JP4562446B2 - Image display panel and image display device - Google Patents

Description

  The present invention forms a plurality of cells partitioned by partition walls between two opposing substrates at least one of which is transparent, encloses an image display medium in the cells, and applies an electric field to the image display medium. The present invention relates to an image display panel that displays an image by moving an image display medium, and an image display device using the same.

  2. Description of the Related Art Conventionally, image display devices using techniques such as an electrophoresis method, an electrochromic method, a thermal method, and a two-color particle rotation method have been proposed as image display devices that can replace liquid crystal (LCD).

  Compared to LCDs, these conventional technologies have advantages such as a wide viewing angle close to that of ordinary printed materials, low power consumption, and a memory function. It is considered as a technology that can be used for mobile phones, and is expected to expand to image display for mobile terminals, electronic paper, and the like. Particularly recently, an electrophoretic method in which a dispersion liquid composed of dispersed particles and a colored solution is encapsulated and disposed between opposing substrates has been proposed and is expected.

  However, the electrophoresis method has a problem that the response speed becomes slow due to the viscous resistance of the liquid because the particles migrate in the liquid. Furthermore, since particles with high specific gravity such as titanium oxide are dispersed in a solution with low specific gravity, it is easy to settle, and it is difficult to maintain the stability of the dispersed state, and there is a problem of lack of image repetition stability. . Even when microencapsulation is performed, the cell size is set to the microcapsule level, and the above-described drawbacks are hardly made to appear, and the essential problems are not solved at all.

  On the other hand, a method in which conductive particles and a charge transport layer are incorporated into a part of a substrate without using a solution is proposed instead of an electrophoresis method using behavior in a solution (see, for example, Non-Patent Document 1). ). However, the structure is complicated because the charge transport layer and further the charge generation layer are arranged, and it is difficult to inject the charges into the conductive particles.

As one method for solving the various problems described above, a cell isolated from each other by a partition is formed between two opposing substrates, at least one of which is transparent, and an image display medium is sealed in the cell. 2. Description of the Related Art An image display panel that displays an image by applying an electric field to an image display medium and moving the image display medium is known.
趙 Kuniori and three others, “New Toner Display Device (I)”, July 21, 1999, Annual Meeting of the Imaging Society of Japan (83 times in total) “Japan Hardcopy'99” Proceedings, p.249-252

  However, in these image display panels, the image display medium is difficult to move at the corners of the cells defined by the partition walls, and even if the image display medium was moving at the beginning, the image display medium gradually becomes stationary. There has been a problem in that the phenomenon that the film stays attached to the partition wall and stops moving, and the image contrast is deteriorated, which is insufficient in terms of durability for repeated use. One of the causes is that the image display medium in the cell formed by the partition wall has an acting force from the surrounding environment, particularly the partition wall, and the corner portion of the cell is a narrow space surrounded by two partition walls. Therefore, it can be considered that a larger acting force is received from the partition wall.

  The object of the present invention is to eliminate the above-mentioned problems, facilitate the movement of the image display medium at the corner of the cell, have excellent image contrast from the beginning, and do not decrease the image contrast even when used repeatedly. An object of the present invention is to provide an excellent and inexpensive image display panel and image display apparatus.

  The image display panel of the present invention forms a plurality of cells partitioned by partition walls between two opposing substrates, at least one of which is transparent, encloses the image display medium in the cells, and the electric field is applied to the image display medium. In the image display panel for displaying the image by moving the image display medium, the structure is characterized in that the intersection portion of the partition walls provided for defining the cells is a space. .

  As a preferred example of the image display panel of the present invention, at the position of the intersection of the partition walls, at least the partition walls defining the same cell are provided with a gap therebetween, and the image display medium is a group of particles or It may be a powder fluid.

  The image display apparatus of the present invention is characterized by mounting the image display panel having the above-described configuration.

  In the present invention, when the partition wall defining the cell is provided on the substrate, the intersection part of the partition wall is made to be a space so that the corner part of the cell is a space, so that the image display medium in the vicinity of the cell corner is separated from the partition wall. The acting force received can be reduced, and the image display medium can be easily moved. As a result, it is possible to obtain an image display panel and an image display device that are excellent in image contrast from the beginning and that do not deteriorate even when used repeatedly, and that have excellent durability.

  First, the basic configuration of the image display panel of the present invention will be described. In the image display panel of the present invention, an electric field is applied to a chargeable image display medium (particle group or powder fluid) sealed between two opposing substrates. The image display medium is attracted by the electric field force, the Coulomb force, or the like along the applied electric field direction, and the image display medium is reciprocated by a change in the electric field direction due to the potential switching, thereby displaying an image. Therefore, it is necessary to design the image display panel so that the image display medium moves uniformly and can maintain stability during repetition or storage. Here, the force applied to the particles or powder fluid used as the image display medium is not only the force attracted by the Coulomb force between the particles or powder fluid, but also the image power, intermolecular force, liquid crosslinking force with the electrode or substrate. , Gravity and so on.

An example of the image display panel of the present invention will be described with reference to FIGS.
In the example shown in FIG. 1, two or more kinds of image display media 3 having different colors (here, white particles 3W and black particles 3B are shown) are applied to the substrates 1 and 2 according to the electric field applied from the outside of the substrates 1 and 2. 2, the black particles 3 </ b> B are visually recognized by the observer and black display is performed, or the white particles 3 </ b> W are visually recognized by the observer and white display is performed. A partition cell 4 is provided between the substrates 1 and 2 in a lattice shape, for example, to define a display cell.
In the example shown in FIG. 2, an image display medium 3 having two or more different colors (here, white particles 3 </ b> W and black particles 3 </ b> B) are provided between an electrode 5 provided on the substrate 1 and an electrode 6 provided on the substrate 2. Depending on the electric field generated by applying a voltage between them, the substrate is moved perpendicularly to the substrates 1 and 2 and the black particles 3B are visually recognized by the observer to display black, or the white particles 3W are observed by the observer. Is displayed in white. A partition cell 4 is provided between the substrates 1 and 2 in a lattice shape, for example, to define a display cell.
In the example shown in FIG. 3, according to the electric field generated by applying a voltage between the electrode 5 and the electrode 6 provided on the substrate 1, one kind of color particle 3 (here, white particle 3W). The white particles 3W are moved in the direction parallel to the substrates 1 and 2 and the white particles 3W are visually recognized by the observer, or the color of the electrode 6 or the substrate 1 is visually recognized by the observer. The color is displayed. A partition cell 4 is provided between the substrates 1 and 2 in a lattice shape, for example, to define a display cell.
The above description can be similarly applied to the case where the white particles 3W are replaced with the white powder fluid and the black particles 3B are replaced with the black powder fluid.

  The image display panel and the image display device according to the present invention are characterized in that a portion where the partition walls 4 defining the cells intersect is left as a space, and the cell does not have a corner portion for the image display medium 3. is there. The image display panel of the present invention will be described below.

  FIG. 4 is a view showing an example of a partition wall in the image display panel of the present invention. In the example shown in FIG. 4, an example of two cells is shown for convenience of explanation. However, in an actual image display panel, the panel is composed of a larger number of cells. In the example shown in FIG. 4, a structure in which the intersection portion 11 of the partition wall 4 provided to define the cell is a space, preferably the partition wall 4 that defines at least the same cell at the position of the intersection portion 11 of the partition wall 4. A structure is adopted in which the gaps 12 are provided between each other.

  The shape of the partition wall 4 in the image display panel of the present invention is not particularly limited, and can be appropriately selected according to the size of the panel or cell as long as the intersection portion 11 is a space. Preferably there is. First, due to strength restrictions, the width of the partition wall 4 is preferably 2 to 100 μm, more preferably 3 to 50 μm. The length of each partition wall 4 (related to the cell size) is preferably 200 to 500 μm. The interval between the gaps 12 of the partition walls 4 is preferably 2 to 50 μm, more preferably 2 to 20 μm. If the gap 12 is smaller than 2 μm, there is no effect on the image display medium 3 as the gap 12 (spatial portion 11), and if it exceeds 50 μm, the image display medium storage function (uneven distribution prevention effect) of the partition 4 is impaired. This is not preferable. In addition, the partition walls may be provided on both substrates, and the tops of the partition walls may be overlapped to overlap the substrates, or may be provided only on one substrate.

  As shown in FIG. 5, the display cell formed by the partition walls 4 is exemplified by a square shape, a triangular shape, a line shape, a circular shape, and a hexagonal shape as viewed from the substrate plane direction. And a mesh shape. It is better to make the portion corresponding to the cross section of the partition wall visible from the display side (the area of the frame portion of the display cell) as small as possible, and the sharpness of the image display increases. Here, examples of the method for forming the partition walls 4 include a screen printing method, a sand blast method, a photolithography method, and an additive method. Of these, the photolithography method using a resist film is preferably used. In any method, the present invention can be suitably used. In the example shown in FIG. 5, for the sake of explanation, an example in which the partition wall 4 is also provided in the intersection portion 11 of the partition wall 4 is shown. However, in the present invention, this intersection portion 11 is a space. Nor.

  FIGS. 6A to 6D are diagrams for explaining an example of the image display panel of the present invention. Although the cell is composed of 3 × 3, an actual image display display panel is composed of a larger number of cells. In the examples shown in FIGS. 6A to 6D, the partition walls 4 each having the intersection portion 11 as a space are shown, and an example in which square cells are arranged in a lattice shape is shown. The shape and arrangement method of the cells are not limited to these, and the various shapes and arrangements described above can be adopted. FIGS. 6A and 6B show examples in which no electrode is provided, and FIGS. 6C and 6D show examples in which the line electrodes 5-1 and 6-1 are combined with the partition wall 4 in a matrix form. 6C and 6D, the pixel formed by the line electrode 5-1 and the line electrode 6-1 and the cell defined by the partition are made to correspond one-to-one. May be.

  In the example shown in FIGS. 6A and 6C, all the intersection portions 11 of the partition walls 4 forming one cell are made space, whereas FIGS. In the example shown in d), the left and right partition walls 4 of the partition walls 4 forming one cell are not provided with a space portion, but the partition walls defining one same cell are provided with a space in between. Become. Further, in the examples shown in FIGS. 6A to 6D, examples of the outermost peripheral part of the partition wall are shown as they are on the left side of the arrow in the figure, and the outermost peripheral part of the partition is shown on the right side of the arrow in the figure. The partition outermost periphery processing part which has arrange | positioned the sealing material 13 to the part is shown. As shown in FIGS. 6 (a) to 6 (d), it is preferable to enclose and seal the partition wall space located at the outermost periphery with a sealing material 13 in order to block outside air. 6C corresponds to Example 1 below, and FIG. 6D corresponds to Example 3 below.

  In the image display panel of the present invention, the method of filling the cells with the image display medium 3 may be a method of scraping the image display medium 3 placed on the substrate or a method of spraying the image display medium 3 from above the substrate. Good. In any case, the image display medium 3 placed on the top of the partition wall 4 is dropped in the cell or in the gap (space portion) of the partition wall 4 so as to be worn out. This makes it possible to fill easily and uniformly as compared with the conventional case where there is no gap between the partition walls. Further, the image display medium 3 entering the gap (space portion) of the partition wall 4 does not contribute to image display, but does not impair image display performance at all. Further, after the image display medium 3 is filled, the substrates are bonded together. The gap between the partition walls at the outermost periphery of the cell is sealed with an adhesive having a sealing function before the substrates are bonded together.

  FIGS. 7A and 7B are diagrams for explaining another example of the image display panel of the present invention. In the examples shown in FIGS. 7A and 7B, hexagonal cells and (pixel) electrodes are provided in a one-to-one correspondence. In the example shown in FIG. 7A, the electrode 5 is also provided in the space portion provided in the intersection portion 11 located at both ends of the partition wall 4, but as shown in FIG. It is also possible to make the electrode smaller than the cell so that the electrode 5 is not provided in this space portion. A line-shaped electrode can also be arrange | positioned with respect to a hexagonal cell. In this case, the cell and the pixel do not correspond one-to-one, and the electrode 5 is also provided in the space portion provided at the intersection portion 11 of the partition wall 4. Further, in the example shown in FIG. 7A, the electrode 5 provided on the substrate extends to the space provided at the intersection portion 11 of the partition wall 4 so that an electric field can be applied to the image display medium 3 in the cell as much as possible. It is provided to protrude.

  FIG. 8 is a view for explaining still another example of the image display panel of the present invention. In the example shown in FIG. 8, an example after the front substrate 1 and the rear substrate 2 are superposed together with the example of the line electrode 5-2 on the rear substrate 2 side and the example of the line electrode 6-2 on the front substrate 1 side. Is shown. In this example, line electrodes 5-2 and 6-2 are arranged in a matrix shape with respect to a square cell so that the cells and the pixels correspond to each other on a one-to-one basis. As shown in FIG. 8, if there is no partition 4 and it is a space, even the image display medium 3 in the vicinity of the intersection portion 11 where the line electrodes 5-2 and 6-2 are not arranged acts from the partition 4. Since there is no force, it can move even with a weak electric field.

  Hereafter, each member which comprises the image display panel of this invention is demonstrated.

  As for the substrate, at least one substrate is the transparent substrate 1 from which the color of the image display medium can be confirmed from the outside of the panel, and a material having high visible light transmittance and good heat resistance is preferable. The substrate 2 may be transparent or opaque. Examples of substrate materials include polymer sheets such as polyethylene terephthalate, polyethersulfone, polyethylene, polycarbonate, polyimide, and acrylic, flexible materials such as metal sheets, and flexible materials such as glass and quartz. There are no inorganic sheets. The thickness of the substrate is preferably 2 to 5000 μm, more preferably 5 to 2000 μm. If it is too thin, it will be difficult to maintain the strength and the uniformity of the distance between the substrates, and if it is thicker than 5000 μm, it will be a thin image display panel. Is inconvenient.

  Electrode forming materials for electrodes provided as necessary include metals such as aluminum, silver, nickel, copper, and gold, conductive metal oxides such as ITO, indium oxide, conductive tin oxide, and conductive zinc oxide, polyaniline , Conductive polymers such as polypyrrole and polythiophene are exemplified, and are appropriately selected and used. As a method for forming an electrode, a method of forming the above-described materials into a thin film by sputtering, vacuum deposition, CVD (chemical vapor deposition), coating, or the like, or mixing a conductive agent with a solvent or a synthetic resin binder. The method of apply | coating is used. The electrode provided on the viewing side substrate needs to be transparent, but the electrode provided on the back side substrate does not need to be transparent. In any case, the above-mentioned material that is conductive and capable of pattern formation can be suitably used. Note that the electrode thickness is not particularly limited as long as the conductivity can be secured and the light transmittance is not hindered, and is preferably 3 to 1000 nm, preferably 5 to 400 nm. The material and thickness of the electrode provided on the back side substrate are the same as those of the electrode provided on the viewing side substrate described above, but need not be transparent. In this case, the external voltage input may be superimposed with direct current or alternating current.

  Next, the powder fluid as an image display medium used in the image display panel of the present invention will be described. As for the name of the powder fluid as the image display medium of the present invention, the present applicant has obtained the right of “Electronic Powder Fluid (registered trademark)”.

  The “powder fluid” in the present invention is a substance in an intermediate state of both fluid and particle characteristics that exhibits fluidity by itself without borrowing the force of gas or liquid. For example, liquid crystal is defined as an intermediate phase between a liquid and a solid, and has fluidity that is a characteristic of liquid and anisotropy (optical properties) that is a characteristic of solid (Heibonsha: Encyclopedia) . On the other hand, the definition of particle is an object with a finite mass even if it is negligible, and is said to be affected by gravity (Maruzen: Physics Encyclopedia). Here, even in the case of particles, there are special states of gas-solid fluidized bed and liquid-solid fluids. When gas is flowed from the bottom plate to the particles, upward force is applied to the particles according to the velocity of the gas. Is a gas-solid fluidized bed that is in a state where it can easily flow when it balances with gravity, and it is also called a liquid-solid fluidized state that is fluidized by a fluid (ordinary) Company: Encyclopedia). As described above, the gas-solid fluidized bed body and the liquid-solid fluid are in a state of using a gas or liquid flow. In the present invention, it has been found that a substance in a state of fluidity can be produced specifically without borrowing the force of such gas and liquid, and this is defined as powder fluid.

  That is, the pulverulent fluid in the present invention is in an intermediate state having both the characteristics of particles and liquid, as in the definition of liquid crystal (liquid and solid intermediate phase), and is the characteristic of the above-mentioned particles. It is a substance that is extremely unaffected and exhibits a unique state with high fluidity. Such a substance can be obtained in an aerosol state, that is, a dispersion system in which a solid or liquid substance is stably suspended as a dispersoid in a gas, and the solid substance is used as a dispersoid in the image display device of the present invention. Is.

The image display panel of the present invention is a powder fluid exhibiting high fluidity in an aerosol state in which solid particles are stably suspended as a dispersoid, for example, as an image display medium between two opposing substrates, at least one of which is transparent. Such a powder fluid can be easily and stably moved by a Coulomb force by applying a low voltage.
As described above, for example, the powder fluid used in the present invention is a substance in an intermediate state between fluid and particles, which exhibits fluidity by itself without borrowing the force of gas or liquid. This powder fluid can be in an aerosol state in particular, and in the image display device of the present invention, a solid substance is used in a state of relatively stably floating as a dispersoid in the gas.

  Next, the particles as the image display medium used in the image display panel of the present invention will be described. The particles can contain a charge control agent, a colorant, an inorganic additive, and the like, if necessary, in the resin as the main component, as in the conventional case. Examples of resins, charge control agents, colorants, and other additives will be given below.

  Examples of the resin include urethane resin, urea resin, acrylic resin, polyester resin, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, acrylic fluororesin, silicone resin, acrylic silicone resin, epoxy resin, polystyrene resin, styrene Acrylic resin, polyolefin resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, fluororesin, polycarbonate resin, polysulfone resin, polyether resin, polyamide resin and the like can be mentioned, and two or more kinds can be mixed. In particular, acrylic urethane resin, acrylic silicone resin, acrylic fluororesin, acrylic urethane silicone resin, acrylic urethane fluororesin, fluororesin, and silicone resin are suitable from the viewpoint of controlling the adhesive force with the substrate.

  The charge control agent is not particularly limited. Examples of the negative charge control agent include salicylic acid metal complexes, metal-containing azo dyes, metal-containing oil-soluble dyes (including metal ions and metal atoms), and quaternary ammonium salt systems. Examples thereof include compounds, calixarene compounds, boron-containing compounds (benzyl acid boron complexes), and nitroimidazole derivatives. Examples of the positive charge control agent include nigrosine dyes, triphenylmethane compounds, quaternary ammonium salt compounds, polyamine resins, imidazole derivatives, and the like. In addition, metal oxides such as ultrafine silica, ultrafine titanium oxide, ultrafine alumina, nitrogen-containing cyclic compounds such as pyridine and derivatives and salts thereof, various organic pigments, resins containing fluorine, chlorine, nitrogen, etc. are also charged. It can also be used as a control agent.

  As the colorant, various organic or inorganic pigments and dyes as exemplified below can be used.

Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon and the like.
Examples of blue colorants include C.I. I. Pigment blue 15: 3, C.I. I. Pigment Blue 15, Bituminous Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Metal-free Phthalocyanine Blue, Phthalocyanine Blue Partial Chlorides, Fast Sky Blue, Indanthrene Blue BC and the like.
Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, Alizarin Lake, Brilliant Carmine 3B, C.I. I. Pigment Red 2 etc.

Yellow colorants include chrome yellow, zinc yellow, cadmium yellow, yellow iron oxide, mineral first yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment Yellow 12 etc.
Examples of green colorants include chrome green, chromium oxide, pigment green B, C.I. I. Pigment Green 7, Malachite Green Lake, Final Yellow Green G, etc.
Examples of the orange colorant include red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK, C.I. I. Pigment Orange 31 etc.
Examples of purple colorants include manganese purple, first violet B, and methyl violet lake.
Examples of white colorants include zinc white, titanium oxide, antimony white, and zinc sulfide.

  Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white. Examples of various dyes such as basic, acidic, disperse, and direct dyes include nigrosine, methylene blue, rose bengal, quinoline yellow, and ultramarine blue.

Examples of inorganic additives include titanium oxide, zinc white, zinc sulfide, antimony oxide, calcium carbonate, lead white, talc, silica, calcium silicate, alumina white, cadmium yellow, cadmium red, cadmium orange, titanium yellow, Examples include bitumen, ultramarine blue, cobalt blue, cobalt green, cobalt violet, iron oxide, carbon black, manganese ferrite black, cobalt ferrite black, copper powder, and aluminum powder.
These pigments and inorganic additives can be used alone or in combination. Of these, carbon black is particularly preferable as the black pigment, and titanium oxide is preferable as the white pigment.

  The particles used as the image display medium used in the image display panel of the present invention have an average particle diameter d (0.5) in the range of 0.1 to 50 μm, and are preferably uniform and uniform. If the average particle diameter d (0.5) is larger than this range, the display is not clear, and if it is smaller than this range, the cohesive force between the particles becomes too large, which hinders the movement of the particles.

Furthermore, in the present invention, regarding the particle size distribution of each particle, the particle size distribution Span represented by the following formula is less than 5, preferably less than 3.
Span = (d (0.9) −d (0.1)) / d (0.5)
(However, d (0.5) is a numerical value expressing the particle diameter in μm that 50% of the particles are larger than this and 50% is smaller than this, and d (0.1) is a particle in which the ratio of the smaller particles is 10%. (Numerical value expressed in μm, and d (0.9) is a numerical value expressed in μm for a particle diameter of 90% or less.)
By keeping Span within a range of 5 or less, the size of each particle is uniform, and uniform particle movement becomes possible.

  Furthermore, regarding the correlation between the particles, the ratio of d (0.5) of the particles having the minimum diameter to d (0.5) of the particles having the maximum diameter among the used particles is set to 50 or less, preferably 10 or less. It is essential.

The particle size distribution and the particle size can be obtained from a laser diffraction / scattering method or the like. When laser light is irradiated onto particles to be measured, a light intensity distribution pattern of diffracted / scattered light is spatially generated, and this light intensity pattern has a corresponding relationship with the particle diameter, so that the particle diameter and particle diameter distribution can be measured. .
Here, the particle size and particle size distribution in the present invention are obtained from a volume-based distribution. Specifically, using a Mastersizer2000 (Malvern Instruments Ltd.) measuring instrument, particles are introduced into a nitrogen stream, and the attached analysis software (software based on volume-based distribution using Mie theory) The diameter and particle size distribution can be measured.

  The charge amount of the image display medium naturally depends on the measurement conditions, but the charge amount of the image display medium in the image display panel is almost the initial charge amount, the contact with the partition wall, the contact with the substrate, and the charge decay with the elapsed time. In particular, it was found that the saturation value of the charging behavior of the image display medium is the dominant factor.

Furthermore, when using a particle group or powdered fluid as an image display medium in the present invention, it is important to manage the gas in the voids surrounding the image display medium between the substrates, which contributes to improved display stability. Specifically, it is important that the relative humidity at 25 ° C. is 60% RH or less, preferably 50% RH or less, more preferably 35% RH or less with respect to the humidity of the gas in the gap.
In FIG. 1 to FIG. 3, this void portion is an area occupied by the electrodes 5 and 6, the image display medium (particle group or powder fluid 3), and an area occupied by the partition wall 4 from the portion sandwiched between the opposing substrates 1 and 2. A gas portion that is in contact with a so-called image display medium, excluding a portion (including a space portion) and a device seal portion, is meant.
The gas in the gap is not limited as long as it is in the humidity region described above, but dry air, dry nitrogen, dry argon, dry helium, dry carbon dioxide, dry methane, and the like are preferable. This gas needs to be sealed in the apparatus so that the humidity is maintained. For example, the image display medium is filled and the substrate is assembled in a predetermined humidity environment. It is important to apply a sealing material and a sealing method to prevent the above.

The distance between the substrates in the image display panel of the present invention is not limited as long as the image display medium can be moved and the contrast can be maintained, but is usually adjusted to 10 to 500 μm, preferably 10 to 200 μm.
The volume occupancy of the image display medium in the space between the opposing substrates is preferably 5 to 70%, more preferably 5 to 60%. If it exceeds 70%, the movement of the image display medium is hindered. If it is less than 5%, the contrast tends to be unclear.

  Hereinafter, the present invention and a comparative example will be shown to specifically describe the present invention, but the present invention is not limited to the following. In addition, the panel for image display of an Example and a comparative example evaluated what produced by the following method according to the following reference | standard.

“Production of image display panels”
First, a transparent glass substrate (7 cm × 7 cm □) with an ITO electrode was prepared as a front substrate and a back substrate, and a partition was formed on one substrate by ribs having a height of 50 μm.
The rib is formed by the following procedure.
The paste is prepared by preparing glass powder obtained by melting, cooling and grinding SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , Bi ₂ O ₃ , ZnO as inorganic powder, and thermosetting epoxy resin as resin. A paste adjusted to a viscosity of 12000 cps with a solvent was prepared. Next, the paste was applied on the entire surface of the substrate, heated and cured at 150 ° C., and this coating to curing was repeated to adjust the thickness (corresponding to the height of the partition wall) to 50 μm. Next, a dry photoresist was attached, and a mask was formed so that a desired partition wall pattern was formed by exposure to etching. Next, excess portions were removed by sandblasting so as to obtain a predetermined partition wall shape, and a partition wall having a desired shape was formed.

  Next, two types of particle groups (particle group A and particle group B) having different colors and charging characteristics are prepared and filled in the cell. The substrate on which the partition walls are formed is transferred into a dry container having a humidity of 40% RH or less. First, the particle group A is dispersed as a first particle group in the container from a nozzle provided in the upper part of the container. Particle group A was filled by spraying into cells on a substrate placed underneath. Subsequently, the particle group B is dispersed into the container from another nozzle provided in the upper part of the container as the second particle group, and the cell on the substrate placed in the lower part of the container (the particle group A is already filled). The particle group A was overlaid and packed by spraying. The packing arrangement amount of the particle group A and the particle group B was set to the same volume amount, and the volume occupation ratio of both particle groups with respect to the space between the substrates formed by bonding the two substrates was adjusted to 25 vol%. Next, the other substrate is superimposed on the substrate in which the particle group is filled and arranged in the cell, and the outer peripheral portion around the substrate is bonded and sealed with an epoxy adhesive to enclose the particle group, and an image display panel Was made.

"Evaluation of display function"
Black-white display was repeated by applying a voltage of 100 V to the display device incorporating the manufactured display panel and inverting the potential. The display function was evaluated by observing the display surface during white display and black display with an optical microscope to examine the uniformity of the image display medium (particle group) in the cell near the intersection of the partition walls. The initial measurement was repeated 100000 times using a Macbeth densitometer as a reflection image densitometer. Here, the contrast ratio is: contrast ratio = reflection density during black display / reflection density during white display.

"Image display medium"
In Examples and Comparative Examples, a black and white two-color particle group (particle group A, particle group B) having different charging characteristics was used as an image display medium.
Particle group A consists of acrylic urethane resin EAU53B (manufactured by Asia Industries) / IPDI crosslinking agent Excel Hardener HX (manufactured by Asia Industries), 4 parts by weight of carbon black (MA100 Mitsubishi Chemical Corporation), charge control. 2 parts by weight of the agent Bontron N07 (Orient Chemical Co., Ltd.) is added, kneaded, pulverized with a jet mill, and further mechanical impact force is applied using a hybridizer device (Nara Machinery Co., Ltd.). In addition, classification was made after making it approximately spherical. The produced particle group A was an approximately spherical and negatively charged black particle group having an average particle diameter of 9.1 μm.

  Particle group B was prepared by dissolving 0.5 parts by weight of AIBN (azobisisobutyronitrile) in 80 parts by weight of tertiary butyl methacrylate monomer and 20 parts by weight of 2- (diethylamino) ethyl methacrylate. The liquid obtained by dispersing 20 parts by weight of titanium oxide made lipophilic by treatment with an agent is suspended and polymerized in an aqueous solution of 0.5% surfactant (sodium lauryl sulfate), filtered, dried. Then, it was prepared using a classifier (MDS-2: Nippon Numatic Industries). The produced particle group B is a positively charged spherical white particle having an average particle diameter of 8.5 μm.

<Example 1>
A display panel is manufactured by the above-described procedure using a substrate on which barrier ribs are formed so that cells are arranged in a square lattice pattern and all intersections of the barrier ribs are spaces. Evaluated. The results are shown in Table 1.

<Example 2>
A display panel is manufactured in the above-described procedure using a substrate on which partition walls are formed so that the cells have a hexagonal and honeycomb-like arrangement, and all the intersections of the partition walls are spaces. Evaluated. The results are shown in Table 1.

<Example 3>
A substrate in which the cells are square and arranged in a lattice pattern, and the partition wall is formed at the intersection of the partition walls so that there is a gap between the partition walls defining the same cell (see FIG. 6D). ) Was used to produce a display panel according to the procedure described above, and the display function was evaluated. The results are shown in Table 1.

<Comparative Example 1>
The partition walls were formed so that the cells were square and arranged in a lattice pattern, and a display panel was prepared by the above-described procedure using the substrate in which the intersections of the partition walls were left as they were, and the display function was evaluated. The results are shown in Table 1.

<Comparative example 2>
The partition walls were formed so that the cells had a hexagonal and honeycomb-like arrangement, and the display panel was prepared by the above-described procedure using the substrate in which the intersections of the partition walls were left as they were, and the display function was evaluated. The results are shown in Table 1.

  From the results of Table 1, it can be seen that in Examples 1 to 3 in which all the image display media (particles) in the cell are easy to move, a good state is maintained even after 100,000 times from the initial stage. Further, in Comparative Example 1 and Comparative Example 2 where the cell has a partition at the corner portion, it is inferred that there is a portion where the contrast ratio is small even in the initial stage and the image display medium (particles) does not move.

  Furthermore, when white solid display with an optical microscope, the inside of the cell in the vicinity of the partition intersection portion at the time of black solid display was observed, in Example 1 to Example 3 where the partition intersection portion is a space, no different color particles were seen, In the comparative example 1 and the comparative example 2 in which the same color particles are uniformly moved to the observation substrate side in the cell but the intersection portion is not a space and is a partition, the surrounding particles are in the vicinity of the partition intersection in the cell. Different color particles were observed, and the color of the particles coming to the observation substrate side was uneven.

  The image display panel according to the present invention includes display units for mobile devices such as notebook computers, PDAs, mobile phones, and handy terminals, electronic papers such as electronic books and electronic newspapers, bulletin boards such as signboards, posters, and blackboards, calculators, and home appliances. It is suitably used for display parts for automobile supplies, card display parts such as point cards and IC cards, electronic advertisements, electronic POPs, electronic price tags, electronic musical scores, and display parts for RF-ID devices.

It is a figure which shows an example of the panel for image display used as the object of this invention. It is a figure which shows the other example of the image display panel used as the object of this invention. It is a figure which shows the further another example of the image display panel used as the object of this invention. It is a figure which shows an example of the partition in the image display panel of this invention. It is a figure which shows an example of the shape of the partition in the image display panel of this invention. (A)-(d) is a figure for demonstrating an example of the image display panel of this invention, respectively. (A), (b) is a figure for demonstrating the other example of the image display panel of this invention, respectively. It is a figure for demonstrating the further another example of the image display panel of this invention.

Explanation of symbols

1, 2 Substrate 3 Image display medium (particle or powder fluid)
3W white particles (white powder fluid)
3B Black particles (black powder fluid)
4 Partition 5, 6 Electrode 5-1, 6-1, 5-2, 6-2 Line electrode 11 Intersection part 12 Gap 13 Sealing material

Claims (4)

  An image display medium is formed by forming a plurality of cells partitioned by partition walls between two opposing substrates at least one of which is transparent, enclosing the image display medium in the cells, and applying an electric field to the image display medium An image display panel for displaying an image by moving a cell having a structure in which an intersection portion of partition walls provided for defining a cell is a space.   2. The image display panel according to claim 1, wherein at the position of the intersection of the partition walls, partition walls defining at least the same cell are provided with a gap therebetween.   The image display panel according to claim 1, wherein the image display medium is a particle group or a powder fluid. An image display device comprising the image display panel according to claim 1.

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