JP2001064039A - Method for polishing glass article and polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for polishing glass articles with which high glass removal efficiency and good polished surface roughness may be obtained. SOLUTION: Slurries containing polishing agent particles are circulated between two slurry tanks 1 and 2 via cyclone type classifying devices 12a to 12c and 14a to 14c and a thickener tank 3, and the states varying in polishing agent grain sizes of a stable slurry concentration are attained in the respective tanks. The slurry on the side where the grain size is larger is used for polishing of a fore stage and the slurry on the side where the grain size is smaller is used for polishing of a post stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for polishing a glass article.

[0002]

2. Description of the Related Art A glass lens and an optical glass substrate are polished to obtain dimensional accuracy such as flatness and optical characteristics of the surface. Similarly, glass panels and glass funnels for cathode ray tubes are polished to obtain dimensional accuracy and optical characteristics.

[0003] These basic polishing methods are carried out by placing and fixing a glass article on a table, rotating the article, and pressing a rotating polishing tool while supplying slurry to the interface with the glass article. The slurry is a polishing liquid in which an abrasive is dispersed in a liquid such as water, and is used at an appropriate abrasive particle size and concentration. Iron, rubber, resin, or the like is used as the polishing tool.

In order to obtain good optical characteristics and good polished surface roughness in a short time, it is generally employed to employ a plurality of polishing steps. For example, a hard and highly tough abrasive is used in the former stage. And use a soft abrasive in the later stage,
A method in which an abrasive having a large particle size is used in the first stage and an abrasive having a small particle size is used in the second stage is employed.

Conventionally, a method of providing a slurry circulation system corresponding to the type and particle size of the polishing agent has been generally used. When polishing is performed in a plurality of stages, equipment and cost are increased. Japanese Patent Application Laid-Open No. Hei 7-186041 proposes a method of preparing slurries having different particle diameters by using a cyclone classifier, but in this method, a cyclone classifier is provided independently in correspondence with a plurality of polishing steps. Therefore, the difference in slurry concentration occurs in accordance with the classification efficiency of the cyclone for providing the particle size difference, and as a result, when the slurry concentration decreases, the effective number of abrasive grains at the interface between the glass and the polishing tool decreases, There has been a problem that the polishing tool directly hits the glass and polishing scratches occur. That is, the slurry concentration cannot be controlled only by a simple cyclone classification operation.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned disadvantages of the prior art, and to provide a method and apparatus for polishing a glass article which have not been known before. Newly provided.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method of polishing a glass article by circulating and using a slurry between a plurality of slurry tanks and a polishing machine, and polishing between the slurry tanks through a cyclone classifier. By circulating the slurry containing the agent particles, the slurry in each slurry tank is kept in a state in which the abrasive particle size is different, and the slurry with the larger particle size is used for rough polishing and the slurry with the smaller particle size is finished Provided is a method for polishing a glass article, which is used for polishing.

The present invention also provides a method for polishing a glass article by supplying a slurry having a large particle diameter to a polishing machine in an initial stage of polishing, switching the slurry during polishing, and supplying a slurry having a small particle diameter in a later stage of polishing. A method for polishing a glass article as described above, characterized by polishing.

Further, the present invention provides two slurry tanks for storing slurries containing abrasive particles having different particle sizes, a slurry tank having a larger particle size and a slurry tank having a smaller particle size between these tanks. A cyclone type classification device provided corresponding to each, a thickener tank attached to a cyclone type classification device of a slurry tank series having a smaller particle size, and a slurry containing abrasive particles having different particle sizes from the slurry tank. A polishing machine for receiving the supply and polishing the glass article, and receiving the slurry from the polishing machine in a slurry tank having a larger particle size, and circulating the slurry in the tank through the slurry cyclone classifier and the thickener tank. By classifying the abrasive particles, the respective slurry tanks are kept in a state where the abrasive particle diameters are different. To provide a polishing apparatus for a glass article form.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below. FIG. 1 shows a slurry circulation system according to one embodiment of the present invention in which there are two slurry tanks. This figure shows a case where the face surface of a glass panel for a cathode ray tube is polished. The slurry tank 1 is used as a slurry tank containing abrasive particles having a large particle diameter.
The tank is provided with a stirrer 18 to prevent the settling of the abrasive particles. The slurry is pumped from this tank
1 is pumped through the piping to the slurry circulation system.

The piping branches off in the middle, and a part of the slurry is supplied to the cyclones 12a, 12b and 12c. These cyclones are cyclone classifiers corresponding to the slurry tank 1 having a larger particle size. The number of cyclones is three for convenience, but can be changed as appropriate.

The slurry is classified by the cyclone, and the slurry having a large particle diameter and high concentration returns to the slurry tank 1 as underflow. The slurry having a small particle size and a low concentration is supplied to the slurry tank 2 as overflow. The slurry tank 2 is a tank for slurry containing abrasive particles having a small particle diameter.

In this case, the flow ratio between the overflow and the underflow can be changed according to the desired classification efficiency. However, if the particle size difference is set to be large, the concentration difference of the slurry also increases, so that the slurry tank 2 is maintained at an appropriate concentration. It becomes difficult. The flow rate ratio is preferably in the range of overflow / underflow = 0.4 to 0.6. One of the branched slurries is supplied to the polishing machine 4 through the valve 15a, or returns to the slurry tank 1 through the bypass pipe through the valve 15b.

The slurry tank 2 is also provided with a stirrer 19, and the slurry is pumped from the slurry tank 2 using a pump 13 in a well-stirred state. This pipe also branches on the way, and a part of the slurry is supplied to the cyclones 14a, 14b, and 14c. These cyclones are cyclone type classification devices corresponding to the slurry tank 2, and a thickener tank 3 is attached to the cyclone 14a. As a result, between the two slurry tanks 1 and 2, two cyclone classifiers corresponding to the respective tanks are installed.

The overflow of the cyclone 14a is supplied to the thickener tank 3, and the underflow is sent to the slurry tank 1. In the thickener tank, fine glass powder and fine abrasive are discharged out of the system as overflow 21 in a dilute slurry state by sedimentation and separation. The underflow slurry concentrated by the thickener tank is returned to the slurry tank 2 and acts to keep the slurry concentration within an appropriate range. The flow rate balance between the overflow and the underflow is adjusted by the orifice 20 provided on the underflow side. The new abrasive 24 corresponding to the consumed fine abrasive discharged out of the system is supplied to the slurry tank 1.

The cyclone 14b works to keep the concentration difference between the slurry tank 1 and the slurry tank 2 within an appropriate range. The overflow is sent to the slurry tank 1, and the underflow returns to the slurry tank 2. It is difficult to completely match the concentrations of the slurry tank 1 and the slurry tank 2 only by the action of the cyclone, but it is possible to stabilize the concentration within a range in which there is no practical problem.

The cyclone 14c functions to maintain the liquid level in the slurry tank 1 and the slurry tank 2 properly.
The overflow always returns to the slurry tank 2, and the underflow returns to the automatic valve 22 a,
By switching 2b, when the liquid level of the slurry tank 2 is high, the slurry is sent to the slurry tank 1, and when the liquid level is low, the slurry is sent to the slurry tank 2. Cyclones 14a, 14
Also for b and 14c, the flow rate ratio is usually preferably in the range of overflow / underflow = 0.4 to 0.6 in order to keep the slurry concentration in an appropriate range.

The slurry on one side of the branch sent from the pump 13 is sent to the polishing machine 4 through a valve 16a or
Slurry tank 2 through valve 16b and bypass pipe
Is returned to.

In the polishing machine 4, the glass panel 6 is placed and fixed on the rotating table 5 and rotated, and while the slurry 9 is supplied from the nozzle, a polishing tool 8 rotating from above is pressed and the glass panel is polished by the polishing pad 7. The slurry supplied during polishing is automatically switched by operating the valves 15a, 15b, 16a and 16b. That is, at the beginning of polishing, 15a: open, 15b: closed, 16a: closed, 1
6b: The slurry having the larger particle size is supplied to the polishing surface by opening. After a predetermined time has passed, 15b: open, 16a: open, 1
5a: Close, 16b: Close, and switch the slurry from the slurry tank 2 to the smaller particle size side.

The ratio between the polishing time in the first stage and the polishing time in the second stage is set according to the difference in grain size, the desired polishing amount, and the surface roughness. In the case of the slurry having a large particle size, the polishing efficiency is high, but the surface roughness is also large. In the slurry with the smaller particle size,
A polished surface with small surface roughness can be obtained. In addition, since the slurry having a smaller particle size does not substantially contain coarse particles or hard foreign matter in the abrasive, a good polished surface with less occurrence of polishing scratches can be obtained.

The slurry polished by the polishing machine 4 collects at the lower portion and returns to the slurry tank 1. In addition to the slurry flowing from the slurry tank 1 through the valves 15a and 15b, the slurry from the slurry tank 2 at the later stage of polishing returns to the slurry tank 1, so that the liquid level in the slurry tank 1 tends to rise. In order to adjust this, the underflow of the cyclone 14c is switched.

In the polishing machine 4, a cleaning water 10 is supplied through a pipe 17 in order to wash away the slurry attached to the glass panel after the polishing is completed. This washing is performed intermittently, but the orifice 20 is adjusted so that the amount of the thickener overflow 21 corresponding to the amount of supplied water is transferred out of the system.

In this figure, one polishing machine and six cyclones are provided for two slurry tanks, but the slurry can be supplied from two slurry tanks to a plurality of polishing machines. In that case, to control the liquid level of both tanks, the slurry tank 1 side and the slurry tank 2
It is generally necessary to relatively increase or decrease the number of cyclones on the side. The slurry after polishing is returned from all the polishing machines to the slurry tank 1 having the larger particle size, and is classified by one slurry circulation system.

As the cyclone, many commercially available cyclones can be used as appropriate, and those having an appropriate size are selected according to the abrasive particle size, the slurry concentration, and the processing amount.

As an arrangement other than that of this embodiment, two polishing machines are successively arranged by dividing into rough polishing and finish polishing, and the slurry in the slurry tank 1 is supplied to the polishing machine for rough polishing in the preceding stage to perform polishing. Thereafter, there is a method in which the glass panel is transferred to a polishing machine at a subsequent stage, and the slurry in the slurry tank 2 is supplied to the polishing machine to perform polishing. The slurry of the subsequent polishing machine is also returned to the slurry tank 1.

In the present invention, it is most preferable that two slurry tanks are usually provided as in this embodiment from the viewpoint of equipment costs and the like. However, three or more slurry tanks may be provided to finely control the abrasive particle size. In this case,
This can be achieved by adding one or more slurry tanks and a cyclone classifier between the two slurry tanks, and the present invention also includes such embodiments. Even when the number of slurry tanks is three or more, the polished slurry is processed by one slurry circulation system, so that all the slurry is returned to the first slurry tank having a large particle diameter.

As the abrasive, a vitreous abrasive made of aluminum oxide, silicon carbide, garnet, or volcanic ash called permis can be used. Water is generally used as the dispersion medium.

The present invention can be used not only for polishing the face of a glass panel for a cathode ray tube and for polishing the seal edge of a glass funnel, but also for polishing a glass lens and a glass substrate.

[0029]

EXAMPLE (Example) An aluminum oxide abrasive having a number of 600 was used as an abrasive, and this abrasive was circulated in a slurry system shown in FIG. A commercially available cyclone (MD-3 manufactured by Daiki Rubber Industries) was used. The settings for each cyclone are
Based on the supply slurry amount = 100 liter / minute, overflow flow rate = 50 liter / minute, underflow flow rate = 50 liter / minute.

At that time, the slurry concentration in the slurry tank 1 was adjusted to 1500 g / liter, and the abrasive particle diameter was 10% by volume (D ₁₀ ) = 10.5 μm, and the particle diameter by volume was 50% (D ₅₀ ) = 20.0 μm, 90% volume particle size (D ₉₀ ) = 3
Stable at 0.5 μm. The slurry tank 2 has a slurry concentration of 1450 g / liter, a particle size of D ₁₀ = 7.0 μm,
It was stable at D ₅₀ = 17.5 μm and D ₉₀ = 25.5 μm.

A glass panel having a diagonal diameter of 17 inches is fixed on a rotary table and rotated at 15 rpm. A disk-shaped polishing tool having an iron polishing pad was rotated at 600 rpm from above, and the slurry was supplied to the interface between the glass panel and the polishing tool while being pressed against the glass panel with a load of 500 kg to perform polishing.

That is, in the initial stage of polishing, polishing is performed with the slurry in the slurry tank 1 through the valve 15a, and after 20 seconds, the valve 15b is opened, and the valve 16a is opened.
a: Close, 16b: Close, then slurry tank 2
Finish polishing with slurry.

The time for polishing with the slurry in the slurry tank 2 was set in increments of 1 second, and the polishing time required for removing irregularities during molding existing on the face before polishing was examined.
As a result, the polishing time with the slurry from the slurry tank 2 required a minimum of 8 seconds. At this time, the glass removal amount (polishing weight) was 25.0 g, and the polished surface roughness was R
_a = 0.7 μm and R _max = 7.2 μm.

(Comparative Example) As Comparative Example 1, only the slurry in the slurry tank 1 was used, and a glass panel was similarly polished with the same polishing time of 28 seconds as in the example.

As Comparative Example 2, only the slurry in the slurry tank 2 was used and polished for 28 seconds in the same manner. The results are shown in Table 1 together with the examples. As is clear from Table 1, only the examples of the present invention were able to remove irregularities on the molding surface and obtain a polished surface with small roughness.

[0036]

[Table 1]

[0037]

According to the present invention, in a method for polishing a glass article by using a slurry, a slurry which has been classified by one slurry circulation system is selectively used, whereby a good polished surface can be obtained in a short time. Is obtained.

With one slurry system, it is possible to obtain at least two types of slurries having a stable slurry concentration and different particle sizes, eliminating the need for installing a slurry system for each type of slurry as in the conventional case, and reducing the cost required for installation. it can.

Further, by switching the slurry during polishing by one polishing machine, there is an effect that both the efficient removal of defects on the glass surface and the good surface roughness can be achieved with a small number of polishing machines. Therefore, the polishing machine installation cost can be reduced.

The present invention is not limited to grinding glass panels for cathode ray tubes, but can be applied to other types of glass polishing.
Similar effects can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a slurry circulation system showing an embodiment of the present invention.

[Explanation of symbols]

 1: Slurry tank 2: Slurry tank 3: Thickener tank 4: Polisher 5: Rotary table 6: Glass panel 7: Polishing pad 8: Polishing tool 9: Slurry 10: Cleaning water 12a, 12b, 12c: Cyclones 14a, 14b, 14c: cyclone 15a, 15b, 16a, 16b: valve

Claims (3)

[Claims] 1. A method for polishing a glass article, wherein a slurry is circulated between a plurality of slurry tanks and a polishing machine, wherein a slurry containing abrasive particles is circulated between each slurry tank via a cyclone classifier. The feature is that the slurry in each slurry tank is kept in a state in which the abrasive particle diameter is different, the slurry having a larger particle diameter is used for rough polishing, and the slurry having a smaller particle diameter is used for finish polishing. Polishing method for glass articles. 2. A method for polishing a glass article by supplying a slurry having a large particle size to a polishing machine in an initial stage of polishing, switching the slurry during polishing, and supplying a slurry having a small particle size in a later stage of polishing. The method for polishing a glass article according to claim 1, wherein: 3. A slurry tank containing slurries containing abrasive particles having different particle sizes, and a slurry tank having a larger particle size and a slurry tank having a smaller particle size between the two tanks. A cyclone type classification device provided with a thickener tank attached to a cyclone type classification device of a slurry tank series having a smaller particle size, and a glass supplied with slurry containing abrasive particles having different particle sizes from the slurry tank. A polishing machine for polishing the article, wherein the slurry from the polishing machine is received in a slurry tank having a larger particle diameter, and the slurry in the tank is circulated through the slurry cyclone type classification device and the thickener tank to perform polishing. Glass material that classifies abrasive particles and keeps the inside of each slurry tank with different abrasive particle sizes Polishing apparatus.