KR20080057389A - Back light assembly and display apparatus having the same - Google Patents

Abstract

A backlight assembly and a display apparatus having the same are provided to form a light scattering pattern to a light receiving portion of a light guide panel, thereby reducing dark portions between the spot light sources. A light guide panel(200) includes a light receiving surface for receiving a light beam. The lower surface of the light guide panel includes the first prism patterns formed separately to each other. A planarizing portion is formed vertically to the light receiving surface between the first prism patterns. The second prism patterns(270) connected with each other are formed on the upper surface of the light guide panel. Plural spot light sources(300) are arranged at the light receiving surface of the light guide panel and generate the light beam. A light scattering pattern(290) is formed at the light receiving portion of the light guide panel adjacent to the spot light source. The light scattering pattern includes a saw-toothed shape formed at the light receiving surface.

Description

BACK LIGHT ASSEMBLY AND DISPLAY APPARATUS HAVING THE SAME}

1 is an exploded perspective view showing a backlight assembly according to an embodiment of the present invention;

FIG. 2 is a combined cross-sectional view of the backlight assembly shown in FIG. 1.

3 is a perspective view showing an embodiment of a light scattering pattern.

4 is a plan view showing another embodiment of the light scattering pattern.

5 is a plan view showing still another embodiment of the light scattering pattern.

6 is a side view illustrating an embodiment of a first prism pattern.

7 is a perspective view illustrating another embodiment of the light guide plate.

8 is a simulation result showing the luminance distribution according to the light scattering pattern.

9 is an exploded perspective view illustrating a display device according to an exemplary embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: backlight assembly 110: reflective sheet

120: optical sheet 200: light guide plate

250: first prism pattern 270: second prism pattern

280: total reflection 290: light scattering pattern

300: point light source 700: display unit

710: display panel 720: driving circuit unit

The present invention relates to a backlight assembly and a display device having the same, and more particularly, to a backlight assembly and a display device having the same, which can improve brightness uniformity and increase brightness.

Among display devices for displaying images, liquid crystal displays are thinner and lighter than other display devices such as CRTs and PDPs, and have low driving voltage and low power consumption, and thus are widely used throughout the industry.

Since the liquid crystal display device is a non-light emitting device that does not emit light by the liquid crystal display panel displaying an image, it requires a backlight assembly for supplying light to the liquid crystal display panel.

BACKGROUND In general, a backlight assembly used in a notebook or monitor or the like includes a light source for generating light, a light guide plate for guiding light from the light source, and optical sheets. Recently, in order to reduce the number of optical sheets to achieve light weight and cost reduction, a prism light guide plate having prismatic patterns formed on the upper and lower surfaces of the light guide plate has been developed. In addition, instead of a cold cathode fluorescent lamp (CCFL), which is mainly used as a light source, research is being conducted to further reduce weight and increase color reproducibility by using light emitting diodes (LEDs).

However, when the prism light guide plate and the light emitting diodes are used, a problem occurs in that a dark portion is generated between the light emitting diodes in the light incident region of the prism light guide plate.

Accordingly, the present invention has been made in view of such a problem, and the present invention provides a backlight assembly capable of achieving light weight and cost reduction by using a prism light guide plate and light emitting diodes and suppressing luminance unevenness generated in the light incident portion of the prism light guide plate. to provide.

In addition, the present invention provides a display device having the above-described backlight assembly.

The backlight assembly according to an aspect of the present invention includes a light guide plate and a plurality of point light sources. The light guide plate may include an incident surface on which light is incident, a first prism pattern formed to be spaced apart from each other, a lower surface including a flat portion formed perpendicular to the incident surface between the first prism patterns, and second prism patterns connected to each other. It includes the upper surface formed. The point light sources are disposed on an incident surface of the light guide plate to generate light. In this case, a light scattering pattern is formed on the light incident portion of the light guide plate adjacent to the point light sources.

The light scattering pattern may include a sawtooth shape formed on the incident surface. In addition, the light scattering pattern may include a hole formed in the light incident portion. In addition, the light scattering pattern may include a hollow formed in the light incident portion.

The light guide plate may further include a total reflection part formed on at least one surface of the lower surface and the upper surface of the light incident part to totally reflect light.

A display device according to an aspect of the present invention includes a light guide plate, a plurality of point light sources, and a display panel. The light guide plate may include an incident surface on which light is incident, a first prism pattern formed to be spaced apart from each other, a lower surface including a flat portion formed perpendicular to the incident surface between the first prism patterns, and second prism patterns connected to each other. It includes the upper surface formed. The point light sources are disposed on an incident surface of the light guide plate to generate light. The display panel is disposed on an upper surface of the light guide plate to display an image. In this case, a light scattering pattern is formed on the light incident portion of the light guide plate adjacent to the point light sources.

According to the backlight assembly and the display device having the same, it is possible to reduce the number of optical sheets to achieve weight reduction and cost reduction, and to improve brightness uniformity by reducing dark portions generated between the point light sources.

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

1 is an exploded perspective view showing a backlight assembly according to an embodiment of the present invention, Figure 2 is a combined cross-sectional view of the backlight assembly shown in FIG.

1 and 2, the backlight assembly 100 according to an embodiment of the present invention includes a light guide plate 200 and a plurality of point light sources 300.

The light guide plate 200 guides a traveling path of light incident from the point light sources 300. The light guide plate 200 is preferably formed of a transparent material to minimize the loss of light. The light guide plate 200 is formed of, for example, a transparent polymethyl methacrylate (PMMA) or polycarbonate (PC) material.

The light guide plate 200 may include an incident surface 210 through which light is incident from the point light sources 300, a lower surface 220 connected to a lower side of the incident surface 210, and an upper surface 230 connected to an upper side of the incident surface 210. Include. The light guide plate 200 has a wedge shape in which the thickness decreases as it moves away from the incident surface 210.

The lower surface 220 of the light guide plate 200 may include first prism patterns 250 formed to be spaced apart from each other, and a flat portion 260 formed perpendicularly to the incident surface 210 between the first prism patterns 250. Can be. In addition, the upper surface 230 of the light guide plate 200 may include second prism patterns 270 that are in contact with each other.

The point light sources 300 are disposed on the incident surface 210 of the light guide plate 200 to generate light. The point light sources 300 are disposed at regular intervals on the incident surface 210 of the light guide plate 200. The point light source 300 is formed of, for example, a light emitting diode.

A light scattering pattern 290 for scattering light incident from the point light source 300 is formed at the light incident portion of the light guide plate 200 adjacent to the point light source 300.

3 is a perspective view showing an embodiment of a light scattering pattern.

1 and 3, the light scattering pattern 290 has a sawtooth shape 291 formed on the incident surface 210. The sawtooth shape 291 may be formed only in regions corresponding to the point light sources 300.

The sawtooth shape 291 may be continuously attached to each other or may be formed to be spaced apart from each other at regular intervals. The vertex angle of the sawtooth shape 291 may be formed, for example, about 90 degrees.

The sawtooth shape 291 formed on the incident surface 210 of the light guide plate 200 spreads the light incident from the point light sources 300 to the area between the point light sources 300 to reduce the dark area generation area.

4 is a plan view showing another embodiment of the light scattering pattern.

Referring to FIG. 4, the light scattering pattern includes holes 292 formed in the light incidence portion of the light guide plate 200 adjacent to the point light sources 300. The holes 292 are formed to penetrate the upper and lower surfaces of the light guide plate 200, and may be formed in various shapes such as a circle, a semicircle, or a quadrangle.

The holes 292 may be arranged in various shapes to achieve optimal scattering in the light incident region. For example, the holes 292 may be disposed in a semicircle shape centering on the point light source 300. In addition, the holes 292 may be formed in a uniform distribution throughout the light incident portion of the light guide plate 200, or an area corresponding to the point light source 300 may be formed at a higher density than an area between the point light sources 300. have.

5 is a plan view showing still another embodiment of the light scattering pattern.

Referring to FIG. 5, the light scattering pattern includes hollows 293 formed in the light incidence portion of the light guide plate 200 adjacent to the point light sources 300.

The hollows 293 are pores formed in the light incident portion of the light guide plate 200, and may be disposed in various forms to achieve optimal scattering in the light incident region. For example, the hollow 293 may be formed only in a region corresponding to the point light source 300 or may be formed as an entire light incident part.

Meanwhile, the light scattering pattern may have a structure in which two or more of the sawtooth shape 291 illustrated in FIG. 3, the holes 292 illustrated in FIG. 4, and the hollow 293 illustrated in FIG. 5 are simultaneously formed.

Referring back to FIGS. 1 and 2, the first prism patterns 250 formed on the lower surface 220 of the light guide plate 200 are formed to be spaced apart from each other, and have a stripe shape formed in parallel with the incident surface 210. Have The first prism patterns 250 are formed at regular intervals, for example. In contrast, the first prism patterns 250 may be formed to have a smaller spacing from the incident surface 210 in order to improve the uniformity of luminance.

The flat part 260 formed on the bottom surface 220 of the light guide plate 200 is formed between the first prism patterns 250. The flat part 260 is formed perpendicular to the incident surface 210 so that the light guided in the light guide plate 200 satisfies the total reflection condition.

Therefore, the light incident into the light guide plate 200 through the incident surface 210 is totally reflected through the flat part 260, and the reflection angle is changed by the first prism pattern 250 to emit vertically toward the upper surface 230. do.

The second prism patterns 270 formed on the upper surface 230 of the light guide plate 200 are connected to each other and have a stripe shape formed in a direction perpendicular to the first prism patterns 250.

The second prism patterns 270 have a substantially triangular cross section perpendicular to the length direction. For example, the vertex angles of the second prism patterns 270 may be formed in a range of about 80 degrees to about 150 degrees, and the pitch between the second prism patterns 270 may be formed in a range of about 50 μm to about 150 μm. have.

Meanwhile, an upper end of the second prism patterns 270, that is, an edge portion where two inclined surfaces meet may have a curved shape. In addition, the second prism patterns 270 may have a curved shape.

Accordingly, the light incident from the point light sources 300 through the incident surface 210 is focused in the vertical direction by the first prism patterns 250 formed on the lower surface 220, and the upper surface 230. Condensing in the horizontal direction is performed by the formed second prism patterns 270.

As such, by forming the first prism pattern 250 and the second prism pattern 270 on the lower surface 220 and the upper surface 230 of the light guide plate 200, the cost is reduced by reducing the number of optical sheets such as the prism sheet. Weight reduction and thickness reduction can be achieved.

6 is a side view illustrating an embodiment of a first prism pattern.

2 and 6, the first prism pattern 250 basically includes grooves having a triangular cross section in order to emit light traveling in the light guide plate 200 in a vertical direction.

In detail, the first prism pattern 250 may include a first inclined surface 252, a second inclined surface 254 connected to the first inclined surface 252, and a third inclined surface 256 connected to the second inclined surface 254. Can be.

The first inclined surface 252 is formed to be inclined in the direction of the upper surface 230 from the flat portion 260 of the previous stage. The second inclined surface 254 is inclined from the first inclined surface 252 toward the lower surface 220. The third inclined surface 256 extends in parallel with the first inclined surface 252 from the second inclined surface 254 and is connected to the subsequent flat portion 260.

The first inclined surface 252 and the second inclined surface 254 have a substantially symmetrical structure with respect to the normal NL of the flat portion 260. In contrast, the first inclined surface 252 and the second inclined surface 254 may have an asymmetrical structure with respect to the normal line NL of the flat portion 260. The first prism pattern 250 may further include a connection surface formed in parallel with the flat surface 260 between the second sloped surface 254 and the third sloped surface 256.

The light guide plate 200 has a first thickness d1 at the incident surface 210, a second thickness d2 thinner than the first thickness d1 at the light facing surface 212, and the first prism pattern 250. The flat part 260 positioned between them has a structure perpendicular to the incident surface 210. Accordingly, the light guide plate 200 may have a thickness difference between a front end and a rear end based on the first prism pattern 250.

The first height h1 of the third inclined surface 256 corresponding to the difference in thickness between the front end and the rear end of the first prism pattern 250 may be obtained by Equation 1 below.

[Equation 1]

h1 = (d1-d2) / m

Here, d1 is a first thickness of the incident surface 210, d2 is a second thickness of the light facing surface 212, and m is a number of steps of the lower surface 220.

That is, the first height h1 of the third inclined surface 256 is determined according to the thickness difference between the incident surface 210 and the light facing surface 212 and the number of steps of the lower surface 240.

Meanwhile, the second height h2 of the first inclined surface 252, the bottom side a of the third inclined surface 256, and the bottom side b of the second inclined surface 254 are light guided in the light guide plate 200. This side emission is optimized so that no lost light is generated.

The first inclined surface 252 preferably has a height at which light that travels below the critical angle α based on the normal of the incident surface 210 does not reach the third inclined surface 256. Therefore, the second height h2 of the first inclined surface 252 can be obtained by the following equation (2).

[Equation 2]

h2 = h1 × [1 + tan (α) tan (β / 2)] / [1-tan (α) tan (β / 2)]

Here, α is a critical angle of the light guide plate 200, and β is an internal angle formed by the first inclined surface 252 and the second inclined surface 254.

In addition, the bottom side a of the third inclined surface 256 can be obtained by the following equation (3).

[Equation 3]

a = h1 × tan (β / 2)

In addition, the bottom side b of the second inclined surface 254 can be obtained by the following equation (4).

[Equation 4]

b = h2 x tan (β / 2)

Meanwhile, the inner angle β formed by the first inclined surface 252 and the second inclined surface 254 to emit light guided in the light guide plate 200 in a vertical direction may have a range of about 60 ° to about 90 °. have. Preferably, the inner angle β formed by the first inclined surface 252 and the second inclined surface 254 is formed at about 78 °.

7 is a perspective view illustrating another embodiment of the light guide plate.

Referring to FIG. 7, the light guide plate 200 may further include a total reflection part 280 formed on at least one of the lower surface 220 and the upper surface 230 of the light incident part to totally reflect the light.

The total reflection part 280 is formed of a mirror surface on which the first prism pattern 250 or the second prism pattern 270 is not formed so that only total reflection of light occurs. Preferably, the total reflection portion 280 is formed in a direction perpendicular to the incident surface 210. The total reflection portion 280 is formed, for example, up to a distance of about 2 mm to 5 mm from the incident surface 210.

Although not shown, a light scattering pattern having a sawtooth shape, a hole, or a hollow may be formed in the light guide plate 200 including the total reflection part 280.

When the first prism pattern 250 is formed in the light incident portion of the light guide plate 200, since the vertical emission by the first prism pattern 250 occurs in the light incident portion, light scattering efficiency may be reduced. Therefore, by forming the total reflection portion 280 in the light incident portion of the light guide plate 200, it is possible to improve the light scattering efficiency by causing only light scattering without light emission from the light incident portion.

8 is a simulation result showing the luminance distribution according to the light scattering pattern. In FIG. 8, (a) is a light guide plate having no light scattering pattern formed therein, (b) is a light guide plate having a serrated light scattering pattern formed therein, (c) is a light guide plate having a light scattering pattern consisting of holes, and (d) is a total reflection portion and a tooth A light guide plate on which a light scattering pattern of a shape is formed, and (e) shows a luminance distribution of the light guide plate on which a light scattering pattern composed of total reflection parts and holes is formed.

Referring to FIG. 8, it can be seen that the light guide plates of (b) and (c) in which the light scattering patterns are formed have improved luminance uniformity compared to the light guide plates of (a) in which the light scattering patterns are not formed. In addition, the light guide plates of (d) and (e), which simultaneously formed the total reflection part and the light scattering pattern, have improved luminance uniformity and significantly reduce the occurrence of dark areas, compared to the light guide plates of (b) and (c), which formed only the light scattering pattern. You can see that.

1 and 2, the backlight assembly 100 may further include a reflective sheet 110 disposed on the bottom surface 220 of the light guide plate 200.

The reflective sheet 110 reflects light leaking to the outside through the lower surface 220 of the light guide plate 200 and enters the light into the light guide plate 200 again. For example, the reflective sheet 110 may be formed of white polyethylene terephthalate (PET) or white polycarbonate (PC) material.

In addition, the backlight assembly 100 may further include an optical sheet 120 disposed on the top surface 230 of the light guide plate 200.

The optical sheet 120 may include a prism sheet 122. Third prism patterns 123 are formed on the upper surface of the prism sheet 122 to be in contact with each other. The third prism patterns 123 have a stripe shape formed in a direction parallel to the second prism patterns 270 formed on the upper surface 230 of the light guide plate 200. In contrast, the third prism patterns 123 may have a stripe shape formed in a direction perpendicular to the second prism patterns 270.

The optical sheet 120 may include a protective sheet 124 disposed on the prism sheet 122. The protective sheet 124 may be disposed on the prism sheet 122 to protect the prism sheet 122 and may prevent adhesion to the display panel disposed on the upper portion, thereby further improving reliability of appearance quality.

9 is an exploded perspective view illustrating a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 9, the display device 600 includes a backlight assembly 100 that supplies light and a display unit 700 that displays an image by using light supplied from the backlight assembly 100.

The backlight assembly 100 may have any one of various embodiments shown in FIGS. 1 to 8. Therefore, detailed description thereof will be omitted.

The display unit 700 includes a display panel 710 for displaying an image using light supplied from the backlight assembly 100, and a driving circuit unit 720 for driving the display panel 710.

The display panel 710 is disposed on the light guide plate 200 and the optical sheet 120. The display panel 710 includes a first substrate 712, a second substrate 714 coupled to the first substrate 712, and a liquid crystal layer interposed between the first substrate 712 and the second substrate 714. (Not shown).

The first substrate 712 may be a TFT substrate in which a thin film transistor (hereinafter, referred to as a TFT) as a switching element is formed in a matrix form. A data line and a gate line are respectively connected to the source terminal and the gate terminal of the TFTs, and a pixel electrode made of a transparent conductive material is connected to the drain terminal.

The second substrate 714 may be a color filter substrate in which RGB pixels for implementing colors are formed in a thin film form. The common electrode made of a transparent conductive material is formed on the second substrate 714. Meanwhile, the color filter may be formed on the first substrate 712.

When power is applied to the gate terminal of the TFT and the TFT is turned on, an electric field is formed between the pixel electrode and the common electrode. By the electric field, the arrangement of liquid crystal molecules of the liquid crystal layer interposed between the first substrate 712 and the second substrate 714 is changed, and the transmittance of light supplied from the backlight assembly 100 is changed according to the arrangement change of the liquid crystal molecules. The image is changed to display an image of a desired gradation.

The driving circuit 720 may include a source printed circuit board 721 for outputting various control signals for driving the display panel 710, and a data driving circuit film connecting the source printed circuit board 721 and the display panel 710. 723 and a gate driving circuit film 725 connected to the display panel 710.

The data driving circuit film 723 is connected to the data line of the first substrate 712, and the gate driving circuit film 725 is connected to the gate line of the first substrate 712. The data driver circuit film 723 and the gate driver circuit film 725 include a driving chip that outputs a driving signal for driving the display panel 710 in response to a control signal supplied from the source printed circuit board 721. can do. The data driving circuit film 723 and the gate driving circuit film 725 are formed of, for example, a tape carrier package (TCP) or a chip on film (COF). Although not shown, the driving circuit unit 720 may further include a gate printed circuit board connected to the gate driving circuit film 725.

According to the backlight assembly and the display device having the same, the first prism pattern and the second prism pattern are formed on the lower surface and the upper surface of the light guide plate, and the light emitting diode is used as the light source, thereby reducing the number of optical sheets, thereby reducing the cost. Light weight and thinness can be achieved.

In addition, by forming the light scattering pattern and the total reflection portion in the light incidence portion of the light guide plate, it is possible to reduce the dark portion generated between the point light sources, and improve the luminance uniformity.

In the detailed description of the present invention described above with reference to the preferred embodiments of the present invention, those skilled in the art or those skilled in the art having ordinary skill in the art will be described in the claims to be described later It will be understood that various modifications and variations can be made in the present invention without departing from the scope of the present invention.

Claims (13)

 An incident surface to which light is incident, a lower surface including a first prism patterns formed to be spaced apart from each other and a flat portion formed perpendicularly to the incident surface between the first prism patterns, and an upper surface on which second prism patterns contacting each other are formed. Light guide plate comprising; And It includes a plurality of point light sources disposed on the incident surface of the light guide plate for generating light, And a light scattering pattern is formed in the light incidence portion of the light guide plate adjacent to the point light sources. The backlight assembly of claim 1, wherein the light scattering pattern comprises a sawtooth shape formed on the incident surface. The backlight assembly of claim 1, wherein the light scattering pattern comprises a hole formed in the light incident portion. The backlight assembly of claim 3, wherein the hole has a shape of any one of a circle, a semicircle, and a rectangle. The backlight assembly of claim 1, wherein the light scattering pattern comprises a hollow formed in the light incident portion. The backlight assembly of claim 1, wherein the light guide plate further comprises a total reflection part formed on at least one of the lower surface and the upper surface of the light incident part to totally reflect light. The backlight assembly of claim 1, wherein the point light source comprises a light emitting diode. The backlight assembly of claim 1, wherein the light guide plate decreases in thickness as it moves away from the incident surface. The backlight assembly of claim 8, wherein the first prism patterns have a stripe shape formed in parallel with the incident surface. The method of claim 9, wherein the first prism pattern is A first inclined surface formed to be inclined from the flat portion in the upper surface direction; A second inclined surface inclined from the first inclined surface toward the lower surface; And And a third inclined surface extending in parallel with the first inclined surface from the second inclined surface and connected to the flat portion. The backlight assembly of claim 9, wherein the second prism patterns have a stripe shape formed in a direction perpendicular to the first prism patterns. An incident surface to which light is incident, a lower surface including a first prism patterns formed to be spaced apart from each other and a flat portion formed perpendicularly to the incident surface between the first prism patterns, and an upper surface on which second prism patterns contacting each other are formed. Light guide plate comprising; A plurality of point light sources disposed on an incident surface of the light guide plate to generate light; And A display panel disposed on an upper surface of the light guide plate to display an image; And a light scattering pattern is formed in the light incident portion of the light guide plate adjacent to the point light sources. The display device of claim 12, wherein the light guide plate further comprises a total reflection part formed on at least one of the lower surface and the upper surface of the light incident part to totally reflect light.

Images