JP4736656B2 - Display device - Google Patents

Description

  The present invention relates to a display device, and more particularly to a display device having a backlight such as a liquid crystal display device.

  When a moving image is displayed on the liquid crystal display device, there is a problem that the moving image is blurred. This is primarily due to the slow response characteristics of the liquid crystal molecules used in the liquid crystal panel. Secondly, the liquid crystal display device also has a major cause of the hold-type driving in which the image for one frame period is continuously displayed. Therefore, a method for improving the above-described fundamental image display image quality (moving image quality) degradation that occurs in a liquid crystal display device has been proposed (see, for example, Non-Patent Document 1).

  That is, the above first problem is improved by improving the characteristics of the liquid crystal molecules and an overdrive circuit that speeds up the rising characteristics of the liquid crystal molecules. On the other hand, the moving image blur due to the hold-type drive, which is the second problem, is caused by the operation principle of the liquid crystal display device itself. As a method for solving this problem, firstly, a method of inserting a black signal into a video signal to a liquid crystal display device, secondly, a method of blinking a backlight, and thirdly, a method of scanning the backlight are proposed. .

Yashiro Kurita, “Principal video quality degradation caused by liquid crystal display and its improvement method”, NHK Broadcasting Technology Laboratory, The Institute of Electronics, Information and Communication Engineers, IEICE Technical Report, TECHNICAL REPORT OF IEICE, EID2000-47 (2000- 09), p. 13-18

  However, among the methods for improving the motion blur by hold-type driving in the conventional liquid crystal display device, the first solution described above is to write the video signal to the liquid crystal and transfer black data to the display device after a certain time within one frame. This is a writing method, and the effect of moving image blur is obtained. However, the backlight is always lit during this time, which is not efficient from the viewpoint of power consumption. In addition, the above second solution for blinking the backlight is not desirable from the viewpoint of image quality because when the backlight blinks, a seam at the time of data switching of a line for writing a video signal is visible.

  On the other hand, the above-mentioned third solution for scanning the backlight is effective in improving the motion blur due to the hold drive. For this purpose, the backlight scanning and data writing timing are controlled well. Must. That is, in the above third solution for scanning the backlight to improve moving image blur, for example, as shown in FIG. 12B, the backlight is arranged in a two-dimensional matrix on the reflection sheet 51. Among the plurality of light sources 50 such as light emitting diodes, the plurality of light sources 50 arranged linearly in the horizontal direction (row direction) of the screen are divided by the crest portions 50a of the reflection sheet 51 and In addition, a diffusion plate 52 and an optical sheet 53 are stacked in the direction of the liquid crystal panel display unit, and a plurality of light sources 50 (one light source column) arranged in one row among the light sources 50 are turned off within one frame period. In addition, the extinguished rows (light source columns) are sequentially moved.

  Accordingly, as shown in FIG. 12B, when only the light source 50 arranged in the fourth row is turned off, light is emitted from the light sources 50 arranged in the third row and the fifth row adjacent to the fourth row. Since the light is blocked by the peak portions 51a of the reflection sheet 51 and does not reach the upper side of the light source 50 arranged in the fourth row, the luminance of the backlight is the fourth as shown in FIG. It's pretty dark on the line and bright otherwise. As a result, as shown in FIG. 13, only the m-th row of the backlight (the fourth row in FIG. 12B) looks like a black band, and the backlight brightness is digitally turned on / off. It becomes a state. The black band is scanned and moved sequentially. Thus, conventionally, the display light from the backlight is intermittently shortened to shorten the hold time, and the blur of the moving image accompanying the movement of the line of sight is improved.

  However, after the video signal data displayed in white having the transmittance c ′ of the liquid crystal shown in FIG. 14 is written in one line of the liquid crystal panel display unit, it corresponds to the data writing line of the backlight shown in FIG. When the black band portion at the position changes to the lit portion at the time indicated by a in FIG. 14, data display is performed with a transmittance a ′ lower than the transmittance c ′ corresponding to the written data, as shown in FIG. As described above, since the response characteristic of the liquid crystal is slow, there is a problem that there is a time delay until the liquid crystal panel is correctly displayed with the transmittance c ′ corresponding to the write data, and the liquid crystal panel cannot be displayed correctly. FIG. 14 shows an example in which black is displayed immediately after one frame period.

  Therefore, in the conventional liquid crystal display device, the effect of improving the moving image blur based on the hold type driving is insufficient. This is a major issue in improving the picture quality of televisions.

  The present invention has been made in view of the above points, and even when the backlight is scanned, the influence of digital on / off of the brightness of the backlight is greatly reduced, and moving picture blur can be greatly reduced. An object of the present invention is to provide a display device capable of accurately displaying data.

To achieve the above object, the present invention is Rutotomoni receives the light emitted from the backlight, a display device for displaying an image on a screen by a plurality of display elements in which the image data for each line is written,
The backlight is irradiated with direct light of N rows (N is an integer of 4 or more) in the vertical direction of the screen. The light source includes N light emitting elements arranged in the vertical direction of the screen, and the vertical direction of the screen from the light source. The direct light of the Lth row (L is any one of 2 to N-1) is limited to the direct light of the Nth row in the direction, and the L-1 and L + 1 rows are adjacent to each other. It is configured to have at least an irradiation range restriction part to be combined with part or all of the direct light of the eye
Within the display period of the screen of the input image data, among the N light emitting elements arranged in the vertical direction of the screen constituting the light source, the adjacent three rows of the L−1, L and L + 1 rows . Each light emitting element is turned off, and each light emitting element other than the three rows among the N light emitting elements is turned on, and the line range of the display element at the timing when the image data is written is set by turning off each light emitting element in the three rows. In synchronization with the line range corresponding to the row with the lowest backlight brightness , the three rows of light emitting elements that are turned off and the light emitting devices that are turned on are sequentially switched in the vertical direction of the screen, and the positions of the three rows that are turned off are displayed on the screen. It has a backlight control means for scanning in the vertical direction.

  In the present invention, the direct light from the light emitting elements in the L-th row is combined with a part or all of the direct light from the light-emitting elements in the adjacent (L-1) th and L + 1th rows. The light has the lowest luminance at a position including at least the Lth row, has intermediate luminance at a position including all or part of the (L-1) th row and the (L + 1) th row, and has the highest luminance at other locations. -1 row, L row, and L + 1 row, the adjacent three rows of light emitting elements are turned off, and among the plurality of light emitting elements constituting the light source, each of the light emitting elements other than the three rows is turned on, Within the display period of the screen of the input image data, the three rows of light emitting elements to be turned off and the light emitting elements to be turned on are sequentially switched in the vertical direction of the screen in synchronization with the writing timing of the image data to the display elements. The position of the 3 lines to turn off Because you to scan in the vertical direction of the screen, can be shortened hold time by the display device light display by the backlight is intermittently. In addition, by associating the display element at the timing when image data is written with the row position where the backlight has the lowest brightness, when the display element is a liquid crystal panel, the light emitted to the pixels before the transmittance rises completely Can be reduced.

  In order to achieve the above object, the display element in the above invention is a liquid crystal display element, and the light source is one light emitting element having a longitudinal direction in the horizontal direction of the screen or one row in the horizontal direction on the reflection sheet. A plurality of light emitting elements arranged in a row, and N light emitting elements arranged in the vertical direction of the screen. The irradiation range limiting portion is formed integrally with the reflective sheet, and the Lth row In the sheet portion having a mountain-shaped cross section, the irradiation range of the direct light from the light emitting element is limited and synthesized with a part or all of the direct light from the adjacent light emitting elements in the (L-1) th row and the (L + 1) th row. The backlight is of a direct type that irradiates the liquid crystal display element with light from a light source.

To achieve the above object, the present invention is Rutotomoni receives the light emitted from the backlight, a display device for displaying an image on a screen by a plurality of display elements in which the image data for each line is written,
The backlight is irradiated with direct light of N rows (N is an integer of 3 or more) in the vertical direction of the screen, and a light source including N light emitting elements arranged in the vertical direction of the screen, and N in the vertical direction of the screen. Of the rows, direct light from the light emitting elements in the Lth row (L is any one of 2 to N-1) is transmitted from each light emitting device in the adjacent L-1 and L + 1 rows. A structure having at least a light guide plate that emits to the outside after being directly combined with direct light,
Among the N light emitting elements arranged in the vertical direction of the screen constituting the light source within the display period of the input image data screen, two adjacent rows of the Lth row and the (L-1) th row or the (L + 1) th row. turns off the respective light emitting elements, or one, with lights the light emitting elements other than the second row of the N light emitting elements, off of each light emitting element of the second row line range of the display device of the timing at which image data is to be written By synchronizing with the line range corresponding to the range of the row where the backlight luminance is lowest , the two rows of light emitting elements to be turned off and the light emitting devices to be turned on are sequentially switched in the vertical direction of the screen to turn off the two rows. It has a backlight control means for scanning the position in the vertical direction of the screen.

  In the present invention, the backlight has the lowest luminance at the position in the horizontal direction of the screen between the light emitting elements in the adjacent two rows that are turned off, and is turned on with the light emitting elements in the two adjacent rows that are turned off. In the horizontal row position between the light emitting element and the light emitting element, the luminance is intermediate, the luminance is brightest otherwise, the backlight has the lowest luminance, and the upper and lower intermediate luminance row positions. However, since the image data is scanned in the vertical direction in synchronization with the writing timing of the image data to the display element within the display period of the screen of the input image data, the display light by the backlight is intermittently generated. The hold time by the display element can be shortened. In addition, by associating the display element at the timing when image data is written with the row position where the backlight has the lowest brightness, when the display element is a liquid crystal panel, the light emitted to the pixels before the transmittance rises completely Can be reduced.

  As described above, according to the present invention, the row position with the lowest backlight brightness and the row positions with the upper and lower intermediate brightness are displayed within the display period of the screen of the input image data. By scanning in the vertical direction of the screen in synchronization with the writing timing to the element, the display light by the backlight is made intermittent and the hold time by the display element can be shortened, which greatly increases the motion blur due to the hold drive Can be reduced.

  In addition, according to the present invention, the display element at the timing at which the image data is written is associated with the row position where the backlight luminance is the lowest, so that the row position where the backlight luminance is the lowest and the intermediate luminance above and below the row position. The position of the backlight that irradiates the display light to the display element at the timing at which the image data is written, even when the row position is scanned in the vertical direction of the screen to reduce moving image blur. When the display element is a liquid crystal panel, the light emitted from the backlight to the pixel before its transmittance completely rises compared to the conventional case. Accordingly, accurate gradation display can be performed by a display element (liquid crystal panel).

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a system configuration diagram of an embodiment of a display device according to the present invention. In the figure, a display device includes a liquid crystal panel display unit 1 for displaying images by a plurality of pixel circuits 2 arranged in a two-dimensional matrix, and a liquid crystal display for performing control for displaying images on the liquid crystal panel display unit 1. Connected to the controller 3, the gate signal line drive circuit 4 for driving the gate signal lines connected to the plurality of pixel circuits 2 provided in the liquid crystal panel display unit 1, and the plurality of pixel circuits 2 of the liquid crystal panel display unit 1. The data signal line driving circuit 5 drives the data signal lines, the backlight 6 irradiates the back surface of the liquid crystal panel display unit 1, and the backlight driving circuit 7 that drives the backlight 6. Each pixel circuit 2 includes a liquid crystal display element and its drive circuit.

  The liquid crystal display controller 3 receives a video signal to be displayed on the liquid crystal panel display unit 1, and the gate signal line drive circuit 4 and the data signal line drive circuit 5 are supplied to the liquid crystal panel display unit 6 based on the input video signal. Performs timing control for writing data. On the other hand, the backlight drive circuit 7 receives a control signal, and controls the brightness of the backlight 6 mainly based on the video signal based on the control signal.

  There are various types of the backlight 6, and a direct type in which a light source composed of a light emitting element such as a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED) is arranged directly under the liquid crystal panel. In addition, there is a light guide plate type in which direct light from the light source enters the light guide plate and irradiates the liquid crystal panel. The light emitted from the backlight 6 to the back surface of the liquid crystal panel display unit 1 has a transmittance corresponding to the image data written in each pixel circuit 2 of the liquid crystal panel display unit 1, and the liquid crystal display element of each pixel circuit 2 And let the image of the whole panel be recognized.

  FIG. 2 shows a schematic perspective view of the first embodiment of the backlight 6 in FIG. The backlight of this embodiment uses LEDs 10 as light emitting elements of the light source, and a plurality of LEDs 10 are fixed on the reflection sheet 11. The plurality of LEDs 10 on the reflection sheet 11 are divided by the reflection sheet 11 having a mountain-shaped vertical cross section for each of the plurality of LEDs arranged linearly in the horizontal direction (row direction) of the screen.

  That is, the plurality of LEDs 10 are divided by the peak portions 11a of the reflection sheet 11 in units of rows composed of the plurality of LEDs 10 arranged in the horizontal direction (row direction) of the screen. This configuration is similar to the conventional backlight shown in FIG. 12, but in this embodiment, the height of the mountain portion 11a is adjacent to the LED in the row where the light is turned off, as will be described later. This is different from the prior art in that it is set to a predetermined height that does not completely block the light from the LED.

  A diffusion plate 12 and an optical sheet 13 are sequentially stacked on the reflection sheet 11 (on the liquid crystal panel display unit 1 side). The optical sheet 13 is appropriately selected from a diffusion sheet, a prism sheet, a polarizing sheet, and the like according to the performance required by the liquid crystal panel display unit 1. The LED 10 as the light source may be any one of (1) a configuration composed of a red light LED, a green light LED, a blue light LED, and (2) a configuration composed of a white light LED. The backlight 6 of this embodiment is a direct type in which the light emitted from the LED 10 is diffused by the diffusion plate 12 and irradiated through the optical sheet 13 to the back surface of the liquid crystal panel display unit 1 of FIG.

  FIG. 3 shows a schematic perspective view of a second embodiment of the backlight 6 in FIG. The backlight according to this embodiment uses a CCFL 20 as a light emitting element serving as a light source, and a plurality of CCFLs 20 are fixed on the reflection sheet 21. The plurality of CCFLs 20 on the reflection sheet 21 are arranged in the longitudinal direction in the horizontal direction of the screen, and are separated one by one by the reflection sheet 21 having a vertical cross section. That is, the plurality of CCFLs 20 are divided by the peak portions 21a of the reflection sheet 21 in units of CCFLs 20 that are arranged so that the longitudinal direction is parallel to the horizontal direction (row direction) of the screen. A diffusion plate 22 and an optical sheet 23 are sequentially laminated on the upper part (the liquid crystal panel display unit 1 side) of the reflection sheet 21. The optical sheet 23 is appropriately selected from a diffusion sheet, a prism sheet, a polarizing sheet, and the like according to the performance required by the liquid crystal panel display unit 1.

  Similarly to the first embodiment, the height of the crest portion 21a of the reflection sheet 21 in this embodiment is such that the light from the CCFL 20 in the row adjacent to the CCFL 20 in the row where the light is extinguished completely, as will be described later. This is different from the prior art in that it is set to a predetermined height that is not interrupted. The backlight 6 of this embodiment diffuses the light emitted from the CCFL 20 by the diffusion plate 22 and irradiates the back surface of the liquid crystal panel display unit 1 of FIG. 1 through the optical sheet 23.

  Note that FIG. 2 and FIG. 3 are different in whether an LED or a CCFL is used as the light source, and the requirements for the optical characteristics are the same. Note that a hot cathode fluorescent lamp (HCFL) may be used instead of the CCFL 20 in FIG. 3, and another light source may be used as long as the same effect can be obtained.

Next, each embodiment of the driving method of the backlight used in the display device of the present invention will be described. FIG. 4 shows a sectional view of a backlight and a luminance distribution diagram thereof in the first embodiment of the display device according to the present invention. In the figure, the same components as those in FIG. In this embodiment, as shown in FIG. 4B, a plurality of LEDs 10 provided in a two-dimensional matrix on the reflection sheet 11 constituting the backlight are arranged in a row in the horizontal direction (row direction) of the screen. separated by the peak portions 11b of the reflection sheet 11 for each LED arranged in the direct light from the LED 10 _k of the k-th row (k is 1 to 7) are intercepts the mountain portion 11b of the reflective sheet 11 to separate the LED string constant However, there is a feature in that the height of the peak portion 11b is set to a height position where direct light from the LEDs 10 _k-1 and 10 _{k + 1} in the adjacent rows is irradiated.

More specifically, of the seventh row from the first row shown in FIG. 4 (B), the light emitted from the LED 10 _k of the k row (k-1) -th row is an adjacent row by a peak portions 11b, the (k + 1) The irradiation range of the light is limited so that each of the diffuser plates 12 above the row is irradiated to the positions corresponding to the (k−1) th row and the (k + 1) th row width.

As a result, as shown in FIG. 4B, if the LEDs 10 ₃ , 10 ₄ , 10 ₅ in the third row, the fourth row, and the fifth row are turned off, the LEDs 10 _{1 in} the first row The emitted light is applied to the regions above the LEDs 10 ₁ and 10 _{2 in} the _first and second rows of the diffusion plate 12. Further, light emitted from the LED 10 ₂ of the second row is irradiated over the region of each LED 10 _{1, 10} 2, 10 ₃ of the third row and the first and second rows of the diffusion plate 12.

Therefore, assuming that the light flux of the LED 10 is constant at any angle within a range not blocked by the peak portion 11b of the reflection sheet 11, the area above the LEDs 10 ₁ and 10 _{2 in} the _first and second rows of the diffusion plate 12 is , the brightness and the light from LED 10 ₁ in the first row and the light from LED 10 ₂ of the second row is added. Also, the region above the LED 10 ₃ of the third row of the diffusion plate 12, only the light from the LED 10 ₂ of the second row is irradiated, the brightness of the light from the LED 10 _2. However, the region above the LED 10 ₄ of the fourth row of the diffusion plate 12, the third row, the fourth row, the fifth row of the LED 10 _{3, 10} 4, 10 ₅ is off, at all irradiation Not.

Also, the region above the LED 10 ₅ of the fifth row of the diffusion plate 12, only the light from the LED 10 ₆ sixth row is irradiated, the brightness of the light from the LED 10 _6. In addition, the area above the LEDs 10 ₆ and 10 ₇ in the sixth row and the seventh row of the diffusion plate 12 is irradiated with the light from the LED 10 _{6 in} the sixth row and the light from the LED 10 _{7 in} the seventh row. The brightness is obtained by adding the lights.

Therefore, when a light beam emitted from the respective LED light source array and each "1", as shown in FIG. 4 (A), the LED 10 ₁ in the upper region of the first row of the diffusion plate 12 "2", the the LED 10 ₂ in the upper region of the second line "2", the LED 10 ₃ above the region of the third row "1", the LED 10 ₄ above the region in the fourth row "0", the fifth row LED 10 ₅ "1" in the area above, "2" in the area above the LED 10 _{6 in} the sixth row, and "2" in the area above the LED 10 _{7 in} the seventh row.

  FIG. 5 shows how the backlight looks at this time. Here, the LED columns in the adjacent three rows of the m−1th row, the mth row, and the m + 1th row (when m = 4 in FIG. 4) of the backlight having the structure shown in FIG. 4B are turned off. In this case, the m-th row appears as a black belt as in the conventional case. However, unlike the conventional case, the upper one row (m−1 row) and the lower one row (m + 1 row). ) Means the brightness (between “2” in the example of FIG. 4 (A)) and the brightness of the black belt (“0” in the example of FIG. 4 (A)). In the example of FIG. 4A, “1”), the luminance change is not steep, and the black band of the backlight can be visually inconspicuous.

  Further, in the present embodiment, when the backlight LEDs 10 are composed of n rows in total, the backlight driving circuit 7 in FIG. 1 controls the drive signal to the LEDs 10 to change m in FIG. 5 within one frame time. By sequentially changing from 1 to n, it is possible to integrally scan a black belt and a portion composed of a relatively dark area above and below it in the vertical direction of the screen.

  The black belt portion (m-th row in FIG. 5) of the backlight 6 is synchronized with a writing line of image data written line-sequentially into the liquid crystal display element by the pixel circuit 2 of the liquid crystal panel display unit 1 in FIG. Scanned. For example, assuming that the number of lines (number of lines) in the vertical direction of the screen of the liquid crystal panel display unit 1 is 768 and the number of lines in the vertical direction of the screen of the LEDs 10 of the backlight 6 is 16, the 16 LED columns Is turned on / off in units of 1/16 frame period per row, and a black band portion (m-th row in FIG. 5) and an intermediate luminance portion (m-1 row and m + 1-th row in FIG. 5) are displayed on the screen. Although scanned from the top to the bottom, line sequential is performed on 48 lines (= 768/16) of the liquid crystal panel display unit 1 at a position corresponding to the black band portion (m-th line in FIG. 5) of the backlight 6 described above. In order to write the image data, the on / off control of the backlight 6 and the line sequential writing of the image data are performed in synchronization.

Here, for simplicity of explanation, when the LEDs 10 of the backlight 6 are composed of, for example, 8 rows in total, the backlight driving circuit 7 in FIG. 1 divides one frame into 8 as shown in FIG. In the first ８ frame period t1, the plurality of LEDs 10 ₁ , 10 ₇ , 10 ₈ arranged in a row in the first row, the seventh row, and the eighth row are schematically shown by black squares. The other LEDs 10 ₂ to 10 ₆ are controlled to be turned off, and in the next 1/8 frame period t2, a plurality of LEDs 10 ₁ arranged in a line in the first row, the second row, and the eighth row, respectively. 10 ₂ and 10 ₈ are turned off, and the other LEDs 10 ₃ to 10 ₇ are turned on.

Furthermore, from the next 1/8 frame period t3 to the last 1/8 frame period t8, a plurality of LEDs 10 _j−1 , 10 _j , 10 _{j + 1} (where j = 2 to 7) are turned off as schematically shown by black squares, and the other LEDs are turned on, and the turned-off three rows of LEDs are turned down by 1 row every 1/8 frame. Scan to shift. Therefore, for example, in the 1/8 frame period t5 in FIG. 6, the backlight 6 has the lowest black band in the fourth row (m-th row in FIG. 5) as shown in FIG. Five lines (m-1 line and m + 1 line in FIG. 5) have an intermediate luminance, and the other first, second, and sixth to eighth lines have the brightest luminance.

  Further, in this case, as shown in FIG. 7, the liquid crystal panel display unit 1 has the black band portions of the backlight 6 in the order of 32a, 32b, 32c, 32d, and 32e in one frame where the image 31 is displayed. Are sequentially scanned from the top to the bottom of the screen, and the intermediate luminance portions adjacent to the top and bottom of the black belt portion are (33a, 34a), (33b, 34b), (33c, 34c), (33d, 34d), respectively. , (33e, 34e) in order from the top to the bottom of the screen, and the other part of the backlight 6 irradiates the liquid crystal panel display unit 1 with light having a predetermined luminance.

  As described above, the image data is line-sequentially written in line-sequentially from the top to the bottom of the screen and from the left to the right of the screen in synchronism with the on / off control of the backlight 6. . In the description of FIG. 6 described above, the periods t1 to t8 have been described as 1/8 frame periods for convenience, but strictly speaking, they are slightly shorter than 1/8 frames. In addition, the backlight extinction period is subjected to variable pulse width modulation (PWM) depending on the brightness of image data and the like, but since it is not the gist of the present embodiment, detailed description thereof is omitted.

  As described above, according to the present embodiment, an image displayed in white with a liquid crystal transmittance c ′ on the liquid crystal panel display unit 1 configured with a liquid crystal display element having response characteristics as shown in FIG. When the signal data is written on one line of the liquid crystal panel display, the portion of the backlight 6 at the position corresponding to the one line is controlled to be the black belt portion (corresponding to the m-th row in FIG. 5). Thereafter, the portion of the backlight 6 is controlled to the original luminance, for example, near the time b shown in FIG. 14 and then to the original luminance immediately before the time c shown in FIG. In the time displayed by the liquid crystal display element at the original liquid crystal transmittance c ′, the backlight having the original luminance is irradiated and correct display can be performed.

  Further, since the black belt portion (m-th row in FIG. 5) and the intermediate luminance portion (m-1 row and m + 1-th row in FIG. 5) are scanned downward from the top of the screen, the display light by the backlight is used. Is held intermittently, the hold time is shortened, and blurring of moving images accompanying the movement of the line of sight can be improved.

Next, a second embodiment of a backlight driving method used in the display device of the present invention will be described. FIG. 8 shows a sectional view of a backlight and a luminance distribution diagram thereof in the second embodiment of the display device according to the present invention. In the figure, the same components as those in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted. In this embodiment, as shown in FIG. 8B, a plurality of LEDs 10 provided in a two-dimensional matrix on the reflection sheet 11 constituting the backlight 6 in FIG. separate the mountain portion 11c of the reflection sheet 11 for each LED arranged in a row direction), the direct light from the LED 10 _k of the k-th row (k is 1 to 7), the mountain portion 11c of the reflection sheet 11 to separate LED strings in interception, but in which Motas a certain radiation range, the height of the mountain portion 11c, the direct light from the LED 10 _k is, LED 10 of the k-1 line adjacent and the k + 1 row _k-1 and _{10 k + 1} It is a direct type backlight characterized in that it is set at a height position so as to be an irradiation range corresponding to the vicinity of the center of the width.

More specifically, of the seventh row from the first row shown in FIG. 8 (B), the light emitted from the LED 10 _k of the k row (k-1) -th row is an adjacent row by a mountain portion 11c, the (k + 1) The irradiation range of light is limited so that each of the diffuser plates 12 on the upper surface of the row is irradiated to the vicinity of the centers of the (k−1) th row and the (k + 1) th row.

As a result, as shown in FIG. 8B, assuming that the LEDs 10 ₃ , 10 ₄ , 10 ₅ in the third row, the fourth row, and the fifth row are turned off, the LEDs 10 _{1 in} the first row light emitted is irradiated onto half area of LED 10 ₁ side of the LED 10 ₂ above the LED 10 the upper region and the second row of the ₁ in the first row of the diffusion plate 12. Further, light emitted from the LED 10 ₂ of the second row, the first and third rows each of LED 10 _1, 10 ₃ above the LED 10 ₂ side halves region of the diffusion plate 12, the second row of LED 10 ₂ The upper region is irradiated.

Therefore, when the light flux of the LED 10 is constant at any angle in a range unobstructed mountain portion 11c of the reflection sheet 11, of the LED 10 ₂ in the upper region of the second row of the diffusion plate 12, half of the LED 10 ₁ side in the region, the brightness and the light is added from LED 10 ₂ light and the second row from the LED 10 ₁ in the first row. In addition, among the regions of the LED 10 ₂ above the second row of the diffusion plate 12, in the area of half of the LED 10 ₃ side, the LED 10 ₃ are off, and the brightness of only the light from the LED 10 ₂ of the second row Become. Further, among the upper region of the LED 10 ₃ of the third row of the diffusion plate 12, in the area of half of the LED 10 ₂ side, since the LED 10 ₃ are off, and the brightness of only the light from the LED 10 ₂ of the second row Become.

However, a half of the LED 10 ₄ side of the LED 10 ₃ above the region of the third row of the diffusion plate 12, and an upper region of the fourth row of the LED 10 _4, of the region above the LED 10 ₅ of the fifth row half of the out LED 10 _{4 side,} so LED10 _3, 10 _4, 10 ₅ is turned off, not illuminated at all light. Further, the LED 10 ₆ side half region of the sixth row of the upper region of the LED 10 ₅ of the diffusion plate 12, the LED 10 ₅ side half region of the upper region of the LED 10 _6, the light from the LED 10 ₆ since only illuminates, the brightness of the light from the only LED 10 _6. Moreover, since the light from the LED 10 ₆ and the light from the LED 10 _{7 in} the seventh row are irradiated to the half of the region on the LED 10 ₇ side of the region above the LED 10 ₆ of the diffusion plate 12, these lights are added. Of the region above the LED 10 ₇ of the diffusion plate 12, the half region on the LED 10 ₆ side has the brightness obtained by adding the light from the LED 10 ₆ and the light from the LED 10 ₇ .

Therefore, when each of the LED light source array a light beam irradiated from the respective "1", as shown in FIG. 8 (A), the half area of the LED 10 ₂ side of the LED 10 ₁ above the area of the diffusion plate 12 , LED 10 in the LED 10 ₁ side half region of the _second upper region "2", LED 10 and half of the LED 10 ₃ side of the _second upper region, LED 10 ₂ side of the region above the LED 10 ₃ half area and the "1", and half of the LED 10 ₄ side in the upper region of the LED 10 _3, and an upper region of the LED 10 _4, half of the LED 10 ₄ side in the upper region of the LED 10 ₅ of in a "0", in a half area of the LED 10 ₆ side in the upper region of the LED 10 _5, the LED 10 ₅ side half region of the LED 10 ₆ the region above the "1" LED 10 and ₆ upper half of the LED 10 ₇ side in the region of, the brightness of "2" in the LED 10 ₆ side half region of the LED 10 ₇ upper region of.

  FIG. 9 shows how the backlight looks at this time. Here, the LED columns in the adjacent three rows of the (m−1) th row, the mth row, and the (m + 1) th row (when m = 4 in FIG. 8) of the backlight having the structure shown in FIG. 8B are turned off. In this case, a total of 2 lines consisting of a half width of the first line (m-1 line) and a half width of the lower line (m + 1 line) of the mth and mth lines. The width of the line is seen as a black band, and the upper one line width composed of the remaining half width of the (m−1) th line and the half width of the (m−2) th line, and the (m + 1) th line The width of the lower row consisting of the remaining half width of the row and the half width of the (m + 2) th row is the brightness of the other region (“2” in the example of FIG. 8A) and the black belt Brightness (“0” in the example of FIG. 8A) (between “1” in the example of FIG. 8A), the luminance change is not steep, and the backlight black The belt can be visually inconspicuous.

  Further, in the present embodiment, when the backlight LEDs 10 consist of n rows in total, the backlight drive circuit 7 in FIG. 1 controls the drive signal to the LEDs 10 to change m in FIG. 9 within one frame time. By sequentially changing from 1 to n, it is possible to integrally scan a black belt and a portion composed of a relatively dark area above and below it in the vertical direction of the screen.

  Further, the black belt portion of the backlight 6 (the width of each half of the mth row, (m−1) th row, and (m + 1) th row in FIG. 9) of the liquid crystal panel display unit 1 in FIG. The pixel circuit 2 scans in synchronization with a writing line of image data written in a line sequential manner on the liquid crystal display element.

  As a result, in the present embodiment, similarly to the first embodiment, the brightness of the backlight is increased by associating the display element at the timing when image data is written with the row position having the lowest backlight brightness. Even when the lowest row position and the upper and lower intermediate luminance row positions are scanned in the vertical direction of the screen to reduce motion blur, display light is emitted to the liquid crystal display element at the timing at which image data is written. Since the position of the backlight to be changed can be changed from the position where the luminance of the backlight is least to the position of the intermediate luminance, the pixel before the transmittance of the liquid crystal display element completely rises is irradiated from the backlight. The amount of light can be reduced as compared with the conventional case, whereby accurate gradation display by the liquid crystal display element can be performed.

  Next, a third embodiment of a backlight driving method used in the display device of the present invention will be described. FIG. 10 shows a sectional view of a backlight and a luminance distribution diagram thereof in the third embodiment of the display device according to the present invention. The backlight of this embodiment is a light guide plate type backlight, and as shown in FIG. 10, there are a plurality of pieces on the reflection sheet 41 (however, in this case, five in the vertical direction of the screen and in the horizontal direction of the screen). Are arbitrarily arranged in a two-dimensional matrix, and a milky white acrylic light guide plate 42 is provided on the reflection sheet 41.

The light guide plate 42, the screen horizontal direction and a longitudinal direction, than the magnitude of the LED40 has five grooves ₄₃ 1 to 43 ₅ of slightly larger becomes wide are formed in parallel to each other, the screen in a groove ₄₃ 1-43 ₅ In the vertical direction, five LEDs 40 are accommodated in units of rows. That is, the grooves _{43 1, 43 2, 43 3} , 43 4, 43 LED40 1 of the first row in the internal space of _5, LED 40 ₂ of the second row, the third row of the LED 40 _3, the fourth row of the LED 40 _4, LED 40 ₅ of the fifth row are arranged. A diffusion sheet 44 is disposed above the light guide plate 42, and an optical sheet 45 is laminated thereon. The optical sheet 45 is appropriately selected from a diffusion sheet, a prism sheet, a polarizing sheet, and the like according to the performance required by the liquid crystal panel display unit 1.

In the backlight 6 of this embodiment, the direct light emitted from the LEDs 40 ₁ to 40 ₅ enters the light guide plate 42, and the grooves 43 ₁ to 43 ₅ of the light guide plate 42 that separate the LEDs 40 ₁ to 40 ₅ for each row. It is limited to a specific irradiation range. For example, the direct light from the LED 40 _k in the k-th row (here, k is an integer of 1 to 5), the grooves 43 _k, the k−1 and k + 1 rows of grooves 43 _k−1 adjacent to both sides by the grooves 43 _k , Light is guided toward the 43 _{k + 1} direction. The guided light is emitted upward in the light guide plate 42 with the liquid crystal panel display unit 1, diffused by the diffusion sheet 44, and irradiates the back surface of the liquid crystal panel display unit 1 of FIG. 1 through the optical sheet 45. .

Here, as shown in FIG. 10 (B), and LED 40 ₂ of the second row off the third row of the LED 40 ₃ are, and other LED40 _{1, 40} 4, _{40 5} think When lit . In this case, the light from the LED 40 ₁ in the first row, LED 40 ₁ in the first row in the light guide plate 42 by the groove 43 ₁ of the light guide plate 42 and toward between the LED 40 ₂ of the second row being guided From above the light guide plate 42. The light from the LEDs 40 _{4 in} the fourth row passes through the light guide plate 42 between the LEDs 40 ₃ and 40 ₄ in the light guide plate 42 and between the LEDs 40 ₄ and the LEDs 40 _{5 in} the fifth row through the grooves 43 ₄ of the light guide plate 42. Then, the light is guided upward toward the upper side of the light guide plate 42. Also, light from the LED 40 ₅ is the groove 43 ₅ of the light guide plate 42 through the light guide plate 42 LED 40 ₄ and the between the LED 40 _5, LED 40 ₅ respectively electrically from being guided toward between the LED 40 ₆ The light is emitted above the light plate 42.

Therefore, if the light beams emitted from the LED 40 _{k in an} arbitrary row among the LEDs 40 ₁ to 40 ₅ to the left and right in the light guide plate 42 in FIG. In the case of the figure (B), as shown in the figure (A), the brightness between the LED rows of the first row and the second row is “1”, and the LED rows of the second row and the third row are The brightness between the LED columns in the third row and the fourth row is “1”, and the brightness between the LED columns in the fourth row and the fifth row is “2”. It becomes.

  Therefore, the appearance of the backlight 6 of the present embodiment is the same as that shown in FIG. FIG. 5 shows a case where there are n rows of LED columns in total. When the backlight 6 is scanned, the LED columns of a total of two rows of the m-th row and the (m-1) -th row or the (m + 1) -th row are turned off, and the other LED rows are turned on, and in synchronization with the frame time, m Is changed by changing from 1 to n. At this time, the black belt portion (m-th row in FIG. 5) of the backlight 6 is synchronized with the writing line of the image data written line-sequentially into the liquid crystal display element by the pixel circuit 2 of the liquid crystal panel display unit 1 in FIG. Scanned.

Here, for simplicity of explanation, if the LEDs 40 of the backlight 6 are composed of, for example, 8 rows in total, the backlight drive circuit 7 in FIG. 1 divides one frame into 8 as shown in FIG. In the first ８ frame period t11, the plurality of LEDs 40 ₁ , 40 ₈ arranged in a line in the first row and the eighth row are turned off as schematically shown by black squares, and the other LEDs 40 _{2-40 7} lighting control, in the next 1/8 frame period t12, the first row, LED 40 ₁ a plurality arranged in respectively a line in the second row, 40 ₂ as well as off the other LED 40 ₃ to lighting control the 40 _8.

Further, from the next 1/8 frame period t13 to the last 1/8 frame period t18, a plurality of LEDs 40 _j−1 , 40 _j arranged in one column in two adjacent rows (where j = 3 to 3). 8) is turned off as schematically shown by a black square, and other LEDs are controlled to be turned on, and the two rows of LEDs that are turned off are shifted downward by 1 row every 1/8 frame. To scan.

  Therefore, for example, in the 1/8 frame period t13 in FIG. 11, the backlight 6 is arranged between the second row and the third row of LED columns (mth in FIG. 5), as shown in FIG. (Corresponding to the row) is the black band with the lowest luminance, and between the LED columns of the first row and the second row (m-1 row in FIG. 5) and the LED rows of the third row and the fourth row. The row (m + 1th row in FIG. 5) has an intermediate luminance, and the other rows have the highest luminance.

  As described above, the black belt portion (the m-th row in FIG. 5) and the intermediate luminance portion (the (m−1) -th row and the m + 1-th row in FIG. 5) are scanned downward from the top of the screen. The backlight 6 is turned on / off so that image data is written line-sequentially to each line of the liquid crystal panel display unit 1 at a position corresponding to the black belt portion of the backlight 6 (m-th row in FIG. 5). Control and line-sequential writing of image data are performed in synchronization.

  In the description of FIG. 11 above, the periods t11 to t18 have been described as 1/8 frame periods for convenience, but strictly speaking, they are slightly shorter than 1/8 frames. In addition, the backlight extinction period is subjected to variable pulse width modulation (PWM) depending on the brightness of image data and the like, but since it is not the gist of the present embodiment, detailed description thereof is omitted.

  As described above, according to the present embodiment, as in the first and second embodiments, one row having the lowest luminance and the intermediate luminance portion of the upper and lower rows are scanned (scanned) in the vertical direction of the screen. Thus, the light of the backlight 6 that irradiates the liquid crystal panel display unit 1 that is driven by the hold type can be arranged in an impulse-like brightness column. For this reason, good moving image characteristics can be obtained. Furthermore, since the intermediate luminance portion is provided in each of the upper and lower rows of one row having the lowest luminance, the transmittance of the liquid crystal display element is not increased completely compared with the conventional backlight even if the above scan is performed. Light applied to the pixels can be reduced, and accurate gradation display can be performed.

In the above embodiment, the LED 10 ₁ to 10 ₈ and the LED 40 ₁ to 40 ₈ are described as the light emitting elements constituting the light source of the backlight. However, the present invention is not limited to this, Of course, the CCFL 20 and HCFL shown in FIG. 3 may be used. The backlight scan driving method according to the present invention is particularly suitable for a liquid crystal display, but can be applied to any display device having a similar display principle.

1 is a system configuration diagram of an embodiment of a display device of the present invention. It is a schematic perspective view of 1st Embodiment of the backlight in FIG. It is a schematic perspective view of 2nd Embodiment of the backlight in FIG. It is sectional drawing and the luminance distribution figure of the backlight in 1st Embodiment of the display apparatus of this invention. It is a figure which shows how the backlight in the case of FIG. 4 looks. It is a figure which shows an example of the drive method of the backlight in 1st Embodiment of the display apparatus of this invention. It is a figure which shows an example of the scanning of the light irradiation part of the backlight in this invention with a display image. It is sectional drawing and the luminance distribution figure of the backlight in 2nd Embodiment of the display apparatus of this invention. It is a figure which shows how the backlight in the case of FIG. 8 looks. It is sectional drawing and the luminance distribution figure of the backlight in 3rd Embodiment of the display apparatus of this invention. It is a figure which shows an example of the drive method of the backlight in 3rd Embodiment of the display apparatus of this invention. It is sectional drawing and the luminance distribution figure of the backlight in an example of the conventional display apparatus. It is a figure which shows how the backlight in the case of FIG. 12 looks. It is a figure which shows an example of the response characteristic of a liquid crystal display (liquid crystal display element).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal panel display part 2 Pixel circuit 3 Liquid crystal display controller 4 Gate signal line drive circuit 5 Data signal line drive circuit 6 Backlight 7 Backlight drive circuit 10 Light emitting diode (LED)
10 ₁ to 10 ₈ , 40 ₁ to 40 ₅ LED array 11, 21, 41 Reflective sheet 11a, 11b, 11c, 21a Irradiation range limiting peak portion 12, 22, 44 Diffusion plate 13, 23, 45 Optical sheet 20 Cold cathode Fluorescent lamp (CCFL)
42 Light guide plate 43 ₁ to 43 ₅ grooves

Claims (3)

Rutotomoni receiving the light emitted from the backlight, a display device for displaying an image on a screen by a plurality of display elements in which the image data for each line is written,
The backlight is
A light source comprising N light emitting elements arranged in the vertical direction of the screen, which irradiates N rows (N is an integer of 4 or more) direct light in the vertical direction of the screen;
Limiting the direct light irradiation range of N rows in the vertical direction of the screen from the light source , direct light of the Lth row (L is any one of 2 to N-1) is adjacent. A configuration including at least an irradiation range limiting unit to be combined with part or all of the direct light of the (L-1) th row and the (L + 1) th row,
Among the N light emitting elements arranged in the vertical direction of the screen constituting the light source within the display period of the image data to be input, adjacent to the L−1, L, and L + 1 rows. each light-emitting element 3 rows turned off to, and as well as light the respective light emitting elements other than the three rows among the N of the light emitting element, the line range of the display device of the timing of the image data is written The three rows of light emitting elements that are turned off and the light emitting devices that are turned on are synchronized with the line range corresponding to the row where the luminance of the backlight is lowest by turning off the light emitting elements of the three rows. A display device comprising backlight control means for scanning in the vertical direction of the screen the positions of the three rows that are sequentially switched to each other and turned off. The display element is a liquid crystal display element;
The light source includes, on a reflective sheet, one light emitting element having a longitudinal direction in the horizontal direction of the screen or a plurality of light emitting elements arranged in a row in the horizontal direction, and in the vertical direction of the screen. N light emitting elements arranged,
The irradiation range limiting unit is formed integrally with the reflection sheet and limits the irradiation range of the direct light from the light emitting elements in the Lth row, so that the adjacent L-1th row and L + 1th row The cross section is a mountain-shaped sheet portion that is combined with part or all of the direct light from each light emitting element of the eye, and the backlight is a direct type that irradiates the liquid crystal display element with light from the light source The display device according to claim 1. Rutotomoni receiving the light emitted from the backlight, a display device for displaying an image on a screen by a plurality of display elements in which the image data for each line is written,
The backlight is
A light source composed of N light emitting elements arranged in the vertical direction of the screen, which irradiates N rows (N is an integer of 3 or more) direct light in the vertical direction of the screen;
Of the N rows in the vertical direction of the screen, direct light from the light emitting element in the L row (L is an arbitrary value of 2 to N-1) is changed to the adjacent L-1 row. A light guide plate that is combined with direct light from each light-emitting element in the (L + 1) th row and then emitted to the outside, and
Within the display period of the screen of the input image data, among the N light emitting elements arranged in the vertical direction of the screen constituting the light source, the L row and the L−1 row or the L + 1 row. It turns off the respective light emitting elements of two adjacent rows, one or prior SL with lighting the each light emitting element other than the second row of the N light emitting elements, the display elements of the timing of the image data is written The light emitting elements to be turned on and the light emitting elements to be turned on in synchronization with the line range corresponding to the line range corresponding to the row range in which the luminance of the backlight is lowest by turning off the light emitting elements in the two rows. And a backlight control means for scanning the positions of the two rows that are turned off in the vertical direction of the screen in the vertical direction of the screen.

Images