JP2013020064A - Image display device and adjustment method of the same - Google Patents

Abstract

An image display apparatus including a driving circuit and using a liquid crystal display element that performs liquid crystal display at a lower applied voltage than that of the prior art, and a cost reduction method, and an adjustment method thereof are provided.
The liquid crystal molecules have initial alignment of liquid crystal molecules formed when no voltage is applied or a low voltage is applied, final alignment of liquid crystal molecules formed when a maximum voltage is applied, and the maximum voltage. An image display device comprising a liquid crystal display element that is displaced to an intermediate alignment of liquid crystal molecules formed when an intermediate voltage lower than the low voltage is applied, wherein the intermediate alignment is used for retardation of liquid crystal molecules. On the other hand, phase compensation means for providing retardation for displaying black or white is provided.
[Selection] Figure 1

Description

  The present invention relates to an image display apparatus, for example, an image display apparatus suitable for a projector that enlarges and projects a small liquid crystal display element onto a projection object, and an adjustment method thereof.

  Conventionally, various types of liquid crystal display elements that switch light using nematic liquid crystals have been proposed and used. In general, a twisted nematic liquid crystal display element is used in which the rubbing directions of the counter substrate sandwiching the liquid crystal are orthogonal to each other. A liquid crystal display element in which the rubbing directions of the counter substrate are the same as each other and the splay alignment (FIG. 9A) is exhibited is also conventionally known.

  In a liquid crystal display element exhibiting such a splay alignment, since all liquid crystal molecules do not have a flow of liquid crystal molecules in the same direction, the response speed of the liquid crystal is slow. Therefore, by applying a voltage, the liquid crystal alignment state is changed to the initial bend alignment (FIG. 9B) so that all liquid crystal molecules have the flow of liquid crystal molecules in the same direction. To do. Such a “π cell” with improved response speed was announced by Bos et al.

  In this “π cell”, that is, an OCB type liquid crystal display element, nematic liquid crystal is injected, and the response speed is much faster than that of the TN type liquid crystal, and responds to the modulation state in about 1 to 3 milliseconds. Therefore, since the display image can be faithfully reproduced, there is an effect that the image can be displayed while maintaining sharpness in the display of the moving image. Further, a normal liquid crystal projector uses three liquid crystal display elements for displaying red, green, and blue, and displays a full color image by color-combining the modulated images.

However, when an OCB type liquid crystal display element is used, since the response speed of modulation is fast, it is possible to perform field sequential display in which red, green, and blue images are time-divided and sequentially modulated and displayed. Thus, a full color image can be displayed with only a single liquid crystal display element. However, the OCB type liquid crystal operates in normally white (displaying white in a low voltage application state or no voltage application state), and the liquid crystal molecules at the interface between the two opposing substrates sandwiching the liquid crystal are Has a pretilt angle. For this reason, there is a problem that even if a voltage is applied, the liquid crystal molecules cannot be displaced perpendicularly to the substrate and the contrast cannot be increased.

  In addition, since the OCB type liquid crystal display element has a strong van der Waals force, a high voltage of 10 V or more must be applied to displace the liquid crystal molecules perpendicularly to the substrate. Regarding the former contrast problem, it is known to arrange a phase compensation plate in the OCB type liquid crystal display element (Patent Document 1).

JP 2001-117100 A

  However, although an improvement in contrast can be realized by arranging a phase compensation plate in the OCB type liquid crystal, no improvement has been made in that it is necessary to apply a voltage of 10 V or more with respect to the operating voltage. As a problem in actual use, in order to apply a driving voltage of 10 V or higher, a driving circuit for operating a transistor that can withstand a high voltage operation of 10 V or higher is required. For example, when the display image conforms to the NTSC standard of 60 Hz, it can be driven using a high voltage compatible transistor.

  Here, when performing field sequential display in which red, green, and blue images are time-divided and sequentially modulated and displayed, an image display of 180 Hz (about 5.5 milliseconds) that is three times 60 Hz is required. . In this case, although the liquid crystal operation itself can respond because the response speed is about 1 to 3 milliseconds, a situation occurs in which the transistor of the drive circuit cannot respond. Furthermore, in order to prevent the occurrence of a color breakup phenomenon (a phenomenon in which the color of a display image appears to be broken when the line of sight is moved) due to field sequential display, the following image display is required.

  That is, when one image is displayed twice in red, green, and blue twice, it is necessary to display an image at 360 Hz (about 2.8 milliseconds), which is twice 180 Hz. In this case, a general high-voltage compatible transistor cannot respond, and it becomes difficult to display an image. In addition, there is a method in which a high-speed operation and a high breakdown voltage transistor are used by using a special semiconductor formation film. However, in this case, since it is essential to use an expensive semiconductor process, the liquid crystal display element itself becomes very expensive.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image display device including a driving circuit and a method for adjusting the image display device that can reduce the cost by a liquid crystal display element capable of performing liquid crystal display at a lower applied voltage than in the past.

  In order to achieve the above object, the typical configuration of the image display device according to the present invention is that the liquid crystal molecules are initially applied with no voltage, or when a low voltage is applied, the initial alignment of the liquid crystal molecules and the maximum voltage. And a liquid crystal display element that is displaced to an intermediate alignment of liquid crystal molecules formed when an intermediate voltage lower than the maximum voltage and higher than the low voltage is applied. The image display device is characterized in that phase compensation means for providing a retardation for performing black display or white display with respect to the retardation of the liquid crystal molecules in the intermediate orientation is provided.

  In addition, a typical configuration of the adjustment method of the image display device according to the present invention is that the liquid crystal molecules are applied with no initial voltage or when the initial voltage of the liquid crystal molecules formed when a low voltage is applied and the maximum voltage is applied. An image display comprising a final alignment of liquid crystal molecules that are sometimes formed and a liquid crystal display element that is displaced to an intermediate alignment of liquid crystal molecules that is formed when an intermediate voltage lower than the maximum voltage and higher than the low voltage is applied. An apparatus adjustment method comprising the step of adjusting phase compensation means so as to give a retardation for performing black display or white display with respect to the retardation of the liquid crystal molecules in the intermediate alignment.

  ADVANTAGE OF THE INVENTION According to this invention, the image display apparatus which can display an image with a high contrast with a lower applied voltage compared with the past, and its adjustment method can be provided.

(A) is a figure which shows the reflectance characteristic with respect to the voltage application of the OCB type liquid crystal display element at the time of not providing a phase compensation board, (b) is embodiment of this invention when a phase compensation board is arranged. It is a figure which shows the reflectance characteristic with respect to the voltage application of the OCB type liquid crystal display element which concerns. (A), (b) is the schematic explaining the splay alignment state and initial bend alignment state of OCB type liquid crystal in the embodiment of the present invention. (A), (b) is the perspective view and top view of a liquid crystal display element which are used for embodiment of this invention. 1 is a perspective view of a configuration of an image display apparatus according to an embodiment of the present invention. It is a block block diagram of the control driver used for embodiment of this invention. It is a figure explaining a field sequential display. Regarding the alignment of the OCB liquid crystal according to the embodiment of the present invention, (a) shows the initial bend alignment (initial alignment) of the OCB type liquid crystal, and (b) shows the intermediate bend alignment (intermediate alignment). Regarding the orientation of the conventional OCB type liquid crystal, (a) is a diagram showing initial bend orientation (initial orientation), (b) is a diagram showing intermediate bend orientation (intermediate orientation), and (c) is vertical bend orientation (final orientation). FIG. It is the schematic explaining the spray alignment state of the conventional OCB type liquid crystal, and an initial bend alignment state.

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

<< First Embodiment >>
Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the image projection apparatus will be described, and then the OCB type liquid crystal will be described.

(Image projection device)
1) Overall Configuration An image projection apparatus according to this embodiment will be described with reference to FIG. FIG. 4 is a main configuration perspective view of the image projection apparatus. The LEDs used as light sources are three RGB LEDs corresponding to the three primary colors of red, green and blue. 1R is an LED light source for R color, 1G is an LED light source for G color, and 1B is an LED light source for B color. is there. Light emitted from the RGB LEDs is converted into a substantially parallel light flux by the R color collimator lens 2R, the G color collimator lens 2G, and the B color collimator lens 2B, and enters the cross dichroic prism 3. .

  The cross dichroic prism 3 has a characteristic of transmitting G color light, and has a characteristic of reflecting the R color and the B color by a dichroic film arranged in a cross shape. Then, the three colors of RGB are arranged so as to pass through the same optical path so as to guide the respective RGB light beams to the right back side in the figure. The light emitted from the cross dichroic prism 3 passes only the polarization component in the vertical direction in the drawing by the polarizing plate 4. The light that has passed through the polarizing plate 4 is transferred to the effective display area of the liquid crystal display element 8 by the relay lens 5.

  In this optical path, the polarization beam splitter 6 reflects the polarization component in the vertical direction in the figure, and guides the light flux in the direction in which the liquid crystal display element 8 is disposed. Further, the light is passed through the phase compensation plate 7 and compensated so that the polarization state of light matches the retardation of the liquid crystal display element 8 in the black display state. The light reaching the liquid crystal display element 8 is reflected with a phase difference in each pixel region according to the modulation state of a plurality of pixels arranged in the display region of the liquid crystal display panel.

2) Control Driver Here, regarding the image information displayed on the liquid crystal and the control of the RGB display frame, the control driver 200 selects the RGB emission color of the LED light source and displays the liquid crystal display element in accordance with the emission color. The image is determined and controlled in time series. The display time series control will be described in detail later. The light subjected to the phase difference modulation of the image by the liquid crystal display element 8 is reflected, passes through the phase compensation plate 7 that compensates for the retardation of the liquid crystal again, and enters the polarization beam splitter 6 again. The light that has entered the polarization beam splitter 6 is reflected as a vertically polarized component (S-polarized light) in the figure and returns to the light source side, and the horizontally polarized component (P-polarized light) in the figure passes through the polarization separation film, and is a projection lens. Guided to the 9th side.

  That is, the state in which the phase difference modulation is applied to each pixel by the liquid crystal display element 8 is converted into information as a light image, and the portion provided with the phase difference is transferred to the projection lens 9 as a light image. The projection lens 9 performs an enlarged conjugate projection on the screen 10 of the image display area surface of the liquid crystal display element 8, and an optical image is projected onto the screen 10. The screen 10 is composed of a light diffusing surface. By diffusing and reflecting the irradiated light, an image can be visually recognized by looking at the screen.

3) Timing Control and Pulse Width Modulation Next, an operation process in which the projection type image display apparatus according to this embodiment displays an image will be described with reference to FIGS. Details of the configuration of the control driver 200 shown in FIG. 4 are shown in FIG. An image signal to be displayed is stored in the frame memory 201 from the main body of the apparatus or an external PC apparatus or video player apparatus. The frame memory 201 can store image information of three frames for R, G, and B colors. On the other hand, the control driver 200 has a control clock 202 and operates by synchronizing the timing based on this clock signal.

  The timing control unit 203 receives a synchronous basic clock from the control clock 202. Regarding the drive of the liquid crystal display element 8, the timing control unit 203 performs information transfer from the frame memory 201 and operation timing control of the image output control unit 204 for transferring image information to the liquid crystal display element 8. On the other hand, for the LED light sources 1R, 1G, and 1B, the timing control unit 203 performs operation timing control of the switching control unit 205 that switches the operation of the R driver 206R, G driver 206G, and B driver 206B that drive light emission.

  In addition, a liquid crystal power source 207 that controls power supply to the liquid crystal display element 8 and an LED power source 208 that controls power supply (pulse width is modulated with a constant voltage) to the LED light sources 1R, 1G, and 1B are provided.

4) Time-division display An image display process by the control driver 200 described above will be described with reference to FIG. The image information displayed on the liquid crystal display element 8 is cyclically repeated with one set for R color, G color, and B color. In synchronism with the cyclically repeated liquid crystal display image, the R color LED light source 1 </ b> R emits light during the time during which the R color image is displayed. Similarly, the LED light source 1G for G color emits light during the time when the image for G color is displayed, and the LED light source 1B for B color emits light during the time when the image for B color is displayed. This process is repeated. On the screen 10, the R color component, the G color component, and the B color component are displayed in time series for one image frame.

  This is generally called a field sequential display method. If the display time of an RGB color image of one image frame is short, a user observing the image recognizes a mixed color of RGB colors. A color image is observed. Generally, 60 Hz image signals are widely used as the image information data that is the source to be displayed at present, and when RGB color display is displayed at 180 Hz for 60 Hz image information, A color image can be recognized.

  Furthermore, in order to prevent the occurrence of a color break-up phenomenon due to field sequential display (a phenomenon in which the color of the displayed image appears to be broken when the line of sight is moved), one image is repeated twice for red, green and blue. Use the method of displaying twice. In this case, 360 Hz image display may be performed.

(OCB type liquid crystal)
Next, the OCB type liquid crystal will be described, and the display mechanism of the conventional OCB type liquid crystal will be described based on FIG. 8, and then the display mechanism of the OCB type liquid crystal according to the present embodiment will be described based on FIGS. To do.

  In addition to the splay alignment of FIG. 2 (a), the OCB type liquid crystal display element has an initial bend alignment of FIGS. 2 (b), 7 (a) and 8 (a), and FIGS. 7 (b) and 8 (b). ) In the intermediate bend orientation and the vertical bend orientation in FIG. 9C are in a stable state. The OCB type liquid crystal display element displays an image based on bend alignment, and performs white display with the initial bend alignment of FIG. 2B, which is a case where a low electric field is applied. As the applied voltage is increased, the liquid crystal molecules are displaced to the vertical bend alignment via the intermediate bend alignment. In the intermediate bend alignment, the liquid crystal molecules are in an intermediate state between the initial bend alignment and the vertical bend alignment.

  Note that if the pretilt angle of the liquid crystal molecules at the interface of the counter substrate where the liquid crystal is sandwiched is increased (when the angle rising from 0 degrees parallel to the substrate is a positive angle), no voltage is applied to the liquid crystal. Both are known to form the initial bend orientation of FIG. That is, with respect to the initial bend alignment, the phase transition from the splay alignment to the initial bend alignment may be performed by applying a voltage, or the pretilt angle may be increased and the initial bend alignment may be used without applying a voltage.

(Display mechanism of conventional OCB type liquid crystal)
1) Black display In the vertical bend alignment (final alignment) shown in FIG. 8C, when a maximum voltage (for example, 10 V) is applied to the liquid crystal, the liquid crystal molecules are perpendicular to the substrate at the intermediate portion between the two substrates. The light incident on the liquid crystal (for example, S-polarized light) is emitted from the liquid crystal and the phase compensation plate while maintaining the polarization state. And it does not permeate | transmit the polarizing beam splitter (P-polarized light is permeate | transmitted by the code | symbol 6 of FIG. 4) provided in the back optical path of a phase compensation plate. That is, black light is displayed by blocking the light to the projection lens 9 that is the projection means.

2) White display In the initial bend alignment (initial alignment) shown in FIG. 8A, the light incident on the liquid crystal (for example, S-polarized light) has the sum of the retardation of the liquid crystal and the retardation of the phase compensation plate is ½ wavelength. The phase compensation plate is adjusted so as to correspond to the phase difference. For this reason, it becomes P-polarized light and is transmitted through the polarization beam splitter (transmitting P-polarized light), that is, white light is displayed by the presence of light to the projection lens 9 which is the projection means. That is, conventionally, a phase compensation plate has been provided in association with white display.

3) Halftone display In the intermediate bend alignment (intermediate alignment) shown in FIG. 8B, an intermediate voltage lower than the maximum voltage for vertical bend alignment is applied, and light incident on the liquid crystal (for example, S-polarized light) is elliptical. The polarized light is emitted from the liquid crystal and the phase compensation plate. The light is partially shielded by a polarizing beam splitter (transmitting P-polarized light) provided behind the phase compensation plate, thereby providing a halftone (gray) display. That is, conventionally, halftones (halftones) have been displayed by intermediate bend alignment.
Was provided in relation to the halftone display.

(Display mechanism of OCB type liquid crystal of this embodiment)
1) Black display In the intermediate bend orientation shown in FIG. 7B, the light incident on the liquid crystal (for example, S-polarized light) under an applied voltage (5 V or less) lower than that of the conventional liquid crystal has retardation of the liquid crystal and retardation of the phase compensation plate. The phase compensator is adjusted so as to cancel out. For this reason, it outputs from a liquid crystal and a phase compensation plate, maintaining a polarization state. Then, it does not pass through a polarizing beam splitter (transmitting P-polarized light) provided behind the phase compensation plate.

  That is, black light is displayed by blocking light to the projection lens. In the present embodiment, the phase compensation plate is not provided in association with white display as in the prior art, but is provided in association with black display. In addition, the intermediate bend orientation does not display halftone as in the prior art, but displays black.

2) White display In the initial bend alignment shown in FIG. 7A, light (for example, S-polarized light) incident on the liquid crystal is emitted from the liquid crystal and the phase compensator as elliptically polarized light. A part of the light is transmitted by the polarizing beam splitter (transmitting the P-polarized light) provided behind the phase compensation plate, so that a white display is obtained.

3) Halftone display Light (for example, S-polarized light) incident on the liquid crystal under an applied voltage lower than that in the case of the black display according to the present embodiment having intermediate bend alignment is emitted from the liquid crystal and the phase compensation plate as elliptically polarized light. The polarization beam splitter 6 provided behind the phase compensation plate provides a halftone (gray) display that is intermediate between black display and white display.

(Function and configuration of reflective liquid crystal display element)
In FIG. 2, the OCB type liquid crystal display element used in the image projection apparatus of this embodiment is a reflective liquid crystal display element, and a liquid crystal layer is sandwiched between two substrates, a liquid crystal circuit substrate 801 and an ITO glass substrate 802. Has been. The liquid crystal molecules 800 are normally white (displaying white in a low voltage application state or no voltage application state) with the initial bend orientation shown in FIG. 2B.

  That is, the arrow I indicates the incidence of light, but the light incident on the liquid crystal display element passes through the transparent ITO glass substrate 802, passes through the liquid crystal layer in the bend alignment state, and reaches the liquid crystal circuit substrate 801. The liquid crystal circuit board 801 is provided with segmented pixel electrode mirrors for displaying an image, and a voltage necessary for the liquid crystal corresponding to the pixel position is applied according to image information.

  The light reaching the liquid crystal circuit board 801 is reflected by the surface of the liquid crystal circuit board 801 having the pixel electrode mirror disposed on the surface, travels back and forth through the liquid crystal layer, passes through the ITO glass substrate 802 again, and is directed in the direction of the arrow O. Come back. By this operation, the light whose polarization state is changed according to the image information is modulated and output as the light indicated by the arrow O.

  FIG. 3 is a schematic configuration diagram of the reflective liquid crystal display element, where (a) is a top view and (b) is a perspective view. The liquid crystal display element in this embodiment is an OCB type liquid crystal display element, and is displaced from the splay alignment (FIG. 2 (a)) to the initial bend alignment (FIG. 2 (b), FIG. 7 (a)) as the initial alignment. Further, an intermediate bend orientation (FIG. 7B) is formed as an intermediate orientation.

  As is generally true for liquid crystal, the OCB type liquid crystal of this embodiment also provides an image including white display and black display by giving a phase difference to light passing therethrough by changing the direction of the liquid crystal having birefringence. Is displayed. Halftone display between white display and black display is achieved by performing voltage modulation with a low voltage value or pulse width modulation for shortening the time width while maintaining a constant voltage as compared with black display.

  The image display area of the liquid crystal display panel is an area indicated by reference numeral 804, and the liquid crystal is arranged in an area sandwiched between ITO glass substrates 802 facing the liquid crystal circuit substrate 801. The liquid crystal layer maintains a thickness of about 6 μm and is sealed and maintained on the outer periphery of the image display region with a sealing material mixed with a gap maintaining material such as beads.

  The image display area 804 is composed of a plurality of pixels arranged in a matrix, and each pixel is electrically controlled by an image signal and a control signal input from the flexible terminal 803. A predetermined voltage corresponding to an image is applied to each electrically controlled pixel, an ITO full-surface electrode is disposed on the opposing glass substrate, and a predetermined constant voltage is applied to the ITO electrode. In this state, a voltage corresponding to image information is applied to the liquid crystal sandwiched between the liquid crystal circuit substrate 801 and the ITO glass substrate 802 at the position of each pixel.

(Phase compensation plate)
The liquid crystal molecules are perpendicular to the substrate surface between the liquid crystal circuit substrates 801 and 802 facing each other so that black can be displayed with the intermediate bend alignment to which a voltage is further applied with respect to the initial bend alignment which is normally white. However, the substrate interface has a predetermined angle that is not perpendicular (90 degrees) to the substrate surface. Even if the applied voltage is increased, the molecules at the interface of the substrate do not become vertical, and a non-zero phase difference is given by the reciprocating light. A means for canceling the phase difference that has been given by giving the opposite phase difference is the phase compensation plate 7 shown in FIG.

  FIG. 1A shows the reflectance characteristics with respect to voltage application of the liquid crystal display element without the phase compensation plate 7 and the reflectance characteristics of the liquid crystal display element with the phase compensation plate 7 disposed. FIG. 1 (b). The reflectivity is displayed with the maximum reflectivity being 1. When the phase compensation plate is not provided, as shown in FIG. 1A, a voltage of 10 V or more is applied and the minimum reflectance (black display state) is lower than the maximum reflectance (white display state). It is about 10: 1.

(Applied voltage of this embodiment)
In the present embodiment, there is provided voltage applying means for applying a voltage of 5 V or less (more preferably 3 V or more and 5 V or less) to the OCB liquid crystal for black display. Then, the phase compensation means is adjustably provided so as to minimize the retardation of the liquid crystal molecules in the state where the applied voltage of 5 V or less is applied. FIG. 1B shows the reflectance characteristics with respect to voltage application of the OCB liquid crystal display element in the case where the phase compensation plate 7 is provided to minimize retardation of liquid crystal molecules. When the phase compensation plate is provided, a reflectance of 1/1000 level or less is obtained at a voltage of 5 V or less. Therefore, a characteristic of black and white contrast of 1000: 1 or more can be obtained.

  By providing this phase compensation plate 7, the voltage applied to the liquid crystal operates at 5V or less, and the potential difference between the liquid crystal circuit substrate 801 and the ITO glass substrate may be operated at 5V or less. If the ITO glass potential is alternately switched between 0 V and 5 V in order not to apply a voltage from one direction to the liquid crystal, it is possible to deal with flicker and image sticking due to uneven distribution of ions in the liquid crystal.

(Adjustment of image projection device)
The image projection apparatus according to the present embodiment including the OCB type liquid crystal has a step of adjusting the phase compensation means so as to give a retardation for performing black display with respect to the retardation of the liquid crystal molecules in the intermediate alignment. That is, the first step of applying an applied voltage of 5V or less to the liquid crystal display element for black display, and the phase compensation means to minimize the retardation of the liquid crystal molecules in the state where the applied voltage of 5V or less is applied. A second stage of adjustment.

(Effect of this embodiment)
In the present embodiment, since the OCB type liquid crystal can be driven with a voltage of 5 V or less, the transistors arranged in the circuit in the liquid crystal circuit substrate 801 can be configured by TTL level or CMOS level elements. In particular, for CMOS level digital drive transistors, semiconductor processes that can operate sufficiently at several hundred megahertz are currently mainly used, and liquid crystal display elements can be operated using this transistor circuit.

  Further, since a digital circuit is used for the circuit in the liquid crystal circuit board 801, the time pulse duty of about 0V and about 5V is modulated (PWM modulation), which is equivalent to that applied to the liquid crystal as a time average voltage. (Because liquid crystal molecules cannot respond to pulse modulation). Therefore, PWM is applied in a region between the time average voltage corresponding to the maximum reflectance of each color (blue, green, red) shown in FIG. 1B and the time average voltage corresponding to the minimum reflectance near 5V. By performing modulation driving, display between white and black can be displayed in pixel units.

  According to this embodiment, the OCB type liquid crystal display element is operated at a high speed using a low voltage transistor, so that a common single liquid crystal display element is used for three-color images without using an expensive transistor. Enables field sequential display. And an inexpensive image projection apparatus can be provided.

(Modification 1)
In the above-described embodiment, the OCB type liquid crystal display element is used. However, a TN type liquid crystal display element may be used. In the TN type, black display is conventionally performed by applying the maximum voltage, but black display is achieved by adjusting the phase compensation plate with the intermediate orientation when an intermediate voltage lower than the maximum voltage is applied and canceling the retardation of the liquid crystal. May be performed.

(Modification 2)
In the embodiment described above, black display is performed in the intermediate orientation, but white display may be performed in the intermediate alignment. In this case, the phase compensation plate is adjusted so that the sum of the retardation of the liquid crystal of the intermediate alignment and the retardation of the phase compensation plate corresponds to ½ wavelength.

(Modification 3)
In the above-described embodiments, it has been shown that halftone display is performed by pulse width modulation with the voltage applied to the liquid crystal display element being constant, but halftone display is performed by modulating the voltage applied to the liquid crystal display element. You may do it.

(Modification 4)
In the above-described embodiment, the voltage applied to the liquid crystal display element for black display is set to 5 V or less. However, a value of 5 V or 3.3 V may be adopted in relation to the semiconductor process rule.

(Modification 5)
In the above-described embodiment, it is shown that a single liquid crystal display element common to red, green, and blue is used. However, a liquid crystal display element that displays each color may be provided individually.

(Modification 6)
The present invention is not limited to being applied to the projector as the image projection apparatus described above, but can also be applied as an image display apparatus such as a liquid crystal television, a digital camera, a video camera, and a portable terminal device.

  1 .... LED light source, 2 .... collimator lens, 3 .... cross dichroic prism, 4 .... polarizing plate, 5 .... relay lens, 6 .... polarizing beam splitter, 7 .... phase compensator, 8 .... liquid crystal display Element 9 Project lens 10 Screen driver 200 Control clock 203 Timing control unit 204 Image output control unit 205 Switching control unit 206 LED driver

Claims (8)

The liquid crystal molecules are initially applied with no voltage or when a low voltage is applied, and the initial orientation of the liquid crystal molecules formed when a maximum voltage is applied. An image display device comprising a liquid crystal display element that is displaced to an intermediate orientation of liquid crystal molecules formed when an intermediate voltage higher than a low voltage is applied,
An image display device comprising phase compensation means for providing a retardation for performing black display or white display with respect to the retardation of the liquid crystal molecules in the intermediate alignment.   The liquid crystal display element is an OCB type liquid crystal display element, which is displaced from a splay alignment as an initial alignment to an initial bend alignment, forms a vertical bend alignment perpendicular to the substrate as the final alignment, and an intermediate bend alignment as the intermediate alignment. The image display apparatus according to claim 1, wherein an applied voltage for forming the intermediate orientation is set to 5 V or less.   The image display device according to claim 2, wherein an applied voltage for forming the intermediate bend alignment is set to 5 V or less and 3 V or more.   4. The image display device according to claim 1, wherein halftone display is performed by pulse width modulation with a voltage applied to the liquid crystal display element being constant. 5.   5. The liquid crystal display element is a single liquid crystal display element common to three color images, and the three color images are displayed in a time-sharing manner on the single liquid crystal display element. The image display device according to any one of the above.   The image display apparatus according to claim 1, further comprising a projection unit that projects the liquid crystal display element onto a screen. The liquid crystal molecules are initially applied with no voltage or when a low voltage is applied, and the initial orientation of the liquid crystal molecules formed when a maximum voltage is applied. An adjustment method of an image display device including a liquid crystal display element that is displaced to an intermediate orientation of liquid crystal molecules formed when an intermediate voltage higher than a low voltage is applied,
A method for adjusting an image display device, comprising: adjusting phase compensation means so as to give a retardation for performing black display or white display with respect to the retardation of the liquid crystal molecules in the intermediate alignment. The liquid crystal display element is an OCB type liquid crystal display element,
8. The method for adjusting an image display device according to claim 7, wherein an applied voltage for forming the intermediate orientation is set to 5 V or less.