KR20080037966A - Backlight unit - Google Patents

Abstract

A backlight unit is provided to reduce a thickness of the backlight unit by reducing the number of used prism sheets according as intaglio patterns for performing functions similar to prism patterns are formed on a light guide plate. A backlight unit comprises a light source unit(328), a light guide plate(334), a reflection sheet(336) and an optical sheet(338). The light source unit includes one or more light sources(330) and a mount unit(332). The optical sheet comprises a diffusion sheet(400), a prism sheet(402) and a protection sheet(404). Plural first intaglio patterns(410) are arranged in one side of the light guide plate and engraved based on one side of the light guide plate. Prism patterns(412) are formed in a direction of crossing the first intaglio patterns.

Description

Backlight Unit {BACKLIGHT UNIT}

1 is a view illustrating a general liquid crystal display device.

2 is a perspective view illustrating a conventional backlight unit.

3 is a diagram illustrating a liquid crystal display using a backlight unit according to an exemplary embodiment of the present invention.

4 is a perspective view illustrating a backlight unit according to an exemplary embodiment of the present invention.

5A is a perspective view illustrating the light guide plate of FIG. 4 according to the first preferred embodiment of the present invention.

FIG. 5B is a diagram illustrating the progress of light in the light guide plate of FIG. 5A.

6 is a perspective view illustrating the light guide plate of FIG. 4 according to a second exemplary embodiment of the present invention.

7 is a perspective view illustrating the light guide plate of FIG. 4 according to a third exemplary embodiment of the present invention.

8 is a perspective view illustrating a backlight unit according to another exemplary embodiment of the present invention.

9 is a diagram illustrating a structure of a backlight unit for optimized luminance according to an exemplary embodiment of the present invention.

The present invention relates to a backlight unit, and more particularly, to a backlight unit including a light guide plate having intaglio patterns capable of serving as a prism sheet.

Since a liquid crystal display (LCD) is not a self-luminous element as a display element, a backlight unit for providing light to the LCD panel is required.

1 is a view illustrating a general liquid crystal display device.

Referring to FIG. 1, a general liquid crystal display includes an LCD panel 100 and a backlight unit 102.

The backlight unit 102 provides light, for example, white light, to the LCD panel 100, and thus the LCD panel 100 displays a predetermined image according to data input from an external device (not shown).

Hereinafter, the structure of the backlight unit 102 will be described in detail.

2 is a perspective view illustrating a conventional backlight unit.

Referring to FIG. 2, the conventional backlight unit 102 includes a light source unit 200, a light guide plate 202, an optical sheet 204, and a reflective sheet 206.

The light source unit 200 includes a light source 220, for example, a light emitting diode (LED), and injects light emitted from the light source 220 into the light guide plate 202.

The light guide plate 202 is an element that propagates the light incident from the light source unit 200 to the optical sheet 204 through its upper surface. In detail, the light incident from the light source unit 200 is diffused through the total reflection inside the light guide plate 202 so that the light incident from the light source unit 200 is uniformly spread throughout the light guide plate 202. Light propagates to the optical sheet 204 through the top surface of the 202.

The reflective sheet 206 reflects the light leaked from the light guide plate 202 to the light guide plate 202 to reduce the consumption of light.

The optical sheet 204 includes a diffusion sheet 210, prism sheets 212a and 212b and a protective sheet 214.

The diffusion sheet 210 uniformly diffuses the light propagated from the light guide plate 202.

The prism sheets 212a and 212b collect light passing through the diffusion sheet 210 and are orthogonal to the first prism sheet 212a and the first direction in which the first prism patterns formed in the first direction are formed. The second prism sheet 212b includes second prism patterns formed in a second direction. The prismatic patterns are formed to be orthogonal to each other in order to improve luminance uniformity of the backlight unit 102.

The protective sheet 214 protects the prism sheets 212a and 212b from external dust or the like.

In other words, the light generated from the light source unit 200 is incident on the LCD panel 100 through the light guide plate 202, the diffusion sheet 210, the prism sheets 212a and 212b, and the protective sheet 214.

In the backlight unit 102 of this structure, a plurality of prism sheets 212a and 212b had to be used to improve the luminance uniformity of the backlight unit 102. In particular, although only two prism sheets 212a and 212b are shown above, a substantial number of prism sheets had to be used in practice, and even in this case, the prism patterns formed on the prism sheets had to be formed at right angles. Therefore, the thickness reduction of the backlight unit 102 was difficult.

In addition, since the coefficients of thermal expansion of the prism sheets 212a and 212b are high, the prism sheets 212a and 212b were stretched at high temperatures and wrinkles occurred on their surfaces, so that prism sheets 212a and 212b were used. There was a problem that the performance of the backlight unit 102 is degraded.

Accordingly, there is a need for a backlight device capable of maintaining the light collection efficiency while reducing the number of prism sheets having such characteristics and having a reduced thickness.

It is an object of the present invention to provide a backlight unit whose thickness is reduced by reducing the number of prism sheets.

In order to achieve the above object, the light guide plate according to the preferred embodiment of the present invention is arranged on one surface of the light guide plate, and includes a plurality of first intaglio patterns formed in an intaglio with respect to one surface of the light guide plate.

The backlight unit according to an exemplary embodiment of the present invention includes a light guide plate, a light source unit, and a diffusion sheet. A plurality of first intaglio patterns are arranged on the bottom surface of the light guide plate. The light source unit is positioned at a side of the light guide plate and provides light to the light guide plate using at least one light source. The diffusion sheet is positioned above the light guide plate and uniformly diffuses the light propagated from the light guide plate. Here, the first intaglio patterns are formed intaglio on the bottom surface of the light guide plate.

In the backlight unit according to the present invention, since intaglio patterns are formed on the light guide plate to perform a function similar to that of the prism pattern, the number of prism sheets used may be reduced, thereby making the thickness of the backlight unit thin.

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

3 is a diagram illustrating a liquid crystal display using a backlight unit according to an exemplary embodiment of the present invention.

Referring to FIG. 3, a liquid crystal display (LCD) includes a liquid crystal display panel 300 (hereinafter referred to as an “LCD panel”) and a backlight unit 302.

The backlight unit 302 provides the LCD panel 300 with light having a predetermined wavelength.

The LCD panel 300 includes a lower polarizing film 304, an upper polarizing film 306, a lower substrate 308, an upper substrate 310, a color filter 312, a black matrix 314, a pixel electrode 316, The common electrode 318 includes a liquid crystal layer 320 and a TFT array 322.

The polarizing films 304 and 306 polarize the external light incident from the backlight unit 302. For example, the polarizing films 304 and 306 pass only horizontal waves of the external light, and block longitudinal waves.

The TFT array 322 switches the pixel electrode 316 as a switching element.

The liquid crystal layer 320 includes liquid crystals arranged in correspondence with the voltage difference between the pixel electrode 316 and the common electrode 318. In this case, external light incident from the backlight unit 302 passes through the liquid crystals and then enters the color filter 312.

The color filter 312 includes sub color filters corresponding to red, green, and blue, as shown in FIG. 3, and the incident external light passes through the color filter 312.

The upper substrate 310 is positioned above the color filter 312.

The backlight unit 302 is a device for providing light, for example, white light, to the LCD panel 300, which will be described in detail with reference to the accompanying drawings.

4 is a perspective view illustrating a backlight unit according to an exemplary embodiment of the present invention. FIG. 5A is a perspective view schematically showing the light guide plate of FIG. 4 according to the first preferred embodiment of the present invention, and FIG. 5B is a view illustrating a process of light in the light guide plate of FIG. 5A. In FIG. 5A, the reflective sheet is not shown.

Referring to FIG. 4, the backlight unit 302 of the present invention includes a light source unit 328, a light guide plate 334, a reflective sheet 336, and an optical sheet 338.

The light source unit 328 is positioned at a side of the light guide plate 334 and includes one or more light sources 330 and a mounting unit 332. The light source 330 according to an embodiment of the present invention may be a light emitting diode (LED) which is a point light source element, a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (CFL) which is a surface light source element. Flourescent Lamp, hereinafter referred to as "EEFL"). Preferably, when the backlight unit 302 is used for a large LCD panel, the surface light source element is used as the light source 330, and when the backlight unit 302 is used for the small LCD panel, the dot light source 330 is used. Light source elements are used. However, the light source 330 is not limited to LED, CCFL and EEFL.

The mounting unit 332 mounts the light source 330 and reflects the light emitted from the light source 330 so that the light emitted from the light source 330 is incident on the side surface of the light guide plate 334. To this end, the mounting portion 332 is made of a highly reflective material, and may also coat silver (Ag) on its surface.

The reflective sheet 336 is disposed under the light guide plate 334 to reflect the light leaked from the light guide plate 334 to the light guide plate 334. The reflective sheet 336 may be generated by coating silver (Ag) on a base material made of aluminum or the like. However, the manufacturing process of the reflective sheet 336 may further perform a titanium coating process to prevent the reflective sheet 336 from being deformed due to heat.

The light guide plate 334 advances the light incident from the light source unit 328 toward the LCD panel 300, and is, for example, a transparent acrylic resin such as polymethyl methacrylate (hereinafter referred to as "PMMA"). Is made of.

The light guide plate 334 is in close contact with the light source unit 328 as shown in FIG. 5A and includes an upper surface, a lower surface, and side surfaces.

In addition, a plurality of first intaglio patterns 410 are arranged in a specific direction on a lower surface of the light guide plate 334. Here, the first intaglio patterns 410 are formed on the light guide plate 334 in an intaglio form based on the bottom surface of the light guide plate 334 as shown in FIG. 5A, and have a pattern similar to the prism patterns described below. . However, the first intaglio patterns 410 are formed in a direction crossing the prism patterns, so that the first intaglio patterns 410 and the prism patterns work together to efficiently light the light incident from the light source unit 328. Condensing

According to an embodiment of the present invention, the pitches P1, which are distances between the first intaglio patterns 410, have the same length, and the depth D1 of at least one of the first intaglio patterns 410 is different. It has a different depth than the intaglio patterns. Preferably, the depth D1 of the first intaglio patterns 410 is such that light incident from the light source unit 328 can be evenly spread over the entire area of the light guide plate 334 as shown in FIG. 5B. 328) the greater it is from the greater.

According to another embodiment of the present invention, the pitch of at least one of the pitches P1 between the first intaglio patterns 410 may have a length different from the remaining pitches, preferably away from the light source unit 328. As the quality increases, the pitches P1 between the first intaglio patterns 410 become smaller. That is, the pitches P1 between the first intaglio patterns 410 may be changed differently according to the designer's intention, so that the change of the pitches P1 does not affect the scope of the present invention. It will be apparent to those skilled in the art.

There is no particular limitation on the vertices of the first intaglio patterns 410.

Referring back to FIG. 4, the optical sheet 338 is positioned on the light guide plate 334 and includes a diffusion sheet 400, a prism sheet 402, and a protective sheet 404.

The diffusion sheet 400 is positioned above the light guide plate 334, and diffuses or condenses the light propagated from the light guide plate 334 to uniformize the light propagated from the light guide plate 334.

The prism sheet 402 is positioned above the diffusion sheet 400, and the light passing through the diffusion sheet 400 in the direction of the LCD panel 300 using the prism patterns 412 having a triangular shape, for example. Condensing Here, the prism patterns 412 are formed in a direction crossing the first intaglio patterns 410, and act together with the first intaglio patterns 410 to emit light from the light source unit 328 to the LCD panel 300. Condensing in the direction. In detail, the light from the light source unit 328 is mostly focused in the direction in which the first intaglio patterns 410 are formed by the first intaglio patterns 410, and the light passing through the diffusion sheet 400 is a prism pattern. Most of the light is concentrated in the direction in which the prism patterns 412 are formed by the holes 412. As a result, the light propagated from the light source unit 328 is uniformly output throughout the backlight unit 302 by the combination of the first intaglio patterns 410 and the prism patterns 412.

The protective sheet 404 is a part that protects the prism sheet 402 from external dust or the like or prevents an external object from being damaged by the prism patterns 412 and is not an essential component.

As described above, in the backlight unit 302 of the present invention, a plurality of first intaglio patterns 410 are arranged on the light guide plate 334, and the first intaglio patterns 410 are prismatic patterns 412. Similar to). Therefore, unlike the conventional backlight unit in which a plurality of prism sheets were required, in the backlight unit 302 of the present invention, only one prism sheet 402 can achieve the desired purpose. Therefore, the backlight unit 302 of the present invention can be thinner than the conventional backlight unit. As a result, the thickness of the liquid crystal display device using the backlight unit 302 of the present invention can also be thinned.

6 is a perspective view illustrating the light guide plate of FIG. 4 according to a second exemplary embodiment of the present invention. However, the reflective sheet is not shown in FIG. 6.

As shown in FIG. 6, first intaglio patterns 410 are formed on a bottom surface of the light guide plate 334 of the present embodiment, and second intaglio patterns 600 formed in an intaglio shape are formed on an upper surface of the light guide plate 334. Are arranged.

According to one embodiment of the present invention, one of the pitches P2 between the second intaglio patterns 600 has a length different from the remaining pitches, and the depth D2 of the second intaglio patterns 600 is same. Preferably, in the region corresponding to the light source 330, for example, the light emitting diodes as the point light source, the pitches P2 between the second intaglio patterns 600 are long and do not correspond to the light source 330. In FIG. 3, the lengths of the pitches P2 between the second intaglio patterns 600 are relatively short.

In general, in the case of using a point light source, the light intensity of the region corresponding to the point light source is the strongest due to the characteristics of the point light source, so that it can be recognized as if a certain floating pattern is formed from the outside. This phenomenon is referred to as a hot-spot phenomenon. In order to prevent such a hot-spot phenomenon, second engraved patterns 600 are formed on the upper surface of the light guide plate 334. Specifically, as shown in FIG. 6, the pitches P2 of the second recessed patterns 600 are formed long in a portion corresponding to the light sources 330, and in a portion not corresponding to the light sources 330. The pitches P2 are formed to be short to uniformly disperse the light that is incident from the light sources 330 and proceeds to the outside through the upper surface of the light guide plate 334. As a result, the light propagating to the outside through the upper surface of the light guide plate 334 is evenly distributed throughout the light guide plate 334, so that no hot-spot phenomenon occurs.

Of course, the height D2 of the second intaglio patterns 600 may also be formed differently for each of the second intaglio patterns 600.

Since the second intaglio patterns 600 become a problem when the point light source element is used as the light source 330, the second intaglio patterns 600 may not be formed on the light guide plate 334 when the surface light source element is used as the light source 330.

7 is a perspective view illustrating the light guide plate of FIG. 4 according to a third exemplary embodiment of the present invention. However, the reflective sheet is not shown in FIG. 7.

As shown in FIG. 7, first intaglio patterns 410 are formed on the bottom surface of the light guide plate 334, and third intaglio patterns 700 are formed on the side surface of the light guide plate 334. Here, the side surface of the light guide plate 334 is in close contact with the light source unit 328.

As shown in FIG. 7, the third intaglio patterns 700 are formed in a vertical direction at the side of the light guide plate 334, and the length L of the third intaglio patterns 700 is formed at the side of the light guide plate 334. Less than height Preferably, the length L of the third intaglio patterns 700 corresponds to half the length of the side of the light guide plate 334.

In addition, the pitches P3 between the third intaglio patterns 700 may have the same length, and the depths D3 of the third intaglio patterns 700 may also have the same length.

The third intaglio patterns 700 evenly diffuse the light incident from the light sources 330 into the light guide plate 334 over the light guide plate 334.

Although not shown in FIG. 7, the second intaglio patterns illustrated in FIG. 6 may be formed on the upper surface of the light guide plate 334.

In FIG. 7, the third engraved patterns 700 are illustrated in a triangular shape, but may have a curved shape. That is, the shape of the third intaglio patterns 700 is not particularly limited.

8 is a perspective view illustrating a backlight unit according to another exemplary embodiment of the present invention.

Referring to FIG. 8, the backlight unit according to the present exemplary embodiment may include a light source unit 800, a light guide plate 802, a reflective sheet 806, a diffusion sheet 810, a prism sheet 812, a protective sheet 814, and a DV layer. Dual Brightness Enhancement Film Layer, 816, DBEF layer).

The remaining components except for the DBEF layer 816 are the same as those of the backlight unit of FIG. 4, and thus descriptions thereof will be omitted.

The DBEF layer 816 reflects some of the light diffused by the protective sheet 814 toward the light guide plate 802, and provides the remaining light to the LCD panel 300. This is because the LCD panel 300 utilizes only part of the light provided from the backlight unit 302 and polarizes the rest. Thus, the DBEF layer 816 is used to utilize the polarized light.

For example, the DBEF layer 816 transmits longitudinal waves (P waves) of light diffused by the protective sheet 814 and reflects transverse waves (S waves).

The reflected shear wave is reflected back by the light guide plate 802 or the reflective sheet 806. In this case, the reflected shear wave is changed back to light including the longitudinal wave and the shear wave by re-reflection. The changed light penetrates the diffusion sheet 810, the prism sheet 812, and the protective sheet 814, and then enters the DBEF layer 816 again.

Subsequently, the longitudinal wave of the incident light proceeds to the LCD panel 300, and the transverse wave is reflected by the DBEF layer 816 and then reflected back by the light guide plate 802 or the reflective sheet 806.

This process occurs repeatedly, so that the efficiency of light output from the backlight unit 302 and incident on the LCD panel 300 is improved.

9 is a diagram illustrating a structure of a backlight unit for optimized luminance according to an exemplary embodiment of the present invention. For convenience of description, only some of the components of the backlight unit are shown, and the backlight unit is assumed to be the backlight unit of FIG. 4.

The experimenter measured the output luminance of the backlight unit 302 while varying the distance DS from the center of the light guide plate 334 to the prism sheet 400 to obtain a result as shown in Table 1 below.

Light guide plate center + 550㎛ ± 50㎛ (A) Area other than A area Illuminance 1692 lx 735.7 lx Intensity 0.5998 cd 0.1829 cd Luminance 1279 nit 451.5 nit

Referring to Table 1 above, when the prism sheet 402 is located at 500 μm to 600 μm from the center of the light guide plate 334, the prism sheet 402 has an effect of increasing brightness about three times than other positions. In this case, the brightness is not significantly affected by the position of the diffusion sheet 400.

Therefore, in embodiments of the present invention, the prism sheet is preferably located 500 to 600 ㎛ from the center of the light guide plate 334.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art having ordinary knowledge of the present invention will be capable of various modifications, changes, additions within the spirit and scope of the present invention, such modifications, changes And additions should be considered to be within the scope of the following claims.

As described above, in the backlight unit according to the present invention, since intaglio patterns are formed on the light guide plate to perform a function similar to that of the prism pattern, the number of prism sheets used is reduced, thereby reducing the thickness of the backlight unit. have.

Claims (23)

In the light guide plate, The light guide plate is arranged on one surface of the light guide plate, and comprises a plurality of first intaglio patterns formed intaglio with respect to one surface of the light guide plate. The light guide plate of claim 1, wherein the first intaglio patterns are arranged on a bottom surface of the light guide plate. The method of claim 1, wherein a plurality of second intaglio patterns are formed on the upper surface of the light guide plate in an intaglio form on the upper surface of the light guide plate, The second recessed patterns are formed in a direction crossing the first recessed patterns. 4. The light guide plate of claim 3 wherein at least one of the pitches (P2) between the second intaglio patterns has a different distance from the remaining pitches, and the depths (D2) of the second intaglio patterns are the same. The light guide plate of claim 4, wherein at least one side surface of the light guide plate is provided with third intaglio patterns arranged in a direction perpendicular to the light guide plate. The light guide plate of claim 5, wherein a length L of the third intaglio patterns is equal to or less than a height of one side of the light guide plate. The light guide plate according to claim 5, wherein the pitches (P3) between the third intaglio patterns have the same length, and the depth (D3) between the intaglio patterns is the same. The method of claim 1, wherein at least one of the pitches P1 between the first intaglio patterns has a length different from the remaining pitches, and at least one of the first intaglio patterns is different from the other intaglio patterns. A light guide plate having a depth D1. The light guide plate of claim 8, wherein the depths D1 of the first intaglio patterns increase in a specific direction. A light guide plate on which a plurality of first intaglio patterns are arranged; A light source unit positioned at a side of the light guide plate to provide light to the light guide plate using at least one light source; And Located on the top of the light guide plate, including a diffusion sheet for uniformly diffusing the light propagated from the light guide plate, The first intaglio pattern is a backlight unit, characterized in that formed in the intaglio on the lower surface of the light guide plate. The method of claim 10, wherein the backlight unit, And a prism sheet positioned on the diffusion sheet and including prism patterns formed in a specific direction and condensing light uniformed by the diffusion sheet using the prism patterns. The backlight unit of claim 11, wherein the prism patterns are formed in a direction crossing the first intaglio patterns. The backlight unit of claim 11, wherein the prism sheet is positioned 500 μm to 600 μm from a center of the light guide plate. The method of claim 11, wherein the backlight unit, A reflection sheet positioned under the light guide plate and reflecting light leaked from the light guide plate to the light guide plate; A protective sheet positioned on the prism sheet; And The backlight unit further comprises a DBEF layer positioned on the protective sheet. The method of claim 10, wherein the pitch of at least one of the pitches P1 between the first intaglio patterns has a length different from the remaining pitches, and at least one of the first intaglio patterns has a different depth than the other intaglio patterns. (D1) having a backlight unit. The backlight unit of claim 15, wherein the depths D1 of the first intaglio patterns increase in a specific direction. The method of claim 10, wherein a plurality of second intaglio patterns are formed on the upper surface of the light guide plate intaglio with respect to the upper surface of the light guide plate, And the second intaglio patterns are formed in a direction crossing the first intaglio patterns. The backlight unit of claim 17, wherein at least one of the pitches P2 between the second intaglio patterns has a different distance from other pitches, and the depths D2 of the second intaglio patterns are the same. . 19. The method of claim 18, wherein the pitch (distance) between the patterns corresponding to the light source among the second engraved patterns is longer than the pitch (distance) between the patterns not corresponding to the light source among the second engraved patterns. Backlight unit, characterized in that. The method of claim 10, wherein the third intaglio pattern is arranged on one side of the light guide plate in a direction perpendicular to the light guide plate, One side of the light guide plate is facing the light source unit. The backlight unit of claim 20, wherein a length L of the third engraved patterns is smaller than a height of one side of the light guide plate. 21. The backlight unit of claim 20, wherein the pitches (P3) between the third intaglio patterns have the same length, and the depth (D3) between the intaglio patterns is the same. The backlight unit of claim 10, wherein the light source unit comprises a plurality of light emitting diodes emitting light.

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