JPS638637A - Electrophoretic display element - Google Patents

Abstract

PURPOSE:To obtain the titled element having improved dispersibility and electric charge property of a pigment powder contd. in a dispersing solution and a large and clear color difference and capable of giving a uniform display by incorporating an organodisilazane to the dispersing solution as a dispersant. CONSTITUTION:The titled element is formed by enclosing a solution dispersed in a colored dispersing medium having a high insulating property, the pigment particle which has a different color tone from that of said colored dispersing medium in a space formed between two sheets of counter electrodes in which one of said electrodes is a transparent. In the titled element, the organodisilazane shown by the formula is incorporated in the dispersing solution or coats the pigment particle. The particle having a positive or a negative polarity in the dispersing medium is used as the pigment particle. Said particle is exemplified by an inorg. pigment such as titanium oxide (a rutile type or an anatase type), etc., as a white color series, and by an inorg. pigment such as a yellow color iron oxide or an org. pigment such as a hansa yellow, etc., as a yellow color series. Thus, the uniform display having the large and clear color difference is obtd.

Description

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 computers, destination display boards, electronic whiteboards, etc. are generally composed of two opposing electrodes (one of which is transparent), as shown in the attached drawings. In the gap 1', a liquid in which electrophoretic particles, such as pigment particles 3, having a color tone different from that of the dispersion medium 2 is dispersed in a highly insulating colored dispersion medium 2 (this 5
In the dispersion liquid, pigment particles are charged either positively or negatively) and are enclosed using spacers 4.

This figure is a cross-sectional view when a voltage is applied (5 in the figure is a driving power source), and the pigment particles 3 are in the colored dispersion medium 2 as described in #-t# when a voltage is applied and therefore not affected by an electric field. Although they are simply dispersed, when subjected to the action of an electric field by applying a voltage, they undergo electrophoresis and adhere to one electrode depending on the polarity of charge.6 When they adhere to the transparent electrode on the display side, they become pigment particles. 3 color tones are displayed, and if the polarity of the fi colored dispersion medium 2 tones is reversed when attached to the electrode on the opposite side, each display becomes opposite to each other.

Therefore, the actual display depends on the difference between the color tone of the pigment particles and the color tone of the colored dispersion medium, that is, the color difference.

Note that the pigment particles once attached to the electrode surface have a so-called memory effect in which they are held 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 general dispersion are 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. There were drawbacks such as decreased clarity and uneven display. Therefore, in order to eliminate these drawbacks, it has been proposed to add various surfactants, alkyd resins, higher fatty acid metal salts, olive oil, etc. to the dispersion solution, but sufficient effects have not been obtained.

Purpose The purpose of the present invention is to greatly improve the dispersion stability and chargeability of pigment particles, thereby increasing the color difference.

An object of the present invention is to provide an electrophoretic display element capable of providing clear and perfect display.

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 dispersed needles are dispersed in a highly insulating colored dispersion medium is sealed in a gap between two opposing electrodes, the general formula is phenyl. represents a group. ) is characterized in that the organodisilazane represented by the following formula 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 type 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 and organic pigments such as Hansa Yellow and Pigment Yellow are used, while red pigments include inorganic pigments such as Red Garla and Cadmium Red, and quinacridone pigments such as Shinkasha Red Y and Phosmepalm Red. Organic pigments such as azo pigments such as Manent Red and Fast Slow Red, and blue pigments include inorganic pigments such as ultramarine blue, navy blue, cobalt blue, and cerulean blue, and 7-p cyanine pigments such as phthalocyanine blue and fast sky blue. , organic pigments such as indanthrene pigments such as indanthremble, green pigments such as 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 7-talocyanine pigments. The above pigments can be used alone or in a mixture of two or more.

On the other hand, as the first colored dispersion medium, a highly insulating organic solvent colored with a dye is used. Specific examples of organic solvents include o-, m-, or p-xylene, toluene, benzene, cyclohexane, n-hexane, chlorobutane, trichloroethane, tetracarbohydrate, kerosene, cyclohexyl chloride, chlorobenzene, ' a”p2+2-Tetrachloroethylene, trifluoroethane, tetrafluorotribromoethane, tetrafluorodifluoroethane, methylene iodide, triiodosilane, methyl iodide, carbon disulfide, etc. alone or in mixtures thereof can be mentioned.

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

The dispersion of the present invention further contains an organodisilazane having the general formula described above as a dispersant. Representative examples thereof include the following compounds.

The above organodisilazane 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 organodisilazane, and then the solvent is removed. In any case, the amount of organodisilazane used is usually 0.1-10% by weight based on the pigment particles.
, preferably 0.5 to 5% by weight.

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 organodisilazane of the above general formula are added to this, or organodisilazane-coated pigment particles are added. After addition, it may be dispersed using a dispersing machine such as a paint shaker, sail mill, 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 of the electrodes, and add particles with a particle size of 10 to Zoooμm to the periphery of the electrode. A thermosetting adhesive in which spacer particles are dispersed is applied, and the other electrode is placed on top of it, and then the adhesive is cured.

The dispersion liquid may be injected into the thus formed cells using a syringe or the like, and the injection port may be sealed.

In the electrophoretic display element thus obtained, display is performed by applying a voltage of about 5 to 200 volts to both electrodes to cause the pigment particles in the dispersion to electrophores to either electrode, as in the prior art. Note that this display is maintained on the electrode surface even if the voltage application is canceled as described in n+1.

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

Example 1 Azo black dye (B
ASF Sudan Black X 60) 0.3.9
was dissolved to prepare a black dispersion medium. This is combined with titanium oxide (
Kronos KR-38ON manufactured by Titan Kogyo Co., Ltd.) 4.51
and compound AI hexamethyldisilazane (Toray Silicone Co., Ltd. s 5z6079) 0.03. F was added and mixed and dispersed using a paint shaker to prepare a dispersion.

On the other hand, 1. T, O, peripheral part K of a transparent glass electrode having a film, a thermosetting adhesive (Struct End, manufactured by Mitsui Toatsu Chemical Co., Ltd.) in which spacer particles (Micro Pearl 5P-210 manufactured by Block Fine Chemical Co., Ltd.) with a diameter of 10 μm are dispersed.
A display cell was created by overlaying 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.

When a voltage of DoloV is applied to this display element.

Titanium oxide particles electrophores and adhere to the positive electrode side,
A clear white display was obtained, and therefore a clear black display was obtained on the negative electrode side.

Next, when the polarity of the applied voltage was reversed, each display color was reversed. The color difference between white and black at this time was determined as ap+ using a color difference meter (CR-100 manufactured by Minolta) and was found to be 35. Furthermore, when we conducted a display test in which the voltage polarity was alternately reversed at a frequency of 10 Hz, there was no drop in color difference or particles sticking to the electrode (and it was possible to repeat display approximately 10 times. Suiko did not cause particle agglomeration or sedimentation in a 700-hour standing test.

Comparative Example 1 A fluorine-based surfactant (70 Lard FC-430 manufactured by 3M Co., Ltd.) was used in place of hexamethyldisilazane when preparing the dispersion liquid.Ike prepared an electric vibration display element in the same manner as in Example 1. , tested similarly.

As a result, the color difference was 25 at the beginning of repeated display, but after about 10 times, a network-like agglomeration pattern of particles was generated and the 1 color difference decreased to 15. Further, in a standing test, particles settled after 1124 hours.

Example 2 0.05.9% of compound A2, tetramethyldisilazane (T2O20, manufactured by Chisso Corporation) was added to 10p of dehydrated benzene, and after stirring the components with a mixer, titanium oxide (Taibaek A-Zoo, Bansyo Sangyo Co., Ltd.) was added. .5y was added thereto, and the mixture was stirred again using a mixer, and the solution was further vacuum-dried to remove the solvent, thereby obtaining organodisilazane-coated titanium oxide particles. 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, as in Example 1, bright white and black saturated water was 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) 1
01 Anthraquinone blue dye (Macrolex Blue RR manufactured by Bayer) 0.3.
! i'Titanium oxide (Ronos KR-31 manufactured by Titan Air Co., Ltd.)
0) 2. Oli compound, thread 4 dioctyltetramethyldisilazane (D5830 manufactured by Chisso Corporation)
0.0IJF With this product, white and blue display were obtained in the same test as in Example 1, and the difference in one color was 31. Other test results were exactly 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 a dispersion absorber.

m-xylene [same as Example 1] 5y Olive oil (same as Example 1)
5JF Azo red dye (Sudan Red 460 manufactured by BASF) 0.3.9 Titanium Yellow (Tie Bake Yellow manufactured by Bancho Sangyo Co., Ltd.) 51 Compound AV diphenyltetramethyldisilazane (D6188 manufactured by Chisso Corporation)
0.05J This product obtained yellow and red display in the same test as Example 1, and the color difference was 28
Met. All other test results were the same as in column 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.

0-Dichlorobenzene (Kanto Kagakusha i1!)
71 Olive? iIl! (Same as Example 1)
3II azo blue dye (13A
sF Sudan Blue 670) 0.1.9 Titanium oxide (same as Example 1) 21 Compound &6 Divinyltetramethyldisilazane (Titanium grains #D6208) 0.02
．． 9' This product showed white and blue display in the same test as in Example 1, and the difference in one color was 33. All other test results were the same as in Example 1.

Example 6 An electrophoretic display element was produced in the same manner as in Example 1, except that a dispersion having the following formulation was used.

0-dichlorobenzene (same as Example 5) 7 g Olive oil (same as Example 1) 31 Azo black dye 8 (same as Example 1) o,
3g titanium oxide (same as Example 1)
4.5 Jil Hexamethyldisilazane of compound AI (same as Example 1) 0°03
This product obtained the same test results as in Example 1, except that the repeated display test result was about 10' times.

Example 7 An electrophoretic display element was prepared in the same manner as in Example 1, except that divinyldiphenyldimethyldisilazane (D6206.8, manufactured by Chisso Corporation) from Compound Shop 8 was used instead of hexamethyldisilazane when preparing the dispersion liquid. did.

This product obtained the same test results as in Example 2, except that the repeated display test a was repeated about 10 times.

Example 8 An electrophoretic display element was prepared in the same manner as in Example 2, except that hexamethyldisilazane of compound M1 (same as in Example 1) was used instead of tetramethyldisilazane when preparing the dispersion liquid. did.

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

Example 9 Instead of m-xylene when preparing the dispersion. - An electrophoretic display element was produced in the same manner as in Example 2, except that dichlorobenzene (same as in Example 5) was used.

This product obtained the same test results as in Example 2, except that the repeated display test result was about 10 times.

Example 10 An electrophoretic display element was prepared in the same manner as in Example 2, except that an azo red dye (same as in Example 4) was used instead of an azo black dye when preparing a dispersion.

This product showed white and red display in the same test as in Example 1, and the difference in one color was 25. The results of the repeated display test were about 10 times, and the results of the standing test were the same as in the other examples.

Effects As described above, since the electrophoretic display element of the present invention uses organodisilazane as a dispersant in the dispersion liquid, the dispersibility and chargeability of pigment particles in one dispersion liquid are greatly improved, and as a result, one color difference is reduced. is large.

A clear and even display can be obtained.

[Brief explanation of the drawing]

The attached figure is a cross-sectional view of a typical electrophoretic display element when voltage is applied. l, 1'... Electrode 2... Colored dispersion medium 3
...Pigment particles 4...Spacer patent question ceremony
Ricoh Co., Ltd. Agent Patent Attorney Shigeru Tsukimura ψυ°１
″: 1 other person ((-3)

Claims (1)

[Claims] 1. A liquid in which pigment particles having a color tone different from that of the dispersion medium are dispersed in a highly insulating colored dispersion medium is placed in the gap between two opposing electrodes, at least one of which is transparent. In the encapsulated electrophoretic display element, there are also general formulas, mathematical formulas, chemical formulas, tables, etc. (However, R_1, R_
2, R_3 may be the same or different and represents a C_1 to C_8 hydrocarbon group or a phenyl group. An electrophoretic display element characterized in that an organodisilazane represented by the following formula is contained in the dispersion liquid or coated on the pigment particles.