JP2009007186A - Polishing material, and method for polishing plate glass using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing material capable of suppressing the formation of a foreign matter during polishing and polishing defects such as unfavorable polishing flaw and also capable of recycling a polished sludge after a polishing process as a law material of a glass product and to provide the polishing method of the plate glass using the polishing material. <P>SOLUTION: In the polishing material prepared by compounding 0.2 to 2 pts.wt. of at least one kind salt selected from alkaline earth metal salts as a dispersant to 100 pts.wt. of polishing material particles containing cerium oxide, a cerium oxide content in the polishing material particles is ≥90 mass%. A polishing method of the plate glass using the polishing material is also provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an abrasive for polishing plate glass, particularly display glass, and a polishing method using the abrasive.

  Among the plate glasses, display plate glasses are required to have high surface smoothness, and in recent years, the demand is becoming stricter. In general, plate glass produced by a float process is known to have relatively good surface smoothness, but even such plate glass has insufficient surface smoothness. Therefore, the surface accuracy of the manufactured plate glass is further improved through a polishing process.

  In general, cerium oxide-based abrasive particles are used as abrasive particles for finishing the surface of a plate glass, and the cerium oxide-based abrasive particles are usually kneaded with water and used as an abrasive slurry. In recent years, as the demand for plate glass for displays has increased, the amount of cerium oxide-based abrasive used has also increased.

  By the way, cerium oxide may be used as a raw material for glass products, and after drying polishing sludge containing a cerium oxide-based abrasive after the polishing step, it can be used by mixing with other glass raw materials. . By doing so, while the usage amount of the cerium oxide-based abrasive is increased, it is reused without adversely affecting the environment, and glass raw material costs, waste disposal costs, and the like are reduced.

  However, since cerium oxide conventionally used as abrasive particles uses natural ore as it is, various impurity elements are inevitably mixed therein. Therefore, when abrasive sludge obtained using such abrasive particles is mixed with glass raw material and melted, the amount of substances that are difficult to remove by exhaust gas treatment such as fluorine in the combustion exhaust gas increases, and the environment It is not preferable from the aspect. Therefore, high-purity cerium oxide obtained by firing cerium carbonate or cerium oxalate has been used as the abrasive particles.

  For example, in Patent Document 1, the cerium oxide content is 95% by mass or more, the chlorine content is 0.2% by mass or less, the fluorine content is 0.2% by mass or less, and the total halogen content is 0.00. An abrasive that is 2% by mass or less has been proposed.

Further, in Patent Document 2, in order to prevent agglomeration of cerium oxide, a polishing material for plate glass characterized by containing a fluorine compound or an organic dispersant in a polishing material mainly composed of a rare earth oxide containing cerium oxide. Has been proposed.
JP 2003-212601 A JP-A-6-330025

  When high-purity cerium oxide is used as an abrasive slurry, as in Patent Document 1, abrasive foreign matter having a size of 50 to 800 μm adheres to the surface of the plate glass during polishing of the plate glass, or unreasonable polishing scratches remain on the plate glass surface. The problem occurs. This is due to aggregation of cerium oxide particles in the abrasive slurry, and it has been found that it is particularly difficult to remove abrasive foreign matters having a size of about 50 μm by cleaning after polishing.

  In the method described in Patent Document 2, a large amount of fluorine compound is mixed in the polishing sludge obtained after the polishing step, and as described above, it is unsuitable for use as a glass raw material from the viewpoint of the environment. Further, when an abrasive slurry containing an organic dispersant is used, it is difficult to completely remove the organic dispersant remaining on the surface of the plate glass in the plate glass cleaning step with the cleaning water after the polishing step. The organic dispersant remaining on the surface of the plate glass is carbonized in the heating process at the time of display manufacturing to become a residue of a conductive material. For example, in the final product of a plasma display panel, a breakdown failure occurs due to the residue. There is a risk of doing. Therefore, a special cleaning process is required to clean the organic dispersant.

  Therefore, the present invention is capable of suppressing polishing defects such as foreign matters and undue polishing flaws during polishing, and polishing sludge after polishing process is recyclable as a glass raw material, for example, a raw material for cathode ray tube panel glass, It is another object of the present invention to provide a method for polishing plate glass using the abrasive.

  As a result of intensive studies, the present inventors have found that the above problem can be solved by using a specific non-organic dispersant as a dispersant in an abrasive containing high-purity cerium oxide. It is what we propose.

  That is, the abrasive of the present invention comprises 0.2 to 2 parts by mass of at least one selected from an alkaline earth metal salt as a dispersant with respect to 100 parts by mass of abrasive particles containing cerium oxide. The content of cerium oxide in the abrasive particles is 90% by mass or more.

  According to the present invention, high-purity cerium oxide that can be used as a glass raw material and alkaline earth metal salt that can also be used as a glass raw material are used as a dispersant. It can be reused by mixing with other glass raw materials.

  In addition, since the alkaline earth metal salt promotes the dispersion and fluidization of the abrasive particles, if the alkaline earth metal salt is added, aggregates are hardly generated, and the abrasive of the present invention is used as an abrasive slurry. In addition, the clogging of the abrasive slurry piping is eliminated, and the generation of 50 to 800 μm abrasive foreign matter adhering to the surface of the plate glass during polishing can be remarkably reduced. In addition, since the abrasive particles are difficult to precipitate in the abrasive slurry, a high concentration slurry can be obtained, and the polishing efficiency can be improved.

  Furthermore, since the dispersant is an inorganic compound, the dispersant does not change due to heat generated by friction between the polishing pad and glass during high-speed polishing, and thermal degradation does not occur. In addition, even if a trace amount of abrasive residue adheres to the surface of the plate glass and is exposed to high temperatures in the heating process during display manufacturing, it does not carbonize like organic dispersants, so it does not become a contaminant of conductive substances. . Therefore, the dielectric breakdown failure of the final plasma display panel product due to the abrasive residue is unlikely to occur.

  Second, the abrasive of the present invention has at least one dispersing agent selected from barium sulfate, a mixture of barium sulfate and calcium sulfate, a mixture of barium sulfate and calcium borate, and a mixture of barium sulfate and strontium sulfate. It is characterized by being.

  Third, the abrasive of the present invention is characterized in that the abrasive particles are substantially free of fluorine. As described above, when fluorine is contained as an impurity in the abrasive, when the polishing sludge after the polishing process is mixed with other glass raw materials and melted, the generated fluorine gas can be removed by exhaust gas treatment. It becomes difficult. In the present invention, it is preferable from the viewpoint of the environment that the abrasive particles do not substantially contain fluorine, so that the combustion exhaust gas contains almost no fluorine. “Substantially free of fluorine” means that the fluorine content in the abrasive particles is less than 0.1% by mass.

  Fourthly, the abrasive according to the present invention is used for polishing display plate glass.

  Fifth, the present invention relates to a method for polishing a plate glass, which is characterized by using the above-mentioned abrasive.

  The abrasive of the present invention is prepared by blending a specific amount of at least one selected from alkaline earth metal salts with abrasive particles containing cerium oxide.

  In the present invention, the content of cerium oxide in the abrasive particles is 90% by mass or more, preferably 95% by mass or more, and more preferably 99% by mass or more. When the content of cerium oxide is less than 90% by mass, the polishing power tends to be inferior. As described above, when used as an abrasive, the abrasive sludge is mixed with other glass raw materials and melted. Since the amount of substances that are difficult to remove by exhaust gas treatment such as fluorine increases, it is not preferable from the environmental viewpoint.

  Of the impurities contained in the abrasive particles, the fluorine content is preferably 0.2% or less, more preferably substantially not contained, from the environmental viewpoint.

  When the abrasive of the present invention is used as an abrasive slurry, the content of abrasive particles in the abrasive slurry is preferably 0.1 to 30% by mass, and preferably 0.5 to 10% by mass. More preferably, the content is 1 to 5% by mass. When the content of the abrasive particles is less than 0.1% by mass, it is difficult to obtain a sufficient polishing effect. On the other hand, when the content of the abrasive particles exceeds 30% by mass, the abrasive particles are aggregated, and an inappropriate abrasive scratch is easily generated on the glass surface.

  As the dispersant in the present invention, an alkaline earth metal salt is used. Specific examples include sulfates such as barium sulfate, calcium sulfate and strontium sulfate; borate salts such as calcium borate and barium borate; chlorides such as calcium chloride and barium chloride. Of these, barium sulfate, a mixture of barium sulfate and calcium sulfate, a mixture of barium sulfate and calcium borate, and a mixture of barium sulfate and strontium sulfate are particularly effective because they have a large dispersion effect on abrasive particles and a large effect of suppressing poor polishing. It is preferable to use at least one selected from

  The content of the dispersant is 0.2 to 2 parts by mass, preferably 0.4 to 1 part by mass, and 0.4 to 0.6 parts by mass with respect to 100 parts by mass of the abrasive particles. It is more preferable. When the content of the dispersant is less than 0.2 parts by mass, the effect of dispersing the abrasive particles cannot be obtained, and the abrasive particles are aggregated, so that inappropriate polishing flaws are likely to occur on the glass surface. If the content of the dispersant exceeds 2 parts by mass, the dispersant tends to cover the surface of the abrasive particles, and the polishing effect tends to be reduced.

  In the abrasive of the present invention, additives such as a thickener and a pH adjuster can be added as needed in addition to the dispersant.

  The polishing apparatus for polishing the plate glass using the polishing material of the present invention is an upper polishing platen that rotates the upper surface of the plate glass placed on the conveyor belt that moves while sliding on the upper surface of the substrate of the polishing apparatus. A polishing machine that polishes by means of the above. The upper polishing surface plate has a diameter of 600 to 800 mm, a polishing pad made of urethane foam resin is attached to the lower surface, and is suspended rotatably through an air cylinder that applies a polishing load. The abrasive is supplied from the center of the upper polishing surface plate to the lower surface of the polishing pad. The polishing speed is appropriately adjusted according to the moving speed of the conveyor belt.

  As polishing conditions, the polishing load is suitably adjusted in the range of 0.2 to 0.4 MPa, the rotation speed of the upper polishing platen is 20 to 60 rpm, and the polishing speed is 1 to 3 m / min. It is also possible to perform high-speed polishing such that the polishing rate of the plate glass exceeds 10 m / min. In that case, it is effective to use a high-concentration abrasive.

  EXAMPLES Next, although this invention is demonstrated in detail using an Example, this invention is not limited to these Examples.

(Examples 1-5)
As shown in Table 1, high purity cerium oxide obtained by firing cerium carbonate or cerium oxalate (cerium oxide content: 99% by mass, average particle size 3.7 μm), as a dispersant, barium sulfate, sulfuric acid At least one alkaline earth metal salt of calcium, calcium borate, and strontium sulfate was added, and water was added to obtain an abrasive slurry. A mixture of barium sulfate and calcium sulfate, calcium borate or strontium sulfate was used as a mixture having a mass ratio of 1: 1.

  Specifically, with respect to 100 parts by mass of the abrasive particles, at least one of the four types of alkaline earth metal salts is mixed as a dispersant in the range of 0.2 to 2 parts by mass, and water is further dispersed in the dispersion medium. To give a 1.2% by weight slurry. Note that water was first added in an amount corresponding to 40% by mass of the abrasive slurry and kneaded once into a paste form, and then water was added to adjust the final concentration.

  The obtained abrasive slurry was used to polish the plate glass to determine the rate of poor polishing. The defective polishing occurrence rate is a percentage of the number of glass plates on which a defective abrasive material foreign material has occurred in a glass plate that has been subjected to predetermined end face processing, cleaning, and appearance inspection after the polishing step. The results are shown in Table 1.

  As the polishing apparatus, a polishing machine was used that polished the upper surface of the plate glass placed on the conveyor belt moving while sliding on the upper surface of the substrate of the polishing apparatus with a rotating upper polishing platen. The upper polishing surface plate had a diameter of 600 mm, and a urethane foam polishing pad was attached to the lower surface, and the upper polishing platen was rotatably suspended through an air cylinder that applied a polishing load. The abrasive slurry was supplied from the center of the upper polishing platen to the lower surface of the polishing pad.

  As polishing conditions, the polishing load was 0.25 MPa, the upper polishing platen was rotated at 40 rpm, and the polishing rate was 1.8 m / min.

(Comparative Examples 1 and 2)
An abrasive slurry was prepared in the same manner as in Examples 1 to 5 except that no dispersant was blended or the blending amount of the dispersant was 2.2 parts by mass with respect to 100 parts by mass of the abrasive particles. Plate glass was polished using the obtained abrasive slurry, and the occurrence rate of polishing failure was determined. The results are shown in Table 1.

  As is apparent from Table 1, the abrasives of Examples 1 to 5 containing 0.2 to 2.0 parts by mass of an alkaline earth metal salt as a dispersant for 100 parts by mass of abrasive particles are aggregates. It can be seen that the occurrence rate of poor polishing can be suppressed to approximately 15% or less. In particular, when barium sulfate is used as the dispersant, it can be seen that poor polishing can be suppressed as compared with other dispersants. Further, when 0.5 part by mass of the dispersant was blended with 100 parts by mass of the abrasive particles, the effect of suppressing the occurrence of poor polishing was the greatest.

  On the other hand, in Comparative Example 1 in which no dispersant was blended, the polishing failure occurrence rate was 25 to 30%, and in Comparative Example 2 in which 2.2 parts by weight of dispersant was blended with respect to 100 parts by weight of abrasive particles, poor polishing occurred. The rate was 23 to 25%, which was poor in polishing performance.

  The abrasive of the present invention and the polishing method using the same are suitable for surface polishing of plate glass, particularly display plate glass such as active matrix LCDs, liquid crystal display element substrates, color filter substrates and the like.

Claims (5)

  An abrasive comprising 0.2 to 2 parts by mass of at least one selected from alkaline earth metal salts as a dispersant with respect to 100 parts by mass of abrasive particles containing cerium oxide, A cerium oxide content of 90% by mass or more.   The dispersing agent is at least one selected from barium sulfate, a mixture of barium sulfate and calcium sulfate, a mixture of barium sulfate and calcium borate, and a mixture of barium sulfate and strontium sulfate. The abrasive described.   The abrasive according to claim 1 or 2, wherein the abrasive particles are substantially free of fluorine.   The abrasive according to any one of claims 1 to 3, which is used for polishing a plate glass for a display.   A method for polishing a plate glass surface, wherein the polishing material according to any one of claims 1 to 4 is used.