KR20080003999A - Light guide plate and liquid crystal display having the same - Google Patents

Abstract

A light guide plate and an LCD including the same are provided to improve the image quality by reducing a hot spot generated on the light exit surface of the light guide plate adjacent to a light source unit. A light source unit(210) emits light. A light guide plate(220) is disposed at the rear of a liquid crystal panel(100). The light guide plate includes a light exit surface through which light is directed towards the liquid crystal panel, a rear surface disposed opposite to the light exit surface, and a light entrance surface into which the light emitted from the light source unit is incident. The light entrance surface connects the light exit surface with the rear surface. A cross-section of the light entrances surface in a staked direction of the liquid crystal panel and the light guide plate includes a light entrance portion facing the light source unit and a curved portion extending from the light entrance portion.

Description

LIGHT GUIDE PLATE AND LIQUID CRYSTAL DISPLAY HAVING THE SAME}

1 is an exploded perspective view of a liquid crystal display according to a first embodiment of the present invention;

2A is a plan view of a light guide plate and a light source unit according to a first embodiment of the present invention;

FIG. 2B is a cross sectional view along IIb-IIb of FIG. 2A;

2C is a view for explaining the principle of reducing the hot spot of the light guide plate according to the first embodiment of the present invention;

3A is a plan view of a light guide plate and a light source unit according to a second embodiment of the present invention;

3B is a cross-sectional view taken along IIIB-IIIb of FIG. 3A,

4A is a perspective view of a light guide plate and a light source unit according to a third embodiment of the present invention;

4B is a plan view of a light guide plate and a light source unit according to a third embodiment of the present invention;

4C is a cross-sectional view taken along IVC-IVc of FIG. 4B;

4d is a cross-sectional view taken along line IVd-IVd of FIG. 4b,

4E is a cross-sectional view taken along IVe-IVe of FIG. 4B;

5 is a perspective view of a light guide plate and a light source unit according to a fourth embodiment of the present invention.

Explanation of Signs of Major Parts of Drawings

1: liquid crystal display device 100: liquid crystal panel

110: thin film transistor substrate 120: color filter substrate

130: data driver 140: gate driver

200: backlight unit 210: light source

211: light emitting diode 220: light guide plate

221: exit surface 222: rear

223: incident surface 230: reflector

240: light control member 300: upper cover

400: lower cover

The present invention relates to a light guide plate and a liquid crystal display device including the same, and more particularly, to a liquid crystal display device having an improved structure of the light guide plate.

Recently, a flat panel display such as a liquid crystal display (LCD), a plasma display panel (PDP), and an organic light emitting diode (OLED) has been developed in place of the conventional CRT. Among them, a liquid crystal display device includes a thin film transistor substrate, a color filter substrate, and a liquid crystal panel in which liquid crystal is positioned between both substrates. Since the liquid crystal panel is a non-light emitting device, a backlight unit is provided to supply light to the rear surface of the thin film transistor substrate. Light transmitted from the backlight unit is adjusted according to the arrangement of the liquid crystals.

The backlight unit is classified into an edge type and a direct type according to the position of the light source unit. The edge type requires a light guide plate for uniformly inducing the light emitted from the light source to the rear surface of the liquid crystal panel.

Here, the light guide plate used for the edge type is located at the rear of the liquid crystal panel, the emission surface for emitting light toward the liquid crystal panel, the rear surface opposite to the emission surface, and the incident surface to which the light emitted from the light source unit is incident It includes.

However, the light incident from the light source unit through the incident surface of the light guide plate is transmitted to the liquid crystal panel through the adjacent exit surface of the incident surface, thereby generating hot spots (high brightness bright spots). This is because when the light incident into the light guide plate through the entrance surface is directed toward the exit surface adjacent to the entrance surface, when the incident angle formed by the light and the exiting surface is smaller than the critical angle is not totally reflected on the exit surface, the light exits through the exit surface. It is generated by transmission. Such hot spots are a factor of degrading the image quality of the liquid crystal display.

Accordingly, an object of the present invention is to provide a light guide plate capable of reducing hot spots generated at an exit surface of a light guide plate proximate to a light source unit and a liquid crystal display including the same.

According to the present invention, there is provided a liquid crystal display device comprising a liquid crystal panel, comprising: a light source unit for emitting light; Located on the rear of the liquid crystal panel, a light guide plate having an emission surface for emitting light toward the liquid crystal panel, a rear surface opposite to the emission surface, and an incident surface connecting the emission surface and the rear surface and the light emitted from the light source unit is incident. And a cross section in which the incident surface is cut in the stacking direction of the liquid crystal panel and the light guide plate comprises an incident portion facing the light source portion and a curved portion extending from the incident portion.

Here, a curved portion is formed in at least a portion of the first edge formed by the incident surface and the exit surface.

The curved surface portion is formed on at least a portion of the second edge formed by the incident surface and the rear surface.

Further, the curved surface portion is formed over the entire longitudinal direction of the incident surface.

Here, the curved portion is formed in an area adjacent to the light source portion of the incident surface.

And it is preferable that the incident part and the light source part of an incident surface contact. This is to prevent leakage of light emitted from the light source unit and to prevent a certain amount of light from being lost by reflection and absorption when there is an air layer between the light source unit and the incident unit.

The light source unit also includes a plurality of light emitting diodes.

According to the present invention, another object of the present invention is to provide a liquid crystal panel with light emitted from a light source unit, comprising: an emission surface on which light is emitted, a rear surface opposite to the emission surface, and an emission surface and a rear surface; A light emitting plate including an incidence surface to which light emitted from the light source unit is incident, and a cross section of the incidence surface in a direction in which light is emitted, the light guide plate including an incidence portion facing the light source portion and a curved portion extending from the incidence portion; Is achieved by.

Here, a curved portion is formed in at least a portion of the first edge formed by the incident surface and the exit surface.

The curved surface portion is formed on at least a portion of the second edge formed by the incident surface and the rear surface.

Further, the curved surface portion is formed over the entire longitudinal direction of the incident surface.

Here, the curved portion is formed in an area adjacent to the light source portion of the incident surface.

Hereinafter, the present invention will be described with reference to the accompanying drawings. In various embodiments, like reference numerals refer to like elements, and like reference numerals refer to like elements in the first embodiment and may be omitted in other embodiments.

Hereinafter, a liquid crystal display according to a first embodiment of the present invention will be described with reference to FIG. 1.

As shown in FIG. 1, the liquid crystal display device 1 includes a liquid crystal panel 100, a backlight unit 200, an upper cover 300, and a lower cover 400. Here, the liquid crystal panel 100 and the backlight unit 200 are accommodated between the upper cover 300 and the lower cover 400.

The liquid crystal panel 100 includes a thin film transistor substrate 110, a color filter substrate 120, a liquid crystal layer (not shown), a data driver 130, and a gate driver 140. Here, since the liquid crystal panel 100 is a non-light emitting device, light must be supplied from the backlight unit 200.

A thin film transistor is formed on the thin film transistor substrate 110, and a color filter layer is formed on the color filter substrate 120. The liquid crystal layer (not shown) is positioned between the thin film transistor substrate 110 and the color filter substrate 120, and the amount of light transmitted from the backlight unit 200 is adjusted according to the arrangement state of the liquid crystal layer (not shown).

The data driver 130 is provided at the side of the thin film transistor substrate 110 and is mounted on the flexible printed circuit board (FPC) 131 and the flexible printed circuit board 131. The flexible printed circuit board 131 And a circuit board (133) connected to the other side of the circuit board).

The gate driver 140 is provided on the side of the thin film transistor substrate 110 and is mounted on the flexible printed circuit board (FPC) 141 and the flexible printed circuit board 141, and the flexible printed circuit board 141. It includes a circuit board (PCB, 143) connected to the other side of the).

The backlight unit 200 is positioned behind the liquid crystal panel 100 and includes a light source unit 210, a light guide plate 220, a reflector plate 230, and a light control member 240.

The light source unit 210 is disposed at each side of the light guide plate 220, and includes a light emitting diode 211, a circuit board 212, and a light source cover 213.

The light emitting diodes 211 supply white light to the light guide plate 220 and are disposed at regular intervals. Each light emitting diode 211 may include sub light emitting diodes emitting red, green, and blue light, respectively, and light supplied from these sub light emitting diodes is mixed to supply white light. The light emitting diode 211 forms a minority carrier (electron or hole) injected by using a p-n type junction structure of a semiconductor, and emits light by recombination thereof. Thus, the brightness of the light emitting diode 211 is controlled by the amount of current flowing.

The circuit board 212 is a plate shape extending in one direction and is perpendicular to the liquid crystal panel 100. A plurality of light emitting diodes 211 is mounted on the circuit board 212.

The light source cover 213 surrounds the light emitting diode 211. The light source cover 213 reflects the light from the light emitting diodes 211 to the light guide plate 220. The light source cover 213 may be made of an aluminum plate having excellent reflectance, or the like, and may have a silver coating on a surface facing the light emitting diodes 211.

The light guide plate 220 is positioned below the light control member 240 and has a rectangular plate type. The light guide plate 220 receives light from the light source unit 210 and supplies the light to the light adjusting member 240 as surface light. The light guide plate 220 may be made of acryl-based polymethyl methacrylate (PMMA) and has a rectangular shape corresponding to the liquid crystal panel 100.

The light guide plate 220 according to the first embodiment of the present invention will be described in detail with reference to FIGS. 2A to 2C.

2A is a plan view showing the light guide plate 220 and the light source unit 210, and the light emitting diode 211 mounted on the circuit board 212 is provided in contact with the light guide plate 220.

As shown in FIG. 2B, the light guide plate 220 includes an emission surface 221 for emitting light toward the liquid crystal panel, a rear surface 222 positioned opposite to the emission surface 221, and an emission surface 221. The back surface 222 includes an incident surface 223 to which light emitted from the light emitting diode 211 is incident. A cross section of the incident surface 223 includes an incident portion 223a facing the light emitting diode 211 and curved portions 223b and 223c extending from the incident portion 223a. More specifically, the first edge formed by the incident surface 223 and the exit surface 221 and the second edge formed by the incident surface 223 and the rear surface 222 are formed as curved portions 223b and 223c, respectively. As shown in FIG. 1, the curved portions 223b and 223c of the light guide plate 220 are formed in a curved surface over the entire length direction. As a result, hot spots generated at the emission surface 221 of the light guide plate 220 adjacent to the light emitting diode 211 can be reduced. The principle for this is described with reference to FIG. 2C.

As illustrated in FIG. 2C, light incident from the light emitting diode 211 is incident to the light guide plate 220 through the incident part 223a. When the incident angles θ1 and θ2 of the light incident into the light guide plate 220 are smaller than the critical angle θc of the total reflection, the light is not totally reflected into the light guide plate 220 and transmitted through the light exit surface 221. do. This transmitted light causes hot spots. Thus, in the present invention, the incidence surfaces 223b have curved portions 223b and 223c so that the incidence angles θ1 and θ2 of the light incident on the light guide plate 220 to the emission surface 221 is greater than the critical angle θc of total reflection. Increasing the incident light into the light guide plate 220 may reduce the transmission of light through the exit surface 221. As a result, hot spots generated at the emission surface 221 of the light guide plate 220 adjacent to the light emitting diode 211 may be reduced.

The reflector 230 is provided below the light guide plate 220, and reflects the light incident to the bottom of the light guide plate 220 among the light from the light emitting diode 211 to face the top. The reflector 230 may be made of polyethylene terephthalate (PET) or polycarbonate (PC), and may be coated with silver or aluminum.

The light adjusting member 240 is positioned behind the liquid crystal panel 100 and may include a diffusion film 241, a prism film 242, and a protective film 243.

The diffusion film 241 is composed of a coating layer comprising a bead-shaped beads formed on the base plate and the base plate. The diffusion film 241 diffuses the light supplied through the light guide plate 220 to make the luminance uniform.

The prism film 242 has a triangular prism-shaped prism formed on an upper surface thereof in a predetermined arrangement. The prism film 242 collects the light diffused from the diffusion film 241 in a direction perpendicular to the arrangement plane of the upper liquid crystal panel 100. Two prism films 242 are generally used, and the micro prisms formed on each prism film 242 have a predetermined angle. The light passing through the prism film 242 proceeds almost vertically to provide a uniform luminance distribution. If necessary, a reflective polarizing film may be used together with the prism film 242, and only the reflective polarizing film may be used without the prism film 242.

The protective film 243 is positioned between the prism film 242 and the liquid crystal panel 100, and protects the prism film 32 that is weak to scratches.

Hereinafter, the second embodiment to the fourth embodiment according to the present invention will be described. However, in the following embodiments, only the shape of the light guide plate 220 is different from the first embodiment, and the description of the same parts as the first embodiment will be omitted, and only the characteristic parts compared with the first embodiment will be described. do.

A second embodiment according to the present invention will be described with reference to Figs. 3A and 3B.

3A is a plan view showing the light guide plate 220 and the light source unit 210, and the light emitting diode 211 mounted on the circuit board 212 is provided in contact with the light guide plate 220.

As shown in FIG. 3B, the light guide plate 220 includes an emission surface 221 through which light is emitted toward the liquid crystal panel, a rear surface 222 positioned opposite to the emission surface 221, and an emission surface 221. And an incident surface 223 connecting the rear surface 222 to which light emitted from the light emitting diode 211 is incident.

A cross section of the incident surface 223 has a first edge formed by the incident portion 223a facing the light emitting diode 211 and the exit surface 221, and is formed of a curved portion 223b, and the incident portion 223a and the rear surface thereof. The second corner formed by 222 is formed at right angles. As a result, in the case of the first embodiment, the second edge is formed at the curved portion 223c (see FIG. 2B), whereas in the second embodiment, the second edge is formed at a right angle. As a result, as in the first exemplary embodiment, hot spots generated at the emission surface 221 of the light guide plate 220 adjacent to the light emitting diode 211 can be reduced. However, unlike the first embodiment, since the second edge is formed at a right angle rather than a curved surface, light incident on the light guide plate 220 through the incident part 223a may be transmitted through the rear surface 222. The light thus transmitted is directed toward the rear surface 222 instead of the emission surface 221, so that the hot spots are generated as compared with the light transmitted directly through the emission surface 221, even if the influence of the reflector 230 is shown. Is weak. As described above, although the reduction of the hot spot is smaller than that of the first embodiment, the second embodiment can provide manufacturing convenience due to not forming the second edge into a curved surface.

A third embodiment according to the present invention will be described with reference to Figs. 4A to 4E.

As shown in FIG. 4A, the light guide plate 220 includes an emission surface 221 for emitting light toward the liquid crystal panel, a rear surface (not shown) opposite to the emission surface 221, and an emission surface 221. ) And a back surface (not shown) and an incident surface 223 to which light emitted from the light emitting diode 211 is incident.

FIG. 4B is a plan view showing the light guide plate 220 and the light source unit 210, and shows positions on the plan views of the cross sections shown in FIGS. 4C to 4E.

As shown in FIG. 4C, a cross section of the incident surface 223 includes an incident portion 223a facing the light emitting diode 211 and curved portions 223b and 223c extending from the incident portion 223a. Specifically, the curved portion 223b is formed only in a region adjacent to the light emitting diode 211 in the first edge formed by the incident surface 223 and the emission surface 221, and the incident surface 223 and the rear surface 222 are formed. The curved portion 223c is formed only in a region adjacent to the light emitting diode 211 in the second corner. This will be described in detail with reference to FIGS. 4D and 4E.

As shown in FIG. 4D, the incident surface 223 except for the adjacent region of the light emitting diode 211 is formed in a plane.

In addition, as illustrated in FIG. 4E, the light guide plate 220 is bent with respect to the emission surface 221 and the rear surface 222 to form curved portions 223b and 223c. As shown in FIG. 4A, the shape of the incident surface 223 is formed to be bent at both the emission surface 221 and the rear surface 222. As a result, as in the first exemplary embodiment, hot spots generated at the emission surface 221 of the light guide plate 220 proximate to the light emitting diode 211 can be reduced. Since the principle thereof is similar to that of the first embodiment, description thereof is omitted.

A fourth embodiment according to the present invention will be described with reference to FIG.

As shown in FIG. 5, the fourth embodiment has a light guide plate 220 in which the second edge formed by the incident surface 223 and the rear surface (not shown) is formed at a substantially right angle, not a curved surface, unlike the third embodiment. It includes. That is, the incident surface 223 is bent only at the exit surface 221 adjacent to the incident portion 223a, and is not formed at the back surface (not shown). As a result, as in the second embodiment, hot spots generated at the emission surface 221 of the light guide plate 220 proximate to the light emitting diode 211 can be reduced. Since the principle thereof is similar to that of the second embodiment, description thereof is omitted.

As described above, according to the present invention, there is provided a light guide plate for reducing hot spots generated at the exit surface of the light guide plate proximate to the light source unit and a liquid crystal display including the same.

Claims (12)

In a liquid crystal display device comprising a liquid crystal panel, A light source unit emitting light; Located at the rear of the liquid crystal panel, an emission surface for emitting light toward the liquid crystal panel, a rear surface opposite to the emission surface, connecting the emission surface and the rear surface and the light emitted from the light source unit is incident It includes a light guide plate having an incident surface, And a cross section in which the incident surface is cut in the stacking direction of the liquid crystal panel and the light guide plate includes an incident portion facing the light source portion and a curved portion extending from the incident portion. The method of claim 1, And the curved portion is formed on at least a portion of the first edge formed by the incident surface and the exit surface. The method of claim 2, And at least a portion of the second edge formed between the incident surface and the back surface is formed with the curved portion. The method according to claim 2 or 3, And the curved portion is formed over the entire length direction of the incident surface. The method according to claim 2 or 3, And the curved portion is formed in an area adjacent to the light source portion of the incident surface. The method of claim 1, And the light source part is in contact with the incident part of the incident surface. The method of claim 6, The light source unit includes a plurality of light emitting diodes. In the light guide plate for providing the light emitted from the light source unit to the liquid crystal panel, An emission surface on which light is emitted, a back surface positioned opposite to the emission surface, and an entrance surface connecting the emission surface and the rear surface to which light emitted from the light source unit is incident; And a cross section in which the incident surface is cut in a direction in which light is emitted includes an incident portion facing the light source portion and a curved portion extending from the incident portion. The method of claim 8, The light guide plate, characterized in that the curved portion formed on at least a portion of the first edge formed between the incident surface and the exit surface. The method of claim 9, The curved part is formed on at least a portion of the second edge formed between the incident surface and the back surface. The method of claim 9 or 10, The curved part is formed over the entire length direction of the incident surface. The method of claim 9 or 10, And the curved portion is formed in an area adjacent to the light source portion of the incident surface.

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