JPS60189731A - Dispersion composition for electrophoresis display device - Google Patents

Abstract

PURPOSE:To obtain a dispersion compsn. having a long life without uneven display by dispersing and dissolving the pigment particles coated with a self-curing resin having the characteristic to be electrified positive as electrophoretic particles as well as long- chain monocarboxylic acid and anionic surface active agent into an org. dispersant. CONSTITUTION:A compsn. prepd. by dispersing and dissolving the electrophoretic particles A prepd. by coating TiO2 or colorable org. or inorg. pigment particles with a self- curing resin having the group which possesses proton site when dissociated, that is, the characteristic to be electrified positive, for example, an alkylated melamine resin, alkylated urea resin, etc. which cure without a catalyst, more particularly alkylated methylomelamine resin and aliphat. monocarboxylic acid of 12-24C in order to improve the positive electrification characteristic of the particles A together with an anionic surface active agent for the stable dispersion of the particles A in an insulating inert org. dispersant, for example, arom. or alicyclic hydrocarbon is prepd. The dispersion for an electrophoresis display element which has good contrast, excellent dispersion stability of the particles A, decreases power consumption and has high liquid resistance is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dispersion composition for an electrophoretic display device, and more particularly, the present invention relates to a dispersion composition for an electrophoretic display device, and more particularly, it exhibits no I5, particularly improved dispersion stability, and ! The present invention relates to a dispersion composition for an electrophoretic display device that has low power consumption because it has lithium fluid resistance.

A dispersion liquid composition in which electrophoretic fine particles are dispersed is sealed in a container sandwiched between a pair of electrode plates, at least one of which is transparent, and the fine particles are electrophoresed to one electrode by an electric field. In recent years, electrophoretic display devices that display images such as the like have been put into practical use. The dispersion liquid composition sealed in such devices usually consists of electrophoretic fine particles such as inorganic pigments uniformly dispersed in a liquid dispersion medium, but the dispersion stability of the dispersion liquid is generally poor and the dispersion during electrophoresis is difficult. Particles may aggregate and the clarity of the display plate may deteriorate, or the electrophoretic particles may stick to the surface of each electrode and do not migrate even when a reverse voltage is applied to the electrode plate, resulting in a decrease in contrast and display. There were problems such as unevenness. In order to stabilize the dispersibility and charge state of the dispersion solution, a surfactant such as Tween 85,
Attempts were made to add alkyd resin, metal soap, or olive oil (for example, in Japanese Patent Publication No. 52-2188
(October, No. 56-19612, etc.) The effect is not sufficient, but it is for electrophoretic display devices that have good display panel clarity, high contrast ratio, are stable for long-term use, and have low power consumption. There is a strong demand for the emergence of a dispersion composition. Therefore, an object of the present invention is to overcome the drawbacks of conventional dispersion compositions for electrophoretic display devices, and to improve the dispersion stability to 9.41° C. without lowering contrast or display unevenness. The object of the present invention is to provide a dispersion composition with low power consumption.

According to the present invention, (A) dissociates and carries a star with a 1 ~ nri 1~
coated with at least one self-curing resin:
Electrophoretic particles consisting of one or more types of face II, < 13
:l At least one monocarboxylic acid type hydrocarbon (C'l) At least one anionic surfactant is dispersed (:3 and/or dissolved in a dispersion medium), ( A) An electric product made by blending (B) 4 to 70 parts by volume of a monocarboxylic hydrocarbon (Jl type hydrocarbon) and (C) 10 to 100 parts by volume of an anionic surfactant (in terms of solid content) per 100 volumes of suspended particles. The above objectives are fully achieved by the dispersion composition for electrophoretic display devices.

In the present invention, (A) electrophoretic particles include one or a combination of two or more arbitrary inorganic and organic pigments that provide a clear color or a clear contrast with a colored dispersion medium in an electrophoretic display device. Both are coated with one type of resin.

Such pigments include inorganic pigments that reflect white, such as titanium oxide (rutile type, anatase type) and zinc white; inorganic pigments that exhibit yellow, such as yellow iron oxide, cadmium yellow, titanium yellow, yellow lead, and organic pigments. Pigments such as Hansa Yellow, Pigment Yellow, and Benzidine Yellow; inorganic pigments that exhibit a red color such as Red Garla and Cadmium Red; and organic pigments such as quinacridone pigments such as Zinkashi 1 Rud Y and Hostapalm Red, permanent red, fast slow red, etc. Azo pigments and blue inorganic pigments include ultramarine, navy blue, cobalt blue, and cerulean blue; organic pigments include phthalocyanine pigments such as phthalocyanine blue and fast sky blue; and indance red pigments. For example, inorganic pigments that give a green color such as indanthremble, such as chrome green, chromium hyridian oxide, etc., and organic pigments that give a nitrosic color, such as pigment green, naphthol green, or phthalocyanine. Examples of the pigments include phthalocyanine green.

In addition, the pigment coating resin is preferably a colorless self-curing resin that has proton sites when dissociated, for example, an amino group, and a resin that exhibits the property of having a positive charge when added with the additives described below. Specific examples include melamine resin, urea resin, isocyanate resin, and blends of these and other resins, with melamine resin being particularly preferred.

Such melamine resins and urea resins are obtained by appropriately selecting the number of moles of melamine or urea and formaldehyde and condensing them.Also, if necessary, alcohols such as methyl alcohol, butyl alcohol, and isobutyl alcohol are added to the resin. A part of the production raw material may be used as an alkylated methylol melamine resin or an alkylated methylol urea resin.

Such melamine resins include, for example, methylated melamine resins such as Cymel 303, Cymel 325 (Mitsui Toatsu), Sumimaru M-4O8 (Sumitomo Chemical +41)
, Nikaratsuku MX-40 (three-phase chemical ■), etc. Butylated melamine resins include Kneepan 20SE, Kneepan 128, L-14-559 (Mitsui Toatsu (4-gradation), etc.), and i-butylated melamine. G 821 as a resin
, [-121 (Inu Nippon Ink (Kikki)), etc.

Such urea resins include, for example, butylated urea resins such as Beckamine G-1850 and Beckamine D-138 (
These include Dainippon Ink ■), Kneepan 108 (Mitsui Toatsu 0 gradient), etc.

These are mixed with pigments, dried, hardened, and pulverized to create fine particles, but the mixing is done using ordinary dispersing machines such as Henschel mixers, planetary mixers, super mixers, etc.
It is done with three rolls and does not require any special method. After drying the mixed dispersion paste, it is heated and cured.

Curing is usually carried out with an acid catalyst, or preferably with a volatile catalyst or without a catalyst, as there is a concern that the acid catalyst may remain in the particles and make the charging characteristics of the particles non-uniform. For pulverization, an ordinary pulverizer may be used, such as a hammer mill, homogenizer, bot mill, etc.

The prepared particles are washed with alcohol and a solvent used as a dispersion medium, and then provided as electrophoretic particles.

Further, a drying device may be used as a method for performing these series of steps more rationally. For example, as such a drying device, a drying granulation device (spray dryer, etc.), a vacuum drying system (Orient Chemical FjACRU X), etc. can be used. However, in this case, it is considered suitable to use up to 4 parts by volume of the coating resin per 100 parts by volume of the pigment.

The monocarboxylic acid type hydrocarbon (B) used in the dispersion composition of the present invention is intended to provide particles with good charging characteristics in the dispersion.

In addition to these, carboxylic acid-type surfactants, polyester resins, and acrylic resins with an acid value added to them may be used to simply impart a good charge to the particles, but as for particles with multiple functional groups, However, agglomeration between particles tends to occur, and those having a polar molecular structure are not preferable because they interact with the electrode plate. moreover,
Among monocarboxylic acid type hydrocarbons, CI2 is preferable.
The range of C24 to C24 is good, but even if it is 012 or less or 024 or more, it is difficult to dissolve in a solvent. Specific examples include uralic acid, oleic acid, linoleic acid, and stearic acid.

The surfactant component which is blended with the monocarboxylic acid type hydrocarbon in the dispersion composition of the present invention and used to improve the display clarity, contrast ratio, service life and power consumption which are the objects of the present invention is (C >Anionic surfactants.Anionic surfactants are usually classified into carboxylic acid type, sulfonic acid type, phosphoric acid type, etc., but they can be of any type, and can be used alone or in combination. Among such anionic surfactants, the present inventors
A compound having a long-chain alkylene moiety or alkyl moiety that promotes particle stabilization and has antistatic properties is preferable, and m-xylene is used as a dispersion medium and at least one surfactant is dissolved or dispersed in the dispersion medium. It has also been observed that anionic surfactants are particularly preferable because they exhibit a liquid resistance of 1×10 9 Ωcm or less when exposed to water. Specifically, Homogenol 1--18, Homogenol M-8 (Kao Atlas 0 Shame, carboxylic acid-based anionic surfactant), Resistit 212 (Daiichi Kogyo Seiyaku ■), Neogen T (Daiichi Kogyo ■)
), ASA-3 (shell), etc., and anionic surfactants having chemical structures similar to these are particularly recommended.

In the present invention, one or more electrophoretic particles (A) coated with at least one resin as described above, at least one monocarboxylic acid type hydrocarbon (B), and at least one
A seed anionic surfactant (C) is dispersed and dissolved in a liquid dispersion medium (D). The electrophoretic particles (A>) are uniformly dispersed in such a dispersion medium, while the resin (B) and surfactant (C) are dispersed and/or dissolved in the dispersion medium.

Any known insulating liquid inert compound may be used as the liquid dispersion medium, such as aromatic, alicyclic, or aliphatic hydrocarbon solvents such as 0-xylene, m-xylene, p-xylene, toluene, Benzene, cyclohexane, n-hexane, etc., and halogenated solvents such as chloro[1-butane,
Trichloroethane, carbon tetrachloride, kerosene, cyclohexyl chloride, chlorobenzene, 1,1,2,2. Ethylene tetrachloride, ethane trifluorofluoride, ethane tribromide tetrafluoride, ethane difluoride tetrachloride, methylene iodide, triiodosilane, methyl iodide, carbon disulfide, etc. Alternatively, it is used in the form of a mixture of two or more types.

As already mentioned, the dispersion composition of the present invention has a liquid dispersion ts
One or more types of electrophoretic particles (A) coated with at least one type of resin are dispersed in (D), and at least one type of monocarboxylic acid type hydrocarbon (B) and an anionic surfactant of at least 1 second. It is essential that the agent (C) is dispersed and/or dissolved in the above dispersion system.

In order to obtain a dispersion composition for an electrophoretic display device which is a stable dispersion liquid and has no contrast reduction or display unevenness, the present inventors first determined that these particles, resins, and surfactants should be 100:4 to 70:10 to 1
It has been found that it is necessary to make it exist at a blending ratio of 0.00. That is, for 100 parts by volume of electrophoretic %1'l,
The monocarboxylic acid type hydrocarbon has a solid content of 4 to 70 parts by volume,
Preferably, the amount is 4 to 40 parts by volume; if the monocarboxylic acid type hydrocarbon is 4% by volume of the particles without vortexing, the charging characteristics of the electrophoretic particles will not be sufficient, and if it exceeds 70% by volume, the viscosity of the dispersion will decrease. This causes problems such as a longer response time to changes in the electric field. In addition, the anionic surfactant is used in a range of 10 to 100% by volume relative to the particles; below this lower limit, the response speed may be insufficient due to improved dispersion stability of electrophoretic particles and repulsion between electrophoretic particles. It has also been found that exceeding the upper limit is undesirable, as the liquid resistance decreases too much and a high voltage is required.

The dispersion composition of the present invention is prepared by dispersing and mixing the above-mentioned components using a conventional dispersion machine such as a paint shaker, ball mill, sand grind mill, etc., and does not require any special method. The components can be introduced into the disperser in any order.

In the present invention, electrical conductivity is not necessarily an essential requirement, but it is necessary to mix a substance having this characteristic at the time of dispersion. This is clear from the fact that the effect diminishes below a certain amount. However, such a dispersion system is not satisfactory in terms of low power consumption and the life of the electrode plates.

After dispersing the dispersion system according to the above-mentioned formulation, the present inventors separated the particles and liquid by some method, washed the particles, and then redispersed them with a dispersion medium. It was discovered that the electrical conductivity can be lowered by removing excess substances from the liquid. That is, the coated pigment, monocarboxylic acid type hydrocarbon, anionic surfactant, and dispersion medium are dispersed in the above-mentioned composition, and the particles and the dispersion are separated by allowing the dispersion to stand still or forcibly settling with a centrifuge. The particles can be taken out and washed (or washed by adding a dispersion medium and performing a similar operation) to have a resistivity of 1010 Ωam or more, and then provided as an electrophoretic dispersion composition.

If desired, the composition of the present invention can be colored by dissolving or dispersing a dye in a fine state to improve the contrast of the electrophoretic particles. As the darkening dye, azo dye, monoazo dye, anthraquinone dye, etc. are used. For example, blue dyes include anthraquinone-based Macrolex 7/L and -RR (Bayer AG), and red dyes include azo-based Oil Red 5303 (Yuisui Kagaku (Kikki)) and 1.c black dye. For example, a mixture of anthraquinone-based Macroresis 1 Ru FR (Bayer AG) and monoazo-based Oil Red XO (Kanto Kagaku (Merger)) is used.

Furthermore, in order to improve the sedimentation stability of the electrophoretic particles, an oil or fat having a high specific gravity, such as a 1-1 hydrogenated oil or fat, may be added to the above dispersion.

Thus, the liquid composition according to the present invention obtained in step 1) exhibits extremely high dispersion stability for dispersion for electrophoretic display devices (1), and exhibits extremely high dispersion stability compared to other compositions, with l' being less likely to cause aggregation between particles and adhesion to the electrode surface. This invention makes it possible to provide an excellent electrophoretic display device that is free from contrast deterioration and display unevenness.

The present invention will be explained below with reference to Examples.

Production Example 1 Production of Electrophoretic Particles 1 25 parts by volume of titanium oxide (DuPont R960) and 11-
After mixing and dispersing 75 parts by volume of butylated melamine resin (number average molecule m1500, average degree of condensation 3.2, degree of alkylation 2.0), 38 parts by volume of butanol, and 38 parts by volume of m-xylene in a Henshi 1 Lumixer for 1 hour. , Polly L Brency l-
After taking it out and drying it in a dryer (100°C for 21 hours), the temperature was raised to 180°C and cured for 2 hours. Take out this b and first coarsely crush it with a homogenizer.
The mixture was ground for 48 hours in a Bottle Mill. Heat this again to 180℃
After heating for 2 hours and curing, the particles were washed with alcohol and m-xylene and dried to produce melamine resin-coated particles.

Production Example 2 Production of Electrophoretic Particles 2 10 volumes of titanium oxide (DuPont R960) and 1 volume of n-butylated melamine resin (number average molecular weight 1500, average degree of condensation 3.0, degree of alkylation 2.4) Ishibe, 100 parts by volume of xylene was dispersed with SG for 2 hours. Melamine resin-coated particles were prepared from this product using a vacuum drying system (CRUX manufactured by Orient Chemical Co., Ltd.).

Production Example 3 Production of Electrophoretic Particles 3 50 parts by volume of Shinkasha Red Y (quinacridone red pigment manufactured by DuPont) and n-butylated melamine resin (number average molecule M1500, average degree of condensation 3.2, degree of alkylation 2.0) )
50 parts of stone, 25 parts of xylene, 25 parts of butanol
Production example 1 after mixing and dispersing the volume by 3 passes with 3 rolls
Red melamine resin-coated particles were prepared according to the procedure described in .

Production Example 11 #A acid-forming titanium oxide R of electrophoretic particles 4
-960>, 50 parts and powdered Beckamine G-1
850 (butylated urea resin, manufactured by Dainippon-Runki Co., Ltd.) 15
After mixing 0 parts by weight in a homogenizing heat oven, heat the mixture to 100°C in a -shaft xx stall furnace to heat melt and knead it, and then heat it in a cold lj
After pulverizing with a hammer mill, particles of 5 μm or less were taken out with a micron air separator to prepare butylated urea resin-coated particles.

Example 1 Macrolex Blue RR (anthraquinone type manufactured by Bayer) 0.4.
o Dissolve to make 12 parts by volume of 4% blue solvent. To this was added 1 part by volume of the particles obtained in Production Example 1 and 0.00 parts by volume of oleic acid.
15 parts by volume, homogenol L-18 (manufactured by Kao Atlas)
0.1 part by volume was added and dispersed for 1 hour using a paint shaker to prepare a dispersion for electrophoretic display.

This was sealed in a gap created by a 15 μm polyester film spacer between two transparent glass electrode plates (indium oxide films) to create a display board. 10V on the display board
When this voltage was applied, white color was obtained on the surface of the cathode plate and blue color was obtained on the surface of the anode plate, and when the polarity of the voltage was reversed, the colors were reversed. The ratio of the Y values of white and blue (hereinafter referred to as contrast ratio) measured with a spectroscopic altimeter (Macbeth KC818) at this time.

) was approximately 10. Additionally, this thread maintained similar contrast at least 2 x 106 times in experiments where the polarity of the voltage was reversed at IHz.

Examples 2 to 6 and Comparative Examples 1 to 2 The electrophoretic particles obtained in Production Examples 1 to 4 and various monocarboxylic acids were used in the same manner as in Example 1, except that the mixing ratios listed in Table 1 below were used. Dispersions for electrophoretic display were prepared, and the performance of these dispersions was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 7 After the dispersion obtained in Example 1 was allowed to stand for one day, the light solution was removed, 10 parts by volume of 4% blue solvent was added, and the operation of stirring was repeated three times. When the resistivity of the dispersion liquid was examined, it was found to be 10ΩCl11.

As a result of performance evaluation according to Example 1, the contrast comparison 10 lifespan was 4×10e times.

Comparative Example 3 A dye solution similar to that in Example 1 was prepared, and 1 part of titanium oxide was added to it.
Part by volume, 0.1 part by volume of oleic acid, 1.1 part by volume of homogenol
8 0.1 part by volume was added to prepare a dispersion liquid for electrophoresis using a paint shaker.

As a result of examining this according to Example 1, the contrast ratio was 15, but the life was only 10' cycles.

patent application agent Patent attorney Takeo Ito

Claims (6)

[Claims] (1) (A) Electrophoresis ('1 particle) consisting of one or more types of pigments coated with at least one type of self-curing resin that carries a group that dissociates and has a - ) at least one monocarboxylic acid type hydrocarbon (C) at least one anionic surfactant dispersed and/or dissolved in (D) an organic dispersion medium, (A>particles 10
B) monocarboxylic acid type hydrocarbon 4.
A dispersion composition for an electrophoretic display device, comprising: ~70 parts by volume, and (C) an anionic surfactant (in terms of solid content) of 10 to 10 parts (lffff). (2) The composition according to claim 1, wherein the self-curing resin carrying a group that dissociates and has blown sites is a melamine resin, a urea resin, or an isocyanate resin. (3) Monocarboxylic acid type hydrocarbon has 12 carbon atoms.
20 (゛Yes!l: I Fl Composition according to claim 1) (4) When j'2A-based interfacial agents are dispersed or dissolved in m-xylene alone or in combination, the liquid resistance lX
The composition according to claim 1, which exhibits 109ΩCll1 or less. (5) Special 8' where the liquid resistance is 1010ΩC11l or more -VC
(The composition according to claim 1. (6) The composition according to claim 11, wherein the electrophoretic particles are resin-coated pigment particles prepared using a vacuum drying granulation device.