RU2198907C1 - Method of luminophore preparing - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: to zinc sulfide solution of CuCl₂ is poured in the amount providing mass ratio Cu : ZnS = (1-5):(99-95) and to the second specimen of ZnS solution of ZnCl₂ is poured in. Mass ratio ZnCl₂ : ZnS = (5-15):(95-85). To the third specimen of ZnS solution of ZnJ₂ is poured in. Mass ratio ZnJ₂ : ZnS = (5-15):(95-85). Prepared intermediate matters are dried at 100-130 C, sieved and stirred in the mass ratio 1:(2.5-3): (0.2-0.3), respectively. To mixture ZnS and S are added in the mass ratio mixture : ZnS : S = 1:(2.5-3):(0.2-0.3), respectively, and prepared charge is calcinated in the presence of carbon- -containing material at 850-1050 C and annealed in air at 500-750 C for 3-35 min. Annealed luminophore is washed out with a mixture of 30% solutions of alkali and H₂O₂ taken in the volume ratio 10:1, washed out with demineralized water, dried and sieved. Prepared electroluminophore exhibits blue or green luminescence color, its brightness in ready articles is 40 KJ/m², not less, drop of brightness after 2000 h of exploitation is 50% of initial value, not above. Invention can be used in production of electroluminescent panels and capacitors. EFFECT: improved method of preparing. 2 cl

Description

The invention relates to inorganic chemistry, to methods for producing sulfide electroluminophores, in particular electroluminophores of type A ₂ B ₆ .

 Electroluminophores are used in the electronics industry. The main requirements for them are to improve their brightness, color purity and increase service life.

 A particularly important class of electroluminophores is activated ZnS: Cu zinc sulfide phosphors, which have the required brightness and color indices.

 Such phosphors can give a blue, green or orange-yellow glow (if activated by manganese). These phosphors may contain other activators and co-activators.

 Described [US patent 4859361, cl. 252 / 301.6S, op. 08/22/1989] a method for producing a zinc sulfide phosphor activated by copper.

 First, the starting material is ZnS, the copper source and mineralizer are mixed and heated to obtain, at the stage of preliminary calcination, a hexagonal material - ZnS, containing copper and chlorine ions.

 Then, hexagonal ZnS is subjected to slow grinding, during which part of the hexagonal ZnS transforms into a cubic crystalline form.

 Finally, the milled material is mixed with zinc and copper sulfate and calcined again at a lower temperature to obtain an electroluminescent material.

The known method [US Patent 5643496, cl. S 09 K 011/54, NKI 252 / 301.6S, op. 07/01/1997] obtaining an electroluminophore, including zinc sulfide activated by copper, having an average particle size of less than 23 microns. The method includes:
(a) preparing a mixture of zinc sulfide, a source of copper, sulfur, a mineralizer and, preferably, zinc oxide;
(b) calcining the mixture first at a temperature of from about 1100 ^{° C.} to a temperature of about 1190 ^° C. and at first from about 3 hours to 7 hours, thereby producing zinc sulfide containing copper having an average particle size of less than 23 microns;
(c) grinding zinc sulfide containing copper to obtain milled material;
(e) calcining this milled material at a second temperature of from 650 to 750 ^{° C.} for a time sufficient to obtain a zinc sulfide phosphor activated by copper.

 Known [Application WO 9116722, cl. S 09 K 11/54, op. 10.31.1991, etc. 04.17.1990] a method for producing phosphors characterized by a long service life. This invention relates to phosphors based on zinc sulfides, obtained under specially controlled conditions of mechanical deformation of the initially calcined zinc-sulfide starting material.

The process of this invention includes the following steps:
(a) the preparation of a mixture mainly containing zinc sulfide, and a small amount of activator is a copper compound,
(b) calcining this mixture to a temperature that provides (more than 50%) of the hexagonal crystal structure,
(c) mechanical grinding of this calcined material,
(e) re-calcining the milled material until the crystalline structure returns to a predominantly cubic modification,
(e) appropriate cooling of the double calcined material to obtain the desired high brightness.

 It is claimed that this invention is mainly applicable to all electroluminophores, regardless of the color of the glow, however, they are especially applicable to phosphors of blue, green and yellow-orange.

 As is well known in the art, color differences can depend on both the constituents and their amount in the starting material. For example, brightness and color can be controlled by the introduction of a mixture containing selenides of copper and / or zinc.

 The challenge facing the developers of this invention was to create a method for producing a phosphor of blue and green glow, providing reliable performance of the finished product - increased brightness and a given color of the glow.

 The problem is solved by carrying out the stages of the process with the following parameters and in a certain sequence of them.

The essence of the invention lies in the fact that a method for producing electroluminophores based on zinc sulfide activated by copper has been developed, which includes the following main stages: preparing the mixture by mixing the starting materials, drying, calcining, annealing and chemical treatment, followed by washing and drying of the finished product. In this case, the initial mixture is prepared from semi-finished products obtained by preliminary mixing (Here and below, weight parts are given):
a) zinc sulfide with an aqueous solution of copper salt, for example, with copper chloride or copper sulphate (obtaining an activator charge). In this case, the ratio Cu: ZnS (1-5) is used :( 99-95);
b) zinc sulfide and an aqueous solution of zinc chloride (charge co-activator 1) in the ratio ZnCI ₂ : ZnS (5-15) :( 95-85);
c) sulfide and an aqueous solution of zinc iodide (charge coactivator 2) in the ratio ZnI ₂ : ZnS (5-15) :( 95:85).

The resulting semi-finished products are dried at a temperature of about 100 ^o C, sieved and mixed in the ratio:
a: b: c, as 1: (2.5-3.0) :( 2.5-3.0), respectively, and get the so-called intermediate charge, from which the working charge is prepared by adding zinc sulfide and sulfur to ratio: charge: ZnS: S, equal to 1: (2.5-3) :( 0.2-0.3), (weight parts), respectively.

Then, the mixture is calcined, which is carried out in the presence of a carbon-containing material, under conditions of limited air access, at a temperature of 850-1050 ^o С. The phosphor calcined under such conditions is subjected to stabilizing annealing, which consists in calcining in air at 500-750 ^o С for 3 -35 minutes. After cooling, the phosphor is chemically treated, freeing it from excess copper sulfide. To do this, a mixture of 30% alkaline solution and 30% hydrogen peroxide in a ratio of 10: 1 is passed through its layer from 1 to 5 cm thick. This mixture is passed through a phosphor layer until the wash liquid is discolored, and then washed with demineralized water until a neutral reaction is obtained.

 When implementing the method, commercially available substances, in powder or crystalline state, are used as starting components for steps a-b. The concentration of aqueous solutions of salts used in these stages are selected so that the result is a consistency that provides good mixing.

To carry out the calcination stage of the charge, it is loaded into crucibles or cuvettes of opaque quartz, covered with a layer of carbon-containing material, then covered with a quartz lid and placed in a furnace heated to a temperature of 850-1050 ^o C.

As a carbon-containing material, you can use coal, graphite or soot with a developed specific surface area of more than 10 m ² / g, dispersion from 0.2 to 3 mm. The layer of this material is about 1 to 50 mm, with activated charcoal being preferred.

Examples
Example 1 - phosphor blue glow
a) obtaining an activator charge: a solution of copper chloride is poured into a weighed portion of zinc sulfide in an amount providing a mass ratio of copper to zinc sulfide of 1: 99. The mixture is thoroughly mixed, dried at a temperature of about 130 ^o C, sieved without residue;
b) a zinc chloride solution is poured onto a sample of zinc sulfide in an amount that provides a mass ratio of ZnS: ZnCl ₂ 5:95. Then the mixture is thoroughly mixed, dried at a temperature of 100 ^o C and sieved without residue - get the mixture of coactivator 1;
c) a solution of zinc iodide in a ratio of ZnI ₂ : ZnS = 15: 85 is poured onto a sample of zinc sulfide. The mixture is also thoroughly mixed, dried at a temperature of about 100 ^o C and sieved.

 Then prepare the intermediate phosphor mixture by mixing mixtures (a), (b) and (c) in a ratio of 1: 2.86: 2.86. Then, zinc sulfide ZnS and elemental sulfur in powder form are added to this mixture (1) in a weight ratio of mixture (1): ZnS: S as 1: 3: 0.25.

The prepared phosphor mixture is loaded into a cuvette made of opaque quartz, a layer (10-15 mm) of granular graphite with a grain size of 2-3 mm is poured over it, then covered with a quartz lid, placed in a preheated oven and calcined at 800 ^° C for 1, 5 hours

Calcined phosphor after it has cooled, unloaded from the cuvette, sieved and subjected to stabilizing annealing. To do this, it is laid out in a quartz cuvette in a thin layer (about 1 cm) and calcined in air at a temperature of about 700 ^o C for 35 minutes.

 After repeated cooling, the phosphor is washed from the surface from the excess phase of copper sulfide with a mixture of 30% solutions of alkali and hydrogen peroxide (volume ratio 10: 1) until a colorless washing liquid appears, after which it is washed with demineralized (distilled) water, dried and sieved.

As a result, a luminophore of a blue color is obtained, which has a stable brightness in the finished products. The brightness of the glow is 40-60 cd / m ² . The decline in brightness after 2000 hours of operation is 50% of the original.

Example 2 - phosphor green glow
a) obtaining an activator charge: a solution of copper chloride is poured onto a sample of zinc sulfide in an amount providing a mass ratio of copper to zinc sulfide of 5: 95. The mixture is thoroughly mixed, dried at a temperature of about 100 ^o C, sieved without residue;
b) a zinc chloride solution is poured onto a sample of zinc sulfide in an amount that provides a mass ratio of ZnS: ZnCI _{2 of} 15:85. Then the mixture is thoroughly mixed, dried at a temperature of 100 ^o C and sieved without residue - get the mixture of coactivator 1;
c) a solution of zinc iodide in a ratio of ZnI ₂ : ZnS = 5: 95 is poured onto a sample of zinc sulfide. The mixture is also thoroughly mixed, dried at a temperature of about 100 ^o C and sieved. Selecting the components in the ratio a: b: c as 1: 3.0: 2.6, respectively, get the so-called working charge (semi-finished product). After stirring, zinc sulfide and sulfur in mass are added to this semi-finished product. the ratio of semi-finished products: ZnS: S, equal to 1: 2.6: 0.23, respectively.

Then, the mixture is calcined, which is carried out in the presence of a carbon-containing material, under conditions of limited air access, at a temperature of 1050 ^° C. The phosphor calcined under such conditions is subjected to stabilizing annealing, which consists in calcining in air at 500 ^{° C.} for 5 minutes. After cooling, the phosphor is chemically treated, freeing it from excess copper sulfide. To do this, a mixture of 30% solutions of alkali and hydrogen peroxide (with a volume ratio of 10: 1, respectively) is passed through a layer with a thickness of about 5 cm until the wash liquid is discolored, and then washed with demineralized water to pH 5.5.

As a result, a green luminophore was obtained with λ _nm = 515 ± 10 nμ and color coordinates: x = 0.180 ± 0.01; y = 0.425 ± 0.02.

When using this phosphor, the luminosity in the finished electroluminescent capacitors is 60-80 cd / m ² in the excitation mode of 100 V, at 400 Hz. The decrease in brightness after 2000 hours of operation does not exceed 30% of the original, which solves the problem.

 Thus, as a result of the method, phosphors are obtained that have the required indicators - luminance and stability.

Claims (2)

1. The method of producing electroluminophores based on zinc sulfides activated by copper, which includes the following main stages: preparation of the mixture by mixing the starting materials, drying, calcining, annealing and chemical treatment and drying, characterized in that the initial mixture is prepared from semi-finished products obtained by preliminary mixing a) zinc sulfide with an aqueous solution of copper salt at a mass ratio of Cu: ZnS = (1-5) :( 99-95), b) zinc sulfide and an aqueous solution of zinc chloride in a mass ratio of ZnCl ₂ : ZnS = (5-15) : (95-85), c) sulfide and in -stand solution of zinc iodide in a weight ratio ZnJ _2: ZnS = (5-15) :( 95:85 ), obtained semifinished dried at a temperature of 100-130 ^o C, sieved and mixed in a weight ratio mixture (a) :( b): (c) as 1: (2.5-3.0) :( 2.5-3.0) respectively, then zinc sulfide and sulfur are added in a weight ratio of the mixture of semi-finished products: ZnS: S equal to 1: (2.5 -3): (0.2-0.3), respectively, after which the mixture is calcined in the presence of a carbon-containing material at a temperature of 850-1050 ^o C, subjected to stabilizing annealing in air at 500-750 ^o C for 3-35 min, and then carry out a chemical o processing of the phosphor with a mixture of 30% solutions of alkali and hydrogen peroxide in a volume ratio of 10: 1, respectively.  2. The method according to claim 1, characterized in that as an aqueous solution of a copper salt using chloride or copper sulfate.