Novel Zinc(II) Phthalocyanine Dyes for Color Photoresists

Abstract

Color photoresists are the key materials for the fabrication of color filters (CFs). Organic dyes offer a promising alternative to the conventional pigment-based system to make CFs with higher resolution. However, the stability of dye molecules is an urgent problem to be solved. Herein, we designed and synthesized a series of highly stable zinc phthalocyanine dyes containing polymerizable acrylamide groups. Upon light exposure, dense and insoluble network structures were formed in the prepared CFs, which increase the thermal stability and anti-migration capacity of these dyes.

Key words

color photoresist - dye-based color filter - zinc phthalocyanine - functional dye - high stability

Publication History

Received: 14 March 2023

Accepted after revision: 26 April 2023

Accepted Manuscript online:
26 April 2023

Article published online:
26 June 2023

• References and Notes

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• 24 Synthesis of N-MP p-Aminophenol (10.00 g, 91.64 mmol, 1.00 equiv) and acetonitrile (70 mL) were added to a flask (250 mL). Under a nitrogen atmosphere, an acetonitrile solution (20 mL) of methacrylic anhydride (13.72 mL, 91.64 mmol, 1.00 equiv) was added dropwise to the flask within 30 min. The reaction was then transferred to an oil bath and refluxed for 3 h until the cloudy solution gradually transformed into a light-yellow transparent liquid with no obvious turbidity. Next, the reaction was allowed to cool to room temperature. After filtering, the product was crystallized from the filtrate as a white solid; yield 56%. ¹H NMR (400 MHz, DMSO-d ₆): δ = 9.52 (s, 1 H), 9.20 (s, 1 H), 7.53–7.31 (m, 2 H), 6.79–6.62 (m, 2 H), 5.75 (s, 1 H), 5.44 (s, 1 H), and 1.93 (s, 3 H). ¹³C NMR (151 MHz, DMSO-d₆ ): δ = 166.71, 154.02, 141.03, 131.01, 122.59, 119.76, 115.36, 19.28. TOF LC–MS: m/z [M – H]^– calcd for C₁₀H₁₀NO₂ ^–: 177.0790; found: 177.0705. Synthesis of α-N-MP2 3-Nitrophthalonitrile (6.5 g, 37.54 mmol, 1.00 equiv), N-MP (7.98 g, 45.05 mmol, 1.20 equiv), and DMF (40 mL) were added to a flask (250 mL). Under nitrogen atmosphere, the mixture was stirred for 30 min. Then, anhydrous potassium carbonate (7.78 g, 56.32 mmol, 1.50 equiv) was added to the flask within 1 h. The reaction’s temperature was gradually increased to 80 °C for 8 h under N₂ protection. Next, the reaction was cooled to room temperature and later poured into 1500 mL water, and the crude product was precipitated. The crude product was filtered and dried; then purified by column chromatography (silica gel, DCM/ethyl acetate) to yield α-N-MP2 (9.48 g, 83%) as a white solid. ¹H NMR (400 MHz, DMSO-d ₆): δ = 9.92 (s, 1 H), 7.91–7.57 (m, 4 H), 7.49–6.94 (m, 3 H), 5.82 (s, 1 H), 5.64–5.33 (m, 1 H), 1.96 (s, 3 H). ¹³C NMR (151 MHz, DMSO-d ₆): δ = 167.32, 160.80, 149.71, 140.77, 137.40, 136.48, 128.40, 122.38, 121.94, 120.90, 120.58, 116.30, 116.13, 113.90, 105.10, 19.18. TOF LC–MS: m/z [M + Cl]^– calcd for C₁₈H₁₃ClN₃O₂ ^–: 338.0702; found: 338.0695. Synthesis of β-N-MP2 β-N-MP2 was synthesized following a similar process for α-N-MP2 by using 4-nitrophthalonitrile as starting material. The crude product was purified by column chromatography (silica gel, DCM/ethyl acetate); yield 49%. ¹H NMR (400 MHz, DMSO-d ₆): δ = 9.92 (s, 1 H), 8.08 (d, J = 8 Hz, 1 H), 7.86–7.79 (m, 2 H), 7.75 (d, J = 4 Hz, 1 H), 7.36 (dd, J = 8, 4 Hz, 1 H), 7.21–7.13 (m, 2 H), 5.81 (s, 1 H), 5.56–5.48 (m, 1 H), 1.96 (s, 3 H). ¹³C NMR (151 MHz, DMSO-d ₆): δ = 167.32, 161.97, 149.43, 140.81, 137.35, 136.75, 122.74, 122.39, 122.01, 121.17, 120.54, 117.12, 116.41, 115.88, 108.32, 19.19. TOF LC–MS: m/z [M + Cl]^– calcd for C₁₈H₁₃ClN₃O₂ ^–: 338.0702; found: 338.0696. Synthesis of Cl-N-MP2 Cl-N-MP2 was synthesized following a similar process for α-N-MP2 by using tetrachlorophthalonitrile as starting material. The crude product was purified by column chromatography (silica gel, DCM/ethyl acetate); yield 37%. ¹H NMR (400 MHz, DMSO-d ₆): δ = 9.81 (s, 1 H), 7.67 (d, J = 8 Hz, 2 H), 6.97 (d, J = 12 Hz, 2 H), 5.78 (s, 1 H), 5.52 (s, 1 H), 1.94 (s, 3 H). ¹³C NMR (151 MHz, DMSO-d ₆): δ = 167.11, 152.41, 151.69, 140.74, 137.12, 135.66, 135.46, 132.66, 122.36, 120.47, 117.81, 115.52, 115.46, 113.43, 113.29, 19.17. TOF LC–MS: m/z [M + Cl]^– calcd for C₁₈H₁₀Cl₄N₃O₂ ^–: 441.9533; found: 441.9500. Synthesis of α-N-ZnPc α-N-MP2 (1 g, 3.30 mmol, 3.00 equiv), anhydrous zinc acetate (0.15 g, 1.10 mmol, 1.00 equiv), and anhydrous N,N-dimethylethanolamine (30 mL) were added to a 100 mL flask, and the reaction was conducted at 140 °C for 12 h under nitrogen atmosphere. Next, the reaction was cooled to room temperature and later poured into 500 mL water, and the crude product was precipitated. The crude product was filtered and dried, then purified by column chromatography (silica gel, DCM/methyl alcohol). Finally, it was subjected to a 48 h Soxhlet extraction with toluene, dichloromethane, and ethyl acetate to yield α-N-ZnPc (0.40 g, 28%) as a green solid. ¹H NMR (400 MHz, DMSO-d ₆): δ = 9.78 (t, J = 8 Hz, 4 H), 9.18 (d, J = 8 Hz, 2 H), 8.81 (t, J = 8 Hz, 1 H), 8.70 (d, J = 8 Hz, 1 H), 8.27–8.06 (m, 3 H), 8.01 (s, 1 H), 7.89–7.62 (m, 10 H), 7.56–7.38 (m, 6 H), 7.23–7.18 (m, 4 H), 5.83 (dd, J = 24, 12 Hz, 4 H), 5.50 (d, J = 24 Hz, 4 H), 2.07– 1.87 (m, 12 H). MALDI-TOF-MS: m/z [M]^– calcd for C₇₂H₅₂N₁₂O₈Zn: 1276.3; found: 1276.3. Synthesis of β-N-ZnPc β-N-ZnPc was synthesized following a similar process for α-N-ZnPc by using intermediate β-N-MP2 as starting material; yield 39%. ¹H NMR (400 MHz, DMSO-d ₆): δ = 9.96 (dd, J = 24, 12 Hz, 4 H), 8.78 (dd, J = 24, 16 Hz, 4 H), 8.36 (d, J = 24 Hz, 4 H), 7.96 (dt, J = 28, 12 Hz, 8 H), 7.71 (dd, J = 20, 12 Hz, 4 H), 7.63–7.37 (m, 8 H), 5.90 (s, 4 H), 5.58 (d, J = 8 Hz, 4 H), 2.03 (s, 12 H), MALDI-TOF-MS: m/z [M]^– calcd for C₇₂H₅₂N₁₂O₈Zn: 1276.3; found: 1276.3. Synthesis of Cl-N-ZnPc
  Cl-N-ZnPc was synthesized following a similar process for α-N-ZnPc by using Cl-N-MP2 as starting material; yield 23%. ¹H NMR (400 MHz, DMSO-d ₆): δ = 9.79 (d, J = 20 Hz, 4 H), 7.68 (d, J = 20 Hz, 8 H), 7.11 (s, 6 H), 6.92 (s, 2 H), 5.80 (d, J = 12 Hz, 4 H), 5.49 (d, J = 8 Hz, 4 H), 1.94 (d, J = 8 Hz, 12 H). MALDI-TOF-MS: m/z [M]⁺ calcd for C₇₂H₄₀Cl₁₂N₁₂O₈Zn: 1691.9; found: 1691.9.
• 25 Measurement of the Solubility of Synthesized Dyes A 2 mL brown bottle was filled with 0.075 g of the produced dye and 0.5 g of the solvent. The vial was subjected to ultrasonography for 10 min and kept standing for 24 h. After filtering the mixture over a 0.1 micron polytetrafluoroethylene membrane, the filtrate was dried for 1 h at 150 °C to extract the dissolved dye solid. Then, the solubility of the dyes was calculated. Preparation of Dye Solutions and CRs Preparation of the green dye solution for a color filter: 0.05 g prepared dye and 0.45 g DMF were placed in a 2 mL vial and sonicated thoroughly. Preparation of the Basic Photoresist 0.765 g photoresist special acrylic binder 1 (AR1, 37wt%), 0.417 g dipentaerythritol hexaacrylate (DPHA), 0.05 g photoinitiator (PI-1), and 0.02 g leveling additive (L, 10wt%) were dissolved in 0.698 g PGMEA and treated with sonication thoroughly. Preparation of the Green Photoresist for a CF 0.20 g of basic photoresist and 0.5 g of green dye solution were placed into a 2 mL brown bottle. After sufficient ultrasonic mixing, it was used as the green photoresist for a CF. Fabrication of the Green Spin-Coated CFs Green photoresists were dropped onto transparent glass substrates with dimensions of 5 × 5 × 0.07 cm. The coating speed was maintained at 500 rpm/min for 12 s. The wet CFs were then baked at 100 °C for 100 s before exposure to UV light (365 nm, 120 mW/cm², 10 s) and then baked at 230 °C for 30 min.