Electrophoretic compositions and methods for their preparation

Abstract

The present disclosure relates to an electrophoretic composition and a method of preparing the same, and more particularly, to an electrophoretic composition and a method of preparing the same suitable for a transmissive variable device using an electrophoresis method. According to exemplary embodiments of the present disclosure, it is possible to provide an electrophoretic composition and a method of preparing the same which minimize a sedimentation problem caused by gravity and allow a pattern in which electrophoretic particles are stably dispersed in a solvent.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2021-0115829, filed with the Korean Intellectual Property Office on August 31, 2021, the disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure relates to electrophoretic compositions and methods for their preparation, and more particularly to electrophoretic compositions and methods for their preparation that can be applied to variable transmission devices using electrophoresis. Background Technology

[0004] Recently, smart windows that control energy loss and light transmission through windows are being rapidly applied to vehicle rearview mirrors, projection screens, and window panels for showrooms.

[0005] Among the smart window implementation methods developed to date, polarized particle methods, liquid crystal methods, electrochromic methods, photochromic methods, and thermochromic methods have been reported. Of these, electrochromic (EC) devices that electrically control light transmission are representative examples. In the case of EC, essentially, the colored thin film partially absorbs light to control transmission, which leads to product stability issues when the temperature rises and makes it difficult to scale up the area due to the technical difficulties of the manufacturing process.

[0006] Another method for realizing smart windows is to employ transmission control technology using electrophoretic particles. According to this method, if charged black nanoparticles in a high-boiling-point organic matrix are injected between finely patterned ITO electrodes and a voltage is applied, the black nanoparticles move in a dispersed state to the patterned electrode region, thereby controlling transmission. The advantage of this electrophoretic nanoparticle smart window is that the transparent / opaque state can be freely adjusted instantaneously depending on whether a voltage is applied.

[0007] However, the solvents used in electrophoretic compositions are typically hydrocarbon-based solvents or silicone oils with low dielectric constants and specific gravities of 0.7 to 0.9. The specific gravities of typical electrophoretic particles are 1.7 to 1.9, which are much higher than those of the solvents. This results in a significant deterioration in particle actuation due to poor particle settling caused by gravity when the electrophoresis apparatus is mounted vertically.

[0008] Meanwhile, Korean Patent Registration No. 10-0711746 discloses an electrophoretic particle and its preparation method, wherein the electrophoretic particle is prepared by controlling the charge polarity and charge amount of the electrophoretic particle to a desired charged state. However, it does not propose a method to minimize particle sedimentation and interparticle aggregation.

[0009] [Related Technical Documents]

[0010] [Patent Literature]

[0011] (Patent Document 1) Korean Patent Registration No. 10-0711746 Summary of the Invention

[0012] The objective of this disclosure is to provide an electrophoretic composition and a method for preparing the same, wherein the electrophoretic composition can be used in a transmission control device employing electrophoresis.

[0013] According to an exemplary embodiment, a method for preparing an electrophoretic composition includes: mixing and refluxing porous carbon particles with an acid; neutralizing with an alkali after cooling; preparing porous carbon particles with COOH and OH groups introduced on their surface by washing and drying; mixing and primary dispersing the porous carbon particles with COOH and OH groups introduced on their surface, a dispersant containing NH groups, and a solvent; forming a porous carbon particle-dispersant complex by heating the primary dispersed mixture; obtaining the porous carbon particle-dispersant complex formed by removing unreacted material; and additionally adding the dispersant and controlling the concentration of the dispersant to form micelles in the complex.

[0014] In some exemplary embodiments, the specific surface area of ​​the porous carbon particles can be 200 m². 2 / g to 2000m 2 / g.

[0015] In some exemplary embodiments, the acid may be nitric acid (HNO3), sulfuric acid (H2SO4), hydrochloric acid (HCl), hydrobromic acid (HBr), hydroiodic acid (HI), perchloric acid (HClO4), or a mixture thereof.

[0016] In some exemplary embodiments, the mixing and reflux of porous carbon particles and acid can be carried out at 100°C to 120°C for 2 to 10 hours.

[0017] In some exemplary embodiments, the base may be sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonia (NH3), lithium acetate (CH3COOLi), sodium acetate, potassium acetate (CH3COOK), sodium bicarbonate (NaHCO3), potassium bicarbonate (KHCO3), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), or a mixture thereof.

[0018] In some exemplary embodiments, the solvent may be an isoparaffin solvent with a specific gravity of 0.6 to 1.0.

[0019] In some exemplary embodiments, the dispersant containing NH groups may be polyisobutylene succinimide (PIBSI).

[0020] In some exemplary embodiments, primary dispersions can be performed 5 to 15 times at pressures ranging from 10,000 Psi to 25,000 Psi.

[0021] In some exemplary embodiments, the mixture after primary dispersion is heated at 50°C to 80°C.

[0022] In some exemplary embodiments, in obtaining the formed porous carbon particle-dispersant complex by removing unreacted material, the lower layer can be collected by primary centrifugation, followed by secondary dispersion, and then the upper layer can be collected by secondary centrifugation.

[0023] In some exemplary embodiments, 30% or less of the lower layer can be collected from the entire solution after primary centrifugation.

[0024] In some exemplary embodiments, one to five secondary dispersions can be performed at pressures ranging from 10,000 Psi to 25,000 Psi.

[0025] In some exemplary embodiments, 70% or less of the upper layer can be collected from the entire solution after two centrifugations.

[0026] In some exemplary embodiments, after the upper layer is collected by secondary centrifugation, an additional dispersant containing NH groups may be added so that the weight ratio of porous carbon particles to dispersant is 1:2 to 7.

[0027] According to an exemplary embodiment, an electrophoretic composition comprising a specific surface area of ​​200 m² can be provided. 2 / g to 2000m 2 / g of porous carbon particles, a complex of dispersant and solvent.

[0028] In some exemplary embodiments, the weight ratio of porous carbon particles to dispersant can be from 1:2 to 7.

[0029] In some exemplary embodiments, the composite may be formed by reacting porous carbon particles containing COOH and OH groups on the surface with a dispersant containing NH groups.

[0030] In some exemplary embodiments, the dispersant may be polyisobutylene succinimide (PIBSI).

[0031] In some exemplary embodiments, the specific gravity of the porous carbon particle-dispersant composite may be 1.1 to 1.2.

[0032] According to exemplary embodiments of the present disclosure, electrophoretic compositions and methods thereof can be provided that minimize sedimentation problems caused by gravity and allow electrophoretic particles to maintain a stable dispersion pattern in a solvent. Detailed Implementation

[0033] Exemplary embodiments of this disclosure will now be described in more detail. However, the following exemplary embodiments described in this specification are illustrative of preferred exemplary embodiments of this disclosure and are intended to further understand the technical spirit of this disclosure in conjunction with the foregoing summary of the invention. Therefore, this disclosure should not be construed as being limited to the following.

[0034] In this specification, "electrophoretic composition" refers to an ink composition for use in an electrophoresis apparatus, and specifically to a composition comprising chargeable particles, a dispersant, and a solvent.

[0035] According to an exemplary embodiment, the method for preparing an electrophoretic composition disclosed herein includes: mixing and refluxing porous carbon particles with an acid, neutralizing with an alkali after cooling, preparing porous carbon particles having COOH and OH groups introduced on the surface by washing and drying, mixing the porous carbon particles having COOH and OH groups on the surface, a dispersant containing NH groups, and a solvent for primary dispersion, forming a porous carbon particle-dispersant complex by heating the primary dispersed mixture, obtaining the formed porous carbon particle-dispersant complex by removing unreacted material, and additionally adding the dispersant, and controlling the concentration of the dispersant to form micelles in the complex.

[0036] In the step of mixing and refluxing porous carbon particles and acid, porous carbon particles and acid are injected into the reactor for mixing and refluxing.

[0037] According to an exemplary embodiment, the porous carbon particles have a regular or irregular structure and have non-uniform micropores formed therein. The porous carbon particles aggregate and have hollow portions formed therein.

[0038] As a specific exemplary embodiment, the specific surface area of ​​the porous carbon particles can be 200 m². 2 / g to 2000m 2 / g, preferably 500m 2 / g to 1700m 2 / g, more preferably 700m 2 / g to 1500mm 2 / g.

[0039] When the specific surface area is less than 200 m² 2 At a specific surface area of ​​2000 m² / g, the settling velocity of electrophoretic particles increases due to gravity. 2 At a concentration of / g, the electrophoretic particles could not be dispersed satisfactorily. The amount of dispersion added to the composition increased significantly, which in turn increased the viscosity and caused a significant decrease in the driving speed.

[0040] As a specific example, the acid can be nitric acid (HNO3), sulfuric acid (H2SO4), hydrochloric acid (HCl), hydrobromic acid (HBr), hydroiodic acid (HI), perchloric acid (HClO4), or a mixture thereof. Preferably, the acid can be a mixture of nitric acid and sulfuric acid, more preferably a mixture of nitric acid and sulfuric acid in a concentration ratio of 3:0.5 to 2.

[0041] As a specific exemplary embodiment, the step of mixing and refluxing the porous carbon particles with the acid can be carried out at 100°C to 120°C for 5 to 24 hours. Preferably, the mixing and refluxing step can be carried out at 105°C to 115°C for 8 to 18 hours, and more preferably at 108°C to 112°C for 10 to 16 hours.

[0042] In the neutralization step following cooling, the reactants are cooled after reflux and then neutralized with alkali to form byproducts that can be removed by washing.

[0043] As a specific exemplary embodiment, the alkali may be sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonia (NH3), lithium acetate (CH3COOLi), sodium acetate (CH3COONa), potassium acetate (CH3COOK), sodium bicarbonate (NaHCO3), potassium bicarbonate (KHCO3), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), or a mixture thereof.

[0044] As a concrete example, alkali can be added until the pH reaches the desired neutral pH. For example, the reactants can be neutralized to a pH in the range of about 5.0 to about 8.0 or about 6.0 to about 7.5.

[0045] In the step of preparing porous carbon particles with COOH and OH groups introduced on the surface by washing and drying, the neutralized reactants are first washed with water or distilled water to remove water-soluble byproducts. During the washing process, impurities or byproducts are removed by filtration using filter cloth, filter, or sieve, for example, a vacuum filter can be used.

[0046] After washing, the porous carbon particles still contain a predetermined amount of moisture, thus exhibiting viscosity and being deformable. Therefore, the moisture is completely removed through a drying process. Porous carbon particles with COOH and OH groups introduced on their surface can be obtained.

[0047] However, the exemplary embodiments are not limited thereto. As a drying method, freeze-drying or supercritical drying can be used, with freeze-drying being preferred. Freeze-drying can be performed using known freeze-drying methods. For example, during freeze-drying, the temperature can be set in the range of about -90°C to -50°C, specifically in the range of about -85°C to -60°C, and more specifically in the range of about -80°C to -70°C. Simultaneously, the drying or freeze-drying is carried out under reduced pressure, with the pressure being about 600 Torr or lower, specifically about 1 Torr to 100 Torr, and more specifically about 2 Torr to 10 Torr.

[0048] The step of mixing and primary dispersing porous carbon particles with COOH and OH groups introduced on the surface, a dispersant containing NH groups, and a solvent is to uniformly mix and disperse the porous carbon particles with COOH and OH groups introduced on the surface with the dispersant and solvent.

[0049] For primary dispersion, known dispersion devices can be used, including dispersers, high-pressure dispersers, nano-high-pressure dispersers, and ultrasonic dispersers. Even without particular limitations, when using a high-pressure disperser, porous carbon particles with COOH and OH groups introduced on their surfaces and the dispersant can be uniformly mixed and dispersed in the solvent. Therefore, the COOH and OH groups on the surface of the porous carbon particles react positively with the NH groups of the dispersant to form a porous carbon particle-dispersant complex.

[0050] A dispersant containing NH groups reacts with COOH groups on the surface of porous carbon particles to form amide bonds, allowing at least a portion to form a porous carbon particle-dispersant complex. This porous carbon particle-dispersant complex can form micelles in a solvent. The dispersant ensures that the porous carbon particles and the porous carbon particle-dispersant complex are uniformly dispersed throughout the solvent, preventing aggregation in one area.

[0051] As a specific exemplary embodiment, the dispersant containing NH groups may be polyisobutylene succinimide (PIBSI).

[0052] As a specific exemplary embodiment, based on porous carbon particles with COOH and OH groups introduced on the surface, a dispersant containing NH groups can be included in a weight ratio of 0.5 to 4:1.

[0053] As a specific exemplary embodiment, a mixture of alkanes having 6 to 13 carbon atoms and an isoparaffin solvent with a specific gravity of 0.6 to 1.0 can be used as the solvent. For example, isopar C, isopar G, isopar E (Exxon), ISOL-C (SK Chem), or ISOL-G (Exxon) can be used.

[0054] As a specific example, 5 to 15 primary dispersions can be performed under pressures of 10,000 Psi to 25,000 Psi. Preferably, 7 to 13 primary dispersions can be performed under pressures of 12,000 Psi to 24,000 Psi, and more preferably 9 to 11 primary dispersions can be performed under pressures of 15,000 Psi to 23,000 Psi. Within this range, the dispersibility and dispersion stability of porous carbon particles with COOH and OH groups introduced on the surface can be significantly improved.

[0055] The step of heating the initially dispersed mixture allows the COOH and OH groups on the surface of the porous carbon particles, which are uniformly mixed and dispersed in the solvent, to react with the NH groups of the dispersant to form a porous carbon particle-dispersant complex. Heating can be carried out at 50°C to 80°C to form the porous carbon particle-dispersant complex through a stable reaction.

[0056] In the step of obtaining the formed porous carbon particle-dispersant complex by removing unreacted material, filtration or centrifugation is used to remove unreacted porous carbon particles, dispersant, and other byproducts.

[0057] As a specific exemplary embodiment, in the step of obtaining the formed porous carbon particle-dispersant complex by removing unreacted material, the reaction solution containing the porous carbon particle-dispersant complex is first centrifuged to collect the lower layer, then secondarily dispersed, and then secondarily centrifuged to collect the upper layer.

[0058] The lower layer, which may be 30% by volume or less, can be collected from the entire solution after primary centrifugation.

[0059] In secondary dispersion, the porous carbon particle-dispersant complex contained in the lower layer can be uniformly dispersed. For secondary dispersion, known dispersion devices such as dispersers, high-pressure dispersers, nano-high-pressure dispersers, and ultrasonic dispersers can be used. Even without particular limitations, high-pressure dispersers are preferably used.

[0060] As a specific example, one to five secondary dispersions can be performed under pressures ranging from 10,000 Psi to 25,000 Psi. Preferably, two to four secondary dispersions can be performed under pressures ranging from 12,000 Psi to 24,000 Psi, and more preferably, three secondary dispersions can be performed under pressures ranging from 15,000 Psi to 23,000 Psi. Within this range, the dispersibility and dispersion stability of the porous carbon particle-dispersant composite can be significantly improved.

[0061] When performing a second centrifugation and collecting the supernatant, centrifugation is used to remove the poorly dispersed lower layer. At this point, 70% or less of the supernatant can be collected from the entire solution after the second centrifugation.

[0062] In the step of adjusting the concentration of the dispersant to form micelles from the complex, the dispersant is added at a critical micelle concentration (CMC) or higher. In this way, the porous carbon particle-dispersant complex can generate micelles in a solvent.

[0063] As a specific exemplary embodiment, a dispersant is added to achieve a porous carbon particle to dispersant weight ratio of 1:2 to 7. When the dispersant is added within the above range, the micelle shape of the porous carbon particle-dispersant composite is not disrupted. When energized, excellent driving performance of the electrophoretic particles and transmission modulation performance of the electrophoresis apparatus can be maintained.

[0064] As an exemplary embodiment, an electrophoretic composition comprising a specific surface area of ​​200 m² can be provided. 2 / g to 2000m 2 / g of porous carbon particles and dispersant complex and solvent.

[0065] In some exemplary embodiments, the weight ratio of porous carbon particles to dispersant is preferably 1:2 to 7.

[0066] The composite is formed by reacting porous carbon particles containing COOH and OH groups on the surface with a dispersant containing NH groups, and the composite can form micelles.

[0067] In some exemplary embodiments, the specific gravity of the porous carbon particle-dispersant composite can be from 1.1 to 1.2. In this case, the specific gravity difference with the solvent is minimized to suppress sedimentation failure due to gravity and to increase the driving velocity of the electrophoretic particles when energized.

[0068] In the electrophoretic composition, the porous carbon particles containing COOH and OH groups, the dispersant containing NH groups, the solvent, and the complex of the porous carbon particles and the dispersant correspond to a configuration substantially the same as that described in the method for preparing the electrophoretic composition. Therefore, a description thereof will be omitted.

[0069] In the following description, although preferred embodiments are presented for better understanding of this disclosure, these embodiments are merely illustrative and not intended to limit the scope of the appended claims. Various modifications and alterations will be apparent to those skilled in the art without departing from the scope and spirit of the invention, and such modifications and alterations are intended to fall within the scope of the appended claims.

[0070] Examples and Comparative Examples

[0071] Example 1

[0072] 10g with a specific surface area of ​​1200m² 2 / g of porous carbon particles, 120ml of nitric acid (HNO3) and 40ml of sulfuric acid (H2SO4) were added to a flask equipped with a reflux apparatus and refluxed at 110°C for 5 hours. Afterwards, the product was neutralized with 5% NaOH after cooling the flask to room temperature. The product was then filtered through a vacuum filter and washed with distilled water, followed by freezing with liquid nitrogen to remove moisture, and then freeze-dried to obtain porous carbon particles with COOH and OH groups introduced on their surface.

[0073] Using a high-pressure disperser, 8 wt% polyisobutylene succinimide (PIBSI) as a dispersant and 4 wt% porous carbon particles with COOH and OH groups introduced on their surface were dispersed 10 times in 88 wt% isopar L as a solvent at approximately 23,000 Psi. After heating to approximately 80 °C, the reaction mixture was centrifuged to collect approximately 30 vol% of the lower layer. The collected lower layer was redistributed three times using a high-pressure disperser at approximately 23,000 Psi. It was then centrifuged to collect approximately 70 vol% of the upper layer. By measuring the absorbance and solids content of the collected upper layer, additional polyisobutylene succinimide (PIBSI) was added to make the weight ratio of dispersant to porous carbon particles (dispersant / porous carbon particles) approximately 5.0 to prepare the electrophoretic composition.

[0074] An electrophoresis apparatus is made by injecting an electrophoresis composition into a pre-prepared electrophoresis cell.

[0075] Example 2

[0076] In addition to using 10g with a specific surface area of ​​approximately 2000m² 2 In addition to porous carbon particles of / g, porous carbon particles, electrophoretic compositions, and electrophoretic apparatus with COOH and OH groups introduced on the surface were prepared using the same method as in Example 1.

[0077] Example 3

[0078] In addition to using 10g with a specific surface area of ​​approximately 200m² 2 In addition to porous carbon particles of / g, porous carbon particles, electrophoretic compositions, and electrophoretic apparatus with COOH and OH groups introduced on the surface were prepared using the same method as in Example 1.

[0079] Example 4

[0080] Except for preparing the electrophoretic composition by adding polyisobutylene succinimide (PIBSI) to make the weight ratio of dispersant to porous carbon particles (dispersant / porous carbon particles) about 7.0, porous carbon particles, electrophoretic compositions, and electrophoretic apparatus with COOH and OH groups introduced on the surface were prepared using the same method as in Example 1.

[0081] Example 5

[0082] Except for preparing the electrophoretic composition by adding polyisobutylene succinimide (PIBSI) to make the weight ratio of dispersant to porous carbon particles (dispersant / porous carbon particles) about 2.0, porous carbon particles, electrophoretic compositions and electrophoretic devices with COOH and OH groups introduced on the surface were prepared using the same method as in Example 1.

[0083] Comparative Example 1

[0084] Using a high-pressure disperser at approximately 23,000 Psi, 8 wt% polyisobutylene succinimide (PIBSI) and 4 wt% polyisobutylene succinimide with a specific surface area of ​​approximately 1200 m² were dispersed as a dispersant. 2 / g porous carbon particles (10g) were dispersed 10 times in 88 wt% isopar L as solvent. The dispersion was centrifuged to collect approximately 70 vol% of the upper layer. By measuring the absorbance and solids content of the collected upper layer, polyisobutylene succinimide (PIBSI) was additionally added to achieve a dispersant-to-porous carbon particle weight ratio (dispersant / porous carbon particles) of approximately 5.0 to prepare the electrophoretic composition.

[0085] An electrophoresis apparatus is made by injecting an electrophoresis composition into a pre-prepared electrophoresis tank.

[0086] Comparative Example 2

[0087] Using a high-pressure disperser, 8 wt% polyisobutylene succinimide (PIBSI) as a dispersant and 4 wt% porous carbon particles with COOH and OH groups introduced on their surface, prepared according to Example 1, were dispersed 10 times in 88 wt% isopar L as a solvent at approximately 23,000 Psi. The dispersion was centrifuged to collect approximately 70 vol% of the upper layer. By measuring the absorbance and solids content of the collected upper layer, additional polyisobutylene succinimide (PIBSI) was added to bring the weight ratio of dispersant to porous carbon particles (dispersant / porous carbon particles) to approximately 5.0 to prepare the electrophoretic composition.

[0088] An electrophoresis apparatus is made by injecting an electrophoresis composition into a pre-prepared electrophoresis tank.

[0089] Comparative Example 3

[0090] Using a high-pressure disperser at approximately 23,000 Psi, 8 wt% polyisobutylene succinimide (PIBSI) and 4 wt% polyisobutylene succinimide with a specific surface area of ​​approximately 1200 m² were dispersed as a dispersant. 2 / g porous carbon particles (10g) were dispersed 10 times in 88% by weight isopar L as solvent. After heating to about 80°C, the reaction mixture was centrifuged to collect about 70% by volume of the upper layer. By measuring the absorbance and solids content of the collected upper layer, polyisobutylene succinimide (PIBSI) was added to make the weight ratio of dispersant to porous carbon particles (dispersant / porous carbon particles) about 5.0 to prepare the electrophoretic composition.

[0091] An electrophoresis apparatus is made by injecting an electrophoresis composition into a pre-prepared electrophoresis tank.

[0092] Comparative Example 4

[0093] Except for the preparation of the electrophoretic composition by adding polyisobutylene succinimide (PIBSI) to make the weight ratio of dispersant to porous carbon particles (dispersant / porous carbon particles) about 1.5, porous carbon particles, electrophoretic compositions and electrophoretic devices with COOH and OH groups introduced on the surface were prepared using the same method as in Example 1.

[0094] Comparative Example 5

[0095] Except for the preparation of the electrophoretic composition by adding polyisobutylene succinimide (PIBSI) to make the weight ratio of dispersant to porous carbon particles (dispersant / porous carbon particles) about 9.0, the porous carbon particles, electrophoretic composition and electrophoretic device with COOH and OH groups introduced on the surface were prepared using the same method as in Example 1.

[0096] Comparative Example 6

[0097] In addition to using 10g with a specific surface area of ​​approximately 2400m² 2 In addition to porous carbon particles of / g, porous carbon particles, electrophoretic compositions, and electrophoretic apparatus with COOH and OH groups introduced on the surface were prepared using the same method as in Example 1.

[0098] Comparative Example 7

[0099] In addition to using 10g with a specific surface area of ​​approximately 100m² 2 In addition to porous carbon particles of / g, porous carbon particles, electrophoretic compositions, and electrophoretic apparatus with COOH and OH groups introduced on the surface were prepared using the same method as in Example 1.

[0100] Experimental Example

[0101] Experimental Example 1: Particle Size Analysis of Electrophoretic Composition

[0102] The particle size of the particles contained in the electrophoretic compositions prepared according to the examples and comparative examples was analyzed. After diluting the electrophoretic compositions with Isopar-L to make the weight ratio of the electrophoretic composition to Isopar-L 1:1000, the particle size was measured using a particle size analyzer (Otsuka Electrons, ELSZ-2000).

[0103] Experimental Example 2: Evaluation of the shielding performance of the electrophoresis apparatus

[0104] The electrophoresis apparatus prepared according to the embodiments and comparative examples was placed on a backlight plate (brightness of 1000 Cd / m²). 2 The brightness was measured using a luminance measurement device (SANPOMETER Co., Ltd., SM208) before the DC voltage was applied.

[0105] Experimental Example 3: Evaluation of the transmittance of the electrophoresis apparatus

[0106] The device prepared according to the embodiments and comparative examples was placed on a backlight panel (brightness of 1000 Cd / m²). 2 The device was driven by applying a 30V DC voltage using a DC power supply (TOYOTECH Corporation, DP20-3TP). The luminance (Max) after 30 seconds of applying the DC voltage was measured using a luminance measurement device (SANPOMETER Co., Ltd., SM208).

[0107] The brightness of the empty device without the electrophoretic composition injected was 900 Cd / m. 2 .

[0108] Experiment Example 4: Evaluation of the driving speed of the electrophoresis apparatus

[0109] The device prepared according to the embodiments and comparative examples was placed on a backlight panel (brightness of 1000 Cd / m²). 2 The particle was driven by applying a 30V DC voltage using a DC power supply (TOYOTECH Corporation, DP20-3TP). After applying the 30V DC voltage, a brightness measurement device (SANPOMETER Co., Ltd., SM208) was used to measure the time it took for the particle movement to reach 80% of its maximum brightness.

[0110] The measurement results of the experimental example are shown in Table 1 below.

[0111] [Table 1]

[0112]

[0113] Referring to Table 1, it was confirmed that, compared to Comparative Examples 1 to 4 and Comparative Examples 7, the driving speed and shielding performance of the electrophoresis apparatus including the electrophoresis compositions of Examples 1 to 5 prepared according to this disclosure were significantly improved. Specifically, it was confirmed that even 20 days after the preparation of the electrophoresis apparatus, the driving speed, shielding, and transmittance remained unchanged or almost unchanged. In contrast, in the cases of Comparative Examples 1 to 7, it was confirmed that the driving speed and transmittance decreased significantly after 20 days of preparation. Specifically, compared to the examples, it was confirmed that in Comparative Examples 1 to 3, which were prepared differently from the preparation method according to this disclosure, the driving speed was reduced by at least 1.3 times to at most 2 times, and the transmittance decreased significantly after 20 days of preparation.

Claims

1. A method for preparing an electrophoretic composition, the method comprising: Mix and reflux porous carbon particles with acid; Neutralize with alkali after cooling; Porous carbon particles with COOH and OH groups introduced on the surface were prepared by washing and drying. The porous carbon particles with COOH and OH groups introduced on the surface, the dispersant containing NH groups, and the solvent are mixed and initially dispersed. A porous carbon particle-dispersant complex is formed by heating a mixture that has undergone primary dispersion, wherein the NH groups of the dispersant react with the COOH groups on the surface of the porous carbon particles to form amide bonds, such that at least a portion of the porous carbon particle-dispersant complex can be formed. The resulting porous carbon particle-dispersant complex was obtained by removing unreacted material; and The dispersant is added in addition, and the concentration of the dispersant is controlled to allow the complex to form micelles.

2. The method for preparing an electrophoretic composition according to claim 1, wherein the porous carbon particles have a specific surface area of ​​200 m². 2 / g to 2000 m 2 / g.

3. The method for preparing an electrophoretic composition according to claim 1, wherein the acid is nitric acid (HNO3), sulfuric acid (H2SO4), hydrochloric acid (HCl), hydrobromic acid (HBr), hydroiodic acid (HI), perchloric acid (HClO4), or a mixture thereof.

4. The method for preparing an electrophoretic composition according to claim 1, wherein the base is sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonia (NH3), lithium acetate (CH3COOLi), sodium acetate, potassium acetate (CH3COOK), sodium bicarbonate (NaHCO3), potassium bicarbonate (KHCO3), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), or a mixture thereof.

5. The method for preparing an electrophoretic composition according to claim 1, wherein the solvent is an isoparaffin solvent with a specific gravity of 0.6 to 1.

0.

6. The method for preparing an electrophoretic composition according to claim 1, wherein the dispersant containing NH groups is polyisobutylene succinimide (PIBSI).

7. The method for preparing an electrophoretic composition according to claim 1, wherein the primary dispersion is carried out 5 to 15 times at a pressure of 10,000 Psi to 25,000 Psi.

8. The method for preparing an electrophoretic composition according to claim 1, wherein in obtaining the formed porous carbon particle-dispersant complex by removing unreacted material, the lower layer is collected by primary centrifugation, a secondary dispersion is performed, and then the upper layer is collected by secondary centrifugation.

9. The method for preparing an electrophoretic composition according to claim 8, wherein 30% by volume or less of the lower layer is collected from the entire solution after primary centrifugation.

10. The method for preparing an electrophoretic composition according to claim 8, wherein the secondary dispersion is carried out 1 to 5 times at a pressure of 10,000 Psi to 25,000 Psi.

11. The method for preparing an electrophoretic composition according to claim 8, wherein 70% by volume or less of the upper layer is collected from the entire solution after two centrifugations.

12. The method for preparing an electrophoretic composition according to claim 1, wherein in controlling the concentration of the dispersant to form micelles of the composite, the dispersant is additionally added to control the concentration such that the weight ratio of the porous carbon particles to the dispersant is 1:2 to 7.

13. An electrophoretic composition comprising: Specific surface area is 200 m² 2 / g to 2000 m 2 / g of a composite of porous carbon particles and a dispersant, wherein the composite is formed by heating a dispersion mixture of porous carbon particles with COOH and OH groups introduced onto their surface, a dispersant containing NH groups, and a solvent; and Solvent.

14. The electrophoretic composition according to claim 13, wherein the weight ratio of the porous carbon particles to the dispersant is 1:2 to 7.

15. The electrophoretic composition according to claim 13, wherein the complex is formed by reacting porous carbon particles containing COOH and OH groups on the surface with a dispersant containing NH groups.

16. The electrophoretic composition of claim 13, wherein the porous carbon particles and the complex of the dispersant form micelles.

17. The electrophoretic composition according to claim 13, wherein the dispersant is polyisobutylene succinimide (PIBSI).

18. The electrophoretic composition according to claim 13, wherein the specific gravity of the porous carbon particles to the dispersant is 1.1 to 1.2.

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