JPS60164720A - Temperature controlling method of optical modulation element - Google Patents

Abstract

PURPOSE:To form a mono-domain of a liquid crystal arranged in one direction by forming an interface of a uniaxial anisotropic phase of the liquid crystal and other phase of a high temperature side, phase-varying other phase to the uniaxial anisotropic phase of the liquid crystal arranged in a parallel direction under a high temperature, and generating it continuously toward the vertical direction. CONSTITUTION:When a liquid crystal 401 of an electrooptic modulating substance in a liquid crystal cell is operating, it is brought to temperature control to SmC*. The electric conduction quantity of a heating resistor 402 is increased, it is set to an isotropic phase by heating of a heater of the first stage, and thereafter, cooled slowly under a temperature gradient. This slow cooling reduces the electric conduction quantity to the heating resistor 402, forms SmA by heating of a heater of the second stage, and thereafter, the temperature gradient is released, and also the liquid crystal 401 is phase-transferred to SmC* by heating of a heater of the third stage of a low heating value. This control is executed by using on multi-stepwise way the heating resistor 402 by a heat sensible element 403 functioning as a temperature sensor.

Description

[Detailed description of the invention] The present invention relates to a temperature control method for an optical modulation element.

Specifically, the present invention relates to a method of controlling the temperature of an optical modulation element suitable for display devices, image forming devices, and the like.

2. Description of the Related Art Recent advances in information processing technology have been remarkable, and as a result, image forming apparatuses are required to have higher density and higher speed. Furthermore, there are strong demands for printing quality, and to date, electrophotographic devices, laser beam printers (LBPs), and optical fiber tube (OF'T) printers have already been put into practical use as image forming devices that satisfy these requirements. There is. However, these image forming apparatuses are expensive and have a complicated structure.

It is difficult to miniaturize the device. Therefore.

Recently, P
Image forming apparatuses using optical shutters such as LZT or liquid crystal, or image forming apparatuses such as LED printers using light emitting diodes have been considered. Among these, liquid crystal shutter printers that utilize the electro-optic effect of liquid crystals are becoming promising as low-cost, high-density image forming devices.

As the liquid crystal used in the head of this liquid crystal shutter printer, there is a method of driving twisted nematic liquid crystal using a two-frequency method, for example, as disclosed in Japanese Patent Application Laid-Open No. 56-94377.
It is stated in the No.

This type of printer head uses a liquid crystal composition that exhibits positive dielectric anisotropy and negative dielectric anisotropy according to the different frequencies of the applied voltage, and selectively switches the applied frequency to apply an electric field to the liquid crystal. It is based on the principle that it is possible to optically distinguish between orientation in the direction of the electric field and orientation in the direction perpendicular to the electric field. Generally, the response speed of a liquid crystal increases as the applied voltage increases. Therefore, if one of the two orientation directions produces a bright state and the other orientation produces a dark state, switching between these two states can be achieved by forcibly applying voltage to both, so the response is acceptable. High-speed response is possible by applying as large a voltage as possible, but the response speed is approximately 1m5ec at most, which is much slower than several tens of nanoseconds for LED printer heads. It was not suitable for printer heads with In addition, since it is difficult for LED printer heads to form an LED array with uniform luminance, if developed with a developer containing toner of opposite polarity to the electrostatic latent image formed in response to this luminance, This method has drawbacks such as the optical density of each dot being non-uniform.

By the way, a ferroelectric liquid crystal with spontaneous polarization has recently been discovered, and the electric dipole of the liquid crystal molecule can respond to an external electric field with a response speed of about 1μSee, which is much faster than the conventional liquid crystal mode. It is known that there are When this ferroelectric liquid crystal is made into cells with a thickness of 1 to 2 μm and operated as a light shutter, a contrast of 1:20 can be achieved, so it can be used as a high-speed printer instead of a printer head using conventional liquid crystal mode. A liquid crystal shutter printer is being developed.

However, the ferroelectric liquid crystal that operates as a liquid crystal shutter is generally in the chiral smectic C phase (SmC).
or in the chiral smectic H phase (SmH*), but this SmC* father is Sm
H* is room temperature) Mokana is near high temperature (for example, about 60℃~
90"C), image formation involves the process of generating a light signal in a printer head using this type of liquid crystal and irradiating this light signal onto, for example, a photosensitive drum of an electrophotographic copying machine. There is a problem that makes it difficult to apply the device.In other words, in order for the image forming device to operate constantly, the liquid crystal of the optical modulation section of the printer head must always be kept at a temperature of 60°C to 90°C.
SmC" or SmH" is required at a temperature around 'C', which consumes unnecessary power.Furthermore, if 8mC' or SmH' is heated more than necessary, smectic physiognomy occurs. (SmA) appears, which may result in a failure to exhibit high-speed response.

An object of the present invention is to provide a temperature control method for an optical modulation element that eliminates the above-mentioned drawbacks.

Another object of the present invention is to provide a method for controlling the temperature of an optical modulation element suitable for display devices and image forming devices.

The object of the present invention is to provide a first step of heating to a temperature higher than the upper limit of the temperature at which a ferroelectric liquid crystal phase is exhibited; It forms a phase interface with another phase on the higher temperature side (nematic phase, cholestic phase, tokiyoshi phase).

Another phase near the phase interface is phase-transformed to a uniaxial auspicious phase of liquid crystals arranged in a direction parallel to the liquid crystal alignment direction of the -axis auspicious phase under temperature reduction, and the phase transition is directed from the phase interface in a direction perpendicular to the liquid crystal alignment direction. a second step of forming monodomains of liquid crystal aligned in one direction by continuously generating the above-mentioned -
The third step involves phase transition of the axially auspicious phase to the ferroelectric liquid crystal phase under slow cooling.
This is achieved by a method of temperature control of the optical modulation element, which has the following steps: and a fourth step of heating before reaching the lower limit temperature exhibiting a ferroelectric liquid crystal phase.

As the ferroelectric liquid crystal used in the present invention, specifically, a liquid crystal having a chiral smectic C phase (SmC') or H phase (SmH') can be used. This liquid crystal has a bistable state consisting of a first optically stable state and a second optically stable state with respect to an electric field, and is therefore different from the optical modulation element used in the TN type liquid crystal described above. The liquid crystal is aligned in a first optically stable state with respect to one electric field vector, and the liquid crystal is aligned in a second optically stable state with respect to the other electric field vector.

For information on ferroelectric liquid crystals, please refer to “LE JOURNAL D
EPHYS IQ hanging I regular TT plate S136 (L-69) 1
975° [Ferroelectric Liquid
Crystals J ; “AI) plied Ph
ysics Letters '″36(11)198
0 [Submicro 5econd B15tab
leE1electrooptie Switching
In the present invention, the ferroelectric liquid crystals disclosed therein can be used.

Specific examples of ferroelectric liquid crystal compounds include desyloxybenzylidene-p'-amino-2-methylbutylcinnamate (DOBAMBC), hexyloxybenzylidene-p'-amino-2-propylcinnamate (DOBAMBC), and hexyloxybenzylidene-p'-amino-2-methylbutylcinnamate (DOBAMBC).
HOBACPC), 4-o-(2-methyl)-
Butylresolsiliten-42-octylaniline (MB
RA8).

The liquid crystal alignment control method according to the present invention forms a phase interface between a uniaxial auspicious phase of liquid crystal aligned in one direction between a pair of substrates and another phase on the high temperature side of the phase, and separates the liquid crystal near the phase interface. The phase is changed to a uniaxial auspicious phase of liquid crystals aligned in a direction parallel to the liquid crystal alignment direction of the -axis auspicious phase under a temperature decrease, and the phase change is caused continuously from the phase interface in a direction perpendicular to the liquid crystal alignment direction. In particular, it is characterized by a liquid crystal alignment control method that forms liquid crystal monodomains aligned in one direction.

Hereinafter, the present invention will be described in further detail with reference to the drawings as necessary.

Particularly suitable liquid crystal materials for use in the present invention include:
It is a liquid crystal that has bistability and ferroelectricity, and specifically has a chiral smectic C phase (Sm
A liquid crystal having a C*) or H phase (SmH'') can be used.

When constructing an element using these materials, the element may be supported by a copper block with a heater embedded, etc., as necessary, in order to maintain the temperature at which the liquid crystal compound becomes the SmC phase or SmH phase. can.

FIG. 1 schematically depicts an example of a cell for explaining the operation of a ferroelectric liquid crystal. 11 and 11' are Int
Os I 5nat or ITO (Indium
- A substrate (glass plate) coated with a transparent electrode made of a thin film such as (Tin Oxide), between which SmC* phase or SmH* phase liquid crystal with liquid crystal molecular layer 12 oriented perpendicular to the glass surface is sealed. has been done. A thick line 13 represents a liquid crystal molecule, and this liquid crystal molecule 13 has a dipole moment (Pl) in the direction perpendicular to the molecule.
It has 14. When a voltage higher than a certain threshold is applied between the electrodes on the substrates 11 and 11', the helical structure of the liquid crystal molecules 13 is unraveled, and the liquid crystal molecules 13 are oriented so that the dipole moment (Pl) 14 is all oriented in the direction of the electric field. If you change the direction, you can make a dot. The liquid crystal molecules 13 are.

It has an elongated shape and exhibits refractive index anisotropy in its long and short axis directions. Therefore, if a cross-niffle polarizer is placed above and below the glass surface, the optical properties change depending on the polarity of voltage application. It is easily understood that this serves as an optical modulation element.

The liquid crystal cell preferably used in the liquid crystal element of the present invention can have a sufficiently thin thickness (for example, 10 μm or less). As the liquid crystal layer becomes thinner, 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.The dipole moment) P or y is Upward (24) or Downward (2
It can be in one of four states. In such a cell, the second
As shown in the figure, an electric field E or E with different polarity above a certain threshold value
When ' is applied to the voltage applying means 21 and 21', the dipole moment changes its direction to upward 24 or downward 24' in response to the electric field vector of E or ', and the liquid crystal molecules accordingly change direction. , the first stable state 23 or the second stable state 23
is oriented in one of the stable states 23'.

As mentioned earlier, there are two advantages to using such ferroelectricity as a liquid crystal element. The first is that the response speed is extremely fast, and the second is that the alignment of liquid crystal molecules has bistability. To further explain the second point, for example, with reference to FIG. 2, when the electric field E is applied, the liquid crystal molecules are oriented in the first stable state 23, but the solid state remains stable even when the electric field is turned off. Also, when applying an electric field E' in the opposite direction,
The liquid crystal molecules are oriented in a second stable state 23' and change their orientation, but they remain in this state even after cutting the stain boundary. Further, as long as the applied electric field E does not exceed a certain threshold value, each orientation state is maintained. K that effectively realizes such fast response speed and bistability
It is preferable for the cell to be as thin as possible.

Forming devices using liquid crystals with such ferroelectricity It is difficult to form cells with high monodomain properties, in which liquid crystal molecules are aligned perpendicular to the substrate surface and liquid crystal molecules are aligned approximately parallel to the substrate surface. The main purpose of the present invention is to provide a solution to this problem.

FIG. 3(4) is a partial plan view of an embodiment of a liquid crystal element obtained by the liquid crystal alignment control method of the present invention, and FIG. 3(B) is a cross-sectional view taken along line A-A' be. In order to make it easier to see the cell structure, the figures are not drawn to an exact scale. In this example, a configuration example of a shutter array for a printer is shown. Liquid crystal cell 100 shown in FIG.
has a cell structure in which a pair of substrates 101 and 101' made of glass plates, plastic plates, etc. are held at a predetermined distance by spacers (not shown), and the pair of substrates are bonded with an adhesive 106. Further, on the substrate 101, an electrode group (for example, a scanning voltage application electrode group in a matrix electrode structure) consisting of a plurality of transparent electrodes 102 is formed in a predetermined pattern such as a strip pattern. On the substrate 101', an electrode group (for example, a signal voltage application electrode group in a matrix electrode structure) consisting of a plurality of transparent electrodes 102' intersecting with the transparent electrode 102 described above is connected to a lead 107' as shown in the figure. It is formed of a pattern of segments connected in a zigzag pattern. The transparent electrode 102 is connected to a lead 107, and the transparent electrode 102' is connected to a lead 107'', and signals from an external circuit are input to the terminals of the leads 107 and 107'', respectively.

For example, one of these substrates 101 and 101' is used.

-Silicon oxide, silicon dioxide, aluminum oxide.

Zirconia, magnesium fluoride, cerium oxide, cerium fluoride, silicon nitride, silicon carbide, boron nitride, polyvinyl alcohol, polycarbonate, polyvinyl acetal.

Polyvinyl chloride, polyamide, polystyrene.

An insulating film (not shown) made of cellulose resin, melamine resin, urea resin, acrylic resin, or the like can be provided. This insulating film also has the advantage of being able to prevent the generation of current caused by trace amounts of impurities contained in the liquid crystal layer 103, and therefore does not deteriorate the liquid crystal compound even if the operation is repeated. There is no.

The cell structure in this specific example includes a liquid crystal layer 103 that exhibits ferroelectricity at a predetermined temperature as described above, a nucleation member 104, and a heating element 105 such as a heater.

The nucleation member 104 is made of, for example, polyvinylalster, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, or mela.

After forming a film using a resin such as Min resin, Yuria resin, or acrylic resin or an inorganic compound such as SiO, 5iOz, or Tilt, it is formed into a band shape by a normal photolithography method.

Further, the nucleation member 104 can also be made of the same material as the substrate 101 or 101'.

The heating element 105 may be made of, for example, indium oxide, tin oxide, or ITO (Indium Tin Oxide).
It is suitable to use a thin film resistor such as

In such a liquid crystal cell 100, polarizers 108 and 108' in a crossed Nicol state or a parallel Nicol state are arranged on both sides of the substrates 101 and 1011, respectively.
Optical modulation will occur when a voltage is applied between 02 and 102'.

To give a more specific example of the liquid crystal cell 100 shown in FIG. 3, for example, the transparent electrode 102 is a strip-shaped scanning electrode group with a width of 62.5 μm, while the transparent electrode 102' forms one pixel. , 62.5 μm×62.5 μm signal electrode group.

The heating element 105 has an average width of 0.6 van and a film thickness of 10
It is preferable that the liquid crystal layer 103 is made of an ITO thin film with a thickness of 00λ and maintained at a thickness of about 2 μm.

Such a liquid crystal cell 100 is housed in a heating case (not shown), and polarizers 108 . and 108
I can be arranged to operate as a liquid crystal shutter array for an electrophotographic printer. In the case of solidity, arrow B in FIG. 3(4) is the direction of rotation of the electrophotographic photosensitive drum.

The nucleation member 104 is produced by applying, for example, a polyimide forming solution (PIQJ manufactured by Hitachi Chemical Co., Ltd., non-volatile content 14.5 wt%) onto the substrate 101 for 10 seconds using a spinner coating machine rotating at 3.000 rPm. Heating was performed at 120°C for 30 minutes to form a 2μ film.Next, a positive resist solution (“AZ1350” manufactured by Shipley) was applied.
) was applied with a spinner and prebaked. This resist layer was exposed to light using a strip mask with a mask width of 0.5 mm.

Next, by developing with a developer containing tetramethylammonium hydroxide "MF312", the resist film in the exposed area and the underlying polyimide film were etched to form through holes, followed by washing with water and drying. Thereafter, the resist film in the non-fogged areas was removed using methyl ethyl ketone. After that, heat at 200℃ for 60 minutes.

Curing was performed by heating at 350"C for 30 minutes.

A nucleation member of PIQ (polyimide) can be formed.

Hereinafter, a case of DOBAMBC as an optical modulation material exhibiting ferroelectric properties at a predetermined temperature will be specifically explained.

FIG. 4 shows the optical path opening/closing means and temperature control means of the optical signal generator provided in the optical modulation element of the present invention. Temperature control means are provided which can control the temperature.

First, the liquid crystal cell 100 shown in FIG. 3 in which DOBAMBC is sealed is set in a heating case (not shown) that uniformly heats the entire cell. Next, the temperature of the heating case is controlled so that the average temperature of the cell is, for example, 90°C. At this time, DOBAMBC
The liquid crystal phase is SmC' phase or 5rrLA phase. Here, when a current is applied to the heating element (heater) 105 and the current value is gradually increased, only the area in the immediate vicinity of the heating element 105 exceeds approximately 118°C, which is the transition temperature of SmA → isotropic phase, and the isotropic phase is reached. In other words, a phase transition occurs in the liquid phase state.-8 Furthermore, as the current is increased, the isokitic phase region expands while maintaining a nearly thousand-line state with the heating element 105, and eventually the entire liquid crystal layer 103 changes to the isokitic phase. In this state, the longitudinal direction of the liquid crystal cell 100 (Fig. 3 (4)
) in the direction C), and the temperature is uniform in the short direction (direction B in FIG. 3 (4)) from the nucleation member 104 to the heating element 10.
A temperature gradient is formed such that the temperature gradually increases in the direction of 5. For example, the side wall surface 104 of the nucleation member 104
A temperature gradient is formed by setting the temperature in the vicinity of ' to 120° C., for example, and setting the temperature in the vicinity of the heating element 105, which is about 1.5 inches away from the temperature, to about 140° C., for example.

Next, if the temperature of the case in which the cell 100 is set is controlled to be gradually lowered from 90°C at a rate of, for example, 10°C/h while applying the above-mentioned temperature gradient to the cell 100, as shown in Fig. 3. In (B), first, the temperature near the side wall surface 104' of the nucleation member 104 becomes lower than the Tokiyoshi phase - 8mA phase inversion temperature (about 116°C), and SmA phase nuclei are formed in this region. . At this time, the side wall surface 104' of the nucleation member 104 and the surface 1 of the carpet board 101
09 has the effect of aligning liquid crystal molecules in the horizontal direction, so when the SmA phase is formed near the side wall surface 104', the liquid crystal molecule axis is within the plane (109) of the substrate 101, and The nuclei of the SmA phase that are subjected to a forcing force that causes alignment parallel to the longitudinal direction of the sidewall surface 104' are monodomains that are oriented horizontally with respect to the sidewall surface 104' and the surface 109 of the substrate 101. It has become. When the temperature of the case is further lowered, the already formed 5rnA
A phase transition occurs in SmA such that the Toyoshi phase near the phase interface between the
The monodomain region of the mA phase is continuously widened. At this time, the growth rate of the phase interface between the monodomain region of the Sm human phase and the isokyoshi phase region is determined in the longitudinal direction of the liquid crystal cell 100 (third
It is desirable that the speed be the same throughout the direction (direction of arrow C in Figure A).

For example, when the temperature of the case reaches about 70°C, the heating element 10
Except for the vicinity of 5, almost the entire liquid crystal undergoes a phase transition to the SmA phase.

Next, the electro-optic modulating substance (liquid crystal) 4o1 in the liquid crystal cell in the device shown in FIG.
The temperature is controlled to mH'.

By the way, in many currently known ferroelectric liquid crystals such as the above-mentioned DOBAMBC, as shown in FIG. 5, the temperature of the liquid crystal cell is raised and lowered. smc"io stable temperature ranges are different, and in general, when the temperature decreases, a stable state is often shown down to the lower temperature range (TI') than when the temperature increases. , ' are almost equal, there is no problem, but if Tt > T, ', it is more effective to maintain the liquid crystal temperature at T1 or TI' because the power consumption of the heater is lower. Therefore, in this example, as shown in FIG. 6, the temperature of the liquid crystal is raised to a temperature of T8 or higher to make it into an isobic phase, and then monodomain SmA (T*~ T3) is formed, and then the current flowing through the heating element 105 is gradually lowered to release the temperature gradient. The temperature of the liquid crystal cell 100 becomes uniformly 70°C (T1' to T2) as a whole, and the liquid crystal undergoes a phase transition to the SmC' phase.

At this time, the temperature range T of the O ferroelectric liquid crystal (SmC"), which is a uniform monodomain in the region where the electrodes 102 and 102' are formed, is defined as TI'+β<
T < Tt-α α, β; constant (however, Tt<T+
The temperature is controlled within the temperature range shown by +β (Tt<Tt−α<T2).

In a preferred embodiment of the present invention, a heating resistor 402 shown in FIG. 4 can be used as the temperature raising means. That is, the heating resistor 402 is energized in a large amount, heated to a high calorific value (first-stage heater heating), and brought to an equilactic phase, and then slowly cooled under a temperature gradient. This gradual cooling is carried out using the heating resistor 40.
After reducing the amount of current applied to 2 and forming SmA by heating with a low calorific value (second stage heater heating), the temperature gradient is canceled and the liquid crystal 401 is further heated with a low calorific value (third stage heater heating). undergoes a phase transition to SmC'. This control is performed by using the heating resistor 402 in multiple stages using a heat sensitive element 403 as a temperature sensor. The flowchart is shown in FIG. This flowchart shows the case of a three-stage heating system consisting of a first stage, a second stage, and a third stage.

The amount of heat generated at this time is 1st stage heating, 2nd stage heating> 3rd stage heating. In other words, the first stage heating is the Tokichi phase, the second stage heating is
The stage heating has a calorific value corresponding to SmA, and the third stage heating has a calorific value corresponding to SmC'.

The sequence shown in FIG. 7 can be controlled by the circuit shown in FIG. 4, for example. 5tep in Figure 7
1 represents a step in which the temperature of the electro-optical liquid crystal 401 in the cell is detected by the thermal element 403 when the main power source 417 is turned on. 5tep 2 is performed when the temperature of the liquid crystal 401 is T,>T (Ye
s), the power supply 416 is activated and the first stage heater heating is turned on.
It becomes NN state. If the temperature of the liquid crystal 401 is Tt<T (No), it is detected whether the temperature is T>T.

5tep 3, the first stage heater is turned on, and a current adjusted by the temperature control circuit 404 controlled by the microprocessor 406 and the current regulator 405 is applied to the heating resistor 402. , LCD 40
1 is heated until T > Ta (Yes).

At 5tep4, the first stage heater heating is turned off, and at the same time, the second stage heater heating and temperature gradient heating are turned on. That is, at 5tep4, the amount of current applied to the heating resistor 402 via the current regulator 405 controlled by the microprocessor 406 decreases,
The amount of heat generated is reduced, the second stage heater heating is turned on under the temperature gradient, and the temperature is lowered. Tt<'r at 5step5
<T, uniform monodomain SmA is formed.

In 5teP6, the temperature gradient heating and the second stage heater heating are canceled (OFF), and at the same time, the third stage heater heating is turned on, and the temperature is further lowered. At this time, SmC is formed.

At step 5, set the liquid crystal 401 of T>Tt to T<Tt a
This represents the step of slowly cooling until (Yes). This step 7 represents the step of ensuring the upper limit temperature of the range in which the liquid crystal 401 exhibits a ferroelectric liquid crystal.In the next step 8, the lower limit temperature of the temperature range in which the liquid crystal 401 exhibits a ferroelectric liquid crystal (T1'+β< This represents a step to ensure T). Therefore, if T>Tt a (5t
Cooling is performed in No. of ep7, and Tl'+β〉
In the case of T (No in 5tep8), the process returns to 5tep6 and the third stage heater heating is turned on again.

5tep 9 is when (Ye
s), an image forming device (e.g., an electrophotographic copying machine)
is in the Copy Read3' fk state, which can be activated at any time.

With this sequence, the liquid crystal 401 in the cell
The temperature curve shown in the figure can be controlled.

In the optical path opening/closing means shown in FIG. 4, a liquid crystal driving circuit 407 applies selective signals to electrodes 408 and 409 provided in the cell, so that the alignment state of the electro-optical liquid crystal 401 is selectively changed. The optical path can be opened and closed under control.

This alignment state modulation is detected by polarizers 410 and 411 placed on both sides. Also, in Figure 4, 414
and 415 represent letterpress plates such as glass or plastic sheets, and 412 and 413 represent insulating films such as SiO, Sin, polyimide, polycarbonate, and polyamide.

FIG. 8 shows another specific example of the optical modulation element used in the present invention. In this specific example, the heating resistor 8o
A heating element 803 having wires 1 and 3 is arranged on the side surface of the liquid crystal cell 802 . The current flowing through the heating resistor 8o1 can be controlled according to the sequence described above.

9 to 11 show examples of driving the optical modulation element of the present invention.

FIG. 9 is a schematic diagram of a cell 91 having a matrix electrode structure in which a ferroelectric liquid crystal compound is sandwiched in the middle. 92 is a scanning electrode (common electrode) group, and 93 is a signal electrode group. FIGS. 10(a) and 10(b) respectively show the electrical signals given to the selected scanning electrode 92(s) and the electrical signals given to the other scanning electrodes (unselected scanning electrodes) 92(n), FIGS. 10(c) and 10(d) represent the electrical signal applied to the selected signal electrode 93(s) and the electrical signal applied to the unselected signal electrode 93(n), respectively. In FIGS. 10(a) to 10(d), the horizontal axis represents time and the vertical axis represents voltage. For example, when displaying a moving image, the scanning electrode groups 92 are sequentially and periodically selected. Now, if the threshold voltage for providing the first stable state of a liquid crystal cell having bistable property is vth, and the threshold voltage for providing the second stable state is -Vtht, then the selected scan electrode 92 ( As shown in FIG. 9(a), the electric signal given to s) is at phase (time) 1+,
is an alternating voltage such that phase (time) 11 is 1. In addition, the other scanning electrodes 92 (n) are
As shown in FIG. 10(b), it is in a grounded state and the electrical signal is 0. On the other hand, the selected signal electrode 93(8)
The electric signal applied to the signal electrode 93(n) which is not selected is V as shown in FIG. 10(e), and the electric signal applied to the unselected signal electrode 93(n) is −V as shown in FIG. 10(d). In the above, the voltage value V is V< Vtb+ < 2
It is set to a desired value that satisfies V and -V>Vtht>2V. FIG. 11 shows the voltage waveform applied to each pixel when such an electric signal is applied. Figures 11(a) to (d) represent pixels A, 'B, and □ in Figure 9, respectively.
C and D correspond. That is, as is clear from FIG.

A voltage of 2V exceeding the threshold value Vths is applied to the pixels on the selected scanning line at phase t.

Further, to the pixel B existing in the same scanning line 1, a voltage -2■ exceeding the threshold value -Vtht is applied at phase t1.

Therefore, depending on whether or not a signal electrode is selected on the selected scanning electrode line, if the signal electrode is selected, the liquid crystal molecules are aligned in the first stable state, and if not selected, the liquid crystal molecules are aligned in the second stable state. Align the orientation to the stable factor of. In any case, it has nothing to do with the previous history of each pixel.

On the other hand, pixel C,! : On the unselected scan line as shown in D, the voltage applied to all pixels C and D is +V.
or -■, neither of which exceeds the threshold voltage. Therefore, the liquid crystal molecules in each pixel C and D maintain the orientation corresponding to the signal state when scanned last time without changing the orientation state. That is, when a scanning electrode is selected, a signal for that one line is written, and -
The signal state can be maintained until the next selection after the end of the frame. Therefore, even if the number of scanning electrodes increases, the actual duty ratio does not change, and contrast reduction and crosstalk do not occur at all. At this time, the value of the voltage value V and the phase (t+ + tt > = T value depend on the liquid crystal material used and the thickness of the cell, but it is usually 3 volts to 70 volts and 0.1 μsec to 2
It is used in the range of m sec. Therefore, in this case, the electrical signal applied to the selected scanning electrode changes from the first stable state (assumed to be in the "bright" state when converted to an optical signal) to the second stable state (assumed to be a "bright" state when converted to an optical signal). It is possible to cause either a change to a "dark" state) or vice versa.

FIG. 12 shows the above-mentioned optical modulation element connected to the optical path switch R120.
4 shows an example of an image forming apparatus (electrophotographic printer) equipped with a photosensitive drum 1201 as indicated by an arrow 120.
First, the photosensitive drum 1201 is uniformly charged by the charger 1203, and the optical path opening/closing means 12
04 to selectively control the opening and closing of the light beam from the lamp 1205 placed behind to generate an optical signal, and irradiate this optical signal onto the charged photosensitive drum 12o1 to form an electrostatic latent image. be done.

FIG. 12 shows an example of an image forming apparatus (electrophotographic printer apparatus) equipped with the above-described optical path opening/closing means 1204, in which a photosensitive drum 1201 is rotationally driven in the direction of an arrow 1202, and a charger 1203 is used to rotate the photosensitive drum 1201. Photosensitive drum 12
An electrostatic latent image is formed on the photosensitive drum by uniformly charging 01, driving the optical path opening/closing means 1204, controlling the opening/closing of the light beam from the exposure light source 1205 disposed behind the drum, and exposing the drum to a light image. Ru. This electrostatic latent image is transferred to the developing device 12.
06 toner, and this toner image is transferred onto the copy paper P that has passed through the transfer guide 1207 by the transfer charger 12.
Transcribed by 08.

The copy paper P on which the image has been transferred has a separation belt load of 120
9, the images are sequentially separated from the photosensitive drum 1201, and then the images are fixed in a fixing device 1210. Further, toner remaining on the surface of the photosensitive drum 12010 after transfer is removed by a cleaning device 1211,
The photosensitive drum 1201 is neutralized by the pre-exposure device 1212 and the next copying cycle is made possible again.Meanwhile, the optical path opening/closing means 1204 in FIG. 12 is equipped with the aforementioned ferroelectric liquid crystal cell. We are hiring. That is, when the light beam from the exposure light source 1205 is imaged on the photoreceptor 1201 via the optical path opening/closing means 1204 including a ferroelectric liquid crystal cell and the lens array 1213, the image is obtained by an original information reading device (not shown). By operating the liquid crystal drive circuit 1214 using a digital signal containing the image information, and turning on and off the ferroelectric liquid crystal shutter, an optical signal having a pattern of image information is transmitted to the photoreceptor 12.
01 is exposed. In this embodiment, the exposure light source 1205 also functions to heat the liquid crystal cell9, and by operating the liquid crystal cooling fan 1217 with the liquid crystal temperature control circuit 1216 connected to the thermal element 1220, overheating of the liquid crystal cell can be prevented. It is possible to prevent this and maintain the liquid crystal cell at a constant temperature. In the figure, 1218 is a reflective shade s, and 1219 is a member for attaching the lens array 1213 to the liquid crystal shutter device.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1 and 2 are perspective views showing a liquid crystal cell used in the present invention. FIG. 3A is a plan view of a liquid crystal element used in the present invention. FIG. 3> is a sectional view taken along the line AA. FIG. 4 is a sectional view showing a device using the optical modulation element of the present invention. FIG. 5 is an explanatory diagram showing the mode of phase change due to temperature. FIG. 6 is an explanatory diagram showing the temperature dependence of the optical modulation element used in the present invention. FIG. 7 is an explanatory diagram showing a flowchart of temperature control used in the optical modulation element of the present invention. FIG. 8 is a perspective view showing another optical modulation element of the present invention. FIG. 9 is a plan view showing a matrix electrode structure used in the optical path opening/closing means of the present invention. Figure 10(a)-(
d) is a waveform diagram representing the electrical signal applied to the matrix electrode structure. FIG. 11(a) to (d) are SmC
1 is a waveform diagram of a voltage applied to a conventional or SmH rice. 1st
FIG. 2 is a sectional view schematically showing the image forming apparatus of the present invention. 100; liquid crystal cell 101.101; substrate 102.102i electrode 103; liquid crystal layer 104; nucleation member 104'; side wall surface 105 of nucleation member; heating element 106; adhesive 107.107', 107; lead wire 108. 108'i polarizer 401; liquid crystal 4027 heating resistor 403; temperature sensing thermosensitive element 404; temperature control circuit 405; current regulator 406; microprocessor 407; liquid crystal drive circuit 408, 409; electrodes 41O, 411; polarizing plate 412 .413; Insulating film 4t4, 41s; a[j 4165 Power supply 417: Main power supply width - @ Wandering

Claims (1)

[Claims] (1) A first step of heating to a temperature higher than the upper limit temperature of the temperature exhibiting a ferroelectric liquid crystal phase, which separates the uniaxially anisotropic phase of the liquid crystal aligned in one direction and the phase on the higher temperature side forming a phase interface with the phase, and causing a phase transition of another phase near the phase interface to a uniaxially anisotropic phase of liquid crystals aligned in a direction parallel to the liquid crystal alignment direction of the -axis anisotropic phase under decreasing temperature; a second step of forming unidirectionally aligned liquid crystal monodomains by causing phase transitions to occur continuously from the phase interface in a direction perpendicular to the phase interface;
It is characterized by comprising a third step of causing a phase transition of the -axis anisotropic phase to a ferroelectric liquid crystal phase under cooling, and a fourth step of heating before reaching a lower limit temperature indicating a ferroelectric liquid crystal phase. Temperature control method for optical modulation elements. (2) The temperature control method for an optical modulation element according to claim 1, wherein the phase interface has linearity. (3) A patent claim in which the uniaxially anisotropic phase that is initially formed is near the interface with a member that promotes the generation of liquid crystal nuclei (hereinafter, the "member that promotes the generation of liquid crystal nuclei" is referred to as the "nucleation member"). A method for controlling the temperature of the optical modulation element described in Scope 1. (4) The phase transition is caused by lowering the temperature of the phase on the vertical side (near the interface with the nucleation member), which has a temperature gradient where the side in the vertical direction is at a high temperature, under such a temperature gradient. A temperature control method for an optical modulation element according to claim 1. (5) The temperature control method for an optical/modulating element according to claim 1, wherein the liquid crystal arranged in one direction has a smectic human face. (6) The temperature control method for an optical modulation element according to claim 1, wherein the ferroelectric liquid crystal phase is a chiral smect C phase or H phase. (7) The temperature control method for an optical modulation element according to claim 6, wherein the chiral smect C phase or H phase is arranged in a non-helical structure. (8) The temperature control method for an optical modulation element according to claim 1, wherein the other phase on the higher temperature side than the -axis anisotropic phase is a nematic phase, a cholesteric phase, or an isotonic phase. (9) A temperature control method for an optical modulation element according to claim 3, wherein the nucleation member and the substrate have the effect of arranging liquid crystals in a horizontal direction. (II@) A temperature control method for an optical modulation element according to claim 3, which is a member having a shape of a nucleation member. A temperature control method for an optical modulation element according to claim 10, wherein the nucleation member is a member having a side wall surface.A temperature control method for an optical modulation element according to claim 3, wherein the nucleation member has a side wall surface. (+31) The temperature control method for an optical modulation element according to claim 3, wherein the nucleation member is made of a resin or an inorganic substance. (14) The resin is polyvinyl alcohol, polyimide, polyamideimide, or polyesterimide. Select at least one type from the resin group consisting of polyparaxylylene, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, Yurya resin, acrylic resin, and photoresist iIt resin. A method for controlling the temperature of an optical modulation element according to claim 13, wherein the optical modulation element is made of a resin that is made of a ferroelectric liquid crystal. A method for controlling the temperature of an optical modulation element according to claim 1, further comprising a fifth step of cooling the optical modulation element.