JPS6040611B2 - lcd light bulb - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to driving means for driving a liquid crystal light valve.

[Prior art]

Recently, the prices of CPUs, memory, etc. have been decreasing due to advances in semiconductor technology, and the number of people who use microcomputers, office computers, and people who come into contact with computer printouts has expanded from the traditional EDPS specialists to a wide range of people. It is expanding to become a general phenomenon.

In other words, output processing at the same level as normal documents,
In other words, there is a growing desire for output using kanji and kana characters. A typical example would be the Japanese word processor. However, as mentioned above, such a system is a circuit.

Memory is becoming cheaper and cheaper, and it is expected that it will continue to be available in the future, but printers, which are the output terminals, require a resolution of about 32 x 32 dots if they are to be used for characters such as kanji. Inevitably, high resolution,
Moreover, unless the printing speed is high enough to cope with the decrease in printing speed due to higher resolution, the performance is insufficient, which inevitably leads to an increase in costs. For example, currently there are only optical printers that use lasers, OFTs, and multi-stylus electrostatic printers that can meet this requirement, but both are extremely expensive and are the biggest factor driving up system costs. .

Therefore, this is a factor that greatly hinders the spread of the various systems described above in the market (despite the market needs). The above circumstances apply to high-speed facsimile,
Basically, the same thing can be said about CRT hard copiers, various terminals, etc.

An overview of the configuration of the secondary liquid crystal light valve type printing device and problems will be described below.

An overview is shown in Figures 1 and 2.

The light source 1 is always on and always illuminates the liquid crystal light valve 2.

The liquid crystal light valve 2 has a plurality of minute shutters 8, which are optically opened and closed independently by a liquid crystal drive circuit 9, and allow or block light from the light source 1 to pass therethrough. This part will be referred to as an optical signal generating section 10. The optical signal obtained in this way reaches the photosensitive section 3, and the photosensitive section 3 made of a photosensitive material is connected to the charging station 6.
Because it is pre-charged, the charged charge disappears at the part where the optical signal reaches. Therefore, an electrostatic port image is formed in response to a write signal from the outside. The electrostatic image formed in this way is developed with colored toner in the developing section 4, and then transferred to a recording material, such as paper, in the transfer section 6.
The image is transferred and fixed by heat or the like in the fixing section 7, thereby completing a completely fixed printed image.

As mentioned above, this method does not require the precision high-speed optical scanning system of a laser printer, for example, so it can be expected to have various benefits, such as simpler structure and lower cost. The conventional idea had a fatal problem, which made it difficult to put it into practical use.

The problem was that the writing speed was decidedly slow. The performance of the printing unit that can be applied to the various systems described above requires a printing speed of about 10 A4 size sheets per minute and a resolution of about 10 dots per minute. In other words, this means that the printing speed is about 500 lines per second, that is, the time required to write one line is less than 2 seconds.

However, if a TN (twisted nematic) type liquid crystal is used and a normal 3-alternating voltage drive is performed as in the conventional idea, an opening time of 2 seconds cannot be achieved.
FIG. 3 is a diagram showing the frequency characteristics of dielectric anisotropy of a liquid crystal material.

At frequencies lower than the crossover frequency nc, the dielectric anisotropy is positive and at higher frequencies it is negative 4. The dielectric anisotropy for M and N is set as △GoL and △GoH, respectively. △Your L＞0
And △doH<0. When a nematic liquid crystal with such characteristics is used as a TN type device, when a signal of nah is applied, the liquid crystal molecules are oriented in the direction of the electric field, and when a signal of nah is applied, they are perpendicular to the direction of the electric field. . If polarizing plates are placed perpendicularly on both sides of a liquid crystal layer with twisted nematic orientation, light will be blocked when Me is applied, and light will be transmitted when Me is applied. FIGS. 4a and 4b show glass substrates constituting a liquid crystal light valve. 11 is a glass substrate 1 provided with a common electrode, and 12 is a glass substrate 2 provided with independent signal electrodes.

13 and 14 are common electrodes, 13 is a metal electrode made of chrome gold or the like, and 14 is a transparent electrode made of indium oxide film or the like.

The light from the light source 1 described above is transmitted only through this transparent electrode. The minute shutter 8 mentioned above corresponds to this.
15 and 16 are signal electrodes, and signals for opening and closing the minute shutters are applied to these electrodes, respectively.

16 is a transparent electrode, and 15 is a metal electrode.

The signal electrodes 15 and 16 and the transparent electrode 14 are 4 in this figure.
Although it is shown as a set, the actual number is about 200.

13 and 15 may have a transparent conductive film above or below the metal electrode.

A liquid crystal light valve is constructed by placing glass substrates 11 and 12 facing each other, sandwiching a liquid crystal layer therebetween, and placing the glass substrates between orthogonal polarizing plates.

Next, FIG. 5 shows the timetable for opening and closing the minute shutter. The key is time. 0 level is a state where the shutter is closed, and 1 level is a state where the shutter is open.

A is a case where the shutter is opened continuously, and B is a case where the shutter is opened once and closed once. Even when opening continuously, as in example A, after opening, the process of closing once and opening again is repeated. If this one cycle time is TI, then the writing time of one dot corresponds to this time.

T2 is a signal that necessarily closes T3, and T2 either adds an open signal (T2 is an open signal in the case of A) or a close signal (T2 is a close signal in the case of B). Here, the opening signal is a signal with a frequency of nah, and the closing signal is a signal with a frequency of nah. The reason why the ner signal is always applied during one write cycle is because of two implications. One is that the dots that result from writing, despite the continuous movement of the photoreceptor,
In order to form the liquid crystal into almost the same shape, and more importantly, by taking the time to always apply a low frequency signal during one write cycle, we can reduce the repulsion effect (specific to liquid crystal materials). This is because it is possible to completely eliminate the (time accumulation effect) and to form dots with good reproducibility.

For example, as shown in FIG. 13, when the signal rh is opened three times in a row and the signal rh is applied to 0 for all of the openings as shown in a, then when it is about to close as shown in b, the application of the embodiment of the present invention The falling speed becomes several times slower than the obtained falling speed. Therefore, the next time a write signal is input, the brim will no longer open as it accumulates more and more. This is just an example, but ordinary TN liquid crystals and dual-frequency drive liquid crystals utilize the temporal accumulation effect to
In contrast to matrix driving, time accumulation effects are detrimental to the purpose of the present invention and must be eliminated as much as possible.

From this point of view, it is important to apply a low-frequency signal during one write cycle to always align the potential level inside the liquid crystal to a constant level, and then drive the liquid crystal so that the next write cycle can be started using a reproducible optical signal. It can be seen that it plays an important role in the development. In other words, the present invention provides a drive method based on a completely different principle in order to meet the requirements for a display, which are completely different from those for a display, even though it is called a dual-frequency drive.

Therefore, FIG. 6 shows applied signals corresponding to the opening and closing of FIGS. 5A and 5B. Always apply a ner signal to TI, and
2, apply the na h signal when opening, and apply the na signal when closing. These signals have voltages of V and V as shown in the figure. By applying these signals to each signal electrode 15 shown in FIG. 4 and setting the common electrode to OV, each shutter opens and closes. The shutter characteristics using this signal are shown in FIG. Signal C has a waveform that is a combination of A and B. This means that na is IKHz and nah is 100KH.
b. Results obtained by applying 30 V' to V at a temperature of 40°C. In this example, the write time TI could be made as fast as 2 seconds. However, in this conventional technology, there is a problem in that it is difficult to line up and wire 200 circuits that can output a signal with a signal voltage y of 30V and a peak-to-peak voltage of 60V. Ta. [Purpose] The present invention overcomes the above-mentioned problems by providing n-digit common electrodes and m signal electrodes, and selecting one of 2n kinds of prepared signals prepared in advance to generate a signal. The present invention provides a liquid crystal light valve in which the number of drive circuits and the number of wiring lines can be halved by applying common electrode signals having mutually different phases to the electrodes.

[Example] Figures 8a and 8b show an example of a glass substrate constituting a liquid crystal light valve used in the present invention.

This corresponds to FIG. The difference from the example shown in FIG. 4 is that the 11 glass substrates 1 have two common electrodes 1 and 2 shown at 17 and 18. 14 is a transparent electrode portion.

In b', 15 and 16 are signal electrodes, and 15 is a transparent electrode. In the example of Figure 4,
The number of signal electrodes was 2000, but in the present invention, only half, 1000, is sufficient. FIG. 9 shows the positional relationship between the common electrode and the signal electrode. The transparent portion 15 of the signal electrode faces the two transparent electrodes 14 of the common electrode. This overlapping portion of the transparent electrodes becomes a minute shutter. There are two minute shutters for each signal electrode,
It will be 2000 pieces. This is the same number as in the example of FIG. Next, the signal applied to this electrode will be explained. FIG. 10 is a schematic diagram of a minute shutter for clarity of explanation.

R1 and R2 are common electrodes 1 and 2. CI to C
4 is a signal electrode. d, to d3 are minute shutters. Diagonal line minute shutters d3, 4, d5 and d
8 is a closed shutter and other d,,d2,d
6 and d7 are open shutters. The driving method of the present invention uses half the number of signal electrodes as shown in FIG. 10, and uses half the driving voltage, and the response characteristics of each minute shutter are almost the same as those shown in FIG. 7. According to FIG. 10, R1, R2 and C
Each drive waveform applied to I, C2, C3, and C4 is
Shown in Figures 1a and b.

d and 11c shown in FIG. 11c are composite drive waveforms actually applied to the minute shutter section.

Incidentally, it is obvious that d7 and d8 have almost the same waveforms as d5. The waveforms R-1 and R-2 applied to the common electrodes 1 and 2 include a high-frequency signal 〆b and a low-frequency signal ner, and the 1/4 period phase is at the 〆h portion of R-1 and R2. It's off.

TI is the cycle time, T3 is applied with the nah signal, and T2 is applied with the nah signal. On the other hand, CI to C4 are signal waveforms applied to each signal electrode, and at timing T3, a negative phase opposite to that of R1 and R2 is applied. At timing T2, waveforms corresponding to both being open (that is, an example of CI), both being closed (C2), and either being open (C3, C4) are applied. In order to open both, CI applies a high frequency wave twice the frequency of Nah applied to the common electrode at timing T2.

Then, the minute shutters d, d2 have a composite waveform as shown in FIG. 11, and both shutters open without variation. Next, in order to close both, C2 applies Me (this frequency may be different from the frequency of Me applied to the common electrode) at the timing of T2. The resulting composite waveform is d3
, d4. In this case it remains completely closed. The case where either one opens is described below, C3, C4
Since they are basically the same, only C3 will be described.

Opening/closing to which the combined waveform of Ri and C3 is applied, R2 and C
C3 is set so that the window to which the composite waveform of C3 is applied is open. Therefore, in the case of T2, the applied waveform is biased at T2, and a modified high frequency is applied at d6. In the case of C4, the only difference is that it has the same phase as R2 at the timing of T2. Next, examples will be described.

First, the liquid crystal drive circuit shown in FIG. 12 will be explained.

The signals AI, A2...A2000 for one line are input to the encoder 50 two by two.
The signal is encoded by a circuit as shown in FIG. 12B, and output as shown in FIG. 12C.

In other words, depending on the state of knowledge and An+1, CE
There is a one-to-one correspondence between n. Therefore, depending on the power of this world, the waveform generator 51 that both open, the signal waveform generator 52 that both closes, the waveform generator 53 that only An opens, and the waveform generator 53 that opens only An.
Select only one of the waveform generators 54 that opens only n+1 (close one of the switches 55 and open the buffer 58).
to communicate. This buffer 58 also includes a function of leveling up the voltage necessary for driving, and its output is input to the liquid crystal panel 59. Of course, the outputs from the two common electrode drive generators 56 and 57 are also input to the liquid crystal panel 59.

A light bulb connected to such a drive circuit is heated to 40°C.
The drive voltage VI is set to 15V, and the voltage is set to IKHz.
, nah was set to 100 KHz, and TI was set to 2 seconds. The opening of the minute shutter is a square with 40 peaks. A halogen lamp having a luminance of approximately 100 Cd/ was used as a light source, and zinc oxide sensitized with rose bengal was used as a photoreceptor. After writing, toner development,
After transfer and fixing, approximately 80 dots were formed in accordance with the print signal, and uniform dots were obtained with almost no dot variations due to differences in signals observed. [Effects] As described above, the present invention provides 2n types of signal waveform generators, selection means for selecting one of the output signals of the signal waveform generator based on the input data signal, and the selection means. m data signal applying means for applying a selection signal from 1 to each of the signal electrodes, and n common electrode signal applying means for applying common electrode signals having mutually different phases to each of the n rows of common electrodes. Therefore, it is possible to provide a liquid crystal light valve that can be driven substantially the same as the conventional one without reducing the voltage applied to the liquid crystal even with half the number of drive circuits and wiring compared to the conventional one.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a conventional printing apparatus. FIG. 2 is a diagram showing a liquid crystal light valve. FIG. 3 is a diagram showing the frequency characteristics of dielectric anisotropy of the liquid crystal used in the present invention. FIGS. 4a and 4b are diagrams showing a glass substrate constituting a liquid crystal light valve. FIG. 5 is a diagram showing a timetable for opening and closing the liquid crystal light valve. Figures 6 and 7
The figure shows a general two-frequency switching signal and optical transmission response. Figure 8a and b are used in the present invention,
FIG. 2 is a diagram showing a glass substrate constituting a liquid crystal light valve. FIG. 9 is a diagram showing the electrode arrangement of the present invention. FIG. 10 is a schematic diagram of the turtle pole configuration of the present invention. Figure 11a
, b, and c are diagrams showing drive signals for the liquid crystal light valve used in the present invention. FIGS. 12a, b, and c show an example of the liquid crystal drive circuit described in the embodiment and its logic table.
2 is a liquid crystal light valve, 9 is a liquid crystal drive circuit, 17, 18
13 is a common electrode, 15 is a signal electrode, and FIGS. 13a and 13b show an example of a drive according to the present invention and an optical response waveform in that case. 2 Figures 11 and 12b are attached to Figures 11a, b,
c and as shown in FIG. 12b. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 12 Figure 10, Figure 1 Figure 12 Figure 11 Figure 12 Figure 13

Claims (1)

[Claims] 1 A liquid crystal is sealed in a transparent integrated substrate, n rows of common electrodes are formed on one side of the substrate, m signal electrodes are formed on the other side, and each signal electrode is arranged to cross the common electrode. In this way, in a liquid crystal light valve having n×m microshutter windows, there are 2^n types of signal waveform generators, and one of the output signals of the signal waveform generators is output based on the input data signal. a selection means for selecting, m data signal application means for applying a selection signal from the selection means to each of the signal electrodes, n data signal application means for applying mutually different phase common electrode signals to each of the n rows of common electrodes; A liquid crystal light valve comprising a common electrode signal applying means.