Liquid crystal displays, electronic equipment, and diagnostic systems

Abstract

To provide a liquid crystal device that can observe a situation where the number of movable ions in liquid crystal gradually increases before the number of the movable ions rapidly increases.SOLUTION: A liquid crystal device comprises: a first electrode; a second electrode; a liquid crystal layer that is arranged between the first electrode and the second electrode; and a measuring circuit that supplies electric potential to the first electrode and the second electrode, and measures a first electrode electric potential being the electric potential of the first electrode. The measuring circuit, in a first period, supplies the electric potential to the first electrode and the second electrode so that the electric potential difference between the first electrode and the second electrode becomes a first electric potential difference, in a second period after the first period, supplies the electric potential to the first electrode and the second electrode so that the electric potential difference becomes a second electric potential difference having a polarity different from that of the first electric potential difference, and in a third period after the second period, stops supply of electric potential to the first electrode and supplies the same electric potential as in the second period to the second electrode.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a liquid crystal device, an electronic device, and a diagnostic system.

Background Art

[0002] Liquid crystal used in a liquid crystal device deteriorates due to the application of a DC voltage component for a long time. Further, when the liquid crystal device is used as a light valve of a projector, the liquid crystal also deteriorates due to chemical action by high-intensity light incidence and heat. The deterioration of the liquid crystal is, for example, a phenomenon in which mobile ions composed of anions and cations in the liquid crystal increase, and thereby the insulation property of the liquid crystal decreases. The decrease in the insulation property appears, for example, as a decrease in the voltage holding ratio of the liquid crystal, and in a liquid crystal panel, it is visually recognized as display defects such as stains and unevenness. Patent Document 1 discloses a method for accelerating the evaluation of such a liquid crystal deterioration phenomenon. In this method, a pair of electrodes for deterioration evaluation are provided outside the display area of the liquid crystal panel, and after performing an acceleration test on the liquid crystal panel for 100 hours, a voltage of 5V is applied between the electrodes for deterioration evaluation for 50 μs, and then, the voltage holding ratio after 16.7 ms is measured to evaluate the deterioration of the liquid crystal.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the research of the present applicant, for example, when an acceleration test involving high-intensity light incidence is performed using a liquid crystal panel, it has been found that there are a stage in which mobile ions in the liquid crystal increase relatively gently and a stage in which mobile ions in the liquid crystal increase rapidly thereafter. Further, when, for example, UV light other than visible light is incident on the liquid crystal panel, the chemical action is enhanced by the high energy of the UV light, and the deterioration of the liquid crystal progresses rapidly.

[0005] Furthermore, when the amount of mobile ions in the liquid crystal becomes significant, it becomes unavoidable that problems such as a decrease in the display quality of the liquid crystal panel will occur. Therefore, from the perspective of preventive maintenance, there was a demand to know when the liquid crystal panel was nearing the end of its lifespan, before it actually reached the end of its lifespan.

[0006] However, the method described in Patent Document 1 had the problem that it was difficult to perform preventive maintenance. Specifically, according to the applicant's verification results, in the method described in Patent Document 1, it was difficult to observe the gradual increase in mobile ions in the liquid crystal during the stage when the number of mobile ions in the liquid crystal increases relatively slowly. [Means for solving the problem]

[0007] A liquid crystal apparatus according to one aspect of the present invention comprises a first electrode, a second electrode, a liquid crystal layer disposed between the first electrode and the second electrode, and a measuring circuit that supplies potential to the first electrode and the second electrode, and measures the first electrode potential, which is the potential of the first electrode. The measuring circuit supplies potential to the first electrode and the second electrode, respectively, in a first period, such that the potential difference between the first electrode and the second electrode becomes a first potential difference. In a second period following the first period, it supplies potential to the first electrode and the second electrode, respectively, such that the potential difference becomes a second potential difference having a different polarity from the first potential difference. In a third period following the second period, it stops supplying potential to the first electrode and supplies the same potential to the second electrode as in the second period.

[0008] An electronic device according to one aspect of the present invention comprises a liquid crystal device according to the above aspect.

[0009] A diagnostic system according to one aspect of the present invention comprises a liquid crystal panel having a first electrode, a second electrode, and a liquid crystal layer disposed between the first electrode and the second electrode, and a diagnostic device having a measurement circuit that supplies potential to the first electrode and the second electrode and measures the potential of the first electrode, the first electrode potential, wherein the measurement circuit supplies potential to the first electrode and the second electrode in a first period such that the potential difference between the first electrode and the second electrode becomes a first potential difference, supplies potential to the first electrode and the second electrode in a second period after the first period such that the potential difference becomes a second potential difference having a different polarity from the first potential difference, and stops supplying potential to the first electrode and supplies the same potential to the second electrode as in the second period in a third period after the second period. [Brief explanation of the drawing]

[0010] [Figure 1] This is a plan view showing the schematic configuration of a liquid crystal panel used in the liquid crystal device of the first embodiment. [Figure 2] This is a cross-sectional view along the line H-H' in Figure 1. [Figure 3] This is an explanatory diagram showing the schematic configuration of the liquid crystal device of the first embodiment. [Figure 4] This is a schematic flowchart illustrating a method for measuring the physical properties of a liquid crystal layer. [Figure 5] This figure shows the temporal change in the potentials of the detection electrode and the common electrode in the first embodiment. [Figure 6] This figure shows the temporal change in the potential difference between the detection electrode and the common electrode during the execution of the first measurement process and the second measurement process in the first embodiment. [Figure 7] This figure shows the relationship between usage time and discharge characteristics. [Figure 8] This figure shows the relationship between usage time and measured values. [Figure 9] This figure shows the effect of the reverse sweep period. [Figure 10] This is an electrical characteristic diagram of the liquid crystal layer. [Figure 11]It is a diagram showing the relationship between the normalized transmittance of the liquid crystal layer and the voltage. [Figure 12] It is a diagram showing the effect of the charging period. [Figure 13] It is FIG. 1 showing the result of tracking the progress of deterioration of the liquid crystal layer. [Figure 14] It is FIG. 2 showing the result of tracking the progress of deterioration of the liquid crystal layer. [Figure 15] It is FIG. 1 showing the result of verifying the measurement reproducibility. [Figure 16] It is FIG. 2 showing the result of verifying the measurement reproducibility. [Figure 17] It is an explanatory diagram showing a schematic configuration of a liquid crystal device of the second embodiment. [Figure 18] It is an explanatory diagram showing a schematic configuration of a liquid crystal device of the third embodiment. [Figure 19] It is a diagram showing the temporal change of the potential difference between the detection electrode and the common electrode in the third embodiment. [Figure 20] It is an explanatory diagram showing a schematic configuration of a projection display device as an electronic device. [Figure 21] It is an explanatory diagram showing an example of a setting menu screen of a projection display device. [Figure 22] It is an explanatory diagram showing an example of a display screen for displaying the deterioration status of the liquid crystal layer.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, in each of the following figures, in order to make each member recognizable, the scale of each member may be different from the actual one. Further, in each of the following figures, as necessary, the XYZ axes are attached as coordinate axes orthogonal to each other, and in each figure, the direction indicated by each arrow along the axis is taken as the + direction, and the direction opposite to the + direction is taken as the - direction.

[0012] Furthermore, the +X direction is sometimes referred to as right or on the right side, and the -X direction as left or on the left side. The +Z direction is sometimes referred to as upward, and the -Z direction as downward, and viewing from the +Z direction is called a planar view or planar perspective. In addition, in the following explanation, for example, when referring to a substrate, the phrase "on the substrate" means that it is placed in contact with the substrate, placed on the substrate via another structure, or partially placed on the substrate and partially placed via another structure.

[0013] 1. First Embodiment 1.1. Overview of the configuration of the LCD panel 100 Figure 1 is a plan view showing the schematic configuration of a liquid crystal panel 100 used in the liquid crystal device 1000 of the first embodiment. For example, the liquid crystal panel 100 in this embodiment is an actively driven liquid crystal panel equipped with a TFT (Thin Film Transistor) 11 as a pixel switching element for each pixel P. This liquid crystal panel 100 is combined with a measurement circuit 200 described later to constitute the liquid crystal device 1000, and can be suitably used as an optical modulation device in electronic devices such as projection display devices.

[0014] The liquid crystal panel 100 comprises an element substrate 10 and a counter substrate 20. The configurations indicated by solid lines inside the outline of the counter substrate 20 are all configurations arranged between the counter substrate 20 and the element substrate 10.

[0015] The sealing material 14 is provided in a frame shape along the outer edge of the opposing substrate 20. The trim portion 27, shown as halftone dots, is made of a light-shielding film and is arranged inside the sealing material 14, along the outer edge of the display area E, surrounding the display area E. The sealing material 14 is an adhesive made of a photocurable resin or thermosetting resin, and includes a gap material such as glass fiber or glass beads to set the gap between the element substrate 10 and the opposing substrate 20 to a predetermined value.

[0016] In the display area E, pixels P are arranged in a matrix. Peripheral circuits such as the scan line drive circuit 24 and the pre-charge circuit 25 are arranged in the peripheral area F between the display area E and the sealing material 14. In addition, a data line drive circuit 23 and multiple external connection terminals 18 are arranged in the portion of the element substrate 10 outside the sealing material 14 that protrudes downward in the -Y direction from the opposing substrate 20 in the drawing.

[0017] Inter-substrate conductive portions 17 are arranged at the four corners of the opposing substrate 20 to provide electrical conductivity between the element substrate 10 and the opposing substrate 20.

[0018] Figure 2 is a cross-sectional view showing the schematic configuration of the liquid crystal panel 100 along the line H-H' in Figure 1. The element substrate 10 and the opposing substrate 20 are arranged with a sealing material 14 in between, and the liquid crystal layer 5 is placed between the element substrate 10 and the opposing substrate 20.

[0019] The element substrate 10 comprises, between the substrate 10a and the liquid crystal layer 5, a light-transmitting pixel electrode 9a provided for each pixel P, a TFT 11 as a pixel switching element arranged corresponding to the pixel electrode 9a, and a first alignment film 12 arranged to cover the pixel electrode 9a.

[0020] The opposing substrate 20 includes a trim portion 27, a common electrode 21, and a second alignment film 22 positioned between the substrate 20a and the liquid crystal layer 5, covering the common electrode 21.

[0021] The trim portion 27 is positioned to overlap with the scan line drive circuit 24 in a planar manner. The trim portion 27 blocks light L from an unillustrated laser light source that is incident from the opposing substrate 20 side, preventing it from entering the peripheral circuit including the scan line drive circuit 24, thereby preventing the peripheral circuit from malfunctioning due to the light L.

[0022] The pixel electrode 9a and the common electrode 21 are formed from a transparent conductive material such as ITO (Indium Tin Oxide). The substrates 10a and 20a are translucent substrates, such as a glass substrate or a quartz substrate. The first alignment film 12 and the second alignment film 22 are formed from an inorganic material such as silicon oxide. The liquid crystal layer 5 is composed of a liquid crystal having negative dielectric anisotropy, for example.

[0023] 1.2. Overview of the configuration of the liquid crystal display unit 1000 Figure 3 is an explanatory diagram showing the schematic configuration of the liquid crystal display device 1000. The liquid crystal display device 1000 comprises a liquid crystal panel 100 and a measurement circuit 200. Although omitted in Figures 1 and 2, the liquid crystal panel 100 includes a detection electrode 30 located in the peripheral region F between the sealing material 14 and the display area E. The detection electrode 30 is one of the electrodes provided on the element substrate 10 and is formed of a transparent conductive material such as ITO, similar to the pixel electrode 9a. The detection electrode 30 is positioned directly below the trim portion 27, for example, surrounding the display area E. Note that only a portion of the trim portion 27 is shown for illustrative purposes. Also, the sealing material 14 is simplified in the illustration by being shown as being applied in a generally frame-like shape.

[0024] The detection electrode 30 may be formed as a so-called solid film pattern, or it may be formed by linking together a plurality of pixel electrodes 9a. When the detection electrode 30 is formed of an ITO film, an aluminum-based lower wiring layer 31 placed beneath the ITO film may be added as auxiliary wiring to improve the potential response of the detection electrode 30. The detection electrode 30 is electrically connected to the lower wiring layer 31 via a plurality of contact holes 32.

[0025] The detection electrode 30 is electrically connected to a first electrode connection terminal 18a, which is one of a plurality of external connection terminals 18. The detection electrode 30 is electrically connected to the measurement circuit 200 via the first electrode connection terminal 18a. The detection electrode 30 is also electrically connected to a continuity test terminal 19. The continuity test terminal 19 is located on the surface of the element substrate 10 in the region between the external connection terminal 18 and the opposing substrate 20. By measuring the electrical resistance between the first electrode connection terminal 18a and the continuity test terminal 19, the electrical connection between the first electrode connection terminal 18a and the detection electrode 30 can be inspected.

[0026] The inter-substrate conductive sections 17 are positioned corresponding to the four corners of the opposing substrate 20 and are electrically connected to each other via a common potential line 16. The common potential line 16 is electrically connected to the second electrode connection terminals 18b, which are located, for example, at the left end and the right end of a plurality of external connection terminals 18. That is, the common electrode 21 of the opposing substrate 20 is electrically connected to the second electrode connection terminal 18b via the common potential line 16 and the inter-substrate conductive sections 17. The common electrode 21 is electrically connected to the measurement circuit 200 via the second electrode connection terminal 18b.

[0027] As can be understood from the above configuration, in the peripheral region F of the liquid crystal panel 100, the liquid crystal layer 5 is positioned between the detection electrode 30 and the common electrode 21. The liquid crystal panel 100 also includes pixel electrodes 9a provided in the display region E, and the detection electrode 30 is provided outside the display region E. In this embodiment, the detection electrode 30 corresponds to the first electrode, and the common electrode 21 corresponds to the second electrode.

[0028] The measurement circuit 200 supplies potential to the detection electrode 30 and the common electrode 21, respectively, and measures the detection electrode potential Vd, which is the potential of the detection electrode 30. The measurement circuit 200 includes a measurement potential generation circuit 40, a common potential generation circuit 41, a level shifter 42, an amplification circuit 43, an A / D converter 44, a central control circuit 45, a measurement value storage circuit 46, a display information generation circuit 47, a first switch SW1, a second switch SW2, a third switch SW3, a fourth switch SW4, a fifth switch SW5, a first capacitor C1, a second capacitor C2, a common electrode line L1, a ground potential line L2, and a first node N1.

[0029] The common electrode wire L1 is electrically connected to the second electrode connection terminal 18b of the liquid crystal panel 100. In other words, the common electrode wire L1 is electrically connected to the common electrode 21 via the second electrode connection terminal 18b. In this embodiment, the common electrode wire L1 corresponds to the second electrode wire.

[0030] The ground potential line L2 is a wire to which the ground potential is applied. The ground potential line L2 is electrically connected at one point to the ground of the digital circuit system within the liquid crystal device 1000. This configuration has the effect of suppressing measurement noise caused by the digital circuit system during the measurement described later. The ground potential line L2 is electrically connected to the common electrode line L1 via the second capacitor C2. In other words, the second capacitor C2 is electrically connected between the common electrode line L1 and the ground potential line L2. For example, the second capacitor C2 has a capacitance value of 0.1 μF or more. The potential of the common electrode 21 is stabilized by the second capacitor C2. Therefore, during the measurement described later, the measurement noise that the detection electrode 30, which has coupling capacitance mainly due to the liquid crystal layer 5, receives with respect to the common electrode 21 is suppressed. In addition, in the liquid crystal device 1000, the liquid crystal panel 100 is held by a holder 110 made of a conductor, and the ground potential line L2 is electrically connected to the holder 110. By electrically connecting the ground potential line L2 to the holder 110, the measurement noise experienced by the detection electrode 30 during the measurement described later is suppressed.

[0031] The first node N1 in the measurement circuit 200 is electrically connected to the first electrode connection terminal 18a of the liquid crystal panel 100. In other words, the first node N1 is electrically connected to the detection electrode 30 via the first electrode connection terminal 18a. The first node N1 is electrically connected to the ground potential line L2 via the first switch SW1. The first node N1 is electrically connected to the output terminal of the measurement potential generation circuit 40 via the second switch SW2. The first node N1 is electrically connected to the ground potential line L2 via the first capacitor C1. In other words, the first capacitor C1 is electrically connected between the first node N1 and the ground potential line L2. For example, the first capacitor C1 has a capacitance value of about 1nF to 10nF. The first capacitor C1 suppresses the measurement noise that the detection electrode 30 receives during measurement, which will be described later. In addition, the detection sensitivity to the increase in mobile ions can be adjusted by the capacitance value of the first capacitor C1.

[0032] The state of the first switch SW1 is controlled by the first control signal S1 output from the central control circuit 45. For example, the first control signal S1 is a logic signal with an amplitude of 5V output from the central control circuit 45, and when the logic is "H", the first switch SW1 is turned ON. The state of the second switch SW2 is controlled by the second control signal S2 output from the central control circuit 45. For example, the second control signal S2 is a logic signal with an amplitude of 5V output from the central control circuit 45, and when the logic is "H", the second switch SW2 is turned ON. In other words, both the first switch SW1 and the second switch SW2 are controlled to be ON by the first voltage (5V).

[0033] The common electrode wire L1 is electrically connected to the ground potential wire L2 via the third switch SW3. The common electrode wire L1 is electrically connected to the output terminal of the measurement potential generation circuit 40 via the fourth switch SW4. The common electrode wire L1 is electrically connected to the output terminal of the common potential generation circuit 41 via the fifth switch SW5.

[0034] The state of the third switch SW3 is controlled by a third control signal S3 output from the central control circuit 45 via the level shifter 42. For example, the central control circuit 45 outputs a logic signal with an amplitude of 5V as the third control signal S3, but this logic signal is converted by the level shifter 42 to a logic signal with an amplitude of, for example, 15V. In other words, the level shifter 42 outputs a third control signal S3 with an amplitude of 15V, and when the logic is "H", the third switch SW3 is turned ON.

[0035] The state of the fourth switch SW4 is controlled by a fourth control signal S4 output from the central control circuit 45 via the level shifter 42. For example, the central control circuit 45 outputs a logic signal with an amplitude of 5V as the fourth control signal S4, but this logic signal is converted by the level shifter 42 to a logic signal with an amplitude of, for example, 15V. In other words, the level shifter 42 outputs a fourth control signal S4 with an amplitude of 15V, and when the logic is "H", the fourth switch SW4 is turned ON.

[0036] The state of the fifth switch SW5 is controlled by the fifth control signal S5 output from the central control circuit 45 via the level shifter 42. For example, the central control circuit 45 outputs a logic signal with an amplitude of 5V as the fifth control signal S5, but this logic signal is converted by the level shifter 42 to a logic signal with an amplitude of, for example, 15V. In other words, the level shifter 42 outputs the fifth control signal S5 with an amplitude of 15V, and when the logic is "H", the fifth switch SW5 is turned ON. As described above, the third switch SW3, the fourth switch SW4, and the fifth switch SW5 are controlled to be ON by a second voltage (15V) which is higher than the first voltage (5V).

[0037] The measurement potential generation circuit 40 outputs a measurement potential Vs that corresponds to the reference voltage Vsref output from the central control circuit 45. For example, the measurement potential generation circuit 40 outputs a measurement potential Vs having the same polarity and absolute value as the reference voltage Vsref. That is, the measurement potential Vs output from the measurement potential generation circuit 40 is variably controlled by the central control circuit 45. Such a measurement potential generation circuit 40 can be realized, for example, by a voltage follower to which the reference voltage Vsref is input.

[0038] The common potential generation circuit 41 outputs a predetermined common potential Vcom. For example, the common potential Vcom is 5V when the liquid crystal panel 100 is normally driven.

[0039] The amplification circuit 43 amplifies the potential of the first node N1, which is electrically connected to the detection electrode 30. In the following description, the potential of the first node N1 may be referred to as the first node potential. The amplification circuit 43 outputs the amplified first node potential to the A / D converter 44. The A / D converter 44 converts the first node potential amplified by the amplification circuit 43 into a digital value. The A / D converter 44 outputs the digital value of the first node potential to the central control circuit 45 as a measured value of the detection electrode potential Vd. Thus, in this embodiment, the amplification circuit 43 and the A / D converter 44 correspond to a potential measurement circuit that measures the potential of the first node N1 as the detection electrode potential Vd and outputs the measured value of the detection electrode potential Vd to the central control circuit 45.

[0040] For example, the amplification circuit 43 is a non-inverting amplification circuit using an operational amplifier. The ground terminal of the amplification circuit 43 is electrically connected to the ground potential line L2 to which the holder 110, the first capacitor C1, and the second capacitor C2 are electrically connected. By electrically connecting the ground terminal of the amplification circuit 43 to the ground potential line L2 in this way, it is possible to suppress the superposition of noise components associated with the operation of the digital circuit system constituting the measurement circuit 200 onto the measured value of the detection electrode potential Vd. As can be understood from the configuration of the amplification circuit 43 described above, the measured value of the detection electrode potential Vd obtained from the A / D converter 44 is a value corresponding to the potential difference between the first node potential, i.e., the potential of the detection electrode 30, and the ground potential.

[0041] The central control circuit 45 controls each circuit included in the measurement circuit 200 when measuring the degradation status of the liquid crystal layer 5. Specifically, the central control circuit 45 outputs a reference voltage Vsref to the measurement potential generation circuit 40. The central control circuit 45 outputs a first control signal S1 to the first switch SW1 and a second control signal S2 to the second switch SW2. The central control circuit 45 outputs the third control signal S3 to the fifth control signal S5 to the third switch SW3 to the fifth switch SW5 via the level shifter 42. Thus, in this embodiment, the central control circuit 45 corresponds to a control circuit that outputs a reference voltage Vsref to the measurement potential generation circuit 40 and controls the first switch SW1 to the fifth switch SW5.

[0042] The central control circuit 45 stores the measured value of the detection electrode potential Vd output from the A / D converter 44 in the measurement value storage circuit 46. The measurement value storage circuit 46 stores the measured value of the detection electrode potential Vd according to the control of the central control circuit 45. The central control circuit 45 includes a determination circuit 45a. The determination circuit 45a determines the deterioration status of the liquid crystal layer 5 based on the measured value stored in the measurement value storage circuit 46. The display information generation circuit 47 generates display information for the deterioration status of the liquid crystal layer 5 based on the measured value and the determination result.

[0043] Furthermore, each circuit constituting the measurement circuit 200 may be configured such that some or all of the functions realized by each circuit are realized by, for example, the control program of the central control circuit 45. Also, the measurement circuit 200 may be a single IC (Integrated Circuit) or it may be divided into multiple ICs.

[0044] Although not shown in the diagram, the liquid crystal device 1000 may also include a panel control circuit for controlling the liquid crystal panel 100 in addition to the measurement circuit 200 described above. The panel control circuit is a circuit that performs the normal operation of the liquid crystal panel 100. In other words, the panel control circuit is a circuit that operates the liquid crystal panel 100 as an optical modulator. The panel control circuit outputs timing signals, image signals, and control signals, etc., to the data line drive circuit 23, the scan line drive circuit 24, and the precharge circuit 25 via the external connection terminals 18 of the liquid crystal panel 100, excluding the first electrode connection terminal 18a and the second electrode connection terminal 18b.

[0045] The data line drive circuit 23, the scan line drive circuit 24, and the precharge circuit 25 are controlled by the panel control circuit. As a result, a scanning signal is supplied to each scan line (not shown) to switch the TFT 11 of each pixel P to the ON state, and the potential applied to the pixel electrode 9a of each pixel P is supplied to each data line (not shown). Consequently, the light transmittance of each pixel P is determined by the potential difference between the pixel electrode 9a and the common electrode 21. In this way, the light transmittance of each pixel P is controlled by the panel control circuit, and the state in which the liquid crystal panel 100 operates as an optical modulator and displays an image is referred to as the normal operation of the liquid crystal panel 100. Furthermore, in the normal operation when displaying an image, AC drive is performed at each pixel P, and the polarity of the applied voltage to the liquid crystal layer 5 of each pixel P is reversed every frame period, which is the time when the transmittance state of the pixels P included in the display area E is updated.

[0046] During normal operation of the liquid crystal panel 100, the central control circuit 45 of the measurement circuit 200 controls the first switch SW1 to the fourth switch SW4 to the OFF state and the fifth switch SW5 to the ON state. As a result, during normal operation of the liquid crystal panel 100, the common potential Vcom output from the common potential generation circuit 41 of the measurement circuit 200 is supplied to the common electrode 21 of the liquid crystal panel 100.

[0047] In the liquid crystal display device 1000, the measurement circuit 200 and the panel control circuit may be arranged on the same substrate, or the measurement circuit 200 and the panel control circuit may be arranged on multiple different substrates. For example, the substrate on which the measurement circuit 200 and the panel control circuit are arranged may be a rigid substrate or an FPC (Flexible Printed Circuits) substrate.

[0048] 1.3. Overview of the method for measuring the physical properties of the liquid crystal layer 5 Figure 4 is a schematic flowchart showing the method for measuring the physical properties of the liquid crystal layer 5 of the liquid crystal panel 100. The method for measuring the physical properties of the liquid crystal layer 5 will be explained below with reference to Figure 4.

[0049] As shown in Figure 4, in step S10, when a predetermined event occurs, the liquid crystal device 1000 switches from a normal drive mode, which performs normal operation, to a measurement mode, which performs physical property measurement of the liquid crystal layer 5, and starts measuring the physical properties of the liquid crystal layer 5. Here, predetermined events include turning the power on and off of the projection display device using the liquid crystal device 1000, and a measurement instruction from the maintenance menu selection on the projection display device using the liquid crystal device 1000. When these events occur, a measurement start command is sent from the projection display device. When the central control circuit 45 of the measurement circuit 200 receives the measurement start command from the projection display device, it starts measuring the physical properties of the liquid crystal layer 5.

[0050] Step S10 illustrates the concept of a measurement mode transition event. In reality, for example, an instruction from the maintenance menu selection is an interrupt process, and the projection display device using the liquid crystal device 1000 is powered on. Furthermore, the measurement mode transition event does not force any of the exemplified "maintenance menu selection," "power on," and "power off." In addition, in this invention, the physical properties of the liquid crystal layer 5 are measured, for example, when the light source of the projection display device is not lit. Alternatively, the measurement is performed in a configuration where light from the light source is shielded by a mechanical light-shielding mechanism. When the physical properties of the liquid crystal layer 5 are measured, if the light source of the projection display device is not lit, no display problems occur in the projection display device.

[0051] When the central control circuit 45 receives a measurement start command, it first resets the count value K, which indicates the number of times the measurement process described later has been executed, to "0" (step S11). Next, the central control circuit 45 adds "1" to the count value K (step S12). Then, the central control circuit 45 determines whether the count value K is odd or not (step S13).

[0052] The central control circuit 45 executes a first measurement process (step S14) if the count value K is odd (step S13: Yes). On the other hand, the central control circuit 45 executes a second measurement process (step S15) if the count value K is even (step S13: No). The specific details of the first and second measurement processes will be described later.

[0053] The central control circuit 45 determines whether the count value K is equal to the upper limit value Kmax after executing the first or second measurement process (step S16). If the count value K is not equal to the upper limit value Kmax (step S16: No), the central control circuit 45 returns to step S12. On the other hand, if the count value K is equal to the upper limit value Kmax (step S16: Yes), the central control circuit 45 proceeds to step S17, which will be described later. The upper limit value Kmax is set in advance in the control program of the measurement circuit 200. Alternatively, the value may be set by an input means, which is not shown in the diagram. The input means may be, for example, an input key provided on the measurement circuit 200, or a PC connected by wired or wireless connection to the projection display device using the liquid crystal display device 1000. If the upper limit value Kmax is set to 2 or more, the average value of multiple measurement results from the first or second measurement process can be calculated to obtain data with good reproducibility. In the detailed measurement examples described later, the upper limit Kmax is 20, and the average value of 10 first measurement processes is calculated.

[0054] As can be understood from the description of the processes from steps S11 to S16 above, the central control circuit 45 alternately executes the first measurement process and the second measurement process until the count value K becomes equal to the upper limit value Kmax. For example, if the upper limit value Kmax is "10", the first measurement process and the second measurement process are each executed 5 times. The first measurement process and the second measurement process will be described in detail below with reference to Figures 5 and 6.

[0055] Figure 5 shows the temporal changes in the potentials of the detection electrode 30 and the common electrode 21 during the execution of the first and second measurement processes. In Figure 5, the horizontal axis represents time, and the vertical axis represents voltage. In Figure 5, for the sake of explanation, the potentials of each electrode are shown differently from the actual values. For example, the value of 1.2V on the vertical axis is drawn at approximately half the value of 5V. In Figure 5, the detection electrode potential Vd, which is the potential of the detection electrode 30, is shown by a solid line except for a few parts, and the common electrode potential Vc, which is the potential of the common electrode 21, is shown by a dotted line.

[0056] Figure 6 shows the temporal change in the potential difference between the detection electrode 30 and the common electrode 21 during the execution of the first and second measurement processes. In Figure 6, the horizontal axis represents time, and the vertical axis represents the voltage of the detection electrode 30 relative to the common electrode 21. In other words, it is the applied voltage of the liquid crystal layer 5 at the detection electrode 30. In Figure 6, the polarity of the potential difference when the detection electrode potential Vd is larger than the common electrode potential Vc is defined as positive polarity.

[0057] In Figures 5 and 6, the first measurement process is performed during the period T10 from time t1 to time t5. In the following description, the period T10 during which the first measurement process is performed may be referred to as the first measurement period T10. The first measurement period T10 includes the first reverse sweep period T1, the first relaxation period T2, the first charging period T3, and the first discharge period T4. The first reverse sweep period T1 is the period from time t1 to time t2. The first relaxation period T2 is the period from time t2 to time t3. The first charging period T3 is the period from time t3 to time t4. The first discharge period T4 is the period from time t4 to time t5.

[0058] During the first reverse sweep period T1, the measurement circuit 200 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes the first potential difference Vp1.

[0059] Specifically, during the first reverse sweep period T1, the central control circuit 45 outputs a reference voltage Vsref of, for example, +5V to the measurement potential generation circuit 40. As a result, a measurement potential Vs of +5V is output from the measurement potential generation circuit 40. Also during the first reverse sweep period T1, the central control circuit 45 controls the second switch SW2 and the third switch SW3 to the ON state, and controls the first switch SW1, the fourth switch SW4, and the fifth switch SW5 to the OFF state.

[0060] During the first reverse sweep period T1, the central control circuit 45 controls the first switch SW1 to the fifth switch SW5 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the detection electrode 30 and electrically connecting the ground potential line L2 to the common electrode 21. As a result, during the first reverse sweep period T1, a measurement potential Vs of +5V is supplied to the detection electrode 30, and the ground potential, i.e., 0V, is supplied to the common electrode 21. Consequently, as shown in Figure 5, during the first reverse sweep period T1, the detection electrode potential Vd becomes +5V and the common electrode potential Vc becomes 0V. Also, as shown in Figure 6, during the first reverse sweep period T1, the potential difference between the detection electrode 30 and the common electrode 21 becomes the first potential difference Vp1, i.e., +5V.

[0061] Thus, during the first reverse sweep period T1, the measurement circuit 200 supplies a measurement potential Vs of +5V to the detection electrode 30 and a ground potential to the common electrode 21, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a first potential difference Vp1 of +5V. In this embodiment, the first reverse sweep period T1 corresponds to the first period.

[0062] During the first relaxation period T2 between the first reverse sweep period T1 and the first charging period T3, the measurement circuit 200 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a third potential difference Vp3 having the same polarity as the first potential difference Vp1 and an absolute value smaller than the absolute value of the first potential difference Vp1.

[0063] Specifically, during the first relaxation period T2, the central control circuit 45 outputs a reference voltage Vsref of, for example, +1.2V to the measurement potential generation circuit 40. As a result, a measurement potential Vs of +1.2V is output from the measurement potential generation circuit 40. Also during the first relaxation period T2, the central control circuit 45 controls the second switch SW2 and the third switch SW3 to the ON state, and controls the first switch SW1, the fourth switch SW4, and the fifth switch SW5 to the OFF state.

[0064] During the first relaxation period T2, the central control circuit 45 controls the first switch SW1 to the fifth switch SW5 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the detection electrode 30 and electrically connecting the ground potential line L2 to the common electrode 21. As a result, during the first relaxation period T2, a measurement potential Vs of +1.2V is supplied to the detection electrode 30 and the ground potential is supplied to the common electrode 21. Consequently, as shown in Figure 5, during the first relaxation period T2, the detection electrode potential Vd becomes +1.2V and the common electrode potential Vc becomes 0V. Also, as shown in Figure 6, during the first relaxation period T2, the potential difference between the detection electrode 30 and the common electrode 21 becomes the third potential difference Vp3, i.e., +1.2V.

[0065] Thus, during the first relaxation period T2, the measurement circuit 200 supplies a measurement potential Vs of +1.2V to the detection electrode 30 and a ground potential to the common electrode 21, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a third potential difference Vp3 (+1.2V) having the same polarity as the first potential difference Vp1 and an absolute value smaller than the absolute value of the first potential difference Vp1. In this embodiment, the first relaxation period T2 corresponds to the fourth period.

[0066] During the first charging period T3, which is after the first reverse sweep period T1 and after the first relaxation period T2, the measurement circuit 200 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a second potential difference Vp2 having a different polarity from the first potential difference Vp1.

[0067] Specifically, during the first charging period T3, the central control circuit 45 outputs a reference voltage Vsref of, for example, +1.2V to the measurement potential generation circuit 40. As a result, a measurement potential Vs of +1.2V is output from the measurement potential generation circuit 40. Also during the first charging period T3, the central control circuit 45 controls the first switch SW1 and the fourth switch SW4 to the ON state, and controls the second switch SW2, the third switch SW3, and the fifth switch SW5 to the OFF state.

[0068] During the first charging period T3, the central control circuit 45 controls the first switch SW1 to the fifth switch SW5 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the common electrode 21 and electrically connecting the ground potential line L2 to the detection electrode 30. As a result, during the first charging period T3, the ground potential is supplied to the detection electrode 30 and the measurement potential Vs of +1.2V is supplied to the common electrode 21. Consequently, as shown in Figure 5, during the first charging period T3, the detection electrode potential Vd becomes +0V and the common electrode potential Vc becomes +1.2V. Also, as shown in Figure 6, during the first charging period T3, the potential difference between the detection electrode 30 and the common electrode 21 becomes the second potential difference Vp2, i.e., -1.2V.

[0069] Thus, during the first charging period T3, the measurement circuit 200 supplies a measurement potential Vs of +1.2V to the common electrode 21 and a ground potential to the detection electrode 30, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a second potential difference Vp2 (-1.2V) having a different polarity from the first potential difference Vp1. In this embodiment, the first charging period T3 corresponds to the second period.

[0070] During the first discharge period T4 following the first charging period T3, the measurement circuit 200 stops supplying potential to the detection electrode 30 and supplies the same potential to the common electrode 21 as during the first charging period T3, and measures the detection electrode potential Vd at least once, for example, at the end of the first discharge period T4.

[0071] Specifically, during the first discharge period T4, the central control circuit 45 outputs a reference voltage Vsref of, for example, +1.2V to the measurement potential generation circuit 40. As a result, a measurement potential Vs of +1.2V is output from the measurement potential generation circuit 40. Also during the first discharge period T4, the central control circuit 45 controls the fourth switch SW4 to the ON state, and controls the first switch SW1, the second switch SW2, the third switch SW3, and the fifth switch SW5 to the OFF state.

[0072] During the first discharge period T4, the central control circuit 45 controls the first switch SW1 to the fifth switch SW5 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the common electrode 21 and electrically disconnecting the ground potential line L2 from the detection electrode 30. As a result, during the first discharge period T4, the common electrode 21 continues to be supplied with a measurement potential Vs of +1.2V, but the potential supply to the detection electrode 30 stops, causing the liquid crystal layer 5 to discharge the charge accumulated during the first charging period T3. Consequently, as shown in Figure 5, during the first discharge period T4, the detection electrode potential Vd1 gradually changes from the ground potential of 0V towards the potential supplied to the common electrode 21 (+1.2V), reaching potential Vd1 at time t5. The value of the detection electrode potential Vd1 depends on the amount of mobile ions contained in the liquid crystal layer 5. Therefore, as will be described later, the degradation status of the liquid crystal layer 5 can be determined by measuring the detection electrode potential Vd1 at the end of the first discharge period T4. As shown in Figure 6, the detection electrode potential Vd1 at the end of the first discharge period T4 corresponds to the potential difference V3 with respect to the common electrode 21.

[0073] The central control circuit 45 measures the detection electrode potential Vd1 at time t5 when the first discharge period T4 ends, for example. Specifically, the detection electrode potential Vd1 is amplified by the amplification circuit 43, and the output of the amplification circuit 43 is input to the A / D converter 44. The central control circuit 45 acquires the digital value output from the A / D converter 44 at time t5 as the measured value of the detection electrode potential Vd1. The central control circuit 45 stores the measured value of the detection electrode potential Vd1 obtained at time t5 in the measured value storage circuit 46.

[0074] Thus, during the first discharge period T4, the measurement circuit 200 stops supplying potential to the detection electrode 30 and supplies the common electrode 21 with a measurement potential Vs of +1.2V, the same as during the first charging period T3, and measures the detection electrode potential Vd1 at least once, for example, at time t5 when the first discharge period T4 ends. In this embodiment, the first discharge period T4 corresponds to the third period.

[0075] The above is a description of the first measurement process. The first reverse sweep period T1 is preferably longer than the duration of one frame in the display area E. For example, if the duration of one frame is approximately 16 milliseconds, the first reverse sweep period T1 is 20 milliseconds or longer. In addition, although the above description illustrates the case where the first potential difference Vp1 in the first reverse sweep period T1 is +5V, the absolute value of the first potential difference Vp1 is preferably greater than or equal to the maximum applied voltage of the liquid crystal layer 5 of the pixel P during normal driving. In other words, the absolute value of the first potential difference Vp1 is preferably greater than or equal to the maximum applied voltage of the liquid crystal layer 5 in the display area E. The reasons for setting the length of the first reverse sweep period T1 and the absolute value of the first potential difference Vp1 as described above will be explained later.

[0076] The first charging period T3 is preferably shorter than the duration of one frame in the display area E. For example, if the duration of one frame is approximately 16 msec, the first charging period T3 is 5 msec. In the above description, the absolute value of the second potential difference Vp2 in the first charging period T3 is given as an example of 1.2 V, but it is preferable that the absolute value of the second potential difference Vp2 is greater than 0 V and smaller than the threshold voltage Vth of the liquid crystal layer 5. For example, in a VA (Vertical Alignment) liquid crystal panel 100, when the gap is about 2.6 μm, the threshold voltage Vth of the liquid crystal layer 5 is approximately 2.1 V. The threshold voltage Vth of the liquid crystal layer 5 is the driving voltage at which the transmittance or brightness of the liquid crystal layer 5 is approximately 10% at its maximum gradation ratio, and more preferably, it is the voltage just before the liquid crystal molecules begin to move, or the voltage just before the orientation state of the liquid crystal molecules begins to change. In this embodiment, the threshold voltage Vth of the liquid crystal layer 5 is defined as described above because it is a normally black type liquid crystal panel 100. In the case of a normally white type liquid crystal panel 100, for example, the threshold voltage Vth of the liquid crystal layer 5 can be defined as the driving voltage at which the transmittance or brightness of the liquid crystal layer 5 reaches approximately 90% of its maximum grayscale ratio. The reasons for setting the length of the first charging period T3 and the absolute value of the second potential difference Vp2 as described above will be explained later.

[0077] Furthermore, the above explanation exemplified a case where the absolute value of the third potential difference Vp3 during the first relaxation period T2 is the same as the absolute value of the second potential difference Vp2, which is 1.2V. However, it is preferable that the absolute value of the third potential difference Vp3 be greater than 0V and less than the threshold voltage Vth of the liquid crystal layer 5. The reason for setting the absolute value of the third potential difference Vp3 as described above will be explained later. Note that the absolute value of the third potential difference Vp3 does not necessarily have to be the same as the absolute value of the second potential difference Vp2. Also, the potential difference may change gradually with respect to time during the process in which the potential difference changes from the first potential difference Vp1 to the third potential difference Vp3.

[0078] Next, I will explain the second measurement process. In Figures 5 and 6, the second measurement process is performed during the period T20 from time t5 to time t9. In the following description, the period T20 during which the second measurement process is performed may be referred to as the second measurement period T20. The second measurement period T20 includes the second reverse sweep period T5, the second relaxation period T6, the second charging period T7, and the second discharge period T8. The second reverse sweep period T5 is the period from time t5 to time t6. The second relaxation period T6 is the period from time t6 to time t7. The second charging period T7 is the period from time t7 to time t8. The second discharge period T8 is the period from time t8 to time t9.

[0079] During the second reverse sweep period T5 following the first discharge period T4, the measurement circuit 200 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a fourth potential difference Vp4, which has a different polarity from the first potential difference Vp1 and the same absolute value as the first potential difference Vp1.

[0080] Specifically, during the second reverse sweep period T5, the central control circuit 45 outputs a reference voltage Vsref of, for example, +5V to the measurement potential generation circuit 40. As a result, a measurement potential Vs of +5V is output from the measurement potential generation circuit 40. Also, during the second reverse sweep period T2, the central control circuit 45 controls the first switch SW1 and the fourth switch SW4 to the ON state, and controls the second switch SW2, the third switch SW3, and the fifth switch SW5 to the OFF state.

[0081] During the second reverse sweep period T5, the central control circuit 45 controls the first switch SW1 to the fifth switch SW5 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the common electrode 21 and electrically connecting the ground potential line L2 to the detection electrode 30. As a result, during the second reverse sweep period T5, a measurement potential Vs of +5V is supplied to the common electrode 21 and the ground potential is supplied to the detection electrode 30. Consequently, as shown in Figure 5, during the second reverse sweep period T5, the detection electrode potential Vd becomes 0V and the common electrode potential Vc becomes +5V. Also, as shown in Figure 6, during the second reverse sweep period T5, the potential difference between the detection electrode 30 and the common electrode 21 becomes the fourth potential difference Vp4, i.e., -5V.

[0082] Thus, during the second reverse sweep period T5, the measurement circuit 200 supplies a measurement potential Vs of +5V to the common electrode 21 and a ground potential to the detection electrode 30, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a fourth potential difference Vp4 (-5V) which has a different polarity from the first potential difference Vp1 and the same absolute value as the first potential difference Vp1. In this embodiment, the second reverse sweep period T5 corresponds to the fifth period.

[0083] During the second relaxation period T6 between the second reverse sweep period T5 and the second charging period T7, the measurement circuit 200 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a sixth potential difference Vp6 having the same polarity as the fourth potential difference Vp4 and an absolute value smaller than the absolute value of the fourth potential difference Vp4.

[0084] Specifically, during the second relaxation period T6, the central control circuit 45 outputs a reference voltage Vsref of, for example, +1.2V to the measurement potential generation circuit 40. As a result, a measurement potential Vs of +1.2V is output from the measurement potential generation circuit 40. Also during the second relaxation period T6, the central control circuit 45 controls the first switch SW1 and the fourth switch SW4 to the ON state, and controls the second switch SW2, the third switch SW3, and the fifth switch SW5 to the OFF state.

[0085] During the second relaxation period T6, the central control circuit 45 controls the first switch SW1 to the fifth switch SW5 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the common electrode 21 and electrically connecting the ground potential line L2 to the detection electrode 30. As a result, during the second relaxation period T6, a measurement potential Vs of +1.2V is supplied to the common electrode 21 and the ground potential is supplied to the detection electrode 30. Consequently, as shown in Figure 5, during the second relaxation period T6, the detection electrode potential Vd becomes 0V and the common electrode potential Vc becomes +1.2V. Also, as shown in Figure 6, during the second relaxation period T6, the potential difference between the detection electrode 30 and the common electrode 21 becomes the sixth potential difference Vp6, i.e., -1.2V.

[0086] Thus, during the second relaxation period T6, the measurement circuit 200 supplies a measurement potential Vs of +1.2V to the common electrode 21 and a ground potential to the detection electrode 30, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a sixth potential difference Vp6 (-1.2V) which has the same polarity as the fourth potential difference Vp4 and an absolute value smaller than the absolute value of the fourth potential difference Vp4. In this embodiment, the second relaxation period T6 corresponds to the eighth period.

[0087] After the second reverse sweep period T5 and during the second charging period T7 after the second relaxation period T6, the measurement circuit 200 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a fifth potential difference Vp5 having a different polarity from the fourth potential difference Vp4.

[0088] Specifically, during the second charging period T7, the central control circuit 45 outputs a reference voltage Vsref of, for example, +1.2V to the measurement potential generation circuit 40. As a result, a measurement potential Vs of +1.2V is output from the measurement potential generation circuit 40. Also during the second charging period T7, the central control circuit 45 controls the second switch SW2 and the third switch SW3 to the ON state, and controls the first switch SW1, the fourth switch SW4, and the fifth switch SW5 to the OFF state.

[0089] During the second charging period T7, the central control circuit 45 controls the first switch SW1 to the fifth switch SW5 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the detection electrode 30 and electrically connecting the ground potential line L2 to the common electrode 21. As a result, during the second charging period T7, the ground potential is supplied to the common electrode 21 and the measurement potential Vs of +1.2V is supplied to the detection electrode 30. Consequently, as shown in Figure 5, during the second charging period T7, the detection electrode potential Vd becomes +1.2V and the common electrode potential Vc becomes 0V. Also, as shown in Figure 6, during the second charging period T7, the potential difference between the detection electrode 30 and the common electrode 21 becomes the fifth potential difference Vp5, i.e., +1.2V.

[0090] Thus, during the second charging period T7, the measurement circuit 200 supplies a measurement potential Vs of +1.2V to the detection electrode 30 and a ground potential to the common electrode 21, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a fifth potential difference Vp5 (+1.2V) having a different polarity from the fourth potential difference Vp4. In this embodiment, the second charging period T7 corresponds to the sixth period.

[0091] During the second discharge period T8 following the second charging period T7, the measurement circuit 200 stops supplying potential to the detection electrode 30 and supplies the same potential to the common electrode 21 as during the second charging period T7, and measures the detection electrode potential Vd at least once, for example, at the end of the second discharge period T8.

[0092] Specifically, during the second discharge period T8, the central control circuit 45 outputs a reference voltage Vsref of, for example, +1.2V to the measurement potential generation circuit 40. As a result, a measurement potential Vs of +1.2V is output from the measurement potential generation circuit 40. Also during the second discharge period T8, the central control circuit 45 controls the third switch SW3 to the ON state, and controls the first switch SW1, the second switch SW2, the fourth switch SW4, and the fifth switch SW5 to the OFF state.

[0093] During the second discharge period T8, the central control circuit 45 controls the first switch SW1 to the fifth switch SW5 as described above, electrically disconnecting the output terminal of the measurement potential generation circuit 40 from the detection electrode 30, and electrically connecting the ground potential line L2 to the common electrode 21. As a result, during the second discharge period T8, the common electrode 21 continues to receive ground potential, but the potential supply to the detection electrode 30 stops, causing the liquid crystal layer 5 to discharge the charge accumulated during the second charging period T7. Consequently, as shown in Figure 5, during the second discharge period T8, the detection electrode potential Vd gradually changes from +1.2V towards the potential supplied to the common electrode 21 (0V), reaching potential Vd2 at time t9. The value of potential Vd2 depends on the amount of mobile ions contained in the liquid crystal layer 5. Therefore, as will be described later, the degradation status of the liquid crystal layer 5 can be determined by measuring the detection electrode potential Vd2 at the end of the second discharge period T8. As shown in Figure 6, the detection electrode potential Vd2 at the end of the second discharge period T8 corresponds to the potential difference V4 with respect to the common electrode 21.

[0094] The central control circuit 45 measures the detection electrode potential Vd2 at time t9 when the second discharge period T8 ends, for example. Specifically, the detection electrode potential Vd2 is amplified by the amplification circuit 43, and the output of the amplification circuit 43 is input to the A / D converter 44. However, considering the drive power supply voltage of the measurement circuit 20 (e.g., 5V), significant amplification is difficult. For example, if Vd2 is obtained as +1.1V, which is a drop of 0.1V from +1.2V, the possible amplification factor is limited to about 4 times. On the other hand, if Vd1 is obtained as +0.1V, which is an increase of 0.1V from 0V, the possible amplification factor can be 20 times or more. Therefore, it is preferable from the viewpoint of detection sensitivity to use the detection electrode potential Vd1 obtained by the first measurement process for determining the degradation of the liquid crystal layer 5. The central control circuit 45 acquires the digital value output from the A / D converter 44 at time t9 as the measured value of the detection electrode potential Vd2. The central control circuit 45 stores the measured value of the detected electrode potential Vd2 obtained at time t9 in the measurement value storage circuit 46.

[0095] Thus, during the second discharge period T8, the measurement circuit 200 stops supplying potential to the detection electrode 30 and supplies the same ground potential to the common electrode 21 as during the second charging period T7, and measures the detection electrode potential Vd2 at least once, for example, at time t9 when the second discharge period T8 ends. In this embodiment, the second discharge period T8 corresponds to the seventh period. Although the description states that the detection electrode potential Vd(Vd1, Vd2) is measured in both the first and second measurement processes, it is sufficient if the measurement is performed in at least one of them.

[0096] The above is a description of the second measurement process. The second reverse sweep period T5 is preferably longer than the duration of one frame in the display area E. For example, if the duration of one frame is approximately 16 milliseconds, the second reverse sweep period T5 is 20 milliseconds or longer. In addition, although the above description illustrates the case where the fourth potential difference Vp4 in the second reverse sweep period T5 is -5V, the absolute value of the fourth potential difference Vp4 is preferably greater than or equal to the maximum applied voltage of the liquid crystal layer 5 of the pixel P during normal driving. In other words, the absolute value of the fourth potential difference Vp4 is preferably greater than or equal to the maximum applied voltage of the liquid crystal layer 5 in the display area E. The reasons for setting the length of the second reverse sweep period T5 and the absolute value of the fourth potential difference Vp4 as described above will be explained later.

[0097] The second charging period T7 is preferably shorter than the duration of one frame in the display area E. For example, if the duration of one frame is approximately 16 milliseconds, the second charging period T7 is 5 milliseconds. In the above description, the absolute value of the fifth potential difference Vp5 during the second charging period T7 was given as an example of 1.2V, but it is preferable that the absolute value of the fifth potential difference Vp5 is greater than 0V and less than the threshold voltage Vth of the liquid crystal layer 5. The reasons for setting the length of the second charging period T7 and the absolute value of the fifth potential difference Vp5 as described above will be explained later.

[0098] Furthermore, the above explanation exemplified a case where the absolute value of the sixth potential difference Vp6 during the second relaxation period T6 is the same as the absolute value of the fifth potential difference Vp5, which is 1.2V. However, it is preferable that the absolute value of the sixth potential difference Vp6 be greater than 0V and less than the threshold voltage Vth of the liquid crystal layer 5. The reason for setting the absolute value of the sixth potential difference Vp6 as described above will be explained later. Note that the absolute value of the sixth potential difference Vp6 does not necessarily have to be the same as the absolute value of the fifth potential difference Vp5. Also, the potential difference may change gradually with respect to time during the process of changing from the fourth potential difference Vp4 to the sixth potential difference Vp6.

[0099] As can be seen from Figure 6, the liquid crystal layer 5 in the region of the detection electrode 30 is driven by AC power by the alternating repetition of the first and second measurement processes described above. This suppresses the degradation of the liquid crystal layer 5 caused by the application of a DC voltage to the liquid crystal layer 5 during the measurement of its physical properties.

[0100] Let's return to Figure 4 and continue the explanation. As already mentioned, the central control circuit 45 alternately executes the first measurement process and the second measurement process until the count value K becomes equal to the upper limit value Kmax. Then, if the count value K is equal to the upper limit value Kmax (step S16: Yes), the central control circuit 45 proceeds to step S17, which will be described later. Once all measurement processes are completed, for example, the central control circuit 45 controls the fifth switch SW5 to the ON state and controls the third switch SW3 and the fourth switch SW4 to the OFF state. As a result, the common potential Vcom is applied to the common electrode 21. Furthermore, the central control circuit 45 outputs the common potential Vcom as a reference voltage Vsref. It also controls the second switch SW2 to the ON state and controls the first switch SW1 to the OFF state. As a result, the common potential Vcom is applied to the first node N1, i.e., the detection electrode 30.

[0101] In step S17, the display information generation circuit 47 creates display data indicating the deterioration status of the liquid crystal layer 5 based on the measured values ​​of the detection electrode potentials Vd1 and Vd2 stored in the measurement value storage circuit 46. Then, during normal operation of the liquid crystal panel 100, the central control circuit 45 displays the display data generated by the display information generation circuit 47 in the display area E of the liquid crystal panel 100 via the panel control circuit. Note that the display of the deterioration status of the liquid crystal layer 5 may be performed only when notification to the user is necessary, such as when the liquid crystal panel 100 is approaching the end of its lifespan and the measured values ​​of the detection electrode potentials Vd1 and Vd2 reach a preset threshold Vd_th.

[0102] Furthermore, the display of the deterioration status of the liquid crystal layer 5 may be performed by a projection display device using a liquid crystal device 1000, as described later. For example, if the projection display device is a three-panel projection display device equipped with three liquid crystal devices 1000 that support RGB, the projection display device may be configured to display the deterioration status of the liquid crystal panels 100 of the three liquid crystal devices 1000 in an integrated manner, rather than each liquid crystal device 1000 individually displaying the deterioration status of the liquid crystal layer 5.

[0103] In step S18, the central control circuit 45 transmits data related to the measurement results to a projection-type display device using the liquid crystal display device 1000. Based on the data indicating the deterioration status of the liquid crystal layer 5, the projection-type display device performs necessary processing, such as notification processing using notification means such as an audio device or a warning light. Note that step S18 may be omitted depending on the specifications of the projection-type display device using the liquid crystal display device 1000.

[0104] The measurement results of the degradation status of the liquid crystal layer 5 can also be displayed from the maintenance menu of the projection-type display device using the liquid crystal device 1000. The maintenance menu is implemented, for example, as part of the settings menu in the projection-type display device. In step S10, when the central control circuit 45 receives a command to display the measurement results from the projection-type display device using the liquid crystal device 1000, it proceeds to step S17 and displays the measurement results in the display area E of the liquid crystal panel 100.

[0105] 1.4. Overview of the relationship between the usage time and discharge characteristics of the LCD panel 100 Figure 7 is a graph showing the relationship between the usage time and discharge characteristics of the liquid crystal panel 100. Usage time refers to, for example, the cumulative usage time. In projection-type display devices, this corresponds to, for example, the cumulative illumination time. Since verifying this cumulative usage time (illumination time) experimentally would require an enormous amount of time, the data will be explained as data obtained when a continuous acceleration test is conducted with increased incident light intensity and temperature compared to actual usage conditions. Specifically, discharge characteristics refer to, for example, the temporal change in the detection electrode potential Vd during the second discharge period T8 shown in Figure 5. The vertical axis of Figure 7 shows the detection electrode potential Vd during the second discharge period T8. The horizontal axis of Figure 7 shows the time during the second discharge period T8. In Figure 7, time t8 corresponds to time t8 shown in Figure 5, i.e., the start time of the second discharge period T8. Also, in Figure 7, time t9 corresponds to time t9 shown in Figure 5, i.e., the end time of the second discharge period T8. For example, time t9 is 150 ms after time t8.

[0106] In Figure 7, discharge curve G0 shows the discharge curve at the start of use of the liquid crystal panel 100, i.e., at usage time h0, which is zero usage time, and discharge curve G3 shows the discharge curve at usage time h3, just before the liquid crystal panel 100 reaches the end of its lifespan. Discharge curve G1 shows the discharge curve at the point when usage time h1 has elapsed from the start of use of the liquid crystal panel 100, and discharge curve G2 shows the discharge curve at the point when usage time h2 has elapsed from the start of use of the liquid crystal panel 100. Here, the relationship of usage time is h0

[0107] In each discharge curve, the detected electrode potential Vd at time t8 is close to +1.2V, but the detected electrode potential Vd at time t9, i.e., the detected electrode potential Vd2, is different. In other words, under continuous acceleration testing, the detected electrode potential Vd2 decreases as the test progresses.

[0108] ​Thus, the longer the liquid crystal panel 100 is used, the lower the detected electrode potential Vd2 at time t9 becomes. This is because, as the liquid crystal panel 100 is used, the number of mobile ions in the liquid crystal layer 5 increases due to chemical reactions caused by high-intensity light incidence, which changes the discharge curve. In this embodiment, the determination circuit 45a determines the degradation status of the liquid crystal layer 5 based on the measured value of the detected electrode potential Vd2 stored in the measured value storage circuit 46.

[0109] Figure 8 is a graph showing the relationship between the usage time of the liquid crystal panel 100 and the detection electrode potential Vd2 at time t9. The vertical axis represents the detection electrode potential Vd2 at time t9, and the horizontal axis represents the usage time of the liquid crystal panel 100.

[0110] As shown in Figure 8, the transition line W1 of the detection electrode potential Vd2 at time t9 changes according to the length of the usage time h0, h1, h2, and h3 of the liquid crystal panel 100. Typically, the value shown by the transition line W1 gradually decreases as the usage time increases. That is, the detection electrode potential Vd2 gradually decreases in the order of Vd2_h0, Vd2_h1, Vd2_h2, and Vd2_h3. Then, the rate of decrease in the value shown by the transition line W1 increases sharply from around the usage time h3, and beyond the usage time h3, the amount of mobile ions in the liquid crystal layer 5 increases sharply, and the liquid crystal panel 100 reaches the end of its lifespan. In this way, the transition line W1 changes nonlinearly with respect to the usage time of the liquid crystal panel 100. Furthermore, in terms of display quality, it has been confirmed that after the time indicated by arrow AR, beyond the usage time h3, the occurrence of stains and unevenness on the display screen becomes significant, and a decrease in brightness occurs along with it, resulting in a decrease in display quality.

[0111] In this embodiment, the threshold Vd_th is set to the value at which the detected electrode potential Vd2 at time t9 has decreased to 70% of the detected electrode potential Vd at time t8. The control program of the central control circuit 45a is programmed to notify the user or administrator that the lifespan of the liquid crystal panel 100 is nearing its end when the measured value of the detected electrode potential Vd2 falls below the threshold Vd_th. Alternatively, as will be described later, the control program of the central control circuit 45 is programmed to check the relationship between the usage time of the liquid crystal panel 100 to date and the detected electrode potential Vd2.

[0112] The measured value of the detection electrode potential Vd2, which is compared with the threshold Vd_th, may be the average of multiple measured values. Furthermore, the threshold Vd_th may be changed depending on the circumstances under which the liquid crystal panel 100 is used. For example, if a higher display quality is required, or if maintenance of the liquid crystal panel 100 takes a long time, the threshold Vd_th may be set to the detection electrode potential Vd2_h2 corresponding to the usage time h2 so that notification can be given earlier.

[0113] Furthermore, the determination circuit 45a may determine the degradation status of the liquid crystal panel 100 based on the measured value of the detection electrode potential Vd1 obtained at the end of the first discharge period T4. In this case, the threshold Vd_th compared with the measured value of the detection electrode potential Vd1 may be set to a different value from the threshold Vd_th compared with the measured value of the detection electrode potential Vd2.

[0114] 1.5. Effects of the first reverse sweep period T1 and the second reverse sweep period T5 As described above, in this embodiment, the first reverse sweep period T1 is inserted at the beginning of the first measurement period T10, and the second reverse sweep period T5 is inserted at the beginning of the second measurement period T20. This allows the mobile ions contained in the liquid crystal layer 5 to be effectively initially positioned on either the common electrode 21 or the detection electrode 30 immediately after the start of the first measurement period T10 and immediately after the start of the second measurement period T20. By arranging the initial position of the mobile ions in this way, it becomes easier to obtain measurement reproducibility. The effect of the internal electric field due to the mobile ions is also reflected in the measured value, so an increase in mobile ions is more likely to appear as a change in the measured value.

[0115] The first reverse sweep period T1 and the second reverse sweep period T5 are preferably longer than one frame period. For example, the first reverse sweep period T1 and the second reverse sweep period T5 are each 20 milliseconds or longer. This allows even mobile ions with low mobility contained in the liquid crystal layer 5 to be effectively initially positioned. Mobile ions with low mobility have difficulty moving within the liquid crystal layer 5. Therefore, if the first reverse sweep period T1 and the second reverse sweep period T5 are the normal frame period, it is difficult to control the initial positioning of mobile ions with low mobility within the normal frame period. Even if measurement values ​​are obtained in a state where the initial positioning of mobile ions with low mobility cannot be controlled in this way, sufficient measurement reproducibility may not be obtained.

[0116] Figure 9 shows the effects of the first reverse sweep period T1 and the second reverse sweep period T5. Figure 9 shows the results of measuring the detection electrode potential Vd during the first discharge period T4 for each of the following cases: when the first reverse sweep period T1 is 20 msec, when the first reverse sweep period T1 is 100 msec, and when the first reverse sweep period T1 is 500 msec. More specifically, the results shown in Figure 9 are the results of measuring the detection electrode potential Vd during the first discharge period T4 for each of the three cases described above, amplified 11 times, at the very beginning of the degradation test of the liquid crystal panel 100.

[0117] In Figure 9, the horizontal axis represents the time from the start of discharge in the first discharge period T4, and the vertical axis represents the measured value of the detection electrode potential Vd during the first discharge period T4. The first discharge period T4 is 200 msec. Also in Figure 9, the vertical axis represents the measured value of the detection electrode potential Vd as a digital value output from the A / D converter 44. In this measurement, a 10-bit A / D converter 52 was used, and the measured value 1023 corresponds to approximately 2.5V.

[0118] As shown in Figure 9, the longer the first reverse sweep period T1, the larger the measured value at the end of the first discharge period T4. This is thought to be because inserting the first reverse sweep period T1 at the beginning of the first measurement period T10 effectively initializes mobile ions, especially those with low mobility, onto either the common electrode 21 or the detection electrode 30. These results suggest that by lengthening the first reverse sweep period T1 and the second reverse sweep period T5, the progression of degradation of the liquid crystal layer 5 can be sensitively tracked from the initial stages of use of the liquid crystal panel 100. Furthermore, although Figure 9 illustrates the differences at the very beginning of the continuous acceleration test, the effect of the first reverse sweep period T1 could also be confirmed in measurements at the end of the test. The discharge characteristics clearly changed between the case where the first reverse sweep period T1 was 20 msec and the case where it was 100 msec. Specifically, when the first reverse sweep period T1 was set to 100 msec, the measured value of the detected electrode potential Vd was significantly larger than when the first reverse sweep period T1 was set to 20 msec.

[0119] Figure 10 shows the electrical characteristics of the liquid crystal layer 5. The horizontal axis represents the voltage applied to the liquid crystal layer 5, and the vertical axis represents the current. These electrical characteristics can be obtained, for example, by measuring the current when a triangular wave voltage of ±5V at 0.1Hz is applied to the liquid crystal layer 5. This method is generally called cyclic voltammetry. As indicated by the symbol A in Figure 10, typically, the current due to mobile ions appears as an incremental current relative to the charging current of the liquid crystal layer 5, and shows a peak current at relatively small voltages. This peak current appears as a large peak, for example, as shown by the dashed line, as the degradation of the liquid crystal layer 5 progresses. With the above method, the presence of mobile ions can be quantitatively evaluated using specialized precision measuring instruments, but it is not cost-effective to implement such a function in a projection-type display device using the liquid crystal device 1000. However, with the configuration of the present invention, the degradation state of the liquid crystal layer 5 can be quantified with a relatively simple circuit configuration.

[0120] The voltage applied to the liquid crystal layer 5 during the first reverse sweep period T1 and the second reverse sweep period T5 is preferably equal to or greater than the maximum applied voltage during normal operation of the liquid crystal panel 100. In other words, the absolute value of the first potential difference Vp1 during the first reverse sweep period T1 and the absolute value of the fourth potential difference Vp4 during the second reverse sweep period T5 are preferably equal to or greater than the maximum applied voltage during normal operation of the liquid crystal panel 100. This allows the measurement to be performed with the influence of the display state of the liquid crystal panel 100 before the measurement to be suppressed. The detection electrode 30 is located along the outer edge of the display area E and observes mobile ions diffusing from the display area E along the substrate surface. However, the movement of mobile ions in each pixel P may be limited by the driving voltage. That is, whether mobile ions are located on the common electrode 21 side or on the detection electrode 30 side depends on the driving voltage of the pixel P and is uncontrolled. However, if the voltage applied to the liquid crystal layer 5 at the detection electrode 21 during the first reverse sweep period T1 and the second reverse sweep period T5 is set to be greater than or equal to the maximum applied voltage applied to the liquid crystal layer 5 at each pixel P during normal driving, then mobile ions that cannot be moved during normal driving can be controlled and initially positioned. Furthermore, if the first reverse sweep period T1 and the second reverse sweep period T5 are made longer than one frame, the travel distance of the mobile ions will be longer than during normal driving, thus having an effect on initial positioning. The voltage applied to the liquid crystal layer 5 during the first reverse sweep period T1 and the second reverse sweep period T5 may be a voltage greater than or equal to the threshold voltage Vth of the liquid crystal layer 5.

[0121] Figure 11 shows the relationship between the normalized transmittance of the liquid crystal layer 5 and the applied voltage. The transmittance characteristics differ depending on the gap and liquid crystal material of the liquid crystal layer 5. For example, if the liquid crystal panel 100 is a normally black type VA liquid crystal panel and the gap of the liquid crystal layer 5 is approximately 2.6 μm, the transmittance of the liquid crystal layer 5 is maximized when a voltage of slightly less than 4 V is applied, as shown in Figure 11. Therefore, in the pixel P that is in the held state during normal operation of the liquid crystal panel 100, the maximum applied voltage of the liquid crystal layer 5 is set to slightly less than 4 V. In this case, for example, during one frame period during normal operation of the liquid crystal panel 100, in other words, during the polarity holding period of the pixel P, it is unclear whether the mobile ions that move with an applied voltage of approximately 4 V of the liquid crystal layer 5 are located on the common electrode 21 or the detection electrode 30. However, during the first reverse sweep period T1 and the second reverse sweep period T5, by applying a voltage of +5V, which is greater than the maximum applied voltage during normal operation of the liquid crystal panel 100, to the liquid crystal layer 5 for a longer period than one frame, mobile ions that move at around 4V can be effectively initially positioned on either the common electrode 21 or the detection electrode 30. The above maximum applied voltage can be determined by observing the potential supplied to the data lines. For example, when the common electrode 21 is driven with a fixed potential, the maximum applied voltage is approximately half the amplitude of the data line supply potential when the liquid crystal panel 100 is set to maximum grayscale display. In another example, when the potential of the common electrode 21 is driven inversely according to the display polarity, the maximum applied voltage is approximately close to the amplitude of the data line supply potential when the liquid crystal panel 100 is set to maximum grayscale display.

[0122] Furthermore, Figure 9 allows us to identify measurement values ​​that do not reflect the effects of the first reverse sweep period T1 and the second reverse sweep period T5. Specifically, as shown in Figure 9, there is almost no difference in the measurement values ​​obtained in each of the three cases during the period from the start of the first discharge period T4 to around 50 msec. In other words, the first discharge period T4 has two stages: the first stage from the start of the first discharge period T4 to around 50 msec, and the second stage from around 50 msec to the end of the first discharge period T4. It can be considered that the measurement values ​​in the first stage reflect the behavior of mobile ions with relatively high mobility, while the measurement values ​​in the second stage reflect the behavior of mobile ions with relatively low mobility.

[0123] Therefore, when focusing on mobile ions with relatively high mobility, the measurement values ​​from the first stage should be used. On the other hand, when focusing on mobile ions with relatively low mobility, the difference between the measurement values ​​obtained at two different points in time during the second stage should be used. For example, the difference between the measurement value obtained 50 milliseconds after the start of the first discharge period T4 and the measurement value obtained at the end of the first discharge period T4. Therefore, the measurement values ​​do not necessarily have to be those obtained at the end of the first discharge period T4 or the second discharge period T8.

[0124] 1.6. Effects of the First Relaxation Period T2 and the Second Relaxation Period T6 As described above, in this embodiment, a first relaxation period T2 is inserted between the first reverse sweep period T1 and the first charging period T3 in the first measurement period T10, and a second relaxation period T6 is inserted between the second reverse sweep period T5 and the second charging period T7 in the second measurement period T20. This avoids the influence of dielectric anisotropy of the liquid crystal layer 5 and allows measurement without moving the accumulated mobile ions.

[0125] As described above, for example, the threshold voltage Vth of the liquid crystal layer 5 is approximately 2.1V. In other words, if the voltage applied to the liquid crystal layer 5 during the first relaxation period T2 and the second relaxation period T6 is smaller than the threshold voltage Vth, the effect of dielectric anisotropy in the liquid crystal layer 5 can be suppressed during measurement. To put it another way, if the absolute value of the third potential difference Vp3 during the first relaxation period T2 and the absolute value of the sixth potential difference Vp6 during the second relaxation period T6 are both greater than 0V and smaller than the threshold voltage Vth, the effect of dielectric anisotropy in the liquid crystal layer 5 can be suppressed during measurement. In other words, the movement of highly mobile ions can be suppressed during the first charging period T3 and the second charging period T7. Furthermore, by charging and discharging the liquid crystal layer 5 with a small voltage, highly mobile ions can be efficiently captured and measured. In addition, the first charging period T3 and the second charging period T7 can be made longer, which increases the design flexibility of the measurement circuit 200. This point will be discussed later.

[0126] As described above, in this embodiment, when transitioning from the first reverse sweep period T1 to the first relaxation period T2, the applied voltage to the liquid crystal layer 5 is switched from +5V to +1.2V without changing polarity. Similarly, when transitioning from the second reverse sweep period T5 to the second relaxation period T6, the applied voltage to the liquid crystal layer 5 is switched from -5V to -1.2V without changing polarity. Therefore, the lengths of the first relaxation period T2 and the second relaxation period T6 are set considering the response time of the liquid crystal layer 5. Considering the response time of the liquid crystal layer 5, it is preferable that the first relaxation period T2 and the second relaxation period T6 be set to be longer than the duration of one frame. For example, the first relaxation period T2 and the second relaxation period T6 may be 20 msec or 50 msec, etc. If a liquid crystal material with a fast response is used, a value shorter than 20 msec may be used.

[0127] 1.7. Effects of the first charging period T3 and the second charging period T7 In general, the first charging period T3 and the second charging period T7 should be as short as possible. This is because shortening the first charging period T3 and the second charging period T7 makes it easier to capture the effects of highly mobile ions as changes in the measured values. For example, it is preferable that the first charging period T3 and the second charging period T7 are shorter than the duration of one frame during normal operation of the liquid crystal panel 100.

[0128] In this embodiment, the measurement circuit 200 controls the potential supplied to the common electrode 21 and the detection electrode 30, respectively. The second capacitor C2, electrically connected to the common electrode 21, has a relatively large capacitance value. The third switch SW3 and the fourth switch SW4 are electrically connected to the common electrode line L1. If the on-resistance of these third switch SW3 and fourth switch SW4 is large, it is difficult to shorten the first charging period T3 and the second charging period T7. For example, the on-resistance of commercially available switch ICs when driven at 5V is about 1kΩ. For example, if the capacitance value of the second capacitor C2 is 0.2μF, then 5τ is 1ms. If the length of the first charging period T3 and the second charging period T7 is set to about 5τ and an amplification circuit 43 that amplifies the detection electrode potential Vd by about 10 times is used, this time constant τ becomes large enough to affect the measured value.

[0129] On the other hand, during the first discharge period T4 and the second discharge period T8, the off-resistances of the first switch SW1 and the second switch SW2, which are electrically connected to the detection electrode 30, must be sufficiently large. If the off-resistances of these first and second switches SW1 and SW2 are small, it will affect the maintenance of the potential at the first node N1, i.e., the detection electrode potential Vd. Also, if there is a large variation in the off-resistances of the first and second switches SW1 and SW2, it may affect the measured values.

[0130] Therefore, in this embodiment, in order to reduce the on-resistance of the third switch SW3 and the fourth switch SW4, a configuration was adopted in which a relatively large second voltage, for example 15V, was applied to the third switch SW3 and the fourth switch SW4. On the other hand, in this embodiment, in order to increase the off-resistance of the first switch SW1 and the second switch SW2, a configuration was adopted in which a relatively small first voltage, for example 5V, was applied to the first switch SW1 and the second switch SW2. Note that driving the first switch SW1 and the second switch SW2 with a first voltage of 5V means that the on-resistance of each switch will increase. However, since the capacitance value of the first capacitor C1 electrically connected to the node of the detection electrode 30 is smaller than that of the second capacitor C2 electrically connected to the node of the common electrode 21, this can be handled without problems in terms of time constant.

[0131] In this embodiment, considering the responsiveness of the common electrode 21 during normal operation of the liquid crystal panel 100, a configuration is adopted in which a relatively large second voltage of 15V is also applied to the fifth switch SW5. Commercially available switch ICs can be used as the first switch SW1 to the fifth switch SW5. That is, a drive voltage of 5V or 15V is applied to the switch ICs used as the first switch SW1 to the fifth switch SW5. In this case, a power supply voltage of 5V or 15V is supplied to each switch IC.

[0132] Figure 12 shows the effects of the first charging period T3 and the second charging period T7. Figure 12 shows the results of measuring the detection electrode potential Vd during the first discharge period T4 for the case where the first charging period T3 is 1 ms and the case where the first charging period T3 is 5 ms. More specifically, the results are shown for each of the above two cases, where the detection electrode potential Vd during the first discharge period T4 was amplified 11 times at the very beginning of the degradation test of the liquid crystal panel 100.

[0133] In Figure 12, the horizontal axis represents the time from the start of discharge in the first discharge period T4, and the vertical axis represents the measured value of the detection electrode potential Vd during the first discharge period T4. For example, the first discharge period T4 is 200 msec. Also in Figure 12, the vertical axis represents the measured value of the detection electrode potential Vd as a digital value output from the A / D converter 44. In this measurement, a 10-bit A / D converter 52 was used, and the measured value 1023 corresponds to approximately 2.5V.

[0134] As shown in Figure 12, the shorter the first charging period T3, the larger the measured value at the end of the first discharging period T4. This is thought to be because shortening the first charging period T3 suppresses the movement of mobile ions during the first charging period T3, and efficiently reflects the action of highly mobile mobile ions. These results suggest that by shortening the first charging period T3 and the second charging period T7, the progression of degradation of the liquid crystal layer 5 can be sensitively tracked from the initial stages of use of the liquid crystal panel 100.

[0135] Furthermore, a detailed observation of the results shown in Figure 12 reveals that after 50 milliseconds have elapsed from the start of the first discharge period T4, the measured values ​​obtained in each of the two cases appear to be moving almost parallel to each other. In other words, as mentioned above, it is thought that this difference in measured values ​​is due to the action of mobile ions with relatively high mobility. Thus, the lengths of the first reverse sweep period T1 and the second reverse sweep period T5, and the first charging period T3 and the second charging period T7 have different effects on the measured values.

[0136] 1.8. Tracking the progression of degradation of liquid crystal layer 5 Figure 13 is the first figure showing the results of tracking the progression of degradation of the liquid crystal layer 5. Figure 14 is the second figure showing the results of tracking the progression of degradation of the liquid crystal layer 5. In detail, the liquid crystal panel 100 was cooled to a temperature of approximately 65°C while being subjected to 12W / cm². 2A continuous acceleration test was conducted in which the display area E was irradiated with blue light for a predetermined time. Figures 13 and 14 show the results of measuring the detection electrode potential Vd during the first discharge period T4 for the case of 0 hours (initial), the case of 166 hours, and the case of 326 hours. Furthermore, the results shown in Figure 13 are the results of measuring the detection electrode potential Vd during the first discharge period T4 under conditions where the first reverse sweep period T1 was set to 500 msec and the first charging period T3 was set to 1 msec. The results shown in Figure 14 are the results of measuring the detection electrode potential Vd during the first discharge period T4 under conditions where the first reverse sweep period T1 was set to 100 msec and the first charging period T3 was set to 5 msec.

[0137] In Figures 13 and 14, the horizontal axis represents the time from the start of discharge in the first discharge period T4, and the vertical axis represents the measured value of the detection electrode potential Vd during the first discharge period T4. The first discharge period T4 is 200 msec. Also in Figures 13 and 14, the vertical axis represents the measured value of the detection electrode potential Vd as a digital value output from the A / D converter 44. In this measurement, a 10-bit A / D converter 52 was used, and the measured value 1023 corresponds to approximately 2.5V.

[0138] As shown in Figures 13 and 14, according to this embodiment, it is possible to sensitively track the progression of degradation of the liquid crystal layer 5 from the time blue light irradiation of the liquid crystal panel 100 is started, that is, from the initial stage of use of the liquid crystal panel 100. Furthermore, since the liquid crystal panel 100 used in the experiment had power supply wiring and other peripheral circuits arranged to reflect the actual product, the experimental results shown in Figures 13 and 14 are experimental results that take into account the influence of parasitic capacitance of the detection electrode 30. Accordingly, from the experimental results shown in Figures 13 and 14, it can be said that the liquid crystal device 1000 of this embodiment has sufficient practicality to detect the progression of degradation of the liquid crystal layer 5 as a change in voltage value.

[0139] 1.9. Verification of measurement reproducibility Figure 15 is Figure 1, showing the results of verifying measurement reproducibility. Figure 16 is Figure 2, showing the results of verifying measurement reproducibility. More specifically, Figure 15 shows the results obtained when the continuous acceleration test had elapsed for 326 hours in the experiment shown in Figure 13. Similarly, Figure 16 shows the results obtained when the continuous acceleration test had elapsed for 326 hours in the experiment shown in Figure 14. Figures 15 and 16 show the results of measuring the detection electrode potential Vd during the first discharge period T4 twice under each measurement condition. In Figures 15 and 16, Measurement 1 shows the result of the first measurement, and Measurement 2 shows the result of the second measurement. The second measurement was performed after a predetermined time had elapsed since the first measurement.

[0140] Furthermore, the results shown in Figure 15 are the results of measuring the detection electrode potential Vd during the first discharge period T4 under conditions where the first reverse sweep period T1 was set to 500 msec and the first charging period T3 was set to 1 msec. The results shown in Figure 16 are the results of measuring the detection electrode potential Vd during the first discharge period T4 under conditions where the first reverse sweep period T1 was set to 100 msec and the first charging period T3 was set to 5 msec.

[0141] In Figures 15 and 16, the horizontal axis represents the time from the start of discharge in the first discharge period T4, and the vertical axis represents the measured value of the detection electrode potential Vd during the first discharge period T4. The first discharge period T4 is 200 msec. Also in Figures 15 and 16, the vertical axis represents the measured value of the detection electrode potential Vd as a digital value output from the A / D converter 44. In this measurement, a 10-bit A / D converter 52 was used, and the measured value 1023 corresponds to approximately 2.5V.

[0142] As shown in Figures 15 and 16, it can be seen that, according to this embodiment, measurements can be taken with sufficient reproducibility. If the first reverse sweep period T1 and the second reverse sweep period T5 are absent, it is possible that such measurement reproducibility cannot be obtained depending on what was done electrically to the liquid crystal layer 5 of the liquid crystal panel 100 before the measurement. For example, when performing a measurement consisting of ±1.2V charging and discharging at the detection electrode 30 (first charging period T3 performed at -1.2V, first discharging period T4, second charging period T7 performed at +1.2V, second discharging period T8), a phenomenon may occur where the measured value changes before and after measuring the optical characteristics such as voltage-transmittance in the display area E of Figure 11.

[0143] (Effects of the first embodiment) As described above, the liquid crystal apparatus 1000 of the first embodiment includes a detection electrode 30, a common electrode 21, a liquid crystal layer 5 disposed between the detection electrode 30 and the common electrode 21, and a measurement circuit 200 that supplies potential to the detection electrode 30 and the common electrode 21 respectively, and measures the detection electrode potential Vd, which is the potential of the detection electrode 30. The measurement circuit 200 supplies potential to the detection electrode 30 and the common electrode 21 respectively during the first reverse sweep period T1 such that the potential difference between the detection electrode 30 and the common electrode 21 becomes the first potential difference Vp1. During the first charging period T3 after the first reverse sweep period T1, it supplies potential to the detection electrode 30 and the common electrode 21 respectively such that the potential difference becomes the second potential difference Vp2, which has a different polarity from the first potential difference Vp1. During the first discharge period T4 after the first charging period T3, it stops supplying potential to the detection electrode 30 and supplies the same potential to the common electrode 21 as during the first charging period T3, and measures the detection electrode potential Vd at least once.

[0144] As described above, in this embodiment, a first reverse sweep period T1 is inserted before the first charging period T3 and the first discharge period T4. This allows the mobile ions contained in the liquid crystal layer 5 to be effectively initially positioned on either the common electrode 21 or the detection electrode 30 during the first reverse sweep period T1. For example, cations are initially positioned on the electrode supplied with a negative potential among the common electrode 21 and the detection electrode 30, and anions are initially positioned on the electrode supplied with a positive potential among the common electrode 21 and the detection electrode 30. By arranging the initial position of mobile ions in this way before the start of the first charging period T3, measurement reproducibility can be obtained for the measured value of the detection electrode potential Vd obtained during the first discharge period T4. Furthermore, since the effect of the internal electric field due to mobile ions is also reflected in the measured value, an increase in mobile ions is more likely to appear as a change in the measured value. As a result, the progression of degradation of the liquid crystal layer 5 can be sensitively tracked from the initial use of the liquid crystal panel 100.

[0145] In the liquid crystal device 1000 of the first embodiment, the first reverse sweep period T1 is longer than the duration of one frame in the display area E during normal operation, and the absolute value of the first potential difference Vp1 is greater than or equal to the maximum applied voltage of the liquid crystal layer 5 in the display area E during normal operation. In this way, by setting the first reverse sweep period T1 to be longer than the duration of one frame, mobile ions with particularly low mobility can be effectively initially positioned on either the common electrode 21 or the detection electrode 30. Furthermore, by setting the absolute value of the first potential difference Vp1, that is, the voltage applied to the liquid crystal layer 5 during the first reverse sweep period T1, to be equal to or greater than the maximum applied voltage to the liquid crystal layer 5 in the display area E during normal operation, mobile ions that move at approximately the maximum applied voltage can be effectively initially positioned on either the common electrode 21 or the detection electrode 30. Therefore, according to the above embodiment, the progression of degradation of the liquid crystal layer 5 can be tracked more sensitively from the initial stages of use of the liquid crystal panel 100, with higher measurement reproducibility.

[0146] In the liquid crystal device 1000 of the first embodiment, the first charging period T3 is shorter than the 1 frame period in the display area E during normal operation, and the absolute value of the second potential difference Vp2 is greater than 0V and less than the threshold voltage Vth of the liquid crystal layer 5. In this way, by setting the first charging period T3 to be shorter than the frame period, the effects of highly mobile ions can be more easily captured as changes in the measured values. Furthermore, by setting the absolute value of the second potential difference Vp2, that is, the voltage applied to the liquid crystal layer 5 during the first charging period T3, to be greater than 0V and less than the threshold voltage Vth of the liquid crystal layer 5, the detection electrode potential Vd during the first discharge period T4 can be measured while suppressing the influence of the dielectric anisotropy of the liquid crystal layer 5. Therefore, according to the above embodiment, the progression of degradation of the liquid crystal layer 5 can be tracked more sensitively from the initial stages of use of the liquid crystal panel 100, with higher measurement reproducibility.

[0147] In the liquid crystal apparatus 1000 of the first embodiment, the measurement circuit 200 supplies potential to the detection electrode 30 and the common electrode 21, respectively, during the first relaxation period T2 between the first reverse sweep period T1 and the first charging period T3, such that the potential difference becomes a third potential difference Vp3 having the same polarity as the first potential difference Vp1 and an absolute value smaller than the absolute value of the first potential difference Vp1. In this way, by inserting the first relaxation period T2 between the first reverse sweep period T1 and the first charging period T3, it is possible to transition from the first reverse sweep period T1 to the first charging period T3 without moving the mobile ions initially positioned in the first reverse sweep period T1. Therefore, according to the above embodiment, the progression of degradation of the liquid crystal layer 5 can be tracked more sensitively from the initial stages of use of the liquid crystal panel 100, with higher measurement reproducibility.

[0148] In the liquid crystal apparatus 1000 of the first embodiment, the absolute value of the third potential difference Vp1 is greater than 0V and less than the threshold voltage Vth of the liquid crystal layer 5. In this way, by setting the absolute value of the third potential difference Vp3, that is, the voltage applied to the liquid crystal layer 5 during the first relaxation period T2, to be greater than 0V and less than the threshold voltage Vth of the liquid crystal layer 5, the effect of suppressing the influence of dielectric anisotropy of the liquid crystal layer 5 is enhanced. Therefore, according to the above embodiment, the progression of degradation of the liquid crystal layer 5 can be tracked more sensitively from the initial stages of use of the liquid crystal panel 100, with higher measurement reproducibility.

[0149] In the liquid crystal apparatus 1000 of the first embodiment, the measurement circuit 200 supplies potential to the detection electrode 30 and the common electrode 21 respectively during the second reverse sweep period T5 after the first discharge period T4, such that the potential difference becomes a fourth potential difference Vp4 having a different polarity from the first potential difference Vp1 and the same absolute value as the first potential difference Vp1. During the second charging period T7 after the second reverse sweep period T5, the measurement circuit 200 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference becomes a fifth potential difference Vp5 having a different polarity from the fourth potential difference Vp4. During the second discharge period T8 after the second charging period T7, the supply of potential to the detection electrode 30 is stopped, and the same potential as in the second charging period T7 is supplied to the common electrode 21, and the detection electrode potential Vd is measured at least once.

[0150] As described above, in this embodiment, a second reverse sweep period T5 is inserted before the second charging period T7 and the second discharge period T8. This allows the mobile ions contained in the liquid crystal layer 5 to be effectively initially positioned on either the common electrode 21 or the detection electrode 30 during the second reverse sweep period T5. By arranging the initial position of the mobile ions before the start of the second charging period T7, measurement reproducibility can be obtained for the measurement value of the detection electrode potential Vd obtained during the second discharge period T8. Furthermore, since the effect of the internal electric field due to the mobile ions is also reflected in the measurement value, an increase in mobile ions is more likely to appear as a change in the measurement value. As a result, the progression of degradation of the liquid crystal layer 5 can be sensitively tracked from the initial use of the liquid crystal panel 100. Furthermore, according to the above embodiment, since the liquid crystal layer 5 is driven by AC, it is possible to suppress deterioration of the liquid crystal layer 5 caused by the application of a DC voltage to the liquid crystal layer 5 when measuring the detection electrode potential Vd.

[0151] In the liquid crystal device 1000 of the first embodiment, the second reverse sweep period T5 is longer than the duration of one frame in the display area E during normal operation, and the absolute value of the fourth potential difference Vp4 is greater than or equal to the maximum applied voltage of the liquid crystal layer 5 in the display area E during normal operation. In this way, by setting the second reverse sweep period T5 to be longer than the period of one frame, mobile ions with particularly low mobility can be effectively initially positioned on either the common electrode 21 or the detection electrode 30. Furthermore, by setting the absolute value of the fourth potential difference Vp4, that is, the voltage applied to the liquid crystal layer 5 during the second reverse sweep period T5, to be equal to or greater than the maximum applied voltage to the liquid crystal layer 5 in the display area E during normal operation, mobile ions that move at approximately the maximum applied voltage can be effectively initially positioned on either the common electrode 21 or the detection electrode 30. Therefore, according to the above embodiment, the progression of degradation of the liquid crystal layer 5 can be tracked more sensitively from the initial stages of use of the liquid crystal panel 100, with higher measurement reproducibility.

[0152] In the liquid crystal device 1000 of the first embodiment, the second charging period T7 is shorter than the 1 frame period in the display area E during normal operation, and the absolute value of the fifth potential difference Vp5 is greater than 0V and less than the threshold voltage Vth of the liquid crystal layer 5. In this way, by setting the second charging period T7 to be shorter than the period of one frame, the effects of highly mobile ions can be more easily captured as changes in the measured values. Furthermore, by setting the absolute value of the fifth potential difference Vp5, that is, the voltage applied to the liquid crystal layer 5 during the second charging period T7, to be greater than 0V and less than the threshold voltage Vth of the liquid crystal layer 5, the detection electrode potential Vd during the second discharge period T8 can be measured while suppressing the influence of the dielectric anisotropy of the liquid crystal layer 5. Therefore, according to the above embodiment, the progression of degradation of the liquid crystal layer 5 can be tracked more sensitively from the initial stages of use of the liquid crystal panel 100, with higher measurement reproducibility.

[0153] In the liquid crystal apparatus 1000 of the first embodiment, the measurement circuit 200 supplies potential to the detection electrode 30 and the common electrode 21, respectively, during the second relaxation period T6 between the second reverse sweep period T5 and the second charging period T7, such that the potential difference becomes a sixth potential difference Vp6 having the same polarity as the fourth potential difference Vp4 and an absolute value smaller than the absolute value of the fourth potential difference Vp4. In this way, by inserting the second relaxation period T6 between the second reverse sweep period T5 and the second charging period T7, the mobile ions initially positioned in the second reverse sweep period T5 can be moved to the second charging period T7 without causing them to shift. Therefore, according to the above embodiment, the progression of degradation of the liquid crystal layer 5 can be tracked more sensitively from the initial stages of use of the liquid crystal panel 100, with higher measurement reproducibility.

[0154] In the liquid crystal apparatus 1000 of the first embodiment, the absolute value of the sixth potential difference Vp6 is greater than 0V and less than the threshold voltage Vth of the liquid crystal layer 5. In this way, by setting the absolute value of the sixth potential difference Vp6, that is, the voltage applied to the liquid crystal layer 5 during the second relaxation period T6, to be greater than 0V and less than the threshold voltage Vth of the liquid crystal layer 5, the effect of suppressing the influence of dielectric anisotropy of the liquid crystal layer 5 is enhanced. Therefore, according to the above embodiment, the progression of degradation of the liquid crystal layer 5 can be tracked more sensitively from the initial stages of use of the liquid crystal panel 100, with higher measurement reproducibility.

[0155] In the liquid crystal apparatus 1000 of the first embodiment, the measurement circuit 200 includes a first node N1 electrically connected to a detection electrode 30, a common electrode line L1 electrically connected to a common electrode 21, a ground potential line L2 to which a ground potential is applied, a first capacitor C1 electrically connected between the first node N1 and the ground potential line L2, a second capacitor C2 electrically connected between the common electrode line L1 and the ground potential line L2, a first switch SW1, a second switch SW2, a third switch SW3, a fourth switch SW4, a measurement potential generation circuit 40 that outputs a measurement potential Vs corresponding to a reference voltage Vsref, a central control circuit 45 that outputs the reference voltage Vs to the measurement potential generation circuit 40 and controls the first switch SW1 to the fourth switch SW4, and a potential measurement circuit (amplifier circuit 43 and A / D converter 44) that measures the potential of the first node N1 as the detection electrode potential Vd and outputs the measured value of the detection electrode potential Vd to the central control circuit 45. The first node N1 is electrically connected to the ground potential line L2 via the first switch SW1. The first node N1 is electrically connected to the output terminal of the measurement potential generation circuit 40 via the second switch SW2. The common electrode line L1 is electrically connected to the ground potential line L2 via the third switch SW3. The common electrode line L1 is electrically connected to the output terminal of the measurement potential generation circuit 40 via the fourth switch SW4. By using the measurement circuit 200 having the above configuration, the functions required of the measurement circuit 200 can be realized with a simple circuit configuration, and noise components included in the measured value of the detection electrode potential Vd can be reduced.

[0156] In the liquid crystal device 1000 of the first embodiment, the first switch SW1 and the second switch SW2 are controlled to be ON by a first voltage (5V), and the third switch SW3 and the fourth switch SW4 are controlled to be ON by a second voltage (15V) which is higher than the first voltage. In this way, the third switch SW3 and the fourth switch SW4, which are electrically connected to the common electrode wire L1, are controlled to be ON by a relatively high second voltage. This reduces the ON resistance of the third switch SW3 and the fourth switch SW4, thereby improving the responsiveness of the common electrode wire L1 and suppressing leakage current from the detection electrode 30. As a result, the first charging period T3 and the second charging period T7 can be shortened, allowing the action of highly mobile ions to be captured as a change in the measured value, and suppressing the influence of characteristic variations of each switch component on the measured value. Furthermore, it is preferable that the first switch SW1 and the second switch SW2 are not integrated with the central control circuit 45. For example, the first switch SW1 and the second switch SW2 are mounted as integrated circuit chip A, and the central control circuit 45 is mounted as integrated circuit chip B. The central control circuit 45 may include a circuit system that is driven at high speed, and may generate heat and become hot. Therefore, if the first switch SW1 and the second switch SW2 are not integrated with the central control circuit 45, the temperature of the first switch SW1 and the second switch SW2 will be reduced, and leakage current through each switch will be suppressed. As a result, the potential change of the detection electrode 30 during the first discharge period T4 and the second discharge period T8 will be more dominated by the action of mobile ions, making it more suitable for measurement.

[0157] 2. Second Embodiment A second embodiment of the present invention will be described below. In each of the embodiments illustrated below, components common to the first embodiment will be denoted by the same reference numerals used in the first embodiment, and detailed descriptions will be omitted as appropriate.

[0158] 2.1. Overview of the configuration of the LCD device 2000 Figure 17 is an explanatory diagram showing the schematic configuration of the liquid crystal device 2000 of the second embodiment. The liquid crystal device 2000 comprises the same liquid crystal panel 100 as in the first embodiment and a measurement circuit 300 that differs from that of the first embodiment.

[0159] The measurement circuit 300 supplies potential to the detection electrode 30 and the common electrode 21, and measures the detection electrode potential Vd, which is the potential of the detection electrode 30. The measurement circuit 300 includes a common potential generation circuit 41, a level shifter 42, an amplification circuit 43, an A / D converter 44, a central control circuit 45, a measurement value storage circuit 46, a display information generation circuit 47, a first measurement potential generation circuit 48, a second measurement potential generation circuit 49, a first switch SW1, a second switch SW2, a third switch SW3, a fourth switch SW4, a fifth switch SW5, a sixth switch SW6, a seventh switch SW7, a first capacitor C1, a second capacitor C2, a common electrode line L1, a ground potential line L2, a first node N1, and a second node N2.

[0160] The first measurement potential generation circuit 48 outputs a predetermined first measurement potential Vs1. For example, the first measurement potential Vs1 is +5V. The second measurement potential generation circuit 49 outputs a predetermined second measurement potential Vs2. For example, the second measurement potential Vs2 is +1.2V. The first measurement potential generation circuit 48 can use the voltage of the 5V power supply used in the measurement circuit 300 if one is available. The second measurement potential generation circuit 49 can use a voltage follower to which the output voltage of a constant voltage circuit using a shunt regulator is input, for example. Alternatively, it can use a voltage follower to which the voltage generated by a resistive voltage divider circuit is input.

[0161] The first node N1 is electrically connected to the ground potential line L2 via the first switch SW1. The first node N1 is electrically connected to the second node N2 via the second switch SW2. The second node N2 is electrically connected to the output terminal of the first measurement potential generation circuit 48 via the sixth switch SW6. The second node N2 is electrically connected to the output terminal of the second measurement potential generation circuit 49 via the seventh switch SW7. The common electrode line L1 is electrically connected to the ground potential line L2 via the third switch SW3. The common electrode line L1 is electrically connected to the second node N2 via the fourth switch SW4. The common electrode line L1 is electrically connected to the output terminal of the common potential generation circuit 41 via the fifth switch SW5.

[0162] The state of the first switch SW1 is controlled by the first control signal S1 output from the central control circuit 45. For example, if the central control circuit 45 outputs a logic signal with an amplitude of 5V as the first control signal S1, and the logic is "H", then the first switch SW1 is turned ON. The state of the second switch SW2 is controlled by the second control signal S2 output from the central control circuit 45. For example, if the central control circuit 45 outputs a logic signal with an amplitude of 5V as the second control signal S2, and the logic is "H", then the second switch SW2 is turned ON. In other words, both the first switch SW1 and the second switch SW2 are controlled to be ON by the first voltage (5V).

[0163] The state of the third switch SW3 is controlled by a third control signal S3 output from the central control circuit 45 via the level shifter 42. For example, the central control circuit 45 outputs a logic signal with an amplitude of 5V as the third control signal S3, but this logic signal is converted by the level shifter 42 into a logic signal with an amplitude of 15V. In other words, when the level shifter 42 outputs a third control signal S3 with an amplitude of 15V and the logic is "H", the third switch SW3 is turned ON.

[0164] The state of the fourth switch SW4 is controlled by the fourth control signal S4 output from the central control circuit 45 via the level shifter 42. For example, the central control circuit 45 outputs a logic signal with an amplitude of 5V as the fourth control signal S4, but this logic signal is converted by the level shifter 42 into a logic signal with an amplitude of 15V. In other words, when the level shifter 42 outputs the fourth control signal S4 with an amplitude of 15V and the logic is "H", the fourth switch SW4 is turned ON.

[0165] The state of the fifth switch SW5 is controlled by the fifth control signal S5 output from the central control circuit 45 via the level shifter 42. For example, the central control circuit 45 outputs a logic signal with an amplitude of 5V as the fifth control signal S5, but this logic signal is converted by the level shifter 42 into a logic signal with an amplitude of 15V. In other words, when the level shifter 42 outputs the fifth control signal S5 with an amplitude of 15V and the logic is "H", the fifth switch SW5 is turned ON.

[0166] The state of the sixth switch SW6 is controlled by the sixth control signal S6 output from the central control circuit 45 via the level shifter 42. For example, the central control circuit 45 outputs a logic signal with an amplitude of 5V as the sixth control signal S6, but this logic signal is converted by the level shifter 42 into a logic signal with an amplitude of 15V. In other words, when the level shifter 42 outputs the sixth control signal S6 with an amplitude of 15V and the logic is "H", the sixth switch SW6 is turned ON.

[0167] The state of the seventh switch SW7 is controlled by the seventh control signal S7 output from the central control circuit 45 via the level shifter 42. For example, the central control circuit 45 outputs a logic signal with an amplitude of 5V as the seventh control signal S7, but this logic signal is converted by the level shifter 42 into a logic signal with an amplitude of 15V. In other words, when the level shifter 42 outputs the seventh control signal S7 with an amplitude of 15V and the logic is "H", the seventh switch SW7 is turned ON. As described above, the third switch SW3 through the seventh switch SW7 are controlled to be ON by a second voltage (15V) which is higher than the first voltage (5V).

[0168] The central control circuit 45 controls each circuit included in the measurement circuit 200 when measuring the degradation status of the liquid crystal layer 5. Specifically, the central control circuit 45 outputs a first control signal S1 to the first switch SW1 and a second control signal S2 to the second switch SW2. The central control circuit 45 outputs the third control signal S3 to the seventh control signal S7 to the third switch SW3 to the seventh switch SW7 via the level shifter 42. In the second embodiment, the central control circuit 45 does not output the reference voltage Vsref described in the first embodiment. Thus, the central control circuit 45 in the second embodiment corresponds to a control circuit that controls the first switch SW1 to the fifth switch SW5, the sixth switch SW6, and the seventh switch SW7.

[0169] Similar to the first embodiment, the central control circuit 45 in the second embodiment stores the measured value of the detection electrode potential Vd output from the A / D converter 44 in the measured value storage circuit 46. The measured value storage circuit 46 stores the measured value of the detection electrode potential Vd according to the control of the central control circuit 45. The central control circuit 45 includes a determination circuit 45a. The determination circuit 45a determines the deterioration status of the liquid crystal layer 5 based on the measured value stored in the measured value storage circuit 46. The display information generation circuit 47 generates display information of the deterioration status of the liquid crystal layer 5 based on the measured value and the determination result. Of the circuits included in the measurement circuit 300, the circuits other than those described above are the same as the circuits included in the measurement circuit 200 of the first embodiment.

[0170] 2.2. Description of the first and second measurement processes in the second embodiment Similar to the first embodiment, the central control circuit 45 in the second embodiment alternately executes the first measurement process and the second measurement process until the count value K becomes equal to the upper limit value Kmax. The contents of the first and second measurement processes in the second embodiment differ from those in the first embodiment. This is because the control of the sixth switch SW6 and the seventh switch SW7 is added. The potential control for the detection electrode 30 and the common electrode 21 is the same as in the first embodiment. The first and second measurement processes in the second embodiment will be described in detail below with reference to Figures 5 and 6.

[0171] During the first reverse sweep period T1, the measurement circuit 300 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes the first potential difference Vp1.

[0172] Specifically, during the first reverse sweep period T1, the central control circuit 45 controls the second switch SW2 and the third switch SW3 to the ON state, and controls the first switch SW1, the fourth switch SW4, and the fifth switch SW5 to the OFF state. Also during the first reverse sweep period T1, the central control circuit 45 controls the sixth switch SW6 to the ON state and controls the seventh switch SW7 to the OFF state.

[0173] During the first reverse sweep period T1, the central control circuit 45 controls the first switch SW1 to the seventh switch SW7 as described above, thereby electrically connecting the output terminal of the first measurement potential generation circuit 48 to the detection electrode 30 and electrically connecting the ground potential line L2 to the common electrode 21. As a result, during the first reverse sweep period T1, a first measurement potential Vs1 of +5V is supplied to the detection electrode 30, and the ground potential, i.e., 0V, is supplied to the common electrode 21. Consequently, as shown in Figure 5, during the first reverse sweep period T1, the detection electrode potential Vd becomes +5V and the common electrode potential Vc becomes 0V. Also, as shown in Figure 6, during the first reverse sweep period T1, the potential difference between the detection electrode 30 and the common electrode 21 becomes the first potential difference Vp1, i.e., +5V.

[0174] Thus, during the first reverse sweep period T1, the measurement circuit 300 supplies a first measurement potential Vs1 of +5V to the detection electrode 30 and a ground potential to the common electrode 21, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a first potential difference Vp1 of +5V.

[0175] During the first relaxation period T2 between the first reverse sweep period T1 and the first charging period T3, the measurement circuit 300 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a third potential difference Vp3 having the same polarity as the first potential difference Vp1 and an absolute value smaller than the absolute value of the first potential difference Vp1.

[0176] Specifically, during the first relaxation period T2, the central control circuit 45 controls the second switch SW2 and the third switch SW3 to the ON state, and controls the first switch SW1, the fourth switch SW4, and the fifth switch SW5 to the OFF state. Also during the first relaxation period T2, the central control circuit 45 controls the sixth switch SW6 to the OFF state and controls the seventh switch SW7 to the ON state.

[0177] During the first relaxation period T2, the central control circuit 45 controls the first switch SW1 to the seventh switch SW7 as described above, thereby electrically connecting the output terminal of the second measurement potential generation circuit 49 to the detection electrode 30 and electrically connecting the ground potential line L2 to the common electrode 21. As a result, during the first relaxation period T2, a second measurement potential Vs2 of +1.2V is supplied to the detection electrode 30 and the ground potential is supplied to the common electrode 21. Consequently, as shown in Figure 5, during the first relaxation period T2, the detection electrode potential Vd becomes +1.2V and the common electrode potential Vc becomes 0V. Also, as shown in Figure 6, during the first relaxation period T2, the potential difference between the detection electrode 30 and the common electrode 21 becomes the third potential difference Vp3, i.e., +1.2V.

[0178] Thus, during the first relaxation period T2, the measurement circuit 300 supplies a second measurement potential Vs2 of +1.2V to the detection electrode 30 and a ground potential to the common electrode 21, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a third potential difference Vp3 (+1.2V) having the same polarity as the first potential difference Vp1 and an absolute value smaller than the absolute value of the first potential difference Vp1.

[0179] After the first reverse sweep period T1 and during the first charging period T3 after the first relaxation period T2, the measurement circuit 300 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a second potential difference Vp2 having a different polarity from the first potential difference Vp1.

[0180] Specifically, during the first charging period T3, the central control circuit 45 controls the first switch SW1 and the fourth switch SW4 to the ON state, and controls the second switch SW2, the third switch SW3, and the fifth switch SW5 to the OFF state. Also during the first charging period T3, the central control circuit 45 controls the sixth switch SW6 to the OFF state and controls the seventh switch SW7 to the ON state.

[0181] During the first charging period T3, the central control circuit 45 controls the first switch SW1 to the seventh switch SW7 as described above, thereby electrically connecting the output terminal of the second measurement potential generation circuit 49 to the common electrode 21 and electrically connecting the ground potential line L2 to the detection electrode 30. As a result, during the first charging period T3, the ground potential is supplied to the detection electrode 30 and the second measurement potential Vs2 of +1.2V is supplied to the common electrode 21. Consequently, as shown in Figure 5, during the first charging period T3, the detection electrode potential Vd becomes +0V and the common electrode potential Vc becomes +1.2V. Also, as shown in Figure 6, during the first charging period T3, the potential difference between the detection electrode 30 and the common electrode 21 becomes the second potential difference Vp2, i.e., -1.2V.

[0182] Thus, during the first charging period T3, the measurement circuit 300 supplies a second measurement potential Vs2 of +1.2V to the common electrode 21 and a ground potential to the detection electrode 30, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a second potential difference Vp2 (-1.2V) having a different polarity from the first potential difference Vp1.

[0183] During the first discharge period T4 following the first charging period T3, the measurement circuit 300 stops supplying potential to the detection electrode 30 and supplies the same potential to the common electrode 21 as during the first charging period T3, and measures the detection electrode potential Vd at least once, for example, at the end of the first discharge period T4.

[0184] Specifically, during the first discharge period T4, the central control circuit 45 controls the fourth switch SW4 to the ON state and controls the first switch SW1, second switch SW2, third switch SW3, and fifth switch SW5 to the OFF state. Also during the first discharge period T4, the central control circuit 45 controls the sixth switch SW6 to the OFF state and controls the seventh switch SW7 to the ON state.

[0185] During the first discharge period T4, the central control circuit 45 controls the first switch SW1 to the seventh switch SW7 as described above, thereby electrically connecting the output terminal of the second measurement potential generation circuit 49 to the common electrode 21 and electrically disconnecting the ground potential line L2 from the detection electrode 30. As a result, during the first discharge period T4, the common electrode 21 continues to be supplied with a second measurement potential Vs2 of +1.2V, but the potential supply to the detection electrode 30 stops, causing the liquid crystal layer 5 to discharge the charge accumulated during the first charging period T3. Consequently, as shown in Figure 5, during the first discharge period T4, the detection electrode potential Vd gradually changes from the ground potential of 0V towards the potential supplied to the common electrode 21 (1.2V).

[0186] The central control circuit 45 measures the detection electrode potential Vd1 at time t5 when the first discharge period T4 ends, for example. Specifically, the central control circuit 45 acquires the digital value output from the A / D converter 44 at time t5 as the measured value of the detection electrode potential Vd1. The central control circuit 45 stores the measured value of the detection electrode potential Vd1 obtained at time t5 in the measured value storage circuit 46.

[0187] Thus, during the first discharge period T4, the measurement circuit 300 stops supplying potential to the detection electrode 30 and supplies a second measurement potential Vs2 of +1.2V, the same as during the first charging period T3, to the common electrode 21, and measures the detection electrode potential Vd1 at least once, for example, at the end of the first discharge period T4 at time t5. This concludes the explanation of the first measurement process.

[0188] During the second reverse sweep period T5 following the first discharge period T4, the measurement circuit 300 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a fourth potential difference Vp4, which has a different polarity from the first potential difference Vp1 and the same absolute value as the first potential difference Vp1.

[0189] Specifically, during the second reverse sweep period T5, the central control circuit 45 controls the first switch SW1 and the fourth switch SW4 to the ON state, and controls the second switch SW2, the third switch SW3, and the fifth switch SW5 to the OFF state. Also, during the second reverse sweep period T2, the central control circuit 45 controls the sixth switch SW6 to the ON state and controls the seventh switch SW7 to the OFF state.

[0190] During the second reverse sweep period T5, the central control circuit 45 controls the first switch SW1 to the seventh switch SW7 as described above, thereby electrically connecting the output terminal of the first measurement potential generation circuit 48 to the common electrode 21 and electrically connecting the ground potential line L2 to the detection electrode 30. As a result, during the second reverse sweep period T5, a first measurement potential Vs1 of +5V is supplied to the common electrode 21 and the ground potential is supplied to the detection electrode 30. Consequently, as shown in Figure 5, during the second reverse sweep period T5, the detection electrode potential Vd becomes 0V and the common electrode potential Vc becomes +5V. Also, as shown in Figure 6, during the second reverse sweep period T5, the potential difference between the detection electrode 30 and the common electrode 21 becomes the fourth potential difference Vp4, i.e., -5V.

[0191] Thus, during the second reverse sweep period T5, the measurement circuit 300 supplies a first measurement potential Vs1 of +5V to the common electrode 21 and a ground potential to the detection electrode 30, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a fourth potential difference Vp4 (-5V) which has a different polarity from the first potential difference Vp1 and the same absolute value as the first potential difference Vp1.

[0192] During the second relaxation period T6 between the second reverse sweep period T5 and the second charging period T7, the measurement circuit 300 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a sixth potential difference Vp6 having the same polarity as the fourth potential difference Vp4 and an absolute value smaller than the absolute value of the fourth potential difference Vp4.

[0193] Specifically, during the second relaxation period T6, the central control circuit 45 controls the first switch SW1 and the fourth switch SW4 to the ON state, and controls the second switch SW2, the third switch SW3, and the fifth switch SW5 to the OFF state. Also during the second relaxation period T6, the central control circuit 45 controls the sixth switch SW6 to the OFF state and controls the seventh switch SW7 to the ON state.

[0194] During the second relaxation period T6, the central control circuit 45 controls the first switch SW1 to the seventh switch SW7 as described above, thereby electrically connecting the output terminal of the second measurement potential generation circuit 49 to the common electrode 21 and electrically connecting the ground potential line L2 to the detection electrode 30. As a result, during the second relaxation period T6, a second measurement potential Vs2 of +1.2V is supplied to the common electrode 21 and the ground potential is supplied to the detection electrode 30. Consequently, as shown in Figure 5, during the second relaxation period T6, the detection electrode potential Vd becomes 0V and the common electrode potential Vc becomes +1.2V. Also, as shown in Figure 6, during the second relaxation period T6, the potential difference between the detection electrode 30 and the common electrode 21 becomes the sixth potential difference Vp6, i.e., -1.2V.

[0195] Thus, during the second relaxation period T6, the measurement circuit 300 supplies a second measurement potential Vs2 of +1.2V to the common electrode 21 and a ground potential to the detection electrode 30, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a sixth potential difference Vp6 (-1.2V) which has the same polarity as the fourth potential difference Vp4 and an absolute value smaller than the absolute value of the fourth potential difference Vp4.

[0196] After the second reverse sweep period T5 and during the second charging period T7 after the second relaxation period T6, the measurement circuit 300 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a fifth potential difference Vp5 having a different polarity from the fourth potential difference Vp4.

[0197] Specifically, during the second charging period T7, the central control circuit 45 controls the second switch SW2 and the third switch SW3 to the ON state, and controls the first switch SW1, the fourth switch SW4, and the fifth switch SW5 to the OFF state. Also during the second charging period T7, the central control circuit 45 controls the sixth switch SW6 to the OFF state and controls the seventh switch SW7 to the ON state.

[0198] During the second charging period T7, the central control circuit 45 controls the first switch SW1 to the seventh switch SW7 as described above, thereby electrically connecting the output terminal of the second measurement potential generation circuit 49 to the detection electrode 30 and electrically connecting the ground potential line L2 to the common electrode 21. As a result, during the second charging period T7, the ground potential is supplied to the common electrode 21 and the second measurement potential Vs2 of +1.2V is supplied to the detection electrode 30. Consequently, as shown in Figure 5, during the second charging period T7, the detection electrode potential Vd becomes +1.2V and the common electrode potential Vc becomes 0V. Also, as shown in Figure 6, during the second charging period T7, the potential difference between the detection electrode 30 and the common electrode 21 becomes the fifth potential difference Vp5, i.e., +1.2V.

[0199] Thus, during the second charging period T7, the measurement circuit 300 supplies a second measurement potential Vs2 of +1.2V to the detection electrode 30 and a ground potential to the common electrode 21, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a fifth potential difference Vp5 (+1.2V) having a different polarity from the fourth potential difference Vp4.

[0200] During the second discharge period T8 following the second charging period T7, the measurement circuit 300 stops supplying potential to the detection electrode 30 and supplies the same potential to the common electrode 21 as during the second charging period T7, and measures the detection electrode potential Vd at least once, for example, at the end of the second discharge period T8.

[0201] Specifically, during the second discharge period T8, the central control circuit 45 controls the third switch SW3 to the ON state and controls the first switch SW1, second switch SW2, fourth switch SW4, and fifth switch SW5 to the OFF state. Also during the second discharge period T8, the central control circuit 45 controls the sixth switch SW6 to the OFF state and controls the seventh switch SW7 to the ON state.

[0202] During the second discharge period T8, the central control circuit 45 controls the first switch SW1 to the seventh switch SW7 as described above, electrically disconnecting the output terminal of the second measurement potential generation circuit 49 from the detection electrode 30, and electrically connecting the ground potential line L2 to the common electrode 21. As a result, during the second discharge period T8, the common electrode 21 continues to receive ground potential, but the potential supply to the detection electrode 30 stops, causing the liquid crystal layer 5 to discharge the charge accumulated during the second charging period T7. Consequently, as shown in Figure 5, during the second discharge period T8, the detection electrode potential Vd gradually changes from +1.2V towards the potential supplied to the common electrode 21 (0V), reaching potential Vd2 at time t9.

[0203] The central control circuit 45 measures the detection electrode potential Vd2 at time t9, for example, when the second discharge period T8 ends. Specifically, the central control circuit 45 acquires the digital value output from the A / D converter 44 at time t9 as the measured value of the detection electrode potential Vd2. The central control circuit 45 stores the measured value of the detection electrode potential Vd2 obtained at time t9 in the measured value storage circuit 46.

[0204] Thus, during the second discharge period T8, the measurement circuit 300 stops supplying potential to the detection electrode 30 and supplies the same ground potential to the common electrode 21 as during the second charging period T7, and measures the detection electrode potential Vd2 at least once, for example, at the end time t9 of the second discharge period T8. This concludes the explanation of the second measurement process. In this explanation, the detection electrode potential Vd (Vd1, Vd2) is measured in both the first and second measurement processes, but it is sufficient if the measurement is performed in at least one of them. Once all measurement processes are completed, for example, the central control circuit 45 controls the fifth switch SW5 to the ON state and the third switch SW3 and fourth switch SW4 to the OFF state. As a result, the common potential Vcom is applied to the common electrode 21. Furthermore, the second switch SW2 is controlled to the ON state and the first switch SW1 is controlled to the OFF state. In addition, the seventh switch SW7 is controlled to the ON state and the sixth switch SW6 is controlled to the OFF state. As a result, the output Vs1=5V=Vcom of the first measurement potential generation circuit 48 is applied to the first node N1, i.e., the detection electrode 30.

[0205] (Effects of the second embodiment) In the liquid crystal apparatus 2000 of the second embodiment, the measurement circuit 300 includes a first node N1 electrically connected to the detection electrode 30, a second node N2, a common electrode line L1 electrically connected to the common electrode 21, a ground potential line L2 to which ground potential is applied, a first capacitor C1 electrically connected between the first node N1 and the ground potential line L2, a second capacitor C2 electrically connected between the common electrode line L1 and the ground potential line L2, a first switch SW1, a second switch SW2, a third switch SW3, and a fourth The system includes a switch SW4, a sixth switch SW6, a seventh switch SW7, a first measurement potential generation circuit 48 that outputs a first measurement potential Vs1, a second measurement potential generation circuit 49 that outputs a second measurement potential Vs2, a central control circuit 45 that controls the first switches SW1 to the fourth switch SW4, the sixth switch SW6, and the seventh switch SW7, and a potential measurement circuit (amplifier circuit 43 and A / D converter 44) that measures the potential of the first node N1 as the detection electrode potential Vd and outputs the measured value of the detection electrode potential Vd to the central control circuit 45. The first node N1 is electrically connected to the ground potential line L2 via the first switch SW1. The first node N1 is electrically connected to the second node N2 via the second switch SW2. The second node N2 is electrically connected to the output terminal of the first measurement potential generation circuit 48 via the sixth switch SW6. The second node N2 is electrically connected to the output terminal of the second measurement potential generation circuit 49 via the seventh switch SW7. The common electrode line L1 is electrically connected to the ground potential line L2 via the third switch SW3. The common electrode line L1 is electrically connected to the second node N2 via the fourth switch SW4. By using the measurement circuit 300 having the above configuration, the functions required of the measurement circuit 300 can be realized with a simple circuit configuration, and noise components included in the measured value of the detection electrode potential Vd can be reduced.

[0206] In the liquid crystal device 2000 of the second embodiment, the first switch SW1 and the second switch SW2 are controlled to the ON state by a first voltage (5V), and the third switch SW3, the fourth switch SW4, the sixth switch SW6, and the seventh switch SW7 are controlled to the ON state by a second voltage (15V) which is higher than the first voltage. In this way, the third switch SW3, fourth switch SW4, sixth switch SW6, and seventh switch SW7, which are electrically connected to the common electrode wire L1, are controlled to be ON by a relatively high second voltage. This reduces the ON resistance of each of these switches, thereby improving the responsiveness of the common electrode wire L1. As a result, the first charging period T3 and the second charging period T7 can be shortened, allowing the action of highly mobile ions to be captured as a change in the measured value, and the influence of variations in the characteristics of each switch component on the measured value can be suppressed.

[0207] 3. Third Embodiment A third embodiment of the present invention will now be described. In each of the embodiments illustrated below, components common to the first embodiment will be denoted by the same reference numerals used in the first embodiment, and detailed descriptions will be omitted as appropriate.

[0208] 3.1. Overview of the configuration of the liquid crystal display unit 3000 Figure 18 is an explanatory diagram showing the schematic configuration of the liquid crystal device 3000 of the third embodiment. The liquid crystal device 3000 comprises the same liquid crystal panel 100 as in the first embodiment and a measurement circuit 400 that is different from that of the first embodiment.

[0209] The measurement circuit 400 supplies potential to the detection electrode 30 and the common electrode 21, respectively, and measures the detection electrode potential Vd, which is the potential of the detection electrode 30. The measurement circuit 400 includes a measurement potential generation circuit 40, a common potential generation circuit 41, an amplification circuit 43, an A / D converter 44, a central control circuit 45, a measurement value storage circuit 46, a display information generation circuit 47, a first switch SW1, a second switch SW2, a first capacitor C1, a second capacitor C2, a common electrode line L1, a ground potential line L2, and a first node N1.

[0210] The first node N1 is electrically connected to the output terminal of the common potential generation circuit 41 via the first switch SW1. The first node N1 is electrically connected to the output terminal of the measurement potential generation circuit 40 via the second switch SW2. The common electrode wire L1 is electrically connected to the output terminal of the common potential generation circuit 41.

[0211] The state of the first switch SW1 is controlled by a first control signal S1 output from the central control circuit 45. For example, as the first control signal S1, a logic signal with an amplitude of 10V is output from the central control circuit 45, and when the logic is "H", the first switch SW1 is turned ON. The state of the second switch SW2 is controlled by a second control signal S2 output from the central control circuit 45. For example, as the second control signal S2, a logic signal with an amplitude of 10V is output from the central control circuit 45, and when the logic is "H", the second switch SW2 is turned ON. In other words, the first switch SW1 and the second switch SW2 are controlled to be turned ON by a third voltage (10V). In this embodiment, a logic signal with an amplitude of 10V is output directly from the central control circuit 45, but a configuration using a level shifter as in the first embodiment may also be used.

[0212] Unlike the first embodiment, the amplification circuit 43 in the third embodiment is a differential amplification circuit in which the first node N1, which is electrically connected to the detection electrode 30, and the output terminal of the measurement potential generation circuit 40 are electrically connected, and it amplifies and outputs the potential difference between the potential of the first node N1 and the measurement potential Vs.

[0213] The central control circuit 45 controls each circuit included in the measurement circuit 400 when measuring the degradation status of the liquid crystal layer 5. Specifically, similar to the first embodiment, the central control circuit 45 outputs a reference voltage Vsref to the measurement potential generation circuit 40. The central control circuit 45 also outputs a first control signal S1 to the first switch SW1 and a second control signal S2 to the second switch SW2. Thus, the central control circuit 45 in the third embodiment corresponds to a control circuit that outputs a reference voltage Vsref to the measurement potential generation circuit 40 and controls the first switch SW1 and the second switch SW2.

[0214] Similar to the first embodiment, the central control circuit 45 in the third embodiment stores the measured value of the detected electrode potential Vd output from the A / D converter 44 in the measured value storage circuit 46. The measured value storage circuit 46 stores the measured value of the detected electrode potential Vd in accordance with the control of the central control circuit 45. The central control circuit 45 includes a determination circuit 45a. The determination circuit 45a determines the deterioration status of the liquid crystal layer 5 based on the measured value stored in the measured value storage circuit 46. The display information generation circuit 47 generates display information indicating the deterioration status of the liquid crystal layer 5 based on the measured value and the determination result.

[0215] During normal operation of the liquid crystal panel 100, the central control circuit 45 of the measurement circuit 400 controls the first switch SW1 to the ON state and the second switch SW2 to the OFF state. As a result, during normal operation of the liquid crystal panel 100, the common potential Vcom output from the common potential generation circuit 41 is supplied to the common electrode 21 and the detection electrode 30 of the liquid crystal panel 100, respectively. This suppresses the deterioration of the liquid crystal layer 5, which is positioned between the common electrode 21 and the detection electrode 30, during normal operation of the liquid crystal panel 100.

[0216] 3.2. Description of the first and second measurement processes in the third embodiment Similar to the first embodiment, the central control circuit 45 in the third embodiment alternately executes the first measurement process and the second measurement process until the count value K becomes equal to the upper limit value Kmax. The contents of the first measurement process and the second measurement process in the third embodiment differ from those of the first measurement process and the second measurement process in the first embodiment. This is because the switch group controls only the first switch SW1 and the second switch SW2, and the potential control for the detection electrode 30 and the common electrode 21 differs from that of the first and second embodiments. The first measurement process and the second measurement process in the third embodiment will be described in detail below with reference to Figure 19.

[0217] Figure 19 shows the temporal change in the potential difference between the detection electrode 30 and the common electrode 21 during the execution of the first and second measurement processes. In Figure 19, the horizontal axis represents time, and the vertical axis represents the voltage of the detection electrode 30 relative to the common electrode 21. In other words, it is the applied voltage of the liquid crystal layer 5 at the detection electrode 30. In Figure 19, the polarity of the potential difference when the detection electrode potential Vd is larger than the common electrode potential Vc is defined as positive polarity.

[0218] In Figure 19, the first measurement process is performed during the period T10 from time t1 to time t5. In the following description, the period T10 during which the first measurement process is performed may be referred to as the first measurement period T10. The first measurement period T10 includes the first reverse sweep period T1, the first relaxation period T2, the first charging period T3, and the first discharge period T4. The first reverse sweep period T1 is the period from time t1 to time t2. The first relaxation period T2 is the period from time t2 to time t3. The first charging period T3 is the period from time t3 to time t4. The first discharge period T4 is the period from time t4 to time t5.

[0219] In the third embodiment, the common potential Vcom output from the common potential generation circuit 41 is supplied to the common electrode 21 throughout the entire duration of the first measurement period T10 and the second measurement period T20.

[0220] During the first reverse sweep period T1, the measurement circuit 400 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes the first potential difference Vp1.

[0221] Specifically, during the first reverse sweep period T1, the central control circuit 45 outputs a reference voltage Vsref, for example, Vcom + 5V, to the measurement potential generation circuit 40. The value of Vcom is the same as the value of the common potential Vcom output from the common potential generation circuit 41. As a result, the measurement potential Vs of Vcom + 5V is output from the measurement potential generation circuit 40. Also, during the first reverse sweep period T1, the central control circuit 45 controls the first switch SW1 to the off state and the second switch SW2 to the on state.

[0222] During the first reverse sweep period T1, the central control circuit 45 controls the first switch SW1 and the second switch SW2 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the detection electrode 30. As a result, during the first reverse sweep period T1, a measurement potential Vs of Vcom + 5V is supplied to the detection electrode 30, and a common potential Vcom is supplied to the common electrode 21. Consequently, during the first reverse sweep period T1, the detection electrode potential Vd becomes Vcom + 5V, and the common electrode potential Vc becomes the common potential Vcom. Also, as shown in Figure 19, during the first reverse sweep period T1, the potential difference between the detection electrode 30 and the common electrode 21 becomes the first potential difference Vp1, i.e., +5V.

[0223] Thus, during the first reverse sweep period T1, the measurement circuit 400 supplies a measurement potential Vs of Vcom + 5V to the detection electrode 30 and a common potential Vcom to the common electrode 21, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a first potential difference Vp1 of +5V.

[0224] During the first relaxation period T2 between the first reverse sweep period T1 and the first charging period T3, the measurement circuit 400 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a third potential difference Vp3 having the same polarity as the first potential difference Vp1 and an absolute value smaller than the absolute value of the first potential difference Vp1.

[0225] Specifically, during the first relaxation period T2, the central control circuit 45 outputs a reference voltage Vsref, for example, Vcom + 1.2V, to the measurement potential generation circuit 40. As a result, the measurement potential Vs of Vcom + 1.2V is output from the measurement potential generation circuit 40. Also during the first relaxation period T2, the central control circuit 45 controls the first switch SW1 to the off state and the second switch SW2 to the on state.

[0226] During the first relaxation period T2, the central control circuit 45 controls the first switch SW1 and the second switch SW2 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the detection electrode 30. As a result, during the first relaxation period T2, a measurement potential Vs of Vcom + 1.2V is supplied to the detection electrode 30, and a common potential Vcom is supplied to the common electrode 21. Consequently, during the first relaxation period T2, the detection electrode potential Vd becomes Vcom + 1.2V, and the common electrode potential Vc becomes the common potential Vcom. Furthermore, as shown in Figure 19, during the first relaxation period T2, the potential difference between the detection electrode 30 and the common electrode 21 becomes the third potential difference Vp3, i.e., +1.2V.

[0227] Thus, during the first relaxation period T2, the measurement circuit 400 supplies a measurement potential Vs of Vcom + 1.2V to the detection electrode 30 and a common potential Vcom to the common electrode 21, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a third potential difference Vp3 (+1.2V) having the same polarity as the first potential difference Vp1 and an absolute value smaller than the absolute value of the first potential difference Vp1.

[0228] During the first charging period T3, which is after the first reverse sweep period T1 and after the first relaxation period T2, the measurement circuit 400 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a second potential difference Vp2 having a different polarity from the first potential difference Vp1.

[0229] Specifically, during the first charging period T3, the central control circuit 45 outputs a reference voltage Vsref, for example, Vcom-1.2V, to the measurement potential generation circuit 40. As a result, the measurement potential Vs of Vcom-1.2V is output from the measurement potential generation circuit 40. Also during the first charging period T3, the central control circuit 45 controls the first switch SW1 to the off state and the second switch SW2 to the on state.

[0230] During the first charging period T3, the central control circuit 45 controls the first switch SW1 and the second switch SW2 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the detection electrode 30. As a result, during the first charging period T3, a measurement potential Vs of Vcom-1.2V is supplied to the detection electrode 30, and a common potential Vcom is supplied to the common electrode 21. Consequently, during the first charging period T3, the detection electrode potential Vd becomes Vcom-1.2V, and the common electrode potential Vc becomes the common potential Vcom. Also, as shown in Figure 19, during the first charging period T3, the potential difference between the detection electrode 30 and the common electrode 21 becomes the second potential difference Vp2, i.e., -1.2V.

[0231] Thus, during the first charging period T3, the measurement circuit 400 supplies a measurement potential Vs of Vcom-1.2V to the detection electrode 30 and a common potential Vcom to the common electrode 21, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a second potential difference Vp2 (-1.2V) having a different polarity from the first potential difference Vp1.

[0232] During the first discharge period T4 following the first charging period T3, the measurement circuit 400 stops supplying potential to the detection electrode 30 and supplies the same potential to the common electrode 21 as during the first charging period T3, and measures the detection electrode potential Vd at least once, for example, at the end of the first discharge period T4.

[0233] Specifically, during the first discharge period T4, the central control circuit 45 controls the first switch SW1 and the second switch SW2 to the OFF state.

[0234] During the first discharge period T4, the central control circuit 45 controls the first switch SW1 and the second switch SW2 as described above, thereby electrically disconnecting the output terminal of the measurement potential generation circuit 40 from the detection electrode 30. As a result, during the first discharge period T4, the common potential Vcom continues to be supplied to the common electrode 21, but the potential supply to the detection electrode 30 is stopped, causing the liquid crystal layer 5 to discharge the charge accumulated during the first charging period T3. In this embodiment, the detection electrode potential Vd1 at the end of the first discharge period T4 in the first and second embodiments corresponds to the potential V3 in Figure 19. The potential difference between potential V3 and the measurement potential Vs (=Vcom-1.2V) is amplified by the amplification circuit 43 and input to the A / D converter 44. In the simplest configuration of the differential amplifier circuit, the detection electrode potential Vd is input to the non-inverting input (+) side of the operational amplifier, and the measurement potential Vs (=Vcom-1.2V) is input to the inverting input (-) side of the operational amplifier.

[0235] The central control circuit 45 measures the detection electrode potential Vd1 at time t5 when the first discharge period T4 ends, for example. Specifically, the central control circuit 45 acquires the digital value output from the A / D converter 44 at time t5 as the measured value of the detection electrode potential Vd1. The central control circuit 45 stores the measured value of the detection electrode potential Vd1 obtained at time t5 in the measured value storage circuit 46.

[0236] Thus, during the first discharge period T4, the measurement circuit 400 stops supplying potential to the detection electrode 30 and supplies the same common potential Vcom as during the first charging period T3 to the common electrode 21, and measures the detection electrode potential Vd1 at least once, for example, at the end of the first discharge period T4. This concludes the explanation of the first measurement process.

[0237] During the second reverse sweep period T5 following the first discharge period T4, the measurement circuit 400 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a fourth potential difference Vp4, which has a different polarity from the first potential difference Vp1 and the same absolute value as the first potential difference Vp1.

[0238] Specifically, during the second reverse sweep period T5, the central control circuit 45 outputs a reference voltage Vsref, for example, Vcom-5V, to the measurement potential generation circuit 40. As a result, the measurement potential Vs of Vcom-5V is output from the measurement potential generation circuit 40. Also during the second reverse sweep period T5, the central control circuit 45 controls the first switch SW1 to the OFF state and the second switch SW2 to the ON state.

[0239] During the second reverse sweep period T5, the central control circuit 45 controls the first switch SW1 and the second switch SW2 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the detection electrode 30. As a result, during the second reverse sweep period T2, a measurement potential Vs of Vcom-5V is supplied to the detection electrode 30, and a common potential Vcom is supplied to the common electrode 21. Consequently, during the second reverse sweep period T5, the detection electrode potential Vd becomes Vcom-5V, and the common electrode potential Vc becomes the common potential Vcom. Furthermore, as shown in Figure 19, during the second reverse sweep period T5, the potential difference between the detection electrode 30 and the common electrode 21 becomes the fourth potential difference Vp4, i.e., -5V.

[0240] Thus, during the second reverse sweep period T5, the measurement circuit 400 supplies a measurement potential Vs of Vcom-5V to the detection electrode 30 and a common potential Vcom to the common electrode 21, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a fourth potential difference Vp4 (-5V) which has a different polarity from the first potential difference Vp1 and the same absolute value as the first potential difference Vp1.

[0241] During the second relaxation period T6 between the second reverse sweep period T5 and the second charging period T7, the measurement circuit 400 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a sixth potential difference Vp6 having the same polarity as the fourth potential difference Vp4 and an absolute value smaller than the absolute value of the fourth potential difference Vp4.

[0242] Specifically, during the second relaxation period T6, the central control circuit 45 outputs a reference voltage Vsref, for example, Vcom-1.2V, to the measurement potential generation circuit 40. As a result, the measurement potential Vs of Vcom-1.2V is output from the measurement potential generation circuit 40. Also during the second relaxation period T6, the central control circuit 45 controls the first switch SW1 to the off state and the second switch SW2 to the on state.

[0243] During the second relaxation period T6, the central control circuit 45 controls the first switch SW1 and the second switch SW2 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the detection electrode 30. As a result, during the second relaxation period T6, a measurement potential Vs of Vcom-1.2V is supplied to the detection electrode 30, and a common potential Vcom is supplied to the common electrode 21. Consequently, during the second relaxation period T6, the detection electrode potential Vd becomes Vcom-1.2V, and the common electrode potential Vc becomes the common potential Vcom. Furthermore, as shown in Figure 19, during the second relaxation period T6, the potential difference between the detection electrode 30 and the common electrode 21 becomes the sixth potential difference Vp6, i.e., -1.2V.

[0244] Thus, during the second relaxation period T6, the measurement circuit 400 supplies a measurement potential Vs of Vcom-1.2V to the detection electrode 30 and a common potential Vcom to the common electrode 21, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a sixth potential difference Vp6 (-1.2V) which has the same polarity as the fourth potential difference Vp4 and an absolute value smaller than the absolute value of the fourth potential difference Vp4.

[0245] After the second reverse sweep period T5 and during the second charging period T7 following the second relaxation period T6, the measurement circuit 400 supplies potential to the detection electrode 30 and the common electrode 21 respectively, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a fifth potential difference Vp5 having a different polarity from the fourth potential difference Vp4.

[0246] Specifically, during the second charging period T7, the central control circuit 45 outputs a reference voltage Vsref, for example, Vcom + 1.2V, to the measurement potential generation circuit 40. As a result, the measurement potential Vs of Vcom + 1.2V is output from the measurement potential generation circuit 40. Also during the second charging period T7, the central control circuit 45 controls the first switch SW1 to the OFF state and the second switch SW2 to the ON state.

[0247] During the second charging period T7, the central control circuit 45 controls the first switch SW1 and the second switch SW2 as described above, thereby electrically connecting the output terminal of the measurement potential generation circuit 40 to the detection electrode 30. As a result, during the second charging period T7, a measurement potential Vs of Vcom + 1.2V is supplied to the detection electrode 30, and a common potential Vcom is supplied to the common electrode 21. Consequently, during the second charging period T7, the detection electrode potential Vd becomes Vcom + 1.2V, and the common electrode potential Vc becomes the common potential Vcom. Furthermore, as shown in Figure 19, during the second charging period T7, the potential difference between the detection electrode 30 and the common electrode 21 becomes the fifth potential difference Vp5, i.e., +1.2V.

[0248] Thus, during the second charging period T7, the measurement circuit 400 supplies a measurement potential Vs of Vcom + 1.2V to the detection electrode 30 and a common potential Vcom to the common electrode 21, such that the potential difference between the detection electrode 30 and the common electrode 21 becomes a fifth potential difference Vp5 (+1.2V) having a different polarity from the fourth potential difference Vp4.

[0249] During the second discharge period T8 following the second charging period T7, the measurement circuit 400 stops supplying potential to the detection electrode 30 and supplies the same potential to the common electrode 21 as during the second charging period T7, and measures the detection electrode potential Vd at least once, for example, at the end of the second discharge period T8.

[0250] Specifically, during the second discharge period T8, the central control circuit 45 controls the first switch SW1 and the second switch SW2 to the OFF state.

[0251] During the second discharge period T8, the central control circuit 45 controls the first switch SW1 and the second switch SW2 as described above, thereby electrically disconnecting the output terminal of the measurement potential generation circuit 40 from the detection electrode 30. As a result, during the second discharge period T8, the common potential Vcom continues to be supplied to the common electrode 21, but the potential supply to the detection electrode 30 is stopped, causing the liquid crystal layer 5 to discharge the charge accumulated during the second charging period T7. In the first and second embodiments, the detection electrode potential Vd2 at the end of the second discharge period T8 corresponds to the potential V4 in Figure 19 in this embodiment. The potential difference between the measurement potential Vs (=Vcom + 1.2V) and the potential V4 is amplified by the amplification circuit 43 and input to the A / D converter 44. In the simplest configuration of the differential amplifier circuit, the measurement potential Vs (=Vcom + 1.2V) is input to the non-inverting input (+) side of the operational amplifier, and the detection electrode potential Vd is input to the inverting input (-) side of the operational amplifier. Here, the electrical connection relationship between the non-inverting input (+) and inverting input (-) of the operational amplifier is different from the connection relationship during the first discharge period T4, so the measured value will be obtained from either the first measurement process or the second measurement process. Alternatively, although not shown in the diagram, another set of differential amplifier circuit and A / D converter may be prepared, and the measured value may be obtained from both the first and second measurement processes.

[0252] The central control circuit 45 measures the detection electrode potential Vd2 at time t9, for example, when the second discharge period T8 ends. Specifically, the central control circuit 45 acquires the digital value output from the A / D converter 44 at time t9 as the measured value of the detection electrode potential Vd2. The central control circuit 45 stores the measured value of the detection electrode potential Vd2 obtained at time t9 in the measured value storage circuit 46.

[0253] Thus, during the second discharge period T8, the measurement circuit 400 stops supplying potential to the detection electrode 30 and supplies the same common potential Vcom as during the second charging period T7 to the common electrode 21, and measures the detection electrode potential Vd2 at least once, for example, at the end of the second discharge period T8. This concludes the explanation of the second measurement process. Once all measurement processes are completed, for example, the central control circuit 45 controls the first switch SW1 to the ON state and the second switch SW2 to the OFF state. As a result, the common potential Vcom is applied to the first node N1, i.e., the detection electrode 30.

[0254] In this embodiment, a first switch SW1 is used, but the first switch SW1 may be eliminated and the system may be configured to output a common potential Vcom from the reference voltage Vsref. In that case, during normal operation, the central control circuit 45 can output the common potential Vcom as the reference voltage Vsref and control the second switch SW2 to the ON state to supply the common potential Vcom to the detection electrode 30.

[0255] (Effects of the third embodiment) In the liquid crystal apparatus 3000 of the third embodiment, the measurement circuit 400 includes a first node N1 electrically connected to the detection electrode 30, a common electrode line L1 electrically connected to the common electrode 21, a ground potential line L2 to which the ground potential is applied, a first capacitor C1 electrically connected between the first node N1 and the ground potential line L2, a second capacitor C2 electrically connected between the common electrode line L1 and the ground potential line L2, a first switch SW1, a second switch SW2, a measurement potential generation circuit 40 that outputs a measurement potential Vs corresponding to a reference voltage Vsref, a central control circuit 45 that outputs the reference voltage Vs to the measurement potential generation circuit 40 and controls the first switch SW1 and the second switch SW2, and a potential measurement circuit (amplifier circuit 43 and A / D converter 44) that measures the potential of the first node N1 as the detection electrode potential Vd and outputs the measured value of the detection electrode potential Vd to the central control circuit 45. The first node N1 is electrically connected to the output terminal of the common potential generation circuit 40 via the first switch SW1. The first node N1 is electrically connected to the output terminal of the measurement potential generation circuit 40 via the second switch SW2. The common electrode wire L1 is electrically connected to the output terminal of the common potential generation circuit 40. By using the measurement circuit 400 having the above configuration, the common electrode 21 exhibits a faster potential response compared to the first and second embodiments because there are no switches that create a large resistance component in the path from the output terminal of the common potential generation circuit 41. Furthermore, since the potential is constant during measurement, the first charging period T3 and the second charging period T7 can be shortened. Therefore, this configuration is suitable for capturing highly mobile ions.

[0256] In the first, second, and third embodiments, if the measured value is obtained from only one of the first measurement process or the second measurement process, the potential of the charging period (first charging period T3 or second charging period T7) may be continuously supplied to the detection electrode 30 during the discharge period that is excluded from measurement (first discharge period T4 or second discharge period T8).

[0257] 4. Overview of Electronic Devices Figure 20 is a schematic diagram showing the configuration of a projection display device as an electronic device according to this embodiment. In the following description, a projection display device 10000 will be used as an example of an electronic device equipped with the liquid crystal device 1000 of the first embodiment.

[0258] The projection display device 10000 is a three-panel projection display device, and includes a lamp unit 1001 as a light source, dichroic mirrors 1011 and 1012 as color separation optical systems, a liquid crystal device 1000B corresponding to blue light B, a liquid crystal device 1000G corresponding to green light G, a liquid crystal device 1000R corresponding to red light R, three reflecting mirrors 1111, 1112, and 1113, three relay lenses 1121, 1122, and 1123, a dichroic prism 1130 as a color synthesis optical system, and a projection lens 1140 as a projection optical system. An image is projected onto the screen 1200 by the projection optical system. Note that the relay lenses 1121, 1122, and 1123, and the reflecting mirrors 1112 and 1113 constitute a relay lens system 1120.

[0259] In addition, the projection display device 10000 includes a panel control circuit <1230> that receives measurement data on the deterioration status of the liquid crystal layer <5> transmitted from the liquid crystal devices <1000B>, <1000G>, and <1000R>, and performs predetermined control based on the received measurement data.

[0260] When the panel control circuit <1230> receives data on the deterioration status of each liquid crystal layer <5> from the liquid crystal devices <1000B>, <1000G>, and <1000R>, it creates and displays display information regarding the deterioration status of the liquid crystal layer <5> for each of the liquid crystal devices <1000B>, <1000G>, and <1000R>.

[0261] Note that the panel control circuit <1230> can notify, by lighting a pilot lamp <1240>, that the life of the liquid crystal panel <100> is approaching based on the measurement data on the deterioration status of the liquid crystal layer <5>. For example, when the life of the liquid crystal panel <100> of the liquid crystal device <1000B> corresponding to blue is approaching, the blue pilot lamp <1240> is lit. In addition, the panel control circuit <1230> may notify the state of the liquid crystal panel <100> by voice using a speaker <1250>. Further, the panel control circuit <1230> may notify the state of the liquid crystal panel <100> on the screen of a remote controller <1260> or a portable terminal (not shown). In addition to the displays on the liquid crystal devices <"1000B">, <"1000G">, and <"1000R"> as described above, means for notifying the state of the liquid crystal panel <100> may be provided.

[0262] Furthermore, when the panel control circuit 1230 detects from the received measurement data that the lifespan of the liquid crystal panel 100 is nearing its end, it changes the control values ​​related to the control of the liquid crystal devices 1000B, 1000G, and 1000R in order to slow down the deterioration of the liquid crystal layer 5. For example, by correcting the control values ​​to lower the brightness of the lamp unit 1001 that illuminates the liquid crystal devices 1000B, 1000G, and 1000R, or by changing the gradation voltage of the liquid crystal devices 1000B, 1000G, and 1000R to a voltage value corresponding to the decrease in brightness of the lamp unit 1001, the usable time of the liquid crystal panel 100 can be extended.

[0263] 5. Overview of the example display screen for measurement results Figure 21 is an explanatory diagram showing an example of the settings menu screen of the projection-type display device 10000, and Figure 22 is an explanatory diagram showing an example of a display screen that shows the deterioration status of the liquid crystal layer 5.

[0264] In Figure 21, when Maintenance M is selected from the setting menu screen D1 projected onto the screen 1200, the maintenance menu is displayed. When the display of the status of the liquid crystal panel 100 is selected from this menu, the panel control circuit 1230 sends a request to the liquid crystal devices 1000B, 1000G, and 1000R to transmit measurement data on the deterioration status of the liquid crystal layer 5. Based on the received measurement data on the deterioration status of the liquid crystal layer 5 from the liquid crystal devices 1000B, 1000G, and 1000R, the display screen D2 shown in Figure 22 is displayed.

[0265] Display screen D2 in Figure 22 shows the deterioration status of the liquid crystal layer 5 of liquid crystal device 1000B. The screens showing the deterioration status of the liquid crystal layer 5 of liquid crystal devices 1000G and 1000R may be displayed individually by switching screens.

[0266] The display screen D2 shows a transition line W2 indicating the history of measurements from the start of use of the liquid crystal unit 1000B to the present, a predicted transition line W3 under standard operating conditions, and a threshold line Vd_th indicating that the liquid crystal panel 100 is nearing the end of its lifespan. Information on liquid crystal units 1000G and 1000R may also be displayed on the display screen D2. By comparing the transition line W2 with the predicted transition line W3, it is possible to determine whether the operating conditions are more severe than expected, allowing for preventative maintenance such as limiting the brightness of the lamp unit 1001 illuminating the liquid crystal units 1000B, 1000G, and 1000R. Furthermore, once the transition line W2 improves to the predicted transition line W3, the brightness limit on the lamp unit 1001 may be removed.

[0267] Regarding the transition line W2 that shows the history of measured values, a smoothed line obtained by averaging multiple measured values ​​may be displayed to make it easier to identify the trend of change. Alternatively, in addition to displaying the transition line W2 that shows the history of measured values, the measured values ​​may simply be displayed as numerical values. In this case, the display color of the measured values ​​may be changed in relation to the threshold Vd_th. For example, values ​​greater than the threshold Vd_th may be displayed in green, values ​​approaching the threshold Vd_th may be displayed in yellow, and values ​​below the threshold Vd_th may be displayed in red.

[0268] Furthermore, the measured values ​​may be displayed as index values ​​normalized to an arbitrary value. In this case, for example, if the index value is calculated from the measured values ​​obtained during the second discharge period T8, the index value displayed in the early stages of use will be close to, for example, "1". This value decreases as the degradation of the liquid crystal layer 5 progresses. Typically, it tends to decrease as the usage time of the projection display device 10000 increases.

[0269] Alternatively, if expressed as a percentage, it would be a value close to "100". This value decreases in accordance with the degradation of the liquid crystal layer 5. Typically, it tends to decrease as the usage time of the projection display device 10000 increases. Alternatively, if the index value is calculated from the measured values ​​obtained during the first discharge period T4, the index value displayed in the early stages of use would be a value close to "0". This value increases in accordance with the degradation of the liquid crystal layer 5. Typically, it tends to increase as the usage time of the projection display device 10000 increases. Using such index values, the degradation state of the liquid crystal panel 100 may be displayed, for example, using a bar graph or a pie chart.

[0270] When the power of the projection display device 10000 is turned on, when the power is turned off, or when the maintenance menu instructs the measurement of the deterioration status of the liquid crystal layer 5, the panel control circuit 1230 sends a command to measure the deterioration status of the liquid crystal layer 5 to the liquid crystal devices 1000B, 1000G, and 1000R. As explained in step S10 of the flowchart in Figure 4, when the liquid crystal devices 1000B, 1000G, and 1000R receive the command to measure the deterioration status of the liquid crystal layer 5 from the panel control circuit 1230, they start the measurement.

[0271] Generally, preventive maintenance refers to planned maintenance to ensure the stable operation of equipment. When determining when to replace parts, there are two methods for determining the appropriate timeframe: one based on the usage time of the parts, and the other based on an evaluation of the degree of deterioration of the parts. Using the liquid crystal panel 100 according to the present invention, the increase in mobile ions, which is an indicator of deterioration of the liquid crystal layer 5 of the liquid crystal panel 100, can be obtained as a measured value. Since changes in the measured values ​​can be observed with high sensitivity even before display abnormalities occur in the liquid crystal panel 100, preventive maintenance can be implemented. Furthermore, by comparing the trends in the changes in measured values ​​across a large number of units and using machine learning analysis, it is possible to detect behaviors in measured values ​​that are prone to stains and unevenness, and perform predictive maintenance.

[0272] Although embodiments of the present invention have been described above, the technical scope of this disclosure is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of this disclosure.

[0273] In the first embodiment, a liquid crystal device 1000 was exemplified, comprising a liquid crystal panel 100 and a measurement circuit 200 provided outside the liquid crystal panel 100. However, a configuration in which the measurement circuit 200 is provided inside the liquid crystal panel 100 may also be adopted. That is, the measurement circuit 200 may be arranged on the element substrate 10 together with a data line drive circuit 23 and a scan line drive circuit 24, etc. The same applies to the second and third embodiments.

[0274] In this embodiment, a projection-type display device 10000 is exemplified as an electronic device, but the electronic devices to which the liquid crystal device 1000 is applied are not limited to this. For example, it may be applied to electronic devices such as 3D printers that use light emitted from the liquid crystal panel 100 to cure resin liquid, HUDs (Head-Up Displays), HMDs (Head-Mounted Displays), personal computers, digital cameras, and LCD televisions. For example, some 3D printers using liquid crystal panels 100 use UV light, and degradation of the liquid crystal panel 100 is a problem. If printing is started without realizing that the liquid crystal panel 100 is nearing the end of its lifespan, resin liquid curing failure may occur midway through printing, and this may not be noticed until printing is complete. However, by using the liquid crystal panel 100 according to the present invention, the degradation state of the liquid crystal panel 100 can be determined. Therefore, it is possible to anticipate in advance that resin liquid curing failure or other problems may occur before printing begins, and replace the liquid crystal panel 100 at an appropriate time as preventive maintenance.

[0275] In the above embodiment, a transmissive liquid crystal device 1000 was exemplified, but the liquid crystal device 1000 may also be a reflective liquid crystal device or an LCOS (Liquid crystal on silicon) type liquid crystal device.

[0276] In the first embodiment, a liquid crystal device 1000 comprising a liquid crystal panel 100 and a measurement circuit 200 provided outside the liquid crystal panel 100 was illustrated. However, a diagnostic system comprising a liquid crystal panel 100 and a diagnostic device which is a different device from the liquid crystal panel 100 may also be configured. In the diagnostic system, the diagnostic device comprises the measurement circuit 200. The same applies to the second and third embodiments.

[0277] [Summary of this disclosure] A summary of this disclosure is provided below.

[0278] (Note 1) A liquid crystal apparatus comprising: a first electrode; a second electrode; a liquid crystal layer disposed between the first electrode and the second electrode; and a measuring circuit that supplies potential to the first electrode and the second electrode, and measures the potential of the first electrode, which is the potential of the first electrode, wherein the measuring circuit supplies potential to the first electrode and the second electrode, respectively, in a first period, such that the potential difference between the first electrode and the second electrode becomes a first potential difference; in a second period after the first period, supplies potential to the first electrode and the second electrode, respectively, such that the potential difference becomes a second potential difference having a different polarity from the first potential difference; and in a third period after the second period, stops supplying potential to the first electrode and supplies the same potential to the second electrode as in the second period. As described above, the first period is inserted before the second and third periods. This allows the mobile ions contained in the liquid crystal layer to be effectively initially positioned on either the first or second electrode during the first period. By arranging the initial position of the mobile ions before the start of the second period, measurement reproducibility can be obtained for the measured value of the detection electrode potential obtained in the third period. Furthermore, the effect of the internal electric field due to the mobile ions is also reflected in the measured value, so an increase in mobile ions is more easily reflected as a change in the measured value. As a result, the progression of deterioration of the liquid crystal layer can be sensitively tracked from the initial stages of use of the liquid crystal panel having the first electrode, second electrode, and liquid crystal layer.

[0279] (Supplementary Note 2) The liquid crystal device according to Supplementary Note 1, further comprising a pixel electrode provided in the display area, wherein the first electrode is provided outside the display area.

[0280] (Supplementary Note 3) In the liquid crystal device according to Supplementary Note 2, the first period is longer than one frame period in the display area, and the absolute value of the first potential difference is not less than the maximum applied voltage of the liquid crystal layer in the display area. Thus, by setting the first period to be longer than one frame period in the display area, mobile ions with particularly low mobility can be effectively initially arranged on either the first electrode or the second electrode. Also, by setting the absolute value of the first potential difference, that is, the voltage applied to the liquid crystal layer during the first period, to be not less than the maximum applied voltage of the liquid crystal layer in the display area, mobile ions that move at about the maximum applied voltage can also be effectively initially arranged on either the first electrode or the second electrode. Therefore, according to the liquid crystal device described in Supplementary Note 3, the progress of deterioration of the liquid crystal layer can be tracked more sensitively from the initial use of the liquid crystal panel with higher measurement reproducibility.

[0281] (Supplementary Note 4) In the liquid crystal device according to Supplementary Note 2 or 3, the second period is shorter than one frame period in the display area, and the absolute value of the second potential difference is greater than 0V and less than the threshold voltage of the liquid crystal layer. Thus, by setting the second period to be shorter than one frame period in the display area, it becomes easier to capture the action of mobile ions with high mobility as a change in the measured value. Also, by setting the absolute value of the second potential difference, that is, the voltage applied to the liquid crystal layer during the second period, to be greater than 0V and less than the threshold voltage of the liquid crystal layer, the potential of the detection electrode in the third period can be measured while suppressing the influence of the dielectric anisotropy of the liquid crystal layer. Therefore, according to the liquid crystal device described in Supplementary Note 4, the progress of deterioration of the liquid crystal layer can be tracked more sensitively from the initial use of the liquid crystal panel with higher measurement reproducibility.

[0282] (Note 5) The liquid crystal apparatus according to any one of Notes 1 to 4, wherein the measuring circuit supplies potential to the first electrode and the second electrode, respectively, during a fourth period between the first period and the second period, such that the potential difference becomes a third potential difference having the same polarity as the first potential difference and an absolute value smaller than the absolute value of the first potential difference. In this way, by inserting a fourth period between the first and second periods, the mobile ions initially positioned in the first period can be moved without transitioning from the first period to the second period. Therefore, according to the liquid crystal device described in Appendix 5, the progression of deterioration of the liquid crystal layer can be tracked more sensitively from the initial stages of use of the liquid crystal panel, with higher measurement reproducibility.

[0283] (Note 6) The liquid crystal apparatus as described in Note 5, wherein the absolute value of the third potential difference is greater than 0V and less than the threshold voltage of the liquid crystal layer. Thus, by setting the absolute value of the third potential difference, that is, the voltage applied to the liquid crystal layer during the fourth period, to be greater than 0V and less than the threshold voltage of the liquid crystal layer, the effect of suppressing the influence of dielectric anisotropy of the liquid crystal layer is enhanced. Therefore, according to the liquid crystal device described in Appendix 6, the progression of deterioration of the liquid crystal layer can be tracked more sensitively from the initial stages of use of the liquid crystal panel, with higher measurement reproducibility.

[0284] (Note 7) The liquid crystal apparatus according to any one of Notes 2 to 6, wherein the measurement circuit supplies potential to the first electrode and the second electrode, respectively, in the fifth period after the third period, such that the potential difference becomes a fourth potential difference having a different polarity from the first potential difference and the same absolute value as the absolute value of the first potential difference; in the sixth period after the fifth period, such that the potential difference becomes a fifth potential difference having a different polarity from the fourth potential difference; and in the seventh period after the sixth period, the supply of potential to the first electrode is stopped and the same potential as in the sixth period is supplied to the second electrode. As described above, period 5 is inserted before periods 6 and 7. This allows the mobile ions contained in the liquid crystal layer to be effectively initially positioned on either the first or second electrode during period 5. By arranging the initial position of the mobile ions before the start of period 6, measurement reproducibility can be obtained for the detection electrode potential measurement obtained during period 7. Furthermore, the effect of the internal electric field due to the mobile ions is also reflected in the measurement value, so an increase in mobile ions is more easily reflected as a change in the measurement value. As a result, the progression of deterioration of the liquid crystal layer can be sensitively tracked from the initial use of the liquid crystal panel. Furthermore, according to the liquid crystal device described in Appendix 7, since the liquid crystal layer is driven by AC, it is possible to suppress deterioration of the liquid crystal layer caused by the application of a DC voltage to the liquid crystal layer when measuring the detection electrode potential.

[0285] (Note 8) The liquid crystal apparatus according to Note 7, wherein the fifth period is longer than the one frame period in the display area, and the absolute value of the fourth potential difference is greater than or equal to the maximum applied voltage of the liquid crystal layer in the display area. In this way, by setting the fifth period to be longer than the duration of one frame in the display area, mobile ions with particularly low mobility can be effectively initially positioned on either the first or second electrode. Furthermore, by setting the absolute value of the fourth potential difference, i.e., the voltage applied to the liquid crystal layer during the fifth period, to be greater than or equal to the maximum applied voltage to the liquid crystal layer in the display area, mobile ions that move at approximately the maximum applied voltage can be effectively initially positioned on either the first or second electrode. Therefore, according to the liquid crystal device described in Appendix 8, the progression of deterioration of the liquid crystal layer can be tracked more sensitively from the initial stages of use of the liquid crystal panel, with higher measurement reproducibility.

[0286] (Note 9) The liquid crystal apparatus according to Note 7 or 8, wherein the sixth period is shorter than the one frame period in the display area, and the absolute value of the fifth potential difference is greater than 0V and less than the threshold voltage of the liquid crystal layer. In this way, by setting the sixth period to be shorter than the duration of one frame in the display area, the effects of highly mobile ions can be more easily captured as changes in the measured values. Furthermore, by setting the absolute value of the fifth potential difference, that is, the voltage applied to the liquid crystal layer during the sixth period, to be greater than 0V and less than the threshold voltage of the liquid crystal layer, the detection electrode potential during the seventh period can be measured while suppressing the influence of dielectric anisotropy of the liquid crystal layer. Therefore, according to the liquid crystal device described in Appendix 9, the progression of deterioration of the liquid crystal layer can be tracked more sensitively from the initial stages of use of the liquid crystal panel, with higher measurement reproducibility.

[0287] (Note 10) The liquid crystal apparatus according to any one of Notes 7 to 9, wherein the measuring circuit supplies potential to the first electrode and the second electrode, respectively, during the eighth period between the fifth period and the sixth period, such that the potential difference becomes a sixth potential difference having the same polarity as the fourth potential difference and an absolute value smaller than the absolute value of the fourth potential difference. In this way, by inserting the eighth period between the fifth and sixth periods, it is possible to transition from the fifth period to the sixth period without moving the mobile ions that were initially positioned in the fifth period. Therefore, according to the liquid crystal device described in Appendix 10, the progression of deterioration of the liquid crystal layer can be tracked more sensitively from the initial stages of use of the liquid crystal panel, with higher measurement reproducibility.

[0288] (Note 11) The liquid crystal apparatus as described in Note 10, wherein the absolute value of the sixth potential difference is greater than 0V and less than the threshold voltage of the liquid crystal layer. Thus, by setting the absolute value of the sixth potential difference, that is, the voltage applied to the liquid crystal layer during the eighth period, to be greater than 0V and less than the threshold voltage of the liquid crystal layer, the effect of suppressing the influence of dielectric anisotropy of the liquid crystal layer is enhanced. Therefore, according to the liquid crystal device described in Appendix 11, the progression of deterioration of the liquid crystal layer can be tracked more sensitively from the initial stages of use of the liquid crystal panel, with higher measurement reproducibility.

[0289] (Note 12) The measurement circuit includes a first node electrically connected to the first electrode, a second electrode line electrically connected to the second electrode, a ground potential line to which a ground potential is applied, a first capacitor electrically connected between the first node and the ground potential line, a second capacitor electrically connected between the second electrode line and the ground potential line, a first switch, a second switch, a third switch, a fourth switch, a measurement potential generation circuit that outputs a measurement potential corresponding to a reference voltage, and a circuit that outputs the reference voltage to the measurement potential generation circuit and controls the first switch to the fourth switch. A liquid crystal apparatus according to any one of appendices 1 to 11, comprising: a control circuit; a potential measurement circuit that measures the potential of the first node as the first electrode potential and outputs the measured value of the first electrode potential to the control circuit, wherein the first node is electrically connected to the ground potential line via the first switch; the first node is electrically connected to the output terminal of the measurement potential generation circuit via the second switch; the second electrode line is electrically connected to the ground potential line via the third switch; and the second electrode line is electrically connected to the output terminal of the measurement potential generation circuit via the fourth switch. By using a measurement circuit with the above configuration, the functions required of a measurement circuit can be realized with a simple circuit configuration, and noise components included in the measured value of the detection electrode potential can be reduced.

[0290] (Note 13) The liquid crystal apparatus according to Note 12, wherein the first switch and the second switch are controlled to be ON by a first voltage, and the third switch and the fourth switch are controlled to be ON by a second voltage that is higher than the first voltage. In this way, by controlling the third and fourth switches, which are electrically connected to the second electrode wire, to be turned on by a relatively high second voltage, the on-resistance of the third and fourth switches can be reduced, thereby improving the responsiveness of the second electrode wire and suppressing leakage current from the first electrode. As a result, the second and sixth periods can be shortened, allowing the effects of highly mobile ions to be captured as changes in the measured values, while also suppressing the influence of variations in the characteristics of each switch component on the measured values.

[0291] (Note 14) The measurement circuit includes a first node electrically connected to the first electrode, a second node, a second electrode line electrically connected to the second electrode, a ground potential line to which a ground potential is applied, a first capacitor electrically connected between the first node and the ground potential line, a second capacitor electrically connected between the second electrode line and the ground potential line, a first switch, a second switch, a third switch, a fourth switch, a sixth switch, a seventh switch, a first measurement potential generation circuit that outputs a first measurement potential, a second measurement potential generation circuit that outputs a second measurement potential, a control circuit that controls the first switch to the fourth switch, the sixth switch, and the seventh switch, and the potential of the first node A liquid crystal apparatus according to any one of appendices 1 to 11, comprising: a potential measuring circuit that measures the potential as a first electrode potential and outputs the measured value of the first electrode potential to the control circuit, wherein the first node is electrically connected to the ground potential line via the first switch, the first node is electrically connected to the second node via the second switch, the second node is electrically connected to the output terminal of the first measuring potential generation circuit via the sixth switch, the second node is electrically connected to the output terminal of the second measuring potential generation circuit via the seventh switch, the second electrode line is electrically connected to the ground potential line via the third switch, and the second electrode line is electrically connected to the second node via the fourth switch. By using a measurement circuit with the above configuration, the functions required of a measurement circuit can be realized with a simple circuit configuration, and noise components included in the measured value of the detection electrode potential can be reduced.

[0292] (Note 15) The liquid crystal apparatus according to Note 14, wherein the first switch and the second switch are controlled to be ON by a first voltage, and the third switch, the fourth switch, the sixth switch, and the seventh switch are controlled to be ON by a second voltage higher than the first voltage. In this way, the third, fourth, sixth, and seventh switches, which are electrically connected to the second electrode wire, are controlled to be ON by a relatively high second voltage. This reduces the ON resistance of each of these switches, thereby improving the responsiveness of the second electrode wire and suppressing leakage current from the first electrode. As a result, the second and sixth periods can be shortened, allowing the effects of highly mobile ions to be captured as changes in the measured values, while also suppressing the influence of variations in the characteristics of each switch component on the measured values.

[0293] (Note 16) The liquid crystal apparatus according to any one of Notes 1 to 11, wherein the measurement circuit comprises a first node electrically connected to the first electrode, a second electrode line electrically connected to the second electrode, a ground potential line to which a ground potential is applied, a first capacitor electrically connected between the first node and the ground potential line, a second capacitor electrically connected between the second electrode line and the ground potential line, a first switch, a second switch, a measurement potential generation circuit that outputs a measurement potential corresponding to a reference voltage, a common potential generation circuit that outputs a predetermined common potential, a control circuit that outputs the reference voltage to the measurement potential generation circuit and controls the first switch and the second switch, and a potential measurement circuit that measures the potential of the first node as the first electrode potential and outputs the measured value of the first electrode potential to the control circuit, wherein the first node is electrically connected to the output terminal of the common potential generation circuit via the first switch, the first node is electrically connected to the output terminal of the measurement potential generation circuit via the second switch, and the second electrode line is electrically connected to the output terminal of the common potential generation circuit. By using a measurement circuit having the above configuration, the functions required for the measurement circuit can be realized with a simpler circuit configuration compared to the liquid crystal devices described in Appendix 12 and Appendix 14, and noise components included in the measured value of the detection electrode potential can be reduced.

[0294] (Note 17) An electronic device equipped with a liquid crystal device as described in any one of Notes 1 to 16.

[0295] (Note 18) A diagnostic system comprising: a liquid crystal panel having a first electrode, a second electrode, and a liquid crystal layer disposed between the first electrode and the second electrode; and a diagnostic device having a measurement circuit that supplies potential to the first electrode and the second electrode and measures the potential of the first electrode, the first electrode potential, wherein the measurement circuit supplies potential to the first electrode and the second electrode in a first period such that the potential difference between the first electrode and the second electrode becomes a first potential difference; supplies potential to the first electrode and the second electrode in a second period after the first period such that the potential difference becomes a second potential difference having a different polarity from the first potential difference; and stops supplying potential to the first electrode and supplies the same potential to the second electrode as in the second period in a third period after the second period. [Explanation of Symbols]

[0296] 1000, 2000, 3000... Liquid crystal device, 100... Liquid crystal panel, 200, 300, 400... Measurement circuit, 5... Liquid crystal layer, 30... Detection electrode (first electrode), 21... Common electrode (second electrode), 40... Measurement potential generation circuit, 41... Common potential generation circuit, 42... Level shifter, 43... Amplification circuit (potential measurement circuit), 44... A / D converter (potential measurement circuit), 45... Central control circuit (control circuit), and 48... First measurement potential generation circuit, 49... Second measurement potential generation circuit, SW1... First switch, SW2... Second switch, SW3... Third switch, SW4... 4 switches, SW5…5th switch, SW6…6th switch, SW7…7th switch, C1…1st capacitor, C2…2nd capacitor, L1…common electrode wire (2nd electrode wire), L2…ground potential wire, N1…1st node, N2…2nd node, T1…1st reverse sweep period (1st period), T2…1st relaxation period (4th period), T3…1st charging period (2nd period), T4…1st discharge period (3rd period), T5…5th reverse sweep period (5th period), T6…2nd relaxation period (8th period), T7…2nd charging period (6th period), T8…2nd discharge period (7th period)

Claims

1. Pixel electrodes provided in the display area, A first electrode provided outside the display area, The second electrode and The pixel electrode and the liquid crystal layer disposed between the first electrode and the second electrode, A measurement circuit that supplies potential to the first electrode and the second electrode, and measures the first electrode potential, which is the potential of the first electrode, Equipped with, The aforementioned measurement circuit is During the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference between them becomes the first potential difference. In the second period following the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference becomes a second potential difference having a different polarity from the first potential difference. In the third period following the second period, the supply of potential to the first electrode is stopped, and the same potential as in the second period is supplied to the second electrode. The first period is longer than the duration of one frame in the display area. The absolute value of the first potential difference is greater than or equal to the maximum applied voltage of the liquid crystal layer in the display area. Liquid crystal display (LCD) device.

2. Pixel electrodes provided in the display area, A first electrode provided outside the display area, The second electrode and The pixel electrode and the liquid crystal layer disposed between the first electrode and the second electrode, A measurement circuit that supplies potential to the first electrode and the second electrode, and measures the first electrode potential, which is the potential of the first electrode, Equipped with, The aforementioned measurement circuit is During the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference between them becomes the first potential difference. In the second period following the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference becomes a second potential difference having a different polarity from the first potential difference. In the third period following the second period, the supply of potential to the first electrode is stopped, and the same potential as in the second period is supplied to the second electrode. The second period is shorter than the duration of one frame in the display area. The absolute value of the second potential difference is greater than 0V and less than the threshold voltage of the liquid crystal layer. Liquid crystal display (LCD) device.

3. First electrode and The second electrode and A liquid crystal layer disposed between the first electrode and the second electrode, A measurement circuit that supplies potential to the first electrode and the second electrode, and measures the first electrode potential, which is the potential of the first electrode, Equipped with, The aforementioned measurement circuit is During the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference between them becomes the first potential difference. In the second period following the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference becomes a second potential difference having a different polarity from the first potential difference. In the third period following the second period, the supply of potential to the first electrode is stopped, and the same potential as in the second period is supplied to the second electrode. In the fourth period between the first and second periods, a potential is supplied to the first and second electrodes respectively such that the potential difference becomes a third potential difference having the same polarity as the first potential difference and an absolute value smaller than the absolute value of the first potential difference. Liquid crystal display (LCD) device.

4. The absolute value of the third potential difference is greater than 0V and less than the threshold voltage of the liquid crystal layer. The liquid crystal apparatus according to claim 3.

5. A pixel electrode provided in the display area, A first electrode provided outside the display area, The second electrode and The pixel electrode and the liquid crystal layer disposed between the first electrode and the second electrode, A measurement circuit that supplies potential to the first electrode and the second electrode, and measures the first electrode potential, which is the potential of the first electrode, Equipped with, The aforementioned measurement circuit is During the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference between them becomes the first potential difference. In the second period following the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference becomes a second potential difference having a different polarity from the first potential difference. In the third period following the second period, the supply of potential to the first electrode is stopped, and the same potential as in the second period is supplied to the second electrode. In the fifth period following the third period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference becomes a fourth potential difference having a different polarity from the first potential difference and having the same absolute value as the absolute value of the first potential difference. In the sixth period following the fifth period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference becomes a fifth potential difference having a different polarity from the fourth potential difference. In the seventh period following the sixth period, the supply of potential to the first electrode is stopped, and the same potential as in the sixth period is supplied to the second electrode. Liquid crystal display (LCD) device.

6. The fifth period is longer than the duration of one frame in the display area. The absolute value of the fourth potential difference is greater than or equal to the maximum applied voltage of the liquid crystal layer in the display area. The liquid crystal apparatus according to claim 5.

7. The sixth period is shorter than the duration of one frame in the display area. The absolute value of the fifth potential difference is greater than 0V and less than the threshold voltage of the liquid crystal layer. The liquid crystal apparatus according to claim 5.

8. The measurement circuit supplies potential to the first electrode and the second electrode, respectively, during the eighth period between the fifth period and the sixth period, such that the potential difference becomes a sixth potential difference having the same polarity as the fourth potential difference and having an absolute value smaller than the absolute value of the fourth potential difference. A liquid crystal apparatus according to any one of claims 5 to 7.

9. The absolute value of the sixth potential difference is greater than 0V and less than the threshold voltage of the liquid crystal layer. The liquid crystal apparatus according to claim 8.

10. First electrode and The second electrode and A liquid crystal layer disposed between the first electrode and the second electrode, A measurement circuit that supplies potential to the first electrode and the second electrode, and measures the first electrode potential, which is the potential of the first electrode, Equipped with, The aforementioned measurement circuit is During the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference between them becomes the first potential difference. In the second period following the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference becomes a second potential difference having a different polarity from the first potential difference. In the third period following the second period, the supply of potential to the first electrode is stopped, and the same potential as in the second period is supplied to the second electrode. A first node electrically connected to the first electrode, A second electrode wire electrically connected to the aforementioned second electrode, A ground potential line to which the ground potential is applied, A first capacitor is electrically connected between the first node and the ground potential line, A second capacitor is electrically connected between the second electrode line and the ground potential line, Switch 1 and The second switch, The third switch, The fourth switch, A measurement potential generation circuit that outputs a measurement potential corresponding to the reference voltage, A control circuit that outputs the reference voltage to the measurement potential generation circuit and controls the first to fourth switches, A potential measurement circuit that measures the potential of the first node as the first electrode potential and outputs the measured value of the first electrode potential to the control circuit, Equipped with, The first node is electrically connected to the ground potential line via the first switch. The first node is electrically connected to the output terminal of the measurement potential generation circuit via the second switch. The second electrode wire is electrically connected to the ground potential wire via the third switch. The second electrode wire is electrically connected to the output terminal of the measurement potential generation circuit via the fourth switch. Liquid crystal display (LCD) device.

11. The first switch and the second switch are controlled to the ON state by the first voltage, The third switch and the fourth switch are controlled to be turned on by a second voltage that is higher than the first voltage. The liquid crystal apparatus according to claim 10.

12. First electrode and The second electrode and A liquid crystal layer disposed between the first electrode and the second electrode, A measurement circuit that supplies potential to the first electrode and the second electrode, and measures the first electrode potential, which is the potential of the first electrode, Equipped with, The aforementioned measurement circuit is During the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference between them becomes the first potential difference. In the second period following the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference becomes a second potential difference having a different polarity from the first potential difference. In the third period following the second period, the supply of potential to the first electrode is stopped, and the same potential as in the second period is supplied to the second electrode. A first node electrically connected to the first electrode, The second node and A second electrode wire electrically connected to the aforementioned second electrode, A ground potential line to which the ground potential is applied, A first capacitor is electrically connected between the first node and the ground potential line, A second capacitor is electrically connected between the second electrode line and the ground potential line, Switch 1 and The second switch, The third switch, The fourth switch, The sixth switch, Switch number 7 and A first measurement potential generation circuit that outputs a first measurement potential, A second measurement potential generation circuit that outputs a second measurement potential, A control circuit that controls the first to fourth switches, the sixth switch, and the seventh switch, A potential measurement circuit that measures the potential of the first node as the first electrode potential and outputs the measured value of the first electrode potential to the control circuit, Equipped with, The first node is electrically connected to the ground potential line via the first switch. The first node is electrically connected to the second node via the second switch, The second node is electrically connected to the output terminal of the first measuring potential generation circuit via the sixth switch. The second node is electrically connected to the output terminal of the second measuring potential generation circuit via the seventh switch. The second electrode wire is electrically connected to the ground potential wire via the third switch. The second electrode wire is electrically connected to the second node via the fourth switch. Liquid crystal display (LCD) device.

13. The first switch and the second switch are controlled to the ON state by the first voltage, The third switch, the fourth switch, the sixth switch, and the seventh switch are controlled to be ON by a second voltage that is higher than the first voltage. The liquid crystal apparatus according to claim 12.

14. First electrode and The second electrode and A liquid crystal layer disposed between the first electrode and the second electrode, A measurement circuit that supplies potential to the first electrode and the second electrode, and measures the first electrode potential, which is the potential of the first electrode, Equipped with, The aforementioned measurement circuit is During the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference between them becomes the first potential difference. In the second period following the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference becomes a second potential difference having a different polarity from the first potential difference. In the third period following the second period, the supply of potential to the first electrode is stopped, and the same potential as in the second period is supplied to the second electrode. A first node electrically connected to the first electrode, A second electrode wire electrically connected to the aforementioned second electrode, A ground potential line to which the ground potential is applied, A first capacitor is electrically connected between the first node and the ground potential line, A second capacitor is electrically connected between the second electrode line and the ground potential line, Switch 1 and The second switch, A measurement potential generation circuit that outputs a measurement potential corresponding to the reference voltage, A common potential generation circuit that outputs a predetermined common potential, A control circuit that outputs the reference voltage to the measurement potential generation circuit and controls the first switch and the second switch, A potential measurement circuit that measures the potential of the first node as the first electrode potential and outputs the measured value of the first electrode potential to the control circuit, Equipped with, The first node is electrically connected to the output terminal of the common potential generation circuit via the first switch. The first node is electrically connected to the output terminal of the measurement potential generation circuit via the second switch. The second electrode wire is electrically connected to the output terminal of the common potential generation circuit. Liquid crystal display (LCD) device.

15. An electronic device comprising a liquid crystal device according to any one of claims 1 to 7.

16. A pixel electrode provided in the display area, a first electrode provided outside the display area, a second electrode, and a liquid crystal layer disposed between the pixel electrode and the first and second electrodes, A liquid crystal panel equipped with, A diagnostic device comprising a measuring circuit that supplies potential to the first electrode and the second electrode, and measures the potential of the first electrode, which is the first electrode potential, Equipped with, The aforementioned measurement circuit is During the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference between them becomes the first potential difference. In the second period following the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference becomes a second potential difference having a different polarity from the first potential difference. In the third period following the second period, the supply of potential to the first electrode is stopped, and the same potential as in the second period is supplied to the second electrode. The first period is longer than the duration of one frame in the display area. The absolute value of the first potential difference is greater than or equal to the maximum applied voltage of the liquid crystal layer in the display area. Diagnostic system.

17. A pixel electrode provided in the display area, a first electrode provided outside the display area, a second electrode, and a liquid crystal layer disposed between the pixel electrode and the first and second electrodes, A liquid crystal panel equipped with, A diagnostic device comprising a measuring circuit that supplies potential to the first electrode and the second electrode, and measures the potential of the first electrode, which is the first electrode potential, Equipped with, The aforementioned measurement circuit is During the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference between them becomes the first potential difference. In the second period following the first period, potential is supplied to the first electrode and the second electrode respectively such that the potential difference becomes a second potential difference having a different polarity from the first potential difference. In the third period following the second period, the supply of potential to the first electrode is stopped, and the same potential as in the second period is supplied to the second electrode. The second period is shorter than the duration of one frame in the display area. The absolute value of the second potential difference is greater than 0V and less than the threshold voltage of the liquid crystal layer. Diagnostic system.

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