JPH0354287A - Abrasive composition for lithium tantalate - Google Patents

Abstract

PURPOSE:To prevent edge sag and scratch from occurring and to improve abrasion speed by incorporating a calcined alumina powder. CONSTITUTION:An alminum hydroxide such as Al(OH) or A10(OH) prepd. by the Bayer method, a liq. phase synthesis, etc., is calcined at 1,100-1,300 deg.C and, if necessary, is ground and classified to obtain a calcined alumina powder with a prim. mean particle diameter of 0.01-4 mum and a sec. mean particle diameter of 0.1-10 mum. Then, 3-40 wt.% this alumina powder and if necessary, a dispersing agent, a surface active agent, etc., are dispersed or suspended in water to obtain an abrasive compsn. for lithium tantalate.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is applicable to surface acoustic wave devices, electro-optical devices, etc.
This invention relates to a polishing composition that quickly polishes lithium tantalate, which is currently widely used, to a mirror finish with high precision.

Prior Art Polishing compositions conventionally used for lithium tantalate are colloidal silica or colloidal silica dissolved in water to a certain concentration. The lithium tantalate is polished by a polishing pad while supplying this polishing composition to the polishing surface.

Problems to be Solved by the Invention However, the above polishing composition has the following problems. 0) The polishing rate is low. (b) The shape of the peripheral portion of the polished surface is likely to collapse, so-called edge sag. When Q9 colloidal silica dries, it solidifies into silica gel and causes scratches.

An object of the present invention is to improve the above-mentioned problems, that is, to provide a polishing composition for lithium tantalate that has a high polishing rate, does not cause fringing, and does not cause scratches.

Means for Solving the Problems The present invention is characterized in that, for the above-mentioned purpose, an abrasive containing calcined alumina powder is used as an abrasive for use in a polishing assembly for lithium tantalate.

Calcined alumina abrasive powder is alumina powder prepared by the Bayer method or liquid phase synthesis method, and compared to the colloidal silica force conventionally used for polishing lithium tantalate,
1> High hardness. 2) By appropriately setting the calcination conditions, the gelatinization rate can be adjusted and an alumina abrasive powder having a desired hardness can be obtained. 3) The calcined alumina powder has the advantage that it is possible to obtain an abrasive material having an arbitrary particle size distribution by pulverizing and classifying it. Therefore, a high polishing rate can be stably obtained, and the occurrence of edge sagging can be suppressed to a low level. Further, the calcined alumina abrasive powder does not gel even when dried and does not cause scratches, so a good surface can be obtained.

The calcined alumina abrasive powder used in the present invention is AN (OR) prepared by Bayer method, liquid phase synthesis, etc.
3.1! It is prepared by calcining aluminum hydroxide represented by a chemical formula such as O (OH) to form α-alumina. The calcination temperature is about 1100-1300℃,
The raw material for calcining may be alumina hydroxide without any particular composition or chemical composition. Further, by subjecting this calcined alumina to pulverization and classification as necessary, a calcined alumina abrasive powder having an arbitrary particle size distribution can be obtained.

The average particle size of the primary particles of the calcined alumina abrasive powder used in the present invention is preferably 0.01 to 41. As the particle size becomes smaller, the roughness of the machined surface becomes smaller, which is preferable, but the polishing rate also becomes smaller.

Therefore, in consideration of machined surface roughness and polishing rate, a more preferable average particle diameter of the alumina primary particles is in the range of 0.05 to 11.

Moreover, the average particle diameter of the secondary particles of the alumina powder used in the present invention is preferably 0.1 to tOW.

In consideration of machined surface roughness and polishing rate, a more preferable average particle size of the alumina secondary particles is in the range of 0,1 to 4-4.

The content of the calcined alumina abrasive powder in the polishing composition of the present invention can be arbitrarily selected. Usually the alumina content is 3-4
A polishing composition made into an aqueous slurry so as to have a concentration of 0% by weight is supplied to the polishing surface and used for polishing. The higher the alumina content in the polishing composition, the higher the polishing rate and the lower the roughness of the machined surface, which is advantageous, but in consideration of economic efficiency, 15 to 25% by weight is more preferable. In addition, the above content is the concentration when supplied to the polishing surface, and it is necessary to prepare a concentrated polishing composition with a high alumina content and dilute it to the desired concentration within the above alumina content range before use. is also possible.

In addition, since the present invention is characterized by using calcined alumina abrasive powder as the abrasive, the polishing composition may contain other components such as a dispersant and a surfactant that improve the dispersibility of calcined alumina. Since there is no problem in adding these other precepts, the present invention also includes the addition of these other precepts.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples. The polishing properties in the Examples and Comparative Examples below were evaluated by the following polishing test. For polishing, a single-sided borising machine (surface plate diameter 620φmm) was used, and the surface plate was equipped with a velor type pad (manufactured by Showa Polishing System ■ S P D
NcL3211) was attached, and five 72φmm lithium tantalate wafers were attached to a 220φmm glass polishing plate with wax and polished for 20 minutes. During polishing, a constant flow of polishing composition was applied. After polishing, the thickness of the wafer was measured, and the polishing rate was determined from the decrease in thickness. In addition, the polished surface was observed to evaluate the surface condition and edge sag.

Example 1 20% by weight of calcined alumina abrasive powder with a primary particle average diameter of 0.1-μ and a secondary particle average diameter of 2μ, which was obtained by calcining and gelatinizing aluminum hydroxide obtained by liquid phase amalgamation. The aqueous slurry contained therein was used as a polishing composition.

The polishing conditions are lower surface plate rotation speed: 12 Orpm, processing pressure;
350g/cj, slurry supply amount 30ml/1n
It is. The test results are shown in the Example 1 column of Table 1.

Comparative Example 1 Instead of the calcined alumina abrasive powder used in Example 1, colloidal silica (average primary particle diameter 0.07 μs), which has been conventionally used for polishing lithium tantalate, was used for polishing. A test was conducted under the same polishing conditions as in Example 1, except that the calcined alumina abrasive powder was changed to colloidal silica powder, and the results are shown in the Comparative Example 1 column of Table 1.

Example 2 Instead of the calcined alumina abrasive powder with a primary particle average diameter of 0.1m and a secondary particle average diameter of 2m used in Example 1, a primary particle average diameter of 0.01m and a secondary particle average diameter of 21m were used. Polishing was carried out using calcined alumina abrasive powder. The average primary particle diameter of the calcined alumina abrasive powder is 0. lts to 0. A test was conducted under the same polishing conditions as in Example 1, except that the polishing conditions were changed to 1, and the results are shown in the column of Example 2 in Table 1.

Example 3 Instead of the calcined alumina abrasive powder with a primary particle average diameter of 0.1- and a secondary particle average diameter of 2-, which was used in Example 1, a temporary one with a primary particle average diameter of 4- and a secondary particle average diameter of 4 us was used. Polishing was performed using calcined alumina abrasive powder. The test was conducted under the same polishing conditions as in Example 1, except that the primary particle average diameter of the calcined alumina abrasive powder was changed from 0.1- to 4-, and the secondary particle average diameter was changed from 2- to 4-. The results are shown in the Example 3 column of Table 1.

Comparative Example 2 Instead of the calcined alumina abrasive powder with a primary particle average diameter of 0.1- and a secondary particle average diameter of 2- used in Example], calcined powder with a primary particle average diameter of 10 m and a secondary particle average diameter of 10 m was used. Polishing was performed using alumina abrasive powder. The test was conducted under the same polishing conditions as in Example 1, except that the average primary particle diameter of the calcined alumina abrasive powder was changed from 0.1 to 1Qm, and the average secondary particle diameter was changed from 2 to 10. The results are shown in the Comparative Example 2 column of Table 1.

Example 4 Instead of the calcined alumina abrasive powder with a primary particle average diameter of 0.1- and a secondary particle average diameter of 2- used in Example 1, a primary particle average diameter of 0.01 and a secondary particle average diameter of 0 were used. Polishing was carried out using a calcined alumina abrasive powder of .1-. The average primary particle diameter of the calcined alumina abrasive powder is 0. l1 to 0.01
tm, the test was conducted under the same polishing conditions as in Example 1, except that the average diameter of the secondary particles was changed from 2- to 0,1-, and the results are shown in the column of Example 4 in Table 1.

Comparative Example 3 Instead of the calcined alumina abrasive powder with a primary particle average diameter of 0.01 m and a secondary particle average diameter of 0.1-, which was used in Example 4, a primary particle average diameter of 0, Olμ and a secondary particle average diameter of 0 were used. ,05-
Polishing was carried out using calcined alumina abrasive powder. A test was conducted under the same polishing conditions as in Example 4, except that the average secondary particle diameter of the calcined alumina abrasive powder was changed from 0.1 m to 0.05 m, and the results were summarized in Example 1. It is shown in the column of Comparative Example 3 in the table.

Example 5 The average diameter of the primary particles used in Example 1 was 0. 1 m,
Polishing was carried out using a calcined alumina abrasive powder with a secondary particle average diameter of 4- and a secondary particle average diameter low instead of a calcined alumina abrasive powder with a secondary particle average diameter of 2-. Except that the average primary particle diameter of the calcined alumina abrasive powder was changed from 0.1- to 4-, and the average secondary particle diameter was changed from 2- to 10-.
A test was conducted under the same polishing conditions as in Example 1, and the results are shown in the column of Example 5 in Table 1.

Comparative Example 4 Instead of the calcined alumina abrasive powder with a primary particle average diameter of 4- and a secondary particle average diameter of 1O- used in Example 5, calcined with a primary particle average diameter of 4- and a secondary particle average diameter of 201B@ Polishing was performed using alumina abrasive powder.

The average secondary particle diameter of the calcined alumina abrasive powder was determined by J. A test was conducted under the same polishing conditions as in Example 5, except that the polishing distance was changed from Om to 20 m, and the results are shown in the Comparative Example 4 column of Table 1.

(The following is a blank space) Example 1 and Comparative Example 1 in Table 1 are the results of polishing using calcined alumina abrasive powder and colloidal silica as abrasives, respectively. It was found that when calcined alumina abrasive powder was used for polishing, the removal rate was higher, the surface condition was better, and fringing was less likely to occur than when colloidal silica was used as the abrasive.

Next, the average primary particle diameter and polishing performance of the calcined alumina abrasive powders will be compared. Example 1, Example 2, Example 3, and Comparative Example 2 in Table 1 are 0. These are the results of polishing using calcined alumina abrasive powder from OluN having an average primary particle diameter of 101. As a result, the primary particle average diameter was 0.01
In the cases of Example 11, Example 2, and Example 3 in which m was in the range of 4-, it was observed that the surface condition was good and sagging was less likely to occur. Furthermore, in the case of Comparative Example 2 in which the average primary particle diameter was LOm, scratches occurred.

Next, the average secondary particle diameter and polishing performance of the calcined alumina abrasive powders will be compared. Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 3, and Comparative Example 4 in Table 1 are as follows:
This is the result of polishing using a calcined alumina abrasive powder having an average primary particle diameter in the range of 0 to 4, and a secondary particle average diameter of 0.1 to 20. As a result, Examples 1, 2, 3, 4, and 5 have secondary particle average diameters in the range of 0.1- to 1O-.
In the case of , it was observed that the surface condition was good and sagging was less likely to occur. In addition, in the case of Comparative Example 4 in which the average diameter of the secondary particles was 20-1, scratches occurred and the surface became satin-like. In addition, in the case of Comparative Example 3 in which the average secondary particle diameter was 0.05 ttm, it was observed that the surface condition was good and fringing was less likely to occur, but the removal rate was low and it was not practical. However, it is effective in polishing where the removal rate is not required and the surface condition of the polished surface is important.

Effects of the Invention Compared to conventional polishing compositions, the polishing composition for lithium tantalate characterized by using the calcined alumina abrasive powder according to the present invention has the following characteristics: (1) It has a high polishing rate, and (2) It is difficult to cause fringing. c) It has many effects such as not gelling even when dried and not causing any itch.

Scratch

Claims (1)

[Claims] A polishing composition for lithium tantalate characterized by using an abrasive material containing calcined alumina powder.