CN118915362A - Pixel-level domain-limiting filling packaging method of electronic paper ink and application thereof - Google Patents

Abstract

The invention discloses a pixel-level domain-limited filling and packaging method of electronic paper ink and application thereof, wherein the method comprises the following steps: filling ink into a packaging environment filled with second phase fluid, and then bonding and packaging an upper substrate and a lower substrate of the electronic paper display device, wherein the second phase fluid is conductive liquid which is not mutually soluble with the ink, a hydrophobic insulating layer is arranged on the lower substrate in the upward substrate direction, at least more than two pixel walls are arranged on the hydrophobic insulating layer at intervals, a rubber frame is arranged on the upper substrate in the downward substrate direction, and the height of the rubber frame meets the following conditions: the pixel wall height is less than the glue frame height. The smart design realizes multiple performance improvement by skillfully introducing a second-phase conductive liquid which is mutually insoluble with ink as a packaging environment in the manufacturing process of the electrophoretic display device, namely introducing a layer of polar liquid as the second-phase conductive fluid in the middle of the device.

Description

A pixel-level limited-domain filling and packaging method for electronic paper ink and its application

Technical Field

The present invention relates to the technical field related to electronic paper preparation, and in particular to a pixel-level confined filling and packaging method for electronic paper ink and an application thereof.

Background Art

In the development of electrophoretic electronic paper technology, achieving effective lateral isolation of charged particles (i.e. ink) between adjacent pixels under high-resolution active matrix TFT drive has always been a core technical challenge. From the essence of device design, this challenge essentially translates into how to implement accurate and efficient pixel-level physical boundary demarcation and isolation of display ink at the micron or even nanoscale.

Currently, the method widely adopted in the industry and proven to be effective is microencapsulation technology. This technology encloses the display ink containing charged particles in a tiny, independent capsule structure, and uses the physical barrier effect of the capsule wall to effectively prevent the migration and mixing of ink particles between different pixels. However, the implementation of microencapsulation technology is not without obstacles: on the one hand, the precise regulation of parameters such as capsule size uniformity and wall thickness control faces huge challenges. These subtle differences often directly lead to fluctuations and inconsistencies in the overall performance of the display film; on the other hand, the capsule wall itself is an additional interface, and its inherent resistance characteristics will introduce additional voltage drop, thereby pushing up the voltage threshold required for the driving circuit, increasing energy consumption and possibly affecting the long-term stability of the device.

In view of the above problems, researchers have begun to explore new non-encapsulated pixel encapsulation paths. For example, display ink is directly filled into a conventional open pixel structure, and then a physical barrier between pixels is constructed using a precisely designed snap-on structure or a sticky material coated on the entire surface. This method aims to simplify the encapsulation process and reduce costs, but it also introduces new problems, such as air bubbles that are difficult to completely eliminate during the encapsulation process, and ink residues that may be formed at the edge of the pixel due to the encapsulation material. These factors may have an adverse effect on the display effect, such as reduced contrast and impaired color uniformity.

Therefore, it is of great significance to develop a new pixel-level confined filling and packaging method for electronic paper ink.

Summary of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a pixel-level limited-domain filling and packaging method for electronic paper ink, which can not only reduce the packaging difficulty of electrophoretic devices, but also avoid problems such as ink residue on the top of the pixel wall and device edge pixel contamination caused by contact between ink and organic glue.

The present invention also proposes the application of the above method.

According to one aspect of the present invention, a pixel-level confined filling and packaging method for electronic paper ink is provided, comprising the following steps:

The lower substrate of the electronic paper display device is placed in a packaging environment filled with a second phase fluid and filled with ink, and then the upper substrate of the electronic paper display device is bonded and packaged with the lower substrate, wherein the second phase fluid is a conductive liquid that is immiscible with the ink, the lower substrate is provided with a hydrophobic insulating layer toward the upper substrate, at least two or more pixel walls are spaced apart on the hydrophobic insulating layer, and the upper substrate is provided with a glue frame toward the lower substrate, and the height of the glue frame satisfies the following condition: pixel wall height < glue frame height.

According to a preferred embodiment of the present invention, at least the following beneficial effects are achieved: by ingeniously introducing a second-phase conductive liquid that is incompatible with ink as a packaging environment during the manufacturing process of the electrophoretic display device, that is, introducing a layer of polar liquid in the middle of the device as a second-phase conductive fluid, this ingenious design achieves multiple performance improvements. First, this design makes full use of the inherent wettability difference between the two-phase fluids and the geometric energy barrier constraints of the edge of the pixel structure itself to achieve pixel-level precise segmentation and effective confinement of ink droplets. This mechanism effectively prevents the cross-pixel movement of ink particles, that is, ensures that the ink is stably maintained in each predetermined pixel area, avoids the "ink overflow" phenomenon, and thus significantly improves the clarity and stability of the displayed image. Secondly, the introduced second-phase conductive fluid can not only be used as a packaging medium, but also because of its good conductivity, without affecting the overall circuit performance, effectively avoids defects such as cavitation that may be formed in the packaging cavity, which are usually the key factors that lead to device performance degradation or even failure. At the same time, its conductive properties ensure smooth current transmission, without introducing significant voltage drop, and maintain the efficient operation of the device. Furthermore, the use of polar fluids such as pure water as the second-phase conductive fluid significantly improves the physical and chemical properties of the packaging interface compared to the organic solvent system commonly used in traditional inks. This transformation reduces the complexity of the solid-liquid contact interface, especially avoids possible adverse interactions between organic solvents and glue, such as swelling, dissolution or chemical reactions, thereby greatly improving the reliability and long-term stability of the package. Therefore, the innovative packaging strategy of introducing a second-phase polar conductive fluid not only simplifies the packaging process of electrophoretic display devices (such as reducing the requirements for the precise fit between the upper substrate and the pixel grid), but also fundamentally improves the packaging quality and operational reliability of the device. This technological innovation effectively solves common problems such as pixel contamination and edge effects, and opens up a new path for the development of electrophoretic display technology.

In some embodiments of the present invention, the second phase fluid is a polar liquid, which can be a polar liquid that is not miscible with the ink solvent (usually an alkane substance).

In some embodiments of the present invention, the second phase fluid is at least one of water, ethanol, ethylene glycol and glycerol. Using conductive liquids such as water, ethanol, ethylene glycol or glycerol that are relatively less toxic to the human body is more environmentally friendly.

In some embodiments of the present invention, the height of the second phase fluid is not higher than the height of the pixel wall. The height of the second phase fluid is precisely regulated to reduce the pressure drop, maintain the system stability and improve the display effect. Too high a height may cause the rupture of the ink phase film due to uneven electric field distribution or local stress concentration under power-on conditions. This rupture will not only cause the lateral diffusion or "interference" of the ink and its particles (such as modified metal conductive particles in the ink), that is, the "ink over the wall" phenomenon, but may also cause image blur or uneven color. In addition, the increase in the height of the second phase fluid will directly reduce the overall transmittance, especially for application scenarios such as electronic paper that require high transmittance. This effect is particularly important. An overly thick fluid layer will absorb or scatter more light, thereby reducing the display effect, reducing the screen brightness, reducing the contrast, and even affecting the clarity and comfort of the user's reading or operation. Precisely controlling the height of the second phase fluid can effectively reduce the pressure drop, avoid the rupture of the ink phase film or the ink interference problem, and ensure sufficient transmittance, thereby significantly improving the display effect and user experience of the product. At the same time, this fine regulation also helps to improve the stability and durability of the system and extend the service life of the product.

In some embodiments of the present invention, the height of the second phase fluid is less than 20 μm. The pixel wall height needs to be greater than 20 microns, and the specific height can be adjusted independently, and the height of the second phase fluid only needs to be no higher than the pixel wall height, but the thinner the better. If the process allows, the optimal thickness is less than 20 microns, as long as it can play the role of ink confinement segmentation.

In some embodiments of the present invention, the height of the glue frame satisfies the following conditions: pixel wall height < glue frame height and the sum of the pixel wall height and the polar liquid height is equal to the glue frame height. The height of the second phase fluid is controlled by controlling the glue frame height.

In some embodiments of the present invention, the ink height is not higher than the pixel wall height. When filling the ink into the gap of the pixel wall, the ink deposition height is precisely controlled to ensure that it strictly does not exceed the boundary of the pixel wall. The main purpose of this control strategy is to maintain the top of the ink film flat and not exceed the top of the pixel wall to achieve a highly ordered pixel-level defined area. This process cleverly utilizes the difference in wettability between the ink and the pixel wall material, as well as the energy barrier effect inherent in the geometric shape of the pixel wall edge, to achieve pixel-level confinement of the ink, strengthen the adhesion of the ink in the predetermined area, and at the same time utilize the geometric features of the pixel wall edge, such as sharp corners or specific surface textures, to form a natural physical barrier, thereby effectively inhibiting the disordered diffusion or "disturbance" of the ink and its internal particles (such as pigment particles, additives, etc.) in the lateral direction, thereby making it more difficult for the ink to jump out of the original pixel wall.

In some embodiments of the present invention, the material of the pixel wall is selected from hydrophilic and oleophobic materials, preferably hydrophilic epoxy resin. The pixel wall needs to be as hydrophilic and oleophobic as possible, and bisphenol A epoxy resin, linear phenolic epoxy resin, etc. can be used.

In some embodiments of the present invention, the ink contains conductive particles, which can be dispersed in the ink solvent but not in the second phase fluid. The conductive particles can be modified using conventional modification methods currently used so that they can be dispersed only in the ink solvent but not in the second phase fluid.

In some embodiments of the present invention, the ink is filled in pixels in a second phase fluid environment by an interfacial self-assembly process, or the ink is filled in pixels by inkjet printing.

In some embodiments of the present invention, the bonding and packaging is performed by applying downward pressure, or the ink is subjected to a frozen phase change and then immersed in a second phase fluid for bonding and packaging, or liquid crystal dropwise (ODF) is used for bonding and packaging.

In some embodiments of the present invention, downward pressure is applied to the middle and both ends of the upper substrate during the bonding process, and the pressure in the middle is greater than the pressure at the two ends. By applying downward pressure, the upper substrate and the lower substrate are bonded, so that the upper and lower substrates can be firmly attached together. By mainly applying force to the middle part of the upper substrate, the upper substrate of the device can be guaranteed to be flat, rather than in a convex state, so that excess second phase fluid can be removed before complete bonding. The pressure in the middle is slightly greater than the pressure at the two ends, and it is only necessary to allow the upper substrate to deform slightly (only slight deformation is required) to allow the middle part of the upper substrate to contact the polar liquid earlier than the sides and edges, so that the polar liquid can be discharged from the edge.

In some embodiments of the present invention, both the upper substrate and the lower substrate are conductive substrates.

According to another aspect of the present invention, application of the above method in preparing an electronic paper display device is proposed.

According to the application of a preferred embodiment of the present invention, there are at least the following beneficial effects: the ink pixel-level confined filling and packaging method of the present invention has good application prospects in the process of preparing electronic paper. The ink packaged by this packaging method can better avoid jumping out of the original pixel grid and enter the adjacent pixel grid, which significantly improves the resolution and accuracy of the electronic paper, so that the electronic paper has clearer, sharper image edges and more stable performance.

Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

FIG. 1 is a schematic structural diagram of a lower substrate in an embodiment of the present invention.

FIG. 2 is a schematic structural diagram of the upper and lower substrate packaging process in an embodiment of the present invention.

FIG. 3 is a schematic structural diagram of a packaged electronic paper display device according to an embodiment of the present invention.

Reference numerals:

1: Upper substrate

2: Second phase fluid

3: Plastic frame

4: Ink

5: Pixel Wall

6: Hydrophobic insulation layer

7: Lower substrate

8: Middle downforce

9: End downward pressure.

DETAILED DESCRIPTION

The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, other embodiments obtained by technicians in this field without creative work are all within the scope of protection of the present invention. The test methods used in the embodiments are conventional methods unless otherwise specified; the materials, reagents, etc. used, unless otherwise specified, can be reagents and materials obtained from commercial channels. Unless otherwise specified, the same parameter in each embodiment has the same value. The embodiments described below are exemplary and are only used to explain the present invention, and cannot be understood as limitations on the present invention.

In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

In the description of the present invention, "thickness" and "height" have the same meaning, and both refer to the distance in the vertical direction.

Example

This example provides a pixel-level limited-area filling and packaging method for electronic paper ink, and the specific process is as follows:

Take the upper substrate 1 and the lower substrate 7 (both are conductive substrates, in this embodiment, glass with indium tin oxide (ITO) is used, and glass with thin film transistors (TFT) can also be used), and prepare the hydrophobic insulating layer 6 on the lower substrate 7 by spin coating and curing.

The pixel wall 5 is prepared by photolithography on the hydrophobic insulating layer 6 (it can also be prepared by other methods such as nanoimprinting), and each two adjacent pixel walls 5 form a pixel grid, and each pixel grid represents a pixel (the size of the pixel grid and the pixel wall 5 can be changed as needed). The processed lower substrate 7 is shown in Figure 1. The ink 4 (the height of the ink 4 is usually above 20μm, which can be adjusted independently, and the ink 4 is an ink containing particles (conductive particles)) is filled in the pixel in the second phase fluid 2 (water) by the interface self-assembly process, and then the second phase fluid 2 environment is fitted and packaged. Specifically, as shown in Figure 2, the lower substrate 7 with the pixel wall 5 and the hydrophobic insulating layer 6 prepared is placed in the second phase fluid 2 environment and filled with ink 4 by interface self-assembly, and then the upper substrate 1 is attached to the glue frame 3, and the upper substrate 1 and the lower substrate 7 are pressed together so that the upper and lower substrates 7 can be firmly attached together. Downward pressure is applied to the middle and both ends of the upper substrate 1, and the downward pressure 8 in the middle is greater than the downward pressure 9 at the end. With the middle as the main force application position, the force around the two ends or sides needs to be less than the downward pressure in the middle, so that the upper substrate can be slightly deformed (only slight deformation is required) to allow the middle part of the upper substrate to contact the polar liquid earlier than the sides and edges, so that the polar liquid can be discharged from the edge, and there is no middle bulge after the device is packaged, so as to achieve a higher flatness. This operation is to ensure that when packaging larger-sized devices, there is no middle bulge on the upper substrate of the device to ensure the flatness of the device. Excess second-phase fluid 2 can be removed before full bonding, so that the upper substrate 1 of the device can be guaranteed to be flat rather than in a convex state. The processed device is shown in Figure 3. The height of the second-phase fluid 2 does not exceed the height of the pixel wall 5. The packaging method of the present invention can be applied to the filling packaging of electrophoretic electronic paper to achieve pixel-level confined packaging.

To ensure the display effect, the ink thickness of the electrophoretic device should generally be above 20μm, so the pixel wall thickness should be greater than this value, that is, greater than 20 microns, and the actual thickness can be adjusted independently. The thickness of the second phase fluid 2 should be as thin as possible. Usually, the thickness of the second phase fluid 2 should be at least not higher than the thickness of the pixel wall 5; the thickness of the conductive fluid is controlled to reduce the pressure drop. If the thickness of the second phase fluid 2 is too high, it is easy to cause the ink phase film to rupture when powered, resulting in lateral interference between the ink and the particle, that is, the ink is easy to flip over the wall; and the thickness of the second phase fluid 2 is too thick, which will affect the transmittance, so controlling its thickness can also ensure its display effect. The pixel wall material can be selected from hydrophilic epoxy resin, as long as it is hydrophilic and stable enough, and there is no specific material requirement. The ink composition is conventional alkane and conductive metal particles. There is no special requirement for the modification method of the conductive particles. Conventional conductive particles can be used. They can be modified by various methods such as modifiers, as long as they are dispersed in alkanes but not in polar liquids. The thickness of the second phase fluid 2 is mainly controlled by controlling the thickness of the glue frame 3. Therefore, the thickness of the glue frame 3 should be as small as possible but slightly larger than the thickness of the pixel wall 5. The thickness of the pixel wall < the thickness of the glue frame < twice the thickness of the pixel wall. The thickness of the ink 4 should not be higher than the thickness of the pixel wall 5. The thickness of the ink 4 should not be higher than the thickness of the pixel wall 5. When the ink 4 is filled into the pixel wall 5, the thickness of the ink 4 should not exceed the pixel wall 5 to ensure that the ink phase film does not exceed the top of the pixel wall. On the one hand, the difference in wettability between the two-phase fluid and the pixel wall 5 and the geometric energy barrier constraint of the edge of the pixel wall 5 structure are used to achieve pixel-level confinement of the ink 4, thereby suppressing the lateral interference of the ink and particles, making it more difficult for the ink 4 to jump out of the original pixel wall 5. The pixel wall 5 is as close to the second phase fluid 2 as possible and as close to the ink 4 as possible. That is, the pixel wall material should be a hydrophilic and oleophobic material such as a hydrophilic epoxy resin; its function is to cooperate with the ink to suppress the lateral interference of the ink and particles. The conductive particles need to be surface modified so that they can be dispersed only in the ink solvent but not in the second phase fluid; the modification method follows the conventional modification method currently used, and this patent has no special requirements for the modification method.

The scheme of the present invention introduces a packaging environment of a second phase immiscible conductive liquid, that is, introduces a layer of polar liquid as the second phase fluid in the middle of the device. On the one hand, the difference in wettability between the two-phase fluid and the pixel structure and the geometric energy barrier constraint of the edge of the pixel structure itself are used to achieve pixel-level segmentation and confinement of the ink, thereby preventing particle interference, that is, the ink jumps out of the original pixel grid and enters the adjacent pixel grid; on the other hand, the introduced second phase fluid can avoid the generation of defects such as cavitation in the packaging cavity, because its conductivity will not cause significant pressure drop; finally, since the packaging liquid can have more selectivity, such as selecting polar fluids such as pure water, better packaging reliability can be obtained compared to the solid-liquid contact interface between the glue and the liquid formed by the organic solvent commonly used in ink.

Therefore, the introduction of the second phase fluid can not only reduce the packaging difficulty of the electrophoretic device (it is no longer necessary to completely fit the upper substrate and the pixel grid), but also improve the packaging reliability of the device (avoiding problems such as ink residue on the top of the pixel wall and pixel contamination at the edge of the device caused by contact between ink and organic glue).

Device testing process: The prepared device is powered on for testing, and the upper and lower substrates are connected to the positive and negative poles respectively (the initial voltage is about 5V). After power-on, the front and back sides of the device appear black and white respectively. It can be seen that the two metal particles move to the positive and negative poles respectively under the action of the electric field. By switching the positive and negative pole connections of the upper and lower substrates (such as switching from positive on top to negative on bottom to positive on top), the color of the front and back sides of the device will also switch accordingly. Increasing the voltage will deepen the color accordingly.

The embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims (10)

1. A pixel-level limited-domain filling and packaging method for electronic paper ink, characterized in that it comprises the following steps: The lower substrate of the electronic paper display device is placed in a packaging environment filled with a second phase fluid and filled with ink, and then the upper substrate of the electronic paper display device is bonded and packaged with the lower substrate, wherein the second phase fluid is a conductive liquid that is immiscible with the ink, the lower substrate is provided with a hydrophobic insulating layer toward the upper substrate, at least two or more pixel walls are spaced apart on the hydrophobic insulating layer, and the upper substrate is provided with a glue frame toward the lower substrate, and the height of the glue frame satisfies the following condition: pixel wall height < glue frame height. 2. The pixel-level confined filling and packaging method of electronic paper ink according to claim 1 is characterized in that the second phase fluid is a polar liquid. 3. The pixel-level confined filling and packaging method of electronic paper ink according to claim 1 is characterized in that the second phase fluid is at least one of water, ethanol, ethylene glycol and glycerol. 4. The pixel-level confined filling and packaging method of electronic paper ink according to claim 1 is characterized in that: the height of the second phase fluid is not higher than the height of the pixel wall; and/or the ink height is not higher than the pixel wall height. 5. The pixel-level confined filling and packaging method of electronic paper ink according to claim 1 is characterized in that: the height of the glue frame satisfies the following conditions: the pixel wall height < the glue frame height and the sum of the pixel wall height and the polar liquid height is equal to the glue frame height. 6 . The pixel-level confined filling and packaging method of electronic paper ink according to claim 1 , wherein the material of the pixel wall is selected from hydrophilic and oleophobic materials, preferably hydrophilic epoxy resin. 7. The pixel-level confined filling and packaging method of electronic paper ink according to claim 1 is characterized in that: the ink is confinedly filled within the pixel in the second phase fluid environment through an interface self-assembly process, or the ink is pixelated and filled by inkjet printing. 8. The pixel-level limited filling and packaging method of electronic paper ink according to claim 1 is characterized in that: the bonding and packaging is performed by applying downward pressure, or the ink is subjected to a frozen phase change and then immersed in a second phase fluid for bonding and packaging, or liquid crystal is dripped and filled for bonding and packaging. 9. The pixel-level confined filling and packaging method of electronic paper ink according to claim 1 is characterized in that: during the bonding process, downward pressure is applied to the middle and both ends of the upper substrate respectively, and the pressure in the middle is greater than the pressure at the two ends. 10. Use of the method according to any one of claims 1 to 9 in preparing an electronic paper display device.