JP2005134846A - Method and apparatus for manufacturing image display medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for manufacturing an electrophoretic image display medium excellent in display quality. <P>SOLUTION: The process of making a display apparatus using electrophoretic particles is characterized in that: microcapsules encapsulating a particle dispersion liquid having electrophoretic particles dispersed therein are spread over a liquid surface; the spread microcapsule layer is compressed; then a conductive substrate is brought into contact with the microcapsule layer to transfer it; and the transferred microcapsule layer is sandwiched by another conductive substrate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image display medium manufacturing method and apparatus for switching display of a microencapsulated particle dispersion based on the principle of electrophoresis.

  Conventionally, a CRT or a liquid crystal display is used as a terminal for displaying so-called images such as characters, still images, and moving images. They can display and rewrite digital data instantly, but it is difficult to always carry the device around, and it has many drawbacks such as eye fatigue when working for a long time and display when turning off the power. is there.

  On the other hand, when a character or a still image is distributed or stored as a document, it is recorded on a paper medium by a printer. This paper medium is widely used as a so-called hard copy. Hard copy is easier to read than display, less fatigue, and can be read freely. Furthermore, it has the characteristics that it is lightweight and can be carried freely. However, the hard copy is discarded and recycled after it is used. However, since the recycling requires a lot of labor and cost, there remains a problem in terms of resource saving.

  There is a great need for a rewritable paper-like display medium that has the advantages of both the above display and hard copy. So far, polymer-dispersed liquid crystals, bistable cholesteric liquid crystals, electrochromic devices, electrophoretic devices The display medium using the above has been attracting attention as a display medium that is reflective and can display bright and has a memory property. Among them, the one using an electrophoretic element is excellent in terms of display quality and power consumption during display operation. For example, Japanese Patent Laid-Open No. 5-173194 (Patent Document 1) and Japanese Patent No. 2612472 (Patent Document 2). ) And the like.

  In an electrophoretic display medium, a dispersion liquid in which a plurality of electrophoretic particles having a color different from the color of a dispersion medium is dispersed in a colored dispersion medium is sealed between a pair of transparent electrodes. In this case, the electrophoretic particles (also simply referred to as electrophoretic particles) are charged on the surface in the dispersion medium, and when a voltage opposite to the electrophoretic particle charge is applied to one of the transparent electrodes, the electrophoretic particles migrate. The particles are deposited there, and the color of the migrating particles is observed. When a voltage having the same direction as the charge of the migrating particles is applied, the migrating particles move to the opposite side, so the color of the dispersion medium is observed. As a result, display can be performed.

  Electrophoretic particles have the disadvantage of being biased when left for a long time due to gravity or the like, but in order to prevent such unevenness of the particles in the dispersion, the one containing the dispersion in microcapsules This is disclosed in Japanese Patent No. 2551783 (Patent Document 3).

  Conventionally, as a method of filling the microcapsules between the electrode substrates, it is known to apply a mixture mixed with a binder resin as an adhesive for two substrates on the substrate and cure the binder resin. On the other hand, high contrast is required to improve display quality. That is, it is necessary to arrange microcapsules in which particles as a display material are encapsulated densely and in a single layer. However, it has been difficult to densely fill capsules even if they are mixed or injected or applied in a binder serving as an adhesive between electrode substrates. It was also difficult to control.

JP-A-5-173194 Japanese Patent No. 2612472 Japanese Patent No. 2551783

  An object of the present invention is to provide an image display medium excellent in display quality in which microcapsules are densely filled, and to provide a manufacturing method and apparatus therefor.

  The inventor conducted a new study on the image display medium. As a result, when a large number of microcapsules are spread on the liquid surface into a liquid having a higher specific gravity, the microcapsules are eventually disposed on the gas-liquid interface to form a single microcapsule layer. When the microcapsule layer is compressed on the gas-liquid interface, it becomes a dense single-layer microcapsule. It has been found that if this is transferred to a substrate, an image display medium in which microcapsules are densely assembled can be obtained. The present invention has been made based on the above findings.

  According to this invention, the said subject is achieved by following (1)-(9).

(1) A particle dispersion liquid in which electrophoretic particles are dispersed in a dispersion medium composed of at least a nonpolar solvent is included between two substrates that are light-transmitting at least one of them arranged with a desired interval. In a method of manufacturing an image display medium comprising a microcapsule and performing a display operation by electrophoresis of the particles by applying a voltage between the two substrates, at least a number of microcapsules on a liquid surface in a liquid tank A step of compressing the microcapsule layer on the liquid surface, a step of transferring the compressed microcapsule layer to one of the substrates, and a microcapsule layer having the other substrate transferred thereon A method for producing an image display medium, comprising the step of bonding to a substrate.

(2) The method for producing an image display medium according to (1), wherein the microcapsule layer on the liquid surface is compressed so as to have a predetermined surface pressure.

(3) The method for producing an image display medium according to (1) or (2), wherein the substrate to which the microcapsule layer is transferred is a substrate coated with an adhesive binder resin.

(4) The method for producing an image display medium according to any one of (1) to (3), further comprising a step of drying the substrate onto which the microcapsule layer has been transferred.

(5) The above (1) to (1), wherein a dispersion liquid in which the microcapsules are dispersed in a dispersion medium is prepared in the step of spreading the microcapsules on the liquid surface, and the dispersion liquid is dropped on the liquid surface. 4) The manufacturing method of the image display medium in any one of.

(6) A particle dispersion liquid in which electrophoretic particles are dispersed in a dispersion medium composed of at least a non-polar solvent is included between two substrates that are light-transmitting at least one of them arranged at a desired interval. In an apparatus for manufacturing an image display medium that contains a microcapsule and performs display operation by electrophoresis of the particles by applying a voltage between the two substrates, the microcapsule layer is developed at least on the gas-liquid interface A liquid tank for storing the developing liquid, a substrate holding means for holding and moving the substrate disposed above the liquid tank, and a microcapsule layer on the gas-liquid interface of the developing liquid. An apparatus for producing an image display medium, comprising: a liquid surface compressing means for compressing.

(7) The apparatus for producing an image display medium according to (6), further comprising a liquid surface pressure measuring means.

(8) The apparatus for producing an image display medium according to (6) or (7), further comprising a microscope for observing the liquid level from above.

(9) An apparatus for producing an image display medium, further comprising substrate drying means.

  According to the first aspect of the present invention, a large number of microcapsules are developed on at least the liquid surface in the liquid tank, the microcapsule layer on the liquid surface is compressed, and the compressed microcapsule layer is It is possible to provide a method for manufacturing a high-contrast image display medium in which microcapsules enclosing electrophoretic particles are densely arranged because transfer onto a substrate and another substrate are bonded to the transferred microcapsule layer. it can.

  According to the invention of claim 2, since the capsule layer on the liquid surface is further compressed to a predetermined surface pressure, a method of manufacturing an image display medium with a high contrast and a constant display quality in which the occupied area of the microcapsules is controlled Can be provided.

  According to the invention of claim 3, since the microcapsule layer is reliably transferred to the substrate because the substrate to be transferred is a substrate coated with an adhesive binder resin, an image display medium with few display defects is manufactured. A method can be provided.

  According to the fourth aspect of the invention, the step of drying the substrate to which the microcapsule layer has been transferred has a step of drying, so that the liquid remaining when transferred to the substrate is quickly removed, so that the time required for manufacturing is shortened. It is possible to provide a method for manufacturing an image display medium capable of performing

  According to the invention of claim 5, since the microcapsules are rapidly and uniformly developed by dropping the microcapsules on the liquid surface as a dispersion, a method for producing an image display medium with few display defects is provided. be able to.

  According to the sixth aspect of the present invention, it is possible to provide an apparatus for manufacturing a high-contrast image display medium in which microcapsules enclosing electrophoretic particles are densely arranged.

  According to the seventh aspect of the invention, since the occupied area of the microcapsules can be controlled by providing the liquid surface pressure measuring means, an apparatus for manufacturing an image display medium with high contrast and constant display quality is provided. Can do.

  According to the eighth aspect of the present invention, since the state of the microcapsule layer filling structure and individual microcapsules can be observed by providing a liquid level observation microscope, an apparatus for manufacturing an image display medium with few display defects is provided. can do.

  According to the ninth aspect of the present invention, since the substrate drying means is provided, the liquid remaining when transferred to the substrate is quickly removed, so that the time required for manufacturing can be shortened. An apparatus for manufacturing a medium can be provided.

An example of an image display medium provided by the present invention will be described with reference to FIG. In FIG. 1, 1 and 2 are conductive substrates, and at least one of them is light transmissive.
As the conductive layer, a metal such as Al, Ag, Ni, Cu or the like, or a transparent conductor such as ITO, SnO ₂ , ZnO: Al, etc. formed into a thin film by a sputtering method, a vacuum deposition method, a CVD method, a coating method, Or what mixed and apply | coated the electrically conductive agent with the solvent or the synthetic resin binder is used.

  Conductive agents include cationic polyelectrolytes such as polymethylbenzyltrimethyl chloride and polyallylpolymethylammonium chloride, anionic polyelectrolytes such as polystyrene sulfonate and polyacrylate, and electronically conductive zinc oxide and tin oxide. Indium oxide fine powder or the like is used. As the conductive substrate, the conductive layer itself may be thick enough to have a self-holding function, or a conductive layer may be provided on the opposite surface of the base body having a self-holding function (not shown). It can be used suitably. Further, the conductive layer may be anisotropic conductive, or may be a layer having a pattern or multi-dot segment in which a conductive portion penetrates in the thickness direction.

  In any case, if a power supply electrode is brought into contact with a part of the conductive substrates 1 and 2, an electric field can be generated between the conductive substrates 1 and 2, so that white or colored particles can move reliably. In order to perform the display, voltage applying means between the conductive substrates 1 and 2 may be prepared, which is convenient.

In FIG. 1, 3 is a microcapsule. 4 is white or colored particles.
As the white particles, solid particles of metal oxides such as silicon dioxide, aluminum oxide, and titanium oxide can be used.
As the black colored particles, for example, carbon black, aniline black, furnace black, lamp black and the like can be used.
Examples of cyan colorants include phthalocyanine blue, methylene blue, Victoria blue, methyl violet, aniline blue, and ultramarine blue.
As the magenta colorant, for example, rhodamine 6G lake, dimethylquinacridone, watching red, rose bengal, rhodamine B, alizarin lake and the like can be used.
Examples of yellow colorants include chrome yellow, benzidine yellow, hansa yellow, naphthol yellow, molybdenum orange, quinoline yellow, and tartrazine.

  In addition, a dispersion or mixture of the above metal oxide or colorant in a binder resin insoluble in a solvent serving as a dispersion medium, or a coating on the resin can be used. In this case, as the binder resin, any of the known thermoplastic resins and thermosetting resins that are insoluble in the dispersion medium can be used, but in particular, a non-adhesive material resin material can be preferably used. As a simple example of such a non-adhesive material-based resin material, an acrylic resin, a polyester resin, styrene such as polystyrene, poly p-chlorostyrene, polyvinyltoluene, or a polymer of a substituted product thereof can be exemplified. .

  The amount of the metal oxide or the colorant that can be used is 0.1 to 300 parts by weight, preferably 1 to 100 parts by weight with respect to 100 parts by weight of the binder resin. Further, the weight ratio of the solid content in the particle dispersion is appropriately set so that a desired concentration of color can be obtained when the particle dispersion-containing microcapsules are applied to an image display medium. The degree is appropriate.

In FIG. 1, reference numeral 5 denotes a colored dispersion medium, which is colored in a color different from the color of white or colored particles.
Examples of the dispersion medium used in the embodiment of the present invention include paraffinic hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane and dodecane, isoparaffinic hydrocarbons such as isohexane, isooctane and isododecane, fluid Alkyl naphthenic hydrocarbons such as paraffin, aromatic hydrocarbons such as benzene, toluene, xylene, alkyl benzene, solvent naphtha, dimethyl silicone oil, phenyl methyl silicone oil, dialkyl silicone oil, alkyl phenyl silicone oil, cyclic polydialkyl siloxane or cyclic Examples thereof include silicone oils such as polyalkylphenylsiloxane.

  Examples of the dye used include oil-soluble dyes that are soluble in the above-mentioned dispersion medium, and dyes classified as Solvent dye in the Coulor Index are preferably used. These dyes include azo dyes, anthraquinone dyes, phthalocyanine dyes, and triallylmethane dyes.

  These oil-soluble dyes include, for example, Spirit Black (SB, SSBB, AB), Nigrosine Base (SA, SAP, SAPL, EE, EEL, EX, EXBP, EB), Oil Yellow (105, 107, 129, 3G, GGS), Oil Orange (201, PS, PR), First 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), Oil Blue (613, 2N, BOS), Oil Black (HBB, 860, BS), Bali First Yellow (1101, 1105, 3108, 4120) , Bali First Range (3209, 3210), Bali First Red (1306, 1355, 2303, 3304, 3306, 3320), Bali First Pink 2310N, Bali First Brown (2402, 3405), Bali First Blue (3405, 1501, 1603, 1605, 1607, 2606, 2610), Bali First Violet (1701, 1702), Vari First Black (1802, 1807, 3804, 3810, 3820, 3830) are typical examples, as long as they are not contrary to the object of the present invention. Oil-based dyes or oil-soluble dyes other than the dyes described herein may be used.

  Other substances can be added to the colored dispersion medium 5 in order to improve the solubility of the dye. These substances are preferably substances that are soluble or miscible in a nonpolar solvent. Examples of these substances include ethers, esters, alcohols, ketones, amides and the like. The mixing ratio of such other solvents is about 0.1 to 10 parts by weight with respect to 100 parts by weight of the dispersion medium.

  In FIG. 1, reference numeral 6 denotes an adhesive support layer that holds the microcapsules between the conductive substrates 1 and 2. Although any known material that adheres to the conductive layer can be used for the adhesive support layer 6, it is preferably transparent and excellent in electrical insulation. A solvent-free curable material is particularly preferable. Examples of such a material include a photocurable epoxy resin, a urethane resin, and an acrylic resin.

  A first embodiment of the present invention will be described with reference to FIG. In the embodiment of the present invention, a method for obtaining an image display medium in which microcapsules encapsulating electrophoretic particles are densely packed in a single layer is as follows.

  First, electrophoretic particles are dispersed in a dispersion medium. In order to make the particle dispersion in the present invention, the above components may be mixed and dispersed in a nonpolar solvent. In this case, a ball mill, a sand mill, an attritor or the like may be used as the dispersing means. The mixing order is not particularly limited. Subsequently, microcapsules are produced. As a method for producing the microcapsules, a known method for forming a polymer film at the interface of an O / W emulsion such as a phase separation method or a coacervation method can be used, and is not particularly limited. The obtained microcapsule 3 is developed on the liquid surface of the liquid tank 7.

  Water is preferably used as the liquid in the liquid tank (developing liquid 8) when the specific gravity of the microcapsules is smaller than that of water. For microcapsules having a large specific gravity, it is preferable to use a liquid having a large specific gravity such as fluorocarbon. In any case, there is no particular limitation as long as the microcapsules float on the liquid surface and the liquid does not chemically affect the microcapsules.

  Next, the microcapsule 3 developed on the liquid surface 8 is compressed. Since the area occupied on the liquid surface of the microcapsule is reduced by the compression, the microcapsule eventually has a structure in which the microcapsule is packed most closely on the liquid surface. In this state, the microcapsule layer is transferred to the conductive substrate by applying the conductive surface of the conductive substrate to the microcapsule layer. Finally, the other substrate is bonded to the surface opposite to the transfer surface to obtain an image display medium.

  In the second embodiment of the present invention, the liquid surface pressure measuring means 10 is used to compress to a predetermined surface pressure, and an image display medium is manufactured in the same manner as in the first embodiment of the present invention. As a result, an image display medium in which the microcapsules are densely packed can be provided.

  In the third embodiment of the present invention, an adhesive binder resin is applied in advance onto a substrate to which the microcapsule layer is transferred. Since the surface of the microcapsule is originally a resin, it can be attached to the substrate simply by contacting the substrate. However, by applying an adhesive binder resin in advance as in the present invention, it is more reliable. The microcapsule layer can be transferred to the substrate. Examples of the binder resin that can be used in the present invention include acrylic resins and epoxy resins that are provided as adhesives.

  In the fourth embodiment of the present invention, the method further includes the step of drying the substrate onto which the microcapsule layer has been transferred. The liquid in the liquid tank in which the microcapsules are spread remains on the substrate onto which the microcapsule layer has been transferred. The time required for manufacturing the image display medium can be shortened by evaporating the liquid by the drying means before the other substrate is bonded. As the drying means, known drying means such as those that apply hot air and those that irradiate infrared rays can be applied.

  In the fifth embodiment of the present invention, microcapsules are dropped onto the liquid surface as a dispersion. Since microcapsules can be handled like powder, they can be developed directly on the liquid surface. However, in this case, there may be a problem that it takes time to loosen the aggregation of the microcapsules or that the microcapsules cannot be uniformly spread. In an embodiment of the present invention, a microcapsule is added in advance to a predetermined dispersion medium to prepare a dispersion in which the microcapsules are uniformly dispersed, and the dispersion is dropped onto the liquid surface of the liquid tank in a short time. It becomes possible to spread microcapsules uniformly. It is preferable to use the same dispersion medium as the liquid in the liquid tank, but in addition to that, if the microcapsules can be uniformly dispersed, they can be mixed with the liquid in the liquid tank or evaporate immediately after deployment. If it is a thing, it will not specifically limit.

Next, a sixth embodiment of the present invention will be described with reference to FIG.
FIG. 2 shows an apparatus for producing an image display medium having microcapsules, 7 is a liquid tank, 8 is a developing liquid, and has a specific gravity greater than that of microcapsules 3. The developing liquid 8 can develop the microcapsule 3 on the liquid surface. Reference numeral 9 denotes a compression barrier. The compression barrier 9 is movable at least in the horizontal direction, and the area occupied by the substance on the gas-liquid interface can be controlled. That is, the occupable area of the microcapsule on the liquid surface can be controlled. Reference numeral 1 denotes a substrate which can be operated by a substrate holding means (not shown). When the substrate 1 is in contact with the microcapsule layer on the liquid surface, the microcapsule layer is transferred to the substrate 1.

  A seventh embodiment of the present invention will be described with reference to FIG. Reference numeral 10 denotes a surface pressure measuring means. Examples of the surface pressure measuring means include a Wilhelmy plate used in a known surface tension meter by the Wilhelmy method. In the surface pressure measuring means 10, it is possible to see the filling state of the microcapsule layer on the liquid surface, and until the microcapsule 3 developed on the liquid surface is compressed by the compression barrier 9 and is closely packed. The surface pressure is almost zero. When compressed to a smaller area, the surface pressure rises.

  In the eighth embodiment of the present invention, an apparatus for producing an image display medium having microcapsules includes a liquid level observation microscope (not shown). The state of the filling structure of the microcapsule layer and the diameter of each microcapsule can be observed with the microscope.

  In the ninth embodiment of the present invention, an apparatus for producing an image display medium having microcapsules includes a substrate drying means (not shown). The liquid in the liquid tank in which the microcapsules are spread remains on the substrate onto which the microcapsule layer has been transferred. The time required for manufacturing the image display medium can be shortened by evaporating the liquid by the drying means before the other substrate is bonded. As the drying means, known drying means such as those that apply hot air and those that irradiate infrared rays can be applied.

  The invention is explained in more detail by means of examples. However, the present invention is not limited to the following examples. The parts used in the following examples are all parts by weight.

Example 1
(Preparation of microcapsules containing electrophoretic particles)
A solution prepared by dissolving 10 parts of urea, 1 part of resorcinol and 10 parts of ethylene-maleic anhydride copolymer in 290 parts of water was adjusted to pH 3.5 with an aqueous sodium hydroxide solution. Separately, 30 parts of a saturated solution of isoparaffin hydrocarbon (Exxon Chemical, Isoper G) dye (Bayer, Macrolex Blue RR) and 1 part of titanium oxide were added and ultrasonically dispersed to prepare a particle dispersion. In addition to the above aqueous solution, 25 parts of a formaldehyde solution was further added and stirred with heating at 50 ° C. for 3 hours. After completion of the reaction, the microcapsules were collected by suction filtration, washing with water and drying.

(Production and operation of image display medium)
Water was filled in the liquid tank shown in FIG. 2 and 10 parts of the microcapsules obtained above were added to 100 parts of water and dispersed, and then dropped onto the water surface. After being allowed to stand for 1 minute, the compression barrier was compressed in a direction in which the area occupied on the water surface of the microcapsules was reduced, and the surface pressure was maintained at 20 mN / m. Next, a glass substrate with an ITO electrode coated with an ultraviolet curable epoxy resin (trade name: ThreeBond 3121) with a wire bar is gently brought into contact with the microcapsule layer from above with the conductive surface facing down, and then pulled upward again. As a result, the microcapsules were transferred onto the ITO substrate. This substrate was heated to 40 ° C. with a heater. Finally, an electrophoretic display medium was prepared by laminating the glass substrate with an ITO electrode coated with an ultraviolet curable epoxy resin with a wire bar.
When +100 V was applied to the upper ITO electrode, the titanium oxide particles quickly electrodeposited on the upper electrode, and looked white when viewed from the upper substrate surface. Next, when −100 V was applied to the upper electrode, the titanium oxide particles moved to the lower electrode, and when viewed from the upper substrate side, the coloring state due to the color of the dye was clearly seen.

It is sectional drawing of the image display medium provided by this invention. It is a schematic diagram of the manufacturing apparatus of the image display medium which shows embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Conductive board | substrate 3 Microcapsule 4 White thru | or colored particle 5 Colored dispersion medium 6 Adhesive support layer 7 Liquid tank 8 Liquid for expansion | deployment 9 Barrier for compression 10 Surface pressure measuring means

Claims (9)

  A microcapsule containing a particle dispersion liquid in which electrophoretic particles are dispersed in a dispersion medium composed of at least a nonpolar solvent, between two substrates that are arranged at a desired interval and at least one of which is light transmissive. In a method of manufacturing an image display medium comprising a display operation by electrophoresis of the particles by applying a voltage between the two substrates, a large number of microcapsules are developed at least on the liquid surface in the liquid tank A step of compressing the microcapsule layer on the liquid surface, a step of transferring the compressed microcapsule layer to one of the substrates, and another substrate bonded to the transferred microcapsule layer A process for producing an image display medium comprising the steps.   2. The method of manufacturing an image display medium according to claim 1, wherein the microcapsule layer on the liquid surface is compressed to have a predetermined surface pressure.   3. The method for producing an image display medium according to claim 1, wherein the substrate to which the microcapsule layer is transferred is a substrate coated with an adhesive binder resin.   The method for producing an image display medium according to claim 1, further comprising a step of drying the substrate onto which the microcapsule layer has been transferred.   The dispersion liquid in which the microcapsules are dispersed in a dispersion medium is prepared in the step of spreading the microcapsules on the liquid surface, and the dispersion liquid is dropped on the liquid surface. The manufacturing method of the image display medium of description.   A microcapsule containing a particle dispersion liquid in which electrophoretic particles are dispersed in a dispersion medium composed of at least a nonpolar solvent, between two substrates that are arranged at a desired interval and at least one of which is light transmissive. A developing liquid for developing a microcapsule layer at least on a gas-liquid interface in an apparatus for manufacturing an image display medium, which comprises a display operation by electrophoresis of the particles by applying a voltage between the two substrates. A liquid tank for storing the substrate, a substrate holding means for holding and moving the substrate disposed above the liquid tank, and a microcapsule layer on the gas-liquid interface of the developing liquid And an apparatus for manufacturing an image display medium.   7. The image display medium manufacturing apparatus according to claim 6, further comprising a liquid surface pressure measuring means.   8. The image display medium manufacturing apparatus according to claim 6, further comprising a microscope for observing the liquid level from above.   The apparatus for producing an image display medium according to claim 6, further comprising a substrate drying means.

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