JPH045365B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a recording device having a liquid crystal shutter in an optical recording section.

[Prior art and its problems]

A recording device has been proposed that uses a liquid crystal as a light shutter and forms an image on a photoreceptor by passing or blocking light according to a recording signal. An outline of a recording apparatus using a liquid crystal as an optical shutter will be explained below with reference to the drawings.

In FIG. 1, a photoreceptor 1 which is a photoconductive recording medium
The surface of is uniformly charged in advance by the charging section 2. The liquid crystal optical shutter section 3 is driven by a recording control section 4 that receives recording information and controls timing and the like, performs electro-optical conversion of the information, and performs optical writing on the surface of the photoreceptor 1.

The electrostatic latent image thus formed on the photoreceptor 1 is visualized by toner in the developing section 5.
The recording paper 6 is fed by a paper feed roll 7, synchronized with the toner image by a standby roll 8, and fed again, and the toner image is transferred onto the recording paper 6 by a transfer section 9. The recording paper 6 separated from the photoreceptor 1 at the separation section 10 has a toner image fixed thereon at a fixing section 11, and is sent out of the machine by a paper discharge roller 12.
On the other hand, after the transfer, the toner charges on the photoreceptor 1 are neutralized in the discharging section 13, the remaining toner is cleaned off in the cleaning section 14, and the surface charges of the photoreceptor 1 are completely neutralized in the eraser 15.

As shown in FIG. 2, the liquid crystal light shutter section 3 is composed of a light source 16, a liquid crystal light shutter 17, and an imaging lens 18. The liquid crystal light shutter 17 is constructed by disposing at least one polarizing plate on a liquid crystal panel 19 as shown in FIG. The liquid crystal panel 19 is formed by sealing a liquid crystal mixture between two glass substrates 20 and 21. The glass substrate 20 is provided with signal electrodes 22 alternately, and the glass substrate 21 is provided with a common electrode 23. There is. The microshutter 24 is constructed of a transparent electrode made of indium (In ₂ O ₃ ), tin oxide (SnO ₂ ), etc. arranged in the required size and shape at the intersection of the signal electrode 22 and the common electrode 23 . . The liquid crystal light shutter 17 modulates the incident light from the light source 16 using the microshutter 24 based on the recording signal, and irradiates the modulated light onto the photoreceptor 1 through the imaging lens 18 .

The structure of the liquid crystal light shutter 17 shown in FIG. 2 is shown in more detail in FIG. 2 glass substrates 2
A gap is maintained between 0 and 21 by a spacer 25, and a mixture 26 of a liquid crystal material for dual-frequency driving and a dye is sealed. The signal electrode 22 shown in FIG.
The microshutter 24 is formed in a portion 31 where the metal electrodes 28 and 30 are partially removed. By disposing a polarizing plate 32 thereon, a guest-host type liquid crystal light shutter is constructed.

In the above-mentioned recording devices, the purpose of improving the response speed of the liquid crystal and reducing the number of electrodes is to use time-division driving or a cross frequency f _H that is higher than the cross frequency f _C and a lower frequency f that makes the dielectric anisotropy of the liquid crystal material zero. Two-frequency driving using _L is performed and will be explained below.

In FIG. 5, 33 and 34 are write selection electrodes. Further, 35 to 38 are recording signal electrodes, which are drawn out alternately in order to increase the aperture ratio of the shutter and to increase the pattern interval. 39,40
is a microshutter made of transparent electrodes. The opening and closing of the microshutter 39 is controlled by signals applied to the write selection electrode 33 and the recording signal electrode 35, and the opening and closing of the microshutter 40 is controlled by signals applied to the write selection electrode 34 and the recording signal electrode 35. 41 represents the moving direction of the photoreceptor 1, that is, the sub-scanning direction.

FIG. 6 shows a conventional example of signal waveforms applied to the write selection electrode and the recording signal electrode.

a is a signal waveform applied to the write selection electrode 33, and b is a signal waveform applied to the write selection electrode 34. These waveforms are repeatedly applied to each electrode with T _W as one period. As is clear from the figure, a and b have waveforms with a 1/2T _W phase shift.

From now on, the signal waveform of a is COM1, and the signal waveform of b is
Call it COM2.

c to f are four types of signal waveforms applied to the recording signal electrodes. From now on, these signal waveforms are called c
SG1 and d are called SG2, e is called SG3, and f is called SG4. Note that f _H in the figure represents a high frequency, and *f _H is a signal obtained by inverting this. Similarly, f _L represents a low frequency, and *f _L is a signal obtained by inverting this.

FIG. 7 shows four types of microshutter drive waveforms generated by the signals of COM1 and SG1 to SG4. A and b are waveforms that close the microshutter, and c and d are waveforms that open the microshutter. As can be seen by comparing FIGS. 6 and 7, the waveform in FIG. 7 is an AC waveform with twice the amplitude of the waveform in FIG. 6.

As shown in Fig. 7, in this drive system, when closing the microshutter, the f _H signal is first applied, but when opening the microshutter, a combined superimposed waveform of f _H and f _L is applied. There is. This means that f _H and
This is because the effect of f _L is large even in the synthesized waveform of f _L , and it essentially works to open the microshutter. Hereinafter, it will be expressed as f _H + f _L.

In the middle of T _W , a signal of f _H + f _L is added, or a no-voltage state occurs where no signal is added. This period is a period during which the microshock that was applied at the beginning of T _W is maintained in the open or closed state, and the superimposed signal of f _H + f _L is used to open the microshutter, and the no-voltage action is used to close the microshutter. works to balance and maintain the previous state.

At the end of T _W , a signal of f _L is applied. This works to open the microshutter, but it works to open the microshutter more strongly than the previous f _H + f _L signal.

FIG. 8 shows the opening and closing states of the microshutter corresponding to each of the drive waveforms a to d in FIG. 7.

As can be seen from FIG. 8, the microshutter is always open at the beginning and end of one write cycle _TW .
This is due to the action of f _L added at the end of T _W in Figure 7 above. The purpose of adding f _L 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 in which the liquid crystal does not turn on immediately even if the _fL signal is applied due to the hysteresis effect. This is harmful to the shutter operation, and if the shutter is closed for a long time, it will not open immediately when you want to open it. Therefore, the f _L signal is applied (in this case 2 cycles at the end of _TW ) to reduce the above-mentioned hysteresis effect.

Up to now, we have explained the opening and closing operations of the shutter when the write selection electrode 33, that is, COM1, is applied.
The opening/closing operation of the shutter when is applied will be explained. According to FIG. 6, the waveform of the first half of COM2 in b is the waveform of the second half of COM1 as described above. That is, according to COM2, the first half of _TW is a period in which the signal previously given to the liquid crystal is maintained, and whether the microshutter is open or closed depends on the situation.
The second half of T _W is a period in which the microshutter is determined to open or close by the signal applied to COM2 and the recording signal electrode.If SG1 is applied to the recording signal electrode, the microshutter is closed, if SG2 is applied, it is open, and if SG3 is applied, the microshutter is closed.
If so, close, if SG4, open. During the subsequent 1/2 T _W , the microshutter above the write selection electrode 34 maintains its state no matter what is added to SG1 to SG4.

From the above, when SG1 is applied, the microshutter 39 enters the closing operation at the beginning of _TW ,
After 1/2T _W has elapsed, the microshutter 40 starts its closing operation. Micro shutter 39 at the end of T _W
completes the closing operation, and the microshutter 40 then maintains this state for 1/2T _W and completes the closing operation at the end of 1/2T _W. Also, when SG2 is applied, the microshutter 39 is closed and 1/2T _W
The rear microshutter 40 is opened. similarly
When SG3 is applied, 39 is open, 40 is closed, SG4
When is applied, both 39 and 40 become open.

As already understood, although this drive method is a two-time division drive, the shutter operation does not complete during 1/2T _W , but operates over a period of _TW , so the LED The situation is different from that of time-division driving, etc.

With this drive method, f _H = 300KHz, f _L = 6K
Figure 9 shows an example of operation at Hz and temperature of 47°C.
In Figure 9, a is 63 from T1 to T63.
This is the operating characteristic when a close signal (Fig. 7a) is applied during T _W , an open signal (Fig. 7 d) is applied at T64, and this is repeated. b is T1 opposite to a
Give an open signal of 63T _W from T63 to T63.
This is the operating characteristic when a close signal is given at step 64 and this is repeated. Also, c is the operating characteristic when the open signal is continuously applied, and d is the operating characteristic when the closing signal is continuously applied. In Figure 9, T6 of a
The characteristics of period 4 are similar to those of c. Further, the characteristics of the period T64 of b are almost the same as those of d. This indicates that the microshutter is operating reliably within _TW without being affected by history effects. In other words, it shows that black and white dots can be completely printed.

Figure 10 shows the exact same liquid crystal microshutter as above, driven by the same drive signal.
The temperature of the liquid crystal is 43°C, which is about 4° lower than that in Figure 9.

Looking at d here, the operation of opening the microshutter by f _L at each end of T _W is not completed completely. This is because the viscosity of the liquid crystal increases due to the low temperature, making the operation slow. Looking at a, the microshutter is not fully opened at the beginning of T64. When the temperature further decreases, T6
In step 4, the micro shutter will not open all the way. In other words, a white dot after a series of black dots cannot be printed.

Figure 11 shows the characteristics when the temperature of the liquid crystal was raised to 55°C. There is no problem with the operation of opening the microshutter, but in the operation of closing the microshutter, the microshutter tries to close in the first half of each T _W , but in the second half of T _W , this operation cannot be maintained and the microshutter closes. The door opens. This is because as the temperature rises, the viscosity of the liquid crystal decreases, and along with this, f _C increases, resulting in f _H in the waveform a in Figure 7.
This is because the influence of +f _L became stronger and the balance with the force that tries to close the microshutter due to no voltage was lost. FIG. 12 shows a graph in which the integrated value of the amount of light during the period T64 is plotted at different temperatures. In Figure 12, A is from Figure 9 to 1.
B is the integrated value of the amount of transmitted light at T64 in a of FIG. 1, and B is the integrated value of the amount of transmitted light at T64 of b in FIGS. 9 to 11. Similarly, C corresponds to c in FIGS. 9 to 11, and D corresponds to d.

As is clear from FIG. 12, below 43°C, the characteristic of A, that is, the opening response after continuous closing, deteriorates, and below 41°C, the microshutter does not open even though an open signal is applied.

Conversely, when the temperature exceeds 53°C, the values of B and D become large. This indicates that the microshutter is on the verge of opening even though a close signal is being applied. Ultimately, this increases light leakage when the microshutter is closed, leading to a decrease in black and white contrast.

As described above, the characteristics of liquid crystal microshutters vary slightly depending on the temperature, and conventionally, accurate temperature control has been required.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional drawbacks, it is an object of the present invention to provide a recording apparatus that improves the response characteristics of a liquid crystal light shutter of an optical recording section and that can obtain high-quality recorded images.

[Key points of the invention]

In order to achieve the above object, the present invention has an optical recording section that performs optical writing corresponding to an image signal on a photoconductive recording medium, and the optical recording section includes a light source, a plurality of recording signal electrodes, and two recording signal electrodes. In a recording device comprising a liquid crystal shutter formed at the intersection with a write selection signal electrode and arranged in dots, and an imaging optical system, the write selection signal electrode has a crossing frequency f at which the dielectric anisotropy of the liquid crystal composition becomes zero. A combination signal including a weekly wave number f _H higher than _C and *f _H having an opposite phase to the f _H is applied, and a combination signal including the f _H and *f _H is applied to the recording signal electrode, and a main scanning signal is applied to the recording signal electrode. By selectively applying a signal consisting of a ground signal for a period in which one line in the direction is written and a DC signal for the same period as the period, the liquid crystal shutter receives the signal of a predetermined polarity during the period when the ground signal is applied. The control means includes a control means for applying a combination signal of f _H and *f _H , and applying a combination signal of f _H and *f _H having a polarity opposite to the predetermined polarity during a period in which the DC signal is applied. Features.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

The structure of the recording apparatus of the present invention and the structure of the liquid crystal optical shutter of the optical recording section thereof are the same as those shown in FIGS. 1 to 5, and redundant explanation thereof will be omitted.

First, driving waveforms of the liquid crystal shutter driving method according to the present invention are shown in FIGS. 13 and 14. 13th
The figure is a signal waveform diagram applied to the write selection electrode and the recording signal electrode shown in FIG. 5, in which a represents the signal waveform applied to the write selection electrode 33 and b represents the signal waveform applied to the write selection electrode 34, respectively. Further, c to f are four types of signal waveforms applied to the recording signal electrodes. From now on, the signal waveform of a is COM1A,
b is COM2A, c is SG1A, d is SG2A, e
is called SG3A, and f is called SG4A. Also, Figure 14a
-d show four types of microshutter drive waveforms generated by the upper air signals COM1A and SG1A to SG4A, respectively. In other words, FIG. 13 corresponds to FIG. 6 showing the conventional example, and FIG. 14 corresponds to FIG.
Corresponds to the figure.

As shown in FIG. 13, the drive waveform of the present invention is T _W f
and T _W s, 2T _W is one period. Further, a feature of the present invention is that the waveform applied to the signal electrode when opening the liquid crystal shutter is fixed at the ground or power supply level during _TW , as typified by FIG. 13f.
However, this is not fixed at the ground or power supply level for a long period of time, but is always repeated at predetermined intervals, for example, every 1 _TW . In other words, in the long term, it is considered as exchange. this is,
In a liquid crystal for dual-frequency driving, the liquid crystal is aligned in the direction of the electric field by f _L , but if f _L is made too low, that is, in an extreme case, if direct current is applied, the liquid crystal itself will be destroyed.

Next, paying attention to FIG. 13a (COM1A), and comparing the period T _W f for writing one line in the main scanning direction and the period T _W s for writing one line in the main scanning direction, T _W s is T _W This is obtained by swerving f and inverting the phase. Other signals b to f are also T _W f and T _W
In s, the relationship is such that the tilt phase is reversed.

Figure 14 shows COM1A and SG1A as shown above.
These are four types of microshutter drive waveforms created by the SG4A signal. Here, in the same figure, T _W
It is shown as a pair of f and T _W s, which is T _W of a
It is not true that the waveform of T _W s of a is always applied to the liquid crystal after f, but if the waveform of T _W f of a is applied during a certain writing period T _W , the next T _W , one of the waveforms at T _Ws a to d is applied. However, the waveform at T _W f is not applied continuously.

Here, when comparing FIG. 7 showing the conventional drive waveform and FIG. 14 showing the drive waveform in the present invention, it is found that FIG. 7 a and b and FIG. The periods during which f _H is applied in a and b are equal. The difference is the period during which f _H +f _L is applied and the period during which f _L is applied at the end of T _W. As can be seen by comparing FIG. 7 and FIG. 14, FIG. 14 has a simpler waveform. In other words, the Y period and the Z period in FIG. 14 have a shape closer to a low frequency in terms of effective value, and a shape closer to a direct current. As mentioned above, applying _fH for a long time is harmful to high-speed shutter operation due to the hysteresis effect of the liquid crystal. To eliminate this, conventionally an f _L signal was inserted at the end of T _W.

Since the driving method according to the present invention can halve the amplitude of the voltage applied to the liquid crystal shutter during the periods T _W f and T _W s, it is possible to fully eliminate the adverse effects of high frequency history. In addition, by halving the amplitude of f _L , the voltage becomes closer to direct current and the liquid crystal shutter can be opened more forcefully.
The application time of f _L can be reduced accordingly.
Moreover, since the period of _fH applied when closing the shutter does not change, the closing operation of the shutter will not deteriorate.

FIG. 15 shows the temperature characteristics when the liquid crystal shutter is driven in this manner. In the figure, A is the response of opening after continuous closing, B is the response of closing after continuous opening, C is the response of continuous opening, and D is the response of continuous closing, and shows the change in characteristics with respect to temperature. This corresponds to FIG. 12, which shows the conventional temperature characteristics. When compared with FIG. 12, which shows the conventional example, it can be seen that although the open and close levels are the same, the temperature range is sometimes expanded on the low temperature side. In other words, the temperature range in which the shutter exhibits good response characteristics has been expanded, and its temperature characteristics have been significantly improved.

As mentioned above, the period of 2T _W of T _W f and T _W is
Thinking of it as a cycle, when opening the shutter, the waveform applied to the signal electrode is fixed at the ground or power supply level, and by creating a waveform that is alternating current over a long period of time, it is possible to avoid damaging the dual-frequency drive liquid crystal.
It is possible to perform good driving.

〔Effect of the invention〕

As explained in detail above, the recording device of the present invention improves the temperature characteristics without reducing the contrast of the liquid crystal light shutter in the optical recording section, provides good response characteristics of the liquid crystal light shutter, and produces high-quality recorded images. can get.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the recording device, Fig. 2 is a block diagram of the liquid crystal light shutter section, Fig. 3 is a block diagram of the liquid crystal panel, Fig. 4 is a cross-sectional block diagram of the liquid crystal light shutter, and Fig. 5 is a block diagram of the liquid crystal light shutter section.
The figure shows the configuration of the microshutter in two-time division drive, Figure 6 shows the signal waveforms applied to the write selection electrode and recording signal electrode, Figure 7 shows the drive waveform applied to the liquid crystal, and Figure 8 shows the liquid crystal optical shutter. Figures 9 to 11 are light transmission characteristic diagrams showing the behavior of the microshutter at 47°C, 43°C, and 55°C using the conventional drive method, respectively, and Figure 12 is the conventional temperature characteristic diagram. , FIG. 13 is a signal waveform diagram applied to each electrode in the present invention, FIG. 14 is a drive waveform diagram applied to the liquid crystal, and FIG. 15 is a temperature characteristic diagram in the present invention. 1... Photoreceptor, 3... Liquid crystal light shutter section, 5...
...Development section, 9...Transfer section, 11...Fixing section, 14
... Cleaning section, 16 ... Light source, 17 ... Liquid crystal light shutter, 18 ... Image forming lens, 19 ... Liquid crystal panel, 22 ... Signal electrode, 23 ... Common electrode, 24, 39, 40 ... Micro Shyatsuta, 3
3, 34...Writing selection electrode, 35, 36, 3
7, 38... Recording signal electrode.

Claims (1)

[Claims] 1. An optical recording section for performing optical writing corresponding to an image signal on a photoconductive recording medium, and the optical recording section includes a light source, a plurality of recording signal electrodes, and two writing selection signal electrodes. In a recording device comprising a dot-aligned liquid crystal shutter and an imaging optical system, the write selection signal electrode has a crossing frequency _f higher than the zero dielectric anisotropy of the liquid crystal composition. frequency
A combination signal including f _H and *f _H having an opposite phase to the f _H is applied, and the f H and the * f _H are applied to the recording signal electrode.
By selectively applying a combination signal including _fH , a signal consisting of a ground signal during a period for writing one line in the main scanning direction and a DC signal during the same period as the period, the liquid crystal shutter is applied to the ground signal. A combination signal of f _H and *f _H having a predetermined polarity is applied during the period in which the signal is applied, and a combination signal of the f H and *f H having the opposite polarity to the predetermined polarity is applied during the period in which the DC signal is applied.
A recording apparatus comprising a control means for applying a combination signal of f _H and *f _H.