JPH0652357B2 - Light control element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a light control element that controls light transmission by an electric field.

[Prior Art] Conventionally, an element that controls the transmission of light by utilizing the electro-optical effect of a dielectric body is a pair of opposing glass substrates 1 as shown in FIG. Electrodes 2 facing each other on the inner surfaces of each of the electrodes and an alignment treatment film 3 are provided on these electrode surfaces to form a liquid crystal cell in which a liquid crystal 4 is sealed between the electrodes 2, and the polarization axes of the liquid crystal cells are orthogonal to each other. A liquid crystal light shutter arranged between two polarizing plates 5 is known. In addition, (Pb _1-x La _x ) (Zr
_In the case of using a PLZT plate or the like represented by _1-y Ti _y ) O ₃ , as shown in FIG. 4, a voltage is applied in parallel to the plate surface between two polarizing plates 6 whose polarization axes are orthogonal to each other. There is known an optical shutter in which a PLZT plate 8 provided with an electrode 7 for applying a voltage is arranged.

These elements can be applied by applying a voltage between the electrodes
The polarization state of the transmitted light is changed, and the light amount of the transmitted light is changed by the two polarizing plates.

[Problems of conventional technology]

Among the above-mentioned elements, the former uses the liquid crystal 4 which is a fluid at room temperature as a dielectric, so that it is possible to form a light shutter having a relatively large area, but the surface is polished to a flat shape.
It is necessary to dispose the glass substrates 1 facing each other with a very small gap and to inject the liquid crystal 4 into the small gap, which complicates the structure of the device and makes manufacturing difficult. In addition, this liquid crystal device changes the polarization state of transmitted light by causing liquid crystal molecules having a large mass to behave by an electric field and changing the alignment state thereof. Therefore, even when two-frequency drive is used at a voltage of 25 V, the rise time is increased. At most 0.5ms at room temperature
Only a response speed of about ec has been realized. To further increase the response speed, for example, a high drive voltage is used to increase the electric field strength applied to the liquid crystal, or the gap between the two glass substrates 1 is increased. Was required to be smaller.

On the other hand, the latter has a relatively simple structure and a high-speed response can be obtained, but the PLZT plate is a ceramic body and it is difficult to uniformly manufacture a large area. Therefore, it is difficult to form an optical shutter with a large area. However, there is a drawback that the driving voltage is high.

Further, both of them are polarization control type which change the polarization state of the transmitted light, so that two polarizing plates are required and the structure is complicated.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a light control element that can obtain a high-speed response with a low drive voltage and has a simple structure.

[Main points of the invention]

In order to achieve the above-mentioned object, the present invention uses an ion conductive glass that contains optically active ions and exhibits higher ion conductivity at room temperature than an insulating glass, and an electric field is applied to the ion conductive glass. By so doing, the ions are unevenly distributed or diffused, and the amount of transmitted light is controlled by absorption, scattering, or reflection of light due to uneven distribution of the ions.

First Embodiment Hereinafter, a first embodiment using the present invention will be described in detail with reference to FIG. FIG. 1 shows the basic structure of the optical shutter, and 10 in the figure is an ion-conducting glass (hereinafter referred to as “ion-conducting glass”, which contains optically active ions and exhibits higher ion conductivity at room temperature than ordinary insulating glass. Super-ion conductive glass), for example, 75 mol% of silver iodide (AgI) and 25 mol% of anhydrous silver molybdate (Ag ₂ M ₀ O ₄ ).
It is a thin film of glass with the composition of and has a film thickness of 1000Å. A transparent first electrode 11 made of a distribution film of indium, tin or the like is formed on one surface of the super-ion conductive glass 10, and the other surface is opposed to the first electrode 11, The second electrode 12 having a smaller area than the first electrode 11 is formed of a transparent layered film of indium, tin, or the like. Below the drawing of the first electrode 11, a light source 13 having an emission wavelength band matching the light absorption wavelength band due to uneven distribution of silver ions is arranged. 14
Is a drive circuit that supplies a drive signal to the first electrode and the second electrode 12.

Next, the operation and action of the above-mentioned light control element will be described.

The silver ion (Ag ⁺ ) that contributes to the ionic conduction of the superion conductive glass (75AgI · 25Ag ₂ M ₀ O ₄ ) is a halide (Ag ⁺
Like I), it is considered to move through a specific conduction path that electrostatically interacts with iodine ion (I ⁻ ). Since glass has a density of about several percent lower than that of crystal and its structure is disordered, it is easy to form a conduction path in which silver ions (Ag ⁺ ) move around. Therefore, the super ionic conductive glass exhibits high ionic conductivity.

Then, when a signal as shown in FIG. 1 is applied from the drive circuit 14, the silver ions move toward the second electrode 12 due to the electric field between the electrodes, and the superion corresponding to the second electrode 12 is generated. Silver ions are concentrated and unevenly distributed on the conductive glass 10. Due to the uneven distribution of silver ions, the absorption wavelength band of light is 4
Since it is in the vicinity of 40 nm, the light beam from the light source 13 having the emission wavelength band matched with this absorption wavelength band is absorbed or scattered by the uneven distribution of the silver ions, and the light amount passing through the second electrode 12 is remarkably large. The optical shutter is lowered and the optical shutter is turned off.

When the signal from the driving circuit 14 is cut off and the electric field is not applied, the diffusion speed of the silver ions is extremely slow, so that the silver ions moved toward the second electrode 12 due to the above-described signal are unevenly distributed. This state is maintained for a long time, and the state in which the amount of light passing through the first electrode 12 is reduced is stored.

To return from this memorized state to the state without light absorption,
A signal having a polarity opposite to that of the signal shown in FIG. 1 is applied to each of the first electrode 11 and the second electrode 12. Due to this signal of the opposite polarity, the first electrode 11 becomes negative and the second electrode 12 becomes positive, and the silver ions move toward the first electrode 11 having a large area and diffuse over the entire superionic conductive glass 10. . Therefore, the light absorption in the portion of the superionic conductive glass 10 corresponding to the second electrode 12 is reduced, and the light shutter is in the ON state in which the amount of transmitted light is increased.

The response speed of the optical shutter is the time t during which silver ions move from one surface to the other surface in the superionic conductive glass 10.
The film thickness of the super ionic conductive glass 10 is 1000Å, the ionic conductivity of silver ion is 1.1 × 10 ^-2 Ω ^-1 cm ^-1 (room temperature), and the applied voltage is 1 V. Has a mobility μ of 4.0 × 10 ⁻⁶ cm ² · Ω ⁻¹ · c ⁻¹ and a drift velocity u of silver ions u: 4.0 × 10 ⁻¹ cm · sec ⁻¹ , and the migration time t of the silver ions is 25 μsec. Is. Therefore, by applying a pulse voltage with a voltage of 1 V and a pulse width of 25 μsec or more between both electrodes, an optical shutter having a high-speed response characteristic of about 25 μsec can be obtained.

As mentioned above, the optical shutter using super-ion conductive glass is turned off at high speed by the pulse voltage with a narrow pulse width.
However, it has an optical memory function of retaining the state even after the pulse voltage is cut off, and is controlled to return to the original ON state by the application of the pulse voltage of the opposite polarity. Since the state in which silver ions are eccentrically distributed to one electrode is maintained, it also has an electric memory function of holding a potential difference between both electrodes.

The electrodes 11 and 12 and the superionic conductive glass 10 of this embodiment can be formed by a thin film forming technique. In this case, the first electrode 11 is formed on the transparent substrate (not shown).
By forming a thin film of the super-ionic conductive glass 10 thereon by a sputtering method or the like, further forming a first electrode 12 on the thin film, and etching the first electrode 12 into a desired shape. The optical shutter is manufactured.

As described above, the optical shutter of the first embodiment has a very simple structure in which the first and second electrodes 11 and 12 are provided on both surfaces of the superionic conductive glass 10, and the response speed is silver. It becomes extremely fast because it depends on the moving speed of ions and the film thickness of the superionic conductive glass 10. Further, since the superionic conductive glass can be formed by the sputtering method or the like, a large-area thin film can be easily formed. The driving voltage can also be made extremely low at about 1V.

[Second Embodiment] FIG. 2 shows a second embodiment using the present invention, in which a transparent common electrode 16 is formed over the entire surface of one surface of a thin film of superionic conductive glass 15. On the other surface, a plurality of transparent signal electrodes 17 having a small area are formed as an example, and these signal electrodes 17 are electrically independent. The portion other than the signal electrode 17 is covered with a mask 18 for preventing the transmission of light.
Each of the openings 18a of the above forms an area of one minute shutter, and a plurality of these minute shutters are arranged to form an optical shutter array 19.

The minute shutters of the optical shutter array 19 are individually driven by individually selecting individual signal electrodes 17 and applying a pulse voltage between the signal electrodes 17 and the common electrode 16. That is, when a write signal is applied so that the common electrode 16 has a positive potential and the selected signal electrode 17 has a negative potential, silver ions are unevenly distributed on the signal electrode 17 side, and this silver ion is unevenly distributed. Light from a light source (not shown) having an emission wavelength band matched with the absorption wavelength band due to is absorbed and does not pass through, the minute shutter is turned off, and the state is maintained even after the drive signal is cut off.

Contrary to the write signal, the common electrode 16 has a negative potential,
When an erasing signal that causes the signal electrode 17 to have a positive potential is applied to both electrodes, silver ions diffuse toward the common electrode 16, and silver ions are scattered, so that light absorption in the minute shutter decreases. The amount of transmitted light increases, and the minute shutter is turned on.

As described above, the optical shutter array 19 has a storage function, so that a large number of minute shutters can be driven at high speed and with high time division.
Can be formed by a sputtering method or the like, so that a large-area thin film can be easily obtained, and the driving voltage is as low as about 1V.
It consumes less power. This optical shutter array 1
9 can be used in an optical writing head such as an optical format printer.

In the first embodiment using the present invention, an example of reversibly controlling transmission / non-transmission of light has been described.
Not limited to this, for example, by applying a high voltage between both electrodes for a long time, silver is deposited on one electrode side,
Permanent optical writing can be performed by reflecting incident light. Further, by utilizing the storage function of the element using the present invention, it can be used as an electro-optical storage device. Further, the present invention is not limited to the optical shutter that controls the transmission of light, and can be used as a display device that displays an electrode having an arbitrary shape and a pattern corresponding to the electrode shape.

〔The invention's effect〕

The present invention moves ions in a superionic conductive glass by an electric field and absorbs light due to uneven distribution of the ions,
Since the amount of transmitted light is controlled by scattering or reflection, no polarizing plate is used and the structure of the element is simplified. In addition, since this super ionic conductive glass can easily form a thin film having a large area, it has an advantage that a high speed response can be obtained by driving at a low voltage.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention, and FIG. 2 is a perspective view showing a second embodiment using the present invention. FIG. 3 is a sectional view showing a conventional light control element using liquid crystal, and FIG. 4 is a perspective view showing a conventional light control element using PLZT. 10 ... Superion conducting glass, 11, 12 ... Electrodes.

Claims (2)

[Claims] 1. An ion-conducting glass containing optically active ions and exhibiting high ion conductivity at room temperature as compared with an insulating glass, and the ion-conducting glass formed on both front and back surfaces of the ion-conducting glass. An optical control element, comprising: electrodes arranged to face each other for applying an electric field to glass. 2. The light control element according to claim 1, wherein the optically active ions are silver ions.