JPS6041818B2 - Method for forming fluorescent coating on tubes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a phosphor coating on the bulb face of a bulb.

Conventionally, when forming a phosphor coating on the inner surface of a bulb such as a fluorescent lamp or a mercury lamp, a water-soluble lacquer is prepared by dissolving a water-soluble organic polymer substance and a surfactant in water, and a fluorescent coating is applied to this lacquer. A phosphor suspension obtained by suspending a small amount of phosphor binder to enhance the bonding force between the phosphor particles and the glass surface is applied to the inner surface of the bulb.
A method in which a phosphor coating is formed by drying under certain conditions, and then the above-mentioned bulb is heated to burn off the organic polymer substance and surfactant remaining in the coating to form a phosphor coating. was being carried out.

However, fine particle aluminum oxide, called colloidal alumina, is generally used as a phosphor binder. However, while this colloidal alumina has a great effect on increasing the bonding force between the phosphor particles and the glass surface, it becomes extremely active against gas adsorption after being heated in the above-mentioned bulb heating process. There is a characteristic that Therefore, in the case of a phosphor film formed by a conventional method, the phosphor binder present in the phosphor film adsorbs a large amount of moisture, carbon dioxide gas, etc. in the air to its surface. This has the disadvantage that the gas is not sufficiently removed and exhausted during the next evacuation process to vacuum the inside of the bulb, and remains as an impure gas inside the bulb, impairing the lamp characteristics of the completed lamp, such as the luminous flux maintenance rate. . The present invention has been made in order to eliminate the above-mentioned drawbacks.The present invention has been made to prevent the phosphor binder from becoming active for gas adsorption even after the heating process of the bulb, so that the phosphor binder does not impair the characteristics of the completed lamp. The object of the present invention is to provide a method for forming a film.

Specifically, a phosphor powder and fine particles of aluminum oxide as a phosphor binder are suspended in a water-soluble lacquer in which a water-soluble organic polymer substance and a surfactant are dissolved in water, and boric acid and hydrogen peroxide are further added. A coating process in which the phosphor suspension obtained by adding the phosphor is applied to the inner surface of the tube bulb and dried to form a phosphor coating; By providing a firing process that burns out the organic polymer substances and surfactants contained in the aluminum oxide particles, and also welds boric acid to the surface of the fine aluminum oxide particles to inactivate the surface, the adhesive strength to the glass surface is strong and the finish is completed. The aim is to form a stable phosphor coating that does not impede the characteristics of the lamp.

Generally, when aluminum oxide is heat-treated, the particle surface becomes active for gas adsorption, and this is particularly noticeable in the case of colloidal fine particles.

In order to weaken this property and make the particle surface inactive, a method can be considered in which a stable substance is adsorbed on the aluminum oxide surface in advance. As a result of various studies based on this idea, it was found that boric acid is the most suitable substance that does not inhibit its effectiveness as a phosphor binder and also makes the surface of fine particle aluminum oxide inert to gas adsorption. did. However, when boric acid is added to a phosphor suspension mainly composed of water-soluble lacquer, when the organic matter that is the lacquer component is heated and burned off in the baking process after coating film formation, the boric acid is added before the organic matter is completely burned. Since the carbon melts and prevents the supply of oxygen necessary for complete combustion, carbon remains in the final phosphor coating and reduces the luminous efficiency of the phosphor. In order to eliminate this drawback, we conducted further studies and found that if peroxyhydrogen was added in advance to the phosphor suspension in which boric acid was suspended, the boric acid would become fine particles that had been heat-treated in the bulb heating process. While retaining the effect of inactivating aluminum oxide, the combustion of the organic matter that is the lacquer component is significantly accelerated, and even with the addition of boric acid, the burned fluorescent light and residual carbon are generated in the body coating. It was possible to prevent it. Examples of the present invention will be described below.

Example water 15000j
Hydroxyethyl cellulose (Cellocise QP-40 manufactured by UCC, USA) 3f surfactant (NP-10 manufactured by Nikko Chemicals) 0.3q fine particle aluminum oxide (AIOn1C manufactured by DegLlSSa, West Germany) 0.5y3 boric acid
0.3f hydrogen peroxide solution (30% aqueous solution)
0.9f calcium halophosphate phosphor
A 100V phosphor suspension having the above composition is prepared, applied to the inner surface of a glass tube for a 40W fluorescent lamp, dried, heated to 600°C in a firing furnace, and then fired for use in a general fluorescent lamp. The lamp was manufactured in the same manner.

The thus completed lamp was manufactured in a similar manner using a conventional method, that is, a phosphor suspension having a composition obtained by removing boric acid and hydrogen peroxide from the phosphor suspension used in the above example. The following table shows the results of comparing the brightness and luminous flux maintenance rate of the lamps. From the table above, it can be seen that the lamp according to the present invention has a 3% improvement in luminous flux maintenance after 100 hours of lighting compared to the conventional lamp.

Note that there was no difference in the bonding strength of the phosphor particles to the glass surface between the two in the table. As explained above, this invention uses fine particle aluminum oxide as a phosphor binder, and further adds boric acid and hydrogen peroxide to a phosphor suspension to which fine particle aluminum oxide is added. This method involves applying a phosphor suspension to the bulb, drying it, then baking the phosphor coating applied to the bulb, and welding boric acid to the surface of the fine aluminum oxide particles. The phosphor coating obtained by this method can suppress gas adsorption even after firing.

Claims (1)

[Claims] 1. A phosphor suspension obtained by suspending phosphor powder and fine particle aluminum oxide in a water-soluble lacquer prepared by dissolving a water-soluble organic polymer substance and a surfactant in water, and further adding boric acid and hydrogen peroxide. 1. A method for forming a phosphor coating on a tube, comprising the steps of applying a liquid to the inner surface of the tube bulb, and heating the applied bulb.