JPH0797657B2 - Optical memory - Google Patents

Description

[Industrial application field]

The present invention relates to optical memories. [Prior Art and its Problems] For example, in a transmission electron microscope, an electron beam emitted from an electron gun is adjusted by a condenser lens so as to have an appropriate electron flow density and irradiates a sample. Then, it passes through the sample and is magnified by the objective / intermediate / projection lens and visualized by a fluorescent plate coated with fluorescent fine powder, or
It is designed so that it can be imaged on photographic film. However, when the electron beam is visualized by the fluorescent plate as described above, phenomena such as blurring and bleeding appear and there is a problem that the resolution is lowered. This analog visualization of invisible rays is
It is a serious problem not only in electron microscopes but also in various fields. Therefore, research on various optical amplifying devices that perform amplification by analog-wavelength converting light rays such as infrared rays, ultraviolet rays, and X-rays is underway. An object of the present invention is to provide an optical memory having a simple structure by utilizing this light-light conversion. [Means for Solving Problems] Therefore, in the present invention, the back electrode of a thin film EL element in which a light emitting layer having a desired emission wavelength is sandwiched between a front electrode and a back electrode is formed of a transparent conductive film. A photoconductive film and a light-shielding dielectric layer are interposed between the light emitting layer and the light emitting layer, a constant voltage (first voltage) is constantly applied between the front electrode and the back electrode, and when light enters. The resistance value of the photoconductive film is reduced, the voltage between the front electrode and the back electrode is increased to a second voltage, and high-luminance light emission is generated in the light emitting layer. The first and second voltages are set so that the light emission of the light emitting layer can be continued even if the second voltage drops to the first voltage. [Operation] For example, as shown in FIG. 1, this optical memory includes a glass substrate 1, a transparent surface electrode 2, a first dielectric layer 3, a light emitting layer 4,
The light-shielding layer S, the second dielectric layer 5, the photoconductive film 6, and the translucent back electrode 7 are sequentially laminated to form a thin film EL element having a double dielectric structure. Thin film EL between surface electrode 2
The voltage V ₀ is applied so that the element does not emit light. When the light L ₁ enters here, the resistance value of the photoconductive film decreases,
The voltage applied to the light emitting layer 4 of the thin film EL element is increased, whereby the light emitting layer 4 emits light L ₂ having a wavelength peculiar to the light emitting layer. In this way, the incident light L ₁
Can also be converted into light L ₂ having a desired wavelength. As shown in FIG. 3, the thin film EL element has a hysteresis in the relationship between the voltage and the bad luminance when the applied voltage rises and falls. Therefore, the following phenomenon may occur. First, when a certain voltage V _1A is applied in advance, the state is A. When the voltage is raised to V _1B in this state, the state becomes B, and this thin film EL element emits light with high brightness. Next, even if the voltage is lowered to the original voltage V _1A , this thin film EL
The element is in the C state, and the luminance is slightly lowered, but sufficiently high luminance is maintained. The present invention has been made paying attention to this point. Here, for example, if a photoconductive film is connected to the back surface of the thin film EL element to form a series connection body, and a predetermined voltage Vo is applied to this, the initial state is V _1A + V _2A = Vo (1 ) Has become. Here, the thin film EL element corresponds to the state A (see FIG. 2). When the resistance value of the photoconductive film decreases due to the incident light, V _1B + V _2B = Vo (2) V _2A > V _{2B and} V _1B > V _{1A In} this way, the voltage applied to the thin film EL element rises and the state of B And emits light with high brightness. After that, even if the resistance value of the high conductive film returns to its original value and the applied voltage to the thin film EL element drops to the state of V _1A , the thin film EL element is in the state of C as shown in FIG. 3 and is sufficiently high. Since the brightness is maintained, it remains as a locus. Therefore, by appropriately selecting the photoconductive film and the light emitting layer in this manner, the optical memory can be formed with an extremely simple structure. [Embodiment] An optical memory according to an embodiment of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 2, this optical memory comprises a surface electrode 12 made of an indium tin oxide layer (ITO) and a first dielectric layer made of a tantalum oxide (TaO _x ) layer on a transparent glass substrate 11. 13, a light emitting layer 14 composed of a zinc sulfide: manganese (ZnS: Mn) columnar polycrystalline layer, and black tantalum oxide (TaO _X , x <2.
5) second dielectric layer 15 consisting of layers and cadmium sulfide (C
It is composed of a photoconductive film 16 made of a dS) layer and a translucent back electrode 17 made of an indium tin oxide layer, and a voltage V is applied between the front electrode 12 and the back electrode 17. . Here, the photoconductive film 16 has a high resistance when light is not incident and has conductivity when light is incident, and when light L ₁ is incident, the voltage applied to the light emitting layer increases at that portion, The light emitting layer is excited to emit light L ₁ . Further, the incident light is blocked by the second dielectric layer, and only the light L ₂ from the light emitting layer is emitted to the surface electrode side. The applied voltage is selected according to the photoconductive film and the light emitting layer so as to satisfy the following relationship, as described in the explanation of the principle. First, when the voltage V _1A is applied in advance, the state is A. When the voltage is raised to V _1B in this state, the state becomes B, and this thin film EL element emits light with high brightness. Next, even if the voltage is lowered to the original voltage V _1A , this thin film EL
The element is in the C state, and the luminance is slightly lowered, but sufficiently high luminance is maintained. Here, for example, if a photoconductive film is connected to the back surface of the thin film EL element to form a series connection body and a first voltage Vo is applied to this, the initial state is V _1A + V _2A = Vo ... ( 1) Here, the thin film EL element corresponds to the state A (see FIG. 2). When the resistance value of the photoconductive film is lowered by the incident light, V _1B + V _2B = Vo (2) V _2A > V _{2B and} V _1B > V _{1A In} this way, the voltage applied to the thin film EL element rises and the state of B And emits light with high brightness. After that, even if the resistance value of the photoconductive film returns to its original value and the voltage applied to the thin film EL element drops to the state of V _1A , the thin film EL element is in the state of C as shown in FIG. 3 and is sufficiently high. In order to maintain the brightness, it is configured to remain as a locus. This optical memory can be formed using ordinary thin film technology, has an extremely simple structure, and provides a simple and good memory by efficient wavelength conversion. Although the second dielectric layer is made of a black film having a light blocking property in the embodiment, a light blocking layer may be provided separately. In addition to cadmium sulfide, other photoconductive materials such as amorphous silicon (a-Si), zinc selenide (ZnSe), and mercury cadmium telluride (HgCdTe) may be used as the photoconductive film. The constituent material of each layer is not limited to the embodiment and can be changed as appropriate. In addition, although the thin film EL element is integrally formed in the embodiment, it may be divided into a plurality of pieces. In this case, a thin film EL element having a normal double-dielectric structure in which the back electrode is composed of a light-shielding metal film is formed, and the photoconductive film and the translucent conductive film are arranged outside the back electrode. You can do this. As such an example, the simplest structure is, as shown in FIG. 4, on the glass substrate 21, the surface electrode 22, the first dielectric layer 23, the light emitting layer 24, the light shielding layer 24, and the light shielding layer as in the above embodiment. Second of sex
Dielectric layers 25 are integrally formed, and a back electrode 27 having a plurality of divided patterns of aluminum, chrome, etc. arranged in a matrix is laminated on the upper layer to form a thin film EL element. At the same time, the photoconductive film 26 and the translucent conductive film 28 are sequentially and integrally formed on the upper layer. [Effect] As described above, according to the optical memory of the present invention,
A photoconductive layer and a light-shielding dielectric layer are interposed between the back electrode and the light emitting layer of the thin film EL element, and the back electrode is composed of a light-transmitting conductive film, and a predetermined distance is provided between the front electrode and the back electrode. Voltage is applied, the voltage applied to the light emitting layer in that part increases due to the decrease in the resistance value of the photoconductive film due to the incident light, and light is emitted, and the voltage between the surface electrode and the back electrode decreases to the original value. Even so, since the light emission is continued due to the hysteresis, an optical memory having a very simple structure and high reliability is provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic structure of an optical memory of the present invention, and FIG.
FIG. 4 is a diagram showing an optical memory according to an embodiment of the present invention, FIG. 3 is a diagram showing a hysteresis characteristic of a thin film EL element, and FIG. 4 is a diagram showing another embodiment of the present invention. 1,11,21 …… Glass substrate, 2,12,22 …… Surface electrode, 3,13,2
3 ... First dielectric layer, 4,14,24 ... Light emitting layer, 5,15,25 ...
… Second dielectric layer, 6,16,26 …… Photoconductive film, 7,17,27 ……
Back electrode, S ... Shading layer, 28 ... Translucent conductive film.

Claims (1)

[Claims] 1. A thin film EL element in which a light emitting layer is sandwiched by a front electrode and a back electrode composed of a light-transmitting conductive film, and a light-shielding dielectric material interposed between the light emitting layer and the back electrode. And a photoconductor layer, the resistance value of the photoconductive film is reduced when a first voltage is applied between the front electrode and the back electrode and light is incident, and the front electrode and the back electrode are formed. The voltage during the period increases to the second voltage, causing high-intensity light emission in the light emitting layer, after which the resistance value returns to the original value and the second voltage drops to the first voltage. Even so, the optical memory is characterized in that the first and second voltages are set so that the light emission of the light emitting layer is continued.