JPS62280826A - Electrophoretic display element - Google Patents

Abstract

PURPOSE:To obtain a display which has large color difference, is sharp and is free from uneven colors by sealing a liquid dispersed with pigment particles of the color tone different from the color tone of a high-insulating coloring dispersion medium into the spacing between electrodes facing each other and incorporating a specific aluminum chelate into the dispersion or coating the same on the pigment particles. CONSTITUTION:This electrophorectic display element is formed by sealing the liquid dispersed with the pigment particles of the color tone different from the color tone of the high-insulating coloring dispersion medium into said dispersion medium into the spacing between two sheets of the electrodes which face each other and at least one of which is transparent. Said element is further formed by incorporating the aluminum chelate expressed by the formula into the dispersion medium or coating the same on the pigment particles. The pigment particles which exhibit a positive or negative polarity in the dispersion medium is used. The white pigment particles are exemplified by titanium oxide, etc., the yellow pigment particles by yellowish iron oxide, etc., and the red pigment particles by iron oxide red, etc. On the other hand, a high-insulating org. solvent colored by a dye is used for the coloring dispersion medium and is exemplified by p-xylene, toluene, etc. The amt. of the aluminum chelate to be used is usually 0.1-10wt%, more preferably 0.5-5wt% by the weight of the pigment particles.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an electrophoretic display element in which a reverse 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 blackboards, etc. generally consist of two facing electrodes 1, at least one of which is transparent, as shown in the accompanying drawings. . is charged either positively or negatively) is enclosed using a spacer 4.

Note that 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 simply dispersed in the colored dispersion medium 2 as described above when the voltage is not applied, so when they are 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 color tone of the pigment particles and the color tone of the colored dispersion medium,
That is, it is due to 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 dispersion liquid are generally unstable, and when used for a long time, the pigment particles aggregate and the hiding power decreases.
As a result, there were drawbacks such as a decrease in color difference and sharpness, and display unevenness. 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 liquid, but no sufficient effect has been obtained.

Object The object of the present invention is to provide an electrophoretic display element that can provide a clear and uniform display with a large color difference by greatly improving the dispersion stability and charging property of pigment particles.

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 highly insulating colored dispersion medium is filled with a liquid in which pigment particles having a color tone different from that of the dispersion medium is sealed in the gap between two opposing electrodes, the general formula (however, X is an acetoalkoxy group or diisopropyl group whose alkyl group has 2 to 7 carbon atoms, m is an integer of 0 to 3,
R represents an alkyl group having 1 to 3 carbon atoms, and n represents an integer of 1 to 3. ) The aluminum chelate 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, red pigments include inorganic pigments such as Red Garla and Cadmium Red, quinacridone M materials such as Shinkasha Red Y, Hostapalm Red, Nozomanent Red, and First. Organic pigments such as azo pigments such as slow red, blue pigments include inorganic pigments such as ultramarine, navy blue, cobalt blue, and cerulean blue, phthalocyanine pigments such as phthalonanine blue, fast sky blue, and indanthremble.
Organic pigments such as indanthrene pigments, green pigments include inorganic pigments such as chrome green, chromium oxide, and viridian, nitroso pigments such as naphthol green, and phthalo-7-anine pigments such as phthalocyanine green. Organic pigments such as The above pigments can be used alone or in a mixture of 2 m or more.

On the other hand, a highly insulating organic solvent colored with a dye is used as the colored dispersion medium. Here are some specific examples of organic solvents: -2m- or p-xylene, toluene, benzene, cyclohexane, n-hexane, chlorobutane, trichloroethane, carbon tetrachloride, kerosene, cyclohexyl chloride, chlorobenzene, 1,1. z, 2-tetrachloroethylene, trichlorofluoroethane, tetrafluorotribromoethane, tetrafluorodifluoroethane, methylene iodide, triiodosilane, methyl iodide, carbon disulfide, etc. alone or a mixture 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, anthraquinone-based Macrolexol-RR (
), azo-based Oil Red 5303 (manufactured by Yusui Kagaku Co., Ltd.) as a red dye, and anthraquinone-based Macrolexol-FR (manufactured by )-inil Co., Ltd. as a black dye, and azo-based Oil Red XO as black dyes. (manufactured by Kanto Kagaku Co., Ltd.).

The dispersion of the present invention further contains an aluminum chelate of the above general formula as a dispersant. Typical examples include the chemical compounds described below.

(Margin below) Compound Mu Structural formula Note that these are easily available as commercial products.

The above aluminum chelate 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 aluminum chelate, and then the solvent is removed. In any case, the amount of aluminum chelate used is usually 0.1 to 10% of the pigment particles.
Coulometric %, 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 an aluminum chelate of the above general formula are added thereto, or aluminum chelate-coated pigment particles are added thereto. After that, the mixture may be dispersed using a dispersing machine such as a paint shaker, I-Lumill, 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 τ and pneumophoretic display elements 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 100 pn to the periphery of the electrode. A thermosetting adhesive having spacer particles dispersed therein is applied, the other electrode is placed on top of the adhesive, the adhesive is cured, and the dispersion is injected into the thus formed cells using a syringe or the like. Just seal the injection port.

In the electrophoretic display element thus obtained, display is performed 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 case.

Note that this display is maintained on the electrode surface even if the voltage application is canceled as described above.

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 l
! Dissolve the black dispersion medium in Kl! ! Manufactured. Titanium oxide (Kronos KR-38ON manufactured by Titan Kogyo Co., Ltd.) 4.
511F and 0.05F of aluminum bisethyl acetate diimpropylate (aluminum chelate LCH manufactured by Yoken Fine Chemical Co., Ltd.) of compound 41 were added and mixed and dispersed in a paint shaker to prepare a dispersion.

On the other hand, 1. T, 0. A thermosetting adhesive (Struct Bond, manufactured by Mitsui Toatsu Chemical Co., Ltd.) in which spacer particles with a diameter of 10 tones (Micropearl SP-210 manufactured by Blockbuster Fine Chemicals Co., Ltd.) are dispersed is adhered to the peripheral edge of a transparent glass electrode having a film, A display cell was created by layering a similar transparent glass electrode on top of it and heating it to harden the adhesive.

Next, inject the dispersion into this cell using a syringe,
By sealing the injection port, the 'e electrophoretic display element of the present invention was prepared.

When a voltage of DCIOV was applied to this display element, 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 was reversed, each display color was reversed. The color difference between white and black at this time was measured with a color difference meter (CR-100 manufactured by Minolta) and was found to be 35. Furthermore, we conducted a test in which the voltage polarity was alternately reversed and displayed at a frequency of 10Hz.
Approximately 106 times of repeated display was possible without any decrease in color difference or adhesion of particles to the electrodes. Also, this display element has 700
No agglomeration or sedimentation of particles occurred in the aging test.

Comparative Example 1 Electrolysis was performed in the same manner as in Example 1, except that a fluorine-based surfactant (3M Co., Ltd. 70 Lard FC-430) was used in place of aluminum bisethylacetoacetate diimpropylate when preparing the dispersion. A electrophoretic display element was created and tested in the same manner.

As a result, the color difference was 25 at the initial stage of repeated display, but a network-like agglomeration pattern of particles occurred at approximately 10" aperture, and the color difference decreased to 15. In addition, in the standing test, the color difference was 25.
Sedimentation of the particles occurred over time.

Example 2 Compound 1 of aluminum bisethylacetoacetate diimpropylate (10.9% of dehydrated benzene)
After adding 0.05 g (same as in Example 1) and thoroughly stirring with a mixer, titanium oxide (Thailand A-A manufactured by Ishihara Sangyo Co., Ltd.)
100) Add 4.5.9, stir again with a mixer, and vacuum-dry this solution to remove the solvent to obtain aluminum chelate-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, similar to Example 1, clear white and black displays were obtained. The color difference between white and black at this time was 33. 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) 1M anthraquinone blue dye (Macrolex Blue RR manufactured by Bayer) 0. x
Titanium 9 oxide (Kronos KR-310 manufactured by Titan Kogyo Co., Ltd.) 1.5.
! i' Compound A2 Aluminum Trisacetylacetonate (Aluminum Clear manufactured by Yoken Fine Chemical Co., Ltd.) A
) 0.01 This is Example 1
In the same test, white and blue display were obtained, and the color difference was 2
5, and the number of repeated displays was approximately 10' times. The results of the storage test 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 the dispersion liquid.

m-xylene (same as in Example 1) 1ag azo blue dye (BAS's Fudan Blue 6go) 0.
2g zinc oxide (Zetsukusuna 2000 manufactured by Sakai Chemical Co., Ltd.) 3.01
Aluminum bisetheracetoacetate/monoacetylacetate of compound No. 4 (Aluminum Clear manufactured by Yoken Fine Chemical Co., Ltd.) D) 0.
041 This product showed white and blue display in the same test as in Example 1, and the color difference at this time was 25. Other test results were exactly the same as in Example 1.

Example 5 An electrophoretic display element was prepared 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) 5F olive oil (same as Example 1) 5 g Anthraquinone blue dye (same as Example 3) 0.3.9 Titanium Yellow (Tie Bake Yellow TY manufactured by Ishihara Sangyo Co., Ltd.) -70) 0.
51 Aluminum bisethylacetoacetate diisopropylate of compound A1 (same as Example 1) o, osI
This product obtained yellow and blue display in the same test as Example 1, the color difference was 23, and the number of repeated display was about 10'.
It was times. The results of the storage test were exactly the same as in Example 1.

Example 6 An electrophoretic display element was prepared in the same manner as in Example 1, except that an azo red dye (Sudan Red 460, manufactured by BASF) was used in place of the azo black dye when preparing the dispersion.

This product showed white and red display in the same test as in Example 1, and the color difference at this time was 28. Other test results were exactly the same as in Example 1.

Example 7 When preparing a dispersion, compound &3 aluminum trisethyl acetoacetenate (LCH-TR containing aluminum chelate manufactured by Yoken Fine Chemical Co., Ltd.) was used instead of aluminum bisethylacetoacetate diisopropylate.
) An electrophoretic display element was produced in the same manner as in Example 1, except that the same method as in Example 1 was used.

This product obtained white and black display in the same test as in Example 1, and the color difference at this time was 30. The pond test results were exactly the same as in Example 1.

Example 8 Substituted m-xylene during preparation of dispersion. - An electrophoretic display element was prepared in the same manner as in Example 1 except that dichlorobenzene (Kanto Kagaku M) was used.

This product was subjected to the same test as in Example 1, and a white and black "mark" was obtained. Other test results were exactly the same as in Example 1.

Example 9 Aluminum trisethylacetoacetenate of compound A3 (Example 7) was used instead of aluminum bisethylacetoacetate diisopropylate when preparing the dispersion
An electrophoretic display element was produced in the same manner as in Example 2, except that the same method as in Example 2 was used.

This product showed white and black display in the same test as in Example 1. The color difference at this time was 33. Other test results were exactly the same as in Example 1.

Example 10 Example 2 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 provided white and blue display in the same test as in Example 1, and the color difference at this time was 30. Other test results were exactly the same as in Example 1.

Effects As described above, since the uninvented electrophoretic display element uses aluminum as a dispersant in the dispersion liquid, the dispersibility and chargeability of pigment particles in the dispersion liquid are greatly improved, and as a result, , it is possible to obtain a clear and uniform display with a large color difference.

[Brief explanation of the drawing]

The attached figure is a cross-sectional view of a typical electrophoretic display element when voltage is applied.

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, X is an acetalkoxy group or diisopropyl group whose alkyl group has 2 to 7 carbon atoms, m is 0 to 3 , R is an alkyl group having 1 to 3 carbon atoms, and n is an integer of 1 to 3.) is contained in the dispersion or coated on the pigment particles. An electrophoretic display element.