JPS60153029A - Liquid-crystal optical device - Google Patents

Abstract

PURPOSE:To prevent defective operation due to temperature variation and obtain a small-sized, high-speed liquid-crystal shutter which has high recording density, high reliability, and high recording quality by detecting the temperature of a liquid-crystal material and varying a higher frequency than a cross frequency according to the detected temperature. CONSTITUTION:The output signal of a temperature sensor 141 fitted to a liquid- crystal microshutter head is inputted to an amplifier 142 and a voltage-controlled oscillator (VCO)143 to output an output signal of the frequency fm which varies with temperature and is lower than the cross frequency; and the signal is applied to the microshutter head 145 through a liquid-crystal microshutter driving circuit 145 controlled by a driving control circuit 146. The frequency fm is varied according to the temperature to prevent defective operation due to temperature variation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a liquid crystal optical device, and more particularly to a driving device for a liquid crystal shank that utilizes the electro-optic effect of liquid crystal in an optical recording section. [Prior art] An overview of a recording device using a liquid crystal optical shack is given in Section 1.2.3.
This will be explained using figures. As shown in FIG. 1, the recording apparatus is comprised of a charging section 1, a transfer section 2, a static eliminating section 3, a developing section 4, a cleaning section 6, and a liquid crystal shutter section 14. In FIG. 1, the surface of a photoconductive recording medium 7 (hereinafter referred to as photoreceptor) is uniformly charged in advance by a charging section 1. As shown in FIG. The liquid crystal light shutter section 14 receives recording information and is driven by a recording control section 15 that controls timing and the like, performs electro-optical conversion of the information, and performs optical writing on the surface of the photoreceptor 7. The electrostatic latent image thus formed is developed with toner in the developing section 4 and becomes a visible image. The recording paper 8 is fed by a paper feed roll 9, and the period with the toner image is determined by a waiting roll 10, and the toner image is transferred onto the recording paper 8 in the transfer section 2. The recording paper separated from the photoreceptor 7 in the separating section 11 is fixed with a 1-toner image in the fixing section.
3, it is sent to the outside. -The force photoreceptor 7 is the static eliminator 3
After the toner charge has been neutralized. The remaining toner is cleaned in the cleaning section 5, and the eraser 6
At this step, the surface charge on the photoreceptor 7 is neutralized and the photoreceptor 7 is prepared for the next step. The process of making an electrostatic latent image into a visible image is known as an electrophotographic method, and many variations have been proposed. The liquid crystal light shutter unit 14 is composed of a light source 16, a liquid crystal light shutter 17, and a condensing lens 18, as shown in FIG. A liquid crystal mixture is sealed between the substrates 20 and 21, and the glass substrate 20 is provided with signal electrodes 22 alternately, and the glass substrate 21 is provided with a common electrode 23. The area where the electrode 22 and the common electrode 23 intersect is made of indium oxide (lnz03), tin oxide (Sn
It is composed of transparent electrodes such as O;・). By disposing at least one polarizing plate on the liquid crystal panel 25 configured in this manner, the liquid crystal light shack 17 is configured to divide the incident light from the light source 1G into the microphones 1-1 and 2 based on the recording signal.
4, and irradiates it onto the photoreceptor 7 through the condenser lens 1B. The liquid crystal is LCD (?lk product display), and the calculator 7
It is widely used for clock displays, and recently it has been actively used for high-density displays such as liquid crystal televisions, personal computers, word processors, and large-screen displays as an alternative to RT displays. Two typical driving modes for the electro-optic effect of liquid crystals are known: the guest-host type (hereinafter referred to as OH type) and the twisted nematic type (hereinafter referred to as TN type). Due to the rearrangement of liquid crystals. Either parallel or perpendicular to the electric field causes the liquid crystal to align in one direction, and the process of returning the two electric fields to the original alignment state and completing one cycle is due to the thermal dilution process of the material. However, the response speed is less than a few ms, so it cannot be adopted as a necessary drive method.The two-frequency drive used in the present invention is capable of controlling dielectric anisotropy by changing the frequency of the electric field. This is an attempt to rearrange the liquid crystal molecules by reversing the polarity Δε, and the details are described in Japanese Patent Application Laid-Open No. 50404.043. The dielectric anisotropy Δε is the dielectric constant in the molecular direction of the secondary liquid crystal (hereinafter referred to as Δεr).
+) and the permittivity in the orthogonal direction (hereinafter referred to as Δε),
It is expressed on Δε−Δεll−Δε. When Δε〉O, the molecules are oriented parallel to each other in the electric field. When Δε<0, it is oriented vertically. Figure 4 shows the Δε characteristics. The frequency when Δε-0 is the cross frequency (hereinafter referred to as fc) and the rim. Therefore, the frequency lower than that of the IC (hereinafter f,
), then Δε−Δε, indicating positive dielectric anisotropy, and at frequencies higher than fc (hereinafter not referred to as r), Δε−
Δε, indicating negative dielectric anisotropy, as described above (:
, each time the fL signal is applied, the liquid crystal molecules can be aligned parallel to the electric field, and the f8 signal 1 can be used to align them perpendicularly, so ? ＋The opening and closing drive of the Shinko Shack 1J
It can be used to The dielectric FC direction Δε, which is not shown in Figure 4, is sensitive to viscosity. tj (l changes greatly depending on 41.1'1 degree. As the temperature increases and the viscosity decreases, fc increases, and Δε in Fig. 4
The characteristics are shifted by 1 on the right side (high frequency side). As a specific example, when the temperature rises from 20°C to 40°C, fc is 5.
It increases by nearly one digit from H1z to 46KIIz. In the figure, if the liquid crystal cell is turned on and off at fL and fH at room temperature, Δε on the fH side increases as the temperature rises.
8 becomes smaller and the off-side conditions for the liquid crystal cell become stricter. If the viscosity is low, it is expected that the liquid crystal molecules will move faster and have a faster response, so it is desirable to use the liquid crystal at a higher temperature. Furthermore, since it is heated by a light source, it is desirable to set the temperature with high accuracy. The liquid crystal light shank 17° liquid crystal panel 25 shown in FIGS. 2 and 3 is further revised and shown in FIG. 5. A gap is maintained between the two glass substrates 20 and 21 by a spacer 27, and an 11ν product mixture 28 or 11 for dual frequency driving is placed. The irises electrode 22 in FIG. 3 is composed of a transparent electrode 29 and a metal electrode 31, and the common electrode 23 is also composed of a transparent electrode 30 and a metal electrode J2, with the metal electrodes 31 and 32 partially removed. A microshanoter 24 is formed in the cut portion 33. By placing a polarizing plate 26 thereon, a GH type liquid crystal optical shank is constructed. Next, a configuration for driving the GH type liquid crystal shutter in two time divisions will be described. Figures 6 and 34 and 35 are selective electrodes. 36 to 39 are recording signal electrodes, which are used to increase the aperture ratio of the shutter.
They are drawn out alternately to ensure wide pattern spacing. 40 and 41 are micro shutters formed of transparent electrodes. The micro jack 40 is opened and closed by the write selection electrode 34.
and a signal applied to the recording signal electrode 36,
Opening and closing of the microshutter 41 is controlled by signals applied to the write selection electrode 35 and the recording signal electrode 36. 4
2 represents the moving direction of the photoreceptor, that is, the sub-scanning direction. FIG. 7 shows signal waveforms applied to the sliding selection electrode and the recording signal electrode. 7-a is the signal waveform applied to the write selection electrode 34, and 7th Ia7-b is the signal waveform applied to the write selection electrode 35. These waveforms are repeatedly applied to each electrode with Tw as one period. As is clear from the same figure, Fig. 7 7-a and 7-b and 1/2 T w
The waveforms are out of phase. Thereafter, the signal waveform of FIG. 77a is COMI. The signal waveform in FIG. 7-b is called C0M2. FIG. 7 7-c to 7-f show the 4
These are different types of signal waveforms. 7-c is SC, 7-d is SG2, 7-e is SG3.
7-r is called SG4. Note that fH in the figure represents a high frequency, and *f8 is a signal obtained by inverting this. Similarly, fL represents a low frequency, and *fL is a signal obtained by inverting this. The 8th panel shows four types of micro shutter drive waveforms created by the signals COMI and SC, 1 to 4. 8-a and 8-b are the waveforms that close the microphone 1-coat ivy, and FIG. 8 3-c and 3-d are the waveforms that open the micro shutter.
It is a waveform. As can be seen by comparing FIGS. 7 and 8, the waveform in FIG. 8 is an AC waveform with twice the amplitude of the waveform in FIG. 7. This method is basically the same as the method generally used for display liquid crystals in watches and calculators, and is made possible by applying signals to both electrodes that sandwich the liquid crystal. As shown in FIG. 8, in the two-frequency drive system, when closing the microshank, the fH signal is first applied, but when opening the shutter, an m-square waveform that is a combination of fH and fL is applied. If this is the case, even if the waveform is a combination of fH and fL, the effect of fL will be large and the Iff will essentially open the shutter.
Because there is power. In the middle of Tw, fH + fL signals are added. Or it may be in a no-voltage state where no signal is applied. This period is a period during which the micro shutter applied at the beginning of TW is maintained in the open state and closed state. This is because the function of opening the shutter by the m-tatami signals of f and +fL and the function of closing the non-voltage r and '-'r shutters work in balance to maintain the previous state. The fL signal is applied to the end of Tw. This works to open the microshaft 7, but the previous fl
, , l+fL, it works to open the shutter more strongly than the signal of l+fL, so it is sufficient to apply the signal for such a short time. FIG. 9 shows the opening and closing states of the micro shutter corresponding to each of drive waveforms 3-a to 8-d in FIG. 8. As can be seen from FIG. 9, the micro shutter is always open at the beginning and end of the T w =1 write cycle. This is due to the function of fL added at the end of TW in FIG. 8 above. The purpose of adding fL in this way is to eliminate the history effect of the liquid crystal. The liquid crystal for dual-frequency driving is turned off by fH, but if this is applied for a long time, a phenomenon occurs that the liquid crystal does not turn on immediately even if fL times the signal is applied due to the history effect. This is harmful to the shutter operation, and if the shack is closed for a long time, it will not open as soon as you want to open it. Therefore, the signal correction period fL is applied (in this case, once at the end of TV to V) to reduce the history effect. Up to now, the operation of the shutter to which the write selection electrode 34, ie, COMI is applied, has been described. What about the write selection electrode 35, ie, the side to which C0M2 is applied? Returning to Figure 7 again, Figure 7 7-, b o
:) As mentioned earlier, the waveform of the first half of COM 2 is the waveform of the second half of COMI. That is, according to C0M2, the first half of 1 W is a period in which the signal previously applied to the liquid crystal is maintained, and whether the shutter is open or closed differs from time to time. The second half of Tw is C0M
2 and the signal applied to the recording signal electrode causes the gloss to open,
If SGI is applied to the recording signal electrode during the period 1 to decide whether to close, the shutter will be closed, and if SG2 is open, the SG will be closed.
If it is 3, it will be closed, and if it is SG4, it will be open. that i
& 1/2 During Tw, no matter what SGI~4 is added, the COM 2 j second microphone 10 jack is part 4.
dog! Have good fortune-telling. To summarize the above, when SGI is applied, the microshaft vine 40 enters the closing operation at the beginning of Tw 1/2
After TW elapses, the microphone 10 and the shell 41 start closing operation. At the end of 1'w, the micro-shutter 40 completes its closing operation, and the micro-shutter 41 then closes at the end of 1'w. / 2
Maintain this state for T w, then 1/2 T w
The closing operation is completed at the end of . Further, when SG2 is applied, the micro shutter 40 is closed, and after 1/2 Tw, the microphone I shutter 41 is opened. Similarly, 40 is open in SG3. 41 is closed, and in SG4, 4.0.41 are both open. As is already understood, although the drive system explained above is a two-time division drive, the shutter operation is completed within 1/2 TW (because it operates over a period of Tw, LIEI). The situation is different from that of time-division driving. With this kind of drive system, 2's = 150K117
．． , f L-2K11z An example of operation at 1A degree and 4.6°C is shown in FIG. In Figure 10, 10-△ is T
A closed signal '+ (8-a in Figure 8) is given between 63TW from I to 'r63, and an open signal (8-a in Figure 8) is given at T64.
d) is given and this is repeated. 1
0-B is 63 from T1 to T63, opposite to 10-8.
This is the operating characteristic when an open signal is applied during TW, a close signal is applied at T64, and this is repeated. 10-C is the operating characteristic when giving Kaishin Death continuously, 1
0-D is the operating characteristic when a close signal is continuously applied. In Fig. 10, the characteristic of T64 period of 10-A is 1
It is equivalent to that of 0-C. Further, the characteristics of the period 'F64 of 10-13 are almost the same as those of 10-D. This r, +: Microshasota is subject to the history effect, 61 [indicates that it is actually operating within Tw. In other words, black and white 1-)1
This indicates that the machine is ready to print completely. In FIG. 11, the same liquid crystal microshaft is driven by the same drive signal, and the state of the liquid crystal is different from that in FIG. 10 at 43°C, which is about 3°C lower. l
1- If you put D, f at every end of TV. The operation of opening the shirt according to the signal is not completed completely. This is because the temperature is low, so the viscosity of the liquid crystal increases?
;+; <5 This is because the movement became stiff. When I got on 11-A, the micro shutter was not fully opened at the beginning of 1゛64. If the temperature drops further, the gloss will not open at all at 1゛64. In other words, the white dots after black dots 1 to 1 cannot be printed. On the other hand, FIG. 12 shows the characteristics when the temperature of the liquid crystal was raised to 53°C. There is no problem with the operation of opening the shutter, but in the operation of closing the shutter, either the shutter tries to close in the first half of each Tw, or this operation cannot be maintained in the second half of each Tw, and the shutter opens. As the temperature rises, the viscosity of the liquid crystal decreases, and at the same time, fc increases, and the influence of f, +fL in the waveform 8-a in Figure 8 becomes stronger, and the shutter closes due to the voltage. This is because the balance with the force that is being used to , its characteristics change slightly depending on the temperature, so temperature control at a temperature of 6'C is a
It is essential. Table 1 Table 1 shows the integrated value of the amount of light during a period of 1゛64. a is the value at T64 of A in FIGS. 10 to 12. Similarly, b is T64 of B in each figure. C corresponds to C, and d corresponds to D. If we pay attention to the e'-a/b, f; c/d columns in Table 1, we can see how the contrast changes. The above is the characteristic when fH is constant at 150KIIz. [Problems with the Prior Art] As explained above, when the values of fL and fH are fixed, the value of fc changes due to changes in the temperature of the liquid crystal. This was causing malfunction of the device. Therefore, there was a drawback that the temperature of the liquid crystal had to be maintained with high precision. [Object of the Invention] The present invention was made in view of the above-mentioned situation. The object of the present invention is to provide a liquid crystal optical device using a liquid crystal shutter that prevents malfunctions due to temperature changes and has high recording density, small size, high reliability, high speed, and high recording quality. [Summary of the Invention] In order to achieve the above object, the present invention provides a liquid crystal optical device that is driven at three frequencies, higher and lower frequencies than the crossing frequency that makes the dielectric anisotropy of the liquid crystal material zero. It is characterized in that the temperature of the material is detected and a frequency higher than the crossover frequency is changed in accordance with the detected temperature. [Embodiment] Therefore, in one aspect of the present invention, the value of fH is changed depending on the temperature. Next, fH was changed depending on the temperature, and the characteristics were measured at fH considered to be optimal, and the results are shown in Table 2. Table 2 As can be seen by comparing Tables 1 and 2, even if the temperature of the LCD microphone 1 rises from 53°C to 58°C, the frequency of fH will be increased accordingly (if done,
It can be seen that the reduction in contrast can be suppressed. In other words, by increasing the frequency of the microshutter, which has the characteristics shown in Figure 12 as the temperature rises, the effect of high frequencies can be greatly increased. By bringing the characteristics of fH+fL closer to the 11-1 side. It is possible to make the characteristics as shown in the original FIG. 10. FIG. 13 shows a block diagram of an embodiment of the present invention. 141 is a temperature sensor such as a thermistor or thermocouple attached to the liquid crystal micro shutter head. This signal is amplified by an amplifier 142 and inputted to a voltage condenser I-rolled oscillator (hereinafter abbreviated as ■c) 143. The output frequency of the VCO 143 changes based on the temperature detected by the temperature sensor 141. The closer the relationship 1 system of temperature and frequency is to that shown in Table 2, the better, but they do not have to match exactly. 144 is a liquid crystal micro shutter drive circuit. The output frequency of the VCOs 14 and 3 is assumed to be f8 of the signal applied to the liquid crystal micro shutter head 145. The drive control circuit 146 provides a signal to the liquid crystal micro shutter drive 144 to control the start, end, etc. of the printing operation. In this example, fH is changed steplessly by the VCO 143, but it is not necessarily necessary to change it continuously;
fH may be supplied in stages. Further, in the case of VC◯, it is also possible to install a limiter to suppress the upper and lower limits of fl, , l. As described above, TIX detects the temperature of the liquid crystal micro shutter and thereby varies fH of the micro shutter driving J waveform in a wide temperature range. It is now possible to perform a control I roll with high contrast. In other words, with one LCD microphone, it is possible to control the evening temperature relatively roughly. This contributes to increasing the stability of recording devices that use this technology. Figure 14 shows the micro shutter drive circuit 1/ of Figure 13.
1. 4 is an explanatory diagram. 200 is fH times signal. Conventionally, it was generated by an internal oscillator, but in the present invention, it is input from VO5 or the like. 20] is a low frequency oscillator, and in the example of the present invention, f, = 5KHz
It is. The waveform generator 203 is . The fL other signals and f)
, L signal S (TTLorCMOS level) 7-a corresponding to 7-a to 7-f in FIG.
Generate '-7-f'. At the same time, a TW signal corresponding to one write cycle is generated,
It is output to the drive control circuit 146 in FIG. On the other hand, from the drive control circuit 146, the video take 206 corresponding to black and white do/no-do is serially input to the shift register 208 by the video data shift 1-clock 205. This serial input inputs data for one line in the main scanning direction. If the operation is completed within one writing cycle) iJ]'rw. The latch pulse 207 is input to the take latch 210 and the flip-flop 212 at the interval of lTw, so that one line of video data input to the shift register 208 is simultaneously transferred to the take latch 210. After the video take is transferred to the take lunch 210, the shift register 208 starts shifting the take for the next line. The video takes already in the data latch 210 are synchronized with the latch pulse, and the odd-numbered takes 211A are input directly to the data selector 214, and the even-numbered data 2 1 1 +3 is input to the flip-flow knob 212. . The take that went into flip-flop 212 is. The next launch pulse causes the take selector 2 to
13. In other words, data is input to the data selector with a difference of one write cycle 'rW between odd and even numbered data. This is due to the fact that there are two selection electrodes and they are arranged in a horizontal or staggered pattern as shown in Part 6. In other words, the micro shack on the C0Ml side has a period including M]
In the first half of ゛w, opening and closing operations are performed using the odd-numbered data lines, and the microphone 1 on the C0M2 side is 1/2 Tw later than this, and the even-numbered opening is performed one line before the odd-numbered data line. Performs opening/closing operations based on data. Therefore, COMl. When widening FF and M during C0M2, the number of flip-flops is increased to 2 or 3 stages, and the even numbered data is 2Tw. It is sufficient that the signal is inputted to the take selector 214 with a delay of 3 Tw. The take selector 214 has four states determined by the video data 2118 and the delayed video data 213 (211Δ is 1 and 213 is also 1, 211A is 1 and 213 is O, down is 0 and 1, both are 0). )
Select one of the signals 7-C' to 7-f' by Now] is black, 0 is white, and 1 corresponds, then 1
．． If it is 1, then 7-C' is 1.0, then 7-d' is 0. If it is 1, 7-e' is selected, and if it is 0.0, 7-f' is selected. Selected faith-';! , 2] - 5 is input to the sofa 216 to high screaming pressure, and the amplitude changes from Rossinoclay to liquid crystal drive level, and it is correct.
8 amplified by Noko COMI, C0M2 (7-a.
7-b), the waveforms 8-a to 8-Eld of the 811a are applied to the liquid crystal to open and close the microphone 1's glow. [Effects of the Invention] As described above, according to the present invention, the temperature control of the liquid crystal can be relatively rough, and high contrast shutter can be obtained in a wide temperature range. In addition, it can be used without having to wait for the liquid crystal to warm up completely as in the conventional case. In other words, the warm amplifier time can be shortened.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a recording device to which the liquid crystal optical device of the present invention is applied, Fig. 2 is a block diagram showing an IIh-type optical shutter which is an embodiment of the present invention, and Fig. 3 is a block diagram showing a liquid crystal panel. Fig. 4 is a characteristic diagram showing the dielectric anisotropy Δε of a liquid crystal for dual-frequency drive. FIG. 7, which is a block diagram of the microshutter in divided driving, shows the signal waveforms applied to the write selection electrode and the recording signal electrode in FIG. 6. Figure 8 shows the driving waveform that is actually applied to the liquid crystal by combining the waveforms in Figure 7. Figure 9 shows the light transmission characteristics of the shutter due to these driving waveforms. ，
Figure 12 shows the behavior of the micro shutter at 53°C. FIG. 13 is a block diagram showing an embodiment of the present invention.
FIG. 4 is a block diagram of a driving circuit for the micro shutter shown in FIG. 13. ■...Charging section, 2...Transfer section. 3... Static elimination section, 4... Development section. 5...Cleaning section, 6, , eraser,
7.19...Photoreceptor, 8...Recording paper, 9...
・Paper feed roll. 10...waiting roll, 11...minute A11 part. 12... Fixing section, 13... Paper ejection roll. 14... Liquid crystal shutter section, 15... Recording control section,
16...Light source. 17...Liquid crystal light shutter, 18...Condenser lens,
20.21...Glass substrate. 22...Signal electrode, 23...Common electrode. 24...Micro shutter, 25...Liquid crystal panel, 26...Polarizing plate. 27...Space number, 28...Liquid crystal mixture for dual frequency drive, 29.30...Transparent electrode, 31.32...
・Metal electrode. 33... Micro shank part, 34. 35...Write selection electrode, 36. , 37. 38, 39... recording signal electrode, 40. 41...Microshank, 42...Sub-scanning direction. 7-a...Waveform applied to write selection electrode 210 (
COM'l), 7=b...Waveform applied to write selection electrode 211 (C0M2), 7-c...Closed. Closed waveform (S
QL) 7-d...Closed and open waveforms (SG2). 7e... Open and close waveform (SG3). 7-f... Open, open waveform (SG4). 3-a - Waveform by COIvll-SGL. 8-b... Waveform by COMI-SG2. 3-c...C O M 1 - S G 3 waveform. 8-d...Waveform by COMI-304. 9-a...Amount of transmitted light by 8-a. 9-b...Amount of transmitted light by 8-b. 9-c・・Transmitted light pressure by 8-c. 9-d... Amount of transmitted light by 3-cl. 141...Temperature sensor, 142...Amplifier. 1
43...VCO. 144...Liquid crystal micro shutter drive circuit. 145...Liquid crystal microsha 7 tags. 146... Drive control concave path, 200... fH times signal 201... fL oscillator. 202... fL signal, 203... waveform generator,
204...Tw times signal 205...Video data shift 1-clock. 206... Video data, 207... Launch pulse, 208... Shift register, 209... Video data. 210... Day latch, 211... Video data, 212... Flip-flop, 213...
Delayed video data, 214...Data selector 2 215...Signal electrode signal. 216, 217...High voltage buffer. 217... Signal electrode signal Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 7-( Fig. 6 7-1 -f Fig. 7 Fig. 12 Fig. 13

Claims (1)

[Claims] In a liquid crystal optical device that is driven by two frequencies, one higher and one lower than the crossing frequency that makes the dielectric anisotropy of the liquid crystal material zero, the temperature of the liquid crystal material is detected, and the crossing frequency is adjusted according to the detected temperature. A liquid crystal optical device characterized by changing a higher frequency.