JPH04196001A - Light emitting element - Google Patents

Abstract

PURPOSE:To form an image to be displayed through photo-writing by furnishing the light emission part with a pair of electrodes, facing each other and a ferro- dielectric substance in which a fluorescent substance is dispersed. CONSTITUTION:An electric field over the high electric field Ec of a ferro- dielectric substance 16 is impressed to the gap between electrodes 17, 18 arranged previously on both sides of this ferro-dielectric substance 16 to cause its polarization, and a voltage lower than the Ec is impressed on these electrodes 17, 18 in the direction opposite the impression of the electric field as described, and meantime a beam of light for forming the image pattern to be displayed is cast onto the ferro-dielectric substance 16 to generate its partial polarization. When electrons are emitted from an electron emitting part 10, they intrude into the ferro-dielectric substance 16 only at the part where polarization inversion has occurred to make bombardment to a fluorescent substance 19, so that only the photo-irradiated part is allowed to make light emission. Thus only that part of the light emission part which is irradiated with the light will emit light, so that display of desired image due to light emission can be made only through irradiating of the light emission part previously with the light of desired image pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a light emitting device, and particularly to an optically writable light emitting device.

[Prior Art] Conventionally, MIM (metal/insulator/metal) type light emitting elements have been used as light emitting elements. FIG. 3 is a schematic explanatory diagram of an MIM type light emitting device. In the figure, 30 indicates an insulating layer. Electrodes 31 and 32 are provided on both sides of the insulating layer 30, respectively. A vacuum layer 33 is provided on the outside of one electrode 31.
A phosphor 34 is placed through the phosphor. The light emitting element 3 is configured in this way.

When this light emitting element emits light, a voltage is first applied between the picture electrodes 31 and 32 so that the electrode 31 is positive (+) and the electrode 32 is negative (-). At this time, electrons pass through the insulating layer 30 from the electrode 32 to the electrode 3 due to the tunnel effect.
Reach 1. These electrons further pass through the electrode 31 and jump out into the vacuum layer 33. These electrons collide with the phosphor 34 and light emission occurs.

[Problems to be Solved by the Invention] However, in order to draw an image using this light emitting element, one pixel must be created with one light emitting element. Therefore, the voltage applied to each pixel must be controlled. Therefore, a control circuit or the like is required for this purpose, which has the drawback of complicating operations and wiring.

The present invention has been made in view of these points, and it is an object of the present invention to provide a light-emitting element in which an image to be displayed is formed by optical writing, and there is no need to control the applied voltage for each pixel as in the past. The purpose is to

[Means for Solving the Problems] The present invention provides a light-emitting element having an electron-emitting part that emits electrons, and a light-emitting part that emits light by receiving the electrons emitted from the electron-emitting part, wherein the light-emitting part The present invention provides a light-emitting element comprising: a pair of opposing electrodes; and a ferroelectric material disposed between the pair of electrodes, in which fluorescent material is dispersed.

Here, as the material of the ferroelectric material, an organic material such as a copolymer of polyvinylidene fluoride/ethylene trifluoride, a ceramic material such as barium titanate, etc. are used. In addition, the thickness of the ferroelectric material may vary depending on the material, or it may be several tens of V
Any thickness is sufficient as long as it can be polarized by applying the following voltage and can maintain the polarized state for a long time even after the voltage application is removed.

As the phosphor, ZnO:Zn is used.

(ZnCd)S:Ag+In2o3, ZnS:AuA
l+In O, ZnS: Mn+In OS Zn
S: Ag+InO, ZnS: CuA1+In2O
3rd grade is used.

As electron emitting means, in addition to those of the MIM (metal/insulator/metal) type structure, thermionic emitters with directly heated filament cathodes and mesho grids can be used. °If an MIM type structure is used as the electron emitting means, the applied voltage required to emit electrons is 10V.
That's about it.

The applied voltage required to polarize the ferroelectric material varies depending on the interest rate, but is approximately several tens of volts.

Among the electrodes provided on both surfaces of the ferroelectric material, at least the electrode provided on the light-emitting surface side is preferably transparent for writing pixels and reading displayed images using laser light or the like.

[Function] The light-emitting element of the present invention includes a light-emitting portion having a pair of opposing electrodes;
It is characterized by comprising a ferroelectric material disposed between a pair of electrodes and in which fluorescent material is dispersed.

In the light emitting section having such a configuration, an electric field greater than the coercive electric field Ec of the ferroelectric is applied between the electrodes placed on both sides of the ferroelectric to polarize the ferroelectric, and further, the ferroelectric is polarized. The ferroelectric material is partially polarized by irradiating the ferroelectric material with light to form an image pattern to be displayed while applying a voltage lower than the coercive electric field Ec in the opposite direction to the previous application of the electric field. bring about

Thereby, when electrons are emitted from the electron emitting part, the electrons enter the ferroelectric body only from the part where polarization inversion has occurred and collide with the phosphor, so that only the part irradiated with light can emit light.

Furthermore, by setting the direction of the initial polarization of the ferroelectric substance in the opposite direction to the above-mentioned direction, only the portion irradiated with light can emit light.

[Embodiments] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.

Example] FIG. 1(A) is a schematic explanatory diagram showing an example of the light emitting device of the present invention. The light-emitting cable 1 includes an electron-emitting section 10
, a light emitting section 11, and a vacuum layer 12 provided between the electron emitting section]0 and the light emitting section.

The electron-emitting section]O consists of an insulating layer]3 and electron-emitting electrodes 1, 4, and 15 provided on both surfaces of the insulating layer]3.
It constitutes an M-type structure. On the other hand, the light emitting section 11 includes a ferroelectric material 16 and polarization electrodes 17 and 18 provided on both surfaces of the ferroelectric material 16.
The fluorescent material 19 is dispersed in the ferroelectric material 16.

Next, the operation of the light emitting element having the above configuration will be explained.

First, between the two polarization electrodes 1, 7, and 18, make sure that the polarization electrode 17 on the vacuum layer]2 side is positive (+) and the other polarization electrode 18 is negative (-). An electric field greater than or equal to the electric field required to cause polarization of the body 16 (hereinafter abbreviated as coercive electric field Ec) is applied. As a result, the ferroelectric material becomes the vacuum layer 12.
Polarization is caused so that the polarization electrode 17 side becomes negative (-).

In this state, even if electrons are emitted from the electron emitting section 10, the light emitting section 11 does not emit light. That is, between both = 6-electron emitting electrodes 14 and 15, the electron emitting electrode 14 on the vacuum layer 12 side is positive (+), and the other electron emitting electrode 15 is
When a voltage of about IOV is applied so that the electron emission electrode 15 becomes negative (-), electrons pass through the insulating layer 13 due to the tunnel effect from the electron emission electrode 15 which is negative (-), and the electron emission electrode 14 on the vacuum layer 12 side , and furthermore, the electron emitting electrode 14
It passes through and jumps out into the vacuum layer 12. However, in this state, as shown in FIG. 1(A), since the polarization electrode 17 side of the ferroelectric material 16 on the vacuum layer 12 side is negatively charged (-), the electrons are repelled by the repulsive force. cannot penetrate into the ferroelectric material 16. Therefore, the electrons in the ferroelectric 1
It cannot collide with the phosphor 19 dispersed within the phosphor 6, and no light is emitted.

Next, between the two polarization electrodes 17 and 18, the polarization electrode 17 in the opposite direction to the above, that is, on the vacuum layer 12 side, is negative (-),
Coercive electric field E is applied so that the other polarization electrode 18 is positive (+).
An electric field of less than c is applied, and at the same time, light such as a laser beam is irradiated onto the light emitting section 11 from the electrode 18 side in accordance with the image pattern to be displayed. By this light irradiation, the portion 20 of the ferroelectric material 16 that is irradiated with light is heated, and the coercive electric field is lowered by the energy generated by the heating, and the electric field being applied exceeds the coercive electric field, so that the polarization of the ferroelectric material 16 is is reversed. As a result, as shown in FIG. 1(B), a portion 20 of the ferroelectric material 16 is irradiated with light.

Only one of the two electrodes becomes positively charged (+).

Therefore, when electrons are subsequently emitted from the electron emitting section 10 into the vacuum layer 12 in the same manner as described above, the electrons enter the ferroelectric material 6 from the irradiated portion 2° of the ferroelectric material 16. . As a result, electrons that have entered the ferroelectric material 6 collide with one of the phosphors to emit light.

As described above, according to the light emitting element of this example, only the portion of the light emitting section that is irradiated with light emits light, so that by simply irradiating the light emitting section with light in a desired image pattern in advance, a desired image can be created by emitting light. can be displayed.

In this embodiment, the vacuum layer 12 is provided between the electron emitting section 10 and the light emitting section 11, but the same effect can be obtained even without providing the vacuum layer 12. In this case, as shown in FIG. 2, the electron emitting electrode 14 and the polarization electrode 17 may be used in common.

Example 2 The above example is a light emitting element that emits light only in the portion that is irradiated with light, but in this example, the portion that is not irradiated with light emits light. Note that the structure of the element is the same as in Example 1.

The operation of this light emitting element will be explained using FIG. 1(A).

First, between the two polarization electrodes 17 and 18, the polarization electrode 17 on the vacuum layer 12 side is negative (-), and the other polarization electrode 18 is positive (+), so that the coercive electric field Ec or higher is established. Apply an electric field. At this time, the ferroelectric material is polarized so that the polarization electrode 17 side on the vacuum layer 12 side becomes positive (+).

When electrons are emitted from the electron emitting section 10 in this state, the light emitting section 11 emits light over the entire surface. That is, when electrons are emitted from the electron emitting section 10, the electrons pass through the vacuum layer 12 and reach the ferroelectric material 16.

In this case, the polarization electrode 1 on the vacuum layer 12 side of the ferroelectric material 16
Since the side 7 is positively charged (+), all the electrons enter the ferroelectric material 16, collide with one phosphor, and emit light over the entire surface.

Next, between the two polarization electrodes 1' and 7.18, the polarization electrode 17 in the opposite direction to the above, that is, on the vacuum layer 12 side, is connected to the positive (+)
, an electric field less than the coercive electric field Ec is applied so that the other polarization electrode 18 becomes negative (=), and at the same time, an image to be displayed with light such as a laser beam from the electrode 18 side to the light emitting part 11. Irradiate according to the pattern. By this light irradiation, the portion 20 of the ferroelectric material 16 that has been irradiated with light is heated, and the coercive electric field is lowered by the energy generated by the heating, and the ferroelectric material 16 is heated.
The polarization of 6 is reversed. As a result, only the portion of the ferroelectric material 16 irradiated with light becomes negatively (-) charged.

Therefore, when electrons are subsequently emitted from the electron emitting section 10 into the vacuum layer 12 in the same manner as described above, the electrons are repelled by the light-irradiated part 20 of the ferroelectric material 16, but the remaining part The light enters into the ferroelectric material 16 and collides with the fluorescent material 19 dispersed within the ferroelectric material 16 to emit light.

In other words, this embodiment is a light emitting element that emits light only in the portions that are not irradiated with light, and can display a desired image similarly to the first embodiment.

[Effects of the Invention] As explained above, the light emitting device of the present invention forms an image to be displayed by optical writing, and although the electrode structure of the device itself is extremely simple, it can easily create any image. It is something that can be displayed.

[Brief explanation of the drawing]

1A and 1B are schematic explanatory diagrams showing one embodiment of the light emitting device of the present invention, FIG. 2 is a schematic explanatory diagram showing another embodiment of the present invention, and FIG. FIG. 2 is a schematic explanatory diagram showing an element. 1.3. Light emitting element, 10... Electron emission part, 11...
Light emitting part, 12.33... Vacuum layer, 13.30... Insulating layer, 14.15... Electrode for electron emission, 16... Ferroelectric layer, 17.18... Electrode for polarization, 19.34 phosphor, 3], 32...electrode. Applicant Casio Computer Co., Ltd.

Claims (1)

[Claims] A light-emitting element having an electron-emitting part that emits electrons, and a light-emitting part that emits light by receiving the electrons emitted from the electron-emitting part, wherein the light-emitting part has a pair of opposing electrodes, and a light-emitting part that is connected to a pair of opposing electrodes. A light emitting element comprising: a ferroelectric material disposed between the ferroelectric material and a ferroelectric material having a phosphor dispersed therein;