KR20100030910A - Backlight unit and liquid crystal display device module including the same - Google Patents

Abstract

PURPOSE: A backlight unit and liquid display device module containing the same are provided to obtain light having uniform brightness by using a light guide plate in which plural irregular pattern is formed. CONSTITUTION: A backlight unit comprises a light guide plate(123), reflection plate, and sub pattern(124c). The light guide plate forms pattern having plural protrusions(124a) and concaves(124b). The reflection plate is placed at the lower portion of the light guide plate. In the sub pattern, one of protrusion and concave is flat form and the other one is convex form.

Description

Backlight unit and liquid crystal display device module including the same

The present invention relates to a liquid crystal display module, and more particularly, to a backlight unit capable of providing a uniform light source and a liquid crystal display module capable of providing a high quality image including the same.

In line with the recent information age, the display field has also been rapidly developed, and a liquid crystal display device (FPD) as a flat panel display device (FPD) having the advantages of thinning, light weight, and low power consumption has been correspondingly developed. LCD, plasma display panel device (PDP), electroluminescence display device (ELD), field emission display device (FED), etc. : It is rapidly replacing CRT.

Among them, the liquid crystal display device is most actively used in the field of notebooks, monitors, TVs, etc. due to its excellent contrast ratio and high contrast ratio. The liquid crystal display device is a device that does not have a light emitting element. It requires a light source.

As a result, a backlight unit having a lamp is provided on the rear side to irradiate light toward the front of the liquid crystal panel, thereby realizing an image of identifiable luminance.

On the other hand, as a light source of the backlight unit, a cold cathode fluorescent lamp (Cold Cathode Fluoresent Lamp), an external electrode fluorescent lamp (External Electrode Fluoresent Lamp), and a light emitting diode (Light Emitting Diode (LED)) is used.

Among them, LEDs are particularly widely used as display light sources having features such as small size, low power consumption, and high reliability.

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

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

The liquid crystal panel 10 is a part that plays a key role in image expression and is composed of first and second substrates 12 and 14 bonded to each other with a liquid crystal layer (not shown) interposed therebetween.

In addition, polarizers (not shown) are attached to upper and lower surfaces of the liquid crystal panel 10, and a backlight unit 20 is provided behind the liquid crystal panel 10.

In this case, the backlight unit 20 includes an LED assembly 29 arranged along at least one edge length direction of the support main 30, a white or silver reflecting plate 25 mounted on the cover bottom 50, and the like. The light guide plate 23 mounted on the reflective plate 25 and a plurality of optical sheets 21 interposed thereon are included.

The LED assembly 29 is configured on one side of the light guide plate 23, and includes a plurality of LEDs 29a emitting light and a flexible printed circuit board 29B on which the LEDs 29a are mounted. As shown, the case where the LED 29a is located on one side of the light guide plate 23 is called a side light type or edge type backlight unit 20. In the liquid crystal display module including the photometric backlight unit 20, the transparent light guide plate 23 is used to project the light from the LED 29a to the entire screen of the liquid crystal panel 10. There is this.

The liquid crystal panel 10 and the backlight unit 20 have a top cover 40 surrounding the top edge of the liquid crystal panel 10 and the back surface of the backlight unit 20 with the edges surrounded by the support main 30 having a rectangular frame shape. Cover cover 50 to cover each is coupled in front and rear are integrated through the support main 30 as a medium.

In the liquid crystal display module as described above, the LED 29a having advantages such as low power consumption is used as the light source. Since the LED 29a has a strong linearity of light, the liquid crystal panel 10 is provided through the light guide plate 23. The light supplied to is not uniform. That is, a difference in brightness occurs between a portion where the LED 29a is located and a portion between the neighboring LEDs 29a, which causes a problem of luminance unevenness called a hot spot. This problem is severe when the LED 29a is placed close to the light guide plate 23 in order to reduce the width of the liquid crystal display module.

In order to solve this problem, a backlight unit has been proposed to form a pattern on the light incidence portion of the light guide plate in contact with the LED to mitigate the straightness of the LED light source.

FIG. 2 is a plan view showing a part of an LED which is a conventional light guide plate and a light source having a patterned light incident portion. As illustrated, the LED 29a, which is a light source, is positioned at one side of the light guide plate 23 to supply light. At this time, a pattern 24 having an uneven shape is formed in the light incidence portion of the light guide plate 23 facing the LED 29a. That is, a plurality of protrusions 24a which are spaced apart from each other and having a flat upper surface and a concave portion 24b having a flat surface are positioned between the adjacent protrusions 24a to form a concave-convex pattern 24. Here, the width | variety of the protrusion part 24a and the recessed part 24b is the same. That is, the protrusion part 24a and the recess part 24b of the same shape are alternately arrange | positioned, and the pattern 24 of the uneven | corrugated form is formed. The plurality of protrusions 24a and the plurality of recesses 24b therebetween are located corresponding to one LED 29a.

In the case where the light guide plate 23 having the uneven pattern 24 is formed, the light incident from the LED 29a is moderated to some extent so that light of more uniform brightness is emitted to the liquid crystal panel 10 (see FIG. 1). Will be supplied to

However, when the light guide plate 23 having the above-described concave-convex pattern 24 is used, the straightness of the light emitted from the LED 29a is somewhat alleviated, but there is still a problem of light uniformity due to the straightness. have. Even when the light guide plate 23 having the pattern 24 of the concave-convex shape is used, since the mixing or scattering of light does not occur greatly, there is still a problem of deterioration of image quality due to uneven brightness.

The present invention is to solve the above problems, the present invention is to provide a backlight unit and a liquid crystal display module that can provide light of uniform brightness by reducing the linearity of the light emitted from the light source LED. do.

Even if a light guide plate having a concave-convex pattern is used in the light-receiving portion, the mixing or scattering of light does not occur easily, because it is considered that a symmetrical pattern is formed corresponding to the LED. Accordingly, the present invention is to provide a light guide plate in which an asymmetrical pattern is formed so as to improve mixing or scattering characteristics of light.

In order to achieve the above object, the present invention provides an LED lamp which is a light source; A light guide plate having a pattern consisting of a plurality of protrusions and recesses alternate with each other on a side facing the LED lamp; And a reflecting plate positioned below the light guide plate, wherein one of the protrusions and the recesses 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 protrusions and the recesses. To provide a backlight unit.

The recess has a flat bottom, a plurality of sub-patterns are formed in the protrusion, the sub-pattern has a first height from the bottom of the recess, and has a second height smaller than the first height from the protrusion. The recess bottom may have a first width, and the protrusion may have a second width that is greater than the first width.

Meanwhile, 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 second surface may have a second height, and an upper surface of the protrusion may have a first width, and the recess may have 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 may be positioned below the light guide plate, and an optical sheet including a diffusion sheet and at least one light collecting sheet may be positioned above the light guide plate.

In another aspect, the present invention is a liquid crystal panel; A light guide plate positioned under the liquid crystal panel to supply light to the liquid crystal panel, the light guide plate having a light source having a light source, a pattern consisting of a plurality of protrusions and recesses alternately disposed on a side facing the LED lamp; A backlight unit including a reflection plate positioned at; A cover bottom covering a lower portion of the backlight unit; A support main for supporting the liquid crystal panel and the backlight; A top cover surrounding an edge of the liquid crystal panel, wherein one of the protrusions and the recesses has a flat surface parallel to the side surface, and a plurality of subpatterns having a mountain shape is formed on the other of the protrusions and the recesses. An object of the present invention is to provide a liquid crystal display module.

The recess has a flat bottom, a plurality of sub-patterns are formed in the protrusion, the sub-pattern has a first height from the bottom of the recess, and has a second height smaller than the first height from the protrusion. The recess bottom may have a first width, and the protrusion may have a second width that is greater than the first width.

Meanwhile, 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 second surface may have a second height, and an upper surface of the protrusion may have a first width, and the recess may have 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.

The reflective plate may be disposed between the cover cover and the light guide plate, and an optical sheet including a diffusion sheet and at least one light collecting sheet may be disposed 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 an LED as a light source, thereby providing light having uniform luminance.

In addition, in the case of the liquid crystal display device module including the backlight unit as described above, since the image is displayed using light having a uniform brightness, it is possible to prevent the cause of deterioration of display quality such as unevenness, thereby providing high quality images.

Hereinafter, embodiments of 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 exemplary embodiment of the present invention.

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

First, the liquid crystal panel 110 plays a key role in image expression and includes a first substrate 112 and a second substrate 114 bonded to each other with a liquid crystal layer interposed therebetween.

In this case, under the premise of an active matrix method, a plurality of gate lines and data lines intersect each other, and pixels are defined on an inner surface of the first substrate 112, which is not shown in the drawings, but is commonly referred to as a lower substrate or an array substrate. Thin film transistors (TFTs), which are switching elements, are provided at intersections of the plurality of gate lines and the plurality of data lines, and are connected one-to-one with the transparent pixel electrodes formed in each pixel.

In addition, a color filter corresponding to each pixel and an inner surface of the second substrate 114 called an upper substrate or a color filter substrate surround each other and cover non-display elements such as gate lines, data lines, and thin film transistors. A black matrix is provided. The color filter may be configured as a sub-color filter of red (R), green (G), and blue (B) color corresponding to each pixel. In addition, a transparent common electrode covering them is provided.

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

In addition, the printed circuit board 117 is connected through at least one edge of the liquid crystal panel 110 via a connecting member 116 such as a flexible printed circuit board or a tape carrier package (TCP) to support the modularization process. The side surface of the main 130 or the cover bottom 150 is bent properly to be in close contact.

Accordingly, in the liquid crystal panel 110 having the above-described structure, when the thin film transistor selected for each gate line is turned on by the on / off signal of the gate driver circuit which is scanned and transmitted, the signal voltage of the data driver circuit is applied to the corresponding pixel through the data line. The direction of the liquid crystal molecules is changed by the electric field between the pixel electrode and the common electrode.

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 panel 110 so that the difference in transmittance is expressed to the outside.

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

The LED assembly 129 described above is located at one side of the light guide plate 123 so as to face the light incident part of the light guide plate 123, and the LED assembly 129 is arranged with a plurality of LEDs 129a spaced at a predetermined interval, The FPCB 129b includes a plurality of LEDs 129a mounted thereon.

At this time, the plurality of LEDs (129a) emits light having a color of red (R), green (G), blue (B), respectively, toward the light incident portion of the light guide plate 123, such a plurality of LEDs (129a) By lighting all at once, white light by color mixing can be realized.

At this time, by using the LED 129a configured with an LED chip (not shown) that emits all the colors of RGB, the white light may be implemented in each LED 129a, or a chip that emits complete white including a chip emitting white. LED 129a may be used.

Meanwhile, a plurality of LEDs 129a emitting RGB light may be bundled and mounted in a cluster, and the plurality of LEDs 129a mounted on the FPCB 129b may be arranged on the FPCB 129b. It is also possible to arrange them side by side or to arrange them side by side in a plurality of columns.

The light guide plate 123 evenly spreads the light incident from the plurality of LEDs 129a to the wide area of the light guide plate 123 while providing the surface light source to the liquid crystal panel 110. The light guide plate 123 may be made of a light transmitting material such as an acrylic resin such as PolyMethylMethAcrylate (PMMA) or a material such as polycarbonate (PC) to guide light efficiently. have.

In this case, in order to alleviate the straightness of the light emitted from the LED 129a, an irregular pattern (not shown) is formed at the light incident portion of the light guide plate 123 facing the LED 129a.

That is, although not shown, the light receiving plate 123 is formed with a pattern consisting of a plurality of recesses which are spaced apart at regular intervals, and which have a flat upper surface and protrusions positioned between adjacent recesses. The protrusions are formed with a plurality of subpatterns having a mountain shape. 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 improving the mixing or scattering characteristics of the light.

The reflective plate 125 is positioned on the rear surface of the light guide plate 123, and reflects light passing through the rear surface of the light guide plate 123 toward the liquid crystal panel 110 to improve the brightness of the light.

The optical sheet 121 on the light guide plate 123 includes a diffusion sheet and at least one light collecting sheet, and diffuses or collects light passing through the light guide plate 123 to provide a more uniform surface light source to the liquid crystal panel 110. Make it incident.

The liquid crystal panel 110 and the backlight unit 120 are modularized through the top cover 140, the support main 130, and the cover bottom 150. The top cover 140 is formed by the top edge of the liquid crystal panel 110. It has a shape covering the side. That is, the top cover 140 has an opening with respect to the display unit of the liquid crystal panel 110, and thereby displays an image implemented in the liquid crystal panel 110.

In addition, the cover bottom 150 has a bottom surface and four sides, thereby providing a space in which the liquid crystal panel 110 and the backlight unit 120 may be seated.

In addition, the support main 130 having a rectangular frame shape seated on the cover bottom 150 and covering the edges of the liquid crystal panel 110 and the backlight unit 120 may include the top cover 140 and the cover bottom 150. Combined.

The light guide plate which is the most characteristic structure of this invention is demonstrated in detail.

4 is a plan view showing a part of the LED which is a light guide plate and a light source of the present invention having a patterned light incident portion. As shown, the LED 129a which is a light source is positioned on one side of the light guide plate 123 to supply light toward the light guide plate 123. At this time, a pattern 124 having an uneven shape is formed in the light incident part of the light guide plate 123 facing the LED 129a. The plurality of protrusions 124a and the plurality of recesses 124b therebetween are located corresponding to one LED 129a. That is, the concave portion 124b is positioned between the plurality of protrusions 124a and the adjacent protrusions 124a which are spaced apart from each other and have a flat bottom, thereby forming a pattern 124 having an uneven shape. That is, the protrusions 124a and the recesses 124b are alternately arranged to form the uneven pattern 124, and each of the protrusions 124a is composed of a plurality of subpatterns 124c having a mountain shape, thereby being asymmetrical. Concave-convex pattern 124 is formed.

In the conventional light guide plate 23 shown in FIG. 2, a symmetric light incident part pattern 24 is formed of protrusions 24a and concave parts 24b having the same shape, and emitted from the LED 29a by the same pattern. Light has the same profile and is scattered so that the mixing of light through neighboring patterns is less likely. However, in the present invention, since the protrusions 124a and the recesses 124b having different shapes are alternately arranged so that an asymmetric uneven pattern 124 is formed at the light incident portion of the light guide plate 123, the adjacent protrusions 124a are formed. The light passing through the recess 124b has a different profile. Therefore, the light passing through the neighboring protrusion 124a and the recess 124b is well mixed with each other, thereby improving the uniformity of the overall brightness and solving a problem such as a hot spot. According to such a structure, the linearity of the light which passed through the LED 129a is alleviated, and not only the hot spot problem in the light incidence part of the light guide plate 123 but also the problem of luminance unevenness in the opposite side of the light incidence part are solved.

At this time, the bottom surface of the concave portion 124b has the first height H1 from the bottom of the sub pattern 124c formed in the protrusion 124a, and the mountain subpattern 124c is formed from the upper surface 124d of the protrusion. It has a second height H2 smaller than the first height H1. The second height H2 may be 1/3 to 1/2 of the first height H1. In addition, the bottom of the recessed portion 124b has a first width W1, and the protrusion 124a has a second width W2 larger than the first width W1. The second width W2 may be 5 to 7 times the first width W1.

In FIG. 4, the second width W2 of the protrusion 124a on which the subpattern 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 recess 124b. In this case, the first width W1 of the recess 124b may be 5 to 7 times the second width W2 of the protrusion 124a.

On the other hand, although not shown, as a modification of the light guide plate 123 shown in Figure 4, such a sub-pattern may be formed in the concave portion, in which case the protrusion has a flat upper surface. At this time, similar to the embodiment of FIG. 4, the protrusion has a first height from the recess, and the subpattern has a second height smaller than the first height from the recess. The second height may be 1/3 to 1/2 of the first height. In addition, the protrusion has a first width and the recess has a second width that is greater than the first width. The second width may be 5 to 7 times the first width.

Also in this modification, the second width of the recess may be smaller than the first width of the protrusion. In this case, the first width of the protrusion 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 modified example, each of the LEDs is formed by forming a flat surface on one of the protrusions and the concave portion, and forming a plurality of mountain-shaped subpatterns on the other. An asymmetric uneven pattern 124 corresponding to 129a is formed in the light incident portion of the light guide plate 123.

As described above, an asymmetric uneven pattern 124 consisting of protrusions 124a and concave portions 124b having different shapes is formed on the light incident portion of the light guide plate 123 facing the LED 129a. The mixing scattering properties of light are maximized. Therefore, the straightness of the light emitted from the LED 129a is alleviated by the asymmetrical pattern formed on the light incident portion of the light guide plate 123, so that light having a uniform luminance as a whole can be supplied, resulting in a hot spot or the like. Can eliminate the poor quality of the picture.

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

First, as shown in FIG. 2, the light guide plate 23 which has the symmetric light-incident part pattern 24 was produced. Specifically, each of the patterns 24 of the light incident portion has a width of 0.98 mm, and protrusions 24a and recesses 24b having the same shape are alternately formed, and the height of the protrusions 24a is 0.2 mm.

4, in the light guide plate 123 of the present invention, recesses 124b having a flat bottom surface are spaced apart from each other, and a plurality of subpatterns 124c having a mountain shape are formed therebetween. Protruding portions 124a are positioned to form a light incident portion pattern 124. Here, the second width W2 of the protrusion 124a is 1.84 mm, the first width W1 of the recess 124b is 0.3 mm, and the first height from the recess 124b to the subpattern 124c ( H1 is 0.27 mm, and the second height H2 from the upper surface 124d of the protrusion 124a to the subpattern 124c is 0.13 mm. Here, the specific value of the light guide plate incident part pattern 124 may be variously changed according to conditions such as the size of the light guide plate.

Referring to FIG. 5A, the backlight unit using the conventional LGP of FIG. 2 has a luminance higher than that of the center portion B at the light incident portion C opposite to the light incident portion A and the light incident portion. This is due to the straightness of the light emitted from the LEDs. Since the light incident portion A of the light guide plate is close to the LED, the luminance unevenness is partially generated. Also, the light incident portion C has the light emitted from the LED reflected by the support main (30 in FIG. 1). to be.

Meanwhile, referring to FIG. 5B, the backlight unit using the conventional LGP of FIG. 4 has an improved luminance uniformity, which can be easily seen through 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 a result of dividing the light guide plate into three parts based on the light incidence portion A, the central portion B, and the light portion C, and measuring luminance at three locations in each portion. As can be seen from Table 1, it can be seen that the average brightness and uniformity in Experimental Example 2 using the light guide plate of the present invention is improved compared to Experimental Example 1 using a conventional light guide plate.

As described above, in the present invention, asymmetrical pattern is formed in the light incidence part of the light guide plate, whereby strong straight light emitted from the LED and incident on the light incidence part of the light guide plate is generated by the asymmetric light incidence pattern. This is because the light mixing or scattering characteristics are enhanced to lead to a uniform luminance as a whole.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art various modifications and changes of the present invention without departing from the spirit and scope of the present invention described in the claims below I can understand that you can.

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

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

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

4 is a plan view showing a part of the LED which is a light guide plate and a light source of the present invention having a patterned light incident portion.

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

Claims (10)

An LED lamp which is a light source; A light guide plate having a pattern consisting of a plurality of protrusions and recesses alternate with each other on a side facing the LED lamp; A reflection plate positioned under the light guide plate, One of the protrusions and the recesses has a flat surface parallel to the side, and the other of the protrusions and the recesses is formed with a plurality of subpatterns having a mountain shape. The method of claim 1, The recess has a flat bottom, a plurality of sub-patterns are formed in the protrusion, the sub-pattern has a first height from the bottom of the recess, and has a second height smaller than the first height from the protrusion. The concave bottom surface has a first width, and the protrusion has a second width greater than the first width. The method of claim 1, The protrusion has a flat upper surface, and a plurality of subpatterns are formed in the recess, the protrusion has a first height from the recess, and the subpattern has a second smaller than the first height from the recess. And a height, wherein an upper surface of the protrusion has a first width, and the recess has a second width greater than the first width. The method of claim 2 or 3, And 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. The method of claim 1, And a reflecting plate under the light guide plate, and an optical sheet including a diffusion sheet and at least one light collecting sheet above the light guide plate. A liquid crystal panel; A light guide plate positioned under the liquid crystal panel to supply light to the liquid crystal panel, the light guide plate having a light source having a light source, a pattern consisting of a plurality of protrusions and recesses alternately disposed on a side facing the LED lamp; A backlight unit including a reflection plate positioned at; A cover bottom covering a lower portion of the backlight unit; A support main for supporting the liquid crystal panel and the backlight; A top cover surrounding an edge of the liquid crystal panel; One of the protrusions and the concave portion has a flat surface parallel to the side, and the other of the protrusion and the concave portion is formed with a plurality of sub-pattern having a mountain shape. The method of claim 6, The recess has a flat bottom, a plurality of sub-patterns are formed in the protrusion, the sub-pattern has a first height from the bottom of the recess, and has a second height smaller than the first height from the protrusion. And a bottom portion of the concave portion has a first width, and the protrusion portion has a second width larger than the first width. The method of claim 6, The protrusion has a flat upper surface, and a plurality of subpatterns are formed in the recess, the protrusion has a first height from the recess, and the subpattern has a second smaller than the first height from the recess. And a height, wherein an upper surface of the protruding portion has a first width, and the concave portion has a second width greater than the first width. The method according to claim 7 or 8, And 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. The method of claim 6, And a reflective plate disposed between the cover cover and the light guide plate, and an optical sheet including a diffusion sheet and at least one light collecting sheet disposed between the liquid crystal panel and the backlight unit.

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