JPH10160898A - Fluorescence element and radiation image observation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the brightness and sharpness of luminous images and obtain high quality luminous images by using a fluorescence element having a light reflection layer arranged in the opposite side of emission side of a fluorescence body converting radiation to visible light and reflecting the light to the emission side of the fluorescence body at over a specific reflection coefficient. SOLUTION: A luminous element 1 consists of a fluorescence layer 3 converting radiation (X-ray) to visible light and a light reflection layer 2 arranged on X-ray incidence side. The X-ray 30 from an X-ray tube 20 irradiates subjects 21 of living bodies and articles and the incident X-ray is attenuated according to the inner state and penetrates the subjects 21. The penetrated X-ray 31 goes in the fluorescence plate 1 (luminous element). The X-ray 31 penetrates without being absorbed by support 4, etc., of the fluorescence plate 1 and goes in a fluorescence body layer 3. Most of the X-ray 31 is absorbed in the fluorescence body layer 3 and generates luminescence in the wave length of visible light. The luminous intensity is determined in accordance with the X-ray intensity and so a luminous image in accordance with the inner state of the subject 21 is formed on the luminous body layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for converting incident radiation into visible, ultraviolet or infrared rays (hereinafter, unless otherwise specified, "visible light" means ultraviolet light in addition to so-called visible light. The present invention relates to a phosphor element and a radiation image observation device that convert light into light and infrared light, which are used in radiation imaging in medical treatment and nondestructive inspection in industry. In particular, the present invention relates to a device using X-rays among radiations, that is, a fluorescent plate for converting X-rays into visible light and an X-ray image observation apparatus.

[0002]

2. Description of the Related Art At present, radiation imaging is roughly classified into:
X-rays are irradiated on the human body to observe the internal structure, and medical radiography used for diagnosing diseases and X-rays are applied to articles (products).
2. Description of the Related Art Nondestructive inspection (industrial) radiography for irradiating a line to observe its internal structure and inspect for foreign substances and defects is performed.

In the medical field, inspection using radiation, that is, radiation inspection, is indispensable in diagnosis. There are various types of radiological examinations. In particular, the living body is irradiated with X-rays from the outside, and the X-rays transmitted through the living body are imaged,
Fluoroscopy for observing the internal state of a living body is very important. Alternatively, a medicine containing a radioisotope may be administered to a living body, gamma rays emitted from the inside of the living body may be detected and imaged, and the internal state of the living body may be observed.

[0004] In the field of industry, nondestructive inspection using X-rays is very important. By irradiating X-rays to an article such as an industrial product from the outside, X-rays transmitted through the article are imaged, the internal structure is observed, and foreign substances and defects are inspected.

[0005] Regardless of the purpose or the case of using any radiation, an invisible radiation that is permeable to the substance to some extent is used, converted to visible light, and an image of the inside of the substance is formed. Gaining is common. Here, the prior art relating to X-rays among radiations will be described. That is, a fluorescent plate that converts an X-ray image into a visible light image and an X-ray image capturing apparatus using the same will be described.

Here, a fluorescent plate conventionally used for X-ray photography will be described with reference to FIG. The fluorescent plate 15 converts X-rays 31 incident from the left side in the drawing into visible light 33. The size of the fluorescent screen 15 is 400 × 400 m according to JIS standard Z4911.
m.

FIG. 15 illustrates a cross-sectional structure of a general fluorescent plate, in which a support 4, an undercoat layer 13, a fluorescent layer 3, and a protective film 5 are provided in this order from the X-ray incident side. I have. The phosphor layer 3 is an essential structural element of the phosphor 15. Next, each of these structural elements will be described.

[0008] Basically, the phosphor layer 3 is made of a phosphor that absorbs X-rays and emits light in the visible light region. Usually, Gd ₂ O ₂ S: Tb which is a rare earth phosphor and ZnCdS: Ag which is a sulfide phosphor are used as the phosphor. Alternatively, a rare earth phosphor such as La ₂ O ₂ S: Tb, La ₂ OBr: Tb, or a phosphor such as CaWO ₄ may be used. The choice of the phosphor is made mainly by the energy of the X-ray used. Here, Gd ₂ O ₂ S: Tb, which is most frequently used in high-pressure imaging, is taken as an example. As shown in FIG. 16, the phosphor Gd ₂ O ₂ S: Tb used here has bright line emission at several wavelengths,
It has the feature that the green light emission intensity of 5 nm is large. Note that, depending on the type of the phosphor, the phosphor may emit light in an ultraviolet region or an infrared region.

Strictly speaking, the phosphor layer 3 is composed of a phosphor and a binder. That is, this phosphor Gd ₂ O
₂ S: Tb is a powder having a particle size of several μm~ several tens [mu] m, are mechanically retained by the binder, and has a phosphor layer 3. As the binder, a polyurethane-based or cellulose-based binder is used. Of course, depending on the type of phosphor, a binder may not be used.

The coating amount of the phosphor Gd ₂ O ₂ S: Tb is usually about 50 to 200 mg / cm ² and the filling rate is 6
If it is 0%, the phosphor layer 3 has a thickness of about 100 to 400 μm. The application amount of the phosphor is determined depending on the energy of the X-ray used and the purpose, but may be other application amounts.

The undercoat layer 13 has a function of reflecting light from the phosphor layer 3. Usually, the undercoat layer 13 is made of white fine particles and has a thickness of about 10 to 20 μm.

The support 4 mainly comprises the phosphor layer 3 and the undercoat layer 1.
3 is mechanically supported. As the material, a paperboard such as cardboard or a resin such as polyester can be used, and the thickness is several 100 μm.

A white pigment is often added to the support 4 so that the support 4 also has a light reflection function in order to assist the light reflection function of the undercoat layer 13. Further, in many cases, such a white support 4 alone can provide a light reflection function without providing an undercoat layer. Usually, the reflectance of the white support 4 is about 90% or less. It is needless to say that the reflectance is substantially constant in the visible light range because the color is white.

The protective film 5 is provided as necessary to protect the phosphor layer 3 from physical contact, moisture, and the like. As the material, a transparent resin or the like is often used so that light emitted from the phosphor layer 3 can be transmitted.

The above is a description of the general fluorescent screen 1 shown in FIG.
5 and the basic function of each component. Among these components, an essential component of the fluorescent plate 15 is the phosphor layer 3 that converts an X-ray image into a visible light image. The next important component of the phosphor plate 15 is the undercoat layer 13 or the support 4 that reflects light emitted from the phosphor layer 3.

Next, the process of forming an X-ray image will be described with reference to FIG.
This will be described with reference to FIG. The fluorescent screen 15 and the observation device 23 are provided in a dark room or a dark box.

In FIG. 17, X-rays emitted from an X-ray generator (not shown) are applied to a subject such as a living body or an article (not shown), and the X-rays incident on the subject are attenuated according to the internal state of the subject. While passing through the subject. Then, the X-rays 31 that have passed through the subject enter the fluorescent screen 15.

The X-rays 31 pass through the support 4 and the undercoat layer 13 without being absorbed, and enter the phosphor layer 3. Most of the X-rays 31 are absorbed by the phosphor layer 3,
The phosphor layer 3 emits light at a wavelength in the visible light region. Then, the emission intensity is in accordance with the X-ray intensity. Thus, a light-emitting image corresponding to the internal state of the subject (not shown) is formed on the phosphor layer 3.

The visible light 33 emitted from the fluorescent screen 15 is
It is detected by an observation device 23 such as a still camera or a video camera, and a still picture (not shown) is obtained or displayed on a monitor (not shown). In this way, an X-ray image obtained by seeing through the subject is obtained.

Next, in the process of forming the X-ray image shown in FIG. 17, the behavior of the luminescence generated by the X-ray until it is emitted from the phosphor layer 3 will be described with reference to FIG. The behavior of the visible light emitted in the phosphor layer and the effect of the undercoat layer and the white support that reflect the visible light will also be described. FIG. 18 shows the thickness t in order from the X-ray incident side.
FIG. 4 is an enlarged view of a part of a fluorescent plate 17 including a white support 18 having a light reflection function at (t = several 100 μm) and a phosphor layer 3. The X-ray is a thin X-ray incident on a pinhole.
This is a line, and a small spot on the phosphor layer emits light.

The visible light emitted from the light emitting section 40 of the phosphor layer 3 travels in all directions. However, in the drawing, a part of the emitted visible light is illustrated. Since the phosphor layer 3 is a scatterer for visible light, the visible light travels while repeating scattering in the phosphor layer 3. However, here, the progress of the visible light in the direction parallel to the surface of the phosphor layer 3 is ignored and not shown. Therefore, the traveling direction of the visible light is roughly divided into the observation side and the opposite direction based on the surface of the phosphor layer 3.

The visible light 41 traveling to the observation side is emitted from the phosphor layer 3, enters an observation device (not shown), and is detected. On the other hand, visible light 42 traveling to the opposite side to the observation side
Is reflected by the support 18. The visible light 43 reflected by the support 18 passes through the phosphor layer 3, exits from the phosphor plate 17, enters an observation device (not shown), and is detected. Here, assuming that the support 18 does not exist, the visible light 42 traveling to the opposite side to the observation side is
Is emitted to the side opposite to the observation side, and the visible light is not detected and is wasted. That is, the luminance of the light emission image of the fluorescent plate is low.

As described above, the support and the undercoat layer having the function of reflecting light increase the luminance of the luminescent image on the fluorescent plate.
With such a support and an undercoat layer, X-ray photography with high sensitivity to some extent is performed.

However, the conventional fluorescent screens (for example, the fluorescent screens 15 and 17) provided with the support having a light reflecting function and the undercoat layer as described above mainly have the following three problems. ing.

The first problem is that the reflectance of the undercoat layer or the support having the function of reflecting light is insufficient. The higher the reflectivity, the higher the luminance of the fluorescent plate. However, the above-mentioned white support has a reflectivity of 90%, and the amount of visible light emitted from the fluorescent plate is insufficient. It is not expensive.

A second problem is that the thickness of the undercoat layer having a light reflecting function and the thickness of the support are relatively large.
For example, according to FIG. 18, the visible light 42 traveling to the opposite side to the observation side is emitted from the phosphor layer 3 and then reflected by the support 18 having a certain thickness t (t = several 100 μm). , visible visible light 42 is returned to a position away from a position where visible light emitted from the phosphor layer, the region d ₂ of larger area than the area d ₁ of the phosphor layer 3 that emits light by X-ray to the observation side Light ray 44 is emitted. That is, the region to be originally observed is the region d ₁ emitting light by X-rays, but a larger region d ₂ is observed.
The sharpness deteriorates.

A third problem is that the undercoat layer or the support having the function of reflecting light is a scatterer for light. For this reason, even if only visible light is reflected in these substances, the visible light is spatially spread. This is a cause of degrading the sharpness of the emission image, as in the second problem.

[0028]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a phosphor element provided with a phosphor layer for converting incident radiation into visible light, in which the luminance and sharpness of an emission image are improved.
Another object of the present invention is to provide a phosphor element which improves both of them and can obtain a high-sensitivity and high-quality light-emitting image, and a radiation image observation device which can obtain a higher-sensitivity and high-quality image.

[0029]

That is, the present invention provides a phosphor layer for converting incident radiation into visible, ultraviolet or infrared rays, and a phosphor layer on the side opposite to the light emitting side of the phosphor layer. And a light reflection layer that reflects the light beam to the light emission side of the phosphor layer at a reflectance of 90% or more. This is hereinafter referred to as a first invention.

According to the phosphor element of the first aspect of the present invention, the phosphor layer is disposed on the side opposite to the light emitting side of the phosphor layer, and transmits the light with a reflectance of 90%.
% (That is, the light reflectance is 0.9 or more), and the light-reflecting layer that reflects the light toward the light-emitting side of the phosphor layer has a sufficient amount of visible light to be emitted. As a result, the luminance of a light-emitting image (image) obtained by the phosphor element can be greatly improved. As will be described in detail later, particularly when the reflectance is 90% or more, the amount of light obtained on the observation side dramatically increases.

Further, the present invention provides a method for making incident radiation visible,
A phosphor layer that converts the light into ultraviolet or infrared light, and a light reflection layer that is disposed on the light emission side of the phosphor layer and that reflects the light toward the light emission side of the phosphor layer. The present invention also provides a phosphor element having a thickness of the light reflection layer of 10 μm or less. This is hereinafter referred to as a second invention.

According to the phosphor element of the second aspect of the present invention, the phosphor element has the light reflecting layer disposed on the side opposite to the light emitting side of the phosphor layer to reflect light toward the light emitting side of the phosphor layer. Since the thickness of the reflective layer is 10 μm or less, the spatial spread of light in the light reflecting portion can be minimized, as will be described in detail later. ) Sharpness can be greatly improved.

Further, the present invention provides a method for making incident radiation visible,
A phosphor layer that converts the light into ultraviolet or infrared light, and a light reflection layer that is disposed on the light emission side of the phosphor layer and that reflects the light toward the light emission side of the phosphor layer. The present invention also provides a phosphor element in which the light-emitting side of the light reflection layer has a mirror surface state or a substantially mirror surface state. This is hereinafter referred to as a third invention.

According to the phosphor element of the third aspect of the present invention, the phosphor element has the light reflecting layer disposed on the side opposite to the light emitting side of the phosphor layer to reflect light toward the light emitting side of the phosphor layer. Since the light emitting side surface of the reflective layer is in a mirror or nearly mirror state, the light is not scattered (or diffused), and the light is reflected in a mirror or nearly mirror state, and the light is reflected in its own space. Since the spatial spread can be minimized, the sharpness of a light-emitting image (image) obtained by this phosphor element can be greatly improved. However, a surface that is in a mirror state or almost in a mirror state means an optically smooth surface.

Further, the present invention provides a radiation source comprising a radiation source, any one of the above-described first, second, and third inventions, and a phosphor element based on the following embodiments, and an observation unit. An image observation device is also provided. In this case, it is preferable to have a radiation source, a phosphor element, and an observation unit in this order.

According to the radiation image observation apparatus of the present invention, since the phosphor element having the above-mentioned features is used, a high-sensitivity and high-quality image can be obtained.

In the first invention, the light reflecting layer having the maximum reflectance when the incident angle of the light beam is 45 degrees is provided, and the thickness of the light reflecting layer is 10 μm or less. It is preferable that the surface of the light reflecting layer on the side from which the light beam is emitted is in a mirror state or a substantially mirror state.

In the second invention, it is preferable that the surface of the light reflection layer on the side from which the light beam is emitted is in a mirror surface state or almost in a mirror surface state.

In the present invention, it is desirable to use a phosphor element having both the features of the phosphor element of the first invention and the features of the phosphor element of the second invention.

That is, a phosphor layer that converts incident radiation into visible, ultraviolet, or infrared light, and a phosphor layer that is disposed on the opposite side of the light emitting side of the phosphor layer and that has a thickness of 10 μm And a light-reflecting layer that reflects the light beam to the light-emitting side of the phosphor layer at a reflectance of 90% or more, if the light-emitting image (image) obtained by the phosphor device is Both luminance and sharpness characteristics can be greatly improved.

A phosphor element having both the features of the phosphor element of the first invention and the features of the phosphor element of the third invention may be used. Third
It may be a phosphor element having the features of the phosphor element of the present invention. Needless to say, it is most preferable that the phosphor element has the features of the phosphor element of the first invention, the features of the phosphor element of the second invention, and the features of the phosphor element of the third invention. .

The phosphor element of the present invention (hereinafter, the phosphor element of the first invention, the phosphor element of the second invention, and the phosphor element of the third invention may be collectively referred to as the phosphor element of the present invention. ), It is preferable to provide the light reflection layer having the maximum reflectance when the incident angle of the light beam is 45 degrees.

In the first, second and third inventions, the support, the light reflecting layer, the phosphor layer, and the optically transparent protective film are arranged in this order from the side opposite to the light emitting side. In this case, an optically transparent protective film for protecting the light reflecting layer is provided on the side of the light reflecting layer on which the phosphor layer is provided, or the light reflecting layer A protective film for protecting the light reflecting layer may be provided on a side of the layer opposite to a side on which the phosphor layer is provided.

The light reflecting layer, the phosphor layer, and the optically transparent support are provided in this order from the side opposite to the light emitting side. In this case, the fluorescent material of the light reflecting layer is provided. On the side where the body layer is provided, an optically transparent protective film for protecting the light reflecting layer is provided, or
A protective film for protecting the light reflecting layer may be provided on a side of the light reflecting layer opposite to a side on which the phosphor layer is provided.

Further, the light reflection layer is made of a metal thin film,
The metal thin film is preferably made of at least one selected from the group consisting of aluminum, silver, gold and copper.

Further, the light reflection layer is a metal thin film, and a dielectric laminate comprising a low-refractive-index dielectric and a high-refractive-index dielectric on the side of the metal thin film on which the phosphor layer is provided. The metal thin film is made of at least one selected from the group consisting of aluminum, silver, gold and copper, and the dielectric laminated film is made of a TiO ₂ layer and a SiO ₂ layer. And 1 to 3 sets of the dielectric laminated film may be provided.

Further, the light reflecting layer is formed of a dielectric laminated film of a low refractive index dielectric and a high refractive index dielectric, and in this case,
The dielectric laminated film may include a TiO ₂ layer and a SiO ₂ layer, and the number of the dielectric laminated film may be 9 to 13 layers.

The radiation image observation apparatus of the present invention includes a radiation source, at least one of the features of the phosphor element of the first invention, the features of the phosphor element of the second invention, and the features of the phosphor element of the third invention. It is preferable to have a phosphor element having one and an observation unit in this order. That is, an observation device in which a radiation source, a phosphor element, and an observation unit are provided in this order is a so-called transmission observation device. However, in the present invention, an observation device in which the radiation source and the observation unit are on the same side of the phosphor element (a so-called reflection observation device) may be used.

[0049]

BEST MODE FOR CARRYING OUT THE INVENTION The phosphor element of the present invention structurally comprises a phosphor layer for converting incident radiation into visible light,
It is basically composed of a phosphor layer and a light reflection layer arranged on the side opposite to the light emission side. The details of the structure will be described in detail with reference to specific examples in the embodiments described later. First, the structure of the fluorescent screen 1 according to the present invention will be briefly described with reference to FIG.

The phosphor element of the present invention basically comprises a phosphor layer 3 for converting incident X-rays into visible light and a light reflecting layer 2 disposed on the X-ray incidence side of the phosphor layer. I do.
The light reflection layer 2 reflects light emitted from the phosphor layer 3 and seems to be similar to the light reflection function of a conventional undercoat layer of a fluorescent plate or a white support, but based on the present invention. The light reflecting layer 2 solves the problem.
It plays a high function of light reflection.

A support 4 for mechanically holding the phosphor layer 3 and the light reflecting layer 2 is provided on the X-ray incident side thereof. In FIG. 1, a protective film 5 for protecting the phosphor layer 3 is provided. Note that the phosphor layer 3 and the protective film 5 can be the same as the conventional phosphor plate.
The size of the fluorescent plate 1 is not limited to the JIS standard or the like, but may be a required size.

Next, an example of X-ray imaging will be described with reference to FIG. The fluorescent screen 1 and the observation device 23 are provided in an observation room 22 such as a dark room or a dark box.

In FIG. 8, an X-ray 30 radiated from an X-ray tube 20 irradiates a subject 21 such as a living body or an article, and the X-ray incident on the subject 21 changes according to the internal state of the subject 21. It passes through the subject 21 while being attenuated. Then, the X-rays 31 that have passed through the subject 21 enter the fluorescent screen 1.

The X-rays 31 pass through the support 4 and the like of the fluorescent screen 1 without being absorbed, and enter the fluorescent layer 3. Most of the X-rays 31 are absorbed by the phosphor layer 3 and cause the phosphor layer 3 to emit light at a wavelength in the visible light region. Then, the emission intensity depends on the X-ray intensity. Thus, a luminescent image corresponding to the internal state of the subject 21 is formed on the phosphor layer 3.

The visible light 32 emitted from the fluorescent screen 1 is detected by an observation device 23 such as a video camera and displayed on a monitor 24. At this time, the image can be digitally captured by a computer (not shown), recorded and stored, and then displayed on the monitor 24, or the image can be printed out on a printer (not shown). Often do. Alternatively, image data digitally captured by a computer (not shown), recorded and stored, is subjected to various types of image processing by a computer (not shown) or another computer (not shown), and then the image is displayed on the monitor 24, or An image can be printed out on a printer (not shown), and in such a case.

The light emission image of the fluorescent screen 1 has high luminance or high sharpness, or high luminance and high sharpness, so that an image suitable for the above image processing can be obtained. Alternatively, when a still camera is used as the observation device 23, a still picture (not shown) is obtained.

The light reflecting layer 2 is made of, for example, an aluminum thin film (thickness: 1500 °) formed by vacuum evaporation on an optically smooth support as in Example 1 described later.
(0.15 μm)), and its reflectance is 54
92% at 5 nm. This light reflection layer 2 and a phosphor Gd ₂ O ₂ having a main emission line at a wavelength of 545 nm
S: It is shown below that the emission image of the phosphor plate 1 composed of the phosphor layer 3 using Tb has high luminance and high sharpness.

First, the basic principle of the function of the light reflecting layer with respect to light reflection will be described. Next, the fluorescent plate of the present invention having a light reflecting layer with a reflectance of 90% or more has a higher luminance than a conventional fluorescent plate. This is shown by a model calculation.

First, the behavior of light in the above-described fluorescent plate will be described theoretically and quantitatively.

The phosphor layer is a light scatterer and has a high reflectance. Light traveling from the phosphor layer to the light reflecting layer is reflected by the light reflecting layer and returns to the phosphor layer. Therefore, the light returned to the phosphor layer is scattered in the phosphor layer. Then, the slight light passes through the phosphor layer and exits to the observation side, but most of the light travels again to the light reflection layer and is reflected. These steps are repeated.

As a result of the repetitive reflection between the light reflecting layer and the phosphor layer, the theoretical formula relating to the amount of light finally emitted to the observation side is well known (see “Auroral X-ray” No. 19, p1
3, Kasei Optonics Co., Ltd.). The present inventors have introduced spectroscopic theory into the theoretical formula, introduced various parameters, and finally observed light of wavelength λ as a result of repeated reflection between the light reflecting layer and the phosphor layer. The following model formula (A) representing the light amount Π (λ) emitted to the side was derived. Here, first, only a certain wavelength λ is considered. This wavelength λ is 545, which is the main emission wavelength of the phosphor Gd ₂ O ₂ S: Tb, for example.
nm.

The amount of light Π (λ) is

(Equation 1) It is represented by Here, E (λ): the emission amount of the phosphor layer at the wavelength λ (emission spectrum) F (λ): the emission amount (emission spectrum) emitted to the observation side with respect to the total emission amount without the reflective layer at the wavelength λ Ratio B (λ): Ratio of light emission amount (emission spectrum) emitted to the side opposite to the observation side with respect to the total light emission amount when there is no reflective layer at wavelength λ Rm (λ): Reflectivity of light reflection layer at wavelength λ (Reflectance spectrum Rm (λ)) Rp (λ): Reflectance of phosphor layer at wavelength λ (scattered reflectance) Tp (λ): Transmittance of phosphor layer at wavelength λ.

That is, as Rm (λ) (reflectance of the light reflecting layer at wavelength λ) increases, Π (λ) (observed light amount)
Becomes larger. Further, for example, the light amount Π (λ) emitted to the observation side at a certain wavelength λ and the reflectance Rm of the light reflecting layer
The relationship of (λ) is graphed and shown in FIG.

However, each condition (the most general condition) is as follows. E (λ) = 1 (E (λ) = 1 for standardization, for example) F (λ) = B (λ) = 0.5 (If there is no light reflection layer, the observation side and its opposite side Rp (λ) = 0.9 (Normal value) Tp (λ) = 1−Rp (λ) = 0.1 (In the phosphor layer, the light amount loss No.)

FIG. 10 shows that when the reflectance (Rm) of the light reflecting layer exceeds 0.9, the amount of light (Π) emitted to the observation side sharply increases. That is, the reflectance of the light reflecting layer is
A little higher than 0.9 is better. As described above, the light reflectance of the conventional light reflection layer, the undercoat layer having the light reflection function, and the support is somewhat smaller than 0.9.

Even if the light reflectance is relatively high at 0.9, the amount of light observed under the above conditions is about 0.7 as a relative value according to the equation (A).

On the other hand, for example, a light reflection layer composed of a silver thin film produced by vacuum evaporation as shown in the examples described later is
At a wavelength of 550 nm, the reflectivity is 0.98, and the amount of light emitted to the observation side is approximately 0.91 in relative value according to equation (A).
Is calculated. That is, it is considered that the luminance of the emission image of the fluorescent plate according to the present invention at the wavelength of the emission image is about 30% higher than that of the conventional fluorescent plate.

The light from the phosphor layer is emitted in all directions. Therefore, light enters the light reflecting layer at any angle. In the above description, the incident angle of light was not considered. The above description is sufficient for a light reflecting layer in which the reflectivity of the light reflecting layer is almost constant regardless of the incident angle. However, some types of light reflective layers
The reflectance depends on the angle of incidence and may vary greatly. In such a case, in the present invention, particularly, the incident angle 45
Since the light reflection layer having the maximum reflectance in each degree is provided, the luminance of the light emission image of the phosphor plate becomes high. This is shown below based on the model formula. Or, if the angle-dependent characteristics of the reflectivity can be changed, what characteristics should be obtained will be described below.

The light emitted from the phosphor layer is emitted by Lambert (Lam
In accordance with bert) 's law, light is emitted at all angles in space. Therefore, light enters the light reflecting layer at various angles.

When the reflectance has an incident angle dependency, the angle-average reflectance is as follows:

(Equation 2) Is represented by the following equation (B). Formula (B) is a model formula for deriving the angle-average reflectance of the light reflection layer by the present inventor.

(Equation 3) Here, Rm (θ, λ): the reflectance of the light reflecting layer at an angle θ at a wavelength λ, and I (θ, λ): the emission intensity of the light reflecting layer at an angle θ at a wavelength λ (per unit solid angle). is there.

According to Lambert's law, the angle-dependent intensity distribution of light emission from the phosphor layer is I (θ) = (B / π) × cos θ.

If this rule is obeyed at any wavelength, then I (θ, λ) = (B (λ) / π) × cos θ. Substituting this into equation (B) and rearranging,

(Equation 4) Becomes

According to the equation (C), the angle average reflectance:

(Equation 5) Is greatly affected by the reflectance near the angle π / 4 (= 45 degrees). Of course, ideally, it is desirable that the reflectance of the light reflecting layer is constant and high at all angles.

Accordingly, the present invention also provides a light reflecting layer having a maximum reflectance particularly at an incident angle of 45 degrees. If the dependency of the reflectance on the incident angle can be changed, first, the reflectance should be maximized at an angle of π / 4 (= 45 degrees). However, even if the reflectance is not the maximum at the angle π / 4 (= 45 degrees), it can be obtained by the equation (C).

(Equation 6) May be maximized at other angles. That is, according to equation (C),

Equation 7 Is important. A typical example in which the reflectance is maximum at an angle π / 4 (= 45 degrees) is obtained by Expression (C).

(Equation 8) Is a symbol of being the largest. In addition,

[Equation 9] Can be used as Rm (λ) in formula (A).

Heretofore, the emission spectrum from the phosphor layer and the reflectance spectrum of the light reflection layer have not been taken into consideration only at a certain wavelength λ. In order to consider the luminance of the fluorescent plate, it is necessary to consider these spectral characteristics.

If only the luminance taking into account the spectral characteristics of the phosphor plate is considered, equation (A) may be integrated over the emission wavelength range of the phosphor layer. However, in order to obtain a good X-ray image, it is necessary to consider not only the luminance in consideration of the spectral characteristics of the fluorescent plate but also the spectral sensitivity of the observation device and the spectral characteristics of the entire detection system. Therefore, the expression (A) is multiplied by the spectral sensitivity of the observation device, integrated over the emission wavelength range of the phosphor layer, and the observed light amount L is obtained by the following expression (D).
However, the following equation (D) is a model equation for deriving the amount of light L observed by the present inventor on the fluorescent screen. Note that Rm in the formula (A) is calculated according to the formula (B).

(Equation 10) Is used.

[Equation 11] Here, S (λ) is the sensitivity of the observation device at the wavelength λ, and k is the light collection rate (constant) of the observation device.

It is desired that the observed light amount L is large. Therefore, the respective spectral characteristics must be well matched. For this purpose, it is best to select each of the phosphor layer, the light reflection layer, the observation device, etc. from the zero base.

Normally, the spectral characteristics of the phosphor layer and the observer have already been matched, and on the premise of this, the conditions of the light reflective layer having good luminance are shown below.

In many cases, the phosphor layer is white, and the above-mentioned Rp (λ) and Tp (λ) can be regarded as constants regardless of the wavelength. Further, F (λ) and B (λ) can be regarded as constants regardless of the wavelength. Therefore, the emission spectrum E (λ) of the phosphor layer (= the spectral sensitivity S (λ) of the observation device)
Spectrum of light and light reflection layer

(Equation 12) What is necessary is just to consider the consistency. Therefore, the amount of light L to be observed can be increased by selecting a light reflection layer having a high reflectance at a wavelength where the emission intensity of the phosphor layer is high (that is, a wavelength at which the sensitivity of the observation device is high). .

However, for example, at a certain wavelength λ, that is, at the main emission wavelength of the phosphor,

(Equation 13) Does not become 90% or more, or does not become the maximum at the incident angle of 45 degrees, as long as the amount of light observed by the fluorescent plate according to the formula (D) becomes the maximum. That is, a fluorescent plate having a light reflecting layer that takes into account the incident angle dependence of the reflectance of the light reflecting layer according to the formula (C) and the spectral characteristics of the light reflecting layer according to the formula (D). This is the basis of the present invention.

Next, it is shown that the emission image of the fluorescent plate, which has a light reflection layer having a thickness of 10 μm or less and a light reflection layer in a mirror surface state or a substantially mirror surface state, is highly sharp.

In the conventional fluorescent screen, the light-reflecting portion is composed of only the undercoat layer and the support or the support. For example, the undercoat layer has a thickness of 10 to 20 μm.
m of the scattering reflection layer. On the other hand, in the phosphor plate according to the present invention, the light reflection layer itself is very thin, and in the case of a light reflection layer made of a metal thin film, the thickness is about 0.1 μm. The thickness of the light reflection layer made of the laminated film of the above is about 10 μm or less.

Because of such an extremely thin film, spatial spread of light emission due to the thickness of the light reflecting portion is almost eliminated. In addition, as shown in the examples described below, the surface of the light reflection layer on the side from which visible light is emitted is in a mirror state or almost mirror state, and light reflection is close to reflection in a mirror state or almost mirror state, Light does not spread spatially by the reflection itself.

FIG. 7 shows this state. FIG. 7 shows the behavior of emission of visible light in the phosphor layer and the effect of the light reflecting layer that reflects visible light.

First, the behavior of the emission (visible light) generated by X-rays in the phosphor layer 3 in the process of forming an X-ray image until the light is emitted from the phosphor layer 3 will be described. In addition, FIG.
FIG. 2 is a partially enlarged cross-sectional view of a phosphor plate 1 including a light reflection layer 2 and a phosphor layer 3 having a thickness T (T = 0.1 μm) in order from the X-ray incident side.

The visible light 45 traveling toward the observation side (the side in which the visible light travels) exits from the phosphor layer 3 and enters an observation device (not shown). On the other hand, the visible light 46 traveling to the opposite side to the observation side is reflected by the light reflection layer 2. The visible light 47 reflected by the light reflection layer 2 passes through the phosphor layer 3, exits from the phosphor plate 1, and is detected by an observer (not shown).

As described above, since the light reflecting layer is extremely thin,
Visible light 47 which is reflected by the light reflecting layer 2 is returned to substantially the light emitting point of the phosphor layer 3, the visible light from the approximately equal area D ₂ in the region D ₁ of the phosphor layer 3 that emits light by X-ray to the observation side 32 is emitted. That is, in comparison with the conventional example of FIG. 17, the region D ₂ approximately the same size of the region D ₁ to be originally observed observed, it can be said that a high sharpness.

In some cases, it is necessary to provide an optically transparent protective film on the surface (light reflecting surface) of the light reflecting layer on the side where visible light is observed, to protect the light reflecting surface. In this case, as is clear from the above principle, it is preferable that the protective film is as thin as possible. However, in order to obtain high luminance, the protective film may sufficiently protect the light reflection surface (the side from which visible light is emitted) of the light reflection layer, and a certain thickness may be required to maintain high reflectance. is there. At this time,
In order to maintain the high reflectance of the metal thin film 2, a thin protective film 6
(See FIG. 2) may be used, but this portion sacrifices sharpness.

The above-mentioned protective film is particularly effective when the material of the light reflection layer is easily susceptible to chemical change. Since silver and the like are easily susceptible to chemical change, it is particularly effective on the surface of the light reflection layer composed of a silver thin film. Is effective.

By the way, at one certain wavelength and one
Mirrors based on known thin-film technology can be used to reflect light at two angles of incidence. A mirror (mirror) according to this technology is provided on a light reflecting layer that reflects light at all emission angles from the phosphor layer of the phosphor plate, that is, light at all incident angles.
Can be used according to the above-described technical idea of the present invention.

Next, specific examples of materials and structures of the light reflecting layer of the present invention will be described. Here, it is roughly divided into 3
Kinds of light reflecting layers are provided. These three types of light reflecting layers are:
Each has its own characteristics, and explains how to choose.

First, in the phosphor element of the present invention,
The light reflection layer is preferably made of a metal thin film. The light reflection layer made of a metal thin film has a feature that the reflection is extremely high. In general, it satisfies the reflectance of 90% or more, which is a preferable condition according to the formula (A). Since the reflectance of the metal thin film does not depend much on the incident angle and is almost constant, the condition of the formula (C) is automatically satisfied. Further, the thickness of the light reflection layer made of a metal thin film is usually as very thin as about 0.3 μm.

From these facts, the fluorescent plate having the light reflection layer made of a metal thin film has high brightness and sharpness. In the light reflection layer made of a metal thin film, the reflectance spectrum has characteristics depending on the material of the metal thin film. Therefore, each of the phosphors of the phosphor layer and the material of the metal thin film of the light reflection layer must be selected appropriately according to the above formula (D).

Further, the metal thin film is desirably a metal thin film selected from the group consisting of aluminum, silver, gold and copper. Also, two or more types may be used.

For example, FIG. 9 shows respective reflectance spectra of respective metal thin films made of aluminum, silver, gold and copper produced by vacuum evaporation. These metal thin films have high reflectivity from the visible light region to the infrared light region due to conduction electrons. For example, aluminum (A
1) The thin film has a high reflectance of approximately 90% or more over almost the entire wavelength range of visible light, and has good reflection characteristics. That is,
In the present invention, an aluminum (Al) thin film can be used as the light reflecting layer as long as the phosphor layer is made of a phosphor that emits light in the wavelength region of visible light. Aluminum is preferable because it has the feature of being inexpensive.

The silver (Ag) thin film also has an excellent high reflectance of 90% or more over almost the entire visible light wavelength region. However, since silver is susceptible to a chemical change, it is desirable to provide a protective film on the silver thin film as in the examples described later so as to prevent the chemical change. Of course, this does not apply if the fluorescent plate is used in an environment where chemical change is unlikely to occur, such as placing a fluorescent plate using a silver thin film for the light reflection layer in a vacuum or the like.

A gold (Au) thin film or a copper (Cu) thin film has a low reflectance in a wavelength range from blue to green (about 400 to 580 nm), but has a low reflectance in a wavelength range from red to infrared (about 600 nm or more). The rate is as high as 90% or more. Therefore, it is preferable to use a thin film made of these metals for a phosphor layer using a phosphor that emits light in the above wavelength region (about 600 nm or more). A metal thin film made of gold is preferable because it has a feature of being extremely stable chemically. Copper is preferable because it has the feature of being inexpensive. However, in the case of copper, a protective film is preferably provided like silver.

Second, in the phosphor element of the present invention,
There is also provided a light reflection layer in which a plurality of dielectric films are provided as a laminated film on a metal thin film surface on a phosphor layer side. Note that a stacked body including a metal thin film and a stacked film of a plurality of dielectric films is referred to as a light reflecting layer. In general, the laminated film of the dielectric films is often composed of a plurality of sets of dielectric films each including a low-refractive-index layer and a high-refractive-index layer.

By appropriately setting the material, thickness, lamination structure, and number of laminations of the plurality of dielectric films, this light reflection layer can be formed of only the above-described first metal thin film. Thus, the reflectance can be increased in a certain wavelength range. Therefore, the preferable condition according to the formula (A) was 9
Satisfies a reflectance of 0% or more.

The light reflecting layer composed of a laminated film of a metal thin film and a dielectric has a feature that the reflectance spectrum shifts to shorter wavelengths as the incident angle increases. Because of this, the reflectance changes depending on the incident angle, and therefore, it is necessary to consider Equation (C). The thickness of the light reflecting layer composed of a metal thin film and a laminated film of a plurality of dielectric films is, for example, 0.5 μm in Example 3 described later, which is extremely thin. For these reasons, a fluorescent plate having a light reflecting layer composed of a metal thin film and a laminated film of a plurality of dielectric films is also high in brightness and sharp.

For example, FIG. 11 shows a reflectance spectrum by a design calculation of a light reflection layer in which a four-layer dielectric thin film is provided on an aluminum thin film and the reflectance near the wavelength of 550 nm is increased. This figure also shows the spectrum of the angle average reflectance calculated by the equation (C). Note that the structure of the light reflection layer is the same as that of Example 3 described later.

According to FIG. 11, near the wavelength of 400 nm or 700 nm, the reflectance is about 80%, which is slightly lower than that of the light reflection layer composed of only the aluminum thin film. However, the reflectivity around the wavelength of 550 nm is about 92% for the light reflection layer composed of only the aluminum thin film, whereas it is about 98% for the light reflection layer composed of the aluminum thin film and the laminated film of a plurality of dielectrics. It has improved by about 6%.

As described above, according to the calculation using the equation (A), if the reflectivity is further improved by 6% in the high reflectivity region,
The amount of light, that is, the luminance, obtained on the observation side will increase by about 10%. That is, in the case of a phosphor layer using a phosphor that emits light in a wavelength region near the wavelength of about 550 nm, the amount of light obtained on the observation side is greatly increased.

As the dielectric film, TiO ₂ , SiO
₂ , a dielectric film made of Al ₂ O ₃ , TaO ₂ , Ta ₂ O _{5 and the} like. By stacking a plurality of dielectric films having different refractive indices, that is, a material having a low refractive index and a material having a high refractive index By combining with a substance, a laminated film that optically reflects light can be obtained.

Incidentally, the width of the wavelength region in which the reflectance is increased is wider as the refractive index ratio of the dielectric is larger. Usually, the phosphor does not emit light only at a certain wavelength but emits light at a certain wavelength region. Therefore, it is desirable that the wavelength width at which the reflectance of the light reflecting layer is increased is wide. Therefore, for example, in particular, a dielectric film in which the TiO ₂ layer and the SiO ₂ layer are a pair is a combination in which the refractive index ratio of the dielectric is large, and a laminated film made of this dielectric is preferable. In addition, by providing two types of dielectric laminated films in which the wavelength range for increasing the reflectance is shifted, a high reflectance can be obtained in a wider wavelength range.

Theoretically, the greater the number of laminated dielectric films, the higher the reflectance of the light reflecting layer 50 can be. According to design calculations, the aluminum thin film, TiO ₂ layer and S
The angle-average reflectance of the light reflecting layer composed of a dielectric film and a pair of an iO ₂ layer, as determined by the equation (C), has a wavelength of 550.
In nm, the number of sets of the low refractive index layer and the high refractive index layer of the dielectric layer as one set is 96.5% for one set, and 98.6 for two sets.
%, 99.4% for three sets and 99.8% for four sets. This is shown in FIG. From the point of actual production, there are no significant differences in the reflectivity for four or more sets, and the smaller the number of sets, the lower the manufacturing cost, and one to three sets of dielectric layers are desirable.

The reflectance of the light reflecting layer composed of the metal thin film and the dielectric film is higher at the wavelength of light emission from the phosphor layer 3 than the reflectance of the light reflecting layer composed of the metal thin film alone. As long as such a material is used, any material, thickness, and number of layers of the dielectric film may be used. That is, as the material, a dielectric film can be formed by appropriately combining the above materials and the like with a low refractive index material and a high refractive index material. The low refractive index layer may be made of a different material for each layer, and the same applies to the high refractive index layer. Further, the thickness of the low refractive index layer may be different for each layer, and the same applies to the high refractive index layer. The same applies to the number of dielectric films.

The specific setting of the material, thickness, lamination structure, and number of laminations of a plurality of dielectric films will be described later in Examples, but it is shown in which wavelength range the reflectance should be increased. First, the reflectivity at the main emission wavelength from the phosphor layer used should be increased, and as described above,
When the angle of incidence is 45 degrees, the reflectance at that wavelength should be maximized. According to this, since the short wavelength shift of the reflectance spectrum from the incident angle of 0 ° to the incident angle of 45 ° is about 50 nm in the above example, it is about 50 nm as compared with the main emission wavelength from the phosphor layer. It suffices to increase the reflectance of long wavelength light at an incident angle of 0 degree. However, such considerations are based solely on the main emission wavelength of the fluorescent screen. As described above, the emission spectrum from the phosphor layer,
It is necessary to comprehensively consider the reflectance spectrum depending on the incident angle of the light reflecting layer and the spectral sensitivity of the observation device. That is, it is necessary to consider equation (D).

Third, in the phosphor element of the present invention,
There is also provided a light reflection layer provided as a laminated film including only a plurality of dielectric films. The laminated film of the dielectric film is composed of a multilayer of a plurality of low refractive index layers and a plurality of high refractive index layers.

By appropriately setting the material, thickness, lamination structure, and number of laminations of a plurality of dielectric films, the light reflecting layer can reflect more than 90%, which is a preferable condition according to the formula (A). A light reflection layer having a high reflectance that satisfies the requirements can be obtained.

The light reflecting layer composed of a dielectric laminated film has a feature that the reflectance spectrum shifts to a shorter wavelength as the incident angle increases. Because of this, the reflectance changes depending on the incident angle, and therefore, it is necessary to consider Equation (C). The thickness of the light reflecting layer formed by laminating a plurality of dielectric films is, for example, about 1.6 μm in Example 4 described later, which is extremely thin. For these reasons, a fluorescent plate having a light reflection layer formed by stacking a plurality of dielectric films is also high in brightness and sharp.

For example, at an incident angle of 0 degree, a wavelength of 600 n
FIG. 13 shows a reflectance spectrum by design calculation of a light reflection layer having a high reflectance near m. This figure also shows the spectrum of the angle average reflectance calculated by the equation (C). The structure of the light reflection layer is the same as that of Example 4 described later. This light reflection layer is designed so that the angle average reflectance at a wavelength of 545 nm is high. That is, at a wavelength of 545 nm, a short wavelength shift of the reflectance spectrum due to the incident angle is considered in advance so that the reflectance becomes maximum at an incident angle of 45 degrees.
It is designed so that the reflectance at 00 nm is high. The shift amount of the reflectance spectrum in this case is
It is about 50 nm.

According to FIG. 13, at the wavelength of 545 nm, the angular average reflectance is about 91%. However, in the angle-averaged reflectance spectrum of this figure, the wavelength range where the reflectance is high is higher than that of the light reflecting layer described in the first and second examples.
It is narrow. A method for widening the wavelength range where the reflectance is high will be described later.

As the dielectric film, TiO ₂ , SiO
₂ , a dielectric film made of Al ₂ O ₃ , TaO ₂ , Ta ₂ O ₅ or the like. By stacking a plurality of dielectric films having different refractive indices, ie, a material having a low refractive index and a material having a high refractive index By combining these substances, a laminated film that optically reflects light can be obtained.

By the way, the width of the wavelength region where the reflectivity is high increases as the refractive index ratio of the dielectric increases. Usually, the phosphor does not emit light only at a certain wavelength, but emits light at a certain wavelength region. Therefore, it is desirable that the reflectance of the light reflecting layer is high and the wavelength width is wide. Thus, for example, in particular, TiO
A dielectric film comprising a pair of _two layers and a SiO ₂ layer is a combination in which the refractive index ratio of the dielectric is large, and a light reflection layer made of this dielectric film is preferable. It should be noted that a high reflectance can be obtained in a wider wavelength range by providing two types of dielectric laminated films in which the wavelength ranges having high reflectances are shifted from each other to form a light reflection layer.

Theoretically, the greater the number of layers of the dielectric laminated film, the higher the reflectance of the light reflecting layer can be. According to the design calculation, the angle-average reflectance of the light reflecting layer made of a dielectric film, obtained by the formula (C), indicates that at a wavelength of 550 nm, as shown in FIG. At 9
It is 1.4%, 94.6% for 11 layers, and 96.0% for 13 layers. If the number of layers is seven or less, it is difficult to make the angular average reflectance 90% or more. From the point of actual production, the smaller the number of sets is, the lower the production cost is. The light reflection layer composed of 9 to 13 dielectric layers is desirable.

The material, thickness, and number of layers constituting the dielectric film may be any as long as the reflectance of the light reflecting layer is high. That is, as the material, a dielectric film can be formed by appropriately combining the aforementioned materials and the like with a low refractive index material and a high refractive index material. The low refractive index layer may be made of a different material for each layer, and the same applies to the high refractive index layer. Further, the thickness of the low refractive index layer may be different for each layer, and the same applies to the high refractive index layer. The same applies to the number of dielectric films. In addition, by appropriately performing the above, a wavelength region where the reflectance of the light reflecting layer is high can be widened.

Although the three types of light reflecting layers have been described above, not only the spectral characteristics but also the chemical stability, mechanical durability, radiation durability, or industrially, the simplicity of the manufacturing process or the manufacturing The choice must be made in consideration of costs and other factors.

[0119]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.

Six examples of the present invention are shown below.
In each of the embodiments, there is a common matter, and the common description is omitted as appropriate in order to simplify the description and facilitate understanding. As the phosphor of the phosphor layer, in addition to Gd ₂ O ₂ S: Tb used in the following examples, a phosphor used in a conventionally known phosphor plate or a known phosphor may be used. For example, Gd ₂ O ₂ S: Eu,
Gd ₂ O ₂ S: Pr, CsI: Na, CsI: Tl and the like.

Embodiment 1 FIG. 1 shows a cross-sectional structure of a fluorescent plate 1A of this embodiment.

In the fluorescent plate 1A, a resin (here, polyethylene terephthalate (P)
ET)), a light reflection layer 5 made of a metal (here, aluminum) thin film 2 and a support 4 (thickness: 300 μm)
0 (thickness: 1500 ° (0.15 μm)), a phosphor layer 3 (thickness: 280 μm) mainly composed of a phosphor (here, Gd ₂ O ₂ S: Tb), resin (here, PET)
Transparent protective film 5 (thickness: 10 μm) made of
Are integrally formed in this order. The phosphor layer 3 may be mixed with a binder (binder) and applied. Note that the protective film 5 may not be provided if not necessary.

The aluminum thin film 2 is formed on the optically smooth surface of the support 4 (the optically smooth surface may be only the surface of the support 4 on the light reflection layer 50 side) by a vacuum evaporation method. Although formed, other physical vapor deposition methods (PVD method),
For example, it can also be formed by a sputtering method, an ion plating method, or the like.

In the case of the light reflection layer made of only a metal thin film (here, the light reflection layer made of an aluminum thin film) as in this embodiment, the thickness may be about 1500 ° (0.15 μm), and is 1000 to 3000 ° ( 0.1-0.3μ
m) is enough. However, if the vapor deposition is too thick, the surface of the aluminum thin film is easily roughened, the mirror surface state is deteriorated, and the mirror surface state is lost. Although a thin oxide film is formed on the surface of aluminum in the air, it is stable after the oxide film is formed, and the oxide film prevents the aluminum film from deteriorating.

As shown in FIG. 9, aluminum (A)
1) The thin film has a high reflectance over the entire visible light wavelength range and has good reflectance characteristics. Phosphor Gd ₂ O ₂ S: Tb
Has an emission spectrum as shown in FIG. Therefore, the aluminum (Al) thin film is formed of the phosphor Gd.
₂ O ₂ S: Tb emission wavelength range (about 380 to 650 n
m) is reflected at a reflectance of 90% or more. That is, the luminance of the emission image of the fluorescent plate 1A of the present embodiment is high.

Since the aluminum thin film 2 is formed on an optically smooth surface of the support 4, the light reflecting surface of the aluminum thin film 2 is a mirror surface. The aluminum thin film 2 has a very small thickness (here, 1500、１).
(0.15 μm)). Therefore, these two
For this reason, as described in FIG. 7, the sharpness of the light emission image of the phosphor plate of this embodiment is high.

By the way, a metal thin film made of silver can be used as the light reflecting layer 50. However, since silver is susceptible to a chemical change, it is preferable to configure it as in Example 2 described later.

When a phosphor layer made of a phosphor emitting light in the red to infrared wavelength region is used, a metal thin film made of gold can be used as the light reflection layer 50. As shown in FIG. 9, the gold (Au) thin film has a high reflectance in the red to infrared wavelength region, and reflects the light emitted from the phosphor layer in the red to infrared wavelength region at a high reflectance. The metal thin film made of gold has a feature of being extremely chemically stable. The metal thin film made of gold can be formed by polishing gold, or by rolling gold, in addition to the above-described physical forming method.

Similarly, when a phosphor layer made of a phosphor emitting light in the red to infrared wavelength region is used, copper (C
A metal thin film made of u) can be used. Copper has the feature that its material cost is low. However, since copper is relatively susceptible to chemical change, it is preferable to configure copper as in Example 2 described later, similarly to silver.

Regardless of which metal thin film is used, the light reflecting surface can be made a mirror surface by forming the metal thin film on the support 4 having an optically smooth surface.
Further, the thickness of the metal thin film may be extremely small. In this case, depending on the type of the metal, a metal thin film can be formed by plating by imparting conductivity or coating a conductive film to the support in advance.

A good metal thin film can be obtained, for example, by rapid vapor deposition in a vacuum by a vacuum vapor deposition method, and its reflectivity is determined by a surface obtained by ordinary polishing or a surface prepared by a sputtering method. Higher than the reflectance.

The support 4 needs to be thin to some extent so as not to hinder the transmission of the incident X-rays. Also from this point, the material of the support 4 must be selected.

Embodiment 2 FIG. 2 shows a cross-sectional structure of a fluorescent plate 1B of this embodiment.

In the fluorescent plate 1B, a support 4 (thickness: 300 μm) made of resin (here, PET), a metal (here, silver) thin film 2 and an optical material made of resin are formed from the side of incidence of the X-rays 31. The light reflection layer 50 composed of the transparent protective film 6 and mainly a phosphor (here, Gd ₂ O ₂ S: T
A phosphor layer 3 (thickness 300 μm) made of b) and an optically transparent protective film 5 (thickness: 10 μm) made of resin (here, PET) are integrally formed in this order. Note that the protective film 5 may not be provided if not necessary.

The metal thin film 2 made of silver is placed on the surface of the optically smooth support 4 (the optically smooth surface is
May be provided only on the four sides of the support. ) Is formed by a vacuum evaporation method, but is formed by another physical evaporation method (PVD).
Method), for example, a sputtering method or an ion plating method. Since silver has a poor adhesion to a resin, a thin film of a substance satisfying the following conditions is preferably attached to the support 4 in advance, and a silver thin film is provided on the thin film of the substance. Such a substance is a substance having an adhesive force to the support 4 and a substance to which silver is adhered to, for example, SnO _x , SiO _x
And so on.

The metal thin film 2 made of silver can be formed by a chemical forming method such as a silver mirror reaction in addition to the above-described physical forming method.

In particular, when a silver thin film is used for the light reflecting layer, silver is susceptible to a chemical change, and the silver thin film alone may not be suitable as a light reflecting layer. Therefore, in this embodiment, the optically transparent protective film 6 is provided. The purpose of the protective film 6 is different from that of the protective film 5 provided on the visible light emitting side of the phosphor layer, but the material may be the same. Further, the material of the protective film 6 may be a thin film such as a dielectric.

It is desirable that the protective film 6 be as thin as possible.
From the viewpoint of sharpness, the thickness of the light reflection layer 50 composed of the metal thin film 2 composed of silver and the protective film 6 is desirably 10 μm or less. Of course, in order to place emphasis on high luminance, a thick protective film 6 may be used to maintain high reflectance of the metal thin film 2, but in that case, sharpness is sacrificed.

When the phosphor is mixed with a binder (binder) when the phosphor layer is formed, the binder is steadily attached to the entire surface of the metal thin film 2.
The protective film 6 can be omitted. Alternatively, when the phosphor layer and the metal thin film are separately manufactured, and both are bonded with an adhesive or a pressure-sensitive adhesive to prepare a fluorescent plate, the adhesive or the pressure-sensitive adhesive should be steadily attached to the entire surface of the metal thin film. However, the protective film 6 can be omitted. In these cases, it is needless to say that the adhesive or pressure-sensitive adhesive must not damage the metal thin film and the phosphor layer. Needless to say, in the process of producing the fluorescent plate, some measures must be taken to prevent the chemical change of the metal thin film.

Since the metal thin film is a thin film, it is necessary to protect not only the light reflecting surface but also the opposite surface. In the present embodiment (the same applies to the above-described first embodiment), the support 4 also functions to protect the metal thin film 2. The support 4 may not be made of the same material as the protective film 6, but preferably has a function of protecting the metal thin film 2. If the support 4 is made of a material that invades the metal thin film 4 made of silver, the support 4 of the metal thin film 2 also
A protective film must be provided.

The relative luminance of the fluorescent plate 1B of this embodiment is represented by CC
The results are shown below while measuring using a D camera and comparing with a conventional fluorescent plate (having no undercoat layer and having a white support). At an incident angle of 45 degrees, green light (about 480
To 580 nm), the reflectance of the light reflecting layer 50 with respect to green light was measured. Measuring reflectance is not spectroscopy,
Measured with total light. Needless to say, the measurement of the reflectance was performed before the fluorescent plate was formed.

The luminance was a relative luminance standardized with a phosphor plate consisting of only the phosphor layer of 0.5. The relative luminance corresponding to the reflectance of the light reflecting layer 50 of the present embodiment is plotted in FIG. 10 (note: the curve in FIG. 10 is based on the formula (A)). FIG. 10 also plots the relative luminance of the conventional fluorescent screen.

The reflectance of the light reflecting layer 50 of the present embodiment was higher than that of the conventional white support of the fluorescent plate, and the relative luminance of the fluorescent plate 1B of the present embodiment was 14% higher than that of the conventional fluorescent plate. In addition,
Both fluorescent plates had smaller values than the curve in FIG. 10 based on the formula (A). One reason is that the reflectance measurement is not a spectroscopic measurement and the relative luminance of the fluorescent plate is measured by the formula (A).
It is considered that this is not based on Equation (D).

Embodiment 3 FIG. 3 shows a cross-sectional structure of a fluorescent plate 1C of the present embodiment.

In the fluorescent plate 1C, a support 4 made of glass (thickness: 1 mm) and a metal (here, aluminum) thin film 2 (thickness: 1500 °) are formed from the side of incidence of the X-ray 31.
(0.15 μm)) and the dielectric film 7 (here, SiO ₂
And a light reflecting layer 50 (thickness: TiO ₂ ).
About 0.5 μm), mainly a phosphor (here, Gd ₂ O
₂ S: Tb) phosphor layer 3 (thickness: 180 μm)
Are integrally formed in this order.

The aluminum thin film 2 can be formed on a support 4 made of optically polished glass (optical polishing may be performed only on the surface on the side of the light reflection layer 50) in the same manner as the aluminum thin film of the first embodiment. it can. The dielectric film 7 is formed on the aluminum thin film 2 on the support 4 by a vacuum evaporation method, but may also be formed by a physical evaporation method (PVD method) such as a sputtering method or an ion plating method. It can also be formed by chemical vapor deposition. Further, depending on the type of the dielectric, it can also be formed by dipping or spin coating.

In this embodiment, the dielectric film 7 is made of a low refractive index layer 7a (here, SiO ₂ (refractive index 1.46, thickness: 9).
4 nm) and a high refractive index layer 7b (here, TiO ₂ (refractive index: 2.3, thickness: 60 nm)).

Normally, the dielectric film 7 is often composed of multiple sets of dielectric films in which the low refractive index layer 7a and the high refractive index layer 7b form one set. And, as described above, the greater the number of sets, the higher the reflectance of the light reflecting layer 50 can be theoretically. In this embodiment, two sets of dielectric films 7 are used in terms of actual production and production cost. As described above, one to three sets may be used.

As described above, as the incident angle increases, the reflectance spectrum of the light reflecting layer shifts to shorter wavelengths. Therefore, taking into account the dependence of the reflectance on the incident angle,
Considering the spectral sensitivity of the observer, that is, considering the equation (D), the wavelength of 545 nm at an incident angle of 0 degree of the light reflecting layer.
The dielectric laminated film is set so as to increase the reflectance of the substrate.

In the phosphor having such a configuration, as described above with reference to FIG. 11, the light reflection layer has an incident angle average reflectance of about 8 at wavelengths around 400 nm and 700 nm.
It is 0%, and the reflectance is slightly lower around those wavelengths than the light reflection layer made of the aluminum thin film of Example 1. However, the light-reflecting layer of this embodiment has an incident angle average reflectance of about 98% near the wavelength of about 550 nm, which is lower than the reflectance of the light-reflecting layer made of the aluminum thin film of Example 1 near that wavelength of 92%. , Around 6% reflectance
To some extent.

By the way, the reflectance of the light reflection layer 50 composed of the metal thin film 2 and the dielectric film 7 is higher at the wavelength of light emission from the phosphor layer 3 than the reflectance of the light reflection layer composed of only the metal thin film. If such a material is used, the dielectric film 7
The material, thickness, and number of layers constituting each layer may be any. That is, other than the above,
Al ₂ O ₃ , TaO ₂ , Ta ₂ O _{5, and the} like can be used as a dielectric film by appropriately combining a low refractive index material and a high refractive index material. The low refractive index layer may be made of a different material for each layer, and the same applies to the high refractive index layer.
Further, the thickness of the low refractive index layer may be different for each layer, and the same applies to the high refractive index layer. The same applies to the number of layers of the dielectric film 7.

The material of the support 4 may be a resin whose surface on the light reflection layer 50 side has an optically smooth surface as in the first embodiment.

Incidentally, in order to protect the metal thin film 2, a protective film may be provided on the phosphor layer 3 side of the dielectric laminated film 7, like the protective film 6 in the second embodiment. However, since the dielectric film 7 in this embodiment is relatively chemically stable,
Not only is the protective film for the dielectric film 7 unnecessary, but also because the dielectric film 7 has the function of protecting the metal thin film 2,
It is not necessary to provide such a protective film, and it is better not to provide it in view of sharpness.

The relative MTF (relative sharpness) of the fluorescent plate 1C of this example was measured using a CCD camera, and the result was compared with that of a conventional fluorescent plate (having no undercoat layer and having a white support). Is shown below. Sharpness (MTF)
It was measured by a method using a slit. MTF is a relative MTF obtained by taking a ratio with respect to a phosphor plate composed of only a phosphor layer.
And The measurement result of the relative MTF is shown in FIG. In addition,
For comparison, the relative MTF of the conventional phosphor plate is also plotted. As is clear from this result, the fluorescent plate 1C of the present embodiment has a higher relative MTF than the conventional fluorescent plate, and a light emission image with good sharpness can be obtained.

Although the luminance was also measured, the luminance of the fluorescent plate of this example and that of the conventional fluorescent plate were the same within the error range of the experiment. Since the light reflecting layer of this example has a higher reflectance than the white support at 545 nm, which is the main wavelength of the phosphor, at that wavelength, the phosphor plate according to the present invention should have higher brightness than the conventional phosphor plate. . But,
In the relative luminance measurement based on the formula (D), it is considered that both fluorescent plates were measured at the same luminance.

The fluorescent plate of this example had the same brightness as that of the conventional fluorescent plate, but had high sharpness.

Embodiment 4 FIG. 4 shows a cross-sectional structure of a fluorescent plate 1D of the present embodiment.

In the fluorescent plate 1D, from the incident side of the X-rays 31, the light reflecting layer 50 composed of the support 4 made of glass (thickness: 1 mm) and the dielectric film 8 (here, SiO ₂ and TiO ₂ ). (Thickness: about 1.6 μm), a phosphor layer 3 (thickness: 280 μm) mainly composed of a phosphor (here, Gd ₂ O ₂ S: Tb), resin (here, PET)
An optically transparent protective film 5 (thickness: 10 μm) is integrally formed in this order.

The dielectric film 8 can be formed on the support 4 made of optically polished glass (optical polishing may be performed only on the surface on the side of the light reflection layer 50) in the same manner as the dielectric film of the third embodiment. it can.

In this embodiment, the dielectric film 8 is made of a high refractive index layer 8b (here, TiO ₂ (refractive index 2.3, thickness: 65).
nm)) and four low-refractive-index layers 8a (here, SiO ₂ (refractive index: 1.46, thickness: 103 nm)) as one set, and further a high-refractive-index layer 8b (here, Then, T
It is composed of a total of nine layers of iO ₂ (refractive index 2.3, thickness: 65 nm). FIG. 13 shows a reflectance spectrum by design calculation of the light reflection layer 50.

Normally, the dielectric film 8 is often composed of multiple sets of dielectric films having one set of the high refractive index layer 8b and the low refractive index layer 8a and one layer of the high refractive index layer 8b. As described above, theoretically, the larger the number of sets, the more the light reflecting layer 50
Can be increased. In the present embodiment, from the viewpoint of actual production, production cost, and the like, a total of nine dielectric layers 7 of four sets plus one layer were used. As described above, 9-1
Three layers may be used.

The material of the support 4 may be a resin whose surface on the light reflection layer 50 side has an optically smooth surface as in the first embodiment.

Note that the dielectric film in this embodiment is relatively stable chemically and does not require a protective film. However, depending on the material of the dielectric, a protective film such as the protective film 6 of the second embodiment may be required.

Embodiment 5 FIG. 5 shows a cross-sectional structure of a fluorescent screen 1E of the present embodiment.

In the fluorescent screen 1E, a protective film 10 made of resin (here, PET) is applied from the incident side of the X-rays 31.
(Thickness: 25 μm), metal (here, aluminum)
A light reflecting layer 50 (thickness: about 0.5 μm) composed of a thin film 2 (thickness: 1500 ° (0.15 μm)) and a dielectric film 7 (here, SiO ₂ and TiO ₂ ), mainly a phosphor (here, In the above, a phosphor layer 3 (thickness: 550 μm) made of Gd ₂ O ₂ S: Tb) and glass (here, lead glass)
An optically transparent support 9 (thickness: 9 mm) made of
It has a structure integrally formed in this order.

In this embodiment, the structure of the light reflecting layer 50 is the same as the structure of the light reflecting layer of the third embodiment. Therefore, it goes without saying that the dielectric layer 7 of this embodiment has a function of protecting the metal thin film 2.

The protective film 10 does not need to be made of an optically transparent material, and unlike the protective film 6 on the light reflecting surface of the metal thin film 2 of the second embodiment, the thickness does not need to be as thin as possible. However, the protective film 10 needs to be thin to some extent so as not to hinder the transmission of incident X-rays, and from that point of view, it is necessary to select a material for the protective film 10.
This is the same as the support 4 of the first embodiment.

The light reflecting layer 50 is previously formed on the protective film 10 having an optically smooth surface. The forming method is the same as that of the third embodiment. At this time, the protective film 10
It serves as a temporary support for the light reflecting layer 50. On the other hand, the phosphor layer 3 is formed on the support 9. Then, the light reflecting layer 50 with the protective film 10 and the phosphor layer 3 with the support 9 are joined to form the phosphor plate 1E.

Alternatively, as another method of forming the light reflecting layer 50, first, the phosphor layer 3 is formed on the support 9.
Since the phosphor layer 3 formed of the phosphor particles has a rough surface, the surface of the phosphor layer 3 on the light reflection layer 3 side is optically smoothed with a lacquer or an alkali resin. Then, the light reflection layer 50 is formed on the phosphor layer 3 that has been optically smoothed. Then, the protective film 10 is formed on the light reflecting layer 50, and the fluorescent plate 1E
Is created.

By the way, it is difficult to obtain a good smooth state by such a smoothing treatment of the phosphor layer 3, so that the obtained light reflecting layer 50 is not in a perfect mirror state but is likely to be in a substantially mirror state. Of course, from the viewpoint of sharpness, it is desirable that the light reflecting layer 50 be in a good mirror surface state. Since such a forming method does not include the bonding step as described above, there is an advantage that the preparation of the fluorescent plate is steady and easy. In this case, the protective film 1
0 is not limited to resin but may be a dielectric thin film such as SiO, and may not be provided if not necessary.
If it is not provided, it can be said that it is preferable because the hindrance of transmission of incident X-rays is reduced.

Further, since optically transparent lead glass is used as the support 9, it is possible to protect the phosphor layer 3 and, as a radiation protection glass, to protect an observation machine or an observer from exposure. it can.

That is, some X-rays pass through the phosphor layer 3, so that the lead glass support 9 absorbs the X-rays. Note that a thin film for preventing reflection may be provided on both surfaces of the support 9. Also, Japanese Unexamined Patent Publication No. 7-218698
As shown in the figure, a dielectric optical multilayer thin film for increasing the brightness in the normal direction of the phosphor screen may be provided.

The description of the brightness and sharpness of the light-emitting image of the fluorescent screen 1E of this embodiment is almost the same as that of the third embodiment, and will not be repeated.

Embodiment 6 FIG. 6 shows a cross-sectional structure of a fluorescent plate 1F of this embodiment.

In the fluorescent screen 1F, the protective film 12 made of resin (PET in this case) is formed from the incident side of the X-rays 31.
(Thickness: 20 μm), a light reflecting layer 50 composed of a metal (here, silver) thin film 2 and an optically transparent protective film 11 made of resin (here, PET), mainly a phosphor (here, Gd _2). Phosphor layer 3 (thickness: O ₂ S: Tb)
550 μm) and an optically transparent support 9 (thickness: 9 mm) made of glass (here, lead glass) is integrally formed in this order.

Since the metal thin film 2 of this embodiment is made of silver and easily subjected to a chemical change, it has a structure in which the protective films 12 and 11 are provided on both surfaces thereof. This is similar to the second embodiment.

The method of forming the fluorescent plate 1F can be the same as that of the fifth embodiment. The function of the support 9 is the same as that of the fifth embodiment. Further, the protective film 11 can be formed as in the second embodiment, and needless to say, may be omitted in some cases.

As described above, the present invention has been described in detail with reference to the embodiments. However, the embodiments can be further modified based on the technical idea of the present invention.

For example, radiation is not limited to X-rays. By using a phosphor layer where phosphors are properly selected,
A fluorescent plate for converting other radiation into visible light and a radiation image observation device can be manufactured.

Further, in the above-described embodiment, an example was described in which the emission of visible light from the fluorescent plate, that is, the observation, was performed on the side opposite to the radiation incident side. On the other hand, emission of visible light, that is, observation can be performed on the radiation incident side.
For example, in the fluorescent plates of Examples 1 to 4, X-rays can be incident from the observation side, and the surface of the fluorescent plate on the X-ray incident side can be observed for the emitted light.

[0181]

As described above, the present invention provides a phosphor layer for converting incident radiation into visible light, and a phosphor layer disposed on the opposite side of the phosphor layer from the observation side to reflect visible light of 90%.
As described above, since the phosphor layer has the light reflecting layer that reflects light toward the visible light emitting side, the amount of visible light emitted is sufficient, and the brightness of an image obtained on the phosphor element is improved. Further, a phosphor layer that converts incident radiation into visible light, and a light reflection layer that is disposed on the opposite side of the phosphor layer from the observation side and reflects the visible light emission side of the phosphor layer has a thickness of 10 μm or less, Alternatively, since the surface of the light reflection layer is in a mirror state or a substantially mirror state, or both, the sharpness of an image obtained on the phosphor element is improved. Therefore, it is possible to provide a radiation image observation (especially X-ray imaging) apparatus with high sensitivity and high image quality.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an example (Example 1) of a phosphor plate of the present invention.

FIG. 2 is a schematic sectional view of another example (Example 2) of the fluorescent plate.

FIG. 3 is a schematic cross-sectional view of another example (Example 3) of the fluorescent plate.

FIG. 4 is a schematic cross-sectional view of another example (Example 4) of the fluorescent plate.

FIG. 5 is a schematic cross-sectional view of another example (Example 5) of the fluorescent plate.

FIG. 6 is a schematic sectional view of another example (Example 6) of the fluorescent plate.

FIG. 7 is a partially enlarged cross-sectional view of the fluorescent plate showing the behavior of visible light in the fluorescent plate.

FIG. 8 is a schematic diagram showing a radiation image observation (imaging) (particularly, X-ray imaging) apparatus.

FIG. 9 is a graph showing reflection spectra (changes in reflectance with wavelength) of metal thin films of various metals.

FIG. 10 is a graph showing a change in the amount of light emitted to the observation side depending on the reflectance of the light reflection layer.

FIG. 11 shows a SiO ₂ layer and T on a reflection surface of an aluminum thin film.
a set of the iO ₂ layer is a graph showing changes in reflectance due to the wavelength of the two pairs (four layers) provided with the light reflecting layer.

FIG. 12 is an angle average reflection of an aluminum thin film (Al) and a light reflecting layer in which one to four sets of dielectric films are provided on the reflecting surface of the aluminum thin film (Al), each of which includes one set of a SiO ₂ layer and a TiO ₂ layer. It is a graph which shows the change of the reflectance (calculated value) with the wavelength of a rate (calculated value).

FIG. 13 is a graph showing a change in reflectance (calculated value) depending on the wavelength of the light reflecting layer in the fluorescent plate of Example 4 of the present invention.

FIG. 14 is a graph showing the relative sharpness of the fluorescent plate of Example 3 and a conventional fluorescent plate.

FIG. 15 is a schematic sectional view of an example of a conventional fluorescent screen.

FIG. 16 shows an emission spectrum of a conventionally used phosphor Gd ₂ O ₂ S: Tb (change in light intensity (relative value) depending on wavelength).
FIG.

FIG. 17 is a schematic view showing a process of forming a radiation image.

FIG. 18 is a partially enlarged cross-sectional view of a fluorescent plate showing a behavior of visible light in the conventional fluorescent plate.

[Explanation of symbols]

1, 1A, 1B, 1C, 1D, 1E, 1F, 15, 16
... phosphor element, 2 ... metal thin film, 3 ... phosphor layer, 4, 9 ...
Support, 5, 6, 10, 11, 12: Protective film, 13: Undercoat layer, 14: Light reflection layer corresponding to undercoat layer, 7, 7
a, 7b, 8, 8a, 8b: dielectric film, 20: X-ray generator (X-ray tube), 21: subject, 22: imaging room (dark room, dark box), 23: observation machine, 24: monitor, 25 ... code, 30, 31 ... X-ray, 32, 33, 41, 42, 4
3, 44, 45, 46, 47, 48 ... visible light, 50 ...
Light reflection layer, 60 ... X-ray imaging device

Claims (54)

[Claims] 1. A phosphor layer that converts incident radiation into visible, ultraviolet, or infrared light, and a phosphor layer that is disposed on a side opposite to a light emission side of the phosphor layer, and that reflects the light with a reflectance of 90% or more. A light reflecting layer for reflecting the light toward the light emitting side of the phosphor layer. 2. The phosphor element according to claim 1, wherein the light reflecting layer has a maximum reflectance when the incident angle of the light beam is 45 degrees. 3. The phosphor element according to claim 1, wherein said light reflecting layer has a thickness of 10 μm or less. 4. The phosphor element according to claim 1, wherein a surface of the light reflecting layer on a side from which the light beam is emitted is in a mirror surface state or a substantially mirror surface state. 5. The fluorescent light according to claim 1, wherein a support, the light reflecting layer, the phosphor layer, and an optically transparent protective film are provided in this order from a side opposite to the light emitting side. Body element. 6. The phosphor according to claim 5, wherein an optically transparent protective film for protecting the light reflecting layer is provided on a side of the light reflecting layer on which the phosphor layer is provided. element. 7. The phosphor element according to claim 5, wherein a protective film for protecting the light reflecting layer is provided on a side of the light reflecting layer opposite to a side on which the phosphor layer is provided. . 8. The phosphor element according to claim 1, wherein the light reflection layer, the phosphor layer, and an optically transparent support are provided in this order from the side opposite to the light emission side. 9. The phosphor according to claim 8, wherein an optically transparent protective film for protecting the light reflecting layer is provided on a side of the light reflecting layer on which the phosphor layer is provided. element. 10. The phosphor element according to claim 8, wherein a protective film for protecting the light reflecting layer is provided on a side of the light reflecting layer opposite to a side on which the phosphor layer is provided. . 11. The phosphor element according to claim 1, wherein said light reflection layer is made of a metal thin film. 12. The phosphor element according to claim 11, wherein said metal thin film is made of at least one selected from the group consisting of aluminum, silver, gold and copper. 13. A dielectric laminate comprising a metal thin film, and a low-refractive-index dielectric and a high-refractive-index dielectric on the side of the metal thin film on which the phosphor layer is provided. 2. The phosphor element according to claim 1, comprising at least one set of films. 14. The phosphor element according to claim 13, wherein said metal thin film is made of at least one selected from the group consisting of aluminum, silver, gold and copper. 15. The method according to claim 15, wherein the dielectric laminated film is made of a TiO ₂ layer and a Si layer.
Consisting of O ₂ layer, a phosphor element according to claim 13. 16. The phosphor element according to claim 13, wherein one to three sets of said dielectric laminated film are provided. 17. The phosphor element according to claim 1, wherein the light reflection layer is made of a dielectric laminated film of a low refractive index dielectric and a high refractive index dielectric. 18. The method according to claim 18, wherein the dielectric laminated film is made of a TiO ₂ layer and a Si layer.
Consisting of O ₂ layer, a phosphor element according to claim 17. 19. The phosphor element according to claim 17, wherein the number of layers of the dielectric laminated film is 9 to 13. 20. A phosphor layer for converting incident radiation into visible, ultraviolet, or infrared light, and a light-emitting side of the phosphor layer, the light-emitting side being arranged on a side opposite to a light emission side of the phosphor layer. A phosphor layer having a light reflection layer for reflecting light toward the light emission side, wherein the thickness of the light reflection layer is 10 μm or less. 21. The surface of the light reflecting layer on the side from which the light beam is emitted is in a mirror state or a substantially mirror state.
The phosphor element described in 1. 22. The fluorescent light according to claim 20, wherein a support, the light reflecting layer, the phosphor layer, and an optically transparent protective film are provided in this order from the side opposite to the light emitting side. Body element. 23. The phosphor according to claim 22, wherein an optically transparent protective film for protecting the light reflecting layer is provided on a side of the light reflecting layer on which the phosphor layer is provided. element. 24. The phosphor element according to claim 22, wherein a protective film for protecting the light reflecting layer is provided on a side of the light reflecting layer opposite to a side on which the phosphor layer is provided. . 25. The phosphor element according to claim 20, wherein the light reflecting layer, the phosphor layer, and an optically transparent support are provided in this order from the side opposite to the light emitting side. 26. The phosphor according to claim 25, wherein an optically transparent protective film for protecting the light reflecting layer is provided on a side of the light reflecting layer on which the phosphor layer is provided. element. 27. The phosphor element according to claim 25, wherein a protective film for protecting the light reflecting layer is provided on a side of the light reflecting layer opposite to a side on which the phosphor layer is provided. . 28. The phosphor element according to claim 20, wherein said light reflection layer is made of a metal thin film. 29. The phosphor element according to claim 28, wherein said metal thin film is made of at least one selected from the group consisting of aluminum, silver, gold and copper. 30. A dielectric laminate comprising a metal thin film, and a low refractive index dielectric and a high refractive index dielectric on the side of the metal thin film on which the phosphor layer is provided. 21. The phosphor element according to claim 20, comprising at least one set of films. 31. The phosphor element according to claim 30, wherein the metal thin film is made of at least one selected from the group consisting of aluminum, silver, gold and copper. 32. The method according to claim 31, wherein the dielectric laminated film is made of a TiO ₂ layer and a Si layer.
Consisting of O ₂ layer, a phosphor element according to claim 30. 33. The phosphor element according to claim 30, wherein one to three sets of said dielectric laminated films are provided. 34. The phosphor element according to claim 20, wherein the light reflection layer is made of a dielectric laminated film of a low refractive index dielectric and a high refractive index dielectric. 35. The method according to claim 35, wherein the dielectric laminated film is formed of a TiO ₂ layer and a Si layer.
Consisting of O ₂ layer, a phosphor element according to claim 34. 36. The phosphor element according to claim 35, wherein the number of layers of said dielectric laminated film is 9 to 13. 37. A phosphor layer that converts incident radiation into visible, ultraviolet, or infrared light, and a light-emitting side of the phosphor layer, which is disposed on a side opposite to a light-emitting side of the phosphor layer. A light reflecting layer for reflecting light toward the light emitting side, wherein the surface of the light reflecting layer on the light emitting side is in a mirror surface state or almost in a mirror surface state. 38. The fluorescent light according to claim 37, wherein a support, the light reflecting layer, the phosphor layer, and an optically transparent protective film are provided in this order from the side opposite to the light emitting side. Body element. 39. The phosphor according to claim 38, wherein an optically transparent protective film for protecting the light reflecting layer is provided on a side of the light reflecting layer on which the phosphor layer is provided. element. 40. The phosphor element according to claim 38, wherein a protective film for protecting the light reflecting layer is provided on a side of the light reflecting layer opposite to a side on which the phosphor layer is provided. . 41. The phosphor element according to claim 37, wherein the light reflection layer, the phosphor layer, and an optically transparent support are provided in this order from the side opposite to the light emission side. 42. The phosphor according to claim 41, wherein an optically transparent protective film for protecting the light reflecting layer is provided on a side of the light reflecting layer on which the phosphor layer is provided. element. 43. The phosphor element according to claim 41, wherein a protective film for protecting the light reflecting layer is provided on a side of the light reflecting layer opposite to a side on which the phosphor layer is provided. . 44. The phosphor element according to claim 37, wherein said light reflection layer is made of a metal thin film. 45. The phosphor element according to claim 44, wherein said metal thin film is made of at least one selected from the group consisting of aluminum, silver, gold and copper. 46. A dielectric laminate in which the light reflecting layer is a metal thin film, and a low refractive index dielectric and a high refractive index dielectric are set on the side of the metal thin film on which the phosphor layer is provided. 38. The phosphor device according to claim 37, comprising at least one set of films. 47. The phosphor element according to claim 46, wherein said metal thin film is made of at least one selected from the group consisting of aluminum, silver, gold and copper. 48. The method according to claim 48, wherein the dielectric laminated film is formed of a TiO ₂ layer and a Si layer.
Consisting of O ₂ layer, a phosphor element according to claim 46. 49. The phosphor element according to claim 46, wherein one to three sets of said dielectric laminated films are provided. 50. The phosphor element according to claim 37, wherein the light reflection layer is made of a dielectric laminated film of a low refractive index dielectric and a high refractive index dielectric. 51. The dielectric laminate film is composed of a TiO ₂ layer and a Si
The phosphor device according to claim 50, comprising an O ₂ layer. 52. The phosphor element according to claim 51, wherein the number of layers of said dielectric laminated film is 9 to 13. 53. A radiation image observation apparatus comprising: a radiation source; the phosphor element according to claim 1; and an observation unit. 54. The radiation image observation apparatus according to claim 53, further comprising a radiation source, the phosphor element according to any one of claims 1 to 52, and an observation unit in this order.