JPS59129836A - Driving method of optical modulating device - Google Patents

Abstract

PURPOSE:To reduce cost, and also to raise reliability by applying constant voltages different in phase each other to a common electrode, and applying the voltage the same in phase and amplitude as the voltage applied to a common electrode of an address line, to a signal electrode. CONSTITUTION:As for an array, a common electrode 10 and 11 of two lines are placed on the first substrate, and on the second substrate opposed to said substrate, signal electrodes 12a-13d crossing the common electrode 10 and 11 of two lines are placed. As for such a liquid crystal-optical shutter array, a polarizing plate is placed on the outside of the first substrate and the second substrate, respectively, and it is in a cross Nichol state indicated with the arrows 12 and 13. Voltage C and C' are applied to the common electrode 10 and 11, respectively. In this case, the voltage C is 90 deg. out-of-phase against the voltage C'. On the other hand, as for the signal electrodes 12b and 12c, on or off of the shutter is determined by keeping them at the voltage the same in phase as the voltage C applied to the common electrode 10 to be addressed, or at some constant voltage level. In this way, the cost is reduced, and also the reliability is elevated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for driving an optical modulation device such as a printer head that can provide optical information to a photoreceptor used in an electrophotographic printer, for example. Regarding the law.

Conventionally, a laser beam printer (LB) is used to apply an electrical image signal in the form of light to an electrophotographic photoreceptor and visualize it.
P) is well known. In addition, in recent years, the optical modulation function of liquid crystals has been utilized to arrange these modulation sections in an array, illuminate them, and use the transmitted light to provide an optical image signal to the photoreceptor. , 1. The device as a printer can be made smaller, 2.
There are no mechanically driven parts like the polygon scanner used in LBP, so there is no noise, and there is less requirement for strict mechanical accuracy. Having such advantages naturally creates the possibility of improving the reliability, reducing the weight, and reducing the cost of the printer itself, but in reality, there are various obstacles. This point will be explained below using an example. FIG. 1 shows an example of a liquid crystal Shack array configuration that will be most easily understood.

As shown in FIG. 1, a shutter opening l is provided, and other hatched areas are usually masked to prevent leakage of light. The liquid crystal is sealed between signal electrodes 3 (3a, 3b, 3c, 3d -------) provided on the inner wall surface of the substrate 2 and a common electrode 4 arranged opposite to the signal electrodes 3. There is. The common electrode 4 is formed on a substrate made of a transparent plate such as glass or plastic, and the substrate 1 on which the signal electrode 3 is provided may similarly be made of a transparent plate such as a glass or plastic plate. The distance between these substrates is maintained at a constant distance using a sealing spacer such as a polyester film, epoxy adhesive mixed with glass fiber, or frit glass. The signal electrode 3 and the common electrode 4 are made of indium oxide, tin oxide, or 5wt of tin oxide.
% indium oxide), etc., and lead wires 5 and 6 are drawn out, respectively.
It is connected to a shutter array drive circuit (not shown).

FIG. 2 is a sectional view of the liquid crystal-light shutter array shown in the plan view of FIG. 1, and shows an example of the operation of this shutter array.

The opening and closing of this shutter array is performed by applying voltage to the signal electrode 3.
By selecting (3a, 3b, 3c -----), the alignment state of the liquid crystal 9 between the signal electrode 3 and the opposing common electrode 4 is controlled, and the transmitted light is T can be determined.

In FIG. 2, polarizing plates 7 and 8 are arranged in a crossed nicol state, and two substrates are further arranged such that the initial orientation of the liquid crystal 9 is at 45 degrees with respect to the polarization direction of polarizing plates 7 and 8. Orientation treatment is performed by a method such as rubbing treatment so that the material becomes oriented. At this time, the liquid crystal 9 is a liquid crystal with positive galvanic anisotropy (
P-type liquid crystal) is used.

Under such settings, the signal electrodes 3a, 3b, 30--
The voltage to be applied to -- is selected, and the common electrode 4 is normally grounded.

In the figure, a relatively large electric current is applied to the signal electrode 3b.
In this case, for example, the P-type liquid crystal molecules are aligned substantially vertically with respect to the cell surface.

At this time, the irradiated light does not pass through the signal electrode 3b portion.

On the other hand, when zero or relatively small voltage is applied to the signal electrodes 3a and 30, the P-type liquid crystal molecules in these portions change their alignment state, and the irradiated light becomes transmitted light T. In this operating method, a greater contrast can be obtained by using monochromatic light as the irradiation light intensity, but contrast can also be obtained with a white light source.

By repeating the above operations, the shutter array provides image signals to the photoreceptor.

However, such conventional liquid crystal-optical shutters have serious obstacles in realizing cost reduction. That's the first
When arranging the openings in the format shown in the figure, for example, if the pixel density of the formed image is 10eLot/1Iri, and you are trying to design a shutter array with the short side length of A4,
Approximately 2,000 signal electrodes are required, and the number of dry electrodes for driving each electrode is also 200.

For a 50-pin device, 40 driver IOs must be used. This naturally limits the ability to reduce costs.

For this reason, it is being considered to reduce the number of No. 43 electrodes by dividing the common electrode into multiple rows and making them correspond to the signal electrodes and the matrix, thereby allowing each row of the common electrode to open and close the shutter in a time-sharing manner. 75; In the case of a liquid crystal shutter array, there is no one that has sufficient performance, such as light passing through the opening/closing part 1 in the shutter-off state outside the shutter opening/closing tool (75).

It is an object of the present invention to overcome the above-mentioned problems and provide a method for driving a sunshade.

Another object of the present invention is to provide a driving method for opening and closing a shutter.

That is, the present invention provides an optical modulation device having a plurality of common electrodes forming a plurality of rows and a plurality of signal electrodes arranged to face each other across the plurality of rows of common electrodes through a liquid crystal, for each row corresponding to the common electrode. In the time-division driving method, a constant voltage having a different phase from each other is always applied to each row to the common electrode, and a voltage of approximately the same phase and a large voltage applied to the common electrode of the addressed row is applied to the signal electrode. The feature is that it is possible to select either to apply voltages of equal magnitude or to maintain the voltage at a constant level.

The present invention will be explained below with reference to the drawings.

FIG. 3 is a plan view showing a portion of the liquid crystal-optical shutter array of the present invention.

In a specific example of the present invention, a liquid crystal-optical shutter array having a 1/2 time-division drive electrode structure shown in FIG. 3 can be used. In the play shown in Figure 3, there are two
Two rows of common electrodes 10 and 11 (indicated by dotted lines in the figure) are arranged, and two rows of common electrodes 1 are arranged on the second substrate opposite to this.
Signal electrode 12 (12a, 12
b, 12Q, 12d −++) are arranged. These common electrodes 10 and 11 and the signal electrode 12 (12a
, 12b, 12c, 12d -----,) are indicated by diagonal lines. These intersecting portions arranged in a staggered pattern can be referred to as openings of the liquid crystal-optical shutter array, and are therefore hereinafter referred to as openings. Further, it is desirable to apply a light-shielding mask (not shown) to areas other than the opening in order to prevent leakage of light.

In such a liquid crystal-optical shutter array, polarizing plates are arranged on the outer sides of the first substrate and the second substrate, respectively, and are in a crossed nicol state as shown by arrows 12 and 13. The first board and the second board
The inner wall surface of the substrate has a P-type liquid crystal sandwiched between them as indicated by the arrow 14.
They are each subjected to an orientation treatment such as a rubbing treatment so that they are initially aligned in the direction of (approximately 45 degrees to the polarization direction of the polarizing plate).

In order to simplify the following explanation, we will focus on the openings A and A2 corresponding to the common electrode 10 and the openings A1 and Alt corresponding to the common electrode 11, and these openings A1m4
The operations at y''1 and A6 will be explained as examples.

FIG. 4 shows a time chart used in the driving method of the present invention. Time T1. T<, Bamboo is the time during which the corresponding opening on the common electrode 10 performs the operation, and the common electrode 1
All openings corresponding to 1 are inactive. The times 'r, l TG l , etc. are times when the corresponding openings on the common electrode 11 operate, and the corresponding openings on the common electrode 10 stop operating. That is, at time 'rtt'r1+bamboo----, the signal electrode 12
The signals S8 and 82 applied to kl and 12c must not affect the opening A1 and the mowing operation, and the time T
2. At T', , q--- the signals S, and 82 must not influence the operation of the apertures A1 and A2. The present invention has an important meaning in that it overcomes the above points.

First, time 114] T+ r T; p da H-1---
- The operation of each opening will be explained. As shown in the time chart of FIG. 4, voltages 0 and 07 are applied to common electrodes 10 and 11, respectively. At this time, voltage C has a phase of 9d:' with respect to voltage 0'? It is shifted. On the other hand, whether the shutter is turned on or off can be determined by maintaining the signal electrodes 12b and 12c at a voltage that is in phase with the voltage O applied to the addressing common electrode 10, or at a certain voltage level.

An example is given in which only the opening A is in a shutter-on state (a state in which irradiated light is transmitted) at time T1 shown in FIG. However, in this example, a time τ is always provided at the end of the time for addressing one row, in which a signal urging the off state is input. Explaining that at time T, the corresponding openings A1 and Al1 of the common electrode 11 are in a shutter-off state M (a state in which irradiation light is blocked), the operation of the liquid crystal at time A is caused by voltage c' It is determined by the electric field caused by the signal S1. Since C' and Sf are voltage signals with a phase difference of 90' from each other, the liquid crystal layer in the human body does not transmit light when subjected to a strong electric field, as explained in the prior art example. state (off state). On the other hand, AS is determined by C' and 82, but since S2 is kept at a certain voltage level, a relatively strong electric field is applied to the liquid crystal layer at A6 due to the voltage 0', which turns it off. . On the other hand, A is determined by the signal S and the voltage 0, but since S is a constant signal level, it is determined by the voltage O. Since a relatively strong electric field acts on the liquid crystal layer at J) ht, it is in an off state. However, in A1, it is determined by 0 and 81, but S
, is a voltage signal that is in phase with C and has approximately the same magnitude, so a voltage that is the absolute value of IC-811 is not applied to the liquid crystal layer at A1. This may result in a relatively weak electric field. This creates a state where light passes through (on state).

Similarly, the time T for addressing the row formed by the common electrode 10
; is an example in which both A1 and A2 are turned on.J)
, A; and AI2 are in the off state due to a relatively strong electric field determined by S1+82 and C', respectively.0 To summarize, at the time of addressing the row formed by the common pole 10, the signals S, and 32 take Regardless of the state, the perforated opening of the common electrode 11 is always reliably in the OFF state.

Next, the time T1 for addressing the row formed by the common electrode 11
r TS y 'f/1---- will be explained. At time T2, only A1 is on, or at T6, 86
An example is given in which only the switch is turned on. T, ,TS,6-
At +-, the voltage O' has a phase difference of 9CP with respect to a. On the other hand, whether the signal voltages S1 and S2 are in phase with C' or kept at a certain voltage level determines whether the comb-2 lid is on or off, and the liquid crystal layer at the openings A1 and A. In the previous time '+ +'I I H
As explained above, a relatively strong electric field always acts on A, ' and AI in 1, so that the off state is maintained. On the other hand, the time T, , r', , f', ·--m
--, A1' and AI can be turned on or off depending on the signals S1 and 82, as explained above for A and A2 in T, T, and T packets.

Here, T, , T2. The τ provided at the end of each time period of Tτ, T(1st arrival, work 7--m-) is for uniformly turning off all the openings, and this is due to the signals S1 and S, This is done by setting the voltage to a certain level.By inserting this extinction signal, it is possible to reliably block light transmission from the opening which should then be in the OFF state.

Above, in order to easily understand the embodiment of the present invention, the example in which the common electrodes have two rows is given.
It can be divided into 4 rows and driven.

In FIGS. 5, 6, and 7, the number of rows of common electrodes is 3.
An example of the basic shutter array configuration and its time chart in the case of a row (common electrodes 15.: 16 and 17) are shown.

In FIG. 5, all the openings other than the hatched areas are masked. Further, the polarization direction and orientation treatment direction of the polarizing plate are the same as those shown in FIG.

The time chart in Figure 6 shows that Alt'A2 is pressed at time T1.
is on, A1 is on at time T2, and A is on at time T.
An example was given where I is in the on state. In FIG. 6, voltages whose phases are shifted from each other are always applied to the common electrodes a, a', and σ', and here, as an example, the phase difference between them is approximately 120°. In this way, when there are three rows of common electrodes, the phase difference between them is 1200
By making it so, the symmetry of the voltage that actually acts on the liquid crystal is improved.

As can be understood from Figure 6, the signal electrode can be turned on and off only in the addressed row by keeping it in phase with the voltage applied to the common electrode corresponding to the addressed row, or at a constant level. , by keeping the extension in the OFF state, and by providing an erasure time τ as shown in FIG.

Here, the present invention can be further summarized as follows.

In the present invention, the rows other than the addressing tool are kept in the on state regardless of the on or off signal applied to the signal electrode, but at this time, the type of voltage that actually acts on the liquid crystal layer in order to realize the off state is There are two main ways to use this method. One of them is the voltage that is generated between the common electrode and the signal electrode because the voltages that are applied to the signal electrode are out of phase with each other. It is determined by the applied voltage at and the voltage applied to the signal electrode as an on signal at that time (in phase with the voltage applied to the common electrode of the addressing row). The other case is when the voltage applied to the signal electrode increases to a certain level as an off signal, and the voltage applied to the common electrode at this time substantially acts on the liquid crystal layer as it is.

Also, among the rows to be addressed, those that obtain an on state are those in which the voltage applied to the common electrode and the voltage applied to the signal electrode are almost in phase; in this case, the common electrode and the signal electrode
The electric field acting on the liquid crystal layer between the electrodes can be made as small as desired.

Of the rows to be addressed, those that attain an off state are those on which the voltage applied to the common electrode substantially acts.

As described above, the present invention allows light transmission only when the component in the layer thickness direction of the electric field acting on the liquid crystal layer is small, and therefore falls under the category of a liquid crystal driving method that utilizes such differences in electric fields. It can be applied to everything.

In addition, in the representative examples cited so far, pulses were used as the applied voltage for ease of understanding, but
Based on the above-described characteristic points, each applied voltage may be a sine wave or the like, but it is effective to use a pulse from the viewpoint of signal processing. Further, as the frequency of the pulse wave or sine wave, a frequency of about 10 KHz is appropriate due to the properties of liquid crystal. Further, it is preferable that the voltage substantially applied to the liquid crystal layer does not exceed 100 V, assuming a cell thickness of 10 μm, even when the shutter is in the off state.

Similarly to the above statement, add 4 more lines of common electrodes,
It can also be 5 lines. If you peel it off, the common electrode
In the case of rows, the voltage applied to the common electrode is set at a phase of 45% relative to the voltage applied to the previous row.
°You can consider delaying it.

However, in the present invention, when the common electrode is divided into five or more rows, S
The effective range of the voltage that actually acts to bring the shutter into the OFF state may be narrowed by the voltage applied to the common electrode in the non-addressed rows and the voltage applied to the signal electrode as an ON signal, but in the 4th row Since the following divisions ψ are driven with sufficiently high precision, the present invention is a particularly effective driving method when the row division is 082 lines, 3 lines, or 4 lines.

A time-division driving method like the one in this method essentially records one line of pixels by dividing them into multiple lines, and in order to align the pixels of one line to be recorded, it is necessary to line up the pixels as in the conventional time-division method. The signal can be modified using memory or the like. Further, FIG. 8 shows a schematic configuration for applying an optical signal to a photoreceptor using a liquid crystal shutter array.

However, the charger etc. are omitted. Reference numeral 18 is a liquid crystal 4 array, 19 is a photosensitive drum, 2 light sources (fluorescent lights, etc.), zl is a SELFOC lens array, and 22 is a condenser cover. As mentioned above, when a liquid crystal-light screen array is used, the printer can be made more compact than a conventional LBP.

In the method of the present invention, other modes such as twisted nematic liquid crystal mode, guest-host mode, cholesteric-nematic phase transition mode, etc. can be used in addition to the above-mentioned mode using P-type liquid crystal. A nematic liquid crystal with a dielectric anisotropy of , a nematic liquid crystal with a negative dielectric anisotropy, a cholesteric liquid crystal, a smectic liquid crystal, a chiral nematic liquid crystal, etc. can be used.

As described above, according to the present invention, it is possible to reliably prevent light leakage from the aperture in the shutter-off state, and the number of required driver ICs can be significantly reduced. , effective for cost reduction. Furthermore, since the wiring density of the signal electrodes is reduced, it also has the effect of eliminating the difficulty in manufacturing.

Furthermore, since the present invention determines the direction and intensity by selecting only the signal voltage applied to the signal electrode, the present invention can be used in the drive circuit to achieve high-performance optical modulation that eliminates disadvantages such as synchronization. A device is obtained.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a conventional liquid crystal-optical shutter array, and FIG. 2 is a sectional view thereof. FIG. 3 is a plan view showing the electrode structure of the liquid crystal-optical shutter array used in the Motomiya invention, and FIG. 4 is an explanatory diagram of the time chart related to its drive. FIG. 5 is a plan view used in the present invention, and FIG. 6 is an explanatory diagram of a time chart used for driving the same. FIG. 7 is an explanatory diagram of another time chart used in the driving method of the present invention. FIG. 8 is a schematic perspective view of a printer head of a liquid crystal-optical shutter array used in the present invention. 4110, 11. , 151'16 , 17, ----
One common electrode 3 (3a+3bt3Qt3d -----
--:) , 12 (-12a, 12b, 12c, 1
2d character -,>-1 signal electrode, 18--liquid crystal-light shutter array, 19--1 photosensitive drum, 20-111 light source, 2
L=-m-self-cleaning lens array, 22 ----
Light condensing cover. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] Driving in a time-division manner for each row corresponding to the common electrode of an optical modulation device having a plurality of common electrodes forming a plurality of rows and a plurality of signal electrodes arranged to face each other across the plurality of rows of common electrodes via a liquid crystal. In the driving method of the optical modulator, a constant voltage having a phase different from each other is always applied to the common electrode in each row. 1. A method for driving an optical modulator, comprising selecting either to apply a voltage equal to L+/1 or to maintain the voltage at a constant level.