METHOD AND APPARATUS OF SYMMETRICALLY CHAMFERING SUBSTRATE

Abstract

A method of symmetrically chamfering a substrate includes repeating, at least a plurality of times, the steps of chamfering an edge of the substrate using a chamfering wheel, measuring an asymmetric chamfering deviation (y) of the edge of the substrate which is chamfered, and controlling a relative position of the chamfering wheel with respect to the substrate by a value of a function f(y) of the variable y. It is possible to constantly symmetrically chamfer the edge of the substrate via active response to a change in the chamfering environment without a hardware-based operation of the related art.

Claims

1. A method of symmetrically chamfering a substrate, comprising repeating cycles a plurality of times, each cycle comprising: chamfering an edge of the substrate using a chamfering wheel; measuring an asymmetric chamfering deviation (y) of the edge of the substrate which is chamfered; and controlling a relative position of the chamfering wheel with respect to a position of the substrate by a value of a predetermined function f(y) of the variable y, wherein different substrates are chamfered in the respective cycles, wherein in each cycle, the relative position of the chamfering wheel that was previously set is corrected by the value of the function f(y) which is generated in the respective cycle.

2. The method of claim 1, wherein the asymmetric chamfering deviation is a difference between a chamfered width of an upper surface of the substrate and a chamfered width of an undersurface of the substrate.

3. The method of claim 2, wherein the relative position of the chamfering wheel is controlled to move upward when the chamfered width of the upper surface of the substrate is greater than the chamfered width of the undersurface of the substrate, and the relative position of the chamfering wheel is controlled to move downward when the chamfered width of the upper surface of the substrate is smaller than the chamfered width of the undersurface of the substrate.

4. The method of claim 1, wherein the relative position of the chamfering wheel is a relative height of the chamfering wheel with respect to a height of the substrate.

5. The method of claim 1, wherein the value of the function f(y) is obtained by multiplying the asymmetric chamfering deviation (y) by a predetermined control constant.

6. The method of claim 1, wherein different substrates are chamfered in the respective cycles.

7. The method of claim 1, wherein in each cycles, a plurality of the asymmetric chamfering deviations are measured at a plurality of points respectively on the edge of the substrate; and a plurality of the relative positions of the chamfering wheel are controlled when chamfering at the plurality of the points on the edge of the substrate.

8. The method of claim 1, wherein the substrate comprises a glass substrate for a display.

9. The method of claim 1, wherein the chamfering wheel has a concave groove in an outer surface of the chamfering wheel along a circumferential direction thereof.

10. The method of claim 1, wherein measuring the asymmetric chamfering deviation (y) comprises measuring the asymmetric chamfering deviation (y) using a vision camera which detects a chamfered width of an upper surface of the substrate and a chamfered width of an undersurface of the substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a schematic view showing the process of chamfering an edge of a substrate;

[0017] FIG. 2 is a side cross-sectional view showing the edge of the substrate which is asymmetrically chamfered;

[0018] FIG. 3 is a flow diagram depicting a method of symmetrically chamfering a substrate according to an embodiment of the invention;

[0019] FIG. 4 is a schematic view showing a plurality of measuring points on the edges of a substrate;

[0020] FIG. 5 is a side cross-sectional view showing an asymmetric chamfering deviation on one edge of a substrate;

[0021] FIG. 6 is a view showing the chamfered width at the upper surface and the chamfered width at the undersurface at each chamfering which is carried out by a method of symmetrically chamfering a substrate according an embodiment of the invention;

[0022] FIG. 7 is a view showing the chamfered width at the upper surface, the chamfered width at the undersurface and an asymmetric chamfering deviation before and after a substrate is symmetrically chamfered by the method of symmetrically chamfering a substrate according an embodiment of the invention;

[0023] FIG. 8 is a view showing a decrease in the asymmetric chamfering deviation before and after the method of symmetrically chamfering a substrate according an embodiment of the invention is applied; and

[0024] FIG. 9 is a schematic view showing an apparatus of symmetrically chamfering a substrate according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] Reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below, so that a person having ordinary skill in the art to which the present invention relates can easily put the present invention into practice.

[0026] Throughout this document, reference should be made to the drawings, in which the same reference numerals and signs are used throughout the different drawings to designate the same or similar components. In the following description of the present invention, detailed descriptions of known functions and components incorporated herein will be omitted when they may make the subject matter of the present invention unclear.

[0027] FIG. 3 is a flow diagram depicting a method of symmetrically chamfering a substrate according to an embodiment of the invention, FIG. 4 is a schematic view showing a plurality of measuring points on the edges of a substrate, and FIG. 5 is a side cross-sectional view showing an asymmetric chamfering deviation on one edge of a substrate.

[0028] The method of symmetrically chamfering a substrate according to the invention repeats a chamfering step, a measuring step and a controlling step at least a plurality of times.

[0029] At the chamfering step, an edge of the substrate is chamfered using a chamfering wheel.

[0030] The substrate 10 is placed on a chamfering table 30. Herein, the terms up (upward), down (downward), left and right are used to describe the positional relationship but not to indicate the absolute position with respect to the surface of the earth. Therefore, the description that the substrate 10 is positioned on or above the chamfering table 30 merely means that the substrate 10 is positioned in a direction that is designated to be upward from the chamfering table 30, but the upward direction does not necessarily indicate that it faces away from the surface of the earth. While the substrate 10 may be a glass substrate for a display device, the invention is not limited thereto. The substrate 10 according to the invention can be made of any material as long as the substrate is supposed to be chamfered.

[0031] The chamfering wheel 20 is made of a material that is more rigid than the substrate 10. When the object to be chamfered is the glass substrate 10, the chamfering wheel 20 typically contains diamond grinding chips. In general, the chamfering wheel 20 is provided as a disk type. Concave grooves are formed in the outer circumference of the chamfering wheel 20 along the circumferential direction thereof. The inner sides of the grooves abut against the edge of the substrate 10, thereby evenly chamfering the edge of the substrate 10. The chamfering wheel 20 is grasped by a dedicated grinding machine and is thereby rotated at a high speed.

[0032] In general, the substrate 10 is moved and the chamfering wheel 20 is rotated in position. However, this is not always required. For instance, the arrangement in which the substrate 10 is fixed and the chamfering wheel 20 is movable is possible, or the arrangement in which both the substrate 10 and the chamfering wheel 20 are movable is possible. In response to the relative movement between the substrate 10 and the chamfering wheel 20, the chamfering wheel 20 chamfers the edge of the substrate 10 while moving along the edge.

[0033] At the measuring step, an asymmetric chamfering deviation (y) of the edge of the substrate is measured.

[0034] According to an exemplary embodiment, the asymmetric chamfering deviation is measured from the difference between the widths of the upper surface and the undersurface of the chamfered substrate 10. However, the present invention is not limited thereto. For instance, it is possible to measure the asymmetric chamfering deviation by directly inspecting the cross-section of the edge of the substrate 10 from the side. A variety of devices, such as a vision camera and a distance sensor, can be used to measure the asymmetric chamfering deviation.

[0035] It is preferred that an asymmetric chamfering deviation is measured from each of a plurality of points on the edge of the substrate. While FIG. 4 shows that this measuring operation is carried out on all of four edges, this is not intended to be limiting. Only a limited number of edges can be measured as required. For example, four vision cameras can be used in order to measuring the four edges of the substrate.

[0036] At the controlling step, the relative position of the chamfering wheel with respect to the substrate is controlled by the value of a function f(y), where the variable y is the asymmetric chamfering deviation.

[0037] Typically, the position of the chamfering wheel that is to be controlled is the relative height of the chamfering wheel with respect to the substrate. As described above, it should be understood that the term height is used in order to describe the relative positional relationship but not to indicate the absolute position. In addition, while the relative position may be changed by moving the chamfering wheel up and/or down, this is not intended to be limiting. For instance, it is possible to move the substrate in the up and down direction while fixing the chamfering wheel, or to move both the chamfering wheel and the substrate.

[0038] For instance, since a glass plate is thin (with a thickness of about 1 mm or less), it is bent along the shape of the upper surface of the chamfering table due to the flatness of the chamfering table and under the influence of the weight of the glass plate. In that state, the glass plate closely adjoins the upper surface of the chamfering table. Therefore, when the chamfering table 30 is not flat, the center point of the cross-section at the edge of the substrate 10 is locally misaligned from the center point of the chamfering wheel 20. When the height of a localized area of the chamfering table 30 is lower than a reference height, the center point of the edge of the substrate 10 is positioned lower than the center point of the chamfering wheel 20, as shown in FIG. 5. In this case, the undersurface of the substrate is more chamfered than the upper surface of the substrate, such that the chamfered width of the undersurface becomes greater than the chamfered width of the upper surface. Accordingly, the relative height of the chamfering wheel with respect to the substrate is controlled in the upward direction.

[0039] In contrast, when the local height of the chamfering table 30 is greater than the reference height, the local center point of the cross-section at the edge of the substrate 10 is positioned higher than the center point of the chamfering wheel 20. In this case, the upper surface of the substrate is more chamfered than the undersurface of the substrate, such that the chamfered width of the upper surface becomes greater than the chamfered width of the undersurface. Accordingly, the relative height of the chamfering wheel with respect to the substrate is controlled in the downward direction.

[0040] It is preferred that the controlling step individually controls the positions of the chamfering wheel when chamfering a plurality of points on the edge of the substrate, like the measuring step. While FIG. 6 and FIG. 7 show that this controlling operation is carried out on all of the four edges, this is not intended to be limiting. The controlling operation can be carried out on only a limited number of edges as required. For example, four chamfering wheels can be used in order to chamfer the four edges of the substrate.

[0041] After the relative position of the chamfering wheel 20 with respect to the substrate 10 is changed, the foregoing steps, including the chamfering step, the measuring step and the controlling steps, are repeated. While the edge of the same substrate 10 can be chamfered and measured again, it is preferable to use another substrate 10. That is, it is possible to chamfer and measure the edge of a plurality of substrates 10 while controlling the relative position of a single chamfering wheel 20 with respect to each of the substrates 10.

[0042] The number of repetitions can be designated in advance and inputted into a program, or the process can be repeated until the asymmetric chamfering deviation (y) has a value within a designated range. Furthermore, the measuring and controlling steps can be constantly carried out, i.e. limitlessly repeated, during the chamfering operation.

[0043] After the chamfering step, the degree of asymmetry of the cross-section at the edge of the substrate is measured, the asymmetric chamfering deviation is fed back, an amount of control f(y) (e.g. f(y)=y*a) is generated by multiplying the deviation (y) with a predetermined constant (a), and the height of the chamfering wheel is precisely determined by the amount of control. After this first cycle, the degree of asymmetry at the same point is measured, an amount of control is generated in the same way, and the position of the chamfering wheel that was previously set is corrected by accumulating this amount of control. When this series of processes is continuously repeated, a deviation in the chamfered width which is continuously changed due to the precision of carriage caused by deterioration of the chamfering operation and due to the flatness can be set to a minimum value.

[0044] FIG. 6 is a view showing the chamfered width at the upper surface and the chamfered width at the undersurface at each chamfering which is carried out by a method of symmetrically chamfering a substrate according an embodiment of the invention, FIG. 7 is a view showing the chamfered width at the upper surface, the chamfered width at the undersurface and an asymmetric chamfering deviation before and after a substrate is symmetrically chamfered by the method of symmetrically chamfering a substrate according an embodiment of the invention, and FIG. 8 is a view showing a decrease in the asymmetric chamfering deviation before and after the method of symmetrically chamfering a substrate according an embodiment of the invention is applied.

[0045] As shown in the figures, it can be appreciated that symmetric chamfering on an edge of a substrate was realized by repeating the chamfering, measuring and controlling steps only several times when the method of symmetrically chamfering a substrate according to the invention is applied. As the result of the operation carried out, it was possible to reach a desired level of about 50 m (an average level of 20 m) by carrying out the operation 5 times or fewer.

[0046] FIG. 9 is a schematic view showing an apparatus of symmetrically chamfering a substrate according to an embodiment of the invention.

[0047] As shown in FIG. 9, the apparatus of symmetrically chamfering a substrate according to an embodiment of the invention includes a chamfering wheel, a measuring unit and a controller.

[0048] The measuring unit measures an asymmetric chamfering deviation (y) of an edge of a substrate which is chamfered. The controller controls the position of the chamfering wheel by a function f(y), where the variable y is the asymmetric chamfering deviation.

[0049] The foregoing descriptions of specific exemplary embodiments of the present invention have been presented with respect to the drawings. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible for a person having ordinary skill in the art in light of the above teachings.

[0050] It is intended therefore that the scope of the invention not be limited to the foregoing embodiments, but be defined by the Claims appended hereto and their equivalents.