JP2009294364A - Residual dc measuring device, residual dc measuring system, residual dc measuring method, residual dc measuring device control program, computer readable recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure residual DC within accurate and in a short period of measuring time, by calculating an offset voltage in the case that transmittance corresponding to the maximum amplitude of an amplitude voltage and transmittance corresponding to the minimum amplitude thereof are equal to each other. <P>SOLUTION: A residual DC measuring device 30 is equipped with: a signal acquiring section 31 which acquires a plurality of data of sets of transmittance at positive polarity time, being maximum transmittance when a rectangular voltage gets positive for each offset voltage, and the offset voltage at that time, and acquires a plurality of data of sets of transmittance at negative polarity time, being minimum transmittance when a rectangular voltage gets negative for each offset voltage, and the offset voltage at that time; and a linear approximation/intersection calculating section 33 which acquires an approximate straight line from a plurality of data sets of the transmittance at positive polarity time and the offset voltage acquired by the signal acquiring section 31, acquires an approximate straight line from a plurality of data sets of the transmittance at negative polarity time and the offset voltage, and acquires an offset voltage corresponding to an intersection of the two approximate straight lines. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to evaluation of a liquid crystal panel, and more particularly to evaluation of the quality of a liquid crystal panel by evaluating residual DC.

  In recent years, liquid crystal display devices have been used in a wide range of fields such as televisions, personal computers, mobile phones, and car navigation systems. On the other hand, the improvement of the response characteristics of the video, the expansion of the chromaticity range, the improvement of the viewing angle characteristics, as well as the occurrence of so-called "burn-in", where the video once displayed remains even after sending video information to switch the screen. High display quality is required such as not allowed.

  The liquid crystal display device includes a liquid crystal panel and a backlight light source, and the liquid crystal panel displays an image by transmitting or blocking light emitted from the backlight light source. This liquid crystal panel is designed to realize a predetermined light transmittance when a certain voltage is applied.

  However, when image sticking occurs in the liquid crystal panel, a predetermined light transmittance cannot be obtained at a portion where the image sticking occurs even if a certain voltage is applied. Such image sticking becomes visible after, for example, the same display on the liquid crystal panel for a very long time of several thousand hours or more.

  Therefore, there is a residual DC as an evaluation parameter for image sticking of the liquid crystal panel. The liquid crystal panel has a mechanism for applying a rectangular wave having a positive polarity and a negative polarity to the liquid crystal layer. However, in practice, it is difficult to obtain a perfectly symmetrical waveform, a slight offset voltage is applied, and charges are accumulated in the liquid crystal panel, for example, at the boundary between the liquid crystal layer and the alignment film.

  As a result, a voltage applied from the outside through the electrode and a voltage due to charges accumulated in the liquid crystal panel are applied to the liquid crystal layer. In this way, when the voltage due to the charge accumulated in the liquid crystal panel is added to the voltage applied from the outside, the voltage applied to the liquid crystal layer differs depending on the positive polarity and the negative polarity, so flicker is generated from the liquid crystal panel. A predetermined transmittance cannot be obtained. The voltage due to the charges accumulated in the liquid crystal panel is called residual DC.

  Furthermore, as a method for evaluating residual DC, there is a means called flicker elimination described in Non-Patent Document 1. First, a certain offset voltage is applied to the liquid crystal panel as a load. Immediately thereafter, the offset voltage is changed while applying a voltage having an amplitude of about halftone. When an offset voltage is reached, the voltage due to the charge accumulated in the liquid crystal panel cancels out, and the flicker of the liquid crystal panel is minimized. The offset voltage at this time is defined as residual DC. Thus, the occurrence of seizure can be evaluated by measuring the residual DC.

  It should be noted that the residual DC can be made very small even if the same offset voltage is applied by devising the liquid crystal material, the alignment film material, the process and the like. That is, seizure can be suppressed.

In addition, as another evaluation method of residual DC, a means called a dielectric absorption method described in Non-Patent Document 2 is also disclosed.
N. Fukuoka, M. Okamoto, Y. Yamamoto, M. Hasegawa, Y. Tanaka, H. Hatoh, K. Mukai: Proc. Of AM-LCD94, p. 216, 1994 Inoue, Manabe, Wataru Nakano: Proceedings of Liquid Crystal Panel Discussion Meeting, p.216, 1997

  However, as described above, the measurement by the conventional residual DC evaluation method is inaccurate. The offset voltage was changed a plurality of times, and the offset voltage when the flicker intensity was minimized was set as the residual DC. However, in this conventional method, the residual DC can be estimated only with the accuracy of the change width of the offset voltage. On the other hand, if the offset voltage is changed very finely for precise measurement, the time for changing the offset voltage becomes long and the measurement takes time, which disturbs the system.

  The present invention has been made in view of the above-described problems, and a residual DC measurement device, a residual DC measurement system, a residual DC measurement method, and a residual DC measurement device control program capable of measuring residual DC in an accurate and short measurement time. An object of the present invention is to provide a computer-readable recording medium.

  In order to solve the above-mentioned problems, the residual DC measuring apparatus according to the present invention is configured to detect the residual DC generated in the liquid crystal panel while driving the liquid crystal panel by applying an amplitude voltage to the transmittance of the transmitted light of the liquid crystal panel. In the residual DC measuring device, the offset voltage is applied to the amplitude voltage every predetermined period, and one of the detected transmittances is in a period of the offset voltage. While acquiring a plurality of sets of data of the maximum amplitude transmittance, which is the transmittance when the amplitude voltage reaches the maximum amplitude, and the offset voltage at that time, one of the detected transmittances, the offset A data acquisition means for acquiring a plurality of sets of data of a minimum amplitude transmittance, which is a transmittance when the amplitude voltage becomes a minimum amplitude during a voltage period, and an offset voltage at that time; and the data From the plurality of sets of data of the maximum amplitude transmittance and the offset voltage acquired by the acquisition means, an approximate straight line indicating the relationship between the maximum amplitude transmittance and the offset voltage is obtained, and the data acquisition means acquires An approximate line indicating the relationship between the minimum amplitude transmittance and the offset voltage is obtained from a plurality of sets of data of the minimum amplitude transmittance and the offset voltage, and further corresponds to the intersection of the two approximate lines. And an arithmetic means for obtaining an offset voltage.

  In order to solve the above-mentioned problem, the residual DC measurement method of the present invention is based on the residual DC generated in the liquid crystal panel detected by driving the liquid crystal panel while applying an amplitude voltage to the liquid crystal panel. In the residual DC measurement method for measuring using the transmittance, a different offset voltage is applied to the amplitude voltage for each predetermined period, and one of the detected transmittances of the offset voltage is added. A plurality of sets of data of a maximum amplitude transmittance that is a transmittance when the amplitude voltage becomes the maximum amplitude in a period and an offset voltage at that time, and one of the detected transmittances is acquired. A data acquisition step of acquiring a plurality of sets of data of a minimum amplitude transmittance that is a transmittance when the amplitude voltage becomes a minimum amplitude during the offset voltage period and an offset voltage at that time; An approximate straight line indicating the relationship between the maximum amplitude transmittance and the offset voltage is obtained from a plurality of sets of the maximum amplitude transmittance and the offset voltage acquired in the data acquisition step, and in the data acquisition step. An approximate line indicating the relationship between the minimum amplitude transmittance and the offset voltage is obtained from the acquired sets of data of the minimum amplitude transmittance and the offset voltage, and at the intersection of the two approximate lines. And calculating a corresponding offset voltage.

  Here, the transmittance at the maximum amplitude is the transmittance at a predetermined time included in the positive polarity in one cycle of the amplitude voltage, and the transmittance at the minimum amplitude is the transmittance at one cycle of the amplitude voltage. The transmittance at a predetermined time included in the negative polarity.

  According to the above configuration, the data acquisition means includes a plurality of sets of data of the maximum amplitude transmittance, which is the transmittance when the amplitude voltage reaches the maximum amplitude during one offset voltage period, and the offset voltage at that time. get. In addition, the data acquisition means acquires a plurality of sets of data of the minimum amplitude transmittance, which is the transmittance when the amplitude voltage becomes the minimum amplitude during one offset voltage period, and the offset voltage at that time. To do.

  Then, the calculation means obtains an approximate straight line indicating the relationship between the maximum amplitude transmittance and the offset voltage from the plurality of sets of data of the maximum amplitude transmittance and the offset voltage acquired by the data acquisition means. . Further, the calculation means obtains an approximate straight line indicating the relationship between the minimum amplitude transmittance and the offset voltage from a plurality of sets of data of the minimum amplitude transmittance and the offset voltage acquired by the data acquisition means. . And the said calculating means calculates | requires the offset voltage corresponding to the intersection of the said two approximate lines. As described above, the offset voltage obtained by the calculation means is an offset voltage when the maximum amplitude transmittance and the minimum amplitude transmittance are equal. This offset voltage is the residual DC.

  Here, as described above, conventionally, the offset voltage is changed a plurality of times, and the offset voltage that minimizes flicker is estimated to be the residual DC.

  The minimum flicker means that the difference between the transmittance corresponding to the maximum amplitude of the amplitude voltage to which the offset voltage is added and the transmittance corresponding to the minimum amplitude of the amplitude voltage to which the offset voltage is added is the smallest. .

  On the other hand, according to the above configuration, by obtaining the intersection of two approximate lines, the offset voltage when the maximum amplitude transmittance and the minimum amplitude transmittance are equal can be obtained as the residual DC. For this reason, it is possible to accurately determine the residual DC as compared with the conventional method.

  Furthermore, since the offset voltage needs to be changed by the number of times corresponding to the number of data that allows the calculation means to obtain the two approximate lines, the number of times of changing the offset voltage can be reduced. For this reason, residual DC can be measured in a short measurement time.

  Thus, according to the above configuration, by calculating the offset voltage when the transmittance corresponding to the maximum amplitude of the amplitude voltage is equal to the transmittance corresponding to the minimum amplitude, the residual DC can be obtained in an accurate and short measurement time. Can be measured.

  Further, according to the above configuration, since the measurement time of the residual DC is short, even if the residual DC is measured a plurality of times at the same location of the liquid crystal panel, the time load can be greatly reduced. It is.

  Thus, according to the above configuration, the residual voltage can be obtained in an accurate and short measurement time by obtaining the offset voltage when the transmittance corresponding to the maximum value of the amplitude voltage and the transmittance corresponding to the minimum value are equal as the residual DC. DC can be determined.

  In the residual DC measuring device, an offset voltage that minimizes the difference between the maximum amplitude transmittance and the minimum amplitude transmittance is acquired as a temporary residual DC, and a predetermined voltage including the acquired temporary residual DC is obtained. Offset voltage control means for outputting a signal for changing the offset voltage within the range of the width, the data acquisition means, the transmittance at the maximum amplitude within the range of the predetermined voltage width including the temporary residual DC, It is preferable to acquire a plurality of sets of data with the offset voltage at that time and to acquire a plurality of sets of data with the transmittance at the minimum amplitude and the offset voltage at that time.

  According to the configuration, the offset voltage control means can change the offset voltage within a predetermined voltage range including the temporary residual DC. The data acquisition means acquires a plurality of sets of data of the maximum amplitude transmittance and the offset voltage at that time within a predetermined voltage range including the temporary residual DC. Further, the data acquisition means acquires a plurality of sets of data of the minimum amplitude transmittance and the offset voltage at that time within a predetermined voltage range including the temporary residual DC.

  For this reason, the intersection of the two approximate straight lines calculated by the calculation means is included in the range of the offset voltage changed by the offset voltage control means. Thus, the arithmetic means can obtain the intersection of the two approximate lines within the range of the offset voltage changed by the offset voltage control means, so that the residual DC can be obtained accurately.

  In the residual DC measuring device, it is preferable that the range of the predetermined voltage width of the offset voltage changed by the offset voltage control means is ± 100 mV of the temporary residual DC.

  Here, assuming that the range of the predetermined voltage width that is changed by the offset voltage control means is a range that exceeds ± 100 mV, for example, ± 200 mV, a plurality of positive-polarity transmittance data and a plurality of negative-polarity data The variation in the transmittance data becomes large, and the calculation means cannot calculate an accurate approximate straight line. Therefore, as in the above-described configuration, by setting the range of the predetermined voltage width of the offset voltage changed by the offset voltage control means to ± 100 mV, each of a plurality of positive transmittances and a plurality of negative polarity Variations in the transmittance data are reduced. For this reason, since the calculation means can calculate an approximate straight line with a small error from each of the plurality of positive transmittances and negative transmittances, the residual DC can be accurately calculated.

  In the residual DC measuring apparatus, the maximum amplitude transmittance is a predetermined value from when the amplitude voltage changes from negative polarity to positive polarity during one offset voltage period to immediately before it changes from positive polarity to negative polarity. The transmittance acquired by the data acquisition means at the time of, and the minimum-amplitude transmittance is just before changing from negative polarity to positive polarity from the change from positive polarity to negative polarity during one offset voltage period. It is preferable that the transmittance is acquired by the data acquisition means during a predetermined time until.

  This means that the liquid crystal of the liquid crystal panel requires a certain amount of time to respond depending on the amplitude voltage. Accordingly, the data acquisition means transmits the transmittance of the liquid crystal panel during a predetermined time from when the amplitude voltage changes from negative polarity to positive polarity until immediately before it changes from positive polarity to negative polarity during one offset voltage period. Is obtained as the maximum amplitude transmittance, and the transmittance of the liquid crystal panel is minimized during a predetermined time from the change from the positive polarity to the negative polarity during one offset voltage period until immediately before the change from the negative polarity to the positive polarity. Acquired as transmittance at amplitude. For this reason, since the data acquisition means acquires the transmittance at which the response of the liquid crystal of the liquid crystal panel is completed, the maximum amplitude transmittance and the minimum amplitude transmittance can be acquired with accurate values.

  In the residual DC measuring device, it is preferable that the predetermined time is from 0.4 period to less than 0.5 period after the amplitude voltage.

  Here, for example, in about 0.1 period from the change of the polarity of the rectangular voltage, the liquid crystal is in the middle of response, the occurrence of flicker is reduced, and the influence of noise is increased. On the other hand, after 0.4 cycles from the change of the amplitude voltage, it is considered that the response of the liquid crystal is almost completed (the alignment of the liquid crystal is almost completed), and the influence of noise can be reduced.

  As in the above configuration, the transmittance of the liquid crystal panel 0.4 cycles after the amplitude voltage changes from negative polarity to positive polarity during the one offset voltage period as the maximum amplitude transmittance. The data acquisition is performed by acquiring the transmittance of the liquid crystal panel 0.4 cycles after the amplitude voltage changes from positive polarity to negative polarity during one offset voltage period as the minimum amplitude transmittance. The means can reliably acquire the transmittance after the liquid crystal responds in response to the amplitude voltage.

  Further, the data acquisition means acquires, as the maximum amplitude transmittance, the transmittance of the liquid crystal panel having a period of less than 0.5 period from the time when the amplitude voltage changes from negative polarity to positive polarity during one offset voltage period. By acquiring the transmittance of the liquid crystal panel of less than 0.5 period from the time when the amplitude voltage changes from positive polarity to negative polarity during one offset voltage period as the minimum amplitude transmittance, the data acquisition means Among the voltages, the maximum amplitude transmittance can be acquired from a half cycle including the maximum amplitude transmittance. In addition, the data acquisition means can acquire the minimum amplitude transmittance from the half cycle including the minimum amplitude transmittance of the amplitude voltage. Therefore, the data acquisition means can accurately acquire the maximum amplitude transmittance and the minimum amplitude transmittance.

  In the residual DC measuring device, the calculation means obtains a predicted residual DC that is an intersection of two approximate lines outside the range of the predetermined voltage width, outputs the predicted residual DC to the offset voltage control means, and outputs the offset voltage When the control unit acquires the predicted residual DC from the arithmetic unit, the control unit outputs an instruction to change the offset voltage within a predetermined voltage range including the acquired temporary residual DC, and the data acquisition unit includes: A plurality of sets of data of the maximum amplitude transmittance and the offset voltage at that time within a predetermined voltage range including the predicted residual DC are acquired, and the minimum amplitude transmittance and the offset voltage at that time are set. It is preferable to acquire a plurality of data.

  According to the configuration, even when the two approximate lines do not intersect within the range of the voltage width of the offset voltage changed by the offset voltage control means, the calculation means determines the position where the two approximate lines intersect. Calculated as the calculated predicted residual DC. And the said offset voltage control means will output the instruction | indication for changing an offset voltage within the range of a predetermined voltage width again, if the prediction residual DC is acquired from the said calculating means.

  Further, the data acquisition means acquires a plurality of sets of data of a maximum amplitude transmittance and an offset voltage at that time within a predetermined voltage range including the predicted residual DC. Further, the data acquisition means acquires a plurality of sets of data of the minimum amplitude transmittance and the offset voltage at that time within a predetermined voltage range including the predicted residual DC.

  Thereby, the said calculating means can acquire the intersection of the said two approximate straight lines within the range of the offset electricity which the said offset voltage control means changed reliably. For this reason, the said calculating means can measure residual DC correctly.

  The residual DC measurement system of the present invention includes a calculation / control means including a system control means for outputting an instruction signal for controlling an amplitude voltage applied to the liquid crystal panel, a light source, and light from the light source. A plurality of liquid crystal panels can be mounted in a transmission region that transmits light, and the mounted liquid crystal panel can be moved in a direction perpendicular to the light emission direction from the light source, the XY stage, and the liquid crystal panel Optical means including light receiving means for receiving light from the light source that has passed through and outputting a voltage, voltage acquisition means for outputting the voltage output from the light receiving means as an electrical signal to the calculation / control means, and A waveform voltage for obtaining an instruction signal for controlling a drive voltage applied to the liquid crystal panel from a system control means and applying an amplitude voltage to the liquid crystal panel It is preferable to provide a raw device.

  According to the said structure, the said waveform voltage generation means applies an amplitude voltage with respect to the said liquid crystal panel mounted on the said XY stage. The liquid crystal panel to which an amplitude voltage is applied from the waveform voltage generating means is driven according to the applied amplitude voltage. The light emitted from the light source passes through the XY stage and the liquid crystal panel and is received by the light receiving means. And the said light-receiving means which received the light which permeate | transmitted the said liquid crystal panel outputs the voltage according to the received light quantity to the said voltage acquisition means. When the voltage is input from the light receiving unit, the voltage acquisition unit outputs the voltage to the calculation / control unit as an electrical signal. The arithmetic / control means calculates the transmittance of the liquid crystal panel when an electric signal is input from the voltage acquisition means. The residual DC measurement device can calculate the residual DC.

  The residual DC measuring system according to the present invention includes: a stress voltage indicating unit that outputs a stress voltage indicating signal to the waveform voltage generating unit that instructs the liquid crystal panel to apply a stress voltage that is a load voltage; The burn-in measurement means for obtaining an electric signal indicating the transmittance before and after the stress voltage is applied from the voltage acquisition means and measuring the burn-in of the liquid crystal panel from the acquired electric signal. The control means is preferably provided.

  According to the above configuration, the image sticking measurement unit acquires in advance the transmittance before a stress voltage is applied to the liquid crystal panel. The waveform voltage generator applies a stress voltage to the liquid crystal panel. Thereafter, the burn-in measurement means acquires the transmittance after a stress voltage is applied to the liquid crystal panel. The burn-in measurement means can calculate burn-in from the transmittance of the liquid crystal panel before and after the stress voltage is applied.

  In addition, since the calculation / control unit includes the residual DC measuring device and the seizure measuring unit, it is possible to measure both the residual DC and seizure of the optical panel. For this reason, when the image sticking occurs in the liquid crystal panel, it is possible to determine whether the cause of the image sticking is a residual DC in direct association.

  The burn-in measurement means preferably calculates the burn-in rate from a ratio between the transmittance of the liquid crystal panel before application of the stress voltage and the transmittance of the liquid crystal panel after application of the stress voltage. Thereby, the image sticking of the liquid crystal panel can be evaluated.

  If the transmittance of the liquid crystal panel before application of the stress voltage and the transmittance of the liquid crystal panel after application of the stress voltage are equal (if the image sticking rate is 1), the image sticking is only caused by residual DC. However, if the transmittance of the liquid crystal panel before application of the stress voltage and the transmittance of the liquid crystal panel after application of the stress voltage are not equal (if the burn-in rate is not 1), there are other factors other than residual DC. Can be determined. Thereby, it is possible to easily determine whether or not the cause of seizure is residual DC.

  In the residual DC measurement system of the present invention, it is preferable that the application of the stress voltage and the measurement of the residual DC are repeated a plurality of times.

  As a result, it is possible to measure the time change of the residual DC of the liquid crystal panel. Accordingly, it is possible to finally specify a combination of a liquid crystal material, an alignment film material, and the like that are less likely to cause image sticking.

  It is also possible to measure the relaxation process of residual DC.

  Here, how long the seizure caused by the residual DC disappears has a strong correlation with the relaxation rate of the residual DC. And when the relaxation rate of residual DC is slow, seizure will remain for a long time. Therefore, it is possible to specify a liquid crystal panel in which image sticking disappears in a short time.

  Furthermore, the XY stage can move the plurality of mounted liquid crystal panels in a direction perpendicular to the light emission direction from the light source. For this reason, when measuring the residual DC multiple times in each of the plurality of liquid crystal panels, a stress voltage is applied to the liquid crystal panel on which the residual DC is measured, and then the measurement points are moved to determine the residual DC of different liquid crystal panels. Can be measured. As described above, the application of the stress voltage and the measurement of the residual DC can be performed in parallel by a plurality of liquid crystal panels. For this reason, it becomes possible to greatly improve the measurement efficiency of residual DC.

  Furthermore, since the residual DC at a plurality of locations can be measured, it is possible to analyze the temporal change and absolute value of the residual DC independently at each measurement point. In addition, when performing multipoint measurement of one sample, it is possible to measure the distribution of residual DC in the optical panel, for example, near the inlet, near the seal material, and in the center.

  In the residual DC measurement system of the present invention, it is preferable to repeat the application of the stress voltage and the measurement of seizure multiple times.

  As a result, it is possible to measure a temporal change in image sticking, and it is possible to specify a combination of a liquid crystal material, an alignment film material, and the like that ultimately cause image sticking.

  In addition, it becomes possible to measure the process of mitigating seizure, and it is possible to specify a liquid crystal panel in which seizure persists.

  Furthermore, since the XY stage includes a plurality of the liquid crystal panels, and the plurality of mounted liquid crystal panels can be moved in a direction perpendicular to the light emission direction from the light source, Burn-in measurement can be performed in parallel on a plurality of liquid crystal panels. For this reason, it becomes possible to greatly improve the measurement efficiency of seizure.

  The above may be realized by a computer. In this case, a residual DC measurement device control program for realizing the above in the computer by operating the computer as each of the above means, and a computer-readable recording medium on which the residual DC measurement device control program is recorded are also included in the scope of the present invention. to go into.

  As described above, in the residual DC measuring device according to the present invention, an offset voltage different for each predetermined period is added to the amplitude voltage, and one of the detected transmittances is in the period of the offset voltage. While acquiring a plurality of sets of data of the maximum amplitude transmittance, which is the transmittance when the amplitude voltage reaches the maximum amplitude, and the offset voltage at that time, one of the detected transmittances, the offset A data acquisition unit for acquiring a plurality of sets of sets of transmittance at a minimum amplitude, which is a transmittance when the amplitude voltage becomes a minimum amplitude during a voltage period, and an offset voltage at that time; and the data acquisition unit acquires From the plurality of sets of data of the maximum amplitude transmittance and the offset voltage, an approximate straight line indicating the relationship between the maximum amplitude transmittance and the offset voltage is obtained, and An approximate straight line indicating the relationship between the minimum amplitude transmittance and the offset voltage is obtained from a plurality of sets of data of the minimum amplitude transmittance and the offset voltage acquired by the data acquisition means, and further, the two Computing means for obtaining an offset voltage corresponding to the intersection of the approximate lines.

  Further, in the residual DC measurement method according to the present invention, an offset voltage different for each predetermined period is added to the amplitude voltage, and the amplitude voltage is maximized during one offset voltage period of the detected transmittance. While obtaining a plurality of sets of data of the maximum amplitude transmittance that is the transmittance at the time of the amplitude and the offset voltage at that time, of the detected transmittance, in the period of the one offset voltage A data acquisition step for acquiring a plurality of sets of data of a minimum amplitude transmittance that is a transmittance when the amplitude voltage becomes the minimum amplitude and an offset voltage at that time, and at the time of the maximum amplitude acquired in the signal acquisition step An approximate straight line showing the relationship between the maximum amplitude transmittance and the offset voltage is obtained from a plurality of sets of transmittance and offset voltage data, and the signal acquisition is performed. From the plurality of sets of data of the minimum amplitude transmittance and the offset voltage acquired in the step, an approximate line indicating the relationship between the minimum amplitude transmittance and the offset voltage is obtained, and further, the two approximate lines And calculating an offset voltage corresponding to the intersection.

  Therefore, by calculating the offset voltage when the transmittance corresponding to the maximum amplitude of the amplitude voltage is equal to the transmittance corresponding to the minimum amplitude, the residual DC can be measured accurately and in a short measurement time. There is an effect.

[Schematic configuration of residual DC measurement system]
An embodiment of the present invention will be described below with reference to FIGS.

  FIG. 2 is a block diagram illustrating a configuration of a residual DC measurement system 1 to which the residual DC measurement device 30 according to the present embodiment is applied.

  As shown in FIG. 2, the residual DC measurement system 1 includes an optical unit (optical unit) 2 as an optical system, a signal acquisition unit (data acquisition unit) 7 that acquires a voltage signal output from the optical unit 2, A waveform signal generation unit (waveform generation means) 8 that outputs a waveform signal to the optical unit 2, a calculation of a signal acquired from the voltage acquisition unit 7, and an instruction to generate a waveform signal to the waveform voltage generation unit 8 A calculation / control unit (calculation / control means) 9 is provided.

  The residual DC measurement system 1 performs two types of measurements. The first type is to measure residual DC, and the second type is to measure the seizure rate.

  The optical unit 2 is disposed in the thermostatic layer 6, and is provided between a light source 3 using a halogen lamp or the like, two polarizing plates (polarizing elements) 4a and 4b having a rotating mechanism, and two polarizing plates 4a and 4b. An XY stage 10 provided with a liquid crystal panel for measuring residual DC, on which one or a plurality of samples can be mounted, and a light receiving unit 5 that converts a received light amount into a voltage signal.

  However, when the temperature of the room where the residual DC measurement system 1 is installed is stable, the thermostatic layer 6 may be replaced with a dark box. The optical unit 2 has an adjustable lens and has a mechanism (not shown) for focusing on the sample.

  The voltage acquisition unit 7 includes a multimeter, an oscilloscope, and the like, and is connected to the light receiving unit 5. The voltage acquisition unit 7 converts the voltage output from the light receiving unit 5 into digital data, and outputs the digital data to the calculation / control unit 9.

  The calculation / control unit 9 includes a residual DC measurement device 30, a system control device 40, a reference measurement unit 44, and a seizure measurement device (seizure measurement means) 45.

  The residual DC measurement device 30 receives the voltage signal output from the voltage acquisition unit 7 and calculates the residual DC from the received voltage signal. Details of the residual DC measuring device 30 will be described later.

  Further, the system control device 40 outputs a drive control signal instructing generation and output of the drive voltage of the liquid crystal panel 20 to the waveform voltage generator 8 and controls the residual DC measurement system 1. Further, the system control device 40 calculates an offset voltage that minimizes the flicker of the liquid crystal panel, and obtains a temporary residual DC.

  Each of the residual DC measurement device 30, the system control device 40, the reference measurement unit 44, and the image sticking measurement device 45 is composed of a personal computer (PC) and may be composed of one PC.

  The waveform voltage generation unit 8 is connected to the calculation / control unit 9. A voltage application terminal (voltage application terminal 12) provided on the XY stage 10 for connection to a connection terminal of the liquid crystal panel is connected. The waveform voltage generator 8 applies the waveform voltage to the liquid crystal panel by receiving the drive control signal from the calculation / control unit 9. In other words, the waveform voltage generator 8 is an arbitrary waveform generator that can apply a rectangular voltage with an arbitrary frequency and amplitude and an arbitrary offset voltage to the liquid crystal panel. One or more waveform voltage generators 8 are mounted on the XY stage 10. When the waveform voltage generator 8 is mounted on the plurality of XY stages 10, the wiring is grouped by using a dedicated rack. In addition, it is preferable to devise such as bonding or embedding the wiring and the voltage application terminal on the XY stage 10. In addition, it is preferable that the voltage application terminal is brought into contact with a connection terminal (ITO or the like) of the liquid crystal panel 20 with a conductive rubber and devised such that it is lightly pressed with a spring mechanism. Further, the plurality of waveform voltage generators 8 can be independently controlled by GPIB or the like.

  Then, an optical system of a microscope may be used as the optical unit 2. At this time, the microscope may be a general transmission microscope, for example, a transmission illumination system having a halogen lamp and a condenser lens, an XY stage 10, and a 1 × to 100 × objective that can be replaced by an electric revolver. It is a trinocular type having a lens and having an objective lens and a camera barrel. Further, as the light receiving unit 5, the lens barrel for the camera has a C-mount PMT (photomultiplier tube) module. The output of the light receiving unit 5 composed of a PMT or the like is taken in by a voltage acquisition unit 7 composed of a multimeter or an oscilloscope, and analyzed by a calculation / control unit 9 composed of a PC. Thereby, it is possible to observe in which part of the liquid crystal panel image sticking occurs. For example, in an MVA mode liquid crystal panel, a pixel has a slit structure or a rib structure, and it is possible to measure a residual DC and a burn-in rate on the pixel electrode, the rib, and the slit.

  Next, the configuration of the XY stage 10 will be described with reference to FIGS.

  FIG. 3A is a plan view showing the configuration of the XY stage 10, and FIG. 3B is a side view of the XY stage 10.

  As shown in FIG. 3A, the XY stage 10 includes a fixing mechanism 13 for supporting and fixing the outer frame of the liquid crystal panel on the XY stage 10, and a light shielding region a for shielding light. .

  The fixing mechanism 13 includes a transmission portion 11 that transmits light and a voltage application terminal 12 for applying a voltage to the liquid crystal panel, and one or a plurality of fixing mechanisms 13 are arranged on the XY stage 10. In the present embodiment, six fixing mechanisms 13 are juxtaposed on the XY stage 10. A liquid crystal panel 20 connected to the voltage application terminal 12 is fixed to each fixing mechanism 13.

  The XY stage 10 is provided with a reference measurement opening 14 and a non-opening 15 in a region other than the transmission part 11. The opening 14 is used to obtain a measurement value of 100% transmittance of light emitted from the light source 3, and the non-opening portion 15 is used to measure 0% transmittance of light emitted from the light source 3. To get the value. The opening 14 is made of a transparent member that transmits light from the light source 3, and the non-opening 15 is made of a member that blocks light from the light source 3.

  As shown in FIG. 3B, the XY stage 10 includes a liquid crystal panel mounting portion 16 for mounting and fixing the liquid crystal panel 20, and a back surface side of the liquid crystal panel mounting portion 16 (the light source 3 is provided). And a transparent hot stage (hot plate) 17 that can be attached and detached.

  Next, details of the calculation / control unit 9 will be described with reference to FIG.

  FIG. 1 is a block diagram showing the configuration of the calculation / control unit 9 according to the present embodiment.

  As shown in FIG. 1, the calculation / control unit 9 includes a residual DC measurement device 30, a system control device 40, a reference measurement unit 44, and a seizure measurement device 45.

  The residual DC measurement device 30 includes a signal acquisition unit 31, a storage unit 32, a linear approximation / intersection calculation unit 33, a residual DC output unit 34, and an offset voltage control unit (offset voltage control means) 35. .

  The system control device 40 controls the residual DC measurement system 1 and outputs an instruction signal (drive control signal) for outputting an amplitude voltage for driving the liquid crystal panel to the waveform voltage generator 8. The offset voltage included in the instruction signal is adjusted. In addition, a temporary residual DC for measuring the residual DC by the residual DC measuring device 30 is calculated.

  The reference measurement unit 44 performs reference measurement, which is an initial setting of the residual DC measurement system 1, calculation of VT characteristics, calculation of a relationship between gradation and voltage, and the like.

  The image sticking measuring device 45 is for measuring the image sticking of the liquid crystal panel 20 in the residual DC measuring system 1.

  The signal acquisition unit 31 acquires a signal indicating the transmittance of the liquid crystal panel 20 (hereinafter simply referred to as transmittance) from the voltage acquisition unit 7. Of the acquired transmittances, the transmittance corresponding to the maximum value of the positive polarity of the instruction signal of the amplitude voltage output from the system control device 40 is defined as the positive transmittance at the time of the positive polarity, and the storage unit 32 and the linear approximation / intersection calculation To the unit 33. Further, among the acquired transmittances, the transmittance corresponding to the minimum negative polarity value of the amplitude voltage instruction signal output from the system control device 40 is set as the negative polarity transmittance, and the storage unit 32 and linear approximation / intersection calculation To the unit 33.

  Further, the signal acquisition unit 31 acquires a plurality of sets of data of the maximum amplitude transmittance and the offset voltage at that time within a predetermined voltage range including the predicted residual DC, and the minimum amplitude transmittance, A plurality of sets of data with the offset voltage at that time are acquired.

  The straight line approximation / intersection calculator 33 calculates an approximate straight line from the plurality of positive polarity transmittances acquired from the signal acquisition unit 31, and approximates the straight line from the plurality of negative polarity transmittances acquired from the signal acquisition unit 31. And the intersection of the two approximate lines is calculated. Then, the straight line approximation / intersection calculator 33 outputs the calculated value of the intersection to the residual DC output unit 34. Further, the residual DC output unit 34 outputs the value of the intersection obtained from the straight line approximation / intersection calculator 33 to the outside as the residual DC.

  Further, the straight line approximation / intersection calculation unit 33, when the offset voltage corresponding to the obtained intersection of the two approximate lines is outside the range of the predetermined voltage width, determines the calculated offset voltage as the predicted residual DC and the offset voltage control unit 35.

  The offset voltage control unit 35 adjusts the offset voltage in order to obtain the residual DC, and an offset voltage control signal for controlling the offset voltage within a predetermined voltage range including the temporary residual DC calculated by the system control device 40. Is output to the system controller 40. Further, when the predicted residual DC is acquired from the linear approximation / intersection calculator 33, the offset voltage control unit 35 outputs an instruction to change the offset voltage within a predetermined voltage range including the acquired temporary residual DC. .

(Initial measurement)
Next, a residual DC measurement method by the residual DC measurement system 1 will be described.

  First, measurement for performing the initial setting of the residual DC measurement system 1 will be described.

  First, reference measurement is performed before residual DC measurement.

  In the present embodiment, the liquid crystal panel 20 is premised on a test cell having a simple structure having a large electrode of about 1 cm × 1 cm. However, the present invention is not limited to this. The liquid crystal panel 20 is installed on the fixing mechanism 13 of the XY stage 10. That is, the liquid crystal panel 20 is installed in the transmission part 11, and the electrode is connected to the voltage application terminal 12.

  First, reference measurement is performed as a reference between the light transmittances 100% and 0% from the light source 3. The XY stage 10 is moved so that the light emitted from the light source 3 is transmitted through the opening 14. Then, the signal acquisition unit 31 acquires a voltage signal emitted from the light source 3, transmitted through the opening 14, and input to the calculation / control unit 9 via the light receiving unit 5 and the voltage acquisition unit 7. Then, the signal acquisition unit 31 outputs the acquired voltage signal to the reference measurement unit 44.

In the reference measurement unit 44, the input voltage signal is set as a voltage signal (maximum transmittance voltage; V ₁₀₀ ) having a luminance of 100% (maximum transmittance).

Next, the XY stage 10 is moved so that the light emitted from the light source 3 is irradiated to the non-opening 15. Since the light emitted from the light source 3 is blocked by the non-opening portion 15, the light receiving portion 5 does not receive the light. In the reference measurement unit 44, the voltage signal at this time is set as a voltage signal having a transmittance of 0% (minimum transmittance) (minimum transmittance voltage; V ₀ ).

  When performing this reference measurement, in order to prevent light from being blocked by the polarizing plates 4a and 4b, the polarizing plates 4a and 4b are made paranicol, or the polarizing plates 4a and 4b are also provided with an XY stage mechanism. The polarizing plates 4a and 4b are removed from the optical axis.

  Next, voltage-transmittance characteristics (VT characteristics) as shown in FIG. 10 are measured.

  The system control device 40 applies the rectangular voltage not including the offset voltage to the liquid crystal panel 20 while gradually increasing the amplitude of the rectangular voltage. Further, the system control device 40 outputs the voltage value of the rectangular voltage to the reference measurement unit 44.

  Then, the signal acquisition unit 31 outputs the transmittance value input from the voltage acquisition unit 7 to the reference measurement unit 44. Then, the reference measurement unit 44 associates the voltage value of the rectangular voltage input from the system control device 40 with the transmittance value input from the signal acquisition unit 31. Thereby, a VT characteristic is obtained.

  The transmittance is calibrated using the result of the reference measurement described above.

  FIG. 10 is a graph showing the VT characteristic of the liquid crystal panel 20. The horizontal axis is the voltage V, and the vertical axis is the transmittance T.

  As shown in FIG. 10, a rectangular voltage that does not include an offset voltage and has a positive and negative amplitude width symmetrical is applied to the liquid crystal panel 20, and the amplitude of the rectangular voltage is gradually increased. A transmittance of 20 is measured.

Further, the reference measurement unit 44 calculates a gradation-voltage characteristic from the VT characteristic measured as described above, and outputs it to the system control device 40. Then, the system control device 40 calculates a voltage (V ₅₀ ) at which the transmittance (transmittance T ₅₀ ) is half of the maximum transmittance of the liquid crystal panel 20 from the gradation-voltage characteristics acquired from the reference measurement unit 44. It calculates a _{V 50} signal. Then, the residual DC described below is measured by adding the offset voltage to a rectangular voltage of the voltage V _50. This makes it possible to observe flicker clearly.

(Residual DC measurement method)
Regarding the method for measuring residual DC according to the present embodiment, first, the method for measuring temporary residual DC will be described with reference to FIGS. 4 (a) to 4 (d), and then FIGS. 5 (a) to 5 (c). A method for measuring residual DC will be described.

  In the present embodiment, the system control device 40 outputs a rectangular voltage to the liquid crystal panel 20 as an amplitude voltage for driving the liquid crystal panel 20. And the signal acquisition part 31 acquires the transmittance | permeability of the liquid crystal panel 20 corresponding to the said rectangular voltage. 4A to 4D show the relationship between the rectangular voltage and the transmittance value corresponding to the rectangular voltage.

  FIG. 4 (a) is a graph showing the rectangular wave voltage with the offset voltage changed and the transmittance of the liquid crystal panel at that time, and FIG. 4 (b) shows the rectangular wave voltage with the stress voltage applied thereto, 4C is a graph showing the transmittance of the liquid crystal panel at the time, FIG. 4C is a graph showing the rectangular wave voltage and the transmittance of the burned-up liquid crystal panel, and FIG. 4D is a graph showing the offset voltage. It is a graph showing the changed rectangular wave voltage and the transmittance | permeability of the liquid crystal panel in that case.

  4A to 4D, the vertical axis represents transmittance (%) or voltage (V), and the horizontal axis represents time.

  As shown in FIG. 4A, the rectangular wave voltage (sa) is a waveform voltage applied to the liquid crystal panel 20, and a voltage value (positive polarity) greater than the amplitude center s and the amplitude center for each period. It consists of a voltage value (negative polarity) smaller than s. Then, an offset voltage is added to this rectangular voltage (A).

  Here, the offset voltage is a voltage of the amplitude center (amplitude center) s in one cycle of the rectangular wave voltage. That is, in the rectangular voltage (A), the voltage when the amplitude voltage has the maximum width during the offset voltage period in one cycle is a positive voltage, and the amplitude voltage has the minimum width during the offset voltage period in one cycle. The voltage when it becomes is a negative voltage.

Note that the system control device 40 acquires the V ₅₀ signal from the reference measurement unit 44 and changes the offset voltage in the vicinity thereof. This is because the VT characteristic has a substantially linear relationship in the vicinity of the transmittance T ₅₀ and the residual DC can be accurately obtained. Details will be described later.

  As shown in FIG. 4A, the rectangular voltage applied to the liquid crystal panel 20 by the system control device 40 is greater than the voltage value (positive polarity) greater than the amplitude center s and the amplitude center s for each cycle. It consists of a small voltage value (negative polarity). Further, the system control device 40 adds an offset voltage to the rectangular voltage (s).

  As shown in FIG. 4A, when the offset voltage is applied to the rectangular voltage (sa), the absolute value of the voltage applied to the liquid crystal differs when the polarity of the rectangular voltage (sa) changes. For this reason, every time the polarity of the rectangular wave voltage changes, the transmittance changes. This change in transmittance is visually recognized as flicker.

  As shown in FIG. 4A, when the value of the offset voltage is changed for each period of the rectangular voltage (sa), there is a portion where the offset voltage becomes 0 (broken line (su)). At this time, since the offset voltage is not applied to the rectangular voltage (sa), the absolute value is equal between the positive voltage value and the negative voltage value of the rectangular voltage (sa) (hereinafter referred to as a symmetrical waveform). Called). In this case, even if the voltage value of the rectangular voltage (sa) changes from the positive polarity to the negative polarity, the transmittance (g) does not change. That is, the flicker is not visually recognized in the broken line (s) region.

In the present embodiment, the amplitude of the rectangular voltage (k) is such that the flicker is easily observed, and set to be the voltage V ₅₀ of about half of the maximum transmittance of the liquid crystal panel (100% transmittance) Yes. Note that the voltage is not strictly limited to the voltage V ₅₀ , and the rectangular voltage (sa) may be approximately symmetric when flicker is minimized. However, uniform evaluation is possible by setting the voltage V ₅₀ as described above.

  Next, as shown in FIG. 4B, the waveform voltage generator 8 applies a rectangular voltage (cell) to which a certain offset voltage is applied to the liquid crystal panel 20.

  This rectangular voltage (C) is a voltage in which the positive voltage and the negative voltage are asymmetric (hereinafter referred to as an asymmetric waveform). For this reason, the transmittance (S) is different from the transmittance value corresponding to the positive voltage of the rectangular voltage (C) and the transmittance value corresponding to the negative voltage, and flicker occurs. Represents the state.

  Like this rectangular voltage (C), a rectangular voltage to which a certain offset voltage is added for a certain period in order to generate flicker in the liquid crystal panel is referred to as a stress voltage. Note that the stress voltage is not limited to an AC voltage, and may be a DC (direct current) voltage or 0 V as long as it can generate flicker in the liquid crystal panel and can be arbitrarily set according to measurement.

  When this stress voltage is applied to the liquid crystal panel for a certain period of time, as shown in FIG. 4C, even if a rectangular wave voltage (ta) having an offset voltage of 0, that is, a symmetrical waveform, is applied, ) Flicker may occur. In this way, a state in which flicker is generated even though a symmetrical waveform voltage is applied to the liquid crystal panel is referred to as a state in which the liquid crystal panel is burned.

  Next, as shown in FIG. 4D, the system control device 40 changes the offset voltage for each round of the rectangular voltage (tsu), and changes in accordance with the voltage change of the rectangular voltage (tsu). The transmittance (te) is measured, and the offset voltage when the flicker is minimized is measured. The offset voltage at this time is assumed to be temporary residual DC. That is, when the residual DC is generated in the liquid crystal panel 20, the flicker is minimized when the offset voltage is not 0 as shown by the broken line portion (g). Therefore, the offset voltage when the flicker is minimized is assumed to be temporary residual DC. The system controller 40 calculates the temporary residual DC value.

  Here, “flicker is minimized” means that the difference between the transmittance corresponding to the positive polarity of the rectangular voltage (tsu) and the transmittance corresponding to the negative polarity is minimized.

At this time, when the offset voltage at the time of applying the stress voltage is V _s , the system control device 40 sets the application range of the offset voltage for obtaining the temporary residual DC from V _s to −V _s. Thus, the temporary residual DC can be obtained more reliably.

  As the stress voltage increases, the absolute value of the voltage at which flicker is minimized tends to increase when the stress voltage is applied for the same time. That is, the absolute value of residual DC tends to increase. However, it differs depending on the combination (system) of the liquid crystal of the liquid crystal panel 20 and the alignment film.

  As described above, the offset voltage when the flicker is minimized is the transmittance when the voltage obtained by adding the positive polarity voltage and the offset voltage to the liquid crystal panel 20 in one cycle of the rectangular voltage (T) is applied. ) And the offset voltage when the difference between the transmittance (te) value when the voltage obtained by adding the negative voltage and the offset voltage is applied to the liquid crystal panel 20 is the smallest. It is calculated by obtaining.

  However, since the response of the liquid crystal takes time with respect to the change in the polarity of the rectangular voltage, the signal acquisition unit 31 does not change until the change from the negative polarity to the positive polarity of the rectangular voltage until immediately before the change from the positive polarity to the negative polarity. The acquired transmittance is defined as the positive transmittance. Further, the transmittance acquired by the signal acquisition unit 31 from when the rectangular voltage is changed from the positive polarity to the negative polarity until immediately before the change from the negative polarity to the positive polarity is defined as the negative-polarity transmittance. In the present embodiment, the time immediately before this is set to 0.05 cycle.

  In other words, the positive transmittance is the temporary transmittance included in the first half of one cycle of the rectangular voltage (tsu), and the negative transmittance is the rectangular voltage (tsu). Is a temporary transmittance included in the first half cycle. The term “temporary” refers to a period from 0.4 period to less than 0.5 period after the voltage of the rectangular voltage (tsu) changes. In this embodiment, it is assumed that 0.45 period has elapsed.

  Here, if the potential difference applied to the liquid crystal of the liquid crystal panel 20 differs depending on whether the polarity of the rectangular voltage (tsu) is positive or negative, the liquid crystal responds to some extent even if the response speed of the liquid crystal is slow. Will occur.

  However, in the relationship between the time when the polarity of the rectangular voltage changes and the positive transmittance and the negative transmittance, it is only necessary to find an offset voltage that does not cause flicker, and the liquid crystal mode is VA, Any liquid crystal mode such as TN or IPS may be used. That is, the response speed of the liquid crystal need not be considered much.

  In addition, when the response speed of the liquid crystal is too slow and it is difficult to measure flicker, or when it is difficult to determine the offset voltage that minimizes flicker due to noise, etc., by reducing the frequency of the rectangular voltage (tu), etc. It is possible to respond. In the present embodiment, the frequency of the rectangular voltage is about 30 Hz.

  Further, the difference between the positive transmittance and the negative transmittance is flicker (strength), which is a luminance difference ΔTi.

  Further, when the residual DC of the liquid crystal panel 20 is automatically measured by the residual DC measurement system 1 (see FIG. 2), the offset voltage is changed within a predetermined voltage every cycle of the rectangular wave voltage to cope with the rectangular voltage. Measure brightness or transmittance.

  In the residual DC measurement system 1 according to the present embodiment, it is possible to estimate the residual DC in an accurate and short measurement time as follows.

  This will be described with reference to FIGS.

  5A to 5C show a residual DC measurement method according to the present embodiment, and FIG. 5A shows a rectangular wave voltage in which an offset voltage is changed and transmission through the liquid crystal panel 20 at that time. 5 (b) is a graph for linearly approximating the transmittance of FIG. 5 (a) to obtain residual DC, and FIG. 5 (c) is a graph for FIG. 5 (a). A graph for obtaining a predicted residual DC by linearly approximating the transmittance is shown.

  As shown in FIG. 5A, a rectangular voltage (A) including an offset voltage that is different every predetermined period is applied to the liquid crystal panel 20. The transmittance (A) is the transmittance of the liquid crystal panel 20 acquired by the signal acquisition unit 31 according to the rectangular voltage (A). The maximum value of the transmittance (i) during one offset voltage period of the rectangular voltage (a) is the positive transmittance, and the transmittance (a) during one offset voltage period of the rectangular voltage (a). The minimum value is the transmittance at the time of negative polarity.

  When the system control device 40 obtains the temporary residual DC that is the offset voltage that minimizes flicker, the system control device 40 outputs the obtained temporary residual DC to the offset voltage control unit 35. Then, as shown in FIG. 5A, the offset voltage control unit 35 generates an offset voltage control signal so as to change the offset voltage a plurality of times in a predetermined voltage range in the vicinity of the temporary residual DC (broken line (c)). In addition to being output to the system control device 40, it is also output to the signal acquisition unit 31. The system control device 40 instructs the waveform voltage generation unit 8 to control the offset voltage based on the offset voltage control signal input from the offset voltage control unit 35.

  The signal acquisition unit 31 acquires the positive-polarity transmittance and the negative-polarity transmittance for each offset voltage changed by the offset voltage control unit 35, and outputs it to the storage unit 32. In the present embodiment, the range of the offset voltage that is changed by the system controller 40 is set to ± 50 mV of the temporary residual DC, and is changed eight times from positive to negative so that the offset voltage continuously decreases. The range of the offset voltage that can be changed by the offset voltage control unit 35 will be described later.

  Further, the positive-polarity transmittance acquired by the signal acquisition unit 31 is the transmittance immediately before the rectangular voltage (A) changes from positive polarity to negative polarity (0.05 period in the present embodiment). The negative-polarity transmittance acquired by the signal acquisition unit 31 is the transmittance immediately before the rectangular voltage (A) changes from negative polarity to positive polarity (in this embodiment, 0.05 period).

  In other words, the positive transmittance is the transmittance included in one half cycle of the rectangular voltage (A), and the negative transmittance is one cycle of the rectangular voltage (A). , Is a temporary transmittance included in the remaining half cycle. The timing is preferably the time when 0.45 period elapses after the voltage of the rectangular voltage (a) changes.

  Note that the positive transmittance and the negative transmittance are not limited to the transmittance 0.45 cycles after the change in the polarity of the rectangular voltage as described above. It is preferable that it is 0.4 cycle or more and less than 0.5 cycle after the change. As described above, a certain amount of time is required for the liquid crystal to respond after the polarity of the rectangular voltage is changed. For example, when the polarity of the rectangular voltage changes from about 0.1 period, the liquid crystal is in the middle of response, the occurrence of flicker is reduced, and the influence of noise is increased. On the other hand, it is considered that the response of the liquid crystal is almost completed (in the case of liquid crystal, the transition is progressing to a certain extent) when the polarity of the rectangular voltage changes from 0.4 cycle to less than 0.5 cycle after the change. The influence of noise can be reduced.

  Then, the signal acquisition unit 31 sets data of a combination of the positive transmittance during one offset voltage period of the offset voltage changed by the offset voltage control unit 35 a plurality of times and the offset voltage at that time, and offset voltage control. The number of times the offset voltage control unit 35 has changed the offset voltage indicates the data of the set of the negative-polarity transmittance during one offset voltage period and the offset voltage at that time of the offset voltage changed by the unit 35 a plurality of times. Obtained from the storage unit 32 (8 times in the present embodiment).

  Here, the number of times the offset voltage control unit 35 changes the offset voltage in order to obtain the residual DC is calculated by calculating one approximate straight line from a plurality of positive transmittances, and further calculating from the plurality of negative transmittances. The number of times may be as long as one approximate straight line can be calculated. If the number of times the offset voltage control unit 35 changes the offset voltage is large, the two approximate straight lines can be accurately calculated, and the residual DC can be obtained more accurately. Conversely, if the number of times the offset voltage controller 35 changes the offset voltage is small, the residual DC can be calculated in a shorter measurement time.

  Then, the signal acquisition unit 31 linearly approximates / intersections the data of the set of the positive-polarity transmittance and the offset voltage acquired from the storage unit 32 and the data of the negative-polarity transmittance and the offset voltage. The result is output to the calculation unit 33.

  Then, as shown in FIG. 5 (b), the straight line approximation / intersection calculator 33 calculates the approximate straight line (from the eight positive-polarity transmittance values input from the signal acquisition unit 31 by, for example, the least square method. D) Further, the straight line approximation / intersection calculator 33 obtains an approximate straight line (e) from the eight negative transmittance values input from the signal acquisition unit 31 by, for example, the least square method.

  Further, the straight line approximation / intersection calculator 33 obtains the intersection of the obtained approximate line (d) and the approximate line (e). The offset voltage corresponding to this intersection is an offset voltage when the positive transmittance and the negative transmittance are equal, and this offset voltage is the residual DC.

  The linear approximation / intersection calculator 33 outputs the value of the offset voltage at this intersection to the residual DC output unit 34. Then, the residual DC output unit 34 outputs the value of the intersection input from the linear approximation / intersection calculator 33 to the outside as the residual DC.

  Further, as shown in FIG. 5C, there are cases where the two straight lines do not intersect within the range of ± 50 mV of the temporary residual DC. As described above, when the intersection of two straight lines cannot be obtained within the range of ± 50 mV of the temporary residual DC, the linear approximation / intersection calculator 33 calculates an approximate straight line (f) obtained from a plurality of positive transmittances. And an intersection where the approximate straight line (ki) obtained from the plurality of negative transmittances intersects outside the range of ± 50 mV. The straight line approximation / intersection calculator 33 outputs the intersection as a predicted residual DC to the offset voltage controller 35.

  When the predicted residual DC is input from the linear approximation / intersection calculator 33, the offset voltage control unit 35 again changes the offset voltage within a range of ± 50 mV of the predicted residual DC. Is output to the system controller 40.

  Then, the signal acquisition unit 31 acquires the positive polarity transmittance and the negative polarity transmittance corresponding to the plurality of offset voltages changed again by the offset voltage control unit 35, and outputs them to the storage unit 32. Next, when the signal acquisition unit 31 stores the positive-polarity transmittance and the negative-polarity transmittance corresponding to the number of offset voltages changed by the offset voltage control unit 35, the stored plurality of positive-polarity transmittances are stored. , And a plurality of negative-polarity transmittances are acquired from the storage unit 32 and output to the straight line approximation / intersection calculation unit 33. Then, the straight line approximation / intersection calculator 33 obtains the residual DC by obtaining the two straight line intersections again, and can output the value to the outside.

  As described above, even if the voltage range changed by the offset voltage control unit 35 in the vicinity of the temporary residual DC is narrow, it is possible to automatically search for and measure the optimum offset voltage range.

  As described above, according to the residual DC measurement system 1, it is possible to measure the residual DC in an accurate and short measurement time.

  In the present embodiment, the predetermined voltage range of the offset voltage applied by the system control device 40 in the vicinity of the temporary residual DC has been described as ± 50 mV, but is not limited to ± 50 mV.

  The predetermined voltage range may be ± 100 mV as long as the linear approximation / intersection calculator 33 can calculate an approximate line with a small error from each of the plurality of positive transmittances and negative transmittances. May be.

  In addition, the predetermined voltage range of the offset voltage applied by the system control device 40 in the vicinity of the temporary residual DC depends on the VT characteristic, and in the case of a liquid crystal panel having a high driving voltage, a linear approximation of the VT characteristic can be performed. In the case of a liquid crystal panel in which the voltage width can be widened and the driving voltage is low, the VT characteristics change in a narrow voltage range, and thus the voltage width needs to be narrowed.

  Therefore, when the drive voltage is low, the change voltage of the offset voltage is reduced to increase the number of measurement points, and linear approximation is performed with a narrow voltage width. The experimental results are shown in FIG.

  FIG. 6 shows a graph for determining the residual DC.

  6 represents the offset voltage (mV), and the vertical axis represents the luminance (au).

  The data series (K) and the data series (K) are measurement results of the actual positive transmittance and negative transmittance of the liquid crystal panel 20. For both the positive transmittance and the negative transmittance, the number of measurement points is increased from the positive transmittance and the negative transmittance shown in FIG.

  The data series (g) is a plot of a plurality of sets of offset voltage and positive polarity transmittance, and the data series (K) is a set of offset voltage and negative polarity transmittance. Are plotted.

  The transmittance at the time of positive polarity is the luminance after the elapse of 0.4 cycles after the polarity change of the rectangular voltage, and the transmittance at the time of negative polarity is the luminance after the elapse of 0.9 cycles after the polarity change of the rectangular voltage.

  Then, when the offset voltage is changed within a range of ± 100 mV in the vicinity of the temporary residual DC as the predetermined voltage range, the approximate straight line (co) of the data series (c) and the approximate straight line (sub) of the data series (ke). ).

  In addition, when the offset voltage is changed within a range of ± 200 mV in the vicinity of the temporary residual DC as the predetermined voltage range, an approximate straight line of the data series (K) and an approximate straight line (S) of the data series (K). ).

  As shown in FIG. 6, it can be seen that within the range of ± 100 mV, the approximate straight line (co) and the data series (ku) overlap, and the error is small. Similarly, in the range of ± 100 mV, the approximate line (sa) and the data series (ke) overlap, and it can be seen that the error is small.

  On the other hand, within the range of ± 200 mV, the approximate line (S) and the data series (K) do not overlap, and the error between the approximate line (S) and the data series (K) is large. Similarly, within the range of ± 200 mV, the approximate straight line (su) and the data series (ke) do not overlap, and the error between the approximate straight line (su) and the data series (ke) is large.

  Thus, when the offset voltage is changed within a range of ± 100 mV in the vicinity of the temporary residual DC as the predetermined voltage range, an approximate straight line can be accurately calculated.

  In this embodiment, the least square method is used as the method of linear approximation, but linear approximation may be performed by a method generally used in other cases. For example, when there is little variation in the extreme value of transmittance, approximation by a curve is performed by spline interpolation (a method in which each measurement is connected by a three-dimensional curve, and the slope of an adjacent curve is equalized at each measurement point). It is also possible to ask for it.

(Residual DC measurement flow)
Next, a measurement flow of residual DC measurement will be described with reference to FIG.

  FIG. 7 is a flowchart showing the flow of residual DC measurement.

  When the system control device 40 changes the offset voltage a plurality of times within a predetermined voltage range in the vicinity of the temporary residual DC, in S101, the offset voltage control unit 35 changes the offset voltage a plurality of times within the voltage range including the temporary residual DC. An offset voltage control signal for causing the system control device 40 to output is output to the system control device 40.

  In S102, the signal acquisition unit 31 acquires the positive-time transmittance and the negative-time transmittance for each offset voltage changed by the offset voltage control unit 35 from the electrical signal acquired from the voltage acquisition unit 7, and stores them. To the unit 32. The signal acquisition unit 31 stores the positive-polarity transmittance and the negative-polarity transmittance corresponding to the number of times of the offset voltage changed by the offset voltage control unit 35 in the storage unit 32, and is stored in the storage unit 32. The plurality of positive and negative transmittances are acquired from the storage unit 32 and output to the straight line approximation / intersection calculator 33.

  In S <b> 103, the straight line approximation / intersection calculator 33 calculates an approximate straight line from the plurality of positive transmittance values acquired from the signal acquisition unit 31. Further, the straight line approximation / intersection calculator 33 calculates an approximate straight line from the plurality of negative transmittance values acquired from the signal acquisition unit 31.

  In S104, the straight line approximation / intersection calculator 33 calculates the intersection of the two approximate lines calculated in S103. Then, the straight line approximation / intersection calculator 33 outputs the calculated value of the intersection to the residual DC output unit 34.

  In S105, the residual DC output unit 34 outputs the value of the intersection obtained from the straight line approximation / intersection calculator 33 to the outside as the residual DC.

  In this way, the residual DC measuring device 30 calculates and outputs the residual DC.

[Embodiment 2]
Next, the case of measuring the time change of the residual DC will be described with reference to FIG. In this embodiment, instead of the liquid crystal panel 20, the results of measuring the time variation of residual DC of three different types of test cells, sample A, sample B, and sample C are shown.

  FIG. 8 is a graph showing the time change of the residual DC of Sample A, Sample B, and Sample C.

  The residual DC measurement system 1 that is a residual DC measurement system and the residual DC measurement method are the same as those described in the first embodiment. FIG. 6 is a graph in which the application of the stress voltage, the measurement of the residual DC described in Embodiment 1, and the measurement of the residual DC are repeated for each of Sample A, Sample B, and Sample C, and the time variation of the residual DC is plotted. The measurement interval can be arbitrarily set.

  The tendency of the time change of the residual DC varies depending on the combination of the liquid crystal material, the alignment film material, and the like. As shown in FIG. 8, sample A always has a higher residual DC value than sample C. If it is such a relationship, it turns out that the necessity of measuring the time change of the residual DC of sample A and sample C is low.

  On the other hand, as in sample B and sample C, the residual DC has a similar value until a certain elapsed time, and sample B has a larger residual DC value from the third measurement to the sixth measurement. However, in the seventh measurement, the value of the residual DC is again approximately the same between sample B and sample C. This is because the rate of increase in the residual DC is faster in the sample B than in the sample C. However, in the sample B, after the residual DC increases to some extent, the value of the residual DC becomes substantially constant. Thus, it can be seen that the sample B is saturated after the residual DC increases to some extent. On the other hand, sample C has a slower increase in residual DC than sample B, but sample C continues to increase in residual DC. For this reason, eventually, the sample C is more seized.

Thus, by measuring the time variation of the residual DC, it becomes possible to specify a combination of a liquid crystal material, an alignment film material, and the like that will ultimately cause large image sticking.
[Embodiment 3]
Next, the case of measuring the relaxation process of residual DC will be described with reference to FIG. In the present embodiment, the results of measurement of the relaxation process of residual DC of sample D, sample E, and sample F, which are different test cells from the second embodiment, are shown.

  FIG. 9 is a graph showing the relaxation process of residual DC of Sample D, Sample E, and Sample F. The residual DC measurement system 1 that is a residual DC measurement system and the residual DC measurement method are the same as those described in the first embodiment.

  First, as in Embodiment 1, after applying a stress voltage to each of Sample D, Sample E, and Sample F, the residual DC is measured. Thereafter, the system control device 40 applies a driving voltage of 0 V to each of the sample D, the sample E, and the sample F. Then, the residual DC measurement device 30 measures the residual DC. Thus, FIG. 9 is a graph in which a driving voltage of 0 V is applied to each of Sample D, Sample E, and Sample F, each residual DC measurement is repeated a plurality of times, and the measurement results of the residual DC are plotted. . The measurement interval can be arbitrarily set.

  As shown in FIG. 9, the initial residual DC of sample D, sample E, and sample F is approximately the same.

  However, the relaxation rate of the residual DC of sample E is the fastest, and the residual DC is almost zero at the time of the fourth measurement. Sample F has the fastest residual DC relaxation rate after sample E, and the residual DC is almost zero at the sixth measurement. Sample D has the slowest relaxation rate, and the residual DC does not become zero after six measurements.

  How long the seizure caused by the residual DC disappears has a strong correlation with the relaxation rate of the residual DC. And when the relaxation rate of residual DC is slow, seizure will remain for a long time. Therefore, there is a need to measure the relaxation process of the residual DC once generated.

  As described above, by measuring the relaxation rate of the residual DC of sample D, sample E, and sample F, it can be seen that sample D remains seized for the longest time.

[Embodiment 4]
Next, a system and a measurement method for measuring residual DC and seizure in parallel at a plurality of locations in the residual DC measurement system 1 with reference to the configuration of the residual DC measurement system 1 in FIGS. 11 will be described.

  FIG. 11 is an explanatory diagram showing the flow of measurement in the multipoint measurement system in the present embodiment.

  Usually, seizure needs to be observed for several tens of minutes to several hours or more, and residual DC needs to be measured over the same time.

  On the other hand, a reliability test such as seizure requires a reproduction experiment and often measures a large number of samples. Since the conventional residual DC measuring device can measure only one point at a time, enormous time is required or a plurality of the same devices must be required.

  In the multipoint measurement system of the present embodiment, parallel processing is possible, and a single measurement system can measure four points. The method for measuring residual DC is basically the same as in the first to third embodiments.

  First, four liquid crystal cells are set on the XY stage 10. Each liquid crystal cell is connected to an independently controlled waveform generator. The measurement points of each liquid crystal cell are set as measurement points S1, S2, S3, and S4.

  First, a drive voltage of 0 V is applied to all measurement points S1 to S4. Then, the optical axis is aligned with the measurement point S1, and the residual DC at the measurement point S1 is measured in the same manner as in the first embodiment.

  That is, in S11, a stress voltage is applied to the measurement point S1. In S12, the residual DC at the measurement point S1 is measured. At this time, a stress voltage is applied to the measurement point S2 in S21.

  Then, after the residual DC measurement at the measurement point S1, the XY stage 10 is moved at S22 to align the optical axis with the measurement point S2. Then, the measurement of the residual DC at the measurement point S2 is started, and a stress voltage is applied to the measurement point S1 in S13. At this time, a stress voltage is applied to the measurement point S3 in S31.

  Next, after the residual DC measurement at the measurement point S2, the XY stage 10 is moved in S32, and the optical axis is aligned with the measurement point S3. Then, the measurement of the residual DC at the measurement point S3 is started, and a stress voltage is applied to the measurement point S2 in S23. At this time, a stress voltage is applied to the measurement point S4 in S41.

  Then, after the residual DC measurement at the measurement point S3, the XY stage 10 is moved at S42 to align the optical axis with the measurement point S4. Then, the measurement of the residual DC at the measurement point S4 is started, and a stress voltage is applied to the measurement point S3 in S33.

  Next, after measuring the residual DC at the measurement point S4, a stress voltage is applied to the measurement point S4 in S43, and the process waits until a predetermined time elapses. Then, after a predetermined time has elapsed, the XY stage 10 is moved in S14, and the optical axis is aligned with the measurement point S1. Then, the measurement of the residual DC at the measurement point S1 is started.

  Then, these steps are repeated. After repeating a predetermined number of times, instead of the stress voltage, a driving voltage 0 V is applied to each of the measurement points S1 to S4, and the relaxation process of the residual DC is measured in parallel. The method for measuring the relaxation process of residual DC at each of the measurement points S1 to S4 is as described in the third embodiment.

  Note that it is not necessary to use all four measurement points S1 to S4, and the design may be changed so that parallel measurement exceeding four points can be performed. When there are many measurement points, it is more practical not to prepare a waveform generator for each measurement point, but to install a waveform generator that generates a measurement waveform and a stress waveform and switch signals using a relay.

  Since each of the measurement points S1 to S4 can independently measure the residual DC, each of the measurement points S1 to S4 can independently analyze the temporal change and absolute value of the residual DC. When performing multipoint measurement of one sample, it is possible to measure the distribution of residual DC in the panel, for example, near the inlet, near the sealing material, and in the center.

[Embodiment 5]
Next, a measurement method for directly measuring the image sticking of the liquid crystal panel 20 as a test cell will be described with reference to FIG.

  FIG. 12 is a flowchart showing a measurement flow for image sticking according to the present embodiment.

  The measurement apparatus for performing the seizure measurement is the same as the residual DC measurement system described in the first to fourth embodiments.

  First, the VT characteristic of the residual DC measurement system 1 is measured in advance. The measurement of the VT characteristic is the same as the method described in the first embodiment.

  In S201, as described in the first embodiment, reference measurement is performed to determine transmittances of 0% and 100%. As described above, when measuring the transmittance of 100%, the polarizing plates 4a and 4b are kept in a crossed Nicols state, or the XY stage 10 is attached to the polarizing plates 4a and 4b and separated from the optical axis. Alternatively, the polarizing plates 4 a and 4 b are attached to the liquid crystal panel 20 from the beginning, and are not attached to the residual DC measurement system 1.

Next, in S202, the VT characteristic is measured for each measurement point of the liquid crystal panel 20 set in advance. In step S <b> 202, the reference measurement unit 44 calculates a gradation-voltage characteristic and outputs the calculated gradation-voltage characteristic to the system control device 40. The system control device 40 obtains a voltage V ₅₀ that is half of the maximum transmittance (transmittance 100%) from the gradation-voltage characteristics input from the reference measurement unit 44, and measures the transmittance T ₅₀ . In this case, the transmittance T ₅₀ is referred to as an initial transmittance (transmittance T0) measured without applying a stress voltage. Then, the system control device 40 determines the gradation voltage setting for the burn-in measurement of the liquid crystal panel 20 and the amplitude of the rectangular voltage during the residual DC measurement.

  Then, the system control device 40 does not apply the stress voltage to the liquid crystal panel 20, and measures the initial residual DC of the liquid crystal panel 20 according to the step shown in S100. Thereby, it is confirmed that the residual DC before applying the stress voltage to the liquid crystal panel 20, that is, the initial residual DC is zero. Here, when the initial residual DC is not 0 ± 10 mV, it is assumed that the liquid crystal panel 20 may be burned from the beginning, and a warning is issued from the program to make it possible to select whether to execute or stop the measurement.

  Next, in S <b> 204, the system control device 40 outputs an instruction signal for applying a stress voltage to the liquid crystal panel 20 for a certain period of time to the waveform voltage generator 8. Then, the waveform voltage generator 8 applies a stress voltage to the liquid crystal panel 20 for a certain period of time. Then, as shown in S100, the residual DC of the liquid crystal panel 20 is measured. It should be noted that programming can be selected so that only residual DC or transmittance measurement can be selected.

  Next, as described in the fourth embodiment, other measurement points are measured and parallel processing is performed. That is, in S205, the XY stage 10 is moved to another measurement point and the optical axis is aligned. Then, reference measurement is performed.

In S206, the reference measurement unit 44 outputs an instruction to measure the transmittance of the selected level _{(V 50)} and (transmittance _{T 50)} to the system controller 40. Then, the system control device 40 outputs an instruction to output the rectangular voltage of the selected gradation to the waveform voltage generator 8. When the waveform voltage generator 8 obtains an instruction to output the rectangular voltage of the selected gradation output from the system control device 40, the waveform voltage generator 8 outputs the rectangular voltage of the selected gradation to the liquid crystal panel 20. Then, the signal acquisition unit 31 acquires a transmittance T ₅₀ that is a transmittance when the V _{50 is} applied to the liquid crystal panel 20 and outputs it to the reference measurement unit 44. Thus, the reference measuring unit 44 _associates the transmission _{T 50} and _{V 50.}

  Then, S204, S100, S205, and S206 described above are repeated.

  In the residual DC measurement system 1, the application time of the stress voltage and the number of times of measurement of the residual DC can be arbitrarily set on the program.

  Then, after repeating S204, S100, S205, and S206 an arbitrary number of times, the relaxation process of residual DC is measured as described in the third embodiment.

  That is, an arbitrary stress condition is applied to the liquid crystal panel 20 in S207. The arbitrary stress conditions include applying a stress voltage which is a rectangular voltage to which no offset voltage is applied, or short-circuiting the electrodes connected to the liquid crystal panel 20. Then, after a predetermined time has elapsed, the processes of S100, S205, and S206 are performed. That is, the residual DC measurement and the transmittance measurement are repeated.

  In this way, residual DC measurement and residual DC relaxation process can be measured.

Moreover, the image sticking rate can also be measured by the steps described above. Here, the seizure rate is represented by T ′ / T _0, where T ′ is the initial transmittance T _{0 at} a predetermined voltage, and T ′ is the transmittance at the same voltage after stress application.

The seizure measuring device 45 acquires the transmittance T ₀ and the transmittance T ₅₀ from the reference measurement unit 44. Then, the seizure measuring device 45 calculates T ′ / T ₀ and outputs it as a seizure rate. Note that it is desirable to confirm the reproducibility of the data by simultaneously measuring the burn-in rate of a pixel having an applied voltage of 0 V with no stress voltage.

When T ′ / T ₀ ≠ 1, the liquid crystal panel 20 is seized. In this case, if the residual DC = 0V, it is understood that the seizure is caused by other than the residual DC. When the residual DC is not 0 V, there is a possibility that the cause of seizure overlaps with the residual DC and other factors. Therefore, an offset voltage at which the flicker is minimized is applied, and the transmittance T ′ of the gradation for measuring the burn-in rate (transmittance T ₅₀ in this embodiment) is measured again. If T ′ / T ₀ = 1, seizure is only due to residual DC, but if T ′ / T ₀ ≠ 1, it can be determined that there are other factors than residual DC.

  In this way, after performing the reference measurement, the transmittance of the gradation for which the image sticking is to be measured is measured, and the image is divided by the initial transmittance to obtain the image sticking rate.

  As described above, stress is applied to the liquid crystal panel 20 by applying a stress voltage, and thereafter, the operation of measuring the residual DC or the image sticking rate of the liquid crystal panel 20 is repeatedly performed for a certain time. A comprehensive evaluation can be made.

  Note that options are provided in the measurement program stored in the system control device 40 so that only the residual DC or only the burn-in rate can be measured as necessary.

  It is also possible to measure the relaxation of residual DC and seizure rate by short-circuiting the upper and lower electrodes connected to the liquid crystal panel 20 after the liquid crystal panel 20 has been baked over a certain period of time, thereby eliminating the addition. is there.

〔Example〕
Next, an example of measuring the burn-in rate of a TFT panel used for a television or the like as the liquid crystal panel 20 will be described.

  The residual DC measurement system 1 was used as the measurement device. The measuring method is as described in the embodiment. The measurement apparatus used a multimeter as the voltage acquisition unit 7 of the residual DC measurement system 1. The residual DC measurement system 1 has a system that takes in the output from the multimeter by a calculation / control unit 9 composed of a PC. The XY stage 10 has a mechanism for placing and fixing one or more liquid crystal panels 20.

  A liquid crystal panel 20 having TFTs is placed on the XY stage 10. Then, the image sticking rate is measured according to the flow shown in FIG.

  FIG. 13 is a flowchart illustrating an example of the seizure rate measurement according to the present embodiment.

First, reference measurement is performed to calculate VT characteristics and gradation-voltage characteristics (see S201 to S203). Next, in S301, by an instruction from the system controller 40, the voltage _{V 50} is applied to the liquid crystal panel 20, was displayed halftone. Then, the transmittance of the liquid crystal panel 20 was continuously measured while moving the XY stage 10 in one direction at a predetermined speed.

  Then, as in S204, a stress voltage was applied to the liquid crystal panel 20.

  FIG. 14 is a schematic diagram showing the state of the stress voltage applied to the liquid crystal panel 20.

  As shown in FIG. 14, a video signal in which a white display pattern and a black display pattern have a checkered pattern is applied to the liquid crystal panel 20 as a stress voltage.

Next, in S302, the voltage _{V 50} is applied to the liquid crystal panel 20 again, it was displayed halftone. And the transmittance | permeability of the same location as the location which measured the transmittance | permeability before applying the stress voltage to the liquid crystal panel 20 was measured, moving the XY stage 10 to predetermined direction. Thereafter, S207 and S302 were repeated an arbitrary number of times.

  FIG. 15A is a schematic diagram showing a display state of the liquid crystal panel 20 displayed in halftone after applying a checkered stress voltage, and FIG. 15B shows the display state of FIG. It is a graph showing the measurement result of the transmittance | permeability of the measurement direction shown to).

  As shown in FIGS. 15 (a) and 15 (b), after applying a checkered stress voltage to the liquid crystal panel 20, even if halftone display is performed by applying the same voltage to the entire surface, a dark gray region, A light gray area is displayed in a checkered pattern. That is, in the liquid crystal panel 20, the area where white is displayed as shown in FIG. 14 is displayed in light gray, and the area where black is displayed is displayed in dark gray.

Then, the burn-in measurement device 45 obtains the transmittance (luminance) T _{0 of the} region displayed in the dark gray and the transmittance (luminance) T ′ of the region displayed in the light gray from the signal acquisition unit 31. Obtained, and the ratio (T ′ / T ₀ ) was calculated as a seizure rate.

  If the liquid crystal panel 20 has in-plane luminance unevenness, a plurality of luminance ratios are calculated near the boundary between the region displaying white and the region displaying black, and the maximum value, minimum value, and average are calculated. Ask. About the measurement location, it set from the measurement program created so that the measurement location could be arbitrarily set memorize | stored in the system control apparatus 40 beforehand. Further, for the halftone, the gradation for which the burn-in rate is to be measured can be selected by the measurement program as necessary.

  In addition, a microscope optical system was used as the optical unit 2 of the residual DC measurement system 1. As a result, when the liquid crystal panel 20 is in the MVA mode, the residual DC and seizure rate in a minute region such as the gap between the rib and the slit, the slit, and the rib can be measured.

  As described above, according to the present invention, residual DC of a plurality of liquid crystal panels or a plurality of liquid crystal panels can be accurately measured simultaneously, and a reference measurement of black luminance and white luminance can be performed immediately before the measurement. It is possible to directly measure the seizure rate of the test cell in the form of transmittance. Furthermore, since it is possible to measure the image sticking rate and the residual DC every arbitrary time, it is possible to measure the time change of the image sticking rate and the residual DC. In addition, since the seizure rate and the residual DC can be measured simultaneously, the cause of seizure can be divided into a residual DC and a non-residual DC.

  As a result, the liquid crystal cell can be developed efficiently.

(Program, computer-readable recording medium)
In addition, each block of the residual DC measuring device described in the first to fifth embodiments and the examples, in particular, the linear approximation / intersection calculator 33 may be configured by hardware logic, or a CPU is used as follows. It may be realized by software.

  That is, the straight line approximation / intersection calculator 33 has a central processing unit (CPU) that executes instructions of a control program that realizes each function, a read only memory (ROM) that stores the program, and a RAM (random) that expands the program. access memory), a storage device (recording medium) such as a memory for storing the program and various data. The object of the present invention is to record the program code (execution format program, intermediate code program, source program) of the control program of the linear approximation / intersection calculator 33, which is software that realizes the above-described functions, in a computer-readable manner. This can also be achieved by supplying the recording medium to the linear approximation / intersection calculator 33 and reading out and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  Alternatively, the straight line approximation / intersection calculator 33 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Also, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  Further, the present invention can also be expressed as a residual DC measuring device, a residual DC measuring system, a residual DC measuring method, a residual DC measuring device control program, and a computer-readable recording medium according to the present invention.

  (1) A residual DC measurement method using a flicker elimination method, in which the offset voltage applied to a rectangular wave is monotonously increased or decreased for each cycle to obtain an offset voltage that minimizes flicker, and in the vicinity of the minimum offset voltage The relationship between transmittance and offset voltage when the polarity of the square wave is positive in the range of ± 100 mV, and the relationship between transmittance and offset voltage when the polarity of the square wave is negative. A residual DC measurement method and a residual DC measurement program.

  (2) The transmittance for linearly approximating the relationship with the offset voltage is the transmittance at 0.4T or more and less than 0.5T after voltage change every half cycle of the rectangular wave. Residual DC measurement program.

(3) If the approximate line does not intersect within the offset voltage change, the intersection of the extension line of the approximate line is set as the predicted residual DC, and the residual voltage is measured by changing the offset voltage again in the vicinity (1) or (2) Residual DC measurement method and residual DC measurement program (4) Residual DC measurement program and residual DC measurement capable of repeating arbitrary time stress application and residual DC measurement any number of times in (1) to (3) Method.

  (5) An optical system comprising a light source, two polarizing elements having a rotation mechanism, an XY stage between the two polarizing elements, and a light receiving unit, and this optical system is arranged in a thermostatic chamber capable of shielding external light A system that converts the signal of the light receiving unit into a voltage and takes it into a personal computer, has an arbitrary waveform generator, a mechanism capable of fixing one or more cells to the XY stage, and the cells A seizure evaluation apparatus provided with a terminal to which a voltage can be applied from an arbitrary waveform generator.

  (6) A residual DC measurement method using the seizure evaluation apparatus according to (5), wherein stress application and residual DC measurement are measured while moving the XY stage for each measurement point designated in advance.

  (7) The method for measuring residual DC in (6), in which stress application and residual DC measurement are repeated.

  (8) First, after measuring the transmittance reference, measure the voltage-transmittance characteristics to calculate the gradation-voltage characteristics, and specify the post-stress application and the transmittance of any gradation in advance. A burn-in measurement method using the burn-in evaluation apparatus (5) that measures while moving the XY stage for each measurement point.

  (9) The burn-in measurement method according to (8), in which stress application and burn-in measurement are repeated.

  (10) The residual DC measurement method according to (8) or (9), wherein a ratio (T / T0) between the transmittance T after application of stress and the initial transmittance T0 is a seizure rate.

  (11) A seizure measurement method using the seizure evaluation apparatus according to (5), in which stress application, residual DC measurement, and transmittance measurement are repeated.

  (12) In (10) and (11), the transmittance T ′ is measured while applying the residual DC voltage as an offset voltage, T ′ / T0 is obtained, and when T ′ / T0 = 1, the cause of seizure Is a seizure evaluation method for determining whether there is a cause of seizure other than the residual DC.

  (13) The burn-in evaluation apparatus according to (5), wherein the optical system is a microscope.

  The residual DC of the liquid crystal panel can be optically measured for quality evaluation, and can be applied to a liquid crystal panel for measuring residual DC or image sticking.

It is a block diagram showing the structure of the residual DC measuring apparatus of this invention. It is a block diagram showing the principal part structure of the residual DC measurement system of this invention. (A) is a top view showing the structure of the XY stage of the residual DC measuring system of this invention, (b) is a side view of (a). (A) is a graph showing the relationship between the rectangular voltage with the offset voltage changed and the transmittance, and (b) is a graph showing the relationship between the rectangular voltage and the transmittance when the stress voltage is applied, (C) is a graph showing the relationship between the rectangular voltage representing the state where the liquid crystal panel is burned and the transmittance, and (d) is a graph showing the relationship between the rectangular voltage and the transmittance at the time of temporary residual DC measurement. It is. (A) is a graph showing the relationship between the rectangular voltage in which the offset voltage is changed and the transmittance, and (b) is a plurality of approximate straight lines of positive transmittance shown in (a) and a plurality of negative electrodes. It is a graph for calculating | requiring residual DC from the approximate straight line of the transmissivity at the time of sex, (c) is the approximate line of the transmissivity at the time of several positive polarity shown in (a), and the approximate of the transmissivity at the time of negative polarity. It is a graph for calculating | requiring predicted residual DC from a straight line. It is a graph showing the residual DC measuring method of this invention, and showing the experimental result for calculating | requiring residual DC from the some approximate line of the transmittance | permeability at the time of positive polarity, and the some approximate line of the transmittance | permeability at the time of negative polarity. It is a flowchart showing the flow of the residual DC measuring method of this invention. It is a graph showing the time change of residual DC measured by the residual DC measuring method of this invention. It is a graph showing the relaxation process of residual DC by the residual DC measuring method of this invention. It is a graph showing an example of the VT characteristic of the liquid crystal panel which concerns on embodiment of this invention. It is explanatory drawing showing the flow of the measurement in the multipoint measuring system of this invention. It is a flowchart showing the measurement flow of image sticking of the present invention. It is a flowchart which shows an example of the image sticking rate measurement of this invention. It is the schematic which shows an example of the stress voltage applied to the liquid crystal panel which concerns on this Embodiment of this invention. (A) is the schematic showing the state of the burning of the liquid crystal panel which concerns on embodiment of this invention, (b) is a graph showing the measurement result of the transmittance | permeability of (a).

Explanation of symbols

1 Residual DC measurement system 2 Optical part (optical means)
3 Light source 4a, 4b Polarizing plate 5 Light receiving part 6 Constant temperature layer 7 Voltage acquisition part (voltage acquisition means)
8 Waveform voltage generator (waveform voltage generator)
9 Calculation / control section (calculation / control means)
DESCRIPTION OF SYMBOLS 10 XY stage 11 Transmission part 12 Voltage application terminal 13 Fixing mechanism 20 Liquid crystal panel (optical panel)
30 Residual DC measuring device 31 Signal acquisition unit (data acquisition means)
32 storage unit 33 straight line approximation / intersection calculation unit (calculation means)
34 Residual DC output unit 35 Offset voltage control unit (offset voltage control means)
40 System Controller 44 Reference Measurement Unit 45 Seizure Measuring Device a Light-shielding area

Claims (14)

A residual DC measuring device that measures residual DC generated in a liquid crystal panel using a transmittance of light transmitted through the liquid crystal panel, which is detected while driving by applying an amplitude voltage to the liquid crystal panel,
A different offset voltage is added to the amplitude voltage every predetermined period,
Among the detected transmittances, a plurality of sets of data including a maximum amplitude transmittance which is a transmittance when the amplitude voltage reaches a maximum amplitude during one offset voltage period and an offset voltage at that time With getting
Among the detected transmittances, a plurality of sets of data of a set of the minimum amplitude transmittance that is the transmittance when the amplitude voltage becomes the minimum amplitude during one offset voltage period and the offset voltage at that time Data acquisition means for acquiring;
From the plurality of sets of data of the maximum amplitude transmittance and the offset voltage acquired by the data acquisition means, an approximate straight line indicating the relationship between the maximum amplitude transmittance and the offset voltage is obtained,
From the plurality of sets of data of the minimum amplitude transmittance and the offset voltage acquired by the data acquisition means, an approximate straight line indicating the relationship between the minimum amplitude transmittance and the offset voltage is obtained, and
A residual DC measuring device comprising: an operation means for obtaining an offset voltage corresponding to an intersection of the two approximate lines. An offset voltage that minimizes the difference between the maximum amplitude transmittance and the minimum amplitude transmittance is acquired as a temporary residual DC, and the offset voltage is within a predetermined voltage range including the acquired temporary residual DC. An offset voltage control means for outputting a signal for changing,
The data acquisition means acquires a plurality of sets of data of the maximum amplitude transmittance and the offset voltage at that time within a predetermined voltage range including the temporary residual DC, and the minimum amplitude transmittance, The residual DC measuring device according to claim 1, wherein a plurality of sets of data with an offset voltage of a plurality of sets are acquired.   3. The residual DC measuring apparatus according to claim 2, wherein a range of the predetermined voltage width of the offset voltage changed by the offset voltage control means is ± 100 mV of the temporary residual DC. The maximum amplitude transmittance is determined by the data acquisition means during a predetermined time from when the amplitude voltage changes from negative polarity to positive polarity until immediately before it changes from positive polarity to negative polarity during one offset voltage period. The transmittance to obtain,
The transmittance at the time of the minimum amplitude is the transmittance acquired by the data acquisition unit during a predetermined time from when the polarity changes from the positive polarity to the negative polarity during one offset voltage period to immediately before the change from the negative polarity to the positive polarity. The residual DC measuring device according to any one of claims 1 to 3, wherein   The residual DC measuring apparatus according to claim 4, wherein the predetermined time is from 0.4 cycles to less than 0.5 cycles after the amplitude voltage. When the offset voltage corresponding to the intersection of the obtained two approximate lines is outside the range of the predetermined voltage width, the calculation means outputs the obtained offset voltage as a predicted residual DC to the offset voltage control means. And
When the predicted residual DC is acquired from the computing means, the offset voltage control means outputs an instruction for changing the offset voltage within a predetermined voltage width including the acquired temporary residual DC,
The data acquisition means acquires a plurality of sets of data of the maximum amplitude transmittance within a predetermined voltage range including the predicted residual DC and the offset voltage at that time, and the minimum amplitude transmittance, The residual DC measuring device according to claim 2, wherein a plurality of sets of data with the offset voltage is acquired. Calculation / control means including residual DC measurement device according to any one of claims 1 to 6, and system control means for outputting an instruction signal for controlling an amplitude voltage applied to the liquid crystal panel;
An XY stage capable of mounting a plurality of liquid crystal panels on a light source, a transmission region that transmits light from the light sources, and capable of moving the mounted liquid crystal panels in a direction perpendicular to the direction of light emission from the light sources; Optical means including light receiving means for receiving light from the light source transmitted through the XY stage and the liquid crystal panel and outputting a voltage;
Voltage acquisition means for outputting the voltage output from the light receiving means to the calculation / control means as an electrical signal;
A residual DC measurement system comprising: an instruction signal for controlling a driving voltage applied to the liquid crystal panel from the system control means; and a waveform voltage generating means for applying an amplitude voltage to the liquid crystal panel. . The calculation / control means includes a stress voltage instruction means for outputting a stress voltage instruction signal for instructing the liquid crystal panel to apply a stress voltage that is a load voltage to the waveform voltage generation means,
The calculation / control unit includes a burn-in measurement unit that acquires an electric signal indicating the transmittance before and after the stress voltage is applied from the voltage acquisition unit, and measures the burn-in of the liquid crystal panel from the acquired electric signal. The residual DC measurement system according to claim 6, further comprising:   The burn-in measurement means calculates the burn-in rate from a ratio between the transmittance of the liquid crystal panel before the stress voltage is applied and the transmittance of the liquid crystal panel after the stress voltage is applied. Item 9. The residual DC measurement system according to Item 8.   9. The residual DC measurement system according to claim 8, wherein the application of the stress voltage and the measurement of the residual DC are repeated a plurality of times.   The residual DC measurement system according to claim 8 or 9, wherein the application of the stress voltage and the measurement of seizure are repeated a plurality of times. A residual DC measurement method for measuring residual DC generated in a liquid crystal panel using a transmittance of light transmitted through the liquid crystal panel, which is detected while driving by applying an amplitude voltage to the liquid crystal panel,
A different offset voltage is added to the amplitude voltage every predetermined period,
Among the detected transmittances, a plurality of sets of data including a maximum amplitude transmittance which is a transmittance when the amplitude voltage reaches a maximum amplitude during one offset voltage period and an offset voltage at that time With getting
Among the detected transmittances, a plurality of sets of data of a set of the minimum amplitude transmittance that is the transmittance when the amplitude voltage becomes the minimum amplitude during one offset voltage period and the offset voltage at that time A data acquisition step to acquire;
From the plurality of sets of data of the maximum amplitude transmittance and the offset voltage acquired in the data acquisition step, an approximate straight line indicating the relationship between the maximum amplitude transmittance and the offset voltage is obtained,
From a plurality of sets of data of the minimum amplitude transmittance and the offset voltage acquired in the data acquisition step, an approximate straight line indicating the relationship between the minimum amplitude transmittance and the offset voltage is obtained,
And a calculation step of obtaining an offset voltage corresponding to the intersection of the two approximate lines.   A residual DC measurement device control program for operating the residual DC measurement device according to any one of claims 1 to 6, wherein the residual DC measurement device control program causes a computer to function as each of the means. .   A computer-readable recording medium on which the residual DC measuring device control program according to claim 13 is recorded.