JPS6148151B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming method using electroradiography.

Conventionally, radiography, or X-ray photography, has been performed by irradiating a silver halide emulsion film (hereinafter simply referred to as a silver halide film) with X-rays that have passed through the subject to reduce the silver in the silver halide milk. The image is visualized by forming a blackening density. However, although X-ray photography using silver salt film as described above has high X-ray sensitivity, it is generally expensive because it consumes silver, and the development process is complicated and takes a long time.
There are drawbacks such as the need for sufficient care in post-processing such as a developer. In order to overcome these drawbacks, various methods using electrophotographic processes have been developed to obtain X-ray photographs without using the above-mentioned silver salt film. For example, xerographic methods that utilize the sensitivity of a photoconductor to X-rays, ionographic methods that utilize the ionization of air or rare gases by X-rays, and electron radiographic methods are already known. Unlike those using conventional silver halide films, both of these methods form images based on electrostatic latent images. It has the advantage of being able to obtain images with a large amount of information on soft tissues such as muscles, tendons, stomachs, and intestines with little difference in line absorption, and can eliminate the drawbacks of the silver halide film described above. However, the photoconductor used in the xeroradiography method is not necessarily highly sensitive to radiation, and in the ionography method and electron radiography method, the chamber consisting of opposing electrodes is placed at a low pressure. Alternatively, high-pressure gas must be sealed in the chamber, which makes it difficult to select a material for the chamber and makes the structure complicated. In order to eliminate these drawbacks, electroradiography using radiation-absorbing liquids has recently been studied. In other words, this method generates electrons and positive polarity ions or positive and negative polarity ions by irradiating radiation such as X-rays between a pair of electrodes arranged approximately parallel to each other with a gap between them. An insulating image receiving sheet is placed in this liquid in contact with one of the electrodes, and while a voltage is applied between the pair of electrodes, the radiation that has passed through the subject is absorbed by the insulating liquid. This method involves exposure to sexual fluid.

The insulating radiation-absorbing liquid is ionized according to the amount of radiation exposure, and the generated electrons and positive ions,
Alternatively, the positive and negative polarity ions move toward the corresponding electrodes, and an electrostatic latent image is formed on the image receiving sheet. The obtained electrostatic latent image is developed into a visible image by a known electrophotographic method. This method includes conventional X-ray photography using silver halide film, xeroradiography, ionography,
Although it is attracting attention as having high sensitivity and high resolution compared to electron radiography, etc., it also has the following drawbacks. That is,
Since an electrostatic latent image is formed on the surface in contact with the radiation-absorbing liquid, the volume resistivity of the radiation-absorbing liquid must be sufficiently high to ensure that the latent image is formed and does not disappear in a short period of time. It is. In addition, it is a liquid substance that strongly absorbs radiation, and it is difficult to obtain a substance that satisfies this condition in normal atmosphere. In other words, in order to absorb strong radiation, for example, I, Br, F
It is necessary to select a material containing atoms with a high atomic number, such as, but liquids containing these atoms are generally easy to decompose and are unstable. For this reason, the liquid is ionized and cannot maintain high resistance. Another drawback is that the above-mentioned liquids generally have a strong tendency to hydrolyze, so even a small amount of moisture in the atmosphere can cause hydrolysis, resulting in a decrease in resistance. Therefore, in order to employ the method described above, it is necessary to perform extremely strict moisture control and blocking of light rays, and the apparatus itself becomes complicated and expensive.

The present invention has been made to eliminate the drawbacks of such electroradiography, and allows the use of a radiation-absorbing liquid with a low resistance in a sealed chamber, which was not previously possible. An electroradiographic method in which an electrostatic latent image is formed in accordance with incident radiation on the surface of a highly insulating film forming a part of the chamber or on the surface of an insulating latent image receiving film placed in contact with it. By providing an image forming method according to the present invention, radiographs having high sensitivity and high resolution can be obtained easily and economically.

The method of forming an image by electroradiography according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a cross-sectional view of a chamber 1 used in the method of the present invention, which has an electrode 2 with high radiation transmission efficiency and a large number of protrusions 6 formed on the entire lower surface, which has high electrical insulation and high strength. Films 3 are arranged in parallel with each other with a gap between them by frame-shaped spacers 4 provided between their peripheral edges. As a method for forming the protrusions 6 of the highly insulating film 3, for example, a method of optically baking a high-resistance photoresist is relatively easy. A sealed chamber 1 is formed between the electrode 2 and the highly insulating film 3 disposed via the spacer 4, and a radiation absorbing liquid 5 with high radiation absorption efficiency is contained in this chamber. It is full. Further, on the side surface of the spacer 4, a radiation absorbing liquid 5 is provided in the chamber 1.
An injection tube 7 for filling and discharging the liquid is provided, and the opening of the injection tube 7 is closed by a stopper 8.

Note that the electrode 2 with high radiation transmittance is as follows:
For example, a plastic substrate with Cr vapor-deposited may be used as the highly electrically insulating film 3.
Polyester or the like with a thickness of about 25 μm is used, and the gap between them is set to about 1 mm. Further, the radiation absorbing liquid 5 filled in the chamber 1
For example, a liquid prepared by dissolving CBr ₄ in the same weight as Ccl ₄ is used. The liquid 5 is
After removing moisture and impurities, a very small amount of benzyl alcohol is added to reduce the volume resistivity to approximately 10 ¹² Ω.
Adjust to around -cm before use.

On the other hand, FIG. 2 shows an apparatus for obtaining a radiation image using the chamber 1, in which a subject 10 to be imaged is placed above the chamber 1, which is positioned below the radiation source 9. At the same time, the electrode 2 of the chamber 1 is grounded, and the highly insulating film 3
On the lower side, a highly insulating latent image receiving film 11 is provided so as to be in contact with the projections 6 of the highly insulating film 3, and a conductive supporting electrode 12 is provided in close contact with the latent image receiving film 11. A high voltage power source 14 is connected to the conductive support electrode 12 via a switch 13 so that a voltage can be applied as desired.
As the latent image receiving film 11, a polyester film having a thickness of, for example, 100 μm is used, and as the supporting electrode 12, aluminum or the like is used.

Next, the method for forming a latent image will be explained. First, while applying a DC voltage between the electrode 2 of the chamber 1 and the conductive support electrode 12, radiation such as X-rays is directed toward the subject 10 from the radiation source 9. shoot In the embodiment, between the electrode 2 and the conductive support electrode 12
Apply a DC voltage of 15000V for 0.15 seconds, and during that time, for example, 30mR for 0.1 seconds with a tube voltage of 75KVp.
(milliroentgen) X-rays were projected.

As a result, as shown in FIG. 3, the radiation-absorbing liquid 5 in the chamber 1 has a portion onto which the radiation is projected and a portion where the radiation is not projected because it is blocked by the subject 10.

The radiation-absorbing liquid in the area where the radiation was projected is
As the radiation is ionized according to the amount of radiation exposure, positive and negative ion pairs (or electron and positive ion pairs) are generated, and these ions are distributed between the electrode 2 and the semiconductor as shown in Fig. 4, depending on the polarity. It is attracted to the supporting electrode 12 side.

Furthermore, a high electric field is generated between the highly insulating film 3 onto which the radiation has been projected and the latent image receiving film 11 due to the movement of ions. A discharge occurs in the air gap, and this discharge generates positive and negative ions in the air gap.

As shown in FIG. 5, these ions move to the highly insulating film 3 and the latent image receiving film 11 according to their polarity, and the
An electrostatic latent image corresponding to the incident radiation dose is formed as shown in FIG. Since ion movement does not occur, the electric field generated between the highly insulating film 3 and the supporting electrode 12 becomes weaker by the distance where the radiation absorbing liquid 5 is present, so no discharge occurs in this area, and as a result, Since no movement of ions occurs, no electrostatic latent image is formed on the latent image receiving film 11 in this portion. In this way, an electrostatic latent image is formed on the surface of the latent image receiving film 11 in accordance with the amount of incident radiation, and the latent image receiving film 11 holding this latent image is separated from the chamber 1 and subjected to normal electrophotography. It can be visualized by performing development using a developer and a developing method. Note that the latent image is also formed on the surface of the highly insulating film 3 of the chamber 1 as an electrostatic latent image of opposite polarity. It is optional whether the latent image is visualized. Further, in the method of the present invention, the chamber 1 is used simply as a switch that operates in response to radiation, and in particular, the highly insulating film 3 of the chamber 1 is sandwiched between the latent image receiving film 11 and the support electrode 12. It can be made thinner, thereby increasing resolution. Furthermore, since the latent image can be transferred to a film separate from the chamber 1, it is advantageous from a practical point of view, such as easy development. In addition, prior to image formation, the highly insulating film 3 of the chamber 1 is
If the highly insulating film 3 and the latent image receiving film 1 are uniformly charged in advance with charges of appropriate polarity,
The electric field strength applied to the gap formed by the protrusions 6 between the protrusions 6 and 1 can be increased. At this time, the applied voltage is determined according to the charging, but for example, 1.3×10 ^-3 coulomb/
If a charge is applied with a density of cm ² , a voltage of 9000 V is preferably applied between the electrode 2 and the support electrode 12 . Further, the projections 6 of the highly insulating film 3 are for forming a gap between the highly insulating film 3 and the latent image receiving film 11, and are not on the side of the highly insulating film 3, but on the latent image receiving film 11. It may be provided on the side of the receiving film 11, and it may be formed with unevenness not only by photoresist but also by a chemical or mechanical method. Also, latent image receiving film 1
Short-circuiting the electrode 2 and the support electrode 12 when separating the support electrode 1 from the chamber 1 also produces good results for stable transfer of the latent image. Furthermore, the X-ray absorbing liquid used in the present invention includes Ccl ₄ , CH ₂ I ₂ , CH ₂ BrI, which are liquids at normal temperature and pressure.
_CH2clI , _C2H5I , _CHBr3 , etc. can be used, and _CBr4 , Xe, Kr, etc., which have high X-ray absorptivity, dissolved in a solvent can also be used _. Furthermore, the method of the invention should not only be applied when using materials with a volume resistivity ^of less than 10 ¹³ Ω-cm, e.g.
The use of an ohm-cm x-ray absorbing liquid is equally applicable, provided that appropriate methods are used to remove residual charges prior to repeated use of chamber 1.
The elements constituting the chamber 1 and the latent image receiving film 11 do not need to be particularly special;
Because of the role of the latent image receiving film 11, it is necessary to retain the electrical latent image for a sufficiently long period of time, so it is desirable to use polyester, vinyl chloride, polycarbonate, or other so-called electrically insulating materials. I as a radiation absorbing liquid;
When a liquid containing atoms such as Br and F is used, these atoms exist in some dissociated form, so use a particularly chemically stable material to avoid submerging any part of chamber 1. It is desirable to do so. Preferred materials for the highly insulating film 3 include polyester resin, fluorinated resin, and epoxy resin. As a conductive material for electrodes,
Gold, platinum, chromium, carbon, etc. are easy to use.

As described in detail above, the present invention generates ions in the air gap existing between the highly insulating film 3 and the latent image receiving film 11 in a region exposed to radiation, and thereby forming the latent image receiving film. The electrostatic latent image is formed on chamber 11, and the charge pattern inside chamber 1 is transferred as it is,
Not only can it provide the same resolution as the internal charge distribution, but in the conventional electron radiography method that uses liquid, a latent image is formed on the surface that comes into contact with the liquid, so it is possible to prevent the latent image from disappearing. 10 ¹³
It is quite difficult to obtain a radiation-absorbing liquid with a volume resistivity of Ω-cm or more, and it is also easily hydrolyzed by minute amounts of moisture in the atmosphere. While it is extremely difficult to maintain a volume resistivity of 10 ¹³ Ω-cm or higher, charge movement occurs in the non-radiation area within a very short period of time during which radiation is projected to form a latent image. If you do not do this, there will be no problem such as the latent image disappearing after it is formed, and therefore it will not be possible to
Since it is not necessary to use a material with a high volume resistivity such as 10 ¹³ Ω-cm, material selection becomes easy.
In addition, since the radiation-absorbing liquid is completely sealed, there is no risk of it being hydrolyzed by contact with the outside air, and there is no risk of contamination with soluble impurities or non-soluble impurity particles due to repeated use. , there is no risk that the characteristics will be affected. This method is very economical because the device itself can be simplified, and the electrostatic latent image obtained can be easily visualized and transferred using a known electrophotographic development method, so it is specially There is no need to manufacture a developing device or the like.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a sectional view of a chamber used in the method of the present invention, FIG. 2 is a schematic explanatory diagram of the method of the present invention, and FIGS. be. 1 is a chamber, 2 is an electrode, 3 is a highly insulating film, 5 is a radiation absorbing liquid, 6 is an insulating projection, 9 is a radiation source, 10 is a subject, 11 is a latent image receiving film, 12 is a conductive support electrode .

Claims (1)

[Claims] 1. A chamber 1 is formed by filling a radiation absorbing liquid with high radiation absorption efficiency between an electrode 2 with high radiation transparency and a highly insulating film 3 placed parallel to this electrode 2 with a gap between them. A latent image receiving film 11 is provided on the highly insulating film 3 in this chamber 1 with air gaps formed by interposing a large number of insulating protrusions 6, and the latent image receiving film 11 is After providing a conductive support electrode 12 in contact with the conductive support electrode 12, radiation is irradiated toward the subject 10 on the chamber 1 while applying a high voltage between the electrode 2 and the conductive support electrode 12. , generating ions in the air gap existing between the highly insulating film 3 and the latent image receiving film 11 in the area exposed to radiation to form an electrostatic latent image on the latent image receiving film 11; An image forming method using electroradiography, characterized by: