WO2016114011A1

WO2016114011A1 - Display device and electronic device

Info

Publication number: WO2016114011A1
Application number: PCT/JP2015/083045
Authority: WO
Inventors: 綾首藤; 平井　基介; 亮加瀬川
Original assignee: ソニー株式会社
Priority date: 2015-01-14
Filing date: 2015-11-25
Publication date: 2016-07-21
Also published as: JP2016130794A

Abstract

The display device according to the present technology includes, in an insulating liquid, migrating particles, a porous layer, and non-migrating particles held by the porous layer. The porous layer has a light reflectivity different from the migrating particles, and comprises a plurality of layers with each layer having a different volume fraction of non-migrating particles.

Description

Display device and electronic device

The present technology relates to a display device and an electronic device using an electrophoretic element.

In recent years, with the spread of mobile devices such as mobile phones or portable information terminals, the demand for display devices (displays) with low power consumption and high quality image quality has increased. In particular, recently, the electronic book distribution business has started, and a display with a display quality suitable for reading applications is desired.

As such a display, various displays such as a cholesteric liquid crystal display, an electrophoretic display, an electrooxidation reduction display, and a twist ball display have been proposed, but a reflective display is advantageous for reading applications. . In the reflective display, bright display is performed using reflection (scattering) of external light as in the case of paper, so that display quality closer to that of paper can be obtained.

Among the reflective displays, electrophoretic displays using the electrophoretic phenomenon are expected to be promising candidates because of their low power consumption and fast response speed. As the display method, the following two methods are mainly proposed.

The first method is to disperse two kinds of charged particles in an insulating liquid and move the charged particles according to the electric field. The two kinds of charged particles have different optical reflection characteristics and opposite polarities. In this method, an image is displayed by changing a distribution state of charged particles according to an electric field.

The second method is to disperse charged particles in an insulating liquid and dispose a porous layer (for example, Patent Document 1). In this method, charged particles move through the pores of the porous layer according to the electric field. The porous layer includes, for example, a fibrous structure made of a polymer material, and non-electrophoretic particles that are held by the fibrous structure and have different optical reflection characteristics from the charged particles.

JP 2012-22296 A

In the electrophoretic display in which such a porous layer is arranged, the display is switched by the charged particles moving through the pores according to the electric field. The display characteristics of the electrophoretic display can be improved by laminating many fibrous structures. This is because the white reflectance is improved by increasing the density of the porous layer. However, as the density of the porous layer increases, the pore diameter decreases. For this reason, there is a possibility that the reaction rate is lowered and the contrast is lowered.

Therefore, it is desirable to provide a display device and an electronic apparatus that can improve the white reflectance without reducing the response speed.

A display device according to an embodiment of the present technology includes migrating particles, a porous layer, and non-migrating particles held in the porous layer in an insulating liquid, and the porous layer is different from the migrating particles. It is composed of a plurality of layers having light reflectivity and different volume fractions of non-electrophoretic particles.

An electronic apparatus according to an embodiment of the present technology includes the display device of the present technology.

In the display device according to an embodiment of the present technology and the electronic apparatus according to the embodiment, the porous layer including the non-electrophoretic particles is configured by a plurality of layers having different volume fractions of the non-electrophoretic particles. It is possible to maintain the pore diameter of the pores in the porous layer while increasing the density.

According to the display device of one embodiment of the present technology and the electronic device of the one embodiment, since the porous layer composed of a plurality of layers having different volume fractions of the non-electrophoretic particles is provided, the density of the porous layer The pore diameter of the pores in the porous layer is maintained while increasing the. Therefore, the white reflectance can be improved without reducing the response speed, and a display device and an electronic apparatus having high display characteristics can be provided. 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 using the electrophoretic element which concerns on one embodiment of this technique. It is an expanded sectional view explaining the porous layer of the electrophoretic element shown in FIG. FIG. 2 is a cross-sectional view for explaining the operation of the display device shown in FIG. 1. FIG. 2 is a cross-sectional view for explaining the operation of the display device shown in FIG. 1. 14 is a perspective view illustrating an appearance of application example 1. FIG. FIG. 4B is a perspective view illustrating another example of the electronic book illustrated in FIG. 4A. 12 is a perspective view illustrating an appearance of application example 2. FIG.

Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description will be given in the following order.
1. Embodiment (Example in which a porous layer comprising two layers having different volume fractions of non-electrophoretic particles is provided)
1-1. Configuration of electrophoretic element 1-2. Configuration of display device 1-3. Action / Effect Application example Example

<1. Embodiment>
(1-1. Configuration of electrophoretic element)
FIG. 1 illustrates a cross-sectional configuration of a display device (display device 1) including an electrophoretic element (electrophoretic element 30) according to an embodiment of the present technology. The electrophoretic element 30 generates contrast using an electrophoretic phenomenon, and is used as a display body of various electronic devices such as tablets. The electrophoretic element 30 includes electrophoretic particles 32 and a porous layer 33 having pores H in an insulating liquid 31. The porous layer 33 is composed of a fibrous structure 34 and non-migrating particles 35 held on the fibrous structure 34 (see FIG. 2). In the present embodiment, the porous layer 33 has a two-layer (first layer 33A, second layer 33B) structure, and the first layer 33A and the second layer 33B are fibrous structures relative to the volume of the display device 1. The volume fractions of the non-electrophoretic particles 35 held by the nozzles 34 are different from each other. FIG. 1 schematically illustrates the configuration of the display device 1 including the electrophoretic element 30 and may differ from actual dimensions and shapes. Here, the volume fraction is the volume of the display device 1 composed of a plurality of electrophoretic elements 30, specifically, the volume of the display portion A provided between the seal layer 16 and the counter electrode 22. The ratio of how much volume the non-electrophoretic particles 35 occupy.

The insulating liquid 31 is made of, for example, an organic solvent such as paraffin or isoparaffin. As the insulating liquid 31, one kind of organic solvent may be used, or a plurality of kinds of organic solvents may be used. It is preferable to make the viscosity and refractive index of the insulating liquid 31 as low as possible. When the viscosity of the insulating liquid 31 is lowered, the mobility (response speed) of the migrating particles 32 is improved. In accordance with this, the energy (power consumption) required to move the migrating particles 32 is reduced. When the refractive index of the insulating liquid 31 is lowered, the difference in refractive index between the insulating liquid 31 and the porous layer 33 is increased, and the reflectance of the porous layer 33 is increased.

For example, a coloring agent, a charge adjusting agent, a dispersion stabilizer, a viscosity adjusting agent, a surfactant, or a resin may be added to the insulating liquid 31.

The migrating particles 32 dispersed in the insulating liquid 31 are one or more charged particles, and the charged migrating particles 32 move through the pores H in response to an electric field. The migrating particles 32 have an arbitrary optical reflection characteristic (light reflectance), and a contrast (CR) is generated due to the difference between the light reflectance of the migrating particles 32 and the light reflectance of the porous layer 33. It has become. For example, the migrating particles 32 may be brightly displayed and the porous layer 33 may be darkly displayed, or the migrating particles 32 may be darkly displayed and the porous layer 33 may be brightly displayed.

When the electrophoretic element 30 is viewed from the outside, when the electrophoretic particles 32 are brightly displayed, the electrophoretic particles 32 are visually recognized as white or a color close to white, and when darkly displayed, for example, black or black It is visually recognized as a color close to. The color of the migrating particles 32 is not particularly limited as long as contrast can be generated.

The migrating particles 32 are made of particles (powder) such as organic pigments, inorganic pigments, dyes, carbon materials, metal materials, metal oxides, glass, or polymer materials (resins). One of these may be used for the migrating particles 32, or two or more of them may be used. The migrating particles 32 may be composed of pulverized particles or capsule particles of resin solids containing the particles. Note that materials corresponding to the carbon material, metal material, metal oxide, glass, or polymer material are excluded from materials corresponding to organic pigments, inorganic pigments, or dyes. The particle size of the migrating particles 32 is, for example, 30 nm to 300 nm.

Examples of the organic pigments include azo pigments, metal complex azo pigments, polycondensed azo pigments, flavanthrone pigments, benzimidazolone pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, and perylene pigments. Perinone pigments, anthrapyridine pigments, pyranthrone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments or indanthrene pigments. Inorganic pigments include, for example, zinc white, antimony white, 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. If it is a high molecular compound which has a light absorption area | region in visible region, the kind will not be specifically limited.

The specific material of the migrating particles 32 is selected according to, for example, the role that the migrating particles 32 play in causing contrast. When the migrating particles 32 display brightly, for example, a metal oxide such as titanium oxide, zinc oxide, zirconium oxide, barium titanate or potassium titanate is used for the migrating particles 32. When the migrating particles 32 display in the dark, the migrating particles 32 may be, for example, a carbon material such as carbon black or copper-chromium oxide, copper-manganese oxide, copper-iron-manganese oxide, copper-chromium-manganese oxide. In addition, metal oxides such as copper-iron-chromium oxide are used. Among these, it is preferable to use a carbon material for the migrating particles 32. Electrophoretic particles 32 made of a carbon material exhibit excellent chemical stability, mobility and light absorption.

The content (concentration) of the migrating particles 32 in the insulating liquid 31 is not particularly limited, and is, for example, 0.1 wt% to 10 wt%. In this concentration range, the shielding and mobility of the migrating particles 32 are ensured. Specifically, if the content of the migrating particles 32 is less than 0.1% by weight, the migrating particles 32 are less likely to shield (conceal) the porous layer 33, and there is a possibility that sufficient contrast cannot be generated. is there. On the other hand, if the content of the migrating particles 32 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 aggregate.

The migrating particles 32 are preferably easily dispersed and charged in the insulating liquid 31 for a long period of time, and are preferably not easily adsorbed to the porous layer 33. For this reason, for example, a dispersant is added to the insulating liquid 31. A dispersant and a charge control agent may be used in combination.

This dispersing agent or charge adjusting agent has, for example, a positive or negative charge, or both, and increases the amount of charge in the insulating liquid 31 and causes the migrating particles 32 to move by electrostatic repulsion. It is for dispersing. Examples of such a dispersant include Solsperce series manufactured by Lubrizol, BYK series or Anti-Terra series manufactured by BYK-Chemical, or Span series manufactured by TCI America.

In order to improve the dispersibility of the migrating particles 32, the migrating particles 32 may be subjected to a surface treatment. This surface treatment is, for example, rosin treatment, surfactant treatment, pigment derivative treatment, coupling agent treatment, graft polymerization treatment or microencapsulation treatment. In particular, long-term dispersion stability of the migrating particles 32 can be maintained by performing a graft polymerization process, a microencapsulation process, or a combination thereof.

For such surface treatment, for example, a material (adsorbent material) having a functional group and a polymerizable functional group that can be adsorbed on the surface of the migrating particle 32 is used. The adsorbable functional group is determined according to the forming material of the migrating particle 32. For example, when the migrating particles 32 are made of a carbon material such as carbon black, an aniline derivative such as 4-vinylaniline, and when the migrating particles 32 are made of a metal oxide, methacrylic acid 3- Organosilane derivatives such as (trimethoxysilyl) propyl can be adsorbed respectively. Examples of the polymerizable functional group include a vinyl group, an acrylic group, and a methacryl group.

A surface treatment may be performed by introducing a polymerizable functional group onto the surface of the migrating particle 32 and grafting it onto the surface (graftable material). The graft material has, for example, a polymerizable functional group and a dispersing functional group. The functional group for dispersion disperses the migrating particles 32 in the insulating liquid 31 and retains dispersibility due to steric hindrance. For example, when the insulating liquid 31 is paraffin, a branched alkyl group or the like can be used as the functional group for dispersion. Examples of the polymerizable functional group include a vinyl group, an acrylic group, and a methacryl group. In order to polymerize and graft the graft material, for example, a polymerization initiator such as azobisisobutyronitrile (AIBN) may be used. In addition, a material having a functional group capable of being adsorbed on the surface of the migrating particle 32 and an alkyl chain for imparting dispersibility can be used. Examples of such materials include titanate coupling agents (for example, KR-TTS manufactured by Ajinomoto Fine Techno Co., Ltd.) and aluminate coupling agents.

For details of the method for dispersing the migrating particles 32 in the insulating liquid 31, see “Dispersion Technology of Ultrafine Particles and its Evaluation: Surface Treatment / Fine Grinding and Dispersion Stabilization in Air / Liquid / Polymer— Science & Technology)).

The porous layer 33 can shield the migrating particles 32, and includes a fibrous structure 34 and non-migrating particles 35 that are modified by the surfactant and held by the fibrous structure 34. Yes. FIG. 2 is an enlarged view of the porous layer 33 surrounded by the dotted line of the display device 1 shown in FIG. The porous layer 33 is a three-dimensional structure (irregular network structure such as a nonwoven fabric) formed by the fibrous structure 34 as shown in FIG. 2, and has a plurality of gaps (pores H). Is provided. By forming the three-dimensional structure of the porous layer 33 by the fibrous structure 34, light (external light) is irregularly reflected (multiple scattering), and the reflectance of the porous layer 33 is increased. Therefore, even when the thickness of the porous layer 33 is small, a high reflectance can be obtained, the contrast of the electrophoretic element 30 can be improved, and the energy required for the movement of the electrophoretic particles 32 can be reduced.

The porous layer 33 of the present embodiment is configured by a first layer 33A and a second layer 33B having different volume fractions of the non-electrophoretic particles 35 held by the fibrous structure 34 with respect to the volume of the display device 1. Yes. Specifically, it is preferable that the volume fraction of the second layer 33B provided on the display surface S1 side is larger than that of the first layer 33A. The difference in volume fraction between the first layer 33A and the second layer 33B can be controlled by changing the fiber diameter of the fibrous structure 34, for example. If the composition ratio of the first layer 33A and the second layer 33B is constant, the smaller the fiber diameter, the higher the volume fraction, and the larger the fiber diameter, the lower the volume fraction. In addition, the measuring method of the volume fraction of the non-electrophoretic particle 35 with respect to the volume of the display part A is measured using the following method, for example. First, the display device 1 is cut using an instrument such as a microtome, the cross section of the cut display portion A is observed using an SEM, and non-electrophoretic particles are mapped. Thereby, the volume fraction of the non-electrophoretic particles 35 with respect to the display part A is calculated. When it is difficult to distinguish non-electrophoretic particles, they can be distinguished by mapping elements using SEM-EDX or FT-TR. Or when the kind and ratio of the non-electrophoretic particles and the polymer already used for production are known, they can be easily calculated from their specific gravity.

As a method of changing the fiber diameter of the fibrous structure 34, for example, there is a method of changing the polymer concentration and the composition of the non-electrophoretic particles 35 in the porous layer forming step. In addition, the fiber diameter of the fibrous structure 34 can also be changed by changing the modification amount of the surfactant that modifies the surface of the non-electrophoretic particles described later, or by changing the amount of the surfactant added to the polymer solution. Can be changed. Further, the particle size of the non-electrophoretic particles 35 used when forming the first layer 33A and the second layer 33B may be changed.

When changing the volume fraction of the first layer 33A and the second layer 33B by changing the particle size of the non-migrating particles 35, the particle size of the non-migrating particles 35 used for the second layer 33B is larger than that of the first layer 33A. It is preferable to use a small one. Thereby, the fiber diameter of the fibrous structure 34 which comprises the 2nd layer 33B becomes small, and the volume fraction of the 2nd layer 33B becomes higher than the 1st layer 33A. For example, the volume fraction of the second layer 33B is preferably 13% or more, and more preferably 13% or more and 25% or less. The volume fraction of the first layer 33A is preferably 5% or more and 10% or less, for example. Note that the volume fraction of the first layer 33A and the second layer 33B constituting the porous layer 33 may be controlled using a method other than the above method.

The overall thickness of the porous layer 33 in the Z-axis direction (hereinafter simply referred to as thickness) is, for example, 5 μm or more and 100 μm or less, depending on the element configuration of the electrophoretic element 30. In order to provide sufficient white reflectance, black reflectance, and response time, it is more preferably 15 μm or more and 50 μm or less. Among these, it is preferable that the thickness of the second layer 33B is 40% or less of the whole. Specifically, when the thickness of the entire porous layer is 30 μm, at least the thickness of the second layer 33B may be 12 μm or less. By setting it as such a structure, the white reflectance of the display apparatus 1 improves with the 2nd layer 33B. In addition, the first layer 33A can keep the pore diameter of the pore H, which is the movement path of the migrating particles 32 in the display device 1, large. That is, the migrating particles 32 are easily moved via the pores H, the response speed is improved, and the energy required to move the migrating particles 32 is further reduced. In addition, the second layer 33B having a high volume fraction is disposed on the display surface S1 side, and the first layer 33A having a low volume fraction is disposed on the opposite side, thereby pressing the display surface S1 side. The effect of dispersing the force is also exhibited, and the durability of the display device 1 is improved.

The fibrous structure 34 is a fibrous substance having a sufficient length with respect to the fiber diameter (diameter). For example, a plurality of fibrous structures 34 are assembled and randomly overlapped to form the porous layer 33. One fibrous structure 34 may be entangled randomly to form the porous layer 33. Or the porous layer 33 by the one fibrous structure 34 and the porous layer 33 by the some fibrous structure 34 may be mixed.

The fibrous structure 34 extends, for example, in a straight line. The shape of the fibrous structure 34 may be any shape. For example, the fibrous structure 34 may be crimped or bent in the middle. Or the fibrous structure 34 may be branched on the way.

The minimum fiber diameter of the fibrous structure 34 is, for example, preferably 500 nm or less, and more preferably 300 nm or less. The average fiber diameter is preferably, for example, from 50 nm to 2000 nm, but may be outside the above range. When the volume fraction of the non-electrophoretic particles of the first layer 33A and the second layer 33B is adjusted by the fiber diameter of the fibrous structure 34, the average fiber diameter of the fibrous structure 34 constituting the first layer 33A is For example, it is preferable that it is 500 nm or more and 1000 nm or less, and it is preferable that the average fiber diameter of the fibrous structure 34 which comprises the 2nd layer 33B shall be 200 nm or more and 500 nm or less, for example. By reducing the average fiber diameter, light is easily diffusely reflected, and the pore diameter of the pores H is increased. The fiber diameter is determined so that the fibrous structure 34 can hold the non-migrating particles 35. The average fiber diameter can be measured, for example, by microscopic observation using a scanning electron microscope or the like. The average length of the fibrous structure 34 is arbitrary. The fibrous structure 34 is formed by, 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 done. By using such a method, the fibrous structure 34 having a sufficient length with respect to the fiber diameter can be easily and stably formed.

The fibrous structure 34 is preferably composed of nanofibers. Here, the nanofiber is a fibrous substance having a fiber diameter of 1 nm to 1000 nm and a length of 100 times or more of the fiber diameter. By using such nanofibers as the fibrous structure 34, light is easily diffusely reflected, and the reflectance of the porous layer 33 can be further improved. That is, the contrast of the electrophoretic element 30 can be improved. Further, in the fibrous structure 34 made of nanofibers, the proportion of the pores H in the unit volume increases, and the migrating particles 32 can easily move through the pores H. Therefore, the energy required for moving the migrating particles 32 can be reduced. The fibrous structure 34 made of nanofibers is preferably formed by an electrostatic spinning method. By using the electrospinning method, the fibrous structure 34 having a small fiber diameter can be easily and stably formed.

It is preferable to use a fibrous structure 34 having a light reflectance different from that of the migrating particles 32. Thereby, a contrast due to a difference in light reflectance between the porous layer 33 and the migrating particles 32 is easily formed. A fibrous structure 34 showing light transparency (colorless and transparent) in the insulating liquid 31 may be used.

The pore H is configured by overlapping a plurality of fibrous structures 34 or entwining one fibrous structure 34. The pore H preferably has an average pore diameter as large as possible so that the migrating particles 32 can easily move through the pore H. The average pore diameter of the pores H is, for example, not less than 0.1 μm and not more than 10 μm.

Non-electrophoretic particles 35 are one or more particles that are fixed to the fibrous structure 34 and do not undergo electrophoresis. The non-migrating particles 35 may be embedded in the held fibrous structure 34 or may partially protrude from the fibrous structure 34.

The average particle diameter of the non-migrating particles 35 is preferably 150 nm or more and 700 nm or less, for example. When the volume fraction of the first layer 33A and the second layer 33B is adjusted by the particle size of the non-migrating particles 35, the average particle size of the non-migrating particles 35 included in the first layer 33A is, for example, 300 nm or more and 700 nm. The average particle diameter of the non-migrating particles 35 included in the second layer 33B is preferably, for example, 150 nm or more and 300 nm or less.

As the non-electrophoretic particles 35, those having a light reflectance different from that of the electrophoretic particles 32 are used. The non-migrating particles 35 can be made of the same material as the migrating particles 32. Specifically, when the non-electrophoretic particles 35 (porous layer 33) display brightly, the material when the electrophoretic particles 32 display brightly, and when the non-electrophoretic particles 35 display darkly, the electrophoretic particles 32 darken. Each material for display can be used. When performing bright display by the porous layer 33, it is preferable that the non-migrating particles 35 are made of a metal oxide. Thereby, it is possible to obtain excellent chemical stability, fixability and light reflectivity. The constituent materials of the non-migrating particles 35 and the migrating particles 32 may be the same or different. The color visually recognized from the outside when the non-electrophoretic particle 35 performs bright display or dark display is the same as that described for the electrophoretic particle 32.

Further, the surface of the non-electrophoretic particle 35 may be modified with a surfactant. Surfactants are, for example, anionic (anionic) surfactants having a carboxylic acid, sulfonic acid or phosphoric acid structure as hydrophilic groups and cationic (cationic) properties having, for example, tetraalkylammonium or alkylamine as hydrophilic groups. Surfactant is mentioned. In addition, nonionic (nonionic) surfactants having a hydrophilic part as a non-electrolyte, that is, a non-ionized hydrophilic part, and amphoteric surfactants having both an anionic part and a cationic part in the molecule may be used. . Examples of amphoteric surfactants include alkyl dimethylamine oxide and alkyl carboxybetaine. In addition, when using metal materials, such as a titanium oxide, as the non-electrophoretic particle 35, it is preferable to use an anionic surfactant. In particular, a surfactant having a hydrophilic group with a small molecular volume such as carboxylic acid is preferable because it easily covers the entire surface of the non-electrophoretic particle 35. Further, it is desirable that the surfactant does not ooze into the insulating liquid 31 so that the display characteristics are not deteriorated for a long time.

Such a porous layer 33 can be formed by the following method, for example. First, as the non-electrophoretic particles 35, for example, titanium oxide having two types of primary particle sizes (for example, 250 nm (small particles) and, for example, 450 nm (large particles)) is prepared, and these are, for example, carboxylic acid anions. The organic surfactant is added to the organic solvent in which it has been dissolved and stirred. Thereby, titanium oxide (non-electrophoretic particles 35) whose surface is coated with a carboxylic acid anionic surfactant is obtained. Next, for example, a constituent material of the fibrous structure 34 such as a polymer material (polymer) is dissolved in an organic solvent to prepare a solution, and then, for example, small non-electrophoretic particles 35 are added to the solution. Is added and stirred sufficiently to prepare a spinning solution in which the non-electrophoretic particles 35 are dispersed. Subsequently, spinning is performed from the spinning solution by, for example, an electrostatic spinning method to fix the non-migrating particles 35 to the fibrous structure 34, thereby forming the first layer 33A. Next, for example, a constituent material of the fibrous structure 34 such as a polymer material (polymer) is dissolved in an organic solvent to prepare a solution, and then, for example, large non-electrophoretic particles 35 are added to the solution. And using the same method as that for the first layer 33A, the second layer 33B having a higher volume fraction than the first layer 33A is formed. The porous layer 33 is completed by stacking the second layer 33B on the second layer 33A. Here, the primary particle size is a minimum particle size. For example, when the particles are aggregated or bonded, the primary particle size represents the particle size of each particle.

Thus, the dispersibility of the non-migrating particles 35 in the spinning solution is improved by using the non-migrating particles 35 previously modified with a surfactant. As a result, an electric field is easily applied to the non-migrating particles 35 during spinning, and a fibrous structure 34 with a reduced fiber diameter, that is, a fine fiber is obtained. Note that the surface of the non-electrophoretic particle 35 fixed to the fibrous structure 34 is covered with a polymer constituting the fibrous structure 34.

Further, the porous layer 33 may be formed by forming holes H in the polymer film by using a laser to form a hole H, and a cloth knitted with synthetic fibers or the like on the porous layer 33, Alternatively, open-cell porous polymer may be used. In this case, the work of kneading the non-electrophoretic particles into the polymer is necessary as a pre-operation. At that time, the final volume fraction is predicted from the particle diameter and the specific gravity, and the mixing ratio of the non-electrophoretic particles is adjusted. Thereby, layers having different volume fractions can be formed.

The fibrous structure is preferably composed of molecules having a main skeleton (main part of the molecule) composed of, for example, carbon atoms, oxygen atoms and hydrogen atoms. In other words, the main skeleton of this molecule does not contain atoms other than carbon atoms, oxygen atoms, and hydrogen atoms, and consists only of these atoms. Such molecules forming the fibrous structure 34 preferably do not contain a highly polar functional group such as a hydroxyl group and a carboxylic acid group. Thereby, the absolute value of the surface potential of the fibrous structure 34 becomes small, and the response speed of the electrophoretic element 30 can be improved. Here, the main skeleton refers to a portion excluding both ends of the molecule. The molecules forming the fibrous structure 34 are preferably composed of carbon atoms, oxygen atoms and hydrogen atoms up to both ends, but the ends contain atoms other than these carbon atoms, oxygen atoms and hydrogen atoms. May be. For example, when a polymer is synthesized by radical polymerization, a polymerization initiator such as azobisisobutyronitrile (AIBN) is used as a catalyst. Nitrogen atoms and the like are contained at both ends of the polymer synthesized in this way, but the atoms at the ends are less than 1/1000 of the whole molecule in terms of molecular weight. Therefore, this terminal atom contributes little to the properties of the molecule. The same applies to polymerization initiators other than AIBN. Thus, the reactivity of the fibrous structure 34 composed of only carbon atoms, oxygen atoms, and hydrogen atoms is low, so that the fibrous structure 34 exists stably in the insulating liquid 31. Therefore, the electrophoretic element 30 can obtain high reliability.

The molecule forming the fibrous structure 34 is a chain polymer. Here, a chain molecule (chain molecule) refers to a molecule that does not include a cyclic atomic arrangement structure. Examples of the cyclic atomic arrangement include a monocyclic compound and a heterocyclic compound. Monocyclic compounds are composed of a single element, and specifically include aromatic compounds, cycloalkenes, cycloalkanes, cycloalkynes, and the like. The heterocyclic compound is composed of two or more kinds of elements, and specifically includes pyrrole, carbazole, cyclic acetal, pyran, furan and thiophene. The chain molecule may be linear or branched. When the fibrous structure 34 is composed of chain molecules, since the steric hindrance is smaller than that of a molecule including a cyclic structure, the migrating particles 32 are easily moved, and the contrast and response speed of the electrophoretic element 30 are improved. To do.

The chain molecule constituting the fibrous structure 34 includes an ester group. For example, the fibrous structure 34 is preferably formed from an acrylic resin. Specific examples of the chain molecule include polyalkyl methacrylate, polyalkyl acrylate, polyalkenyl methacrylate, polyalkenyl acrylate, polyalkynyl methacrylate and polyalkynyl acrylate. This chain molecule does not have a functional group having a polarity higher than that of the ester group, and the absolute value of the surface potential of the fibrous structure 34 is, for example, 20 mV or less. It is more preferable to select chain molecules so that the absolute value of the surface potential of the fibrous structure 34 is 10 mV or less. That is, the ester group has a smaller polarity than the cyano group and the like, but this is sufficiently large for spinning using the electrospinning method, and the fibrous structure 34 can be easily formed by the electrospinning method. can do.

For the chain molecule constituting the fibrous structure 34, it is preferable to use a material that is not easily decomposed by microorganisms. That is, the chain molecule is preferably resistant to biodegradation. Examples of the biodegradable polymer include polylactic acid, polyvinyl alcohol, cellulose acetate, collagen, gelatin, and chitosan. Since such a polymer is easily decomposed, there is a possibility that the characteristics of the fibrous structure cannot be maintained when some kind of stimulus is applied to the electrophoretic element from the outside. In addition, many of such polymers are water-soluble and may be dissolved by moisture in the electrophoretic element, so that the shape of the fibrous structure cannot be maintained. On the other hand, when the fibrous structure 34 is formed of chain molecules having resistance to biodegradation, the stability of the fibrous structure 34 is increased. Therefore, the reliability of the electrophoretic element 30 can be improved. The surface of the fibrous structure 34 may be covered with an arbitrary protective layer.

(1-2. Configuration of display device)
Next, the overall configuration and operation principle of the display device 1 will be described.

1 and 3A show an example of a cross-sectional configuration of a display device (display device 1) using the electrophoretic element 30. FIG. The display device 1 is an electrophoretic display (so-called electronic paper display) that displays an image (for example, character information) using an electrophoretic phenomenon, and an electrophoretic element between a driving substrate 10 and a counter substrate 20. 30 is provided. The space between the driving substrate 10 and the counter substrate 20 is adjusted to a predetermined distance by the spacer 40.

The drive substrate 10 includes, for example, a TFT (Thin Film Transistor) 12, a protective layer 13, a pixel electrode 14, and an adhesive layer 15 in this order on one surface of the support member 11. For example, the TFT 12 and the pixel electrode 14 are arranged in a matrix or a segment according to the pixel arrangement.

The support member 11 is made of, for example, an inorganic material, a metal material, a plastic material, or the like. As the inorganic materials, for example, silicon (Si), silicon oxide (SiOX), such as silicon nitride (SiN _X) or aluminum oxide (AlOx) may be mentioned. Silicon oxide includes glass or spin-on-glass (SOG). Examples of the metal material include aluminum (Al), nickel (Ni), and stainless steel, and examples of the plastic material include polycarbonate (PC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyethyl ether. Ketone (PEEK) etc. are mentioned.

Since the display device 1 displays an image on the counter substrate 20 side, the support member 11 may be non-light transmissive. The support member 11 may be configured by a rigid substrate such as a wafer, or may be configured by a flexible thin glass or film. By using a flexible material for the support member 11, the flexible display device 1 can be realized.

TFT 12 is a switching element for selecting a pixel. The TFT 12 may be an inorganic TFT using an inorganic semiconductor layer as a channel layer, or an organic TFT using an organic semiconductor layer. The protective layer 13 and the adhesive layer 15 are made of, for example, an insulating resin material such as polyimide. If the surface of the protective layer 13 is sufficiently flat, the adhesive layer 15 can be omitted. The pixel electrode 14 is made of a metal material such as gold (Au), silver (Ag), or copper (Cu). The pixel electrode 14 is connected to the TFT 12 through a contact hole (not shown) provided in the protective layer 13 and the adhesive layer 15.

The counter substrate 20 includes, for example, a support member 21 and a counter electrode 22, and the counter electrode 22 is provided on the entire surface of the support member 21 (a surface facing the drive substrate 10). Similarly to the pixel electrode 14, the counter electrode 22 may be arranged in a matrix or a segment.

The support member 21 is made of the same material as the support member 11 except that it is light transmissive. For the counter electrode 22, for example, a light-transmitting conductive material such as indium oxide-tin oxide (ITO), antimony oxide-tin oxide (ATO), fluorine-doped tin oxide (FTO), or aluminum-doped zinc oxide (AZO). (Transparent electrode material) can be used.

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 (transmittance) of the counter electrode 22 is preferably as high as possible. 80% or more. Further, the electrical resistance of the counter electrode 22 is preferably as low as possible, for example, 100Ω / □ or less.

The electrophoretic element 30 includes an electrophoretic particle 32 and a porous layer 33 having a plurality of pores H in an insulating liquid 31. The insulating liquid 31 is filled in the space between the driving substrate 10 and the counter substrate 20, and the porous layer 33 is supported by the spacer 40, for example. The space filled with the insulating liquid 31 is divided into, for example, a retreat area R1 closer to the pixel electrode 14 and a display area R2 closer to the counter electrode 22 with the porous layer 33 as a boundary. . The configurations of the insulating liquid 31, the migrating particles 32, and the porous layer 33 are the same as those described in the above embodiments and the like. In FIG. 3A and FIG. 3B described later, the pores H are omitted to simplify the illustrated contents.

The porous layer 33 may be adjacent to one of the pixel electrode 14 and the counter electrode 22, and the retreat area R1 and the display area R2 may not be clearly separated. The migrating particles 32 move toward the pixel electrode 14 or the counter electrode 22 according to the electric field.

The thickness of the spacer 40 is, for example, 10 μm to 100 μm, and is preferably as thin as possible. Thereby, power consumption can be suppressed. The spacer 40 is made of, for example, an insulating material such as a polymer material, and is provided, for example, in a lattice shape between the drive substrate 10 and the counter substrate 20. The arrangement shape of the spacer 40 is not particularly limited, but it is preferable that the spacer 40 is provided so as not to disturb the movement of the migrating particles 32 and to uniformly distribute the migrating particles 32.

In the display device 1 in the initial state, the migrating particles 32 are arranged in the retreat area R1 (FIG. 3A). In this case, since the migrating particles 32 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 (an image is not 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 32 are moved from the retreat area R1 to the porous layer 33 for each pixel. It moves to the display area R2 via (pore H). 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.

In addition, according to the display device 1, the electrophoretic element 30 having a high response speed can display a high-quality image suitable for, for example, colorization and moving image display.

In general electrophoretic displays, as described above, contrast is generated by the difference between the light reflectance of the migrating particles and the light reflectance of the porous layer. Specifically, among the migrating particles and the porous layer, the light reflectance for bright display is higher than the light reflectance for dark display. It is preferable that the light reflectance of the non-electrophoretic particles is higher than that of the electrophoretic particles so that the porous layer displays light and the electrophoretic particles display dark. By performing such a display, the light reflectance at the time of bright display is remarkably increased by utilizing the irregular reflection of light by the porous layer (three-dimensional structure). Accordingly, the contrast is remarkably improved accordingly.

In the electrophoretic element, the electrophoretic particles move through the pores of the porous layer within the range where the electric field is applied. Depending on the area where the migrating particles have moved or not moved, either bright display or dark display is performed, and an image is displayed.

The display characteristics of the electrophoretic display are not yet sufficient, and further improvement in the reflectance has been demanded. The reflectance can be improved by, for example, laminating many fibrous structures or using non-electrophoretic particles having a large particle size (for example, 400 to 700 nm). For example, in a display device in which migrating particles are darkly displayed and the porous layer is brightly displayed, the density of the porous layer can be increased by laminating many fibrous structures, and the ability to shield the migrating particles can be improved. It is considered possible. Further, it is considered that the ability to shield the migrating particles can be improved by increasing the particle size of the non-migrating particles fixed to the fibrous structure and increasing the amount thereof. However, as the density of the porous layer increases, the reflectance improves, but the reaction speed decreases because the pore diameter decreases, and for example, it becomes difficult to move the migrating particles to the display surface, resulting in a contrast. May decrease.

On the other hand, in the display device 1 including the electrophoretic element 30 according to the present embodiment, the porous layer 33 includes two layers having different volume fractions of the non-electrophoretic particles 35 with respect to the volume of the display portion A. Includes a first layer 33A in which the volume fraction of the non-electrophoretic particles 35 is lower than that of the second layer 33B, and a second layer 33B in which the volume fraction of the non-electrophoretic particles 35 is higher than that of the first layer 33A. I made it. As a result, it is possible to maintain the pore diameter in the porous layer 30 while improving the density of the porous layer 30.

In particular, the second layer 33B having a higher volume fraction of the non-migrating particles 35 than the first layer 33A is disposed on the display surface S1 side, thereby improving the white reflectance and migrating particles in the porous layer 33. It is possible to secure 32 moving speeds.

As described above, in the display device 1 including the electrophoretic element 30 according to the present embodiment, the porous layer 33 has the first layer 33A and the volume fraction of the non-electrophoretic particles 35 with respect to the volume of the display portion A is the first. The second layer 33B is higher than the first layer 33A. Thereby, the density of the porous layer 30 is improved and the white reflectance is improved. Moreover, since the pore diameter of the pores in the porous layer 30 is ensured, the moving speed of the migrating particles 32 is maintained, and the response speed can be maintained. That is, it is possible to provide a display device and an electronic device that maintain high response speed and have high display characteristics with improved white reflectance.

<2. Application example>
Next, an application example of the display device 1 will be described.

The display device 1 according to an embodiment of the present technology is applicable to electronic devices for various purposes, and the type of the electronic device is not particularly limited. This display device 1 can be mounted on, for example, the following electronic devices. However, the configuration of the electronic device described below is merely an example, and the configuration can be changed as appropriate.

(Application example 1)
4A and 4B show the external configuration of the 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 shown in FIG. 4A or may be provided on the upper surface as shown in FIG. 4B. The display unit 110 is configured by the display device 1. The display device 1 may be mounted on a PDA (Personal Digital Assistants) having the same configuration as the electronic book shown in FIGS. 4A and 4B.

(Application example 2)
FIG. 5 shows the appearance of a tablet personal computer. The tablet personal computer has, for example, a touch panel unit 310 and a housing 320, and the touch panel unit 310 is configured by the display device 1.

<3. Example>
Next, embodiments of the present technology will be described in detail.

Display devices (Experimental Examples 1 to 9) were produced using black (dark display) migrating particles and a white (bright display) porous layer (particle-containing fibrous structure) by the following procedure.

(Experimental example 1)
First, a mixed solution of 400 ml of tetrahydrofuran and 400 ml of methanol was prepared, and then 50 g of composite oxide fine particles (copper-iron-manganese oxide: Daipi Seika Kogyo Co., Ltd. Daipyroxide Side Color TM9550) were added to the solution. Ultrasonic stirring (at 25 ° C. to 35 ° C. for 30 minutes) was performed in an ultrasonic bath. Next, 40 ml of 28% ammonia water was added dropwise to the dispersion of the composite oxide fine particles over 30 minutes, and then a solution in which 10 g of preneact KR-TTS (manufactured by Ajinomoto Fine Techno Co., Ltd.) was dissolved in 80 ml of tetrahydrofuran was added over 30 minutes. And dripped. Subsequently, the ultrasonic bath was heated to 60 ° C. and held for 3 hours, and then cooled to room temperature, followed by centrifugation (at 6000 rpm for 10 minutes) and decantation. Subsequently, the precipitate after decantation was redispersed in a mixed solvent of tetrahydrofuran and methanol (volume ratio 1: 1), followed by centrifugation (at 6000 rpm for 10 minutes) and decantation. The precipitate obtained by repeating this washing operation three times was dried overnight in a vacuum oven at 70 ° C. As a result, black electrophoretic particles coated with a dispersing group were obtained.

After preparing the migrating particles, 16.7 g of a dispersant and a charge control agent (OLOA 1200 manufactured by Chevron-Chemicals) were dissolved in 83.3 g of insulating liquid. Isoparaffin (Isopar G manufactured by ExxonMobil) was used as the insulating liquid. 1 g of the migrating particles was added to 9 g of this insulating liquid, and ultrasonic dispersion was performed. Subsequently, centrifugation (90 minutes at 6000 rpm) was performed, followed by decantation, and then redispersed in an insulating liquid. This washing operation was repeated three times, and an insulating liquid was added to the resulting precipitate so that the pigment component was 10% by weight. Subsequently, 3.34 g of OLOA 1200 顔料 and 20 g of the electrophoretic particle dispersion were added to 76.7 g of this insulating liquid and stirred to obtain an insulating liquid containing an additive and a black pigment.

On the other hand, the porous layer was formed as follows. First, titanium oxide with an average primary particle size of 450 nm and titanium oxide with a thickness of 200 nm are prepared as non-electrophoretic particles, and mixed to 4 wt% in tetrahydrofuran in which a carboxylic acid anionic surfactant is dissolved. Stir for 1 hour using a paint shaker. Then, it is centrifuged (5000 rpm for 10 minutes), and the solvent is removed by decantation. After washing 3 times, it was dried at 70 ° C. overnight. As a result, titanium oxide coated with a carboxylic acid anionic surfactant was obtained. Here, titanium oxide having a primary particle diameter of 450 nm is referred to as non-electrophoretic particle T-1, and titanium oxide having a primary particle diameter of 200 nm is referred to as non-electrophoretic particle T-2.

Next, polymethyl methacrylate was prepared as a constituent material of the fibrous structure. After 13 g of this polymethyl methacrylate was dissolved in 87 g of N, N′-dimethylformamide, 2 g of non-electrophoretic particles T-1 were added to 8 g of this solution and mixed with a bead mill. As a result, a spinning solution for forming a fibrous structure was obtained. After a pixel electrode made of ITO having a predetermined pattern was formed on the driving substrate, spinning was performed using this spinning solution. Specifically, the spinning solution was put into a syringe, and spinning for 5.5 g / cm 2 was performed on the driving substrate. The obtained fibrous structure is designated as NW-1. Spinning was performed using an electrospinning apparatus (NANON manufactured by MEC Co., Ltd.).

Subsequently, 10 g of polymethyl methacrylate was dissolved in 87 g of N, N′-dimethylformamide, 2 g of non-electrophoretic particles T-2 were added to 8 g of this solution, and mixed by a bead mill. As a result, a spinning solution for forming a fibrous structure was obtained. Spinning was performed using this spinning solution. Specifically, the spinning solution was put in a syringe, and spinning for 2 g / cm 2 was performed on the driving substrate. The obtained fibrous structure is designated as NW-2. This fibrous structure NW-2 was overlaid on the previously formed fibrous structure NW-1, and a porous layer (a fibrous structure holding non-electrophoretic particles) was formed on the drive substrate. The average fiber diameter of the fibrous structure NW-1 was 500 nm, and the average fiber diameter of the fibrous structure NW-2 was 400 nm.

After forming the porous layer on the driving substrate, the unnecessary porous layer was removed from the driving substrate. Specifically, the porous layer where the pixel electrode is not provided was removed. As a counter substrate, a counter electrode made of ITO was formed on a plate-like member, and a spacer was disposed on the counter substrate. As the spacer, a photo-curing resin (photosensitive resin Photorec A-400 (registered trademark) manufactured by Sekisui Chemical Co., Ltd.) containing beads (outer diameter 15 μm) is used, and this is overlapped with the driving substrate. In a position not overlapping with the porous layer. After providing the spacer on the counter substrate, this was overlapped with the driving substrate on which the porous layer was formed. At this time, the porous layer was separated from the pixel electrode and the counter electrode by holding the porous layer with the spacer. Next, an insulating liquid in which the migrating particles were dispersed was injected between the driving substrate and the counter substrate. Finally, the light curable resin was irradiated with ultraviolet light to complete the display device. The volume fraction of titanium oxide in the display device was 14% and 7.1% from the display surface side.

(Experimental example 2)
A display device (Experimental Example 2) was produced in the same procedure as in Experimental Example 1, except that the fibrous structure NW-1 was spun at 7 g / cm2 min. The volume fraction of the porous layer was 17% and 8.8% from the display surface side.

(Experimental example 3)
A display device (Experimental Example 3) was produced in the same procedure as in Experimental Example 1 except that the fibrous structure NW-1 was spun at 7 g / cm2 min and the fibrous structure NW-2 was spun at 1 g / cm2 min. The volume fraction of the porous layer was 15% and 8.1% from the display surface side.

(Experimental example 4)
A display device (Experimental Example 4) was produced in the same procedure as in Experimental Example 1, except that the fibrous structure NW-1 was spun at 8 g / cm2 min and the fibrous structure NW-2 was spun at 1 g / cm2 min. The volume fraction of the porous layer was 17% and 9.1% from the display surface side.

(Experimental example 5)
The fibrous structure NW-3 was prepared at 7 g / cm 2 min by 14 g of polymelacrylate constituting the fibrous structure, 86 g of N, N′-dimethylformamide, and 15 g of titanium oxide. Further, 11 g of polymelacrylate constituting the fibrous structure, 89 g of N, N′-dimethylformamide, and 40 g of titanium oxide were prepared to produce the fibrous structure NW-4 at 2.5 g / cm 2 min. Was overlaid on the fibrous structure NW-3. Except for this, a display device (Experimental Example 5) was produced in the same procedure as in Experimental Example 1. The volume fraction of the porous layer was 14% and 8.4% from the display surface side, the average fiber diameter of the fibrous structure NW-3 was 500 nm, and the average fiber diameter of the fibrous structure NW-4 was 700 nm. It was.

(Experimental example 6)
A display device (Experimental Example 6) was produced in the same procedure as in Experimental Example 1, except that the porous layer was composed only of the fibrous structure NW-1 spun at 7.5 g / cm2 min. The volume fraction of the porous layer was 7.8%.

(Experimental example 7)
A display device (Experimental Example 6) was produced in the same procedure as in Experimental Example 1, except that the porous layer was composed only of the fibrous structure NW-1 spun at 9 g / cm2 min. The volume fraction of the porous layer was 9.3%.

(Experimental example 8)
A display device (Experimental Example 6) was produced in the same procedure as in Experimental Example 1 except that the porous layer was composed only of the fibrous structure NW-1 spun at 11 g / cm2 min. The volume fraction of the porous layer was 11%.

(Experimental example 9)
A display device (Experimental Example 6) was produced in the same procedure as in Experimental Example 1 except that the porous layer was composed only of the fibrous structure NW-2 spun at 9 g / cm2 min. The volume fraction of the porous layer was 12%.

The performance of the display devices of Experimental Examples 1 to 9 includes the volume fraction (%) of non-electrophoretic particles in the fibrous structure, white reflectance (%) immediately after production, black reflectance (%), contrast (CR ) And 15 V after applying for 200 ms were examined for white reflectance (%). The results are shown in Table 1.

The white reflectance and the black reflectance were measured using a spectrocolorimeter (CD100 manufactured by Yokogawa Electric Corporation) after applying an alternating voltage of 15 V for 12 seconds to the display device. The contrast (CR) was calculated from the white reflectance and the black reflectance as CR = white reflectance (%) / black reflectance (%). The white reflectance after 200 ms of voltage application shows how much the white reflectance has improved after applying a reverse bias of the same time (200 ms) after applying a voltage of 15 V to the display device to display black. The higher the response speed, the higher the white reflectance value.

When comparing Experimental Examples 1 to 5 in which the porous layer is composed of two layers having different volume fractions of non-electrophoretic particles and Experimental Examples 6 to 9 in which the porous layer is configured as a single layer, Experimental Examples 1 to 5 are more in white reflectance. And the contrast tended to be high. In addition, the white reflectance when applied for a short time of 200 ms was generally higher in Experimental Examples 1 to 5. On the other hand, in Example 7, although the white reflectance was improved by increasing the amount of the fibrous structure, the contrast was lowered, and the white reflectance after the application time of 200 ms was as follows. It was lower than Experimental Examples 1 to 5 composed of two layers and was similar to the other Experimental Examples 6 and 8 composed of a single layer. Moreover, in Experimental Example 8 in which the amount of the fibrous structure was further increased, sealing was not possible. Furthermore, in Experimental Example 9 in which the volume fraction was increased by changing the particle size of titanium oxide, which is a non-electrophoretic particle, the white reflectance and the white reflectance after 200 ms of application time decreased.

Although the present technology has been described with reference to the embodiments and examples, the present technology is not limited to the above-described embodiments and the like, and various modifications are possible.

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 technique can also take the following structures.
(1) Insulating liquid includes electrophoretic particles, a porous layer, and non-electrophoretic particles held in the porous layer, and the porous layer has light reflectivity different from that of the electrophoretic particles. A display device comprising a plurality of layers in which the volume fraction of the non-electrophoretic particles is different from each other.
(2) The porous layer includes a first layer and a second layer in which the volume fraction of the non-electrophoretic particles is larger than that of the first layer, and the second layer is disposed on the display surface side. The display device according to (1).
(3) The display device according to (2), wherein a volume fraction of the non-electrophoretic particles in the second layer is 13% or more.
(4) The display device according to (2) or (3), wherein the non-electrophoretic particles included in the first layer and the second layer have different average primary particle sizes.
(5) The display device according to any one of (2) to (4), wherein a thickness of the first layer is larger than that of the second layer.
(6) The porous layer is constituted by a fibrous structure, and the fiber diameters of the fibrous structures constituting the first layer and the second layer are different from each other, among (2) to (5) The display device according to any one of the above.
(7) The display device according to any one of (5) and (6), wherein an average primary particle size of the migrating particles included in the second layer is smaller than that of the first layer.
(8) The display device according to (6) or (7), wherein a fiber diameter of the fibrous structure constituting the second layer is smaller than that of the first layer.
(9) The display device according to any one of (1) to (8), wherein the fibrous structure is configured by nanofibers.
(10) The display device according to any one of (1) to (9), wherein the fibrous structure is formed by an antistatic method.
(11) 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 porous layer perform bright display. The display device according to any one of (10).
(12) It is provided with a display device, and the display device includes electrophoretic particles, a porous layer, and non-electrophoretic particles held in the porous layer in an insulating liquid, and the porous layer includes An electronic apparatus comprising a plurality of layers having light reflectivity different from electrophoretic particles and different volume fractions of the non-electrophoretic particles.

This application claims priority on the basis of Japanese Patent Application No. 2015-005048 filed on January 14, 2015 at the Japan Patent Office. The entire contents of this application are hereby incorporated by reference. Incorporated into.

Those skilled in the art will envision various modifications, combinations, subcombinations, and changes, depending on design requirements and other factors, which are within the scope of the appended claims and their equivalents. It is understood that

Claims

In the insulating liquid, including migrating particles, a porous layer, and non-migrating particles held in the porous layer,
The porous layer includes a plurality of layers having light reflectivity different from that of the migrating particles and different volume fractions of the non-migrating particles.
The porous layer has a first layer and a second layer having a larger volume fraction of the non-electrophoretic particles than the first layer,
The display device according to claim 1, wherein the second layer is disposed on a display surface side.
The display device according to claim 2, wherein a volume fraction of the non-electrophoretic particles in the second layer is 13% or more.
The display device according to claim 2, wherein the non-electrophoretic particles contained in the first layer and the second layer have different average primary particle sizes.
The display device according to claim 2, wherein the thickness of the first layer is larger than that of the second layer.
The porous layer is composed of a fibrous structure,
The display device according to claim 2, wherein fiber diameters of the fibrous structures constituting the first layer and the second layer are different from each other.
The display device according to claim 4, wherein an average primary particle size of the migrating particles contained in the second layer is smaller than that of the first layer.
The display device according to claim 6, wherein a fiber diameter of the fibrous structure constituting the second layer is smaller than that of the first layer.
The display device according to claim 1, wherein the fibrous structure is composed of nanofibers.
The display device according to claim 1, wherein the fibrous structure is formed by an antistatic method.
The display device according to claim 1, wherein the light reflectance of the non-migrating particles is higher than the light reflectance of the migrating particles, the migrating particles perform dark display, and the non-migrating particles and the porous layer perform bright display. .
A display device,
The display device
In the insulating liquid, including migrating particles, a porous layer, and non-migrating particles held in the porous layer,
The said porous layer is an electronic device which consists of a several layer from which the volume fraction of the said non-electrophoretic particle differs while having light reflectivity different from the said electrophoretic particle.