JPS60162229A - Recording device - Google Patents

Abstract

PURPOSE:To improve temperature characteristics and obtain an excellent image by applying a direct current which is inverted in polarity at a specific period to a liquid-crystal shutter used for an optical recording system at a frequency higher than a cross frequency at which the dielectric anisotropy of a liquid- crystal compound is zero. CONSTITUTION:Two glass substrates 20 and 21 hold a gap with a spacer 25 and a liquid-crystal material 26 is charged therein to constitute the liquid-crystal shutter. A signal electrode consists of a transparent electrode 27 and a metallic electrode 28 and a common electrode consists of a transparent electrode 29 and a metallic electrode 30. A microshutter is formed at a part 31 where the metallic electrodes 28 and 30 are partially removed. Microshutters 39 and 40 are formed of the transparent electrodes at intersections of write selection electrodes 33 and 34, and recording signal electrodes 35-38, and the shutter 39 and 40 are opened and closed by a controller which is not shown in the figure. The shutters are opened and closed at the frequency higher than the cross frequency at which the dielectric anisotropy of the liquid-crystal material is zero, and the applied DC voltage is inverted in polarity at a low period. Consequently, a temperature rise of the liquid crystal is prevented to obtain an image of good quality.

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 tV has been proposed in which a liquid crystal is used as an optical shutter and an image is formed 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, the surface of a photoreceptor 10, which is a photoconductive recording medium, is uniformly charged in advance by a charging section 2. As shown in FIG. The liquid crystal light 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 l is visualized by toner in the developing section 5.

The recording paper 6 is fed by a paper feed roll 7, and then placed on a standby roll 8.
At , the toner image is synchronized with the toner image and fed again, and the toner image is transferred onto the recording paper 6 at the transfer section 9 . The recording paper 6 separated from the photoreceptor 1 at the separating section 10 is transferred to the fixing section 1.
1, the toner image is fixed and sent out of the machine by a paper ejection roller 12.

On the other hand, after the transfer, the toner charge on the photoreceptor 1 is neutralized in the neutralization section 13, the remaining toner is cleaned off in the cleaning section 14, and the surface charge of the photoreceptor 1 is completely neutralized in the eraser 15.

As shown in FIG. 2, the liquid crystal light shank section 3 includes a light source 16. LCD light shutter 17. An imaging lens 18 is configured. 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 has 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. The micro-shutter 24 is formed of a transparent electrode made of indium (In203), tin oxide (SnO2), etc. arranged in a necessary size and shape at the intersection of the signal electrode 22 and the common electrode 23.

The liquid crystal light shutter 17 is.

Based on the recording signal, incident light from the light source 16 is modulated by the micro shutter 24 and irradiated onto the photoreceptor 1 through the imaging lens 18 .

FIG. 4 shows the structure of the liquid crystal light shutter 17 shown in FIG. 2 in more detail. A gap is maintained between the two glass substrates 20° 21 by a spacer 25.

A mixture 26 of a liquid crystal material for dual frequency driving and a dye is sealed. The signal electrode 22 shown in FIG. 3 is composed of a transparent electrode 27 and a metal electrode 28, and the common electrode 23 is composed of a transparent electrode 29 and a metal electrode 30.
．． A micro-shutter 24 is placed on the part 31 where part 30 is removed.
is formed. By disposing a polarizing plate 32 thereon, a guest-host type liquid crystal light shutter is constructed.

In recording devices such as those described above, in order to improve the response speed of the liquid crystal and reduce the number of electrodes, a higher frequency fH and a lower frequency fL are used than the cross frequency fc that makes the dielectric anisotropy of the liquid crystal material zero. Two-frequency driving is performed, and will be explained below.

In FIG. 5, 33 and 34 are write selection electrodes. Further, numerals 35 to 38 are recording signal electrodes, which are drawn out alternately in order to increase the aperture ratio of the shank and to increase the pattern interval. 39 and 4Q are micro shutters formed of transparent electrodes.

Opening and closing of the micro-shutter 39 is controlled by signals applied to the write selection electrode 33 and recording signal electrode 35, and opening and closing of the micro-shutter 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 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 and JJ as one period. As is clear from the figure, waveforms (0) and (b) are out of phase by 1/2'r.

From now on, the signal waveform of (a) will be changed to C0M1. The signal waveform in (b) is called C0M2.

(C) to (f) are four types of signal waveforms applied to the recording signal electrode. Hereinafter, these signal waveforms tc) will be referred to as SG.
l, (dl is SG2. (e) is SG3. (f) is SG4
It is called. Note that fM in the figure represents a high frequency, and IfH is a signal obtained by inverting this. Similarly, fL represents low frequency,
*f, , is a signal obtained by inverting this.

FIG. 7 shows four types of micro-shutter drive waveforms created by the signals of C6M1 and SG1 to sG4. (a
l, (bl is the waveform that closes the micro shutter,
(C) and +d) are waveforms that open the micro shutter. Comparing FIG. 6 and FIG. 7, it is clear that 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 microshank, the fH signal is first applied, but when opening the microshutter, a combined superimposed waveform of fH and fL is applied. This is because even in the combined waveform of fH and fL, the effect of f is large and has the effect of essentially opening the micro shutter. Hereinafter, it will be expressed as fH+fL.

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 the period during which the micro shack that was added at the beginning of T and JJ remains open or closed, and fH + fL
The function of opening the microshutter by the superimposed signal and the function of closing the microshank by no voltage are balanced and work to maintain the previous state.

The T2 signal is applied at the end of Tw. This works to open the micro shutter.

The micro shutter is opened more strongly than the previous fH+fL signal.

FIG. 8 shows the opening and closing states of the micro shack corresponding to each of the drive waveforms +8) to (dl) in FIG. 7.

As shown in FIG. 8, the micro shutter is always open at the beginning and end of one writing period Tw.

This is due to the function of f added at the end of Tw in FIG. 7 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 in which the liquid crystal does not turn on immediately even when the f 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 won't open immediately when you want to open it. Therefore, the fL signal is applied (in this case at the end of T, 2 cycles) to reduce the above-mentioned hysteresis effect.

Up to now, the shutter opening/closing operation when the write selection electrode 33, ie, C0M1, is applied has been described, but the shutter opening/closing operation when the write selection electrode 34, ie, C0M2 is applied, will now be described. According to Figure 6 (
The first half waveform of C0M2 in b) is the same as the second half waveform of C0M1 as described above. That is, according to C0M2, the first half of Tw is a period in which the signal previously applied to the liquid crystal is maintained, and whether the microshutter is open or closed depends on the situation.

The second half of Tw is a period in which opening and closing of the micro shutter is determined by the signal applied to C0M2 and the recording signal electrode.If S01 is applied to the recording signal electrode, the My 40 shutter is closed, if SG2 is applied, it is open, and if S03 is applied, it is closed. , SG4 will open it. During the subsequent 1/2 Tw, the microshutter on the write selection electrode 34 maintains its state no matter what is added to SGI to SG4.

From the above, when sci is applied, the micro shutter 39 enters the closing operation at the beginning of Tw.

After 1/2 Tw has elapsed, the micro shutter 40 starts its closing operation. At the end of T', the micro shutter 39 completes the closing operation, and the micro shank 40 then closes 1/2
This state is maintained for Tw, and the closing operation is completed at the end of 1/2 Tw. Further, when S02 is applied, the microshank 39 is closed, and after 1/ZTw, the microshutter 40 is opened. Similarly, when S03 is applied, 39
is open.

40 is closed, and when SG4 is applied, both 39 and 40 become open.

As already understood, the single drive system is a two-time division drive, but the shank operation does not complete the operation during 1/2T□, but operates over the 'ru+ period, so the LED The situation is different from time-division driving.

With such a driving method, f s =300 Kll,z
, f L-6KHz + temperature of 47° C. is shown in FIG. 9. In Fig. 9, (a) gives an open signal (Fig. 7 (a)) on 63 upper w from T1 to T63, and gives an open signal (Fig. 7 (d)) at T64. , is the operating characteristic when this is repeated. (b) is (a
), on the contrary, an open signal is applied for 63 Tw from T1 to T63, and a close signal is applied at T64, and this is repeated. In addition, (C1 is the operating characteristic when the open signal is continuously applied, and (d) is the operating characteristic when the closed signal is continuously applied. In Fig. 9, the period 764 of (al) The characteristics of (C) are equivalent to those of (C).

In addition, (the characteristics of period 764 in BL are almost the same as those in (d). This indicates that the micro shutter is not subject to the hysteresis effect (it certainly operates within Tuu. In other words, , indicates that black and white dots can be printed completely.

In FIG. 10, the same liquid crystal microshutter as above is driven by the same drive signal.

Unlike the case shown in Figure 9, the temperature of the liquid crystal is 43 degrees Celsius, which is about 4 degrees Celsius.
°low.

Here (dl), the operation of opening the microshutter by fL at each end of Tw is not completed completely. This is because the viscosity of the liquid crystal increases due to the low temperature, and the operation becomes slow. This is because (8) shows that T6
At the beginning of step 4, microchamber 7 is not fully opened. If the temperature further decreases, the micro shutter will not open at all at 764. In other words, a white dot after a series of black dots cannot be printed.

On the other hand, FIG. 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 micro shutter, but when closing the micro shutter, each Tw
In the first half of Tw, the micro-shutter tries to close, but in the second half of Tw, this operation cannot be maintained and the micro-shutter opens. This is because as the temperature rises, the viscosity of the liquid crystal decreases, and along with this, fc increases, and the influence of f+fL in the waveform of (a) in Figure 7 becomes stronger, causing the microshutter to close due to no voltage. This is because the balance with the force that is trying to move has been disrupted. 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 76 in (a) of Figures 9 to 11.
4, and B is the integrated value of the amount of transmitted light in FIG.
This is the integrated value of the amount of transmitted light at T64 in FIG. 11(b). Similarly, C is at (0) in Figures 9 to 11, and D is at (d
) is supported.

As is clear from FIG. 12, the characteristic of A, that is, the opening response after continuous closing, deteriorates below 43°C, 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 micro-shutter is on the verge of opening even though a close signal is being applied.

In other words, this increases the amount of light leaking when the micro shutter is off, leading to a decrease in black and white contrast.

As described above, since the characteristics of the liquid crystal microshutter change slightly depending on the temperature, accurate temperature control has conventionally been necessary.

[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 optical 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 dot-aligned liquid crystal shutter, and an imaging optical system. The liquid crystal shutter is configured to be driven by the application of alternating current and direct current at a frequency higher than the crossing frequency at which the dielectric anisotropy of the liquid crystal composition becomes zero, and the direct current is applied at predetermined intervals. It is characterized by reversing the polarity.

[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 shank of its optical recording section 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. FIG. 13 is a signal waveform diagram applied to the write selection electrode and the recording signal electrode shown in FIG.
3 and (b) are signal waveforms applied to the write selection electrodes 34, respectively. Further, (C) to (f) are four types of signal waveforms applied to the recording signal electrode. From now on, the signal waveform of (a) is COMIA.

(bl is C0M2A, (e) is 5CIA, (di is S
G2A.

+a) is called 5G3A, and (f) is called 5G4A. Also the first
Figures 4 (a) to (d) are COMIA and 5GIA- in the upper air.
Seven types of micro shutter drive waveforms are shown, each generated by the 3G4A signal. That is, FIG. 13 corresponds to FIG. 6 showing the conventional example, and FIG. 14 corresponds to FIG. 7.

As shown in FIG. 13, the drive waveforms of the present invention are Twf and Tws.
2T and JJ are taken as one cycle. Another 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 between T and J, as typified by FIG. 13(f).

However, this should not be fixed at ground or power supply level for a long period of time, but only at regular intervals.

For example, this is repeated for each ITw.

In other words, in the long term, it is considered as exchange. This is because the liquid crystal for dual-frequency driving uses fL to align the liquid crystal in the direction of the electric field, but if fL is 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. 13(a) (COMIA>, T.

Comparing f and TwS, TuIs is exactly TuJf with its phase reversed. Other signals (b) ~ (
f) also has a relationship in which the construction phase is reversed between Twf and Tws.

Figure 14 shows COMIA and 5GIA to 5G4A as shown above.
These are four types of microshafter drive waveforms created by the signals. Here, the figure shows a pair of Twf and Tuls, which is always (a) after TuJfO.
It is not that the 'ru+s waveform in a) is applied to the liquid crystal, but in a certain writing period Tw, the Twf in (a) is applied to the liquid crystal.
If the waveform at 'l'ws of (a) to Td) is applied at the next Tw, any one of the waveforms at 'l'ws of (a) to Td) will be applied.
is applied. However, the waveform at Twf is not applied continuously.

Here, a comparison will be made between FIG. 7 showing the conventional drive waveform and FIG. 14 showing the drive waveform according to the present invention.

In both figures, the periods during which fH in FIG. 7 (al and (b) and FIG. 14 Ta) and (b), which are closed signals, are applied are equal.

The difference is the period during which fH+fL is applied and the period during which f is applied at the end of TuJ. Figures 7 and 14
As can be seen by comparing the figures, 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, if fH is applied for a long time, it is harmful to high-speed shutter operation due to the hysteresis effect of the liquid crystal.

In order to eliminate this, conventionally an fL times signal was inserted at the end of TuJ.

The driving method according to the present invention can be said to be a driving method that maximizes the effect of eliminating history effects. Moreover, since the period of fH applied when closing the shutter does not change, the closing operation of the shutter does not deteriorate.

FIG. 15 shows the temperature characteristics when the liquid crystal shank is driven in this manner. In the figure, A is the open response after continuous closing, and B
is the response of closing after continuous opening, C is the response of continuous quantity, and D is the response of continuous quantity, which shows the characteristic change with respect to temperature. This corresponds to FIG. 12, which shows the conventional temperature characteristics. When compared with FIG. 12 showing the conventional example, it can be seen that although the open and close levels are the same, the temperature range is expanded, especially 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, consider the 2TuI period of TuIf and Tws as one large cycle, and when opening the shutter, fix the waveform applied to the signal electrode to the ground or power supply level, and create a waveform that is alternating current in the long term. Therefore, good driving can be performed without damaging the liquid crystal for dual frequency driving.

〔Effect of the invention〕

As explained in detail above, the recording device of the present invention can improve the temperature characteristics of the liquid crystal light shutter without reducing the contrast of the liquid crystal light shutter in the optical recording section, obtain good response characteristics of the liquid crystal light shutter, and produce high-quality recorded images. is obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a recording apparatus, FIG. 2 is a block diagram of a liquid crystal light shutter section, and FIG. 3 is a block diagram of a liquid crystal panel. FIG. 4 is a cross-sectional configuration diagram of a liquid crystal optical shutter, and FIG. 5 is a configuration diagram of a microshank in two-time division driving. Figure 6 is a signal waveform diagram applied to the write selection electrode and recording signal electrode, Figure 7 is a drive waveform diagram applied to the liquid crystal, and Figure 8 is a diagram of the drive waveform applied to the liquid crystal.
The figure shows the light transmission characteristics of the liquid crystal optical shutter. Figures 9 to 11 each show a four-wheel drive system using the conventional drive system.
A light transmission characteristic diagram showing the behavior of the micro shutter at 7°C, 43°C, and 55°C. Figure 12 is a conventional temperature characteristic diagram. Figure 13 is a signal waveform diagram applied to each electrode in the present invention. Figure 14 is a diagram of the signal waveform applied to each electrode in the present invention. FIG. 15, which is a diagram of driving waveforms applied to the liquid crystal, is a diagram of temperature characteristics 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...Imaging lens,
19...LCD panel. 22...Signal electrode, 23...Common electrode. 24.39.40...Micro shutter. 33.34...Write selection electrode. 35.36.37.38 Recording signal electrode patent applicant Casio Computer Co., Ltd. Same as above Yoshiyuki Osuga, patent attorney for ID Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7° Figure 8 Figure 9 Figure 10 Figure 11 Figure 12

Claims (1)

[Claims] The present invention includes an optical recording section that performs optical writing on a photoconductive recording medium in accordance with an image signal, and the optical recording section includes a light source. In a recording device comprising a dot-aligned liquid crystal shutter and an imaging optical system, the liquid crystal shutter is driven by application of alternating current and direct current at a frequency higher than a crossing frequency at which the dielectric anisotropy of the liquid crystal composition becomes zero. At the same time, the recording apparatus is characterized in that the polarity of the DC application is reversed at predetermined intervals.