JP2000038572A - Glass or quartz abrasive composition and preparation thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive composition for efficiently effecting mirror finish at an extremely high, finished surface roughness of glass, quartz or the like and a method for preparing the same which, more specifically, relate to the particle size distribution of cerium oxide to be used as the abrasive grain in the abrasive composition. SOLUTION: This glass or quartz abrasive composition is composed of an aqueous dispersion containing fine cerium oxide particles composed of two main peaks in the particle size-in-diameter distribution with a peak value DL of the larger peak of 1-10 μm at a ratio (DL/DS) of the peak value DL of the larger peak to the peak value DS of the smaller peak of 3-25, preferably 5-15. The concentration of the cerium oxide in the abrasive composition is 3-20 wt.% and the ratio (WL/WS) of the weight WL of the larger particles to that of the smaller particles WS is in the range of 0.2-9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing composition for efficiently performing mirror finishing with extremely high finished surface roughness on glass, quartz and the like, and a method for producing the same. More specifically, the present invention relates to the particle size distribution of cerium oxide used as abrasive grains in the polishing composition. The glass in the present invention refers to silicate glasses containing silicic acid as a main component, and includes a thermal oxide film on a silicon wafer surface and an interlayer insulating film on a device surface.

[0002]

2. Description of the Related Art In recent years, glass or quartz has been used for building materials, containers, decorative articles, optical lenses, and the like.
Significant development in new applications related to electronic components such as magnetic disk substrates, photomasks, liquid crystal glass, and crystal oscillators.
In particular, in the case of a magnetic disk substrate or a crystal oscillator, an extremely high-precision finished surface roughness is required, and at the same time, an improvement in productivity is also required.

[0003] Conventionally, a polishing process for finishing a plate-like material such as glass, metal material, semiconductor material, ceramics or carbon material, etc., which requires extremely high flatness and parallelism, to a mirror-finished surface is used for polishing. Polishing cloth,
A rotatable surface plate to which a so-called polishing pad is attached is arranged, and a workpiece is placed thereon, and the workpiece is pressed against the surface plate while a working fluid containing an abrasive is supplied quantitatively. The surface plate and the workpiece are rotated, and the surface roughness is improved by the action. Various polishing pads are used, for example, non-woven fabric, synthetic resin foam, synthetic leather or a composite thereof, and those having a small amount of abrasive grains contained therein. used.

As abrasives, abrasive fine particles such as aluminum oxide, silicon carbide, garnet, diamond, silicon oxide, cerium oxide, chromium oxide, calcium carbonate, barium carbonate, manganese oxide and zirconium oxide are generally used. However, the type is appropriately selected and used according to the type and processing purpose of each workpiece, and is particularly used in polishing using glass or quartz (hereinafter abbreviated as glass or the like) as a workpiece. Heretofore, abrasive grains of cerium oxide (CeO ₂ ) have been selectively used. Regarding the particle size, it is usual to use those classified so that they are normally distributed around a certain particle diameter according to the purpose, but the average particle diameter of cerium oxide used in polishing of glass or the like is The size is from the submicron size to at most about 20 microns, and there is no size larger than that, and it is difficult to manufacture fine ones.

[0005] The working fluid for polishing is an aqueous dispersion in which abrasive grains serving as an abrasive are dispersed in a slurry state at a concentration of several% to several tens%, and a dispersant, an alkali component,
An organic solvent and further other additives are added as required. The contained abrasive grains are substantially normally distributed around the displayed particle diameter, and in the case of cerium oxide abrasive grains, secondary aggregates may be contained. Further, ore the case of cerium oxide abrasive grains starting material, because it contains many rare earth屬元element other than cerium, purity is relatively low generally cerium oxide abrasive what CeO ₂ content of more than 45% It is referred to as a grain.

[0006] Polishing of glass or the like is different from processing by general mechanical force due to scratching action or fine crushing action of abrasive grains having hardness higher than that of a workpiece, and intervenes with a material constituting glass or the like. Polishing proceeds by a so-called mechanochemical action that utilizes a hydration reaction with water and a chemical reaction of the hydration reaction with water and cerium oxide, and adds a mechanical removal action thereto. In other words, the surface of the workpiece such as glass becomes chemically activated due to the strain energy and frictional heat associated with plastic deformation when the cerium oxide abrasive particles come into contact with the surface of the workpiece such as glass and melts. The removal is promoted, and it is removed by the mechanical action of the abrasive particles. The use of cerium oxide, which has a lower hardness than glass etc., as the abrasive particles causes less damage and a mirror surface with excellent surface roughness. This enables ultra-precision finishing.

However, the reaction between the material constituting glass and the like and water is extremely weak and slow,
Therefore, the polishing processing speed (removal speed) is extremely low, and its low efficiency has been pointed out as a problem of the polishing of glass or the like. This effect can be somewhat accelerated by making the working fluid alkaline, but not very noticeable. Usually, the improvement of these processing efficiencies is supported by using abrasive fine particles having a large particle diameter.However, in the case of processing of glass or the like by cerium oxide, the processing proceeds by the mechanism described above. Does not contribute to the improvement of the processing efficiency, but rather leads to the occurrence of undesired phenomena such as scratches and latent scratches, and cannot achieve the expected effects.

The use of fine particles of cerium oxide as abrasive grains for polishing processing of glass or the like is a conventionally known technique. As an improvement technique, a technique for preventing secondary aggregation and hardening of cerium oxide is known, for example. JP-A-3-14
No. 6584 or JP-A-3-146585. These techniques have a great effect on the continuity of the processing efficiency and the prevention of the occurrence of abnormal defects such as scratches, but they are not aimed at improving the processing efficiency itself. Attempts have been made to increase the concentration of cerium oxide in the working fluid or to increase the working pressure for the purpose of improving the working efficiency, but none of these methods can achieve the desired effects. A method is also disclosed in which abrasive grains other than cerium oxide, for example, zirconium oxide are used as abrasive grains for polishing a glass or the like (see, for example, Japanese Patent Application Laid-Open No. HEI-1).
No. 46584) The processing speed does not reach cerium oxide. Therefore, there is no decisive measure for improving the processing efficiency (processing speed), and in reality, this polishing processing is a bottleneck in a series of processing of glass or the like.

[0009]

In view of the above-mentioned problems in the conventional polishing of glass or the like, the present inventors have conducted intensive studies and as a result, have devised the particle size distribution of the cerium oxide abrasive used. By doing so, it has been found that the processing efficiency can be improved without adversely affecting the finished surface roughness, and the present invention has been completed, and the object thereof is glass, quartz, etc. An object of the present invention is to provide a polishing composition for efficiently performing mirror finishing with a finished surface roughness, and still another object is to provide a method for producing the polishing composition.

[0010]

The object of the present invention is to provide a polishing composition for glass or quartz comprising an aqueous dispersion containing fine particles of cerium oxide as abrasive grains, wherein the particle size distribution of the fine particles of cerium oxide is two. The peak value DL of a large particle diameter is 1 μm or more and 10 μm or more.
A glass having a peak value DS of the following particle diameter and a small particle diameter in a range of 3 to 25, preferably 5 to 15 in a ratio DL / DS to the larger peak value DL. Achieved by a polishing composition for quartz. It is preferable that the concentration of cerium oxide as abrasive grains is 3 to 20% by weight in the polishing composition. Further, the polishing composition for glass or quartz includes a weight WL occupied by particles larger than a value of a particle diameter intermediate between two main peak values of a particle size distribution of cerium oxide fine particles, and a weight occupied by particles smaller than that. Preferably, the WS ratio WL / WS is in the range of 0.2 to 9. Still another object of the present invention is to provide a polishing composition comprising cerium oxide having a peak value DL of a particle size distribution of 1 μm or more and 10 μm or less,
The peak value DS of the particle size distribution is DL with respect to the peak value DL.
This is achieved by a method of manufacturing a polishing composition for glass or quartz by mixing a polishing composition containing cerium oxide having a ratio of / DS of 3 to 25.

The size and particle size distribution of the abrasive grains of the fine particles used in the present invention can be measured by various methods such as a sedimentation test method, an electric resistance test method, a magnifying microscope photographing method, and a laser scattering particle size distribution measuring method. In the present invention, a laser scattering measurement method is used, and in actual measurement, a MICROTRAC-SPA type (HONE
Measurement by a laser scattering particle size distribution analyzer, and CPS DISK CENTRI
It has been confirmed with a FUGE type (Central Science Trading) centrifugal sedimentation method particle size distribution analyzer. Therefore, DL and DS representing the particle diameter specified in the present invention are all numerical values based on the present apparatus. The reason why the centrifugal sedimentation type particle size distribution analyzer is used as auxiliary is that this method has higher resolution and is better.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A polishing machine used in the present invention has a rotatable surface plate to which a polishing pad is attached, and on which a glass or quartz plate-like material to be processed is placed. The polishing is performed by rotating the platen while quantitatively supplying an aqueous dispersion liquid containing slurry-like cerium oxide fine particles as a processing liquid. FIG. 1 is an explanatory sectional view of a main part of a polishing machine used in the present invention. The workpiece 5 is pressed against the polishing pad 4 on the surface plate 1 while being adhered to the holder 2. The polishing composition 6 is quantitatively supplied from the nozzle 3 onto the polishing pad.

The cerium oxide fine particles contained in the polishing composition used in the present invention are collected from ores such as monazite and bastnaesite, and have a CeO ₂ pure content of about 50%, which is almost the same as the raw material ore. In addition, any of these types can be used in the present invention. Generally, the abrasive particles are classified so that the displayed particle size is a peak value and a normal distribution is centered on the peak value. The particle size here is measured according to a laser scattering type particle size distribution analyzer. The DL defined in the present invention is the aforementioned MICRO
TRAC-SPA (manufactured by HONEYWELL) showing the value of the particle size of the larger main peak in the particle size distribution curve (indicated by weight) measured according to the laser scattering type particle size distribution analyzer, and DS is the smaller value. It shows the value of the particle size of the main peak. WL is DL and DS
, And WS is a numerical value indicating the ratio of the weight of particles having a particle diameter smaller than the intermediate value between DL and DS. A polishing composition is obtained by adding such a cerium oxide abrasive to a stable slurry after adding a dispersant, a pH adjuster, and other necessary additives, but the cerium oxide abrasive included here is It may be secondary aggregated.

In the polishing composition according to the present invention, the cerium oxide contained has not a single particle but a so-called double peak having two main peaks. The main purpose is to obtain a processing speed (removal speed). By having both large and small particles,
The object of the present invention is to increase the effective contact area of the abrasive fine particles with the surface of the workpiece, thereby improving the polishing processing rate (removal rate) of the single-peak polishing composition. The larger particles have a particle size of 1 to 10 μm,
The above-mentioned effect can be obtained by mixing small particles having a size of about 1/25 from the above. The effect is reduced if the size of the smaller particles is larger or smaller than this range. Also, it should be particularly noted in the present invention that the use of such double-peak abrasive grains improves the polishing speed, but does not affect the obtained surface roughness at all, It does not cause undesired phenomena such as an increase in abnormal scratches. Note that the double peak here means that there are two main peaks, and it is natural that there are some other small peaks with low peaks.

The concentration of cerium oxide fine particles as abrasive grains is 3 to 20% by weight, preferably 10 to 15% by weight during polishing. When the concentration is 3% by weight or less, the polishing processing speed relatively decreases, and when the concentration increases, the processing speed relatively increases.
When the content exceeds 5% by weight, the value reaches the peak value under the condition, and beyond that, the meaning of increasing the concentration becomes meaningless.
Furthermore, when the circulating use is performed, the processing wastes associated with the processing remain in the liquid and increase the solid concentration in the liquid. If the concentration of the abrasive grains is high from the beginning, the concentration of the recycled liquid increases and the viscosity increases, so that the slurry lacks stability.

Further, the particle size of cerium oxide contained in the polishing composition according to the present invention is divided into two main peaks as described above, and the preferable ratio is as follows. That is, the ratio WL / WS of the weight WL occupied by the particles larger than the intermediate value DM between DL and DS and the weight WS occupied by the smaller particles is in the range of 0.2 to 9, more preferably 0.4 to 8. In this case, a remarkable improvement in the polishing efficiency according to the present invention is recognized. That is, when the polishing processing speed reaches a peak when the ratio between the two is almost the same, that is, when the numerical value of WL / WS is approximately 1, and when the numerical value of WL / WS is out of the above-mentioned range, the improvement effect by the mixing of the two is obtained. Can hardly be admitted. Furthermore, in the present invention, the sharpness of the distribution of the fine particles of cerium oxide is not limited, but if the distribution is too broad, the effect of the present invention is reduced.

In the production of cerium oxide fine particles as abrasive grains, a powder as a raw material is classified by elutriation, for example, and it is difficult to intentionally produce a double peak. Therefore, in order to obtain a double peak as in the present invention, those having respective expected peaks can be mixed and used in a predetermined amount. If you want more simplicity,
A commercially available polishing composition having an intended particle size can be produced by appropriately mixing as necessary.

[0018]

EXAMPLES The polishing composition of the present invention and the polishing method using the polishing composition of the present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not particularly limited thereto. Polishing compositions in Examples and Comparative Examples were prepared by preparing five commercially available cerium oxide abrasive grains having different average particle diameters as shown in Table 1, mixing them appropriately and dispersing them in water. Slurries having DL, DS values and WL, WS values were prepared. As the workpiece, a 25 mm × 25 mm size test piece made of non-alkali glass having a surface roughness Ra of 12 nm was selected.

[0019]

[Table 1]

The polishing apparatus and the processing conditions by the polishing apparatus were as follows, and the above-mentioned mirror polishing of the workpiece was performed. Polishing equipment: Doctor lap type single-side processing machine manufactured by Maruto Co., Ltd. Polishing pad: Cerium pad MH14E (manufactured by Rodel Nitta) Polishing conditions Surface plate rotation speed: 150 rpm, pressure plate rotation speed: 100 rpm, processing pressure 165 g / cm ² , polishing composition Material supply amount: 20 ml / min Processing time: 10 minutes In addition, measurement of various amounts required for evaluation was performed by the following method using the following apparatus. Measurement of surface roughness: 10 μm using an AFM atomic microscope.
The surface roughness (Ra) in the mx10 μm region was measured. Processing speed: The weight of the test piece before and after processing was measured, and the difference was taken as the removal amount and converted per unit time to obtain the processing speed. Particle size distribution: MICROTRAC-SPA (HONEYW
The measurement was performed using a laser scattering particle size distribution analyzer (manufactured by ELL). CPS DISK CENTRIFU
Confirmation was appropriately performed using a GE (Central Science Trade) centrifugal sedimentation particle size distribution analyzer.

Example 1 Cerium oxide abrasive grains B and E shown in Table 1 were mixed, polishing compositions having compositions of Experiment Nos. 1 to 15 were prepared, and polishing experiments were performed. Table 2 summarizes the experimental results.

[0022]

[Table 2]

Example 2 Cerium oxide abrasive grains A and D shown in Table 1 were mixed, polishing compositions having compositions of Experiment Nos. 16 to 19 were prepared, and polishing experiments were performed. The experimental results are summarized in Table 3.

[0024]

[Table 3]

Example 3 Cerium oxide abrasive grains C and D shown in Table 1 were mixed, polishing compositions having compositions of Experiment Nos. 20 to 23 were prepared, and polishing experiments were performed. Table 4 summarizes the experimental results.

[0026]

[Table 4]

Example 4 Cerium oxide abrasive grains A and C shown in Table 1 were mixed, polishing compositions having the compositions of Experiment Nos. 24 to 27 were prepared, and polishing experiments were performed. Table 5 summarizes the experimental results.

[0028]

[Table 5]

Comparative Example Using cerium oxide abrasive grains A to E shown in Table 1, the concentrations of the cerium oxide abrasive grains were appropriately changed to prepare polishing compositions of 28 to 36, and polishing experiments were respectively performed. Table 6 summarizes the experimental results.

[0030]

[Table 6]

[0031]

As is apparent from the above description, the polishing composition of the present invention having a double peak of the distribution of cerium oxide abrasive grains is preferred because it deteriorates the finished surface roughness in polishing of glass or the like. The polishing speed can be increased by about 30% without any adverse effect. According to the present invention, in the production process of a magnetic disk substrate or a crystal oscillator that requires ultra-precision processing, particularly in glass or quartz, there is a problem in efficiency in particular, which has been a bottleneck in the process. The efficiency of the polishing process can be significantly improved. In addition, the production of the polishing composition according to the present invention can be easily produced by appropriately mixing a conventional polishing composition having a different abrasive particle system, and according to the present invention, the production of ultra-precision processing of glass or the like is performed. It is possible to significantly improve the performance.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a main part of a single-side polishing machine;

FIG. 2 is a graph plotting experiment numbers 4, 5, 6, 7, and 8 (Example 1) and experiment numbers 29 and 33 (comparative examples) among polishing results using the polishing composition according to the present invention. It is. In the table, 〇 indicates a plot of processing speed, and △ indicates a plot of finished surface roughness.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Surface plate 2 Holder 3 Nozzle 4 Polishing pad 5 Workpiece 6
Polishing composition プ ロ ッ ト Plot of processing speed △ Plot of finished surface roughness

Claims (4)

[Claims] 1. A polishing composition for glass or quartz comprising an aqueous dispersion containing fine particles of cerium oxide as abrasive particles, wherein the particle size distribution of the fine particles of cerium oxide is composed of two main peaks. Diameter peak value DL
Is not less than 1 μm and not more than 10 μm, and the peak value DS of the small particle size is in the range of 3 to 25, preferably 5 to 15 in the ratio DL / DS to the peak value DL of the large particle size. Characteristic polishing composition for glass or quartz. 2. The glass or quartz according to claim 1, wherein the concentration of cerium oxide as abrasive grains in the polishing composition is 3 to 20% by weight in the polishing composition. Polishing composition. 3. A weight WL occupied by a particle larger than a value of a particle diameter intermediate between two main peak values of a particle size distribution of cerium oxide fine particles, and a weight W occupied by a particle smaller than the value WL.
3. The polishing composition for glass or quartz according to claim 1, wherein a ratio WL / WS of S is in a range of 0.2 to 9. 4. The peak value DL of the particle size distribution is not less than 1 μm and not more than 10 μm.
a polishing composition containing cerium oxide of not more than μm, and a peak value DS of the particle size distribution is DL / DS with respect to the peak value DL.
4. The method for producing a polishing composition for glass or quartz according to claim 1, wherein a polishing composition containing cerium oxide having a ratio of 3 to 25 is mixed.