Liquid crystal shutter, driving method of the same and image display system

In one embodiment, the liquid crystal shutter is equipped with a first liquid crystal panel in the OCB mode to control the transmissivity of the light entering into left eye and a second liquid crystal panel in the OCB mode to control the transmissivity of the light entering into right eye, and a drive portion to control the transmissivity. The drive portion applies a normal voltage of a normal drive in a pulse shape and a retention voltage having a pulse shape with lower frequency than the normal voltage or lower voltage than normal voltage to the first liquid crystal panel and the second liquid crystal panel. The drive portion switches between the normal drive and the retention drive while maintaining bend alignment state.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2010-084063, filed Mar. 31, 2010, the entire contents of which are incorporated herein by reference.

FIELD

This invention relates to a liquid crystal shutter, a driving method of the same and an image display system.

BACKGROUND

In recent years, various technologies for displaying a three-dimensional image are proposed. As the above-mentioned technology, the three-dimensional image display technology, for example, using a liquid crystal shutter of an active shutter type and display devices such as a liquid crystal display device etc. of a time sharing type is known (for example, refer to Japanese Laid Open Patent Applications (1) to (3)).

Japanese Laid Open Patent Applications No. H10-191399 (1)

Japanese Laid Open Patent Applications No. 2000-275575 (2)

Japanese Laid Open Patent Applications No. 2007-110683 (3)

The liquid crystal display device displays the image for left eye and the image for right eye by turns. The liquid crystal shutter switches a liquid crystal panel for right eye and a liquid crystal panel for left eye to a transmissive state (ON) or a non-transmissive state (OFF) corresponding to the displayed images in the liquid crystal display device.

While the liquid crystal display device displays the image for left eye, the light emitted from the liquid crystal display device penetrates the liquid crystal panel for left eye, and is shut in the liquid crystal panel for right eye. Similarly, while the liquid crystal display device displays the image for right eye, the light emitted from the liquid crystal display device penetrates the liquid crystal panel for right eye, and is shut in the liquid crystal panel for left eye.

Thereby, the user wearing the liquid crystal shutter watches the image for right eye and the image for left eye by turns by right and left eyes, and the two-dimensional images displayed on the liquid crystal display can be perceived as a three-dimensional image. In this case, the liquid crystal shutter conducts a normal drive in synchronism with the image displayed by the liquid crystal display device based on the synchronization signal transmitted from the liquid crystal display device.

By the way, when the synchronization signal which a liquid crystal shutter receives stops according to a certain obstacle, if a sight line of the liquid crystal shutter user moves to other portion than the liquid crystal display, an interferential action arises between other light sources and the liquid crystal shutter. Therefore, the liquid crystal shutter user becomes unpleasant. Moreover, since high frequency driving of 120 Hz is performed in the normal drive and power consumption is large, the normal drive is unnecessary except viewing the three-dimensional image.

Moreover, since high-speed response is required for the liquid crystal shutter, it is desirable to use OCB (Optically Compensated Bend) liquid crystal for the liquid crystal shutter. However, in case of using the OCB liquid crystal, since the liquid crystal is in a splay alignment state in an initial stage, it is necessary to operate the liquid crystal after making the liquid crystal transit to a bend alignment state in the initial stage by applying a predetermined voltage. Moreover, if the predetermined voltage is not impressed to the OCB liquid crystal for a certain period, the OCB liquid crystal has character that the OCB liquid crystal reverse-transits from the bend alignment state to the splay alignment state. For this reason, when a power supply is turned off at the time of non-use of the liquid crystal shutter or the synchronization signal fails for a short-time, the OCB liquid crystal reverse-transits to the initial alignment state, that is, the splay alignment state. Accordingly, it is necessary to make the OCB liquid crystal transit to the bend alignment state from the splay alignment state again for continuous use, and further, there is a possibility that stability may be missing on that operation.

DETAILED DESCRIPTION OF THE INVENTION

A liquid crystal shutter, a driving method of the same and an image display system according to an exemplary embodiment of the present invention will now be described with reference to the accompanying drawings wherein the same or like reference numerals designate the same or corresponding portions throughout the several views.

According to one embodiment, a liquid crystal shutter includes: a first liquid crystal panel having a pair of electrode substrates and liquid crystal layer held between the electrode substrates and covering left eye, the first liquid crystal panel being driven by the OCB mode capable of controlling transmissivity of light entering into left eye; a second liquid crystal panel having a pair of electrode substrates and liquid crystal layer held between the electrode substrates and covering right eye, the second liquid crystal panel being driven by the OCB mode capable of controlling transmissivity of light entering into right eye; and a drive portion to switch a normal drive and a retention drive of the first and second liquid crystal panels; wherein the normal drive switches the first and second liquid crystal panels between a transmissive state and a non-transmissive state respectively by applying a normal voltage in a pulse shape while the first and second liquid crystal panels are set in a bend alignment state, and the retention drive applies a retention voltage in a pulse shape having lower frequency than the normal voltage or lower voltage than the normal voltage to the first and second liquid crystal panels to maintain bend alignment.

According to other embodiment, a driving method of a liquid crystal shutter includes a first liquid crystal panel having a pair of electrode substrates and liquid crystal layer held between the electrode substrates and covering left eye, the first liquid crystal panel being driven by the OCB mode capable of controlling transmissivity of light entering into left eye; a second liquid crystal panel having a pair of electrode substrates and liquid crystal layer held between the electrode substrates and covering right eye, the second liquid crystal panel being driven by the OCB mode capable of controlling transmissivity of light entering into right eye. The driving method of a liquid crystal shutter includes the steps: performing a normal drive to switch the first and second liquid crystal panels between a transmissive state and a non-transmissive state respectively by applying a normal voltage in a pulse shape while the first and second liquid crystal panels are bend alignment state, performing a retention drive to apply a retention voltage in a pulse shape having lower frequency than normal voltage or lower voltage than the normal voltage to the first and second liquid crystal panels to maintain the bend alignment, and switching between the normal drive and the retention drive.

According to other embodiment, an image display system comprises: a liquid crystal shutter including: a first liquid crystal panel having a pair of electrode substrates and liquid crystal layer held between the electrode substrates and covering left eye, the first liquid crystal panel being driven by the OCB mode capable of controlling transmissivity of light entering into left eye; a second liquid crystal panel having a pair of electrode substrates and liquid crystal layer held between the electrode substrates and covering right eye, the second liquid crystal panel being driven by the OCB mode capable of controlling transmissivity of light entering into right eye; and a drive portion to switch a normal drive and a retention drive; wherein the normal drive switches the first and second liquid crystal panels between a transmissive state and a non-transmissive state respectively by applying a normal voltage in a pulse shape while the first and second liquid crystal panels are bend alignment state, and the retention drive applies a retention voltage in a pulse shape having lower frequency than normal voltage or lower voltage than the normal voltage to the first and second liquid crystal panels to maintain the bend alignment, and a display device to display image and transmitting a synchronization signal in synchronism with the image to the liquid crystal shutter; wherein the drive portion performs the normal drive base on the synchronization signal in synchronism with the image displayed by the display device upon receiving the synchronization signal.

Hereinafter, the structure of the image display system with a liquid crystal shutter and a driving method of the liquid crystal shutter are explained referring to drawings in details. First, the structure of the image display system is explained. As shown inFIG. 1, the image display system includes a liquid crystal shutter1of an active shutter type, and a liquid crystal display device2as a display device.

As shown inFIG. 1toFIG. 3, the liquid crystal shutter1includes a first liquid crystal panel3L, a second liquid crystal panel3R, a glasses frame4, a driving circuit5, a power supply portion6, a receiver7, and a case8. In this embodiment, the liquid crystal shutter1is a glasses wearable type liquid crystal shutter.

The first and second liquid crystal panels3L and3R respectively include a liquid crystal layer30held between a pair of electrode substrates10and20. The electrode substrate10includes a glass substrate11as a transparent insulating substrate, a first electrode12formed on the glass substrate11, an alignment film13on the glass substrate11and the first electrode12. As the insulating substrate, a plastic substrate or a resin film, etc. are applicable other than the glass substrate. An optical compensation film14and a polarizing plate15are arranged on the electrode substrate10. The optical compensation film14and the polarizing plate15are located in the opposite side of the first electrode12, and are arranged on an external surface of the glass substrate11in order.

The electrode substrate20includes a glass substrate21as a transparent insulating substrate, a second electrode22formed on the glass substrate21, an alignment film23on the glass substrate21and the first electrode22. Similarly, as the insulating substrate, a plastic substrate or a resin film, etc. are applicable other than the glass substrate21. An optical compensation film24and a polarizing plate25are arranged on the electrode substrate20. The optical compensation film24and the polarizing plate25are located in the opposite side of the second electrode22, and are arranged on an external surface of the glass substrate21in order.

The first electrode12and the second electrode22are formed of transparent conductive materials, for example, ITO (Indium Tin Oxide). The rubbing treatment is respectively performed to the alignment films13and23in the same direction. The polarizing plate15and the polarizing plate25are made in a cross Nichol arrangement so that they cross at approximately 45° to the alignment direction.

The electrode substrate10and the electrode substrate20are arranged so as to oppose each other with a predetermined gap by a plurality of spherical spacers31as spacers, and are attached by a seal material32. A pillar-shaped spacer can be formed integrally on one of the substrates in place of the spherical spacers31. The liquid crystal layer30is formed with a nematic liquid crystal filled up in a space surrounded by the electrode substrate10, the electrode substrate20, and the seal material32.

As mentioned above, the first liquid crystal panel3L is formed of a liquid crystal panel of the OCB (optically compensated bend) mode in which π cell is combined with the optical compensation films14and24. Here, the first liquid crystal panel3L is normally white type in which the panel is in a transmissive state when a voltage is not impressed. The first liquid crystal panel3L covers eyesight of left eye, and can control the transmissivity of light entering to left eye.

A driving voltage is impressed to the liquid crystal layer30by applying a voltage Vd to the first electrode12, and a voltage Vcom to the second electrode22. As shown inFIG. 4andFIG. 5, the liquid crystal molecules30mare transitted from a splay alignment state to a bend alignment state by impressing a driving voltage of more than a threshold voltage, for example, 20V to the liquid crystal layer30(initial transition). Furthermore, the first liquid crystal panel3L can be switched between a transmissive state and a non-transmissive state while maintaining the bend alignment state of the liquid crystal molecule30mby impressing a predetermined driving voltage to the liquid crystal layer30. The first liquid crystal panel3L is excellent in high-speed response due to the bend alignment and a flow effect.

As shown inFIG. 1andFIG. 3, the second liquid crystal panel3R is formed like the first liquid crystal panel3L. The second liquid crystal panel3R includes a pair of electrode substrates10and20and a liquid crystal layer30held between the electrode substrates10and20. The second liquid crystal panels3R is formed of a liquid crystal panel of the OCB (optically compensated bend) mode and covers the eyesight of right eye, and can control transmissivity of the light entering to the right eye. Here, the second liquid crystal panel3R is normally white mode type in which the second liquid crystal panel3R becomes the transmissive state when a voltage is not applied.

In addition, although not illustrated, the positions of electrical terminals may be arranged at different locations mutually in the first liquid crystal panel3L and the second liquid crystal panel3R. Thereby, it becomes possible to distinguish which of the first liquid crystal panel3L and the second liquid crystal panel3R is for left eye or for right eye. As shown inFIG. 1, the first liquid crystal panel3L and the second liquid crystal panel3R are equipped to the glasses frame4.

The driving circuit5is respectively connected to the first and second electrodes of the first liquid crystal panel3L and the second liquid crystal panel3R through a flexible printed circuit (FPC) as shown inFIG. 2. The driving circuit5switches between two drive operations. One is a normal drive in which the driving circuit5applies normal voltages Vd and Vcom respectively to the first liquid crystal panel3L (liquid crystal layer30) and the second liquid crystal panel3R (liquid crystal layer30), and the other drive operation is a retention drive in which a retention voltage in a pulse shape is applied to the first liquid crystal panel3L (liquid crystal layer30) and the second liquid crystal panel3R (liquid crystal layer30) so as to maintain the bend alignment state while achieving less consumption than the normal drive.

The driving circuit5can switch the transmissive state and the non-transmissive state by turns by performing the normal drive while the liquid crystal molecules30mof the first liquid crystal panel3L and the second liquid crystal panel3R are respectively set to the bend alignment state.

The power supply portion6and the receiver7are connected to the driving circuit5. The power supply portion6supplies electric power to the driving circuit5. The receiver7receives data (synchronization signal) by a cable or wireless communication. The driving circuit5applies the driving voltage to the first liquid crystal panel3L and the second liquid crystal panel3R based on the data received with the receiver7. The case8accommodates the driving circuit5, the power supply portion6, and the receiver7, and is equipped to the glasses frame4. The liquid crystal shutter1is formed as mentioned-above.

As shown inFIG. 1andFIG. 6, the liquid crystal display device2includes a liquid crystal display panel50, a backlight unit90, and a control portion100. The liquid crystal display panel50includes an array substrate60, a counter substrate70arranged opposite the array substrate60and a liquid crystal layer80held between the array substrate60and the counter substrate70.

As shown inFIG. 6andFIG. 7, the array substrate60includes a rectangular glass substrate61as a transparent insulating substrate. On the glass substrate61, a plurality of signal lines62and a plurality of scanning lines63are formed. The signal lines62and the scanning lines63intersect orthogonally each other. Moreover, a plurality of auxiliary capacitance lines64are arranged in parallel with the scanning lines63on the glass substrate61. In this embodiment, a pixel PX is formed in each region surrounded by adjacent two signal lines62and adjacent two scanning lines63. The pixels PX are arranged in the shape of a matrix on the glass substrate61.

Next, one pixel PX is explained in detail. The pixel PX includes a TFT (thin film transistor) as a switching element65formed near intersection of the signal line62and the scanning line63, a pixel electrode66connected to the TFT65, and an auxiliary capacitance element67connected to the pixel electrode66. The auxiliary capacitance line64forms one electrode of the auxiliary capacitance element67.

Although not illustrated, a color filter with three colored layers of red, green and blue is formed on the glass substrate61. In addition, the above-mentioned pixel electrode66is formed on the color filter using transparent electric conductive material, such as ITO. Moreover, for example, a plurality of pillar-shaped spacers68are formed as spacers on the color filter. As mentioned-above, an array pattern60P is formed on the glass substrate61. An alignment film69is formed on the glass substrate61and the array pattern60P.

The counter substrate70includes a rectangular glass substrate71as a transparent insulating substrate. On the glass substrate71, a counter electrode72and an alignment film73are formed in order. In addition, rubbing treatment is performed to the alignment films69and73in the same direction. Thus, the counter substrate70is formed.

The gap between the array substrate60and the counter substrate70is held by a plurality of pillar-shaped spacers68. The array substrate60and the counter substrate70are attached by a seal material81arranged along with a perimeter of a display region. The liquid crystal layer80is formed by nematic liquid crystal material which fills up a space surrounded by the array substrate60, the counter substrate70, and the seal material81.

On the external surface of the array substrate60, an optical compensation film51and a polarizing plate52are formed in order. Similarly, on the external surface of the counter substrate70, an optical compensation film53and a polarizing plate54are formed in order. The polarizing plate52and the polarizing plate54are made in a cross Nichol arrangement so that they cross at approximately 45° to the alignment direction. As mentioned above, the liquid crystal display panel50is a OCB mode liquid crystal. Here, the liquid crystal layer50is a normally white mode type in which the liquid crystal layer50becomes the transmissive state when a voltage is not applied.

As shown inFIG. 6, the backlight unit90is formed in the external surface side of the array substrate60. The backlight unit90includes a light guide92with a light guide plate opposing to the polarizing plate52, a light source93arranged at one edge side of the light guide92, for example, formed of a cold cathode fluorescent tube, and a reflector94.

Next, the above-mentioned liquid crystal shutter1and the driving method of the liquid crystal shutter1in the image display system are explained. According to this embodiment, in the case of displaying a three-dimensional image using the image display system, when the synchronization signal transmitted to the liquid crystal shutter1from the liquid crystal display device2is stopped by a certain obstacle, the driving circuit5switches the operation from the normal drive to the retention drive.

First, the operation of the liquid crystal shutter1and the liquid crystal display device2, particularly the normal drive by the driving circuit5to display the three-dimensional display using the image display system is explained. As shown inFIG. 6andFIG. 8, the control portion100controls the driving of the liquid crystal display panel50to display the image for left eye and the image for right eye by turns, for example, in a frame frequency of 120 Hz when displaying the three-dimensional image. Here, one frame (1F) means time during scanning all the pixels PX one by one and till scanning the same pixel PX again.

As apparent from the above explanation, the liquid crystal display device2enables the display of the three-dimensional image without the fall of resolution substantially using the frequency of 60 Hz.

The driving circuit5applies the normal voltage in a pulse shape to the first liquid crystal panel3L and the second liquid crystal panel3R, and performs the normal drive to switch the transmissive state and the non-transmissive state by turns while the liquid crystal molecules30mof the first liquid crystal panel3L and the second liquid crystal panel3R are respectively set to the bend alignment state.

In detail, as shown inFIG. 1,FIG. 2, andFIG. 8, the driving circuit5switches the second liquid crystal panel3R to the transmissive state (ON) during one arbitrary frame period while the first liquid crystal panel3L is switched to the non-transmissive state (OFF) in synchronism with the displayed image for right eye by the liquid crystal display device2. Thereby the transmissivity of the first liquid crystal panel3L is about 0% during this frame period.

During following one frame period, the driving circuit5switches the second liquid crystal panel3R to the non-transmissive state (OFF) while the first liquid crystal panel3L is switched to the transmissive state (ON) in synchronism with the displayed image for left eye by the liquid crystal display device2. If the first liquid crystal panel3L is switched to the transmisissve state (ON), the first liquid crystal panel3L shows a high-speed response, and the transmissivity of the first liquid crystal panel3L rises from 0%. Accordingly, the first liquid crystal panel3L becomes the transmissive state during this frame period.

After that, the first liquid crystal panel3L and the second liquid crystal panel3R are switched to the transmissive state by turns in synchronism with the displayed image in the liquid crystal display device2. When the driving circuit5switches the first liquid crystal panel3L and the second liquid crystal panel3R to the transmissive state (ON) respectively, the first and second liquid crystal panels3L and3R are switched in 1/60 seconds after being switched to the transmissive state (ON) last time. Thereby, the user who wears the liquid crystal shutter1can watch the image for left eye and the image for right eye by turns by right and left eyes, and the three-dimensional image is displayed to the user.

Next, the operation of the above-mentioned liquid crystal shutter1, particularly the retention drive by the driving circuit5, is explained when the synchronization signal transmitted to the liquid crystal shutter1from the liquid crystal display device2is stopped by a certain obstacle, in the case of displaying the three-dimensional image using the image drive system. Hereinafter, the retention drive by the driving circuit5of the liquid crystal shutter1according to the first to fourth embodiments is explained.

The first to fourth embodiments show examples of the retention drive to maintain the bend alignment state of the liquid crystal molecules30mof the liquid crystal shutter1. The retention drive according to the embodiments can reduce more power consumption than the normal drive. The retention drive is performed by applying at least one of retention voltages of a pulse shape which have lower frequency than the normal voltage or have relatively lower voltage than the normal voltage to the first liquid crystal panel3L and the second liquid crystal panel3R.

First, the liquid crystal shutter1and the retention drive (the driving method) of the liquid crystal shutter1according to the first embodiment are explained. The retention drive of the liquid crystal shutter1is performed by applying the retention voltage whose frequency is lower than the normal voltage to the first liquid crystal panel3L and the second liquid crystal panel3R using polarity inversion driving method. The liquid crystal shutter1is configured so that the first liquid crystal panel3L and the second liquid crystal panel3R are maintained in the transmissive state at any time.

In detail, as shown inFIG. 2,FIG. 3, andFIG. 9, in the retention drive period changed from the normal drive to the retention drive, the frequency of the retention voltage applied to the first liquid crystal panel3L is set lower than 120 Hz.

During the retention drive period, the driving circuit5performs the polarity-inversion drive which inverts the polarity of the voltage Vd applied to the first liquid crystal panel3L (the first electrode12). The driving circuit5applies the voltage Vd of a pulse shape in which the voltage VSL and the voltage VSH are changed by turns to the first electrode12of the first liquid crystal panel3L at equal intervals, and applies the voltage Vcom of 0V to the second electrode22. The second electrode22is always set as an earth potential.

The voltage VSL and the voltage VSH are respectively set larger than the critical voltage (threshold voltage value) VTL and VTH in which the liquid crystal molecule30mreverse-transits to the splay alignment from the bend alignment. In other words, the absolute value of the voltages VSL and the voltage VSH are larger than the absolute value of the critical voltage VTL and VTH.

As for the retention voltage, the voltage level is set relatively smaller than the normal voltage. Here, the voltage VSL is −4V and is set smaller than the voltage VBL of −10V. The voltage VSH is +4V and is set smaller than the voltage VBH of +10V.

The retention voltage during the retention period is adjusted so that the transmissivity of the whole retention drive period (as described below: 15%) is almost same level as the average transmissivity of the normal drive period (as described below: 30%/0%). Here, when the voltage level of the voltage Vd is 0V, the first liquid crystal panel3L shows the transmissivity of 30%, when the voltage level of the voltage Vd is ±10V (the voltages VBL, VBH), the transmissivity of 0%, and when the voltage level of the voltage Vd is ±4, the transmissivity of 15%. Since the driving circuit5carries out the retention drive of the first liquid crystal panel3L by the above-mentioned voltage setup while maintaining the bend alignment state without a black display (black insertion), it becomes possible to always maintain the first liquid crystal panel3L in the transmissive state without increase of power consumption.

In addition, during the retention drive period, the driving circuit5carries out the retention drive of the second liquid crystal panel3R like the first liquid crystal panel3L. The driving circuit5can perform the retention drive by self-driving based on an internal clock signal even if the synchronization signal from the liquid crystal display2stops.

During the retention drive, since the bend alignment state is maintained when the liquid crystal shutter1returns to the state which the synchronization signal from the liquid crystal display2can receive by the liquid crystal shutter1, it is possible to change from the retention drive to the normal drive immediately, and to achieve stabilized operation of the driving circuit5by the above configuration.

Moreover, when not returning to the state in which the synchronization signal from the liquid crystal display2can be received by the liquid crystal shutter1for predetermined interval, for example, 1 minute, it is also possible to configure so that the drive of the first liquid crystal panel3L and the second liquid crystal panel3R may be stopped by the driving circuit5.

In this embodiment, although the voltage Vcom of 0V is always impressed to the second electrode22, an alternate voltage which alternates in reverse phase to the voltage applied to the first electrode12may be used. In this case, there is an advantage that amplitude of the voltage applied to the respective electrodes is made small. Moreover, one of the voltages applied to the electrodes12and22or voltage applied to both of the electrodes may be controlled. This point is the same as the following embodiments.

Next, the liquid crystal shutter1and the retention drive (the driving method) of the liquid crystal shutter1according to the second embodiment are explained. In this embodiment, the retention voltage during the retention period is set as follows. The voltage level of the normal voltage (the voltages VBL, VBH) during the normal drive in which the liquid crystal shutter1is in the non-transmissive state is gradually lowered so as not to be lowered beyond the critical voltages VTL and VTH. On the other hand, the voltage level of the normal voltage (the voltage of 0V) during the normal drive in which the liquid crystal shutter1is in the transmissive state is gradually raised beyond the critical voltage VTL and VTH. The retention voltage adjusted as described-above, that is, the retention voltage with amplitude larger than the critical voltage VTL and VTH is applied to the first liquid crystal panel3L and the second liquid crystal panel3R, respectively. The second embodiment is different from the first embodiment in the point that the retention voltage is gradually changed at the changing time from the normal drive to the retention drive.

Thereby, the transmissivity of the first liquid crystal panel3L and the second liquid crystal panel3R during the whole retention drive period can be maintained almost same level as the average transmissivity of the normal drive period of the first liquid crystal panel3L and the second liquid crystal panel3R. Thus, user can not check the change from the normal drive to the retention drive visually due to the gradual voltage change.

In detail, in the initial retention drive period in which the normal drive is changed to the retention drive, as shown inFIG. 2,FIG. 3, andFIG. 10, although the frequency of the retention voltage applied to the first liquid crystal panel3L is 120 Hz at first, the frequency is set lower than 120 Hz after a predetermined period.

During the retention drive period, the driving circuit5gradually lowers the voltage level of the voltage Vd applied to the first liquid crystal panel3L (the first electrode12) from the voltage VBL so that the voltage may not become smaller than the critical voltage VTL. Moreover, the voltage level of the voltage Vd is gradually lowered from the voltage VBH so that the voltage may not become smaller than the critical voltage VTH. Furthermore, the voltage level of the voltage Vd (0V) is gradually raised so that the voltage may become larger than the critical voltages VTL and VTH. Here, the second electrode22is always set to earth potential.

The retention voltage is set relatively smaller than the normal voltages (VBH and VBL). Here, the critical voltage VTL is −5V and the critical voltage VTH is +5V.

Here, the first liquid crystal panel3L shows the following transmissivity depending on the voltage level of the voltage Vd. For instance, the first liquid crystal panel3L shows the transmissivity of 30% at 0 V, the transmissivity of 0% at the ±10V (the voltages VBL, VBH), and less than 15% at ±5 V. The driving circuit5can always maintain the first liquid crystal panel3L in the transmissive state without increase of power consumption after a predetermined period since changing to the retention drive without the black-display (black-insertion). In addition, during the retention drive period, the driving circuit5carries out the retention drive of the second liquid crystal panel3R like the first liquid crystal panel3L.

Next, the liquid crystal shutter1and the retention drive (the driving method) of the liquid crystal shutter1according to the third embodiment are explained referring toFIG. 11. In this embodiment, the retention voltage with the same frequency as the normal voltage is applied to the first liquid crystal panel3L and the second liquid crystal panel3R, respectively while different frequency is used in the first and second embodiments. The first liquid crystal panel3L and the second liquid crystal panel3R can always be maintained in the transmissive state during the retention drive period as well as the first and second embodiments.

In detail, as shown inFIG. 2,FIG. 3, andFIG. 11, in the retention drive period changed from the normal drive to the retention drive, the frequency of the retention voltage applied to the first liquid crystal panel3L is set to 120 Hz.

During the retention drive period, the driving circuit5performs the polarity-inversion drive which inverts the polarity of the voltage Vd applied to the first liquid crystal panel3L (the first electrode12). The driving circuit5applies the voltage Vd of a pulse shape, that is, voltage VSL and the voltage VSH changed by turns, to the first electrode12of the first liquid crystal panel3L at equal intervals, and applies the voltage Vcom of 0V to the second electrode22. The second electrode22is always set as earth potential.

The voltage VSL and the voltage VSH are set larger than the critical voltages (threshold voltage value) VTL and VTH in which the liquid crystal molecule30mreverse-transits to the splay alignment from the bend alignment. As for the retention voltage, the voltage level is set relatively smaller than the normal voltage (voltages VBL and VBH). Here, the voltage VSL is −4V and is set smaller than the voltage VBL of −10V. The voltage VSH is +4V and is set smaller than the voltage VBH of +10V.

The retention voltage during the retention period is adjusted so that the liquid crystal panel3L is always in the transmissive state for maintaining almost same level as the average transmissivity of the normal drive period. Here, when the voltage level of the voltage Vd is 0V, the first liquid crystal panel3L shows the transmissivity of 30%, when the voltage level of the voltage Vd is ±10V (the voltage VBL, VBH), the transmissivity of 0%, and when the voltage level of the voltage Vd is ±4V, the transmissivity of 15%. Since the driving circuit5carries out the retention drive of the first liquid crystal panel3L by the above-mentioned voltage setup while maintaining the bend alignment state without a black display (black insertion), it becomes possible to always maintain the first liquid crystal panel3L in the transmissive state without increase of power consumption. In addition, during the retention drive period, the driving circuit5carries out the second liquid crystal panel3R like the first liquid crystal panel3L.

Next, the liquid crystal shutter1and the retention drive (the driving method) of the liquid crystal shutter1according to the fourth embodiment are explained. In this embodiment, it is assumed the same structure of the third embodiment except that the retention voltage (voltages VSL and VSH) is gradually changed.

Thereby, the transmissivity of the first liquid crystal panel3L and the second liquid crystal panel3R during the retention driving period can be gradually raised from the average transmissivity of the normal drive period to maintain the first liquid crystal panel3L and the second liquid crystal panel3R in the transmissive state during the retention drive period.

In detail, as shown inFIG. 2,FIG. 3, andFIG. 12, in the retention drive period which is changed from the normal drive to the retention drive, the frequency of the retention voltage applied to the first liquid crystal panel3L is set to 120 Hz.

During the retention drive period, the driving circuit5gradually lowers the voltage Vd applied to the first liquid crystal panel3L (the first electrode12) from the voltage VSL to the voltage VWL so that the voltage may not become smaller than the critical voltage VTL. Moreover, the voltage Vd is lowered from the voltage VSH to the voltage VWH so that the voltage may not become smaller than the critical voltage VTH. In addition, the second electrode22is always set to earth potential.

The retention voltage is set comparatively lower than the normal voltage. The voltages VWL and VWH are set larger than the critical voltages VTL and VTH in which the liquid crystal molecule30mreverse-transits to the splay alignment from the bend alignment.

The retention voltage is adjusted so that the transmissivity of the retention drive period may be raised gradually from the average transmissivity of the normal drive period. Here, the first liquid crystal panel3L shows the transmissivity of 30% when Vd is 0V, the transmissivity of 0% when the voltages VBL, VBH are ±10V, the transmissivity less than 15% when the voltages are VSL and VSH, and further the transmissivity larger than 15% and less than 30% when the voltages are VWL and VWH. The driving circuit5can always maintain the first liquid crystal panel3L in the transmissive state without increase of power consumption after a predetermined period since changing to the retention drive without the black-display (black-insertion). In addition, during the retention drive period, the driving circuit5carries out the retention drive of the second liquid crystal panel3R like the first liquid crystal panel3L.

Next, a relation between the liquid crystal shutter1and the display device2in the display system of the above embodiment is explained further. Hereinafter, an explanation is made about the liquid crystal shutter1using the polarity-inversion drive in which the polarity of the voltage Vd is inverted every period of the transmissive state (ON) and non-transmissive state (OFF) to reduce the flicker phenomenon as one example. Although the liquid crystal display device2can display an image (video image) and a still image, here the case where the liquid crystal display device2displays the image (video image) is explained.

As shown inFIG. 1, the liquid crystal display device2displays images and simultaneously outputs an identifying signal that shows which image for left eye and for right eye is displayed now. As shown inFIG. 1andFIG. 2, the receiver7of the liquid crystal shutter1receives the outputted identifying signal from the liquid crystal display device2, and transmits the identifying signal to the driving circuit5. Thereby, the driving circuit5can conduct an opening-and-closing operation of the first liquid crystal panel3L and the second liquid crystal panel3R in synchronism with the displayed image for left eye and right eye by the liquid crystal display device2.

FIG. 13shows the structure of the liquid crystal display device2. As shown inFIG. 13, the image signals for left eye and for right eye are inputted to an input terminal110of the liquid crystal display device2. The signals may be any of signals acquired from a broadcast signal and a signal reproduced from a recording medium. Although the image signal for the two-dimensional image display is also inputted to the input terminal110, the case where the image signal for the three-dimensional display (the image signal for left eye and the image signal for right eye) is inputted is explained hereinafter.

The image signal inputted to the input terminal110is transmitted to an image signal processing circuit111and a synchronized signal processing circuit113. The synchronized signal processing circuit113separates and outputs a horizontal synchronization signal H and a vertical synchronization signal V from the image signal.

The horizontal synchronization signal H and the vertical synchronization signal V are inputted to the image signal processing circuit111and are used as timing pulses for signal processing. Moreover, the horizontal synchronization signal H and the vertical synchronization signal V are inputted to the display portion112of the liquid crystal display device2and are used as timing pulses for a horizontal scan and a vertical scan. The liquid crystal display device2displays the image for left eye based on a signal L and an image for right eye based on a signal R by turns outputted from the image signal processing circuit111.

Here, an identifying signal RID is inserted in a portion of the image signal R for right eye in the horizontal period which does not usually appear in the display region, for example, immediately after a vertical blanking period. The R identifying signal RID is extracted in the image signal processing circuit111. The R identifying signal RID is inputted to the synchronized signal transmitting circuit114. Moreover, above-mentioned vertical synchronization signal V is also inputted to the synchronized signal transmitting circuit114.

The synchronized signal transmitting circuit114generates a second liquid crystal panel synchronized signal RG_SYNC using the vertical synchronization signal V and the R identifying signal RID, and transmits the signal RG_SYNC to the receiver7. In this embodiment, although the second liquid crystal panel synchronized signal RG_SYNC is transmitted, a first liquid crystal panel synchronized signal, or both of the first and second synchronized signals may be transmitted.

FIG. 14shows the receiver7of the liquid crystal shutter1. Moreover,FIG. 15shows signal waveforms at each portion of the receiver7. As shown inFIG. 14andFIG. 15, a signal receiving circuit211demodulates the second liquid crystal panel synchronized signal RG_SYNC. The second liquid crystal panel synchronized signal RG_SYNC is inputted to a voltage controlled oscillator212as a phase synchronized signal “a”. The voltage controlled oscillator212contains a phase lock loop and a divider circuit, and generates and outputs a pulse signal “b” synchronized with the second liquid crystal panel synchronized signal RG_SYNC. The pulse signal “b” is changed from a low level to a high level for every one-frame period. The pulse signal “b” is inputted to an amplifier213and is transformed to a positive and negative symmetrical waveform with respect to the reference voltage and is inputted to a switch215. Moreover, the pulse signal “b” is inputted to a ½ divider214, and the ½ divider214outputs a switch control pulse signal “c”.

When the switch control pulse “c” is positive, the switch215is connected to a terminal A, and when the switch control pulse “c” is negative, the switch215is connected to a terminal B. The terminal A is connected to the amplifiers216and219, and the terminal B is connected to the amplifiers217and218. The amplifier216amplifies the signal “d” from the terminal A, and the amplifier217amplifies the signal “e” from the terminal B. The signals amplified with the amplifiers216and217are synthesized and are outputted to the output terminal221as a second liquid crystal panel driving signal “h” (voltage Vd). Here, the amplification rate of the amplifier216is set smaller than that of the amplifier217.

On the other hand, the amplifier219amplifies the signal “g” (=d) from the terminal A, and the amplifier218amplifies the signal “f” (=e) from the terminal B. The signals amplified with the amplifier219and the amplifier218are synthesized and are outputted to an output terminal222as a first liquid crystal panel driving signal “i” (voltage Vd). Here, the amplification rate of the amplifier218is set smaller than that of the amplifier219.

The second liquid crystal panel3R and the first liquid crystal panel3L are respectively driven by the above-mentioned second liquid crystal panel driving signal “h” and the first liquid crystal panel driving signal “i”. InFIG. 15, “j” shows an opening-and-closing sequence of the first liquid crystal panel3L (for left eye) and the second liquid crystal panel3R (for right eye). Moreover, “k” shows a sequence of the images for left eye and for right eye displayed on the liquid crystal display device2.

According to the image display system with the liquid crystal shutter1configured as above and the driving method of the liquid crystal shutter1, the image display system includes the glasses wearing type liquid crystal shutter1and the liquid crystal display device2which displays the image for left eye (video image) and the image for right eye (video image) by turns. The liquid crystal shutter1includes the first liquid crystal panel3L in the OCB mode for left eye, the second liquid crystal panel3R in the OCB mode for right eye, and the driving circuit5.

The driving circuit5performs the normal drive by applying normal voltages in the pulse shape to the first liquid crystal panel3L and the second liquid crystal panel3R respectively, and switches the first liquid crystal panel3L and the second liquid crystal panel3R to the transmissive state (ON) or the non-transmissive state (OFF) by turns, respectively while the liquid crystal molecules of the first liquid crystal panel3L and the second liquid crystal panel3R are in the bend alignment state.

The liquid crystal display device2displays the image for left eye (video image) and the image for right eye (video image) in the frequency of 120 Hz by turns, and the first liquid crystal panel3L and the second liquid crystal panel3R are switched to the transmissive state (ON) or the non-transmissive state (OFF) by turns in the frequency of 120 Hz. Accordingly, a clear three-dimensional image as well as the case where the image is displayed in the frequency of substantially 60 Hz is achieved for the user who wears the liquid crystal shutter1.

The driving circuit5applies the retention voltage of the pulse shape in which the frequency is lower than the normal voltage or the voltage level is lower than the normal voltage to the first liquid crystal panel3L and the second liquid crystal panel3R. Thereby, the driving circuit5can perform the retention drive to maintain the bend alignment state of the liquid crystal molecules30mby changing from the normal drive.

In the first and second embodiments, the retention voltage has the characteristic that the frequency is smaller than the normal voltage. In the first to fourth embodiments, the retention voltage has the characteristic that the voltage level is relatively lower than the normal voltage. For this reason, the liquid crystal shutter1(driving circuit5) according to the first to fourth embodiments can perform the retention drive to maintain the bend alignment of the liquid crystal molecule30mwith lower power consumption than the normal drive.

In the first to third embodiments, since the retention voltage is adjusted so that the transmissivity during the whole retention drive period may become almost the same as the average transmissivity of the normal drive period, the driving circuit5can change from the normal drive to the retention drive without giving the user equipped with the liquid crystal shutter1sense of discomfort.

In the fourth embodiment, the retention voltage is also adjusted so that the transmissivity of the retention drive period may be gradually raised from the average transmissivity of the normal drive period. Since the field of view of the user equipped with the liquid crystal shutter1does neither become bright nor dark suddenly, the driving circuit5can change the normal drive to the retention drive while suppressing the sense of discomfort given to the user equipped with the liquid crystal shutter1.

As described-above, according to the embodiments, it is possible to provide the liquid crystal shutter1, the driving method of the liquid crystal shutter1, and the image display system capable of reducing power consumption and securing stabilized operation.

For example, the frequency of the retention voltage is preferably within 10 Hz to 0.01 Hz. The retention drive to maintain the bend alignment of the liquid crystal molecules can be performed using the retention voltage having above frequency with lower power consumption than the normal drive.

During the normal drive period, the slew rate of the driving electric power at the time of switching the first liquid crystal panel3L and the second liquid crystal panel3R to the transmissive state or the non-transmissine state may be lowered respectively, that is, rising and falling characteristics of the voltage Vd may be made worsened. In detail, the slew rate of the driving electric power may be set to sufficiently low value within a range in which the charging operation is completed faster than the response time of the liquid crystal (faster one of the ON/OFF operations of the first and second liquid crystal panels3L and3R). Thereby, since peak current falls, low power consumption can be attained.

However, when the slew rate is made low, the switching time from the transmissive state to the non-transmissive state is delayed. In the case, what is necessary is to set the duty to small value by the reduced portion of the slew rate, and to set early the timing to switch the transmissivity of the first liquid crystal panel3L and the second liquid crystal panel3R (timing to switch from the transmissive state to the non-transmissive state in this example).

When a user removes the liquid crystal shutter1, the above-mentioned liquid crystal shutter1and the driving method of the liquid crystal shutter1may be configured so that the driving5may change from the normal drive to the retention drive. In this case, the retention drive can be performed without taking into consideration the transmissivity of the first liquid crystal panel3L and the second liquid crystal panel3R. In addition, it is easily detectable whether the user removed the liquid crystal shutter1or not, if a sensor is provided in the glasses frame4.

During the retention drive, when the user wears again the liquid crystal shutter1, the driving circuit5may change from the retention drive to the normal drive. Moreover, when the user does not wear the liquid crystal shutter1during a specific time, the driving circuit5may stop the drive of the first liquid crystal panel3L and the second liquid crystal panel3R.

The value of the above-mentioned voltage Vd and voltage Vcom are not limited to the above-mentioned examples, and can be changed variously. That is, the value of the voltage Vd and voltage Vcom should be adjusted so as to fit to the design of the first liquid crystal panel3L and the second liquid crystal panel3R.

In the above embodiments, the liquid crystal display device2displays the image for left eye (video image) and the image for right eye (video image) by turns in the frequency of 120 Hz, and the first liquid crystal panel3L and the second liquid crystal panel3R are switched to the transmissive state (ON) or the non-transmissive state (OFF) by turns in the frequency of 120 Hz. However, such frequency is not limited to 120 Hz.

Although the first liquid crystal panel3L and the second liquid crystal panel3R use a normally white mode type, they may be a normally black mode type in which the light is shut out in the state where voltage is not applied by adjusting the design.

Although the driving circuit5is accommodated in the case8, the accommodation method is not limited to this, and can be changed variously. For example, a portion or whole of the driving circuit5may be provided in the first liquid crystal panel3L and the second liquid crystal panel3R.

The liquid crystal shutter1is not limited to the glasses wearing type liquid crystal shutter, and can be changed variously. That is, the liquid crystal shutter may be equipped to components other than the glasses frame4.

The above-mentioned display device may not be limited to the liquid crystal display device2, and can be changed variously. That is, the display devices may be PDP (Plasma Display Panel) display device or a CRT (cathode-ray tube) display device.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. In practice, the structural and method elements can be modified without departing from the spirit of the invention. Various embodiments can be made by properly combining the structural and method elements disclosed in the embodiments. For example, some structural and method elements may be omitted from all the structural and method elements disclosed in the embodiments. Furthermore, the structural and method elements in different embodiments may properly be combined. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall with the scope and spirit of the inventions.