JPH03223717A - Liquid crystal element, liquid crystal display element, liquid crystal display device, and recording device - Google Patents

Abstract

PURPOSE:To eliminate a flicker and to obtain fast response by arranging a polarizer and an analyzer at the best positions when there is a domain where attenuation or variation in size is caused. CONSTITUTION:When there is the domain where attenuation or variation in size is caused, the polarizer and analyzer are arranged so that the domain is present in a light state. When an electric field E is applied, liquid crystal molecules are oriented in a 1st stable state 33. When a reverse-directional electric field E' is applied, the liquid crystal molecules are oriented in a 2nd stable state 33' to change in direction; and the molecules stay in the direction in either case when the electric field is ceased. Namely, the speediness of the response speed and bistability are realized effectively. Consequently, the flicker is eliminated and the fast response is obtained.

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to a liquid crystal element using a ferroelectric smectic liquid crystal, which is installed in an image display or recording device, and particularly relates to a liquid crystal element that uses a ferroelectric smectic liquid crystal and is particularly concerned with the generation of flickering and afterimage during multiplex leg driving. The present invention relates to a ferroelectric smectic liquid crystal display element that improves contrast ratio or transmittance while preventing the above problems.

[Conventional technology]

Clark (C1ark) and Lage Wall (C1ark) and Lage Wall (C1ark) are display devices that utilize the refractive index anisotropy of liquid crystal molecules to control transmitted light in combination with a polarizing element.
(U.S. Pat. No. 4,367).
No. 924 specification, US Pat. No. 4,639,089, etc.).

This liquid crystal generally has a chiral smectic C phase (SmC') or H phase (SmH'') in a specific temperature range, and in this state, the first
and a second optically stable state. In addition, this liquid crystal has the property of maintaining its state when no electric field is applied, that is, it has bistability, and it also responds quickly to changes in the electric field, so it can be widely used as a high-speed and memory-type display element. is expected.

The aforementioned smectic liquid crystal element incorporates a matrix electrode composed of a scanning electrode and a signal electrode, a scanning signal is sequentially applied to the scanning electrode, and an information signal is applied to the signal electrode in synchronization with the scanning signal. Ru. When applying this multiplexing drive to a smectic liquid crystal element, when a refresh drive is used in which scanning signals are repeatedly applied to the scanning electrodes and applied periodically, flickering occurs on the display screen (this occurs because the brightness of the entire screen changes periodically). There is a problem that flickering may occur.

[Problem to be solved by the invention]

An object of the present invention is to provide a novel liquid crystal element that solves the problems of conventional liquid crystal display elements as described above.

Another object of the present invention is to provide a liquid crystal display element with high-speed response.

[Means and Effects for Solving the Problems] It is an object of the present invention to provide a liquid crystal display element having a smectic liquid crystal having ferroelectricity and electrode portions sandwiching the smectic liquid crystal and facing each other. This is achieved by optimally locating the polarizer and analyzer when there are domains that attenuate or vary in size with writing time. As a result, display quality such as contrast or transmittance is improved while flickering is eliminated and afterimages are improved, making it possible to provide a liquid crystal display element with high-speed response.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described using the drawings. FIG. 11 is a block diagram showing a driving system for a liquid crystal element according to the present invention, FIG. 6(A) is a plan view of the liquid crystal element used in the present invention, and FIG.
FIG. 2 is a schematic cross-sectional view taken along line AA' of FIG.

First, the outline of the liquid crystal display device according to the present invention will be explained.

FIG. 11 is a block diagram of a liquid crystal display device according to the present invention. In FIG. 11, 100 is a liquid crystal element according to the present invention, 111 is a driving means for driving the liquid crystal element 100 based on an image signal, and a common driver 112 for applying a scanning voltage to a common electrode is a driving means for driving the liquid crystal element 100 based on an image signal. A segment driver 11 that applies a signal voltage to segment electrodes serves as a driving means for driving the liquid crystal element 100.
3 is a backlight 114 which is a light source as illumination means;
F is means for controlling the driving of the liquid crystal display element 100.
LC controller 115 is a power supply controller as a power supply means for the liquid crystal display element 100 and backlight 113, and 116 is a computer that controls the operation of the entire liquid crystal display device.

FIG. 1 schematically depicts an example of a ferroelectric liquid crystal element. 21 is 21' is I n 20, . 5n02
Or ITO (Indium-Tin Oxide)
) is a substrate (glass plate) coated with a transparent electrode made of a thin film such as SmC", SmH"SmF",
Chiral smectic phase liquid crystals such as mI'' and SmG'' are sealed. A thick line 23 represents a liquid crystal molecule, and this liquid crystal molecule 23 has a dipole moment (P) 24 in a direction perpendicular to the molecule. Substrate 21
When a voltage higher than a certain threshold is applied between the electrodes 21' and 21', the helical structure of the liquid crystal molecules 23 is unraveled, and the liquid crystal molecules 23 change their alignment direction so that all the dipole moments (P±) 24 are directed in the direction of the electric field. It can be changed. liquid crystal molecule 23
has an elongated shape and exhibits refractive index anisotropy in its major and minor axis directions. Therefore, for example, if cross-niffle polarizers are placed above and below a glass surface, a liquid crystal optical modulation element whose optical characteristics change depending on the polarity of applied voltage is obtained.

The liquid crystal cell preferably used in the present invention can have a sufficiently thin thickness (for example, 10 μm or less).

As the liquid crystal layer becomes thinner in this way, the helical structure of the liquid crystal molecules unwinds and becomes a non-helical structure even when no electric field is applied, as shown in Figure 2, and the dipole moment P or P' is directed upward. (arrow 34) or downward (arrow 34'). When an electric field E or E' with a different polarity above a certain threshold value is applied to such a cell by a voltage applying means (not shown) as shown in FIG. 2, the dipole moment changes to the electric field vector of the electric field E or E'. Correspondingly, the liquid crystal molecules change their orientation upwards 34 or downwards 34', and accordingly the liquid crystal molecules enter the first stable state 3.
3 or the second stable state 33'.

As mentioned earlier, there are two advantages to using such a ferroelectric liquid crystal cell.

The first is that the response speed is extremely fast.

The second is that the alignment of liquid crystal molecules has bistability.

The second point will now be further explained with reference to FIG. 2, for example. When an electric field E is applied, the liquid crystal molecules enter the first stable state 33
This state is stable even when the electric field is turned off.

Furthermore, when an opposite electric field E' is applied, the liquid crystal molecules
The molecules are oriented to a stable state 33' and change their orientation, but they remain in this state even after the electric field is turned off. Also,
As long as the applied electric field E does not exceed a certain threshold value, each orientation state is maintained. In order to effectively realize such fast response speed and bistability, it is preferable that the cell be as thin as possible.

Generally 0.5 μm to 20 μm 1 Especially 1 μm to 5 μm
is suitable. A liquid crystal electro-optical device having a matrix electrode structure using this type of ferroelectric liquid crystal is described, for example, by Clark and Lagarwa 11.
proposed in US Pat. No. 4,367,924.

The present inventors discovered a method as a result of studying optimization of a liquid crystal element based on the arrangement state of molecules of a smectic liquid crystal having ferroelectricity and a combination of a polarizer and an analyzer. In other words, liquid crystal molecules do not always take the simple arrangement state described above, but take different forms of arrangement depending on the substrate processing method, liquid crystal material, liquid crystal cell thickness, etc., and the writing time within the display effective area may vary. There may be domains whose size attenuates or fluctuates as the temperature increases.

As a result of further investigation, by arranging the polarizer and analyzer so that the domain exists in a bright state,
It has been found that improvements regarding flickering, afterimages and contrast are possible.

FIG. 3 is a perspective view showing an embodiment of a substrate used in the liquid crystal display element of the present invention. In the figure, 11 is a substrate made of glass or plastic, 12 is a transparent electrode made of ITO, etc., and 13 is
14 represents a low-resistance connection line formed of a metal such as aluminum, chromium, molybdenum, or an alloy thereof, 14 represents a stepped portion extending in one direction, and 15 represents its ridgeline. The number of transparent electrodes 12 is 300 to 5000, preferably 500.
The low resistance connection line 13 is provided with a thickness of 300 to 5000, preferably 500 to 3000.

Further, in the present invention, an insulating film (not shown) for preventing short circuit between the upper and lower electrodes may be provided on the substrate 11, and an alignment film may be further provided on this insulating film. On this occasion,
As the insulating film, 5i02 film, Tie film, etc. can be used, and as the alignment film, polyvinyl alcohol film,
A polyimide film, a polyamide film, a polyester film, a polyamide-imide film, a polyester-imide film, etc. can be used.

FIG. 4(A) shows an embodiment in which two substrates shown in FIG. 3 are prepared. In this liquid crystal display element, as shown in FIG.
Two substrates 11a and llb shown in FIG. 1 are arranged facing each other at points Aa and Ab and points Ba and Bb. Arrow Ra in the diagram
4 and Rb4 are uniaxial alignment processing axes such as rubbing processing axes applied to the respective substrates. By arranging the two substrates 11a and llb facing each other as described above, the low resistance connection line 1
3a and the transparent electrode 12a are each connected to a low resistance connection line 13.
b and the transparent electrode 12b, forming a pixel P4 shown in FIG. 4(B).

In the pixel P4 shown in FIG. 4(B), the -axis alignment processing axis Ra
4 is set in a direction perpendicular to the low resistance connection line 13a corresponding to the linear protrusion existing in the pixel P4, and is oriented toward the low resistance connection line 13a.

In the liquid crystal element in which the pixel P4 shown in FIGS. 4(A) and 4(B) is formed, a plurality of pairs of hairpin defects 14 and lightning defects 15 are formed, and a plurality of pairs of hairpin defects 14 and lightning defects are formed. The hairpin defect portion 14 and the lightning defect portion 1 form a pair of hairpin defect portions 15 that are regularly generated parallel to the -axis alignment processing axis Ra4.
5, the lightning defect portion 15 is the hairpin defect portion 14.
This occurs near the low-resistance connection line 13a, which corresponds to a twisted linear protrusion.

The aforementioned hairpin defect portion 14 and lightning defect portion 15 occur in pairs, and are caused by bead spacers or fiber spacers dispersed within the cell. Therefore, the number of hairpin defect portions 14 and lightning defect portions 15 that form a pair is correlated with the number of bead spacers and fiber spacers dispersed. In addition, even if there is no bead spacer or fiber spacer, it can also be caused by lightly pressing the cell with a finger.

FIGS. 7(A) to 7(C) are diagrams schematically sketching aspects of hairpin defects and lightning defects. Figure 7 (A
) represents a hairpin defect 71 and a lightning defect 72 caused by the bead spacer. FIG. 7(B) shows a defective state in which the defect is further grown by lightly pressing the cell with the defective state shown in FIG. 7(A) with a finger, and FIG. 7(C) shows the defective state. This reveals how the situation has grown even further.

As clarified in FIGS. 7(A) to (C), the hairpin defect 71 and the lightning defect 72 are generated in pairs, and the surrounding domain (chiral smectic C2 domain 74) and optical state (for example, transparent The line width W of the hairpin defect 71 is generally larger than the line width W2 of the lightning defect 72, and the line width Wl of the hairpin defect 71 is generally 2 to 10 μm.
The line width W2 of the lightning defect 72 is 2 μm or less, forming a chiral smectic C phase with a different orientation from the domain 73 surrounded by the hairpin defect 71 and the lightning defect 72 and the surrounding domain 74, respectively. The domain of chiral smectic C domain 73
and chiral smectic C, domain 74, these two different domains generally exhibit different optical states (transmittance) and can be distinguished microscopically.

Further, the above-mentioned hairpin defect and lightning defect are clarified in October 1988 Liquid Crystal Conference Proceedings P, 114-115, "Considerations regarding the structure of 5SFLC state by microspectroscopy."

The present inventors performed writing using the multiplexing method shown in FIG. 5 at a frame frequency of 1 to the liquid crystal element forming the pixel P4 shown in FIGS.
When the test was conducted at 0 Hz, it was discovered that when the pixels were in a dark state (black display state), flickering was observed, which caused the brightness of the screen to change periodically.

In addition, when the above-mentioned liquid crystal element was observed under a microscope under multiplex puff drive, a voltage of 1±V, I exceeding the threshold voltage of 1±V1.1 was applied, and pixel P4 was brought into a dark state (black display state). In this case, the side A away from the low resistance connection wire 13a
It has been found that an inverted portion 16 (a domain that decreases or changes in size with writing time) is formed in the region every frame period, and that the occurrence of such an inverted portion 16 is the cause of the above-mentioned flicker. Incidentally, FIG. 5 shows the waveform of the voltage applied to the pixel P4 in time series.

Furthermore, when the pixel P4 is in a bright state (white display state), an inverted portion 17 (a domain that decreases or changes in size with writing time) is formed on the side surface of the hairpin defect every frame period, but the above-mentioned flickering occurs. was not seen.

Figure 4 is a sketch of a micrograph at 200x magnification.

As the smectic liquid crystal having ferroelectricity used in the liquid crystal element of the present invention, chiral smectic C phase (Sm
C”), H phase (SmH”), F phase (SmF”),
I phase (SmI”), J phase (SmJ”), G phase (SmG
) or monophase (SmK) liquid crystals are suitable. Regarding this ferroelectric liquid crystal, please refer to “LEJOURNAL
DE PHYSIQUE LETTER3”36(
L-69) 1975, rFerroelectri
c Liquid CrystalsJ;”Appli
ed Physics Letters”36 (
11) 1980rsubmicro 5econd
B15table ElectroopticSwit
Ching in Liquid Crystal
sJ: “Solid State Physics” 16 (141) 1981
ferroelectric liquid crystals disclosed in these documents can be used in the present invention.

Also, for example, US Pat. No. 4,561,726, US Pat. No. 4,614,609, and US Pat. No. 4,589,996.
Chiral smectic liquid crystals described in US Pat. No. 4,596,667, US Pat. No. 4,613,209, and US Pat. No. 4,615,586 can be used.

FIGS. 6A and 6B schematically show an embodiment of the liquid crystal element of the present invention. FIG. 6(A) is a plan view of the liquid crystal element of the present invention, and FIG. 6(B) is a cross-sectional view taken along the line AA'.

The liquid crystal element 100 shown in FIG. 6 consists of a pair of substrates 601 and 601' made of glass plates, plastic plates, etc., held at a predetermined distance by a spacer 604, and bonded with an adhesive 606 to seal the pair of substrates. Furthermore, on the substrate 601, an electrode group (for example, a scanning voltage application electrode group of a matrix electrode structure) consisting of a plurality of transparent electrodes 602 is arranged in a predetermined pattern such as a strip pattern. It is formed of. On the substrate 601', an electrode group (for example, a signal voltage application electrode group of the matrix electrode structure) is formed, which is made up of a plurality of transparent electrodes 602' intersecting with the transparent electrode 602 described above. The transparent electrodes 602 and 602' each have a low resistance adhesive wire 61.
0.61O' is provided.

The substrate 601' provided with such a transparent electrode 602' may contain, for example, silicon oxide, silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cerium oxide, cerium fluoride, silicon nitride, silicon carbide, boron nitride. Inorganic insulating materials such as objects, polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylerin, polyester, polycarbonate,
polyvinyl acetal, polyvinyl chloride, polyamide,
The alignment film 605 may be formed using an organic insulating material such as polystyrene, cellulose resin, melamine resin, urea resin, or acrylic resin.

This alignment film 605 is formed by forming a film of an inorganic insulating material or an organic insulating material as described above, and then coating the surface with velvet,
Obtained by rubbing in one direction with cloth or paper.

In another preferred embodiment of the present invention, SiO or Sin.

The alignment film 605 can be obtained by forming a film of an inorganic insulating material such as the above on the substrate 601' by oblique vapor deposition.

In another specific example, after forming a film of the above-mentioned inorganic insulating material or organic insulating material on the surface of the substrate 601' made of glass or plastic or on the substrate 601',
By etching the surface of the film by an oblique etching method, an orientation control effect can be imparted to the surface.

The above-mentioned alignment film 605 preferably functions as an insulating film at the same time, and for this reason, the thickness of the alignment film 605 is generally 100 to 1 μm, preferably 500 to 50 μm.
It can be set to a range of 00 people. This insulating film is
It also has the advantage of being able to prevent the generation of current caused by impurities etc. contained in a small amount in the liquid crystal layer 603, so that even if the operation is repeated, the liquid crystal compound will not deteriorate.

Further, in the liquid crystal element of the present invention, a film similar to the above-described alignment film 605 can be provided on the other substrate 601.

This cell structure 100 has a chiral smectic liquid crystal 603 in which a plurality of layers organized by a plurality of molecules are formed adjacently, and the film thickness of the chiral smectic liquid crystal 603 forms a unique helical structure in a bulk state. set thin enough to suppress This point is detailed in US Pat. No. 4,367,924.

Such a cell structure 100 includes substrates 601 and 601'.
Polarizers 607 and 608 in a crossed Nicol state or a parallel Nicol state are arranged on both sides of the electrode, respectively, and optical modulation occurs when a voltage is applied between the electrodes 602 and 602'.

An example of actual production will be shown below.

<Example 1> Two 1.1 mm thick glass plates were prepared, and striped ITO electrodes were formed on each glass plate. A metal wiring made of molybdenum was formed on this substrate to a thickness of 1000 mm, spanning between the ITO electrode and the pixel, like the low resistance connection line 13 in FIG. Further, 500 SIO layers were formed by sputtering as short-circuit prevention layers for the upper and lower electrodes.

A 0.1% aminosilane IPA (isopropyl alcohol) solution was applied thereon for 15 seconds using a spinner with a rotational speed of 200 rpm, and after baking at 150°C, a 2% solution of polyimide forming liquid 5P510 (manufactured by Toshi Co., Ltd.) (NMP: n-butyl cellosolve) was applied. =2: 1) was applied for 30 seconds using a spinner with a rotation speed of 300 rpm. Approximately 1 hour 30 minutes after film formation
A polyimide alignment film was formed by performing heating and baking treatment at 0°C. The film thickness of this coating was 200 polyimide films.

Next, on one glass (first substrate), a rubbing treatment was applied to the fired polyimide film in the direction of Rb4 shown in FIG. 4(A). On the other glass plate (second substrate), the fired polyimide film was subjected to rubbing treatment in the direction of Ra4 shown in FIG. 4(A).

After that, after scattering alumina beads with an average particle size of about 1.5 μm on one glass plate, each rubbing axis and its direction become parallel rubbing as shown in Fig. 4 (A) and (B). A cell was created by gluing one glass plate and the other glass plate together.

The cell thickness of this cell was measured using a Bereck phase plate (measurement based on phase difference) and was found to be approximately 1.5 μm. Inside this cell is rC3-1014J manufactured by Chisso Corporation.
(Product Name) was injected under vacuum in the Tokichi phase and then slowly cooled from the Tokichi phase to 60°C at a rate of 0.5°C/h to achieve orientation.

Subsequent experiments were conducted at 25°C.

Incidentally, the phase change of rcs-, 1014J mentioned above was as follows.

-21℃ 54.4℃ 69.1℃ 80.5℃
Cry, −+SmCa −+5mA−−+Ch
-+Is.

However, SmA indicates a smectic A phase, ch indicates a cholesteric phase, and Iso indicates an isokichi phase.

When this cell was observed under crossed nicols, monodomains were obtained that formed a chiral smectic C phase with a -like, defect-free, non-helical structure.

In addition, this liquid crystal element was kept at 60°C, brought into an SmA orientation state, and observed under a polarizing microscope with orthogonal crossed Nicols.
The direction of the layer was measured using the fact that liquid crystal molecules are aligned perpendicularly to the layer under mA conditions.

As a result, it was confirmed that the rubbing direction was perpendicular to the rubbing direction.

This liquid crystal element was multiplexed driven using the driving method shown in FIG.

This driving method is a method in which a bright state and a dark state can be written in one frame, and is a 3ΔT driving method that requires one line scanning period of 3ΔT for a write pulse intensity ΔT.

FIG. 5(A) shows the scanning signal applied to the n-th scanning line Sn, and FIG. 5(B) shows the information word I applied to a certain information line I, white-white one white one white one black. It is a one-white, one-white information signal. FIG. 5(C) shows a composite waveform applied to the intersection of the scanning line Sn and the information line I.

FIG. 8 is a layout diagram of the light source/polarizer/liquid crystal cell/analyzer as seen with the eye placed on the optical path.

The axis O is the rubbing direction (-axis direction), and Pl
, P2 and A1, A2 indicate the transmission axis (or absorption axis) of the polarizer and analyzer, respectively. As mentioned earlier, in the SmC'' phase obtained by slow cooling from the Tokichi phase, two types of stable states can be observed. That is, the transmission axis (or absorption axis) of the polarizer and analyzer When observed orthogonally, when the angle between them and the axis 0 of the liquid crystal cell is set appropriately, the liquid crystal cell usually has a mottled pattern2.
It can be seen that it is divided into species domains.

For example, when the temperature of the liquid crystal cell is 50°C, and the angle between axis 0 and the transmission axis (or absorption axis) Pl of the polarizer is 6°, as shown in Figure 8, the transmission axis (or absorption axis) of the polarizer is When the angle between the transmission axis (or absorption axis) Pl and the analyzer's transmission axis (or absorption axis) A1 is 90°C, the two domains are observed with the greatest contrast in this system, and are dark (black).
and exhibits a bright (white) color. Also, the transmission axis (or absorption axis) of the polarizer/analyzer is set with respect to axis 0 as shown in Figure 8.
When rotated to the symmetrical position (P2ZA,), respectively, the domains are reversed, i.e. the domains that were dark (black) in the (P, /A,) configuration become light (white), while the domains that were dark (white) ) domain changes to dark (black).

Also, the transmission axis (or absorption axis) Pl of the polarizer and analyzer
and A1 are arranged with a crossing angle of 90°, and when a DC voltage pulse of a specific polarity (for example, 10) is applied between the two opposing substrates, the entire surface turns dark (black). Next, when a DC voltage pulse of opposite polarity (-) is applied, the whole becomes bright (
white).

From the above, we believe that the two stable states are a state in which the projection axis of the liquid crystal molecular axis onto the substrate surface points on average in the direction of axis P1, and a state in which it points in the direction of axis P2. be able to. Furthermore, since these states are transferred by DC voltage pulses of opposite polarity, each of these two states has a finite average electric current polar moment in the direction perpendicular to the substrate surface and opposite polarity to each other. I understand.

Next, in Figure 8, the transmission axis (or absorption axis) of the polarizer
When Pl is Pl, and the transmission axis (or absorption axis) of the analyzer is A, the darkest and maximum contrast was obtained in one stable state.

When the orientation state within the pixel at this time is observed using a microscope with a magnification of 200 times, as shown in FIG. 4, domains with hairpin defects and lightning defects caused by the alumina beads are formed.

When writing was performed using the multiplexing method shown in FIG. 5 at a frame frequency of 10 Hz on the liquid crystal element in which the pixel P4 shown in FIGS. 4(A) and 4(B) was formed, the pixel was in a dark state (black display). (condition), flickering was observed in which the brightness of the screen periodically changed. In addition, when the above-mentioned liquid crystal element was observed under a microscope under multiplex leg drive, the threshold voltage was 1±V, and the voltage exceeding 11 was 1±V.
, 1 is applied to bring the pixel P4 into a dark state (black display state), the inverted portion 1 is placed in the area on the side A where the low resistance connection line 13a is not provided.
6 (domains that decrease or vary in size with writing time) are formed every frame period, and it has been found that the occurrence of such inverted portions 16 is the cause of the above-mentioned flickering. Note that FIG. 5 shows the waveform of the voltage applied to the pixel P4 in time series.

Furthermore, when the pixel P4 is in a bright state (white display state), an inverted portion 17 (a domain that decreases or changes in size with writing time) is formed on the side surface of the hairpin defect every frame period, but the flickering described above I couldn't see it.

Therefore, in FIG. 8, the transmission axis (or absorption axis) of the polarizer is set as P3, and the transmission axis (or absorption axis) of the analyzer is set as A2. At this time, the other stable state is the darkest and provides the maximum contrast, and the display direction of the pixel and the direction of the domain are reversed. That is, FIG. 4(B) becomes like FIG. 4(C). .

Similarly to the above, pixel P4 shown in FIGS. 4(A) and (C)
When writing was performed using the multiplexing method shown in Fig. 5 at a frame frequency of 10 Hz on a liquid crystal element with a 3D display, when the pixels were in a dark state (black display state), flickering caused by periodic changes in screen brightness was observed. was not seen. In addition, when the above-mentioned liquid crystal element was observed under a microscope under multiplex leg driving, it was found that when a voltage of 1+V,I exceeding the threshold voltage of 1±V1 was applied to bring the pixel P4 into a bright state (white display state). , an inversion part 16 (a domain whose size decreases or changes with writing time) is formed in the area of side A where there is no low resistance connection line 13a every frame period, but the occurrence of such an inversion part 16 is caused by the above-mentioned flicker. It was found that this was not the cause. In addition, FIG. 5 shows pixel P4.
The waveforms of the voltages applied to the circuit are shown in time series.

Furthermore, when pixel P4 is in a dark state (black display state), an inverted portion 17 (a domain that decreases or changes in size with writing time) is formed on the side surface of the hairpin defect every frame period, but no flickering is observed. There wasn't.

From the above, in FIG. 8, when the transmission axis (or absorption axis) of the polarizer is set to P2 and the transmission axis (or absorption axis) of the analyzer is set to A2, flickering can be suppressed under multiplex leg driving. That is, if there are domains that attenuate or change in size with writing time, polarizers and analyzers are used so that the sum of the areas of the domains that exist in the bright state is larger than the sum of the areas of the domains that exist in the dark state. The flickering was improved by placing the .

Also, when the polarizer and analyzer are arranged P, /A, and P
When comparing the afterimage time and contrast ratio at 2/A2, the results are shown in Table 1 below.

That is, according to the present invention, flickering, afterimage time, and contrast ratio can be significantly improved.

As mentioned above, the reason why the occurrence of the inversion part and the variation in area cause flickering is as described below.

Consider the case where the pixel is showing black in FIG. 4(B). Here, let W be the luminance of the part displaying white, and B be the luminance of the part displaying black.

That is, when most of the pixels are displaying black with a luminance of B, the inverting section 16 is displaying with a luminance of W.

At this time, the ratio of the area of the entire pixel to the area of the inverted part is 1:n
Then, the ratio of the brightness of the inversion part to the brightness of the entire pixel is as follows. On the other hand, considering the case where the pixel is displaying white in FIG. 4 (C), the ratio of the brightness of the inverted portion to the brightness of the entire pixel is as follows. In general, n is about 0.01 (1%), and Wl
By substituting the value when B is θ; 0 (W=80, B=20), the value of the ■formula is 3.9xlO-'', and the value of the ■formula is 2.5
In the case of the formula (2), which is X10-s, the brightness ratio of the inverted portion is about 16 times as large as that in the case of the formula (2), and the change in brightness is that much more noticeable and causes flickering.

Here, W/B in formula (2) is a contrast ratio, and the larger this value (contrast ratio) is, the smaller the value of formula (2) becomes, and the above-mentioned flicker prevention effect increases.

In FIG. 8, when the polarizer and analyzer are arranged so that the polarizer and analyzer maintain a cross Nicol relationship and display one of the two stable states of the smectic liquid crystal in the darkest state (for example, , P , /A , or P , /A ,), the polarizer and analyzer are moved in the direction such that the other stable state becomes brighter. When the photon transmission axis is rotated by θ=6° while maintaining crossed Nicols, (P,'
/A.

or P,'/A,'') had similar effects.

Also, when either the polarizer or the analyzer is shifted by θ = 6° in the direction where the stable state of the other becomes brighter (P
, '/A, or P, '/A,) had similar effects.

Furthermore, Table 2 and FIG. 10 show the transmittance, contrast ratio, and brightness measured with various values of θ. However, in Figure 10, the reference is (
θ=0'), and it can be seen that θ' shown in FIG. 8 is 20°. In this case, the direction in which the first stable state becomes brighter is defined as the direction in which the polarizing plate angle becomes positive on the coordinate axis in FIG. In Figure 1O, when the polarizer and analyzer are kept in crossed nicols and rotated in the direction where the first stable state becomes brighter (θ is positive direction), the rotation angle is 25°.
In the range up to (=45°-θ') (0<θ≦25°), there was no flickering (with respect to the afterimage time, the same results as in Table 1 were obtained.

In this range, although the contrast ratio decreases somewhat, the transmittance increases, making it possible to display a brighter screen. In such a bright display screen, the change in brightness due to the change in the area of the reversing portion is relatively small compared to the brightness of the screen, so the effect of preventing flicker is increased.

(The following is a blank space) <Example 2> A liquid crystal cell was created in exactly the same manner as in Example 1, except that the rubbing direction was oriented as shown in Figure 9 (A), and the same tests as in Example 1 were carried out. I did it.

At this time, as shown in FIG. 9(B), the direction of change in pixel writing (
For example, a reverse inversion domain (inversion portion 16) in the opposite direction (for example, black to white) was generated.

Furthermore, when observing the orientation state within the pixel, Fig. 9(B)
As shown in , there were hairpin defects and lightning defects caused by alumina beads, and a reverse inversion domain (inversion part 17) in the opposite direction to the direction of change in pixel writing occurred on the side of the lightning defect. .

In this case as well, exactly the same effect as in Example 1 was obtained.

That is, when the domain exists as shown in FIG. 9(B), flickering is visible, and when the polarizer and analyzer are arranged so that the direction of the domain is as shown in FIG. 9ffl(C), No flickering was observed, and the contrast ratio or transmittance was improved while improving afterimages.

<Examples 3 to 8> Cells similar to those in Example 1 were created and tested, except that the alignment films and liquid crystal materials listed in Table 3 below were used, and results similar to those in Example 1 were obtained. Met.

(Margin below) In the table, rsElooJ, rsE4110J and rLP
64J is a resin liquid for forming a polyimide film.

〔Effect of the invention〕

As explained above, according to the present invention, the positions of the polarizer and analyzer can be optimized when there is a domain in the effective display area of a liquid crystal display element that attenuates or changes in size with writing time. Layout JP-A-3-223717 (
12) Therefore, it is possible to eliminate flickering on the entire screen, improve display quality in terms of contrast or transmittance while improving afterimages, and provide a liquid crystal display element with high-speed response.

Next, instead of an image display device, an image recording device using the aforementioned liquid crystal element will be described. FIG. 12 shows an example of an electrophotographic image recording apparatus that uses the aforementioned liquid crystal element as a liquid crystal shutter to modulate and control exposure onto a photoreceptor. In Fig. 12, 1 is an exposure lamp as a light source, 2
is a liquid crystal shutter (including two polarizing plates not shown); 3 is a short-focus imaging element array; 4 is a photosensitive drum; 5 is a charger;
6 is a developing device, 7 is a developing sleeve, 8 is a transfer guide, 9 is a transfer charger, 10 is a cleaning device, 11 is a cleaning blade, and 12 is a conveyance guide. In the figure, first, the photosensitive drum 4 rotating in the direction of the arrow is charged by the charger 5. Thereafter, light modulated according to the image signal is irradiated onto the photoreceptor drum to form an electrostatic latent image. As shown in FIG. 13, the direction of this light modulation is achieved by blocking or transmitting the light from the exposure lamp 1 with liquid crystal shutters 2 arranged in the axial direction of the photoreceptor drum 4. In order to increase the performance, a large number of liquid crystals are arranged in a staggered manner as shown in the figure. Further, a rod lens 15 may be used to focus the light from the exposure lamp onto the liquid crystal shutter.

Further, the electrostatic latent image formed in this way is visualized by adhering the charged toner on the developing sleeve 7. The toner image on the photosensitive drum 4 is transferred onto the transfer material 13 by being discharged from the transfer charger 9 from the back side of the transfer material 13 fed and conveyed from a paper feed cassette (not shown). Thereafter, the toner image on the transfer material 13 is fixed by a fixing device (not shown). On the other hand, toner remaining on the photosensitive drum 4 without being transferred is scraped off from the drum surface by the cleaning blade 11 and collected in the cleaning device IO. Further, the charge remaining on the photosensitive drum 4 is irradiated by the pre-exposure lamp 14 and disappears.

[Brief explanation of drawings]

FIGS. 1, 2, and 3 are perspective views of the substrates used in the present invention, FIG. 4(A) is a plan view of a pair of substrates used in the present invention, and FIGS. 4(B) and (C). ) is a plan view of the pixel in FIG. 4(A), FIGS. 5(A) to (C) are waveform diagrams of the driving voltage used in the present invention, and FIG. 6(A) is the liquid crystal element used in the present invention. 6(B) is a sectional view taken along line AA' in FIG. 6(A), FIGS. 7(A) to (C) are schematic sketches of hairpin defects and lightning defects, and FIG. 8 FIG. 9(A) is a plan view of another pair of substrates used in the present invention, FIG. 9(B) and ( C) is a plan view of the pixel in FIG. 9(A), FIG. 1O is a diagram showing the polarizing plate angle characteristics of the liquid crystal element according to the present invention, and FIG. 11 is a diagram showing the driving system of the liquid crystal element used in the present invention. FIG. 12 is a block diagram; FIG. 12 is a schematic diagram of an image recording device using a liquid crystal element according to the present invention; FIG. 13 is a perspective view showing an example of the image recording device. 0 knee axis direction

Claims (14)

[Claims] (1) A smectic liquid crystal that has ferroelectricity and has two types of stable molecular arrangement states, electrodes that sandwich the smectic liquid crystal and face each other, and one of the molecular arrangement states is in a dark state and the other is in a dark state. In a liquid crystal element having a polarizer and an analyzer disposed near a substrate so as to display a bright state, a domain whose size attenuates or whose size changes with writing time within an effective display area is located in the dark state. A liquid crystal element, characterized in that a polarizer and an analyzer are arranged so that when one of the bright states exists, the domain exists in the bright state. (2) The polarizer and the analyzer maintain a cross-Nicol relationship, and the polarizer and the analyzer maintain a cross-Nicol relationship so that one of the two stable molecular arrangement states of the smectic liquid crystal displays the darkest state. 2. The liquid crystal element according to claim 1, further comprising photons. (3) The polarizer and the analyzer are arranged so that a cross Nicol relationship is maintained between the polarizer and the analyzer, and one of the two stable molecular arrangement states of the smectic liquid crystal displays the darkest state. With the transmission axis of the polarizer or analyzer as a reference, the following condition (i) is applied while maintaining the cross-Nicol relationship between the transmission axes of the polarizer and analyzer in the direction where the other stable molecular arrangement state becomes brighter. The liquid crystal element according to claim 1, wherein the liquid crystal element is rotated by an angle θ that satisfies the condition (i) θ≦45°−θ′, where θ′ is the first of the two stable molecular alignment states.
The first state is a state in which the polarizer and analyzer are arranged so that the darkest state is displayed in the state of The state in which the detector and analyzer are arranged is defined as the second state, and the angle between the transmission axes of the polarizer in the first state and the polarizer in the second state, or the angle between the analyzer in the first state and the analyzer in the second state. Let the angle formed by the transmission axis of (4) The polarizer and the analyzer are arranged so that a cross Nicol relationship is maintained between the polarizer and the analyzer, and one of the two stable molecular arrangement states of the smectic liquid crystal displays the darkest state. At least one of the transmission axes of the polarizer or analyzer is set at an angle that satisfies the following condition (i), with the transmission axis of the polarizer or analyzer as a reference, in the direction in which the other stable molecular arrangement state becomes brighter. The liquid crystal element according to claim 1, wherein the liquid crystal element is arranged rotated by θ; Condition (i) θ≦45°−θ′; where θ′ is the maximum in the first state of the two stable molecular alignment states; The first condition is the state in which the polarizer and analyzer are arranged so as to display the dark state.
A state in which a polarizer and an analyzer are arranged so as to display the darkest state in the second state among the two stable molecular arrangement states is defined as a second state, and a polarizer in the first state and a second This is the angle formed by the transmission axis of the polarizer in the state or the angle formed by the transmission axes of the analyzer in the first state and the analyzer in the second state. (5) A smectic liquid crystal having ferroelectricity and having two types of stable molecular arrangement states, electrodes sandwiching the smectic liquid crystal and facing each other, and one of the molecular arrangement states being in a dark state and the other being in a dark state. In a liquid crystal device having a polarizer and an analyzer disposed near a substrate so as to display a bright state, a domain whose size attenuates or changes with writing time within an effective display area exists in the dark state and the The polarizer and the analyzer are arranged such that when the domains exist in both bright states, the sum of the areas of the domains that exist in the bright state is larger than the sum of the areas of the domains that exist in the dark state. A liquid crystal element featuring: (6) The polarizer and the analyzer are arranged so that the polarizer and the analyzer maintain a cross Nicol relationship and one of the two stable molecular arrangement states of the smectic liquid crystal displays the darkest state. 6. The liquid crystal element according to claim 5, wherein: (7) The polarizer and the analyzer are arranged so that the polarizer and the analyzer maintain a cross Nicol relationship and one of the two stable molecular arrangement states of the smectic liquid crystal displays the darkest state. With the transmission axis of the polarizer or analyzer as a reference, the following condition (i) is applied while keeping the transmission axis of the polarizer or analyzer in a cross-Nicol relationship in the direction where the other stable molecular arrangement state becomes brighter. The liquid crystal element according to claim 5, wherein the liquid crystal element is rotated by an angle θ that satisfies the condition (i) θ≦45°−θ′; where θ′ is the first state of the two stable molecular arrangement states. The first condition is the state in which the polarizer and analyzer are arranged so that the darkest state is displayed.
A state in which a polarizer and an analyzer are arranged so as to display the darkest state in the second state among the two stable molecular arrangement states is defined as a second state, and a polarizer in the first state and a second This is the angle formed by the transmission axis of the polarizer in the state or the angle formed by the transmission axes of the analyzer in the first state and the analyzer in the second state. (8) The polarizer and the analyzer are arranged so that a cross Nicol relationship is maintained between the polarizer and the analyzer, and one of the two stable molecular arrangement states of the smectic liquid crystal displays the darkest state. At least one of the transmission axes of the polarizer or analyzer is set at an angle that satisfies the following condition (i), with the transmission axis of the polarizer or analyzer as a reference, in the direction in which the other stable molecular arrangement state becomes brighter. The liquid crystal element according to claim 5, wherein the liquid crystal element is arranged rotated by θ; Condition (i) θ≦45°−θ′; where θ′ is the maximum in the first state of the two types of stable molecular arrangement states; The first condition is the state in which the polarizer and analyzer are arranged so as to display the dark state.
A state in which a polarizer and an analyzer are arranged so as to display the darkest state in the second state among the two stable molecular arrangement states is defined as a second state, and a polarizer in the first state and a second This is the angle formed by the transmission axis of the polarizer in the state or the angle formed by the transmission axes of the analyzer in the first state and the analyzer in the second state. (9) A liquid crystal display element comprising: the liquid crystal element according to claim 1; means for driving the liquid crystal element based on an image signal; and a light source. (10) A liquid crystal display device comprising the liquid crystal display element according to claim 9, means for controlling driving of the liquid crystal display element, and means for controlling power supply to the liquid crystal display element. Display device. (11) A recording device comprising the liquid crystal element according to claim 1, means for driving the liquid crystal element based on an image signal, a photoreceptor, and a developing device. (12) A liquid crystal display element comprising the liquid crystal element according to claim 5, means for driving the liquid crystal element based on an image signal, and a light source. (13) A liquid crystal display comprising the liquid crystal element according to claim 12, means for controlling driving of the liquid crystal display element, and means for controlling power supply to the liquid crystal display element. Device. (14) A recording apparatus comprising the liquid crystal element according to claim 5, means for driving the liquid crystal element based on an image signal, a photoreceptor, and a developing device.