JP2005283483A - X-ray detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray detector improved in resolution characteristic. <P>SOLUTION: This X-ray detector comprises a protective film 18 having a columnar structure and provided on the surface of a scintillator layer 17 converting incident X-ray to fluorescence. An inorganic matter 45 reflecting the fluorescence converted by the scintillator layer 17 is dispersed in the protective film 18, whereby deterioration of resolution characteristic by the protective film 18 is prevented. According to this the resolution characteristic can be improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an X-ray detector provided with a protective film disposed on the surface of a scintillator layer.

  As a new generation detector for X-ray diagnosis, a flat detector using an active matrix has been developed. By detecting the irradiated X-rays in this flat detector, an X-ray image or a real-time X-ray image is output as a digital signal. In this flat panel detector, X-rays are converted into visible light, that is, fluorescence by a scintillator layer, and the fluorescence is converted into signal charges by a photoelectric conversion element such as an amorphous silicon (a-Si) photodiode or a CCD (Charge Coupled Device). An image is acquired by converting to.

The scintillator layer is generally made of cesium iodide (CsI): sodium (Na), cesium iodide (CsI): thallium (Tl), sodium iodide (NaI), or gadolinium oxysulfide (Gd ₂ O _2). S) or the like is used, and grooves are formed by dicing or the like, or deposited such that a columnar structure is formed, thereby providing a columnar structure and improving resolution characteristics.

  Since many materials used for the scintillator layer exhibit strong hygroscopicity, a protective film for preventing moisture absorption of the scintillator layer is generally provided.

  For example, it is known that a protective film is formed so as to cover each columnar scintillator of a columnar structure scintillator layer, thereby providing a moisture-proof effect and suppressing deterioration due to a change in luminance characteristics over time (for example, Patent Documents) 1).

  In addition, a structure in which a resin is formed as a thin film layer on a scintillator layer having a columnar structure so as to penetrate into a groove between the columnar scintillators and a moisture seal layer is formed on the thin film is also known (for example, a patent) Reference 2).

In each of the above structures, the protective film of the scintillator layer has a structure that covers the entire surface of the columnar scintillator, and a protective film of an organic material is formed on the surface of the scintillator layer, so that there is no gap between the photoelectric conversion element and the scintillator layer. Alternatively, a protective film is provided between the light reflection film that reflects backscattered light toward the photoelectric conversion substrate provided with the photoelectric conversion element and the scintillator layer.
Japanese Patent Laid-Open No. 5-60871 (page 3-4, FIG. 1) JP-A-5-196742 (page 3-5, FIG. 1)

  However, in the configuration described in each of the above patent documents, as a result of forming a protective film so as to cover the columnar scintillator, deterioration of luminance characteristics due to aging can be prevented by the moisture-proof effect of the protective film, but there is no protective film Compared to the above, there is a problem that the resolution characteristic is deteriorated.

  For example, when a protective film having a conventional structure is formed when a scintillator layer is directly formed on a photoelectric conversion substrate, an organic protective film exists between the scintillator layer and the light reflecting film. The film thickness of this protective film is, for example, 0.25 mm to 1 mm in the configuration described in Patent Document 2, and if a protective film with this thickness exists between the scintillator layer and the light reflecting film, this protective film Scattering of light occurs in the image, and resolution characteristics deteriorate.

  Further, in each of the above prior art configurations, since a protective film made of an organic material is present on the side wall of the scintillator layer, the difference in refractive index between the scintillator layer and the substance existing on the surface of the scintillator layer is not present. Since it is smaller than the case, there is a problem that the reflectance on the surface of the scintillator is lowered and the resolution characteristic is deteriorated.

  The present invention has been made in view of these points, and an object thereof is to provide an X-ray detector having improved resolution characteristics.

  The present invention relates to an X-ray detector including an X-ray conversion unit that converts incident X-rays into visible light, and a photoelectric conversion element that converts visible light converted by the X-ray conversion unit into an electrical signal. The X-ray conversion unit is provided in the photoelectric conversion element, has a columnar structure, and includes a scintillator layer that converts incident X-rays into visible light, and a protective film provided on the surface of the scintillator layer. The light-reflecting material particles that reflect visible light converted by the scintillator layer are dispersed and contained in the protective film. Then, the light reflecting material particles that reflect the visible light converted by the scintillator layer are dispersed in the protective film, thereby preventing the resolution characteristic from being deteriorated by the protective film and improving the resolution characteristic.

  According to the present invention, the light reflecting material particles that reflect the visible light converted by the scintillator layer are dispersed in the protective film, thereby preventing the resolution characteristic from being deteriorated by the protective film and improving the resolution characteristic.

  Hereinafter, the configuration of the X-ray detector according to the first embodiment of the present invention will be described with reference to FIGS.

  1 and 2, reference numeral 1 denotes an X-ray detector. The X-ray detector 1 is an X-ray flat sensor that detects an X-ray image that is radiation, and is used for, for example, general medical use. The X-ray detector 1 includes a TFT array substrate 2 as a photoelectric conversion element and an X-ray conversion for converting incident X-rays provided on the surface which is one main surface of the TFT array substrate 2 into visible light. Part 3.

  The TFT array substrate 2 converts the visible light converted by the X-ray conversion unit 3 into an electrical signal. The TFT array substrate 2 has a substantially rectangular shape that is provided on the glass substrate 11 and functions as an optical sensor. A plurality of photoelectric conversion units 12, control lines 13 arranged along the horizontal direction of the TFT array substrate 2 shown in FIG. 2, and data arranged along the vertical direction of the TFT array substrate 2 shown in FIG. Line 14, control circuit 15 to which each control line 13 is electrically connected, and amplification / conversion unit 16 to which each data line 14 is electrically connected. In addition, the X-ray conversion unit 3 includes a scintillator layer 17 disposed on the surface of the TFT array substrate 2 and a protective film 18 provided on the scintillator layer 17.

  In the photoelectric conversion unit 12, pixels 19 having the same structure are formed in a matrix, and a photodiode 21 as a photoelectric conversion member is disposed in the center of each pixel 19. These photodiodes 21 are arranged facing the lower part of the scintillator layer 17.

  Each pixel 19 includes a thin film transistor (TFT) 22 as a switching element electrically connected to the photodiode 21, and a storage capacitor 23 as a charge storage unit for storing the signal charge converted by the photodiode 21. I have.

  Each thin film transistor 22 accumulates and emits charges generated by the incidence of light on the photodiode 21, and is an amorphous silicon (a-Si) as an amorphous semiconductor, which is a crystalline semiconductor material, At least a part of the crystal semiconductor is polysilicon (P-Si). The thin film transistor 22 includes a gate electrode 25, a source electrode 26, and a drain electrode 27, respectively. The drain electrode 27 is electrically connected to each of the photodiode 21 and the storage capacitor 23.

  The storage capacitor 23 is formed in a rectangular flat plate shape and is provided opposite to the lower portion of each photodiode 21.

  The photoelectric conversion unit 12 includes a plurality of photodiodes 24 as a substantially L-shaped photoelectric conversion member that converts incident light into signal charges.

  The control line 13 is disposed between the pixels 19 along the row direction, and is electrically connected to each of the gate electrodes 25 of the thin film transistors 22 of the pixels 19 in the same row.

  The data line 14 is disposed between the pixels 19 along the column direction, and is electrically connected to the source electrode 26 of the thin film transistor 22 of each pixel 19 in the same column.

  The control circuit 15 controls the operating state of each thin film transistor 22, for example, on and off of each thin film transistor 22, and is mounted on one side edge along the row direction on the surface of the glass substrate 11.

  The amplifying / converting unit 16 includes a plurality of charge amplifiers 31 arranged corresponding to the respective data lines 14, a parallel / serial converter 32 to which the charge amplifiers 31 are electrically connected, and the parallel / serial A converter 32 has an analog-to-digital converter 33 electrically connected thereto.

  The charge amplifier 31 is configured by an operational amplifier (not shown), for example, and includes a pair of input terminals 35 and 36 and an output terminal 37.

  Each of the negative-side input terminals 35 of one of the pair of input terminals 35 and 36 is electrically connected to one end of the data line 14. The positive input terminal 36, which is the other of the pair of input terminals 35 and 36, is grounded.

  A series circuit of a capacitor 38 is connected in parallel between the negative input terminal 35 and the output terminal 37, and the capacitor 38 is configured to have an integration function. Further, a series circuit of switches 39 is connected in parallel between the negative-side input terminal 35 and the output terminal 37. The switch 39 is connected in parallel to the capacitor 38, and is configured so that the charge remaining in the capacitor 38 can be discharged by closing the switch 39.

  The parallel / serial converter 32 converts a plurality of electric signals input in parallel from the charge amplifiers 31 to the parallel / serial converter 32 into serial signals, and has one end in the column direction on the TFT array substrate 2. It is provided at the edge.

  The analog-digital converter 33 converts an analog signal into a digital signal, and is provided on the other side edge along the row direction of the TFT array substrate 2.

The scintillator layer 17 converts incident X-rays into visible light, that is, fluorescence, and is formed in a columnar structure having columnar scintillators 41 and grooves 42 alternately. Here, the scintillator layer 17 is formed, for example, by forming the columnar scintillator 41 by vacuum deposition using cesium iodide (CsI): thallium (Tl) or sodium iodide (NaI): thallium (Tl), or gadolinium oxysulfide. The (Gd ₂ O ₂ S) phosphor particles are mixed with a binder resin, applied onto the TFT array substrate 2, fired and cured, and formed into groove portions 42 by dicing with a dicer to form the column scintillator 41 into a square columnar shape. Such as those formed. The grooves 42 are filled with an atmosphere or an inert gas such as nitrogen (N ₂ ) for preventing oxidation. The groove portion 42 can be in a vacuum state.

  The protective film 18 protects the scintillator layer 17 from moisture, and is an organic film made of an organic material such as a para-xylylene thin film. The protective film 18 is formed by binding an inorganic material 45 as light reflecting material particles with an organic material. For this reason, the inorganic substance 45 is dispersed and contained in the protective film 18. Therefore, the protective film 18 also has a function as a light reflecting film. Further, the protective film 18 slightly permeates the upper part of the scintillator layer 17 and surrounds the scintillator layer 17 at the peripheral edge of the TFT array substrate 2.

Inorganic 45, for example, such as titanium dioxide (TiO _2), a substance having an X-ray absorption factor of 5% or less, and the refractive index and n _r, and the refractive index of the scintillator layer 17 was n _s, the One formula has a relationship of n _r > n _s . Furthermore, inorganic 45, the volume packing density _{F r,} the average particle size when the _{D r,} when the thickness of the protective film 18 was set to _{T r,} the _{T r × F r / D r} > 10 as the second equation Have a relationship.

で表される。 Note that the X-ray absorption rate, when the intensity of the previous X-rays transmitted through the transparent material I _0, the intensity of X-rays after passing through the transparent material was _{I, I / I 0 × 100} ( %). Here, I and I ₀ are e, the base of the natural logarithm, the absorption coefficient determined by the X-ray quality and the type of permeate, and μ (thickness) of the permeate. When

It is represented by

  Next, the operation of the first embodiment will be described.

  The resolution characteristics of the X-ray detector 1 having the scintillator layer 17 depend on the resolution characteristics (CTF (Contrast Transfer Function), MTF (Modulation Transfer Function)) of the scintillator layer 17.

Then, the fluorescence resolution characteristic δ until reaching the TFT array substrate 2 is expressed by the following equation: δ = δ, where δ _s is the resolution characteristic of the scintillator layer 17 and δ _b is the resolution characteristic due to fluorescence diffusion in the protective film 18. represented by _s × [delta] _b. That is, the resolution of the fluorescence reaching the TFT array substrate 2 is obtained by multiplying the resolution characteristic of the scintillator layer 17 by the resolution characteristic of the protective film 18.

For this reason, for example, even when the protective film thickness t is the conventional minimum film thickness, that is, when t = 50 μm, δ _b = 50% due to the resolution characteristic of the protective film shown in FIG. The resolution characteristic of the fluorescence reaching the substrate is about half that of the scintillator layer. Note that the resolution characteristic of the protective film in FIG. 3 is that the light of the point light source is incident from the incident surface that is one end surface of the protective film, and this light is reflected by the metal film provided on one surface of the protective film and reflected on the incident surface. It represents the MTF (2 lp / mm) when it comes out.

  For this reason, in the first embodiment, by dispersing the inorganic substance 45 as the light reflecting material particles that reflect the fluorescence converted by the scintillator layer 17 in the protective film 18, the protective film 18 has a light reflecting film. Thus, the diffusion of light in the protective film 18 is prevented to prevent the deterioration of the resolution characteristic, and the resolution characteristic of the X-ray detector 1 can be made equal to the resolution characteristic of the scintillator layer 17. The resolution characteristics can be improved.

Further, the fluorescence generated in the columnar scintillator 41 is repeatedly reflected by the side wall of the columnar scintillator 41 and reaches the photodiode 21. Therefore, the diffusion of the fluorescence depends on the reflectance R1 on the side wall of the columnar scintillator 41. Then, the reflectance R1 is a refractive index of the material forming the columnar scintillator 41 and n _s, and the refractive index of the material in contact with the side wall of the columnar scintillator 41 and n _m, a fourth formula R1 = (n _s −n _m ) / (n _s + n _m ).

Furthermore, in order to improve the resolution characteristics of the X-ray detector 1, since it is necessary to suppress the diffusion of fluorescence in the scintillator layer 17, the reflectance R1 on the side wall of the columnar scintillator 41 must be improved. Therefore, the fourth type, in order to improve the resolution characteristics of the X-ray detector 1, the difference between the refractive index n _m and the refractive index n _s is large and it is desirable to have a relation of n _s> n _m .

Here, FIG. 4 shows the refractive indexes of various materials. For example, if the material constituting the scintillator layer 17 is cesium iodide: thallium, sodium iodide: thallium, or gadolinium oxysulfide, the refractive index n _s of these materials is about 1.8 to 2.4. On the other hand, acrylic as a material for forming the protective film 18, polycarbonate, or name a para-xylylene, the refractive index n _m of these materials is about 1.4 to 1.6.

Therefore, in the structure of the conventional protective film, whereas the protective film because it is completely penetrated into the grooves between the columnar scintillator, the difference between the refractive index n _m and the refractive index n _s is relatively small, the In the first embodiment, air or an inert gas is sealed in almost the entire area excluding a part of the groove part 42 between the columnar scintillators 41, or the substantially entire area excluding a part of the groove part 42 is evacuated. as shown in FIG. 4, the difference between the refractive index n _m and the refractive index n _s increases, better than the conventional configuration reflectance R1 at the side wall of the columnar scintillator 41 by the fourth equation, X-rays The resolution characteristics of the detector 1 can be further improved.

  In addition, when the fluorescent light penetrates into the protective film 18, the reflection of the fluorescent light at the protective film 18 occurs at two places, the boundary between the scintillator layer 17 and the inorganic substance 45 and the boundary between the protective film 18 and the inorganic substance 45, respectively. To do.

Therefore, the reflectance R2 of the fluorescence at the protective film 18 is _expressed by the following equation as R2 = α (n _r −, where n _r is the refractive index of the inorganic material 45 and n _b is the refractive index of the organic material of the protective film 18. (n _s ) / (n _r + n _s ) + β (n _r −n _b ) / (n _r + n _b ) Here, α indicates the probability that reflection will occur at the boundary between the scintillator layer 17 and the inorganic material 45, and β indicates the probability that reflection will occur at the boundary between the inorganic material 45 and the organic material of the protective film 18.

Since the relationship between α and β often satisfies α <β, the reflectance R2 of the protective film 18 is determined by the relationship between the inorganic material 45 and the organic material of the protective film 18 when the fluorescence enters the protective film 18. The influence of the reflection effect due to the difference in refractive index is large. Therefore, by the fifth equation, in order to improve the reflectance R2 of the protective film 18, the difference between the refractive index n _r and the refractive index n _s, and the difference between the refractive index n _b and the refractive index n _r Larger is better. Further, the refractive index _{n s} 4 is approximately 1.8 to 2.4, from the refractive index _{n b} is about 1.4 to 1.6, as in the first embodiment In addition, since the relationship between the refractive index n _r and the refractive index n _s satisfies the relationship of the first formula, a reflection effect can be obtained at the boundary between the scintillator layer 17 and the inorganic material 45, and the inorganic material 45 and the protective film 18 can be obtained. The reflection effect at the boundary with the organic material can be improved. The greater the difference between the refractive index n _r and the refractive index n _s , the more remarkable the reflection effect on the protective film 18.

Further, as shown in FIG. 5, the inorganic substance 45 satisfies the relationship of the second formula when the volume filling density is F _r and the average particle diameter is D _r , and the film thickness of the protective film 18 is T _r. Thus, the reflectance R2 of the protective film 18 shows a stable value with a high reflectance, and the luminance characteristics of the X-ray detector 1 can be further improved.

  Next, a second embodiment will be described with reference to FIG. In addition, about the structure and effect | action similar to the said 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 6, the X-ray detector 1 has a structure in which the protective film 18 is located above the scintillator layer 17 and does not penetrate into the grooves 42 between the columnar scintillators 41. The protective film 18 has a structure that does not penetrate into the groove portion 42 by being applied to the upper portion of the scintillator layer 17 as, for example, a paste-like high-viscosity coating liquid.

  Further, by not allowing the protective film 18 to permeate the scintillator layer 17, the reflectance R1 at the side wall of the columnar scintillator 41 of the scintillator layer 17 can be further improved, and the resolution characteristics can be further improved.

  Next, a third embodiment will be described with reference to FIG. In addition, about the structure and effect | action similar to said each embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 7, an organic film 46 such as an acrylic film is formed on the protective film 18. The organic film 46 is provided so as to cover the entire upper portion of the protective film 18.

  Then, by covering the upper part of the protective film 18 with the organic film 46, the moisture-proof effect of the scintillator layer 17 by the protective film 18 is reinforced by the organic film 46, and deterioration over time such as luminance characteristics due to the aging of the scintillator layer 17 is prevented. Can be suppressed.

  In the third embodiment, the organic film 46 may have a configuration in which an inorganic substance is dispersed therein and an X-ray absorption rate is 5% or less. In this case, deterioration over time such as luminance characteristics due to change over time of the scintillator layer 17 can be more reliably suppressed.

  Next, a fourth embodiment will be described with reference to FIG. In addition, about the structure and effect | action similar to said each embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 8, an inorganic film 47 such as a silicon dioxide film is formed on the protective film 18. The inorganic film 47 is provided so as to cover the entire upper part of the protective film 18. The inorganic film 47 has an X-ray absorption rate of 5% or less.

  Then, by covering the upper part of the protective film 18 with the inorganic film 47 having an X-ray absorption rate of 5% or less, the moisture-proof effect of the scintillator layer 17 by the protective film 18 is reinforced by the inorganic film 47, and the change with time of the scintillator layer 17 It is possible to suppress deterioration over time such as luminance characteristics due to.

  In each of the above embodiments, various other particles can be selected as the light reflecting material particles in place of the inorganic substance 45.

  Next, an embodiment of the present invention will be described.

  In this example, the conventional example shown in FIG. 9 corresponding to the prior art, Example 1 and Example 2 corresponding to the first embodiment and the second embodiment, respectively, and Example 3 shown in FIG. Example 4 shown in FIG. 11 and Examples 5 and 6 corresponding to the third embodiment and the fourth embodiment, respectively, will be discussed.

  In the conventional example, as shown in FIG. 9, a cesium iodide: thallium film having a thickness of 500 μm is formed as the scintillator layer 17, a paraxylylene thin film is formed as a protective film 18 on the scintillator layer 17, and a columnar scintillator 41 is provided. An aluminum (Al) film was formed as a light reflecting film 51 on the protective film 18 by a sputtering method.

  In Example 1, a cesium iodide: thallium film having a film thickness of 500 μm was formed as the scintillator layer 17, and a film thickness of 200 μm bonded to the scintillator layer 17 with a resin using titanium dioxide particles as the inorganic substance 45. A protective film 18 was formed. Here, since the refractive index of cesium iodide: thallium is about 1.8 and the refractive index of titanium dioxide is 2.2, the first formula is satisfied. Further, the volume filling density of the titanium dioxide particles in the protective film 18 was 70%, and the average particle size was 1 μm. Therefore, Example 1 satisfy | fills 2nd Formula. Furthermore, the protective film 18 penetrates about 50 μm between the columnar scintillators 41.

  In the second embodiment, a scintillator layer 17 and a protective film 18 made of the same material as in the first embodiment are formed, and this protective film 18 does not penetrate between the columnar scintillators 41.

  In Example 3, a cesium iodide: thallium film having a thickness of 500 μm was formed as the scintillator layer 17 on the photodiode 21, and the scintillator layer 17 was made of resin using silicon dioxide particles as the inorganic substance 45. A bonded protective film 18 having a thickness of 200 μm was formed. Further, the volume filling density of silicon dioxide particles in the protective film 18 was set to 70%, and the average particle size was set to 1 μm. Further, the protective film 18 does not penetrate between the columnar scintillators 41. That is, Example 3 uses the inorganic substance 45 of Example 2 as silicon dioxide particles, and the other conditions are the same as Example 2. Since the refractive index of cesium iodide: thallium is about 1.8 and the refractive index of silicon dioxide particles is 1.5, Example 3 does not satisfy the first formula.

  In Example 4, a cesium iodide: thallium film having a thickness of 500 μm was formed as the scintillator layer 17 on the photodiode 21, and the scintillator layer 17 was made of resin using titanium dioxide particles as the inorganic substance 45. A bonded protective film 18 having a thickness of 20 μm was formed. The volume filling density of titanium dioxide particles in the protective film 18 was 40%, and the average particle size was 1 μm. Further, the protective film 18 does not penetrate between the columnar scintillators 41. That is, in Example 4, the thickness of the protective film 18 of Example 2 was reduced and the volume packing density of the titanium dioxide particles was reduced. Other conditions were the same as in Example 2. And Example 4 does not satisfy the second formula.

  In Example 5, an acrylic film having a film thickness of 500 μm was formed as the organic film 46 on the protective film 18 of Example 2.

  In Example 6, a 200 μm-thick silicon dioxide film was formed as the inorganic film 47 on the protective film 18 of Example 2.

  And the result of having measured the brightness | luminance of the said prior art example and each Example, the brightness | luminance after one day, a luminance degradation rate, and CTF is shown in FIG. 12, respectively, Each example is examined, referring this FIG.

  First, the conventional example and Example 1 are compared. In Example 1, although the luminance after one day showing the moisture-proof effect of the protective film 18 is slightly deteriorated compared to the conventional example, the CTF showing the resolution characteristics is improved as compared with the conventional example. Therefore, as shown in the first embodiment, it was shown that the resolution characteristic can be improved by providing the protective film 18 with the function of a light reflecting film.

  Next, Example 1 and Example 2 are compared. In Example 2, the CTF is improved as compared with Example 1. Therefore, it was shown that the resolution characteristics can be further improved by not allowing the protective film 18 to penetrate between the scintillator layers 17 as in the second embodiment.

  Moreover, Example 2 and Example 3 are compared. In the third embodiment, the reflectance of the protective film 18 is lowered, and the luminance characteristics are deteriorated as compared with the second embodiment. Therefore, the effect that the luminance characteristics can be improved by satisfying the first expression as in the above embodiments has been shown.

  Furthermore, Example 2 and Example 4 are compared. In the fourth embodiment, the reflectance of the protective film 18 is lowered, and the luminance characteristics are deteriorated as compared with the second embodiment. Therefore, the effect that the luminance characteristic can be improved by satisfying the second expression as in the above embodiments has been shown.

  And Example 2 and Example 5 and Example 6 are compared. In each of Examples 5 and 6, the organic film 46 or the inorganic film 47 is formed on the protective film 18, so that the moisture-proof effect is improved. As shown by the luminance after one day, the change with time The degree of deterioration of the luminance characteristics due to is reduced. Therefore, it has been shown that the moisture-proof effect can be improved by forming the organic film 46 and the inorganic film 47 as in the third and fourth embodiments.

It is a longitudinal section showing the X-ray detector of a 1st embodiment of the present invention. It is a top view which shows a X-ray detector same as the above. It is a graph which shows the relationship between the film thickness of the protective film of a X-ray detector same as the above, and the resolution characteristic of a protective film. It is a table | surface which shows the example of each refractive index of the material of the scintillator layer of the same X-ray detector, and the material of a protective film. Same as above, the relationship T _r × F _r / D _r between the protective film thickness T _r , the volume filling density F _r of the light reflector particles and the average particle diameter D _r, and the light reflection at the protective film It is a graph which shows the relationship with a rate. It is a longitudinal cross-sectional view which shows the X-ray detector of the 2nd Embodiment of this invention. It is a longitudinal cross-sectional view which shows the X-ray detector of the 3rd Embodiment of this invention. It is a longitudinal cross-sectional view which shows the X-ray detector of the 4th Embodiment of this invention. It is a longitudinal cross-sectional view which shows the X-ray detector of the prior art example of one Example of this invention. It is a longitudinal cross-sectional view which shows the X-ray detector of Example 3 same as the above. It is a longitudinal cross-sectional view which shows the X-ray detector of Example 4 same as the above. It is a table | surface which shows the brightness | luminance of each Example and each comparative example same as the above, the brightness | luminance after one day, a luminance degradation rate, and CTF.

Explanation of symbols

1 X-ray detector 2 TFT array substrate as photoelectric conversion element 3 X-ray conversion unit
17 Scintillator layer
18 Protective film
45 Inorganic materials as light reflector particles
46 Organic membrane
47 Inorganic membrane

Claims (8)

In an X-ray detector comprising an X-ray conversion unit that converts incident X-rays into visible light, and a photoelectric conversion element that converts visible light converted by the X-ray conversion unit into an electrical signal,
The X-ray converter is
A scintillator layer provided in the photoelectric conversion element, having a columnar structure, and converting incident X-rays into visible light;
A protective film provided on the surface of the scintillator layer,
In this protective film, the light-reflecting material particle which reflects the visible light converted by the said scintillator layer is disperse | distributed and contained. X-ray detector characterized by the above-mentioned. The X-ray detector according to claim 1, wherein the protective film is not provided between the columnar structures of the scintillator layer. The X-ray detector according to claim 1, wherein the X-ray conversion unit includes an organic film provided on an upper portion of the protective film. The X-ray detector according to claim 1, wherein the X-ray conversion unit includes an inorganic film having an X-ray absorption rate of 5% or less provided on the upper part of the protective film. The X-ray detector according to claim 1, wherein the X-ray conversion unit includes an organic film having an X-ray absorption rate of 5% or less, in which an inorganic substance is dispersed and contained, on an upper part of the protective film. X-ray converter
An organic film,
An inorganic film having an X-ray absorption rate of 5% or less,
3. The X-ray detection according to claim 1, wherein one of the organic film and the inorganic film is provided on an upper part of the protective film, and the other is provided on the upper part of either one. vessel. The refractive index of the light reflecting material particles and n _r, and the refractive index of the scintillator layer and n _s,
The X-ray detector according to claim 1, wherein a relationship of n _r > ns is _satisfied . The thickness of the protective film and T _r, the volume packing density of the light reflecting material particles and F _r, the average particle diameter of the light reflecting material particles When D _r,
The X-ray detector according to claim 1, wherein a relationship of T _r × F _r / D _r > 10 is satisfied.

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