JP5034033B2 - Plate-like phosphor and display using it - Google Patents

Description

The present invention relates to a phosphor that is a plate-like crystal obtained by rare earth metal ion exchange of zeolite, and a method for producing the same. The present invention also relates to a method of forming a coating film in which the plate phosphor exhibits its characteristics. The invention further relates to a display using this phosphor combination of the three primary colors (RGB).

Since zeolite is easy to uniformly disperse a rare earth element serving as a luminescence center in its pores by ion exchange, many phosphors using zeolite as a mother crystal or raw material are known. A rare earth metal ion is complexed with a ligand mixed in the zeolite cavity, and this ligand is selected with respect to the electronic structure so that it can absorb excitation electromagnetic radiation in a wavelength range lower than the emission radiation of the rare earth metal. In addition, it has been disclosed that the triplet level of the ligand is higher than the radiation level of the rare earth metal (Patent Document 1). The presence of moisture in the zeolite hinders excitation, so that after exchanging the ions of the zeolite, the zeolite functions by functioning as a phosphor by firing to remove the moisture.

Various rare earth elements can be used, and europium Eu is particularly useful. However, zeolite takes in water lost during production of the phosphor again from the environment, and as a result, the phosphor loses the function of emitting fluorescence. Therefore, in order to maintain this function, means for preventing moisture from being re-adsorbed on the zeolite has been considered. For example, an attempt has been made to locate an organic compound such as bipyridine inside the Y-zeolite as a complex with Eu (Non-patent Document 1). A proposal has also been made in which a transition metal oxide such as molybdenum oxide, tungsten oxide, niobium oxide, or tantalum oxide is added to zeolite containing Eu or Tb ions (Patent Document 2).

As a technology for achieving the above-mentioned purpose of maintaining the fluorescence performance, a composite of a single-crystal zeolite with a metal oxide for a light-emitting matrix, specifically a tin, zinc or indium oxide with a rare-earth metal for a light-emitting center. Some are supported (Patent Document 3). A part of the inventors disclosed a phosphor obtained by ion-exchanging faujasite-type zeolite with Eu ³⁺ and then firing (Patent Document 4). Disperse ceramic crystal particles in an aluminosilicate amorphous matrix in order to obtain a phosphor with uniform particle shape, easy particle size control, and strong light emission even when the particle size is small. There is also a proposal of a complex made (Patent Document 5).

A so-called next-generation fluorescent material typified by a phosphor for field emission display is required to have a characteristic that it can be excited by a low-speed electron beam in addition to high resolution and high luminous efficiency. For this purpose, a nano-sized phosphor is suitable. However, if the conventional phosphor is simply nano-sized, a decrease in emission intensity accompanying an increase in surface area is inevitable. The way to solve this problem is to make the phosphor nano-sized only in the thickness direction and large in the plane direction, but in the known method, the desired plate-like phosphor is manufactured. I can't do it. Conventional methods for producing oxide-based or sulfide-based phosphors are a solid-phase reaction method and a flux method, and it is difficult to control the crystal form and particle size by these methods.

The plate-like phosphors known so far are borate-based a (M ¹ _1-x M ² _x ) ₂ O ₃ .B ₂ O ₃ (M ¹ is Y, La or Gd, M ² is a compound represented by a composition formula of Eu, Tb or Ce, 0.005 ≦ x ≦ 0.2, 0.5 ≦ a ≦ 2) (Patent Document 6). Although the maximum diameter is 1 to 5 μm and the thickness is 0.05 to 0.5 μm, it is not easy to control the form and particle size.
JP 05-194941 Special table flat 11-504064 JP2003-246981 JP2005-048107 JP-A-2005-314573 JP 2002-309245 A Journal of Luminescence 72-74 (1997) 532-534

A central object of the present invention is a phosphor formed by using zeolite as a base material and ion-exchange of a rare earth element thereto, and is nano-sized in the thickness direction, but sufficiently widened in the plane direction according to the application. It is an object to provide a plate-like body having a diameter, particularly a product in which the light emission characteristics are not substantially lowered even if zeolite resorbs moisture from the environment during use, and a method for producing the same.

An incidental object of the present invention is to contain the above-described plate-like phosphor, and the phosphor exists in a nano-size in the thickness direction but has a high coverage in the surface direction. It is providing the method of forming a coating film. This realizes a phosphor screen that emits light with high brightness even by a relatively weak excitation electromagnetic wave such as a low-speed electron beam or vacuum ultraviolet rays.

A further object of the present invention is to provide an RGB display in which the phosphors of the present invention are combined with those having fluorescence spectrum peaks in the red, green and blue wavelength regions, respectively.

The plate-like phosphor of the present invention has a composition of K ₂ O.Al ₂ O ₃ .2SiO ₂ .xH ₂ O and has at least 20% of “Linde Q” type zeolite having a hexagonal plate-like crystal form. It is a plate-like phosphor that performs ion exchange at an exchange rate to disperse ions of rare earth elements and emits fluorescence when excited by an electron beam or ultraviolet rays.

In the method of the present invention for producing this plate-like phosphor, the above-mentioned “Linde Q” type zeolite is immersed in an aqueous solution of a soluble salt of a rare earth metal, and the trivalent or divalent of K ⁺ and the rare earth metal in the zeolite. After ion exchange with ions and presence of rare earth metal ions at an exchange rate of at least 20%, filtration, washing and drying are carried out, followed by firing at a temperature of 200 to 900 ° C. The fired product is in a powder state and can be used without being pulverized.

What characterizes the phosphor of the present invention is that Linde Q-type zeolite is selected as a base material. Linde Q-type zeolite has a hexagonal plate-like crystal form, and can be easily synthesized with a thickness of 10 to 200 nm, a diameter of 0.5 to 10 μm, and an aspect ratio of 5 or more. By using zeolite in a crystalline form that is highly flat and nano-sized in the thickness direction, it can be excited by relatively low-speed electromagnetic waves, and it can avoid a decrease in luminous performance due to miniaturization. it can.

This zeolite also has a large ion exchange capacity and can contain a large amount of rare earth metal ions serving as a luminescent center, so that it is easy to obtain a phosphor with high brightness. The remarkable advantage of the phosphor of the present invention is that, as seen in the examples to be described later, after calcination at the time of production and exhibiting the fluorescence performance, even if the zeolite re-adsorbs moisture in the environment, the fluorescence The performance is not substantially reduced. The phosphor of the present invention is in a state of being dehydrated by firing at the time of manufacture. In use, it seems that the emission intensity is reduced by taking in moisture from the environment, but there is substantially no influence. Was confirmed.

The phosphor manufactured by the conventional solid phase reaction has to be pulverized after firing, but the phosphor of the present invention is powdered in the fired state as described above, and therefore does not need to be pulverized. Although the pulverization causes the surface of the particles to become rough, and it is inevitable that the light emission intensity decreases due to the irregular reflection caused by the roughness, but according to the present invention, there is no such disadvantage.

The rare earth metal serving as the emission center in the plate-like phosphor of the present invention is selected from among europium Eu, terbium Tb, samarium Sm, thulium Tm, cerium Ce and the like according to a desired emission color. If Eu ³⁺ is selected as the rare earth metal ion, a phosphor emitting a red light having a fluorescence peak wavelength of 610 nm can be obtained. If Tb ³⁺ is selected, a green phosphor having a fluorescence peak wavelength of 540 nm can be obtained. Further, if Tm ³⁺ is selected, a phosphor emitting blue light having a fluorescence peak wavelength of 453 nm can be obtained. By combining these, an RGB three-color display can be constructed from the phosphor of the present invention.

Examples of soluble salts of rare earth metals include nitrates, chlorides, acetates, sulfates, etc., and those that are readily available may be selected and used. Ion exchange between K ⁺ and rare earth metal ions in the zeolite can be easily performed by immersing the zeolite in an aqueous solution of a soluble salt having an appropriate concentration and holding it at a temperature of less than 100 ° C. for several to several tens of hours. . The ion exchange rate needs to be at least 20% as described above in order to cause the phosphor to emit light having a practical luminance. However, the exchange rate is increased in the region of a high ion exchange rate exceeding 60%. Even if it makes it, the tendency for luminescence energy to saturate is seen, and the meaning of increase becomes scarce. Since the ion exchange rate reached is approximately proportional to the concentration of soluble salt, an aqueous solution with an appropriate concentration for the desired ion exchange rate should be used.

By adding Gd ³⁺ as an activation component to the rare earth metal ion, the emission intensity of the plate-like phosphor of the present invention can be increased. However, if the amount of Gd ³⁺ added is increased, there is a limit because the product phosphor tends to become unstable.

After ion exchange, it is filtered, washed with water and dried. The ion exchanger dried at a temperature of 100 ° C. or less has very low luminescence properties and is not practical. This is because excitation energy is absorbed by the water coordinated to the rare earth metal ions. Thus, after drying, also in the present invention, the luminescence characteristics are improved by firing the ion exchange sample to drive out moisture. In a conventional phosphor made of (zeolite + rare earth metal ions), the zeolite structure is destroyed by firing to make it amorphous, or else it is made into an aluminosilicate structure that is denser and does not show water absorption. Was done.

However, such a change also causes a change in crystal form and does not meet the purpose of obtaining a plate-like phosphor. Therefore, in the present invention, the firing is performed at a temperature of 200 ° C. or higher at which the coordinated water of the rare earth metal ions can be surely released and no change in crystal form occurs.

In the plate-like phosphor, each crystal is nano-sized in the thickness direction and occupies a certain large area in the plane direction, so each crystal particle is oriented parallel to the surface of the substrate. It is preferable to use it in a state where a coated film is formed. Such a coating film is realized by selecting the following application method according to the present invention. That is, the coating material formed by dispersing the plate-like phosphor of the present invention in an appropriate vehicle is applied using a coating means in which the plate-like body is oriented along the surface of the substrate, and is nanosized in the thickness direction. What is necessary is just to employ | adopt the coating-film formation method of obtaining the coating film in which this plate-like fluorescent substance exists. Means for orienting the plate-like crystal along the surface of the substrate includes brush coating and coating using a doctor blade.

Since the phosphor of the present invention is nano-sized, high luminous efficiency can be expected by excitation with a low-speed electron beam. The plate-like crystal shape has high applicability to the substrate, and the coating film can withstand some bending. A coating film in which plate-like crystals are oriented has an advantage of high light hiding properties and is useful for forming various screens. For this reason, the phosphor of the present invention is expected to be used for a field emission display which is a next generation panel display. High applicability and concealment can, of course, be used conveniently to improve the performance of fluorescent paints.

A K-type Linde Q zeolite (hereinafter abbreviated as “Linde Q”) having a hexagonal plate-like crystal form with a particle size of about 1 μm and a thickness of about 100 nm was produced. To each 8 g of this Linde Q, 60 mL each of an aqueous solution of europium chloride EuCl ₃ having different concentrations (0.01, 0.02, 0.03, 0.04, 0.05, 0.10 or 0.15 mol / dm ³ ). In addition, it was kept at 90 ° C. for 24 hours for ion exchange treatment. After filtration and washing, the sample was dried, and the obtained ion exchange sample was heated at 800 ° C. or 1000 ° C. for 1 hour to obtain a calcined sample.

The graph of FIG. 1 was obtained by examining the Eu ³⁺ ion exchange rate of the ion exchange sample and plotting the relationship with the concentration of the EuCl ₃ aqueous solution. From this graph, it was confirmed that the ion exchange rate was proportional to the concentration of the solution used for the ion exchange treatment. The ion exchange rate was calculated by acid-decomposing the sample and quantifying Eu and K with an induction plasma emission analyzer.

The ion exchange sample was subjected to thermal analysis. The obtained TG-DTA curve is shown in FIG. Linde Q that has not undergone ion exchange has an endothermic peak that appears to be due to dehydration at around 250 ° C. and an exothermic peak that accompanies crystallization at around 1100 ° C., whereas an ion exchange sample that has been exchanged with Eu ³⁺ Although there was an endothermic peak, no exothermic peak was observed. This suggests that the structure has been changed by firing.

An X-ray diffraction analysis was performed on a fired sample obtained by firing an ion exchange sample having an ion exchange rate of 45% at 400 ° C., 800 ° C., or 1000 ° C. to obtain the chart of FIG. Although Linde Q is said to undergo structural decomposition when heated to 300 ° C., 45% ion exchanged with Eu ³⁺ is stable even when heated to 800 ° C., and a hexagonal plate-like crystal structure was observed. On the other hand, it was found that when heated to 1000 ° C., the crystal structure of Linde Q was lost and caryophyllite was produced. Regarding the relationship between the ion exchange rate and thermal stability, the ion exchange sample with an exchange rate of 22% was stable when heated at 400 ° C., but the sample with 18% was unstable. From this fact, it can be said that if the ion exchange rate is about 20% or more, it becomes stable against heating.

What was baked at 800 degreeC or 1100 degreeC was observed with the scanning electron microscope. A photograph of the one fired at 800 ° C. is shown in FIG. The above hexagonal plate-like crystal form can be confirmed from this photograph. When heated to 1100 ° C., the crystal form was lost and it was close to the sintered state.

In order to investigate the fluorescence characteristics, 800 ° C. calcined samples with different Eu ³⁺ ion exchange rates were excited at an excitation wavelength of 395 nm to obtain fluorescence spectra. The results are as shown in FIG. 5, and it can be seen that there is a peak at 610 nm and the color is red. When an ultraviolet lamp with a wavelength of 365 nm was irradiated, red light could be seen visually. When the fluorescence spectrum is compared with that of Y ₂ O ₂ S: Eu ³⁺ which is a commercially available red phosphor, the peak wavelength is slightly shifted (the present invention is 610 nm as described above, and the commercial product is 620 nm). Both of them are red with slightly different colors.

Looking at the difference in Eu ³⁺ ion exchange rate, it can be seen that the peak intensity is higher at 45% than at 22%, and the increase in the amount of Eu ³⁺ brings about the increase in the emission intensity. However, the emission intensity at an ion exchange rate of 64% was almost the same as that at 45%. This is thought to be due to concentration quenching.

Next, the result of FIG. 6 was obtained as an excitation spectrum at a fluorescence wavelength of 610 nm. From this data, it was confirmed that 395 nm was appropriate as the excitation wavelength for obtaining fluorescence emission of 610 nm.

An Eu ³⁺ ion exchange rate of 45% and a calcined sample at 800 ° C. were placed in an environment at room temperature and a relative humidity of 58% to re-adsorb moisture. The water-covering behavior at that time is shown in FIG. It was found that the water re-adsorption for about 8 hours took in nearly saturated water, and a maximum weight increase of about 16% was observed. FIG. 8 shows a fluorescence spectrum of the phosphor re-adsorbed with water at an excitation wavelength of 395 nm compared with that immediately after baking at 800 ° C. There was no significant difference in peak intensity, and in the phosphor of the present invention, it was found that the presence of moisture did not significantly affect the fluorescence action. This fact suggests that the firing moved Eu ³⁺ to a narrow crystalline atomic position that did not rehydrate.

In a phosphor using a rare earth element, it is known that the emission intensity is increased by replacing part of Y with Gd, for example. Therefore, also in the phosphor of the present invention, an activation effect by replacing a part of Eu ³⁺ with Gd ³⁺ was expected. An attempt was made to confirm that this expectation was correct.

30 mL of aqueous solution of EuCl ₃ concentration 0.1 mol / dm ³ and 30 mL of GdCl ₃ concentration 0,0.00025,0.0005,0.001,0.002,0.01 or 0.1 mol / dm ³ aqueous solution And added to 4 g of Linde Q. In the same manner as in Example 1, a calcination treatment was performed by heating to 800 ° C. for 1 hour through ion exchange, filtration, washing and drying. The ion exchange sample was analyzed in the same manner as in Example 1, and the relationship between the ion exchange rate and the concentration of the solution used for the ion exchange treatment was examined, and the results shown in Table 1 were obtained.

Table 1

The proportional relationship between the Eu ³⁺ ion exchange solution and the ion exchange amount in Example 1 was also confirmed for Gd ³⁺ . Since the rare earth elements have similar chemical behavior, it can be seen that Eu ³⁺ and Gd ³⁺ behave similarly in the ion exchange of Linde Q, and there is no difference in ion exchange selectivity. When the total concentration of the ion exchange solution of Eu ³⁺ and Gd ³⁺ reaches 0.2 mol / dm ³ , the ion exchange reaches a level close to saturation.

For this ion exchange sample, the TG-DTA curve was examined in the same manner as in Example 1. The results are shown in FIG. For all the samples, endothermic peaks accompanied by weight reduction appear at around 90 ° C. and around 170 ° C., which are considered to be caused by dehydration of physically adsorbed water and zeolite water, respectively. Further, in each sample, a mild exothermic reaction was observed from around 940 ° C., which is considered to be due to the decomposition of the zeolite structure. From this, it was found that the thermal stability of the structure seen in Linde Q was not changed by the coexistence of Gd.

An X-ray diffraction chart for the 800 ° C. sintered sample is shown in FIG. As described above, the structural stability of the material not containing Gd (No. 1) was confirmed here, but No. 1 containing a large amount of Gd ³⁺ was confirmed. No. 7 shows a tendency that the structure becomes thermally unstable. The electron micrographs of each material showed that the hexagonal plate-like crystal form of Linde Q was maintained in all cases.

With respect to this phosphor, fluorescence spectra at excitation wavelengths of 395 nm and 250 nm were examined. A sintered sample of Eu ^{3 +} · Gd ³⁺ ion exchanger also showed a fluorescence peak at 610 nm and was confirmed to emit red light, similar to that of Eu ³⁺ ion exchanger. FIG. 9 shows the fluorescence spectrum when the excitation wavelength is 250 nm. In this spectrum, the width of the emission peak near the wavelength of 615 nm was widened, and an increase in the integrated intensity was observed. In particular, the strength of the shoulder portion on the short wavelength side is increased.

A Tb ^{3 +} exchanged zeolite was produced in the same manner as in Example 1 except that an aqueous solution of terbium chloride TbCl ₃ having a concentration of 0.1 mol / dm ³ was used instead of the aqueous solution of europium chloride EuCl ₃ . Similarly, the phosphor of the present invention was obtained by heating at 800 ° C. for 1 hour in an air atmosphere. When the crystal structure was confirmed by X-ray diffraction, the crystal structure of Linde Q zeolite was maintained. Fluorescence characteristics were measured with a spectrophotometer, and emission of 540 nm (green) was observed at an excitation wavelength of 370 nm. The fluorescence spectrum is shown in FIG.

In Example 1, a similar operation was performed except that an aqueous solution of thulium acetate Tm (CH ₃ CO ₂ ) ₃ having a concentration of 0.1 mol / dm ³ was used instead of the aqueous solution of europium chloride EuCl ₃ , and Tm ³⁺ Exchanged zeolite was produced. Similarly, the phosphor of the present invention was obtained by heating at 800 ° C. for 1 hour in an air atmosphere. When the crystal structure was confirmed by X-ray diffraction, the crystal structure of Linde Q zeolite was maintained also in this case. The fluorescence characteristics were measured with a spectrophotometer, and emission of 453 nm (blue) was observed at an excitation wavelength of 360 nm. The fluorescence spectrum is shown in FIG.

A data of Example 1 of the present invention, a graph showing the relationship between EuCl ₃ solution of concentration and Eu ³⁺ ion exchange rate which is used in the ion exchange process. It is the data of Example 1 of this invention, Comprising: The TG-DTA curve of Eu3 ⁺ ion-exchange sample. It is data of Example 1 of this invention, Comprising: The X-ray-diffraction chart about a baking sample. It is the data of Example 1 of this invention, Comprising: The scanning electron micrograph about an 800 degreeC baking sample. It is the data of Example 1 of this invention, Comprising: The fluorescence spectrum obtained by exciting the fluorescent substance of this invention with excitation wavelength 395nm. It is data of Example 1 of this invention, Comprising: The excitation spectrum in the fluorescence wavelength of 610 nm of the fluorescent substance of this invention. It is the data of Example 2 of this invention, Comprising: The TG-DTA curve of Eu3 ⁺ * Gd3 ⁺ ion-exchange sample. It is data of Example 2 of this invention, Comprising: The X-ray-diffraction chart about an 800 degreeC baking sample. It is the data of Example 2 of this invention, Comprising: The fluorescence spectrum obtained by exciting the fluorescent substance of this invention with the excitation wavelength of 250 nm. It is the data of Example 3 of this invention, Comprising: The fluorescence spectrum obtained by exciting the fluorescent substance of this invention with the excitation wavelength of 370 nm. It is the data of Example 3 of this invention, Comprising: The fluorescence spectrum obtained by exciting the fluorescent substance of this invention with the excitation wavelength of 360 nm.

Claims (9)

Rare earths obtained by ion exchange with “linde Q” type zeolite having a composition of K ₂ O.Al ₂ O ₃ .2SiO ₂ .xH ₂ O and having a hexagonal plate-like crystal form at an exchange rate of at least 20%. A plate-like phosphor made by dispersing element ions and emitting fluorescence when excited by an electron beam or ultraviolet rays. 2. The plate-like phosphor according to claim 1, wherein the rare earth element ion is Eu ³⁺ and the fluorescence peak wavelength is 610 nm (red). 2. The plate-like phosphor according to claim 1, wherein the rare earth element ion is Tb ³⁺ and the fluorescence peak wavelength is 540 nm (green). 2. The plate-like phosphor according to claim 1, wherein the rare earth element ion is Tm ³⁺ and the fluorescence peak wavelength is 453 nm (blue). The plate-like phosphor according to claim 2, wherein Gd ³⁺ is added as an activating component. A method for producing a plate-like phosphor according to claim 1, wherein "Linde Q" type zeolite is immersed in an aqueous solution of a soluble salt of a rare earth metal, and K ⁺ and rare earth metal trivalent or 2 A process comprising performing ion exchange with a valence ion, causing rare earth metal ions to exist at an exchange rate of at least 20%, followed by filtration, washing, and drying, followed by firing at a temperature of 200 to 900 ° C. Method. The coating material formed by dispersing the plate-like phosphor according to claim 1 in a vehicle is applied using an application means in which the plate-like body is oriented along the surface of the substrate, and is nanosized in the thickness direction. A method for forming a coating film of a plate-like phosphor comprising obtaining a coating film in which a plate-like phosphor is present. A plate-like phosphor emitting red fluorescence according to claim 2, a plate-like phosphor emitting green fluorescence according to claim 3, and a plate-like phosphor emitting blue fluorescence according to claim 4 RGB light emitter. A display configured by providing excitation means to the RGB luminous body according to claim 8.

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