JPS6230236B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phosphor slurry suitable for forming a phosphor surface of a color display cathode ray tube for information processing system terminals and the like.

Cathode ray tubes for color display in information processing system terminals have a phosphor that forms the phosphor surface so that displayed characters, figures, etc. do not flicker even when the phosphor surface scanning speed is slowed down. Moderate afterglow (i.e. longer afterglow than in television broadcast picture tubes)
Fluorescent materials with phosphors have come to be used.
As a phosphor with such a moderate afterglow property, a manganese-activated zinc orthophosphate phosphor Zn ₃ is used for red.
(PO ₄ ) ₂ :Mn, etc., and Zn ₂ SiO ₄ :Mn, As, etc. are now used for green. Note that blue does not have a phosphor with an appropriately long afterglow property, so ZnS:Ag, which has been conventionally used in color television picture tubes, or the red Zn ₃ (PO ₄ ) ₂ :Mn, which has a long afterglow property, Green Zn ₂ SiO ₄ :Mn,
A light blue to white phosphor made of a mixture of As and ZnS:Ag is used.

The method for forming the fluorescent surface of a cathode ray tube for three-color color display is the same as that of a well-known color television picture tube. A photosensitive phosphor slurry is applied to the inner surface of the face plate, and after drying, a shadow mask with a desired pattern is formed. UV light is irradiated through the photoreceptor, followed by development to remove unexposed areas and form phosphor dots. This process is performed sequentially for green, blue, and red (or green, white, and red) to obtain a fluorescent film for a color display cathode ray tube.

The photosensitive phosphor slurry is usually a suspension containing phosphor powder, polyvinyl alcohol, dichromate, and water. In many cases, antifoaming agents are added to prevent the formation of fluorophores, emulsifiers to prevent the coating film from peeling off caused by oily substances, and dispersants to improve the dispersibility of the phosphor in the liquid. Good coatings are usually obtained with such phosphor slurries. For example, the green phosphor Zn ₂ SiO ₄ :Mn, As, the blue phosphor ZnS: Ag, or the green phosphor ZnS: Cu, Al, ZnS: Cu, Au for color television picture tubes.
Al, ZnCdS: Cu, Al, red phosphor Y ₂ O ₂ S: Eu,
A good coating film can be obtained from any slurry such as Y ₂ O ₃ :Eu.

However, the red phosphor with long afterglow time, i.e.
When Zn ₃ (PO ₄ ) ₂ :Mn is mixed into a slurry, the viscosity of the slurry increases in 1 to 2 hours, and furthermore, the phosphor coagulates and solidifies in several hours, making it difficult to obtain a good coating film. It was extremely difficult.

The object of the present invention is to eliminate the drawback that slurry containing a phosphate phosphor such as the Zn ₃ (PO ₄ ) ₂ :Mn phosphor is agglomerated and solidified in a short period of time, and to produce a slurry containing this phosphor that is good. An object of the present invention is to provide a phosphor slurry that can form a fluorescent film.

As a result of research to achieve the above objective, it was confirmed that the increase in the viscosity of the slurry and the coagulation and solidification of the phosphor when the phosphor was mixed into the slurry were mainly due to the gelation reaction of polyvinyl alcohol in the slurry. It was done. Note that dichromate also caused aggregation of the phosphor. The present inventor investigated various agents, especially surfactants, to suppress the above-mentioned gelation, and found that sodium naphthalene sulfonate, which is a formalin condensate of naphthalene sulfonate, sodium lignin sulfonate, which is lignin sulfonate, It has been found that riboflavin sodium phosphate, which is a phosphate ester salt, is extremely effective in inhibiting the above-mentioned gelation. As one method of determining the state of gelation in the slurry, changes in slurry viscosity over time were measured. An example of the results is shown in FIG. First, Zn ₃ (PO ₄ ) ₂ :Mn phosphor
A slurry containing 25% by weight of polyvinyl alcohol, 2.5% by weight of polyvinyl alcohol, 0.15% by weight of ammonium dichromate, and 72.35% by weight of pure water was prepared. In Figure 1, 1 is a sample in which no drug (gelling inhibitor) was added to this slurry;
2 is a sample with 0.1% by weight of ammonia water added, 3
indicates a sample to which 0.1% by weight of formalin condensate of sodium naphthalene sulfonate was added. In case of No. 3, the viscosity immediately after slurry preparation was low and remained stable for more than 10 days. Prepare these sample slurries in step 1.
After a few days, I applied it to the inner surface of the face plate.
Sample 1 could only form a rough film, and Sample 2 had a slightly rough film, whereas Sample 3
A good coating film was obtained, and a good coating film was still obtained even after 10 days or more had passed since the preparation of the sample.

Examples will be further described below.

Example 1 Corresponds to sample 3 in Fig. 1, Zn ₃ (PO ₄ ) ₂ :Mn
25% by weight of red phosphor, 2.5% by weight of polyvinyl alcohol, 0.15% by weight of ammonium dichromate, formalin condensate of sodium naphthalene sulfonate.
A slurry consisting of 0.1% by weight and 72.25% by weight of water was prepared. The viscosity of this slurry remained almost constant for more than 10 days, and a good coating film was obtained.

Example 2 Zn ₃ (PO ₄ ) ₂ :Mn red phosphor and Zn ₂ SiO ₄ :Mn, As
25% by weight of pale blue phosphor mixed with green phosphor and ZnS:Ag blue phosphor, polyvinyl alcohol
A slurry consisting of 2.5% by weight of ammonium dichromate, 0.15% by weight of ammonium dichromate, and 0.1% by weight of sodium ligninsulfonate was prepared, and a good coating film could be obtained.

Example 3 Zn ₃ (PO ₄ ) ₂ :Mn red phosphor and Zn ₂ SiO ₄ :Mn, As
White phosphor mixed with green phosphor and ZnS:Ag blue phosphor 25% by weight, polyvinyl alcohol 2.5%
Weight%, ammonium dichromate 0.15% by weight, riboflavin sodium phosphate 0.1% by weight
A good coating film was obtained by preparing a slurry consisting of:

Note that the above example is an example in which a gelation inhibitor was added to the slurry, but it is also possible to add a gelation inhibitor to the phosphor powder in advance, or add about 0.1% of the gelation inhibitor to the phosphor powder at the time of manufacturing the phosphor. A similar effect was obtained even when the phosphor was treated with an aqueous solution containing a gelation inhibitor and the gelation inhibitor was attached to the surface of the phosphor.

Furthermore, according to numerous experimental results, if the amount of gelation inhibitor added to the phosphor is less than 0.05%, no effect will be observed, and if it is more than 0.5%, it will tend to be somewhat difficult to photocure during exposure; was within the permissible limit.

As explained above, according to the present invention, the viscosity of the phosphor slurry is stabilized for a long period of time, a phosphor film of good quality can be stably obtained, and the production yield of cathode ray tubes is greatly improved.

[Brief explanation of the drawing]

FIG. 1 shows the change in viscosity of three types of samples over time.

Claims (1)

[Claims] 1 A formalin condensate of naphthalene sulfonate, a lignin sulfonate, and a phosphate ester are added to a phosphor slurry consisting of a manganese-activated zinc phosphate phosphor, polyvinyl alcohol, dichromate, water, etc. A phosphor slurry characterized by adding at least one type of surfactant among salts. 2. The phosphor slurry according to claim 1, wherein the manganese-activated zinc phosphate phosphor is a manganese-activated zinc orthophosphate phosphor.