Abstract:
A panel with a blocker comprising: an upper plate, a lower plate opposite to said upper plate, a liquid crystal layer, with which a gap between the upper plate and lower plate is filled, a blocker formed on the edge of said lower plate; and a sealant formed next to said blocker, wherein the blocker separates the sealant from the liquid crystal layer. The panel of the present invention can be a LCD panel or a LCOS panel.

Description:
This application incorporates by reference of Taiwan application Serial No. 90114488, filed on Jun. 14, 2001. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates in general to a panel, and more particularly to a panel with a sealant blocker. 
   2. Description of the Related Art 
   Due to the high popularity of portable products, e.g., personal digital assistant (PDA) and cellularphone, the display technology develops rapidly. By employing a silicon plate, a glass plate, and liquid crystal molecules, a LCOS (liquid crystal on silicon) panel is more compact and has higher resolution than the traditional liquid crystal display (LCD), in which liquid crystal molecules are filled between two glass plates. 
     FIG. 1  is a cross section of a single pixel on a reflective-type LCOS. The LCOS has a lower plate  102  and an upper plate  101 . The lower plate  102  includes a silicon substrate  103 , and further includes a thin film transistor (TFT)  106 , a capacitor  108 , a pixel electrode  110 , scan lines  107 , data lines  111 , and a reflective layer  112  on the silicon substrate  103 , wherein the scan lines  107  are parallel to each other and so are the data lines  111 . The upper plate  101  includes a glass substrate  120  and an opaque electrode  118 , such as ITO electrode, on the glass substrate  120 . 
   The upper plate  101  and the lower plate  102  are opposite to each other, and the gap between the two plates is filled with liquid crystal molecules. The liquid crystal molecules with spacers  132  constitutes a liquid crystal layer  114 . A sealant  130  is next to the liquid crystal layer  114 . The sealant  130  is used to connect the upper plate  101  and the lower plate  102 , and the spacer  132  is used to support the spacing of the gap. The spacer  132  can be formed by direct spraying. To distinguish photo spacers from the other spacers, the photo spacers are labeled as  132 (2), and the other spacers are labeled as  132 (1). 
   The driving circuit of LCOS applies a voltage signal to the pixel electrode  110  to control the operations of each pixel by enabling scan lines  107  and data lines  111 . The polarization of the light passing through the liquid crystal layer  114  is modulated by the alignment of the liquid crystal molecules in the liquid crystal layer  114 , which varies with the voltage applied to the pixel electrode  110 . After the incident ray (labeled as I in  FIG. 1 ) passes through the liquid crystal layer  114 , the reflected ray (labeled as O in  FIG. 1 ) is produced by the reflective layer  112  and passes through a polarizing film (not shown in  FIG. 1 ). The polarized reflected ray O has the brightness corresponding to the voltage applied to the pixel electrode  110 . 
   Another method to form a uniform gap, which is more commonly used now a days, is to apply a long-shaped photo spacer in the spacing between the pixels. Referring to  FIG. 2 , it shows a cross-sectional view of LCOS with long-shaped photo spacer  205  before the upper plate  201  and the lower plate  202  are compressed. The manufacturing of the upper plate  201  and the lower plate  202  are completed respectively. The lower plate  202  has the long-shaped photo spacers  205 , extending upwardly and including an optical fiber therein. Then, a sealant  203  is also formed on the periphery of the lower plate  202 . The upper plate  201  and the lower plate  202  are aligned to each other and are compressed towards each other. After the compressing of the upper plate  201  and the lower plate  202 , the width of the gap can be sustained to be uniform by the long-shaped photo spacer  205 . 
   Referring to  FIG. 3 , it shows a LCOS with the liquid crystal molecules filled in cell room  304  of each pixel. The cell room  304  is the spacing separated by the long-shaped photo spacer  305 . After the compressing, liquid crystal molecules are injected into the cell rooms  304  and the manufacturing of the LCOS is completed. 
   However, the sealant utilized in  FIG. 2  and  FIG. 3  will contaminate the liquid crystal molecules in the peripheral cell room  304 (1), which is disposed on the edge of the lower plate  302 . And the polluted and un-polluted liquid crystal molecules will have different alignments, although the voltage signals applied to the pixel electrodes are the same. Therefore, the display quality on the panel edge is not consistent with the other area of the panel. 
   Furthermore, a hot pressing process is needed to cure the sealant to seal the upper plate and the lower plate tightly. The high temperature of the hot pressing process on the devices of the upper plate and the lower plate, and shortens the panel lifetime. 
   Moreover, the structure of the LCOS is easily destroyed by the hot pressing process due to the different coefficient of expansion for the sealant, upper plate, and lower plate. So that the residual stress will decrease the yield of the LCOS. 
   Also, a UV gel, which is a substitute of the sealant  303 , is cured by irradiating UV light and does not have the disadvantages caused by the hot pressing process. However, the liquid crystal molecules are polluted more seriously by the UV gel than by the sealant, which limits the using of the UV gel in the traditional method. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to provide a panel without the issues of sealant pollution, residual stress, and lifetime shortening. The present invention provides a panel with a blocker and the panel comprises an upper plate, a lower plate, and a liquid crystal layer. The lower plate is opposite to the upper plate, and the blocker is formed on the edge of the lower plate, wherein a sealant is formed in the blocker. The liquid crystal layers, with which a gap between the upper plate and lower plate is filled, are separated from the sealant by the blocker. 
   The blocker comprises a blocking plate positioned between the sealant and the liquid crystal layer. Another embodiment comprises an inner blocking plate and an outer blocking plate, wherein the sealant is positioned between the outer blocking plate and the inner blocking plate. The panel of the present invention can be a LCD or a LCOS panel. 
   Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a single pixel on a reflective-type LCOS in a cross-sectional view according to a traditional method. 
       FIG. 2  shows a cross-sectional view of LCOS with long-shaped photo spacer before the upper plate and the lower plate are compressed by another traditional method. 
       FIG. 3  shows a LCOS with the liquid crystal molecules filled in cell rooms according to another traditional method. 
       FIG. 4A  shows that a blocker is applied before the formation of a sealant according to a preferred embodiment of the present invention. 
       FIG. 4B  shows that a sealant is formed on the lower plate according to a preferred embodiment of the present invention. 
       FIG. 4C  shows that liquid crystal molecules are filled in the cell rooms according to a preferred embodiment of the present invention. 
       FIGS. 5A˜5E  show the various configurations of blocking plates. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The technical feature of the invention is the application of a blocker on the lower plate to prevent the contamination of the liquid crystal molecules by the sealant in the manufacturing processes of liquid crystal on silicon (LCOS). 
   Referring to  FIG. 4A , it shows that a blocker is applied before the formation of a sealant according to a preferred embodiment of the present invention. The blocker  403  comprises two blocking plates  406 . The blocker  403  is positioned on the periphery of the lower plate  402 , and photo spacers  405  are positioned on the other area of the lower plate  402 . The blocker  403  and photo spacers  405  can be formed on the lower plate  402  concurrently. The cell rooms  410  are the spacing separated by the photo spacers  405 . A trench is formed between the two blocking plates  403 . The blocker  403  and the photo spacers  405  are formed within the same photo step of semiconductor manufacturing. 
   Referring to  FIG. 4B , it shows that a sealant is formed on the lower plate  402  according to a preferred embodiment of the present invention. After the formation of photo spacers  406  and the blocker  403 , a sealant  407  is coated between the two blocking plates  406 . The two blocking plates  406  can support the sealant  407  and limit the sealant  407  within the trench. Then, the upper plate  401  and the lower plate  402  are aligned to each other and are compressed. Without the photo fiber applied in the traditional method, the blocking plates  406  of the present invention does not need adding the photo fiber into the sealant  407 . 
   Referring to  FIG. 4C , it shows that liquid crystal molecules  408  are filled in the cell rooms. After the upper plate  401  and the lower plate  402  are compressed, liquid crystal molecules  408  are filled in the cell rooms  410  of the pixels. The liquid crystal molecules  408  have no contact with the sealant  407  and will not be polluted by the sealant  407 , which accordingly improves the image quality of the LCOS. 
   The sealant  407  of the present invention can be also a UV gel because the contamination issue is solved. Moreover, the application of UV gel also does not have the disadvantages of the device lifetime shortening and the residual stress as in the hot pressing process. 
   Please referring to  FIGS. 5A˜5E , they show various configurations of the blocking plates. Besides the two blocking plates  406  of rectangle shape as in  FIG. 4A , two blocking plates  503 (1),  503 (2) of trapezoidal shape shown in  FIG. 5A  are also applicable, wherein the blocking plate  503 (1) is an inner blocking plate and the blocking plates  503 (2) is an outer blocking plate. 
   In  FIG. 5B , the length of the outer blocking plate  504 (2) is shorter than that of the inner blocking plate  504 (1), wherein the inner blocking plate  504 (1) separates the sealant  508  from the liquid crystal molecules, and the outer blocking plate  504 (2) can allow the surplus sealant overflow when the upper plate and the lower plate are compressed together. The same structure is designed in  FIG. 5C , except that the blocking plates  505 (1),  505 (2) are of trapezoidal shape. 
   In  FIG. 5D , the blocker has only one inner blocking plate  506  of rectangular shape, which separates the sealant  508  from the liquid crystal molecules, and also allows the surplus sealant overflow during the compressing of the upper plate and the lower plate. Similarly as in  FIG. 5E , the inner blocking plate  507  can be of trapezoidal shape. 
   The photo spacer, blocker, and sealant can be formed as in general semiconductor process, and the blocker of the present invention is applicable in LCOS structure and other liquid crystal display (LCD) structure. The advantages are described as follows. 
   First, the problem that the liquid crystal molecules are contaminated by the sealant is prevented from the formation of the blocker. The blocker at least comprises a blocking plate positioned between the sealant and the pixel to block the contacting of sealant from the liquid crystal molecules. 
   Second, the process that a photo fiber is formed in the sealant is reduced and the process of forming a blocker does not need extra process steps, wherein the blocker has the function to support the sealant and is formed in the same process step when the photo spacer is formed. Therefore, no extra process cost is needed. 
   Third, the applicability of UV gel in the present invention solves the problems of lifetimes shortening and residual stress, which is caused by the hot pressing process. The UV gel is simply cured by irradiating a UV ray, which causes no heating reaction in the upper plate, lower plate and the devices. So, the yield of the display is increased. 
   While the invention has been described by way of examples and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.