A color filter developer composition for flexible OLEDs and a method of preparing the same

Abstract

The application discloses a color filter developing solution composition for flexible OLED and a preparation method thereof, and belongs to the field of wet electronic chemicals. The developing solution composition is prepared from inorganic alkali, alkylcyclohexylphenyl polyoxyethylene ether, castor oil polyoxyethylene ether, a cosolvent, and the rest is high-purity water. The special non-nonionic surfactant is used to produce a synergistic effect. The developing solution system has excellent stability under high alkali concentration, can meet the color filter process requirements of the flexible OLED, is easy to clean, cannot cause yield fluctuation due to residues, can effectively reduce production and transportation costs, and can prolong the storage period of the material inventory of customers.

Description

Technical Field

[0001] This invention belongs to the field of flexible OLED display manufacturing, specifically relating to a color filter developer composition for flexible OLEDs, which is mainly used in the polarizer-free process of flexible OLEDs for developing negative photoresist in the color filter manufacturing process. Technical Background

[0002] Organic light-emitting diodes (OLEDs), as a display technology that is lighter, thinner, clearer, and has a faster refresh rate than traditional liquid crystal displays, have been widely used in displays for mobile phones, televisions, and other devices. Flexible OLEDs, with their foldable, lightweight, thin, low-cost, and superior performance characteristics, have broad prospects in wearable and foldable electronic devices.

[0003] OLEDs contain numerous metal electrodes. When ambient light shines on an OLED screen, it passes through the encapsulation layer and is reflected back from the metal cathode. Early OLED processes used circular polarizers to enhance electrode and specular reflection, suppressing ambient light interference and improving contrast in bright environments. As OLED displays rapidly evolve towards curved and flexible designs, the industry urgently needs perfect dark-state compensation to achieve curved, flexible, thin, and competitively priced products. However, while circular polarizers excel at reducing reflection, they increase display thickness by 50µm to 100µm and reduce brightness. Most importantly, especially in foldable display development, the presence of both polarizing and compensation layers significantly impacts the folding performance of OLED products. Therefore, completely eliminating reflected light interference and removing circular polarizers has become a crucial technological focus for OLED panel manufacturers. Currently, the implemented COE (Color On Encapsulation) technology involves adding a color filter outside the encapsulation layer. This process can eliminate the circular polarizer, significantly reducing the thickness of the anti-reflective layer (which was originally a circular polarizer) by more than 90%, making it highly advantageous for application in foldable AMOLED technology with extremely small inner bending radius.

[0004] Therefore, the color filters used in flexible OLEDs currently require five photomasks to be added for the development of BM, RGB color filters and OC layers. At the same time, due to the requirements of low temperature and protection of the underlying layer, the current mainstream developing solutions are not good in terms of adaptability, development speed, development accuracy and residue verification. Summary of the Invention

[0005] The main technical problem solved by this invention is to provide a developer composition for use in the polarizer-free process of flexible OLED display manufacturing, specifically for color filters. By adding specific surfactants and nonionic surfactants in combination, the developer composition exhibits low surface tension, excellent wetting and dispersing capabilities, and can quickly and effectively obtain the high-resolution patterns required by the process. It also effectively reduces problems such as film residue after development, achieving excellent stability of the developer system. Furthermore, its specific alkalinity range makes it easy to clean, preventing yield fluctuations due to residue.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A color filter developer composition for flexible OLEDs, with a total mass percentage of 100%, has the following composition: Inorganic base 4%-10%, Alkylcyclohexylphenylphenol polyoxyethylene ether 5%-15%, Castor oil polyoxyethylene ether 3%-6% 5%-10% cosolvent The remainder is water.

[0007] Furthermore, in the aforementioned developer composition for a flexible OLED color filter, the inorganic alkali is selected from K2CO3 and KOH, preferably KOH. This is because the potassium ions generated in water after the inorganic alkali hydrolyzes have better water solubility than the potassium salt formed after the photoresist reaction. Therefore, it effectively avoids increasing the water solubility of the photoresist after the reaction, greatly reducing the formation of film slag and effectively maintaining system stability. Simultaneously, in the developer composition system of this patent, the KOH concentration can be adjusted to a high alkali concentration of 8%-9%, which can effectively reduce production and transportation costs and extend the material inventory reserve period for customers.

[0008] Furthermore, in the aforementioned flexible OLED color filter developer composition, the alkylcyclohexylphenylphenol polyoxyethylene ether is selected from nonylcyclohexylphenylphenol polyoxyethylene (10) ether, undecylcyclohexylphenylphenol polyoxyethylene (10) ether, nonylcyclohexylphenylphenol polyoxyethylene (12) ether, and undecylcyclohexylphenylphenol polyoxyethylene (12) ether. This surfactant has a structure similar to that of photoresist molecules, resulting in uniform, stable, and easily controllable development, producing neat edges on the obtained patterns without undercutting.

[0009] Furthermore, in the aforementioned flexible OLED color filter developer composition, the castor oil polyoxyethylene ether specifically refers to castor oil polyoxyethylene (12) ether. When this surfactant is compounded with alkylcyclohexylphenylphenol polyoxyethylene ether at a ratio of 3:7, it can effectively improve the alkali resistance of the developer system, increasing the inorganic alkali content of the developer to 8%-10%. This prevents turbidity and stratification during normal production, transportation, and use, effectively ensuring the stability of the developer.

[0010] Furthermore, in the above-mentioned flexible OLED color filter developer composition, the co-solvent is 1,3-diyl-2-imidazolinone (DMI). This solvent is a polar solvent, which can increase the dissolution of organic soluble salts generated after the photoresist reacts with alkaline substances in an aqueous system, effectively reducing residue.

[0011] Furthermore, in the above-mentioned flexible OLED color filter developer composition, the water can be deionized water, and its resistivity is not less than 18MΩ at 25°C.

[0012] The preparation method of the above-mentioned color filter developer composition for flexible OLED is as follows: at room temperature, high-purity water weighed in proportion is added to a stirred tank. Inorganic base, co-solvent, alkylcyclohexylphenylphenol polyoxyethylene ether and castor oil polyoxyethylene ether are added sequentially at a speed of 90 r / m. After each material is added, the mixture is stirred until the system is clear before adding the next material. After all materials are added, the mixture is stirred for another 30 minutes. Then, the mixture is filtered through two filter elements with pore sizes of 1 μm and 0.5 μm to obtain the developer.

[0013] The significant advantages of this invention are: Using specially customized alkylcyclohexylphenylphenol polyoxyethylene ether surfactants and castor oil polyoxyethylene ether surfactants in a specific ratio to achieve a synergistic effect, the product has low surface tension, low foaming, and easy wetting by the developer. Through the principle of similar compatibility, it dissolves and disperses photoresist molecules, effectively improving the uniformity and accuracy of the developed pattern. This meets the requirements of flexible OLED color filter manufacturing processes, resulting in low film residue and preventing secondary pollution and filter clogging. Simultaneously, the increased inorganic alkali concentration in the developer system effectively reduces production and transportation costs and extends the customer's material inventory lead time. Detailed Implementation

[0014] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0015] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0016] The invention is further illustrated by the following embodiments, but the invention is not limited to the scope of the embodiments described herein.

[0017] Examples and Comparative Examples: A color filter developer composition for flexible OLEDs.

[0018] The color filter developer composition for flexible OLEDs was prepared according to the formula in Table 1. The specific preparation method is as follows: at room temperature, high-purity water weighed according to the proportion is first added to a stirred tank. Inorganic base, co-solvent, alkylcyclohexylphenylphenol polyoxyethylene ether and castor oil polyoxyethylene ether are added in sequence at a speed of 90 r / m. After each material is added, the mixture is stirred until the system is clear before adding the next material. After all materials are added, the mixture is stirred for another 30 minutes. Then, the mixture is filtered through two filter elements with pore sizes of 1 μm and 0.5 μm to obtain the developer.

[0019] in: NCPEO10 - Nonylphenol cyclohexylphenylphenol polyoxyethylene (10) ether NCPEO12 - Nonylphenol cyclohexylphenylphenol polyoxyethylene (12) ether C11CPEO10 - Undecylcyclohexylphenylphenol polyoxyethylene (10) ether C11CPEO12 - Undecylcyclohexylphenylphenol polyoxyethylene (12) ether C11CPEO16 - Undecylcyclohexylphenylphenol polyoxyethylene (16) ether OP-10 - Dodecylphenol polyoxyethylene (10) ether AES-Sodium dodecyl ether sulfate All the above materials were purchased from Quanzhou Bituo Fine Chemical Co., Ltd. EL Series - Castor Oil Polyoxyethylene Ether - Jiangsu Haian Petrochemical Plant T-20 - Tween 20 - Jiangsu Haian Petrochemical Plant AEO-9 - Fatty Alcohol Polyoxyethylene Ether—Quanzhou Zhongshan Chemical Co., Ltd. FMEE - Fatty Acid Methyl Ethoxylates - Shanghai Xihe Fine Chemical Co., Ltd. The performance of the developer compositions prepared in the examples and comparative examples was evaluated, and the specific test methods were as follows: I. Temperature stability: 10 mL of different developer formulations were placed in test tubes, and a mercury thermometer was added. All tubes were then placed in a water bath and heated slowly. Heating was stopped when the developer became cloudy or separated into layers, and the relevant temperatures were recorded for the following baseline evaluation: ○: >42℃ △: 35~42℃ ×: <35℃ If any sample exhibits layering or turbidity below 35℃, it indicates that the formulation's performance is unstable due to temperature variations during production, storage, transportation, and use. This instability prevents the developer from maintaining uniformity during use, thus affecting the developing effect and causing fluctuations in yield. Therefore, the presence of layering or turbidity indicates that the sample does not meet the basic requirements and will not be further tested.

[0020] II. Development Effect Test: To evaluate the developing performance of the developing solution composition on photoresist, the present invention prepared developing solutions according to the dosages of the above-described embodiments and comparative examples, and prepared glass substrate samples. A 1.0 μm layer of BM negative photoresist or R, G, B photoresist was spin-coated onto each glass substrate. The preparation process is as follows: The glass substrate was cleaned with a special cleaning agent, rinsed with ultrapure water, and dried with nitrogen. Photoresist was spin-coated using a spin coater. After vacuuming to remove most of the solvent, the substrate was pre-baked at 110°C for 100 seconds in an oven. Then, a pattern mask was used for exposure to transfer the pattern from the mask onto the glass substrate.

[0021] Based on the proportions commonly used in actual panel manufacturers, Examples 1, 2, 3, and Comparative Example 4 were diluted 100 times with high-purity water, and Examples 4, 5, 6, and Comparative Examples 1-3 and 5-15 were diluted 200 times with high-purity water to prepare developing solutions of process use concentrations.

[0022] 1. Development test The developer was adjusted to 23℃ and sprayed onto the sample slide at a constant pressure using an oscillating motion for 60 rpm for 60 seconds. The slide was then rinsed with high-purity water, dried with nitrogen, and baked in a 110℃ oven for 40 minutes. The slides were then observed under a microscope. ① Is the developed pattern clear? ○: The image is clear and complete. ×: The pattern is incomplete, with some parts stuck together or missing. ② Are there any rough edges or undercuts on the edges of the graphic? ○: The edges of the graphic are clear. ×: The edges of the graphic have burrs or undercutting. ③Is there any photoresist residue due to insufficient development? ○: No photoresist residue ×: You can see some photoresist outside the graphic area. The development test is the most basic test of development capability. If the developer is not compatible with the development process, it will cause incomplete development pattern, poor resolution, burrs, or even large-area peeling, resulting in serious yield problems and waste of substrates and materials.

[0023] 2. Test of the developer's ability to dissolve photoresist The developed solution was filtered through 0.2μm filter paper to observe for clogging. If no clogging occurred, it can be considered that the solution has good solubility for small-molecule photoresist particles after development and will not cause filter clogging. The evaluation criteria are as follows: ○: The filter paper is not clogged. △: A small amount of photoresist clogs the filter paper. ×: The filter paper is difficult to filter and is clogged.

[0024] If the developer's dispersion ability and its ability to dissolve small-molecule photoresist are poor, the small-molecule photoresist will gradually accumulate on the filter element of the substrate, causing unstable pressure, severely affecting the filter element's lifespan, leading to fluctuations in development yield and additional costs.

[0025] III. Test of the developer's rinsing ability Prepare four 200mL beakers, labeled 1, 2, 3, 4, and 5. Add 100mL of deionized water to each beaker. At 20℃, measure the conductivity of the deionized water using a conductivity meter and record the value. Place the sample that has been sprayed with developer solution in beaker 1 (as per the "Developing Effect Evaluation"), soak for 15 seconds, then remove and place in beaker 2. Repeat this process for 15 seconds in beaker 3, and so on until beaker 5. Measure the conductivity of the deionized water in each beaker according to its number. When the conductivity of the washed deionized water and the unused deionized water in the beaker are the same, the smaller the beaker number, the lower the possibility of developer residue on the surface.

[0026] The evaluation results are as follows: ○: ≤3 △: No. 4 and No. 5 ×: > 5 After development, the substrate typically undergoes 2-3 water rinsing processes to remove any residual developer. If the developer is not thoroughly cleaned, it can lead to coating defects in subsequent photolithography processes or the appearance of mura (any color or brightness unevenness that can be detected during later inspection).

[0027] The test results are shown in Table 2: As can be seen from combining Table 1 and Table 2: Comparing Comparative Example 1 with Example 4, it can be found that because the inorganic base used is NaOH, Na + The compound formed with small molecule photoresist has weaker water solubility than K. + Therefore, it puts greater pressure on the filter element's filtration end.

[0028] Compared with Example 4, Comparative Example 2 shows that dodecylphenol polyoxyethylene ether separates at higher alkalinity, thus failing to meet the development requirements.

[0029] Compared with Example 4, Comparative Example 3 shows that as the EO end of the EL surfactant is elongated, the stability of the developer system decreases. Instability also occurs in the developing performance.

[0030] Compared with Example 4, Comparative Examples 4 and 2 show that while reducing the alkali concentration helps improve the stability of the system, it directly affects the development effect.

[0031] Compared with Example 4, Comparative Examples 5, 6, and 3 show that neither a single RCPEO surfactant nor a single EL surfactant can maintain system stability at high alkali concentrations without a synergistic effect. It is also worth noting that EL surfactants can only form good compatibility with RCPEO surfactants at specific molecular chain lengths, which requires extensive experiments and data comparison and analysis to obtain a stable and efficient ratio.

[0032] Compared with Example 4, Comparative Examples 7 and 8 show that when the ratio of the two surfactants EL and RCPEO is not 3:7, it will affect the alkali resistance of the system and the development effect.

[0033] Compared with Example 4, Comparative Example 9 shows that the co-solvent improves the solvent properties of small molecule photoresist and also improves the rinsing performance of the developer. Without the co-solvent, the performance of the developer would be affected.

[0034] Comparative Examples 10-15, compared with Example 4, revealed that various combinations of non-ionic and anionic surfactants were tried, but the required process ratios of 3:7 or other ratios failed to meet the requirements during development. Although anionic surfactants have good alkali resistance, their dispersibility and uniformity are poor, resulting in uneven patterns after development. Various combinations and ratios were tried, but none met the requirements.

[0035] The above embodiments provide a detailed description of the present invention, but they are merely examples and are not intended to limit the scope of the patent. Any equivalent modifications and substitutions made to the present invention based on this specification are also within the scope of the present invention and are included within the patent protection scope of the present invention.

Claims

1. A color filter developer composition for flexible OLEDs, characterized in that, With the sum of mass percentages equal to 100%, its composition is as follows: Inorganic base 4%-10%, Alkylcyclohexylphenylphenol polyoxyethylene ether 7%-11.6%, Castor oil polyoxyethylene ether 3%-5% 5%-10% cosolvent The remainder is water; The alkylcyclohexylphenylphenol polyoxyethylene ether is selected from one of nonylcyclohexylphenylphenol polyoxyethylene (10) ether, undecylcyclohexylphenylphenol polyoxyethylene (10) ether, nonylcyclohexylphenylphenol polyoxyethylene (12) ether, and undecylcyclohexylphenylphenol polyoxyethylene (12) ether. The inorganic base is selected from K2CO3 and KOH; The castor oil polyoxyethylene ether is castor oil polyoxyethylene (12) ether; The mass ratio of the alkylcyclohexylphenylphenol polyoxyethylene ether to the castor oil polyoxyethylene ether is 7:

3.

2. The color filter developing solution composition for flexible OLEDs according to claim 1, characterized in that, The cosolvent is 1,3-diyl-2-imidazolinone.

3. The color filter developing solution composition for flexible OLEDs according to claim 1, characterized in that, The water in question is deionized water with a resistivity greater than 18 MΩ / cm.

4. A method for preparing a color filter developer composition for flexible OLEDs as described in any one of claims 1-3, characterized in that, Includes the following steps: At a rotation speed of 90 r / m, inorganic alkali, co-solvent, alkylcyclohexylphenylphenol polyoxyethylene ether and castor oil polyoxyethylene ether were added sequentially to high-purity water. After the addition was complete, the mixture was stirred for 30 min. Then, it was filtered sequentially through two filter elements with pore sizes of 1 μm and 0.5 μm to obtain a color filter developer composition for flexible OLEDs.

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