JP2006058643A - Panel for image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a panel for image display capable of obtaining a desired contrast ratio, by optimizing the voltage waveform applied to one display unit. <P>SOLUTION: In the panel for image display, the image display medium is enclosed between two sheets of substrates of which at least one sheet is transparent, the image display medium is moved by applying an electric field to the image display medium, and thereby, an image is displayed, the inclination of a voltage applied per one display unit is set to be 200/sec or higher (first invention), the inclination of a voltage rise at the voltage at which the inclination of a driving voltage/density (reflectance) becomes the largest is set to 1,000/sec or higher (second invention) or the product of area per one display unit and resistance per one display unit is set to 2,500 Ωm<SP>2</SP>or lower (third invention). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image display panel for displaying an image by moving an image display medium by enclosing the image display medium between two substrates, at least one of which is transparent, and applying an electric field to the image display medium. It is.

  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, after encapsulating the image display medium between two opposing substrates, at least one of which is transparent, or by forming cells isolated from each other by a partition wall, An image display panel that displays an image by enclosing an image display medium in a cell and then applying an electric field to the image display medium to move 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 the image display panel described above, in order to apply an electric field to the image display medium, a voltage is applied to the electrode provided on the substrate to display an image. However, the waveform of the voltage applied to one display unit electrode In some cases, the required contrast ratio cannot be obtained.

  An object of the present invention is to provide an image display panel capable of obtaining a required contrast ratio by solving the above-described problems and optimizing a voltage waveform applied to one display unit.

In the image display panel according to the first aspect of the present invention, an image display medium is sealed between two substrates, at least one of which is transparent, and an electric field is applied to the image display medium, thereby moving the image display medium. In the image display panel for displaying an image, the gradient of the voltage applied to one display unit is 200 / sec or more.
Here, the voltage gradient means the reciprocal of the time to reach the drive voltage.

  The image display panel according to the second invention of the present invention moves the image display medium by enclosing the image display medium between two substrates, at least one of which is transparent, and applying an electric field to the image display medium. In the image display panel for displaying an image, the rising slope of the voltage at a voltage having the largest driving voltage / density (or reflectance) slope is 1000 / sec or more.

Furthermore, the image display panel according to the third aspect of the present invention moves the image display medium by enclosing the image display medium between two substrates, at least one of which is transparent, and applying an electric field to the image display medium. In the image display panel for displaying an image, the product of the area of one display unit and the resistance applied to one display unit is 2500 Ωm ² or less.

  In addition, as a suitable example of the panel for image display which concerns on 1st invention-3rd invention of this invention, an image display medium may consist of a particle group or a powder fluid.

In the present invention, the drive voltage for applying an electric field to the image display medium is applied by (1) so that the slope of the drive voltage applied to one display unit is 200 / sec or more (first). (Invention), (2) by applying the drive voltage / density (or reflectance) so that the slope of the drive voltage at a voltage having the largest slope is 1000 / sec or more (second invention), or (3) Since the product of the area of one display unit and the resistance applied to one display unit is 2500 Ωm ² or less (third invention), the image display panel is driven in any case. Therefore, an optimum driving voltage waveform can be realized, and as a result, a required contrast ratio can be obtained.

  First, a basic configuration of an image display panel that is an object of the present invention will be described. In the image display panel of the present invention, an electric field is applied to the image display medium sealed between two opposing substrates. Along with the applied electric field direction, the image display medium charged at a low potential toward the high potential side is attracted by the force of the electric field or the Coulomb force, and is charged at a high potential toward the low potential side. The image display medium is attracted by an electric field force, a Coulomb force, or the like, 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, as the force applied to the particles constituting the image display medium, in addition to the force attracted by the Coulomb force between the particles, the electric image force with the electrode and the substrate, the intermolecular force, the liquid cross-linking force, gravity and the like can be considered. .

An example of an image display panel which is an object of the present invention will be described with reference to FIGS. 1 (a) and (b) to FIGS. 2 (a) and 2 (b).
In the example shown in FIGS. 1A and 1B, at least two types of image display media 3 (here, white particles 3W and black particles 3B) having different charging characteristics and colors composed of at least one kind of particles are shown. ) Is moved perpendicularly to the substrates 1 and 2 in accordance with the electric field applied from the outside of 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 A white color is displayed by the observer. In the example shown in FIG. 1B, in addition to the example shown in FIG. 1A, partition walls 4 are provided, for example, in a lattice shape between the substrates 1 and 2 to define display cells.
In the example shown in FIGS. 2A and 2B, at least two types of image display media 3 (here, white particles 3W and black particles 3B) having different charging characteristics and colors composed of at least one kind of particles are shown. ) Is moved perpendicularly to the substrates 1 and 2 according to the electric field generated by applying a voltage between the electrode 5 provided on the substrate 1 and the electrode 6 provided on the substrate 2, and the black particles 3B are observed. The viewer can visually recognize the black color, or the white particles 3W can be visually recognized by the viewer. In the example shown in FIG. 2B, in addition to the example shown in FIG. 2A, partition walls 4 are provided, for example, in a lattice form between the substrates 1 and 2 to define display cells.
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 according to any one of the first to third aspects of the present invention is characterized in that, in any example, the waveform of the drive voltage when a drive voltage for applying an electric field to the image display medium is applied to the electrodes. In addition, by optimizing the shape and resistance of the electrodes, the image display panel can obtain a required contrast ratio. Hereinafter, each invention will be described.

<First invention>
Density difference when performing black display and white display with voltages having various slope waveforms, with two voltages V and Vb applied to one display unit for an image display panel having the same configuration. = Black density-White density was measured. Here, as an example, the voltage gradient represents the reciprocal 1 / t (/ sec) of the time t to reach the voltage V in the waveform of the voltage V shown in FIG. The results are shown in FIG. From the results of FIG. 4, it can be seen that the density difference increases up to the slope 200 regardless of the value of the voltage V, and the density difference is substantially constant above the slope 200. That is, it can be seen that a voltage gradient of 200 / sec or more is necessary to obtain a predetermined concentration. From this, it is understood that the voltage for applying the electric field to the image display medium needs to be applied so that the gradient of the voltage applied to one display unit is 200 / sec or more.

<Second invention>
It is known that when the product (time constant) of the capacitance and resistance of the capacitor increases due to the transient current, the waveform of the voltage V changes as shown in the equation of FIG. It has been newly found that the image display panel to which the present invention is applied also has a capacitance, and the waveform changes as the product of the capacitance of one display unit and the resistance changes in the same manner as the capacitor.

  On the other hand, as shown in FIG. 6 as an example, a γ curve representing drive voltage characteristics of an image display panel is known. Then, as shown in FIG. 7 showing an example in which the γ curve is differentiated, the differentiation of the γ curve represents the amount of change in driving of the image display panel. Here, the voltage at which the derivative of the γ curve shown in FIG. 7 shows the maximum value, in other words, the voltage Vmax with the largest slope of the drive voltage / density (or reflectivity) is the largest in the drive system where the voltage is gradually increased. This is the voltage at which the contrast ratio changes, in other words, the voltage at which the image display medium moves. For this reason, since many image display media move at Vmax and the contrast ratio changes greatly, the slope of the voltage waveform at Vmax is important.

  From the above examination, an image display panel in which the product of the capacitance and the resistance of the capacitor of one display image is changed in three steps with respect to the image display panel having the same configuration at different voltages Va, Vb, and Vc. It was driven, and the voltage gradient (/ sec) and density difference at Vmax were measured. The results are shown in FIG. From the results of FIG. 8, it can be seen that the concentration difference gradually increases until the voltage gradient at Vmax reaches 1000 / sec and becomes constant after 1000 / sec. That is, in order to obtain a predetermined concentration, it can be seen that the slope at Vmax needs to be 1000 / sec or more. From this, it can be seen that the rising slope of the voltage at the voltage having the largest driving voltage / density (or reflectance) slope needs to be 1000 / sec or more.

<Third invention>
As described in the above description of the second invention, the slope of the voltage waveform is determined by the product of the capacitance C and the resistance R. Here, since the capacitance C is proportional to the area S of the opposing electrode, an image display of a stable density difference (contrast ratio) can be achieved by defining S × R by design at a voltage sufficiently higher than Vmax. Panel can be obtained. The results are shown in FIG. From the result of FIG. 10, it can be seen that S × R is constant up to 2500 Ωm ² but decreases thereafter. From this, it can be seen that the product of the area of one display unit and the resistance applied to one display unit needs to be 2500 Ωm ² or less.

  Hereinafter, each member which comprises the image display panel used as the object of this invention is demonstrated.

  As for the substrate, at least one panel is the transparent substrate 1 on which the color of the image display medium can be confirmed from the outside of the apparatus, 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 on the substrate as necessary include metals such as aluminum, silver, nickel, copper, and gold, and conductive metal oxides such as ITO, indium oxide, conductive tin oxide, and conductive zinc oxide , Conductive polymers such as polyaniline, polypyrrole, polythiophene and the like 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.

  The shape of the partition 4 provided as necessary is optimally set according to the type of image display medium involved in the display, and is not limited in general. However, the width of the partition is 2 to 100 μm, preferably 3 to 50 μm. Is adjusted to 10 to 500 μm, preferably 10 to 200 μm. In forming the partition walls, a both-rib method in which ribs are formed on each of the opposing substrates and then bonded, and a one-rib method in which ribs are formed only on one substrate are conceivable. In the present invention, any method is preferably used.

  As shown in FIG. 10, the display cells formed by the partition walls made of these ribs are illustrated in a square shape, a triangular shape, a line shape, a circular shape, and a hexagonal shape as viewed from the substrate plane direction. The shape and the mesh shape are exemplified. 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 include a mold transfer method, a screen printing method, a sand blast method, a photolithography method, and an additive method. Among these, a photolithography method using a resist film and a mold transfer method are preferably used.

  Next, the powder fluid as the image display medium used in the image display panel which is the subject 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 which is the object of the present invention exhibits high fluidity in an aerosol state in which solid particles are stably suspended as a dispersoid as an image display medium, for example, as an image display medium between opposing substrates, at least one of which is transparent. The powder fluid is sealed, and such powder fluid can be easily and stably moved by Coulomb force or the like 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 that is the subject 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.

  Moreover, it is preferable that 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 20 μm and are 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 set to 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 indicating 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 size 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 is 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 particles constituting the image display medium naturally depends on the measurement conditions, but the charge amount of the particles constituting the image display medium in the image display panel is almost equal to the initial charge amount, contact with the partition walls, and the substrate. It was found that the saturation value of the charging behavior of the particles constituting the image display medium is a dominant factor, depending on the charge decay with contact and elapsed time.

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.
This void portion refers to the electrodes 5 and 6 and the image display medium (particles) from the portion sandwiched between the opposing substrate 1 and substrate 2 in FIGS. 1 (a), 1 (b) to 2 (a), (b). A gas portion in contact with a so-called image display medium excluding an occupied portion of the group or powdered fluid 3), an occupied portion of the partition wall 4 (portion provided with the partition wall), and a panel seal portion for image display.
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 image display panel so that the humidity is maintained. For example, filling of the image display medium, assembly of the image display panel, and the like are performed in a predetermined humidity environment. It is important to apply a sealing material and a sealing method that prevent moisture from entering from the outside.

The distance between the substrates in the image display panel that is the subject of the present invention is only required to be able to move the image display medium and maintain the contrast, but is usually adjusted to 10 to 500 μm, preferably 10 to 200 μm.
The volume occupation ratio 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, experiments related to the second invention and the third invention will be described.

<About 2nd invention and 3rd invention>
First, in the configuration of the image display panel shown in FIG. 11, the display numbers shown in Table 2 below are based on the panel specifications shown in Table 1 below. A panel having a display unit area of 1 to 6 and a wiring electrode length was manufactured, and the white / black contrast was measured by driving at 120 V. As a result, when the display of S × R was 2500 (Ωm ² ) or less, the slope was 1000 (1 / Sec) and maintain a high contrast state, but when the display of S × R exceeds 2500 (Ωm ² ), the slope is less than 1000 (1 / sec) and the contrast is reduced by 10 to 30%. The unevenness of contrast was 70%.

  From the data in Table 2 below, first, there is a relationship between the slope at Vmax according to the second invention and the S × R according to the third invention, and the slope at Vmax decreases as S × R increases. I understand that. FIG. 12 shows the relationship between the slope at Vmax according to the second invention from the data in Table 2 and the contrast, and FIG. 13 shows the relationship between S × R and the contrast from the data in Table 2 according to the third invention.

<Improving means of the third invention>
First, based on the panel specifications shown in Table 3 below, the display numbers shown in Table 4 below are shown. When a panel having display unit areas of 11 to 21 and wiring electrodes was designed, no. 12, it was found that there was a display of S × R of 2500 (Ωm ² ) or more as shown in Table 5 below. In order to further reduce the resistance value, only the width of the wiring electrode for the display portion of 12 is changed from 20 μm to 80 μm. In all of the examples 11 to 21, an electrode material having a low sheet resistance was used on the front surface (30Ω / mm ² → 10Ωmm ² ). When driven at 80 V, as shown in Table 5 below, it was possible to perform display with uniform contrast. Thus, it can be seen that it is effective to increase the width of the wiring electrode and to specify the electrode material having a low sheet resistance for the adjustment of S × R according to the second invention.

  Image display panels subject to the present invention include display devices for mobile devices such as notebook computers, PDAs, mobile phones, handy terminals, electronic papers such as electronic books and electronic newspapers, signboards, posters, bulletin boards such as blackboards, and calculators. It is suitably used for display units for home appliances, automobile products, etc., card display units for point cards, IC cards, etc., electronic advertisements, electronic POPs, electronic price tags, electronic musical scores, and display units for RF-ID devices.

(A), (b) is a figure which shows an example of the panel for image display used as the object of this invention, respectively. (A), (b) is a figure which shows the other example of the panel for image displays used as the object of this invention, respectively. It is a figure for demonstrating an example of the voltage waveform in the drive of the image display panel of this invention. It is a graph which shows the relationship between the inclination in the drive of the image display panel of this invention, and a density difference. It is a graph which shows the change of the waveform of the drive voltage in the drive of the image display panel of this invention. It is a graph which shows the relationship between the drive voltage and contrast ratio in the drive of the image display panel of this invention. It is a graph which shows the relationship between the drive voltage in the drive of the image display panel of this invention, and a differential value. It is a graph which shows the relationship between the inclination in the drive of the image display panel of this invention, and a density difference. It is a graph which shows the relationship between S * R and a density difference in the drive of 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 used as the object of this invention. It is a figure which shows the structure of an example of the image display panel used in an Example. It is a graph which shows the relationship between the inclination in Vmax which concerns on 2nd invention, and contrast from the result of the Example of this invention. It is a graph which shows the relationship between S * R which concerns on 3rd invention, and contrast from the result of the Example of this invention.

Explanation of symbols

1, 2 Substrate 3 Image display medium (particle group or powder fluid)
3W White particle group 3B Black particle group 4 Bulkhead 5, 6 Electrode

Claims (4)

  In an image display panel for displaying an image by moving the image display medium by enclosing the image display medium between two substrates, at least one of which is transparent, and applying an electric field to the image display medium. An image display panel, wherein the applied voltage has a slope of 200 / sec or more.   In an image display panel that displays an image by moving an image display medium by enclosing the image display medium between two substrates, at least one of which is transparent, and applying an electric field to the image display medium. An image display panel, wherein a voltage rising slope at a voltage having the largest slope of (or reflectance) is 1000 / sec or more. In an image display panel that displays an image by moving an image display medium by enclosing the image display medium between two substrates transparent at least one and applying an electric field to the image display medium, one display unit An image display panel, wherein the product of the area and the resistance per display unit is 2500 Ωm ² or less.   The image display panel according to claim 1, wherein the image display medium is made of a particle group or a powder fluid.

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