KR101446355B1 - Porous charged particle for image display device and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a porous charged particle filled for image realization of an image display device such as an electronic paper and a method of manufacturing the same. According to the present invention, it is possible to reduce the amount of charged particles without adding a fluorescent pigment, It is possible to provide an improved charged particle for an image display apparatus and an image display apparatus including the same.

Image display device, charged particle, porous

Description

TECHNICAL FIELD [0001] The present invention relates to a porous charged particle for an image display device,

The present invention relates to charged particles used in an image display apparatus and a method of manufacturing the same. More specifically, the present invention relates to a charged particle having improved reflectivity filled for image realization of an image display device such as an electronic paper, and a method of manufacturing the same.

An image display apparatus using charged particles is a reflective display in which a transparent conductive film is coated on a thin and bendable film substrate such as paper or plastic to form a substrate and an electrified particle is driven between the substrates. The image display device is an image display device which is attracting attention as a next generation electronic paper (e-paper) followed by a liquid crystal display (LCD), a plasma display panel (PDP) and an organic light emitting device.

Particularly, the electronic paper display device is a key element in the implementation of a flexible display, and imparts an electromagnetic field to a conductive material to provide mobility. That is, after distributing the charged particles between the thin flexible substrates, the data is represented by the change of the orientation of the charged particles due to the polarity change of the electromagnetic field. In this case, if a directional arrangement of charged particles occurs at any polarity, there is no change in position of the particles even if the voltage is removed due to the memory effect, so that the image remains unchanged and the same effect as that printed on the paper can be obtained. Therefore, since visual fatigue is very low because there is no self-luminous light, comfortable viewing is possible like viewing an actual book, flexibility and portability are secured by using a flexible substrate, which is highly anticipated as a future type flat panel display technology. In addition, as described above, since the image once implemented is maintained for a long time unless the substrate is reset, the power consumption is very low, and thus the portable display device has excellent usability.

1 is a cross-sectional view showing a structure of a general electronic paper display device.

As shown in Fig. 1, the cell structure of a conventional electronic paper display device using charged particles is composed of upper and lower substrates 10 and 60 formed of any one of plastic or glass, a driving voltage of the device on the upper and lower substrates Upper and lower electrodes 20 and 70 formed of a transparent electrode (ITO) for applying a voltage to the upper and lower electrodes, upper and lower insulating layers 30 and 80 selectively coated on the upper and lower electrodes, And black and white charged particles 50 charged with (-) and (+) electric charges existing between the electrodes, respectively.

In the electronic paper display device having the above structure, when a sufficient voltage is applied to the electrodes 20 and 70, the charged particles 50 move to the respective electrodes according to the polarity. For example, when negative (-) and positive (+) voltages are applied to the upper and lower electrodes 20 and 70, black and white charged particles are respectively directed toward the lower substrate 10 and the upper substrate 60 by Coulomb force . Therefore, when the upper substrate is the observation surface, it is displayed as white. Using this principle, the voltage is applied so that all the cells appear to be white at first, and then the reverse voltage is applied to only the desired cells, so that black can be displayed to express pictures or characters.

The most important characteristic in the so-called toner type electronic paper display device as described above is the high contrast ratio of the display. White particles must be sufficiently bright to have a high contrast ratio, and black particles should be sufficiently dark. That is, the white particles should have a high white reflectance and the black particles should have a low reflectance.

 In order to increase the white reflectance of the white particles, there is a method of stacking several layers of particles in the barrier ribs. In this case, however, the height of the barrier ribs is increased and the driving voltage is necessarily increased. However, in addition to increasing the white reflectance, it is also important for the electronic paper display device to exhibit a low driving voltage. In order to exhibit a low driving voltage, the height of the partition wall capable of filling particles must be lowered together. Therefore, there is a limitation in the height of the partition wall, and it is most preferable that the particles are filled in only about one layer in the partition wall having a limited height.

 On the other hand, most of the white particles have a white reflectance of 90% or more when they are piled up in several layers, but it is difficult to show white reflectance of 10% or more in the case of the first layer, Studies are underway to increase the white reflectance.

The present invention aims to provide a method for producing charged particles for an image display apparatus which can further improve the optical characteristics of an electronic paper display device by increasing the white reflectance of one white particle and thereby provide the charged particles.

(B) preparing a dispersion by dispersing a pigment in a solution containing an acrylic monomer, a crosslinking agent, and an organic charge control agent; (c) And (d) mixing the aqueous continuous phase solution and the dispersed phase liquid to form a polymer. The present invention also provides a method for producing porous charged particles for an image display device, comprising the steps of: .

The progress of the steps (b) and (c) is not particularly limited in the order. That is, they can be performed in reverse order or simultaneously if necessary.

In general, when the charged particles are produced, the step of attaching silica to the surface of the charged particles is included. However, according to the present invention, a porous surface is provided and sufficient fluidity can be secured without attaching silica particles. In addition, there may be no problem that silica particles adhered from the charged particles are desorbed during driving of the image display apparatus.

The present invention also provides a porous charged particle for an image display device formed by polymerization of an acrylic monomer including a cosolvent, a crosslinking agent, an organic charge control agent and a pigment in a water-based continuous phase liquid.

Further, the present invention provides an image display apparatus including the upper and lower substrates, partition walls provided between the substrates, and the charged particles filled between the partition walls.

According to the present invention, it is possible to provide a charged particle for an image display apparatus and an image display apparatus including the charged particle which are sufficiently improved in reflection efficiency while reducing the amount of charged particles without adding a fluorescent pigment or the like.

In order to increase the white reflectance of the charged particle 1 layer, charged particles containing titanium dioxide (TiO ₂ ) as a white pigment were prepared and the white reflectance of the particle 1 layer was measured. As a result, it was confirmed that the white reflectance was increased as the amount of titanium dioxide added increased I could. However, since addition of titanium dioxide alone has a limitation in showing a sufficient white reflectance required for display, a method of separately adding a fluorescent pigment or a fluorescent whitening agent in addition to titanium dioxide has been tried. However, a fluorescent pigment is added to the charged particles, When the image display device including the organic EL device is used together with the UV shielding film, there is a problem that the effect is canceled, and the organic EL device does not contribute sufficiently to increase the whiteness.

In the present invention, various methods are devised. In addition to adding a pigment to a mixed liquid of a monomer, a crosslinking agent, and an organic charge control agent in a water-based continuous phase liquid, a dispersion phase further containing a cosolvent is mixed, It is possible to obtain an effect of improving the white reflectance of one charged particle by using a manufacturing method in which the surface of the particle is made porous to make the surface irregularities and the light is scattered by the surface irregularities to further increase the reflectance there was.

Hereinafter, the present invention will be described in detail.

The aqueous continuous phase solution can be prepared by dissolving the dispersion stabilizer in water. Examples of the dispersion stabilizer include polyvinyl alcohol, methyl cellulose, ethyl cellulose, polyvinyl pyrrolidone, styrene-methylmethacrylate copolymer, , Styrene-maleic anhydride copolymer; water-soluble polymers such as styrene-maleic anhydride copolymer; Anionic surfactants such as sodium oleic acid and sodium lauryl sulfate, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, poly Nonionic surfactants such as oxyethylene fatty acid esters, sorbitane fatty acid esters, polyoxy sorbitan fatty acid esters, polyoxyethylene alkyl amines and glycerin fatty acid esters; and nonionic surfactants such as lauryl amine acetate, alkylamine salts, Surfactants such as cationic surfactants including quaternary ammonium such as lauryltrimethyl ammonium chloride; Or phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate, pyrophosphoric acid calcium, magnesium pyrophosphoric acid, aluminum pyrophosphoric acid, pyrophosphoric acid salts such as zinc pyrophosphoric acid, And inorganic dispersants such as calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium lactate, barium sulfate, colloidal silica and fumed silica, , A continuous aqueous phase liquid can be prepared by dissolving polyvinyl alcohol in water.

The dispersion stabilizer is preferably used in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the acrylic monomer or copolymer. When the amount of the dispersion stabilizer is less than 0.1 part by weight, the dispersion stability is insufficient. When the amount is more than 10 parts by weight, the remaining dispersion stabilizer is difficult to remove.

Examples of the acrylic monomer include C _{1 -12} alkyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl acrylate, 2-hydroxyethyl (meth) acrylate, glycidylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, acrylate], polyethyleneglycol (meth) acrylate, glycidyl (meth) acrylate, and dimethyl (ethyl) aminoethyl (meth) ) aminoethyl (meth) acrylate].

Examples of the crosslinking agent include allyl compounds such as divinylbenzene, diallyphtalate, diallyacrylamide and trially (iso) cyanurate, (poly (Meth) acrylate], (poly) propylene glycol di (meth) acrylate], trimethylolpropane tri (meth) acrylate, (Meth) acrylate, trimethylol propane tri (meth) acrylate, glycerol tri (meth) acrylate, ally (meth) acrylate, At least one compound selected from the group consisting of (meth) acrylate [(poly) alkylene glycol di (meth) acrylate]

The crosslinking agent is preferably in the range of 20 to 80 parts by weight based on 100 parts by weight of the monomer. When the content of the crosslinking agent is less than 20 parts by weight, porosity is not formed on the surface of the charged particles, and when the content exceeds 80 parts by weight, there arises a problem that the polymerization reaction is not desired and the yield is lowered.

The charge control agent for controlling the charge on the monomer is used. The charge control agent is not particularly limited, but a cation or an anion is substituted for a styrene type resin, an acrylic type resin, a styrene type and an acrylic type copolymer, It is preferable to use an organic charge control agent having a positive charge or a negative charge. At this time, since the monomer is polymerized, it is more nonpolar than the polymer region formed with the organic charge control agent, and is polarized rather than the cosolvent, so that phase separation occurs between the polymer region and the cosolvent and is advantageous for forming porous particles.

In addition to the use of the organic charge control agent, the amount of charge can be controlled with an inorganic charge control agent, and styrene and an acrylic copolymer or an acrylic polymer having an intermediate polarity between the formed polymer and the co- Phase separation to produce porous particles. Examples of the inorganic charge control agent include an azo alloy complex including vanadium, cobalt, nickel or copper, a salicylic acid chelate metal complex including copper, titanium or iron, a calixarene compound, a boron- -) electrification charge control agents, and positive (+) charge control agents such as negrosine dyes and quaternary ammonium salts.

The charge controlling agent is preferably used in an amount of 0.1 to 10 parts by weight per 100 parts by weight of a mixture of an acrylic monomer and a crosslinking agent. When the charge control agent is less than 0.1 parts by weight, the charge amount is too low. When the charge control agent is more than 10 parts by weight, the charge amount becomes excessively high, and the reaction stability is deteriorated, thereby causing excessive coagulation.

The pigment contained in the dispersion phase solution is titanium dioxide as a white pigment (TiO _2), barium sulfonic fade (BaSO _4), barium titanate marinade (BaTiO _3), strontium titanate marinade (SrTiO _3), calcium titanate (CaTiO _3), lead titanate marinade (PbTiO _3), tin dioxide (SnO _2), magnesium oxide (MgO), aluminum oxide (Al ₂ O _3), silica (SiO _2), iron oxide (Fe ₂ O _3), zirconia (ZrO _2), etc. , And it is particularly preferable to use titanium dioxide.

The pigment is preferably used in an amount of 5 to 100 parts by weight per 100 parts by weight of the mixture of the acrylic monomer and the crosslinking agent. When the amount of the pigment is less than 5 parts by weight, the coloring effect is insignificant. When the amount is more than 100 parts by weight, the pigment may escape to the outside of the particles.

In order to produce the above-mentioned porous charged particles, a co-solvent should be used together, and the co-solvent preferably has a property of being more polar than the polymer region formed by polymerization. The co-solvent is not particularly limited and may be selected from cyclohexane, n-hexane, hexane, n-heptane, isoheptane, isooctane, methyl ethyl ketone and methyl isobutyl ketone. The above-mentioned co-solvent content is preferably 5 to 200 parts by weight based on 100 parts by weight of the monomer. When the co-solvent content is less than 5 parts by weight, the porosity is lowered and reflectance is lowered. When the co-solvent content exceeds 200 parts by weight, the porosity is increased and the uniformity is lost.

In the present invention, the co-solvent is introduced into the dispersion liquid together with the acrylic monomer, the crosslinking agent, the charge control agent and the white pigment, and the polymerization reaction is carried out. During the polymerization process, the co- ≪ / RTI >

The dispersion liquid may contain a polymerization initiator for inducing polymerization of the monomers. The polymerization initiator is not particularly limited as long as a person skilled in the art can use them in the art.

The charged particles according to the present invention can be formed by polymerizing an acrylic monomer, an acrylic crosslinking agent, a charge control agent, and a pigment on a water-based continuous phase liquid and a co-solvent.

The charged particles preferably have a particle diameter of 0.5 to 50 탆. When the particle diameter is less than 0.5 탆, the white reflectance decreases and cohesion between particles increases. When the particle diameter exceeds 50 탆, the driving voltage increases, There is a problem that a large number of particles can not be obtained.

The porosity of the charged particles was confirmed by SEM (scanning electron microscope) and TEM (transmission transfer microscope).

Further, the present invention provides an image display apparatus including the upper and lower substrates, partition walls provided between the substrates, and the charged particles filled between the partition walls.

At least one side of the image display device may be provided with a UV blocking film, if necessary. The UV blocking film is not particularly limited as long as it is commonly used by those skilled in the art.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

Example 1

 600 g of distilled water and 2 g of polyvinyl alcohol were dissolved in a 1 L reactor and the reactor temperature was maintained at 60 캜 to prepare a water-based continuous phase liquid.

0.75 g of FCA201PS manufactured by Fujikura Kasei as an organic positive charge control agent was dissolved in 90 g of methylmethacrylate as a monomer and 60 g of ethylene glycol dimethacrylate as a cross-linking agent, 15 g of TAF520J manufactured by Fuji Titan Co., Ltd. and 100 g of 0.3 mm zirconia beads were dispersed for 1 hour at a speed of 1000 rpm and the beads were completely removed to prepare a dispersion. 0.5 g of V-65 (2-2'-azobis (2,4-dimethylvaleronitrile), manufactured by Wako Co., Ltd.) as a polymerization initiator was dissolved in a mixture of 110.5 g of the above dispersion and 50 g of cyclohexane to prepare a dispersion liquid .

The dispersed phase liquid was poured into the aqueous continuous phase liquid, emulsified at 6500 rpm for 5 minutes by a homogenizer, polymerized for 10 hours, and washed and dried to prepare white positive charged particles.

  In order to observe the surface of the prepared particles, the content of titanium dioxide in the particles was measured using a scanning electron microscope S4800 of Hitachi, Inc. and using a thermal gravimetric analyzer (TGA: Thermal gravity analysis).

  The average particle size and particle size standard deviation of the particles thus obtained were determined using a BECJMAN COULTER particle size analyzer.

 An AR (Anti-reflective) film treated with a pressure-sensitive adhesive was used in order to prepare a sample having the above-mentioned particles arranged in one layer. After sufficiently contacting the particles to be evaluated with the adhesive surface of the AR film, To remove the particles except for the particles directly adhered to the surface of the pressure-sensitive adhesive, thereby preparing a specimen in which the particles were arranged in one layer.

The prepared specimens were measured for transmission reflectance at a wavelength of 550 nm using a Shimadzu UV Vis spectrometer (UV-3600).

Example 2

White positive charge particles were prepared by the same method as in Example 1 except that FCA207P was used instead of FCA201PS of Fujikura Chemical Co., Ltd. as an organic positive charge control agent. Observation with a scanning electron microscope showed that porous particles were produced.

Example 3

White positive charged particles were prepared in the same manner as in Example 1 except that 20 g of co-solvent cyclohexane was used instead of 50 g. Observation with a scanning electron microscope showed that porous particles were produced.

Example 4

White charged particles were prepared in the same manner as in Example 1, except that 7.5 g of FCA1001NS, an organic negative charge control agent, was used in place of FCA201PS of Fujikura Chemical Co., Ltd., an organic-based charge control agent.

Comparative Example  One

White positive charged particles were prepared by the same method as in Example 1, except that Bontron P51 of orient chemical company, quaternary ammonium salt compound, was used instead of FCA201PS which is an organic positive charge control agent. Observation with a scanning electron microscope confirmed that no porous particles were formed.

Comparative Example  2

White positive charged particles were prepared in the same manner as in Example 1, except that TAF520J, which is titanium dioxide, was not used. Observation with a scanning electron microscope showed that porous particles were produced.

Comparative Example  3

White positive charge grains were prepared in the same manner as in Example 1, except that the co-solvent cyclohexane was not used. Observation with a scanning electron microscope confirmed that no porous particles were formed.

Comparative Example  4

White electrostatic particles were prepared in the same manner as in Example 1, except that 135 g of methyl methacrylate was used and 15 g of ethylene glycol dimethacrylate was used. Observation with a scanning electron microscope confirmed that no porous particles were formed.

The contents of the compositions used in Examples 1 to 4 and Comparative Examples 1 to 4 are summarized in Table 1, and physical properties of the charged particles according to Examples and Comparative Examples are shown in Tables 2 and 3, respectively.

As shown in Table 2, all of the charged particles produced in Examples 1 to 4 contain about 10% of titanium dioxide, and the transmission reflectance of one layer of the particles is 20% or more.

On the other hand, as shown in Table 3, Comparative Examples 1, 3, and 4 exhibit a low transmittance reflectance when the particles are not porous even when containing 10% of titanium dioxide as in Examples. Further, in the case of Comparative Example 2, it was found that even when the surface of the particle was porous but contained no titanium dioxide, it also exhibited a low transmittance reflectance.

Therefore, it has been found that it is more effective to use porous particles containing titanium dioxide in order to increase the transmission reflectance of the first particle layer.

1 is a cross-sectional view showing the structure of an electronic paper display device using general charged particles.

Claims (21)

(b) preparing a dispersion by dispersing a pigment in a solution containing an acrylic monomer, a crosslinking agent and a charge control agent; (c) adding a co-solvent to the dispersion to prepare a dispersion liquid And (d) mixing the aqueous continuous phase solution and the dispersed phase liquid to form a polymer. The method according to claim 1, wherein the steps (b) and (c) are carried out at the same time or at the same time. [4] The method according to claim 1, wherein the aqueous continuous phase solution is selected from the group consisting of polyvinyl alcohol, methyl cellulose, ethyl cellulose, polyvinyl pyrrolidone, styrene-methyl methacrylate copolymer styrene-maleic anhydride copolymer, sodium oleic acid, sodium lauryl sulfate, polyoxyethylene alkyl (meth) acrylate, ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitane fatty acid ester, polyoxy sorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin fatty acid ester, lauryl Lauryl amine acetate, alkylamine salts, lauryltrimethylammonium chloride ( lauryltrimethyl ammonium chloride, calcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium pyrophosphoric acid, magnesium pyrophosphoric acid, aluminum pyrophosphoric acid, zinc pyrophosphoric acid, calcium carbonate, magnesium carbonate , At least one dispersion stabilizer selected from the group consisting of calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium lactate, barium sulfate, colloidal silica and fumed silica Wherein the method comprises the steps of: The method of claim 1, wherein the cross-linking agent is selected from the group consisting of divinyl benzene, diallyphtalate, diallyacrylamide, trially (iso) cyanurate, Acrylates such as ethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate and trimethylolpropane tri (meth) acrylate, (Meth) acrylate, trimethylol propane tri (meth) acrylate, glycerol tri (meth) acrylate, ally (meth) acrylate, Wherein at least one compound selected from the group consisting of glycol di (meth) acrylate [(poly) alkylene glycol di (meth) acrylate] The method according to claim 1, wherein the pigment is titanium dioxide (TiO _2), barium sulfonic fade (BaSO _4), barium titanate marinade (BaTiO _3), strontium titanate marinade (SrTiO _3), calcium titanate (CaTiO _3), lead titanate marinade (PbTiO _3), tin dioxide (SnO _2), magnesium oxide (MgO), aluminum oxide (Al ₂ O _3), silica (SiO _2), iron oxide from the group consisting of (Fe ₂ O ₃₎ and zirconia (ZrO ₂₎ Wherein said method comprises the steps of: The method according to claim 1, wherein the charge control agent is polar rather than polymer region formed by polymerizing the monomer, and is more non-polar than the co-solvent. [7] The charge control agent according to claim 6, wherein the charge controlling agent is a resin consisting of a styrene resin, an acrylic resin, and a charge control agent having positive (+) or negative (-) charge by substituting cation or anion for a styrene- Wherein the porous electroconductive particles are selected from the group consisting of polyvinylidene fluoride and polyvinylidene fluoride. The process according to claim 1, wherein the co-solvent is selected from the group consisting of cyclohexane, n-hexane, hexane, nomole-heptane, isoheptane, isooctane, methyl ethyl ketone and methyl isobutyl ketone Wherein the method comprises the steps of: [4] The method according to claim 3, wherein the dispersion stabilizer is mixed in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the monomer. The method according to claim 1, wherein the charge control agent is mixed in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of a mixture of a monomer and a crosslinking agent. The method according to claim 1, wherein the cross-linking agent is mixed in an amount of 20 to 80 parts by weight based on 100 parts by weight of the monomer. The method according to claim 1, wherein the pigment is mixed in an amount of 5 to 100 parts by weight based on 100 parts by weight of the mixture of the monomer and the crosslinking agent. The method according to claim 1, wherein the co-solvent is mixed in an amount of 5 to 200 parts by weight based on 100 parts by weight of the monomer. A porous charged particle for an image display device formed by polymerization of an acrylic monomer including a cosolvent, a crosslinking agent, a charge control agent, and a pigment in a water-based continuous phase liquid. 15. The porous charged particle for an image display device according to claim 14, wherein a dispersion liquid containing an acrylic monomer, a crosslinking agent, a charge control agent, a pigment and a co-solvent is added to the aqueous continuous liquid. The method according to claim 14, wherein the pigment is titanium dioxide (TiO _2), barium sulfonic fade (BaSO _4), barium titanate marinade (BaTiO _3), strontium titanate marinade (SrTiO _3), calcium titanate (CaTiO _3), lead titanate marinade (PbTiO _3), tin dioxide (SnO _2), magnesium oxide (MgO), aluminum oxide (Al ₂ O _3), silica (SiO _2), iron oxide from the group consisting of (Fe ₂ O ₃₎ and zirconia (ZrO ₂₎ And the ratio of the number of particles to the total number of particles of the porous charged particle for use in an image display apparatus is determined. 15. The porous charged particle for an airbrush market as claimed in claim 14, wherein the charge control agent is polar rather than polymer region formed by polymerization of the monomer, and is more non-polar than the co-solvent. [19] The charge control agent according to claim 17, wherein the charge controlling agent is a resin consisting of a styrene resin, an acrylic resin, and a charge control agent having positive (+) or negative (-) charge by substituting cation or anion for a styrene- Of the total weight of the porous charged particles. 15. The process according to claim 14, wherein the co-solvent is selected from the group consisting of cyclohexane, n-hexane, hexane, n-heptane, isohexane, isooctane, methyl ethyl ketone and methyl isobutyl ketone Porous charged particles for image display apparatus. The image display device according to any one of claims 14 to 19, which is filled between the upper and lower substrates, the barrier ribs provided between the substrates and the barrier ribs. The image display apparatus according to claim 20, wherein a UV blocking film is attached to at least one surface of the upper and lower substrates.

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