JPH04155297A - Highly sharp x-ray fluorescence sensitive paper - Google Patents

Abstract

PURPOSE:To improve sharpness with preventing a reduction of sensitivity by letting the quantity of 2/3 or more of the dyes in a phosphor layer of X-rays fluorescence sensitive paper containing dyes exit position in the layer near a carrier. CONSTITUTION:It is desirable from the point of compatibility of sensitivity and sharpness that dyes are contained in a phosphor layer of this intensifying screen is contained in quantity of 2/3 or more or preferably of 70% or more of the total dyes in a half side near a carrier about the total thickness of the phosphor layer. The method making solutions of different dye contents multilayer coating in two or more layers is general as a method changing dye contents of the carrier side and the protective side in the phosphor layer. The dye solution is usually added to the phosphor coating solution to let the dyes contain in the phosphor layer but it also is desirable that the dyes are dispersed and added as powder. Thus, the generation of scattered light and the arrival of crossover light to a sensitive material of the opposite side are prevented by making the dye concentration at the carrier side more and the sensitivity reduction can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an X-ray fluorescent intensifying screen, and more particularly to an X-ray fluorescent intensifying screen that has good sharpness and high sensitivity.

[Background of the invention]

When taking medical X-ray photographs, in order to convert the wavelength of X-rays that have passed through the subject into the wavelength range that silver halide photosensitive materials are sensitive to, the X-rays are first absorbed by a phosphor screen.
It is exposed to light according to the intensity of fluorescence in the sensitive wavelength range generated by radiation stimulation, and an X-ray image is created by development processing.

The phosphor screen may be an intensifying screen for direct photography depending on the application.
There are fluorescent screens for indirect photography (generally called intensifying screens) and fluorescent screens for indirect photography (fluorescent screens, generally called fluorescent screens), in which a phosphor that emits fluorescence when exposed to X-rays is coated on a support that does not interfere with X-ray photography. established,
Generally, the formed phosphor layer is further covered with a protective layer.

The X-ray film used for photography has photosensitive layers coated on the front and back sides of the film support (double coating), so the intensifying screen is applied to each photosensitive layer to increase light reception efficiency. For fluorescent screens, leaded glass is provided on the camera side to block X-rays.

Both the intensifying screen and the fluorescent screen allow X-rays to pass through an object such as a human body and become an image X-ray flux having a pattern of intensity and weakness, and the image X-ray flux stimulates the phosphor particles in the core layer absorbed by the phosphor layer. The X-ray film generates fluorescence and becomes an image fluorescent flux, and the X-ray film is exposed to the image fluorescent flux to form a fixed image.

For diagnostic purposes, X-ray images require high sharpness and high image quality, and due to the effects on the human body, short exposure times, that is, high sensitivity are desired. However, the effect of the fluorescent sensitizer paper or fluorescent screen used is also large.

There are two types of fluorescent intensifying screens: the regular type, in which the phosphor emits blue light, and the ortho type, in which the phosphor emits green light.

The former is calcium tungstate, and the latter is a phosphor such as rare earth-activated lanthanum oxypromi-deutrium tantalate and gadolinium oxysulfide, which has an X-ray conversion efficiency of at least 1 compared to that of calcium tungstate. .5 times. Moreover, since the photosensitive materials used are combined with regular and orthophotosensitive materials, there is a fairly large difference in sensitivity as a system.

In the phosphor layer of these intensifying screens, the emitted light hits the support and is reflected, causing so-called halation, or is scattered, causing irradiation. Furthermore, as mentioned above, X-ray photosensitive materials have emulsion layers coated on both sides, and each is sensitized. The paper is stuck together. This causes a so-called crossover. Crossover refers to the fact that the phosphor emission from one side of the intensifying screen passes through the emulsion layer and is exposed to the emulsion layer on the opposite side.

All of the above phenomena reduce sharpness and degrade image quality.

As a countermeasure to this problem, it is desirable to reduce the thickness of the phosphor layer, but this results in a decrease in sensitivity. Therefore, a method is generally used to absorb undesirable scattered light and improve sharpness by adding a dye. However, even with this method, a decrease in sensitivity occurs.

In particular, the regular type emits blue light, and adding a blue absorber, such as a dye such as an ultraviolet absorber, significantly lowers the sensitivity and is hardly ever applied in practice.

In the case of orthotypes, there are examples of using dyes such as those described in US Pat. The current situation is that

[Purpose of the invention]

In order to solve the above-mentioned problems, an object of the present invention is to provide an X-ray fluorescence intensifying screen that has high sharpness and less decrease in sensitivity.

[Structure of the invention]

The above object of the present invention is to provide an X-ray fluorescence intensifying screen containing a dye, characterized in that two-thirds or more of the dye in the phosphor layer is present in a layer close to the support. This is achieved by an intensifying screen.

The present invention will be explained in more detail below.

The dye contained in the phosphor layer of the present invention is contained in the half of the total thickness of the phosphor layer near the support, which accounts for 2/3 of the total amount of dye.
The content is preferably 70% or more from the viewpoint of compatibility between sensitivity and sharpness. The method of changing the dye content on the support side and the protective layer side in the phosphor layer is not particularly limited, but a common method is to coat two or more layers of coating solutions with different dye contents.

In order to incorporate a dye into the phosphor layer, a dye solution is usually added to the phosphor coating solution, but the dye may also be dispersed and added as a powder.

In the present invention, as mentioned above, by increasing the dye concentration on the support side, scattering light such as Halley/con and irradiation can be generated, and crossover light can be produced on the opposite side of the photosensitive material! = to prevent the dye from reaching the target and reduce the dye concentration on the side closer to the photosensitive material! This effectively utilizes the phosphor emission from the photosensitive material to prevent a decrease in sensitivity.

The dye used in the present invention is not particularly limited in terms of its ability to absorb the scattered light; blue-absorbing dyes are effective for blue-emitting phosphors, and green-absorbing dyes are effective for green-emitting phosphors. For example, finely dispersed carbon black In the case of orthotype green-emitting phosphors, blue-absorbing dyes have been found to be effective in terms of sensitivity. M;
is preferably a blue dye that also has green absorption.

Examples of such dyes include the following yellow dye described in US Pat. No. 4,259,588.

CH3 The above dyes are particularly useful for terbium-activated gadolinium phosphors. The maximum green emission of this phosphor is 545 nm, and the maximum blue emission is 440 and 490 nm.

The above dye has maximum absorption around 490 nm, so it is effective in small amounts.

The general structure of an intensifying screen is to provide a phosphor layer on a support and a protective film layer on top of the phosphor layer.

Various polymeric materials can be used as the support for the intensifying screen of the present invention.

Furthermore, in terms of handling, it is preferable to use a material that can be processed into a visible sheet or web, and from this point of view, for example, cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, polycarbonate film, etc. Plastic films are preferred.

The layer thickness of these supports varies depending on the material of the support used, but for boat fishing it is 80 μm to 1000 μm, and from the viewpoint of handling, it is more preferably 80 μm to 50 μm.
It is 0μ crane.

The surface of these supports may be a smooth surface, or may be a cloak surface for the purpose of improving adhesion to the phosphor layer.

Furthermore, these supports may be provided with an undercoat layer on the surface on which the phosphor layer is provided for the purpose of improving adhesion to the phosphor layer.

Phosphors used in the present invention include conventionally known CatOt, Gd102SiTb, ZnSiAg, etc., as well as those described in Japanese Patent Application Laid-open Nos. 50-116268 and 1986-52.
-115685, Special Publication No. 55-33560, same 5g
- Phosphors disclosed in No. 2640, etc., or Japanese Patent Application Laid-open No. 1973-
No. 80487, No. 51-29889, No. 54-478
No. 83, No. 57-148285 and No. 58-8048
The phosphor disclosed in No. 8 and the like is used.

The phosphors used in the intensifying screen of the present invention are specifically described below.
Y, O, S: Tb, GdxOxS:
Tb, La, OxS: Tb.

(Y, Gd)zOzs: Tb, (Y, Gd), 0.
5: Tb, T intestine, y, o, s: Eu, Gd2O
2S: Eu1(Y,Cd)toss: Eus
YzOs' EL1%Gd201: EL1% (
Y, Gd)zOa: Eus YVO4: Eus
YPO4' Tb5GdPO4: Tb, LaPO4
: Tb, YPO, : Eu%La0Br : Tb
.

La0Br: Tb, Tm, La0Br: Ce,
La0Cff: Tb, La0Cff: Tb,
Ts, La0(jl: Ce, Gd0Br: T
b,,Gd0CI2: Tb.

Ca1FO,, CaWO: Pb, MgWOi Ba5
O,: Pb, BaSO4:E,! +, (Ba, 5r
) So, : Eu”, Ba3(Po4)z :E””
, (Ba.

5r)x(pot)z: Eu”, BaFC+Q:
Eu”, BaFBr: Eu”, BaFCQ: E
u”, Tb, BaFBr: Eu”, Tb, Ba
Fx, BaCL.

1 [Cff: Eu”1 BaF, , BaCL, Ba
5O,, Ki: Eu”, (Ha, Mg)Fx, Ba
C(1, KCn: Eu”, Csl:
NB% Csl: TQ, Nap% 2nS
: Ag, (Zn, Cd)S: kg,
ZnS: Cu, ZnS: Cu.

An, (Zn, Cd)S: Cu, CZn, Cd)S
: Cu, Al1. (Zn, Cd)S: Au, Af
f%HfP, Or: Examples include X-ray phosphors such as Cu.

The average particle diameter of the phosphor used is 0.1 to 100 μm, preferably 1 to 30 μm, in consideration of the sensitivity and granularity of the phosphor. These phosphors may be used in combination.

In the intensifying screen of the present invention, the above-mentioned phosphor is applied by a vapor deposition method such as vapor deposition or by being dispersed in a suitable binder. As the binder, binders commonly used for forming layers such as proteins such as gelatin, polyvinyl butyral, polyvinyl acetate, ethyl cellulose, vinyl chloride-vinyl acetate copolymer, polyurethane, etc. are used. Generally, the amount of binder is 0.0% per part by weight of the phosphor. It is used in a range of 1 to 1 part by weight.

However, in terms of the sensitivity and sharpness that can be obtained, it is preferable to use less binder, and from the viewpoint of ease of application, 0.
A range of 0.03 to 0.2 parts by weight is more preferred.

The layer thickness of the phosphor layer of the intensifying screen of the present invention varies depending on the sensitivity of the intensifying screen to radiation, the type of phosphor, etc., but when formed by vapor deposition and does not contain a binder, it is lθμm to 1000μm.
It is preferable that the grain size is selected from the range of 20 μm to 800 μm, and 10 μm if it contains a binder.
m-1000μm, more preferably 50μ-~500μ
(2), more preferably selected from the range of 90μ11 to 300μ2.

The material for the protective layer used in the present invention is preferably moisture resistant; for example, cellulose acetate,
polycarbonate, polyvinyl acetate, polyacrylic acid,
Polymethacrylic acid, polyethylene terephthalate, polyethylene, polyvinyl chloride, polyamide (nylon),
Examples include polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and polystyrene.

Further, thermosetting resins or photocuring resins such as epochene resins, alkyd resins, amino resins, unsaturated polyester resins, polyurethane resins, and silicone resins may be used.

゛ [Example] Next, the present invention will be specifically explained with reference to Examples.

Phosphor particles Gd2O□S:Tb2 with an average particle diameter of lOμ■
0vt% and polyvinyl butyral 2v as binder
A phosphor coating liquid (1) was prepared by mixing t% and 78vt% of butyl acetate to form a slurry.

■Preparation of an intensifying screen with a single phosphor layer Place the phosphor coating solution (1) on a glass plate and dry it with a doctor blade on the white support (250 μm thick) coated with the subbing layer. The amount of phosphor applied after is 40mg/c■
1. The coating was applied evenly to a thickness of 140 μm.

Immediately after application, put it into a dryer and gradually raise the temperature inside the dryer to 25-100°C to dry.
. On top of this phosphor layer, a transparent film of polyethylene terephthalate with a thickness of 12μ and pre-applied with a polyester adhesive is glued with the adhesive side facing down.
A transparent protective film is formed and intensifying screen No.

1 was created.

In addition, the dyes shown in Table 1 were added to the phosphor coating liquid (1) in the amounts shown in Table 1 per unit area for coloring.

The coating liquid was applied and dried in the same manner as above, and a fluorescent intensifying screen N was prepared. .

2-3 were created.

(2) Preparation of an intensifying screen having two phosphor layers The dyes listed in Table 1 were added and dissolved in the amount shown in Table 1 per unit area in the phosphor coating liquid (1).

This coating solution was placed on a glass plate and a subbed white pigment support (thickness 250μ■) was coated with a doctor blade so that the phosphor coating weight after drying was 20mg/c■2 and the thickness was 7.
It was applied uniformly so that the thickness was 0μ. The support with the coating film formed thereon is immediately placed in a dryer, and the temperature in this drying path is gradually raised to 25 to 100°C to dry the coating film and remove the first (lower) phosphor layer. Created. Next, a second layer was applied on top of the first phosphor layer. The tjg2 layer was created in the same manner as the first layer except that the amount of dye was changed to the amount listed in Table 1.

On this second layer, a protective film layer similar to that in the case of the single layer (1) was formed, and two-layer phosphor intensifying screens No. 4 to No. 15 were prepared.

Sensitivity and sharpness were measured using the following photosensitive materials.

Preparation of photosensitive material A pattern similar to emulsion number 1-5 in Examples of JP-A-59-178447 with an average grain size (area average grain size) of 0.4.
Silver iodobromide monodisperse particles of 8 µm were prepared and subjected to chemical maturation by adding thiocyanate at 1.8 x 10-'' mol per mol of silver and optimal amounts of chloroauric acid and hypo. 8X 10-' moles of potassium iodide per mole of silver were added, followed by the addition of sensitizing dyes (A) and (B) as shown below.
500 mg per mole of silver, respectively.

The following emulsion coating solution containing the following additives was prepared using particles to which 25 mg was added and adsorbed at 55° C. for 1 minute. The emulsion coating solution had a silver content of 2.3 g per side of the support.
■ Apply the following protective layer solution on top of it so that the amount of gelatin is 0.98g/■2 7Qs/
It was coated on both sides at the same time at a speed of 2.00 to 30.00 and dried for 2 minutes and 25 minutes.

Sensitizing dye (A) Sensitizing dye (B) (Composition of emulsion coating solution) Per 1Q of coating solution (a) Lime-treated ossein gelatin 51g (b) 5
-Methyl-1,3,4,7a-tetrazeindene-7-
All 1.2gCC'') Silver halide grains 0.6mol (d) S)I (e) Nitrone 0.05gCI)
Copolymer fine particles of styrene and styrene (average particle size 0.03 μm) 2.5 g (g) Copolymer of styrene and maleic acid 1.5 g (h) 2.2-dihydroxy/methyl-1-butanol g (protective layer liquid) Composition) 49 lime-treated inert gelatin 68 g per coating solution Iff, acid-treated gelatin 2 g.

CH, -α soc, IIH! 1 ■ NaO,5-CH-COOCJ,.

1.0 g, 30 g of Ludox AM (colloidal silica, manufactured by DuPont), 1.2 g of trimethyl methacrylate particles (projected area average particle diameter 3.5 μm),
2.4-Dichloro-6-hydroxy-1,3,5-triazine sodium salt aqueous solution (2%) IIQ Formalin aqueous solution (35%) 0.8+f
f Also, antistatic agent dispersion (below) 140 ■Q Product name Megafac F-'172 (manufactured by Dainippon Ink Chemical Co., Ltd.) 0
．． 6g was dissolved in tricresyl phosphate (hereinafter abbreviated as TCP) Ig and ascent lOg, and 5g containing sodium triisopropylnaphthalene sulfonate Ig was added.
A dispersion liquid (dispersion liquid) processed in vt% gelatin aqueous solution 601IQ, dispersed in a Manton Goring dispersion system, emulsified and dispersed to an average particle size of 0.5μ or less, and evaporated to reduce Ascent to 2WL% or less. Mega Futsuku F per 70mQ
-172 (containing 0.6g) was prepared.

(Method of Measuring Sensitivity) The above double-sided emulsion medical X-ray film was sandwiched between two fluorescent intensifying screens with the same numbers 1 to 15 in Table 1, and a Wratten filter No. was applied to a JISB light source.

58 (E, made by Kodak paper) and insert o, og.
Stepwise exposure for o seconds was performed. This sample was processed using an automatic processor K.
Developer solution XD-90 with X-500 (manufactured by Nika Co., Ltd.)
(ff=manufactured by Chikara Co., Ltd.). Sensitivity is expressed as the reciprocal of the amount of light that gives a blackening density of fog + 1.0 of the exposed sample photographed using fluorescent intensifying screen No. 1 in Table 1.
The relative sensitivity was set to 0.

(Method for Measuring Sharpness) MTF was measured to determine sharpness. Using the same film used when measuring the sensitivity, it was sandwiched between two fluorescent intensifying screens with the same number shown in Table 1, and a square wave chart was photographed. The development method was the same as in the sensitivity measurement.

The MTF was measured by the contrast method and showed a value of 2.0 lines and 7 am of MTF spatial frequency.

The higher the MTF value, the higher the sharpness.

According to Table 1, samples No. 7 to No. 15 of the present invention are comparative samples. It can be seen that the sensitivity is higher and the higher TFT (MTF) can be obtained compared to No. 2.3.

〔Effect of the invention〕

According to the present invention, it was possible to provide a fluorescent intensifying screen with high sharpness and high sensitivity.

Claims (1)

[Claims] An X-ray fluorescence intensifying screen containing a dye, characterized in that two-thirds or more of the dye in the phosphor layer is present in a layer close to the support.