JPS62299937A - Optical shutter array - Google Patents

Abstract

PURPOSE:To reduce a driving voltage, to suppress the generation of crosstalk and to increase the density of an optical shutter array by thinning the thickness of a thin film consisting of a ferroelectric substance provided with electro-optic effect, and forming a sandwich structure consisting of an electrode, a ferroelectric substance and an electrode. CONSTITUTION:The optical shutter array is provided with a thin film 23 consisting of a ferroelectric substance (PLZT) indicating electro-optic effects, a light transmissible common electrode 22 formed on one side of the thin film 23, plural band-like individual electrodes 24 formed on the other side of the thin film 23, and having large optical reflection factors, and a driving part for selecting any one of the individual electrodes 24 and applying a voltage between the selected electrode 24 and the common electrode 22. The optical shutter array 31 connected to a driving power source 32 is arranged so as to form 45 deg. respectively from a polarizer 33 and an analyzer 34. Since the thickness of the PLZT thin film 23 having the electro-optic effects can be thinned, the driving voltage can be reduced and the generation of crosstalk can be suppressed. In addition, the high density formation of the optical shutter array can be attained by the simple sandwich structure consisting of the common electrode 22, the thin film 23 and the individual electrode 24.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical shutter array using a ferroelectric material exhibiting an electro-optic effect.

Conventional technology Currently, laser printers are used in high-speed ranges as printers that use light beams, and printers with optical heads that use light-emitting diodes or liquid crystals are used in medium- to low-speed ranges. .

However, laser printers have problems such as the optical system being complicated and expensive, and the printer itself becoming large. Printers using liquid crystals cannot be required to print more than 7 to 12 pages per minute because the liquid crystal itself has poor responsiveness. In addition, printers using light emitting diodes are
Although increasing the speed is relatively easy, there are still problems such as variations in the amount of light between the elements and the drive circuit requiring a power source with a capacity of several amperes or more.

Therefore, an optical shutter that utilizes the electro-optic effect (Kerr effect, Pockels effect) of ferroelectric materials is being researched as an optical head that can meet the demands for higher speeds and can be made smaller. A typical ferroelectric material is PLZT (lead lanthanum zirconate titanate, or Pbx-xLax
(ZryTi+-y)1-xOa). The composition with the largest force constant is X=0.09°Y=0.65.

An example of an optical shutter array using the electro-optic effect will be described with reference to FIG. In FIG. 3, short upper electrodes 2, 3, . ... and lower electrodes 3, 3. . . . parallel to each other, equally spaced, and of P L Z T flat plates I."
They are arranged so that they overlap when viewed from one side. This optical shutter array is of a transverse mode type, and the incident light 4 enters in the direction shown by the arrow. Both end faces of the P L Z T flat plate l are optically polished parallel to each other, and although not shown,
A polarizer is placed on the incident surface side, and an analyzer is placed on the exit surface side. The polarization directions of the polarizer and analyzer are orthogonal to each other.

In this optical shutter array, light is transmitted or blocked depending on whether a voltage 5 is applied to the electrodes 2 and 3. That is, when no voltage is applied, the parallel light beam 4 transmitted through the polarizer becomes PLZ without changing the polarization state.
The light passes through the T-plate 1 and is blocked by the analyzer. On the other hand, when a voltage is applied, an electric field is generated in the PLZT flat plate l in a direction perpendicular to the optical path, resulting in birefringence and elliptically polarized light. Therefore, some light is transmitted through the analyzer.

FIG. 4 shows another example of an optical shutter array.

In this example, electrode 1 is placed on piece 1 of P L Z T flat plate l.
A comb-shaped common electrode 13 is provided. When a voltage is applied by switch 6 between electrodes 12.13,
Similarly, light is transmitted through the electro-optic effect.

Problems to be Solved by the Invention In the optical shutter array shown in FIG. 3, 1) L Z
Since the T-plate 1 has a thickness of about several hundred microns, a large drive voltage of several hundred volts is required to apply an electric field that exhibits a sufficient electro-optical effect. In the arrangement of the electrodes shown in FIG. 3, the width of the electrodes is not sufficiently wide compared to the film thickness of the PLZT flat plate 1, so crosstalk with adjacent electrodes also occurs. In a planar arrangement of electrodes, it is difficult to increase the shutter density.

Various attempts have been made to solve these problems. To prevent crosstalk, JP-A-58-130
In Japanese Patent No. 321, grooves are provided between the electrodes 2.2, . . . . Further, in Japanese Patent Laid-Open No. 58-130.323 and Japanese Patent Laid-Open No. 58-88721, the shape and arrangement of electrodes are devised to prevent crosstalk, but the shutter density cannot be increased. Japanese Patent Laid-Open No. 60-97318 proposes an attempt to increase the shutter density by providing a sealing material (Si02) on the electrode in order to prevent creeping discharge in a single-sided electrode arrangement. These suggestions are
However, this did not solve the essential problem of requiring a high driving voltage.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical shutter array that uses an electro-optic effect that has a low driving voltage, does not cause crosstalk, and can be increased in density.

Means for Solving the Problems The optical shutter array according to the present invention comprises a thin film of a ferroelectric material exhibiting an electro-optic effect, a light-transmissive common electrode provided on one side of the thin film, and the other side of the thin film. a plurality of band-shaped individual electrodes provided on the side of the electrode and having a large optical reflectance, and a drive unit that selects the individual electrodes and applies a voltage between the individual electrodes and the common electrode. It is characterized by

Since the thin film of the ferroelectric material having the electro-optic effect can be made thinner, the driving voltage can be reduced and crosstalk does not occur.

Since it has a simple sandwich structure of common electrode-thin film-individual electrodes, high density is possible.

Example Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a schematic cross-sectional view of an embodiment of the invention. A transparent common electrode (22) made of ITO is provided on the entire surface of a heat-resistant smooth quartz substrate 21. Next, a PLZT thin film (23) is grown by RF sputtering.

To explain how to shape this PLZT thin film (23), first, it is heated to 600°C or higher, and then the IQ Torr
Evacuate to a vacuum level above. PLZ as a target
Ar and 02 using T powder with an appropriate amount of pbo added.
Sputtering is performed in a mixed atmosphere for a predetermined period of time. As a result, in this example, the I) L7. has a thickness of approximately 311 m.
A T thin film (23) was obtained. Furthermore, a strip-shaped individual electrode (24) made of a metal with high optical reflectance (for example, platinum) is grown on top of it. The shaded area in FIG. 1 indicates a portion (shaft window) where an electric field is generated when a voltage is applied to the individual electrode (24). Although not shown, the individual electrodes (24) are connected to a power source via switching means.

FIG. 5 shows an elevated version of the previously described embodiment.

This modification differs from the above-described embodiment in that individual electrodes (24) are provided on the substrate (21) side.
The materials and manufacturing methods are exactly the same.

Therefore, from the substrate (21) side, the individual electrodes (24),
A PLZT thin film (23) and a transparent common electrode (22) are arranged in this order.

In this embodiment, since the thickness of the PLZT thin film 23 is very thin, crosstalk does not occur and the driving voltage can be reduced. That is, according to the present invention, the thickness of the PLZT thin film is about 05-50 μm, preferably 05-30 μm.
m, which is considerably thinner than the conventional film.If the film thickness is 50 μm or more, the shutter efficiency (transmittance) will improve, but there is a drawback that the applied voltage must also be increased.Furthermore, P L ZT thin films are typically formed using RF
This is done by sputtering, but the growth rate is generally 0.4~0.
Since the speed is very slow at 6 μm/hr, increasing the thickness is severely restricted in terms of manufacturing (time, cost). On the other hand, if the film thickness is 0.5 μm or less, the shutter efficiency will be poor.

In addition, in the present invention, since the thickness of the P L Z T thin film is small, the electrode width can be made sufficiently longer (for example, about 40 μm width for a 1 μm thick thin film), and the electrode can be made denser (for example, 20 dots/mm). ), there is no crosstalk and high resolution can be obtained.

In this example, PT and ZT, which have the largest Kerr effect, were used as dielectric materials exhibiting an electro-optic effect, but B
aTi0a, S r T i Oa, KTi03, etc. may also be used. Furthermore, if necessary, it is also possible to provide an anti-reflection film on the surface of the P L Z T (23) between the solid electrodes (24) shown in FIG.

FIG. 2 shows a configuration in which the optical shutter array 31 shown in FIGS. 1 and 5 is used in an optical head of an optical printer. An optical shutter array 31 connected to a driving power source 32 is arranged at an angle of 45° to a polarizer 33 and an analyzer 34, respectively. The light source 35 and the collimating mirror 36 are
The arrangement is such that the light generated from the light source 35 is reflected by a collimating mirror 36 and enters the polarizer 33 as a parallel beam. The light incident on the polarizer 33 is linearly polarized, enters the optical shutter array 31, is reflected by the individual electrodes 24, and is guided to the analyzer 34. After being linearly polarized again by the analyzer 34, the light enters the photoreceptor drum 37 through the converging lens 36 and exposes the photoreceptor. When light is directly incident on the optical shutter array 31, the optical path and the electric field in the PLZT become parallel, and no elliptical polarization occurs. The reason why the optical shutter array 31 is arranged obliquely to the direction of light is to generate elliptically polarized light.

Since the light transmitted through the polarizer is reflected by the individual electrodes 24, the length of the optical path in the PLZT thin film 23 is substantially doubled. Retardation is proportional to film thickness d (r=d・△n
), and is small in the case of thin films.

However, by using a reflective optical path, a large terdition can be obtained.

In the optical system arrangement shown in FIG. 2, each element (shutter window) constituting the optical shutter array 31 is opened and closed by a drive circuit 32 (driving voltage: 20 volts) according to image information, and an image is displayed on a photoreceptor 37. Writing (exposure) was performed. Although not shown, image forming processes such as charging, development, and transfer are the same as those used in ordinary electrophotographic printers.

The image thus obtained had very high resolution since there were no cross strokes, and also had sufficient contrast, and was in no way inferior to conventional laser beam printers.

Effects of the Invention In the optical shutter array according to the present invention, since the thickness of the ferroelectric material having an electro-optic effect can be made thin, a large electro-optic effect can be obtained with a small driving voltage. Also,
No cross stroke occurs and the cost is low.

lO- Since the incident light is reflected by the common electrode, the optical path is doubled,
A large electro-optic effect can be obtained.

Since it has a sandwich structure of electrode-ferroelectric material-electrode, it is possible to increase the density. In addition, since the transparent electrode is a common electrode, the electrical resistance component of the transparent electrode can be reduced, and there is no heat generation even when driven at a relatively high frequency (stable shutter characteristics can be obtained, and the individual electrodes are strip-shaped electrodes). This reduces the amount of light reflected from areas other than the shutter area, improving resolution.

FIG. 2 is a schematic cross-sectional view of an electro-optical element.

FIG. 2 is a diagram showing the configuration of an optical printer using the optical shutter array according to the present invention as an optical head.

FIGS. 3 and 4 are diagrams each schematically showing a conventional optical shutter array.

21... Substrate, 22... Common transparent electrode, 23...
PLZT thin film, 24...individual reflective electrode.

Applicant: Minolta Camera Co., Ltd. −11= Kaya I box Figure 5 Figure 3 Figure 2 vinegar Figure 4

Claims (1)

[Claims] (1) A thin film of ferroelectric material exhibiting an electro-optic effect, a light-transmitting common electrode provided on one side of the thin film, and a plurality of common electrodes with high optical reflectance provided on the other side of the thin film. An optical shutter array comprising band-shaped individual electrodes and a drive unit that selects the individual electrodes and applies a voltage between the individual electrodes and a common electrode.