JPS6242126A - Driving circuit for liquid crystal optical shutter - Google Patents

Abstract

PURPOSE:To supply a driving signal which has no phase shift and to drive an optical shutter into an open or closed state securely by providing the 1st driving means which has plural buffers for driving signal electrodes and the 2nd driving means which has a buffer for driving common electrodes, and forming those buffers integrally in one body. CONSTITUTION:Superposed waveforms applied between both electrodes of microshutters 22a-22f, etc., are formed at every period Tw in synchronism with a clock signal. Further, high dielectric strength buffers arranged in LSIs 34a-34m which drive signal electrodes as driving circuits for driving the common electrodes 20a-20c are utilized, so there is no variance in characteristics among the driver circuits and driving signals supplied to the common electrodes 20a-20c coincide with driving signals supplied to signal electrodes in one write period Tw, so that no phase shift is caused. Further, the LSIs have the same characteristics, so the driving signals supplied to the microshutters 22a-22f, etc., have no phase shift.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a drive circuit for a liquid crystal optical shutter that controls opening and closing of a liquid crystal optical shutter.

[Traditional technique]

A liquid crystal optical shutter is an element used when optically writing on a recording medium by controlling the opening and closing of individual microshanks that constitute the liquid crystal optical shutter. In order to control the opening and closing of this liquid crystal light shutter 7 (micro shutter), as shown in FIG. The micro shutter 1 is driven in a matrix by applying a high frequency or low frequency voltage (waveform) to the common electrode 2a connected to the common electrode 2a. Also.

The voltage (
The waveform) must not only be high frequency or low frequency, but also be a large amplitude alternating current, and must be compatible with liquid crystals, which are capacitive in nature (capacitive load). In particular, since the common electrode 2a supplies current to a large number of microshades 1 at once,
Requires a driver circuit with large driving capacity.

Therefore, in the conventional liquid crystal optical shutter drive circuit.

The driver circuit 3 connected to the common electrode is individually assembled using discrete components. For example, one line of common electrode is composed of about 35 elements (resistors, power transistors, etc.), and has an area of 45×1
It has a large shape of 20 mm.

[Problems with conventional technology]

Therefore, in the drive circuit for the liquid crystal light shuffler configured as described above, it is necessary to provide a driver circuit for the common electrode having a large area, and a large space for the driver circuit is required within the device.

Furthermore, an even bigger problem is that when the liquid crystal optical shutter is driven in a matrix as described above, a nine-phase shift becomes a problem. This phase shift is that the phases of the signals supplied to the signal electrode 1a and the common electrode 2a that constitute the micro-shutter 1 are shifted from each other, and when this phase shift occurs, the signals supplied to the signal electrode 1a and the common electrode 2a are shifted from each other. The micro shutter 1 driven by the (superimposed waveform) cannot be completely opened or closed. In addition, when the driver circuit 3 on the common electrode 2a side is composed of discrete components as in the past, variations in components occur due to manufacturing reasons, and the signal electrode 1a (J[lI driver circuit (LSI) 4 The characteristics do not match, and the above-mentioned problem is likely to occur.

[Purpose of the invention]

In view of the above-mentioned conventional drawbacks, the present invention uses a part of the high voltage buffer in the driver circuit on the signal electrode side as the driver circuit on the common electrode side, so that the superimposed waveform with a nine-phase shift is transmitted to the liquid crystal optical shutter (microshaft). ) and to provide a drive circuit for a liquid crystal light shutter that can reliably open and close a liquid crystal light shutter (micro shutter).

[Key points of the invention]

In order to achieve the above object, the present invention includes a liquid crystal substance sealed between two glass plates, a plurality of common electrodes provided on one of the glass plates, and a plurality of common electrodes provided on the other of the glass plates. In a drive circuit for a liquid crystal optical shutter, the drive circuit includes a signal electrode and a light opening/closing means formed at an intersection of the signal electrode and the common electrode, and selectively transmits external light by opening/closing operations of the light opening/closing means. a first driving means that drives the common electrode and has at least a plurality of buffers; a second driving means that drives the common electrode and has a buffer;
The plurality of buffers and the buffer are integrally formed.

[Embodiments of the invention]

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

First, a simple configuration of a recording apparatus in which a driving circuit for a liquid crystal optical shutter according to the present invention is used will be explained.

FIG. 2 is a block diagram of this recording apparatus.

In the figure, the surface of a photosensitive drum (photoconductive recording medium) 5 is uniformly charged in advance by a charging section 5a. The liquid crystal light shutter unit 6 receives recording information and is driven by a signal from a drive circuit 13 that controls timing and the like, performs electro-optical conversion of the information, and performs optical writing on the photosensitive surface of the photosensitive drum 5. The electrostatic latent image formed in this way is developed with toner in the developing section 5b, and is visualized. The developed image is transferred by a transfer device 5c onto a transfer paper 9 fed by a paper feed roll 7 and a standby roll 8. Furthermore, the separation section 10
The toner image is thermally fixed on the transfer paper 9 separated from the photosensitive surface in the fixing section 11, and the paper is sent out of the machine by a paper discharge roller I2. On the other hand, on the second photosensitive surface, after neutralization of toner charges is performed in a static eliminating section 5d, residual toner is cleaned off in a cleaning section 5e, and surface charges on the photosensitive surface are neutralized in an eraser 5f. The process of visualizing an electrostatic latent image and creating a recorded image in this way is a technique known as electrophotography.

As shown in FIG. 3, the liquid crystal light shutter unit 6 includes a light source 16, a liquid crystal light shutter 17. It is composed of an imaging lens 18.

Since this liquid crystal light shutter 17 is driven in three time divisions, three common electrodes 20a, 20b, 20c are provided as shown in FIG.
and signal electrodes 21a arranged alternately from opposite directions,
2 l b, 21 c.

21d etc. Moreover, the common electrodes 20a, 2
Micro shutters 22a, 22b are provided at the intersections of 0b, 20c and the signal electrode 21a, etc.

22C etc. are configured. The micro shutters 22a, 22b, 22c, etc. configured in this way are sequentially driven from the A direction during one writing period Tuu.

FIG. 5 is a sectional view showing more specifically the structure of a part of the liquid crystal light shutter 17 constructed in this way. This figure is a cross-sectional view taken along the line AA' in FIG. 4. As shown in the figure, a liquid crystal optical shutter 17 is provided.

A gap is maintained between the two glass substrates 23 and 24 by a spacer 25, and a liquid crystal mixture 26 for dual-frequency driving is sealed. The signal electrode 21a described above is a transparent electrode 27.
It is constituted by a metal electrode 28, and also the above-mentioned common electrode 2.
0b is composed of a transparent electrode 29 and a metal electrode 30, and a micro shutter 22b is formed in a portion 31 where a part of the metal electrode 28, 30 is removed. Also, polarizing plate 3
2 is provided on the top of the glass plate 24.

・Here, to briefly explain the dual-frequency drive used in this example, the dual-frequency drive rearranges liquid crystal molecules by changing the frequency of the electric field and utilizing inversion caused by dielectric anisotropy. It is.

For example, as shown in Figure 6, at a frequency (hereinafter referred to as fL) lower than the crossover frequency (hereinafter referred to as fc), the dielectric anisotropy Δ
ε becomes positive, indicating positive dielectric anisotropy.

At a frequency higher than fc (hereinafter referred to as fH), the dielectric anisotropy becomes negative, indicating negative dielectric anisotropy. By applying the fL signal, the liquid crystal molecules can travel parallel to the electric field, and by applying the rH signal, the liquid crystal molecules can be aligned perpendicular to the electric field. In this embodiment, the properties of liquid crystal are utilized to drive the micro shanks 22a to 22c, etc., which are mainly composed of the liquid crystal mixture 26, to open and close.

Next, returning to the explanation of the structure, the liquid crystal light shutter unit 6 having the above-mentioned structure and the liquid crystal light shutter drive circuit 13 of the present invention are connected as shown in FIG. Micro shutter 22a constituting shutter section 6
, 22d, etc. are connected to an Xo terminal of an LSI (Large Scale Integrated Circuit) 34a for driving a signal electrode. Similarly, the micro shutters 22b and 22e
The common electrode 20b to which these are connected is also connected to the Xo terminal of the LSI 34b for driving the signal electrode. Further, a common electrode 20 to which the micro shutters 22C, 22f, etc. are connected
c is connected to the Xo terminal of LSI 34m for signal electrode drive.

In this way, the LS connected to the common electrodes 20a to 20c
I34a ~ 34m Xa line terminal, each LSI348
~34m is connected to the input terminal X+ via a buffer described later. Further, a drive signal, which will be described later, is supplied to the input terminals X1 of the LSIs 348 to 34m.

On the other hand, the signal electrode 21a to which the micro shutters 22a to 22c are connected is connected to the Y terminal of the 5I 34a as described above. Similarly, the micro shutters 22d to 22f
The signal electrode 21b connected to is also connected to the Y terminal of the LSI 34a. but.

At this time, the Y terminals of the LSI 34a are individual Y1 to Y.

Since it is composed of terminals, the electrodes 21a and 21-b are connected to the respective Y1 to Yn terminals. In this embodiment, m LSIs (the last LSI is 34m) are provided in which n signal electrodes 21a, 21b, etc. are connected in this way. Input terminal of this LSI348~34m P T I-P T
A is supplied with a drive signal 35, which will be described later, via a pass line 35a.
enters.

FIG. 7+a) is a circuit diagram illustrating the internal circuits of the LSIs 34a to 34m described above. The figure shows (LSI34a~
34m), shift register 36. Latch circuit 37. Delay circuit 38. It is composed of a data selector 39 and a high voltage buffer 40.

Data stored in a RAM (random access memory) in the drive circuit 13 or an external device (computer, etc.) not shown is input to the shift registers 36 of the LSTs 34a to 34m from the D1N terminal. D1N of LSI34a
The data input from the terminal is the same (shift register 36
In order to serially shift the recording data into the shift register 36 in synchronization with the clock signal CK+ input to the GK terminal of the Output.

In this way, when recording data for one line (one common electrode) is input to the shift register 36 of all LSIs 348 to 34m, the shift register 36 and the launch circuit 37
The recorded data in the shift register 3G is transferred from the Q) to Q1 terminals to the latch circuit 3 by a control signal (not shown) input to the
7 are output to the D+"D, , l terminals, respectively.

The recorded data input to the launch circuit 37 is
Data selector 3 is output from Q1 to Q, 1 terminals of latch circuit 37 by clock signal CK2 input to CK terminal of 7.
9 and the delay circuit 38. At this time, the recording data output from the Ql, Ql...C7, 2 terminals of the launch circuit 37 are A I=A of the data selector 39,
C2, Ql, Qyu, 1 of the launch circuit 37
The recording data output from the delay flip-flop (hereinafter simply referred to as F, F) 38a of the delay circuit 38
+.

...Input to D terminal of 38an, C of latch circuit 37
3, C6...The recording data output from the Q1 terminal is F.
, F38b1...38bo are input to the D terminals.

The recording data input to F, F38a + -...38a is based on the primary clock signal CK2.

The recording data in F, F39a+...38a is output to terminals 81 to Bn of the data selector 39.

At this time, the recording data in F, F38b+ . . . 38bn is simultaneously output to the Dil child of F, F38cI . Furthermore, F, F38c+...38c
, , is outputted to the CI-C terminal of the data selector 39 in response to the next clock signal CK2.

In this manner, recording data is sequentially input to the data selector 39 from terminals A1 to An, terminals B1 to Bn, and terminals C1 to Cn in synchronization with the clock signal CK2.

In the data selector 39, according to the recording data to be input,
Data selector 390 selects a micro shutter drive signal input from input terminals PT+ to PTe. For example, at the timing of 3 clock signals CK2, terminals A1
→B+ = Recorded data input to C+ closes the micro shutter 22a.

If the data is to drive the device closed (off, off, off), select the drive signal (waveform) a shown in FIG. 8 that is input to the input terminal PT+. In addition, sequential terminals A + -B
+ = Recorded data input to CI is micro shutter 2
2a open, close, close (on, off.

If the data is to drive the input terminal P
Select the drive signal (waveform) b shown in FIG. 8 to be input to T2. Similarly, the microshaft 22a is closed, opened, closed (off, on, off), open, open, closed (on, on, off) 2 closed, open, open (off, on).

When driving (on, open, open), open, open, open (on, on, on), input terminals PT3. P.T.A.

P T 5 , P T 6 , P T t ,
Drive signal (waveform) input to PTe c,
Select d, e, f, g+h.

Selection of these drive signals a-h is made at the other terminal A2.

82, C2 (not shown), ~A, , Bn, C, . . .

The drive signals a to h selected in this manner are output from the output terminal W r =W of the data selector 39 to the high voltage buffer 40 . At this time, the drive signal output from the output terminal WI to the high voltage buffer 40-1 is output from the terminal A +
= One of the drive signals a to h selected by the recording data input to C+, and is a drive output from the output terminal W2 (not shown) to the high voltage buffer 40-2 (not shown). The signal a-h is one of the drive signals aw h selected by the recording data input to the terminals A2 to C2, and is also a drive signal output from the output terminal Wn to the high voltage buffer 40-n. are terminals A, ~Cn
The drive signal a-, selected by the recording data input to
It is one of -11. The drive signals a-h input to the high voltage buffers 40-1 to 40-n in this way are L
S I 34 a ~34. m output terminals Y1 to Yn
The signal is then output to the signal electrode 21a of the liquid crystal light shutter 17 mentioned above.

On the other hand, the signal inputted from the input terminals of the LSIs 3.la to 34m is one of the drive signals (waveforms) i= shown in FIG. 9 selected by a control circuit (not shown).

In addition, the drive signal (waveform) imk has the same frequency as the above-mentioned fl, I signal, fL times signal, and fM times signal, but is out of phase by 180 degrees. *fL signal shifted by 180°. This drive signal i-k has one write period T,
Although the waveforms in JJ are different, as can be seen from the figure, they are composed of waveforms obtained by shifting the same waveform by 1/3 T w.

The times T and JJ are the same as the time between the output timings of the clock signal CK2 described above.

In this way, one of the drive signals ixk input from the X1 terminals of the LSIs 34a to 34m is sufficiently amplified in the high voltage buffer 40 to drive the common electrode 20a, etc. It is supplied from the terminal to the common electrode 20a and the like.

The circuit configuration of the LSIs 34a to 34m as described above is different from the case where discrete components are used on the common electrodes 20a to 20c side (compared to FIG. 7(bl)).
0-X and input/output terminals X+ and Xo connected to the high voltage buffer 40-x are added.

The operation of the liquid crystal optical shutter drive circuit 13 of the present invention having the above configuration will be explained below using the superimposed waveforms shown in FIGS. 10(a) and 10(b).

As mentioned above, the common electrodes 20a to 20c connected from the Xo terminals of the LSIs 34a to 34m to the common electrodes 20a to 20c shown in FIG.
A drive signal (waveform) as shown in k is output. This drive signal (waveform) is, for example, the first one of the 1w cycle Tw.
In the period /3Tw, the *fH signal of the drive signal i is supplied to the common electrode 20a, the fH times signal of the drive signal j, the continuation of this fH times signal <*rL signal, is supplied to the common electrode 20b, and the common electrode 20c receives the *fH signal of the drive signal i. A signal multiplied by fH of the drive signal is supplied. This period of 1/3 T uu is synchronized with the clock signal CK2 as described above, and at this time, the LSIs 34a to 34m are simultaneously synchronized with the clock signal CK2.
Drive signals a to h outputted from the drive signals a to h are also supplied to the signal electrodes 21a and the like. Therefore, the micro shutters 22a to 22f where the common electrodes 20a to 20c and the signal electrodes 21a, etc. intersect
etc., the above-mentioned drive signal i w h and drive signal a% supplied to the common electrodes 20a to 20C1 signal electrode 21a, etc.
A superimposed waveform of h will be applied between the electrodes of the liquid crystal mixture 26 (FIG. 5).

For example, when a drive signal i is supplied from the common electrode 20a to the micro shutter 22a and a drive signal a is supplied to the signal electrode 21a, the superimposed waveform l is This means that it is applied between both electrodes 20a and 21a of the shutter 22a. Similarly, when a drive signal i is supplied from the common electrode 20a to the micro-shutter 22a and a drive signal i is supplied to the signal electrode 21a, a superimposed waveform P shown in FIG.
w, both electrodes 20a, 21a of the micro shutter 22a
It was added in between. Furthermore.

Similarly, when the micro shutter 22a is supplied with the drive signal i from the common electrode 20a and the drive signal C from the signal electrode 21a, the same II! When the superimposed waveform q shown in J(a) is generated in one writing period Tw, both electrodes 20a of the micro shutter 22a,
It will be added between 21a and 21a.

Furthermore, by supplying the drive signal i and the drive signal d.

The superimposed waveform r is applied to the microshafter 22a.

By supplying the drive signal i and the drive signal d, a single superimposed waveform W (FIG. 10(b)) is applied to the micro shutter 22a,
A superimposed waveform X is applied to the micro shutter 22a by supplying the drive signal i and the drive signal f.

The superimposed waveform y is applied to the micro shutter 22a by supplying the drive signal i and the drive signal g, and the superimposed waveform 2 is applied to the micro shutter 22a by supplying the drive signal i and the drive signal 2. Further, although not shown, if the micro-shutter 22b to which the drive signal j is supplied from the common electrode 20b or the micro-shutter 22c to which the drive signal k is supplied from the common electrode 20c is similarly supplied with the drive signal a-%-h, A superimposed waveform is applied between both electrodes 20b and 21a, 20c and 21a. The application of this superimposed waveform is also applied to the drive signals a-s to other micro shutters 22d to 22f, etc.
The same operation is performed by supplying -h and drive signal i-.

The superimposed waveform 1. applied between both electrodes of the micro shutters 22a to 22f in this way. p, q.

r, w, x, )F,2 is formed every period of Tu, in synchronization with the clock signal CK2. Moreover, in the nine examples,
LSI 34a that drives the signal electrode 21a and the like as a driver circuit for driving the common electrodes 20a to 20C.
Since it utilizes a high-voltage buffer 40 located within ~34m, there is no need to use a driver circuit with a discrete configuration as in the past, and variations in characteristics between driver circuits due to manufacturing processes etc. ), the drive signals i-k supplied to the common electrodes 20a to 20c reliably match the drive signals a-h supplied to the signal electrodes 21a, etc. in the write cycle TIIJ, and there is no phase shift as in the conventional case. will not occur. In addition, LSI33a to 33c, 34
A to 34m are LSIs that drive capacitive loads, and since they have the same characteristics compared to the case where a special driver circuit is provided for the common electrodes 20a to 20c, they are supplied to the micro shutters 22a to 22f, etc. Drive signal a
~h, no phase shift occurs in i-wk.

In this embodiment, the common electrode 20a is connected to the Xo of the LSI 34a.
The common electrode 20b was connected to the Xo wire terminal of LSI 34b, and the common point 20c was connected to the Xo wire terminal of LSI 34m. There is no problem with the liquid crystal light shutter 17, which is used in small numbers, but the micro shutter 22
Since a large current flows through the common electrode in liquid crystal light shields that are used in large numbers such as a to 22d, L other than the L S I mentioned above is used.
The common electrodes 20a to 20e may be connected in parallel to all SIs.

For example, FIG. 1 fb) is an example of this, where the common electrode 20
a is connected to the Xo line terminal of LSI 34a and 34b, and common electrode 20b is connected to LSI 34. The Xo line terminals of a and 34f are connected, and the common electrode 20c is connected to LSI341-1 and LSI341-1.
It is connected to the 34m Xa terminal. In this way, the common electrodes 20a to 20C are connected to the LSIs 34a, 34b, 34e, 34.
f, 34. -+.

By connecting to 34m, the common electrodes 20a to 20c
The driving capacity of is doubled. In addition, in such a connection, the same drive signal is applied to the input terminals X1 of the LSIs 34a and 34b, and the same drive signal is applied to the input terminals X1 of the LSIs 34a and 34b.

By applying the same drive signal to each of the common electrodes 34f and the LSIs 34m-+, 34m, no phase shift occurs between the drive signals supplied to the respective common electrodes 20a to 20c.

In addition, a drive signal with an even larger drive capacity is applied to the common electrode 20.
In order to supply signals to a to 20c, instead of relying on the above-mentioned embodiment, another LSI X for signal electrodes is used.

Of course, the common electrodes 20a to 20c may be connected to the terminals.

〔Effect of the invention〕

As explained in detail above, according to the present invention, a part of the buffer in the LSI connected to the signal electrode is connected to the common electrode, and an LSI for capacitive load is used, thereby controlling the liquid crystal optical shutter. A drive signal (waveform) with no phase shift can be supplied to each of the constituent microshutters, and the liquid crystal light shutter (microshutter) can be reliably driven to an open or closed state.

Furthermore, compared to the case where a common electrode driver circuit is configured with discrete components, the number of components (elements) such as resistors and power transistors can be reduced, and the device can be made smaller.

Furthermore, when the number of microshutters increases, the driving ability of the liquid crystal optical shutter can be increased by connecting the common electrode to an LSI in parallel, depending on the capacity for driving the common electrode.

[Brief explanation of the drawing]

Figures 1(a) and (bl are circuit block diagrams of a driving circuit for a liquid crystal optical shutter of the present invention. Figure 2 is a configuration diagram of a recording device in which a driving circuit for a liquid crystal optical shutter of the present invention is used. is a block diagram of the liquid crystal light shutter section in FIG. 2. FIG. 4 is a block diagram of a part of the liquid crystal light shutter section in FIG. 2. FIG. 5 is a cross-sectional view taken along line AA' in FIG. 4. is a characteristic diagram explaining the dielectric anisotropy of liquid crystal. Figure 7 (al, (bl) is a circuit block diagram of LSI. Figure 8 is a waveform diagram of the drive signal supplied to the signal electrode. Figure 9 is a common electrode. FIG. 10 is a diagram of the superimposed waveforms applied to the micro-shutter. FIG. 11 is a circuit block diagram of a conventional drive circuit for the liquid crystal optical shutter of the present invention. 17... Liquid crystal light shutter. 2, Oa to 20c... Common electrode. 21a to 21d... Signal electrode. 22a to 22f... Micro shutter. 33a to 33c, 34a to 34m... LSI. 36 ...Shift register. 37...Latch circuit. 3rd...Delay circuit. 39...Data selector. 40...High voltage buffer. Patent applicant Casio Computer Co., Ltd. Same as above.
Casio Electronics Co., Ltd. 2a (b) ○~16 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] A liquid crystal substance sealed between two glass plates, a plurality of common electrodes provided on one of the glass plates, a plurality of signal electrodes provided on the other of the glass plates, and the signal electrode and the common electrode. and an optical opening/closing means formed at the intersection of the
A drive circuit for a liquid crystal light shutter that selectively transmits external light by opening and closing operations of the light opening/closing means, comprising a first driving means for driving the signal electrode and having at least a plurality of buffers, and a buffer for driving the common electrode. A driving circuit for a liquid crystal optical shutter, characterized in that the driving circuit has a second driving means, and the plurality of buffers and the buffer are integrally formed.