CN110568609A - A bistable electrowetting display device and its preparation method - Google Patents

Abstract

The invention discloses a bistable electrowetting display device and a preparation method thereof, the bistable electrowetting display device comprises an upper conductive substrate and a lower conductive substrate which are oppositely arranged, and a charge storage layer arranged on one side of the lower conductive substrate, which faces to the upper conductive substrate, wherein the charge storage layer comprises a dielectric layer and a fluorine resin layer, and the dielectric layer is arranged between the lower conductive substrate and the fluorine resin layer. According to the bistable electrowetting display device, the charge storage layer is arranged, and the fluorine resin layer in the charge storage layer has a hydrophobic characteristic, is loose and porous in structure and is easy to store charges; when the electrowetting display device is used, the negative electrode of the power supply assembly is connected with the upper conductive substrate, the positive electrode of the power supply assembly is connected with the lower conductive substrate, negative bias driving is adopted, the charge storage layer can be more beneficial to storing charges, and further the pixel opening state can be still kept under a passive condition after the device is powered off in the pixel opening state, so that the low-power-consumption bistable performance of the electrowetting display device is realized, the whole structure is simple, and the electrowetting display device is suitable for industrial production and application.

Description

A bistable electrowetting display device and its preparation method

technical field

The invention relates to the technical field of electrowetting display, in particular to a bistable electrowetting display device and a preparation method thereof.

Background technique

Electrowetting electronic display is a new reflective display technology that uses an external electric field to manipulate the surface tension of polar liquids in pixels, thereby promoting ink spreading and contraction, and realizing optical switching and grayscale control. With the continuous development of electrowetting display devices and the continuous expansion of application fields, low power consumption bistability has become a higher standard pursued by electrowetting display devices, and it is also an indispensable performance index for the commercialization of electrowetting display devices. The bistable phenomenon in the electrowetting display device is: when no voltage is applied, the pixel has two states of on and off, and it can be maintained continuously. The main difficulty of its research lies in how to keep the pixel in the on state stably for a period of time when no voltage is applied.

In order to realize the bistable display of electrowetting display devices, many researchers have done a lot of work. For example, the University of Cincinnati in the United States proposed a double-layer stereoscopic electrowetting display pixel, which can achieve bistable phenomenon, and the pixel’s stability after power off The display effect is good, but the pixel unit is too large, which is not suitable for the preparation of commercial electrowetting devices; some bistable electrowetting display devices have complex structures and are difficult to prepare.

Contents of the invention

In order to solve the above technical problems, the present invention provides a bistable electrowetting display device and a preparation method thereof.

The technical solution adopted in the present invention is: a bistable electrowetting display device, including an upper conductive substrate and a lower conductive substrate oppositely arranged, and a A charge storage layer, the charge storage layer includes a dielectric layer and a fluororesin layer, and the dielectric layer is provided between the lower conductive substrate and the fluororesin layer.

According to a specific embodiment of the present invention, the fluororesin layer is processed by plasma etching and thermal annealing.

According to a specific embodiment of the present invention, the material of the fluororesin layer is selected from at least one of amorphous fluororesin, Cytop, and Hyflon.

According to a specific embodiment of the present invention, the material of the dielectric layer is selected from materials with a dielectric constant greater than or equal to 2.

According to a specific embodiment of the present invention, the material of the dielectric layer is selected from at least one of polyimide, polytetrafluoroethylene, and epoxy negative photoresist.

According to a specific embodiment of the present invention, the upper conductive substrate includes an upper substrate and an upper conductive layer arranged on the surface of the upper substrate facing the lower conductive substrate; the lower conductive substrate includes a lower substrate and an upper conductive layer arranged on the upper substrate. The lower conductive layer on the surface of the lower substrate facing the upper conductive substrate.

According to a specific embodiment of the present invention, a power supply assembly is further included, the power supply assembly includes a positive pole and a negative pole, the positive pole is electrically connected to the lower conductive substrate, and the negative pole is electrically connected to the upper conductive substrate.

The present invention also provides a method for preparing the above bistable electrowetting display device, comprising the following steps:

S1, setting a dielectric layer on the lower conductive substrate, and then setting a fluororesin layer on the dielectric layer;

S2. Prepare a pixel wall on the fluororesin layer;

S3, filling the packaging liquid, and then attaching and packaging the upper conductive substrate and the lower conductive substrate.

Preferably, in step S1, after the fluororesin layer is provided on the dielectric layer, plasma etching is performed on the fluororesin layer, and then thermal annealing is performed.

The driving method of the above bistable electrowetting display device adopts negative bias driving. Specifically, negative electricity is applied to the upper conductive substrate of the bistable electrowetting display device (ie, connected to the negative pole of the power supply component), and positive electricity is applied to the lower conductive substrate (ie, connected to the positive pole of the power supply component).

The beneficial technical effects of the present invention are: the present invention provides a bistable electrowetting display device and a preparation method thereof, the bistable electrowetting display device is provided with a charge storage layer, due to the fluororesin in the charge storage layer The layer has hydrophobic characteristics, and its structure is loose and porous, which is easy to store charges; when in use, by electrically connecting the negative pole of the power supply component to the upper conductive substrate, and electrically connecting the positive pole of the power supply component to the lower conductive substrate, it is driven by negative bias In this way, the charge storage layer can be more conducive to storing charges, so that the device can still maintain the pixel on state under passive conditions after the device is powered off in the on state of the pixel, so as to realize the low power bistable performance of the electrowetting display device , and the overall structure is simple, suitable for industrial production applications.

Instructions attached

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the drawings that need to be used in the description of the embodiments will be briefly described below.

FIG. 1 is a schematic structural view of an embodiment of a bistable electrowetting display device of the present invention;

Fig. 2 is a flow chart of the manufacturing process of the bistable electrowetting display device shown in Fig. 1;

Fig. 3 is a schematic diagram of an embodiment of driving voltage control of the bistable electrowetting display device shown in Fig. 1;

Fig. 4 is a working principle diagram of the bistable electrowetting display device shown in Fig. 1 under negative bias driving state;

FIG. 5 is an effect diagram of device 1 in a negative bias driving state in an application effect test;

Fig. 6 is an effect diagram of device 2 in a positive bias driving state in the application effect test;

FIG. 7 is an effect diagram of the device 2 in a negative bias driving state in an application effect test.

Detailed ways

The conception, specific structure and technical effects of the present invention are clearly and completely described below in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, scheme and effect of the present invention. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

The descriptions of upper, lower, left, right, etc. used in the present invention are only relative to the mutual positional relationship of the various components of the present invention in the drawings, and the terms "comprising" and "having" and any deformation thereof are intended to cover not exclusive inclusion.

Reference herein to an "embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present invention. The occurrences of this phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those skilled in the art understand explicitly and implicitly that the embodiments in the present application and the features in the embodiments can be combined with each other under the condition of no conflict.

Please refer to FIG. 1 . FIG. 1 is a schematic structural diagram of an embodiment of a bistable electrowetting display device of the present invention. As shown in FIG. 1, the bistable electrowetting display device of this embodiment includes an upper conductive substrate 1 and a lower conductive substrate 2 arranged oppositely, and a charge storage layer arranged on the lower conductive substrate 2 facing the upper conductive substrate 1 side. 3. The charge storage layer 3 includes a dielectric layer 31 and a fluororesin layer 32 . The fluororesin layer 32 is provided with pixel walls 4, and the pixel walls 4 enclose to form a pixel grid array; the upper conductive substrate 1 and the lower conductive substrate 2 are packaged by a packaging plastic frame (not shown in the figure) to form a closed cavity, which is sealed. The cavity is filled with an encapsulation liquid 5, and the encapsulation liquid 5 is specifically a complementary and compatible first fluid 51 and a second fluid 52; the first fluid 51 is filled in the pixel grid, and ink can be used specifically; the second fluid 52 and the upper conductive substrate 1, the second fluid 52 can specifically be water.

In this embodiment, the dielectric layer 31 is provided between the lower conductive substrate 2 and the fluororesin layer 32 . Specifically, the dielectric layer 31 is disposed on the surface of the lower conductive substrate 2 facing the upper conductive substrate 1 , and the fluororesin layer 32 is disposed on the surface of the dielectric layer 31 facing away from the lower conductive substrate 2 .

The upper conductive substrate 1 and the lower conductive substrate 2 can be a single-layer conductive substrate, or can be formed by combining a substrate and a conductive layer on the substrate. The material of the dielectric layer 31 is generally a material with a dielectric constant greater than or equal to 2, specifically at least one of polyimide, polytetrafluoroethylene, and epoxy negative photoresist. The fluororesin layer 32 can play a role in changing the contact angle of the packaging liquid 5 when the device is powered on. The fluororesin layer 32 has hydrophobic properties, and the structure is loose and porous, and it is easier to trap charges and maintain them for a long time; the specific optional The fluororesin layer 32 is made of one or more of amorphous fluororesin, Cytop, and Hyflon. In addition, in this embodiment, the fluororesin layer 32 has undergone plasma etching and thermal annealing treatment, the hydrophilic and hydrophobic state of the fluororesin layer 32 can be changed through the above treatment, so that the fluoropolymer surface of the fluororesin layer 32 is modified, and then It can make the charge storage layer easier to trap charges, improve the stability of the bistable state of the device, and at the same time ensure the normal progress of the photoresist coating process and the drive device during the preparation of the pixel wall.

In this embodiment, the bistable electrowetting display device needs to be used in conjunction with a power supply component. Specifically, the negative pole of the power supply component is electrically connected to the upper conductive substrate 1, and the positive pole of the power supply component is electrically connected to the lower conductive substrate 2, so as to pass The device is driven in a negative bias driving mode. Specifically, the bistable electrowetting display device can be used with an external power supply component, or the power supply component can be set as a part of the bistable electrowetting display device itself.

Please refer to FIG. 2 . FIG. 2 is a flow chart of the manufacturing process of the bistable electrowetting display device shown in FIG. 1 . As shown in Figure 2, the preparation process of the above bistable electrowetting display device includes the following steps:

1) Clean the rigid lower conductive substrate, which specifically includes: first wipe the rigid lower conductive substrate twice with 90% ethanol, then put it in an ultrasonic cleaner for ultrasonic treatment, and then dry it with nitrogen; then clean the rigid lower conductive substrate. The conductive surface of the substrate is put into the UV ultraviolet cleaning machine for UV ozone treatment to achieve deep cleaning;

2) Preparing the dielectric layer, specifically preparing the functional dielectric layer on the conductive surface of the conductive substrate under rigidity, different functional dielectric layers are prepared by different methods. Solution-type materials (such as polyimide, etc.) can be formed into films by spin coating, screen printing, inkjet printing, etc., and pre-baked and cured after film formation; while solid-state materials (such as polytetrafluoroethylene, etc. ) can be formed into a film by spraying or target sputtering. After this step, a layer of functional dielectric film can be obtained on the rigid conductive substrate;

3) Prepare the fluororesin layer, including selecting a fluoropolymer solution (such as Teflon AF 1600, Cytop, Hyflon, etc.), and curing the film on the dielectric layer by spin coating, screen printing, inkjet printing, etc. The combination of the layer and the dielectric layer constitutes the charge storage layer;

4) Etching the fluororesin layer by using a plasma etching machine, and then performing thermal annealing;

5) Prepare the pixel wall structure, including:

a. Coating of photoresist: Specifically, a negative photoresist is coated on the fluororesin layer first, and a photocrosslinking curing reaction will occur under ultraviolet light irradiation. After the coating is completed, it will be cured at high temperature to form a film;

b. Photolithography forming pixel wall: The substrate with the formed photoresist film and the mask plate are completely attached and aligned accurately, and then heated and cured again after exposure by the ultraviolet exposure machine; then the excess components are washed away with the developer, and the integrity is retained. Pixel wall structure; then high temperature reflow to restore the fluororesin layer to the hydrophobic state, and strengthen the pixel wall structure;

6) Filling and encapsulation: Specifically, first fill ink into the pixel grid formed by the pixel wall, and then perform freezing treatment to solidify the ink; immerse it in water to keep the ink in a solidified state; then raise the water temperature to melt the ink, and then take it clean The upper conductive substrate and the lower conductive substrate are arranged oppositely and bonded and packaged to obtain a bistable electrowetting display device.

In the above bistable electrowetting display device, a charge storage layer is provided on the lower conductive substrate, and the fluororesin layer in the charge storage layer has hydrophobic properties, and its structure is loose and porous, which is easy to store charges. When in use, connect the negative pole of the power supply component to the upper conductive substrate, connect the positive pole of the power supply component to the lower conductive substrate, and use a negative bias driving method. Specifically, the driving circuit control method shown in Figure 3 can be used.

Specifically, please refer to FIG. 4. FIG. 4 is a working principle diagram of the bistable electrowetting display device shown in FIG. 1 under negative bias driving state, where (N ₁ ) is the Schematic diagram of driving voltage, (N ₂ ) is the working principle diagram of the corresponding bistable electrowetting display device; N represents a, b, c, d, and the bistable liquid crystal display device in the working principle diagram omits the upper conductive substrate.

As shown in Figure 4, the working principle of the bistable electrowetting display device in the negative bias driving state is as follows: first, at zero voltage, the pixel is in the off state, as shown in Figure 4 (a ₁ ) and (a ₂ ) as shown in ); a negative bias is applied between the lower conductive substrate and the upper conductive substrate, and the surface of the fluororesin layer begins to trap charges, as shown in (b ₁ ) and (b ₂ ) in Figure 4; as the negative bias is applied With the extension of time, most of the trapped charges are stored in the fluororesin layer, and a small amount of trapped charges are stored in the dielectric layer, as shown in (c ₁ ) and (c ₂ ) in Figure 4; after power off (that is, at zero bias) , the charge storage layer presents a negative potential due to the presence of negative trapping charges, while the water environment has zero potential and presents a positive potential. At this time, the ink shrinks and the pixel is turned on, as shown in (d ₁ ) and (d ₂ ) in Figure 4 ) shown.

It can be seen from the above that by driving the above bistable electrowetting display device with a negative bias voltage, the charge storage layer can be more conducive to storing charges, so that the device can still keep the pixel on under passive conditions after the device is powered off in the pixel on state. states to achieve low-power bistable performance of electrowetting display devices.

Application effect test

Using polyimide as the dielectric layer material and Hyflon as the fluororesin layer material, the bistable electrowetting display device (referred to as device 1) was prepared by the above preparation method, and a negative bias of 30V was applied to the device 1, using The display effect of the device 1 was observed under a microscope, and the obtained results are shown in FIG. 5 . In Figure 5, (a) shows the effect diagram when a negative bias voltage of 30V is applied to the device 1, (b) shows the effect diagram after power off, (c) shows the effect diagram after power off for 1min, and (d) shows the effect diagram after power off for 2min (e) shows the rendering after 3 minutes of power failure.

In addition, using epoxy resin negative photoresist as the dielectric material and Teflon AF as the fluororesin layer material, the bistable electrowetting display device (referred to as device 2) was prepared by the above preparation method, and the device 2 was respectively applied The positive bias voltage is 24V and the negative bias voltage is 24V, and the display effect of the device 2 is observed with a microscope. The obtained results are shown in FIG. 6 and FIG. 7 . Fig. 6 is an effect diagram of device 2 in a positive bias driving state, wherein (a) in Fig. 6 represents the effect diagram of device 2 at zero bias, and (b) represents the effect of device 2 when a positive bias voltage of 24V is applied. Effect diagram, (c) shows the effect diagram after 1.5min of power failure. 7 is an effect diagram of the device 2 in a negative bias driving state, wherein (a) in FIG. 7 represents an effect diagram when a negative bias voltage of 24V is applied to the device 2, and (b) represents an effect diagram after power-off; ( c) shows the effect diagram after 2 minutes of power failure.

It can be seen from Figures 5-7 above that the bistable electrowetting display device of the present invention is driven by a negative bias voltage, and the bistable phenomenon is good.

Although the present invention has been particularly shown and described in conjunction with preferred embodiments, it will be understood by those skilled in the art that changes in form and details may be made to the present invention without departing from the spirit and scope of the invention as defined by the claims. Making various changes is within the protection scope of the present invention.

Claims (9)

1. The bistable electrowetting display device is characterized by comprising an upper conductive substrate, a lower conductive substrate and a charge storage layer, wherein the upper conductive substrate and the lower conductive substrate are oppositely arranged, the charge storage layer is arranged on one side, facing the upper conductive substrate, of the lower conductive substrate, the charge storage layer comprises a dielectric layer and a fluorine resin layer, and the dielectric layer is arranged between the lower conductive substrate and the fluorine resin layer.

2. The bistable electrowetting display device of claim 1, wherein said fluororesin layer is plasma etched and thermally annealed.

3. The bistable electrowetting display device of claim 1, wherein said fluororesin layer is made of at least one material selected from the group consisting of amorphous fluororesin, Cytop, and Hyflon.

4. The bistable electrowetting display device of claim 1, wherein said dielectric layer is made of a material having a dielectric constant greater than or equal to 2.

5. the bistable electrowetting display device of claim 4, wherein said dielectric layer is made of a material selected from at least one of polyimide, teflon, and epoxy negative photoresist.

6. The bistable electrowetting display device of claim 1, wherein said upper conductive substrate comprises an upper substrate and an upper conductive layer disposed on a surface of said upper substrate facing a side of said lower conductive substrate; the lower conductive substrate comprises a lower substrate and a lower conductive layer arranged on the lower substrate and facing to the surface of one side of the upper conductive substrate.

7. The bistable electrowetting display device of any of claims 1-6, further comprising a power supply assembly, said power supply assembly comprising a positive electrode and a negative electrode, said positive electrode being electrically connected to said lower conductive substrate, said negative electrode being electrically connected to said upper conductive substrate.

8. a method of manufacturing a bistable electrowetting display device according to any of claims 1 to 7, comprising the steps of:

S1, arranging a dielectric layer on the lower conductive substrate, and arranging a fluorine resin layer on the dielectric layer;

S2, preparing a pixel wall on the fluorine resin layer;

and S3, filling packaging liquid, and attaching and packaging the upper conductive substrate and the lower conductive substrate.

9. The method of manufacturing a bistable electrowetting display device according to claim 8, wherein in step S1, after disposing a fluororesin layer on the dielectric layer, the fluororesin layer is subjected to plasma etching and then to thermal annealing.