JPS5941470B2 - Method for producing fine particle dispersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a uniform and stable fine particle dispersion, and more specifically, for use in forming a phosphor layer on the inner surface of a lamp tube in a method for producing a fluorescent lamp. The present invention relates to a method for producing a stable dispersion of fine powder such as aluminum oxide as a binder to be added to a suspension of a phosphor in a water-soluble lacquer.

Generally, in order to form a phosphor layer on the inner surface of a lamp tube in the manufacturing process of fluorescent lamps or mercury lamps, a water-soluble lacquer is prepared by dissolving a nonionic water-soluble organic polymer substance as an adhesive in water. A method is used in which a phosphor suspension is prepared by suspending a phosphor in a phosphor, and further adding a particulate metal oxide or the like as a phosphor binder, and then applying the phosphor suspension to the inner surface of a glass tube and drying it.

The phosphor binder used here is used to prevent the phosphor from falling off the glass surface after the adhesive remaining in the formed phosphor layer is burned out in the baking process. It is added to strengthen the adhesion between particles and between the phosphor particles and the surface of the glass tube, and is generally made of fine particles of aluminum oxide, calcium phosphate, or calcium borate with an average particle size of 100 mμ or less. has been done.
In other words, fine powder such as aluminum oxide, which is fine particles,
When the voids between the phosphor particles in the phosphor layer formed on the inner surface of the glass tube are filled, Vanderwaal's force strengthens the binding force between the phosphor particles and between the phosphor particles and the surface of the glass tube. This takes advantage of the property of being Therefore, strengthening the binding force by adding fine particles is most effective when the fine particles added are completely dispersed, but if the dispersion deteriorates due to agglomeration of particles, the effect will be significantly reduced. . However, when a phosphor suspension is created by directly adding fine particle powder as a binder to a suspension of a phosphor in a water-soluble lacquer, agglomeration between the fine particles as a binder occurs. occurs, and it is nearly impossible to completely disperse it.

For this reason, in the past, a fine particle powder as a binder was dispersed in water and a dispersion liquid was made by using a pole mill etc. to improve the dispersion state, and this was then made into a suspension of a phosphor suspended in a water-soluble lacquer. The method of adding However, even with this method, it is difficult to completely disperse fine particle powder as a binder with an average particle size of 100 mμ or less.
Further, there was a drawback that fine particles uniformly dispersed by an operation such as a ball mill re-agglomerated before being added to a suspension of a phosphor in a water-soluble lacquer.

This invention aims to improve the above-mentioned drawbacks and provide a method for producing a stable fine particle dispersion with a good dispersion state.
The manufacturing method of this invention will be explained below.The average particle size is 10.
A binder, which is a fine particle powder such as aluminum oxide, calcium phosphate, or calcium borate, which is substantially insoluble in water and has a size of 0 mμ or less, is dispersed in water, and this is mixed with an organic or mineral acid such as acetic acid or hydrochloric acid, or an anion. A colloidal dispersion is prepared by adding an appropriate amount of at least one type or two or more types of surfactants such as type or cationic type as a dispersant and stirring. After adding and dissolving an ionic water-soluble polymer substance and thickening it, a purified ion exchange resin is mixed with this thickened dispersion liquid to dissolve the acid groups present in the dispersion liquid or the surfactant. By removing impurities such as metal salts, a stable and well-dispersed fine particle dispersion was obtained.

That is, depending on the surface condition of the fine particles to be dispersed, an appropriate amount of organic acid, mineral acid, or surfactant is added.
If a species or two or more species are selected and an appropriate amount is added as a dispersant, the fine particles will be completely and uniformly dispersed in the water, and the purpose of dispersing the fine particles can be achieved at this stage, but there are no particles in the dispersion liquid. Because the acid added as a dispersant or sodium contained in a surfactant exists in ionic form, it is difficult to form a suspension of a phosphor in a water-soluble lacquer in this state. If added, ionic acids and the like will act as impurities and have an adverse effect on the phosphor, making it practically unusable.

Therefore, in order to use this dispersion as a suspension in which a phosphor is suspended in a water-soluble solution, it is necessary to remove the above-mentioned ionic acids, which are originally dispersants. Therefore, when this is removed, agglomeration of fine particles immediately occurs, and the fine particle dispersion liquid loses its original characteristic of good dispersion. Therefore, in the embodiment of the present invention, after creating the above-mentioned dispersion liquid, a nonionic water-soluble polymer substance used in the production of a phosphor suspension is added to the dispersion liquid and dispersed. After increasing the viscosity of the liquid,
This method uses an ion exchange resin to remove acids and the like present in the dispersion. Even if ionic acids, etc. acting as dispersants are removed in this way, water-soluble polymer substances are added and increase the viscosity of the dispersion.
Re-agglomeration of fine particles is difficult to occur, and since the water-soluble polymer substance itself also acts as a protective colloid, it can maintain a good dispersion state even when stored for a long period of time. Next, an example of the manufacturing method of the present invention will be described. Fine particle aluminum oxide (Aluminum oxide C type manufactured by Degusa Co., Ltd.) 509 is gradually added to pure water 11 as a binder with an average particle size of about 50 mμ. Add acetic acid to pH5. while stirring with a stirrer. Add until O~4.0 and continue stirring for an additional hour.

Next is hydroxyethyl cellulose, a nonionic water-soluble polymer substance (Union Carbide Chemicals (Union Carbide Chemicals)
Add Zero Size QP-40) 109 manufactured by iOnCarbideCh-Emicals and stir until completely dissolved. Next, 50 cc of each of a cation exchange resin and an anion exchange resin that had been purified in advance were added and stirred for 30 minutes, and then the ion exchange resin was separated through a 50 mesh filter cloth. In the thus produced dispersion, the aluminum oxide particles were extremely well dispersed, with almost no agglomeration, and even after being left for one month after production, no reaggregation occurred. Then, this dispersion was added to a suspension of a water-soluble phosphor in which the phosphor was suspended so that the amount of aluminum oxide was 0.5% based on the phosphor. When a fluorescent lamp was manufactured by preparing a suspension of fluorescent material and applying this suspension to the lamp tube of a fluorescent lamp to form a fluorescent layer, the adhesion strength of the fluorescent layer was found to be extremely good. Ta.

Although acetic acid was used as a dispersant in the above embodiments, various other agents such as hydrochloric acid or anionic or cationic surfactants can be used depending on the type of particles and the surface condition.

Further, after the dispersant is added, stirring is performed using a stirrer in the above examples, but it goes without saying that the same effect can be obtained by stirring using a ball mill, colloid mill, etc. instead. As described above, the present invention is an effective method for uniformly and stably dispersing fine particle powder in water, and the final dispersion liquid is free of impurities other than the dispersed powder and organic polymer material. It is extremely effective for use in a suspension for forming a phosphor layer because it does not contain any of these substances.

As described above, this invention involves dispersing fine solid particles with an average particle size of 100 mμ or less in water, adding one or more of organic acids, mineral acids, or surfactants, and stirring to uniformly disperse the particles. In addition, after completely dispersing the solid particles and then adding a nonionic water-soluble organic polymer material to dissolve and thicken the dispersion, acid groups and other ionic impurities in the dispersion are removed using the ion exchange resin. Since the dispersion liquid produced in this way does not contain any impurities other than the dispersed solid fine particles and the organic polymer material, the solid fine particles are always uniformly and completely dispersed. This has the effect of making it possible to produce a dispersion.

In addition, it is extremely effective to use the thus produced dispersion in which the solid particles are uniformly and completely dispersed as a suspension for forming a phosphor layer.

Claims (1)

[Claims] 1 Disperse solid fine particles that are substantially insoluble in water with an average particle size of 100 mμ or less in water, add one or more of organic acids, mineral acids, and surfactants, and stir to form a colloidal dispersion. A step of adding a nonionic water-soluble polymer material to the colloidal dispersion to dissolve and thicken the dispersion, and mixing a purified ion exchange resin to the thickened dispersion to disperse the dispersion. A method for producing a solid fine particle dispersion liquid comprising the step of removing acid radicals or other ionic impurities present in the liquid.