JPH0853666A - Production of phosphor particle coated with polymer - Google Patents

Abstract

PURPOSE:To obtain phosphor particles completely coated with a polymer film by treating the surfaces of phosphor particles with a surface modifier. coating the surfaces with a polymerizable monomer, and polymerizing the monomer. CONSTITUTION:Phosphor particles coated with a polymer are obtd. by treating the surfaces of 1 pt.wt. phosphor particles with 0.001-0.1 pt.wt. surface modifier which has, in the same molecule, both a group having the affinity with the phosphor particle and a group having the affinity with a monomer for coating the particles or its polymer to modify the surfaces, mixing 1 pt.wt. phosphor particles treated as above with 0.001-10 pts.wt. polymerizable monomer contg. 0.01-10wt.% polymn. initiator to coat the surfaces with the monomer, dispersing the particles in a dispersion medium such as water using a dispersion mill, if necessary in the presence of a dispersant such as a surfactant, polymerizing the monomer on the surfaces at room temp. to 90 deg.C for at least 15hr, and separating, washing, and drying the particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a phosphor for CDT (color display tube), and provides a technique for forming a polymer film without defects on the surface of phosphor particles for CDT. To do.

[0002]

2. Description of the Related Art In a phosphor for CDT, in order to improve contrast, for example, a blue or red phosphor is so-called a blue or red phosphor spread on the surface of the phosphor by using an organic or inorganic binder. A pigmented phosphor is used. In the CDT manufacturing process, the pigmented phosphor is made into a water-dispersed slurry, mixed with an ultraviolet curable resin and other chemicals, applied to a CDT face plate, and a dot-shaped or stripe-shaped phosphor pattern is formed and fixed. The extra pigmented phosphor that has not been fixed is washed with water, collected, and used again. In the pigmented phosphor fixed on the face plate, the organic binder is thermally decomposed and removed in the firing step.

The pigment-containing phosphor slurry, which has been repeatedly used in the coating process, is applied for reasons such as a decrease in the phosphor concentration, peeling of the pigment due to the shearing action of the slurry transfer pump, and mixing of a solidified product due to ultraviolet irradiation. When no longer suitable for use, it is discarded and replaced with a freshly prepared slurry. Conventionally used gelatin, gum arabic, various resin emulsions, alumina sol, silica sol, water glass and the like are used as the binder between the pigment and the phosphor particles. These binders exhibit a binding action due to the charge property and / or the adhesive action, but according to the experiments of the present inventor, they have industrially large defects and are insufficient.

Even if cross-linked, gelatin, gum arabic and other water-soluble polymers are easily affected by the chemicals added in the CDT face plate coating step, and the pigment is easily peeled off. In addition, many polymers are subject to deterioration and decomposition by microorganisms, or have weak bonding force with the surface of the phosphor, and are easily peeled off. When the resin emulsion is used as a binder for the pigment and the phosphor, the resin emulsion is added to the aqueous phase in which the pigment and the phosphor are dispersed, and the dispersion state of the resin particles is adjusted by adjusting pH, salt concentration, temperature, etc. The resin particles are destroyed and the resin particles are coagulated and deposited on the surface of the phosphor particles together with the pigment particles.
However, this method does not limit the agglomeration site of the resin particles to the surface of the phosphor particles, and the agglomeration proceeds even in the region where the phosphor particles do not exist, resulting in a large number of agglomerated particles that do not adhere to the phosphor particles However, it is difficult to control the amount of pigment spread and the amount of resin spread on the surface of the phosphor particles, and in particular, it is insufficient as a method for spreading a high concentration pigment to manufacture a phosphor for high definition CDT. Technology.

As a technique for avoiding the above-mentioned drawbacks, a method of radically polymerizing a vinyl monomer in an aqueous phase in which a pigment and a phosphor are dispersed has been proposed (JP-A-54-85192 and JP-A-55-164282). JP-A-62-
No. 253683, Japanese Patent Publication No. 62-41273). This method supplements the drawbacks of the above-mentioned technique because the produced polymer is deposited on the surface of the phosphor particles in the state of containing the pigment particles. However, the polymer on the surface of the phosphor particles, which is deposited by this method, has an island shape and does not cover the surface with a uniform film. When the amount of the polymer is increased by increasing the amount of the charged monomer, the island-shaped polymer expands and becomes continuous with each other to approach the film, but the aggregation of the phosphor particles also increases, so that the independent phosphor particles are uniformly dispersed. This is an incomplete method for covering with a polymer film.

[0006] In addition, although the valuable phosphor is recovered and regenerated from the phosphor slurry discarded in the CDT face plate coating step, the pigmented phosphor covered with such a polymer film is recovered, The protective effect of the polymer coating against alkali and / or acid used during regeneration is insufficient, and the elution of elements constituting the phosphor cannot be sufficiently suppressed. For example, an expensive pigmented red phosphor (Y ₂ O ₂ S: E
When u) is treated with 0.1N dilute hydrochloric acid, several hundred ppm
Yttrium (as Y ₂ O ₃ ) elutes in 1 hour, which is very inconvenient. It is considered that this is because it is inevitable that a thin film portion or a filmless portion is generated in the process of forming the polymer film.

[0007]

SUMMARY OF THE INVENTION In view of the above situation, the present invention provides an independent phosphor in which the surface of the phosphor particles is covered with a polymer film having no defects while avoiding the aggregation of the phosphor particles. A method of making particles is provided.

[0008]

In order to solve the above-mentioned problems, the present invention treats the surface of phosphor particles with a monomer and / or
Alternatively, increasing the affinity of the particle surface for the polymer, independently dispersing such phosphor particles in the dispersion medium while being covered with the monomer layer, and then converting the monomer layer into the polymer layer. Then, a polymer-coated phosphor having no defect in the polymer layer is obtained.

That is, the gist of the present invention is to subject the phosphor particles to a surface treatment with a surface modifier, coat them with a polymerizable monomer, and then disperse the particles in a dispersion medium to obtain a polymerizable monomer. A method for producing phosphor particles is characterized in that a polymer layer is formed by polymerizing a body. According to the present invention, a method of forming a polymer layer on the surface of a phosphor particle having a pigment-containing layer, a method of incorporating a pigment in the polymer layer, or a pigment-containing layer is formed on the polymer coating layer. By using the method, a phosphor with a pigment can be obtained.

In the method for producing a phosphor coated with the polymer of the present invention, first, the surface of a red phosphor particle such as Y ₂ O ₂ S: Eu is treated with a surface modifier. The surface modifier may be a compound having a functional group having affinity with the surface of the phosphor particles and having affinity with the coating monomer or polymer in the same molecule, and is not particularly limited. is not. Examples of the functional group having affinity with the surfaces of phosphor _{particles, -OH, -COOH, -NH 2,} -SO x (x: 1~
3) group, -PO _x (x: 1 to 3) group, alkoxysilane group, hydroxysilane group, alkoxytitanium group, hydroxytitanium group, and other functional groups that bond to the surface of the phosphor particles. Further, as the functional group having an affinity for the coating monomer or the polymer, a double bond-containing group, an amide bond or an imide bond-containing group, -OH, -COOH, -N
Examples thereof include functional groups reactive with addition and / or condensation polymerization such as H ₂ .

Examples of the surface modifier include saturated or unsaturated fatty acids such as stearic acid, lauric acid and myristic acid; saturated or unsaturated alcohols such as stearyl alcohol; polyvinylamine, polyvinyl alcohol and polyvinyl acetate moieties. Main chain of saponification product, methoxycellulose, carboxycellulose, gelatin etc. and /
Alternatively, active polymer compounds having active functional groups in side chains; surfactants; silane coupling agents, titanate coupling agents, phosphoric acid ester coupling agents, and other coupling agents can be used. These surface modifiers can be used alone or in combination. In the present invention, the surface of the phosphor particles is modified by dispersing and mixing the phosphor particles and the surface modifier in the solution. The mixing is usually performed at room temperature for 10 minutes to 4 hours, and 0.001 of the surface modifier is added to 1 part by weight of the phosphor particles.
1 to 0.1 parts by weight is preferable.

The surface-modified phosphor particles are coated with a polymerizable monomer. As the monomer used in the present invention, a compound having one or more double bonds rich in radical polymerization reactivity in the same molecule is used. Although there are many such compounds, there is a step of heating and removing the organic binder in the CDT production step, and a substance having a property of easily thermally decomposing and volatilizing in this step is particularly preferable. It is desirable to include a depolymerizable monomer that facilitates depolymerization of those polymers such as methyl methacrylate, styrene, and tetrafluoroethylene.

It is not necessary to use a single type of monomers, but the physical properties required for the polymer layer, such as the hydrophilicity of the surface,
Lipophilicity, physical and chemical properties of polymer layer, that is, impact resistance, abrasion resistance, lubricity, tackiness, adhesiveness, heat distortion temperature, conductivity, antistatic property, UV deterioration resistance, chemical resistance Two or more types can be combined depending on the sex and the like. In addition to the above depolymerizable monomer, if necessary,
Other copolymerization components such as methacrylic acid esters other than methyl methacrylate, acrylic acid esters, styrenes having substituents such as methylstyrene, vinyl alcohol esters, diene monomers, olefins, divinylbenzene, diallyl phthalate, etc. May coexist.

Further, pigments such as iron oxide, dyes, fillers, surfactants, plasticizers, polymer compounds and the like can be optionally added and used in combination depending on the physical properties. Further, the type of the monomers and the additives may be changed according to the progress of the polymerization reaction to form a structure in which layers having different physical and chemical properties are laminated, and / or a sea-island structure. The coating of these monomers is performed by mixing and dissolving the phosphor in the monomer. Usually, it is preferable to mix and dissolve it at room temperature within 1 hour, and more preferably 0.001 to 10 parts by weight of the monomer per 1 part by weight of the phosphor particles.

The phosphor particles covered with the monomers are independently dispersed in a dispersion medium such as water using a disperser.
As the disperser, a stirrer with rotating blades, a disperser utilizing ultrasonic vibration, a disperser combining an orifice and a blade are used, and a homomixer combining a high-speed rotating blade and a collision plate is used. The advantage is that the dispersed state can be easily adjusted and selected. The monomer-coated phosphor particles may be monodispersed, and when a homomixer is used, the dispersion is generally performed for about 10 seconds to 2 hours at 100 ° C. or lower. The dispersion medium is 1 to 1 part by weight of the phosphor particles.
100 parts by weight is preferred.

Since the phosphor particles dispersed in the dispersion medium are covered with the monomer layer, when the particles come into contact with each other, coalescence and agglomeration of the particles occur. In addition, adhesion to the reactor wall and stirrer is also likely to occur. In order to avoid such an unfavorable phenomenon, a surfactant is added to the dispersion liquid;
Polymeric substances such as partially saponified polyvinyl acetate, cellulose derivatives, gelatin and gum arabic; and dispersants such as inorganic particles such as calcium phosphate are preferably added. These substances are widely used in the field of polymer synthesis industry. For example, a partially saponified polyvinyl acetate is stable in properties, is commercially produced, and is easily available. These substances may be used alone or in combination as required, for example, a surfactant and inorganic particles may be used in combination, or a surfactant and polymer substances may be used in combination. The dispersant is 0.001 to 0.
1 part by weight is preferred.

The phosphor particles coated with these monomers are polymerized by a polymerization reaction in the presence of a dispersant. To convert the monomers into polymers, it is convenient to use so-called polymerization initiators. As the polymerization initiator, there are many examples of use in emulsion polymerization methods and suspension polymerization methods in the field of polymer synthesis industry, and it may be selected from them.For example, peroxides such as benzoyl peroxide, azobisiso Azo compounds such as butyronitrile and the like are preferable because there are few residues after the reaction. This polymerization initiator may be used alone or in combination as required.

During the polymerization reaction, the monomer eluted into the dispersion medium is polymerized, so that, in addition to the phosphor particles coated with the polymer, small-sized polymer particles containing no phosphor particles are formed as sub-products. To live. To suppress the generation of such particles, a monomer elution inhibitor such as sodium nitrite or methylene blue can be added to the dispersion medium. The polymerization reaction temperature and reaction time are appropriately selected according to the type of monomer, the type of initiator, the type of additive, the molecular weight of the polymer, etc., but usually room temperature to about 90 ° C., within 15 hours It is preferably selected within about 9 hours. The polymerization initiator is preferably 0.0001 to 0.1 part by weight with respect to 1 part by weight of the monomer. The phosphor slurry coated with the polymer is separated from a dispersion medium layer such as an aqueous layer by a method such as a gradient method, a filtration method or a centrifugal separation method, washed, and dried to obtain a product.

When the surface properties of the phosphor particles coated with the polymer do not meet the required performance of the CDT manufacturing process, the pigment and the surfactant are further added before the separation from the slurry or after the separation or the drying. Surface modification treatments such as spreading of polymer compounds, colloidal silica, zinc oxide particles, chemical treatment with chemicals such as acid and alkali, physical treatment with plasma, sputtering and the like can be performed.

[0020]

The present invention will be described in more detail with reference to the following examples. Example 1 A surface modifier (New Frontier A229E, Daiichi Kogyo Seiyaku Co., Ltd.) was added to 10 g of deionized water treated with an ion exchange resin.
0.060 g was dissolved, 10 g of red phosphor (Y ₂ O ₂ S: Eu, Kasei Optonix) was mixed, and the mixture was stirred at room temperature for 2 hours. The slurry was filtered, the phosphor was separated, and dried in an oven kept at 110 ° C. for 2 hours. Then, the same phosphor was washed with acetone to remove the free surface modifier and dried to obtain a surface-treated red phosphor.

2.3 g of styrene and divinylbenzene (5
5%) / ethylbenzene (45%) mixture (0.20 g) and benzoyl peroxide (0.020 g) are mixed and dissolved, surface-treated red phosphor (10 g) is added, and the mixture is stirred at room temperature for 5 minutes to prepare a monomer. The class and phosphor particles were well blended. Partially saponified polyvinyl acetate (saponification degree 88%, 4% aqueous solution viscosity 23 cps) 1.0 in 100 g of deionized water
g and 20 ppm of sodium nitrite were dissolved. The solution is mixed with the monomer / peroxide / phosphor particle mixture, and a homomixer (M type, Tokushu Kika Kogyo Co., Ltd.) is used.
The mixture was stirred at 100 rpm for 10 minutes at room temperature, and the phosphor particles covered with the monomers were independently dispersed and suspended in the aqueous phase to obtain a slurry.

The slurry was reacted at 80 ° C. for 8 hours while introducing nitrogen in a reactor having a stirrer, a reflux condenser and a nitrogen introducing tube to convert monomers into a polymer. The slurry was filtered, washed with water, and dried under reduced pressure at 85 ° C. for 2 hours to remove volatile matter, and polymer-coated phosphor particles free of phosphor particle aggregates were obtained. Lead acetate (special grade reagent) (0.5 g) was dissolved in deionized water (5 g) and absorbed into a strip of chemical filter paper to prepare a lead acetate test paper.

In a 30 ml glass sample bottle, 0.20 g of phosphor sample and 4.0 g of 0.1N hydrochloric acid (reagent) were placed, the phosphor sample was dispersed in hydrochloric acid, and lead acetate test paper was suspended in the upper space. Then, the container was sealed and left at room temperature, and the degree of coloring of the test paper with hydrogen sulfide was observed. The degree of coloration of the test paper after 60 minutes was- (no coloration was observed with the naked eye). Further, 0.250 g of the phosphor sample was dispersed in 25.0 g of 0.1N hydrochloric acid (reagent), and left still at room temperature for 60 minutes.
Next, the hydrochloric acid portion was filtered with a micropore filter having a pore size of 0.1 μm to obtain a sample for yttrium elution concentration analysis. The yttrium concentration in the sample was measured by inductively coupled plasma (ICP) emission spectroscopy. The yttrium elution concentration was 80 ppm (Y ₂ O ₃ conversion).

Example 2 In Example 1, 0.60 g of styrene and divinylben were added.
Zen (55%) / ethylbenzene (45%) mixture.
050 g was mixed and benzoyl peroxide 0.00
The same operation was performed except that 5 g of the phosphor particles were mixed and dissolved.
A polymer-coated phosphor particle that does not contain child aggregates
Obtained. After 60 minutes, the degree of coloring of the lead acetate test paper was ± (visually
It was slightly colored). By ICP emission spectroscopy
The measured yttrium elution concentration was 260 ppm (Y
₂O₃Conversion).

Example 3 In Example 1, the monomers were methyl methacrylate 3.
The same operation as in Example 1 was carried out except that 8 g and 0.20 g of diallyl phthalate were changed to 0.032 g of azobisisobutyronitrile as a polymerization initiator, and 0.025 g of iron oxide fine particles treated with A229E was further mixed. This was performed to obtain phosphor particles coated with a polymer containing a pigment. 0.3 g of the phosphor particles were dispersed in 8 g of deionized water, shaken in an ultrasonic cleaner (Shibuya Seisakusho, SUC2820A type) for 10 minutes, and allowed to stand for 20 minutes. The color tone of the precipitated phosphor was uniform and no peeling of the pigment was observed.

Comparative Example 1 The procedure of Example 1 was repeated except that the surface-treated red phosphor was used to obtain polymer-coated phosphor particles. With respect to the phosphor particles, the degree of coloring of the test paper with hydrogen sulfide using a lead acetate test paper was observed. Coloring degree after 60 minutes +++
(Colored brown), indicating that the coating of the phosphor particles with the polymer was incomplete.

Comparative Example 2 The procedure of Example 1 was repeated except that the homomixer was not used for dispersion.
The phosphor particles coated with the polymer were obtained. It was found that the phosphor particles contained a large amount of phosphor particle aggregates having a diameter of 0.1 to 0.5 mm and were not suitable for CDT use.

Example 4 In Example 1, the amount of partially saponified polyvinyl acetate was adjusted to 0.
Operations were as described in the same example except that the amount was changed to 01 g. Using a homomixer, 4100 rpm at room temperature,
It was found that the monomer / polymerization initiator / phosphor mixture at the stage of stirring for 10 minutes had a large amount of adhesion to the homomixer and the vessel wall, and was insufficiently dispersed in water. A partially saponified product of polyvinyl acetate was added so that the total amount was 0.85 g, and the mixture was dispersed again using a homomixer, and then the operation was performed as described in the same example. The obtained phosphor particles were fine powder.

Example 5 In Example 1, 0.15 g of styrene and divinylben were added.
Zen (55%) / ethylbenzene (45%) mixture.
010 g were mixed and benzoyl peroxide 0.00
The same operation was repeated except that 2 g of the phosphor particles were dissolved.
Polymer coated red phosphor particles free of child aggregates
Got a child The degree of coloring of the lead acetate test paper after 60 minutes is ++
(Colored brown). Measured by ICP emission spectroscopy
The yttrium elution concentration was 430 ppm (Y ₂O₃Exchange
It was).

Example use: Surface modifier (New Frontier A229E, Daiichi Kogyo Seiyaku Co., Ltd.)

[Chemical formula 1] CH ₂ = C (CH ₃ ) -COO (R ₁ O) x-PO (OH) (OR ₂ )

[0031]

According to the present invention, on the surface of the phosphor particles,
A uniform polymer film without defects can be formed,
The chemical resistance of the polymer-coated phosphor particles is remarkably improved, and, for example, phosphor particles suitable for CDT production can be obtained.

Claims (6)

[Claims] 1. The phosphor particles are surface-treated with a surface modifier, coated with a polymerizable monomer, and then the particles are dispersed in a dispersion medium to polymerize the polymerizable monomer. A method for producing phosphor particles, which comprises forming a polymer layer. 2. The surface modifier has an affinity functional group for the surface of the phosphor particles and an affinity functional group for the polymerizable monomer or polymer in the same molecule. The method for producing phosphor particles according to claim 1. 3. The polymerizable monomer is a compound having one or more double bonds in the same molecule.
Alternatively, the method for producing the phosphor particles according to the item 2. 4. The method for producing phosphor particles according to claim 1, wherein a disperser is used when the phosphor particles coated with the polymerizable monomer are dispersed in the dispersion medium. 5. The phosphor particles according to claim 1, wherein a dispersant is present in the dispersion medium when the phosphor particles coated with the polymerizable monomer are dispersed in the dispersion medium. Manufacturing method. 6. The method for producing phosphor particles according to claim 1, wherein a polymerization initiator is used in polymerizing the polymerizable monomer.