KR20060111997A - Backlight panel employing white light emitting diode - Google Patents

Abstract

A backlight panel is provided to improve the brightness, save the manufacture cost, and reduce the thickness, by using a white light emitting diode and a light guiding plate. A white light emitting diode(23w) is disposed under a diffusion plate(27), and separated from the diffusion plate. A light guiding plate(25) is disposed between the diffusion plate and the white light emitting diode. The light guiding plate transforms a light emitted from the white light emitting diode into a surface light, and outputs the surface light to the diffusion plate. The white light emitting diode includes a blue light emitting diode chip, a red fluorescent above the blue light emitting diode chip, and a green fluorescent above the blue light emitting diode chip.

Description

BACKLIGHT PANEL EMPLOYING WHITE LIGHT EMITTING DIODE}

1 is a cross-sectional view illustrating a conventional backlight panel.

2 is a cross-sectional view illustrating a backlight panel according to an embodiment of the present invention.

3 is a cross-sectional view for describing a backlight panel according to another exemplary embodiment of the present invention.

4 is a cross-sectional view for describing a backlight panel according to another embodiment of the present invention.

The present invention relates to a backlight panel for backlighting a display panel, and more particularly, a white light emitting diode having a red phosphor and a green phosphor as a light source to improve the brightness of the display panel and to reduce the thickness of the backlight panel. It is about.

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.

1 is a partial cross-sectional view for explaining a conventional backlight panel that backlights the LCD panel 17 by adopting a light emitting diode.

Referring to FIG. 1, an LED array is positioned on a printed circuit board 1. The LED array is an array in which red (3r), green (3g) and blue (3b) LEDs are arranged at predetermined intervals. These LEDs are arranged regularly on the printed circuit board 1 to form an LED module, and a plurality of LED modules are used to backlight the LCD panel 17.

The LEDs employ a lens designed to emit side light and emit daylight almost in the lateral direction.

The reflective sheet 5 is positioned below the light exit surface of the LEDs. The reflective sheet may have a reflective layer 5a thereon. The reflective sheet reflects the light emitted from the LEDs to the upper side.

Meanwhile, the light transmitting layer 7 is positioned on the LEDs. The light transmitting layer is a layer through which light emitted from the LEDs can pass, and is made of a transparent resin such as poly methyl methacrylate (PMMA). The light transmitting layer 7 has light blocking patterns 9 at positions corresponding to the LEDs. The light blocking patterns are used to prevent light emitted upward from the LEDs from passing through the light-transmitting layer and directed toward the LCD 17. The light-shielding patterns are formed by ESR (eletroslag remelting).

The light transmitting layer 7 and the reflective sheet 5 are spaced apart by a predetermined interval to form a first gap 6a formed of an air layer. The first interval is an area in which red, green, and blue light emitted from the LEDs 3r, 3g, and 3b are mixed with each other.

The diffusion plate 11 is positioned on the reflective sheet 7 to be spaced apart from the reflective sheet 7.

The diffusion plate 11 diffuses the incident light to make the light uniform. The diffusion plate and the reflective sheet 7 are spaced apart by a predetermined interval to form a second gap 10a formed of an air layer. Therefore, the light transmitted through the light transmitting layer 7 is mixed again in the second gap 10a and is incident on the diffusion plate 11.

A brightness enhancement film (BEF) 13, such as a prism sheet, is positioned on the diffusion plate 11. The BEF may consist of two sheets, each of which has an upward prism formed in the longitudinal and transverse directions, respectively. In addition, a dual brightness enhancement film (DBEF) 15, such as a dual brightness enhancement-embossed DBEF-E, may be positioned on the BEF 13. These BEF films 13 and 15 refract light emitted from the diffuser plate 11 at a large directing angle at a narrow directing angle to enter the LCD panel 17. Accordingly, the brightness of the LCD panel is increased.

According to the prior art, since the red, green and blue LEDs are used as the light source, color reproducibility can be improved. However, as using red, green and blue LEDs, it is necessary to mix the light emitted from the LEDs to get uniform light. Accordingly, it is necessary to prevent the light emitted from the LEDs from passing through the light-transmitting layer 7 toward the diffuser plate 11 by using the light shielding pattern 9, and the first gap 6a and the second gap. An air layer such as the spacing 10a is required. This leads to an increase in the thickness of the backlight panel.

In addition, light loss occurs while mixing the light emitted from the LEDs. Therefore, this light loss is compensated for by increasing the amount of current supplied to the LEDs, using a larger number of LEDs, or using BEF 13 and DBEF 15 or the like. However, increasing the amount of current or using multiple LEDs increases power consumption. In particular, an increase in the amount of current leads to an increase in heat generated in the LEDs, which may degrade the light shielding layer. In addition, the use of BEF films further increases the thickness of the entire backlight panel and increases the manufacturing cost of the backlight panel.

The technical problem to be achieved by the present invention is to provide a backlight panel that can reduce the manufacturing cost compared to the prior art, and has a thinner thickness.

Another technical problem to be achieved by the present invention is to provide a backlight panel capable of improving luminance compared to the prior art while ensuring color reproducibility.

In order to achieve the above technical problem, the present invention provides a backlight panel employing a white light emitting diode. The backlight panel includes a diffusion plate. A white light emitting diode is spaced apart from the diffusion plate and positioned below the diffusion plate. In addition, a light guide plate is positioned between the diffusion plate and the white light emitting diode. The light guide plate converts the incident light from the white light emitting diode into surface light and emits the light to the diffusion plate. Accordingly, by adopting a white light emitting diode having three wavelengths of red, green, and blue, it is possible to improve luminance while ensuring color reproducibility of the liquid crystal display screen, and to omit a space for mixing three wavelengths of color. The thickness of the backlight panel can be reduced. In addition, the luminance can be improved to omit the BEFs, thereby further reducing the manufacturing cost and thickness of the backlight panel.

The white light emitting diode may be a top light emitting diode that emits light in an upward direction. In this case, the light guide plate may include a plane adjacent to the diffusion plate, an upper surface including an inclined surface that forms a groove portion enclosed by the plane and positioned above the white light emitting diode, and a flat bottom surface of the groove portion; It may have an inclined bottom surface opposite the face. Light incident on the bottom surface of the white light emitting diode is directly emitted to the diffusion plate, and light incident on the inclined surface of the recess portion is reflected from the inclined surface to the lower surface of the light guide plate, so that the diffused surface is inclined. Reflected in a direction almost perpendicular to the plate.

In contrast, the white light emitting diode may be a side light emitting diode that emits light in a lateral direction.

In this case, the light guide plate may have an upper surface adjacent to the diffusion plate, a lower surface facing the upper surface and including a receiving groove for receiving the white light emitting diode and an inclined surface extending from the receiving groove. have. Light emitted from the white light emitting diode in a lateral direction and incident on the inclined surface is reflected in a direction substantially perpendicular to the diffuser plate at the inclined surface.

The light guide plate may further include a lower surface including an upper surface adjacent to the diffusion plate, an upper surface facing the upper surface and receiving a base for receiving the white light emitting diode and a base surface extending with a plurality of protrusions in the receiving groove. It can have a face. Light emitted from the white light emitting diode in a lateral direction and reflected from the upper surface to the lower surface is reflected in a direction substantially perpendicular to the diffusion plate in the plurality of protrusions.

The white light emitting diode may emit blue light by mounting a blue light emitting diode chip, a red light emitting diode chip, and a green light emitting diode chip. Alternatively, the white light emitting diode may include a blue light emitting diode chip, and a red phosphor and a green phosphor may be positioned above the blue light emitting diode chip. Accordingly, the white light is emitted by the blue light emitted from the blue light emitting diode chip and the red and green light wavelength-converted by the phosphors. Alternatively, the white light emitting diode UV light emitting diode chip may be mounted, and a red phosphor, a green phosphor, and a blue phosphor may be positioned on the ultraviolet light emitting diode chip. Accordingly, the white light emitting diode may convert white light emitted from the ultraviolet light emitting diode chip into red, green, and blue light to emit white light.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention; The following embodiments are provided as examples to sufficiently convey the spirit of the present invention to those skilled in the art. Accordingly, the invention is not limited to the embodiments described below and may be embodied in other forms. And, in the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience.

Like numbers refer to like elements throughout.

2 is a cross-sectional view for describing a backlight panel for backlighting a liquid crystal display panel 29 (hereinafter, referred to as an LCD panel) according to an exemplary embodiment of the present invention.

Referring to FIG. 2, a diffusion plate 27 is positioned below the LCD panel 29. The diffusion plate 27 may be a thin sheet. The diffusion plate 31 diffuses the light incident through the light guide plate 25 to make uniform light. In addition, a brightness enhancement film (BEF) and / or a dual brightness enhancement film (DBEF, not shown) may be further interposed between the diffusion plate 27 and the LCD panel 29. Can be. The BEFs condense the light emitted from the diffuser plate 27 to a certain direction angle to increase the brightness.

A white light emitting diode (23w, hereinafter, a white LED) is disposed below the diffusion plate 27 and spaced apart from the diffusion plate by a predetermined distance. In the present embodiment, the white light emitting diode is an upper light emitting LED that emits light toward the diffusion plate 27. The upper light emitting LED may have a convex lens on the top thereof to emit white light within a predetermined direction angle. The white LED may be mounted on the printed circuit board 21, and a plurality of LEDs may be mounted on one printed circuit board 21 to constitute an LED module. The LEDs 23w mounted on the printed circuit board 21 may be simultaneously driven through a circuit printed on the printed circuit board.

Meanwhile, the LEDs may be arranged at regular intervals on the same plane and may be arranged in units of the LED module.

The white LED 23w may have a blue LED chip, and may have a green phosphor positioned on the blue LED chip to convert a portion of the blue light into green light and a red phosphor converting the wavelength into red light. In contrast, the white LED 23w may implement white light by mounting a blue LED chip, a green LED chip, and a red LED chip. In addition, the white LED (23w) has an ultraviolet LED chip, a blue phosphor located above the ultraviolet LED chip to convert a portion of the ultraviolet light into blue light, green phosphor to convert the wavelength into green light and red phosphor to convert the wavelength into red light It can have

The light guide plate 25 is positioned between the white LED and the diffusion plate 27. The light guide plate converts light emitted from the light source 23w into surface light and emits the light upward. The light guide plate 27 may be made of transparent resin such as transparent acrylic resin, polycarbonate or epoxy resin, glass, or the like. Both surfaces of the light guide plate may be processed into various patterns, such as grooves, lens shapes, prism shapes, or hologram patterns, as necessary. In addition, a reflective sheet (not shown) may be attached to the lower portion of the light guide plate.

In the present embodiment, the light guide plate 25 has an upper surface 25a close to the diffusion plate 27 and a lower surface 25b opposite the upper surface. The upper surface includes a plane adjacent to the diffusion plate 27, an inclined surface that forms a recess 25c enclosed by the plane and positioned above the white light emitting diode, and a flat bottom surface of the recess. The upper surface 25a may be in contact with the diffusion plate 27, but is not limited thereto and may be spaced a predetermined interval apart. On the other hand, the lower surface has a surface inclined with respect to the diffusion plate. The inclined surface may be a convex surface having a constant curvature, and as shown, may be a Fresnel surface in which the inclined surfaces are cascaded. The inclined surfaces may have a larger inclination angle as they move outward. When the Fresnel surface is adopted, the thickness of the light guide plate can be reduced compared to the convex surface.

Meanwhile, the lower surface of the light guide plate adjacent to the white LED 23w may be formed as a concave groove to have a curvature similar to that of the lens of the white LED. Accordingly, the light loss generated by the light emitted from the white LED 23w is reflected by the lower surface 25b can be reduced.

Light incident from the white LED 23w to the bottom surface of the recess 25c passes through the bottom surface and immediately exits to the diffusion plate 27. On the other hand, light incident from the white LED 23w to the inclined surface of the recess 25c is reflected from the inclined surface to the lower surface 25b of the light guide plate. Thereafter, the light is reflected from the inclined lower surface 25b in a direction substantially perpendicular to the diffuser plate and exits to the diffuser plate 27.

The inclination of the inclined surface of the groove portion 25c, the size of the bottom surface, and the shape of the inclined lower surface 25b are determined in consideration of the light emission characteristics of the white light emitting diode 23w, and the luminance on the LCD panel 29 is increased. Can be evaluated and optimized.

According to the present embodiment, the white light emitted from the top emitting white LED 23w is converted into surface light in the light guide plate 25 and is emitted to the diffuser plate 27. Therefore, the intervals for mixing light (6a, 10a in FIG. 1) can be omitted, and light loss can be reduced. Accordingly, the thickness of the backlight panel can be reduced, and the brightness of the LCD panel 29 can be improved.

3 is a cross-sectional view illustrating a backlight panel for backlighting an LCD panel 39 according to another embodiment of the present invention.

Referring to FIG. 3, as described with reference to FIG. 2, a diffusion plate 37 may be positioned below the LCD panel 39, and BEFs may be interposed between the diffusion plate and the LCD panel.

In addition, a white LED 33w is disposed below the diffusion plate 37 to be spaced apart from the diffusion plate by a predetermined interval. As described with reference to FIG. 2, the white LED may be mounted on a printed circuit board 31, and a plurality of LEDs may be mounted on a single printed circuit board 31 to form an LED module. . In addition, the light guide plate 35 may be positioned between the diffusion plate 37 and the white LED 33w. Hereinafter, a configuration different from the backlight panel of FIG. 2 will be described in detail.

In the present embodiment, the white LED 33w is a side light emitting LED that emits light almost parallel to the diffuser plate 37. The side emitting LED emits a part of light toward the diffuser plate 37, and emits the remaining light in a direction substantially parallel to the diffuser plate 37, that is, the side surface.

 The light guide plate 35 has an upper surface 35a adjacent to the diffusion plate 37 in parallel and has a lower surface 35b opposite to the upper surface. In addition, the lower surface includes an accommodating groove 35c for accommodating the white LED 33w and an inclined surface extending from the accommodating groove. The inclined surface may be a convex surface or a Fresnel surface as described with reference to FIG. 2.

The emission surface of the white LED 33w is accommodated in the accommodation groove 35c. A part of the light emitted through the emission surface of the white LED 33w proceeds in a direction perpendicular to the diffuser plate 37 and is incident into the light guide plate 35, and the other part is emitted in a lateral direction so that the light guide plate 35 is emitted. Incident inside. Light incident in the direction perpendicular to the diffuser plate 37 passes through the light guide plate and enters the diffuser plate 37. On the contrary, the light incident on the light guide plate 35 in the lateral direction directly travels to the lower surface 35b or is reflected from the upper surface 35a of the light guide plate to the lower surface 35b. Light propagated to the lower surface 35b is reflected in a direction substantially perpendicular to the diffusion plate 37 on the inclined surface of the lower surface and is incident to the diffusion plate.

The lower surface of the light guide plate 35 is determined in consideration of the light emission characteristics of the white LED 33w, and may be optimized by evaluating the luminance characteristic on the LCD panel 39.

According to the present exemplary embodiment, the structure of the light guide plate 35 is simple compared to the light guide plate 25 of FIG. 2, so that the backlight panel may be more easily manufactured.

4 is a cross-sectional view illustrating a backlight panel for backlighting an LCD panel 59 according to another embodiment of the present invention.

Referring to FIG. 4, as described with reference to FIG. 3, a diffusion plate 57 may be positioned below the LCD panel 59, and BEFs may be interposed between the diffusion plate and the LCD panel.

In addition, a white LED 53w is disposed below the diffusion plate 57 at a predetermined interval from the diffusion plate 57. As described with reference to FIG. 2, the white LED may be mounted on a printed circuit board 51, and a plurality of LEDs may be mounted on a single printed circuit board 51 to constitute an LED module. . In addition, the light guide plate 55 may be positioned between the diffusion plate 57 and the white LED 53w. On the other hand, the white LED 53w is a side light emitting LED as described with reference to FIG. 3. In addition, the light guide plate 55 has an upper surface 55a adjacent to the diffusion plate 57 in parallel and has a lower surface 55b opposite to the upper surface. In addition, the lower surface is formed with a receiving groove 55c for accommodating the white LED 53w. However, the lower surface 55b of the light guide plate 55 has a base surface extending parallel to the top surface 55a in the receiving groove 55c, and a plurality of protrusions 55d are regularly arranged on the base surface. .

As described with reference to FIG. 3, a part of the light emitted through the emission surface of the white LED 53w proceeds in a direction perpendicular to the diffuser plate 57 and is incident into the light guide plate 55, and the other side thereof is a side surface. It is emitted in the direction is incident to the light guide plate 55. Light incident in a direction perpendicular to the diffuser plate 57 passes through the light guide plate and is incident to the diffuser plate 57. On the contrary, the light incident on the light guide plate 55 in the lateral direction is directly directed to the lower surface 55b or reflected from the upper surface 55a of the light guide plate to the lower surface 55b. Light propagated to the lower surface 55b is reflected toward the diffuser plate 57 at the protrusions 55d of the lower surface. Diffuse reflection may occur due to the protrusions 55d, but light reflected in a direction substantially perpendicular to the diffuser plate 57 is incident on the diffuser plate 57, and the light reflected obliquely is upper part of the light guide plate 55. It is reflected back from the surface 55a and proceeds to the lower surface 55b. Through this process, light almost perpendicular to the diffuser plate 57 is incident on the diffuser plate.

The shape and arrangement of the protrusions are determined in consideration of the light emission characteristics of the white LED 53w, and can be optimized by evaluating the luminance characteristics on the LCD panel 59.

According to the present exemplary embodiment, the lower surface 55b of the light guide plate 55 may be substantially parallel to the upper surface 55a, thereby further reducing the thickness of the light guide plate. As a result, the thickness of the backlight panel can be further reduced.

 According to the embodiments of the present invention, it is possible to provide a backlight panel with improved brightness compared to the prior art by using a white light emitting diode and a light guide plate, and to reduce the manufacturing cost and thickness of the backlight panel.

Claims (4)

Diffuser plate; A white light emitting diode spaced apart from the diffusion plate and positioned below the diffusion plate; And And a light guide plate positioned between the diffusion plate and the white light emitting diode to convert light incident from the white light emitting diode into surface light and to be emitted to the diffusion plate. The method according to claim 1, The white light emitting diode includes a blue light emitting diode chip and a red phosphor and a green phosphor positioned on the blue light emitting diode chip. The method according to claim 1, The white light emitting diode includes a blue light emitting diode chip, a green light emitting diode chip and a red light emitting diode chip. The method according to claim 1, The white light emitting diode includes a ultraviolet light emitting diode chip and a red phosphor, a green phosphor, and a blue phosphor positioned on the ultraviolet light emitting diode chip.

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