JP2009271243A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the possibility that the images may be deteriorated by charged particles accumulated in liquid crystal elements. <P>SOLUTION: An operation of floating charged particles and an operation of dispersing charged particles in a liquid crystal layer are controlled by determining strengths of electric fields to be applied to a liquid crystal element in accordance with a state of irradiation of light from a light source of a liquid crystal display device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device using a liquid crystal modulation element.

  Conventionally, as a liquid crystal display device using a liquid crystal element, a liquid crystal projector, a liquid crystal display, etc. are known, for example. Examples of the liquid crystal element used in this type of liquid crystal display device include a TN (twisted nematic) liquid crystal element used as a transmissive liquid crystal element and a VAN (vertical alignment nematic) type used as a reflective liquid crystal element. There are liquid crystal elements.

  These liquid crystal elements include a liquid crystal between a first transparent substrate having a transparent electrode (common electrode) and a second transparent substrate having a transparent electrode (pixel electrode) forming a pixel, wiring, a switching element, and the like. It has a structure that encloses. The portion enclosing the liquid crystal is particularly called a liquid crystal layer.

  These liquid crystal elements form images by controlling the polarization state of light passing through the liquid crystal. This utilizes the property that by controlling the voltage between the electrodes of the liquid crystal element, an electric field is generated in the liquid crystal layer, the orientation direction of the liquid crystal molecules is changed, and the polarization state of the passing light is changed.

  However, charged particles are present inside 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 element having an organic alignment film, in addition to drift of charged particles caused by driving the liquid crystal in a high temperature environment, an organic material such as an alignment film, a liquid crystal, or a sealing material is obtained when light enters the liquid crystal element. May be 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.

  If the effective electric field applied to the liquid crystal changes due to the charged particles deposited in a specific region of these liquid crystal layers, the polarization state cannot be controlled as planned, and the quality of the image is deteriorated. End up.

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 element, and a DC voltage is applied to the ion trap electrode so that the ion trap electrode region in the non-display region does not affect image display. A method for adsorbing impurity ions is disclosed.

  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, the quality of image display can be improved by controlling the charged particles inside the liquid crystal 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 element, the manufacturing process of the liquid crystal 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 for attracting ions to the non-display area is newly provided, the manufacturing process 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.

  An object of the present invention is to provide a liquid crystal display device which can avoid the influence of the deposition of charged particles in a liquid crystal layer without adding a new switching unit, ion trap electrode, or the like to the liquid crystal element. To do.

  In order to solve such problems, a liquid crystal display device according to the present invention includes a liquid crystal element having a structure in which liquid crystal is sealed between a first electrode layer and a second electrode layer, and image formation of the liquid crystal element. A first mode in which time-average intensities of electric fields applied to the liquid crystal at a plurality of positions in the plane are substantially equal to each other, or electric fields applied to the liquid crystals at a plurality of positions in the image forming plane of the liquid crystal element. Liquid crystal driving means for controlling a voltage applied to the first electrode layer and the second electrode layer in order to operate the liquid crystal element in a second mode in which the time average intensity is different from each other. And an irradiating means for irradiating the liquid crystal element with light, and a control means for determining an applied intensity of the electric field in the first mode or the second mode according to the light irradiation state of the irradiating means. With features That.

  According to the present invention, since the intensity of the electric field applied to the liquid crystal layer is determined according to the light irradiation state of the irradiation means, the charged particles deposited in the liquid crystal layer are forcibly suspended or diffused. You can make it. For this reason, it is possible to suppress deterioration in image quality due to the influence of charged particles without adding a new configuration such as a switching unit or an ion trap electrode to the liquid crystal element.

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

  A projector will be described as a liquid crystal display device including a liquid crystal element.

FIG. 1 is a diagram illustrating main components of the projector according to the present embodiment.
Reference numeral 101 denotes a control unit for controlling each block of the projector. Reference numeral 102 denotes a data bus through which various signals such as control signals and video signals come and go. Reference numeral 103 denotes an operation unit that receives an operation from the user. A power supply unit 104 controls power supply to each block of the projector.

  An input unit 105 receives a video signal from a PC, a DVD player, a TV tuner, a memory card, or the like. 106 converts the number of pixels of the video signal input from the input unit in accordance with the number of pixels of a liquid crystal panel, which will be described later, and doubles the frame of the input video signal for AC driving of a liquid crystal element, which will be described later. An image processing unit that performs correction suitable for image formation by an element. The image processing unit 106 corrects the gamma characteristic of the input image or corrects the luminance unevenness generated by the optical system.

  Reference numeral 107 forms an image on a liquid crystal element in the liquid crystal unit 108 based on the video signal corrected by the image processing unit. For example, in the case of a projector that uses three liquid crystal elements, the liquid crystal elements are controlled for three colors, and an image for each color is formed on the liquid crystal elements. In this case, light input from the light source 109 described later is separated into three colors, light of each color is supplied to the liquid crystal element corresponding to each color, an optical image for each color is formed, and the optical image is again displayed. These are combined and output to the projection optical system 111 described later. In this embodiment, the liquid crystal element uses, for example, a vertical alignment mode (VAN mode) in which liquid crystal molecules of the liquid crystal layer are aligned substantially perpendicular to the electrode layer.

  Reference numeral 109 denotes a light source that emits light for projecting an image onto a screen (not shown). Reference numeral 110 denotes a light source control unit that controls the on / off operation of the light source 109 and the amount of light. A projection optical system 111 projects an optical image obtained by passing through the liquid crystal unit 108 onto a screen (not shown). Reference numeral 112 denotes an optical system control unit that controls the projection optical system 111 to adjust the zoom, focus, and the like of the projection optical system 111.

  Reference numeral 113 denotes a temperature detection unit arranged in the vicinity of the light source, which measures the temperature related to the light source 109 (performs temperature measurement) and transmits the result to the control unit 101. Reference numeral 114 denotes a timer that is operated by a battery (not shown), and performs a time measurement operation and transmits the result to the control unit 101. Reference numeral 115 denotes an optical sensor that measures (measures) the light reaching the projection optical system, and transmits the result to the control unit 101.

  The control unit 101 uses at least one of the data acquired from the temperature detection unit 113, the timer 114, and the optical sensor 115 to control the projector power supply unit 104, the liquid crystal drive unit 107, the light source control unit 109, and the like. Take control.

  Here, the operation of a normal projector will be described.

  The control unit 101 of the projector according to the present embodiment instructs the power supply unit 104 to supply power to each block when the operation unit 103 is instructed to turn on the power, and puts each block in a standby state. After the power is turned on, the control unit 101 instructs the light source control unit 110 to start light emission from the light source 109. Next, the control unit 101 instructs the optical system control unit 112 to adjust the projection optical system 111. The optical system control unit 112 acquires a distance from a screen (not shown) and automatically controls the projection optical system 111 to control zoom and focus. Further, the optical system control unit 112 may adjust the projection optical system 111 by the operation of the operation unit 103 by the user.

  In this way, the projection is ready. Next, the video signal input from the input unit 105 is converted into a resolution suitable for the liquid crystal unit 108 by the image processing unit 106, and gamma correction and luminance unevenness correction are applied. The video signal corrected by the image processing unit 106 is formed as an image on the liquid crystal unit 108 by the liquid crystal driving unit 107.

  Usually, a liquid crystal element to which a video signal is input employs a line inversion drive method that inverts the positive / negative polarity of an applied electric field for each line of array pixels and switches the polarity at a predetermined cycle such as 60 hertz. 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. This utilizes the property that even if the polarity of the electric field applied to the liquid crystal is reversed, the polarization direction of the light can be changed by changing the orientation direction of the molecules.

  Next, structural examples of the liquid crystal element of the liquid crystal portion 108 will be described with reference to FIGS. In this embodiment, a liquid crystal element used in a reflective liquid crystal projector will be described.

FIG. 2 shows a partial cross-sectional structure of the liquid crystal element.
In FIG. 2, 201 is an AR coat film, 202 is a glass substrate, and 203 is a transparent electrode film (first electrode layer) formed by a transparent electrode formed on the glass substrate 202. Reference numeral 204 denotes a first alignment film disposed between the transparent electrode film 203 and a liquid crystal layer 205 described later.

  Reference numeral 205 denotes a liquid crystal layer disposed between the first alignment film 204 and the second alignment film 206. Reference numeral 207 denotes a reflective pixel electrode layer (second electrode layer) which is disposed to face the transparent electrode film 203 and is formed of a metal such as aluminum. Reference numeral 208 denotes a Si substrate on which the reflective pixel electrode layer 207 is formed. The transparent electrode film 203 and the reflective pixel electrode layer 207 may be collectively referred to as an electrode layer hereinafter.

FIG. 3 is a view of the liquid crystal element as viewed from the glass substrate 202 side.
In FIG. 3, 301 is the director direction (pretilt direction) of the liquid crystal molecules aligned by the alignment film 204, 302 is the director direction (pretilt direction) of the liquid crystal molecules aligned by the alignment film 206, and 303 is the liquid crystal effective on the image forming surface. It is a display area. In the liquid crystal element, when the electric field is applied to the liquid crystal, the tilt of the liquid crystal molecules arranged on the alignment film is tilted several degrees in advance so that the liquid crystal molecules tilt in a predetermined direction. Is called the director direction. The director directions 301 and 302 are both inclined several degrees in the direction perpendicular to the plane of the alignment film, and are mutually contradictory, with respect to the short side 303a and the long side direction 303b of the effective display area 303. Orientation processing is performed in a direction of about 45 degrees.

  During normal operation, in order to form an image on the liquid crystal element, the liquid crystal driving unit 107, for example, keeps the voltage of the transparent electrode film 203 constant (for example, 7 V) and the voltage of the reflective pixel electrode layer 207 to an AC waveform. To. As a result, an alternating electric field is generated between the transparent electrode film 203 and the reflective pixel electrode layer 207. The method for generating the alternating electric field is not limited to this method. An example of the voltage applied to the transparent electrode film 203 and the reflective pixel electrode layer 207 at this time is shown in FIG.

FIG. 4 is a diagram illustrating a state of a voltage applied to the transparent electrode film 203 and the reflective pixel electrode layer 207.
In FIG. 4, 401 is a voltage applied to the transparent electrode film 203, and 402 is a voltage applied to the reflective pixel electrode layer 207. The voltage 402 applied to the reflective pixel electrode layer 207 is an AC voltage having an amplitude of 7 V centered at 7 V and a frequency of 60 Hz. In general, regardless of the polarity of the potential difference between the transparent electrode film 203 and the reflective pixel electrode layer 207, the rate of change in the polarization state of light depends on the absolute value of the potential difference, so that flicker does not occur. The center voltage of the voltage 402 is substantially the same as the voltage 401.

Here, the state of the liquid crystal element when the projector of this embodiment is used for a long time will be described.

  The liquid crystal element 104 is in a state where the temperature has risen for a long time due to irradiation with high-intensity light emitted from the light source. When the liquid crystal molecules are driven in this state, charged particles having a charge travel in the director (pretilt) direction of the liquid crystal molecules along the interface of the alignment film 206 on the reflective pixel electrode 207 side. The charged particles are present in the liquid crystal layer 205 and the sealing material, which is an organic substance around the liquid crystal layer 205, the alignment film interfaces 204 and 206, the electrode layer interfaces 203 and 207, and the like. It will move by driving.

  The charged particles have a characteristic of moving in the tilted direction (alignment direction) of the liquid crystal molecules of the liquid crystal in the image forming surface of the liquid crystal element.

  The charged particles are deposited in the liquid crystal layer 205 at a place depending on the orientation direction such as a corner in the effective display area after the movement. FIGS. 5 and 6 show how charged particles are deposited.

  FIG. 5 shows a partial cross-sectional structure of the liquid crystal element, in which the charged particles are indicated by 501. FIG. 6 is a view of each liquid crystal element as viewed from the glass substrate side. In FIG. 6, the charged particles are indicated by 501.

  When charged particles are deposited in this way, even if a predetermined voltage is applied between the electrodes, the intensity of the electric field applied to the liquid crystal layer is reduced or increased by the charge of the charged particles and is substantially applied to the liquid crystal layer. The electric field will be attenuated or increased. Then, the charged electric particles deposited in a specific region of the liquid crystal layer change the substantial electric field strength applied to the liquid crystal, and the polarization state is not controlled as scheduled, thereby degrading the image quality. The problem occurs.

Thus, in order to avoid the state where the charged particles 501 are deposited, the charged particles deposited in a specific region of the liquid crystal layer are first separated from the electrode layer and then diffused throughout the liquid crystal layer. To. Specifically, when charged particles having a negative charge have been deposited, an electric field is applied from the electrode layer on the side of the deposition toward the opposite electrode layer, Float in the liquid crystal layer. Then, in order to diffuse the charged particles throughout the liquid crystal layer, a voltage lower than the voltage applied to other positions is applied to a position where many charged particles exist,
Diffuse charged particles.

  Therefore, in this embodiment, the liquid crystal driving unit 107 operates the liquid crystal element of the liquid crystal unit 108 as follows.

  In this case, for example, a driving method in which the polarity of the electric field applied to the liquid crystal layer does not change is used instead of the driving method in which the polarity of the electric field applied to the liquid crystal layer is reversed and the polarity is switched at a predetermined cycle (direct current is applied to the liquid crystal layer). Apply a field).

  In order to float the charged particles 501 deposited in the state shown in FIG. 5, the liquid crystal driving unit 107 applies a positive voltage to the transparent electrode film 203 of the liquid crystal element and a negative voltage to the reflective pixel electrode layer 207, for example. Adjust the voltage as follows. Then, the control unit 101 controls the voltage application time by the liquid crystal driving unit 107 to be a predetermined time. As a result, the charged particles 501 having negative charges deposited on the reflective pixel electrode layer 207 side repel the negative voltage applied to the reflective pixel electrode layer 207 and float as shown in FIG. become. The state of the voltage applied to the transparent electrode film 203 and the reflective pixel electrode layer 207 at this time is shown in FIG.

  FIG. 8 is a diagram illustrating a state of a voltage applied to the transparent electrode film 203 and the reflective pixel electrode layer 207. In FIG. 8, 801 indicates a voltage applied to the transparent electrode film 203, and 802 indicates a voltage applied to the reflective pixel electrode layer 207.

  Further, the polarity of the voltage is not limited as long as the voltage applied to the reflective pixel electrode layer 207 is lower than the voltage applied to the transparent electrode film 203. In other words, any voltage that does not substantially change the polarity of the electric field applied to the liquid crystal layer 205 may be used.

  Further, it is only necessary that the time-average strength of the electric field applied to the liquid crystal layer 205 is substantially the same at each of a plurality of positions in the image forming surface of the liquid crystal element.

  In the present embodiment, when an electric field is applied to the reflective pixel electrode layer 207 from the transparent electrode film 203 on an average over time, the voltage applied to the reflective pixel electrode layer 207 is temporarily changed to the transparent electrode film 203. The voltage applied to may be exceeded.

  Thus, the charged particles 501 in the liquid crystal layer 205 can be suspended by the driving mode (first mode) in which an electric field is applied.

  Next, an operation for diffusing the suspended charged particles 501 will be described.

  In order to diffuse the suspended charged particles 501, the liquid crystal driving unit 107 causes the electrodes to attract the charged particles 501 in a diagonal direction opposite to the diagonal on which the suspended charged particles 501 are deposited. Apply voltage to the layer. Therefore, for example, the voltage of the reflective pixel electrode layer 207 is changed depending on the display position of the liquid crystal element, and the charged particles 501 are moved by Coulomb force by applying the voltage for a predetermined time.

  The case where the voltage applied to the transparent electrode film 203 is constant at about 7 V and the voltage applied to the reflective pixel electrode layer 207 is constant will be described. FIG. 9 is a diagram showing a distribution of voltages applied to the reflective pixel electrode layer 207.

  In FIG. 9, a portion where the voltage applied to the reflective pixel electrode layer 207 is high is expressed in white, and a portion where the voltage is low is expressed in black. The positions 901 and 902 in FIG. 9 are positions where the amount of the charged particles 501 is large, and the positions 903 and 904 are positions where the amount of the charged particles 501 is small. Therefore, when the polarity of the charged particles 501 is negative, a positive voltage is applied to the reflective pixel electrode layer 207 at the positions 903 and 904 to attract the charged particles 501.

  In FIG. 9, the voltage applied to the position 905 is low, the voltage applied to the position 907 is high, the voltage applied to the position 906 is larger than the voltage applied to the position 905, and the voltage applied to the position 907. It becomes a smaller value.

  In the present embodiment, the voltage applied to the reflective pixel electrode layer 207 has been described as a constant value, but this may be an irregularly varying voltage or an alternating voltage. In other words, the integral value of the electric field strength applied to the liquid crystal at the position 905 should be smaller than the integral value of the electric field strength applied to the liquid crystal at the positions 906 and 907, and the integral of the electric field strength applied to the liquid crystal at the position 907. It is sufficient that the value is larger than the integral value of the electric field strength applied to the liquid crystal at the positions 905 and 906. FIG. 10 shows voltages applied to the reflective pixel electrode layer 207 at positions 905 to 907. In this embodiment, a case where the voltage applied to the reflective pixel electrode layer 207 is a constant voltage will be described.

  FIG. 10 is a diagram illustrating a voltage applied to the reflective pixel electrode layer 207 for each display position of the liquid crystal element. 10, 1001 indicates the voltage of the reflective pixel electrode layer 207 at the position 907, 1002 indicates the voltage of the reflective pixel electrode layer 207 at the position 906, and 1003 indicates the reflective pixel electrode layer 207 at the position 905. Indicates the voltage. Reference numeral 1004 denotes a voltage applied to the transparent electrode film 203.

  The liquid crystal element of this embodiment does not transmit light when, for example, the voltage applied to the transparent electrode film 203 is 7 V and the voltage applied to the reflective pixel electrode layer 207 is 7 V (a state where almost no electric field is generated). Suppose that It is assumed that the liquid crystal element transmits most of light in a certain polarization direction when the voltage applied to the reflective pixel electrode layer 207 is 14V. Then, an image having a pattern as shown in FIG. 9 is formed on the liquid crystal element.

  In addition, when the voltage applied to the position 905 is 0 V, the liquid crystal element transmits light in a certain polarization direction, and thus becomes bright. Therefore, an image having a pattern in which the position of 905 becomes bright, the position of 906 becomes dark, and the position of 907 becomes bright again can be formed.

  When the voltage applied to the reflective pixel electrode layer 207 at the position 907 is 7 V, the liquid crystal element does not transmit light and therefore becomes dark. Therefore, an image having a pattern in which the position 905 becomes bright, the position 906 becomes light and the position 907 becomes dark can be formed.

  Further, the time-average intensity of the electric field applied to the liquid crystal may be different from each other at each of a plurality of positions in the image forming surface of the liquid crystal element. Thus, the charged particles 501 in the liquid crystal layer 205 can be diffused by the driving mode (second mode) in which an electric field is applied.

  By applying such a voltage to the reflective pixel electrode layer 207, the electric field applied to the liquid crystal layer 205 can be controlled to float and diffuse the charged particles 501 having a negative charge. It is possible to suppress the deterioration of quality.

  In this embodiment, an example in which the charged particles have a negative charge has been described. However, charged particles having a positive charge may be deposited on the transparent electrode layer 203 side. Needless to say, even when charged particles having a positive charge are deposited, the charged particles can be floated and diffused by changing the polarity in the same manner as in this embodiment.

  Next, among the operations of the projector described above, control of the operation for floating the charged particles 501 and the operation for diffusing the charged particles 501 will be described with reference to FIGS. 1 and 11 to 15. In this embodiment, each operation according to the state of the light source is performed in order to reduce the possibility that each pattern image which is formed on the liquid crystal element for diffusion and is unnecessary for the user will be visually recognized due to floating. Is controlling. In this embodiment, the operation for floating the charged particles 501 of the liquid crystal element is referred to as “floating operation”, and the operation for diffusing the charged particles 501 is referred to as “diffusion operation”. Also in this embodiment, it is assumed that the charged particles 501 have a negative charge.

  FIG. 11 is a flowchart for explaining control of the floating operation and the diffusion operation of the projector according to the present embodiment.

  First, in response to an instruction to turn on the power by the operation unit 103, the control unit 101 instructs the power supply unit 104 to supply power to each block of the projector. Then, the control unit 101 reads from the timer 114 the time ta from when the power was last turned off until the present time (S1101).

  Then, the control unit 101 determines whether or not the read time ta is longer than the stop time t1 (for example, about 5 minutes) (S1102).

  If the read time ta is longer than the stop time t1 (Yes in S1102), a sufficient time has passed from the projector power-off to power-on again, so that the light source 109 is completely turned on from the power-on. Takes some time. If the read time ta is shorter than the stop time t1 (No in S1102), since almost no time has passed from the power-off of the projector to the power-on again, the light source 109 is completely turned on from the power-on. There is almost no time until.

  In this embodiment, the state of the light source 109 is estimated from the time obtained by the timer 114, and the electric field applied to the liquid crystal layer 205 of the liquid crystal element during the floating operation and the diffusing operation is controlled.

  When the read time ta is longer than the stop time t1 (Yes in S1102), the control unit 101 first resets the timer 114 to measure the time from power ON (S1103). When the control unit 101 causes the liquid crystal driving unit 107 to perform a floating operation, the upper limit value of the potential difference (potential difference between the transparent electrode film 203 and the reflective pixel electrode layer 207) applied to the liquid crystal layer 205 is set to V1 ( For example, an instruction to set to 4V) is issued (S1104). When the upper limit value of the potential difference applied to the liquid crystal layer 205 is set to 4V, the liquid crystal driving unit 107 sets the voltage of the reflective pixel electrode layer 207 from 3V, assuming that the voltage of the transparent electrode film 203 is a constant voltage of 7V. It can be controlled in the range of 11V.

  Here, when the upper limit value of the potential difference applied to the liquid crystal layer 205 is set to V1, it can be controlled by setting the upper limit value in the DA converter of the liquid crystal driving unit 107. The upper limit value of the potential difference applied to the liquid crystal layer 205 can also be controlled by changing the correction setting of the gamma correction unit of the liquid crystal driving unit 107. The same applies to the following embodiments.

  Subsequently, the control unit 101 instructs the liquid crystal driving unit 107 to perform a floating operation (S1105).

  The liquid crystal driving unit 107 instructed to perform the floating operation by the control unit 101 controls the voltage of the transparent electrode film 203 and the reflection pixel electrode layer 207 in order to control the electric field applied to the liquid crystal layer 205 of the liquid crystal element. Control the voltage. At this time, since the charged particles 501 are deposited on the reflective pixel electrode layer 207, for example, the voltage of the transparent electrode film 203 is set to 7V and the voltage of the reflective pixel electrode layer 207 is set to 3V. This is because the potential difference applied to the liquid crystal layer 205 is set to the previously set value V1 (here, 4V).

  Then, the control unit 101 sequentially receives the time information measured by the timer 114, and determines whether or not the floating operation time At2 (for example, 8 seconds after the power is turned on) has elapsed since the power is turned on (for example, 8 seconds). S1106). When it is determined that the time t2 after the power is turned on has passed the floating operation time At2, the control unit 101 causes the upper limit of the potential difference applied to the liquid crystal layer 205 when the liquid crystal driving unit 107 performs the diffusion operation. An instruction is issued to set the value to V2 (for example, 4V) (S1107).

  Subsequently, the control unit 101 instructs the liquid crystal driving unit 107 to perform a diffusion operation (S1108).

  The liquid crystal driving unit 107 instructed to perform the diffusion operation by the control unit 101 controls the voltage of the transparent electrode film 203 and the reflection pixel electrode layer 207 in order to control the electric field applied to the liquid crystal layer 205 of the liquid crystal element. Control the voltage. At this time, for example, the voltage of the transparent electrode film 203 is set to 7V. Then, since the charged particles 501 have a negative charge, the voltage at the position where the charged particles 501 of the reflective pixel electrode layer 207 should be attracted is 11V, and the voltage at the position where the charged particles 501 should be separated is 7V. To do. This is because the potential difference applied to the liquid crystal layer 205 is set to the previously set value V2 (4V in this case), so that the voltage at the position to be attracted where the most potential difference occurs is higher than the voltage of the transparent electrode film 203. This is because the value is increased by V2.

  An example of a pattern image generated on the liquid crystal element at this time is shown in FIG. FIG. 12 is an example of a pattern image generated in the liquid crystal element when the upper limit value of the potential difference applied to the liquid crystal layer 205 is V2.

  In addition, the voltage at the position where the charged particles 501 of the reflective pixel electrode layer 207 should be attracted may be 11V, and the voltage at the position where the charged particles 501 should be separated may be 3V. Alternatively, the voltage at the position where the charged particles 501 of the reflective pixel electrode layer 207 should be attracted may be 7V, and the voltage at the position where the charged particles 501 should be separated may be 3V. When the voltage applied to the reflective pixel electrode layer 207 is changed, a pattern image different from the pattern image shown in FIG. 12 is obtained, but the brightness at the brightest position is not substantially changed.

  Then, the control unit 101 sequentially receives the time information measured by the timer 114, and determines whether or not the diffusion operation time At3 (for example, 12 seconds after the power is turned on) has elapsed since the power is turned on (for example, 12 seconds). S1109).

  When it is determined that the time t3 after the power is turned on has passed the diffusion operation time At3, the control unit 101 sets the upper limit of the potential difference applied to the liquid crystal layer 205 when the liquid crystal driving unit 107 performs the diffusion operation. An instruction is issued to set the value to V3 (for example, 3V) (S1110).

  Here, the light source 109 starts to brighten gradually when a diffusion operation time At3 (for example, 12 seconds) elapses after the power is turned on. In addition, the liquid crystal element of this embodiment becomes easier to transmit light as the potential difference applied to the liquid crystal layer 205 is larger. At this time, if the potential difference applied to the liquid crystal layer 205 is about V2, there is a high possibility that the difference between light and dark will be visible to the user when light transmitted through the liquid crystal is projected onto the screen.

  Therefore, by changing the upper limit value of the potential difference applied to the liquid crystal layer 205 to V3 which is smaller than V2, the difference in brightness is reduced so that it is difficult for the user to visually recognize.

  When the upper limit value of the potential difference applied to the liquid crystal layer 205 is changed from V 2 to V 3 by the control unit 101, the liquid crystal driving unit 107 controls the voltage of the transparent electrode film 203 and the voltage of the reflective pixel electrode layer 207. . Then, the voltage at the position where the charged particles 501 of the reflective pixel electrode layer 207 should be attracted is changed from 11V to 10V. This is because the potential difference applied to the liquid crystal layer 205 is set to the previously set value V3 (here, 3V). This is because the value is increased by V3.

  An example of a pattern image generated on the liquid crystal element at this time is shown in FIG. FIG. 13 is an example of a pattern image generated in the liquid crystal element when the upper limit value of the potential difference applied to the liquid crystal layer 205 is V3. Compared with the brightness at the brightest position in FIG. 12, the brightness at the brightest position in FIG. 13 is darker, and the difference in brightness in the display surface is smaller than in FIG.

  In addition, the voltage at the position where the charged particles 501 of the reflective pixel electrode layer 207 should be attracted may be 10V, and the voltage at the position where the charged particles 501 should be separated may be 4V. Alternatively, the voltage at the position where the charged particles 501 of the reflective pixel electrode layer 207 should be attracted may be 7V, and the voltage at the position where the charged particles 501 should be separated may be 4V. When the voltage applied to the reflective pixel electrode layer 207 is changed, a pattern image different from the pattern image shown in FIG. 13 is obtained, but the brightness at the brightest position is not substantially changed. The difference in brightness is smaller than that of the pattern image.

  Then, the control unit 101 sequentially receives the time information measured by the timer 114, and determines whether or not the diffusion operation time Bt4 (for example, 16 seconds from the power-on) has elapsed since the power-on. S1111). When it is determined that the time t after the power is turned on has passed the diffusion operation time Bt4, the control unit 101 sets the upper limit of the potential difference applied to the liquid crystal layer 205 when the liquid crystal driving unit 107 performs the diffusion operation. An instruction is issued to set the value to V4 (for example, 2V) (S1112).

  Here, the light source 109 starts to become brighter when a diffusion operation time Bt4 (for example, 16 seconds) elapses after the power is turned on. At this time, if the potential difference applied to the liquid crystal layer 205 is about V3, when light transmitted through the liquid crystal is projected onto the screen, there is a high possibility that the difference in brightness will be visible to the user. Therefore, by changing the upper limit value of the potential difference applied to the liquid crystal layer 205 to V4 that is smaller than V3, the difference in brightness is reduced so that the user can hardly see it.

  When the upper limit value of the potential difference applied to the liquid crystal layer 205 is changed from V3 to V4 by the control unit 101, the liquid crystal driving unit 107 controls the voltage of the transparent electrode film 203 and the voltage of the reflective pixel electrode layer 207. . Then, the voltage at the position where the charged particles 501 of the reflective pixel electrode layer 207 should be attracted is changed from 10V to 9V. This is because the potential difference applied to the liquid crystal layer 205 is set to the previously set value V4 (here, 2V), so that the voltage at the position where the potential difference is most likely to be generated is higher than the voltage of the transparent electrode film 203. This is because the value is increased by V4.

  An example of a pattern image generated on the liquid crystal element at this time is shown in FIG. FIG. 14 is an example of a pattern image generated in the liquid crystal element when the upper limit value of the potential difference applied to the liquid crystal layer 205 is V4. Compared to the brightness at the brightest position in FIGS. 12 and 13, the brightness at the brightest position in FIG. 14 is darker, and the difference in brightness in the display surface is smaller than that in FIGS. 12 and 13.

  In addition, the voltage at the position where the charged particles 501 of the reflective pixel electrode layer 207 should be attracted may be 9V, and the voltage at the position where the charged particles 501 should be separated may be 5V. Alternatively, the voltage at the position where the charged particles 501 of the reflective pixel electrode layer 207 should be attracted may be 7V, and the voltage at the position where the charged particles 501 should be separated may be 5V. When the voltage applied to the reflective pixel electrode layer 207 is changed, a pattern image different from the pattern image shown in FIG. 14 is obtained, but the brightness at the brightest position is not substantially changed. The difference in brightness is smaller than that of the pattern image of FIG.

  Next, the control unit 101 sequentially receives the time information measured by the timer 114, and determines whether or not the diffusion operation time Ct5 (for example, 22 seconds from the power-on) has elapsed since the power-on. (S1113). When it is determined that the diffusion operation time Ct5 has elapsed after the power-on time t, the control unit 101 instructs the liquid crystal drive unit 107 to stop the diffusion operation (S1114).

  Here, when a diffusion operation time Ct4 (for example, 22 seconds) elapses after the power is turned on, a sufficient time has elapsed for the diffusion of the charged particles 501 of the liquid crystal element, and thus the diffusion operation is terminated. Then, the control unit 101 instructs the liquid crystal driving unit 107 to operate the liquid crystal unit 108 as usual (S1115).

  Then, the projector is used in a normal usage form by the user.

  Next, after projecting a normal image, the control unit 101 instructs the power supply unit 104 to supply power to each block of the projector in response to a power-off instruction from the operation unit 103 (S1116). Out. Then, the control unit 101 resets the timer 114, measures the time since the power is turned off (S1117), and ends the operation of the projector.

  Here, a case where the read time ta is longer than the stop time t1 (No in S1102) will be described. First, the control unit 101 resets the timer 114 to measure the time from power ON (S1118). When the control unit 101 causes the liquid crystal driving unit 107 to perform a floating operation, the upper limit value of the potential difference (potential difference between the transparent electrode film 203 and the reflective pixel electrode layer 207) applied to the liquid crystal layer 205 is set to V5 ( For example, an instruction to set to 1V) is issued (S1119).

  At this time, it is desirable to set the upper limit value V5 to a potential difference such that the pattern image is hardly visible to the user even if the light source is completely lit. The application time is preferably set longer because the potential difference is small.

  Subsequently, the control unit 101 instructs the liquid crystal driving unit 107 to perform a floating operation (S1120).

  The liquid crystal driving unit 107 instructed to perform the floating operation by the control unit 101 controls the voltage of the transparent electrode film 203 and the reflection pixel electrode layer 207 in order to control the electric field applied to the liquid crystal layer 205 of the liquid crystal element. Control the voltage. At this time, since the charged particles 501 are deposited on the reflective pixel electrode layer 207, for example, the voltage of the transparent electrode film 203 is set to 7V and the voltage of the reflective pixel electrode layer 207 is set to 6V.

  Then, the control unit 101 sequentially receives the time information measured by the timer 114, and determines whether or not the floating operation time Bt6 (for example, 30 seconds from the power ON) has elapsed since the power ON. S1121). When it is determined that the floating operation time Bt6 has elapsed from the time when the power is turned on, the control unit 101 causes the upper limit of the potential difference applied to the liquid crystal layer 205 when the liquid crystal driving unit 107 performs the diffusion operation. An instruction is issued to set the value to V6 (for example, 1V) (S1122).

  Subsequently, the control unit 101 instructs the liquid crystal driving unit 107 to perform a diffusion operation (S1123).

  The liquid crystal driving unit 107 instructed to perform the diffusion operation by the control unit 101 controls the voltage of the transparent electrode film 203 and the reflection pixel electrode layer 207 in order to control the electric field applied to the liquid crystal layer 205 of the liquid crystal element. Control the voltage. At this time, for example, the voltage of the transparent electrode film 203 is set to 7V. Then, since the charged particles 501 have a negative charge, the voltage at the position where the charged particles 501 of the reflective pixel electrode layer 207 should be attracted is set to 8V, and the voltage at the position where the charged particles 501 should be separated is set to 7V. To do. This is because the potential difference applied to the liquid crystal layer 205 is set to the previously set value V6 (here, 1 V). This is because the value is increased by V6. At this time, the upper limit value V6 is set to a potential difference such that the pattern image is hardly visible to the user even if the light source is completely lit.

  An example of the pattern image generated on the liquid crystal element at this time is shown in FIG. FIG. 15 is an example of a pattern image generated in the liquid crystal element when the upper limit value of the potential difference applied to the liquid crystal layer 205 is V6.

  In addition, the voltage at the position where the charged particles 501 of the reflective pixel electrode layer 207 should be attracted may be 8V, and the voltage at the position where the charged particles 501 should be separated may be 6V. Alternatively, the voltage at the position where the charged particles 501 of the reflective pixel electrode layer 207 should be attracted may be 7V, and the voltage at the position where the charged particles 501 should be separated may be 6V. When the voltage applied to the reflective pixel electrode layer 207 is changed, a pattern image different from the pattern image shown in FIG. 15 is obtained, but the brightness at the brightest position is substantially unchanged.

  Next, the control unit 101 sequentially receives time information measured by the timer 114, and determines whether or not the diffusion operation time Dt7 (for example, 40 seconds from the power-on) has elapsed since the power-on. (S1124). If it is determined that the diffusion operation time Dt7 has elapsed after the power is turned on, the process proceeds to S1114.

  As described above, the projector of this embodiment estimates the state of the light source from the information obtained by the timer 114, and controls the electric field applied to the liquid crystal layer 205 in the floating operation and the diffusion operation. By controlling in this way, the projector according to the present embodiment can reduce the possibility that the user can visually recognize the pattern image generated in the liquid crystal element in accordance with the floating operation and the diffusing operation.

  In the present embodiment, the state of the light source is estimated from the information obtained by the timer 114. In addition to this, the temperature of the light source is estimated from the information obtained by the temperature detection unit 113, and the state of the light source is estimated. You may perform the operation | movement according to 11 flows.

  In this case, in S1102 of FIG. 11, the control unit 101 determines whether the temperature T of the light source obtained by the temperature detection unit 113 is lower than the stop temperature T1. Thereby, it is possible to estimate whether or not the light source 109 of the projector is ready to be completely turned on.

  In S1106 of FIG. 11, the control unit 101 determines whether or not the temperature T of the light source obtained by the temperature detection unit 113 is higher than the floating operation temperature AT2. This makes it possible to determine whether or not the floating operation has been performed for a sufficient time.

  Similarly, in S1109, S1111, S1113, S1121, and S1124 in FIG. 11, the control unit 101 determines whether the temperature T of the light source obtained by the temperature detection unit 113 is higher than the predetermined temperature in each step. Determine whether. Thereby, it can be determined whether the lighting state of the light source 109 has reached a predetermined state.

  Further, it may be determined by the timer 114 whether or not the floating operation and the diffusion operation are sufficiently performed.

  In addition, the state of the light source may be estimated from the information obtained from the light sensor 115 with respect to the light amount of the light source, and the operation according to the flow of FIG. 11 may be performed.

  In this case, in S1102 of FIG. 11, the control unit 101 determines whether or not the light amount P obtained by the optical sensor 115 is lower than the stop temperature P1. Thereby, it is possible to estimate whether or not the light source 109 of the projector is immediately completely turned on.

  In S1106 of FIG. 11, the control unit 101 determines whether or not the light amount P obtained by the optical sensor 115 is larger than the floating operation light amount AP2. This makes it possible to determine whether or not the floating operation has been performed for a sufficient time.

  Similarly, in S1109, S1111, S1113, S1121, and S1124 of FIG. 11, the control unit 101 determines whether or not the light amount P obtained by the optical sensor 115 is greater than the predetermined light amount in each step. To do. Thereby, it can be determined whether the lighting state of the light source 109 has reached a predetermined state.

  Further, it may be determined by the timer 114 whether or not the floating operation and the diffusion operation are sufficiently performed.

  In addition, the state of the light source may be estimated by combining the information obtained by the temperature detection unit 113, the information obtained by the timer 114, and the information obtained by the optical sensor 115.

  Further, the optical sensor 115 may measure the amount of light or the light flux.

  In this embodiment, the case where the voltage applied to the transparent electrode film 203 is constant and the voltage applied to the reflective pixel electrode layer 207 is constant is described. However, this is a voltage that fluctuates irregularly. Alternatively, an AC voltage may be used. In this embodiment, since the electric field applied to the liquid crystal layer 205 is controlled by controlling the potential difference between the transparent electrode film 203 and the reflective pixel electrode layer 207, a constant voltage is not necessarily applied. There is no need.

  In this embodiment, the projector has been described. However, any display device having a liquid crystal element can be applied to, for example, a liquid crystal television, a liquid crystal display, a digital camera, a portable game machine, and a mobile phone.

(Other examples)
Embodiments 1 and 2 are for a vertical alignment mode liquid crystal modulation element, but the applied voltage control of the above embodiment is in a form suitable for TN, STN, OCB type liquid crystal modulation elements other than the vertical alignment mode. It may be modified and applied to these liquid crystal modulation elements. Further, the present invention may be carried out by modifying the form suitable for a transmissive liquid crystal modulation element.

  It goes without saying that the object of the present invention can also be achieved by supplying a storage medium storing software program codes for realizing the functions of the above-described embodiments to the apparatus. At this time, the computer (or CPU or MPU) including the control unit of the supplied apparatus reads and executes the program code stored in the storage medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code itself and the storage medium storing the program code constitute the present invention.

  As a storage medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  Further, the OS (basic system or operating system) running on the apparatus performs part or all of the processing based on the instruction of the program code described above, and the functions of the above-described embodiments are realized by the processing. Needless to say, cases are also included.

  Further, the program code read from the storage medium may be written into a memory provided in a function expansion board inserted into the apparatus or a function expansion unit connected to the computer, and the functions of the above-described embodiments may be realized. Needless to say, it is included. At this time, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

It is a block diagram of a projector to which the present invention is applied. It is the figure which showed the cross section of the liquid crystal element. It is the figure which showed the pretilt direction of the display surface of a liquid crystal element. It is the figure which showed the voltage applied to a transparent electrode film and a reflective pixel electrode layer. It is the figure which showed a mode that the charged particle deposited on the liquid crystal element. It is the figure which showed a mode that the charged particle deposited on the liquid crystal element. It is the figure which showed a mode that the charged particle floated in the liquid crystal layer. It is the figure which showed the voltage applied to a transparent electrode film and a reflective pixel electrode layer. It is the figure which showed distribution of the voltage applied to a reflective pixel electrode layer. It is a figure which shows the voltage applied to the reflective pixel electrode layer for every display position of a liquid crystal element. It is a flowchart for demonstrating control of floating operation | movement and spreading | diffusion operation | movement. It is the figure which showed an example of the pattern image produced | generated by a liquid crystal element. It is the figure which showed an example of the pattern image produced | generated by a liquid crystal element. It is the figure which showed an example of the pattern image produced | generated by a liquid crystal element. It is the figure which showed an example of the pattern image produced | generated by a liquid crystal element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Control part 102 Data bus 103 Operation part 104 Power supply part 105 Input part 106 Image processing part 107 Liquid crystal drive part 108 Liquid crystal part 109 Light source 110 Light source control part 111 Projection optical system 112 Optical system control part 113 Temperature detection part 114 Timer 115 Optical sensor

Claims (8)

A liquid crystal element having a structure in which liquid crystal is sealed between the first electrode layer and the second electrode layer;
After the first mode in which the time average strength of the electric field applied to the liquid crystal is substantially the same at each of a plurality of positions in the image forming surface of the liquid crystal element, each of the plurality of positions in the image forming surface of the liquid crystal element is Voltage applied to the first electrode layer and the second electrode layer in order to operate the liquid crystal element in the second mode in which the time average strength of the electric field applied to the liquid crystal is different from each other. Liquid crystal driving means for controlling
An irradiation means for irradiating the liquid crystal element with light;
A liquid crystal display device comprising: control means for determining an electric field strength applied to the liquid crystal layer in the first mode or the second mode according to the light irradiation state of the irradiation means.   The liquid crystal display device according to claim 1, wherein the control unit determines an application time of the electric field in the first mode or the second mode according to a light irradiation state of the irradiation unit. The control means includes a time until the charged particles deposited on the first electrode layer or the second electrode layer in the liquid crystal layer float in the liquid crystal layer, and the liquid crystal element in the first mode. Controlling the liquid crystal driving means to operate,
The control means includes a time until the charged particles in the liquid crystal layer move in a direction different from the direction in which the liquid crystal molecules of the liquid crystal are inclined in the image forming surface of the liquid crystal element, and the second mode. The liquid crystal display device according to claim 1, wherein the liquid crystal driving means is controlled to operate the liquid crystal element.   In the second mode, the time average intensities of the electric fields applied to the liquid crystal at a plurality of positions in directions different from the pretilt direction of the liquid crystal molecules of the liquid crystal in the image forming plane of the liquid crystal element are mutually 4. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is in a different mode. Having time measuring means for measuring the time associated with the irradiation means;
5. The liquid crystal display device according to claim 1, wherein the control unit determines a light irradiation state of the irradiation unit from information obtained by the time measuring unit. Having temperature measuring means for measuring the temperature associated with the irradiating means;
6. The liquid crystal display device according to claim 1, wherein the control unit determines a light irradiation state of the irradiation unit from information obtained by the temperature measurement unit. Photometric means for measuring the light emitted by the irradiation means,
The liquid crystal display device according to claim 1, wherein the control unit determines a light irradiation state of the irradiation unit from information obtained by the photometry unit.   8. The liquid crystal element according to claim 1, wherein liquid crystal molecules of the liquid crystal are aligned substantially perpendicular to the first electrode layer and the second electrode layer. 9. Liquid crystal display device.

Images