KR101080098B1 - Backlight panel for backlighting a display panel - Google Patents

Abstract

Disclosed is a backlight panel for backlighting a display panel using a light emitting diode (LED). The backlight panel includes at least one LED and white LED selected from the group consisting of red LEDs, green LEDs, and blue LEDs. By using white LEDs, the brightness of the display can be enhanced.

Display, Backlight, Light Emitting Diode (LED), Phosphor

Description

Backlight panel for backlighting a display panel

1 is a schematic cross-sectional view for explaining a conventional liquid crystal display (LCD).

2 is a schematic cross-sectional view for describing a liquid crystal display according to an embodiment of the present invention.

FIG. 3A is a plan view illustrating LEDs disposed in the backlight panel of FIG. 2, and FIG. 3B is a cross-sectional view of the backlight panel taken along the line II ′ of FIG. 3A.

4 is a schematic cross-sectional view for describing a liquid crystal display according to another embodiment of the present invention.

FIG. 5A is a plan view illustrating LEDs disposed in the backlight panel of FIG. 4, and FIG. 5B is a cross-sectional view of the backlight panel taken along cut line II-II ′ of FIG. 5A.

6 is a plan view illustrating LEDs disposed on a backlight panel according to another exemplary embodiment of the present invention.

7 is a plan view illustrating LEDs disposed in a backlight panel according to another exemplary embodiment of the present invention.

Explanation of reference numerals for the main parts of the drawing

30: liquid crystal display, 32: light guide portion,                 

34: polarization filter, 36: thin film transistor array (TFT array),

38: color filter, 40: liquid crystal layer

42: transparent conductive layer, 44: polarizing filter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight panel for backlighting a display panel, and more particularly, to display brightness of a display by backlighting a display using at least one of red, green, and blue LEDs together with a white LED. It relates to a reinforced backlight panel.

Passive display devices, such as liquid crystal displays, can reflect or absorb ambient sunlight or room light to produce an image. Thus, ambient sunlight or room light is required to view the displayed image. However, there is a problem in that the displayed image cannot be viewed when the intensity of ambient sunlight or room light is not sufficient to illuminate the display panel. As an alternative to this problem, a backlight panel for backlighting the display panel is generally adopted.

The backlight panel includes a light source such as an incandescent lamp, a fluorescent lamp or a light emitting diode (LED). The light emitted from the light source illuminates the LCD panel to realize the image. On the other hand, LED is often used as a backlight light source due to its excellent color reproduction, and it is expected to increase its use in the future as it is environmentally friendly.

An example of a backlight panel using the LED as a light source is disclosed in US Patent Publication No. 2004 / 0061810A1 entitled "Backlight for a color LCD using wavelength-converted light emitting devices." Title has been disclosed by Lowery et al.

1 is a schematic partial cross-sectional view for explaining the LCD 10 disclosed in the above-mentioned US Patent Publication No. 2004 / 0061810A1.

Referring to FIG. 1, the LCD 10 includes a light emitting diode (LED) array 27. The LED array 27 consists of red, blue and green LEDs. The number of LEDs here depends on the size of the display and the brightness required. In addition, the LEDs in the LED array 27 may be aligned in line along the edge of the mixing light guide 26. The light generated by the LED array 27 is mixed with white light and reflected from the reflecting mirror 28 to the light guide 12. The white light incident on the light guide portion 12 is converted into a homogenous plane white light and output in a direction perpendicular to the upper surface of the light guide portion 12.

Meanwhile, the LCD 10 includes two glass sheets spaced apart by the liquid crystal layer 20. The glass sheet close to the LED array 27 includes a polarizing filter 14 and a thin film transistor (TFT) array 16. The polarization filter 14 linearly polarizes white light. The polarized white light is directed to the TFT array 16 having one transistor for each pixel. The liquid crystal layer 20 is positioned on the TFT array 16, and the transparent conductive layer 22 grounded on the liquid crystal layer 20 is positioned.

In addition, the glass sheet far from the LED array 27 includes a color filter 18 and a polarization filter 24. The color filter 18 may be composed of a red filter layer, a green filter layer, and a blue filter layer. The color filter 18 filters the light output from the TFT array 16 to pass only the color required for each pixel. On the other hand, the polarization filter 24 passes the light orthogonal to the light polarized by the preceding polarization filter 14.

The LCD 10 disclosed in US Patent Publication No. 2004 / 0061810A1 uses red, green, and blue LEDs as a light source, so color reproduction may be good.

However, as LCDs use color filters, the brightness of the displayed image is limited. The color filter filters about two-thirds of the light emitted from the light source and reaching the color filter.

Therefore, it is necessary to increase the power delivered to the LEDs or to use a large number of LEDs to increase the brightness of the LCD. However, the increased power can increase the heat generated in the LED, which may worsen the characteristics of the emission color. In addition, the number of LEDs that can be mounted in a limited area is limited.

An object of the present invention is to provide a backlight panel that can enhance the brightness of the display by mounting the LEDs within a limited area.

Another object of the present invention is to provide a backlight panel that can enhance the brightness of a display while ensuring color reproducibility.                         

Another object of the present invention is to provide a display device having improved brightness by adopting the backlight panel.

In order to achieve the above technical problem, the present invention provides a backlight panel for backlighting a display panel using a light emitting diode (LED). The backlight panel according to embodiments of the present invention includes at least one LED and a white LED selected from the group consisting of a red LED, a green LED, and a blue LED. The white LEDs have a spectrum of red, green and blue wavelengths. Accordingly, the brightness of the display panel may be enhanced in the limited area.

In one embodiment of the present invention, the backlight panel includes at least one LED array. The LED array includes a printed circuit board. The at least one LED and the white LED are mounted on the printed circuit board.

In addition, the backlight panel further includes a light guide plate, and the LED array is disposed at a side portion or a bottom of the light guide plate.

The backlight panel may further include a diffuser, and the LED array may be located below the diffuser. The light guide plate may be interposed between the diffuser and the LED array.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Accordingly, the invention is not limited to the embodiments described below and may be embodied in other forms. In the drawings, lengths, thicknesses, and the like of layers and regions may be exaggerated for convenience of description. Like numbers refer to like elements throughout.

2 is a schematic cross-sectional view illustrating an LCD 30 according to an embodiment of the present invention, FIG. 3A is a plan view illustrating LEDs disposed in the backlight panel of FIG. 2, and FIG. 3B is a cutout line of FIG. 3A. A cross-sectional view of the backlight panel taken along II ′.

Referring to FIG. 2, the LCD 30 includes a light emitting diode (LED) array 47. The LED array 47 includes red, blue, green and white LEDs. The white LEDs have a spectrum of red, blue and green wavelengths. The number of LEDs here depends on the size of the display and the brightness required. On the other hand, since the white LED has a spectrum of the red, blue, and green wavelengths, the LED array 47 may not include all of the red, blue, and green LEDs. That is, the LED array 47 may include a red LED, a blue LED, a green LED, or a combination thereof. The structure of the LED array 47 and the arrangement of the LEDs will be described in detail below with reference to FIGS. 3A and 3B.

The LED array 47 is disposed at the side portion of the light guide portion 32. The LED array 47 may be disposed on both side portions of the light guide portion 32, respectively. The light guide part 32 uniformly outputs the light emitted from the LEDs. A mixed light guide portion (not shown) and a reflection mirror may be interposed between the LEDs and the light guide portion, as in a conventional backlight panel. Light incident on the light guide part 32 in the LEDs is converted into a homogenous plane white light and output in a direction perpendicular to the upper surface of the light guide part 32. The structure of the light guide portion 32 is described below with reference to FIG. 3B.

Meanwhile, the LCD 30 includes two glass sheets spaced apart by the liquid crystal layer 40, as described with reference to FIG. 1. The glass sheet close to the LED array 47 includes a polarizing filter 34 and a thin film transistor (TFT) array 36. The polarization filter 34 linearly polarizes white light. The polarized white light is directed to the TFT array 36 having one transistor for each pixel. The liquid crystal layer 40 is positioned on the TFT array 36, and the transparent conductive layer 42 grounded on the liquid crystal layer 40 is positioned.

In addition, the glass sheet far from the LED array 47 includes a color filter 38 and a polarization filter 44. The color filter 38 is composed of a red filter layer, a green filter layer, and a blue filter layer. The color filter 38 filters the light output from the TFT array 36 to pass only the color required for each pixel. On the other hand, the polarization filter 44 passes the light orthogonal to the light polarized by the preceding polarization filter 34.

3A and 3B, the LED array 47 is disposed at the side surface of the light guide portion 32. As shown, the LED array 47 may be disposed on both side portions of the light guide part 32.

The LED array includes a printed circuit board 51 and LEDs 47r, 47b, 47g, 47w. Lowercase letters (r, b, g, w) in the reference numbers represent a red LED, a blue LED, a green LED and a white LED, respectively. The LEDs 47r, 47b, 47g, 47w are mounted on the printed circuit board 51 and electrically connected to the printed circuit board 51. At this time, the LEDs 47r, 47b, 47g, 47w may be connected in series, but is not limited thereto. Meanwhile, among the LEDs, the red, blue, and green LEDs 47r, 47b, and 47g may employ LED dies emitting light of red, blue, and green colors, respectively. Alternatively, the LEDs 47r, 47b, and 47g may use a light emitting diode die and a phosphor for converting light emitted from the light emitting diode die into red, blue, and green colors as a light source. For example, the red, blue, and green LEDs each employ a light emitting diode die that emits ultraviolet light as a light source, and employs phosphors that convert the light emitted from the light emitting diode die into red, blue, and green colors, respectively. can do. On the other hand, the white LED 47w includes a light emitting diode die and phosphors. The light emitting diode die may emit ultraviolet or blue light. In addition, the phosphors absorb ultraviolet light to emit light of red and green wavelengths, or absorb blue light to emit light of red, blue and green wavelengths.

The ratio of the number of LEDs can be determined so that the light emitted from the LEDs can be mixed to form uniform white light. For example, as shown in FIG. 3A, the green LEDs 47g and the white LEDs 47w are arranged in the same number, and the red LEDs 47r and the blue LEDs 47b are green. It may be arranged to be one half of the number of LEDs 47g. Alternatively, a plurality of units may be arranged using the green-red-blue-green LEDs as one unit, and the white LEDs may be arranged between the units. The arrangement of the LEDs 47r, 47g, 47b, 47w is very diverse and is not limited to any one. In addition, the red, green and blue LEDs do not all need to be included. However, the relative ratio of the LEDs 47r, 47g, 47b, 47w may be limited by color reproducibility. That is, in order to improve color reproducibility, the ratio of the LEDs 47r, 47g, 47b, and 47w may have an optimum value according to the light emission characteristics of the LEDs 47r, 47g, 47b, and 47w.

The light guide part 32 may include a light guide plate 55, and may further include a diffuser 57 and / or a brightness enhancement film (BEF) 59. The light guide plate 55 mixes the light incident from the LEDs into white light and outputs the light to the upper surface of the light guide plate 55 in a vertical direction. To this end, a reflective surface 55 is positioned below the light guide plate 55, and deformations such as ridges for reflecting light upward may be formed. Examples of such modifications have been disclosed in US Pat. Nos. 6,672,734, 6,712,481, 6,768,525, and the like. In addition, the deformation parts may be formed on an upper surface of the light guide plate 55. Lenses for outputting light within a predetermined angle may be provided on the light guide plate 55.

The LED array 47 is positioned below the edge of the light guide plate 55. In addition, the light guide plate 55 may have holes or grooves through which the LEDs may be inserted. The LEDs are inserted into the holes or grooves to laterally emit light to the light guide plate.

The diffuser 57 further mixes the light output from the light guide plate 55 to make the light more uniform. On the other hand, the brightness enhancement film 59 concentrates the light input from the light guide plate 55 within the required viewing angle to enhance the brightness of the light.

According to the above embodiment, by adding a white LED in addition to the red and / or green and / or blue LEDs, a small number of LEDs may be added in a limited area to enhance the brightness of the display panel. Meanwhile, in the present exemplary embodiment, the LED array 47 is described below the edge of the light guide part 32, but the LED array 47 may be positioned to be adjacent to the side surface of the light guide part 32. have. At this time, the upper surface of the LEDs toward the side of the light guide portion (32).

4 is a schematic cross-sectional view illustrating an LCD 60 according to another embodiment of the present invention, FIG. 5A is a plan view illustrating LEDs disposed in the backlight panel of FIG. 4, and FIG. 5B is a cutout line of FIG. 5A. A cross-sectional view of the backlight panel taken along II-II '.

Referring to FIG. 4, the LCD 60 of this embodiment includes respective layers of the same LCD panel as the LCD 30 described with reference to FIG. 2. Therefore, below, the light guide part 62 and LED array 67 of the backlight panel different from the LCD 30 of FIG. 2 are demonstrated. That is, in this embodiment, the LED array 67 is located below the light guide portion 62.

5A and 5B, a plurality of LED arrays 67 may be positioned below the light guide 62. The LED array 67 includes a printed circuit board 71 and LEDs 67r, 67b, 67g, and 67w. Lowercase letters (r, b, g, w) in the reference numbers represent red LEDs, blue LEDs, green LEDs and white LEDs, respectively, as described above. The LEDs 67r, 67b, 67g, and 67w are mounted on the printed circuit board 71 and electrically connected to the printed circuit board 71. In this case, the LEDs 67r, 67b, 67g, and 67w may be connected in series, but are not limited thereto.

The ratio of the number of LEDs can be determined so that the light emitted from the LEDs can be mixed to form uniform white light. For example, as shown in FIG. 5A, the green LEDs 67g and the white LEDs 67w are arranged in the same number, and the red LEDs 67r and the blue LEDs 67b are green. It may be arranged to be one half of the number of LEDs 67g. Alternatively, a plurality of units may be arranged using the green-red-blue-green LEDs as one unit, and the white LEDs may be arranged between the units. The method of arranging the LEDs 67r, 67g, 67b, 67w is very diverse and is not limited to any one. In addition, the red, green and blue LEDs do not all need to be included. However, the relative ratio of the LEDs 67r, 67g, 67b, and 67w may be limited by color reproducibility. That is, in order to improve color reproducibility, the ratio of the LEDs 67r, 67g, 67b, and 67w may have an optimum value according to the light emission characteristics of the LEDs 67r, 67g, 67b, and 67w.

The light guide portion 62 may include a diffuser 77 and may include a light guide plate 75 and / or a brightness enhancement film BEF 79. The light guide plate 75 mixes the light incident from the LEDs into white light and outputs the light in a direction perpendicular to the top surface of the light guide plate 75. As described with reference to FIGS. 3A and 3B, a reflecting surface is positioned below the light guide plate 75, and deformations such as ridges and lenses for reflecting light to the top may be formed. have.

Holes or grooves through which the LEDs may be inserted may be formed below the light guide plate 75. The LEDs are inserted into the holes or grooves to laterally emit light to the light guide plate.

The diffuser 77 mixes the light output from the LEDs into a uniform light. When the diffuser 77 is used, the light guide plate 75 may be omitted. At this time, the LEDs emit light toward the diffuser 77.

On the other hand, the brightness enhancement film 79 concentrates the light input from the light guide plate 75 within the required viewing angle to enhance the brightness of the light.

According to the above embodiment, by adding a white LED in addition to the red, green, and blue LEDs, a small number of LEDs may be added in a limited area to enhance the brightness of the display panel. In addition, a plurality of LEDs may be used by disposing the LED arrays 67 under the light guide 62.

 6 is a plan view illustrating LEDs disposed in a backlight panel according to another exemplary embodiment of the present invention.

Referring to FIG. 6, the above embodiment describes an LED array 67 in which the LEDs 67r, 67g, 67b, and 67w are aligned in a line on the printed circuit board 71. The LEDs 87r, 87g, 87b, 87w are arranged in a plurality of rows on the printed circuit board 91.

Here, the arrangement of the LEDs 87r, 87g, 87b, and 87w is the same as described with reference to FIGS. 5A and 5B.

Meanwhile, the LEDs 87r, 87g, 87b, and 87w may be arranged in various forms. For example, the LEDs can be arranged radially or in multiple circles. In addition, as shown in FIG. 7, they may be arranged in random order without any regular rules.

According to the present invention, it is possible to provide a backlight panel that can mount LEDs within a limited area to enhance the brightness of a display while ensuring color reproducibility.

Claims (9)

A backlight panel for backlighting a display panel using a light emitting diode (LED), Red LED; Green LED; Blue LED; And Include white LEDs, And the number of red LEDs and blue LEDs is less than the number of green LEDs, respectively. The apparatus of claim 1, further comprising at least one LED array, wherein the LED array comprises: a printed circuit board; And the red LED, the green LED, the blue LED, and the white LED mounted on the printed circuit board. The backlight panel of claim 2, further comprising a light guide plate, wherein the LED array is disposed at a side portion of the light guide plate. The backlight panel of claim 2, further comprising a diffuser, wherein the LED array is located below the diffuser. The backlight panel of claim 4, further comprising a light guide plate interposed between the diffuser and the LED array. The backlight panel of claim 5, wherein holes or grooves in which the LEDs are inserted are formed at a lower portion of the light guide plate. The backlight panel according to any one of claims 1 to 6, wherein the number of red LEDs and blue LEDs is 1/2 of the number of green LEDs, respectively. The backlight panel of claim 7, wherein the number of white LEDs is the same as the number of green LEDs. The method according to any one of claims 1 to 6, wherein the LEDs are arranged on a printed circuit board, a plurality of units are arranged using a green LED-red LED-blue LED-green LED as one unit, And a white LED arranged to add white LEDs between the units.

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