CN100565288C - Liquid crystal display - Google Patents

Abstract

The invention discloses a kind of liquid crystal display, this equipment can prevent to produce flicker in long-time.This equipment comprises liquid crystal modulation element spare, second electrode that this liquid crystal modulation element spare comprises first electrode, made by the material of the material that is different from first electrode, at the liquid crystal layer between first and second electrodes, at first aligning film between first electrode and the liquid crystal layer and second aligning film between second electrode and liquid crystal layer.This equipment also comprises controller, this controller change will to electromotive force that first electrode applies and will be in the center electromotive force of electromotive force that second electrode applies (will to electromotive force that second electrode applies with respect to center electromotive force periodic variation between positive and negative) at least one so that flicker is suppressed in a certain scope.

Description

Liquid crystal display

Technical field

The present invention relates to the liquid crystal display of the use liquid crystal modulation element spare such as liquid crystal projection apparatus.

Background technology

Some liquid crystal modulation element spare is to put between second transparent substrates of first transparent substrates that has formed transparency electrode (common electrode) thereon and the transparency electrode (pixel electrode) that has formed pixel on it, wiring, on-off element or the like by the nematic liquid crystal that will have positive dielectric anisotropy to realize.Liquid crystal modulation element spare is called as " twisted-nematic (TN) liquid crystal modulation element spare ", and wherein the main shaft of liquid crystal molecule twists 90 degree continuously between two glass substrate.This liquid crystal modulation element spare is used as transmittance liquid crystal modulation element spare.

Some liquid crystal modulation element spare utilization has formed the circuitry substrate of catoptron, wiring, on-off element or the like thereon, rather than utilizes second transparent substrates referred to above.This is called " homeotropic alignment is to row (VAN) liquid crystal modulation element spare ", and wherein the main shaft of liquid crystal molecule is aimed in the mode vertical (homeotropic) that is substantially perpendicular to two substrates.This liquid crystal modulation element spare is used as the reflective lcd modulator element.

Usually, in these liquid crystal modulation element spares, use electronically controlled birefringence (ECB) effect to come for the light wave by liquid crystal layer provides delay, so that the variation of the polarization of control light wave, thereby image formed from light.

Utilizing the ECB effect to come in the liquid crystal modulation element spare of modulate light intensity, applying electric field to liquid crystal layer and make the ionic species that exists in the liquid crystal layer move.When liquid crystal layer applies the DC electric field continuously, ionic species is pulled to one of them in two electrode of opposite.Even applying to electrode under the situation of constant voltage, eliminated the part of the electric field that applies to liquid crystal layer by charged ion, thus the electric field of having decayed basically and having applied to liquid crystal layer.

For avoiding such phenomenon, use line counter-rotating (line inversion) driving method usually, wherein for each bar line of the pixel of arranging, the polarity of the electric field that applies is put upside down between positivity and negativity and is changed with the predetermined period such as 60Hz or the like.In addition, also use the field reversal driving method, wherein between positive and negative, put upside down the polarity of the electric field that the pixel to all arrangements applies with predetermined period.These driving methods can avoid only applying to liquid crystal layer a kind of electric field of polarity, to prevent unbalanced ion.

The effective electric field that this applies to liquid crystal layer corresponding to control is so that it has identical value with the voltage that applies to electrode all the time.

Yet, not only can pass through moving of ionic species referred to above, but also can make the effective electric field that applies to liquid crystal layer change by other factors.A kind of in these other factors makes such as the liquid crystal alignment film of being made by insulating material, reflection enhancement film and be used for preventing that the electronics of the non-conductive film the inorganic passivating film of dissolving metal or the electric charge in hole are hunted down.Catch and cause on the interface of film, charging, and make electrostatic charge change the effective electric field that applies to liquid crystal layer along with the time.

Because the shape of transmittance liquid crystal modulation element spare, charging phenomenon can be seen, and take place significantly in the reflective lcd modulator element that comprises the comparative electrode of being made by different materials (mirror metal and tin indium oxide (ITO) film).

For avoiding charging phenomenon, following technology is disclosed in Japanese Patent Laid-Open Publication No.2005-49817.Therein in the disclosed method, on reflective pixel electrode, form work function and regulate rete, the work function that controls to respect to the transparency electrode relative with it (ITO membrane electrode) with the work function with reflecting electrode is ± 2% or few slightly, thereby reduce the charging on the middle layer of liquid crystal, go up flicker or afterimage take place at the liquid crystal modulation element spare liquid crystal display of (or have this liquid crystal modulation element spare) avoiding.

In addition, the excitation of catching the energy barrier that requires dielectric film of electric charge is jumped.In Japanese Patent Laid-Open Publication No.2005-49817, make and to encourage the probability of jump to be equal to each other basically, thereby produce charging owing to the charge-trapping of same amount two electrode sides from speculum electrode and ito transparent electrode.

This has caused the electromotive force displacement of the electric field that applies to liquid crystal layer in the inversion driving method on the scene, and the size of electric field can not change.Because the electric field that produces in liquid crystal depends on the relative value between the electrode of opposite, so the operation of liquid crystal does not change.

Yet only the film that is provided for regulating the difference of the work function between the electrode of opposite to liquid crystal modulation element spare is not enough to the reliability of guaranteeing that it is long-term.Charged electric charge is little by little to accumulate along with the working time of liquid crystal modulation element spare in the liquid crystal layer, thereby the electric potential difference between mirror electrode and the ITO electrode is reaching the hundreds of millivolt from several thousand hours to several ten thousand hours working time.Along with photon energy that enters liquid crystal modulation element spare and luminous energy total amount increase, this phenomenon takes place more frequently.

Electric potential difference between mirror electrode and the ITO electrode causes depending on the difference of delay modulation of liquid crystal of the polarity of the electric field that applies on liquid crystal layer, thereby under situation about driving with 60Hz by the field reversal driving method, optical modulation intensity is vibrated with 60Hz.Light intensity can not be by the human eye perception with the vibration of 60Hz.

When the amplitude of vibration increases so that the electric potential difference between the electrode of opposite surpasses 200mV when above, the low frequency component of vibration increases, thus the big vibration that causes producing light intensity, and this is that human eye can observablely glimmer.When the intensification modulation (wherein the gradual change gamma changes tempestuously) of carrying out 50%, its visibility is high especially.

In addition, the electric potential difference between mirror electrode and ito transparent electrode that causes owing to the charging on the liquid crystal middle layer causes other problem.Specifically, apply constant DC electric field to liquid crystal layer continuously, so that the ionic species that exists on a small quantity in the liquid crystal layer is pulled to an electrode in the electrode of opposite.The polarity that depends on the electric charge of ion, ionic species can be pulled to the interface of the both sides of liquid crystal layer.

Move according to the amplitude that drives electromotive force in the field reversal driving owing to be attached to the ion of the interface of electrode, therefore, the attachment state of ion changes along with the rank of the amplitude that drives electromotive force.This will make the diverse location in the viewing area change to the effective electric field that liquid crystal layer applies, thereby cause ghost.When the same image of long-time demonstration, when showing different images then, see former image as after image.This is called " afterimage " (or abbreviate as " ghost ").

Summary of the invention

The invention provides a kind of liquid crystal display, this equipment can prevent to produce flicker and ghost in long-time.

One aspect of the present invention provides a kind of liquid crystal display, this equipment comprises liquid crystal modulation element spare, and this liquid crystal modulation element spare comprises: first electrode, second electrode of being made by the material of the material that is different from first electrode, at the liquid crystal layer between first and second electrodes, at first aligning film between first electrode and the liquid crystal layer and second aligning film between second electrode and liquid crystal layer.This liquid crystal display utilization comes display image from the light that the first electrode side enters liquid crystal layer.This equipment also comprises controller, the electromotive force that the control of this controller will apply to first and second electrodes, so that the electric potential difference periodic variation between positive and negative that applies to liquid crystal layer, the electromotive force that apply to second electrode is with respect to center electromotive force periodic variation between positive and negative.Controller change will to electromotive force that first electrode applies and will be in the center electromotive force of the electromotive force that second electrode applies at least one so that flicker is suppressed in a certain scope.

By reading the following explanation of with reference to the accompanying drawings preferred embodiment being carried out, other purposes of the present invention and characteristics will be apparent.

Description of drawings

Fig. 1 is the schematic views that has shown as the operation of the reflective lcd modulator element of prerequisite technology of the present invention.

Fig. 2 is the figure that is used to illustrate as the energy barrier configuration of the reflective lcd modulator element of prerequisite technology of the present invention.

Fig. 3 is the figure that is used for illustrating as the charging phenomenon in the liquid crystal middle layer of the liquid crystal modulation element spare of prerequisite technology of the present invention.

Fig. 4 is the figure of the structure of the liquid crystal modulation element spare in the explanation embodiments of the invention 1 to 6.

Fig. 5 A is used for illustrating the electromotive force that applies to liquid crystal modulation element spare of embodiment 1 and the figure of minimum flicker ITO electrode potential.

Fig. 5 B is used for illustrating the electromotive force that applies to liquid crystal modulation element spare of embodiment 2 and the figure of minimum flicker ITO electrode potential.

Fig. 6 is the figure that is used for illustrating the method for the charge volume in the liquid crystal middle layer of control liquid crystal modulation element spare of embodiment 1 and 2.

Fig. 7 is the process flow diagram that has shown the control process among the embodiment 1.

Fig. 8 is the figure of the effective electric field in the explanation liquid crystal layer.

Fig. 9 is the figure of the minimum flicker ITO electrode potential of liquid crystal modulation element spare in the explanation short-term.

Figure 10 is the schematic views that has shown the image projection equipment in the embodiments of the invention 3.

Figure 11 is used for illustrating the electromotive force that applies to liquid crystal modulation element spare of embodiments of the invention 4 and the figure of minimum flicker ITO electrode potential.

Figure 12 is used for illustrating the electromotive force that applies to liquid crystal modulation element spare of embodiments of the invention 5 and the figure of minimum flicker ITO electrode potential.

Figure 13 is used for illustrating the electromotive force that applies to liquid crystal modulation element spare of embodiments of the invention 6 and the figure of minimum flicker ITO electrode potential.

Figure 14 is used for illustrating the electromotive force that applies to liquid crystal modulation element spare of modified example of embodiment 5 and the figure of minimum flicker ITO electrode potential.

Embodiment

The preferred embodiments of the present invention are described below with reference to the accompanying drawings.

Before describing embodiment, prerequisite technology of the present invention will be described.

Fig. 1 has shown the light path in the liquid crystal display.As shown in Figure 1, the light of being represented by arrow IW from light source enters polarization beam splitter 401.In the light that enters polarization beam splitter 401, the P polarized light component passes through light beam release surface (light beam diffusion barrier) 401a in the direction transmission of arrow IWB, and the S polarized light component is polarized the 401a reflection of beam separation surface in arrow IWA direction.The S polarized light component is the linearly polarized photon of polarization direction perpendicular to the paper of Fig. 1.

The pre-tilt angle of liquid crystal becomes 45 degree with respect to the polarization direction of S polarized light component in the reflective lcd modulator element 400.Liquid crystal layer to reflective lcd modulator element 400 applies electric field, so that liquid crystal layer provides the delay of half-wavelength for the light that enters.The light that enters reflective lcd modulator element 400 is propagated by liquid crystal layer with two kinds of AD HOC.When light is reflected and in the direction of arrow OW during from 400 outgoing of reflective lcd modulator element, light has the phase differential δ (λ) by following expression formula (1) expression between two kinds of AD HOC:

δ(λ)＝2π(2dΔn)/λ (1)

Wherein, λ represents the light wavelength that enters, and d represents the thickness of liquid crystal layer, and Δ n is illustrated in the anisotropy of the refractive index of liquid crystal layer under the state that has applied predetermined electric field.

In the direction of arrow OW from the light of reflective lcd modulator element 400 outgoing, its polarization direction is polarized the 401a reflection of beam separation surface perpendicular to the light component (with respect to the S polarized light component of polarization beam splitter 401) of the paper of Fig. 1, and returns towards light source in the direction of arrow B W.On the other hand, its polarization direction light component (with respect to the P polarized light component of polarization beam splitter 401) of being parallel to the paper of Fig. 1 in the direction transmission of arrow MW by light beam release surface 401a.

Being reflected property liquid crystal modulation element spare 400 reflection is also expressed by following expression formula (2) at the direction transmission of arrow MW light quantity or the light transfer rate R (λ) by the light of polarization beam splitter 401:

R(λ)＝0.5{1-cosδ(λ)} (2)

Wherein, δ (λ) represents phase differential referred to above.The aperture of the nonpolarized light of the transmissivity of the reflectivity of S polarized light and P polarized light, reflective lcd modulator element 400 ratio and reflectivity are set to 100% in polarization beam splitter 401.

The modulation of the electric field that the subtend liquid crystal layer applies makes liquid crystal molecule move to the pitch angle that is arranged essentially parallel to substrate from the pitch angle of the substrate that is substantially perpendicular to the liquid crystal layer both sides.As a result, the anisotropy Δ n of refractive index obviously changes.Phase differential δ (λ) becomes δ ≈ 90 degree from δ ≈ 0 degree.

Next, will the basic structure that can be with (energy barrier) in the reflective lcd modulator element be described with reference to figure 2.In the reflective lcd modulator element, the incident by being positioned at light and the ito transparent electrode of exiting side and serve as electrode and the speculum electrode of minute surface apply electric field to liquid crystal layer.The speculum electrode is mainly made by aluminum or aluminum alloy.

In Fig. 2, Reference numeral 102 expression ito transparent electrodes, 103 expressions speculum electrode made of aluminum.Reference numeral 100 expression liquid crystal layers, 101a and 101b are represented the porous liquid crystal alignment film that evaporates obliquely to be used to provide the VAN liquid crystal alignment.Liquid crystal alignment film 101a and 101b are made by the inorganic non-conducting material of mainly forming with silicon dioxide.

Liquid crystal layer 100 is clipped between liquid crystal alignment film 101a and the 101b.The reflective lcd modulator element has such basic structure: ito transparent electrode 102 contacts with speculum electrode 103 and its are outside.Vertical direction among Fig. 2 is represented the rank of energy barrier, and there is vacuum tightness in more top position.

Because the ito transparent electrode 102 work function energy that begin from vacuum tightness are roughly 5.0eV, and the work function energy of aluminum metal mirror electrode 103 is roughly 4.2eV, therefore, they have the energy potential difference that is roughly 0.8eV in their material.

Liquid crystal layer 100 (non-conductive insulator) and the liquid crystal alignment film 101a that is made by silicon dioxide and the Fermi level of 101b are locked in the energy barrier rank (being substantially equal to electron mobility and hole mobility) that equals aluminium.

Be difficult to directly measure the liquid crystal alignment film 101a that makes by porous silica and the width that can be with of 101b.The characteristic that depends on film, the width that can be with of silicon dioxide roughly between 6eV between the 9eV.Consider porous structure, hypothesis is roughly 6eV here.

So, between mirror electrode 103 made of aluminum, liquid crystal layer 100 and liquid crystal alignment film 101a, suppose to be used for the energy that the excitation of electronics catches and be roughly 3eV, also hypothesis is used for the energy that the excitation in hole catches and is roughly 3eV.

By contrast, between ito transparent electrode 102, liquid crystal layer 100 and liquid crystal alignment film 101b, suppose to be used for the energy that the excitation of electronics catches and be roughly 3.8eV, and hypothesis is used for the energy that the excitation in hole catches and is roughly 2.2eV.

As described above, the reflective lcd modulator element can be with the basic structure that has as shown in Figure 2.Yet this band structure has the unbalanced excitation charging in electronics and hole.Therefore, owing to charging along with increasing service time of liquid crystal modulation element spare, the DC electric field between the relative aligning film in the both sides of liquid crystal layer increases tempestuously.

Japanese Patent Application Publication publication No.2005-49817 as described above discloses method shown in Figure 3, to overcome this problem.Fig. 3 has shown the work function adjusting film of being made by nickel, rhodium, lead, platinum or its oxide 104, and its work function is greater than the work function of the aluminium between speculum electrode 103 made of aluminum and the liquid crystal alignment film 101b.This makes the work function of speculum electrode 103 approach the work function of ito transparent electrode 102.

In Fig. 3, ENI and ENM have shown the excitation of electronics.EPI and EPM have shown the excitation in hole.ENI and EPI have shown from the excitation of ito transparent electrode (102) side.ENM and EPM have shown from the excitation of speculum electrode (103) side.

According to the structure among Fig. 3, with substantially the same excitation probability, from electrode 102 and 103 excited electrons and hole.For this reason, the electronics of being caught by liquid crystal layer 100 and liquid crystal alignment film 101a and 101b and the charge volume in hole are identical in the both sides of electrode.This can be avoided producing electric field between ito transparent electrode 102 and speculum electrode 103.

In the operating process of liquid crystal modulation element spare, drive electromotive force as field reversal, apply the electric field of representing by the arrow VPP among Fig. 3 (AC component) to speculum electrode 103.This electric field makes the energy barrier distortion.The excitation probability in electronics or hole changes along with the amount of luminous energy of being represented by the arrow hv among Fig. 3 and photon energy.

The structure of the improvement of expection liquid crystal modulation element spare as described above can prevent early stage generation flicker or the ghost in the use of liquid crystal modulation element spare.

Yet, in practice, the value of the work function of the value of the work function of ito transparent electrode side and speculum electrode side, i.e. their energy barrier, because the restriction of the material of work function adjusting film 104 and the variation of creating conditions thereof can be not consistent each other, can have the roughly difference of 0.1eV between them.

In long-time, along with the increase of service time of liquid crystal modulation element spare, the mild accumulation that this difference causes liquid crystal alignment film 101a and 101b to go up trapped charges.In addition, unbalanced excitation probability produces electric field between ito transparent electrode 102 and speculum electrode 103.So, from for a long time, visible flicker and ghost take place.It should be noted that above-mentioned

" visible flicker " refer to have can by the easy observed rank of human eye or cause people's discomfort the level other flicker.This " visible flicker " be not meant have almost can not by eye-observation to and when it is visible, do not cause other flicker of level of people's discomfort.

Embodiment 1

Below with reference to Fig. 4,5A and 6 to 9 embodiments of the invention 1 are described.

Fig. 4 has shown the ito transparent electrode 102 of control in liquid crystal modulation element spare 400 and the configuration of the circuit of the voltage that applies of speculum electrode 103, and this is the basic configuration of the liquid crystal display of embodiments of the invention 1.Identical in the material of the configuration of liquid crystal modulation element spare 400 and each electrode and each aligning film and the prerequisite technology as described above.

Reference numeral 201 expression dc voltage output circuits, 202 presentation video signal output/reverse drive circuit, 203 remarked pixel electrode sweep circuits, and 204 expressions are as the liquid crystal modulation element spare control circuit of controller.

204 pairs of dc voltage output circuits 201 of liquid crystal modulation element spare control circuit are controlled.Dc voltage output circuit 201 applies predetermined DC voltage to ito transparent electrode 102.

Liquid crystal modulation element spare control circuit 204 is based on the image information that provides equipment 500 to provide from the image such as personal computer, DVD player and TV tuner, to picture signal output/reverse drive circuit 202 output signals.Image provides equipment 500 and liquid crystal display to constitute image display system.

Picture signal output/reverse drive circuit 202 is based on the signal from liquid crystal modulation element spare control circuit 204, to the predetermined alternating voltage of pixel electrode sweep circuit 203 outputs.Pixel electrode sweep circuit 203 applies alternating voltage according to the alternating voltage from picture signal output/reverse drive circuit 202 to speculum electrode 103.

Thereby, applying alternating voltage to speculum electrode 103, this voltage has the square wave shape, and it with respect to the voltage that applies to ito transparent electrode, changed between positive status and negative state in certain one-period.

In the present embodiment, refer to electromotive force to each voltage that each electrode and liquid crystal layer 100 apply with respect to ground (0V) (not shown), that is, and with respect to the electric potential difference on ground.In addition, the central value of the alternating voltage that applies to speculum electrode 103 is called as " center electromotive force ".Yet, in the following description, can be called " electromotive force that applies to speculum electrode 103 " simply to the center electromotive force that speculum electrode 103 applies.In addition, in the following description, the ito transparent electrode side of liquid crystal layer 100 can be called " ITO electrode side " simply, and the speculum electrode side of liquid crystal layer 100 can be called " mirror electrode side " simply.

Reference numeral 210 has shown the light source that sends illumination light hv, and this illumination light hv is radiated on the liquid crystal modulation element spare 400.

Fig. 8 has shown the effective electric field that produces by speculum electrode 103 and ito transparent electrode 102 in liquid crystal layer 100.Transverse axis is represented the time, and Z-axis is represented the effective electric field (electric potential difference) in the liquid crystal layer 100.

Is the AC field V2 with a certain period alpha by speculum electrode 103 to the electric field that the mirror electrode side of liquid crystal layer 100 applies, and is represented by solid line.Is DC electric field V1 by ito transparent electrode 102 to the electric field that the ITO of liquid crystal layer 100 electrode side applies, and is illustrated by the broken lines.

Poor according between these AC field and the DC electric field produces effective electric field in liquid crystal layer 100, perhaps, and with a certain period alpha, at electric field PV with have between the electric field NV of negative polarity and switch with positive polarity.In the following description, the electric field NV that has the electric field PV of positive polarity and have a negative polarity can be called " positive electric field PV " and " negative electric field NV " simply.

Described a certain period alpha in the TSC-system formula corresponding to 1/120 second, and in pal mode corresponding to 1/100 second, its each all corresponding to cycle of a field.One two field picture showed in two field duration (1/60 second or 1/50 second).This a certain period alpha can be corresponding to the display cycle of a two field picture.

By all voltage drops and small electric field being overlapped on the electric field that each electrode in electrode 102 and 103 applies, produce each among positive electric field PV and the negative electric field NV, voltage drop is that the impedance of the aligning film that provided by the interface at electrode and liquid crystal is caused, produces and small electric field is electric charge by capturing enemy personnel or the like.

Liquid crystal modulation element spare control circuit 204 comprises computer program, and has according to computer program and depend on and control the function of dc voltage output circuit 201 service time of liquid crystal modulation element spare 400.

Here refer to the service time of employed liquid crystal modulation element spare 400 and be used to modulate the accumulated time length of operation that enters the light of element from light source.Can repeat accumulation service time (that is the accumulated time length that, is used for the operation of display image) service time of liquid crystal modulation element spare 400 into liquid crystal display.

Below with reference to Fig. 5 A the control of being carried out by liquid crystal modulation element spare control circuit 204 to dc voltage output circuit 201 is described, that is, and the control of the DC voltage that applies by dc voltage output circuit 201 subtend ito transparent electrodes 102.

Figure A among Fig. 5 A shown when the electromotive force that the electromotive force that applies to ito transparent electrode 102 equals to apply to speculum electrode 103, for minimizing the electromotive force that flicker need apply to ito transparent electrode 102 (below abbreviate " minimum flicker ITO electrode potential " as) over time.

Reaching in the present embodiment among described after a while other embodiment that employed " flicker " comprise can not be by the variation of (sightless) light quantity of human eye perception.

In addition, as described above, when the difference between the absolute value of positive electric field PV and negative electric field NV during greater than 400mV, generation can be by the flicker of the easy perception of human eye.On the contrary, invisible in order to make flicker to human eye, under the preferable case, suppress poor between the absolute value of positive electric field PV and negative electric field NV, so that be equal to or less than 400mV (be more preferably and be equal to or less than 300mV, it is good especially to be equal to or less than 200mV).Difference between this electromotive force corresponding to ito transparent electrode (describing below) and the minimum flicker ITO electrode potential is equal to or less than 200mV (preferably be equal to or less than 150mV, be equal to or less than 100mV good especially).

In routine techniques, in the use of liquid crystal modulation element spare, apply and use the identical electromotive force (0V) of early stage minimum flicker ITO electrode potential to ito transparent electrode 102 continuously.

Figure A among Fig. 5 A is that the mean value by the result of the measurement of drawing minimum flicker ITO electrode potential obtains, and measurement is to carry out having on a plurality of liquid crystal modulation element spares of identical configuration.The peak value of the alternating voltage that applies to speculum electrode 103 is fixed.

Liquid crystal modulation element spare generally has such feature: when its each use, minimum flicker ITO electrode potential reduces, up to from bringing into use (beginning optical modulation operation) time T 1 after passing through about 30 minutes, and after time T 1, become a steady-state value Vc, shown in the D graphics among Fig. 9.Using the early stage of liquid crystal modulation element spare, for example, when using for the first time, the minimum flicker of stable state ITO electrode potential Vc is 0V.

Minimum flicker ITO electrode potential as described above is meant over time: along with the increase of access times, promptly, along with increase service time (hourage) of liquid crystal modulation element spare, the minimum flicker of stable state ITO electrode potential Vc can change (increase) when each the use.

In Fig. 5 A, when minimum flicker ITO electrode potential use liquid crystal modulation element spare become steady-state value in early days the time time point be defined as zero hour.Figure A has shown that minimum flicker ITO electrode potential over time after this zero hour.

Liquid crystal display for reality, here employed " using for the first time " is meant the time of the optical modulation operation of liquid crystal modulation element spare being tested before factory's shipment, perhaps in the shop or by the user liquid crystal modulation element spare carried out the optical modulation operation so that the time of display image after the shipment.

Here employed " in early days " comprised " using for the first time " as described above and the preset time section after bringing into use, as 10 hours or 100 hours.This also is applicable to the figure B in the present embodiment, C and described after a while embodiment 2,4 to 6.

In routine techniques, from figure A be appreciated that when the work of liquid crystal modulation element spare 2,000 hours time point roughly, minimum flicker ITO electrode potential uses the value (0V) when early stage to increase roughly 200mV (0.2V).In addition, when the work of liquid crystal modulation element spare 3,000 hours time point roughly, it has increased more than the 300mV.

If applying with respect to minimum flicker ITO electrode potential to ito transparent electrode 102 is 200mv or higher electric potential difference, then particularly in the green glow zone with high relative visibility, the rank of flicker reaches visible easily rank.

In addition, with respect to the situation when using for the first time, the ghost characteristic remarkable worsens.Therefore, in use, if apply and use the identical electromotive force (0V) of early stage minimum flicker ITO electrode potential to ito transparent electrode 102 continuously, then the life-span of liquid crystal modulation element spare is shortened roughly 2,000 hours.

By contrast, in this embodiment, the DC voltage (DC potential) that control applies to ito transparent electrode 102 from dc voltage output circuit 201 is shown in the figure B among Fig. 5 A.

The electromotive force that control applies to ito transparent electrode 102 refers to control ito transparent electrode 102 and speculum electrode 103 electric potential difference between the two.

In the present embodiment, using in early days, the DC potential that applies to ito transparent electrode 102 is set to be the electromotive force that hangs down 50mV (0.05V) than minimum flicker ITO electrode potential (0V).

This means, the shown minimum of figure A flicker ITO electrode potential has the feature that changes monotonously along with the positive direction of being increased in of service time (a certain direction), and the electromotive force that applies to ito transparent electrode 102 with respect to the electromotive force that applies to speculum electrode 103 negative direction (with a certain side in the opposite direction) be shifted.

" variation monotonously " is meant in a certain direction and changes (allowing its time to pause) continuously, and be included in the indeclinable basically in the opposite direction variation with a certain side.Here, if the minimum flicker of stable state ITO electrode potential does not change in negative direction, then liquid crystal modulation element spare is regarded as having feature as described above.

In addition, in this embodiment, electrode 102 and 103 electric potential difference between the two is set to be different from the value of electric potential difference between minimum flicker electrode (this is for minimizing the electric potential difference that flicker applies at electrode 102 and 103 between the two), so that the electromotive force of ito transparent electrode 102 is than the low 50mV of minimum flicker ITO electrode potential.

In addition, in this embodiment, shown in the figure E among Fig. 9, from using (promptly for the first time, from when the time point that when using for the first time, enters liquid crystal modulation element spare for the first time from the light of light source), apply electromotive force to ito transparent electrode 102 than the low 50mV of minimum flicker ITO electrode potential.

To illustrate the definition of the minimum flicker ITO electrode potential (electric potential difference between minimum flicker electrode) of liquid crystal modulation element spare below.Minimum flicker ITO electrode potential depends on the various extra factors such as illumination light intensity.

For example, when utilizing about 3mW/cm ²High-strength light irradiating liquid crystal modulator element the time, in about 30 minutes, minimum flicker ITO electrode potential can change about 200mV in time.Consider such situation, minimum flicker ITO electrode potential is defined in the interior indeclinable stationary potential of short time of about a few minutes.

Specifically, stable state refers to such state: when in 2 minutes, measuring minimum flicker ITO electrode potential continuously, in first 1 minute and the difference of the mean value of the minimum of measuring in next 1 minute flicker ITO electrode potential be equal to or less than 10mV.

Figure A among Fig. 5 A has shown the minimum flicker of this stable state ITO electrode potential.For general liquid crystal modulation element spare, the value of 10mV is the enough values as steady-state value.Yet if the liquid crystal modulation element spare that consideration has unusual (singular) feature, this value can be 30mV.

Next, will apply the effect of the electromotive force that is lower than minimum flicker ITO electrode potential with reference to early stage (below abbreviate " using early stage " as) that figure 6 is described in service time to ito transparent electrode 102.

To ito transparent electrode 102 apply be lower than minimum flicker ITO electrode potential electromotive force in liquid crystal layer positive electric field and negative electric field between produce asymmetry.This asymmetric electric field produces DC electric field VDC between the two at electrode 102 and 103, shown in the arrow among Fig. 6.

Fig. 6 has shown the energy barrier that is out of shape owing to this DC electric field.

When light hv entered liquid crystal modulation element spare under this state, near the interface between liquid crystal layer 100 and the liquid crystal alignment film 101a, the electronics that uses liquid crystal modulation element spare to catch was encouraged forcibly by light hv, shown in arrow RNI.

These electronics are moved to the ito transparent electrode side owing to applied electric field by the inclination of energy level.On the other hand, near the hole of catching the interface between liquid crystal layer 100 and the liquid crystal alignment film 101b is encouraged forcibly by light hv, shown in arrow RPM.These holes are moved to speculum electrode side owing to applied electric field by the inclination of energy level.

In other words, near the electric charge of catching the interface between liquid crystal layer 100 and liquid crystal alignment film 101a and the 101b is energized and moves to electrode 102 and 103 so that be removed, thereby has reduced the positive electric field of generation in liquid crystal layer 100 and the difference of negative electric field.

These effects can be reduced near the accumulative speed of the electric charge of the charging of interface between liquid crystal layer 100 and liquid crystal alignment film 101a and the 101b.

Under the preferable case, use in early days to be and the difference of minimum flicker ITO electrode potential electromotive force less than 200mV to the electromotive force that will apply to ito transparent electrode 102.This is because the flicker that the difference that is equal to or greater than 200mV can make the green glow with high relative visibility as seen.Enter under the situation of liquid crystal modulation element spare at ruddiness that only has low relative visibility or blue light, preferably, the electromotive force that apply to ito transparent electrode 102 is and the difference of the minimum flicker ITO electrode potential electromotive force less than 250mV.

On the other hand, should be to consider under the situation of individual difference of liquid crystal modulation element spare to the minimum potential that ito transparent electrode 102 applies in early days, the electromotive force of 30mV or higher difference is provided between the absolute value of the positive and negative electric potential difference in liquid crystal layer 100.This is because this difference can obtain effect referred to above.In the case, the electromotive force that apply to ito transparent electrode 102 is 15mV with the difference of minimum flicker ITO electrode potential.

In this embodiment, for guaranteeing to obtain effect as described above, using the electromotive force that will be set to be to the electromotive force that ito transparent electrode 102 applies in early days than the low 50mV of minimum flicker ITO electrode potential.Because the electric potential difference of 50mV is less than 200mV, therefore, this electromotive force that hangs down 50mV than minimum flicker ITO electrode potential can not produce flicker.

Liquid crystal modulation element spare has such feature: the absolute value of the positive potential difference in the liquid crystal layer 100 is along with the increase of service time, changes in the direction that becomes greater than the absolute value of negative electricity potential difference.

Certainly, also having a kind of situation is that liquid crystal modulation element spare has such feature: the absolute value of the positive potential difference in the liquid crystal layer 100 changes in the direction that becomes less than the absolute value of negative electricity potential difference.Yet, in this embodiment the situation that it changes in the direction that becomes bigger will be described.

In this embodiment, using in early days, move in the direction of the absolute value that makes positive potential difference referred to above to the electromotive force that ito transparent electrode 102 applies greater than the absolute value of negative electricity potential difference.

For example, move (perhaps, the electromotive force that applies to speculum electrode 103 moves in positive direction) in negative direction to the electromotive force that ito transparent electrode 102 applies, so that the absolute value of positive potential difference becomes greater than the absolute value of negative electricity potential difference.

In other words, when the long-time use owing to liquid crystal modulation element spare has produced asymmetry (positive electric field PV as shown in Figure 8 is greater than negative electric field NV), in early days electric field is arranged so that in its use positive electric field PV becomes greater than negative electric field NV.

Yet, depend on condition such as configuration of the film of liquid crystal modulation element spare and illumination light quantity, along with the increase of its service time, the absolute value of the negative electricity potential difference in the liquid crystal layer changes in the direction that becomes greater than the absolute value of positive potential difference.

In the case, using in early days, move in the direction of the absolute value that makes negative electricity potential difference referred to above to the electromotive force that ito transparent electrode 102 applies greater than the absolute value of positive potential difference.

In other words, when having produced asymmetry (positive electric field PV is less than negative electric field NV), in early days electric field is arranged so that in use positive electric field PV becomes less than negative electric field NV.

In addition, in this embodiment, the electric potential difference that provides between electrode 102 and 103 changes like this, so that the absolute value sum of the as described above positive and negative electric potential difference in the liquid crystal layer 100 is constant.

This brightness of image that can prevent liquid crystal modulation element spare is owing to positive variation with the absolute value electric potential difference of bearing produces fluctuation.

In addition, minimum flicker ITO electrode potential (that is electric potential difference between minimum flicker electrode) when becoming the feature of steady-state value, can carry out the following description of relevant this embodiment after liquid crystal modulation element spare has the wherein variation in each the use.

In this embodiment, becoming the time point of steady-state value, apply the electromotive force that is different from the minimum flicker of stable state ITO electrode potential to ito transparent electrode 102 when minimum flicker ITO electrode potential in each the use.

In other words, the electric potential difference that provides between ito transparent electrode 102 and the speculum electrode 103 is provided the time point when electric potential difference becomes steady-state value between minimum flicker electrode, so that the electric potential difference that is provided is different from electric potential difference between the minimum flicker of stable state electrode.

Yet, using early stage voltage setting as described above can not suppress accumulation fully along with the electric charge of the increase charging of service time.

Correspondingly, in this embodiment, the electromotive force that apply to ito transparent electrode 102 is along with the increase of the service time of liquid crystal modulation element spare, with roughly per hour the speed of 0.6mV increase.

In other words, be controlled at the electric potential difference that provides between ito transparent electrode 102 and the speculum electrode 103, so that change electric potential difference to follow the minimum flicker ITO electrode potential that changes along with the time.

In the present embodiment, the minimum output voltage resolution of dc voltage output circuit 201 is approximately 3mV, and every about 5 hours, the electric potential difference between ito transparent electrode 102 and the speculum electrode 103 is carried out replacement.This suppressed the as described above positive and negative electric potential difference that causes owing to the electric charge of catching absolute value difference over time, thereby can suppress flicker and ghost in the long-time section.

Cause minimum flicker ITO electrode potential to change in the combination of using the control of early stage voltage setting as described above and voltage follow as described above, shown in the figure C among Fig. 5 A.Difference between figure C and B increases to 200mV (0.2V) or more for a long time, the flicker beginning is visible.Therefore, combinations thereof can prolong about 700 hours from 2,000 hours of routine with life-span of liquid crystal modulation element spare.

In addition, when reached 5,000 hours the service time of liquid crystal modulation element spare, the value of minimum flicker ITO electrode potential changed 450mV from using early stage value, and becomes steady-state value.Finish when therefore, voltage follow is controlled at about 5,000 hours.Control as described above can make the risk minimization that generates visible flicker.

To describe below and change the electromotive force that will apply to ito transparent electrode 102, be i.e. the timing of the electric potential difference that provides between the two at electrode 102 and 103.In the present embodiment, because the varying width of each variation of the electric potential difference that provides at electrode 102 and 103 is roughly 3mV, therefore, the disturbance of shown image can not take place when changing electric potential difference between the two.

Therefore, even in the process of display image, change electric potential difference based on the arrival of time of predetermined change electric potential difference.If owing to the disturbance of image takes place in the change of electric potential difference, then can not work as when having image to show and change electric potential difference, for example, and when energized, when deenergization, and in the operating period that does not have the image information input.This time that changes electric potential difference also is applicable to the embodiment 2 that describes after a while.

Fig. 7 is the process flow diagram that has shown according to the process of the computer program that provides in the liquid crystal modulation element spare control circuit 204.

In step (being abbreviated as S in the drawings) 1, the timer that wherein provides is provided liquid crystal modulation element spare control circuit 204.

In step 2, liquid crystal modulation element spare control circuit 204 determines whether reach the predetermined electromotive force change time by the time of timer institute timing.When reaching predetermined electromotive force and change the time, process enters step 3, and when not reaching predetermined electromotive force and change the time, liquid crystal modulation element spare control circuit 204 repeating steps 2.

In step 3, the ITO electrode of liquid crystal modulation element spare control circuit 204 from be stored in the internal storage (not shown) is provided with to read in the table distributes to the ITO electrode potential data that the electromotive force that has arrived changes the time.In addition, liquid crystal modulation element spare control circuit 204 is also controlled dc voltage output circuit 201, so that apply DC voltage (DC potential) corresponding to ITO electrode potential data to ito transparent electrode 102.

In step 4, liquid crystal modulation element spare control circuit 204 judges whether distribute all electromotive forces of ITO electrode potential data to change the timing of time to it finishes (that is, whether having used all ITO electrode potential data).If then this flow process finishes.If not, then in step 1, start new timer timing.

Charging rate in the liquid crystal modulation element spare depend on liquid crystal modulation element spare service condition (for example, environment temperature, the light intensity that enters or spectrum, to electromotive force that ito transparent electrode applies and use poor between the early stage minimum flicker ITO electrode potential).In addition, it also depends on poor between the absolute value of positive and negative electric potential difference as described above.

Therefore, the measurement for the change amount of the charging rate of the various changes of service condition is carried out in suggestion in advance, then, change according to service condition, change the electromotive force that (correction) will apply to ito transparent electrode 102, that is, and electrode 102 and 103 electric potential difference between the two.This also is applicable to described after a while embodiment 2.

Embodiment 2

Fig. 5 B has shown in the liquid crystal display of embodiments of the invention 2, is applied the control of DC voltage to ito transparent electrode 102 by liquid crystal modulation element spare control circuit 204.The basic configuration of the liquid crystal display in the present embodiment is identical with basic configuration among the embodiment 1.The assembly identical with assembly among the embodiment 1 by with embodiment 1 in the same reference numerals of assembly indicate.

In Fig. 5 B, figure A has shown that minimum flicker ITO electrode potential over time when the electromotive force that the electromotive force that applies to ito transparent electrode 102 equals to apply to speculum electrode 103.Figure B has shown the electromotive force that applies to ito transparent electrode 102 in the present embodiment.Figure C has shown that minimum flicker ITO electrode potential over time when applying the shown electromotive force of figure B to ito transparent electrode 102.

In the present embodiment, using in early days, the DC voltage (DC potential) that applies to ito transparent electrode 102 is set to be the electromotive force that hangs down 150mV (0.15V) than minimum flicker ITO electrode potential (0V).

In other words, using in early days, electrode 102 and 103 electric potential difference between the two is set to be different from the value of electric potential difference between minimum flicker electrode (this is to minimize flicker and the electric potential difference that need apply at electrode 102 and 103 between the two), so that the electromotive force that applies to ito transparent electrode 102 is than the low 150mV of minimum flicker ITO electrode potential.

As described above, the electric potential difference between ito transparent electrode 102 and the speculum electrode 103 be 200mV or higher feasible flicker as seen.Therefore, as seen the electromotive force of ito transparent electrode 102 can not make flicker than the low 150mV of minimum flicker ITO electrode potential.

Poor (its greater than among the embodiment 1 poor) between ito transparent electrode 102 and the minimum flicker ITO electrode potential makes the asymmetry of the positive and negative electric field that produces in liquid crystal layer 100 greater than the asymmetry among the embodiment 1.Thereby, shown in Figure 6 electrode 102 and 103 between the two (that is, in liquid crystal layer 100) DC electric field VDC of producing further increase.

This DC electric field further makes the energy barrier distortion in the liquid crystal layer 100.Therefore, when light hv entered liquid crystal modulation element spare, the light hv that the electronics that uses element to catch is entered encouraged forcibly, thereby had improved the amount of the electronics that moves to the ito transparent electrode side.

In addition, near the hole of catching the interface of liquid crystal layer 100 and liquid crystal alignment film 101b, the hole number that moves to speculum electrode side increases.Compare with embodiment 1, this can further be reduced near the accumulative speed of the electric charge that charges the interface of liquid crystal layer 100 and liquid crystal alignment film 101a and 101b.

In the present embodiment, except using early stage such voltage setting, the electromotive force that will apply to ito transparent electrode 102 is along with the increase of the service time of liquid crystal modulation element spare increases with the low speed that is roughly 0.4mV/ hour, so that will change, to follow the change of minimum flicker ITO electrode potential to the electromotive force that ito transparent electrode 102 applies.As among the embodiment 1, this can suppress the generation of flicker and ghost in long-time section.

Cause minimum flicker ITO electrode potential to change in the combination of using the control of early stage voltage setting as described above and voltage follow as described above, shown in the figure C among Fig. 5 B.Difference between figure C and B reaches 200mV (0.2V) before, and flicker is sightless, when this difference increases to 200mV or when higher, the flicker beginning can be visible.Therefore, combinations thereof can prolong about 4,000 hours from 2,000 hours of routine with life-span of liquid crystal modulation element spare.

In addition, when reached 10,000 hours the service time of liquid crystal modulation element spare, the value of minimum flicker ITO electrode potential changed 600mV from using early stage value, becomes steady-state value then.Finish when therefore, voltage follow is controlled at about 10,000 hours.Control as described above can make the risk minimization that generates visible flicker.

This embodiment is effectively for the variation that suppresses minimum flicker ITO electrode potential (that is, electric potential difference between minimum flicker electrode), for example, when it under situation about changing greatly in the process service time of liquid crystal modulation element spare.

The pushing the speed of the electric potential difference that provides between the two at electrode 102 and 103 described in the embodiment 1 and 2 depended on the parameter such as light wavelength that enters liquid crystal modulation element spare and chilling temperature thereof.

In addition, as flicker become the electric potential difference of visible threshold value depend on such as the parameter red, that green is relevant with blue wavelength.

Therefore, preferably measure the feature be installed in the single liquid crystal modulation element spare in the liquid crystal display, to be identified for carrying out the optimal parameter of the control described in each in embodiment 1 and 2.

In addition, when showing that minimum flicker ITO electrode potential can be similar to by nonlinear curve with the curve that changes service time, preferably also the curve of the controlled electromotive force of ito transparent electrode 102 is set to nonlinear curve.

In addition, the situation that applies DC voltage and alternating voltage to ito transparent electrode and speculum electrode has been described respectively in embodiment 1 and 2.Yet, when in certain one-period, in liquid crystal layer, periodically producing positive and negative electric field, can apply alternating voltage to two electrodes.Identical principle also is applicable to described after a while embodiment 4 to 6.

Embodiment 3

Figure 10 has shown a liquid crystal projection apparatus (image projection equipment), and it is in the liquid crystal display described in embodiment 1 and 2 one.Figure 10 is the planimetric map (part side view) that has shown the optical arrangement of projector.

The liquid crystal panel driver that Reference numeral 3 expressions have the function of as shown in Figure 4 liquid crystal modulation element spare control circuit 204, picture signal output/reverse drive circuit 202 and pixel electrode sweep circuit 203.The image information that liquid crystal panel driver 3 will provide equipment 500 to import from image as shown in Figure 4 is converted to and is used for redness, green and blue panel driving signal.

Be used for redness, green and blue panel driving signal and be imported into red liquid crystal panel 2R, green liquid crystal panel 2G and blue liquid crystal panel 2B respectively.Thereby three liquid crystal panel 2R, 2G and 2B are driven independently of one another.Each liquid crystal panel all is the reflective lcd modulator element.

Reference numeral 1 expression lamp optical system.The left side in the square frame has in the drawings shown the planimetric map of lamp optical system 1, and has shown its side view on the right.Lamp optical system 1 comprises illuminator, parabolic mirror, fly's-eye lens, polarization conversion device, collector lens or the like, and sends illumination light as the linearly polarized photon (S polarized light) with identical polarization direction.

Illumination light from lamp optical system 1 incides on the dichronic mirror 30, the light of these dichronic mirror 30 reflects magenta, and the light of transmit green.The magenta component of illumination light is reflected by dichronic mirror 30, and transmission is by Blue-Cross chromatic polarimeter 34 then, and this chromatic polarimeter provides half-wave retardation for the polarized light of blueness.Thereby, produced blue linearly polarized photon (P polarized light) and red linearly polarized photon (having S polarized light) perpendicular to the polarization direction of paper with polarization direction of the paper that is parallel to this figure.

Blue P polarized light enters first polarization beam splitter 33, and transmission is by its light beam diffusion barrier, to arrive blue liquid crystal panel 2B then.Red S polarized light is by the reflection of the light beam diffusion barrier of first polarization beam splitter 33, to arrive red liquid crystal panel 2R.

The S polarized light transmission of transmission by the green of dichronic mirror 30 enters second polarization beam splitter 31 then by being used to proofread and correct the virtual glass 36 of green optical path length.Green S polarized light is by the reflection of the light beam diffusion barrier of second polarization beam splitter 31, to arrive green liquid crystal panel 2G.

As described above, utilize illumination light irradiation redness, green and blue liquid crystal panel 2R, 2G and 2B.

Depend on be arranged in the liquid crystal panel and reflected with from the modulation condition of the pixel of outgoing wherein by liquid crystal panel, the delay of polarization is provided for the light that enters each liquid crystal panel.In reflected light, has polarized light component backpropagation on optical path of illuminating light of the polarization direction identical, to turn back to lamp optical system 1 with the polarization direction of illumination light.

On the other hand, in reflected light, have perpendicular to the polarized light component (light modulated) of the polarization direction of the polarization direction of illumination light and propagate as follows.

By the light beam diffusion barrier of the P polarized light transmission of the redness of red liquid crystal panel 2R modulation by first polarization beam splitter 33.Then, red P polarized light is converted into the S polarized light by means of transmission by Red Cross chromatic polarimeter 35, and Red Cross chromatic polarimeter 35 provides half-wave retardation to the polarized light of redness.Red S polarized light enters the 3rd polarization beam splitter 32, by its light beam diffusion barrier reflection, arrives projecting lens (projection optical system) 4 then.

The S polarized light of the blueness by blue liquid crystal panel 2B modulation is by the reflection of the light beam diffusion barrier of first polarization beam splitter 33, and transmission receive delay effect by Red Cross chromatic polarimeter 35 and not then is to enter the 3rd polarization beam splitter 32.Blue S polarized light is arrived projecting lens 4 then by the reflection of the light beam diffusion barrier of the 3rd polarization beam splitter 32.

The P polarized light transmission of the green by green liquid crystal panel 2G modulation is by the light beam diffusion barrier of second polarization beam splitter 31, and transmission is by being used to proofread and correct the virtual glass 37 of green optical path length, to enter the 3rd polarization beam splitter 33 then.Green P polarized light transmission arrives projecting lens 4 then by the light beam diffusion barrier of the 3rd polarization beam splitter 32.

The modulated light of three kinds of colors of combination like this is projected lens 4 and projects on the light diffusing screen 5 (projection surface).Thereby demonstration full-colour image.

As described above, differ from one another for the minimum of red, the green and blue liquid crystal panel interelectrode electric potential difference of glimmering.Therefore, for each liquid crystal panel, can carry out independently and use early stage voltage setting and voltage follow control.

Embodiment 4

In above-described each embodiment,, bring into use equipment having a mind to make under the state that will be lower than minimum flicker ITO electrode potential to the electromotive force that ito transparent electrode applies.In the method, because as seen the reduction amount that surpasses 200mV of the electromotive force of ito transparent electrode makes flicker, therefore, maximum reduction amount is 200mV.Yet for some structure of the film that constitutes liquid crystal modulation element spare, the reduction amount of 200mV may be not enough to suppress charging.

In the present embodiment, will describe for having wherein by reducing the control method that the charging depression effect that will obtain to the electromotive force that ito transparent electrode 102 applies is the liquid crystal modulation element spare of little membrane structure.

Assembly identical with assembly among the embodiment 1 and the assembly among the embodiment 1 have identical Reference numeral.Yet the structure of the aligning film in the liquid crystal modulation element spare is different from the situation among the embodiment 1.

At first, different with described method in embodiment 1 and 2 with describing, to suppress the minimum ITO electrode potential method over time of glimmering to the electromotive force that ito transparent electrode 102 applies by reducing.

In the disclosed typical method, liquid crystal apparatus comprises photodetector in Jap.P. No.3079402, and by using photodetector to regulate the electromotive force of common electrode, so that minimize flicker.

Use this method of photodetector also can suppress to take place owing to the flicker that minimum flicker ITO electrode potential causes over time.Yet this method has following point.

At first, utilize the photo-detector measurement flicker to require invariant in time output rest image, thereby the output rest image should be the grayscale image that is suitable for measuring flicker.Therefore, disclosed method also requires to adjust sequence in addition among the use Jap.P. No.3079402, is used for temporarily exporting a certain grayscale image for adjusting (measurement), and this can disturb the normal image display operation.

In addition, carry out when adjusting sequence normally when the liquid crystal display energized or at deenergization, thereby in use can not suppress the big variation of minimum flicker ITO electrode potential.

Next, will this embodiment be described with reference to Figure 11.Figure 11 shown carry out by liquid crystal modulation element spare control circuit 204, to the control of the DC voltage that will apply to ito transparent electrode 102.

In Figure 11, figure G has shown that minimum flicker ITO electrode potential over time when the electromotive force that the electromotive force that applies to ito transparent electrode 102 equals to apply to speculum electrode 103.

In this embodiment, the DC voltage (DC potential) that control will apply to ito transparent electrode 102 from dc voltage output circuit 201 is shown in the figure H among Figure 11.Pattern I has shown that minimum flicker ITO electrode potential over time when applying the shown electromotive force of figure H to ito transparent electrode 102.

Using early stage (0 hour), the electromotive force that adjusting will apply to ito transparent electrode 102 is so that consistent with minimum flicker ITO electrode potential.

Then, automatically change the electromotive force that will apply to ito transparent electrode 102, so that it is being followed with the minimum flicker ITO electrode potential that changes service time by 0.08mV/ hour speed roughly.

Based on the end value of from experiment of prior art or the like, obtaining, determine the change speed of the electromotive force that will apply to ito transparent electrode 102.According to the curve of the typical minimum flicker ITO electrode potential that obtains from experimental result, can determine will be in the value of setting of the electromotive force that ito transparent electrode 102 the applies scope at ± 200mV.

Based on the tendency of the variation between the single liquid crystal modulation element spare or the like, determine the detailed value of setting.With will be to the electromotive force that ito transparent electrode 102 the applies relevant data storage that is provided with in liquid crystal modulation element spare control circuit 204 in the included internal storage.

In this embodiment, when minimum flicker ITO electrode potential is saturated over time (about 5.000 hours), the automatic change control that carry out to the electromotive force that ito transparent electrode 102 applies is finished.

Compare with conventional equipment, flicker can be begun to want about 2,000 hours of descried time lengthening the control of the electromotive force that will apply to ito transparent electrode 102.

In addition, this embodiment makes also that in the common display operating process carrying out the real-time basically adjustment that is used to minimize flicker becomes possibility, and need not the new add-on assemble such as photodetector, also can not felt by the user.

Embodiment 5

In embodiment 4, the real-time basically adjustment of the electromotive force that subtend ito transparent electrode 102 applies has been described.By contrast, can carry out adjustment at interval, that is, can carry out by the mode of stepping with preset time.

Figure 12 shown carry out by liquid crystal modulation element spare control circuit 204, to the control of the DC voltage that will apply to ito transparent electrode 102.Figure G, H among Figure 12 and the implication of I are identical with implication among the embodiment 4.

In this embodiment, from using in early days, (for example every the preset time section, 1,000 hour), liquid crystal modulation element spare control circuit 204 all based on the prediction to the change of minimum flicker ITO electrode potential, makes and will move to the electromotive force that ito transparent electrode 102 applies.

Should note, when the electromotive force that applies every preset time Duan Yaoxiang ito transparent electrode moves, (following closely after moving) after moving will be set to less than 200mV (that is, glimmering to human eye in the sightless scope) to electromotive force and the difference between the minimum flicker ITO electrode potential that ito transparent electrode applies.This difference is best less than 50mV, is more preferably less than 30mV.Identical principle also is applicable to described after a while embodiment 6.

In this embodiment, the electromotive force that (follows closely after moving) after moving will to apply to ito transparent electrode 102 is different from minimum flicker ITO electrode potential in the opposite direction of change direction (a certain direction is a positive dirction) with minimum flicker ITO electrode potential here.This can postpone the change of minimum flicker ITO electrode potential.

Yet allowing (to follow closely after moving) after moving will be different from minimum flicker ITO electrode potential in a certain direction to the electromotive force that ito transparent electrode 102 applies, as at described embodiment 6 after a while (Figure 13 and 14).This makes after the long time period and to move the electromotive force that will apply to ito transparent electrode 102.

In addition, though in this embodiment, after surpassing 4,000 hours, finish move (figure H is shown) of the electromotive force that will apply to ito transparent electrode 102,, the present invention is not limited only to this.In other words, after surpassing 4,000 hours, can continue to the moving of electromotive force that ito transparent electrode 102 applies, thereby make flicker invisible human eye.

So, change the generation that will can suppress to glimmer in the direction that reduces flicker to the electromotive force that ito transparent electrode 102 applies.In addition, this embodiment can also save the internal storage that comprises in the liquid crystal modulation element spare control circuit 204.

In addition, though in cycle of 1,000 hour, move the electromotive force that will apply to ito transparent electrode 102 in this embodiment,, moving period can certainly be 100 hours cycle or 10 hours cycle.

Embodiment 6

Figure 13 illustrates the embodiment 6 as the modified example of embodiment 5.In this embodiment, from using in early days, every the preset time section, liquid crystal modulation element spare control circuit 204 will be changed into less times greater than the value of the change value of the prediction of minimum flicker ITO electrode potential to the electromotive force that ito transparent electrode 102 applies by the mode of stepping.Consider the change subsequently of minimum flicker ITO electrode potential, determine bigger value.

So, even in that change to the direction that reduces flicker will be under the situation of the electromotive force that ito transparent electrode 102 applies, the electromotive force that apply to ito transparent electrode 102 also needn't be consistent with the minimum ITO electrode potential that glimmers.

In the case, with reference to the electromotive force 500 that make to change and change difference between the electromotive force 501 of tight front for just with the amount of the hypermetamorphosis acceleration that prevents minimum flicker ITO electrode potential, with the amount of movement of the electromotive force determining to apply to ito transparent electrode 102.

In addition, because the membrane structure of liquid crystal modulation element spare and taking place hardly by will under the situation that the generation of the flicker that variation caused of the electromotive force that ito transparent electrode 102 applies is quickened, using the shown control of Figure 14 for what follow that minimum flicker ITO electrode potential causes.

In this control, can be based on the glimmer change of ITO electrode potential of minimum, the electromotive force that setting will apply to ito transparent electrode 102, and need not to consider condition each the size in electromotive force 502 that changes and the electromotive force 503 that changes tight front, as shown in figure 14.

In this embodiment, permission (follows closely after moving) after moving will be different from minimum flicker ITO electrode potential in a certain direction to the electromotive force that ito transparent electrode 102 applies, and the difference between them is 0 among Figure 13 in 20mv and Figure 14 basically 10 to 50mv.

(following closely after moving) after moving will preferably be equal to or less than 100mV to electromotive force that ito transparent electrode 102 applies and the difference between the minimum flicker ITO electrode potential, is more preferably and is equal to or less than 50mV, and preferred is to be equal to or less than 30mV.

If the electromotive force that applies to ito transparent electrode 102 is little to the acceleration action of the change of minimum flicker ITO electrode potential in the difference of a certain direction with minimum flicker ITO electrode potential, so, difference as described above can be for greatly.

The control method of the liquid crystal modulation element spare described in each of embodiment 4 to 6 also goes for the liquid crystal display such as the liquid crystal projection apparatus described in the embodiment 3.

As described above, in each embodiment, the electromotive force that apply to ito transparent electrode 102 changes with the increase of service time, so that will be suppressed at not by in the scope of human eye perception (a certain scope) as the flicker of the variation of light quantity.In other words, the electromotive force that will apply to ito transparent electrode 102 changes with the increase of service time, so that the difference between the absolute value of the positive and negative electric potential difference that produces in liquid crystal layer is suppressed in the difference range corresponding to a certain scope (that is, to electromotive force that ito transparent electrode 102 applies and the difference between the minimum flicker ITO electrode potential scope less than 200mV).

This can suppress the generation of visible flicker, ghost or the like effectively in the long-term use of liquid crystal modulation element spare.

Therefore, can realize in long-time section, to reduce the liquid crystal modulation element spare of the quality decline of display image.

In addition, the control method described in each embodiment among the embodiment 1,2 and 4 to 6 also goes for the liquid crystal display different with liquid crystal projection apparatus, as the liquid crystal display of direct viewing type.

In addition, the situation that the electromotive force that apply to ito transparent electrode changes with the increase of service time has been described.Yet the center electromotive force of the electromotive force that will apply to the speculum electrode can change with the increase of service time, and will be set to steady state value to the electromotive force that ito transparent electrode applies.

In the case, the center electromotive force (minimum spinthariscope electrode potential) of the minimum mirror electrode of flicker is being changed for the increase of negative direction with service time with respect to the electromotive force that applies to ito transparent electrode 102 (0V).Therefore, the center electromotive force of the electromotive force that apply to the mirror electrode should be positive direction with respect to the moving direction of minimum spinthariscope electrode potential.

In addition, can change with the increase of service time to the electromotive force that ito transparent electrode and mirror electrode apply.

In addition, described and from storer, read electromotive force and data are set with according to the situation that changes the electromotive force that will apply to electrode service time.Yet, in the present invention, can use flicker sensor as optical sensors, change the electromotive force that will apply to electrode with sensor-based testing result.

In addition, the present invention is not limited only to these preferred embodiments, under the situation that does not depart from scope of the present invention, can carry out various modifications.

Claims (6)

1, a kind of liquid crystal display comprises:

Liquid crystal modulation element spare, second electrode that this liquid crystal modulation element spare comprises first electrode, made by the material of the material that is different from first electrode, at the liquid crystal layer between first and second electrodes, at first aligning film between first electrode and the liquid crystal layer and second aligning film between second electrode and liquid crystal layer, this liquid crystal display utilization comes display image from the light that the first electrode side enters liquid crystal layer; And

Controller, the electromotive force that the control of this controller will apply to first and second electrodes, so that electric potential difference periodic variation between positive and negative that will apply to liquid crystal layer, the electromotive force that apply to second electrode is with respect to center electromotive force periodic variation between positive and negative

Wherein, along with service time of liquid crystal modulation element spare increases, this controller changes will be to electromotive force that first electrode applies and will be at least one electromotive force in the center electromotive force of the electromotive force that second electrode applies,

Wherein, when controller changed described at least one electromotive force, the change of described at least one electromotive force reduced flicker.

2, liquid crystal display according to claim 1, wherein, this controller changes described at least one electromotive force, makes flicker for human eye in the sightless scope so that be suppressed at the difference of the absolute value of the positive and negative electric potential difference that will apply to liquid crystal layer during showing a two field picture.

3, liquid crystal display according to claim 1, wherein, when first electromotive force is indicated to electromotive force that first electrode applies and will be in the center electromotive force of the electromotive force that second electrode applies one, when second electromotive force is represented in described two electromotive forces another,

Liquid crystal modulation element spare has such feature: under the situation that will be equal to each other to first and second electromotive forces that two electrodes apply, increase along with service time of liquid crystal modulation element spare, with respect to second electromotive force that applies that will be in two electrodes, change monotonously in a certain direction and to make at each minimum stable state first electromotive force of flicker when using liquid crystal modulation element spare, and

Controller changes first electromotive force that will apply to another electrode in two electrodes in described a certain direction with respect to second electromotive force that will an electrode in two electrodes applies.

4, liquid crystal display according to claim 3, wherein, controller is early stage service time of liquid crystal modulation element spare, with described a certain side make in the opposite direction must be in two electrodes this another first electromotive force that applies be different from will be in two electrodes this second electromotive force that applies.

5, liquid crystal display according to claim 1, wherein, the work function of the material of first and second electrodes differs from one another.

6, liquid crystal display according to claim 1, wherein, controller changes by the mode of stepping will be to electromotive force that first electrode applies and will be in the center electromotive force of the electromotive force that second electrode applies one.

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