JP2001202038A - Image display medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display medium which makes image display by holding microcapsules for display including coloring balls having surfaces composed of >=2 kinds of regions varying in optical characteristics and electrostatic charge characteristics and an insulative liquid on a base and rotating the coloring balls by controlling the electric fields to be applied to the coloring balls and has flexible paper-like characteristics. SOLUTION: The microcapsules formed by coating the coloring balls and the insulative liquid with resin shells consisting of aminoplasts resins are used. The particle size of the microcapsules is suitably 1.0 to 2.0 times the particle size of the coloring balls.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microcapsule for display having different optical characteristics and charging characteristics.
The present invention relates to a display medium that performs display by rotating a colored ball having a surface composed of at least three types of regions, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the development of information equipment, needs for low power consumption and thin display devices have increased, and research and development of display devices meeting these needs have been actively conducted. Among them, the liquid crystal display device is capable of electrically controlling the arrangement of liquid crystal molecules to change the optical characteristics of the liquid crystal, and has been actively developed and commercialized as a display device capable of meeting the above needs. However, these liquid crystal display devices have not yet sufficiently solved the difficulty in seeing characters on the screen due to the angle at which the screen is viewed or the reflected light, and the visual burden caused by flickering and low brightness of the light source. For this reason, research on a new display device with a small burden on vision is being actively studied.

A new display device is disclosed in US Pat.
No. 3,103, and No. 4,126,854, a particle rotating type for displaying an image using display particles having a configuration in which each hemisphere of a spherical material is color-coded. Displays are known. Microencapsulation of display particles is disclosed in JP-A-8-234686.

This display device uses minute colored balls, one of the colored balls being white and the other hemispherical being black, and the colored balls are arranged in a gap formed in a support. Each space is filled with a high-resistance liquid so that the ball can freely rotate in the liquid. In this case, the black and white hemispherical portions of the ball have different charging states, and by applying an external electric field, the rotation can be controlled so as to face the side where the white or black hemispherical surface of the ball is observed, The intended display can be made. As a manufacturing method, a minute colored ball and silicone rubber are mixed and solidified, and then immersed in silicone oil to swell the silicone rubber to form a space filled with oil around the ball. Next, it is manufactured by being sandwiched between two glass substrates on which electrode patterns are formed. Such a mechanical display method is extremely stable against temperature changes and electrical noise, and does not require power during display because of its memory properties. Furthermore, since the display is performed by using the reflection and scattering of natural light on the ball surface, there is an advantage that eye fatigue caused by flickering of a light source as seen in a liquid crystal device or a cathode ray tube can be suppressed.

On the other hand, portable information devices have recently been developed and spread at a very high speed. In these devices, not only the conventional low power consumption and thin type, but also a lighter and more flexible display device that can be installed to some extent in accordance with the shape of the device is required, and its development is urgently required.

[0006]

However, it has been difficult to produce a display device that satisfies all of the requirements by the conventional method. That is, the colored ball rotating display device has excellent characteristics in terms of low power consumption, thinness, and low eye fatigue, but it has been difficult to be flexible due to the following problems.

In the colored ball rotating type display device, since the silicone rubber is swelled by being immersed in a silicone oil liquid to form a space around the colored ball, two silicone rubbers swollen by the oil are removed. Due to the structure sandwiched between the substrates, the oil causes very poor adhesion between the glass substrate and the silicone rubber. Therefore, when a flexible structure is used by using a polymer film or the like for the substrate, the silicone rubber moves between the flexible substrates due to low adhesion and softness,
A problem arises because the colored balls are unbalanced. Therefore, it was difficult to manufacture a flexible colored ball rotating display device. In order to avoid such difficulties, coating a colored ball with microcapsules is disclosed in
No. 234686, which illustrates a capsule manufacturing method called an orifice method (curing in liquid coating method) in which a mixture of a colored ball and a dielectric liquid is put into a film forming liquid to form a capsule coating. However, such a method does not allow fine control of the thickness of the capsule film, which adversely affects the visibility of the colored ball.

[0008]

The present invention employs the following image display medium to solve the above-mentioned problems.

A colored ball having a surface constituted by two or more regions having different optical characteristics and charging characteristics and a display microcapsule containing an insulating liquid are held on a support, and an electric field applied to the colored ball And an image display medium for displaying an image by rotating the colored ball by controlling the colored ball and the insulating liquid to form a display microcapsule in which the colored ball and the insulating liquid are covered with a resin outer shell made of aminoplast resin. An image display medium characterized by the following.

2. The image display medium according to claim 1, wherein the particle size of the display microcapsules is 1.0 to 2.0 times the particle size of the colored balls.

A display medium is manufactured by sandwiching the display microcapsules together with an adhesive or the like between, for example, two substrates on which electrode patterns are formed. In the present invention, at least one of the two substrates only needs to be light-transmitting. This is because the observer can check the display if light can pass through only the display side film where the observer is located.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The display device of the present invention rotates a colored ball in a display microcapsule at a desired position by applying a voltage to striped electrodes orthogonal to each other formed on upper and lower substrates. Then, white or black display is performed. An image can be displayed by sequentially performing this scanning in the plane.

The colored balls used are made of a synthetic resin such as polystyrene, polymethyl methacrylate, or polyethylene, which has good insulating properties. In addition, a white material such as titanium oxide, zinc oxide or aluminum oxide may be used with magnesium fluoride. Each of the hemispheres is electrically charged, such as those coated with a colored material such as an aluminum co-deposited layer or a titanium carbide layer, or vice versa, or those obtained by laminating a colored material and a white material on a hemispherical portion of a transparent material ball such as glass. Also, balls having different display colors can be used.

The smaller the particle size of the colored ball, the higher the resolution of image display. However, if the particle size is too small, it is difficult to manufacture the ball and the density of the display color becomes insufficient.
Those having a size of about μm are preferably used.

By coating a colored layer on the surface of the colored ball, two surfaces having different optical characteristics such as the color of reflected light and the reflection intensity are created. The coloring layer is preferably a material that is stable in an insulating liquid, has high mechanical strength, and has good adhesion to the ball surface. Further, the color of the colored layer is not limited to white and black,
Yellow, magenta, cyan and the like may be used.

An example of the image display medium of the present invention will be described.
A minute colored ball with a colored layer and a display microcapsule containing an insulating liquid are provided between two substrates on which an electrode pattern is formed together with an adhesive, and the colored ball can be freely placed in the display microcapsule. And a driving means comprising a power supply and an electrode sandwiched on both sides for rotating the colored ball to display a desired colored layer side. This is based on the premise that the present invention is used as a paper-like display.
When using as `` paper '', that is, as a rewritable sheet, it is not necessary to form a special electrode pattern in advance because existing electrostatic latent image forming methods such as laser printer and ion deposition printer can be applied. .

An example of the driving principle of the display device of the present invention will be described. It is known that, in a colored ball in an insulating liquid, electric charges are transferred between the colored ball and the insulating liquid to form an electric double layer, and the particles are positively or negatively charged.
In the colored ball of the present invention, a black colored layer is formed on the surface of the hemisphere, and the other hemisphere is white, so that it has regions composed of two different substances. Therefore, positive ion particles or negative ion particles are specifically adsorbed on the surface of the colored ball from the insulating liquid, and a surface potential is generated on the surface of the colored ball. For this reason, in the insulating liquid, the charging characteristics are different in each region, and the colored ball has a dipole moment in the pole direction. When an electric field is applied to the colored ball, a torque acts on the colored ball to align the pole direction with the electric field direction,
The colored ball aligns any hemisphere in one direction. Assuming that the white microball area is negatively charged and the black layer is positively charged, the white microball side comes to the electrode to which plus is applied by the power source, and the colored layer side to the electrode to which minus is applied. Thus, when the display device of the present invention is observed from above, a white color is seen. If the direction of the electric field is reversed, the minute balls are reversed, and the black layer side is turned to the observation side, and black is seen.

As the liquid used for the insulating liquid, any liquid having a high electrical insulating property may be used, and an organic solvent such as toluene or acetone or water can be used. It is preferable to use a non-volatile liquid so as not to cause such a problem. Particularly, a transparent silicone oil is a liquid having a low content of ions and impurities and a high resistance, and is therefore preferable. Also, the insulating liquid comes into contact with the colored ball,
It has the property of surface-activating the surface of the colored ball to induce two different charged states.

The size of the gap filled with the insulating liquid is preferably slightly larger than the colored ball in order to prevent the translation of the colored ball as much as possible and to have a memory property. That is, the average particle size of the display microcapsules is preferably greater than 1.0 times and up to about 2.0 times the average particle size of the colored balls. When the particle size of the microcapsules becomes larger, the difference in the refractive index adversely affects the transparency of the capsule wall due to the insulating liquid interposed between the colored ball and the resin outer shell, impairing the visibility of the colored ball. I do.

Conventionally, microcapsules have been produced by coacervation, in situ polymerization,
An interfacial polymerization method, an orifice method (curing in liquid coating method) and the like are known. The coacervation method is an encapsulation method that utilizes the phase separation phenomenon of water-soluble polymers such as gelatin, gum arabic, and carboxymethyl cellulose.This method requires a long manufacturing time, complicated processes, and low-concentration capsule dispersion. Since only a liquid can be obtained, and natural polymer materials are used, there are problems such as poor quality stability, spoilage and water resistance. In addition, the orifice method (curing-in-liquid coating method) involves putting a mixture of colored balls and a dielectric liquid into a film-forming liquid, but with such a method, it is difficult to finely control the capsule film thickness. This has an adverse effect on the visibility of the colored ball. On the other hand, the in-situ method is a method in which a synthetic polymer such as a urea-formaldehyde resin and a melamine-formaldehyde resin is mainly used as a capsule membrane, and is suitable for the purpose of the present invention in which durability and pressure resistance are required. .

Next, a method for producing the display microcapsule of the present invention will be described in detail. The aminoplast resin used in the present invention refers to a resin obtained by a polymerization reaction of an amino compound and formaldehyde, and specifically includes urea-formalin resin, melamine-formalin resin, benzoguanamine-formalin resin and the like. However, melamine-formalin resins are most preferred. Microencapsulation with these aminoplast resins is generally obtained by the following procedure. 1. A step of preparing an aminoplast resin precondensate. 2. A step of emulsifying and dispersing the colored balls and the insulating liquid in an aqueous dispersant solution. After adding the initial condensate of 3.1 to the emulsified dispersion of 2.
A step of forming a film around the colored ball and the insulating liquid by heating and stirring.

1. As a method for producing an aminoplast resin precondensate, a specific example in the case of a melamine resin is as follows. Melamine powder and formalin (37% aqueous formaldehyde solution) are mixed at a molar ratio of 1: 1 to 1: 4, By heating to a temperature of about 60 ° C. or more in a weak alkaline state, a water-soluble melamine-formalin precondensate can be obtained.

The amount of the aminoplast resin is about 1 to 30 (wt / wt) based on the total weight of the colored balls and the insulating liquid.
%, Preferably in the range of 5 to 20%. If the amount is less than this, the strength as a microcapsule is insufficient, and if it is more than this range, the proportion of the film material in the colored ball and the insulating liquid is increased, which adversely affects the visibility of the colored ball. Is not preferred.

2. Specific examples of the dispersant include acrylic acid copolymer, ethylene-maleic anhydride copolymer, methyl vinyl ether-maleic anhydride copolymer, styrene-maleic anhydride copolymer, butadiene-maleic anhydride copolymer. Copolymers, vinyl acetate-maleic anhydride copolymers, and their sodium salts are used. These dispersants are added in the range of 1.0 to 20.0 (wt / wt)% based on the aqueous solution of the dispersant.

The pH of the aqueous dispersant solution is set to a value at which the film-forming reaction of the aminoplast resin proceeds most efficiently.
It is adjusted in the range of 3 to 6.

In the step of emulsifying the colored ball and the insulating liquid mixture, the colored ball and the insulating liquid mixture are added to an aqueous dispersant solution, and the emulsified particle diameter becomes about 10 to 200 μm using a commercially available emulsifying and dispersing apparatus. The stirring is performed until the stirring is completed. Naturally, since the particle diameter of the colored ball is about 10 to 200 μm, the emulsified particle diameter including the insulating liquid cannot be smaller than that.

Next, the aminoplast resin precondensate prepared above is mixed with an emulsion of a mixture of a colored ball and an insulating liquid, and the mixture is heated and stirred to polymerize the precondensate around the emulsified particles. To form a water-insoluble resin to obtain a microcapsule containing a colored ball and an insulating liquid. The heating temperature at the time of encapsulation is 40 to 100 ° C., preferably 60 to 80 ° C., and the stirring is performed for 30 minutes to 4 hours.

When the microencapsulated product thus obtained is prepared as a solid preparation, it is dried and solidified by freeze-drying, spray-drying, drying under reduced pressure, etc., and if necessary, a solvent and a dispersing agent. , A binder, a surfactant, a carrier, a stabilizer, a fragrance, a dye, and the like. When the microencapsulated product is prepared as a liquid preparation, the microencapsulated product, as necessary, a solvent, a dispersant, a binder, a surfactant, a thickener, a deicing agent,
Water, preservatives, stabilizers, perfumes, pigments, etc. are added.

Examples of the binder used in the composition of the present invention include inorganic binders, natural organic binders, semi-synthetic binders, synthetic resin binders, waxes and the like. Examples of the inorganic binder include bentonite, montmorillonite, water glass, and colloidal silica. Examples of the natural organic binder include starch, dextrin, casein, gelatin, glue, agar, gum arabic, corn starch, natural rubber, pulp solution and the like. As a semi-synthetic binder, carboxymethylcellulose, carboxymethylcellulose sodium salt, hydroxypropylmethylcellulose, nitrocellulose, cellulose acetate, methylcellulose,
Cellulose binders such as ethyl cellulose and hydroxypropyl cellulose, and lignin binders such as lignin, sodium ligninsulfonate and ammonium ligninsulfonate. Examples of synthetic resin binders include polyolefins such as high-density polyethylene, low-density polyethylene, and polypropylene; halogenated polyolefins such as polychloroethylene and polychlorinated propylene; acrylic polymers such as polyacrylonitrile and polymethyl methacrylate; polystyrene; acrylonitrile -Polystyrene-butadiene copolymer, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl polymers such as chlorinated vinyl chloride, polyvinyl ether, polyvinylidene chloride, ketone-formalin resin, phenoxy resin , Polybutadiene, polyisobutylene, polyisoprene and other synthetic rubbers, silicone resins, polyvinylidene fluoride, polytrifluoroethylene and other fluorocarbon resins, polyacetal and other acetal trees Polyesters such as nylon 6, nylon 66, polyethylene terephthalate, olefin oxides such as polyamide, polyimide, polyethylene oxide and polyphenylene oxide; carbonate resins such as polycarbonate; polysulfone resins; polyurethanes such as polyurethane and polyurethane urea; epoxy resins; Resin, melamine resin, maleic acid resin, urea resin, polyvinylpyrrolidone and the like. Examples of the wax include natural wax, petroleum wax, and synthetic wax. Examples of natural waxes include candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, beeswax, lanolin, whale wax,
Tallow, ozokerite, ceresin and the like can be mentioned. Examples of the petroleum wax include paraffin wax and microcrystalline wax. Examples of the synthetic wax include montan wax, polyethylene wax, Fischer-Tropsch wax, Sasol wax, hardened castor oil, 12-hydroxystearic acid, stearic acid, stearyl alcohol, laurone,
Examples include stearone, isopropyl myristate, glycerin fatty acid ester, glycol fatty acid ester, and sorbitan fatty acid ester.

When the binder is water-soluble, the binder used in the composition of the present invention may be dissolved in water and added as an aqueous solution, may be added as a powder, or may be melted by heating. It may be used as an emulsion or as an emulsion in which these fine particles are dispersed in water. When the binder is insoluble in water, it is added as an emulsion dispersed in water, used as a melt melted by heating, used as an emulsion in which these fine particles are dispersed in water, or dissolved in an organic solvent. It is preferable to use them. Two or more kinds of binders may be mixed and used in an arbitrary ratio. The amount of the binder may vary depending on the type of the binder, but is usually 0.1 to 40% by weight, preferably 0.5 to 30% by weight based on the total weight of the composition of the present invention.

Further, the electrodes used to drive the colored balls need to be light-transmitting so that the colored layer formed on the surface of the minute balls can be observed from the observation side. For this reason, SnO2, TiO2, ZnO, ITO
And the like.

The substrate (light-transmitting film) is not particularly limited as long as it needs to be optically transparent in order to display the colored layer of the colored ball and has sufficient strength as a panel. Although not limited thereto, for example, a hard resin such as polyimide, polycarbonate, acrylic, polyethylene terephthalate, polyethylene, or polystyrene, or silicone rubber can be used.

The image display medium of the present invention can be applied to a light-receiving display device that displays image information such as characters, graphics, and videos by utilizing the rotation of a colored ball. Further, the present invention can be applied to a paper display which can be viewed like paper, can be moved like paper, can write an image, can copy an image, can read an image, and can erase an image.

Through the above steps, an image display medium for displaying images by rotating the colored balls can be manufactured.

[0035]

EXAMPLES Examples will be shown below, but the present invention is not limited to these examples.

Example 1 A dispersion liquid was prepared by mixing 40 g of silicone oil and 40 g of zirconia balls having a diameter of 55 μm and having a hemispherical color in two black and white colors. On the other hand, 13 g of a 37% aqueous formaldehyde solution and 30 g of water were added to 10 g of the melamine powder to adjust the pH to 8, and then heated to about 70 ° C. to obtain an aqueous solution of a melamine-formalin precondensate. 80 g of the above dispersion was added to 100 g of a 5% styrene-maleic anhydride copolymer whose pH was adjusted to 4.5, and emulsification was performed until the particle diameter became about 100 μm. Melamine- in the emulsion
Add the entire formaldehyde precondensate aqueous solution to 70 ° C
After stirring for 2 hours, the pH was adjusted to 9 to complete the encapsulation. The aqueous phase was removed from the obtained capsule using a centrifuge, and the capsule particles were taken out as a powder. 10 g of the obtained capsule particles are dispersed in 50 g of a 10% aqueous solution of polyvinylpyrrolidone and sandwiched between two film substrates each having a transparent electrode pattern formed thereon, so that an image display medium in which a colored ball is encapsulated in a strong capsule. It was created. By applying an electric field according to the image signal between the electrodes, the colored ball was rotated and the black portion was visually recognized.

Example 2 A dispersion liquid was prepared by mixing 30 g of silicone oil and 30 g of zirconia balls having a diameter of 30 μm, which were hemispherically colored into two black and white colors. 60 g of the dispersion was added to 100 g of a 5% concentration isobutylene-maleic anhydride copolymer whose pH was adjusted to 3.2, and emulsified until the dispersion became 40 μm. To this emulsion, an aqueous solution obtained by adding 24 g of a 37% aqueous formaldehyde solution to 10 g of urea powder, 1 g of resorcinol and 30 g of water was added. After heating and stirring at 60 ° C. for 2 hours, the pH was adjusted to 9 to complete the encapsulation. The aqueous phase was removed from the obtained capsule using a centrifuge, and the capsule particles were taken out as a powder. 10 g of the obtained capsule particles was added to an aqueous solution 50% of 10% polyvinylpyrrolidone.
g), and sandwiched between two film substrates each having a transparent electrode pattern formed thereon to produce an image display medium in which a colored ball was encapsulated in a strong capsule. By applying an electric field according to the image signal between the electrodes, the colored ball was rotated and the black portion was visually recognized.

COMPARATIVE EXAMPLE A dispersion was prepared by dispersing 4 parts of zirconia balls having a diameter of 40 microns, which were hemispherically colored into two black and white colors, in a solution obtained by mixing 40 parts of silicone oil with 10 parts of ethyl acetate. On the other hand, the above dispersion was added to 100 parts of a 5% acid-treated gelatin aqueous solution adjusted to pH 9.0 and a temperature of 50 ° C., followed by stirring and emulsification until the particle diameter became about 120 to 130 μm. Next, 50% aqueous 5% gum arabic solution was added to the above emulsion.
Then, the temperature was lowered to 40 ° C. while stirring, and a 5% acetic acid solution was gradually added until the pH reached 4.0. After the temperature was further lowered to 5 ° C. and the mixture was stirred for 4 hours, 4 parts of a 37% aqueous formaldehyde solution was added, and the mixture was stirred for 2 hours to raise the pH to 9, thereby completing the encapsulation. The aqueous phase was removed from the obtained capsule using a centrifuge, and instead, washing water was added, followed by stirring and redispersion. This washing operation was performed six times, and the capsule particles were taken out as a powder with a freeze dryer. An image display medium was prepared by dispersing 10 parts of the obtained capsule particles in 50 parts of a 10% aqueous solution of polyvinylpyrrolidone and sandwiching each between two film substrates on which a transparent electrode pattern was formed. The colored ball was rotated by applying an electric field corresponding to the image signal between the electrodes, but most of the microcapsules were broken, and the black portion could not be clearly seen.

[0039]

As described in detail above, the present invention has the following functions and effects. 1. By sandwiching the display capsule containing the colored balls between the two film substrates on which the transparent electrode patterns are formed, the flexibility of the display device can be sufficiently maintained. 2. Since the film holding the ball is used in a non-swelled state, it has high strength and is hard to break.

Claims (2)

[Claims] 1. A colored ball having a surface constituted by two or more regions having different optical characteristics and charging characteristics, and a display microcapsule containing an insulating liquid are held on a support, and added to the colored ball. An image display medium for displaying an image by rotating a colored ball by controlling an applied electric field, the display microcapsule in which the colored ball and the insulating liquid are covered with a resin outer shell made of aminoplast resin. An image display medium characterized by being formed. 2. The image display medium according to claim 1, wherein the particle size of the display microcapsules is 1.0 to 2.0 times the particle size of the colored balls.