WO2013062339A1 - Particle dispersion solution, sheet comprising same, and display device - Google Patents

Abstract

The present invention relates to a particle dispersion solution, a sheet comprising same, and a display device. The particle dispersion solution, according to one embodiment of the present invention, comprises: an electric insulation fluid; light-absorbing electrophoretic particles, which are dispersed in the electric insulation fluid, having a first area density (S_K) with respect to the electric insulation fluid; and reflective electrophoretic particles, which are dispersed in the electric insulation fluid with the light-absorbing electrophroetic particles, having a second area density (S_C) with respect to the electric insulation fluid, wherein the area ratio (S_C/S_K) of the particles can be selected to satisfy 4 ≤ S_C/S_K ≤ 10.

Description

Particle dispersion solution, sheet and display device comprising same

The present invention relates to display technology, and more particularly, to a particle dispersion solution, a sheet comprising the same, and a display device.

As an information display apparatus for replacing a liquid crystal display apparatus, a display apparatus using a technique such as electrophoresis, electro-chromic, or dichroic particles rotary method is proposed. Has been. These techniques have been extensively studied as next generation display devices that can replace liquid crystal display devices due to advantages such as wide viewing angle, low power consumption and memory effect in proximity to conventional print media. Among these display devices, an electrophoretic display device has two electrodes and electrophoretic particles dispersed between the two electrodes, and utilizes a phenomenon in which the particles flow by an electric field applied between the electrodes. To display visual information.

In the electrophoretic display device, electrophoretic particles dispersed in one pixel or subpixel may include two or more kinds of particles having different sizes, masses, electrical and optical properties. Electrophoretic particles charged within a pixel or sub-pixel may affect display quality, such as contrast and color reproducibility, depending on various factors such as their mixing ratio, particle mobility, particle interaction, and layer formation at the electrode of the particle. I can receive it. Conventionally, it is common to find a family register range of display quality by repetitive experiments through individual control of these factors. However, individual considerations of these factors do not encompass or be independent of various factors such as particle mobility, particle interactions, and layer formation at the electrode of the particle, thus finding a direct association with the display quality of the electrophoretic display device. It is difficult and it is difficult to control the display quality independently through its adjustment.

The technical problem to be achieved by the present invention is the weight, volume, mobility, particles and particles, interaction between particles and electrodes, and particles of different kinds of particles dispersed in a pixel or subpixel of an electrophoretic display device, and Even if the mixing ratio of these materials and the electrically insulating fluid is different, it is to provide a particle dispersion solution which can ensure uniformity of display quality such as contrast ratio and color reproducibility.

Another object of the present invention is to provide an electrophoretic display device having the aforementioned advantages.

In addition, another technical problem to be achieved by the present invention is to provide an electrophoretic display sheet having the above-described advantages.

In addition, another technical problem to be achieved by the present invention is to provide a method for producing a particle dispersion solution having the aforementioned advantages.

Particle dispersion solution according to an embodiment of the present invention for solving the above problems, the electrically insulating fluid; Light absorbing electrophoretic particles dispersed in the electrically insulating fluid and having a first surface area density S _K for the electrically insulating fluid; And the light absorbing type is being dispersed in the electrically insulating liquid with the electrophoretic particles and the second surface area density of the dispersed particles comprising a reflective electrophoretic particles having the (S _C) for the electrical insulation fluid solution. The surface area ratio S _C / S _K of the particles may be selected to satisfy 4 ≦ S _C / S _K ≦ 10.

In some embodiments, the first surface area density (S_K) Is 2,000 cm per 1 ml of the particle dispersion solution.²1 ml of solution ≤ S_K ≤ 8,000 cm²It may be in the range of 1 ml of solution. Further, the second surface area density (S_C15,000 cm per 1 ml of the particle dispersion solution²Solution 1 ml ≤ S_C≤ 25,000 cm²It may be in the range of 1 ml of solution. In addition, the reflective electrophoretic particles may include white or color electrophoretic particles. The electrically insulating fluid may be transparent.

According to an embodiment of the present invention for solving the other problem, there is provided an electrophoretic display sheet comprising an array of a plurality of electrophoretic pixels. The electrophoretic display sheet includes a plurality of electrophoretic pixels comprising two or more adjacent color subpixels, each color subpixel comprising an electrically insulating fluid; Light absorbing electrophoretic particles dispersed in the insulating fluid and having a surface area density (S _K ) for the electrically insulating fluid; And being dispersed in the electrically insulating liquid with the light absorbing type electrophoretic particles and the second surface area density (S _C) for having the reflection type comprising the electrophoretic particles, the surface area ratio of the particles (S for the electrical insulation fluid _C / S _K ) can be selected to satisfy 4 <S _C / S _{K <} 10.

In some embodiments, the first surface area density (S_K) Is 2,000 cm per 1 ml of the particle dispersion solution.²1 ml of solution ≤ S_K ≤ 8,000 cm²It may be in the range of 1 ml of solution. Further, the second surface area density (S_C15,000 cm per 1 ml of the particle dispersion solution²Solution 1 ml ≤ S_C≤ 25,000 cm²It may be in the range of 1 ml of solution.

In some embodiments, the color subpixels comprise yellow, magenta and cyan subpixels, and the color subpixels each comprise reflective electrophoretic particles having a corresponding color with the absorbing electrophoretic particles. Can be. In another embodiment, the color subpixels may comprise red, green and blue subpixels, and the color subpixels may each include reflective electrophoretic particles having a corresponding color together with the absorbing electrophoretic particles. .

In another embodiment, the plurality of electrophoretic pixels may further include white subpixels adjacent to the color subpixels. In this case, the white subpixel may include white reflective electrophoretic particles together with the light absorbing electrophoretic particles.

According to an embodiment of the present invention for solving the above another problem, there is provided an electrophoretic display device comprising a drive element and an array of a plurality of electrophoretic pixels driven by the drive element. The electrophoretic display apparatus, wherein the plurality of electrophoretic pixels comprises two or more adjacent color subpixels, each color subpixel comprising an electrically insulating fluid; Light absorbing electrophoretic particles dispersed in the insulating fluid and having a surface area density (S _K ) for the electrically insulating fluid; And being dispersed in the electrically insulating liquid with the light absorbing type electrophoretic particles and the second surface area density (S _C) for having the reflection type comprising the electrophoretic particles, the surface area ratio of the particles (S for the electrical insulation fluid _C / S _K ) can be selected to satisfy 4 <S _C / S _{K <} 10.

In some embodiments, the first surface area density (S_K) Is 2,000 cm per 1 ml of the particle dispersion solution.²1 ml of solution ≤ S_K ≤ 8,000 cm²It may be in the range of 1 ml of solution. Further, the second surface area density (S_C15,000 cm per 1 ml of the particle dispersion solution²Solution 1 ml ≤ S_C≤ 25,000 cm²It may be in the range of 1 ml of solution.

In some embodiments, the color subpixels comprise yellow, magenta and cyan subpixels, and the color subpixels each comprise reflective electrophoretic particles having a corresponding color with the absorbing electrophoretic particles. Can be. In another embodiment, the color subpixels may include red, green and blue subpixels, and the color subpixels may each include reflective electrophoretic particles having a corresponding color together with the absorbing electrophoretic particles. .

In some embodiments, the plurality of electrophoretic pixels further comprises white subpixels adjacent to the color subpixels, the white subpixels comprising white reflective electrophoretic particles together with the light absorbing electrophoretic particles. can do.

According to an embodiment of the present invention for solving the another problem, the electrically insulating fluid; A method of preparing a particle dispersion solution comprising absorbing electrophoretic particles and reflective electrophoretic particles dispersed together in the electrically insulating fluid is provided. _Mixing the absorbing electrophoretic particles and the reflective electrophoretic particles in the electrically insulating fluid such that the surface area ratio S _C / S _K of the particles satisfies 4 ≦ S _C / S _K ≦ 10. It may include. Where S _K is the first surface area density for the particle dispersion solution of the absorbing electrophoretic particles and S _C is the second surface area density for the particle dispersion solution of the reflective electrophoretic particles.

In some embodiments, the first surface area density (S_K) Is 2,000 cm per 1 ml of the particle dispersion solution.²1 ml of solution ≤ S_K ≤ 8,000 cm²It may be in the range of 1 ml of solution. Further, the second surface area density (S_C15,000 cm per 1 ml of the particle dispersion solution²Solution 1 ml ≤ S_C≤ 25,000 cm²It may be in the range of 1 ml of solution.

According to embodiments of the present invention, by controlling the surface area ratio of the absorbing electrophoretic particles and the reflective electrophoretic particles to the particle dispersion solution, the contents of the reflective electrophoretic particles and the electrically insulating fluid in the particle dispersion solution. The particle dispersing solution is characterized by contrast ratio and color reproducibility, without dependence on the weight, volume, mobility, particle-to-particle interaction, particle-to-electrode interaction, and mixing ratio of the particles to the electrically insulating fluid. Quality control can be performed, and uniform display quality can be provided for each display device.

In addition, according to other embodiments of the present invention, an electrophoretic display device having the above-described advantages may be provided.

In addition, according to another embodiment of the present invention, an electrophoretic display sheet having the above-described advantages can be provided.

In addition, according to another embodiment of the present invention, a method for preparing a particle dispersion solution having the above-described advantages can be provided.

1 is a cross-sectional view showing pixels of an electrophoretic display device according to an embodiment of the present invention.

2A and 2B are graphs illustrating a change in reflectance according to the surface area densities of absorbing electrophoretic particles and reflective electrophoretic particles of a particle dispersion solution according to an exemplary embodiment of the present invention.

3 is a graph showing a change in contrast ratio according to the surface area ratio (S _C / S _K ) of the absorbing electrophoretic particles and the reflective electrophoretic particles obtained based on the measured reflectance values shown in FIGS. 2A and 2B.

4 is a view schematically showing an electrophoretic pixel according to an embodiment of the present invention.

5 is a cross-sectional view showing an electrophoretic display device according to an embodiment of the present invention.

6 is a cross-sectional view showing an electrophoretic display sheet according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art, and the following examples can be modified in various other forms, and the scope of the present invention is It is not limited to an Example. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept to those skilled in the art.

In addition, the thickness or size of each layer in the drawings is exaggerated for convenience and clarity, the same reference numerals in the drawings refer to the same elements. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. Also, as used herein, "comprise" and / or "comprising" specifies the presence of the mentioned shapes, numbers, steps, actions, members, elements and / or groups of these. It is not intended to exclude the presence or the addition of one or more other shapes, numbers, acts, members, elements and / or groups.

Although the terms first, second, etc. are used herein to describe various members, parts, regions, and / or parts, these members, parts, regions, and / or parts should not be limited by these terms. Is self explanatory. These terms are only used to distinguish one member, part, region or part from another region or part. Thus, the first member, part, region, or portion, which will be described below, may refer to the second member, component, region, or portion without departing from the teachings of the present invention.

Embodiments of the present invention will now be described with reference to the drawings, which schematically illustrate ideal embodiments of the present invention. In the drawings, for example, the size and shape of the members may be exaggerated for convenience and clarity of description, and in actual implementation, variations of the illustrated shape may be expected. Accordingly, embodiments of the present invention should not be construed as limited to the specific shapes of the regions shown herein.

As used herein, the term "absorption type electrophoretic particle" means charged particles that absorb electromagnetic waves belonging to most regions of the visible light band, and generally refer to black charged particles. In addition, in this specification, "reflective electrophoretic particles" are charged particles that reflect electromagnetic waves belonging to most regions of the visible light band, for example, white charged particles or charged particles that reflect electromagnetic waves belonging to specific regions of the visible light band. As particles, they refer to colored particles that are not black or white, for example red, green and blue, or color charged particles such as yellow, magenta and cyan.

1 is a cross-sectional view illustrating a pixel 100 of an electrophoretic display device according to an embodiment of the present invention.

Referring to FIG. 1, the pixel 100 includes a particle dispersion solution 30 disposed between first and second substrates 10 and 20 facing each other. At least one of the first substrate 10 and the second substrate 20, for example, the second substrate 20 (also referred to as an upper substrate) may be transparent.

The particle dispersion solution 30 may be stored in an area defined by the plurality of capsules 30S, as shown in FIG. 1. The particle dispersion solution 30 may include an electrically insulating fluid 31, which is a dispersion medium, and electrophoretic particles 32 and 33 dispersed in the electrically insulating fluid 31.

The electrically insulating fluid 31 is a fluid having high viscosity and low viscosity to increase the mobility of the particles 32 and 33. The electrically insulating fluid may have a dielectric constant between about 2 and 30, preferably between 2 and 15.

The electrically insulating fluid 31 may be a single fluid or a mixture of two or more fluids. For example, the electrically insulating fluid 31 is a hydrocarbon-containing solution such as decahydronaphthalene (DECALIN), 5-ethylidene-2-norbornene, fatty acid ester and paraffin oil, toluene, xylene, phenylxylylylethane, dodecylbenzene and aromatic hydrocarbon-containing solutions such as alkylnaphtalene, perfluorodecalin, perfluorotoluene, perfluoroxylene, dichlorobenzotrifluoride, 3,4,5-trichlorobenzotrifluoride, chloropentafluro-benzene, dichlorononane, pentachlorobenzene and tetrachloroethylene. In addition to the electrophoretic particles 32, 33, the electrically insulating fluid 31 contains a charge-controlling agent, a cationic or anionic surfactant, a metal soap, a resin material, a metal-based coupling agent, and a stabilizer. Various functional additives, such as stabilizing agents, can be added.

Electrophoretic particles 32 and 33 dispersed in the electrically insulating fluid 31 are absorbing electrophoretic particles 32 and reflective electrophoretic particles 33 having distinct reflectances that are at least two different types of particles. ) May be included. A plurality of electrodes (not shown) for driving these electrophoretic particles 32 and 33 may be provided between the substrates 10 and 20, and generated when an electrical signal is applied between the plurality of electrodes. These particles 32 and 33 may flow in accordance with the changed electric field, and display information may be provided to the observer 1.

For example, for convenience of description, it is assumed that the light absorbing electrophoretic particles 32 are charged with + and the reflective electrophoretic particles 33 are charged with −. When the second substrate 20 side has a higher voltage than the first substrate 10 side, a vertical electric field from the second substrate 20 toward the first substrate 10 is generated, thereby absorbing electrophoretic particles. The fields 32 are directed towards the first substrate 10 and the reflective electrophoretic particles 33 are directed towards the second substrate 20. As a result, the electrophoretic particles 32 and 33 have a dispersed state as shown in FIG. 1. In this case, the incident light i introduced into the pixel 100 may be reflected by the reflective electrophoretic particles 33 so that the reflected light r may be turned on. In this case, the observer 1 observes light belonging to a wavelength range of the light reflected by the reflective electrophoretic particles 33, and when the plurality of pixels 100 is provided, the reflected light is mixed together with other adjacent pixels. The observer 1 can see the information by the mixed light. If the reflective electrophoretic particles 33 are white particles, the pixel 100 displays white, and if the reflective electrophoretic particles 33 are yellow, magenta or cyan particles, or red, green Or, in the case of blue particles, the pixel 100 displays the corresponding color. In this case, the observer 1 will observe the combined information with the pixel or another adjacent pixel.

When the second substrate 20 side is switched to have a lower voltage than the first substrate 10 side, a vertical electric field is generated from the first substrate 10 to the second substrate 20, thereby absorbing electricity The electrophoretic particles 32 are directed towards the second substrate 20, and the reflective electrophoretic particles 33 are directed towards the first substrate 10. In this case, the incident light i introduced into the pixel 100 may be absorbed by the absorption type electrophoretic particles 32 so that the reflected light r may be turned off. As a result, black information may be displayed to the observer 1.

The particles 32, 33 may differ not only in terms of optical, but also in terms of electrophoretic mobility for distinct drive. To this end, the absorption type electrophoretic particles 32 and the reflection type electrophoretic particles 33 may have different electrical polarities as described above. However, even if the electrical polarities of these particles 32 and 33 are the same, when the mass and / or the charge amount are different from each other, the behavior distinguished from these particles, for example, by controlling the pulse width of the applied voltage signal By assigning this, various information can be displayed.

The electrophoretic particles 32, 33 may be formed by suitable pigments, dyes, polymeric binders or a combination of two or more thereof. The polymer binder which may be applied to the electrophoretic particles 32 and 33 may be a urethane resin, a urea resin, an acrylic resin, a polyester resin, an acrylic urethane resin ( acryl urethane resin, acryl urethane silicone resin, acryl urethane fluoro-carbon polymers, acryl fluorocarbon polymers, silicone resin, acrylic silicone resin (acryl silicone resin), polystyrene resin, styrene acrylic resin, polyolefin resin, butyral resin, vinylydine chloride resin, melamine Melamine resins, phenolic resins, fluorocarbon polymers, polycarbonate resins, polysulfon resins, It is a polymer resin material such as Li ether resin (polyether resin), polyethylene resin (polyethylene resin) and polyimide resin (polyamide resin), and these materials may be used in combination of two or more materials. However, this is exemplary and the present invention is not limited thereto. For example, the resin may be gelatin, alginic acid, latex polymer, polystyrene, polyvinyl formal, polyvinyl butyral, polymethyl acrylate, polybutyl acrylate, polymethyl meta It may also be formed from other polymeric materials such as acrylates, polybutyl methacrylates.

The pigments, dyes and polymeric binders may have inherent charges, but in some embodiments, suitable charge modifiers within or on the polymeric binder surface to actively control the polarity and charge of these particles. It is also possible to disperse or bind the control agent (CCA). For example, anionic polyesters can be used as polymer binders to produce particles with + polarity, and additional charge control agents such as Bontron P5 (available from Orient) can be used to control the amount of + charge. In addition,-in order to produce particles having polarity, anionic polyester can be used as the polymer binder, and Bontron E8 (available from Orient) can be added to control the amount of charge.

From the above-described embodiment, those skilled in the art will appreciate that the weight, volume, mobility, particles of different kinds of particles 32, 33 in which the information displayed to the observer 1 is dispersed in a pixel or subpixel of the electrophoretic display device. It can be appreciated that and may be affected by such parameters as and the interaction between the particles, the particles and the electrode, and the mixing ratio of the particles (32, 33) and the electrically insulating fluid (21). However, having a more determinative effect on the display quality than the microscopic parameters in such a pixel or sub-pixel, and effectively controlling the display quality of the pixel, rather than controlling the characteristics of the particles themselves, disperse the particles as in embodiments of the present invention. This can be achieved through macroscopic property control of the solution itself. Therefore, according to the embodiment of the present invention, it is possible to ensure a uniform display quality for each product through the property control of the particle dispersion solution.

The particle dispersion solution 30 includes the above-described electrically insulating fluid 31 and the absorbing electrophoretic particles 32 and the reflective electrophoretic particles 32 dispersed therewith, and in the particle dispersion solution 30 The surface area ratio _Sc / S _{K of the} absorption type electrophoretic particles 32 and the reflection type electrophoretic particles 32 may be mixed or selected to satisfy Equation 1 below.

[Equation 1]

4 ≤ S _C / S _K ≤10

In Equation 1, S _K is the first surface area density of the absorption type electrophoretic particles 32 for 1 ml of the particle dispersion solution 30, and S _C is the reflection type for 1 ml of the particle dispersion solution 30. Second surface area density of the electrophoretic particles 33. The surface area density of the particles 32, 33 can be obtained by measuring the average particle size of the particles in the particle dispersion solution using the commercially available Zetasizer Nano ZS from Malvern, and converting the surface area assuming that they are spherical particles. .

If the first surface area density S _K and the second surface area density S _C do not satisfy the condition of Equation 1, other microscopic factors in the particle dispersion solution 30, for example reflective electrophoretic particles And controlling the contents of the electrically insulating fluid, the weight, volume, and mobility of the particles, the interaction between the particles and the particles and between the particles and the electrodes, and the mixing ratio of the particles and the electrically insulating fluid, to about 8 or more, preferably It is very difficult to achieve a contrast ratio of 10 or more. However, according to the embodiment of the present invention, the display quality can be controlled only by controlling the surface area ratio (S _C / S _K ) between the solution and the particles, which are macroscopic characteristics of the particle dispersion solution, and within this range. In addition, uniform display quality may be obtained for each display device. This advantage will be described later with reference to FIGS. 2A to 3.

2A and 2B are graphs illustrating a change in reflectance according to the surface area densities of absorbing electrophoretic particles and reflective electrophoretic particles of a particle dispersion solution according to an exemplary embodiment of the present invention.

To prepare absorbing electrophoretic particles, cationic polyester was used as the binder resin, carbon black was used as the black pigment, and it was designed to have a positive charge using Bontron E84 available from Orient Co. as the charge control agent. . Subsequently, after dissolving Bontron NO7 as a charge control agent in the dispersion, polymer compound was induced to prepare light absorbing electrophoretic particles having + polarity. To prepare the reflective electrophoretic particles, similar to the above black electrophoretic particles, an anionic polyester as a binder resin, TiO ₂ as a white pigment was used, and Bontron P84 available from Orient as a charge control agent was used. Thus, white electrophoretic particles were obtained. These particles were prepared in various ways such that the weight, size, and charge amount all differed in the samples below. Light-absorbing electrophoretic particles and white electrophoretic particles prepared in Isopar G (specific gravity 0.75) as an electrically insulating fluid are mixed within a suitable range to prepare particle dispersion solutions having various surface area densities, and filled into electrophoretic display pixels. Reflectance was measured.

In the graphs shown in Figs. 2A and 2B, the reflectance (%) is the pixel when the absorbing electrophoretic particles (see 32 in Fig. 1) are raised to the front of the pixel and the white electrophoretic particles (see 33 in Fig. 1) are pixels. It is measured from the intensity of the reflected light with respect to the intensity of the incident light respectively observed when floating to the front. The reflectance measurement is performed by producing an electrophoretic pixel as shown in FIG. 1, irradiating halogen light as a light source in a dark room and evaluating the luminance of the reflected light using a luminance measuring device (CS-200) of Konica Minolta Co. It was. In addition, a standard white reflector (SRS-99) from Labspher Co. was used. Table 1 below shows the surface area density (S _K , S _C ), surface area ratio (S _C / S _K ), reflectance and contrast ratio of the black and white particles in 1 ml of various particle dispersion solutions prepared.

Table 1

Sample	Black Electrophoretic Particles (S K )	White Electrophoretic Particles (S C )	S C / S K	Black particle reflectance (%)	White particle reflectance (%)	Contrast
One	515.2	25470.1	49.4	26.07	57.1	2.2
2	1320.8	24750.5	18.7	10.48	52.62	5.0
3	2561.3	19047.6	7.4	3.23	47.86	14.8
4	2590.0	21628.8	8.4	3.42	49.54	14.5
5	2697.9	24371.5	9.0	3.78	43.38	11.5
6	2747.3	19447.8	7.1	3.3	49.3	14.9
7	3187.4	20037.1	6.3	3.14	46.43	14.8
8	3251.1	23026.2	7.1	3.78	38.14	10.1
9	3275.1	23854.4	7.3	3	39.92	13.3
10	3383.7	21039.0	6.2	3.6	44.3	12.3
11	3475.4	19447.8	5.6	3.3	43.4	13.2
12	3821.0	15300.0	4.0	3.2	30.6	9.6
13	4021.0	13200.0	3.3	3.2	21.6	6.8
14	4041.5	19447.8	4.8	3	42.2	14.1
15	4081.0	14200.0	3.5	3.2	23.6	7.4
16	4161.3	23099.6	5.6	2.67	35.96	13.5
17	4359.0	18520.0	4.2	3.1	26.5	8.5
18	6215.0	24923.0	4.0	3.1	40.2	13.0
19	8420.0	19447.8	2.3	3.7	25.3	6.8

Referring to Table 1, the surface area density (S _K ) of the black electrophoretic particles of the prepared particle dispersion solution was 515.2, 1320.8, 2561.3, 2590.0, 2697.9, 2747.3, 3187.4, 3251.1, 3275.1, 3383.7, 3475.4, 3821.0, 4021, 0, may be present in a 500 cm ² / 1ml solution to 10,000 cm ² / 1ml solution containing a range 4041.5, 4081.0, 4161.3, 4359.0, 6215.0 and 8420.0. Likewise, the surface area density (S _C ) of white electrophoretic particles is from 13,000 to 13,0000.0, 14200.0, 15300.0, 18520.0, 19074.6, 19447.8, 20037.1, 21039.0, 21628.8, 23026.2, 23099.6, 23854.4, 24371.5, 24750.5, 24923.0, and 25470.1. 30,000 cm may be present in the ² / 1ml solution range. The specific gravity and size of these particles are different for each sample.

Referring to FIG. 2A, for black electrophoretic particles, for the first surface area density S _K of the black electrophoretic particles, the black reflectance follows a hypothetical curve (VC) with y = 2522x ^-0.804 (R² = 0.7391). Indicates. In contrast, in the case of white electrophoretic particles, referring to FIG. 2B, the second surface area density S _C of the white electrophoretic particles is 13,000 cm ² / solution 1ml ≤ S _K ≤ 30,000 cm ² / solution 1ml, the reflectance is, It can be seen that it appears discretely in the range of 20% to 60% without any obvious tendency.

In some embodiments, as shown in FIG. 2A, the first surface area density S_K) 2,000 cm per 1 ml of the particle dispersion solution ²1 ml of solution Within the above range, a reflectance of 5% or less can be obtained when displaying black information. 2B, the second surface area density S_C15,000 cm per 1 ml of the particle dispersion solution²When the solution is 1 ml or more, a reflectance of 25% or more can be obtained.

Although the above-described embodiments relate to white electrophoretic particles and black electrophoretic particles, those skilled in the art, even in the case of electrophoretic particles having a color other than white instead of white electrophoretic particles, reflectivity required for that color It will be appreciated that it can be controlled to have a suitable surface area density within the ranges illustrated. When the reflective electrophoretic particles have a color other than black and white, the second surface area density (S) based on the absorption type electrophoretic particles (S)_C15,000 cm ²1 ml of solution If less, the surface area density of the light-absorbing electrophoretic particles 32 may be relatively high, thereby reducing color reproducibility. The first surface area density (S) of such absorption type electrophoretic particles_C8,000 cm ²1 ml of solution It is preferable that it is the following. Further, the second surface area density (S_C25,000 cm²/ 1ml solution may weaken the black expressive power. In the case of color reproducibility, it may be competitive with the reflectance, but it is possible to secure a certain level of color and black reflectance without losing color reproducibility within the above range.

3 is a graph showing a change in contrast ratio according to the surface area ratio (S _C / S _K ) of the absorbing electrophoretic particles and the reflective electrophoretic particles obtained based on the measured reflectance values shown in FIGS. 2A and 2B. The contrast ratio values of the graphs are shown in Table 1.

Referring to FIG. 3, when the surface area ratio S _C / S _K is less than 4, the control ratio has a value of less than 8, with 6.8 (samples 13, 19), and 7.4 (sample 15). In addition, even when the surface area ratio S _C / S _K exceeds 10, it has a value of less than 8, 5.0 (sample 2) and 2.2 (sample 1). Typically, a suitable contrast ratio is 8 or more for the electrophoretic display device to be commercialized.

When the surface area ratio is 10 or less, the change in reflectance by the light absorbing electrophoretic particles is not large, but the change in reflectance by the reflecting electrophoretic particles is large. However, according to the embodiment of the present invention, by controlling the surface area ratio _Sc / S _K within the range of 4 to 10, the electrophoretic display device can be designed to have an excellent contrast ratio of 8 or more.

Although the above-described embodiment relates to white electrophoretic particles and black electrophoretic particles, those skilled in the art, even in the case of electrophoretic particles having a color other than white instead of white electrophoretic particles, reflectivity required for that color It will be appreciated that within the ranges exemplified in accordance with the present invention, it can be controlled to have a suitable surface area ratio for the absorption type electrophoretic particles.

As mentioned above, in a two particle system comprising at least black / white electrophoretic particles, an excellent contrast ratio can be obtained when the surface area ratio of each particle in the particle dispersion solution satisfies Equation 1. While the foregoing embodiments relate to a two-particle system with black / white electrophoretic particles, the particle dispersion solution may include colorants exhibiting color, i.e. transparent particles that do not include pigments and / or dyes. The invention is not limited thereto. It may also be applied to a two particle system comprising black electrophoretic particles and colored electrophoretic particles having a color other than white, as described below.

4 is a diagram schematically showing an electrophoretic pixel 200 according to an embodiment of the present invention.

Referring to FIG. 4, the electrophoretic pixel 200 may include two or more subpixels adjacent to each other. In some embodiments, in order to implement a multi-color display device, the electrophoretic pixel 200 may include a plurality of color sub pixels 40Y, 40M, and 40C. The color sub pixels 40Y, 40M, and 40C may be yellow, magenta, and cyan sub pixels, respectively. In this case, the color subpixels 40Y, 40M, and 40C, together with the above-mentioned absorption type electrophoretic particles 32, respectively, have reflective electrophoretic particles having a corresponding color, that is, yellow, magenta and cyan ( 33Y, 33M, 33C). In another embodiment, the color sub pixels 40Y, 40M, 40C may be red, green and blue sub pixels, respectively. In this case, the color subpixels 40Y, 40M, and 40C, respectively, together with the above-described light-absorbing electrophoretic particles 32, have reflective electrophoretic particles 33Y having a corresponding color, that is, red, green, and blue. 33M, 33C).

The particle dispersion solution 30 constituting the electrophoretic pixel 200 includes particles prepared to have a surface area density determined by Equation 1, and preferably, the electrically insulating fluid 31 may be colorless and transparent. . Accordingly, control of the display quality can be easily achieved by merely controlling the surface area density of the particles with respect to the electrically insulating fluid, and ensuring excellent color reproduction of the electrophoretic pixel 200.

In some embodiments, the electrophoretic pixel 200 further adds a white subpixel 40W adjacent to the aforementioned color subpixels 40Y, 40M, 40C to increase the white and black saturation to further improve the contrast ratio. It may include. The white sub-pixel 40W may include white reflective electrophoretic particles 33W together with the absorption type electrophoretic particles 32 as described above.

The subpixels that make up the electrophoretic pixel 200 may be arranged in a quadrangular shape, as shown in FIG. 4, but this is exemplary. For example, the sub-pixels constituting the electrophoretic pixel 200 may be arranged in the form of a line, or may have a polygonal shape such as hexagon, octagon, concentric circles, or a combination thereof, but the present invention is not limited thereto. . In addition, although FIG. 4 illustrates the microcapsule 30S as a means for storing the particle dispersion solution, this is exemplary, and the cavity is defined by a partition structure as described below between each pixel or subpixel, The microcapsules 30S may be disposed in the cavity, or the particle dispersion solution may be directly stored in the cavity without the microcapsules 30S. In another embodiment, the particle dispersion solution may be stored in a known microcup structure or other various types of cavity structures, polymer dispersed structures, but the present invention is not limited thereto.

5 is a cross-sectional view of an electrophoretic display apparatus 300 according to an embodiment of the present invention.

Referring to FIG. 5, at least one cavity V1 and V2 between a first substrate 10 (which may be a lower substrate in this drawing) and a second substrate 20 (which may be an upper substrate in this drawing) facing each other. , A light conversion layer 70 comprising V3) may be provided. At least one of the lower substrate 10 and the upper substrate 20, for example, the upper substrate 20 on the observer 1 side may be formed of a transparent material such as glass and transparent resin.

The cavities V1, V2, V3 may be defined by the partition 30R, which is a separating member, as shown. However, this is exemplary and the cavities V1, V2, V3 may be defined by other separating members such as microcup structures or microcapsules as is well known in the art. The cavities V1, V2, V3, alone or in combination with other adjacent one or more cavities, may constitute one sub-pixel or pixel.

In one embodiment, the electrophoretic display device 300 may include electrodes 41 (42Y, 42M, 42C) for driving the electrophoretic particles 32 (33Y, 33M, 33C). The electrodes 41 and 42 may have a configuration opposite to each other so as to generate an electric field perpendicular to the main surfaces of the substrates 10 and 20, as shown. The electrodes 42Y, 42M, 42C disposed on the lower substrate 10 may be individual electrodes that can be independently addressed for each pixel by a suitable switching element such as a transistor, and the electrodes 41 on the upper substrate 20 may be provided. ) May be a common electrode opposite the individual electrodes. However, the above-described electrode configuration is exemplary and the present invention is not limited thereto. For example, it may have a known in-plane configuration or a combination thereof. In addition, at least one of these electrodes 41 and 42, for example, the common electrode, may be a transparent electrode formed of Indium-Tin-Oxide (ITO) or another transparent conductor.

Individual electrodes 42Y, 42M, 42C can be driven by an active matrix that includes transistors 50 as switching elements. However, this is only illustrative, and those skilled in the art will appreciate that a passive matrix type electrode configuration, or a segment type electrode configuration and wiring structure for static driving are also included in the embodiments of the present invention.

In the cavity (V1, V2, V3) is filled with an electrically insulating fluid 31, reflective electrophoretic particles (33Y, 33M) for displaying white or color information with the above-mentioned absorbing electrophoretic particles (32) , 33C) is dispersed in the electrically insulating fluid 31. According to an embodiment of the present invention, by controlling the surface area density of the light-absorbing electrophoretic particles and the reflective electrophoretic particles, which are electrically insulating fluids and information display particles, the weight, volume, mobility, between particles and particles, Pixels of a two-particle system with uniform display quality, such as contrast ratio and color reproducibility, can be provided without being greatly affected by the interaction between and the electrode.

6 is a cross-sectional view showing an electrophoretic display sheet 400 according to an embodiment of the present invention. Components having the same reference numerals as those of FIG. 5 among the components illustrated in FIG. 6 may refer to the above-described disclosure as long as there is no contradiction, and a description thereof will be omitted below.

Referring to FIG. 6, the electrophoretic display sheet 400 includes two support substrates 15 and 20 facing each other that do not include a drive element. At least one of the support substrates 15 and 20, for example, the support substrate 20 on the observer side may be a transparent substrate. In some embodiments, the support substrate 15 may include a wiring layer 45 for electrical coupling with a substrate 10 (also referred to as a backplane) on which drive elements are described below. The wiring layer 45 may include conductive patterns formed on both main surfaces of the support substrate 15 and conductive vias connecting the conductive patterns. As another example, the wiring layer 45 may not be formed on the supporting substrate 15. In this case, the individual electrodes 42 and the cavities V1, V2, V3 formed on the lower substrate 10 are electrically separated by the supporting substrate 15.

A plurality of partition walls 30R, which are separation members, may be disposed between the support substrates 15 and 20. A plurality of cavities V1, V2, and V3 may be provided between the supporting substrates 15 and 20 by the plurality of partitions 30R. These cavities V1, V2, V3, alone or in combination with other adjacent one or more cells, may constitute the aforementioned sub-pixel or pixel. The separating member defining the cavities V1, V2, V3 may be, for example, in addition to the illustrated partition structure, for example, known microcapsules, microcup structures, various other types of cavity structures, polymer dispersed structures, or their It may have a combined configuration as described above.

Within each of the cavities V1, V2, V3, the above-mentioned absorption type electrophoretic particles 32 as information display particles and reflective electrophoretic particles having white or color for implementing the corresponding sub-pixel or pixel ( 33Y, 33M, 33C) can be dispersed, and by these particles, the display quality of the corresponding subpixel or pixel can be made uniform.

As such, when the electrophoretic display sheet 400 is completed, the electrophoretic display sheet 400 as shown in FIG. 5 is bonded by coupling the electrophoretic display sheet 400 to the lower substrate 10 including the driving element 50. Can be provided. Bonding between the electrophoretic display sheet 400 and the lower substrate 10 may be accomplished by an adhesive layer 85. The adhesive layer 85 may be any suitable resin-based adhesive layer or an anisotropic conductive adhesive layer. When the adhesive layer 85 is an anisotropic conductive adhesive layer, the adhesive layer 85 may extend over the entire area of the electrophoretic display sheet 400 and the lower substrate 10.

In the embodiment shown, the electrodes 41, 45 for driving the electrophoretic particles 32, 33Y, 33M, 33C have opposite electrode configurations, but this is exemplary and the invention is not limited thereto. For example, it is to be understood that known in-plane electrode configurations in which drive electrodes are formed on any of the substrates are within the scope of the present invention.

Features disclosed with respect to the electrophoretic display device and the electrophoretic display sheet described above may be implemented interchangeably or in combination, as long as there is no contradiction. In addition, although the above-described embodiments disclose a multi-color electrophoretic display device, the monochrome display device may be implemented by filling the cavities V1, V2, and V3 with only white electrophoretic particles and black electrophoretic particles.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and alterations are possible within the scope without departing from the technical spirit of the present invention, which are common in the art. It will be apparent to those who have knowledge.

Claims (20)

1. Electrically insulating fluids;

   Light absorbing electrophoretic particles dispersed in the electrically insulating fluid and having a first surface area density S _K for the electrically insulating fluid; And

   A particle dispersion solution comprising reflective electrophoretic particles dispersed in the electrically insulating fluid with the light absorbing electrophoretic particles and having a second surface area density (S _C ) for the electrically insulating fluid,

   And the surface area ratio (S _C / S _K ) of the particles is selected to satisfy 4 ≦ S _C / S _K ≦ 10.
2. The method of claim 1,

   The first surface area density (S_K) Is 2,000 cm per 1 ml of the particle dispersion solution.²1 ml of solution ≤ S_K ≤ 8,000 cm²It is in the range of 1 ml of solution / particle dispersion solution characterized by the above-mentioned.
3. The method of claim 1,

   Wherein said second surface area density (S _C ) is in the range of 15,000 cm ² / solution 1 ml ≤ S _C ≤ 25,000 cm ² / solution 1 ml per 1 ml of the particle dispersion solution.
4. The method of claim 1,

   Wherein said reflective electrophoretic particles comprise white or colored electrophoretic particles.
5. The method of claim 1,

   And the electrically insulating fluid is transparent.
6. An electrophoretic display sheet comprising an array of a plurality of electrophoretic pixels,

   The plurality of electrophoretic pixels comprises two or more adjacent color subpixels, each color subpixel comprising an electrically insulating fluid; Light absorbing electrophoretic particles dispersed in the insulating fluid and having a surface area density (S _K ) for the electrically insulating fluid; And reflective electrophoretic particles dispersed with the absorbing electrophoretic particles in the electrically insulating fluid and having a second surface area density (S _C ) for the electrically insulating fluid,

   The surface area ratio (S _C / S _K ) of the particles is selected to satisfy 4 <S _C / S _{K <} 10.
7. The method of claim 6,

   The first surface area density (S_K) Is 2,000 cm per 1 ml of the particle dispersion solution.²1 ml of solution ≤ S_K ≤ 8,000 cm²It is in the range of 1 ml of solution / particle dispersion solution characterized by the above-mentioned.
8. The method of claim 6,

   Wherein said second surface area density (S _C ) is in the range of 15,000 cm ² / solution 1 ml ≤ S _C ≤ 25,000 cm ² / solution 1 ml per 1 ml of the particle dispersion solution.
9. The method of claim 6,

   Wherein said color subpixels comprise yellow, magenta and cyan subpixels, said color subpixels each comprising reflective electrophoretic particles having a corresponding color together with said absorbing electrophoretic particles. Youngdong display sheet.
10. The method of claim 6,

    Wherein said color subpixels comprise red, green and blue subpixels, said color subpixels each comprising reflective electrophoretic particles having a corresponding color together with said absorbing electrophoretic particles. Sheet.
11. The method of claim 6,

    The plurality of electrophoretic pixels further comprises a white subpixel adjacent to the color subpixels,

    And said white sub-pixel comprises white reflective electrophoretic particles together with said absorbing electrophoretic particles.
12. An electrophoretic display device comprising a drive element and an array of a plurality of electrophoretic pixels driven by the drive element.

    The plurality of electrophoretic pixels comprises two or more adjacent color subpixels, each color subpixel comprising an electrically insulating fluid; Light absorbing electrophoretic particles dispersed in the insulating fluid and having a surface area density (S _K ) for the electrically insulating fluid; And reflective electrophoretic particles dispersed with the absorbing electrophoretic particles in the electrically insulating fluid and having a second surface area density (S _C ) for the electrically insulating fluid,

    The surface area ratio (S _C / S _K ) of the particles is selected to satisfy 4 ≦ S _C / S _K ≦ 10.
13. The method of claim 12,

    The first surface area density (S_K) Is 2,000 cm per 1 ml of the particle dispersion solution.²1 ml of solution ≤ S_K ≤ 8,000 cm²It is in the range of 1 ml of solution / particle dispersion solution characterized by the above-mentioned.
14. The method of claim 12,

    Wherein said second surface area density (S _C ) is in the range of 15,000 cm ² / solution 1 ml ≤ S _C ≤ 25,000 cm ² / solution 1 ml per 1 ml of the particle dispersion solution.
15. The method of claim 12,

    Wherein said color subpixels comprise yellow, magenta and cyan subpixels, said color subpixels each comprising reflective electrophoretic particles having a corresponding color together with said absorbing electrophoretic particles. Youngdong display device.
16. The method of claim 12,

    Wherein said color subpixels comprise red, green and blue subpixels, said color subpixels each comprising reflective electrophoretic particles having a corresponding color together with said absorbing electrophoretic particles. Device.
17. The method of claim 12,

    The plurality of electrophoretic pixels further comprises a white subpixel adjacent to the color subpixels,

    And the white subpixel comprises white reflective electrophoretic particles together with the light absorbing electrophoretic particles.
18. Electrically insulating fluids; A method of preparing a particle dispersion solution comprising absorbing electrophoretic particles and reflective electrophoretic particles dispersed together in the electrically insulating fluid,

    _Mixing the absorbing electrophoretic particles and the reflective electrophoretic particles in the electrically insulating fluid such that the surface area ratio S _C / S _K of the particles satisfies 4 ≦ S _C / S _K ≦ 10. Include,

    Wherein S _K is a first surface area density for the particle dispersion solution of the absorbing electrophoretic particles, and S _C is a second surface area density for the particle dispersion solution of the reflective electrophoretic particles. Way.
19. The method of claim 18,

    The first surface area density (S_K) Is 2,000 cm per 1 ml of the particle dispersion solution.²1 ml of solution ≤ S_K ≤ 8,000 cm²It is in the range of 1 ml / solution, The manufacturing method of the particle-dispersion solution characterized by the above-mentioned.
20. The method of claim 18,

    And said second surface area density (S _C ) is in the range of 15,000 cm ² / solution 1 ml ≤ S _C ≤ 25,000 cm ² / solution 1 ml per 1 ml of the particle dispersion solution.

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