Fluorine-containing quartz glass and preparation method thereof

Abstract

The invention provides fluorine-containing quartz glass and a preparation method thereof.The preparation method comprises the steps that porous quartz particles are heated through a fluorine-containing solution, and dried porous quartz particles are obtained through dehydration and drying; carrying out dehydration and pore closing treatment on the dried porous quartz particles to obtain pore-closed quartz particles; and carrying out plasma melting or electric melting treatment on the closed-cell quartz particles to obtain the fluorine-containing quartz glass. The fluorine-containing quartz glass according to the present invention has an internal fluorine concentration of 1000 wt ppm or more and an internal OH group concentration of 2 wt ppm or less. The fluorine-containing quartz glass can be used for an optical lens, can transmit ultraviolet light with the wavelength of 300 nm or below, and has good laser durability.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorine-containing fused silica glass, and particularly relates to a fluorine-containing fused silica glass and a preparation method thereof. Background Art

[0002] As is well known, adding fluorine to fused silica glass can improve its ultraviolet light transmittance, and this property enables it to be applied to light cleaning, light patterning, light etching technologies using short-wave light sources such as ArF lasers and KrF laser lamps. In the prior art, the VAD method is usually used to introduce fluorine into the fused silica sintered body. For example, the patent with the publication number CN106116136A discloses the technology of introducing fluorine into the fused silica sintered body by the VAD method, and also discloses that introducing fluorine can change the refractive index of fused silica, and fluorine-containing fused silica can be used as an optical fiber ferrule. However, the fluorine-containing fused silica glass prepared by the VAD method has the problem of poor homogeneity. For optical fiber ferrules, since the requirement for homogeneity is relatively low, there will be no obvious problems when using the fluorine-containing fused silica prepared by the VAD method. However, for the lens of an exposure device, the situation is different. Since such lenses are large in size and have extremely high requirements for homogeneity, if the VAD method is still used to introduce fluorine into the fused silica sintered body, it will be difficult to meet the actual application requirements. Therefore, it is necessary to provide a new fluorine-containing fused silica glass. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a fluorine-containing fused silica glass and a preparation method thereof.

[0004] The present invention provides the following technical solutions:

[0005] A fluorine-containing fused silica glass for transmitting ultraviolet light with a wavelength below 300 nm, wherein the average fluorine concentration inside the glass is above 1000 wtppm, and the average OH group concentration inside the glass is below 2 wtppm.

[0006] Further, the fluorine concentration inside the glass is 1300 to 1800 wtppm.

[0007] The present invention also provides a preparation method of a fluorine-containing fused silica glass, comprising the following steps:

[0008] S1: Prepare porous quartz particles;

[0009] S2: Heat-treat the porous quartz particles obtained in step S1 with a fluorine-containing solution, and after dehydration and drying, obtain dried porous quartz particles;

[0010] S3: Perform dehydration and closed-pore treatment on the dried porous quartz particles obtained in step S2 to obtain closed-pore quartz particles;

[0011] S4: Perform plasma melting or electro-melting treatment on the closed-pore fossil quartz particles obtained in step S3 to obtain fluorine-containing quartz glass.

[0012] Further, the fluorine-containing solution in step S2 is hydrofluoric acid or ammonium fluoride aqueous solution, and the F concentration in the fluorine-containing solution is 0.5 wt% to 5 wt%. - Concentration is 0.5 wt% to 5 wt%.

[0013] Further, the heat treatment in step S2 is to heat the porous quartz particles and the fluorine-containing solution at 25 - 70 °C for 1 h, then add ultrapure water and boil at 90 °C for 2 h.

[0014] Further, during the dehydration process in step S2, dehydration is carried out while spraying ultrapure water, and the drying temperature during the drying process is 300 °C to 1000 °C.

[0015] Further, step S2 obtains dry porous quartz particles with a fluorine concentration of 3000 to 4000 wtppm, and step S3 obtains closed-pore fossil quartz particles with a fluorine concentration of 1500 to 2500 wtppm. Further, the temperature during the dehydration and closed-pore treatment in step S3 is 1100 °C to 1200 °C, and the time is 5 to 20 h, obtaining closed-pore fossil quartz particles with a mesh size of 80 to 180.

[0016] Further, the plasma melting conditions in step S4 are: using argon as the plasma gas with a flow rate of 50 L / min; the output power is 100 kW, the frequency is 10 MHz, the voltage is 210 V, and the DC current is 570 A; the deposition rate is 2.5 kg / h; the raw material powder input speed is 3.0 kg / h. kg

[0017] The present invention also provides the application of the fluorine-containing quartz glass in optical lenses.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The fluorine-containing quartz glass provided by the present invention has good homogeneity, and the average fluorine concentration inside the glass is above 1000 wtppm, so it has a high transmittance in the ultraviolet region below 300 nm in wavelength. In addition, since the average OH group concentration inside the glass is below 2 wtppm, it is not easy to form oxygen-deficient defects of ≡Si-Si≡, so it has good laser resistance to ArF (193 nm) or KrF (248 nm) lasers. Detailed embodiments

[0020] The manufacturing method of the porous quartz particles of the present invention is not particularly limited and may be produced by hydrolysis of organosilane, manufactured by the sol-gel method, manufactured by hydrolysis of water glass, and so on. It should only be a high-purity product that contains as little impurities as possible that can reduce the transmittance in the ultraviolet region. These porous quartz particles have minute open pores with a size of several nm to 20 nm inside. The present invention uses a fluorine-containing aqueous solution as a fluorine doping reagent, such as hydrofluoric acid, ammonium fluoride aqueous solution, etc. The fluorine-containing aqueous solution will enter the surface and inside of the porous particles through the open pores and react with the quartz. Specifically, —Si—OH + F - → —Si—F reaction occurs, and F replaces OH. The bond of Si–F is strong and stable. The doping amount of fluorine is determined by the concentration of the fluorine reagent, reaction temperature, and time. However, since subsequent washing with pure water, drying, sintering, and melting will also reduce it, it is necessary to adjust the conditions through the process route.

[0021] For example, first, in the reaction of porous quartz particles and a fluorine-containing aqueous solution, the higher the concentration of F - in the fluorine-containing aqueous solution, the more fluorine is doped into the porous quartz particles. However, when the concentration of F - exceeds 5 wt%, a large amount of the porous quartz particles will be converted into hexafluorosilicic acid, which is not desirable. Therefore, the concentration of F - should be set between 0.5 wt% and 5 wt%. The reaction temperature is between room temperature and 70°C. The higher the reaction temperature, the faster the reaction proceeds. However, since hexafluorosilicic acid is easily formed, a more suitable temperature range is 50°C to 70°C. Since the boiling point of hydrogen fluoride is relatively low, it cannot exceed 70°C under normal pressure. At 60°C, the reaction time is generally completed within 60 minutes.

[0022] After the heat treatment is completed in the fluorine-containing aqueous solution, a dehydration operation is carried out. During this process, ultra-pure water is sprayed while dehydrating to remove the unreacted fluorine-containing aqueous solution. Then, the dehydrated porous quartz particles are dried. The drying temperature should be controlled between 300°C and 1000°C. If the fluorine concentration of the dried porous quartz particles is between 3000 and 4000 wtppm, there is no problem. If it is less than 3000 wtppm, it is necessary to use the fluorine-containing aqueous solution for heat treatment again.

[0023] The dry porous quartz particles with a fluorine concentration of 3000 to 4000 wtppm are dehydrated and closed-pored by sintering. The temperature at this time is between 1100 °C and 1200 °C. During this process, fluorine also detaches from the quartz particles. When sintering, if the pressure changes from atmospheric pressure to pressurized, the fluorine concentration will become 1500 to 2500 wtppm, and if it is depressurized, it will become 500 to 1000 wtppm. Since the fluorine concentration fluctuates greatly and is difficult to control under pressure changes, it is advisable to carry out the sintering process at atmospheric pressure, which can ensure a slow decrease in the fluorine concentration, thereby improving the stability and controllability of the process.

[0024] The quartz particles with a fluorine concentration of 1500 to 2500 wtppm are subjected to plasma melting or electro-melting treatment. In the case of plasma melting treatment, the fluorine concentration hardly changes. If electro-melting is carried out in a vacuum, the fluorine concentration will decrease by 50 to 500 wtppm.

[0025] The fluorine-containing quartz ingot is formed into a desired size at atmospheric pressure. However, since the fictive temperature of the fluorine-containing quartz ingot is lower than that of the quartz ingot without fluorine, it is also necessary to lower the forming temperature. This is because when the fluorine concentration is between 1000 and 2000 wtppm, the fictive temperature will be between 900 °C and 1000 °C. Regarding the calculation of the fictive temperature, through infrared spectroscopic analysis, using the peak position ν near 2260 cm-1, it is calculated as Tf(K)=43809.21(ν - 2228.64). In addition, when sintering and forming with a mold such as graphite, the reaction of Si-F + F-Si → ≡Si-Si≡ + F2 will occur at the contact part, and since it will cause a decrease in the transmittance of the outer surface, it is necessary to grind the outer surface after forming.

[0026] In this way, fluorine-containing quartz glass with a fluorine concentration of 1000 to 2000 wtppm can be manufactured. However, if the fluorine concentration of the quartz glass is lower than 1000 wtppm, even if the bond strength of —Si—F is strong, under the action of excimer laser, F- will detach, forming oxygen-deficient defects of ≡Si-Si≡. Due to these oxygen-deficient defects, the transmittance at wavelengths below 300 nm will decrease, so this is not advisable. Furthermore, when the fluorine concentration in the quartz glass exceeds 2000 wtppm, reductive defects will occur, resulting in a decrease in transmittance, which is also not advisable. The most ideal fluorine concentration of the quartz glass is 1300 to 1800 wtppm.

[0027] The Si-OH group is not advisable because it absorbs in the vacuum ultraviolet region of 160 nm, which reduces the transmittance. However, in traditional pure silica glass, in order not to generate oxygen-deficient defects of ≡Si-Si≡, it contains 100-300 wtppm of OH. In addition, in order to have the performance against excimer lasers, traditional pure silica glass is also doped with about 2E16 atom / cm2 of hydrogen. Since the fluorine-containing silica glass of the present invention contains fluorine, the lower the OH content, the better. Moreover, due to the doping of fluorine, —Si—OH will become —Si—F, thereby reducing the OH content. When the fluorine concentration of the silica glass is 1000 wtppm or more, the OH content will be 2 wtppm or less.

[0028] In the present invention, the quantitative determination of fluorine in quartz particles is carried out in accordance with Ingram, B.L. (1970), 《Determination of fluoride in silicate rocks without separation of aluminum using a specificion electrode. Analytical Chemistry, 42, 1825-1827》. In addition, the quantitative determination of fluorine in the fluorine-containing silica glass is carried out by a Raman scattering spectrophotometer (JASCO Corporation: NR-1000), according to the ratio of the Si-F Raman scattering intensity at 940 cm -1 to the Si-O Raman scattering intensity at 800 cm -1 .

[0029] In an exposure apparatus using an excimer laser, there is another requirement for the lens. That is, the difference in refractive index should be small. As described above, in the VAD method, the fluctuation of the fluorine concentration is large, and the refractive index distribution also becomes large. This situation is called vein texture and can be easily detected by an inspection apparatus using the Schlieren method and the shadow method. If it is to be used as a lens, the deviation of the fluorine content needs to be controlled within 5%. When the deviation of the fluorine concentration is within 5%, the homogeneity Δn will be 2E(-6) or less.

[0030] The determination of the excimer laser tolerance is carried out by finding the difference in refractive index after irradiation with the excimer laser. Due to the irradiation of the excimer laser, the dissociation of Si-F occurs, resulting in a decrease in the refractive index. Only the binding force of Si-F is larger than that of Si-OH, so it is not easily dissociated. However, when the fluorine concentration exceeds 2000 wtppm, reductive defects will be generated, resulting in a decrease in the transmittance.

[0031] The content of the OH group in quartz particles is determined using an infrared absorption spectroscopic apparatus in CCl4. The content of the OH group in the silica glass is directly measured by an infrared absorption spectroscopic apparatus.

[0032] The vacuum ultraviolet transmittance was measured using a KV-200 manufactured by a spectrometer company. As representative values, the values at 248 nm, 193 nm, and 157 nm were measured.

[0033] Hereinafter, the present invention will be specifically described according to embodiments, but the present invention is not limited by the embodiments shown below.

[0034] Example 1

[0035] 20.7 kg of fumed silica was mixed with 27.9 kg of a 48 wt% aqueous potassium hydroxide solution, and 167 L of pure water was added, and the reaction was carried out at 120 °C for 2 h. Subsequently, filtration was carried out using a 0.5-micron polytetrafluoroethylene filter to obtain water glass. The water glass solution was passed through 750 L of a strongly acidic cation exchange resin (Amberlite IR120B, H+ type, manufactured by DuPont, USA) to obtain a colloidal silica solution. The pH value of the obtained colloidal silica solution was adjusted to 5 with a 10 wt% ammonium hydroxide solution to cause gelation. The silica gel was frozen at -60 °C for 3 h and then thawed with hot water at 70 °C. At this time, the silica gel was in a granular form, and it was centrifugally dehydrated and dried at 100 °C to obtain porous quartz particles. 150 L of 5 wt% hydrochloric acid was added to the porous quartz particles with a mesh size of 50 to 120, and the mixture was boiled at 90 °C for 2 h. Thereafter, after separating the acid with a centrifuge, the porous quartz particles were boiled with 150 L of ultrapure water at 90 °C for 2 h and then dehydrated.

[0036] 250 kg of porous quartz particles were heated with 150 L of 1 wt% hydrofluoric acid at 70 °C for 1 h, then 150 L of ultrapure water was added, and the mixture was boiled at 90 °C for 2 h, and then dehydration treatment was carried out. The specific dehydration process was to dehydrate while spraying ultrapure water.

[0037] In a rotary electric furnace at 1000 °C, the porous quartz particles obtained in the previous step were supplied into the electric furnace at a supply rate of 10 kg / h for drying, and the drying time was about 10 minutes.

[0038] Thereafter, the porous quartz particles were fired at 1200 °C for 10 h to obtain 16 kg of closed-cell fossil quartz particles with a mesh size of 80 to 180.

[0039] The closed-cell fossil quartz particles were subjected to plasma melting treatment. The melting conditions were as follows: argon was used as the plasma gas with a flow rate of 50 L / min; the output power was 100 kW, the frequency was 10 MHz, the voltage was 210 V, and the DC current was 570 A; the deposition rate was 2.5 kg / h; the feeding rate of the raw material powder was 3.0 kg / h. The obtained ingot was a cylinder with a diameter of about 160 mm and a height of 320 mm. It was placed in a graphite mold with an inner diameter of 200 mm and a height of 300 mm and held at 1800 °C for 3 h to obtain a block with an outer diameter of 200 mm and a height of 200 mm. Subsequently, its two ends and outer surface were ground to make a plate with an outer diameter of 160 mm and a thickness of 5 mm. It was held in air at 950 °C for 20 h. Grinding was carried out again, and mirror polishing was performed on both ends. The mirror polishing was completed using a 1000# alumina, cerium oxide, and colloidal silica-based abrasive. After that, it was etched with 5 wt% hydrofluoric acid and washed with pure water to obtain fluorine-containing quartz glass.

[0040] Example 2

[0041] 20.7 kg of fumed silica was mixed with 27.9 kg of 48 wt% potassium hydroxide aqueous solution, and 167 L of pure water was added, and the reaction was carried out at 120 °C for 2 h. Subsequently, filtration was carried out using a 0.5-micron polytetrafluoroethylene filter to obtain water glass. The water glass solution was passed through 750 L of strongly acidic cation resin (Amberlite IR120B, H+ type, manufactured by DuPont, USA) to obtain a colloidal silica solution. The pH value of the obtained colloidal silica solution was adjusted to 5 with 10 wt% ammonium hydroxide solution to cause gelation. The silica gel was frozen at -60 °C for 3 h and then thawed with hot water at 70 °C. At this time, the silica gel was in a granular state, and it was centrifugally dehydrated and dried at 100 °C to obtain porous quartz particles. 150 L of 5 wt% hydrochloric acid was added to the porous quartz particles with a mesh size of 50 to 120, and it was boiled at 90 °C for 2 h. After that, after separating the acid with a centrifuge, the porous quartz particles were boiled with 150 L of ultrapure water at 90 °C for 2 h and then dehydrated.

[0042] 250 kg of porous quartz particles were heated with 150 L of 2 wt% hydrofluoric acid at 70 °C for 1 h, then 150 L of ultrapure water was added, and it was boiled at 90 °C for 2 h, and then dehydration treatment was carried out. The specific dehydration process was to dehydrate while spraying ultrapure water.

[0043] The porous quartz particles obtained in the previous step were fed into a rotary electric furnace at 1000 °C at a supply rate of 10 kg / h for drying, and the drying time was about 10 minutes.

[0044] Thereafter, the porous quartz particles were fired at 1200 °C for 10 h to obtain 16 kg of closed-cell fossil quartz particles with a size of 80 to 180 mesh.

[0045] The closed-cell fossil quartz particles were subjected to plasma melting treatment. The melting conditions were as follows: argon was used as the plasma gas with a flow rate of 50 L / min; the output power was 100 kW, the frequency was 10 MHz, the voltage was 210 V, and the DC current was 570 A; the deposition rate was 2.5 kg / h; the feed rate of the raw material powder was 3.0 kg / h. The obtained ingot was a cylinder with a diameter of about 160 mm and a height of 320 mm. It was placed in a graphite mold with an inner diameter of 200 mm and a height of 300 mm and held at 1800 °C for 3 h to obtain a block with an outer diameter of 200 mm and a height of 200 mm. Subsequently, its two ends and outer surface were ground to form a plate with an outer diameter of 160 mm and a thickness of 5 mm. It was held in air at 950 °C for 20 h. Grinding was performed again, and mirror polishing was carried out on both ends. The mirror polishing was completed using a 1000# alumina, cerium oxide, and colloidal silica-based abrasive. Thereafter, it was etched with 5 wt% hydrofluoric acid and washed with pure water to obtain fluorine-containing quartz glass.

[0046] Example 3

[0047] 20.7 kg of fumed silica was mixed with 27.9 kg of 48 wt% potassium hydroxide aqueous solution, and 167 L of pure water was added, and the reaction was carried out at 120 °C for 2 h. Subsequently, filtration was carried out using a 0.5-micron polytetrafluoroethylene filter to obtain water glass. The water glass solution was passed through 750 L of strongly acidic cation resin (Amberlite IR120B, H+ type, manufactured by DuPont, USA) to obtain a colloidal silica solution. The pH value of the obtained colloidal silica solution was adjusted to 5 with 10 wt% ammonium hydroxide solution to cause gelation. The silica gel was frozen at -60 °C for 3 h and then thawed with hot water at 70 °C. At this time, the silica gel was in a granular state, and it was centrifugally dehydrated and dried at 100 °C to obtain porous quartz particles. 150 L of 5 wt% hydrochloric acid was added to the porous quartz particles with a size of 50 to 120 mesh, and the mixture was boiled at 90 °C for 2 h. Thereafter, after separating the acid with a centrifuge, the porous quartz particles were boiled with 150 L of ultrapure water at 90 °C for 2 h and then dehydrated.

[0048] 250 kg of porous quartz particles were heated with 150 L of 4 wt% hydrofluoric acid at 70 °C for 1 h, then 150 L of ultrapure water was added, and the mixture was boiled at 90 °C for 2 h, and then dehydration treatment was carried out. The specific dehydration process was to dehydrate while spraying ultrapure water.

[0049] The porous quartz particles obtained in the previous step were supplied into a rotary electric furnace at 1000 °C at a supply rate of 10 kg / h for drying, and the drying time was about 10 minutes.

[0050] Thereafter, the porous quartz particles were fired at 1200 °C for 10 h to obtain 16 kg of closed-cell fossil quartz particles with a particle size of 80 to 180 mesh.

[0051] The closed-cell fossil quartz particles were subjected to plasma melting treatment. The melting conditions were as follows: argon was used as the plasma gas with a flow rate of 50 L / min; the output power was 100 kW, the frequency was 10 MHz, the voltage was 210 V, and the direct current was 570 A; the deposition rate was 2.5 kg / h; the raw material powder feeding rate was 3.0 kg / h. The obtained ingot was a cylinder with a diameter of about 160 mm and a height of 320 mm. It was placed in a graphite mold with an inner diameter of 200 mm and a height of 300 mm and held at 1800 °C for 3 h to obtain a block with an outer diameter of 200 mm and a height of 200 mm. Subsequently, both ends and the outer surface were ground to produce a plate with an outer diameter of 160 mm and a thickness of 5 mm. It was held in air at 950 °C for 20 h. Grinding was performed again, and mirror polishing was carried out on both ends. The mirror polishing was completed using a 1000# alumina, cerium oxide, and colloidal silica-based abrasive. Thereafter, etching was performed with 5 wt% hydrofluoric acid and washed with pure water to obtain fluorine-containing quartz glass.

[0052] Example 4

[0053] 20.7 kg of fumed silica was mixed with 27.9 kg of 48 wt% potassium hydroxide aqueous solution, and 167 L of pure water was added, and the reaction was carried out at 120 °C for 2 h. Subsequently, filtration was performed using a 0.5-micron polytetrafluoroethylene filter to obtain water glass. The water glass solution was passed through 750 L of strongly acidic cation exchange resin (Amberlite IR120B, H+ type, manufactured by DuPont, USA) to obtain a colloidal silica solution. The pH value of the obtained colloidal silica solution was adjusted to 5 with 10 wt% ammonium hydroxide solution to cause gelation. The silica gel was frozen at -60 °C for 3 h and then thawed with hot water at 70 °C. At this time, the silica gel was in a granular form, which was centrifugally dehydrated and dried at 100 °C to obtain porous quartz particles. 150 L of 5 wt% hydrochloric acid was added to the porous quartz particles with a particle size of 50 to 120 mesh, and the mixture was boiled at 90 °C for 2 h. Thereafter, after separating the acid with a centrifuge, the porous quartz particles were boiled with 150 L of ultrapure water at 90 °C for 2 h and then dehydrated.

[0054] 250 kg of porous quartz particles were heated with 150 L of hydrofluoric acid at a concentration of 6 wt% at 70 °C for 1 h. Then, 150 L of ultrapure water was added, and the mixture was boiled at 90 °C for 2 h. Subsequently, dehydration treatment was carried out. The specific dehydration process was to dehydrate while spraying ultrapure water.

[0055] The porous quartz particles obtained in the previous step were fed into a rotary electric furnace at 1000 °C at a supply rate of 10 kg / h for drying, and the drying time was about 10 minutes.

[0056] Thereafter, the porous quartz particles were fired at 1200 °C for 10 h to obtain 16 kg of closed-cell fossil quartz particles with a mesh size of 80 to 180.

[0057] The closed-cell fossil quartz particles were subjected to plasma melting treatment. The melting conditions were as follows: argon was used as the plasma gas with a flow rate of 50 L / min; the output power was 100 kW, the frequency was 10 MHz, the voltage was 210 V, and the direct current was 570 A; the deposition rate was 2.5 kg / h; the feeding rate of the raw material powder was 3.0 kg / h. The obtained ingot was a cylinder with a diameter of about 160 mm and a height of 320 mm. It was placed in a graphite mold with an inner diameter of 200 mm and a height of 300 mm and held at 1800 °C for 3 h to obtain a block with an outer diameter of 200 mm and a height of 200 mm. Subsequently, both ends and the outer surface were ground to produce a plate with an outer diameter of 160 mm and a thickness of 5 mm. It was held in air at 950 °C for 20 h. Grinding was carried out again, and both ends were mirror-polished. The mirror polishing was completed using a 1000# alumina, cerium oxide, and colloidal silica-based abrasive. Then, it was etched with 5 wt% hydrofluoric acid and washed with pure water to obtain fluorine-containing quartz glass.

[0058] The OH group content and fluorine content in the closed-cell fossil quartz particles in the above examples were measured, and the measurement results are shown in Table 1:

[0059] Table 1 OH group concentration and fluorine concentration of quartz particles

[0060]

[0061] The properties of the fluorine-containing quartz glass obtained in the above examples were measured, and the measurement results are shown in Table 2:

[0062] Table 2 Properties of fluorine-containing quartz glass

[0063]

[0064] In Table 2, the OH concentration refers to the average OH concentration inside the glass, and the F concentration refers to the average F concentration inside the glass.

[0065] The obtained fluorine-containing fused silica glass in the above embodiments was tested by ArF laser irradiation, and the test results are shown in Table 3 as follows:

[0066] Table 3 Test Results of ArF Laser Irradiation

[0067]

[0068] The foregoing description of the disclosed embodiments enables those skilled in the art to practice or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. Fluorine-containing quartz glass, used for transmitting ultraviolet light with a wavelength below 300nm, characterized in that: The fluorine concentration inside the glass is above 1000 wtppm, and the OH group concentration inside the glass is below 2 wtppm.

2. The fluorine-containing quartz glass according to claim 1, characterized in that The fluorine concentration inside the glass is 1300 to 1800 wtppm.

3. A method for preparing fluorine-containing quartz glass, characterized in that: The following steps are involved: S1: preparing porous quartz particles; S2: heating the porous quartz particles obtained in step S1 with a fluorine-containing solution, dehydrating and drying to obtain dry porous quartz particles; S3: dehydrating and closing the dried porous quartz particles obtained in step S2 to obtain closed-cell quartz particles; S4: performing plasma melting or electric melting treatment on the closed-cell quartz particles obtained in step S3 to obtain fluorine-containing quartz glass.

4. The method for preparing fluorine-containing quartz glass according to claim 3, characterized in that: The fluorine-containing solution in step S2 is hydrofluoric acid or ammonium fluoride aqueous solution, and the fluorine-containing solution contains - The concentration is 0.5wt% to 5wt%.

5. The method for preparing fluorine-containing quartz glass according to claim 3, characterized in that: The heating treatment in step S2 is to heat the porous quartz particles and the fluorine-containing solution at 25-70° C. for 1 hour, then add ultrapure water and boil at 90° C. for 2 hours.

6. The method for preparing fluorine-containing quartz glass according to claim 3, characterized in that: In step S2, the dehydration process is performed while spraying ultrapure water, and the drying temperature during the drying process is 300° C. to 1000° C.

7. The method for preparing fluorine-containing quartz glass according to claim 3, characterized in that: Step S2 obtains dry porous quartz particles having a fluorine concentration of 3000 to 4000 wtppm, and step S3 obtains closed-cell quartz particles having a fluorine concentration of 1500 to 2500 wtppm.

8. The method for preparing fluorine-containing quartz glass according to claim 3, characterized in that: The temperature for dehydration and closed-cell treatment in step S3 is 1100° C. to 1200° C. for 5 to 20 hours, and closed-cell quartz particles with a mesh size of 80 to 180 are obtained.

9. The method for preparing fluorine-containing quartz glass according to claim 3, characterized in that: The plasma melting conditions in step S4 are: using argon as the plasma gas with a flow rate of 50 L / min; the output power is 100 kW, the frequency is 10 MHz, the voltage is 210 V, and the DC current is 570 A; the deposition rate is 2.5 kg / h; and the raw material powder input speed is 3.0 kg / h.

10. Use of the fluorine-containing quartz glass according to claim 1 or 2 in an optical lens.

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