), synthetic waxes, and the like. When these materials are heated during electrophoresis or softened by applying a solvent, they are particularly suitable for holding (storing) display contents.
[0007]
[Problems to be solved by the invention]
However, in the method described in the above publication, since the dispersion medium changes in two states of liquid and solid, the solubility of the dye in the dispersion medium and the dispersion characteristics of the electrophoretic particles are affected by these two states. I found a bug that changed.
[0008]
The former problem, that is, the problem of solubility of the dye in the dispersion medium will be described. When the dispersion medium is heated and in a liquid state, the dye is dissolved in the dispersion medium. However, when the dispersion medium is in a solid state under a normal temperature environment, the dye loses solubility and precipitates from the dispersion medium. As a result, there arises a problem that the dye color of the dispersion solution is decolorized. This problem indicates that the stability of display color is low when an electrophoretic display device using such a dispersion medium is repeatedly used.
[0009]
Consider the latter problem, that is, the problem that the dispersion characteristics of the electrophoretic particles change. The change in the dispersion characteristics means that the conditions for causing electrophoresis of the electrophoretic particles change. As a result, when an electrophoretic display device using such a dispersion medium is used about several times, the display characteristics change, and the display content is lowered, in other words, the life of the electrophoretic display device is substantially increased. Means that. That is, the change in the dispersion characteristic indicates that the electrophoretic display device cannot be used for a long time, and the life of the electrophoretic display device is substantially short.
[0010]
For the above reasons, no electrophoretic display device using electrophoretic particles has been developed that has stable display retention (memory) characteristics for a long period of time and can be used repeatedly. .
[0011]
An object of the present invention is to provide an electrophoretic display device that exhibits high display retention characteristics while exhibiting high display quality in a normal display state. In particular, it is an object of the present invention to provide a long-life electrophoretic display device that stably exhibits display holding (memory) characteristics for a long period of time in a display holding state and can be used repeatedly.
[0012]
[Means for Solving the Problems]
The inventor of the present application considers the above-described problems in the case of using a dispersion solution composed of electrophoretic particles, a dispersion medium, a dye, and a dispersant, as a dispersion medium that is solid at room temperature and becomes liquid when heated. As a result of investigating electrophoretic particles that exhibit long-term display retention characteristics and can be used repeatedly, the dispersion medium coexists in two phases, liquid and solid, at room temperature (room temperature), and is heated during electrophoresis (display) Then, when a mixed solvent that forms one uniform liquid phase is used, the display quality in the normal display state is not impaired, and in the display holding state, (1) since it has no fluidity as a liquid, it exhibits high display holding characteristics, (2) In addition, the dissolution state of the dye in the dispersion medium and the dispersion state of the electrophoretic particles are hardly changed, and the display characteristics are not changed. However.
Therefore, such a dispersion medium is used in the electrophoretic display device of the present invention.
Note that it was confirmed that such a dispersion medium can be applied to the microcapsule type electrophoretic display device described in Japanese Patent No. 2551783, and can also be applied to the spacer type electrophoretic display device.
[0013]
  Therefore, the electrophoretic display device of the present invention is disposed in a gap between a pair of counter electrodes, at least one of which is a transparent electrode, arranged opposite to each other with a predetermined gap therebetween, Electrophoretic particles, dispersion media, dyes andDispersantAnd a voltage applying means for applying a voltage between the counter electrodes, and depending on a voltage direction when applying a voltage between the counter electrodes.AboveBy electrophoresis of electrophoretic particles to one of the counter electrodesAboveElectrophoretic particle color orAboveDissolved in dispersion mediumAboveIt is an electrophoretic display device that displays any one of the colors of the dye, and the dispersion medium has two phases of liquid and solid coexisting at room temperature.Phase part ofHas the property of dissolving and forming a uniform liquid phase,Dissolve the dye at room temperatureIt is a mixed solvent.
[0014]
  The mixed solvent is liquid at room temperature, and includes a first organic solvent that exhibits electrophoretic properties of the electrophoretic particles, and room temperature.Is solidIt is a mixture of a second organic solvent that is a body and has a melting point near the temperature to be heated at the time of electrophoresis, and that dissolves in the first organic solvent and becomes a uniform liquid state.
  The first organic solvent is a saturated hydrocarbon, an unsaturated hydrocarbon, or an oil, and the second organic solvent is a wax, a wax based on the wax, a higher alcohol, or an aromatic. It is a group hydrocarbon.
[0015]
  In the electrophoretic display device, the electrophoretic particles, the dispersion medium, the dye andDispersantA dispersion solution containing is encapsulated between the counter electrodes.
  Alternatively, in the electrophoretic display device, the electrophoretic particles, the dispersion medium, the dye, andDispersantIs dispersed in a space partitioned by a space provided between the counter electrodes.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
First embodiment
As a first embodiment of the electrophoretic display device of the present invention, a microcapsule electrophoretic display device 1 will be described with reference to FIG.
[0017]
The microcapsule type electrophoretic display device 1 illustrated in FIG. 1 includes a first transparent electrode 14 and a second transparent electrode 15 which are disposed facing each other with a predetermined distance d, and these transparent electrodes 14 and 15. The microcapsule 16 is inserted into the gap between the back substrate 12, the transparent substrate 13, and the transparent electrodes 14, 15 located on the back surface of the substrate, and the binder 18 is interposed around the microcapsule 16.
[0018]
  The binder 18 is transparent and fixes the arrangement of the microcapsules 16.
  The microcapsule 16 includes a dispersion medium 19, electrophoretic particles 17, a dye (not shown),DispersantAnd a dispersion solution containing.
[0019]
In the microcapsule electrophoretic display device 1, voltage application means (not shown) is provided so as to apply a predetermined voltage between the transparent electrode 14 and the transparent electrode 15.
In the microcapsule type electrophoretic display device 1, one of the transparent electrode 14 and the transparent electrode 15 only needs to be a transparent electrode, and both need not be transparent electrodes as in the above embodiment.
[0020]
The operation of the microcapsule type electrophoretic display device 1 will be briefly described.
When a voltage is applied from the voltage application means according to the display content of the transparent electrode 14 and the transparent electrode 15, the electrophoretic particle 17 moves inside the electrophoretic particle 17 according to the direction (direction) of voltage application. Move towards. This phenomenon is called electrophoresis phenomenon. As a result, either the color of the electrophoretic particles 17 or the color of the dye dissolved in the dispersion medium 19 is displayed.
[0021]
Thus, the dispersion solution encapsulated in the microcapsule 16 is composed of the electrophoretic particles 17, the dye, the dispersion medium 19, and the mixed solvent.
Details of these will be described below.
[0022]
Electrophoretic particles
As the electrophoretic particles 17, organic and inorganic colored pigment particles are usually used.
As such white particles of electrophoretic particles, for example, titanium dioxide, zinc sulfide, and barium titanate can be used.
As the black particles of such electrophoretic particles, for example, carbon black and black iron oxide can be used.
As the red particles of the electrophoretic particles, for example, pigments known by names such as lake red and resol red can be used.
As the yellow particles of such electrophoretic particles, for example, organic pigments known by names such as benzine yellow and Hansa yellow can be used.
As the blue particles of the electrophoretic particles, for example, inorganic pigments known by names such as phthalocyanine blue and cobalt blue can be used.
In the present embodiment, each microcapsule 16 can be displayed with a different color, so that the electrophoretic particles of the above-described color particles are selected as appropriate, and between the transparent electrode 14 and the transparent electrode 15. When the electrophoretic display device is disposed, the electrophoretic display device can be configured as an electrophoretic display device capable of color display.
[0023]
The electrophoretic particles described above have a particle size of about 0.1 to 5 μm. Desirably, the particle diameter of the electrophoretic particles is preferably 0.2 to 2 μm. The reason why the particles having such a particle size are 0.1 μm or more is that the effect of visibility becomes remarkable, and the electrophoretic property can be secured at 5 μm or less.
[0024]
dye
The dye has a role of determining a solvent color that is dissolved in the mixed solvent and is paired with the color of the electrophoretic particles.
As such a dye, all dyes that can be dissolved in a mixed solvent, which will be described later in detail, can be used. In particular, an azo dye having chemical affinity for an organic solvent is preferable as such a dye.
[0025]
  Dispersant
  DispersantThe role of is to provide the dispersion stability of the electrophoretic particles 17 with time, and to increase the zeta potential that the electrophoretic particles 17 spontaneously emit in a mixed solvent described later. The details of the zeta potential are described in the above-mentioned Japanese Patent Publication No. 50-15115. By increasing the zeta potential using a dispersant, it is possible to increase the migration speed of the electrophoretic particles when a voltage is applied. As a result, the display speed can be increased.
  Such dispersionAgent andAs long as the two roles described above are exhibited, various types can be used. For example, a surfactant can be used as such a dispersant. Among such surfactants, those having polar groups such as sodium dodecyl sulfate, aerosil OT, and oleic acid are particularly preferable. However, the dispersant is not limited to the above-described surfactant, and a coupling agent or a polymer that exhibits the above-described two roles can be used. Examples of such coupling agents include titanate coupling agents, silica coupling agents, and aluminum coupling agents. Such a polymer
Examples thereof include polyvinyl pyrrolidone and polyethylene glycol.
[0026]
Mixed solvent
The mixed solvent is an organic solvent that is liquid at room temperature (room temperature) (hereinafter referred to as a first organic solvent or a liquid organic solvent) and an organic solvent that is almost solid at room temperature and dissolves at a temperature heated during electrophoresis. (Hereinafter referred to as a second organic solvent or a solid organic solvent) is used.
[0027]
The first organic solvent is a solvent that is liquid at room temperature and exhibits the electrophoretic characteristics of the electrophoretic particles.
Examples of such solvents include saturated hydrocarbons such as hexane, cyclohexane, octane, and dodecane, unsaturated hydrocarbons such as toluene, xylene, and dodecylbenzene, and vegetable oils, animal oils, mineral oils, or synthetic oils. Oils such as oil can be used.
[0028]
As said 2nd organic solvent, it has melting | fusing point near the temperature heated at the time of electrophoresis, and has a big dependence of solubility with respect to said 1st organic solvent, ie, it is a solid without melt | dissolving at normal temperature. However, it is desirable that the liquid be completely dissolved in the first organic solvent and be in a uniform liquid state in the vicinity of the temperature to be heated during electrophoresis.
As such a solvent, for example, waxes such as plant waxes and mineral waxes, and paraffin waxes and synthetic waxes based on these waxes can be used. Furthermore, as such a solvent, for example, higher alcohols such as dodecyl alcohol, tetradecyl alcohol, hexadecyl alcohol, and octadecyl alcohol, or aromatic hydrocarbons such as benzophenone and naphthalene can be used.
[0029]
In this specification, the terms normal temperature and room temperature mean the room temperature in the natural environment, or the temperature at which normal air conditioning is performed, and the temperature at which electrophoretic phenomenon occurs, for example, a temperature lower than 55 ° C. Means state. In other words, it means a temperature at which no electrophoresis phenomenon occurs. For example, room temperature is 0 to 30 ° C. Since the content displayed on the electrophoretic display device is held at this normal temperature, it can be said to be a display holding temperature.
[0030]
Method for producing mixed solvent
First, the mixing ratio of the first organic solvent and the second organic solvent in the mixed solvent will be described.
As described above, the first organic solvent is a liquid at room temperature, and can ensure the electrophoretic properties of the electrophoretic particles and the solubility of the dye. On the other hand, the second organic solvent is a solid that hardly dissolves in the first organic solvent at room temperature, has a melting point near the heating temperature at the time of electrophoresis, dissolves at the heating temperature at the time of electrophoresis, and is dissolved in the first organic solvent. It has the property of dissolving in an organic solvent to form a uniform liquid. That is, since the second organic solvent itself is solid at room temperature, the dye solubility at room temperature is low. Therefore, in order to maintain the solubility of the dye in the mixed solvent, the weight of the second organic solvent needs to be about 25% or less with respect to the weight of the first organic solvent. Further, when the mixed solvent is solidified, the weight of the second organic solvent needs to be about 3% or more with respect to the weight of the first organic solvent so as not to have fluidity as a liquid. Therefore, when the mixed solvent is prepared by mixing the weight of the second organic solvent at about 3 to 25% with respect to the weight of the first organic solvent, the above-described characteristics are exhibited. The optimum value of this ratio is determined by the combination conditions of the specific material of the first organic solvent and the specific material of the second organic solvent.
[0031]
That is, the mixed solvent prepared by such a method becomes a uniform liquid at a temperature equal to or higher than the heating temperature at the time of electrophoresis, and exhibits desired electrophoretic characteristics for the electrophoretic particles. Therefore, high display quality is exhibited in the normal display state. After that, when the application of voltage is stopped and cooled to room temperature, for example, the second organic solvent is solidified, and the mixed solvent loses its fluidity as a liquid, so the state as it is is maintained. The display content of the electrophoretic display device is maintained as it is. In other words, the electrophoretic display device exhibits high display holding characteristics at room temperature.
For example, in a state where the voltage application to the transparent electrode 14 and the transparent electrode 15 is released and the mixture is cooled to room temperature, the mixed solvent is partially in a liquid state, so that the electrophoretic particles and the dye are in a liquid state. In the organic solvent (eg, in the first organic solvent). As a result, the solubility of the dye in the dispersion medium and the dispersibility of the electrophoretic particles are hardly changed. Therefore, when such a mixed solvent is used in an electrophoretic display device, the electrophoretic display device maintains a display performance in a normal state and maintains a high display holding characteristic for a long period of time even at a normal temperature. Even if such an electrophoretic display device is used repeatedly many times, the change in display holding characteristics and display characteristics is small and the lifetime is long.
[0032]
Dispersing solvent
The above-described electrophoretic particles, dye, dispersant, and mixed solution are mixed to prepare a dispersion solvent.
These ratios are set as follows, for example.
[0033]
[Table 1]
Table 1
Electrophoretic particle weight fraction 5-20%
Dye weight fraction 0.5-3%
Weight fraction of dispersant 0.2-2%
Mixed solvent weight fraction 75 to 93%
[0034]
These weight fractions will be described. As for the weight fraction of electrophoretic particles, the contrast between the particle color and the dye color is maximized. As for the weight fraction of the dye, the solubility in the mixed solvent is maintained. , A weight fraction range for maximizing zeta potential. However, these optimum values are determined by the specific combination conditions of each component.
In addition, according to experiment, as a preferable ratio, it was the numerical value of the following table | surface, for example.
[0035]
[Table 2]
Table 2
Electrophoretic particle weight fraction 10-17%
Dye weight fraction 1-2%
Dispersant weight fraction 0.5-1%
Mixed solvent weight fraction 80-90%
[0036]
As a method for preparing the dispersion solvent, the electrophoretic particles, the dye, the dispersant, and the mixed solution are mixed at the above-described weight fraction at a temperature equal to or higher than the melting point of the mixed solvent using a mixing device such as a ball mill or a homogenizer for a predetermined time. Mix to prepare the dispersion solvent.
The temperature above the melting point of the mixed solvent is preferably 150 to 250 ° C. The mixing time is, for example, 1 to 2 hours.
[0037]
Encapsulation in microcapsules
The dispersion solution thus formed is encapsulated (contained) in the microcapsule 16 and incorporated into the electrophoretic display device 1 illustrated in FIG.
Such microcapsules can be produced by methods such as interfacial polymerization, interfacial precipitation, phase separation, and interfacial precipitation.
The size of the microcapsules is, for example, an average particle diameter of 20 to 80 μm. The particle size of the microcapsules is preferably uniform in order to prevent display unevenness. When the particle size is 20 μm or less, the surface protection effect and display stability are lacking. When the particle size is 80 μm or more, the transparency is lowered and the display stability is lowered. According to experiments, it is desirable to have a uniform particle size of 40 to 60 μm.
[0038]
Urethane resin coating
Although it is not essential, when the microcapsule 16 coated with urethane resin as a film material is generated as the microcapsule 16, charging by an external electric field due to static electricity at room temperature can be prevented, and display disturbance can be prevented. Holding characteristics are improved.
[0039]
Integration into electrophoretic display devices
An electrophoretic display device is configured in which the microcapsules 16 containing the dispersion solvent and the dispersion solution produced as described above are inserted at least between a pair of opposed electrodes of the transparent electrode 14 and the transparent electrode 15.
[0040]
When the electrophoretic display device described above is operated, the display content can be fixed by returning to normal temperature while maintaining normal display characteristics. In this display holding state, it is not necessary to apply a voltage to the electrodes, so that the electrophoretic display device can be operated with power saving.
[0041]
【Example】
Examples of the present invention will be described.
As electrophoretic particles, 15 g of titanium dioxide, 1 g of an azo blue dye as a dye, and 0.5 g of oleic acid as a dispersant were used. As a mixed solvent, 85 g of dodedecibenzene and 5 g of paraffin wax (melting point: 50 ° C.) were prepared.
That is, in this example, the weight fraction of titanium dioxide as the electrophoretic particles is 15 / 106.5 = 14%, the weight fraction of the azo blue dye as the dye is 1 / 106.5 = 0.9%, As a dispersant, the weight fraction of oleic acid is 0.5 / 106.5 = 0.47%, and the weight fraction of the mixed solvent is (85 + 5) /106.5=84.5%.
These were mixed with a harmonicizer while heating at 200 ° C. for 1 hour to form a dispersion solution.
[0042]
Microcapsules enclosing the dispersion were produced by an interface deposition method with urethane resin as the film material and having an average particle size of 50 μm.
[0043]
Two transparent sheets on which conductive transparent electrode films (ITO) to be the transparent electrodes 14 and 15 are formed are prepared, the two transparent electrode surfaces are opposed to each other, and the transparent electrode film surfaces are interposed between the transparent electrode surfaces. The prepared microcapsules were rolled with a roller so as not to break the microcapsules, and were arranged in a plane so as to have a thickness of about 50 μm, thereby producing a microcapsule type electrophoretic display device 1 illustrated in FIG. .
[0044]
An operation test was performed on the microcapsule-type electrophoretic display device 1 produced as described above. By applying the voltage between the transparent electrode 14 and the transparent electrode 15 from a voltage application means (not shown), it was possible to display information such as desired characters, numbers, symbols, and figures at a temperature of 55 ° C. or higher. Thereafter, the application of voltage to the transparent electrode 14 and the transparent electrode 15 is stopped, and the electrophoretic display device 1 is left to stand for one year while being cooled to room temperature (room temperature, for example, 25 ° C.). The display state of the information displayed on is maintained at the original display quality. That is, in the electrophoretic display device of this example, no fading of the particle color (dye color) was observed. Furthermore, the display operation of the electrophoretic display device 1 at 55 ° C. or higher and the cooling to room temperature were repeated 1000 times or more. However, the display quality during electrophoresis was maintained, and the room temperature cooling period for holding the display. Also, the display content was not changed, and the display quality such as particle color (dye color) was not deteriorated.
That is, in the electrophoretic display device of the above-described embodiment, the display quality at the time of electrophoresis is maintained, and the display holding characteristics are not deteriorated and the display characteristics are not deteriorated due to repetitive operation in the state where electrophoresis is not performed. It was.
[0045]
Second embodiment
FIG. 2 shows a microcapsule type electrophoretic display device 1A as a second embodiment of the electrophoretic display device of the present invention.
2 replaces the microcapsule-type electrophoretic display device 1 illustrated in FIG. 1 by narrowing the distance between the transparent electrode 14 and the transparent electrode 15 to flatten the microcapsule 16 to obtain a flat microcapsule 16a. When the electrophoretic particles 17 move to the transparent electrode 14 or the transparent electrode 15, the density of the electrophoretic particles 17 is substantially uniform.
When such a flat microcapsule 16a is used, the display quality is improved, display unevenness is eliminated, and the distance between the transparent electrode 14 and the transparent electrode 15 is narrowed, so that the transparent electrode 14 and the transparent electrode 14 are transparent from the voltage applying means (not shown). The voltage applied to the electrode 15 can be lowered.
The conditions for the mixed solvent in the microcapsule 16a are the same as those in the first embodiment. Therefore, also in the second embodiment, the same effect as the first embodiment using the mixed solvent, that is, the display holding characteristic can be realized.
[0046]
Third embodiment
FIG. 3 shows a spacer type electrophoretic display device as a third embodiment of the electrophoretic display device of the present invention.
The spacer-type electrophoretic display device 2 illustrated in FIG. 3 has a first transparent electrode 14 and a second transparent electrode, which are disposed to face each other with a predetermined distance d, as illustrated in FIGS. The electrode 15 includes a back substrate 12 and a transparent substrate 13 positioned on the back surface of the transparent electrodes 14 and 15.
[0047]
Spacers 21 are arranged at a predetermined interval between the transparent electrode 14 and the transparent electrode 15 to define a space in which the plurality of microcapsules 16 are accommodated. That is, a polyester spacer 21 having a thickness of 50 μm, for example, is inserted at predetermined intervals along the longitudinal direction of the electrophoretic display device between the transparent electrodes 14 and 15 facing each other to dissolve the dispersion solution. Introduced.
[0048]
In the microcapsule type electrophoretic display device 1, 1 A illustrated in FIGS. 1 and 2, the electrophoretic particles 17 accommodated in the microcapsule 16 correspond to the voltages applied to the transparent electrode 14 and the transparent electrode 15. However, in the spacer type electrophoretic display device 2 of FIG. 3, the microcapsule 16 has moved to one of the electrodes, in the space partitioned between the spacer 21, the transparent electrode 14, and the transparent electrode 15. The electrophoretic particles 17 move to the transparent electrode 14 side or the transparent electrode 15 side. The spacer type electrophoretic display device 2 is substantially different from the microcapsule type electrophoretic display device 1 except for the difference in the structure in which the microcapsule 16 is not used using the spacer 21 and the behavior of the electrophoretic particles 17. Works on the same principle.
[0049]
The dispersion solution introduced into the space between the spacer 21 and the transparent electrode 14 and the transparent electrode 15, that is, the dispersion solution composed of the electrophoretic particles 17, the dye, the dispersion medium 19, and the mixed solvent is a microcapsule. This is the same as the dispersion solution contained in 16.
[0050]
The inventor of the present application also conducted an experiment on the spacer type electrophoretic display device 2 illustrated in FIG. As a result, as with the microcapsule type electrophoretic display device, it was confirmed that the display retention characteristics were high over a long period of time, and the characteristics did not change even after repeated use.
[0051]
Although one embodiment of the electrophoretic display device of the present invention has been described above, the present invention is not limited to the above-described embodiment, and the above-described embodiment has the same effects as the above-described embodiment.
[0052]
In the electrophoretic display device of the present invention, the embodiment of the present invention described above is merely an example, and the dispersion medium coexists in two phases of liquid and solid at room temperature. By using the mixed solvent, (1) since it does not have fluidity as a liquid, it exhibits high display retention (memory) characteristics during the display retention period, and (2) the state of dissolution of the dye in the dispersion medium and the electrophoretic particles The concept of mixing such a dispersion solution, electrophoretic particles, dispersion medium, and dye at a predetermined ratio, for example, a predetermined weight fraction, is used. Various other embodiments based on mixed solvents can be taken.
[0053]
【The invention's effect】
The electrophoretic display device of the present invention exhibits high display quality during normal display operation, and further stably exhibits high display retention characteristics for a long period of time in the display retention state, and can be used repeatedly many times. Long life.
[Brief description of the drawings]
FIG. 1 is a diagram showing a microcapsule type electrophoretic display device as a first embodiment of an electrophoretic display device of the present invention.
FIG. 2 is a diagram showing a microcapsule type electrophoretic display device as a second embodiment of the electrophoretic display device of the present invention.
FIG. 3 shows a spacer type electrophoretic display device as a third embodiment of the electrophoretic display device of the present invention.
[Explanation of symbols]
1. Microcapsule type electrophoretic display device
12. Back substrate
13. Transparent substrate
14. Transparent electrode
15. Transparent electrode
16. Microcapsule
17. Electrophoretic particles
18. Binder
19. Dispersion medium
2. Spacer type electrophoretic display device
21. ・ Spacer

Claims (7)

A pair of counter electrodes, at least one of which is a transparent electrode, facing each other with a predetermined gap therebetween;
A dispersion solution containing electrophoretic particles, a dispersion medium, a dye and a dispersant, which is accommodated in a gap between the counter electrodes;
And a voltage applying means for applying a voltage between the counter electrode by means of electrophoresis to either one of between the counter electrodes the electrophoretic particles by the voltage direction when a voltage is applied between the counter electrode in the electrophoretic display device for displaying one color of the color of the dye dissolved in color or the dispersion medium of the electrophoretic particles,
Mixing the dispersion medium to the normal temperature coexist two phases of a liquid and a solid, during electrophoresis, has the property that portions of the solid phase becomes the phase homogeneous liquid dissolved, dissolving the dye at room temperature An electrophoretic display device characterized by being a solvent. The mixed solvent is
A first organic solvent having an electrophoretic property of the liquid der Ri the electrophoretic particles at room temperature,
It has a melting point in the vicinity of the heating temperature at the time of a solid body electrophoresis at normal temperature, and is obtained by mixing the second organic solvent comprising a uniform liquid state dissolved in the first organic solvent,
The electrophoretic display device according to claim 1. The first organic solvent is a saturated hydrocarbon, an unsaturated hydrocarbon, or an oil, and the second organic solvent is a wax, a wax based on the wax, a higher alcohol, or an aromatic The electrophoretic display device according to claim 2, which is a group hydrocarbon. The electrophoretic particles, the dispersion medium, the dispersion solution containing the dye and the dispersing agent is fitted between the counter electrode is microencapsulated,
The electrophoretic display device according to claim 1. The electrophoretic particles, the dispersion medium, wherein the dispersive solution dye and the dispersing agent are inserted into the partitioned spaces in the space disposed between the opposed electrodes,
The electrophoretic display device according to claim 1. A transparent resin coating was applied to the surface of the microencapsulated one,
The electrophoretic display device according to claim 4. The microencapsulated material is flattened to approximately the same thickness between the counter electrodes,
The electrophoretic display device according to claim 4 or 6.

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