JPH083541A - Precision abrasive - Google Patents

Abstract

PURPOSE:To obtain a precision abrasive capable of abrading the surface of a material in a high accuracy leading to improve the smoothness and accuracy of abraded surface, consisting of an alkaline ceric oxide sol containing an organic acid bearing two or more carboxyl groups. CONSTITUTION:This precision abrasive consists of an alkaline ceric oxide sol (with an average particle diameter of pref. 2-200nm) containing an organic acid bearing two or more carboxyl groups (pref. tartaric acid or citric acid). It is preferable that the sol concentration should be 10-60wt.% on a CeO2 basis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precision polishing agent, and provides a precision polishing agent comprising an alkaline stable cerium oxide sol as a polishing agent capable of improving the smoothness and surface accuracy of a polished surface.

[0002]

2. Description of the Related Art Color liquid crystal displays, solar cell displays, LSI photomask displays, active matrix LCDs, camera LCDs, glass substrates used for optical disks and magnetic disks, optical modulators, surface acoustic wave filters, and phases. Optical crystal such as LiNbO ₃ , LiTaO ₃ , quartz, quartz used for compensators, polarizing prisms, optical disks, etc., optical filters and optical stainless steel, etc. require precise polishing of the material surface. .

Conventionally, as abrasives used for precision polishing of such materials, abrasives of cerium oxide, zirconium oxide and silicon dioxide based fine powder abrasive grains have been used.
Among silicon dioxide-based polishing agents, silica sol, in particular, is often used as a finishing polishing agent in precision polishing. However, since the silica sol has extremely strong dry cohesive force, it easily forms lumps, and when the lumps are peeled off, there is a problem that the polished surface of the material is scratched.
The maximum value is about 3 nm, and it is difficult to obtain the surface accuracy of the material that has been required in recent years. Therefore, the method of selecting the type of polishing machine and polishing pad has been devised to improve the surface accuracy.
(Rmax) 2 nm is the limit.

On the other hand, cerium oxide and zirconium oxide have been widely used because of their excellent polishing power as compared with silicon dioxide-based abrasives. In JP-A-3-146584 and JP-A-3-146585, Abrasives composed of cerium oxide and zirconium oxide have been proposed. However, when these abrasives are used in the form of a slurry, they tend to form a precipitate of abrasive grains, which scratches the polished surface.
Since (scratches) are generated and the particle size of the abrasive particles is large, it is difficult to obtain a highly accurate polished surface as a precision abrasive.

Therefore, the conventional cerium oxide, zirconium oxide, and silicon dioxide-based abrasives are currently used while being properly used in each polishing step of material polishing, and the polishing accuracy of scratches does not occur. At present, there is a demand for the appearance of an excellent polishing agent for precision polishing.

[0006]

Under the circumstances described above, the present inventors have proposed a new precision polishing agent as a substitute for the conventional polishing agent made of cerium oxide powder or silica sol. The cerium oxide sol developed by the inventors (Japanese Patent Laid-Open No. 1-148710) was applied. However, although this cerium oxide sol is superior in polishing accuracy to the conventional silica sol and the like, it causes a new problem of corroding the polishing machine because the sol solution is acidic.

Further, JP-A-4-26528 discloses an acidic cerium oxide sol obtained by hydrolyzing a cerium salt of an organic acid and using an ultrafiltration membrane. The sol thus obtained is polished. When used as an agent, it is the same as the above sol. Furthermore, the alkaline cerium oxide sol developed by the present inventors (Japanese Patent Application Laid-Open No. 4-300644) was applied, but in this case the problem of adsorption and retention of the abrasive on the polishing surface that cannot be removed by normal cleaning occured.

[0008]

Under the circumstances as described above, the present inventors have further studied to apply cerium oxide sol as an abrasive having excellent polishing accuracy to an abrasive for precision polishing. As a result, it was found that by adding an organic acid having a specific carboxyl group to an acidic cerium oxide sol, an abrasive having excellent polishing accuracy that solves the above-mentioned problems can be obtained, and the present invention is based on such findings. Is completed. That is, the present invention relates to a precision abrasive containing an alkaline cerium oxide sol containing an organic acid having two or more carboxyl groups.

[0009]

The precision polishing agent of the present invention will be described in more detail below. The cerium oxide sol used in the present invention can be obtained by the method described in Japanese Patent Application Laid-Open No. 1-148710 and Japanese Patent Application Laid-Open No. 5-132311, which are the inventions previously filed by the present inventors. That is, a cerium chloride sol can be obtained by reacting cerium chloride with an alkali metal hydroxide or ammonia to form a gel and then hydrothermally treating the gel. The cerium oxide sol can also be obtained by reacting cerium carbonate with an oxidizing agent such as hydrogen peroxide to form a cerium oxide gel, and then peptizing the gel with an acid. However, the cerium oxide used as the raw material of the present invention is not limited to those obtained by these production methods. The ceric oxide used in the precision polishing agent of the present invention may be crystalline or amorphous, and may contain ceric hydroxide.

In the present invention, an acidic cerium oxide sol is used, an organic acid having two or more carboxyl groups is added to the sol, and the pH of the sol is adjusted to 7 with an alkaline agent.
By the above, an alkaline cerium oxide sol is obtained. The types of organic acids having two or more carboxyl groups include tartaric acid, citric acid, oxalic acid, malonic acid,
Examples thereof include succinic acid and glutaric acid. However, of these organic acids, the use of tartaric acid or citric acid is desirable because it is stable even when the particle size of the sol described later is increased and a polishing agent with high polishing efficiency can be obtained. Also, p
As the type of alkali agent used for H adjustment, alkali metal hydroxide, aqueous ammonia, water-soluble alkanolamine such as tetramethylammonium hydroxide or monoethanolamine, and the like can be used.

Next, regarding the particle size of the cerium oxide sol of the precision polishing agent of the present invention, it is important that the average particle size is in the range of 2 to 200 nm when the above acidic sol is obtained. . That is, if the particle size of the sol is less than 2 nm,
Not enough lubricity with the polishing pad, damage to the polishing material surface easily occurs due to the polishing pad, and 200 nm
If the particle size exceeds, the particles are likely to cause scratches on the polishing surface, and are not suitable as precision polishing agents.
In addition, the cerium oxide sol having such a particle diameter can be appropriately obtained by adjusting the hydrothermal treatment temperature and the treatment time during the production of the acidic cerium oxide sol. The particle diameter in the present invention means the diameter of sol particles in a sol dispersed state measured by a dynamic light scattering method.

Regarding the sol concentration of the precision polishing agent of the present invention, the sol concentration of the polishing agent varies greatly depending on the particle size of the sol, the type and amount of the organic acid used, and the pH of the sol. Is a concentration of about 10 to 60% as CeO ₂ . Incidentally, such an abrasive may be used by appropriately diluting it to a desired concentration.

Regarding the usage ratio of the organic acid having two or more carboxyl groups to cerium oxide, the carboxyl group (COO
H) The equivalent weight is in the range of approximately 0.02 to 2.0. If it deviates from this range, it is impossible to obtain the polishing agent having high polishing accuracy, which is the object of the present invention. That is, when this ratio is less than 0.02, the long-term storage stability of the polishing agent is significantly reduced, and when it is more than 2.0, the salt concentration in the solution becomes high, which makes it difficult to remove salts in the subsequent stage. Therefore, it is not industrial.

The sol solution after the addition of an organic acid having two or more carboxyl groups and the pH adjustment with an alkaline agent is then desalted by ultrafiltration or the like to remove salts in the solution. By such a method, it is possible to obtain the precision polishing agent comprising the alkaline ceric oxide sol of the present invention.

[0015]

The present invention will be further described below with reference to examples of the present invention, but the present invention is not limited to these examples. Also,
All percentages are by weight unless otherwise specified.

Example 1 Ceric Sulfate Aqueous Solution (CeO)
To ₂ 8.0%) 10kg, ammonia water (NH ₃ 4.0%) 10.28kg was added under stirring to produce a gel. This gel was added to the
₄ ^2- ions and thoroughly washed with water until no CeO ₂ 2
1.0% gel was obtained. Acetic acid (100%) 146 g and water 2054 g were added to 2000 g of this gel so that the CH ₃ COOH / CeO ₂ molar ratio was 1.0, and this was placed in an autoclave and subjected to hydrothermal treatment at 200 ° C. for 6 hours to obtain an acidic sol. It was

To 1000 g of this acidic sol (CeO ₂ 10.0%), 1 mol of cerium oxide was mixed with the carboxyl group of citric acid.
(COOH) equivalent to 0.62 citric acid (monohydrate) 24.4g
, And then sodium hydroxide to adjust the pH of the sol solution.
Adjusted to 10. This sol solution is used as an ultrafiltration device (Asahi Kasei Co., Ltd.)
Manufactured by SLP-1053) to obtain an alkaline cerium oxide sol. By further adjusting the pH of this sol and then subjecting it to concentration treatment, a precision polishing agent of the present invention having a pH of 10 and CeO ₂ 40.0% was obtained. Further, the particle size of the sol in the polishing agent thus obtained, a particle size distribution measuring device by dynamic light scattering method (Pacific Scientific Co., Nicomp370HPL
The average particle size of the sol was 90 nm.

(Comparative Examples 1 to 3) For comparison, Example 1 was used.
To the acidic cerium oxide sol stabilized with acetic acid obtained in 1., only sodium hydroxide was added without adding citric acid, the pH of the sol solution was adjusted to 10, and this was further filtered with an ultrafiltration device. Used for desalting. Then wash this, pH
An abrasive was prepared by adjusting and concentrating it (Comparative Example 1), but it became a gel and precipitated with the passage of time.

The abrasives obtained in Example 1 and Comparative Example 1, and also a commercially available silica sol abrasive (manufactured by Company A, SiO ₂ 40%, particle diameter 80 nm) (Comparative Example 2) and commercially available cerium oxide powder polishing An agent (manufactured by Company B, particle diameter 2 to 3 μm) (Comparative Example 3) was used, and an evaluation test of its abrasiveness was performed using quartz. The polishing conditions and the evaluation method of the polishing effect are as follows. <Polishing conditions> ・ Polishing pressure: 120 g / cm ²・ Surface plate rotation speed: 70 rpm ・ Abrasive agent concentration: 15% aqueous solution ・ Polishing machine model: Udagawa Iron Works, Oscar type ＜ Evaluation method ＞ ・ Surface roughness (Ra: (Center line average roughness): Based on the display method described in JIS B-0601 (Definition and display of surface roughness), extract the part of the measurement length L from the roughness curve in the direction of the center line, and extract this The center line of the part is the X axis, and the vertical magnification direction is Y.
When the axis and roughness curve are represented by Y = f (x), the value obtained by the following equation (Equation 1) is shown in nanometer (nm).

[0020]

[Equation 1]

Surface roughness (Rmax: maximum roughness): When the roughness curve is sampled by the reference length L and the sampling line is sandwiched by two straight lines parallel to the center line, the interval between these two straight lines is roughened. The value measured in the direction of the longitudinal magnification of the curve is shown in nanometer (nm). -Presence or absence of kiss: Presence or absence of kiss on the polished surface is evaluated by observing the surface with a microscope. The results are shown in Table 1.

[0022]

[Table 1]

When the same abrasive was repeatedly used for the evaluation of this polishing property, a test was carried out.
In (Comparative Example 2), lumps were formed because the dry cohesive force was strong, and due to the peeling of the lumps, scratches were generated on the quartz surface during the third polishing operation. Further, it is difficult to wash and remove the abrasive adhered in the polishing machine by using this silica sol abrasive. Further, in the cerium oxide powder abrasive (Comparative Example 3), the dry matter of the cerium oxide powder was easily scattered and attached around the polishing machine, and the workability was poor.

Example 2 Cerous carbonate (CeO ₂ 51.3)
%, Particle size 50-70 μm) 1000 g of 2420 g of water was added, and the mixture was stirred to form a slurry.
200 g of ₂ O ₂ 34.5%) was added. 1 this slurry at room temperature
After stirring for an hour, the liquid was heated to a temperature of 93 ° C., and the reaction was carried out while further stirring for 1 hour. To the gel slurry of cerium oxide thus obtained, 95 g of hydrochloric acid (HCl 35.4%) and 1815 g of water were added so that the HCl / CeO ₂ molar ratio was 0.3, and further
An acidic ceric oxide sol (CeO ₂ 9.6%) was obtained by performing peptization treatment by heating at 90 ° C. for 1.5 hours.

To this acidic cerium oxide sol, 179 g of tartaric acid was added so that the carboxyl group (COOH) equivalent of tartaric acid was 0.8 with respect to 1 mol of cerium oxide.
Ammonia water was further added to adjust the sol pH to 9. This was desalted using an ultrafiltration device to obtain an alkaline cerium oxide sol. Furthermore, the pH of this sol was adjusted using monoethanolamine, and further concentrated treatment was performed to obtain pH 10, CeO ₂
30.0% of the abrasive of the present invention was obtained. The average particle size of the sol in the polishing agent of the present invention was 18 nm.

(Comparative Examples 4 and 5) For comparison, Example 2 was used.
Similarly, an alkaline ceric oxide sol was prepared by using lactic acid (Comparative Example 4) and formic acid (Comparative Example 5) in place of the tartaric acid of Example 2 in the acidic cerium oxide sol stabilized with hydrochloric acid obtained in 1. However, these abrasives were in gel form.

Using the abrasives of Example 2 and Comparative Examples 4 and 5, and using soda lime glass, the abrasiveness evaluation test was conducted. Since the abrasives of Comparative Examples 4 and 5 were gelled and settled, the evaluation test was performed while stirring the abrasives. <Polishing conditions> ・ Polishing pressure: 84 g / cm ²・ Surface plate rotation speed: 70 rpm ・ Abrasive agent concentration: undiluted solution ・ Polishing machine model: Udagawa Iron Works, Oscar type Incidentally, the evaluation method was the same as in Example 1. . The results are shown in Table 2.

[0028]

[Table 2]

Example 3 Cerous carbonate (CeO ₂ 48.2)
%) 1.6 kg was dissolved in hydrochloric acid (HCl 2%) 29.6 kg, and sodium hydroxide aqueous solution (NaOH 10%) 11 kg was added thereto with stirring to carry out a reaction. After the reaction, the resulting gel was filtered and washed, and 258 g of hydrogen peroxide solution (H ₂ O ₂ 31%) was added to this, and the cerium was changed from a cerium cerium gel to a cerium gel,
This is filtered and ceric hydroxide gel (CeO ₂ 24.1%) 3.
I got 2kg.

Hydrochloric acid (HCl 2%) (5100 g) was added to this gel (1000 g), and the mixture was heated at 90 ° C. for 1.5 hours for peptization treatment to obtain acidic cerium oxide sol (CeO ₂ 4.0%). . Next, 135 g of oxalic acid (dihydrate) was added to this sol so that the carboxyl group (COOH) equivalent of oxalic acid was 1.5 with respect to 1 mol of ceric oxide, and monoethanolamine was further added to the sol. PH was adjusted to 8. This sol solution was desalted using an ultrafiltration device to obtain an alkaline cerium oxide sol. Next, the sol was subjected to pH adjustment using monoethanolamine and further concentrated to obtain a precision polishing agent of the present invention having pH 9 and CeO ₂ 20.0%. Further, the particle diameter of the sol in the polishing agent thus obtained was measured using a particle size distribution measuring device by the dynamic light scattering method, and as a result, the average particle diameter of the sol was 12 nm.

The polishing agent thus obtained was used to perform an evaluation test of its polishing property. <Polishing conditions> ・ Polishing pressure: 30 g / cm ²・ Surface plate rotation speed: 20 rpm ・ Abrasive agent concentration: undiluted solution ・ Polishing machine model: Udagawa Iron Works, Oscar type The evaluation method was the same as in Example 1. . As a result, the surface roughness (Ra) was 0.2 nm, the surface roughness (Rmax) was 1.8 nm, and there was no kiss on the polished surface.

[0032]

As described in detail above, the present invention is a precision polishing agent comprising an alkaline cerium oxide sol containing an organic acid having two or more carboxyl groups, which has excellent polishing accuracy and is a material for polishing. No residue on the polished surface.

Therefore, the precision polishing agent of the present invention is the most suitable polishing agent for electroceramics which is required to have higher precision in the future. Specific applications include liquid crystals in the field of optoelectronics, optical glass substrates, optical modulators, surface acoustic wave filters, phase compensators, polarizing prisms, LiNbO ₃ crystals, LiTaO ₃ crystals, quartz, quartz, etc. The polishing can be exemplified. More specifically, as polishing materials for these applications, glass substrates, quartz, quartz, lithium tantalate, lithium niobate, alumina, fluorspar, lead molybdate, YAG, GGG, YIG, ferrite, P
Materials such as ZT, metallic aluminum, titanium, beryllium, and stainless can be exemplified.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Shin Yamamoto 575-60 Ishimori, Kamino-cho, Kakogawa-shi, Hyogo Prefecture (72) Inventor Hiroshi Nishikura 94-14 Hirats, Yoneda-cho, Kakogawa-shi, Hyogo (72) Inventor Yoichi Oka Hyogo 1406-1 Shinnobe, Beppu Town, Kakogawa City

Claims (1)

[Claims] 1. A precision polishing agent comprising an alkaline cerium oxide sol containing an organic acid having two or more carboxyl groups.