JPS61170740A - Intensifying screen - Google Patents

Abstract

PURPOSE:To enhance the diagnostic capacity of radiography for medical treatment by coloring a phosphor layer with a coloring agent having the principal peak of an absorption spectrum in a specified wavelength range. CONSTITUTION:When an intensifying screen is composed essentially of a support and a phosphor layer of a green luminous phosphor formed on the support, the phosphor layer is colored with a coloring agent having the principal peak of an absorption spectrum in the wavelength range of 420-540nm. Lu2O2S:Tb or Lu2O2S may be used as the green luminous phosphor, and the coloring agent is selected among yellowish orange or red dyes or pigments each capable of absorbing part of light having about 500nm wavelength in light emitted from the green luminous phosphor. It is preferable that the coloring agent is selected among the dyes because the dyes enable uniform coloring. The sharpness of the intensifying screen can be remarkably enhanced, and the graininess is also improved.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention provides an orthochromatic type X-ray film (
The present invention relates to an intensifying screen that, when used in combination with an "orthofilm" (hereinafter referred to as "orthofilm"), provides an X-ray photograph with improved photographic image quality, particularly sharpness.

``Prior Art'' As is well known, intensifying screens are used in various fields such as medical X-ray photography such as X-ray photography for the purpose of medical diagnosis, and industrial radiography for the purpose of non-destructive testing of materials. To improve the sensitivity of the shooting system during shooting! It is used in close contact with Ic X-ray film. This intensifying screen basically consists of a support such as paper or plastic and a phosphor layer provided on one side of the support.

The phosphor layer has a phosphor that emits high-intensity near-ultraviolet, blue or green light when excited by radiation, dispersed in a binder resin, and the surface of this phosphor layer (the surface opposite to the support) is Generally polyethylene terephthalate membrane, cellulose acetate membrane,
It is protected by a transparent protective layer such as a polymethacrylate film.

By the way, in addition to the high sensitivity of intensifying screens,
It is important that the photographic image quality is good, but as a method to improve the photographic image quality, especially the sharpness, of an intensifying screen, for example, the arrangement of the phosphor particles in the phosphor layer is fixed with respect to the particle size. A method of arranging with the regularity of
No. 560), a method of coloring a phosphor layer by varying the degree of coloring from one side to the other (Japanese Patent Application Laid-Open No. 1983-
70787) etc., various methods are being considered.

"Problems to be Solved by the Invention" The present invention has a phosphor layer made of a green-emitting phosphor, and when used in combination with an orthofilm, can improve diagnostic performance, especially in medical radiography. The purpose of this invention was to provide an intensifying screen with good photographic image quality, especially sharpness.

The present inventors have focused on the fact that by coloring the phosphor layer of an intensifying screen, the photographic image quality of the resulting intensifying screen can be improved. and,
As a result of various studies regarding the relationship with the sharpness of the resulting intensifying screen, we found that the phosphor layer of an intensifying screen uses a phosphor layer that emits near-ultraviolet light or blue light when excited by radiation. f
It has been discovered that the photographic image quality of an intensifying screen can be improved by coloring it with a colorant having a main absorption spectrum peak in the wavelength range of 400 nm to 600 nm,
Although it was proposed in Japanese Patent Application No. 59-216435, Gd
The phosphor layer of an intensifying screen using a phosphor layer that emits green light when excited by radiation, such as 2O2S:Tb phosphor or La0Br:Tb phosphor, selectively emits light of a specific wavelength. The inventors have discovered that the quality of photographic images can be improved by coloring with a coloring agent that can be absorbed by the intensifying screen, especially when this intensifying screen is used in combination with an orthofilm, leading to the completion of the present invention.

"Means for Solving the Problems" That is, the intensifying screen of the present invention essentially consists of a support and a phosphor layer comprising a green-emitting phosphor provided on the support. The paper is characterized in that the phosphor layer is colored with a colorant having a main absorption spectrum peak in a wavelength range of 420 nm to 540 nm.

The present invention will be explained in detail below.

The intensifying screen of the present invention is manufactured as follows.

First, green-emitting phosphor particles that emit green light when excited by radiation and a coloring agent are mixed with a binder resin such as nitrified cotton, and an appropriate amount of solvent is added to this to obtain the optimal viscosity of the fluorescein. A phosphor coating solution is prepared, and this phosphor coating solution is applied to paper using a roll coater, knife coater, etc.

It is coated onto a support made of plastic or the like to form a phosphor layer. In addition, in the case of a structure having a light reflection layer, a light absorption layer or a metal foil layer between the support and the phosphor layer, a light reflection layer, a light absorption layer or a metal foil layer is placed on the support in advance. A phosphor coating solution is applied thereon and dried to form a phosphor layer. Then, if necessary, a protective layer such as a transparent protective film is formed on the phosphor layer to obtain an intensifying screen. The method for forming the protective film is to prepare a resin coating solution for the protective film by adding an appropriate amount of solvent to a resin such as polymethacrylate or cellulose acetate to adjust the viscosity to the optimum level, then apply this onto the phosphor layer, and dry it. Alternatively, a method may be used in which a thin transparent film such as I-lyethylene terephthalate is laminated on the phosphor layer. In the intensifying screen of the present invention, the transparent protective film may be colored with the same coloring agent as that used to color the phosphor layer. Should I add a certain amount of coloring agent first? One or both sides of a transparent protective film such as polyethylene terephthalate is colored in advance with a coloring agent, and then this is laminated onto the phosphor layer to obtain the intensifying screen of the present invention in which the protective film is colored. . Also,
By coating a liquid mixture of phosphor particles and a coloring agent with a binder resin on a support, the τ solid phosphor particles settle to the bottom of the phosphor layer and the top of the layer becomes colored. The present invention also includes a case where the film is made of a binder resin and acts as a protective film.

The phosphor used in the phosphor layer of the intensifying screen of the present invention is Ln2O2S :T'b AIJn20□S :Tb
, TmShin202S:Tb, Dy.

LnPO4:Tb, LnPOa:'rb, Tm
4 LnPO4:Tb, Dy, (Zn1=X
, Cdz) S:Ag (However, Lnij: La
at least one of mGtl and Y, and Y
Only when the content exceeds 50 atoms/base cents of the total Ln content, the Tb content is O, OO 5 gram atoms or more, and X is a number that satisfies the condition 0.2≦x≦0.5. approximately 470 nm to 56 nm by radiation excitation, such as
The main peak of the emission spectrum is in the wavelength range of 0 nm,
A phosphor that emits green light is used.

In addition, as a coloring agent for coloring the phosphor layer of the intensifying screen of the present invention, 500% of the light emitted by the green-emitting phosphor mentioned above may be used.
Something that partially absorbs light in the wavelength range around 42 nm.
Various yellow-orange to red dyes and pigments having a main peak of absorption spectrum in the wavelength range of 0 nm to 540 nm can be used, but it is preferable to use dyes because they can be colored uniformly, and among them, fluorescent dyes are preferred. Orange dyes such as Solvent Orange 63, 68, 71, and 78, and Solvent Red 152, 155, and 176 because of their excellent compatibility with the binder resin in the light layer and the organic solvent in the phosphor coating solution. Oil-soluble dyes such as ゜177 and Dis/4-Thread)'5/
It is more preferable to use disperse dyes such as. In addition, from the point of view that the sharpness can be further improved, it is particularly important to
It is more preferable to use a red dye having a main absorption peak in the wavelength range of 5 nm.

Note that the degree of coloring of the phosphor layer by the colorant can be changed depending on the type of colorant used and the amount added.
In the intensifying screen of the present invention, if the degree of coloring is low, the sensitivity of the intensifying screen will not decrease much, but the sharpness will not improve much. On the other hand, if the degree of coloring is too high, the sharpness will improve but the sensitivity will decrease. Both are undesirable as they grow larger. Therefore, from a practical point of view, the degree of coloring of the phosphor layer is compared when comparing intensifying screens having phosphor layers with the same phosphor and coating weight, and when the phosphor layer is colored. It is preferable to adjust the photographic sensitivity so that it is in the range of 95% to 30% of that when the phosphor layer is not colored, and particularly in the range of 9(l to 50%).

Table 1 shows the sensitivity, sharpness, and granularity of intensifying screens (&1 to &8) with a phosphor layer made of Gd2O2S:Tb phosphor colored with an embedded dye when used in combination with orthofilm. The measured values are shown in comparison with those of the intensifying screen (R) in which the phosphor layer is not colored at all. The sensitivity can be adjusted by changing the thickness of the phosphor layer of each intensifying screen (phosphor coating weight) and the amount of dye added to the phosphor layer, so that the phosphor layer is not colored at all. The sensitivity was adjusted to be almost the same as that of the intensifying screen (R).

(Note 1) Sensitivity, sharpness, and graininess are relative evaluation values determined by using orthofilm and irradiating X-rays that transmitted through a 10-stroke water fan dome with 80 kV X-rays.

(Note 2) Sharpness is MTF at 2 spatial frequencies/■
Relative value of the value.

(Note 3) Graininess is evaluated visually: ◎, O1Δ, ×
This means that the graininess worsens in the order of .

As is clear from Table 1, Gd2O is used as a green-emitting phosphor.
□S: When using Tb, when comparing intensifying screens with almost the same sensitivity, there is a difference in the sharpness of the intensifying screen depending on the colorant (dye) used, and in the wavelength range of 420 nm to 540 nm. When using a colorant that has a main absorption spectrum peak in the wavelength range of 450 nm to 525 nm, the sharpness is higher than that of a conventional intensifying screen that does not use a colorant, and the main peak of the absorption spectrum is in the wavelength range of 450 nm to 525 nm. The sharpness of the intensifying screen is further improved when it is colored with a colorant having the following properties. In addition, Gd2O2S:
Even if other phosphors other than Tb are used, which have a main peak in the emission spectrum in the wavelength range of approximately 470 nm to 560 nm, the resulting intensifying screen will have the same sensitivity. However, the cost is several cents higher than that of an intensifying screen in which the phosphor layer is not colored. Therefore, the type of colorant used varies depending on the type of green-emitting phosphor used, but in the intensifying screen of the present invention, 4
It is preferable to use a colorant that has a main peak of its absorption spectrum in the wavelength range of 20 nm to 540 nm, and it is particularly preferable to use a colorant that has a main peak of its absorption spectrum in the wavelength range of 450 nm to 525 nm. .

Also, as is clear from this table, by coloring the phosphor layer with a colorant having a specific absorption spectrum distribution, the sharpness was significantly improved and the graininess of the intensifying screen was also improved.

Curve A drawn as a solid line in Figure 1 shows the result when the intensifying screen of the present invention, which has a phosphor layer made of Gd2O2S:Tb phosphor colored with Solvent Orange 68, which is an orange dye, is irradiated with X-rays. This is an example of a luminescent 4 vector, and the curve B drawn with a broken line has a phosphor layer made of the same <Gd2O□S:Tb phosphor, and is not colored by the phosphor layer. This is the emission spectrum when a conventional intensifying screen is irradiated with X-rays. 1st
As is clear from the figure 1, by coloring the phosphor layer of the intensifying screen with Solvent Orange 68, 480 nm in the emitted light of Gd2O2S:Tb, which is a green-emitting phosphor, can be detected.
It can be seen that the emitted light in the nearby wavelength range is attenuated by the absorption of the colorant. Furthermore, FIG. 2 shows an example of the spectral sensitivity curve of a commercially available orthofilm.
The reason why the sharpness is increased by coloring with a colorant having a main absorption spectrum peak in the 40 nm wavelength range, especially when used with Orntaig's film, is as follows.
As is clear from Figures 1 and 2, the spectral sensitivity of the film is relatively low (i.e., it is easy to pass through the film), and the phosphor layer strength in the wavelength range of 420 nm to 540 nm). This seems to be because a portion of the emitted light is selectively absorbed by the colorant in the phosphor layer, resulting in a smaller cross-over effect.

"Example" Example 1 Solvent Orange 71 having an absorption spectrum distribution shown by curve a in FIG. (Mitsubishi Chemical Industries KKMDIARESIN R
ED Z ) were mixed and thoroughly stirred to prepare a phosphor coating solution. The amount of Solvent Orange 71 added was adjusted so that the photographic sensitivity of the final intensifying screen obtained was 90% of the photographic sensitivity of an intensifying screen prepared in the same manner without the addition of Solvent Orange 71. The phosphor coating solution thus obtained was coated on a support made of polyethylene terephthalate using a knife coater so that the phosphor coating weight after drying was approximately 35 m9/cm, and then dried. Then, a solution of acetylcellulose was coated on the phosphor layer with a knife coater so that the film thickness after drying was approximately 10μ, and dried to form acetylcellulose. An intensifying screen (I) was obtained in which a transparent protective layer was formed and the phosphor layer was colored orange.

For comparison, Solvent Orange 71 was added to the phosphor coating solution.
Solvent Blue 90 (Mitsubishi Chemical Industries K K
If! An intensifying screen with a blue phosphor layer was prepared in the same manner as intensifying screen (1) except that the phosphor coating solution was exploded by mixing DIARESIN BLUE G. Intensifying screen (I) except that Solvent Orange 71 was not added to the phosphor coating solution and the phosphor coating solution was coated on the support so that the phosphor coating solution after drying became 321Ql tan wing. An intensifying screen (R) was prepared in the same manner as described above.

The intensifying screen (I) produced in this way was used in combination with an orthotag X-ray film.

The photographic sensitivity is almost the same as that of the intensifying screen (I') and the intensifying screen (R), and the MTF value, which is a measure of sharpness, is
- The sharpness was approximately 1.04 times that of paper (R), and the sharpness was significantly improved. On the other hand, the MTF value of an intensifying screen (I) whose phosphor layer is colored blue is about 0.9 of that of an intensifying screen (R).
It was 8 times larger, and the sharpness was lower.

Also, according to visual observation, the intensifying screen (I) had better graininess.

Example 2 Solvent Orange 68 (DIARESIN manufactured by Mitsubishi Chemical Industries, Ltd. KK) having an absorption spectrum distribution shown by the curve in FIG.
An intensifying screen (II) in which the phosphor layer was colored orange was obtained in the same manner as the intensifying screen (I) of Example 1 except that 0RANGE G) was used.

When the thus prepared intensifying screen (n) was used in combination with an orthotype X-ray film, the photographic sensitivity was as follows: It is almost equivalent to the intensifying screen (R) of Example 1 in which the phosphor layer is not colored, and the MTF value, which is a measure of sharpness, is about 1 of that of the intensifying screen (R). At .04x, the sharpness was significantly improved.

Furthermore, according to visual observation, the intensifying screen (II) had better graininess.

"Effects of the Invention" As described above, according to the present invention, the phosphor layer k of the intensifying screen is made of a green-emitting phosphor such as Gd2O2S:Tb.
The sharpness of the intensifying screen can be improved by coloring it with a colorant whose absorption spectrum has a main peak in the wavelength range of 420 nm to 540 nm and selectively absorbing a specific wavelength range of the light emitted by the green-emitting phosphor. In addition to significantly improving graininess, graininess is also improved.

[Brief explanation of the drawing]

FIG. 1 is a graph illustrating the emission spectra of the intensifying screen of the present invention and a conventional intensifying screen. FIG. 2 is a graph illustrating a spectral sensitivity curve of an orthofilm. FIG. 3 is a graph illustrating the absorption torque (wavelength dependence of absorbance when measured in a solution state) of main colorants. Patent applicant: Kasei Optonics Co., Ltd. Figure 1 Skin conduit (nm) Figure 2

Claims (1)

[Scope of Claims] 1) An intensifying screen consisting essentially of a support and a phosphor layer provided on the support with a green-emitting phosphor, wherein the phosphor layer has a wavelength of 420 nm. An intensifying screen characterized by being colored with a colorant having a main peak of an absorption spectrum in a wavelength range of 540 nm to 540 nm. 2) The intensifying screen according to claim 1, which has a protective layer on the phosphor layer. 3) The intensifying screen according to claim 1 or 2, wherein the colorant has a main peak of its absorption spectrum in a wavelength range of 450 nm to 525 nm. 4) The green light-emitting phosphor is Ln_2O_2S:Tb phosphor, Ln_2O_2S:Tb, Tm phosphor, Ln_2O
_2S: Tb, Dy phosphor, LnPO_4: Tb phosphor, LnPO_4: Tb, Tm phosphor, LnPO_4:T
b, Dy fluorophore and (Zn_1_-_x, Cd_x)
The intensifying screen according to any one of claims 1 to 3, characterized in that it is at least one of S:Ag phosphors. (However, Ln is at least one of La, Gd, and Y.
And only when the Y content exceeds 50 atomic percent of the total Ln content, the Tb content is 0.005 gram atom or more, and x is 0.2≦x≦0.5. ). 5) The intensifying screen according to claims 1, 2, 3 and 4, wherein the colorant is a dye. 6) The intensifying screen according to claim 5, wherein the dye is an oil-soluble dye. 7) Claims 1, 2, 3, and 7, characterized in that the photographic sensitivity thereof is 95% to 30% of the photographic sensitivity of the intensifying screen not colored with the colorant. The intensifying screen according to any one of Items 4 and 5 to 6.