JP5702903B2 - Luminescent material, scintillator including the luminescent material, X-ray detection element including the scintillator, and X-ray detector including the X-ray detection element - Google Patents

Description

  The present invention relates to a luminescent material, a scintillator including the luminescent material, an X-ray detection element including the scintillator, an X-ray detector including the X-ray detection element, an image display device using the luminescent material, and the light emission The present invention relates to a light source using a material.

  In recent years, with an increase in the speed and definition of X-ray CT (Computed Tomography), an X-ray detector having a higher response speed and higher sensitivity is required. Currently used X-ray detectors are mainly combined with a scintillator that converts X-rays into light and a light-receiving element that converts light into an electrical signal. For this reason, in order to realize an X-ray detector having a high response speed and higher sensitivity, it is necessary to improve the characteristics of the scintillator, and it is necessary to improve the light emission characteristics of the light emitting material constituting the scintillator. In order to realize an X-ray detector with a high response speed, a light emitting material with a short afterglow time is required. For example, it is desirable that the afterglow time when the emission intensity attenuates to 10% is 10 μs or less. In order to realize a highly sensitive X-ray detector, it is necessary that the light emission efficiency be high, but it is desirable that the emission spectrum of the light emitting material matches the sensitivity spectrum of the light receiving element.

  At present, silicon photodiodes are mainly used as the light receiving elements of X-ray detectors, and the peak of this spectral sensitivity distribution is in the near infrared region, so the wavelength of the light emitting material is also close to the deep red region of 650 nm or more. It is desirable to be in the infrared region.

Known scintillators for X-ray detectors include single crystal scintillators made of NaI: Tl, single crystal scintillators made of CdWO ₄ , ceramic scintillators made of Gd ₂ O ₂ S: Pr, and the like. Since the afterglow time of these scintillators is less than 10 μs, it is suitable for an X-ray detector having a high response speed. However, the emission peak wavelengths are 415 nm, 470 nm, and 510 nm, respectively, which is insufficient when considering matching with a silicon photodiode. In addition, a ceramic scintillator made of (Y, Gd) ₂ O ₃ : Eu is known. This scintillator has an emission peak wavelength of 610 nm and a wavelength larger than that of the above-mentioned scintillator. However, it is still insufficient for a silicon photodiode, and the afterglow time is 1 ms or more. This is not suitable for a fast X-ray detector. The symbol (Y, Gd) means a mixed crystal of Y (yttrium) and Gd (gadolinium).

As one of means for obtaining a light emitting material having a short afterglow time, it is conceivable to use Eu ²⁺ that exhibits light emission by allowable transition as a light emission center. Non-Patent Document 1 shows a list of light emitting materials using Eu ²⁺ as a light emission center. Luminescent materials having an emission wavelength of 650 nm or more described in this list are limited to chemically unstable substances that easily react with water, such as CaO and CaS, or nitrides that are difficult to synthesize.

  In addition, phosphors are used as important materials that influence the performance of devices in various fields such as lighting, displays, and medical devices. Here, the phosphor refers to a part of the light emitting material, and can be regarded as synonymous in the following text. For example, in the lighting field, the phosphor greatly affects the performance such as efficiency and color rendering in a device such as a fluorescent lamp and a white LED whose technological progress has been remarkable in recent years. In the display field, the light emission characteristics of phosphors dominate image display performance in self-luminous display devices such as plasma display panels (PDP) and field emission displays (FED). In a non-light-emitting display such as a liquid crystal display, it is not an exaggeration to say that the backlight greatly affects the display performance, and therefore the phosphor used for the backlight greatly affects the image display performance of the liquid crystal display. Thus, in various devices using light emission, since the phosphor becomes an important material that affects them, a phosphor having more excellent light emission characteristics is demanded.

In response to such demands, various light emitting materials have been developed so far, and some of them are put into practical use as phosphors. Major phosphors have been introduced in various documents such as Non-Patent Document 2, for example. A direct-view cathode ray tube (CRT) can be given as a typical display device for excitation with an electron beam. Typical phosphors used for this are blue light-emitting phosphors of ZnS: Ag, Cl or ZnS: Ag, Al, green light-emitting phosphors of ZnS: Cu, Al, and red light-emitting phosphors of Y ₂ O ₂ S: Eu. These phosphors emit light with high efficiency when excited by an electron beam having a relatively low energy density, such as a direct-view type CRT, but emit light due to saturation when the energy density is high even when excited by the same electron beam. Efficiency will decrease. For this reason, when excited by an electron beam having a high energy density as in the projection type CRT, high energy density such as Y ₂ SiO ₅ : Tb as a green light emitting phosphor and Y ₂ O ₃ : Eu as a red light emitting phosphor. A phosphor that emits light with high brightness under the excitation of electron beam is used. However, with respect to the blue light-emitting phosphor, no phosphor has been known that has higher luminance and excellent emission color than the ZnS phosphor under excitation with an electron beam with a high energy density.

In the display field, in recent years, flat panel displays have been frequently used in place of CRTs, and attention is paid to FED or SED (Surface-Conduction Electron-Emitter Display) for electron beam excitation. In these, since the phosphor is excited by an electron beam having a higher energy density than the direct-view type CRT, a phosphor with less luminance saturation is required. In particular, the blue phosphor is ZnS fluorescent under FED or SED excitation conditions. The appearance of phosphors with higher brightness than the body is awaited. The light source most commonly used for the backlight of the liquid crystal display is a cold cathode fluorescent lamp. As a typical phosphor used for this, blue light emitting BaMgAl ₁₀ O ₁₇ : Eu (BAM), green light emitting A mixture of LaPO ₄ : Ce, Tb and Y ₂ O ₃ : Eu that emits red light may be mentioned.

On the other hand, recently, attempts have been made to use a white LED light source as a backlight. A typical white LED light source is a combination of a blue light emitting diode (LED) and a yellow light emitting (Y, Gd) ₃ Al ₅ O ₁₂ : Ce phosphor. In order to increase the color reproduction range of the liquid crystal display, it is desirable that the area of the triangle formed by the red, blue, and green display colors on the chromaticity diagram when the light source and the color filter are combined is desirable. Therefore, the phosphor used for the backlight light source is required to have an emission spectrum that satisfies these requirements, and the appearance of a phosphor capable of realizing a wider color reproduction range is awaited. Also, from the viewpoint of manufacturing, it is easier to manage the spectrum of the light source when white light is obtained with one kind of phosphor than to obtain a white color by mixing a plurality of phosphors. The appearance of phosphors that emit light is desirable. Although various phosphors are publicly known as in the above-described example, the appearance of phosphors having better light emission characteristics is awaited depending on the respective demands in the use of individual phosphors.
P. Dorenbos: J. Lumin. 104 (2003) pp.239-260 PHOSPHOR HANDBOOK Edited by S. Shionoya and WM Yen, pp.391-394, pp.511-520, etc., CRC Press (1999)

  As described above, there is no conventional scintillator that satisfies the conditions that the afterglow time is short and the emission wavelength is long.

  In addition, as described above, there are many uses where the characteristics of known light-emitting materials are insufficient, and the appearance of new phosphor materials is awaited. For example, a backlight light source capable of realizing a wider color gamut when combined with a blue light-emitting phosphor or a color filter of a liquid crystal display, which has higher luminance than a ZnS phosphor under high energy density electron beam excitation and excellent emission color. Such as white phosphors that make possible.

  The present invention has been made in view of the above circumstances, and a light emitting material having a short afterglow time of 10 μs or less and an emission wavelength of 650 nm or more, a scintillator made of the light emitting material, and an X equipped with the scintillator A line detection element and an X-ray detector equipped with the X-ray detection element are provided. At the same time, it is brighter and brighter than ZnS phosphor under excitation with a high energy density electron beam, and has a wider color reproduction. An object of the present invention is to provide a luminescent material capable of realizing a light emitting region, an image display device using the luminescent material, and a light source using the luminescent material.

In the light emitting material according to the first aspect of the present invention, A represents at least one element of Na, K, Rb, and Cs, and R represents at least one element of Y, La, Gd, and Lu. And a material whose composition is represented by ARS ₂ : Eu.

  A scintillator according to the second aspect of the present invention is characterized by being made of the above-described light emitting material.

  An X-ray detection element according to the third aspect of the present invention includes the scintillator described above and a silicon photodiode that receives light from the scintillator.

  An X-ray detector according to the fourth aspect of the present invention is provided with a plurality of X-ray detection elements described above arranged in a matrix and corresponding to each column, and the X-ray detection in the same column. And a signal line connected to the output of the element.

In the luminescent material according to the fifth aspect of the present invention, A represents at least one element of Na, K, Rb, and Cs, and R represents at least one element of Y, La, Gd, and Lu. When represented, the composition of the matrix is represented by ARS ₂ .

  According to a sixth aspect of the present invention, there is provided an image display device comprising: a first substrate; a red light emitting pixel, a green light emitting pixel, which is provided on the first substrate and emits red, green, and blue light, respectively; A blue light emitting pixel, a second substrate disposed to face the surface of the first substrate on which the respective pixels are provided, and a surface of the second substrate facing the first substrate. A plurality of electron beam sources provided corresponding to the pixels and emitting electron beams to the corresponding pixels, wherein the blue light emitting pixel has a light emitting material according to the fifth aspect activated by Bi. It is characterized by.

  The light source according to the seventh aspect of the present invention excites the light emitting material of the fifth aspect activated by Bi and Pr, and the light emitting material is irradiated with light having a peak wavelength of 400 nm or less to excite the light emitting material. And a light emitting element.

  According to the present invention, the afterglow time is as short as 10 μs or less, the emission wavelength is 650 nm or more, and the matching with the sensitivity spectrum of the silicon photodiode is good, the scintillator including the light emitting material, and the X equipped with the scintillator A line detection element and an X-ray detector including the X-ray detection element can be provided. In addition, a light-emitting material that is brighter than a ZnS phosphor under excitation with an electron beam with a high energy density, has an excellent emission color, and can realize a wider color reproduction range, an image display device using the light-emitting material, and this A light source using a light-emitting material can be provided.

  Hereinafter, embodiments of the present invention will be described in detail.

(First embodiment)
A first embodiment of the present invention will be described.

The composition of the luminescent material of the present embodiment is represented by NaYS ₂ : Eu. This luminescent material is obtained by adding Eu to a NaYS ₂ matrix. As far as the present inventor is aware, the phosphor represented by this composition formula is not known. Furthermore, the present inventor has found that this phosphor exhibits a specific light emission different from that of a normal Eu-activated phosphor.

Usually, when Eu is added to a base material containing a rare earth element such as Y, Eu exists in a + 3-valent form, and shows a linear emission spectrum having a peak in the vicinity of 610 nm to 630 nm, which is characteristic of Eu ³⁺ .

On the other hand, when Eu is added to a matrix containing an alkaline earth metal such as Ba or Sr, it is known that Eu often exists in a + 2-valent form and shows a band spectrum peculiar to Eu ²⁺ .

However, when Eu is added to the NaYS ₂ matrix, the present inventor shows that a band spectrum peculiar to + 2-valent Eu is exhibited even though the matrix contains rare earth elements and does not contain alkaline earth metal. I found it. Furthermore, the present inventor has also found that this phosphor exhibits light emission in the longest wavelength region among the light emission of Eu ²⁺ . The reason for this is unknown, but there is a possibility that there is some causal relationship between the fact that the emission of Eu ²⁺ is present in the longest wavelength range even though the matrix does not contain an alkaline earth metal. .

  Next, the method for manufacturing the light emitting material according to the present embodiment will be described.

First, Na ₂ S, Y ₂ S ₃ and Eu ₂ O ₃ as raw materials have a molar ratio of 1.05: 0.997: 0.003, and specific weights are 20.49 g, 68.29 g, and 0.264 g, respectively. Were weighed and mixed. This was filled in a carbon crucible and fired at 1000 ° C. for 1.5 hours in a hydrogen sulfide atmosphere. The body color after firing is pink. This was pulverized with a mortar, washed with water, and dried to obtain a powdery luminescent material. There was no significant dissolution or decomposition of the luminescent material even when washed with water.

When the luminescent material of the powder was analyzed by X-ray diffraction, it was confirmed that NaYS ₂ was formed, and it was confirmed that this luminescent material was NaYS ₂ : Eu. When this luminescent material was excited by an electron beam pulse with an acceleration voltage of 10 kV and the afterglow characteristics were evaluated, the afterglow time for the emission intensity to drop to 10% was 7 μs, and it was a sufficiently short afterglow time of 10 μs or less. Was confirmed.

  Next, an emission spectrum was measured when the powdered luminescent material was irradiated with X-rays under the conditions of using a tungsten anode, a tube voltage of 120 kV, and a 30 mm thick Al filter. According to this measurement result, it was found that long-wave band emission having a peak at about 690 nm as shown in FIG. The emission spectrum when the wavelength of this emission spectrum is converted into photon energy and displayed is shown in FIG. The conversion was performed using a conversion formula of photon energy = hc / λ, where h is the Planck constant, c is the speed of light, and λ is the wavelength of light. As can be seen from FIG. 2, the full width at half maximum of the emission spectrum of the luminescent material of this embodiment was 0.28 eV.

Next, an existing light emitting material made of Gd ₂ O ₂ S: Pr is used as a comparative example. Then, the scintillator made of the light emitting material Gd ₂ O ₂ S: Pr of this comparative example has a main peak at about 510 nm as shown in FIG. 3, and exhibits linear light emission.

From the emission spectrum of each light emitting material of the present embodiment and the comparative example, when combined with a silicon photodiode, the intensity of the current signal obtained from the silicon photodiode when each light emitting material emits light of unit energy. The ratio was calculated. Then, when the intensity of the current signal of Gd ₂ O ₂ S: Pr, which is the light emitting material of the comparative example, is 100, the intensity of the current signal of NaYS ₂ : Eu, which is the light emitting material of the present embodiment, is 125. It was found to be higher than

The scintillator is preferably a bulk body such as a single crystal or ceramics because of its usage. However, the luminescent material of this embodiment is a powder. As a technique for obtaining a scintillator by sintering using a light emitting material of powder as a raw material, a method of manufacturing a scintillator by a hot isostatic pressing method using a metal capsule disclosed in JP-A-62-275072 is known. ing. This method is suitable for obtaining a scintillator from a light emitting material containing sulfur as a component. Using this method, the scintillator according to the present embodiment is created. First, about 60 g of a powder luminescent material made of NaYS ₂ : Eu of this embodiment was made into a cylindrical shape by press molding, covered with molybdenum foil, and sealed in a cylindrical capsule made of tantalum. Then, after applying a hot isostatic press for 3 hours at 2000 atmospheric pressure and 1200 ° C. using argon gas, the capsule was peeled off to obtain a ceramic scintillator material of NaYS ₂ : Eu. This scintillator material is cut into a size (for example, 1 to 3 mm) that can sufficiently absorb X-rays in the vertical and horizontal sizes required for applications such as an X-ray detector. In the present embodiment, the scintillator was manufactured by cutting to a length of about 4 mm, a width of about 1 mm, and a thickness of 2 mm, followed by polishing.

In this embodiment, since the temperature of the hot isostatic pressing can be lowered to about 1000 ° C., iron capsules having a lower melting point can be used instead of tantalum capsules.

  Next, as shown in FIG. 4, the scintillator 11 manufactured as described above and the silicon photodiode 12 that receives light from the scintillator 11 are bonded to an optically transparent adhesive, for example, an epoxy resin-based adhesive. The detection element 10 was produced by bonding using the material 13.

  Subsequently, as shown in FIG. 5, the X-ray detector 20 according to the present embodiment in which the detection elements 10 are arranged in a matrix on the substrate 21 was manufactured. The produced X-ray detector 20 according to the present embodiment is configured such that the outputs of the detection elements 10 in the same column are output to the outside via the same signal line 22 as shown in FIG. .

On the other hand, a scintillator having the same shape as that of the present embodiment is also produced for the light emitting material made of Gd ₂ O ₂ S: Pr of the comparative example, and bonded to a silicon photodiode to form detection elements. The X-ray detector of the comparative example was formed by arranging in a matrix on the substrate.

  Comparing the photodiode output when both X-ray detectors were irradiated with X-rays under the conditions of using tungsten anode, tube voltage 120 kV, and 30 mm thick Al filter, this embodiment was compared with the X-ray detector of the comparative example. X-ray detectors showed a sensitivity of 110%.

  Further, when the attenuation characteristic was measured by irradiating the X-ray detector of this embodiment with pulsed X-rays, it was confirmed that the afterglow time when the output was attenuated to 10% was 10 μs or less.

  As described above, according to the present embodiment, the afterglow time is as short as 10 μs or less, the light emitting wavelength is 650 nm or more, and the matching with the sensitivity spectrum of the silicon photodiode is good, and the scintillator including this light emitting material And an X-ray detector provided with this scintillator can be provided.

In the first embodiment, showing a case of using the Nays ₂ as a matrix. However, when A is at least one element of Na, K, Rb, and Cs and R is at least one element of Y, La, Gd, and Lu, the composition is a light emitting material represented by ARS ₂ : Eu. The same effect as the first embodiment can be obtained. These light emitting materials are obtained by adding Eu to the base of ARS ₂ . The FWHM of the emission spectrum of these luminescent materials is 0.25 eV to 0.35 eV. Further, if the concentration of Eu to be added is too high, the light emission efficiency is lowered. Therefore, the amount of Eu added is desirably about 3 mol% or less. A more preferable Eu addition amount is 0.01 mol% to 1 mol%.

In general, the matrix represented by ARS ₂ has a cubic or hexagonal crystal structure, but the present inventor has found that only the hexagonal crystal exhibits light emission. It was. Among the combinations of A and R, those that exhibit light emission are those in which A is Na and R is Y, Gd, or Lu, or A is at least one of K, Rb, and Cs, and R Is one of Y, La, Gd, and Lu. When the base material is a crystal structure of NaCl type such as NaLaS ₂ , light emission is not recognized or the light emission intensity is very weak as described later, which is not practical.

Among the light emitting materials, a light emitting material of NaGdS ₂ : Eu will be described as a second embodiment.

(Second Embodiment)
The light emitting material according to the second embodiment of the present invention is formed as follows.
First, 20.49 g, 102.4 g, and 0.264 g of Na ₂ S, Gd ₂ S ₃ , and Eu ₂ O ₃ were weighed as raw materials, respectively, and fired at 1000 ° C. for 3 hours in a hydrogen sulfide atmosphere. A luminescent material was obtained. The obtained luminescent material still showed a pink body color. When the afterglow characteristic was evaluated by exciting the light emitting material of the present embodiment with an electron beam pulse having an acceleration voltage of 10 kV, the afterglow time when the emission intensity decreased to 10% was 7 μs, and a sufficiently short afterglow time of 10 μs or less. It was confirmed that.

In addition, when the emission spectrum when the X-ray was irradiated to the luminescent material of this embodiment under the conditions of using a tungsten anode, a tube voltage of 120 kV, and a 30 mm thick Al filter was used, a peak was observed at about 750 nm as shown in FIG. It was found to show band-like light emission with a sufficiently long wavelength. The full width at half maximum when converted to photon energy in this emission spectrum was 0.29 eV. From this emission spectrum, when combined with a silicon photodiode, the signal intensity of the current obtained from the silicon photodiode when the luminescent material of the present embodiment emitted light of unit energy was calculated. Then, assuming that the case of Gd ₂ O ₂ S: Pr, which is the light emitting material of the comparative example described in the first embodiment, is 100, NaGdS ₂ : Eu, which is the light emitting material of the present embodiment, is 132, which is a comparative example. It turned out to be expensive.

  As described above, according to the present embodiment, it is possible to provide a light emitting material having a short afterglow time of 10 μs or less, an emission wavelength of 650 nm or more, and a good matching with the sensitivity spectrum of the silicon photodiode.

In addition to the light emitting material described in the first and second embodiments, a light emitting material in which the ratio of Eu ₂ O ₃ was set to 0.01 and 0.001 was manufactured for NaYS ₂ : Eu. In the former, the emission peak shifted to about 700 nm, and in the latter, about 690 nm, both of which showed long wavelength emission.

In contrast, Li ₂ S, Y ₂ S ₃ , Eu ₂ O ₃ as raw materials were weighed and mixed at a ratio of 1.05: 0.997: 0.003, and Na ₂ S, La ₂ S ₃ , Eu ₂ O ₃ was weighed and mixed at a ratio of 1.05: 0.997: 0.003, and samples were fired at 1000 ° C. for 3 hours in a hydrogen sulfide atmosphere. After these were pulverized in a mortar and then tried to wash with water, there was an indication that they were partially dissolved by moisture, so unwashed powder was evaluated. When the emission intensity was compared with the NaYS ₂ : Eu powder by electron beam excitation at an acceleration voltage of 10 kV, the emission energy was only less than 1% of NaYS ₂ : Eu.

(Third embodiment)
The light emitting material according to the third embodiment of the present invention has a matrix composition represented by ARS ₂ . Here, A represents at least one element of Na, K, Rb, and Cs, and R represents at least one element of Y, La, Gd, and Lu. In addition, as the activator element, rare earth elements Ce, Pr, Eu, Tb, transition metals Mn, Cu, ions having two s electrons, and light emission by transition such as Tl ⁺ , Sn, Sb, Bi, etc. can be selected. Note that the activator element refers to an element doped to make the emission center. In general, the concentration of the activator element has an optimum value, and it is known that the light emission characteristics such as the light emission efficiency decrease if the concentration is too much or too little. This optimum concentration varies depending on the type of the matrix and the activator ion, but is often within the range of about 0.01 mol% to 10 mol%. The literature (P. Dorenbos: J. Lumin. 91 (2000) pp.155-176) shows Ce-doped NaYS ₂ , ie NaYS ₂ : Ce, but does not show any emission. Therefore, it is considered that the intended substance NaYS ₂ : Ce may not be obtained in this document. As far as the present inventor is aware, a light-emitting material having a matrix composition represented by ARS ₂ including a combination of other elements is not known.

As described above, the matrix represented by ARS ₂ has a cubic or hexagonal crystal structure, but the present inventor also shows strong light emission in this crystal structure with respect to an activating element other than Eu. It was found that the thing was only a hexagonal one. Among the combinations of A and R, those that exhibit light emission are those in which A is Na and R is Y, Gd, or Lu, or A is at least one of K, Rb, and Cs, and R Is one of Y, La, Gd, and Lu. When the base crystal structure such as NaLaS ₂ is a cubic NaCl type, light emission is not observed or the light emission intensity is very weak, which is not practical.

  The phosphor material of the present embodiment can be synthesized by firing other compounds such as sulfides and oxides of constituent metal elements in an atmosphere containing sulfur such as hydrogen sulfide. However, controlling the atmosphere during firing is important. Since it is easily oxidized when fired in an atmosphere containing oxygen, firing in an atmosphere containing as little oxygen as possible is necessary. In addition, when an oxygen-containing material such as an oxide is used, it is necessary to perform firing in a reducing atmosphere such as hydrogen sulfide in order to remove oxygen. Also, the control of the firing temperature is important. If the firing temperature is too high, the alkali metal constituting the matrix may be volatilized or the crystal structure may be transferred to a cubic system, so that the emission intensity may be significantly reduced. Although the upper limit of the preferable firing temperature depends on the combination of the matrix constituent elements, it is approximately 1200 ° C. according to the knowledge of the present inventor.

When Mn, Cu, In, Sn, Sb, or Bi is used as the activator element, these exhibit light emission in a band spectrum corresponding to the combination of the matrix constituent elements. In particular, when the activator is Bi and the base is NaYS ₂ , an emission color comparable to that of ZnS: Ag, Cl, which is a representative phosphor for electron beam excitation, is obtained, and under excitation with a high energy density electron beam. Then, the present inventors have found that a luminance exceeding ZnS: Ag, Cl can be realized.

In addition, when Ce is used as the activator element, emission of a band spectrum corresponding to the combination of the matrix constituent elements is also exhibited, but as a general emission of Ce ³⁺ ions, abnormally long wavelength orange to red emission is exhibited.

In addition, when Pr is used as the activator element, light emission having peaks near 500 nm and 670 nm peculiar to the transition from the ³ P ₀ level of Pr ³⁺ ions is exhibited. When Tb is used as the activating element, light emission having a main peak in the vicinity of 550 nm peculiar to Tb ³⁺ ions is exhibited.

In addition, when Eu is used as the activating element, as described in the first embodiment, a band spectrum peculiar to +2 valent Eu is exhibited even though the base material contains +3 valent rare earth element. It is known that when Eu is added to a matrix containing an alkaline earth metal, Eu often exists in a + 2-valent form and exhibits a band spectrum specific to Eu ²⁺ . However, it is an extremely rare phenomenon that light emission peculiar to Eu ²⁺ is observed in a matrix that does not contain an alkaline earth metal.

It is also possible to use two or more of the above-mentioned activation elements at the same time. For example, when NaYS ₂ is doped with Bi and Pr, light emission having peaks at around 440 nm, around 500 nm, and around 670 nm can be obtained.

(Fourth embodiment)
Next, an image display apparatus according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a part of a cross-sectional view of the image display apparatus of the present embodiment. The image display device according to the present embodiment includes a front glass substrate 31, a blue light emitting pixel 32, a green light emitting pixel 33, and a red light emitting pixel 34 formed on one surface of the glass substrate 31. Each pixel is provided on the black matrix 35 provided, the aluminum thin film 36 covering the pixels, the back substrate 37 provided so as to face the glass substrate 31, and the surface of the back substrate 37 facing the glass substrate 31. And an electron beam source 38 provided so as to be opposed to each other. These electron beam sources 38 are SCE (Surface-Conduction Electron-Emitter). When electrons are emitted from these electron beam sources 8 to the opposing pixels, the pixels to which the electrons are incident emit light. A person sees this light from the surface of the glass substrate 31 opposite to the surface on which the pixels are formed. In the image display device according to the present embodiment, ARS ₂ : Bi in which the base is ARS ₂ and the activating element is Bi is used as the blue phosphor applied to the blue light emitting pixels 32. In this embodiment, for example, Y ₂ SiO ₅ : Tb is used as the green light-emitting phosphor applied to the green light-emitting pixel 33, and Y ₂ O ₃ is used as the red light-emitting phosphor applied to the red light-emitting pixel 34. : Eu is used.

Thus, in this embodiment, since the ARS ₂ : Bi phosphor is used instead of the conventional blue phosphor, for example, the ZnS: Ag, Cl phosphor, even under the excitation condition of high luminance, that is, high energy density. High-luminance blue light emission with little decrease in luminous efficiency can be obtained. In order to obtain an emission color equivalent to that of a conventional blue phosphor such as ZnS: Ag, Cl or ZnS: Ag, Al, it is preferable to select NaYS ₂ as a base material.

  As an image display device according to a modification of the present embodiment, a filter layer 40 that selectively transmits blue light may be provided between the blue light emitting pixels 32 and the front glass substrate 31 as shown in FIG. . A filter layer 40 that selectively transmits green between the green light emitting pixel 33 and the front glass substrate 31 is provided, and a filter layer that selectively transmits red between the red light emitting pixel 34 and the front glass substrate 31. 40 may be provided.

(Fifth embodiment)
Next, the light source by 5th Embodiment of this invention is shown in FIG. The light source of the present embodiment is a light source that combines an ARS ₂ : Bi, Pr phosphor and a near-ultraviolet light emitting diode as a light emitting element. Here, the near ultraviolet light emitting diode is a light emitting diode (LED) having a peak wavelength shorter than about 400 nm. In the light source of this embodiment, the near-ultraviolet light-emitting diode 60 is flip-chip mounted on a submount 76 disposed in a ceramic package (envelope) 73 to disperse the ARS ₂ : Bi, Pr phosphor material. The resin 72 is sealed. In the light source of the present embodiment, a submount 76 is formed on a lead electrode 77 provided so as to penetrate the bottom of the recess of the ceramic package 73 having a recess. A pair of bumps 75 are provided on the submount 76, and the light emitting diode 60 is flip-chip mounted on the pair of bumps 75 so that the pair of electrodes 68 and 69 of the light emitting diode 60 are connected. Metal bumps and solder are used as the material of the bumps 75, but gold bumps are preferably used. The bump 75 and the lead electrode 77 are electrically connected by penetrating the inside of the submount 76 with a conductive wire such as a gold wire. The lead electrode 77 is required to have good electrical conductivity. As the material of the lead electrode 77, iron, copper, a copper alloy or the like, or a material in which a metal plating such as silver, aluminum, or gold is applied can be used.

In addition, the ceramic package 73 and the light emitting diode 60 are bonded with a resin 72 or the like for hermetically sealing. In the resin 72, ARS ₂ : Bi, Pr phosphors that absorb at least part of light emitted from the light emitting diode 60 and convert the wavelength to emit light are dispersed.

  With this configuration, a part of the light emitted from the light emitting diode 60 is wavelength-converted by the phosphor when passing through the sealing resin 72 in which the phosphor is dispersed. White light capable of realizing a wider color gamut is obtained by color mixing of the wavelength-converted light and the light that has passed through the sealing resin 72 without being wavelength-converted.

When the light source of this embodiment is used as a backlight of a liquid crystal display, it is desirable that the peak wavelength of the blue light emitting component of the phosphor is short in order to further widen the color reproduction range, and NaYS ₂ should be selected as the base material. Is preferred.

  In the light source of this embodiment, the pair of electrodes 68 and 69 of the light emitting element are formed on the same side, but for example, as shown in FIG. 21, the electrodes 68 and 69 formed on the opposite side are provided. The light emitting element 60A may be used. In this case, the electrode 68 is electrically connected to the pad 75 via the bonding wire 78. The n-side electrode 68 is in contact with a substrate made of n-type GaN. The n-side electrode 68 and the p-side electrode 69 may be arranged upside down.

In the present embodiment, the light emitting diode is described as an example of the light emitting element. However, the light emitting element may be a semiconductor laser element.
Examples of the third to fifth embodiments will be described in detail below.

Example 1
Na ₂ S, Y ₂ S ₃ , and Bi ₂ O ₃ as raw materials have a molar ratio of 1.1: 0.999: 0.001, and specific weights are 21.5 g, 68.3 g, and 0.116 g, respectively. And mixed. This was filled in a carbon crucible and fired at 1000 ° C. for 1.5 hours in a hydrogen sulfide atmosphere. This was pulverized with a mortar, washed with water, and dried to obtain a powder phosphor material made of NaYS ₂ : Bi of Example 1. The phosphor screen of the phosphor was formed on a glass substrate by a sedimentation method using an aqueous solution of barium salt and water glass. Next, an organic film was formed, and after passing through aluminum vapor deposition and baking, a phosphor screen having an aluminum thin film formed on the back surface was produced.

Further, as a comparative example, a phosphor screen of a known phosphor ZnS: Ag, Cl was prepared in the same manner. When these phosphor screens were excited by a pulse drive electron beam having an acceleration voltage of 10 kV, a pulse width of about 100 μs and a current density of about 5 mA / cm ² , and the luminance was measured, the phosphor screen of the phosphor of Example 1 was a comparative example. The brightness was as high as 136% with respect to the phosphor screen of the phosphor. Also, the emission spectrum of the phosphor screen using the phosphor of Example 1 is as shown in FIG. 9, and the chromaticity of the emission color is (0.154, 0.096), which can be used as a blue light emitting phosphor. Met.

  Next, a display panel in which the phosphor of Example 1 was applied to the blue light emitting pixels 32 of the image display device of the fourth embodiment shown in FIG. 7 was produced. For comparison, a display panel using a phosphor made of ZnS: Ag, Cl as a comparative example as a blue phosphor applied to the blue light emitting pixel 32 is manufactured, and a display panel using the phosphor of Example 1 is used. And the display panel using the phosphor of the comparative example were compared in luminance when blue was displayed under the maximum luminance driving condition. According to this comparison result, the display panel using the phosphor of Example 1 was 120% brighter than the display panel using the phosphor of the comparative example.

(Example 2)
Na ₂ S, Y ₂ S ₃ , Bi ₂ O ₃ , Pr ₆ O ₁₁ as raw materials in a molar ratio of 1.05: 0.996: 0.001: 0.003, specific weights of 20.5 g, 68.3 g, 0.129, and 0.766 g were weighed and mixed. This was filled in a carbon crucible and fired at 1000 ° C. for 1.5 hours in a hydrogen sulfide atmosphere. This was pulverized with a mortar, washed with water, and dried to obtain a powder phosphor material made of NaYS ₂ : Bi, Pr of Example 2. When this was excited with a near-ultraviolet LED having a peak wavelength of about 385 nm and an emission spectrum was measured, an emission spectrum as shown in FIG. 10 was obtained.

  Next, the resin layer which disperse | distributed the fluorescent substance of Example 2 was formed on the near ultraviolet LED element, and the white LED light source was produced. When the display color on the xy chromaticity diagram when this light source and the blue, green and red color filters used in the liquid crystal display are combined is measured, as shown in FIG. .12, 0.21), green was (0.16, 0.61), and red was (0.61, 0.28). On the chromaticity diagram, the area of the triangle 52 formed by the blue-green-red color was 63% when compared with the area of the NTSC triangle 51, which is a typical standard. On the other hand, when a cold cathode fluorescent lamp using an existing phosphor was used as the light source, the area of the triangle 54 was 53% of the NTSC triangle 51. Further, when a commercially available white LED of a type combining a blue LED and a yellow light emitting phosphor was used as a light source, the area of the triangle 53 was 49% of the triangle 51 of NTSC. That is, it was found that the light source using the phosphor of Example 2 can have a wider color reproduction range than the existing light source when used as a backlight.

In addition, phosphors of Examples 3 to 13 shown in Table 1 were produced. When these were irradiated with ultraviolet rays having a wavelength of 254 nm, the emission colors described in the table were observed.

  FIGS. 12 to 19 show emission spectra when the phosphors of Examples 3, 5, 6, 7, 8, 9, 11, and 12 are excited with ultraviolet light having a wavelength of 254 nm, respectively.

  As described above, it is brighter than ZnS phosphors under excitation with an electron beam with a high energy density and has excellent emission color, and a wider color gamut can be realized when combined with a color filter of a liquid crystal display. A phosphor, an image display device using the phosphor, and a light source using the phosphor can be provided.

It shows an emission spectrum of the luminescent material consisting of Eu: Nays ₂ according to the first embodiment. The figure when the photon energy is plotted on the horizontal axis for the emission spectrum shown in FIG. Comparative Example by _Gd 2 _O 2 S: shows emission spectra of the light-emitting materials consisting of Pr. Sectional drawing of an X-ray detection element. The block diagram which shows an X-ray detector. It shows an emission spectrum of the luminescent material consisting of Eu: NaGdS ₂ according to the second embodiment. The figure which shows the cross section of the image display apparatus by 4th Embodiment. The figure which shows the cross section of the blue light emission pixel of the image display apparatus by the modification of 4th Embodiment. The figure which shows the emission spectrum by the electron beam excitation of the fluorescent screen using the fluorescent substance of Example 1. FIG. The figure which shows the emission spectrum by the near-ultraviolet excitation of the fluorescent substance of Example 2. The figure which shows the color reproduction range at the time of combining the color reproduction range of NTSC specification, and the filter for various light sources and a liquid crystal display. The figure which shows the emission spectrum at the time of exciting with the ultraviolet-ray of wavelength 254nm of the fluorescent substance of Example 3. FIG. The figure which shows the emission spectrum at the time of exciting with the ultraviolet-ray of wavelength 254nm of the fluorescent substance of Example 5. FIG. The figure which shows the emission spectrum at the time of exciting with the ultraviolet-ray of wavelength 254nm of the fluorescent substance of Example 6. FIG. The figure which shows the emission spectrum at the time of exciting with the ultraviolet-ray of wavelength 254nm of the fluorescent substance of Example 7. FIG. The figure which shows the emission spectrum at the time of exciting with the ultraviolet-ray of wavelength 254nm of the fluorescent substance of Example 8. FIG. The figure which shows the emission spectrum at the time of exciting with the ultraviolet-ray of wavelength 254nm of the fluorescent substance of Example 9. FIG. The figure which shows the emission spectrum at the time of exciting with the ultraviolet-ray of wavelength 254nm of the fluorescent substance of Example 11. FIG. The figure which shows the emission spectrum at the time of exciting with the ultraviolet-ray of wavelength 254nm of the fluorescent substance of Example 12. FIG. Sectional drawing of the light source by 5th Embodiment. Sectional drawing of the light source by the modification of 5th Embodiment.

Explanation of symbols

10 X-ray detection element 11 Scintillator 12 Silicon photodiode 13 Adhesive layer 20 X-ray detector 21 Substrate 22 Signal line 31 Front glass substrate 32 Blue light emitting pixel 33 coated with blue light emitting phosphor 33 Green light emitting pixel 34 Red light emitting pixel 35 Black matrix 36 Aluminum thin film 37 Back substrate 38 Electron source 41 Front glass substrate 42 Filter layer 43 that selectively transmits blue light Phosphor layer 44 coated with blue light-emitting phosphor of the present invention Black matrix 45 Aluminum thin film 51 On CIE chromaticity diagram A triangle showing the color reproduction range of the NTSC standard at 52 A triangle showing a color reproduction range when the white LED light source using the phosphor of Example 2 and a color filter for liquid crystal display are combined 53 Blue LED and yellow light emitting phosphor A combination of commercially available white LED and liquid Triangle 54 showing color gamut when combined with color filter for display Triangle 60 showing color gamut when combined with cold cathode fluorescent lamp using existing phosphor and color filter for liquid crystal display Light emitting element 60A Light emitting element 68 N side electrode 69 P side electrode 72 Resin 73 Ceramic package 75 Bump 76 Submount 77 Lead electrode 78 Bonding wire

Claims (6)

It includes a material whose composition is any one of NaYS ₂ : Eu and NaGdS ₂ : Eu , an afterglow time is 10 μs or less, an emission wavelength is 650 nm or more, and the half-value width of the emission spectrum of the material is 0.25 eV to A light emitting material which is 0.35 eV. The light emitting material according to claim 1, wherein the base material of the material has a hexagonal crystal structure. The light emitting material according to claim 1, wherein the material is NaYS ₂ : Eu . The scintillator comprised from the luminescent material in any one of Claims 1 thru | or 3 . An X-ray detection element comprising the scintillator according to claim 4 and a silicon photodiode that receives light from the scintillator. A plurality of X-ray detection elements according to claim 5 arranged in a matrix;
A signal line provided corresponding to each column and connected to the output of the X-ray detection element in the same column;
An X-ray detector comprising:

Images