KR101537561B1 - Backlight unit and Liquid crystal display device module including the same - Google Patents

Abstract

The present invention relates to a liquid crystal display module, and more particularly, to a liquid crystal display module including a light-measuring type backlight unit using an LED as a light source, to solve the problem of image quality such as hot spot by alleviating the directivity of light emitted from the LED .

To this end, there is provided a backlight unit including a light guide plate having an asymmetrical pattern formed on a light-incident portion facing the LED, and a liquid crystal display module including the backlight unit.

Light guide plate, LED

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE MODULE INCLUDING THE SAME

The present invention relates to a liquid crystal display (LCD) module, and more particularly, to a backlight unit capable of providing a uniform light source and a liquid crystal display module capable of providing high quality images.

2. Description of the Related Art In recent years, the display field has rapidly developed in line with the information age, and a liquid crystal display device (FPD) has been developed as a flat panel display device (FPD) having advantages of thinning, light weight, A plasma display panel (PDP), an electroluminescence display device (ELD), and a field emission display device (FED) : CRT).

Among these, the liquid crystal display device is excellent in moving picture display and is most actively used in the fields of notebook computers, monitors, TVs and the like due to its high contrast ratio. The liquid crystal display device does not have a self- A light source is required.

Accordingly, a backlight unit having a lamp is provided on the back surface, and light is irradiated toward the front of the liquid crystal panel, thereby realizing an image of a brightness that can be recognized only through the backlight unit.

As a light source of the backlight unit, a cold cathode fluorescent lamp, an external electrode fluorescent lamp, and a light emitting diode (LED) are used.

Among them, LEDs are widely used as a display light source, combining features of small size, low power consumption, and high reliability.

1 is a cross-sectional view of a typical liquid crystal display module using an LED as a light source.

As shown in the figure, a general liquid crystal display module includes a liquid crystal panel 10, a backlight unit 20, a support main body 30, a cover bottom 50, and a top cover 40.

The liquid crystal panel 10 is composed of a first substrate 12 and a second substrate 14 which are in contact with each other with a liquid crystal layer (not shown) therebetween.

A polarizing plate (not shown) is attached to each of the upper and lower surfaces of the liquid crystal panel 10, and a backlight unit 20 is provided behind the liquid crystal panel 10.

At this time, the backlight unit 20 includes an LED assembly 29 arranged along the longitudinal direction of at least one edge of the support main body 30, a white or silver reflective plate 25 seated on the cover bottom 50, A light guide plate 23 resting on the reflection plate 25, and a plurality of optical sheets 21 interposed therebetween.

The LED assembly 29 is formed on one side of the light guide plate 23 and includes a plurality of light emitting LEDs 29a and a flexible printed circuit board 29b on which the LEDs 29a are mounted. As shown in the figure, the case where the LED 29a is disposed on one side of the light guide plate 23 is referred to as a side light type or edge type backlight unit 20. In the liquid crystal display module including the light measuring type backlight unit 20, the light from the LED 29a is projected onto the entire screen of the liquid crystal panel 10 by using the transparent light guide plate 23, .

The liquid crystal panel 10 and the backlight unit 20 are covered with a top cover 40 covering the top edge of the liquid crystal panel 10 in a state where the edge is surrounded by the support main 30 having a rectangular frame shape, And the cover bottoms 50 are integrally joined to each other through the support main body 30.

The LED 29a has the advantage of low power consumption and the like because the LED 29a is strong in the straightness of the light. Therefore, the liquid crystal panel 10 is guided through the light guide plate 23, The uniformity is reduced. That is, a difference in brightness occurs between the portion where the LED 29a is located and the portion between the adjacent LED 29a, which causes a problem of luminance unevenness called a hot spot. Such a problem is severe when the LED 29a is positioned close to the light guide plate 23 to reduce the width of the liquid crystal display module.

In order to solve such a problem, a backlight unit has been proposed in which a pattern is formed in a light-incoming portion of a light guide plate in contact with an LED to alleviate the linearity of the LED light source.

2 is a plan view showing a conventional light guide plate having a patterned light-incident portion and a part of an LED as a light source. As shown in the figure, an LED 29a as a light source is disposed on one side of the light guide plate 23 to supply light. At this time, a concave-convex pattern 24 is formed in the light-incoming portion of the light guide plate 23 facing the LED 29a. That is, the concave portion 24b having a flat surface is located between the plurality of protruding portions 24a and the adjacent protruding portions 24a, which are located apart from each other and have a flat upper surface, to form the pattern 24 of the concavo-convex shape. Here, the projections 24a and the recesses 24b have the same width. That is, the projections 24a and the recesses 24b of the same shape are alternately arranged to form the pattern 24 of the concavo-convex shape. The plurality of protrusions 24a and the plurality of recesses 24b therebetween are positioned corresponding to one LED 29a.

In the case of using the light guide plate 23 having the concavo-convex pattern 24 formed thereon, the light incident from the LED 29a is relaxed to some extent and light of more uniform brightness is transmitted to the liquid crystal panel 10 Respectively.

However, in the case of using the light guide plate 23 having the concavo-convex pattern 24 described above, there is an effect that the straightness of the light emitted from the LED 29a is alleviated to some extent, however, have. Even when the light guide plate 23 having the conventional concavo-convex pattern 24 is used, there is still a problem of image quality deterioration due to non-uniform brightness, since light mixing or scattering does not occur to a large extent.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a backlight unit and a liquid crystal display module that can emit light of a uniform brightness by reducing the directivity of light emitted from an LED as a light source do.

The reason why light mixing or scattering does not occur even if a light guide plate having a concavo-convex pattern is used in the light-incoming portion is considered to be that a symmetrical pattern is formed corresponding to the LED. Accordingly, it is an object of the present invention to provide a light guide plate having an asymmetrical pattern formed therein so as to improve light mixing or scattering characteristics.

According to an aspect of the present invention, there is provided an LED lamp comprising: an LED lamp as a light source; A light guide plate having a plurality of projections and recesses alternating with each other on a side opposite to the LED lamp; Wherein one of the protruding portion and the concave portion has a flat surface parallel to the side surface and a plurality of sub-patterns having a mountain shape are formed on the other of the protruding portion and the concave portion To provide a backlight unit.

Wherein the recess has a flat bottom surface and a plurality of subpatterns are formed on the protrusions, the subpattern has a first height from a bottom surface of the recess, a second height less than the first height from the protruding portion, The recessed bottom surface may have a first width and the protruding portion may have a second width greater than the first width.

The protrusion has a flat upper surface, and a plurality of sub patterns are formed in the recess, the protrusion has a first height from the recess, and the sub pattern is smaller than the first height from the recess The upper surface of the protrusion has a first width, and the recess has a second width greater than the first width.

The second height may be 1/3 to 1/2 of the first height and the second width may be 5 to 7 times the first width.

A reflective plate is positioned below the light guide plate, and an optical sheet including a diffusion sheet and at least one light condensing sheet is positioned above the light guide plate.

In another aspect, the present invention provides a liquid crystal display comprising: a liquid crystal panel; A light guide plate disposed below the liquid crystal panel and supplying light to the liquid crystal panel, the light guide plate having an LED lamp as a light source, a pattern including a plurality of projections and recesses alternating with each other on a side facing the LED lamp, A backlight unit including a reflection plate positioned at a predetermined position; A cover bottom covering the bottom of the backlight unit; A support main body for supporting the liquid crystal panel and the backlight; And a top cover surrounding the edge of the liquid crystal panel, wherein one of the protruding portion and the recess has a flat surface parallel to the side surface, and a plurality of sub-patterns having a mountain shape on the other of the protruding portion and the recessed portion To provide a liquid crystal display device module.

Wherein the recess has a flat bottom surface and a plurality of subpatterns are formed on the protrusions, the subpattern has a first height from a bottom surface of the recess, a second height less than the first height from the protruding portion, The recessed bottom surface may have a first width and the protruding portion may have a second width greater than the first width.

The protrusion has a flat upper surface, and a plurality of sub patterns are formed in the recess, the protrusion has a first height from the recess, and the sub pattern is smaller than the first height from the recess The upper surface of the protrusion has a first width, and the recess has a second width greater than the first width.

The second height may be 1/3 to 1/2 of the first height and the second width may be 5 to 7 times the first width.

A reflective plate is positioned between the cover bottom and the light guide plate, and an optical sheet including a diffusion sheet and at least one light condensing sheet is positioned between the liquid crystal panel and the backlight unit.

The backlight unit according to the present invention uses a light guide plate having a plurality of irregular patterns formed on a surface facing the LED, which is a light source, to provide light having a uniform brightness.

Further, in the case of the liquid crystal display device module including the above-described backlight unit, since an image is displayed using light of uniform brightness, a cause of deterioration of display quality such as a smear is prevented and a high quality image is displayed.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.

3 is an exploded perspective view of a liquid crystal display module according to an embodiment of the present invention.

The liquid crystal display module includes a liquid crystal panel 110, a backlight unit 120, a support main body 130, a cover bottom 150, and a top cover 140.

First, the liquid crystal panel 110 plays a key role in image display and includes a first substrate 112 and a second substrate 114 which are bonded to each other with a liquid crystal layer (not shown) interposed therebetween.

At this time, a plurality of gate lines and data lines intersect to define a pixel on the inner surface of the first substrate 112, which is not shown in the drawings but is generally referred to as a lower substrate or an array substrate, A thin film transistor (TFT), which is a switching element, is provided at each intersection of a plurality of gate lines and a plurality of data lines, and is connected in a one-to-one correspondence with transparent pixel electrodes formed in each pixel.

On the inner surface of the second substrate 114 called an upper substrate or a color filter substrate, a color filter corresponding to each pixel and a color filter corresponding to each of the non-display elements such as a gate line, a data line, A black matrix is provided. The color filter may be composed of red (R), green (G), and blue (B) sub-color filters corresponding to each pixel. In addition, a transparent common electrode covering these elements is provided.

A polarizing plate (not shown) for selectively transmitting only specific light is attached to the outer surfaces of the first and second substrates 112 and 114, respectively.

The printed circuit board 117 is connected to at least one edge of the liquid crystal panel 110 via a connection member 116 such as a flexible circuit board or a tape carrier package (TCP) And is appropriately bent and adhered to the side surface of the main body 130 or the back surface of the cover bottom 150.

When the selected thin film transistor is turned on for each gate line by the on / off signal of the gate driving circuit to be scanned, the liquid crystal panel 110 having the structure described above turns on the signal voltage of the data driving circuit through the data line, And the alignment direction of the liquid crystal molecules is changed by the electric field between the pixel electrode and the common electrode, thereby exhibiting a difference in transmittance.

In addition, the liquid crystal display module according to the present invention is provided with a backlight unit 120 for supplying light from the rear surface of the liquid crystal display device module so that a difference in transmittance represented by the liquid crystal panel 110 is externally expressed.

The backlight unit 120 includes an LED assembly 129, a white or silver reflective plate 125, a light guide plate 123 seated on the reflective plate 125, and an optical sheet 121 interposed therebetween .

The LED assembly 129 is disposed on one side of the light guide plate 123 so as to face the light incident portion of the light guide plate 123. The LED assembly 129 includes a plurality of LEDs 129a spaced apart from each other, And an FPCB 129b on which the plurality of LEDs 129a are mounted.

The plurality of LEDs 129a emit light of red (R), green (G), and blue (B) colors toward the front of the light guide plate 123, The white light by the color mixing can be realized.

At this time, by using the LED 129a constituted by an LED chip (not shown) that emits all the colors of RGB, the white light can be realized in each LED 129a, or the white light can be emitted, LED 129a may also be used.

On the other hand, a plurality of LEDs 129a emitting RGB light may be bundled into one cluster, and a plurality of LEDs 129a mounted on the FPCB 129b may be arrayed on the FPCB 129b It is also possible to arrange them in parallel or in a plurality of rows.

The light guiding plate 123 uniformly spreads the light incident from the plurality of LEDs 129a to the wide area of the light guiding plate 123 to provide a surface light source to the liquid crystal panel 110 while traveling in the light guiding plate 123. [ The light guide plate 123 may be made of a transparent material such as acrylic resin such as polymethyl methacrylate (PMMA) or polycarbonate (PC) to efficiently guide light. have.

At this time, an irregular pattern (not shown) is formed in the light-incoming portion of the light guide plate 123 facing the LED 129a in order to alleviate the directivity of the light emitted from the LED 129a.

That is, although not shown, a pattern is formed in the light-incoming portion of the light guide plate 123, which is composed of a plurality of recesses which are spaced apart from each other by a predetermined distance and which have a flat upper surface and protrusions which are located between neighboring recesses. And a plurality of sub-patterns having a mountain shape are formed on the protrusions. That is, the plurality of protrusions and the plurality of recesses correspond to the respective LEDs 129a, and the protrusions and the recesses have different patterns, thereby enhancing the light mixing or scattering characteristics.

The reflection plate 125 is disposed on the back surface of the light guide plate 123 and reflects light passing through the back surface of the light guide plate 123 toward the liquid crystal panel 110 to improve the brightness of light.

The optical sheet 121 on the light guide plate 123 includes a diffusion sheet and at least one light condensing sheet and diffuses or condenses the light passing through the light guide plate 123 to provide a more uniform surface light source to the liquid crystal panel 110 Let it enter.

The liquid crystal panel 110 and the backlight unit 120 are modularized through a top cover 140, a support main 130 and a cover bottom 150. The top cover 140 is disposed on the top edge of the liquid crystal panel 110 And has a shape covering the side surface. That is, the top cover 140 has an opening with respect to the display portion of the liquid crystal panel 110, and displays an image formed on the liquid crystal panel 110 therethrough.

The cover bottom 150 is formed of a lower surface and four sides to provide a space where the liquid crystal panel 110 and the backlight unit 120 can be seated.

The support main body 130 of a square shape which rests on the cover bottom 150 and covers the edges of the liquid crystal panel 110 and the backlight unit 120 is divided into a top cover 140, .

The light guide plate, which is the most characteristic construction of the present invention, will be described in detail.

4 is a plan view showing a part of an LED as a light source and a light guide plate of the present invention having a patterned light-incoming portion. As shown in the figure, an LED 129a as a light source is disposed on one side of the light guide plate 123 to supply light toward the light guide plate 123. At this time, a concave-convex pattern 124 is formed in the light-incoming portion of the light guide plate 123 facing the LED 129a. The plurality of protrusions 124a and the plurality of recesses 124b therebetween are positioned corresponding to one LED 129a. That is, the concave portion 124b is located between the plurality of protruding portions 124a and the adjacent protruding portions 124a, which are located apart from each other and have a flat bottom surface, to form a pattern 124 of concavo-convex shape. That is, the protrusions 124a and the recesses 124b are alternately arranged to form the pattern 124 of concavo-convex shape, and each of the protrusions 124a is composed of a plurality of sub-patterns 124c having a mountain shape, Like concavo-convex pattern 124 is formed.

The conventional light guide plate 23 shown in Fig. 2 is provided with a light-projecting portion pattern 24 symmetrical to the projecting portion 24a having the same shape and the concave portion 24b. Light has the same profile and is scattered so that the light that passes through neighboring patterns does not mix well. However, in the present invention, since the projections 124a and the recesses 124b having different shapes are alternately arranged and the asymmetrical projections and recesses 124 are formed in the light-incident portion of the light guide plate 123, the adjacent projections 124a, And the concave portion 124b have different profiles. Therefore, the light that has passed through the neighboring protruding portions 124a and the concave portions 124b is well mixed with each other, thereby improving the uniformity of brightness as a whole and solving the problem of hot spot. According to such a configuration, the straightness of light passing through the LED 129a is relaxed, so that not only the hot spot problem at the light incident portion of the light guide plate 123 but also the problem of the luminance non-uniformity at the opposite side of the light incident portion is also solved.

At this time, the first height H1 from the bottom surface of the concave portion 124b to the end of the sub pattern 124c formed on the protruding portion 124a, and the mountain-shaped sub pattern 124c extends from the protruding portion upper surface 124d And has a second height H2 less than the first height H1. The second height H2 may be 1/3 to 1/2 of the first height H1. The bottom surface of the concave portion 124b has a first width W1 and the protruding portion 124a has a second width W2 that is larger than the first width W1. The second width W2 may be 5 to 7 times the first width W1.

4 shows that the second width W2 of the protrusion 124a on which the sub pattern 124c is formed is larger than the first width W1 of the recess 124b, The second width W2 may be smaller than the first width W1 of the concave portion 124b. In this case, the first width W1 of the concave portion 124b may be 5 to 7 times the second width W2 of the protruding portion 124a.

Although not shown, as a modification of the light guide plate 123 shown in FIG. 4, such a sub pattern may be formed in the concave portion, and in this case, the projecting portion has a flat upper surface. Similar to the embodiment of Fig. 4, the protrusion has a first height from the recess and the sub-pattern has a second height less than the first height from the recess. The second height may be 1/3 to 1/2 of the first height. Further, the projecting portion has a first width, and the recess has a second width larger than the first width. The second width may be 5 to 7 times the first width.

In this modified example, the second width of the concave portion may be smaller than the first width of the protruding portion. In this case, the first width of the projection may be 5 to 7 times the second width of the recess.

That is, as can be seen from the embodiment of FIG. 4 and its modifications, a flat surface is formed in either the protruding portion or the recessed portion, and a plurality of mountain-shaped subpatterns are formed in the other portion, An asymmetrical concavo-convex pattern 124 corresponding to the light guide plate 129a is formed in the light-incoming portion of the light guide plate 123. [

As described above, the asymmetrical concave-convex pattern 124 formed of the protruding portions 124a and the concave portions 124b having different shapes is formed in the light-incident portion of the light guide plate 123 facing the LED 129a, The scattering characteristics of light are maximized. Accordingly, since the directivity of the light emitted from the LED 129a is relaxed by the asymmetrical pattern formed in the light-incident portion of the light guide plate 123, it is possible to supply light with uniform luminance as a whole, It is possible to eliminate the defective image quality of the image.

5A and 5B are photographs showing the brightness of light emitted from the backlight using the light guide plate of FIGS. 2 and 4, respectively.

First, as shown in Fig. 2, a light guide plate 23 having a symmetrical light-incoming portion pattern 24 was produced. Specifically, the pattern 24 of the light-landing portion has a width of 0.98 mm and projections 24a and recesses 24b having the same shape alternately formed, and the height of the projections 24a is 0.2 mm.

On the other hand, as shown in Fig. 4, the light guide plate 123 of the present invention is formed with a plurality of sub-patterns 124c each having a mountain-like shape between the concave portions 124b having a flat lower surface, And the light-incoming portion pattern 124 is formed. The first width W1 of the concave portion 124b is 0.3 mm and the second width W2 of the projection 124a is 1.84 mm. The first width W1 of the concave portion 124b is 0.3 mm. H1 and the second height H2 from the upper surface 124d of the protrusion 124a to the sub pattern 124c is 0.13 mm. Here, the concrete numerical values of the light guide plate light-incoming portion pattern 124 may be variously changed according to the conditions such as the size of the light guide plate.

Referring to FIG. 5A, in the case of the backlight unit using the conventional light guide plate of FIG. 2, the brightness is higher in the light-incident portion A and the light-out portion C opposite to the light-incident portion than in the central portion B. This is due to the linearity of the light emitted from the LED. Since the light-incident portion A of the light guide plate is close to the LED, the brightness unevenness occurs partially. Also, since the light emitted from the LED is reflected to the support main (30 in FIG. 1) to be.

Meanwhile, referring to FIG. 5B, the backlight unit using the conventional light guide plate of FIG. 4 has improved luminance uniformity, which can be easily seen from the luminance measurement results shown in Table 1 below.

Table 1

Experimental Example 1 Experimental Example 2
Luminance
A 4256 4577 4250 6135 5889 6053 B 5411 5282 5388 6306 5884 6233 C 6081 6069 5956 6214 6223 6224 Average luminance [nit] 5252 6129 Uniformity [%] 70 93

This is the result of measuring the brightness of the light guide plate at three places on the basis of the light incident portion (A), the central portion (B), and the large light portion (C). As can be seen from Table 1, it can be seen that the average luminance and the uniformity in Experimental Example 2 using the light guide plate of the present invention are improved as compared with Experimental Example 1 using the conventional light guide plate.

As described above, in the present invention, the asymmetrical pattern is formed in the light-incident portion of the light guide plate, so that strong straight-line light emitted from the LED and incident on the light-incident portion of the light guide plate is reflected by the asymmetric light- This is because the light mixing or scattering property is enhanced and thus the entire brightness is uniform.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It can be understood that

1 is a cross-sectional view of a typical liquid crystal display module using an LED as a light source.

2 is a plan view showing a conventional light guide plate having a patterned light-incident portion and a part of an LED as a light source.

3 is an exploded perspective view of a liquid crystal display module according to an embodiment of the present invention.

4 is a plan view showing a part of an LED as a light source and a light guide plate of the present invention having a patterned light-incoming portion.

5A and 5B are photographs showing the brightness of light emitted from the backlight using the light guide plate of FIGS. 2 and 4, respectively.

Claims (10)

A plurality of LED lamps as a light source; And a light guide plate having a plurality of projections and recesses alternating with each other on a side opposite to the plurality of LED lamps, Wherein the concave portion has a flat surface parallel to the side surface, a plurality of sub-patterns having a mountain shape are formed in the protruding portion, At least one of the plurality of projections and at least one of the plurality of recesses corresponds to one of the plurality of LED lamps, Wherein the sub pattern has a first height from a bottom surface of the recess and a second height from the protrusion smaller than the first height, the bottom surface of the recess has a first width, the protrusion has a first width larger than the first width, Two widths, Wherein the second height is 1/3 to 1/2 of the first height and the second width is 5 to 7 times the first width. delete delete delete The method according to claim 1, Wherein a reflective plate is positioned below the light guide plate, and an optical sheet including a diffusion sheet and at least one light condensing sheet is positioned above the light guide plate. A liquid crystal panel; And a light guide plate disposed below the liquid crystal panel to supply light to the liquid crystal panel and including a light source LED lamp and a plurality of protrusions and recesses alternating with each other on a side facing the LED lamp, and; A cover bottom covering the bottom of the backlight unit; A support main body for supporting the liquid crystal panel and the backlight; And a top cover surrounding the edge of the liquid crystal panel, Wherein the concave portion has a flat surface parallel to the side surface, a plurality of sub-patterns having a mountain shape are formed in the protruding portion, At least one of the plurality of projections and at least one of the plurality of recesses corresponds to one of the plurality of LED lamps, Wherein the sub pattern has a first height from a bottom surface of the recess and a second height from the protrusion smaller than the first height, the bottom surface of the recess has a first width, the protrusion has a first width larger than the first width, Two widths, Wherein the second height is 1/3 to 1/2 of the first height and the second width is 5 to 7 times the first width. delete delete delete The method according to claim 6, Wherein a reflective plate is positioned between the cover bottom and the light guide plate, and an optical sheet including a diffusion sheet and at least one light condensing sheet is positioned between the liquid crystal panel and the backlight unit.

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