Method and apparatus of electrophoretic deposition   

Abstract: A method of electrophoretic deposition includes: providing an electrophoresis tank, an anode substrate, and a cathode substrate; disposing the anode substrate and the cathode substrate oppositely in the electrophoresis tank; adjusting relative positions of the cathode substrate and the anode substrate for varying each of the distances between corresponding regions on the cathode substrate and the anode substrate; and inputting cathode voltage and anode voltage respectively to a cathode electrode of the cathode substrate and a anode electrode of the anode substrate for performing the electrophoretic deposition.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus of electrophoretic deposition, and more particularly, to a method and an apparatus of electrophoretic deposition improving the uniformity of the electrophoretic deposition while a voltage distribution of electrodes is non-uniform.

2. Description of the Prior Art

Electrophoresis is a reaction that charged particles in an electrophoresis buffer may move toward two electrode substrates with opposite charges under an effect of an electric field. Materials carried by the charged particles may gather on the electrode substrate for forming a coating layer in the electrophoresis buffer called an electrophoretic deposition.

The electrophoretic deposition may be employed for depositing coating materials, metal oxides, and fluorescent powders. In recent years, related technologies and applications of carbon nanotubes (CNT) have been rapidly developed, and the electrophoretic deposition also has been employed for depositing CNT films. Electrophoresis in the electrophoresis buffer is driven by the electrical field between two electrodes. Uniformity of the electrophoretic deposition may be difficult to control because the voltage drop issue on the electrode may be serious, especially when the pattern of the electrode is linear or when the area of the electrode is enlarged. The voltage distribution of different regions on the electrode may become non-uniform, and the uniformity of the electrophoretic deposition may be therefore affected. Display quality and manufacturing yield of a display device, such as a large-sized display device, may be affected when the electrophoretic deposition is employed for forming material layers in the display device.

SUMMARY

It is one of the objectives of the present invention to provide a method and an apparatus of electrophoretic deposition for improving the non-uniform distribution of voltage caused by the shape and the size of the electrodes and the uniformity of the electrophoretic deposition may then be enhanced.

To achieve the purposes described above, a preferred embodiment of the present invention provides a method of electrophoretic deposition. The method of the electrophoretic deposition includes the following steps. First, an electrophoresis tank, an anode substrate, and a cathode substrate are provided. The electrophoresis tank contains an electrophoresis buffer. The anode substrate includes at least one anode electrode, and the cathode substrate includes at least one cathode electrode. The anode substrate and the cathode substrate are then disposed in the electrophoresis buffer, and the anode substrate and the cathode substrate are disposed oppositely in the electrophoresis tank. Relative positions of the cathode substrate and the anode substrate are adjusted for varying each of the distances between corresponding regions on the cathode substrate and the anode substrate. Cathode voltage and anode voltage are inputted respectively to the cathode electrode of the cathode substrate and to the anode electrode of the anode substrate for performing the electrophoretic deposition.

To achieve the purposes described above, another preferred embodiment of the present invention provides a method of electrophoretic deposition. The method of the electrophoretic deposition includes the following steps. First, an electrophoresis tank, an anode substrate, and a cathode substrate are provided. The electrophoresis tank contains an electrophoresis buffer. The anode substrate includes a plurality of anode electrodes, and the cathode substrate includes at least one cathode electrode. The anode substrate and the cathode substrate are then disposed in the electrophoresis buffer, and the anode substrate and the cathode substrate are disposed oppositely and parallel to each other in the electrophoresis tank. Cathode voltage is inputted to the cathode electrode of the cathode substrate, and anode voltage with different values is inputted respectively to each of the anode electrodes of the anode substrate for performing the electrophoretic deposition.

To achieve the purposes described above, a preferred embodiment of the present invention provides an apparatus of electrophoretic deposition. The apparatus of the electrophoretic deposition includes a power supply, an electrophoresis tank, a cathode substrate, and an anode substrate. The power supply includes an anode terminal and a cathode terminal. The electrophoresis tank is used to contain an electrophoresis buffer. The cathode substrate is disposed in the electrophoresis tank. The cathode substrate includes at least one cathode electrode electrically connected to the cathode terminal of the power supply. The anode substrate is disposed correspondingly to the cathode substrate in the electrophoresis tank. The anode substrate includes at least one anode electrode electrically connected to the anode terminal of the power supply. The anode substrate is disposed tiltedly toward the cathode substrate, and a distance between one region on the anode substrate and a corresponding region on the cathode substrate is different from a distance between another region on the anode substrate and another corresponding region on the cathode substrate.

To achieve the purposes described above, another preferred embodiment of the present invention provides an apparatus of electrophoretic deposition. The apparatus of the electrophoretic deposition includes a power supply, an electrophoresis tank, a cathode substrate, and an anode substrate. The power supply includes a plurality of anode terminals and a cathode terminal. The electrophoresis tank is used to contain an electrophoresis buffer. The cathode substrate is disposed in the electrophoresis tank. The cathode substrate includes at least one cathode electrode electrically connected to the cathode terminal of the power supply. The anode substrate is disposed parallel to the cathode substrate in the electrophoresis tank. The anode substrate includes a plurality of anode electrodes electrically connected to the anode terminals of the power supply respectively. Each of the anode terminals is employed for providing anode voltage with different values to each of the anode electrodes, and the cathode terminal is employed for providing cathode voltage to the cathode electrode.

In the present invention, the distances between regions on two electrode substrates may be adjusted and a plurality of anode electrodes may be employed for compensating the voltage drop issue on the cathode substrate. The problem caused by the non-uniform distribution of voltage on the cathode substrate due to the effect of the voltage drop may be improved, and the uniformity of the electrophoretic deposition rate may then be enhanced.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view diagram illustrating an apparatus of electrophoretic deposition according to a preferred embodiment of the present invention.

FIG. 2 is a stereoscopic view diagram illustrating an apparatus of electrophoretic deposition according to a preferred embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a cathode substrate of an apparatus of electrophoretic deposition according to another preferred embodiment of the present invention.

FIG. 4 is a cross-sectional view diagram illustrating an apparatus of electrophoretic deposition according to further another preferred embodiment of the present invention.

FIG. 5 is a stereoscopic view diagram illustrating an apparatus of electrophoretic deposition according to further another preferred embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating an anode substrate of an apparatus of electrophoretic deposition according to further another preferred embodiment of the present invention.

DETAILED DESCRIPTION

Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will understand, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include” and “include” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . . ” In addition, to simplify the descriptions and make it more convenient to compare between each embodiment, identical components are marked with the same reference numerals in each of the following embodiments. Please note that the figures are only for illustration and the figures may not be to scale.

Please refer to FIG. 1 and FIG. 2. FIG. 1 is a cross-sectional view diagram illustrating an apparatus of electrophoretic deposition according to a preferred embodiment of the present invention. FIG. 2 is a stereoscopic view diagram illustrating the apparatus of the electrophoretic deposition according to the preferred embodiment of the present invention. As shown in FIG. 1 and FIG. 2, in this embodiment, an apparatus of electrophoretic deposition 10 includes a power supply 11, an electrophoresis tank 12T, a cathode substrate 14, and an anode substrate 13. The power supply 11 includes an anode terminal 11A and a cathode terminal 11C. The electrophoresis tank 12T is used to contain an electrophoresis buffer 12. The cathode substrate 14 is disposed in the electrophoresis tank 12T. The cathode substrate 14 includes at least one cathode electrode 16 electrically connected to the cathode terminal 11C of the power supply 11. In this embodiment, the cathode substrate 14 includes a plurality of cathode electrodes 16, but the present invention is not limited to this and the cathode substrate 14 may include only one cathode electrode 16.

The cathode substrate 14 may have a first cathode region 14Z1 and a second cathode region 14ZX. Each of the cathode electrodes 16 within the first cathode region 14Z1 is electrically connected to the cathode terminal 11C of the power supply 11, and voltage VCZX of each the cathode electrodes 16 within the second cathode region 14ZX is lower than voltage VCZ1 of each the cathode electrodes 16 within the first cathode region 14Z1 due to an effect of voltage drop on the cathode electrodes 16.

The anode substrate 13 is disposed correspondingly to the cathode substrate 14 in the electrophoresis tank 12T. The anode substrate 13 includes at least one anode electrode 15. In this embodiment, the anode electrode 15 may include a pattern such as a rectangular pattern with an area nearly equal to a surface of the anode substrate 13, but the present invention is not limited to this and the anode electrode 15 may include other appropriate patterns. As shown in FIG. 1, in this embodiment, the anode substrate 13 is disposed tiltedly toward the cathode substrate 14, and a distance between one region on the anode substrate 13 and a corresponding region on the cathode substrate 14 is different from a distance between another region on the anode substrate 13 and another corresponding region on the cathode substrate 14. The anode substrate 13 may have a first anode region 13Z1 corresponding to the first cathode region 14Z1 of the cathode substrate 14, and the anode substrate 13 may have a second anode region 13ZX corresponding to the second cathode region 14ZX of the cathode substrate 14. The anode electrode 15 within the first anode region 13Z1 is electrically connected to the anode terminal 11A of the power supply 11. A first electrophoretic deposition rate RZ1 generated between the first anode region 13Z1 and the first cathode region 14Z1 may be equal to a second electrophoretic deposition rate RZX generated between the second anode region 13ZX and the second cathode region 14ZX, and a distance DZ1 between the first anode region 13Z1 and the first cathode region 14Z1 may be larger than a distance DZX between the second anode region 13ZX and the second cathode region 14ZX.

It is worth noticing that, in this embodiment, the voltage VCZX of the cathode electrodes 16 within the second cathode region 14ZX, which is away from the region connected to the power supply 11, may be affected more seriously by the voltage drop issue caused by properties such as shape and resistivity of the cathode electrode 16. The voltage VCZX of the cathode electrode 16 within the second cathode region 14ZX may therefore become lower than the voltage VCZ1 of the cathode electrode 16 within the first cathode region 14Z1. The distance DZX between the second anode region 13ZX and the second cathode region 14ZX may be reduced, and the distance DZ1 between the first anode region 13Z1 and the first cathode region 14Z1 may become larger than the distance DZX between the second anode region 13ZX and the second cathode region 14ZX for compensating the influence of the voltage VCZX which is lower than the voltage VCZ1.

The first electrophoretic deposition rate RZ1 generated between the first anode region 13Z1 and the first cathode region 14Z1 may therefore become equal to the second electrophoretic deposition rate RZX generated between the second anode region 13ZX and the second cathode region 14ZX. Additionally, in this embodiment, main components of the electrophoresis buffer 12 may include carbon nanotubes, fluorescent powders, or metal oxides such as lanthanum strontium manganite (LSM), cerium gadolinium oxide (CGO), yttria-stabilized zirconia (YSZ) and lanthanum strontium gallium magnesium oxide (LSGM), but not limited thereto. The electrophoresis buffer 12 may further include solvents, dispersing agents, or salts such as sodium nitrite magnesium nitrite, yttrium nitrite, or aluminium nitrite, but the electrophoresis buffer 12 of this invention is not limited to this and may include other necessary components. In addition, materials of the anode electrodes 15 and the cathode electrode 16 may include conductive metals, transparent conductive materials or other appropriate conductive materials. The conductive materials may include aluminum, chromium, molybdenum, titanium, copper, silver, or alloys of these materials. The transparent conductive materials may include indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO) or other transparent conductive materials.

As shown in FIG. 2, in this embodiment, the cathode substrate 14 may include a plurality of stripe cathode electrodes 16, but the cathode substrate 14 of the present invention is not limited to this and may include only one cathode electrode or the cathode electrodes with other appearances. Please refer to FIG. 3. FIG. 3 is a schematic diagram illustrating a cathode substrate of an apparatus of electrophoretic deposition according to another preferred embodiment of the present invention. As shown in FIG. 3, the cathode substrate 14 may include a cathode electrode 17, and the cathode electrode 17 may be an “S”-shaped pattern meandering over the cathode substrate 14. Except for the cathode electrode 17, the apparatus of the electrophoretic deposition of this embodiment is similar to the apparatus of the electrophoretic deposition 10 mentioned above and will not be redundantly described.

Please refer to FIG. 1 and FIG. 2 again. As shown in FIG. 1 and FIG. 2, a preferred embodiment of the present invention provides a method of electrophoretic deposition. The method of the electrophoretic deposition includes the following steps. First, the apparatus of the electrophoretic deposition 10 mentioned above is provided. The anode substrate 13 and the cathode substrate 14 are disposed in the electrophoresis buffer 12. Relative positions of the cathode substrate 14 and the anode substrate 13 are then adjusted for varying each of the distances between corresponding regions on the cathode substrate 14 and the anode substrate 13. Subsequently, cathode voltage and anode voltage are inputted respectively to the cathode electrode 16 of the cathode substrate 14 and to the anode electrode 15 of the anode substrate 13 for performing the electrophoretic deposition.

In this embodiment, voltage VCZ1 exists on the cathode electrodes 16 within the first cathode region 14Z1, voltage VCZX exists on the cathode electrodes 16 within the second cathode region 14ZX, voltage VAZ1 exists on the anode electrode 15 within the first anode region 13Z1, and voltage VAZX exists on the anode electrode 15 within the second anode region 13ZX. The voltage VCZX of the cathode electrodes 16 within the second cathode region 14ZX is lower than the voltage VCZ1 of the cathode electrodes 16 within the first cathode region 14Z1 because of the voltage drop issue on the cathode electrodes 16.

In this embodiment, the anode electrode 15 may be a rectangular pattern with an area nearly equal to a surface of the anode substrate 13, and then the voltage VAZ1 of the anode electrode 15 within the first anode region 13Z1 may be equal to the voltage VAZX of the anode electrode 15 within the second anode region 13ZX, but the voltage VAZX of this invention is not limited to this and may be different from the voltage VAZ1. It is worth noticing that, in this embodiment, the voltage VCZX of the cathode electrodes 16 within the second cathode region 14ZX, which is away from the region connected to the power supply 11, may be affected more seriously by the voltage drop issue especially when each of the cathode electrodes 16 is a linear electrode with high aspect ratio or the cathode electrodes 16 include high resistivity materials. The voltage VCZX of the cathode electrode 16 within the second cathode region 14ZX may therefore become lower than the voltage VCZ1 of the cathode electrode 16 within the first cathode region 14Z1.

In this embodiment, the anode substrate 13 is disposed tiltedly toward the cathode substrate 14, and the distance DZ1 between the first anode region 13Z1 and the first cathode region 14Z1 may become larger than the distance DZX between the second anode region 13ZX and the second cathode region 14ZX for compensating the influence of the voltage VCZX on the second electrophoretic deposition rate RZX generated between the second anode region 13ZX and the second cathode region 14ZX. Additionally, in other embodiments of the present invention, the positions and tilted angles of the anode substrate 13 and the cathode substrate 14 may be further modified in the electrophoresis buffer 12 for improving the uniformity of the deposition rate, which may be influenced by the non-uniform voltage distribution on the anode substrate 13 and the cathode substrate 14. In addition, the components of the electrophoresis buffer and the design of the electrodes may be further modified for depositing materials on the anode electrodes or the cathode electrodes by the electrophoretic deposition.

Please refer to FIGS. 4-6. FIG. 4 is a cross-sectional view diagram illustrating an apparatus of electrophoretic deposition according to another preferred embodiment of the present invention. FIG. 5 is a stereoscopic view diagram illustrating the apparatus of the electrophoretic deposition in this embodiment. FIG. 6 is a schematic diagram illustrating an anode substrate of the apparatus of the electrophoretic deposition in this embodiment. To simplify the description, the identical components in each of the embodiments of this invention are marked with identical symbols. As shown in FIGS. 4-6, in this embodiment, an apparatus of electrophoretic deposition 20 includes a power supply 11, an electrophoresis tank 12T, a cathode substrate 14, and an anode substrate 13. The power supply 11 includes a plurality of anode terminals 11A and a cathode terminal 11C. The electrophoresis tank 12T is used to contain an electrophoresis buffer 12. The cathode substrate 14 is disposed in the electrophoresis tank 12T. The cathode substrate 14 includes at least one cathode electrode 16 electrically connected to the cathode terminal 11C of the power supply 11. In this embodiment, the cathode substrate 14 includes a plurality of cathode electrodes 16, but the present invention is not limited to this and the cathode substrate 14 may include only one cathode electrode 16. In addition, the cathode substrate 14 may have a first cathode region 14Z1 and a second cathode region 14ZX. Each of the cathode electrodes 16 within the first cathode region 14Z1 is electrically connected to the cathode terminal 11C of the power supply 11, and voltage VCZX of each the cathode electrodes 16 within the second cathode region 14ZX is lower than voltage VCZ1 of each the cathode electrodes 16 within the first cathode region 14Z1 due to an effect of voltage drop on the cathode electrodes 16.

The anode substrate 13 is disposed parallel to the cathode substrate 14 in the electrophoresis tank 12T. The anode substrate 13 includes a plurality of anode electrodes 18. Each of the anode electrodes 18 is electrically connected to each of the anode terminals 11A of the power supply 11 respectively. The anode terminals 11A are employed for providing anode voltage with different values to each of the anode electrodes 18, and the cathode terminal 11C is employed for providing cathode voltage to the cathode electrodes 16. In this embodiment, voltage VAZ1 exists on the anode electrode 18 within a first anode region 13Z1, which is corresponding to the first cathode region 14Z1. Voltage VAZX exits on the anode electrode 18 within a second anode region 13ZX, which corresponds to the second cathode region 14ZX. The voltage VAZ1 of the anode electrode 18 within the first anode region 13Z1 is lower than the voltage VAZX of the anode electrode 18 within the second anode region 13ZX, and a first electrophoretic deposition rate RZ1 generated between the first anode region 13Z1 and the first cathode region 14Z1 may be equal to a second electrophoretic deposition rate RZX generated between the second anode region 13ZX and the second cathode region 14ZX.

In this embodiment, the appearance of the cathode electrode 16 includes a stripe pattern, and the voltage VCZX of the cathode electrodes 16 within the second cathode region 14ZX, which is away from the region connected to the power supply 11, may be affected more seriously by the voltage drop issue caused by properties such as length and resistivity of the cathode electrode 16. The voltage VCZX of the cathode electrode 16 within the second cathode region 14ZX may therefore become lower than the voltage VCZ1 of the cathode electrode 16 within the first cathode region 14Z1. It is worth noticing that, in this embodiment, a plurality of the anode electrodes 18, which are stripe patterns and disposed parallel to each other, are electrically connected to the anode terminals 11A of the power supply 11, and voltage with different values may exist on different regions of the anode substrate 13. The voltage VAZ1 of the anode electrode 18 within the first anode region 13Z1 may then be lower than the voltage VAZX of the anode electrode 18 within the second anode region 13ZX. In other words, in this embodiment, the anode voltage with different values may be provided to each of the anode electrodes 18, and the voltage existing on the anode electrodes 18 may be increasing from the top of the anode substrate 13 to the bottom of the anode substrate 13 for compensating the voltage drop issue on different regions of the cathode substrate 14, but the present invention is not limited to this and the voltage on each of the regions of the anode substrate 13 may be modified for compensating the voltage drop issue on the different regions of the cathode substrate 14. The first electrophoretic deposition rate RZ1 generated between the first anode region 13Z1 and the first cathode region 14Z1 may then be equal to the second electrophoretic deposition rate RZX generated between the second anode region 13ZX and the second cathode region 14ZX.

As shown in FIG. 6, each of the anode electrodes 18 of this embodiment are disposed parallel to each other, but the present invention is not limited to this and other allocation approaches may be applied for tuning the condition of the electrophoretic deposition. For example, in other embodiments of the present invention, the patterns and the positions of the anode electrodes may be further modified, and the voltage existing on the anode electrodes may then be different from a center region of the anode substrate to an outer region of the anode substrate for compensating the voltage drop issue on different regions of the cathode substrate. Additionally, the components and material properties of the electrophoresis buffer 12 in this embodiment are similar to the embodiment mentioned above and will not be redundantly described.

Please refer to FIGS. 4-6 again. As shown in FIGS. 4-6, another preferred embodiment of the present invention provides a method of electrophoretic deposition. The following description will detail the differences between the method of the electrophoretic deposition in this embodiment and the method of the electrophoretic deposition in the above-mentioned embodiment. In the method of the electrophoretic deposition of this embodiment, the anode substrate 13 and the cathode substrate 14 are disposed oppositely and parallel to each other in the electrophoresis buffer 12. In other words, the distance DZ1 between the first anode region 13Z1 and the first cathode region 14Z1 is equal to the distance DZX between the second anode region 13ZX and the second cathode region 14ZX, but not limited thereto. In this embodiment, the anode substrate 13 may include a plurality of anode electrodes 18.

The method of the electrophoretic deposition in this embodiment may include inputting cathode voltage to the cathode electrode 16 of the cathode substrate 14 and inputting anode voltage with different values respectively to each of the anode electrodes 18 of the anode substrate 13 for keeping the voltage VAZ1 of the first anode region 13Z1 lower than the voltage VAZX of the second anode region 13ZX. Specifically, the voltage on each regions of the anode substrate 13 may be separately controlled for compensating the voltage drop issue on the cathode substrates 14, and the first electrophoretic deposition rate RZ1 generated between the first anode region 13Z1 and the first cathode region 14Z1 may then be equal to the second electrophoretic deposition rate RZX generated between the second anode region 13ZX and the second cathode region 14ZX. As shown in FIG. 6, the anode electrodes 18 in this embodiment are disposed parallel to each other, but the present invention is not limited to this and other allocation approaches may be employed for modifying the process conditions of the electrophoretic deposition. Additionally, in other embodiments of the present invention, the above-mentioned method of adjusting the distances between regions on the anode substrate 13 and the cathode substrate 14 may be combined with the method of tuning the voltage distribution on the anode substrate 13 for optimizing the uniformity of the electrophoretic deposition.

To summarize the above descriptions, in the present invention, the method of adjusting each of the distances between regions on the anode substrate and the cathode substrate, and the design of the electrodes may be employed for improving the issue that the voltage distribution on the cathode substrate may be non-uniform because of the pattern of the cathode electrode or the material properties of the cathode electrode. The uniformity of the electrophoretic deposition rate may then be effectively enhanced.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.