JP2001311929A - Evaluating method and evaluating device for spray-bend alignment transition time - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaluating method wherein a transition time from spray alignment to bend alignment can be easily and highly reliably evaluated in an OCB mode liquid crystal cell. SOLUTION: A spray-bend alignment transition time evaluating method is used, wherein a stage for applying voltage to a homogenous cell showing the spray alignment and a stage for monitoring the change of a cell volume against time after applying the voltage are included and the transition time is evaluated by using the type of the curve showing the change of the cell volume against time, the change ratio of the cell volume against time or the intensity of the hysteresis of voltage-volume (C-V) characteristics. Or, a spray-bend alignment transition time evaluating method is used, wherein the transition time is evaluated by using a time needed for the cell to be transited from a bend alignment state formed by applying the voltage to a spray alignment state formed by decreasing the voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an evaluation method for evaluating the easiness of transition from splay alignment to bend alignment in an optical compensation bend mode (OCB mode) liquid crystal display device.

[0002]

2. Description of the Related Art Liquid crystal display devices are thin, lightweight, and low power consumption display devices, and are widely used in image display devices such as televisions and videos, and in OA equipment such as monitors, word processors, and personal computers.

Conventionally, for example, a twisted nematic (TN) using a nematic liquid crystal as a liquid crystal display element.
Mode liquid crystal display devices have been put to practical use, but have disadvantages such as slow response and a narrow viewing angle. There are also display modes such as a ferroelectric liquid crystal (FLC) or an antiferroelectric liquid crystal (AFLC), which have a quick response and a wide viewing angle, but have major drawbacks such as shock resistance and temperature characteristics, and are widely used. It has not been realized yet. In addition, the polymer dispersion type liquid crystal display mode using light scattering does not require a polarizing plate and can display a high luminance, but it cannot essentially control the viewing angle by a phase plate and has a problem in response characteristics. Have
There is little advantage over the TN mode.

On the other hand, an optical compensation bend (OCB) mode has recently been proposed as a display mode having a quick response and a wide viewing angle (Japanese Patent Laid-Open No. 7-84254). As shown in FIG. 22, the liquid crystal display element in this mode is arranged between a glass substrate 1 on which a transparent electrode 2 is formed, a glass substrate 8 on which a transparent electrode 7 is formed, and substrates 1 and 8. And a liquid crystal layer 4 to be formed. Alignment films 3, 6 are formed on the electrodes 2, 7, and the alignment films 3, 6 are subjected to an alignment treatment so as to align liquid crystal molecules in parallel and in the same direction. Outside the substrates 1 and 8, deflection plates 10 and 12 are arranged in crossed Nicols, and a negative phase difference is given to the transmitted light between the deflection plates 10 and 12 and the substrates 1 and 8. The phase compensators 11 and 13 are interposed. In the liquid crystal cell having such a structure, a bend alignment including a bend alignment or a twist alignment is induced at the center of the cell by applying a voltage, and the phase compensating plates 11 and 13 are provided for low voltage driving and a wide viewing angle. In terms of performance, high-speed response is possible even in a halftone display area, and at the same time, it has a wide viewing angle characteristic.

[0005]

In the OCB mode, as shown in FIG. 22, the splay alignment state 5a changes from the splay alignment state 5a.
An initialization process for applying a voltage of about 30 V to the bend alignment state 5b is performed, and then a liquid crystal display is performed by driving a voltage of about several V. Therefore, in the OCB mode, the initialization processing is indispensable.

However, in the current OCB mode liquid crystal display element, when performing initialization by applying a voltage of about several volts, a time in units of minutes is required, which is one of the problems of the OCB mode. Therefore, a liquid crystal material having a high transition speed, in which bend alignment is easily formed by applying a voltage of about several volts, is desired.

If the OCB mode liquid crystal display element is to be driven by a TFT, a liquid crystal material that transitions from the splay alignment to the bend alignment at a low voltage is required. Therefore, in the course of research and development of an OCB mode liquid crystal display device, it is necessary to measure the transition time when selecting a liquid crystal material, and by measuring the transition time, it is possible to rank the liquid crystal materials in selection. Becomes

[0008] The transition time is conventionally defined by measuring the time required for the entire area of the electrode area to change from the splay alignment to the bend alignment by visual observation and defining the value. More specifically, a polarizing plate having a polarization axis direction orthogonal to each other is provided on both outer sides of the measurement liquid crystal cell, a voltage is applied to the measurement liquid crystal cell, and the color change (black, The transition time was defined by the time until visually recognizing that bend orientation was reached by visually observing an achromatic shade of gray or the like).

However, since the above evaluation method is based on visual observation by a human, there is an individual difference in the transfer time, and the transfer time varies. Therefore, reproducibility is poor, and it is not suitable for automatic measurement. In particular, in the transition from the splay alignment to the bend alignment, since most of the liquid crystal molecules are standing, the color change under the crossed Nicols is black.
It appears as an achromatic shade of gray or the like, and it is difficult to determine the time when the entire area of the electrode area is in the bend orientation, making the evaluation more difficult.

Incidentally, for reference, when the above-described evaluation method based on visual observation is used, it is possible to evaluate a large number of samples by changing various parameters such as a tilt angle and a temperature which affect the orientation transition. The variation in the above measurement can be reduced as a whole. However, such an evaluation method involves a problem that the number of samples increases, the number of measurement steps for evaluation increases, and the evaluation takes a long time.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a spray apparatus which can easily and reliably evaluate a transition time from a splay alignment to a bend alignment.
An object of the present invention is to provide a method for evaluating a bend transition time (meaning a transition time from a splay alignment to a bend alignment).

[0012]

Means for Solving the Problems In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention is a method for evaluating a splay-bend transition time, wherein a splay alignment is applied to a homogeneous liquid crystal cell showing a splay alignment. The method includes the steps of applying a constant voltage within a voltage range that allows transition from the bend orientation to the bend orientation, and monitoring the time change of the cell capacity after the voltage is applied. The time until the transition is performed is used as an evaluation index of the transition time from the splay alignment to the bend alignment, and the ease of the alignment transition of the cell is evaluated based on the evaluation index.

According to the above configuration, when a voltage is applied to the homogeneous cell exhibiting the splay alignment, a nucleus of the bend alignment is generated in the splay alignment region after a certain period of time.
The nucleus grows with the passage of time, and the entire region of the liquid crystal layer transitions to bend alignment. On the other hand, the transition from the splay alignment to the bend alignment means that each liquid crystal molecule sequentially rises in the vertical direction, so that the state of the transition appears as a change in the capacity of the cell. Here, in consideration of the above-described generation and growth of nuclei in the bend orientation, the capacitance change curve maintains a constant capacitance value until a certain time has elapsed after voltage application, and thereafter, the capacitance value increases. It is considered that the curve is drawn to reach the saturation capacity value. Therefore, the time from when the voltage is applied to when the bending point of the capacitance change (the point at which the capacitance value starts to increase) or when the voltage is applied and when the capacitance change reaches the saturation point is determined as an evaluation index of the transition time. Then, the ease of transition from the splay alignment to the bend alignment of the cell can be evaluated based on this evaluation index. Such an evaluation method enables easy and reliable evaluation of the splay-bend transition time.

According to a second aspect of the present invention, there is provided an apparatus for evaluating a splay-to-bend transition time, wherein a uniform liquid crystal cell exhibiting a splay alignment is maintained within a voltage range within which a transition from the splay alignment to the bend alignment is possible. Means for applying a voltage, means for monitoring a time change of the cell capacity after the voltage is applied, and, based on the monitoring result of the monitoring means, the time from the time of the voltage application to the time of reaching the inflection point of the capacity change or the saturation point. It is characterized by including means for calculating at least one of the time until the arrival, and means for displaying and / or printing the time calculated by the calculating means.

With the above configuration, the inflection point of the capacitance change (the point at which the capacitance value starts to increase) from the time when the voltage is applied as the evaluation index
, Or the time from when the voltage is applied to when the capacitance change reaches the saturation point can be automatically measured and displayed and / or printed.

According to a third aspect of the present invention, there is provided a method for evaluating a splay-bend transition time, wherein a step of applying a voltage to a homogeneous liquid crystal cell showing a splay alignment while gradually increasing a set voltage. Applying a voltage to the liquid crystal cell showing bend alignment while stepwise decreasing the same set voltage as the set voltage at the time of increasing the voltage, and for each set voltage value at the time of increasing and decreasing the applied voltage. Monitoring the time change of the cell capacity,
Obtain a voltage-cell capacity curve based on the monitoring result,
The magnitude of the hysteresis of the voltage-cell capacity curve is used as an evaluation index of the transition time from the splay alignment to the bend alignment, and the ease of alignment transition of the cell is evaluated based on the evaluation index.

A transition from splay alignment to bend alignment;
Voltage for transition from bend orientation to splay orientation-
In the cell capacity curve, it was not generally considered that hysteresis was present. However, the inventor of the present invention focused on the change in capacitance and conducted an experiment on whether or not the transition time can be evaluated by the change in capacitance, and found that hysteresis was present. Therefore, paying attention to hysteresis, the magnitude of this hysteresis is used as an evaluation index of the transition time from splay alignment to bend alignment,
It has been found that the ease of orientation transition of the cell can be evaluated based on the evaluation index. An effect similar to that of the first aspect of the present invention can also be obtained by the evaluation method using the magnitude of the hysteresis.

The reason why the magnitude of the hysteresis can be used as an evaluation index of the transition time from the splay alignment to the bend alignment is as follows.

It is considered that the difference between the energy required for the alignment transition from the splay alignment to the bend alignment and the energy required for the alignment transition from the bend alignment to the splay alignment appears as the magnitude of the hysteresis. This point is described in detail in the embodiment section described later. Therefore, the ease of transition from splay alignment to bend alignment is
This is because it corresponds to the magnitude of the hysteresis, so that the magnitude of the hysteresis can be used as an evaluation index of the transition time.

According to a fourth aspect of the present invention, there is provided an apparatus for evaluating a splay-bend transition time, wherein a voltage is applied to a homogeneous liquid crystal cell showing a splay alignment while increasing a set voltage stepwise. Means for applying a voltage to the liquid crystal cell exhibiting the bend alignment while gradually lowering the same set voltage as the set voltage at the time of the voltage increase, and for each set voltage value at the time of the increase and decrease of the applied voltage. Means for monitoring the time change of the cell capacity, means for calculating the magnitude of the hysteresis on the voltage-cell capacity curve based on the monitoring result of the monitoring means, and displaying the magnitude of the hysteresis calculated by the calculating means. And / or means for printing.

According to the above configuration, the voltage-
The magnitude of the hysteresis of the cell capacity curve can be automatically measured and displayed and / or printed.

According to a fifth aspect of the present invention, there is provided a method for evaluating a splay-bend transition time, wherein a step of applying a voltage to a homogeneous liquid crystal cell showing a splay alignment while gradually increasing a set voltage. And monitoring the time change of the cell capacity for each set voltage value when the applied voltage rises, based on the monitoring result, a voltage value of which the capacitance value increases among the plurality of set voltage values The time until the cell capacity is saturated to a certain value with respect to this voltage value is used as an evaluation index of the transition time from the splay alignment to the bend alignment, and the ease of alignment transition of the cell is evaluated based on the evaluation index. It is characterized by doing.

As described above, the time required for the cell capacitance to reach a certain value with respect to the specific voltage value can be used as an evaluation index of the transition time from the splay alignment to the bend alignment for the following reason.

As described in the operation of the first aspect of the present invention, the capacity of the cell changes according to the transition.
Considering the transition in this case in detail, when a voltage is applied in the state of the splay orientation, the transition from the initial splay orientation to the bend orientation does not occur at once, but the degree of the splay orientation first increases, and the splay orientation increases. It is known that the maximum deformation state of the splay alignment is reached, and the maximum deformation state of the splay alignment jumps to the bend alignment. Then, as described above, when the applied voltage is increased, the liquid crystal molecules rise immediately after the switching of the set voltage, and usually reach a certain capacitance value within a few seconds.
Such a change in capacitance occurs until a specific set voltage is reached. Between the application of the minimum level voltage and the application of the specific set voltage, the maximum deformation state of the splay orientation propagates over the entire surface of the electrode. When the voltage reaches a specific set voltage, the voltage rapidly rises to a certain capacitance value within a few seconds, and at a certain inclination angle, the capacitance increases, and it takes a long time until the capacitance value is saturated. It costs. This is considered to be due to the relaxation of the orientation from the splay orientation to the bend orientation, that is, the phenomenon of jumping from the maximum deformation state of the splay orientation to the bend orientation. Therefore, it is considered that the shorter the time required for the relaxation of the orientation is, the more easily the splay orientation is easily transferred to the bend orientation. Therefore, the orientation relaxation time can be used as an evaluation index of the transition time.

According to a sixth aspect of the present invention, there is provided an apparatus for evaluating a splay-bend transition time, wherein a voltage is applied to a homogeneous liquid crystal cell showing a splay alignment while increasing a set voltage stepwise. Means for monitoring the time change of the cell capacity for each set voltage value when the applied voltage rises, and the capacity value of the plurality of set voltage values increases based on the monitoring result of the monitor means. Calculating a voltage value, calculating means for calculating a time until the cell capacity is saturated to a constant value with respect to the voltage value, and means for displaying and / or printing the time until the saturation calculated by the calculating means, It is characterized by including.

According to the above configuration, the saturation time when the set voltage as the evaluation index rises can be automatically measured and displayed and / or printed.

According to a seventh aspect of the present invention, there is provided a method for evaluating a splay-bend transition time, which comprises applying a voltage to a liquid crystal cell exhibiting a bend alignment while gradually decreasing a set voltage. Monitoring the time change of the cell capacity for each set voltage value when the applied voltage falls, based on the monitoring result, the voltage value of the plurality of set voltage values, the capacitance value of which is decreasing, With respect to this voltage value, the time until the cell capacity is saturated to a certain value is used as an evaluation index of the transition time from the splay alignment to the bend alignment, and the ease of the alignment transition of the cell is evaluated based on the evaluation index. It is characterized by the following.

As described above, the time required for the cell capacity to be saturated to a certain value with respect to a specific voltage value can be used as an evaluation index of the transition time from the splay alignment to the bend alignment for the following reason.

As for the specific voltage value, the capacitance decreases and it takes time until the capacitance is saturated to a constant value. This is thought to be due to the relaxation of the orientation from the bend orientation to the splay orientation, which is the opposite phenomenon to the case of the above voltage rise, that is, the jumping phenomenon from the bend orientation to the maximum deformation state of the splay orientation. Can be Therefore, the shorter the time required for relaxing the orientation, the easier the transition from the bend orientation to the splay orientation occurs. Therefore, it is considered that the transition from the splay alignment to the bend alignment occurs more easily as the relaxation time becomes longer. Therefore, the orientation relaxation time can be used as an evaluation index of the transition time.

The invention according to claim 8 of the present invention is an apparatus for evaluating a splay-bend transition time, which comprises means for applying a voltage to a liquid crystal cell showing a bend alignment while gradually decreasing a set voltage. Means for monitoring the time change of the cell capacity for each set voltage value when the applied voltage falls; and a voltage for decreasing the capacity value among the plurality of set voltage values based on a monitoring result of the monitor means. Means for calculating a value and calculating a time until the cell capacity is saturated to a certain value with respect to this voltage value, and means for displaying and / or printing the time until the saturation calculated by the calculating means. It is characterized by the following.

According to the above configuration, it is possible to automatically measure and display and / or print the saturation time when the set voltage falls as an evaluation index.

According to a ninth aspect of the present invention, there is provided a method for evaluating a splay-bend transition time, wherein a step of applying a voltage to a homogeneous liquid crystal cell showing a splay alignment while gradually increasing a set voltage. And monitoring the time change of the cell capacity for each set voltage value when the applied voltage rises, based on the monitoring result, a voltage value of which the capacitance value increases among the plurality of set voltage values The change rate of the cell capacity with respect to this voltage value is used as an evaluation index of the transition time from the splay alignment to the bend alignment,
It is characterized in that the ease of the orientation transition of the cell is evaluated based on the evaluation index.

As described above, the orientation relaxation time can be used as an evaluation index. However, if the orientation relaxation time is used as an evaluation index, the measurement time becomes longer, so that the capacitance change within a certain time range, that is, the capacitance change, It is designed to be evaluated at a rate.

According to a tenth aspect of the present invention, there is provided an apparatus for evaluating a splay-bend transition time, wherein a voltage is applied to a homogeneous liquid crystal cell exhibiting a splay alignment while gradually increasing a set voltage. Means for monitoring the time change of the cell capacity for each set voltage value when the applied voltage rises, and the capacity value of the plurality of set voltage values increases based on the monitoring result of the monitor means. Means for calculating a voltage value and calculating a rate of change in cell capacity with respect to the voltage value; and means for displaying and / or printing the rate of change in cell capacity calculated by the calculating means. .

According to the above configuration, the rate of change of the cell capacity when the set voltage as an evaluation index rises can be automatically measured and displayed and / or printed.

An eleventh aspect of the present invention is a method for evaluating a splay-bend transition time, in which a voltage is applied to a homogeneous liquid crystal cell exhibiting a splay alignment while gradually decreasing a set voltage. And a step of monitoring a time change of the cell capacity for each set voltage value when the applied voltage falls, based on the monitoring result,
A voltage value at which the capacitance value decreases among the plurality of set voltage values is obtained, and a change rate of the cell capacitance with respect to this voltage value is used as an evaluation index of a transition time from the splay alignment to the bend alignment, based on the evaluation index. To evaluate the ease of orientation transition of the cell.

Even at the time of voltage drop, evaluation can be made by the capacitance change rate instead of the orientation relaxation time.

According to a twelfth aspect of the present invention, there is provided an apparatus for evaluating a splay-bend transition time, wherein a voltage is applied to a homogeneous liquid crystal cell exhibiting a bend alignment while gradually decreasing a set voltage. Means for monitoring the time change of the cell capacity for each set voltage value when the applied voltage falls, and the capacity value of the plurality of set voltage values decreases based on the monitoring result of the monitor means. Means for calculating a voltage value and calculating a rate of change in cell capacity with respect to the voltage value; and means for displaying and / or printing the rate of change in cell capacity calculated by the calculating means. .

According to the above configuration, the rate of change of the cell capacity when the set voltage as the evaluation index falls can be automatically measured and displayed and / or printed.

The thirteenth aspect of the present invention is a method for evaluating a splay-to-bend transition time, which comprises applying a voltage to a homogeneous liquid crystal cell exhibiting a splay alignment to form a bend alignment, Including the step of forming a splay alignment by reducing the voltage applied to the liquid crystal cell showing that the transition from bend alignment to splay alignment by visual observation, the time required for this transition, from splay alignment to The method is characterized in that the transition time to the bend orientation is used as an evaluation index, and the ease of the alignment transition of the cell is evaluated based on the evaluation index.

As described above, the transition time from the bend alignment to the splay alignment is measured by visual observation, and the measured time is used as an evaluation index of the transition time from the splay alignment to the bend alignment. With such an evaluation index, transfer can be evaluated easily and with high accuracy for the following reasons. That is, when the transition from the splay alignment to the bend alignment is visually observed, the change under crossed Nicols is an achromatic change such as black or gray, so it is difficult to confirm the time of the transition. However, in the case of the transition from the bend orientation to the splay orientation, the change under crossed Nicols involves a chromatic color change, so that it is easy to confirm the time of the transition and the accuracy is improved.

According to a fourteenth aspect of the present invention, there is provided an apparatus for evaluating a splay-bend transition time, comprising: means for applying a voltage to a homogeneous liquid crystal cell exhibiting a splay alignment to form a bend alignment; Means for forming a splay alignment by reducing the voltage applied to the liquid crystal cell, and a microscope for inspecting the alignment state of the liquid crystal cell,
An image analysis unit that analyzes an image obtained by the microscope to determine whether a color change has occurred on the entire surface of the liquid crystal cell; and, in response to a determination signal from the image analysis unit, changes a bend alignment to a splay alignment. The time required for transfer is indicated and / or
Or means for printing.

With the above configuration, the time required for transition from the bend orientation to the splay orientation as an evaluation index can be automatically measured and displayed and / or printed.

[0044]

(Embodiment 1) A method for evaluating a splay-bend transition time according to Embodiment 1 is as follows.
The above steps are performed. A voltage is applied to a homogeneous cell showing a splay alignment. The time change of the cell capacity after voltage application is monitored. From the results of the monitoring, the time T from when the voltage is applied to when it reaches the bending point of the capacitance change is T
1 or a time T2 from when the voltage is applied to when the saturation point of the capacitance change is reached. The above time T1 or time T2
Is used as an evaluation index to evaluate the splay-bend transition time.

By the evaluation method according to the first embodiment, the transition time can be evaluated easily and with high reliability. Hereinafter, the reason and details of the evaluation method will be described based on the experimental results of the present inventors.

FIG. 1 is a configuration diagram of a test liquid crystal cell used in the method for evaluating a splay-bend transition time according to the first embodiment. This liquid crystal cell is a homogeneous cell that shows splay alignment when no voltage is applied, and is a bend alignment mode liquid crystal cell in which an alignment transition is made to bend alignment by applying a voltage. The liquid crystal cell was manufactured by the following method.

First, an alignment film paint SE-74 manufactured by Nissan Chemical Industries is placed on two glass substrates 1 and 8 having transparent electrodes 2 and 7.
92 was applied by a spin coating method,
The alignment films 3 and 6 are formed by curing for 1 hour. Thereafter, rubbing treatment is performed on the surfaces of the alignment films 3 and 6 in the direction shown in FIG. 2 using a rubbing cloth made of rayon. In FIG. 2, 15 indicates a rubbing direction on the substrate 1 side, and 16 indicates a rubbing direction on the substrate 8 side.

Then, using Sekisui Fine Chemical Co., Ltd. spacer 5 and Structbond 352A (trade name of seal resin manufactured by Mitsui Toatsu Chemicals, Inc.), the substrates were bonded together so that the substrate spacing was 5.3 μm. Two cells 9 were created. Next, to form the liquid crystal layer 4, liquid crystal materials LC2 and LC4 having the physical properties shown in Table 1 were injected into each empty cell 9 by a vacuum injection method, thereby producing test cells A and B.

[Table 1]

Next, the evaluation method according to the first embodiment was performed using the test cells A and B.

10 V was applied to the test cells A and B, and the time change of the cell capacity was measured. FIG. 3 shows the measurement results. The cell capacity was measured using a precision LCR meter (Hewlett-Packard Co., product number HP-4284A), and the applied voltage waveform was a 1 kHz sine wave.

In FIG. 3, points a and a 'are points at which nuclei of bend alignment have begun to be generated during splay alignment, and the slopes of the line segments ab and a'b' indicate the rate of nuclear growth. Yes, it is. Points c and c ′ are points where the bend orientation is formed over the entire cell. From FIG. 3,
Cell A has a shorter time than cell B in both time T1 from the time of voltage application to reaching the inflection point of the capacitance change and time T2 from the time of voltage application to the point of reaching the saturation point of the capacitance change. Is recognized. Therefore, it can be evaluated that the cell A is easier to transfer than the cell B.

The transition time from the splay alignment to the bend alignment can be evaluated by using the time T1 or T2 for the following reason.

That is, as shown in FIG. 4A, when a constant voltage is applied to the liquid crystal cell showing the splay alignment 20, after a lapse of a certain period of time, as shown in FIG. Bend oriented nuclei 21 are generated in some of them. Then, it is known that the bend alignment nucleus 21 grows in the entire cell region (FIG. 4C) and the bend alignment is formed. Therefore, it is considered that faster generation of bend nuclei and higher nucleus growth rate mean faster orientation transition.

On the other hand, the change in the orientation is expressed as a change in the capacity of the cell according to the change. Then, the point at which the nucleus of the bend orientation occurs corresponds to the bending point where the capacitance changes on the capacitance change curve. In addition, the time when the entire region of the cell is in the bend orientation corresponds to a saturation point where the capacitance change increases after the capacitance change and saturates to a constant value on the capacitance change curve. Therefore, regarding the transition time from the splay orientation to the bend orientation, the time T1 from the application of the voltage to the bending point or the time T2 from the application of the voltage to the saturation point may be used as an evaluation index of the transition time. it can.

As is clear from FIG. 3, according to the first embodiment, the time required for generation of nuclei of bend alignment, the speed of nucleus growth, and the time required for bend alignment can be measured separately. , Its practical value is extremely large.

In the above example, the applied voltage is 10 V, 1
Although a kHz sine wave is applied, it goes without saying that other voltage values and waveform voltages may be applied. Further, it has been confirmed that the measurement result of the first embodiment matches the visual observation result.

Next, an evaluation device 30 for automatically measuring the evaluation index according to the above embodiment will be described. FIG.
FIG. 1 is a block diagram showing a configuration of an evaluation device according to the present embodiment. The evaluation device 30 includes input operation means 31 such as a keyboard and a mouse, a capacity measurement device 32 for measuring the capacity of a liquid crystal cell, and a printing means 33 such as a printer and a plotter.
A display means 34 such as a CRT or a liquid crystal display;
PU (central processing circuit) 35. Capacity measuring device 3
Reference numeral 2 denotes, for example, a precision LCR meter (Hewlett-Packard Company product number HP-4284A), a voltage application unit 36 for applying a predetermined voltage to the liquid crystal cell, a cell capacitance measurement unit 37 for measuring a change in the capacitance of the liquid crystal cell, and Having. The CPU 35 has a ROM (read only memory) 38 and a RAM (random access memory) 39 in which a system program, an arithmetic program and the like are stored in advance. The table 40 for storing the time ti and the cell capacity value ci in association with each other, the timer TM1 and the timer TM2 are connected. The timer TM1 is a cell capacity sampling notification timer that derives a signal indicating the cell capacity readout period to the CPU 25 every period W1. The timer TM2 is a timer for notifying the current time from the time when the voltage is applied to the test cell.

FIGS. 7 to 9 are flowcharts showing the operation of the evaluation device. The evaluation operation of the evaluation device will be described with reference to FIGS. First, in step s1, it is determined whether any of the modes 1 to 7 has been input. Here, mode 1 is a mode corresponding to the first embodiment, mode 2 is a mode corresponding to the second embodiment described later, and mode 3 is a mode corresponding to the orientation relaxation time T3 of the third embodiment described later. Mode 4 is a mode corresponding to the orientation relaxation time T4 in Embodiment 3 described later, and Mode 5 is a mode corresponding to the cell capacitance change rate E at the time of voltage increase in Embodiment 3 described later. Mode 6 is a mode 6 in the cell capacitance change rate E at the time of voltage drop in the third embodiment described later.
And mode 7 is a mode corresponding to a fourth embodiment described later.

The mode is set by the input operation means 31.
Is operated to input a predetermined code signal.

If there is a mode input, step s2
It is determined whether the mode is mode 1 or not.
Mode 1 processing is executed. If No, the process proceeds to step s3 to determine whether or not the mode is 2. If Yes, the process of the mode 2 is executed. Hereinafter, the processing corresponding to the mode input is similarly performed.

Next, processing in mode 1 corresponding to the first embodiment will be described. The specific processing operation of this mode 1 is shown in FIG. 8 and FIG. First, in step n1, a constant voltage Va is applied to the liquid crystal cell.
Specifically, the CPU 35 applies a constant voltage V to the voltage applying unit 36.
A command signal indicating a is derived. As a result, the voltage applying means 36 applies a constant voltage Va to the liquid crystal cell. At the same time, the cell capacity measuring means 37 starts measuring the change in the capacity of the liquid crystal cell. The cell capacitance measuring means 37 measures the capacitance of the liquid crystal cell when no voltage is applied before the start of the measurement, and the capacitance at this time is read out by the CPU 35.
It is stored in the table 40. The constant voltage value Va
Is a voltage value within a range generally considered as a voltage value at which the liquid crystal cell can transition from the splay alignment to the bend alignment. This is because even when a small voltage value of, for example, about 1 [V] is applied to the liquid crystal cell for a long time, the liquid crystal cell does not transition from the splay alignment to the bend alignment. Therefore, it is necessary to apply a somewhat large voltage value. In the first embodiment, the constant voltage Va is set to 10 [V]. The applied voltage waveform used was a 1 kHz sine wave.

Next, the process proceeds to step n2 where the timer TM
1, TM2 is set, and it is determined in step n3 whether a predetermined period W1 has elapsed. This period W1 is a period for sampling the analog capacitance value measured by the cell capacitance measuring means 37. Then, after the elapse of the predetermined period W1, in step n4, the cell capacity measuring means 3
7, the cell capacitance value c1 is read out, and in step n5, the current time t1 (corresponding to the period from the voltage application to the first sampling time) is read out from the timer TM2. The cell capacitance value c1 and the time t1 are written to the address "1" of the cell. Then, the timer TM1 is reset. Then, in step n8, it is determined whether or not a predetermined period W2 has elapsed.
Here, the period W2 is generally set to a time sufficient to allow a transition from the splay alignment to the bend alignment when a voltage Va is applied to the liquid crystal cell.

If the predetermined period W2 has not elapsed in step n8, the process returns to step n3. Thus, step n3 → step n4 → step n5 → step n6
→ The processing from step n7 → step n8 → step n3 is performed until the period W2 elapses, and the capacitance change from the time of voltage application until the period W2 elapses is monitored, and the capacitance value ci and the measurement time ti as the monitoring result are stored in a table. 40
Is written to.

When the predetermined time period W2 has elapsed, step n
8 to the evaluation index calculation processing routine shown in FIG. In the evaluation index calculation processing routine, first, step n9
Sets the variable k to 1. Next, in step n10, the addresses “k” and “k + 1” of the table 40 are designated and c
k, ck + 1 are read, and in step n11, ck + 1>
ck is determined. For example, when k = 1, c1 and c2 are read, and it is determined whether c2 is greater than c1. Here, when ck + 1> ck, it means that there has been a change in capacity increase.

If ck + 1> ck is not satisfied in step n11, the process returns to step n10. This step n1
0 → step n11 → step n12 → step n10
, The capacitance value at the inflection point where the capacity increase starts is obtained.

If ck + 1> ck, step n
In step 13, the address “k + 1” in the table 40 is specified, the measurement time tk + 1 corresponding to ck + 1 is read, and stored in the RAM 39 in step n14. Here, the measurement time tk + 1 corresponds to a time T1 from when the voltage is applied to when the bending point of the capacitance change is reached.

Next, at step n15, the variable k is set to m, and at step n16, m is incremented by one. Then, at step n17, the addresses "m" and "m + 1" of the table 40 are designated, and cm and cm + 1 are read out. At step n18, it is determined whether cm = cm + 1. Here, the capacitance value increases and changes for a certain time after the bending point. Accordingly, No is determined in step n18. Then, after a certain time, the capacitance value is saturated.
Therefore, when the saturation capacity value is reached, cm = cm
+1 and the capacitance value at the time when the capacitance value is saturated is obtained. Then, the process proceeds to step n19, in which the address m + 1 at this time is specified, and this m +
The measurement time tm + 1 corresponding to 1 is read. Then, at step n20, the time tm + 1 is stored in the RAM 39. This measurement time tm + 1 corresponds to the time T2 required from the time of voltage application until the capacitance is saturated. Thus, the time T1 from the voltage application to the inflection point of the capacitance change and the time T from the voltage application to the saturation point T
2 are automatically calculated and stored in the RAM 39.

Next, in order to visually check the evaluation index,
Times T1 and T2 are displayed by printing or display input operation (steps n21 and n22) and printed (steps n23 and n24).

Thus, the evaluation index according to the first embodiment can be automatically measured.

(Embodiment 2) The method for evaluating the splay-bend transition time according to Embodiment 2 is performed by the following steps (1) to (4). While gradually increasing the set voltage, a voltage is applied to the homogeneous cell liquid crystal cell showing the splay alignment. The time change of the cell capacity at each set voltage at the time of the voltage rise is monitored. A voltage is applied to the liquid crystal cell showing the bend alignment while gradually decreasing the same set voltage as the set voltage at the time of the voltage increase. The time change of the cell capacity for each set voltage at the time of the voltage drop is monitored. The magnitude S of the hysteresis of the voltage-cell capacity curve is obtained from the above monitoring results. The splay-bend transition time is evaluated using the magnitude S of the hysteresis as an evaluation index. Here, the magnitude S of the hysteresis is represented by the area of a region surrounded by a CV hysteresis curve described later.

With the evaluation method according to the second embodiment, it is possible to easily and reliably evaluate the transition time. Hereinafter, the reason and details of the evaluation method will be described based on the experimental results of the present inventors.

First, two liquid crystal cells having the same structure as in the first embodiment were prepared except that the distance between the substrates was 5.2 μm, and the liquid crystal materials LC5 and LC6 having the physical properties shown in Table 1 were vacuum-injected. Test cells C and D were manufactured by injection according to the method.

Thereafter, for each of the cells C and D,
As shown in FIG. 10, the applied voltage was increased stepwise, and the time change of the cell capacity with respect to each set voltage was measured.

Further, the voltage was lowered and the time change of the cell capacity was measured. When the voltage was decreased, a voltage of 30 V (voltage for surely transitioning to bend orientation) was applied once, the bend orientation was visually checked, and then the voltage was decreased stepwise at the rate shown in FIG. . Cell C for each set voltage
FIG. 11 and FIG. FIG. 11 shows a case where the set voltage rises, and FIG. 12 shows a case where the set voltage drops.

Next, the capacitance at each set voltage value was defined as an average capacitance for 595 seconds to 600 seconds after voltage application, and a capacitance-voltage (CV) characteristic was obtained. FIG. 13 shows a graph of such a capacitance-voltage (CV) characteristic. Here, the reason for setting the period to 595 seconds to 600 seconds is that, except for the specific set voltage value (2.6 V, 2.7 V in FIG. 11), the capacitance change is completely completed after the voltage is applied, and the capacitance is stable. The selected time is, for example, 595 seconds to 600. In the case of the specific set voltage value, the reason why the capacitance is increased is that jump from the maximum splay alignment to the bend alignment, that is, so-called relaxation of the alignment occurs. As shown in FIG.
The reason why the average capacitance value is set to 5 seconds to 600 seconds is the same as the reason at the time of the voltage rise. However, in FIG.
The specific set voltage value at which the capacitance decreases (1.8 V in FIG. 12,
In the case of 1.6V), the reason why the capacitance is reduced is that jumping from bend alignment to splay alignment, that is, relaxation of alignment has occurred.

Next, the CV characteristics of the cell D are determined in the same procedure as that of the cell C. FIG. 14 is a graph of CV characteristics of the cell D. 6 and 7 showing the time change of the capacity of the cell C are omitted, but the time change of the capacity of the cell D is obtained in advance when obtaining the CV characteristic of the cell D. .

The specific set voltage value corresponds to the voltage value near the upper limit of the hysteresis in FIGS. 13 and 14 when the voltage rises, and the voltage near the lower limit of the hysteresis in FIGS. 13 and 14 when the voltage drops. Equivalent to the value. This means that there is an energy difference between the splay alignment and the bend alignment.

As is clear from FIGS. 13 and 14, there is a hysteresis. In this regard, conventionally, it has generally been considered that a bend alignment mode liquid crystal display element has no hysteresis. However, the present inventor paid attention to the change in capacitance, and discovered that hysteresis was present during the experiment described in the first embodiment. Therefore, the present inventor has focused on this hysteresis and has come to obtain the evaluation method of the second embodiment.

Here, CV in FIGS. 13 and 14 is used.
The width of the region surrounded by the hysteresis curve corresponds to the difference between the energy of the splay alignment and the energy of the bend alignment, and corresponds to the ease of the splay-bend transition. This is because, in the case of transition from the bend orientation to the splay orientation, the transition is automatically performed by setting the voltage to 0V.
This is considered that, considering the magnitude of each free energy, the transition from the bend orientation to the splay orientation is considered to occur rapidly when the voltage is set to 0 V. In FIG. You can see that it is doing. Therefore, the line L2 is ideal for the transition between the splay alignment and the bend alignment. Therefore, the line L1 indicating the transition from the splay alignment to the bend alignment should be essentially the same as the line L2. However, since there is a difference between the energy required for the transition from the splay alignment to the bend alignment and the energy required for the transition from the bend alignment to the splay alignment, the line L1 rises slowly. Therefore, it is considered that the transition from the splay alignment to the bend alignment is easier when the line L1 approaches the line L2.

Based on the above inference, the area ratio between the hysteresis regions of cell C and cell D is compared.
5: 8, indicating that the liquid crystal material LC6 shows a faster bend transition than the liquid crystal material LC5.

Note that 10 V is applied to the cells C and D,
The results of separately measuring the time required from the splay alignment to the bend alignment by visual observation are 150 seconds and 85 seconds, respectively, demonstrating the effectiveness of the above inference and the effectiveness of the present invention.

The size of the CV hysteresis region in the splay-bend transition time evaluation method according to the second embodiment is a function of (anchoring energy A of the alignment film / elastic constant K). When comparing cells having different liquid crystal materials, or when comparing cells containing liquid crystal materials of different systems such as a cyano system and a fluorine system, it is necessary to also measure the anchoring energy.

Next, an evaluation apparatus for automatically measuring an evaluation index according to the second embodiment will be described. The evaluation device according to the second embodiment uses the evaluation device 30 according to the first embodiment, and is configured to automatically measure an evaluation index when mode 2 is selected.

FIG. 15 is a flowchart showing the processing operation when mode 2 is selected. The operation of automatically measuring the magnitude S of the hysteresis will be described below with reference to FIG.

First, in step m1, the initial voltage V
1 is set, the voltage V1 is applied to the liquid crystal cell in step m2, and the cell capacitance value measurement processing is executed in step m3. The cell capacity value measurement processing in step m3 is basically the same processing as in steps n1 to n9. Then, it is determined in step m4 whether a predetermined period W3 has elapsed. If the period W3 has not elapsed, the process returns to step m3. Here, the period W3 indicates a cell capacity measurement time for each set voltage. Then, in step m4, it is determined whether or not the set application voltage V is the maximum set voltage 30 [V]. If the set applied voltage V has not reached 30 [V], the process proceeds to step m6.
Increases the set applied voltage V by a predetermined value, and returns to step m2. In this way, the closed loop processing of step m2 to step m6 allows the maximum set voltage 30
The cell capacity change for each of the plurality of set voltages up to [V] is measured, and the measurement time ti as the capacity change for each set voltage and the capacitance value ci at that time are stored in the table 40. As a result, a change in the cell capacity at a plurality of set voltages when the voltage rises is monitored and stored in the table 40.

Next, by the closed loop processing of steps m7 to m11, the maximum set voltage is reduced from 30 [V] to 0.
A change in cell capacity for each of a plurality of set voltages up to [V] is measured, and a measurement time as a change in capacity for each set voltage and a capacitance value at that time are stored in a table 40. More specifically, in step m7, the set voltage is reduced by a predetermined value. The decreasing value at this time is the same as the increasing value when the set voltage rises, whereby the same set voltage value is applied when the voltage rises and when the voltage falls. Then, in step m8, the set voltage is applied to the liquid crystal cell, the capacitance change is measured in step m9, stored in the table 40, and it is determined in step m10 whether the set voltage measurement time W3 has elapsed. If has not elapsed, the flow returns to step m9. When the time W3 has elapsed, step m1
Then, it is determined whether the set voltage is 0 [V] or not.
If the voltage has not reached [V], the flow returns to step m7, where the set voltage is reduced, and the set voltage is applied to the liquid crystal cell.

In this way, the change in capacitance of the liquid crystal cell is monitored by increasing the set voltage, and the change in capacitance of the liquid crystal cell is monitored by decreasing the set voltage. These results can be stored in the table 40.

Next, an evaluation index according to the second embodiment is calculated based on the data stored in the table 40. Specifically, in step m11, the average value of the capacitance change within a certain period after the voltage application is calculated. During this fixed period, the specific set voltage value (2.6 V when the voltage rises, 2.
7V, 1.8V, 1.6V when the voltage drops)
The capacitance change is completely completed after the voltage is applied, and it is a time when the capacitance is stabilized.
0 seconds. This takes into account the convenience of calculating the capacitance-voltage curve (CV curve). The calculated average capacity value Cm is stored in the table 40. Next, the process proceeds to step m13, where the magnitude of the hysteresis on the CV curve is calculated. Specifically, the area S on the CV curve shown in FIG. 13 or FIG. 14 is calculated. Then, the process proceeds to step m14, where the calculated area S is printed and displayed.

In this way, the evaluation index according to the second embodiment is automatically measured, displayed and printed by the evaluation device.

(Embodiment 3) The evaluation method of the splay-bend transition time according to the third embodiment is similar to the evaluation method of the second embodiment. However, in the second embodiment, although the magnitude of the hysteresis is used as the evaluation index, in the third embodiment, the time required for the orientation relaxation (hereinafter, referred to as the orientation relaxation time) T3 described in the second embodiment, or Cell capacity change rate E with normalized orientation relaxation time T3 for convenience of measurement
Is used as an evaluation index to evaluate the splay-bend transition time.

The evaluation method according to the third embodiment makes it possible to easily and reliably evaluate the transition time. Hereinafter, the reason and details of the evaluation method will be described based on the experimental results of the present inventors.

(1) In the case of the orientation relaxation time T3 The same experiment was performed on the same cells C and D as in the second embodiment, and FIG. 11 was obtained. Here, although the orientation relaxation phenomenon has already been simply described in the second embodiment, it will be described in more detail with reference to FIG.
When a voltage is applied in the state of the splay alignment, the splay alignment does not transition from the initial splay alignment to the bend alignment at a stretch, but the degree of the splay alignment first increases, and reaches the maximum deformation state of the splay alignment. Is known to jump from the maximum deformation state to the bend orientation. Then, as shown in FIG. 11, the specific set voltage value (2.6 V, 2.7
Regarding V), the capacity will increase. That is,
When the voltage is increased from the set voltage of 1.0 V, the liquid crystal molecules rise immediately after the switching of the voltage.
Reach a certain capacity value within seconds. Such a change in capacitance occurs until a specific set voltage is reached. From the setting voltage of 1.0 V, it is considered that the maximum deformation state of the splay orientation propagates over the entire surface of the electrode during the application of the specific setting voltage.

When the voltage reaches the specific set voltage, 2-3
After rapidly increasing to a certain capacitance value within a second, the capacitance increases at a certain inclination angle, and it takes a long time until the capacitance value is saturated. This is considered to be due to the relaxation of the orientation from the splay orientation to the bend orientation, that is, the phenomenon of jumping from the maximum deformation state of the splay orientation to the bend orientation. Therefore, it is considered that the shorter the orientation relaxation time T3, the easier the transition from the splay orientation to the bend orientation occurs. Therefore, the orientation relaxation time T3 can be used as an evaluation index of the transition time.
When the set voltage is 2.7 V or more, the capacitance value reaches a certain value within 2 to 3 seconds, as before reaching the specific set voltage. This is because the liquid crystal molecules rise further near the substrate interface while the liquid crystal cell maintains the bend alignment state.

In the above example, the case where the set voltage increases is described. However, as shown in FIG. 12, the alignment relaxation time T4 from the bend alignment to the splay alignment when the set voltage decreases is evaluated. It may be used as an index. However, in this case, it is considered that the transition from the splay alignment to the bend alignment occurs more easily as the alignment relaxation time T4 is longer. This is because, as described in the description regarding the hysteresis, the ease of transition from the splay alignment to the bend orientation is opposite to the ease of the transition from the bend alignment to the splay alignment.

(2) In the case of the cell capacitance change rate E Since the measurement of the orientation relaxation time T3 requires a long time, the cell relaxation rate T is defined as a normalized value of the orientation relaxation time T3 in consideration of the convenience of the measurement. E is used as an evaluation index.

Here, the cell capacity change rate E means a value obtained by dividing a substantial capacity change value caused by orientation relaxation within the measurement time by a difference between the maximum cell capacity and the minimum cell capacity within the measurement range. I do. Specifically, it is defined by the following equation.

Cell capacity change rate E = (cell capacity at the time of maximum measurement of orientation relaxation time−cell capacity after 5 seconds of voltage application) / (cell capacity at the time of applying the maximum voltage of the set voltage) In the numerator of the above formula, the difference between the cell capacity at the time when the maximum measurement time of the orientation relaxation time has elapsed and the cell capacity at 5 seconds after the voltage application is subtracted is as follows. This is because the cell capacity after 5 seconds from the application of the voltage is not a change in capacity due to the relaxation of the orientation. The larger the rate of change in cell capacity, the easier the splay-bend transition.

In the experiment shown in FIG. 11, the cell capacity change rate E was defined by the following equation.

That is, the cell capacity change rate = (cell capacity after 10 minutes of voltage application−cell capacity after 5 seconds of voltage application) / (2
(Cell capacity when a voltage of 0 V is applied−cell capacity when no voltage is applied).

The above-mentioned capacity change rates of the cells C and D were determined to be 0.00299 and 0.0299, respectively.
0588. Therefore, it can be evaluated that the splay-bend transition is easier in the cell D than in the cell C, which is consistent with the evaluation in the second embodiment.

In the above example, the case where the set voltage rises has been described. However, the cell capacity change rate may be calculated for the case where the set voltage falls, and this may be used as an evaluation index. However, in this case, the bend-spray cell capacity change rate is opposite to the above-described spray-bend cell capacity change rate, and the smaller the capacity change rate, the easier the transition from the splay orientation to the bend orientation. Become.

(3) Other Standardized Values A value obtained by dividing the above-mentioned cell capacity change rate by the cell gap may be used as an evaluation index.

Next, a description will be given of an evaluation apparatus according to the third embodiment for automatically measuring evaluation indices (orientation relaxation times T3, T4, cell capacity change rate E). The evaluation device according to the third embodiment uses the evaluation device 30 according to the first embodiment, and uses the mode 3, the mode 4, the mode 5,
When the mode 6 is selected, the evaluation index is automatically measured. Mode 3 is for obtaining the orientation relaxation time T3 when the set voltage rises.
Is for obtaining the orientation relaxation time T4 when the set voltage falls, mode 5 is for obtaining the cell capacity change rate E when the set voltage is rising, and mode 6 is for obtaining the cell capacity change rate E when the set voltage drops. Things.

First, the processing operation when mode 3 is selected will be described with reference to FIG.

The processing in mode 3 is basically similar to that in mode 2. That is, the processing of step p1 to step p6 is the same as the processing of step m1 to step m6, whereby the capacitance change of the liquid crystal cell when a plurality of set voltages increase is measured.

Next, at step p7, a specific voltage Vup at which the capacitance value increases is determined. It should be noted that a change in capacitance from the time of voltage application to about 5 seconds is ignored, and for example, an increase in capacity with respect to a measurement time of 10 seconds or later is obtained. Specifically, it is determined whether or not the applied voltage V1, V2, V3,... At a certain time, for example, 10 seconds, is compared with the capacitance value at the time of the next measurement to determine whether the applied voltage is increased. Then, the increasing specific voltage Vup is obtained.

Next, in step p8, the saturation time T (corresponding to the orientation relaxation time T3) of the cell capacitance with respect to the increasing specific voltage Vup is determined. Specifically, with respect to the specific voltage Vup obtained in step p7, a capacitance value at which the capacitance value ci and the capacitance value ci + 1 are equal is obtained, and the address of the table 40 is designated by “i + 1” at this time. T3 is required. The orientation relaxation time T3 is stored in the RAM 39.

Next, in order to visually observe the orientation relaxation time T3, a printing or display input operation is performed to adjust the orientation relaxation time T3.
3 is displayed and printed (step p
9). Thus, the evaluation device can automatically measure the orientation relaxation time T3.

Next, the processing operation when mode 4 is selected will be described with reference to FIG. The processing in mode 4 is basically similar to that in mode 2. That is, the processing of steps r1 to r6 is the same as the processing of steps m1 to m6 described above, whereby the change in the cell capacity when a plurality of set voltages decrease is measured.

Next, at step p7, a specific voltage Vdown at which the capacitance value decreases is obtained. It should be noted that a change in capacitance from the time of voltage application to about 5 seconds is ignored, and for example, an increase in capacity with respect to a measurement time of 10 seconds or later is obtained. Specifically, the applied set voltage Vr (Vr = 30), Vr-1, Vr
,... Are compared with the capacitance value c + 1 at the time of the next measurement to determine whether or not the capacitance value c has decreased. Then, a specific voltage Vdown that is decreasing among the set voltages is obtained.

Next, in step p8, the saturation time T of the cell capacitance with respect to the decreasing specific voltage Vdown.
(Corresponding to the orientation relaxation time T4). Specifically, with respect to the specific voltage Vdown obtained in step r7, a capacitance value at which the capacitance value ci and the capacitance value ci + 1 become equal is obtained, and the address of the table 40 is designated by “i + 1” at this time. T4 is required.
The orientation relaxation time T4 is stored in the RAM 39.

Next, in order to visually check the orientation relaxation time T4, a printing or display input operation is performed.
4 is displayed and printed (step p
9). Thus, the evaluation device can automatically measure the orientation relaxation time T4.

Next, the processing operation when mode 5 is selected will be described with reference to FIG. The processing in mode 5 is basically similar to mode 3. However, in mode 3, a predetermined measurement time W3
Although the change in cell capacity was measured at a time (sufficiently longer than the saturation time T2), the difference is that in mode 5, an arbitrary time W4 can be set.
Thereby, the measurement time can be shortened. In the mode 5, the maximum set voltage Vmax can be arbitrarily specified. From this point, Mode 5
Thus, the measurement time can be reduced.

First, at the time of measurement, the measurer inputs the measurement time W4 and the maximum set voltage Vmax. As a result, the process proceeds to step q3 via steps q1 and q2. Then, step q4 → step q5 →
By the closed loop processing of step q6 → step q7 → step q8 → step q4, a change in the cell capacity at the time of increasing a plurality of set voltages from 0 [V] to the maximum set voltage Vmax is measured. Step q3 to step q8
Is basically the same as the above-mentioned steps p1 to p6 except for the processing relating to the measurement time and the maximum set voltage.
Is the same as the closed loop processing.

Next, at step q9, the cell capacity change rate E is calculated. In step q9, as a prerequisite for calculating the cell capacitance change rate E, the specific voltage Vup at which the capacitance value increases is obtained by the same processing as in step p7. Then, the data stored in the table 40 is read out, and the arithmetic processing of the first equation is performed. Then, the cell capacity change rate E calculated by the arithmetic processing is printed / displayed (step q10). In this way, the evaluation device can automatically measure the cell capacity change rate E when the set voltage rises.

Next, the processing operation when mode 6 is selected will be described with reference to FIG. The processing in mode 6 is basically similar to mode 3. However, in mode 3, a predetermined measurement time W3
Although the change in cell capacity was measured at a time (sufficiently longer than the saturation time T2), the difference is that an arbitrary time W4 can be set in the mode 6.
Thereby, the measurement time can be shortened. In the mode 6, the maximum set voltage Vmax can be arbitrarily specified. From this point, Mode 6
Thus, the measurement time can be reduced.

First, at the time of measurement, the measurer inputs the measurement time W4 and the maximum set voltage Vmax. As a result, the processing goes through steps d1 and d2, and in step d3 and step d4, 30 [V] is applied to the liquid crystal cell.
Is applied for a predetermined time. As a result, the liquid crystal cell is in a bend alignment state in all regions.

Next, in step d5, the applied voltage is set to the maximum set voltage Vmax. Then, the maximum set voltage Vm is obtained by the closed loop processing of steps d6 to d10.
A change in cell capacity is measured when a plurality of set voltages fall from ax to 0 [V]. Step d6 → step d7 → step d8 → step d9 → step d1
0 → The closed loop processing of step d6 is basically the same as that of step r6 except for the processing relating to the measurement time and the maximum set voltage.
This is the same as the closed loop processing of 2 → step r3 → step r4 → step r5 → step r6 → step r2.

Next, at step d11, the cell capacity change rate E is calculated. In step d11,
As a premise for calculating the cell capacitance change rate E, the specific voltage Vdown at which the capacitance value decreases is obtained by the same processing as in step r7. Then, the data stored in the table 40 is read out, and the arithmetic processing of the first equation is performed. Then, the cell capacity change rate E calculated by the arithmetic processing is printed and displayed (step d12). Thus,
The evaluation device can automatically measure the cell capacity change rate when the set voltage drops.

In the above evaluation apparatus, the cell capacity change rate is calculated as a normalized value of the orientation relaxation time, but the cell gap is input and the cell capacity change rate is divided by the cell gap. May be calculated.

As described above, by using the evaluation apparatus having the above configuration, it is possible to automatically measure the evaluation index (the orientation relaxation time T3, T4, the cell capacity change rate E) according to the third embodiment. it can.

(Embodiment 4) The method for evaluating the splay-bend transition time according to Embodiment 4 is performed by the following steps (1) to (4). A voltage is applied to a homogeneous cell showing a splay alignment to form a bend alignment. The spray orientation is formed by reducing the applied voltage. By visual observation,
After confirming the transition from the bend orientation to the splay orientation, the time T4 required for this transition is determined. The above time T
Using 4 as an evaluation index, the splay-bend transition time is evaluated.

By the evaluation method according to the fourth embodiment, the transition time can be easily and reliably evaluated. Hereinafter, the reason and details of the evaluation method will be described based on the experimental results of the present inventors.

Four liquid crystal cells having the same structure as in the first embodiment were prepared except that the distance between the substrates was 5.5 μm.
4, LC3, LC2 and LC1 were injected by a vacuum injection method to obtain test cells E, F, G and H.

Thereafter, a 20 V rectangular wave was applied to the cell for 2 minutes to completely bend alignment, then the voltage was dropped to 20 mV, and the time required for the entire electrode portion to be in splay alignment was measured. , 30 seconds, 43 seconds and 65 seconds.

As described in the second embodiment, in a system in which the transition from the splay alignment to the bend alignment is easy (high speed), the energy difference between the two is small. Become slow. Therefore, the ease of transition to bend alignment can be evaluated using the transition time to splay alignment as an evaluation index. In the case of the above experimental example, the transition to the bend alignment becomes easier in the order of the cells H, G, F, and E.

In the evaluation method according to the fourth embodiment,
Evaluation is easy. This is because, when visually observing the transition from the splay alignment to the bend alignment, as described in the section of the related art, under crossed nicols, the color change is small and it is not easy to confirm the transition. On the other hand, when visually observing the transition from the bend alignment to the splay alignment, the color change under crossed Nicols (for example, a change in a chromatic color such as blue or yellow) is large, and the measurement is very easy.

Here, the application of the voltage of 20 mV is usually performed by changing the bend alignment to the splay alignment by stopping the application of the voltage in the bend alignment state. However, even when the voltage application is stopped in this way, the state does not immediately shift to the splay alignment. Because, in the bend alignment state, the liquid crystal layer is in a charged state,
Even if the application of the voltage is stopped, it takes a considerable time until the state changes to the splay alignment. This is not suitable for conducting experiments. Therefore, a small voltage of about several mV is applied so that the charge amount can be regarded as substantially zero.

The cells E, F, G and H have 10
When V was applied and the time required from the splay alignment to the bend alignment was separately measured by visual observation,
Seconds, 20 seconds, 3 seconds, and 1 second. Therefore, the evaluation method of the fourth embodiment is consistent with the visual observation regarding the transition to the bend orientation, and the effectiveness of the present invention is clear.

The evaluation method according to the fourth embodiment is different from the spray-bend transition, and its speed largely depends on the surface state of the alignment film. Therefore, if a uniform film surface is guaranteed, the evaluation method according to the fourth embodiment is an extremely effective method for evaluating the ease of transition from splay alignment to bend alignment.

Next, an evaluation apparatus for automatically measuring an evaluation index according to the above embodiment will be described. FIG. 20 is a block diagram showing a configuration of the evaluation device according to the present embodiment. This evaluation device 50 is similar to the evaluation device 30,
Corresponding parts have the same reference characters allotted. In the evaluation device 50, a microscope 51 and an image analysis device 52 are used instead of the capacity measuring device 32 used in the evaluation device 30. Further, a voltage applying means 53 is connected to the CPU 35 so that a voltage is applied to the liquid crystal cell by the voltage applying means 53. In this evaluation device 50, the polarizing plates 10 and 11 are arranged in crossed Nicols on both outer sides of the liquid crystal cell. At the time of measurement, a light source (not shown) irradiates light from one polarizing plate 10 side,
The transition state is observed by the microscope 51 provided on the other polarizing plate 11 side, the observed image is analyzed by the image analyzer 52, and the analysis data is transmitted to the CPU 35.

FIG. 21 is a flowchart showing the processing operation of the evaluation device 50. First, for example, 30
[V] is applied for a certain period of time to bring the entire region of the liquid crystal cell into a bend alignment state (steps e1 and e2). Next, in Step e3, a minute voltage of, for example, about 20 mV is applied to the liquid crystal cell (Step e3), and at the same time, the timer TM3 is set (Step e4). Next, in step e5, the image from the microscope 51 is fetched, and the range of color change of the image is analyzed. When the range of color change reaches the entire electrode surface, the process proceeds from step e6 to step e7, and the current time is set by the timer TM3. Is read. This means that the transition time from bend to spray has been measured. Next, at step e8, the transfer time is displayed and printed. Thus, the evaluation device 50 can automatically measure the transition time from the bend to the spray, which is the evaluation index according to the fourth embodiment.

[0133]

According to the present invention as described above,
Moreover, it is possible to evaluate the spray-bend transition time with high reliability.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a test cell used in a spray-bend transition time evaluation method according to Embodiments 1 to 4.

FIG. 2 is a view showing a rubbing direction of the test cell substrate of FIG. 1;

FIG. 3 shows test cells A and B used in the first embodiment.
FIG. 9 is a diagram showing a change over time in cell capacity when V is applied.

FIG. 4 is a diagram for explaining a process of transition from splay alignment to bend alignment.

FIG. 5 is a block diagram illustrating a configuration of an evaluation device 30 according to the first embodiment.

FIG. 6 is a schematic diagram of a store area of a table 40. 5 is a flowchart illustrating an operation of the evaluation device.

FIG. 7 is a flowchart showing a judgment process at the time of mode input by the evaluation device 30.

FIG. 8 is a flowchart showing processing in mode 1 by the evaluation device 30.

FIG. 9 is a flowchart showing a mode 1 process performed by the evaluation device 30.

FIG. 10 is a timing chart illustrating a temporal change of a voltage applied to a test cell according to the second embodiment.

FIG. 11 shows a test cell C used in the second embodiment,
FIG. 9 is a diagram illustrating a time change of the capacitance after switching of each voltage value when a voltage is applied at a timing of 0.

FIG. 12 shows a test cell C used in the second embodiment,
FIG. 9 is a diagram showing a time change of the capacitance after each voltage value switching when the voltage is dropped at the same timing as 0.

FIG. 13 shows the capacitance of the test cell C used in the second embodiment.
It is a figure which shows a voltage (CV) hysteresis characteristic.

FIG. 14 shows the capacitance of the test cell D used in the second embodiment.
It is a figure which shows a voltage (CV) hysteresis characteristic.

FIG. 15 is a flowchart showing a mode 2 process performed by the evaluation device 30.

FIG. 16 is a flowchart showing a mode 3 process performed by the evaluation device 30.

FIG. 17 is a flowchart showing processing in mode 4 by the evaluation device 30.

FIG. 18 is a flowchart showing processing in mode 5 by the evaluation device 30.

FIG. 19 is a flowchart showing processing in mode 6 by the evaluation device 30.

FIG. 20 is a block diagram illustrating a configuration of an evaluation device 50 according to a fourth embodiment.

FIG. 21 is a flowchart showing processing by the evaluation device 50.

FIG. 22 is a diagram for explaining a panel configuration of an optical compensation bend (OCB) mode cell and an arrangement of liquid crystal directors.

[Explanation of symbols]

 1, 8 ... glass substrate 2, 7 ... transparent electrode 3, 6 ... alignment film 4 ... liquid crystal layer 5 ... spacer 5a ... liquid crystal when no voltage is applied Alignment (spray alignment) 5b Liquid crystal alignment (bend alignment) when voltage is applied 9 Test cell 10, 12 Polarizing plate 11, 13 Phase compensator 30, 50 Evaluation device 31 Input Operating means 32 ... Capacity measuring device 33 ... Printing means 34 ... Display means 35 ... CPU 36,53 ... Voltage applying means 38 ... ROM 39 ... RAM 40 ... Table 51 ... Microscope 52 ... Image analyzer

Claims (14)

[Claims] 1. A method comprising the steps of: applying a constant voltage to a homogeneous liquid crystal cell exhibiting a splay alignment within a voltage range capable of transitioning from a splay alignment to a bend alignment; and monitoring a time change of the cell capacity after the voltage is applied. The time from the application of the voltage to the point at which the capacitance change reaches the bending point or the saturation point is used as an evaluation index of the transition time from the splay alignment to the bend alignment, and based on this evaluation index, the ease of the alignment transition of the cell is determined. A method for evaluating a splay-bend transition time characterized by evaluating. 2. A means for applying a constant voltage to a homogeneous liquid crystal cell exhibiting a splay alignment within a voltage range capable of transitioning from the splay alignment to the bend alignment; a means for monitoring a time change of the cell capacity after applying the voltage; A means for calculating at least one of a time from when a voltage is applied to a point at which a capacitance change reaches a bending point or a time until a saturation point is reached, based on a monitoring result of the monitoring means; and Means for displaying and / or printing the elapsed time, and an apparatus for evaluating a splay-bend transition time. 3. A step of applying a voltage to a homogeneous liquid crystal cell exhibiting a splay alignment while increasing the set voltage stepwise, and reducing the bend while stepwise decreasing the same set voltage as the set voltage when the voltage is increased. A step of applying a voltage to the liquid crystal cell showing the orientation, and a step of monitoring a time change of a cell capacity for each set voltage value when the applied voltage rises and falls, and a voltage-cell capacity curve based on the monitoring result. ,
The magnitude of the hysteresis of the voltage-cell capacity curve is used as an evaluation index of the transition time from the splay alignment to the bend alignment, and the splay is characterized by evaluating the ease of the alignment transition of the cell based on the evaluation index. -Method for evaluating bend transition time. 4. A means for applying a voltage to a homogeneous liquid crystal cell exhibiting splay alignment while increasing a set voltage stepwise, and a step of lowering a set voltage which is the same as the set voltage at the time of increasing the voltage in a stepwise manner. Means for applying a voltage to the liquid crystal cell showing the orientation; means for monitoring the time change of the cell capacity for each set voltage value when the applied voltage rises and falls; and voltage-cell based on the monitoring result of the monitor means. Means for calculating the magnitude of the hysteresis on the capacity curve; and means for displaying and / or printing the magnitude of the hysteresis calculated by the calculating means. apparatus. 5. A step of applying a voltage to a homogeneous liquid crystal cell showing a splay alignment while gradually increasing a set voltage, and monitoring a time change of a cell capacity for each set voltage value when the applied voltage is increased. Determining a voltage value at which the capacitance value increases among the plurality of set voltage values based on the monitoring result, and determining a time required for the cell capacitance to saturate to a constant value with respect to the voltage value. A method for evaluating a splay-bend transition time, which comprises evaluating an ease of the orientation transition of the cell based on the evaluation index as an evaluation index of a transition time from a to a bend orientation. 6. A means for applying a voltage to a homogeneous liquid crystal cell exhibiting splay alignment while increasing a set voltage stepwise, and monitoring a time change of a cell capacity for each set voltage value when the applied voltage is increased. Means for determining, based on the monitoring result of the monitoring means, a voltage value of which the capacitance value increases among the plurality of set voltage values,
Calculation means for calculating the time until the cell capacity is saturated to a certain value with respect to this voltage value, and the time until saturation calculated by the calculation means,
A spray-bend transition time evaluation device, comprising: means for displaying and / or printing. 7. A step of applying a voltage to a liquid crystal cell exhibiting a bend alignment while gradually lowering a set voltage, and monitoring a time change of a cell capacity for each set voltage value when the applied voltage decreases. Including the step, based on the monitoring result, the voltage value of the capacitance value of the plurality of set voltage value is determined to decrease, the time until the cell capacitance is saturated to a constant value with respect to this voltage value, from the spray orientation. A method for evaluating a splay-bend transition time, which comprises evaluating an ease of orientation transition of the cell based on the evaluation index as an evaluation index of a transition time to a bend orientation. 8. A means for applying a voltage to a liquid crystal cell showing a bend alignment while stepwise decreasing a set voltage, and monitoring a time change of a cell capacity for each set voltage value when the applied voltage decreases. Means, based on the monitoring result of the monitoring means, to determine a voltage value of which the capacitance value decreases among the plurality of set voltage values,
Means for calculating the time until the cell capacity is saturated to a certain value with respect to this voltage value, and the time until the saturation calculated by the calculating means,
A spray-bend transition time evaluation device, comprising: means for displaying and / or printing. 9. A step of applying a voltage to a homogeneous liquid crystal cell exhibiting a splay alignment while gradually increasing a set voltage, and monitoring a time change of a cell capacity for each set voltage value when the applied voltage is increased. Determining a voltage value at which the capacitance value of the plurality of set voltage values increases, based on the monitoring result, and changing the rate of change of the cell capacitance with respect to the voltage value from the splay alignment to the bend alignment. A method for evaluating a splay-bend transition time, wherein the ease of orientation transition of the cell is evaluated based on the evaluation index as a time evaluation index. 10. While gradually increasing the set voltage,
Means for applying a voltage to a homogeneous liquid crystal cell showing a splay alignment; means for monitoring a time change of a cell capacity for each set voltage value when the applied voltage is increased; and The voltage value at which the capacitance value increases among the set voltage values of
A means for calculating a change rate of the cell capacity with respect to the voltage value; and a means for displaying and / or printing the change rate of the cell capacity calculated by the calculating means. Evaluation device. 11. While gradually lowering the set voltage,
Applying a voltage to a homogeneous liquid crystal cell showing bend alignment, and monitoring a time change of a cell capacity for each set voltage value when the applied voltage decreases, based on the monitoring result, the plurality of settings The voltage value at which the capacitance value decreases among the voltage values is obtained, and the rate of change of the cell capacitance with respect to this voltage value is used as an evaluation index of the transition time from the splay alignment to the bend alignment, and the cell is evaluated based on the evaluation index. A method for evaluating a splay-bend transition time, which comprises evaluating the ease of orientation transition. 12. While gradually decreasing the set voltage,
Means for applying a voltage to the homogeneous liquid crystal cell exhibiting the bend alignment; means for monitoring a time change of the cell capacity for each set voltage value when the applied voltage is lowered; and From the set voltage values of, find the voltage value at which the capacitance value decreases,
A means for calculating a change rate of the cell capacity with respect to the voltage value; and a means for displaying and / or printing the change rate of the cell capacity calculated by the calculating means. Evaluation device. 13. A step of applying a voltage to a homogeneous liquid crystal cell showing a splay alignment to form a bend alignment, and a step of forming a splay alignment by reducing a voltage applied to the liquid crystal cell showing a bend alignment, By visual observation, it was confirmed that the transition from the bend alignment to the splay alignment was performed, and the time required for the transition was used as an evaluation index of the transition time from the splay alignment to the bend alignment. A method for evaluating a splay-bend transition time, characterized by evaluating the ease of the spraying. 14. A means for forming a bend alignment by applying a voltage to a homogeneous liquid crystal cell showing a splay alignment, a means for forming a splay alignment by reducing the voltage applied to the liquid crystal cell showing a bend alignment, A microscope for inspecting an orientation state of the cell; an image analyzing means for analyzing an image obtained by the microscope to determine whether a color change has occurred on the entire surface of the liquid crystal cell; and a response to a determination signal from the image analyzing means. Means for displaying and / or printing the time required for the transition from the bend orientation to the splay orientation, and an apparatus for evaluating a splay-to-bend transition time.