JPH04165779A - Driving method for projection liquid crystal television and liquid crystal panel - Google Patents

Abstract

PURPOSE:To realize a display picture with less flickering by using two liquid crystal display devices against one light or primary light color and applying signals with reserved polarities each other to the devices so as to drive them. CONSTITUTION:Two liquid crystal display devices 11 and 12 are arranged against R, G, B lights, the reflection is performed so that the projection picture of the picture element in the identical position of the device can be the identical position of a screen. The video signals with polarities reversed each other are applied to the two liquid crystal display devices 11 and 12. Thus, the flickering can be prevented since the voltage to be applied to the liquid crystal differs in the positive and reverse polarities of the video signal and they are cancelled in the state projected on a screen 21 even when the difference of luminance occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal projection television that enlarges and projects an image displayed on a liquid crystal panel onto a screen, and a method for driving the liquid crystal panel.

BACKGROUND OF THE INVENTION In recent years, television receivers using CRTs have become larger in size. However, when a TV receiver using a CRT has a large screen of 40 inches or more, it weighs more than 100 kg.
It is unsuitable for household use. Therefore, liquid crystal projection televisions, which can be made lighter and display enlarged images on a screen, are attracting attention. However, in this LCD projection TV, a phenomenon in which the displayed image flickers (hereinafter referred to as flicker) occurs, and reducing the flicker is an important issue when commercializing the product.Please refer to the drawings below. A conventional liquid crystal projection television and a method for driving its liquid crystal panel will be explained. First, an active matrix liquid crystal display panel (hereinafter referred to as a liquid crystal panel) used in a liquid crystal projection television will be explained. FIG. 12 is a configuration diagram of the liquid crystal panel. Note that in FIG. 12, parts unnecessary for explanation are omitted. The above also applies to the following drawings. In Figure 12, 61-G
, is the gate signal line, 81~Sゎ is the source (line 8, TI
I, TII, TII are thin film transistors (hereinafter referred to as TPT) as switching elements, Ca, , C
a,! , Ca is an additional capacitor, C11°Cr1. C
II is a liquid crystal. 41 is a gate signal line 61 to G7
An IC (hereinafter referred to as a gate drive IC) for applying a voltage to turn on the TPT (hereinafter referred to as an on-state voltage) or a voltage to turn off the TPT (hereinafter referred to as an off-state voltage); 42 is a source; This is an IC that outputs a voltage to be applied to the liquid crystal to the signal lines 51 to S. The transmittance of the liquid crystal changes with the application of the voltage, thereby modulating light. Although the number of pixels is shown to be very small in FIG. 12, usually more than one enemy pixel is formed on one panel. Furthermore, TPT and the like are formed near the intersections of each gate signal line and source signal line. Regarding the operation of the liquid crystal panel, the gate drive IC 41 connects gate signal lines G1 to G. (where m is the number of gate signal lines), the on-voltage is sequentially applied. In synchronization with this, the source drive IC 42 outputs a voltage to be applied to each pixel to the source signal lines 51 to Sn (where n is the number of source signal lines). Therefore, a voltage that makes the liquid crystal transmit a predetermined amount is applied to each pixel and is maintained. The voltage is maintained until each TPT is turned on again in the next cycle.

The voltage changes the amount of transmission of the liquid crystal of each pixel, and the light transmitted or reflected from each pixel is modulated. Note that the cycle from when voltage is applied to all pixels until the next voltage is applied again is called one frame. In addition, l frame is 1730 in the case of 6 normal TV images consisting of 2 fields.
Since one screen is redrawn every second, 1/30 second is one frame time. In the case of a liquid crystal panel, one screen is often rewritten every 1/60 seconds, and in this case, 1 field = 1 frame. Further, since the source drive IC 42 and the gate drive TC 41 need to be driven in synchronization, the timing is determined by the control circuit 133 as shown in FIG. Note that in this specification, a liquid crystal panel equipped with a source drive IC and a gate drive IC is referred to as a liquid crystal display device.

Further, polarizing films are arranged on both sides of the liquid crystal display device. Furthermore, in this specification, driving a liquid crystal panel is treated as driving a liquid crystal display device.

FIG. 14 is a circuit explanatory diagram of a conventional liquid crystal projection television. In FIG. 14, 141a is a liquid crystal display device that modulates red light (hereinafter referred to as R light), 141b is a liquid crystal display device that modulates green light (hereinafter referred to as G light), 1
41C is a liquid crystal display device that modulates blue light (hereinafter referred to as B light), and also resistors R, , R2 and transistor Q.
This constitutes a phase dividing circuit that creates positive and negative polarity video signals for the video signal input to the base.

Reference numerals 142a, 142b, and 142c are output switching circuits that output AC video signals whose polarities are inverted for each field to the liquid crystal display device.

The operation of the circuit of a conventional liquid crystal projection television will be described below. After the video signal is gain adjusted to a predetermined value,
-GB is divided into signals corresponding to G-B. This video signal is divided into video signal (R), video signal (G), video signal (
B). Each video signal (R-G-B) is input to a phase division circuit, and this circuit produces two video signals of positive polarity and negative polarity. Next, the two video signals are transferred to respective output switching circuits 142a and 142b.
.

142c, and the circuit outputs a video signal whose polarity is inverted for each field. The reason for inverting the polarity for each field is to prevent deterioration of the liquid crystal by applying an alternating voltage to the liquid crystal.
Next, the video signals from each output switching circuit are input to the source drive IC 42. The control circuit 133 synchronizes the source drive IC 42 and the gate drive IC 41 and displays an image on the liquid crystal panel.

Next, the visibility of the human eye will be explained. The human eye has the worst wavelength around 555 nm. Of the three primary colors of light, green is the highest, followed by red, and blue is the dullest. In order to obtain a luminance signal proportional to this sensitivity, red should be
%, just add 60% green and 10% blue. Therefore, to obtain white color on TV images, R:G:B=
It may be added in a ratio of 3:6:1. Furthermore, as mentioned earlier, the liquid crystal needs to be driven with alternating current. The AC driving is performed by alternately applying signals of positive polarity and reverse polarity to the voltage (hereinafter referred to as common voltage) applied to the opposing electrode of the liquid crystal panel. In this specification, a state in which a signal of positive polarity is applied to the liquid crystal panel and modulates light with an intensity of visibility n is defined as +n, and a state in which a signal of opposite polarity is applied to the liquid crystal panel modulating light with an intensity of visibility n is defined as +n.
The state in which light with an intensity of If it is +3・+6・
It shall be expressed as +1. In addition, R:G:B=3:6:
1 is for an NTSC television image, and in a liquid crystal projection television, the above ratio differs depending on the characteristics of the light source lamp, gicroic mirror, etc. Therefore the 14th
As shown in the figure as +3, +6, +1, R:G:
It is shown that light of B=3:6:1 is irradiated and positive signals are applied to the three liquid crystal panels. After one field, it is expressed as -3, -6, and -1.

Next, the optical system of a conventional liquid crystal projection television will be explained. FIG. 15 is a layout diagram of the optical system of a conventional liquid crystal projection television. In FIG. 15, 21 is a screen, 22 is a condensing optical system, 62 is a B-light reflecting gichroic mirror, 6
3 is a G-light reflecting guichroic mirror, 64 is a mirror, 6
5a, 65b.

65c is a field lens, 66a, 66b.

66c, 67a, 67b, and 67c are projection lenses.

As is clear from FIG. 15, the dichroic ink mirror 62 separates the B light emitted from the condensing optical system 22 and guides it to the liquid crystal display device 141C, and the dichroic ink mirror 63 separates the G light. , is guided to the liquid crystal display device 141b. The liquid crystal display device 1 whose direction of the last remaining R light can be changed by a total reflection mirror 64
41a. The aforementioned guided light drives and modulates the liquid crystal display device by the circuit shown in FIG. The modulated light is focused by a projection lens and projected onto a screen 21.
will be projected on.

Hereinafter, a method for driving a liquid crystal panel of a conventional liquid crystal projection television will be described. FIG. 16 is an explanatory diagram of a conventional method for driving a liquid crystal panel. In FIG. 16, 31 is a common voltage potential. Note that FIG. 16(a) shows the applied waveform of the liquid crystal display device 141a for R light modulation, and FIG. 16(b)
is the applied waveform of the liquid crystal display device 141b for G light modulation,
FIG. 16(C) shows the applied waveform of the liquid crystal display device for B light modulation. As is clear from Figure 16, in the conventional liquid crystal panel driving method, a signal of the same polarity is applied to each R-G-B liquid crystal panel within one field, and the polarity is reversed for each field. .

Problems to be Solved by the Invention Consider the case where a still image is displayed on a liquid crystal panel.
The same waveform that differs only in polarity should be applied to each field of the video signal.

However, in reality, there is a slight potential difference between the even and odd fields in the voltage applied to the liquid crystal panel, resulting in flickering. The causes of this flicker are thought to be the difference in retention characteristics of the alignment film or liquid crystal due to the application of a positive electric field and a negative electric field, and the fact that the on-current and off-current of the TPT differ depending on the voltage polarity of the video signal.

Furthermore, even if the common voltage is adjusted to reduce flicker, the degree of occurrence changes as the temperature changes, and changes as the liquid crystal panel changes over time.

The above-mentioned flicker causes the screen to flicker, making it extremely difficult to see and significantly reducing the image quality.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a liquid crystal projection television set according to the first aspect of the present invention, in which a set of liquid crystal projection televisions having substantially the same characteristics for light displaying one primary color is provided. Place the LCD display device of
Video signals whose polarities are reversed within one field are applied to the liquid crystal display device, and light modulated by the liquid crystal display device is projected onto the same position on the screen.

Further, in the liquid crystal projection television of the second aspect of the present invention, a plurality of liquid crystal display devices are arranged for each primary color light, and the visibility of the primary color light and the polarity of the video signal applied to the liquid crystal display device are adjusted. Taking this into consideration, the light modulated by the liquid crystal display device is projected onto the same position on the screen.

Further, in the first method of driving a liquid crystal panel of the present invention, signals are applied to a set of liquid crystal panels so that the potentials applied to opposing electrodes of the liquid crystal panels have different polarities, and The polarity of the signal applied to the liquid crystal panel is switched every at least one of one field time and one frame time.

Furthermore, in the method for driving a liquid crystal panel according to the second aspect of the present invention, a positive polarity signal is applied to one of the plurality of liquid crystal display devices that modulates light having an intensity of X including the first wavelength at an arbitrary time. +X indicates that the signal is being applied, and -X indicates that the signal of negative polarity is being applied. +y1 indicates that a signal of negative polarity is applied, -y indicates that a signal of negative polarity is applied, and -y indicates that a signal of positive polarity is applied among a plurality of liquid crystal display devices that modulate light of intensity 2 including the third wavelength. If +z indicates that the signal is being applied, and -2 indicates that a signal of negative polarity is being applied, then the children x, -x, y, -
Light is made incident on the plurality of liquid crystal panels such that the sum of y, +z, and -z becomes zero or a value close to zero, and the light is modulated by the liquid crystal panels.

In the liquid crystal projection television of the first aspect of the present invention, two liquid crystal display devices are arranged for each of R, G, and B lights, and the projected images of pixels at the same position on the device are at the same position on the screen. Project it like this.

Then, video signals having opposite polarities are applied to the two liquid crystal display devices. Therefore, even if there is a difference in the voltage applied to the liquid crystal depending on the positive polarity and the reverse polarity of the video signal, and a difference in brightness occurs, it is canceled out when the image is projected on the screen, and no flicker occurs.

Next, in the liquid crystal projection television of the second aspect of the present invention, three liquid crystal display devices are arranged for each of R light, G light, and B light. Three liquid crystal display devices for R light and one liquid crystal display device for G light have positive polarity, and the remaining two liquid crystal display devices for G light and three liquid crystal display devices for B light have negative polarity. If a sexual video signal is applied, (3R+G):
(2G+3B) = -15:15, so that even if there is a difference in the voltage applied to the liquid crystal between the positive and reverse polarity of the video signal, it can be canceled out when projected on the screen, and flicker will not occur. I can do it. However, the ratios shown above are calculated on the assumption that R=3, G=6, and B=1. In addition, in the liquid crystal projection type television of the present invention, by using a plurality of liquid crystal display devices for one primary color, the image brightness on the screen can be made sufficiently bright for practical use, and it can correspond to a large screen.

EXAMPLES Hereinafter, a first liquid crystal projection television of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit explanatory diagram of a liquid crystal projection television according to the first aspect of the present invention. In FIG. 1, 11 and 12 are liquid crystal display devices. Note that it is desirable that the two liquid crystal display devices have substantially the same characteristics. Further, the resistors R, , R2 and the transistor Q constitute a phase dividing circuit which generates a positive polarity video signal and a negative polarity video signal input to the base terminal. Reference numeral 13 denotes an output switching circuit that outputs an AC video signal whose polarity is inverted for each field to the liquid crystal display device, and video signals having opposite polarities are outputted from signal output terminals 14 and 15.

Hereinafter, the circuit operation of the first liquid crystal projection television set according to the invention will be explained. The video signal is gain-adjusted to a predetermined value, subjected to signal processing, and input to the phase division circuit. Two video signals of positive polarity and negative polarity are generated by the circuit and input to the next output switching circuit 13. The output switching circuit 13 performs processing such as timing adjustment and signal level conversion, and then applies the signal to the liquid crystal display device 11.12 from the signal output terminal 14.15. In the liquid crystal display device, as shown in FIG. 13, the source drive IC 42 and gate drive IC 41 are synchronized by the control circuit 133, and an image is displayed on the liquid crystal panel.

Next, the optical system of the liquid crystal projection television according to the first aspect of the present invention will be explained. FIG. 2 is a layout diagram of the optical system of the liquid crystal projection television according to the first aspect of the present invention. In FIG. 2, 21 is a screen, 22 is a condensing optical system that condenses the light of the lamp, and 23
is a half mirror 124 is a total reflection mirror, 25a, 25b
26a, 26b, 27a, and 27b are projection lenses. 26a, 26b, 27a, and 27b are projection lenses. As is clear from Fig. 2, the condensing optical system 2
The light irradiated from 2 is divided into 1/2 by a half mirror 23, and the light of equal intensity is incident on the liquid crystal display devices 11 and 12. The aforementioned light is modulated by driving a liquid crystal display device by the circuit shown in FIG. The modulated light is focused by a projection lens and projected onto the screen 21. At this time, pixels at the same position on the liquid crystal display devices 11 and 12 are projected so as to overlap with each other. In the above embodiment, the displayed image is a black and white image, but by arranging a color filter at position A in FIG. 2, a monochromatic color display can be obtained. Further, for example, by arranging a red reflecting dichroic mirror at the A position and arranging a green reflecting dichroic mirror at the half mirror 23, a two-color display of green and blue can be obtained.

Hereinafter, a method for driving a liquid crystal panel according to the first aspect of the present invention will be explained. FIGS. 3(a) and 3(b) are explanatory diagrams of the method for driving a liquid crystal panel according to the present invention. Note that FIG. 3(a) shows the waveform applied to the liquid crystal display device 11, and FIG. 3(b) shows the waveform applied to the liquid crystal display device 12. Figure 3(a),
As is clear from (b), in the method for driving a liquid crystal panel according to the first aspect of the present invention, signals of opposite polarity are applied to two liquid crystal panels within one field, and the polarity is reversed for each field. Then, the light modulated by the liquid crystal panel is projected onto the same position on the screen. By doing this, even if there is a difference between the applied video signals of positive polarity and negative polarity, they are canceled out and no flicker occurs.

Next, a method for driving a liquid crystal panel in a second embodiment of the first invention will be described. Figure 4(a).

(b), (C1, and (d) are explanatory diagrams thereof. The second embodiment is the same in that signals of opposite polarity are applied within one field to two liquid crystal display devices.

In the second embodiment, voltages of the same polarity are applied to pixels in the vertical direction, and voltages of opposite polarity are applied to pixels adjacent to the pixels in the vertical direction. Focusing on the source signal line S6, a negative voltage is applied to the TPT connected to the source signal line S6, and a positive voltage is applied to the TPT connected to the source signal lines S5 and 57 adjacent to the source signal line S6. Apply. In other words, the source signal line S2. (However, m is an integer) is a negative voltage S t
A positive voltage is applied to m-+. Naturally, the polarity of the voltage is reversed every field. Hereinafter, such a driving method will be referred to as 1.inversion driving. therefore,
Fig. 4 shows a simulation of the driving state.

FIG. 4(b) shows the driving state of the liquid crystal display device 11, and FIG. 4(C) shows the driving state of the liquid crystal display device 12. After 1 field, the liquid crystal display device 11 is in the driving state shown in FIG. 4C, and the liquid crystal display device 12 is in the driving state shown in FIG. The modulated light as shown in FIGS. 4(b) and 4(c) is projected onto the same position on the screen. By performing the driving as described above, the occurrence of flicker can be further reduced compared to the method of driving the liquid crystal panel of the first embodiment, and good image quality can be obtained. In addition, FIG. 4(a).

In (b) and (C), the polarity of the signal is reversed in the vertical direction and applied, but the polarity of the signal may be reversed in the horizontal direction as shown in FIG. 4(d). Hereinafter, such a driving method will be referred to as IH inversion driving.

Hereinafter, a second embodiment of the liquid crystal projection television according to the first invention will be described with reference to the drawings.

FIG. 5 is a circuit explanatory diagram of a second embodiment of the liquid crystal projection television according to the first invention. In FIG. 5, 51a, 51
b, 51c, 52a, 52b.

52c is a liquid crystal display device, 53a, 53b.

53c is an output switching circuit, 54a, 54b.

54c is a phase division circuit. In FIG. 5, liquid crystal display devices 51a and 52a are used for modulating R light, liquid crystal display devices 51b and 52b are used for modulating G light, and liquid crystal display devices are used for modulating B light. In other words, this is equivalent to the liquid crystal projection television of the first embodiment in which three circuits are arranged for R, G and H light modulation. As shown in FIG. 5, even if there is an intensity difference between the +3 light of the liquid crystal display device 51a that modulates the R light and the -3 light of the liquid crystal display device 52a, they almost cancel each other out on the screen, causing flicker. Similarly, between the -6 light of the liquid crystal display device 51b that modulates the G light and the +6 light of the liquid crystal display device 52b, the +1 light of the liquid crystal display device 51c that modulates the B light and the -6 light of the liquid crystal display device 52c. Even if there is a difference in intensity between the two lights, they are almost canceled out on the screen and no flicker occurs. In addition, the liquid crystal display device 51b is +6, and the liquid crystal display device 52b is −6.
For example, the liquid crystal display device 51a is not marked as 6.
, 51b, 51c or liquid crystal display devices 52a, 52
This is because the arrangement is such that the flicker that occurs even when displaying images on three panels, b and 52c, can be reduced as much as possible. That is, the liquid crystal display devices 51a, 51b,
When displaying in 51c, (R+B)+G=4+(76)
= -2, and they almost cancel each other out. In addition, the output switching circuits 53a, 53b, and 53c are formed with analog switches as two switches so that the liquid crystal display device that does not require a display displays black so that only three panels can be displayed as described above. I'll keep it.

Next, an optical system of a liquid crystal projection television according to a second embodiment of the first invention will be described. FIG. 6 is a layout diagram of the optical system described above. In FIG. 6, 62 is a gicchroic mirror that reflects blue light (hereinafter referred to as a blue-reflecting gicchroic mirror), and 63 is a dichroic mirror that reflects green light (hereinafter referred to as a green-reflecting gicchroic mirror). , 64 is a total reflection mirror, 65a, 65b, and 65c are field lenses for guiding light to the display area of the liquid crystal display device, and 66a, 66b, and 66c.

67a, 67b, and 67c are projection lenses. As is clear from FIG. 6, the light irradiated from the condensing optical system 22 is transmitted to the liquid crystal display device 51a by the dichroic ink mirrors 62, 63 and the mirror 64.

The screen is guided to display areas 51b and 51c. The aforementioned light is the fifth
A liquid crystal display device is driven and modulated by the circuit shown in the figure. The modulated light is focused by a projection lens and projected onto the screen 21. A second optical system, which is the same as the optical system shown in FIG. 6, is formed on the optical system shown in FIG.
The light from the second optical system is divided into 1/2 and guided to the second optical system.

The light is arranged within a second optical system! The light is guided to the display areas of the liquid crystal display devices 52a, 52b, and 52c, and is similarly optically modulated and projected onto the screen.

At this time, the liquid crystal display devices 51a and 52a are responsible for R light, the liquid crystal display devices 51b and 52b are responsible for G light, and the liquid crystal display devices 51c and 52c are responsible for B light. It goes without saying that the light splitting mirror 61 may not be provided and two condensing optical systems 22 may be used.

A method for driving the liquid crystal panel of the liquid crystal projection television according to the second embodiment will be described below with reference to FIG. In addition, the first
This method is similar to the method for driving a liquid crystal panel according to the invention, so it will be briefly explained. In FIG. 7, FIG. 7(al) is a waveform applied to the liquid crystal display device 51a, FIG. 7(C2) is a waveform applied to the liquid crystal display device 52a, and similarly FIG.
bl) is shown in FIG. 7 (b2) to the liquid crystal display device 51b.
is the waveform applied to the liquid crystal display device 52b, FIG. 7(C1) is the applied waveform to the liquid crystal display device 51c, and FIG. 7(C2) is the applied waveform to the liquid crystal display device 52c.

FIG. 7 (al), (C2), (bl), (b2).

(cl), (C2), the liquid crystal display devices 51a, 52a, the liquid crystal display devices 51b, 5
2b, liquid crystal display device 51c.

52c is driven by applying signals of opposite polarity to each other. Further, the polarity is reversed for each field.

Then, the modulated light is projected onto a screen by a liquid crystal panel. By doing this, even if there is a difference between the applied signals of positive polarity and negative polarity, they are canceled out and no flicker occurs. Incidentally, the occurrence of flicker can be further reduced by using the driving method shown in FIG. 7 in combination with at least one of 1-inversion driving and IH inversion driving.

Hereinafter, the second liquid crystal projection television of the present invention will be described with reference to FIGS. 8 and 9.

FIG. 8 is a circuit explanatory diagram of a liquid crystal projection television according to the second invention. In FIG. 8, 81a.

81b, 81c, 82a, 82b, 82c.

84a, 84b, 84c are liquid crystal display devices, 84a,
84b, 84c are output switching circuits, 85a, 85b,
85c is a phase division circuit.

In FIG. 8, a liquid crystal display device 81a.

82a and 83a are liquid crystal display devices Bl for modulating R light;
b, 82b, and 83b are for modulating G light, and liquid crystal display devices 81c, 82c, and 83c are for modulating B light. As in the previous explanation, the R-G-B ratio for obtaining white color is R,:G:B=3:6:1. It should be noted that this ratio naturally varies depending on the light source spectrum, the characteristics of the dichroic mirror, etc.

Hereinafter, the circuit operation of the liquid crystal projection television according to the second aspect of the present invention will be explained. The video signal is gain adjusted to a predetermined value,
Video signal (R) after signal processing.

(G), (B), and the phase division circuits 85a and 85b
.

85c. Two video signals of positive polarity and negative polarity are created by the circuit, and the next output switching circuit 84
a, 84b, and 84c.

The output switching circuits 84a, 84b, and 84c perform timing adjustment, signal level conversion, etc., and then output the signal from the signal output terminal, and apply the signal to the liquid crystal display device number.

At this time, at a certain time in one field, the R light modulation liquid crystal display device 81a.

82a, 83a, 1 of G light modulation liquid crystal display devices
A positive polarity signal is applied to the device, for example 81b, and a negative polarity signal is applied to the other liquid crystal display devices.

Naturally, after one field, a signal of the opposite polarity to the above polarity is applied to each liquid crystal display device. By driving as described above, positive polarity: negative polarity=(3R+G):(2G+3B)=15:15. Therefore, even if there is a difference between the positive and negative polarity signals applied to the liquid crystal, they can be canceled out within one field, and no flicker occurs.

In addition, as mentioned above, (3R+G): (2G+3B)=1
5:15, but it is not limited to this, for example, (3R+c+B): (2G+2B)-16
:14, the occurrence of linkers does not become so large. Furthermore, as described above, since a plurality of liquid crystal display devices are used for one primary color, the image brightness on the screen can be made brighter, and the screen can be made larger than 200 inches. - Regarding the optical system, a second optical system and a third optical system, which are the same as the optical system shown in FIG. 6, are formed on the optical system shown in FIG. The light from the condensing optical system is divided into 1/3 and guided to the optical system. The rest is the same as the optical system of the liquid crystal projection television according to the second embodiment of the first invention, so the explanation will be omitted. In addition,
It goes without saying that the light splitting mirror 61 may not be provided and three condensing optical systems 22 may be used.

Hereinafter, a method for driving a liquid crystal panel according to the second aspect of the present invention will be explained. FIG. 9 is an explanatory diagram of a method for driving a liquid crystal panel according to the second invention. In FIG. 9, FIG. 9(al) is the applied waveform to the liquid crystal display device 81a, FIG. 9(a2) is the applied waveform to the liquid crystal display device 82a, and FIG. 9(a3) is the applied waveform to the liquid crystal display device 82a.
is the waveform applied to the liquid crystal display device 83a, FIG.
) is the waveform applied to the liquid crystal display device 81b, FIG.
2) is the waveform applied to the liquid crystal display device 82b, FIG.
b3) is the waveform applied to the liquid crystal display device 83b, and FIG. 9 (C1) is the waveform applied to the liquid crystal display device 81c.
FIG. 9 (C2) shows the waveform applied to the liquid crystal display device 82c, and FIG. 9 (C3) shows the waveform applied to the liquid crystal display device 83c. Figure 9 (al), (a2), (a3), (bl)
.

(b2), (b3), (cl), (C2)
.

(C3) and the explanation of the liquid crystal projection television of the second invention, the signal polarity to the liquid crystal panel used for modulating R-G-B light is changed to positive polarity and negative polarity in consideration of visibility. Select and apply the characteristics and drive.

Further, the polarity is reversed for each field. By performing the above-described driving, even if there is a difference in the voltage applied to the liquid crystal during positive polarity and negative polarity, it is almost canceled out on the screen and no flicker occurs. Incidentally, by using the driving method shown in FIG. 9 in combination with at least one of 1V inversion drive and IH inversion drive, the occurrence of flicker can be further reduced.

In the liquid crystal projection television and liquid crystal panel driving method of the second invention described above, the liquid crystal display devices 81a, 82
a, 83a, etc. are not limited to +3 or -3 (when multiple liquid crystal display devices are arranged, it is sufficient to appropriately determine the polarity of the applied signal in consideration of visibility). Needless to say.

Hereinafter, a second embodiment of the liquid crystal projection television according to the second invention will be described with reference to FIG. In addition, regarding the optical system, the first part of the liquid crystal projection type television of the second invention
Since this embodiment is the same as that of the embodiment, the explanation will be omitted, and only the differences will be explained regarding the circuit. In FIG. 10, 101,
Reference numeral 102 denotes a signal phase inversion circuit, which is usually composed of a transistor or the like. Further, 103 and 104 are switching circuits, which are usually composed of analog switches, etc., and switch between two modes: a state where the signal from the output switching circuit is applied to the liquid crystal display device through-through, and a state where the signal is connected to the signal phase inversion circuit. be able to. Note that switching of the switching circuits can be performed synchronously with field synchronization.

In the first embodiment of the liquid crystal projection television of the second invention,
When the screen display on the screen is only R light display or only B light display, all three panels that modulate light are driven by signals of the same polarity at certain times.

In other words, during R light display, the liquid crystal display devices 81a, 82
A, 83a are both of positive polarity or negative polarity, and during B light display, negative or positive polarity video signals are applied to liquid crystal display devices 81a, 81b, and 81c. Therefore, flicker becomes noticeable on the screen.

At this time, the switching circuit is switched so that the signal passes through the signal phase inversion circuits 101 and 102, and a signal having an opposite phase is applied to only one liquid crystal display device. In other words, R
A signal having an opposite phase to that of other devices is applied to the liquid crystal display device 83a during optical display, and to the liquid crystal display device 83c during B-light display. Therefore, in the case of monochromatic display, the modulated light of the positive polarity signal applying device: the modulated light of the negative polarity signal applying device -2:1 or 1:2.

By performing such driving, it is possible to substantially prevent flicker from occurring even during monochromatic display. In addition, to determine whether or not it is a monochrome display, each of the video signals (R), (G), and (B) is integrated into a capacitor for one field time, and one video signal has an integral value. When the integral value of the two video signals is quite small, it is determined that monochrome display has occurred. in this way,
The switching circuit is switched based on the integrated value result of one field. It goes without saying that flicker can be further reduced by combining with IH or 1/2 inversion drive. This also applies to the liquid crystal projection television of the first aspect of the invention.

By providing a switching circuit or the like as described above, flicker can be significantly reduced even during monochromatic display.

In addition, in the method for driving a liquid crystal panel of the present invention, the polarity of the applied signal is reversed every 1 field, but the polarity of the applied signal is not limited to this, and it is also possible to reverse the polarity every frame. Needless to say.

Further, in the liquid crystal projection television of the present invention, although the projection images of the plurality of liquid crystal display devices are projected at the same position, the invention is not limited to this, and even if the images are shifted by about 1 to 2 pixels, the same effect can be obtained. Needless to say, you can obtain Further, in the liquid crystal projection television and liquid crystal panel driving method of the first aspect of the present invention, the case where two liquid crystal display devices are used for one light or primary color light has been described, but the invention is not limited to this. It doesn't matter if it's a multiple of 2, such as 4 or 6.

Furthermore, in the liquid crystal projection television and liquid crystal panel driving method according to the second aspect of the present invention, the number of liquid crystal display devices for modulating R-B-G light is not limited to three. Needless to say, this is not limited to only destination B. Furthermore, although the liquid crystal projection television of the present invention has been described as one that projects images onto a screen like a movie projector, it goes without saying that it may be a rear type television that uses a transmissive screen. A diagram of this rear type liquid crystal projection television is shown in FIG. Note that FIG. 11 is a configuration diagram of a rear type projection television, in which 111 is a transmission screen, 112 and 115 are mirrors, 113 is a cabinet, and 114 is a condensing optical system.

Effects of the Invention As described above, in the liquid crystal projection television and liquid crystal panel driving method of the first invention, two liquid crystal display devices are used for one light or primary color light, and Since they are driven by applying signals of opposite polarity to each other, even if the voltages applied to the liquid crystal of the pixel of the liquid crystal display device are different between positive and negative polarities, they cancel out on the screen, resulting in extremely low flicker. It is possible to realize fewer displayed images.

In addition, in the liquid crystal projection television and liquid crystal panel driving method according to the second aspect of the present invention, the visibility of the light is taken into consideration and the structure is made so that the entire screen is canceled out, so that the same effect as in the above case is applied. A display image with extremely little flicker can be realized.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of the liquid crystal projection type television of the first invention, FIGS. 3 and 7 are explanatory diagrams of the driving method of the liquid crystal panel of the first invention, and FIG. FIGS. 5 and 6 are explanatory diagrams of another liquid crystal panel driving method according to the invention. FIGS. 5 and 6 are explanatory diagrams of a liquid crystal projection television according to another embodiment of the first invention. FIG. Explanatory diagram of LCD projection television,
Fig. 9 is an explanatory diagram of a method for driving a liquid crystal spring according to the second invention, Fig. 1O is an explanatory diagram of a liquid crystal projection type television according to another embodiment of the second invention, and Fig. 1I is an explanatory diagram of a rear type television. A configuration diagram of a projection television; FIGS. 12 and 13 are configuration diagrams of a liquid crystal display device; FIGS. 14 and 15 are explanatory diagrams of a conventional LCD projection television; and FIG. 16 is a diagram of driving a conventional liquid crystal panel. It is an explanatory diagram of a method. 11.12.51a, 51b, 51c, 52a. 52b, 52c, 81a, 81b, 81c. 82a, 82b, 82c, 83a, 83b. 83c, 132, 141a, 141b, 141c...
...Liquid crystal display device, R,, R2...Resistor, Q...Transistor, 14.15...
・Signal output terminal, 2-1...Screen, 22
, 114...Condensing optical system, 23...Half mirror 124, 64, 112°115-==-Mirror, 25a, 25b, 65a. 65b, 65c...Field lens, 26a
. 26b, 27a, 27b, 66a, 6
6b. 66c, 67a, 67b, 61cm--Projection lens, 31...Common voltage potential, 41...
・Gate drive IC, 42...Source drive rc, c, ~G8...Gate signal line, S1~
S8...Source signal line, Ca...CaI! ,
Ca,,---additional capacitor, C18,C,! , C!
l...Liquid crystal, Tll"I!. T...TFT, 13.53a, 53b, 53
c. 84a, 84b, 84c, 142a,
142b. 142c...Output switching circuit, 16.54a
. 54b, 54c, 85a, 85b, 8
5c, --- Phase splitting circuit, 61... Light splitting mirror, 62... Blue reflective gicroic mirror. 63...Green reflective mirror,
101, 102... Signal phase inversion circuit, 103
, 104... switching circuit, 111...
... Transmissive screen, 113 ... Cabinet, 131 ... Liquid crystal panel, 133 ...
...Control circuit. Name of agent: Patent attorney Haruaki Ogata and 2 others +I, +2-
--fire" Jino i4 13 --- Output cut) Multiplying number b \ 14, "Dah - < @ to hit the force) Q ---) 5" J Jisug 41 --- Gate Y Ligo IC +2 --- Source V Ic (4I1.CIhIIlm---IM force rJ] v;:J
YCIl, C+t, C*l-8 m(t-Jk, 8--Sfc, RkJ5cm--miaJ
++Jj&Device Ml,l・! --I lesson f Hi word nt
vato Figure 11 II+ -- Itton j1 forked screen +12. If 5 --- Miu -- Figure 12 Figure 13
151...muhe°ne! ShiL-11111-
---First 16v4

Claims (6)

[Claims] (1) first and second liquid crystal display devices that modulate light using applied signals; a phase splitting circuit that outputs signals with the positive phase and opposite phase of the input signal; and The signals of positive phase and reverse phase are inverted at predetermined time intervals, and the first liquid crystal display device and the second liquid crystal display device are connected to each other.
an output switching circuit for applying a signal to the liquid crystal display device so that the signals are in opposite phases to each other; and a second optical means for projecting light modulated by the first and second liquid crystal display devices to at least one of the same position and the vicinity of the position. Projection TV. (2) The liquid crystal projection television set according to claim 1, further comprising first and second liquid crystal display devices corresponding to red light, green light, and blue light. (3) The liquid crystal projection television set according to claim 1, wherein the first and second liquid crystal display devices modulate light emitted from one light generating means. (4) A signal is applied to a set of liquid crystal panels so that the polarity is different from the potential applied to the opposing electrodes of the liquid crystal panels, and at least one of one field time and one frame time is applied. A method for driving a liquid crystal panel, characterized in that the polarity of a signal applied to the liquid crystal panel is changed every time. (5) A plurality of liquid crystal display devices that modulate light with a visibility x including a first wavelength, a plurality of liquid crystal display devices that modulate light with a visibility y including a second wavelength, and a plurality of liquid crystal display devices that modulate light with a visibility x including a second wavelength; a plurality of liquid crystal display devices that modulate light with visibility z, a plurality of phase splitting circuits that output signals of the positive polarity and the opposite polarity of the input signal, and a plurality of phase splitting circuits that output signals of the positive polarity and the opposite polarity of the input signal; a plurality of output switching circuits for inverting and outputting a signal at predetermined time intervals and applying the signal to the plurality of liquid crystal display devices; an optical means, and a second projecting light modulated by the plurality of liquid crystal display devices to at least one of the same position and the vicinity of the position.
A liquid crystal projection television, characterized in that it is equipped with optical means. (6) At any given time, among the plurality of liquid crystal display devices that modulate light with an intensity of x including the first wavelength, a signal of positive polarity is applied, and a signal of negative polarity is applied. +y indicates that a positive polarity signal is applied among the plurality of liquid crystal display devices that modulate light of intensity y including the second wavelength, and +y indicates that a negative polarity signal is applied. -y means that a signal of positive polarity is applied among the plurality of liquid crystal display devices that modulate light of intensity z including the third wavelength, and +z means that a signal of negative polarity is applied. When the fact that the above is +x, -x, +
A method for driving a liquid crystal panel, comprising making light enter the plurality of liquid crystal panels so that the sum of y, -y, +z, and -z2 becomes zero or a value close to zero, and modulating the light with the liquid crystal panel. .