JP2006133379A - Measuring method and measuring device in display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple means for measuring an absolute value of a residual DC accumulated on a display element and a time constant in the display element composed of a multilayer dielectric. <P>SOLUTION: The absolute value of the residual DC accumulated on a display layer and the time constant thereof are measured by applying a periodical measuring voltage to the display element composed of the multilayer dielectric before and after residual DC accumulation respectively and measuring a phase change of a peak of a current caused by ions in the display layer brought about in response to the periodical measuring voltage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for measuring residual DC accumulated in a display layer in a display device composed of a multilayer dielectric including at least a display layer.

  Examples of display elements made of a multilayer dielectric include liquid crystal elements and electrophoretic display elements. A typical structure of the liquid crystal element includes an alignment film layer, a liquid crystal layer, and an alignment film layer. On the other hand, the structure of a typical electrophoretic display element includes an insulating layer, an electrophoretic layer, and an insulating layer. In the present specification, a layer directly related to display such as a liquid crystal layer in a liquid crystal element or an electrophoretic layer in an electrophoretic display element is hereinafter referred to as a display layer, and an alignment film layer in the liquid crystal element or an insulating film in the electrophoretic display element. The layer will be referred to as a membrane layer.

  Due to the difference in the time constant of each of these layers, the display voltage of each layer varies even during the period when the same voltage is applied to the display element from the outside. I will do it. Typically, since the time constant of the film layer is large and the time constant of the display layer is small, the voltage is mainly divided into the display layer immediately after voltage application, and is divided into the film layer over time. Become so. This amount of change in voltage in the display layer is called residual DC. Residual DC subsequently affects the effective voltage that is divided into the display layer even when the voltage is stopped or when a voltage of a different value is applied. Cause.

  Thus, since the residual DC deteriorates the display characteristics of the display element, there is a need for a method for accurately measuring the residual DC in order to improve the display characteristics.

  Conventionally, as a method for measuring residual DC, the flicker elimination method (Sasaki, Tsumura, Nagae, Suzuki, Iwata: Shingaku Technical Bulletin EID93-128 (1994), p. 25) and the dielectric absorption method (Manabe, Inoue, Nakano Wataru: No. 1) 22th Liquid Crystal Discussion Group Proceedings 3C11 (1996), p. 365) has been proposed.

  In the flicker erasing method, generally, stress (temperature, heat) is applied to a liquid crystal panel, a symmetric AC signal is applied thereafter, a bias voltage is applied so as to eliminate the generated flicker, and the value of the bias voltage is applied. Is a residual DC amount.

  On the other hand, in the dielectric absorption method, a DC voltage is applied to the display element for a certain period of time, then a short discharge occurs (the applied voltage to the display element is 0 V), and then the voltage between both electrodes of the display element is measured to determine the residual DC voltage. It is a means of measuring.

As another conventional example, as a method of measuring the residual charge in a vertical electric field type liquid crystal display element, a flicker erasing voltage immediately after superimposing a DC voltage of 3 V on a rectangular wave of 30 Hz and 2 V for 1 hour, and after 30 minutes A liquid crystal display element (see, for example, Patent Document 1) in which the flicker erasing voltage is measured and the absolute value of this value is the residual charge can be given.
JP 2004-86184 A

  However, since the flicker elimination method is difficult to automate the measurement, the measurement result may differ depending on the measurer.

  On the other hand, the dielectric absorption method observes the voltage and current including not only the display layer but also the insulating film, etc., and it means that the voltage applied to the display layer is directly measured. In other words, accurate residual DC may not be measured.

The present invention has been made to solve the above problems,
In a display element composed of a multilayer dielectric including at least a display layer and having two or more electrodes, the absolute value and time of the residual DC accumulated in the display layer of the display element when a working voltage including a direct current component is applied A method for measuring a display element, characterized in that the constant is measured by measuring a change in phase of a current peak derived from ions in the display layer that appears in response to a periodic measurement voltage.

Also,
The method for measuring a display element is characterized in that the periodic measurement voltage is applied after the residual DC is accumulated and before it is substantially accumulated.

Also,
The display element measuring method according to claim 1, wherein the periodic measurement voltage applied before the residual DC is substantially accumulated is a periodic measurement voltage in which an offset voltage is superimposed.

Or
A method for measuring a display element, wherein after the residual DC is accumulated, the periodic measurement voltage is applied to estimate a relative increase / decrease in the residual DC.

Also,
A display element measuring method, wherein the display element is composed of a multilayer dielectric including at least a display layer and has two or more electrodes, and is an electrophoretic display device.

Also,
It is a measuring device of a display element using the measuring method.

  As described above, by using the measuring method and measuring apparatus disclosed in the present invention, it is possible to measure the residual DC accumulated in the display layer in the display element made of a multilayer dielectric.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings with respect to the measuring method and measuring apparatus of the present invention.

  FIG. 1 is a block diagram showing an outline of a measuring apparatus. In FIG. 1, a voltage waveform generated from an arbitrary waveform generator 12 is amplified by a power amplifier 13 according to a command from an information processing apparatus 11 such as a personal computer, and the amplified voltage is applied to a display element 14 to be measured. At the same time, the amplified voltage is monitored by the oscilloscope 15. The current flowing through the display element 14 during voltage application is amplified using the current amplifier 16 and converted into voltage, and the voltage waveform is observed by the oscilloscope 15. The voltage value data with respect to time is temporarily stored in the oscilloscope 15 and then stored in the storage device 17 attached to the information processing device 11 through the information processing device 11. The operations of the arbitrary waveform generator 12 and the oscilloscope 15 are controlled by the information processing device 11. A processing program executed by the information processing apparatus 11 is stored in the storage device 17.

  Next, the measurement procedure will be described with reference to the block diagram shown in FIG. 1 and the flowcharts shown in FIGS.

  The measurement method for measuring the residual DC accumulated in the display layer of the display element according to the present invention is sequentially performed according to the first step in FIG. 2, the second step in FIG. 3, and the third step in FIG.

  First, the first step will be described. The first step is to apply a periodic measurement voltage to the display element 14 in a state where substantially no residual DC is accumulated in the display element 14, and to display the response in response to the periodic measurement voltage. In this step, the phase of the current peak derived from the ions in the layer is used as the reference phase. First, in step S <b> 21 of FIG. 2, the periodic measurement voltage generated from the arbitrary waveform generator 12 is amplified by the power amplifier 13, and the amplified periodic measurement voltage is applied to the display element 14. In step S22, the current flowing through the display element 14 during voltage application is amplified using the current amplifier 16 and converted into voltage. The voltage waveform is observed by the oscilloscope 15 and detected in the waveform. Let the phase of the current peak derived from the ions to be generated be the reference phase. The first step has been described above.

  Next, the second step will be described. In the second step, in order to accumulate the residual DC to the display element 14 in which the residual DC is not substantially accumulated, in the display layer after applying the working voltage including the direct current component for a certain period of time. In this step, the phase of the current peak derived from ions is measured, and the amount of change between the phase of the current peak and the reference phase obtained in the first step is obtained. The working voltage including the direct current component here is an arbitrary voltage whose integrated value does not become zero when the applied voltage is integrated in the voltage acting period. At this time, a voltage on which a direct current component is substantially superimposed is applied to the display element 14, and residual DC is accumulated. In step S <b> 31 of FIG. 3, the voltage waveform including the DC component generated from the arbitrary waveform generator 12 is amplified by the power amplifier 13, and the voltage waveform including the amplified DC component is applied to the display element 14. In step S32 immediately after that, the periodic measurement voltage generated from the arbitrary waveform generator 12 is amplified by the power amplifier 13, and the amplified periodic measurement voltage is applied to the display element. In step S33, the current flowing through the display element 14 during voltage application is amplified using the current amplifier 16 and converted into voltage. The voltage waveform is observed by the oscilloscope 15 and observed in the waveform. The phase of the current peak derived from the ion to be measured is measured. In step S34, the amount of change between the phase of the current peak derived from the ions measured in step S33 and the reference phase obtained in the first step is set as the first shift amount. The second step has been described above.

  Further, the third step will be described. The third step is derived from ions in the display layer when a voltage obtained by superimposing a DC offset voltage on a periodic measurement voltage is applied to the display element 14 in which residual DC is not substantially accumulated. The amount of change between the phase of the current peak and the reference phase obtained in the first step is obtained, the amount of change is compared with the first amount of shift obtained in the second step, and the offset voltage is applied until they match. Is incremented step by step, and the offset voltage when they match is determined as the residual DC amount. First, in step S41 of FIG. 4, the periodic measurement voltage generated by superimposing the DC offset voltage generated from the arbitrary waveform generator 12 is amplified by the power amplifier 13, and the amplified periodic measurement voltage is applied to the display element 14. The current flowing through the display element 14 during voltage application is amplified using the current amplifier 16 and converted into voltage, and the voltage waveform is observed by the oscilloscope 15. In step S42, the phase of the current peak derived from the ions in the waveform observed in step S41 is measured. In step S43, the amount of change between the phase of the current peak derived from the ions measured in step S42 and the reference phase obtained in the first step is set as the second shift amount. In step S44, the first shift amount obtained in the second step is compared with the second shift amount, and whether or not they match is checked. If they do not match, the DC offset voltage is set in step S45. After one step up, the process returns to step S41. If they match, the process proceeds to step S46, and the matched shift amount is set as the residual DC amount. The operations from step S41 to step S45 are repeated until the first shift amount and the second shift amount coincide with each other in step S44, or until the second shift amount exceeds the first shift amount. If the second shift amount exceeds the first shift amount, the DC offset voltage is finely adjusted in step S45 until the first shift amount and the second shift amount coincide with each other. The operation up to S45 is repeated. The third step has been described above.

  Note that when the working voltage including the direct current component in step S31 is a direct current voltage having a constant voltage value, the absolute amount and time constant of the residual DC of the display element can also be obtained. The method is shown below. If the third step is applied to each of the first shift amounts generated by successively changing the period in which the working voltage including the DC component is applied in step S31 of the second step, the residual for each working voltage application period. The amount of DC is obtained. FIG. 10 is a graph in which the working voltage application period is taken on the horizontal axis, and the residual DC amount in each case is taken on the vertical axis. From this graph, the residual DC amount and the time constant of the residual DC can be seen at a glance.

  FIG. 5 is a schematic diagram illustrating an example of a periodic measurement voltage waveform applied to the display element 14 in order to determine a reference phase of a current peak derived from ions in the display layer in the first step.

  FIG. 6 shows the display element 14 in order to measure the phase of the current peak derived from the ions in the display layer after a DC voltage is applied to the display element 14 for a certain period in the second step. It is a schematic diagram which shows an example of the direct-current voltage applied with respect to and a periodic measurement voltage waveform.

  FIG. 7 shows the measurement of the phase of the current peak derived from ions in the display layer when a voltage obtained by superimposing a DC offset voltage on the periodic measurement voltage is applied to the display element 14 in the third step. FIG. 6 is a schematic diagram illustrating an example of a periodic measurement voltage waveform in which a DC offset voltage applied to the display element 14 is superimposed.

  Heretofore, an example of the embodiment of the present invention has been shown.

  By the way, there is a case where the relaxation of the residual DC proceeds during the time until the peak is detected after measuring the current response when the periodic measurement voltage is applied to the display element. In such a case, it is difficult to estimate the absolute residual DC amount by the above-described method, and instead, the following aspect in which the increase or decrease in the relative residual DC amount is estimated can be considered.

  First, a first step of setting a phase of a current peak derived from ions in the display layer as a reference phase, which is detected when a periodic measurement voltage is applied to the display element 14 and a current response is measured, is performed. Next, an operating voltage containing a direct current component is applied to one of the electrodes of the display element 14 for a certain period of time with respect to one of the electrodes of the display element 14, and immediately thereafter, to the display element 14. A second step of setting the difference between the phase of the current peak derived from the ions in the display layer and the reference phase, which is detected when the periodic measurement voltage is applied and the current response is measured, to the first shift amount is performed. . The first shift amount obtained in the second step is considered as a relative increase / decrease in the residual DC amount. As described above, when the periodical measurement voltage is applied to the display element and the current response is measured and the relaxation proceeds in the time until the peak is detected, the residual DC amount of the display element and the display layer are effectively increased. A method for measuring the relative increase and decrease of the applied voltage is shown.

  In addition, the measuring method and measuring apparatus of the present invention disclosed in the claims can be applied to all display elements made of a multilayer dielectric in addition to an electrophoretic display element and a liquid crystal display element.

  In this embodiment, the present invention is applied to an electrophoretic display element, and the residual DC accumulated in the electrophoretic layer is directly estimated. In the second step S31 of the present invention, a DC voltage having a constant voltage value is applied to the electrophoretic display element, and the time for applying the DC voltage having the constant voltage value is varied to determine the residual DC in each case. Measure quantity.

  First, as in the first step shown in FIG. 2, a periodic triangular wave voltage as shown in FIG. 5 is applied to the electrophoretic display element in a state where residual DC is not substantially accumulated, Set the phase. 8 and 9 show the reference phase. Next, in the second step shown in FIG. 3, as shown in FIG. 6, a certain constant is first applied to one of the electrodes of the electrophoretic display element in a state where residual DC is not substantially accumulated. The phase of the current peak derived from the ions in the display layer, which is detected when a direct current voltage is applied for a period and then a periodic triangular wave voltage is applied to the electrophoretic display element to measure the current response. And a second step of setting the difference between the reference phase and the reference phase as the first shift amount. FIG. 8 shows how the current peak derived from ions in the display layer of the electrophoretic display element moves when the DC voltage application time is changed. Finally, a periodic triangular wave voltage superimposed with a DC offset voltage as shown in FIG. 6 is applied to the electrophoretic display element in a state where residual DC is not substantially accumulated, and the current response is measured. The difference between the phase of the current peak derived from the ions in the display layer and the reference phase detected when the second shift amount is set, and the first shift amount and the second shift amount coincide with each other. A third step is performed in which the offset voltage is changed, and the offset voltage when the two coincide with each other is the residual DC for each case where the DC voltage application time is changed. In FIG. 9, when a periodic triangular wave voltage on which the DC offset voltage is superimposed is applied and the current response is measured, the current peak derived from the ions in the display layer is detected depending on the value of the DC offset voltage. Shows how it moves.

  By the above method, the residual DC amount for each case when the DC voltage application period in the second step was varied was obtained.

  FIG. 10 is a graph in which the horizontal axis represents the DC voltage application period and the vertical axis represents the residual DC amount in each case. From this graph, the residual DC amount and the time constant of the residual DC can be seen at a glance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram of a measuring apparatus for explaining embodiments and examples of the present invention. The flowchart (the 1) for demonstrating Embodiment and the Example of this invention. The flowchart (the 2) for describing embodiment and the Example of this invention. The flowchart (the 3) for describing embodiment and the Example of this invention. FIG. 2 is an input waveform diagram (part 1) for explaining the embodiment and the example of the present invention. The input waveform figure for demonstrating Embodiment and the Example of this invention (the 2). FIG. 6 is an input waveform diagram (part 3) for explaining the embodiment and the example of the present invention. FIG. 4 is an output waveform diagram (part 1) for explaining the embodiment and the example of the present invention. FIG. 6 is an output waveform diagram (part 2) for explaining the embodiment and the example of the present invention. The graph which shows residual DC of the display element obtained by this invention.

Explanation of symbols

11 Information processing device such as personal computer 12 Arbitrary waveform generator 13 Power amplifier 14 Display element 15 Oscilloscope 16 Current amplifier 81 Current peak reference phase 91 Current peak reference phase

Claims (6)

  In a display element composed of a multilayer dielectric including at least a display layer and having two or more electrodes, the absolute value and time of residual DC accumulated in the display layer of the display element when a working voltage including a direct current component is applied A method for measuring a display element, comprising measuring a constant by measuring a change in phase of a current peak derived from an ion in a display layer that appears in response to a periodic measurement voltage.   2. The method of measuring a display element according to claim 1, wherein the periodic measurement voltage is applied after the residual DC is accumulated and before it is substantially accumulated. Measuring method of display element.   3. The display element measuring method according to claim 2, wherein the periodic measurement voltage applied before the residual DC is substantially accumulated is a periodic measurement voltage in which an offset voltage is superimposed. The method for measuring a display element according to claim 2.   2. The method of measuring a display element according to claim 1, wherein after the residual DC is accumulated, the periodic measurement voltage is applied to estimate a relative increase / decrease in the residual DC. Of measuring display element.   5. The display element measuring method according to claim 1, wherein the display element is made of a multilayer dielectric including at least a display layer, and the display element having two or more electrodes is an electrophoretic display device. The method for measuring a display element according to claim 1.   A display device measuring apparatus using the measuring method according to claim 1.

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