JP2733687B2 - Electrophoretic display device and dispersion system for display - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a display device using electrophoretic particles and a display dispersion system thereof. More specifically, while effectively using both a titanate coupling agent and a sorbitan fatty acid ester surfactant as a surface treatment agent for the electrophoretic particles, the aggregation of the electrophoretic particles is prevented,
The present invention relates to a dispersion system for electrophoretic display having excellent display properties without causing adhesion or sedimentation of electrophoretic particles to an electrode while favorably affecting the movement of the particles due to an electric field, and to an electrophoretic display device using the dispersion system.

2. Description of the Related Art As shown in FIG. 3, this type of electrophoretic display device using electrophoretic particles has a required display electrode pattern using an appropriate transparent conductive member such as indium tin oxide on the opposing surfaces. Two transparent glass plates 1 and 3 formed separately from each other
And a dispersing system 7 in which electrophoretic particles 6 are dispersed in a liquid dispersing medium, and a sealing member 5 also serving as a spacer is provided on an outer peripheral portion so as to enclose a gap between the electrophoretic particles 6. During the display operation, a display driving voltage is applied to the electrode patterns 2 and 4 to cause the electrophoretic particles 6 to move to the electrode patterns 2 and 4.
A method in which an electric field is applied to the dispersion system 7 to change the distribution state of the electrophoretic particles 6 so that the dispersion system 7 can be adsorbed and separated from the dispersion system 4, thereby changing the optical characteristics of the dispersion system 7 to perform a desired display operation. It is.

In the case where the dispersion system 7 is formed in a continuous phase by the sealing member 5 provided at the end as described above, the dispersion system 7 is caused by non-uniform electric field strength due to uneven spacing between the two electrode patterns 2 and 4. As a result, the electrophoretic particles 6 move in a direction parallel to the electrode pattern surface, causing a bias in the concentration distribution of the electrophoretic particles. As a result, when the electrophoretic display device is used repeatedly for a long time, the concentration of the electrophoretic particles locally increases. There is a problem that the display becomes uneven or display unevenness occurs.

Therefore, in order to solve such inconvenience, as shown in FIG. 4, the dispersion system 7 is reduced by enclosing the dispersion system in each of the perforations using a porous spacer 8 having a large number of perforations. JP-A-49-32038 also discloses a structure in which a section is divided and enclosed in a discontinuous phase.
JP-A-59-34518 or JP-A-59-171930 or JP-A-63-131241, JP-A-63-131242, JP-A-1-043609,
It is known in the above publications.

[Problems to be Solved by the Invention] However, in the case of the above-described known example of the dispersion-type divisional electrophoretic display device in which the dispersion system is divided into small sections by using a porous spacer, When each of the substrate films is used as a plate, a gap is easily generated between the porous spacer and the electrode plate due to deformation of the film or the like, so that there is a possibility that uneven distribution of the electrophoretic particles may occur. When both electrode plates are made of a glass plate substrate, a portion where a gap is left between the porous spacer 8 and the electrode plate due to the relationship between the flatness of the glass plate and the distribution of the thickness of the porous spacer 8. Therefore, it is not easy to prevent uneven distribution of the electrophoretic particles even with such a structure.

Further, in the case of a cell structure in which both electrode plates and the interposed porous spacer are bonded in advance, it is very difficult to uniformly inject the dispersion into each hole of the porous spacer. In addition to various manufacturing difficulties associated with the processing, there is a possibility that an incomplete portion of the injection of the dispersion system may be caused to cause a display defect, and a problem to be solved in obtaining a highly reliable display device. Are many.

Therefore, by configuring one of the opposing electrode plates as a rigid body and the other as a flexible member, the structural strength of the display device is secured, and the electrode plate and the porous spacer can be in close contact with each other. The applicant of the present application has previously provided a structure and a method capable of satisfactorily enclosing the display dispersion system in each hole of the spacer.For example, such a display device is installed vertically and switching switching tests are performed. It can be seen that the electrophoretic particles adhere to the electrode pattern, and that the porous spacer 8
In the upper part of each hole 8A, as shown in FIG. 5, the concentration of the electrophoretic particles 6 is reduced to produce a portion 7A where the color of the dye is visible, and the electrophoretic particles 6 precipitate below the lower part. Occurs. Therefore, as a result of examining various surfactants, it was found that the addition of a single surfactant could solve the two problems described above, namely, the problems of adhesion and precipitation of electrophoretic particles. I could not do it. Therefore, it is necessary to sufficiently study the stability of the display dispersion system or the improvement of the durability of the display operation, etc., associated with the mode of installation and use of this type of electrophoretic display device from the practical viewpoint.

"Objects and Configurations of the Invention" The present invention provides, as a powerful means for solving the above-mentioned problems, a surface treatment agent for electrophoretic particles of a dispersion system for display, a titanate coupling agent and a sorbitan fatty acid ester surfactant. It is an object of the present invention to provide a display dispersion system and an electrophoretic display device using the same, which can effectively prevent situations such as adhesion and sedimentation of electrophoretic particles to an electrode pattern by using both. . In other words, a single surfactant addition technique cannot achieve both functions of preventing the adhesion of the electrophoretic particles and preventing the precipitation of the electrophoretic particles. Both of these functions have been achieved.

As the titanate coupling agent as described above, isopropyl triisostearoyl titanate is preferable, and as the sorbitan fatty acid ester surfactant, sorbitan sesquiolate is preferable.For the treatment of the electrophoretic particles with the surface treatment agent, titanate is used. A further remarkable effect can be obtained by first treating with a coupling agent and then treating with a sorbitan fatty acid ester. That is, in a solution obtained by dissolving the titanate coupling agent in a solvent, after immersing and mixing the required electrophoretic particles and sufficiently reacting,
Evaporate the solvent and then add the treated electrophoretic particles to a dispersion pre-mixed with sorbitan fatty acid ester, or immerse and mix the electrophoretic particles in a dispersion with a titanate coupling agent added After sufficient reaction, a method of adding a sorbitan fatty acid ester thereto is preferable. The addition amount of the titanate coupling agent and the sorbitan fatty acid ester is 0.5 to 10% by weight based on the electrophoretic particles, and
It is preferably 0% by weight.

"Example" Hereinafter, the present invention will be described in more detail with reference to the illustrated example. In FIG. 1, reference numeral 10 denotes a transparent glass plate as a base material for forming a transparent display-side rigid electrode plate, on the upper surface of which a transparent conductive material such as tin oxide or indium tin oxide is used. The required electrode patterns 11 are formed appropriately. On the upper surface of the rigid electrode plate, a porous spacer 12 for dividing and enclosing the display dispersion system into small sections is provided. Further, on the upper surface of the porous spacer 12, the electrode pattern of the rigid electrode side plate is provided. A flexible electrode plate composed of a film substrate 13 having another electrode pattern 14 formed on a surface facing 11 is provided. In this flexible electrode plate, the dispersion 7 excessively supplied to each hole 12B of the porous spacer 12 was subjected to a pressing force from the upper surface of the flexible electrode plate by using a steel roller 16 as shown in the figure. While keeping the spacer in close contact with 12, the extra dispersion system 7
Are sequentially extruded, and the flexible electrode plate and the spacer 12 are
By using the adhesive 15 to perform the bonding process with the surrounding adhesive layer 12A, it is possible to perform a good encapsulation process of the dispersion system 7 having no voids in each hole of the spacer 12.

The electrophoretic particles used in the dispersion system 7 are preferably zinc sulfide. In addition to titanium oxide and various known colloidal particles, fine powders of various organic and inorganic pigments, dyes, ceramics, resins, and the like can be appropriately used. As the dispersion medium of the dispersion system 7, various kinds of natural or synthetic oils and the like can be arbitrarily used in addition to hydrocarbons, halogenated hydrocarbons, aromatic hydrocarbons, and the like. And if necessary for the dispersion system 7, an electrolyte,
In addition to surfactants, metal soaps, as well as charge control agents consisting of particles such as resins, rubbers, oils, varnishes, and compounds,
A dispersant, a lubricant, a stabilizer or the like can be appropriately added. In addition to unifying the charge of the electrophoretic particles to positive or negative, increasing the zeta potential, the electrode pattern of the electrophoretic particles
Adjustment of the adsorptivity to 11 and 14, the viscosity of the dispersion medium, and the like can also be appropriately performed.

In one embodiment, the electrophoretic particles 10 g zinc sulfide,
KR T manufactured by Ajinomoto Co. as a titanate coupling agent
0.5 g of isopropyl triisostearoyl titanate composed of TS, 2 g of sorbitan sesquiolate for sorbitan fatty acid ester, 0.4 g of oil blue BA manufactured by Chuo Gosei Co., Ltd. for coloring dye, and hexyl benzene 34 for dispersion medium.
g were each prepared as a dispersion compounding component.

First, 0.5 g of isopropyl triisostearoyl titanate was added to hexylbenzene and stirred, and zinc sulfide previously dried at a temperature of 150 ° C. for 2 hours was added, and this was sufficiently dispersed in a ball mill for 12 hours. . Then
After adding 2 g of sorbitan sesquiolate and further dispersing in a ball mill for 1 hour, 0.4 g of oil blue BA was added and finally sufficiently dispersed in a ball mill for 1 hour to prepare a dispersion system.

An electrophoretic display device in which the display dispersion system was sealed by the above-described method was installed vertically, and a switching test was performed by repeatedly applying a DC voltage between the electrode plates. here,
The thickness of the porous spacer was 50 μm, and the diameter of each hole was 1 mm. The switching field strength was 1 V / μm, and the on / off speed was 1 cycle / sec. As a result, even after 1 million switching operations, there was no adhesion or sedimentation of the electrophoretic particles to the electrode pattern, and a favorable display operation was maintained.

Comparative Example 1 The composition of the above example was prepared by removing TTS from the composition of the above example. The solution was prepared by dissolving sorbitan sesquiolate in hexylbenzene, adding zinc sulfide thereto, and then dispersing in a ball mill for 12 hours. Thereafter, a dye was added, and the mixture was prepared in the same manner as in the above examples.

In the case of this dispersion system, a good switching life of one million times was exhibited in the conventional horizontal installation, but a so-called half-meshed precipitation state as shown in FIG.

Comparative Example 2 The composition was the same as that of the above example except that sorbitan sesquiolate was omitted. In the liquid preparation sequence, TTS was dissolved in hexylbenzene, zinc sulfide was added thereto, and the mixture was dispersed in a ball mill for 12 hours as described above. Thereafter, a dye was added, and a liquid was prepared in the same manner as in the above examples.

In the case of this dispersion system, initial switching was slow, particles were adhered to the electrode surface, and the display could not be completely turned off. However, after several tens of switching operations, the electrophoretic particles exhibited good switching, and had a high switching speed, about 100 msec for both ON and OFF.
It was faster than sec. However, the delay at the time of the initial switching and the phenomenon of particle adhesion to the electrode surface occurred every time the display operation was stopped and then the display operation was performed again.

"Effect of the Invention" The electrophoretic display device according to the present invention and the dispersion for display used therefor, as described above, as a surface treatment agent for the electrophoretic particles of the dispersion for display, preferably from isopropyl triisostearoyl titanate Using both a titanate coupling agent as well as a sorbitan fatty acid ester, preferably also comprising sorbitan sesquiolate,
Moreover, desirably, the electrophoretic particles are firstly treated with the above-described titanate coupling agent, and then the sorbitan fatty acid ester is added in an appropriate amount as a subsequent step, so that the electrophoretic particles adhere to or sediment to the electrode pattern. A display dispersing system capable of reliably preventing the above situation can be configured.

Then, by using such a stable display dispersion system, it is possible to provide an electrophoretic display device sealed between the rigid electrode plate and the flexible electrode plate.

Therefore, it is possible to provide a distributed electrophoretic display device of a dispersion system having high durability and high reliability against repeated display operations regardless of the installation and use mode.

[Brief description of the drawings]

FIG. 1 In accordance with one embodiment of the present invention, electrophoretic particles are treated by using both a titanate coupling agent composed of isopropyl triisostearoyl titanate and a sorbitan fatty acid ester composed of sorbitan sesquiolate as a surface treating agent for the electrophoretic particles. By doing so, an explanatory view of an embodiment in which a stable electrophoretic display dispersion system without adhesion or precipitation to the electrode pattern is encapsulated between the rigid electrode plate and the flexible electrode plate via the porous spacer, FIG. 2 is an enlarged partial plan view of a main portion of a porous spacer used in the above-mentioned dispersion type split-type electrophoretic display device. FIG. 3 is a conceptual sectional view of a conventional structure of an electrophoretic display device using no porous spacer. FIG. 4 is a conceptual cross-sectional configuration diagram of a dispersion-type divided electrophoretic display device having a conventional structure using a porous spacer, To, FIG. 5 is a diagram for explaining the precipitated state of the vertical in the electrophoretic particles in the case of performing the switching operation of the cell enclosing a dispersion system of a conventional composition. 1: Transparent glass plate 2: Electrode pattern 3: Transparent glass plate 4: Electrode pattern 5: End spacer 6: Electrophoretic particles 7: Dispersion system for display 10: Transparent glass plate 11: Electrode pattern 12: Porous spacer 12A: Spacer adhesive layer 12B: Spacer through hole 13: Film substrate 14: Electrode pattern 15: Solid adhesive 16: Pressure roller

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Mori 757 Tenhoki, Kusazaki-cho, Inashiki-gun, Ibaraki Japan Nippon Mektron, Inc. KUTRON Co., Ltd. Minami-Ibaraki Factory

Claims (7)

(57) [Claims] An electrophoretic display dispersion comprising both a titanate coupling agent and a sorbitan fatty acid ester surfactant as a surface treatment agent for electrophoretic particles of the electrophoretic display dispersion. 2. The dispersion for electrophoretic display according to claim 1, wherein the titanate coupling agent is isopropyl triisostearoyl titanate and the sorbitan fatty acid ester surfactant is sorbitan sesquiolate. 3. The dispersion for electrophoretic display according to claim 1, wherein the electrophoretic particles are zinc sulfide. 4. The dispersion for electrophoretic display according to claim 1, wherein the dispersion medium is an alkylbenzene colored with a dye. 5. The electrophoretic particle according to claim 1, wherein the first surface treatment agent is a titanate coupling agent, and the second surface treatment agent is a sorbitan fatty acid ester surfactant.
The dispersion system for electrophoretic display according to (4). 6. The electrophoretic display dispersion system according to any one of claims (1) to (5), wherein at least one of the transparent electrode plates is enclosed between a pair of transparent electrode plates. By changing the distribution state of the electrophoretic particles in the dispersion system under the action of the applied display control voltage, a change is made to the optical reflection characteristics to perform a required display operation. Electrophoretic display. 7. One of the opposed electrode plates is constituted by a rigid electrode plate and the other is constituted by a flexible electrode plate, and the dispersion system is divided into small sections into a discontinuous phase and sealed between these two electrodes. The electrophoretic display device according to claim 6, further comprising a porous spacer for performing the following operations.