JP2017003685A - Display device and electronic apparatus - Google Patents

Abstract

Provided are a display device and an electronic apparatus capable of multicolor display while improving display quality. A display device according to the present disclosure includes a plurality of types of migrating particles having different average particle diameters and a plurality of porous layers formed of a fibrous structure and having different average pore diameters. [Selection] Figure 1

Description

  The present disclosure relates to a display device and an electronic apparatus that perform image display using an electrophoresis phenomenon.

  In recent years, with the widespread use of various electronic devices such as mobile phones and personal digital assistants (PDAs), there is an increasing demand for display devices with low power consumption and high quality image quality. Among them, recently, with the birth of the electronic book distribution business, electronic book terminals for reading purposes aimed at reading character information for a long time have been attracting attention, so a display device having a display quality suitable for that purpose Is desired. As reading applications, display devices of a cholesteric liquid crystal type, an electrophoretic type, an electrooxidation reduction type, a twist ball type, and the like have been proposed, and among them, a display device classified as a reflection type is preferable. This is because bright display is performed using reflection (scattering) of external light as in the case of paper, and display quality close to that of paper can be obtained. In addition, since a backlight is unnecessary, power consumption can be suppressed.

  A promising candidate for a reflective display device is an electrophoretic display device that produces a contrast (contrast) using an electrophoretic phenomenon. Various studies have been made on display methods of electrophoretic display devices. Specifically, a method has been proposed in which two types of charged particles having different optical reflection characteristics and polarities are dispersed in an insulating liquid, and each charged particle is moved using the difference in polarity. In this method, since the distribution of the two types of charged particles changes according to the electric field, contrast is generated using the difference in optical reflection characteristics.

  In the electrophoretic display device, since display is performed using the contrast of reflected light as described above, the display is basically monochrome (monochrome) display. However, in Patent Document 1, for example, a pair of opposing substrates is displayed. There is disclosed an image display device in which a layer having a gap is provided between the two, and two types of migrating particles having different colors and particle sizes are used. The gap of the layer disposed between the pair of substrates is large enough to prevent one of the two types of migrating particles from entering, thereby enabling multicolor display.

JP 2007-240758 A

  However, in the image display device of Patent Document 1, a method for controlling the concentration of a plurality of migrating particles on the display surface has not been established, and it is difficult to actually perform multicolor display using a plurality of migrating particles having different colors. Met. Further, since the display is switched depending on the difference in moving speed of the migrating particles, there is a problem that it takes a certain time.

  The present disclosure has been made in view of such problems, and an object of the present disclosure is to provide a display device and an electronic apparatus capable of multicolor display while improving display quality.

  The display device of the present disclosure includes a plurality of types of migrating particles having different average particle diameters, and a plurality of porous layers formed of a fibrous structure and having different average pore diameters.

  An electronic device according to the present disclosure includes the display device according to the present disclosure.

  In the display device and the electronic device of the present disclosure, migration is performed by using a plurality of types of migrating particles having different average particle diameters and a plurality of porous layers formed of a fibrous structure and having different average pore diameters. The moving distance of the particles is adjusted by the particle size of the migrating particles and the pore size of the porous layer.

According to the display device and the electronic apparatus of the present disclosure, by using a plurality of types of migrating particles having different average particle diameters and a plurality of porous layers having different average pore diameters, the moving distance of the migrating particles can be determined. Adjustment was made according to the particle size and the pore size of the porous layer. As a result, the time required for display switching can be shortened. Therefore, it is possible to provide a display device and an electronic device that can perform multicolor display while improving display quality. Note that the effects described here are not necessarily limited, and may be any effects described in the present disclosure.

It is sectional drawing showing the structure of the display apparatus which concerns on one embodiment of this indication. It is a top view of the display apparatus shown in FIG. It is a schematic diagram explaining operation | movement of the display apparatus shown in FIG. It is a schematic diagram explaining operation | movement of the display apparatus shown in FIG. It is a schematic diagram explaining operation | movement of the display apparatus of this indication. It is a conceptual diagram explaining the cyan display in the display apparatus shown in FIG. It is a characteristic view explaining the waveform of the applied voltage at the time of the cyan display shown to FIG. 5A. It is a conceptual diagram explaining the magenta display in the display apparatus shown in FIG. FIG. 6B is a characteristic diagram illustrating a waveform of an applied voltage during magenta display shown in FIG. 6A. It is a conceptual diagram explaining the yellow display in the display apparatus shown in FIG. It is a characteristic view explaining the waveform of the applied voltage at the time of yellow display shown to FIG. 7A. It is a conceptual diagram explaining the yellow display in the display apparatus as a comparative example. It is a characteristic view explaining the waveform of the applied voltage at the time of yellow display shown to FIG. 8A. FIG. 10 is a cross-sectional view illustrating a configuration of a display device according to a modified example of the present disclosure. It is a schematic diagram explaining the white display in the display apparatus shown in FIG. It is a schematic diagram explaining the black display in the display apparatus shown in FIG. It is a schematic diagram explaining the red display in the display apparatus shown in FIG. It is a perspective view showing the external appearance of the electronic book using the display apparatus of this indication. FIG. 11B is a perspective view illustrating another example of the electronic book illustrated in FIG. 11A. It is a perspective view showing the external appearance of the tablet personal computer using the display apparatus of this indication.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The order of explanation is as follows.
1. Embodiment (display device having electrophoretic particles having a plurality of types of particle sizes and a porous layer having a plurality of types of pore sizes)
1-1. Configuration of electrophoretic element 1-2. Configuration of display device 1-3. Preferred display method of electrophoretic element 1-4. Action / Effect Modified example (display device having a plurality of types of migrating particles and a plurality of types of porous layers, each having a different charge amount)
2-1. Configuration of electrophoretic element 2-2. Action and effect 3. Application example (electronic equipment)

<1. Embodiment>
FIG. 1 illustrates a cross-sectional configuration of a display device (display device 1) according to an embodiment of the present disclosure. FIG. 2 shows a planar configuration of the electrophoretic element 30 constituting the display device 1. The display device 1 is applied to various electronic devices such as a display device that displays an image by using an electrophoretic phenomenon and displays an image, for example, an electronic paper display. The display device 1 includes, for example, a display layer including an electrophoretic element 30 between a drive substrate 10 and a counter substrate 20 that are disposed to face each other with a spacer 40 interposed therebetween. The electrophoretic element 30 includes an electrophoretic particle 32 and a porous layer 33 having a plurality of pores 333 in an insulating liquid 31. The porous layer 33 has a fibrous structure 331 and non-migrating particles 332 held by the fibrous structure 331. 1 and 2 schematically show the configuration of the electrophoretic element 30 and may differ from actual dimensions and shapes.

(1-1. Configuration of electrophoretic element)
In the present embodiment, the migrating particles 32 have a plurality of types of average particle sizes, and the porous layer 33 has a configuration in which layers having a plurality of types of average pore sizes are stacked.

  The insulating liquid 31 is, for example, any one type or two or more types of non-aqueous solvents such as an organic solvent, and specifically includes paraffin or isoparaffin. It is preferable that the viscosity and refractive index of the insulating liquid 31 be as low as possible. This is because the mobility (response speed) of the migrating particles 32 is improved, and the energy (power consumption) required to move the migrating particles 32 is lowered accordingly. In addition, since the difference between the refractive index of the insulating liquid 31 and the refractive index of the porous layer 33 is increased, the light reflectance of the porous layer 33 is increased. Note that a weak conductive liquid may be used instead of the insulating liquid 31.

  The insulating liquid 31 may contain various materials as necessary. This material is, for example, a colorant, a charge control agent, a dispersion stabilizer, a viscosity modifier, a surfactant or a resin.

  The electrophoretic particles 32 are one or two or more charged particles that are electrically movable, and are dispersed in the insulating liquid 31. As described above, the migrating particles 32 in the present embodiment have a plurality of types of average particle diameters, and are composed of one or more charged particles for each average particle diameter. Specifically, the migrating particles 32 have the same number of types of average particle diameter as the number of porous layers 30 to be described later. Here, for example, four types of migrating particles 32A and 32B having different average particle diameters are used. , 32C, 32D.

The migrating particles 32 also have arbitrary optical reflection characteristics (light reflectivity). The light reflectance of the migrating particles 32 is not particularly limited, but is preferably set so that at least the migrating particles 32 can shield the porous layer 33. This is because contrast is generated by utilizing the difference between the light reflectance of the migrating particles 32 and the light reflectance of the porous layer 33. In the present embodiment, the four types of migrating particles 32A, 32B, 32C, and 32D constituting the migrating particle 32 have different colors for each average particle diameter. Specifically, for example, cyan (electrophoretic particles 32A), magenta (electrophoretic particles 32B), yellow (electrophoretic particles 32C), and black (electrophoretic particles 32D) are colored. The particle size of the migrating particles 32 is preferably in the range of, for example, 100 nm or more and 2 μm or less, and the average particle size of the migrating particles 32A, 32B, 32C, and 32D is, for example, 1.2 μm (electrophoretic particle 32A), 1 μm (electrophoretic particle 32B), 0.8 μm (electrophoretic particle 32C), and 0.6 μm (electrophoretic particle 32D). The average particle size of each migrating particle 32A, 32B, 32C, 32D is not limited to the above value. For example, the smaller migrating particle has an average particle size a ₁ and a particle size dispersion value σ ₁ and a larger side. If the electrophoretic particles and the average particle diameter a ₂ and a particle size distribution value sigma _2, may be a relationship between _{a 1 -2σ 1> a 2 +} 2σ 2.

  The migrating particles 32 (32A, 32B, 32C, 32D) can move between the pixel electrode 14 and the counter electrode 22 in the insulating liquid 31. The migrating particles 32 are, for example, one kind or two or more kinds of particles (powder) such as an organic pigment, an inorganic pigment, a dye, a carbon material, a metal material, a metal oxide, glass, or a polymer material (resin). . The migrating particles 32 may be pulverized particles or capsule particles of resin solids containing the above-described particles. However, materials corresponding to carbon materials, metal materials, metal oxides, glass, or polymer materials are excluded from materials corresponding to organic pigments, inorganic pigments, or dyes.

  Organic pigments include, for example, azo pigments, metal complex azo pigments, polycondensed azo pigments, flavanthrone pigments, benzimidazolone pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, perylene pigments, perinones. Pigments, anthrapyridine pigments, pyranthrone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments or indanthrene pigments. Examples of inorganic pigments include zinc white, antimony white, carbon black, iron black, titanium boride, bengara, mapico yellow, red lead, cadmium yellow, zinc sulfide, lithopone, barium sulfide, cadmium selenide, calcium carbonate, barium sulfate, Lead chromate, lead sulfate, barium carbonate, lead white or alumina white. Examples of the dye include nigrosine dyes, azo dyes, phthalocyanine dyes, quinophthalone dyes, anthraquinone dyes, and methine dyes. The carbon material is, for example, carbon black. The metal material is, for example, gold, silver or copper. Examples of metal oxides include titanium oxide, zinc oxide, zirconium oxide, barium titanate, potassium titanate, copper-chromium oxide, copper-manganese oxide, copper-iron-manganese oxide, and copper-chromium-manganese oxide. Or copper-iron-chromium oxide. The polymer material is, for example, a polymer compound in which a functional group having a light absorption region in the visible light region is introduced. As long as the polymer compound has a light absorption region in the visible light region, the type of the compound is not particularly limited.

  The specific forming material of the migrating particles 32 (32A, 32B, 32C, 32D) is selected according to, for example, the role that the migrating particles 32 play in order to cause contrast. For example, the material in which white display is performed by the migrating particles 32 is, for example, a metal oxide such as titanium oxide, zinc oxide, zirconium oxide, barium titanate or potassium titanate, and among these, titanium oxide is preferable. This is because it is excellent in electrochemical stability and dispersibility and has high reflectance. On the other hand, the material in the case where black display is performed by the migrating particles 32 is, for example, a carbon material or a metal oxide. The carbon material is, for example, carbon black, and the metal oxide is, for example, copper-chromium oxide, copper-manganese oxide, copper-iron-manganese oxide, copper-chromium-manganese oxide, or copper-iron. -Chromium oxide and the like. Among these, a carbon material is preferable. This is because excellent chemical stability, mobility and light absorption are obtained.

  In the present embodiment, as described above, the migrating particles 32A, 32B, 32C, and 32D exhibit cyan, magenta, yellow, and black, respectively. Among these, the electrophoretic particles 32D exhibiting black are formed of the carbon material or the metal oxide. The migrating particles 32A exhibiting a cyan color, the migrating particles 32B exhibiting a magenta color, and the migrating particles 32C exhibiting a yellow color can each be formed using a pigment exhibiting a corresponding color. Specific materials include, for example, quinacridone, perylene, perinone, isoindolinone, dioxazine, isoindoline, anthraquinone, quinophthalone, diketopyrrolopyrrole and other polycyclic pigments, phthalocyanine pigments, azo lake red, azo lake red, piazolone, Examples thereof include azo pigments such as disazo, monoazo, condensed azo, naphthol, and pendimidazolone, and inorganic pigments such as cadmium yellow, strontium chromate, viridian, oxide chromium, cobalt blue, and ultramarine.

  The content (concentration) of the migrating particles 32 (32A, 32B, 32C, 32D) in the insulating liquid 31 is not particularly limited, but the entire migrating particles 32 are, for example, 0.1 wt% to 10 wt%. It is preferable. This is because shielding (concealment) and mobility of the migrating particles 32 are ensured. If the amount is less than 0.1% by weight, the migrating particles 32 may hardly shield the porous layer 33. On the other hand, when the amount is more than 10% by weight, the dispersibility of the migrating particles 32 is lowered, so that the migrating particles 32 are difficult to migrate and may be aggregated in some cases. Depending on the particle diameter, the electrophoretic particles 32A, 32B, 32C, and 32D colored in the respective colors may be, for example, 0.1 wt% to 4 wt% in the electrophoretic particles 32A having the largest particle size, and the next largest electrophoretic migration For particles 32B, 0.1% to 4% by weight, for the next larger migrating particles 32C, 0.1% to 4% by weight, and for the smallest migrating particles 32D, 0.1% to 4% by weight. Preferably there is. However, it is desirable to change the weight ratio of each particle according to the expected display characteristics, color gamut, and contrast.

  In addition, it is preferable that the migrating particles 32 are easily dispersed and charged in the insulating liquid 31 for a long period of time and are not easily adsorbed by the porous layer 33. For this reason, in order to disperse the electrophoretic particles 32 by electrostatic repulsion, a dispersant (or a charge adjusting agent) may be used, or the electrophoretic particles 32 may be subjected to a surface treatment, or both may be used in combination.

  Examples of the dispersing agent include Solsperse series manufactured by Lubrizol, BYK series or Anti-Terra series manufactured by BYK-Chemie, or Span series manufactured by ICI Americas.

  The surface treatment is, for example, rosin treatment, surfactant treatment, pigment derivative treatment, coupling agent treatment, graft polymerization treatment or microencapsulation treatment. Among these, graft polymerization treatment, microencapsulation treatment, or a combination thereof is preferable. This is because long-term dispersion stability and the like can be obtained.

  The material for the surface treatment is, for example, a material (adsorbing material) having a functional group capable of being adsorbed on the surface of the migrating particle 32 and a polymerizable functional group. The type of functional group that can be adsorbed is determined according to the material for forming the migrating particles 32. For example, carbon materials such as carbon black are aniline derivatives such as 4-vinylaniline, and metal oxides are organosilane derivatives such as 3- (trimethoxysilyl) propyl methacrylate. . Examples of the polymerizable functional group include a vinyl group, an acrylic group, and a methacryl group.

  The surface treatment material is, for example, a material (graftable material) that can be grafted onto the surface of the migrating particles 32 into which a polymerizable functional group has been introduced. The graft material preferably has a polymerizable functional group and a dispersing functional group that can be dispersed in the insulating liquid 31 and can maintain dispersibility due to steric hindrance. The kind of polymerizable functional group is the same as that described for the adsorptive material. The dispersing functional group is, for example, a branched alkyl group when the insulating liquid 31 is paraffin. In order to polymerize and graft the graft material, for example, a polymerization initiator such as azobisisobutyronitrile (AIBN) may be used.

  For reference, the details of the method of dispersing the migrating particles 32 in the insulating liquid 31 as described above are described in “Dispersion Technology of Ultrafine Particles and its Evaluation—Surface Treatment / Fine Grinding and Air / Liquid / Polymer” It is published in books such as "Dispersion Stabilization ~ (Science & Technology)".

  The porous layer 33 is, for example, a three-dimensional structure (irregular network structure such as a nonwoven fabric) formed of a fibrous structure 331 as shown in FIG. The porous layer 33 has a plurality of gaps (pores 333) through which the migrating particles 32 pass in places where the fibrous structure 331 does not exist. In FIG. 1, the illustration of the porous layer 33 is simplified.

  The fibrous structure 331 is a fibrous substance having a sufficiently large length with respect to the fiber diameter (diameter). The shape (external appearance) of the fibrous structure 331 is not particularly limited as long as the fibrous structure 331 has a fibrous shape that is sufficiently long with respect to the fiber diameter as described above. Specifically, it may be linear, may be curled, or may be bent in the middle. Moreover, you may branch to 1 or 2 or more directions on the way, not only extending in one direction. The formation method of the fibrous structure 331 is not particularly limited. For example, a phase separation method, a phase inversion method, an electrostatic (electric field) spinning method, a melt spinning method, a wet spinning method, a dry spinning method, a gel spinning method, A sol-gel method or a spray coating method is preferred. This is because a fibrous material having a sufficiently large length with respect to the fiber diameter can be easily and stably formed.

  The average fiber diameter of the fibrous structure 331 is not particularly limited, but is preferably as small as possible. This is because light easily diffuses and the average pore diameter of the pores 333 increases. However, the average fiber diameter needs to be determined so that the fibrous structure 331 can hold the non-migrating particles 332. For this reason, it is preferable that the average fiber diameter of the fibrous structure 331 is 10 micrometers or less. In addition, although the minimum of an average fiber diameter is not specifically limited, For example, it is 0.1 micrometer and may be less than that. This average fiber diameter is measured, for example, by microscopic observation using a scanning electron microscope (SEM) or the like. Note that the average length of the fibrous structure 331 may be arbitrary.

  The fibrous structure 331 includes one or more non-migrating particles 332, and the non-migrating particles 332 are held by the fibrous structure 331. In the porous layer 33 which is a three-dimensional structure, one fibrous structure 331 may be entangled at random, or a plurality of fibrous structures 331 may be gathered and overlap at random. However, both may be mixed. When there are a plurality of fibrous structures 331, each fibrous structure 331 preferably holds one or more non-migrating particles 332. FIG. 2 shows a case where the porous layer 33 is formed by a plurality of fibrous structures 331.

  The reason why the porous layer 33 is a three-dimensional structure is that the irregular three-dimensional structure easily causes external light to be irregularly reflected (multiple scattering), so that the light reflectance of the porous layer 33 increases and the high light This is because the porous layer 33 can be thin in order to obtain the reflectance. As a result, the contrast increases and the energy required to move the migrating particles 32 decreases. In addition, since the average pore diameter of the pores 333 is increased and the number thereof is increased, the migrating particles 32 can easily pass through the pores 333. As a result, the time required to move the migrating particles 32 is shortened, and the energy required to move the migrating particles 32 is also reduced.

  The reason why the non-migrating particles 332 are included in the fibrous structure 331 is that the light reflectance of the porous layer 33 becomes higher because external light is more easily diffusely reflected. Thereby, contrast becomes higher.

  In the present embodiment, the porous layer 33 is composed of a plurality of layers having different average pore diameters of the pores 333 as described above. Specifically, the porous layer 33 has a multilayer structure in which the same number as the type of the average particle diameter of the migrating particles 32, in other words, the same number of layers as the migrating particles 32 are laminated, Here, it has a configuration in which four types of layers (porous layers 33A, 33B, 33C, 33D) having different average pore diameters are stacked. These four types of porous layers 33A, 33B, 33C, and 33D are laminated so that the average pore diameter decreases from the display surface S1 side to the back surface S2 side.

  The pore size of the porous layer 33 is not particularly limited, but is generally preferably as large as possible. This is because the migrating particles 32 easily pass through the pores 333. However, in the present embodiment, the pore diameters of the porous layers 33A, 33B, 33C, and 33D are determined by the particle diameters of the migrating particles 32A, 32B, 32C, and 32D described above. Specifically, as shown in the schematic diagram of FIG. 4, the porous layer 33A preferably has a pore diameter through which all the migrating particles 32A, 32B, 32C, and 32D can pass, and the average pore diameter is, for example, It is preferably in the range of 100 nm to 5 μm. The porous layer 33B preferably has a pore diameter through which the migrating particles 32B, 32C, and 32D other than the migrating particle 32A can pass, and the average pore diameter is preferably in the range of, for example, 1.11 μm to 1.3 μm. . The porous layer 33C preferably has a pore diameter through which the migrating particles 32C and 32D other than the migrating particles 32A and 32B can pass, and the average pore diameter is preferably in the range of 0.91 μm to 1.1 μm, for example. . The porous layer 33D has only to have a pore size through which only the migrating particles 32D can pass, and the pore size is preferably in the range of 0.71 μm to 0.9 μm, for example. Thereby, the moving distance between the driving substrate 10 and the counter substrate 20 of the migrating particles 32A, 32B, 32C, and 32D is controlled.

  The thickness of the porous layers 33A, 33B, 33C, and 33D is not particularly limited. For example, the entire porous layer 33 is preferably 5 μm to 100 μm. This is because the shielding property of the porous layer 33 is enhanced and the migrating particles 32 easily pass through the pores 333. Note that at least the thickness of the porous layer 33A disposed on the display surface side is at least a thickness capable of shielding the electrophoretic particles 32A when the electrophoretic particles 32A having the largest pore diameter move to the back surface S2. Is preferred. In addition, the porous layers 33A, 33B, 33C, and 33D may have the same thickness as long as they are within the above range, but considering the time required for display switching, the migrating particles 32A, 32B, and 32C The moving distance of 32D is preferably shorter. For these reasons, the thicknesses of the porous layers 33A, 33B, 33C, and 33D are preferably set in the following ranges, respectively. The thickness of the porous layer 33A is preferably, for example, 10 μm or more and 30 μm or less, the thickness of the porous layer 33B is, for example, preferably 2 μm or more and 15 μm or less, and the thickness of the porous layer 33C is, for example, The thickness is preferably 2 μm or more and 15 μm or less, and the thickness of the porous layer 33D is preferably, for example, 2 μm or more and 15 μm or less.

  As a material constituting the fibrous structure 331, for example, one or two or more of polymer materials such as acrylic resins or inorganic materials are included, and other materials may be included. Polymer materials include, for example, nylon, polylactic acid, polyamide, polyimide, polyethylene terephthalate, polyacrylonitrile, polyethylene oxide, polyvinyl carbazole, polyvinyl chloride, polyurethane, polystyrene, polyvinyl alcohol, polysulfone, polyvinyl pyrrolidone, polyvinylidene fluoride, polyhexa Fluoropropylene, cellulose acetate, collagen, gelatin, chitosan or copolymers thereof. The inorganic material is, for example, titanium oxide. Among these, a polymer material is preferable as a material for forming the fibrous structure 331. This is because the reactivity (photoreactivity, etc.) is low (chemically stable), so that an unintended decomposition reaction of the fibrous structure 331 is suppressed. Note that in the case where the fibrous structure 331 is formed of a highly reactive material, the surface of the fibrous structure 331 is preferably covered with an arbitrary protective layer.

  In particular, the fibrous structure 331 is preferably a nanofiber. Since the three-dimensional structure is complicated and external light is likely to be diffusely reflected, the light reflectance of the porous layer 33 is further increased, and the volume ratio of the pores 333 to the unit volume of the porous layer 33 is increased. This is because the migrating particles 32 can easily pass through the pores 333. Thereby, the contrast becomes higher and the energy required to move the migrating particles 32 becomes lower. Nanofiber is a fibrous substance having a fiber diameter of 0.001 μm to 0.1 μm and a length that is 100 times or more of the fiber diameter. The fibrous structure 331 that is a nanofiber is preferably formed by an electrospinning method using a polymer material. This is because the fibrous structure 331 having a small fiber diameter can be easily and stably formed.

  The fibrous structure 331 preferably has an optical reflection characteristic different from that of the migrating particles 32A, 32B, 32C, and 32D. Specifically, the light reflectance of the fibrous structure 331 is not particularly limited, but is preferably set so that at least the porous layer 33 can shield the migrating particles 32 as a whole. As described above, this is because contrast is generated by utilizing the difference between the light reflectance of the migrating particles 32 and the light reflectance of the porous layer 33. Accordingly, the fibrous structure 331 having light transparency (colorless and transparent) in the insulating liquid 31 is not preferable. However, the light reflectivity of the fibrous structure 331 hardly affects the light reflectivity of the entire porous layer 33, and the light reflectivity of the entire porous layer 33 is substantially the light reflectivity of the non-migrating particles 332. , The light reflectance of the on-fiber structure 331 may be arbitrary.

  The non-migrating particles 332 are particles that are fixed to the fibrous structure 331 and do not migrate electrically. The material for forming the non-electrophoretic particles 332 is, for example, the same as the material for forming the electrophoretic particles 32, and is selected according to the role played by the non-electrophoretic particles 332 as described later.

  In addition, as long as the non-migrating particle 332 is held by the fibrous structure 331, the non-migrating particle 332 may be partially exposed from the fibrous structure 331 or embedded therein.

  The non-migrating particles 332 have optical reflection characteristics different from those of the migrating particles 32A, 32B, 32C, and 32D. The light reflectance of the non-migrating particles 332 is not particularly limited, but is preferably set so that at least the porous layer 33 can shield the migrating particles 32 as a whole. This is because the contrast is displayed by utilizing the difference between the light reflectance of the migrating particles 32 and the light reflectance of the porous layer 33 as described above.

  Here, the specific forming material of the non-migrating particles 332 is selected according to the role that the non-migrating particles 332 play in order to generate contrast, for example. Specifically, when the migrating particles 32A, 32B, 32C, and 32D are responsible for four-color display of cyan, magenta, yellow, and black, respectively, the non-migrating particles 332 are preferably responsible for white display, for example. . In this case, it is preferable to use the materials mentioned when the electrophoretic particles 32 perform white display. Specifically, a metal oxide is preferable and titanium oxide is more preferable. This is because it is excellent in electrochemical stability and fixability, and high reflectance can be obtained. As long as a contrast can be generated, the material for forming the non-migrating particles 332 may be the same material as the material for forming the migrating particles 32 or may be a different material.

  The spacer 40 includes, for example, an insulating material such as a polymer material. However, the configuration of the spacer 40 is not particularly limited, and may be a sealing material mixed with fine particles.

  The shape of the spacer 40 is not particularly limited, but is preferably a shape that does not hinder the movement of the migrating particles 32 between the pixel electrode 14 and the counter electrode 22 and that can be uniformly distributed. is there. In addition, the thickness of the spacer 40 is not particularly limited, but in particular, it is preferably as thin as possible in order to reduce power consumption, for example, 10 μm to 100 μm. In addition, in FIG. 1, the structure of the spacer 40 is simplified and shown.

(1-2. Configuration of display device)
As described above, the display device 1 includes a pair of substrates, the drive substrate 10 and the counter substrate 20 that are arranged to face each other via the spacer 40, and includes a display layer therebetween.

  For example, the drive substrate 10 is formed by laminating a thin film transistor (TFT) 12, a protective film 13, and a pixel electrode 14 in this order on one surface of a support member 11. The TFT 12 and the pixel electrode 14 are divided and formed in a matrix according to the pixel arrangement, for example, in order to construct an active matrix drive circuit.

The support member 11 is formed of, for example, one or more of inorganic materials, metal materials, plastic materials, and the like. The inorganic material is, for example, silicon (Si), silicon oxide (SiO _x ), silicon nitride (SiN _x ), aluminum oxide (AlO _x ), or the like. Examples of the silicon oxide include glass or spin-on-glass (SOG). Etc. are included. Examples of the metal material include aluminum (Al), nickel (Ni), and stainless steel. Examples of the plastic material include polycarbonate (PC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethyl ether ketone (PEEK), cycloolefin polymer (COP), polyimide (PI), and polyether sulfone (PES). Etc.

  The support member 11 may be light transmissive or non-light transmissive. The support member 11 may be a rigid substrate such as a wafer, or may be a flexible thin glass or film. However, since a flexible (foldable) electronic paper display can be realized, it is desirable to be made of a flexible material.

  The TFT 12 is a switching element for selecting a pixel. The TFT 12 may be, for example, an inorganic TFT using an inorganic semiconductor layer such as amorphous silicon, polysilicon, or oxide as a channel layer (active layer), or an organic TFT using an organic semiconductor layer such as pentacene. The TFT 12 is covered with, for example, a protective layer 13. A planarization insulating film (not shown) made of an insulating material such as polyimide may be further provided on the protective layer 13.

  The pixel electrode 14 is formed independently for each pixel and includes, for example, one or more of conductive materials such as gold (Au), silver (Ag), and copper (Cu). . The pixel electrode 14 is electrically connected to the TFT 12. Note that the number of TFTs 12 arranged for one pixel electrode 14 is arbitrary, and is not limited to one, and may be two or more.

  The adhesive layer 15 is bonded to the drive substrate 10 and a display layer to be described later, and is made of, for example, acrylic resin, urethane resin, or rubber, and has a thickness of, for example, 1 μm to 100 μm. For example, an anionic additive, a cationic additive, or a lithium salt additive may be added to the adhesive layer 15 for the purpose of providing conductivity.

  The counter substrate 20 is provided with a counter electrode 22 on one surface side (display layer side) of the support member 21. In addition, for example, a color filter, an adhesive layer, and the like (none of which are shown) may be laminated.

  The support member 21 is made of the same material as the support member 11 except that it is light transmissive. This is because the image is displayed on the upper surface side of the counter substrate 20, and thus the support member 21 needs to be light transmissive. The thickness of the support member 21 is, for example, 1 μm to 250 μm.

  The counter electrode 22 includes, for example, any one type or two or more types of light-transmitting conductive materials (transparent conductive materials). Examples of such a conductive material include indium oxide-tin oxide (ITO), antimony-tin oxide (ATO), fluorine-doped tin oxide (FTO), and aluminum-doped zinc oxide (AZO). The counter electrode 22 has a thickness of, for example, 0.001 μm to 1 μm. For example, the counter electrode 22 is formed on the entire surface of the support base 21, but may be formed separately for each pixel, for example, like the pixel electrode 14.

  When displaying an image on the counter substrate 20 side, since the electrophoretic element 30 is viewed through the counter electrode 22, the light transmittance of the counter electrode 22 is preferably as high as possible, for example, 80% or more. It is. The electric resistance of the counter electrode 22 is preferably as low as possible, for example, 100Ω / □ (square) or less.

  In the display layer, for example, an electrophoretic element 30 whose voltage is controlled for each pixel is provided. The electrophoretic element 30 generates contrast using an electrophoretic phenomenon, and includes electrophoretic particles 32 that can move between the pixel electrode 14 and the counter electrode 22 in accordance with an electric field. The electrophoretic element 30 includes, for example, a porous layer 33 together with electrophoretic particles 32 in an insulating liquid 31. Here, the insulating liquid 31 and the porous layer 33 are provided in common for each pixel. Yes.

  The display device 1 is manufactured as follows, for example. First, the counter electrode 22 is provided on one surface of the support member 21 using an existing method such as various film forming methods, and the counter substrate 20 is formed. Next, the spacer 40 is formed on the counter electrode 22. The spacer 40 can be formed by, for example, the following imprint method. First, a solution containing a constituent material of the spacer 40 (for example, a photosensitive resin material) is applied on the counter electrode 22. Next, a mold having a recess on the coated surface is pressed and exposed to light, and then the mold is removed. Thereby, the columnar spacer 40 is formed.

  Subsequently, the porous layer 33 is disposed between the adjacent spacers 40, that is, in the cells 34. The porous layer 33 is formed through the following steps. First, a spinning solution is prepared by dispersing or dissolving a material for forming the fibrous structure 331 (for example, a polymer material) in an organic solvent or the like. Subsequently, after adding the non-migrating particles 332 to the spinning solution, the non-migrating particles 332 are dispersed in the spinning solution by sufficiently stirring. Next, using this spinning solution, for example, spinning is performed by an electrostatic spinning method. Thereby, the porous layer 33 in which the non-migrating particles 332 are held by the fibrous structure 331 is formed. The pore diameter of the porous layer 33 is controlled by controlling the viscosity of the spinning solution, the particle diameter of the non-electrophoretic particles 332, and the scanning speed during electrostatic spinning. For example, the thickness compression amount of the porous layer 33A is 0% to 10%, the porous layer 33B is 10% to 20%, the porous layer 33C is 20% to 30%, and the porous layer 33D is 30% to 40%. The porous layer 33A, 33B, 33C, 33D having the above average pore diameter range is formed by compressing the porous membrane using the% condition. The fibrous structure 331 is formed by a phase separation method, a phase inversion method, a melt spinning method, a wet spinning method, a dry spinning method, a gel spinning method, a sol-gel method, a spray coating method, or the like instead of the electrostatic spinning method. May be.

  Subsequently, after applying the insulating liquid 31 in which the migrating particles 32A, 32B, 32C, and 32D are dispersed to the counter substrate 20 on which the porous layer 33 is disposed, this is treated with, for example, a sealing agent (not shown). ), A peeling member (not shown) provided with the seal layer 16 is opposed. Finally, after peeling off the peeling member, the driving substrate 10 on which the TFT 12, the pixel electrode 14 and the like are formed on the seal layer 16 via the adhesive layer 15 is fixed. The display device 1 is completed through the above steps.

(1-3. Preferred Display Method of Electrophoretic Element)
In the electrophoretic element 30, as described above, contrast is generated by utilizing the difference between the light reflectance of the electrophoretic particles 32 and the light reflectance of the porous layer 33.

  3A and 3B are schematic diagrams for explaining the display operation of the electrophoretic element 30. FIG. Here, for the sake of clarity, the porous layer 33 is shown as a single layer, and the region in which the migrating particles 32 are disposed between the porous layer 33 and the drive substrate 10 and the counter substrate 20 (standby region R1). And the display region R2). Further, the migrating particle 32D having the smallest particle size will be described as an example.

  In the electrophoretic element 30 in the initial state, for example, the migrating particles 32D are arranged in the standby region R1 (FIG. 3A). In this case, since the migrating particles 32D are shielded by the porous layer 33 in all the pixels, no contrast is generated when the electrophoretic element 30 is viewed from the counter substrate 20 side (no image is displayed). Is in a state.

  On the other hand, when a pixel is selected by the TFT 12 and an electric field is applied between the pixel electrode 14 and the counter electrode 22, as shown in FIG. 3B, the migrating particles 32D are transferred from the standby region R1 to the porous layer 33 for each pixel. It moves to the display region R2 via the pore 333. In this case, since the pixels in which the migrating particles 32 are shielded by the porous layer 33 and the pixels that are not shielded coexist, when the electrophoretic element 30 is viewed from the counter substrate 20 side, a contrast is generated. become. Thereby, an image is displayed.

  The drive substrate 10 is provided with a peripheral circuit (not shown) for driving the electrophoretic element 30 for each pixel (applying a drive voltage between the pixel electrode 14 and the counter electrode 22). The peripheral circuit includes, for example, a voltage control driver for forming an active matrix driving circuit, a power source, a memory, and the like, and corresponds to an image signal for one or more selective sub-pixels. A drive voltage can be applied.

  As described above, the electrophoretic element 30 according to the present embodiment has a plurality of types of average particle diameters in the insulating liquid 31, and the electrophoretic particles 32A, 32B, 32C, which are color-coded according to the average particle diameter. 32D and porous layers 33A, 33B, 33C, and 33D having pores 333 having different average pore diameters.

  FIG. 4 is a schematic diagram for explaining the operation of the display device 1. As shown in FIGS. 1 and 4, the porous layer 33 has a larger average pore diameter from the display surface S1 side, here, the porous layer 33A, the porous layer 33B, and the porous layer 33C from the display surface S1 side. , Porous layer 33D in this order. The average pore diameter of the porous layers 33A, 33B, 33C, and 33D is determined by the migrating particles 32A, 32B, 32C, and 32D. That is, the pore size of the porous layer 33A is such a size that all the migrating particles 32A, 32B, 32C, and 32D can pass through. The pore size of the porous layer 33B cannot pass through the migrating particle 32A, but the migrating particles 32B, 32C, and The porous layer 33C cannot pass through the migrating particles 32A and 32B, but the porous layer 33C can pass through the migrating particles 32A, 32B, and 32C. Can not pass through, but the migrating particles 32D are formed in sizes that can pass through. Thus, when an electric field is applied between the pixel electrode 14 and the counter electrode 22, the migrating particles 32A, 32B, 32C, and 32D can be kept at different positions.

  5A to 7B are conceptual diagrams (FIGS. 5A, 6A, and 7A) showing movement of the migrating particles 32A, 32B, 32C, and 32D for explaining the display operation of the display device 1, and waveforms of applied voltages (FIG. 5B). 6B and FIG. 7B). The electrophoretic particles 32A, 32B, 32C, and 32D are colored cyan (electrophoretic particles 32A), magenta (electrophoretic particles 32B), yellow (electrophoretic particles 32C), and black (electrophoretic particles 32D), respectively. . In the following, the movement of the migrating particles 32A, 32B, 32C, and 32D and the waveform of the applied voltage during cyan display, magenta display, and yellow display will be described in this order.

  First, cyan display will be described. In the electrophoretic element 30 of the present embodiment, as described above, in the initial state (a state in which no voltage is applied between the pixel electrode 14 and the counter electrode 22), the electrophoretic particles 32A, 32B, 32C, and 32D are on standby. It is localized in the region R1. Specifically, the migrating particles 32A, 32B, 32C, and 32D are respectively disposed on the back surface S2 side of the porous layers 33A, 33B, 33C, and 33D that can pass (time 0 in FIG. 5A). At this time, the display color is the color of the porous layer 33, that is, white. Here, for example, when a positive voltage is applied between the pixel electrode 14 and the counter electrode 22, the migrating particles 32A, 32B, 32C, and 32D move to the display surface S1 side. At this time, as shown in FIG. 5B, when a positive voltage is applied for a certain time and then stopped, as shown in FIG. 5A, the migrating particles 32A are placed on the outermost surface of the porous layer 33, and the migrating particles 32B, 32C, 32D is in a state of being disposed in the porous layer 33. That is, the display color of the pixel including the electrophoretic element 30 is cyan.

  Next, magenta display will be described. For example, when a positive voltage is applied for a longer time than when cyan is displayed and then a negative voltage is applied for a predetermined time and then stopped, the migrating particles 32B colored in magenta are arranged on the display surface S1 side. 32C and 32D are arranged in the porous layer 33. Specifically, as shown in FIG. 6B, by applying a positive voltage for a longer time than in the cyan display mode, as shown in FIG. 6A, the electrophoretic particles 32A are positioned on the back surface S2 side in the initial state. The migrating particles 32B move to the display surface S1. Thereafter, by applying a negative voltage, the migrating particles 32A having a larger moving speed than the migrating particles 32B move to the back surface S2 side of the migrating particles 32B. Here, by stopping the application of voltage, the migrating particles 32B are arranged on the outermost surface of the porous layer 33, and the migrating particles 32A and the other migrating particles 32C and 32D are arranged in the porous layer 33. That is, the display color of the pixel including the electrophoretic element 30 is magenta.

  Next, yellow display will be described. For example, when a positive voltage is applied for a longer time than when magenta is displayed and then a negative voltage is applied for a longer time than when magenta is displayed and then stopped, the electrophoretic particles 32C colored yellow are arranged on the display surface S1 side. The migrating particles 32 </ b> A, 32 </ b> B, and 32 </ b> D are arranged in the porous layer 33. Specifically, as shown in FIG. 7A, by applying a positive voltage for a longer time than when displaying magenta, as shown in FIG. 7B, in the initial state, the back side S2 side of the migrating particles 32A and 32B. The positioned migrating particles 32C move to the display surface S1. Thereafter, when a negative voltage is applied, the migrating particles 32A, 32B, 32C, and 32D start to move toward the back surface S2. At this time, since the migrating particles 32A and 32B have a higher moving speed than the migrating particles 32C, they move to the back surface S2 side before the migrating particles 32C. Here, by stopping the application of voltage, the migrating particles 32C are arranged on the outermost surface of the porous layer 33, and the migrating particles 32A, 32B, and 32D are arranged in the porous layer 33. That is, the display color of the pixel including the electrophoretic element 30 is yellow.

  Although not shown, when the display color of the pixel including the electrophoretic element 30 is black, for example, a positive voltage is applied for a longer time than yellow display, and then a negative voltage is applied from yellow display. In addition, by stopping after being applied for a long time, the migrating particles 32D colored black on the outermost surface of the porous layer 33 are in a state in which the migrating particles 32A, 32B, and 32C are arranged in the porous layer 33. As a result, the display color of the pixel including the electrophoretic element 30 is black.

  As described above, the electrophoretic element 30 controls the direction of the applied voltage (positive / negative) and the application time to display multiple colors, in this case, five colors of cyan, magenta, yellow, black, and white. Is possible.

(1-4. Action and effect)
As described above, as a method for performing multicolor display in an electrophoretic display device, a display device using a plurality of electrophoretic particles having different colors and particle sizes is disclosed (for example, Patent Document 1). However, in this display device, since the display color is controlled only by the difference in moving speed of the electrophoretic particles of each color, it takes a certain time to switch the display color.

  8A and 8B are a conceptual diagram (FIG. 8A) showing movement of electrophoretic particles in an electrophoretic element as a comparative example, and a waveform diagram (FIG. 8B) of an applied voltage. This electrophoretic element controls the display color only by the difference in the moving speed of the electrophoretic particles of each color, like the electrophoretic element provided in the display device described in Patent Document 1. Here, it is assumed that the electrophoretic element has four types of electrophoretic particles 132A, 132B, 132C, and 132D as in the present embodiment. In addition, the size and the color of each migrating particle 132A, 132B, 132C, 132D are the same as those of the migrating particle 32A, 32B, 32C, 32D of the present embodiment, respectively.

  For example, in order to display the pixel including the electrophoretic element in yellow, as shown in FIGS. 8A and 8B, for example, a positive voltage is applied, and at least the yellow color arranged on the back surface S200 is displayed. It is necessary to move the electrophoretic particles 132C to the display surface S100. In the electrophoretic element, the electrophoretic particles 132A, 132B, 132C, and 132D are all localized on the back surface S200 in the initial state. For this reason, the time required to move the yellow migrating particles 132C to the display surface S100 is longer than that of the electrophoretic element 30 of the present embodiment (see FIGS. 8A and 8B). In addition, the time required to place only the electrophoretic particles 132C on the display surface S100 out of the electrophoretic particles 132A, 132B, and 132C that have moved to the display surface S100 by applying a negative voltage is later than that of the electrophoretic element 30. It takes a long time.

  As described above, when the multicolor display is performed only by the difference in the moving speed of the migrating particles, it is difficult to switch the display color in a short time. In addition, since a method for controlling the concentration of electrophoretic particles of a plurality of colors has not been established on the display surface, it is actually possible to simultaneously display a plurality of colors on the display surface using the electrophoretic element having such a configuration. It has been difficult to realize a display device.

  In addition, a reflective display device capable of multicolor display includes a display device provided with a color filter. However, when the color filter is provided, there is a risk that the contrast and the luminance may be significantly reduced due to a decrease in reflectance due to the provision of the color filter and absorption of reflected light by the color filter.

  On the other hand, in the display device 1 of the present embodiment, as the migrating particles 32, four types of migrating particles 32A, 32B, 32C, which have different average particle sizes and are colored in different colors for each average particle size. 32D was used. In addition, the porous layer 33 was formed by laminating four kinds of porous layers 33A, 33B, 33C, and 33D having different average pore diameters of the pores 333 in order of decreasing average pore diameter from the display surface S1 side to the back surface S2. Thereby, the moving distance of each color migrating particle 32A, 32B, 32C, 32D is limited by the particle diameter and the pore diameter of the porous layers 32A, 32B, 32C, 32D. That is, the migrating particles 32A, 32B, 32C, and 32D are localized on the back surface S2 side of the porous layers 33A, 33B, 33C, and 33D that can pass, respectively, in the initial state, for example. The moving distance of the particles 32A, 32B, 32C, 32D is shorter in the migrating particles 32A, 32B, 32C other than the migrating particle 32D having the smallest particle size.

  As described above, in the display device 1 according to the present embodiment, the plurality of types of migrating particles 32 having different average particle diameters and colored in different average particle diameters from the display surface S1 side to the back surface S2 side. The electrophoretic element 30 including a plurality of types of porous layers 33 stacked in order of decreasing average pore diameter is used as a display element. Thereby, for example, the position of the migrating particle 32 (32A, 32B, 32C, 32D) in the initial state is controlled by the pore diameter of the laminated porous layer 33 (33A, 33B, 33C, 33D). That is, the migrating particle 32A having the largest particle size is arranged at the position closest to the display surface S1, and the migrating particle 32D having the smallest particle size is arranged at the position farthest from the display surface S1. Therefore, when performing a certain color display, the electrophoretic particles exhibiting a desired color are arranged on the display surface S1 by applying a voltage, and the electrophoretic particles of other colors are moved and shielded in the porous layer. It is possible to shorten the sorting time. That is, it is possible to shorten the time required for display switching. Therefore, it is possible to provide the display device 1 capable of multicolor display while improving display quality.

<2. Modification>
Hereinafter, modifications of the above embodiment will be described. In the following description, the same components as those in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  FIG. 9 illustrates a cross-sectional configuration of a display device (display device 2) according to a modification of the above embodiment. The display device 2 is applied to various electronic devices such as an electronic paper display, for example, an electronic paper display that generates contrast by using an electrophoretic phenomenon and displays an image. The display device 2 includes, for example, a display layer including the electrophoretic element 30 between the drive substrate 10 and the counter substrate 20 which are disposed to face each other via the spacer 40. The electrophoretic element 40 includes an electrophoretic particle 42 and a porous layer 43 having a plurality of pores in an insulating liquid 41. The porous layer 43 has a fibrous structure and non-migrating particles held by the fibrous structure (none of which are shown). FIG. 9 schematically shows the configuration of the electrophoretic element 30 and may differ from the actual size and shape.

(2-1. Configuration of electrophoretic element)
The migrating particles 40 of this modification have plural types of average particle diameters as the migrating particles 42, for example, migrating particles 42 </ b> A and 42 </ b> B having an average pore diameter, and the porous layer 43 has plural types of averages. The porous layer 43A and the porous layer 32 have different pore sizes, for example, different average pore sizes. In this modification, the migrating particles 42A and 42B and the porous layers 43A and 43B are charged, and the charge amounts are different from those of the above embodiment. Moreover, the point from which the porous layer 43A with a small hole diameter is arrange | positioned at the display surface S1 side and the porous layer 43A with a large hole diameter at the back surface S2 side is different from the said embodiment.

  As in the above embodiment, the insulating liquid 41 is, for example, any one type or two or more types of non-aqueous solvents such as organic solvents, and specifically includes paraffin or isoparaffin. Yes. It is preferable that the viscosity and refractive index of the insulating liquid 41 are as low as possible. This is because the mobility (response speed) of the migrating particles 32 is improved, and the energy (power consumption) required to move the migrating particles 32 is lowered accordingly. In addition, since the difference between the refractive index of the insulating liquid 41 and the refractive index of the porous layer 33 is increased, the light reflectance of the porous layer 33 is increased. Note that a weak conductive liquid may be used instead of the insulating liquid 41. The insulating liquid 41 may contain various materials (for example, a colorant, a charge control agent, a dispersion stabilizer, a viscosity modifier, a surfactant, or a resin) as necessary.

  The migrating particles 42 are one or more charged particles that are electrically movable, and are dispersed in the insulating liquid 41. As described above, the migrating particles 42 in the present modification include the migrating particles 42A and 42B having different average particle diameters, and are each composed of one or two or more charged particles. Furthermore, the migrating particles 42A and 42B are colored in different colors. Specifically, the electrophoretic particles 42A and 42B are colored, for example, red (electrophoretic particles 42A) and black (electrophoretic particles 42B). The particle size of the migrating particles 42 is preferably in the range of, for example, 0.1 μm or more and 2 μm or less, and the migrating particles 42A and 42B have, for example, 0.3 μm (migrating particles 42A) and 0.2 μm in this range. (Electrophoretic particle 42B). In addition, the average particle diameter of each migrating particle 42A and 42B is not limited to the said range, For example, an average particle diameter should just be 0.1 micrometer or more.

  The migrating particles 42A and 42B may be any of organic pigments, inorganic pigments, dyes, carbon materials, metal materials, metal oxides, glass, polymer materials (resins), and the like, as with the migrating particles 32 in the above embodiment. Or one kind or two or more kinds of particles (powder).

  The content (concentration) of the migrating particles 42A and 42B in the insulating liquid 41 is not particularly limited, but the entire migrating particle 42 is preferably, for example, 0.1 wt% to 10 wt%. This is because shielding (concealment) and mobility of the migrating particles 32 are ensured. If the amount is less than 0.1% by weight, the migrating particles 32 may hardly shield the porous layer 33. On the other hand, when the amount is more than 10% by weight, the dispersibility of the migrating particles 32 is lowered, so that the migrating particles 32 are difficult to migrate and may be aggregated in some cases. For example, both the migrating particles 42A and the migrating particles 42B are preferably 0.1% by weight to 4% by weight, although the migrating particles 42A and 42B depend on the particle size, surface modification, or material.

  The migrating particles 42A and 42B in this modification are charged and have different charge amounts. This difference in charge amount can be added, for example, by performing a surface treatment. Specifically, for example, when the migrating particles 42A and 42B each have a negative charge, for example, a charge difference can be provided by modifying an electron-withdrawing functional group having a different charge amount. . In addition, when the migrating particles 42A and 42B have positive charges, for example, a charge difference can be provided by modifying functional groups having electron donating properties having different charge amounts. The charge difference can also be provided by changing the amount of the functional group to be modified on the surfaces of the migrating particles 42A and 42B.

  The charge amount of the migrating particle 42A and the migrating particle 42B is determined from the relationship with the charge amount of the porous layer 43A and the porous layer 43B described later. This is to make a difference in the moving speed of the migrating particles 42A and 42B when a voltage is applied, thereby further improving the display switching speed. Specifically, the mobility of the migrating particles 42 increases in the case of a combination with a small charge difference between the migrating particles 42 and the porous layer 43, and the migration of the migrating particles 42 in a combination with a large charge difference. The degree is small. If the charge difference is too large, the migrating particles 42 cannot pass through the porous layer 43. Accordingly, the charge amount of the migrating particle 42B is preferably larger than the charge amount of the migrating particle 42A having a smaller particle diameter than the migrating particle 42A, for example, and the charge amount of the migrating particle 42A is, for example, 10 mV or more and 50 mV or less. The charge amount of the migrating particles 42B is preferably 20 mV or more and 100 mV or less, for example.

  The porous layer 43 is a three-dimensional solid structure (irregular network structure such as a nonwoven fabric) formed of a fibrous structure as in the above embodiment. The porous layer 43 in this modification has two types of porous layers 43A and 32B having different pore diameters. The porous layers 43A and 43B are charged and have different charge amounts. The order of stacking the porous layers 43A and 43B is such that a porous layer 43A having a small average pore diameter is arranged on the display surface S1 side, and a porous layer 43B having a large average pore diameter is arranged on the back surface S2 side. Yes.

  As a material constituting the porous layer 43, the materials mentioned in the above embodiment can be used. The porous layer 43A disposed on the display surface S1 side may have light reflectivity. However, in this modification, the pore diameter of the porous layer 43A cannot pass through the migrating particles 42B, and thus the translucent layer 43A is not transparent. It is preferable to have properties. In that case, the fibrous structure constituting the porous layer 43A is formed without including non-electrophoretic particles that add optical reflection characteristics. The porous layer 43B disposed on the back surface S2 side is composed of a fibrous structure including one or two or more non-electrophoretic particles, like the porous layer 33 in the above embodiment, and the electrophoretic particles 42A, It has a light reflection characteristic different from 42B.

  The average pore diameter of the porous layers 43A and 43B is not particularly limited, but the average pore diameter of the porous layer 43B disposed on the back surface S2 side is preferably as large as possible. This is because the migrating particles 42A and 42B easily pass through the pores. For this reason, it is preferable that the average pore diameter of the pores of the porous layer 43B is, for example, in the range of 0.1 μm to 5 μm. On the other hand, it is desirable that the average pore size of the pores of the porous layer 43A is a pore size through which the large migrating particles 42B cannot pass. For this reason, the average pore diameter of the pores of the porous layer 43B is preferably in the range of 0.5 μm or more and 1.5 μm or less, for example.

  Although the thickness of porous layer 43A, 43B is not specifically limited, For example, it is preferable that the thickness of the porous layer 43 whole is 5 micrometers-100 micrometers, for example. This is because the shielding property of the porous layer 43 is enhanced and the migrating particles 42 easily pass through the pores. When the porous layer 43A having an average pore size smaller than the particle size of the migrating particles 42B is arranged on the display surface S1 side as in the present modification, the thickness of the porous layer 43A is at least the migrating particles. The thickness may be any thickness as long as 42A can be shielded, and is preferably in the range of 10 μm to 30 μm, for example. The thickness of the porous layer 43B may be any thickness that can shield the migrating particles 42B, and is preferably in the range of 2 μm to 15 μm, for example.

  The porous layers 43A and 43B are charged and have different charge amounts. The porous layers 43A and 43B can be charged, for example, by containing an inorganic pigment. The difference in charge amount can be provided, for example, by changing the surface treatment method. The charge amount of the porous layer 43A and the porous layer 43B is determined from the relationship with the charge amount of the migrating particles 42A and the migrating particles 42B. The charge amount of the porous layer 43A disposed on the display surface S1 side is preferably smaller than the charge amount of the porous layer 43B. When the charge amounts of the migrating particles 42A and the migrating particles 42B are in the above-described range, the charge amounts of the porous layer 43A and the porous layer 43B are, for example, 0 mV or more and 50 mV or less (porous layer 43A), respectively. For example, it is preferably 20 mV or more and 100 mV or less (porous layer 43B).

(2-2. Action and effect)
As described above, the electrophoretic element 40 of this modification includes the electrophoretic particles 42A and 42B having different average particle diameters and the porous layers 43A and 43B having different average pore diameters. The electrophoretic particles 42A and 42B and the porous layers 43A and 43B are charged and have different charge amounts. Specifically, the charged amount of the electrophoretic particle 42B having a larger particle diameter than that of the electrophoretic particle 42A is increased, and the charged amount of the porous layer 43B having a larger pore diameter than that of the porous layer 43A is increased. Thereby, the difference in the moving speed of the migrating particles 42A and 42B at the time of voltage application is increased. Therefore, it is possible to further reduce the time required for display switching. Therefore, it is possible to provide the display device 2 capable of multicolor display with improved display quality.

  In the display device 2 of this modification, the porous layers 43A and 43B having different pore diameters are arranged, the porous layer 43A having a small pore diameter is arranged on the display surface S1, and the porous layer 43B having a large pore diameter is arranged on the back surface S2. Of the migrating particles 42A and 42B having different particle diameters, the migrating particles 42B having a larger particle diameter cannot pass through the migrating particles 42A. However, as in the above-described embodiment, the display surface S1 has a large pore size. You may make it arrange | position the quality layer 43B. In that case, the porous layer 43A preferably has the same light reflection characteristics as the porous layer 43B, and preferably contains non-electrophoretic particles. In this case, since the effect of the particle size difference is opposite to that in the above embodiment, it is preferable to further increase the charging difference between the electrophoretic elements 42A and 42B. For example, it is desirable that the charge amount of the migrating particle 42B is 50 mV or more and 250 mV or less (same for the porous layer 43B) with respect to the charge amount of 10 mV or more and 50 mV or less for the migrating particle 42A (same for the porous layer 43A).

  In this modification, the particle diameters of the migrating particles 42A and 42B are different from each other, but may be the same as each other. The porous layers 43A and 43B may have the same pore diameter. In that case, the charge amount of the electrophoretic particles 42A and 42B and the difference between them and the charge amount and the difference between the porous layers 43A and 43B may be the same as the above range. A display device capable of multicolor display can be realized only by the difference in charge amount between 42A and 42B and the porous layers 43A and 43B.

  10A, 10B, and 10C schematically show the display operation of the electrophoretic particles 52A and 52B in the electrophoretic element 50 including the electrophoretic particles 52A and 52B having the same particle diameter and the porous layers 53A and 53B having the same pore diameter. It is a representation. In the display device 3, the migrating particles 52A and 52B and the porous layers 53A and 53B have different charge amounts. Specifically, for example, the migrating particles 52A are charged to 25 mV, the migrating particles 52B are charged to 100 mV, the porous layer 53A is charged to 0 mV, and the porous layer 53B is charged to 100 mV. In addition, the migrating particles 52A are colored red, the migrating particles 52B are colored black, and the porous layer 53A disposed on the display surface S1 side is translucent.

  In the electrophoretic element 50, as shown in FIG. 10A, when the migrating particles 52A and 52B are both moved to the back surface S2, the migrating particles 52A and 52B are shielded by the porous layer 53B and displayed white. (Initial state). In the initial state, when a voltage is applied for a certain period of time, in the electrophoretic element 50, the electrophoretic particles 52B having a larger charge amount move toward the display surface S1 before the electrophoretic particles 52A. However, since the potential difference between the migrating particles 52B and the porous layer 53A is large, the migrating particles 52B cannot pass through the porous layer 53A and remain at the boundary between the porous layer 53A and the porous layer 53B. When the applied voltage is erased here, as shown in FIG. 10B, the migrating particle 52B remains at the boundary between the porous layer 53A and the porous layer 53B, and the migrating particle 52B having a lower moving speed than the migrating particle 52A. Returns to the back surface S2 side (pixel electrode side). As a result, the electrophoretic element 50 displays black. Further, when a voltage is applied for a longer time than when displaying black from the initial state, both the migrating particles 52A and the migrating particles 52B move to the boundary between the porous layer 53A and the porous layer 53B. Here, since the charge difference between the migrating particles 52A and the porous layer 53A is relatively small, the migrating particles 52A pass through the porous layer 53A and reach the display surface S1. Thereafter, when the applied voltage is erased, as shown in FIG. 10C, the migrating particles 52A remain on the display surface S1, and the migrating particles 52B remain on the boundary between the porous layer 53A and the porous layer 53B. The electrophoretic element 50 is displayed in red by the child.

<3. Application example>
Next, application examples of the display devices 1 to 3 according to the above embodiment will be described. However, the configuration of the electronic device described below is merely an example, and the configuration can be changed as appropriate.

(Application example 1)
11A and 11B show the external configuration of an electronic book. The electronic book includes, for example, a display unit 110, a non-display unit 120, and an operation unit 130. Note that the operation unit 130 may be provided on the front surface of the non-display unit 120 as illustrated in FIG. 11A, or may be provided on the upper surface as illustrated in FIG. 11B. The display unit 110 is configured by the display device 1 (or 2, 3). The display device 1 (or the display devices 2 and 3) may be mounted on a PDA (Personal Digital Assistants) having the same configuration as the electronic book shown in FIGS. 11A and 11B.

(Application example 2)
FIG. 12 shows the appearance of a tablet personal computer. The tablet personal computer has, for example, a touch panel unit 210 and a housing 220, and the touch panel unit 210 is configured by the display device 1 (or the display devices 2 and 3).

  In addition, the display devices 1 to 3 according to the above-described embodiments and modifications may be applied to an electronic bulletin board or the like.

  As described above, the embodiments and modifications have been described, but the present disclosure is not limited to the aspects described in the embodiments and the like, and various modifications are possible. For example, in the above-described embodiment and the like, the same number of types of migrating particles 32 having different particle diameters and the same number of types of porous layers 30 having different hole diameters of the pores 333 are used. May be. For example, the porous layer 30 having different pore diameters of the pores 333 may be stacked with a larger number of layers than the types of the migrating particles 32 having different particle diameters.

  Moreover, in the said embodiment etc., although the structure provided with the insulating liquid 31, the electrophoresis element 32, and the porous layer 33 was illustrated as the electrophoretic element 30 (display layer 30), the structure of the display layer 30 is as follows. It is not limited to the one using the porous layer 33 as long as it can form a contrast by light reflection for each pixel using the electrophoresis phenomenon.

  In addition, the effect described in this specification is an illustration to the last, and is not limited, Moreover, there may exist another effect.

In addition, this indication can also take the following structures.
(1) A display device comprising a plurality of types of migrating particles having different average particle diameters and a plurality of porous layers formed of a fibrous structure and having different average pore diameters.
(2) The display device according to (1), including a display surface, wherein the plurality of porous layers are laminated to each other, and an average pore diameter decreases from the display surface toward the back surface.
(3) The display device according to (1) or (2), wherein the plurality of types of migrating particles have different colors.
(4) The display device according to any one of (1) to (3), wherein the number of the plurality of porous layers is equal to or more than the number of types of the migrating particles.
(5) The plurality of porous layers have a first layer and a second layer having a smaller average pore diameter than the first layer from the display surface side, and the thickness of the first layer is larger than that of the second layer. The display device according to any one of (2) to (4), which is larger.
(6) The display device according to any one of (1) to (5), wherein each of the plurality of types of migrating particles is charged and has a different charge amount.
(7) The display device according to any one of (1) to (6), wherein each of the plurality of porous layers is electrically charged and has a different charge amount.
(8) The display device according to any one of (1) to (7), wherein an average particle diameter of the plurality of types of migrating particles is 100 nm to 2 μm.
(9) The display device according to any one of (1) to (8), wherein an average pore diameter of the plurality of fibrous structures is not less than 0.1 μm and not more than 2 μm.
(10) The display device according to any one of (1) to (9), wherein the fibrous structure is formed by an electrostatic spinning method.
(11) The porous layer has non-electrophoretic particles held by the fibrous structure, and the light reflectance of the non-electrophoretic particles is higher than the light reflectance of the electrophoretic particles, and the electrophoretic particles are dark. The display device according to any one of (1) to (10), wherein the display, the non-migrating particles, and the fibrous structure perform a bright display.
(12) The migrating particles and the non-migrating particles are composed of at least one of an organic pigment, an inorganic pigment, a dye, a carbon material, a metal material, a metal oxide, glass, and a polymer material. The display device according to any one of (1) to (11).
(13) The display device according to any one of (1) to (12), wherein the fibrous structure is made of an acrylic resin.
(14) The display device according to any one of (1) to (13), wherein the insulating liquid contains a dispersant that disperses the electrophoretic particles.
(15) An electronic device including a display device, wherein the display device includes a plurality of types of migrating particles having different average particle diameters, and a plurality of porous layers formed of a fibrous structure and having different average pore diameters. machine.

  DESCRIPTION OF SYMBOLS 1, 2, 3 ... Display apparatus, 10 ... Drive board, 11 ... Support member, 12 ... TFT, 13 ... Protective layer, 14 ... Pixel electrode, 15 ... Adhesive layer, 16 ... Seal layer, 20 ... Counter substrate, 21 ... Support member, 22 ... counter electrode, 30 ... electrophoretic element, 31 ... insulating liquid, 32 (32A, 32B, 32C, 32D) ... electrophoretic particles, 33 (33A, 33B, 33C, 33D) ... porous layer, 34 ... cells, 40 ... spacers, 331 ... fibrous structures, 332 ... non-electrophoretic particles, 333 ... pores.

Claims (15)

A plurality of types of migrating particles having different average particle sizes,
A display device comprising a plurality of porous layers formed of a fibrous structure and having different average pore diameters.   The display device according to claim 1, comprising a display surface, wherein the plurality of porous layers are laminated with each other, and an average pore diameter decreases from the display surface toward the back surface.   The display device according to claim 1, wherein the plurality of types of migrating particles have different colors.   The display device according to claim 1, wherein the number of the plurality of porous layers is equal to or more than the number of types of the migrating particles. The plurality of porous layers have a first layer from the display surface side and a second layer having a smaller average pore diameter than the first layer,
The display device according to claim 2, wherein a thickness of the first layer is larger than that of the second layer.   The display device according to claim 1, wherein each of the plurality of types of migrating particles is charged and has a different charge amount.   The display device according to claim 1, wherein each of the plurality of porous layers is charged and has a different charge amount.   The display device according to claim 1, wherein an average particle diameter of the plurality of types of migrating particles is 100 nm or more and 2 μm or less.   The display device according to claim 1, wherein an average pore diameter of the plurality of fibrous structures is 0.1 μm or more and 5 μm or less.   The display device according to claim 1, wherein the fibrous structure is formed by an electrostatic spinning method. The porous layer has non-migrating particles held in the fibrous structure,
2. The display device according to claim 1, wherein the light reflectance of the non-electrophoretic particles is higher than the light reflectance of the electrophoretic particles, the electrophoretic particles perform dark display, and the non-electrophoretic particles and the fibrous structure perform bright display. .   The electrophoretic particles and the non-electrophoretic particles are composed of at least one of an organic pigment, an inorganic pigment, a dye, a carbon material, a metal material, a metal oxide, glass, and a polymer material. The display device described in 1.   The display device according to claim 1, wherein the fibrous structure is made of an acrylic resin.   The display device according to claim 1, further comprising a dispersant that disperses the migrating particles in the insulating liquid. A display device,
The display device
A plurality of types of migrating particles having different average particle sizes,
An electronic device having a plurality of porous layers formed of a fibrous structure and having different average pore diameters.

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