JPH09203689A - Method for inspecting liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve easy and quick inspection to clarify whether residue is generated or not by arranging a polarizing plate closely at a fixed angle or at a fixed interval on a liquid crystal substrate to generate a phase change in a liquid crystal layer under a specified temperature during a specified period. SOLUTION: A polarizing plate is fitted closely or at a fixed interval on the surfaces of both substrates of a liquid crystal display device 2 built sealing a liquid crystal layer between both the substrates having a pixel electrode or an opposed electrode so that the axis of transmission is almost at 0 deg. or 90 deg. with respect to the direction of the array of liquid crystal molecules of the surfaces of the substrates. Phase change is caused in the liquid crystal layer from a nematic phase to an isotropic phase or vice versa under a high temperature environment of a specified temperature (80-150 deg.C) for a specified period of time (5-60sec.) and an image signal of the phase change taken by a camera 3 undergoes an image processing 7 to store 8 the results. The image with the phase change is compared with the image without the phase change to find a different image on a screen. Thus, the state of orientation and the surface shape of the substrates attributed to rubbing are inspected thereby comprehensively verifying whether any residual image exists or not.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a liquid crystal display device.

[0002]

2. Description of the Related Art A matrix display device centering on liquid crystal,
In particular, the display image quality of an active matrix display device that drives a liquid crystal using a TFT (thin film transistor) as a switching element has been rapidly improved in recent years.
There are still many points to be improved compared to CRTs.

An afterimage is one of the items to be improved. The afterimage is caused by a liquid crystal molecule affected by a lateral electric field that acts between the gate line and the pixel electrode or between the source line and the pixel electrode when the screen is switched, forming a reverse tilt domain, and in particular, rubbing rubs in which the alignment of the liquid crystal is weak. At the lower part, it is observed as light leakage with a time constant.

Therefore, as conventional measures against afterimage, there are 1) management method in manufacturing process, measures from production method, 2) fundamental measures by feedback to board design, etc. Regarding the improvement of alignment accuracy by mitigating the warpage of the substrate, etc., 2), the substrate design simulated from the actual measurement of the afterimage generation state is included and fed back to the production, and a certain effect is achieved.

[0005]

However, the afterimage caused by the orientation state by rubbing is inspected by a qualitative inspection such as visual inspection, which cannot be detected quantitatively, and the surface of the substrate cannot be detected. Regarding the uneven shape, the height difference is 0. SEM because it is on the order of several μm to several μm
Since it may not be possible to inspect without using an evaluation device such as, the current detection method for the afterimage, control in the process, and countermeasures are insufficient, and the afterimage still occurs even if the above countermeasures are taken. is there.

Therefore, according to the present invention, the surface shape of the substrate constituting the liquid crystal panel and the alignment state of the liquid crystal by rubbing are inspected to check whether or not an afterimage is comprehensively produced by a relatively easy method. An object of the present invention is to provide a method for inspecting a liquid crystal display device that can perform the inspection.

[0007]

In order to achieve the above-mentioned object, the present invention has a pixel electrode on a first substrate and a counter electrode on a second substrate, and a liquid crystal layer is sealed between both substrates. In the above liquid crystal display device, polarizing plates are placed on both substrate surfaces in close contact with each other or at regular intervals so that their transmission axes are approximately 0 ° or 90 ° with respect to the alignment direction of liquid crystal molecules on the substrate surfaces. Then, the predetermined period S0 is 5 (sec) ≤S0≤60 (s
ec), the predetermined temperature T0 is 80 (° C) ≤T0≤
Under a high temperature environment of 150 (° C.), the liquid crystal layer is changed from a nematic phase to an isotropic phase or from an isotropic phase to a nematic phase, and the quality of the liquid crystal display device is judged by the phase change of the liquid crystal layer of the substrate at this time. To do.

By placing the liquid crystal panel in a high temperature environment for a certain period of time and changing the liquid crystal layer from the nematic phase to the isotropic phase or from the isotropic phase to the nematic phase, the surface shape of the substrate constituting the liquid crystal panel, The phase change changes depending on the alignment state of the liquid crystal due to rubbing. Therefore, the alignment state by rubbing and the substrate surface shape are inspected by a relatively easy method, and it is inspected whether or not an afterimage is generated comprehensively. You can Further, since the inspection can be performed without attaching the polarizing plate to the liquid crystal substrate, the polarizing plate is not damaged by heat.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an inspection device using the inspection method for a liquid crystal display device of the present invention.

In FIG. 1, reference numeral 1 is an inspection table having a built-in heater. A liquid crystal display device 2 to be inspected is placed on the inspection table 1, and a CCD camera device 3 is arranged facing the liquid crystal display device 2. Are arranged. A temperature sensor 4 is attached to the inspection table 1, and a temperature detection signal from the temperature sensor 4 is used by a temperature controller 5 for controlling the temperature of the inspection table 1.
Used as a feedback signal for.

The liquid crystal display device 2 has a pixel electrode on the first substrate and a counter electrode on the second substrate, and is constituted by sealing a liquid crystal layer between the two substrates. The polarizing plates are arranged in close contact with each other or at regular intervals so that the transmission axis thereof is approximately 0 ° or 90 ° with respect to the alignment direction of the liquid crystal molecules on the substrate surface.

The video signal of the camera device 3 is input to the high-speed image processing device 7, and the image signal processed by the image processing device 7 is stored in the image storage device 8 and displayed on the monitor 9. An image processing unit 10 is formed by the image processing device 7, the image storage device 8 and the monitor 9.

A liquid crystal driving device 11 for changing the liquid crystal layer of the liquid crystal display device 2 from a nematic phase to an isotropic phase or from an isotropic phase to a nematic phase is provided. The liquid crystal driving device 11 and the image processing section 10 are provided. There is provided a main controller 12 for controlling the temperature control and outputting the set temperature T0 to the temperature controller 5.

The control operation by the main controller 12 will be described with reference to the flowchart of FIG. First,
Set temperature T0 to temperature controller 5 {80 (℃) ≤T0
≤150 (° C)} is output (step-1), and then
When the timer is driven (step-2) and the timer predetermined time S0 {5 (sec) ≤S0≤60 (sec)} has elapsed (step-3), the image processing unit 10 is sent to the camera device 3.
Image pickup start signal, image processing start signal of the image processing device 7,
An image processing drive command signal composed of a display start signal of the monitor 9 is output (step-4), and then the liquid crystal drive device 11
A liquid crystal drive command signal is output to (step-5).

Then, an image determination command signal is output to the image processing unit 10 (step-6), and a set temperature of the normal temperature is output to the temperature controller 5 (step-7). The judgment signal is input and output to the outside (step-8), and the process is ended.

With the above structure, the liquid crystal display device 2 is changed from the nematic phase to the isotropic phase or from the isotropic phase to the nematic phase under the environment of constant temperature S0 and constant high temperature T0. The phase change of the liquid crystal layer at this time is stored in the image storage device 8 by the image processing device 7, and the phase change is inspected (described later).

3 to 6 are pixel diagrams of a liquid crystal display device imaged by the camera device 3, where a is a gate electrode and a gate wiring, b is a source electrode and a source wiring, c is a drain electrode, and d is a pixel electrode. , E indicate capacitor electrodes, and an arrow f indicates the rubbing direction.

FIG. 3 shows a panel having a weak orientation, and FIG. 4 shows a panel having a good orientation in an environment of 10 seconds and 120 ° C., respectively, and schematically shows the moment of the phase change from the nematic phase to the isotropic phase of the liquid crystal layer. To indicate.

It can be seen that when heat is applied to a panel having poor orientation as shown in FIG. 3, a phase change starts from a rubbing rubbed portion where the orientation of the liquid crystal is weak and unstable, and the inside of the pixel does not change uniformly. The portion where the phase change occurs earliest is indicated by the shaded portion g. This is an afterimage on the display. The shaded part g looks different in contrast from other parts. That is, if the polarizing plate is arranged in normally white, it looks black, and if the polarizing plate is arranged in normally black, it looks white.

On the other hand, in the liquid crystal panel shown in FIG. 4 in which the orientation is sufficient, it can be seen that the phase change occurs uniformly in the pixel, and no afterimage is generated. In general, an afterimage is generated at a rubbing rubbed portion where liquid crystal has poor orientation.

Next, FIG. 5 shows a panel with large unevenness on the substrate surface, and FIG. 6 shows a panel with small unevenness on the substrate surface under the environment of 10 seconds and 120 ° C., respectively. The moment of the phase change to the phase is schematically shown.

In a panel having large irregularities on the substrate surface as shown in FIG. 5, a phase change occurs from a portion having large irregularities on the surface (hatched portion g), and no uniform variation is observed in the pixel. In such a panel with small unevenness, the phase change instantaneously and uniformly occurs in the pixel. The portion where the phase change occurs earliest is indicated by the shaded portion g.

The predetermined period (timer setting time) S0
However, it was confirmed that the same phase change occurs in a high temperature environment where the predetermined temperature T0 is 80 (° C) ≤ T0 ≤ 150 (° C) during the period of 5 (sec) ≤ S0 ≤ 60 (sec).

A predetermined period (timer setting time) S0 is set to 5
(Sec) ≤ S0 is the time required for the temperature to be uniform in the liquid crystal layer, and S0 ≤ 60 (sec) is when the liquid crystal display device 2 is heated for a longer time. ,
This is because it may cause deterioration of the liquid crystal element.

Further, the predetermined temperature T0 is 80 (° C.) ≤T0≤
The reason why the temperature is 150 (° C.) is that the nematic-isotropic transition point of many liquid crystal materials is usually in this range.

Since the phase change occurs instantaneously in the image processing device 7, the video signal is stored in the image storage device 8 at a high speed, and the stored screen is advanced frame by frame in response to the image determination command signal to change the phase. By finding a different image on the screen as compared with a screen without a screen, it is possible to determine whether or not the alignment state of the liquid crystal display device 2 due to rubbing (the shaded portion g is generated in the rubbing abrasion part) and the substrate surface shape (the shaded portion g is It is possible to judge the quality of (irregularly generated), output the quality judgment signal, and inspect different images quantitatively by the area. The screen in which the phase change has occurred can be displayed on the monitor 9 as a still screen.

As described above, by detecting the phase change of the liquid crystal layer, the alignment state by rubbing and the substrate surface shape can be inspected, and by discarding the liquid crystal display device 2 having an abnormality, the image quality without afterimage can be obtained. Only a good liquid crystal display device can be provided. Further, it is possible to improve the afterimage detection power by a relatively simple method, and it is also possible to quantitatively inspect the change of the image by its area.

In this embodiment, the polarizing plate is attached to the liquid crystal substrate, but the inspection can be performed even when the polarizing plate is isolated for a certain period. At this time, it is possible to avoid damaging the polarizing plate with heat. Further, the means for raising the temperature of the liquid crystal display device 2 may be any other means such as a device for blowing hot air, regardless of the heater.

[0029]

As described above, according to the present invention, the alignment state and the substrate surface shape by rubbing can be inspected by detecting the phase change of the liquid crystal layer by a relatively simple method, and the image quality without afterimage can be obtained. It is possible to provide a good liquid crystal display device, which is extremely useful in actual use. Furthermore, since the inspection can be performed even when the polarizing plate is not attached to the liquid crystal substrate, it is possible to prevent the polarizing plate from being damaged by heat.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an inspection device using a liquid crystal display device inspection method of the present invention.

FIG. 2 is a flowchart illustrating an operation of a main controller of the inspection apparatus.

FIG. 3 is a pixel diagram of a liquid crystal display device, schematically showing a moment of a phase change from a nematic phase of a liquid crystal layer to an isotropic phase when a liquid crystal panel having poor alignment is observed in an environment of 120 ° C. for 10 seconds. It is a figure.

FIG. 4 is a pixel diagram of a liquid crystal display device, schematically showing an instant of a phase change from a nematic phase to an isotropic phase of a liquid crystal layer observed in a liquid crystal panel having good orientation in an environment of 120 ° C. for 10 seconds. It is a figure.

FIG. 5 is a pixel diagram of a liquid crystal display device, and schematically shows a moment of a phase change of a liquid crystal layer from an isotropic phase to a nematic phase, which is observed in a panel with large irregularities on a substrate surface in an environment of 120 seconds for 10 seconds. It is the figure shown.

FIG. 6 is a pixel diagram of a liquid crystal display device, and schematically shows a moment of a phase change of a liquid crystal layer from an isotropic phase to a nematic phase, which is observed in a panel with small irregularities on a substrate surface in an environment of 120 ° C. for 10 seconds. It is the figure shown.

[Explanation of symbols]

 1 inspection table 2 liquid crystal display device 3 camera device 4 temperature sensor 5 temperature controller 7 image processing device 8 image recording device 9 monitor 10 liquid crystal drive device 11 main controller a gate electrode / wiring b source electrode / wiring c drain electrode d pixel electrode e Capacitor electrode f Rubbing direction g Location where phase change occurs first

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirofumi Minen 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A method for inspecting a liquid crystal display device, comprising a pixel electrode on a first substrate and a counter electrode on a second substrate, wherein a liquid crystal layer is sealed between both substrates, the method comprising: The polarizing plates are placed in close contact with each other or at regular intervals so that the transmission axis thereof is approximately 0 ° or 90 ° with respect to the alignment direction of the liquid crystal molecules on the substrate surface, and the liquid crystal layer is placed under an environment of high temperature T0 for a predetermined period S0. A method for inspecting a liquid crystal display device, characterized by changing from a nematic phase to an isotropic phase or from an isotropic phase to a nematic phase, and judging the quality of the liquid crystal display device based on the phase change of the liquid crystal layer of the substrate at this time. . 2. The predetermined period S0 is set to 5 (sec) ≦ S0 ≦
The method for inspecting a liquid crystal display device according to claim 1, wherein the inspection time is 60 (sec). 3. The high temperature T0 is set to 80 (° C.) ≦ T0 ≦ 150.
(° C.) The method for inspecting a liquid crystal display device according to claim 1, wherein