JPH05271650A - Pigmented stimulable phosphor - Google Patents

Abstract

PURPOSE:To obtain a pigmented stimulable phosphor protected against the release of the pigment and improved in the hydrophilicity of the phosphor. CONSTITUTION:As a binder for binding a pigment to the surface of stimulable phosphor particle, a polyvinyl acetal prepared by modifying a polyvinyl alcohol(PVA) with an aldehyde is used. The PVA insolubilized by the modification can bind a pigment firmly and can improve the hydrophilicity in a slurry. The firmly bonded pigment does not release from the phosphor in the application step, and its desirable hydrophilicity can improve its dispersibility in a phosphor slurry.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pigmented phosphor mainly used in a color cathode ray tube.

[0002]

2. Description of the Related Art Generally, a fluorescent substance for a color cathode ray tube uses a fluorescent substance with a pigment to which a pigment is attached via a binder as a filter substance for improving contrast. Although the pigmented phosphor has an effect of remarkably improving the contrast, it has a number of problems as compared with the phosphor to which the pigment is not attached. For example, in a fluorescent film manufacturing process of a color cathode ray tube, when a coating slurry containing this phosphor with a pigment is prepared and the slurry is coated, the adhesion of the pigment is insufficient, so that the pigment peels from the phosphor particles. However, the color purity and brightness of the screen are reduced. In addition, since the hydrophilicity and dispersibility of the phosphor in this slurry are not sufficient, a good phosphor film cannot be obtained. The slurry mainly contains polyvinyl alcohol (hereinafter referred to as PVA) or polyvinyl stilbazolium (PVSQ) as a binder for the fluorescent surface, ammonium dichromate or sodium dichromate as a photosensitizer, and a surfactant as a dispersant. A mixed aqueous solution is used.

These problems are due in part to the binder that attaches the pigment to the phosphor. Various binders have been proposed in the past. For example, there are those using an acrylic resin (JP-A-52-109488), a combination of gelatin and gum arabic (JP-A-53-50880), and the like. However, those using an acrylic resin have poor phosphor hydrophilicity and dispersibility. Further, those using gelatin etc. have the drawback that the adhesion of the pigment to the phosphor is poor.

[0004]

As described above, it has been extremely difficult to achieve both the hydrophilicity of the phosphor and the adhesive strength of the pigment with the conventional binder. In order to solve this problem, Japanese Patent Publication No. 56-33437 discloses a pigmented phosphor using carboxyl-modified polyvinyl acetate as a binder. However, this phosphor is still insufficient.

Therefore, the present invention has been made in view of the above circumstances, and provides a pigmented phosphor having good adhesion of the pigment to the phosphor and hydrophilicity and dispersibility in the coating slurry. ..

[0006]

The inventors of the present invention focused on PVA contained in a coating slurry, and conducted various experiments on a substance having an affinity with this PVA and having a sufficient adhesive force as a binder. As a result, the present invention has been completed. That is, the phosphor of the present invention is a pigmented phosphor in which a pigment is attached to the surface of phosphor particles with a binder, wherein the binder contains polyvinyl acetal obtained by modifying PVA with an aldehyde. ..

The polyvinyl acetal, which is the binder of the pigmented phosphor of the present invention, is a product obtained by reacting PVA with an aldehyde to acetalize a part or most of the hydroxyl groups, for example, a condensate of PVA and formalin. Examples thereof include polyvinyl formal and polyvinyl butyral which is a condensation product of PVA and butyraldehyde.

The phosphor of the present invention can be obtained by gradually adding an aldehyde to a suspension obtained by suspending the phosphor and a pigment, while adding PVA and sufficiently stirring. By adding an aldehyde, PVA is modified and a part of it is acetalized, so that it becomes insoluble in water and the pigment can be attached. Before or after adding the aldehyde, a small amount of acetic acid, hydrochloric acid, sulfuric acid or the like may be added as an acid catalyst to promote the reaction.

The amount of PVA added is 0.00 based on the phosphor.
It is adjusted to a range of 1% to 5.0%, preferably 0.005 to 0.5%. If the range is less than 0.001%, the adhesive strength is insufficient, and if it is more than 5.0% by weight, the phosphor tends to aggregate. The amount of aldehyde added is 1% or more with respect to polyvinyl alcohol. If it is 1% or less, the modification is insufficient and a sufficient adhesive force cannot be obtained.

The phosphor used in the present invention may be any phosphor as long as it is used as a phosphor for a cathode ray tube. For example, the general formula Zn _X Cd _1-X S: M, A (provided that X
Is 0 ≦ X ≦ 1, M is at least one of Cu, Ag, and Au, A is a halogen element, and at least one of Al), and a zinc cadmium sulfide-based phosphor, Y ₂ O ₂ S: Eu,
A rare earth type phosphor such as Y ₂ O ₃ : Eu can be used.

As preferable pigments, conventionally known pigments such as chrome green and cobalt green as green pigments, cobalt blue as blue pigment, ultramarine blue and red pigment as red pigment can be used.

[0012]

The pigment-attached phosphor of the present invention is very compatible with PVA contained in the coating slurry because the pigment is attached by the polyvinyl acetal obtained by modifying polyvinyl alcohol with an aldehyde. Easy to quickly disperse in slurry. Further, polyvinyl acetal is colorless and transparent, has toughness and flexibility, and can strongly adhere the pigment to the phosphor.

To obtain the pigmented phosphor of the present invention,
FIG. 1 is a diagram showing the relationship between the amount of aldehyde added and the peeling rate of the pigment. This is Y ₂ O ₂ S: Eu phosphor 1 kg
, Bengal 1g, PVA 0.1g {Kuraray Poval P
VA-124 (saponification degree: 98.5 mol%, PVA content: 94%): Kuraray trade name} in a suspension prepared by mixing 1 liter of water with the addition of formalin as an aldehyde to change the pigment. About the attached pigmented phosphor,
FIG. 6 is a diagram showing the peeling rate of the pigment peeled from the phosphor on the vertical axis and the addition amount of formalin on the horizontal axis, and showing the peeling rate of the adhesion of the pigment to the phosphor. The formalin used had a concentration of 35%.

The peeling rate of the pigment is 2.1: 0.0 for water, PVA, ammonium dichromate and the pigmented phosphor.
Coating slurry 1 mixed in a weight ratio of 6: 0.004: 1
Put 00 ml in a beaker, put the hose on the suction side and the discharge side of the pump in this beaker, operate the pump at a flow rate of 1 liter / min for a fixed time (10 minutes), pump and circulate the phosphor, The slurry was put into a settling tube, the pigment peeled from the surface of the phosphor was separated from the phosphor, and the amount of the peeled pigment was analyzed and expressed as a ratio with the amount of the pigment initially attached.

As can be seen from this figure, the peeling rate tends to decrease as the amount of added formalin increases. Actually, the degree of formalization of PVA differs depending on the amount of formalin and the conditions such as acid catalyst.
Since there is no means to analyze the degree of formalization of a very small amount of polyvinyl formal attached to the phosphor and involved as a binder, the adhesive strength was evaluated by the addition amount of formalin.

The reaction of adding formalin to PVA to form formal is known as a technique for producing vinylon.
The reaction for actually obtaining vinylon is carried out in a formalin bath containing Glauber's salt under strong acidity, and 30% of the hydroxyl group of PVA is used.
It is carried out by formalizing about 40 to 40 mol%, but in the case of the present invention, since it is used only for the purpose of attaching a pigment, it is not necessary to formalize the hydroxyl group of PVA like vinylon, and the reaction conditions are very high. P because it is gentle
It is presumed that only a small part of the hydroxyl group of VA is formalized.

Further, in the pigmented phosphor of the present invention, the adhesion strength of the pigment changes when the amount of PVA added is changed. By increasing the amount of PVA used as a binder, the pigment adheres more strongly to the phosphor. In the peel test described above, PV
When the amount of A added is about 3% by weight with respect to the phosphor, peeling of the pigment is almost eliminated.

Furthermore, in the phosphor of the present invention, PVA
Other conventional binders may be used in combination with the polyvinyl acetal modified by.

[0019]

EXAMPLES The present invention will be described in detail below with reference to examples.

[Example 1] Y ₂ O ₂ as a red light emitting phosphor
5 kg of S: Eu phosphor and red pigment (Fe ₂
And O ₃₎ 5 g, to a suspension of ion-exchanged water 5 l, 10% PVA aqueous solution (PVA-124) 5
Add 0 ml and stir well. While continuing to stir, 3
After adding 3 ml of 5% formalin and confirming that the pigment adhered to the phosphor, stirring was stopped and the phosphor was allowed to settle. After settling, the supernatant was discarded and the mixture was washed several times, dried overnight at 150 ° C., and passed through a sieve to obtain the pigment-containing phosphor of the present invention in which 0.1% of red halo was attached to the red-emitting phosphor. Obtained. When the pigment peeling ratio of this phosphor was measured as described above, it was 3.5%.

[Example 2] To the same phosphor suspension as in Example 1, 50 ml of a 10% PVA aqueous solution was added, and further 35
A pigmented phosphor of the present invention was obtained in the same manner as in Example 1, except that 10 ml of 10% formalin was added. The pigment peeling ratio of this phosphor was 2.2%.

[Example 3] To the same phosphor suspension as in Example 1, 100 ml of 10% PVA aqueous solution was added, and further 3
A pigmented phosphor of the present invention was obtained in the same manner as in Example 1 except that 20 ml of 5% formalin was added. The pigment peeling rate of this phosphor was further improved to 1.5%.

Example 4 A pigmented phosphor of the present invention was obtained in the same manner as in Example 1 except that 5 ml of 20% butyraldehyde was added instead of formalin.
The pigment peeling ratio of this phosphor was 3.4%.

[Example 5] Zn as a blue light emitting phosphor
A phosphor suspension was prepared in the same manner as in Example 1 with 5 kg of S: Ag, Cl phosphor, 100 g of cobalt blue as a blue pigment, and 5 liters of water, and a 10% PVA aqueous solution {Kuraray Poval PVA- 224 (saponification degree 88.0
mol%, PVA content 94%: Kuraray brand name} 100
In the same manner as in Example 1 except that 20 ml of 35% formalin was added, a pigment-containing phosphor of the present invention in which 2% of cobalt blue was attached to the blue-emitting phosphor was obtained. The pigment peeling ratio of this phosphor was 1.7%.

[Embodiment 6] To the same phosphor suspension as in Embodiment 5, 350 m of 40% PVA aqueous solution (PVA-224) is added.
1 was added, and 120 ml of 35% formalin was added, and a pigmented phosphor of the present invention was obtained in the same manner as in Example 1. The pigment peeling ratio of this phosphor was 0.2%, which was almost not peeled off.

[Example 7] Zn as a green-emitting phosphor
S: Cu, Al phosphor 5 kg and titanium green 50 g as a green pigment are suspended in a suspension of 5 liters of water, and 50 ml of a 10% PVA aqueous solution (PVA-224) is added.
Then, 3 g of euroid (manufactured by Mitsui Toatsu) as a urea resin binder and 4 g of gelatin are added and sufficiently stirred. While continuing stirring, 3 ml of 35% formalin
Was added, and thereafter, in the same manner as in Example 1, a pigmented phosphor of the present invention was obtained in which 5% of titanium green was attached to the green light emitting phosphor. The pigment peeling ratio of this phosphor was 3.2%.

Comparative Example In the same manner as in Example 7 except that the aqueous PVA solution and formalin were not added, a pigmented phosphor having 5% of titanium green deposited with euroid and gelatin was obtained. Peeling rate of this pigmented phosphor is 12%
Met.

As described above, the pigmented phosphors of the present invention obtained in Examples 1 to 7 were very compatible with the coating slurry used in the peeling test and immediately dispersed, while the phosphors of Comparative Examples were The phosphor surface is water repellent, and the amount of surfactant added is 2
Doubling and no dispersion without stirring for a few minutes.

[0029]

The pigment-containing phosphor of the present invention is made of water-soluble PV.
The pigment is attached to the surface of the phosphor by a binder which is insoluble by modifying A with an aldehyde. In addition to having excellent adhesive strength, this binder has a very preferable hydrophilic property in the coating slurry. Therefore, it is possible to effectively prevent the pigment from peeling off from the phosphor when applied to the cathode ray tube. Therefore, it is possible to prevent the deterioration of the color purity of the phosphor screen caused by the peeled pigment and to obtain a high quality phosphor film. Further, since the phosphor has a preferable hydrophilicity, it is easy to adapt to the slurry when it is made into a coating slurry, and it can be immediately dispersed to form a uniform phosphor film.

As the binder, in addition to polyvinyl acetal modified with PVA, PVSQ (polyvinyl stilbazolium) modified with aldehyde at the same time as PVA can be used in combination or alone. Is.

[Brief description of drawings]

FIG. 1 is a graph showing a peeling rate of a pigment with respect to an added amount of formalin.

Claims (1)

[Claims] 1. A pigmented phosphor in which a pigment is attached to the surface of phosphor particles with a binder, wherein the binder contains polyvinyl acetal obtained by modifying polyvinyl alcohol with an aldehyde.