JPS59102978A - Phosphate fluorescent material and its preparation - Google Patents

Abstract

PURPOSE:To prepare a phosphate fluorescent material having particular shape and characteristics, high and stable luminance, and excellent resistance to hydrolysis, by using an orthophosphate of a bivalent metal containing zinc as a main component, and manganese as a main dopant. CONSTITUTION:The objective phosphate fluorescent material contains an orthophosphate of a bivalent metal containing zinc as a main component and manganese as a main dopant, wherein >=50wt% of the fluorescent particle is nearly rectangular parallelopiped plate crystals having the ratio of the longest side to the shortest side of 2:1-4:1, and the glow characteristic curve at 25-300 deg.C has its peak at 100-200 deg.C and/or the ratio of the peak fluorescent intensity excited by the light having a wavelength of 200-280nm to the peak intensity excited by the light with 380-420nm wavelength is 0.6-3.0.

Description

[Detailed description of the invention] The present invention relates to phosphate phosphors and methods of manufacturing the same.

More specifically, the present invention relates to a phosphate phosphor having a specific shape and specific characteristics, which has high brightness and a high brightness maintenance rate, and a method for manufacturing the same.

Phosphate phosphor consisting of manganese as the main activator and melt phosphate of a divalent metal containing 1 as the main matrix (hereinafter simply ``father'' is necessary) 1) Phosphate phosphor (abbreviated as ``body'') exhibits a high-4 degree red luminescence under beam excitation, and ``1''
Used in phosphors for 144Th ray tubes. In addition, this JtE light body has a long afterglow time (the time required for the luminance to drop to 10% after excitation stops), so it In particular, computer terminal display equipment,
It has a scanning speed that is higher than that of color television cathode ray tubes, such as those used in the display equipment of the 1+11 system, and is widely used in the camera's case.

This kind of fi 71? i) Light ('*Ke, the basic composition is a phosphate phosphor whose composition formula is Zn3(PO4)2:Mn, and the method is based on known technology, for example, Japanese Patent Publication No. 53-18
No. 471, and JP-A-56-12, which the present applicant proposed earlier.
No. 1258, JP-A-56-136873, JP-A-57
-87487,! As shown in Japanese Patent No. 56-139'072, a part of the parent substance is substituted, or other co-activators and additives are included in the composition. However, these phosphate phosphors exhibit a significantly lower F of 7 elasticity than other general phosphors due to long-term electron beam excitation, and the initial 1'4 degree is also sufficient. It wasn't. Therefore, when used for cathode rays, α, etc. for displays, color shifts may occur due to a decrease in brightness, and due to insufficient initial 4 degrees, other light-emitting color luminescent bodies may be caused to change. However, there are disadvantages such as inevitably large differences in the currents used, which impairs the so-called current balance.

Phosphates and phosphors have the property of being highly soluble in water and easily hydrolyzed to form water salts.
As a result, a phenomenon was observed in which the surface portion of the phosphor gradually became non-luminescent. In order to avoid this, various measures were taken to prevent the water from remaining wet for a long time during the phosphor preparation process, the post-baking process, and the cathode ray/U/-1 light film production process. However, they require special processing means and are not economically viable as well as technically.

Accordingly, an object of the present invention is to provide an rj tetra-acid salt/fluorophore which has an improved initial 4 degree, a high 4 retention rate, and is resistant to hydrolysis.

In order to achieve the above object, the present inventors have conducted extensive research on various j4-acid fluorophores, and found that 1 ton lead carbonate,
When a quick lead compound consisting of at least one of quick lead oxide and lead hydroxide is reacted mainly with orthophosphoric acid, and the reaction product is used as a raw material for manufacturing a phosphor, unexpectedly... It has been found that the purpose of the invention can be achieved.

Accordingly, the phosphate rod light body of the present invention has the following groove bottom and characteristics.

The shape of the phosphor σ) particles is about 5 out of all the θ phosphor particles.
0 iir amount φ or more, the ratio of the longest side to the shortest side is 2 = 1 ~
4:1 and is dominated by rectangular parallelepiped plate-shaped crystal grains. Moreover, (1) in the glow characteristic curve of the three phosphors at 25 to 300°C, the highest intensity position is in the range of 10o0 to 200°C, and/or (II) the phosphor has an excitation wavelength of 200°C. ~280 nm and 580~42
When excited with an excitation energy of 0 nm, if the maximum intensities of their emission are all ta and Ib, respectively, then Ia
/Ib is within the range of 0.6 to 3.0.

One specific example of the method for producing the philosophic phosphor of the present invention is to use a divalent metal consisting of a lead compound and, if necessary, at least one of magnesium, calcium, strontium, and barium. Co-precipitation with at least one carbonate, diide or hydroxide of orthophosphate with orthophosphoric acid, and then the coprecipitate of orthophosphate of divalent metal containing active lead obtained in this way. It is characterized by the use of manganese as a base material.

The conventional method for preparing a phosphate phosphor is to dryly mix an i+i lead compound, a phosphate such as diammonium phosphate, a manganese compound, and a flux. A method used was to mix the raw materials in a stream and then fire them. In addition, instead of mechanically mixing each phosphor raw material to obtain a phosphor raw material mixture as described above, the host constituent element, activator element, and coactivator element are co-precipitated as an orthophosphate. was also proposed.

However, the conventional coprecipitation method involves reacting a zinc compound such as zinc sulfate or zinc nitrate with a solution of a phosphoric acid compound such as an acid salt such as ammonium hydrogen phosphate or sodium phosphate. Phosphate phosphors produced using the coprecipitate obtained by such a method as a phosphor raw material did not satisfy the objects and effects of the present invention at all.

In short, if the present invention is viewed from a certain aspect, part of the characteristics of the invention lies in the use of "orthophosphoric acid". By the way, other phosphoric acids such as "meta-""para-" [poIJ-
It has been found that various phosphoric acids such as J and their salts cannot achieve the object of the present invention.

Therefore, the method for manufacturing the phosphate phosphor of the present invention will be explained in more detail below.

First, zinc and if necessary magnesium, calcium,
At least one divalent metal carbonate, oxide, or hydroxide consisting of at least one of strontium, barium, and beryllium is dispersed in pure water. Next, an orthophosphoric acid solution is gradually added to the liquid. In this way, a coprecipitate of divalent metal orthophosphate containing zinc is obtained. Alternatively, at least one manganese compound, such as a manganese carbonate, is added to a divalent metal dispersed in pure water.
By gradually adding a solution of orthophosphate in which the seeds are dissolved, a coprecipitate of manganese orthophosphate is obtained.

The coprecipitate thus obtained is dehydrated and dried to be used as a matrix raw material for a phosphor or a raw material for a matrix and an activator.

A manganese compound such as chloride, carbonate, or sulfide salt is added and mixed as an activator to the base raw material obtained by coprecipitation. Incidentally, the co-activator, additives, and flux are appropriately mixed as necessary. Compounds such as oxides, carbonates, or hydroxides of elements other than those mentioned above, which are the constituent elements of the phosphate phosphor that is particularly desired, may be added to the solution and co-precipitated.

Even when the above-mentioned phosphor raw materials are coprecipitated or mixed, each phosphor raw material is coprecipitated or weighed in such a proportion that the chemical formula of the phosphor is chemically determined.

In the thus obtained coprecipitate, most of the missing particles are rectangular parallelepiped plate-shaped crystal grains having two or more longest sides/shortest sides.

Mixing is done by a conventional method. In other words, it may be carried out (dryly) using a mill, mixer mill, mortar, etc., or it may be carried out using water,
It may also be carried out in the form of a paste (wet method) using alcohol, weak acid, or the like as a medium. In addition, for the purpose of improving the luminance, powder characteristics, etc. of commonly obtained phosphors,
Although a flux is often added to the phosphor raw material mixture, in the production of the phosphor of the present invention, especially ammonium chloride (NH4Ce), ammonium carbonate [(NH4
)2CO3] can be added in an appropriate amount to the phosphor raw material mixture as a fluxing agent to achieve the purpose mentioned above.

Next, above 1. The F phosphor raw material mixture is filled into a heat-resistant container such as an amine pot or a quartz pot and fired. Firing is performed in air (oxidizing atmosphere), in a neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere, or in a reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas or a carbon atmosphere. Once or twice at temperatures between ℃ and 1100℃
Do it more than once.

Note that the final firing (or the firing if it is performed only once) is always performed in a reducing atmosphere.

The firing time varies depending on the quality of the phosphor raw material mixture to be filled in the heat-resistant container, the degree of firing used, etc., but in general, 0.5 to 5 hours is appropriate within the above casting temperature range. After firing, the resulting fired product is pulverized, washed, dried, and sieved by various operations generally employed in the production of isophosphors to obtain the phosphor particles of the present invention.

When one example of the phosphate phosphor of the present invention thus obtained is compared with a conventional phosphate phosphor, it is completely hazy as shown below.

The phosphate phosphor of the present invention has an initial brightness that is 5 to 10% higher than conventional phosphate phosphors.

1a and 1b are electron micrographs (1) of a conventional phosphate phosphor and a phosphate phosphor of the present invention, respectively.
, 0 [10 times), but as is clear from this figure,
While conventional phosphate phosphors are archetypal particles, in the phosphate phosphor of the present invention, at least 50% by weight of all phosphor particles has a ratio of the longest side to the shortest side. They are rectangular parallelepiped plate-shaped crystal grains with a ratio of 2:1 to 4:1.

These crystal particles cannot necessarily be obtained as perfect rectangular parallelepiped plate-shaped crystal particles, depending on the crystal growth conditions and treatment conditions such as mixing, crushing, and sieving, and may have defects in a small portion of the particles. be. In the case of non-invention, an object having such a defect is also regarded as a rectangular parallelepiped plate-like object, and the ratio of the longest side to the shortest side is calculated.

Also, in Figure 2, the compositional formula is Z n 3 (PO, i ) 2
: 25 to the phosphate phosphor represented by Mn! +, 7
After irradiating with ultraviolet light of nm for 1 minute, immediately store at room temperature (25
C) This is a so-called glow characteristic curve obtained by measuring the thermoluminescence using a photomachine when the temperature was raised at a heating rate of 6.5°C to 500°C, and determining the relationship between temperature and thermoluminescence intensity.

Curve 1 in FIG. 2 is a conventional phosphate phosphor and curve 2 is a phosphate phosphor of the present invention.

As is clear from this figure, the conventional phosphate phosphor is
It has a maximum strength position within the range of °~100 °C,
Rather, the phosphate phosphors of the present invention have a maximum intensity position in the range of 1 nn' to 200°C. As described above, the uninvented phosphor has various physical properties related to light that are significantly superior to conventional phosphors.

In general, uninvented phosphate phosphors have slightly different glow characteristic curves depending on the manufacturing method.

However, there are peaks in the range of 25" to 100°C and
The ratio of peaks in the range of ° to 200 °C is 2:3 to 1:
Preference is given to using those listed in No. 10.

Next, FIG. 3 shows the luminescence intensity when a phosphate phosphor having a compositional formula of zng(po4)2:Mn is irradiated with ultraviolet light of 200 nm to 500 nm.

Curve 1 is with a conventional phosphate phosphor, curve 2
This is due to the phosphate phosphor of the present invention.

As is clear from this figure, the light emission characteristics of the two are completely different. For example, when the excitation wavelength is 200-280 nm and 380 nm,
When excited with an excitation energy of ~420 nm, the maximum intensity of emission is Ia/Ib''r 3.7 for the conventional phosphate phosphor, and the phosphate phosphor of the present invention, assuming that the maximum intensity of emission is la and 1b, respectively. is Ia/Ibζ1.8.That is, the phosphate phosphor of the present invention does not emit light as quickly in ultraviolet rays (particularly short-wave ultraviolet rays) as compared to conventional phosphate phosphors, and also has a lower I a / I b ratio. is also significantly lower than the conventional one.

The non-invention is partly characterized by the fact that the present inventors have discovered that there is a close relationship between this Ia/Ib ratio and the luminance deterioration characteristics of the phosphor. To give a more specific example, when the phosphor film of a phosphate phosphor sample was irradiated with cathode sand at an accelerating voltage of 20 KV and a flow density of 1071 A/cm2 for 15 minutes (forced deterioration test),
The ratio of the initial brightness to 100 and the brightness after irradiation is determined as the so-called brightness maintenance rate (chi), and the above-mentioned Is/I
When the relationship with b was investigated, the results shown in FIG. 4 were obtained. In FIG. 4, the X mark is a conventional phosphate phosphor, and the ○ mark is a phosphate phosphor of the present invention. As is clear from this figure, the conventional phosphate phosphor has an Ia/Ib ratio of 3.5 or more and a luminance maintenance rate of 83% or less. - The phosphate phosphor of the old invention has an Ia/Ib ratio of 3
and the brightness maintenance rate is 90% or more.As a result of more experiments, the brightness maintenance rate is 87%.
In order to achieve the above (no burns for a long period of time), Ia
It was confirmed that /Ib must be 3.0 or less. On the other hand, those with a value of 1 a/l b of 0.6 or less tended to have unfavorable defects in other properties. Therefore, Ia/Ib=0.6 to 5.
0, especially I a / I b = 1.0 to 2.
A range of 5 is preferred.

In addition, the characteristics (1) and (II) of the present invention are as follows:
In the present invention, it is essential to have at least one of them.

Phosphate phosphors also have high solubility in water.

Therefore, it tends to be easily hydrolyzed in aqueous solutions such as polyvinyl alcohol aqueous solutions for fluorescent coating.
This causes problems such as low brightness, viscosity changes for phosphor coating, and generally lack of stability.

FIG. 5 shows the change over time (during stirring) of a phosphate phosphor slurry placed in an aqueous polyvinyl alcohol solution in terms of the relationship between time and viscosity change. Curve 1 is a conventional phosphate phosphor and Curve 2 is an uninvented phosphate phosphor.

As is clear from this figure, conventional phosphate phosphors hydrolyze and the slurry viscosity changes significantly, so it was necessary to choose a special coating process different from the usual coating method. Since the slurry viscosity of the phosphate phosphor does not change much as shown in curve 2, it has the advantage that conventional coating methods well known in the art can be used.

As described above, the phosphate phosphor of the present invention has structural characteristics such as a specific shape that can be clearly distinguished from that of conventional phosphate phosphors, and has an initial luminance of 5 to 5. The brightness retention rate is improved by 10% or more, the brightness maintenance rate is improved by 10 to 17%, and it is stable against water pressure, which shows remarkable effects in industrial implementation.

The present invention will be explained in more detail with reference to Examples below.

Example 1 Zinc carbonate ZnCO3576,1? phosphoric acid
H3PO4230,6g man carbonate y MnC
O35,85' First, various raw materials having the above F blending ratio were co-precipitated in pure water. The obtained hydrated zinc orthophosphate was packed into quartz M [7], then placed in an electric and air furnace, and heated in air for 9
It was baked at a temperature of 00°C for 1.5 hours. In this way, a phosphor having the composition formula Zn3(PO4)2:0, D5Mn was obtained. This phosphor exhibited glow characteristics having a peak at 170C similar to curve a2 in FIG.

It also exhibited an excitation spectrum υ as shown in curve eI2 in FIG. 3, and an excitation overlap ratio of 1.92. Moreover, it had a particle shape as shown in FIG. 1b.

(Approximately 90% of the particles were rectangular plate-like particles with a long side to short side ratio of 1.5 to 6 times.) Next, the obtained phosphor was placed in a glass/arm flannel with polyvinyl alcohol, heavy It was applied using a coating liquid such as ammonium chromate. The brightness of the resulting cathode ray tube was 110%, and the brightness maintenance rate was 92.9.
It was %.

Example 2 Zinc oxide ZnO244,1! i' phosphoric acid
H3PO4230,6! i' carbonated mangann Mn
CO35, 8P First, various raw materials with a blending ratio of H['' were co-precipitated in pure water.The obtained zinc orthophosphate manganese hydrate was charged into a quartz crucible, and then placed in a thunder 1 furnace. The composition formula is Zn3(PO
4) A phosphor of 2:0,05 Mn was obtained. This phosphor exhibited glow characteristics having a peak at 170°C, similar to curve 2 in FIG.

Moreover, the excitation spectrum ν approximated to curve 2 in FIG. 3 was shown. (Excitation torque ratio IA/l8=2.42) Furthermore, 85% of the particles were rectangular plate crystals.

Next, the obtained phosphor was applied to a glass panel using a coating solution such as polyvinyl alcohol and weight ai (977 stoneium).The brightness of the obtained cathode ray tube was 109%. The retention rate was 90%.

Example 3 Zinc hydroxide Zn(OH)2 29 B -I P
Phosphoric acid H3PO4230, 6P man carbonate:/MnCO35, 81f First, the raw materials of the above formulation were co-precipitated in pure water.

The obtained zinc manganese orthophosphate hydrate was filled into a quartz crucible, then placed in an electric furnace, and heated in air at a temperature of 900°C for 1.
It was baked for 5 hours. Kagu” [compositional formula is Zn3(PO4)2
: (] - [15Mn) A phosphor was obtained. This phosphor showed a glow characteristic similar to that of 170C as shown in curve 2 in FIG. (Excitation spectrum IA/
IB=1.56). Regarding the shape of the particles, 80% of the total particles were rectangular plate crystals as shown in FIG. 1b. Next, the obtained phosphor was coated on a glass panel using a coating solution such as 4-vinyl alcohol or am[ium] dichromate. The brightness of the obtained cathode ray tube was 110 cm, and the brightness maintenance rate was 94.5%.

Example 4 Zinc carbonate ZnCO3376-1? phosphoric acid
H3PO4230,6P First, the above-mentioned raw materials were reacted in pure water.

Manganese sulfate (MnSO) was added to the obtained zinc orthophosphate hydrate.
After thoroughly mixing 47 and 6F in a ball mill and filling it into quartz M, it was placed in an electric furnace TC at a temperature of 900°C in air.
It was baked for 2.0 hours. Kagute composition formula is Zn3 (PO4)
A phosphor represented by 2: [), D 5 Mn was obtained.

This phosphor exhibited glow characteristics having a peak close to 100° C. as shown by curve 2 in FIG.

In addition, the particle shape was similar to that shown in Fig. 1b, and the particle shape was similar to that in Fig. 1b, with a 90% overlap.
The above were rectangular plate crystals. Next, the obtained phosphor was applied to a glass panel using a coating solution such as polyvinyl alcohol or ammonium dichromate. The brightness of the resulting cathode ray tube was 107 cm, and the brightness maintenance rate was 92.8%.
Met.

[Brief explanation of the drawing]

FIG. 1a is an electron micrograph (1,000x magnification) of a phosphate phosphor obtained by a conventional method. FIG. 1b is an electron micrograph (1,G [10x) of the phosphate phosphor obtained according to the invention. FIG. 2 is a glow characteristic curve. In the figure, 1 is a conventional phosphate phosphor, and 2 is a phosphate phosphor of the present invention. FIG. 3 shows the luminescence intensity when the phosphate phosphor is irradiated with ultraviolet light from 200 nm to 550 nn1. In the figure, 1 is a conventional phosphate phosphor, and 2 is a phosphate phosphor of the present invention. FIG. 4 shows the relationship between the brightness maintenance rate (%) and Ia/Ib. FIG. 5 shows the change over time of a phosphate phosphor slurry placed in an aqueous polyvinyl alcohol solution in terms of the relationship between time and viscosity change. Fig. 10 Fig. 1b (X 1000/#) Fig. 2 Ratio (1) Fig. 3 JjL table (surface) Fig. 4 Luminance string (%)

Claims (1)

[Scope of Claims] (1) A phosphate phosphor whose main matrix is orthophosphate of a divalent metal containing at least zinc and which contains manganese as a main activator, (A) particles of the phosphor; 50% by weight or more are almost rectangular parallelepiped plate-shaped crystal grains with a ratio of the longest side to the shortest side of 2:1 to 4:1, and the glow characteristic surface &l at 25°C to 500°C has a maximum strength position of 100°C. Is it within the range of ℃~200℃? or (8) the wavelength is 200-280nrn and 580-420nrn
When the maximum intensity of luminescence when excited with an excitation energy of nm is Ia and Ib, respectively, the ratio is 0.6
3.0 or having at least one of the properties of (A) and (B). (2) A phosphate phosphor whose main matrix is an orthophosphate of a divalent metal containing at least zinc and which contains manganese as a main activator, in which the raw materials for producing the main matrix are zinc and optionally magnesium, calcium, A divalent metal containing zinc obtained by co-precipitating orthophosphoric acid with at least one carbonate, oxide or hydroxide of a divalent metal consisting of at least one of strontium, barium and beryllium. The method for producing the phosphate phosphor described above, characterized in that it is a coprecipitate of orthophosphate.