KR20210020400A - Backlight unit and Liquid Crystal Display using the same - Google Patents

Abstract

The present invention relates to a local dimming backlight unit capable of implementing a narrow bezel by applying to a heterogeneous display device such as a display device for an automobile or the like, and to a heterogeneous liquid crystal display device using the same. The local dimming backlight unit is composed of a plurality of local dimming blocks. K (k is a natural number greater than or equal to 2) number of light sources are disposed in each of the local dimming blocks in a display area, and n (n is a natural number less than k) number of light sources and m (m is a natural number less than k) number of dummy resistors are disposed in the local dimming blocks at the edge of the display area, wherein n + m = k.

Description

Backlight unit and liquid crystal display using the same {Backlight unit and Liquid Crystal Display using the same}

The present invention relates to a backlight unit, and more particularly, to a local dimming backlight unit capable of implementing a narrow bezel by applying to a release display device such as an automobile display device, and a liquid crystal display device using the same.

The liquid crystal display device has a tendency to gradually expand its application range due to features such as light weight, thinness, and low power consumption. Such liquid crystal display devices are widely used as portable computers such as notebook PCs, office automation devices, audio/video devices, indoor and outdoor advertisement display devices, and display devices for automobiles.

Such a liquid crystal display device includes a liquid crystal display panel and a backlight unit.

The backlight unit includes a plurality of light sources to irradiate light to the liquid crystal display panel.

The liquid crystal display panel includes a thin film transistor array substrate on which a thin film transistor array is formed on a glass substrate, a color filter array substrate on which a color filter array is formed on a glass substrate, and between the thin film transistor array substrate and the color filter array substrate. It has a filled liquid crystal layer. In addition, a voltage is applied to the electric field generating electrode to generate an electric field in the liquid crystal layer, and directions of liquid crystal molecules of the liquid crystal layer are determined through this, and polarization of light incident from the backlight unit is controlled to display an image.

The image quality of such a liquid crystal display device depends on the contrast characteristic. However, there is a limit to improving the contrast characteristic only by controlling the data voltage applied to the liquid crystal layer to correct the light transmittance of the liquid crystal layer.

Accordingly, in order to improve the contrast characteristic of the liquid crystal display device, a backlight dimming method for adjusting the brightness of a backlight unit according to an image has been proposed.

The backlight dimming method includes a global dimming method for adjusting the luminance of the entire display surface, and a local dimming method for locally adjusting the luminance of the display surface.

The global dimming method may improve dynamic contrast measured between two consecutive frames. The local dimming method may improve static contrast, which is difficult to improve by the global dimming method, by locally controlling the luminance of the display surface within one frame period.

In the local dimming method, the backlight is divided into a plurality of blocks and the dimming value is adjusted for each block to increase the backlight luminance of a block having a bright image, while lowering the backlight luminance of a block having a dark image.

Since recent automotive display devices require differentiated image quality and differentiated design, various variants such as Circle type, Corner-cut type, and Curved type in the conventional rectangular display device (異形, Free from) There is a demand for a liquid crystal display device.

In such a release type liquid crystal display, image quality can be improved by using a direct type backlight unit and applying a local dimming algorithm to reduce light leakage and improve contrast.

However, in the direct backlight unit, each local dimming block must be formed in a square shape, and each local dimming block must have the same number of light sources disposed. In the case of a release liquid crystal display, the local dimming block of the release part (the border part) Since an unnecessary light source must be disposed, there is a problem in that the size of the printed circuit board of the backlight unit increases and the bezel increases.

In addition, material cost increases due to unnecessary arrangement of light sources.

The present invention is to solve the conventional problems as described above, a backlight capable of reducing the size of a printed circuit board of a backlight unit, suppressing an increase in material cost, and implementing a narrow bezel An object thereof is to provide a unit and a release type liquid crystal display using the same.

The backlight unit according to the present invention to achieve the above object is composed of a plurality of local dimming blocks, k (k is a natural number of 2 or more) number of light sources are arranged in each of the local dimming blocks in the display area, and display Local dimming blocks at the edge of the region have n (n is a natural number less than k) light sources and m (m is a natural number less than k) dummy resistors, and n + m = k.

Here, each of the local dimming blocks in the display area is formed in a square shape, and the local dimming blocks at an edge of the display area are formed to have a curved surface at one side corresponding to the shape of the liquid crystal display.

The local dimming blocks at the edge of the display area are characterized in that the number of light sources disposed in proportion to an area located in the display area varies.

Light sources or light sources and dummy resistors disposed in each of the local dimming blocks are connected in series with each other.

The m dummy resistors are disposed outside the display area.

In addition, the release type liquid crystal display device according to the present invention for achieving the above object is characterized by comprising a backlight unit configured as described above and a liquid crystal display panel positioned above the backlight unit to display an image. There is this.

In the backlight unit and the release liquid crystal display using the same according to the present invention having the above characteristics, there are the following effects.

First, the local dimming blocks at the edge of the display area of the release type liquid crystal display reduce the amount of light sources that are disposed according to the area located inside the display area of the release type liquid crystal display, and instead, the dummy resistor is disposed. This can be prevented from being placed.

Second, it is possible to reduce the size of the printed circuit board (PCB) of the backlight unit and also reduce the bezel.

1 is a configuration diagram of a liquid crystal display according to an exemplary embodiment of the present invention.
2 is an explanatory diagram illustrating a principle for implementing local dimming in a release liquid crystal display device.
3 is an explanatory diagram of the bezel size according to FIG. 2.
4 is a configuration diagram of a backlight unit of a release liquid crystal display according to an exemplary embodiment of the present invention.
5A to 5D illustrate connection states of light sources disposed in each local dimming block of a backlight unit of a release liquid crystal display according to an exemplary embodiment of the present invention.
5A is a diagram illustrating a connection state of four light sources LED1 to LED4 disposed in the local dimming blocks LDB1 formed in a square shape in FIG. 4,
5B shows three light sources LED1 to LD3 and one dummy resistor R1 disposed in the “A” local dimming block among the local dimming blocks LDB2 at the edge of the display area of the release liquid crystal display in FIG. 4. Shows the connection status of
5C illustrates two light sources LED1 to LD2 and two dummy resistors R1 to “B” disposed in the “B” local dimming block among the local dimming blocks LDB2 at the edge of the display area of the release liquid crystal display in FIG. 4. It shows the connection status of R2),
5D illustrates one light source LED1 and three dummy resistors R1 to R3 disposed in the “C” local dimming block among local dimming blocks LDB2 at the edge of the display area of the release liquid crystal display in FIG. 4. It shows the connection status of

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. The present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only the embodiments are intended to complete the disclosure of the present invention, and those of ordinary skill in the art to which the present invention pertains. It is provided to completely inform the scope of the invention, and the invention is only defined by the scope of the claims.

The shape, size, ratio, angle, number, etc. disclosed in the drawings for explaining the embodiments of the present invention are exemplary, and the present invention is not limited to the items shown in the drawings. The same reference numerals refer to substantially the same components throughout the specification. In addition, in describing the present invention, when it is determined that a detailed description of related known technologies may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

When "having", "including", "having", "consisting of" and the like mentioned in the present specification are used, other parts may be added unless'only' is used. When a constituent element is expressed in a singular number, it can be interpreted as a plural unless specifically stated otherwise.

In interpreting the constituent elements, it is interpreted as including an error range even if there is no explicit description.

In the case of a description of the positional relationship, for example, when the positional relationship between the two components is described such as'on the top','on the top of the','the bottom of the', and the'next to the', ' One or more other constituent elements may be interposed between those constituent elements for which direct' or'direct' is not used. When an element or layer is referred to as “on” another element or layer, it includes all cases in which another layer or other element is interposed directly on or in the middle of another element.

The first, second, etc. may be used to classify the components, but these components are not limited in function or structure by an ordinal number or component name in front of the component.

The following embodiments may be partially or entirely combined or combined with each other, and technically various interlocking and driving are possible. Each of the embodiments may be implemented independently of each other or may be implemented together in a related relationship.

Hereinafter, a backlight unit and a release liquid crystal display device using the same according to the present invention will be described in more detail with reference to the accompanying drawings.

1 is a configuration diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a liquid crystal display device according to an embodiment of the present invention includes a liquid crystal display panel 10, a timing controller 11, a data driving circuit 12, a gate driving circuit 13, and a dimming control circuit 14. , A backlight driving circuit 15 and a backlight unit 16 are provided.

The liquid crystal display panel 10 includes two glass substrates and a liquid crystal layer formed therebetween. A plurality of data lines DL and a plurality of gate lines GL cross the lower glass substrate of the liquid crystal display panel 10. Liquid crystal cells Clc are arranged in a matrix form in the liquid crystal display panel 10 due to the cross structure of the data lines DL and the gate lines GL. Each of the liquid crystal cells Clc includes a TFT, a pixel electrode 1 connected to the TFT, a storage capacitor Cst, and the like. A black matrix, a color filter, and a common electrode 2 are formed on the upper glass substrate of the liquid crystal display panel 10. The common electrode 2 is formed on the upper glass substrate in a vertical electric field driving method such as TN (Twisted Nematic) mode and VA (Vertical Alignment) mode, and the IPS (In Plane Switching) mode and FFS (Fringe Field Switching) mode It is formed on the lower glass substrate together with the pixel electrode 1 in the same horizontal electric field driving method.

The liquid crystal cells Clc include R liquid crystal cells for red display, G liquid crystal cells for green display, B liquid crystal cells for blue display, and W liquid crystal cells for white display. R liquid crystal cell, G liquid crystal cell, B liquid crystal cell, and W liquid crystal cell constitute one unit pixel. Here, the W liquid crystal cells may be excluded.

A polarizing plate is attached to each of the upper and lower glass substrates of the liquid crystal display panel 10, and an alignment layer for setting a pretilt angle of the liquid crystal is formed on an inner surface in contact with the liquid crystal.

The timing controller 11 supplies digital image data (RGB) input from a system board on which an external image source is mounted to the dimming control circuit 14, and the correction data R'G calculated by the dimming control circuit 14 'B') is supplied to the data driving circuit 12. In addition, the timing controller 11 is a timing control for controlling the operation timing of the data driving circuit 12 and the gate driving circuit 13 based on timing signals (Vsync, Hsync, DE, DCLK) from the system board. It generates signals (DDC, GDC).

The timing controller 11 inserts an interpolation frame between frames of an input image signal input at a frame frequency of 60 Hz and multiplies the data timing control signal (DDC) and the gate timing control signal (GDC). It is possible to control the operation of the data driving circuit 12 and the gate driving circuit 13 at a frame frequency of 2 or more) Hz.

The data driving circuit 12 includes a plurality of data drive integrated circuits. Each data drive integrated circuit has a shift register for sampling a clock signal, a register for temporarily storing correction data (R'G'B'), and correction data (R'G'B') in response to a clock signal from the shift register. Latch for storing 1 line at a time and outputting data for 1 line at the same time, digital/analog for selecting positive/negative gamma voltage with reference to gamma reference voltage corresponding to the digital data value from the latch A converter, a multiplexer for selecting the data line DL to which the analog data voltage converted by the positive/negative gamma voltage is supplied, and an output buffer connected between the multiplexer and the data line DL are provided. The data driving circuit 12 latches the correction data R'G'B' under the control of the timing controller 11, and applies the latched correction data R'G'B' to a positive/negative gamma compensation voltage. After converting into a positive/negative analog data voltage by using, it is supplied to the data lines DL.

The gate driving circuit 13 includes a plurality of gate drive integrated circuits. Each gate drive integrated circuit includes a shift register, a level shifter for converting an output signal of the shift register into a swing width suitable for driving a TFT of a liquid crystal cell, and an output buffer. The gate driving circuit 13 selects a horizontal line to which a data voltage is to be applied by sequentially outputting scan pulses (or gate pulses) under the control of the timing controller 11 and supplying them to the gate lines GL. The gate driving circuit 13 may be directly formed on the display panel 10 according to a gate driver in panel (GIP) process.

The dimming control circuit 14 analyzes the input image data (RGB) to be written in the liquid crystal display panel 10 to calculate a representative value for each block, and calculates the light sources of the backlight unit 16 in block units according to the representative value for each block. Set the dimming value (DIM) for each block to be controlled with. After calculating a pixel compensation value for compensating for a decrease in luminance due to the dimming value DIM for each block, the input image data RGB is corrected based on the pixel compensation value. The dimming control circuit 14 supplies correction data R'G'B' to the timing controller 11.

The dimming control circuit 14 increases the representative value for each block according to a modified average picture level (MAPL) having different weights for each preset data gray level, thereby combining the dimming value (DIM) for each block. Since it can be set near the target dimming value without this, gradation aggregation can be prevented in advance. That is, the dimming control circuit 14 may preemptively minimize grayscale aggregation when calculating the representative value for each block. Here, in order to increase the representative value for each block, the weight may be set differently within a range of one or more for each data gray level, but may be set higher in proportion to the data gray level. In addition, in order to minimize an increase in power consumption due to one or more weights, the weight in a specific data grayscale interval may be adjusted as low as possible in proportion to the number of pixels belonging to the corresponding data grayscale interval and the upper data grayscale within a predetermined weight range.

The backlight driving circuit 15 uses a Pulse Width Modulation (PWM) signal according to a block-specific dimming value (DIM) input from the dimming control circuit 14 to convert the light sources of the backlight unit 16 in block units. Drive. The PWM duty ratio is proportional to the dimming value (DIM) for each block, and the larger the PWM duty ratio, the longer the lighting time of the light sources.

The backlight unit 16 divides a surface light source irradiated onto the liquid crystal display panel 10 including a plurality of light sources into matrix-shaped blocks. The backlight unit 16 may be implemented as a direct type. The direct type backlight unit 16 has a structure in which a plurality of optical sheets and a diffusion plate are stacked under the liquid crystal display panel 10 and a plurality of light sources are disposed under the diffusion plate. Light sources may be implemented as point light sources such as light emitting diodes (LEDs).

FIG. 2 is an explanatory diagram illustrating a principle for implementing local dimming in a release liquid crystal display device, and FIG. 3 illustrates a bezel size according to FIG. 2.

In FIG. 2, the display area A/A of the release (circular) liquid crystal display device and the printed circuit board (PCB) of the backlight unit are shown.

The printed circuit board (PCB) of the backlight unit is divided into a plurality of local dimming blocks LDB1 and LDB2 in order to implement a local dimming method. At this time, each local dimming block LDB is formed in a square shape. In addition, a plurality of local dimming blocks disposed on a printed circuit board (PCB) of the backlight unit must cover all of the display areas A/A of the modified (circular) liquid crystal display device.

Accordingly, among the plurality of local dimming blocks LDB1 and LDB2, the local dimming blocks LDB2 at the edge of the display area A/A of the deformed (circular) liquid crystal display device are completely deformed (circular). It is not located inside the display area A/A of the liquid crystal display, and a predetermined portion of the local dimming blocks LDB2 is located inside the display area A/A of the deformed (circular) liquid crystal display. , The remaining part is disposed outside the display area A/A of the release (circular) liquid crystal display device.

In addition, the local dimming blocks LDB2 at the edge of the display area A/A of the modified (circular) liquid crystal display device are, depending on their position, in the display area A/ A) The area located inside is different from the area located outside the display area A/A of the modified (circular) liquid crystal display device.

In addition, in order to implement local dimming, the same number of light sources must be arranged at regular intervals in each local dimming block. If the same number of light sources is not disposed in each local dimming block, and a different number of light sources are disposed, a high current is applied to each light source of the local dimming block in which a small number of light sources are disposed, and a relatively large number of light sources is disposed. Since a low current is applied to each light source of the local dimming block in which the light source is disposed, even if the same voltage is applied, a difference in luminance occurs in each local dimming block. Therefore, the same number of light sources must be disposed in each local dimming block.

However, even if the same number of light sources (e.g., four light sources) are disposed in each local dimming block, the local dimming blocks at the edge of the display area A/A of the modified (circular) liquid crystal display device ( LDB2), depending on the location, is an area located inside the display area (A/A) of the modified (circular) liquid crystal display device and an area located outside the display area (A/A) of the modified (circular) liquid crystal display device. Since the areas are different, the local dimming blocks LDB2 at the edge of the display area A/A of the deformed (circular) liquid crystal display device include the number of light sources disposed in the display area A/A and the display area. (A/A) The number of external light sources is different.

In addition, light emitted from a light source disposed outside the display area A/A of the modified (circular) liquid crystal display should be blocked. Therefore, in order to block light emitted from a light source disposed outside the display area (A/A) of the release (circular) liquid crystal display device, as shown in FIG. 3, the bezel size of the release (circular) liquid crystal display device is increased. do.

In the present invention, a light source is not disposed in the non-display area of each local dimming block, but a dummy resistor is disposed instead, thereby preventing unnecessary light sources from being disposed in the local dimming block, and reducing the size of the printed circuit board (PCB) of the backlight unit. Decreases and decreases the bezel.

This will be described in detail as follows.

4 is a configuration diagram of a backlight unit of a release liquid crystal display according to an exemplary embodiment of the present invention.

First, the printed circuit board (PCB) of the backlight unit on which the light source is mounted is formed in a shape corresponding to the behavior of the release type liquid crystal display device, and is formed to be wider than the display area of the release type liquid crystal display device.

And, as described above, the backlight unit (printed circuit board (PCB) is divided into a plurality of local dimming blocks (LDB1, LDB2)). Each local dimming block (LDB1) is basically formed in a rectangular shape, but a release liquid crystal display device The local dimming blocks LDB2 at the edge of the display area of are not formed in a quadrangular shape, but are in the form of a shaped liquid crystal display (Circle type, Corner-cut type, Curved type, etc.). ), one side is formed to have a curved surface.

In addition, the same number of light sources (LEDs) are disposed on each of the local dimming blocks (LDB1) formed in the square shape, and the local dimming blocks (LDB2) at the edge of the display area of the release liquid crystal display are formed in the square shape. A smaller number of light sources (LEDs) than the local dimming block is disposed. Instead, a number of dummy resistors R corresponding to the number of light sources disposed less is disposed.

The local dimming blocks (LDB2) at the edge of the display area (A/A) of the release (circular) liquid crystal display device, depending on the position, are displayed in the display area (A/A) of the release (circular) liquid crystal display device. The areas located inside are different.

Accordingly, the local dimming blocks LDB2 at the edge of the display area A/A of the modified (circular) liquid crystal display are located inside the display area A/A of the modified (circular) liquid crystal display. The number of light sources disposed in proportion to the area is different from each other.

For example, four light sources LED1 to LED4 are disposed in each of the rectangular dimming blocks LDB1.

The local dimming blocks LDB2 at the edge of the display area of the release type liquid crystal display device include one light source LED1 and two light sources LED1 according to the area located inside the display area A/A of the release type liquid crystal display. , LED2) or three light sources (LED1 to LED3) are disposed, and a dummy resistor is disposed instead.

Here, the light source disposed in each of the local dimming blocks is a point light source such as an LED.

The dummy resistor is disposed on a printed circuit board PCB outside the display area A/A of the release liquid crystal display for each local dimming block LDB2.

That is, the local dimming blocks LDB2 at the edge of the display area of the release-type liquid crystal display device are formed when one light source LED1 is disposed inside the display area A/A of the release-type liquid crystal display device. Three dummy resistors R1 to R3 are disposed on the printed circuit board PCB outside the display area A/A.

When two light sources (LED1 to LED2) are disposed inside the display area A/A of the release liquid crystal display, the local dimming blocks LDB2 at the edge of the display area of the release liquid crystal display device Two dummy resistors R1 to R2 are disposed on the printed circuit board PCB outside the display area A/A.

When three light sources (LED1 to LED3) are disposed inside the display area A/A of the release liquid crystal display, the local dimming blocks LDB2 at the edge of the display area of the release liquid crystal display One dummy resistor R1 is disposed on the printed circuit board PCB outside the display area A/A.

The four light sources disposed in the rectangular local dimming blocks LDB1 are connected in series, and the light sources and dummy resistors disposed in the local dimming blocks LDB2 at the edge of the display area of the release liquid crystal display are also Are connected in series.

5A to 5D illustrate connection states of light sources disposed in each local dimming block of a backlight unit of a release liquid crystal display according to an embodiment of the present invention, and FIG. 5A is a local dimming block formed in a square shape in FIG. 4. It shows the connection state of the four light sources (LED1 to LED4) disposed in the field LDB1, and FIG. 5B is “A” among local dimming blocks LDB2 at the edge of the display area of the release liquid crystal display in FIG. 4 It shows the connection state of three light sources (LED1 to LD3) arranged in the local dimming block and one dummy resistor (R1).

5C illustrates two light sources LED1 to LD2 and two dummy resistors R1 to “B” disposed in the “B” local dimming block among the local dimming blocks LDB2 at the edge of the display area of the release liquid crystal display in FIG. 4. It shows the connection state of R2), and FIG. 5D shows one light source LED1 disposed in the “C” local dimming block among local dimming blocks LDB2 at the edge of the display area of the release liquid crystal display in FIG. It shows the connection status of three dummy resistors (R1 to R3).

As shown in FIGS. 5A to 5D, a light source and a dummy resistor disposed in each local dimming block are connected in series with each other, and each of the dummy resistors R1 to R3 has a resistance value corresponding to one light source.

Therefore, when a voltage of 12V is supplied to a local dimming block in which four light sources (LED1 to LED4) are connected in series as shown in FIG. 5A, light corresponding to 3V is emitted to each light source, and as shown in FIGS. 5B to 5D, at least When a voltage of 12V is supplied to a local dimming block in which one light source and at least one resistor are connected in series, 3V of light is emitted to each light source.

4 and 5A to 5D show that four light sources LED1 to LED4 are disposed in each of the local dimming blocks LDB1 formed in the quadrangular shape, but are not limited thereto and at least two may be disposed.

When the same voltage is applied to the light sources of each local dimming block, each light source emits light of the same intensity in proportion to the area occupied by the display area.

Accordingly, the present invention can prevent unnecessary light sources from being disposed on the local dimming block, reduce the size of the printed circuit board (PCB) of the backlight unit, and reduce the bezel.

It will be appreciated by those skilled in the art through the above description that various changes and modifications can be made without departing from the technical idea of the present invention. Therefore, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be determined by the claims.

A/A: Display area PCB: Printed circuit board
LED1~LED4: Light source R1~R4: Dummy resistance

Claims (6)

It is composed of a plurality of local dimming blocks,
Each of the local dimming blocks in the display area has k (k is a natural number of 2 or more) number of light sources,
A backlight unit, characterized in that n (n is a natural number less than k) light sources and m (m is a natural number less than k) dummy resistors are disposed in the local dimming blocks at the edge of the display area, and n + m = k . The method of claim 1,
Each local dimming block in the display area is formed in a square shape,
The backlight unit is formed such that one side of the local dimming blocks at the edge of the display area has a curved surface according to the shape of the liquid crystal display. The method of claim 1
The backlight unit in which the number of light sources disposed in the local dimming blocks at the edge of the display area is varied in proportion to an area located in the display area. The method of claim 1,
Light sources or light sources and dummy resistors disposed in each of the local dimming blocks are connected in series to each other. The method of claim 1,
The m dummy resistors are disposed outside the display area. The backlight unit configured as in any one of claims 1 to 5, and
A liquid crystal display device having a liquid crystal display panel positioned above the backlight unit to display an image.

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