JP4593650B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device that displays an image by illuminating a liquid crystal display panel with a backlight light source, and more particularly to a liquid crystal display device that prevents motion blur that occurs when displaying a moving image by bringing it closer to an impulse-type display. is there.

  In recent years, flat panel display devices (FPD) such as liquid crystal display devices (LCD) that can realize high definition, low power consumption, and space saving have been actively developed, and in particular, computer display devices and television display devices. The spread of LCDs for such applications is remarkable. However, in contrast to a cathode ray tube (CRT) display device that has been mainly used for such applications, the LCD has a blurred outline of the moving part when a moving image is displayed. It has been pointed out the disadvantage of the so-called “motion blur” that it is perceived.

  It has been pointed out that the motion blur in moving image display is caused not only by the delay of the optical response time of the liquid crystal but also by the LCD display method itself as described in, for example, JP-A-9-325715. In a CRT display device that scans an electron beam and emits phosphors to perform display, each pixel emits light almost in an impulse form although there is a slight afterglow of the phosphors. Yes.

On the other hand, in the LCD display device, the charge stored by applying the electric field to the liquid crystal is held at a relatively high rate until the next electric field is applied (particularly TFT LCD).
In this case, a TFT switch is provided for each dot constituting the pixel, and usually an auxiliary capacitor is provided for each pixel, so that the ability to hold the stored charge is extremely high). This is a so-called hold type display system in which light emission is continued until rewriting is performed by applying an electric field based on image information of a frame.

  In such a hold-type display device, since the impulse response of the image display light has a temporal spread, the temporal frequency characteristic is deteriorated, and the spatial frequency characteristic is also lowered accordingly, and the visual image is blurred. . Therefore, in the above-mentioned Japanese Patent Application Laid-Open No. 9-325715, display light is viewed only in the second half of each field period of a display image by controlling on / off of a shutter or a light source lamp (backlight) provided on the display surface. There has been proposed a display device that improves the motion blur of a viewing image by presenting to a person and limiting the temporal spread of the impulse response.

  Further, as in Japanese Patent Laid-Open No. 9-325715, an image signal within one vertical period to be displayed is written, and after a predetermined time has elapsed, the backlight light source is turned on to produce a moving image display. In contrast to methods for improving image quality degradation such as motion blur, Japanese Patent Laid-Open No. 2000-275604 and Japanese Patent Laid-Open No. 2000-321551, for example, divide a liquid crystal display panel into a plurality of display areas and deal with each area. A so-called scanning-type backlight lighting method has been proposed in which image quality degradation such as motion blur that occurs during moving image display is improved by sequentially turning on a backlight light source that performs scanning lighting within one vertical period.

  A case where the backlight is blinked at high speed in order to bring the display state of the hold-type drive closer to the display of the impulse-type drive such as a CRT will be described with reference to FIGS. In FIG. 23, reference numeral 1 denotes an active matrix type liquid crystal display panel having a liquid crystal layer and electrodes for applying scanning signals and data signals to the liquid crystal layer, and 2 denotes data of the liquid crystal display panel 1 based on an input image signal. An electrode driving unit 3 for driving the electrodes and the scanning electrodes is a direct type backlight light source disposed on the back surface of the liquid crystal display panel 1.

  Further, 4 is a light source driving unit for intermittently driving the backlight light source 3, 5 is a synchronizing signal extracting unit for extracting a vertical / horizontal synchronizing signal from the input image signal, and 6 is a vertical / vertical extracted by the synchronizing signal extracting unit 5. Based on the horizontal synchronization signal, the control CPU controls the timing for sequentially scanning and lighting the light emitting areas of the backlight light source 3 in the vertical direction. The backlight light source 3 can use a plurality of fluorescent lamps (CCFT), light emitting diodes (LEDs), and the like, and a predetermined number (number) of light emitting areas is used as a plurality of divided display areas in the liquid crystal display panel 1. It corresponds to each of.

  When the liquid crystal display panel 1 is divided into, for example, three screen areas (1) to (3), as shown in FIG. 24, image writing of a horizontal line group (display divided area) in a screen area of the liquid crystal display panel 1 is performed. After the scanning is completed, the light emitting area (a certain fluorescent lamp lamp group or LED group) of the backlight light source 3 corresponding to the horizontal line group is turned on and turned off at the timing when the image writing scanning of the next frame is started. To do.

  By repeating this in the up and down direction with the next region,..., The backlight lighting period corresponds to the writing scan location of the image signal as shown by the white area in FIG. Accordingly, it is possible to sequentially shift in units of light emitting areas. In order to simplify the explanation, the response delay of the liquid crystal is not taken into consideration here. However, considering this, an appropriate time is set between the completion timing of image writing scanning and the backlight lighting timing in each screen area. A liquid crystal response period may be provided.

  Thus, after writing the image signal, the operation of irradiating the backlight light to each screen area is sequentially repeated within one frame period (for example, 16.7 msec in the case of 60 Hz progressive scan). It is possible to realize a pseudo impulse type display by shortening the light emission time (image display period) of a pixel from the scanning of a frame to the scanning of the next frame. Can be prevented.

However, in the above-described scanning backlight lighting method, since the backlight blinking drive is performed, there is a problem with the optical characteristics of the backlight, that is, the light emission and afterglow characteristics. For example, when the afterglow characteristics of Green are longer than those of other colors, coloring (in this case, Green is colored) occurs, and even though the video performance can be improved, the display quality is degraded. .

  Therefore, for example, in Japanese Patent Application Laid-Open No. 2001-159871, for example, as shown in FIG. 25, the backlight light source 3 disposed on the back surface of the transmissive liquid crystal display panel 1 is always lit (continuous light emission) and between the two. Disclosed is a liquid crystal optical shutter 7 (shielding member) provided in the above, which realizes a pseudo impulse drive display without causing deterioration of image quality due to coloring described above by blocking backlight light for a certain period of time. ing.

Here, the input of the image signal to the transmissive liquid crystal display panel 1 and the drive timing of the liquid crystal optical shutter 7 in the drive circuit 8 are adjusted by the display controller 9. The display controller 9 can display different images on the transmissive liquid crystal display panel 1 at a constant cycle, for example, 60 cycles per second, that is, display a moving image of 60 frames per second. The drive circuit 8 synchronizes with a vertical synchronization signal indicating the start of a frame period of a moving image, and a liquid crystal optical shutter so as to block the backlight light from irradiating each area of the transmissive liquid crystal display panel 1 for a certain time 7 is driven.
JP-A-9-325715 JP 2000-275604 A JP 2000-321551 A JP 2001-159871 A

  However, as described above, when the backlight light to the liquid crystal display panel 1 is blocked (extinguished) for each of the divided display areas for a certain period, the backlight light applied to the image non-display area is not effectively used for image display. There is a problem that it is difficult to improve the display luminance of an image due to low light utilization efficiency.

  The present invention has been made in view of the above-described problems, and a liquid crystal display device capable of improving the light use efficiency and improving the display brightness of the image by effectively using the backlight light for the image non-display area. Is to provide.

  1st invention of this application is a liquid crystal display device which displays an image by irradiating a liquid crystal display panel using a backlight light source, Comprising: The said backlight light source with respect to each division | segmentation display area of the said liquid crystal display panel Optical shutter means for intermittently supplying the backlight light within one vertical period to each of the divided display areas of the liquid crystal display panel by transmitting / shielding the backlight light from the optical display panel; The shutter means is configured using a dynamic scattering liquid crystal that reflects at least a part of the backlight light to the backlight light source side when the backlight light is blocked.

  The second invention of the present application is characterized in that the optical shutter means is configured by providing polarized light separating means on each of the backlight light source side and the liquid crystal display panel side of the dynamic scattering liquid crystal.

  The third invention of the present application is characterized in that each of the polarization separating means is arranged so that the polarization axis directions thereof are perpendicular to each other.

  The fourth invention of the present application is characterized in that each of the polarized light separating means is arranged so that directions of polarization axes thereof are parallel to each other.

  A fifth invention of the present application is characterized in that a black display signal is supplied to a divided display area of a liquid crystal display panel corresponding to the optical shutter means during a period in which the optical shutter means blocks backlight light.

  According to a sixth aspect of the present invention, when the number of divided display areas is N, frame frequency conversion means for converting the frame frequency of the input image signal to (N-1) times, and the image signal obtained by converting the frame frequency And a black insertion means for switching and outputting a black display signal at a predetermined timing.

  According to the liquid crystal display device of the present invention, the backlight light to the liquid crystal display panel is shielded for a certain period for each divided display region, thereby preventing motion blur that occurs during moving image display and improving the moving image quality. By condensing the backlight light for the image non-display area of the liquid crystal display panel in the image display area, it is possible to increase the use efficiency of the backlight light and improve the display brightness of the image.

  Since the liquid crystal display device of the present invention is configured as described above, it prevents motion blur that occurs during moving image display by blocking the backlight to the liquid crystal display panel for a certain period for each divided display area. In addition to improving the quality of moving images, the backlight light for the non-display area of the liquid crystal display panel can be focused on the image display area, thereby improving the use efficiency of the backlight light and improving the display brightness of the image. It becomes.

Hereinafter, reference example of the first invention will be described in detail with FIGS. 1-8, the same reference numerals are given to the prior art the same parts described above, a description thereof will be omitted. Here, FIG. 1 is a functional block diagram illustrating the substantial part of a liquid crystal display device of the reference example, FIG. 2 is a schematic perspective view for explaining an optical shutter in the liquid crystal display device of the reference example, FIG. 3 of the reference example It is explanatory drawing for demonstrating the display operation principle in a liquid crystal display device.

4 is a schematic side sectional view for explaining a state in which the upper part of the screen in the liquid crystal display device of the reference example is an image display region, and FIG. 5 is a state in which the lower part of the screen in the liquid crystal display device of the reference example is an image display region. schematic cross-sectional view for explaining a 6 is an explanatory diagram for explaining another example of the display operation principle of the liquid crystal display device of the reference example, FIG. 7 is hidden image the entire screen of the liquid crystal display device of reference example FIG. 8 is a schematic sectional side view for explaining a state where the entire screen in the liquid crystal display device of the reference example is used as an image display region.

As shown in FIG. 1, the liquid crystal display device of this reference example is provided between an active matrix transmissive liquid crystal display panel 1 and a direct backlight light source 3 disposed on the back surface of the liquid crystal display panel 1. In addition, an optical shutter 17 capable of switching transmission / reflection of backlight light is provided for each of a plurality of divided light emitting areas by the shutter driving unit 18. The shutter drive unit 18 is driven and controlled by the control CPU 6 based on the synchronization signal extracted from the input image signal by the synchronization signal extraction unit 4.

Here, as shown in FIG. 2, the optical shutter 17 in the present reference example is composed of a plurality of thin plate-like reflecting members, one of which is a light reflecting surface and the other surface is a light absorbing surface. Are arranged so that their longitudinal directions are parallel to the scanning line direction of the liquid crystal display panel 1. Further, the reflection member of the optical shutter 17 is rotatably provided so that the longitudinal direction thereof coincides with the rotation axis direction, and is provided for each of the plurality of reflection members corresponding to each divided display region of the liquid crystal display panel 1. Independently, the rotation state can be electrically controlled.

  That is, the optical shutter 17 not only can transmit the backlight light and irradiate the image display area of the liquid crystal display panel 1 according to the rotation state of the reflecting member, but also the backlight by the reflecting member. By reflecting the light, the light directed to the image non-display area of the liquid crystal display panel 1 is blocked, and the reflected light is condensed on the image display area, thereby increasing the backlight light that irradiates the image display area. Thus, it is possible to improve the utilization efficiency of the backlight light.

In this reference example , in order to simplify the description, the number of divided display areas of the liquid crystal display panel 1 is set to 2, and the image display period and the image non-display period are repeated in one frame period for each screen area. Now, a description will be given of what realizes a pseudo-impulse display with an impulse rate (the ratio of an image display period within one frame period) of 50%, but the number of divided display areas of the liquid crystal display panel 1 is arbitrarily set to 3 or more. Needless to say, the numbers are good. As the backlight light source 3, in addition to a direct fluorescent lamp, a direct or side illumination LED light source, an EL light source, and the like can be used.

Next, as shown in FIG. 3, the liquid crystal display device according to the present reference example displays one frame to be displayed in one frame period (for example, 16.7 msec in the case of 60 Hz progressive scan) over the entire screen of the liquid crystal display panel 1. The image signal is written and scanned. The backlight light source 3 is always lit (continuous light emission) regardless of the image writing scan.

  Here, when the image writing scan of the upper half of the screen is completed, as shown in FIG. 4, the reflection corresponding to the area so that the optical shutter 17 corresponding to the display area of the upper half of the screen is in the transmission state. While rotating the member, the reflecting member corresponding to the area is rotated so that the optical shutter 17 corresponding to the display area in the lower half of the screen is in a reflection (light-shielding) state. As a result, it is possible to irradiate only the image display area in the upper half of the screen of the liquid crystal display panel 1 with the backlight, so that the lower half of the screen of the liquid crystal display panel 1 becomes an image non-display area.

  At this time, the backlight light totally reflected by the reflecting member corresponding to the lower half area of the liquid crystal display panel 1 is reflected again by the reflecting plate 3a provided in the backlight light source 3 and is directed to the liquid crystal display panel 1 side. Since it heads, it can concentrate on an image display area. As a result, the utilization efficiency of the backlight light can be increased, and the image display brightness in the image display area can be improved.

  Similarly, when the image writing scan of the lower half of the screen is completed, as shown in FIG. 5, the reflection corresponding to the area is so arranged that the optical shutter 17 corresponding to the display area of the lower half of the screen is in the transmission state. While rotating the member, the reflecting member corresponding to the area is rotated so that the optical shutter 17 corresponding to the display area on the upper half of the screen is in a reflecting (light-shielding) state. As a result, only the image display area in the lower half of the screen of the liquid crystal display panel 1 is irradiated with the backlight, and the upper half of the screen of the liquid crystal display panel 1 can be set as an image non-display area.

  Here again, the backlight light totally reflected by the reflecting member corresponding to the upper half area of the liquid crystal display panel 1 is reflected again by the reflecting plate 3 a provided in the backlight light source 3 and is directed to the liquid crystal display panel 1 side. Since it heads, it can concentrate on an image display area. As a result, the utilization efficiency of the backlight light can be increased, and the image display luminance in the image display region can be improved.

As described above, according to the present reference example , the image non-display is performed by movably controlling the reflecting member of the optical shutter 17 corresponding to each divided display area of the liquid crystal display panel 1 in accordance with the synchronization signal of the input image signal. Since the backlight light emitted from the light emitting area corresponding to the area can be reflected by the optical shutter 17 and condensed on the image display area, the backlight light from the backlight light source 3 is effective for image display. This makes it possible to improve the display brightness of the image by increasing the light utilization efficiency. Here, by providing a light diffusion sheet between the optical shutter 17 and the liquid crystal display panel 1, it is possible to prevent the occurrence of uneven brightness on the screen due to the reflecting member.

  In the above example, immediately after the image writing scan of a certain horizontal line group (divided display area) is completed, the divided display area is irradiated with backlight light without considering the response time of the liquid crystal. Although the display is performed, the timing for driving the optical shutter 17 may be controlled in consideration of the response time of the liquid crystal.

  For example, as shown in FIG. 6, after the image writing scanning of a certain horizontal line group (divided display area) is completed, the divided display is performed after being delayed by the response time of the liquid crystal (here, 1/8 frame period). By driving the reflecting member of the optical shutter 17 corresponding to the area to the transmissive state, it is possible to display a good image without uneven brightness on the screen due to incomplete response of the liquid crystal.

  In this case, there is a period in which all the divided display areas, that is, the entire screen area are in the non-display state of the image. In this period, as shown in FIG. 7, all the reflecting members constituting the optical shutter 17 are reflected. What is necessary is just to rotate to a (light-shielding) state. Further, since backlight light is not used in any of the divided display areas during this period, the backlight light source 3 may be turned off to reduce power consumption.

  When all the divided display areas, that is, the entire screen area are set to the image display state, as shown in FIG. 8, all the reflection members constituting the optical shutter 17 may be rotated to the transmission state. Needless to say. However, in this state, since there is no image non-display area, it is not possible to perform the condensing action of the backlight light on the image display area due to the reflection of the optical shutter 17, and the display brightness of the image is reduced. It is necessary to increase the luminance of the backlight light source 3 itself.

Next, in the above-described reference example , the description has been given of the one that mechanically switches the transmission / reflection of the backlight light to each divided display region of the liquid crystal display panel 1, but this may be performed optically. Will be described in detail below.

The first embodiment of the present invention will be described in detail with reference to FIGS. 9 to 13, but the same parts as those in the reference example described above are denoted by the same reference numerals, and the description thereof will be omitted. Here, FIG. 9 is an explanatory diagram for explaining a display operation principle in the liquid crystal display device of the present embodiment, and FIG. 10 is a schematic perspective view for explaining an optical shutter in the liquid crystal display device of the present embodiment.

  FIG. 11 is a schematic sectional side view for explaining a state in which the central portion of the screen in the liquid crystal display device of the present embodiment is an image non-display region, and FIG. 12 is a diagram illustrating the lower portion of the screen in the liquid crystal display device of the present embodiment. FIG. 13 is a schematic side sectional view for explaining a state where the upper part of the screen in the liquid crystal display device of the present embodiment is an image non-display area.

  In the liquid crystal display device of this embodiment, an optical shutter 27 using dynamic scattering liquid crystal is provided between the liquid crystal display panel 1 and the backlight light source 3 as an optical shutter for switching between transmission / reflection of backlight light. In addition, a shutter drive unit 28 for electrically switching and controlling the transmission / reflection modes of the optical shutter 27 in units of areas corresponding to the divided display areas of the liquid crystal display panel 1 is provided.

  In the present embodiment, in order to simplify the description, the number of divided display areas of the liquid crystal display panel 1 is set to 3, and the image display period and the image non-display period are repeated in one frame period for each screen area. Now, as shown in FIG. 9, a description will be given of a case where the pseudo-impulse type display is realized by shortening the image display period of each divided display area to 2/3 frame period. It is clear that the number of areas is not limited to this.

  The optical shutter 27 in the present embodiment is, for example, as shown in FIG. 10, in which a transparent polymer film in which microcapsules encapsulating nematic liquid crystals are dispersed is sandwiched between two polyester films with a transparent conductive film, The application of voltage is arbitrarily controlled for each of the regions (1) to (3) corresponding to the divided display regions of the liquid crystal display panel 1, and the transmission / reflection of the backlight light is switched. The applied voltage can be AC driven to prevent the life of the liquid crystal material from deteriorating.

That is, in the optical shutter 27, when no voltage is applied, the liquid crystals represented as rod-like molecules are arranged along the inner wall of the microcapsule. Birefringence causes refraction and scattering on the surface and inside of the microcapsule. Further, when a voltage is applied, the liquid crystal molecules try to line up parallel to the direction in which the voltage is applied, and thus are aligned perpendicular to the electrodes. In this state, if the liquid crystal has a refractive index that matches that of the polymer, the liquid crystal is equivalent to the absence of the microcapsule interface, and the incident light is transmitted without being scattered.

As such a dynamic scattering liquid crystal sheet, for example, Um film (trade name) manufactured by Nippon Sheet Glass Um Products Co., Ltd. is known, and if this Um film is used, reflection (scattering) state to transmission is about 1 / The transmission / reflection (scattering) state is 1000 seconds, and the transmission / reflection mode in a predetermined region can be switched at a speed of about 1/100 second. Since this type of liquid crystal material is usually vulnerable to high heat, it is desirable to dispose it at a position that does not directly contact the backlight source 3 (for example, in the case of a side-illuminated backlight, on the liquid crystal display panel side of the light guide plate).

  Next, the operation of the liquid crystal display device of this embodiment will be described. When the image writing scanning of the upper part (1/3) of the liquid crystal display panel 1 is completed, as shown in FIG. 11, the optical shutter 27 corresponding to the divided display areas at the upper and lower parts of the screen is in a transmissive state. In addition, while applying a voltage to the dynamic scattering liquid crystal corresponding to the region, the dynamic shutter corresponding to the region is reflected (scattered) so that the optical shutter 27 corresponding to the divided display region in the center of the screen is in a reflection (scattering) state. Stop application of voltage to the scattering liquid crystal. As a result, the backlight light is irradiated only to the upper (1/3) and lower (1/3) screen display areas of the liquid crystal display panel 1, and the other screen center (1/3) is not displayed. Can be an area.

  At this time, the backlight light reflected by the dynamic scattering liquid crystal corresponding to the divided display area located at the center of the screen of the liquid crystal display panel 1 is reflected again by the reflector 3 a provided in the backlight light source 3 and is liquid crystal. Since it goes to the display panel 1 side, it can concentrate on the image display area located in the upper and lower parts of the screen of the liquid crystal display panel 1. As a result, the utilization efficiency of the backlight light can be increased, and the image display brightness in the image display area can be improved.

  Further, when the image writing scanning at the center (1/3) of the screen is completed, as shown in FIG. 12, the optical shutter 27 corresponding to the divided display areas at the top and center of the screen is in a transmissive state. In addition to applying a voltage to the dynamic scattering liquid crystal corresponding to the region, the dynamic scattering liquid crystal corresponding to the region so that the optical shutter 27 corresponding to the divided display region at the bottom of the screen is in a reflective (light-shielding) state. Stop applying voltage to. As a result, the backlight is irradiated only on the image display areas of the upper part (1/3) and the central part (1/3) of the liquid crystal display panel 1, and the lower part (1/3) of the other screen is not displayed. Can be an area.

  Here again, the backlight light reflected by the dynamic scattering liquid crystal corresponding to the divided display region located at the lower part of the screen of the liquid crystal display panel 1 is reflected again by the reflecting plate 3a provided in the backlight light source 3, and the liquid crystal display Since it goes to the panel 1 side, it can concentrate on the image display area located in the upper part and center part of the screen of the liquid crystal display panel 1. As a result, the utilization efficiency of the backlight light can be increased, and the image display luminance in the image display region can be improved.

  Similarly, when the image writing scan at the lower part of the screen is completed, as shown in FIG. 13, the optical shutter 27 corresponding to the central display part and the lower divided display area corresponds to the corresponding area. The voltage is applied to the dynamic scattering liquid crystal to be applied, and the voltage is applied to the dynamic scattering liquid crystal corresponding to the region so that the optical shutter 27 corresponding to the divided display region at the upper part of the screen is in a reflection (light-shielding) state. To stop. As a result, the backlight is irradiated only on the image display areas at the center (1/3) and the center (1/3) of the screen of the liquid crystal display panel 1, and the upper part (1/3) of the other screen is imaged. It can be a non-display area.

  Here again, the backlight light reflected by the dynamic scattering liquid crystal corresponding to the divided display region located at the upper part of the screen of the liquid crystal display panel 1 is reflected again by the reflector 3 a provided in the backlight light source 3 to be displayed on the liquid crystal display. Since it goes to the panel 1 side, the liquid crystal display panel 1 can be focused on the image display area located at the center and lower part of the screen. As a result, the utilization efficiency of the backlight light can be increased, and the image display luminance in the image display region can be improved.

  As described above, according to the present embodiment, image non-display is performed by switching the voltage application of the optical shutter 27 corresponding to each divided display area of the liquid crystal display panel 1 in accordance with the synchronization signal of the input image signal. Since the backlight light emitted from the light emitting area corresponding to the area can be reflected by the optical shutter 27 and condensed on the image display area, the backlight light from the backlight light source 3 is effective for image display. This makes it possible to improve the display brightness of the image by increasing the light utilization efficiency.

  In the above-described embodiment, the liquid crystal response time is not taken into account, and the divided display area is irradiated with backlight immediately after the image writing scan of a certain horizontal line group (divided display area) is completed. Although image display is performed, it goes without saying that the timing for driving the optical shutter 27 may be controlled in consideration of the response time of the liquid crystal.

In the first embodiment, the backlight light corresponding to the image non-display area of the liquid crystal display panel 1 is reflected (shielded) by utilizing the light scattering action of the dynamic scattering liquid crystal. About half of the backlight is transmitted to the image non-display area of the liquid crystal display panel 1 and cannot be completely reflected (shielded), and is condensed on the image display area of the liquid crystal display panel 1. The efficiency is also low. What improves the light collection efficiency of the backlight light to the image display area will be described in detail below.

The second embodiment of the present invention will be described in detail with reference to FIGS. 14 to 19, but the same parts as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted. Here, FIG. 14 is a schematic perspective view for explaining an example of the optical shutter in the liquid crystal display device of the present embodiment, and FIG. 15 explains the operation principle of the optical shutter for the image display area in the liquid crystal display device of the present embodiment. FIG. 16 is a schematic sectional side view for explaining the operation principle of the optical shutter for the image non-display area in the liquid crystal display device of this embodiment.

  FIG. 17 is a schematic perspective view for explaining another example of the optical shutter in the liquid crystal display device of the present embodiment, and FIG. 18 explains the operation principle of the optical shutter for the image display area in the liquid crystal display device of the present embodiment. FIG. 19 is a schematic sectional side view for explaining the operation principle of the optical shutter for the image non-display area in the liquid crystal display device of the present embodiment.

As shown in FIG. 14, the optical shutter 37 in the present embodiment is a two sheet that reflects linearly polarized light in a specific direction and transmits linearly polarized light in a direction orthogonal to the dynamic scattering liquid crystal described above as the first embodiment. Each of the regions (1) to (3) in the dynamic scattering liquid crystal corresponding to the divided display region of the liquid crystal display panel 1 is sandwiched between the reflective polarizing sheets (light polarization selective reflection / transmission sheet). The application of voltage is controlled, and the transmission / reflection of backlight light is switched.

Here, the reflective polarizing sheet on the backlight light source 3 side and the reflective polarizing sheet on the liquid crystal display panel 1 side are arranged so that their transmission polarization axis directions are perpendicular to each other, that is, the backlight light source. The reflective polarizing sheet on the third side transmits P-polarized light and reflects S-polarized light, and the reflective polarizing sheet on the liquid crystal display panel 1 side transmits S-polarized light and reflects P-polarized light.

  As described above, as the reflective polarizing sheet having the property of transmitting the light of the polarization direction component in the direction parallel to the polarization transmission axis and reflecting the light of the polarization direction component perpendicular to the polarization transmission axis, for example, DBEF (product name) manufactured by Sumitomo 3M Limited can be used.

  Next, the operation of the liquid crystal display device of this embodiment will be described. When irradiating backlight light to the image display area of the liquid crystal display panel 1, as shown in FIG. 15, the application of voltage to the dynamic scattering liquid crystal is turned off to make the dynamic scattering liquid crystal in a scattering state. Therefore, the backlight having the P-polarized light transmitted through the reflective polarizing sheet on the backlight source 3 side is converted into circularly polarized light by the dynamic scattering liquid crystal, and only the S-polarized light is reflected on the liquid crystal display panel 1 side. While passing through the sheet, the P-polarized light is reflected by the reflective polarizing sheet on the liquid crystal display panel 1 side and reenters the dynamic scattering liquid crystal.

  On the other hand, the backlight light having S-polarized light reflected by the reflective polarizing sheet on the backlight source 3 side is reflected by the reflecting plate 3a of the backlight light source 3 to become P-polarized light, and the reflective polarizing sheet on the backlight light source 3 side. Is then input to the dynamic scattering liquid crystal and converted to circularly polarized light. As described above, in this state, it is possible to irradiate the image display area of the liquid crystal display panel 1 with the backlight that has passed through the reflective polarizing sheet on the liquid crystal display panel 1 side.

  Further, when the backlight for the image non-display area of the liquid crystal display panel 1 is shielded, as shown in FIG. 16, the application of voltage to the dynamic scattering liquid crystal is turned on so that the dynamic scattering liquid crystal is in a transmissive state. To do. Therefore, the backlight light having P-polarized light that has passed through the reflective polarizing sheet on the backlight light source 3 side passes through the dynamic scattering liquid crystal as it is, and is reflected by the reflective polarizing sheet on the liquid crystal display panel 1 side. Re-enters the scattering liquid crystal.

  On the other hand, the backlight light having S-polarized light reflected by the reflective polarizing sheet on the backlight source 3 side is reflected by the reflecting plate 3a of the backlight light source 3 to become P-polarized light, and the reflective polarizing sheet on the backlight light source 3 side. And then enters the dynamic scattering liquid crystal. As described above, in this state, the backlight light for the image non-display area of the liquid crystal display panel 1 can be blocked almost completely.

  At this time, the backlight light reflected by the reflective polarizing sheet corresponding to the image non-display area of the liquid crystal display panel 1 is reflected again by the reflector 3 a provided in the backlight light source 3 and is then reflected on the liquid crystal display panel 1. Since it goes to the side, it can concentrate on the image display area of the liquid crystal display panel 1. As a result, the utilization efficiency of the backlight light can be increased, and the image display brightness in the image display area can be improved.

  In the example of the present embodiment (optical shutter 37), the two reflection-type polarizing sheets are arranged so that the transmission polarization axis directions thereof are perpendicular to each other, so that the image of the liquid crystal display panel 1 is not imaged. The backlight light for the display area can be almost completely shielded, and a good impulse type display is possible. However, the transmittance of the backlight light to the image display area of the liquid crystal display panel 1 (the effective utilization ratio of the backlight light) ) Is slightly lower.

  Therefore, in order to improve the transmittance of the backlight light to the image display area of the liquid crystal display panel 1 (effective utilization ratio of the backlight light), as shown in FIG. What is necessary is just to arrange | position a reflection-type polarizing sheet so that the transmission polarization axis direction may become mutually parallel. The optical shutter 47 provided with two reflective polarizing sheets having such an arrangement relationship will be described below.

  That is, when irradiating the image display area of the liquid crystal display panel 1 with backlight light, as shown in FIG. 18, the application of voltage to the dynamic scattering liquid crystal is turned on to bring the dynamic scattering liquid crystal into a transmission state. Accordingly, the backlight having the P-polarized light that has passed through the reflective polarizing sheet on the backlight source 3 side passes through the dynamic scattering liquid crystal as it is, and then also passes through the reflective polarizing sheet on the liquid crystal display panel 1 side. The display panel 1 is irradiated.

  On the other hand, the backlight light having S-polarized light reflected by the reflective polarizing sheet on the backlight source 3 side is reflected by the reflecting plate 3a of the backlight light source 3 to become P-polarized light, and the reflective polarizing sheet on the backlight light source 3 side. And then enters the dynamic scattering liquid crystal. As described above, in this state, it is possible to transmit the backlight light almost completely and irradiate the image display area of the liquid crystal display panel 1.

  Further, when the backlight for the image non-display area of the liquid crystal display panel 1 is shielded, as shown in FIG. 19, the application of the voltage to the dynamic scattering liquid crystal is turned off so that the dynamic scattering liquid crystal is in the scattering state. To do. Therefore, the backlight having the P-polarized light transmitted through the reflective polarizing sheet on the backlight source 3 side is converted into circularly polarized light by the dynamic scattering liquid crystal, and only the S-polarized light is reflected on the liquid crystal display panel 1 side. While passing through the sheet, the P-polarized light is reflected by the reflective polarizing sheet on the liquid crystal display panel 1 side and reenters the dynamic scattering liquid crystal.

  On the other hand, the backlight light having S-polarized light reflected by the reflective polarizing sheet on the backlight source 3 side is reflected by the reflecting plate 3a of the backlight light source 3 to become P-polarized light, and the reflective polarizing sheet on the backlight light source 3 side. And then enters the dynamic scattering liquid crystal. As described above, in this state, it is possible to reduce the backlight light for the image non-display area of the liquid crystal display panel 1.

  At this time, the backlight light reflected by the reflective polarizing sheet corresponding to the image non-display area of the liquid crystal display panel 1 is reflected again by the reflector 3 a provided in the backlight light source 3 and is then reflected on the liquid crystal display panel 1. Since it goes to the side, it can concentrate on the image display area of the liquid crystal display panel 1. As a result, the utilization efficiency of the backlight light can be increased, and the image display brightness in the image display area can be improved.

  Here, since the above-mentioned reflective polarizing sheet has a different coefficient of thermal expansion depending on the direction of the transmission polarization axis, when the two reflection type polarization sheets are arranged so that the transmission polarization axis directions thereof are perpendicular to each other, Due to the difference in shape between the two, at least one of the two may be bent or wrinkled, resulting in uneven brightness. However, as in the other examples in the present embodiment, two reflective polarized lights By arranging the sheets so that their transmission polarization axis directions are parallel to each other, the shape changes of both are the same, and it is possible to flexibly cope with heat.

  As described above, in another example of the present embodiment, two reflective polarizing sheets are arranged so that their transmission polarization axis directions are parallel to each other, thereby displaying an image on the liquid crystal display panel 1. Although the backlight light for the area can be transmitted almost completely and the image display luminance can be improved, the degree of the light shielding of the backlight light for the image non-display area of the liquid crystal display panel 1 is slightly lowered. For such backlight leakage in the image non-display area, a black display signal is supplied to the image non-display area of the liquid crystal display panel 1 to realize complete image non-display (black display). This is possible and will be described in detail below.

The third embodiment of the present invention will be described in detail with reference to FIGS. 20 to 22, but the same parts as those of the second embodiment described above are denoted by the same reference numerals, and the description thereof is omitted. Here, FIG. 20 is a functional block diagram showing a schematic configuration of the main part of the liquid crystal display device of the present embodiment, FIG. 21 is a timing chart showing an operation example of each part of the liquid crystal display device of the present embodiment, and FIG. It is explanatory drawing for demonstrating the display operation principle in a liquid crystal display device.

  As shown in FIG. 20, in the liquid crystal display device of the present embodiment, when the liquid crystal display panel 1 is divided into N in the vertical direction to form each divided display region, the frame frequency of the input image signal is multiplied by (N−1) times. A frame frequency converting unit 51 for converting to a black signal, a black signal generating unit 52 for generating a black display signal with a fixed black level, and an image signal converted by the frame frequency converting unit 51 and the black signal generating unit 52 A signal switching unit 53 (black insertion unit) that switches and outputs a black display signal based on a control signal from the control CPU 56 is provided.

  Here, the frame frequency conversion unit 51 includes, for example, a frame memory. After the image for one frame of the input image signal is stored in the frame memory, based on the control signal from the control CPU 56 (N− 1) An image signal in which the frame display period (vertical display period) for the liquid crystal display panel 1 is time-axis-compressed to 1 / (N-1) by repeatedly reading the image signal (N-1) times at a double frame frequency. Is output.

Here, in order to simplify the description, the number of divided display areas of the liquid crystal display panel 1 is set to 3, and as shown in FIG. 21B, the image signal is read out twice at a double frame frequency (120 Hz). Thus, a description will be given of outputting an image signal whose time axis is compressed to 1/120 second (8.3 msec) for the frame display period (vertical display period) for the liquid crystal display panel 1. Needless to say, the number N may be an arbitrary number.

Further, as shown in FIG. 21 (c), the signal switching unit 10 performs image non-display on the liquid crystal display panel 1 based on the control signal from the control CPU 56 as shown in FIG. A black display signal is inserted during a period in which writing scanning is performed on the display area, and is output to the electrode driver 2. As shown in FIG. 22, the electrode drive unit 2 outputs the image signal and black display signal in each vertical display period within one scanning period (1/2 frame period = 8.3 msec) with respect to the entire screen of the liquid crystal display panel 1. Write scan. That is, the entire screen of the liquid crystal display panel 1 is scanned twice within one frame period (16.7 msec) of the input image signal to display an image.

  As described above, according to the liquid crystal display device of the present embodiment, in the image non-display period in which the optical shutter 47 is in the light shielding (scattering) state, it corresponds to the optical shutter 47 in the light shielding (scattering) state. The black display signal can be supplied to the non-display area of the liquid crystal display panel 1, so that even if the backlight light leaks from the optical shutter 47 to the image non-display area, the black display signal is completely black. Display can be performed, and a good impulse-type display can be realized.

It is a functional block diagram which shows the principal part schematic structure in the reference example of the liquid crystal display device of this invention. It is a schematic perspective view for demonstrating the optical shutter in the reference example of the liquid crystal display device of this invention. It is explanatory drawing for demonstrating the display operation principle in the reference example of the liquid crystal display device of this invention. It is a schematic sectional side view for demonstrating the state which made the upper part of the screen the image display area in the reference example of the liquid crystal display device of this invention. It is a schematic sectional drawing for demonstrating the state which made the screen lower part the image display area in the reference example of the liquid crystal display device of this invention. It is explanatory drawing for demonstrating the other example of the display operation principle in the reference example of the liquid crystal display device of this invention. It is a schematic sectional side view for demonstrating the state which made the whole screen in the reference example of the liquid crystal display device of this invention the image non-display area | region. It is a schematic sectional side view for demonstrating the state which made the whole screen in the reference example of the liquid crystal display device of this invention the image display area. It is explanatory drawing for demonstrating the display operation principle in 1st Embodiment of the liquid crystal display device of this invention. It is a schematic perspective view for demonstrating the optical shutter in 1st Embodiment of the liquid crystal display device of this invention. It is a schematic sectional side view for demonstrating the state which made the center part of the screen the image non-display area | region in 1st Embodiment of the liquid crystal display device of this invention. Is a schematic side sectional view for explaining a state in which the bottom of the screen the image non-display area in the first embodiment form status of the liquid crystal display device of the present invention. It is a schematic sectional side view for demonstrating the state which made the upper part of the screen the image non-display area | region in 1st Embodiment of the liquid crystal display device of this invention. It is a schematic perspective view for demonstrating an example of the optical shutter in 2nd Embodiment of the liquid crystal display device of this invention. It is a schematic sectional side view for demonstrating the operation principle with respect to the image display area | region of an example of the optical shutter in 2nd Embodiment of the liquid crystal display device of this invention. It is a schematic sectional side view for demonstrating the operation | movement principle with respect to the image non-display area | region of an example of the optical shutter in 2nd Embodiment of the liquid crystal display device of this invention. It is a schematic perspective view for demonstrating the other example of the optical shutter in 2nd Embodiment of the liquid crystal display device of this invention. It is a schematic sectional side view for demonstrating the operation principle with respect to the image display area of the other example of the optical shutter in 2nd Embodiment of the liquid crystal display device of this invention. It is a schematic sectional side view for demonstrating the operation principle with respect to the image non-display area | region of the other example of the optical shutter in 2nd Embodiment of the liquid crystal display device of this invention. It is a functional block diagram which shows the principal part schematic structure in 3rd Embodiment of the liquid crystal display device of this invention. It is a timing chart which shows the operation example of each part in 3rd Embodiment of the liquid crystal display device of this invention. It is explanatory drawing for demonstrating the display operation principle in 3rd Embodiment of the liquid crystal display device of this invention. It is a functional block diagram which shows the principal part schematic structure in the conventional liquid crystal display device (scanning type backlight lighting system). It is explanatory drawing for demonstrating the display operation principle in the conventional liquid crystal display device (scanning type backlight lighting system). It is a schematic sectional side view for demonstrating the conventional liquid crystal display device (scanning optical shutter system).

DESCRIPTION OF SYMBOLS 1 Liquid crystal display panel 2 Electrode drive part 3 Backlight light source 4 Light source drive part 5 Synchronization signal extraction part 6, 56 Control CPU
17, 27, 37, 47 Optical shutter 18, 28 Shutter drive unit 51 Frame frequency conversion unit 52 Black signal generation unit 53 Signal switching unit

Claims (6)

A liquid crystal display device that displays an image by irradiating a liquid crystal display panel using a backlight light source,
By transmitting / blocking backlight light from the backlight light source to each divided display area of the liquid crystal display panel, the backlight light is transmitted to each divided display area of the liquid crystal display panel within one vertical period. Optical shutter means for supplying intermittently;
A shutter drive unit for controlling the optical shutter means;
The optical shutter means is configured using a dynamic scattering liquid crystal that reflects at least a part of the backlight light to the backlight light source side when the backlight light is blocked .
The shutter driving unit, said optical shutter means modes of the transmission / reflection of a liquid crystal display device comprising that you switch control in region units corresponding to each divided display area of the liquid crystal display panel. The liquid crystal display device according to claim 1,
The liquid crystal display device, wherein the optical shutter means is configured by providing polarization separation means on each of the backlight light source side and the liquid crystal display panel side of the dynamic scattering liquid crystal. The liquid crystal display device according to claim 2,
Each of the polarization separation means is disposed such that the polarization axis directions thereof are perpendicular to each other. The liquid crystal display device according to claim 2,
Each of the polarization separation means is disposed so that the polarization axis directions thereof are parallel to each other. In the liquid crystal display device according to any one of claims 1 to 4,
A liquid crystal display device, wherein a black display signal is supplied to a divided display area of a liquid crystal display panel corresponding to the optical shutter means during a period in which the optical shutter means blocks backlight light. The liquid crystal display device according to claim 5,
A frame frequency conversion means for converting the frame frequency of the input image signal to (N-1) times, where N is the number of divided display areas;
A liquid crystal display device, comprising: black insertion means for switching and outputting the image signal having the frame frequency converted and the black display signal at a predetermined timing.

Images