DE1764940C3 - Solid-state imager - Google Patents

Description

3. Image converter according to claim !, characterized in that that the intermediate layer (MMI) has a non-linear specific resistance.

4. Image converter according to claim 2 or 3, characterized in that the intermediate layer (600) contains a ferroelectric material.

5. Image converter according to one of claims 2 to 4, characterized in that the third Electrode adjacent to the interface between the intermediate layer and the energy sensitive one Layer is arranged.

6 image converter according to claim 2, characterized in that the third electrode across the interface between the intermediate layer and the energy-sensitive layer is.

7. Image converter according to claim 2, characterized in that the third electrode is in the intermediate layer is embedded.

8. Image converter according to one of claims 1 to 7, characterized in that the resistance over the thickness of the electroluminescent / enzschicht (100) is less than the maximum resistance across the thickness of the energy sensitive Layer (100).

Lent layer adjoining second electrode and a third electrode arranged between the first and the second electrode S-Absland of these, having openings, the individual electrode elements of which are coated with a f ^ ^kt " ^s material, according to patent 1764 079

Through this subject of the main patent is achieved that the solid-state image converter with a energy-sensitive layer can be built,

to which has a low specific dark resistance or a low dark impedance, and Nevertheless, a satisfactory converter characteristic zciEt The isolated third electrode works here in such a way that from the electric field that

is on the tension between the first and the second Electrode is built up in the dark state Portion is subtracted from the electroluminescent layer, which is due to the relatively low dark resistance the photoconductive layer without one

ao such influencing would be applied to the electroluminescent layer ^3. In this way, the influence of the film on the electroluminescent layer can be kept very low when there is no irradiation. Here, the working characteristics of the image converter can be

The invention relates to a solid state imager with an electrolumines / enzschichi. one on one side of the electroluminescent layer arranged energy-sensitive layer made of a material whose impedance depends on the Excitation is changeable by radiated energy. one on the outer surface of the cnergicomplindeine wide range can be freely controlled or changed if at least one of the relationships between Amplitude, polarity and phase of the between the first and second electrodes and between the first and the third electrode applied to the two voltages is freely adjustable or variable.

Image converters with a third electrode embedded in the screen are known per se (DT-Gbm 1 869 477) in the form of a grid electrode, which is connected to one of the external electrodes and built into the energy-sensitive layer, the transverse conductivity of which practically amounts to an enlargement of the grid electrode when exposed, which intercepts part of the total exciting current.

It is also known (DT-AS 1087 608, Fig. 21, 22) a WGE layer called a pereote by an applied alternating voltage to generate Lichler and in their light intensity by a direct voltage superimposed on the alternating voltage ^ to use controlled layer as electroluminescent layer. By using such a Layer, particularly favorable characteristics can be achieved because the alternating current excitation is constant remains and the controlling DC voltage is easier to avoid while avoiding capacitive jamming nuts can be influenced by the energy-sensitive layer. Here too, however, an energy-sensitive Material with a relatively low dark resistance lead to unfavorable phenomena, since the AC voltage superimposed on the applied DC voltage if the resistance of the energy-sensitive ones is too low Layer a high ohmic alternating current component which contains the constancy of excitation and the control characteristic is adversely affected by the DC voltage.

The invention is based on the object, you also be advantages of the subject matter of the main patent Use of a layer that provides the more favorable properties of the WGE layer. aMS / unut / en So the alternating current excitation from the changing ohmic resistance of the energy-sensitive Make shift as independent as possible / u. According to the Er (indun <

further developed in that the electroluminescent layer one that can be excited by alternating voltage and by direct voltage in its luminescence output controllable WGE-layer and that between the first and second electrode the direct voltage and the alternating voltage is applied between the first and the third electrode.

Through this training are the favorable characteristics the WGE layer can be exploited, and the alternating voltage is generated by the in the screen embedded third electrode having insulated openings applied to the WGE layer. Corresponding Due to the position of this third electrode, the alternating field lies only over layers caused by the radiation are not directly influenced, so that the changes in the resistivity of the energy-sensitive Shift does not directly affect the AC power and therefore in this Regarding the material of the energy-sensitive layer there are no restrictions.

For safe distribution of the alternating voltage field over the entire surface of the electroluminescent layer the execution may be appropriate that between the electroluminescent layer and the Energy-sensitive layer, an intermediate layer is arranged which has an electrical resistance. It is also possible to choose a material for the intermediate layer that is specific to a nonlinear Has resistance. This also influences the exciting alternating voltage field given by the local direct current and thus by the irradiating energy, however this influence can correspond to one of the desired characteristics of the image converter Senses are chosen.

Further details of the invention emerge from the patent claims. In the following description shows

F i g. 1 schematically and partially in section an embodiment of the invention with the associated electrical circuit and

F i g. FIG. 2 shows a simplified electrical circuit which is equivalent to the circuit of the embodiment according to FIG. 1 Circuit!

Fig. 1 shows a solid-state image converter with an electroluminescent layer 100 in the form of a WGE layer, which is between the top of a first, transparent electrode 110 made of a heat-resistant and transparent metal oxide, For example, made of tin oxide, which is on a support plate 120 made of a transparent and heat-resistant material such as glass is coated and an energy-sensitive, e.g. photoconductive layer 200 is arranged.

The term "WGE layer" denotes a layer made of an electtroluminescent material, that is dispersed in a dielectric medium that has a contradiction or is an electret. When an external polarizing field is applied in a fixed direction, it holds a residual component this field upright, even if the external tension no longer acts on it. The luminescence output the WGE layer due to a dekttrischcn Alternating field excitation can be controlled by a DC electric field applied to it.

The WGE layer is applied to the first electrode 110 in a thickness of 20 to 50 μm and fused to it. It is made using a powder of the dielectric material that has an electrical resistance or can be polarized in a storable manner, for example from a glass enamel that contains an electrically resistive, i.e. slightly conductive metal oxide such as SnO ₂ and also Li and / or Ti . The dielectric material is mixed with a powder of an electroluminescent fluorescent material such as ZnS.

ίο The energy sensitive layer 200, its more specific Resistance changes depending on the excitation by an incident energy, stands with a second electrode 210 in contact, which is permeable to the ice fall energy.

In this embodiment, the energy-sensitive layer 200 consists of a mixture of a binder, such as epoxy resin, and a photoconductive material, such as CdS, CdSe or CdS.Se. The mixture is applied in layers and set by heating for 5 minutes at 600 ^° C. in a vacuum or an inert nitrogen atmosphere.

The sintered energy-sensitive layer has approximately linear voltage-photocurrent characteristics, which, in comparison with non-sined elements, enables operation with very high sensitivity do.

The specific resistance of the energy-sensitive layer 200 increases depending on the Incident energy, such as light or X-rays.

3a The specific dark resistance should be greater than 10 ⁹ ohm-cm, for example. The thickness of the energy-sensitive layer 200 is 50 to 500 µm in order that the dark resistance in the direction of its thickness is equal to or better than the specific resistance of the electroluminescent layer 100 in the direction of its thickness.

The second electrode 210 is, for example, as a thin foil made of gold or aluminum, as in a vacuum Vaporized thin metal layer or made with silver stricli. It can also be grid-like be formed and consist of metal wires that have a diameter of 10 to 50 (in and a distance have from 100 to 500 μνη. If the second electrode 210 is designed to be perforated in this way, then it can be partially or completely sunk into the energy-sensitive layer 200. Such a second Electrode also has the advantage that fluctuations in the specific resistance in the direction the level can be exploited.

A subdivided or perforated third electrode 310 having openings is made of electrically conductive electrode elements 301 made with dielectric material 302 high specific Resistance are coated. The pierced electrode 310 is between the first and second Electrode arranged. Your electrode elements 310 consist for example of tungsten or Copper wire of 10 to 30 μm in diameter, and the high dielectric constant dielectric material 302 consists for example of polyester resin or glass and has a thickness of 2 to 10 (im. In the embodiment described here, the third electrode 310 has the shape of a grid adjacent grid lines. It can also be coated by crosslinking the described Conductor or by coating a metallic network with the dielectric material be. The space factor of the conductor 301 of the third

Electrode 310 is to be chosen so that it can be avoided in spite of its increase in direct current,

openwork structure with regard to an electronic

tric alternating field has about the same effect as CdS: Cl or SiC instead of the resistance

is sufficient, like a solid plate electrode, if a metal oxide is used for the

AC drive voltage V _{A used} between the first electrical 5 setting. In this case at least

electrode 110 and the third electrode 310, one of the two reflective or opaque

will. The third electrode 310 should therefore be omitted with permeable resistance layers constructed in such a way that

The third electrode 310 is on the intermediate layer

low alternating current power due to fluctuations in the 600 or when they cease to exist on the electroluminescent

specific resistance of the energy-sensitive io zenzschicht 100 arranged.

Layer 200 is not greatly affected. The distance In order to ensure the equivalence of the third electrode 310 to between two conductors lying next to one another in a fixed plate electrode with regard to the Aus-F i g. The third electrode 310 shown in FIG. 1 should, as far as possible, have an effect on an alternating electric field that is certainly too small than 400 μm. If placed in a mesh grid electrode, in the plane of the third electrode 310, the network should be finer than 50 mesh. Such an auxiliary resistance layer 700 is provided, which allows the spacing of the conductors at the electrode 310 to fill at least part of the openings in the third electrode for direct current from the electrode 310 to pass through. The specific resistance of the luminescent layer 100 to the energy-sensitive auxiliary resistance layer 700 has a value of layer 200. If you have selected the second electrode 210 and the one that prevents a stronger scattering of the direct current third electrode 310 the form of similar grids, then 20. It is experimentally demonstrable that the grid of the second electrode 210 should be arranged on a resistance auxiliary layer 700 with a special one that the parts of its grid cross those surface ^{spacing of 10 ° to 10 9} ohms of the grid of the electrode 310 or in horizons satisfactory Yields results. Fulfilled zontal projection come to lie between these. The WGE layer is an intermediate layer 600 25 troluminescent layer 100 applied together with the intermediate, which is also an electrical back layer 600. This condition is a resistance layer, i.e. a low conductivity on the auxiliary layer 700 is not necessary. The third points. It is, for example, made of a mixture of an electrode 310 can then be arranged on the intermediate layer of epoxy resin with a powder of a resistance 600 or the electroluminescent layer 100 directly material such as carbon or SnO ₂ or of a mixture, or also partially or entirely in the mixture Powder of a frit with an inorganic intermediate layer 600 or the electroluminescent niches black pigment and a powder of a layer 100 can be countersunk. In the latter case, resistor material such as SnO ₂ can be made. It is assumed that the auxiliary resistance layer was caused to set by heating to 700 equivalently in the opaque layer, as a result of which it becomes an electrically resistive 35 or the reflective layer of the intermediate layer and opaque 600 or in the WGE layer, so the electrical layer was made. If the alternating current impedance of the luminescent layer 100 is to be present,
If the resulting layer is low, the intermediate layer 600 and the dielectric insulation can expediently contain a ferroelectric Irish material 302 for the coating of glass material such as BaTiO ₃ . The intermediate 40-like material, then the auxiliary resistance layer layer 600 prevents the luminescent input 700 from powder of an epoxy resin or a frit of the electroluminescent layer 100 on the example, which is mixed _{with a photoconductive energy-sensitive layer sending a resistance metal oxide such as SnO 2} is. The Mi-200 is fed back. If a certain feedback has been fused by heating and is desired for development, then the intermediate layer 600 is caused to set. If the intermediate layer is designed to be speaking semipermeable. The intermediate 600 and the dielectric material 302 of the coating layer 600 can also be formed as a composite layer made of a binding material with low melting point, with additional layers in between, for example made of an epoxy resin, so they and the electroluminescent layer 100 look similar Binder can be placed in a mixture with a one. The additional layer can be used with the resistive metal oxide. For example, from a mixture of a frit powder in this case, powder of a dielectric material or epoxy resin with a powder of a ferroelectric high dielectric constant, in particular an Irish and light-reflecting material, preferably ferroelectric material such as BaTiO _3, the mixture as BaTiO ₃ , or an electrical resistor - Be added in order to reduce the alternating current impedance of the metal oxide containing the material, such as SnO _2, produced 55 resulting layer. Be the fat one. This mixture was melted and set by heating, for example, IC resistive auxiliary layer, so that an electrical resistance to 50 µm, in order to keep the reflective resistance exhibiting over its thickness, small. The resistance auxiliary layer was created. The thickness of the single or additional layer 700 can also be highly non-linear, contradicting the interlayer 600, with light stability, to layers impermeable to direct voltage 5 to 10 μm and with losses over its thickness and direct current scattering of the reflective layers, 10 to 20 μm, so decrease direction of plane. These properties can be obtained through the thickness of the intermediate layer 600 and the resistive layer 700 by an electrical resistance such as CdS: Cl or SiC, which is sufficiently small compared to the resistance of the electrical use of a material with a nonlinear speciluminescent layer 100. The intermediate layer 600 may also have a particular non-linear specific resistance attaining the above-described composition for the resistive metal oxide for L.C11 practical. The auxiliary resistance layer 700 can

or or

further ₍ properties of a

to whom one chooses the ur this purpose wutc or *, η angj bencn matenahen. Be, V cmc, ι lun ^ tncr du "carried resistance auxiliary layer let s. _L n simplify the aumuu of the image converter.
Is in a layer structure and its polarity is reversible. This makes it possible to use a WGE layer of electrical

_zschicht 100 different Betriebskcnn- ^ ^. ^ ^ _dependence ". ^^ _{whether dcr}

^ _{the contact / 7 or the} contacts / _c i _c h <- _{Fig 1} is in} contact, the first electrode 110 is biased negatively or positively. Im ^ g image converter mainly for

chert. «, Net. Crazy

and, ur luminescence display of the stored

dfc

aie

layer 700 over the ~

or the intermediate layer 600 ε _ the third electrode 310 but not completely ι troluminescent layer 100 or the intermediate 600, so the resistor! ™ is designed so that it fills ^{the intermediate 1.} In the one described here, the third electrode 310 lies between the clektro luminescent layer 100 and the energy-sensitive layer 200. In this structure, the total thickness of the layers, including. The layer 600, the resistance layer 700 or other additional elements equal to the thickness of the third electrode or smaller than this, so that the layers can at least partially be introduced into the openings of the third electrode 310 . Such a structure is des - »- -rtP, lh., Ft. Because a leakage of the direct current, the third electrode 310 may be partially embedded in the iroluminescent layer 100 or the ene - "lent layer 200. The ν of the third electrode 310 ir * ^A '"" ^{h Hl} electroluminescent layer IU. - --- ^ - ■ sensitive layer 200. It only has to be less than the distance between the first electrode 110 and the second electrode 210. As far as the position of the third electrode 310 is concerned, it only has to be between the first electrode 110 and the second electrode 210. Other conditions have to be met Therefore, at least either the electroluminescence protection 100 or the energy-sensitive protection system can close free openings in the third electrode 310

be brought. . ", _.__ am

The first electrode 110 is connected to a terminal 401 of an alternating voltage source 400, the other terminal 402 of which the 'poor electrode elements 301 of the third electrode 310 are connected via a terminal rail 303. The B * ™ ** alternating voltage V _A is applied in this way between the electrode HO and the electrode 310 is, whereby the second .Electrode 210 ^, ne bias voltage V _{B is} supplied. The G e.chspannungs queileSOO is arranged in such a way that the bias voltage V _n representing a direct voltage is variable approx.

F i g. FIG. 2 shows, in simplified form, an equivalent circuit of the circuit shown above with reference to FIG. 1 described arrangement. In order to simplify the explanation, FIG. 2 does not take into account the functions of the auxiliary resistance layer 700 and the intermediate layer 600. The energy-sensitive layer 200 has a variable resistance R _1,. As a result of the dielectric material 302 of the coating on the third electrode 310 having openings, a capacitance C ”is obtained via this coating, one electrode of which is the conductor 301. The electroluminescent layer 100 has a capacitance C _£ and a resistance / ?,.- over its thickness. The resistance R ₁ drops as a function of the intensity of an incident energy L ₁ . As a result, the DC bias voltage V ₁₁ applied to the electroluminescent layer rises. The result of this change in the bias voltage is that the course of the alternating current luminescence output L. "which is produced by the alternating current power supplied via the capacitance C _n , is controlled and the amplitude of the periodic luminescence output is significantly changed in a certain half-period of each period of the alternating voltage.

In this way, in the embodiment described, the incident _{energy L 1} distributed over the screen surface as an image is converted and amplified to a negative image with high sensitivity and a high gain factor. It should be noted that in the image converter according to the invention, the DC bias voltage V _{B is applied} between the energy-sensitive layer represented by the variable resistor R _P and the dielectric material represented by the capacitance C _n. Correspondingly, the dielectric breakdown strength of the capacitance C _n , at which there is a relatively low bias voltage corresponding to the DC bias voltage V _[} , does not have to be very high. Adjustment of the source voltage V _B does not affect the AC power supplied to the electroluminescent layer 100.

As described above, the energy sensitive layer is photoconductive. Stat Another energy-sensitive layer can also be used, for example a piezoelectric layer

or a magnetoresistive layer whose specific resistance is due to elastic energy or ma gnetic energy is controllable, come into question.

For this purpose 2 sheets of drawings

Claims (2)

Patent claims: 1. Solid-state ^imager with a ΕΙ <* | ^Γ ° - luminescent layer, one on one side of the BLek-trolumineszenzschicht arranged energieempnndlichen layer of a material whose impedance varies in response to the excitation by the irradiated energy '^ ^emer on the outer surface of the energieempfindlicnen layer subsequent second electrode and between the first and second lead electrode at a distance from these arranged ^ oniiungen exhibiting third electrode, uv, rcn individual electrode elements are coated with a Krrischen material, according to patent 1,764,079, thereby denotes, the electroluminescent layer (100) has an excitable by alternating voltage and by direct voltage in its Luminescence output is controllable WGE layer and that the DC voltage is applied between the first (110) and second (210) electrodes and the AC voltage is applied between the first (IUM and the third (310) electrode). 2 image converter according to claim 1, characterized by dadurcn, that between the electroluminescent layer (100) and the energy-sensitive Layer (200) an intermediate layer (600) is arranged, which autwcist an electrical resistance.