JP2004157237A - Display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve display quality by enhancing a visibility of electrifying electrons electrophoresed on a display face side in an electrophoresis display (EPD) using a plurality of microcapsules sealing dispersion medium containing the electrifying particles. <P>SOLUTION: A display side substrate 20 having a recess part 24 storing the microcapsules 6 on a contact face side with the microcapsule 6. When the microcapsules 6 are sandwiched together with a rear face part substrate 30, the microcapsules 6 are stored in the recess part 24. Thus, the display side substrate 20 and the microcapsules 6 are brought into contact with each other in a wider range as compared with a case that the microcapsules 6 are sandwiched with the conventional flat substrate, and a change in a display contrast due to a visual angle method is suppressed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, a plurality of microcapsules enclosing a dispersion medium containing charged particles is sandwiched between a display-side substrate and a back-side substrate, and a predetermined voltage is applied between the two substrates to cause electrophoresis of the charged particles. The present invention relates to a display device that performs display according to the following.
[0002]
[Prior art]
2. Description of the Related Art There is known a display device in which charged particles dispersed in an insulating dispersion medium are electrophoresed on a display surface by the action of an electric field and collected, and display is performed based on optical characteristics (for example, color) of the dispersion medium and the charged particles. (Hereinafter referred to as "electrophoretic display"). Electrophoretic displays (EPDs) achieve lower power consumption and higher brightness than liquid crystal displays (LCDs), and have a memory function that can maintain the display state without power supply, thus realizing "electronic paper." It is drawing attention as a possible technology.
[0003]
FIG. 6 is a conceptual diagram showing an example of a basic structure of a (microcapsule type) electrophoretic display using microcapsules enclosing a dispersion medium containing charged particles. An electrophoretic display using microcapsules supports a plurality of microcapsules 6 having a diameter of about several tens to 100 μm in which a dispersion medium 4 and charged particles 2 are sealed with an appropriate binder 8 to form a light-transmitting flat plate. It has a structure in which the display side substrate 20 on which the electrodes 22 and 32 are respectively formed and the back side substrate 30 are sandwiched. In the figure, the observer U looks at the display-side substrate 20 from above. That is, the upper surface of the display-side substrate 20 becomes the display surface. Since the observer U views from the display side substrate 20, the electrode 22 must be a transparent electrode.
[0004]
The electrodes 22 and 32 are arranged, for example, orthogonally with one as X columns and the other as Y rows to form an XY orthogonal coordinate system. Therefore, the display control of the display pixel is defined by the XY coordinates. The number of electrodes and microcapsules 6 corresponding to one display pixel is appropriately set according to the size of the circuit structure of the electrodes 22 and 32 and the like.
[0005]
When a display pixel is to be in a display state, as shown in FIG. 6A, a voltage is applied such that the polarity of the electrode 22 of the pixel desired to be in the display state is opposite to that of the charged particles 2 (the electrode 22 in the figure). "+" And "-" symbols indicating the polarity of are shown.) When a voltage is applied and an electric field is generated in the microcapsule 6, the charged particles 2 move toward the display-side substrate 20 by electrophoresis, and the charged particles 2 become visible from the observer U. For example, if the charged particles 2 are colored with a white pigment and the dispersion medium 4 is colored with a black pigment, a white dot is displayed on a black background on the display surface in the case of FIG.
To return to the non-display state, a voltage is applied so that the electrode 22 has the same polarity as the charged particles 2 as shown in FIG. The charged particles 2 move toward the back side substrate 30 by electrophoresis and become invisible to the observer U. That is, the color of the dispersion medium 4 is observed at the position of the pixel, and the pixel is in a non-display state.
[0006]
As a method of improving the display quality and the like of an electrophoretic display using such microcapsules, for example, a low-cost, high-contrast display is realized by adding a third electrode orthogonal to either the X column or the Y row. There are things that I try to do. (For example, refer to Patent Document 1).
[0007]
[Patent Document 1]
JP 2001-122512 A
[Problems to be solved by the invention]
However, in the electrophoretic display using the microcapsules, the difference in the appearance of the charged particles 2 occurs between the contact portion A between the display-side substrate 20 and the microcapsules 6 and the peripheral region, and the display contrast depends on the viewing angle direction. And the display contrast when viewed from a direction inclined with respect to the display surface is reduced.
[0009]
That is, in the contact portion A, the distance from the display surface to the charged particles 2 is the smallest, and when the display is viewed from the vertical direction of the display surface, the color of the charged particles 2 is displayed with high contrast. However, since the outer shape of the microcapsule 6 has a curved surface, a gap S is generated between the microcapsule 6 and the display-side substrate 20 in the area around the contact portion A. Therefore, when the display is viewed from a direction inclined from the vertical direction of the display surface, the observer U sees the charged particles 2 through the binder 8 interposed in the gap S. A part of the light that enters from the display surface and is reflected by the charged particles 2 is absorbed or reflected by the binder 8 or the boundary surface thereof, so that the contrast is lower than that of the contact portion A.
[0010]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrophoretic display (EPD) using a plurality of microcapsules in which a dispersion medium containing charged particles is enclosed, on a display surface side. An object of the present invention is to improve the visibility of the electrophoresed charged particles, suppress a change due to the viewing angle method, and improve the display quality.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a plurality of microcapsules in which a dispersion medium containing charged particles is sealed are sandwiched between a display-side substrate and a back-side substrate, And a display device that performs display by applying a predetermined voltage between the back side substrate and electrophoresing the charged particles, at least, the contact surface of the display side substrate with the micro capsule, the micro capsule is It is characterized in that a recess that fits therein is formed.
[0012]
According to the first aspect of the present invention, a concave portion for accommodating the microcapsules is formed on a contact surface of the display-side substrate with the microcapsules. When the microcapsules are sandwiched between the display-side substrate and the back-side substrate, the microcapsules are accommodated in the concave portions. The outer shape of the microcapsule has a curved surface, and the microcapsule contained in the concave portion comes into contact with more places (areas) as compared with the contact with a flat surface. In the contact part, the charged particles can be viewed under good conditions in a wide viewing angle range because the charged particles do not need to be seen through the binder, and the change in display contrast due to the viewing angle method is suppressed, and the display quality is improved. Can be.
[0013]
It is to be noted that the concave portion is not limited to the display side substrate, and a concave portion for accommodating the microcapsule is formed on the contact surface of the back side substrate with the microcapsule as in the invention according to claim 2. It is good to be.
[0014]
Further, as in the invention described in claim 3, the recess may be formed by a plurality of parallel grooves. In this case, since the concave portion can be easily formed in the display side substrate, the production becomes easy. Further, since the microcapsules are arranged and sandwiched in a substantially parallel state in accordance with the arrangement of the electrodes in a matrix, the boundaries between the display pixels can be clarified.
[0015]
Further, as in the invention according to claim 4, the length in the width direction of the opening surface of the concave portion is set to a length between 0.5 times and 1.5 times the average particle diameter of the microcapsules. Is preferred.
[0016]
When the length in the width direction of the opening surface of the concave portion is at least 0.5 times the average particle diameter of the microcapsule, the microcapsule can be stably accommodated in the concave portion. Further, by setting the upper limit of the length to 1.5 times, a plurality of microcapsules can be prevented from being accommodated in one recess. Therefore, the contact relationship between the concave portion and the microcapsule can be made more effective in increasing the display contrast.
[0017]
Further, as in the invention according to claim 5, the concave portion in the display-side substrate or the back-side substrate may be formed by etching the substrate, and may be formed by existing chemical etching, The concave portion can be easily formed by applying a technique such as patterning.
[0018]
Further, as in the invention according to claim 6, at least one of the display-side substrate and the back-side substrate has a first member formed of a flat plate having electrodes formed thereon, and a second member having the recess formed therein. The electrodes may be joined to each other. In this case, since the electrodes are formed on a flat plate, the occurrence of disconnection of the electrodes can be reduced.
[0019]
In this case, the second member may be made of a plastic resin, and the concave portion may be formed along the outer shape of the microcapsule. For example, by pressing a second member made of a plastic resin against the microcapsule and curing the same, the concave portion can be easily formed in a shape along the outer shape of the microcapsule, and the contact state between the microcapsule and the substrate concave portion Can be further improved, and the display quality can be further improved.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
Next, a first embodiment to which the present invention is applied will be described with reference to FIGS. Note that a control mechanism and a control method for applying a voltage to the electrodes can be realized by the same technology as that of a known electrophoretic display (EPD), and a description thereof will be omitted.
[0021]
FIG. 1 is a conceptual sectional view showing an example of the configuration of the electrophoretic display according to the present embodiment. In the figure, the upper surface side of the display-side substrate 20 is a display surface, and the charged particles 2 are gathered on the display-side substrate 20 side by electrophoresis, so that the display state is visible to the observer U.
[0022]
As shown in the figure, the electrophoretic display according to the present embodiment is characterized in that the display-side substrate 20 and the back-side substrate 30 have concave portions 24 and 34 on the contact surface side with the microcapsules 6, respectively. . Then, the plurality of microcapsules 6 in which the dispersion medium 4 containing the charged particles 2 is sealed are supported by the binder 8, and the microcapsules 6 are accommodated in the concave portions 24 and 34 so as to be in close contact with each other. It is sandwiched between the side substrates 30.
[0023]
The charged particles 2 are particles made of a material capable of maintaining a charged state in the dispersion medium 4, and the shape thereof is not particularly limited. The color of the charged particles 2 may be the color of the material itself, or a colorant may be appropriately added or laminated on the particle surface. Specifically, for example, a material obtained by mixing a known coloring material with polyethylene, acrylic resin, or the like, titanium oxide, aluminum oxide, or the like is used.
[0024]
The dispersion medium 4 is an insulating liquid material that transmits visible light. For example, oils such as silicone oil, toluene, paraffinic hydrocarbons and the like are used.
The dispersion medium 4 is desirably a low-viscosity liquid so that the charged particles 2 can easily migrate. A surfactant for improving the dispersibility of the charged particles 2 and a charge control agent for controlling the chargeability may be appropriately added.
[0025]
The microcapsules 6 are made of a material having insulating properties and transmitting visible light. For example, resins such as acrylic and polyethylene terephthalate (PET), gelatin, and the like are used. Then, for example, the charged particles 2 and the dispersion medium 4 are encapsulated by using an interfacial polymerization method, an insolubilization reaction, a phase separation method, an interfacial precipitation method, or the like.
[0026]
The ratio of the charged particles 2 and the dispersion medium 4 enclosed in the microcapsules 6 is determined so that the color of the charged particles 2 when viewed in one direction can be visually recognized. The diameter is appropriately set according to the requirements of the display pixels. In the present embodiment, the microcapsules 6 are spherical, but may have shapes other than spherical.
[0027]
The display-side substrate 20 is formed by forming an electrode 22 on the upper surface of the concave portion 24 by a known chemical etching, patterning, or the like on a base substrate 26 having the concave portion 24.
[0028]
The base substrate 26 is made of, for example, a light-transmitting material such as glass, quartz, or a resin such as polyethylene terephthalate (PET), and the concave portion 24 is formed by known chemical etching, patterning, stamper, or the like.
[0029]
As a specific manufacturing method of the concave portion 24, for example, after forming a base plate 26 in the form of a base, the surface on which the concave portion 24 is to be formed is coated with a photoresist. Next, patterning is performed so as to form stripe-shaped openings at a pitch for forming the concave portions 24. Next, isotropic etching is performed to form a groove-shaped recess centered on the patterned stripe-shaped opening. Finally, the resist is removed. By appropriately performing patterning and etching and performing the process a suitable number of times, the concave portions 24 having various shapes can be formed.
[0030]
FIG. 2 is a conceptual perspective view illustrating an example of the arrangement of the concave portions 24 in the present embodiment. In the present embodiment, the concave portions 24 are formed as periodic wavefront-shaped grooves that are repeated at a predetermined pitch d. The length of the concave portion 24 in the opening surface width direction (corresponding to the pitch d in this case) is 0.5 to 1.5 times the average particle diameter of the microcapsules 6, and one microcapsule 6 is provided in one concave portion 24. Make sure it fits stably.
[0031]
In the back-side substrate 30, an electrode 32 paired with the electrode 32 is formed on a base substrate 36 having a recess 34 similar to the recess 24. In the case where the base substrate 36 and the electrode 32 are not observed from the back side, it is a matter of course that a light-impermeable material may be used.
[0032]
As an assembling method, for example, the following method is used.
First, the microcapsules 6 are mixed with a binder 8 such as a silicone resin or an acrylic resin, and applied on the back substrate 30. Preferably, it is applied thinly and uniformly so that the microcapsules 6 form one layer without overlapping. Next, the display-side substrate 20 is attached to the back-side substrate 30 on which the microcapsules 6 and the binder 8 have been applied so that the electrodes 22 and the electrodes 32 face each other, and is appropriately fixed with an adhesive or the like. At this time, if the microcapsules 6 are adhered by applying pressure to such an extent that a part of the microcapsules 6 is deformed, the microcapsules 6 are fitted so as to be in close contact with the concave portions 24 and 34, which is effective. Further, the arrangement of the microcapsules 6 may be facilitated to move along the concave portions 24 and 36 by applying a minute vibration at the time of bonding.
[0033]
FIG. 3 is a conceptual top view and a schematic sectional view showing a display state. In the conceptual top view, the outer periphery of each microcapsule 6 is indicated by a broken line. FIG. 3A shows the present embodiment, and FIG. 3B shows a case where the conventional display-side substrate 20 has no recess 24.
[0034]
As shown in FIG. 3A, according to the present embodiment, the microcapsules 6 are accommodated in the concave portions 24, and the gap S between the microcapsules 6 and the display-side substrate 20 is reduced. By contacting them in a larger range, the area ratio of the contact portion A occupied on the display surface where the charged particles 2 can be recognized under favorable conditions increases, and the portion where the charged particles 2 are viewed through the binder 8 interposed in the gap S is increased. The area ratio is relatively reduced. Therefore, display contrast can be improved.
[0035]
As described above, an embodiment has been described, but the application of the present invention is not limited to this, and addition, deletion, design change, and the like of components may be appropriately performed without departing from the spirit of the invention.
[0036]
For example, the concave portions 24 and 36 are not limited to the stripe shape, and may have a configuration in which hemispherical concave portions 24 and 36 are intermittently arranged as shown in FIG.
[0037]
Further, the concave portions 24 and 36 are formed integrally with the base substrates 26 and 36, but the present invention is not limited to this. For example, as shown in FIG. Is also good.
[0038]
Specifically, for example, after the electrodes 22 are formed on the base substrate 26, the concave array 25 of another component is bonded or welded to form the display-side substrate 20. Alternatively, conversely, the electrodes 22 may be formed on the display surface side (the surface without the concave portions) of the concave array 25 first, and the protective film corresponding to the base substrate 26 may be formed. The back side substrate 30 is prepared in the same manner. Then, the microcapsules 6 and the binder 8 are applied to the concave array 35 (the surface having the concave) of the back substrate 30, and the display substrate 20 is attached to assemble. In this case, since the electrodes 22 and 32 are formed on a plane, the design and forming process of the electrodes are facilitated.
[0039]
Further, the concave arrays 25 and 35 may be formed at the time of assembly. For example, the recessed arrays 25 and 35 are made of a plastic resin. First, the electrodes 22 are formed on the flat surface of the base substrate 26, and then the plastic resin is applied to the base substrate on which the electrodes 22 are formed to form the display-side substrate 20. . The back side substrate 30 is similarly configured. Then, the microcapsules 6 are applied to the back side substrate 30 in advance. Next, the display-side substrate 20 and the rear substrate 30 are bonded together with pressure so as to sandwich the microcapsules 6. As a result, the plastic resin flows and deforms according to the outer shape of the microcapsule 6 and fills the gap S.
[0040]
When the plastic resin is cured in this state, as a result, a concave array 35 closely contacting the outer shape of the microcapsule 6 is formed. As the plastic resin, for example, a thermoplastic resin may be used. In this case, the resin can be easily cured in a state where the concave array 35 is formed. Further, an ultraviolet curable resin may be used as the plastic resin, and the same effect can be obtained.
[0041]
【The invention's effect】
According to the present invention, the concave portion for accommodating the microcapsules is provided at least on the contact surface of the display-side substrate with the microcapsules. For this reason, when the microcapsules are held between the display-side substrate and the back-side substrate, the microcapsules can be accommodated in the concave portions. The outer shape of the microcapsule has a curved surface, and the microcapsule contained in the concave portion comes into contact with more places (areas) as compared with the contact with a flat surface. As a result, since the area for viewing the charged particles through the binder is reduced, the charged particles can be visually recognized under good conditions in a wide viewing angle range, and a change in display contrast due to the viewing angle method is suppressed, thereby improving display quality. Can be.
[0042]
Further, when the concave portion is formed by a plurality of parallel grooves, the concave portion can be easily formed on the display-side substrate, so that the production becomes easy. In addition, since the microcapsules are arranged and sandwiched in a substantially parallel state in accordance with the electrode arrangement in a matrix, the boundaries between display pixels can be clearly defined.
[0043]
Furthermore, the microcapsules can be stably accommodated in the concave portions by setting the length in the width direction of the opening surface of the concave portions to be 0.5 times or more the average particle diameter of the microcapsules. Further, by setting the upper limit of the length to 1.5 times, a plurality of microcapsules can be prevented from being accommodated in one recess. Therefore, the contact relationship between the concave portion and the microcapsule can be made more effective in increasing the display contrast.
[0044]
Further, by forming at least the display-side substrate by joining a flat plate on which the electrode is formed and a member with the concave portion, occurrence of disconnection of the electrode can be reduced. Further, by forming the member having the concave portion from a plastic resin and forming the concave portion along the outer shape of the microcapsule, the contact state between the microcapsule and the concave portion can be further improved, and the display quality can be further improved. Can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a display unit illustrating an example of a configuration of an electrophoretic display.
FIG. 2 is a conceptual perspective view illustrating an example of an arrangement of concave portions.
FIG. 3 is a conceptual top view and a schematic sectional view of a display state. (A) shows the present embodiment, and (b) shows a case where the display side substrate 20 has no concave portion 24.
FIG. 4 is a conceptual perspective view showing a modification of the arrangement of the concave portions.
FIG. 5 is a conceptual cross-sectional view showing an example of a configuration in a case where a recess is formed as a separate component.
FIG. 6 is a conceptual sectional view showing an example of a configuration of an electrophoretic display using microcapsules.
[Explanation of symbols]
2 Charged particle 4 Dispersion medium 6 Microcapsule 8 Binder 20 Display side substrate 22 Electrode 24 Depression 25 Depression array 26 Base substrate 30 Back side substrate 32 Electrode 34 Depression 35 Depression array 36 Base substrate A Contact part d Pitch S Gap U Observer

Claims (7)

A plurality of microcapsules in which a dispersion medium containing charged particles is enclosed are sandwiched between a display-side substrate and a back-side substrate, and a predetermined voltage is applied between the display-side substrate and the back-side substrate to form the charged particles. In a display device that performs display by performing electrophoresis,
A display device, characterized in that at least a recess for accommodating the microcapsules is formed on a contact surface of the display-side substrate with the microcapsules. The display device according to claim 1, wherein a concave portion for accommodating the microcapsule is formed on a contact surface of the back substrate with the microcapsule. The display device according to claim 1, wherein the recess is formed by a plurality of parallel grooves. The length in the width direction of the opening surface of the concave portion is a length between 0.5 times and 1.5 times the average particle diameter of the microcapsules. The display device according to claim 1. The display device according to claim 1, wherein the recess in the display-side substrate or the back-side substrate is formed by etching the substrate. At least one of the display-side substrate and the back-side substrate is formed by joining a first member formed of a flat plate having electrodes formed thereon and a second member having the recess formed therein. Item 6. The display device according to any one of Items 1 to 5. The display device according to claim 6, wherein the second member is made of a plastic resin, and the concave portion is formed along an outer shape of the microcapsule.

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