JP4930978B2 - Microcapsules for electrophoretic display with good memory - Google Patents

Description

  The present invention relates to a microcapsule for electrophoretic display, and more particularly to a microcapsule for electrophoretic display having a good memory property.

  As an electrophoretic display device, for example, two substrates having at least one transparent substrate are arranged to face each other with a required interval through a spacer to form a sealed space, and dispersed particles are dispersed in the sealed space. Some particles are filled with a display liquid dispersed in a dispersion medium having a different color tone to form a display panel, and an electric field is applied to the display panel to obtain a display. The transparent substrate surface is the display surface. Become.

The display liquid for the electrophoretic display device filled in the sealed space is a hydrophobic dispersion medium such as xylene or isoparaffin, electrophoretic particles such as titanium dioxide, and a dye for providing a color contrast with the electrophoretic particles. It is composed of a dispersing agent such as a surfactant and an additive such as a charge imparting agent, or a positively charged particle and a negatively charged particle, or a positively or negatively charged particle as an electrophoretic particle. When two types of particles are used, such as particles that are not used, a colorless hydrophobic dispersion medium is used. By applying an electric field to the display liquid, the dispersed particles in the display liquid move to the transparent plate side, and the color of the dispersed particles appears on the surface. By applying an electric field in the opposite direction, the dispersed particles move to the back side, and the color of the dispersion medium appears on the surface. There is also known a method in which the display liquid is enclosed in microcapsules and used as display particles, and various proposals have been made for resin components constituting the walls of the microcapsules (see, for example, Patent Documents 1 to 5). .
JP 2000-0666249 A JP 2004-113840 A JP 2004-310050 A JP 2004-333589 A JP 2005-266432 A

Conventionally, various resins have been proposed as wall-constituting substances for microcapsules containing display liquids, but this is not always sufficient in terms of memory properties.
An object of the present invention is to provide a microcapsule for electrophoretic display having excellent memory properties by constituting a wall of a microcapsule with a specific resin composition.

The microcapsule for electrophoretic display of the present invention is a microcapsule for electrophoretic display containing electrophoretic particles and a dispersion medium, and the wall of the microcapsule is composed of a graft copolymer, and the side chain portion of the graft copolymer The difference between the SP value (solubility parameter value) and the SP value of the dispersion medium contained in the microcapsule is in the range of −1.5 to +1.5 (cal / cm ³ ) ^1/2 And

In the microcapsules for electrophoretic display of the present invention, the difference between the SP value of the side chain portion of the graft copolymer and the SP value of the dispersion medium contained in the microcapsule is −1.5 to +1.5 (cal / cm ^3). ) By being within the range of ^1/2 , the side chain of the graft copolymer extends into the inside of the microcapsule during the production of the microcapsule, and the movement of the electrophoretic particles in the microcapsule Is limited and the memory performance is excellent.

The microcapsule for electrophoretic display of the present invention is a microcapsule for electrophoretic display containing electrophoretic particles and a dispersion medium, and the wall of the microcapsule is composed of a graft copolymer, and the side chain portion of the graft copolymer The difference between the SP value of the dispersion medium and the SP value of the dispersion medium contained in the microcapsule is in the range of −1.5 to +1.5 (cal / cm ³ ) ^1/2 .

In the microcapsules for electrophoretic display of the present invention, the difference between the SP value of the side chain portion of the graft copolymer and the SP value of the dispersion medium contained in the microcapsule is −1.5 to +1.5 (cal / cm ^3). ) By being within the range of ^1/2 , the side chain of the graft copolymer extends into the inside of the microcapsule during the production of the microcapsule, and the movement of the electrophoretic particles in the microcapsule Is limited and has excellent memory characteristics. When the difference between the SP value of the side chain portion of the graft copolymer and the SP value of the dispersion medium contained in the microcapsule is out of the range of −1.5 to +1.5 (cal / cm ³ ) ^1/2 In the production of microcapsules, the side chain of the graft copolymer extends not only to the inside of the microcapsule but also to the outside, and the amount of the side chain that restricts the movement of the electrophoretic particles in the microcapsule is reduced, There is a tendency for memory performance to be insufficient.

  In the microcapsules for electrophoretic display of the present invention, it is preferable that a graft copolymer having a mass ratio of side chains to main chains of 10 to 80% by mass constitutes the walls of the microcapsules. As a result, the amount of the side chain of the graft copolymer extending into the inside of the microcapsule during the production of the microcapsule becomes relatively large, and the memory property is excellent. Moreover, it is preferable that the weight average molecular weight of only a principal chain part is 500-500000.

  Furthermore, it is preferable that the graft copolymer having a reactive functional group in the main chain portion constitutes the wall of the microcapsule. This makes it possible to increase the reflection intensity by providing a bridge between the microcapsules and reducing the gap between the microcapsules.

  In the microcapsules for electrophoretic display according to the present invention, known techniques can be used as they are for the electrophoretic particles and dispersion media encapsulated in the microcapsules and the method for producing the microcapsules.

  As the electrophoretic particles, inorganic pigment particles or organic pigment particles can be used. Examples of inorganic pigment particles include lead white, zinc white, lithopone, titanium dioxide, zinc sulfide, antimony oxide, calcium carbonate, kaolin, mica, barium sulfate, gloss white, alumina white, talc, silica, calcium silicate, and cadmium yellow. , Cadmium lipoton yellow, yellow iron oxide, titanium yellow, titanium barium yellow, cadmium orange, cadmium lipoton orange, molybdate orange, bengara, red lead, silver vermilion, cadmium red, cadmium lipoton red, amber, brown iron oxide, Zinc iron chrome brown, chrome green, chromium oxide, viridian, cobalt green, cobalt chrome green, titanium cobalt green, bitumen, cobalt blue, ultramarine, cerulean blue, cobalt aluminum chrome -Cobalt violet, mineral violet, carbon black, iron black, manganese ferrite black, cobalt ferrite black, copper chrome black, copper chrome manganese black, titanium black, aluminum powder, copper powder, lead powder, bell powder, zinc powder, etc. Can be used. These pigment components can be used not only as fine particles of pigment alone but also in various surface-treated states.

  Examples of organic pigment particles include fast yellow, disazo yellow, condensed azo yellow, anthrapyrimidine yellow, isoindoline yellow, copper azomethine yellow, quinophthaloin yellow, benzimidazolone yellow, nickel dioxime yellow, monoazo yellow lake, dinitroaniline. Orange, pyrazolone orange, perinone orange, naphthol red, toluidine red, permanent carmine, brilliant fast scarlet, pyrazolone red, rhodamine 6G lake, permanent red, resol red, bon lake red, lake red, brilliant carmine, Bordeaux 10B, naphthol red , Quinacridone magenta, condensed azo red, naphthol carmine, perylene scar red, condensed Scarred, benzimidazolone carmine, anthraquinonyl red, perylene red, perylene maroon, quinacridone maroon, quinacridone scarred, quinacridone red, diketopyrrolopyrrole red, benzimidazolone brown, phthalocyanine green, Victoria blue lake, phthalocyanine blue, Fast sky blue, alkali blue toner, indanthrone blue, rhodamine B lake, methyl violet lake, dioxazine violet, naphthol violet and the like can be used. These pigment components can be used not only as fine particles of pigment alone but also in various surface-treated states.

  Examples of the dispersion medium include aromatic hydrocarbons such as benzene, toluene, xylene, phenylxylylethane, diisopropylnaphthalene, and naphthenic hydrocarbons, and aliphatic carbonization such as hexane, dodecylbenzene, cyclohexane, kerosene, and paraffinic hydrocarbons. Hydrogens, halogenated hydrocarbons such as chloroform, trichloroethylene, tetrachloroethylene, trifluoroethylene, tetrafluoroethylene, dichloromethane, ethyl bromide, phosphorus such as tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, tricyclohexyl phosphate Acid esters, dibutyl phthalate, dioctyl phthalate, dilauryl phthalate, dicyclohexyl phthalate, butyl oleate, diethylene glycol dibenzoate, Dioctyl silicate, dibutyl sebacate, dioctyl adipate, trioctyl trimellitic acid, acetyl triethyl citrate, octyl maleate, dibutyl maleate, ethyl acetate and other carboxylic acid esters, isopropyl biphenyl, isoamyl biphenyl, chlorinated paraffin, diisopropyl Naphthalene, 1,1-ditolylethane, 1,2-ditolylethane, 2,4-ditertiaryaminophenol, N, N-dibutyl-2-butoxy-5-tertioctylaniline, and the like can be used. These organic solvents can be used alone or in combination of two or more.

  In the microcapsules for electrophoretic display of the present invention, known graft copolymers constituting the walls of the microcapsules can be used as they are. For example, a graft copolymer obtained by copolymerizing a relatively high molecular weight macromonomer having an addition polymerizable group at one end and an addition polymerizable monomer, and incorporating the macromonomer into the graft copolymer, Monomer derived graft chains can be introduced into the graft copolymer.

In the microcapsule for electrophoretic display of the present invention, the difference between the SP value of the side chain portion of the graft copolymer and the SP value of the dispersion medium contained in the microcapsule is −1.5 to +1.5 (cal / cm ³ ) Use an appropriate combination of the above dispersion medium and graft copolymer so as to be within the range of ^1/2 .

Hereinafter, the synthesis of the graft copolymer or copolymer used to constitute the wall of the microcapsule will be described in detail.
<Graft copolymer A>
19 g of 12-hydroxystearic acid self-condensate (SP value = 8.5) having an acid value of 20 mg KOH / g was reacted with 1 g of glycidyl methacrylate to obtain a macromonomer that becomes a side chain of the graft copolymer. 25 g of an aliphatic hydrocarbon solvent (mineral spirit: SP value = 7.8) and 25 g of an aromatic hydrocarbon solvent (Solvesso 100: SP value = 8.8) were added thereto, and the temperature was maintained at 90 ° C. . Furthermore, a mixture obtained by sufficiently mixing 2.5 g of tertiary butyl methacrylate, 2.5 g of styrene, 15 g of methacryloyloxyethyl isocyanate and 2.5 g of 2,2′-azobis- (2,4-dimethylvaleronitrile). Was uniformly added dropwise over 1 hour. Then, after maintaining for 30 minutes, 10 g of the above aliphatic hydrocarbon solvent was added to obtain a graft copolymer.

<Graft copolymer B>
11.4 g of a 12-hydroxystearic acid self-condensate (SP value = 8.5) having an acid value of 20 mgKOH / g was reacted with 0.6 g of glycidyl methacrylate to obtain a macromonomer serving as a side chain of the graft copolymer. 25 g of an aliphatic hydrocarbon solvent (mineral spirit: SP value = 7.8) and 25 g of an aromatic hydrocarbon solvent (Solvesso 100: SP value = 8.8) were added thereto, and the temperature was maintained at 90 ° C. . Furthermore, a mixture obtained by sufficiently mixing 6.5 g of tertiary butyl methacrylate, 6.5 g of styrene, 15 g of methacryloyloxyethyl isocyanate, and 2.5 g of 2,2′-azobis- (2,4-dimethylvaleronitrile). Was uniformly added dropwise over 1 hour. Thereafter, after maintaining for 30 minutes, 10 g of an aliphatic hydrocarbon solvent was added to obtain a graft copolymer.

<Graft copolymer C>
3 g of a 12-hydroxystearic acid self-condensate (SP value = 8.5) having an acid value of 20 mg KOH / g was reacted with 0.2 g of glycidyl methacrylate to obtain a macromonomer serving as a side chain of the graft copolymer. 50 g of n-butyronitrile (SP value = 10.5) was added thereto, and the temperature was maintained at 90 ° C. Further, a mixture obtained by sufficiently mixing 10.9 g of tertiary butyl methacrylate, 10.9 g of styrene, 15 g of methacryloyloxyethyl isocyanate and 2.5 g of 2,2′-azobis- (2,4-dimethylvaleronitrile). Was uniformly added dropwise over 1 hour. Thereafter, after maintaining for 30 minutes, 10 g of an aliphatic hydrocarbon solvent was added to obtain a graft copolymer.

<Copolymer D>
25 g of an aliphatic hydrocarbon solvent (mineral spirit) and 25 g of an aromatic hydrocarbon solvent (Sorvesso 100) were mixed and the temperature was maintained at 90 ° C. Furthermore, a mixture obtained by sufficiently mixing 12.5 g of tertiary butyl methacrylate, 12.5 g of styrene, 15 g of methacryloyloxyethyl isocyanate and 2.5 g of 2,2′-azobis- (2,4-dimethylvaleronitrile). Was uniformly added dropwise over 1 hour. Thereafter, after maintaining for 30 minutes, 10 g of an aliphatic hydrocarbon solvent was added to obtain a copolymer.

<Copolymer E>
25 g of an aliphatic hydrocarbon solvent (mineral spirit) and 25 g of an aromatic hydrocarbon solvent (Sorvesso 100) were mixed and the temperature was maintained at 90 ° C. Furthermore, a mixture obtained by sufficiently mixing 20 g of tertiary butyl methacrylate, 20 g of styrene and 2.5 g of 2,2′-azobis- (2,4-dimethylvaleronitrile) was added dropwise uniformly over 1 hour. Thereafter, after maintaining for 30 minutes, 10 g of an aliphatic hydrocarbon solvent was added to obtain a copolymer.

<Preparation of microcapsules>
Oil Blue N 1.5g, Diisopropyl Naphthalene 75g, Titanium Oxide 10g, Pigment Dispersant (Solsperse 17000) 0.5g and the above Graft Copolymers A, B, C and Copolymers D, E 8g are mixed and dispersed. Was prepared. Using polyvinyl alcohol (PVA) having a polymerization degree of 500, 30 g of a 5% by mass PVA aqueous solution was prepared. While stirring, 10 g of the above dispersion was added thereto, and further 20 g of a 5% by mass bisaminoethoxyethane aqueous solution was added. Added. The liquid temperature was raised to 40 ° C., and the mixture was gently stirred at 40 ° C. for 1 hour to obtain electrophoretic particle-encapsulated microcapsules. Classification was performed with a sieve to obtain microcapsules of 85 μm to 90 μm. The obtained microcapsules were thoroughly washed to remove bisaminoethoxyethane. By this preparation, five types of microcapsules were obtained.

The five types of microcapsules obtained as described above were evaluated as follows. That is, two glass plates on which ITO was deposited were used as electrodes, and classified microcapsules were sandwiched between the two electrodes, and the gap between the electrodes was adjusted to 50 μm. A voltage of ± 27 V is alternately applied at intervals of 2 seconds, and this is repeated for about 20 seconds. Finally, a voltage of +27 V is applied to the upper electrode sandwiching the macrocapsule for 10 seconds, and the white color maintenance property is determined according to the following criteria. It was evaluated with.
◎: Very good,
○: Good,
×: bad
XX: Not encapsulated.

  The results were as shown in Table 1. Table 1 shows the type of copolymer used, SP value difference (SP value of the dispersion medium contained in the microcapsule−SP value of the side chain portion of the graft copolymer), and the mass ratio of the side chain to the main chain. And the presence or absence of crosslinking in the microcapsule wall.

Claims (4)

In an electrophoretic display microcapsule containing electrophoretic particles and a dispersion medium, the wall of the microcapsule is composed of a graft copolymer, and the SP value (solubility parameter value) of the side chain portion of the graft copolymer and the microcapsule A microcapsule for electrophoretic display, characterized in that the difference from the SP value of the dispersion medium contained in is in the range of -1.5 to +1.5 (cal / cm ³ ) ^1/2 .   The microcapsule for electrophoretic display according to claim 1, wherein the graft copolymer having a mass ratio of the side chain to the main chain of 10 to 80% by mass constitutes the wall of the microcapsule.   The microcapsule for electrophoretic display according to claim 1 or 2, wherein the graft copolymer having a reactive functional group in the main chain portion constitutes the wall of the microcapsule. The difference between the SP value of the side chain portion of the graft copolymer and the SP value of the dispersion medium contained in the microcapsule is in the range of −1.5 to +1.5 (cal / cm ³ ) ^1/2 4. The microcapsule for electrophoretic display according to claim 1, 2, or 3, wherein the side chain of the graft copolymer is extended into the inside of the microcapsule during the production of the microcapsule.