JP2016057427A - Electro-optic device and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electro-optic device and electronic equipment capable of sweeping out ionic impurities without an external battery attached thereto in a period when an image is not formed.SOLUTION: A liquid crystal device 1 includes a liquid crystal layer 40 comprising a liquid crystal having negative dielectric anisotropy and held between a counter substrate 30 and an element substrate 20, a common electrode 34 disposed on the counter substrate 30, a pixel electrode 28a disposed on the element substrate 20, and a pixel electrode 28b and a pixel electrode 28c disposed two-dimensionally outside the pixel electrode 28a, and forms an image by applying a voltage between the common electrode 34 and the pixel electrode 28a. In a normal drive mode, a voltage applied between the common electrode 34 and the pixel electrode 28b is equal to or lower than a voltage applied between the common electrode and the pixel electrode 28a. In an ion sweep-out drive mode, a first voltage applied between the common electrode 34 and the pixel electrode 28a is higher than 0 V, a second voltage applied between the common electrode and the pixel electrode 28b is equal to or higher than the first voltage, and a third voltage applied between the common electrode and the pixel electrode 28c is equal to or higher than the first voltage.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an electro-optical device and an electronic apparatus.

  As an electro-optical device, a liquid crystal device in which a liquid crystal layer is sandwiched between a pair of substrates is known. When light enters such a liquid crystal device, the liquid crystal material or alignment film of the liquid crystal layer and the incident light may undergo a photochemical reaction, and ionic impurities may be generated as a reaction product. It is also known that there are ionic impurities that diffuse from a sealing material or a sealing material into the liquid crystal layer during the manufacturing process of the liquid crystal device. In particular, in a liquid crystal device used for a light modulation means (light valve) of a projection display device (projector), the luminous flux density of incident light is higher than that in a direct-view type liquid crystal device, so that ionic impurities affect the display. It is necessary to suppress the effect.

  As a means for suppressing the influence of ionic impurities on the display, for example, Patent Document 1 has an external battery, and in a non-operating state in which the power is turned off, ions that accumulate inside the liquid crystal are swept out of the display area by the external battery. A liquid crystal device (liquid crystal display panel) that performs intermittent driving is disclosed. In a normal use state in which an image is formed, the liquid crystal molecules are disturbed due to the intermittent drive for sweeping ions out of the display area, and the display quality deteriorates. Therefore, it is not visible to the user.

JP 2008-89938 A

  However, according to the configuration of the liquid crystal device described in Patent Document 1, a space for providing an external battery for performing intermittent driving in a non-operating state in which the power is turned off is required, so that the size of the liquid crystal device is increased. There is. Further, since a drive circuit for performing intermittent drive with an external battery is required, there is a problem that the circuit configuration becomes complicated. Furthermore, there is a problem that the product cost increases due to these.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 An electro-optical device according to this application example includes a liquid crystal layer including a liquid crystal having negative dielectric anisotropy sandwiched between a pair of substrates, and the liquid crystal of one of the pair of substrates. A first electrode provided on the layer side; a second electrode provided on the liquid crystal layer side of the other substrate of the pair of substrates; and a liquid crystal layer side of the other substrate; A third electrode arranged on the outer side of the second electrode, a fourth electrode provided on the liquid crystal layer side of the other substrate, and arranged on the outer side of the third electrode; An electro-optical device that forms an image by applying a voltage to the liquid crystal layer between the first electrode and the second electrode, and in the first state set during the image formation, The voltage applied to the liquid crystal layer between the first electrode and the third electrode is the first electrode and the second electrode. The voltage applied to the liquid crystal layer between the first electrode and the second electrode is lower than the voltage applied to the liquid crystal layer between the electrodes and in the second state set when the power is turned off. The first voltage is higher than 0V, the second voltage applied to the liquid crystal layer between the first electrode and the third electrode is equal to or higher than the first voltage, and the first electrode and the fourth voltage The third voltage applied to the liquid crystal layer between the electrodes is not less than the first voltage.

  According to the configuration of this application example, since the liquid crystal layer including the liquid crystal having negative dielectric anisotropy is sandwiched between the pair of substrates, the liquid crystal molecules stand substantially vertically when no voltage is applied. The liquid crystal device is aligned in the above state, and the higher the applied voltage, the larger the inclination of the liquid crystal molecules with respect to the vertical direction, and the lower the state. In the second state that is set when the power of the liquid crystal device is turned off, the second voltage is disposed because the first voltage applied between the second electrode and the first electrode is higher than 0V. In such a region, the liquid crystal molecules are aligned more tilted than when no voltage is applied, so that the ionic impurities are easily moved. The second voltage applied between the first electrode and the third electrode is equal to or higher than the first voltage, and the third voltage applied between the first electrode and the fourth electrode is equal to or higher than the first voltage. For this reason, in the region where the third electrode and the fourth electrode are arranged, the inclination of the liquid crystal molecules with respect to the vertical direction is equal to or greater than that of the region where the second electrode is arranged, so that the ionic impurities easily move. It becomes a state. For this reason, ionic impurities generated in the region where the second electrode is disposed at the time of image formation can be swept out to the region where the third electrode and the fourth electrode on the outer surface are disposed when the power is turned off. As a result, it is possible to sweep out ionic impurities without providing an external battery in a state other than the first state in which an image is formed. This eliminates the need for a space for providing an external battery and complicates the circuit configuration. And increase in product cost can be avoided. Also, in the first state when the power is turned off and then turned on and reused, the voltage applied between the first electrode and the third electrode is between the first electrode and the second electrode. In the region where the third electrode is disposed, the inclination of the liquid crystal molecules with respect to the vertical direction is equal to or smaller than that in the region where the second electrode is disposed. Therefore, it is possible to prevent ionic impurities that have been swept into the region where the fourth electrode is disposed when the power is turned off from returning to the region where the second electrode is disposed during image formation. As a result, it is possible to provide an electro-optical device in which deterioration in display quality due to ionic impurities is suppressed is smaller and at a lower cost.

  Application Example 2 In the electro-optical device according to the application example, in the second state, the second voltage is higher than the first voltage, and the third voltage is higher than the first voltage. preferable.

  According to the configuration of this application example, in the second state that is set when the power is turned off, the second voltage applied between the first electrode and the third electrode is generated between the first electrode and the second electrode. The third voltage applied between the first electrode and the fourth electrode is higher than the first voltage applied between the first electrode and the second electrode. Therefore, in the region where the third electrode and the fourth electrode are disposed, the inclination of the liquid crystal molecules with respect to the vertical direction is larger than in the region where the second electrode is disposed, and the ionic impurities are more easily moved. Therefore, the ionic impurities generated in the region where the second electrode is disposed can be more efficiently moved to the region where the third electrode and the fourth electrode on the outer side are disposed in a plane.

  Application Example 3 In the electro-optical device according to the application example described above, illumination light is irradiated in the first state, and the second state is set after irradiation of the illumination light is stopped. It is preferable.

  According to the configuration of this application example, the second state is set after the irradiation of the illumination light is stopped. When the illumination light is irradiated, it takes a longer time to move the ionic impurities than when the illumination light is not irradiated. Therefore, by setting the second state after the illumination light irradiation is stopped, the ionic impurities can be quickly swept out without being visually recognized by the user.

  Application Example 4 In the electro-optical device according to the application example described above, the electro-optical device includes a switching element electrically connected to each of the second electrode and the third electrode. In a third state set after two states, a voltage applied to the liquid crystal layer between the first electrode and the second electrode, and the liquid crystal between the first electrode and the third electrode The voltage applied to the layer and the voltage applied to the liquid crystal layer between the first electrode and the fourth electrode are preferably 0V.

  According to the configuration of this application example, in the third state that is set when the power is turned off, the first electrode and the second electrode, the first electrode and the third electrode, and the first electrode By applying a voltage of 0 V between the first electrode and the fourth electrode, the charge accumulated at the time of image formation can be discharged to the switching element electrically connected to the second electrode and the third electrode. In this third state, since the liquid crystal molecules are aligned in a substantially vertical state in the region where the second electrode is disposed and the region where the third electrode and the fourth electrode are disposed, the movement of ionic impurities is inhibited. Is done. Therefore, by setting the second state where the ionic impurities are swept out before the third state, the ionic impurities can be swept out satisfactorily.

  Application Example 5 In the electro-optical device according to the application example described above, in the second state, the third voltage applied to the liquid crystal layer between the first electrode and the fourth electrode is the second voltage. It is preferable that the voltage be higher than the voltage.

  According to the configuration of this application example, the fourth electrode is arranged on the outer side in plan of the third electrode, and the third voltage applied to the fourth electrode with the first electrode when the power is turned off. Is equal to or higher than the second voltage applied to the third electrode, and in the region where the fourth electrode is disposed, the inclination of the liquid crystal molecules with respect to the vertical direction is equal to or greater than the region where the third electrode is disposed. The ionic impurities are easily moved. Therefore, the ionic impurities generated in the region where the second electrode is arranged at the time of image formation are arranged on the fourth electrode which is further planarly outer than the region where the third electrode is arranged when the power is turned off. It can be swept out into the area.

  Application Example 6 In the electro-optical device according to the application example, it is preferable that in the second state, the third voltage is higher than the second voltage.

  According to the configuration of this application example, when the power is turned off, the third voltage applied to the fourth electrode between the first electrode and the first electrode is higher than the second voltage applied to the third electrode. In the region where the electrode is disposed, the inclination of the liquid crystal molecules with respect to the vertical direction is larger than that in the region where the third electrode is disposed, and the ionic impurities are more easily moved. Therefore, the ionic impurities generated in the region where the second electrode is arranged can be moved more efficiently to the region where the fourth electrode on the outer side in a plane is arranged than the region where the third electrode is arranged. .

  Application Example 7 An electronic apparatus according to this application example includes the above-described electro-optical device.

  According to the configuration of this application example, since the electronic apparatus includes the electro-optical device described above, it is possible to provide a small and cost-competitive electronic apparatus with excellent display quality.

Schematic which shows the structure of the projector as an electronic device which concerns on this embodiment. Schematic which shows the structure of the liquid crystal device which concerns on this embodiment. FIG. 3 is an equivalent circuit diagram illustrating an electrical configuration of the liquid crystal device according to the embodiment. FIG. 3 is a schematic plan view showing a pixel region of the liquid crystal device according to the embodiment. FIG. 3 is a schematic plan view showing a relationship between an alignment direction and display unevenness caused by ionic impurities in a liquid crystal device. FIG. 6 is a schematic cross-sectional view illustrating the relationship between the alignment direction and the movement of ionic impurities in a liquid crystal device. FIG. 2 is a block diagram illustrating a schematic configuration of a circuit unit that drives the liquid crystal device according to the embodiment. FIG. 4 is a diagram showing a power-off sequence of the projector according to the embodiment. The figure explaining the ion sweep-out result which concerns on this embodiment.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings. The drawings to be used are appropriately enlarged, reduced or exaggerated so that the part to be described can be recognized. In addition, illustrations of components other than those necessary for the description may be omitted.

(First embodiment)
<Configuration of electronic equipment>
First, an example of an electronic apparatus including the electro-optical device according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating a configuration of a projector as an electronic apparatus according to the present embodiment. As shown in FIG. 1, a projector 100 as an electronic apparatus according to the present embodiment is a projection display device that modulates light incident from a light source unit with a light modulation element and projects the light onto a screen 130 by a projection optical system. is there.

  The projector 100 includes a polarization illumination device 110 as a light source unit, two dichroic mirrors 104 and 105 as light separation elements, three reflection mirrors 106, 107, and 108, and five relay lenses 111, 112, 113, and 114. , 115, three liquid crystal light valves 121, 122, 123 as light modulation elements, a cross dichroic prism 116 as a light combining element, and a projection lens 117 as a projection optical system.

  The polarization illumination device 110 includes a lamp unit 101 as a light source composed of a white light source such as an ultra-high pressure mercury lamp or a halogen lamp, an integrator lens 102, and a polarization conversion element 103. The lamp unit 101, the integrator lens 102, and the polarization conversion element 103 are disposed along the system optical axis Lx.

  The dichroic mirror 104 reflects red light (R) and transmits green light (G) and blue light (B) out of the polarized light flux of illumination light emitted from the polarization illumination device 110. Another dichroic mirror 105 reflects the green light (G) transmitted through the dichroic mirror 104 and transmits the blue light (B).

  The red light (R) reflected by the dichroic mirror 104 is reflected by the reflection mirror 106 and then enters the liquid crystal light valve 121 via the relay lens 115. The green light (G) reflected by the dichroic mirror 105 enters the liquid crystal light valve 122 via the relay lens 114. The blue light (B) transmitted through the dichroic mirror 105 is incident on the liquid crystal light valve 123 via a light guide system composed of three relay lenses 111, 112, 113 and two reflection mirrors 107, 108.

  The liquid crystal light valves 121, 122, and 123 are transmissive light modulation elements, to which the liquid crystal device 1 (see FIGS. 2A and 2B) as an electro-optical device according to this embodiment is applied. is there. The liquid crystal light valves 121, 122, 123 are arranged with a gap between a pair of polarizing elements arranged in crossed Nicols on the incident side and emission side of each color light. The liquid crystal light valves 121, 122, and 123 are disposed to face the incident surfaces of the cross dichroic prism 116 for each color light. The color light incident on the liquid crystal light valves 121, 122, 123 is modulated based on video information (video signal) and emitted toward the cross dichroic prism 116.

  The cross dichroic prism 116 is formed by bonding four right-angle prisms, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are formed in a cross shape on the inner surface thereof. Yes. By these dielectric multilayer films, the three color lights modulated by the liquid crystal light valves 121, 122, and 123 are combined, and the light representing the color image is combined.

  The projection lens 117 enlarges and projects the light combined by the cross dichroic prism 116 on the screen 130. As a result, the full color image is enlarged and displayed on the screen 130.

  Although illustration is omitted, the projector 100 has an operation unit having a power switch and the like for the user to operate the projector 100. This operation unit is provided in the main body of the projector 100 and the remote controller. When the user presses the power switch while each part of the projector 100 is stopped, each part of the projector 100 starts an operation when turning on the power. In addition, when the user presses the power switch while each unit of the projector 100 is operating, a series of operations when each unit of the projector 100 turns off the power supply is started. A series of operations when turning off the power is hereinafter referred to as a power-off sequence. Details of the power-off sequence will be described later.

<Configuration of electro-optical device>
Next, a liquid crystal device as an electro-optical device according to the present embodiment will be described with reference to FIGS. FIG. 2 is a schematic diagram illustrating a configuration of the liquid crystal device according to the present embodiment. Specifically, FIG. 2A is a schematic plan view showing the configuration of the liquid crystal device, and FIG. 2B is a schematic cross-sectional view taken along the line HH ′ of FIG. FIG. 3 is an equivalent circuit diagram showing an electrical configuration of the liquid crystal device according to the present embodiment.

  Here, the liquid crystal device 1 will be described by taking an active matrix type liquid crystal device including a thin film transistor (TFT) as a pixel switching element as an example.

  As shown in FIGS. 2A and 2B, the liquid crystal device 1 according to this embodiment is sandwiched between the counter substrate 30 and the element substrate 20 as a pair of substrates, and the counter substrate 30 and the element substrate 20. The liquid crystal layer 40 is provided. The counter substrate 30 that is one substrate and the element substrate 20 that is the other substrate are disposed so as to face each other. For the base material 31 of the counter substrate 30 and the base material 21 of the element substrate 20, for example, transparent substrates such as a quartz substrate and a glass substrate are used.

  The counter substrate 30 and the element substrate 20 are bonded to each other with a gap interposed therebetween through a sealing material 42 arranged in a frame shape along the outer edge. The liquid crystal layer 40 is sealed in a space surrounded by the counter substrate 30, the element substrate 20, and the sealing material 42. The sealing material 42 is made of an adhesive such as a thermosetting or ultraviolet curable epoxy resin. Spacers (not shown) are mixed in the sealing material 42 to keep the distance between the counter substrate 30 and the element substrate 20 constant.

  Inside the sealing material 42, a pixel region 10 in which a plurality of pixels P are arranged in a matrix is provided. The display pixel area 10a is disposed on the innermost side of the pixel area 10, the color matching pixel area 10b is disposed so as to surround the display pixel area 10a, and the dummy pixel area 10c is surrounded so as to surround the color matching pixel area 10b. Has been placed. In a state where normal display is performed, the display pixel region 10a is a region that substantially contributes to display, and the color-matching pixel region 10b and the dummy pixel region 10c do not substantially contribute to display (so-called parting portions). It is.

  The dummy pixel region 10c is shielded from light by a light shielding portion 32 (see FIG. 2B) provided on the counter substrate 30. Although not shown, in the pixel region 10 (the display pixel region 10a, the color matching pixel region 10b, and the dummy pixel region 10c), a light shielding portion (black matrix: BM) provided in a lattice shape on the element substrate 20 is used. ), The plurality of pixels P are divided in a plane.

  A data line driving circuit 51 and a plurality of external connection terminals 54 are provided along one side of the sealing material 42 on one side of the element substrate 20 in plan view. Further, a scanning line driving circuit 52 is provided inside the sealing material 42 along two sides that are orthogonal to the one side and face each other. The data line driving circuit 51 and the scanning line driving circuit 52 are connected to a plurality of external connection terminals 54 via wiring not shown. At the four corners of the counter substrate 30 and the element substrate 20, vertical conduction portions 56 for providing electrical continuity between the counter substrate 30 and the element substrate 20 are provided.

  In the following description, a direction along one side where the data line driving circuit 51 is provided is defined as an X direction, and a direction along two sides where the scanning line driving circuit 52 is provided is defined as a Y direction. The direction of the H-H ′ line in FIG. 2A is a direction along the Y direction. Further, a direction orthogonal to the X direction and the Y direction and directed upward in FIG. In this specification, viewing the liquid crystal device 1 from the normal direction (Z direction) of the surface of the counter substrate 30 is referred to as “plan view”. The arrangement in plan view is called “planar”.

  As shown in FIG. 2B, on the liquid crystal layer 40 side of the counter substrate 30 (base material 31), the light shielding portion 32, the interlayer 33, the common electrode 34 as the first electrode, and the common electrode 34 And an alignment film 35 is provided.

  The light shielding portion 32 is provided in a frame shape so as to extend along the X direction and the Y direction at a position overlapping with the scanning line driving circuit 52 (see FIG. 2A) in plan view and a plurality of wirings (not shown) in plan view. Yes. The light shielding portion 32 is made of, for example, a light shielding metal or metal oxide. The light shielding portion 32 serves to shield light incident from the counter substrate 30 side and prevent malfunction due to light in peripheral circuits including these drive circuits. Further, unnecessary stray light is shielded so as not to enter the display pixel region 10a, and a high contrast in the display of the display pixel region 10a is ensured.

The interlayer 33 shown in FIG. 2B is formed so as to cover the light shielding portion 32. The interlayer 33 is formed of an insulating film such as a silicon oxide film (SiO ₂ ), for example, and has optical transparency. The interlayer 33 is provided so that unevenness caused by the light shielding portion 32 and the like is alleviated and the surface on the liquid crystal layer 40 side on which the common electrode 34 is formed is flat. Examples of a method for forming the interlayer 33 include a method of forming a film using a plasma CVD (Chemical Vapor Deposition) method.

  The common electrode 34 is made of a light-transmitting conductive film such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide), for example, covers the interlayer layer 33, and as shown in FIG. Are electrically connected to the wiring on the element substrate 20 side by vertical conduction portions 56 provided at the four corners. Note that the interlayer electrode 33 may be omitted by forming the common electrode 34 so as to directly cover the conductive light shielding portion 32.

  On the element substrate 20 (base material 21) side of the liquid crystal layer 40, a TFT 24, which is a switching element provided for each pixel P, a wiring portion and a contact portion (not shown), and a light transmission provided for each pixel P. A pixel electrode 28 and an alignment film 29 covering the pixel electrode 28 are provided. The TFT 24, the wiring portion, the contact portion, etc. have a known configuration. The pixel electrode 28 is made of a light-transmitting conductive film such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide).

  The alignment film 29 and the alignment film 35 are selected based on the optical design of the liquid crystal device 1. The alignment film 29 and the alignment film 35 are, for example, an organic alignment film in which an organic material such as polyimide is formed and the surface thereof is rubbed so that liquid crystal molecules are subjected to a substantially vertical alignment process, or a gas phase. Examples thereof include an inorganic alignment film in which an inorganic material such as SiOx (silicon oxide) is formed by a growth method and is aligned substantially perpendicularly to liquid crystal molecules having negative dielectric anisotropy.

  The liquid crystal constituting the liquid crystal layer 40 modulates light and enables gradation display by changing the orientation and order of the molecular assembly depending on the applied voltage level. This is a so-called normally black mode in which the transmittance for incident light increases according to the voltage applied in units of each pixel P, and light having a contrast corresponding to an image signal is emitted from the liquid crystal device 1 as a whole. .

  In the present embodiment, the liquid crystal device 1 includes an alignment film 29 and an alignment film 35 formed by obliquely depositing an inorganic material, and a liquid crystal layer 40 including a liquid crystal having negative dielectric anisotropy, and is normally. This is a VA (Vertical Alignment) mode liquid crystal device to which a black optical design is applied.

  Next, the electrical configuration of the liquid crystal device 1 will be described with reference to FIG. As shown in FIG. 3, the scanning line 2 and the data line 3 are formed in the pixel region 10 so as to be insulated and intersect with each other. The direction in which the scanning line 2 extends is the X direction, and the direction in which the data line 3 extends is the Y direction. The pixel P is provided corresponding to the intersection of the scanning line 2 and the data line 3. Each pixel P is provided with a pixel electrode 28 and a TFT 24 (Thin Film Transistor) as a switching element.

  A source electrode (not shown) of the TFT 24 is electrically connected to the data line 3 extending from the data line driving circuit 51. Image signals (data signals) S1, S2,..., Sn are supplied to the data line 3 from the data line driving circuit 51 (see FIGS. 2A and 2B) in a line sequential manner. A gate electrode (not shown) of the TFT 24 is a part of the scanning line 2 extending from the scanning line driving circuit 52. The scanning lines 2 are supplied with scanning signals G1, G2,..., Gm from the scanning line driving circuit 52 in a line sequential manner. A drain electrode (not shown) of the TFT 24 is electrically connected to the pixel electrode 28.

  The image signals S1, S2,..., Sn are written to the pixel electrode 28 through the data line 3 at a predetermined timing by turning on the TFT 24 for a certain period. The image signal of a predetermined level written in the liquid crystal layer 40 through the pixel electrode 28 in this way is liquid crystal formed between the common electrode 34 (see FIG. 2B) provided on the counter substrate 30. It is held for a certain period in capacity.

  In order to prevent the retained image signals S1, S2,..., Sn from leaking, the storage capacitor 5 is provided between the capacitor line 4 formed in parallel with the data line 3 and the pixel electrode 28. Is formed and arranged in parallel with the liquid crystal capacitor. Thus, when a voltage signal is applied to the liquid crystal of each pixel P, the alignment state of the liquid crystal changes depending on the applied voltage level. As a result, the light incident on the liquid crystal layer 40 (see FIG. 2B) is modulated to enable gradation display.

  Next, a more detailed configuration of the pixel region 10 of the liquid crystal device 1 will be described with reference to FIG. FIG. 4 is a schematic plan view showing a pixel region of the liquid crystal device according to the present embodiment. As shown in FIG. 4, in the pixel area 10, a color matching pixel area 10b is disposed outside the display pixel area 10a in a plane, and a dummy pixel area 10c is positioned outside the color matching pixel area 10b in a plane. Is arranged. In FIG. 4, the color matching pixel region 10b has a shape surrounded by one pixel, but may have a shape surrounded by a plurality of pixels.

  Among the plurality of pixels P arranged in a matrix in the pixel area 10, the pixel P arranged in the display pixel area 10a is set as the display pixel Pa, and the pixel P arranged in the color matching pixel area 10b is set as the color matching pixel. Let Pb be a pixel P arranged in the dummy pixel region 10c as a dummy pixel Pc.

  Of the pixel electrodes 28 provided corresponding to the pixels P, the pixel electrode 28 corresponding to the display pixel Pa is set as the pixel electrode 28a as the second electrode, and the pixel electrode 28 corresponding to the color-matching pixel Pb is set as the second electrode. The pixel electrode 28b serving as the three electrodes is used, and the pixel electrode 28 corresponding to the dummy pixel Pc is used as the pixel electrode 28c serving as the fourth electrode. The pixel electrodes 28a, 28b, 28c are each electrically connected to the TFT 24 (see FIG. 2B).

  The display pixel region 10 a is a region that substantially contributes to display for performing normal display in the liquid crystal device 1. When the liquid crystal device 1 is compatible with full high-definition, display pixels Pa of 1920 (X direction) × 1080 (Y direction) are arranged in the display pixel region 10a.

  The color matching pixel area 10b is an area for use in alignment of the liquid crystal devices 1 when a plurality of liquid crystal devices 1 are used as in the projector 100 described above, for example. In the projector 100, the three liquid crystal devices 1 are mechanically aligned to form one image by combining the three color lights modulated by the three liquid crystal devices 1. When the positional shift between the display pixels Pa of the three liquid crystal devices 1 cannot be adjusted by this mechanical alignment, the color-aligned pixel Pb corresponding to the shifted position is used as the display pixel Pa. Or, conversely, the display pixel Pa may be used as the color matching pixel Pb.

  As described above, the color matching pixel region 10b does not contribute to display in a state where there is no mechanical displacement, but is not shielded because it contributes to display when there is mechanical displacement. If there is no mechanical misalignment of the three liquid crystal devices 1, the color-matching pixel region 10b functions as a part of the parting part in a normal use state. Therefore, black display is performed in the color matching pixels Pb, and light leakage in the color matching pixel region 10b is suppressed.

  The dummy pixel region 10c has the same cross-sectional structure as the display pixel region 10a that contributes to display and the matching pixel region 10b for each color that may contribute to display, so that the liquid crystal layer in the entire pixel region 10 This is a region for making the layer thickness of 40 (see FIG. 2B) uniform and preventing color unevenness caused by variations in the layer thickness of the liquid crystal layer 40. The dummy pixel region 10c is a parting part that does not contribute to display, and is shielded from light by the light shielding part 32 (see FIG. 2B).

<Normal drive mode and ion sweep drive mode>
In general, when light is incident on a liquid crystal device, the liquid crystal material or alignment film of the liquid crystal layer and the incident light may undergo a photochemical reaction, and ionic impurities may be generated as a reaction product. It is also known that there are ionic impurities that diffuse from a sealing material or a sealing material into the liquid crystal layer during the manufacturing process of the liquid crystal device. In particular, in the liquid crystal device 1 used as the light valve of the projector 100 as in the present embodiment, the luminous flux density of incident light is higher than that in the direct-view type liquid crystal device, so that ionic impurities affect the display. It is necessary to suppress it.

  The state in which illumination light is irradiated onto the liquid crystal device 1 in the projector 100 and an image formed by the liquid crystal device 1 is projected is referred to as a normal drive mode as a first state set at the time of image formation. When the liquid crystal device 1 is continuously operated in the normal drive mode for a long time, ionic impurities are generated as described above. Therefore, in the projector 100 according to the present embodiment, the ionic impurities in the liquid crystal device 1 are swept out during the power-off sequence when the power is turned off. The sweeping of ionic impurities performed in the power-off sequence is referred to as an ion sweep driving mode as a second state set when the power is turned off.

  Hereinafter, the normal drive mode and the ion sweep drive mode of the liquid crystal device 1 and the projector 100 according to the present embodiment will be described. FIG. 5 is a schematic plan view showing the relationship between the alignment direction and display unevenness due to ionic impurities in the liquid crystal device. FIG. 6 is a schematic cross-sectional view illustrating the relationship between the alignment direction and the movement of ionic impurities in the liquid crystal device.

  5A and 5B, the display pixel region 10a, the color-matching pixel region 10b, and the dummy pixel region 10c of the liquid crystal device 1 are simplified. FIG. 5A is a diagram illustrating a state after the liquid crystal device 1 is continuously operated in the normal drive mode for a long time. FIG. 5B is a diagram illustrating a state after the ion sweep drive mode of the power-off sequence is executed. Here, it is assumed that there is no mechanical displacement of the liquid crystal device 1 and the color matching pixel region 10b functions as a part of a parting part that does not contribute to display.

  5A and 5B, for example, the oblique deposition direction in the alignment film 29 on the element substrate 20 side is a predetermined azimuth angle θa from the lower left to the upper right as indicated by a broken arrow 29a in the drawing. The direction intersects with the Y direction. The oblique deposition direction in the alignment film 35 on the counter substrate 30 side is a direction that intersects the Y direction at a predetermined azimuth angle θa from the upper right to the lower left as indicated by a solid arrow 35a in the drawing. In the present embodiment, the predetermined azimuth angle θa is, for example, 45 °. The oblique deposition directions shown in FIGS. 5A and 5B are directions in a plan view when the liquid crystal device 1 is viewed from the counter substrate 30 side.

  6 (a), 6 (b), and 6 (c), arrows 29a and 35a indicate the portions where the display pixel region 10a, the color matching pixel region 10b, and the dummy pixel region 10c of the liquid crystal device 1 are adjacent to each other. The cross section along the oblique deposition direction is shown enlarged. FIG. 6A is a diagram showing a state in the normal drive mode, and FIG. 6B is a diagram showing a state in the ion sweep drive mode. FIG. 6C is a diagram showing a state in the normal drive mode after the power is turned off and the ionic impurities are swept out.

  6A, 6 </ b> B, and 6 </ b> C, the oblique deposition direction in the alignment film 29 on the element substrate 20 side is a direction from left to right as indicated by an arrow 29 a in the drawing, and the counter substrate 30. The oblique deposition direction in the alignment film 35 on the side is a direction from right to left as indicated by an arrow 35a in the drawing. The alignment films 29 and 35 are inorganic alignment films, and are made of, for example, an assembly of columns (not shown) grown in a columnar shape by depositing an inorganic material such as silicon oxide obliquely from a predetermined direction.

  As shown in FIG. 6A, with respect to the alignment films 29 and 35, the liquid crystal molecules 40a having negative dielectric anisotropy contained in the liquid crystal layer 40 are aligned in the normal direction of the alignment film surface. On the other hand, it has a pretilt angle θp in the column tilt direction and is substantially vertically aligned (VA). The pretilt angle θp is, for example, about 3 ° to 5 °. By applying an alternating voltage between the pixel electrode 28 (28a, 28b, 28c) and the common electrode 34 to drive the liquid crystal layer 40, the liquid crystal molecules 40a are common to the pixel electrode 28 (28a, 28b, 28c). It behaves (vibrates) so as to incline in the direction of the electric field generated between it and the electrode 34.

  As shown in FIG. 6A, in the normal drive mode, in the display pixel region 10a, within a predetermined voltage range between each pixel electrode 28a and the common electrode 34, based on a video signal forming an image. The set AC voltage is applied. In the present embodiment, the predetermined voltage range is, for example, 0 V to 5 V (−5 V to +5 V). The voltage applied to each pixel electrode 28a varies depending on the gradation of the image to be formed.

  Therefore, the inclination of the liquid crystal molecules 40a in the display pixel region 10a is inclined so as to be along the alignment film surface from a state of being substantially perpendicular to the alignment film surface at the pretilt angle θp with a change in applied voltage. It changes variously to the state of sleeping. At this time, the direction in which each liquid crystal molecule 40a is inclined is the side to which the pretilt angle θp is given with respect to the normal direction of the alignment film surface, that is, the left side indicated by the arrow 35a.

  In the following, the small inclination of the liquid crystal molecules 40a with respect to the normal direction of the alignment film surface is simply referred to as “small inclination”, and the large inclination with respect to the normal direction of the alignment film surface is simply “high inclination”. That's it. The state in which the tilt of the liquid crystal molecules 40a is reduced and the pretilt angle θp is reached (or the state in which the pretilt angle θp is close) is also referred to as “the state in which the liquid crystal molecules 40a are standing”. A state along the film surface is also referred to as “a state in which the liquid crystal molecules 40 a are laid down”.

  As described above, since the display pixel region 10a is irradiated with illumination light from the polarized illumination device 110 (see FIG. 1), the liquid crystal material of the liquid crystal layer 40, the alignment films 29 and 35, and the incident illumination light undergo a photochemical reaction. And ionic impurities 45 may be generated as a reaction product. When the ionic impurities 45 are generated, the moment that the liquid crystal molecules 40a are tilted, that is, the left side indicated by the arrow 35a acts on the ionic impurities 45 due to the vibration of the liquid crystal molecules 40a. Therefore, the ionic impurities 45 move toward the color matching pixel region 10b side.

  In the color matching pixel region 10b, a voltage equal to or lower than the voltage applied between the pixel electrode 28a and the common electrode 34, more specifically, a voltage of 0 V is applied between the pixel electrode 28b and the common electrode 34. Is done. As a result, the liquid crystal molecules 40a stand at the pretilt angle θp, and the color matching pixel region 10b displays black (see FIG. 5A). For this reason, the ionic impurities 45 generated in the display pixel region 10a and moving to the left side of the drawing accumulate on the right side of the liquid crystal molecules 40a standing in the color matching pixel region 10b.

  Since the dummy pixel region 10c is shielded from light and is not visible to the user, the voltage applied between the pixel electrode 28c and the common electrode 34 is not particularly limited. For example, the dummy pixel region 10c is connected to the pixel electrode 28a in the display pixel region 10a. The voltage is appropriately set within a predetermined voltage range applied to the common electrode 34. FIG. 6A shows a state in which the maximum voltage (5 V) is applied between the pixel electrode 28 c and the common electrode 34.

  In the plan view shown in FIG. 5A, the ionic impurity 45 (see FIG. 6A) moves from the upper right to the lower left indicated by the arrow 35a in the display pixel region 10a. Then, since the liquid crystal molecules 40a standing in the color matching pixel region 10b surrounding the display pixel region 10a become walls, the ionic impurities 45 accumulate in the lower left corner of the display pixel region 10a.

  FIG. 5A shows a state in which an ion pool 46 is generated in the lower left corner of the display pixel region 10a due to the large amount of ionic impurities 45 gathering in this way. In the region where the ion reservoir 46 is formed, the specific resistance is deteriorated by the collected ionic impurities 45 and is visually recognized by the user as display unevenness.

  Therefore, the projector 100 according to the present embodiment has an ion sweeping drive mode that is executed to sweep out the ionic impurities 45 to the outside of the display pixel region 10a in a plane. In the ion sweep drive mode, the first voltage applied to the liquid crystal layer 40 between the pixel electrode 28a and the common electrode 34 in the display pixel region 10a is set to a voltage higher than 0V. Note that when the first voltage is 0 V, the liquid crystal molecules 40a stand at the pretilt angle θp in the display pixel region 10a, so that the movement of the ionic impurities 45 is hindered and stays in the display pixel region 10a. It will be.

  Then, the second voltage applied to the liquid crystal layer 40 between the pixel electrode 28b and the common electrode 34 in the color matching pixel region 10b is set to a voltage equal to or higher than the first voltage, and in the dummy pixel region 10c, the pixel electrode 28c The third voltage applied to the liquid crystal layer 40 between the common electrode 34 is set to a voltage equal to or higher than the second voltage. The first voltage, the second voltage, and the third voltage are fixed voltages that become fixed gradation signals.

  In the present embodiment, the first voltage, the second voltage, and the third voltage are all set to the maximum voltage (5 V) in the normal drive mode. With this setting, as shown in FIG. 6B, the inclination of the liquid crystal molecules 40a is increased and the entire display pixel region 10a, the color-matching pixel region 10b, and the dummy pixel region 10c are in a lying state. .

  Therefore, in the ion sweep drive mode, the walls of the color matching pixel region 10b are eliminated, and the entire ionic impurities 45 can flow from the display pixel region 10a to the dummy pixel region 10c. Therefore, the ionic impurities 45 generated in the display pixel region 10a in the normal drive mode pass through the color matching pixel region 10b from the display pixel region 10a and are collected by being swept to the dummy pixel region 10c side.

  In the plan view shown in FIG. 5B, in the ion sweep drive mode, the ionic impurities 45 collected in the lower left corner of the display pixel region 10a further move in the lower left direction, and the corner of the dummy pixel region 10c. Collected to the department. As a result, even when a large amount of ionic impurities 45 are collected in the normal drive mode as shown in FIG. 5A and an ion reservoir 46 is formed, as shown in FIG. The reservoir 46 moves to the corner portion of the shielded dummy pixel region 10c. As a result, display unevenness caused by the ion reservoir 46 is not visually recognized by the user.

  In the present embodiment, the first voltage, the second voltage, and the third voltage applied in the ion sweep drive mode are set to the maximum voltage (5 V) in the normal drive mode. It may be set to a voltage higher than the maximum voltage.

  As shown in FIG. 6C, in the normal drive mode in which the projector 100 is turned off and the ionic impurities 45 are swept out and then turned on and reused, the dummy pixel region 10c is not turned on. The collected ionic impurities 45 are unlikely to move to the right side, which is the reverse direction of the flow of the ionic impurities 45 along the alignment direction indicated by the arrow 35a. Since the liquid crystal molecules 40a standing in the color matching pixel region 10b serve as walls, the ionic impurities 45 once collected in the dummy pixel region 10c are prevented from returning to the display pixel region 10a.

  Further, in the normal drive mode after sweeping out the ionic impurities 45, even when ionic impurities 45 are newly generated in the display pixel region 10a, the ion sweep drive mode is executed when the power is turned off. The newly generated ionic impurities 45 can be swept out to the dummy pixel region 10c outside the display pixel region 10a.

  According to the experiments by the inventors, the ionic impurities 45 are generated from the start of the use of the projector 100, but the ion reservoir 46 is so large that display unevenness is visually recognized by the user as shown in FIG. Occurrence occurs after continuous use in a normal driving mode, for example, for 16 to 24 hours or more. In general user use, it is rare to use the projector 100 for such a long time. Therefore, like the projector 100 according to the present embodiment, if the ionic impurities 45 are swept out every time the power is turned off after being used in the normal drive mode, display unevenness as seen by the user is generated. Can be deterred.

  Next, a configuration of a circuit unit that drives the liquid crystal device 1 according to the present embodiment and a power-off sequence of the projector 100 will be described with reference to FIGS. 7, 8, and 9. FIG. 7 is a block diagram illustrating a schematic configuration of a circuit unit that drives the liquid crystal device according to the present embodiment. FIG. 8 is a diagram illustrating a power-off sequence of the projector according to the present embodiment. FIG. 9 is a diagram for explaining the result of ion sweeping according to the present embodiment.

<Configuration of circuit section>
As shown in FIG. 7, the projector 100 according to the present embodiment includes a circuit unit 140 for driving the liquid crystal device 1. The circuit unit 140 includes a parting circuit 141, a composition circuit 142, a color matching circuit 143, a fixed gradation generation circuit 144, an output selection circuit 145, and an output control circuit 146. From the circuit unit 140, pixel input signals of three color lights of red light (R), green light (G), and blue light (B) are output to the liquid crystal light valves 121, 122, 123 (liquid crystal device 1). Is done.

  The parting generation circuit 141 generates a voltage to be applied between the pixel electrodes 28b and 28c of the color matching pixel region 10b and the dummy pixel region 10c, which are parting parts, and the common electrode 34 in the normal driving mode. Output to. In the present embodiment, the parting generation circuit 141 applies a voltage of 0 V between the pixel electrode 28b and the common electrode 34 in the color matching pixel region 10b, and the pixel electrode 28c and the common electrode 34 in the dummy pixel region 10c. A voltage of 5V is applied between them.

  In the normal drive mode, the combining circuit 142 applies the voltage applied between the pixel electrode 28a and the common electrode 34 in the display pixel region 10a determined based on the video signal, and the pixel electrode of the parting part output from the parting generation circuit 141. The voltages to be applied between 28b and 28c and the common electrode 34 are synthesized. The video signal is a signal input from a control unit (not shown) to form an image and display the video, and is prepared for each color light of R, G, and B.

  The color matching circuit 143 is a circuit that electrically matches the position of the pixel P of each color light of R, G, and B. As described above, when the positional deviations of the liquid crystal light valves 121, 122, and 123 (liquid crystal device 1) cannot be adjusted by mechanical alignment, the color-aligned pixel Pb is set for the target liquid crystal device 1. The display pixel Pa is used as the display pixel Pa, or conversely, the display pixel Pa is used as the color matching pixel Pb. In such a case, the color matching circuit 143 determines the color matching pixel Pb used as the display pixel Pa and the display pixel Pa used as the color matching pixel Pb for each color light of R, G, and B. Then, a video signal based on the determination is output.

  The fixed gradation generation circuit 144 is common to each of the pixel electrodes 28a, 28b, and 28c in each of the display pixel region 10a, the color matching pixel region 10b, and the dummy pixel region 10c in the ion sweep driving mode of the power-off sequence. A voltage (first voltage, second voltage, and third voltage) to be applied to the electrode 34 is generated. In the present embodiment, the fixed gradation generation circuit 144 outputs an applied voltage of 5V as the same fixed gradation signal to each of the pixel electrodes 28a, 28b, and 28c.

  The output selection circuit 145 selects either the video signal output from the color matching circuit 143 or the fixed gradation signal output from the fixed gradation generation circuit 144 based on the selection signal input from the control unit. Select and output. In response to the selection signal, the video signal from the color matching circuit 143 is output in the normal drive mode, and the fixed gradation signal from the fixed gradation generation circuit 144 is output in the ion sweep drive mode of the power-off sequence.

  The output control circuit 146 sends R, G for each pixel P (Pa, Pb, Pc) to the liquid crystal light valves 121, 122, 123 (liquid crystal device 1) based on the signal selected and output by the output selection circuit 145. , B color light signals are output.

<Power off sequence>
As shown in FIG. 8, the projector 100 according to the present embodiment performs a series of operations from step S1 to step S9 as a power-off sequence. The power-off sequence is started when the user performs an operation for turning off the power, such as pressing a power switch, in a state where each unit of the projector 100 is operating.

  First, in step S1, the emission of illumination light from the polarization illumination device 110 is stopped. Thereby, the illumination light is not irradiated to the liquid crystal light valves 121, 122, and 123 (the liquid crystal device 1), and the projection of the image onto the screen 130 is stopped.

  Next, in step S2, the mode is switched to the ion sweep drive mode, and the fixed gradation generation circuit 144 outputs a fixed gradation signal. Then, the output selection circuit 145 selects and outputs a fixed gradation signal, and drives the liquid crystal light valves 121, 122, 123 (liquid crystal device 1) in the ion sweep drive mode as shown in FIG. 6B. This ion sweep drive mode is maintained for a predetermined time in step S3.

  In addition, when illumination light is irradiated, it takes time to move the ionic impurities 45 as compared with the case where illumination light is not irradiated. Therefore, by switching to the ion sweep drive mode after the illumination light irradiation is stopped, the ionic impurities 45 can be quickly swept without being visually recognized by the user.

  The predetermined time in step S3 is necessary until the ionic impurity 45 (ion reservoir 46) moves to the outside of the display pixel region 10a in the ion sweep driving mode and the display unevenness as seen by the user is eliminated. The time is appropriately set. In the present embodiment, the predetermined time for maintaining the ion sweep drive mode is, for example, 8 seconds. The reason will be described with reference to FIG.

  FIG. 9 shows a driving time and display unevenness when the liquid crystal device 1 was driven in the normal drive mode for 16 hours and the display unevenness was visually recognized as an experimental sample, and was driven in the ion sweep drive mode. It shows the relationship with the determination result of the visual recognition status. Driving in the ion sweep drive mode is started after the emission of illumination light is stopped, and is common to each of the pixel electrodes 28a, 28b, and 28c in the display pixel region 10a, the color matching pixel region 10b, and the dummy pixel region 10c. The voltages (first voltage, second voltage, and third voltage) applied between the electrodes 34 were set to 5V.

  As shown in FIG. 9, when the drive time was 0.5 seconds, no reduction in display unevenness could be confirmed (judgment result: C). When the driving time was 1 to 3 seconds, it was confirmed that the display unevenness was reduced, but it did not reach an acceptable level (judgment result: B). When the driving time was 5 seconds, display unevenness was remarkably reduced to an acceptable level (judgment result: A). When the driving time is 8 seconds to 10 seconds, display unevenness is not visually recognized (judgment result: AA). That is, it was found that the display unevenness can be reduced to an acceptable level by setting the driving time to 5 seconds or more, and the display unevenness can be eliminated (moved to the parting portion) by setting the driving time to 8 seconds or more. .

  In order to eliminate the display unevenness, the longer the predetermined time maintained in step S3, the better. However, if the time of step S3 becomes longer, the time taken for a series of operations from step S1 to step S9 becomes longer. The user's convenience may be reduced. Accordingly, in the present embodiment, the predetermined time in step S3 is set to 8 seconds necessary until a level at which display unevenness cannot be visually recognized (determination result: AA).

  Next, in step S4 shown in FIG. 8, the mode is switched to the charge discharge drive mode as the third state in the power-off sequence. The charge discharge drive mode is a mode for discharging charges accumulated in the TFT 24 electrically connected to the pixel electrodes 28a, 28b, 28c in the normal drive mode. In the charge discharge drive mode, the fixed gradation generation circuit 144 outputs an applied voltage of 0 V as the same fixed gradation signal to each of the pixel electrodes 28a, 28b, and 28c. This charge discharge drive mode is maintained for a predetermined time in step S5. In the present embodiment, the predetermined time for maintaining the charge discharge drive mode is, for example, 0.18 seconds (180 msec).

  Here, in the charge discharge drive mode, a voltage of 0 V is applied between the pixel electrodes 28a, 28b, 28c and the common electrode 34 in all the display pixel region 10a, the color matching pixel region 10b, and the dummy pixel region 10c. Therefore, the liquid crystal molecules 40a in all these regions are in a state of standing with respect to the alignment film surface in the same manner as the liquid crystal molecules 40a in the color matching pixel region 10b shown in FIG. Therefore, in this state, the movement of the ionic impurity 45 is inhibited in the entire region.

  Therefore, if step S4 is executed before step S2, the ionic impurities 45 are difficult to move in the entire region of the liquid crystal device 1, and the ionic impurities 45 are favorably swept out in the ion sweep drive mode of step S2. May not be possible. In the present embodiment, since the ion sweep drive mode of step S2 is executed before the charge discharge drive mode of step S4 is executed, the ionic impurities 45 can be favorably swept in the ion sweep drive mode.

  Next, in step S6 shown in FIG. 8, the driving of the liquid crystal light valves 121, 122, 123 (liquid crystal device 1) is stopped. And it waits for predetermined time, for example, 0.1 second (100 msec) (step S7). Next, in step S8, I / O setting at power-on is performed. In step S8, a control signal or the like is set to a predetermined state so that the initial operation of the IC of the control unit is correctly performed at the next power-on.

  Next, in step S9, the power of each unit of the projector 100 is turned off. After step S9, the user can unplug the power plug of the projector 100 from the outlet, or can turn off the main power switch of the outlet into which the power plug of the projector 100 is inserted. Therefore, it is preferable not to increase the time required for a series of operations from step S1 to step S9 in order not to reduce the convenience for the user.

  Thus, in the liquid crystal device 1 and the projector 100 according to the present embodiment, the ionic impurities 45 generated in the display pixel region 10a in the normal drive mode are removed from the plane of the display pixel region 10a in the power supply sequence when the power is turned off. Can be swept outward. Therefore, sweeping out of the ionic impurities 45 can be executed in a state other than the normal drive mode in which the user can visually recognize an image and without providing an external battery. This eliminates the need for a space for providing an external battery and avoids complicated circuit configuration and an increase in product cost. Therefore, it is possible to provide a compact and cost competitive projector 100 with excellent display quality.

(Second Embodiment)
Next, a second embodiment will be described. The second embodiment is different from the first embodiment in the voltages (first voltage, second voltage, and voltage) applied between each of the pixel electrodes 28a, 28b, and 28c and the common electrode 34 in the ion sweep drive mode. And the third voltage) have the same configuration except that the setting is different. Here, differences from the first embodiment will be described with reference to the drawings used in the first embodiment, and other descriptions will be omitted.

<Ion sweep drive mode>
In the ion sweep drive mode according to the second embodiment, the second voltage applied to the pixel electrodes 28b and 28c in the color matching pixel region 10b and the dummy pixel region 10c of the liquid crystal device 1 shown in FIG. The three voltages are set to a voltage higher than the first voltage applied to the pixel electrode 28a in the display pixel region 10a.

  For example, the first voltage applied between the pixel electrode 28a and the common electrode 34 in the display pixel region 10a is set to a voltage that is about the middle value of the voltage range in the normal drive mode, for example, a voltage of 3V. Then, the second voltage and the third voltage applied between the pixel electrodes 28b, 28c and the common electrode 34 in the color matching pixel region 10b and the dummy pixel region 10c are set to the maximum voltage (5 V) in the normal drive mode. .

  If the first voltage, the second voltage, and the third voltage are set in this way, the inclination of the liquid crystal molecules 40a becomes larger in the color-matching pixel region 10b and the dummy pixel region 10c than in the display pixel region 10a, and the ionic impurities 45 becomes easy to move. Accordingly, in the second embodiment, as in the first embodiment, the ionic impurities 45 generated in the display pixel region 10a in the normal drive mode can be swept out toward the dummy pixel region 10c.

  When viewed from a different viewpoint, the inclination of the liquid crystal molecules 40a is smaller in the display pixel area 10a than in the color-matching pixel area 10b and the dummy pixel area 10c. Therefore, in the second embodiment, it is possible to prevent the ionic impurities 45 that have been swept out toward the dummy pixel region 10c from flowing back to the display pixel region 10a while being driven in the ion sweep driving mode. it can.

  In order to make the setting of the first voltage different from the setting of the second voltage and the third voltage as in the second embodiment, the fixed gradation generation circuit 144 shown in FIG. And for setting the second voltage and the third voltage separately.

(Third embodiment)
Next, a third embodiment will be described. The third embodiment is different from the above-described embodiment in that the voltages (first voltage, second voltage, and second voltage) applied between the pixel electrodes 28a, 28b, and 28c and the common electrode 34 in the ion sweep drive mode. The configuration is the same except that the setting of (3 voltage) is different. Here, differences from the above embodiment will be described with reference to the drawings used in the first embodiment, and other descriptions will be omitted.

<Ion sweep drive mode>
In the ion sweep drive mode according to the third embodiment, the second voltage applied to the pixel electrode 28b of the color matching pixel region 10b of the liquid crystal device 1 shown in FIG. 6B is applied to the pixel electrode of the display pixel region 10a. The voltage is set higher than the first voltage applied to 28a. Then, the third voltage applied to the pixel electrode 28c in the dummy pixel region 10c is set to a voltage higher than the second voltage applied to the pixel electrode 28b in the color matching pixel region 10b.

  For example, the first voltage applied between the pixel electrode 28a and the common electrode 34 in the display pixel region 10a is set to a voltage that is about the middle value of the voltage range in the normal drive mode, for example, 3V, and the color matching pixel region The second voltage applied between the pixel electrode 28b of 10b and the common electrode 34 is set to the maximum voltage (5 V) in the normal drive mode. Then, the third voltage applied between the pixel electrode 28c and the common electrode 34 in the dummy pixel region 10c is set to a voltage of 5.5V that is higher than the maximum voltage in the normal drive mode.

  If each voltage is set in this way, the inclination of the liquid crystal molecules 40a becomes larger in the color matching pixel region 10b than in the display pixel region 10a, and in the dummy pixel region 10c than in the color matching pixel region 10b. Becomes easy to move. Therefore, compared to the above embodiment, the ionic impurities 45 generated in the display pixel region 10a in the normal driving mode can be more efficiently swept out to the dummy pixel region 10c side.

  Further, when viewed from different viewpoints, the inclination of the liquid crystal molecules 40a is smaller in the color matching pixel region 10b than in the dummy pixel region 10c, and in the display pixel region 10a is smaller than in the color matching pixel region 10b. Accordingly, the ionic impurities 45 swept out to the dummy pixel region 10c are prevented from flowing back to the color matching pixel region 10b while driving in the ion sweep driving mode. It is possible to more effectively prevent the ionic impurities 45 thus made from flowing back to the display pixel region 10a and returning.

  In order to make the first voltage setting, the second voltage setting, and the third voltage setting different from each other as in the third embodiment, the fixed gradation generation circuit 144 shown in FIG. It is required separately for the 1 voltage setting, the second voltage setting, and the third voltage setting.

  The above-described embodiments merely show one aspect of the present invention, and can be arbitrarily modified and applied within the scope of the present invention. As modifications, for example, the following can be considered.

(Modification 1)
In the above embodiment, the liquid crystal device 1 is a transmissive liquid crystal device that transmits light, and the projector 100 is a transmissive projector that includes the transmissive liquid crystal device 1 as a light modulation unit. It is not limited to. The liquid crystal device may be a reflective liquid crystal device that reflects light, and the projector may be a reflective projector that includes a reflective liquid crystal device as light modulation means. Even when the present invention is applied to a reflective liquid crystal device and a projector, the same effect as that of a transmissive liquid crystal device and a projector can be obtained.

(Modification 2)
The projector 100 according to the above embodiment includes the three liquid crystal light valves 121, 122, and 123 to which the liquid crystal device 1 is applied, but the present invention is not limited to such a form. The projector 100 may have a configuration including two or less liquid crystal light valves (the liquid crystal device 1), or may have a configuration including four or more liquid crystal light valves (the liquid crystal device 1).

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal device (electro-optical device), 20 ... Element substrate (the other substrate), 24 ... TFT (switching element), 28a (28) ... Pixel electrode (second electrode), 28b (28) ... Pixel electrode (first) 3 electrodes), 28c (28) ... pixel electrodes (fourth electrode), 30 ... counter substrate (one substrate), 34 ... common electrode (first electrode), 40 ... liquid crystal layer, 100 ... projector (electronic device).

Claims (7)

A liquid crystal layer including a liquid crystal having negative dielectric anisotropy sandwiched between a pair of substrates;
A first electrode provided on the liquid crystal layer side of one of the pair of substrates;
A second electrode provided on the liquid crystal layer side of the other substrate of the pair of substrates;
A third electrode provided on the liquid crystal layer side of the other substrate and disposed on the outside of the second electrode in a plane;
A fourth electrode provided on the liquid crystal layer side of the other substrate and disposed on the outer side in plan of the third electrode;
An electro-optical device that forms an image by applying a voltage to the liquid crystal layer between the first electrode and the second electrode,
In the first state set at the time of image formation, the voltage applied to the liquid crystal layer between the first electrode and the third electrode is the liquid crystal between the first electrode and the second electrode. Less than the voltage applied to the layer,
In the second state set when the power is turned off, the first voltage applied to the liquid crystal layer between the first electrode and the second electrode is higher than 0 V, and the first electrode and the first electrode The second voltage applied to the liquid crystal layer between three electrodes is equal to or higher than the first voltage, and the third voltage applied to the liquid crystal layer between the first electrode and the fourth electrode is An electro-optical device having a voltage equal to or higher than a first voltage. The electro-optical device according to claim 1,
In the second state, the second voltage is higher than the first voltage, and the third voltage is higher than the first voltage. The electro-optical device according to claim 1, wherein
In the first state, illumination light is irradiated,
The electro-optical device is characterized in that the second state is set after the irradiation of the illumination light is stopped. The electro-optical device according to claim 3,
A switching element electrically connected to each of the second electrode and the third electrode;
In a third state set after the second state when the power is turned off, a voltage applied to the liquid crystal layer between the first electrode and the second electrode, the first electrode and the The voltage applied to the liquid crystal layer between the third electrode and the voltage applied to the liquid crystal layer between the first electrode and the fourth electrode is 0V. . The electro-optical device according to claim 1,
In the second state, the third voltage applied to the liquid crystal layer between the first electrode and the fourth electrode is equal to or higher than the second voltage. The electro-optical device according to claim 5,
In the second state, the third voltage is higher than the second voltage.   An electronic apparatus comprising the electro-optical device according to claim 1.

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