CN1300278C - Fluocerite-contained series abrasive and manufacturing method thereof - Google Patents

Abstract

The cerium-based abrasive material of the present invention contains fluorine, the mass ratio of total rare earth oxide conversion mass (TREO) to the abrasive material mass is more than 90wt%, and the total content of Th and U to the mass ratio of the TREO ((Th+U) /TREO) is 0.05wt% or less, and the average particle size ( _DB ) according to the Bryan method is 1.5 μm to 2.5 μm. In order to secure a necessary polishing rate, the particle size distribution of the abrasive particles was controlled for the cerium-based abrasive whose particle diameter was set based on the average particle diameter ( _DB ) of the Bryan method. Therefore, if the Bryan method average particle size ( _DB ) is used as the particle size setting standard in the manufacture of cerium-based abrasive materials, cerium-based abrasive materials with reduced content of thorium and uranium and high grinding speed can be obtained. .

Description

Fluorine-containing cerium-based abrasive material and method for producing the same

technical field

The invention relates to a fluorine-containing cerium-based abrasive material and a manufacturing method thereof.

Background technique

As a cerium-based abrasive, there is a material manufactured using bastnaesite concentrate as a raw material (refer to Japanese Patent Application Laid-Open No. 2003-213250). The method simply means that the bastnaesite is subjected to wet crushing, the obtained slurry is dried, roasted, cooled, and then the obtained roasted product is crushed, and then classified. When utilizing this manufacturing method to make the grinding material with high grinding accuracy that is not easy to produce grinding damage, etc., the firing temperature in the firing step is set at a lower temperature, and when making the grinding material with higher grinding speed, the firing temperature is set at higher temperature.

However, although the concentrate of bastnaesite has good characteristics as a raw material for cerium-based abrasives such as containing an appropriate amount of fluorine, on the other hand, the content of thorium (Th) and uranium (U) is different from that of bastnaesite. The ratio ((Th+U)/TREO) of the total rare earth oxide equivalent (TREO) of the concentrate is about 0.1 wt%. Thus, a method for producing a cerium-based abrasive having reduced thorium and uranium content is provided. In simple terms, this manufacturing method is to chemically process rare earth ores such as bastnaesite concentrate to obtain light rare earth carbonates with reduced contents of radioactive elements such as thorium and uranium, alkali metals, and alkaline earth metals, etc. Finally, hydrofluoric acid is added to the light rare earth carbonate to partially fluorinate the carbonate, and then the product obtained is roasted (for the above background technology, refer to Japanese Patent Application Laid-Open No. 9-183966).

Therefore, according to the latter manufacturing method, it is possible to obtain a cerium-based abrasive having a reduced content of thorium and uranium. However, in the latter method, even if the calcination temperature is set to a higher temperature to manufacture a high-polishing-rate abrasive, it is impossible to obtain such a high-polishing-rate abrasive as the cerium-based abrasive obtained by the former method. Material.

Therefore, an object of the present invention is to provide a cerium-based abrasive having a reduced content of thorium, uranium, etc., and a high polishing rate equal to or higher than conventional products, and a method for producing the same.

Contents of the invention

The present invention has accomplished the above-mentioned problems, and it is a fluorine (F) cerium-based abrasive material, which is characterized in that the mass ratio of total rare earth oxide conversion mass (hereinafter referred to as TREO) to the mass of the abrasive material is 90 wt% or more, The mass ratio ((Th+U)/TREO) of the total content of thorium (Th) and uranium (U) to the equivalent amount of all rare earth oxides is 0.05 wt % or less, and the average particle diameter ( _DB ) of the Bryan method is 1.5μm～2.5μm.

As a result of research, the cerium-based abrasive material of the present invention has a high grinding rate equal to or higher than that of conventional cerium-based abrasive materials produced from bastnaesite concentrate regardless of the type of raw material. The cerium-based abrasive can be used, for example, for primary polishing or intermediate polishing of glass substrates for liquid crystals, hard disks, or photomasks, or polishing of optical glass. The reason for preventing the decrease of the grinding speed is still unclear, but it may have a lot to do with the Bryan method average particle size ( _DB ) as the benchmark for the particle size of the abrasive material. In the production of cerium-based abrasives, for example, the particle size of the abrasives to be produced is set according to the use of the abrasives such as "finishing". In setting the particle size, the particle size (D ₅₀ ) of particles whose cumulative volume is 50 wt% from the small particle size side measured by laser diffraction/scattering particle size distribution measurement method is used. However, when producing a cerium-based abrasive with a reduced content of thorium and uranium and a high polishing rate, even if the particle size (D ₅₀ ) is used as a standard for setting the particle size, in most cases the obtained abrasive has a Grinding speed is low. Therefore, even if the particle size is set using the conventional particle size (D ₅₀ ) as a benchmark, the particle size distribution of the abrasive particles cannot be controlled to ensure the necessary grinding speed. An abrasive material having a particle size distribution exhibiting the above-required level of grinding rate performance can be produced. On the contrary, the cerium-based abrasives obtained by adopting the Bryan method average particle size ( _DB ) as the benchmark in particle size setting have the above-mentioned required level or even higher grinding speed. Therefore, the cerium-based abrasive whose particle size is set on the basis of the Bryan method average particle size ( _DB ) is an abrasive whose particle state (eg, particle size distribution) of the abrasive is controlled so as to ensure a necessary polishing rate. That is, the standard for setting the particle size is the Bryan method average particle size ( _DB ), and the cerium-based abrasive of the present invention having the average particle size within the above-mentioned range has a particle state capable of exhibiting the above-mentioned required level of polishing rate performance.

When used in the above-mentioned applications, especially when a high polishing rate is required, the preferred range of the Bryan method average particle size ( _DB ) of the cerium-based abrasive is 1.5 μm to 2.5 μm as described above. If the average particle diameter ( _DB ) is less than the lower limit, a sufficient polishing rate cannot be secured. On the other hand, if it exceeds the upper limit, large damage and distortion will occur on the surface to be polished, and cannot be removed even if finishing polishing is performed thereafter. Therefore, considering these two aspects, the Bryan method average particle size ( _DB ) is more preferably 1.7 μm to 2.3 μm. In addition, the mass ratio ((Th+U)/TREO) of the total content of thorium and uranium to the TREO of the cerium-based abrasive is at most 0.05 wt%, preferably at most 0.005 wt%, more preferably at most 0.0005 wt%. . It is preferable to reduce the content of radioactive elements such as uranium and thorium as much as possible.

The mass ratio of the TREO to the cerium-based grinding material is above 90 wt%. More specifically, the proportion of TREO is preferably at least 90 wt%, more preferably at least 92 wt%, most preferably at least 93 wt%. When the proportion of each rare earth element is constant, the higher the mass ratio of TREO, the higher the proportion of cerium oxide, which is most useful for grinding among the rare earth oxides, in the mass of the grinding material, which can ensure a high grinding speed. In addition, the content of impurities, which is one of the causes of damage, is reduced, and the occurrence of damage can be reliably prevented.

However, as a result of research, the proportion of cerium oxide (CeO ₂ ) in TREO (CeO ₂ /TREO) is preferably 50 wt% to 70 wt%. If the ratio of cerium oxide is high, scratches are likely to occur, and if it exceeds the above upper limit, abrasive damage is likely to occur. On the other hand, the lower the ratio of cerium oxide, the slower the polishing rate, and if it is below the above-mentioned lower limit, a sufficient polishing rate cannot be ensured.

The content of fluorine (F) is preferably from 4.0 wt% to 10 wt%. This is because if the fluorine content is too low, a sufficient polishing rate cannot be ensured, and on the other hand, if it is too high, polishing damage will occur. Therefore, taking these two factors into consideration, the fluorine content is more preferably 5.0 wt% to 9.0 wt%.

Ores used as raw materials for cerium-based abrasives, such as bastnaesite concentrate, contain a large amount of calcium (Ca), barium (Ba), iron (Fe), and phosphorus in addition to radioactive substances such as uranium and thorium. (P) and other elements. Therefore, cerium-based abrasives containing a large amount of impurities formed from these elements are sometimes produced. Most of the grinding materials containing such impurities are prone to grinding damage and the grinding speed is low. In addition, if these impurities (especially iron) remain on the surface to be polished, the electrical or magnetic properties of the polished part will be degraded. Therefore, as a cerium-based abrasive material, the mass ratio ((Ca+Ba+Fe+P)/TREO) of the total content of calcium, barium, iron, and phosphorus to TREO is preferably 2.0 wt % or less, more preferably 1.0 wt % or less. wt% or less, preferably 0.5 wt% or less. As the raw material, the mass ratio ((Ca+Ba+Fe+P)/TREO) is preferably at most 2.0 wt%, more preferably at least 1.0 wt%, most preferably at most 0.5 wt%.

The BET method specific surface area of the cerium-based abrasive is preferably from 1.0 m ² /g to 3.5 m ² /g. The larger the specific surface area of the BET method, the slower the polishing rate. If the above upper limit is exceeded, a sufficient polishing rate cannot be ensured. On the other hand, the smaller the BET method specific surface area is, the easier it is to cause damage. If it is less than the above-mentioned lower limit, grinding damage that is not allowed in the aforementioned fields requiring high-precision polishing will occur. Considering these two aspects, the specific surface area by the BET method is preferably 1.2m ² /g to 3.0m ² /g.

The above is the description of the cerium-based abrasive of the present invention, and the method for producing the cerium-based abrasive will be described below. Rare earth carbonic acid obtained by chemically treating ore raw materials such as bastnaesite concentrate, monazite concentrate, and Chinese complex ore concentrate to reduce the content of impurities such as radioactive elements, alkali metals, and alkaline earth metals. A method for producing a cerium-based abrasive using a rare earth compound such as a salt as a raw material generally includes a step of firing the raw material. In addition, in the production method of the cerium-based abrasive material, wet processing such as a crushing step, a drying step, a fluoridation treatment, and a treatment for removing impurities is performed before the firing step, and a crushing step, a drying step, and a classification step are performed after the firing step. wait.

In this way, in the production method of the cerium-based abrasive material having the step of roasting the raw material, as the raw material supplied to the aforementioned roasting step, if the oxidation of the fluorine-containing rare earth compound obtained through roasting is used, The mass ratio of the conversion mass of the material to the conversion mass of all rare earth oxides of the raw material is more than 30wt%, the total content of thorium (Th) and uranium (U) to the conversion mass of the total rare earth oxides (( Th+U)/TREO) below 0.05wt% material, then can be made to have with the concentrate of bastnaesite as the cerium series grinding material that raw material makes etc. the same or even higher Grinding speed of cerium-based abrasives.

The reason why this raw material can be used is not clear at present, and it may have a lot to do with the fluorine-containing rare earth compounds obtained through roasting in the raw material. The fluorine-containing rare earth compound in the raw material is roasted in the production stage of the fluorine-containing rare earth compound, and further roasted in the production stage of the abrasive material. That is, the fluorine-containing rare earth compound in the raw material is fired twice or more in total before becoming the cerium-based abrasive. As a result of the research, the particle state of the cerium-based abrasives produced by the fluorine-containing state through multiple firing steps is significantly different from that of the cerium-based abrasives fired only once. After comparing the two cerium-based abrasive materials, it was found that although there was no difference in the particle size (D ₅₀ ) measured by laser diffraction and scattering particle size distribution measurement, the cerium-based abrasive materials prepared after several roasting steps were in the actual process. The damage condition of the polished surface obtained by grinding and the grinding value (polishing speed) are superior.

As described above, as a raw material for producing a practical abrasive, a material having a ratio of fluorine-containing rare earth compound of 30% by weight or more is used. This is because if the ratio is lower than the above value, the occurrence of scratches cannot be sufficiently prevented, and a sufficient polishing value (polishing speed) cannot be ensured. Therefore, the proportion of the fluorine-containing rare earth compound is preferably at least 50 wt%, more preferably at least 70 wt%. More specifically, the fluorine-containing rare earth compound used as a part of the raw material of the manufacturing method of the abrasive material of the present invention may, for example, be carbonates of rare earths, monohydroxycarbonates, basic carbonates, It is obtained by mixing rare earth compounds such as acid salts, hydroxides or oxides with fluorine-containing compounds such as hydrofluoric acid, ammonium fluoride or ammonium bifluoride, and then roasting the resulting mixture (a mixture of rare earth compounds and fluorine-containing compounds). materials etc.

The calcination temperature of the fluorine-containing rare earth compound is preferably from 300°C to 1100°C, more preferably from 400°C to 1000°C. When a fluorine-containing rare earth compound obtained by firing at a temperature lower than the lower limit is used as a raw material, it is easy to obtain a cerium-based abrasive having a slow polishing rate. On the other hand, if the particle size of the fluorine-containing rare earth compound obtained by firing at a firing temperature exceeding the upper limit is large, it is easy to form a hard material, and when this material is used as a raw material, it is easy to produce Cerium-based abrasives that cause grinding damage. Examples of the fluorine-containing rare earth compound obtained by firing include compounds obtained by various methods. For example, in the production of fluorine-containing cerium-based abrasives, when the classification step is performed after the firing step to obtain particulate abrasives, the coarse powder side is recovered in the classification step.

As a part other than the fluorine-containing rare earth compound in the raw material, it is confirmed that rare earth compounds such as rare earth carbonates, monohydroxy carbonates, basic carbonates, oxalates, hydroxides and roasting (or Trial roasting) The substances obtained from these rare earth compounds. Among them, the part other than the fluorine-containing rare earth compound is particularly good, and the strong heat loss obtained by trial roasting the exemplified rare earth compound is below 20wt%, preferably below 15wt%, more preferably below 10wt% materials, and oxides with strong thermal weight loss of almost 0 wt% obtained by firing the exemplified rare earth compounds for a long time at high temperature. Because it is easy to obtain cerium-based abrasive materials with larger particle sizes in the end.

In the method for producing the cerium-based abrasive material of the present invention described above, various methods can be employed as a method of supplying a raw material (intermediate raw material) having a reduced content of thorium and uranium in the firing step. For example, if a material with a reduced content of radioactive elements such as thorium and uranium is used as the starting material, the raw material (intermediate material) with a reduced content of thorium and uranium can be supplied in the roasting step. As the raw material, the mass ratio ((Th+U)/TREO) of the total content of thorium (Th) and uranium (U) to the total rare earth oxide conversion amount of the raw material is preferably 0.05 wt % or less, More preferably less than 0.005% by weight of material, most preferably less than 0.0005% by weight of material. If this raw material is used, the mass ratio ((Th+U)/TREO) of the total content of thorium (Th) and uranium (U) to the total rare earth oxide conversion amount can be reduced, and it has the same Cerium-based abrasives such as cerium-based abrasives made from raw materials are cerium-based abrasives with the same or even higher grinding speed than conventional cerium-based abrasives. Various known methods such as the chemical treatment method described in Patent Document 2 can be used as a method of producing a raw material having a reduced content of radioactive elements such as thorium and uranium from ores containing radioactive elements such as thorium and uranium. For example, for example, using sulfuric acid decomposition method or alkali decomposition method to decompose bastnaesite concentrate and other concentrates, and then carry out fractional precipitation and step-by-step dissolution, etc., by reducing and removing uranium, thorium, calcium, barium, Impurities such as iron, phosphorus obtain rare-earth solution, after adjusting the composition of the rare-earth component of gained rare-earth solution, mix the adjusted rare-earth solution and precipitation agent (for example, ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, sodium carbonate , ammonia, oxalic acid, ammonium oxalate, sodium oxalate, urea, etc.), to generate precipitation of rare earth compounds (such as carbonic acid, basic carbonate, monohydroxycarbonate, hydroxide, oxalate, etc.), and to precipitate A method for obtaining the raw material for cerium-based abrasives of the present invention by filtering and washing with water. In addition, oxides obtained by firing (trial firing) the above-mentioned raw materials or intermediates with oxides can also be used as raw materials. In this way, the content of impurities such as calcium, barium, iron, and phosphorus can be reduced at the same time by the above-mentioned method.

As mentioned above, since the particle size (D ₅₀ ) measured by the laser diffraction/scattering particle size distribution measurement method cannot determine the quality of the polishing characteristics, the quality of the polishing characteristics such as the damage evaluation and the polishing value (polishing speed) cannot be judged. The relationship between various physical properties and the state of the abrasive particles was studied. As mentioned above, the cerium-based abrasives with the Bryan method average particle diameter (D _B ) within the specified range had better damage evaluation and grinding value ( The grinding properties in terms of grinding speed) are good. Therefore, the particle size setting standard when the cerium-based abrasive material is manufactured is the Bryan method average particle diameter ( _DB ), and the cerium-based abrasive material of the present invention with the average particle diameter within the above-mentioned range has a grinding speed that can bring into play the above-mentioned required level. The particle state of the performance.

Hereinafter, the correlation among the multiple firing steps will be studied. As a result, the calcination temperature in the calcination step of the fluorine-containing rare earth compound-containing raw material is in the range of 900°C to 1200°C, and is preferably 10°C higher than the calcination temperature when the fluorine-containing rare earth compound contained in the raw material is generated. above.

If the calcination temperature is low, the particle size of the finally obtained grinding material will not increase, and the grinding speed will tend to decrease. If it is less than the lower limit of the above-mentioned temperature range, the particle size will not be sufficiently large, and the grinding rate will be reduced. The speed will not increase sufficiently. On the other hand, if the calcination temperature is higher, the particle diameter of the abrasive material finally obtained becomes large, and there is a tendency for grinding damage to occur easily. If the upper limit of the above-mentioned temperature range is exceeded, the particle diameter becomes too large. At the same time, more abrasive damage will occur. Therefore, from these points of view, the firing temperature is more preferably from 950°C to 1150°C.

The smaller the temperature difference between the calcination temperature in the calcination process of the production method and the calcination temperature when the fluorine-containing rare earth compound contained in the raw material is generated, the more difficult it is to sinter during calcination. When the temperature difference is less than 10°C, the resulting The cerium-based abrasive tends to be a material with a small particle size and a slow polishing rate. From this point of view, the temperature difference is more preferably at least 20°C, most preferably at least 50°C.

In addition, when the production method of the cerium-based abrasive material having a fluoridation treatment step is adopted, the content of thorium and uranium can be reduced by the following production method, and it has Cerium-based abrasives made from raw materials, such as conventional cerium-based abrasives, are cerium-based abrasives with the same or even higher grinding speed.

That is, the production method is a production method of a cerium-based abrasive material having at least one fluorination treatment step of making the raw material of the cerium-based abrasive material fluorine-containing, and a calcination step carried out after the fluoridation treatment step. The number of roasting steps performed after the first fluorination treatment step is two or more, and the total content of thorium (Th) and uranium (U) in the roasting object (intermediate raw material) supplied to the first roasting step is related to the total rare earth oxidation The mass ratio ((Th+U)/TREO) of the material conversion amount is 0.05 wt% or less.

In the research, it is clear that the desired cerium-based abrasive materials cannot be obtained only by performing more than two roasting steps, and each roasting step must be a step of roasting the raw materials (including intermediate raw materials) of fluorine-containing cerium-based abrasive materials. , thus completing the present invention. Therefore, this production method includes a fluorination treatment step performed before the firing step, and the first fluorination treatment is performed before the first firing step. Focusing on the second and subsequent firing steps, it is preferable to perform an additional fluorination treatment between this firing step and the previous firing step. In consideration of cost, production efficiency, etc., it is preferable to perform the roasting step twice. According to the above-mentioned production method, it is possible to produce a cerium-based abrasive having a grinding rate equal to or higher than conventional cerium-based abrasives such as cerium-based abrasives prepared from bastnaesite concentrate as a raw material. If the object to be roasted is a fluorine-containing material, a roasted product with a moderately large particle size can be produced by roasting, and it is easy to produce an abrasive with a higher grinding rate.

It has been confirmed that it can be obtained by using rare earth compounds such as rare earth carbonates, monohydroxy carbonates, basic carbonates, oxalates, hydroxides, etc., and roasting (or trial roasting) these rare earth compounds. s material. Among them, it is particularly preferable that the strong heat loss obtained by trial roasting of the exemplified rare earth compounds is below 20wt%, preferably below 15wt%, more preferably below 10wt%. Exemplary rare earth compounds are calcined for a long time to obtain oxides with strong heat loss of almost 0 wt%. In this way, it is easy to obtain cerium-based abrasive materials with larger particle sizes in the end.

The fluoridation treatment can be performed by mixing raw materials (including intermediate raw materials) of the cerium-based abrasive and a fluorine-containing compound. The fluorine-containing compound can be fluorine-containing compounds such as hydrofluoric acid, ammonium fluoride, ammonium bifluoride, etc., fluorine-containing rare earth compounds such as rare earth fluorides, rare earth hydroxy fluorides, etc. However, the fluorine-containing rare earth compound is not necessarily a compound obtained by firing, and may be obtained by mixing a rare earth compound such as a rare earth carbonate and a fluorine-containing compound such as hydrofluoric acid, for example. This is because the raw material subjected to the fluorination treatment with the fluorine-containing rare earth compound has to go through two or more roasting steps.

Various methods can be employed as a method for producing a cerium-based abrasive having reduced content rates of thorium, uranium, and the like by this production method. For example, if a raw material having a reduced content of radioactive elements such as thorium and uranium is used as a starting material in this production method, a cerium-based abrasive having a reduced content of thorium, uranium, etc. can be produced. As the raw material, as mentioned above, it is preferable that the mass ratio ((Th+U)/TREO) of the total content of thorium (Th) and uranium (U) to the equivalent amount of all rare earth oxides of the raw material is 0.05 wt % or less, more preferably less than 0.005 wt%, most preferably less than 0.0005 wt%. The method of producing a raw material with reduced content of radioactive elements such as thorium and uranium from an ore containing radioactive elements such as thorium and uranium is as described above, and the description of the method is omitted here.

As a result of the research, the firing temperature of each firing step including the initial firing step is preferably at least 700°C, the firing temperature of the final firing step is preferably 900°C to 1200°C, and the firing temperature of each firing step after the second time is preferably 700°C or higher. The calcination temperature is preferably higher than the calcination temperature of the previous calcination step of each calcination step by more than 10°C.

If the calcination temperature in each calcination step is less than 700° C., the effect of particle growth by calcination is hardly obtained, and a polishing material having a desired polishing rate cannot be obtained. In addition, even if the calcination temperature of each calcination step is above 700°C, if the calcination temperature of the final calcination step is lower, the particle size of the finally obtained grinding material will not increase, and the grinding speed will tend to decrease. If it is less than 900°C, the particle size is not large enough, and the polishing rate is not high enough. On the other hand, if the calcination temperature of the final calcination step is higher, the particle size of the abrasive material finally obtained becomes larger, but there is a tendency to easily produce grinding damage at the same time, if it exceeds 1200 ° C, the particle size becomes too large, At the same time, a large amount of grinding damage will occur. Therefore, considering the above aspects, the firing temperature is more preferably 950°C to 1150°C. When focusing on the calcination steps after the second time, the calcination temperature of this calcination step is preferably higher than the calcination temperature of the previous calcination step of this calcination step, but the smaller the temperature difference between the two calcination temperatures, the more difficult the sintering during calcination conduct. When the temperature difference is less than 10° C., the obtained cerium-based abrasive tends to have a small particle size and a slow polishing rate. Therefore, it is preferable that the roasting temperature of each roasting step after the second time is higher than the roasting temperature of the previous roasting step of each roasting step by more than 10°C, more preferably by more than 20°C, and most preferably by 50°C above.

Unlike the production method of the cerium-based abrasive material described here, the above-mentioned production method (the production method in which the raw material supplied to the roasting step is a raw material containing a fluorine-containing rare earth compound obtained by roasting) is not necessarily a fluorination treatment step. A production method. By using this production method, it is possible to produce a cerium-based abrasive having excellent damage occurrence state and polishing value (polishing speed) on the surface to be polished. This is because the aforementioned production method is a method using a raw material containing a fluorine-containing rare earth compound. If the raw material contains a fluorine-containing rare earth compound that already contains a fluorine component, no further fluorination treatment is required at the stage of abrasive material production.

In each of the production methods of the present invention described here, when producing abrasives with a predetermined particle size (for example, abrasives with a Bryan method average particle size (D _B ) of 1.5 μm to 2.5 μm), as in the embodiment described later, As mentioned above, pulverization and classification are carried out at appropriate stages.

As a method of producing a cerium-based abrasive with reduced content of calcium (Ca), barium (Ba), iron (Fe), and phosphorus (P) by using each of the above-mentioned production methods of the present invention, including raw materials thereof A method of using materials with reduced calcium, barium, iron, and phosphorus content. When adopting these raw materials, as the raw material of cerium series grinding material, preferably the mass ratio ((Ca+Ba+Fe+P )/TREO) at 2.0 wt% or less. If this raw material is used, the mass ratio ((Ca+Ba+Fe+P)/TREO) of the total content of calcium, barium, iron, and phosphorus to the total amount of rare earth oxides can be reduced to 2.0 wt% or less. Cerium-based abrasives. As mentioned above, since raw materials with reduced content of radioactive elements such as thorium and uranium are manufactured simultaneously with raw materials with reduced content of calcium, barium, iron, and phosphorus, the discussion on calcium, barium, and phosphorus is omitted here. Explanation of the production method of raw materials with reduced iron and phosphorus content.

In any one of the methods for producing cerium-based abrasives described above, the mass ratio (F/TREO) of the fluorine content to the total rare earth oxide (TREO) of the raw material supplied in the final roasting step is preferably 5.0 to 12 wt. %, particularly preferably 6.0 to 11 wt%. When F/TREO is within this range, a cerium-based abrasive having a fluorine content of 4.0 to 10 wt%, more preferably 5.0 to 9.0 wt%, can be easily obtained.

As described above, the present invention can provide a cerium-based abrasive having a reduced content rate of thorium, uranium, etc., and having a polishing rate equal to or higher than that of a conventional product, and excellent polishing characteristics.

Detailed ways

Hereinafter, preferred embodiments of the fluorine-containing cerium-based abrasive of the present invention will be described.

Embodiment 1

In Embodiment 1, two types of raw materials for cerium-based abrasives having physical properties shown in Table 1 were prepared.

Table 1 TREO (wt%) CeO ₂ /TREO(wt%) Th+U/TREO(wt%) Ca+Ba+Fe+P/TREO(wt%) Fluorine (F) content (wt%) F/TREO (wt%) Strong heat loss (wt%) Raw material A (rare earth carbonate trial firing product) 90 61 <0.0005 <0.4 <0.1 <0.1 9.7 Raw material B (concentrate of bastnaesite) 70 49.3 0.10 6.8 5.6 8 -

Among the two kinds of raw materials, raw material A is a material obtained by trial-calcining a rare earth carbonate at 650° C. for 12 hours. Rare earth carbonate prepared for obtaining raw material A has a total rare earth oxide conversion mass (TREO) of 45 wt%, CeO ₂ /TREO is 61 wt%, (Th+U)/TREO is less than 0.0005 wt%, (Ca +Ba+Fe+P)/TREO is less than 0.4 wt%, and fluorine (F) is less than 0.1 wt%.

Example 1

Raw material A was used in this embodiment. Briefly, the raw material A is wet pulverized, then fluorinated (first time), washed and filtered, dried, pulverized, roasted (first time), dry pulverized, and fluorinated (second time). 1 time), washing and filtering, drying, pulverization, re-calcination (2nd time), and then dry pulverization and classification to obtain the method of cerium-based abrasive materials. The details will be described below. First, pure water twice the mass of the raw material was mixed with the raw material A, and the obtained mixture was wet-pulverized with an attritor. The grinding medium used in this grinding was zirconia balls with a diameter of 5 mm, and the grinding time was 8 hours. Then, 10 wt% of hydrofluoric acid was added to the raw material slurry obtained after pulverization, and stirring was continued for 1 hour thereafter (first fluorination treatment). The amount of 10 wt% hydrofluoric acid added is the mass ratio (F/TREO) of the mass of fluorine added by the addition of 10 wt% hydrofluoric acid to the total rare earth oxide equivalent mass (TREO) of the raw material slurry is 4.5 wt%. amount. Then, so-called reslurry washing is performed by precipitating solid components in the slurry, taking out the supernatant and adding pure water, and filtering the washed slurry by a filter press method. Next, the obtained filter cake was dried at 150° C. for 24 hours, and the obtained dried filter cake was pulverized by a roll crusher. The average particle diameter (D ₅₀ ) of the obtained pulverized product was 1.12 μm. Then, the obtained pulverized product is fired (the first firing step). The calcination conditions are that the calcination temperature is 950° C., and the calcination time is 12 hours. After firing, dry pulverization was performed with a sample pulverizer.

Then, in the obtained pulverized product, 2 times the mass of pure water of the pulverized product was mixed to prepare a slurry, and 10 wt% of hydrofluoric acid was added thereto while stirring the slurry, and then stirred for 1 hour, that is, the fluorine Chemical treatment (second fluorination treatment). The amount of 10 wt% hydrofluoric acid added is the sum of the mass of fluorine (F1) contained in the roasted product to be fluoridated and the mass of fluorine added by adding 10 wt% of hydrofluoric acid (F2) and the total mass of the roasted product. The mass ratio ((F1+F2)/TREO) in terms of mass of rare earth oxides (TREO) was an amount of 6.0 wt%. (F1+F2)/TREO is also represented by F/TREO when F1+F2=F. Then, re-slurry washing is carried out, the slurry after washing is filtered by pressure filtration, and the obtained filter cake is dried at 150° C. for 24 hours. After the obtained dried filter cake is pulverized with a roll crusher, the obtained pulverized product is roasted (second second firing step). The calcination conditions are that the calcination temperature is 1050° C., and the calcination time is 12 hours. After calcination, dry pulverize the obtained calcined product with a sample pulverizer, and then classify the obtained pulverized product with a turbo classifier (the classification point is set at 9 μm) to obtain a cerium-based abrasive material. (Th+U)/TREO of the obtained abrasive material was less than 0.0005 wt%, and (Ca+Ba+Fe+P)/TREO was less than 0.4 wt%.

Comparative example 1

This comparative example is compared with Example 1, except that the dry pulverization step that carries out after the 1st roasting step, the addition amount of 10wt% hydrofluoric acid in the fluoridation treatment and roasting temperature are different, others are all the same as Example 1 is the same.

In this comparative example, after the dry pulverization after calcination, the fluorination treatment (second time) performed in Example 1 was not carried out, but a turbine classifier (the classification point was set at 9 μm) was used to classify the powder obtained by dry pulverization. The pulverized product (average particle diameter (D ₅₀ )=1.17 μm) was classified to obtain a cerium-based abrasive. In the fluoridation treatment, 10 wt% hydrofluoric acid is added so that the mass ratio (F/TREO) of the mass of fluorine added by adding 10 wt% hydrofluoric acid to the total rare earth oxide equivalent mass (TREO) of the raw material slurry reaches Specified mass ratio. Table 2 shows the predetermined mass ratio (F/TREO) and firing temperature conditions.

Embodiment 2～6 and comparative example 2～5

Compared with Example 1, these Examples and Comparative Examples are the same as Example 1 except that the addition amount of 10 wt% hydrofluoric acid and the calcination temperature in the fluoridation treatment are different. In the first fluoridation treatment, 10 wt % hydrofluoric acid was added, and the mass ratio (F/ TREO) to reach the specified mass ratio. In the second fluoridation treatment, 10 wt% of hydrofluoric acid was added, and the fluorine mass (F1) contained in the roasted product as the fluoridation treatment target was adjusted to the fluorine mass (F2) added by adding 10 wt% hydrofluoric acid. ) to the mass ratio ((F1+F2)/TREO=F/TREO) of the total rare earth oxide equivalent mass (TREO) of the calcined product to be fluorinated to reach a predetermined mass ratio. Table 2 shows the predetermined mass ratio (F/TREO) and firing temperature.

Example 7

Compared with Example 1, this example is the same as Example 1 except that the addition amount of 10 wt% hydrofluoric acid in the fluoridation treatment is different before the dry pulverization step after the first roasting step.

In this example, the fluoridation treatment (second time) performed in Example 1 was not performed after dry pulverization after calcination, but the pulverized product obtained by formula pulverization was subjected to a second calcination. Then, dry pulverize the roasted product obtained in the second roasting step, and classify to obtain a cerium-based abrasive material. The steps after the second firing step are the same as in Example 1. In the first fluoridation treatment, 10 wt % hydrofluoric acid was added, and the mass ratio (F/ TREO) to reach the specified mass ratio. Table 2 shows the predetermined mass ratio (F/TREO) and the firing temperature of each firing step.

Comparative Example 6

This comparative example is an example of producing conventional cerium-based abrasive materials. It uses raw material B (bastnaesite concentrate) and roasts it at a relatively high temperature to obtain a cerium-based abrasive material with a high grinding speed. example of. First, the raw material was subjected to wet pulverization under the same conditions as in Example 1. Then, 35% hydrochloric acid was added thereto in an amount corresponding to 5% by weight of the solution mass of the slurry while stirring the raw material slurry obtained by pulverization, and stirring was continued for 1 hour. The addition of hydrochloric acid can reduce the content of impurities such as calcium to a certain extent. Next, so-called reslurry washing is performed by precipitating the solid components in the slurry, taking out the supernatant and adding pure water, and filtering the washed slurry by a filter press method. Then, the obtained filter cake was dried at 150° C. for 24 hours, and the obtained filter cake was pulverized by a roll crusher. The average particle diameter (D ₅₀ ) of the obtained pulverized product was 1.15 μm. The obtained pulverized product is roasted, and then the roasted product obtained by roasting is dry pulverized with a sample pulverizer, and then the obtained pulverized product is classified with a turbo classifier (the classification point is set at 9 μm) to obtain a cerium-based ground product. Material. The conditions of the firing temperature in the firing step are shown in Table 2.

Evaluation of Cerium-based Abrasives

The fluorine content of the cerium-based abrasives obtained in Examples and Comparative Examples, the average particle diameter (D _B ) by the Blaine method, the average particle diameter (D ₅₀ ) based on the particle size distribution by the laser diffraction and scattering method, and the specific surface area by the BET method were measured. . In addition, a polishing test was carried out using the cerium-based abrasives obtained in Examples and Comparative Examples, and the polishing value (polishing speed) and damage evaluation of the obtained polished surface were performed. Table 2 shows the measured values and evaluation results. The measurement methods, polishing test methods, and evaluation methods of various polishing characteristics are as follows.

Fluorine content: Alkaline melting of the cerium-based abrasives obtained in Examples and Comparative Examples with an alkaline reagent (sodium carbonate, potassium carbonate, sodium hydroxide, or potassium hydroxide, etc.), and the warm water extract as a measurement sample Use, using alkaline melting · warm water extraction · fluoride ion electrode method.

Bryan's method average particle size (D _B ): According to [7.1 Specific Surface Area Test] of JIS K 5201-1997 (Physical Test Methods for Cement), the specific surface area S of the cerium-based abrasive powder obtained in each Example and Comparative Example (m ² /g) was measured, and the density ρ (g/cm ³ ) of the cerium-based abrasive powder was measured in accordance with the method described in JIS R 1620-1995. The Bryan method average particle size ( _DB ) was calculated according to the following formula (1).

Formula 1

D _B =6/(S×ρ)...(1)

Average particle diameter (D ₅₀ ) based on laser diffraction and scattering method particle size distribution: use a laser diffraction and scattering method particle size distribution measuring device (manufactured by Shimadzu Corporation: SALD-2000A), measure the particle size distribution of the cerium-based abrasive, The average particle diameter (D ₅₀ : particle diameter at 50% by weight of cumulative volume from the small particle diameter side) was determined.

BET specific surface area (BET): Measured in accordance with [6.2 Flow method (3.5) one-point method] of JIS R 1626-1996 (Measurement method of specific surface area of fine porcelain powder by gas adsorption BET method). At this time, a mixed gas of helium as a carrier gas and nitrogen as an adsorbate gas was used.

Grinding test: As a grinding machine, a grinding tester (HSP-2I type, manufactured by Taito Seiki Co., Ltd.) was prepared. In this polishing tester, the surface to be polished is polished using a polishing table while supplying an abrasive slurry to the surface to be polished. The grinding table was made of polyurethane, and in this grinding test, a new one was replaced for each test. In addition, glass for a flat plate of 65 mmφ was prepared as an object to be polished. Powdered cerium-based abrasive powder and pure water were mixed to prepare 50 L of abrasive slurry having a solid content concentration of 15 wt%. The surface of the glass for flat plates is polished with this abrasive slurry. In this polishing test, the abrasive slurry was supplied at a rate of 5 liters/minute, and the abrasive slurry was recycled. The pressure of the grinding table against the grinding surface is 19.6 kPa (200 g/cm ² ), and the rotation speed of the grinding tester is set at 200 rpm. Evaluation of polishing value (polishing speed): 30 minutes after the start of polishing, the glass for a flat plate to be polished was replaced with the glass for a flat plate for measuring the polishing value. Replacement flat panels have had their mass determined with glass. Grinding was performed for 10 minutes after replacing the glass for the flat plate, and the weight reduction of the glass due to grinding was obtained, and the grinding value was obtained from this value. The abrasive value of the abrasive material of Comparative Example 1 was used as a benchmark (100).

Evaluation of grinding damage: The polished flat plate glass was washed with pure water, and the damage evaluation was performed on the polished surface after drying in a dust-free state. The damage evaluation is carried out by observing the glass surface with the reflection method using a halogen lamp of 300,000 lux as the light source, counting the number of large damage and small damage, and taking 100 points as the full score. In this evaluation, the grinding|polishing precision required for grinding|polishing the glass substrate for hard disks or LCD was made into a judgment criterion. Specifically, "○" in Table 2 and Table 4 indicates a score of 92 or more (suitable for grinding of glass substrates for HD and LCD), and "△" indicates a score of less than 92 but a score of 85 or more (suitable for polishing of glass substrates for HD and LCD). Polishing of glass substrates for LCD), "×" means less than 85 points (not applicable for polishing of glass substrates for HD and LCD).

Table 2 Example/Comparative example ^*1) Manufacturing conditions Cerium-based abrasives ^*2) Initial raw material Fluorination treatment (first time) F/TREO (wt% Roasting step (first time) Roasting temperature (°C) Fluorination treatment (second time) F/TREO (wt% Roasting step (2nd time) Roasting temperature (°C) TREO (wt%) Th+U/TREO(wt%) Ca+Ba+Fe+P/TREO(wt%) Fluorine (F) content (wt%) ^*3) Average particle size D _B (μm) ^*4) Average particle size D ₅₀ (μm) Specific surface area by BET method (m ² /g) Grinding properties grinding value ^*5) Damage evaluation than 1 A 8.0 1050 - - 94.2 <0.0005 <0.4 6.5 1.23 2.45 2.5 100 △ than 2 A 3.0 950 4.0 1050 96.8 <0.0005 <0.4 3.2 1.35 2.31 1.9 152 △ real 1 A 4.5 950 6.0 1050 95.3 <0.0005 <0.4 5.1 1.59 2.42 1.7 215 ○ real 2 A 6.0 950 8.0 1050 94.0 <0.0005 <0.4 6.8 2.07 2.65 1.6 257 ○ real 3 A 8.0 950 12 1050 91.9 <0.0005 <0.4 9.4 2.43 3.24 1.4 287 △ than 3 A 10 950 15 1050 91.5 <0.0005 <0.4 11.3 2.74 3.12 0.94 305 x than 4 A 6.0 750 8.0 850 93.4 <0.0005 <0.4 7.2 0.89 1.57 4.8 72 ○ real 4 A 6.0 850 8.0 950 93.8 <0.0005 <0.4 6.9 1.52 2.24 2.8 183 ○ real 2 A 6.0 950 8.0 1050 94.0 <0.0005 <0.4 6.8 2.07 2.51 1.6 257 ○ real 5 A 6.0 1050 8.0 1150 94.4 <0.0005 <0.4 6.1 2.46 2.87 1.2 295 △ than 5 A 6.0 1200 8.0 1300 96.0 <0.0005 <0.4 4.3 2.71 2.92 0.9 314 x real 6 A 6.0 1050 8.0 1050 93.6 <0.0005 <0.4 6.9 1.82 2.45 2.2 206 △ real 7 A 8.0 950 - 1050 93.6 <0.0005 <0.4 6.6 1.73 2.56 2.4 201 △ than 6 B - 1050 - - 86.1 0.10 5.2 6.2 1.78 2.38 1.9 193 △

*1) "-" in the table indicates that no fluoridation treatment and/or roasting steps were performed.

*2) Refer to Table 1 for detailed data of each raw material (A and B).

*3) D _B : Bryan method average particle diameter.

*4) D ₅₀ : particle diameter of particles with a cumulative volume of 50 wt% from the small particle diameter side in the laser diffraction/scattering particle size distribution.

*5) ○: Almost no grinding damage, suitable as an abrasive, △: Some grinding damage, but small amount, suitable as an abrasive, ×: Very much grinding damage, not suitable as an abrasive.

As shown in Table 2, comparing the abrasive materials of each embodiment and the abrasive material of Comparative Example 6, there is no difference in fluorine content, average particle diameter ( _DB ) or BET method specific surface area, but the abrasive materials of each embodiment The grinding characteristics are significantly better. As a result, when producing a higher cerium-based abrasive material with a grinding value (grinding speed), as its raw material, using a rare earth carbonate trial firing product (raw material A) is more important than using a bastnaesite concentrate (raw material B). )good.

Compared with the abrasives of Examples 1 to 3, the abrasives of Comparative Example 1 and Comparative Example 2 had smaller grinding values and slightly damaged. In addition, compared with the abrasive materials of Examples 1-3, the abrasive material of Comparative Example 3 was more prone to grinding damage. In contrast, the abrasives of Examples 1 to 3 all had good abrasive properties. Therefore, focusing on the average particle diameter of the abrasive, there is no difference in the average particle diameter (D ₅₀ ), but there is a difference in the average particle diameter ( _DB ). As a result of examining the value of the average particle diameter ( _DB ), the Bryan method average particle diameter ( _DB ) is preferably from 1.5 μm to 2.5 μm. In addition, focusing on the production conditions of the abrasive, it is preferable to perform two firing steps as the production conditions.

In addition, the abrasive of Comparative Example 4 had a smaller grinding value than the abrasives of Examples 2, 4, and 5. Compared with the abrasive materials of Examples 2, 4, and 5, the abrasive material of Comparative Example 5 is more prone to grinding damage. Therefore, as a result of examining the average particle diameter ( _DB ) of the abrasive, an abrasive having a Bryan method average particle diameter ( _DB ) of 1.5 μm to 2.5 μm is preferable. In addition, focusing on the production conditions of the abrasive, as the production conditions, the calcination temperature in the final calcination step is preferably 900°C to 1200°C.

Compared with the abrasive material of Example 2 and the abrasive material of Example 6, the abrasive properties of Example 2 are better. As a result, when the firing step is performed twice, it is preferable that the firing temperature in the second firing step is higher than the firing temperature in the first firing step.

Compared with the abrasive material of Example 3 and the abrasive material of Example 7, the abrasive properties of Example 3 are better. As a result, when performing the second firing step, it is preferable to perform the fluorination treatment before the second firing step.

Embodiment 2

In this embodiment, the material formed by mixing a rare earth carbonate trial product (raw material A) with a fluorine-containing rare earth compound obtained by firing the rare earth carbonate trial product after fluoridation treatment is used as a cerium-based material. Abrasive materials are used as raw materials. Here, the raw material A used as the raw material for the cerium-based abrasive in Embodiment 1 was used as the rare-earth carbonate trial fired product. On the other hand, various kinds of fluorine-containing rare earth compounds mixed with rare earth carbonate test products are manufactured. The physical properties of the prepared fluorine-containing rare earth compounds (D1-D5 and E1) are shown in Table 3.

Manufacture of fluorine-containing rare earth compounds (D1): wet pulverization of the rare earth carbonate trial fired product (raw material A), fluoridation treatment, washing and filtering, drying, pulverization, and roasting to obtain fluorine-containing rare earth compounds (D1 ). The conditions of each step from wet pulverization to pulverization are the same as in Example 1 from the initial wet pulverization to the first step except that the addition amount of 10% hydrofluoric acid in the fluorination treatment and the calcination temperature during calcination are different. The conditions of each step up to the next pulverization step are the same. The mass ratio (F/TREO) of fluorine (F) to the total rare earth oxide equivalent mass (TREO) of the slurry obtained by the fluorination treatment was 20 wt%. The firing temperature in the firing step was 700° C. (refer to Table 3).

Production of fluorine-containing rare earth compounds (D2-D5): the production methods of these fluorine-containing rare earth compounds are different from those of fluorine-containing The production method of the rare earth compound (D1) is the same. Mass ratio (F/TREO) of fluorine (F) to total rare earth oxide equivalent mass (TREO) of slurry obtained by fluorination treatment in the production of each fluorine-containing rare earth compound (D2 to D5) and firing conditions as shown in Table 3. As shown in Table 3, no firing was performed in the production of the fluorine-containing rare earth compound (D2). In addition, the firing conditions in the production of the fluorine-containing rare earth compounds (D3 to D5) are the same as those of the fluorine-containing rare earth compound (D1) except that the firing temperature is different.

Manufacture of fluorine-containing rare earth compound (E1): In the steps of wet pulverization of the prepared rare earth carbonate trial calcined product (raw material A), fluoridation treatment, washing and filtration, dry pulverization, and roasting, Except for the addition amount of 10% hydrofluoric acid in the fluoridation treatment and the calcination temperature in the calcination step, the other steps are the same as those of the fluorine-containing rare earth compound (D1). The mass ratio (F/TREO) of fluorine (F) to total rare earth oxide equivalent mass (TREO) of the slurry obtained by the fluorination treatment was 8.0 wt%, and the firing temperature in the firing step was 850°C (see Table 3) . In the production of the fluorine-containing rare earth compound (E1), the roasted product obtained by roasting was dry pulverized with a sample pulverizer, and the obtained pulverized product was classified with a turbo classifier (the classification point was set at 6 μm). Next, the particles collected on the coarse powder side by the classification were dry-pulverized with a sample pulverizer, and the obtained pulverized product was classified with a turbo-type classifier (the classification point was set to 4 μm). The particles collected on the coarse powder side by this classification are fluorine-containing rare earth compounds (E1).

table 3 Fluorine-containing rare earth compounds (D1～D5, E1) manufacturing conditions composition Fluorination treatment condition F/TREO (wt%) Calcination temperature (℃) TREO (wt%) Fluorine (F) content (wt%) F/TREO (wt%) D1 20 700 87.1 15.2 17.5 ^*1) D2 15 - 83.8 10.5 14.5 D3 15 700 89.1 11.6 13.0 D4 15 1200 94.3 7.3 7.7 D5 10 700 93.8 7.6 8.1 E1 8.0 850 94.4 6.8 7.2

*1) No firing was performed in the manufacture of D2.

Embodiment 8,9,11 and comparative example 8,9

In these Examples and Comparative Examples, a mixture of a rare earth carbonate (raw material A) and a fluorine-containing rare earth compound (D1 to D4, E1) was used as a raw material for the cerium-based abrasive. The ratios of rare earth carbonates and fluorine-containing rare earth compounds are shown in Table 4.

In these Examples and Comparative Examples, the mixed raw materials were subjected to wet pulverization, dry pulverization, calcining, dry pulverization, and classification to obtain cerium-based abrasives. The manufacturing method of the abrasive material of each example consisting of these steps is the same as the manufacturing method of Comparative Example 1 of Embodiment 1, except that the fluorination treatment and subsequent washing and filtration are not performed. Therefore, a detailed description of each step is omitted.

Embodiment 10, 12 and comparative example 7

In these Examples and Comparative Examples, a mixture of a mixed rare earth carbonate (raw material A) and a fluorine-containing rare earth compound (D1, D5, E1) was used as a raw material for the cerium-based abrasive. The ratios of rare earth carbonates and fluorine-containing rare earth compounds are shown in Table 4.

In these examples and comparative examples, the raw materials obtained by mixing were subjected to wet pulverization, then fluoridated, washed and filtered, dried, pulverized, calcined, dry pulverized, and classified to obtain cerium-based abrasives. That is, these Examples and Comparative Examples are the same as Comparative Example 1 except that the raw materials are different and the addition amount of 10 wt % hydrofluoric acid in the fluorination treatment is different. The amount of 10 wt% hydrofluoric acid added in the fluoridation treatment is the mass of fluorine (F1) contained in the raw material (raw material slurry) to be treated with fluorination and the mass of fluorine added by adding 10 wt% hydrofluoric acid The mass ratio ((F1+F2)/TREO=F/TREO) of the total of (F2) and the total rare earth oxide conversion mass (TREO) of the raw material slurry was an amount of 8.0 wt%.

Evaluation of Cerium-based Abrasives

The fluorine content of the cerium-based abrasives obtained in Examples and Comparative Examples, the average particle diameter (D _B ) by the Blaine method, the average particle diameter (D ₅₀ ) based on the particle size distribution by the laser diffraction and scattering method, and the specific surface area by the BET method were measured. . In addition, a polishing test was carried out using the cerium-based abrasives obtained in Examples and Comparative Examples, and the polishing value (polishing speed) and damage evaluation of the obtained polished surface were performed. Table 4 shows the measured values and evaluation results. Measurement methods, polishing test methods, and evaluation methods of various polishing characteristics are the same as those in Embodiment 1.

Table 4 Example/Comparative example ^*1) Manufacturing conditions Cerium-based abrasives ^*2) Composition of raw materials Mixing ratio of raw materials (%) (TREO standard) Fluorinated F/TREO(wt%) Calcination temperature (℃) TREO (wt%) Th+U/TREO(wt%) Ca+Ba+Fe+P/TREO(wt%) Fluorine (F) content (wt%) ^*3) Average particle size D _B (μm) ^*4) Average particle size D ₅₀ (μm) Specific surface area by BET method (m ² /g) Grinding properties Rare earth carbonate trial firing product (raw material A) Fluorine-containing rare earth compounds (D1～D5, E1) grinding value ^*5) Damage evaluation real 8 A+D1 55 45 - 1050 94.3 <0.0005 <0.4 6.5 1.73 2.41 1.6 239 △ than 7 A+D1 75 25 8.0 1050 94.2 <0.0005 <0.4 6.4 1.31 2.53 2.1 135 △ than 8 A+D2 45 55 - 1050 93.7 <0.0005 <0.4 6.8 1.27 2.17 2.6 122 △ real 9 A+D3 40 60 - 1050 94.2 <0.0005 <0.4 6.7 1.98 2.73 1.5 263 ○ than 9 A+D4 0 100 - 1050 93.6 <0.0005 <0.4 7.1 2.69 3.03 0.91 298 x Real 10 A+D5 50 50 8.0 1050 93.9 <0.0005 <0.4 6.5 2.11 2.62 1.7 285 ○ real 11 A+E1 10 90 - 1050 95.3 <0.0005 <0.4 5.5 1.83 2.52 1.6 234 ○ real 12 A+E1 10 90 8.0 1050 93.5 <0.0005 <0.4 6.9 2.24 2.65 1.5 259 ○

*1) "-" in the table indicates that no fluorination treatment has been performed.

*2) Refer to Table 1 and Table 3 for detailed data of substances (A, D1-D5, E1) in each raw material.

*3) D _B : Bryan method average particle diameter.

*4) D ₅₀ : particle diameter of particles with a cumulative volume of 50 wt% from the small particle diameter side in the laser diffraction/scattering particle size distribution.

*5) ○: Almost no grinding damage, suitable as an abrasive, △: Some grinding damage, but small amount, suitable as an abrasive, ×: Very much grinding damage, not suitable as an abrasive.

As shown in Table 4, the abrasives of Comparative Example 7 and Comparative Example 8 had smaller grinding values than the abrasives of Examples. In addition, the polishing material of Comparative Example 9 was more prone to grinding damage than the polishing material of Examples. In contrast, the abrasive materials of Examples all had good abrasive properties. Therefore, as a result of examining the average particle diameter ( _DB ) of the abrasive, it is preferred that the average particle diameter ( _DB ) according to the Bryan method is 1.5 μm to 2.5 μm. Focusing on the raw materials of abrasive materials, for example, comparing Example 9 and Comparative Example 8, it can be found that the case of using more fluorine-containing rare earth compounds with low fluorine content is more than that of using less fluorine-containing rare earth compounds with high fluorine content. The situation is good.

Compared with the grinding material of Comparative Example 7, the grinding material of Example 8 is a more ideal raw material. That is, it is preferable that the raw material contains a fluorine-containing rare earth compound obtained by roasting, and the ratio of the oxide conversion mass of the aforementioned fluorine-containing rare earth compound to the total rare earth oxide conversion mass of the raw material is 30wt % above raw materials. In addition, comparing the grinding material of Example 8 with the grinding material of Comparative Example 8, it can be seen that the fluorine-containing rare earth compound D1 contained in the raw material is better than D2. That is, as shown in Table 3, the fluorine-containing rare earth compound obtained by roasting is better than the compound not roasted. In addition, it can be seen from the comparison between the abrasive material of Example 1 and the abrasive material of Example 12 that the abrasive material with better abrasive properties can be obtained by performing the fluorination treatment step before the firing step.

The cerium-based abrasive material of the present invention can be used, for example, for optical discs and magnetic discs, glass substrates, active matrix LCDs (Liquid Crystal Displays), color filters for liquid crystal TVs, clocks, desktop computers, LCDs for cameras, solar cells, etc. Polishing of glass substrates, glass substrates for LSI photomasks, glass substrates such as optical lenses, and optical lenses.

Claims (9)

1. cerium based abrasive material, its (F) cerium based abrasive material that is fluorine-containing, it is characterized in that, the mass ratio of full rare-earth oxide reduced mass (TREO) and abrasive substance quality is more than 90wt%, the mass ratio of the total content of thorium (Th) and uranium (U) and full rare-earth oxide conversion amount ((Th+U)/TREO) below 0.05wt%, Brian method median size (D _B) be 1.5 μ m～2.5 μ m.

2. cerium based abrasive material as claimed in claim 1, its feature also are, cerium oxide (CeO ₂) shared ratio (CeO in full rare-earth oxide reduced mass (TREO) ₂/ TREO) be 50wt%～70wt%.

3. cerium based abrasive material as claimed in claim 2, its feature are that also the containing ratio of fluorine is 4.0wt%～10wt%.

4. as each described cerium based abrasive material in the claim 1～3, its feature is that also ((Ca+Ba+Fe+P)/TREO) is below 2.0wt% for the mass ratio of the total content of calcium (Ca), barium (Ba), iron (Fe), phosphorus (P) and full rare-earth oxide reduced mass (TREO).

5. the manufacture method of the described cerium based abrasive material of claim 1, it possesses the step of raw material being carried out roasting, it is characterized in that, the raw material of supplying with aforementioned calcination steps comprises the fluorine-containing rare-earth compounds that obtains through roasting under 700～1100 ℃ condition, and shared ratio is more than 30wt% in the full rare-earth oxide reduced mass of this raw material for the oxide compound reduced mass of aforementioned fluorine-containing rare-earth compounds, and ((Th+U)/TREO) is below 0.05wt% with the mass ratio of this full rare-earth oxide conversion amount for the total content of thorium (Th) and uranium (U).

6. the manufacture method of cerium based abrasive material as claimed in claim 5, its feature also is, maturing temperature in the calcination steps of the aforementioned raw material that comprises fluorine-containing rare-earth compounds is 950 ℃～1150 ℃, and the maturing temperature of the roasting when generating than fluorine-containing rare-earth compounds is high more than 10 ℃.

7. the manufacture method of the described cerium based abrasive material of claim 1, it is to have at least to make fluoridation step fluorine-containing in the raw material of cerium based abrasive material for 1 time, and has a manufacture method of the cerium based abrasive material of the calcination steps that is carried out after the fluoridation step, it is characterized in that, the maturing temperature of each calcination steps is more than 700 ℃, and the number of times of the calcination steps that is carried out after the initial fluoridation step is more than 2 times, and ((Th+U)/TREO) is below 0.05wt% with the mass ratio of full rare-earth oxide conversion amount for the total content of supplying with the thorium (Th) of roasting object of initial calcination steps and uranium (U).

8. the manufacture method of cerium based abrasive material as claimed in claim 7, its feature also is, the maturing temperature of last calcination steps is 900 ℃～1200 ℃, and the maturing temperature of the 2nd each later calcination steps is higher more than 10 ℃ than the maturing temperature of the last calcination steps of each calcination steps.

9. as the manufacture method of each described cerium based abrasive material in the claim 5～8, its feature is that also ((Ca+Ba+Fe+P)/TREO) is below 2.0wt% with the mass ratio of full rare-earth oxide conversion amount (TREO) for the total content of the calcium (Ca) of the raw material of the cerium based abrasive material of supply calcination steps, barium (Ba), iron (Fe), phosphorus (P).