JPS6025473B2 - X-ray fluorescent film - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an X-ray fluorescent screen such as an X-ray intensifying screen, an
It relates to fluorescent films such as the input surface of line fluorescence multiplier tubes.

[Technical background of the invention and its issues]

The intensifying screen will be described in detail as the main application of the present invention.

The intensifying screen 1 is used with a film 3 interposed therebetween as shown in FIG. 1, and emits light when stimulated by X-rays, and the film is exposed to light by the emitted light. A portion of the incident X-rays is absorbed by the intensifying screen 1 located at the front of the film, and further absorbed by the intensifying screen 2 located at the rear of the film. Intensifying screen 1 due to X-ray absorption
and 2 emit light, and the film 3 is exposed to light by the emitted light. Conventionally, in order to improve the image quality of film, studies have been made on the type of phosphor applied to the intensifying screen, the structure of the intensifying screen, etc. Regarding phosphors, phosphors with high X-ray absorption and high luminous efficiency have been developed, and CaW0, which is currently used, has been developed.
Other than 4, ○Bte/Tb, (Y, Gd)2QS/Tb,
As for La2QS/Tb and G, 02S/Tb and the like have been studied and put into practical use. Regarding the intensifying structure, for example, by making the phosphor layer multi-layered and reducing the luminous efficiency of the layer near the film, it is possible to reduce the X-ray quantum/width, or by using a colored intensifying screen mount. By absorbing the emitted light from the phosphor, the scattering of light reflected by the mount is eliminated and the contrast of the image is improved.

[Purpose of the invention]

The present invention was made in order to satisfy the above-mentioned conventional demands, and it is an X
The line aims to provide a fluorescent waist.

[Summary of the invention]

The present invention uses CaWQ as a matrix, Cu, Fe, Mn, Sn
, Co, Ni, and Ti.

In other words, the present invention differs from the conventional ones and is based on a new idea, in which a portion of the emitted light from the phosphor is absorbed by the phosphor's own body color, reducing light scattering and improving image contrast and resolution. The aim is to reduce the quantum noise of X-rays by using a multilayer colored fluorescent layer.

FIG. 2 shows an intensifying screen according to an embodiment of the present invention, in which a colored phosphor 11 is coated in one layer on a base 12 made of cardboard. Considering the component A perpendicular to the intensifying screen surface and the component B directed from the perpendicular direction to the light emitted from the phosphor particles 11a in the figure, it is clear that the optical path until it reaches the film 13 is B. It will be longer. By the way, the rate of decrease of light in the middle of the optical path increases in the colored fluorescent layer, so A,
The difference in intensity of B light on the film surface is much larger than in the conventional case without body color. Moreover, the difference becomes larger as the turbulence from the vertical direction of the light increases, and as a result, the scattering of light within the intensifying screen is greatly reduced, and the contrast and resolution of the image are improved. Figure 3 shows a two-layer intensifying screen.
Figure 2 and the part with the same number show the part of the aircraft. Here, the C layer of the fluorescent film 14 is a colored phosphor layer, and the D layer is a non-colored phosphor layer. The effect is that the body color of the C layer reduces light scattering and improves contrast, and the C layer near the film surface absorbs X-rays because of its body color, the emission intensity is lower than that of the D layer, which is farther from the film surface. The density of light emission due to the variation in light emission is reduced on the film surface, resulting in a reduction in quantum/is. FIG. 4 shows a three-layer coating intensifying screen, in which a three-layer fluorescent film 15 is coated on a substrate 12.

The E and G layers are colored phosphor layers, and the F layer is a phosphor layer with no body color or a very weak body color. The E layer is weakly colored, and the G layer is strongly colored. The effect is that the strong body color of the G layer weakens the light reflected from the mount, improving the contrast, and as in the case of FIG. 3, the effects of the E and F layers reduce quantum noise. As the colored phosphor described here, for example, a phosphor based on CaW04 can be used.

When 0.01 to 1.0% of Cu is added to give body color, a phosphor having a reflection spectrum as shown in FIG. 5 can be obtained. Due to this body color, the short-wave most side of the emission of the CaW04 phosphor, which has an emission peak at about 43 points in the secondary column, is absorbed. FIG. 6 shows the relationship between the amount of Cu and the luminous efficiency, and when the amount of Cu is 0.01%, the efficiency decreases by about 10%.

In addition to Cu, the body color can also be imparted by adding up to 1.0% by weight of Fe, Mn, Co, Ni, Ti, etc. FIG. 7 shows the reflection spectra depending on the body color when Fe, Mn, and Sn elements are added. [Embodiments of the Invention] Specific embodiments will be described below.

Example 1 A CaW04 phosphor containing 0.01% Cu is made.

First, CaW04 precipitates 10 females and CuS04 spots 200.0
Add 3 foundations, CaCL2/Gen 2020 Yu and pure water to dissolve and mix well. The mixed powder obtained by drying this is 700~8
A phosphor is obtained by firing at 00°C for 3 to 6 hours and washing the resulting fired product with water to remove CaCL2. This phosphor has a weak body color and absorbs some of the emitted light. Luminous efficiency is approximately 5
-10% reduction, but this reduction can be overcome by increasing the size of the phosphor particles. In other words, the emission intensity when excited by X-rays changes depending on the particle size, and the emission intensity is reduced by 10%.
To increase the particle size, increase the particle size by about 2 degrees. This saddle phosphor is coated in a single layer as shown in Figure 2 to make an intensifying candle, and compared with a conventional intensifying screen of the same sensitivity in terms of contrast and resolution. As shown in Fig. 9, if we take the response function (MTF) with spatial frequency as its axis, we can see that the contrast and resolution of the large medium are improved compared to the conventional one. Example 2 As shown in FIG. 3, the phosphor layer is divided into two layers, and the C layer is Cuo. CaW○4 phosphor containing 1% D
The conventional colorless CaW4 phosphor layer is coated to a thickness of 50 mm each.

The emission intensity of the C layer is about 83% of that of the ○ layer. Such an intensifying screen reduces light scattering and at the same time reduces X-ray doji noise. In other words, since X-rays are selectively absorbed by the intensifying screen, dark and light spots appear on the film, blurring the details of the image, but with the above-mentioned intensifying screen, the emission of light from the C layer near the film surface. Since the light emission from the D layer, which is separated from the film surface, is weak and the light emission is strong, the difference in intensity of light reaching the film surface is smaller than that of conventional screen screens, and quantum noise is reduced by about 15% compared to the conventional screen. Example 3 As shown in FIG. 4, phosphor is applied in three layers.

Cuo. in the E layer. Apply 30r' of CaW04 containing 1%, apply 60r' of conventional CaW04 to the F layer, and apply C to the G layer.
ul. Apply 20 coats of 0% CaW04. The G layer is a phosphor layer with a strong body color. This three-layered Kasukanori is G
The light absorption of the layer prevents light reflection by the mount and improves the contrast. At the same time, the E and F layers reduce X-ray quantum noise with the same effect as in Example 2, so compared to the conventional one, as shown in Figure 10. The contrast resolution was improved to a large extent, and the quantum noise was reduced by about 10% compared to its predecessor. Example 4 Similar effects were obtained by using CaW04 containing 1% Sn in place of CaW04 containing 0.01% Cu in Example 1.

Example 5 CaW containing 0.001% Fe in the C layer in Example 2
A similar effect can be obtained using 04, with a quantum/z of 10%.
Diminished.

Example 6 CaW0 containing 0.01% Mn in the G layer in Example 3
Similar effects can be obtained by using CaW04 containing 1.0% Sn in the 4 or E layer, improving contrast and resolution.
In addition to these examples in which quantum noise was reduced by 8%, CaW0
0.001 of Ni, Co, and Ti to give the body color of 4.
% or more may be included.

Although the above embodiments 1 to 6 have been described with reference to intensifiers, similar effects can be obtained by using a similar phosphor film as an input phosphor screen of an X-ray fluorescence intensifier.

[Brief explanation of the drawings] Figure 1 is a schematic cross-sectional view of a conventional intensifying screen, Figures 2 to 4 are cross-sectional diagrams of an intensifying screen, and Figures 5, 7, and 8 are phosphor screens. Figure 6 shows the reflection spectrum distribution of
The luminous efficiency of W04, FIGS. 9 and 10 are diagrams showing the relationship between the spatial frequency of the sensitizer and the sponse function. 11... Colored phosphor, 12... Substrate, 13
...Film. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 7 Figure 6 Figure 8 Ship diagram Ball

Claims (1)

[Claims] 1 CaWO_4 as a matrix, Cu, Fe, Mn, Sn
, Co, Ni, and Ti. 2. The X-ray fluorescent film according to claim 1, wherein when the metal is Cu, the metal content is 0.01 to 1.0% by weight based on the base material. 3. A patent claim characterized in that when the metal is at least one of Fe, Mn, Sn, Co, Ni, and Ti, the metal content is 0.001 to 1.0% by weight based on the base material. The X-ray fluorescent film according to item 1.