Abstract:
An exemplary LCD device ( 2 ) includes a liquid crystal panel ( 23 ), a light source ( 25 ), and a polarizer ( 24 ). The polarizer has a multilayer structure having a polarizing layer ( 245 ) and a light guide layer ( 247 ). The polarizer is adjacent to a main face of the liquid crystal panel. The light source is disposed adjacent to a peripheral edge of the light guide layer. The light source and the polarizer cooperate to provide a substantially planar light source to illuminate the liquid crystal panel.

Description:
FIELD OF THE INVENTION  
       [0001]    The present invention relates to liquid crystal display (LCD) devices, and particularly to an LCD device with a polarizer having a light guide layer. 
       BACKGROUND 
       [0002]    A typical liquid crystal display device is capable of displaying a clear and sharp image through thousands or even millions of pixels that make up the complete image. The liquid crystal display has thus been applied to various electronic equipment in which messages or pictures need to be displayed, such as mobile phones and notebook computers. However, liquid crystal in the liquid crystal display does not itself emit light. Rather, the liquid crystal has to be lit up by a light source so as to clearly and sharply display text and images. The light source may be ambient light, or a backlight module attached to the liquid crystal display. 
         [0003]      FIG. 5  is a schematic, exploded, side view of a conventional LCD device. The LCD device  1  includes an LCD panel  11  and a backlight module  19 . The backlight module  19  is arranged under the LCD panel  11  in order to provide sufficient light beams to the LCD panel  11 . Thereby, the LCD panel  11  is able to display images. 
         [0004]    The LCD panel  11  includes a top polarizer  12 , a bottom polarizer  14 , and a liquid crystal (LC) panel  13 . The top polarizer  12  and the bottom polarizer  14  are attached to two outer surfaces of the LC panel  13  that are at opposite sides of the LC panel  13 . 
         [0005]    The backlight module  19  includes a light source  15 , a light guide plate (LGP)  16 , and a reflective plate  17 . The LGP  16  includes a light incident surface  161 , a top light emitting surface  162  adjoining the light incident surface  161 , and a bottom surface  163  also adjoining the light incident surface  161 . The bottom surface  163  includes a plurality of pattern dots  160  thereat. The pattern dots  160  are in the form of recesses. The light source  15  is disposed adjacent to the light incident surface  161  of the LGP  16 . The reflective plate  17  is disposed adjacent to the bottom surface  163 . The LCD panel  11  is disposed adjacent to the light emitting surface  162 . 
         [0006]    Also referring to  FIG. 6 , this is an enlarged, side view of part of the bottom polarizer  14 . The bottom polarizer  14  includes an adhesive layer  141 , a top protective layer  143 , a polarizing layer  145 , and a bottom protective layer  147 . The adhesive layer  141 , the top protective layer  143 , the polarizing layer  145 , and the bottom protective layer  147  are arranged in that order from top to bottom. The top polarizer  12  has a structure similar to that of the bottom polarizer  14 . 
         [0007]    Light beams emitted by the light source  15  enter the LGP  16  through the light incident surface  161 . Most of the light beams are reflected at the pattern dots  160  of the LGP  16 , and then transmit through the light emitting surface  162 . Some of the light beams transmit out of the LGP  16  through the bottom surface  163 , and then are reflected back into the LGP  16  by the reflective plate  17 . These light beams then also transmit through the light emitting surface  162 . All the light beams passing through the light emitting surface  162  illuminate the LCD panel  11 . Thereby, the LCD panel  11  is able to display images. 
         [0008]    The LCD device  1  includes the LCD panel  11  and the backlight module  19 . The backlight module  19  in particular is typically quite thick, and adds significantly to the overall thickness of the LCD device  1 . That is, the LCD device  1  typically occupies much space. This means the LCD device  1  cannot be used in certain applications and environments which are space critical. 
         [0009]    Accordingly, what is needed is an LCD device that can overcome the above-described deficiencies. 
       SUMMARY 
       [0010]    An exemplary LCD device includes a liquid crystal panel, a light source, and a polarizer. The polarizer has a multilayer structure having a polarizing layer and a light guide layer. The polarizer is adjacent to a main face of the liquid crystal panel. The light source is disposed adjacent to a peripheral edge of the light guide layer. The light source and the polarizer cooperate to provide a substantially planar light source to illuminate the liquid crystal panel. 
         [0011]    Another exemplary LCD device includes a liquid crystal panel, a light source, and an optical film. The optical film includes a light guide layer configured for guiding and converting light beams emitted from the light source to a substantially planar light source, and a polarizing layer configured for polarizing light of the substantially planar light source such that the polarized light illuminates the liquid crystal panel. 
         [0012]    Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, all the views are schematic. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is an exploded, side cross-sectional view of an LCD device according to a first embodiment of the present invention, the LCD device including a bottom polarizer and a light source, essential optical paths also being shown. 
           [0014]      FIG. 2  is an enlarged view of the light source and part of the bottom polarizer of the LCD device of  FIG. 1 . 
           [0015]      FIG. 3  is an exploded, side cross-sectional view of an LCD device according to a second embodiment of the present invention, the LCD device including a polarizer, essential optical paths also being shown. 
           [0016]      FIG. 4  is an enlarged view of part of the polarizer of the LCD device of  FIG. 3 . 
           [0017]      FIG. 5  is an exploded, side cross-sectional view of a conventional LCD device, the LCD device including a bottom polarizer, essential optical paths also being shown. 
           [0018]      FIG. 6  is an enlarged view of part of the bottom polarizer of the LCD device of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0019]    Reference will now be made to the drawings to describe embodiments of the present invention in detail. 
         [0020]    Referring to  FIG. 1 , this is an exploded, side view of an LCD device according to a first embodiment of the present invention. The LCD device  2  includes a top polarizer  22 , an LC panel  23 , a bottom polarizer  24 , a reflective plate  27 , and a light source  25 . The top polarizer  22 , the LC panel  23 , the bottom polarizer  24 , and the reflective plate  27  are arranged in that order from top to bottom. The light source  25  is disposed at one side edge of the bottom polarizer  24 . The light source  25  can for example be a light emitting diode (LED) or a cold cathode fluorescent lamp (CCFL). The LC panel  23  can be a transmission type LC panel or a transflective type LC panel. 
         [0021]    Also referring to  FIG. 2 , this is an enlarged, side view of the light source  25  and part of the bottom polarizer  24 . The bottom polarizer  24  includes an adhesive layer  241 , a top protective layer  243 , a polarizing layer  245 , a diffusion layer  246 , and a bottom protective light guide layer  247 . The adhesive layer  241 , the top protective layer  243 , the polarizing layer  245 , the diffusion layer  246 , and the bottom protective light guide layer  247  are arranged in that order from top to bottom. The bottom protective light guide layer  247  is used for guiding and converting light beams emitted from the light source  25  to a substantially planar light source. When the substantially planar light eventually emits from the adhesive layer  241 , the substantially planar light illuminates the LC panel  23 . 
         [0022]    The bottom protective light guide layer  247  includes a top boundary  262  adjacent to the diffusion layer  246 , a light incident surface  261  adjoining the top boundary  262 , and a bottom surface  263 . The bottom surface  263  includes a plurality of pattern dots  260  thereat. In the illustrated embodiment, the pattern dots  160  are in the form of recesses. The light source  25  is disposed adjacent to the light incident surface  261 . 
         [0023]    The polarizing layer  245  is made of a polyvinyl alcohol (PVA) film, which has ductility and optical polarity. The top protective layer  243  and the bottom protective light guide layer  247  are made of material with characteristics of high light transparence, water resistance, and mechanical strength; for example, triacetyl cellulose (TAC), or the like. In one embodiment, the light source  25  is an LED, which typically has a thickness (i.e. height) of 0.35 mm. The bottom protective light guide layer  247  has a thickness corresponding to that of the light source  25 . That is, the thickness of the bottom protective light guide layer  247  is typically 0.35 mm or a little more than 0.35 mm. With the ongoing progress of light source technology, it is believed that the thickness of the light source  25  may be less than 0.35 mm. Whatever the thickness of the light source  25 , the bottom protective light guide layer  247  should be correspondingly thick in order to work well with the light source  25 . 
         [0024]    A typical method of making the bottom polarizer  24  includes the following steps. Iodine ions are permeated into a PVA film. The PVA film is heated and then stretched, so that the iodine ions are rotated and become oriented in a same direction. This ensures that light beams transmitting through the PVA film can be polarized. Then the diffusion layer  246  is attached on one surface of the PVA film. The top protective layer  243  is coated on the other surface of the PVA film, and the bottom protective light guide layer  247  is coated on the diffusion layer  246 , in order to protect the PVA film and prevent the PVA film from shrinking. Finally, the adhesive layer  241  is pasted on the top protective layer  243 . 
         [0025]    Light beams emitted by the light source  25  enter the bottom protective light guide layer  247  though the light incident surface  261 . Most of the light beams are reflected at the pattern dots  260  of the bottom protective light guide layer  247 , and then transmit through the top boundary  262  to the diffusion layer  246 . Some of the light beams transmit out of the bottom protective light guide layer  247  through the bottom surface  263 , and then are reflected back into the bottom protective light guide layer  247  by the reflective plate  27 . These light beams then also transmit through the top boundary  262  to the diffusion layer  246 . All the light beams transmitting to the diffusion layer  246  eventually illuminate the LC panel  23 , which can thereby display images. 
         [0026]    In alternative embodiments, the pattern dots  260  at the bottom surface  263  can have other suitable shapes, as long as the pattern dots  260  can provide reflection of light beams with an incident angle larger than a critical angle, and provide refraction of light beams with an incident angle less than the critical angle. 
         [0027]    In summary, the bottom polarizer  24  of the LCD device  2  includes the bottom protective light guide layer  247 . The bottom protective light guide layer  247  is capable of guiding and converting the light beams emitted from the light source  25  to a substantially planar light source, which eventually illuminates the LC panel  23  for displaying of images. With this configuration, the LCD device  2  does not need an LGP. This means an overall thickness of the LCD device  2  is reduced, so that the LCD device  2  is more compact and occupies less space. 
         [0028]    Referring to  FIG. 3 , an LCD device  3  according to a second embodiment of the present invention includes a polarizer  32 , an LC panel  33  arranged under the polarizer  32 , and a light source  35  disposed at one side edge of the polarizer  32 . The LC panel  33  is a reflection type LC panel. The light source  35  is, in general, an LED or a CCFL. 
         [0029]    Also referring to  FIG. 4 , this is an enlarged, side view of part of the polarizer  32 . The polarizer  32  includes a top protective light guide layer  321 , a polarizing layer  322 , a bottom protective layer  323 , and a retardation film  324 . The top protective light guide layer  321 , the polarizing layer  322 , the bottom protective layer  323 , and the retardation film  324  are arranged in that order from top to bottom. The top protective light guide layer  321  is used for achieving a substantially planar light source for the LC panel  33 , which can thereby display images. The retardation film  324  causes phase retardation of light beams passing therethrough. The retardation film  324  can for example be a quarter wave plate or a half wave plate. 
         [0030]    The top protective light guide layer  321  includes a bottom boundary  362  adjacent to the polarizing layer  322 , a light incident surface  361  adjoining the bottom boundary, and a top surface  363  adjoining the light incident surface  361 . The top surface  363  defines a plurality of elongate grooves  360  thereat. Each of the grooves  360  is substantially parallel to the light incident surface  361 . All the grooves  360  have the same configuration. In particular, each groove  360  has a generally V-shaped configuration as viewed from a lateral side of the LCD device  3 . Each groove  360  is bounded by two face portions of the top surface  363 . Ridges of the top surface  363  between the grooves  360  are coplanar. The common plane shared by the ridges is perpendicular to the light incident surface  361 . For each groove  360 , an absolute value of an angle of a first one of the face portions nearer to the light incident surface  361 , relative to a plane parallel to the light incident surface  361 , is less than an absolute value of an angle of the other second face portion farther from the light incident surface  361 , relative to the same plane parallel to the light incident surface  361 . Thus, the first face portion and the second face portion have different sizes. 
         [0031]    The grooves  360  can provide reflection of light beams that transmit up thereto when such light beams have an incident angle at the top surface  363  which is greater than a critical angle. These reflected light beams transmit back down in the top protective light guide layer  321 . The grooves  360  can also provide separation of light beams with an incident angle less than the critical angle. These light beams are separated into two parts. One part of the light beams are reflected and transmit to other grooves  360 . The other part of the light beams are refracted and transmit out from the top surface  363  of the polarizer  32 . 
         [0032]    Thus in operation of the LCD device  3 , light beams emitted by the light source  35  transmit into the top protective light guide layer  321  through the light incident surface  361  and substantially reach the grooves  360 . Then some of the light beams are reflected back down in the top protective light guide layer  321  and transmit down through the polarizer  32 . Other of the light beams are reflected and transmit to other grooves  360  to be re-utilized. Still other of the light beams are refracted and transmit out from the top surface  363  of the polarizer  32 . The light beams transmitting down through the polarizer  32  eventually illuminate the LC panel  33 , for displaying of images by the LCD device  3 . 
         [0033]    In summary, the polarizer  32  has the top protective light guide layer  321 . The top protective light guide layer  321  is capable of guiding and converting the light beams emitted from the light source  35  to a substantially planar light source, which eventually illuminates the LC panel  33  for displaying of images. With this configuration, the LCD device  3  does not need an LGP. This means an overall thickness of the LCD device  3  is reduced, so the LCD device  3  is more compact and occupies less space. 
         [0034]    It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.