KR100392995B1 - A method and apparatus for measuring ion density of liquid crystal panel - Google Patents

Abstract

The ion density of the liquid crystal display panel can be measured nondestructively. The ion density distribution of the liquid crystal display panel can be grasped.

A flickering wave is observed by applying a square wave of a low frequency of about 1 kHz (step S303). The amplitude of the observed flicker is measured (step S306). The ion density in the liquid crystal panel is calculated from the calibration curve (a diagram showing the correlation between the amplitude of the flicker and the ion density) previously obtained (step S307).

Description

A method for measuring ion density of a liquid crystal panel and a device therefor {A METHOD AND APPARATUS FOR MEASURING ION DENSITY OF LIQUID CRYSTAL PANEL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the density (concentration) of impurity ions in a liquid crystal display panel and a device thereof, and more particularly, to a method for measuring the ion density of a liquid crystal in a nondestructive manner.

Since impurity ions in the nematic liquid crystal display panel directly affect the electrical parameters of the panel, it causes a display defect of the liquid crystal display panel or a deterioration of display quality. Therefore, at the time of industrial production work, it is required to measure the impurity ion density in the liquid crystal display panel of a product simultaneously with the problem in an inspection process.

As a conventional method, ion species and concentrations in a liquid crystal extracted by breaking a panel are known as an electrochemical analysis method, or a liquid crystal extracted by breaking a panel is re-injected into an evaluation cell, and the electrical response is measured to determine the ion concentration. How to determine the. However, since either method requires panel breakdown, it is inevitable to measure at a point in time when a considerable time has elapsed since the occurrence of a problem, which leads to recontamination of liquid crystals in the course of a sample preparation operation, and it is difficult to increase the accuracy of the measurement.

In addition, since poor display of the liquid crystal display panel is often caused by nonuniformity of the in-plane distribution of ions in the liquid crystal display panel, information on the in-plane distribution of ions is required, but the above-described method of destroying the liquid crystal display panel It is impossible to measure the in-plane distribution. In order to obtain information about the ions in the liquid crystal display panel by non-destructive, it is only necessary to independently measure the electrical characteristics of each pixel forming the liquid crystal display panel. This is because the information on the ions is often derived from the response current waveform with respect to the applied voltage. However, the electric driving method of the liquid crystal display is a simple matrix type liquid crystal display panel by optimizing the driving conditions, so that the response current of only a certain independent pixel will be obtained and information on the ions will be obtained. You cannot completely block the effects of In addition, for an active matrix liquid crystal display panel driven by a thin film transistor (TFT) driving method or the like, it is very difficult to obtain electrical information of each pixel independently on a constituent circuit.

Since the conventional method for measuring impurity ion density was to destroy a liquid crystal display panel, the time and the number of steps were increased, and there was a problem in measurement accuracy. Moreover, in the conventional measuring method, the in-plane ion distribution which is important information in management of a liquid crystal display panel manufacturing process was unknown.

An object of the present invention is to solve the above-described problems of the prior art, the object of which is to first determine the ion density of the liquid crystal panel by non-destructive, and secondly to determine the in-plane distribution of the ion density.

In order to achieve the above object, according to the present invention, there is provided a method for measuring the ion density of a liquid crystal panel, wherein an alternating voltage is applied to the liquid crystal panel and the ion density in the liquid crystal is detected from the flicker waveform of the transmitted light intensity.

Preferably, the ion density is obtained from the amplitude of the flicker waveform of the transmitted light intensity or the area of the flicker waveform. In addition, preferably, the intensity of the transmitted light from the partial region of the liquid crystal panel is individually measured, and the ion density for each partial region is obtained.

Further, in order to achieve the above object, according to the present invention, an arbitrary waveform generator for driving a liquid crystal panel, a light source for irradiating light to the liquid crystal panel, an area image sensor for observing the intensity of the light passing through the liquid crystal panel; And an ion density measuring device of a liquid crystal panel having an information processing device having a storage device which oversees the operation of the arbitrary waveform generator and the area image sensor, wherein the detection data for each pixel of the area image sensor is individually processed. An ion density measuring apparatus for a liquid crystal panel is provided, wherein flicker can be detected for each pixel.

The oscilloscope may further include an oscilloscope for monitoring the output waveform of the area image sensor, and the information processing apparatus collects output data of the area image sensor through the oscilloscope.

In the present invention, attention is paid to flicker (blinking) of transmitted light intensity caused by ions in the liquid crystal in order to obtain information about impurity ions in the liquid crystal display panel. In general, an alternating voltage having positive and negative symmetry is applied to each pixel of the nematic liquid crystal display panel, and when no ions are present, the same voltage is applied to the liquid crystal in each of the applied fields in the alternating voltage application. In this case, the liquid crystal molecules do not change with a constant inclination angle according to the magnitude of the applied voltage, and flicker of transmitted light intensity does not appear.

Therefore, although not disclosed in detail at this time, an internal voltage may be generated in the liquid crystal cell for some reason. In this case, since the internal voltage overlaps the applied voltage, a voltage having a different magnitude is applied to the liquid crystal for each applied field. Takes For example, when the TN mode using the nematic liquid crystal with dielectric anisotropy is normally white mode, the voltage applied to the liquid crystal increases when a voltage having the same sign as the internal voltage is applied. Becomes lower. On the other hand, when a voltage having an inverse sign and an internal voltage is applied, the voltage applied to the liquid crystal is lowered, and the inclination angle of the liquid crystal is also smaller than the inclination angle above, and the transmitted light intensity is increased. This is an example of flicker in a liquid crystal display panel. The period of the flicker (the period of the flicker not dependent on the ions) is the same as that of the applied voltage.

On the other hand, when there are movable ions that can move in response to an applied voltage period in the liquid crystal, electric field decreases due to drift of ions occurs in each applied field, and the voltage applied to the liquid crystal is attenuated with time. For example, in a field in which a positive voltage is applied, the highest voltage is applied to the liquid crystal at the moment when the voltage is applied, and the liquid crystal moves and rises in response to this. At the same time, since the ions in the liquid crystal start drift in the direction of the electrode opposite to the polarity, the voltage applied to the liquid crystal decays with time. Because of this drop in voltage, the liquid crystal begins to tilt at some time. As the liquid crystal moves, the light transmittance also decreases until a certain time, but rises thereafter (in the case of normally white). The same phenomenon occurs in a field where a negative voltage is subsequently applied. Therefore, the flicker when the movable ions which can move in response to the applied frequency in the liquid crystal have a frequency twice the applied frequency.

As described above, the flicker has a frequency dependence of the applied voltage, and flicker disappears at a high applied frequency at which the ions cannot move in response, and saturates in a low frequency region that can sufficiently move in response. Therefore, if voltage is applied in a frequency range low enough so that ions can move in response to the liquid crystal display panel, and the flicker generated at that time is observed, the presence of ions in the liquid crystal can be confirmed without destroying the liquid crystal display panel. . Since the size of the flicker (the amplitude of the flicker, etc.) depends on the ion density in the liquid crystal display panel, the ion density can be known nondestructively by observing the size of the flicker. Moreover, the size of the flicker depends on the local ion density of each part of the panel through which light is transmitted. In other words, the local flicker size of each part within the panel surface depends on the ion density in that part of the panel. Therefore, in the present invention, by using an image sensor of an area type such as a CCD camera, flicker information for each part in the panel surface is collected, and the ion density in each in-plane portion is calculated based on this. Therefore, according to the present invention, the ion density distribution in the liquid crystal panel plane can be recognized.

BRIEF DESCRIPTION OF THE DRAWINGS The flowchart for demonstrating embodiment and Example of this invention.

2 is a flowchart for explaining embodiments and examples of the present invention.

3 is a flowchart for explaining embodiments and examples of the present invention.

4 is a schematic configuration diagram of a measuring device for explaining embodiments and examples of the present invention.

5 is a circuit diagram and a voltage waveform diagram for explaining embodiments and examples of the present invention.

6 is a waveform diagram for explaining an embodiment of the present invention.

7 is a waveform diagram for explaining an embodiment of the present invention.

8 is a pattern diagram and a cross-sectional view for explaining the first embodiment of the present invention.

9 is a layout view of a polarizer for explaining a first embodiment of the present invention.

10 is a characteristic diagram for explaining the first embodiment of the present invention.

11 is a characteristic diagram for explaining the first embodiment of the present invention.

12 is a waveform diagram for explaining a first embodiment of the present invention.

Fig. 13 is a waveform diagram for explaining the first embodiment of the present invention.

14 is a characteristic diagram for explaining the second embodiment of the present invention.

Fig. 15 is a characteristic diagram for explaining a second embodiment of the present invention.

Fig. 16 is a waveform diagram for explaining a second embodiment of the present invention.

17 is a configuration diagram of a measuring device for explaining a third embodiment of the present invention.

Fig. 18 is a characteristic view for explaining a third embodiment of the present invention.

Fig. 19 is a waveform diagram for explaining a third embodiment of the present invention.

20 is an ion density distribution diagram for illustrating a third embodiment of the present invention.

Fig. 21 is a display pattern diagram for explaining a fourth embodiment of the present invention.

Fig. 22 is a display pattern diagram for explaining a fourth embodiment of the present invention.

Fig. 23 is an ion density distribution diagram for explaining the fourth embodiment of the present invention.

24 is an ion density distribution diagram for illustrating the fourth embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

41: light source

42, 43: polarizer

44: liquid crystal cell

45: light detector

46: arbitrary waveform generator

47: oscilloscope

48: information processing device

49: storage device

71: saturated region of the transmittance change

72: minimum transmittance

73: flicker amplitude

74: flicker area

81: glass substrate

82: pixel electrode

83: lead-out electrode

84: polyimide alignment film

85: epoxy adhesive

86: nematic liquid crystal

91, 92: polarization direction of the polarizing plate

93: rubbing direction

161: flicker area

170: liquid crystal display panel

171: liquid crystal cell

172, 173: polarizer

174, 175 lens

176: CCD Detector

177: light source

EMBODIMENT OF THE INVENTION Next, embodiment of this invention is described with reference to drawings. 1-3 is a flowchart which shows embodiment of this invention, and FIG. 4 is a block diagram which shows the outline of the measuring apparatus in which the ion density measuring method which concerns on this invention is performed.

In FIG. 4, the light emitted from the light source 41 passes through the liquid crystal cell 44 through the polarizing plate 42, and is then detected by the photo detector 45 through the polarizing plate 43, and temporarily to the oscilloscope 47. After data is collected, it is transmitted to an information processing device 48 such as a personal computer and stored in the storage device 49 attached to the information processing device 48. The voltage application to the liquid crystal cell 44 is performed by the arbitrary waveform generator 46, and data of the voltage value with respect to time is accumulated in the oscilloscope 47 at the same time as the transmitted light intensity and then transmitted to the information processing device 48. The operation of these arbitrary waveform generators 46, the photo detector 45, and the oscilloscope 47 are overseen by the information processing device 48. The processing program executed by the information processing device 48 is stored in the storage device 49.

As the light source 41, a halogen lamp, a metal halogen lamp, or a cold cathode tube can be used to irradiate the entire liquid crystal cell 44, and a visible light laser can be used to locally irradiate the liquid crystal cell 44. . As the photodetector 45, a general photodetector capable of measuring the light intensity can be used in the case of measuring the average light intensity of the entire surface of the liquid crystal panel. In the case of measuring the partial transmitted light intensity on the liquid crystal cell 44, a CCD is used. (charge coupled device) An area image sensor such as a solid state imaging device is used. In the latter case, the data of the detection light for each pixel of the area image sensor or for each pixel divided into groups is collected and processed by the information processing device 48.

If necessary, a lens system for condensing the light on the light source 41 side or the photodetector 45 side of the liquid crystal cell 44 or for obtaining parallel rays can be disposed.

In a conventional liquid crystal display panel, the polarizing plate is integrally fixed to both surfaces of the liquid crystal cell. Therefore, when measuring with respect to the liquid crystal panel to which the polarizing plate is already fixed, it is not necessary to arrange | position the polarizing plates 42 and 43 in a measuring apparatus.

Measurement of the ion density according to the present invention is sequentially performed in accordance with stage I shown in FIG. 1, stage II shown in FIG. 2, and stage III shown in FIG. Among these, stage I and stage II are flowcharts showing the procedure in the preparation step for carrying out stage III, which forms an essential part of the measuring method of the present invention. Therefore, when data obtained by stage I or stages I and II has already been obtained, the processing of stage I or stages I and II can be omitted.

Conventionally, the transmitted light intensity of the mainstream nematic liquid crystal display panel is susceptible to the drift of ions in the steepest region of the transmitted light intensity characteristic curve on the graph showing the correlation between the applied voltage and the transmittance, that is, near the halftone voltage. Therefore, it is preferable in terms of measurement efficiency that the voltage applied to the liquid crystal display panel at the time of detecting the ion information is determined to be a portion where the transmitted light intensity characteristic curve on the voltage-transmission graph is abrupt. Thus, in stage I, a steep region of the voltage-transmittance curve is obtained and determined to be the applied voltage value for flicker measurement.

First, a measurement start voltage is specified in step S101, an alternating voltage at the voltage specified in step S102 is applied to the liquid crystal cell 44 by the arbitrary waveform generator 46, and the transmittance at that time is detected by the photodetector 45. The data is introduced into the oscilloscope 47 together with the applied voltage and then transmitted to the information processing device 48. Subsequently, it is checked whether or not the applied voltage has reached the predetermined measurement end voltage in step S103. If not, the applied voltage is increased by one unit in step S104 to return to step S102. When the measurement end voltage has been reached, the process proceeds to step S105, and the processing is terminated by determining the voltage whose change is most rapid in the obtained VT (voltage-transmittance) characteristic curve as the applied voltage used for the measurement (an example of the obtained VT characteristic curve). Is shown in FIG. 10).

In addition, the liquid crystal cell used here does not contain any ion, and contains only a very small amount of ions as a reference liquid crystal cell. In addition, although the liquid crystal cell used in stage I may be selected from the product cells, the liquid crystal cell for determining the applied voltage manufactured so that an ion may not be doped may be sufficient.

The voltage values determined in stage I will be used in stages II and III, but it is not necessary to strictly enforce the voltage values determined in stage I in stages II and III. The voltage value near the halftone display is often sufficient. However, it is necessary to use the same applied voltage in stages II and III.

In stage II, a calibration curve is created using a plurality of liquid crystal cells for calibration curve creation having different ion concentrations. Although the liquid crystal cell used in stage II may be selected from the cell for products, the liquid crystal cell for calibration curve preparation prepared by containing an ion previously may be sufficient.

First, in step S201, a plurality of ion contaminating liquid crystal cells having different impurity ion concentrations are prepared. In step S202, one of the prepared liquid crystal cells is selected, and in step S203, for example, a square wave of a voltage value obtained in stage I of 1 Hz is applied, and the transmitted light intensity at the time of voltage application is thus observed, and flicker is observed. Here, 1 kHz, which is selected as the frequency of the applied voltage, is determined by saturating the ion transport sufficiently. Therefore, any frequency suitable for this purpose can be appropriately changed. Subsequently, in step S204, it is checked whether the area where flicker does not appear, that is, whether the constant area of transmitted light appears. If there is no constant area of transmitted light intensity, the flow advances to step S205 to decrease the frequency and apply voltage to perform flicker measurement. Is performed, and the flow returns to step S204. In step S204, when the existence of the transmitted light constant region is confirmed, the flow advances to step S206 to obtain flicker amplitude or flicker area. Here, the flicker amplitude is the maximum value of the vibration (absolute value) seen from the constant area of transmitted light, and the flicker area is the area surrounded by the horizontal line and the flicker waveform indicating the constant level of transmitted light.

Next, in step S207, a triangular wave voltage of low frequency (for example, 0.01 mA) is applied, at which time the current flowing through the liquid crystal cell is measured. At this time, since the current flowing through the cell depends on the density of ions contained in the cell, the ion density of the liquid crystal cell can be known by this current measurement. Therefore, the ion density is calculated from the ion current peak appearing in the response current waveform obtained in step S208. Subsequently, it is checked whether or not the measurement has been performed for all of the liquid crystal cells prepared in step S209. If the measurement is not completed, the process returns to step S202 to select the next liquid crystal cell. When the measurement with respect to the prepared all liquid crystal cell is completed, a calibration curve is created in step S210. That is, the flicker amplitude or the combination of the flicker area and the ion density is created on the correlation chart, and a calibration curve is obtained (an example of the obtained calibration curve is shown in FIG. 11).

When a special liquid crystal cell is prepared for stage I or stage II in stage I and stage II, a cell having a single pixel is produced. In the case where the applied voltage and the calibration curve for measuring the active matrix liquid crystal display panel are used by the cells of a single pixel, the applied voltage and the calibration curve are obtained by operating the pseudo active matrix of the liquid crystal cell of the single pixel. The pseudo active matrix operation is performed by the circuit shown in FIG. 5A. In Fig. 5A, reference numeral 51 denotes a waveform generator, reference numeral 52 denotes an impedance converter, and reference numeral 53 denotes a liquid crystal cell. Here, the impedance converter 52 performs an operation in which the high impedance state and the low impedance state are alternately repeated to prepare the operation of the thin film transistor TFT. The input / output side signal pattern of the impedance converter 52 is shown in Figs. 5B and 5C.

In addition, when a liquid crystal panel of an actual product is used in stages I and II, the front surface of the liquid crystal panel is driven in the same display state. In this case, it is assumed that the active matrix drive is performed in step S102 or the like for the active matrix panel.

Stage III is a process which is the core of the measuring method of the present invention, and is performed according to the flowchart shown in FIG. First, in step S301, it is determined whether movable ions exist in the liquid crystal cell 44. At this time, the applied voltage is determined in stage I, and the applied frequency is 10 kHz, for example, but this frequency is appropriately changed according to the gap of the cell or the mobility of the desired ion, and in the liquid crystal The saturation frequency or the saturation frequency may be used as long as the ion can move in response to the applied voltage. In the case of detecting the influence of trace ions, it is preferable that the saturation frequency of the drift distance of the ions is long in order to maximize the influence due to the drift of the ions. However, since the effect of ions is caused by the movement of ions, ions can be detected even at frequencies that are not saturated, and in this case, the measurement time is shortened. When flicker based on impurity ions occurs, as shown in FIG. 6, flicker at twice the frequency of the applied voltage as shown in the upper portion of the figure is observed with respect to the lower applied input voltage. It is determined whether or not flicker has been generated in step S302. If flicker is not observed, the measurement of the liquid crystal cell 44 is terminated at this point.

When flicker is detected, the applied frequency is set to 1 Hz, for example, so that the drift of ions ends in the application field in step S303, that is, the area where the transmittance does not change after the flicker waveform appears in the application field. Observe flicker by making it low. In the case where it is known that flicker due to impurity ions has already been generated, as shown by the broken line in the figure, the process starts from step S303 without passing through steps S301 and 302.

Subsequently, it is determined in step S304 whether there is a region where the transmitted light intensity is constant. If the region cannot be confirmed, the flow advances to step S305, where the frequency of the applied voltage is reduced and the area where the transmitted light intensity is constant is determined. This operation is continued until it shows up, and when it exists that presence of the constant area of transmitted light intensity is confirmed, it progresses to step S306. Fig. 7 is a graph showing the change in transmittance and the applied voltage observed in this case. That is, the saturation region 71 of the change in transmittance is shown in the applied field. Here, the difference between the transmittance and the minimum transmittance 72 of the saturated region 71 of the change in transmittance is defined as the flicker amplitude 73 and measured. Alternatively, the area surrounded by the horizontal line representing the saturation region 71 of the flicker and the flicker waveform is defined as the flicker area 74 and measured.

Next, the ion density is calculated | required from the analytical curve which shows the relationship between the ion density previously calculated | required in step S307, and flicker amplitude (or flicker area).

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

[First Embodiment]

In this embodiment, a method of obtaining the ion density from the flicker amplitude when a square wave is applied to a homogeneous alignment cell of a nematic liquid crystal will be described.

The liquid crystal cell used in the present Example was produced as shown to FIG. 8A and FIG. 8B.

As shown in FIG. 8, an indium tin oxide (ITO) film is formed on a 3 cm x 4 cm glass substrate 81 made of Corning 7059, and a pixel electrode 82 of 1 cm x 1 cm is formed in the center. In addition, the lead electrode 83 was formed. After the formation of the electrode, the polyamine acid was spin-coated thereon and subjected to plasticity at 90 ° C. for 30 minutes, followed by main baking at 200 ° C. for 1 hour to form a polyimide alignment film 84. Moreover, two sheets of the said alignment film are required for one cell assembly. Poly (4, 4 oxy diphenylene pyromellitic amine acid) was used for polyamic acid. In addition, the film thickness of the polyimide aligning film measured with the reflective ellipsometer was 780 kPa-820 kPa.

Rubbing was performed once using the roll of a rayon on condition of the rotation speed 800 rotation / min, the press injection 0.6mm, and the stage speed 20mm / s. After rubbing, two glass substrates 81 were superposed so that the rubbing direction became the opposite direction, respectively, and it fixed with the epoxy adhesive 85 which mixed the spacer particle of 6 micrometers in diameter. The fluorine-based nematic liquid crystal 86 was isotropically injected into this cell, the hole was sealed with ultraviolet curable resin, and it was set as the anti-parallel cell (cell in which the opposing two-side orientation directions differ 180 degrees). Although not shown, a light shielding film is formed on the glass substrate excluding the pixel electrode.

Although the liquid crystal cell formed in this way is arrange | positioned in the measuring apparatus shown in FIG. 4, the relationship of the rubbing direction of the polarizing plates 42 and 43 and the alignment film 84 at this time is shown in FIG. In the figure, the polarization directions of the polarizing plates 42 and 43 are shown by arrows 91 and 92, respectively, and the rubbing direction of the polyimide alignment film 84 is shown by the arrow 93. As shown in Fig. 9, the polarization directions of the polarizing plates 42 and 43 are orthogonal to each other, and the polarization directions are 45 ° to the rubbing direction, respectively.

As described above, a plurality of liquid crystal cells are prepared, the ion density is obtained from the response current of the triangular wave voltage application, and the ion current cannot be confirmed as a reference liquid crystal cell for measuring the transmitted light intensity characteristic curve on the voltage-transmittance graph. What was confirmed was used as the liquid crystal cell for a measurement.

In addition, the liquid crystal cell which forcibly contaminated for the preparation of the analytical curve at the time of calculating | requiring ion density from the amplitude of the transmittance | permeability mentioned later was created. Although preparation conditions are the same as the above, before joining a board | substrate, it immersed in methanol, the immersion time was changed, the liquid crystal cell from which the contamination level of the alignment film surface differs was created, and it was set as the liquid crystal cell for calibration curve preparation.

Initially, the transmitted light intensity characteristic curve on the voltage-transmission graph of the reference liquid crystal cell was measured (FIG. 1: stage I). That is, using the measuring apparatus of FIG. 4 described above, a square wave of 10 Hz is applied using the arbitrary waveform generator 46 in steps of 0 V to ± 10 V in 0.1 V steps, and the transmitted light intensity for each voltage value is applied to the surface of the liquid crystal cell. It was measured by irradiating light on a part or the front side of the. Thereafter, the information processing device 48 converts the transmitted light intensity to transmittance by setting the transmitted light intensity at the time of applying 0V to 100% and the transmitted light intensity at the time of applying ± 10V to 0% by a program stored in the storage device 49. I was. The transmitted light intensity characteristic curve on the voltage-transmittance graph obtained as a result was created as shown in FIG. In this voltage-transmittance characteristic curve, the voltage at the point where the change in transmittance with respect to the voltage displacement becomes the maximum is used as the flicker measurement voltage. In the case of FIG. 10, it was determined as 2.7V as a result of analysis by the information processing device 48.

Next, a calibration curve for calculating the ion density from the flicker amplitude was created. From the response current when applying a square wave voltage of ± 2.7 V and 1 kHz to a liquid crystal cell for calibration curve generation to obtain flicker amplitude (stage II: steps S203 to 206), and subsequently applying a triangular wave voltage of 10 V and 0.01 kHz. Ion density was calculated | required (stage II: step S207, 208). The calibration curve obtained as a result of measuring a plurality of liquid crystal cells is shown in FIG. 11. The ion density is expressed as the number per cm 3 assuming that the ions contained are monovalent and both positive and negative ions are equal. The formula of the calibration curve obtained is

Ion density = 2.6 * 10 ¹² X flicker amplitude

It was.

Seven liquid crystal cells for a measurement were prepared in this example, and their ion densities were measured by the present invention. The flicker measurement voltage is already determined at 2.7V. According to the flowchart of stage III (FIG. 3), the square wave of +/- 2.7V and 10 Hz is applied first, and an example of the flicker waveform shown at that time is shown in FIG. As shown in Fig. 12, since the flicker has a frequency twice the applied frequency, the presence of movable ions was confirmed. Next, the flicker amplitude was determined by changing the frequency of the applied voltage to 1 kHz. An example of the flicker waveform obtained at this time is shown in FIG. From each flicker amplitude, the ion density was calculated using the calibration curve.

[evaluation]

Table 1 shows the result of comparing the ion density obtained in this way and the ion density determined from the response current when the triangle wave voltage is applied. Although there are some differences, the results of both are in good agreement, and it can be seen that the present invention is effective for the ion density measurement.

The present invention 1.2 5.4 2.4 1.8 3.1 2.9 2.2 Triangle wave 1.4 5.2 2.1 1.9 2.9 2.8 2.1

(Unit: × 10 ¹³ pieces / cm 3)

Second Embodiment

In the present Example, the method of calculating | requiring ion density rather than the flicker area on the graph produced by generation | occurrence | production of the flicker shown below is demonstrated concretely. That is, in the present Example, the calibration curve of the flicker area was calculated | required in stage II, and the ion density was computed using this calibration curve in stage III.

The liquid crystal cell used in the present embodiment is a twisted nematic (TN) liquid crystal cell produced as follows, and the alignment direction of the liquid crystal molecules is 90 ° by sandwiching liquid crystals having positive dielectric anisotropy between substrates having different orientation directions of 90 °. It is twisted continuously.

The liquid crystal cell is a sandwich structure in which chiral nematic liquid crystal is sandwiched between two glass substrates. The glass substrate used Corning 7059 of 3 cm x 4 cm. In the same manner as in the first embodiment shown in FIG. 8, an indium tin oxide film was formed to form a pixel electrode of 1 cm × 1 cm in the center of the glass substrate, and the extraction electrode was formed. After the formation of the electrode, the polyamine acid was spin-coated thereon to perform plasticity at 90 ° C. for 30 minutes, and then main baking was performed at 230 ° C. for 1 hour to form a polyimide alignment film. Poly (4,4'oxy diphenylene pyromellitic amine acid) was used for polyamic acid. The film thickness of the alignment film measured by the reflective ellipsometer was 520 kPa to 550 kPa.

Rubbing was performed once using the roll of a rayon on condition of rotation speed 600 revolutions / min, press fit 0.5 mm, and stage speed 20 mm / s. After rubbing, two glass substrates were superposed so that a rubbing direction orthogonally crossed, and it fixed with the epoxy adhesive which mixed spacer particle of diameter of 6 micrometers. A fluorine-based chiral nematic liquid crystal material was isotropically injected into this cell, the hole was sealed with an ultraviolet curable resin, and a twisted nematic cell was produced. A plurality of such liquid crystal cells were created, the ion density was determined from the response current of the triangular wave voltage application, and the reference liquid crystal cell for transmission light intensity characteristic curve measurement was used as the reference liquid crystal cell for which the ion current could not be confirmed, and the measurement liquid crystal cell was used. .

Moreover, the liquid crystal cell which forcibly contaminated for the preparation of the analytical curve at the time of calculating | requiring ion density in the area | region which arisen by flicker was created. Although preparation conditions were substantially the same as the above, it immersed in methanol before bonding a board | substrate, the immersion time was changed, the other liquid crystal cell of the contamination level of the alignment film surface was created, and it was set as the liquid crystal cell for calibration curve preparation.

The measurement was performed similarly to the case of a 1st Example as follows. First, the transmitted light intensity of the reference liquid crystal cell was measured, and the transmitted light intensity characteristic curve was created. That is, a liquid crystal cell is installed in the measuring device, and a square wave of 10 Hz is applied in 0.1V steps from 0V to ± 10V, and the transmitted light intensity for each voltage value is irradiated to a part or the entire surface of the liquid crystal display panel surface. Measured. Thereafter, the program stored in the storage device 49 converted the transmitted light intensity to 100% and the transmitted light intensity to 0% when ± 10V was applied and the transmitted light intensity to transmittance. As a result, a transmitted light intensity characteristic curve having the horizontal axis as the voltage and the vertical axis as the transmittance was created as shown in FIG. In this transmitted light intensity characteristic curve, the voltage at the point where the transmittance change with respect to the displacement of voltage becomes the maximum was made into flicker measurement voltage. In the case of Figure 14 it was induced to 3.1V.

Next, a calibration curve for calculating the ion density in the area generated by the flicker was created. The stage II of FIG. 2 was processed by the apparatus structure of FIG. 4 using the analytical curve action liquid crystal cell. That is, ion density was calculated | required from the response current at the time of applying a triangular wave voltage of amplitude 10V and 0.01 Hz, and the square wave voltage of +/- 3.1V and 1 Hz was applied and the flicker area was calculated | required. The calibration curve obtained by measuring several liquid crystal cells is shown in FIG. 15. The ion density is expressed as the number per cm 3 assuming that the contained ions are monovalent and both positive and negative ions are equal. The formula of the calibration curve obtained is

Ion density = 2.3 * 10 ¹² * flicker area

It was.

Next, a square wave of ± 3.1 V and 10 Hz was applied in accordance with the flowchart of the stage III shown in FIG. 3, and the presence of ions was confirmed in the same manner as in the first embodiment. Next, the frequency of the applied voltage was changed to 1 kHz, and the flicker waveform was measured to determine the flicker area. An example of the generated flicker waveform is shown in FIG. 16. In FIG. 16, the flicker area is indicated as 161. Using two sums of the flicker areas 161, the ion density can be calculated with reference to the calibration curve obtained first.

[evaluation]

Table 2 shows the results of comparing the ion density obtained in this way with the ion density determined from the response current when the triangle wave voltage is applied. Although there are some differences, the results of both are in good agreement, and it can be seen that the present invention is effective for the ion density measurement.

The present invention 2.8 1.4 0.7 1.7 3.4 Triangle wave 2.4 1.7 0.5 1.9 3.2

(Unit: × 10 ¹³ pieces / cm 3)

Third Embodiment

In this embodiment, the ion density in the active matrix liquid crystal display panel of the monochrome display driven by a thin film transistor (TFT) is measured. In this embodiment, the measurement voltage is used as the halftone voltage, the stage I is not measured, and the measurement of the stage II is performed using the liquid crystal cell produced in the same manner as in the second embodiment (only polarizing plates on both sides of the cell). And an active matrix liquid crystal panel were used only in stage III.

As shown in Fig. 17, only the optical system was changed from the apparatus shown in Fig. 4, and the configuration of the measuring apparatus was the same as that in Fig. 4. As the liquid crystal display panel 170 to be measured, ones in which the polarizing plates 172 and 173 are attached to the liquid crystal cell 171 are used. A halogen lamp was used for the light source 177, and the lens 174 on the incidence side was converted into parallel light and irradiated to a part or the entire surface of the liquid crystal display panel 170 surface. The light was collected again by the lens 175 on the output side and detected by the CCD detector 176.

The ion contamination concentration of the liquid crystal cell for calibration curve preparation was changed by changing the time to leave to process atmosphere. The ion density of these liquid crystal cells was calculated | required from the response current at the time of applying a triangular wave voltage of amplitude 10V and 0.01 Hz. In addition, flicker measurement was performed in the circuit shown in FIG. 5A, and it was made to become the same conditions as the test panel measurement attempted test panel measurement. The obtained calibration curve is shown in FIG. The equation of the calibration curve

Ion density = 3.3 x 10 ¹¹ x flicker amplitude

It was. This coefficient is smaller by about one order than in the first and second embodiments. This is because, in the application of the square wave, electric charge is supplied to the electrode according to the electric field change in the liquid crystal cell, but during the sustain period in the active matrix operation, there is no charge supply to the electrode, and voltage drop due to drift of ions occurs more presumably. do.

As the liquid crystal display panel for measurement, two kinds of ones produced by a normal manufacturing process and those left in a process atmosphere longer than usual before bonding the thin film transistor substrate and the counter substrate were prepared.

A charge voltage for charge supply to each pixel by the thin film transistor was set to 100 Hz, and a halftone voltage was applied and held for 0.4999 s. 19 is an example of the flicker waveform obtained under these driving conditions for the former liquid crystal panel. Accordingly, the ion density in the corresponding region was found to be about 4.5 x 10 ¹² atoms / cm 3 in the calibration curve.

It is a measurement result in the front panel of the latter sample (sample exposed to process atmosphere). In FIG. 20, the black area has an ion density of less than 1 × 10 ¹² pieces / cm 3 and the white area has an ion density of 1 × 10 ¹² pieces / cm 3 or more. In the figure, the ion density of the area | region enclosed by the white circle reached 1.4 * 10 <^13> / cm <3>, and the contrast nonuniformity was observed even if visually confirmed.

It was found that the present invention is effective for evaluating the in-plane ion density distribution of a product level liquid crystal display panel, that is, an active matrix liquid crystal display panel.

[Example 4]

By the ion density measuring method of this invention, the display flammability of the active-matrix type liquid crystal display panel was inspected. The monochrome active matrix liquid crystal panel for measurement was produced in the same manner as in the third embodiment and left in the process for a longer time than in the case of the third embodiment before bonding the substrate. The black and white pattern display shown in FIG. 21 was applied by applying a pulse voltage of ± 10 V to the black display portion with a charging time of 100 ms and a holding period of 49.9 ms, and not applying a voltage to the white display portion. . After the display was continued for 48 hours, halftone gray display was performed on the entire liquid crystal display panel, and as shown in FIG. 22, a pattern remained darker than a portion where white was displayed.

The change of the ion density with this pattern residual was measured. 23 shows an ion density distribution in the panel surface before pattern display. In the figure, the black region has an ion density of less than 5 × 10 ¹² cells / cm 3, and the white region has an ion density of 5 × 10 ¹² cells / cm 3 or more. The ion density is higher and uniformly distributed than in the third embodiment whether the process atmosphere leaving time is long. 24 shows an ion density distribution immediately after performing pattern display for 48 hours. It can be seen that the ion density of the black display portion is lower than that of the white display portion. This decrease in ion density is probably due to the adsorption of ions on the surface of the alignment film. Thus, the adsorption of ions to the alignment film reduces the density of movable ions in the liquid crystal and increases the voltage retention, which is an important electrical parameter for the active matrix liquid crystal display panel. In this way, the voltage retention was partially increased, resulting in a difference in transmittance and flammability.

As described above, according to the present invention, the correlation between the operation of the liquid crystal display panel and the ions can be investigated. Therefore, it is possible to distinguish whether the cause of the display failure is caused by ions or else. Effective means can be provided.

Moreover, this invention is applicable to not only a liquid crystal display panel but a general liquid crystal panel.

As described above, since the ion measurement method of the liquid crystal panel of the present invention detects the size of the flicker appearing in the transmitted light of the liquid crystal panel and measures the ion density, the ion density in the panel can be known by non-destructive. Moreover, according to this invention, since distribution of ion density in the panel surface and ion density in a local area are known, it is possible to provide an effective means for operation analysis / failure analysis of the liquid crystal panel. In addition, according to the present invention, since the time from the occurrence of the problem to the acquisition of the ion density information in the liquid crystal is short, the industrial use value is very large.

Claims (16)

In the ion density measuring method of a liquid crystal panel, By applying an alternating voltage of a low frequency such that the ions can move in response to the liquid crystal panel, by changing the electric field applied to the liquid crystal by ion drift in the liquid crystal in response to the applied alternating voltage to change the tilt angle of the liquid crystal And detecting an ion density in the plane of the liquid crystal panel based on the flicker waveform of transmitted light intensity resulting from the change in the tilt angle of the liquid crystal during light transmission. delete The method of claim 1, A method for measuring the ion density of a liquid crystal panel, characterized by including a step of confirming the presence of ions. delete The method of claim 1, The voltage value of said alternating voltage is a value which the said liquid crystal panel can display near halftone, The ion density measuring method of the liquid crystal panel characterized by the above-mentioned. The method of claim 1, The ion density measurement method of the liquid crystal panel characterized by obtaining an ion density from the amplitude of the flicker waveform of transmitted light intensity. The method of claim 1, An ion density measuring method of a liquid crystal panel, wherein the ion density is obtained from an area surrounded by a horizontal line and a flicker waveform when there is no flicker waveform generated by the flicker waveform of transmitted light intensity. The method of claim 1, The liquid crystal panel is driven by a square wave or an active matrix, The ion density measuring method of the liquid crystal panel characterized by the above-mentioned. The method of claim 1, A method of measuring an ion density of a liquid crystal panel characterized by irradiating uniform visible light to the entire liquid crystal panel to which an alternating voltage is applied. The method of claim 1, A method of measuring the ion density of a liquid crystal panel characterized by irradiating uniform visible light to a portion of the liquid crystal panel to which an alternating voltage is applied. The method according to claim 1 or 9, A method for measuring the ion density of a liquid crystal panel, characterized by measuring the average intensity of transmitted light emitted from the front of the panel. The method according to any one of claims 1, 9, 10, The intensity of transmitted light is individually measured from the partial region of the said liquid crystal panel, and ion density is measured for every partial region, The ion density measuring method of the liquid crystal panel characterized by the above-mentioned. The method of claim 12, The transmission light of the liquid crystal panel is observed by an imaging device, and the transmitted light of the liquid crystal panel is measured for each pixel of the imaging device or for each pixel divided into groups to measure the ion density of the liquid crystal panel. Arbitrary waveform generator for driving a liquid crystal panel, a light source for irradiating light to the liquid crystal panel, an area image sensor for observing the intensity of light passing through the liquid crystal panel, the arbitrary waveform generator and the area image sensor An ion density measuring device of a liquid crystal panel including an information processing device having a storage device which oversees operation, And the detection data can be processed individually for each pixel of the area image sensor, and flicker can be detected for each pixel. The method of claim 14, And an oscilloscope capable of monitoring the output waveform of the area image sensor. The method of claim 15, And the information processing device collects output data of the area image sensor through the oscilloscope.