JPH0160519B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a sulfide phosphor with improved moisture resistance and water resistance, and a method for producing the same. As a group of sulfide phosphors, magnesium,
Sulfide phosphors are known in which a sulfide matrix containing at least one divalent metal selected from strontium and barium as a cationic component is activated with a suitable activator. These sulfide phosphors generally emit high-intensity light under electron beam excitation, and they also exhibit good current density-emission brightness characteristics and temperature-emission brightness characteristics, so they are used as phosphors for cathode ray tubes, especially for projection type cathode ray tubes. It is useful as a fluorescent material. For example, a cerium-activated strontium sulfide green-emitting phosphor (SrS:Ce) is a copper- and aluminum-activated zinc sulfide green-emitting phosphor (ZnS:Cu), which has been used as a phosphor for the green-emitting component of color television cathode ray tubes. ，
Al) or gold-, copper- and aluminum-activated zinc sulfide green-emitting phosphors (ZnS: Au, Cu, Al). Terebrium-activated cadrinium oxysulfide green-emitting phosphor (Cd ₂ O ₂ S: Tb) or terebrium-activated yttrium oxysulfide green-emitting phosphor (Y ₂ O ₂ S:Tb) has higher luminance. As described above, the sulfide phosphor has excellent luminescent properties, but as explained below, its moisture resistance and water resistance are extremely poor, and for this reason, it has hardly ever been put to practical use. That is, the sulfide phosphor is chemically unstable with respect to water, and when left in the air, it absorbs moisture and is hydrolyzed, resulting in a decrease in luminance. This hydrolysis progresses over time from the surface of the phosphor particle toward the inside, and eventually the phosphor no longer exhibits nearly any fluorescence. As described above, the sulfide phosphor has poor moisture resistance and therefore has poor storage stability. In addition, fluorescent films for cathode ray tubes and the like are generally produced by a fluorescent film manufacturing method that uses an aqueous dispersion, such as a slurry coating method or a sedimentation method. is made into a fluorescent film by the method used to make the fluorescent film, the sulfide has a relatively high solubility in water (i.e., due to its poor water resistance). During the production of the optical film, a portion of the phosphor dissolves in water, and as a result, the luminance of the phosphor decreases, resulting in a resulting phosphor film with low luminance. In particular, when the phosphor film made of the above-mentioned sulfide phosphor is produced by a very common precipitation method using an aqueous water glass solution as a dispersion medium, at least one of magnesium, strontium and barium eluted from the phosphor is Ions of one type of divalent metal react with water glass, and as a result, the water glass aqueous solution dispersion containing phosphor particles gels, and the phosphor particles no longer settle, producing a phosphor film. become unable to do so. Several methods have been proposed to improve the moisture resistance and water resistance of the sulfide phosphors. One known method is to wash the portion of the sulfide phosphor that is unstable to water (temperature) with a specific buffer solution. however,
This method simply dissolves and removes the part of the sulfide phosphor that is particularly unstable to water obtained by manufacturing the phosphor, and improves the moisture resistance of the sulfide phosphor. It does not essentially improve water resistance. Another known method is to form a hydrophobic silica coating on the surface of the sulfide phosphor particles to cover the phosphor particles. However, with this method, a relatively thick silica film must be formed in order to provide the sulfide phosphor with sufficient moisture and water resistance, which reduces the luminance of the sulfide phosphor. It decreases considerably. In addition, the adhesion of the silica coating to the sulfide phosphor particles is relatively weak, and therefore, when sieving the phosphor particles for the purpose of classification, etc., or dispersing the phosphor particles during the preparation of the phosphor film. The silica coating peels off due to the mechanical impact applied to the phosphor particles during repeated stirring of the liquid, and this peeling off of the silica coating reduces the moisture resistance once imparted to the sulfide phosphor. and water resistance is significantly impaired. Due to the above-mentioned drawbacks, the sulfide phosphor whose particles are coated with a hydrophobic silica film cannot be put to practical use. Yet another method for improving the moisture resistance and water resistance of the sulfide phosphor is a method of forming a water-insoluble polymer coating on the surface of the sulfide phosphor particles to coat the phosphor particles. It has been known. The water-insoluble polymer coating is formed on the surface of the sulfide phosphor particles in the following two ways. That is,
The first method involves mixing the sulfide phosphor with a solution of a polymer such as polyethylene, polymethyl methacrylate, polycarbonate, acrylonitrile-styrene copolymer, etc., dispersing the sulfide phosphor in the polymer solution, and then dispersing the sulfide phosphor in the polymer solution. A method of adding a polymeric non-solvent to a dispersion to form a polymer-rich phase on the surface of sulfide phosphor particles, and then separating the sulfide phosphor particles encapsulated by the polymer-rich phase. It is. The second method uses a sulfide phosphor and styrene, methacrylate, glycidyl methacrylate, hydroxyethyl methacrylate, diallyl phthalate, α-methylstyrene, divinylbenzene, diallyl phthalate prepolymer,
1,4-cis polybutadiene, bisphenol type epoxy prepolymer, vinyl siloxane,
The sulfide phosphor particles are dispersed in the liquid monomer or prepolymer by mixing with a liquid monomer or prepolymer such as a modified silicone prepolymer or polyester, and then this dispersion is mixed with a non-solvent for the monomer or prepolymer. to form a thick monomer or prepolymer phase on the surface of the sulfide phosphor particles, and then the sulfide phosphor particles encapsulated by this monomer or prepolymer thick phase are separated, and then This is a method in which the monomers or prepolymers on the surface of the phosphor particles are aggregated and cured by an appropriate method such as using a post-catalyst, irradiation with radiation or ultraviolet rays, or heating. However, like the above-mentioned hydrophobic silica coating, water-insoluble polymer coatings have relatively weak adhesion to sulfide phosphor particles, and for this reason, when handling the phosphor such as sieving or when preparing the phosphor film. The polymer coating peels off due to the mechanical impact applied to the phosphor particles during repeated stirring of the phosphor particle dispersion, and this peeling of the polymer coating causes the sulfide phosphor to Moisture resistance and water resistance once imparted are significantly impaired. Furthermore, the water-insoluble polymer coatings are formed by the above two methods, but the water-insoluble polymer coatings formed by these methods are relatively thick, and therefore the luminescence of the sulfide phosphor is limited. Brightness decreases considerably. Because of these drawbacks, the sulfide phosphors whose particles are coated with a water-insoluble polymer coating are also not practical. The present invention was made under the above-mentioned circumstances, and provides the above-mentioned sulfide phosphor with improved moisture resistance and water resistance, which can be put to practical use as a fluorescent film for cathode ray tubes, etc., and a method for producing the same. The purpose is to provide. In order to achieve the above object, the present inventors have conducted various studies regarding the water-insoluble coating that covers the sulfide phosphor particles. As a result, by mixing the above sulfide phosphor particles with an aqueous solution of an alkali metal salt or ammonium salt of a polysaccharide, it was found that among the magnesium, strontium and barium produced by dissolving the surface of the sulfide phosphor particles in water, and at least one divalent metal ion of the polysaccharide and an alkali metal salt or ammonium salt of the polysaccharide to form the divalent metal salt of the polysaccharide that coats the surface of the sulfide phosphor particles. discovered that the above object could be achieved and completed the present invention. The sulfide phosphor of the present invention with improved moisture resistance and water resistance has a sulfide matrix containing at least one divalent metal selected from magnesium, strontium, and barium as a cation component, and this matrix is activated. particles of a sulfide phosphor activated with an agent;
2 above of the polysaccharide that coats the surface of the phosphor particles.
It consists of a coating made of a valent metal salt. Further, the method for producing a sulfide phosphor with improved moisture resistance and water resistance of the present invention uses a sulfide containing at least one divalent metal of magnesium, strontium, and barium as a cationic component as a matrix, By mixing the sulfide phosphor particles obtained by activating this matrix with an activator and an aqueous solution of an alkali metal salt or ammonium salt of a polysaccharide, and dissolving the surface of the sulfide phosphor particles in water, The resulting divalent metal ion is reacted with the alkali metal salt or ammonium salt of the polysaccharide to produce the divalent metal of the polysaccharide covering the surface of the sulfide phosphor particles. shall be. As mentioned above, it is known that the moisture resistance and water resistance of the sulfide phosphor can be improved by forming a film of a water-insoluble polymer on the surface of the sulfide phosphor particles. ing. However, the water-insoluble polymer used as the coating is a specific polymer as described above, and the use of the divalent metal salt of a polysaccharide, which is a carbohydrate, as the coating is completely unknown. Of course,
The manufacturing method of the present invention for forming a film made of the divalent metal salt of polysaccharide on the surface of sulfide phosphor particles is also not known at all. The present invention will be explained in detail below. In the production method (coating treatment method) of the present invention, a sulfide containing at least one divalent metal of magnesium, strontium, and barium as a cationic component is used as a matrix, and this matrix is treated with an appropriate activator. Activated sulfide phosphor particles are mixed with an aqueous solution of an alkali metal or ammonium salt of a polysaccharide. Here, the sulfide containing at least one divalent metal selected from magnesium, strontium, and barium as a cationic component means any one of the following sulfides), ), and). ) At least one divalent metal of magnesium, strontium and barium such as magnesium sulfide (MgS), strontium sulfide (SrS), barium sulfide (BaS), strontium/barium sulfide [(Sr,Ba)S], etc. Sulfide is an ionic component. ) Magnesium/calcium sulfide [(Mg,
At least one divalent metal selected from magnesium, strontium, and barium, such as strontium/calcium sulfide [(Sr,Ca)S], barium/calcium sulfide [(Ba,Ca)S], and calcium, for example, Above 2 like
A sulfide whose cationic component is a divalent metal other than a valent metal. ) Magnesium thiogallate (MgGa ₂ S ₄ ),
Strontium thiogallate (SrGa ₂ S ₄ ), barium thiogallate (BaGa ₂ S ₄ ), strontium calcium thiogallate [(Sr,Ca)
A composite sulfide of a _divalent metal sulfide represented by the _above ) or ) and a sulfide of a metal with a valence other than divalent. In addition, the alkali metal salt or ammonium salt of a polysaccharide refers to an alkali metal salt or ammonium salt of a carbohydrate produced by dehydration condensation of a monosaccharide for 2 minutes or more, and any water-soluble salt can be used in the present invention. It can be used in coating treatment methods. Particularly preferred alkali metal or ammonium salts of polysaccharides for use in the coating process of the invention are those of carboxymethylcellulose, alginic acid and mannan. The sulfide phosphor and the aqueous solution of the alkali metal salt or ammonium salt of the polysaccharide may be mixed by any method, but the sulfide phosphor is added to the aqueous solution while stirring the water-soluble material in a container. It is preferable to do so. In this case, the sulfide phosphor may be added as is to the aqueous solution, but it is better to first disperse the sulfide phosphor in the form of primary particles as much as possible in the solution medium, and then add this dispersion to the aqueous solution. More preferred. As the liquid medium, water is most suitable from the viewpoint of dispersibility of the sulfide phosphor, but in order to minimize dissolution of the sulfide phosphor, sulfide phosphor such as methyl alcohol or ethyl alcohol is used. It is preferable to use a mixed liquid of water and a liquid that hardly dissolves the liquid and is miscible with water. By mixing the sulfide phosphor with an aqueous solution of an alkali metal salt or ammonium salt of a polysaccharide, the surface of the sulfide phosphor particles is dissolved, and the magnesium, strontium, and barium contained as cationic components of the parent body are dissolved. At least one type of divalent metal among them is eluted as an ion, and at the same time as the divalent metal ion is eluted, it reacts with an alkali metal salt or ammonium salt of the polysaccharide on the surface of the phosphor particle,
As a result, the divalent metal salt coating of the water-insoluble polysaccharide is formed on the surface of the phosphor particle. This polysaccharide divalent metal salt coating formation reaction is completed in a short time (several seconds). This occurs when the eluted divalent metal ion reacts with the alkali metal salt or ammonium salt of the polysaccharide to form a divalent metal salt of the polysaccharide on the surface of the phosphor particle. The surface of the phosphor particles is cut off from contact with water,
This is because it will hardly dissolve beyond that point.
Therefore, only a small amount of dissolution of the surface of the phosphor particles is necessary to form a polysaccharide divalent metal salt coating, and the luminance of the sulfide phosphor is hardly reduced by this dissolution. In addition, when calcium is included as a cationic component in the matrix of the sulfide phosphor together with at least one divalent metal among the above-mentioned magnesium, strontium, and barium, this calcium is also present on the surface of the phosphor particle. During dissolution, it is eluted as ions, and at the same time as it elutes, it reacts with the alkali metal salt or ammonium salt of the polysaccharide on the surface of the phosphor particle, thereby forming a water-insoluble polysaccharide calcium salt on the surface of the phosphor particle. It is produced together with the polysaccharide divalent metal salt. The polysaccharide calcium salt together with the polysaccharide divalent metal salt constitutes a water-insoluble film that coats the surface of the phosphor particles. The amount of the polysaccharide divalent metal salt produced on the surface of the sulfide phosphor particles can be changed by changing the concentration of the polysaccharide alkali metal salt or ammonium salt aqueous solution (the polysaccharide in the aqueous solution Not all of the alkali metal salts or ammonium salts react with the eluted divalent metal ions, but only those present near the surface of the sulfide phosphor particles react with the eluted divalent metal ions).
That is, when the concentration of polysaccharide alkali metal salt or ammonium salt is increased, a large amount of polysaccharide divalent metal salt is generated on the surface of the sulfide phosphor particles (that is, a thick polysaccharide divalent metal salt film is formed). ), conversely, when the concentration of polysaccharide alkali metal salt or ammonium salt is lowered, a small amount of polysaccharide divalent metal salt is generated on the surface of the sulfide phosphor particles (i.e., a thin polysaccharide divalent metal salt is formed). a film is formed). Although it varies depending on the type of polysaccharide, it is generally 0.001 to 10 of the weight of the sulfide phosphor before coating.
% of polysaccharide divalent metals (including calcium salts if the phosphor matrix contains calcium as a cationic component and therefore polysaccharide calcium salts are also produced). The concentration of the alkali metal salt or ammonium salt is selected, preferably such that 0.01 to 3% of the polysaccharide divalent metal salt is produced. Due to differences in surface conditions among sulfide phosphor particles, there are two types of particles whose surfaces are easily soluble in water (high amount of eluted divalent metal ions) and those which are difficult to dissolve in water (elution 2).
Particles with a small amount of valent metal ions are thought to exist, but the former have a thick polysaccharide divalent metal salt coating formed on their surfaces, while the latter have a thin polysaccharide divalent metal salt coating formed on their surfaces. It seems likely that it will be done. Furthermore, even in a single sulfide phosphor particle, there are likely to be parts on the surface that are easily soluble in water and parts that are difficult to dissolve in water; however, a thick polysaccharide divalent metal coating is formed on the former; It is thought that a thin polysaccharide divalent metal coating is formed on the latter. In this way, the greater the amount of eluted divalent metal ions on a particle, the thicker the polysaccharide divalent metal salt coating is formed, and even in a single particle, the surface area with a greater amount of eluted divalent metal ions forms a thicker polysaccharide divalent metal salt coating. The formation of a coating is a major advantage of the coating process of the present invention. This is believed to be one of the reasons for the excellent moisture and water resistance exhibited by the sulfide phosphor after coating. The sulfide phosphor described above is mixed with an aqueous solution of an alkali metal salt or ammonium salt of a polysaccharide, and after a polysaccharide divalent metal coating is formed on the surface of the sulfide phosphor particles, the sulfide phosphor is The body is separated from the aqueous solution, washed, dehydrated and dried. The sulfide phosphor coated by the method of the present invention described above has a sulfide matrix containing at least one divalent metal selected from magnesium, strontium, and barium as a cationic component;
It consists of particles of a sulfide phosphor whose matrix is activated with an activator, and a polysaccharide film made of the divalent metal mentioned above that coats the surface of the phosphor particles. The sulfide phosphor of the present invention, the particle surface of which is coated with a film made of a polysaccharide divalent metal salt, has good moisture resistance and water resistance, as will be specifically explained below. Furthermore, the coated sulfide phosphor of the present invention is different from conventional sulfide phosphors whose particle surfaces are coated with a hydrophobic silica coating or a specific water-insoluble polymer coating in the following two respects. and are superior to those conventional coated sulfide phosphors. Firstly, the coated sulfide phosphor of the present invention exhibits almost no reduction in luminance compared to the sulfide phosphor before coating. One of the reasons for this is that, as mentioned earlier, the surface of the phosphor particles is only slightly dissolved during the coating process, and the other is that the polysaccharide divalent metal coating that is generally formed This seems to be because it is considerably thinner than the hydrophobic silica coating or the water-insoluble polymer coating. Second,
The polysaccharide divalent metal salt coating has a very strong adhesion force to the sulfide phosphor particles, and therefore the polysaccharide divalent metal coating is used as a phosphor during sieving of the phosphor particles or during the preparation of the phosphor film. It does not peel off due to mechanical impact applied to the phosphor particles during stirring of the particle dispersion. One of the reasons for the strong adhesion of the polysaccharide divalent metal coating to the sulfide phosphor particles is that the divalent metal ions eluted at the same time as the surface of the phosphor particle dissolves on the polysaccharide surface. This is thought to be due to the fact that the phosphor particles react with the alkali metal salt or ammonium salt, that is, the surface of the phosphor particle reacts with the above salt, thereby forming a polysaccharide divalent metal coating. Another reason seems to be that the polysaccharide divalent metal salt coating that is generally formed is considerably thinner than the hydrophobic silica coating or the water-insoluble polymer coating. Above 2
From these points, unlike conventional coated sulfide phosphors, the coated sulfide phosphor of the present invention can be put to practical use in the fluorescent film of cathode ray tubes and the like. The drawings illustrate the moisture resistance of coated sulfide phosphors of the present invention in comparison to the moisture resistance of uncoated sulfide phosphors, and the phosphors were exposed to temperatures of 25°C, It is a graph showing the relationship between the number of days left (horizontal axis) and the luminance of the phosphor (vertical axis) when left in a constant temperature and humidity chamber with a relative humidity of 50%. In the drawing, curve a is an uncoated sulfide phosphor (SrS:Ce phosphor), and curve b is a coated sulfide phosphor of the present invention (the particle surface is coated with a strontium alginate film). SrS:Ce fluorophore). As is clear from the drawings, the luminance of the uncoated sulfide phosphor decreases significantly as the number of days left increases, but in contrast, the coated sulfide phosphor of the present invention Even after 70 days have elapsed, the luminance hardly decreases. In other words, an uncoated sulfide phosphor absorbs moisture in the air and undergoes hydrolysis, and this hydrolysis progresses over time from the surface of the phosphor particle toward the inside. The coated sulfide phosphor of the present invention absorbs almost no moisture from the air because the phosphor particle surface is coated with a water-insoluble polysaccharide divalent metal salt, and therefore hardly absorbs water from the air. The drawings indicate that it will not be disassembled. As illustrated in the drawings, the coated sulfide phosphors of the present invention have significantly better moisture resistance than uncoated sulfide phosphors, and therefore have a longer shelf life. It is in extremely good condition. Table 1 below illustrates the water resistance of the coated sulfide phosphors of the present invention in comparison to the water resistance of uncoated sulfide phosphors, and shows that the phosphors are 3 g 10 days after the start of the test, the coated sulfide phosphor of the present invention was subjected to a forced water resistance test by pouring each into 30 ml of pure water with a pH of 7.0 and stirring at high speed. For uncoated sulfide phosphors, the PH value of the test water is shown 3 days after the start of the test. The PH value of the test water 3 days after the start of the test for uncoated sulfide phosphors is shown in brackets in the PH value column in the table.

[Table] An increase in the pH value of the test water means that the sulfide fluorophore is dissolved in the water. As is clear from Figure 1, in any case for uncoated sulfide phosphors, the PH value of the test water changed in just 3 days after the start of the test.
However, in contrast, for the coated sulfide phosphor of the present invention, the PH value of the test water was 7.5 even 10 days after the start of the test.
below, and the increase in PH value is slight. In other words, even if the coated sulfide phosphor of the present invention is immersed in water for three times or more time as the uncoated sulfide phosphor, the amount dissolved is less than that of the uncoated sulfide phosphor. It is significantly less than fluorescent material. As described above, the coated sulfide phosphor of the present invention has significantly better water resistance than the uncoated sulfide phosphor. As illustrated in Table 1, the coated sulfide phosphor of the present invention has significantly improved water resistance. Therefore, when the coated sulfide phosphor of the present invention is made into a fluorescent film for a cathode ray tube or the like by a slurry coating method or a sedimentation method that uses an aqueous dispersion medium, The dissolution of the phosphor in water during film preparation is negligible and the resulting phosphor film is comparable to that made using uncoated sulfide phosphors. The luminance is extremely high. What is particularly noteworthy here is that, as mentioned earlier, uncoated sulfide phosphors cannot be gelled by a general precipitation method using a water glass aqueous solution as a dispersion medium. However, the coated sulfide phosphor of the present invention can be formed into a fluorescent film by the above method if the preparation of the fluorescent film is carried out immediately after preparing the phosphor particle dispersion. This means that it is possible. Incidentally, after the fluorescent film of cathode ray tubes, etc. is formed, it is heat-treated (baked) at a temperature of 420 to 500°C, but the polysaccharide divalent metal salt film is decomposed and evaporated by this baking (note that the phosphor The matrix contains calcium as a cationic component, so if polysaccharide calcium salts are also produced, they are also decomposed and evaporated by baking). In particular, divalent metal salts of carboxymethyl cellulose, alginic acid, and mannan have good decomposition and evaporation properties during baking.
Among these three types of divalent metal salts of polysaccharides, the divalent metal salt of carboxymethyl cellulose has the best decomposition and evaporation properties during baking. As mentioned above, the polysaccharide divalent metal coating coating the sulfide phosphor particles improves the moisture resistance and water resistance of the sulfide phosphor, but this polysaccharide divalent metal salt coating also improves the sulfide phosphor particles. It also improves body dispersion. Table 2 below shows particles whose surfaces were coated with a strontium salt film of carboxymethyl cellulose.
This figure shows the luminance of the fluorescent film when five types of SrS:Ce phosphors were made into a fluorescent film by a precipitation method using a 1% by weight aqueous water glass solution as a dispersion medium. As shown in the table, the five types of phosphors differ in the concentration of the sodium salt aqueous solution of carboxymethyl cellulose used in the coating treatment, and therefore the amount of strontium salt of carboxymethyl cellulose that coats the phosphor particles varies. However, the luminance is almost the same. The coating treatment is performed by adding a dispersion of 40 g of SrS:Ce phosphor dispersed in 1 part of pure water to the aqueous solution of sodium salt of carboxymethyl cellulose with stirring as shown in the table. It was carried out by.

[Table] As is clear from Table 2 above, although the five types of phosphors have approximately the same luminance, the phosphor films made using these phosphors are based on sodium carboxymethyl cellulose. The luminance increases depending on the concentration of the salt aqueous solution, that is, the amount of strontium salt of carboxymethyl cellulose produced. This is because the strontium salt of carboxymethylcellulose produced on the surface of the sulfide phosphor particles enhances the dispersion of the phosphor particles, thereby creating a phosphor film with a high packing density of phosphor particles. Seem. As explained above, the present invention provides a sulfide phosphor that has improved moisture resistance, water resistance, etc. and can be used as a fluorescent film for cathode ray tubes, and a method for producing the same. The utility value is extremely large. Next, the present invention will be explained with reference to Examples. Example 1 0.005% by weight sodium alginate aqueous solution 3
While stirring, add SrS:Ce phosphor 40 to the aqueous solution.
A dispersion prepared by dispersing g in 800 ml of pure water was added.
By mixing this aqueous solution and the dispersion, a strontium alginate film was rapidly formed on the surface of the SrS:Ce phosphor particles. Stirring was continued for 5 minutes after addition of the dispersion, after which the SrS:Ce phosphor particles coated with the strontium alginate coating were separated, washed with water, dehydrated and dried. The SrS:Ce phosphor coated in this way remains uncoated under electron beam excitation.
It showed almost the same luminance as SrS:Ce phosphor.
Further, this coated SrS:Ce phosphor exhibited good moisture resistance as shown in FIG. 1, and also showed good water resistance almost equivalent to the water resistance exemplified in Table 2. Example 2 0.001% by weight sodium alginate aqueous solution 6
Add SrS:Ce fluorophore 40 to this aqueous solution while stirring.
g was added through a 500 mesh sieve. By mixing this aqueous solution and SrS:Ce phosphor, SrS:Ce
A strontium alginate film was quickly formed on the surface of the phosphor particles. Stirring was continued for 5 minutes after the addition of the SrS:Ce phosphor, after which the SrS:Ce phosphor particles coated with the strontium alginate coating were separated, washed with water, dehydrated, and dried. The SrS:Ce phosphor coated in this way remains uncoated under electron beam excitation.
It showed almost the same luminance as SrS:Ce phosphor.
Moreover, this coated SrS:Ce phosphor exhibited good moisture resistance and water resistance almost equivalent to that of the phosphor of Example 1. Example 3 0.004% by weight sodium alginate aqueous solution 2
While stirring, add SrS:Eu fluorophore 40 to this aqueous solution.
A dispersion prepared by dispersing g in pure water 2 was added.
By mixing this aqueous solution and the dispersion, a strontium alginate film was rapidly formed on the surface of the SrS:Eu phosphor particles. Stirring was continued for 5 minutes after addition of the dispersion, after which the SrS:Eu phosphor particles coated with the strontium alginate coating were separated, washed with water, dehydrated and dried. The thus coated SrS:Eu phosphor remains uncoated under electron beam excitation.
SrS: Exhibited luminance almost equivalent to Eu phosphor.
Furthermore, this coated SrS:Eu phosphor exhibited good moisture resistance and water resistance almost equivalent to that of the phosphor of Example 1. Example 4 While stirring a 0.016% by weight sodium salt aqueous solution 3 of carboxymethyl cellulose, a dispersion of 40 g of (Sr _0.9 , Ca _0.1 ) S:Ce phosphor dispersed in 1 pure water was added to this aqueous solution. . By mixing this aqueous solution and dispersion, (Sr _0.9 , Ca _0.1 )S:Ce
A film consisting of strontium salt and calcium salt of carboxymethyl cellulose was rapidly formed on the surface of the phosphor particles. Stirring was continued for 5 minutes after the addition of the dispersion, after which the (Sr _.9 , Ca _0.1 ) S:Ce was coated with a coating of strontium and calcium salts of carboxymethyl cellulose.
The phosphor particles were separated, washed with water, dehydrated, and dried. Coated in this way (Sr _.9 , Ca _0.1 )
The S:Ce phosphor exhibited almost the same luminance as the uncoated (Sr _0.9 , Ca _0.1 ) S:Ce phosphor under electron beam excitation. Further, this coated (Sr _0.9 , Ce _0.1 )S:Ce phosphor exhibited good moisture resistance and water resistance almost equivalent to that of the phosphor of Example 1. Example 5 While stirring 0.01% by weight konjac mannan (Himannan, Mannan Foods Co., Ltd.) aqueous solution 3, 40 g of SrS:Ce phosphor was added to the aqueous solution with pure water.
A dispersion in 800 ml was added. By mixing this aqueous solution and the dispersion, a strontium salt film of mannan was rapidly formed on the surface of the SrS:Ce phosphor particles. Stirring was continued for 5 minutes after addition of the dispersion, after which the SrS:Ce phosphor particles coated with the mannan strontium salt coating were separated, washed with water, dehydrated and dried. The SrS:Ce phosphor coated in this way remains uncoated under electron beam excitation.
It showed almost the same luminance as SrS:Ce phosphor.
Moreover, this coated SrS:Ce phosphor exhibited good moisture resistance and water resistance almost equivalent to that of the phosphor of Example 1.

[Brief explanation of drawings]

The drawings illustrate the moisture resistance of the coated sulfide phosphors of the present invention in comparison to the moisture resistance of uncoated sulfide phosphors, and show that the phosphors were placed in a constant temperature and humidity chamber. 2 is a graph showing the relationship between the number of days the fluorescent material is left and the luminance of the phosphor.

Claims (1)

[Scope of Claims] 1. A sulfide phosphor having a sulfide matrix containing at least one divalent metal selected from magnesium, strontium, and barium as a cationic component, and activating this matrix with an activator. A sulfide phosphor having improved moisture resistance and water resistance, comprising particles of the above-mentioned particles and a film made of the divalent metal salt of a polysaccharide that coats the surface of the phosphor particles. 2. The phosphor according to claim 1, wherein the polysaccharide is carboxymethyl cellulose. 3. The phosphor according to claim 1, wherein the polysaccharide is alginic acid. 4. The phosphor according to claim 1, wherein the polysaccharide is mannan. 5. Sulfide phosphor particles containing a sulfide containing at least one divalent metal of magnesium, strontium, and barium as a cationic component as a cation component, and sulfide phosphor particles activated with an activator and polysaccharide. Mixing an aqueous solution of an alkali metal salt or ammonium salt, and causing the divalent metal ions generated by dissolving the surface of the sulfide phosphor particles in water to react with the alkali metal salt or ammonium salt of the polysaccharide. . A method for producing a sulfide phosphor with improved moisture resistance and water resistance, which comprises producing the divalent metal salt of the polysaccharide that coats the surface of the sulfide phosphor particles. 6. The manufacturing method according to claim 5, wherein the sulfide phosphor particles to be mixed with the aqueous solution are dispersed in a liquid medium. 7. The manufacturing method according to claim 5 or 6, wherein the polysaccharide is carboxymethylcellulose. 8. The manufacturing method according to claim 5 or 6, wherein the polysaccharide is alginic acid. 9. The manufacturing method according to claim 5 or 6, wherein the polysaccharide is mannan.