JPS6338689B2 - - Google Patents

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to the structure of a liquid crystal light valve.

[Prior art]

FIG. 1 shows the configuration of the optical writing unit including the liquid crystal light valve. The optical writing unit consists of a light source such as a fluorescent lamp, a liquid crystal light valve, and an imaging lens 115, and the liquid crystal light valve consists of a substrate 114 on which a liquid crystal panel 112 and a liquid crystal driving circuit 113 are mounted. The light emitted from the light source is modulated by a liquid crystal light valve. This optical signal 116 is imaged onto the photosensitive drum 102 by an imaging lens 115. An erect image can be obtained by using a focusing optical fiber array as the imaging lens. FIGS. 2 and 3 show the structure of the liquid crystal panel. The liquid crystal panel includes a liquid crystal composition 125 sealed between a glass substrate 117 having common signal electrodes 119 and 120, a glass substrate 118 having signal electrodes 121 and 122, and a spacer 126, and polarizing plates 123 on both sides of the glass substrate. and 124.
The common signal electrode consists of a transparent electrode 119 and an optically opaque metal electrode 120, and the signal electrodes 121 and 122 are transparent electrodes. Polarizing plates 123 and 12
4 are arranged so that their polarization planes are orthogonal to each other. The light is modulated by the microshutter portion formed by the transparent portion 119 of the common electrode and the signal electrode. As a liquid crystal composition, an optically active substance 4-(2-methyl
A high-speed liquid crystal light valve can be obtained by using a long-period cholesteric liquid crystal obtained by adding 3% by weight of -bulyl)-4'-cyanobiphenyls. The frequency characteristics of the dielectric potential sotropy of this liquid crystal are shown in FIG. The frequency at which the dielectric anisotropy is zero is called the crossover frequency and is expressed by fc. frequency lower than fc
Let f _L be the higher frequency, and let f _H be the higher frequency. The liquid crystal light valve operates by applying signals of frequencies f _L and f _H to each signal electrode. FIG. 5b shows the response of the applied signal and the light transmitted through the liquid crystal light valve a. A signal at time f _H indicated by T2 and a signal at time f _L at T3 are applied. T1 is the write cycle, T
2 is called the opening time, and T3 is called the non-opening time. The liquid crystal light valve opens by applying the _fH signal, and closes by the _fL signal. By the method described above, we were able to obtain a revolutionary high-speed liquid crystal light valve. However, in order to print a high-quality seal, it is necessary to arrange microshutters at a high density of about 10 per 1mm, and in order to print on A4 size paper, the width of 20mm
The number of microshutters is 2000 because they have to be arranged in cm. Therefore, in the method described above, the number of signal electrodes is 2,000, and the number of drive circuits and their mounting terminals are also 2,000 and 2,000, which has the disadvantage of lowering manufacturing yield and increasing cost. However, by using the 1/2 time division dynamic drive method, we were able to reduce the number of signal electrodes by half.

First, the structure of the electrode is shown in FIG. 401 and 40
2 are common signal electrodes, 403 to 405 are signal electrodes, and 410 and 412 are microshutters. Next, various signal waveforms are shown in FIG. The common electrode signal 420 has a repetition period Tf, and Ta and Tb each have a half period. In 1/2 time division, the first half 421 and the second half of one cycle of the common electrode signal 420 are selected, respectively. 420 signal waveform C
1,421 is named C2. The selection signal is composed of a high frequency f _H having a frequency higher than the crossover frequency fc and a low frequency f _L having a lower frequency than fc, and the respective times are Th and Tc. When not selected, only the low frequency f _L is available.

On the other hand, the signal waveform applied to the signal electrode side is a signal 422 for opening the microshutter (FON) and a signal 423 for closing the microshutter (Foff). Both FON and Foff have half the period of the common electrode signal C1 or C2 (Ta
or Tb), the open signal FON is C1 (or C2)
It is composed of a high frequency part that is the same (Th) as the high frequency part of and has an opposite phase, and a low frequency part of C1 (or C2) and a low frequency part that has an opposite phase. Close signal Foff is C1 (or C2)
There are only low frequencies that are in opposite phase to the low frequency f _L of .

Now, the common electrode signal C1 is applied to the common electrode 401 in FIG.
When C2 is applied to each of the microshutters 402 and FON or Foff is applied to the signal electrode according to the data, the voltage waveform applied to the microshutter 410 is
Shown in Figures a, b, c, and d. Further, microshutter light transmission characteristics corresponding to the applied waveforms shown in FIG. 8 are shown in FIGS. 9a, b, c, and d. The horizontal axis of each graph in FIG. 9 is time, which corresponds to Th, Ta, and Tf in FIG. 8. The vertical axis is the transmittance of the microshutter when the light transmittance when two polarizing plates are stacked in parallel is 100%. The result in Figure 9 is fh=
130KHz, f _L = 5KHz, applied voltage ±30V, Tf = 2m
sec, Ta=1 msec, and Th=0.7 msec. The transmission characteristics of 430, 431, 432, 433 are 424, 425, 426, 42, respectively.
7 signal voltages.

Here, in the electrode structure as shown in FIG.
The common electrode side, except for the windows 410 and 411, is made of opaque metal, so even if the signal electrode 40
Even if 3 to 406 are transparent, they are still shielded from light. However, in the case of the multi-digit common electrode structure shown in the figure, since there is a gap between the common electrodes 401 and 402, there is a problem that light leakage occurs regardless of whether or not a voltage is applied to the liquid crystal layer. Ta.

〔the purpose〕

The present invention overcomes the above problems, and
An object of the present invention is to provide a liquid crystal light valve that can prevent light leakage between common electrodes by providing an opaque layer on a portion of the signal electrode.

〔Example〕

FIGS. 10a, b, and c show the signal electrodes, common electrodes, and their combinations in this embodiment. a is the second
In the signal electrode 500 formed on the glass, the electrodes other than the shaded area are transparent electrodes, and the shaded area 501 is a metal film that blocks light. The electrode terminals extend in the vertical direction of the drawing in an interdigital manner, and the pitch P1 between the electrodes on one side is 400 μm, and there are 500 on each side. This improves reliability in high-density mounting of electrode terminals.
Spacing 50 between adjacent electrodes near center line 503
2 is 10 μm. b is a common signal electrode formed on the first glass. Common signal electrodes 504 and 505 are divided with respect to a center line 507, and the interval 508 is 10 μm. The shaded area is a metal electrode, and the microshutter window 506 is a transparent electrode. The microshutters are arranged in a staggered pattern with 2000 pieces at a pitch of P ₂ = 100 μm (1000 pieces at a pitch of 200 μm on each side). When these two pieces of glass are stacked so that the center lines 503 and 507 match
It is a diagram. The shaded area slightly cuts the light, and the light transmitted through the microshutter 511 is modulated. Therefore, light leakage from parts other than the microshutter causes background noise, which is not desirable.
Light leakage from the spacing 508 between the two common signal electrodes is geometrically unavoidable. Therefore, in this embodiment, a portion 501 of the signal electrode is masked with metal to minimize the portion 512 that causes light leakage to the extent that it does not pose a practical problem. Moreover, since the sides of the signal electrodes intersect at right angles to the center line, the distance between the signal electrodes can be maximized with respect to the light leakage portion 512 in a certain area, which is advantageous in panel manufacturing.

Next, by making the signal electrode 500 transparent except for the shaded portion 501, the error margin when combined with the first glass can be increased both in the vertical direction, and the yield is improved.

In addition, the interval l between the two rows of microshutter arrays arranged in a staggered manner (Figure b) is determined by the writing speed and photoconductor movement speed, since the written dots do not shift by half a pitch when driving in 1/2 time division. That is, it is limited by the pitch of the written dots in the moving direction of the photoreceptor. This time, I wrote at a pitch of 100 μm, so l = 250 μm. To do this, not only do we have to delay the data from the microshutter on one side by two lines, but we also have to increase the margin when creating one panel.

Next, FIG. 11 shows the overall profile of the signal electrode. I have included the dimensions of the panel I made this time (units are mm), but if something of this shape were constructed only from transparent electrodes, the impedance of the terminals themselves would be too large to be ignored. Therefore, as shown in the figure, a metal film was formed on a certain portion of the terminal to lower the impedance of the terminal.

〔effect〕

As described above, in the present invention, the common electrode consists of a window made of a transparent conductive film and a conductive region other than the window made of an opaque metal conductive film, and the signal electrode has a region corresponding to the window made of a transparent conductive film, Since the region corresponding to the gap between the plurality of common electrodes is formed of an opaque material, light is almost completely shielded except for the window portion even in the configuration of a multi-digit common electrode, regardless of whether or not a voltage is applied to the liquid crystal. It has the effect of being able to or,
This light shielding can be simply formed using an opaque member on the signal electrode of the transparent conductive film, so that the process can be simplified.

[Brief explanation of the drawing]

FIG. 1 shows an optical write signal generating section. FIGS. 2 and 3 show the structure of a liquid crystal panel. FIG. 4 is a diagram showing the frequency characteristics of dielectric anisotropy of the liquid crystal material used in the present invention. FIG. 5 is a diagram showing the response characteristics of the liquid crystal material used in the present invention and the driving signals at that time. FIG. 6 is a diagram showing the electrode configuration used in the present invention. FIG. 7 shows liquid crystal driving waveforms according to the present invention, 420 and 421 are common electrode signal waveforms, and 422 and 423 are open and closed signal waveforms, respectively. FIG. 8 shows the voltage waveform actually applied to the liquid crystal, and the combination of the common electrode waveform and the signal electrode waveform results in four types of waveforms as shown in the figure. 9th
The figure shows the light transmission characteristics of the microshutter when the four types of signals shown in FIG. 8 are applied. 4
24 becomes 430, 425 becomes 431, 426 becomes 4
32 and 427 correspond to 433, respectively. FIG. 10 is a diagram showing the shape of the electrodes constituting the microshutter. A is a signal electrode, b is a common signal row electrode, and c is a diagram in which the above two are superimposed. FIG. 11 is a schematic diagram of the entire signal electrode.

Claims (1)

[Claims] 1 A liquid crystal is sealed in a pair of transparent substrates, a plurality of rows of common electrodes are formed on one of the substrates, and a plurality of signal electrodes are formed on the other, and each signal electrode is arranged to cross the common electrode. In a liquid crystal light valve having a plurality of micro-shutter windows, the common electrode consists of a window made of a transparent conductive film and a conductive region other than the window made of an opaque metal conductive film, and the signal electrode is arranged on the window. A liquid crystal light valve characterized in that the corresponding regions are formed of a transparent conductive film, and the regions corresponding to at least the gaps between the plurality of common electrodes are formed of an opaque material.