JP4082198B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device that performs color display by sequentially switching light applied to a liquid crystal panel surface in time series with red light, green light, and blue light.
[0002]
[Prior art]
In general, in a liquid crystal panel composed of liquid crystal and thin film transistors, pixel driving elements are arranged in a matrix at intersections of a plurality of scanning signal wirings and image signal wirings intersecting the scanning signal wirings, and pixel electrodes are formed on the surface. The liquid crystal layer is filled between an active matrix substrate and a light transmissive substrate having a light transmissive common electrode deposited on a surface facing the active matrix substrate.
[0003]
Here, an example of the configuration of the equivalent circuit of the liquid crystal panel will be described with reference to FIG. Here, a plurality of image signal lines X arranged in parallel and a plurality of scanning signal lines Y arranged in parallel are arranged so as to be orthogonal to each other, and at the intersections of the signal lines X and Y, respectively. Each pixel P is arranged as a unit pixel. In FIG. 6, i and j representing integers are written as subscripts in the symbols X, Y, and P, respectively, and pixels at arbitrary positions are generalized. The unit pixel P of the liquid crystal panel includes a transistor TR, a charge storage capacitor C, a liquid crystal layer LC, and the like. The liquid crystal layer LC is common to each pixel P. As described above, it is possible to form a screen by arranging the pixels P in a two-dimensional matrix and scanning in the column direction (X direction) and the row direction (Y direction).
[0004]
In general, the scanning signals are simultaneously applied to the gate terminals of the transistors TR connected to the same scanning signal line Y, and the transistors TR are turned on all at once to supply the image signals supplied via the plurality of image signal lines X. Are written as charges in the charge storage capacitor C through the source and drain of the transistor TR turned on, and the terminal voltage of the capacitor C is applied to the liquid crystal layer LC to change the alignment state of the liquid crystal molecules. A screen is formed by line-sequential scanning in which this is sequentially scanned in the row direction.
[0005]
FIG. 7 shows an example of a liquid crystal panel configured using a liquid crystal and a thin film transistor in a conventional liquid crystal display device. In the figure, a drain 2 made of polycrystalline silicon in which impurities are diffused is formed in a matrix substrate 1 and further connected to a pixel electrode 4 through an opening of an insulating layer 3. Note that a source (not shown) and a gate made of polycrystalline silicon diffused with impurities are formed on the matrix substrate 1 and constitutes a transistor together with the drain 2. A polarizing plate 5 is provided on the surface of the matrix substrate 1 opposite to the surface on which the pixel electrodes 4 are formed.
[0006]
On the other hand, a light transmissive common electrode 8 is deposited on the surface of a light transmissive substrate 6 such as ITO via a color filter 7. In the matrix substrate 1 and the light transmissive substrate 6 described above, the surface on which the pixel electrode 4 is formed and the surface on which the common electrode 8 is formed are arranged to face each other with the alignment layers 9 and 10 therebetween, and the liquid crystal is interposed therebetween. Layer 11 is filled. A polarizing plate 12 is formed on the surface of the light transmissive substrate 6 opposite to the common electrode 8. Inside the liquid crystal panel having the above-described structure, a color filter 7 in which green is diagonally arranged with 4 pixels as a unit is provided.
[0007]
A liquid crystal display device formed using a liquid crystal panel is shown in FIG. The liquid crystal display device includes a liquid crystal panel 15, a liquid crystal panel drive circuit 16, and a light source 17 that irradiates the liquid crystal panel 15. The liquid crystal panel 15 has the configuration shown in FIG. In this liquid crystal display device, many pixels are formed on the liquid crystal panel 16, and the resolution is determined by the number of pixels.
[0008]
FIG. 9 shows the pixel positions and display colors of the liquid crystal panel 15. Green is displayed at the pixel position (A) and the diagonal pixel position (C), blue is displayed at the pixel position (B), and red is displayed at the pixel position (D). As described above, when displaying four pixels as one unit, it is generally known from a display method of a plasma display panel (PDP) that the resolution can be increased by arranging green with high visibility on the diagonal. .
[0009]
[Problems to be solved by the invention]
In the conventional liquid crystal display device, as shown in FIG. 9, there is known a technique for increasing the resolution with a color filter in which green display pixels are diagonally arranged with 4 pixels as one unit. In order to increase the resolution by providing each pixel for green and blue, since 4 pixels are used as one unit, there are problems that the liquid crystal panel becomes large and the manufacturing yield is remarkably reduced.
[0010]
The present invention has been made in view of the above points, and provides a liquid crystal display device capable of easily realizing high-definition color display without increasing the size of the liquid crystal panel and suppressing the driving frequency to be low. For the purpose.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has pixels arranged in a matrix at intersections of a plurality of scanning signal wirings parallel to each other and a plurality of image signal wirings orthogonal to the scanning signal wirings. An active matrix substrate having electrodes formed thereon, a light transmissive electrode substrate having a light transmissive common electrode formed on a surface opposite to the surface of the active matrix substrate, and the active matrix substrate and the light transmissive electrode substrate A liquid crystal panel having a liquid crystal layer sandwiched between the light source, a light source that irradiates the liquid crystal panel with a selected primary color light of red light, green light, and blue light, and at least one or more sheets A pixel shift element that includes a liquid crystal cell and at least one birefringent plate, and that shifts the display pixel position of the primary color light of each pixel incident from the liquid crystal panel based on an external drive signal; The image data of the three primary colors red, green, and blue supplied to the liquid crystal panel are scanned while sequentially switching in a predetermined primary color order and in a predetermined time unit, and the light source is driven in synchronization with the liquid crystal. The primary color light irradiating the panel surface is applied to the liquid crystal cell of the pixel shift element in synchronization with the first drive circuit that switches sequentially in time series in the same order as the primary color order of the image data and switching of the image data and the light source. And a second drive circuit that sequentially switches the display pixel position of the primary color light of each pixel incident from the liquid crystal panel. Here, in the present invention, the second driving circuit is configured such that the first pixel out of the total of four pixels including the first to fourth pixels adjacent to each other in the horizontal direction and the vertical direction is a green image, A second display pixel that is adjacent to the first pixel in the vertical direction or the horizontal direction has an image of one primary color of red and blue, an image of the other primary color, and a diagonal position of the first display pixel. The green image is displayed on the third display pixel, and the fourth display pixel adjacent to the third display pixel and the first display pixel is sequentially displayed in order of one primary color image and the other primary color image of red and blue. In this way, the display pixel position by the pixel shift element is switched.
[0012]
In the present invention, the image data of the three primary colors supplied to the liquid crystal panel are scanned while being switched sequentially in a predetermined primary color order and in a predetermined time unit, and the light source is driven in synchronism with this to scan the liquid crystal panel surface. The primary color light emitted to the pixel is sequentially switched in time series in the same order as the primary color order of the image data, and the primary color light of each pixel incident from the liquid crystal panel is synchronized with the switching of the image data and the light source by the pixel shift element. because the display has been to sequentially switch the pixel position of, for you to display having high visibility green pixel diagonal and improve the resolution.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an embodiment of a liquid crystal display device according to the present invention. In the figure, the liquid crystal display device includes a liquid crystal panel 21, a light source 22 that irradiates the liquid crystal panel 21, a pixel shift element 23 that includes at least one liquid crystal cell and at least one birefringent plate. The liquid crystal panel drive circuit 24 drives the liquid crystal panel 21 and the pixel shift element drive circuit 25 drives the pixel shift element 23.
[0015]
FIG. 2 is a structural cross-sectional view of an example of a liquid crystal panel 21 configured using liquid crystals and thin film transistors. In the figure, the same components as those in FIG. 7 are denoted by the same reference numerals, and the description thereof is omitted. The liquid crystal panel 21 is the same as the conventional structure except that the liquid crystal panel 21 is different from the liquid crystal panel shown in FIG.
[0016]
The polycrystalline silicon diffused with impurities on the matrix substrate 1 constitutes the source, drain 2 and gate of the transistor constituting the pixel, and the polycrystalline silicon diffused with impurities and the metal wiring form a charge storage capacitor. Further, the pixel electrode 4 made of a metal oxide such as ITO is formed on the matrix substrate 1, and a light transmissive substrate 6 in which a light transmissive electrode such as ITO as a common electrode 8 is deposited on the opposing surface. In between, the liquid crystal layer 11 is filled through the alignment layers 9 and 10. Here, in the present embodiment, no color filter is provided between the light transmissive substrate 6 and the common electrode 8.
[0017]
FIG. 3 shows an equivalent electric circuit of one embodiment of each pixel P of the liquid crystal panel 21. Each pixel P includes a first transistor TR1, a second transistor TR2, a charge storage capacitor C, and a liquid crystal cell LC. The gate of the first transistor TR1 is connected to the scanning signal line Y, the source is connected to the image signal line X, the drain is connected to one end of the capacitor C, and the gates of the second transistors TR2 are connected to the trigger signal line Z in common. , The source is connected to one end of the capacitor C in the same pixel, and the drain is connected to the pixel electrode (liquid crystal cell LC). The liquid crystal cell LC is common to each pixel P and is constituted by the liquid crystal layer 11. In FIG. 3, i and j representing integers are written as subscripts in the symbols X, Y, and P, respectively, and pixels at arbitrary positions are generalized.
[0018]
As described above, a screen can be configured by arranging the pixels P in a two-dimensional matrix on the matrix substrate 1 and scanning in the column direction (X direction) and the row direction (Y direction). That is, a scanning signal is simultaneously applied from the liquid crystal panel driving circuit 24 to the gate terminals of the first transistors TR1 of a plurality of pixels connected to the same scanning signal line Y, and the transistors TR1 are turned on at the same time. The image signals supplied from the liquid crystal panel drive circuit 24 via the plurality of image signal lines X are simultaneously written as charges in the charge storage capacitor C through the source and drain of the first transistor TR1 that is turned on.
[0019]
This operation is sequentially advanced in units of scanning lines, and when the writing to all the scanning lines (gate electrode lines) is completed, that is, the image data is written as charges on the charge storage capacitors C of all the pixels. After that, a trigger signal is applied from the liquid crystal panel drive circuit 24 to the signal line Z that is commonly connected to the gates of the second transistors TR2 of all the pixels at the screen switching timing, and the second transistors TR2 of all the pixels. At the same time. As a result, the capacitor terminal voltage generated by the charge written in the charge storage capacitor C is simultaneously applied to the liquid crystal cell LC via the source and drain of the second transistor TR2, and the screen writing is completed. However, in this embodiment, as will be described later, pixel signals are thinned out every other pixel in both the horizontal direction and the vertical direction.
[0020]
Referring back to FIG. 1 again, the light source 22 has, for example, a red light emitting element, a green light emitting element, and a blue light emitting element. For example, red light, green light, and blue light are generated by a signal from the liquid crystal panel drive circuit 24. Can be selectively emitted. The light source 22 is not limited to the above-described configuration, and any light source 22 may be used as long as it can selectively output red light, green light, and blue light. For example, a white light source and white light from the white light source may be used. Alternatively, a mechanism provided with a rotary filter that sequentially and selectively transmits primary light of red light, green light, and blue light may be used.
[0021]
Next, the configuration and operation of the pixel shift element 23 shown in FIG. 1 will be described. FIG. 4 shows a configuration diagram of an embodiment of the pixel shift element 23. As shown in FIG. 4, the pixel shift element 23 has a configuration in which a liquid crystal cell 231, a birefringent plate 232, a liquid crystal cell 233, and a birefringent plate 234 are arranged at predetermined intervals. Here, the liquid crystal cells 231 and 233 are for controlling the polarization direction. The birefringent plates 232 and 234 are made of, for example, quartz, and the thickness is selected so that an image is displayed at a position shifted by a 1/2 pixel pitch by passing an ordinary ray and an extraordinary ray. The direction to shift is determined. Note that two liquid crystal cells and two birefringent plates are provided in FIG.
[0022]
The apparent pixel position by the pixel shift element 23 changes as shown in FIG. For example, FIG. 5 shows four square pixels PA, PB, PC, and PD. The original pixel position, that is, the pixel position when no voltage is applied to the liquid crystal cells 231 and 233 of FIG. Is assumed to be PA, the pixel PA moves by 1/2 pixel pitch with reference to this pixel PA.
[0023]
For example, when a voltage is applied only to the liquid crystal cell 231, the pixel PB is positioned on the right side of the pixel PA, and when a voltage is applied to both the liquid crystal cells 231 and 233, the pixel PC is positioned above the pixel PB. When a voltage is applied only to the liquid crystal cell 233, the pixel PD on the left side of the pixel PC is positioned.
[0024]
Next, the basic operation of the liquid crystal display device of the present embodiment shown in FIG. 1 will be described. In the above-described configuration, the light emitted from the light source 22 enters the liquid crystal panel 21, and only one polarization component is transmitted through the polarizing plate on the incident light side of the liquid crystal panel 21. It is incident on the layer (11 in FIG. 2), where it undergoes modulation according to the image signal. The modulated light is transmitted through the polarizing plate on the outgoing light side and only one polarization component is transmitted and visualized as an optical image, and then passes through the pixel shift element 23 in FIG. 1 to become an image.
[0025]
Here, the liquid crystal panel driving circuit 24 thins out the video signal of one screen every other pixel in the horizontal and vertical directions, supplies the images of these fields to the liquid crystal panel 21 and displays them, and in synchronism with the pixels, A voltage is selectively applied from the shift element driving circuit 25 to the pixel shift element 23. By selectively turning on and off the voltages applied to the two liquid crystal cells 231 and 233 of the pixel shift element 23 separately and independently, the polarization direction in each of the liquid crystal cells 231 and 233 can be changed by 90 °. Therefore, the ordinary light and the extraordinary light passing through the birefringent plates 232 and 234 can be selectively controlled. The two birefringent plates 232 and 234 can display images at four positions, two horizontal positions and two vertical positions, by making the crystal axis directions orthogonal to each other.
[0026]
FIG. 5 shows a pixel position by the pixel shift element 23 that realizes color display according to the present invention. As described above, the image signal of one screen is thinned out every other pixel in the horizontal and vertical directions by the liquid crystal panel driving circuit 24, and each is further decomposed into green, red, and blue image data. The image data is supplied to the liquid crystal panel 21 and is sequentially switched and displayed.
[0027]
At the same time, the liquid crystal panel drive circuit 24 controls each color light emitting element of the light source 22 so that the light irradiating the liquid crystal panel 21 in synchronization with the screen rewriting is sequentially converted into green light and red light. Switch between light and blue light. In synchronization with this, voltages are selectively applied to the two liquid crystal cells 231 and 233 of the pixel shift element 23 individually.
[0028]
At this time, if all the green, red, and blue image data are displayed on the four-position shifting pixels PA, PB, PC, and PD, respectively, 12 times faster driving is required than the conventional liquid crystal panel. That is, the green, red, and blue image data are sequentially switched and displayed on the pixel PA, and similarly, the three image data of green, red, and blue are sequentially switched and displayed on each of the pixels PB, PC, and PD. When shifting from one pixel to the next pixel, it is not practical because a high-speed drive of 12 times is required to go around the four pixels PA, PB, PC, and PD.
[0029]
Therefore, in the present embodiment, first, green image data is displayed at the position of the pixel PA, then red and blue image data are sequentially switched and displayed at the position of the pixel PB, and then green at the position of the pixel PC. The image data is then displayed, and then the red and blue image data are sequentially switched and displayed at the position of the pixel PD, and then the image is displayed such that it returns to the position of the original pixel PA. On the entire screen, the image display in units of these four pixels is performed in parallel. Therefore, according to the display method of the present embodiment, the four pixels PA, PB, PC, and PD are rotated at a speed that is six times faster than that of the conventional liquid crystal panel, and green with high visibility is diagonally displayed. A high resolution can be obtained by displaying the image on the pixels PA and PC.
[0030]
According to the liquid crystal display device of the present embodiment, an afterimage corresponding to each color light is synthesized on a human retina and recognized as a color image, so that a color filter is unnecessary, and red, green, and blue are formed with a single pixel. By displaying all the colors and arranging the green image display pixels diagonally, high resolution can be obtained even in color display.
[0031]
In the above embodiment, the positions of the pixels are shifted in the order of PA → PB → PC → PD. However, the order may be any order, and the image is displayed in the order of green → red → blue. However, this order is not limited to the order described above. Although the liquid crystal panel has been described as being a transmissive type, it goes without saying that the liquid crystal panel can be realized without any change in the concept of the present invention even if it is a reflective type.
[0032]
【The invention's effect】
As described above, according to the present invention, the image data of the three primary colors to be supplied to the liquid crystal panel are scanned while being switched sequentially in a predetermined primary color order and in a predetermined time unit. The primary color light that drives the light source and irradiates the liquid crystal panel surface is sequentially switched in time series in the same order as the primary color order of the image data, and further from the liquid crystal panel by the pixel shift element in synchronization with the switching of the image data and the light source. By sequentially switching the display pixel position of the primary color light of each incident pixel, the afterimage corresponding to each primary color light is synthesized on the human retina and recognized as a color image, so that a color filter can be eliminated, As a result, an increase in the size of the liquid crystal panel and a decrease in product yield can be suppressed.
[0033]
Further, according to the present invention, the display pixel position by the pixel shift element is six times faster than that of the conventional four pixels composed of the first to fourth pixels adjacent to each other in the horizontal direction and the vertical direction. A green image with high visibility is displayed with one diagonal pixel while driving, and the remaining two primary colors of the three primary colors are displayed with the other diagonal pixel, so the drive frequency is kept low. Therefore, it is possible to provide a high-resolution color liquid crystal display device that can be easily realized.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an embodiment of a liquid crystal display device of the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of a liquid crystal panel of a liquid crystal display device of the present invention.
FIG. 3 is an equivalent circuit diagram showing an example of a configuration of a unit pixel of the liquid crystal panel of the present invention.
FIG. 4 is a configuration diagram of an embodiment of a pixel shift element in the device of the present invention.
FIG. 5 is an explanatory diagram of an example of a pixel position and a display color by a pixel shift element in the device of the present invention.
FIG. 6 is an equivalent circuit diagram of an example of a unit pixel of a liquid crystal panel in a conventional device.
FIG. 7 is a cross-sectional view of an example of a liquid crystal panel in a conventional device.
FIG. 8 is a schematic configuration diagram of an example of a conventional liquid crystal display device.
FIG. 9 is a diagram illustrating an example of a color arrangement and display color of a color filter in a conventional liquid crystal display device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Matrix substrate 2 Drain 4 Pixel electrode 5, 12 Polarizing plate 6 Light transmissive substrate 8 Common electrode 21 Liquid crystal panel 22 Light source 23 Pixel shift element 24 Liquid crystal panel drive circuit 25 Pixel shift element drive circuit 231, 233 Liquid crystal cell 232, 234 Compound Refractor

Claims (1)

An active matrix substrate in which pixels are arranged in a matrix at intersections of a plurality of scanning signal wirings parallel to each other and a plurality of image signal wirings orthogonal thereto, and the pixel electrodes of the pixels are formed on the surface And a light-transmitting electrode substrate having a light-transmitting common electrode formed on the surface facing the surface of the active matrix substrate, and the active matrix substrate and the light-transmitting electrode substrate. A liquid crystal panel provided with a liquid crystal layer;
A light source that irradiates the liquid crystal panel with a selected primary color light among red light, green light and blue light;
A pixel shift that includes at least one liquid crystal cell and at least one birefringent plate, and shifts the display pixel position of the primary color light of each pixel incident from the liquid crystal panel based on an external drive signal. Elements,
The image data of the three primary colors of red, green and blue supplied to the liquid crystal panel are scanned in a predetermined primary color order and sequentially in a predetermined time unit, and the light source is driven in synchronization therewith. A first drive circuit that sequentially switches the primary color light applied to the liquid crystal panel surface in time series in the same order as the primary color order of the image data;
Out of a total of four pixels composed of two pixels in the horizontal direction and two pixels in the vertical direction adjacent to each other, the first pixel is a green image, and the first pixel is adjacent in the vertical direction or the horizontal direction. An image of one of the primary colors of red and blue and an image of the other primary color, a green image on a third display pixel at a diagonal position of the first display pixel, and the third display For switching the image data and the light source so that one primary color image of red and blue and the other primary color image are sequentially displayed on a fourth display pixel adjacent to the pixel and the first display pixel. A second drive circuit that sequentially switches drive signals applied to the liquid crystal cells of the pixel shift element and sequentially switches display pixel positions of primary color light incident on the pixels from the liquid crystal panel. LCD device characterized by Place.

Images