JP2001318113A - Apparatus and method for inspection of electro-optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely and efficiently detect the defect of a drive circuit inside a liquid crystal device. SOLUTION: A detection part which detects the power-supply current value of the drive circuit inside the liquid crystal device as an object to be inspected is provided. A judgment part which judges whether the defect of the drive circuit exists or not on the basis of the output of the detection part is provided. The judgment part detects the latent defect of an active element in the drive circuit by detecting the abnormal place of a change in the current value within one data write cycle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an inspection apparatus and an inspection method for an electro-optical device including a liquid crystal display device.

[0002]

2. Description of the Related Art An apparatus / method for inspecting a transistor (TFT) of each pixel of a liquid crystal display device is disclosed.
JP-A-57-38498, JP-A-3-10232
No. 8, JP-A-10-104300, JP-A-10-104300
There is 1-95250.

[0003] These are all intended to inspect line defects and pixel defects on a liquid crystal substrate. A line defect is a disconnection or failure of the wiring up to the TFT of each pixel.
A pixel defect is a defect in the TFT of each pixel.

For example, Japanese Patent Application Laid-Open No. 10-104300 discloses that, in a test of a liquid crystal display, a voltage near a maximum specified value is applied to each auxiliary capacitor to charge a maximum charge, thereby stray capacitance of a data line and video line. The charge of the floating capacitance is discharged to near zero, and the S / N ratio is improved to 10 times or more of the conventional device, and the inspection of the open / short of each pixel is performed. Specifically, before the liquid crystal is sealed, the common ground terminal of the auxiliary capacitor of the liquid crystal display device is grounded, and first, an H voltage close to the specified upper limit is applied to the video terminal to open the gate of the TFT. Charge the auxiliary capacitor to the maximum. The so-called writing is performed. Subsequently, the common ground potential L
A voltage is applied to the video terminal, the column selection switch is turned on, the data line is turned on, and the charges in the data line stray capacitance and the video line stray capacitance are sufficiently discharged. Thereafter, the gate is turned on again, each pixel is sequentially driven selectively, the charge information of the auxiliary capacitor is read, and the presence of an image defect is checked by the image processing device via the sample and hold circuit 34 and the like.

[0005] To this end, the inspection apparatus according to the above-mentioned prior art includes a driver for outputting an H voltage or an L voltage as a reference voltage based on a signal from a scanning timing generator, and a driver for outputting the H voltage and the L voltage in real time to a liquid crystal display device. And an IV conversion circuit for reading an output signal from the video terminal after supplying the signal to the video terminal and outputting the read signal to the sample and hold circuit.

[0006]

However, after inspection, it is often the case that the TFT used in the TFT liquid crystal driver fails, resulting in display failure, not line defects or pixel defects on the liquid crystal substrate. ing. In the inspection
Although heating operation screening is performed, there is a case where it cannot be detected by the screening. There is a need to reliably and efficiently find defects not only in the pixels of the liquid crystal display device but also in the driver itself that drives the pixels.

An object of the present invention is to provide an inspection apparatus and an inspection method for an electro-optical device capable of reliably and efficiently finding a defect in a driver circuit. .

[0008]

An inspection apparatus for an electro-optical device according to the present invention includes a detecting section for detecting a power supply current value of a drive circuit in an electro-optical apparatus to be inspected, and a detecting section for detecting an output of the detecting section. A determining unit for determining whether there is a defect in the drive circuit.

Preferably, the determination unit detects a potential defect of an active element of the drive circuit by detecting an abnormal portion of a current value change within one cycle of data writing.

Preferably, the determination section determines that the drive circuit has a defect when a current value in one cycle of data writing is larger than a predetermined value.

Preferably, the determination section determines that the drive circuit has a defect when a current value in one cycle of data writing is smaller than a predetermined value.

Preferably, the detection section is provided for each of the positive and negative power supplies of the drive circuit, and the determination section determines presence or absence of a defect in the drive circuit based on current values of both the positive and negative power supplies.

Preferably, the detection section includes a current amplifier circuit for integrating a power supply current value of a drive circuit in the electro-optical device, and a current-voltage converter for converting the integrated current value to a voltage value.

Preferably, the determination unit includes a sampling unit that samples an output of the detection unit at a predetermined timing, an A / D converter that converts a sampled analog value into a digital value, and a predetermined specification. A processing unit that evaluates the digital value based on the value to determine the presence or absence of a defect.

Preferably, the sampling means performs sampling every data writing cycle.

Preferably, the sampling means performs sampling in accordance with on / off operation timing of an active element of the drive circuit.

The method for inspecting an electro-optical device according to the present invention includes a step of obtaining a power supply current value of a drive circuit in the electro-optical device to be inspected, a step of integrating the obtained current value,
Converting the integrated current value to a voltage value; sampling the voltage value at a predetermined timing; converting the sampled analog value to a digital value; and Evaluating a digital value to determine the presence or absence of a defect.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An inspection apparatus and an inspection method for an electro-optical device according to an embodiment of the present invention will be described. FIG. 1 is a block diagram showing a case where an inspection device according to an embodiment of the present invention is connected to a liquid crystal display device. FIG. 2 is a block diagram showing the internal structure of the determination unit 14 in FIG. FIG. 3 is an operation explanatory diagram of the inspection apparatus according to the embodiment of the present invention. FIG. 4 is a flowchart showing an inspection method according to the embodiment of the present invention. FIG. 5 is a diagram showing a schematic waveform of each part of the inspection apparatus. FIG. 6 is an explanatory diagram of the inspection method according to the embodiment of the present invention. FIG. 7 is a diagram showing the internal configuration of the liquid crystal panel. FIG. 8 is an operation timing chart of the liquid crystal panel.

In FIG. 1, current amplifier circuits 12a to 12a
d, an inspection device including the current-voltage converters 13 a to 13 d and the determination unit 14 is connected to a power supply line of a driver of the liquid crystal device 10. The liquid crystal device 10 includes an X driver 10
1 positive and negative power supplies 11a, 11b and Y driver 104
Positive and negative power supplies 11c and 11d are connected, but between the power supply and the liquid crystal device 10, current amplification circuits 12a to 12d are connected.
d is inserted. These current amplifier circuits 12a to 12a
Based on the output of d, the determination unit 14 determines whether the driver has a defect. Current amplifier circuits 12a to 12d
Integrates the power supply current, further amplifies it, and sends it to the current-voltage converters 13a to 13d. Current-voltage converters 13a-1
3d converts the current value into a voltage value and sends it to the determination unit 14. The detailed structure of the liquid crystal device will be described later.

In FIG. 2, a plurality of amplifiers 141 to A / D converters 143 are provided corresponding to the current / voltage converters 13a to 13d. FIG. 2 shows one of them.
The amplifier 141 amplifies the input voltage signal, and the sampling means 142 samples a predetermined portion of the amplified voltage signal. The A / D converter 143 converts the sampled voltage value into a digital value and sends it to the personal computer 144. The personal computer 144 checks the input digital value and determines whether or not the value is within a specified range. If it is within the specified range, it is determined that there is no defect. If it is out of the range, it is determined that there is a possibility of a defect, and the result of the determination is output. In the embodiment of the present invention, whether or not the TFT of the driver has a defect is determined by checking current consumption for each shift operation. As will be described in detail later, since the shift operation is periodic, the timing signal generation circuit 145 generates a periodic sampling signal in accordance with the shift operation. The sampling timing is determined so that the defect can be easily detected. For example, when determining the presence or absence of a defect based on the total current consumption in one cycle, it is desirable to sample the voltage of the last part in one cycle. Timing signal generating circuit 145 outputs a signal corresponding to a portion to be sampled.

In FIG. 7, the liquid crystal device includes, as peripheral circuits, a data line driving circuit 101 (X driver) for supplying a data signal to a data line 35 and a scanning line driving circuit for supplying a scanning signal to a scanning line 32. Circuit 104 (Y driver)
, A precharge circuit 201 that supplies a precharge signal NRS of a predetermined voltage level to the plurality of data lines 35 in advance of the image signals Sl, S2,..., Sn, respectively, and the image signals Sl, S2,.
.. And a sampling circuit 301 for sampling Sn and supplying the sampled data to the plurality of data lines 35, respectively.

The scanning line driving circuit 104 supplies a scanning signal to the scanning line 32 at a predetermined timing based on a power supplied from an external control circuit, a reference clock CLY and its inverted clock, and the like.
Gl, G2,..., Gm are applied in a pulse-wise line-sequential manner.

The data line drive circuit 101 scans the scan signals G1 and G based on the power supplied from the external control circuit, the reference clock CLX and its inverted clock, and the like.
2,..., Gm, the sampling circuit drive signals X1, X2,. It is supplied at a predetermined timing via 306.

The precharge circuit 201 includes, for example, a TFT 202 as a switching element for each data line 35, a precharge signal line 204 connected to the drain or source electrode of the TFT 202, and a precharge circuit drive signal line. 206 is connected to the gate electrode of TFT202. In operation, power of a predetermined voltage required for writing the precharge signal NRS is supplied from an external power supply via a precharge signal line 204, and each data line 35 is supplied via a precharge circuit drive signal line 206. About the image signals Sl, S
The precharge circuit drive signal NRG is supplied from the external control circuit so that the precharge signal NRS is written at a timing preceding Sn. Precharge circuit 201
Are preferably image signals Sl, S2,.
Supply a precharge signal NRS (image auxiliary signal) corresponding to Sn.

The sampling circuit 301 includes a TFT 302 for each data line 35, an image signal line 304 is connected to the source electrode of the TFT 302, and a sampling circuit driving signal line.
306 is connected to the gate electrode of the TFT 302. And
Via the image signal line 304, the image signals S1, S2,..., Sn
Are input, these are sampled. That is, the sampling circuit driving signals X1, X2,... From the data line driving circuit 101 via the sampling circuit driving signal line 306.
, Xn are input, the image signals Sl, S2,..., Sn are sequentially applied to the data lines 35 for each of the image signal lines 304.

In this figure, the data lines 35 are configured to be selected one by one. However, as described above, the data lines 35 may be supplied in groups of a plurality of data lines.

As shown in FIG. 8, the data line driving circuit 101
Has a selection time t1 per pixel.
(Dot frequency) is input as a reference for horizontal scanning. When a transfer start signal DX is input, sampling circuit drive signals X1, X2,... Are sequentially supplied from this shift register. You. In each horizontal scanning period, a precharge circuit drive signal (NRG) is supplied to the precharge circuit 201 at a timing prior to the input of the transfer start signal DX. More specifically, the clock signal CLY, which is the reference for vertical scanning, goes high and the image signal (VID) reverses its polarity with reference to the voltage center value of the signal (VID center). After a lapse of time t3, which is a margin before charging, the precharge circuit drive signal (NRG)
High level. On the other hand, precharge signal (NRS)
Is set to a predetermined level having the same polarity as the image signal (VID) during the horizontal retrace period in response to the inversion of the image signal (VID). Therefore, the precharge is performed at the time t2 when the precharge circuit drive signal (NRG) is set to the high level. Then, a time t4 before the end of the horizontal blanking period and the start of the effective display period, that is, a margin from the end of precharge to the writing of an image signal is set to the time t4.
As a result, the precharge circuit drive signal (NRG) is at a low level. As described above, the precharge circuit 201
Indicates the precharge signal (NR
S) is supplied to the plurality of data lines 35 prior to the image signal.

As described above, the X driver 101 outputs the sampling circuit drive signals X1, X2,... For each data line 35 based on the power supplied from the external control circuit, the reference clock CLX and its inverted clock, and the like. Xn is supplied at a predetermined timing. The Y driver 104 sequentially applies the scanning signals G1, G2,..., Gm to the scanning line 32 at a predetermined timing based on the power supplied from the external control circuit, the reference clock CLY, its inverted clock, and the like. In order to perform such an operation, the X driver 101 and the Y driver 104 include a number of shift registers (S / R) connected in series inside. FIG. 3 shows this state. A common power supply line is connected to these shift registers. These shift registers operate in order from left to right. When the shift register operates, that is, when the internal TFT operates, a predetermined current flows. FIG. 5A schematically shows the current waveform. Since the clock supplied to the shift register is periodic, the current consumption waveform is also periodic. The peak of the current waveform is the time when the shift register operates, that is, the timing at which a signal is supplied to a data line or a scanning line. As described above, since the shift register operates in order from left to right, the chevron waveform in FIG. 5A corresponds to the operation of one shift register. If any of the shift registers has a defect, an abnormality is found in the current consumption of the shift register. That is, when observing the current waveform in FIG. 5A and finding an abnormal mountain-shaped waveform different from the others,
It can be determined that the TFT of the shift register corresponding to the waveform has a defect. The inspection method according to the embodiment of the present invention is based on such an idea. According to this method, the defect of the driver can be accurately determined, and
The defect site can be specified.

Next, an inspection method according to an embodiment of the present invention will be described with reference to the flowchart of FIG. A TFT that has a potential defect will exhibit abnormal current during on / off operation. Therefore, a potential defect of the TFT is inspected by amplifying the power supply current for driving the TFT in an analog manner and detecting an abnormal portion of the current value change within one cycle of data writing.

The current value is obtained by the current amplifying circuit 12 inserted into the power supply line of the liquid crystal device 10, and the current value is integrated (S1). When a current waveform as shown in FIG. 5A is obtained, an integral waveform as shown in FIG. 5B is obtained by integrating the current waveform. This integrated waveform is periodic in accordance with the operation of the shift register. By integrating, the presence or absence of a defect can be determined based on the entire current value within one cycle,
Inspection reliability is improved.

The current output from the current amplifier circuit 12 is converted into a voltage by the current / voltage converter 13 (S2).

The converted voltage is amplified by the amplifier 141 (S3). The waveform after amplification is as shown in FIG.

A part of the amplified voltage signal is sampled by the sampling means 142 (S4). The sample timing is immediately before the upper voltage waveform in FIG. In order to satisfy the setup time and the hold time required by the sampling means 142,
Sampling is performed at a timing that is a predetermined time before the waveform returns to the zero level from the peak. The lower part of FIG. 5C shows a sampling waveform, which is sampled at the rising edge of the sampling waveform. Depending on the selection of the sampling waveform, sampling may be performed at the falling edge.

The sampled current value is converted into a digital value by the A / D converter 143 (S5). Computers can be handled by digital conversion.

The digital data is analyzed by the personal computer 144 to determine the presence or absence of a defect. The personal computer 144 has a database (not shown) in which a normal current value range is stored in advance. For example, X for each model and operating frequency
The power supply currents of the driver and the Y driver are obtained in advance and stored. These values may be design values or measured values of products. Also, some types may be stored according to the required level of reliability. The personal computer 144 compares the specified value of the database with the observed digital value,
A defect is determined when the observed value deviates from the standard value.

This will be described based on a specific example. In FIG. 3, the shift registers 101-a to 101-d operate in order from the left. It is assumed that the output of the amplifier 141 at that time has a waveform as shown in FIG.
Symbols a to d in FIG. 6A indicate shift registers 101-a to 101-a.
This corresponds to 01-d. Shift registers 101-a, b,
The waveform of d is aligned at a relatively low level. On the other hand, only the waveform of the shift register 101-c is extremely high. Even though the shift register having such a waveform is operating at that time, there is a high possibility that a malfunction will occur over time. Therefore, it is determined that the shift register having such a waveform c has a defect. Since the sampled data of waveform c is well above normal levels,
The personal computer 144 can determine the defect. Similarly, FIG. 6B shows a specific example in a case where the waveform is extremely low. Since the sampled data of the waveform c is sufficiently lower than the normal level as in the case of the extremely high level, the personal computer 144 can determine the defect.

In the embodiment of the present invention, observation is made for both the positive and negative power supplies, but it is also possible to observe only one of them. When observing both, the determination may be made separately, or the determination may be made by combining the two observation results. For example, when either the positive or negative is out of the specified value, it is determined to be a defect, when both are out of range, it is determined to be a defect, or when both positive and negative data are added to make a determination. Can be used to determine.

As described above, according to the inspection apparatus / inspection method according to the embodiment of the present invention, it is possible to find a potential defect of a TFT of a driver of a liquid crystal device, which was difficult to find conventionally. Conventionally, after normal inspection, TFT
The TFT used for the liquid crystal driver often breaks down, resulting in a display failure. The heating operation screening is performed, but the screening operation cannot detect it. According to the embodiment of the present invention, based on the knowledge that a subtle change occurs in the operating current value of the driver having such a defect, the defect detection is performed by electrically detecting and processing the change in the driver's current value. It can be carried out. Therefore, a potential defect in the TFT can be found in the inspection process, so that a defect can be found before delivery, CS can be improved, and the return rate can be reduced.

The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the invention described in the appended claims, which are also included in the scope of the present invention. Needless to say, this is done.

In this specification, means does not necessarily mean physical means, but also includes a case where the function of each means is realized by software.
Further, the function of one unit may be realized by two or more physical units, or the function of two or more units may be realized by one physical unit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a case where an inspection device according to an embodiment of the present invention is connected to a liquid crystal display device.

FIG. 2 is a block diagram showing an internal structure of a determination unit 14 of the inspection device according to the embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of the inspection device according to the embodiment of the present invention.

FIG. 4 is a flowchart showing an inspection method according to the embodiment of the present invention.

FIG. 5 is a diagram showing a schematic waveform of each part of the inspection apparatus according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram of an inspection method according to the embodiment of the present invention.

FIG. 7 is a diagram showing an internal configuration of a liquid crystal panel.

FIG. 8 is an operation timing chart of the liquid crystal panel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Liquid crystal device 11 Driver power supply 12 Current amplifier circuit 13 Current-voltage converter 14 Judgment part 101 X driver 104 Y driver 141 Amplifier 142 Sampling means 143 A / D converter 144 Personal computer 145 Timing signal generation circuit

Claims (19)

[Claims] 1. An electric apparatus comprising: a detection unit that detects a power supply current value of a drive circuit in an electro-optical device to be inspected; and a determination unit that determines presence or absence of a defect in the drive circuit based on an output of the detection unit. Inspection equipment for optical devices. 2. The device according to claim 1, wherein the determination unit detects a potential defect in an active element of the drive circuit by detecting an abnormal portion of a current value change within one cycle of data writing. Inspection equipment for electro-optical devices. 3. The device according to claim 2, wherein the determining unit determines that the drive circuit has a defect when a current value in one cycle of data writing is larger than a predetermined value. Inspection equipment for electro-optical devices. 4. The device according to claim 2, wherein the determination unit determines that the drive circuit has a defect when a current value in one cycle of data writing is smaller than a predetermined value. Inspection equipment for electro-optical devices. 5. The method according to claim 1, wherein the detection unit is provided for each of the positive and negative power supplies of the drive circuit, and the determination unit determines presence or absence of a defect in the drive circuit based on current values of both the positive and negative power supplies. Item 2. An inspection device for an electro-optical device according to Item 1. 6. The detecting section includes a current amplifier circuit for integrating a power supply current value of a drive circuit in the electro-optical device, and a current-voltage converter for converting the integrated current value to a voltage value. The inspection apparatus for an electro-optical device according to claim 1, wherein: 7. The sampling unit, wherein the determination unit samples the output of the detection unit at a predetermined timing.
An A / D converter that converts a sampled analog value into a digital value, and a processing unit that evaluates the digital value based on a predetermined specified value and determines whether or not there is a defect. Item 2. An inspection device for an electro-optical device according to Item 1. 8. The inspection apparatus for an electro-optical device according to claim 7, wherein the sampling means performs sampling every data writing cycle. 9. The inspection apparatus for an electro-optical device according to claim 7, wherein said sampling means performs sampling in accordance with an on / off operation timing of an active element of said drive circuit. 10. A step of obtaining a power supply current value of a drive circuit in an electro-optical device to be inspected, a step of integrating the obtained current value, a step of converting the integrated current value to a voltage value, Sampling the voltage value at a predetermined timing; converting the sampled analog value to a digital value; and evaluating the digital value based on a predetermined specified value to determine the presence or absence of a defect. An inspection method for an electro-optical device comprising: 11. A detecting step of detecting a power supply current value of a driving circuit in an electro-optical device to be inspected, and a determining step of determining whether the driving circuit has a defect based on a result of the detecting step. Inspection method for electro-optical devices. 12. The method according to claim 11, wherein the determining step detects a potential defect of an active element of the driving circuit by detecting an abnormal portion of a current value change within one cycle of data writing. Inspection method for electro-optical devices. 13. The method according to claim 12, wherein the determining step determines that the drive circuit has a defect when a current value in one cycle of data writing is larger than a predetermined value. Inspection method for electro-optical devices. 14. The method according to claim 12, wherein the determining step determines that the drive circuit has a defect when a current value within one cycle of data writing is smaller than a predetermined value. Inspection method for electro-optical devices. 15. The detecting step detects current values of positive and negative power supplies of the drive circuit, and the determining step determines presence or absence of a defect in the drive circuit based on current values of both the positive and negative power supplies. The inspection method for an electro-optical device according to claim 11, wherein 16. The electro-optical device according to claim 11, wherein in the detecting step, a power supply current value of a drive circuit in the electro-optical device is integrated, and the integrated current value is converted into a voltage value. Inspection method. 17. The determining step samples a detection result of the detecting step at a predetermined timing, converts a sampled analog value into a digital value, and evaluates the digital value based on a predetermined specified value. The method for inspecting an electro-optical device according to claim 11, wherein presence / absence of a defect is determined by performing the determination. 18. The method according to claim 1, wherein in the determining step, sampling is performed every data writing cycle.
8. The method for inspecting an electro-optical device according to claim 7. 19. The inspection apparatus for an electro-optical device according to claim 17, wherein the determining step performs sampling in accordance with an on / off operation timing of an active element of the drive circuit.