KR20180021597A - Backlight unit, display device including backlight unit, and its driving method - Google Patents

Abstract

An example of the present invention is a backlight unit capable of realizing a normal mode for providing a wide viewing angle image and a privacy mode for providing a narrow viewing angle image without reducing luminance or arranging wiring between pixels separately, ≪ / RTI > The backlight unit according to an exemplary embodiment of the present invention includes a reflective plate, a normal mode light guide plate disposed on an upper portion of the reflector, a normal mode backlight disposed on a side of the normal mode light guide plate to emit wide viewing angle light, A light guide plate, a privacy mode backlight disposed on a side surface of the privacy mode light guide plate to emit narrow viewing angle light, and a lens sheet disposed on the privacy mode light guide plate. A prism pattern for condensing the narrow viewing angle light and emitting the light in the lens sheet direction is disposed on the lower surface of the privacy mode light guide plate of the present invention.

Description

BACKLIGHT UNIT, DISPLAY DEVICE HAVING THE SAME, AND METHOD OF DRIVING THE BACKLIGHT UNIT

One example of the present invention relates to a backlight unit, a display device including the backlight unit, and a driving method thereof.

As the information society develops, display devices capable of expressing images are increasingly being used. Particularly, personal display devices such as a portable terminal, a notebook computer, a tablet computer, a smart clock, and the like, which provide images only for individual users, are increasingly used.

The personal display device displays a wide viewing angle image in which an image is viewed even at an oblique angle with an oblique angle and a narrow viewing angle image in which an image is viewed only in front and an image is not viewed at an oblique angle. A case where a wide viewing angle image is provided is defined as a normal mode, and a case where a narrow viewing angle image is provided is defined as a privacy mode. In particular, the narrow viewing angle image is a mode frequently used in a personal display device to protect the privacy of the user.

The most widely used method for controlling the viewing angle is to arrange a viewing angle control sub-pixel between normal sub-pixels to control the viewing angle. In the case of displaying a wide viewing angle image, only normal sub-pixels are driven in all pixels, and the viewing angle control sub-pixels are not driven. When a narrow viewing angle image is displayed, the normal sub-pixels are driven with a relatively low luminance and the view angle control sub-pixel is driven.

One example of the viewing angle control sub-pixel is Electrically Controlled birefringence (ECB) sub-pixel. The electric birefringence control sub-pixel can control the refractive index depending on the direction differently according to the electric field to be supplied. Accordingly, an image is not visually recognized outside the viewing angle range.

However, when the viewing angle is controlled using the viewing angle control sub-pixel, the light emitted to the side can not be completely blocked. Also, the viewing angle control sub-pixel has a lower luminance than that of a general sub-pixel, resulting in a problem that the overall luminance of the image is lowered.

Another method for controlling the viewing angle is to arrange a separate viewing angle control partition in the display panel between the pixels. The viewing angle control barrier is formed of a material capable of controlling the light transmittance. In the case of displaying a wide viewing angle image, the light transmittance of the viewing angle control partition is controlled to be high, and the light emitted diagonally is not blocked. In the case of displaying a narrow viewing angle image, the light transmittance of the viewing angle control partition is controlled to be low so that the light emitted in the diagonal direction is blocked to prevent the image from being visually recognized outside the viewing angle range.

However, in the case where the barrier rib for controlling the viewing angle is disposed between the pixels, a separate signal for controlling the light transmittance must be supplied for each barrier rib, so that separate wiring must be disposed between the pixels, There is an increasing problem.

An example of the present invention is a backlight unit capable of realizing a normal mode for providing a wide viewing angle image and a privacy mode for providing a narrow viewing angle image without reducing luminance or arranging wiring between pixels separately, Method.

The backlight unit according to an exemplary embodiment of the present invention includes a reflective plate, a normal mode light guide plate disposed on an upper portion of the reflector, a normal mode backlight disposed on a side of the normal mode light guide plate to emit wide viewing angle light, A light guide plate, a privacy mode backlight disposed on a side surface of the privacy mode light guide plate to emit narrow viewing angle light, and a lens sheet disposed on the privacy mode light guide plate. A prism pattern for condensing the narrow viewing angle light and emitting the light in the lens sheet direction is disposed on the lower surface of the privacy mode light guide plate of the present invention.

A display device according to an exemplary embodiment of the present invention includes a display panel on which pixels for displaying an image are arranged, a data driver for supplying a data voltage to the pixels, a gate driver for supplying a gate signal to the pixels, A timing controller for supplying a gate driver control signal to the gate driver, a system board for supplying digital video data to the timing controller, a backlight unit for emitting a backlight to the display panel, a backlight unit for supplying a driving voltage to the backlight unit, And a backlight unit control signal for controlling the backlight unit driving unit on the basis of the information of the mode signal is supplied to the driving unit and the system board in response to the mode signal for setting the privacy mode for providing the normal mode or the narrow viewing angle image for providing the wide viewing angle image Generating backlight oil And a controller.

A method of driving a backlight unit according to an exemplary embodiment of the present invention includes the steps of supplying a mode signal for setting a privacy mode for providing a normal mode or a narrow viewing angle image providing a wide viewing angle image on a system board to a backlight unit controller, Generating a backlight unit control signal based on the information of the mode signal in the backlight unit driving unit, and supplying a driving voltage to the backlight unit by receiving the backlight unit control signal from the backlight unit control unit in the backlight unit driving unit.

A prism pattern is disposed on a lower portion of the privacy mode light guide plate to condense the narrow viewing angle light and emit the light toward the lens sheet, on the upper portion of the privacy mode light guide plate included in the backlight unit according to an exemplary embodiment of the present invention. Accordingly, the present invention emits both the wide viewing angle light and the narrow viewing angle light in the backlight unit, and the narrow viewing angle light implements the privacy mode in the lens sheet disposed at the top of the backlight unit. Accordingly, the backlight unit according to the present invention can realize the normal mode for providing the wide viewing angle image without reducing the luminance of the display device or the wiring arrangement between the pixels, and the privacy mode for providing the narrow viewing angle image.

1 is a block diagram of a display device according to an embodiment of the present invention.
2 is a circuit diagram of a pixel according to an example of the present invention.
3 is a cross-sectional view of a backlight unit according to an exemplary embodiment of the present invention.
4 is a cross-sectional view of one of the prism patterns according to an embodiment of the present invention.
5 is a cross-sectional view showing a unit lens of a lens sheet and five prism patterns arranged adjacent to each other according to an example of the present invention.
6 is a flowchart illustrating a method of driving a backlight unit according to an exemplary embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers, and the like disclosed in the drawings for describing the embodiments of the present invention are illustrative, and thus the present invention is not limited thereto. Like reference numerals refer to like elements throughout the specification. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

Where the terms "comprises," "having," "consisting of," and the like are used in this specification, other portions may be added as long as "only" is not used. Unless the context clearly dictates otherwise, including the plural unless the context clearly dictates otherwise.

In interpreting the constituent elements, it is construed to include the error range even if there is no separate description.

In the case of a description of the positional relationship, for example, if the positional relationship between two parts is described as 'on', 'on top', 'under', and 'next to' Or " direct " is not used, one or more other portions may be located between the two portions.

In the case of a description of a temporal relationship, for example, if the temporal relationship is described by 'after', 'after', 'after', 'before', etc., May not be continuous unless they are not used.

The first, second, etc. are used to describe various components, but these components are not limited by these terms. These terms are used only to distinguish one component from another. Therefore, the first component mentioned below may be the second component within the technical spirit of the present invention.

The terms "X-axis direction "," Y-axis direction ", and "Z-axis direction" should not be construed solely by the geometric relationship in which the relationship between them is vertical, It may mean having directionality.

It should be understood that the term "at least one" includes all possible combinations from one or more related items. For example, the meaning of "at least one of the first item, the second item and the third item" means not only the first item, the second item or the third item, but also the second item and the second item among the first item, May refer to any combination of items that may be presented from more than one.

It is to be understood that each of the features of the various embodiments of the present invention may be combined or combined with each other, partially or wholly, technically various interlocking and driving, and that the embodiments may be practiced independently of each other, It is possible.

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

1 is a block diagram of a display device 100 according to an example of the present invention. A display device 100 according to an exemplary embodiment of the present invention includes a display panel 110, a data driver 120, a gate driver 130, a timing controller 140, a system board 150, a backlight unit 210, A unit driver 220, and a backlight unit controller 230. [

2 is a circuit diagram of a pixel P according to an example of the present invention. The display device 100 according to an exemplary embodiment of the present invention includes all kinds of display devices that display an image using the backlight unit 210. [ A typical example of a display device using the backlight unit 210 is a liquid crystal display. Therefore, the following description will be made on the assumption that the display device 100 according to an exemplary embodiment of the present invention is implemented as a liquid crystal display device.

The display panel 110 displays an image using the pixels P. [ The display panel 110 includes a lower substrate, an upper substrate, and a liquid crystal layer interposed between the lower substrate and the upper substrate. The data lines D and the gate lines G are arranged on the lower substrate of the display panel 110. The data lines D are arranged so as to intersect with the gate lines G. [

The pixels P are arranged at the intersections of the data lines D and the gate lines G, respectively. Each of the pixels P is connected to the data line D and the gate line G. [ Each of the pixels P includes a transistor T, a pixel electrode 11, a common electrode 12, a liquid crystal layer 13, and a storage capacitor Cst. The transistor T is turned on by the gate signal of the gate line G. The turned-on transistor T supplies the data voltage of the data line D to the pixel electrode 11. The common electrodes 12 are connected to a common line to receive a common voltage from the common line.

Each of the pixels P drives the liquid crystal of the liquid crystal layer 13 by an electric field generated by a potential difference between a data voltage supplied to the pixel electrode 11 and a common voltage supplied to the common electrode 12. [ The arrangement of liquid crystals changes according to the presence or absence of an electric field and the intensity of an electric field, and the amount of light transmitted through the backlight unit 210 can be adjusted. As a result, the pixels P can display an image with the set gradation. The storage capacitor Cst is disposed between the pixel electrode 11 and the common electrode 12. The storage capacitor Cst maintains the potential difference between the pixel electrode 11 and the common electrode 12 constant.

The common electrode 12 is disposed on the upper substrate in a vertical electric field driving system such as a TN (Twisted Nematic) mode or a VA (Vertical Alignment) mode. The common electrode 12 is disposed on the lower substrate together with the pixel electrode 11 in a horizontal electric field driving method such as an IPS (In Plane Switching) mode or an FFS (Fringe Field Switching) mode. The liquid crystal mode of the display panel 110 may be implemented in any liquid crystal mode as well as the TN mode, the VA mode, the IPS mode, and the FFS mode described above.

A black matrix, a color filter, and the like may be disposed on the upper substrate of the display panel 110. The color filters may be disposed in openings that are not covered by the black matrix. When the display panel 110 has a color filter on TFT (COT) structure, the black matrix and the color filters may be disposed on the lower substrate of the display panel 110.

An alignment film may be provided on each of the lower substrate and the upper substrate of the display panel 110 to set a pre-tilt angle of the liquid crystal to which a polarizer is attached. A column spacer for maintaining a cell gap of the liquid crystal layer may be provided between the lower substrate and the upper substrate of the display panel 110. [

The data driver 120 receives the data driver control signal DCS and the digital video data DATA from the timing controller 140. The data driver 120 converts the digital video data DATA to a positive or negative gamma compensation voltage according to the data driver control signal DCS to generate analog data voltages. The data driver outputs analog data voltages. The analog data voltages output from the data driver 120 are supplied to the data lines D of the display panel 110.

The gate driver 130 receives the gate driver control signal GCS from the timing controller 140. The gate driver 130 generates gate signals according to the gate driver control signal GCS. The gate driver 130 sequentially supplies the gate signals to the gate lines G of the display panel 110. Accordingly, the data voltage of the data line D can be supplied to the pixel P to which the gate signals are supplied.

The timing controller 140 receives the digital video data DATA and the timing signals TS from the system board 150. The timing signals TS include a horizontal synchronizing signal Hsync, a vertical synchronizing signal Vsync, a data enable signal DE and a dot clock Dck . ≪ / RTI >

The timing controller 140 generates the gate driver control signal GCS and the data driver control signal DCS based on the timing signals TS. The timing controller 140 supplies the gate driver control signal GCS to the gate driver 130. The timing controller 140 supplies the data driver 120 with the data driver control signal DCS and the digital video data DATA.

The system board 150 transmits the digital video data DATA to the display panel controller 140 through an interface such as a Low Voltage Differential Signaling (LVDS) interface and a Transition Minimized Differential Signaling (TMDS) . The system board 150 supplies the timing signals TS to the display panel control unit 140.

The system board 150 supplies the mode signal MODE to the backlight control unit 230. The mode signal MODE is a signal for setting whether the current mode is a normal mode for providing a wide viewing angle image or a privacy mode for providing a narrow viewing angle image. For example, it can be set to indicate the normal mode when the mode signal MODE has the first logic level voltage and to indicate the privacy mode if the mode signal MODE has the second logic level voltage.

The backlight unit 210 emits a backlight to the display panel 110. [ The display panel 110 according to an exemplary embodiment of the present invention can not emit light by itself, and a backlight is required to display an image. A detailed description of the backlight unit 210 will be given later with reference to FIGS. 3 to 5. FIG.

The backlight driver 220 receives the backlight unit control signal BCD from the backlight controller 230. The backlight driver 220 supplies the driving voltage DV to the backlight unit 210 according to the backlight unit control signal BCD.

The backlight unit control signal BCD supplies the driving voltage DV to the normal mode backlight included in the backlight unit 210 when the mode signal MODE sets the normal mode. The backlight unit control signal BCD controls the backlight unit driving unit 220 to supply the driving voltage DV to the privacy mode backlight included in the backlight unit 210 when the mode signal MODE sets the privacy mode .

The driving voltage can be selectively supplied to the normal mode backlight or the privacy mode backlight in accordance with the backlight unit control signal BCD. Accordingly, the normal mode or the privacy mode can be selectively set. In the normal mode, a wide viewing angle is displayed. In the privacy mode, a narrow viewing angle is displayed. Therefore, a wide viewing angle or a narrow viewing angle can be realized without additional components on a separate display panel 110.

The backlight control unit 230 receives the mode signal MODE from the system board 150. The backlight control unit 230 generates a backlight unit control signal BCD according to the mode signal MODE and supplies the backlight unit control signal BCD to the backlight driving unit 220. As described above, the backlight unit control signal BCD controls the supply of the driving voltage DV to the backlight driver 220. [

The backlight unit control signal (BCD) can be transmitted in the SPI (Serial Peripheral Interface) data format. In addition, the backlight controller 230 may be included in the timing controller 140. That is, the timing controller 140 and the backlight controller 230 may be formed of one IC.

3 is a cross-sectional view of a backlight unit 210 according to an exemplary embodiment of the present invention. The backlight unit 210 according to an exemplary embodiment of the present invention includes a reflection plate 211, a normal mode backlight 212, a normal mode light guide plate 213, an optical sheet 214, a privacy mode backlight 215, a privacy mode light guide plate 216 , A prism pattern 217, and a lens sheet 218. [

The reflection plate 211 is disposed at the lowermost end of the backlight unit 210. Since the present invention includes a plurality of light guide plates and a plurality of backlights, it is preferable to have an edge type backlight in order to prevent the backlights from interfering with each other. When the backlight unit 210 has an edge-type backlight, the reflection plate 211 generates the backlight incident on the side surface of the backlight unit 210 and reflects the incident backlight in the front direction of the backlight unit 210. The reflection plate 211 may be formed of any material having a high light reflectance such as a metal.

The normal mode backlight 212 is disposed on the side of the normal mode light guide plate 213. The normal mode backlight 212 emits wide viewing angle light LN. The wide viewing angle light LN is not light that is set in advance but is light that is incident on the display panel 110 via the normal mode light guide plate 213 and used to display an image in the normal mode having a wide viewing angle. The normal mode backlight 212 is implemented by a light emitting diode array (LED array). However, the normal mode backlight 212 is not limited thereto and may be realized as any type of light source.

The normal mode light guide plate 213 is disposed on the upper side of the reflection plate 211. The normal mode light guide plate 213 guides the wide viewing angle light LN incident on the normal mode backlight 212 toward the display panel 110. When the backlight guided by the normal mode backlight 212 reaches the display panel 110, the display panel 110 displays an image in the normal mode. That is, the normal mode light guide plate 213 guides the wide view angle light LN to display the image having the wide viewing angle to the display panel 110. The normal mode light guide plate 213 has the same function and structure as the light guide plate used in the general display device 100 having a backlight.

The optical sheet 214 is disposed on the upper portion of the normal mode light guide plate 213. Preferably, the optical sheet 214 is disposed between the normal mode light guide plate 213 and the privacy mode light guide plate 216. The optical sheets may be stacked in plural to improve the properties of light. The optical sheet includes a diffusion sheet for diffusing light, a light-converging sheet for condensing light, and a polarizing sheet for polarizing light.

Conventionally, optical guides are provided on all light guide plates to control the direction of light emission, and the brightness of light can be controlled through polarized light. However, in the backlight unit of the present invention, the optical sheet 214 is disposed only on the upper portion of the normal mode light guide plate 213 and the privacy mode light guide plate 216. That is, the optical sheet is not disposed on the privacy mode light guide plate 216. This is because the lens sheet 218 disposed on the privacy mode light guide plate 216 performs all the functions of adjusting the light. Thus, the optical sheet disposed on the privacy mode light guide plate 216 can be omitted, thereby reducing the thickness of the backlight unit and reducing the manufacturing cost.

The privacy mode backlight 215 is disposed on the side surface of the privacy mode light guide plate 216. The privacy mode backlight 215 emits the narrow viewing angle light (LP). The narrow viewing angle light LP is not the light that is set in advance but is the light used to display an image in the normal mode having a narrow viewing angle incident on the display panel 110 via the privacy mode light guide plate 216. [ The privacy mode backlight 215 is implemented by a light emitting diode array (LED array). However, the privacy mode backlight 215 is not limited thereto and may be realized as any kind of light source.

The privacy mode light guide plate 216 is disposed on the upper portion of the normal mode light guide plate 213. The privacy mode light guide plate 216 guides the narrow viewing angle light LP incident on the privacy mode backlight 215 toward the display panel 110. When the backlight guided by the privacy mode backlight 215 reaches the display panel 110, the display panel 110 displays an image in the privacy mode. That is, the privacy mode light guide plate 216 guides the narrow viewing angle light LP to display the image having the narrow viewing angle to the display panel 110. [ An image having a narrow viewing angle means an image displayed on the image display panel 110 corresponding to the privacy mode.

The prism pattern 217 is disposed on the lower surface of the privacy mode light guide plate 216. The prism pattern 217 condenses the narrow viewing angle light LP and emits it toward the lens sheet 218.

The presence of the prism pattern 217 allows the privacy mode light guide plate 216 to emit the narrow viewing angle light LP. If there is no prism pattern 217, the light emitted from the privacy mode backlight 215 will also scatter in all directions the same as the wide viewing angle light LN. Therefore, the prism pattern 217 is an essential element in implementing the privacy mode by controlling the backlight on the backlight unit 210 without adding any additional components on the display panel 110. [

The lens sheet 218 is disposed on the privacy mode light guide plate 216. The lens sheet 218 transmits the incident narrow viewing angle light LP and supplies the light to the display panel 110. The lens sheet 218 transmits the narrow viewing angle light LP so that the narrow viewing angle light LP is incident on the lower surface of the display panel 110 at right angles. The lens sheet 218 can be formed of any material when the light transmittance is high and the refractive index and the air are different. The shape of the unit lens constituting the lens sheet 218 may be any shape that can serve as a convex lens, such as a circle, an ellipse, or a lenticular shape.

The presence of the lens sheet 218 allows the narrow viewing angle light LP emitted from the privacy mode light guide plate 216 to be incident perpendicularly to the lower surface of the display panel 110. [ The light vertically incident on the lower surface of the display panel 110 is emitted vertically and does not proceed in the lateral direction of the display panel 110. [ In this case, it is possible to realize a complete privacy mode in which the image is not visually recognized in the lateral direction. Thus, the lens sheet 218 is a component that allows the backlight to be controlled on the backlight unit 210 to implement a complete privacy mode without adding any additional components on the display panel 110. [

4 is a cross-sectional view of one of the prism patterns 217 according to an example of the present invention.

The angle of the vertex disposed at the upper end of the prism pattern 217 is 60 degrees or more and 65 degrees or less based on the reference line perpendicular to the base of the prism pattern 217. [ As a result of observation through the experiment, when the angle of the upper apex of the prism pattern 217 is 60 degrees or less with respect to the reference line perpendicular to the base of the prism pattern 217, sufficient condensing effect does not occur and the light spreads to the side , A complete privacy mode can not be implemented. Therefore, the angle of the vertex disposed at the upper end should be at least 60 degrees with respect to the reference line perpendicular to the base of the prism pattern 217, so that a complete privacy mode can be realized.

However, as the angle of the vertex disposed at the upper side with respect to the reference line perpendicular to the base of the prism pattern 217 is larger, the area of the lower surface per prism pattern 217 increases. In particular, when the angle of the vertex disposed at the upper end of the prism pattern 217 is 65 degrees or more with reference to the reference line perpendicular to the base of the prism pattern 217, the area of the lower surface increases sharply. When the area of the bottom surface of each prism pattern 217 increases, the number of prism patterns that can be disposed per unit area is reduced, so that the backlight is not uniformly radiated to the display panel 110, , The prism pattern 217 itself may be visually recognized.

In this respect, when the angle of the vertex disposed at the top of the prism pattern 217 is 60 degrees or more and 65 degrees or less with reference to the reference line perpendicular to the base of the prism pattern 217, the prism pattern 217 It is possible to prevent the size of the area of the lower surface from increasing.

5 is a cross-sectional view showing a unit lens of a lens sheet 218 according to an example of the present invention and a prism pattern 217 in which five unit lenses are arranged adjacent to each other.

Five prism patterns 217 according to an exemplary embodiment of the present invention are disposed adjacent to each other. However, the present invention is not limited to this, and it is also possible that the number of the prism patterns 217 is larger or smaller than the number of the prism patterns 217 adjacent to each other depending on the size of the display panel 110.

In order for the prism pattern 217 to efficiently perform the light converging function, a certain number of the prism patterns 217 must be disposed adjacent to each other. As a result of the experiment, when the display panel 110 of the size that is applied to most models is arranged in a structure in which five prism patterns 217 are arranged in a row adjacent to each other, I could. However, in some models, there may be cases where the prism patterns 217 are arranged to be arranged in a line and arranged in a row or in a group of four or six.

The focal length of the lens sheet 218 is important for emitting the narrow viewing angle light LP incident on the lower surface of the lens sheet 218 in a direction perpendicular to the display panel 110. Particularly, in the structure in which the prism patterns 217 are arranged adjacent to each other in a row, the focal length of the lens sheet 218 is set such that the focal length of the lens sheet 218 in the prism pattern 217 disposed at both ends of the five prism patterns 217, To the display panel 110 in a direction perpendicular to the display panel 110.

In this setting, the light reflected by the prism patterns 217 disposed at both ends in the direction of the lens sheet 218 is emitted in a direction perpendicular to the display panel 110, due to the nature of the focal length of the lens in the optical system do. Also, the light reflected by the prism pattern 217 disposed at the center except for both ends in the direction of the lens sheet 218 is emitted in a direction perpendicular to the display panel 110 at a maximum ratio with respect to other design structures. Accordingly, light can be emitted in a direction perpendicular to the display panel 110 at a maximum ratio, and a more complete privacy mode can be realized.

6 is a flowchart illustrating a method of driving the backlight unit 210 according to an exemplary embodiment of the present invention.

First, the system board 150 supplies a mode signal MODE for setting a privacy mode for providing a wide viewing angle image or a normal mode for providing a wide viewing angle image to the backlight unit control unit 230. (S101 in Fig. 6)

Secondly, the backlight unit control unit 230 generates the backlight unit control signal BCD based on the information of the mode signal MODE. At this time, the backlight unit control unit 230 determines whether the mode signal MODE is a signal for setting the normal mode, and generates a backlight unit control signal BCD corresponding to the mode signal MODE in the normal mode and the privacy mode do. (S102 in Fig. 6)

Thirdly, the backlight unit driving unit 220 receives the backlight unit control signal BCD from the backlight unit control unit 230 and supplies the driving voltage DV to the backlight unit 210.

At this time, when the mode signal MODE is set to the normal mode, the backlight unit control signal BCD is supplied to the backlight unit driver 210 to supply the driving voltage DV to the normal mode backlight 212 included in the backlight unit 210. [ (220). (S103 in Fig. 6)

When the mode signal MODE sets the privacy mode, the backlight unit control signal BCD is supplied to the backlight unit driver (not shown) to supply the driving voltage DV to the privacy mode backlight 215 included in the backlight unit 210 220). (S104 in Fig. 6)

A prism pattern is disposed on a lower portion of the privacy mode light guide plate to condense the narrow viewing angle light and emit the light toward the lens sheet, on the upper portion of the privacy mode light guide plate included in the backlight unit according to an exemplary embodiment of the present invention. Accordingly, the present invention emits both the wide viewing angle light and the narrow viewing angle light in the backlight unit, and the narrow viewing angle light implements the privacy mode in the lens sheet disposed at the top of the backlight unit. Accordingly, the backlight unit according to the present invention can realize the normal mode for providing the wide viewing angle image without reducing the luminance of the display device or the wiring arrangement between the pixels, and the privacy mode for providing the narrow viewing angle image.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

100: display device 110: display panel
120: Data driver 130: Gate driver
140: timing controller 150: system board
210: backlight unit 211: reflector
212: Normal mode backlight 213: Normal mode light guide plate
214: optical sheet 215: privacy mode backlight
216: Privacy mode light guide plate 217: Prism pattern
218: lens sheet 220: backlight unit driving part
230: backlight unit control unit

Claims (9)

Reflector;
A normal mode light guide plate disposed above the reflection plate;
A normal mode backlight disposed on a side surface of the normal mode light guide plate to emit wide viewing angle light;
A privacy mode light guide plate disposed on the upper portion of the normal mode light guide plate;
A privacy mode backlight disposed on a side surface of the privacy mode light guide plate to emit narrow viewing angle light; And
And a lens sheet disposed on an upper portion of the privacy mode light guide plate,
And a prism pattern for condensing the narrow viewing angle light and emitting the narrow viewing angle light toward the lens sheet is disposed on a lower surface of the privacy mode light guide plate. The method according to claim 1,
And an optical sheet disposed between the normal mode light guide plate and the privacy mode light guide plate. The method according to claim 1,
Wherein an angle of a vertex disposed at an upper end of the prism pattern is at least 60 DEG and at most 65 DEG with respect to a reference line perpendicular to a base of the prism pattern. The method according to claim 1,
Wherein the prism patterns are disposed adjacent to each other. 5. The method of claim 4,
Wherein the focal length of the lens sheet is set so as to emit light incident in the direction of the lens sheet in a direction perpendicular to the display panel in a prism pattern disposed at both ends of the five prisms arranged adjacent to each other. A display panel on which pixels for displaying an image are arranged;
A data driver for supplying a data voltage to the pixels;
A gate driver for supplying a gate signal to the pixels;
A timing controller for supplying a data driver control signal to the data driver and supplying a gate driver control signal to the gate driver;
A system board for supplying digital video data to the timing controller;
A backlight unit according to any one of claims 1 to 5 for emitting a backlight to the display panel;
A backlight unit driver for supplying a driving voltage to the backlight unit of any one of claims 1 to 5; And
A mode signal for setting a privacy mode for providing a normal mode or a narrow viewing angle image for providing a wide viewing angle image from the system board and receiving a backlight unit control signal for controlling the backlight unit driving unit based on the information of the mode signal And a backlight unit control unit for generating a backlight unit control signal. The method according to claim 6,
The backlight unit control signal includes:
Wherein when the mode signal sets the normal mode, the driving voltage is supplied to the normal mode backlight included in the backlight unit, and when the mode signal sets the privacy mode, the privacy mode backlight included in the backlight unit And controls the backlight unit driving unit to supply the driving voltage. Supplying a mode signal to a backlight unit control unit to set a privacy mode for providing a normal mode or narrow viewing angle image providing a wide viewing angle image on the system board;
Generating a backlight unit control signal based on information of the mode signal in the backlight unit control unit; And
And supplying a backlight unit control signal from the backlight unit control unit in the backlight unit driving unit to supply the driving voltage to the backlight unit of any one of claims 1 to 5. [ 9. The method of claim 8,
The backlight unit control signal includes:
Wherein when the mode signal sets the normal mode, the driving voltage is supplied to the normal mode backlight included in the backlight unit, and when the mode signal sets the privacy mode, the privacy mode backlight included in the backlight unit And controls the backlight unit driving unit to supply the driving voltage.

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