KR20090123667A - Polarized light source, back-light unit and lcd module employing the light source - Google Patents

Abstract

PURPOSE: A polarized light source, a BLU equipping the same and an LCD module for offering a polarized light BLU are provided to reduce the light loss by a DBEF(Double Brightness Enhancement Film) by equipping polarized light source. CONSTITUTION: A BLU(Backlight Unit) is arranged on a lower substrate and irradiates the light polarized to the lower plate. The BLU includes a LGP(Light Guide Plate)(63) which beneath locates an LCD panel(50) and an LED(Light Emitting Diode)(61). Non-polar LED is arranged in the side of LGP and emits the light polarized to LGP. A lower polarized film locates between the lower plate and BLU. An upper polarized film(57) emits the polarization value.

Description

Polarized light source, backlight unit and liquid crystal display module employing it {POLARIZED LIGHT SOURCE, BACK-LIGHT UNIT AND LCD MODULE EMPLOYING THE LIGHT SOURCE}

The present invention relates to a liquid crystal display module, and more particularly, to a polarizing light source, a backlight unit employing the same, and a liquid crystal display module.

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 a liquid crystal display (LCD) panel. As an alternative to this problem, a back light unit (BLU) for backlighting the display panel is generally employed.

The backlight unit 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 schematic diagram showing a conventional LCD module according to the related art employing a side type LED light source.

Referring to FIG. 1, a conventional LCD module includes an LCD panel 10 and a backlight unit 20. The LCD panel 10 includes a liquid crystal layer 15 between the upper substrate 11 and the lower substrate 13, and also the upper polarizing film 17 and the lower substrate positioned on the upper substrate 11. (13) a lower polarizing film 19 positioned below. In general, the upper polarizing film 17 and the lower polarizing film 19 are disposed such that the polarization directions are perpendicular to each other. Meanwhile, the backlight unit 20 includes a light guide plate 23 and LEDs 21 as a light source, and a diffuser plate 25 and a brightness enhancement film 27 for mixing light emitted from the light sources 21. and brightness enhancement film (BEF). In addition, the backlight unit may further include a dual brightness enhancing film 29 (DBEF).

The LEDs 21 are disposed on the side of the light guide plate 23 to emit light to the light guide plate. Such LEDs 21 may be arranged on a substrate 31, such as a printed circuit board, to form an array, and the LEDs 21 may include red, green and blue LEDs or may include white LEDs. . These LEDs may be attached to the substrate, for example, via solder 35, and may be regularly arranged on the substrate and used to backlight the LCD panel 10 by constructing an LED module. The light guide plate 23 may be attached onto the substrate 31 through the adhesive tape 33. In addition, the light guide plate 23 may include a reflective film (not shown) attached to a lower surface thereof.

Light L emitted from the LEDs 21 and then passed through the light guide plate 23, the diffusion plate 25, the BEF 27, and the DBEF 29 is incident to the LCD panel 10. The lower polarizing film 19 polarizes the light L, and the polarized light is incident on the liquid crystal layer. The light incident on the liquid crystal layer is incident on the upper polarizing film by maintaining the polarization direction or rotating 90 degrees according to the arrangement of the liquid crystal layer. Thereafter, the light maintaining the polarization direction is shielded by the upper polarizing film 17, and the light rotated 90 degrees passes through the upper polarizing film 17 to realize an image.

That is, according to the prior art, the light emitted from a light source such as an LED is firstly polarized using the lower polarizing film 19, and the direction of the polarized light is controlled using the liquid crystal layer 15, and again the upper polarizing film ( 17) to implement the image by the second polarization. Thus, since this prior art uses the first polarized light using the lower polarizing film 19, most of the light emitted from the light source (about 50%) is shielded by the lower polarizing film 19 and lost. As the light passes through the various films and many layers including the polarizing film, the light that makes up the final image is less than 10% of the total light. In addition, the use of BEF and DBEF, lower and upper polarizing films thickens the LCD panel and backlight unit.

Meanwhile, a reflective polarized DBEF film (Vikuiti ^™ DBEF) has been developed and used to reduce light loss and reduce overall power consumption. The reflective polarized DBEF film passes polarized light (eg, P wave) in one direction among light incident on the DBEF film and reflects polarized light (eg, S wave) in the other direction. The light reflected from the reflective polarized DBEF film is reflected back in the reflective film, and the DBEF film passes the polarization in one direction of the reflected light and reflects the polarization in the other direction again. That is, the reflective polarization DBEF film may increase the utilization of light by using both reflection and polarization. However, because light loss occurs when light is reflected, the DBEF film has a limit in reducing light loss. In addition, the reflective polarization DBEF film has a disadvantage of high manufacturing cost.

An object of the present invention is to provide an LCD module that can reduce the total power consumption by reducing the light loss.

Another object of the present invention is to provide an LCD module capable of reducing the thickness of the LCD panel and / or backlight unit.

Another object of the present invention is to provide an LCD module capable of realizing an image without using a lower polarizing film and / or a reflective polarizing DBEF film.

Another object of the present invention is to provide a backlight unit and a light emitting diode light source capable of reducing the total power consumption of the LCD module.

Another object of the present invention is to provide a backlight unit and a light emitting diode light source capable of providing polarized light to an LCD panel without using a lower polarizing film or a polarizing DBEF film.

To solve the above problems, an aspect of the present invention provides a liquid crystal display (LCD) module employing a polarized light source. The liquid crystal display module includes a liquid crystal display panel including an upper substrate, a lower substrate, a liquid crystal layer positioned between the upper substrate and the lower substrate, and an upper polarizing film positioned on the upper substrate, and disposed below the lower substrate. It includes a backlight unit for irradiating the polarized light to the lower substrate. The backlight unit may include a light guide plate positioned below the liquid crystal display panel and a non-polar or semi-polar light emitting diode (LED) disposed on a side of the light guide plate to emit polarized light to the light guide plate. do.

Herein, non-polar or semi-polar light emitting diodes (hereinafter, weakly referred to as non-polar light emitting diodes unless otherwise specified) are distinguished from polar light emitting diodes including a compound semiconductor layer grown in the c-axis direction. It refers to a light emitting diode comprising a compound semiconductor layer grown on -plane or a-plane. The light emitting diode includes GaN-based nitride semiconductor layers such as GaN, InGaN, AlGaN, and AlInGaN. The GaN-based nitride semiconductor layer may be grown on the m-plane or a-plane of the GaN substrate, and the nitride semiconductor light emitting diode may emit light in the ultraviolet and visible light regions by adjusting the composition ratio.

Unlike the polar light emitting diode, the non-polar light emitting diode exhibits the characteristic of emitting polarized light, as reported in the Japanese Journal of Applied Physics, Vol 46, No. 42, 2007, pp. L1010-L1012. have.

Therefore, the present invention can extract polarized light from the light source by using the non-polar light emitting diode as a light source, and accordingly the lower polarizing film (19 of FIG. 1) or the reflective polarization DBEF ( 29) can be removed.

Meanwhile, the nonpolar light emitting diode may emit some unpolarized light. In this case, in order to polarize the non-polarized light, the liquid crystal display panel may further include a lower polarizing film positioned between the lower substrate and the backlight unit. However, since the ratio of the unpolarized light is relatively low, the lower polarizing film may have a lower polarization degree and a higher transmittance than the upper polarizing film.

In general, the polarization degree of the polarizing film used in the LCD module is 98 to 100%, the transmittance is 40 to 50%. However, since the light emitted from the non-polar light emitting diode has a high ratio of polarized light, the lower polarizing film used in the embodiments of the present invention may have a polarization degree of 70 to 90%, and transmittance of 60 to 80%. Can have

The backlight unit may further include a diffusion plate on the light guide plate. In addition, the backlight unit may further include a brightness enhancement film.

The light guide plate converts light incident from the nonpolar light emitting diode into a surface light source. The light guide plate reflects the polarized light incident from the nonpolar light emitting diode toward its upper surface to maintain the properties of the polarized light.

The non-polar light emitting diode may be provided in a package form, for example, may be provided in a side light emitting diode package. Accordingly, the side light emitting diode package may include a package body having an elongated opening, a plurality of leads exposed outward from the package body, and at least one non-polar or semi-polar light emitting diode mounted in the openings and electrically connected to the leads. non-polar or semi-polar LED) chip.

In addition, the side light emitting diode package may further include a phosphor for wavelength converting light emitted from the light emitting diode chip. Alternatively, the side light emitting diode package may include at least three nonpolar or semipolar light emitting diode chips, and the light emitting diode chips may emit blue, green, and red light, respectively. Accordingly, the side light emitting diode package may emit white light.

According to embodiments of the present invention, by adopting a polarized light source it is possible to reduce the light loss by the conventional polarizing film or reflective polarization DBEF, thus reducing the overall power consumption of the LCD module. In addition, the lower polarizing film and / or the reflective polarizing DBEF film can be removed to reduce the thickness of the LCD panel and / or backlight unit. In addition, according to the present invention, it is possible to provide a side light emitting diode package and a backlight unit for emitting polarized light.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention; The following embodiments are provided as examples to ensure that the spirit of the present invention can be fully conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. In the drawings, widths, lengths, thicknesses, and the like of components may be exaggerated for convenience. Like numbers refer to like elements throughout.

2 is a schematic diagram illustrating an LCD module according to an embodiment of the present invention.

2, the LCD module includes an LCD panel 50 and a backlight unit 60. The LCD panel 50 is positioned on the upper substrate 51, the lower substrate 53, the liquid crystal layer 55 positioned between the upper substrate 51 and the lower substrate 53, and the upper substrate 51. An upper polarizing film 57. In addition, the LCD panel 50 may include a lower polarizing film 59 positioned below the lower substrate 13.

Meanwhile, the backlight unit 60 includes a light guide plate 63 and non-polar or semi-polar LEDs 61 as a light source, and mixes the light emitted from the light sources 61. The diffusion plate 65 and a brightness enhancement film (BEF) 67 may be included.

The LEDs 61 may be arranged on a substrate 71 such as a printed circuit board to form an array, and the LEDs 61 may include red, green and blue LEDs or may include white LEDs. . These LEDs may be attached via a conductive bonding material 75 such as solder on the substrate 71 and may be arranged regularly to constitute an LED module. Such LED module (s) can be used to backlight the LCD panel 50.

The light guide plate 63 may be attached onto the substrate 71 through an adhesive tape 73, and may include a reflective film (not shown) on a lower surface thereof. The LEDs 61 are disposed on the side of the light guide plate 63 to emit light to the light guide plate 63. The LEDs 61 may be provided in a package in which a non-polar LED chip is mounted, which will be described later in detail with reference to FIGS. 4 and 5.

The nonpolar LEDs 61 are distinguished from polar light emitting diodes including a compound semiconductor layer grown in the c-axis direction. For example, by growing a GaN-based nitride semiconductor layer such as GaN, InGaN, AlGaN, or AlInGaN on the m-plane or a-plane of a GaN substrate, there is no spontaneous polarization or piezoelectrice polarization. Alternatively, a semipolar light emitting diode can be manufactured.

In addition, the light emitting diode using the nitride semiconductor may be manufactured to emit light of a wavelength required in the ultraviolet to visible region by adjusting the composition ratio of the nitride semiconductor.

A nonpolar gallium nitride-based light emitting diode device having a polarization ratio of 0.80 has been reported in the Journal of the Korean Society for Applied Physics (Vol. 46, No. 42, 2007, pp. L1010-L1012). It can be further increased by the improvement of the crystallinity of the layer, the sidewall polishing technique of the light emitting diode chip and the like.

Meanwhile, the light L emitted from the LEDs 61 and then passed through the light guide plate, the diffusion plate 65, and the BEF 67 is incident on the LCD panel 50. At this time, since the ratio of the polarized light of the light (L) is relatively high, the polarization degree of the lower polarizing film 59 may be lower than the prior art. That is, the polarization degree of the lower polarizing film 59 may be relatively lower than the polarization degree of the upper polarizing film 57, and thus, the transmittance of the lower polarizing film 59 may be relatively increased to reduce light loss. have.

In general, a polarization degree of 98 to 100% is required for the polarizing film used in the LCD panel, and thus the transmittance does not exceed about 40 to 50%. However, in this embodiment, for example, a polarizing film having a polarization degree of 70 to 90% and a transmittance of 60 to 80% may be used as the lower polarizing film 59.

The light transmitted through the lower polarizing film 59 is incident on the liquid crystal layer, and the light incident on the liquid crystal layer is incident on the upper polarizing film by maintaining the polarization direction or rotating 90 degrees according to the arrangement of the liquid crystal layer. The image is realized by being shielded or passed by this upper polarizing film 57.

According to this embodiment, the light loss due to the polarizing film can be reduced without using a DBEF film such as the conventional reflective polarizing DBEF. Therefore, the manufacturing cost of the LCD panel can be reduced, and also the thickness of the backlight unit can be reduced. In addition, the transmittance of the lower polarizing film may be increased to further reduce light loss.

Meanwhile, when the polarization ratio of the nonpolar LEDs 61 is relatively high, the lower polarizing film 59 may also be removed.

3 is a schematic diagram illustrating an LCD module from which the lower polarizing film 59 is removed according to another embodiment of the present invention.

Referring to FIG. 3, the LCD module according to the present embodiment includes the backlight unit 60 as described with reference to FIG. 2. In addition, the LCD module includes an LCD panel 70, wherein the LCD panel 70 includes an upper substrate 51, a lower substrate 53, a liquid crystal layer 55, and the like as described with reference to FIG. 2. An upper polarizing film 57. However, the LCD panel 70 is different from the LCD panel 50 of FIG. 2 in that a lower polarizing film is not used.

That is, when the polarization ratio of the non-polar LEDs 61 is relatively high, both the lower polarizing film 59 and the DBEF may be removed, and thus the thickness of the LCD panel 70 may be further reduced.

In the embodiments of the present invention, it has been described that the diffusion plate 65 and the BEF 67 are used, but these may also be removed.

4 and 5 are a plan view and a perspective view showing a side light emitting diode package as an example of a non-polar light emitting diode in a package form that may be adopted in embodiments of the present invention.

4 and 5, the side light emitting diode includes a package body 85 having an opening, a plurality of leads 81 and 83, and a nonpolar or semipolar light emitting diode chip 87.

A plurality of leads, such as the first and second leads 81 and 83, are exposed by the openings of the package body 85 and outwardly from the package body 85. The leads and package body may be formed using insert molding techniques.

For convenience of description, the package body 85 may be divided into an upper package body 85a and a lower package body 85b based on the positions of the leads 81 and 83. The upper package body 85a has an opening that exposes the leads 81 and 83, and the leads 81 and 83 are located on the bottom of the opening, ie, the lower package body 85b, and are spaced apart from each other in the opening. have. The opening has an elongated shape surrounded by the inner wall 85w. In addition, the leads 81 and 83 protrude to the outside of the package body 85 to be electrically connected to an external power source. The leads 81 and 83 protruding to the outside may have various shapes and may be bent into various shapes. 4 and 5 show leads 81 and 83 that are bent laterally from the bottom surface of package body 85 for surface mounting.

In the opening, for example, a non-polar LED chip 87 emitting blue light is mounted on the first lead 81. The LED chip 87 is electrically connected to the second lead 83 through a bonding wire. The LED chip 87 is a light emitting diode made of GaN, InGaN, AlGaN, or AlGaInN-based nitride semiconductor, and may be formed by growing on the m-plane or a-plane of a GaN substrate. The LED chip 87 has two electrodes to be connected to an external power source. The electrodes may be located on the same side or opposite sides of the LED chip 87. The electrodes may be electrically connected to the first lead 81 through an adhesive or connected to the lead through a bonding wire. In the case of an LED chip having electrodes formed on the same side, two bonding wires may be electrically connected by connecting the LED chip 87 and the leads 81 and 83, respectively. On the other hand, when the electrodes are located on opposite sides of each other, one electrode is connected to the first lead 81 using a conductive adhesive, and the other electrode is connected to the second lead 83 through a bonding wire. Can be connected.

On top of the blue LED chip 87 is mixed with a part of the light emitted from the LED chip 87 is excited by blue light to emit white light and excited by the red phosphor 91r and blue light to emit red light and green light A green phosphor 91g emitting light is positioned. The red phosphor 91r may be, for example, an alkaline earth metal sulfide-based red phosphor, and the green phosphor 91g may be a thigallate green phosphor. The red and green phosphors may be coated on the LED chip 87 or may be contained and positioned in the molding member 86 as shown. The molding member 86 may be formed of an epoxy resin or a silicone resin, and may be formed of a single layer or multiple layers.

In the present embodiment, the white light may be implemented by the blue LED chip 87 and the phosphor, thereby providing a light source capable of realizing a natural color image. On the other hand, instead of using a phosphor, the white, blue, green, and red LED chips 87 are mounted in packages, and the packages are arranged, or the blue, green, and red LED chips 87 are mounted in one package. It can also be implemented. At this time, the blue, green and red LED chips 87 are composed of non-polar LEDs.

1 is a schematic view for explaining a liquid crystal display module according to the prior art.

2 is a schematic diagram illustrating a liquid crystal display module according to an embodiment of the present invention.

3 is a schematic diagram illustrating a liquid crystal display module according to another embodiment of the present invention.

4 and 5 are a plan view and a perspective view for explaining an example of a non-polar light emitting diode package that can be used in embodiments of the present invention.

Claims (12)

A liquid crystal display panel including an upper substrate, a lower substrate, a liquid crystal layer positioned between the upper substrate and the lower substrate, and an upper polarizing film positioned on the upper substrate; And A backlight unit disposed under the lower substrate to irradiate polarized light onto the lower substrate, The backlight unit includes a light guide plate positioned below the liquid crystal display panel and a non-polar or semi-polar LED that is disposed on a side of the light guide plate to emit polarized light to the light guide plate. Display module. The liquid crystal display module of claim 1, wherein the liquid crystal display panel further comprises a lower polarizing film positioned between the lower substrate and the backlight unit, wherein the lower polarizing film has a lower polarization degree and a higher transmittance than the upper polarizing film. The liquid crystal display module as claimed in claim 1, wherein the light emitted from the backlight unit is incident directly on the lower substrate. The liquid crystal display module of claim 3, wherein the backlight unit further comprises a brightness enhancement film. The liquid crystal display module of claim 1, wherein the backlight unit further comprises a diffusion plate positioned on the light guide plate. Light guide plate; And And a non-polar or semi-polar light emitting diode (LED) disposed on the side of the light guide plate to emit light polarized by the light guide plate. The backlight unit of claim 6, further comprising a brightness enhancing film. The backlight unit of claim 6, further comprising a light guide plate positioned on the light guide plate. A package body having an elongated opening; A plurality of leads exposed outward from the package body; And And at least one non-polar or semi-polar LED chip mounted in the opening and electrically connected to the leads. The side light emitting diode package of claim 9, further comprising a phosphor for wavelength converting light emitted from the light emitting diode chip. 10. The side light emitting diode package of claim 9, comprising at least three nonpolar or semipolar light emitting diode chips, wherein the light emitting diode chips emit blue, green and red light. The side light emitting diode package of claim 9, wherein the side light emitting diode emits white light.

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