JP2008250174A - Backlight device, method for controlling backlight and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent unevenness in luminance, when a screen is viewed from an oblique direction. <P>SOLUTION: In a backlight of a liquid crystal display device, a light source control part for controlling the backlight turns on only a center LED chip 174 out of a plurality of divided LED chips 174 so as to emit light at a narrower angle, when necessary backlight luminance BL<SB>i, j</SB>is low backlight luminance and turns on all the LED chips 174 so as to emit light at a wider angle, when the necessary backlight luminance BL<SB>i, j</SB>is high backlight luminance. The present invention can be applied, for example, to a backlight device for the liquid crystal device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a backlight device, a backlight control method, and a liquid crystal display device, and in particular, a backlight device, a backlight control method, and a liquid crystal that can prevent luminance unevenness when viewed from an oblique direction. The present invention relates to a display device.

  A liquid crystal display (LCD) is composed of a color filter substrate colored with red, green and blue, a liquid crystal panel having a liquid crystal layer, etc., and a backlight arranged on the back side thereof. The

  In the liquid crystal display device, the twist of the liquid crystal molecules in the liquid crystal layer is controlled by changing the voltage, and the white light of the backlight transmitted through the liquid crystal layer according to the twist of the liquid crystal molecules is a color filter of red, green, or blue By passing through, the light becomes red, green, or blue light, and an image is displayed.

  In the following, changing the light transmittance by controlling the twist of the liquid crystal molecules by changing the voltage is referred to as controlling the liquid crystal aperture ratio. In addition, the luminance of light emitted from the backlight, which is a light source, and incident on the liquid crystal layer is referred to as “backlight luminance (light emission luminance)”, and the light felt by the viewer viewing the image displayed on the liquid crystal display device. The luminance of light emitted from the front surface of the liquid crystal panel, which is the intensity, is referred to as “display luminance”.

  Conventionally, in a liquid crystal display device, the backlight illuminates the entire screen of the liquid crystal panel with uniform and maximum brightness, and only the liquid crystal aperture ratio of each pixel of the liquid crystal panel is controlled, so that it is necessary for each pixel of the screen. Control was performed to obtain display brightness. Therefore, for example, even when the entire screen is dark, the backlight emits light with the maximum backlight luminance, so that there are problems that the power consumption is large and the contrast ratio is low.

  To solve this problem, for example, it has been proposed to divide the screen into a plurality of areas and control the backlight luminance in units of the divided areas (see, for example, Patent Documents 1 and 2).

  Control of the backlight luminance in units of divided areas is hereinafter referred to as backlight division control.

  1 and 2 are diagrams schematically showing the structure of a conventional backlight 1 that performs backlight division control.

  FIG. 1 is a front view of the backlight 1 when the lighting area of the backlight 1 is viewed from the front, and FIG. 2 is a cross-sectional view of the backlight 1 when the backlight 1 is viewed from above (vertical direction). It is.

The lighting area of the backlight 1 shown in FIG. 1 is, for example, divided into 4 blocks in the horizontal direction (horizontal direction) and 6 blocks in the vertical direction (vertical direction), for a total of 24 blocks A _{i, j} (i = 1). To 6, j = 1 to 4). In the backlight 1, the backlight luminance can be variably controlled for each block A _{i, j} according to the input image signal. The two shaded blocks A _2,3 and A _3,3 will be described later.

  As shown in FIG. 2, the backlight 1 includes a substrate 11 on which electrodes 33 (FIG. 3) and the like are wired, an LED package 12 including an LED (Light Emitting Diode) chip as a light emitting element, It comprises a diffusion plate 13 that diffuses light and a support 14 that supports the diffusion plate 13. The liquid crystal panel 15 of the liquid crystal display device is disposed in front of the diffusion plate 13 of the backlight 1.

In each block A _{i, j} of the backlight 1, a number of the same LED packages 12 are arranged, and the backlight luminance is controlled for each LED package 12 arranged in one block A _{i, j} . The

  FIG. 3 is an enlarged view of one LED package 12 portion of the backlight 12.

  The substrate 11 includes a metal plate 31 as a base, an insulating material 32 formed on the metal plate 31, and an electrode (wiring) 33 formed on the insulating material 32.

  The LED package 12 includes an LED chip 34, a submount substrate 35, a heat conductive adhesive 36, a bonding wire 37, and a sealing resin 38.

  The submount substrate 35 on which the LED chip 34 is mounted is bonded and fixed to the insulating material 32 of the substrate 11 with a heat conductive adhesive 36, and electrode terminals (not shown) on the submount substrate 35 and the substrate 11 are fixed. The electrode 33 is connected by a bonding wire 37. The LED chip 34, the submount substrate 35, the heat conductive adhesive 36, and the bonding wire 37 are sealed with a sealing resin 38.

  Consider a case where the backlight 1 configured as described above emits light corresponding to the original image P1 shown in FIG. The original image P1 in FIG. 4 has an elliptical darkest region R1 in a substantially central portion, and the image gradually becomes brighter from the region R1 toward the outer peripheral side. However, the rate of change in luminance from the dark region R1 to the outer peripheral direction is larger in the upper direction than in the lower direction in the drawing.

The backlight 1 is turned on by suppressing the backlight luminance of the two blocks A _2,3 and A _3,3 shaded in FIG. 1 according to the luminance of the region R1 of the original image P1 (dimming). To do).

  As a result, with respect to the original image P1, as shown in FIG. 5, it is possible to obtain a luminance distribution in which the substantially central portion of the lighting area of the backlight 1 is the darkest and becomes brighter uniformly in the outer peripheral direction. Thus, by dimming a part of the backlight 1, it is possible to reduce power consumption and expand the dynamic range of display luminance.

  Since the number of divisions of the lighting area is usually smaller than the number of pixels of the liquid crystal panel, the luminance distribution of the original image P1 in FIG. 4 does not match the backlight luminance distribution in FIG. Like the pixels on the QQ 'line, there are many pixels with different backlight luminance even if the luminance of the original image P1 is constant. With respect to the pixels on the QQ ′ line, in the backlight division control, the liquid crystal aperture ratio is set to be larger than that in the case where the backlight division control is not performed, so that more light is transmitted. In this way, by changing the liquid crystal aperture ratio from the setting when the backlight division control is not performed, the amount of light that is apparently emitted by the liquid crystal aperture ratio control, which compensates for the suppression of the backlight luminance, is corrected to the liquid crystal correction luminance. That's it.

  FIG. 6 is a conceptual diagram showing the relationship between backlight luminance and liquid crystal correction luminance in backlight division control.

The backlight control unit of the backlight division control is configured such that the liquid crystal correction luminance distribution M _CL is opposite to the backlight luminance distribution M _BL in order to achieve the same display luminance T ₀ in a predetermined region. In addition, the liquid crystal aperture ratio is controlled. At this time, how much the liquid crystal aperture ratio is set and how much the liquid crystal correction luminance is set is determined by the transmittance characteristic of the liquid crystal shown in FIG.

  Normally, the transmittance characteristic of the liquid crystal is based on the time when the screen of the liquid crystal display device is viewed from the front. Therefore, the transmittance characteristic shown in FIG. 7 is also when the screen is viewed from the front (hereinafter referred to as 0 degree). (Also referred to as direction), which is a property that has been evaluated and determined in advance.

JP 2004-221503 A JP 2004-246117 A

  By the way, since the user does not always see the image displayed on the screen of the liquid crystal display device from the front, when viewing from an oblique direction, the liquid crystal has a viewing angle characteristic. The transmittance characteristics of the liquid crystal vary depending on the angle when viewing the screen (viewing angle). FIG. 8 is a diagram in which the transmittance characteristic when the screen is moved from the front of the liquid crystal display device in the horizontal direction and the screen is viewed from the 45 degree direction is superimposed on the transmittance characteristic in the 0 degree direction shown in FIG. .

  The horizontal axis in FIG. 8 represents a set gradation which is an 8-bit set value for setting the transmittance of the liquid crystal, and the vertical axis represents the brightness of each set gradation at a predetermined backlight brightness. Further, FIG. 9 divides the luminance when viewed from the 45 degree direction by the luminance when viewed from the 0 degree direction for comparing the luminance in the 0 degree direction and the 45 degree direction of FIG. The luminance ratio between 0 degree and 45 degrees obtained in this way is shown.

  As can be seen with reference to FIG. 8 and FIG. 9, in the set gradation lower than the α point, the luminance (transmittance) is higher when viewed from 45 degrees than 0 degrees, and the luminance every time one gradation is changed. The rate of change of the ratio is also large. On the other hand, at the set gradation higher than the α point, the luminance is higher when viewed from 0 degree than 45 degrees, and the change rate of the luminance ratio for every change of one gradation is smaller than that at the low gradation side. . Note that the transmittance characteristics of the liquid crystal are different depending on the liquid crystal mode such as VA (Vertical Alignment) and IPS (In-Plane-Switching), so the characteristics shown in FIGS. 8 and 9 are not all.

The relationship between the backlight luminance and the liquid crystal correction luminance shown in FIG. 6 is normally calculated based on the transmittance characteristics of the liquid crystal when the screen is viewed from the 0 degree direction. Therefore, when the liquid crystal correction luminance distribution M _CL ′ when viewed from the 45 degree direction is obtained based on the transmittance characteristic of the liquid crystal in the 45 degree direction indicated by the dotted line in FIG. 8, it is as shown in FIG. .

In FIG. 10, the pixel with the minimum liquid crystal correction luminance (the pixel with the maximum backlight luminance) corresponds to the α point where there is no luminance difference when viewed from either 0 ° or 45 ° in FIGS. The pixel x _α is a backlight luminance at that time, BL _α , and the liquid crystal correction luminance is LC _α . Further, it is assumed that the set gradation of pixels other than the pixel x _α is set to a value larger than the set gradation of the α point.

In this case, the pixels other than the pixel x _alpha, 45 ° crystal corrected luminance distribution M _CL of 'is lower than the liquid crystal correction luminance distribution M _CL of 0 degrees. As a result, the display luminance when viewed from the direction of 45 degrees is the difference between the liquid crystal correction luminance distribution M _CL and the liquid crystal correction luminance distribution M _CL ′ in the pixels other than the pixel x _α as indicated by the thick dotted line. Only different from the target display brightness T ₀ .

That is, when the user views the screen from the direction of 45 degrees despite the control to have the same display luminance T ₀ , the luminance distribution M _{BL of the} backlight luminance in the pixels other than the pixel x _α. difference in display luminance is generated in response to, when the ratio [Delta] T / T ₀ of the display luminance T ₀ to the maximum value [Delta] T of the difference is large, becomes visible as luminance unevenness.

As one of the measures for reducing this luminance unevenness, it is conceivable to reduce the luminance ratio of the backlight luminance of adjacent blocks so that the distribution shape of the backlight luminance distribution _MBL changes gradually. .

  However, if it does so, it will be close to the state where the backlight division control is not performed, so that the merit of the backlight division control such as expansion of the dynamic range of display luminance and reduction of power consumption is reduced.

  The present invention has been made in view of such a situation, and is intended to prevent uneven brightness when viewed from an oblique direction, which occurs during backlight division control.

  The backlight device according to the first aspect of the present invention is a backlight device in which a lighting region is divided into a plurality of blocks, and the emission luminance can be individually changed in each of the divided blocks. And a light emission control means for controlling the light emission, wherein the light emission means comprises a predetermined number of light emitting elements arranged in a predetermined arrangement, the light emission control means depending on the required light emission luminance. The number of the light emitting elements to emit light is changed.

  When the required light emission luminance is low, the light emission control unit can emit light only from the light emitting element arranged on the center side.

  The light emission control means can emit light in order from the light emitting element disposed on the center side as the required light emission luminance increases.

  In the backlight control method according to the first aspect of the present invention, the lighting area is divided into a plurality of blocks, a plurality of light emitting means provided in each of the divided blocks, and a light emission control means for controlling the light emission. In the backlight control method of a backlight device comprising a predetermined number of light emitting elements arranged in a predetermined arrangement, the number of the light emitting elements that emit light is changed according to the required light emission luminance. Including a step.

  The liquid crystal display device according to the second aspect of the present invention is a liquid crystal display device in which the lighting region is divided into a plurality of blocks, and the light emission luminance can be individually changed in each of the divided blocks. And a light emission control means for controlling the light emission, wherein the light emission means comprises a predetermined number of light emitting elements arranged in a predetermined arrangement, and the light emission control means emits light according to the light emission luminance. The number of light emitting elements is changed.

  In the first and second aspects of the present invention, the number of light emitting elements to emit light is changed according to the light emission luminance.

  According to the first and second aspects of the present invention, the power consumption can be reduced and the dynamic range of display luminance can be expanded.

  In addition, according to the first and second aspects of the present invention, luminance unevenness when viewed from an oblique direction can be prevented.

  Embodiments of the present invention will be described below. Correspondences between the constituent elements of the present invention and the embodiments described in the specification or the drawings are exemplified as follows. This description is intended to confirm that the embodiments supporting the present invention are described in the specification or the drawings. Therefore, even if there is an embodiment which is described in the specification or the drawings but is not described here as an embodiment corresponding to the constituent elements of the present invention, that is not the case. It does not mean that the form does not correspond to the constituent requirements. Conversely, even if an embodiment is described here as corresponding to a configuration requirement, that means that the embodiment does not correspond to a configuration requirement other than the configuration requirement. It's not something to do.

  In the backlight device according to the first aspect of the present invention, the lighting region is divided into a plurality of blocks, and the light emission luminance can be individually changed in each of the divided blocks (for example, in FIG. 11). The liquid crystal display device 101) includes a plurality of light emitting means (for example, the LED package 152 in FIG. 12) and light emission control means (for example, the light source control unit 132 in FIG. 11) for controlling the light emission. And a predetermined number of light emitting elements (for example, LED chip array 174 in FIG. 14) arranged in a predetermined array, and the light emission control means is configured to emit light according to the required light emission luminance. Change the number.

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

  FIG. 11 shows a configuration example of an embodiment of a liquid crystal display device to which the present invention is applied.

  A liquid crystal display device 101 of FIG. 11 includes a color filter substrate colored red, green, and blue, a liquid crystal panel 111 having a liquid crystal layer, a backlight 112 disposed on the back side of the liquid crystal panel 111, and The control unit 113 controls the liquid crystal panel 111 and the backlight 112.

  The liquid crystal display device 101 displays an original image corresponding to the input image signal in a predetermined display area (display unit 121). The image signal input to the liquid crystal display device 101 corresponds to, for example, an image with a frame rate of 60 Hz (hereinafter referred to as a frame image).

  The liquid crystal panel 111 includes a display unit 121 in which a plurality of openings for transmitting light from the backlight 112 are arranged, and a transistor (TFT: Thin Film Transistor) (not shown) provided in each of the openings of the display unit 121. The source driver 122 and the gate driver 123 are configured to send drive signals.

  The light that has passed through the opening is converted into red, green, or blue light by a red, green, or blue color filter that is formed on a color filter substrate (not shown). A set of three openings that emit red, green, and blue light corresponds to one pixel of the display unit 121, and each opening that emits red, green, or blue light has sub-pixels constituting the pixel. It becomes.

The backlight 112 emits white light in a lighting area corresponding to the display unit 121. Here, the lighting area of the backlight 112 is divided into 24 blocks A _{i, j} (i = 1 to 6, j = 1 to 4), similarly to the backlight 1 described with reference to FIG. The lighting is controlled individually for each of the divided blocks A _{i, j} .

  The control unit 113 includes a display luminance calculation unit 131, a light source control unit 132, and a liquid crystal panel control unit 133.

The display luminance calculation unit 131 is supplied with an image signal corresponding to the frame image from another device. The display luminance calculation unit 31 obtains the luminance distribution of the frame image from the supplied image signal, and further calculates the display luminance PN _{i, j} necessary for the block A _{i, j} from the luminance distribution of the frame image. The calculated display brightness PN _{i, j} is supplied to the light source control unit 132 and the liquid crystal panel control unit 133.

The light source control unit 132 calculates the backlight luminance BL _{i, j} of each block A _{i, j} based on the display luminance PN _{i, j} of each block A _{i, j} supplied from the display luminance calculation unit 131. The light source controller 132 variably controls each block A _{i, j} of the backlight 112 so that the calculated backlight luminance BL _{i, j} is obtained. The backlight 112 and the light source control unit 132 constitute a backlight device.

The backlight luminance BL _{i, j} of each block A _{i, j} calculated by the light source control unit 132 is supplied to the liquid crystal panel control unit 133.

The liquid crystal panel control unit 133 displays the display luminance PN _{i, j} for each block A _{i, j} supplied from the display luminance calculation unit 131 and the backlight luminance BL for each block A _{i, j} supplied from the light source control unit 132. Based on _{i, j} , the liquid crystal aperture ratio of each pixel of the display unit 121 is calculated. Then, the liquid crystal panel control unit 133 supplies drive signals to the source driver 122 and the gate driver 123 of the liquid crystal panel 111 so as to obtain the calculated liquid crystal aperture ratio, and drives and controls the TFTs of each pixel of the display unit 121. .

  In the present embodiment, it is assumed that liquid crystal panel 111 is in a normally black mode. That is, it is assumed that the transmittance is 100% when the voltage is applied to the TFT of each pixel at the maximum, and the transmittance is 0% when no voltage is applied.

  FIG. 12 shows a cross-sectional view of the liquid crystal display device 101 corresponding to FIG. 2 when viewed from above.

  The cross-sectional configuration when the liquid crystal display device 101 is viewed from above (vertical direction) will be described with reference to FIG. 2 except that the detailed configuration of the LED package 152 (described later in FIGS. 13 and 14) is different. The conventional liquid crystal display device has the same configuration.

  That is, the backlight 112 includes a substrate 151, a large number of LED packages 152 disposed on the substrate 151, a diffusion plate 13 that diffuses light from the LED package 152, and a support body 14 that supports the diffusion plate 13. The A liquid crystal panel 111 is disposed in front of the backlight 112.

In the block A _{i, j} , a large number of LED packages 152 are arranged in a predetermined order. Each of the LED packages 152 emits red, green, or blue light. By mixing the red, green, and blue light, white light is emitted from the entire block A _{i, j} .

  FIG. 13 shows an enlarged view of one LED package 152 portion of the backlight 112.

  13A is a side view of the LED package 152 as viewed from the side (surface direction parallel to the plane of the substrate 151), and FIG. 13B is a top view of the LED package 152 as viewed from above.

  The substrate 151 includes a metal plate 171 as a base, an insulating material 172 formed on the metal plate 171, and an electrode (wiring) 173 formed on the insulating material 172.

  The LED package 152 includes an LED chip array 174 and a sealing resin 175. The sealing resin 175 is formed in a predetermined semicircular shape in consideration of scattering of light emitted from the LED chip array 174. The submount substrate, the heat conductive adhesive, the bonding wire, and the like are also provided in the same manner as in FIG. 3, but are not illustrated because they are not particularly different.

  As will be described later with reference to FIG. 14, the LED chip array 174 is divided into a plurality of LED chips, and the backlight luminance is controlled individually for each LED chip or for each LED chip. Therefore, two electrodes are sufficient for the LED chip 34 of FIG. 3, whereas the LED chip array 174 requires more electrodes. Therefore, the substrate 151 has the insulating material 172 and the electrodes. 173 has a two-layer structure as shown in FIG. 13A.

  FIG. 14 shows a top view of the LED chip array 174.

  As shown in FIG. 14, the LED chip array 174 includes LED chips 174-1 to 174-9 arranged in a 3 × 3 manner, and the LED chip 174-that emits light according to the required backlight luminance. 1 to 174-9 is appropriately selected. It is assumed that the total light emitting area of the LED chip array 174 composed of the LED chips 174-1 to 174-9 is the same as that of the LED chip 34 in FIG.

  The light emission control of the LED chips 174-1 to 174-9 according to the required backlight luminance will be described in detail with reference to FIGS. 15 to 17 show a side view and a top view of an LED package 152 similar to FIG. However, in the top view, the electrode 173 and the LED chip array 174 that are originally hidden by the sealing resin 175 are also illustrated.

For example, if the backlight luminance is roughly divided into three levels of low backlight luminance, medium backlight luminance, and high backlight luminance, a light source control unit is used when the block A _{i, j} emits light with low backlight luminance. As shown in FIG. 15, 132 turns on only the central LED chip 174-5 with hatching among the LED chips 174-1 to 174-9.

On the other hand, when the block A _{i, j} is caused to emit light with medium backlight luminance, the light source control unit 132, as shown in FIG. Chips 174-2, 174-4 to 174-6, and 174-8 are turned on.

In addition, when the block A _{i, j} is caused to emit light with high backlight luminance, the light source control unit 132 turns on all the LED chips 174-1 to 174-9 hatched as shown in FIG.

  Accordingly, the drive units of the LED chips 174-1 to 174-9 are the center LED chip 174-5, the cross-line LED chips 174-2, 174-4, 174-6 and 174-8 except for the center, and 4 LED chips 174-1, 174-3, 174-7, and 174-9. Connection lines for supplying drive current to the LED chips 174-1 to 174-9 may be wired in units of these LED chips, or may be wired independently for each of the LED chips 174-1 to 174-9. Drive control may be performed in conjunction with each LED chip group.

  Based on the semicircular shape of the sealing resin 175 and the positional relationship of the LED chips 174-1 to 174-9 with respect to the semicircular shape, the central LED chip 174-5 (hereinafter referred to as the central LED chip 174 as appropriate) was caused to emit light. In the case of emitting light from one of the peripheral LED chips 174-1 to 174-4 and 174-6 to 174-9 (hereinafter appropriately referred to as the peripheral LED chip 174), the light emission direction is different. .

  That is, when the central LED chip 174 emits light, light is emitted mainly in the forward direction as shown in FIG. 18A, and when the peripheral LED chip 174 emits light, as shown in FIG. 18B. In addition, light is emitted at a wider angle than when the central LED chip 174 emits light.

  FIG. 18C shows a light emission intensity angle distribution 180 when the central LED chip 174 emits light and a light emission intensity angle distribution 181 when the peripheral LED chip 174 emits light, and the central LED chip indicated by a solid line The light emission intensity angle distribution 180 when 174 is emitted is distributed farther in the front direction (z direction) of the backlight 112 than when the peripheral LED chip 174 indicated by the dotted line is caused to emit light. On the other hand, with respect to the planar direction (x direction and y direction) of the backlight 112, the case where the peripheral LED chip 174 emits light is distributed at a wider angle than the case where the central LED chip 174 emits light.

  The backlight luminance ratio of 0 degrees and 45 degrees shown in FIG. 9 indicates that the light component in the oblique direction increases at a low gradation of about 0 to 50, that is, when the backlight luminance is set low. It was.

  Therefore, if light is emitted at a narrow angle at low backlight luminance, the oblique light component is reduced, so the luminance ratio at the low gradation in FIG. 9 is reduced, and backlight division control is performed. Therefore, it is possible to suppress the luminance unevenness generated in the above.

In the backlight 112, as described with reference to FIGS. 15 to 17, when the block A _{i, j} emits light with low backlight luminance, the LED at the center of each LED package 152 in the block A _{i, j} is used. Since only the chip 174-5 is turned on, the light radiates at a narrow angle (narrow angle), and when the block A _{i, j} emits light with high backlight luminance, each LED package in the block A _{i, j} Since all the LED chips 174-1 to 174-9 of 152 are turned on, the light is emitted at a wider angle. Therefore, it is possible to suppress uneven brightness that occurs in the backlight division control.

  Next, display control processing of the liquid crystal display device 101 will be described with reference to the flowchart of FIG.

  First, in step S11, the display luminance calculation unit 131 receives an image signal supplied from another device. This image signal corresponds to one frame image.

In step S12, the display luminance calculation unit 131 obtains the luminance distribution of the frame image. In step S12, the display luminance calculating unit 131 calculates the display luminance PN _{i, j} necessary for the block A _{i, j} from the luminance distribution of the frame image. The calculated display brightness PN _{i, j} is supplied to the light source control unit 132 and the liquid crystal panel control unit 133.

In step S13, the light source control unit 132 calculates the backlight luminance BL _{i, j} from the display luminance PN _{i, j} .

In step S14, the liquid crystal panel control unit 133 determines the liquid crystal aperture ratio for each pixel of the block A _{i, j} based on the display luminance PN _{i, j} and the backlight luminance BL _{i, j} .

In step S15, the light source control unit 132 causes the LED chip to emit light from the LED chips 174-1 to 174-9 of each LED chip array 174 of the block A _{i, j} according to the backlight luminance BL _{i, j.} To decide. The LED chips 174-1 to 174-9 determined here are hereinafter referred to as LED chips 174 D.

In step S _< b> 16, the light source control unit 132 controls driving of the LED chip 174 </ b> D that emits light in each LED chip array 174 of the block A _{i, j} . More specifically, the light source control unit 132 determines the pulse width of the pulse signal supplied to the LED chip 174D that emits light based on the number of LED chips 174D and the backlight luminance BL _{i, j} determined in step S15. To do. A predetermined current is supplied to the LED chip 174D by supplying a pulse signal having a determined pulse width to a switching element (not shown) such as an FET (Field Effect Transistor) connected to the LED chip 174D. The

In step S17, the liquid crystal panel control unit 133 supplies drive control signals to the source driver 122 and the gate driver 123 of the liquid crystal panel 111, and the TFTs of the pixels of the blocks A _{i, j} so that the determined liquid crystal aperture ratio is obtained. Is controlled.

  In step S <b> 18, the display luminance calculation unit 131 determines whether an image signal is no longer supplied. If it is determined in step S18 that an image signal has been supplied, the process returns to step S11, and the processes of steps S11 to S18 are executed. Thereby, the liquid crystal display device 1 displays the next frame image.

  On the other hand, if it is determined in step S18 that the image signal is no longer supplied, the process ends.

As described above, in the backlight 112 of the liquid crystal display device 101, when the required backlight luminance BL _{i, j} is low backlight luminance, the central LED chip 174 is radiated so as to emit light at a narrower angle. Only −5 is turned on, and when the required backlight brightness BL _{i, j} is high backlight brightness, all the LED chips 174-1 to 174-9 are turned on so that light is emitted at a wider angle. Therefore, it is possible to suppress luminance unevenness that occurs in the backlight division control.

Further, in the backlight 112 of the liquid crystal display device 101, PWM control corresponding to the required backlight luminance BL _{i, j} is performed for each of the LED chips 174D that emit light, so that the maximum luminance ratio of the backlight 112 is increased. There is also an effect of contributing to the increase.

  For example, assuming that the backlight brightness can be changed by setting a pulse width between 5% and 100% in each of the LED chip 34 and the LED chips 174-1 to 174-9 in FIG. The maximum luminance ratio of the LED chip 34 is 5: 100 = 1: 20.

  On the other hand, in the backlight 112, as described with reference to FIGS. 15 to 17, the LED chip 174D that emits light is only the central LED chip 174-5, and the LED chips 174-2, 174 in the cross line. -4 to 174-6, and 174-8, and all LED chips 174-1 to 174-9, and the minimum backlight brightness is 5% only for the central LED chip 174-5. Since the light emission is performed with the pulse width set, the maximum luminance ratio of the backlight 112 is 5% × 1/9: 100 = 1: 180, which is nine times that in the case of FIG.

  Next, another embodiment of the backlight 112 will be described with reference to FIGS.

  In the embodiment shown in FIG. 20, the LED chip array 174 is connected to the substrate 151 as in FIG. 13, but there is no sealing resin 175 covering the LED chip array 174, and the LED chip array 174 is shown in the upper part of the drawing. In the (light emission direction), a convex lens (plano-convex lens) 201 having a semicircular shape and a convex surface directed toward the LED chip array 174 is fixed to the lens holder 202. The lens 201 may be formed of a glass material or a sealing resin 175.

In the configuration including the bare LED chip array 174 and the lens 201, the LED chip 174D that emits light has the required backlight luminance BL _{i, j} as described with reference to FIGS. Even when it is changed accordingly, the light emission intensity angle distribution of FIG. 18 can be obtained, so that luminance unevenness caused by backlight division control can be suppressed.

  In the embodiment shown in FIG. 21, the LED packages 211 and the LED packages 212 are alternately arranged on the substrate 151, and the LED packages 211 and the LED packages 212 are molded on the LED chip array 174. The shape of the sealing resin is different. Specifically, the sealing resin 221 of the LED package 211 has a small curvature (small protrusion), and the sealing resin 222 of the LED package 212 has a large curvature (large protrusion).

  In the backlight 112 of FIG. 21, when light is emitted with a low backlight luminance, the light source control unit 132 lights the LED package 211 formed with a small curvature because it is desired to emit light at a narrow angle. The LED package 212 is not lit. On the other hand, when the light source controller 132 emits light with high backlight luminance, the light source control unit 132 turns on only the LED package 212 molded to have a large curvature, or the LED package 211 with a small curvature and the LED package with a large curvature. Both 212 are turned on.

  As a result, when the backlight brightness is low, the oblique light components are reduced, so that uneven brightness caused by backlight division control can be suppressed.

  The viewing angle characteristics of liquid crystal display devices vary depending on the characteristics of liquid crystal modes such as VA (Vertical Alignment) and IPS (In-Plane-Switching), and retardation films. The position and number of chips can be optimally determined as necessary. Therefore, the number of divisions of the LED chip array and the positions and the number of LED chips to be lit are merely examples, and are not limited to this example.

  In the above-described example, light is emitted at a narrow angle when emitting light with low backlight luminance, and light is emitted at a wide angle when emitting light with high backlight luminance, but conversely with low backlight luminance. It is also possible to set so that light is emitted at a wide angle when light is emitted and light is emitted at a narrow angle when light is emitted with high backlight luminance. In the example shown in FIG. 21, when light is emitted with low backlight luminance, only the LED package 212 having a large curvature is turned on, or both the LED package 211 having a small curvature and the LED package 212 having a large curvature are turned on. In order to emit light with high backlight luminance, only the LED package 211 having a small curvature needs to be lit.

  Furthermore, although the light source control unit 132 has been described as performing PWM control in the above-described example, it goes without saying that the present invention can also be applied to performing PAM control.

  In this specification, the steps described in the flowcharts include processes that are executed in parallel or individually even if they are not necessarily processed in time series, as well as processes that are executed in time series in the described order. Is also included.

  The embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

It is a front view of the conventional backlight. It is sectional drawing of the conventional backlight. It is a figure which shows the LED light emission part of the conventional backlight. It is a figure which shows the example of the original image displayed on a liquid crystal display device. It is a figure explaining light emission of the backlight corresponding to the original image of FIG. It is a conceptual diagram which shows the relationship between the backlight brightness | luminance and liquid crystal correction brightness | luminance in backlight division | segmentation control. It is a figure which shows the transmittance | permeability characteristic of the liquid crystal of a 0 degree direction. It is a figure which shows the transmittance | permeability characteristic of the liquid crystal of a 0 degree direction and a 45 degree direction. It is a figure which shows the luminance ratio of a 0 degree direction and a 45 degree direction. It is a figure explaining the brightness nonuniformity by the diagonal view at the time of backlight division control. It is a block diagram which shows the structural example of one Embodiment of the liquid crystal display device to which this invention is applied. It is sectional drawing of the liquid crystal display device of FIG. It is a figure which shows the enlarged view of a LED package part. It is a figure which shows an LED chip array. It is a figure which shows light emission of the LED chip at the time of low backlight brightness | luminance. It is a figure which shows light emission of the LED chip at the time of medium backlight brightness | luminance. It is a figure which shows light emission of the LED chip at the time of high backlight brightness | luminance. It is a figure explaining the light emission intensity angle distribution of a LED chip array. It is a flowchart explaining a display control process. It is a figure explaining other embodiment of a backlight. It is a figure explaining further another embodiment of a back light.

Explanation of symbols

  101 liquid crystal display device, 112 backlight, 132 light source control unit, 152 LED package, 174 LED chip array

Claims (5)

In the backlight device in which the lighting area is divided into a plurality of blocks and the emission luminance can be individually changed in each of the divided blocks.
A plurality of light emitting means, and a light emission control means for controlling the light emission,
The light emitting means comprises a predetermined number of light emitting elements arranged in a predetermined array,
The light emission control means is a backlight device that changes the number of the light emitting elements to emit light according to the required light emission luminance. The backlight device according to claim 1, wherein when the required light emission luminance is low, the light emission control unit causes only the light emitting element disposed on the center side to emit light. The backlight device according to claim 1, wherein the light emission control unit emits light in order from the light emitting element arranged on the center side as the required light emission luminance increases. The lighting area is divided into a plurality of blocks, and each of the divided blocks includes a plurality of light emitting means and a light emission control means for controlling the light emission, and the light emitting means are arranged in a predetermined arrangement. In a backlight control method of a backlight device composed of a predetermined number of light emitting elements,
A backlight control method including a step of changing the number of light emitting elements to emit light according to required light emission luminance. In the liquid crystal display device in which the lighting area is divided into a plurality of blocks and the emission luminance can be individually changed in each of the divided blocks.
A plurality of light emitting means, and a light emission control means for controlling the light emission,
The light emitting means comprises a predetermined number of light emitting elements arranged in a predetermined array,
The light emission control means includes: a liquid crystal display device comprising: changing the number of the light emitting elements that emit light according to the required light emission luminance.

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