Liquid crystal device, electronic device, and method for measuring physical properties of liquid crystal layer

Abstract

To provide a liquid crystal device for which situation of increasing mobile ions in the liquid crystals can be observed before the mobile ions suddenly increase.SOLUTION: A liquid crystal device 1000 includes: a first electrode 1; a pixel electrode 9a as a second electrode; a liquid crystal layer 5 to which a drive voltage is applied at each refresh period of time as a first refresh period of time; and a measurement circuit 301 for applying an inspection voltage V1 to the liquid crystal layer between a common electrode 21 and a pixel electrode 9a, setting a longer period of time than one refresh period of time after the application of the inspection voltage V1 is stopped, and measuring a voltage Vm between the common electrode 21 and the pixel electrode 9a.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a liquid crystal device, an electronic device including the liquid crystal device, and a method for measuring the physical properties of a liquid crystal layer used in the liquid crystal device. [Background technology]

[0002] The liquid crystal used in liquid crystal devices deteriorates when subjected to DC voltage for a long period of time. Furthermore, when a liquid crystal device is used as a light bulb in a projector, the liquid crystal also deteriorates due to high-intensity light and chemical reactions caused by heat. Liquid crystal deterioration occurs, for example, when the number of mobile ions (anions and cations) in the liquid crystal increases, resulting in a decrease in the liquid crystal's insulating properties. This decrease in insulating properties manifests itself, for example, as a decrease in the liquid crystal's voltage holding ratio, which is visually noticeable on the liquid crystal panel as display defects such as stains and unevenness. Patent Document 1 discloses a method for accelerating the evaluation of such liquid crystal degradation. In this method, a pair of degradation evaluation electrodes is provided outside the display area of ​​the liquid crystal panel. After a 100-hour accelerated test, a 5V voltage is applied between the degradation evaluation electrodes for 50 μs, and the voltage holding ratio is measured 16.7 ms later to evaluate the liquid crystal degradation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-215048 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the applicant's research, when an accelerated test involving the incidence of high-intensity light is performed on a liquid crystal panel, it is found that there is a stage in which the mobile ions in the liquid crystal increase relatively slowly, followed by a stage in which the mobile ions in the liquid crystal increase rapidly. Furthermore, when light other than visible light, such as UV light, is incident on a liquid crystal panel, the high energy of the UV light intensifies chemical reactions, accelerating the deterioration of the liquid crystal.

[0005] Furthermore, when the amount of mobile ions in the liquid crystal becomes significant, problems such as a decline in the display quality of the liquid crystal panel are unavoidable. Therefore, from the perspective of preventive maintenance, there has been a demand for information on when the liquid crystal panel is nearing the end of its life before it reaches that point.

[0006] However, the method of Patent Document 1 has a problem in that it is difficult to perform preventive maintenance. Specifically, according to the results of verification by the present applicant, the method of Patent Document 1 makes it difficult to observe the gradual increase in mobile ions in the liquid crystal at a stage where the mobile ions in the liquid crystal increase relatively slowly. [Means for solving the problem]

[0008] The liquid crystal device comprises a first electrode, a second electrode, a liquid crystal layer to which a driving voltage equal to or greater than a threshold voltage is applied, and a measurement circuit that applies a test voltage equal to or less than the threshold voltage of the liquid crystal layer and higher than 0V as a voltage to be applied to the liquid crystal layer between the first electrode and the second electrode, and measures the potential of the first electrode after stopping the application of the test voltage.

[0009] An electronic device includes the liquid crystal device.

[0011] The method for measuring the physical properties of a liquid crystal layer is a method for measuring the physical properties of a liquid crystal layer in a liquid crystal device in which a driving voltage equal to or greater than the threshold voltage of the liquid crystal layer is applied, by applying a test voltage equal to or less than the threshold voltage and higher than 0 V to the liquid crystal layer between a first electrode and a second electrode arranged to apply an electric field to the liquid crystal layer, and detecting the potential of the first electrode after stopping the application of the test voltage. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a plan view showing a schematic configuration of a liquid crystal panel used in a liquid crystal device according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line H-H' in FIG. [Figure 3] FIG. 2 is an explanatory diagram showing a schematic configuration of the liquid crystal panel of FIG. [Figure 4] 10 is a flowchart showing a method for measuring a liquid crystal device. [Figure 5] 4 is a timing chart showing a method for measuring a liquid crystal device. [Figure 6A] 10 is a graph showing the relationship between usage time and discharge characteristics. [Figure 6B] Graph showing the relationship between usage time and measurement values. [Figure 7A] 4 is a graph showing discharge characteristics measured at an inspection voltage according to the first embodiment. [Figure 7B] 10 is a graph showing discharge characteristics measured at an inspection voltage according to a comparative example. [Figure 8] FIG. 10 is an explanatory diagram showing a schematic configuration of a liquid crystal device according to a second embodiment. [Figure 9] FIG. 3 is an explanatory diagram showing the configuration of a holding member of the liquid crystal device. [Figure 10] FIG. 10 is an explanatory diagram showing a schematic configuration of a liquid crystal device according to a third embodiment. [Figure 11] FIG. 10 is an explanatory diagram showing a schematic configuration of a liquid crystal device according to a fourth embodiment. [Figure 12] FIG. 10 is an explanatory diagram showing a schematic configuration of an electronic device according to a fifth embodiment. [Figure 13A] FIG. 10 is an explanatory diagram showing an example of a setting menu screen of a projection display device as an electronic device. [Figure 13B] FIG. 10 is an explanatory diagram showing an example of a display screen that displays the deterioration state of a liquid crystal layer. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scale of each component may differ from the actual scale in order to make each component recognizable. Furthermore, in the following drawings, X, Y, and Z axes are provided as mutually orthogonal coordinate axes as necessary, and in each drawing, the direction indicated by each arrow along the axis is the + direction, and the direction opposite to the + direction is the - direction.

[0014] Note that the +Z direction is sometimes referred to as upward and the -Z direction as downward, and a view from the +Z direction is referred to as a planar view or planar. Furthermore, in the following description, for example, the expression "on a substrate" with respect to a substrate means either a case where the substrate is placed in contact with the substrate, a case where the substrate is placed via another structure, or a case where a portion of the substrate is placed in contact with the substrate and a portion of the substrate is placed via another structure.

[0015] 1. Embodiment 1 1.1. LCD Panel Overview 1 is a plan view showing a schematic configuration of a liquid crystal panel used in a liquid crystal device of embodiment 1. In this embodiment, an active-drive liquid crystal panel 100 having a TFT (Thin Film Transistor) as a pixel switching element for each pixel will be described as an example of the liquid crystal panel 100. This liquid crystal panel 100 is combined with a driving IC (Integrated Circuit) (described later) and a measurement circuit for measuring the physical properties of the liquid crystal layer to form a liquid crystal device, and can be suitably used as a light modulation device in electronic devices such as projection display devices.

[0016] The liquid crystal panel 100 includes an element substrate 10 and a counter substrate 20. The components depicted in solid lines inside the outline of the counter substrate 20 are all components disposed between the counter substrate 20 and the element substrate 10.

[0017] The sealing material 14 is provided in a frame shape along the outer edge of the counter substrate 20. A parting portion 27 indicated by 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 so as to surround the display area E. The sealing material 14 is an adhesive made of a photocurable resin, a thermosetting resin, or the like, and contains a gap material such as glass fiber or glass beads for setting the gap between the element substrate 10 and the counter substrate 20 to a predetermined value.

[0018] Pixels P are arranged in a matrix in the display region E. Peripheral circuits such as a scanning line driving circuit 24 and a precharge circuit 25 are arranged in a peripheral region F between the display region E and the sealant 14. Furthermore, a data line driving circuit 23 and a plurality of external connection terminals 18 are arranged in a portion of the element substrate 10 outside the sealant 14 that extends downward in the −Y direction from the counter substrate 20 of the element substrate 10.

[0019] Inter-substrate conductive portions 17 for establishing electrical conduction between the element substrate 10 and the counter substrate 20 are arranged at the four corners of the counter substrate 20 .

[0020] 1.2. Overview of the cross-sectional structure of the LCD panel Fig. 2 is a cross-sectional view showing a schematic configuration of a liquid crystal panel taken along line H-H' in Fig. 1. The element substrate 10 and the counter substrate 20 are arranged with a sealant 14 interposed therebetween, and a liquid crystal layer 5 is disposed between the element substrate 10 and the counter substrate 20.

[0021] Between the substrate 10a and the liquid crystal layer 5, the element substrate 10 includes a light-transmitting pixel electrode 9a provided for each pixel P, a TFT 11 serving 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.

[0022] The counter substrate 20 has, between its substrate 20a and the liquid crystal layer 5, a parting portion 27, a common electrode 21, and a second alignment film 22 disposed to cover the common electrode 21.

[0023] The parting portion 27 is provided at a position overlapping the scanning line driving circuit 24 in plan view. The parting portion 27 blocks light L from a laser light source (not shown) that is incident from the counter substrate 20 side, preventing it from entering peripheral circuits including the scanning line driving circuit 24, thereby preventing the peripheral circuits from malfunctioning due to the light L.

[0024] The pixel electrode 9a and the common electrode 21 are formed of a transparent conductive material such as ITO (Indium Tin Oxide). The substrates 10a and 20a are each a light-transmitting substrate, and may be, for example, a glass substrate or a quartz substrate. The first alignment film 12 and the second alignment film 22 are formed of an inorganic material such as silicon oxide. The liquid crystal layer 5 is composed of, for example, liquid crystal having negative dielectric anisotropy.

[0025] 1.3. Overview of LCD device configuration 3 is an explanatory diagram showing a schematic configuration of a liquid crystal device. The liquid crystal device 1000 includes a liquid crystal panel 100, a control board 200 on which a driving IC 201 is mounted, and a measurement board 300 on which a measurement circuit 301 is mounted. The control board 200 is, for example, an FPC (Flexible Printed Circuits) board, and is electrically connected to the external connection terminals 18 of the liquid crystal panel 100. The control board 200 is also electrically connected to the measurement board 300 via a connector (not shown). Alternatively, the control board 200 and the measurement board 300 may be integrally formed, and a separate FPC board may be used to electrically connect the control board 200 to the external connection terminals 18 of the liquid crystal panel 100.

[0026] The liquid crystal panel 100 has, in its display area E, a plurality of scanning lines 3 and a plurality of signal lines 4 intersecting the plurality of scanning lines 3, and has pixels P at positions corresponding to each intersection of each scanning line 3 and each signal line 4.

[0027] The pixel P has a pixel electrode 9a, a TFT 11 that controls the electrical connection between the signal line 4 and the pixel electrode 9a, a storage capacitor 7 that has one end electrically connected to the pixel electrode 9a and the other end electrically connected to the capacitance line 6, and a liquid crystal layer 5 that is arranged between the pixel electrode 9a and the common electrode 21.

[0028] A scanning line driving circuit 24, a data line driving circuit 23, a precharge circuit 25, an inter-substrate conductive section 17, etc. are arranged in the peripheral region F. The scanning line driving circuit 24 supplies a scanning signal to the scanning lines 3 to control the on / off of the TFTs 11.

[0029] The data line driving circuit 23 includes sample switches 222 that control the electrical connection between the image signal supply lines 223 and the signal lines 4, and a shift register 221 that supplies control signals that control the on / off of the sample switches 222. In this embodiment, the data line driving circuit 23 supplies image signals to each pixel electrode 9 a by a phase expansion driving method that collectively selects sample switches 222 that are electrically connected to a predetermined number of adjacent signal lines 4.

[0030] The precharge circuit 25 supplies the precharge voltage, which is supplied from the reference potential generation circuit 35, which also serves as a precharge voltage generation unit, via the precharge signal line 8, to the signal line 4. The precharge switch 251 controls the electrical connection between the precharge signal line 8 and the signal line 4 based on a control signal supplied from the driving IC 201.

[0031] The inter-substrate conductive portions 17 are arranged 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 a node N of the measurement substrate 300 via an external connection terminal 18. The node N is a wiring electrically connected to the common electrode 21. It is preferable to provide a stabilizing capacitance C1 at the node N to stabilize the measurement voltage.

[0032] A measurement circuit 301 is mounted on the measurement board 300. The measurement circuit 301 has a central control circuit 30, a measurement value storage circuit 32, a determination circuit 31, a display information generation circuit 33, a test voltage generation circuit 34, a reference potential generation circuit 35, a capacitance line voltage generation circuit 36, an amplifier circuit 38, and an A / D converter 39.

[0033] The central control circuit 30 controls each circuit included in the measurement circuit 301 when measuring the deterioration state of the liquid crystal layer 5 of the liquid crystal panel 100. The measurement value storage circuit 32 stores the measured values. The judgment circuit 31 judges the deterioration state of the liquid crystal layer 5 based on the measurement values ​​stored in the measurement value storage circuit 32. The display information generation circuit 33 generates display information based on the measurement values ​​and the judgment results. The test voltage generation circuit 34 outputs a test voltage V1 to node N via a switch 37 during measurement. The switch 37 is controlled by the central control circuit 30. The reference potential generation circuit 35 outputs a reference potential V2 that serves as a reference for the test voltage V1 applied to the pixel electrode 9a during measurement. The amplifier circuit 38, which is composed of, for example, a voltage follower, outputs the potential of node N as a measurement voltage during measurement. The A / D converter 39 A / D converts the measurement voltage output from the amplifier circuit 38 and outputs it as a digital measurement value to the measurement value storage circuit 32 via the central control circuit 30.

[0034] The circuits constituting the measuring circuit 301 may be configured such that some or all of the functions realized by each circuit are implemented by, for example, a control program of the central control circuit 30. The measuring circuit 301 may also be stored in a single IC or divided into multiple ICs.

[0035] Each circuit may also be configured to perform multiple functions. For example, the test voltage generation circuit 34 may function as a common potential generation circuit that outputs a common potential to the common electrode 21 during normal driving. The reference potential generation circuit 35 may function as a precharge voltage generation circuit that applies a precharge voltage to the signal line 4 during normal driving. The capacitance line voltage generation circuit 36 ​​applies a storage capacitance potential V3 to the capacitance line 6.

[0036] The measurement board 300 is electrically connected to the liquid crystal panel 100 via the control board 200. The measurement circuit 301 can also be mounted on the control board 200.

[0037] A driving IC 201 is mounted on the control board 200. The driving IC 201 outputs timing signals, image signals, control signals, etc. to peripheral circuits such as the data line driving circuit 23, the scanning line driving circuit 24, and the precharge circuit 25. The control board 200 is formed, for example, from an FPC board, and one end terminal is electrically connected to the external connection terminal 18 of the liquid crystal panel 100.

[0038] 1.4. Overview of liquid crystal layer property measurement methods FIG. 4 is a schematic flowchart showing a method for measuring the physical properties of a liquid crystal layer of a liquid crystal panel, and FIG. 5 is a timing chart showing the change in potential of a measurement target node over time when the method for measuring the physical properties of a liquid crystal layer is performed.

[0039] The method for measuring the physical properties of the liquid crystal layer 5 will be described below mainly with reference to the flowchart in FIG. 4, and also with reference to FIGS. 3 and 5 as appropriate.

[0040] In step S10, when a predetermined event occurs, the liquid crystal device 1000 transitions from the normal driving mode to the measurement mode and begins measuring the physical properties of the liquid crystal layer 5. The predetermined events include powering on or off the projection display device using the liquid crystal device 1000, and a measurement instruction from a maintenance menu selection in the projection display device using the liquid crystal device 1000. The occurrence of these events triggers a measurement start command from the projection display device. Upon receiving the measurement start command from the projection display device, the central control circuit 30 begins measuring the physical properties of the liquid crystal layer 5. Note that 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 necessarily force all of the exemplified actions of "maintenance menu selection," "power on," and "power off." In the present invention, the physical properties of the liquid crystal layer 5 are measured, for example, with the light source of the projection display device turned off. Alternatively, a mechanical light-blocking mechanism may be used to block light from the light source. This is because the inspection electrodes and reference electrodes provided on the liquid crystal panel 100 are electrically controlled to have a period that is different from one refresh period of the liquid crystal panel 100. Control of the inspection electrodes and reference electrodes will be described in detail later. If the light source of the projection display device is in a non-illuminated state, no display problems will occur in the projection display device.

[0041] In step S11, a test voltage V1 is charged to a liquid crystal capacitance formed by the common electrode 21, the plurality of pixel electrodes 9a, and the liquid crystal layer 5. The test voltage generation circuit 34 starts outputting the test voltage V1, and the reference potential generation circuit 35 starts outputting a reference potential V2 that serves as a reference for the test voltage V1. The switch 37 is controlled to an on state between time T1 and time T2 in FIG. 5. Therefore, the test voltage V1 output from the test voltage generation circuit 34 is applied to the common electrode 21 via the node N, the common potential line 16 serving as a test electrode, and the inter-substrate conductive portion 17.

[0042] Here, the absolute value of the voltage applied to the liquid crystal layer 5, i.e., |V1-V2|, is a voltage equal to or less than the threshold voltage of the liquid crystal layer 5 but equal to or greater than 0 V. In this embodiment, the threshold voltage of the liquid crystal layer 5 is approximately 2.2 V, and the test voltage V1 is 1.2 V. The threshold voltage of the liquid crystal layer 5 is a drive voltage at which the transmittance or brightness of the liquid crystal layer 5 is approximately 10% at its maximum gray scale ratio. More preferably, it is a voltage just before the liquid crystal molecules begin to move or just before the alignment state of the liquid crystal molecules begins to change. In this embodiment, the threshold voltage of the liquid crystal layer 5 is defined as above because the liquid crystal panel 100 is a normally black type. In the case of a normally white type liquid crystal panel 100, for example, the threshold voltage of the liquid crystal layer 5 can be defined as a drive voltage at which the transmittance or brightness of the liquid crystal layer 5 is approximately 90% at its maximum gray scale ratio. In any case, setting the test voltage V1 based on the threshold voltage of the liquid crystal layer 5 is effective in improving the measurement sensitivity of the physical properties of the liquid crystal layer 5, as described below.

[0043] The reference potential V2 output from the reference potential generating circuit 35 is supplied to the precharge circuit 25 via the precharge signal line 8. At time T1 in FIG. 5, the precharge switches 251 connected to all signal lines 4 are controlled to change from an OFF state to an ON state. At the same time, scanning signals are output to all scanning lines 3, turning on the TFTs 11 of all pixels P. As a result, all pixels P are selected, and the reference potential V2 is applied to the pixel electrodes 9a of all pixels P. Here, the reference potential V2 is GND, and the pixel electrodes 9a to which the reference potential V2 is applied are the reference electrodes. The state in which all pixels P are selected continues until measurement of the physical properties of the liquid crystal layer 5 is completed.

[0044] In this way, between time T1 and time T2 in Figure 5, the liquid crystal capacitance consisting of the common electrode 21, the multiple pixel electrodes 9a, and the liquid crystal layer 5 is charged with a positive polarity test voltage of 1.2 V |V1-V2| = |V1-GND| = V1, based on the potential of the pixel electrode 9a.

[0045] 5, switch 37 is controlled to the OFF state. This starts discharging the liquid crystal capacitance formed by common electrode 21 and the plurality of pixel electrodes 9a, and measurement circuit 301 starts observing the discharge of the liquid crystal capacitance. The discharge of the liquid crystal capacitance is observed by measuring the voltage of node N as the potential of common electrode 21, which serves as an inspection electrode. For convenience of explanation, the voltage of node N will be described as being synonymous with the potential of common electrode 21.

[0046] The measurement circuit 301 converts the voltage of node N into a digital value by an A / D converter 39 via an amplifier circuit 38 electrically connected to node N, and stores the digital value as a measurement value Vm in the measurement value storage circuit 32. In this way, the voltage of node N stored in the measurement value storage circuit 32 may be referred to as voltage Vm, measurement value Vm, or measurement value.

[0047] In step S13, it is determined whether a predetermined period has elapsed since time T2. The measurement circuit 301 continues to monitor the discharge of the liquid crystal capacitance until the predetermined period has elapsed since time T2. Here, the predetermined period is a period longer than one refresh period of the liquid crystal panel 100, and in this embodiment, it is, for example, approximately 150 ms. The predetermined period is not limited to this, and may be, for example, 200 ms. Alternatively, in consideration of the controllability of the liquid crystal panel 100, a period equivalent to one refresh period × N (N is an integer equal to 2 or greater) may be set.

[0048] 5, if a predetermined period has elapsed since time T2 and it becomes time T3 (S13_Yes), the process proceeds to step S14. If the predetermined period has not elapsed (S13_No), the process returns to step S12. In step S14, the measurement circuit 301 resets the potentials of the common electrode 21 and the plurality of pixel electrodes 9a to the same potential, GND, from time T3 to time T4. That is, in response to a command from the central control circuit 30, the test voltage V1 output from the test voltage generation circuit 34 is set to GND. In addition, the reference potential V2 output from the reference potential generation circuit 35 is set to GND.

[0049] At time T4 in FIG. 5, the process proceeds to step S15, where the measurement circuit 301 again starts charging the liquid crystal capacitance. In step S15, the reference potential generating circuit 35 supplies 1.2 V as the reference potential V2 to the plurality of pixel electrodes 9 a, and the test voltage generating circuit 34 supplies GND to the common electrode 21. Unlike step S11, step S15 applies a negative test voltage V1 to the common electrode 21, which serves as a test electrode, based on the potential of the plurality of pixel electrodes 9 a. In other words, -1.2 V is applied. Steps S11 and S15 are, so to speak, in an AC drive relationship. This configuration suppresses the application of DC current when measuring the physical properties of the liquid crystal layer 5.

[0050] Then, between time T4 and time T5 in Figure 5, switch 37 is controlled to the on state, and the liquid crystal capacitance consisting of the multiple pixel electrodes 9a, the common electrode 21, and the liquid crystal layer 5 is charged to the negative polarity test voltage V1 of -1.2V, based on the potential of the multiple pixel electrodes 9a.

[0051] At time T5 in FIG. 5, the process proceeds to step S16. In step S16, at time T5 in FIG. 5, switch 37 is controlled to the OFF state. This starts discharging the liquid crystal capacitance formed by the common electrode 21 and the plurality of pixel electrodes 9a, and measurement circuit 301 starts monitoring the discharge of the liquid crystal capacitance. Similar to step S12, the discharge of the liquid crystal capacitance is monitored by measuring the voltage at node N as the potential of the common electrode 21. Also, in the description of the embodiment, step S12 was described as obtaining the measured value from a discharge curve after the detection electrode was positively charged with respect to the reference electrode, but step S16 may also be described as obtaining the measured value from a discharge curve after the detection electrode was negatively charged with respect to the reference electrode.

[0052] In step S17, it is determined whether a predetermined period has elapsed since time T5. If the predetermined period has elapsed since time T5 in FIG. 5 and it becomes time T6 (S17_Yes), the process proceeds to step S18. If the predetermined period has not elapsed (S17_No), the process returns to step S16. In step S18, the measurement circuit 301 resets the potentials of the common electrode 21 and the plurality of pixel electrodes 9a to the same potential, GND, from time T6 to time T7. That is, in response to a command from the central control circuit 30, the test voltage V1 output from the test voltage generation circuit 34 is set to the GND potential. In addition, the reference potential V2 output from the reference potential generation circuit 35 is set to the GND potential.

[0053] In step S19, it is determined whether the flow from step S11 to step S18 has been repeated a predetermined number of times. If the central control circuit 30 has performed the measurement flow from step S11 to step S18 a predetermined number of times (S19_Yes), it proceeds to step S20. If it has not been performed the predetermined number of times (S19_No), it returns to step S11. The predetermined number of times is, for example, 10 times. By observing multiple discharge processes and calculating the average value, the measured value of the voltage at node N can be stabilized. Needless to say, when calculating the average value of the voltage at node N, measured values ​​from discharge processes of the same polarity are used. Note that the measured value may be described as the average value calculated in this manner.

[0054] In step S20, the display information generating circuit 33 generates display data indicating the deterioration status of the liquid crystal layer 5 based on the measured value of the voltage of node N stored in the measurement value storage circuit 32. Then, during normal driving of the liquid crystal panel 100, the central control circuit 30 displays the display data generated by the display information generating circuit 33 in the display area E of the liquid crystal panel 100 via the drive IC 201. Note that the display of the deterioration status of the liquid crystal layer 5 may be performed only when it is necessary to notify the user, such as when the liquid crystal panel 100 is nearing the end of its life and the measured value of the voltage of node N has reached a set threshold value S1.

[0055] Furthermore, the display showing the deterioration state of the liquid crystal layer 5 may be performed by a projection display device using a liquid crystal device 1000, as will be described later. For example, if the projection display device is a three-panel projection display device equipped with three liquid crystal devices 1000 corresponding to RGB, the projection display device may be configured to display an integrated deterioration state of the liquid crystal panels 100 of the three liquid crystal devices 1000, rather than each liquid crystal device 1000 individually displaying the deterioration state of the liquid crystal layer 5.

[0056] In step S21, the central control circuit 30 transmits data relating to the measurement results to a projection display device using the liquid crystal device 1000. The projection display device performs necessary processing, such as display processing, based on the data indicating the deterioration state of the liquid crystal layer 5. Note that the flow of transmitting the measurement results may be omitted depending on the specifications of the projection display device using the liquid crystal device 1000.

[0057] The measurement results of the deterioration state of the liquid crystal layer 5 can also be displayed from a maintenance menu of a projection display device using the liquid crystal device 1000. The maintenance menu is implemented, for example, as part of a setting menu in the projection display device. In step S10, when the central control circuit 30 receives a command to display the measurement results from the projection display device using the liquid crystal device 1000, the central control circuit 30 proceeds to step S20 and displays the measurement results in the display area E of the liquid crystal panel 100.

[0058] 1.5. Overview of the relationship between LCD panel usage time and discharge characteristics FIG. 6A is a graph showing the relationship between the usage time of a liquid crystal panel and the discharge characteristics. The usage time is, for example, the cumulative usage time. In a projection display device, it corresponds to, for example, the cumulative lighting time. The discharge characteristics are specifically, for example, the discharge curve observed in step S12. The vertical axis represents the measured voltage Vm of node N. The horizontal axis represents the time during discharge in step S12, with time T2 corresponding to the discharge start time T2 in FIG. 5 when measurement begins, and time T3 corresponding to the measurement end time T3 in FIG. 5. In this embodiment, time T3 is 150 ms after time T2.

[0059] In FIG. 6A, discharge curve G0 indicates the discharge curve of the liquid crystal capacitance of the liquid crystal panel 100 at the start of use of the liquid crystal panel 100, i.e., at use time h0 when the use time is zero, and discharge curve G3 indicates the discharge curve at use time h3 just before the liquid crystal panel 100 reaches the end of its life. Discharge curve G1 indicates the discharge curve at the point when use time h1 has elapsed since the start of use of the liquid crystal panel 100, and discharge curve G2 indicates the discharge curve at the point when use time h2 has elapsed since the start of use of the liquid crystal panel 100. Here, the relationship between use time is

[0060] In each discharge curve, the measured value at discharge start time T2 is close to V1-V2=V1-GND=1.2V, but the measured value at discharge end time T3 is different. In discharge curve G0, the measured value Vma at discharge end time T3 is lower by, for example, about 5% compared to the test voltage V1 at discharge start time T2. Similarly, in discharge curve G1, the measured value Vmb at discharge end time T3 is lower by, for example, about 11%; in discharge curve G2, the measured value Vmc at discharge end time T3 is lower by, for example, about 24%; and in discharge curve G3, the measured value Vmd at discharge end time T3 is lower by, for example, about 44%.

[0061] As described above, the measured values ​​Vma, Vmb, Vmc, and Vmd at the discharge end time T3 differ depending on the usage times h0, h1, h2, and h3 of the liquid crystal panel 100. This is because, as the usage time of the liquid crystal panel 100 increases, the number of mobile ions in the liquid crystal layer 5 increases due to chemical reactions caused by the incidence of high-intensity light, changing the discharge curve. The measurement method of this embodiment determines the deterioration state of the liquid crystal layer 5 based on the measured values ​​Vma, Vmb, Vmc, and Vmd at the discharge end time T3.

[0062] 6B is a graph showing the relationship between the usage time of the liquid crystal panel and the measurement value at the discharge end time T3, where the vertical axis represents the measurement value Vm at the discharge end time T3, and the horizontal axis represents the usage time of the liquid crystal panel 100.

[0063] ​As shown in FIG. 6B , the transition line W1 of the measured value Vm at the discharge end time T3 varies depending on the duration of use of the liquid crystal panel 100 (h0, h1, h2, and h3). Typically, the value indicated by the transition line W1 gradually decreases as the duration of use increases. That is, the values ​​of the measured values ​​Vma, Vmb, Vmc, and Vmd gradually decrease. The rate of decrease of the value indicated by the transition line W1 then rapidly increases once the duration of use exceeds h3. Once the duration of use exceeds h3, the amount of mobile ions in the liquid crystal layer 5 increases rapidly, and the liquid crystal panel 100 reaches the end of its life. Thus, the transition line W1 varies nonlinearly with the duration of use of the liquid crystal panel 100. It has also been confirmed that, with regard to display quality, after the time indicated by the arrow K beyond the duration of use h3, the occurrence of blemishes and unevenness on the display screen becomes more pronounced, accompanied by a decrease in brightness and resulting in a deterioration in display quality.

[0064] In this embodiment, the threshold value S1 is set to a value at which the measurement value Vm at the discharge end time T3 has dropped to 70% of the test voltage V1 at the discharge start time T2. The control program of the central control circuit 30 is programmed to notify the user or manager that, when the measurement value Vm drops below the threshold value S1, the liquid crystal panel 100 is nearing the end of its life. Alternatively, as will be described later, the control program of the central control circuit 30 is programmed to check the relationship between the usage time of the liquid crystal panel 100 and the measurement value Vm.

[0065] The threshold value S1 may be changed depending on the situation in which the liquid crystal panel 100 is used. For example, when higher display quality is required or when maintenance of the liquid crystal panel 100 takes time, the threshold value S1 may be set to the measurement value Vmc corresponding to the usage time h2 so that an early notification can be given.

[0066] 1.6. Overview of test voltage and measurement time for measuring discharge characteristics Next, with reference to FIGS. 7A and 7B, the reason why a voltage equal to or lower than the threshold voltage of the liquid crystal layer 5 and equal to or higher than 0 V is used as the test voltage V1 for the discharge characteristics of the liquid crystal capacitor in this embodiment will be described.

[0067] FIG. 7A is a graph showing discharge characteristics measured at the test voltage of this embodiment, and FIG. 7B is a graph showing discharge characteristics measured at the test voltage of a comparative example.

[0068] Each discharge characteristic is a discharge curve obtained in step S12. The vertical axis represents the potential of the common electrode 21, which serves as an electrode for testing the discharge characteristics of the liquid crystal capacitance, i.e., the measured value Vm of the voltage at node N. While the measured value Vm is actually the output value of the A / D converter 39, it is converted to a voltage value for the sake of explanation. For the voltage at node N, FIG. 7A shows a voltage range from approximately V1 / 2 to V1. Also, FIG. 7B shows a voltage range from approximately V4 / 2 to V4. The horizontal axis represents the time from the start of discharge, with the time at which discharge begins being 0. In this embodiment, the test voltage V1 is 1.2 V, while the test voltage V4 in the comparative example is 2.5 V, which exceeds the threshold voltage of the liquid crystal layer 5, which is approximately 2.2 V.

[0069] Each discharge characteristic was obtained by fabricating a simulated panel simulating the liquid crystal panel 100. In this simulated panel, an ITO electrode corresponding to the display area E of the element substrate 10 was provided, and a reference potential V2 was applied. The peripheral circuit portion of the element substrate 10 was provided with a fixed potential line simulating the peripheral circuit of the liquid crystal panel 100. Therefore, the common electrode 21, which serves as an inspection electrode, has a parasitic capacitance component with the peripheral circuit. Then, an accelerated light resistance test was performed using the simulated panel, and the discharge characteristics were evaluated for simulated panels with different usage times.

[0070] In FIG. 7A, discharge curve G0 shows the discharge curve at test time h0 at the start of the accelerated light fastness test. Discharge curve G3 shows the discharge curve at test time h3 during the accelerated light fastness test. Discharge curve G4 shows the discharge curve at test time h4 at the end of the accelerated light fastness test. At test time h3 during the accelerated light fastness test, it was difficult to visually recognize any significant changes in the display of the simulated panel. On the other hand, at test time h4 at the end of the accelerated light fastness test, significant stains (blackening) were observed on the display of the simulated panel.

[0071] 7A, the discharge curve G0 shows almost no drop from the test voltage V1 600 ms after the start of discharge, while the discharge curve G3 shows a drop of about 20% and the discharge curve G4 shows a drop of more than 60% within 600 ms after the start of discharge. That is, the difference between the discharge curve G0 and the discharge curve G3 before the liquid crystal reaches the end of its life is large, about 20%, and this difference allows the discharge curve G0 and the discharge curve G3 to be clearly distinguished from each other. Therefore, if we consider this as the liquid crystal panel 100, the change in the discharge curve before the display abnormality occurs, i.e., the history of the change in the measured value Vm, can be recorded as a significant difference.

[0072] On the other hand, in FIG. 7B for the comparative example, the discharge curve J0 is approximately 8% lower than the test voltage V4 600 ms after the start of discharge, the discharge curve J3 is approximately 10% lower 600 ms after the start of discharge, and the discharge curve J4 is more than 60% lower.

[0073] That is, the difference between the discharge curve J0 and the discharge curve J3 before the liquid crystal panel 100 reaches the end of its life is extremely small, at about 2%, making it difficult to monitor the deterioration state of the liquid crystal layer 5. To distinguish and measure this difference, a high-precision measurement circuit is required. However, such a high-precision measurement circuit is expensive and requires a large circuit configuration and area, making it difficult to incorporate into a product.

[0074] In the comparative example, when the test voltage V4 is set to a voltage exceeding the threshold voltage, the difference between the discharge curve J0 and the discharge curve J3 becomes smaller. This can be understood as follows: Because the test voltage V4 is high, mobile ions move from one electrode, e.g., the pixel electrode 9a, to the other electrode, e.g., the common electrode 21, during charging in step S11, reducing the amount of mobile ions available for use after discharge begins. Furthermore, when the test voltage V4 exceeds the threshold voltage of the liquid crystal layer 5, the liquid crystal molecules in the liquid crystal layer 5 move, which changes the liquid crystal capacitance due to a change in the dielectric constant of the liquid crystal. This can be understood as a result of which the change in the discharge curve due to the action of mobile ions becomes difficult to see.

[0075] On the other hand, when the test voltage V1 is set to a voltage equal to or lower than the threshold voltage but equal to or higher than 0 V, as in this embodiment, the discharge curves G0 and G3 can be clearly distinguished. This can be understood as a result of the test voltage V1 being small, reducing the amount of mobile ions that move from one electrode (e.g., the pixel electrode) to the other electrode (e.g., the counter electrode) during charging in step S11, and increasing the amount of mobile ions that move after the discharge starts. Furthermore, because the test voltage V1 is smaller than the threshold voltage of the liquid crystal layer 5, the effect of the movement of liquid crystal molecules in the liquid crystal layer 5, i.e., the change in liquid crystal capacitance due to a change in the dielectric constant of the liquid crystal, is not affected. Therefore, it can be understood that the effect of mobile ions is effectively reflected in the observation.

[0076] 7A, the reason why the measurement method of this embodiment determines the deterioration state of the liquid crystal layer 5 based on the measurement value after a predetermined period has elapsed since the discharge start time will be described. Note that in this embodiment, the predetermined period is longer than one refresh period of the liquid crystal panel 100, and more specifically, is approximately 150 ms.

[0077] 7A, time Ta is a time equivalent to one refresh period of liquid crystal panel 100. For example, if the frame rate of the video signal of the content video displayed on liquid crystal device 1000 is 60 fps (frames per second), the refresh rate of liquid crystal panel 100 is set to, for example, 60 fps or 120 fps. When the refresh rate of liquid crystal panel 100 is 60 fps, one refresh period is approximately 16.7 ms, so time Ta corresponds to the time 16.7 ms after the start of discharge. Time Tb is longer than one refresh period and corresponds to, for example, 150 ms after the start of discharge.

[0078] 7A, the transition of the discharge curve G3 can be roughly distinguished into two stages: the first stage, in which the measured value decreases rapidly from the discharge start time beyond time Ta (16.7 ms) to approximately 90 ms, and the second stage, in which the measured value decreases gradually thereafter.

[0079] From this, it can be seen that if the potential of the common electrode 21 is measured as a measured value Vm after a period longer than one refresh period has elapsed since the start of discharge, a measured value Vm that can determine the deterioration state of the liquid crystal layer 5 can be obtained before the mobile ions increase rapidly and before the liquid crystal panel 100 reaches the end of its life.

[0080] The reason for this type of discharge curve is thought to be due to the effect of mobile ions in the first stage and the effect of the resistivity of the bulk liquid crystal and leakage from the measurement circuitry in the second stage. As mentioned above, the test voltage V1 is low, so time is required for the mobile ions to migrate. Therefore, by setting a predetermined period longer than one refresh period from the start of discharge, the effect of mobile ion migration can be effectively reflected in the measured value Vm, allowing the deterioration status of the liquid crystal layer 5 to be determined. Normally, in the early stages of deterioration of the liquid crystal layer 5, the liquid crystal layer 5 has sufficient voltage retention capacity within one refresh period. Therefore, it is extremely difficult to find clear differences by observing the discharge curves for one refresh period.

[0081] As described above, the liquid crystal device 1000 of this embodiment can provide the following advantages. The liquid crystal device 1000 includes a common electrode 21 as a first electrode, a pixel electrode 9a as a second electrode, a liquid crystal layer 5 to which a drive voltage is applied for each refresh period as a first refresh period, and a measurement circuit 301 that applies a test voltage V1 between the common electrode 21 and the pixel electrode 9a and measures the common electrode 21 potential Vm after a period longer than one refresh period has elapsed, for example, 150 ms, since the application of the test voltage V1 was stopped.

[0082] In this way, the liquid crystal device 1000 of this embodiment measures the potential Vm of the common electrode 21 after the period Tb, which is longer than one refresh period, e.g., 150 ms, has elapsed since the application of the test voltage V1 was stopped.

[0083] Therefore, the passage of a period longer than one refresh period ensures time for the mobile ions to move between the common electrode 21 and the pixel electrode 9a. As a result, the discharge curve changes efficiently in accordance with the amount of mobile ions in the liquid crystal layer 5, and the change in the amount of mobile ions due to deterioration of the liquid crystal layer 5 can be accurately observed from the measured value Vm.

[0084] In the liquid crystal device 1000, the measurement circuit 301 applies a test voltage V1 that is equal to or lower than the threshold voltage of the liquid crystal layer 5 but higher than 0 V. Because the test voltage V1 is low, it reduces the movement of mobile ions during the charging period before starting to measure the discharge curve. Furthermore, the measured value Vm is not affected by the movement of liquid crystal molecules, i.e., by changes in the liquid crystal capacitance due to changes in the dielectric constant of the liquid crystal, so the amount of mobile ions in the liquid crystal layer 5 can be accurately measured.

[0085] In the liquid crystal device 1000, the threshold voltage of the liquid crystal layer 5 is approximately 2.2 V. When the current when a triangular wave voltage is applied to the liquid crystal layer 5 is examined by electrical measurement, a current due to mobile ions is distributed when a voltage greater than 0 V to around 1.5 V is applied to the liquid crystal layer 5. This current increases as the liquid crystal layer 5 deteriorates.

[0086] Therefore, if the threshold voltage of the liquid crystal layer 5 is about 2.2 V, a discharge curve that reflects the action of mobile ions can be obtained while avoiding the influence of the dielectric anisotropy of the liquid crystal. Therefore, a voltage that is equal to or lower than the threshold voltage of the liquid crystal layer 5 and higher than 0 V is applied as the test voltage V1.

[0087] In the electrical measurement, a current peak due to mobile ions is observed around 0.5 V. Therefore, it is preferable to apply the test voltage V1 at a voltage equal to or lower than the threshold voltage of the liquid crystal layer 5 and equal to or higher than 0.5 V. In this way, a discharge curve that efficiently reflects the amount of mobile ions can be obtained.

[0088] The liquid crystal device 1000 includes a common electrode 21 as a first electrode, a pixel electrode 9a as a second electrode, a liquid crystal layer 5 to which a driving voltage equal to or greater than a threshold voltage is applied, and a measurement circuit 301 that applies a test voltage V1 between the common electrode 21 and the pixel electrode 9a that is equal to or less than the threshold voltage of the liquid crystal layer 5 and higher than 0V, and measures the potential Vm of the common electrode 21 after stopping the application of the test voltage V1.

[0089] In this way, the liquid crystal device 1000 of this embodiment applies a test voltage V1 that is lower than the threshold voltage of the liquid crystal layer 5 and higher than 0 V, and measures the potential Vm of the common electrode 21 after stopping the application of the test voltage V1.

[0090] Therefore, the voltage Vm is not affected by the movement of the liquid crystal molecules, i.e., by the change in the liquid crystal capacitance due to the change in the dielectric constant of the liquid crystal, so the amount of mobile ions in the liquid crystal can be accurately observed.

[0091] Since the pixel electrode 9a is at a constant potential when measuring the voltage Vm between the common electrode 21 and the pixel electrode 9a, the potential difference between the common electrode 21 and any constant potential including GND may be measured as a voltage reflecting the voltage Vm. The constant potential used in the liquid crystal device 1000 is, for example, the constant voltage used in the measurement substrate 300, the liquid crystal panel 100, and the control substrate 200.

[0092] These constant voltages drive the central control circuit 30 and the like included in the measurement board 300, or drive the data line drive circuit 23, the scanning line drive circuit 24, and the precharge circuit 25 included in the liquid crystal panel 100, or drive the drive IC 201 on the control board 200.

[0093] In the liquid crystal device 1000, the liquid crystal panel 100 applies a driving voltage to the liquid crystal layer 5 for each refresh period of the liquid crystal panel 100, which is the first refresh period, and the measurement circuit measures the potential of the common electrode 21 after a period longer than one refresh period has elapsed since the application of the test voltage was stopped.

[0094] Therefore, the passage of a period longer than one refresh period ensures time for the mobile ions to move between the common electrode 21 and the pixel electrode 9a. As a result, the discharge curve changes efficiently in accordance with the amount of mobile ions in the liquid crystal layer 5, and the change in the amount of mobile ions due to deterioration of the liquid crystal layer 5 can be accurately observed from the measured value Vm.

[0095] In the liquid crystal device 1000, the period longer than one refresh period is a period of 60 ms to 150 ms. In this way, for example, the measurement of the amount of mobile ions can be completed quickly and with good sensitivity without unnecessarily lengthening the time required to turn on and off the power of a projection display device using the liquid crystal device 1000.

[0096] In the liquid crystal device 1000, the first electrode is the common electrode 21, and the second electrode is the pixel electrode 9a.

[0097] The liquid crystal device 1000 displays the state of the liquid crystal panel 100 to the user based on the measurement result of the common electrode 21.

[0098] A method for measuring the physical properties of a liquid crystal layer used in a liquid crystal device 1000 is a method for measuring the physical properties of a liquid crystal layer 5 of a liquid crystal device 1000 that has a liquid crystal layer 5 and applies a driving voltage to the liquid crystal layer 5 every refresh period as a first refresh period, in which a test voltage V1 is applied between a common electrode 21 as a first electrode and a pixel electrode 9a as a second electrode, which are arranged to apply an electric field to the liquid crystal layer 5, a period Tb longer than one refresh period Ta is set after the application of the test voltage V1 is stopped, and a voltage Vm between the common electrode 21 and the pixel electrode 9a is measured.

[0099] In a method for measuring the physical properties of the liquid crystal layer 5 used in the liquid crystal device 1000, a voltage equal to or lower than the threshold voltage of the liquid crystal layer 5 and higher than 0 V is applied as the test voltage V1.

[0100] The method for measuring the physical properties of the liquid crystal layer 5 used in the liquid crystal device 1000 is a method for measuring the physical properties of the liquid crystal layer 5 in the liquid crystal device 1000 to which a driving voltage equal to or greater than the threshold voltage of the liquid crystal layer 5 is applied, in which a test voltage V1 equal to or less than the threshold voltage and higher than 0 V is applied between the common electrode 21 as a first electrode and the pixel electrode 9a as a second electrode, which are arranged to apply an electric field to the liquid crystal layer 5, and the potential Vm of the common electrode 21 is measured after the application of the test voltage V1 is stopped.

[0101] In a method for measuring the physical properties of a liquid crystal layer 5 used in a liquid crystal device 1000, the liquid crystal panel 100 applies a driving voltage to the liquid crystal layer 5 for each refresh period of the liquid crystal panel 100, which is a first refresh period, and the measurement circuit measures the potential of the common electrode 21 after a period longer than one refresh period has elapsed since the application of the test voltage was stopped.

[0102] 2. Embodiment 2 2.1. Overview of LCD device configuration 8 is an explanatory diagram showing a schematic configuration of a liquid crystal device. In the following description, the same components and flowchart steps as those in embodiment 1 are designated by the same reference numerals, and duplicated explanations will be omitted.

[0103] A liquid crystal device 2000 of this embodiment includes a liquid crystal panel 100b, a control substrate 200b, and a measurement substrate 300. The liquid crystal panel 100b differs from the first embodiment in that its data line driving circuit 23b includes a demultiplexer circuit made up of a predetermined number of sample switches 222b electrically connected to each of a predetermined number of signal lines 4. The liquid crystal device 2000 supplies image signals to each pixel electrode 9a using a demultiplexer system.

[0104] The driving IC 201b includes an amplifier 220 that outputs a voltage according to an image signal, a switch 231 that electrically connects the amplifier 220 and the image signal supply line 223b when writing the voltage, and a switch 232 that electrically connects the reference potential generating circuit 35 and the image signal supply line 223b when measuring and precharging. Thus, in the second embodiment, unlike the first embodiment, the driving IC 201b functions as a precharge circuit, and when measuring, the test voltage V1 is supplied to the pixel electrode 9a via the switch 232 of the driving IC 201b.

[0105] 2.2. Overview of the structure of the holding member of the liquid crystal device 9 is a perspective view showing the configuration of a holding member of a liquid crystal device. Holding member 70 is made up of a holder 50 and a lid member 60 attached to holder 50 with a hook 61. Both holder 50 and lid member 60 are made of a conductive material.

[0106] After being placed in the holder 50, the liquid crystal device 2000 is held within the holding member 70 by attaching the lid member 60. The holder 50 has a fixing portion 51 that serves as a connection portion to GND and is electrically connected to GND via the fixing portion 51. The lid member 60 attached to the holder 50 is also electrically connected to GND via the holder 50. A portion of the lid member 60 corresponding to the display area E of the liquid crystal panel 100b is cut out to function as a partition. Although not shown, in the holder 50, the element substrate 10 is disposed on the lid member 60 side. In this case, incident light L is irradiated from the bottom to the top in FIG. 9. Therefore, the counter substrate 20 is disposed on the incident light side. The lid member 60 may be made of a non-conductive material. In this case, only the holder 50 of the holding member 70 is electrically connected to GND.

[0107] As described above, the liquid crystal device 2000 of this embodiment can achieve the following effects in addition to the effects of Embodiment 1. The liquid crystal device 2000 includes a conductive holding member 70 that holds the liquid crystal device 2000. The liquid crystal device 2000 and the holding member 70 are electrically connected to the same GND. In Embodiment 2, the common electrode 21 of the counter substrate 20 functions as a test electrode. When measuring the physical properties of the liquid crystal layer 5, the switch 37 is turned off, and the common electrode 21 is electrically isolated from the test voltage generating circuit 34. At this time, the common electrode 21 is also a large-area electrode and is therefore susceptible to noise from external circuits. However, by electrically connecting the holding member 70 to GND, it is possible to suppress noise superimposition on the common electrode 21, which serves as a test electrode, thereby enabling stable measurement of discharge characteristics.

[0108] 3. Embodiment 3 3.1. Overview of LCD device configuration 10 is an explanatory diagram showing a schematic configuration of a liquid crystal device. In the following description, the same components and flowchart steps as those in the above embodiments are designated by the same reference numerals, and duplicated explanations will be omitted.

[0109] A liquid crystal device 3000 of this embodiment includes a liquid crystal panel 100c, a control board 200c, and a measurement board 300c. The liquid crystal panel 100c differs from the first and second embodiments in that it includes testing electrodes 42a, 42b, 42c, and 42d in a peripheral region F between a sealant 14 and a display region E.

[0110] A dummy pixel electrode 55 connected to the common potential line 16 is arranged around the testing electrode 42b. The dummy pixel electrode 55 has, for example, a substantially rectangular pattern similar to that of the pixel electrode 9a, which is connected to each other at the center of each side. In this case, the distance between the testing electrode 42b and the dummy pixel electrode 55 should be larger than the gap between the dummy pixel electrodes 55 to prevent an electrical short circuit between the testing electrode 42b and the dummy pixel electrode 55. A similar configuration can be used when arranging dummy pixel electrodes 55 around the other testing electrodes 42a, 42c, and 42d.

[0111] Inspection electrode 42a and inspection electrode 42c are electrically connected to connection line 43a and to node N1 via external connection terminal 18a. Inspection electrode 42b and inspection electrode 42d are electrically connected to connection line 43b and to node N2 via external connection terminal 18b. In this way, liquid crystal panel 100c has two sets of inspection electrode systems connected to different nodes N1 and N2. Node N1 is provided with stabilizing capacitance C1 to stabilize the measured value. Similarly, node N2 is provided with stabilizing capacitance C2 to stabilize the measured value.

[0112] The main wiring portions of the connection line 43a and the connection line 43b along each side of the element substrate 10 are arranged in the area outside the sealant 14. By arranging them in this manner, unnecessary parasitic capacitance formed between the connection line 43a and the fixed potential line or signal line arranged in the peripheral area F, and unnecessary parasitic capacitance formed between the connection line 43b and the fixed potential line or signal line arranged in the peripheral area F, are suppressed, thereby improving the sensitivity of the inspection electrodes 42a, 42b, 42c, and 42d to detect deterioration of the liquid crystal layer 5.

[0113] Inspection electrode 42a is electrically connected to continuity test terminal 19a, inspection electrode 42b is electrically connected to continuity test terminal 19b, inspection electrode 42c is electrically connected to continuity test terminal 19c, and inspection electrode 42d is electrically connected to continuity test terminal 19d. Control board 200c includes drive IC 201c. With this configuration, electrical connection to inspection electrode 42a can be confirmed by conducting a continuity test by touching external connection terminal 18a and continuity test terminal 19a. Electrical connection to inspection electrode 42c can be confirmed by conducting a continuity test by touching external connection terminal 18a and continuity test terminal 19c. Electrical connection to inspection electrode 42b can be confirmed by conducting a continuity test by touching external connection terminal 18b and continuity test terminal 19b. By conducting a continuity test by touching external connection terminal 18b and continuity test terminal 19d, the electrical connection to test electrode 42d can be confirmed.

[0114] The measurement board 300c includes a test voltage generating circuit 34c, a reference potential generating circuit 35c, amplifier circuits 38c1 and 38c2, and A / D converters 39c1 and 39c2.

[0115] The test voltage generating circuit 34c is electrically connected to a node N2 via a switch 37c1 and to a node N1 via a switch 37c2. The reference potential generating circuit 35c is electrically connected to a node N2 via a switch 41c1 and to a node N1 via a switch 41c2. The on / off of these switches 37c1, 37c2, 41c1, and 41c2 is controlled by the central control circuit 30. Note that the reference potential generating circuit 35c may function as a common potential generating circuit that outputs a common potential to the common electrode 21 via the inter-substrate conductive part 17 during normal driving.

[0116] The amplifier circuit 38c2 is electrically connected to the node N1, and the A / D converter 39c2 converts the output voltage of the amplifier circuit 38c2 into a digital value and outputs the measurement value to the storage circuit 32 via the central control circuit 30. The amplifier circuit 38c1 is electrically connected to the node N2, and the A / D converter 39c1 converts the output voltage of the amplifier circuit 38c1 into a digital value and outputs the digital value to the measurement value storage circuit 32 via the central control circuit 30.

[0117] As described above, the liquid crystal device 3000 of this embodiment has the following advantages in addition to the advantages of the first and second embodiments. In the liquid crystal device 3000, the first electrodes are testing electrodes 42a, 42b, 42c, and 42d as peripheral electrodes arranged in an area outside the display area in a plan view, and the second electrode is the common electrode 21. The measurement circuit 301c applies a reference potential serving as a reference for the testing voltage to the common electrode 21, and applies the testing voltage to the testing electrodes 42a and 42c or the testing electrodes 42b and 42d. Above these testing electrodes is the common electrode 21 to which a reference potential on the counter substrate 20 side is applied, and below the testing electrodes are arranged various wiring layers formed on the element substrate 10 and to which potentials are applied. Therefore, the common electrode 21 and the various wiring layers formed on the element substrate 10 function as shields, making it possible to obtain stable measurement values.

[0118] In the liquid crystal panel 100c, mobile ions tend to accumulate in the corners of the display region E, causing display defects such as stains at the corners of the display region E. Such mobile ions tend to move easily along the alignment directions of the first alignment film 12 and the second alignment film 22. For example, stains that occur at the corners of the display region E tend to occur at diagonally opposite corners of the display region E.

[0119] Therefore, by using inspection electrodes 42a and 42c as one detection system and inspection electrodes 42b and 42d as another detection system, it becomes possible to detect signs of stains occurring at the corners of the display area E by referring to the difference between the measurement values ​​of both.

[0120] 4. Embodiment 4 4.1. Overview of LCD device configuration 11 is an explanatory diagram showing a schematic configuration of a liquid crystal device. In the following description, the same components and flowchart steps as those in the above embodiments are designated by the same reference numerals, and duplicated explanations will be omitted.

[0121] A liquid crystal device 4000 of this embodiment includes a liquid crystal panel 100d, a control board 200d, and a measurement board 300d. The liquid crystal panel 100d includes a test electrode 44 in a peripheral area F between the sealant 14 and the display area E. The test electrode 44 is disposed so as to surround the display area E. One end of the test electrode 44 is electrically connected to a node N via an external connection terminal 18d, and the other end is electrically connected to a continuity test terminal 19. With this configuration, electrical connection to the test electrode 44 can be confirmed by touching the external connection terminal 18d and the continuity test terminal 19. In this case, as shown in FIG. 11 , if the test electrode 44 is formed as a pattern with a gap and an electrical connection portion with the external connection terminal 18d and the continuity test terminal 19 is provided at both ends of the pattern, a disconnection of the test electrode 44 can also be detected.

[0122] The test voltage generating circuit 34d is electrically connected to the node N via a switch 37d. The reference potential generating circuit 35d is electrically connected to the node N via a switch 41d, and is also electrically connected to the inter-substrate conductive portion 17. During normal driving, the reference potential generating circuit 35d functions as a common potential generating circuit that outputs a common potential to the common electrode 21 via the inter-substrate conductive portion 17.

[0123] As described above, the liquid crystal device 4000 of this embodiment has the following advantages in addition to the advantages of the first, second, and third embodiments. In the liquid crystal device 4000, the inspection electrode 44 as a peripheral electrode is arranged along the display region E. Since the inspection electrode 44 is arranged along the display region E in the peripheral region F, the area of ​​the inspection electrode 44 can be made large. Therefore, the sensitivity of the inspection electrode 44 in detecting deterioration of the liquid crystal layer 5 can be increased.

[0124] As described above, the liquid crystal device 4000 of this embodiment can achieve the following effect in addition to the effects of Embodiments 1, 2, and 3. In the liquid crystal device 4000, the first electrode is the testing electrode 44 as a peripheral electrode arranged in an area outside the display area in a plan view, the second electrode is the common electrode 21, and the measurement circuit 301d applies a reference potential that serves as a reference for the testing voltage to the common electrode 21, and applies the testing voltage to the testing electrode 44.

[0125] In the liquid crystal panel 100c, mobile ions tend to accumulate in the corners of the display area E, causing display defects such as stains at the corners of the display area E. Therefore, as in this embodiment, by arranging the inspection electrodes 44 in the peripheral area F at positions corresponding to the corners of the display area E, it becomes easier to detect mobile ions.

[0126] 5. Embodiment 5 5.1. Overview of Electronic Devices 12 is a schematic diagram showing the configuration of a projection display device as an electronic device according to this embodiment. In this embodiment, a projection display device 10000 will be described as an example of an electronic device equipped with the above-described liquid crystal device 1000.

[0127] The projection display device 10000 of this embodiment is a three-panel projection display device and includes a lamp unit 1001 as a light source, dichroic mirrors 1011 and 1012 as a color separation optical system, 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 a screen 1200 by the projection optical system. The relay lenses 1121, 1122, and 1123 and the reflecting mirrors 1112 and 1113 constitute a relay lens system 1120.

[0128] The projection display device 10000 also includes a control circuit 1230 that receives measurement data on the deterioration state 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.

[0129] When the control circuit 1230 receives data on the deterioration state of the liquid crystal layer 5 from each of the liquid crystal devices 1000B, 1000G, and 1000R, it creates and displays display information on the deterioration state of the liquid crystal layer 5 for each of the liquid crystal devices 1000B, 1000G, and 1000R.

[0130] The control circuit 1230 can notify the user that the liquid crystal panel 100 is nearing the end of its life by lighting the pilot lamp 1240 based on measurement data of the deterioration state of the liquid crystal layer 5. For example, if the liquid crystal panel 100 of the liquid crystal device 1000B, which corresponds to blue, is nearing the end of its life, the control circuit 1230 lights the blue pilot lamp 1240. The control circuit 1230 may also notify the user of the status of the liquid crystal panel 100 by voice using the speaker 1250. The control circuit 1230 may also notify the user of the status of the liquid crystal panel 100 on the screen of the remote controller 1260 or a mobile terminal. In addition to the display on the liquid crystal devices 1000B, 1000G, and 1000R as described above, a means for notifying the user of the status of the liquid crystal panel 100 may be provided.

[0131] Furthermore, when the control circuit 1230 detects from the received measurement data that the liquid crystal panel 100 is nearing the end of its life, it changes the control values ​​related to the control of the liquid crystal devices 1000B, 1000G, and 1000R in order to delay the deterioration of the liquid crystal layer 5. For example, the control values ​​may be modified to reduce the brightness of the lamp unit 1001 that irradiates the liquid crystal devices 1000B, 1000G, and 1000R, or the grayscale voltage of the liquid crystal devices 1000B, 1000G, and 1000R may be changed to a voltage value corresponding to the reduction in brightness of the lamp unit 1001.

[0132] 5.2. Overview of the measurement results display screen example 13A is an explanatory diagram showing an example of a setting menu screen of the projection display device 10000, and FIG. 13B is an explanatory diagram showing an example of a display screen that displays the deterioration state of the liquid crystal layer 5. As shown in FIG.

[0133] In Figure 13A, when Maintenance M is selected from the setting menu screen D1 projected and displayed on the screen 1200, a maintenance menu is displayed, and when display of the status of the liquid crystal panel 100 is selected from the maintenance menu, the control circuit 1230 sends a request to the liquid crystal devices 1000B, 1000G, and 1000R to send measurement data on the deterioration status of the liquid crystal layer 5, and displays the display screen D2 as shown in Figure 13B based on the received measurement data on the deterioration status of the liquid crystal layer 5 of the liquid crystal devices 1000B, 1000G, and 1000R.

[0134] 13B is a screen showing the deterioration state of the liquid crystal layer 5 of the liquid crystal device 1000B. Note that the screens showing the deterioration states of the liquid crystal layers 5 of the liquid crystal devices 1000G and 1000R may be displayed separately by screen switching.

[0135] Display screen D2 displays a trend line W2 indicating the history of the measured value Vm from the start of use of liquid crystal device 1000B to the present, a predicted trend line W3 under standard usage conditions, and a threshold line S1 indicating that the liquid crystal panel 100 is nearing the end of its life. Information about liquid crystal devices 1000G and 1000R may also be displayed on display screen D2. By comparing trend line W2 with predicted trend line W3, it is possible to determine whether usage conditions are more severe than expected, allowing preventive maintenance measures such as limiting the brightness of lamp unit 1001 irradiating liquid crystal devices 1000B, 1000G, and 1000R. When trend line W2 improves to predicted trend line W3, the brightness limit on lamp unit 1001 may be lifted.

[0136] The trend line W2 showing the history of the measured value Vm may be displayed as a smooth line obtained by averaging multiple measured values ​​Vm to make it easier to discern the change trend. Furthermore, instead of displaying the trend line W2 showing the history of the measured value Vm, the value of the measured value Vm may simply be displayed as a numerical value. In this case, the display color of the measured value Vm may be changed in accordance with the threshold value S1. For example, when the value is greater than the threshold value S1, it may be displayed in green, when it approaches the threshold value S1, it may be displayed in yellow, and when it is equal to or less than the threshold value S1, it may be displayed in red.

[0137] The measured value Vm may be displayed as an index value normalized by an arbitrary value. In this case, for example, when the index value is calculated from the measured value in step S12 of the first embodiment, the displayed index value immediately after the start of use is, for example, a value close to "1."

[0138] Or, if it is displayed as a percentage, it is, for example, a value close to "100." Alternatively, if the index value is calculated from the measurement value in step S16 of the first embodiment, the index value displayed shortly after the start of use is, for example, a value close to "0." Using such index values, the deterioration state of the liquid crystal panel 100 may be displayed using, for example, a bar graph or a pie chart.

[0139] Control circuit 1230 transmits a command to measure the deterioration state of liquid crystal layer 5 to liquid crystal devices 1000B, 1000G, and 1000R when projection display device 10000 is powered on or off, or when an instruction to measure the deterioration state of liquid crystal layer 5 is given from the maintenance menu. As described in step S10 of the flowchart in Figure 4, when liquid crystal devices 1000B, 1000G, and 1000R receive the command to measure the deterioration state of liquid crystal layer 5 from control circuit 1230, they start measurement.

[0140] Generally, preventive maintenance refers to planned maintenance to ensure stable operation of equipment. In determining the timing of part replacement, there are two methods: dividing the time period by the length of time the part is in use and evaluating the degree of deterioration of the part. By 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 Vm. Changes in the measured value Vm can be sensitively observed before display abnormalities occur in the liquid crystal panel 100, enabling preventive maintenance. Furthermore, by comparing the trends in the measured value Vm of multiple individual units and analyzing using machine learning, behaviors in the measured value Vm that are prone to blemishes, unevenness, and the like can be detected and predictive maintenance can be performed. For example, in the third embodiment, this can be applied to detecting blemishes, etc. that tend to appear in the corners of the display area E in advance.

[0141] In this embodiment, the projection-type display device 10000 is used as an example of an electronic device. However, the liquid crystal device 1000 is not limited to this. For example, the liquid crystal device 1000 may be used in 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 that use the liquid crystal panel 100 use UV light, and deterioration of the liquid crystal panel 100 is a problem. If a modeling operation is started without realizing that the liquid crystal panel 100 is nearing the end of its life, the resin liquid may not cure properly during the modeling operation, and this problem may not be noticed until the modeling is complete. In this case, the liquid crystal panel 100 according to the present invention can be used to determine the deterioration state of the liquid crystal panel 100. Therefore, problems such as poor curing of the resin liquid during modeling can be predicted in advance, allowing the liquid crystal panel 100 to be replaced at the appropriate time as preventive maintenance.

[0142] In the above embodiment, a transmissive liquid crystal device is exemplified as the liquid crystal device 1000. However, the liquid crystal device 1000 may be a reflective liquid crystal device or an LCOS (Liquid Crystal on Silicon) liquid crystal device.

[0143] As described above, the projection display device 10000 of this embodiment can achieve the following effects in addition to the effects of the above embodiments: The projection display device 10000 as an electronic device preferably includes the liquid crystal device 1000, 2000, 3000, or 4000 according to the above embodiments.

[0144] The projection display device 10000 as an electronic device further includes a control circuit 1230, which notifies the deterioration state of the liquid crystal layer 5 based on the measurement results of the measurement circuit 301.

[0145] Projection-type display device 10000 as an electronic device further includes control circuit 1230, which changes the control values ​​of liquid crystal device 1000 based on the measurement results of measurement circuit 301. This configuration makes it possible to provide an excellent electronic device that allows preventive maintenance in accordance with the deterioration state of liquid crystal layer 5. [Explanation of symbols]

[0146] 3...scanning line, 4...signal line, 5...liquid crystal layer, 6...capacitance line, 7...storage capacitance, 8...precharge signal line, 9a...pixel electrode, 10...element substrate, 11...TFT, 14...sealing material, 16...common potential line, 17...inter-substrate conductive portion, 18...external connection terminal, 20...opposing substrate, 21...common electrode, 23...data line driving circuit, 24...scanning line driving circuit, 25...precharge circuit, 27...partition portion, 30...central control circuit, 31...determination circuit, 32...measurement value memory circuit, 33...display information generating circuit, 34...inspection voltage generating circuit, 34c...inspection voltage generating circuit, 36...capacitance line voltage generating circuit, 38...amplification circuit, 39...A / D converter, 42a, 42b, 42c, 42d...inspection electrodes, 43a, 43 b...connecting wire, 44...test electrode, 50...holder, 51...fixing part, 55...dummy pixel electrode, 60...cover member, 61...hook, 70...holding member, 100...liquid crystal panel, 200...control board, 201...driving IC, 223...image signal supply line, 300...measurement board, 301...measurement circuit, 1000, 2000, 3000, 4000...liquid crystal device, 1230...control circuit, 1240...pilot lamp, 1250...speaker, 1260...remote controller, 10000...projection display device, D1...setting menu screen, D2...display screen, N, N1, N2...node, S1...threshold value, V1...test voltage, V2...reference potential, V3...storage capacitance potential, V4...test voltage of comparative example.

Claims

1. A first electrode; A second electrode; a liquid crystal layer to which a driving voltage equal to or higher than a threshold voltage is applied; a measurement circuit that applies a test voltage that is equal to or lower than a threshold voltage of the liquid crystal layer and higher than 0 V as a voltage to be applied to the liquid crystal layer between the first electrode and the second electrode, and measures the potential of the first electrode after stopping the application of the test voltage; Liquid crystal device.

2. the first electrode is a common electrode, the second electrode is a pixel electrode; The liquid crystal device according to claim 1 .

3. a conductive holding member that holds the liquid crystal device, The liquid crystal device and the holding member are electrically connected to the same GND. The liquid crystal device according to claim 2 .

4. the first electrode is a peripheral electrode disposed in an area outside a display area in a plan view, The second electrode is a common electrode. The liquid crystal device according to claim 1 .

5. The peripheral electrode is arranged along the display area. The liquid crystal device according to claim 4 .

6. performing a display corresponding to the measurement result of the potential of the first electrode; 6. The liquid crystal device according to claim 1.

7. 7. An electronic device comprising the liquid crystal device according to claim 1.

8. the measurement circuit measures the physical properties of the liquid crystal layer when the electronic device is started or stopped.

8. The electronic device according to claim 7.

9. Further comprising a control circuit; The control circuit notifies information corresponding to the measurement result of the measurement circuit.

9. The electronic device according to claim 7 or 8.

10. Further comprising a control circuit; the control circuit changes a control value of the liquid crystal device based on the measurement result of the measurement circuit.

10. The electronic device according to claim 7.

11. A method for measuring physical properties of a liquid crystal layer in a liquid crystal device to which a driving voltage equal to or higher than a threshold voltage of the liquid crystal layer is applied, comprising the steps of: applying a test voltage to the liquid crystal layer between a first electrode and a second electrode arranged to apply an electric field to the liquid crystal layer, the test voltage being equal to or lower than the threshold voltage and higher than 0 V; detecting the potential of the first electrode after stopping the application of the inspection voltage; Method for measuring the physical properties of liquid crystal layers.

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