CN103241025B - Ink jet printing method of organic thin film - Google Patents

Abstract

The invention relates to the technical field of inkjet printing, and discloses an inkjet printing method of an organic thin film. In the inkjet printing method, the method includes: adjusting the surface energy of the printing substrate; printing the organic thin film on the printing substrate, so that The droplets spread evenly on the printed substrate. By adopting the technical solution of the present invention, the surface energy of the printing substrate is adjusted so that the printing substrate is suitable for the spreading of liquid droplets, so the uniformity of the thickness of the printing film is improved, and the quality of the inkjet pattern is greatly improved. In addition, the present invention also proposes a printing method of variable column spacing, which also suppresses the problem of uneven thickness of the printed film.

Description

A kind of inkjet printing method of organic thin film

technical field

The invention relates to the technical field of inkjet printing, in particular to an inkjet printing method of an organic thin film.

Background technique

Inkjet printing technology has the characteristics of high efficiency, low cost, non-contact form and flexible processing. Therefore, the pattern formed by inkjet printing is widely used in the processing of organic electronic devices. By printing functional polymer solutions, Inkjet printing has realized the deposition and patterning of functional polymer films, and realized the processing of organic light-emitting diodes, organic thin film transistors (Organic Thin Film Transistor, OTFT for short) and their integrated devices.

Inkjet printing generally forms a continuous film by overlapping ink droplets. Compared with printing single-dot or single-line patterns, the process of forming a large-area continuous film by overlapping multiple lines can easily lead to problems such as uneven film thickness, discontinuity, or pattern deformation. To solve this problem, the prior art adopts the change of substrate temperature to control the drying process of ink, so as to realize the printing of continuous organic film. Printing small molecule organic semiconductor inks at too low a substrate temperature will cause pattern deformation during the drying process, while too high a substrate temperature will easily lead to discontinuous films. Pattern deformation can be reduced to a certain extent, and a continuous and uniform film can be obtained at the same time. However, when using this method of controlling the substrate temperature to print large-area films, the printing speed is often relatively slow, especially when the substrate temperature is low, and increasing the substrate temperature will bring about the problem of low crystallinity of the film. Therefore, in the inkjet printing process, the range of adjusting the temperature of the substrate is relatively limited.

Ink using mixed solvents will cause Marangoni convection inside the droplet due to the difference in surface tension of the two solvent components. In the case of the simplest single ink drop printing, as the solvent volatilizes, the movement of the contact line between the circular ink drop on the substrate and the substrate usually recedes isotropically. When the solute concentration reaches a certain threshold, the contact line The wire stops moving, and the solute starts to self-assemble from the edge to the middle to form a thin film. In this case, the shape and morphology of the thin film are easier to control. But in the case of printing lines or two-dimensional films, the ink droplets overlap each other. In the initial stage of printing, the speed of solvent replenishment on the substrate through printing is greater than the speed of solvent volatilization, while in the later stage of printing, the speed of solvent volatilization and solute crystal growth are both increased due to the increase of liquid surface area. In this case, controlling the geometry and microscopic morphology of thin films requires dynamic tuning of the self-assembly environment. For example, in the 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, mainly because the rapid crystallization of the solute during the ink drying process causes a concentration gradient and drives the solute molecules. directed migration. In different parts of the printed line, the change of assembly speed and even the change of growth mode due to the difference of ink concentration causes the thickness and shape of the film to be uneven.

As shown in Figure 1, in the inkjet printing method of the prior art, 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 shower head 11 can be set according to a certain pattern. Frequency continuous jetting of ink droplets, the distance between the landing point of the previous droplet and the landing point of the next droplet is the dot pitch. Here, the lines printed along the Y direction are columns, and the lines printed along the X direction are One row, printing one time along the Y direction is one stroke. When printing, the nozzle 11 first prints a column along the Y direction, then moves a column spacing along the X direction, and then prints the next column along the Y direction. Repeat this process to form a certain area of printing film. Now In the existing technologies, 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 moving distance of the substrate are determined according to the dot pitch of the ink dots. Usually the printed dot pitch is the same in both X and Y directions. A continuous thin film can be formed when the dot spacing is small enough. When printing an organic film of a certain width, multiple strokes are required to print a film of sufficient width. During the printing process of a long stroke, due to the relatively fast drying speed of the ink, the problem that often occurs is that the gap between adjacent lines There will be discontinuous overlap or unevenness between them.

From the above analysis, it can be known that the existing inkjet printing technology may have the problems of non-uniform thickness of the film, discontinuity of the film or deformation of the pattern.

Contents of the invention

The object of the present invention is to provide an inkjet printing method for improving the uniformity of film thickness and further improving the quality of inkjet patterns.

The inkjet printing method of the organic thin film of the present invention comprises:

Adjust the surface energy of the printing substrate;

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

Preferably, the uniform spreading of the droplets on the printing substrate specifically includes making the diameter of the spreading droplets on the printing substrate 2 to 4 times the diameter of the spherical droplets ejected from the printer nozzle.

Preferably, the adjusting the surface energy of the printing substrate is specifically forming a surface energy gradient on the surface of the printing substrate along the printing row direction or perpendicular to the printing row direction.

Preferably, 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 a plurality of openings and a warp arranged at each opening of the mask base, the warp The angle between the plane where the film is located and the plane where the mask plate base is located is 10° to 100°, and the opening corresponds to the area on the printing substrate where the organic film needs to be printed. When the printing substrate is subjected to ultraviolet light through the three-dimensional mask During ozone cleaning, a surface energy gradient is formed on the printing substrate where the organic film needs to be printed.

Preferably, the adjusting the surface energy of the printing substrate is specifically performing hydrophobic treatment and/or hydrophilic treatment on the printing substrate. The hydrophobic treatment can be treated with fluorination to make the surface of the substrate form a hydrophobic surface; the hydrophilic treatment can be cleaned with ultraviolet ozone to make the surface of the substrate form a hydrophilic surface. According to the inkjet ink and the surface properties of the substrate, Hydrophobic treatment and/or hydrophilic treatment is performed on the substrate, so that the surface of the substrate and the ink cooperate, so that the ink can be properly spread on the surface of the substrate.

Preferably, the hydrophobic treatment and/or hydrophilic treatment of the printing substrate is specifically:

Fluorinating the printed substrate to render the surface of the printed substrate hydrophobic; and/or

The printed substrate is cleaned with ultraviolet ozone to make the surface of the printed substrate hydrophilic.

Preferably, for the above inkjet printing method, the organic thin film is formed by printing with variable column pitch.

Preferably, the column spacing of the variable column spacing printing decreases according to the sequence of printing columns. For example, assuming that 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 according to the law of N times, N-1 times, N-2 times, and finally 1 times the droplet diameter. , that is, the column spacing between the first printed column and the second column is N times the droplet diameter, the column spacing between the printed second column and the third column is N-1 times the droplet diameter, etc., the printed lines are in The print starts loose and becomes denser later in the print.

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

Taking a 10 picoliter print head as an example, that is, the volume V of a single droplet ejected by the nozzle is 10 picoliters, and the diameter is about 20 microns, and the printing column spacing of the single-pass multi-column printing is 5 to 50 microns (μm), for example The column spacing can be 5 microns, 10 microns, 15 microns, 20 microns, 25 microns, 30 microns, 45 microns, 50 microns, and the printing column spacing can be equal to or different from the printing point spacing, preferably , the column spacing is equal to the point spacing. In the case of printing with other sizes of print nozzles, the dot pitch is proportional to the cube root of the volume of the spherical droplet ejected from the nozzle, or proportional to the diameter of the spherical droplet ejected from the nozzle. Preferably, the dot spacing of the printed lines is equal in the X direction and the Y direction, and is equivalent to the diameter of the spherical droplet.

Preferably, the single-pass multi-column printing is single-pass three-column printing.

Preferably, the organic thin film is also printed with variable stroke pitch.

The inkjet printing method of the present invention can be applied to the production of organic thin films in flat panel displays, solar cell panels, or other optoelectronic products.

In the inkjet printing method of the present invention, the form of adjusting the surface energy of the printing substrate is used to control the spread of the inkjet droplets on the surface of the printing substrate, so that the droplets spread evenly on the surface of the printing substrate, so that the organic film The thickness is uniform and the quality of the pattern formed by the organic thin film can be improved.

Description of drawings

1 is a schematic diagram of an inkjet printing method in the prior art;

2 is a schematic diagram of the first embodiment of the inkjet printing method of the present invention;

Fig. 3 is the photo of the organic thin film that the first embodiment of the inkjet printing method of the present invention prints;

Fig. 4 is the photo of the organic thin film that the first comparative example prints of existing ink-jet printing method;

Fig. 5 is the photo of the organic thin film that the second comparative example of existing ink-jet printing method prints;

Fig. 6 is the photo of the organic thin film that the second embodiment of the inkjet printing method of the present invention prints;

Fig. 7 is a schematic diagram of the printing mode of the third embodiment of the inkjet printing method of the present invention;

Fig. 8 is the photo of the organic thin film that the third embodiment of the inkjet printing method of the present invention prints;

9 is a schematic diagram of a fourth embodiment of the inkjet printing method of the present invention;

FIG. 10 is a schematic diagram of a fifth embodiment of the inkjet printing method of the present invention.

Reference signs:

11-Nozzle 12-Nozzle 13-Source electrode 14-Print area 15-Drain electrode

16-Three-dimensional mask version 17-Through hole 18-Warp 19-Print substrate

Detailed ways

In order to improve printing efficiency and improve the quality of printed organic thin films, the invention provides an inkjet printing method for organic thin films. In this technical solution, the form of adjusting the surface energy of the printing substrate is used to control the spread of the inkjet droplets on the surface of the printing substrate, so that the droplets spread evenly on the surface of the printing substrate, so that the thickness of the organic film is uniform and The quality of the pattern formed by the organic thin film can be improved. In order to make the purpose, technical solution and advantages of the present invention clearer, the following examples are given to further describe the present invention in detail.

The inkjet printing method of the organic thin film of the embodiment of the present invention comprises:

Adjust the surface energy of the printing substrate;

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

In the embodiment of the present invention, if the pattern itself has a gradient change, such as non-parallel channels or gradient surface energy, it can have an effect on the inkjet droplet above it. Proper use of this effect can effectively overcome the directional migration of solute molecules. The resulting changes in film graphics and topography, preferably, the uniform spreading of the droplets on the printing substrate is specifically, when the adjusted printing substrate surface can make the diameter of the spreading droplets on the printing substrate be When the diameter of the spherical droplet ejected from the printer nozzle is 2 to 4 times, the uniformity and shape of the film are the best. Take the 10 picoliter print head as an example, that is, the diameter of a single spherical droplet ejected from the nozzle of the print head The diameter is about 20 μm. After adjusting the surface energy of the printing substrate, the diameter of the droplets spread on the printing substrate is 40-80 μm. Such droplet spreading is conducive to film formation on the surface of the printing substrate. Therefore, The surface energy of the printing substrate can be adjusted to overcome the film pattern and shape changes caused by the directional migration of solute molecules, so that the film thickness is uniform, and the quality of inkjet patterns can be improved.

Preferably, the adjusting the surface energy of the printing substrate is specifically forming a surface energy gradient on the surface of the printing substrate along the printing row direction or perpendicular to the printing row direction. Preferably, 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 a plurality of openings and a warp arranged at each opening of the mask base, the warp The angle between the plane where the film is located and the plane where the mask plate base is located is 10° to 100°, and the opening corresponds to the area on the printing substrate where the organic film needs to be printed. When the printing substrate is subjected to ultraviolet light through the three-dimensional mask During ozone cleaning, a surface energy gradient is formed on the printing substrate where the organic film needs to be printed.

In the embodiment of the present invention, there are many ways to form the surface energy gradient. It is preferable to use a three-dimensional mask with openings and warps to process the printing substrate. Due to the partial shielding effect of the warps on the opening area, it is necessary to print A gradient of surface energy is formed over regions of the organic thin film.

Preferably, the adjusting the surface energy of the printing substrate is specifically performing hydrophobic treatment and/or hydrophilic treatment on the printing substrate. The hydrophobic treatment can be treated with fluorination to make the surface of the substrate form a hydrophobic surface; the hydrophilic treatment can be cleaned with ultraviolet ozone to make the surface of the substrate form a hydrophilic surface. According to the inkjet ink and the surface properties of the substrate, Hydrophobic treatment and/or hydrophilic treatment is performed on the substrate, so that the surface of the substrate and the ink cooperate, so that the ink can be properly spread on the surface of the substrate.

In the embodiment of the present invention, since the surface energy of some printing substrates is not suitable for direct inkjet printing, fluorination treatment is used to form a hydrophobic substrate surface, and then ultraviolet and ozone cleaning is used to form a suitable surface with certain hydrophilicity. on the substrate surface for printing organic thin films.

Preferably, the organic thin film is formed by printing with variable column pitch. Preferably, the column spacing of the variable column spacing printing decreases according to the sequence of printing columns.

In the existing inkjet printing process, the column spacing of the multi-lines constituting the film is equal, usually that is to control the dot spacing of the printed single line, and two unfavorable situations often occur. One case is that the ink drying process develops from the surrounding to the middle, and finally the film quality formed in the central area of the film is poor; the other case is that if the printing direction is from left to right, the film is dried from left to right , but at the same time the solute will migrate from right to left, causing the thickness of the film to be higher on the left and lower on the right, often accompanied by a sudden change in the morphology of the film. Both of these situations can lead to a decrease in film uniformity and material properties, or to a substantial reduction in the available effective film area. Although it is possible to print patterned thin-film devices by increasing the printing area and employing appropriate pattern offsets, the efficiency of printing patterned thin-films is significantly limited.

In the embodiment of the present invention, the printing technology of variable column spacing can be used. For example, in the process of printing a large-area film pattern from left to right, the column spacing of printing from left to right is set to gradually decrease, so that it can effectively Preventing the phenomenon that the film is high on the left and low on the right can make the thickness of the film more uniform and the morphology of the film more uniform. Using the single-pass multi-column printing technology with variable column spacing can not only print large-scale continuous films with high efficiency, but also effectively solve the problem of uneven film thickness.

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

In the embodiment of the present invention, the method of printing one stroke in multiple rows avoids the problem of uneven film thickness in the existing single-row printing, and improves printing efficiency. For the one-pass multi-column printing method, the printer that can be used is a printer with multiple parallel nozzles, and the nozzles of the multiple parallel nozzles eject ink droplets simultaneously to realize multi-column printing.

Preferably, the organic thin film is also printed with variable stroke pitch.

In the embodiment of the present invention, the distance between one stroke and the next stroke can be the same or different. When the stroke distance decreases according to the order of printing strokes, it is also similar to the variable column distance, which can effectively solve the problem of uneven film thickness. question.

Taking a 10 picoliter printing nozzle as an example, that is, the volume V of a single droplet ejected by the nozzle is 10 picoliters. Preferably, the printing column spacing of the single-pass multi-column printing is 5 to 50 microns (μm), for example, the column spacing It can be 5 microns, 10 microns, 15 microns, 20 microns, 25 microns, 30 microns, 45 microns, 50 microns. In the case of other printhead sizes, the column spacing is proportional to the cube root of the individual droplet volume.

Preferably, the single-pass multi-column printing is single-pass three-column printing. One-way multi-column printing can print three columns in one stroke, two columns in one stroke, four columns in one stroke, or five columns in one stroke. Generally, it is determined according to the printing stroke. The longer the printing stroke, the more necessary The more columns are printed in a single pass.

The inkjet printing method of the present invention can be applied to the production of organic thin films in flat panel displays, solar cell panels, or other optoelectronic products.

The following specific examples are given to illustrate the inkjet printing method of the present invention. The following examples all take a 10 picoliter printing nozzle as an example, that is, the diameter of the spherical droplet ejected from the nozzle is about 20 μm.

Example 1

In this embodiment, the organic thin film is printed in a single-pass multi-column printing method, and the surface energy of the printing substrate is adjusted before printing the organic film, and multiple nozzles are used to achieve multi-column printing. The following uses multi-nozzle inkjet printing of organic thin film transistors in contact with the bottom as an example. Be explained.

This embodiment adopts multi-jet printing, as shown in Figure 2, the spatial period of the nozzles 11 arranged along the X direction is the printing column pitch, and the jetting of the nozzles 12 of each nozzle 11 is controlled by each other according to the same frequency and a determined phase difference. Independent pulse voltage waveform control.

The printing substrate is a silicon wafer prepared with a gold (Au) electrode (thermal silicon oxide with a thickness of 300nm is pre-grown on the surface of the silicon wafer), and poly 3-hexylthiophene (referred to as P3HT for short) is required to be printed between the source electrode 13 and the drain electrode 15. , an organic polymer semiconductor) ink solution, the solvent is o-dichlorobenzene, and the concentration of poly-3-hexylthiophene is 0.25-0.75wt.%.

Since the thermal silicon oxide substrate is highly hydrophilic, it is not conducive to inkjet printing, so first adjust the surface energy of the printing substrate:

Step 1. Fluoride treatment of the silicon wafer, preferably dry fluorination treatment (FDTS), to make the surface of the silicon wafer hydrophobic;

Step 2. Put the fluorinated silicon wafer into the UV-ozone cleaning machine, set the temperature to 35°C for 8 minutes, and press the start button to automatically complete the UV-ozone cleaning, so that the surface of the silicon wafer has a certain degree of hydrophilicity;

Step 3, as shown in FIG. 2 , inkjet print the P3HT thin film on the printed area 14 between the source electrode 13 and the drain electrode 15 of the bottom contact OTFT device to form an organic semiconductor layer. Taking the spherical droplet ejected from the nozzle 12 of the nozzle 11 as an example with a diameter of 20 μm, after the printing substrate is processed, the diameter of a single droplet spreading on the surface of the printing substrate is between 40 and 80 μm, and the size of the droplet is uniform . In the embodiment of the present invention, three nozzles 11 are used to print three columns at the same time, the set column spacing is the diameter of a single droplet, that is, 20 μm, and the width of single-pass printing just covers a parallel channel of 45 μm.

Figure 3 is an optical photograph of a bottom-contact OTFT device formed after ink drying using single-pass three-column printing. It can be seen from the photo that the straight line of the printed area is good, the pattern is uniform, and there is no deformation.

Fig. 4 is an optical photo of TIPS pentacene (full name: 6,13-bis(triisopropylsilylethynyl) pentacene) ink dried in single-pass single-column printing using the prior art. It can be seen from the photo that two adjacent printed columns partially overlap, 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 of sufficient width to cover the channel area. The problem that often occurs is that there will be discontinuous overlap between adjacent lines, while multi-column printing Discontinuous overlap between lines can be avoided, improving film uniformity.

Example 2

In this embodiment, a rectangular thin film is printed by changing the column spacing, and the surface energy of the printing substrate is adjusted before printing the organic thin film.

When the crystallization rate of the solute molecules in the ink on the substrate is significantly higher than the volatilization rate of the solvent, the crystallization of the solute molecules will cause the solute molecules to migrate in the opposite direction of the X direction, which will adversely affect the shape and morphology of the film. In order to overcome this solute migration effect, in addition to increasing the temperature, a printing method with variable column spacing can also be used, which is characterized in that the dot spacing along the Y direction is constant, but the column spacing along the X direction is gradually changed.

Adjust the surface energy of the silicon oxide substrate according to step 1 and step 2 in embodiment 1. The diameter of the spherical droplet ejected from the nozzle 12 of the shower head 11 is 20 μm as an example. After the printing substrate is processed, a single droplet is The diameter of the printed substrate after spreading is between 40 and 80 μm, and the droplet size is uniform. Figure 5 shows three strip-shaped TIPS pentacene films printed with a conventional printing method, that is, the dot spacing in the X direction and the Y direction is the same, and the dot spacing is 15 μm, 10 μm and 5 μm, respectively. It can be seen from the photos that the three strip films are not regular rectangles, but have different degrees of graphic variation. As shown in Figure 6, two films were printed using the printing method of variable column spacing. Specifically, a dot spacing in the Y direction of 15 μm was used. The dot spacing was equivalent to the diameter of the spherical droplets ejected from the nozzle. The sequence of columns decreases successively 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 consistent with the set printing pattern.

Example 3

In this embodiment, a single-pass multi-column printing method with variable stroke pitch is used to print a rectangular film. Among them, single-pass multi-column printing adopts multi-nozzle printing, and the stroke distance here refers to the distance between one stroke and the next stroke in single-pass multi-column printing.

Large-scale repetitive array patterns, such as the printing efficiency of the drive circuit OTFT array of flat panel display, are directly proportional to the printing stroke in the Y direction and the number of nozzles used at the same time. The printing pattern shown in Figure 7 is characterized in that the dot spacing along the Y direction is constant, and the stroke spacing in the X direction is also fixed, but the column spacing along the X direction changes periodically, as shown in Figure 7 For example, the unit pattern is composed of three lines, and each line is composed of three columns of dot matrix in the Y direction. Each line is printed by three nozzles at the same time. The 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 repeating periods of the unit pattern in the Y direction. However, the number of repeat cycles is limited by the drying speed of the ink and the number of print heads used at the same time. Appropriately increasing the number of nozzles used at the same time can correspondingly increase the number of repeating cycles of the unit pattern along the Y direction, thereby greatly improving the efficiency of printing large-scale arrays. Figure 8 shows the rectangular TIPS pentacene thin film unit pattern of the organic thin film array printed on the PVP (poly(4-vinylphenol)) insulating substrate. And dense. However, it can still be seen that the solute has a tendency to move to the left, that is, the left side of the pattern is prominent. The distance between the thick lines can also be gradual. Taking 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 distance between the first stroke and the second stroke. The stroke spacing of the stroke is beneficial to inhibit the solute from migrating to the left to form the left protrusion.

Example 4

In this embodiment, single-pass multi-column printing is adopted, and the printing substrate is a non-parallel channel OTFT with geometric gradients.

As shown in Figure 9, the structure of trapezoidal finger-shaped source electrode 13 and trapezoidal finger-shaped drain electrode 14 is adopted, which is characterized in that the width of the finger changes gradually, and the printing area 14 between the fingers, that is, the width of the channel also changes gradually along the X direction. . The printing process of the OTFT device structure with such non-parallel channels can use the geometric gradient of the pattern to control the flow direction of the ink and suppress the directional migration of solutes. Therefore, a single-pass multi-column printing method is adopted, specifically, multi-nozzle printing is adopted, and a printing pattern with a periodic variable pitch as shown in FIG. 7 is used for printing.

Example 5

In the process of printing the organic semiconductor layer of the organic thin film transistor, the growth direction of the thin film of the organic semiconductor layer in the plane parallel to the substrate surface has a decisive effect on the performance of the organic thin film transistor device. The treatment is performed to create a surface energy gradient.

In this embodiment, single-pass multi-column printing is adopted, that is, multiple nozzles are used to realize multi-column printing, and the surface energy of the printing substrate is firstly adjusted so that the variation range of the dispersion component and polar component of the surface energy is 0 to 50 mN/m. Taking the spherical droplet ejected from the nozzle 12 of the nozzle 11 as an example with a diameter of 20 μm, after the printing substrate is processed, the diameter of a single droplet spreading on the surface of the printing substrate is between 40 and 80 μm, and the size of the droplet is uniform . The magnitude of the surface energy is the algebraic sum of the dispersive and polar components. The gradient of the surface energy can be the magnitude of the surface energy or one or both of the two components have a gradient change tendency along the X direction or along the Y direction.

Forming a surface energy gradient on the surface of the printing substrate specifically includes:

As shown in FIG. 10, the printing substrate 19 can be selected as a silicon oxide wafer. To prepare a thin film transistor array with a top contact on the silicon oxide wafer, it is first necessary to prepare an organic semiconductor layer positioned between the source electrode and the drain electrode. Before the organic semiconductor, the surface of the printing substrate 19 is fluorinated, specifically self-assembling a monomolecular layer of perfluorododecyltrichlorosilane on the surface of the printing substrate 19 to obtain a hydrophobic printing substrate surface; The stencil 16 is used to selectively clean the surface of the printing substrate 19 with ultraviolet ozone. The rectangular through hole 17 of the three-dimensional mask 16 is projected on the printing substrate 19 to form a rectangular projection area. In this rectangular projection area, the organic film of the thin film transistor needs to be printed. The semiconductor layer, the raised metal sheet on the three-dimensional mask 16, that is, the warped sheet 18, and the angle α between the mask base and the mask base can be designed as an angle in the range of 10° to 100°, for example, the angle α is 10° , 20°, 30°, 40°, 50°, 80°, 85°, 90° or 100°. When the rectangular projection area corresponding to the through hole 17 on the printing substrate is cleaned with ultraviolet ozone through the rectangular through hole 17, due to the partial shielding effect of the warp sheet 18, the rectangular projection area on the surface of the printing substrate 19 is cleaned by ultraviolet ozone. Surface energy with a gradient change, as shown in Figure 10, the hydrophilicity of each rectangular projection area increases gradually from left to right, that is, the surface energy gradually increases, so that each rectangular projection area on the substrate surface forms a surface energy gradient.

After the surface energy gradient is formed on the printing substrate, the ink used to form the organic semiconductor layer can be printed in multiple rows in each rectangular projection area by using a multi-nozzle head. This 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 film properties, reducing the process cost. In the embodiment of the present invention, the surface energy of the printing substrate surface from the source electrode to the drain electrode gradually decreases or increases gradually, forming a surface energy gradient, such a surface energy gradient will make the molecular orientation in the ink form a single orientation, and then 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 thin-film devices.

The method for forming a surface energy gradient using a three-dimensional mask described in this embodiment is not limited to the combination of the above process steps, and may also be a combination of other surface treatment methods. The three-dimensional mask is suitable for dry gas phase surface treatment (such as ultraviolet ozone cleaning, plasma surface treatment), and also suitable for optical treatment (such as ultraviolet light). The gradient of the action intensity of the dry gas-phase surface treatment in the exposed area is adjusted by the angle between the designed warp and the mask base. In addition, the size and shape of the warped warps are variable, and the number of warped warps And the position is also changeable, for example, each rectangular through hole can be provided with two symmetrical warps. This can be applied to achieve different gradient patterns.

The five embodiments cited above are unconventional inkjet printing methods and their combinations. According to the physical properties of the ink, the characteristics of the substrate material and patterns, the above-mentioned different printing methods and combinations can overcome the impact of solute migration in the ink drying process. The adverse effects of film morphology can improve the uniformity and repeatability of printing large-area continuous films, improve printing accuracy and optimize film morphology; high-speed printing of large-scale arrays can also be achieved.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (8)

1. an inkjet printing methods for organic film, is characterized in that, comprising:

Regulate the surface energy of printed substrate, the surface energy of described adjustment printed substrate is specially and forms Surface Energy Gradients on printed substrate surface along print line direction or perpendicular to print line direction;

Printed substrate prints organic film, makes the drop uniform spreading in printed substrate.

2. inkjet printing methods as claimed in claim 1, is characterized in that, described in the drop uniform spreading in printed substrate is specially, make the liquid-drop diameter sprawled in printed substrate be 2 ~ 4 times of the spherical droplets diameter of printer nozzle ejection.

3. inkjet printing methods as claimed in claim 1, it is characterized in that, described formation Surface Energy Gradients comprises:

Fluorination treatment is carried out to printing substrate surface;

By stereo mask version, UV ozone cleaning is carried out to printing substrate surface, described stereo mask version comprises the mask plate substrate with multiple opening and the fin being arranged at each opening part of mask plate substrate, the angle of described fin place plane and mask plate substrate place plane is 10 ° ~ 100 °, the corresponding printed substrate of described opening needs the region printing organic film, when carrying out UV ozone cleaning through described stereo mask version to printed substrate, printed substrate need the region printing organic film form Surface Energy Gradients.

4. the inkjet printing methods as described in any one of claims 1 to 3, is characterized in that, described organic film adopts and becomes column pitch printing formation.

5. inkjet printing methods as claimed in claim 4, is characterized in that, the column pitch that described change column pitch prints successively decreases according to the sequencing of print line.

6. the inkjet printing methods as described in any one of claims 1 to 3, is characterized in that, described organic film adopts one way multiple row to print and formed.

7. inkjet printing methods as claimed in claim 6, is characterized in that, described one way multiple row prints to one way three and arranges printing.

8. inkjet printing methods according to claim 6, is characterized in that, described organic film also adopts and becomes stroke span printing.