JPS62296127A - Electrophorectic display element - Google Patents

Abstract

PURPOSE:To increase a color difference at all times and to obtain a sharp and uniform display by incorporating a titanium coupling agent into a liquid dispersion or coating the same on pigment particles. CONSTITUTION:The liquid dispersed with the pigment particles 3 of the color tone different from the color tone of a color dispersion medium 2 having a high insulating characteristic is sealed into the spacing between two sheets of opposed electrodes 1, 1' one of which is transparent. The titanium coupling agent is incorporated into the liquid dispersion or coated on the pigment particles 3. About 5-200V voltage is impressed to the electrodes 1, 1' to migrate the pigment particles in the liquid dispersion electrically to either of the electrodes, by which the display is executed.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Technical Field The present invention relates to an electrophoretic display element in which a display operation is performed by electrophoresis of pigment particles in a dispersion when a voltage is applied.

[Prior art] Electrophoretic display elements used for display and memory in various devices such as the Noviator 1 destination display board and the 'fIL Kojima board are generally made of 2 opposing panels, at least one of which is transparent, as shown in the attached drawing. A liquid in which electrophoretic particles 3 having a color tone different from that of the dispersion medium are dispersed in a highly insulating colored dispersion medium 2 in the gap between the electrodes 1 and 1' (in such a dispersion, pigment The particles are charged either positively or negatively) and are enclosed using a spacer 4. Note that this opening is a cross-sectional view when a voltage is applied (in the figure, 5 is a driving power source), and the pigment particles 3 are simply dispersed in the colored dispersion medium 2 as described above when the voltage is not applied and therefore not affected by the electric field. However, when subjected to the action of an electric field by applying a voltage, it causes electrophoresis and adheres to one electrode depending on its charged polarity. When attached to the transparent electrode on the display side, the color tone of the pigment particles 3 is displayed, and when attached to the electrode on the opposite side, the color tone of the colored dispersion medium 2 is displayed. If the polarity of the applied voltage is reversed, each display will be reversed. Therefore, the actual display is based on the difference between the 8 tones of the pigment particles and the color tone of the colored dispersion medium, that is, the color difference. It should be noted that the pigment particles once attached to the electrode surface have a so-called memory effect in which they are retained by electrical and physical forces with the electrode surface even after the voltage application is removed.

However, in conventional electrophoretic display elements, the dispersion and charging state of the pigment particles in the dispersion liquid are generally unstable, and when used for a long time, the pigment particles aggregate with each other and the hiding power decreases, resulting in a single color difference or sharpness. There were drawbacks such as poor performance and uneven display. Therefore, in order to eliminate these defects, various surfactants and pigment dispersion resins are added to the dispersion liquid.

Addition of higher fatty acid metal salts, olive oil, etc.

It has also been proposed to coat the surface of pigment particles with a dispersing resin (for example, in JP-A-59-165028, an anionic surfactant and a dispersing resin are added to a dispersion medium. In Japanese Patent Publication No. 56-47461, a highly fluorinated polymer is used as a dispersing resin to cover a small portion (at least a portion) of the surface of pigment particles, but a sufficient effect has not yet been obtained.

Purpose The purpose of the present invention is to provide an electrophoretic display element that can always provide a clear and uniform display with a large color difference by greatly improving the dispersion stability and chargeability of pigment particles. be.

Structure The electrophoretic display element of the present invention has two parts, at least one of which is transparent.
In an electrophoretic display element in which a liquid in which pigment particles having a color tone different from that of the dispersion medium is sealed in a highly insulating colored dispersion medium is sealed in the gap between two opposing electrodes, a titanium coupling agent is used. , it is characterized in that it is contained in the dispersion or coated on the pigment particles.

To explain the dispersion used in the present invention, first, pigment particles that exhibit positive or negative polarity in the dispersion medium are used. Specific examples of such pigments include inorganic pigments such as titanium oxide (rutile or anatase type) and zinc white for white pigments, and yellow iron oxide, cadmium yellow, titanium yellow, yellow lead, etc. for yellow pigments. Inorganic pigments such as Henza Yellow, Pigment Yellow, and other organic pigments are red.

Inorganic pigments such as cadmium red, Shinkasha Red Y,
Organic pigments such as quinacridone W pigments such as Hostapalm Red, permanent red, and azo pigments such as 7 Earth Throw Red are used, and blue pigments include inorganic pigments such as ultramarine, deep blue, cobalt crew, and cerulean blue, and phthalocyanine blue and fast sky. 7 talocyanine pigments such as blue,
Organic pigments such as indanthrene pigments such as indanthrene pigments, green pigments include inorganic pigments such as chrome green, chromium oxide, and pyridian, nitroso pigments such as pigment green and naphthol green, and phthalocyanine green. Examples include organic pigments such as phthalocyanine pigments. The above pigments can be used alone or in a mixture of zaf or more. Note that these pigment particles are usually an uncolored dispersion medium.

It is used in an amount of 1 to 100 parts by weight.

On the other hand, as the colored dispersion medium, a highly insulating @m medium colored with a dye is used. Here, specific examples of organic solvents include o-, m- or Fip-mil-xylene toluene, benzene, cyclohexane, n-hexane, chlorobutane, trichloroethane, tetracarboxylic 1 kerosene, cyclohexyl chloride, chlorobenzene, t, 1 ．． z, z-? Examples include trichlorethylene, trichlorofluoroethane, tetrafluorotribromoethane, tetrafluorodifluoroethane, methylene iodide, triiodocrane, methyl iodide, carbon disulfide, etc. alone or in mixtures thereof. It will be done.

Dyes for coloring these organic solvents include oil-soluble dyes, particularly azo dyes and anthraquinone dyes from the viewpoint of ease of use. Specifically, anthraquinone-based McFlex Blue RR (manufactured by Bayer) was used as a blue dye, and azo-based Oil Red 5303 (manufactured by Kanmoto Chemical Co., Ltd.) was used as a red dye.

As black dyes, anthraquinone-based Macrolex Sol-FR (manufactured by Bayer) and azo-based Oil Red XO (
(manufactured by Kanto Kagaku Co., Ltd.). These dyes are usually used in an amount of 0.1 to 100 parts by weight of the organic solvent.
1 ON part is used.

A titanium coupling agent is further used as a dispersant in the dispersion of the present invention. As a titanium coupling agent, the general formula % formula % (however, an alkyl group having 1 to 4 carbon atoms, X is a carbon number 8 to 18
alkyl group, fatty acid residue, hydroxyphenyl group or hydrocarbon residue ft.

m ij represents an integer from 1 to 4; n represents an integer from 1 to 3;

) are preferably used. Specific examples of the titanium coupling agent represented by the above general formula are isopropyl triisostearoyl titanate, isopropyl tridecyl pensulfonyl titanate, and isopropyl tris(diocternoyl phosphate) titanate.

Isopropyl trioctanoyl titanate.

Isopropyl dimethacrylic O isostearoyl titanate, isopropyl diacryl isostearoyl titanate, inpropyl tri(dioctylphosphate) titanate, isopropyl tricumylphenyl titanate, isopropyl tri(N-aminoethylamine ethyl) titanate, tetraisopropyl ·Screw(
Dioctyl phosphite cotitanate, tetraoctyl bis(ditridecyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl) bis(di-tridecyl) phosphite titanate, bis(
Dioctyl pyrophosphate) oxyacetate titanate, dicumylphenyl oxyacetate titanate, diisostearoyl ethylene titanate, bis(dioctyl pyrophosphate) ethylene titanate, and the like. These products are commercially available from Ajinomoto Co., Ltd. under the trade name Plain Act.

The above titanate coupling agent may be contained in the dispersion as described above, or may be coated on the pigment particles. As a method for coating pigment particles, for example, there is a method in which pigment particles are added and mixed into a solution of a titanate coupling agent, and then the solvent is removed. In any case, the amount of the titanate coupling agent used is usually 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the pigment particles.

To prepare the dispersion of the present invention, a dye is dissolved in a highly insulating organic solvent to obtain a colored dispersion medium, and pigment particles and a titanate coupling agent of the above general formula are added to this, or a titanate coupling agent of the general formula is added thereto. After adding the coated pigment particles,
It may be dispersed using a dispersing machine such as a paint shaker, l-luminium, or sand grind mill. Incidentally, in order to further improve dispersibility and chargeability, the same additives as conventional ones can be added to the dispersion liquid.

To make the electrophoretic display element of the present invention using the dispersion liquid as described above, first prepare two electrodes, one of which is transparent, fix one electrode, and add particles with a particle size of about 10 to 100 μm to the periphery of the electrode. A thermosetting adhesive in which spacer particles are also dispersed is attached, the other electrode is placed on top of it, the adhesive is cured, the dispersion is injected into the thus formed cells using a syringe, and the injection port is All you have to do is seal it.

The thus obtained electrophoretic display element performs display by applying a voltage of about 5 to 200 V to both electrodes to cause the pigment particles in the dispersion to electrophoresis to either electrode, as in the conventional art. Note that this indication is maintained on the electrode surface even if the voltage application is removed as described above.

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

Example 1 Azo black dye (B
A black dispersion medium was prepared by dissolving Sudan Black X60 (0.39) manufactured by ASF.

Titanium oxide (Cross KR-38 manufactured by Titan Kogyo Co., Ltd.) was added to this.
ON ) 45 I! Isopropyl triisostearoyl titanate (Plenac manufactured by Ajinomoto Co., Ltd. TTS) 0.045I shown by the formula
Add i and mix and disperse with a paint shaker for about 1 hour.
Dispersion liquid v! 4 were made.

On the other hand, one side 1. A thermosetting adhesive (Strak, manufactured by Mitsui Toatsu Chemical Co., Ltd.) J in which spacer particles with a diameter of 10 μm (Micro Pearl 5P-210, manufactured by AJ Water Fine Chemicals Co., Ltd.) are dispersed on the periphery of a transparent glass electrode having a T, O, film. A display cell was created by adhering a similar transparent glass electrode on top of the adhesive and heating it to harden the adhesive.

Next, inject the dispersion into this cell using a syringe,
An electrophoretic display element of the present invention was produced by sealing the injection port.

DCIOV(2) for this display element! When pressure was applied, titanium oxide particles electrophoresed and adhered to the positive electrode side, resulting in a clear white display, and therefore a clear black display was obtained on the negative electrode side.

Next, when the polarity of the applied voltage m is reversed, '4! rk display color has been reversed. The color difference between white and black at this time was measured with a color difference meter (CR-Zoo, manufactured by Minolta) and found to be 35. Furthermore, when we conducted a test in which the voltage polarity was alternately reversed at a frequency of 1 OHZ, there was no decrease in color difference by 1, or
There were no particles sticking to the t-pot, and it was possible to repeatedly display about 10 times. Furthermore, this display element did not cause particle aggregation or sedimentation during a 700-hour standing test.

Comparative Example An electrophoretic display element was prepared in the same manner as in Example 1, except that a fluorine-based surfactant (3M Fluorado P'C-430) was used instead of isopropyl triisostearoyl titanate when preparing the dispersion. and tested in the same way. As a result, the color difference was 25 at the initial stage of repeated display, but after about 10'' times, mesh-like aggregation and turns of particles occurred, and the color difference decreased to 15. Sedimentation occurred.

Example 2 10 g of dehydrated benzene was mixed with isopropyl tridecylbenzenesulfonyl titanate (Plenaku, manufactured by Ajino Yuisha Co., Ltd. 38S) O, Q as shown by the formula %.
! After stirring thoroughly, 4.5 J of titanium oxide (Tiebake A-100, manufactured by Ishihara Sangyo Co., Ltd.) was added, and the mixture was stirred again. The liquid was vacuum-dried to remove the solvent, and a titanate coupling agent was added. Coated titanium oxide particles were obtained. Next, the titanium oxide particles were added to the black dispersion medium used in Example 1, and dispersed for about 1 hour using a paint shaker to prepare a dispersion liquid of the present invention.

An electrophoretic display element was prepared using this dispersion in the same manner as in Example 1, and tested in the same manner. As a result, similar to Example 1, clear white and black displays were obtained. The color difference between white and black at this time was 30. Other than that, the results of the repeated display test and the standing test were exactly the same as in Example 1.

Example 3 An electrophoretic display element was produced in the same manner as in Example 1, except that the following formulation was used as the dispersion liquid.

m-xylene (same as Example 1) 1o1
Anthraquinone blue dye (Macrolex Blue RR manufactured by Bayer) o, 3g Titanium oxide (Kronos KR-310 manufactured by Titan Kogyo) 3.0
．． 9bis (diocternozoylophosphate) oxyacetate titanate (Plenact 1388, manufactured by Ajinomoto Co.) 0.
0211 This product showed white and back color display in the same test as Example 1, the difference in one color was 28, and the number of repeated displays was about 1.
It was 0 times. The results of the standing test were the same as in Example 1.

Example 4 An electrophoretic display element was produced in the same manner as in Example 1, except that the following formulation was used as the dispersion liquid.

m-xylene (same as Example 1) la
t/Azo red dye (Sudan Red 46 manufactured by BASF)
0) g, IJ titanium oxide (Tiebake R8 manufactured by Ishiwa Sangyo Co., Ltd.)
30) 1. OJi'bis(dioctylpyrophosphate coethylene titanate (GlenAct 2388 manufactured by Ajinomoto Co., Inc.) 0.
0211 This product obtained white and red display in the same test as Example 1, and the color difference was 25. The number of times it is displayed repeatedly is approximately 1.
It was 0' times. The results of the standing test were the same as in Example 1.

Example 5 An electrophoretic display element was produced in the same manner as in Example 1, except that the following formulation was used as the dispersion liquid.

m-xylene (same as Example 1)
5.51 Olive oil (same as Example 1)
5Jil azo blue dye (BASF Sudan Blue 670) 0.21! Titanium Yeo - (Tie Bake Yellow TY50 manufactured by Gohara Sangyo Co., Ltd.) 3
．． 0J inpropyl tridecylbenzenesulfonyl titanate (Plenact 98 manufactured by Ajinomoto Co.) 0.0
1F This product obtained yellow and blue display in the same test as Example 1, the color difference was 25, and the number of repeated displays was about 106.
It was times. The results of the standing test were the same as in Example 1.

Example 6 Example 1 except that inpropyl-trioctanoyl titanate (Plenact 28, manufactured by Ajinomoto Co., Ltd.) shown by the formula was used instead of inpropyl triinostearoyl titanate when preparing the dispersion liquid.
An electrophoretic display element was created using the same method as described above.

The various test results of this product were all the same as in Example 1.

Example 7 An electrophoretic display element was prepared in the same manner as in Example 1, except that zinc oxide (ZEX≠4000, manufactured by Sakai Chemical Co., Ltd.) was used instead of titanium oxide when preparing the dispersion liquid.

This product showed white and black display in the same test as in Example 1, and the color difference was 23. Other test results were the same as in Example 1.

Example 8 An electrophoretic display element was prepared in the same manner as in Example 1, except that bis(dioctylpyrophosphate)oxyacetate titanate (same as in Example 3) was used instead of isopropyl triisostearoyl titanate when preparing the dispersion. Created.

With this product, white and black displays were obtained in the same test as in Example 1, the color difference was 28, and the number of repeated displays was approximately 10 times. The results of the standing test were the same as in Example 1.

Example 9 An electrophoretic display element was prepared in the same manner as in Example 1, except that bis(dioctylpyrophosphate) ethylene titanate (same as in Example 4) was used instead of isopropyl e-triisostearoyl titanate when preparing the dispersion. did.

This product showed white and black display in the same test as in Example 1, and the color difference was 25. Other test results were exactly the same as in Example 1.

Example 10 Example 1 except that an anthraquinone blue dye (same as Example 3) was used instead of the azo black dye when preparing the dispersion.
An electrophoretic display element was created using the same method as described above.

This product displayed white and blue colors in the same test as in Example 1, the difference in one color was 30, and the number of repeated displays was approximately 10 times. The results of the standing test were the same as in Example 1.

Effects As described above, since the electrophoretic display element of the present invention uses a titanate coupling agent as a dispersant in the dispersion liquid, the dispersibility and chargeability of pigment particles in one dispersion liquid are greatly improved.
As a result, it is possible to obtain a display with a wide color difference (clear and even display).

[Brief explanation of the drawing]

The attached figure is a cross-sectional view of a typical electrophoretic display element when voltage is applied. 1.1'... Electrode 2... Colored dispersion medium 3
... Pigment particles 4 ... Spacer patent applicant Ricoh Co., Ltd. Agent Patent attorney Tsukimura Shigegai 1 person

Claims (1)

[Claims] 1. Electrophoresis in which a liquid in which pigment particles with a color tone different from that of the dispersion medium are dispersed in a highly insulating colored dispersion medium is sealed in the gap between two opposing electrodes, at least one of which is transparent. An electrophoretic display element, characterized in that a titanium coupling agent is contained in the dispersion or coated on the pigment particles.