CN105097672A - Preparation method for electrowetting display substrate - Google Patents

Abstract

The invention provides a method for preparing a lower substrate of an electrowetting display. A template method is used to first prepare a pixel wall, and then transfer it to a hydrophobic insulating layer, thereby realizing patterning on a flat substrate surface or a curved substrate surface. Compared with traditional photolithography technology, the process is simple and easy to implement, and the cost is low. The template can be reused up to 100 times or more, and there is no precision limit brought by light scattering, and complex three-dimensional structures can be manufactured with high precision. The control is also good, and it overcomes the deficiency that the pixel wall prepared by the traditional photolithography process cannot be realized on the curved substrate, and the microstructure manufacturing on the curved surface can be realized. The present invention can be used in electrowetting devices.

Description

A method for preparing an electrowetting display lower substrate

technical field

The invention relates to the technical field of electrowetting display, and in particular to a method for preparing a lower substrate of an electrowetting display, especially a method for preparing a lower substrate of an electrowetting display capable of preparing pixel walls on a curved substrate.

Background technique

Electrowetting (EFD, Electrofluidic Display), also known as electrowetting, is a display technology that controls the movement of ink by controlling the wettability of the substrate surface material by controlling the voltage. Referring to Figure 1 and Figure 2, the electrowetting display device includes an upper substrate 1, an encapsulant frame 2 and a lower substrate 4, and the lower substrate 4 includes a conductive layer 3 (TFT, ITO substrate, metal electrode substrate, polymer conductive film), hydrophobic Insulation layer 5, pixel wall 6. The sealed cavity composed of the upper substrate 1 and the lower substrate 4 is filled with a non-conductive first fluid 7 (alkane, silicone oil, etc.), and a conductive second fluid 8 (water, salt solution or ionic liquid), the fluids are in contact with each other and immiscible. The hydrophobic insulating layer 5 of the electrowetting display is its core functional structure. This layer covers the conductive layer 3 of the lower substrate 4, and a wall pattern, that is, a pixel wall 6 is arranged on it, and a pixel grid 9 surrounded by the pixel wall 6 The structure is the display area, and the electrowetting display device produces a display effect on this display area.

The pixel wall material is generally a photoresist material, also known as a photoresist, which is patterned on the surface of the hydrophobic insulating layer through a traditional photolithography process. Using the photochemical reaction characteristics of the photoresist, under ultraviolet irradiation, Through the photochemical reaction of photoresist, the pattern on the mask plate is accurately printed on the surface of the workpiece coated with photoresist, and then the photoresist is developed to obtain complex and fine patterns. The process of coating, baking, exposure, development and other steps is relatively complicated.

Moreover, due to the technical limitations of exposure and other processes at this stage, the patterning of pixel wall materials requires a flat substrate, and it is difficult to perform photolithography for curved substrates, thus limiting the application of electrowetting technology in the field of curved displays. It is of great significance to find a method for preparing pixel walls that can realize curved display screens.

Contents of the invention

In view of the above problems, the object of the present invention is to provide a method for preparing a lower substrate of an electrowetting display.

The technical scheme that the present invention takes is:

A method for preparing a lower substrate of an electrowetting display device, comprising the step of forming a pixel wall on a hydrophobic insulating layer of the lower substrate of an electrowetting display device, the step being specifically:

S10: Prepare a patterned template according to the arrangement of the pixel walls;

S20: Fill the template with pixel wall material, semi-finalized;

S30: Transfer the pixel wall from the template to the hydrophobic insulating layer of the lower substrate of the electrowetting display.

Preferably, the template is an inorganic material, a metal material or a polymer material. Preferably, the inorganic material is glass or single crystal silicon, the polymer material is any one of PDMS, PMMA, PI, PET, PEN, PC, PCO, PES and PAR; the metal material is aluminum, Copper or steel, more preferably aluminum.

Further preferably, the template is a flexible template that can be bent, which facilitates the preparation of pixel walls on the surface of the curved substrate.

Preferably, in said S20, the filling method of the pixel wall material is any one of spin coating, roll coating, slit coating, dip coating, spray coating, doctor blade coating, gravure printing, embossing, screen printing and inkjet printing. kind.

Preferably, in the S20, the semi-setting is performed by heating, the heating temperature is 80-120° C., and the heating time is 1 min-1 h.

Preferably, the semi-finalized pixel wall material contains a solvent, and the solvent content A is: 20wt%≤A≤65wt%; more preferably, 30wt%≤A≤50wt%.

Further preferably, said S30 specifically includes the following steps:

Fit the side of the template filled with the pixel wall material closely with the hydrophobic insulating layer; the tight fit can be achieved by applying pressure and/or vacuuming;

Heating to remove the solvent in the pixel wall material, curing and molding;

Remove the mold to further solidify the pixel wall.

The beneficial effects of the present invention are: the present invention provides a method for preparing the lower substrate of an electrowetting display. The template method is used to prepare the pixel wall first, and then transfer it to the hydrophobic insulating layer, so that it can be realized on the surface of the flat substrate or Compared with the traditional photolithography technology, the patterning of the surface of the curved substrate is simple and easy to implement, and the cost is low. The template can be reused up to 100 times or more, and there is no precision limit caused by light scattering, which can Manufacture complex three-dimensional structure, precision control is also good, and solve the problem that the traditional photolithography process cannot be used to prepare pixel walls on curved substrates, and can realize microstructure manufacturing on curved surfaces. The present invention can be used in electrowetting devices.

Description of drawings

Figure 1 is a schematic diagram of the structure of an electrowetting display device.

Fig. 2 is a schematic diagram of a pixel lattice structure of an electrowetting display device.

Fig. 3 is a template making flow chart of the present invention.

Fig. 4 is a flow chart of the preparation of the pixel wall of the present invention.

Fig. 5 is a microstructure diagram and a height distribution diagram of the base template, the template and the obtained pixel wall according to a specific embodiment of the present invention.

Fig. 6 is a schematic diagram of the shape of the base template (Fig. 6-(a)) and the template (Fig. 6-(b)) corresponding to the inverted trapezoidal pixel wall (Fig. 6-(c)) in other embodiments of the present invention.

Detailed ways

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. The various technical features in the invention can be combined interactively on the premise of not conflicting with each other.

The lower substrate of the electrowetting display described in the present invention may also be called an electrowetting substrate or an electrowetting display front plate, etc.

Referring to Figures 3-4, a method for preparing the lower substrate 4 of an electrowetting display device includes the step of forming a pixel wall 6 on the hydrophobic insulating layer 5 of the lower substrate 4 of an electrowetting display device, specifically:

S10 : Prepare a patterned template 11 according to the arrangement of the pixel walls 6 .

The template 11 can be an inorganic material, a metal material or a polymer material. Preferably, the inorganic material is glass or single crystal silicon, the polymer material is any one of PDMS, PMMA, PI, PET, PEN, PC, PCO, PES and PAR; the metal material is aluminum, Copper or steel, etc., preferably aluminum.

For example, when the material of the template 11 is a rigid material such as glass or metal, it can be patterned by a photolithography process or an etching process to obtain a template 11 matching the pattern arrangement of the pixel walls 6 .

If the material of the template 11 is a polymer, it can be prepared by liquid casting, and the template 11 can be made to have a certain degree of flexibility by adjusting the ratio of the prepolymer to the curing agent, and can have a certain degree of rigidity while being bendable, or it can be The hardness of the template 11 is improved by adjusting the baking temperature and time. For the specific process of liquid casting, please refer to Figure 3, which will be described in detail later.

Preferably, the template 11 is a flexible template, which facilitates the preparation of pixel walls on the curved surface of the lower substrate 4 .

Those skilled in the art can comprehensively consider the properties of the template 11 material, process complexity, pattern complexity, precision control and other requirements, and select an appropriate processing technology to obtain the template 11 .

In addition, in order to remove the water molecules on the surface of the template 11, the patterned template 11 may be pre-heated. The heating temperature is 80-120° C. and the heating time is 1-10 min. For example, the specific heating temperature can be 80°C, 85°C, 90°C, 100°C, 110°C, 120°C, etc., and the heating time can be 1min, 2min, 3min, 5min, 7min, 10min; according to the nature of the material and the heating time to make sure.

S20: filling the template 11 with the pixel wall material 12, semi-finalized;

Specifically, the pixel wall material 12 with an appropriate concentration can be applied by any method of spin coating, roller coating, slit coating, dip coating, spray coating, doctor blade coating, gravure printing, embossing, screen printing and inkjet printing. Filled in template 11.

The pixel wall material 12 can be any hydrophilic substance, including hydrophilic polymers, hydrophilic inorganic materials, hydrophilic organic/inorganic hybrid materials, and the like. For example, commonly used positive photoresists, negative photoresists, SOG materials, and the like.

For the pixel wall material 12 with a large solvent content, usually greater than 65%, due to the low concentration, after filling, deformation or material dripping may occur in the subsequent transfer process. Preferably, part of the solvent can be evaporated by heating. For semi-setting, the heating temperature is generally 80-120°C, and the heating time is 1min-1h. The heating time is selected by the solvent content and the properties of the material; after heating, the solvent evaporates, which can realize the semi-setting of the material, but at the same time Pay attention to controlling the temperature and time of heating so that the pixel wall material 12 also has a suitable viscosity, so that in the subsequent transfer process, there is no need to add an additional adhesive layer, and the viscosity of the pixel wall material 12 itself is used to realize the combination with the hydrophobic insulating layer 5 .

For the pixel wall material 12 with a proper solvent content, there is no need to heat this step. After filling, use a scraper to remove excess material, or heat it slightly, such as at 80°C for 1 minute, to solidify the outer layer. Simple semi-setting is enough.

Preferably, the solvent content A in the semi-finalized pixel wall material 12 is: 20wt%≤A≤65wt%; more preferably, 30wt%≤A≤50wt%, so that the pixel wall material 12 has a suitable viscosity and can be transferred During the process, there will be no phenomena such as material dripping, and at the same time, the combination with the hydrophobic insulating layer 5 can be achieved by utilizing its own viscosity.

S30: Transfer the pixel wall 6 from the template 11 to the hydrophobic insulating layer 5 of the lower substrate 4 of the electrowetting display.

There are many transfer methods, the pixel wall 6 can be demolded from the template 11 first, and then transferred and combined with the hydrophobic insulating layer 5; since the material of the pixel wall 6 is a flexible material, it is difficult to guarantee the accuracy after demoulding and then transferring. , using the method of first transfer and then demoulding, including the following steps:

1) The side of the template 11 filled with the material of the pixel wall 6 is tightly attached to the hydrophobic insulating layer 5; the bonding can be achieved by pressurization and/or vacuuming, preferably, pressurization and vacuuming are carried out at the same time, and kept until The solvent evaporation process of the pixel wall 6 is completed, so that the close combination of the pixel wall 6 and the hydrophobic insulating layer 5 is realized.

In order to facilitate the combination with the pixel wall 6, the surface of the hydrophobic insulating layer 5 may be treated with hydrophilicity in advance.

2) Heating to remove the solvent in the material of the pixel wall 6, curing and molding.

Curing and shaping the pixel wall 6 facilitates demoulding; at the same time, the shape of the pixel wall 6 can be better controlled by utilizing the limiting function of the template 11 .

3) Remove the mold and further solidify the pixel wall.

After demoulding, a further curing process is performed so that the shape of the pixel wall 6 is fixed. Because, if the material of the pixel wall 6 is a positive photoresist material, or other polymer solution, because it is a highly polymerized material, the solvent will cure itself after volatilization, and no further exposure and curing treatment is required; and if the pixel wall 6. The material is a negative photoresist. After the solvent is removed by heating, full exposure is required to realize the curing of the pixel wall 6. When the template 11 is a transparent polymer template, the full exposure step can occur in the demoulding process. Before, it can also happen after demoulding. Preferably, the pixel wall 6 is cured by full exposure first, and then the demoulding 11 is performed.

In addition, for the substrate 11 after demoulding, the surface cleaning treatment is first performed, and the cleaning agent can be selected as a solvent for the material of the pixel wall 6, and then further heating and hardening treatment is performed for the next use, and the heating temperature is generally 80-200°C. The time is 1min-2h.

The preparation method of the template 11 of the present invention will be described in detail below, mainly taking the liquid casting method as an example, and reference can be made to FIG. 3 for details.

Firstly, patterning is performed on a rigid substrate such as glass or silicon wafer by using a photolithography process or an etching process to obtain a base template 10 . The base template 10 forms a convex structure corresponding to the pattern of the pixel wall 6 on the bottom surface. If it is prepared by photolithography, the type of photoresist that can be used for the base template 10 is not limited. Both positive and negative resists are acceptable, such as commonly used SU -8 photoresist.

Next, the plastic polymer material is cast on the surface of the base template 10 obtained above, and solidified, so that the pattern of the base template 10 is reversely copied to obtain a template 11, and the template 11 is formed on its top surface to be prepared. The concave structure corresponding to the pixel wall 6 pattern. The polymer material can be but not limited to polydimethylsiloxane (PDMS), polymethylmethacrylate (PMMA), polyimide (PI), polyethylene terephthalate (PET) , polyethylene naphthalate (PEN), polycarbonate (PC), polycyclic olefin (PCO), polyarylethersulfone (PES), polyarylate (PAR), etc.

Taking PDMS as an example, the specific preparation process is as follows: mix the PDMS prepolymer and curing agent at a mass ratio of 8-12:1, and use vacuum to make the air bubbles in the mixture float to the surface and burst; then cast in The surface of the base template 10 is heated and solidified at 70-150° C. for 0.5-3 hours to solidify and cross-link the PDMS material, and then cooled. In this process, by adjusting the ratio of prepolymer and curing agent, the PDMS template can be made to have a certain degree of flexibility, and can be bent while having a certain rigidity. Adjusting the baking temperature and time can also adjust the softness and hardness of the PDMS template.

Finally, the template 11 is peeled off from the base template 10 to obtain the template 11 .

The prepared template 11 can also be baked on a hot plate or in an oven at a temperature of 90° C. for 10 minutes to remove water molecules on the surface of the template 11 .

Further, by adopting the above steps, the pixel wall 6 is prepared on the surface of the hydrophobic insulating layer 5 .

Fig. 5 shows a specific embodiment of the present invention, with the scheme shown in Fig. 3 and Fig. 4 of the present invention, the microstructure (5a-1) of the PDMS-based template 10 used and the height distribution diagram measured by the step meter ( 5a-2), and the microstructure (5b-1) of the template 11 obtained from the base template 10 shown in FIG. The microstructure (5c-1) of the pixel wall 6 prepared by the template 11 and the height distribution map (5c-2) measured by the step meter; it can be seen from the figure that the obtained pixel wall 6 has a uniform structure and good size control.

The shapes of the base template 10 and the template 11 of the present invention are not limited to those shown in FIG. 3 , and specifically vary according to the shape of the pixel wall 6 , such as the shape shown in FIG. 6 . If it is desired to obtain an inverted trapezoidal pixel wall structure (as shown in Figure 6-(c)), the base template 10 and template 11 used are shown in Figure 6-(a) and Figure 6-(b) respectively.

It can be seen that the template 11 of the present invention is easy to manufacture, low in cost, and has good precision, and due to the selection of flexible materials, it has good wear resistance, and the template can be reused up to 100 times or more, which is far greater than that of traditional glass. The utilization rate of the rigid planar template is equal, and there is no precision limitation brought by light scattering, and complex three-dimensional structures can be manufactured with good precision control, and microstructure fabrication on curved surfaces can be realized.

Claims (10)

1. electricity soaks a preparation method for display infrabasal plate, and the drain insulating layer being included in electric moistening display part infrabasal plate is formed the step of pixel wall, it is characterized in that, this step is specially:

S10: the template of patterning is prepared in the arrangement according to pixel wall;

S20: filler pixels walling material in template, semidefinite form;

S30: pixel wall is soaked the drain insulating layer of display infrabasal plate from template transfer to electricity.

2. preparation method according to claim 1, is characterized in that, described template is inorganic material, metal material or polymeric material.

3. preparation method according to claim 2, is characterized in that: described inorganic material is glass or monocrystalline silicon, and described polymeric material is any one in PDMS, PMMA, PI, PET, PEN, PC, PCO, PES and PAR; Described metal material is aluminium, copper or steel.

4. preparation method according to claim 3, is characterized in that, described template is Flexible formwork assembly.

5. preparation method according to claim 1, is characterized in that, in described S20, the filling mode of pixel wall material is any one in spin coating, roller coating, slit painting, dip-coating, spraying, blade coating, gravure, convex print, silk screen printing and inkjet printing.

6. preparation method according to claim 1, is characterized in that, in described S20, adopt mode of heating to carry out semidefinite form, heating-up temperature is 80-120 DEG C, and heating time is 1min-1h.

7. the preparation method according to claim 1 or 6, is characterized in that, containing solvent in the pixel wall material after described semidefinite form, solvent A is: 20wt%≤A≤65wt%.

8. preparation method according to claim 7, is characterized in that, described solvent A is: 30wt%≤A≤50wt%.

9. preparation method according to claim 8, is characterized in that, described S30 specifically comprises the steps:

The one side of pixel wall material is had by template filling to fit tightly with drain insulating layer;

Add the solvent in heat abstraction pixel wall material, curing molding;

The demoulding, solidifies pixel wall further.

10. preparation method according to claim 9, is characterized in that, described fits tightly by pressurize and/or the mode that vacuumizes realizes.