JP2005010796A - Method for manufacturing electrophoretic display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrophoretic display apparatus with easy injection and sealing of a migration dispersion liquid. <P>SOLUTION: The method for manufacturing an electrophoretic display apparatus, in which migration particles dispersed in an insulating liquid are moved in accordance with the direction of an electric field to display, includes processes of: forming a plurality of barrier walls on a flexible supporting body and injecting a migration dispersion liquid having the migration particles dispersed in an insulating liquid into divisions formed by the supporting body and the plurality of barrier walls; applying a liquid on both of the migration dispersion liquid injected into the divisions and the barrier walls, the liquid being incompatible with the insulating liquid and hardened by light, heat or drying; and hardening the applied liquid to produce a top plate to seal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an electrophoretic display device.

  In recent years, with the development of information equipment, there is an increasing need for rewritable electronic paper that combines the convenience of paper media and the electronic media function of a portable personal computer, so-called “paper-like display”. A display device used for a paper-like display has low power consumption, is thin, has flexibility like paper and can be bent, and such a display device or a plurality of display devices form one paper-like display device. Used in displays.

  Therefore, research and development of display devices that meet these needs have been actively conducted. Among them, a liquid crystal display device is capable of electrically controlling the arrangement of liquid crystal molecules to change the optical characteristics of the liquid crystal, and has been actively developed as a display device that can meet the above needs. However, in these liquid crystal display devices, the visual burden caused by the angle at which the screen is viewed, the difficulty of seeing characters on the screen due to reflected light, the flickering of the light source, low luminance, etc. has not been sufficiently solved. Further, since it is necessary to control the alignment of liquid crystal molecules and to precisely control the liquid crystal cell gap, it is difficult to achieve both flexibility.

  An electrophoretic display device that performs display by moving colored charged particles in an insulating liquid is known as one of the technologies that can realize a flexible reflective display device (for example, a US patent). No. 3668106). FIG. 4 shows a cross-sectional view of the most typical electrophoretic display device.

  The apparatus shown in the figure includes an electrophoretic dispersion composed of colored charged particles (electrophoretic particles) 46 and an insulating liquid (colored dispersion medium) 47, and a pair of electrodes 42 and 43 facing each other with the electrophoretic dispersion interposed therebetween. Yes. Reference numeral 41 denotes a substrate constituting a support together with the electrode 42, and 48 denotes a top plate. By applying a voltage to the electrophoretic dispersion through the electrodes 42 and 43, the electrophoretic particles 46 are electrophoresed and fixed on the electrodes biased to the opposite polarity, thereby performing display. The display is made by the color of the electrophoretic particles 46 and the color of the colored dispersion medium 47 that has been dyed. That is, when the migrating particles 46 are attached to the first electrode 42 close to the observer (a), the color of the migrating particles 46 is displayed, and conversely, the migrating particles 46 are attached to the second electrode 43 far from the observer (b ) Indicates the color of the colored dispersion medium 47.

  In principle, this device can be thinned, and a flexible display material can be obtained by using a flexible material for the substrate and the constituent members.

  The display image retention performance (hereinafter referred to as “memory performance of display”) holds the charge on the electrode by opening the circuit immediately after the voltage is applied, and adsorbs and holds the colored charged fine particles by the Coulomb force of the electrode retention charge. Is given by.

  If the electrode retention charge decreases with time by selecting the material of the insulating layer, etc., the migrating particles are retained on the electrode for a relatively long time. Can be continued for a long time.

The electrophoretic display device originally operates at a lower current than other methods such as a liquid crystal display device, but thanks to this memory property, the average power consumption is further reduced when the display is not frequently rewritten. be able to.
U.S. Pat. No. 3,668,106

However, the conventional electrophoretic display device has the following problems.
That is, there is a problem in injecting the electrophoretic dispersion liquid between the substrates when manufacturing the electrophoretic display device. In an example of the manufacturing process, first, the upper and lower two substrates constituting the electrophoretic display device are bonded together leaving the electrophoretic dispersion inlet. The electrophoretic dispersion liquid is injected from the injection port. However, the spacer / partition provided to keep the distance between the two substrates constant is an obstacle, and cannot be injected smoothly. Also, when the electrophoretic dispersion is injected from the end, the dispersion medium easily enters, but the electrophoretic particles may be caught by the spacer / partition wall, so the concentration of electrophoretic particles is high near the injection port, and as the distance from the injection port increases. The migrating particle concentration is lowered, and the uniformity of display is adversely affected.

In another example of the manufacturing process of the electrophoretic display device, after providing a spacer / partition on the lower substrate, the electrophoretic dispersion liquid is uniformly dropped on the lower substrate, and then the upper substrate is adhered to seal the periphery. . However, in this method, the in-plane uniformity of the migrating particle concentration can be realized, but there is a problem that bubbles are easily mixed when the upper substrate is bonded.
An object of the present invention is to provide a method of manufacturing an electrophoretic display device in which an electrophoretic dispersion liquid can be easily injected and sealed.

As a result of repeated studies to solve the above-mentioned problems, the present inventor has reached the following inventions. That is,
The method for manufacturing an electrophoretic display device of the present invention is a method for manufacturing an electrophoretic display device that performs display by moving electrophoretic particles dispersed in an insulating liquid according to the direction of an electric field, and has flexibility. Providing a plurality of partition walls on a support, and injecting an electrophoretic dispersion liquid in which electrophoretic particles are dispersed in an insulating liquid into a partition formed by the support and the plurality of partition walls; and A step of applying a liquid that is incompatible with the insulating liquid and cured by light, heat, or drying on both the electrophoretic dispersion and the partition; and curing the applied liquid to form a top plate as a whole. And a step of sealing.

  By manufacturing in this way, it is possible to inject an electrophoretic dispersion liquid having a uniform electrophoretic particle concentration into any section of the display device. The application of the liquid is preferably performed by spraying using a spray device.

  According to the present invention, it is easy to inject and seal the electrophoretic dispersion into the display section. The electrophoretic display device manufactured by the method of the present invention has flexibility corresponding to bending deformation and does not lose display memory property even when deformed, and thus is suitable for a paper-like display.

Embodiments of the present invention will be described below.
Configuration Figure 1 is a sectional view showing an example of an electrophoretic display device of the present invention. A basic configuration of the display device of the present invention will be described with reference to FIG.
In FIG. 1, a film-like first electrode 12 is provided on a flexible substrate 11, and a plurality of line-like second electrodes 13 are provided above the flexible substrate 11 in parallel with each other at a constant interval. In FIG. 1, the first electrode 12 extends in the left-right direction. An insulating layer 14 is provided between the first electrode 12 and the second electrode 13 and around the second electrode to maintain insulation between the electrodes and prevent the electrodes from directly touching the electrophoretic dispersion. Each of the second electrodes 13 extends in the front and back direction in FIG. The width of the second electrode 13 (the width in the left-right direction in the figure) is narrower than the width of the first electrode (not shown). Here, the flexible substrate 11, the first electrode 12, the second electrode 13, and the insulating layer 14 are collectively referred to as a flexible support 20.

  On the insulating layer 14 of the flexible support 20, a plurality of flexible partition walls 15 are provided in parallel with each other, and in parallel with the second electrode 13 at the same interval. A pixel is formed by a combination of a wide first electrode 12 and a narrow second electrode 13 that are orthogonal to each other. The partition wall has a rectangular (or square) frame shape surrounding the pixel including each body of the electrodes 12 and 13. The upper part of the flexible partition 15 is entirely covered with a top plate 18 parallel to the flexible substrate 11. The top plate 18 can be deformed together with the substrate 11. The term “deformation” means including bending or expansion / contraction.

  A space surrounded by the flexible support 20, the flexible partition wall 15 and the flexible / extensible top plate (hereinafter simply referred to as “stretchable top plate”) 18 is a display section. An electrophoretic dispersion composed of a dispersion medium 17 is contained.

  A protective film 19 may be coated on the stretchable top plate 18 as shown in FIG. For example, a film made of a polymer material or the like is used as the top plate, and it is conceivable that a low molecular weight substance passes through the film. The protective film 19 may be used for the purpose of preventing evaporation of the components of the electrophoretic dispersion, improving the gas barrier performance of the stretchable top plate 18, and improving the mechanical strength.

Materials Next, materials used for the electrophoretic display device of the present invention will be described.
1. Flexible Substrate For the flexible substrate 11, many transparent and flexible resin materials can be used. Examples thereof include polyester, polyethylene, polypropylene, polyethersulfone, polycarbonate, polymethacrylate, and acrylic. The thickness is about 50 to 200 μm.

2. Insulating layer As the material of the insulating layer 14, the same resin material as that of the flexible substrate can be used. Polyimide or the like can also be used. The thickness is about 0.5 to 2.0 μm.

3. Flexible partition As a material of the flexible partition 15, the resin material similar to a flexible substrate is mentioned. The height of the partition wall is about 10-50 μm, the width is about 5-15 μm, and the aspect ratio (height / width) is about 2-3. The flexible partition may be molded integrally with the flexible support, or may be provided on the flexible support using a photosensitive material later. The flexible partition is preferably not bonded to the top plate 18. In that case, the partition wall and the top plate are displaced when the display device is bent. In order to shift the position, it is preferable to select a material that is less compatible with each other.

4). Stretchable top plate The stretchable top plate 18 is preferably made of a material that can be stretched or contracted according to the deflection of the flexible substrate, that is, the top plate bends together with the substrate. In terms of Young's modulus, it is 100% or less, preferably 0.001 to 10% of the substrate. The thickness is about 10 to 500 μm. Examples of such materials include rubber resins such as isoprene, butadiene, and silicone, and copolymers of styrene or acrylonitrile with isoprene or butadiene. In addition, polyvinylidene chloride, copolymer nylon, and ethylene-propylene copolymer may be used. In particular, in the case of a block copolymer, a material that is excellent in both mechanical strength and stretchability, and hardly cracks even when bent is obtained.
These stretchable materials can be made into a top plate by dissolving in an appropriate solvent, applying onto the partition walls and the electrophoretic dispersion by spraying, and drying from the surface.
In addition, a liquid in which a polymerizable monomer and an appropriate polymerization initiator that reacts with heat or light are blended with the rubber-based resin or copolymer described above is applied by spraying or the like, and heated or irradiated with light to polymerize and cure, It can also be a top board.

5. Protective film Although the protective film 19 is not necessarily required if the gas barrier performance and mechanical strength of the stretchable top plate are sufficient, the range of selection of the stretchable top plate material is expanded by using the protective film. The protective film needs to be stretchable, but since it may be a thin film of several μm, the same resin material as that of the flexible substrate can be used. Specifically, it is about 1 to 10 μm, preferably about 1 to 3 μm.

6). Electrophoretic dispersion 6-1. Dispersion medium As the insulating dispersion medium 17, paraffinic hydrocarbons (normal paraffin, isoparaffin), halogenated hydrocarbons, silicone oil, and the like can be used. Among these, isoparaffin is suitable because it has characteristics such as good dispersibility of dielectric particles, low cost, and low harmfulness to the human body. Typical isoparaffins on the market are Shellsol 70, 71, 72 (above, manufactured by Shell Japan Co., Ltd.), Isopar G, H, L, M (above, manufactured by Exxon Chemical Co., Ltd.), IP Solvent 1620. , 2028, 2835 (above, manufactured by Idemitsu Petrochemical Co., Ltd.).

6-2. Electrophoretic Particles As the electrophoretic particles 16, various inorganic and organic dielectrics can be widely used.
Examples of the inorganic substance include glass, alumina, zirconia, titanium oxide, and silicon nitride.
Various pigments and resins can be used as the organic substance. Examples of the resin include rubber resins such as polystyrene, polyacrylate ester, polymethacrylate ester, polyacrylonitrile, inoprene and butadiene, polyester, polyurethane, polyamide, epoxy resin, rosin, polycarbonate, phenol resin, chlorinated paraffin, Examples include polyethylene, polypropylene, silicone resin, Teflon and derivatives thereof, and copolymers and mixtures thereof.

6-3. Electrophoretic particle colorant When resin-made electrophoretic particles are used, they are colored with carbon black, various pigments, various dyes, etc. if coloring is necessary.
The migrating particle material mixed with the colorant is processed into particles having a diameter of about 0.1 μm to several tens of μm. The shape of the particles is preferably spherical.

6-4. Charge Control Agent It is desirable to mix a proper amount of a charge control agent (charge control agent) in order to give a specific charge to the surface of the migrating particles 16 and improve the electrophoretic characteristics and dispersion stability in the insulating dispersion medium.
Examples of the charge control agent include sodium dioctyl sulfosuccinate (American cyanamide), metal soap, and the like as the positive charge control agent. As the negative charge control agent, soybean lecithin, alkenyl succinic acid polyimide (for example, OLOA-1200 and OLOA-4375H manufactured by Oronite Japan), petroleum calcium sulfonates basic calcium petronate and basic barium petronate (witcochemical) Manufactured).
The charge control agent is used by being dissolved in an insulating liquid. When the migrating particles are dispersed and stirred here, the charge control agent is adsorbed on the surface of the migrating particles and generates a specific charge in the liquid. The charge control agent is added from about 0.01 to about 10 weight percent of the electrophoretic dispersion composition, but the optimum amount varies depending on the type of charge control agent.

Viewing Direction The display surface of the electrophoretic display device of the present invention can be on the flexible substrate 11 side or on the stretchable top plate 18 side. When the substrate 11 side is used as the display surface, the substrate 11 may be transparent, and the top plate 18 may be mixed with a reflective material powder, or a reflective layer may be provided on the back of the top plate 18. When the top plate 18 side is used as the display surface, the top plate 18 and the protective film 19 may be transparent, and the substrate 11 may be mixed with a reflective material powder, or a reflective layer may be provided on the back of the substrate 11. . Further, a light emitting layer may be provided instead of the reflective layer.
As the reflective material powder, white pigment powder such as titanium oxide, tin oxide, aluminum oxide, or metal powder may be used.

Manufacturing Method FIGS. 3A to 3G are cross-sectional views showing an example of the manufacturing method of the electrophoretic display device of the present invention. The manufacturing process will be described with reference to FIG.
(A) The first electrode 12 is formed on the flexible substrate 11.
(B) An insulating layer 14 is formed on the first electrode, and a plurality of line-shaped second electrodes 13 are provided on the insulating layer 14 in parallel with each other at a constant interval.
(C) The insulating layer 14 is formed so as to cover the second electrode.
(D) On this insulating layer, a plurality of flexible partition walls 15 are provided in parallel with each other and with the second electrode in parallel and at the same pitch.
(E) A dispersion liquid for electrophoresis composed of an insulating dispersion medium, electrophoretic particles, and a charge control agent is injected into a section surrounded by the flexible partition wall 15 and the insulating layer 14. It is preferable that the injection amount is slightly higher than the height of the flexible partition wall. Since the opening of the compartment is large and easy to inject, it is possible to inject an electrophoretic dispersion liquid having a uniform migrating particle concentration into any compartment.
(F) A solution containing the material for the stretchable top plate is sprayed and applied in a mist form using a spray device. As the spray device, for example, a droplet discharge technology (so-called inkjet technology) that can control the droplet discharge amount and the position accuracy of the discharge destination very severely, such as Nordson microspray and Canon bubble jet printer head, etc. it can.
The stretchable top plate 18 is formed by solidifying the applied top plate material. The curing step is performed by heating or light irradiation depending on the material used.
(G) Finally, the protective film 19 is applied on the stretchable top plate.

The electrophoretic display device having flexibility and memory has a film-like appearance. When this display device is bent, it has flexibility. This is because one side (substrate) is made of a flexible material and the other side (top plate) is made of a stretchable material. This is thought to be due to supplement or absorb.
In addition, regarding the memory performance of the display, the stress when the electrophoretic display device is bent is absorbed by the stretchable material of the top plate being deformed, so that the flow of the insulating dispersion medium can be suppressed. Is not swept away, so the display is retained.

Examples of the present invention will be described below.
First Embodiment Preparation of migrating particles 1 part of azobisisobutyronitrile was mixed and dissolved in 50 parts of styrene, and 20 parts of carbon black was further mixed to obtain a monomer solution. On the other hand, 1.5 parts of Aergel # 200 (manufactured by Nippon Aergel) was dissolved in 450 parts of deionized water, and the above monomer solution was added thereto, and stirred at 5000 rpm using a homogenizer to form an emulsion. Thereafter, the whole was heated to 80 ° C. and stirred for about 1 hour to carry out polymerization. Next, the entire system was transferred to another container, and the polymerization reaction was continued at 80 ° C. for 6 hours while stirring the propeller at 200 rpm. Then, it cooled, repeated filtration and washing with water, and finally dried to obtain black electrophoretic particles having an average particle diameter of 1.5 μm.

2. Preparation of electrophoretic dispersion liquid In 100 parts of Isopar G (manufactured by Exxon Chemical), 5 parts of the electrophoretic particles and 0.1 part of cobalt naphthenate were dispersed and stirred for about 1 hour to obtain an electrophoretic dispersion liquid.
When the surface zeta potential of the migrating particles was measured with an Otsuka Electronics zeta potential measuring device, the average was +100 mV.

3. Production of electrophoretic display device An insulating layer having a thickness of 2 μm by applying an acrylic resin on a 100 μm-thick polycarbonate film (Eleclear HA-B200, manufactured by Teijin Co., Ltd.) on which an ITO electrode (first electrode) is formed. (Manufactured by JSR, Optomer) was formed. Next, a linear aluminum electrode (second electrode) having a width of 10 μm and a pitch of 100 μm was provided thereon. On the aluminum electrode, an acrylic resin (optomer) was applied again to form an insulating layer having a thickness of 2 μm.

  On this insulating layer, an ultraviolet curable resin made of acrylic resin (manufactured by JSR, THB) is applied to a thickness of 30 μm, exposed to a partition pattern using a photomask, and developed to dissolve unnecessary portions. And dried to produce a partition wall. Then, in the space surrounded by the partition walls and the insulating layer, the above 2. The electrophoretic dispersion was injected.

Next, a mixed solution of 70 parts OBR (manufactured by Tokyo Ohka Kogyo Co., Ltd.) mainly composed of cyclized isoprene rubber and 30 parts aluminum oxide fine particles is uniformly applied from the upper part of the electrophoretic dispersion liquid with a Nordson microspray apparatus and dried. Thus, a top plate film serving also as a reflective layer having a thickness of about 100 μm was formed. In addition, OBR is a liquid, and a solvent component is contained in 70 parts.
The electrophoretic dispersion liquid in the completed electrophoretic display device had a uniform electrophoretic particle concentration in the plane.

Subsequently, the electrophoretic display operation was confirmed.
When the first electrode was grounded and the potential of the second electrode was set to +100 V, the migrating particles spread apart on the second electrode, and when observed from the polycarbonate film substrate side, black display was shown.
Next, when the potential of the second electrode was set to −100 V, the migrating particles gathered on the second electrode having a narrow width, and when observed from the polycarbonate film substrate side, the reflected light of the aluminum oxide mixed with the OBR of the top plate was observed. It was observed and showed a white display.

Further, when the potential of the second electrode was alternately modulated at +100 V and −100 V at 1 Hz, the display changed alternately between black and white in synchronization with the modulation of the potential.
Subsequently, when no voltage was applied and the electrophoretic display device was bent, it was flexible. Further, the display was not disturbed by bending, and the display was maintained.

Second Example Except for using PMER (manufactured by Tokyo Ohka Kogyo Co., Ltd.) made of novolac resin as an ultraviolet curable resin for forming the partition walls, the injection of the electrophoretic dispersion liquid was performed by the same materials and operations as in the first example.
Next, a mixture of 60 parts of styrene isoprene block polymer, 40 parts of maleate ester and 1 part of benzoyl ether is uniformly applied by microspray (manufactured by Nordson) from the upper part of the electrophoretic dispersion, and then the whole is uniformly exposed to ultraviolet rays. Then, a transparent top plate film having a thickness of 100 μm was formed by removing the solvent at 120 ° C. for several minutes (about 30 to 1 hour in the case of an oven) with a hot plate.
The electrophoretic dispersion liquid in the completed electrophoretic display device had a uniform electrophoretic particle concentration in the plane.
It was confirmed that this electrophoretic display device also operated in the same manner as in the first example.

Example 3 As the insulating layer provided on the aluminum electrode, a mixture of alumina particles and acrylic resin (optomer) mixed at a weight ratio of 100: 30 was applied to form an insulating / reflective layer having a thickness of 2 μm. The injection of the electrophoretic dispersion was carried out by the same materials and operations as in the second example.

Next, a liquid mixture containing 65 parts of terminal hydrogenated polybutadiene, 35 parts of fumaric acid ester and 1 part of benzyl ketal is uniformly applied from above the electrophoretic dispersion liquid with a microspray apparatus (manufactured by Nordson), and then the whole is uniformly irradiated with ultraviolet rays. The film was exposed to form a transparent top plate film having a thickness of about 100 μm.
The electrophoretic dispersion liquid in the completed electrophoretic display device had a uniform electrophoretic particle concentration in the plane.

Subsequently, the electrophoretic display operation was confirmed.
When the first electrode was grounded and the potential of the second electrode was set to +100 V, the migrating particles spread away on the second electrode and observed from the top plate side, indicating black display.
Next, when the potential of the second electrode was set to −100 V, the migrating particles gathered on the second electrode having a narrow width, and when observed from the top plate side, the reflected light of alumina mixed in the insulating layer was observed. It showed white display.

Further, when the potential of the second electrode was alternately modulated at +100 V and −100 V at 1 Hz, the display changed alternately between black and white in synchronization with the modulation of the potential.
Subsequently, when no voltage was applied and the electrophoretic display device was bent, it was flexible. Further, the display was not disturbed by bending, and the display was maintained.

It is a schematic sectional drawing which shows one embodiment of the electrophoretic display device of this invention. It is a schematic sectional drawing which shows another embodiment of the electrophoresis type display apparatus of this invention. It is explanatory drawing of the manufacturing process of the electrophoresis type display apparatus of this invention. It is a schematic sectional drawing which shows the conventional electrophoresis type display apparatus.

Explanation of symbols

  11: flexible substrate, 12: first electrode, 13: second electrode, 14: insulating layer, 15: flexible partition, 16: electrophoretic particles, 17: insulating dispersion medium, 18: stretchable top plate, 19: protective film, 20: flexible support, 41: substrate, 42: first electrode, 43: second electrode, 45: partition walls, 46: electrophoretic particles, 47: colored dispersion medium, 48: top plate.

Claims (2)

A method of manufacturing an electrophoretic display device that performs display by moving electrophoretic particles dispersed in an insulating liquid according to the direction of an electric field,
Providing a plurality of partition walls on a flexible support, and injecting an electrophoretic dispersion liquid in which electrophoretic particles are dispersed in an insulating liquid into a partition formed by the support and the plurality of partition walls; A step of applying a liquid that is incompatible with the insulating liquid and cured by light, heat, or drying on both the electrophoretic dispersion and the partition injected into the liquid; and curing the applied liquid. A method for manufacturing an electrophoretic display device comprising a step of sealing as a top plate. The manufacturing method according to claim 1, wherein the liquid is applied by spraying using a spray device.

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