Ink composition with improved sedimentation properties and transmittance-variable display using same

Abstract

The present invention relates to an electrophoretic ink composition having variable transmittance properties. The ink composition comprises: nano-ink particles which have a coating layer and consist of porous parent particles; a solvent in which the nano-ink particles are mixed; and a dispersant which is mixed in the solvent and performs a function of uniformly dispersing the nano-ink particles in the solvent, wherein the nano-ink particles have a sedimentation rate of <0.5 μm / day in the solvent.

Description

Ink composition with improved sedimentation characteristics and variable transmittance display using the same

[0001] The present invention relates to an ink composition and a transmittance variable display using the same, and more particularly, to an ink composition with improved sedimentation characteristics applied to a film whose transmittance varies according to an external electrical signal, and a transmittance variable display using the same.

[0002] An electrically variable transmittance film is a film that can control the amount of light transmitted through it. A variable transmittance film can be constructed by inserting a variable transmittance layer containing liquid crystals or dispersed polarization particles between two opposing transparent conductive films. When no electric field is applied, the liquid crystals or dispersed polarization particles are irregularly arranged, scattering light and reducing transmittance. However, when an electric field is applied, the particles become more regular, increasing transmittance.

[0003] For the variable transmittance layer whose transmittance is controlled by such an electric field, ink in the form of particles capable of blocking light dispersed in a solvent is typically used. When a variable transmittance film is manufactured using the ink, the particles settle due to gravity over time. If the particle sedimentation phenomenon occurs, the variable transmittance film may not operate quickly even when an electric field is applied, or the particle may clump together, preventing normal variable transmittance operation.

[0004] To solve these problems, research and development is currently being conducted in the form of microbanks or microcapsules to limit the distance at which particles can settle.

[0005] However, these methods of limiting the sedimentation distance had a problem in that the permeability variable characteristics were reduced compared to existing inks because bank materials or capsule wall materials existed together with particles.

[0006] The present invention aims to solve various problems, including the above-described problems, by improving the sedimentation characteristics of ink applied to a variable transmittance film, thereby providing an ink composition that can be commercialized without additional sedimentation distance restrictions, and a variable transmittance film using the same. However, these tasks are exemplary and the scope of the present invention is not limited thereby.

[0007] In order to solve the above problem, an ink composition with improved sedimentation characteristics according to the idea of ​​the present invention comprises nano ink particles made of porous mother particles having a coating layer; a solvent in which the nano ink particles are mixed; and a dispersant mixed in the solvent to perform the function of evenly dispersing the nano ink particles within the solvent; wherein the nano ink particles can have a sedimentation velocity characteristic of <0.5 μm / day within the solvent.

[0008] Additionally, according to the present invention, the porous particles may be made of an organic pigment or an inorganic pigment.

[0009] Additionally, according to the present invention, the porous particles may include at least one of carbon black, titanium dioxide, barium dioxide, manganese dioxide, copper oxide, polystyrene, and polymethacrylate.

[0010] Additionally, according to the present invention, the porous particles may have an average particle size of 10 nm to 200 nm.

[0011] Additionally, according to the present invention, the porosity of the porous particles may be 50% or more.

[0012] In addition, according to the present invention, the coating layer may include a primary coating layer composed of an inorganic material and an organic material; and a secondary coating layer formed with a negative charge on the primary coating layer to increase the repulsive force of particles.

[0013] Additionally, according to the present invention, the thickness of the coating layer may be 2 nm to 50 nm, and preferably 2 nm to 20 nm.

[0014] Additionally, according to the present invention, the surface zeta potential of the nano ink particles may be -15 mV to -50 mV.

[0015] Additionally, according to the present invention, the solvent may include at least one selected from the group comprising isoparaffinic hydrocarbons.

[0016] Additionally, according to the present invention, the density difference between the solvent and the nano ink particles may be 0.6 or less (greater than 0).

[0017] According to the present invention for solving the above problem, a variable transmittance film comprises: a first transparent electrode layer; a second transparent electrode layer formed to face the first transparent electrode layer; and an electrophoretic ink layer formed between the first transparent electrode layer and the second transparent electrode layer; wherein the electrophoretic ink layer comprises: nano-ink particles formed of porous mother particles having a coating layer; a solvent in which the nano-ink particles are mixed; and a dispersant mixed in the solvent to perform the function of evenly dispersing the nano-ink particles in the solvent; wherein the nano-ink particles may be characterized in that they have a sedimentation velocity characteristic of <0.5 μm / day in the solvent.

[0018] Additionally, according to the present invention, the porous particles may be made of an organic pigment or an inorganic pigment.

[0019] Additionally, according to the present invention, the porous particles may include at least one of carbon black, titanium dioxide, barium dioxide, manganese dioxide, copper oxide, polystyrene, and polymethacrylate.

[0020] Additionally, according to the present invention, the porous particles may have an average particle size of 10 nm to 200 nm.

[0021] Additionally, according to the present invention, the porosity of the porous particles may be 50% or more.

[0022] In addition, according to the present invention, the coating layer may include a primary coating layer composed of an inorganic material and an organic material; and a secondary coating layer formed with a negative charge on the primary coating layer to increase the repulsive force of particles.

[0023] Additionally, according to the present invention, the thickness of the coating layer may be 2 nm to 50 nm, and preferably 2 nm to 20 nm.

[0024] Additionally, according to the present invention, the surface zeta potential of the nano ink particles may be -15 mV to -50 mV.

[0025] Additionally, according to the present invention, the solvent may include at least one selected from the group comprising isoparaffinic hydrocarbons.

[0026] Additionally, according to the present invention, the density difference between the solvent and the nano ink particles may be 0.6 or less (greater than 0).

[0027] According to various embodiments of the present invention, as described above, by utilizing an ink composition with improved sedimentation characteristics, a variable permeability film with improved durability and permeability characteristics can be provided. Of course, the scope of the present invention is not limited by these effects.

[0028] FIG. 1 is an exemplary drawing showing the structure of nanoparticles used in an ink composition with improved sedimentation characteristics according to one embodiment of the present invention.

[0029] Figure 2 is a drawing showing the results of measuring sedimentation characteristics according to an embodiment of the present invention.

[0030] Figure 3 is a drawing showing the results of measuring sedimentation characteristics according to a comparative example of the present invention.

[0031] FIG. 4 is an exemplary drawing showing the structure of a variable transmittance film using an ink composition with improved sedimentation characteristics according to one embodiment of the present invention.

[0032] <Explanation of symbols>

[0033] 10: Nano ink particles

[0034] 12: Porous particles

[0035] 14: Coating layer

[0036] 20: Solvent

[0037] 100: Variable transmittance film

[0038] 110: Electrophoretic ink layer

[0039] 120: First transparent electrode layer

[0040] 140: Second transparent electrode layer

[0041] Hereinafter, various preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

[0042] The embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. The following embodiments may be modified in various ways, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to more faithfully and completely explain the present disclosure and to fully convey the spirit of the present invention to those skilled in the art. In addition, the thickness and size of each layer in the drawings are exaggerated for convenience and clarity of explanation.

[0043] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the present invention. As used herein, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. Furthermore, when used herein, the words "comprise" and / or "comprising" specify the presence of stated features, numbers, steps, operations, parts, elements, and / or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, parts, elements, and / or groups thereof.

[0044] Hereinafter, embodiments of the present invention will be described with reference to drawings schematically illustrating ideal embodiments of the present invention. In the drawings, variations in the shapes depicted may be expected, for example, depending on manufacturing techniques and / or tolerances. Therefore, embodiments of the present invention should not be construed as limited to the specific shapes of the regions depicted herein, but should include, for example, variations in shapes resulting from manufacturing processes.

[0045] FIG. 1 is an exemplary drawing showing the structure of nanoparticles used in an ink composition with improved sedimentation characteristics according to one embodiment of the present invention.

[0046] Referring to FIG. 1, an ink composition with improved sedimentation characteristics according to one embodiment of the present invention includes nano ink particles (10). In the ink composition, the sedimentation rate of the nano ink particles (10) can satisfy a rate of settling a distance of less than 0.5 μm per day in a solvent (<0.5 μm / day).

[0047] Specifically, these nano ink particles may be composed of porous mother particles (12) having a coating layer (14). In general, the settling properties of particles in an ink composition are affected by the type of mother particles, the coating layer coated on the surface of the mother particles, the solvent, and the dispersant.

[0048] [Formula 1]

[0049]

[0050] (Here, V s is the particle settling velocity (cm / sec), and g is the acceleration of gravity (980 cm / sec 2 ) and ρ s is the density of the particles (g / cm 3 ) and ρ is the density of the liquid (g / cm 3 ), d is the particle diameter (cm), and μ is the viscosity coefficient of the liquid (g / cm·sec).

[0051] As shown in the above equation 1, referring to Stokes' law, the above equation 1 is a formula for calculating the frictional force that a fluid exerts on an object in fluid dynamics, and can be understood as a law regarding the settling velocity of a particle in a fluid.

[0052] Accordingly, the smaller the particle size and the higher the particle porosity, the lower the particle density itself, which can improve sedimentation in ink. Taking this into account, the present invention utilized porous particles (12) with small particle size and low density.

[0053] For example, the porous particles (12) may be composed of an organic pigment or an inorganic pigment. The porous particles (12) may include, for example, at least one of carbon black, titanium dioxide, barium dioxide, manganese dioxide, copper oxide, polystyrene, and polymethacrylate.

[0054] The porous mother particles (12) may have an average particle size of 10 nm to 200 nm. The average particle size of the porous mother particles (12) is measured by the dynamic light scattering (DLS) method using a Nanoparticle Sizer device. The average particle size refers to the average value of the values ​​of the diameter of the porous mother particles (12) repeatedly measured more than 100 times using the above-described method. If the size of the porous mother particles (12) is less than 10 nm, the particle size is too small, which makes it difficult to control when applied to a variable transmittance film. On the other hand, if the size of the porous mother particles (12) exceeds 200 nm, the particle size becomes very large, making it impossible to obtain an improved sedimentation rate.

[0055] In order to maintain an appropriate settling speed, the porosity of the porous mother particle (12) must be at least 50% or more. If the porosity is less than 50%, the density increases and the effect of improving the settling speed cannot be obtained.

[0056] In addition, if these porous particles are used as they are, there may be a problem in that it is difficult to control the repulsive force between particles as the lipid-soluble solvent flows into the porous portion of the particles.

[0057] To solve this problem, in the present invention, a coating layer (14) was formed by coating the surface of the porous particle (12) with inorganic and organic materials to prevent solvent from flowing into the surface.

[0058] The thickness of the coating layer (14) may be 2 nm to 50 nm. If the thickness of the coating layer (14) is less than 2 nm, the porous portion of the particles may not be blocked, which may increase the possibility of the lipid-soluble solvent flowing in. On the other hand, if the thickness of the coating layer (14) exceeds 50 nm, the coating layer (14) becomes excessively thick, making it difficult to control the particles, and the density of the nano ink particles increases, making it difficult to obtain the effect of improving the sedimentation rate. Therefore, based on these contents, the thickness of the coating layer (14) may be controlled to 2 nm to 50 nm, and preferably 2 nm to 20 nm. More preferably, the coating layer (14) may be formed with a thickness of 2 nm to 10 nm.

[0059] The coating layer (14) may include at least two layers, for example, a primary coating layer (14a) made of inorganic materials and organic materials, and a secondary coating layer (14b) formed with a negative charge on the primary coating layer to maximize the repulsive force of particles.

[0060] The primary coating layer (14a) formed of inorganic and organic materials may be formed of, for example, any one of silica, titanium dioxide, polystyrene, and polymethacrylate. The terminal group of the secondary coating layer (14b) formed with a negative charge may be formed of, for example, any one of -F, -OH, and -COOH.

[0061] The surface zeta potential of the nano ink particles (10) on which the secondary coating layer (14b) having a negative charge is formed may be -15 mV to -50 mV. If the surface zeta potential of the nano ink particles (10) exceeds -15 mV, the repulsive force between particles cannot be maintained, whereas if it is less than -50 mV, the repulsive force between particles becomes excessively high, which causes a problem in that it is difficult to control the ink particles.

[0062] In addition, the ink composition includes a solvent (not shown) in which nano ink particles (10) are mixed, and further includes a dispersant (not shown) mixed into the solvent to perform the function of evenly dispersing the nano ink particles (10) within the solvent.

[0063] The solvent may include at least one selected from the group consisting of isoparaffinic hydrocarbons. In addition, the density difference between the solvent and the nano ink particles (10) may be 0.6 or less (greater than 0). If the density difference between the solvent and the nano ink particles (10) exceeds 0.6, the effect of improving the sedimentation rate cannot be obtained, and therefore, the density difference must be controlled to be 0.6 or less. In addition, if there is no density difference, it is difficult to expect not only the sedimentation of the nano ink particles (10) but also the dispersion effect, and therefore, the density difference must be controlled to maintain an appropriate density difference.

[0064] Hereinafter, a method for manufacturing an electrophoretic ink layer (110) applied to a variable transmittance display (100) using the aforementioned nano ink particles (10) is briefly described.

[0065] First, nano ink particles (10) having a coating layer (14) formed thereon are manufactured using the materials described above. Thereafter, the nano ink particles (10) having a coating layer (14) formed thereon are dispersed in a solvent in which a dispersant is dissolved to manufacture electrophoretic ink. At this time, the dispersant may include any one of glycol ether, acetylene glycol, alkanolamide, sorbitol derivative, alkyl amine, quaternary amine, imidazoline, dialkyl oxide, and sulfosuccinate. Accordingly, use as a dispersant is not particularly limited, and any substance having similar properties to the above materials may be used.

[0066] The manufactured electrophoretic ink is injected between the first transparent electrode layer (120) and the second transparent electrode layer (140) to manufacture the electrophoretic ink layer (110). At this time, in order to maintain the gap between the first transparent electrode layer (120) and the second transparent electrode layer (140), a partition wall (not shown) of a certain height may exist between the two electrodes (120, 140). The height of the partition wall (not shown) is not limited, but is set to 15 µm to 120 µm. The height of the partition wall (not shown) is exemplary, and may be controlled differently depending on the size and extent of the nano ink particles (10) dispersed in the electrophoretic ink.

[0067] Alternatively, when applying electrophoretic ink to electrodes (120, 140) without a barrier, microbeads at a desired interval can be mixed with the electrophoretic ink and applied to produce an electrophoretic ink layer (110). At this time, the size of the microbeads is not limited, but is set to 10 μm to 100 μm. The height of the microbead size is also exemplary, and can be controlled differently depending on the size and extent of inclusion of nano ink particles (10) dispersed in the electrophoretic ink.

[0068] Hereinafter, in order to confirm the difference in sedimentation velocity according to the size and shape of the porous mother particles of the present invention, the sedimentation velocity of nano ink particle samples with organic and inorganic coatings on particles having the characteristics described in Table 1 below was analyzed and shown in FIGS. 2 and 3, respectively.

[0069] Example of classification (Fig. 2) Comparative example (Fig. 3) Total density (g / cm) 3 )Coating particle 1.30771.7487Bare@Organic / inorganic coating Instability Index 0.0010.0148 Sedimentation velocity (㎛ / day) 0.2×10 -3 37.9×10 -3

[0070] Figures 2 and 3 are results of measuring sedimentation characteristics according to examples and comparative examples of the present invention. (In the drawings, the position on the horizontal axis represents time, and the sedimentation rate (%) on the vertical axis represents the sedimentation speed of the particles.)

[0071] Referring to Table 1, Figures 2 and 3, it was confirmed that the true density of the nano ink particles according to the embodiment of the present invention was lower than that of the nano ink particles according to the comparative example, and that the sedimentation velocity of the nano ink particles according to the embodiment was improved by about 200 times compared to the sedimentation velocity of the nano ink particles according to the comparative example.

[0072] Below, a variable permeability film using the ink composition with improved sedimentation characteristics described above is specifically described. Hereinafter, a detailed description of the same composition as described above for the ink composition is omitted.

[0073] FIG. 4 is an exemplary drawing showing the structure of a variable transmittance film using an ink composition with improved sedimentation characteristics according to one embodiment of the present invention.

[0074] Referring to FIG. 4, a variable transmittance film (100) according to one embodiment of the present invention includes a first transparent electrode layer (120), a second transparent electrode layer (140), and an electrophoretic ink layer (110). The second transparent electrode layer (140) is formed to face the first transparent electrode layer (120). The electrophoretic ink layer (110) is formed between the first transparent electrode layer (120) and the second transparent electrode layer (140).

[0075] The electrophoretic ink layer (110) includes the nano ink particles (10) described above with reference to FIG. 1, and has a structure in which a plurality of nano ink particles (10) are uniformly dispersed in a solvent (20) to which a dispersant (not shown) is added.

[0076] The first transparent electrode layer (120) and the second transparent electrode layer (140) are implemented as front electrodes in a planar shape, and examples of the conductive material forming the first transparent electrode layer (120) and the second transparent electrode layer (140) include metals or transparent conductive oxides such as ITO. The first transparent electrode layer (120) and the second transparent electrode layer (140) are not limited to the term and may be implemented as a transparent conductive material as well as a translucent conductive material.

[0077] The nano ink particles (10) provided in the electrophoretic ink layer (110) are particles that can move by an electric field, and may be, for example, particles having a positive (+) or negative (-) charge, or particles having a zeta charge.

[0078] Nano ink particles (10) uniformly dispersed within the solvent (20) included in the electrophoretic ink layer (110) have their positions changed by an electric field. For example, when no electric field is applied, the nano ink particles (10) are dispersed and positioned within the solvent (20). The light transmittance is reduced by the dispersed nano ink particles (10). Conversely, when an electric field is applied, the nano ink particles (10) move downward or upward due to the electric field, thereby changing the transmittance. At this time, the positions of the nano ink particles (10) can be controlled depending on the strength of the electric field.

[0079] While the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will appreciate that various modifications and equivalent alternative embodiments are possible. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the appended claims.

Claims

1. Nano ink particles composed of porous particles having a coating layer; A solvent in which the nano ink particles are mixed; and A dispersant is mixed into the solvent and performs the function of evenly dispersing the nano ink particles within the solvent; An ink composition wherein the nano ink particles have a sedimentation velocity characteristic of <0.5 μm / day in the solvent.

2. In paragraph 1, An ink composition wherein the porous particles are made of an organic pigment or an inorganic pigment.

3. In paragraph 1, The above porous particles include at least one of carbon black, titanium dioxide, barium dioxide, manganese dioxide, copper oxide, polystyrene and polymethacrylate. Ink composition.

4. In paragraph 1, An ink composition wherein the porous particles have an average particle size of 10 nm to 200 nm.

5. In paragraph 1, An ink composition wherein the porosity of the porous particles is 50% or more.

6. In paragraph 1, An ink composition, wherein the coating layer comprises a first coating layer made of an inorganic material and an organic material; and a second coating layer having a negative charge formed on the first coating layer to increase the repulsive force of particles.

7. In paragraph 1, An ink composition wherein the thickness of the coating layer is 2 nm to 50 nm.

8. In paragraph 1, An ink composition wherein the surface zeta potential of the above nano ink particles is -15 mV to -50 mV.

9. In paragraph 1, An ink composition wherein the solvent comprises at least one selected from the group consisting of isoparaffinic hydrocarbons.

10. In paragraph 1, An ink composition wherein the density difference between the solvent and the nano ink particles is 0.6 or less (greater than 0).

11. First transparent electrode layer; A second transparent electrode layer formed to face the first transparent electrode layer; and An electrophoretic ink layer formed between the first transparent electrode layer and the second transparent electrode layer; The electrophoretic ink layer comprises nano ink particles made of porous particles having a coating layer; a solvent in which the nano ink particles are mixed; and a dispersant mixed in the solvent to perform the function of evenly dispersing the nano ink particles in the solvent. A variable transmittance display, wherein the nano ink particles have a sedimentation velocity characteristic of <0.5 μm / day in the solvent.

12. In paragraph 11, The above porous particles are a display with variable transmittance, made of organic pigments or inorganic pigments.

13. In paragraph 11, A display having variable transmittance, wherein the porous particles comprise at least one of carbon black, titanium dioxide, barium dioxide, manganese dioxide, copper oxide, polystyrene, and polymethacrylate.

14. In paragraph 11, A display with variable transmittance, wherein the porous particles have an average particle size of 10 nm to 200 nm.

15. In paragraph 11, A display having variable transmittance, wherein the porosity of the porous particles is 50% or more.

16. In paragraph 11, A display with variable transmittance, wherein the coating layer comprises a first coating layer made of an inorganic material and an organic material; and a second coating layer having a negative charge formed on the first coating layer to increase the repulsion of particles.

17. In paragraph 11, A display with variable transmittance, wherein the thickness of the coating layer is 2 nm to 50 nm.

18. In paragraph 11, A display having variable transmittance, wherein the surface zeta potential of the nano ink particles is -15 mV to -50 mV.

19. In paragraph 11, A display having variable transmittance, wherein the solvent comprises at least one selected from the group consisting of isoparaffinic hydrocarbons.

20. In paragraph 11, A display having variable transmittance, wherein the difference in density between the solvent and the nano ink particles is 0.6 or less (greater than 0).

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