Inkjet printing of small molecule thin films to eliminate the "coffee ring" phenomenon

Abstract

The present invention discloses a process for preparing an inkjet-printed small molecule film that eliminates the "coffee ring" phenomenon, belonging to the field of inkjet printing technology. The process comprises preparing an inkjet-printed solution containing a small molecule material, wherein the solution comprises the small molecule material, an organic solvent, a surfactant, and a viscosity regulator. The inkjet-printed solution is homogenized by ultrasonic treatment, and the homogenized solution is uniformly sprayed onto a substrate surface through an inkjet print head. Finally, the sprayed film is cured by heat treatment or ultraviolet light irradiation to improve the mechanical strength and stability of the film. By optimizing solution components, homogenization, precise control of spraying parameters, and multiple modification treatment methods, the "coffee ring" phenomenon is effectively eliminated, and the uniformity, mechanical strength, light transmittance, and adhesion of the film are improved. The film is suitable for a variety of substrates and application scenarios, and has significant industrial application value and promotion prospects.

Description

Technical Field

[0001] The present invention relates to the field of inkjet printing technology, and more particularly to an inkjet printing small molecule film preparation process for eliminating the "coffee ring" phenomenon. Background Art

[0002] In recent years, inkjet printing, as a non-contact, high-precision, and low-cost patterning method, has been widely used in electronics, optics, flexible displays, sensors, and biomedicine. In particular, inkjet printing has shown great potential for the preparation of small molecule thin films due to its precise material control and patterning capabilities. However, in practical applications, inkjet printing still faces several technical challenges, among which the "coffee ring" phenomenon is one of the key issues that needs to be addressed.

[0003] The "coffee ring" phenomenon occurs when, during the evaporation process of a droplet, the solute in the solution aggregates at the edge of the droplet due to the edge flow effect, forming a ring-shaped deposit. This phenomenon not only affects the uniformity and surface quality of the film, but also leads to unstable optical and electrical properties of the film, seriously restricting the application of inkjet printing technology in the preparation of high-performance films. To eliminate the "coffee ring" phenomenon, researchers have proposed various methods, including adjusting the composition of the solution, optimizing the spraying parameters, and adopting different curing treatment methods. However, no method has been found that can significantly improve or even eliminate the "coffee ring" phenomenon.

[0004] Therefore, there is an urgent need for an inkjet printing small molecule film preparation process that can eliminate the "coffee ring" phenomenon to solve the above problems. Summary of the Invention

[0005] 1. Technical problems to be solved

[0006] In response to the problems existing in the prior art, the purpose of the present invention is to provide an inkjet-printed small molecule film preparation process that eliminates the "coffee ring" phenomenon. By optimizing solution components, homogenization treatment, precise control of spray parameters and various modification treatment methods, the "coffee ring" phenomenon is effectively eliminated, and the uniformity, mechanical strength, transmittance and adhesion of the film are improved. It is suitable for a variety of substrates and application scenarios, and has significant industrial application value and promotion prospects.

[0007] 2. Technical solution

[0008] To solve the above problems, the present invention adopts the following technical solutions.

[0009] The inkjet printing small molecule film preparation process for eliminating the "coffee ring" phenomenon includes the following steps:

[0010] S1. preparing an inkjet printing solution containing a small molecule material, wherein the solution comprises the small molecule material, an organic solvent, a surfactant, and a viscosity modifier;

[0011] S2. homogenizing the inkjet printing solution by ultrasonic treatment to ensure the uniformity of the solution;

[0012] S3, spraying the homogenized solution evenly onto the surface of the substrate through an inkjet print head;

[0013] S4. During the spraying process, the spraying parameters are controlled to stabilize the droplet formation and deposition process;

[0014] S5. Curing the sprayed film by heat treatment or ultraviolet irradiation to improve the mechanical strength and stability of the film.

[0015] As a further improvement of the present invention, the organic solvent is ethanol, isopropanol or a mixture thereof, the surfactant is sodium dodecyl sulfate (SDS), polyethylene glycol (PEG) or a mixture thereof, the viscosity modifier is polyvinyl alcohol (PVA) or a derivative thereof, the amount of the small molecule material is 1-10 mg / mL, the amount of the organic solvent accounts for 90-99% (v / v) of the total solution, the amount of the surfactant accounts for 0.1-1% (w / v) of the total solution, and the amount of the viscosity modifier accounts for 0.1-2% (w / v) of the total solution.

[0016] As a further improvement of the present invention, the frequency of the ultrasonic treatment is 20 kHz to 40 kHz, and the treatment time is 10 minutes to 30 minutes.

[0017] As a further improvement of the present invention, the spraying parameters include spraying speed, spraying frequency and spraying spacing, wherein the spraying speed is 1 mm / s to 10 mm / s, the spraying frequency is 10 Hz to 100 Hz, and the spraying spacing is 10 μm to 100 μm.

[0018] As a further improvement of the present invention, the substrate is glass, silicon wafer or flexible polymer substrate.

[0019] As a further improvement of the present invention, the curing treatment temperature is 60°C to 150°C, the treatment time is 10 minutes to 60 minutes, the wavelength of the ultraviolet light irradiation is 200nm to 400nm, and the irradiation time is 5 minutes to 30 minutes.

[0020] As a further improvement of the present invention, a modifying agent accounting for 10-20% of the mass fraction of the small molecule material is also added to the solution, and the modifying agent and the solution are stirred and reacted at room temperature for 30 minutes to 2 hours. The modifying agent is one of polyacrylic acid, polyethyleneimine, APTES or PEG-methacrylate.

[0021] As a further improvement of the present invention, in step S1, the small molecule material is pre-functionalized using functional nanoparticles, wherein the functional nanoparticles are silicon dioxide nanoparticles or aluminum oxide nanoparticles, and the amount thereof accounts for 1-10% of the mass of the small molecule material. The specific steps are as follows:

[0022] S11, dispersing the functional nanoparticles in ethanol, adding an appropriate amount of modifier (0.1-1% v / v), stirring at room temperature for 2-4 hours, and then removing the unreacted modifier by centrifugation or filtration;

[0023] S12, redispersing the modified functional nanoparticles in an organic solvent at a concentration of 1-10 mg / mL;

[0024] S13, dissolving the small molecule material in the same solvent at a concentration of 1-10 mg / mL;

[0025] S14. At room temperature, slowly add the functional nanoparticle dispersion to the small molecule material solution while stirring for 1-2 hours.

[0026] As a further improvement of the present invention, the step S3 is to perform silanization modification on the substrate before spraying to form a self-assembled monolayer on the surface to increase the surface energy and improve the wettability. The specific steps are as follows:

[0027] S31, the silane reagent is selected from one of 3-aminopropyltriethoxysilane and APTES, dissolved in anhydrous ethanol at a concentration of 0.1-1% (v / v);

[0028] S32, immersing the substrate in the silane solution and reacting at room temperature for 30 minutes to 1 hour;

[0029] S33, taking out the substrate, and rinsing it with anhydrous ethanol and deionized water in sequence to remove unreacted silane molecules;

[0030] S34. Dry the substrate at 120°C for 30 minutes to ensure that the silane layer is firmly attached.

[0031] As a further improvement of the present invention, the thickness of the film is 100 nm to 1 μm, and a small molecule film with a multi-layer structure can also be prepared by multiple inkjet printing and curing processes.

[0032] 3. Beneficial effects

[0033] (1) This solution effectively eliminates the "coffee ring" phenomenon by optimizing solution components, homogenization treatment, precise control of spray parameters, and a variety of modification treatment methods, thereby improving the uniformity, mechanical strength, transmittance, and adhesion of the film. It is suitable for a variety of substrates and application scenarios and has significant industrial application value and promotion prospects.

[0034] (2) This solution further enhances the adhesion and mechanical properties of the film by adding modifying agents such as polyacrylic acid and polyethyleneimine, thereby improving the overall performance of the film. At the same time, the dispersion of small molecule materials in the inkjet solution is better, effectively eliminating the "coffee ring" effect, and further improving the uniformity of the film.

[0035] (3) This scheme uses functional nanoparticles for modification, such as silica or alumina nanoparticles, which significantly improves the transmittance, mechanical strength and adhesion of the film, giving the film more functionality. At the same time, the dispersion of small molecule materials in the inkjet solution is better, and the uniformity of the film is further improved.

[0036] (4) This solution forms a self-assembled monolayer on the surface of the substrate by silanization treatment of the substrate, which improves the surface energy and wettability of the substrate, enhances the bonding strength between the film and the substrate, and effectively eliminates the "coffee ring" effect, thereby improving the quality of inkjet printed small molecule films. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the process of the present invention;

[0038] Figure 2 This is a quality test table of the small molecule films prepared in Examples 1-8 of the present invention. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] Example 1:

[0041] See also Figure 1 The inkjet printing small molecule film preparation process for eliminating the "coffee ring" phenomenon includes the following steps:

[0042] S1. preparing an inkjet printing solution containing a small molecule material, wherein the solution comprises the small molecule material, an organic solvent, a surfactant, and a viscosity modifier;

[0043] S2. homogenizing the inkjet printing solution by ultrasonic treatment to ensure the uniformity of the solution;

[0044] S3, spraying the homogenized solution evenly onto the surface of the substrate through an inkjet print head;

[0045] S4. During the spraying process, the spraying parameters are controlled to stabilize the droplet formation and deposition process;

[0046] S5. Curing the sprayed film by heat treatment or ultraviolet irradiation to improve the mechanical strength and stability of the film.

[0047] The organic solvent is ethanol, the surfactant is polyethylene glycol (PEG), the viscosity modifier is polyvinyl alcohol (PVA), the dosage of the small molecule material is 5 mg / mL, the dosage of the organic solvent accounts for 95% (v / v) of the total solution, the dosage of the surfactant accounts for 0.5% (w / v) of the total solution, and the dosage of the viscosity modifier accounts for 1% (w / v) of the total solution.

[0048] The frequency of ultrasonic treatment was 30 kHz, and the treatment time was 20 minutes.

[0049] The spraying parameters include spraying speed, spraying frequency and spraying spacing, wherein the spraying speed is 5 mm / s, the spraying frequency is 50 Hz and the spraying spacing is 50 μm.

[0050] The substrate is glass.

[0051] The curing temperature was 100° C. and the curing time was 30 minutes.

[0052] Example 2:

[0053] The difference from Example 1 is that the amount of small molecule material is 10 mg / mL, the amount of organic solvent accounts for 90% (v / v) of the total solution, the amount of surfactant accounts for 0.5% (w / v) of the total solution, and the amount of viscosity regulator accounts for 2% (w / v) of the total solution.

[0054] The frequency of ultrasonic treatment was 25 kHz, and the treatment time was 15 minutes.

[0055] The spraying parameters include spraying speed, spraying frequency and spraying spacing, wherein the spraying speed is 7 mm / s, the spraying frequency is 70 Hz and the spraying spacing is 70 μm.

[0056] The substrate is glass.

[0057] The curing temperature was 120° C. and the curing time was 20 minutes.

[0058] Example 3:

[0059] Different from Example 1, in step S5, ultraviolet light is used to cure the sprayed film, the wavelength of the ultraviolet light is 300 nm, and the irradiation time is 20 minutes.

[0060] Example 4:

[0061] The difference from Example 1 is that a modifying agent accounting for 15% by mass of the small molecule material is further added to the solution, and the modifying agent and the solution are stirred and reacted at room temperature for 1 hour. The modifying agent is polyacrylic acid.

[0062] Example 5:

[0063] The difference from Example 1 is that in step S1, the small molecule material is pre-functionalized using functional nanoparticles. The functional nanoparticles are silicon dioxide nanoparticles or aluminum oxide nanoparticles, and the amount used accounts for 5% of the mass of the small molecule material. The specific steps are as follows:

[0064] S11, dispersing the functional nanoparticles in ethanol, adding an appropriate amount of modifier (0.5% v / v), stirring at room temperature for 3 hours, and then removing the unreacted modifier by centrifugation or filtration;

[0065] S12, redispersing the modified functional nanoparticles in an organic solvent at a concentration of 5 mg / mL;

[0066] S13, dissolving the small molecule material in the same solvent at a concentration of 5 mg / mL;

[0067] S14. At room temperature, slowly add the functional nanoparticle dispersion to the small molecule material solution while stirring for 1.5 hours.

[0068] When the functional nanoparticles are silica nanoparticles, the modifier is APTES; when the functional nanoparticles are alumina nanoparticles, the modifier is MPTMS.

[0069] The introduction of functional nanoparticles can significantly improve the performance of inkjet printing solutions, including enhancing uniform dispersion and eliminating the "coffee ring" phenomenon, while effectively improving various properties of the film.

[0070] Example 6:

[0071] Based on Example 1, step S3 is to perform silanization modification on the substrate before spraying to form a self-assembled monolayer on the surface to increase the surface energy and improve the wettability. The specific steps are as follows:

[0072] S31, silane reagent is selected as APTES, dissolved in anhydrous ethanol, the concentration is 0.5% (v / v);

[0073] S32, immersing the substrate in the silane solution and reacting at room temperature for 45 minutes;

[0074] S33, taking out the substrate, and rinsing it with anhydrous ethanol and deionized water in sequence to remove unreacted silane molecules;

[0075] S34. Dry the substrate at 120°C for 30 minutes to ensure that the silane layer is firmly attached.

[0076] By treating the substrate surface to improve the wettability and drying behavior of the solution, the "coffee ring" effect can be effectively eliminated, thereby improving the quality of inkjet-printed small molecule films.

[0077] Example 7:

[0078] Based on Example 4, step S3 is to perform silanization modification on the substrate before spraying to form a self-assembled monolayer on the surface to increase the surface energy and improve the wettability. The specific steps are as follows:

[0079] S31, silane reagent is selected as APTES, dissolved in anhydrous ethanol, the concentration is 0.5% (v / v);

[0080] S32, immersing the substrate in the silane solution and reacting at room temperature for 45 minutes;

[0081] S33, taking out the substrate, and rinsing it with anhydrous ethanol and deionized water in sequence to remove unreacted silane molecules;

[0082] S34. Dry the substrate at 120°C for 30 minutes to ensure that the silane layer is firmly attached.

[0083] Example 8:

[0084] On the basis of Example 5, step S3 is to perform silanization modification on the substrate before spraying to form a self-assembled monolayer on the surface to increase the surface energy and improve the wettability. The specific steps are as follows:

[0085] S31, silane reagent is selected as APTES, dissolved in anhydrous ethanol, the concentration is 0.5% (v / v);

[0086] S32, immersing the substrate in the silane solution and reacting at room temperature for 45 minutes;

[0087] S33, taking out the substrate, and rinsing it with anhydrous ethanol and deionized water in sequence to remove unreacted silane molecules;

[0088] S34. Dry the substrate at 120°C for 30 minutes to ensure that the silane layer is firmly attached.

[0089] See also Figure 2It can be seen that Example 1 is the basic process of the present invention, without adding modifiers or performing special treatments, with balanced performance, and is suitable as a control group. In Example 2, the concentration of small molecule materials is increased, the ultrasonic treatment time is reduced, the spray parameters are adjusted, the film thickness and mechanical strength are improved, but the surface roughness and uniformity are slightly reduced. In Example 3, ultraviolet light curing is used, with lower surface roughness and higher transmittance, and the film quality is more uniform. In Example 4, polyacrylic acid modification agent is added, the film thickness is increased, the adhesion and mechanical strength are slightly improved, and the uniformity is slightly reduced. In Example 5, functional nanoparticles are used for modification, the film transmittance and mechanical strength are improved, and the thickness and adhesion are moderately increased. In Example 6, the substrate is silanized, and the various properties of the film are improved. In Example 7, relative to Example 4, the various properties of the film are slightly improved. In Example 8, relative to Example 5, the various properties of the film are slightly improved.

[0090] Compared with Example 1, the performance of the films of Examples 4-8, except for the film thickness, has been significantly improved.

[0091] The above are only preferred embodiments of the present invention; however, the scope of protection of the present invention is not limited thereto. Any person skilled in the art who, within the technical scope disclosed by the present invention, makes equivalent substitutions or modifications based on the technical solutions and improved concepts of the present invention shall be covered by the scope of protection of the present invention.

Claims

1. An inkjet printing small molecule film preparation process that eliminates the "coffee ring" phenomenon is characterized by: The following steps are involved: S1. Prepare an inkjet printing solution containing a small molecule material, wherein the solution includes the small molecule material, an organic solvent, a surfactant, and a viscosity modifier. The small molecule material is pre-functionalized using functional nanoparticles. The functional nanoparticles are silica nanoparticles or aluminum oxide nanoparticles, and the amount used accounts for 1-10% of the mass of the small molecule material. The specific steps are as follows: S11, dispersing the functional nanoparticles in ethanol, adding a modifier in an amount of 0.1-1% v / v, when the functional nanoparticles are silica nanoparticles, the modifier is APTES, when the functional nanoparticles are alumina nanoparticles, the modifier is MPTMS, stirring at room temperature for 2-4 hours, and then removing unreacted modifier by centrifugation or filtration; S12, redispersing the modified functional nanoparticles in an organic solvent at a concentration of 1-10 mg / mL; S13, dissolving the small molecule material in the same solvent at a concentration of 1-10 mg / mL; S14. Slowly add the functional nanoparticle dispersion to the small molecule material solution at room temperature while stirring for 1-2 hours; S2. homogenizing the inkjet printing solution by ultrasonic treatment to ensure the uniformity of the solution; S3, spraying the homogenized solution evenly onto the surface of the substrate through an inkjet print head; S4. During the spraying process, the spraying parameters are controlled to stabilize the droplet formation and deposition process; S5. Curing the sprayed film by heat treatment or ultraviolet irradiation to improve the mechanical strength and stability of the film.

2. The process for preparing a small molecule film by inkjet printing for eliminating the "coffee ring" phenomenon according to claim 1, characterized in that: The organic solvent is ethanol, isopropanol or a mixture thereof, the surfactant is sodium dodecyl sulfate (SDS), polyethylene glycol (PEG) or a mixture thereof, the viscosity modifier is polyvinyl alcohol (PVA) or a derivative thereof, the amount of the small molecule material is 1-10 mg / mL, the amount of the organic solvent accounts for 90-99% v / v of the total solution, the amount of the surfactant accounts for 0.1-1% w / v of the total solution, and the amount of the viscosity modifier accounts for 0.1-2% w / v of the total solution.

3. The process for preparing a small molecule film by inkjet printing to eliminate the "coffee ring" phenomenon according to claim 1, characterized in that: The frequency of the ultrasonic treatment is 20 kHz to 40 kHz, and the treatment time is 10 minutes to 30 minutes.

4. The process for preparing a small molecule film by inkjet printing to eliminate the "coffee ring" phenomenon according to claim 1, characterized in that: The spraying parameters include spraying speed, spraying frequency and spraying spacing, wherein the spraying speed is 1 mm / s to 10 mm / s, the spraying frequency is 10 Hz to 100 Hz, and the spraying spacing is 10 μm to 100 μm.

5. The process for preparing a small molecule film by inkjet printing for eliminating the "coffee ring" phenomenon according to claim 1, characterized in that: The substrate is glass, silicon wafer or flexible polymer substrate.

6. The process for preparing a small molecule film by inkjet printing for eliminating the "coffee ring" phenomenon according to claim 1, characterized in that: The curing treatment temperature is 60° C. to 150° C., the treatment time is 10 minutes to 60 minutes, the ultraviolet light irradiation wavelength is 200 nm to 400 nm, and the irradiation time is 5 minutes to 30 minutes.

7. The process for preparing a small molecule film by inkjet printing for eliminating the "coffee ring" phenomenon according to claim 1, characterized in that: A modifying agent accounting for 10-20% of the mass fraction of the small molecule material is also added to the solution, and the modifying agent and the solution are stirred and reacted at room temperature for 30 minutes to 2 hours. The modifying agent is one of polyacrylic acid, polyethyleneimine, APTES or PEG-methacrylate.

8. The process for preparing a small molecule film by inkjet printing for eliminating the "coffee ring" phenomenon according to claim 1, characterized in that: The step S3 is to perform silanization modification on the substrate before spraying to form a self-assembled monolayer on the surface, thereby increasing the surface energy and improving the wettability. The specific steps are as follows: S31, the silane reagent is selected from one of 3-aminopropyltriethoxysilane and APTES, dissolved in anhydrous ethanol at a concentration of 0.1-1% v / v; S32, immersing the substrate in the silane solution and reacting at room temperature for 30 minutes to 1 hour; S33, taking out the substrate, and rinsing it with anhydrous ethanol and deionized water in sequence to remove unreacted silane molecules; S34. Dry the substrate at 120°C for 30 minutes to ensure that the silane layer is firmly attached.

9. The process for preparing a small molecule film by inkjet printing for eliminating the "coffee ring" phenomenon according to claim 1, characterized in that: The thickness of the film is 100 nm to 1 μm, and a small molecule film with a multi-layer structure is prepared by multiple inkjet printing and curing processes.

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