KR20170080313A - Backlight unit and liquid crystal display device having the same - Google Patents

Abstract

The backlight unit of the present invention and the liquid crystal display device having the same are provided with a flat area instead of a prism mountain in an upper prism sheet located in a light entrance part of a light guide plate, in a backlight unit of a thin structure using a partial wedge type light guide plate Thereby blocking light traveling between the crests and the valleys of the prism sheet.
Accordingly, the light leakage at the light-incident portion of the light guide plate is reduced and the uniformity of the hot spot is improved.

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THE SAME [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit, and more particularly, to a backlight unit using a partial wedge-type light guide plate and a liquid crystal display device having the same.

In recent information society, the importance of display devices as visual information delivery media is getting more emphasized, and in order to take a major position in the future, it is necessary to meet requirements such as low power consumption, thinning, light weight, and high image quality.

The display device includes a cathode ray tube (CRT), an electroluminescence (EL), a light emitting diode (LED), a vacuum fluorescent display (VFD) A non-light emitting type in which light can not be emitted, such as a light emitting type such as a field emission display (FED), a plasma display panel (PDP), and a liquid crystal display (LCD) .

The liquid crystal display device is an apparatus for displaying an image using the optical anisotropy of a liquid crystal, and is superior in visibility compared to a conventional cathode-ray tube and has a smaller average power consumption than a cathode-ray tube of the same screen size, have.

The liquid crystal display device includes a liquid crystal panel in which pixels are arranged in a matrix form, a driver for driving the pixels, and a backlight unit for supplying light to the liquid crystal panel.

1 is a perspective view illustrating an exemplary structure of a general backlight unit.

1 shows a backlight unit using a wedge type light guide plate for a thin structure.

1, an LED array 31 for generating light is provided on one side of the light guide plate 42, and a reflection plate (not shown) is provided on the back surface of the light guide plate 42 .

The light emitted from the LED array 31 is incident on the side surface of the light guide plate 42. The reflection plate disposed on the back surface of the light guide plate 42 guides the light transmitted through the back surface of the light guide plate 42 to the light guide plate 42, To the optical sheets 43 on the upper surface.

At this time, the optical sheet 43 is composed of the diffusion sheet 43a, the lower prism sheet 43b and the upper prism sheet 43c.

The recently developed smartphone model has a thin structure, and the light guide plate 42 in the backlight unit is divided into an incident light area and a light guide area having different thicknesses.

The step between the light incident area and the light guide area is designed in a slope shape, and a part of the light emitted from the LED array 31 is emitted in this inclined area.

The light emitted to the inclined region advances to an empty space between the crests and valleys of the upper prism sheet 43c (see arrows indicated by dotted lines), and is visually recognized as light leakage during driving. This light leakage phenomenon occurs more severely when the step between the light incident area and the light guide area of the light guide plate 42 is larger.

That is, the prism mountains 44 of the same shape are continuously arranged on the upper prism sheet 43c located at the uppermost portion of the backlight unit. At this time, when the step of the inclined region of the light guide plate 42 is designed to be maximized in order to reduce the thickness of the light guide plate 42, light emitted to the inclined region is increased, and a part of the light emitted from the light guide plate 42 And is directly incident on the prism sheet 43c. At this time, light is emitted through the empty space between the mountains and the valleys of the upper prism sheet 43c to be visually recognized as light leakage.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a backlight unit of a thin structure having a partial wedge type light guiding plate for preventing light leakage by blocking light traveling between the mountains and the valleys of a prism sheet, Device. ≪ / RTI >

Other objects and features of the present invention will be described in the following description of the invention and the claims.

In order to achieve the above object, a backlight unit according to an embodiment of the present invention includes a light guide plate having a different thickness between an incident light region and a light guiding region.

A lower prism sheet is disposed on the light guide plate.

On the lower prism sheet, an upper prism sheet having a first region having prism mountains and a second region having a flat upper surface is disposed.

The liquid crystal display device according to an embodiment of the present invention may further include a liquid crystal panel positioned above the backlight unit.

At this time, the second region may extend in the direction in which the light source is arranged close to the light source, and the prism mountain may extend in a direction perpendicular to the extending direction of the second region.

The top surface of the second region may be located on the same plane as the apex of the prism mountain.

The upper surface of the second region may protrude from the vertex of the prism mountain.

As described above, the backlight unit and the liquid crystal display device having the same according to an embodiment of the present invention include a flat region in the upper prism sheet located in the light entrance portion of the light guide plate instead of the prism mountain, It can block the light. Accordingly, the light leakage in the light-incident portion of the light guide plate is reduced, and the effect of improving the uniformity of the hot spot can be provided.

1 is a perspective view exemplarily showing the structure of a general backlight unit;
2 is an exploded perspective view showing an example of the structure of a liquid crystal display device according to a first embodiment of the present invention.
FIG. 3 is a perspective view illustrating an exemplary structure of a backlight unit in the liquid crystal display according to the first embodiment of the present invention shown in FIG. 2; FIG.
FIG. 4 is a schematic view showing a cross-sectional structure of a backlight unit in the liquid crystal display according to the first embodiment of the present invention shown in FIG. 2. FIG.
5A and 5B are graphs showing luminance uniformity according to the position of the light-entering portion.
6 is a schematic view showing a cross-sectional structure of a backlight unit according to a second embodiment of the present invention.

Hereinafter, preferred embodiments of a backlight unit and a liquid crystal display device having the same according to the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification. The dimensions and relative sizes of the layers and regions in the figures may be exaggerated for clarity of illustration.

It will be understood that when an element or layer is referred to as being another element or "on" or "on ", it includes both intervening layers or other elements in the middle, do. On the other hand, when a device is referred to as "directly on" or "directly above ", it does not intervene another device or layer in the middle.

The terms spatially relative, "below," "lower," "above," "upper," and the like, And may be used to easily describe the correlation with other elements or components. Spatially relative terms should be understood to include, in addition to the directions shown in the drawings, terms that include the different directions of the elements in use, or in operation. For example, when inverting an element shown in the figures, an element described as "below" or "beneath" of another element may be placed "above" another element. Thus, the exemplary term "below" can include both downward and upward directions.

The terminology used herein is for the purpose of describing embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. &Quot; comprise "and / or" comprising ", as used in the specification, means that the presence of stated elements, Or additions.

2 is an exploded perspective view showing an example of the structure of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 3 is a perspective view illustrating an exemplary structure of a backlight unit in the liquid crystal display according to the first embodiment of the present invention shown in FIG. 2. Referring to FIG.

4 is a schematic view showing a cross-sectional structure of a backlight unit in the liquid crystal display according to the first embodiment of the present invention shown in FIG.

2 to 4, the liquid crystal display according to the first embodiment of the present invention roughly includes a liquid crystal panel 110 for injecting liquid crystal between a color filter substrate 105 and an array substrate 115 to output an image, A backlight unit 140 installed on the rear surface of the liquid crystal panel 110 to emit light over the entire surface of the liquid crystal panel 110 and a lower cover 150 for accommodating the liquid crystal panel 110 and the backlight unit 140. [ As shown in FIG.

The liquid crystal panel 110 includes a color filter substrate 105 and a color filter substrate 105. The color filter substrate 105 is arranged so that pixels are arranged in a matrix form to output an image, And a liquid crystal layer formed in a cell gap between the array substrate 115 and the liquid crystal layer.

Although not shown in detail, a common electrode and a pixel electrode are formed on the liquid crystal panel 110 in which the color filter substrate 105 and the array substrate 115 are bonded together to apply an electric field to the liquid crystal layer, The liquid crystal of the liquid crystal layer is rotated by dielectric anisotropy according to the electric field between the common electrode and the pixel electrode so that light is transmitted or blocked for each pixel to display a character or an image can do.

At this time, a switching element such as a thin film transistor (TFT) may be separately provided in the pixels to control the voltage of the data signal applied to the pixel electrode on a pixel-by-pixel basis.

That is, a gate line and a data line are vertically and horizontally arranged on the array substrate 115 to define a pixel region, and a thin film transistor, which is a switching device, may be formed in a crossing region between the gate line and the data line.

The thin film transistor may include a gate electrode connected to the gate line, a source electrode connected to the data line, and a drain electrode connected to the pixel electrode.

The color filter substrate 105 includes a color filter composed of a plurality of sub-color filters that implement the colors of red, green, and blue, a black matrix that separates sub-color filters and blocks light transmitting through the liquid crystal layer, Filter and an overcoat layer formed over the black matrix.

Polarizing plates 101 and 111 may be respectively attached to the outer sides of the color filter substrate 105 and the array substrate 115. The lower polarizing plate 111 polarizes the light transmitted through the backlight unit 140, (101) polarizes light passing through the liquid crystal panel (110).

In one example, the bottom cover 150 may include a bottom and a plurality of side portions. The floor can have a square shape. The side portions may extend vertically to have a predetermined height from each edge of the bottom. The edges of the side portions adjacent to each other can be connected to each other. The space surrounded by the side portions and the bottom forms a storage space in which the liquid crystal panel 110 and the backlight unit 140 are housed.

The guide panel 145 mounts the above-described liquid crystal panel 110 on the inner step portion, and supports and fixes the liquid crystal panel 110 by the shielding tape 146. Then, the backlight unit 140 is wrapped around the inner wall.

The liquid crystal panel 110 including the color filter substrate 105 and the array substrate 115 is mounted on the upper part of the backlight unit 140 through the guide panel 145 and the lower cover 150 is coupled to the lower part thereof Thereby constituting a liquid crystal display device.

A light source unit 130 including a light source 131 for generating light is installed on one side of the light guide plate 142, And a reflector 141 may be provided on the back surface of the light guide plate 142. [

A plurality of optical sheets 143 for irradiating the liquid crystal panel 110 with improved efficiency of light emitted from the light guide plate 142 may be disposed on the upper surface of the light guide plate 142. [

The light guide plate 142 receives light from the light source 131 and guides the light to the liquid crystal panel 110 side. At this time, the light provided from the light source 131 is provided as an incident surface (or a light-incident portion) of the light guide plate 142. This incidence surface faces one of the side portions of the lower cover 150. That is, the light source 131 is disposed on one side surface of the lower cover 150, and the light incident surface of the light guide plate 142 faces the light emitting surface of the light source 131.

The light guide plate 142 may be made of PMMA (polymethyl methacrylate) or PC (polycarbonate) plastic.

In particular, the light guide plate 142 according to the first embodiment of the present invention is characterized in that a partial wedge shape divided into an incident light region 142c having a different thickness and a light guiding region 142a is applied.

The light guiding area 142a may have a thinner thickness than the light incident area 142c for the thin structure and each of the light incident area 142c and the light guiding area 142a may have a substantially uniform thickness.

The step between the light incident region 142c and the light guiding region 142a may be designed in a slope manner and a part of the light emitted from the light source 131 may be emitted to the inclined region 142b.

The reflection plate 141 is positioned between the bottom of the lower cover 150 and the back surface of the light guide plate 142. The reflection plate 141 reflects light from the light source 131 and light from the light guide plate 142 to the liquid crystal panel 110 side.

At this time, the light source 131 is a means for emitting light. For example, a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL), an external electroluminescence lamp (EEFL) But is not limited thereto. Hereinafter, for convenience of explanation, a case where an LED is used as the light source 131 is taken as an example.

LEDs that are the light sources 131 may be red, green, and blue LEDs that emit red, green, and blue monochromatic lights, or LEDs that emit white light.

In the case of an LED array emitting monochromatic light, monochromatic LEDs of red, green, and blue are alternately arranged at regular intervals, monochromatic light emitted therefrom is mixed into white light, and then supplied to the liquid crystal panel 110, In the case of an LED array, a plurality of LEDs are arranged at regular intervals to supply white light to the liquid crystal panel 110.

In this case, the white light LED may be composed of a blue LED emitting blue light and a phosphor emitting yellow light by absorbing blue monochromatic light, and the blue monochromatic light output from the blue LED and the yellow monochromatic light emitted from the phosphor are mixed, To the liquid crystal panel 110. [

The LED array may comprise a light emitting package having at least one LED.

The LED array as the light source 131 may be installed on the printed circuit board 132 such that the light exit surface looks at the incident surface of the light guide plate 142. [

At this time, the printed circuit board 132 according to the first embodiment of the present invention may be formed of a flexible printed circuit board (FPCB) having a copper foil layer inside.

The printed circuit board 132 may be installed above the light incident area 142c of the light source 131 and the light guide plate 142. For example, the printed circuit board 132 may be installed above the light incident area 142c of the light source 131 and the light guide plate 142 through a heat dissipation tape (not shown). As shown in FIG. 4, the printed circuit board 132 may include not only an upper part of the light incident area 142c of the light source 131 and the light guide plate 142 but also a part of the inclined area 142b It can be installed up to the upper part. In this case, the printed circuit board 132 may be partially bent according to the inclination of the inclined region 142b.

A plurality of power lines (not shown) and electrical components (not shown) for transmitting power to the light source 131 may be formed on the printed circuit board 132.

The light emitted from the light source 131 is incident on the side surface of the light guide plate 142 made of a transparent material. The reflection plate 141 disposed on the back surface of the light guide plate 142 reflects light transmitted to the back surface of the light guide plate 142 toward the optical sheets 143 on the upper surface of the light guide plate 142 to reduce light loss and improve uniformity .

At this time, the optical sheets 143 include a diffuser sheet 143a and upper and lower prism sheets 143b and 143c, and a protective sheet may be added.

The prism sheets 143b and 143c condense the light from the light guide plate 142 and the diffusion sheet 143a diffuses the light from the prism sheets 143b and 143c. The protective sheet serves to protect the prism sheets 143b and 143c and the diffusion sheet 143a. Light passing through the protective sheet is provided to the liquid crystal panel 110 side.

At this time, the diffusion sheet 143a may protrude further than the upper prism sheets 143b and 143c and may be positioned above the light guiding area 143a of the light guide plate 142. [ This is for minimizing the case where the backlight not passing through the diffusion sheet 143a is directly incident on the prism sheets 143b and 143c.

Accordingly, the prism sheets 143b and 143c may be located a certain distance from the boundary between the inclined region 142b of the light guide plate 142 and the light guide region 143a.

The prism sheets 143b and 143c are disposed on the lower prism sheet 143b so as to contact the lower prism sheet 143b and the lower prism sheet 143b located above the diffusion sheet 143a so as to be in contact with the diffusion sheet 143a. And an upper prism sheet 143c.

The upper prism sheet 143c and the lower prism sheet 143b may be prism mountains arranged in a direction intersecting with each other. 3, the lower prism sheet 143b 'is arranged such that the lower prism sheet 143b has an angle of about 0 degrees with respect to the direction in which the light sources 131 are arranged, and the upper prism sheet 143c includes the light source 131, The upper prism mountains 143c 'are arranged to have an angle of about 90 degrees with respect to the arrangement direction of the upper prism mountains 143c'. However, the present invention is not limited thereto.

At this time, the lower prism sheet 143b according to the first embodiment of the present invention is formed with the lower prism mountain 143b 'over the entire surface, that is, the entire surface of the back surface. On the other hand, the upper prism sheet 143c includes a first region 144a in which the upper prism mountain 143c 'is formed and a second region 144b in which the upper surface is substantially flat without forming the upper prism mountain 143c' .

The second region 144b may be located close to the light source 131 and may have a constant width along the direction in which the light sources 131 are arranged. That is, the second region 144b may extend along the arrangement direction of the light source 131 in the vicinity of the light source 131, and the upper prism mountain 143c 'may extend perpendicular to the extending direction of the second region 144b Lt; / RTI >

In addition, the upper surface of the second region 144b may be located on the same plane as the vertex of the upper prism mountain 143c '. However, the present invention is not limited thereto, and the bottom surface of the second region 144b may be located on the same plane as the vertex of the upper prism mountain 143c '. That is, the upper surface of the second region 144b may protrude from the vertex of the upper prism mountain 143c '.

The second region 144b is at least larger than the wavelength (? 550 nm) of light and may have a width up to the shielding region A covered by the shielding tape 146. If the second region 144b has a width smaller than the wavelength of light, light leakage may occur through the second region 144b as in the conventional case. If the second region 144b has a width exceeding the light blocking region A, ) Will not function properly.

For reference, B in Fig. 4 represents the bezel width excluding the active area in which the actual image is displayed.

For example, the backlight unit 140 having the above-described structure can be attached and fixed to the liquid crystal panel 110 by the light shielding tape 146, and is housed in the bottom of the lower cover 150 located at the bottom. Particularly, the shielding tape 146 not only attaches and fixes the liquid crystal panel 110 and the backlight unit 140 but also leaks light emitted from the backlight unit 140 through the side surface of the liquid crystal panel 110 You can also play the role of blocking out.

The light shielding tape 146 may be attached to the upper surface of the printed circuit board 132 and extend to the second area 144b of the upper prism sheet 143c to be attached to the upper surface thereof.

The liquid crystal panel 110 including the color filter substrate 105 and the array substrate 115 is seated on the light shielding tape 146 through the guide panel 145. In addition, a lower cover 150 is coupled to the lower part to constitute a liquid crystal display device.

The liquid crystal display according to the present invention having such a structure as described above has the second prism sheet 143c located in the light entrance portion of the light guide plate 142 and a flat second region 144b instead of the upper prism mountain 143c ' Thereby blocking light traveling between the crests and valleys of the upper prism sheet 143c.

That is, when a conventional wedge-shaped light guide plate 142 of a thin structure is applied, a step is generated in the inclined region 142b of the light guide plate 142, and a part of the light emitted to the inclined region 142b, It can proceed to the empty space between the mountains and the valleys of the sheet 143c and be visually recognized as light leakage.

In order to prevent this, the present invention is characterized in that the upper prism sheet 143c close to the light source 131 of the backlight unit is provided with a flat second region 144b without distinction of mountains and valleys. That is, a portion of the upper prism sheet 143c close to the light source 131 forms a second region 144b having a flat shape without a prism shape, so that light incident through the inclined region 142b of the light guide plate 142, And guided to the first area 144a to prevent light leakage.

According to this, the light leakage in the light incident portion of the light guide plate 142 is reduced and the uniformity of the hot spot is improved.

5A and 5B are graphs showing luminance uniformity according to the position of the light-incident portion.

5A shows luminance uniformity according to the position of the light-incident portion in the case of the comparative example in which the prism acid is formed on the entire surface of the upper prism sheet. FIG. 5B shows the luminance uniformity in the case of the embodiment having the flat second region and the first region Simulation shows the luminance uniformity according to the position of the light part.

The diffusion sheet, the lower prism sheet, and the upper prism sheet used in the simulation at this time have a thickness of about 0.04 mm, 0.065 mm, and 0.070 mm, and the light guide plate has a thickness of about 0.40 mm and 0.28 mm For example.

In the graphs shown in Figs. 5A and 5B, the abscissa represents 70 points in the light-incident portion, and the ordinate represents the luminance.

The luminance of the vertical axis is expressed in an arbitrary unit, where 1 means the maximum luminance.

The larger the luminance difference between adjacent points, the greater the luminance unevenness judged by the light leakage or the hot spot.

Referring to FIGS. 5A and 5B, simulation results show that the luminance difference between adjacent points is smaller than that of the comparative example.

Therefore, in the case of the embodiment, light leakage caused by the mountains and the valleys of the prism sheet is prevented and the uniformity of the hotspot of the light-incident portion is improved as compared with the comparative example.

The luminance uniformity of the comparative example was measured to be about 54.9%, while the luminance uniformity of the embodiment was measured to be about 61.5%, which is about 10.7% improved.

The present invention is also applicable to a case in which the partial wedge-shaped light guide plate has an inclined light incident area instead of an incident light area having a uniform thickness, which will be described in detail through the following second embodiment of the present invention.

6 is a schematic view illustrating a cross-sectional structure of a backlight unit according to a second embodiment of the present invention.

In this case, the second embodiment of the present invention shown in FIG. 6 has substantially the same structure as the backlight structure of the first embodiment of the present invention except for the structure of the light guide plate.

Referring to FIG. 6, the liquid crystal display according to the second embodiment of the present invention roughly includes a liquid crystal panel 210 for injecting liquid crystal between a color filter substrate 205 and an array substrate 215 to output an image, A backlight unit installed on the back surface of the panel 210 to emit light over the entire surface of the liquid crystal panel 210, and a liquid crystal panel 210 and a lower cover (not shown) for accommodating the backlight unit.

As described above, the liquid crystal panel 210 includes a color filter substrate 205 to which pixels are arranged in a matrix form to output an image, and the color filter substrate 205 is bonded so as to face each other and maintain a uniform cell gap, And a liquid crystal layer formed in a cell gap between the substrate 205 and the array substrate 215.

Polarizing plates 201 and 211 may be attached to the outer sides of the color filter substrate 205 and the array substrate 215. The lower polarizing plate 211 polarizes the light transmitted through the backlight unit and the upper polarizing plate 201, Polarizes the light transmitted through the liquid crystal panel 210. [

In one example, the bottom cover may include a bottom and a plurality of side portions. The floor can have a square shape. The side portions may extend vertically to have a predetermined height from each edge of the bottom. The edges of the side portions adjacent to each other can be connected to each other. The space surrounded by the side portions and the bottom forms a storage space in which the liquid crystal panel 210 and the backlight unit are housed.

The guide panel 245 mounts the above-described liquid crystal panel 210 on the inner stepped portion, supports and fixes the liquid crystal panel 210 by the shielding tape 246, and surrounds the backlight unit with the inner wall.

The liquid crystal panel 210 including the color filter substrate 205 and the array substrate 215 is mounted on the upper part of the backlight unit through the guide panel 245 and the lower cover is coupled to the lower part to constitute the liquid crystal display device do.

A light source unit 230 including a light source 231 for generating light may be installed on one side of the light guide plate 242. The light source unit 230 may include a light guide plate 242, A reflection plate 241 may be provided on the back surface of the reflector.

A plurality of optical sheets 243 for illuminating the liquid crystal panel 210 can be disposed on the upper surface of the light guide plate 242 by improving the efficiency of light emitted from the light guide plate 242.

The light guide plate 242 receives light from the light source 231 and guides the light to the liquid crystal panel 210 side. At this time, the light provided from the light source 231 is provided to the incident surface (or the light incoming portion) of the light guide plate 242. This incidence surface faces one of the side portions of the lower cover 250. That is, the light source 231 is located on one side of the lower cover 250, and the incident surface of the light guide plate 242 faces the light emitting surface of the light source 231.

The light guide plate 242 may be made of plastic of PMMA or PC.

In particular, the light guide plate 242 according to the second embodiment of the present invention is characterized in that a partial wedge shape is used, which is divided into an incident light region 242c having a different thickness and a light guiding region 242a.

The light guiding area 242a may have a thickness thinner than the light incident area 242c for the thin structure and the light guiding area 242a may have a substantially uniform thickness at this time, And may have an inclined shape in which the thickness decreases toward the region 242a.

Therefore, unlike the first embodiment of the present invention described above, the light incident area 242c can be expressed as an inclined area, and a part of the light emitted from the light source 231 can be emitted to the inclined area.

As described above, the light guide plate 242 according to the second embodiment of the present invention can also reduce the length of the light guide plate 242 as compared with the first embodiment of the present invention by having the light incident area 242c also serve as an inclined area It is advantageous in terms of area, and has an effect that design freedom can be imparted with respect to placement of other parts.

The reflection plate 241 is positioned between the bottom of the lower cover and the back surface of the light guide plate 242. The reflection plate 241 reflects light from the light source 231 and light from the light guide plate 242 toward the liquid crystal panel 210 side.

At this time, the light source 231 is a means for emitting light, and for example, any one of CCFL, HCFL, EEFL, and LED may be selected and used, but the present invention is not limited thereto. Hereinafter, for the sake of convenience of explanation, a case where an LED is used as the light source 231 is taken as an example.

The LED array may comprise a light emitting package having at least one LED.

As the light source 231, the LED array may be installed on the printed circuit board 232 such that the light exit surface faces the incident surface of the light guide plate 242. [

At this time, the printed circuit board 232 according to the second embodiment of the present invention may be formed of an FPCB having a copper foil layer inside.

The printed circuit board 232 may be installed above the light incident area 242c of the light source 231 and the light guide plate 242. For example, the printed circuit board 232 may be installed on the upper portion of the light source 231, the light guide plate 242, and a part of the light incident region 242c through a heat radiation tape (not shown). Therefore, the printed circuit board 232 can be partially bent according to the inclination of the light incident area 242c.

A plurality of power lines (not shown) and electrical components (not shown) for transmitting power to the light source 231 may be formed on the printed circuit board 232.

The light emitted from the light source 231 is incident on the side surface of the light guide plate 242 made of a transparent material. The reflection plate 241 disposed on the back surface of the light guide plate 242 reflects light transmitted to the back surface of the light guide plate 242 toward the optical sheets 243 on the upper surface of the light guide plate 242 to reduce light loss and improve uniformity .

The optical sheets 243 include a diffusion sheet 243a and upper and lower prism sheets 243b and 243c, and a protective sheet may be added.

The prism sheets 243b and 243c condense light from the light guide plate 242 and the diffusion sheet 243a diffuses the light from the prism sheets 243b and 243c. The protective sheet serves to protect the prism sheets 243b and 243c and the diffusion sheet 243a. Light passing through the protective sheet is provided to the liquid crystal panel 210 side.

The diffusion sheet 243a may protrude further than the upper prism sheet 243b or 243c and may be positioned above the light guide region 243a of the light guide plate 242 as described above. This is to minimize the case where the backlight not passing through the diffusion sheet 243a is directly incident on the prism sheets 243b and 243c.

Accordingly, the prism sheets 243b and 243c may be located a certain distance from the boundary between the light incident region 242c and the light guiding region 243a of the light guide plate 242. [

The prism sheets 243b and 243c are disposed on the lower prism sheet 243b so as to contact the lower prism sheet 243b and the lower prism sheet 243b positioned above the diffusion sheet 243a so as to be in contact with the diffusion sheet 243a And an upper prism sheet 243c.

Although not shown in detail, the upper prism sheet 243c and the lower prism sheet 243b may be prism mountains arranged in a direction crossing each other. In this case, for example, the lower prism sheet 243c is arranged such that the lower prism sheet 243b has an angle of about 0 degrees with respect to the arrangement direction of the light sources 231, The upper prism mountains may be arranged so as to have an angle of 90 degrees. However, the present invention is not limited thereto.

In this case, the lower prism sheet 243b according to the second embodiment of the present invention is formed with a lower prism mountain over the front surface, that is, the entire surface of the rear surface, substantially the same as the first embodiment of the present invention described above. On the other hand, the upper prism sheet 243c is formed of a first region in which an upper prism mountain is formed and a second region in which an upper surface is substantially flat without forming an upper prism acid.

The second region may be located close to the light source 231 and may have a constant width along the arrangement direction of the light sources 231. [ That is, the second region 244b may extend along the arrangement direction of the light source 231 close to the light source 231, and the upper prism mountain may extend in a direction perpendicular to the extending direction of the second region 244b have.

In addition, the upper surface of the second region 244b may be located on the same plane as the vertex of the upper prism mountain. However, the present invention is not limited thereto as described above, and the bottom surface of the second region 244b may be located on the same plane as the vertex of the upper prism mountain. That is, the upper surface of the second region 244b may protrude from the vertex of the upper prism mountain.

The second region is at least larger than the wavelength (? 550 nm) of light and may have a width up to the shielding region covered by the shielding tape 246.

As an example, the backlight unit of the above-described structure can be attached and fixed to the liquid crystal panel 210 by the light shielding tape 246, and is housed in the bottom of the lower cover located below. Particularly, the shielding tape 246 serves not only to attach and fix the liquid crystal panel 210 and the backlight unit, but also to prevent the light emitted from the backlight unit from leaking out through the side surface of the liquid crystal panel 210 Can be performed.

The light shielding tape 246 may be attached to the upper surface of the printed circuit board 232 and extend to the second area of the upper prism sheet 243c and attached to the upper surface thereof.

The liquid crystal panel 210 including the color filter substrate 205 and the array substrate 215 is seated on the light shielding tape 246 through the guide panel 245. In addition, a lower cover 250 is coupled to the lower portion to constitute a liquid crystal display device.

The liquid crystal display according to the present invention having the above-described structure includes the upper prism sheet 243c located in the light-incident portion of the light guide plate 242, and the upper prism sheet 243c, And blocks the light traveling between the mountains and the valleys.

According to this, the light leakage at the light-incident portion of the light guide plate 242 is reduced and the uniformity of the hot spot is improved.

While a great many are described in the foregoing description, it should be construed as an example of preferred embodiments rather than limiting the scope of the invention. Therefore, the invention should not be construed as limited to the embodiments described, but should be determined by equivalents to the appended claims and the claims.

110, 210: liquid crystal panel 131, 231:
132, 232: printed circuit boards 141, 241:
142, 242: a light guide plate 142a, 242a:
142b: an inclined region 142c, 242c:
143, 243: optical sheet 143a, 243a: diffusion sheet
143b, 243b: lower prism sheet 143c, 243c: upper prism sheet
144a: first region 144b: second region

Claims (13)

A light guide plate having a different thickness of the light incident area and the light guide area;
A light source disposed toward an incident light area of the light guide plate;
A lower prism sheet positioned above the light guide plate; And
And an upper prism sheet disposed on the lower prism sheet, the upper prism sheet having a first region provided with a prism mountain and a second region having a flat upper surface. The backlight unit according to claim 1, wherein the second region extends along the arrangement direction of the light source in proximity to the light source, and the prism mountain extends in a direction perpendicular to the extending direction of the second region. The backlight unit according to claim 1, wherein the upper surface of the second region is located on the same plane as the apex of the prism mountain. 2. The backlight unit according to claim 1, wherein the upper surface of the second region is a backlight unit The backlight unit according to claim 1, further comprising a diffusion sheet disposed between the light guide plate and the lower prism sheet. The backlight unit according to claim 5, wherein the diffusion sheet further protrudes from the lower prism sheet and the upper prism sheet, and is positioned above the light guiding area of the light guide plate. The backlight unit according to claim 1, wherein the light guiding area has a thickness smaller than that of the light incident area, and each of the light incident area and the light guiding area has a uniform thickness. The backlight unit according to claim 1, wherein the step between the light incident area and the light guiding area comprises an inclined area having a slope shape. The backlight unit of claim 1, further comprising a printed circuit board that transmits power to the light source and is disposed above the light source and the light incident area of the light guide plate. The backlight unit according to claim 9, further comprising a light shielding tape covering the printed circuit board and extending to a second area of the upper prism sheet and attached to an upper surface of the printed circuit board. 11. The backlight unit according to claim 10, wherein the second region has a width at least equal to a wavelength of light and a width to a light-shielding region covered by the light-shielding tape. The light guide plate according to claim 1, wherein the light guiding area has a thickness smaller than that of the light incident area, the light guiding area has a uniform thickness, but the light incident area has an inclined shape in which the thickness decreases from the light entering part to the light guiding area Backlight unit. A backlight unit according to any one of claims 1 to 12;
A liquid crystal panel on the backlight unit; And
And a lower cover for accommodating the liquid crystal panel and the backlight unit.

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