Patent Publication Number: US-2006017878-A1

Title: Method for repairing white spots in liquid crystal display panel

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a method of repairing defective spots on a liquid crystal display panel. More particularly, the present invention relates to a method of using micro-lens technique to repair white spots in a liquid crystal display panel.  
      2. Description of the Related Art  
      In recent years, there are a number of breakthroughs in the manufacturing of display devices such as computer monitors and televisions. In compared with a cathode ray tube (CRT), a liquid crystal display (LCD) has gradually become one of the mainstream display products in the market since the advantages of low operating voltage, low power consumption, no radiation, light weight, thin thickness and compact package.  
      However, due to a variety of technological limitations, the screen size of a liquid crystal display devices is limited to be below 30 inches. For a larger size display panel such as a screen size between 30 to 60 inches, the plasma display panel (PDP) is a potential candidate. However, the high cost of the production the plasma panel display renders other types of display devices such as a projection display device to be more economical and feasible. A variety of reflective projection display devices, for example, such as liquid crystal display (LCD), digital light projector (DLP) and liquid crystal on silicon (LCOS), has been developed in order to reduce the cost of production of a large size display. Although the LCD and DLP devices are still the dominant devices of the displays in the mean while, the liquid crystal on silicon (LCOS) has great potential for future development. In general, the LCOS display has a low cost of production, a high opening rate (up to 90%) and a high resolution (a pixel pitch down to 12 μm). With these advantages, a lot of display device manufacturers are actively engaged in the development of related technologies to prevail in the micro-display market.  
      As to both of the liquid crystal display (LCD) device and the liquid crystal on silicon (LCOS) display device, a liquid crystal display panel is required. In the manufacturing process of a liquid crystal display panel, a major factor affecting the yield of the display quality is the generation of defect spots. The so-called defect spots are the constant bright or constant dark spots on a liquid crystal display panel that can not be control and can no longer be repaired. The defect spots are typically generated in the manufacturing process of the liquid crystal display panel by various factors such as one or more particles failed on the panel, a damage caused by the electrostatic charge or the improper control of the process parameters. In general, the defect spots can be classified into white spots or dark spots. The white spots are any pixel points that show up bright no matter which type of pictures is displayed by the display screen. The white spots are revealed when the display of frame is switched to a black frame. On the other hand, the dark spots are pixel points that show up dark no matter which type of pictures is displayed by the display screen. The dark spots are revealed when the display of frame is switched to a white frame. Because the white spots are more abhorrent to user than the dark spots, the prevention of generation of the white spots during the manufacturing process is required.  
     SUMMARY OF THE INVENTION  
      Accordingly, at least one object of the present invention is to provide a method of converting the white spots on a manufactured liquid crystal display into dark spots.  
      To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a method for repairing white spots on a liquid crystal display panel and a white spot free liquid crystal display panel device. To repair the white spot on a liquid crystal display panel, a repairing spot is formed over the white spot. The repairing spot has important interference properties for absorbing, diverting or scattering the light from the white spot. Alternatively, the repairing spot may have important properties for changing the optical path and the polarity or the polarity distribution of the light from the white spot so that the light from the white spot can be blocked by an analyzera or a polarizer to convert the white spot into a dark spot.  
      In one embodiment of this invention, a method for repairing the white spots on a liquid crystal display panel is provided. The method includes detecting the presence of any white spots on a liquid crystal display panel. When a white spot is detected, a repairing spot is coated on the surface of the liquid crystal display panel above the white spot to convert the white spot into a dark spot.  
      In the method of repairing white spots on a liquid crystal display panel according to one embodiment of this invention, a material of the repairing spots for repairing white spots on a liquid crystal display panel includes an organic material.  
      In the method of repairing white spots on a liquid crystal display panel according to one embodiment of this invention, the method of converting a white spot into a dark spot includes a method of absorbing, diverging or scattering the light traveling through the white spot. In a preferred embodiment, a structure of the repairing spot includes a micro-lens structure.  
      In the method of repairing white spots on a liquid crystal display panel according to one embodiment of this invention, the method of converting a white spot into a dark spot includes a method of changing the optical path of the light traveling from the white spot through a repairing spot. After changing the optical path of the incoming light, an analyzer can convert the white spot into a dark spot. In a preferred embodiment, a structure of the repairing spot includes a micro-lens structure.  
      In the method of repairing white spots on a liquid crystal display panel according to one embodiment of this invention, the method of converting a white spot into a dark spot includes a method of changing the polarity or the polarity distribution of the light traveling from the white spot through a repairing spot. After changing the polarity or the polarity distribution of the light, a polarizer can convert the white spot into a dark spot. In a preferred embodiment, a structure of the repairing spot includes a micro-lens structure.  
      In the method of repairing white spots on a liquid crystal display panel according to one embodiment of this invention, the method of converting a white spot into a dark spot includes a method of absorbing, diverging or scattering the light reflected from the white spot. In a preferred embodiment, a structure of the repairing spot includes a micro-lens structure.  
      In the method of repairing white spots on a liquid crystal display panel according to one embodiment of this invention, the method of converting a white spot into a dark spot includes a method of changing the optical path of the light reflected from the white spot through a repairing spot. After changing the optical path of the reflected light, an analyzer can convert the white spot into a dark spot. In a preferred embodiment, a structure of the repairing spot includes a micro-lens structure.  
      In the method of repairing white spots on a liquid crystal display panel according to one embodiment of this invention, the method of converting a white spot into a dark spot includes a method of changing the polarity or the polarity distribution of the light reflected from the white spot through a repairing spot. After changing the polarity or the polarity distribution of the light, a polarizer can convert the white spot into a dark spot. In a preferred embodiment, a structure of the repairing spot includes a micro-lens structure.  
      This invention also provides a white spot free liquid crystal display panel. The method of removing the white spots on a liquid crystal display panel includes coating a repairing spot on the liquid crystal display panel above each white spot.  
      In the white spot free liquid crystal display panel according to one embodiment of this invention, a material of the repairing spots for repairing white spots on a liquid crystal display panel includes an organic material.  
      In the white spot free liquid crystal display panel according to one embodiment of this invention, the method of converting a white spot into a dark spot includes a method of absorbing, diverging or scattering the light traveling through the white spot through a repairing spot. In a preferred embodiment, a structure of the repairing spot includes a micro-lens structure.  
      In the white spot free liquid crystal display panel according to one embodiment of this invention, the method of converting a white spot into a dark spot includes a method of changing the optical path of the light traveling from the white spot through a repairing spot. After changing the optical path of the incoming light, an analyzer can convert the white spot into a dark spot. In a preferred embodiment, a structure of the repairing spot includes a micro-lens structure.  
      In the white spot free liquid crystal display panel according to one embodiment of this invention, the method of converting a white spot into a dark spot includes a method of changing the polarity or the polarity distribution of the light traveling through the white spot through a repairing spot. After changing the polarity or the polarity distribution of light, a polarizer can convert the white spot into a dark spot. In a preferred embodiment, a structure of the repairing spot has a micro-lens structure.  
      In the white spot free liquid crystal display panel according to one embodiment of this invention, the method of converting a white spot into a dark spot includes a method of absorbing, diverging or scattering the light reflected from the white spot through a repairing spot. In a preferred embodiment, a structure of the repairing spot includes a micro-lens structure.  
      In the white spot free liquid crystal display panel according to one embodiment of this invention, the method of converting a white spot into a dark spot includes a method of changing the optical path of the light reflected from the white spot through a repairing spot. After changing the optical path of the reflected light, an analyzer can convert the white spot into a dark spot. In this embodiment, the repairing spot has a micro-lens structure.  
      In the white spot free liquid crystal display panel according to one embodiment of this invention, the method of converting a white spot into a dark spot includes changing the polarity or the polarity distribution of the light reflected from the white spot through a repairing spot. After changing the polarity or the polarity distribution of light, a polarizer can convert the white spot into a dark spot. In a preferred embodiment, a structure of the repairing spot includes a micro-lens structure.  
      Accordingly, this invention provides a method of repairing white spots on a liquid crystal display (LCD) panel and a white spot free LCD panel using thereof. The method includes the steps of detecting any irreparable white spots on the liquid crystal display panel and then coating a repairing spot on the surface of the liquid crystal display panel above each white spot so that the white spots are converted into dark spots.  
      It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
       FIG. 1  is a schematic cross-sectional view illustrating the structure of a normal liquid crystal display panel.  
       FIG. 2  is a schematic cross-sectional view of a liquid crystal display panel with a white spot and a repairing structure according to one embodiment of this invention.  
       FIG. 3  is a schematic cross-sectional view illustrating the structure of a normal liquid crystal on silicon display panel.  
       FIG. 4  is a schematic cross-sectional view of a liquid crystal on silicon display panel with a white spot and a repairing structure according to one embodiment of this invention.  
       FIGS. 5A and 5B  are transparent diagrams illustrating two micro-lens structures according to one embodiment of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.  
       FIG. 1  is a schematic cross-sectional view illustrating the structure of a normal liquid crystal display panel. Referring to  FIG. 1 , a liquid crystal display panel  100  is provided. The liquid crystal display panel  100  includes a back light module  102 , a first polarizer  104 , a first compensation film  106 , a first glass  108 , a first transparent conductive layer  110  (e.g., an indium tin oxide (ITO) layer), a first poliemid layer  112 , a liquid crystal layer  114 , a second poliemid layer  116 , a second transparent conductive layer  118  (e.g., an indium tin oxide (ITO) layer), a color filter  120 , a second glass  122 , a second compensation film  124 , a second polarizer  126  and a top surface  128 . In a normal liquid crystal display panel  100 , the liquid crystal layer  114  is free from dust, particle or scratch marks. In the normal operation of the liquid crystal display panel  100 , a beam of light  130  is emitted from the back light module  102 . If the liquid crystal layer  114  is set to an opaque operating mode, the light  130  from the back light module  102  is totally blocked by the liquid crystal layer  114 . Hence, the screen of the display panel is black as shown in  FIG. 1 .  
       FIG. 2  is a schematic cross-sectional view of a liquid crystal display panel with a white spot and a repairing structure according to one embodiment of this invention. As shown in  FIG. 2 , for example, dust particles, scratch marks or impurities  240  may be disposed in the liquid crystal layer  114  during the manufacturing process. Therefore, an irreparable damage in a portion of the liquid crystal layer  114  is generated when the panel  100  is completed. When the liquid crystal layer  114  is set to an opaque operating mode, most of the light  130  from the back light module  102  is blocked. However, a portion of the light  130  may leak to the top surface  128  through the damaged region wherein the impurities  240  are located because the region only has very few liquid crystal molecules to block the light  130 . Hence, a white spot  242  is generated on the top surface  128 .  
      Accordingly, the invention provides a method of repairing the white spots on a liquid crystal display panel. After an irreparable white spot on the liquid crystal display panel is detected, a repairing spot  250  is formed on the panel above the white spot  242 . The repairing spot  250  is manufactured from an organic material having the properties that can interfere with the light  130  traveling through the white spot. In one embodiment, for example, the light  130  traveling to the white spot  242  can be absorbed by the repairing spot  250 . In another embodiment, the light  130  traveling to the white spot  242  can be refracted. In yet another embodiment, the light  130  traveling to the white spot  242  can be scattered to various directions. Furthermore, to increase the scattering efficiency and the uniformity of scattering of the light  130 , the structure of the repairing spot  250  includes a micro-lens structure.  
       FIG. 3  is a schematic cross-sectional view illustrating the structure of a normal liquid crystal on silicon display panel. As shown in  FIG. 3 , a liquid crystal on silicon (LCOS) display panel  300  is provided. The LCOS display panel  300  includes a light source  302 , a polarizer  304 , a cover glass  306 , a first transparent conductive layer  308  (e.g., an indium-tin-oxide (ITO) layer), an alignment layer  310 , a liquid crystal layer  312 , a high-reflectance metallic layer  314 , a complementary metal-oxide-semiconductor (CMOS) substrate  316  and an analyzer  318 . In a normal LCOS display panel  300 , the liquid crystal layer  312  is free from any dust, particle or scratch mark. In the normal operation of the LCOS display panel  300 , a beam of light  320  is emitted from the light source  302 . If the liquid crystal layer  312  is set to an opaque operating mode, the light  320  from the light source  302  is totally blocked by the liquid crystal molecules in the liquid crystal layer  312  and hence will not reach the high-reflectance metallic layer  314 . Hence, the light  302  no longer travels to the analyzer  318  to form an image and the screen of the display panel is black as shown in  FIG. 3 .  
       FIG. 4  is a schematic cross-sectional view of a liquid crystal on silicon display panel with a white spot and a repairing structure according to one embodiment of this invention. As shown in  FIG. 4 , dusts, particles, scratch marks or impurities  240  is disposed in the liquid crystal layer  312  during the manufacturing process. Therefore, an irreparable damage in a portion of the liquid crystal layer  312  is formed when the panel  300  is completed. When the liquid crystal layer  312  is set to an opaque operating mode, most of the light  320  from the light source  302  is blocked. However, a portion of the light  320  may leak to the analyzer  318  via the damaged region wherein the impurities  430  are located to the cover glass  306  because the damaged region contains very few liquid crystal molecules. Hence, a white spot  432  is generated on the analyzer  318 .  
      Therefore, the invention provides a method of repairing white spots on a liquid crystal on silicon (LCOS) display panel. After an irreparable white spot  432  on the LCOS display panel is detected, a repairing spot  440  is formed on the cover glass  306  of the LCOS display panel  300  above the white spot  432 . The repairing spot  440  is manufactured from an organic material having the properties that can absorb, refract or scatter the light  320 , or can change the polarity or the polarity distribution of the light  320 . Furthermore, to increase the scattering efficiency and the uniformity of scattering of the light  320 , the structure of the repairing spot  440  includes a micro-lens structure.  
       FIGS. 5A and 5B  are transparent diagrams illustrating two micro-lens structures according to one embodiment of this invention. An inscribed ellipsoidal type of micro-lens structure is shown in  FIG. 5A  and a square cushion type of micro-lens structure is shown in  FIG. 5B . The micro-lens is manufactured by using an organic material. In general, the micro-lens has at least two major functions. First, the micro-lens can absorb, diverge or scatter the light from a white spot as in a liquid crystal display panel in  FIG. 2  and a liquid crystal on silicon (LCOS) display panel in  FIG. 4 . In addition, the micro-lens is also capable of changing the optical path or the polarity or the polarity distribution of light coming from a white spot so that a polarizer or an analyzer can block the light. These functions can be utilized to convert the white spot on the liquid crystal in  FIG. 2  or the white spot on the liquid crystal on silicon display panel in  FIG. 4  into a black spot.  
      Accordingly, the invention provides a method of repairing the white spots on a liquid crystal display panel and a white spot free LCD panel using thereof. A repairing spot is formed on the surface of the liquid crystal display panel above each white spot. Furthermore, the structure of the repairing spot can includes a micro-lens structure. The repairing spot can absorb, diverge or scatter the light from the white spot. Alternatively, the repairing spot can also change the optical path or the polarity or the polarity distribution of the light from the white spot so that a polarizer or an analyzer can block the light. Hence, the white spot is converted into a dark spot.  
      It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.