WO2014176845A1

WO2014176845A1 - Inkjet printing method for organic film

Info

Publication number: WO2014176845A1
Application number: PCT/CN2013/081602
Authority: WO
Inventors: 王向华; 邱龙臻; 刘则
Original assignee: 京东方科技集团股份有限公司
Priority date: 2013-04-28
Filing date: 2013-08-16
Publication date: 2014-11-06
Also published as: CN103241025B; CN103241025A

Abstract

Disclosed is an inkjet printing method for an organic film, the method comprising: adjusting the surface energy of a printing substrate; and printing an organic film on the printing substrate, such that liquid drops on the substrate are spread out uniformly when printing. By adopting the inkjet printing method, the uniformity of the thickness of a printing film and the quality of an inkjet pattern are improved.

Description

Organic film inkjet printing method

Technical field

Embodiments of the present invention relate to an inkjet printing method of an organic thin film. Background technique

Due to the high efficiency, low cost, non-contact form and flexible processing of inkjet printing technology, patterns formed by inkjet printing are widely used in the processing of organic electronic devices. By printing a functional polymer solution, inkjet printing realizes deposition and patterning of a functional polymer film, and realizes processing of an organic light emitting diode, an organic thin film transistor (OTFT), and an integrated device thereof.

Inkjet printing generally forms a continuous film by overlapping the ink droplets. The process of forming a large-area continuous film by overlapping multiple lines is likely to cause problems such as uneven thickness of the film, discontinuity, or pattern deformation, as compared with printing a single-point or single-line pattern. In response to this problem, the prior art uses a change in the temperature of the substrate to control the drying process of the ink to achieve printing of a continuous organic film. Printing small molecule organic semiconductor inks at too low a substrate temperature, the printed pattern will cause pattern distortion during the drying process, and too high substrate temperature will easily lead to film discontinuity, so the appropriate substrate temperature is constant. To the extent that pattern distortion can be reduced, a continuous uniform film is obtained. However, when printing a large-area film by using the method of controlling the substrate temperature, the printing speed tends to be slow, especially in the case where the substrate temperature is low, and raising the substrate temperature causes a problem of low crystallinity of the film. Therefore, in the inkjet printing process, the adjustment range of the substrate temperature is relatively limited.

Ink using a mixed solvent, due to the difference in surface tension between the two solvent components, causes Marangoni convection inside the droplet. In the case of the most single single drop printing, as the solvent evaporates, the movement of the line of contact of the circular ink droplets on the substrate with the substrate is typically an isotropic retraction. When the solute concentration reaches a certain threshold, the contact line stops moving, and the solute begins to form a film from the edge to the middle by self-assembly. In this case, the shape and morphology of the film are relatively easy to control. However, in the case of printing a line or a two-dimensional film, the ink droplets overlap each other. Both the rate of solvent evaporation at the initial stage of printing and the rate of crystallization of solute crystals increase due to an increase in the surface area of the liquid. In this case, controlling the geometry and microstructure of the film requires dynamic adjustment of the self-assembled environment. For example, in a process of printing a line shape in a single pass, the film near the beginning of the line is thicker than the end, and the crystallinity is generally higher. This is mainly because the rapid crystallization of the solute during the drying of the ink causes a concentration gradient and drives the directional migration of the solute molecules. In different parts of the printed line, variations in assembly speed and even changes in growth mode due to different ink concentrations result in uneven thickness and morphology of the film.

Figure 1 shows the existing inkjet printing method. According to the needs of graphic printing, if the printing area 14 is an organic semiconductor layer between the source electrode 13 and the drain electrode 15, the nozzle 12 at the lower end of the head 11 can continuously eject ink droplets at a certain frequency. The spacing between the drop point of the previous drop and the drop of the next drop is the dot pitch. Here, the lines printed in the Y direction are columns, and the lines printed in the X direction are lines, and printing in the Y direction is one stroke. When printing, the print head 11 first prints a column in the Y direction, then moves a column pitch in the X direction, and then prints the next column in the Y direction, and thus repeats to form a printed film of a certain area. In the prior art, the movement of the substrate is mostly used to realize the movement in the Y direction and the X direction, and the moving speed and the moving distance of the substrate are determined according to the dot pitch of the ink dots. The dot pitch usually printed is the same in both the X and Y directions. A continuous film can be formed when the dot pitch is sufficiently small. When printing an organic film of a certain width, multiple strokes are required to print a film of sufficient width. In the printing process of a long stroke, since the drying speed of the ink is relatively fast, a problem often arises in that discontinuous overlap or unevenness occurs between adjacent lines.

As is apparent from the above analysis, there is a problem that the thickness of the film is uneven, the film is discontinuous, or the pattern is deformed by the conventional ink jet printing technique. Summary of the invention

Embodiments of the present invention provide an ink jet printing method for improving the uniformity of film thickness and thereby improving the quality of an ink jet pattern.

According to an aspect of the invention, an inkjet printing method for an organic film is provided, comprising: adjusting a surface energy of a printing substrate;

The organic film is printed on the printed substrate such that the droplets on the printed substrate are spread.

According to an embodiment of the invention, said uniformly spreading the droplets on the printing substrate comprises causing the spread droplet diameter on the printing substrate to be 2-4 times the diameter of the spherical droplets ejected from the printer nozzle.

According to an embodiment of the invention, the adjusting the surface energy of the printing substrate comprises forming a surface energy gradient in the printing column direction or perpendicular to the printing column direction on the surface of the printing substrate. According to an embodiment of the invention, the forming a surface energy gradient comprises:

Fluorizing the surface of the printed village;

Performing ultraviolet ozone cleaning on the bottom surface of the printing village through a three-dimensional mask, the three-dimensional mask comprising a mask substrate having a plurality of openings and a warping sheet disposed at each opening of the mask substrate, the warping The angle between the plane of the film and the plane of the reticle substrate is 10. ~100. The opening corresponds to printing an area on the bottom of the village where the organic film needs to be printed. When the printed village bottom is subjected to ultraviolet ozone cleaning through the stereo mask, the area on the bottom of the village where the organic film needs to be printed forms a surface energy gradient.

According to an embodiment of the invention, the adjusting the printing of the bottom surface energy comprises performing a hydrophobic treatment and/or a hydrophilic treatment on the printing village bottom.

According to an embodiment of the present invention, the performing hydrophobic treatment and/or hydrophilic treatment on the printing village bottom comprises:

The fluorination treatment of the printed village bottom makes the printing village bottom surface hydrophobic; and/or the UV cleaning of the printing village bottom makes the printing village bottom surface hydrophilic.

According to an embodiment of the present invention, in the above inkjet printing method, the organic film is formed by variable pitch printing.

According to an embodiment of the present invention, the column pitch of the variable column pitch printing is decreased in the order of the printing columns.

For the above inkjet printing method, the organic film is formed by one-pass multi-column printing.

According to an embodiment of the invention, the one-way multi-column printing is a one-way three-column printing.

According to an embodiment of the invention, the organic film is also printed with variable pitch spacing.

The inkjet printing method of the present invention can be applied to the production of an organic thin film in a flat panel display, and can also be applied to the production of an organic thin film in a solar cell panel, and can also be applied to the production of an organic thin film in other optoelectronic products. Therefore, the present invention does not Limited to the applications listed above. DRAWINGS

The embodiments of the present invention will be described in more detail below with reference to the accompanying drawings, in which FIG.

1 is a schematic view of a conventional inkjet printing method;

2 is a schematic view showing a first embodiment of an inkjet printing method of the present invention;

3 is a photograph of an organic film printed by a first embodiment of the inkjet printing method of the present invention; FIG. 4 is a photograph of an organic film printed by a first comparative example of the conventional inkjet printing method; 5 is a photograph of an organic thin film printed by a second comparative example of the conventional ink jet printing method; FIG. 6 is a photograph of an organic thin film printed by the second embodiment of the ink jet printing method of the present invention; A schematic diagram of a printing method of the third embodiment;

8 is a photograph of an organic film printed by a third embodiment of the inkjet printing method of the present invention; FIG. 9 is a schematic view showing a fourth embodiment of the inkjet printing method of the present invention;

Figure 10 is a schematic view showing a fifth embodiment of the ink jet printing method of the present invention.

Reference mark:

11-head 12-nozzle 13-source electrode 14-printing area 15-drain electrode

16-stereo mask 17-through hole 18-warpage 19-printing substrate

The technical solutions of the embodiments of the present invention will be clearly and completely described in the following with reference to the accompanying drawings. It is apparent that the described embodiments are only a part of the exemplary embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the described exemplary embodiments of the present invention without the need for creative labor are within the scope of the present invention.

In order to improve printing efficiency and improve the quality of a printed organic film, an embodiment of the present invention provides an ink jet printing method of an organic film. In this technical solution, the form of adjusting the surface energy of the printing substrate is used to control the spreading of the ink droplets on the surface of the printing substrate, so that the droplets are uniformly spread on the surface of the printing substrate, thereby making the organic film uniform in thickness and capable of Improve the quality of the pattern formed by the organic film.

An inkjet printing method for an organic thin film according to an embodiment of the present invention, comprising: adjusting surface energy of a printing substrate; printing an organic thin film on the printing substrate such that droplets on the printing substrate are uniformly spread.

In embodiments of the invention, if the pattern itself has a gradient change, such as a non-parallel channel or a gradient varying surface energy, it can act on the inkjet droplets above it. Appropriate use of this effect can effectively overcome the film pattern and morphology changes caused by the directional migration of solute molecules. For example, said uniformly spreading the droplets on the printed substrate comprises: when the adjusted printed substrate surface enables the spread droplet diameter on the printed substrate to be about 2 diameters of the spherical droplets ejected from the printer nozzle When ~4 times, the film has the best effect on the hook and shape. Taking a 10 picoliter print nozzle as an example, when the diameter of a single spherical droplet ejected from the nozzle of the nozzle is about 20 μm, the surface energy of the printing substrate is adjusted, so that The droplets that are spread on the bottom of the printing village have a diameter of about 40 to 80 μm, and such droplet spreading facilitates film formation on the bottom surface of the printing village. Therefore, the surface energy of the printed substrate can be adjusted to overcome the change of the film pattern and the morphology caused by the directional migration of the solute molecules, so that the film thickness is uniform, thereby improving the quality of the inkjet pattern.

According to an embodiment of the invention, the adjusting the surface energy of the printing substrate comprises forming a surface energy gradient in the printing column direction or perpendicular to the printing column direction on the printing village bottom surface. For example, the forming the surface energy gradient comprises: performing a fluorination treatment on the printed village bottom surface; and performing ultraviolet ozone cleaning on the printed village bottom surface through the stereo mask. The reticle plate may include a reticle substrate having a plurality of openings and a ridge plate disposed at each opening of the reticle substrate, and an angle between a plane of the ridger and a plane of the reticle substrate may be About 10. ~100. The opening corresponds to printing an area on the bottom of the village where the organic film is to be printed. When the printed substrate is subjected to ultraviolet ozone cleaning through the stereo mask, the area on the bottom of the substrate where the organic film is to be printed forms a surface energy gradient.

In embodiments of the invention, there may be many ways to form a surface energy gradient. For example, a printed mask substrate is treated with a three-dimensional mask having an opening and a warp sheet, and a partial gradient of surface energy is formed on the area where the organic film is to be printed due to the partial blocking effect of the warp sheet on the open area.

According to an embodiment of the invention, the adjusting the printing of the bottom surface energy comprises performing a water repellent treatment and/or a hydrophilic treatment on the printing village bottom. The hydrophobic treatment may be performed by a fluorination treatment to form a hydrophobic surface on the surface of the substrate; the hydrophilic treatment may be performed by ultraviolet ozone cleaning to form a hydrophilic surface on the surface of the substrate, according to the inkjet ink and the surface properties of the substrate. The bottom of the village is subjected to hydrophobic treatment and/or hydrophilic treatment, so that the surface of the village and the ink are matched to make the ink spread properly on the surface of the village.

In the embodiment of the present invention, since the surface energy of some printing village bottoms is not suitable for direct inkjet printing, the fluorination treatment is used to form a hydrophobic village bottom surface, and then ultraviolet ozone cleaning is used to form a certain hydrophilicity. Print the bottom surface of the organic film.

According to some embodiments of the invention, the organic film may be formed by variable pitch printing. For example, the column spacing of the variable column spacing printing is decremented in the order of the printing columns.

If the ink jet printing process is employed, the column spacing of the multiple lines constituting the film is equal, and usually the dot pitch of the printed single line is controlled. In this way, two disadvantages often occur. In one case, the drying process of the ink is developed from the periphery to the middle, and finally the film formed in the central portion of the film is of poor quality; the other case is that if the printing direction is from left to right, the film is dried from left to right. However, at the same time, the solute migrates from right to left, causing the film thickness to be left high and low right, often accompanied by a sudden change in the morphology of the film. Both of these conditions can lead to a decrease in film properties and material properties, or The effective film area available is greatly reduced. Although the patterned thin film device can be printed by increasing the print area and offsetting with an appropriate pattern, this has significantly limited the efficiency of the printed pattern film.

In some embodiments of the invention, a variable column spacing printing technique may be employed. For example, in the process of printing a large-area film pattern from left to right, the column pitch of printing from left to right is gradually reduced, which can effectively prevent the film from appearing to be left high and right, and can make the film thickness more uniform. , to make the film more uniform. Moreover, the single-pass multi-column and variable-column spacing printing technology can not only efficiently print a continuous film of a large number of films, but also effectively solve the problem of uneven film thickness.

In the above inkjet printing method, the organic film may be formed by one-pass multi-column printing. In some embodiments of the present invention, by using a plurality of columns to print one stroke, it is possible to avoid the problem that the thickness of the film is uneven due to single-line printing, and the printing efficiency is improved. For the single-pass multi-column printing method, the printer that can be used is a printer having a plurality of side-by-side nozzles, and the nozzles of the plurality of side-by-side nozzles simultaneously eject ink droplets to realize multi-column printing.

According to some embodiments of the invention, the organic film may also be printed with variable pitch spacing. In the embodiment of the present invention, the stroke interval of one stroke and the next stroke may be the same or different. When the stroke pitch is decreased in the order of the printing stroke, it is similar to the variable column spacing, which can effectively solve the problem of uneven film thickness. For example, if the column spacing is N times the droplet diameter and N is a positive integer, the column spacing of the variable column spacing printing can be reduced by N times, N-1 times, N-2 times up to 1 times the droplet diameter. , that is, the column spacing of the first column and the second column of the printing is N times the droplet diameter, the column spacing of the printed second column and the third column is N-1 times the droplet diameter, etc., and the printed lines are The print starts less loosely and is denser at the end of the print.

Taking a 10 picoliter printhead as an example, the volume V of a single droplet ejected by the nozzle is 10 picolitres. According to an embodiment of the invention, the single-row multi-column printing has a print column spacing of 5 to 50 micrometers (μηι), for example, the column spacing may be 5 micrometers, 10 meters, 15 meters, 20 meters, 25 meters, 30 meters, 45 meters, 50 meters. In the case of other printhead sizes, the column spacing can be, for example, proportional to the cube root of a single drop volume.

According to an embodiment of the invention, the one-way multi-column printing may be a one-way three-column printing. One-way multi-column printing can print three columns in one stroke, or two columns in one stroke, or four columns in one stroke, or five columns in one stroke. Generally, it is determined according to the stroke of printing. The longer the stroke is required. The number of columns printed in a single pass is greater.

The inkjet printing method of the embodiment of the invention can be applied to the production of an organic thin film in a flat panel display, and can also be applied to the production of an organic thin film in a solar panel, and can also be applied to other light. The production of an organic film in an electronic product, but the invention is not limited thereto.

The ink jet printing method of the present invention will be described below by way of an exemplary embodiment. The following examples each take the case of a 10 picoliter print head, i.e., the spherical droplets ejected from the nozzle have a diameter of about 20 μm.

Example 1

In this embodiment, the organic film is printed by a single-pass multi-column printing method, and the surface energy of the printing substrate is adjusted before the organic film is printed, and multi-column printing is realized by using multiple nozzles. The following is an example of an organic thin film transistor with multi-head inkjet printing bottom contact. Be explained.

In this embodiment, multi-nozzle printing is adopted. As shown in FIG. 2, the spatial period in which the nozzles 11 are arranged along the X direction is the printing column spacing, and the ejection of the nozzles 12 of each of the nozzles 11 are respectively performed by the same frequency and the determined phase difference. Independent pulse voltage waveform control.

The printing substrate was a silicon wafer prepared with a gold (Au) electrode, and a thermal silicon oxide having a thickness of about 300 nm was previously grown on the surface of the silicon wafer. This embodiment requires printing a poly-3-hexylthiophene (a tube called P3HT, an organic polymer semiconductor) ink solution between the source electrode 13 and the drain electrode 15 in a solvent concentration of o-dichlorobenzene and poly-3-hexylthiophene. It is about 0.25~0.75wt.%.

Since the thermal silicon oxide substrate is too hydrophilic to facilitate ink jet printing, the surface energy of the printing substrate is first adjusted.

Step 1. Fluorinating the silicon wafer, preferably using dry fluorination treatment (FDTS), so that the surface of the silicon wafer is hydrophobic;

Step 2: Put the fluorinated silicon wafer into the ultraviolet ozone cleaning machine, set the temperature to 35 ° C, and the time is 8 min. Press the start button to automatically complete the ultraviolet ozone cleaning, so that the surface of the silicon wafer exhibits certain hydrophilicity; Step 3 As shown in FIG. 2, an ink-jet printed P3HT film is formed on the printing region 14 between the source electrode 13 and the drain electrode 15 of the OTFT device at the bottom to form an organic semiconductor layer. Taking the diameter of the spherical droplets ejected from the nozzles 12 of the nozzle 11 as about 20 μm, after processing the printed substrate, a single droplet is spread on the surface of the printing substrate after a diameter of about 40 to 80 μm, and the droplets The size is even. In the embodiment of the present invention, three nozzles 11 are used to simultaneously print three columns, the column pitch is set to a single droplet diameter, i.e., about 20 μm, and the width of the one-pass printing covers just about 45 micrometers of parallel channels.

Figure 3 is an optical photograph of a bottom contact OTFT device formed by drying a single pass three-column ink. It can be seen from the photograph that the print area has a good straight line shape, a uniform pattern, and no deformation.

Figure 4 is an optical photograph of dried TIPS pentacene (collectively referred to as 6,13-bis(triisopropylsilylethynyl) pentacene) ink using conventional single pass single line printing. As can be seen from the photo, The adjacent columns of the print overlap partially, and the film cannot be formed well.

It can be seen that in the case of single-column printing, multiple strokes are required to print a film covering the channel area with a sufficient width. A problem often arises that discontinuous overlap occurs between adjacent lines, and multi-column printing is used. It is possible to avoid discontinuous overlap between the lines and improve film uniformity.

Example 2

This embodiment prints a rectangular film by varying the pitch of the columns and adjusts the surface energy of the printed substrate before printing the organic film.

When the crystallization rate of the solute molecules in the ink on the substrate is significantly higher than the solvent volatilization rate, the crystallization of the solute molecules causes the solute molecules to migrate in the opposite direction of the X direction, which adversely affects the shape and morphology of the film. In order to overcome this solute migration effect, in addition to increasing the temperature, a variable column pitch printing method can be employed, which is characterized in that the dot pitch along the Y direction is constant, but the column pitch along the X direction is gradual.

The surface energy of the silicon oxide substrate is adjusted according to the first step and the second step in the embodiment 1. The diameter of the spherical liquid droplets ejected from the nozzle 12 of the shower head 11 is about 20 μm, for example, after the printing substrate is processed, a single liquid droplet is processed. After spreading on the surface of the printing substrate, the diameter is between about 40 and 80 μm, and the droplet size is uniform. Fig. 5 is a three-bar TIPS pentacene film printed by a conventional printing method in which the X-direction and the Υ direction dot pitch are the same, and dot pitches of 15 μm, ΙΟμηι and 5 μηι are respectively printed. It can be seen from the photograph that the three strip films are not regular rectangles, and all have different degrees of pattern variation. As shown in Fig. 6, the two films printed by the variable column spacing printing method, for example, use a Y-direction dot pitch of 15 μm, the dot pitch is equivalent to the diameter of the spherical droplets ejected from the nozzle, and the column spacing in the X direction is as follows. The order of the print columns is sequentially decreased from 60 μm, 45 μm, 30 μm to 15 μm. The shape of the film shown in Fig. 6 is a regular rectangle, which is visible in accordance with the set print pattern.

Example 3

In this embodiment, a rectangular film is printed by a single-pass multi-column and variable stroke pitch printing method. One-way multi-column printing uses multi-nozzle printing, where the stroke spacing refers to the distance between one stroke and the next stroke in a single pass and multiple columns.

Large-scale repeating array patterns, such as flat-panel display drive circuit OTFT arrays, print efficiency is proportional to the number of print passes in the Υ direction and the number of simultaneously used nozzles. The printing pattern shown in Fig. 7 is characterized in that the dot pitch along the x direction is constant, and the stroke pitch in the X direction is also fixed, but the column pitch along the X direction is periodically changed. For example, as shown in FIG. 7, the unit pattern includes three segments, each of which includes three rows of Υ-direction lattice portions overlapping, each segment adopting three nozzles When printing, each nozzle can print one column of dot matrix lines, and one unit pattern uses three nozzles to print at the same time and needs to print three strokes. Printing efficiency can be improved by increasing the number of repetition periods of the unit pattern in the Y direction. However, the number of repetition cycles is limited by the speed at which the ink is dried and the number of nozzles used at the same time. By appropriately increasing the number of nozzles used at the same time, the number of repetition periods of the unit pattern along the Y direction can be increased correspondingly, thereby greatly improving the efficiency of printing a large-scale array. Figure 8 shows a rectangular TIPS pentacene film unit pattern printed on an organic thin film array on a PVP (poly(4-ethoxyphenyl)) insulating substrate, the film being formed by overlapping four lines of three nozzles. Continuous and dense. However, it can still be seen that the solute has a tendency to move to the left, that is, the pattern protrudes to the left. The spacing between the thick lines can also be gradual. Take the three lines shown in Figure 7 as an example. Appropriately increase the distance between the first thick line and the second thick line from left to right, that is, increase the first stroke and the second. The stroke distance of the stroke is beneficial to inhibit the migration of the solute to the left to form a left protrusion.

Example 4

This embodiment employs single pass multi-column printing, and the printing substrate is a non-parallel channel OTFT having a geometric gradient.

As shown in FIG. 9, a trapezoidal finger-shaped source electrode 13 and a trapezoidal finger-shaped drain electrode 14 are used, which are characterized in that the width of the finger is gradually changed, and the printing area 14 between the fingers, that is, the channel width is also gradually changed along the X direction. . The printing process of an OTFT device structure having such a non-parallel channel can utilize the geometric gradient of the pattern to control the flow direction of the ink, inhibiting the directional migration of the solute. Therefore, single-pass multi-column printing is used, for example, multi-nozzle printing, and printing is performed using a periodically variable pitch printing pattern as shown in FIG.

Example 5

In the process of printing an organic semiconductor layer of an organic thin film transistor, the organic semiconductor layer functions as a film, in which case the surface of the substrate needs to be processed to form a surface energy gradient.

In this embodiment, single-row multi-column printing is adopted, that is, multi-column printing is realized by using multiple nozzles, and the surface energy of the printing substrate is first adjusted so that the dispersion component and the polar component of the surface energy vary from about 0 to 50 mN/m. . Taking the diameter of the spherical droplets ejected from the nozzles 12 of the nozzle 11 as about 20 μm, after processing the printed substrate, a single droplet is spread on the surface of the printing substrate after a diameter of about 40 to 80 μm, and the droplets The size is even. The magnitude of the surface energy is the algebraic sum of the dispersion component and the polar component. The gradient of the surface energy may be a gradient of one or both of the surface energy magnitude or the two components in the X direction or in the Υ direction. Forming a surface energy gradient on the surface of the printed substrate can be performed as follows.

As shown in FIG. 10, the print substrate 19 can be selected as a silicon oxide wafer, and a thin film transistor array having a top contact is prepared on the silicon oxide wafer. First, an organic semiconductor layer between the source electrode and the drain electrode is prepared. Before the organic semiconductor, the surface of the printing village bottom 19 is fluorinated, for example, a self-assembled perfluorododecyltrichlorosilane monolayer on the surface of the printed substrate 19 to obtain a hydrophobic printed substrate surface; The film 16 is provided with a selective ultraviolet odor on the surface of the printing substrate 19 in which the organic semiconductor layer of the thin film transistor is printed. The metal sheet which is lifted up by the three-dimensional mask 16 is warped, and the angle α with the bottom of the mask can be designed to be about 10. ~100. An angle within the range, such as an angle α of about 10°, 20°, 30°, 40°, 50°, 80°, 85°, 90° or 100°. When the rectangular projection area corresponding to the through hole 17 on the printing village bottom is subjected to ultraviolet ozone surface cleaning through the rectangular through hole 17, the rectangular projection area of the surface of the printing substrate 19 is printed after the ultraviolet ozone cleaning due to the partial shielding effect of the warping piece 18. Surface energy with gradient changes. As shown in Fig. 10, the hydrophilicity of each rectangular projection area is gradually increased from left to right, that is, the surface energy is gradually increased, so that a surface energy gradient is formed in each rectangular projection area of the bottom surface of the substrate.

After the surface energy gradient is formed on the printing village bottom, the ink for forming the organic semiconductor layer is printed in a single pass and multiple columns in each rectangular projection area by using multiple nozzles, and the surface energy gradient can be used to control the inkjet printed organic semiconductor film. Improve the process stability of the printed film and reduce the distribution range of the film properties, reducing the process cost. In the embodiment of the present invention, the surface energy of the printed substrate bottom surface from the source electrode to the drain electrode is gradually reduced or gradually increased to form a surface energy gradient, and the surface energy gradient causes the molecular orientation in the ink to form a single orientation, and further The conductivity between the source electrode and the drain electrode is improved. Of course, the surface energy gradient formed on the surface of the printed substrate can be adjusted and optimized according to the performance of the thin film device.

The method of forming the surface energy gradient using the stereo mask as described in this embodiment is not limited to the combination of the above process steps, and may be a combination of other surface treatment methods. The stereo mask is suitable for dry gas phase treatment (eg UV ozone cleaning, plasma surface treatment) and for optical processing (eg UV light). The gradient of the strength of the dry gas phase surface treatment in the exposed area is adjusted by the angle between the designed blade and the bottom of the mask. In addition, the size and shape of the raised blade are variable, and the number of the pieces is The position is also variable. For example, each rectangular through hole can be provided with two symmetrical pieces. This can be applied to patterns that achieve different gradient changes.

The above five exemplary embodiments are unconventional inkjet printing methods and combinations thereof, according to ink The physical properties of water, the characteristics of the material and pattern of the substrate, using the above different printing methods and combinations, can overcome the adverse effects of solute migration on the film morphology during ink drying, and improve the uniformity and repeatability of printing large-area continuous film. , Improve printing accuracy and optimize film topography; also enable high-speed printing of large gauge arrays.

In the inkjet printing method of the embodiment of the present invention, the form of adjusting the surface energy of the printing substrate is used to control the spreading of the inkjet droplets on the surface of the printing village, so that the droplets spread evenly on the surface of the printing village bottom. The organic film is made uniform in thickness and can improve the quality of the pattern formed by the organic film. The spirit and scope of the invention. The invention is also intended to cover such modifications and variations, and equivalents thereof.

Claims

claims

1. An inkjet printing method for organic thin films, which includes:

Adjust the surface energy of the printing substrate;

The organic film is printed on the printing substrate so that the droplets on the printing substrate are evenly spread.

2. The inkjet printing method according to claim 1, wherein causing the droplets to spread uniformly on the printing substrate includes making the diameter of the droplets spread on the printing substrate be the diameter of the spherical droplets ejected from the printer nozzle. About 2~4 times.

3. The inkjet printing method according to claim 1 or 2, wherein adjusting the surface energy of the printing substrate includes forming a surface energy gradient on the surface of the printing substrate along the printing column direction or perpendicular to the printing column direction.

4. The inkjet printing method according to any one of claims 1-3, wherein said forming a surface energy gradient includes:

Fluoride the surface of the printing substrate;

The surface of the printing substrate is cleaned with ultraviolet ozone through a three-dimensional mask. The three-dimensional mask includes a mask base with multiple openings and a warp provided at each opening of the mask base. The warp is The angle between the plane of the film and the plane of the mask base is about 10. ~100. , the opening corresponds to the area on the printing substrate where the organic film needs to be printed. When the printing substrate is cleaned with ultraviolet ozone through the three-dimensional mask, the area on the printing substrate where the organic film needs to be printed forms a surface energy gradient.

5. The inkjet printing method according to any one of claims 1 to 4, wherein the adjusting the surface energy of the printing substrate includes performing hydrophobic treatment and/or hydrophilic treatment on the printing substrate.

6. The inkjet printing method according to any one of claims 1 to 5, wherein the hydrophobic treatment and/or hydrophilic treatment of the printing substrate includes:

Perform fluorination treatment on the printing substrate to make the surface of the printing substrate appear hydrophobic; and/or perform UV ozone cleaning on the printing substrate to make the surface of the printing substrate appear hydrophilic.

7. The inkjet printing method according to any one of claims 1 to 6, wherein the organic film is formed by variable column spacing printing.

8. The inkjet printing method according to claim 7, wherein the column spacing of the variable column spacing printing decreases according to the order of printing columns.

9. The inkjet printing method according to any one of claims 1 to 8, wherein the organic film is formed by single-pass multi-column printing.

10. The inkjet printing method as claimed in claim 9, wherein the single-pass multi-column printing is a single-pass three-column printing.

11. The inkjet printing method according to any one of claims 1 to 10, wherein the organic film is also printed using variable stroke spacing.