JPH0453923A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain this stable and high-definition liquid crystal display device by providing a monitor picture element in the invalid picture element part of a liquid crystal display panel, and also, providing a sensor for measuring the translucent light quantity of the liquid crystal display panel. CONSTITUTION:On a part of a display frame body 22, a sensor 23 for detecting light which transmits through a liquid crystal panel 21 is pressent and on the liquid crystal panel 21 of the part covered with the display frame body 22, is a monitoring picture element 27 are both in the invalid picture element part 28 of the liquid crystal display panel 21. Accordingly, partial picture elements in the liquid crystal display panel which is driven actually become the monitoring picture elements, and a voltage is controlled so that the light quantity of the monitoring picture element becomes optimal, therefore, the liquid crystal display device can always be driven in the optimal condition irrespective of the variation of the light quantity of backlight.

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention relates to an active matrix liquid crystal display device.
In particular, the present invention relates to an active matrix liquid crystal display device characterized in that the driving voltage of an active element is adjusted depending on the amount of light from an internal light source.

(B) Conventional technology Conventionally, in active matrix liquid crystal display devices that use thin film transistors (TPT) made of materials such as amorphous silicon (A-8I) as driving elements, the voltage due to the parasitic capacitance of the TPT is due to the structure. It has been pointed out that a voltage drop Δv1 and a voltage drop Δv2 due to discharge occur, and the source signal becomes asymmetric with respect to the median value of the data signal ("Application to personal information equipment", Electronic Technology, May special edition) No. 32, No. 7, P36 (1990)
).

FIG. 8 shows a waveform diagram of each signal of TPT.

In FIG. 8, the source signal (1) is shifted in the negative direction compared to the data signal (2).

Therefore, the level of the counter electrode signal is at the center of the data signal (3
), but is set to the center of the source signal (4).

As shown in Figure 8, the voltage drop ΔVl due to the parasitic capacitance of TPT
Although (5) is in the negative direction, the voltage drop ΔV2 due to discharge
In (6), the direction is reversed for each field.

The difference between the center of the data signal (3) and the center of the source signal (4) is D
If superimposed on the counter electrode as C bias ΔV'(7),
No DC component is applied to the liquid crystal, preventing deterioration of the liquid crystal.

However, the optimum C bias (7) for an active matrix type liquid crystal display device is dependent on voltage, position, and time, and a single DC bias (7) value for the entire liquid crystal panel will cause light unevenness on the display surface of the liquid crystal display device. was occurring.

Conventionally, a separate ROM writer is used to write data on the unevenness of light intensity of a portable liquid crystal display device to the FROM in the liquid crystal display device.
A uniform screen was obtained by reading out data for each horizontal line and applying a voltage corresponding to the data to a common electrode or data line (Japanese Unexamined Patent Publication No. 148781/1983).

FIG. 9 shows a block diagram of a liquid crystal display device using FROM.

In FIG. 9, a control signal was applied from the FROM (10) to the counter electrode (8) and the data line drive circuit (9) of the liquid crystal display device.

However, FROM cannot be rewritten in portable liquid crystal display devices, and cannot compensate for the voltage and time dependence of the DC bias (7).

Therefore, there has conventionally been a liquid crystal display device in which the voltage of the pixel electrode of the liquid crystal display device is monitored by a source follower circuit to adjust the liquid crystal driving voltage (Japanese Patent Publication No. 8830/1983).

FIG. 10 shows a circuit diagram for monitoring the signal of 11 poles of pixels.

In Figure 10, the TPT (13) is connected near the intersection of the gate input terminal (11) and the data input terminal (12), and the auxiliary capacitor (14) connected to ground and the pixel electrode (15) connected to the source of the TPT are connected. I was prepared.

In the same figure, the pixel electrode (15) is a depletion type FE.
T-A (16) is electrically connected, a source follower circuit consisting of FET-A (16) and FET-B (17) is provided with a drain voltage supply terminal (18), and a monitor output terminal (1
9), the liquid crystal driving voltage was measured.

Although the configuration shown in FIG. 10 allows easy temperature compensation and drive voltage control, it is insufficient to adjust the amount of transmitted light, which is the most important aspect of an optical element.

FIG. 11 is a characteristic diagram showing changes in TPT characteristics depending on the amount of light.

That is, as shown in FIG. 11, even with the same driving voltage, in an active matrix type liquid crystal display device, an increase in the amount of light transmitted through the liquid crystal display panel causes the TPT to turn OFF', and the threshold voltage and saturation gate voltage increase. In some cases, the display on the liquid crystal display panel was different and the desired image quality could not be obtained.

(c) Problems to be Solved by the Invention As described above, since a fixed DC bias was supplied to the liquid crystal display device and the drive voltage of the liquid crystal was used as the observed quantity in the monitor pixel, the characteristics of the liquid crystal display device changed due to light. This causes a direct current component to be applied to the liquid crystal, resulting in problems such as generation of flicker and deterioration of the liquid crystal.

The present invention measures the amount of light transmitted through the liquid crystal display panel by arranging monitor pixels in the liquid crystal display device, and adjusts the amount of light to a desired amount, thereby improving the display quality of the liquid crystal display device by applying a DC component to the liquid crystal. The purpose is to solve the problem of deterioration.

(d) Means for Solving the Problems In order to solve the above problems, it is sufficient to monitor the amount of light and adjust the drive voltage and DC bias so as to obtain the desired amount of light.

The present invention is an active matrix type liquid crystal display panel consisting of an active matrix type liquid crystal display panel, a backlight, monitor pixels in the liquid crystal display panel to which light from the backlight is irradiated, and a display frame defining an invalid surface area of the liquid crystal display panel. The active matrix type liquid crystal display device is characterized in that the monitor pixel is located in an invalid pixel area of the liquid crystal display panel and is equipped with a sensor for measuring the amount of light transmitted through the liquid crystal display panel.

(E) Function In the liquid crystal display device with the above configuration, data signals are not controlled by measuring the fixed DC bias or liquid crystal drive voltage by the conventional FROM, but by controlling the data signal within the liquid crystal display panel that is actually being driven. Some of the pixels are used as monitor pixels, and the voltage is controlled to optimize the amount of light of the monitor pixels, so that stable display can be provided.

(F) Embodiment FIG. 1 shows a characteristic diagram of the light transmittance T and the data signal Vd in the liquid crystal display device of the present invention.

In FIG. 1, as described in the prior art, it is necessary to increase the drive tJE of the liquid crystal according to the amount of light. ! I have to change it to vb of
As is clear from the figure, it is sufficient to simply adjust the data signal Vd so that the light transmittance T is fixed at Tc.

FIG. 2 shows a relationship diagram between the data signal of the liquid crystal display panel in non-transmission mode and the amount of light of the backlight.

In FIG. 2, as the amount of light from the backlight increases, the data signal Vd increases II! I know it will happen.

FIG. 3 shows a cross-sectional view of a liquid crystal display device equipped with a backlight according to the present invention.

In Figure 3, the light from the backlight (20) passes through an active matrix liquid crystal display channel (21), is restricted to the display frame (22), and is perceived by the human eye as an image. be done.

A sensor (23) is provided in a part of the display frame (22) for detecting light transmitted through the liquid crystal display (21).

The liquid crystal display panel (21) consists of a TPT substrate (24) and a counter substrate (25), and is connected to the TPT in the liquid crystal display panel 21) in the part not covered by the display frame (22). There are effective pixels (26), - real display frame (26)
There is a monitor pixel (27) fully connected to the TPT in the portion of the liquid crystal panel (21) covered by.

The sensor (23) and the monitor pixel (27) are both located in the invalid pixel section (28) of the liquid crystal display panel (21).

FIG. 4 shows a plan view of a liquid crystal display panel having monitor pixels.

In Figure 4, the TFT substrate (24
), a plurality of gate lines (29) are arranged on the gate line (29).
9) Above is a gate insulating film (30
).

A data line (31) and TPT (
32) and pixel electrodes are arranged.

The pixel electrode fully connected to the TPT (32) has an effective pixel area (
There are a valid pixel (26) in the area 33) and a monitor pixel (27) in the invalid pixel area.

A TPT substrate (24) is placed on the TPT substrate away from the pixel electrode.
A resin seal (34) is provided to bond the substrate and the counter substrate (25) together.

FIG. 5 shows a control diagram of a liquid crystal display device in which monitor pixels are provided at both ends of an effective pixel portion in the gate line direction.

In FIG. 5, the gate line (29) and the data line (31)
One pixel electrode corresponds to one intersection point, and a monitor pixel (27) and a sensor (23) corresponding to the monitor pixel (27) are installed outside the effective pixel section (33).

When a disconnection IN (35) occurs in one of the gate lines (29), a non-lighted pixel (36) is generated that does not respond to the magnitude of the data signal applied to the data m (31).

After converting the amount of transmitted light from the monitor pixels (27) at both ends in FIG. ) sends a control signal to a selector (39) that generates a selection signal for selecting two gate line drive circuits (38) connected to both ends of the gate line (29).

When the sensor (23) facing the monitor pixel (27) detects a disconnection (35) in the gate line (29), the signal generator (37) and selector (39) act to
) A gate signal is applied from the gate I/I dynamic circuit (3B) to both ends of the gate line, so that disconnection of the gate line can be compensated for.

Up to this point, we have described the control of data signals in response to changes in TPT characteristics caused by light.
An optical characteristic diagram corresponding to a constant light amount in which bias is also controlled is shown.

In Figure 6, the vertical axis is the amount of light when not transmitted! , the tank axis is DC
The bias ΔV° is shown respectively.

Figure 6 (7) A is the data signal [Vd] (2) is Vd
=Va shows the variation in the amount of light transmitted through the liquid crystal display panel with respect to the change in DC bias, and B in the figure shows Vb>
It shows the variation in the amount of transmitted light when the data signal vb is larger than A, which is Va.

As mentioned in Fig. 1 at the beginning of the embodiment, in order to reduce the amount of transmitted light of the monitor pixel, first change the characteristic to A in Fig. 6.
The data signal can be increased by changing from to B to B, but in order to avoid applying a DC component to the liquid crystal, next adjust the DC bias to minimize the light intensity l.

Data signal and DC bias as above! III! An adjustment circuit diagram for performing this is shown in FIG.

In Figure 7, transmitted light (4
0) is converted into an electrical signal by a sensor (23).

The electric signal from the sensor (23) causes the signal generator (37
) to the data line drive circuit (9) and the opposing tS drive circuit (
A control signal is sent to 41), and the liquid crystal display panel is controlled so that the amount of light (2) during non-transmission is minimized.

(G) Effects of the Invention According to the present invention, the liquid crystal can be driven with alternating current under the best conditions regardless of the amount of light from the backlight, so a liquid crystal display device with an easy-to-read screen can be provided.

Further, in a liquid crystal display device composed of a plurality of liquid crystal display panels, it is possible to easily equalize the brightness at of each wavelength of the liquid crystal display panels and the brightness of the liquid crystal display panels in the same wavelength band.

As described above, according to the present invention, the liquid crystal display device can always be driven under optimal conditions regardless of changes in the light amount of the backlight, and therefore a stable and high-image-quality liquid crystal display device can be realized.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram of the light transmittance and data signal in the liquid crystal display device of the present invention, FIG. 2 is a characteristic diagram of the data signal and backlight light amount when the liquid crystal display panel is not transmitting, and FIG. 3 is a characteristic diagram of the light intensity of the backlight. FIG. 4 is a sectional view of the liquid crystal display device of the present invention, and FIG. 51 is a plan view of the liquid crystal display panel of the present invention! i is a control diagram of a liquid crystal display device of the present invention in which monitor pixels are provided at both ends of the effective pixel portion in the gate line direction, and FIG. 6 is an optical diagram for controlling data signals and DC bias in the liquid crystal display device of the present invention. The characteristic diagram, FIG. 7, shows the data signal and DC bias in the liquid crystal display device of the present invention! Ill! Adjustment circuit diagram to perform
Figure 8 is a waveform diagram of each signal of a normal TPT, Figure 9 is a block diagram of a liquid crystal display device using a conventional FROM, @1o
The figure shows a circuit diagram for monitoring conventional pixel electrode signals.
FIG. 11 is a characteristic diagram showing changes in TPT characteristics depending on the normal amount of light. (1)...Source signal, (2)...Data signal,
(3)...data signal center, (4)...source signal center, (5)...voltage drop, (6)...voltage drop,
(7) - D C / < 47 s, (8) - * direction tJI
. (9)...Data line drive circuit, (1o)...FRO
M, (11)...gate λ power terminal, data input terminal for (12), (13)...TPT, auxiliary capacitor for (14), (15)...pixel electrode, (16)...・FETA,
(17)...-FET-B, (1g)...Drain voltage supply terminal, (19)...Monitor output terminal, (20)
... Backlight, (21) ... Liquid crystal display panel,
(22)...Display frame body, (23)...Sensor, (2
4)... TPT substrate, (25)... Counter substrate, (2
6)...Effective pixels, (27)...Monitor ill, (
28)...Invalid display section, (29)...Gate line, (
30)...Gate insulating film, (31)...Data line,
(32)...TFT, (33)...Effective pixel section, (
34)...M Pilgrimage sticker, (35)...Disconnection, (36
)...Illustrator, (37)...Signal generator, (3
8)...Gate line drive circuit, (39)...Selector,
(4o)...Transmitted light, (41)...Counter electrode drive circuit. Applicant: Sanyo Gunki Co., Ltd. Agent Patent attorney: Kusatsugu Nishino (2 others) Figure 1 Figure 2 Small A Ha'.../Flight f) Princess (Figure 6 DC High 1 Iasm V' Figure 4 Figure 7 Figure 8 Figure U S-F electric foot v9

Claims (1)

[Claims] (1) Active matrix type Active matrix type consisting of an active matrix liquid crystal display panel, a backlight, monitor pixels in the liquid crystal display panel that are irradiated with light from the backlight, and a display frame that defines the invalid display area of the liquid crystal display panel. 1. An active matrix liquid crystal display device, characterized in that the monitor pixel is located in an invalid pixel area of a liquid crystal display panel, and the monitor pixel is provided with a sensor that measures the amount of light transmitted through the liquid crystal display panel.