High-dispersibility polishing liquid for precision polishing of BAK-4 optical prism and preparation method thereof

Abstract

This invention discloses a highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms and its preparation method. By strictly controlling the solid-liquid ratio of abrasive particles to branched polyethyleneimine, the reaction temperature, and the reaction time, branched polyethyleneimine is modified on the surface of the abrasive particles. A small amount of polyacrylic acid-polyethylene oxide with a special molecular segment structure is introduced into the polishing slurry, which achieves concentrated particle size distribution of abrasive particles and eliminates the agglomeration of large particles in the polishing slurry, thereby ensuring that the surface of the polished parts will not be scratched. It has good application prospects.

Description

Technical Field

[0001] This invention relates to the field of ultra-precision machining technology for optical components. Specifically, it relates to a highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms and its preparation method. Background Technology

[0002] BAK-4 optical prisms are high-precision optical components, belonging to the planar optical prism type. Primarily composed of barium crown glass, they are commonly used in optical equipment such as telescopes, microscopes, and lasers to achieve effects such as light deflection, beam splitting, and reflection. To ensure high imaging quality in the optical system, the prism surface must be ultra-smooth and undamaged after chemical mechanical polishing (CMP). Furthermore, BAK-4 optical prisms typically have aspherical or non-planar curved surface structures; therefore, precise control of the radius of curvature and shape is crucial to their optical performance.

[0003] Polishing slurry, as an important polishing material, is a key factor affecting the quality of CMP processing. Its components include abrasive grains, dispersants, and pH adjusters. Abrasive grains, as the main component of the polishing slurry, function to remove minor depressions and imperfections on the material surface during polishing, resulting in a smoother surface. Therefore, appropriate abrasive grain size distribution and excellent dispersibility in the polishing slurry are crucial prerequisites for ensuring damage-free surface processing. Furthermore, the synergistic coupling between the components in the polishing slurry affects the polishing efficiency. The application of CeO2 as an abrasive grain in CMP slurries for optical components has been extensively reported. Existing polishing slurries typically incorporate large amounts of homopolymer and macromonomer dispersants and alkaline solution systems to improve dispersibility (CN110872471B, CN115141548B). However, these dispersants are significantly affected by ionic strength and can only function within a narrow pH range. Excessive addition can lead to supersaturation adsorption on the abrasive grain surface, causing bridging and flocculation. Alkaline solutions can also chemically corrode components, thus reducing the surface quality after processing. On the other hand, to improve polishing efficiency, excessive abrasive particles and fluorides are usually introduced (CN111100558B, CN107629701B), but the high solid content can easily damage the component surface. Meanwhile, La... 3+ The addition of cerium can easily lead to the formation of large agglomerates in cerium-containing samples. Therefore, effectively suppressing abrasive particle agglomeration in the polishing slurry while balancing post-processing surface roughness and polishing efficiency is key to preparing high-quality chemical mechanical polishing slurries. Summary of the Invention

[0004] The purpose of this invention is to provide a highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms and its preparation method, which solves the problem of poor abrasive particle dispersibility and easy agglomeration in the existing polishing slurry, while taking into account both the surface roughness and polishing efficiency after processing.

[0005] The technical solution of the present invention: In order to achieve the above content, the present invention provides a highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms. The polishing slurry comprises: main modified dispersible abrasive particles, auxiliary modified dispersible abrasive particles, 0.1~0.5wt% polyacrylic acid-polyethylene oxide, pH adjuster, 0.1~0.8wt% organosilicon defoamer, and the balance being ultrapure water.

[0006] In this invention, the main modified dispersing abrasive particles are spherical polyethyleneimine-modified CeO2 with a particle size gradient, ranging from 200 to 500 nm, and account for 3.0 to 5.0% of the total mass of the polishing slurry by mass percentage. The auxiliary modified dispersing abrasive particles are one or both of spherical polyethyleneimine-modified ZrO2 and spherical polyethyleneimine-modified SiC, with a particle size ranging from 40 to 80 nm, and account for 8 to 15% of the mass of the main modified dispersing abrasive particles.

[0007] Preferably, based on the total mass of the polishing slurry, the main modified dispersed abrasive particles and the auxiliary modified dispersed abrasive particles comprise the following components by weight percentage:

[0008] Main modified dispersed abrasive particles: 3.2% of 400 nm spherical polyethyleneimine modified CeO2, 0.8% of 200 nm spherical polyethyleneimine modified CeO2;

[0009] Auxiliary modification and dispersion of abrasive particles: 0.2% of 80 nm spherical polyethyleneimine-modified ZrO2, and 0.15% of 50 nm spherical polyethyleneimine-modified SiC.

[0010] In this invention, the pH adjuster is one or more of phosphoric acid, anhydrous citric acid, potassium dihydrogen phosphate, DL-malic acid, and tannic acid.

[0011] The second aspect of this invention provides a method for preparing the aforementioned main modified dispersing abrasive particles and auxiliary modified dispersing abrasive particles, comprising: adding a certain amount of a mixed dispersion solution of ethylene glycol and dimethylformamide to a CeO2 or ZrO2 or SiC initial abrasive particle reaction vessel containing the corresponding particle size, and ultrasonically stirring and dispersing for 5-30 min, during which the temperature inside the vessel is controlled not to exceed 30°C; and then adding a certain amount of branched polyethyleneimine (M... w =60000), set the temperature to 50~90℃, and heat under nitrogen atmosphere and reflux for 8~15 h to carry out the grafting reaction. After the reaction is completed, stop heating and continue stirring until room temperature. Finally, pour the solution into a centrifuge tube, centrifuge at 6000rpm for 10 min, pour out the supernatant, wash the precipitate three times with anhydrous ethanol and nitric acid, wash with deionized water until neutral, and dry in a 70℃ oven for 10 h to obtain the main modified dispersed abrasive particles or auxiliary modified dispersed abrasive particles.

[0012] In this invention, the solid-liquid ratio of the CeO2, ZrO2, or SiC abrasive particles to the mixed dispersion solution is preferably 1 g: 60~100 mL, more preferably 1 g: 80 mL; the volume ratio of ethylene glycol to dimethylformamide in the mixed dispersion solution is 5:2.

[0013] In this invention, the preferred ratio of CeO2, ZrO2, or SiC abrasive particles to branched polyethyleneimine is 1 g: 1.5 to 3 mL, more preferably 1 g: 2.2 mL.

[0014] The third aspect of this invention also provides a method for preparing a highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms, comprising: adding ultrapure water to a container containing main modified dispersing abrasive particles and auxiliary modified dispersing abrasive particles under mechanical stirring conditions, adding polyacrylic acid-polyethylene oxide, then slowly adding a pH adjuster until dissolved, adjusting the pH of the solution to 6.5~7.5, then adding an organosilicon defoamer, and finally immersing an ultrasonic breaker probe into the solution for ultrasonic + mechanical stirring co-dispersion, controlling the temperature of the solution in the container not to exceed 35°C.

[0015] In this invention, the ultrasonic power is 80 W; the ultrasonic + mechanical stirring co-dispersion time is preferably 10~60 min, more preferably 30 min.

[0016] The present invention has at least the following beneficial effects:

[0017] 1. This invention modifies the surface of the abrasive grains with branched polyethyleneimine by strictly controlling the solid-liquid ratio of the abrasive grains to the branched polyethyleneimine, the reaction temperature and the reaction time, and introduces a small amount of polyacrylic acid-polyethylene oxide with a special molecular segment structure into the polishing fluid. This achieves the concentration of the abrasive grain size distribution and the elimination of large agglomerates in the polishing fluid, thereby ensuring that the surface of the polished parts will not be scratched.

[0018] 2. This invention configures a new system of highly dispersible polishing fluid for BAK-4 optical prism fine polishing, which is dominated by main modified dispersed abrasive particles (relatively high content, large size and low hardness, which provide cutting force and mechanical scratching effect during polishing) and auxiliary modified dispersed abrasive particles (relatively low content, small size and high hardness, which accumulate in the prism recesses during polishing to form a barrier layer, preventing the main modified dispersed abrasive particles from excessively removing the recessed areas and improving the processing accuracy). This system takes into account both the surface roughness after processing and the polishing efficiency.

[0019] 3. The polishing liquid of the present invention has stable dispersion performance and concentrated abrasive particle size distribution. No obvious agglomeration phenomenon was observed after storage at room temperature for 3 months. The surface after polishing can reach the sub-nanometer level.

[0020] 4. The mechanisms of action of the modified abrasive particles and the dispersant are as follows: By modifying the surface of the abrasive particles with branched polyethyleneimine, on the one hand, the electrostatic repulsion energy between the abrasive particles is increased due to the grafting of polyethyleneimine onto the abrasive particle surface, thus preventing the abrasive particles from approaching and attracting each other. On the other hand, the polyethyleneimine chain is rich in a large number of negatively charged primary and secondary amine groups, which increases the hydrophilicity of the abrasive particles, allowing them to be uniformly dispersed in the polishing fluid. In addition, the dispersant in the polishing fluid is a comb-like copolymer of polyacrylic acid-polyethylene oxide, which has a comb-like structure with polycarboxylic acid anchoring segments as the "back" and polyether solvation segments as the "teeth". The polycarboxylic acid anchoring segments are located on the same side of the polymer chain and are closely connected, preventing different anchoring segments from adsorbing onto different abrasive particle surfaces, effectively reducing bridging flocculation and improving the utilization rate of the dispersant. Simultaneously, the polyether solvation segments extend into the solvent phase, increasing the thickness of the adsorption layer on the abrasive particle surface, thereby improving the dispersion effect of the abrasive particles in the polishing fluid. Attached Figure Description

[0021] Figure 1 This is a particle size distribution diagram of the polishing liquid in Example 1 of the present invention, where a is the differential particle size distribution diagram and b is the cumulative particle size distribution diagram.

[0022] Figure 2 This is a particle size distribution diagram of the polishing liquid in Example 2 of the present invention, where a is a differential particle size distribution diagram and b is a cumulative particle size distribution diagram.

[0023] Figure 3 This is a particle size distribution diagram of the polishing liquid in Example 3 of the present invention, where a is a differential particle size distribution diagram and b is a cumulative particle size distribution diagram.

[0024] Figure 4 This is a transmission electron microscope image of the polishing liquid in Example 3 of this invention.

[0025] Figure 5 These are scanning electron microscope (SEM) images of BAK-4 optical prisms before and after chemical mechanical polishing using the polishing solution in Example 3 of this invention, where a is the surface of the BAK-4 optical prism sample before polishing and b is the surface of the BAK-4 optical prism sample after polishing.

[0026] Figure 6 This is a particle size distribution diagram of the polishing liquid in Comparative Example 1 of this invention, where a is the differential particle size distribution diagram and b is the cumulative particle size distribution diagram.

[0027] Figure 7 This is a particle size distribution diagram of the polishing liquid in Comparative Example 2 of this invention, where a is the differential particle size distribution diagram and b is the cumulative particle size distribution diagram.

[0028] Figure 8 This is a comparison diagram of the Zeta potentials of the polishing liquids in Examples 1-3 and Comparative Examples 1 and 2 of this invention. Detailed Implementation

[0029] The following embodiments are provided to specifically describe the present invention. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements or adjustments made to the present invention by those skilled in the art based on the embodiments are still within the scope of protection of the present invention.

[0030] Example 1:

[0031] By mass percentage, the polishing fluid consists of 3.0% of 500 nm spherical polyethyleneimine-modified CeO2 and 1.0% of 200 nm spherical polyethyleneimine-modified CeO2 as the main modified and dispersed abrasive particles, 0.32% of 80 nm spherical polyethyleneimine-modified ZrO2 as an auxiliary modified and dispersed abrasive particles, 0.1% of polyacrylic acid-polyethylene oxide, phosphoric acid, 0.2% of organosilicon defoamer, and the balance being ultrapure water.

[0032] The preparation method of the main modified dispersing abrasive particles and the auxiliary modified dispersing abrasive particles is as follows:

[0033] Add 500 nm CeO2, 200 nm CeO2, or 80 nm ZrO2 required for preparing the polishing slurry to a round-bottom flask. Add a mixed solution of ethylene glycol and dimethylformamide at a solid-liquid ratio of 1 g:70 mL, where the volume ratio of ethylene glycol to dimethylformamide is 5:2. Then, ultrasonically disperse the mixture for 5 min with stirring. After dispersion, turn off the ultrasonic treatment and continue stirring for 10 min. Add branched polyethyleneimine at a ratio of 1 g:1.5 mL to the abrasive particles, and heat under reflux at 50℃ for 9 hours under nitrogen protection. After heating, stop the reaction. Continue stirring the reaction solution until it cools to room temperature. Pour the reaction solution into a 50 mL centrifuge tube and centrifuge at 6000 rpm for 10 min. After centrifugation, discard the supernatant and retain the precipitate. Wash the precipitate three times alternately with anhydrous ethanol and nitric acid, then wash with deionized water until neutral. Finally, dry the neutral precipitate in a 70℃ oven for 10 h to obtain the main modified dispersed abrasive particles and the auxiliary modified dispersed abrasive particles.

[0034] The preparation method of the highly dispersible polishing slurry for fine polishing of the BAK-4 optical prism is as follows:

[0035] Under mechanical stirring conditions, according to the polishing slurry composition ratio, 3.0 wt% of 500 nm spherical polyethyleneimine-modified CeO2 and 1.0 wt% of 200 nm spherical polyethyleneimine-modified CeO2 as the main modified and dispersed abrasive particles, and 0.32 wt% of 80 nm spherical polyethyleneimine-modified ZrO2 as the auxiliary modified and dispersed abrasive particles were added to a beaker with ultrapure water, followed by 0.1 wt% of polyacrylic acid-polyethylene oxide. Phosphoric acid was then slowly added to adjust the pH of the solution to 6.0. After that, 0.2 wt% of defoamer was added. Finally, the ultrasonic breaker probe was immersed in the solution and ultrasonically and mechanically stirred for 20 min for co-dispersion. During this period, the solution temperature in the container was controlled not to exceed 35°C. After completion, a highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms was formed.

[0036] Particle size distribution tests were performed on this embodiment, and the results are as follows: Figure 1 As shown, by Figure 1 It can be seen that the particle size of the polishing slurry is concentrated in the range of 99.28-762.35 nm, with no large particle agglomeration. Among them, the median diameters are D50=250.57 nm, D10=149.38 nm, and D90=424.85 nm. According to the particle size distribution dispersion calculation formula [(D90-D10) / D50], the dispersion is calculated to be 1.1667, indicating that the abrasive particle distribution is relatively concentrated and the polishing slurry has excellent dispersion performance.

[0037] Example 2:

[0038] By mass percentage, the polishing fluid consists of 3.5% of 400 nm spherical polyethyleneimine-modified CeO2 and 1.5% of 300 nm spherical polyethyleneimine-modified CeO2 as the main modified and dispersed abrasive particles, 0.75% of 50 nm spherical polyethyleneimine-modified SiC as an auxiliary modified and dispersed abrasive particles, 0.2% of polyacrylic acid-polyethylene oxide, anhydrous citric acid, DL-malic acid, 0.8% of organosilicon defoamer, and the balance being ultrapure water.

[0039] The preparation method of the main modified dispersing abrasive particles and the auxiliary modified dispersing abrasive particles is as follows:

[0040] Add 400 nm CeO2, 300 nm CeO2, or 50 nm SiC required for preparing the polishing slurry to a round-bottom flask. Add a mixed solution of ethylene glycol and dimethylformamide at a solid-liquid ratio of 1 g:90 mL, where the volume ratio of ethylene glycol to dimethylformamide is 5:2. Then, ultrasonically disperse the mixture for 20 min under stirring. After dispersion, turn off the ultrasonic treatment and continue stirring for 30 min. Add branched polyethyleneimine at a ratio of 1 g:3.0 mL to the abrasive particles, and heat under reflux at 60℃ for 10 hours under nitrogen protection. After heating, stop the reaction. Continue stirring the reaction solution until it cools to room temperature. Pour the reaction solution into a 50 mL centrifuge tube and centrifuge at 6000 r / min for 10 min. After centrifugation, discard the supernatant and retain the precipitate. Wash the precipitate three times alternately with anhydrous ethanol and nitric acid, then wash with deionized water until neutral. Finally, dry the neutral precipitate in a 70℃ oven for 10 h to obtain the main modified dispersed abrasive particles and the auxiliary modified dispersed abrasive particles.

[0041] The preparation method of the highly dispersible polishing slurry for fine polishing of the BAK-4 optical prism is as follows:

[0042] Under mechanical stirring conditions, according to the polishing slurry composition ratio, 3.5 wt% of 400 nm spherical polyethyleneimine-modified CeO2 and 1.5 wt% of 300 nm spherical polyethyleneimine-modified CeO2 as the main modified and dispersed abrasive particles, and 0.75 wt% of 50 nm spherical polyethyleneimine-modified SiC as the auxiliary modified and dispersed abrasive particles were added to a beaker with ultrapure water, followed by 0.2 wt% of polyacrylic acid-polyethylene oxide. Then, equal amounts of anhydrous citric acid and DL-malic acid were slowly added to adjust the pH of the solution to 7.0. After that, 0.8 wt% of defoamer was added. Finally, the ultrasonic breaker probe was immersed in the solution and ultrasonically and mechanically stirred for 60 min for co-dispersion. During this period, the solution temperature in the container was controlled not to exceed 30°C. After completion, a highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms was formed.

[0043] Particle size distribution tests were performed on this embodiment, and the results are as follows: Figure 2 As shown, by Figure 2 It can be seen that the particle size of the polishing slurry is concentrated in the range of 99.28-651.73 nm, with no large particle agglomeration. Among them, the median diameters are D50=225.63 nm, D10=139.60 nm, and D90=368.22 nm. According to the particle size distribution dispersion calculation formula [(D90-D10) / D50], the dispersion is calculated to be 1.0133, indicating that the abrasive particle distribution is relatively concentrated and the polishing slurry has excellent dispersion performance.

[0044] Example 3:

[0045] By mass percentage, the polishing fluid consists of 3.2% of 400 nm spherical polyethyleneimine-modified CeO2 and 0.8% of 200 nm spherical polyethyleneimine-modified CeO2 as the main modified and dispersed abrasive particles, 0.2% of 80 nm spherical polyethyleneimine-modified ZrO2, 0.15% of 50 nm spherical polyethyleneimine-modified SiC as an auxiliary modified and dispersed abrasive particles, 0.5% of polyacrylic acid-polyethylene oxide, DL-malic acid, potassium dihydrogen phosphate, tannic acid, 0.3% of organosilicon defoamer, and the balance being ultrapure water.

[0046] The preparation method of the main modified dispersing abrasive particles and the auxiliary modified dispersing abrasive particles is as follows:

[0047] Add 400 nm CeO2, 200 nm CeO2, 80 nm ZrO2, or 50 nm SiC required for preparing the polishing slurry to a round-bottom flask. Add a mixed solution of ethylene glycol and dimethylformamide at a solid-liquid ratio of 1 g:80 mL, where the volume ratio of ethylene glycol to dimethylformamide is 5:2. Then, ultrasonically disperse the solution for 10 min with stirring. After dispersion, turn off the ultrasonication and continue stirring for 20 min. Add branched polyethyleneimine at a ratio of 1 g:2.2 mL to the abrasive particles, and heat under reflux at 70 °C for 13 hours under nitrogen protection. After reflux, stop heating. Continue stirring the reaction solution until it cools to room temperature. Pour the reaction solution into a 50 mL centrifuge tube and centrifuge at 6000 rpm for 10 min. After centrifugation, the supernatant was removed, leaving the precipitate. The precipitate was washed three times with anhydrous ethanol and nitric acid alternately, and then washed with deionized water until neutral. Finally, the neutral precipitate was placed in a 70℃ oven and dried for 10 h to obtain the main modified dispersing abrasive particles and the auxiliary modified dispersing abrasive particles.

[0048] The preparation method of the highly dispersible polishing slurry for fine polishing of the BAK-4 optical prism is as follows:

[0049] Under mechanical stirring conditions, according to the composition ratio of the polishing slurry, 3.2 wt% of 400 nm spherical polyethyleneimine-modified CeO2 and 0.8 wt% of 200 nm spherical polyethyleneimine-modified CeO2 as the main modified and dispersed abrasive particles, 0.2 wt% of 80 nm spherical polyethyleneimine-modified ZrO2, and 0.15 wt% of 50 nm spherical polyethyleneimine-modified SiC as auxiliary modified and dispersed abrasive particles were added to a beaker along with ultrapure water and 0.5 wt% of polyacrylic acid-polyethylene oxide. Then, equal amounts of DL-malic acid, potassium dihydrogen phosphate, and tannic acid were slowly added to adjust the pH of the solution to 8.0. After that, 0.3 wt% of defoamer was added. Finally, the ultrasonic breaker probe was immersed in the solution and ultrasonically and mechanically stirred for 30 min for co-dispersion. During this period, the solution temperature in the container was controlled at 28°C. After completion, a highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms was formed.

[0050] Particle size distribution tests were performed on this embodiment, and the results are as follows: Figure 3 As shown, by Figure 3 It can be seen that the particle size of the polishing slurry is concentrated in the range of 99.28-348.07 nm, with no large particle agglomeration. Among them, the median diameters are D50=178.56 nm, D10=125.67 nm, and D90=251.28 nm. According to the particle size distribution dispersion calculation formula [(D90-D10) / D50], the dispersion is calculated to be 0.7035, indicating that the abrasive particles are concentrated and the polishing slurry has excellent dispersion performance.

[0051] The polishing slurry of Example 3 was analyzed by transmission electron microscopy, and the results are as follows: Figure 4 As shown. From Figure 4 In (a), it can be observed that the abrasive particles in the polishing slurry are evenly distributed and no obvious agglomeration has occurred; from Figure 4 As can be seen in (b), the dispersed abrasive particles in the polishing slurry are spherical and have smooth surfaces.

[0052] Actual polishing was performed using Example 3. The microstructure of the workpiece surface before (a) and after (b) polishing is shown in the figure. Figure 5 As shown, the polishing process parameters were: polishing pressure 45 kPa, polishing disc rotation speed 150 rpm, polishing fluid flow rate 1.5 mL / min. The BAK-4 optical prism sample was a circular thin sheet with a diameter of 20 mm, and the surface roughness before polishing was 669.683 nm. After polishing, the surface roughness was reduced to 0.7253 nm, and the calculated material removal rate was 53.72 nm / min. Furthermore, the polished surface was free of scratches and had a high degree of smoothness.

[0053] Comparative Example 1:

[0054] Comparative Example 1 is a commercially available alkaline CeO2 polishing slurry with high abrasive content for fine polishing of optical components.

[0055] The polishing slurry of Comparative Example 1 was subjected to particle size testing, and the results are as follows: Figure 6 As shown, by Figure 6 It can be seen that the particle size distribution of the polishing slurry exhibits a concentration region of small particles (<1 μm) and a concentration region of large particles (>1 μm). The small particle size concentration region is concentrated in the range of 99.28-891.81 nm, accounting for 92.68% of the total particle size distribution, while the large particle size concentration region accounts for 7.32%. Furthermore, the median diameters of this polishing slurry are D50 = 369.95 nm, D10 = 190.01 nm, and D90 = 789.22 nm. Based on the particle size distribution dispersion calculation formula [(D90-D10) / ], the dispersion is calculated to be 1.6197, indicating relatively poor dispersion performance of the polishing slurry.

[0056] Comparative Example 2

[0057] Comparative Example 2 is a commercially available low-abrasive-content, weakly acidic CeO2 polishing slurry for fine polishing of optical components.

[0058] The polishing slurry of Comparative Example 2 was subjected to particle size testing, and the results are as follows: Figure 7 As shown, by Figure 7 It can be seen that the particle size distribution of the polishing slurry exhibits both a small particle size concentration region (<1 μm) and a large particle size concentration region (>1 μm). The small particle size concentration region is concentrated in the 158.91-557.15 nm range, accounting for 94.63% of the total particle size distribution, while the large particle size concentration region accounts for 5.37%. The presence of large-sized agglomerated particles can easily cause scratches on the glass surface during polishing. Furthermore, the median diameters of this polishing slurry are D50 = 276.61 nm, D10 = 189.98 nm, and D90 = 432.21 nm. Based on the particle size distribution dispersion calculation formula [(D90-D10) / ], the dispersion is calculated to be 0.8757, indicating good dispersion performance of the surface polishing slurry.

[0059] Zeta potential tests were performed on Examples 1, 2, and 3, and Comparative Examples 1 and 2. The results are as follows: Figure 8 As shown, by Figure 8It can be seen that the absolute values ​​of the Zeta potentials in Examples 1, 2, and 3 are all greater than 45 mV, indicating that the polishing slurry has good dispersibility at pH 6-8. This further demonstrates that introducing modified dispersing abrasive particles and polyacrylic acid-polyethylene oxide dispersant into the polishing slurry can reduce the sensitivity of the abrasive dispersion system to acids and alkalis. Notably, compared to Examples 1 and 2, the Zeta potential value of Example 3 is greater than 50 mV, exhibiting excellent dispersion stability. This indicates that the composition of the polishing slurry, the proportions of the main modified dispersing abrasive particles, the auxiliary modified dispersing abrasive particles, the dispersant addition route, and the polishing slurry preparation method all have a significant impact on the dispersion stability of the abrasive particles. Therefore, it is necessary to strictly control the range of process variables.

[0060] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms, characterized in that, The polishing fluid consists of: main modified and dispersed abrasive particles, auxiliary modified and dispersed abrasive particles, 0.1~0.5 wt% polyacrylic acid-polyethylene oxide, pH adjuster, 0.1~0.8 wt% silicone defoamer, and the balance ultrapure water; The main modified dispersing abrasive particles are spherical polyethyleneimine-modified CeO2 with a particle size gradient, ranging from 200 to 500 nm, and account for 3.0% to 5.0% of the total mass of the polishing slurry by weight. The auxiliary modified dispersing abrasive particles are one or both of spherical polyethyleneimine-modified ZrO2 and spherical polyethyleneimine-modified SiC, with a particle size ranging from 40 to 80 nm, and account for 8% to 15% of the mass of the main modified dispersing abrasive particles. The preparation method of the main modified dispersing abrasive particles or auxiliary modified dispersing abrasive particles includes: adding a certain amount of ethylene glycol and dimethylformamide mixed dispersion solution to a reaction vessel containing initial abrasive particles of the corresponding particle size, and ultrasonically stirring and dispersing for 5-30 min, during which the temperature inside the vessel is controlled not to exceed 30℃; then adding a certain amount of branched polyethyleneimine, setting the temperature to 50-90℃, and heating under nitrogen atmosphere and reflux for 8-15 h to carry out the grafting reaction; after the reaction is completed, stopping the heating and continuously stirring until room temperature; finally, pouring the solution into a centrifuge tube, centrifuging at 6000 rpm for 10 min, discarding the supernatant, washing the precipitate three times with anhydrous ethanol and nitric acid, washing it with deionized water until neutral, and drying it in a 70℃ oven for 10 h to obtain the main modified dispersing abrasive particles or auxiliary modified dispersing abrasive particles.

2. The highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms according to claim 1, characterized in that, Based on the total mass of the polishing slurry, the main modified and dispersed abrasive particles and the auxiliary modified and dispersed abrasive particles comprise the following components by weight percentage: Main modified dispersed abrasive particles: 3.2% of 400 nm spherical polyethyleneimine modified CeO2 and 0.8% of 200 nm spherical polyethyleneimine modified CeO2; Auxiliary modification and dispersion of abrasive particles: 0.2% of 80 nm spherical polyethyleneimine-modified ZrO2 and 0.15% of 50 nm spherical polyethyleneimine-modified SiC.

3. The highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms according to claim 1, characterized in that, The pH adjuster is one or more of phosphoric acid, anhydrous citric acid, potassium dihydrogen phosphate, DL-malic acid, and tannic acid.

4. The highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms according to claim 1, characterized in that, The initial abrasive particles to the mixed dispersion solution have a solid-liquid ratio of 1 g: 60~100 mL; the volume ratio of ethylene glycol to dimethylformamide in the mixed dispersion solution is 5:

2.

5. The highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms according to claim 1, characterized in that, The ratio of initial abrasive particles to branched polyethyleneimine is 1 g: 1.5–3 mL.

6. The method for preparing the highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms according to claim 1, characterized in that, The process includes the following steps: Under mechanical stirring conditions, ultrapure water is added to a container containing the main modified dispersing abrasive particles and the auxiliary modified dispersing abrasive particles, followed by the addition of polyacrylic acid-polyethylene oxide. Then, a pH adjuster is slowly added until dissolved, adjusting the pH of the solution to 6.5~7.

5. After that, an organosilicon defoamer is added. Finally, the ultrasonic breaker probe is immersed in the solution for ultrasonic and mechanical stirring co-dispersion, while controlling the temperature of the solution in the container to not exceed 35°C.

7. The method for preparing the highly dispersible polishing slurry for fine polishing of BAK-4 optical prisms according to claim 6, characterized in that, The ultrasonic power was 80 W; the co-dispersion time of ultrasonic and mechanical stirring was 10~60 min.

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