JP2007334126A - Electrophoretic display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophoretic display device, particularly capable of performing white display with high reflectance and display with high contrast and easily recognizable chroma, without complicated manufacturing processes. <P>SOLUTION: The electrophoretic display device comprises an electrophoretic display liquid 40 containing at least white electrophoretic particles sealed in a space 30 between substrate electrodes of a transparent front plate 10 having a light transmitting electrode 11 and a back plate 20 having an electrode 21, both electrodes opposing to each other. The electrode 21 formed on the back plate 20 is made of a conductive material containing at least a white metal, or the electrode is subjected to a surface treatment with a conductive material containing at least a white metal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophoretic display device capable of reversibly changing a visual state by the action of an electric field or the like.

  In recent years, with the development of information equipment, the demand for low power consumption, thinning, and flexibility of display devices has increased, and research and development of display devices that meet these demands have been actively conducted. .

  As one of such display devices, Harold D. et al. An electrophoretic display device invented by Lees et al. Is known. In this electrophoretic display device, two electrode substrates, at least one of which is transparent, are arranged to face each other via an appropriate spacer, and a dispersion medium in which fine particles (pigment particles) are colored in a different color between the electrode substrates. The display panel is filled with a display liquid dispersed therein, and an electric field is applied to the display panel to obtain a display on the transparent electrode surface (see, for example, Patent Document 1). ).

The liquid for electrophoretic display filled between the electrode substrates is a low particle such as white fine particles such as titanium dioxide, xylene, tetrachloroethylene, paraffin, silicone oil or the like in which a dye for color contrast with the white fine particles is dissolved. It is composed of a dispersion medium of dielectric constant, a dispersant such as a surfactant, and an additive such as a charge imparting agent.
By applying an electric field to the electrophoretic display liquid, the fine particles in the display liquid move to the transparent electrode side, the color of the fine particles appears on the display surface, and by applying an electric field in the opposite direction, The fine particles move to the opposite side, and the color of the dispersion medium colored with the dye appears on the display surface.
Such an electrophoretic display device is a display device that can obtain a desired display by controlling the direction of an electric field, is low in cost, has a viewing angle as wide as that of a normal printed material, consumes less power, and displays. It has attracted attention as an inexpensive display device because of its advantages such as having a memory property.

  However, the display liquid of the electrophoretic display device described in Patent Document 1 or the like generally has a high refractive index such as titanium dioxide in a hydrophobic low dielectric constant dispersion medium colored by dissolving a dye or the like. Since the inorganic pigment is dispersed, white display with high reflectance cannot be performed due to adsorption of the dye to the pigment surface and the like, and there is a disadvantage that the contrast is lowered.

In particular, there is a strong demand for white display with high reflectivity similar to that of copy paper and high-quality paper, and high contrast display similar to that of print media. In particular, white display with high reflectivity is strongly demanded. In order to solve this problem, many developments have been made to improve display characteristics.
As a means for improving the reflectance and contrast of white display, for example, a dye that is non-adsorptive with respect to the pigment surface is used as a dye used for coloring the dispersion medium (see Non-Patent Document 1), or dispersion. It is known to reduce the dye concentration in the medium (see Non-Patent Document 2).
However, the methods of Non-Patent Documents 1 and 2 have not yet completely solved the drawbacks caused by the dye solution described above, and still have practical problems.

  Therefore, an electrophoretic display device that does not use a dye solution is known as a means for solving the problems and the like of a system using a dispersion medium colored with a dye. For example, in a cell in which a liquid in which at least two types of electrophoretic fine particles having different color tones and electrophoretic properties are dispersed in a colorless dispersion medium is formed via a spacer between at least one transparent electrode There is known an electrophoretic display element enclosed in (see, for example, Patent Document 2).

  However, in the technique described in Patent Document 2, since the charged charges of different electrophoretic fine particles are a combination of positive and negative, electric attractive force is generated between the fine particles, and the aggregation of the fine particles is likely to occur. And the white display reflectivity and contrast are liable to decrease due to color mixing.

On the other hand, unlike the electrophoretic display device which is displayed by moving fine particles (vertical movement) between the front substrate and the rear substrate which are arranged to face each other as shown so far, the first substrate is arranged on the rear substrate side. A so-called In-Plane type electrophoretic display device in which one electrode and a second electrode are formed and fine particles are moved in the lateral direction has been proposed (for example, see Patent Documents 3 and 4).
In this electrophoretic display device, for example, one of the electrodes is colored white, and black particles are moved to display black and white. That is, when black display is desired, the black particles are moved so as to cover the white electrode, and when white display is desired, the black particles are moved so as to be removed from the white electrode.

  However, such an electrophoretic display device has a complicated electrode configuration. For example, it is necessary to secure a space for collecting (hidden) black particles moved from the white electrode. For this reason, there are problems in the surface of white display and high contrast display with high reflectivity.

Furthermore, a device for increasing the contrast by making the color of the back substrate the same as the color of the fine particles is known. For example, a method has been proposed in which the back substrate, spacers, spacer concealing members, etc. are made the same as black, transparent, or the color of the fine particle group to make the display stand out (for example, see Patent Document 5).
However, such a display medium requires a process of performing coating or the like on the electrode surface after arranging the electrode, and is complicated in manufacturing. Further, when the coating film formed on the electrode surface is made of a color material such as a resin and a pigment, there is a problem that the film may be dissolved by the dispersion medium of the electrophoretic display liquid.
US Pat. No. 3,612,758 (Claims, Examples, etc.) Philips Lab: Conference Record of 1980 Biennial Disp. Res. Conf. XeroxPaloAlto: Proc. SID, Vol. 18 3/4, 1977. JP-A-62-269124 (Claims, Examples, etc.) JP-A-11-202804 (Claims, Examples, etc.) JP 2000-171839 (Claims, Examples, etc.) JP 2002-139748 (Claims, Examples, etc.)

  The present invention has been made in view of the above-described conventional problems and the current situation, and is intended to solve this problem. In particular, electrophoresis with which white display with high reflectivity and clear and light color saturation can be easily recognized. An object of the present invention is to provide a display device without going through a complicated manufacturing process.

  As a result of intensive studies on the above-described problems and the like of the prior art, the electrophoretic display device according to the above object can be obtained by configuring the electrode formed on the back plate from a conductive material containing at least a white metal. They found out that they were obtained and came to complete the present invention.

That is, the present invention resides in the following (1) to (3).
(1) An electrophoretic display liquid having at least white electrophoretic particles is enclosed between a light-transmitting electrode formed on a transparent front plate and a substrate electrode on which the electrodes formed on the back plate are arranged to face each other. An electrophoretic display device, wherein the electrode formed on the back plate is made of a conductive material containing at least a white metal.
(2) An electrophoretic display liquid having at least white electrophoretic particles is sealed between a light-transmitting electrode formed on a transparent front plate and a substrate electrode on which the electrodes formed on the back plate are arranged to face each other. An electrophoretic display device, wherein the electrode formed on the back plate is surface-treated with a conductive material containing at least a white metal.
(3) The electrode formed on the back plate has L> 50, a <2, and −10 <b <10 in the Lab chromaticity coordinates of the color difference display method based on JIS Z 8730: 2002. The electrophoretic display device according to (1) or (2) above.

  According to the present invention, an electrophoretic display device capable of displaying a white display with a particularly high reflectance, a clear contrast, and an easily recognizable chroma is provided without going through a complicated manufacturing process.

Hereinafter, embodiments of the present invention will be described in detail.
The electrophoretic display device of the present invention is an electrophoretic display having white electrophoretic particles between a light-transmitting electrode formed on a transparent front plate and a substrate electrode on which electrodes formed on a back plate are arranged to face each other. An electrophoretic display device in which a display liquid is sealed, wherein the electrode formed on the back plate is made of a conductive material containing at least a white metal.
In addition, the electrophoretic display device of the present invention is characterized in that the electrode formed on the back plate is subjected to a surface treatment with a conductive material containing at least a white metal.

  FIG. 1 shows an example of an embodiment of the present invention. As shown in FIG. 1, the electrophoretic display device A of the present embodiment is a substrate in which a light transmissive electrode 11 formed on a transparent front plate 10 and an electrode 21 formed on a back plate 20 are arranged to face each other. It is composed of a multilayer structure having an electrophoretic display liquid layer formed by sealing an electrophoretic display liquid 40 between the electrodes 30. In addition, 15 is a partition wall part and 25 is a spacer member.

The transparent front plate 10 used in the present invention can be used without particular limitation as long as it has optical transparency so as to be a display surface as an electrophoretic display device. For example, transparent resin films, such as PET, vinyl chloride, and polycarbonate, transparent glass, etc. can be mentioned.
As this transparent front plate 10, a material that is not dissolved or altered by the electrophoretic display liquid 40, and an optimal one can be selected as appropriate according to chemical and physical characteristics. Moreover, it is desirable that the material suppresses / prevents volatilization of the dispersion medium of the electrophoretic display liquid 40 and permeation of air, moisture, and the like.
Furthermore, a gas barrier film such as polyvinyl alcohol or polyethylene vinyl alcohol is applied to the transparent front plate 10 by a laminating method or the like for the purpose of highly suppressing / preventing volatilization of the dispersion medium and permeation of air, moisture and the like. It is also possible to use a combination of resin films such as polyvinyl butyral for the purpose of preventing the glass from being laminated or being scattered.
The thickness of the front plate 10 is preferably 10 to 1100 μm from the viewpoint of the reliability and light transmittance of the electrophoretic display device.

Examples of the light transmissive electrode 11 used in the present invention include an electrode formed using a transparent electrode material such as ITO (Indium Tin Oxide) and IZO (Indium Zinc Oxide).
The light transmissive electrode 11 may be formed by applying a transparent conductive material such as ITO to a transparent resin film such as PET or transparent glass, for example, by a vapor deposition method such as a coating method, an ion plating method, or a sputtering method. it can. The light-transmitting electrode 11 can be a so-called solid electrode that is uniformly formed over the entire front plate 10, or can be patterned by a conventionally used method such as photoetching. Although what was formed can also be used, this can be suitably combined or selected according to the electrode configuration of the back plate 20.
In order to realize white display with a high reflectance, it is particularly desirable that the visible light transmittance is 80% or more in a state where the transparent electrode 11 is formed on the transparent front plate 10. .
In addition, the thickness of the electrode 11 is preferably 0.01 to 20 μm from the viewpoint of the reliability, light transmittance, and surface resistance value of the electrophoretic display device.

The back plate 20 used in the present invention is not particularly limited as long as it is a material that can suppress leakage of the electrophoretic display liquid 40 and volatilization of the solvent. However, in order to obtain a thin electrophoretic display device. For example, it is desirable to use a thin back plate such as a resin film, a resin plate, a glass plate, a ceramic plate, or a metal plate.
The back plate 20 is also laminated with a gas barrier film such as polyvinyl alcohol or polyethylene vinyl alcohol by a laminating method or the like for the purpose of highly suppressing and preventing the volatilization of the dispersion medium and the permeation of air, moisture and the like. In order to prevent the glass from being broken or scattered, it is also possible to use a resin film such as polyvinyl butyral in combination.
The thickness of the back plate 20 is preferably 10 to 2000 μm from the viewpoint of reliability of the electrophoretic display device and matching with the manufacturing process.

The electrode 21 used in the present invention is formed from a conductive material containing at least a white metal.
The white metal in the present invention refers to a metal having an achromatic and white metal color, such as aluminum, platinum, nickel, chromium, silver, tin, zinc, lead, titanium, iron, palladium, Indium, rhodium, ruthenium, molybdenum, magnesium, cobalt, tungsten, metal silicon, and the like can be given.

As a conductive material containing a white metal used in the present invention, one kind of white metal can be used, or an alloy containing the above various metals can be used as long as it contains at least a white metal.
In particular, in order to obtain a white display with high reflectivity, an alloy of white metals is preferable, but the white display performance of the electrophoretic display device can be improved even with an alloy with a metal other than a white metal such as gold or copper. It can use without being limited to this in the range which does not impair.

The electrode 21 in the present invention can be formed on the surface of the back plate 20 by a conventionally used electrode forming method. For example, it can be formed by coating a conductive material containing a white metal on the surface of the back plate 20, bonding a conductive material thin film, vapor deposition, plating, or the like. The thickness of the electrode 21 is preferably 0.01 to 50 μm from the viewpoint of display reliability and workability of the electrophoretic display device.
Further, the electrode 21 formed on the back plate 20 can also be a so-called solid electrode formed uniformly over the entire back plate 20, and has been used conventionally such as photoetching. Depending on the method, it is also possible to use a pattern-formed one, which can be appropriately combined or selected according to the configuration of the light transmissive electrode 11 formed on the transparent front plate 20. It is. Furthermore, it is possible to use a TFT (Thin Film Transistor) substrate or the like that is generally used in liquid crystal or the like. However, if a conductive material containing at least a white metal is used, these may be used. It is not limited.

As shown in FIG. 2, the electrode 21 formed on the back plate 20 of the present embodiment is a metal other than a white metal such as gold or copper, or a white metal and a white metal. In the case of an alloy made of a metal other than that and formed of an alloy having a color other than white (reference numeral 21a in the figure), the electrode surface is surface-treated with a conductive material containing at least a white metal. Can be used.
For example, after forming the electrode 20a using copper for the back plate 20, a method of forming a white metal 20b such as nickel on the surface of the copper electrode 20a by a method such as plating or vapor deposition can be cited. As a result, the same effect as when electrodes are formed in advance with a conductive material containing white metal can be exhibited, and even when using an inexpensive general-purpose substrate such as formed of copper, at least white metal By surface-treating the electrode surface with a conductive material containing, white display with high reflectance can be realized. Note that the thickness of the surface of the electrode surface treated with a conductive material containing at least a white metal is preferably 0.01 to 20 μm from the viewpoint of display reliability of the electrophoretic display device.

As described above, any electrode 21 made of a conductive material containing a white metal (including an electrode whose surface has been surface-treated) can be used as long as it is an achromatic and white metal color. The electrode 21 formed of a conductive material containing at least the above-mentioned white metal has L> 50, a <2, in which the whiteness is Lab-based chromaticity coordinates of the color difference display method in accordance with JIS Z 8730: 2002. Those satisfying −10 <b <10 are desirable, and those satisfying 50 <L ≦ 100, −2 <a <2, and −10 <b <10 are desirable. By setting the range of the preferable Lab-based chromaticity coordinates, the contrast can be further improved together with the white display having a high reflectance.
As an electrode 21 (including an electrode whose surface is surface-treated) 21 made of a conductive material containing a particularly preferred white metal, each of the various metals used in the preferred Lab-based chromaticity coordinate range, or these In particular, from the viewpoint of ease of electrode formation and cost, each of aluminum, silver, nickel, or an alloy containing these, which is the preferred Lab-based chromaticity coordinate range, is used. It is desirable to use it.

  Next, in the electrophoretic display device of the present invention, the light transmissive electrode 11 formed on the transparent front plate 10 and the electrode 21 formed on the back plate 20 are disposed so as to face each other and between the electrode substrates 30. The electrophoretic display liquid 40 is sealed.

The electrode substrates used in the present invention are arranged to face each other so as to prevent short-circuiting due to contact between electrodes and to obtain a uniform display without unevenness. That is, the opposing electrode substrate interval 30 is configured to keep the interval constant by various methods used in conventionally known liquid crystals, electrophoretic display devices, and the like. In the embodiment of FIG. 1, the electrode substrate interval is kept constant by the partition portions 15, 15... And the spacer members 25, 25.
Further, as shown in FIG. 3 (a), spherical fine particles 50 having a uniform particle diameter are sandwiched between the electrode substrates 30, and as shown in FIG. 3 (b), a photolithographic method or nanoimprint is applied to one electrode substrate 20. After the rib 51 having a certain height is raised by a method or the like, the distance between the electrode substrates can be kept constant by a method of bonding the other electrode substrate 10 or the like. The same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted (the same applies to the following FIG. 4 and subsequent figures).

Furthermore, in addition to the effect of keeping the distance between the electrode substrates constant, in order to suppress aggregation and uneven distribution of the electrophoretic particles and obtain a uniform display, as shown in FIG. 1, the space formed between the electrode substrates is partitioned. It can also be configured to be divided into small rooms (cells) by the sections 15, 15.
Furthermore, as shown in FIGS. 4 (a) to 4 (c), a synthetic resin such as a PET film having a certain thickness is formed by laser processing with holes having a square, hexagonal, or circular shape, and FIG. As shown in (a) to (c), a fabric body 52 formed by knitting fibers 52a having a constant diameter is sandwiched between electrode substrates 30, and further shown in FIGS. 6 (a) and 6 (b). As described above, it is also possible to use a structure 53 in which a cross-shaped structure material is formed by a method such as hot embossing using a thermoplastic resin.
Preferably, a structure having a high aperture ratio and capable of forming a fine small cell (cell) so as to suppress aggregation and uneven distribution of the electrophoretic particles is preferable. It is desirable to form a square, hexagonal, or circular hole in a PET film that is easy to form by laser processing, and a woven body formed by knitting fibers that can be easily filled with an electrophoretic display solution. Particularly desirable.

  The electrode substrates arranged opposite to each other as described above form a space for enclosing the electrophoretic display liquid 40 between the substrates by a photo-curing adhesive or a thermosetting adhesive around the display surface. Then, they are bonded together in a form having a constant substrate interval.

As a thermosetting adhesive that can be used, for example, an epoxy-based adhesive or a urethane-based adhesive can be used. Moreover, as a photocurable adhesive, epoxy acrylate, urethane acrylate, polyester acrylate, or the like can be used.
These may be selected and used in combination in order to obtain desirable scientific, physical and mechanical properties such as strength, flexibility, flexibility and the like.

The electrophoretic display liquid 40 having white electrophoretic particles used in the present invention is obtained by dispersing the white electrophoretic particles in an insulating dispersion medium.
As the dispersion medium having an insulating property used in the present invention, various types conventionally used for electrophoretic display can be used. Specifically, as aromatic hydrocarbons, alkylbenzenes such as benzene, toluene, xylene, ethylbenzene, dodecylbenzene, phenylxylylethane, 1,1-ditolylethane, 1,2-ditolylethane, 1,2-bis ( Diarylalkanes such as 3,4-dimethylphenylethane) (BDMF), alkylnaphthalenes such as diisopropylnaphthalene, alkylbiphenyls such as monoisopropylphenyl, isopropylbiphenyl, isoamylbiphenyl, and terphenyl hydrogenated in various proportions And triaryldimethanes such as dibenzyltoluene, benzylnaphthalenes, phenylene oxides, diallylalkylenes, allylindanes, polychlorinated biphenyls, naphthenic hydrocarbons, and the like.

  Also, aliphatic hydrocarbons such as hexane, cyclohexane, kerosene, isopar, paraffinic hydrocarbons, halogenated hydrocarbons such as chloroform, trichloroethylene, tetrachloroethylene, trifluoroethylene, tetrafluoroethylene, dichloromethane, ethyl bromide, phosphorus Phosphate esters such as tricresyl acid, trioctyl phosphate, octeldiphenyl phosphate, tricyclohexyl phosphate, dibutyl phthalate, dioctyl phthalate, dilauryl phthalate, dicyclohexyl phthalate, butyl oleate, Carboxylic acid esters such as diethylene glycol dibenzoate, dioctyl sebacate, dibutyl sebacate, octyl maleate, dibutyl maleate, ethyl acetate, chlorinated paraffin, N, N- Butyl-2-butoxy-5-tert-octyl aniline, and the like, but not limited thereto.

  Furthermore, in the present invention, these dispersion media can be used alone or in admixture of two or more. In particular, the dispersion medium is preferably a solvent having a low dielectric constant (5.0 or less), and is preferably selected so as to have a value equal to or closer to the specific gravity of the fine particles.

As the white electrophoretic particles used in the present invention, white pigment particles, polymer fine particles, and the like can be used. The pigment particles referred to here are those having low solubility in the insulating liquid in combination with the insulating liquid used as the dispersion medium, and can exist in a dispersed particle state in the insulating liquid. .
As white pigment particles, titanium dioxide, zinc sulfide, calcium carbonate, silica, calcium silicate and the like can be suitably used.

  Further, as the polymer fine particles, polymer fine particles composed of an organic polymer produced by a conventionally known method can be used. For example, a method using emulsion polymerization, a seed emulsion polymerization method, a soap-free polymerization method. , Dispersion polymerization method, suspension polymerization method, seed polymerization method, method using seed polymerization + polymerization shrinkage, method using suspension polymerization of W / O / W emulsion, method using surface drying of spray-dried droplets, Examples thereof include a seed agglomeration method in which a polymer emulsion is agglomerated by adding electrolyte solid particles, but is not limited to those produced by these methods.

  As the material of the polymer fine particles, a material selected from conventionally known polymer materials can be used in a combination that does not dissolve in the dispersion medium used for electrophoretic display. Examples of these are styrene-based, styrene-acrylic. , Styrene-isoprene, divinylbenzene, methyl methacrylate, methacrylate, ethyl methacrylate, ethyl acrylate, n-butyl acrylate, acrylic acid, acrylonitrile, acrylic rubber-methacrylate, ethylene, ethylene Acrylic acid, nylon, silicone, urethane, melamine, benzoguanamine, phenol, fluorine (tetrachloroethylene), vinylidene chloride, quaternary pyridinium salt, synthetic rubber, cellulose, cellulose acetate, chitosan Examples thereof include polymer materials such as calcium alginate and polymer materials whose solvent resistance function has been improved by crosslinking these polymer materials. Particularly, a material containing a crosslinked acryl as a component is preferably solvent resistant. However, it is not limited to these polymer materials.

  Furthermore, these polymer fine particles may be colored with a white pigment by a known method. For example, a method of producing the polymer fine particles using the above method after coloring the monomers before the synthesis of the polymer fine particles. Examples thereof include a method of coloring during the production of the polymer fine particles and a method of coloring after producing the polymer fine particles. As another method, the pigment can be obtained by physically dispersing the pigment in the polymer material obtained by synthesis in advance, and then pulverizing to a desired particle size. The polymer fine particles are not limited to those obtained by these methods.

In the present invention, at least white electrophoretic particles are used. However, when only white electrophoretic particles are used, the color and color tone of the electrophoretic particles are different, and the contrast is increased as the particles move. It is used in combination with a dispersion medium colored in a displayable color with a dye or the like.
For example, it is used as a type in which the color of the insulating dispersion medium is colored with an oil-soluble dye such as oil blue having a different color tone that can be displayed in contrast with white electrophoretic particles.

Any dye may be used as long as it can be dissolved and colored in the dispersion medium. For example, Spirit Black (SB, SSBB, AB), Nigrosine Base (SA, SAP, SAPL, EE, EEL) , EX, EXBP, EB), Oil Orange (201, PS, PR), Fast Orange, Oil Red (5B, RR, OG), Oil Scarlet, Oil Pink 312, Oil Violet 730, Macrolex Blue RR, Sumiplast Green G, Oil Brown (GR, 416), Sudan Black X60, Oil Green (502, BG), Bali First Orange (3209, 3210), Bali First Red (1306, 1355, 2303, 3304, 3306, 3320), Bali First Pink 23 0N, Bali First Brown (2402, 3405), Bali First Blue (3405, 1501, 1603, 1605, 1607, 2606, 2610), Bali First Violet (1701, 1702), Bali First Black (1802, 1807, 3804, 3810) , 3820, 3830) and the like.
These dyes can also be color-adjusted using 2 or more types.

On the other hand, when white electrophoretic particles and non-white electrophoretic particles are used, electrophoretic particles that are opposite to each other in charge and combined with electrophoretic particles with different colors that can be displayed in contrast. Will be used.
For example, when negatively charged white electrophoretic particles are selected, positively charged black particles can be selected and combined as the other particles. In this case, the color of the insulating dispersion medium is preferably colorless and transparent. However, the insulating dispersion medium may be further colored and used. Furthermore, two or more kinds of particles having different charge amount and color of the electrophoretic particles can be appropriately combined and used.

As the electrophoretic particles other than white, colored inorganic pigment particles, organic pigment particles, polymer fine particles, and the like can be used.
Examples of the inorganic pigment particles include yellow iron oxide, titanium yellow, cadmium orange, molybdate orange, bengara, red lead, silver vermilion, cadmium red, brown iron oxide, zinc iron, chrome brown, chrome green, chromium oxide, viridian, Examples include cobalt green, bitumen, cobalt blue, ultramarine, cerulean blue, cobalt violet, carbon black, iron black, black low-order titanium oxide, aluminum powder, copper powder, lead powder, tin powder, and zinc powder.

  Examples of organic pigment particles include fast yellow, disazo yellow, condensed azo yellow, isoindoline yellow, quinophthaloin yellow, benzimidazolone yellow, monoazo yellow lake, dinitroaniline orange, perinone orange, naphthol red, toluidine red, Permanent Carmine, Brilliant Fast Scarlet, Rhodamine 6G Lake, Permanent Red, Lake Red, Brilliant Carmine, Naphthol Red, Quinacridone Magenta, Condensed Azo Red, Naphthol Carmine, Perylene Car Red, Condensed Azo Scar Red, Perylene Red, Quinacridone Red, Diketopyrrolo Pyrrole red, benzimidazolone brown, phthalocyanine green, Victoria blue lake, phthalos Ninburu, fast sky blue, rhodamine B lake, methyl violet lake, dioxazine violet, and the like are exemplified.

  The polymer fine particles can be obtained by coloring the polymer fine particles composed of the organic polymer produced by the known method or the like with a dye or a pigment by the known method.

  The electrophoretic particles may be subjected to a surface treatment such as a lipophilic treatment such as a treatment with a coupling agent for the purpose of adjusting the charge amount, improving the dispersibility, and improving the stability.

Furthermore, in the electrophoretic display device according to the present invention, in addition to the insulating dispersion medium and the electrophoretic particles, a charge adjusting agent, a dispersing agent, a surfactant, a hygroscopic agent and the like are conventionally used for electrophoretic display. Various types can be used as appropriate.
For example, by using an electrophoretic display liquid to which an alkyl polyetheramine is added, a white display with higher reflectance and a vivid chromatic display can be achieved. In addition to the liquid type, the electrophoretic display liquid may be an electropowder fluid having a high response speed in which the electrophoretic particles move in the air.

In the electrophoretic display device of the present invention configured as described above, it is preferable that the electrode 21 formed on the back plate 20 is composed of a conductive material containing at least a white metal or an electrode obtained by surface-treating the electrode surface. The Lab-based chromaticity coordinate measurement value obtained by surface-treating the conductive material containing at least a white metal or the surface of the electrode is configured such that L> 50, a <2, −10 <b <10. It is possible to improve the reflectivity of the entire electrophoretic display device, which makes the electrophoretic display device capable of displaying colors with distinct colors, clear shading, and easy to recognize saturation. Therefore, it can be provided without going through a complicated manufacturing process.
Therefore, not only white and black (achromatic) display but also white display with particularly high reflectivity, especially when displaying between chromatic colors such as white and red (red and white, blue and white, etc.) Vivid chromatic display is possible.

At the time of white display of the electrophoretic display device of the present invention, white electrophoretic particles are aggregated on the surface of the light-transmitting electrode 11 formed on the front plate 10 to display white. It is assumed that a part of the light reaches the electrode 21 formed on the back plate 20 and is reflected there.
It is assumed that the reflectance of the entire display surface of the electrophoretic display device of the present invention is increased by these reflected lights. Thus, by using at least a white metal as an electrode on the back plate, it is troublesome to paint or the like. It is possible to provide a “base” for obtaining a display with a high reflectivity. This white metal may be used as an electrode as it is, but it is preferable that a display with higher reflectivity can be obtained by configuring the white metal to be a mirror surface toward the display surface. is there.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in full detail, this invention is not limited to the following Example.

[Examples 1 to 3 and Comparative Example 1]
Example 1
An electrophoretic display device was obtained by the following steps.
1) Substrates 10 and 20 used
Front plate 10 and back plate 20: PET film (100 μm)
Distance between substrates: 50 μm
2) Electrode used Front electrode: ITO (18 μm / 100Ω / □)
Back electrode: Aluminum (12μm ・ 0Ω / □)
A front electrode was formed on the front plate 10 by sputtering. A back electrode was formed on the back plate 20 by a laminating method.
3) Preparation of electrophoretic display liquid An electrophoretic display liquid having the following composition was used.
Black particles: Love Color 220MD Black (manufactured by Dainichi Seika Kogyo Co., Ltd.) 20 parts by weight White particles: ITT-2TiO2 CR-50 (manufactured by Nikko Chemicals) 10 parts by weight Dispersant: 3 parts by weight of sorbitan trioleate Naimine L-201 [hydroxy Ethyllaurylamine, manufactured by Nippon Oil & Fats Co., Ltd.] 3 parts by weight Dispersion medium: 30 parts by weight of xylene SAS296 (diallyl alkane, manufactured by Shin Nippon Petrochemical Co., Ltd.) 34 parts by weight 4) Production of electrophoretic display device Front plate with electrode and above electrode A back plate with a thickness of 50 μm is placed oppositely through a spacer in which a PET film having a thickness of 50 μm / 500 μm is formed in the shape of FIG. An electrophoretic display device was produced by enclosing the electrophoretic display liquid prepared by the above formulation. A UV curable material was used for the seal portion.

(Example 2)
An electrophoretic display device was obtained by the following steps.
1) Substrates 10 and 20 used
Front plate 10 and back plate 20: PET film (100 μm)
Distance between substrates: 50 μm
2) Electrode used Front electrode: ITO (9μm / 300Ω / □)
Back electrode: Aluminum (9μm ・ 0Ω / □)
A front electrode was formed on the front plate 10 by sputtering. A back electrode was formed on the back plate 20 by a laminating method.
3) Preparation of electrophoretic display solution Same as Example 1.
4) Production of electrophoretic display device The front plate with electrodes and the back plate with electrodes are arranged opposite to each other with a spacer of 23 μm allylate fibers plain-woven with a size of 150 mesh × 150 mesh shown in the shape of FIG. Then, an electrophoretic display device was produced by enclosing the electrophoretic display liquid prepared in the above-described composition in this space. A UV curable material was used for the seal portion.

(Example 3)
An electrophoretic display device was obtained by the following steps.
1) Substrates 10 and 20 used
Front plate 10 and back plate 20: PET film (100 μm)
Distance between substrates: 50 μm
2) Electrode used Front electrode: ITO (20 μm, 80Ω / □)
Back electrode: Copper foil 12μm + Nickel chrome plating 10μm (22μm ・ 0Ω / □)
A front electrode was formed on the front plate 10 by sputtering. A back electrode was formed on the back plate 20 by a laminating method or a plating method.
3) Preparation of electrophoretic display solution Same as Example 1.
4) Fabrication of electrophoretic display device A square opening having a line / space of 25 μm / 500 μm was formed in the shape of FIG. 6 by photoetching a 25 μm thick epoxy sheet on the front plate with electrodes and the back plate with electrodes. The electrophoretic display device was produced by placing the electrophoretic display liquid prepared in the above-mentioned composition in the space while facing each other through a spacer. A UV curable material was used for the seal portion.

(Comparative Example 1)
An electrophoretic display device was obtained by the following steps.
1) Substrates 10 and 20 used
Front plate 10 and back plate 20: PET film (100 μm)
Distance between substrates: 50 μm
2) Electrode used Front electrode: ITO (18 μm / 100Ω / □)
Back electrode: Copper (12μm ・ 0Ω / □)
A front electrode was formed on the front plate 10 by sputtering. A back electrode was formed on the back plate 20 by a laminating method.
3) Preparation of electrophoretic display solution Same as Example 1.
4) Production of electrophoretic display device The front plate with electrodes and the back plate with electrodes have a square opening with a line / space of 50 μm / 500 μm in the shape of FIG. An electrophoretic display medium was produced by placing the electrophoretic display liquid prepared in the above-described composition in the space, facing each other through the formed spacer. A UV curable material was used for the seal portion.

About the back electrodes and electrophoretic display devices obtained in Examples 1 to 3 and Comparative Example 1, the following evaluation methods were used to measure the whiteness of the back electrodes (Lab-based chromaticity coordinate measurement) and the properties of the electrophoretic display devices. Evaluation (reflectance), visual evaluation of white display and coloring display, aggregation / adhesion state of particles, evaluation of responsiveness, and evaluation of contrast ratio were performed.
These results are shown in Table 1 below.

(Measurement of whiteness of back electrode: measurement method of Lab chromaticity coordinates of back electrode)
Using a multi-light source spectrocolorimeter (MSC-5N) manufactured by Suga Test Instruments Co., Ltd., measurement conditions: no regular reflection, measurement hole: 15 mm, light source: C2 deg, Lab system chromaticity coordinates Was measured.

(Evaluation of physical properties of electrophoretic display media)
For each of the electrophoretic display media of Examples and Comparative Examples prepared by the above method, a voltage of +50 V or −50 V is applied through the electrode of the medium to cause electrophoresis, and the reflectance of the formed white or colored display surface Was measured using MSC-5N (manufactured by Suga Test Instruments Co., Ltd.).
At the same time, visual evaluation of white display and color display, particle aggregation, adhesion state evaluation, and contrast ratio evaluation were performed by the following methods.

(Evaluation of visual white display and colored display)
The sensory evaluation was visually performed according to the following evaluation criteria for the whiteness of the white display surface displayed by applying a voltage and the color density of the colored display surface.
Visual evaluation criteria for white display surface:
○: White △: Slightly tinted ×: Strong tint Visual evaluation criteria for colored display surface:
○: Beautiful and strong △: Slightly white ×: Whitish

(Evaluation of particle aggregation / adhesion state and response)
For particle aggregation and adhesion to the electrode surface, + 50V or -50V voltage is alternately applied 100 times at 1 second intervals, the display is switched, and the color change and state of the display portion are visually observed and Evaluation was based on the evaluation criteria.
Furthermore, the responsiveness of the display change according to the voltage switching was also evaluated based on the following evaluation criteria.
Evaluation criteria for particle agglomeration and adhesion state ○: Almost no aggregation or adhesion △: Slight aggregation or adhesion ×: Aggregation or adhesion Evaluation criteria for responsiveness:
○: Change quickly △: Slightly delayed reaction ×: Slow reaction

(Evaluation of contrast ratio)
Contrast ratio is the opposite of the first after applying voltage of + 50V or -50V and focusing on the outermost display surface with one visual display part as white display and measuring white reflection by 45 irradiation-vertical light reception By applying a voltage of -50V or + 50V of polarity to make the visual display portion colored, the reflectance of the colored surface is measured in the same manner, and the ratio (reflectance of the white display surface / reflectance of the colored display surface) is calculated. Calculated.

  As is clear from the results in Table 1 above, the electrophoretic display devices of Examples 1 to 3 that fall within the scope of the present invention have whiteness and whiteness compared to the electrophoretic display device of Comparative Example 1 that falls outside the scope of the present invention. It has been found that the reflectance of the display surface and the colored display surface is excellent, the visual white display and the color of the colored display are excellent, and there is no aggregation and adhesion of fine particles, and the response and contrast are excellent.

It is a longitudinal section showing an example of an embodiment of an electrophoretic display device of the present invention. It is a longitudinal cross-sectional view which shows an example in which the electrode formed in the backplate of FIG. 1 is surface-treated by the electroconductive material containing a white metal at least. (A) is a longitudinal cross-sectional view which shows an example which hold | maintains the board | substrate space | interval of the electrophoretic display device of this invention, (b) is a longitudinal cross-sectional view which shows the other example which hold | maintains the board | substrate space | interval of the electrophoretic display device of this invention. . (A) to (c), in addition to the effect of keeping the electrode substrate interval constant, the pore shape of the structure used to suppress aggregation and uneven distribution of the electrophoretic particles and obtain a uniform display is square, hexagonal FIG. 3 is a partial plan view showing a circular shape. (A)-(c) is an electrophoretic display device using a woven fabric used for obtaining a uniform display by suppressing aggregation and uneven distribution of electrophoretic particles in addition to the effect of keeping the electrode substrate interval constant. It is a partial longitudinal cross-sectional view, the longitudinal cross-sectional view of a textile body, and a top view. (A) And (b) is a top view which shows the other example of the structure used in order to suppress the aggregation and uneven distribution of electrophoretic particles, and to obtain a uniform display in addition to the effect which keeps an electrode board | substrate space | interval constant, It is a perspective view.

Explanation of symbols

A Electrophoretic display device 10 Front plate 11 Electrode 20 Back plate 21 Electrode

Claims (3)

  An electrophoretic display liquid having at least white electrophoretic particles is sealed between a light-transmitting electrode formed on a transparent front plate and a substrate electrode on which the electrodes formed on the back plate are arranged to face each other. An electrophoretic display device, wherein the electrode formed on the back plate is made of a conductive material containing at least a white metal.   An electrophoretic display liquid having at least white electrophoretic particles is sealed between a light-transmitting electrode formed on a transparent front plate and a substrate electrode on which the electrodes formed on the back plate are arranged to face each other. An electrophoretic display device, wherein an electrode formed on the back plate is surface-treated with a conductive material containing at least a white metal.   The electrode formed on the back plate has L> 50, a <2, and −10 <b <10 in the Lab chromaticity coordinates of the color difference display method based on JIS Z 8730: 2002. Item 3. The electrophoretic display device according to Item 1 or 2.

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