Low reflectance black dispersion and method of making
By using a combination of organic black pigments and color pigment derivatives, the problems of poor development and poor adhesion of carbon black-based black matrix photoresist compositions in large-screen displays were solved, achieving the preparation of black dispersions with low reflectivity and high stability, suitable for color filters of liquid crystal displays.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG KAIRUIER OPTOELECTRONICS TECH CO LTD
- Filing Date
- 2024-07-31
- Publication Date
- 2026-06-30
AI Technical Summary
In the prior art, carbon black as the main component of black matrix photoresist composition has problems such as poor development, high exposure energy, poor adhesion, and insufficient resolution during the preparation process. This is especially evident in large-screen displays. Furthermore, the viscosity increases after adding colored pigments, which affects stability and reflectivity.
Organic black pigments were used to replace carbon black as the black base, and blue and red pigments and their derivatives were added. By optimizing the combination of dispersant and resin, the viscosity and particle size of the dispersion were reduced, and the dispersion stability was improved, thus preparing a low-reflectivity black dispersion.
It achieves a significant reduction in reflectivity while maintaining blackness, improves the stability and adhesion of the dispersion, expands the process margin, and meets the high brightness requirements of large-screen displays.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of display materials technology, and particularly relates to a low-reflectivity black dispersion and its preparation method. Background Technology
[0002] Color filters (CFs) are an important component of liquid crystal displays (LCDs), directly determining the quality of the display's color images. To improve the vibrancy of the display and prevent light leakage from the color filters, a black matrix (BM) pattern is designed between the color pixels of the color filters.
[0003] Currently, most black photoresist compositions are prepared using a pigment dispersion method for light shielding. The pigment composition typically uses carbon black. Patterns are formed through exposure and development, primarily using ultraviolet light. Like colored photoresists, black photoresists are negative photoresists. After exposure and development, the non-photosensitive areas of the negative photoresist dissolved in the developer, while the exposed areas are preserved. However, the carbon black in the black photoresist composition absorbs ultraviolet light during exposure, resulting in underexposure and incomplete development. Therefore, higher exposure energy is required. Since color exposure and development are also involved in the process, higher exposure energy cannot be achieved in production. Low exposure energy, on the other hand, cannot guarantee pattern quality, especially for large screens. Large screens achieve high brightness by increasing the backlight brightness, requiring superior light shielding performance from the black matrix. Therefore, the carbon black content in the black photoresist composition needs to be increased. However, increasing the carbon black content increases the processing difficulty of the black matrix. As the carbon black content increases, more ultraviolet light is absorbed. When the pattern area is cured by ultraviolet radiation, it is difficult for the light to reach the bottom of the film. The curing degree of the film is inconsistent from top to bottom, the adhesion becomes poor, and during development, some parts are moved away or the bottom is sunken, or the undercut is too large during development, resulting in a poor final pattern.
[0004] To address the issues of poor development, high exposure energy requirements, or inability to achieve the desired resolution in black matrix photoresist compositions, extensive research is currently underway on black matrix photoresist compositions that improve adhesion, broaden the development process range, and enhance photosensitivity. Chinese invention patent CN101573663B achieves excellent patterning characteristics by controlling the properties of the binder to improve the range of process characteristics; the colorant containing the black pigment is a mixture of carbon black and at least one colored pigment. Chinese invention patent CN105504890B uses carbon black, silicon dioxide, and a phthaloyl synergist with sulfonic acid groups. Chinese invention patent application CN117270319A uses a carbon black dispersion and a cesium tungsten dispersion to create a black dispersion, resulting in a film with high resistivity and low reflectivity. Chinese invention patent application CN102766353A uses an acid treatment method to prepare a high-performance PBK31 black pigment synergist, which is then added to the black pigment. The aforementioned patents all use carbon black as the primary black base for light shielding, and then supplement it with other materials to improve its performance. They prepare black matrix photoresist compositions by adding other pigments to the black pigment. However, colored pigments differ from carbon black; their light shielding performance is poor. Adding colored pigments to black pigments reduces reflectivity but also affects blackness. Moreover, adding colored pigments to a black photoresist composition containing 25% carbon black increases the viscosity of the composition, worsens viscosity stability, or necessitates the addition of more additives, which can affect the development performance of the film on the production line. Therefore, it is necessary to reduce reflectivity without affecting blackness and to prepare a stable black photoresist composition.
[0005] Generally, organic black pigments have lower reflectivity than regular carbon black; high reflectivity results in poor screen visibility. However, organic black pigments are more difficult to disperse than carbon black, and dispersion becomes even more challenging when mixed with other organic pigments. Therefore, it is necessary to improve the dispersion stability of organic black pigment systems. Summary of the Invention
[0006] To address the shortcomings of the existing technology, this invention provides a low-reflectivity black dispersion and its preparation method. The specific technical solution is as follows:
[0007] The first objective of this invention is to provide a low-reflectivity black dispersion comprising the following components in parts by weight:
[0008] 15-20 parts organic black pigment, 1-5 parts blue pigment, 1-5 parts red pigment, 0.1-2 parts red derivative, 0.1-2 parts black derivative, 3-6 parts dispersant, 3-6 parts acrylic resin, and 54-78 parts solvent;
[0009] The structural formula of the red derivative is shown in formula (1):
[0010]
[0011] The structural formula of the black derivative is shown in formula (2):
[0012]
[0013] This invention uses organic black pigment instead of carbon black as the black base. Table 1 shows that the blackness of films containing 15% organic black pigment and films containing 25% carbon black is similar. Figure 1 The reflectance spectra of organic black pigment and high-resistivity carbon black show that the reflectance of organic black pigment containing 15% is lower than that of high-resistivity carbon black containing 25%, with only an increase in the wavelength range of 730-780 nm. The average reflectance in the 380-780 nm range is 0.075 for organic black pigment and 0.099 for carbon black pigment containing 25%. Adding blue and red pigments reduces the reflectance of the organic black pigment photoresist composition. However, when the total pigment content reaches 25% (organic black pigment + colored pigment), many problems arise, including high viscosity, poor dispersibility and stability, and large particle size, which are difficult to reduce. Therefore, this invention adds red and black derivatives to improve dispersion stability and reduce the viscosity and particle size of the dispersion. The low-reflectance black dispersion of this invention combines blackness and low reflectance.
[0014] Table 1 Comparison of Blackness between Organic Black and High-Resistance Carbon Black
[0015] Blackness MC Blackness MY Film containing 15% organic black pigment 118.34 123.41 Contains 25% carbon black film layer 118.33 118.38
[0016] Furthermore, the low-reflectivity black dispersion composition comprises the following components in parts by weight:
[0017] 15-20 parts organic black pigment, 1-3 parts blue pigment, 1-3 parts red pigment, 0.3-0.6 parts red derivative, 0.3-0.6 parts black derivative, 3-6 parts dispersant, 3-6 parts acrylic resin, and 54-76.4 parts solvent.
[0018] Further, the preparation method of the red derivative is as follows: by weight, at room temperature, 200-250 parts of Pigment Red 2 are added to 300 parts of 102% fuming sulfuric acid (H2SO4 + 2% SO3), and after stirring for 2-4 hours, the mixture is added dropwise to 1000-2000 parts of 0-5℃ methyl ethyl ketone for 25-40 minutes to precipitate, filtered, and washed with 2000-3000 parts of 0-5℃ methyl ethyl ketone. The precipitate is transferred to a dialysis bag with a molecular weight of 200-1000, and the dialysis bag is placed in 2-6L of 0-5℃ deionized water. After washing for 3-5 hours, the 2-6L of 0-5℃ deionized water is replaced, and the operation is repeated 5 times. The substance in the dialysis bag is transferred to a freeze dryer and freeze-dried at -25 to -15℃ for 60-80 hours to obtain the red derivative.
[0019] Further, the preparation method of the black derivative involves, by weight, adding 60 parts of organic black pigment to 250-350 parts of 105% fuming sulfuric acid (H2SO4 + 20% SO3) at room temperature, stirring for 3 hours, and then adding the mixture dropwise to 1000-2000 parts of methyl ethyl ketone at 0-5°C within 30 minutes to obtain a precipitate. The precipitate is filtered, and the filter cake is washed with ice water at 0-5°C until neutral. It is then dried at 80-120°C for 20-30 hours to obtain the black derivative.
[0020] Furthermore, the red pigment is CI Pigment Red 177.
[0021] Furthermore, the blue pigment is CI Pigment Blue 15:4.
[0022] Furthermore, the dispersant is BYK-160.
[0023] Furthermore, the dispersant has a solid content of 46%.
[0024] Furthermore, the solvent is propylene glycol methyl ether acetate (PMA).
[0025] Furthermore, the solid content of the acrylic resin is 30%.
[0026] A second objective of this invention is to provide a method for preparing the aforementioned low-reflectivity black dispersion, comprising the following steps:
[0027] Solvent, acrylic resin, and dispersant are added to a container. Blue and red pigments are added while stirring, followed by red and black derivatives. Finally, organic black pigment is added and stirred for 2–4 hours. The mixture is then poured into a grinder and ground with 0.1–0.3 mm zirconium balls for 15–20 hours to obtain a low-reflectivity black dispersion.
[0028] The beneficial effects of this invention are as follows:
[0029] This invention uses organic black pigment to replace carbon black as the black base, adds blue and red pigments to reduce the reflectivity of the organic black photoresist composition film, and adds red and black derivatives to improve the stability of dispersion and reduce the viscosity and particle size of the dispersion. The low reflectivity black dispersion of this invention has small particle size and stable dispersion, which reduces the reflectivity after film formation while ensuring blackness. Attached Figure Description
[0030] Figure 1 Reflectance spectra of organic black and high-resistivity carbon black;
[0031] Figure 2 The mass spectrum of the red derivative prepared in this invention;
[0032] Figure 3 The mass spectrum of the black derivative prepared in this invention;
[0033] Figure 4 The photoresist reflectance spectra of the black dispersion liquid in the embodiments and comparative examples of the present invention are shown. Detailed Implementation
[0034] The principles and features of the present invention are described below with reference to embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.
[0035] Organic black pigment: CAS No.265997-72-6, benzofuranone-based black pigment, BLACK S0100CF, manufactured by BASF, with an initial particle size of 40-80 nm.
[0036] Synthesis of red derivatives:
[0037] Add 60g of Pigment Red 2 (CAS 6041-94-7, molecular formula C) to 300g of 102% fuming sulfuric acid (H2SO4 + 20% SO3) at room temperature. 23 H 15 C l2 N3O2 (molecular weight 436.29), stirred at room temperature for 3 hours, was then added dropwise to 1500g of 0-5℃ methyl ethyl ketone over 30 minutes to obtain a precipitate. The precipitate was filtered and washed with 2500 parts of 0-5℃ methyl ethyl ketone. The precipitate was transferred to a dialysis bag with a molecular weight of 500. The dialysis bag was placed in 5L of 0-5℃ deionized water and washed for 4 hours. The dialysis bag was then replaced with 5L of 0-5℃ deionized water, and this process was repeated 5 times. The contents of the dialysis bag were then transferred to a lyophilizer and lyophilized at -20℃ for 72 hours to obtain 59.7g of a red derivative. Figure 2 As shown in the mass spectrum, two sets of molecular ion peaks were detected at 513.96 and 593.93, corresponding to the molecular ion peaks of the monosulfonated product and the disulfonated product, respectively. Two sets of molecular ion peaks were detected at 535.95 and 615.93, corresponding to the molecular ion peaks of the monosulfonated product and the disulfonated product after binding with sodium ions, respectively.
[0038] The reaction equation is as follows:
[0039]
[0040] Synthesis of black derivatives:
[0041] In 300g of 105% fuming sulfuric acid (H2SO4 + 20% SO3), 60g of organic black pigment was added at room temperature. After stirring at room temperature for 3 hours, the mixture was added dropwise to 1500g of methyl ethyl ketone at 0-5℃ over 30 minutes, resulting in a precipitate. The precipitate was filtered, and the filter cake was washed with ice water at 0-5℃ until neutral. The cake was then dried at 100℃ for 24 hours to obtain 61.4g of a black derivative. Figure 3 As shown in the mass spectrum, two sets of molecular ion peaks were detected at 528.03 and 608.00, corresponding to the molecular ion peaks of the monosulfonated product and the disulfonated product, respectively.
[0042] The reaction equation is as follows:
[0043]
[0044] The above components were used in the preparation of the black dispersions in the following examples and comparative examples.
[0045] Example 1:
[0046] Preparation of a low-reflectivity black dispersion:
[0047] Weigh 48.17g of solvent PMA, 16.67g of acrylic resin, and 9.6g of dispersant BYK-160 (solid content 46%) and add them to a container. While stirring, add 1.0g of C.I. Pigment Blue 15:4 and 3.0g of C.I. Pigment Red 177, then add 0.6g of the prepared red derivative and 0.3g of the black derivative. Finally, add 17g of organic black pigment and stir to disperse for 3 hours. Then pour the mixture into a grinder and grind it for 16 hours using 0.3mm zirconium balls to obtain a low-reflectivity black dispersion MS-1.
[0048] Example 2:
[0049] Preparation of a low-reflectivity black dispersion:
[0050] Weigh 48.17g of solvent PMA, 16.67g of acrylic resin, and 9.6g of dispersant BYK-160 (solid content 46%) and add them to a container. While stirring, add 3.0g of C.I. Pigment Blue 15:4 and 1.0g of C.I. Pigment Red 177, then add 0.4g of the prepared red derivative and 0.4g of the black derivative. Finally, add 15g of organic black pigment and stir to disperse for 3 hours. Then pour the mixture into a grinder and grind it for 16 hours using 0.3mm zirconium balls to obtain a low-reflectivity black dispersion MS-2.
[0051] Example 3:
[0052] Preparation of a low-reflectivity black dispersion:
[0053] Weigh 48.17g of solvent PMA, 16.67g of acrylic resin, and 9.6g of dispersant BYK-160 (solid content 46%) and add them to a container. While stirring, add 2.0g of C.I. Pigment Blue 15:4 and 2.0g of C.I. Pigment Red 177, then add 0.3g of the prepared red derivative and 0.6g of the black derivative. Finally, add 20g of organic black pigment and stir to disperse for 3 hours. Then pour the mixture into a grinder and grind it for 16 hours using 0.3mm zirconium balls to obtain a low-reflectivity black dispersion MS-3.
[0054] Comparative Example 1:
[0055] Preparation of a black dispersion:
[0056] Weigh 48.17g of solvent PMA, 16.67g of acrylic resin, and 9.6g of dispersant BYK-160 (solid content 46%) and add them to a container. While stirring, add 1.0g of C.I. Pigment Red 177, then add 0.4g of the prepared red derivative, and finally add 15g of organic black pigment. Stir and disperse for 3 hours, then pour into a grinder for grinding. Grind with 0.3mm zirconium balls for 16 hours to obtain black dispersion MD-1.
[0057] The viscosity and particle size of the black dispersions prepared in the examples and comparative examples were measured using a viscometer (model: LVDV-2T) and a particle size analyzer (model: 90Plus Pals). The results are shown in Table 2.
[0058] Photoresist compositions were prepared using the black dispersion and mother liquor (solvent PMA 86.6%, acrylic resin 5%, trimethylolpropane triacrylate monomer 8%, and photoinitiator 0.4%) in a mass ratio of 1:1. The compositions were then spin-coated onto a 50*50 mm blank glass surface using a spin coater at 500 rpm. The film was allowed to stand at 25°C for 3 minutes, then preheated at 120°C for 90 seconds and 230°C for 30 minutes. After baking, the glass slides were cooled to room temperature, and resistance was measured using a high-resistivity meter (model: ZC-36) and reflectance and blackness were measured using a high-precision colorimeter (model: HACA-3650). The results are shown in Table 2. The reflectance spectrum of the photoresist film is shown in Table 2. Figure 4 .
[0059] Table 2. Performance test results of the black dispersion and film in the examples and comparative examples.
[0060]
[0061] As can be seen from the data in Table 2, the resistivity of the low-reflectivity black dispersion photoresist of this invention is 10 ohms. 14At this level, belonging to the high resistivity category, adding 15-20% organic black pigment can achieve the same effect as high-resistivity carbon black requiring 25% content, thus improving process tolerance. For example... Figure 4 As shown, in the examples, the addition of colored pigments and derivatives to the organic black pigment resulted in a significant decrease in reflectance in the wavelength range of 680–780 nm. At 780 nm, the reflectance decreased from 12.9% (organic black pigment alone) to 8.5%. The blackness MY remained unchanged, indicating that adding organic colored pigments and derivatives to the organic black pigment is beneficial for reducing the reflectance of the black photoresist composition. In the comparative example, without the addition of blue pigment and black derivatives, both particle size and viscosity increased, indicating that the combination of blue pigment, red pigment, red derivative, and black derivative is beneficial for viscosity stability and particle size reduction.
[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A low-reflectivity black dispersion, characterized in that, The components include the following parts by weight: The mixture comprises 15-20 parts of benzofuranone-based black pigment, 1-5 parts of CI Pigment Blue 15:4, 1-5 parts of CI Pigment Red 177, 0.1-2 parts of red derivative, 0.1-2 parts of black derivative, 3-6 parts of dispersant, 3-6 parts of acrylic resin, and 54-78 parts of solvent; wherein the benzofuranone-based black pigment is the compound shown in CAS No. 265997-72-6. The structural formula of the red derivative is shown in formula (1): Equation (1) The structural formula of the black derivative is shown in formula (2): Equation (2).
2. The low-reflectivity black dispersion according to claim 1, characterized in that, The components include the following parts by weight: 15-20 parts of benzofuranone-based black pigment, 1-3 parts of CI pigment blue 15:4, 1-3 parts of CI pigment red 177, 0.3-0.6 parts of red derivative, 0.3-0.6 parts of black derivative, 3-6 parts of dispersant, 3-6 parts of acrylic resin, and 54-76.4 parts of solvent.
3. The low-reflectivity black dispersion according to claim 1, characterized in that, The preparation method of the red derivative is as follows: by weight, 60 parts of Pigment Red 2 are added to 250-350 parts of 105% fuming sulfuric acid at room temperature. After stirring for 3 hours, the mixture is added dropwise to 1000-2000 parts of 0-5℃ ice water within 30 minutes to obtain a precipitate. The precipitate is filtered and transferred to a dialysis bag with a molecular weight of 200-1000. The dialysis bag is placed in 2-6L of 0-5℃ deionized water and washed for 3-5 hours. The dialysis bag is then replaced with 2-6L of 0-5℃ deionized water and the process is repeated 5 times. The substance in the dialysis bag is then transferred to a freeze dryer and freeze-dried at -25 to -15℃ for 60-80 hours to obtain the red derivative.
4. The low-reflectivity black dispersion according to claim 1, characterized in that, The method for preparing the black derivative involves, by weight, adding 60 parts of benzofuranone-based black pigment to 250-350 parts of 105% fuming sulfuric acid at room temperature, stirring for 3 hours, and then adding the mixture dropwise to 1000-2000 parts of methyl ethyl ketone at 0-5°C within 30 minutes to obtain a precipitate. The precipitate is filtered, and the filter cake is washed with ice water at 0-5°C until neutral. It is then dried at 80-120°C for 20-30 hours to obtain the black derivative.
5. The low-reflectivity black dispersion according to claim 1, characterized in that, The dispersant has a solid content of 46%.
6. The low-reflectivity black dispersion according to claim 1, characterized in that, The solvent is propylene glycol methyl ether acetate.
7. The low-reflectivity black dispersion according to claim 1, characterized in that, The acrylic resin has a solid content of 30%.
8. A method for preparing a low-reflectivity black dispersion as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Solvent, acrylic resin, and dispersant are added to a container. CI pigment blue 15:4 and CI pigment red 177 are added while stirring. Then, red derivative and black derivative are added. Finally, benzofuranone-based black pigment is added. The mixture is stirred and dispersed for 2-4 hours. Then, it is poured into a mill and ground with 0.1-0.3 mm zirconium balls for 15-20 hours to obtain a low-reflectivity black dispersion.