Patent Publication Number: US-2015062490-A1

Title: Backlight unit and liquid crystal display device including same

Description:
TECHNICAL FIELD 
     The present invention relates to a backlight unit (BLU) of a liquid crystal display, and more particularly, to a backlight unit capable of improving optical efficiency of a liquid crystal display and a liquid crystal display including the backlight unit. 
     BACKGROUND ART 
     In general, a liquid crystal display is composed of a liquid crystal panel converting various items of electric image information into video information, using a change in transmittance of a liquid crystal due to an applied voltage, and a backlight unit supplying light to the liquid crystal panel. A plurality of liquid crystal pixels in the liquid crystal panel is composed of R, G, and B subpixels that make red (R), green (G), and blue (B) images, respectively, and R, G, and B color filters are disposed on the fronts of the subpixels. 
     In LCDs of the related art, most of the power of white light from a backlight unit is lost by a polarizing sheet and a color filter on the front and rear of liquid crystal pixels, and the aperture ratio of liquid crystal pixels and only light of about 5 to 10% comes outside the liquid crystal panel, so there is a problem in that the optical energy efficiency of the LCDs is considerably low. Accordingly, it is an important matter to improve the optical energy efficiency of the LCDs, for strengthening competitiveness of the LCDs and saving energy. In particular, the color filter causes a large amount of loss of power of the LCDs by making the most loss of light, because its transmittance of light is only about 30%. 
     For this reason, an FSC (Field Sequential Color) technology is one of the technologies that are being developed to increase the optical energy efficiency of the LCDs. The technology, which has been made to remove the color filter having much of the loss of optical energy, uses three of R, G, and B LEDs as the light sources of backlight, separates a screen image signal into three of R, G, and B image signals, sequentially and quickly spreads the R-image signal, the G-image signal, and the B-image signal to a liquid crystal panel while an R-LED, a G-LED, and a B-LED are turned on, respectively to enable an observer to feel a color image. 
     Although the FSC LCD technology has been considerably progressed by many researches, because it does not need subpixels and color filters and its light transmittance efficiency is improved, there is a need of about six times the speed of a circuit adjusting images in comparison to the existing common LCDs and there are problems such as flickering and color break-up of moving images, so it has not been made practicable yet. 
     Taira et al. have attempted to implement an LCD without a color filter by separating a white light source into red, green, and blue, using a diffraction grating, and by sending them into red, green, and blue color filters, using a lenticular lens. His technology, which is a technology basically for removing the color filters in a liquid crystal panel, needs an angle correction device having a complicated structure due to a problem with the traveling angle of light separated by a diffraction grating and is difficult to manufacture because its structure is too complicated. 
     The applicant(s) of the present invention has made applications of “Liquid crystal display without color filter” (Registration No. 10-0993695, US2009/0262280) and “Liquid crystal display” (10-1033071), which increase efficiency of liquid crystal. Those patents have direct type structures and there is a problem in that the thickness of the backlight unit increases and a diffusion layer is required in the liquid crystal panels. 
     The present invention has been made to improve the light transmittance of an LCD using new optical structure and principle for solving the problems of Taira, as described above, and the main problems in “Liquid crystal display” (10-1033071). 
     DISCLOSURE 
     Technical Problem 
     The present invention has been made in an effort to solve the problems and an object of the present invention is to provide a backlight unit of a liquid crystal display which can improve light transmittance efficiency by using a light guide plate or a direct type backlight, which are easily manufactured with a simple structure, and by arranging a lenticular lens array or a color-matching sheet with RGB subpixels or RGB color filters, between a three-color light source array and a liquid crystal panel so that RGB lights are matched and travel into the RGB subpixels and the RGB color filters, and which can improve optical energy efficiency by having optical design and arrangement according to obtained color-matching conditions. 
     Technical Solution 
     According to the present invention for achieving the objects, there is provided a backlight unit that is disposed under a liquid crystal panel including a plurality of subpixels corresponding to three color lights, respectively, and radiates three color of red, green, and blue lights. The backlight unit includes: a light guide plate that guides light, using internal total reflection; a plurality of short wavelength light sources that are disposed on a side of the light guide plate and emit short wavelength lights into the light guide plate; a three-color light source array that is disposed on the bottom or the top of the light guide plate and includes a plurality of color conversion materials exciting the short wavelength lights from the short wavelength light sources into red or green or blue; and a lenticular lens array sheet that is disposed between the three-color light source array and the liquid crystal panel and focuses the three color lights radiated from the three-color light source array into the subpixels. 
     Further, the present invention provides a backlight unit that is disposed under a liquid crystal panel including a plurality of subpixels corresponding to three color lights, respectively, and emits three color of red, green, and blue lights. The backlight unit includes: a transparent substrate; a straight three-color self-light emitting source array that is disposed on the bottom or the top of the transparent substrate, emits red, green, and blue, and is sequentially arranged; and a lenticular lens array that is disposed between three-color self-light emitting source array and the liquid crystal panel and focuses the three color lights emitted from the three-color self-light emitting source array into the subpixels. 
     Further, the present invention provides a backlight unit that is disposed under a liquid crystal panel including a plurality of subpixels corresponding to three color lights, respectively, and emits three color of red, green, and blue lights. The backlight unit includes: a light guide plate that guides light, using internal total reflection, and has a scattering pattern that scatters light with regular intervals, on the bottom; a plurality of short wavelength light sources that are disposed on a side of the light guide plate and emitting short wavelength lights into the light guide plate; and a color-matching sheet that is disposed between the light guide plate and the liquid crystal panel, converts light radiated from the light guide plate into three color lights, and refracts the three color lights into the subpixels. 
     Further, the present invention provides a backlight unit that is disposed under a liquid crystal panel including a plurality of subpixels corresponding to three color lights, respectively, and emits three color of red, green, and blue lights. The backlight unit includes: a diffusion plate that diffuses light; a plurality of short wavelength light sources that are disposed under the diffusion plate and radiating short wavelength lights to the diffusion plate; and a color-matching sheet that is disposed between the diffusion plate and the liquid crystal panel, converts light radiated from the diffusion plate into three color lights, and refracts the three color lights into the subpixels. 
     Advantageous Effects 
     The backlight unit according to the present invention and the liquid crystal display including the backlight unit have the following effects. 
     First, it is possible to improve light transmission efficiency of a liquid crystal liquid display by using a backlight unit that spreads red, green, and blue lights directly onto subpixels and color filters corresponding to red, green, and blue, respectively, using a three-color light source array corresponding to three of red, green, and blue light sources. 
     Second, since the lenticular lens array sheet and the color-matching sheet which have simple structures are used, they can be easily manufactured. 
     Third, since the R, G, B three color lights are produced by using R, G, B phosphors or R, G, B quantum dots which receive UV LED light and emit R, G, B light as the three-color light source array, it is possible to maintain a simple structure and achieve high efficiency. 
     Fourth, since R and G color lights are produced by using a blue (B) LED and phosphors or quantum dots, respectively, emitting red (R) and green (G) by receiving light from the blue (B) LED, and blue color light is produced by scattering a blue light through a scattering pattern, it is possible to maintain a simple structure and achieve high efficiency. 
     Fifth, since a light source array such as R, G, B OLEDs or R, G, B quantum dots are used as the three-color light source array, instead of LEDs, it is possible to simplify the structure of the light sources and keep all of advantages of a liquid crystal display and a light source array, such that it is possible to achieve high efficiency and image quality. 
     Sixth, since R, G, B lights are supplied to the R, G, B subpixels, it is possible to remove R, G, B color filters. Further, it may be possible to keep the color filters in order to reduce color crosstalk between adjacent pixels and stabilize the image quality. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view illustrating a first embodiment of the present invention. 
         FIG. 2  is a perspective view of  FIG. 1 . 
         FIG. 3  is a view illustrating an application example of the first embodiment of the present invention. 
         FIG. 4  is a view illustrating a color conversion material and a three-color light source array. 
         FIG. 5  is a view illustrating a second embodiment of the present invention using an OLED or a quantum dot (QD) as a three-color light source. 
         FIG. 6  is an application example of  FIG. 5 . 
         FIG. 7  is a view illustrating a third embodiment of the present invention. 
         FIG. 8  is a view illustrating a fourth embodiment of the present invention. 
         FIG. 9  is a perspective view illustrating color-matching sheets illustrated in  FIGS. 7 and 8 . 
     
    
    
     BEST MODE 
     Hereinafter, exemplary embodiments of the present invention will be described with reference to accompanying drawings. The terms and words used in the present specification and claims should not be interpreted as being limited to typical meanings or dictionary definitions, but should be interpreted as having meanings and concepts relevant to the technical scope of the present invention based on the rule according to which an inventor can appropriately define the concept of the term to describe most appropriately the best method he or she knows for carrying out the invention. 
     A backlight unit according to the present invention and a liquid crystal display using the backlight unit will be described in detail with reference to drawings. 
       FIG. 1  is a view illustrating a first embodiment of the present invention,  FIG. 2  is a perspective view of  FIG. 1 ,  FIG. 3  is a view illustrating an application example of the first embodiment of the present invention, and  FIG. 4  is a view illustrating a color conversion material and a three-color light source array. 
     Referring to  FIG. 1 , a backlight unit is composed of a liquid crystal panel  1100  and a backlight under the liquid crystal panel  1100 , the backlight is composed of a light guide plate  1200 , blue LEDs, as short wavelength light sources  1300 , disposed on a side of the light guide plate  1200  and radiating light into the light guide plate  1200 , a three-color light source array  1400  including RGB color conversion materials  1410  ( 1410 R,  1410 G,  1410 B) sequentially disposed in parallel under the light guide plate  1200 , and a white light reflection layer  1600 . 
     The liquid crystal panel  1100  is composed of subpixels  1110  ( 1110 R,  1110 G,  1110 B) or color filters  1120  ( 1120 R,  1120 G,  1120 B), a front glass substrate  1130 , and a rear glass substrate  1160 , and a lenticular lens array sheet  1500  to be described below is composed of a lens transparent substrate  1510  and lenticular lenses  1520  disposed in series on the lens transparent substrate  1510 . 
     The color conversion materials  1410  ( 1410 R,  1410 G,  1410 B) are composed of RGB phosphors, RGB quantum dots (QD), and a white scattering material, of combinations of them. When a blue LED is used as the short wavelength light source  1300 , the color conversion materials  1410  ( 1410 R,  1410 G,  1410 B) sequentially disposed in parallel may be a red phosphor, a green phosphor, and a white phosphor, or may be composed of a red quantum dot, a green quantum dot, and a white quantum scatterer. The blue can be obtained simply from scattering of the white scatterer. 
     The lenticular lens array  1500  is disposed between the light guide plate  1200  and the liquid crystal panel  1100  and may be integrally formed on the light guide plate  1200 . 
     The three-color light source array  1400  including the RGB color conversion materials  1410  ( 1410 R,  1410 G,  1410 B) sequentially disposed in parallel, the lenticular lens sheet  1520  of the lenticular lens array sheet  1500 , and the RGB subpixels  1110  or the RGB color filters  1120  of the liquid crystal panel  1100  should be arranged along the same colors. 
     A blue light (for example, 470 nm of wavelength) from the blue LED that is the short wavelength light source  1300  generates RGB lights by hitting against the RGB color conversion materials  1410  ( 1410 R,  1410 G,  1410 B) sequentially disposed in parallel on a straight line on the bottom of the light guide plate  1200  while traveling through the light guide plate  1200  by total reflection. 
     The light traveling downward in the red, green, and blue lights generated by the blue light emitted from the blue LED and traveling into the color conversion materials  1410  ( 1410 R,  1410 G,  1410 B) reflects from the white reflection layer  1600  under the light guide plate  1200  and fully travels up toward the liquid crystal panel  1100 . There is little optical difference, if the blue LED is replaced by a blue LD (Laser Diode). 
     The white reflection layer  1600  may be a separate sheet or may be coated integrally on the bottom of the light guide plate  1200 . The red, green, and blue lights are sent into the red, green, and blue subpixels  1110 R,  1110 G,  1110 B or the RGB color filters  1120 , respectively, in the liquid crystal panel  1100  by the lenticular lens array sheet  1500  at the upper portion, thereby increasing transmittance. 
     In  FIG. 1 , the light from any one color conversion material (for example,  1410 G) is uniformly diffused in all directions, the light  1910  vertically traveling upward is collected by the lenticular lenses  1520  vertically arranged and travels into the lower liquid crystal pixel  1110 G or the color filter  1120 G vertically disposed and having the same color, but the light  1920  diffused in another direction becomes a lost light that does not contribute to improving the transmittance or travels into the other subpixels  1110 R,  1110 B and color filters  1120 R,  1120 B which have different colors, thereby decreasing the image quality. In order to guide the light  1920  diffused in another direction into the lower liquid crystal pixel  1110 G or the color filter  1120 G which has the same color, the thickness t 1  of the light guide plate  1200 , the thickness t 2  of the lenticular lens array sheet  1500 , the vertical gap t 3  between the liquid crystal panel  1110  and the backlight unit, and the thickness t 4  of the rear glass substrate  1160  of the liquid crystal panel  1100  should be set to satisfy a color-matching condition. 
     A horizontal displacement A generated when the light  1920  coming out of any color conversion material (for example,  1410 G) at an angle passes through the light guide plate  1200  and the lenticular lens array sheet  1500 , a horizontal displacement B generated when the light passes through the vertical gap t 3  between the liquid crystal panel  1100  and the backlight unit, and a horizontal displacement C generated when the light passes through the rear glass substrate  1160  of the liquid crystal panel  1100  are given as follows, 
         A =( t   1   +t   2 )tan Φ
 
         B=t   3  tan θ
 
         C=t   4  tan Φ
 
     where Snell&#39;s law of sin θ=n sin Φ (n is a refraction ratio) is applied. The color-matching condition is that the sum W of A, B, and C should be three times the period P of the subpixels  1110  or the color filters  1120  at the point where the light  1920  coming out at an angle reaches the lower liquid crystal pixel  1110 G or the color filter  1120 G. 
     That is, 
         W=A+B+C=mP  ( m =a multiple of three)  (color-matching condition 1)
 
       Or 
       ( t   1   +t   2   +t   4 )tan Φ+ t   3  tan θ= mP  ( m =a multiple of three)
 
     when the above mathematical relationships are satisfied, the light  1920  coming out at an angle also travels into the lower liquid crystal pixel  1110 G or the color filter  1120 G which has the same color (for example, G), so it contributes to improving the light transmittance. 
     The method of satisfying the color-matching condition can be achieved by adjusting the thickness t 1  of the light guide plate  1200 , the thickness t 2  of the lenticular lens array sheet  1500 , the vertical gap t 3  between the liquid crystal panel  1110  and the backlight unit, and the thickness t 4  of the rear glass substrate  1160  of the liquid crystal panel  1100  to coincide with the color-matching condition. In particular, once the thicknesses of the light guide plate  1200 , the lenticular lens array sheet  1500 , and the rear glass substrate  1160  of the liquid crystal panel  1100  are determined, it is difficult to change them, so the vertical gap t 3  between the liquid crystal panel  1110  and the backlight unit can be set as follows to satisfy the color-matching condition, when the liquid crystal panel  1100  and the backlight unit are combined. 
     
       
         
           
             
               t 
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                    
                   
                       
                   
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     As a detailed example, for a Full HD LCD of 47 inches, the color-matching condition is satisfied by setting t 3 =0.99 mm, using m=3, P=0.18 mm, t 1 =1 mm, t 2 =0.2 mm, and t 4 =0.9 mm. 
       FIG. 2  is a perspective view of  FIG. 1 , blue LEDs that are the short wavelength light sources  1300  are disposed on a side of the light guide plate  1200 , a three-color light source array  1400  ( 1400 R,  1400 G,  1400 B) is sequentially disposed on the bottom of the light guide plate  1200 , and the lenticular lens array sheet  1500  is disposed on the top of the light guide plate  1200 . The liquid crystal panel  1100  is disposed over the backlight unit composed of the light guide plate  1200  and the lenticular lens array sheet  1500 . Polarizing films attached on the outer sides of the front glass substrate  1130  and the rear glass substrate  1160  of the liquid crystal panel  1100  are not illustrated in the figure. The short wavelength light sources  1300  may be disposed on both left and right sides of the light guide plate  1200 . 
     In  FIGS. 1 ,  2 , and  4 , although the three-color light source array  1400  ( 1400 R,  1400 G,  1400 B) is disposed on the bottom of the light guide plate  1200 , the three-color light source array  1400  ( 1400 R,  1400 G,  1400 B) may be disposed on the top of the light guide plate  1200 . 
       FIG. 3  is a view illustrating such an application example. Referring to  FIG. 3 , the three-color light source array  1400  ( 1400 R,  1400 G,  1400 B) is disposed on the top of the light guide plate  1200  and a plurality of blue LEDs that are short wavelength light sources  1300  are disposed on a side of the light guide plate  1200 . When the lights from the blue LEDs hit against the red, green, and blue light change materials  1410  ( 1410 R,  1410 G,  1410 B), red, green, and blue lights are emitted in several directions. 
     The color-matching condition in  FIG. 3  is as follows. 
         A=t   1′  tan θ
 
         B=t   2′  tan Φ+ t   3′  tan θ
 
         C=t   4′  tan Φ
 
     In the color-matching condition, the displacement W of an inclined light of the lower liquid crystal pixel  1110  is given as follows. 
         W=A+B+C=mP  ( m =a multiple of three)  (color-matching condition 2)
 
     The color-matching condition 2 can be expressed as follows. 
       ( t   4′   +t   2′ )tan Φ+( t   1′   +t   3′ )tan θ= mP  ( m =a multiple of three)
 
     The light  1930  vertically emitted toward to the liquid crystal panel  1100  from any one color conversion material (for example,  1410 G) travels into the lower liquid crystal pixel  1110 G or the color filter  1120 G which have the same color by the lenticular lens  1520 , thereby having high transmittance. Further, the light  1940  emitted upward at an angle is refracted on the surfaces of the lenticular lens  1520  and the liquid crystal panel  1100  arranged in accordance with the color-matching condition and also travels into the lower liquid crystal pixel  1110 G or the color filter  1120 G which has the same color, thereby contributing to increasing light transmittance. 
     In order to prevent that about 50% of the lights emitted from the RGB color conversion materials  1410  ( 1410 R,  1410 G,  1410 B) travels downward and causes a loss of light and deterioration of image quality, a right-angled prism array  1700  is disposed on the bottom of the light guide plate  1200 . The right-angled prism array  1700  is composed of a plurality of right-angled prisms  1710  on the bottom of the light guide plate  1200  and a reflection layer  1720  selectively coated on the bottoms of the right-angled prisms  1710 . The light  1950  emitted downward reflects twice from the right-angled prism array  1700 , returns to the initial position, and travels into the lower liquid crystal pixel  1110 G of the same color or the color filter  1120 G, thereby contributing to improving light transmittance. 
     Although the same as the structure of  FIG. 1  or  FIG. 3 , the blue LEDs may be replaced by near ultraviolet LEDs (for example, wavelength of 405 nm). In this case, the RGB color conversion materials  1410  ( 1410 R,  1410 G,  1410 B) may be sequentially arranged in accordance with the colors of RGB phosphors or RGB quantum dots, without a white scatterer. The optical structure or the color-matching condition is the same as those in  FIG. 1  or  FIG. 3 . 
       FIG. 4  illustrates a more detailed structure of the three-color light source array  1400  ( 1400 R,  1400 G,  1400 B) illustrated in  FIG. 1  or  FIG. 3 . In general, since the lights from the short wavelength light sources  1300  on the side decrease in while traveling through the light guide plate  1200 , for uniformity of the red, green, and blue lights emitted from the three-color light source array  1400  ( 1400 R,  1400 G,  1400 B), RGB phosphors are disposed in a fine pattern, the pattern density of the RGB color conversion materials  1410  ( 1410 R,  1410 G,  1410 B) is increased in the area close to the short wavelength light sources  1300 , and the pattern density of the RGB color conversion materials  1410  ( 1410 R,  1410 G,  1410 B) is increased or the pattern size of the RGB color conversion materials  1410  ( 1410 R,  1410 G,  1410 B) is gradually increased in the area far away from the short wavelength light sources  1300 , thereby obtaining uniform fluorescence. 
     MODE FOR INVENTION 
     Hereinafter, other embodiments of the present invention will be described with reference to the accompanying drawings. 
       FIG. 5  illustrates a second embodiment applied from the first embodiment of the present invention. Referring to  FIG. 5 , a backlight unit under a liquid crystal panel  2100  is composed of a lenticular lens array sheet  2500 , a transparent substrate  2200 , a three-color self-light emitting source array  2300  or a three-color quantum array. 
     In  FIG. 5 , RGB OLEDs or RGB quantum dots for the three-color self-light emitting source array  2300  are excited by a current applied from electrodes on the top and the bottom and emit red, green, and blue lights. 
     An encapsulation  2600  blocking water vapor or oxygen is required, when the RGB OLEDs are used for the three-color self-light emitting source array  2300 . Three color lights from the RGB OLEDs travels into RGB subpixels  2110  or RGB color filters  2120 , respectively, in the liquid crystal panel  2100  by lenticular lenses  2520 , thereby increasing transmittance. 
     In  FIG. 5 , similarly, it is possible to satisfy the color-matching condition described with reference to  FIG. 1  and improve light transmittance by adjusting the thickness t 11  of the transparent substrate  2200 , the thickness t 12  of the lenticular lens array sheet  2500 , the vertical gap t 13  between the liquid crystal panel  2100  and the backlight unit, and the thickness t 14  of a rear glass substrate  2160  of the liquid crystal panel  2100 . 
       FIG. 6  is an application example of the present invention of  FIG. 5 . The difference from  FIG. 5  is that the three-color self-light emitting source array  2300  is disposed on a substrate and the lenticular lens array sheet  2500  is disposed between the liquid crystal panel  2100  and the three-color self-light emitting source array  2300 , but the optical principle is the same as that in  FIG. 5 . The structure of  FIG. 6  is the same as the application example of the first embodiment illustrated in  FIG. 3 , except that the three-color light source array  1400  ( 1400 R,  1400 G,  1400 B) is replaced by the three-color self-light emitting source array  2300 , so the color-matching condition is applied in the same way as the color-matching condition 2. 
       FIGS. 7 and 8  illustrate a third embodiment and a fourth embodiment of the present invention. 
       FIG. 7  illustrates a structure in which a color-matching sheet  3500  is disposed between a backlight unit having a light guide plate  3200  and a plurality of short wavelength light sources  3300 , and a liquid crystal panel  3100 . The short wavelength light sources  3300  for backlight are blue LEDs or ultraviolet LEDs. 
     The blue lights from the blue LEDs, which are the short wavelength light sources  3300 , totally reflect in the light guide plate  3200  and then are diffused by a diffusion pattern  3210  under the light guide plate  3200  or reflected from a reflection sheet  3220  under the light guide plate  3200 , such that their illuminance is made more uniform and the viewing angle is adjusted by a diffusion sheet  3600  or a light-concentrating sheet  3700 , and then the lights travel into the color-matching sheet  3500 . The structure of the light-concentrating sheet  3700  usually has the type of a prism sheet having the structure of a prism array or the type of a micro lens array sheet having a micro lens array. 
       FIG. 8  illustrates the structure of a fourth embodiment applied from the third embodiment illustrated in  FIG. 7 , in which a color-matching sheet  4500  is disposed between a liquid crystal panel  4100  and a direct type backlight having short wavelength light sources  4300 , without the light guide plate  3200 . 
     The short wavelength light sources  4300  are blue LEDs or ultraviolet LEDs. The blue lights from the blue LEDs that are the short wavelength light sources  4300  travel into the color-matching sheet  4500 , after the illuminance is made more uniform and the viewing angle is adjusted by the diffusion plate  4200 , the diffusion sheet  4600 , and the light-concentrating sheet  4700 . 
       FIG. 9  illustrates the detailed structure and the optical principle of the color-matching sheets  3500  and  4500  used in the third embodiment and the fourth embodiment. The color-matching sheets  3500  and  4500  are composed of transparent substrates  3510  and  4510 , lenticular lens arrays  3520  and  4520 , and three-color fluorescent material arrays  3530  and  4530 , respectively, and may additionally include reflection color filters  3540  and  4540 . 
     In the color-matching sheets  3500  and  4500 , the lenticular lens arrays  3520  and  4520  are disposed on the transparent substrates  3510  and  4510 , the straight three-color fluorescent material arrays  3530  and  4530  are disposed with the same gaps as the lenticular lens arrays  3520  and  4520  on the bottom of the transparent substrates  3510  and  4510 . 
     The three-color fluorescent material arrays  3530  and  4530  are composed of a plurality of fluorescent materials  3530  ( 3530 R,  3530 G,  3530 B) exciting the short wavelength lights from the short wavelength light sources  14300  into red, or green, or blue, and the reflection color filters  3540  and  4540  filtering the light traveling into the three-color fluorescent materials arrays  3530  and  4530  may be additionally provided under the three-color fluorescent material arrays  3530  and  4530 . 
     Reflection layers  3534  and  4534  reflecting the light traveling into the transparent substrates  3510  and  4510  are disposed between the fluorescent materials  3530  ( 3530 R,  3530 G,  3530 B) of the three-color fluorescent material arrays  3530  and  4530 . 
     The three-color fluorescent material arrays  3530  and  4530  are arranged with the same colors as the color filters  3210  and  4120  of the liquid crystal panels  3100  and  4100  in the color-matching sheets  3500  and  4500 , and the lenticular lens arrays  3520  and  4520  are arranged in the same period and sequence as the subpixels  3110  and  4110  or the color filters  3120  and  4120 . 
     The principle of the color-matching sheets  3500  and  4500  contributing to improving transmittance of the liquid crystal panels  3100  and  4100  is as follows. When the blue lights from the blue LEDs that are the short wavelength light sources  3300  and  4300  are made uniform by the light guide plate  3200 , or the diffusion plate  3200  and the diffusion sheet  3600  and  4600 , and the light-concentrating sheets  3700  and  4700 , and sent upward into the color-matching sheets  3500  and  4500 , the three-color fluorescent material arrays  3530  and  4530  emit red, green, and blue in the arrangement order by the blue lights. 
     Since the lights traveling into the color-matching sheets  3500  and  4500  are blue lights, the blue fluorescent material  3532   b  in the three-color fluorescent material arrays  3530  and  4530  may be a white scatterer simply for scattering or may be left transparent in this case. The produced red, green, and blue lights are concentrated by the lenticular lenses of the lenticular lens array  3530  and  4520 , respectively, and travel into the red, green, and blue color filters  3120  and  4120  in the liquid crystal panels  3100  and  4100 , such that the light transmittance of the liquid crystal panels  3100  and  4100  is increased. When ultraviolet LEDs are used as light sources, red, green, and blue fluorescent materials are used for the three-color fluorescent material arrays  3530  and  4530 . 
     When the relationship equations of the thicknesses t 21 ,t 31  of the color-matching sheets  3500  and  4500 , the gaps t 23 ,t 33  between the color-matching sheets  3500  and  4500  and the liquid crystal panels  3100  and  4100 , and the thicknesses t 24 ,t 34  of the rear glass substrates  3160  and  4160  of the liquid crystal panels  3100  and  4100 , and an incident angle θ, and a refraction angle Φ, satisfy the following equations, 
     
       
      
       W=A+B+C=uP  
      
     
       or, 
       ( t   21   +t   24 )tan Φ+ t   23  tan θ= uP  ( u =a multiple of three)  (color-matching condition 3)
 
     the highest light transmittance is achieved,
 
where,
 
         A=t   21  tan Φ
 
         B=t   23  tan θ
 
         C=t   24  tan Φ
 
     sin θ=n sin Φ Snell&#39;s law  sin θ=n sin Φ is satisfied and n is the refraction ratio of the rear glass substrates  3160  and  4160  and the transparent substrates  3510  and  4510 . 
     In the color-matching condition 3, the thicknesses t 21  of the color-matching sheets  3500  and  4500 , the gaps t 23  between the color-matching sheets  3500  and  4500  and the liquid crystal panels  3100  and  4100 , and the thicknesses t 24  of the rear glass substrates  3160  and  4160  of the liquid crystal panels  3100  and  4100  are expressed on the basis of the third embodiment, but the color-matching condition 4 of the fourth embodiment is also the same as the color-matching condition of the third embodiment, so the detailed description is not provided. 
     The red, green, and blue fluorescent lights from the three-color fluorescent material arrays  3530  and  4530  uniformly travel up and down, so it is possible to further improve the light transmittance by additionally disposing the refraction color filters  3540  and  4540 , which transmit the blue light passes and reflect the red and green lights, close to the bottoms of the color-matching sheets  3500  and  4500 . The reflection color filter  3540  and  4540  may be integrally combined with the color-matching sheets  3500  and  4500 . 
     Some of the blue lights traveling into the color-matching sheet  3500  and  4500  reflect from the reflection layers  3534  and  4534 , and the reflecting lights are recycled by reflecting again from the light guide plate  3200  or the reflection sheets  3220  and  4800  under the diffusion plate  4200 , and then travel back into the three-color fluorescent material arrays  3530  and  4530 . A phosphor, a quantum dot, and a white scattering bead may be used for the fluorescent materials of the three-color fluorescent material arrays  3530  and  4530 . 
     Accordingly, it is possible to improve light transmission efficiency of a liquid crystal liquid display by using a backlight unit that spreads red, green, and blue lights directly onto subpixels or color filters corresponding to red, green, and blue, respectively, using a three-color light source array corresponding to three of red, green, and blue light sources. 
     Although the present invention has been described with reference to the exemplary embodiments illustrated in the drawings, those are only examples and may be changed and modified into other equivalent exemplary embodiments from the present invention by those skilled in the art. Therefore, the technical protective scope of the present invention should be determined by the scope described in claims. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be used for the backlight unit (BLU) of liquid crystal displays (LCD).