Abstract:
A color filter device includes a transparent substrate, a phosphor layer, and a color filter layer. The phosphor layer is provided on the transparent substrate to transform incoming light having a short wavelength into white light having a broad range of wavelengths. The color filter layer is provided on the transparent substrate and has multiple filter sections for filtering the white light to generate desired light components of primary colors.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    (a) Field of the Invention 
         [0002]    The invention relates to a color filter device, and particularly to a color filter device for a display using a short-wavelength (10 nm-490 nm) light source as its backlight source. 
         [0003]    (b) Description of the Related Art 
         [0004]      FIG. 1  shows a schematic diagram illustrating a conventional color filter device. As shown in  FIG. 1 , the conventional color filter device  100  includes a glass substrate  102 , a color filter layer  104 , and an overcoat layer  106 , where the color filter layer  104  and the overcoat layer  106  are sequentially provided on the glass substrate  102 . The color filter layer  104  includes a red filter section  104   a , a green filter section  104   b , a blue filter section  104   c , and a black matrix  104   d  provided between two neighboring filter sections for shielding light in the peripheries of sub-pixels. Each of the filter sections is distinguished by a different color of an organic pigment. When white light  108  transmits through the color filter layer  104 , lights with different colors, such as red light  110 , green light  112  and blue light  114 , can be filtered out. By adjusting the intensities of the lights with different colors, a desired displaying color is shown after mixing these lights. 
         [0005]    Recently, in the design of using light emitting diodes (LED) as a backlight source in combination with a light guide plate to transform a point or linear light source to a planar light source, the color of the light entering a color filter device depends on the color of the light irradiated from the light emitting diodes. Under the circumstance, since the light incident to the color filter layer  104  needs to be white light, white light emitting diodes are always used for an LED backlight module of a color display. However, the cost of the white light emitting diode is high. It has a great demand in using an LED having a short wavelength (10 nm-490 nm) for the LED backlight source, such as a blue LED or an ultraviolet LED, so as to lower the fabrication cost and to increase the intensity and the color temperature of transmission light in a color display. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    Hence, an object of the invention is to provide a color filter device capable of coupling with a backlight source with a short wavelength in a display for not only increasing the intensity and the color temperature of transmission light in a color display to improve light transformation efficiency but also lowering the fabrication cost. 
         [0007]    According to the invention, a color filter device includes a transparent substrate, a phosphor layer, and a color filter layer. The phosphor layer provided on the transparent substrate transforms incoming light having a short wavelength (10 nm-490 nm) into white light having a broad range of wavelengths. The color filter layer provided on the transparent substrate has multiple filter sections for filtering the white light to generate multiple light components of primary colors. 
         [0008]    Through the design of the invention, by integrating a phosphor layer into the color filter device, a low cost LED with a short wavelength (10 nm-490 nm), such as a blue LED or an ultraviolet LED, can be used as a backlight source instead of an expensive white LED without the need of additional manufacturing processes and facilities. Therefore, the design of the invention not only lowers the fabrication cost of a backlight module but also increases the intensity and the color temperature of transmission light in a color display due to the short-wavelength LED so as to improve the light transformation efficiency. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The features and advantages of the invention are illustrated by way of example and are by no means intended to limit the scope of the invention to the particular embodiments shown, and in which: 
           [0010]      FIG. 1  shows a schematic diagram illustrating the design of a conventional color filter device. 
           [0011]      FIG. 2  shows a schematic diagram illustrating an embodiment of the invention. 
           [0012]      FIG. 3  shows an example of transforming blue light to white light by Ce activated yttrium aluminum garnet (YAG). 
           [0013]      FIG. 4  shows an example of transforming ultraviolet light having wavelength of 300 nm to white light by inorganic luminescent materials. 
           [0014]      FIG. 5  shows a schematic diagram illustrating another embodiment of the invention. 
           [0015]      FIG. 6  shows a schematic diagram illustrating another embodiment of the invention. 
           [0016]      FIG. 7  shows a schematic diagram illustrating another embodiment of the invention. 
           [0017]      FIG. 8  shows a schematic diagram illustrating another embodiment of the invention. 
           [0018]      FIG. 9  shows a schematic diagram illustrating another embodiment of the invention. 
           [0019]      FIG. 10  shows a schematic diagram illustrating another embodiment of the invention. 
           [0020]      FIG. 11  shows a schematic diagram illustrating another embodiment of the invention, where a color filter device is used in a four-color LCD having red, green, blue, and white sub-pixels. 
           [0021]      FIG. 12  shows a schematic diagram illustrating another embodiment of the invention, where a color filter device is used in a four-color LCD having red, green, blue, and white sub-pixels. 
           [0022]      FIG. 13  shows a schematic diagram illustrating another embodiment of the invention, where a color filter device is used in a four-color LCD having red, green, blue, and white sub-pixels. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]      FIG. 2  shows a schematic diagram illustrating a color filter device  10  according to an embodiment of the invention. As shown in  FIG. 2 , the color filter device  10  includes a transparent substrate  12 , a color filter layer  14 , a phosphor layer  16 , and an overcoat layer  18 . The transparent substrate  12  is a glass substrate and has a light-receiving surface  12   a  facing a backlight module  20  and a light-transmitting surface  12   b  opposite to the light-receiving surface  12   a . According to this embodiment, the color filter layer  14 , the phosphor layer  16 , and the overcoat layer  18  are provided sequentially on the light-receiving surface  12   a  of the transparent substrate  12 . Note that, as used in the specification and the appended claims, the meaning of the phrase “layer A is provided on layer B” is not limited to a direct contact between the upper layer A and the lower layer B. For instance, in an embodiment where laminates are interposed between the upper layer A and the lower layer B is encompassed within the scope of the phrase “layer A is provided on layer B”. 
         [0024]    The color filter layer  14  includes red, green, and blue filter sections  14   a ,  14   b , and  14   c , and a black matrix  14   d  provided between two neighboring filter sections for shielding light in the peripheries of sub-pixels. Each of the filter sections is distinguished by a different color of an organic pigment, and the phosphor layer  16  is formed from a mixture of phosphorescent materials and binder materials. 
         [0025]    According to the invention, by including the phosphor layer  16  in the color filter device  10 , the light from the backlight module  20  incident to the color filter device  10  is not limited to white light. The phosphorescent materials of the phosphor layer  16  can be the materials absorbing visible light, as the light from the backlight module  20  is visible light. For example, when the light from the backlight module  20  is blue visible light (about 400 nm-490 nm), the materials of the phosphor layer  16  can be inorganic luminescent materials that are excited by blue light, such as the following:
   1. yttrium aluminum garnet (YAG);   2. terbium aluminum garnet (TAG);   3. sulfides, such as MGa 2 S 2  and ZnS;   4. aluminates, such as SrAl 2 O 4 ;   5. halides, such as Ca 10 (PO 4 ) 6 Cl 2 ;   6. rare earth borates, such as YBO 4 .   
 
         [0032]    These compounds are mixed with a trace element of activation metal to have fluorescent excitation effects. The activation metal element may be cerium (Ce), europium (Eu), terbium (Tb), bismuth (Bi), or manganese (Mn). The materials for the phosphor layer  16  may also be organic luminescent materials, such as organic pigments or organic dyes. The fluorescence characteristic of the organic luminescent material depends on the number and the positions of its functional groups and the effect of the trace element. When the blue light from the backlight module  20  transmits through the phosphor layer  16 , a portion of the blue light is absorbed by the luminescent material and the rest of the blue light mixes with the yellow light emitted from the luminescent material to produce white light.  FIG. 3  shows a spectrum illustrating an example of transforming blue light to white light by Ce activated yttrium aluminum garnet (YAG). As shown in  FIG. 3 , the emitting spectrum includes a narrow band and a broad band, where the major peaks are at the blue LED emitting peak with a wavelength of 460 nm and at the YAG luminescence peak with a wavelength of 550 nm. After transformation, the white light transmits through the color filter layer  14  to filter out lights with different colors, such as red light  24 , green light  26  and blue light  28 . By adjusting respective intensities of the lights with different colors, a desired displaying color can be shown after mixing these lights. 
         [0033]    Further, the light from the backlight module  20  is not limited to visible light. For example, the light source of the backlight module  20  may be an ultraviolet LED. When the incident light is ultraviolet light (about 10 nm-380 nm) that has higher energy compared with the white light, the afore-mentioned organic or inorganic luminescent materials may also transform the ultraviolet light to the white light. In addition, silicates and vanadates also have the same functionality. Alternatively, the materials of the phosphor layer  16  may include red, green and blue phosphor materials that would respectively emit red, green and blue lights, if excited. After the red, green and blue phosphor materials with specific contents are excited by ultraviolet light, the emitted red, green and blue lights are mixed together to produce white light.  FIG. 4  shows a spectrum illustrating an example of transforming ultraviolet light having a wavelength of 300 nm to white light by inorganic luminescent materials. In this case, the light transformation efficiency as well as the white light emitting efficiency is increased, since the ultraviolet light possesses high energy. 
         [0034]    Through the design of the invention, by integrating a phosphor layer  16  into the color filter device  10 , a low cost LED with a short wavelength (10 nm-490 nm), such as a blue LED or an ultraviolet LED, can be used as a backlight source instead of an expensive white LED, without the need of additional manufacturing processes and facilities. Therefore, the design of the invention not only lowers the fabrication cost of a backlight module but also increases the intensity and the color temperature of transmission light in a color display due to the short-wavelength LED so as to improve the light transformation efficiency. 
         [0035]      FIG. 5  shows a schematic diagram illustrating another embodiment of the invention. According to the invention, the relative positions of a color filter layer, a phosphor layer, and an overcoat layer are not limited. For example, as shown in  FIG. 5 , the color filter device  30  is formed by sequentially forming the phosphor layer  16 , the color filter layer  14  and the overcoat layer  18  on the light-transmitting surface  12   b  rather than the light-receiving surface  12   a  of the transparent substrate  12 . 
         [0036]      FIG. 6  shows a schematic diagram illustrating another embodiment of the invention. As shown in  FIG. 6 , the phosphor layer  17  in the color filter device  32  is formed from a mixture of phosphorescent materials, binder materials, and surface-protecting materials such as polyacrylate, so that the phosphor layer  17  also functions as a surface-protecting layer. 
         [0037]      FIG. 7  shows a schematic diagram illustrating another embodiment of the invention. According to the invention, the color filter layer and the phosphor layer are not limited to be provided on the same side of the transparent substrate  12 . Referring to  FIG. 7 , in the color filter device  34 , the phosphor layer  16  is provided on the light-receiving surface  12   a  of the transparent substrate  12  to transform visible blue light or ultraviolet light into white light, while the color filter layer  14  is provided on the light-transmitting surface  12   b  of the transparent substrate  12  to filter out red light  24 , green light  26 , and blue light  28 . 
         [0038]      FIG. 8  shows a schematic diagram illustrating another embodiment of the invention. In all the above embodiments, the phosphor layer  16  is a planar phosphor layer covering the filter sections  14   a ,  14   b  and  14   c  and the black matrix  14   d . However, the distribution of the phosphor layer  16  according to the invention is not limited. As shown in  FIG. 8 , the phosphor layer  16  in the color filter  36  is formed in multiple separate regions, each of which is positioned corresponding to only one filter section  14   a ,  14 b or  14   c , and two adjacent phosphor regions are spaced apart by the black matrix  14   d , with a overcoat layer  18  covering all the phosphor regions. 
         [0039]      FIG. 9  shows a schematic diagram illustrating another embodiment of the invention. In the case of forming the phosphor layer  16  in multiple separate regions, the positions of the separate phosphor regions formed on the transparent substrate  12  are not limited according to the invention. As shown in  FIG. 9 , the separate regions of the phosphor layer  16  in the color filter device  38  are provided on the light-transmitting surface  12   b  of the transparent substrate  12  without the formation of the overcoat layer  18 . 
         [0040]      FIG. 10  shows a schematic diagram illustrating another embodiment of the invention. As shown in  FIG. 10 , in the color filter device  40 , when the incident light is selected as blue visible light, a transparent light-transmitting section  14 e can be provided to replace both the blue filter section  14   c  and the potion of the phosphor layer  16  corresponding to the blue filter section  14   c , because the blue visible light  22  can be directly output without the need of transformation and then mixed with the output red light  24  and green light  26  to display color images. Moreover, the manner of forming the transparent light-transmitting section  14   e  is not limited. For example, the light-transmitting section  14   e  that allows for direct transmission of the blue visible light may be formed as an opening with removal of any materials, or formed as an enclosed space filled with transparent materials. 
         [0041]      FIG. 11  shows a schematic diagram illustrating another embodiment of the invention, where a color filter device  42  is used in a four-color LCD having red, green, blue, and white sub-pixels. Referring to  FIG. 11 , the color filter layer  14  of the color filter device  42  further includes multiple transmissive non-color sections  14   e  besides the red, green and blue filter sections  14   a ,  14   b  and  14   c  to provide white sub-pixels capable of enhancing the panel brightness of a display. According to this embodiment, the phosphor layer  16  provided on the light-receiving surface  12   a  of the transparent substrate  12  transforms incident blue light or ultraviolet light  22  into white light, and then the color filter layer  14  provided on the light-transmitting surface  12   b  of the transparent substrate  12  filters out red light  24 , green light  26  and blue light  28  by the different filter sections and meanwhile outputs the white light  29  via the non-color sections  14   e  to enhance panel brightness. 
         [0042]      FIG. 12  shows a schematic diagram illustrating another embodiment of a color filter device  44  used in a four-color LCD. Referring to  FIG. 12 , the phosphor layer  16  are provided in separate regions respectively corresponding to the positions of the red, green and blue filter sections  14   a ,  14   b  and  14   c  and the transmissive non-color sections  14   e . In this embodiment; the phosphor layer  16  and the color filter layer  14  are provided on the light-transmitting surface  12   b  of the transparent substrate  12 , as shown in  FIG. 12 ; alternatively, they may be provided on the light-receiving surface  12   a  of the transparent substrate  12 , as shown in  FIG. 13 . Besides, it can be seen the position of the separate phosphor region corresponding to the transmissive non-color section  14   e  can be altered, as illustrated in the different embodiments shown in  FIGS. 12 and 13 . 
         [0043]    While the invention has been described by way of examples and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.