JP2007016169A - Cerium-based abrasive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cerium-based abrasive for finishing a glass substrate in a hard disk, a photomask, a flat panel display, etc., which yields a polished surface showing extremely small surface roughness and micro-waviness. <P>SOLUTION: The cerium-based abrasive contains fluorine and has a ratio of CeO<SB>2</SB>/TREO of ≥40 mass%. A pore size distribution is calculated as a differential pore volume (dV/dD) obtained from an adsorption isotherm measurement by a gas adsorption method. The pores size distribution is specified by classifying the cerium-based abrasive within a pore size range covering at least 3.2-100 nm into a plurality of grades and setting the width of each grade so that a value obtained by subtracting the common logarithm of the lower limit value from the common logarithm of the upper limit value of the grade becomes ≤0.10. The differential pore volume (dV/dD) within a range between the minimum pore size grade and the pore size grade including 100 nm reaches its maximum at the grade whose median falls within the range of 5.0-30 nm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cerium-based abrasive containing fluorine, a method for producing the same, and a glass substrate polished with the cerium-based abrasive.

Conventionally, as a cerium-based abrasive for a glass substrate containing a fluorine component, for example, La and Nd are contained in an amount of 0.5 atomic% or more based on cerium (Ce), and a specific surface area is 12 m ² / g or less. The range of the ratio of the peak intensity of the rare earth trifluoride to the intensity of the main peak of the rare earth oxide containing CeO ₂ in the X-ray diffraction is defined. In addition, the range of the ratio of the intensity of the rare earth oxyfluoride is defined. Cerium-based abrasives are known. (See Patent Document 1 and Patent Document 2). There is also a cerium-based abrasive having a total pore volume of 0.002 to 0.1 cm ³ (see Patent Document 3).
JP 2002-97457 A JP 2002-97458 A JP 2002-241740 A

  Cerium-based abrasives, which are essentially composed of rare earth element cerium (Ce) and oxygen, and in some cases fluorine, are mainly used for glass substrates for hard disks (HD), photomasks, liquid crystals (LCD), etc. Used for polishing semiconductor substrates. This cerium-based abrasive is required to have characteristics such as increasing the polishing rate, reducing adhesion of the abrasive to the object to be polished, and easily cleaning it even if it adheres.

  The cerium-based abrasives disclosed in Patent Document 1 and Patent Document 2 are excellent abrasive materials that are excellent in polishing speed and have few scratches. However, in recent years, the requirements for reducing the surface roughness and microwaviness of polished glass substrates (for hard disks, photomasks, flat panel displays, etc.) and quartz substrates have become very strict. Cerium-based abrasives are difficult to apply to finish polishing of glass substrates that are particularly required to reduce surface roughness and microwaviness. Further, although the cerium-based abrasive of Patent Document 3 can be polished to some extent, it can be satisfied as a final polishing application on a recent glass substrate, like the cerium-based abrasives of Patent Document 1 and Patent Document 2. is not.

  Accordingly, the present invention provides a fluorine-containing cerium-based abrasive that can be polished to a state in which the surface roughness of the object to be polished, in particular, the surface roughness and microwaviness of the glass substrate and the quartz substrate are minimized, and a method for producing the same. Objective. Another object of the present invention is to realize a polished glass substrate with extremely harsh surface properties after polishing, that is, surface roughness and minute waviness as much as possible.

The present invention relates to a cerium-based abrasive containing fluorine and having CeO ₂ / TREO ≧ 40% by mass, and the pore size distribution is calculated from a differential pore volume (dV) from an adsorption isotherm obtained by measuring the cerium abrasive by a gas adsorption method. / DD), it is divided into a plurality of classes in a range including at least a pore diameter of 3.2 nm to 100 nm, and the width of each class is changed from the common logarithm value of the upper limit value of the class to the common use of the lower limit value of the class. The pore diameter distribution is specified such that the value obtained by subtracting the logarithmic value is 0.10 or less, and the differential pore volume (dV / dD) between the smallest pore diameter class and the class including the pore diameter of 100 nm is The center value of the class takes the maximum value in the class in the range of 5.0 to 30 nm.

  The present invention is characterized in that the cerium-based abrasive is specified by the differential pore volume (dV / dD) calculated from the pore diameter distribution obtained from the adsorption isotherm measured by the gas adsorption method. This differential pore volume (dV / dD) is used when expressing a wide range of pore distribution, and is a factor that can express a small value of the pore diameter particularly by emphasizing the pore size distribution of the region. . The differential pore volume (dV / dD) means the difference pore volume (dV) divided by the class width, that is, the difference between the upper limit value of the class and the lower limit value of the class. The differential pore volume (dV) refers to the volume of pores having each grade of pore diameter when specifying the pore diameter distribution. Since the differential pore volume varies greatly depending on the class width, it can be said that it is almost meaningless to characterize the cerium-diameter abrasive with the maximum value of the differential pore volume for the pore size distribution with different class widths. On the other hand, as in the present invention, by dividing the differential pore volume (dV) by the class width (dD), the influence of the class width is eliminated, and the maximum value of the differential pore volume (dV / dD) is used. When the abrasive material is specified, the polishing characteristics can be expressed accurately.

  The terms relating to the pore size distribution in the present invention are those described in JIS Z 8101-1: Statistics-Terms and Symbols-Part 1 Probability and General Statistical Terms. By the way, “class” refers to a series of sections created by sequentially dividing the entire range of variation of the metric characteristics, and “class width” refers to the difference between the upper and lower limits of the class for the metric characteristics. "Means the arithmetic average of the upper and lower limits of the class for the metric properties.

  The measurement of the pore size distribution when specifying the cerium diameter abrasive according to the present invention will be described. In the present invention, the pore size distribution is specified from an adsorption isotherm measured by a so-called gas adsorption method. At this time, the measurement range of the pore diameter includes at least the pore diameter of 3.2 nm to 100 nm. The class width for specifying the distribution state is such that the value obtained by subtracting the common logarithmic value of the lower limit value of the class from the common logarithm value of the upper limit value of the class is 0.10 or less. Based on the pore diameter distribution specified in this way, the differential pore volume (dV / dD) in each class is calculated, and the maximum value is found. The cerium diameter abrasive of the present invention has a maximum differential pore volume that exists in a class having a class center value in the range of 5.0 to 30 nm.

  In the cerium-based abrasive of the present invention, when the class showing the maximum value of the differential pore volume is present in a region where the center value of the class is less than 5 nm, the surface roughness and micro-waviness of the polished surface of the object to be polished are present. It becomes easy to grow. Further, when the center value of the class is in a class exceeding 30 nm, the polishing rate tends to be low. Practically, it is preferably in the range of 7 to 25 nm, more preferably in the range of 10 to 20 nm as the center value of the class. In the present invention, the class for specifying the pore size distribution is determined so that the value obtained by subtracting the common logarithm of the lower limit from the common logarithm of the upper limit defining the class width is 0.10 or less. However, it is preferably 0.08 or less, more preferably 0.06 or less. When the width of this class is too wide, that is, when it exceeds 0.10, the accuracy of the maximum value of the pore diameter distribution is deteriorated, and the reliability of the cerium-based abrasive according to the present invention tends to decrease. .

  The cerium-based abrasive according to the present invention is premised on containing fluorine, and if it does not contain fluorine, the polishing rate is low. The fluorine content is preferably 3.0 to 5.5% by mass, more preferably 4.0 to 5.0% by mass. If it is less than 3.0% by mass, the polishing rate tends to be low. On the other hand, if it exceeds 5.5% by mass, the surface roughness of the polished surface tends to increase.

Further, the cerium-based abrasive of the present invention requires CeO ₂ / TREO, that is, cerium oxide / total rare earth rare earth, 40 mass% or more from the point of practical polishing speed, desirably 50 mass% or more. It is. Further, the upper limit may be 95% by mass or less, preferably 90% by mass or less, more preferably 80% by mass in consideration of the fact that the volatilization of fluorine is small during roasting and the control of the fluorine content is easy. It is as follows. In addition, in the cerium-based abrasive of the present invention, (U + Th) / TREO, that is, (uranium + thorium) / total rare earth oxide is preferably 0.01% by mass or less, more preferably 0.001% by mass. % Or less. Of course, in the cerium-based abrasive of the present invention, it is preferable that the amount of radioactive elements is small.

And in the cerium type abrasive of this invention, it is preferable that a BET method specific surface area is 10-30 m < ² > / g. If it is less than 10 m ² / g, the surface roughness of the polished surface tends to increase, and if it exceeds 30 m ² / g, the polishing speed tends to decrease. The specific surface area is more preferably 11~25m ² / g, more preferably 12~20m ² / g.

Next, the cerium-based abrasive of the present invention preferably has a 50% diameter (D ₅₀ ) in a volume-based cumulative fraction of particle size distribution measurement by laser diffraction scattering method of 0.3 to 1.2 μm. . If it is less than 0.3 μm, the polishing speed tends to be low, and if it exceeds 1.2 μm, the surface roughness of the polished surface tends to increase. The D ₅₀ is more preferably 0.4 to 1.1 μm, and further preferably 0.5 to 1.0 μm.

Furthermore, the cerium-based abrasive of the present invention calculates the pore size distribution as a differential pore volume (dV) and a differential pore volume (dV / dD) from an adsorption isotherm obtained by measuring the cerium abrasive with a gas adsorption method. In this case, in a range including at least a pore diameter of 3.2 nm to 200 nm, the range was divided into a plurality of classes, and the width of each class was subtracted from the common logarithm of the upper limit of the class and the common logarithm of the lower limit of the class. The pore diameter distribution is specified so that the value is 0.10 or less, the differential pore volume (dV) between the class having the smallest pore diameter and the class including the pore diameter of 200 nm is calculated, and the smallest pore diameter is obtained. Integration of differential pore volume (dV) from the minimum class of pore diameter to a class where the upper limit of the class does not exceed 50 nm with respect to the integrated value of differential pore volume (dV) from class to class including pore diameter of 200 nm The value ratio is preferably 50% or more. There. In this case, the measurement range of the pore diameter when specifying the pore diameter distribution from the adsorption isotherm measured by the gas adsorption method includes at least a pore diameter of 3.2 nm to 200 nm. Then, in the same manner as described above, the width of the pore diameter distribution class is determined, and the differential pore volume of each class between the class having the smallest pore diameter and the class including the pore diameter of 200 nm is calculated. From the differential pore volume of each class, the integrated value (here, ΣdV ₂₀₀ ) of the differential pore volume (dV) from the class having the smallest pore diameter to the class including the pore diameter of 200 nm, and the smallest pore diameter. The integrated value of the differential pore volume (dV) from the class to the class where the upper limit value of the class does not exceed 50 nm is calculated (here, ΣdV ₅₀ ), and the ratio (ΣdV ₅₀ / ΣdV ₂₀₀ × 100) is calculated. . A cerium-based abrasive having this ratio of 50% or more has excellent polishing characteristics.

When the ratio (ΣdV ₅₀ / ΣdV ₂₀₀ × 100) is less than 50%, the surface roughness and microwaviness of the polished surface tend to increase. Although there is no particular limitation on the upper limit of this ratio, it is preferably 95% or less in consideration of ease of manufacture. Practically, it may be 90% or less, more desirably 85% or less.

In the above-described cerium-based abrasive of the present invention, other conditions include total pore volume, coarse particle content, LnF ₃ / CeO ₂ peak intensity ratio and LnOF / CeO ₂ in X-ray diffraction.
It is desirable to satisfy the peak intensity ratio. First, the total pore volume of the cerium-based abrasive of the present invention is preferably 0.03 to 0.11 cm ³ . Easily scratches occurred polished surface to be 0.03cm less than ^3, the polishing rate greater than 0.11 cm ³ tends to decrease. Preferably it is 0.04-0.10 cm < ³ >, and it is still more preferable that it is 0.05-0.09 cm < ³ >. The total pore volume is different from the total integrated value of the differential pore volume in the pore diameter distribution described above, and indicates the total pore volume of the target cerium-based abrasive. It is measured by the so-called T-plot method in the adsorption method (reference: Patent Document 3).

  The coarse particle content of the cerium-based abrasive of the present invention is preferably such that the content of abrasive particles having a Stokes diameter of 5 μm or more is 200 mass ppm or less, more preferably 100 mass ppm or less, and 50 mass ppm or less. Is more preferable. This is because if the content of coarse particles increases, scratches are likely to occur on the polished surface.

When subjected to X-ray diffraction measurement of the cerium-based abrasive of the present _invention, LnF 3 / CeO ₂ peak intensity ratio is preferably 0.1 or less. Specifically, in X-ray diffraction using CuKα rays, 2θ = 24.2 ± 0 with respect to the peak intensity of the maximum peak of a rare earth oxide mainly composed of cubic CeO ₂ appearing at 2θ = about 28 °. It is preferable that the peak intensity ratio of the maximum peak in this range of the rare earth trifluoride (LnF ₃ ) appearing at .5 ° is 0.1 or less. More preferably, it is 0.05 or less, and it is still more preferable that it is not observed substantially. This is because when the ratio exceeds 0.1, the generation of abrasive scratches increases. In CeO ₂ peaks of pure rare earth oxides to the CeO ₂ cubic mainly the peak pure CeO ₂ at 2 [Theta] = about 28.6 ° of the rare earth oxide mainly composed of CeO ₂ cubic It appears at 2θ = about 28.6 °, but when the content of La ₂ O ₃ or Nd ₂ O ₃ increases, it shifts to the lower angle side and may be 2θ = 28.0 ° or less.

Furthermore, when the X-ray diffraction measurement of the cerium-based abrasive of the present invention is performed, the LnOF / CeO ₂ peak intensity ratio is preferably 0.25 or less. Specifically, in X-ray diffraction using CuKα rays, 2θ = 26.0 ± 0 with respect to the peak intensity of the maximum peak of a rare earth oxide mainly composed of cubic CeO ₂ appearing at 2θ = about 28 °. The ratio of the peak intensity of the maximum peak in this range of the rare earth oxyfluoride (LnOF) appearing at .5 ° is preferably 0.25 or less, and more preferably 0.1 or less. If it exceeds 0.25, it tends to cause abrasive scratches more easily than in the case of LnF ₃ .

  The cerium-based abrasive of the present invention described above can be produced from the following raw materials. First, as the raw material of the abrasive, (1) cerium-based rare earth carbonate, (2) cerium-based rare earth oxide, or (3) cerium-based rare earth carbonate and cerium-based rare earth oxide are mixed to determine the dry mass basis. An ignition loss of 5 to 20%, preferably 5 to 15%, or (4) calcined cerium-based rare earth carbonate to give an ignition loss on a dry mass basis of 5 to 20%, preferably 5 What was made 15% can be used. The raw material (1) or (4) is preferable from the viewpoint of few polishing scratches on the polished surface, and the raw material (2), (3) or (4) is preferable from the viewpoint of high polishing speed. The bust nesite concentrate containing fluorine may be used as a raw material without further purification treatment, but the fluorine content is slightly too much even without fluorination treatment, and the contents of U and Th are slightly There are many problems.

And the fluorine content of a raw material and F / TREO are 0.5 mass% or less normally in the raw material of (1)-(4). Since the calculation of the fluorine addition amount becomes complicated for a raw material with a varying fluorine content, it is preferable that the raw material is stable at 0.5 mass% or less. Further, CeO ₂ / TREO and (U + Th) / TREO in the raw material are the same as those of the cerium-based abrasive of the present invention.

  As a manufacturing method for the raw material of the above-mentioned cerium-based abrasive, for example, Ce-containing rare earth concentrates such as bastonite concentrate, monazite concentrate, Chinese complex ore concentrate are decomposed by sulfuric acid decomposition method or alkali decomposition method etc. Ce-based rare earth solution in which rare earth elements other than Ce are reduced as needed by performing solvent extraction to reduce impurities such as F, U, Th and other rare earth elements after performing treatments such as fractional precipitation and fractional dissolution. The rare earth solution and a carbonate-based precipitant such as ammonium hydrogen carbonate are mixed to form a precipitate, which is filtered and washed with water to obtain a Ce-based rare earth carbonate. A Ce-based rare earth oxide is obtained by sufficiently roasting this Ce-based rare earth carbonate to almost completely convert it into an oxide. A Ce-based rare earth carbonate can be calcined so as not to become an oxide completely to obtain a raw material adjusted for loss on ignition based on the dry mass.

About the above-mentioned raw material, it is set as the following particle size by grind | pulverizing. As for the particle size of the pulverized raw material, the 50% diameter (D ₅₀ ) in the volume-based integrated fraction in the laser diffraction / scattering method particle size distribution is 0.5 to 1.3 μm (more preferably 0.6 to 1.0 μm). The 90% diameter (D ₉₀ ) is 1.4 to 2.5 μm (more preferably 1.5 to 2.3 μm). When D ₅₀ is less than 0.5 μm, the polishing speed of the manufactured abrasive tends to be low, and when it exceeds 1.3 μm, the surface roughness of the surface polished with the manufactured abrasive tends to increase. Become. Further, when D ₉₀ is less than 1.4 μm, the polishing speed of the manufactured abrasive is likely to be low, and when it exceeds 2.5 μm, polishing scratches are likely to occur when polishing is performed with the manufactured abrasive.

Although there is no restriction | limiting in the method of making said particle size by grinding | pulverization, since it is easy to achieve the said particle size, multistage grinding | pulverization, especially 2 stage grinding | pulverization is preferable. In the case of a medium mill, the number average volume of the grinding medium used in the first stage is preferably 0.065 to 530 mm ³ (in the case of a spherical medium, the diameter corresponds to 0.5 to 10 mm), and preferably 0.26 to 280 mm ³ (spherical). In the case of a medium, the diameter is more preferably 0.8 mm, and more preferably 0.52 to 150 mm ³ (in the case of a spherical medium, the diameter is equivalent to 1.0 to 6.5 mm). Further, the number average volume of the grinding medium used in the second stage and thereafter is preferably 0.1 to 55%, more preferably 0.2 to 45% of the number average volume of the grinding medium used in the previous stage, 0 More preferably, it is 5 to 35%.

The ground material is subjected to the following fluorination treatment. The ground raw material is fluorinated by mixing with a water-soluble fluorine-containing compound such as hydrogen fluoride, ammonium fluoride, or ammonium hydrogen fluoride. In this case, in order to uniformly perform the fluorination treatment, it is preferable to use the pulverized raw material as a slurry and the fluorine-containing compound as an aqueous solution for mixing. In addition, in the case of rare earth fluoride insoluble in water, a method in which the rare earth fluoride is pulverized into fine particles and then mixed with the pulverized raw material can be applied, but the fluorination treatment is more effective than the case of using a water-soluble fluorine compound. It is preferable to use a water-soluble fluorine compound because it becomes non-uniform and tends to cause abnormal grain growth during roasting and becomes an abrasive with many coarse particles. The fluorination treatment is performed by adjusting the fluorine in the abrasive to the target content in consideration of the volatilization of fluorine by roasting. In addition, the volatilization of fluorine by roasting increases as the CeO ₂ / TREO content of the raw material increases and the roasting temperature increases.

  The raw material after the fluorination treatment is preferably dried after the acid and salt are reduced by washing, followed by solid-liquid separation by filtration or the like. The dried product is preferably crushed and then used for roasting.

  Subsequently, the raw material (filter cake, dried cake or dried cake crushed product) after fluorination treatment is roasted at a roasting temperature of 700 to 1000 ° C. More preferably, the temperature is 750 to 950 ° C., but if it is less than 700 ° C., the polishing speed of the produced abrasive tends to be low, and if it exceeds 1000 ° C., the surface roughness and micro-waviness of the polished surface increase. Easy to become an abrasive. The roasting time is preferably 0.2 to 72 hours, more preferably 0.5 to 60 hours, and further preferably 1 to 48 hours. If the time is less than 0.2 hours, the polishing rate of the produced abrasive is likely to be low, and conversely, even if roasting is performed for more than 72 hours, there is almost no change, and energy is wasted.

  After roasting, the powdered cerium-based abrasive of the present invention can be obtained by carrying out dry pulverization or dry classification. In order to obtain this powdery cerium-based abrasive, usually both dry pulverization and dry classification are carried out. Moreover, a powdery cerium-based abrasive of the present invention can also be obtained by drying and pulverizing the slurry abrasive. And after baking, the cerium type abrasive | polishing material of this invention of a slurry can be obtained by implementing wet grinding or wet classification. When obtaining a cerium-based abrasive of slurry, both wet pulverization and wet classification may be performed, but only wet pulverization may be performed. The slurry of the cerium-based abrasive of the present invention can also be obtained by wet classification after dry pulverization or wet pulverization after dry classification.

  When a glass substrate is polished using the above-described cerium-based abrasive of the present invention, the surface roughness and fine waviness of the polished surface are very small, and it is suitable for applications such as hard disks, photomasks, flat panel displays (liquid crystal, plasma), etc. It will be something. The surface property on the polished surface of the glass substrate is 0.5 nm or less in terms of arithmetic average surface roughness (Ra). More preferably, it is 0.4 nm or less, and further desirably 0.3 nm or less. In addition, the arithmetic average microwaviness as the surface property is 0.6 nm or less, more preferably 0.5 nm or less, and further preferably 0.4 nm or less. The arithmetic average surface roughness can be measured with an atomic force microscope (AFM), and the arithmetic average microwaviness is measured using a three-dimensional surface structure analysis microscope (New View 200 manufactured by Zygo) with a measurement wavelength of 0.2. It is possible to measure by scanning a predetermined area of the substrate with white light as ˜1.4 mm.

  As described above, according to the present invention, the surface roughness and micro-waviness of the polished surface are very small, and cerium-based polishing for finishing glass substrates such as hard disks, photomasks, flat panel displays (liquid crystal, plasma), etc. It becomes a very suitable material.

  The best embodiment of the present invention will be described in detail with reference to examples and comparative examples. First, the raw materials used when manufacturing the cerium-based abrasives of this example and the comparative example will be described. Table 1 shows the ignition loss of each raw material, total oxidized rare earth (TREO), the amount of other composition components, and the like.

  As shown in Table 1, the raw material is a Ce-based rare earth oxide (symbol O), a Ce-based rare earth carbonate (symbol C), a mixture of Ce-based rare earth oxide and Ce-based rare earth carbonate (symbol M), Ce rare earth carbonate calcined product (symbol S), bastonite concentrate (symbol B), Ce rare earth oxide and basnetite concentrate (symbol BC) used. The raw material symbols in Table 1 indicate the respective raw materials, and those with different numbers attached to the symbols indicate the raw materials having different mixing ratios, ignition loss, etc. even for the same type of raw materials. About the M1-M6 raw material of Table 1, the raw material symbol C1 and the raw material symbol O1 obtained by baking this raw material symbol C1 at 850 degreeC for 10 hours are mixed by a predetermined ratio. For the M7 to M13 raw materials in Table 1, Ce-based rare earth oxides each having a composition different from that of the raw material symbol O1, and Ce-based rare earth oxides obtained by roasting the carbonates at 850 ° C. for 10 hours; Are mixed at a predetermined ratio. Further, the BM1 raw material in Table 1 is a mixture of the O1 raw material and the B1 raw material in a 1: 1 ratio. The raw material symbol S1 is obtained by baking the raw material symbol C1 at 500 ° C. for 12 hours.

  Moreover, (U + Th) / TREO of each raw material in Table 1 is 0.089 mass% for the B1 raw material, 0.037 mass% for the BM1 raw material, and 0.0005 mass% or less for all other raw materials. And as for F / TREO of each raw material, B1 raw material is 7.0 mass%, BM1 raw material is 4.1 mass%, and all other raw materials are 0.1 mass% or less.

  Next, the production of each cerium-based abrasive will be described. A basic manufacturing flow is shown in FIG. As a production procedure, the raw material is pulverized, fluorinated, washed, dried and roasted, and then pulverized and classified sequentially. About each Example and comparative example in this embodiment, it is the cerium type abrasive | polishing material manufactured on each manufacturing condition shown in Table 2 and Table 3. FIG.

  First, manufacturing conditions for Examples 1 to 7 and Comparative Examples 1 and 2 will be described. The conditions of the raw material (M3) and the raw material pulverization by the wet medium mill were fixed, and the roasting temperature was changed. Moreover, about the fluorination process, it implemented with the target that the fluorine content of the cerium type abrasive | polishing material manufactured will be 4.5 mass%. In this fluorination treatment, the amount of fluorination treatment was changed in consideration of the fact that the easiness of volatilization of fluorine during roasting changes depending on the roasting temperature.

  Next, the raw material (M3), raw material grinding | pulverization conditions, and the baking temperature (850 degreeC) were made constant as the manufacturing conditions of Examples 8-13. And the amount of fluorination treatment was changed.

  The production conditions of Examples 14 to 20 (Example 4) were such that the dry mass reference ignition loss of the raw material was changed, and the raw material pulverization condition, the fluorination treatment condition, and the roasting temperature were constant.

  The production conditions of Examples 21 to 25 (Example 4) and Comparative Examples 3 to 5 were as follows: the raw material (M3), the fluorination treatment conditions and the roasting temperature were constant, and the raw material grinding conditions (details of each ground state are shown in Table 3). As shown in FIG.

In the production conditions of Examples 24 to 30 (Example 4), the raw material grinding conditions and the roasting temperature were constant, and the CeO ₂ / TREO content of the raw material was changed. Further, the fluorination treatment was changed according to the CeO ₂ / TREO content of the raw material so as to be almost constant in the abrasive.

  The production conditions of Examples 31 and 32 and Comparative Example 6 were the conditions shown in Table 3 using rare earth carbonate calcined products, bastosite concentrate or a mixture of bastonesite concentrate and rare earth oxide as raw materials. .

  In addition, (U + Th) / TREO of each cerium-based abrasive obtained under the production conditions shown in Tables 2 and 3 is 0.037% by mass in Example 31, 0.089% by mass in Comparative Example 6, and others. All were 0.0005 mass% or less.

  Regarding the cerium-based abrasives of Examples and Comparative Examples produced as described above, specific surface area, pore size distribution, total pore volume, coarse particle content, X-ray diffraction, etc., and glass substrate Tables 4 and 5 show the results of the polishing evaluation.

  Here, each measurement condition and polishing evaluation condition shown in Table 4 and Table 5 will be described.

Measurement of BET specific surface area (BET):
The measurement was performed in accordance with “6.2 Flow Method (3.5) Single Point Method” in JIS R 1626-1996 (Method for Measuring Specific Surface Area of Fine Ceramic Powder by Gas Adsorption BET Method). At that time, a mixed gas of helium as a carrier gas and nitrogen as an adsorbate gas was used. In the measurement of the slurry abrasive, the BET method specific surface area was measured for a dried product obtained by sufficiently drying (heating to 105 ° C.) the slurry.

Measurement of average particle size (D ₅₀ ):
By measuring the particle size distribution using a laser diffraction / scattering particle size distribution measuring device (Horiba, Ltd .: LA-920), the average particle size (D ₅₀ : cumulative mass 50 from the small particle size side) The particle diameter <median diameter>) in mass% was determined.

Measurement conditions of pore size distribution and total pore volume:
Here, as shown in Tables 4 and 5, the center value of the class in which the differential pore volume (dV / dD) shows the maximum value (in this embodiment, the center value of this class is referred to as the average pore diameter), the pore volume The measurement conditions of the pore diameter distribution and the total pore volume of the cerium-based abrasive, which were performed to obtain the measured values of the ratio and the total pore volume, will be described.

  The pore size distribution and the total pore volume were measured with a specific surface area / pore distribution measuring device (SA3100 BECKMAN COULTER). The measurement procedure will be described. First, a glass sample cell for pore volume measurement was dried and weighed (Ag). Next, about 0.3 g of a cerium-based abrasive to be measured was weighed and introduced into this sample cell. Then, the sample cell in which this abrasive was put was set in a degassing port in the measuring apparatus, degassed (heated to 120 ° C., held for 15 minutes while being sucked with a vacuum pump), and allowed to cool to room temperature. . The cooled sample cell is removed from the degassing port, set in the measuring port in the measuring device, and the sample cell is evacuated and then placed in the liquid nitrogen in the dewar (liquid nitrogen insulation container). The part was immersed. In this state, the free volume in the sample cell was measured with helium gas at 3 standard gas pressures. This free volume is the volume in the sample cell, and varies depending on the volume occupied by the abrasive material put into the sample cell. The sample cell is in a sealed state when moving between the ports, and has a device structure that allows only the measurement gas to flow through the sample cell when the measurement port is set.

  Subsequently, adsorption isotherm measurement was performed using nitrogen gas as an adsorbate. This adsorption isotherm is obtained by dividing the nitrogen gas pressure when the adsorption phenomenon is in an equilibrium state when a certain volume of nitrogen gas is added to the sample cell by the relative pressure and the value obtained by dividing the nitrogen gas pressure by the nitrogen gas saturated vapor pressure. Alternatively, it is obtained by plotting the adsorbed nitrogen gas volume on the Y axis. The volume of nitrogen gas adsorbed is the volume of nitrogen gas added to the sample cell, the volume of nitrogen gas in the free volume (the volume obtained by subtracting the volume occupied by the abrasive from the total volume inside the sample cell) (in the standard state) It is obtained by subtracting (converted). The adsorption isotherm was measured by repeating the measurement and plotting while changing the pressure of the adsorbate nitrogen gas to a maximum of about 101 kPa (760 mmHg). After measurement of the adsorption isotherm, the sample cell was removed, and the drying process for removing water adhering to the cell was performed, and the sample cell was weighed (Bg).

Central value (average pore diameter) of the class in which the differential pore volume (dV / dD) shows the maximum value:
The average pore diameter of the class in which the differential pore volume (dV / dD) shows the maximum value is 64 in the variable range of the pore diameter of 3.19 to 211.57 nm in the measurement of the specific surface area / pore distribution measuring apparatus described above. It is calculated from the result of specifying the pore size distribution by classifying into a class. The calculation method is based on the adsorption (desorption) isotherm measured using nitrogen gas as described above, assuming that the pores of the abrasive to be measured are cylindrical, and the Kelvin equation (nitrogen gas condenses). Applying the quantification formula of the relationship between the capillary thickness and the equilibrium gas pressure), the pore size distribution is analyzed by the BJH (Barrett, Joyner, Halenda) method, the differential pore volume (dV) for each class, the differential fineness The pore volume (dV / dD) is automatically calculated, and the maximum value of the differential pore volume (dV / dD) is found in the class including the pore diameter of 100 nm from the minimum class of the pore diameter, and the maximum value exists. The class is specified. The center value (average pore diameter) of the class in which the maximum value exists is shown in Table 4 and Table 5 (in Table 4 and Table 5, “Pore Diameter Distribution (dV / dD) MAX Average Pore Diameter” column) .

  As for the class in the pore size distribution, the width of the class in each of the 64 sections, that is, the value obtained by subtracting the common logarithm of the lower limit of the class from the common logarithm of the upper limit of the class, was the smallest value. Was 0.0147, and the largest value was 0.0658. The minimum class had an upper limit of 3.33 nm and a lower limit of 3.19 nm, and the maximum class had an upper limit of 211.57 nm and a lower limit of 190.68 nm.

Pore volume ratio:
The pore volume ratio was calculated from the result of the differential pore volume (dV) obtained as described above. The calculation method is the integration of the differential pore volume from the class having the smallest pore diameter (3.19 nm to 3.33 nm) to the class having the upper limit pore diameter of the class not exceeding 50 nm (49.29 to 46.65 nm). The value (ΣdV ₅₀ ) was determined, and the difference fineness from the class having the smallest pore diameter (from 3.19 nm to 3.33 nm) to the class including the upper limit pore diameter of 200 nm (190.68 to 211.57 nm). The integrated value (ΣdV ₂₀₀ ) of the pore volume was determined, and the ratio (ΣdV ₅₀ / ΣdV ₂₀₀ × 100) was calculated. The results are shown in Tables 4 and 5.

Total pore volume:
This total pore volume was calculated from the adsorption isotherm data obtained by the measurement by the above-mentioned pore diameter measuring instrument. The calculation method is a “T-plot” in which the film thickness t is plotted against the measured adsorbed gas volume (nitrogen gas volume) converted into the adsorbate molecule film thickness t by the so-called Harkins and Jura equation. Create a graph (film thickness t on the X-axis, adsorbed gas volume on the Y-axis), read the Y-intercept value from this 'T-plot' graph, and weigh the abrasive weight obtained by weighing this Y-intercept value The pore volume of each abrasive was calculated based on the value (BA) g. The adsorption isotherm, T-plot graph, and pore volume calculation related to the above-described measurement of the pore volume are automatically created and calculated by the measuring device. Moreover, all the volumes in this measurement are the values converted into the standard state (see: Patent Document 3). The measurement results of the total pore volume are shown in Tables 4 and 5.

Coarse particles with a Stokes diameter of 5 μm or more:
The coarse particle content was determined according to the following procedure. First, 200 g of the cerium-based abrasive to be measured was placed in a measurement container, and a 0.1% sodium hexametaphosphate aqueous solution was placed up to the upper line of the container and mixed thoroughly. After the designated time had elapsed, the slurry between the upper marked line and the lower marked line was extracted. When the slurry has been extracted, a new 0.1% sodium hexametaphosphate aqueous solution is again added up to the container upper marking line and mixed thoroughly. After allowing the container to settle and settle for a specified time, from the upper marking line. Repeated a series of operations (operation consisting of injection of sodium hexametaphosphate aqueous solution, standing and settling, extraction of slurry) of extracting the slurry between the lower marked lines (in this embodiment, a total of 8 operations) Performed). After the last operation, the abrasive particles remaining below the lower marked line were sufficiently dried at 105 ° C. The mass A (g) of the dry residual particles thus obtained was measured in the same manner as a precision balance. The content S (mass ppm) of coarse particles having a Stokes diameter of 5 μm or more was calculated using a calculation formula (S = A ÷ 200 × 1000000). The specified time (stationary / sedimentation time) is the time required for the particles with a Stokes diameter of 5 μm at the position of the upper marked line (the upper surface of the slurry) to settle to the lower marked line, and between the upper marked line and the lower marked line. Is divided by the sedimentation velocity calculated from the Stokes equation. If the above series of operations is performed only once, a large amount of particles having a Stokes diameter of 5 μm or less are mixed in the portion below the lower marked line, but the amount of mixing is reduced by increasing the number of operations. In addition, when a measuring object is a slurry abrasive, when obtaining a dry product by BET method specific surface area measurement, the ratio of the weight of the dry product to the slurry weight is measured in advance, and the slurry amount corresponding to 200 g from this ratio Was taken as a sample.

X-ray diffraction peak intensity ratio:
Crystal diffraction analysis of each cerium-based abrasive was performed with an X-ray analyzer (MXP18, manufactured by Mac Science Co., Ltd.). Specifically, in X-ray diffraction using CuKα rays, 2θ = 24.2 ± 0 with respect to the peak intensity of the maximum peak of a rare earth oxide mainly composed of cubic CeO ₂ appearing at 2θ = about 28 °. The ratio of the peak intensity of the maximum peak in this range of rare earth trifluoride (LnF ₃ ) appearing at .5 ° to the maximum of the rare earth oxide mainly composed of cubic CeO ₂ appearing at 2θ = about 28 °. The ratio of the peak intensity of the maximum peak in this range of rare earth oxyfluoride (LnOF) appearing at 2θ = 26.0 ± 0.5 ° to the peak intensity was calculated.

Polishing speed:
A polishing tester (HSP-2I type, manufactured by Taito Seiki Co., Ltd.) was prepared as a polishing machine. This polishing tester polishes the polishing target surface with a polishing pad while supplying a slurry-like polishing material to the polishing target surface. The abrasive grain concentration of the abrasive slurry was 100 g / L (dispersion medium was water only). In this polishing test, a slurry-like abrasive was supplied at a rate of 5 liters / minute, and the abrasive was circulated. The polishing object was 65 mmφ flat panel glass. A polishing pad made of polyurethane was used. The polishing pad pressure on the polishing surface was 9.8 kPa (100 g / cm ² ), the rotation speed of the polishing tester was set at 100 min ⁻¹ (rpm), and polishing was performed for a predetermined time. Then, a polishing treatment was performed for a specific time, the glass weight before and after polishing was measured to determine the amount of reduction in glass weight by polishing, and the polishing value was determined based on this value. In this polishing evaluation, the polishing rate was evaluated using this polishing value. In addition, as shown in Table 4, this polishing rate evaluation value was calculated based on the polishing value obtained with the cerium-based polishing material of Comparative Example 1 as a reference (100).

Abrasion wound:
Abrasion scratches are evaluated by a method of observing the polished glass surface by a reflection method using a 300,000 lux halogen lamp as the light source, scoring the number of large and fine scratches, and deducting the score from 100 points. It was. In this scratch evaluation, the polishing accuracy required for finish polishing of a glass substrate for hard disk or LCD was used as a criterion. Specifically, in Tables 4 and 5, “◎” is 98 points or more (very suitable for finishing polishing of glass substrates for HD and LCD), and “◯” is 95 points less than 98 points. That it is above (suitable for finishing polishing of HD / LCD glass substrates), and “△” is less than 95 points and 90 points or more (can be used for finishing polishing of HD / LCD glass substrates). "X" indicates that it is less than 90 points (cannot be used for finish polishing of glass substrates for HD and LCD).

Arithmetic mean surface roughness:
Arithmetic average surface roughness (Ra) is 10 μm × 10 μm of the polished surface in DFM mode (dynamic force microscope mode) using a probe microscope SP-400 (manufactured by SSI Nanotechnology Co., Ltd.). It was obtained by measurement.

Arithmetic mean swell:
Arithmetic mean microwaviness was measured by using a three-dimensional surface structure analysis microscope (New View 200 manufactured by Zygo Co., Ltd.), measuring a wavelength of 0.2 to 1.4 mm, and scanning a polished surface with white light over a predetermined region of the substrate.

  From the results shown in Tables 4 and 5, it was found that the cerium-based abrasive of each example was much superior in polishing characteristics than the comparative example. The average pore diameter <(dV / dD) MAX average pore diameter> indicating the maximum value of the differential pore volume for each example is in the range of 5.0 nm to 30 nm, and the pore volume ratio is 50% or more. It turns out that there is. On the other hand, some of the cerium diameter abrasives of the comparative examples had a pore volume ratio of 50% or more (Comparative Example 2, Comparative Example 4, and Comparative Example 6), but (dV / dD) MAX average fine particles were present. It was found that the pore diameter was out of the range of 5.0 nm to 30 nm. According to the polishing evaluation results in Table 4 and Table 5, in each example, the surface roughness and microwaviness of the polished surface are extremely small, such as a hard disk, a photomask, a flat panel display (liquid crystal, plasma), etc. It has been found that the glass substrate is very suitable for the application.

Schematic production flow diagram of cerium-based abrasive.

Claims (6)

In the cerium-based abrasive containing fluorine and having CeO ₂ / TREO ≧ 40% by mass,
When calculating the pore size distribution as the differential pore volume (dV / dD) from the adsorption isotherm measured by the gas adsorption method for the cerium abrasive,
In a range including at least a pore diameter of 3.2 nm to 100 nm, the range is divided into a plurality of classes, and the width of each class is a value obtained by subtracting the common logarithmic value of the lower limit value of the class from the common logarithm value of the upper limit value of the class. Specify the pore size distribution to be 10 or less,
The differential pore volume (dV / dD) between the minimum pore size class and the class including the pore diameter of 100 nm has the maximum value in the class having the center value of the class in the range of 5.0 to 30 nm. A cerium-based abrasive. The cerium-based abrasive according to claim 1, wherein the fluorine content is 3.0 to 5.5%. The cerium-based abrasive according to claim 1 or ^{2, wherein the} BET method specific surface area is 10 to 30 m ² / g. The cerium-based abrasive according to any one of claims 1 to 3, wherein a 50% diameter (D ₅₀ ) in a volume-based integrated fraction of laser diffraction / scattering particle size distribution measurement is 0.3 to 1.2 µm. . When calculating the pore size distribution as the differential pore volume (dV) and differential pore volume (dV / dD) from the adsorption isotherm measured by the gas adsorption method for the cerium abrasive,
In a range including at least a pore diameter of 3.2 nm to 200 nm, the width of each class is 0, and the value obtained by subtracting the common logarithm of the lower limit of the class from the common logarithm of the upper limit of the class is 0. Identify the pore size distribution so that it is 10 or less,
The differential pore volume from the minimum pore diameter class to the class in which the upper limit of the class does not exceed 50 nm with respect to the integrated value of the differential pore volume (dV) from the minimum pore diameter class to the class including the pore diameter of 200 nm The ratio of the integrated value of (dV) is 50% or more. The cerium-based abrasive according to claim 1. A glass substrate polished with the cerium-based abrasive according to any one of claims 1 to 5,
An arithmetic average surface roughness on a polished surface of a glass substrate is 0.5 nm or less, and an arithmetic average microwaviness is 0.6 nm or less.