JP2002251169A - Inspection method for, liquid crystal display device, and inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the inspection method of a liquid crystal display device capable of obtaining the optimum supply voltage minimizing the flicker of a liquid crystal panel to be measured easier than in the conventional practice. SOLUTION: In this inspection method, transmitted rays of light P2 are measured with photoelectric converting elements 3 while changing a voltage to be applied from a driving circuit 4 to the common substrate of a liquid crystal panel 1 to be measured and the level of an detected AC signal is observed with an oscilloscope 6 (or a digital multi-meter) and the voltage at the time when the level of the AC signal becomes the minimum is evaluated as the optimum voltage value with which the flicker of the liquid crystal panel 1 to be measured becomes the minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display quality inspection apparatus for a liquid crystal panel used in a liquid crystal display device. More specifically, the present invention relates to an inspection method for obtaining and inspecting an optimum voltage value that minimizes flicker (brightness flicker) of a liquid crystal panel.

[0002]

2. Description of the Related Art In a liquid crystal panel, a liquid crystal is sealed in a cell formed between a common substrate and an electrode substrate in which a transistor and a pixel electrode are formed at pixel positions, and the transistor is driven to drive the common electrode. A drive voltage is applied between the pixel electrode and the liquid crystal to align the liquid crystal, and in a transmission type liquid crystal panel, transmission light is controlled to perform display.

Since the flicker generated when the liquid crystal panel is irradiated with light is affected by the voltage supplied to the common substrate, it is necessary to find an optimum supply voltage for each liquid crystal panel. Conventional inspection equipment that determines this optimum supply voltage value
For example, an inspection apparatus described in JP-A-1-270099 is known.

[0004] This type of flicker inspection apparatus is configured as shown in FIG. A light source (backlight) 2 and a photoelectric conversion element 3 such as a photodiode are arranged with a liquid crystal panel 1 interposed therebetween. When a voltage is supplied from the drive circuit 4 to the common substrate of the liquid crystal panel 1, the light P1 emitted from the light source 2 passes through the liquid crystal panel 1, and the transmitted light P2 is received by the photoelectric conversion element 3, and the photoelectric conversion element 3 The output signal 3 is input to a spectrum analyzer (frequency analyzer) 5. In the spectrum analyzer 4, the frequency change component of the output signal of the photoelectric conversion element 3 is displayed with the horizontal axis representing the frequency and the vertical axis representing the level.

[0005]

However, in the above inspection method, in order to determine the minimum flicker level from the display of the spectrum analyzer 5, for example,
Since the optimum supply voltage value is obtained by extracting the flicker level of the 30 Hz component from the output signal from the photoelectric conversion element 3, there is a problem that the inspection time becomes long.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for inspecting a liquid crystal display device in which an optimum supply voltage value for minimizing flicker of a liquid crystal panel can be more easily obtained than in the prior art.

[0007]

According to a method for inspecting a liquid crystal display device of the present invention, transmitted light or reflected light of a liquid crystal panel is converted into an electric AC signal by a photoelectric conversion element, and an optimum voltage value is converted from the converted AC signal. It is characterized by seeking.

According to the present invention, the frequency analysis of the flicker level does not need to be performed, so that the detection time of the optimum supply voltage can be shortened.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a first aspect of the present invention, there is provided an inspection method for a liquid crystal display device, wherein a liquid crystal is provided between a common substrate and an electrode substrate provided with a driving transistor and opposed to the common substrate. When inspecting flicker by irradiating the filled liquid crystal panel with light, photoelectric conversion of transmitted light of the measured liquid crystal panel or reflected light from the measured liquid crystal panel while changing the voltage of the common substrate of the measured liquid crystal panel. Converting the voltage of the common substrate when the level of the converted electrical AC signal is minimized to an optimal voltage value that minimizes flicker of the liquid crystal panel to be measured. Features.

According to a second aspect of the present invention, there is provided a method for inspecting a liquid crystal display device according to the first aspect, wherein the electrical AC signal converted by the photoelectric conversion element is converted into a voltage applied to the common substrate of the liquid crystal panel to be measured. When the output voltage of the driving device becomes a voltage value at which the level of the AC signal converted by the photoelectric conversion element takes a minimum value, the voltage value of the common substrate is fed back to the generated driving device side. It is characterized by being evaluated as an optimum voltage value.

According to a third aspect of the present invention, there is provided a liquid crystal display device.
An inspection device for inspecting flicker by irradiating a liquid crystal panel filled with liquid crystal between a common substrate and an electrode substrate formed with a driving transistor and facing the common substrate for flicker, A drive circuit for supplying a voltage to the substrate, a photoelectric conversion element for converting transmitted light or reflected light received through the liquid crystal panel to be measured into an electric AC signal, and an AC signal converted by the photoelectric conversion element for an input signal. And controlling the output voltage of the drive circuit and comparing the output voltage of the drive circuit with the past signal level input from the start of the test, the output of the drive circuit at a voltage value at which the level of the AC signal converted by the photoelectric conversion element becomes a minimum value. A control unit for automatically controlling the voltage to a stable state.

Hereinafter, a method for inspecting a liquid crystal display device according to the present invention will be described based on specific embodiments. (Embodiment 1) FIG. 1 shows an inspection apparatus used for carrying out an inspection method of a liquid crystal display device of the present invention.

The components having the same functions as those of the prior art shown in FIG. 4 are denoted by the same reference numerals. In FIG. 1, a device for analyzing the output of the photoelectric conversion element 3 is different from a conventional frequency analyzer.

The inspection device is a liquid crystal panel 1 which is an object to be measured.
A light source (backlight) 2 and a photoelectric conversion element 3 such as a photodiode are arranged on both sides. When a voltage is supplied from the drive circuit 4 to the common substrate of the liquid crystal panel 1, the light source 2
Is transmitted through the liquid crystal panel 1 and received by the photoelectric conversion element 3, and the output signal of the photoelectric conversion element 3 is input to the oscilloscope 6, and the signal level at each time is displayed in a waveform.

At this time, the oscilloscope 6 is set to the AC input mode for measuring and displaying only the AC component of the input signal, and observes the waveform. Furthermore, the running range (time axis) is 1
The observation was set at 0 ms / div. Since the displayed waveform itself does not relate to this inspection, the following inspection work can be performed regardless of whether the synchronization state is locked or unlocked.

While watching the waveform of the oscilloscope 6,
An operator variably operates the output voltage of the drive circuit 4, and suppresses the output voltage of the drive circuit 4 when the peak value (the width of the AC signal) of the AC signal level becomes minimum from the voltmeter 7 to suppress flicker. Read as the optimal voltage to. In addition,
As the light source 2, a light source having a stable output level was used.

In this embodiment, the photoelectric conversion element 3
The waveform of the output signal was displayed on an oscilloscope 6 to vary the output voltage of the drive circuit 4. However, as shown in FIG. 2, a digital multimeter 8 was used instead of the oscilloscope 6, and this digital multimeter 8 was connected to an AC voltage. In this measurement range, the level of the output signal of the photoelectric conversion element 3 was digitally displayed, and the operator variably operated the output voltage of the drive circuit 4 while viewing the measured value, and the AC signal level became minimum. The same can be implemented by reading the output voltage of the drive circuit 4 as the optimum voltage for the common substrate that can suppress flicker.

(Embodiment 2) FIG. 3 shows another inspection apparatus used for carrying out the inspection method of the liquid crystal display device of the present invention.

In the first embodiment, the liquid crystal panel 1 to be measured is
The operator had to manually operate the drive circuit 4 after connecting to the inspection apparatus.
Then, the optimum voltage to the common substrate, which can suppress flicker, can be read simply by connecting the liquid crystal panel 1 to be measured to the inspection apparatus.

Here, the output of the digital multimeter 8 is fed back to the drive circuit 4 via the control section 9 to form an automatic control circuit. The control unit 9 controls the output voltage of the drive circuit 4 using the voltage output from the output terminal of the digital multimeter 8 as an input signal, that is, using the electrical AC signal converted by the photoelectric conversion element 3 as an input signal. The output voltage of the drive circuit 4 is automatically set to a stable state at a voltage value at which the level of the electrical AC signal converted by the photoelectric conversion element becomes a minimum value while comparing with the past signal level input from the start of the test. Control.

As described above, the drive circuit 4 is provided with the control unit 9 interposed.
Is automatically controlled, the output voltage of the drive circuit 4 when the level of the electric AC signal converted by the photoelectric conversion element 3 is minimized without the operator operating the drive circuit 4 You can read from the display.

With such a configuration, the supply voltage for minimizing flicker can be easily and automatically detected from the level of the AC signal, and the present invention can be applied as an automatic measuring device capable of shortening the detection time of the optimum supply voltage.

In this (Embodiment 2), the case where the control unit 9 is provided between the digital multimeter 8 and the drive circuit 4 shown in FIG. 2 has been described as an example, but the oscilloscope shown in FIG. The same operation can be performed by providing a control unit 9 between the drive circuit 4 and the output terminal for outputting the signal under observation 6.

In each of the above embodiments, the case where the liquid crystal panel to be measured is of the transmission type has been described as an example. However, in the case of the reflection type, the liquid crystal panel 1 is illuminated by the light source 2 and the photoelectric conversion element 3 is provided. The measurement can be carried out similarly by measuring the reflected light from the liquid crystal panel 1.

[0025]

As described above, according to the inspection method of the liquid crystal display device of the present invention, the liquid crystal is filled between the common substrate and the electrode substrate which is arranged to face the common substrate and on which the driving transistor is formed. When inspecting flicker by irradiating the liquid crystal panel with light, the transmitted light or the reflected light received through the liquid crystal panel to be measured is converted into an electric AC signal by a photoelectric conversion element while changing the voltage of the common substrate. By setting the voltage of the common substrate when the level of the converted AC signal is minimized to an optimal voltage value that minimizes flicker of the liquid crystal panel, the evaluation of the optimal voltage value that minimizes flicker can be performed in a short time. This makes it possible to greatly reduce the time required for in-screen distribution measurement and automatic measurement.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an inspection apparatus used to execute an inspection method according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of another inspection apparatus according to the embodiment;

FIG. 3 is a configuration diagram of an inspection apparatus used to execute an inspection method according to (second embodiment) of the present invention.

FIG. 4 is a configuration diagram of a conventional inspection device for a liquid crystal display device.

[Explanation of symbols]

 2 light source 1 liquid crystal panel 4 drive circuit 3 photoelectric conversion element 6 oscilloscope 7 voltmeter 8 digital multimeter 9 control unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 611 G09G 3/20 611E 5G435 670 670Q F-term (Reference) 2H088 FA11 HA08 MA20 2H092 JA24 NA25 2H093 NC21 NC34 ND10 5C006 AB05 AF53 AF63 AF64 BB11 EB01 FA23 5C080 AA10 BB05 DD15 EE25 FF09 JJ02 5G435 AA17 BB12 KK05 KK10

Claims (3)

[Claims] When a flicker is inspected by irradiating light to a liquid crystal panel filled with liquid crystal between a common substrate and an electrode substrate provided with a driving transistor and opposed to the common substrate, While changing the voltage of the common substrate of the measurement liquid crystal panel, the transmitted light of the measured liquid crystal panel or the reflected light from the measured liquid crystal panel is converted into an electric AC signal by a photoelectric conversion element, and the level of the converted electric AC signal is converted. A method for testing a liquid crystal display device, wherein the voltage value of the common substrate at the time when the value is minimum is evaluated as the optimal voltage value at which flicker of the liquid crystal panel to be measured is minimized. 2. An electric AC signal converted by the photoelectric conversion element is fed back to a driving device which generates a voltage to be applied to the common substrate of the liquid crystal panel to be measured, so that an output voltage of the driving device is 2. The method according to claim 1, wherein the voltage value of the common substrate is evaluated as an optimum voltage value when the level of the AC signal converted by the photoelectric conversion element has a minimum value. 3. An inspection apparatus for inspecting flicker by irradiating light to a liquid crystal panel filled with liquid crystal between a common substrate and an electrode substrate provided with a driving transistor and disposed opposite to the common substrate. A driving circuit that supplies a voltage to the common substrate; a photoelectric conversion element that converts transmitted light or reflected light received via the liquid crystal panel to be measured into an electrical AC signal; A voltage value at which the level of the AC signal converted by the photoelectric conversion element is minimized while controlling the output voltage of the drive circuit with an AC signal as an input signal and comparing the output signal with the past signal level input from the start of inspection. A control unit for automatically controlling the output voltage of the drive circuit to a stable state;