JP4565257B2 - Display unit group, manufacturing method thereof, and display device - Google Patents

Description

The present invention is a display device that can be used as a display of a personal computer, a mobile phone, a mobile terminal or the like, or a display body that can acquire information from them and carry it independently, such as an electronic paper or a digital book, The present invention also relates to a display unit group forming the same and a manufacturing method thereof .

  A fluid whose rheological properties change in response to on / off of an electric field is called an electrorheological fluid (ER fluid). A typical electrorheological fluid is a mixed liquid in which insulating solid particles are dispersed in an insulating liquid, and has a property of solidifying instantaneously when an electric field is applied and reversibly flowing when the electric field is removed. It is said that when an electric field is applied, the particles are polarized to form particle bridges in the direction of the electric field, and the attractive force between the bridges increases the viscosity of the fluid. The mechanism by which the bridge structure is formed has not been fully elucidated, but the presence of water dissociates ion dissociation groups on the particle surface to form an electric double layer, which is distorted when an electric field is applied, and the particles are electrostatically charged. The electric double layer theory of attracting people is proposed. Electrorheological fluids having such properties have been studied for application to clutches, valves, dampers, actuators, robot control, and vibration control using the characteristics.

In order to put an electrorheological fluid into practical use for the above applications, the dispersed phase should not settle or aggregate, the water content of traces should be controlled, and the electrorheological properties should be stable over a wide range of temperatures. When the temperature of the rheological fluid is increased, there is a problem that the performance of electrorheological properties is significantly deteriorated due to water evaporation).
In order to improve the precipitation and aggregation of the dispersed phase of the electrorheological fluid, the dispersed phase is an inorganic / organic composite particle having a specific gravity decreased by providing an inorganic fine particle layer such as titanium hydroxide or silica on the surface of the organic particle. Electrorheological fluids have been reported (see, for example, Non-Patent Document 1 and Non-Patent Document 2).

In addition, it has been reported that this inorganic / organic composite particle is applied to an electrorheological fluid and used in a light control device (see, for example, Non-Patent Document 2).
In Non-Patent Document 2, display is performed using the difference between the light transmittance of the electrorheological fluid dispersion system when no electric field is applied and the light transmittance of the bridged electrorheological fluid when an electric field is applied.
Since the electrorheological fluid of Non-Patent Document 2 exhibits a blue color due to the pigment used for the surface coating of the polymer particles, the transmitted light intensity has a maximum value at a wavelength of 490 nm in the absence of an electric field. On the other hand, when the electric field strength is increased, the transmitted light intensity increases and the wavelength at which the transmitted light intensity reaches the maximum value becomes longer. The wavelength at which the transmitted light intensity in a high electric field is maximum is 600 nm and has the same spectrum as the incident light. In other words, the light control element of Non-Patent Document 2 is brightened by applying an electric field, and the color tone is changed.
Industrial Materials, 1994, Vol. 142, No. 3, p104-106 Journal of Colloid and Interface Science, 1996, No. 177, p250-256

  However, when the light control element as in Non-Patent Document 2 is used in a display device, there are various problems. That is, in Non-Patent Document 2, it is necessary to enclose the electrorheological fluid in the transparent electrode cell, and a complicated process is required. Further, when used as a large display device, it is necessary to inject a spacer in order to keep the distance between the transparent electrodes constant. Furthermore, because of the particle dispersion system, sedimentation and agglomeration of particles over time cannot be avoided, and there is a problem in the repeated durability of display.

Therefore, the present inventors previously proposed to solve the above problems by encapsulating an electrorheological fluid in a microcapsule (Japanese Patent Application No. 2002-214977). In this proposal, an electrorheological fluid is microencapsulated, mixed with a binder, and coated on a substrate with an electrode to form a sheet. And the transparent electrode is made to contact the board | substrate opposite surface of the sheet-shaped display element. In this proposed display device, the transmittance of the microcapsules is changed by applying a voltage to both electrodes, and display can be performed.
With this proposed microencapsulation, a display device can be produced by an easy manufacturing method called coating. Further, since the electrorheological fluid is encapsulated in the microcapsule, a spacer or the like is not necessary, and a large screen can be achieved. Furthermore, the electrorheological fluid was encapsulated in the microcapsule, which improved the problem of repeated display durability due to sedimentation and aggregation of particles.

However, the display device according to the above proposal also has a problem because it is based on the microcapsule technology. That is, in the synthesis of microcapsules, this is a problem caused by difficulty in obtaining microcapsules having a sharp size distribution.
If the size of the microcapsules is not uniform, it is difficult to produce a display layer having a uniform thickness. Furthermore, if the size of the microcapsules is uneven, the aggregation behavior of the electrorheological fluid in each microcapsule will be different. Therefore, there is a problem that the response time required for switching the display differs among the individual microcapsules, resulting in a display device with uneven response time.

In addition, since it is difficult to obtain uniform microcapsules at the time of synthesis, a method of selecting only uniform microcapsules by filtering or the like is also conceivable. However, in this case, another problem that the microcapsule breaks in the middle of passing through the filter is likely to occur.
Such brittleness of the microcapsules becomes a serious problem not only at the time of manufacture but also when actually used by a user as a product. For example, when such a display device is formed on a flexible substrate for electronic paper in the future, it is conceivable that the microcapsule is broken when it is bent, and the electrorheological fluid leaks therefrom.

In view of the above circumstances, the present invention provides a display unit group, a manufacturing method thereof, and a display device that can obtain a uniform response time over the entire display region and are less likely to be damaged even when bent and stretched using electronic paper or the like. The issue is to provide.

As a result of studying the above problems, the present inventors have conceived the following invention by using a display unit using hollow fibers instead of microcapsules.
[1] A display unit group in which a large number of display units are intertwined into a sheet,
The plurality of display units each have a light-transmitting hollow fiber sealed at both ends, and a fluid sealed in the hollow fiber, and the fluid disperses insulating solid particles in an insulating liquid. A display unit group comprising an electrorheological fluid comprising a dispersed liquid.
[2] A display device, wherein the display unit group according to [1] is arranged in a display area, and an electric field applying unit for applying an electric field to each display unit of the display unit group.
[3] A display unit in which a large number of display units are dispersed in a liquid containing a binder component, spread on a mesh-like support, and the liquid is removed, so that a large number of display units are intertwined to form a sheet. A group of manufacturing methods,
The plurality of display units each have a light-transmitting hollow fiber sealed at both ends, and a fluid sealed in the hollow fiber, and the fluid disperses insulating solid particles in an insulating liquid. producing how the display unit group, which is a electro-rheological fluid comprising a dispersion obtained by.

  The display unit of the present invention can form a uniform and strong display unit by using hollow fibers that are strong and easy to have a uniform size, compared to the case of using microcapsules. is there. Therefore, when the display unit of the present invention is used, a display device that has no uneven response time and is strong and is not easily damaged even when bent and stretched using electronic paper or the like can be manufactured.

  Moreover, the hollow fiber can make an internal display part larger than it actually is by the so-called convex lens effect. Therefore, the area of the apparent display portion that occupies the entire display area is increased, and as a result, good contrast can be obtained.

  As shown in FIGS. 1 and 2, the display unit of the present invention is one in which an electrorheological fluid is enclosed in a sealed hollow fiber 1. The sealed hollow fiber 1 is formed by sealing both ends of a cylindrical hollow fiber whose outer shape is cylindrical and whose inner surface is hollow on a substantially concentric circle with the outer peripheral surface. The electrorheological fluid is a dispersion liquid in which the insulating solid particles 3 are dispersed in the insulating liquid 2.

  Examples of the insulating liquid 2 include insulating oils such as silicone oil, diphenyl chloride, trans oil, and liquid paraffin. The insulating liquid 2 needs to be light transmissive and is preferably colorless and transparent. The insulating liquid 2 may contain a colorant such as a dye or a pigment as long as the light transmittance is not hindered.

  Examples of the insulating solid particles include silica gel, cellulose, starch, corn starch, soybean casein, polystyrene ion exchange resin, polyvalent metal oxide, hydrotalcite, polyvalent metal acid salt, hydroxyattapite, pesticide type compound, Examples include viscous minerals and potassium titanate. The shape of the solid particles is not limited, but it is preferable to use a needle-like shape. Further, as described in Non-Patent Document 1, inorganic / organic composite particles may be used.

As a material constituting the sealing hollow fiber 1, a light-transmitting material is used so that the inside of the hollow fiber can be visually recognized from the outside. It is particularly preferable to use a transparent material as the hollow fiber material.
Such transparent materials include polyester resin, polyolefin resin, acrylic resin, urethane resin, polystyrene resin, acrylonitrile-butadiene-styrene copolymer (ABS resin), silicon resin, nylon resin, vinyl chloride-vinyl acetate copolymer. (Vinyl chloride resin), tetrafluoroethylene / perfluoropropyl vinyl ether resin (PFA resin), and the like.
In addition, you may make these transparent materials contain colorants, such as dye and a pigment, in the range which does not inhibit light transmittance.

The sealed hollow fiber 1 is obtained by sealing the hollow fiber. This hollow fiber can be manufactured as follows, for example.
(1) A substantially concentric two-layer polymer fiber is produced by a melt spinning method or the like, and the fiber is drawn to obtain a fiber having an outer shape of about 20 to 200 μm. At this time, the inner layer is a resin that is dissolved by washing with water or an organic solvent after molding. And hollow fiber is obtained by removing resin of an inner layer by melt | dissolution.

(2) Using a nozzle having a concentric discharge port, the resin constituting the hollow fiber is extruded from the outer ring-shaped discharge port while discharging the fluid from the circular discharge port at the center. In this case, the fluid substitutes for the soluble resin of the inner layer in the method (1). Since the fluid can be easily removed, it is not necessary to remove the resin later as in the method (1), and the hollow fiber can be more easily produced. As the fluid to be introduced at this time, a gas such as nitrogen gas or air is preferable.

The display unit of the present invention can be manufactured as follows, for example.
First, an electrorheological fluid is prepared in advance, and the hollow fiber is impregnated with the electrorheological fluid. Specifically, a number of long hollow fibers are bundled and placed in a chamber, and the chamber is evacuated. Subsequently, the hollow fibers are filled with the electrorheological fluid by introducing the electrorheological fluid into the chamber.
After that, the end of the hollow fiber filled with electrorheological fluid is sealed, or each end is sealed while fusing to an appropriate length, so that the electrorheological fluid is sealed inside the hollow fiber Units can be formed.

In the display unit of the present invention, the arrangement state of the insulating solid particles 3 varies depending on whether or not an electric field is applied. This will be described with reference to FIGS.
FIG. 1 shows the state of the display unit when no electric field is applied. In this case, the insulating solid particles 3 in the sealed hollow fiber 1 perform a Brownian motion and are uniformly dispersed in the insulating liquid 2. On the other hand, FIG. 2 shows a state of the display unit when an electric field is applied. In this case, the insulating solid particles 3 are polarized by applying an electric field, attract each other, form a bridge in a direction parallel to the electric field, and are separated from the insulating liquid 2.

The display device according to the present invention includes a large number of display units arranged in a display area, and includes an electric field applying means for applying an electric field to the display units.
The display unit is preferably formed into a sheet because electrodes are arranged on both sides thereof. And it is preferable that the major axis direction of each display unit is a direction parallel to the display surface, that is, each display unit is placed in a state where it is laid on the display surface.

Since the display units of the present invention are independent of each other, it is possible to manufacture a display unit group that is formed into a sheet by a simple method such as coating as in the case of the microcapsules.
For example, the display unit can be produced by dispersing it in a liquid containing a binder component and coating it on a sheet-like support.
It is also possible to form a display layer by a technique similar to papermaking. That is, the display units can be entangled with each other by spreading on a mesh support and removing the liquid to form a sheet.

The arrangement of the display units in the sheet-like display unit group is not limited to the random arrangement as described above, and may be an arrangement arranged in a certain direction.
The arrangement arranged in a certain direction is, for example, arranging a large number of continuous yarn windings of hollow fibers containing an electrorheological fluid, and simultaneously feeding them together and feeding the base fabric from the winding. Adhere to a sheet while aligning and arranging a large number of yarns. Subsequently, the yarn can be pressed and sealed at regular intervals with a heat seal bar, and the intermediate portion of the seal portion can be cut together with the base sheet with a cutter.
Further, if display units are stacked in the same manner in the orthogonal (vertical) direction to the display units arranged in one direction in this way, it is also possible to arrange the display units in a grid pattern.

By providing electric field applying means for applying an electric field to each part of the sheeted display unit group, information can be entered / erased / rewritten. As the electric field applying means, known means can be applied, and preferably a power source for applying a voltage between desired positions of the electrode plates arranged on both surfaces of the sheet-like display unit group and the pair of electrode plates. It consists of devices.
Of the pair of electrode plates, at least the electrode plate on the viewing side needs to be light transmissive. The other electrode plate may be light transmissive or light non-transmissive. If the other electrode plate is also light transmissive, a transmissive display device can be obtained. Further, if the other electrode plate is light-impermeable, a reflective display device can be obtained. Further, when a light absorption layer is disposed on any one surface of the other electrode plate, a reflective display device can be obtained regardless of whether the electrode plate has light transmittance.
As a substrate material for the transparent electrode plate, glass is generally used. However, a transparent plastic, for example, polycarbonate resin, acrylic-based polymethyl methacrylate, or styrene-based styrene-acrylonitrile copolymer is used. Also good. Those obtained by depositing ITO on these substrates can be suitably used. Examples of the light-impermeable electrode plate material include gold, silver, copper, and iron.

In the case of a transmission type display device, when no electric field is applied, the insulating solid particles 3 are uniformly dispersed in the insulating liquid 2 as shown in FIG. For this reason, light incident from the side opposite to the observer does not reach the eyes of the observer (dark state).
On the other hand, when an electric field is applied, the insulating solid particles 3 form a bridge in a direction parallel to the electric field and separate from the insulating liquid 2 as shown in FIG. Incident light reaches the eyes of the observer (bright state).

On the other hand, in the case of a reflective display device, when no electric field is applied, the insulating solid particles 3 are uniformly dispersed in the insulating liquid 2 as shown in FIG. When hit, it reflects irregularly and looks white.
On the other hand, when an electric field is applied, the insulating solid particles 3 form a bridge in a direction parallel to the electric field and separate from the insulating liquid 2 as shown in FIG. Then, some of the light is reflected by the bridge-like insulating solid particles 3, but the other light is transmitted through the insulating liquid 2 between the bridges. Therefore, the light absorption layer disposed on the electrode plate opposite to the viewing side or on one of the surfaces is visualized. Therefore, when an electric field is applied, the color changes from white display to the color of the electrode plate or the light absorption layer, for example, black.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
Silicone oil (Trademark: TSF-451-10, manufactured by GE Toshiba Silicon, dielectric constant = 2.6 F / m) and organic-inorganic composite particles (composite particles described in Journal of Japan Printing Society Vol. 38, No. 4, P17) 1.3 g, 0.228 g of a surfactant (trademark: TSF4700, manufactured by GE Toshiba Silicon) was added and dispersed with an ultrasonic disperser for 10 minutes to obtain an electrorheological fluid.

Next, hollow fibers were produced. The hollow fiber uses a nozzle having a concentric discharge port, and nitrogen gas is allowed to flow from the circular discharge port at the center, while the ethylene vinyl acetate copolymer having a vinyl acetate copolymerization ratio of 25% from the outer ring-shaped discharge port. It was prepared by extruding a polymer.
The extruder temperature was 230 ° C., and nitrogen gas was maintained at almost atmospheric pressure. The extrusion rate of the melted ethylene vinyl acetate copolymer was 0.15 kg / hr. The molten fiber at the exit of the extruder was stretched to obtain a hollow fiber having an outer diameter of 160 μm and an inner diameter of 80 μm.

  Subsequently, many hollow fibers were bundled and placed in a chamber, the chamber was evacuated, and the electrorheological fluid was introduced into the chamber, thereby filling the hollow fibers with the electrorheological fluid.

  Thereafter, the hollow fiber containing the electrorheological fluid was cut into a cut length of about 3 mm using a cutter with heated blades. When the cut surface portion of the hollow fiber was melted and crushed while being cut, the end portion was sealed, and a display unit having an electrorheological fluid could be formed inside the hollow fiber. At this time, the display unit was bent, but the display unit was not broken, and therefore, the internal electrorheological fluid did not leak.

  This display unit is dispersed in a liquid containing water-dispersed polyurethane (trademark: HUX-381, manufactured by Asahi Denka Kogyo Co., Ltd.) having a weight ratio of 10% in terms of solid content with respect to the display unit as a binder component. A base fabric made of 66 filament yarns was needled and entangled to form a sheet. At this time, the thickness of the sheet was about 500 μm.

Next, the display unit formed into a sheet is sandwiched between transparent electrode plates from above and below, and a black standard plate attached to the Macbeth reflection densitometer RD-914 is provided as a light absorption layer on the back side of the lower electrode to obtain a display device. . The electrode plate is obtained by depositing ITO on one side of a PET (polyethylene terephthalate) film. When an electric field is not applied, it becomes cloudy. When a DC power supply is used, a positive charge is given to the upper electrode, a negative charge is given to the lower electrode, and the voltage difference between the electrodes is set to 1000 V, indicating a transparent state. The black standard plate behind the lower electrode was visualized.
The optical reflection image density at this time was measured with a Macbeth densitometer, and the ratio of the image density at the time of white turbidity (white display) and the image density at the time of transparency (black display) was obtained as a contrast ratio. Yes, it was almost the same as the print quality of newspapers.

It is a figure which shows the state of the display unit when the electric field is not applied. It is a figure which shows the state of a display unit when an electric field is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sealing hollow fiber, 2 ... Insulating liquid, 3 ... Insulating solid particle

Claims (3)

A display unit group in which a large number of display units are intertwined into a sheet,
The plurality of display units each have a light-transmitting hollow fiber sealed at both ends, and a fluid sealed in the hollow fiber, and the fluid disperses insulating solid particles in an insulating liquid. A display unit group comprising an electrorheological fluid comprising a dispersed liquid.   A display device comprising: the display unit group according to claim 1 disposed in a display area; and an electric field applying unit for applying an electric field to each display unit of the display unit group. Manufacturing a display unit group in which a large number of display units are dispersed in a liquid containing a binder component, spread on a mesh-like support, and the liquid is removed to entangle a large number of display units into a sheet. A method,
The plurality of display units each have a light-transmitting hollow fiber sealed at both ends, and a fluid sealed in the hollow fiber, and the fluid disperses insulating solid particles in an insulating liquid. A method for producing a display unit group, wherein the display unit group is an electrorheological fluid comprising a dispersed liquid.

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