Tempered glass cutting method and cutting apparatus

Abstract

The present invention is devised to solve the problems of the above-described conventional technologies. The purpose of the present invention is to provide a tempered glass cutting method and cutting apparatus which can prevent the defects of the tempered glass breaking when same is cut and improve the reliability of the product. To this end, provided is a tempered glass cutting method which comprises: a tempering step of generating compressive stress on a glass sheet to temper the glass sheet; a compressive stress relaxation step of applying heat to the cut portion of the tempered glass sheet to relax the compressive stress; and a cutting step of cutting the cut portion.

Claims

1. A method of cutting toughened glass comprising: toughening a raw glass plate by generating compressive stress in a surface layer of the raw glass plate; reducing the compressive stress in the surface layer at portions of the toughened raw glass plate to be cut by applying heat to the surface layer at the portions to be cut; and cutting the toughened raw glass plate along the portions to be cut while applying heat to the surface layer at the portions to be cut so that the compressive stress in the surface layer at the portions to be cut remains reduced.

2. The method according to claim 1, wherein the compressive stress in the surface layer at the portions to be cut is reduced by applying the heat to the surface layer at the portions to be cut with hot wires.

3. The method according to claim 1, wherein the compressive stress in the surface layer at the portions to be cut is reduced to 100 MPa or less by the step of reducing the compressive stress.

4. The method according to claim 1, wherein a width of each of the portions to be cut is 5 mm or less.

5. The method according to claim 1, wherein the raw glass plate is toughened by chemical toughening or thermal toughening.

6. The method according to claim 5, wherein the chemical toughening comprises coating a surface of the raw glass plate with an ion exchange solution in which a potassium nitrate solution and zinc oxide powder are mixed, followed by drying and subsequently heating a resultant structure.

7. The method according to claim 1, wherein the toughened raw glass plate is cut along the portions to be cut using a laser or a scribing device.

8. The method according to claim 1, wherein a temperature of the heat applied to the surface layer at the portions to be cut at the step of reducing the compressive stress is equal to or higher than a transition point and is lower than a melting point of the raw glass plate.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic flowchart illustrating an exemplary embodiment of a method of cutting toughened glass according to the present invention;

(2) FIG. 2 is a schematic flowchart illustrating an exemplary embodiment of an apparatus for cutting toughened glass according to the present invention;

(3) FIG. 3 is a transmission microscopy picture of a portion cut from a raw glass plate without being heat-treated with hot wires; and

(4) FIG. 4 is a transmission microscopy picture of a portion cut from a raw glass plate after being heat-treated with hot wires.

MODE FOR INVENTION

(5) Reference will now be made in detail to exemplary embodiments of a method and apparatus for cutting toughened glass according to the present invention in conjunction with the accompanying drawings, so that a person skilled in the art to which the present invention relates could easily put the present invention into practice.

(6) Throughout this document, reference should be made to the drawings, in which the same reference numerals and symbols 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 in the case that the subject matter of the present invention is rendered unclear.

(7) FIG. 1 is a schematic flowchart illustrating an exemplary embodiment of a method of cutting toughened glass according to the present invention.

(8) Referring to FIG. 1, the method of cutting toughened glass according to an exemplary embodiment of the present invention includes a toughening step S100, a compressive stress-reducing step S200 and a cutting step S300.

(9) At S100, a raw glass plate is toughened by generating compressive stress on the raw glass plate in order to facilitate dividing the toughened raw glass plate into unit pieces of glass having a predetermined size.

(10) The method of toughening the raw glass plate by generating compressive stress on the raw glass plate includes chemical toughening and thermal toughening. However, the method of toughening glass by generating compressive stress on the glass is applicable without being restrictive.

(11) More particularly, the toughening step according to this embodiment may be implemented as dry chemical toughening that toughens a raw glass plate by coating the surface of the raw glass plate with the slurry of an ion exchange solution in which a potassium nitrate solution and zinc oxide powder are mixed, followed by drying and subsequently heating the resultant structure.

(12) The zinc oxide powder forms a uniform film on the glass surface and is easily attached to the glass surface due to its superior spreadability. The zinc oxide powder also serves to remove impurities from potassium nitrate salt (nitric acid potassium salt). After the ion exchange, the zinc oxide powder may be easily cleaned with water.

(13) In this manner, the raw glass plate is toughened using a common firing furnace without the use of an ion exchange furnace. Accordingly, it is possible to improve the productivity of the toughened glass and prevent the characteristics of ion exchange from being dampened by impurities within the potassium nitrate solution.

(14) It is preferable that the density of the potassium nitrate solution ranges from 10 g per 100 ml water to solubility. If the density of the potassium nitrate solution is less than 10 g per 100 ml water, the density of potassium required for ion exchange becomes insufficient. Consequently, the ion exchange slows down, and a sufficient degree of compressive stress is not formed on the glass surface, such that the strength is not increased to a significant level. In contrast, if the density of the potassium nitrate solution is greater than the solubility, potassium nitrate is not sufficiently dissolved, causing localized ion exchange on the glass surface. Consequently, uniform compressive stress is not formed on the glass surface. When potassium nitrate is dissolved into water, it is preferable that the dissolving temperature is maintained at room temperature or 90 C.

(15) In addition, it is preferable that the average particle size of the zinc oxide powder is 1 m or less in order to make ion exchange uniform and improve the fluidity of a mixture solution.

(16) Furthermore, it is preferable that the amount of the zinc oxide powder mixed to 100 ml of the potassium nitrate solution ranges from 15 to 50 g. If the amount of the zinc oxide powder is less than 15 g for the 100 ml potassium nitrate solution, it is impossible to form a significant degree of compressive stress on the glass surface. In contrast, if the amount of the zinc oxide powder is greater than 50 g, the viscosity of the solution is significant. It is difficult to make the mixture solution uniform, and the glass surface is coated with an excessive amount of the slurry from the ion exchange solution.

(17) Afterwards, at S200, the compressive stress is reduced by heating portions of the toughened raw glass plate to be cut.

(18) Here, the temperature of the heat applied to the portions to be cut is equal to or higher than the transition point and is lower than the melting point of the toughened raw glass plate. It is preferable that the portions to be cut are heated to a temperature ranging from 300 to 400 C.

(19) It is preferable that the heat is applied for a short time period of 10 seconds or less.

(20) When the glass toughened with the compressive stress is heated to a temperature that is equal to or higher than the transition point and is lower than the melting point thereof in this manner, the compressive stress within the glass is reduced, thereby reducing the strength and hardness of the glass.

(21) It is preferable that the compressive strength of the portions to be cut reduced at the compressive stress-reducing step S200 is 100 MPa or less.

(22) The width of the portion to be cut is 5 mm or less, more preferably, 2 mm or less. The narrower the width of the portions to be cut is, the greater the yield of unit pieces of glass produced by the cutting is.

(23) The compressive stress-reducing step may be realized by applying heat to the portions to be cut with hot wires. Due to the application of heat with the hot wires, the width of the portions to be cut may become very small, thereby improving the yield of the unit pieces of glass.

(24) The above-described compressive stress-reducing step may be realized by an apparatus for cutting toughened glass, as illustrated in FIG. 2.

(25) Referring to FIG. 2, the apparatus for cutting toughened glass according to an exemplary embodiment of the present invention includes a substrate 100 having grooves on one surface thereof on which a toughened raw glass plate to be cut is to be seated and wires 200 disposed in the grooves.

(26) With this configuration, it is possible to simply and efficiently reduce the compressive strength of the toughened raw glass plate by seating the toughened raw glass plate on the substrate 100 on which the hot wires 200 are disposed.

(27) The grooves may be a plurality of grooves, and the hot wires 200 may be a plurality of hot wires disposed in the plurality of grooves.

(28) In this manner, it is possible to concurrently reduce the compressive stress on a plurality of portions of the toughened raw glass plate to be cut using the plurality of hot wires 200 disposed in the plurality of grooves, thereby improving productivity.

(29) The substrate 100 may be formed of heat-resistant glass since it must withstand heat from the hot wires 200.

(30) Finally, at S300, the toughened glass plate is cut along the portions to be cut, the compressive strength of which is reduced, whereby the toughened glass plate is divided into a plurality of unit pieces of glass.

(31) Although the process of cutting the portions to be cut may be carried out using a laser or a scribing device, this is not intended to be limiting. The cutting process may be carried out by a variety of other methods using, for example, a water jet.

(32) In this manner, the toughened raw glass plate is divided into unit pieces of glass by reducing compressive stress on the portions of the raw glass plate to be cut by applying heat to the portions to be cut and subsequently cutting the raw glass plate along the portions to be cut. Accordingly, it is possible to prevent defects with which the raw glass plate or the unit pieces of glass may deformed or broken due to stress caused by mechanical processing during the process of cutting the raw glass plate into the unit pieces of glass.

(33) FIG. 3 is a transmission microscopy picture of a portion cut from a raw glass plate without being heat-treated with a hot wire, and FIG. 4 is a transmission microscopy picture of a portion cut from a raw glass plate after being heat-treated with a hot wire.

(34) As illustrated in FIG. 3, the portion cut from the toughened raw glass plate without being heat-treated with the hot wire has a defect, such as breakage. In contrast, as illustrated in FIG. 4, according to an exemplary embodiment of the present invention, the portion cut from the toughened raw glass plate after being heat-treated with the hot wire is smooth and does not have a defect, such as breakage.

(35) The foregoing descriptions of the 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 present invention to the precise forms disclosed, and obviously many modifications and variations are possible for a person skilled in the art in light of the above teachings.

(36) It is intended therefore that the scope of the present invention not be limited to the foregoing embodiments, but be defined by the Claims appended hereto and their equivalents.