CN105445927A - Printing ink motion controllable electrowetting display and preparation method thereof - Google Patents

Abstract

The invention discloses an electrowetting display with controllable ink movement and a preparation method thereof. The display comprises a conductive layer, an insulating layer arranged on the upper surface of the conductive layer, and a pixel wall arranged on the upper surface of the insulating layer. The layer is a double-layer insulating layer. The double-layer insulating layer includes a hydrophilic insulating layer and a hydrophobic insulating layer. The hydrophilic insulating layer completely covers the upper surface of the conductive layer, and the hydrophobic insulating layer covers the upper surface of the hydrophilic insulating layer. The insulating layer exposes part of the upper surface of the hydrophilic insulating layer. The thickness of the ink decreases gradually from the side of the hydrophobic insulating layer to the side of the hydrophilic insulating layer. After the voltage is applied, the ink ruptures at the thinnest point, and the ink is broken from the side of the hydrophilic insulating layer to the side of the hydrophobic insulating layer. The contraction in the side direction realizes the effective control of the ink rupture position and the contraction direction of the ink movement when the electrowetting display pixel unit is powered on.

Description

An electrowetting display with controllable ink movement and its preparation method

technical field

The invention relates to the technical field of electrowetting display devices, in particular to an electrowetting display with controllable ink movement and a preparation method thereof.

Background technique

Referring to Figures 1-2, a traditional electrowetting display includes a first substrate and a second substrate, the first substrate includes an upper substrate 1', an upper conductive layer 2' and an encapsulant frame 3', and the second substrate includes a lower substrate 6' , lower conductive layer 9', insulating layer 8', hydrophobic layer 5', pixel wall 4', ink 10' and electrolyte solution 7' are filled between the first substrate and the second substrate, wherein the ink 10' is filled in Inside the pixel grid 11' surrounded by the pixel wall 4'. The switching of the electrowetting display pixel unit starts with the rupture of the ink, followed by the formation of non-polar liquid (ink 10') / polar liquid (electrolyte solution 7') / solid surface (hydrophobic layer 5', usually fluoropolymer Object material, AF1600, AF1600x, etc.) three-phase contact line, the contact line moves and develops under the action of electric field force, and the difference in ink contraction state forms the effect of pixel opening and grayscale in the optical sense. In particular, to obtain a good optical display effect when the display device is powered on, it is necessary to reliably control the position and direction of the ink rupture. At present, the more commonly used method, referring to Figure 1, is to form a local cavity 12' (usually called notch) of the driving electrode layer (such as ITO) at a corner of the pixel unit; use the local uneven distribution of the applied electric field to realize ink movement Shrink to the corner of the pixel (notch part). A large number of experiments and theoretical simulation results show that the selection of the ink rupture point and the position of the thinnest ink thickness occur preferentially, and the threshold voltage required for ink rupture depends on the thickness of the thinnest part of the ink; obviously the role of notch is to control the shrinkage end point of the ink position, it is impossible to effectively control the rupture position of the ink and reduce the turn-on voltage of the pixel. More importantly, in the process of etching the conductive backplane (such as the commonly used ITO conductive glass) to manufacture the notch, it is easy to appear irregular jagged edges as shown in the enlarged view in Figure 1. When power is applied to drive, the electric field will be uneven due to the charge distribution layout on the jagged edge. During the electrical measurement, the charges will tend to gather at the irregular conductive tips, forming a local high charge density, which is very easy to cause the breakdown of the insulating layer. , causing the display to be damaged.

Contents of the invention

The technical problem to be solved by the present invention is to provide an electrowetting display with controllable ink movement and a preparation method thereof.

The technical scheme that the present invention takes is:

An electrowetting display with controllable ink movement, comprising an upper substrate and a lower substrate, the lower substrate includes a conductive layer, an insulating layer arranged on the upper surface of the conductive layer, and an insulating layer arranged on the upper surface of the insulating layer A pixel wall, the pixel wall encloses a plurality of pixel grids, the insulating layer is a double-layer insulating layer, the double-layer insulating layer includes a hydrophilic insulating layer and a hydrophobic insulating layer, and the hydrophilic insulating layer completely covers the The upper surface of the conductive layer, the hydrophobic insulating layer is disposed on the upper surface of the hydrophilic insulating layer, and the hydrophobic insulating layer exposes part of the upper surface of the hydrophilic insulating layer in the pixel grid.

Preferably, one side edge of the hydrophilic insulating layer exposed in each pixel grid is flush with one side in the same direction of each pixel grid.

Further preferably, the exposed hydrophilic insulating layer in the pixel grid is elongated, and one side edge of the exposed elongated hydrophilic insulating layer is flush with one side of the pixel grid.

Preferably, the proportion of the area of the hydrophilic insulating layer exposed in the pixel grid to the area of the pixel grid is less than or equal to 5%.

Preferably, the contact angle of water droplets of the hydrophilic insulating material is less than or equal to 40°.

Preferably, the material of the hydrophobic insulating layer is a fluorine-containing polymer material or a polyimide material.

The present invention also provides a method for preparing an electrowetting display with controllable ink movement, comprising the step of preparing a double-layer insulating layer, the double-layer insulating layer comprising a hydrophilic insulating layer and a hydrophobic insulating layer, the hydrophilic insulating layer The layer completely covers the upper surface of the conductive layer of the lower substrate, the hydrophobic insulating layer covers the upper surface of the hydrophilic insulating layer, and the hydrophobic insulating layer exposes part of the upper surface of the hydrophilic insulating layer in the pixel grid .

Preferably, the step of preparing a double insulating layer specifically includes:

Coating a layer of hydrophilic insulating material on the upper surface of the conductive layer of the lower substrate, curing, and preparing a hydrophilic insulating layer;

Coating a layer of hydrophobic insulating material on the upper surface of the hydrophilic insulating layer and curing it to prepare a hydrophobic insulating layer;

Part of the hydrophobic insulating layer is etched by a patterned dry etching process to expose part of the hydrophilic insulating layer.

Preferably, the contact angle of water droplets of the hydrophilic insulating material is less than or equal to 40°.

Preferably, the material of the hydrophobic insulating layer is a fluorine-containing polymer material or a polyimide material.

The beneficial effects of the present invention are:

The invention provides an electrowetting display with controllable ink movement and a preparation method thereof. The electrowetting display includes an upper substrate and a lower substrate, and the lower substrate includes a conductive layer disposed on the upper surface of the conductive layer. An insulating layer and a pixel wall arranged on the upper surface of the insulating layer, the pixel walls enclose a plurality of pixel grids, the insulating layer is a double-layer insulating layer, and the double-layer insulating layer includes a hydrophilic insulating layer and a A hydrophobic insulating layer, the hydrophilic insulating layer completely covers the upper surface of the conductive layer, the hydrophobic insulating layer covers the upper surface of the hydrophilic insulating layer, and the exposed part of the hydrophobic insulating layer in the pixel grid The upper surface of the hydrophilic insulating layer. Since the material of the hydrophilic insulating layer is a hydrophilic material, due to the difference in wettability between the ink material and the hydrophilic insulating layer and the hydrophobic insulating layer, the thickness of the ink is from the side of the hydrophobic insulating layer to the The direction of the side of the hydrophilic insulating layer decreases gradually, even at the edge of the exposed hydrophilic insulating layer, a three-phase contact line (ink, electrolyte solution and insulating layer) will be pre-formed, and after the voltage is applied, the ink is at the thinnest thickness Crack occurs at the position of the insulating layer and shrinks from the side of the hydrophilic insulating layer to the side of the hydrophobic insulating layer. The present invention can realize the power supply of the electrowetting display pixel unit without changing the electric field distribution substantially. In this case, the effective control of the ink rupture position and the ink movement contraction direction, because the threshold voltage required for ink rupture depends on the thickness of the thinnest part of the ink, the display of the present invention can effectively reduce the threshold voltage for pixel opening, and can also effectively avoid notch Design approach Risk of insulation breakdown due to localized high charge density.

Description of drawings

1 is a cross-sectional view of a conventional electrowetting display;

FIG. 2 is a structural diagram of a pixel wall of a conventional electrowetting display;

Figure 3 is a cross-sectional view of an electrowetting display with controllable ink movement when no voltage is applied;

Figure 4 is a cross-sectional view of an electrowetting display with controllable ink movement upon application of a voltage.

detailed description

The idea, specific structure and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, features and effects of the present invention. Apparently, the described embodiments are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts belong to The protection scope of the present invention. In addition, all the connection/connection relationships involved in the patent do not simply refer to the direct connection of components, but mean that a better connection structure can be formed by adding or reducing connection accessories according to specific implementation conditions. The various technical features in the invention can be combined interactively on the premise of not conflicting with each other.

The invention provides an electrowetting display with controllable ink movement and a preparation method thereof. The electrowetting display is also called an electrowetting display, and the invention is also applicable to the electrowetting display. The cross-sectional view of the electrowetting display with controllable ink movement is shown in Figure 3, the display includes an upper substrate and a lower substrate, and the lower substrate includes a substrate 10, a conductive layer 6, and The insulating layer and the pixel wall 4 arranged on the upper surface of the insulating layer, the pixel wall 4 encloses a plurality of pixel grids, the insulating layer is a double-layer insulating layer, and the double-layer insulating layer includes a hydrophilic insulating layer 9 and a hydrophobic insulating layer 5, the hydrophilic insulating layer 9 completely covers the upper surface of the conductive layer 6, the hydrophobic insulating layer 5 is arranged on the upper surface of the hydrophilic insulating layer 9, in the pixel grid The hydrophobic insulating layer 5 exposes part of the upper surface of the hydrophilic insulating layer 9 . Since the hydrophilicity of the exposed hydrophilic insulating layer 9 is greater than that of the hydrophobic insulating layer 5, the surface of the exposed hydrophilic insulating layer 9 will be covered with a layer of electrolyte solution, and the surface of the hydrophobic insulating layer 5 will be covered with a layer of ink 8. The thickness of the exposed ink 8 on the side of the hydrophilic insulating layer 9 will be smaller than the thickness of the ink 8 on the side of the hydrophobic insulating layer 5, reducing the thickness of the side of the ink 8 can achieve the effect of reducing the driving threshold voltage. The second substrate includes an upper substrate 1 , a conductive layer 2 and an encapsulant frame 3 , an electrolyte solution 7 and ink 8 are filled between the first substrate and the second substrate, and the ink 8 is filled in the pixel cells. The upper substrate and the lower substrate seal the electrolyte solution 7 and the ink 8 between the upper substrate and the lower substrate through the encapsulant frame 3 . In a preferred embodiment, the contact angle of water droplets of the hydrophilic insulating material is less than or equal to 40°. In a further preferred embodiment, the material of the hydrophilic insulating layer 9 is silicon dioxide or titanium dioxide, and the hydrophobic insulating layer The material of layer 5 is fluoropolymer material or polyimide material. The material of the hydrophilic insulating layer 9 is a hydrophilic material. Due to the difference in wettability between the ink 8 material and the hydrophilic insulating layer 9 and the hydrophobic insulating layer 5, the thickness of the ink 8 is from the hydrophobic insulating layer The direction from the side of the layer 5 to the side of the hydrophilic insulating layer 9 is decreasing, and the three-phase contact line (ink 8, electrolyte solution 7 and insulating layer) is pre-formed at the edge where the hydrophilic insulating layer 9 is exposed, and the ink 8 Cracks occur at the thinnest position, and shrink from the hydrophilic insulating layer 9 side to the hydrophobic insulating layer 5 side. Effective control of ink 8 rupture position and ink 8 movement contraction direction when power is applied to wet display pixel unit. Since the threshold voltage required for the rupture of the ink 8 depends on the thickness of the thinnest part of the ink 8, the display of the present invention can effectively reduce the threshold voltage for turning on the pixel. The threshold voltage of the traditional electrowetting display is 24V~26V, and the aperture ratio reaches The driving voltage of 60% is about 35V, the threshold voltage of the electrowetting display of the present invention is 5V, and the driving voltage of 60% aperture ratio is 24V, which is significantly lower than the traditional electrowetting display, and the The inventive electrowetting display can also effectively avoid the risk of insulation layer breakdown caused by the notch design method due to local high charge density.

In a preferred embodiment, one side edge of the hydrophilic insulating layer 9 exposed in each pixel grid is flush with one side in the same direction of each pixel grid. In a further preferred embodiment, the hydrophilic insulating layer 9 exposed in the pixel grid is elongated, and one side edge of the exposed elongated hydrophilic insulating layer 9 is flush with one side of the pixel grid . The proportion of the area of the hydrophilic insulating layer 9 exposed in the pixel grid to the area of the pixel grid is less than or equal to 5%. The size of the area of the hydrophilic insulating layer 9 that needs to be exposed is related to the hydrophilic performance of the material of the hydrophilic insulating layer 9. The stronger the hydrophilicity of the material, the larger the area of the hydrophilic insulating layer 9 that needs to be exposed. smaller. The larger the exposed area of the hydrophilic insulating layer 9 of the same material, the lower the driving voltage, but at the same time, it should be considered that the exposed hydrophilic insulating layer 9 will also have openings when no voltage is applied because of its hydrophilicity. In order to ensure the performance of the display, the exposed area should not be too large.

The present invention also provides a method for preparing an electrowetting display with controllable ink movement as described above, including the step of preparing a double-layer insulating layer, the double-layer insulating layer comprising a hydrophilic insulating layer 9 and a hydrophobic insulating layer 5 , the hydrophilic insulating layer 9 completely covers the upper surface of the conductive layer 6 of the lower substrate, the hydrophobic insulating layer 5 covers the upper surface of the hydrophilic insulating layer 9, and the hydrophobic insulating layer 5 in the pixel grid Layer 5 exposes part of the upper surface of the hydrophilic insulating layer 9 . The step of preparing a double-layer insulating layer specifically includes: coating a layer of hydrophilic insulating material on the upper surface of the conductive layer 6 of the lower substrate, curing, and preparing a hydrophilic insulating layer 9; The upper surface of 9 is coated with a layer of hydrophobic insulating material and cured to prepare a hydrophobic insulating layer 5; a part of the hydrophobic insulating layer 5 is etched by a patterned dry etching process to expose a part of the hydrophilic insulating layer 9. The etched pattern can be any pattern. In a preferred embodiment, one side edge of the pattern of the hydrophobic insulating layer 5 in each etched pixel grid is the same as one side of each pixel grid in the same direction. flush. In a further preferred embodiment, the etched pattern of the hydrophobic insulating layer 5 in each pixel grid is long and narrow, and one side edge of the long and narrow pattern is flush with one side of the pixel grid. The dry etching process includes sputtering etching, reactive ion etching and high density plasma etching. The contact angle of water droplets of the hydrophilic insulating material is less than or equal to 40°. In a preferred embodiment, the material of the hydrophilic insulating layer is silicon dioxide or titanium dioxide. The material of the hydrophobic insulating layer is a fluorine-containing polymer material or a polyimide material.

Claims (10)

1. An electrowetting display with controllable ink movement, comprising an upper substrate and a lower substrate, the lower substrate comprising a conductive layer, an insulating layer arranged on the upper surface of the conductive layer and an upper surface of the insulating layer The pixel wall on the surface, the pixel wall encloses a plurality of pixel grids, it is characterized in that the insulating layer is a double-layer insulating layer, and the double-layer insulating layer includes a hydrophilic insulating layer and a hydrophobic insulating layer, and the hydrophilic insulating layer The insulating layer completely covers the upper surface of the conductive layer, the hydrophobic insulating layer is arranged on the upper surface of the hydrophilic insulating layer, and the hydrophobic insulating layer exposes part of the hydrophilic insulating layer in the pixel grid. surface. 2. The electrowetting display with controllable ink movement according to claim 1, characterized in that, one side edge of the hydrophilic insulating layer exposed in each pixel grid is in contact with each pixel grid. One side in the same direction is flush. 3. The electrowetting display with controllable ink movement according to claim 2, wherein the hydrophilic insulating layer exposed in the pixel grid is elongated, and the elongated hydrophilic insulating layer exposed The edge of one side of the is flush with one side of the pixel grid. 4. The electrowetting display with controllable ink movement according to claim 1, wherein the proportion of the area of the hydrophilic insulating layer exposed in the pixel grid to the area of the pixel grid is less than or equal to 5%. 5 . The electrowetting display with controllable ink movement according to claim 1 , wherein the contact angle of the water droplets of the hydrophilic insulating material is less than or equal to 40°. 6 . The electrowetting display with controllable ink movement according to claim 1 , wherein the material of the hydrophobic insulating layer is a fluorine-containing polymer material or a polyimide material. 7. A method for preparing an electrowetting display with controllable ink movement, characterized in that it comprises the step of preparing a double-layer insulating layer, the double-layer insulating layer comprising a hydrophilic insulating layer and a hydrophobic insulating layer, the hydrophilic The insulating layer completely covers the upper surface of the conductive layer of the lower substrate, the hydrophobic insulating layer covers the upper surface of the hydrophilic insulating layer, and the hydrophobic insulating layer exposes part of the hydrophilic insulating layer in the pixel grid surface. 8. The preparation method according to claim 7, wherein the step of preparing a double insulating layer specifically comprises: Coating a layer of hydrophilic insulating material on the upper surface of the conductive layer of the lower substrate, curing, and preparing a hydrophilic insulating layer; Coating a layer of hydrophobic insulating material on the upper surface of the hydrophilic insulating layer and curing it to prepare a hydrophobic insulating layer; Part of the hydrophobic insulating layer is etched by a patterned dry etching process to expose part of the hydrophilic insulating layer. 9. The preparation method according to claim 7, characterized in that, the contact angle of the water droplet of the hydrophilic insulating material is less than or equal to 40°. 10. The preparation method according to any one of claims 7-9, characterized in that, the material of the hydrophobic insulating layer is a fluorine-containing polymer material or a polyimide material.