Disclosure of Invention
In order to solve the above technical problems, the present invention provides a bistable electrowetting display device and a method for manufacturing the same.
The technical scheme adopted by the invention is as follows: a bistable electrowetting display device comprises 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 the lower conductive substrate and faces one side of the upper 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.
according to an embodiment of the present invention, the fluorine resin layer is subjected to plasma etching and thermal annealing.
according to an embodiment of the present invention, the material of the fluororesin layer is selected from at least one of amorphous fluororesin, Cytop, Hyflon.
according to an embodiment of the present invention, the dielectric layer is made of a material having a dielectric constant greater than or equal to 2.
According to an embodiment of the present invention, the material of the dielectric layer is at least one selected from polyimide, teflon, and epoxy negative photoresist.
According to an embodiment of the present invention, the upper conductive substrate includes an upper substrate and an upper conductive layer disposed on a surface of the upper substrate facing one side of the 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.
According to an embodiment of the present invention, the power supply further includes a power supply assembly, the power supply assembly includes a positive electrode and a negative electrode, the positive electrode is electrically connected to the lower conductive substrate, and the negative electrode is electrically connected to the upper conductive substrate.
The invention also provides a preparation method of the bistable electrowetting display device, which comprises the following steps:
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 then attaching the upper conductive substrate and the lower conductive substrate for packaging.
preferably, in step S1, after the fluororesin layer is disposed on the dielectric layer, the fluororesin layer is subjected to plasma etching and then to thermal annealing.
The driving method of the bistable electrowetting display device adopts negative bias driving. Specifically, the upper conductive substrate of the bistable electrowetting display device is negatively charged (i.e., connected to the negative electrode of the power supply assembly) and the lower conductive substrate is positively charged (i.e., connected to the positive electrode of the power supply assembly).
The beneficial technical effects of the invention are as follows: the invention provides a bistable electrowetting display device and a preparation method thereof, the bistable electrowetting display device is provided with a charge storage layer, and as a fluorine resin layer in the charge storage layer has hydrophobic property and is loose and porous in structure, charges are easy to store; when the electrowetting display device is used, the negative electrode of the power supply assembly is electrically connected with the upper conductive substrate, the positive electrode of the power supply assembly is electrically connected with the lower conductive substrate, a negative bias driving mode is adopted, the charge storage layer is more favorable for storing charges, and further the pixel opening state can be still kept under a passive condition after the pixel opening state is removed, 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.
Drawings
In order to more clearly illustrate the technical solution in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below.
FIG. 1 is a schematic structural diagram of a bistable electrowetting display device according to an embodiment of the invention;
FIG. 2 is a flow chart of a process for fabricating the bistable electrowetting display device shown in FIG. 1;
FIG. 3 is a schematic diagram of one embodiment of the bistable electrowetting display device drive voltage control of FIG. 1;
FIG. 4 is a schematic diagram of the bistable electrowetting display device of FIG. 1 operating in a negative bias drive state;
FIG. 5 is a graph showing the effect of the device 1 in the negative bias driving state in the application effect test;
FIG. 6 is a graph showing the effect of the device 2 in a forward bias driving state in an application effect test;
Fig. 7 is a graph showing the effect of the device 2 in the negative bias driving state in the application effect test.
Detailed Description
The conception, the specific structure and the technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings to fully understand the objects, the schemes and the effects of the present invention. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terms "comprising" and "having," and any variations thereof, as used herein, are intended to cover non-exclusive inclusions, since the description of the invention as applied to the above figures is merely relative to the positional relationship of the various elements of the invention with respect to one another in the figures.
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 invention. The appearances of the 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. It is explicitly and implicitly understood by a person skilled in the art that the embodiments and features of the embodiments in the present application can be combined with each other without conflict.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a bistable electrowetting display device according to an embodiment of the 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 disposed opposite to each other, and a charge storage layer 3 disposed on the lower conductive substrate 2 on a side facing the upper conductive substrate 1, the charge storage layer 3 including a dielectric layer 31 and a fluororesin layer 32. The fluorine resin layer 32 is provided with pixel walls 4, and the pixel walls 4 are enclosed to form a pixel grid array; a sealed cavity is formed between the upper conductive substrate 1 and the lower conductive substrate 2 through a sealing rubber frame (not shown in the figure), and a sealing liquid 5 is filled in the sealed cavity, wherein the sealing liquid 5 is specifically a first fluid 51 and a second fluid 52 which are complementary and compatible; the first fluid 51 is filled in the pixel cells, and ink can be adopted specifically; the second fluid 52 is in contact with the upper conductive substrate 1, and water may be used as the second fluid 52.
In the present embodiment, the dielectric layer 31 is provided between the lower conductive substrate 2 and the fluororesin layer 32. Specifically, the dielectric layer 31 is provided on the surface of the lower conductive substrate 2 on the side facing the upper conductive substrate 1, and the fluororesin layer 32 is provided on the surface of the dielectric layer 31 on the side facing away from the lower conductive substrate 2.
The upper conductive substrate 1 and the lower conductive substrate 2 may be single-layer conductive substrates, or may be formed by combining substrates and conductive layers provided on the substrates. The material of the dielectric layer 31 is generally selected from materials with a dielectric constant greater than or equal to 2, and specifically, at least one of polyimide, teflon, and epoxy negative photoresist can be selected. The fluororesin layer 32 can play a role in changing the contact angle of the packaging liquid 5 when the device is powered on, and the fluororesin layer 32 has hydrophobic property, is loose and porous in structure, is easier to trap charges, and is easy to keep trapping charges for a long time; specifically, the fluororesin layer 32 may be made of one or more of amorphous fluororesin, Cytop, and Hyflon. In addition, in the embodiment, the fluororesin layer 32 is subjected to plasma etching and thermal annealing treatment, and the hydrophilic and hydrophobic states of the fluororesin layer 32 can be changed through the treatment, so that the fluoropolymer surface of the fluororesin layer 32 is modified, the charge storage layer can be more easily trapped by charges, the bistable stability of the device is improved, and meanwhile, the photoresist coating process and the normal operation of the driving device in the pixel wall preparation process can be ensured.
In the bistable electrowetting display device of the embodiment, when the display device is used, the display device needs to be matched with a power supply assembly, specifically, the negative electrode of the power supply assembly is electrically connected with the upper conductive substrate 1, the positive electrode of the power supply assembly is electrically connected with the lower conductive substrate 2, and the display device is driven in a negative bias driving mode. In particular, the bistable electrowetting display device may be used with an external power supply component, or the power supply component may be provided as part of the bistable electrowetting display device itself.
Referring to fig. 2, fig. 2 is a flow chart of a process for fabricating the bistable electrowetting display device shown in fig. 1. As shown in fig. 2, the above process for manufacturing a bistable electrowetting display device includes the following steps:
1) the washing is conductive substrate under the rigidity, specifically includes: wiping a rigid lower conductive substrate twice with 90% ethanol, then placing the rigid lower conductive substrate in an ultrasonic cleaning machine for ultrasonic treatment, and then drying the rigid lower conductive substrate by using nitrogen; putting the cleaned rigid lower conductive substrate into a UV ultraviolet cleaning machine with the conductive surface facing upwards for UV ozone treatment to realize deep cleaning;
2) And preparing a dielectric layer, namely preparing a functional dielectric layer on the conductive surface of the rigid lower conductive substrate, wherein different functional dielectric layers are prepared by different methods. The solution type material (such as polyimide and the like) can be formed into a film by adopting modes of spin coating, screen printing, ink-jet printing and the like, and a pre-baking and curing process is carried out after the film is formed; while solid materials (such as polytetrafluoroethylene) can be formed into films by spraying or sputtering a target material. Through the steps, a functional dielectric layer film can be obtained on the rigid lower conductive substrate;
3) preparing a fluorine resin layer, wherein a fluorine-containing polymer solution (such as Teflon AF 1600, Cytop, Hyflon and the like) is selected, the fluorine resin layer and the dielectric layer are combined to form a charge storage layer, and the dielectric layer is solidified into a film by spin coating, screen printing, ink jet printing and other modes;
4) Etching the fluorine resin layer by using a plasma etching machine, and then carrying out thermal annealing treatment;
5) preparing a pixel wall structure, comprising:
a. Coating a photoresist: specifically, a negative photoresist is coated on a fluororesin layer, a photocrosslinking curing reaction can occur under the irradiation of ultraviolet light, and a film is formed by high-temperature curing after the coating is finished;
b. forming a pixel wall by photoetching: completely attaching the substrate with the formed photoresist film to a mask plate, accurately aligning, exposing by an ultraviolet exposure machine, and then carrying out heat curing again; then washing off redundant components by using a developing solution, and reserving a complete pixel wall structure; then high-temperature reflux is carried out to enable the fluorine resin layer to recover the hydrophobic state and reinforce the pixel wall structure;
6) Filling and packaging: specifically, filling ink into pixel cells formed by enclosing a pixel wall, and then freezing to solidify the ink; immersing the ink in water to keep the ink in a solidified state; and then raising the water temperature to melt the ink, and then arranging the clean upper conductive substrate and the clean lower conductive substrate oppositely, bonding and packaging to obtain the bistable electrowetting display device.
In the bistable electrowetting display device, the charge storage layer is arranged on the lower conductive substrate, and the fluorine resin layer in the charge storage layer has hydrophobic property, loose and porous structure and easy charge storage. When the power supply is used, the negative electrode of the power supply component is connected with the upper conductive substrate, the positive electrode of the power supply component is connected with the lower conductive substrate, and a negative bias driving mode is adopted, specifically, a driving circuit control mode shown in fig. 3 can be adopted.
Specifically, referring to fig. 4, fig. 4 is a schematic diagram illustrating the operation of the bistable electrowetting display device shown in fig. 1 in a negative bias driving state, wherein (N)1) Is a driving voltage diagram of a bistable electrowetting display device, (N)2) Is a working schematic diagram of a corresponding bistable electrowetting display device; n represents a, b, c and d, and the bistable liquid crystal display device omits an upper conductive substrate in the working schematic diagram.
As shown in fig. 4, the operation 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 in FIG. 4 (a)1) And (a)2) Shown; applying a negative bias between the lower conductive substrate and the upper conductive substrate, trapped charges begin to appear on the surface of the fluororesin layer, as shown in FIG. 4 (b)1) And (b)2) Shown; with the application of the negative bias for a prolonged period of time, most of the trapped charges are stored in the fluororesin layer and a small amount of the trapped charges are stored in the dielectric layer, as shown in FIG. 4 (c)1) And (c)2) Shown; after power-off (i.e., zero-bias), the charge storage layer exhibits a negative potential due to the presence of negative trapped charges, while the aqueous environment exhibits a positive potential at zero potential, at which time the ink contracts and assumes a pixel-on state, as shown in FIG. 4 (d)1) And (d)2) As shown.
therefore, the bistable electrowetting display device is driven by negative bias, so that the charge storage layer is more favorable for storing charges, and the device can still keep the pixel opening state under a passive condition after the pixel opening state is de-electrified, thereby realizing the low-power consumption bistable performance of the electrowetting display device.
Application effect test
The bistable electrowetting display device (device 1 for short) is prepared by using polyimide as a dielectric layer material and Hyflon as a fluorine resin layer material according to the preparation method, negative bias voltage of 30V is applied to the device 1, the display effect of the device 1 is observed by using a microscope, and the obtained result is shown in FIG. 5. Fig. 5 (a) shows an effect diagram when a negative bias voltage of 30V is applied to the device 1, (b) shows an effect diagram after power-off, (c) shows an effect diagram after power-off for 1min, (d) shows an effect diagram after power-off for 2min, and (e) shows an effect diagram after power-off for 3 min.
In addition, an epoxy negative photoresist is used as a dielectric material, Teflon AF is used as a fluorine resin layer material, the bistable electrowetting display device (device 2 for short) is prepared by the above preparation method, a positive bias voltage 24V and a negative bias voltage 24V are respectively applied to the device 2, and the display effect of the device 2 is observed by a microscope, and the obtained results are shown in fig. 6 and 7. Fig. 6 is an effect diagram of the device 2 in a forward bias driving state, in which (a) in fig. 6 shows an effect diagram of the device 2 at zero bias, (b) shows an effect diagram of the device 2 at 24V of forward bias, and (c) shows an effect diagram after power-off for 1.5 min. Fig. 7 is an effect diagram of the device 2 in the negative bias driving state, wherein (a) in fig. 7 shows an effect diagram when a negative bias 24V is applied to the device 2, and (b) shows an effect diagram after power-off; (c) the effect graph after 2min of power failure is shown.
As can be seen from fig. 5-7, the bistable electrowetting display device of the present invention is driven by negative bias, and the bistable state is good.
While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.