JPS606783A - Phosphate phosphor and its preparation - Google Patents

Abstract

PURPOSE:To prepare a phosphate phosphor having a high luminance and a high luminance retention, by adding Mn as main activator to a phosphor consisting mainly of a coprecipitate of a specified salt of a divalent metal including Zn and an orthophosphate. CONSTITUTION:At least one of carbonate, oxide and hydroxide of a divalent metal comprising zinc and, when necessary, at least one of Mg, Ca, Sr, Ba and Be, are dispersed in pure water. An orthophosphoric acid soln. is added slowly to the dispersion to produce a coprecipitate of orthophosphates of the divalent metals icluding Zn. The coprecipitate is dehydrated and dryed for use as raw material for matrix of the phosphor or for the phosphor and activator. A manganese compd. such as chloride, carbonate and sulfide is mixed as activator into raw material comprising the above precipitate. When necessary, coactivator, additive and flux are added. The mixing may be done by dry process in a ball mill, mortar, etc. or by wet process by use of a medium such as water or alcohol.

Description

[Detailed description of the invention] do.

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.

A phosphate phosphor (hereinafter simply or abbreviated as ``salt phosphor'' as necessary), which uses manganese as the main activator and contains zinc-containing orthophosphate as the main matrix, is It emits high-intensity red light and is not normally used as a phosphor for cathode ray tubes. In addition, this phosphor has a long /θ% afterglow time (the time taken for the luminance to drop to 70% of its luminance after excitation stops), so it is especially useful for computer It is widely used in display cathode ray tubes that have a slower scanning speed than color television cathode ray tubes, such as terminal booth display devices and display devices for aircraft control systems.

This type of phosphate phosphor has a composition formula of 2.5(PO4)2
': The basic composition of the phosphate phosphor expressed as Mn and l
-, known techniques, such as JP-Ko-Ko-Ko-Ko-Sho-3-/g-77, and JP-A-Ko-Ko-Ko-Ko-Ko/C2/. which was previously devised by the present applicant. 2sg issue, Tokukai Shoshio Otsuichi/3 Otsugq. y, Japanese Patent Application Publication No. 7-73907.2, Japanese Patent Application No. 6-73907.2, etc. 5 Part of the tIC matrix is replaced, or a co-activator or additive is used. is included in the composition. However, these phosphate phosphors suffer from a significant decrease in brightness compared to the general phosphors of III due to long-term evanescent beam excitation, and their initial brightness is also not sufficient. There wasn't. Therefore, when used in a negative F7 ray tube for display, etc., color shift may occur due to a decrease in brightness, and due to insufficient initial brightness, there is a problem in the power consumption between the electron gun and the electron gun that excites the phosphor of other emission colors.
Inevitably, the difference in currents would become large, causing problems such as poor current balance in some places.

Furthermore, phosphate phosphors have the property that their solubility in water is large and that they are easily hydrolyzed to form hydrated salts, and as a result, the surface portion of the phosphor gradually becomes non-luminescent. was seen. In order to avoid this, various measures have been taken to prevent the moisture layer state from continuing for a long time during the post-baking process during phosphor manufacturing and during the cathode ray tube phosphor film fabrication process, but these techniques require special processing means. need,
It could not be said to be desirable not only technically but also economically.

Therefore, an object of the present invention is to provide a phosphate phosphor that has improved initial brightness, high brightness retention, and is difficult to hydrolyze.
be.

In order to achieve the above object, the present inventors have conducted extensive research on various phosphate phosphors, and have developed a zinc compound consisting of at least seven of the following: zinc carbonate, zinc oxide, and zinc hydroxide, and orthophosphoric acid. It has been found that when the reaction product is used as a raw material for producing a phosphor, the object of the present invention can be achieved in addition to μ.

However, the mackerel of the present invention. Phosphate phosphors have the following composition and characteristics.

The particle shape of the phosphor is approximately SO weight f among all the phosphor particles.
it:% or more, the ratio of the longest side to the shortest side is 2:/-4:/
, and is almost dominated by rectangular parallelepiped plate-shaped crystal grains. Shigamo (T) In the glow characteristic curve of the phosphor at 2ta 0~llo o'c, the highest intensity position is between λθ0°~g0
0° C., and/or 0) the phosphor is excited at an excitation wavelength of . 200-2gOnm and 3gO~4t.
When excited with an excitation energy of 20 nm, let the high intensity of their emission be la and ib, respectively.
I a / (b is in the range of θ.t~, ?.0. It is within the song.

Further, an example of the method for forming a horn of a phosphate phosphor of the present invention is as follows:
Zinc compounds and optionally magnesium, calcium,
It was obtained by co-precipitating carbonates, oxides, or hydroxides of divalent metals consisting of at least seven types of strontium, barium, and perylium with orthophosphoric acid. I41 It is characterized in that manganese activation is performed using a coprecipitate of orthophosphate of a divalent metal containing lead as a base material.

Conventional methods for producing phosphate phosphors include dry mixing of a decoction lead compound, a phosphate such as ammonium phosphate, a manganese compound, and a flux, or using a solvent in a coated state. A method was used in which the mixed konban was fired. In addition, instead of mechanically mixing each phosphor raw material to obtain a phosphor raw material mixture as described above, it is also possible to coprecipitate the host constituent element, activator element, and coactivator element as an orthophosphate. It was planned.

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 to form a coprecipitate. However, a phosphor produced using the coprecipitate obtained by such a method as a raw material for a phosphor does not achieve the purpose or effect 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 "meth", "nor(ra"), "poly"
It has been found that the objects of the present invention cannot be achieved with phosphoric acids such as phosphoric acids and their salts.

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 carbonate group, a solubilide, or a hydroxide of a λ-valent metal consisting of at least seven types of strontium, barium, and beryllium is dispersed in pure water. Next, orthophosphoric acid solution is gradually added to the glue solution. Thus, a coprecipitate of orthophosphates of Ω-valent metals containing zinc is obtained. Alternatively, a manganese compound, such as a manganese carbonate group, is added to a solution in which a divalent metal is dispersed in pure water.
By gradually adding an orthophosphoric acid solution in which the seeds are dissolved, a white coprecipitate of manganese orthophosphate is obtained.

The thus obtained coprecipitate 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 group, sulfide salt, etc. is added and mixed as an activating agent to the base material obtained by coprecipitation. Incidentally, appropriate amounts of coactivating agents, additives, and fluxing agents are mixed as necessary. In particular, compounds such as oxides, carbonate groups, or hydroxides of elements other than the above-mentioned constituent elements of the phosphate phosphor may be added to the solution and co-precipitated.

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 composition and theoretical composition of the phosphor is obtained.

In the thus obtained coprecipitate, most of the secondary particles are rectangular parallelepiped plate-shaped crystal particles with the longest side/shortest side being λ or less.

Mixing is done by a conventional method. That is, it may be carried out using a ball mill, mixer mill, mortar, etc. (in the Sho style), or by 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 brightness, powder characteristics, etc. of commonly obtained phosphors,
Although a fluxing agent is often added to the phosphor raw material mixture, in the production of the phosphor of the present invention, ammonium chloride (NH4C6), carbonic acid 7y-[-=rum[
(NH4)2co3] can be appropriately added to the phosphor raw material mixture as a flux to achieve the above purpose.

Next, the phosphor raw material mixture is filled into a heat-resistant container such as an alumina crucible or a quartz crucible, and fired. Firing is carried out in air (zero oxidation atmosphere), in neutral atmosphere such as nitrogen gas, argon gas, or in a reduced nitrogen atmosphere containing a small amount of hydrogen gas, carbon atmosphere, etc. The test is carried out 7 times or at least 2 times at temperatures ranging from goθ°C to 7,100°C in the atmosphere.

Note that the final firing (or the firing if only seven firings are performed) is always carried out in a reducing atmosphere.

The firing time varies depending on the amount of the phosphor raw material mixture filled in the heat-resistant container, the firing temperature employed, etc., but generally 5 to 3 hours is appropriate within the above firing temperature range. After firing, the resulting fired product is processed by various operations generally employed in the production of phosphors, such as pulverization, washing, drying, and sieving, 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 different as follows.

The phosphate phosphor of the present invention has an initial luminance that is 5 to 70% higher than that of conventional phosphate phosphors.

Furthermore, FIGS. 1a and 1b show electron microcasting and photographs (
1000 times), but as is clear from this figure, while the conventional phosphate phosphor has round particles, the phosphate phosphor of the present invention has a particle size of 30% by weight of the total phosphor particles. The above is a rectangular parallelepiped plate-shaped crystal grain having a ratio of the longest side to the shortest side in the range of 2:/ to 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 present invention, an object having such a notch is also regarded as a rectangular parallelepiped plate-like object, and the ratio of the longest side to the shortest side is calculated as q.

Further, Fig. 62 shows a phosphate phosphor K whose composition formula is 2°3(PO4)2:Mn. After being irradiated with ultraviolet rays of 23.3.7 nm for 7 minutes, it was immediately lowered from room temperature (23°C) to 000°C. ℃, the thermoluminescence when exposed to the outer edge at a temperature increase rate of 7°Q/sec was measured using a photomul, and this is a so-called glow characteristic curve that shows the relationship between temperature and thermoluminescence intensity. Song # in Figure 2
Curve 1 is the conventional phosphate phosphor and curve 2 is the 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 0 to 0℃, but
The phosphate phosphor of the present invention is rather! 00°～ii, o
It has the highest strength position in the range of θ°C. As described above, the phosphor of the present invention is significantly different from conventional phosphors in various physical properties related to light.

Generally, the phosphate phosphors of the present invention have slightly different glow characteristic curves depending on the manufacturing method.

However, the peaks in the range of 25° to /SO°C and 1.2
The ratio with the peak with pressure in the range of 000 to 900°C is 2:3 to
/near 0 is preferably used.

Next, FIG. 3 shows the luminescence intensity when a phosphate phosphor having a compositional formula of zn3(Po4)2:Mn is irradiated with ultraviolet light from 200 nm to 00 nm on the left.

Curve 1 is with conventional phosphate phosphor and curve 2
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, if the excitation wavelength is 200~2 g Onm and 3
When excited with an excitation energy of go-1I2θnm, the maximum and highest intensity of emission are respectively Ia.

tb, the conventional phosphate phosphor has Ia/I
b#3.7, the phosphate phosphor of the present invention is Ta/Ib:76
It is g. In other words, the phosphate phosphor of the present invention emits less light under ultraviolet light (particularly short-wave ultraviolet light) than conventional phosphate phosphors, and also has a significantly lower T a /I b ratio than conventional phosphate phosphors. It has become.

The present invention is characterized in part by the fact that the present inventors have discovered that there is a close relationship between this l a / I b ratio and the luminance deterioration characteristics of the phosphor. To give a more specific example, when a fluorescent film of a phosphate phosphor sample is irradiated with cathode rays at an accelerating voltage of 20 and a current density of 70μ for a minute (forced deterioration test), the initial brightness is 700 and the brightness after irradiation is taken as the so-called brightness maintenance rate (maximum), and the above-mentioned T a / I b
When we investigated the relationship between Note that in FIG. 7, the X mark is a conventional phosphate phosphor, and the O mark is a phosphate phosphor of the present invention.

It is clear from the diagram of q (, the conventional phosphate phosphor is I
a/Ib ratio is 3. It is more than the left, and the luminance maintenance rate is g3% or less. -The phosphate phosphor invented by Rikiki is
The Ta/Ib ratio is 3 or less, and the brightness maintenance rate is 90.
% or more.

As a result of many more experiments, in order for the brightness retention rate to be 7% or higher (no burnout for a long period of time), Ta/I
b is 3. It was confirmed that it is necessary to be less than or equal to θ. On the other hand, those whose T a / T b value is less than θ, A tend to have unfavorable defects in other properties. Therefore, Ta/Ib=0. Otsu ~ 3. The range of θ, especially T a / (b = 7.0 to 2. The left range is preferable. Also, the above-mentioned (1) and (It) in the present invention
It is essential for the present invention to have at least one of these characteristics.

In addition, phosphate phosphors have high solubility in water.

Therefore, it tends to be easily hydrolyzed in aqueous solutions such as polyvinyl alcohol aqueous solutions for coating phosphors.
This leads to a decrease in brightness and a change in the viscosity of the phosphor coating liquid.
There were problems such as a lack of stability.

FIG. S shows the change over time (during stirring) of a phosphate phosphor slurry placed in an aqueous polyvinyl alcohol solution as a function of time and change in viscosity. Curve 1 is the conventional phosphate phosphor and Curve 2 is the phosphate phosphor of the present invention.

As is clear from this figure, the slurry viscosity of conventional phosphate phosphors changes significantly when hydrolyzed, so it was necessary to select a special coating method different from the usual coating method. Since the slurry viscosity of the phosphate phosphor hardly changes 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 70%. The above results are high, the brightness maintenance rate is improved by 70 to 77%, and furthermore, it is stable against water, which shows extremely remarkable effects in industrial implementation.

The present invention will be explained in more detail with reference to one embodiment.

Example/ Zinc carbonate Zn Co 5 37 A/f phosphoric acid
H3PO4λ3θot2 Manganese carbonate MnCO3 left g? First, each glaze raw material having the above-mentioned mixing ratio was co-precipitated in pure water.

The obtained zinc manganese orthophosphate hydrate was filled into a quartz crucible, placed in an electric furnace, and heated in air at a temperature of 7.
It was baked for 5 hours. Thus, the compositional formula is zn3(po4)2
: 0. A phosphor designated by OS vn was obtained. This phosphor exhibited glow characteristics similar to curve 2 in FIG. 2, with a peak at about 0.degree. C.

Further, it exhibited an excitation spectrum as shown in curve 2 in FIG. 3, and the excitation spectrum was expressed as /,q2. Moreover, it had a particle shape as shown in FIG. 1b.

(The ratio of the long side to the short side was about 90% of the rectangular plate-like particles.) Next, the obtained phosphor was placed in a glass tube with polyvinyl alcohol and dichromic acid. Coating was performed using a coating liquid such as ammonium. The brightness of the obtained cathode ray tube was 770%, and the brightness maintenance rate was 92.9%.

Example λ Zinc oxide ZnO2'i"1./? Phosphoric acid H3PO4230,Ay Carbonic acid-ry gun MnCO3!r g ?First, the obtained ortho solution was prepared by co-precipitating various raw materials with the above blending ratio in pure water. Zinc manganese phosphate hydrate was filled into a quartz rut, then placed in an electric furnace and fired in air at a temperature of 900°C for 5 hours, resulting in a composition with a composition formula of Zn3(PO4)2: 0-0.
! ; A phosphor represented by Mn was obtained. This phosphor exhibited glow characteristics similar to curve 2 in FIG. 2 with a peak at about 0°C. Furthermore, an excitation spectrum similar to curve 2 in FIG. 3 was shown.

(Excitation spectroscopy tA/tB=2.11.2)
Furthermore, the particle shape was rectangular plate-like crystals with a total g%.

Next, the replaced phosphor was applied to a glass A panel using a coating solution such as polyvinyl alcohol or ammonium dichromate. The brightness of the obtained cathode ray tube was 709%, and the brightness maintenance rate was wa θ%.

Example 3 Water! (1 [Lead Zn(OH)2.29g, / phosphoric acid
H3PO423θot2 Manganese carbonate MnC06 left g? First, the above-mentioned raw materials 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 9θ0°C.
Baked for an hour. Thus, the compositional formula is Znx(PO4)2:
A phosphor indicated by 0-0 left Mn was obtained.

This phosphor exhibited glow characteristics approximately approximating 260 as shown by curve 2 in FIG. In addition, an excitation spectrum approximated to curve 2 in Fig. 3 was shown (excitation spectrum I A
/ T B2/, 3 Otsu). In addition, the particle shape is determined by the total g
θ% was a rectangular plate crystal as shown in FIG. 1b. 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 obtained cathode ray tube was 710%, and the brightness maintenance rate was qlLt, %.

Example Zinc carbonate ZnCO337 Otsu/2 Phosphoric acid HPo, 230/,! 4 First, the above formulation was reacted in pure water.

Obtained zinc orthophosphate hydrate Km acid manganese MnSO
47. After thoroughly mixing Otsu 2 in a ball mill and filling it into a quartz crucible, put it in an electric furnace and heat it in air at a temperature of 900°C.
．． It was baked for 0 hours. Thus, the composition formula is zn3(po4)2
: 0.03 Mn was obtained.

This phosphor exhibited glow characteristics having a peak close to 0° C. as shown in track #2 of the Ω diagram. Also, the excitation curve approximated to curve 2 in Fig. 3? showed the kutle. (
Excitation switch ratio IA/IB=7. g2) Also, the particle shape is similar to Figure Hani/b, and 909
The above were rectangular plate crystals. Next, the obtained phosphor was applied to a glass panel with a coating solution such as polyvinyl alcohol or ammonium okichromate.
The brightness of the I-ray tube is 707%, and the brightness maintenance rate is octopus, g
%Met.

[Brief explanation of drawings]

FIG. 1a is a micrograph (7000x magnification) of a phosphate phosphor obtained by a conventional method. FIG. 1b is an electron micrograph (4000x magnification) of a phosphate phosphor obtained according to the present invention. Figure 1 shows the glow characteristic curve. In the figure, 1 is the conventional phosphate phosphor, 2 is the phosphor #1 of the present invention. This is due to the phosphor. Figure 3 shows ultraviolet light from 1,20θ nm to S Q nm.
It shows the luminescence intensity when irradiating a phosphate phosphor. In the figure, 1 is a conventional phosphate phosphor, and 2 is a phosphate phosphor of the present invention. Figure 2 shows the relationship between the brightness maintenance rate (c) 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. 2: Error PA ('c) Engraving of the drawing (no changes to the content) Fig. 3: Fluid length (nm) 1 meter and 1 point of cleanliness? ! 1 (No change in content) Dimensions of 4th drawing, brightness brocade (%) Procedural amendment (method) 1. Display of the case 1981 Patent No. 11/176
No. 1, No. 2, Title of the invention Phosphate teiko and its manufacturing method 3, Relationship with the case of the person making the amendment Applicant 4, Agent 5, Motive for ordering the amendment November 27, 1980, 5, Sai 1su L'-

Claims (2)

[Claims] (1) In a phosphate phosphor whose main matrix is an orthophosphate of a divalent metal containing at least zinc and which contains manganese as a main additive, (A) 30% by weight or more of the particles of the phosphor are It is a nearly rectangular parallelepiped plate crystal grain with a ratio of the shortest sides of 2:/~ll:/, and (A) its glow characteristic curve at 23°C to 0θ°C has a maximum intensity position of λθθ°C to l/-0
(B) The wavelength is θ0~2gOnm and 3gO~l
When the maximum intensity of light emission when excited with an excitation energy of 120 nm is Ia and Ib, respectively, the ratio is between 0.6 and 3.0, and whether it is in the pronation or in (A) and ( The above-mentioned phosphate phosphor is characterized by having at least one of B). (2) In a phosphate phosphor whose main host is an orthophosphate of a covalent metal containing a small amount of zinc and which also contains manganese as a main activator, the raw materials for producing the core host are zinc and, if necessary, magnesium and calcium. , carbonates of covalent metals consisting of at least seven types of strontium, nomarium and beryllium,
The phosphate fluorescence described above is a coprecipitate of an orthophosphate of a divalent metal containing zinc, obtained by coprecipitating at least seven types of oxides or hydroxides with orthophosphoric acid. How the body is manufactured.