JP2009098531A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid influence affected by accumulation of particles having charge properties in a liquid crystal layer without adding any new constituent such as a switching part and an ion trap electrode to a liquid crystal modulation element. <P>SOLUTION: A liquid crystal display has liquid crystal modulation elements 3R, 3G and 3B and control means 302 and 303. Each of the liquid crystal modulation elements includes first and second electrodes 103 and 107, a liquid crystal layer 105 and first and second alignment layers 104 and 106. The control means apply first and second potentials to the both electrodes so that polarities of electric field generated in the liquid crystal layer are periodically reversed to subject the liquid crystal modulation elements to optical modulation operation. The control means apply third and fourth potentials by which the polarity of the electric field generated in the liquid crystal layer is made constant and difference is changed in an in-plane direction of the liquid crystal layer in a first effective optical modulation region to the first and the second electrodes before optical modulation operation in a second effective optical modulation region when an effective optical modulation region of the liquid crystal modulation element is altered from the first effective optical modulation region to the second effective optical modulation region is started. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device such as a projector using a liquid crystal modulation element.

  The liquid crystal modulation element includes a dielectric difference between a first transparent substrate having a transparent electrode (common electrode) and a second transparent substrate having a transparent electrode (pixel electrode), a wiring, a switching element, and the like forming a pixel. Some have nematic liquid crystal sealed with positive isotropic. This liquid crystal modulation element is called a so-called TN (Twisted Nematic) liquid crystal modulation element in which the major axis of liquid crystal molecules is continuously twisted by 90 ° between two glass substrates, and is used as a transmission type liquid crystal modulation element. . There is also a circuit board using a circuit board having a reflecting mirror, wiring, switching elements and the like instead of the second transparent board. This liquid crystal modulation element is called a so-called VAN (Vertical Arrangement Nematic) liquid crystal modulation element in which the major axis of liquid crystal molecules is homeotropically aligned almost perpendicularly to two substrates, and is used as a reflective liquid crystal modulation element. ing.

  In these liquid crystal modulation elements, in general, an ECB (Electrically Controlled Birefringence) effect is used to control an action of imparting retardation (changing the polarization state) to light waves passing through the liquid crystal layer to form an image.

  In a liquid crystal modulation element that modulates light intensity using such an ECB effect, charged particles (ionic substances) existing in the liquid crystal layer move by applying an electric field to the liquid crystal layer. When the direct current electric field is continuously applied to the liquid crystal layer, the charged particles are attracted to one of the two opposing electrodes. Thereby, even if the voltage applied to the electrode is constant, the electric field applied to the liquid crystal layer is increased or decreased by the charge of the charged particles, and the electric field applied to the liquid crystal layer is substantially attenuated or increased.

  In order to avoid such a phenomenon, a line inversion drive method is generally adopted in which the polarity of the applied electric field is inverted and the polarity is switched at a predetermined cycle such as 60 Hz for each line of the array pixels. In addition, a field inversion drive method is also used in which the polarity of the electric field applied to all of the array pixels is inverted at a predetermined period. By these drive methods, it is possible to prevent the electric field applied to the liquid crystal layer from having a constant polarity, and to prevent ion bias.

  This corresponds to making the effective electric field for the liquid crystal layer always have the same value with respect to the voltage applied to the electrode.

  However, charged particles are also present in the liquid crystal layer and the outer wall material surrounding the liquid crystal layer, and these charged particles drift (move) by driving the liquid crystal particularly in a high temperature environment. These charged particles become a DC electric field component inside the liquid crystal layer, adhere to the alignment film or electrode interface at the interface of the liquid crystal layer, and drift and deposit along the alignment direction of the liquid crystal molecules.

  In addition, in a liquid crystal modulation element having an organic alignment film, in addition to the drift of charged particles caused by driving the liquid crystal in a high temperature environment, light is incident on the liquid crystal modulation element, so that the alignment film, liquid crystal, sealing material, etc. The organic material is decomposed to generate charged particles. These charged particles also become a DC electric field component inside the liquid crystal layer, adhere to the alignment film or electrode interface at the liquid crystal layer interface, and further drift and deposit in the alignment direction of the liquid crystal molecules.

  Then, the effective electric field applied to the liquid crystal is changed by the charged particles deposited in the specific region of the liquid crystal layer, so that desired ECB modulation is not performed and the image quality is deteriorated. For example, uneven brightness is caused in the effective display area of the liquid crystal display element.

  Measures relating to such a problem are disclosed in Patent Documents 1 to 4.

  Patent Document 1 discloses that ions other than those at the time of image display operation cause a phenomenon of image sticking by aligning at least one potential of a pixel electrode and a counter electrode of a liquid crystal cell to a ground level. A method of dissociation from the interface is disclosed.

  Further, in Patent Document 2, an ion trap electrode region is provided in a non-display region of a liquid crystal modulation element, and an ion trap electrode region in a non-display region that does not affect image display by applying a DC voltage to the ion trap electrode. Discloses a method for adsorbing impurity ions.

  In Patent Document 3, a metal film electrode is arranged at a position different from the pixel electrode, and a DC voltage is applied between the metal film electrode and the common electrode to reduce the concentration of mobile ions in the display region. A method for suppressing the flicker phenomenon is disclosed.

  Furthermore, in Patent Document 4, an ion trap electrode provided independently of a transparent electrode is provided on opposing surfaces provided on two electrode substrates in the vicinity of a liquid crystal sealing port, and a voltage is applied to the ion trap electrode. Thus, a method for trapping ionic impurities is disclosed.

As described above, it is possible to improve the quality of image display by controlling the charged particles inside the liquid crystal modulation element by controlling the voltage from the outside.
JP-A-2005-55562 JP-A-8-201830 Japanese Patent Laid-Open No. 11-38389 JP-A-5-323336

  However, in the method disclosed in Patent Document 1, since it is necessary to provide a switching unit for dropping the counter electrode to the ground level inside the circuit of the liquid crystal modulation element, the manufacturing process of the liquid crystal modulation element increases. Further, if the counter electrode is simply set to the ground level, the force for peeling off the ions attached to the alignment film and the electrode interface is weaker than the Coulomb force, and the effect is low.

  In addition, in the methods disclosed in Patent Documents 2 to 4, since an ion trap electrode that attracts ions to the non-display area is newly provided, the number of manufacturing steps is also increased. Moreover, although the ion impurity is attracted by the Coulomb force, the Coulomb force is inversely proportional to the square of the distance, and therefore, ions generated at a position away from the ion trap electrode cannot be attracted efficiently.

  The present invention provides a liquid crystal display device capable of avoiding the influence of the accumulation of charged particles in a liquid crystal layer without adding a new switching unit, ion trap electrode, or the like to the liquid crystal modulation element.

  A liquid crystal display device according to one aspect of the present invention includes a liquid crystal modulation element and control means for controlling the liquid crystal modulation element. The liquid crystal modulation element includes a first electrode and a second electrode, a liquid crystal layer disposed between the first electrode and the second electrode, and a first electrode disposed between the first electrode and the liquid crystal layer. And a second alignment film disposed between the second electrode and the liquid crystal layer. In addition, the control unit applies the first and second potentials to the first and second electrodes, respectively, so that the sign of the electric field generated in the liquid crystal layer is periodically reversed, and causes the liquid crystal modulation element to perform the light modulation operation. . The control means performs the light modulation operation in the second effective light modulation region when the effective light modulation region in the liquid crystal modulation element is changed from the first effective light modulation region to the second effective light modulation region. Before starting, in the first effective light modulation region, the third and fourth potentials, in which the sign of the electric field generated in the liquid crystal layer is constant and the difference changes in the in-plane direction of the liquid crystal layer, are Each of the two electrodes is provided.

  In the present invention, the sign of the electric field generated in the liquid crystal layer in the effective light modulation area before the change is made constant in the first and second electrodes to which the potential for light modulation operation is applied, and the difference is in the in-plane direction of the liquid crystal layer. The third and fourth potentials that change are applied, and then the effective light modulation region is changed. This makes it possible to forcibly diffuse the charged particles existing in a distribution in the liquid crystal layer in the effective light modulation region before the change into the liquid crystal layer. For this reason, it is displayed in the effective light modulation region after the change due to the influence of the charged particles existing in the effective light modulation region before the change without adding a new switching unit, an ion trap electrode, or the like to the liquid crystal modulation element. It can suppress that the quality of the image which falls is reduced.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration of a liquid crystal projector (image projection apparatus) as a liquid crystal display apparatus that is Embodiment 1 of the present invention.

  Reference numeral 303 denotes a liquid crystal panel driver. The driver 303 receives a video signal, a horizontal synchronization signal (Hsync), and a vertical synchronization signal (Vsync) from an image supply device 350 such as a personal computer, a DVD player, or a TV tuner. The driver 303 generates red, green and blue panel drive signals from these input signals. Each panel drive signal is input to a red liquid crystal panel 3R, a green liquid crystal panel 3G, and a blue liquid crystal panel 3B, which are reflective liquid crystal modulation elements. As a result, the three liquid crystal panels 3R, 3G, 3B are driven independently of each other.

  The liquid crystal panels 3R, 3G, and 3B modulate light (color-separated light) from an illumination optical system, which will be described later, by a modulation operation according to the panel drive signal. Thus, an image corresponding to each color component of the image information input from the image supply device 350 is displayed.

  The liquid crystal panel of this embodiment has 1400 × 1050 pixels corresponding to the SXGA standard, and the size of the effective display area (all pixel areas) is 11.3 mm × 8.5 mm. Alternatively, a liquid crystal panel having 1920 × 1080 pixels corresponding to the full HD standard and having an effective display area (all pixel areas) of 15.4 mm × 9.6 mm may be used.

  A light source 301 converts light from a lamp (not shown) into linearly polarized light having the same polarization direction (S-polarized light having a polarization direction perpendicular to the paper surface of the drawing) and emits it as illumination light.

  Illumination light from the light source 301 is incident on a dichroic mirror 305 that reflects magenta and transmits green. The magenta color component of the illumination light is reflected by the dichroic mirror 305 and passes through a blue cross-color polarizer 311 that gives half-wave retardation to blue polarized light. Thus, blue linearly polarized light (P-polarized light) having a polarization direction parallel to the paper surface of the figure and red linearly polarized light (S-polarized light) having a polarization direction perpendicular to the paper surface of the figure are generated.

  The blue P-polarized light enters the first polarization beam splitter 310, passes through the polarization separation film, and is guided to the blue liquid crystal panel 3B. The red S-polarized light is reflected by the polarization separation film of the first polarization beam splitter 310 and guided to the red liquid crystal panel 3R.

  On the other hand, the green linearly polarized light (S-polarized light) transmitted through the dichroic mirror 305 passes through the dummy glass 306 for correcting the optical path length and enters the second polarizing beam splitter 307. The green S-polarized light is reflected by the polarization separation film of the second polarization beam splitter 307 and guided to the green liquid crystal panel 3G.

  In this way, the red, green, and blue liquid crystal panels 3R, 3G, and 3B are illuminated by the illumination light.

  The light incident on each liquid crystal panel is provided with polarization retardation according to the modulation state of the pixels arranged in each liquid crystal panel, and is reflected and emitted by the liquid crystal panel. Of the reflected light, a polarized light component having the same polarization direction as that of the illumination light traces back the optical path of the illumination light and returns to the light source 301 side.

  In addition, a polarization component (modulated light) having a polarization direction orthogonal to the polarization direction of the illumination light in the reflected light proceeds as follows. The modulated light from the red liquid crystal panel 3R that is P-polarized light passes through the polarization separation film of the first polarization beam splitter 310. Next, the light passes through a red cross color polarizer 312 that gives half-wave retardation to the red polarized light and is converted into S polarized light. The red S-polarized light is incident on the third polarization beam splitter 308, reflected by the polarization separation film, and guided to the projection optical system 304.

  The modulated light from the blue liquid crystal panel 3B, which is S-polarized light, is reflected by the polarization separation film of the first polarization beam splitter 310, passes through the red cross color polarizer 312 without being subjected to retardation, and passes through the third polarization beam. The light enters the splitter 308. The blue S-polarized light is reflected by the polarization separation film of the third polarization beam splitter 308 and guided to the projection optical system 304.

  The modulated light by the green liquid crystal panel 3G that is P-polarized light is transmitted through the polarization separation film of the second polarization beam splitter 307, is transmitted through the dummy glass 309 for correcting the optical path length, and the third polarization beam splitter. Incident at 308. The green P-polarized light passes through the polarization separation film of the third polarization beam splitter 308 and is guided to the projection optical system 304.

  The three colors of modulated light thus synthesized are projected onto the light diffusion screen 313 which is the projection surface by the projection optical system 304. Thereby, a full color image is displayed.

  The liquid crystal panel for red 3R, the liquid crystal panel for green 3G, and the liquid crystal panel for blue 3B used in this embodiment are vertical alignment mode (for example, VAN type) reflective liquid crystal modulation elements.

  Reference numeral 330 denotes a display area selection switch. The user can select (change) an effective display area (effective light modulation area) in each liquid crystal panel by operating the display area selection switch 330. The effective display area selectable in each liquid crystal panel includes a pixel area corresponding to the SXGA standard, a pixel area corresponding to the full HD standard, a pixel area corresponding to the HD standard, and the like. In this embodiment, the effective display area, that is, the effective light modulation area, is an area for performing a light modulation operation to display an ornamental image corresponding to an input video signal to the liquid crystal panel driver 303, and is described later with a black mask. This does not include the area where (formed) is formed.

  The liquid crystal panel driver 303 outputs a command signal to the power control unit 302 in response to an ON / OFF operation (turning on / off operation) of a power switch (not shown). The power control unit 302 turns on / off the power supply to the liquid crystal panels 3R, 3G, 3B and turns on / off the power supply to the light source 301 (lights / extinguishes) in response to a command signal from the liquid crystal panel driver 303. To control. Further, the liquid crystal panel driver 303 sets an effective display area in each liquid crystal panel in accordance with a selection signal from the display area selection switch 330. The liquid crystal panel driver 303 and the power supply control unit 302 constitute control means.

  FIG. 2 shows a cross-sectional structure common to the red liquid crystal panel 3R, the green liquid crystal panel 3G, and the blue liquid crystal panel 3B.

  In order from the side on which the illumination light from the light source 301 enters, 101 is an AR coat film, and 102 is a glass substrate. Reference numeral 103 denotes a transparent electrode film (first electrode) formed of ITO or the like formed on the glass substrate 102. Reference numeral 104 denotes a first alignment film disposed between the transparent electrode film 103 and a liquid crystal layer described later. Reference numeral 105 denotes a liquid crystal layer disposed between the first alignment film 104 and the second alignment film 106. Reference numeral 107 denotes a reflective pixel electrode layer (second electrode) which is disposed to face the transparent electrode film 103 and is formed of a metal such as aluminum. Reference numeral 108 denotes a Si substrate on which the reflective pixel electrode layer 107 is formed. Note that the transparent electrode film 103 and the reflective pixel electrode layer 107 are also generally referred to as counter electrodes. In the following description, the transparent electrode film 103 and the reflective pixel electrode layer 107 may be referred to as electrode layers.

  In FIG. 10, the light source 301 is turned on and applied to the electrode layers 103 and 107 by the liquid crystal panel driver 303 in a state where the light modulation operation is performed by the liquid crystal panels 3R, 3G, and 3B (light modulation operation state or display drive state). Voltage. The horizontal axis represents time, and the vertical axis represents applied voltage. The liquid crystal panel driver 303 stores a computer program therein and controls applied voltages to the electrode layers 103 and 107 according to the program.

  In the following description, the voltage applied to each electrode or liquid crystal layer means a potential (potential difference from the ground) with respect to a ground (0 V) not shown.

  An AC voltage (second potential) V107 that alternately switches between a positive voltage 120 and a negative voltage 121 at a specific period is applied to the reflective pixel electrode layer 107. Further, a DC voltage (first potential) V103 is applied to the transparent electrode film 103.

  The effective electric field generated in the liquid crystal layer 105 is an AC electric field that is generated according to the difference between the AC voltage V107 and the DC voltage V103, and alternately switches between a positive electric field and a negative electric field at a specific period. That is, the potential difference generated in the liquid crystal layer 105 periodically changes between positive and negative. In other words, in this embodiment, a potential (potential difference) is applied to the electrode layers 103 and 107 so that the sign of the electric field generated in the liquid crystal layer 105 is periodically inverted (changes periodically between positive and negative). The light modulation operation is performed on the liquid crystal panel. In general, in order to suppress so-called flicker, the applied voltages to both electrode layers 103 and 107 are set so that the positive potential difference and the negative potential difference generated in the liquid crystal layer 105 are equal to each other.

  Here, the specific period is 1/120 second in the NTSC system and 1/100 second in the PAL system, which corresponds to a period of one field. One frame image is displayed in two field periods (1/60 seconds or 1/50 seconds). However, the specific period may correspond to a display period of one frame image.

  In addition, the electric field generated in the liquid crystal layer 105 is caused by a voltage drop (electric field) applied to both electrode layers 103 and 107, a voltage drop due to the resistance of the alignment films 104 and 106, and charges trapped in each alignment film (electrons and holes). All of the minute voltages (electric fields) generated by the electric charges are superimposed.

  FIG. 3 shows the liquid crystal panel as viewed from the glass substrate 102 side. Reference numeral 110 denotes a director direction (pretilt direction) which is an alignment direction of liquid crystal molecules aligned by the first alignment film 104. Reference numeral 111 denotes a director direction (pretilt direction) which is an alignment direction of liquid crystal molecules aligned by the second alignment film 106. The director directions 110 and 111 are both inclined by several degrees with respect to the normal of the alignment film surface, and the directions in which they are inclined are opposite to each other.

  Reference numeral 112 denotes an effective display area corresponding to all pixels of the liquid crystal panel. Orientation processing is performed in a direction of about 45 degrees with respect to the short side 112a and the long side direction 112b of the effective display area 112.

  In the projector, the temperature of the liquid crystal panels 3R, 3G, and 3B rises due to light irradiation from a high-intensity lamp, and is controlled to be about 40 degrees under a normal temperature operating environment. However, when the projector is used for a long time, the liquid crystal panels 3R, 3G, and 2B are in a temperature rising state (high temperature state) for a long time, and the liquid crystal molecules are driven for image display. Arise.

  4 is a cross-sectional view of the liquid crystal panel, and FIG. 5 is a view of the liquid crystal panel as viewed from the glass substrate 102 side. As shown in FIGS. 4 and 5, the sealing material which is an organic substance in and around the liquid crystal layer 105, the interface between the first alignment film 104, the second alignment film 106, the electrode layers 103 and 107, etc. Are charged particles 113. The charged particles 113 travel in the director direction of the liquid crystal molecules (first direction) along the interface between the liquid crystal layer 105 and the second alignment film 106 on the reflective pixel electrode layer 107 side by the long-term use. The effective display area 112 is deposited in a diagonal area on the second alignment film 106 side. The charge of the chargeable particles 113 here is a negative sign charge.

  The effective electric field generated in the liquid crystal layer 105 is changed by the charged particles 113 deposited at the interface between the second alignment film 106 and the liquid crystal layer 105 as described above. As a result, the quality of the image of the area where charged particles are deposited is degraded.

  In this embodiment, in order to float the charged particles 113 deposited in this way from the interface of the second alignment film 106 and the diagonal region of the effective display region 112, the liquid crystal panel driver 303 moves the electrode layers 103 and 107. The applied voltage is controlled (first control).

  In the first control, when the effective display area in the liquid crystal panels 3R, 3G, 3B is changed according to the operation of the display area selection switch 330, the first effective control area is changed to the electrode layers 103, 107 in the changed effective display area. This is performed in a state where the first and second potentials are not applied. That is, when the effective light modulation area in the liquid crystal panels 3R, 3G, and 3B is changed from the first effective light modulation area to the second effective light modulation area, the light modulation operation in the second effective light modulation area The first control is performed before the operation is started.

  When the effective display area is changed, not only when the effective display area is changed during the use of the current projector, but also the effective display area that was set at the end of the previous projector use at the start of the current projector use. Including a case where an effective display area different from the above is selected.

  In the first control, as shown in FIG. 6, in order to float the deposited charged particles 113 inside the liquid crystal layer 105, a positive voltage (fifth potential) is applied to the transparent electrode film 103 to reflect pixel electrodes. A negative voltage (sixth potential) is applied to the layer 107.

  FIG. 7 shows applied voltages V103a and V107a for both electrode layers 103 and 107 in the first control. The applied voltage (sixth potential) V107a to the reflective pixel electrode layer 107 is a negative voltage with respect to the applied voltage (fifth potential) V103a to the transparent electrode film 103. The applied voltages V103a and V107a are constant DC voltages that do not change with time. However, the constant voltage mentioned here includes not only a voltage that does not vary at all, but also a voltage that varies only within a range that can be regarded as the same voltage due to a variation in power supply voltage, a control error, or the like. This is the same in other embodiments described later.

  As a result, a negative DC electric field that does not periodically change between positive and negative is generated in the liquid crystal layer 105.

  Note that the strength of the DC electric field may vary within a range in which the DC electric field is applied to the liquid crystal layer 105 so as not to periodically change between positive and negative. That is, the voltage (potential) applied to both electrode layers 103 and 107 may change as long as the sign of the electric field generated in the liquid crystal layer 105 does not change.

  The voltages applied to the transparent electrode film 103 and the reflective pixel electrode layer 107 here are in the in-plane direction of the liquid crystal layer 105, that is, the direction orthogonal to the thickness direction (in the in-plane direction of the liquid crystal panel or The same (uniform) in the modulation in-plane direction).

  As described above, the liquid crystal panel driver 303 applies the same potential to the respective electrode layers 103 and 107 in the in-plane direction of the liquid crystal layer 105 with the sign of the electric field generated in the liquid crystal layer 105 being constant (positive or negative). The first control is performed. The voltage difference (potential difference) applied to both electrode layers 103 and 107 is, for example, a potential difference of 1.0 V to 2.0 V.

  The liquid crystal panel driver 303 applies such voltage application (first control) to both the electrode layers 103 and 107 for a first predetermined time (for example, while the effective display area in the liquid crystal panels 3R, 3G, and 3B is changed). For 1 second).

  Thereby, the negatively charged particles 113 deposited and deposited on the interface between the liquid crystal layer 105 and the second alignment film 106 as shown in FIG. 8 are caused by the Coulomb force with respect to the negative voltage applied to the reflective pixel electrode layer 107. The repulsive force dissociates from the interface and floats inside the liquid crystal layer 105.

  Here, the first predetermined time means that most (for example, 70% or more) or all of the deposited charged particles 113 are separated from the interface of the second alignment film 106 and enter the liquid crystal layer 105. It is the time to float.

  In addition, as described above, the sign of the voltage applied to the reflective pixel electrode layer 107 on the second alignment film side where the charged particles 113 are deposited on the interface with the liquid crystal layer 105 is the sign of the charged particles 113. Same negative.

  Here, the voltage applied to the reflective pixel electrode layer 107 is not necessarily a negative voltage with respect to the ground level. Specifically, when the voltage applied to the reflective pixel electrode layer 107 and the voltage applied to the transparent electrode film 103 are compared, the voltage applied to the reflective pixel electrode layer 107 is higher than the voltage applied to the transparent electrode film 103. It should be low. Also in this case, in this embodiment, the voltage applied to the reflective pixel electrode layer 107 is negative. As long as this condition is satisfied, both the voltage applied to the reflective pixel electrode layer 107 and the voltage applied to the transparent electrode film 103 may be positive voltages with reference to the ground level, or both may be set to the ground level. It may be a negative voltage with reference to.

  Next, in this embodiment, control of the voltage applied to both electrode layers 103 and 107 is performed so that the charged particles 113 are attracted and diffused (moved) in a diagonal direction different from the diagonal direction in which the charged particles 113 are deposited. (Second control) is performed. This second control is also a case where the effective light modulation area in the liquid crystal panels 3R, 3G, and 3B is changed from the first effective light modulation area to the second effective light modulation area. This is performed before the light modulation operation is started.

  Specifically, the distribution is changed so that the difference in voltage applied to the transparent electrode film 103 and the reflective pixel electrode layer 107 in the in-plane direction of the liquid crystal layer 105 (hereinafter referred to as an interelectrode potential difference) changes. Apply voltage to hold. More specifically, the voltage applied to the transparent electrode film 103 and the reflective pixel electrode layer 107 is controlled so that a larger interelectrode potential difference is generated in a region where more charged particles in the liquid crystal layer 105 are deposited. The

  In other words, the liquid crystal panel driver 303 sets the third and fourth potentials, in which the sign of the electric field generated in the liquid crystal layer 105 is constant and the difference in the in-plane direction of the liquid crystal layer 105 changes, to the transparent electrode film 103 and the reflective pixel electrode layer. Second control given to 107 is performed. In this embodiment, such applied voltage control (second control) is performed for a second predetermined time.

  FIG. 9 shows the distribution of voltage (third potential) in the effective display area 112 applied to the reflective pixel electrode layer 107 in the second control. A region 122 where the applied voltage is high is shown bright (in white), is shown as a region 123 that becomes dark (becomes gray) as the applied voltage is reduced, and a region 124 where the applied voltage is 0 is shown in black. Reference numeral 125 denotes a pixel effective area of the reflective pixel electrode layer 107 corresponding to the effective display area 112.

  As can be seen from FIG. 9, in the diagonal direction A (the direction parallel to the pretilt directions 110 and 111 of the liquid crystal molecules) A in which the charged particles 113 are deposited, the potential difference between the electrodes is constant, and on the diagonal line in the diagonal direction A The potential difference between the electrodes in the region 124 in the vicinity thereof is set to zero. On the other hand, in another diagonal direction B, that is, a diagonal direction different from the diagonal direction A, the change in the interelectrode potential difference is increased, and the closer to the diagonal region, the higher the interelectrode potential difference.

  The region 122 is a region where the charged particles 113 are most deposited, and corresponds to a first deposition region. Further, the region 123 and the region 124 correspond to a second deposition region with respect to the region 122. Further, each of the region 123 and the region 124 corresponds to a first deposition region and a second deposition region.

  In the present embodiment, as shown in FIGS. 11 to 13, applied voltages (third and fourth potentials) to both electrode layers 103 and 107 are set.

  FIG. 11 shows the applied voltage in the region 124 in FIG. The applied voltage (third potential) V103b to the transparent electrode film 103 and the applied voltage (fourth potential) V107b to the reflective pixel electrode layer 107 are both constant DC voltages that do not change over time. Further, the applied voltages V103b and V107b are the same, and the potential difference between the electrodes is zero.

  Note that the term “match” includes not only a case where there is a complete match, but also a case where there is a difference only within a range that can be regarded as a match due to a control error or the like. This is the same in other embodiments described later.

  FIG. 12 shows the applied voltage in the region 122 in FIG. The applied voltage (fourth potential) V107b to the reflective pixel electrode layer 107 is an alternating voltage, and the minimum value of the alternating voltage matches the applied voltage (third potential) V103b to the transparent electrode film 103. . The applied voltage V103b to the transparent electrode film 103 is a DC voltage.

  In such applied voltage control, a positive DC voltage corresponding to a time integral value (indicated by a dotted line in the figure) of the voltage V107b applied to the reflective pixel electrode layer 107 is applied to the reflective pixel electrode layer 107. Is equivalent.

  FIG. 13 shows the applied voltage in the region 123 in FIG. Similar to the region 122, the applied voltage (fourth potential) V107b to the reflective pixel electrode layer 107 is an alternating voltage, and the minimum value of the alternating voltage and the applied voltage (third potential) 103b to the transparent electrode film 103 are used. And are consistent. The applied voltage V103b to the transparent electrode film 103 is a DC voltage. However, the maximum value of the AC voltage applied to the reflective pixel electrode layer 107 is lower than the maximum value of the AC voltage applied to the reflective pixel electrode layer 107 in the region 122.

  Such applied voltage control is equivalent to applying to the reflective pixel electrode layer 107 a positive DC voltage corresponding to the time integral value (indicated by a dotted line in the figure) of the applied voltage V107b to the reflective pixel electrode layer 107. It is.

  As a result, an interelectrode potential difference 120 ′ larger than the interelectrode potential difference 120 ″ in the region 123 is given to the region 122, and a higher DC voltage is applied.

  In this embodiment, the maximum inter-electrode potential difference in the diagonal direction B is 2 V, and the frequency of the AC voltage applied to the pixel electrode layer 107 is 120 Hz in the NTSC system and 100 Hz in the PAL system. The second predetermined time is a time until most (for example, 70%) or all of the charged particles 113 deposited in the diagonal direction A diffuse in the diagonal direction B, for example, 1 second. It is.

  FIG. 14 shows a cross-sectional structure of the liquid crystal panel. This figure shows the sign of the voltage applied to the liquid crystal layer 105 in the regions 122 and 123 excluding the region 124 where the applied voltage of the liquid crystal layer 105 is 0 among the regions 122, 123 and 124. As described above, the applied voltage V107b of the reflective pixel electrode layer 107 is a positive voltage with respect to the applied voltage V103b of the transparent electrode film 103. Accordingly, the liquid crystal layer 105 does not periodically change between positive and negative. A direct current electric field is generated.

  The sign of the voltage applied to the reflective pixel electrode layer 107 on the second alignment film side where the charged particles 113 are deposited at the interface with the liquid crystal layer 105 is positive, which is different from the sign of the charged particles 113. In addition, the voltage V107b applied to the reflective pixel electrode layer 107 increases toward a diagonal region in a diagonal direction B different from the diagonal direction A in which the charged particles 113 are deposited.

  For this reason, the negatively charged particles 113 deposited in the diagonal direction A at the interface of the second alignment film 106 are attracted in the diagonal direction B by the Coulomb force as shown in FIG. Spread with.

  In this way, by performing the second control subsequent to the first control described above, the charged particles 113 deposited in the diagonal direction A are suspended in the liquid crystal layer 105 and then diffused in the diagonal direction B. Can be made. Therefore, it is possible to suppress the deterioration of the image quality due to the influence of the accumulation of the charged particles 113.

  Also in the second control, the voltage applied to the reflective pixel electrode layer 107 does not necessarily have to be a positive voltage with respect to the ground level. Specifically, when the voltage applied to the reflective pixel electrode layer 107 and the voltage applied to the transparent electrode film 103 are compared, the voltage applied to the reflective pixel electrode layer 107 is higher than the voltage applied to the transparent electrode film 103. It should be high. Also in this case, in this embodiment, the voltage applied to the reflective pixel electrode layer 107 is positive. As long as this condition is satisfied, both the voltage applied to the reflective pixel electrode layer 107 and the voltage applied to the transparent electrode film 103 may be positive voltages with reference to the ground level, or both may be set to the ground level. It may be a negative voltage with reference to. This is the same in other embodiments described later.

  In this embodiment, the case where the negatively charged particles 113 deposited at the interface between the liquid crystal layer 105 and the second alignment film 106 are dissociated from the interface has been described. However, the liquid crystal layer 105 and the first alignment film 104 are separated. There is a possibility that positively charged particles are deposited on the interface. In this case as well, by controlling the applied voltage in the same manner as above, the charged particles are dissociated from the interface and floated, and the charged particles deposited in a specific diagonal direction are diffused in other diagonal directions. Can do. In this case, the sign of the voltage applied to the transparent electrode film 103 on the first alignment film 104 side on which positive charged particles are deposited at the interface with the liquid crystal layer 105 may be the same as the sign of the charged particles. .

  Next, FIG. 19 shows an internal configuration of the liquid crystal panel driver 303 shown in FIG. The contrast adjustment circuit 201 adjusts the contrast of the video signal input to the liquid crystal panel driver 303. The video signal subjected to contrast adjustment is corrected by the gamma correction circuit 202 according to the applied voltage-reflectance (or transmittance) characteristics of the liquid crystal panels 3R, 3G, 3B. The output signal of the gamma correction circuit 202 is input to the data rearrangement circuit 204 through the selector 203. The data rearrangement circuit 204 rearranges data for display on the liquid crystal panels 3R, 3G, and 3B.

  The output of the data rearrangement circuit 204 is converted into an analog signal by the D / A converter 205 and then input to the liquid crystal panels 3R, 3G, 3B.

  The horizontal synchronization signal (Hsync) and the vertical synchronization signal (Vsync) are input to the timing signal generation circuit (TG) 209 in the liquid crystal panel driver 303. The TG 209 generates signals necessary for driving the liquid crystal panels 3R, 3G, and 3B based on Hsync and Vsync.

  The central processing circuit (CPU) 207 sets various parameters for each circuit in the liquid crystal panel driver 303. The output of the CPU 207 is converted into a format suitable for reading by each circuit by the interface circuit 208, and is input to the contrast adjustment circuit 201, the gamma correction circuit 202, the data rearrangement circuit 204, and the TG 209 through the data bus 210.

  The DC pattern generation circuit 211 outputs an applied voltage pattern (uniform pattern) corresponding to the applied DC electric field for performing the first control for floating the charged particles shown in FIGS. 6 and 7. When the effective display area of the liquid crystal panel is changed, the direct current pattern generation circuit 211 generates a uniform pattern corresponding to the effective display area (first effective light modulation area) before the change. That is, a uniform pattern is generated so that the applied voltages to the electrode layers 103 and 107 are the same in the in-plane direction of the liquid crystal layer 105 in the effective display area before the change. The output from the DC pattern generation circuit 211 is input to the selector 203.

  The diagonal pattern generation circuit 206 outputs an applied voltage pattern (diagonal pattern) corresponding to the applied voltage distribution for performing the second control for diffusing the charged particles shown in FIGS. 9 and 11 to 14. . When the effective display area of the liquid crystal panel is changed, the diagonal pattern generation circuit 206 generates a diagonal pattern corresponding to the effective display area (first effective light modulation area) before the change. That is, a diagonal pattern is generated such that the difference in applied voltage to the electrode layers 103 and 107 changes in the diagonal direction B (see FIG. 9) in the effective display area before the change. The output from the diagonal pattern generation circuit 206 is input to the selector 203.

  21A to 21C show examples of effective display areas when a liquid crystal panel of the SXGA standard (1400 × 1050 pixels, 11.3 mm × 8.5 mm) is used.

  FIG. 21A shows a case in which all pixels (1400 × 1050 pixels) of the liquid crystal panel are driven to display a video signal (an ornamental image) by all the pixels. In this case, the entire pixel area becomes the effective display area 115, and the charged particles 113 are deposited along the diagonal direction A of the effective display area 115. In the figure, only a region 124 where the applied voltage difference to the electrode layers 103 and 107 is 0 in the diagonal pattern (see FIG. 9) necessary for diffusing the charged particles 113 is shown in black. . The diagonal pattern is set so that the applied voltage difference to the electrode layers 103 and 107 changes in the other diagonal direction of the effective display area 115. This also applies to other examples shown in FIGS. 21B to 21F described below.

  FIG. 21B shows a case where all the pixels in the horizontal direction of the liquid crystal panel and some pixels (1400 × 788 pixels) in the vertical direction are driven in order to set the aspect ratio of the effective display area to 16: 9 HD standard. ing. Reference numeral 116 denotes a pixel area that is not driven, and 117 denotes an effective display area (1400 × 788 pixels).

  In this case, the charged particles 113 are deposited along the diagonal direction A1 of the effective display area 117. In the drawing, only the region 124-1 where the applied voltage difference to the electrode layers 103 and 107 is 0 in the diagonal pattern necessary for diffusing the charged particles 113 is shown in black. The diagonal direction A1 in which the region 124-1 extends is different from the diagonal direction A in which the region 124 in FIG. 21A extends because the effective display region 117 is narrow in the vertical direction.

  FIG. 21C shows a case where all the pixels (1400 × 1050 pixels) of the liquid crystal panel are driven and a black mask is displayed in the upper and lower regions 128. At this time, the effective display area 126 is 1400 × 788 pixels excluding the pixels displaying the black mask.

  In this case, the charged particles 113 are deposited along the diagonal direction A2 of the effective display region 126. In the drawing, only the region 124-2 where the difference in applied voltage to the electrode layers 103 and 107 is 0 is shown in black in the diagonal pattern necessary for diffusing the charged particles 113. The diagonal direction A2 in which the region 124-2 extends differs from the diagonal directions A and A1 in which the regions 124 and 124-1 extend in FIGS. 21A and 21B because the effective display region 126 is narrower in the vertical direction. Yes.

  FIGS. 21D to 21F show examples of effective display areas when a liquid crystal panel of the full HD standard (1920 × 1080 pixels, 15.4 mm × 9.6 mm) is used.

  FIG. 21D shows a case where all the pixels (1920 × 1080 pixels) of the liquid crystal panel are driven and a black mask is displayed in the left and right regions 130 in order to set the aspect ratio of the effective display region to 4: 3. . The effective display area 131 in this case is 1440 × 1080 pixels excluding the pixels that display the black mask.

  In this case, the charged particles 113 are deposited along the diagonal direction A3 of the effective display region 131. In the figure, only the region 124-3 in which the difference in the applied voltage to the electrode layers 103 and 107 is 0 in the diagonal pattern necessary for diffusing the charged particles 113 is shown in black. The diagonal direction A3 in which the area 124-3 extends is smaller than the diagonal direction A in which the area 124 (see FIG. 9) in which the entire pixel area is the effective display area extends. Is different.

  FIG. 21E shows a case in which all the pixels in the horizontal direction and some pixels in the vertical direction of the liquid crystal panel are driven and black masks are displayed in the left and right regions 136. Reference numeral 135 denotes a pixel region that is not driven. In this case, the effective display area 134 is 1440 × 810 pixels.

  In this case, the charged particles 113 are deposited along the diagonal direction A4 of the effective display area 134. In the drawing, only the region 124-4 in which the difference in applied voltage to the electrode layers 103 and 107 is 0 in the diagonal pattern necessary for diffusing the charged particles 113 is shown in black. The diagonal direction A4 in which the area 124-4 extends is compared to the diagonal directions A and A3 in which the area 124 (see FIG. 9) when the entire pixel area is an effective display area and the area 124-3 in FIG. 21D extends. Thus, the effective display area 134 is different because it is wide in the horizontal direction and narrow in the vertical direction.

  FIG. 21F shows a case where all the pixels of the liquid crystal panel are driven and a black mask is displayed in the upper, lower, left and right peripheral areas 138. In this case, the effective display area 140 has the same 1440 × 810 pixels as in FIG. 21E. However, the effective display area 140 is located below the effective display area 134 of FIG. 21E.

  In this case, the charged particles 113 are deposited along the diagonal direction A5 of the effective display area 140. In the drawing, only the region 124-5 in which the difference in applied voltage to the electrode layers 103 and 107 is 0 is shown in black in the diagonal pattern necessary for diffusing the charged particles 113. The diagonal direction A5 in which the region 124-5 extends is substantially the same as the diagonal direction A4 in the case of FIG. 21E. However, since the effective display area 140 is positioned lower than in the case of FIG. 21E, the position of the area 124-5 is also positioned lower than the area 124-4 in FIG. 21E.

  In accordance with the operation of the display area selection switch 330, the effective display area on the liquid crystal panel can be selected from the effective display areas shown in FIGS. 21A to 21C or FIGS. 21D to 21F. Then, the DC pattern generation circuit 211 and the diagonal pattern generation circuit 206 respectively generate a uniform pattern and a diagonal pattern corresponding to the position and size of the effective display area, that is, corresponding to the effective display area.

  However, the effective display area shown in FIGS. 21A to 21F is only a representative example, and an effective display area other than the representative example can be selected by changing the position and size of the non-driving pixel area and the black mask. May be. A uniform pattern and a diagonal pattern may be generated (or selected) for each position and size of the effective display area.

  As shown in FIG. 22, when the director directions (pretilt directions) 110 and 111 of the liquid crystal molecules are reversed in the left-right direction with respect to the director direction shown in FIG. 3, the charged particles 113 are diffused. The diagonal pattern necessary for this is also reversed in the left-right direction. In FIG. 22, only the region 124 where the applied voltage difference to the electrode layers 103 and 107 is 0 is shown in black.

  In FIG. 19, the selector 203 selects one of the output of the direct current pattern generation circuit 211, the output of the diagonal pattern generation circuit 206, and the output of the gamma correction circuit 202 in accordance with an instruction from the CPU 207.

  The effective display area storage circuit 212 stores data relating to the position and size of the effective display areas of the liquid crystal panels 3R, 3G, and 3B (hereinafter referred to as effective display area data). The effective display area storage circuit 212 outputs the effective display area data at that time to the TG 209 through the data bus 210 in response to a command signal from the CPU 207.

  Based on the signal from the TG 209, the mask signal generation circuit 213 generates a mask signal indicating a region for forming a black mask among all the pixel regions of the liquid crystal panels 3R, 3G, and 3B, and outputs the mask signal to the data rearrangement circuit 204. . The data rearrangement circuit 204 sets a black mask in the area specified by the mask signal in the above-described data rearrangement.

  When a voltage is applied to the electrode layers 103 and 107 according to the diagonal pattern from the diagonal pattern generation circuit 206, the brightness of each liquid crystal panel changes along the diagonal direction B corresponding to the diagonal pattern. Image (diagonal pattern image) is formed. Further, when a voltage is applied to the electrode layers 103 and 107 according to the uniform pattern from the DC pattern generation circuit 211, an image having uniform brightness is formed on each liquid crystal panel corresponding to the uniform pattern on the entire screen. .

  The on / off control of power supply to the light source 301 and the liquid crystal panels 3R, 3G, 3B and the control of the voltage applied to the liquid crystal panels 3R, 3G, 3B including the first and second controls are shown in FIG. This is performed according to the flowchart shown.

  In step (abbreviated as S in FIG. 20) 501a in FIG. 20, the CPU 207 starts an operation in response to an ON operation of the power switch of the projector. The CPU 207 starts power supply to each unit such as the light source (lamp) 301 and each liquid crystal panel through the power control unit 302.

  In step 501b, the CPU 207 starts normal image display (light modulation operation) in the effective display area selected when the power switch is turned on among the liquid crystal panels 3R, 3G, and 3B. At this time, the CPU 207 causes the effective display area storage circuit 212 to store the effective display area data of the liquid crystal panels 3R, 3G, and 3B.

  In step 501c, the CPU 207 determines whether or not the display area selection switch 330 has instructed to change the effective display area. When the change of the effective display area is not instructed, the process returns to step 501b to continue normal image display. On the other hand, if an instruction to change the effective display area is given, the process proceeds to step 502.

  In step 502, the CPU 207 causes the TG 209 to output the effective display area data for the effective display area before the change stored in the effective display area storage circuit 212 in step 501b.

  In step 503a, the CPU 207 causes the selector 203 to select the output of the DC pattern generation circuit 211, and applies the potentials (fifth and sixth potentials) according to the uniform pattern output from the DC pattern generation circuit 211 to the electrode layer. 103 and 107 are applied.

  At this time, the direct current pattern generation circuit 211 is uniform corresponding to the effective display area (first effective light modulation area) before the change based on the signal from the TG 209 that has obtained the effective display area data before the change in step 502. Generate a pattern.

  Thereby, the first control (DC electric field application) for floating the charged particles 113 deposited in the liquid crystal layer 105 in the effective display area before the change in the liquid crystal layer 105 is started. In addition, the CPU 207 starts measuring the first predetermined time.

  In step 503b, the CPU 207 determines whether or not a first predetermined time has elapsed. If the first predetermined time has not elapsed, the process returns to step 503a. On the other hand, if the first predetermined time has elapsed, the process proceeds to step 504.

  In step 504, the CPU 207 causes the diagonal pattern generation circuit 206 to generate a diagonal pattern corresponding to the effective display area before the change based on the signal from the TG 209.

  The diagonal pattern generation circuit 206 may generate a diagonal pattern each time based on the signal from the TG 209, but stores a plurality of diagonal patterns according to the effective display area in advance and before the change. A diagonal pattern corresponding to the effective display area may be selected.

  Next, in step 505, the CPU 207 causes the selector 203 to select the output of the diagonal pattern generation circuit 206, and potentials according to the diagonal pattern output from the diagonal pattern generation circuit 206 (third and fourth potentials). Is applied to the electrode layers 103 and 107. Thereby, the second control for diffusing the charged particles in the liquid crystal layer 105 in the effective display area before the change is started. Further, the CPU 207 starts measuring the second predetermined time.

  Here, in step 501c, for example, the effective display area is changed from the effective display area (first effective light modulation area) shown in FIG. 21A to the effective display area (second effective light modulation area) shown in FIG. 21B. Suppose you are instructed. In this case, the effective display area data for the effective display area of FIG. 21A stored in the effective display area storage circuit 212 in step 502 is read, and the direct current and diagonal pattern generation circuit 211, based on the effective display area data, 206 generates uniform and diagonal patterns, respectively. Then, the first and second controls based on the uniform and diagonal patterns are sequentially performed.

  In step 506, the CPU 207 determines whether or not a second predetermined time has elapsed. If the second predetermined time has not elapsed, the process returns to step 505. On the other hand, if the second predetermined time has elapsed, the process proceeds to step 507.

  In step 507, the CPU 207 stops (erase) the output from the diagonal pattern generation circuit 206.

  Subsequently, in step 508, the CPU 207 displays the changed effective display area (second effective light modulation area) on the liquid crystal panels 3R, 3G, and 3B according to the instruction from the display area selection switch 330 in step 501c. specify. Further, the CPU 207 causes the TG 209 to output the effective display area data after the change. When it is necessary to form a black mask on the liquid crystal panels 3R, 3G, and 3B, data for generating the black mask is output to the mask signal generation circuit 213.

  In step 509, the CPU 207 causes the effective display area storage circuit 212 to store the changed effective display area data specified in step 508. The data stored here is used to generate DC and diagonal patterns in the DC and diagonal pattern generation circuits 211 and 206 when the effective display area is further changed.

  In step 510, the CPU 207 causes the selector 203 to select the output of the gamma correction circuit 202. The data rearrangement circuit 204 displays an image in the changed effective display area on the liquid crystal panels 3R, 3G, and 3B based on the signals from the gamma correction circuit 202, the TG 209, and the mask signal generation circuit 213 (light modulation operation). The data is rearranged. Then, the rearranged data is output to the liquid crystal panels 3R, 3G, 3B. Thereby, normal image display (light modulation operation) is performed in the effective display area after the change.

  Thereafter, in step 511, the CPU 207 determines whether or not the power switch is turned off. If the power switch is not turned off, the CPU 207 returns to step 501b and continues displaying the image in the changed effective display area. On the other hand, if the power switch is turned off, the power supply from the power control unit 302 to each unit is stopped in step 512, and the operation of the projector is terminated.

  As described above, in this embodiment, when the effective display area of the liquid crystal panel is changed, the first and second controls are sequentially performed using the uniform and diagonal patterns corresponding to the effective display area before the change. Thereby, in the effective display area before the change, the charged particles deposited on the interface between the liquid crystal layer and the alignment film can be forcibly dissociated from the interface and diffused in the liquid crystal layer. Therefore, it is possible to avoid a display luminance defect in the effective display area after the change due to the influence of the charged particles accumulated in the effective display area before the change. That is, it is possible to suppress degradation of image quality due to the influence of the accumulation of charged particles before the change of the effective display area.

  Note that the changed effective display area data stored in the effective display area storage circuit 212 in step 509 in FIG. 20 is retained even when the operation of the projector is ended in steps 511 and 512. For this reason, the first and second controls described above can be performed even when an effective display area different from the effective display area until the end of the previous use is selected at the next start of use of the projector.

  That is, in step 501a, the effective display area data for the effective display area (effective display area before the change) until the end of the previous use of the projector is output from the effective display area storage circuit 212 to the TG 209. Then, the selector 203 sequentially selects the outputs of the direct current and diagonal pattern generation circuits 211 and 206. Thereby, the first and second controls are performed in the effective display area before the change. Thereafter, image display (light modulation operation) in the effective display area after the change is started in step 501b.

  In this way, even when the effective display area is changed with the projector power cut off, the change after the change (during the current use) is caused by the influence of charged particles accumulated in the effective display area before the change (during the previous use). It is possible to avoid a display luminance defect from occurring in the effective display area.

  Next, a second embodiment of the present invention will be described. In this embodiment, components having the same or similar functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  Also in the present embodiment, as in the first embodiment, when the effective display area of the liquid crystal panels 3R, 3G, and 3B is changed, the sign of the electric field generated in the liquid crystal layer 105 is constant, and the in-plane direction of the liquid crystal layer 105 The first control for applying the same potential to each of the electrode layers 103 and 107 is performed. After that, second control is performed in which the sign of the electric field generated in the liquid crystal layer 105 is made constant, and third and fourth potentials whose difference changes in the in-plane direction of the liquid crystal layer 105 are applied to the electrode layers 103 and 107. Further, the first and second controls are performed so as to correspond to the effective display area before the change.

  However, the present embodiment is different from the first embodiment in that a DC voltage is applied to the reflective pixel electrode layer 107 in the second control.

  The voltages (third and fourth potentials) applied to the transparent electrode film 103 and the reflective pixel electrode layer 107 in the second control in this embodiment are shown in FIGS.

  FIG. 16 shows the applied voltage in the region 124 in FIG. The applied voltage V103b to the transparent electrode film 103 and the applied voltage V107b to the reflective pixel electrode layer 107 are both constant DC voltages that do not change over time. Moreover, both applied voltages V103b and 107b are in agreement, and the potential difference between the electrodes is zero.

  FIG. 17 shows the applied voltage in the region 122 in FIG. The applied voltage V103b to the transparent electrode film 103 and the applied voltage V107b to the reflective pixel electrode layer 107 are both constant DC voltages that do not change over time. The applied voltage V107b to the reflective pixel electrode layer 107 is set higher than the applied voltage V103b to the transparent electrode film 103 by the interelectrode potential difference 120 ′.

  FIG. 18 shows the applied voltage in the region 123 in FIG. Similar to the applied voltage in the region 122, the applied voltage V103b to the transparent electrode film 103 and the applied voltage V107b to the reflective pixel electrode layer 107 are both constant DC voltages that do not change over time. The voltage V107b applied to the reflective pixel electrode layer 107 is set higher than the voltage V103b applied to the transparent electrode film 103 by the interelectrode potential difference 120 ″. The interelectrode potential difference 120 ″ is the interelectrode potential difference 120 in the region 122. Smaller than ′.

  As a result, an interelectrode potential difference 120 ′ larger than the interelectrode potential difference 120 ″ in the region 123 is given to the region 122, and a higher DC voltage is applied.

  As described above, even when a DC voltage is applied to the reflective pixel electrode layer 107 in the second control, as shown in FIGS. 14 and 15 of the first embodiment, the first control is deposited in the diagonal direction A. The charged particles 113 suspended by the above can be attracted in the diagonal direction B and diffused into the liquid crystal layer 105.

  In the present embodiment, as compared with the case where the applied voltage V107b to the reflective pixel electrode layer 107 is an alternating voltage as in the first embodiment, the charged particles 113 are always attracted in the diagonal direction B by the Coulomb force. The diffusion effect of the particles 113 can be further enhanced. For this reason, it is also possible to shorten the 2nd predetermined time which performs 2nd control.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

  For example, each of the above embodiments is for a vertical alignment mode liquid crystal modulation element, but the applied voltage control of the above embodiment is suitable for various liquid crystal modulation elements such as TN, STN, OCB modes other than the vertical alignment mode. The liquid crystal modulation element may be modified into a form and applied. Further, the present invention may be carried out by modifying it into a form suitable for a transmissive liquid crystal modulation element.

  In the above embodiments, the liquid crystal projector has been described. However, the present invention can also be applied to a liquid crystal display device using a liquid crystal modulation element other than the liquid crystal projector.

1 is a diagram illustrating a configuration of a liquid crystal projector that is Embodiments 1 and 2 of the present invention. FIG. Sectional drawing of the liquid crystal panel used in Example 1,2. The figure explaining the pretilt direction of the vertical alignment mode in the said liquid crystal panel. Sectional drawing which shows the chargeable particle deposited in the liquid crystal panel in Example 1,2. The Example seen from the glass substrate side which shows the charged particle deposited in the liquid crystal panel in Example 1,2. In Example 1, 2, the figure which shows a mode that the applied voltage for suspending a chargeable particle is applied to a counter electrode. The figure which shows the applied voltage to the counter electrode in FIG. The figure explaining the charged particle which floated by the voltage application to a counter electrode in Example 1,2. FIG. 6 is a diagram illustrating an in-plane distribution of a voltage applied to a reflective pixel electrode layer in order to diffuse deposited charged particles in Examples 1 and 2; The figure explaining the normal alternating current drive of the liquid crystal panel in Example 1,2. FIG. 10 is a diagram illustrating a voltage applied to the counter electrode in a region 124 in FIG. 9 according to the first embodiment. FIG. 10 is a diagram illustrating a voltage applied to the counter electrode in a region 122 in FIG. 9 according to the first embodiment. FIG. 10 is a diagram illustrating a voltage applied to the counter electrode in a region 123 in FIG. 9 according to the first embodiment. The figure which shows a mode that the applied voltage for diffusing a chargeable particle is applied to a counter electrode in Examples 1-3. The figure which shows a mode that the charged charged particle diffused by the voltage application shown in FIG. FIG. 10 is a diagram illustrating a voltage applied to the counter electrode in a region 124 in FIG. 9 according to the second embodiment. FIG. 10 is a diagram illustrating a voltage applied to the counter electrode in a region 122 in FIG. 9 according to the second embodiment. FIG. 10 is a diagram illustrating a voltage applied to the counter electrode in a region 123 in FIG. 9 according to the second embodiment. FIG. 3 is a diagram illustrating a configuration of a liquid crystal panel driver in Examples 1 and 2. 6 is a flowchart showing the operation of the liquid crystal projector in the first and second embodiments. The figure which shows the relationship between the effective display area in a liquid crystal panel, and a diagonal pattern. The figure which shows the relationship between the effective display area in a liquid crystal panel, and a diagonal pattern. The figure which shows the relationship between the effective display area in a liquid crystal panel, and a diagonal pattern. The figure which shows the relationship between the effective display area in a liquid crystal panel, and a diagonal pattern. The figure which shows the relationship between the effective display area in a liquid crystal panel, and a diagonal pattern. The figure which shows the relationship between the effective display area in a liquid crystal panel, and a diagonal pattern. The figure which shows the relationship between the orientation direction in a liquid crystal panel, and a diagonal pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 AR coat film 102 Glass substrate 103 Transparent electrode film 104 1st alignment film 105 Liquid crystal layer 106 2nd alignment film 107 Reflective pixel electrode layer 108 Si substrate 110,111 Director direction (pretilt direction)
113 Charged Particles 303 Liquid Crystal Panel Driver

Claims (7)

A first electrode and a second electrode; a liquid crystal layer disposed between the first electrode and the second electrode; a first liquid disposed between the first electrode and the liquid crystal layer; A liquid crystal modulation element including an alignment film, and a second alignment film disposed between the second electrode and the liquid crystal layer;
Control means for applying a first potential and a second potential to the first and second electrodes, respectively, so that the sign of the electric field generated in the liquid crystal layer is periodically reversed, and causing the liquid crystal modulation element to perform a light modulation operation; Have
The control means performs the light modulation operation in the second effective light modulation region when the effective light modulation region in the liquid crystal modulation element is changed from the first effective light modulation region to the second effective light modulation region. Before the start, in the first effective light modulation region, the third and fourth potentials that make the sign of the electric field generated in the liquid crystal layer constant and the difference changes in the in-plane direction of the liquid crystal layer are A liquid crystal display device, characterized by being applied to each of the first and second electrodes. In the in-plane direction of the liquid crystal layer, a region in which the charged particles in the liquid crystal layer are deposited is a first deposition region, and a region in which the charged particles are less deposited than the first deposition region is a second deposition region. When the deposition area
The control means makes the difference between the third and fourth potentials in the second deposition region larger than the difference between the third and fourth potentials in the first deposition region. The liquid crystal display device according to claim 1. When the alignment direction of the liquid crystal in the in-plane direction of the liquid crystal layer is the first direction and the direction different from the first direction is the second direction,
The liquid crystal display device according to claim 1, wherein the control unit changes a difference between the third and fourth potentials in the second direction.   The control means uses the third or fourth potential as an electrode on the alignment film side where the charged particles in the liquid crystal layer are deposited at the interface with the liquid crystal layer among the first and second electrodes. The liquid crystal display device according to claim 1, wherein a potential having a sign different from the sign of the charged particles is applied.   The control means makes the sign of the electric field generated in the liquid crystal layer constant in the first effective light modulation region before applying the third and fourth potentials to the first and second electrodes, and 5. The liquid crystal according to claim 1, wherein fifth and sixth potentials having the same potential in the in-plane direction of the liquid crystal layer are respectively applied to the first and second electrodes. Display device.   The control means uses the fifth or sixth potential as an electrode on the alignment film side where the charged particles in the liquid crystal layer are deposited at the interface with the liquid crystal layer among the first and second electrodes. 6. The liquid crystal display device according to claim 5, wherein a potential having the same sign as that of the charged particles is applied. The liquid crystal display device according to claim 1, wherein the liquid crystal modulation element is a reflective liquid crystal modulation element.