Method and apparatus for cutting substrate using coolant

Abstract

Disclosed is a coolant for cooling a selectively heated portion of a liquid crystal display substrate to cut the selected portion using thermal stress and a method of cutting the substrate using the same. A rapidly heated portion of the substrate is rapidly cooled using water having a high specific heat or a mixed coolant in which a material for improving characteristics of surface tension, viscosity and thermal conductivity is dissolved in water. Therefore, the cutting quality of the substrate is improved, and a cutting speed is also enhanced.

What is claimed is:  
     
         1 . A coolant for cooling a selected portion of a substrate to cut the selected portion from the substrate by applying thermal stress onto the selected portion which is previously heated, wherein the coolant has a specific heat equal to or higher than about 3.7 KJ/KgK.  
     
     
         2 . A coolant for cooling a selected portion of a substrate to cut the selected portion from the substrate by applying thermal stress onto the selected portion which is previously heated, wherein the coolant has a surface tension equal to or lower than about 73 dyn/cm.  
     
     
         3 . A coolant for cooling a selected portion of a substrate to cut the selected portion from the substrate by applying thermal stress onto the selected portion which is previously heated, wherein the coolant has a viscosity equal to lower than about 15 cP(Normal temperature).  
     
     
         4 . A coolant for cooling a selected portion of a substrate to cut the selected portion from the substrate by applying thermal stress onto the selected portion which is previously heated, wherein the coolant has a thermal conductivity equal to or higher than about 0.37 W/mK.  
     
     
         5 . A coolant for cooling a selected portion of a substrate to cut the selected portion from the substrate by applying thermal stress onto the selected portion which is previously heated, wherein the coolant has a specific heat equal to or higher than about 3.7 KJ/KgK, a thermal conductivity equal to or higher than about 0.4 W/mK, a surface tension equal to or lower than about 73 dyn/cm, and a viscosity equal to or lower than about 1.1 cP(normal temperature).  
     
     
         6 . A method of cutting a liquid crystal display (LCD) unit cell from an LCD assembly panel using a coolant, comprising the steps of: 
 heating a cutting path formed on the LCD assembly panel in which the LCD unit cell is surrounded by the cutting path; and    applying the coolant having a specific heat equal to or higher than about 3.7 KJ/KgK, a thermal conductivity equal to or higher than about 0.4 W/mK, a surface tension equal to or lower than about 73 dyn/cm, and a viscosity equal to or lower than about 15 cP, onto the heated cutting path so that the LCD assembly panel is partially cut to a predetermined depth along the cutting path.    
     
     
         7 . The method of  claim 6 , further comprising the step of sucking the coolant to remove the applied coolant from the cutting path of the LCD assembly panel.  
     
     
         8 . The method of  claim 7 , further comprising the step of heating the cutting path from which the applied coolant is removed to fully cut the LCD assembly panel along the cutting path.  
     
     
         9 . An apparatus for cutting a selected portion from a substrate, comprising: 
 a base body;    a laser beam generating member disposed at the base body, for generating a laser beam having a selected wavelength to heat the selected portion of the substrate; and    a coolant supplying member disposed at the base body, for supplying a liquid coolant to the heated portion of the substrate such that the supplied coolant stays on the substrate for a predetermined time period.    
     
     
         10 . The apparatus of  claim 9 , wherein the liquid coolant has a specific heat between about 3.7 KJ/KgK and about 4.18 KJ/KgK.  
     
     
         11 . The apparatus of  claim 10 , wherein the liquid coolant is deionized water having a specific heat of about 4.18 KJ/KgK.  
     
     
         12 . The apparatus of  claim 9 , wherein the liquid coolant is a mixture of water and at least any one selected from the group consisting of ethanol, ethylene glycol, methanol, acetone and surfactant.  
     
     
         13 . The apparatus of  claim 9 , wherein the liquid coolant has a surface tension equal to or lower than about 73 dyn/cm.  
     
     
         14 . The apparatus of  claim 9 , wherein the liquid coolant has a thermal conductivity of about 0.37 W/mK.  
     
     
         15 . The apparatus of  claim 9 , wherein the liquid coolant has a viscosity of about 1.1 cP(normal temperature).  
     
     
         16 . The apparatus of  claim 9 , further comprising: 
 a coolant sucking device for removing the supplied liquid coolant from the selected portion of the substrate; and    a cutting laser beam generating device for generating a cutting laser beam onto the selected portion from which the liquid coolant is removed, thereby cutting the selected portion from the substrate.    
     
     
         17 . The apparatus of  claim 16 , wherein the laser beam generated from the laser beam generating member has a shape of an elongate ellipse, and the cutting laser beam generated from the cutting laser beam generating device has a circular shape.  
     
     
         18 . The apparatus of  claim 16 , wherein the substrate has a virtual scribe line corresponding to the selected portion, the laser beam generating member and the cutting laser beam generating device generating the laser beam and the cutting laser beam onto the virtual scribe line, respectively.  
     
     
         19 . The apparatus of  claim 18 , wherein the substrate is a liquid crystal display (LCD) assembly panel, and the selected portion is an LCD unit cell to be cut and separated from the LCD assembly panel.