JP3557475B2 - Liquid crystal display device with driver circuit - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a liquid crystal display device having a plurality of driver circuits and capable of easily detecting a failed driver circuit.
[0002]
[Prior art]
A TFT (thin film transistor) liquid crystal display device provided with a driver circuit is known. FIG. 5 shows a configuration example of this type of TFT liquid crystal display device. In FIG. 5, reference numeral 111 denotes a TFT panel in which TFTs, pixel electrodes, gate lines, drain lines, and the like are formed in a matrix. A liquid crystal display element is formed by bonding the TFT panel 111 and the counter substrate with a sealant therebetween and sealing liquid crystal therebetween.
[0003]
Gate drivers (gate driver circuits) 112A and 112B are connected to the gate lines of the TFT panel 111 using a COG (chip-on-glass) method, a TAB (tape automated bonding) method, or the like. Are connected to drain drivers (drain driver circuits) 113A to 113C. The start pulse input terminals IN of the drain drivers 113B and 113C are connected to the start pulse output terminals OUT of the drain drivers 113A and 113B of the preceding stage via cascade lines 115A and 115B on the printed wiring board 114.
[0004]
A start pulse is supplied to the start pulse input terminal IN of the first-stage drain driver 113A from the input terminal 116 on the printed wiring board 114 from the outside via a start pulse supply line 117.
Further, an image signal (gradation signal) is supplied to the drain drivers 113A to 113C via the input terminal 116 and the image signal supply line 118.
[0005]
When the start pulse is supplied to the first-stage drain driver 113A, the drain driver 113A samples the image signal, and supplies the start pulse to the second-stage drain driver 113B when the sampling is completed. In response to the start pulse, the second-stage drain driver 113B starts sampling the image signal.
In this way, the drain drivers 113A to 113C sequentially sample the image signals, and when the sampling is completed, apply a voltage signal corresponding to the display gray scale to the drain lines all at once.
[0006]
The gate drivers 112A and 112B turn on the TFTs in each column by sequentially applying a gate pulse to the gate line, and write a voltage signal to each pixel.
An arbitrary image is displayed by repeating the above operation.
[0007]
[Problems to be solved by the invention]
In such a liquid crystal display device, when one of the drivers fails, it is necessary to determine which driver has failed.
As a method of this determination, a method of confirming the input and output of the start pulse of each driver is known.
[0008]
For example, when the regions corresponding to the drain drivers 113B and 113C are not displayed and a start pulse cannot be detected on the cascade line 115A, it is necessary to determine which of the drain driver 113A and the drain driver 113B has failed. is there.
In this case, the cascade line 115A is disconnected, the start pulse supply line 117 is connected to the start pulse input terminal IN of the drain driver 113B by a jumper wire or the like, and the start pulse is forcibly supplied to the drain driver 113B. Check whether a signal is output or not, and determine the location of the failure.
[0009]
However, in this determination method, complicated processing such as disconnection of a wiring and connection of a jumper wire is required, and it takes time to determine a failed drain driver, which is inefficient. When the surface of the printed wiring board is covered with an insulating protective film or the like, an operation of removing the insulating protective film is also required, and the working efficiency is further reduced.
[0010]
The present invention has been made in view of the above situation, and has as its object to provide a liquid crystal display device capable of efficiently determining a failed or damaged driver circuit.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a liquid crystal display device according to the present invention includes a plurality of electrodes, a liquid crystal display element for displaying an image in accordance with a signal supplied to the electrodes, and a starter connected to the electrodes of the liquid crystal display element. An image signal is captured in response to a start pulse supplied to a pulse input terminal, and when capture is completed, a plurality of driver circuits cascaded in n stages that output a start pulse to a start pulse output terminal, and an externally supplied driver circuit. Start pulse input means for supplying the start pulse to the start pulse input terminal of the first stage driver circuit, image data supply means for supplying image data to each of the n-stage driver circuits, and second to n-th It is arranged corresponding to the driver circuit and is connected to the start pulse output terminal of the driver circuit in the preceding stage of the corresponding driver circuit. A first pad connected to a start pulse input terminal of the corresponding driver circuits, and a second pad connected to the first pad during normal, is connected to the start pulse input means, second during inspection (N-1) short pads, which are connected to the first pad and the third pad for supplying the start pulse supplied from the start pulse input means to the start pulse input terminal of the corresponding driver circuit. It is characterized by having.
[0012]
[Action]
According to the above configuration, in the normal state, the first and second pads are connected, and the first and second pads are insulated and the second and third pads are connected at the time of inspection. Since the start pulse from the start pulse input means can be easily supplied directly to each driver circuit, a failed driver circuit can be easily identified.
[0013]
【Example】
A liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a plan view showing the structure of a TFT panel and a printed wiring board connected to the TFT panel of the liquid crystal display device according to this embodiment, FIG. 2 is a plan view showing the structure of the TFT panel, and FIG. FIG. 4 is a plan view, and FIG. 4 is a diagram illustrating an example of the configuration of the drain driver.
[0014]
As shown in FIG. 2, a TFT panel 11 of a liquid crystal display element includes a matrix of TFTs 12 and pixel electrodes 13 connected to source electrodes of the TFTs 12, and a gate line 14 connected to a gate electrode of the TFT 12 in each row. The drain line 15 is connected to the drain electrode of the TFT 12 in each column.
[0015]
As shown in FIG. 1, drain drivers 21 </ b> A to 21 </ b> C are fixed to the TFT panel 11 using a COG method, a TAB method, or the like, and are connected to a terminal portion of the drain line 15. Similarly, the gate drivers 22A and 22B are connected to the terminal of the gate line 14.
[0016]
To the drain drivers 21A to 21C, an image signal (gradation signal), a clock signal, an inhibit signal, and the like are supplied from an input terminal 32 formed on a printed wiring board 31 via a wiring group 33.
Further, a start pulse is supplied from the input terminal 32 to the start pulse input terminal IN of the first stage drain driver 21A via the start pulse supply line 34.
[0017]
Further, on the printed wiring board 31, first and second short pads 41 and 42 are arranged.
The short pad 41 includes a first pad 411 connected to the start pulse output terminal OUT of the drain driver 21A of the preceding stage, a second pad 412 connected to the start pulse input terminal IN of the drain driver 21B of the subsequent stage, A third pad 413 connected to the pulse supply line 34. The short pad 42 includes a first pad 421 connected to the start pulse output terminal OUT of the drain driver 21B in the preceding stage, and a second pad 422 connected to the start pulse input terminal IN of the drain driver 21C in the subsequent stage. , A third pad 423 connected to the start pulse supply line 34.
Normally, the first pads 411 and 421 of the short pads 41 and 42 and the second pads 412 and 422 are connected to each other by a conductor 414 such as solder or aluminum foil as shown in FIG. Pads 413 and 423 are insulated from other pads.
[0018]
The printed wiring board 31 is entirely covered with a protective insulating film except for connection pads to the drivers 21A to 21C and 22A and 22B and short pads 41 and 42.
[0019]
Next, the configuration of the drain driver will be described with reference to FIG.
As shown in FIG. 4, each of the drain drivers 21A to 21C includes a shift register 211, a level shifter 212, a sample and hold circuit 213, and an output circuit (drive circuit) 214.
[0020]
The shift register 211 sequentially shifts the supplied start pulse in accordance with the clock pulse and outputs the shifted start pulse to the driver at the subsequent stage.
The level shifter 212 shifts the signal level of the output signal of the shift register 211 and supplies the signal to the sample and hold circuit 213.
The sample and hold circuit 213 includes a plurality of sample and hold elements, and sequentially samples and holds the supplied image signals at the timing when each signal supplied from the level shifter 212 is at an active level.
The output circuit 214 keeps its output open when the inhibit signal is at the active level, and amplifies the output signal of the sample and hold circuit 213 and applies it to the drain line 15 when the inhibit signal is at the inactive level.
[0021]
Next, the operation of the liquid crystal display device having the above configuration will be described.
First, a start pulse and an image signal are supplied to the input terminal 32. The start pulse is supplied to the shift register 211 of the first-stage drain driver 21A. The shift register 211 sequentially shifts the start pulse, and the sample-and-hold circuit 213 samples the video signal according to the shift.
[0022]
When the sampling operation of the drain driver 21A of the first stage is completed, the shift register 211 outputs a start pulse, and the start pulse is transmitted through the first and second pads 411 and 412 of the first short pad 41. It is supplied to the shift register 211 of the two-stage drain driver 21B. Thereafter, similarly, sampling processing of the second and third stage drain drivers 21B and 21C is performed.
[0023]
When the sampling operation of the video signal is completed in all the drain drivers 21A to 21C, the inhibit signal becomes an inactive level, and the signal held in the sample and hold circuit 213 of each of the drain drivers 21A to 21C is amplified by the output circuit 214. It is supplied to the corresponding drain line 15.
At this timing, the gate driver 22A or 22B applies a gate pulse to the selected gate line 14, turns on the TFT 12, and writes a voltage signal corresponding to the display gradation to each pixel.
[0024]
By repeating such an operation, an arbitrary gradation signal is written to the pixels in each row, and an image is displayed.
[0025]
Here, it is assumed that the second-stage and third-stage drain drivers 21B and 21C have stopped operating for some reason. In this case, it is checked from the signal on the short pad 41 whether or not the start pulse is normally supplied from the first-stage drain driver 21A to the second-stage drain driver 21B.
When the start pulse is not detected, the case where the first drain driver 21A has failed, and the case where the second and subsequent drain drivers 21B and 21C have failed are considered.
[0026]
In this case, the conductor 414 connecting the first pad 411 and the second pad 412 of the first short pad 41 is melted or scraped off to insulate both pads.
Next, a start pulse is input from the input terminal 32, and it is determined whether or not the first stage drain driver 21A operates normally and outputs the start pulse normally. Next, the second and third pads 412 and 413 of the first short pad 41 are connected to each other with solder or a contact member for connection (a connection member having a conductive rubber or the like disposed at a tip end) or the like, and the input terminal 32 is connected. Then, a start pulse is input to check the operation of the second-stage drain driver 21B.
A similar operation is performed for the third drain driver as needed.
[0027]
By performing such a test, a failed drain driver can be easily determined without using a complicated procedure such as disconnecting a wiring or arranging a jumper line. In particular, since the short pads 41 and 42 are exposed, the above-described inspection procedure is very easy.
[0028]
The present invention is not limited to the above embodiment, and can be applied to various liquid crystal display devices of a type in which a plurality of driver circuits are arranged and a control signal is sequentially supplied from a preceding driver to a subsequent driver to control operation timing. It is.
For example, as shown in FIG. 1, when the second stage gate driver 22B starts operating in response to a signal from the first stage gate driver 22A, the first stage and the second stage gate driver A short pad may be arranged between 22A and 22B.
[0029]
In the above embodiment, the flow of the control signal (start pulse) was controlled by arranging the short pads 41 and 42. However, for example, a switch is disposed between each driver circuit, and the signal flow is controlled by switching the switch. Other configurations for signal switching, such as control, may be used.
[0030]
In the above-described embodiment, an example has been described in which the drain driver and the gate driver are arranged on the TFT panel side of the pair of panels forming the liquid crystal display element, but the arrangement position of the driver is arbitrary. For example, drivers may be arranged on both one panel and the other panel, the drivers on one panel may be connected to odd-numbered lines, and the drivers on the other panel may be staggered to even-numbered lines. Good.
[0031]
Further, the present invention is not limited to a TFT liquid crystal display device, and can be applied to an active matrix type liquid crystal display device using an MIM as an active element. Further, the present invention can be applied to a simple matrix type liquid crystal display device having a plurality of segment drivers and a common driver. The present invention is also applicable to a liquid crystal display device.
[0032]
In addition, the present invention is not limited to the above-described embodiment, and is applied to various circuits of a type in which a plurality of circuits are arranged and cascade-connected such that a subsequent-stage circuit starts operating by a control signal from the preceding-stage circuit. It is possible.
[0033]
【The invention's effect】
As described above, according to the present invention, since a short pad for controlling transmission of a control signal is arranged between driver circuits, a failed driver circuit can be easily identified.
[Brief description of the drawings]
FIG. 1 is a plan view showing a configuration of a TFT panel and a printed wiring board according to one embodiment of the present invention.
FIG. 2 is a diagram showing a plan configuration of the TFT panel shown in FIG.
FIG. 3 is a diagram showing a configuration of a short pad.
FIG. 4 is a block diagram illustrating a configuration of a drain driver.
FIG. 5 is a plan view showing a configuration of a conventional TFT panel and a printed wiring board.
[Explanation of symbols]
11 TFT panel, 12 TFT, 13 pixel electrode, 14 gate line, 15 drain line, 21A to 21C drain driver, 22A, 22B gate Driver, 31: printed wiring board, 32: input terminal, 33: wiring group, 34: start pulse supply line, 41, 42 ... short pad, 411, 421 ... first Pads, 412, 422: second pads, 413, 423: third pads, 111: TFT panels, 112A, 112B: gate drivers, 113A to 113C: drain drivers, 114: printed wiring board, 115A, 115B: cascade line, 116: input terminal, 117: start pulse supply line, 11 ... image signal supply line

Claims (2)

A liquid crystal display device comprising a plurality of electrodes, and displaying an image according to a signal supplied to the electrodes,
It is connected to the electrode of the liquid crystal display element, captures an image signal in response to a start pulse supplied to a start pulse input terminal, and, when the capture is completed, is cascaded to an n-stage that outputs a start pulse to a start pulse output terminal. A plurality of driver circuits,
Start pulse input means for supplying a start pulse supplied from the outside to a start pulse input terminal of the first stage driver circuit;
Image data supply means for supplying image data to each of the n-stage driver circuits;
A first pad arranged corresponding to the second to nth driver circuits and connected to a start pulse output terminal of a driver circuit at a stage preceding the corresponding driver circuit, and connected to a start pulse input terminal of the corresponding driver circuit; And a start pulse supplied from the start pulse input means connected to the second pad at the time of inspection and connected to the second pad connected to the first pad at normal times and connected to the start pad input means. (N-1) short pads, which are supplied to the start pulse input terminal of the corresponding driver circuit .
A liquid crystal display device comprising a driver circuit, comprising: Each of the (n-1) short pads is formed on a printed wiring board on which a start pulse input unit and an image data supply unit are formed, and the first to third pads are formed to be exposed. A liquid crystal display device comprising the driver circuit according to claim 1.

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