DE1589369C - Solid-state image storage, especially for use with X-rays as excitation radiation - Google Patents

Description

The invention relates to a solid-state image memory, especially for use with X-rays as excitation radiation, with two flat electrodes, of which at least one is transparent to the excitation radiation and one to visible light is and between which a layer of a material responsive to the excitation radiation with photo dielectric properties, especially zinc oxide, as well as a layer of an electroluminescent Material are arranged, the two electrodes connected to an AC voltage source are.

If, in such a solid-state image memory (known from French patent specification 1,398,598), the material layer with photo-dielectric properties is exposed to excitation radiation with an intensity distribution corresponding to an image, this image is emitted in visible light from the electroluminescent material layer, provided that one is exposed during the exposure the excitation radiation or some time after that, an alternating voltage is applied to the surface electrodes. Despite only brief exposure to the excitation radiation, the visible image can be emitted over a longer period of time, e.g. B. over half an hour at room temperature. The duration of storage of the image in the photo dielectric material layer may be more than 24 hours at low temperatures, / .. B. when stored in a domestic refrigerator. If the AC voltage is switched off, the image disappears. When the alternating voltage is applied again within the specified time periods, the image is created again. By heating or irradiating with infrared rays, the photodielectric material layer can be restored to its original state, ie the stored image can be deleted.

The disadvantage of the known solid-state image memory is that it only operates with relatively low alternating voltages can be operated. The image quality is therefore only mediocre. The one between the surface electrodes arranged zinc oxide layer must be relatively thick in order to make the image memory functional, ίο The thicker the zinc oxide layer, the smaller it is however, the resolution achievable with the emitted, visible light and that achievable with this image Contrast.

The invention is based on the object of providing a solid-state image memory of the type mentioned at the beginning further develop in such a way that an improved image quality is obtained.

According to the invention, this object is achieved in that between the photodielectric layer and the one electrode is provided with a layer of a high dielectric constant material.

This additional layer of a material with a high dielectric constant has the following advantages:

a) The image memory can radiate the visible image with a significantly higher AC voltage operated, creating an image with higher resolution and better Contrast is obtained;

b) the thickness of the zinc oxide layer can be reduced, which also benefits the image quality comes;

c) the reliability of the image memory is significantly improved, since there is a risk of a spark breakdown is reduced when the AC voltage is applied. This point is of particular importance because, with known image memories has shown that the moment the alternating voltage is applied, there is a risk of a spark breakdown consists. This spark breakdown is due to the rapid change in load on the electrodes arranged between the surface electrodes Layers when an electric field is applied;

d) due to the high dielectric constant layer, the amount of light is reduced, the during the operation of the image memory on the layer with photodielectric properties would fall. Accordingly, an image memory according to the invention can also be used when no dark room is available;

e) an image memory which has a layer with a high dielectric constant, in particular,

if this layer contains an element with a high atomic number (e.g. barium), has one greater absorption capacity for X-rays than an image memory without this layer. One such increased absorption capacity is advantageous if such an image memory with X-rays should be used as excitation radiation.

An exemplary embodiment of the invention is described in more detail below with reference to the drawing, in which a solid-state image memory is shown in cross section.

represents one that is permeable to visible light

3 4

Glass plate, on one surface of which a plane tension depends. The thickness of the zinc oxide layer 13 if more conductive to visible light, the thickness of layers 12 and 14 together is allowed Film 11 e.g. B. made of tin oxide in a known manner and can, for example, up to]% is brought. The film 11 is the thickness of the electroluminescent layer 12 in a conventional manner an electrical lead 16 is connected, so 5 wear.

that the glass plate 10 with the film 11 has one surface. It has been shown that the functionality

Chenelectrode of the image memory forms. On the image memory according to the invention of the quality

FiIm 11 is a layer of an electrolumi- tate that depends on the zinc oxide used. Will therefore

nescent material such as B. zinc sulfide, which is not satisfactory in organic quality with zinc oxide

nic resin or varnish is embedded. The layer that produces results must be of a different zinc oxide quality

12 can be tried on the usual electrical from the manufacture. Instead of zinc oxide, others can also be used

Troluminescent lamps known way made materials with photodielectric properties

and it can find a common use with these lamps.

Have thickness. After this elec- tric has dried, an image memory produced in the above way has

troluminescent layer 12 for about 30 to 15, especially when used with X-ray

45 minutes at about 100 to 120 ° C and after it has been used as an excitation radiation. The x-ray

Cooling is the electroluminescent layer 12 image of an object can be obtained by

with a thin zinc oxide layer 13 in a nitro the object brought in front of the image memory and

cellulose butyl acetate varnish coated. After evaporation, the image memory is exposed to the X-rays

This composite body 20 becomes fen the solvent. The object can then be removed again

another 30 to 45 minutes at 100 to 120 ° C. After applying an alternating voltage between

heated. see the surface electrodes is then from that

The zinc oxide layer 13 is then with a layer of image storage the X-ray image of the object in the

14 high dielectric constant, the z. B. radiated from in the visible area. This x-ray

An organic binder embedded fine-25 remains for several minutes or even up to a half

powdery barium titanate, barium strontium titanate hour and more on the image memory, with the

or titanium dioxide is coated. As a result, the image quality is only slightly degraded. the

the construction again 20 to 30 minutes at 90 deterioration in image quality can be in certain

heated to 100 ° C. Cases by changing the amplitude and / or

The high dielectric constant layer 14 becomes the frequency applied to the image memory

then be reduced with an electrically conductive layer 15 alternating voltage,

neither by painting colloidal graphite nor has it been found that a greater risk of

Silver or by vapor deposition of an aluminum deterioration of the memory image, if

or gold film coated. The electrically conductive the applied alternating voltage or its frequency

Layer 15 is also connected to an electrical supply 35 is too high. Therefore, usually with such

Line 17 is connected and forms the second, for image storage with about 240 volts and 50 Hertz or

the excitation radiation of the image memory worked through 110 volts and 60 hertz. For reinforcement

casual surface electrode. the x-rays can be in the image memory too

An image memory produced in this way, des- z. B. embedded a material such as calcium tungstate

sen a surface electrode for the excitation 40, which then z. B. part of the dielectric

radiation, but not for visible light through material.

is casual, can also be used without a darkroom. The image memory according to the present invention The saved image is not only suitable for fluoroscopy the contrast of the picture being of course medical and dental purposes, but also for By shielding the ambient light, non-destructive material testing by means of X-rays is improved can. shine. Another use is in

For the functionality of an inventive tracking of z. B. radioactive rays or

In terms of image storage, the thicknesses of the individual laser beams are. Of course, the Internet

Layers and their evenness are important. The intensity of this radiation should not be so great that the at

The thickness of the electroluminescent layer 12 and 50 of the manufacture of the image memory used binding

of the layer 14 with a high dielectric constant are decayed. The image memory can also

speaks of the ordinary electroluminescent lamp after a uniform excitation z. B. by means of

pen of usual thickness, those skilled in the art will know that X-rays are used to detect infrared rays

the exact layer thickness will be used in part by the working.

1 sheet of drawings

Claims (4)

Patent claims: 1. Solid-state image memory, in particular for use with X-rays as excitation radiation, with two flat electrodes, one of which at least one for the excitation radiation and one for visible light is transparent and between which a layer of a material responsive to the excitation radiation with photo dielectric properties, especially zinc oxide, as well as a layer of an electroluminescent Material are arranged, the two electrodes to an AC voltage source are connected, characterized in that between the photo dielectric Layer (13) and one electrode (15) a layer (14) of a material with a high dielectric constant is provided. 2. Image memory according to claim 1, characterized in that the material with a high dielectric constant is a titanium compound. 3. Image memory according to claim 2, characterized in that that the titanium compound is barium titanate, barium strontium titanate or titanium dioxide. 4. Image memory according to one of the preceding claims, characterized in that the Thickness of the layer (13) having photodielectric properties not less than 1% of the thickness of the electroluminescent layer (12).