JP2012226011A - Display sheet, display device and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display sheet with high reliability capable of exerting excellent display characteristics, a display device equipped therewith, and an electronic apparatus with high reliability.SOLUTION: A display device 20 includes a display layer 400 filled with dispersion liquid 100 obtained by dispersing white particles A and black particles B into a dispersion medium 7. The white particles A each has a base substance A1 and a coating layer A2 coating a periphery of the base substance A1, and is disposed inside the display layer 400 such that a distance between the neighboring white particles A is five times a mean particle size thereof or smaller. The thickness of the coating layer A2 is within twice and a hundred times a mean particle size of the black particles B, and there is formed a space A22 that allows movement of the black particles B inside the coating layer A2. The black particles B are negatively charged and electrophoresed through the space A22 by an electric field that acts on the display layer 400.

Description

  The present invention relates to a display sheet, a display device, and an electronic apparatus.

For example, an electrophoretic display using particle electrophoresis is known as an image display unit of electronic paper (see, for example, Patent Document 1). The electrophoretic display has excellent portability and power saving, and is particularly suitable as an image display unit for electronic paper.
The electrophoretic display has a pair of electrodes arranged opposite to each other and a display layer provided between them, and the display layer includes, for example, positively charged white particles and negatively charged black particles. Are dispersed in a liquid phase dispersion medium. Such an electrophoretic display is configured to display a desired image by applying a voltage between a pair of electrodes and causing white particles and black particles to migrate in a desired direction.

  Here, the configuration of the display layer is roughly divided into a “partition wall type” in which the display layer is divided into a plurality of cells by partition walls as in Patent Document 1, and a dispersion liquid is filled in each cell, as in Patent Document 2. A “microcapsule type” in which a plurality of microcapsules filled with a dispersion liquid are arranged and fixed by a binder, and the display layer is formed as one space (that is, not divided by a partition wall or the like) as in Patent Document 3. The liquid crystal type is filled with the dispersion liquid.

However, the “partition wall type” has a problem in that the effective display area (area in which the display color can be changed) in the display surface is reduced by the partition wall, and the display characteristics are deteriorated. Further, in the “microcapsule type”, a gap is generated between adjacent microcapsules, so that an effective display area in the display surface is reduced and display characteristics are deteriorated. When a voltage is applied between a pair of electrodes, a binder is used. There is a problem that display characteristics deteriorate due to the occurrence of leakage current. In the “liquid crystal type”, almost the entire display area can be used as an effective display area. For example, when the display is set up like a book, white particles and black particles move downward in the vertical direction due to their own weight. (Sedimentation) and unevenness of particles occur, so that a uniform and uniform image cannot be displayed.
As described above, the conventional electrophoretic display cannot exhibit excellent display characteristics in any format, and has a problem of poor reliability.

JP 2010-44114 A JP 2003-140202 A Japanese National Patent Publication No. 8-510790

  An object of the present invention is to provide a display sheet that has high reliability and can exhibit excellent display characteristics, a display device including the display sheet, and a highly reliable electronic device.

Such an object is achieved by the present invention described below.
The display sheet of the present invention includes a first substrate,
A second substrate disposed opposite the first substrate;
Dispersed with the first particles and the second particles that have a hue different from that of the first particles and are charged positively or negatively between the first substrate and the second substrate. A display layer filled with a dispersion liquid dispersed,
The first particles have a base and a coating layer formed so as to cover the periphery of the base.
The coating layer has a thickness that is not less than 2 times and not more than 100 times the average particle diameter of the second particles, and has a space inside which the second particles can move to open to the outer peripheral surface,
In the display layer, a plurality of the first particles are filled such that the occupation ratio of the first particles in the display layer is 50% or more and 80% or less,
The second particle is configured to migrate through the space of the first particle by an electric field acting on the display layer.
Thereby, it is possible to provide a display sheet that is highly reliable and can exhibit excellent display characteristics.

In the display sheet of the present invention, it is preferable that movement due to its own weight is restricted by the second particles being held in the coating layer.
Thereby, sedimentation due to the weight of the second particles can be prevented or suppressed, and a display image can be maintained for a long time without continuing to apply an electric field. Furthermore, increase or decrease of the number of second particles in each pixel can be prevented or suppressed, and the state in which the second particles are uniformly dispersed in the display layer can be maintained in a plan view of the display layer. Can do. Therefore, the display characteristics of each pixel can be maintained uniformly, and a clear image without unevenness can be displayed over a long period of time.

In the display sheet of this invention, it is preferable that the said coating layer is porous.
This simplifies the configuration of the first particles.
In the display sheet according to the aspect of the invention, it is preferable that the coating layer has a plurality of protrusions protruding from the surface of the base, and a gap between the plurality of protrusions constitutes the space.
This simplifies the configuration of the first particles.

In the display sheet of the present invention, the first particles are preferably uncharged.
Thereby, an electrical action (repulsion or adsorption) does not work between the first particles and the second particles. Therefore, the second particles can be moved smoothly, and excellent display characteristics, particularly excellent response speed can be exhibited.
In the display sheet of the present invention, the diameter of the substrate is preferably 1 to 20 times the average particle diameter of the second particles.
Thereby, the clearance gap between adjacent 1st particle | grains can be suppressed comparatively small, and sedimentation of a 2nd particle | grain can be suppressed effectively.

In the display sheet of the present invention, the occupation ratio of the space with respect to the coating layer is preferably 50% or more and 90% or less.
Thereby, many 2nd particle | grains can penetrate | invade in space, and can move 2nd particle | grains smoothly in space.
In the display sheet of the present invention, it is preferable that the first particles have a white color.
Thereby, white color with higher reflectivity can be displayed.

In the display sheet of the present invention, the dispersion liquid further includes a plurality of third particles that exhibit a hue different from that of the first particles and the second particles and are charged to the opposite pole to the second particles. It is preferable that they are dispersed.
Thereby, more colors can be displayed.
The display device of the present invention includes the display sheet of the present invention.
Thereby, a highly reliable display device is obtained.
An electronic apparatus according to the present invention includes the display device according to the present invention.
As a result, a highly reliable electronic device can be obtained.

It is sectional drawing which shows 1st Embodiment of the display apparatus of this invention. It is an expanded sectional view of the white particle which the display apparatus shown in FIG. 1 has. It is a figure which shows an example of the manufacturing method of the white particle shown in FIG. It is sectional drawing explaining the drive of the display apparatus shown in FIG. It is sectional drawing which shows 2nd Embodiment of the display apparatus of this invention. It is sectional drawing explaining the drive of the display apparatus shown in FIG. It is an expanded sectional view of white particles which a 3rd embodiment of a display of the present invention has. It is an expanded sectional view of the white particle which 4th Embodiment of the display apparatus of this invention has. It is a schematic perspective view which shows 5th Embodiment of the display apparatus of this invention. It is sectional drawing of the display sheet shown in FIG. It is a perspective view which shows embodiment at the time of applying the electronic device of this invention to electronic paper. It is a figure which shows embodiment at the time of applying the electronic device of this invention to a display. It is a top view for demonstrating the measuring method of an Example.

Hereinafter, a display sheet, a display device, and an electronic device of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
1. Display Device First, a display device incorporating the display sheet of the present invention will be described.
<First Embodiment>
1 is a cross-sectional view showing a first embodiment of the display device of the present invention, FIG. 2 is an enlarged cross-sectional view of white particles of the display device shown in FIG. 1, and FIG. 3 is a production of the white particles shown in FIG. FIG. 4 is a cross-sectional view for explaining driving of the display device shown in FIG. 1. In the following description, for convenience of explanation, the upper side in FIGS. 1 and 4 is described as “upper” and the lower side is described as “lower”.

A display device 20 (display device of the present invention) shown in FIG. 1 is an electrophoretic display device that displays a desired image using particle migration. The display device 20 includes a display sheet (front plane) 21 and a circuit board (back plane) 22.
As shown in FIG. 1, the display sheet 21 is provided on a substrate (first substrate) 12 including a flat base 2 and a second electrode 4 provided on the lower surface of the base 2, and the substrate 12. And a display layer 400 filled with the dispersion liquid 100. In such a display sheet 21, the upper surface of the substrate 12 constitutes the display surface 121. Hereinafter, the display surface 121 refers to a region overlapping the display layer 400 on the upper surface of the substrate 12 in a plan view of the display device 20, and other regions (for example, a region overlapping a sealing portion 9 described later). Shall be excluded.

On the other hand, the circuit board 22 is provided with a counter substrate (second substrate) 11 including a flat base 1 and a plurality of first electrodes 3 provided on the upper surface of the base 1, and the counter substrate 11. And a circuit (not shown). The circuit includes, for example, TFTs (switching elements) arranged in a matrix, gate lines and data lines formed corresponding to the TFTs, a gate driver that applies a desired voltage to the gate lines, and a desired data line. A data driver for applying the voltage of the gate driver, and a control unit for controlling the driving of the gate driver and the data driver.
In such a display device 20, the counter substrate 11 also serves as the second substrate of the display sheet 21.

Hereinafter, the structure of each part is demonstrated sequentially.
The base 1 and the base 2 are each composed of a sheet-like (flat plate) member, and have a function of supporting and protecting each member disposed therebetween. Each of the base portions 1 and 2 may be either flexible or hard, but is preferably flexible. By using the bases 1 and 2 having flexibility, it is possible to obtain a display device 20 having flexibility, that is, for example, a display device 20 useful in constructing electronic paper.

  When the bases 1 and 2 are flexible, the constituent materials thereof are, for example, polyesters such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate), polyolefins such as polyethylene, modified polyolefins, polyamides, respectively. Various thermoplastic elastomers such as thermoplastic polyimide, polyether, polyetheretherketone, polyurethane, chlorinated polyethylene, etc., or copolymers, blends, polymer alloys, etc. mainly composed of these. One or two or more of them can be used in combination.

  The average thicknesses of the bases 1 and 2 are appropriately set depending on the constituent material, application, and the like, and are not particularly limited. More preferably, it is about 25 μm or more and 250 μm or less. Thereby, size reduction (especially thickness reduction) of the display apparatus 20 can be achieved, aiming at harmony with the softness | flexibility and intensity | strength of the display apparatus 20. FIG.

  The first electrode 3 and the second electrode 4 that form a layer (film shape) are provided on the surfaces of the bases 1 and 2 on the display layer 400 side, that is, on the upper surface of the base 1 and the lower surface of the base 2, respectively. ing. In the present embodiment, the second electrode 4 is a common electrode, and the first electrode 3 is an individual electrode (pixel electrode connected to a TFT) divided in a matrix (matrix). In such a display device 20, a region where one first electrode 3 and the second electrode 4 overlap constitute one pixel.

The constituent materials of the electrodes 3 and 4 are not particularly limited as long as they are substantially conductive, for example, metal materials such as gold, silver, copper, aluminum or alloys containing these, carbon black, etc. An ionic substance such as NaCl, Cu (CF ₃ SO ₃ ) ₂ is dispersed in a carbon-based material, an electroconductive polymer material such as polyacetylene, polyfluorene or a derivative thereof, or a matrix resin such as polyvinyl alcohol or polycarbonate. Various conductive materials such as ion conductive polymer materials, conductive oxide materials such as indium oxide (IO), indium tin oxide (ITO), fluorine-doped tin oxide (FTO), etc. 1 type or 2 types or more can be used in combination.

Further, the average thickness of the electrodes 3 and 4 is appropriately set depending on the constituent material and application, and is not particularly limited, but is preferably about 0.01 μm or more and 10 μm or less, preferably 0.02 μm or more and 5 μm or less. More preferred is the degree.
Here, among the bases 1 and 2 and the electrodes 3 and 4, the base and the electrode disposed on the display surface 121 side are each transparent, that is, substantially transparent (colorless and transparent, colored Transparent or translucent). In the present embodiment, since the upper surface of the substrate 12 constitutes the display surface 121, at least the base 2 and the second electrode 4 are substantially transparent. Thereby, the information (image) displayed on the display device 20 can be easily recognized visually from the display surface 121 side.

A sealing portion 9 is provided between the substrate 12 and the counter substrate 11 along the edges. The display layer 400 is hermetically sealed by the sealing portion 9. Thereby, it is possible to prevent moisture from entering the display device 20 and more reliably prevent display performance deterioration of the display device 20.
The constituent material of the sealing portion 9 is not particularly limited. For example, a thermoplastic resin such as an acrylic resin, a urethane resin, or an olefin resin, an epoxy resin, a melamine resin, or a heat such as a phenol resin. Various resin materials such as a curable resin can be used, and one or more of these can be used in combination.

The display layer 400 is filled with the dispersion liquid 100. The dispersion liquid 100 is a dispersion medium 7 in which a plurality of first particles A that are uncharged, that is, substantially uncharged, and a plurality of second particles B that are positively or negatively charged are dispersed.
The hues of the first particles A and the second particles B are not particularly limited as long as they are different from each other, and may be freely selected from chromatic colors, achromatic colors, metal colors, and the like according to the purpose. In the following, a configuration that can display a black and white image with the first particle A being white and the second particle B being black will be described as a representative. In the following, for convenience of explanation, the first particles A are referred to as “white particles A”, and the second particles B are referred to as “black particles B”.

  As the dispersion medium 7, a medium having a relatively high insulating property is preferably used. Examples of the dispersion medium 7 include various types of water (for example, distilled water, pure water, etc.), alcohols such as methanol, cellosolves such as methyl cellosolve, esters such as methyl acetate, ketones such as acetone, pentane and the like. Aliphatic hydrocarbons (liquid paraffin), cyclohexane and other alicyclic hydrocarbons, benzene and other aromatic hydrocarbons, methylene chloride and other halogenated hydrocarbons, pyridine and other aromatic heterocycles and acetonitrile Nitriles such as amides, amides such as N, N-dimethylformamide, carboxylates, silicone oils or other various oils, and the like, and these can be used alone or as a mixture.

  Among these, as the dispersion medium 7, an aliphatic hydrocarbon (liquid paraffin) or a material mainly composed of silicone oil is preferable. The dispersion medium 7 containing liquid paraffin or silicone oil as the main component is preferable because it has a high aggregation suppressing effect on the white particles A and the black particles B. Thereby, it can prevent or suppress more reliably that the display performance of the display apparatus 20 deteriorates with time. In addition, liquid paraffin or silicone oil is preferable from the viewpoint of excellent weather resistance and high safety because it does not have an unsaturated bond.

  Further, in the dispersion medium 7, for example, an electrolyte, a surfactant such as an alkenyl succinate (anionic or cationic), a metal soap, a resin material, a rubber material, an oil, a varnish, a compound, as necessary. Various additives such as a charge control agent composed of particles such as a dispersant, a dispersant such as a silane coupling agent, a lubricant, and a stabilizer may be added. When the dispersion medium 7 is colored, various dyes such as anthraquinone dyes, azo dyes, and indigoid dyes may be dissolved in the dispersion medium 7 as necessary.

Next, the white particles A and the black particles B will be described in detail.
(Black particles B)
The black particles B are particles that are charged and can be electrophoresed in the dispersion medium 7 by the action of an electric field. Any black particles B can be used as long as they have a charge. Although not particularly limited, at least one of pigment particles, resin particles, or composite particles thereof is preferably used. These particles have the advantage that they are easy to manufacture and the charge can be controlled relatively easily.

  Examples of the pigment constituting the pigment particles include black pigments such as aniline black, carbon black, titanium black and copper chromite, white pigments such as titanium oxide and antimony oxide, azo pigments such as monoazo, isoindolinone, Yellow pigments such as yellow lead, red pigments such as quinacridone red and chrome vermilion, blue pigments such as phthalocyanine blue and indanthrene blue, green pigments such as phthalocyanine green, etc. They can be used in combination.

Examples of the resin material constituting the resin particles include acrylic resin, urethane resin, urea resin, epoxy resin, polystyrene, polyester, and the like, and one or more of these are combined. Can be used.
The composite particles include, for example, those in which the surface of the pigment particles is coated with a resin material or other pigment, those in which the surface of the resin particles is coated with a pigment, or a mixture in which the pigment and the resin material are mixed at an appropriate composition ratio. The particle | grains comprised by these, etc. are mentioned.
In particular, as the black particles B, carbon black particles or particles covering the surface thereof can be suitably used.

Further, the shape of the black particles B is not particularly limited, but is preferably spherical. Further, the average particle diameter of the black particles B is not particularly limited, but is preferably 10 nm or more and 500 nm or less, more preferably 20 nm or more and 300 nm or less. If the average particle diameter of the black particles B is less than 10 nm, sufficient chromaticity cannot be obtained, and the contrast may be lowered and the display may become unclear. Conversely, when the average particle diameter of the black particles B exceeds 300 nm, it is necessary to increase the coloring degree of the particles themselves more than necessary, and the amount of pigment used increases, or a portion where voltage is applied for display. In this case, it is difficult to move the particles quickly, and the response speed may decrease.
In addition, the average particle diameter of the black particle B means the volume average particle diameter measured with a dynamic light scattering particle size distribution measuring apparatus (for example, product name: LB-500, manufactured by Horiba, Ltd.). The same applies to white particles A described later.

(White particles A)
The white particles A are particles for displaying white on the display surface 121 and have a function of preventing or suppressing sedimentation due to the weight of the black particles B. By using such white particles A, it is possible to use almost the entire display surface 121 as an effective display area, to exhibit high display contrast, and to prevent sedimentation due to the weight of the black particles B or Therefore, a clear image with no unevenness can be displayed on the display surface 121. Further, the displayed image can be maintained for a long time after the action of the electric field is stopped.
Thereby, the display apparatus 20 which can exhibit the outstanding reliability and the outstanding display characteristic is obtained.

Here, the thickness of the display layer 400 in which the white particles A are enclosed is not particularly limited, but is preferably 2 to 50 times the average particle diameter of the white particles A. Specifically, the thickness of the display layer 400 is preferably about 20 to 80 μm.
By setting the thickness of the display layer 400 within the above numerical range, a plurality of white particles A can be arranged in an overlapping manner in the thickness direction of the display layer 400. Therefore, when the display layer 400 is visually recognized from the display surface 121 side, the white particles A can be positioned in almost the entire area of the display surface 121. For example, the base 2 side can be seen through a gap between adjacent or overlapping white particles A. It can prevent being visually recognized. Therefore, the display device 20 can display white having a high reflectance without unevenness over the entire display surface 121, and can exhibit excellent display characteristics. Moreover, since the thickness of the display layer 400 can be kept thin, the moving distance of the black particles B for switching the display image can be kept short, and an excellent response speed can be maintained.

The white particles A are uncharged, that is, not substantially charged. Thereby, an electric action (repulsion or adsorption) does not work between the black particles B. Therefore, the black particles B can be smoothly moved in the dispersion medium 7, and excellent display characteristics, particularly excellent response speed can be exhibited.
As shown in FIG. 1, the white particles A are filled in the display layer 400 at a relatively high density, and movement in the display layer 400 is restricted. Specifically, the white particles A are filled in the display layer 400 at a density such that the occupation ratio in the display layer 400 is 50% or more and 80% or less. Thereby, the movement of the white particles A is regulated by contacting at least one of the base 1, the base 2, and the other white particles A.

The occupation ratio may be 50% or more and 80% or less, but more preferably 60% or more and 70% or less.
Thereby, the movement of the white particles A is effectively regulated (restricted) in the display layer 400, and the white particles A are uniformly arranged in the entire area of the display layer 400 regardless of the orientation of the display device 20. Can be maintained. Therefore, it is possible to display white with high reflectance without unevenness over the entire area of the display surface 121. Further, the sedimentation of the black particles B can be prevented or suppressed in the entire display layer 400.

  When the occupancy is less than the lower limit, the white particles A themselves easily settle in the display layer 400, the white particles are biased, and the black particle retention is reduced. Therefore, it is impossible to display a clear image without unevenness on the display surface. On the other hand, if the occupation ratio exceeds the upper limit, the space for the black particles in the display layer 400 becomes narrow, and the movement of the black particles is restricted more than necessary, or the number of black particles B must be reduced. Display characteristics may deteriorate.

  From another point of view, when the occupancy of the white particles A in the display layer 400 when the white particles A are packed most closely in the display layer 400 is A [%], the white particles A are in the display layer 400. It is preferable to be filled to 0.7A or more and 0.9A or less, and more preferably to be about 0.8A. Thereby, the movement of the white particles as described above in the display layer 400 can be effectively controlled, and the white particles A can be prevented from being excessively packed in the display layer 400. Therefore, for example, when the display device 20 is bent, a space is created in which the white particles A slightly move following the deformation (a plurality of white particles are misaligned), thereby preventing stress concentration and an excellent machine. It becomes the display apparatus 20 which can exhibit the target strength.

As shown in FIG. 2, such white particles A have a substantially spherical base A1 and a coating layer A2 that covers the periphery of the base A1.
The white particles A may be white as a whole. For example, both the base A1 and the coating layer A2 (projection A21 described later) may be white, or one of the base A1 and the coating layer A2 may be white. It may be white and the other may be substantially colorless and transparent, for example. In the latter case, it is preferable that the substrate A1 is white and the coating layer A2 is colorless and transparent.

The coating layer A2 has a space A22 therein, and the black particles B can move in the space A22. That is, the black particles B move continuously to the base 1 (first electrode 3) side or the base 2 (second electrode 4) side by passing through the space A22 of the plurality of white particles A.
Further, the coating layer A2 holds the black particles B by accommodating the black particles B in the space A22, thereby preventing or suppressing the sedimentation of the black particles. Specifically, the black particles B come into contact with at least one protrusion A21 to be described later, so that the sedimentation of the black particles B is prevented or suppressed.

  Such a coating layer A2 has a plurality of protrusions A21 protruding from the surface of the base A1, and a space A22 opened to the surface (outer peripheral surface) of the coating layer A2 is formed by gaps between the plurality of protrusions A21. Has been. The plurality of protrusions A21 are preferably provided so as to protrude radially from the center of the base A1. Thus, space A22 can be easily formed by making coating layer A2 into the structure which has several protrusion A21.

  The protrusion A21 of the present embodiment has a needle shape (long shape). By forming the protrusion A21 in such a shape, the space A22 becomes larger as it approaches the surface of the coating layer A2, and the space A22 having a large opening can be formed. Therefore, the black particles B can easily enter the space A22, and the black particles B can move smoothly. Moreover, by setting it as such a shape, more protrusion A21 can be provided in the surface of base | substrate A1. Therefore, the probability that the black particles B are in contact with the protrusions A21 is increased, and the retention of the black particles B in the coating layer A2 is further increased.

The aspect ratio (length / width) of the protrusion A21 is not particularly limited, but is preferably about 10 or more and 1000 or less. Thereby, the above effect becomes more remarkable.
The shape of the protrusion A21 is not limited to this as long as the space A22 can be formed. For example, the shape of the protrusion A21 may be a conical shape, a truncated cone shape, a cylindrical shape, or the like.
The thickness of the covering layer A2 (that is, the length of the protrusion A21) is not less than 2 times and not more than 100 times the average particle diameter of the black particles B. By setting the thickness of the coating layer A2 within the above range, the black particles B can be smoothly moved in the space A22, and the black particles B can be effectively held by the coating layer A2. Therefore, an excellent response speed can be exhibited, and a clear image without unevenness can be displayed on the display surface 121.

When the thickness of the coating layer A2 is less than the above lower limit value, the black particles B hardly enter the space A22, and it takes a long time for the black particles B to move to the base 1 side or the base 2 side. Therefore, the response speed is significantly reduced. Further, the amount of the black particles B that can be held in the coating layer A2 is small, and the sedimentation of the black particles B cannot be prevented. On the other hand, when the upper limit is exceeded, the space A22 becomes too wide, the black particles B cannot be held by the coating layer A2, and the black particles B precipitate.
Here, as described above, the thickness of the coating layer A2 may be not less than 2 times and not more than 100 times the average particle size of the black particles B, but is not less than 10 times and not more than 50 times the average particle size of the black particles B. More preferably, it is more preferably 10 times or more and 30 times or less. Thereby, the above effect becomes more remarkable.

  Further, the occupation ratio of the space A22 with respect to the coating layer A2 (that is, the space ratio of the coating layer A2) is not particularly limited, but is preferably 50% or more and 90% or less, and is 70% or more and 80% or less. Is more preferable. By setting the occupation ratio of the space A22 in the above range, more black particles B can enter the space A22 and move in the space A22. Therefore, the black particles B can be moved more smoothly during voltage application. it can. Therefore, an excellent response speed can be exhibited. Moreover, since many black particle B can be accommodated in space A22, sedimentation of the black particle B can be prevented more effectively.

  The diameter of the substrate A1 is not particularly limited, but is preferably 1 to 20 times the average particle diameter of the black particles B, and more preferably 5 to 10 times. Thereby, the size of the base A1 becomes appropriate, and in particular when the base A1 is white, white having high reflectance can be displayed on the display surface 121. Therefore, the display contrast of the display device 20 is improved. Furthermore, the particle size of the white particles A can be prevented from becoming larger than necessary, and the gap between the adjacent white particles A can be kept relatively small. Therefore, the number of black particles B located in the gap is reduced, and more black particles B are retained in the space A22 of the coating layer A2, so that the sedimentation of the black particles B can be effectively suppressed. .

The substrate A1 is not particularly limited, and at least one of pigment particles, resin particles, or composite particles thereof is preferably used. Specific examples of the pigment particles, the resin particles, and the composite particles are the same as those of the black particles B described above, and thus description thereof is omitted. In particular, titanium oxide particles or silicon oxide particles can be suitably used as the substrate A1.
The configuration of the white particles A has been described in detail above.

Such white particles A can be produced, for example, as follows.
First, as shown in FIG. 3A, a Si substrate 900 is prepared. The thickness of the Si substrate 900 is substantially equal to the thickness of the coating layer A2. Next, as shown in FIG. 3B, a sacrificial layer 910 made of titanium oxide (TiO ₂ ) corresponding to the shape of the protrusions 21 </ b> A is formed on the Si substrate 900. Next, after the Si substrate 900 is etched through the sacrificial layer 910, the sacrificial layer 910 is removed. Thereby, as shown in FIG.3 (c), several protrusion A21 is formed. The plurality of protrusions A21 are negatively charged.

Next, as shown in FIG. 3D, the base A1 is rolled on the protrusion A21. The base A1 is made of silicon oxide (SiO ₂ ) and is positively charged. Therefore, the protrusion A21 adheres to the surface of the base A1 by electrical adsorption. Thereby, the white particle A is obtained. In addition, although protrusion A21 is joined to base A1 by electrical adsorption, in order to strengthen this joining, you may roll base A1 which applied the adhesive to the surface on protrusion A21. Further, after the protrusion A21 is adsorbed on the surface of the base A1, the surface may be coated with a polymer or the like.
The white particles A produced in this way have a positively charged substrate A1 and a negatively charged protrusion A21, but are uncharged as a whole.
The configuration of the display device 20 has been described in detail above.

  According to such a display device 20, as will be described later, when an electric field is applied between the first electrode 3 and the second electrode 4, the black particles B are in the space A22 of the white particles A or white. It migrates to the first electrode 3 side or the second electrode 4 side through the gap between the particles A. A desired image can be displayed on the display surface 121 by controlling such migration of the black particles B for each pixel.

In addition, since the display device 20 does not use “partition walls” or “microcapsules” as in the related art, the display surface 121 can be used as an effective display area, and high display contrast can be exhibited. Therefore, the display device 20 can exhibit excellent display characteristics.
Further, in the display device 20, an increase or decrease in the number of black particles B in each pixel can be prevented or suppressed, and the black particles B are uniformly dispersed in the display layer 400 in a plan view of the display layer 400. Can be maintained. Therefore, the display characteristics (white and black reflectance) of each pixel can be kept substantially equal, and a clear image without unevenness can be displayed on the display surface 121 over a long period of time.

Specifically, for example, when the display device 20 is erected like a book, that is, when the display surface 121 is in a posture that is substantially parallel to the vertical direction, the black particles B are vertical due to their own weight. Try to move downward in the direction. However, since the white particles A are filled in the display layer 400 at a high density, most of the black particles B are held by the white particles A, and movement thereof is restricted. Moreover, about the black particle B which is not hold | maintained at the white particle A (namely, black particle B which exists in the clearance gap between the white particles A), it is hold | maintained at the white particle A immediately after the movement is started, and the movement is Be regulated. In this way, in the display device 20, the black particles A move in the plane direction of the display layer 400 (the horizontal direction in FIG. 1, the depth direction in the drawing, and the synthesis direction thereof), in other words, the pixel that is currently located Are effectively prevented or suppressed from moving to different pixels.
Therefore, as described above, the display device 20 can maintain a state in which the black particles B are uniformly dispersed in the display layer 400, and can display a clear image without unevenness on the display surface 121 over a long period of time. it can.

  Further, in the display device 20, since the white particles A are filled in the display layer 400 at a high density, the white particles A also function as a reinforcing member that reinforces the strength of the display layer 400. Therefore, the display device 20 is excellent in mechanical strength. In addition, when the display device 20 is curved, the white particles A exhibit a function of suppressing a change in thickness of the display layer 400 (change to a thinner side), and thus the thickness of the display layer 400 is constant. The display characteristics caused by the change in the thickness of the display layer 400 can be prevented from being deteriorated.

In addition, when the display device 20 is curved, the white particles A move somewhat following the deformation (a plurality of white particles are misaligned), so stress concentration can be prevented. , Can exhibit excellent mechanical strength.
Such a display device 20 is driven as follows, for example.
When a voltage is applied between the electrodes 3 and 4, an electric field is generated between them. According to this electric field, the black particles B move (electrophoresis) toward the electrode 3 or 4 through the space A22 of the white particles A. Below, for convenience of explanation, a case where negatively charged black particles B are used will be described as a representative. Hereinafter, for convenience of explanation, one pixel will be described as a representative.

-White display state-
When a voltage is applied between the first electrode 3 and the second electrode 4 so that the first electrode 3 has a positive potential and the second electrode 4 has a negative potential, the electric field generated by the voltage application is displayed on the display layer. Acts on black particles B in 400. Then, the black particles B migrate to the first electrode 3 side while passing through the space A22 of the white particles A, and gather at the first electrode 3 as shown in FIG. Thereby, white, which is the color of the white particles A, is displayed on the display surface 121.

Here, when the particles (first particles) filled in the display layer 400 with high density are white particles A, excellent light reflectivity and light scattering can be exhibited, and the reflectivity is higher. , Bright white can be displayed.
In addition, irregular irregularities formed on the surface of the plurality of white particles A (protrusions A21) are present in the vicinity of the display surface 121, so that the white color displayed on the display surface 121 is a paper such as a copy sheet. It feels less glossy like a material (matte feeling similar to paper). For this reason, the user can have a paper-like sensation and can be used without a sense of incongruity. Such a configuration is particularly advantageous when constructing electronic paper.

−Black display state−
When a voltage is applied between the first electrode 3 and the second electrode 4 so that the first electrode 3 has a negative potential and the second electrode 4 has a positive potential, the electric field generated by the voltage application is displayed on the display layer. Acts on black particles B in 400. Then, the black particles B migrate to the second electrode 4 side while passing through the space A22 of the white particles A, and gather at the second electrode 4 as shown in FIG. Thereby, black which is the color of the black particles B is displayed on the display surface 121.

  In addition, when the display device 20 is erected in this state, the second electrode is used for the particles that are in contact with the second electrode 4 and the particles that are located in the vicinity of the second electrode 4 among the black particles B. The position can be maintained by the adsorption force with 4. Even if the adsorption force is weak, these particles move irregularly and slightly in the dispersion medium 7 (Brownian motion), so that their positions can be maintained macroscopically. it can. The same applies to the white display state described above.

  In such a display device 20, by selecting a white display state or a black display state for each pixel, that is, by combining a pixel in the white display state and a pixel in the black display state, a desired display surface 121 is displayed on the display surface 121. An image can be displayed. As described above, since the black particles B are held in the coating layer A2 of the white particles A, the black particles B are settled both when the voltage application is stopped and when the display device 20 is set up. It is prevented and the desired image can be maintained.

Second Embodiment
FIG. 5 is a cross-sectional view showing a second embodiment of the display device of the present invention, and FIG. 6 is a cross-sectional view illustrating driving of the display device shown in FIG.
Hereinafter, the second embodiment will be described with a focus on differences from the above-described embodiment, and description of similar matters will be omitted.

The display device according to the second embodiment of the present invention is the same as the display device of the first embodiment, except that the configuration of the dispersion liquid filled in the display layer is different. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment mentioned above.
As shown in FIG. 5, the dispersion liquid 100 ′ of the display device 20 of the present embodiment is opposite to the plurality of first particles A, the plurality of positively or negatively charged second particles B, and the black particles B. And a plurality of third particles C charged in the poles are dispersed in a dispersion medium 7. By using such a dispersion 100 ′, more colors can be displayed on the display surface 121 as described later.

  The hues of the first particle A, the second particle B, and the third particle C are not particularly limited as long as they are different from each other, and can be freely selected from chromatic colors, achromatic colors, metallic colors, and the like according to the purpose. Just choose. In the following, a configuration that can display a color image with the first particle A being white, the second particle B being black, and the third particle C being red will be described as a representative. Hereinafter, for convenience of explanation, the first particle A is referred to as “white particle A”, the second particle B is referred to as “black particle B”, and the third particle C is referred to as “red particle C”. .

The average particle size of the red particles C is not particularly limited, but is preferably substantially the same as the average particle size of the black particles B. Thereby, the white particles A can hold the red particles C in addition to the black particles B. Therefore, the sedimentation of the red particles C can also be prevented or suppressed.
Such a display device 20 is driven as follows, for example.

Below, for convenience of explanation, a case where negatively charged particles are used as the black particles B and positively charged particles are used as the red particles C will be representatively described. Hereinafter, for convenience of explanation, one pixel will be described as a representative.
−Black display state−
When a voltage is applied between the first electrode 3 and the second electrode 4 so that the first electrode 3 has a negative potential and the second electrode 4 has a positive potential, the electric field generated by the voltage application is displayed on the display layer. Acts on black particles B and red particles C in 400. Then, the black particles B migrate to the second electrode 4 side while passing through the space A22 of the white particles A, and gather at the second electrode 4, and the red particles C pass through the space A22 of the white particles A. 1 migrates to the electrode 3 side and collects on the first electrode 3. Thereby, as shown to Fig.6 (a), the black which is the color of the black particle B is displayed on the display surface 121. FIG.

-Red display status-
When a voltage is applied between the first electrode 3 and the second electrode 4 so that the first electrode 3 has a positive potential and the second electrode 4 has a negative potential, the electric field generated by the voltage application is displayed on the display layer. Acts on black particles B and red particles C in 400. Then, the black particles B migrate to the first electrode 3 side while passing through the space A22 of the white particles A, and gather at the first electrode 3, while the red particles C pass through the space A22 of the white particles A. 2 migrate to the second electrode 4 side and gather on the second electrode 4. Thereby, as shown in FIG. 6B, red, which is the color of the red particles C, is displayed on the display surface 121.

-White display state-
For example, after a black display state is applied, when a voltage is applied between the first electrode 3 and the second electrode 4 so that the first electrode 3 has a positive potential and the second electrode 4 has a negative potential, An electric field generated by applying a voltage acts on the black particles B and red particles C in the display layer 400. Then, the black particles B migrate to the first electrode 3 side while passing through the space A22 of the white particles A, and the red particles C migrate to the second electrode 4 side while passing through the space A22 of the white particles A. . Then, the voltage application is stopped in a state where both the black particles B and the red particles C are located in the central portion of the display layer 400 in the thickness direction. Thereby, as shown in FIG.6 (c), the white which is the color of the white particle A is displayed on the display surface 121. FIG.

  Note that it is preferable to set the migration speeds of the black particles B and the red particles C to be approximately equal in order to ensure a white display state. As a result, it is possible to easily create a state in which both the black particles B and the red particles C are located in the central portion of the display layer 400 in the thickness direction. Similarly to the switching from the black display state to the white display state, the red display state can be easily switched to the white display state.

<Third Embodiment>
FIG. 7 is an enlarged cross-sectional view of white particles included in the third embodiment of the display device of the present invention.
Hereinafter, the third embodiment will be described with a focus on differences from the above-described embodiment, and description of similar matters will be omitted.
The display device according to the third embodiment of the present invention is the same as the display device of the first embodiment except that the configuration of the coating layer of white particles is different. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment mentioned above.

  As shown in FIG. 7, the coating layer A2 ′ of the white particles A has a number of fine pores through which the black particles B can pass, and is composed of a porous body in which these pores communicate with each other. . And the space formed inside the porous body constitutes the space A22. With the coating layer A2 'having such a configuration, the space A22 can be easily formed in the coating layer A2'. Further, since the space A22 has an irregular and complicated shape, the retention of the black particles B is further improved.

  Such a coating layer A2 'is not particularly limited, but a ceramic porous body can be suitably used. As a ceramic porous body, the porous body formed by sintering metal powders, such as titanium, silicon, nickel, is mentioned, for example. The ceramic porous body is excellent in that the size of the pores can be easily controlled by adjusting the particle size of the metal powder.

  Moreover, you may use the foam comprised with the resin material as the white particle A. FIG. Examples of the resin material include urethane resins, urea resins, ester resins, ether resins, olefin resins such as polyethylene and polypropylene, ethylene vinyl acetate copolymer (EVA), ethylene methyl methacrylate copolymer (EMMA), and ethylene. Various resin materials, such as ethylene copolymers, such as a cyclic olefin copolymer (COC), and an acrylic resin, are mentioned.

<Fourth embodiment>
FIG. 8 is an enlarged cross-sectional view of white particles included in the fourth embodiment of the display device of the present invention.
Hereinafter, the fourth embodiment will be described with a focus on differences from the above-described embodiment, and description of similar matters will be omitted.
The display device according to the fourth embodiment of the present invention is the same as the display device of the first embodiment except that the configuration of the coating layer of white particles is different. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment mentioned above.

As shown in FIG. 7, the coating layer A2 ″ of the white particles A has a plurality of porous bodies A23 bonded to the surface of the base A1. Further, the black particles B pass through each porous body A23. There are many possible fine pores, and these pores communicate irregularly. In such a coating layer A2 ″, the space formed inside each porous body A23 and the adjacent porous body A gap between A23 forms a space A22. With the coating layer A2 ″ having such a configuration, the space A22 can be easily formed in the coating layer A2 ″.
The constituent material of each porous body A23 is not particularly limited, and various resin materials as mentioned in the third embodiment can be used.

<Fifth Embodiment>
FIG. 9 is a schematic perspective view showing a fifth embodiment of the display device of the present invention, and FIG. 10 is a cross-sectional view of the display sheet shown in FIG.
Hereinafter, the fifth embodiment will be described with a focus on differences from the above-described embodiments, and description of similar matters will be omitted.

The display device according to the fifth embodiment of the present invention is the same as that of the first embodiment except that the display sheet is configured as a separate body.
As shown in FIG. 9, the display device 20E of the present embodiment includes a display sheet 21E and a writing device 22E.
As shown in FIG. 10, the display sheet 21E includes a substrate (first substrate) 12E, a substrate (second substrate) 11E disposed opposite to the substrate 12E, and a display provided between the substrates 12E and 11E. It has the layer 400, the sealing part 9 which seals the display layer 400, and the dispersion liquid 100 with which the display layer 400 was filled. Since the substrates 12E and 11E have the same configuration as the base 2 of the substrate 12 of the first embodiment described above, description thereof is omitted.

  The writing device 22E is a device used when writing a desired image (pattern, color, character, picture, or a combination thereof) on the display sheet 21E. As shown in FIG. 9, the writing device 22E is common to a pedestal 221E, a sheet-like common electrode 222E provided on the pedestal 221E, and a writing pen (input tool) 224E provided with a partial electrode 223E at the tip. Voltage application means 225E for applying a voltage between the electrode 222E and the partial electrode 223E.

Such a display device 20E is used as follows, for example.
First, the display sheet 21E in which the entire display surface 121 is in a white display state is placed on the common electrode 222E of the writing device 22E with the display surface 121 facing upward. Next, a voltage at which the partial electrode 223E side is at a low potential is applied between the common electrode 222E and the partial electrode 223E by the voltage applying means 225E. In this state, by moving the writing pen 224E along a desired locus while being in contact with the display surface 121, particles migrate in an area corresponding to the locus, and the display color changes from white to black.

According to such a display device 20E, a desired character or the like can be drawn on the display surface 121 of the display sheet 21E with the same feeling as drawing a character or the like on paper with a pencil. Therefore, the operability (operation feeling) of the display device 20E is improved.
Each of the display devices 20 described above can be incorporated into various electronic devices. As an electronic apparatus of the present invention provided with an electrophoretic display device, for example, an electronic paper, an electronic book, a television, a viewfinder type, a monitor direct view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, an electronic newspaper, Examples include a word processor, a personal computer, a workstation, a videophone, a POS terminal, and a device equipped with a touch panel.

Of these electronic devices, an electronic paper will be described as an example for specific description.
FIG. 11 is a perspective view showing an embodiment when the electronic apparatus of the present invention is applied to electronic paper.
An electronic paper 600 shown in FIG. 11 includes a main body 601 composed of a rewritable sheet having the same texture and flexibility as paper, and a display unit 602. In such electronic paper 600, the display unit 602 includes the display device 20 as described above.

Next, an embodiment when the electronic apparatus of the present invention is applied to a display will be described.
FIG. 12 is a diagram showing an embodiment when the electronic apparatus of the present invention is applied to a display. Among these, (a) in FIG. 12 is a sectional view and (b) is a plan view.
A display (display device) 800 shown in FIG. 12 includes a main body 801 and an electronic paper 600 that is detachably attached to the main body 801. The electronic paper 600 has the same configuration as described above, that is, the configuration shown in FIG.

  The main body 801 has an insertion port 805 into which the electronic paper 600 can be inserted on its side (right side in FIG. 12A), and two pairs of conveying rollers 802a and 802b are provided inside. Yes. When the electronic paper 600 is inserted into the main body 801 through the insertion port 805, the electronic paper 600 is installed in the main body 801 in a state of being sandwiched between the pair of conveyance rollers 802a and 802b.

  A rectangular hole 803 is formed on the display surface side of the main body 801 (the front side in FIG. 12B), and a transparent glass plate 804 is fitted in the hole 803. . Thereby, the electronic paper 600 installed in the main body 801 can be viewed from the outside of the main body 801. That is, in the display 800, the display surface is configured by visually recognizing the electronic paper 600 installed in the main body 801 on the transparent glass plate 804.

Further, a terminal portion 806 is provided at the leading end of the electronic paper 600 in the insertion direction (left side in FIG. 12A), and the electronic paper 600 is installed in the main body 801 inside the main body 801. A socket 807 to which the terminal portion 806 is connected in the state is provided. A controller 808 and an operation unit 809 are electrically connected to the socket 807.
In such a display 800, the electronic paper 600 is detachably installed on the main body 801, and can be carried and used while being detached from the main body 801. This improves convenience.
As described above, the display sheet, the display device, and the electronic apparatus according to the present invention have been described based on the illustrated embodiment. It can be replaced with that of the configuration. In addition, any other component may be added to the present invention. Moreover, you may combine each embodiment suitably.

Next, specific examples of the present invention will be described. However, the present invention is not limited to these examples.
1. Manufacture of display device (Example 1)
<1> First, titanium black particles were prepared as black particles. The average particle diameter of the titanium black particles was 50 nm. The titanium black particles were subjected to graft modification on the surface so as to be negatively charged.

Further, as white particles, particles obtained by adhering many protrusions made of silicon to the surface of a substrate made of silicon oxide were prepared. The white particles were manufactured by the manufacturing method described in the first embodiment. The average particle diameter of the substrate was 50 nm, and the thickness of the coating layer (projection length) was 1000 nm. That is, the thickness of the coating layer was 20 times the average particle size of the black particles. The space ratio of the coating layer was 76%.
Then, these particles were dispersed in dimethyl silicone oil (dispersion medium) to prepare a dispersion.

<2> Next, a PET-ITO substrate on which an electrode composed of ITO (second electrode) was formed was prepared. Subsequently, the sealing part which consists of an epoxy-type adhesive agent was formed in the edge (outer peripheral part) of a PET-ITO substrate.
Subsequently, the dispersion was supplied into the recess formed by the PET-ITO substrate and the sealing portion, and the recess was filled with the dispersion. At this time, a display layer was obtained thereby. Subsequently, the circuit board in which the individual electrode made of ITO was formed on the display layer was disposed, and then the display device was obtained by bonding to the sealing portion using a roll laminator. The thickness of the display layer of the obtained display device was 50 μm.
Further, the occupation ratio of the white particles in the display layer was 65%. Note that the occupation ratio is determined by taking out all the white particles in the display layer after completing all the measurements described below, obtaining the sum of these volumes (volumes including space), the sum of the obtained volumes, and the display layer 400. The volume was calculated by comparing the volume.

(Example 2)
A display device of Example 2 was obtained in the same manner as Example 1 except that the thickness of the coating layer of white particles (the length of the protrusions) was 2000 nm. That is, in the obtained display sheet, the thickness of the coating layer was 40 times the average particle diameter of the black particles. Further, the occupation ratio of the white particles in the display layer was 60%.

(Example 3)
A display device of Example 3 was obtained in the same manner as Example 1 except that the thickness of the coating layer of white particles (the length of the protrusions) was 150 nm. That is, in the obtained display sheet, the thickness of the coating layer was three times the average particle diameter of the black particles. Further, the occupation ratio of the white particles in the display layer was 68%.

Example 4
A display device of Example 4 was obtained in the same manner as Example 1 except that the thickness of the coating layer of white particles (length of the protrusions) was 4500 nm. That is, in the obtained display sheet, the thickness of the coating layer was 90 times the average particle diameter of the black particles. Further, the occupation ratio of the white particles in the display layer was 63%.

(Example 5)
A display device of Example 5 was obtained in the same manner as Example 1 except that the occupation ratio of white particles in the display layer was changed to 55%.
(Example 6)
A display device of Example 6 was obtained in the same manner as in Example 1 except that the occupation ratio of the white particles in the display layer was 75%.

(Example 7)
A display device of Example 7 was obtained in the same manner as Example 1 except that the space ratio of the coating layer was 55%.
(Example 8)
A display device of Example 8 was obtained in the same manner as Example 1 except that the space ratio of the coating layer was 88%.

(Comparative Example 1)
A display device of Comparative Example 1 was obtained in the same manner as Example 1 except that the thickness of the coating layer of white particles (length of the protrusions) was 50 nm. That is, in the obtained display sheet, the thickness of the coating layer was one time the average particle diameter of the black particles. Further, the occupation ratio of the white particles in the display layer was 62%.
(Comparative Example 2)
A display device of Comparative Example 2 was obtained in the same manner as in Example 1 except that the thickness of the coating layer of white particles (the length of the protrusions) was 5500 nm. That is, in the obtained display sheet, the thickness of the coating layer was 110 times the average particle diameter of the black particles. Further, the occupation ratio of the white particles in the display layer was 68%.

(Comparative Example 3)
A display device of Comparative Example 3 was obtained in the same manner as in Example 1 except that the occupation ratio of the white particles in the display layer was 45%.
(Comparative Example 4)
A display device of Comparative Example 4 was obtained in the same manner as Example 1 except that the occupation ratio of the white particles in the display layer was 95%.
(Comparative Example 5)
A display device of Comparative Example 5 was obtained in the same manner as Comparative Example 1 except that the occupation ratio of the white particles in the display layer was 45%.

(Comparative Example 6)
A display device of Comparative Example 6 was obtained in the same manner as Comparative Example 2 except that the occupation ratio of the white particles in the display layer was 45%.
(Comparative Example 7)
A display device of Comparative Example 7 was obtained in the same manner as Comparative Example 1 except that the occupation ratio of the white particles in the display layer was 95%.
(Comparative Example 8)
A display device of Comparative Example 8 was obtained in the same manner as Comparative Example 2 except that the occupation ratio of the white particles in the display layer was 95%.

2. Evaluation (2-1) Measurement of Black Reflectance <1> First, with respect to Examples 1 to 8 and Comparative Examples 1 to 8, the display surface is in a state where black particles are dispersed almost uniformly in the display layer. The black area was measured for the black reflectance A at this time. The reflectance A was measured in two different regions (region 1 and region 2) that were arbitrarily defined three seconds after the switching to the black display state was completed. In this measurement, as shown in FIG. 13, the region 1 was set on the left edge of the display surface, and the region 2 was set on the right edge.

  <2> Next, for Examples 1 to 8 and Comparative Examples 1 to 8, the display surface was parallel to the vertical direction and the region 1 from the state where the black particles were dispersed almost uniformly in the display layer. Was tilted so that the region 2 was positioned on the upper side in the vertical direction and the region 2 was positioned on the lower side in the vertical direction, and left in that state for 10 minutes. And after leaving it for ten, the whole display surface was made into the black display state, and the black reflectance B of the area | regions 1 and 2 at this time was measured.

Note that the black reflectances A and B of each display device indicate the ratio of the reflection amount of the display color of the display device when the reflection amount of the reference white (standard sample) is 100. Moreover, the reflectances A and B were measured using a color luminance meter ("BM-5A" manufactured by Topcon Corporation).
Table 1 shows the reflectances A and B in Examples 1 to 10 and Comparative Examples 1 and 2 obtained as described above. The numerical values in parentheses in Table 1 indicate the difference from the reflectance A.

  As shown in Table 1, the reflectances A and B measured by the display devices of Examples 1 to 8 were values having almost no difference. Thereby, it was confirmed that the movement (sedimentation) of the black particles downward in the vertical direction is prevented by the coating layer of the white particles. Moreover, the reflectances A and B measured by the display devices of Examples 1 to 8 were sufficiently low values, and it was confirmed that excellent display contrast can be exhibited.

  On the other hand, a large difference occurred in the reflectances A and B measured by the display devices of Comparative Examples 1 to 8. Specifically, in the region 2, the changes in the reflectances A and B were small, but in the region 1, the reflectance B was greatly increased with respect to the reflectance A. This is a result of the reduction of black particles in region 1 due to the settling of black particles. Therefore, it was confirmed that the display devices of Comparative Examples 1 and 2 cannot prevent the black particles from settling.

(2-2) Change in white reflectance The white reflectance was measured in the same manner as the measurement of the black reflectance.
<1> First, in each of Examples 1, 5, 6 and Comparative Example 3, the entire display surface is changed to a white display state from the state in which the white particles are substantially uniformly arranged in the display layer. The reflectance C was measured. Note that the reflectance C was measured in two different regions (region 1 and region 2) arbitrarily defined three seconds after the switching to the white display state was completed. In this measurement, as shown in FIG. 10, the region 1 was set on the left edge of the display surface, and the region 2 was set on the right edge.

<2> Next, for Examples 1, 5, 6 and Comparative Example 3, from the state where the white particles are substantially uniformly arranged in the display layer, the display surface is parallel to the vertical direction and the region 1 Was tilted so that the region 2 was positioned on the upper side in the vertical direction and the region 2 was positioned on the lower side in the vertical direction. And after leaving it for ten, the whole display surface was made into the white display state, and the white reflectance D of the area | regions 1 and 2 at this time was measured.
Table 2 shows the reflectances C and D in Examples 1 to 3 and Comparative Example 1 obtained as described above. The numerical values in parentheses in Table 2 indicate the difference from the reflectance C.

As shown in Table 1, the reflectances C and D measured by the display devices of Examples 1, 5, and 6 were values having almost no difference. Thereby, it was confirmed that sedimentation of white particles was prevented. Further, the reflectances C and D measured by the display devices of Examples 1, 5, and 6 are sufficiently high values, and it was confirmed that excellent display contrast can be exhibited.
On the other hand, a large difference occurred in the reflectances C and D measured by the display device of Comparative Example 3. Specifically, in the region 2, changes in the reflectances C and D were small, but in the region 1, the reflectance D was greatly reduced with respect to the reflectance C. This is a result of the white particles settling and the white particles in region 1 being reduced.

  DESCRIPTION OF SYMBOLS 1 ... Base part 2 ... Base part 3 ... 1st electrode 4 ... 2nd electrode 7 ... Dispersion medium 9 ... Sealing part 100 ... Dispersion liquid 11, 11E ... Opposite substrate 12, 12E ... Substrate 121 ... Display surface 20, 20E ... Display device 21, 21E ... Display sheet 22 ... Circuit board 22E ... Writing device 221E ... Base 222E ... Common electrode 223E ... Partial electrode 224E ... Writing pen 225E ... Voltage application means 400 ... Display layer 600 ... Electronic paper 601 ... Main body 602 ... Display unit 800 ... Display 801 ... Main body 802a, 802b ... Conveying roller pair 803 ... Hole 804 ... Transparent Glass plate 805 ... Insertion slot 806 ... Terminal part 807 ... Socket 808 ... Controller 809 ... Operation part 900 Si substrate 910 Sacrificial layer A First particle (white particle) A1 Substrate A2, A2 ', A2 "Cover layer A21 Projection A22 Space A23 Porous body B 2nd particle (black particle) C 3rd particle (red particle)

Claims (11)

A first substrate;
A second substrate disposed opposite the first substrate;
Dispersed with the first particles and the second particles that have a hue different from that of the first particles and are charged positively or negatively between the first substrate and the second substrate. A display layer filled with a dispersion liquid dispersed,
The first particles have a base and a coating layer formed so as to cover the periphery of the base.
The coating layer has a thickness that is not less than 2 times and not more than 100 times the average particle diameter of the second particles, and has a space inside which the second particles can move to open to the outer peripheral surface,
In the display layer, a plurality of the first particles are filled such that the occupation ratio of the first particles in the display layer is 50% or more and 80% or less,
A display sheet, wherein the second particles migrate through the space of the first particles by an electric field acting on the display layer.   The display sheet according to claim 1, wherein movement of the second particles due to their own weight is restricted by being held in the coating layer.   The display sheet according to claim 1, wherein the coating layer is porous.   The display sheet according to claim 1, wherein the coating layer has a plurality of protrusions protruding from a surface of the base, and a gap between the plurality of protrusions constitutes the space.   The display sheet according to claim 1, wherein the first particles are uncharged.   The display sheet according to any one of claims 1 to 5, wherein a diameter of the substrate is 1 to 20 times the average particle diameter of the second particles.   The display sheet according to claim 1, wherein an occupation ratio of the space with respect to the coating layer is 50% or more and 90% or less.   The display sheet according to claim 1, wherein the first particles are white.   2. The dispersion liquid further includes a plurality of third particles that exhibit a hue different from that of the first particles and the second particles and are charged to a pole opposite to the second particles. The display sheet in any one of 8 thru | or 8.   A display device comprising the display sheet according to claim 1.   An electronic apparatus comprising the display device according to claim 10.

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