JPH01126390A - Production of fluorescent material - Google Patents

Abstract

PURPOSE:To obtain a fluorescent material emitting near ultraviolet ray by ultraviolet excitation and capable of improving the initial luminance and the maintenance of the luminance when used in a fluorescent lamp, by adding a specific amount of a boric acid (salt compound) to an yttrium phosphate fluorescent material doped with Ce and baking the mixture. CONSTITUTION:(A) 1mol. of a Ce-doped yttrium phosphate fluorescent material is mixed with (B) 0.1-20mol.% of boric acid or a boric acid salt compound easily giving a boric acid group component by thermal decomposition (e.g. ammonium borate) and the mixture is baked at 1,200 deg.C for 4hr in a weakly reducing atmosphere e.g. in an alumina crucible to obtain the objective fluorescent material of formula (x is 0.003-0.6).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a cerium-activated yttrium phosphate phosphor that emits near-ultraviolet light of around 350 nm by ultraviolet excitation.

[Prior Art and Problems] Recently, health line fluorescent lamps using a near-ultraviolet-emitting phosphor that emits near-ultraviolet light with near-ultraviolet light around 350 nm as its main component have been attracting attention, especially for use against sunburns that burn the skin. .

Conventionally, a lead-activated barium silicate phosphor is known as a phosphor that has a peak wavelength near ultraviolet light around 350 nm, but a fluorescent lamp using this lead-activated barium silicate phosphor is However, there were problems in that the light output was weak and the output maintenance rate of this initial output over the course of closing was insufficient.

In order to solve these problems, it has been proposed that a cerium-activated yttrium phosphate phosphor, which has been conventionally used in flying spot cathode ray tubes and has extremely short afterglow characteristics when stimulated with cathode rays, be used in fluorescent lamps. There is. for example,
Japanese Patent Publication No. 50-23670 proposes a cerium- and thorium-activated yttrium phosphate phosphor whose emission intensity is improved by introducing thorium, and Japanese Patent Publication No. 49-91084 proposes a phosphor using yttrium. Cerium and thorium activated yttrium phosphate phosphors are disclosed that have enhanced luminous output by substitution with the same trivalent aluminum and/or gallium.

However, these cerium- and thorium-activated yttrium phosphate phosphors use expensive thorium, so there is a problem that they are extremely expensive. In addition, since thorium is a radioactive isotope, there are handling problems, and furthermore, cerium and thorium-activated yttrium phosphate phosphors undergo significant heat deterioration, so the lamp manufacturing process where the phosphor layer is exposed to high temperatures is a problem. There is a disadvantage that the heating process causes a decrease in initial brightness and a decrease in the maintenance rate of light emission output.
The cerium-activated yttrium phosphate phosphor shown in Japanese Patent Application No. 61-182092 is practical for use in i1 store line replacement lamps.

However, when cerium-activated yttrium phosphate is used in a fluorescent lamp, it is desired that the fluorescent lamp has better luminous efficiency and improved luminous flux maintenance factor of light output.

This invention was made in view of the above circumstances, and
The purpose is to provide a method for producing a cerium-activated yttrium phosphate phosphor that emits near-ultraviolet light through ultraviolet excitation and can improve initial output and output retention when used in a fluorescent lamp. It is in.

[Means for Solving the Problems] The object of the present invention is to emit near ultraviolet rays by ultraviolet excitation, and to produce a compound having a compositional formula of Yl-xcexPO4 (where X is 0.00
3 to 0.6), the boric acid group component is The problem is solved by a method for producing a phosphor, which is characterized by adding boric acid corresponding to 0.1 to 20 mol% as a phosphor or a borate compound that easily becomes a boric acid group component by thermal decomposition and firing. can.

That is, the present inventors have repeatedly conducted various experiments to develop a cerium-activated yttrium phosphate phosphor that exhibits less brightness deterioration during the heating process in fluorescent lamp manufacturing. For example, by adding a specific amount of boric acid, ammonium borate, etc. and firing it, brightness decreases even during the heating process during the lamp manufacturing process, compared to conventional phosphors that do not contain boric acid components. less,
It has been newly discovered that it is possible to obtain a phosphor with improved lamp characteristics such as luminescence intensity and light output maintenance rate.

The manufacturing method of the present invention is disclosed in Japanese Patent Application No. 107481/1982, and is based on a cerium-activated yttrium phosphate phosphor which is a mixed crystal of a xenotime structure and a monazite structure (the amount of cerium substituted is 0.08 to 0.6) and a cerium-activated yttrium phosphate phosphor (cerium substitution amount (X in the above-mentioned compositional formula is o, ooa to 0.0B).

Generally, in the emission spectrum of a cerium-activated yttrium phosphate phosphor, when there is a large amount of xenotime type crystal structure, peaks are obtained at wavelengths of 336 nm and 352 to 355 nm, whereas when there is many monazite type crystal structure, A peak from 315 to 320 nm is added.

When the present invention is applied, the peaks of the emission spectrum are not affected.

Next, in the manufacturing method of the present invention, while referring to FIGS. 1 and 2 showing the experimental results of changing the boric acid group component for a cerium-activated yttrium phosphate phosphor, The reason for specifying the amount added will be explained.

In FIG. 1, the composition formula is Y O, 9Ce 0. IP O4
The graph shows the measurement results of the relationship between the amount of boric acid group component added and the rate of decrease in luminance of powder due to heat treatment when ammonium borate is used in a cerium-activated yttrium phosphate phosphor. It is shown as follows.

As shown by the curve in Figure 1, in the case of conventional phosphors that do not contain boric acid group components, the rate of reduction in luminance due to heat treatment decreases to 8.0%, while the composition formula In the same phosphor of the present invention, when the amount added is about 20 mol % or less per 1 mol of the phosphor, the rate of decrease in luminance is small. Preferably, when the content of the additive layer is 1 to 4 mol %, the reduction rate can be lowered by about 5% or more than before.

Here, the rate of decrease in luminance is calculated using the following formula.

Decrease rate (%) = (1-11/10)X100 However, 1
1 is the luminescence intensity at room temperature after heat treatment at 600°C for 30 minutes, and 10 is the luminescence intensity at room temperature of 20°C.

FIG. 2 is a graph showing the relationship between the amount of the boric acid group component added and the luminescence intensity of the powder when ammonium borate is used.

As in the case of Figure 1, the amount of boric acid group component added is 1
When the amount is 20 mol% or less, the luminescence intensity of the powder is improved compared to conventional phosphors that do not contain boric acid group components, and preferably when the amount is in the range of 1-15 mol%. In some cases, the luminescence intensity can be increased to 115% or more compared to conventional methods.

In addition, in FIGS. 1 and 2, the composition formulas are Yo, 9Ce0,
1PO4 is illustrated, but this is merely an example; in a cerium-activated yttrium phosphate phosphor, if the cerium substitution amount A reduction rate curve of luminescence brightness and a luminescence intensity curve similar to those shown in FIG. 2 and FIG. 2 are obtained.

[Example] Examples 1 to 6 of this invention will be described below.

In Examples 1 to 6, ammonium borate corresponding to 3.3 mol % of boric acid groups per 1 mol of the phosphor was added to the phosphor raw material during firing.

Regarding the manufacturing method of the phosphor and the lamp deterioration test except for the ratio of yttrium oxide and cerium carbonate, see Examples 1 to 3.
6 are the same, so the compositional formula of the phosphor is Y O,975
The case of Ce 0.025P O4 will be described in detail below.

1100.8 g of high purity yttrium oxide and 57.5 g of cerium carbonate were dissolved in 3 liters of 30% salt. Then, 1960 g of 50% phosphoric acid solution is mixed with this solution. While stirring the mixture, 15% ammonia water was gradually added to adjust the pH to 4, and yttrium phosphate was precipitated.

After drying this precipitate using a filtered water method, ammonium borate [(NH4) 205 B2O3.8H20 corresponding to 3.3 mol% of boric acid groups per mol of phosphor was added.
] 18g and calcined in an alumina crucible at a temperature of 1200° C. for 4 hours in a weakly reducing atmosphere.

This baked product is pulverized in a wet ball mill, washed with water, dried, and sieved through a 200-mesh sieve.

As a result, a cerium-activated yttrium phosphate phosphor was obtained, and as a result of X-ray diffraction measurement, its crystal structure was approximately the seven-time type, and its composition formula was YO,975Ce.
O,025P O4, with approximately 30pp of boron element
It contained m.

Next, a method for producing a fluorescent lamp using the fluorescent material produced in this manner will be explained.

Dissolve 100 g of nitrocellulose in 9.900 g of butyl acetate. Collect 600g of this solution into 21 beakers,
Y 0.975Ce O, 025P O4 phosphor of the present invention (particle size 5.
3μ) 500g is stirred well to prepare a coating solution. This coating solution was injected from the top of each of the five vertical glass tubes for wattage, each having a diameter of 32 mm and a diameter of 4θ, and was coated on the inner surface and dried. The average weight of the five coating films was 5.3 g/cm', and the average visible light transmittance was 40.8%.

Next, these coated glass tubes are baked for 10 minutes in an electric furnace heated to 600 degrees to burn off the nitrocellulose. Furthermore, a filament was attached to each glass tube, attached to an exhaust stand, and argon and mercury were injected to create FL4.
An OS type fluorescent lamp was manufactured.

The output energy of these fluorescent lamps over a range of 300 to 400 nm at 0 hours, 100 hours and 500 hours was measured and the average values are shown in Example 3 in the table below.

For comparison, a fluorescent lamp was prepared using a phosphor manufactured in the same manner as described above except that ammonium borate was not added during firing, and the output energy of the lamp was measured. The results are shown as Comparative Example 3 in the table.

In addition, cerium-activated yttrium phosphate phosphors were manufactured in the same manner as described above except for changing the mixing amount of yttrium oxide and cerium carbonate, and these phosphors were used to increase the output energy of the lamp. I got it. These results are shown as Examples 1.2 and 4-6 in the table.

Furthermore, for comparison, the output energy results of fluorescent lamps using phosphors obtained without adding ammonium borate during firing are shown as Comparative Examples 1.2 and 4 to 6 in the table.

As is clear from the table, the fluorescent lamp using the phosphor of the present invention is superior to the fluorescent lamp using the conventional phosphor in terms of composition.

That is, 2% to 4% at the initial output, 3% to 100 hours after the leap
Even in the 12%500 time leap, there is an improvement of 6 to 13%.

In addition, in the table, Y O,997 obtained by the conventional method
Based on the output energy of 300-400 nm in a fluorescent lamp using Ce 0.003P O4 phosphor (1
00%).

In the above examples, only the case where ammonium borate was added during firing was explained, but boric acid, such as orthoboric acid, and other borate compounds that easily become boric acid components by thermal decomposition, such as , even when added as yttrium borate, results similar to those described above were obtained.

[Effects of the Invention] As explained above, according to the method of the present invention, by adding a specific amount of a boric acid group component and firing, the phosphor can be made to have a higher brightness than a conventional phosphor without adding a boric acid group. Therefore, it is possible to obtain a phosphor that exhibits little reduction in brightness even in the heating process during the lamp manufacturing process and has improved lamp characteristics such as luminous intensity and light output maintenance rate.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the amount of boric acid group component added and the rate of reduction in luminance in a cerium-activated yttrium phosphate phosphor according to the method of the present invention, and FIG.
FIG. 2 is a graph diagram showing the relationship between the amount of boric acid component added and the luminescence intensity in a phosphor similar to the one shown in the figure. Patent applicant: Nichia Chemical Industries, Ltd.

Claims (1)

[Claims] Emit near ultraviolet rays by ultraviolet excitation, and the composition formula is Y_1
____xCe_xPO_4 (however, x is 0.003 to 0
．． In manufacturing a cerium-activated yttrium phosphate phosphor having a value in the range of 6), 0.1 as a boric acid group component per mole of the cerium-activated yttrium phosphate phosphor. 1. A method for producing a phosphor, which comprises adding boric acid or a borate compound which easily becomes a boric acid group component by thermal decomposition in an amount of 20 to 20 mol %, and firing.