JP2019028257A - Display device and method for driving display device - Google Patents

Abstract

To provide a display device capable of improving a sweeping effect on ionic impurities of a liquid crystal device to be used as optical modulation means, and a driving method of a display device.SOLUTION: A projection type display device 1000 as a display device includes: a liquid crystal device 100 having a liquid crystal layer 50 containing a liquid crystal, held between an element substrate 10 and a counter substrate 20, a pixel electrode 15a disposed in a display region E, and a pixel electrode 15b adjoining to the pixel electrode 15a; heating means 510 capable of heating the liquid crystal layer 50 to a temperature equal to or higher than Tni of the liquid crystal; cooling means 520 capable of cooling the liquid crystal layer to a predetermined temperature lower than Tni, or lower; and a lamp unit 1101 for irradiating the liquid crystal layer 50 with light. When the temperature of the liquid crystal layer 50 is elevated to Tni or higher by the heating means 510, an AC signal V1 is applied to the pixel electrode 15a, while an AC signal V2 at the same frequency as the AC signal V1, with a shifted phase is applied to the pixel electrode 15b.SELECTED DRAWING: Figure 13

Description

  The present invention relates to a display device and a display device driving method.

  Conventionally, a display device using an active drive type liquid crystal device provided with a transistor as a liquid crystal light valve has been known. In such a display device, the light flux incident on the liquid crystal device has a higher density than the liquid crystal device for direct-view display. For this reason, ionic impurities derived from liquid crystal device members such as liquid crystal materials, alignment films, and sealing materials may diffuse into the liquid crystal layer and cause display defects such as display unevenness.

  Thus, in order to suppress the occurrence of display defects due to ionic impurities, for example, Patent Document 1 proposes a liquid crystal display device that sweeps ionic impurities by an ion trap electrode.

  Patent Documents 2 and 3 propose a technique for generating a lateral electric field and sweeping ionic impurities using an effective pixel region in a non-display period.

  Further, Patent Document 4 proposes a display device in which the temperature of the liquid crystal device in the off sequence is higher than the temperature of the liquid crystal device after the start-up period in order to enhance the sweep effect of the ionic impurities during the off sequence. Yes.

JP 2007-279172 A JP 2008-292861 A JP 2015-1111247 A JP 2013-235171 A

  However, the techniques described in Patent Documents 1 to 4 have a problem that it is difficult to improve the sweeping effect of ionic impurities. For example, in the techniques described in Patent Document 1 to Patent Document 3, it may be difficult to obtain the sweep effect of ionic impurities. In particular, in a VA (Vertical Alignment) type liquid crystal device, the movement of ionic impurities in the lateral direction tends to be slow in the initial vertical alignment state, which may make it difficult to obtain the sweep effect.

  In addition, in the technique described in Patent Document 4, although a heating unit that relatively increases the temperature of the liquid crystal device is provided, the temperature at which the liquid crystal device and the liquid crystal are heated is not clearly described. Therefore, depending on the type of liquid crystal contained in the liquid crystal layer, it may be difficult to improve the sweeping effect of ionic impurities.

  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] A display device according to this application example includes a first substrate, a second substrate disposed opposite to the first substrate, a liquid crystal layer including liquid crystal sandwiched between the first substrate and the second substrate, , A liquid crystal device having a first pixel electrode disposed in the display area of the first substrate, and a second pixel electrode adjacent to the first pixel electrode, and the temperature of the liquid crystal layer, the liquid crystal Tni (nematic-isotropy) A heating means capable of heating the liquid crystal layer to a predetermined temperature lower than Tni, and a light source for irradiating the liquid crystal layer with light. When the temperature of the liquid crystal layer is set to Tni or higher, the first AC signal is applied to the first pixel electrode, and the second AC signal having the same frequency as the first AC signal is applied to the second pixel electrode. The

  According to this application example, the sweeping effect of the ionic impurities can be improved as compared with the conventional example. Specifically, the temperature of the liquid crystal layer can be set to Tni or higher of the liquid crystal by heating means, and the mobility of ionic impurities can be increased as an isotropic phase by changing the anisotropy of the liquid crystal. In particular, in the VA liquid crystal device, by making the liquid crystal isotropic, the lateral mobility of the ionic impurities can be increased and the ionic impurities adsorbed on the alignment film can be easily dissociated. It becomes.

  By heating to above Tni of the liquid crystal, the liquid crystal becomes isotropic regardless of the type of liquid crystal contained in the liquid crystal layer. At this time, by applying the first AC signal and the second AC signal that are out of phase, a lateral electric field from the first pixel electrode toward the second pixel electrode is generated. Therefore, ionic impurities in the liquid crystal layer can be swept from the first pixel electrode toward the second pixel electrode.

  Since the mobility of ionic impurities in the liquid crystal layer increases, the time required for sweeping ionic impurities can be shortened. Further, the liquid crystal layer heated to Tni or higher by the cooling means can be cooled to a predetermined temperature lower than Tni to align the liquid crystal. Therefore, even if sweeping of ionic impurities is performed during the on-sequence period of the display device, the start-up time of the display device (time until display can be performed) is shortened compared to the case where there is no cooling means. Can do.

  As described above, since display defects such as display unevenness due to ionic impurities are suppressed, a display device with improved display quality can be provided.

  In the display device described in the application example, Tni is preferably 80 ° C. or higher and lower than 100 ° C.

  According to this, compared with the case where Tni is 100 degreeC or more, the time of a heating and cooling can be shortened. Therefore, the time required for sweeping ionic impurities can be shortened and the driving energy can be reduced. Alternatively, the heating means and the cooling means can be simplified.

  In the display device described in the application example, the temperature of the liquid crystal layer is set to Tni or higher by the heating unit during the on-sequence period, and the temperature of the liquid crystal layer is set to a predetermined temperature or less by the cooling unit after the on-sequence period. preferable.

  According to this, before the display device starts display, ionic impurities diffused during a period when the display device is not operated can be swept to the outside of the display region. Thereby, it is possible to display the display device with a display quality better than the conventional one. In addition, since the temperature of the liquid crystal layer is cooled to a predetermined temperature or less by the cooling means, the start-up time until the display device can display can be shortened including the on-sequence period.

  In the display device described in the application example, the temperature of the liquid crystal layer is set to Tni or higher by the heating unit during the off sequence period, and the temperature of the liquid crystal layer is set to a predetermined temperature or less by the cooling unit after the off sequence period. preferable.

  According to this, ionic impurities generated from a member of the liquid crystal device or the like can be swept to the outside of the display region during a period in which the display device is displayed. Therefore, it is possible to reduce ionic impurities that diffuse during a period when the display device is not operated. In addition, since the temperature of the liquid crystal layer is cooled to a predetermined temperature or lower, it is possible to shorten the fall time of the display device including the off-sequence period.

  In the display device described in the above application example, after both the on-sequence period and the off-sequence period are finished, the temperature of the liquid crystal layer is set to Tni or more by the heating unit in both the on-sequence period and the off-sequence period. The temperature of the liquid crystal layer is preferably set to a predetermined temperature or lower by the cooling means.

  According to this, sweeping of ionic impurities can be performed before display of the display device in the on-sequence period, and the display device can be displayed with better display quality than before. In addition, ionic impurities can be swept during the off-sequence period, and ionic impurities generated from a member of the liquid crystal device or the like can be swept to the outside of the display region during the display period of the display device. Furthermore, since the temperature of the liquid crystal layer is cooled to a predetermined temperature or less, the rise time until the display device including the on-sequence period can be displayed, and the fall time of the display device including the off-sequence period, Both can be shortened.

  In the display device according to the application example, the first AC signal and the applied voltage are the same during a period in which the first AC signal is applied and at least one peripheral electrode is provided outside the display area of the first substrate. Or a large positive or negative DC or AC signal is preferably applied to the peripheral electrodes.

  According to this, ionic impurities swept by the first AC signal and the second AC signal can be swept to the outside of the display area. Therefore, ionic impurities in the display region are further reduced, and the display quality of the display device can be further improved.

  [Application Example] A display device driving method according to this application example includes a first substrate, a second substrate disposed opposite to the first substrate, and a liquid crystal sandwiched between the first substrate and the second substrate. A liquid crystal device having a liquid crystal layer, a first pixel electrode disposed in a display region of the first substrate, a second pixel electrode adjacent to the first pixel electrode, and a light source for irradiating the liquid crystal layer with light. A driving method of a display device provided, wherein when the liquid crystal layer is heated and the temperature of the liquid crystal layer is equal to or higher than Tni of the liquid crystal, a first AC signal is applied to the first pixel electrode and the second pixel electrode After applying the second AC signal whose phase is shifted at the same frequency as the first AC signal and applying the first AC signal and the second AC signal, the liquid crystal layer is cooled, and the temperature of the liquid crystal layer is set to be higher than Tni. The temperature should be lower than the predetermined temperature.

  According to this application example, the sweeping effect of the ionic impurities can be improved as compared with the conventional example. Specifically, since the temperature of the liquid crystal layer is set to Tni or higher, the mobility of ionic impurities can be increased using the liquid crystal as an isotropic phase. In particular, in the VA liquid crystal device, by making the liquid crystal isotropic, the lateral mobility of the ionic impurities can be increased and the ionic impurities adsorbed on the alignment film can be easily dissociated. It becomes.

  By heating the liquid crystal to Tni or higher, the ionic impurity sweeping effect can be improved with the liquid crystal in an isotropic phase regardless of the type of liquid crystal contained in the liquid crystal layer.

  Since the mobility of ionic impurities in the liquid crystal layer increases, the time required for sweeping ionic impurities can be shortened. In addition, it is possible to align the liquid crystal by cooling the liquid crystal layer heated to Tni or higher to a predetermined temperature lower than Tni. Therefore, even when the ionic impurities are swept during the on-sequence period, the start-up time of the display device (the time until the display can be displayed) can be shortened compared to the case where the ionic impurities are not cooled.

  Due to the first AC signal and the second AC signal, the distribution of the electric field generated between the first pixel electrode and the second pixel electrode moves from the first pixel electrode toward the second pixel electrode. Therefore, ionic impurities in the liquid crystal layer can be swept from the first pixel electrode toward the second pixel electrode.

  As described above, it is possible to provide a method for driving a display device that suppresses the occurrence of display defects such as display unevenness due to ionic impurities.

  In the display device driving method described in the application example, the liquid crystal layer is heated and the first AC signal is applied to the first pixel electrode and the second AC signal is applied to the second pixel electrode during the on-sequence period. Then, it is preferable to cool the liquid crystal layer after the on-sequence period ends.

  According to this, since the ionic impurities are swept before the display of the display device, the display device can be displayed in a state where the ionic impurities are reduced. In addition, since the temperature of the liquid crystal layer is cooled to a predetermined temperature or lower, the start-up time until the display device can display can be shortened including the on-sequence period.

  In the display device driving method described in the application example, the liquid crystal layer is heated and the first AC signal is applied to the first pixel electrode and the second AC signal is applied to the second pixel electrode during the off-sequence period. The liquid crystal layer is preferably cooled after the off sequence period.

  According to this, ionic impurities generated from a member of the liquid crystal device or the like can be swept to the outside of the display region during a period in which the display device is displayed. In addition, since the temperature of the liquid crystal layer is cooled to a predetermined temperature or lower, it is possible to shorten the fall time of the display device including the off-sequence period.

  In the display device driving method described in the application example, the liquid crystal layer is heated in both the on-sequence period and the off-sequence period, the first AC signal is applied to the first pixel electrode, and the second It is preferable to cool the liquid crystal layer after applying the second AC signal to the pixel electrode and completing the on-sequence period and the off-sequence period.

  According to this, since the ionic impurities are swept before the display of the display device, the display device can be displayed in a state where the ionic impurities are swept to the outside of the display region. In addition, the display device can be swept to the outside of the display area, which is generated from a member of the liquid crystal device or the like during a period in which the display device is displayed. Furthermore, since the temperature of the liquid crystal layer is cooled to a predetermined temperature or less, the rise time until the display device including the on-sequence period can be displayed, and the fall time of the display device including the off-sequence period, Both can be shortened.

FIG. 2 is a schematic plan view showing the configuration of the liquid crystal device according to the first embodiment. FIG. 2 is a schematic cross-sectional view taken along the line H-H ′ of the liquid crystal device illustrated in FIG. 1. FIG. 3 is an equivalent circuit diagram illustrating an electrical configuration of the liquid crystal device. FIG. 3 is a schematic cross-sectional view mainly illustrating a pixel structure in a liquid crystal device. Schematic which shows the structure of the display apparatus provided with the liquid crystal device. The block diagram which shows the control function of the heating means and the cooling means in a display apparatus. FIG. 3 is a schematic plan view of a liquid crystal device for explaining a method for applying a voltage to a pixel electrode. FIG. 8 is a schematic cross-sectional view taken along line A-A ′ of the liquid crystal device illustrated in FIG. 7. FIG. 5 is a schematic plan view showing the types of AC signals applied to pixel electrodes arranged corresponding to each scanning line. The timing chart which shows each alternating current signal. The timing chart which shows each alternating current signal. The timing chart which shows each alternating current signal. The schematic plan view which shows the polarity of the alternating current signal applied to a pixel electrode for every screen. The schematic plan view which shows the polarity of the alternating current signal applied to a pixel electrode for every screen. The schematic plan view which shows the polarity of the alternating current signal applied to a pixel electrode for every screen. The schematic diagram which shows the time of the application of the alternating current signal with respect to the temperature of a liquid crystal layer. FIG. 6 is a schematic diagram showing the timing of application of an AC signal with respect to the temperature of the liquid crystal layer according to the second embodiment. FIG. 10 is a schematic plan view illustrating a configuration of a liquid crystal device according to Modification Example 4. FIG. 15 is a schematic cross-sectional view taken along line B-B ′ of the liquid crystal device illustrated in FIG. 14.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment described below describes an example of the present invention. The present invention is not limited to the following embodiments, and various modifications that are implemented without departing from the spirit of the present invention are also included in the present invention.

  In the following drawings, the scale of each layer and each member is made different from the actual scale so that each layer and each member can be recognized. Further, in the following description, for example, with respect to the substrate, the description “on the substrate” means that the substrate is disposed on the substrate, the substrate is disposed on another structure, Or it shall represent either the case where a part is arrange | positioned on a board | substrate and a part is arrange | positioned through another structure.

(Embodiment 1)
In the present embodiment, an active drive type liquid crystal device including a thin film transistor (hereinafter referred to as “TFT”) for each pixel will be described as an example of the liquid crystal device. This liquid crystal device can be suitably used, for example, as a light modulation element (liquid crystal light valve) of a projection display device (liquid crystal projector) as a display device described later.

<Configuration of liquid crystal device>
First, the configuration of the liquid crystal device used in the display device of this embodiment will be described with reference to FIGS. FIG. 1 is a schematic plan view illustrating the configuration of the liquid crystal device according to the first embodiment. 2 is a schematic cross-sectional view taken along the line HH ′ of the liquid crystal device shown in FIG. FIG. 3 is an equivalent circuit diagram showing an electrical configuration of the liquid crystal device.

  As shown in FIGS. 1 and 2, the liquid crystal device 100 according to the present embodiment includes an element substrate 10 as a first substrate, a counter substrate 20 as a second substrate disposed opposite to the element substrate 10, and the element substrate 10. And a liquid crystal layer 50 including a liquid crystal sandwiched between the counter substrates 20.

  As the base material 10s of the element substrate 10, for example, a substrate such as a glass substrate or a quartz substrate is used. As the base material 20s of the counter substrate 20, for example, a transparent substrate such as a glass substrate or a quartz substrate is used.

  The element substrate 10 is larger than the counter substrate 20. The element substrate 10 and the counter substrate 20 (hereinafter, also referred to as “a pair of substrates”) are bonded together via a sealing material 40 disposed along the outer edge of the counter substrate 20. A liquid crystal layer 50 is formed by sealing liquid crystal having positive or negative dielectric anisotropy in a gap between the pair of substrates.

  For the sealing material 40, for example, an adhesive such as a thermosetting or electron beam curable epoxy resin is employed. A spacer (not shown) is mixed in the sealing material 40 to keep the distance between the pair of substrates constant.

  Inside the sealing material 40, a display area E including a plurality of pixels P arranged in a matrix is provided. A parting part 21 is provided between the sealing material 40 and the display area E so as to surround the display area E. For the parting portion 21, for example, a light-shielding metal or metal oxide is used.

  Around the display region E, a dummy pixel region (not shown) that does not contribute to display is provided. Although not shown in FIGS. 1 and 2, in the display area E, a light shielding portion (black matrix: BM) that divides each of the plurality of pixels P in a plane is provided on the counter substrate 20.

  The element substrate 10 is provided with a terminal portion in which a plurality of external connection terminals 104 are arranged. A data line driving circuit 101 is provided between the first side portion along the terminal portion and the sealing material 40. In addition, an inspection circuit 103 is provided between the sealing material 40 and the display area E along the second side facing the first side.

  A scanning line driving circuit 102 is provided between the seal material 40 and the display region E along the third side and the fourth side that are orthogonal to the first side and face each other. A plurality of wirings 105 that connect the two scanning line driving circuits 102 are provided between the sealing material 40 on the second side and the inspection circuit 103.

  Wirings connected to the data line driving circuit 101 and the scanning line driving circuit 102 are connected to a plurality of external connection terminals 104 arranged along the first side. Hereinafter, the direction along the first side is defined as the X direction, and the direction along the third side and the fourth side that are orthogonal to the first side and face each other is defined as the Y direction. Note that the arrangement of the inspection circuit 103 is not limited to this, and the inspection circuit 103 may be provided between the seal material 40 and the display region E along the data line driving circuit 101.

  As shown in FIG. 2, on the surface of the base material 10s on the liquid crystal layer 50 side, a light-transmitting pixel electrode 15 provided for each pixel P, a TFT 30 serving as a switching element, a signal wiring, and an orientation covering these A film 18 is formed.

  In addition, a light shielding structure is employed that prevents light from entering the semiconductor layer in the TFT 30 to make the switching operation unstable. The element substrate 10 includes a base material 10s, a pixel electrode 15, a TFT 30, a signal wiring, and an alignment film 18 formed on the base material 10s.

  On the surface of the base material 20 s on the liquid crystal layer 50 side, the parting portion 21, the insulating layer 22 formed so as to cover it, the counter electrode 23 provided so as to cover the insulating layer 22, and the counter electrode 23 And an alignment film 24 is provided. The counter substrate 20 in this embodiment includes at least a parting part 21, a counter electrode 23, and an alignment film 24.

  As shown in FIG. 1, the parting part 21 surrounds the display area E and is provided at a position overlapping the scanning line driving circuit 102 and the inspection circuit 103 in plan view. Thus, the light incident on these circuits from the counter substrate 20 side is shielded to prevent the circuit from malfunctioning due to the light. Further, unnecessary stray light is shielded from entering the display area E, and high contrast in the display of the display area E is ensured.

  The insulating layer 22 is made of, for example, an inorganic material such as silicon oxide having optical transparency, and is provided so as to cover the parting portion 21. Examples of the method for forming the insulating layer 22 include a method of forming a film using a plasma CVD (Chemical Vapor Deposition) method.

  The counter electrode 23 is made of a transparent conductive film such as ITO (Indium Tin Oxide), for example, covers the insulating layer 22 and is electrically connected to the vertical conduction portion 106 provided at the corner of the counter substrate 20 as shown in FIG. It is connected. The vertical conduction part 106 is electrically connected to the wiring on the element substrate 10 side.

  The alignment film 18 that covers the pixel electrode 15 and the alignment film 24 that covers the counter electrode 23 are selected based on the optical design of the liquid crystal device 100. As the alignment films 18 and 24, an inorganic alignment film formed by depositing an inorganic material such as SiOx (silicon oxide) using a vapor phase growth method and approximately vertically aligning with liquid crystal molecules having negative dielectric anisotropy. Is mentioned.

  Such a liquid crystal device 100 is, for example, a transmissive type, and a normally white mode in which the transmittance of the pixel P when no voltage is applied is larger than the transmittance when a voltage is applied, or a pixel when no voltage is applied. A normally black mode optical design is adopted in which the transmittance of P is smaller than the transmittance when a voltage is applied. In the liquid crystal panel 110 including the element substrate 10 and the counter substrate 20, polarizing elements are respectively arranged on the light incident side and the light emitting side according to the optical design.

  In the present embodiment, an example in which a normally black mode optical design is applied using the inorganic alignment film described above as the alignment films 18 and 24 and a liquid crystal having negative dielectric anisotropy will be described.

  As shown in FIG. 3, the liquid crystal device 100 is arranged in parallel along the data lines 6 a with a plurality of scanning lines 3 a and a plurality of data lines 6 a as signal wirings insulated and orthogonal to each other at least in the display region E. Capacitance line 3b. The direction in which the scanning line 3a extends is the X direction, and the direction in which the data line 6a extends is the Y direction.

  A pixel electrode 15, a TFT 30, and a capacitor element 16 are provided in a region divided by the scanning line 3 a, the data line 6 a, the capacitor line 3 b, and these signal lines, and these constitute the pixel circuit of the pixel P. It is composed.

  The scanning line 3a is electrically connected to the gate of the TFT 30, and the data line 6a is electrically connected to the data line side source / drain region (one source / drain region) of the TFT 30. The pixel electrode 15 is electrically connected to the pixel electrode side source / drain region (the other source / drain region) of the TFT 30.

  The data line 6a is electrically connected to the data line driving circuit 101 (see FIG. 1), and supplies image signals D1, D2,..., Dn supplied from the data line driving circuit 101 to the pixels P. The scanning line 3a is connected to the scanning line driving circuit 102 (see FIG. 1), and supplies the scanning signals SC1, SC2,..., SCm supplied from the scanning line driving circuit 102 to each pixel P.

  The image signal D1 to the image signal Dn supplied from the data line driving circuit 101 to the data line 6a may be supplied line-sequentially in this order, and for each of a plurality of adjacent data lines 6a for each group. You may supply. The scanning line driving circuit 102 supplies the scanning signal SCm from the scanning signal SC1 to the scanning line 3a in a pulse-sequential manner at a predetermined timing.

  In the liquid crystal device 100, the TFT 30 as a switching element is turned on for a certain period by the input of the scanning signal SCm from the scanning signal SC1, so that the image signal Dn from the image signal D1 supplied from the data line 6a is predetermined. The pixel electrode 15 is written at this timing. A predetermined level of the image signal D1 to the image signal Dn written to the liquid crystal layer 50 through the pixel electrode 15 is constant between the pixel electrode 15 and the counter electrode 23 arranged to face the liquid crystal layer 50. Hold for a period.

  In order to prevent the image signal Dn from leaking from the held image signal D1, the capacitive element 16 is connected in parallel with the liquid crystal capacitance formed between the pixel electrode 15 and the counter electrode 23. The capacitive element 16 is provided between the pixel electrode side source / drain region of the TFT 30 and the capacitive line 3b. The capacitive element 16 has a dielectric layer between two capacitive electrodes.

<Configuration of pixels constituting liquid crystal device>
Next, the structure of the pixels constituting the liquid crystal device 100 will be described with reference to FIG. FIG. 4 is a schematic cross-sectional view mainly showing a pixel structure in the liquid crystal device. FIG. 4 shows the cross-sectional positional relationship of each component and is expressed on a scale that can be clearly shown.

  As shown in FIG. 4, the scanning line 3 a is formed on the base material 10 s of the element substrate 10. As a forming material of the scanning line 3a, it has a light shielding property, for example, a metal such as Al (aluminum), Ti (titanium), Cr (chromium), W (tungsten), Ta (tantalum), and Mo (molybdenum). Examples thereof include simple metals, alloys, metal silicides, polysilicides, nitrides, or a laminate of these, including one or more of them.

  A first insulating film (base insulating film) 11a made of, for example, silicon oxide is formed so as to cover the scanning line 3a, and a semiconductor layer 30a is formed in an island shape on the first insulating film 11a. The semiconductor layer 30a is made of, for example, a polycrystalline silicon film, and is doped with impurity ions to have a data line side source / drain region, a junction region, a channel region, a junction region, and a pixel electrode side source / drain region. A structure is formed.

  A second insulating film (gate insulating film) 11b is formed so as to cover the semiconductor layer 30a. Further, a gate electrode 30g is formed at a position facing the semiconductor layer 30a in the channel region with the second insulating film 11b interposed therebetween.

  A third insulating film 11c is formed so as to cover the gate electrode 30g and the second insulating film 11b. Two contact holes CNT1 and CNT2 penetrating the second insulating film 11b and the third insulating film 11c are formed at positions overlapping the respective end portions of the semiconductor layer 30a.

  A source electrode 31 and a data line 6a connected to the data line side source / drain region are formed through the contact hole CNT1 so as to fill the two contact holes CNT1 and CNT2 and cover the third insulating film 11c. The source electrode 31 and the data line 6a are formed by forming a conductive film using a light-shielding conductive material such as Al (aluminum) or an alloy thereof and patterning the conductive film. Further, a drain electrode 32 (first relay electrode 6b) connected to the pixel electrode side source / drain region via the contact hole CNT2 is formed.

  A first interlayer insulating film 12 is formed to cover the data line 6a, the first relay electrode 6b, and the third insulating film 11c. The first interlayer insulating film 12 is made of, for example, silicon oxide or nitride. The first interlayer insulating film 12 is subjected to a flattening process for flattening the surface irregularities generated by covering the region where the TFT 30 is provided. Examples of the planarization method include chemical mechanical polishing (CMP) and spin coating.

  A contact hole CNT3 penetrating the first interlayer insulating film 12 is formed at a position overlapping the first relay electrode 6b. A wiring 7a and a second relay electrode 7b electrically connected to the first relay electrode 6b through the contact hole CNT3 are formed so as to cover the contact hole CNT3 and cover the first interlayer insulating film 12. ing. The wiring 7a and the second relay electrode 7b are formed, for example, by forming a conductive film made of a light-shielding metal such as Al (aluminum) or an alloy thereof and then patterning the conductive film.

  The wiring 7a is formed so as to overlap the semiconductor layer 30a and the data line 6a of the TFT 30 in a plan view, and functions as a shield layer when given a fixed potential.

  A second interlayer insulating film 13a is formed so as to cover the wiring 7a and the second relay electrode 7b. Examples of the material for forming the second interlayer insulating film 13a include Si (silicon) oxide, nitride, and oxynitride. The second interlayer insulating film 13a is subjected to a planarization process such as a CMP process.

  A contact hole CNT4 is formed at a position overlapping the second relay electrode 7b of the second interlayer insulating film 13a. A first capacitor electrode 16a and a third relay electrode 16d are formed so as to cover the contact hole CNT4 and cover the second interlayer insulating film 13a. The first capacitor electrode 16a and the third relay electrode 16d are formed, for example, by forming a conductive film made of a light-shielding metal such as Al (aluminum) or an alloy thereof and then patterning the conductive film.

  The insulating film 13b is patterned to cover the outer edge of the portion of the first capacitor electrode 16a that faces the second capacitor electrode 16c with the dielectric layer 16b formed later. Further, the insulating film 13b is patterned so as to cover the outer edge of the third relay electrode 16d excluding the portion overlapping the contact hole CNT5.

A dielectric layer 16b is formed to cover the insulating film 13b and the first capacitor electrode 16a. As a material for forming the dielectric layer 16b, a single layer film such as Si (silicon) nitride film, hafnium oxide (HfO ₂ ), alumina (Al ₂ O ₃ ), tantalum oxide (Ta ₂ O ₅ ), or a single layer thereof. You may use the multilayer film which laminated | stacked 2 or more types of single layer films among the layer films. A portion of the dielectric layer 16b that overlaps the third relay electrode 16d in plan view is removed by etching or the like.

  A second capacitor electrode 16c that is disposed to face the first capacitor electrode 16a and is connected to the third relay electrode 16d is formed so as to cover the dielectric layer 16b. The second capacitor electrode 16c is formed by, for example, forming a conductive film such as TiN (titanium nitride) and then patterning it. The capacitive element 16 is configured by the dielectric layer 16b, the first capacitive electrode 16a and the second capacitive electrode 16c which are arranged to face each other with the dielectric layer 16b interposed therebetween.

  Next, a third interlayer insulating film 14 that covers the second capacitor electrode 16c and the dielectric layer 16b is formed. The third interlayer insulating film 14 is made of, for example, Si (silicon) oxide or nitride, and is subjected to planarization processing such as CMP processing. Further, a contact hole CNT5 that penetrates the third interlayer insulating film 14 is formed so that the second capacitor electrode 16c is in contact with the third relay electrode 16d.

  A transparent conductive film (electrode film) such as TO is formed so as to cover the contact hole CNT5 and cover the third interlayer insulating film 14. The pixel electrode 15 is formed by patterning the transparent conductive film (electrode film). Thereby, the pixel electrode 15 is electrically connected to the second capacitor electrode 16c and the third relay electrode 16d through the contact hole CNT5.

  The second capacitor electrode 16c is electrically connected to the drain electrode 32 of the TFT 30 through the third relay electrode 16d, the contact hole CNT4, the second relay electrode 7b, the contact hole CNT3, and the first relay electrode 6b, and is in contact with the second relay electrode 16c. The pixel electrode 15 is electrically connected via the hole CNT5.

  The first capacitor electrode 16a is formed so as to straddle a plurality of pixels P, and functions as the capacitor line 3b in the equivalent circuit (see FIG. 3). A fixed potential is applied to the first capacitor electrode 16a. Therefore, the potential applied to the pixel electrode 15 through the drain electrode 32 of the TFT 30 can be held between the first capacitor electrode 16a and the second capacitor electrode 16c.

  As described above, since a plurality of wirings are formed on the base material 10 s of the element substrate 10, the wiring layer is represented using the reference numerals of the insulating film and the interlayer insulating film that insulate the wirings. To do. That is, the first insulating film 11a, the second insulating film 11b, and the third insulating film 11c are collectively referred to as the wiring layer 11. A typical wiring of the wiring layer 11 is the scanning line 3a.

  The second interlayer insulating film 13a, the insulating film 13b, and the dielectric layer 16b are collectively referred to as a wiring layer 13, and a representative wiring is the wiring 7a. Similarly, the representative wiring of the wiring layer 13 is the first capacitor electrode 16a (capacitor line 3b).

  An alignment film 18 is formed so as to cover the pixel electrode 15, and an alignment film 24 is formed so as to cover the counter electrode 23 of the counter substrate 20 disposed to face the element substrate 10 with the liquid crystal layer 50 interposed therebetween. As described above, the alignment films 18 and 24 are inorganic alignment films, and are formed of an aggregate of columns 18a and 24a grown in a columnar shape by, for example, oblique deposition of an inorganic material such as silicon oxide from a predetermined direction.

  The liquid crystal molecules LC having negative dielectric anisotropy with respect to the alignment films 18 and 24 have a pretilt angle θp of 3 ° to 5 ° in the inclination direction of the columns 18a and 24a with respect to the normal direction of the alignment film surface. Then, substantially vertical alignment (VA) is performed. A liquid crystal molecule LC is generated between the pixel electrode 15 and the counter electrode 23 by driving the liquid crystal layer 50 by applying an AC voltage (drive signal, AC signal) between the pixel electrode 15 and the counter electrode 23. It behaves (vibrates) so as to tilt in the electric field direction. In the present embodiment, nematic liquid crystal having a Tni (nematic-isotropic phase transition temperature) of 110 ° C. is used as the liquid crystal having negative dielectric anisotropy.

<Configuration of display device>
Next, a projection type display device as a display device of the present embodiment will be described with reference to FIG. FIG. 5 is a schematic diagram illustrating a configuration of a display device including a liquid crystal device.

  As shown in FIG. 5, the projection display apparatus 1000 according to the present embodiment includes a polarization illumination device 1100 arranged along the system optical axis L, two dichroic mirrors 1104 and 1105 as light separation elements, and three Reflective mirrors 1106, 1107, 1108, five relay lenses 1201, 1202, 1203, 1204, 1205, three transmissive liquid crystal light valves 1210, 1220, 1230 as light modulation means, and a cross dichroic as a light combiner A prism 1206, a projection lens 1207, a heating unit 510, and a cooling unit 520 are provided.

  The polarized light illumination device 1100 is generally configured by a lamp unit 1101 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 1102, and a polarization conversion element 1103.

  The dichroic mirror 1104 reflects red light (R) and transmits green light (G) and blue light (B) out of the polarized light beam emitted from the polarization illumination device 1100. Another dichroic mirror 1105 reflects the green light (G) transmitted through the dichroic mirror 1104 and transmits the blue light (B).

  The red light (R) reflected by the dichroic mirror 1104 is reflected by the reflection mirror 1106 and then enters the liquid crystal light valve 1210 via the relay lens 1205. Green light (G) reflected by the dichroic mirror 1105 enters the liquid crystal light valve 1220 via the relay lens 1204. The blue light (B) transmitted through the dichroic mirror 1105 enters the liquid crystal light valve 1230 via a light guide system including three relay lenses 1201, 1202, 1203 and two reflection mirrors 1107, 1108.

  The liquid crystal light valves 1210, 1220, and 1230 are disposed to face the incident surfaces of the cross dichroic prism 1206 for each color light. The color light incident on the liquid crystal light valves 1210, 1220, and 1230 is modulated based on video information (video signal) and is emitted toward the cross dichroic prism 1206.

  In this prism, four right-angle prisms are bonded together, 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. The three color lights are synthesized by these dielectric multilayer films, and the light representing the color image is synthesized. The synthesized light is projected on the screen 1300 by the projection lens 1207 which is a projection optical system, and the image is enlarged and displayed.

  The liquid crystal light valve 1210 is the one to which the liquid crystal device 100 described above is applied. The liquid crystal device 100 is arranged with a gap between a pair of polarizing elements arranged in crossed Nicols on the incident side and the outgoing side of colored light. The same applies to the other liquid crystal light valves 1220 and 1230.

  In addition to the projection display device 1000, the liquid crystal device 100 includes an EVF (Electrical View Finder), a mobile mini projector, a head-up display, a smartphone, a mobile phone, a mobile computer, a digital camera, a digital video camera, a display, and an in-vehicle device. It may be mounted on various electronic devices such as audio devices, exposure apparatuses, and lighting devices.

<Heating means and cooling means>
The projection display device 1000 includes a heating unit 510 capable of heating the temperature of the liquid crystal layer 50 to Tni or higher of the liquid crystal contained in the liquid crystal layer 50, and the temperature of the liquid crystal layer 50 to a predetermined temperature lower than the above Tni. Cooling means 520 capable of cooling.

  The heating means 510 and the cooling means 520 of the liquid crystal device 100 in the projection display device 1000 are not particularly limited, and a known technique can be adopted according to the Tni of the liquid crystal. Specifically, examples of the heating unit 510 include a heating wire, a warm air machine, an infrared lamp, a Peltier element, and the like, and liquid crystal is used directly by using one or more of these or indirectly through a medium. The apparatus 100 is heated. Examples of the cooling unit 520 include a cooler, a cool air fan, and a Peltier element, and the liquid crystal device 100 is cooled directly using one or more of these or indirectly through a medium. Further, as the cooling means 520, an electric fan (not shown) for cooling the lamp unit 1101 or the like may be used.

  A medium used for the heating unit 510 or the cooling unit 520 is not particularly limited, and a liquid or gel such as water or a solvent, a solid such as a metal having a relatively high thermal conductivity, or a gas such as ammonia can be employed. When a material other than solid is used, the medium may be circulated by connecting the heating means 510 or the cooling means 520 and the liquid crystal device 100 with a pipe.

  The installation form of the heating unit 510 and the cooling unit 520 with respect to the liquid crystal device 100 is not particularly limited, and is set according to the type described above, the presence or absence of a medium, and the like. In the present embodiment, Peltier elements are used as the heating means 510 and the cooling means 520, ethylene glycol is adopted as a medium, and the tube 550 filled with the medium is drawn, so that the liquid crystal device 100 (liquid crystal light valves 1210, 1220, 1230).

  Further, a thermistor (not shown) is attached to the liquid crystal device 100 (liquid crystal light valves 1210, 1220, 1230), and the temperature of the liquid crystal device 100 (liquid crystal layer 50) can be measured.

  Next, control functions of the heating unit 510 and the cooling unit 520 will be described with reference to FIG. FIG. 6 is a block diagram illustrating control functions of the heating unit and the cooling unit in the display device.

  As shown in FIG. 6, the thermistor 540 is installed in the liquid crystal device 100. The thermistor 540 measures the temperature of the liquid crystal layer 50 of the liquid crystal device 100. This temperature information is transmitted to the current control circuit 560 as an electrical signal. In the current control circuit 560, the current (output) of a DC power source (not shown) is changed according to the operation timing of the heating means 510 and the cooling means 520 described later, temperature information, the target temperature of the liquid crystal layer 50 to be adjusted. Adjust and supply to the polarity inversion circuit 570. The polarity inversion circuit 570 controls the direct current applied to the Peltier elements (heating unit 510 and cooling unit 520) according to the temperature information and the target temperature of the liquid crystal layer 50, and inverts the polarity of the drive current. When the Peltier element is driven, heating or cooling is performed, and the temperature is transmitted to the liquid crystal device 100 through the medium to change the temperature of the liquid crystal layer 50. Then, the changed temperature is measured again, and the above-described control loop is repeated. Thereby, the temperature of the liquid crystal layer 50 is adjusted to a desired temperature.

  Here, the temperature equal to or higher than Tni of the liquid crystal in the liquid crystal layer 50 is not particularly limited because it depends on Tni of the liquid crystal to be used. For example, the upper limit of the temperature is 140 ° C. The predetermined temperature lower than the Tni of the liquid crystal in the liquid crystal layer 50 is not particularly limited because it depends on the Tni of the liquid crystal to be used, but is, for example, 70 ° C.

  In the present embodiment, the heating unit 510 and the cooling unit 520 using one Peltier element are illustrated, but the present invention is not limited to this. The heating unit 510 and the cooling unit 520 may be separate systems, and a plurality of Peltier elements may be used separately for the heating unit and the cooling unit.

  The above-described heating of the liquid crystal layer 50 is performed together with the application of a voltage (AC signal) to the pixel electrode 15 described below.

<Voltage application to pixel electrode>
Next, a method of applying a voltage to the pixel electrode 15 for sweeping ionic impurities will be described with reference to FIGS. FIG. 7 is a schematic plan view of a liquid crystal device for explaining a method of applying a voltage to the pixel electrode. FIG. 8 is a schematic cross-sectional view taken along the line AA ′ of the liquid crystal device shown in FIG.

  As shown in FIG. 7, the liquid crystal device 100 includes a display area E in which pixels P that contribute to display are arranged, and a parting portion 21 that is arranged so as to surround the display area E. A sealing material 40 is arranged around the parting portion 21 in a frame shape. In the display area E, a plurality of pixel electrodes 15 are arranged in a matrix.

  On the element substrate 10 of the liquid crystal device 100, for example, a plurality of scanning lines 3a electrically connected to the scanning line driving circuit 102 (see FIG. 1) extend along the long side (X direction) in the display region E. Is formed. As described above, the plurality of pixel electrodes 15 (15a, 15b, 15c) arranged along the extending direction of the scanning line 3a are electrically connected to each scanning line 3a. That is, the liquid crystal device 100 includes a pixel electrode 15a as a first pixel electrode disposed in the display area E, a pixel electrode 15b as a second pixel electrode adjacent to the pixel electrode 15a, and a third electrode adjacent to the pixel electrode 15b. And a pixel electrode 15c as a pixel electrode. That is, in the Y direction, the pixel electrode 15a and the pixel electrode 15b are adjacent to each other, and the pixel electrode 15b and the pixel electrode 15c are adjacent to each other. An AC signal is supplied from the data line driving circuit 101 to the plurality of pixel electrodes 15.

  Here, a region surrounding the plurality of pixel electrodes 15a arranged with respect to the first scanning line 3a1 is referred to as a first pixel electrode region 15a1. A region surrounding the plurality of pixel electrodes 15b arranged with respect to the second scanning line 3a2 is referred to as a second pixel electrode region 15b2. A region surrounding the plurality of pixel electrodes 15c arranged with respect to the third scanning line 3a3 is referred to as a third pixel electrode region 15c3.

  As shown in FIG. 8, the element substrate 10 of the liquid crystal device 100 has a plurality of wiring layers on a base material 10s. A plurality of pixel electrodes 15 are provided on the third interlayer insulating film 14. Each pixel electrode 15 is electrically connected to the scanning line 3a via a lower interlayer insulating film and a relay electrode provided in the wiring layer.

  The width of the pixel electrode 15 is 7.5 μm, for example. The gap between the adjacent pixel electrode 15 and the pixel electrode 15 is, for example, 0.5 μm.

  When the ionic impurities 60 staying in the display area E are swept from the display area E to the outside of the display area E, an electric field generated between the adjacent pixel electrodes 15 is generated in the pixel electrodes 15 (15a, 15b, 15c). An AC signal is applied so that the direction of the electric lines of force moves from the center of the display area E toward the outside of the display area E (on the sealing material 40 side).

  The AC signal is a signal that transitions between a high potential and a low potential using the common potential (LCCOM) applied to the counter electrode 23 as a reference potential. The positive (+) or negative (−) ionic impurities 60 are displayed as the electric field direction moves from the pixel electrode 15 (for example, the pixel electrode 15a) to the pixel electrode 15 (for example, the pixel electrode 15b). Sweeped outside area E.

<Driving method of liquid crystal device>
Next, a method for driving a liquid crystal device according to application of an AC signal will be described with reference to FIGS. 9 to 11C. FIG. 9 is a schematic plan view showing the types of AC signals applied to the pixel electrodes arranged corresponding to the respective scanning lines. 10A, 10B, and 10C are timing charts showing each AC signal. 11A, 11B, and 11C are schematic plan views showing the polarity of the AC signal applied to the pixel electrode for each screen.

  As described above, a region of the plurality of pixel electrodes 15 electrically connected to one scanning line 3a is defined as a pixel electrode region. A pixel electrode region at the center of the display region E is defined as a first pixel electrode region 15a1. In the display region E, the second pixel electrode region 15b2 and the third pixel electrode region 15c3 are repeatedly arranged in this order toward the long side of the sealing material 40 with the center first pixel electrode region 15a1 as the center.

  For example, in one direction of the first pixel electrode region 15a1 at the center of the display region E (for example, downward in FIG. 9), the second pixel electrode region 15b2, the third pixel electrode region 15c3, and then the first pixel electrode region 15a1. Are arranged in the order.

  Similarly, the second pixel electrode region 15b2, the third pixel electrode region 15c3, and then the first pixel electrode region 15a1 are arranged in the other direction of the center first pixel electrode region 15a1 (for example, upward in FIG. 9). Has been.

  An AC signal V1 as a first AC signal is applied to the first pixel electrode region 15a1. An AC signal V2 as a second AC signal is applied to the second pixel electrode region 15b2. An AC signal V3 as a third AC signal is applied to the third pixel electrode region 15c3.

  10A, 10B, and 10C show timing charts of the AC signals V1, V2, and V3. A rectangular wave AC signal of 5V is applied to the pixel electrodes 15a, 15b, 15c of the pixel electrode regions 15a1, 15b2, 15c3. The frequency is the same for the AC signals V1, V2, and V3, and is, for example, 10 mHz to 50 mHz. In the case of 50 mHz, the period of one cycle of the AC signal is 20 seconds.

  As a precondition for the frequency, the counter electrode 23 is disposed at a position facing the pixel electrode 15. A potential difference of +5 V to −5 V is generated between the pixel electrodes 15 by application of AC signals V1, V2, and V3. For example, as described above, the width of the pixel electrode 15 is 7.5 μm in plan view. The gap between the pixel electrodes 15 is, for example, 0.5 μm. The cell gap is, for example, 2.5 μm.

  The frequency is preferably 10 mHz to 50 mHz. However, if the frequency is too low, the state is the same as when a DC signal is applied between the pixel electrode 15 and the counter electrode 23, and the liquid crystal is decomposed, burned, and stained. Display defects may occur. If the frequency is higher than the above range, the ionic impurity 60 cannot follow the electric field scroll (moving speed), and the ionic impurity 60 may not be able to be swept.

  An AC signal V2 having a phase delayed by 120 ° with respect to the AC signal V1 applied to the first pixel electrode region 15a1 is applied to the pixel electrode 15b of the second pixel electrode region 15b2. An AC signal V3 having a phase delayed by 120 ° with respect to the AC signal V2 applied to the second pixel electrode region 15b2 is applied to the pixel electrode 15c of the third pixel electrode region 15c3.

  That is, the phase is delayed by 120 ° (1/3 period) from the first pixel electrode region 15a1 in the center of the display region E toward the outside of the display region E (the long side of the sealing material 40). AC signals V1, V2, and V3 are applied.

  The AC signal V1 is applied again to the first pixel electrode region 15a1 outside the third pixel electrode region 15c3. Similarly, the AC signal V2 is applied to the second pixel electrode region 15b2. That is, the same AC signal is repeatedly applied every three scanning lines.

Specifically, between t ₀ of t _3, the pixel electrode 15a, the AC signal V1 + potential difference 5V is generated (see FIG. 10A). In contrast, in the pixel electrode 15b, -5V potential difference is generated between t ₀ of t ₂ by an AC signal V2, the potential difference between the + 5V during t ₃ is generated from t ₂ (see FIG. 10B). Further, the pixel electrode 15c, the potential difference of + 5V between t ₁ from t ₀ is generated by the AC signal V3, -5V potential difference is generated between t ₁ of t ₃ (see FIG. 10C).

Next, between t ₃ and t ₆ , a potential difference of −5 V is generated in the pixel electrode 15a by the AC signal V1 (see FIG. 10A). In contrast, in the pixel electrode 15b, a potential difference of + 5V during t ₅ is generated continues from t ₃ from t ₂ by an AC signal V2, -5V potential difference is generated between the t ₅ of t ₆ (Fig. 10B). Further, the pixel electrode 15c, -5V potential difference is generated subsequently to between t ₃ of t ₄ from t ₁ by an AC signal V3, a potential difference of + 5V during t ₆ is generated from t ₄ (see FIG. 10C) .

Next, from t ₆ , a potential difference of −5 V is generated in the pixel electrode 15 a by the AC signal V 1 (see FIG. 10A), and in the pixel electrode 15 b, a potential difference of −5 V is continuously generated from t ₅ by the AC signal V 2 ( see FIG. 10B), the pixel electrode 15c, the potential difference continues + 5V from t ₄ is generated by an AC signal V3 (see FIG. 10C), also repeated in the same manner as described above or later. Here, in FIGS. 10A to 10C, the time from t ₀ to t ₆ is 20 seconds, but is not limited thereto.

  The rectangular wave AC signals V1, V2, and V3 shown in FIGS. 10A to 10C transition to a high potential (+ 5V) and a low potential (−5V) with the reference potential set to 0V. The setting of the reference potential, the high potential, and the low potential is not limited to this, but in order to sweep both the positive (+) ionic impurities 60 and the negative (−) ionic impurities 60. In addition, it is preferable that the high potential is a positive potential and the low potential is a negative potential. Thus, the negative (−) ionic impurity 60 can be attracted to the positive potential region, and the positive (+) ionic impurity 60 can be attracted to the negative potential region.

  Therefore, the polarity of the potential between the pixel electrode regions is reversed by the applied AC signals V1, V2, and V3, and the positive and negative ionic impurities 60 can be attracted and moved one after another. That is, as described above, the ionic impurities 60 are applied by applying the AC signals V1, V2, and V3 whose phases are shifted by 120 ° from the center in the Y direction of the display region E toward the outside of the display region E. Are sequentially swept outward from the display area E in which the first pixel electrode area 15a1, the second pixel electrode area 15b2, and the third pixel electrode area 15c3 are repeatedly arranged.

Specifically, for example, ionic impurities 60 negative polarity, when present in the first pixel electrode region 15a1 in t _0, by the potential of the first pixel electrode region 15a1 in t ₃ is shifted to a negative potential, It is repelled and moved by being attracted to the second pixel electrode region 15b2 having a positive potential adjacent to the first pixel electrode region 15a1. Further, at t ₃ , since the third pixel electrode region 15c3 has a negative potential, the ionic impurity 60 is repelled by the third pixel electrode region 15c3 and hardly moves.

Next, the potential of the second pixel electrode region 15b2 at t ₅ is shifted to a negative potential, ionic impurities 60 are repelled, adjacent to the second pixel electrode regions 15b2, the third pixel electrode region of positive potential It is attracted to 15c3 and moves. Further, at t ₅ , the first pixel electrode region 15a1 has a negative potential, and thus the ionic impurity 60 hardly moves to the first pixel electrode region 15a1.

Then, by the potential of the third pixel electrode region 15C3 at t ₇ is shifted to a negative potential, ionic impurities 60 are repelled, adjacent to the third pixel electrode regions 15C3, the first pixel electrode region of positive potential It is attracted to 15a1 and moves. Further, at t ₇ , the second pixel electrode region 15b2 has a negative potential, and thus the ionic impurity 60 hardly moves to the second pixel electrode region 15b2. Thereafter, the ionic impurities 60 are sequentially attracted and moved in accordance with the transition of the potential. Even if the ionic impurity 60 has a positive polarity, it moves in the same manner as the negative ionic impurity 60, although the drawing timing is different.

  The time-average reference potential difference of the voltages of the applied AC signals V1, V2, and V3 is approximately 0V. Specifically, it is preferably 100 mV or less. When it is 100 mV or more, there is a possibility that burn-in may occur. If it is 100 mV or less, seizure hardly occurs.

Here, combinations of polarities in the AC signals V1, V2, and V3 applied to the pixel electrode 15 are (V1, V2, V3): t ₁ (+, −, −), t ₂ (+, +, −). , T ₃ (−, +, −), t ₄ (−, +, +), t ₅ (−, −, +), and t ₆ (+, −, +). These six combinations are sequentially repeated after t ₇ .

As a result, as shown in FIGS. 11A to 11C, the ionic impurities 60 are sequentially attracted and moved from the center in the Y direction to the upper and lower long sides (outside the display region E). Specifically, when the negative ionic impurity 60 is at the center in the Y direction (regardless of the left-right direction) at t ₁ (FIG. 11A), the ionic impurity 60 is changed to t ₃ (FIG. 11C). , It is attracted to the adjacent pixel electrode region to which the AC signal V2 is applied. Next, when shifting to t ₅ (FIG. 11C), the ionic impurity 60 is attracted to the adjacent pixel electrode region to which the AC signal V3 is applied. In this way, the combination of the six polarities described above is sequentially repeated, so that the ionic impurity 60 is swept toward either the upper or lower long side so as to move away from the center.

  Even when the ionic impurity 60 is positive, the pulling timing is different from that of the negative polarity, but is swept away from the center as in the case of the negative polarity. Even when the ionic impurity 60 is not in the center but in a region closer to the long side, the ionic impurity 60 is still swept away from the center. In this way, the ionic impurities 60 are swept toward the outside of the display area E.

  The application of the AC signals V1, V2, and V3 is performed by setting the temperature of the liquid crystal layer 50 to Tni or higher of the liquid crystal and making the liquid crystal isotropic by the heating means described above. Therefore, the mobility of the ionic impurity 60 is increased, and the sweep effect of the ionic impurity 60 can be improved.

  In addition, for example, in this embodiment, since the potential difference is generated between the pixel electrode regions by shifting the phase, the electric field strength can be increased as compared with the method of creating the potential difference by changing the amplitude in 5V. The ionic impurities 60 can be efficiently swept.

<Driving method of display device>
Next, a driving method of the projection display apparatus 1000 related to heating and cooling of the liquid crystal layer 50 and application of AC signals V1 and V2 to the pixel electrodes 15a and 15b will be described with reference to FIG. FIG. 12 is a schematic diagram showing the timing of application of an AC signal with respect to the temperature of the liquid crystal layer.

  In the driving method of the projection display device 1000 of the present embodiment, when the liquid crystal layer 50 is heated by the heating means 510 during the on-sequence period and the temperature of the liquid crystal layer 50 is set to Tni or higher of the liquid crystal, the pixel electrode 15a is applied. An AC signal V1 is applied, and an AC signal V2 having the same phase as the AC signal V1 is applied to the pixel electrode 15b. Then, after the on-sequence period, the liquid crystal layer 50 is cooled by the cooling means 520, and the temperature of the liquid crystal layer 50 is set to a predetermined temperature lower than Tni.

  In FIG. 12, the horizontal axis represents time, one of the vertical axes (upper side in FIG. 12) represents the polarity and magnitude of the drive current supplied to the Peltier element, and the other vertical axis represents the liquid crystal layer. A temperature of 50 is represented. In the lower part of FIG. 12, the period during which an AC signal (V1, V2, etc.) is applied and the operating state (power supply) of the projection display device 1000 are associated with the broken-line sections dividing the horizontal axis (time). (From the OFF period to the display period) are indicated by arrows.

  As shown in FIG. 12, during the power OFF period when the projection display device 1000 is not in an operating state, no driving current is supplied to the Peltier element, and the temperature of the liquid crystal layer 50 is relatively low (for example, projection) Environment temperature where the type display device 1000 is placed).

  Next, when the on-sequence period is started by turning on the power to operate the projection display apparatus 1000, a positive drive current is supplied to the Peltier element. Thereby, heating to the liquid crystal layer 50 is started, and the temperature of the liquid crystal layer 50 rises. Since the polarity of the drive current of the Peltier element is determined by the surface of the Peltier element used as the heating means 510 and the cooling means 520, heating may be performed with the polarity of the drive current being negative.

  Next, when the temperature of the liquid crystal layer 50 reaches Tni, the temperature of the liquid crystal included in the liquid crystal layer 50 also becomes Tni. When the temperature of the liquid crystal layer 50 becomes equal to or higher than Tni, application of the AC signal described above is started. Since the liquid crystal has an isotropic phase, the mobility of the ionic impurities in the lateral direction is larger than that in the vertical alignment state. Since AC signals V1 and V2 are applied in this state, the sweeping effect of ionic impurities can be improved. The length of the on-sequence period is not particularly limited, but is, for example, about 10 seconds to 20 seconds. Note that the driving current of the Peltier element is intermittently supplied in order to keep the temperature of the liquid crystal layer 50 (liquid crystal) at a constant temperature equal to or higher than Tni and prevent excessive temperature rise.

  Next, when the on-sequence period ends, the polarity of the drive current of the Peltier element is reversed, a negative drive current is supplied, and cooling of the liquid crystal layer 50 is started. As a result, the temperature of the liquid crystal layer 50 decreases. This cooling is performed until the temperature of the liquid crystal layer 50 is equal to or lower than a predetermined temperature lower than Tni of the liquid crystal, that is, equal to or lower than the upper limit temperature at which the projection display device 1000 (liquid crystal device 100) can display. The upper limit temperature that can be displayed by the projection display apparatus 1000 depends on the type of liquid crystal contained in the liquid crystal layer 50 and is not particularly limited, but is, for example, about 70 ° C. Note that, while the liquid crystal layer 50 is being cooled, it is preferable to continue application of an AC signal from the viewpoint of suppressing re-diffusion of ionic impurities.

  Next, when the temperature of the liquid crystal layer 50 becomes equal to or lower than a predetermined temperature lower than Tni, the cooling and the application of the AC signal are finished. As described above, the start-up of the projection display apparatus 1000 is completed, the display period is started, and display is possible. Here, in the display period of the projection display apparatus 1000, the temperature of the liquid crystal layer 50 may rise due to the incidence of light. Therefore, the liquid crystal layer 50 may be cooled by using a Peltier element and a mechanism for cooling the projection display device 1000 such as the electric fan described above. For example, the driving current of the Peltier element may be supplied at a current value smaller than that during cooling after the on-sequence period, and the liquid crystal layer 50 may be cooled while suppressing power consumption.

  The projection type display device 1000 is provided with an integration counter for the display period. When a certain integration display period has elapsed, the liquid crystal layer 50 is heated and the AC signals V1, V2, etc. are applied to the pixel electrodes 15, and the liquid crystal layer 50 is supplied. The cooling may be performed. Here, a series of operations of heating the liquid crystal layer 50, applying the AC signals V1, V2, and the like to the pixel electrode 15 and cooling the liquid crystal layer 50 are hereinafter simply referred to as “ionic impurity sweeping operation”. The display quality of the projection display apparatus 1000 may be further improved by periodically performing the ionic impurity sweeping operation in this manner.

  As described above, according to the projection display apparatus 1000 and the driving method of the projection display apparatus 1000 according to the present embodiment, the following effects can be obtained.

  Compared with the prior art, the sweeping effect of ionic impurities can be improved. Specifically, the temperature of the liquid crystal layer 50 can be set to be equal to or higher than Tni of the liquid crystal by the heating unit 510, and the mobility of ionic impurities can be increased as an isotropic phase by changing the anisotropy of the liquid crystal. . In particular, in the VA liquid crystal device 100, by making the liquid crystal isotropic, the mobility of the ionic impurities in the lateral direction is increased and the ionic impurities adsorbed on the alignment film can be easily dissociated. It becomes possible.

  By heating up to Tni or more of the liquid crystal, the liquid crystal becomes isotropic regardless of the type of liquid crystal contained in the liquid crystal layer 50. At this time, a lateral electric field from the pixel electrode 15a toward the pixel electrode 15c is generated by applying the AC signals V1, V2, and V3 that are out of phase. That is, the electric field direction changes from the first pixel electrode region 15a1 to the second pixel electrode region 15b2 and from the second pixel electrode region 15b2 to the third pixel electrode region 15c3, so that the Y direction ( The ionic impurities can be swept from the center side (in the vertical direction) toward the outside (long side).

  Since the mobility of the ionic impurities in the liquid crystal layer 50 increases, the time required for sweeping the ionic impurities can be shortened. Further, the liquid crystal layer 50 heated to Tni or higher can be cooled to a predetermined temperature lower than Tni by the cooling means 520 to align the liquid crystal. Therefore, even if the ionic impurities are swept during the on-sequence period of the projection display apparatus 1000, the startup time of the projection display apparatus 1000 (until the display becomes possible) as compared with the case where there is no cooling means 520. Time).

  It is possible to sweep ionic impurities before starting the display of the projection display device 1000 and sweep out the ionic impurities diffused during the period when the projection display device 1000 is not operated to the outside of the display region E. Become. Thereby, the projection display apparatus 1000 can be displayed with better display quality than before. In addition, since the temperature of the liquid crystal layer 50 is cooled to a predetermined temperature or less by the cooling unit 520, the start-up time until the projection display device 1000 can display can be shortened including the on-sequence period. .

  As described above, since occurrence of display defects such as display unevenness due to ionic impurities is suppressed, it is possible to provide a projection display device 1000 with improved display quality and a driving method thereof.

(Embodiment 2)
<Driving method of display device>
A driving method of the projection display apparatus 1000 according to the second embodiment will be described with reference to FIG. FIG. 13 is a schematic diagram illustrating the timing of application of an AC signal with respect to the temperature of the liquid crystal layer according to the second embodiment. In addition, about the component same as Embodiment 1, the same code | symbol is used and the overlapping description is abbreviate | omitted.

  In the second embodiment, in the projection display device 1000 to which the liquid crystal device 100 similar to the first embodiment is applied, the driving method is changed from the first embodiment as described below.

  In the driving method of the projection display apparatus 1000 of this embodiment, the liquid crystal layer 50 is heated by the heating unit 510 in both the on-sequence period and the off-sequence period, and the temperature of the liquid crystal layer 50 is set to Tni or more. The AC signal V1 is applied to the pixel electrode 15a and the AC signal V2 is applied to the pixel electrode 15b. After the on-sequence period and the off-sequence period are finished, the liquid crystal layer 50 is cooled by the cooling unit 520, and the liquid crystal The temperature of the layer 50 is set to a predetermined temperature or lower.

  As shown in FIG. 13, in this embodiment, the ionic impurity sweeping operation is performed during the on-sequence period, and in addition to this, the ionic impurity sweeping operation is also performed during the off-sequence period.

  After the display period ends, an off-sequence period is started, and the operation for lowering the projection display apparatus 1000 is started. At this time, a positive drive current is supplied to the Peltier element. Thereby, heating to the liquid crystal layer 50 is started, and the temperature of the liquid crystal layer 50 rises. Since the polarity of the drive current of the Peltier element is determined by the surface of the Peltier element used as the heating means 510 and the cooling means 520, heating may be performed with the polarity of the drive current being negative.

  Next, when the temperature of the liquid crystal layer 50 reaches Tni, the temperature of the liquid crystal included in the liquid crystal layer 50 also becomes Tni. When the temperature of the liquid crystal layer 50 becomes equal to or higher than Tni, application of AC signals V1, V2, etc. is started. At this time, since the liquid crystal is in an isotropic phase, the mobility of the ionic impurities in the lateral direction is larger than that in the vertical alignment state. Since an AC signal is applied in this state, the sweeping effect of ionic impurities can be improved. The length of the off sequence period is not particularly limited, and is, for example, about 10 seconds to 20 seconds. Note that the driving current of the Peltier element is intermittently supplied in order to keep the temperature of the liquid crystal layer 50 (liquid crystal) at a constant temperature equal to or higher than Tni and prevent excessive temperature rise.

  Next, when the off sequence period ends, the polarity of the drive current of the Peltier element is reversed, a negative drive current is supplied, and cooling of the liquid crystal layer 50 is started. As a result, the temperature of the liquid crystal layer 50 decreases. This cooling is performed until the temperature of the liquid crystal layer 50 is equal to or lower than a predetermined temperature lower than Tni of the liquid crystal, that is, equal to or lower than an upper limit temperature at which the projection display device 1000 (liquid crystal device 100) can operate. The upper limit temperature at which the projection display apparatus 1000 can operate depends on the type of liquid crystal contained in the liquid crystal layer 50 and is not particularly limited, but is about 70 ° C., for example. Here, while the liquid crystal layer 50 is being cooled, it is preferable to continue the application of the AC signal from the viewpoint of suppressing re-diffusion of ionic impurities.

  Next, when the temperature of the liquid crystal layer 50 becomes equal to or lower than a predetermined temperature lower than Tni, the cooling and the application of the AC signal are finished. As described above, the shutdown of the projection display device 1000 is completed, and the power-off period is started. Here, when the environmental temperature in which the projection display device 1000 is placed is lower than the temperature of the liquid crystal layer 50 at the time when the cooling is finished, the temperature of the liquid crystal layer 50 is gradually lowered to near the environmental temperature by cooling. I will do it. At this time, the cooling means 520 may be operated using standby power or the like, and the temperature of the liquid crystal layer 50 may be actively lowered to the vicinity of the environmental temperature.

  The projection display apparatus 1000 may be provided with a display period integration counter, and the ionic impurities may be swept when a certain integration display period has elapsed. Thus, by periodically sweeping ionic impurities, the display quality of the projection display apparatus 1000 can be further improved.

  As described above, according to the projection display apparatus 1000 and the driving method of the projection display apparatus 1000 according to the present embodiment, the following effects can be obtained in addition to the effects of the first embodiment.

  During the period (display period) in which the projection display device 1000 is displayed, ionic impurities generated from the members of the liquid crystal device 100 can be swept to the outside of the display region E. Therefore, it is possible to reduce ionic impurities that diffuse during the period in which the projection display apparatus 1000 is displayed. In addition, since the temperature of the liquid crystal layer 50 is cooled to a predetermined temperature or less, the fall time of the projection display device 1000 including the off-sequence period can be shortened.

(Embodiment 3)
<Driving method of display device>
A driving method of the projection display apparatus 1000 according to the third embodiment will be described. About the same component as Embodiment 1, the same code | symbol is used and the overlapping description is abbreviate | omitted.

  In the third embodiment, in the projection display device 1000 to which the liquid crystal device 100 similar to the first embodiment is applied, the driving method is changed from the first embodiment as described below.

  In the present embodiment, the projection display apparatus 1000 is provided with a display period integration counter. Using this integration counter, when a certain integration display period has elapsed, an ionic impurity sweeping operation is performed during the power OFF period. The fixed integration display period is not particularly limited, and is, for example, 1000 hours to 2000 hours. Further, the threshold value (a constant integrated display period) for performing the sweep operation of the ionic impurities may be set to different values in the liquid crystal light valves 1210, 1220, and 1230. For example, the threshold value of the liquid crystal light valve 1230 on which blue light (B) is incident may be set to a value smaller than the others.

  As described above, according to the projection display apparatus 1000 and the driving method of the projection display apparatus 1000 according to the present embodiment, the following effects can be obtained in addition to the effects of the first embodiment.

  By periodically sweeping ionic impurities, the diffused ionic impurities are reduced when the system is not operated for a relatively long time, and the display quality of the projection display apparatus 1000 can be further improved. Further, the periodic implementation can simplify the sweeping of ionic impurities during the off-sequence period or the on-sequence period. For this reason, the startup time or the shutdown time of the projection display apparatus 1000 can be shortened.

(Modification 1)
<Driving method of display device>
A method for driving the projection display apparatus 1000 according to Modification 1 will be described. About the same component as Embodiment 1, the same code | symbol is used and the overlapping description is abbreviate | omitted.

  In the present modification, in the driving method of the projection display apparatus 1000 according to the second embodiment, the ionic impurity sweeping operation performed before the display period is omitted. That is, during the off-sequence period, the liquid crystal layer 50 is heated by the heating unit 510, the temperature of the liquid crystal layer 50 is set to Tni or higher, the AC signal V1 is applied to the pixel electrode 15a, and the AC signal V2 is applied to the pixel electrode 15b. After the off sequence period, the liquid crystal layer 50 is cooled by the cooling means 520, and the temperature of the liquid crystal layer 50 is set to a predetermined temperature or lower.

  Thus, the start-up time (on-sequence period) of the projection display apparatus 1000 can be shortened by performing the sweep operation of the ionic impurities only when the projection display apparatus 1000 is lowered.

(Modification 2)
<Configuration of display device>
A configuration of the display device according to Modification 2 will be described. The same components as those of the second embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In this modification, in the configuration of the display device (projection display device 1000) of the second embodiment, Tni included in the liquid crystal layer 50 used in the liquid crystal device 100 is replaced with liquid crystal having 110 ° C., and Tni is 80 ° C. or higher. A nematic liquid crystal having a negative dielectric anisotropy that is less than 100 ° C. is used. Specifically, the Tni of the liquid crystal contained in the liquid crystal layer 50 of this modification is 80 ° C. In addition, as a medium used for the heating unit 510 and the cooling unit 520, water is employed instead of the ethylene glycol of the second embodiment. Other configurations are the same as those of the display device of the second embodiment.

  According to this, in addition to the effects of the second embodiment, the following effects can be obtained. Since Tni is 80 ° C., the temperature at which the ionic impurity sweep operation is performed can be made lower than that in the second embodiment. Therefore, when heating to the temperature using the heating means 510, time and energy required for heating can be reduced. In addition, when cooling from the temperature to a predetermined temperature lower than Tni, the time and energy required for cooling can be reduced. Thus, since the heating and cooling periods are shortened, the startup and shutdown time of the projection display apparatus 1000 can be shortened. Furthermore, since water is used as the medium, the medium can be handled easily.

(Modification 3)
<Configuration of display device>
A configuration of the display device according to Modification 3 will be described. The same components as those of the modified example 2 are denoted by the same reference numerals, and redundant description is omitted.

  In this modification, in FIG. 5 showing the configuration of the display device (projection display device 1000) of Embodiment 1, the heating means 510 and the cooling means 520 are connected via a tube 550 filled with a medium (water). The liquid crystal light valve 1230 is disposed in contact with only the liquid crystal light valve 1230. In this configuration, the ionic impurity sweeping operation is performed only on the liquid crystal light valve 1230. That is, in this modification, the liquid crystal light valves 1210 and 1220 are not heated and cooled, and the ionic impurities in the liquid crystal layer 50 are not swept.

  According to this, in addition to the effect of the modified example 2, the following effect can be obtained. Since the liquid crystal light valves 1210 and 1220 are not heated and cooled, the configuration of the projection display apparatus 1000 can be simplified, for example, the heating means 510 and the cooling means 520 can be made smaller than the second modification. Specifically, blue light (B) is incident on the liquid crystal light valve 1230. Blue light (B) has a wavelength shorter than that of red light (R) and green light (G) and is close to ultraviolet light, and thus is derived from members of the liquid crystal device 100 such as the liquid crystal material, the alignment film 18, and the sealing material 40. Ionic impurities are likely to occur. Therefore, the projection display device 1000 can be simplified by sweeping ionic impurities only in the liquid crystal light valve 1230 where ionic impurities are likely to be generated.

  Further, since blue light (B) is incident on the liquid crystal light valve 1230, the temperature rise of the liquid crystal layer 50 during the display period is smaller than that of the liquid crystal light valves 1210 and 1220. Therefore, the liquid crystal layer 50 of the liquid crystal light valve 1230 can use a liquid crystal having a lower Tni than the liquid crystal light valves 1210 and 1220. Specifically, in the liquid crystal light valves 1210 and 1220, when a liquid crystal having a relatively low Tni is used, the temperature of the liquid crystal layer 50 is increased by red light (R) or green light (G) incident (irradiated) during the display period. Tni may be easily exceeded and display may become impossible. On the other hand, in the liquid crystal light valve 1230 (blue light (B)), since the temperature rise is relatively small, the heating and cooling time in the sweeping operation of the ionic impurities using the liquid crystal having a relatively low Tni. Or energy can be reduced.

(Modification 4)
<Configuration of display device>
A configuration of a liquid crystal device according to Modification 4 will be described with reference to FIGS. 14 and 15. FIG. 14 is a schematic plan view illustrating a configuration of a liquid crystal device according to Modification 4. 15 is a schematic cross-sectional view taken along the line BB ′ of the liquid crystal device shown in FIG. About the same component as Embodiment 1, the same code | symbol is used and the overlapping description is abbreviate | omitted.

  As shown in FIGS. 14 and 15, the liquid crystal device 300 according to the present modification includes at least one peripheral electrode 130 outside the display region E of the element substrate 10, and the alternating current signal V <b> 1 is applied during the period of alternating current signal V <b> 1. An AC signal having the same or larger applied voltage as the signal V <b> 1 is applied to the peripheral electrode 130. That is, in addition to sweeping ionic impurities to the outside of the display region E using the pixel electrode 15, the peripheral electrode 130 may be provided for sweeping.

  The liquid crystal device 300 includes, for example, an actual display area E1 that contributes to display, a dummy pixel area E2 that is disposed so as to surround the actual display area E1, and a frame-shaped sealing material 40 that surrounds the dummy pixel area E2. ing. A parting area E3 is provided between the sealing material 40 and the dummy pixel area E2.

  As shown in FIG. 15, a peripheral electrode 130 for sweeping the ionic impurities 60 to the parting region E3 is provided in a region overlapping the parting region E3 on the third interlayer insulating film 14 in plan view. The peripheral electrode 130 includes a first electrode 131, a second electrode 132, and a third electrode 133, and each has a rectangular frame shape in plan view.

  In the first electrode 131, the second electrode 132, and the third electrode 133, the direction of the electric field (electric field lines) generated between adjacent electrodes is in the direction from the first electrode 131 close to the display area E to the third electrode 133. An AC signal is given to move.

  In the counter substrate 20 of the present modification, for example, the counter electrode 23 is provided so as to overlap with the actual display area E1 and the dummy pixel area E2 in a plan view, and is not provided so as to overlap with the parting area E3. . Specifically, the counter electrode 23 is not provided in a portion facing each of the first electrode 131, the second electrode 132, and the third electrode 133 through the liquid crystal layer 50.

  Therefore, an electric field is hardly generated between each of the first electrode 131, the second electrode 132, and the third electrode 133 and the counter electrode 23. That is, the movement of the ionic impurity 60 is not hindered by the electric field generated between each of the first electrode 131, the second electrode 132, and the third electrode 133 and the counter electrode 23, and the ionic impurity 60 moves to the parting region E3. Swept efficiently.

  Further, at least one peripheral electrode 130 is sufficient, and only the first electrode 131 may be provided without providing the second electrode 132 and the third electrode 133. When there is one peripheral electrode 130, only the first electrode 131 may be provided, and a positive or negative DC signal may be applied to the first electrode 131 to sweep the ionic impurities 60. As described above, the number of the peripheral electrodes 130 is not limited to three, that is, the first electrode 131 to the third electrode 133, and the number of the peripheral electrodes 130 may be increased or decreased depending on the size of the region.

  As described above, the ionic impurities 60 swept by the AC signal V1 and the AC signal V2 can be easily swept to the outside of the display area E. Therefore, ionic impurities in the display region E are further reduced, and the display quality of the display device can be further improved.

  Further, as shown in FIG. 15, the ionic impurities 60 may be swept using the dummy pixel electrodes 121 and 122 in the dummy pixel region E2.

  Specifically, the ionic impurity 60 is removed by the pixel electrode including the pixel electrode 15 of the display area E as in the first embodiment and the dummy pixel electrodes 121 and 122 of the dummy pixel area E2 of this modification. You may make it sweep.

  In the dummy pixel region E2, dummy pixel electrodes 121 and 122 having the same configuration as the pixel electrode 15 in the actual display region E1 are provided. By using the dummy pixel electrodes 121 and 122, the ionic impurities 60 can be swept (delivered) to a region far away from the outer periphery of the actual display region E1 (for example, to the peripheral electrode 130). Thereby, for example, it is possible to prevent the ionic impurities 60 from diffusing and returning to the actual display region E1 while the power of the projection display device 1000 is turned off. As a result, it is possible to suppress the influence on the display characteristics. Note that the dummy pixel electrodes 121 and 122 may be further increased in order to sweep the ionic impurities 60 farther.

(Modification 5)
The liquid crystal device used in the display device of the present invention is not limited to the transmissive type, and may be a reflective type liquid crystal device. That is, it may be a projection display device using a reflective liquid crystal device.

  DESCRIPTION OF SYMBOLS 10 ... Element substrate as 1st board | substrate, 15 ... Pixel electrode, 15a ... Pixel electrode as 1st pixel electrode, 15b ... Pixel electrode as 2nd pixel electrode, 20 ... Counter substrate as 2nd board | substrate, 50 ... Liquid crystal Layer: 100 ... Liquid crystal device, 130 ... Peripheral electrode, 131 ... First electrode as peripheral electrode, 132 ... Second electrode as peripheral electrode, 133 ... Third electrode as peripheral electrode, 510 ... Heating means, 520 ... Cooling Means 1000 ... Projection type display device, 1101 ... Lamp unit as light source, E ... Display area, V1 ... AC signal as first AC signal, V2 ... AC signal as second AC signal.

Claims (10)

A first substrate; a second substrate disposed opposite the first substrate; a liquid crystal layer including liquid crystal sandwiched between the first substrate and the second substrate; and a display region of the first substrate. A liquid crystal device having a first pixel electrode formed and a second pixel electrode adjacent to the first pixel electrode;
Heating means capable of heating the liquid crystal layer to a temperature equal to or higher than Tni of the liquid crystal;
A cooling means capable of cooling the temperature of the liquid crystal layer to a predetermined temperature lower than Tni;
A light source for irradiating the liquid crystal layer with light,
When the temperature of the liquid crystal layer is set to Tni or higher by the heating means, a first AC signal is applied to the first pixel electrode, and a phase shifts at the same frequency as the first AC signal to the second pixel electrode. A display device to which a second AC signal is applied.   The display device according to claim 1, wherein the Tni is 80 ° C. or higher and lower than 100 ° C. During the on-sequence period, the temperature of the liquid crystal layer is set to the Tni or higher by the heating means,
The display device according to claim 1, wherein after the on-sequence period, the temperature of the liquid crystal layer is set to be equal to or lower than the predetermined temperature by the cooling unit. During the off-sequence period, the temperature of the liquid crystal layer is set to the Tni or higher by the heating means,
3. The display device according to claim 1, wherein the temperature of the liquid crystal layer is set to be equal to or lower than the predetermined temperature by the cooling unit after the off-sequence period. In both the on-sequence period and the off-sequence period, the temperature of the liquid crystal layer is set to the Tni or higher by the heating means,
3. The display device according to claim 1, wherein after the on-sequence period and the off-sequence period are ended, the temperature of the liquid crystal layer is set to the predetermined temperature or less by the cooling unit. Having at least one peripheral electrode outside the display area of the first substrate;
The positive or negative DC signal or AC signal having the same or larger applied voltage as the first AC signal or a larger voltage is applied to the peripheral electrode during the period in which the first AC signal is applied. Item 6. The display device according to any one of Items 5. A first substrate; a second substrate disposed opposite the first substrate; a liquid crystal layer including liquid crystal sandwiched between the first substrate and the second substrate; and a display region of the first substrate. A liquid crystal device having a first pixel electrode formed and a second pixel electrode adjacent to the first pixel electrode;
A driving method of a display device comprising: a light source that irradiates light to the liquid crystal layer,
When the liquid crystal layer is heated so that the temperature of the liquid crystal layer is equal to or higher than Tni of the liquid crystal, a first AC signal is applied to the first pixel electrode and the first AC signal is applied to the second pixel electrode. Apply a second AC signal that is out of phase at the same frequency as
A driving method of a display device, wherein after applying the first AC signal and the second AC signal, the liquid crystal layer is cooled so that the temperature of the liquid crystal layer is equal to or lower than a predetermined temperature lower than the Tni. During the on-sequence period, the liquid crystal layer is heated, the first AC signal is applied to the first pixel electrode, and the second AC signal is applied to the second pixel electrode,
The method for driving the display device according to claim 7, wherein the liquid crystal layer is cooled after the on-sequence period ends. During the off-sequence period, the liquid crystal layer is heated, the first AC signal is applied to the first pixel electrode, and the second AC signal is applied to the second pixel electrode,
The method for driving a display device according to claim 7, wherein the liquid crystal layer is cooled after the off-sequence period. In both the on-sequence period and the off-sequence period, the liquid crystal layer is heated and the first AC signal is applied to the first pixel electrode, and the second AC signal is applied to the second pixel electrode. And
The method for driving a display device according to claim 7, wherein the liquid crystal layer is cooled after the on-sequence period and the off-sequence period are ended.

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