KR101533106B1 - Lcd module employing polarized light source - Google Patents

Abstract

A liquid crystal display (LCD) module employing a polarized light source is disclosed. The LCD 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 disposed on the upper substrate, And a backlight unit for irradiating the polarized light to the substrate, wherein the backlight unit includes a non-polarized light emitting diode that emits polarized light. By adopting the non-polarized light emitting diode that emits the polarized light, the light loss can be reduced and the thickness of the LCD panel or the backlight unit can be reduced.

Liquid crystal display, backlight unit, non-polar light emitting diode, polarizing film

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal display (LCD)

The present invention relates to a liquid crystal display module, and more particularly, to a liquid crystal display module employing a polarized light source.

A passive display device, such as a liquid crystal display, can reflect or absorb ambient sunlight or room light to create an image. Therefore, in order to view an image to be displayed, surrounding sunlight or room light is required. However, there is a problem that if the intensity of ambient light or room light is not enough to illuminate a liquid crystal display (LCD) panel, the displayed image can not be seen. As an alternative to such a problem, a backlight unit (BLU) for backlighting a display panel is generally adopted.

The backlight unit includes a light source such as an incandescent lamp, a fluorescent lamp, or a light emitting diode (LED). An image is realized by the light emitted from the light source illuminating the LCD panel. On the other hand, LED has excellent color reproducibility and is often used as a backlight light source, and is expected to be used in the future because it is environmentally friendly.

1 is a schematic view showing a conventional general LCD module employing an 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 an upper substrate 11 and a lower substrate 13 and includes an upper polarizing film 17 and a lower polarizing film 17 disposed on the upper substrate 11, And a lower polarizing film (19) positioned below the lower polarizing film (13). Generally, the upper polarizing film 17 and the lower polarizing film 19 are arranged so that their polarization directions are orthogonal to each other. The backlight unit 20 includes LEDs 23 as a light source and includes a diffusion plate 25 and a brightness enhancement film (BEF) for mixing light emitted from the light sources 23, . In addition, the backlight unit may further include a double brightness enhancement film (DBEF).

The LEDs 23 may be arranged on a substrate (not shown) such as a printed circuit board to form an array, and the LEDs 23 may include red, green, and blue LEDs or may include white LEDs . These LEDs are regularly arranged on a printed circuit board to constitute an LED module, and a plurality of LED modules can be used for backlighting the LCD panel 10. [ A reflective film 21 is positioned below the light exit surface of the LEDs 23 to reflect the light emitted from the LEDs toward the upper side.

The light L having passed through the diffusion plate 25, the BEF 27 and the DBEF 29 after being emitted from the LEDs 23 is incident on 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 keeps the polarization direction according to the arrangement of the liquid crystal layer or rotates by 90 degrees and is incident on the upper polarizing film. Thereafter, the light that maintains the polarization direction is shielded by the upper polarizing film 17, and the light rotated by 90 degrees passes through the upper polarizing film 17 to realize an image.

That is, according to the related art, light emitted from a light source such as an LED is primarily polarized by using the lower polarizing film 19, the direction of the polarized light is controlled by using the liquid crystal layer 15, 17) to realize an image. Thus, this conventional technique uses the primary polarized light using the lower polarizing film 19, so that the majority (about 50%) of the light emitted from the light source is shielded and lost by the lower polarizing film 19. As light passes through various films and many layers including polarizing films, the light that implements the final image is less than 10% of the total light. Also, the use of BEF and DBEF, lower and upper polarizing films, thickens the LCD panel and the backlight unit.

On the other hand, a reflective polarized DBEF film (Vikuiti ^™ DBEF) has been developed and used to reduce the total power consumption by reducing the optical loss. The reflective polarized DBEF film allows one direction of polarized light (for example, P wave) of light incident on the DBEF film to pass through and reflects another polarization (for example, S wave). The light reflected from the reflective polarized DBEF film is reflected back on the reflective film 21, and the DBEF film passes the polarized wave in one direction among the reflected light and reflects the polarized wave in the other direction again. That is, the reflection polarized DBEF film can increase the utilization rate of light by using reflection and polarization together. However, since light loss occurs when light is reflected, the DBEF film has a limitation in reducing light loss. In addition, the reflective polarized DBEF film has a disadvantage of high manufacturing cost.

An object of the present invention is to provide an LCD module capable of reducing the total power consumption by reducing optical loss.

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

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

In order to solve the above problems, the present invention provides a liquid crystal display (LCD) module employing a polarized light source. The LCD 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 disposed on the upper substrate, And a backlight unit for irradiating the polarized light to the substrate, wherein the backlight unit includes a non-polar LED that emits polarized light.

Here, the nonpolar light emitting diode is distinguished from a polarized light emitting diode including a compound semiconductor layer grown in the c-axis direction, and includes a compound semiconductor layer grown on the m-plane or the a- And includes semi-polar light emitting diodes as well as non-polar.

The light emitting diode includes a GaN-based nitride semiconductor layer such as GaN, InGaN, AlGaN, and AlInGaN. The nitride semiconductor light emitting diode may emit light in the ultraviolet and visible light regions by adjusting the composition ratio thereof.

Unlike the polarized light emitting diode, the non-polarized light emitting diode has been reported to exhibit the characteristic of emitting polarized light in the Japanese Journal of Applied Physics, Vol. 46, No. 42, 2007, pp. L1010-L1012 have.

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

On the other hand, the non-polarized light emitting diode may partially emit non-polarized light. In this case, in order to polarize the unpolarized 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.

Generally, the polarizing film used in the LCD module has a polarization degree of 98 to 100% and a transmittance of 40 to 50%. However, since the light emitted from the non-polarized light emitting diode has a high proportion of the already polarized light, the lower polarizing film used in embodiments of the present invention may have a degree of polarization of 70-90% and transmittance of 60-80% Lt; / RTI >

According to embodiments of the present invention, by adopting a polarized light source, it is possible to reduce the light loss due to the conventional polarizing film or the reflective polarized light DBEF, thereby reducing the total power consumption of the LCD module. Further, the lower polarizing film and / or the reflection polarizing DBEF film can be removed, and the thickness of the LCD panel and / or the backlight unit can be reduced.

Hereinafter, 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. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, etc. of components may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

2 is a schematic view for explaining an LCD module according to an embodiment of the present invention.

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

The backlight unit 60 includes non-polar LEDs 63 as a light source and includes a diffusion plate 65 for mixing light emitted from the light sources 63, and a brightness enhancement film (BEF, 67).

The LEDs 63 may be arranged on a substrate (not shown) such as a printed circuit board to form an array, and the LEDs 63 may include red, green, and blue LEDs or may include white LEDs . These LEDs are regularly arranged on a printed circuit board to constitute an LED module, and a plurality of LED modules can be used for backlighting the LCD panel 50. [ The reflective film 61 may be positioned below the light exit surface of the LEDs 63 to reflect the light emitted from the LEDs toward the upper side. The reflective film 61 may be formed on a printed circuit board on which LEDs are arranged. The LEDs 63 may be provided in the form of a package including a non-polarized light emitting diode chip, which will be described later in detail with reference to FIG.

The non-polar LEDs 63 are distinguished from a polarized light emitting diode including a compound semiconductor layer grown in the c-axis direction. For example, a GaN-based nitride semiconductor layer such as GaN, InGaN, AlGaN, AlInGaN or the like is grown on the m- or a-plane to grow a nonpolar light-emitting diode having no spontaneous polarization or piezoelectrically- A light emitting diode can be manufactured.

In addition, the light emitting diode using the nitride semiconductor can be manufactured to emit light of a desired wavelength in the ultraviolet to visible region by controlling 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 Japanese Society of Applied Physics (Vol. 46, No. 42, 2007, pp. L1010-L1012) The crystal quality of the layer, the side wall polishing technique of the light emitting diode chip, and the like.

The light L having passed through the diffusion plate 65 and the BEF 67 after being emitted from the LEDs 63 is incident on the LCD panel 50. At this time, since the ratio of the polarized light to the light L is relatively high, the polarization degree of the lower polarizing film 59 may be lower than that of the prior art. That is, the polarization degree of the lower polarizing film 59 can be relatively lower than the polarization degree of the upper polarizing film 57, so that the transmittance of the lower polarizing film 59 can be relatively increased, have.

Generally, a polarizing film used for an LCD panel requires a degree of polarization of 98 to 100%, and thus the transmittance does not exceed about 40 to 50%. However, in the present embodiment, for example, a polarizing film having a polarization degree of 70 to 90% and a transmissivity of 60 to 80% can 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 keeps the polarization direction according to the arrangement of the liquid crystal layer or rotates 90 degrees and is incident on the upper polarizing film, Is shielded by or passes through the upper polarizing film 57, whereby an image is realized.

According to this embodiment, the optical loss due to the polarizing film can be reduced without using a DBEF film such as a conventional reflective polarized light DBEF. Accordingly, the manufacturing cost of the LCD panel can be reduced, and the thickness of the backlight unit can be reduced. Further, the transmittance of the lower polarizing film can be increased, and the light loss can be further reduced.

On the other hand, when the polarization ratio of the non-polar LEDs 63 is relatively high, the lower polarizing film 59 can also be removed.

3 is a schematic view illustrating an LCD module in which a 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 a backlight unit 60 as described with reference to FIG. 2, the LCD module 70 includes an upper substrate 51, a lower substrate 53, a liquid crystal layer 55, and a liquid crystal layer And an upper polarizing film 57. However, the LCD panel 70 differs 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-polarized LEDs 63 is relatively high, the lower polarizing film 59 and the DBEF can be all removed, and the thickness of the LCD panel 70 can be further reduced.

In the embodiments of the present invention, although the diffusion plate 65 and the BEF 67 are described as being used, they can also be removed. For example, by arranging the LEDs 63 at a narrow interval on the plane, it is possible to realize planar light of high luminance by the LEDs 63, thereby eliminating the diffusion plate and the BEF.

4 is a cross-sectional view for explaining an example of a package type non-polarized light emitting diode that can be adopted in embodiments of the present invention.

Referring to FIG. 4, the non-polarized light emitting diode has a package body 71. The package body is formed to have a groove portion, and the lead terminals 73 are exposed in the groove portion. In addition, the side wall of the concave portion may be inclined at a predetermined angle.

The lead terminals 73 extend outward and protrude out of the package body 71. Lead terminals 73 protruding to the outside are connected to the printed circuit board and electrically connected to the external power source. The lead terminals 73 may be bent externally to enable surface mounting.

A heat sink 75 may be mounted on the lower portion of the package body 71. The heat sink is mounted to easily discharge the heat generated from the LED chip 77 to the outside. The heat sink 75 may have protrusions that protrude upward from the central portion of the base and base. The projecting portion is inserted into the package body and exposed to the recessed portion. The heat sink may be inserted into the through hole of the package body after the package body 71 having the through hole is formed. Alternatively, the heat sink 75 may be mounted on the package body 71 by positioning the lead terminals 73 and the heat sink 75 and forming the package body using the insert molding technique. The heat sink 75 may be electrically insulated from the lead terminals 73, but may be electrically connected to one of the lead terminals.

And a non-polarized LED chip 77 for emitting blue light is mounted on the heat sink 75. The LED chip 77 is a light emitting diode made of a nitride semiconductor of a GaN, InGaN, AlGaN or AlGaInN series, and is grown on an m-plane or an a-plane. The LED chip 77 has two electrodes for connection to an external power source. The electrodes may be on the same side or opposite sides of the LED chip 77. The electrodes may be electrically connected to the lead terminal through an adhesive, or may be connected to the lead terminal through a bonding wire as shown. In the case of the LED chip having electrodes formed on the same side, as shown in the figure, the LED chip 77 and the lead terminals can be connected to each other by two bonding wires to be electrically connected. Alternatively, when the electrodes are positioned on opposite sides, one electrode may be connected to the heat sink 75 using a conductive adhesive, one lead terminal may be connected to the heat sink 75 with a bonding wire, The lead terminals and the LED chip 77 can be electrically connected.

A red phosphor 81r is excited by the blue light to emit red light so that white light is mixed with a part of the light emitted from the LED chip 77, Green fluorescent material 81g is emitted. The red and green phosphors may be coated on the LED chip 77, or contained and contained in the molding member 79, as shown. The molding member 79 may be formed of an epoxy resin or a silicone resin, and may be formed as a single layer or a multilayer.

The red phosphor 81r may be, for example, an alkaline earth metal sulfide based red phosphor, and the green phosphor 81g may be a thiogallate green phosphor.

On the other hand, the lens 83 may cover the LED chip 77 and the phosphors 81r and 81g, and the lens may have various shapes. For example, to implement the top emission LED according to aspects of the present invention, the lens may have the shape of a convex lens, as shown. At this time, the curvature of the lens is determined according to the required directivity angle.

In this embodiment, white light can be realized by the blue LED chip 77 and the fluorescent material, thereby providing a light source capable of realizing a color image. On the other hand, instead of using the phosphors, the blue, green and red LED chips 77 can be mounted on the packages and the packages can be arranged respectively, or the blue, green and red LED chips 77 can be mounted in one package, It can also be implemented. At this time, the blue, green, and red LED chips 77 are composed of non-polar LEDs.

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

2 is a schematic view for explaining a liquid crystal display module according to an embodiment of the present invention.

3 is a schematic view for explaining a liquid crystal display module according to another embodiment of the present invention.

4 is a cross-sectional view illustrating an example of a non-polarized light emitting diode package that can be used in embodiments of the present invention.

Claims (6)

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, a lower polarizing film positioned below the lower substrate, and an upper polarizing film positioned on the upper substrate; And And a backlight unit disposed below the lower substrate for irradiating light polarized to the lower substrate, The backlight unit includes a non-polar LED that emits polarized light,  Wherein the lower polarizing film is positioned between the lower substrate and the backlight unit, the lower polarizing film has a lower polarization degree and a higher transmittance than the upper polarizing film, and the transmittance of the lower polarizing film is 60 to 80% And a separate structure for polarizing the light emitted from the non-polarized light emitting diode is not included under the lower polarizing film. The liquid crystal display module according to claim 1, wherein the polarization degree of the lower polarizing film is 70 to 90%. 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 disposed on the upper substrate; And And a backlight unit disposed below the lower substrate and configured to irradiate light polarized to the lower substrate, wherein the backlight unit includes a non-polar LED that emits polarized light, Is directly incident on the lower substrate, And a separate structure for polarizing the light emitted from the non-polarized light emitting diode is not included in the lower portion of the lower substrate. The liquid crystal display module according to claim 3, wherein the backlight unit further comprises a diffusion plate for mixing light emitted from the non-polarized light emitting diode. The liquid crystal display module according to claim 3, wherein the backlight panel further comprises a brightness enhancement film. The liquid crystal display module according to any one of claims 1 to 5, wherein the polarization degree of the upper polarizing film is 98 to 100%, and the transmissivity of the upper polarizing film is 40 to 50%.

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