JPS61207483A - White luminous screen for projection cathode-ray tube and its production - Google Patents

Abstract

PURPOSE:To obtain the titled screen which is small in current saturation as well as in lowering in luminous efficiency even at a high temperature, by forming a film of a specific mixed phosphor by sedimentation on the inside of the face of a cathode-ray tube. CONSTITUTION:A LaOCl:Tb phosphor of which the Tb concentration is 0.2-1.5 pts.wt. per 100pts.wt. lanthanum oxychloride is mixed with a LaOCl:Eu phosphor of which the Eu concentration is 0.5-20pts.wt. per 100pts.wt. lanthanum oxychloride in a weight ratio of 10:1-1:1 to obtain a mixed phosphor. The mixed phosphor is suspended in a settling liquid comprising water glass and barium nitrate or barium acetate in a weight ratio of 20-40 to obtain a suspension. The suspension is poured into a cathode-ray tube and allowed to stand to form a film by sedimentation in the inside of the face of the cathode-ray tube.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention has low current saturation and little decrease in luminous efficiency even at high temperatures (60°C or higher) (JEDIC (Joi
nt ElectromDevice Hnglner
The present invention relates to a novel white light emitting screen for a projection tube that emits white light within the standards of the United States and the United States Council, and a method for manufacturing the same.

[Technical background of the invention and its problems]

White emitting phosphors used for black and white TVs are usually P-
It is composed of a mixed phosphor of ZnS:Ag and ZnCd8:Ag called 4, or a mixed phosphor of Zn8:Ag and ZnCd5:Cu, Aj, and its luminescent color has a chromaticity point A (x −0 ,286,1=0.329),
B(x-0,290, 7=0.303), C(x-
0,265°7-0.270), D (x = 0.
255. y = 0.270), Fl(X −0,
255, Y -0, 293) R is located within the enclosed area.

Now, when reproducing a white IIi surface on a projection screen with a projection type video device, in order to make the brightness as high as possible, the phosphor screen of the projection tube is over 10 times larger than that of a normal direct-view color cathode ray tube. It is necessary to add linear energy. For this reason, the temperature of the phosphor screen usually rises to 60 degrees Celsius or more in the previous work.

The above P-4 phosphor has a luminescent color that deviates significantly from the white color within the JBDEC standard under strong electron beam energy and at high temperatures (60
The luminance of the light decreases as the temperature rises above 30°F (°C), making it unsuitable for use in projection tubes.

On the other hand, it is known that terbium-activated yttrium oxysulfide phosphor, rather than mixed phosphor, emits white light by itself when the amount of terbium activation is reduced, and this has already been put to practical use in projection tubes for aircraft simulation. ing. However, in the case of this projection tube, according to the research conducted by the present inventors, when the temperature of the outer surface of the face becomes high (80°C), the emitted light color becomes yellowish, and the emitted light brightness is lower than the emitted light brightness at room temperature. It was found that the temperature dropped to about 70 inches. Therefore, it is not necessarily suitable to form a white luminescent screen for a projection tube using this terbium-activated yttrium sulfide phosphor.

In addition, Liu has developed a white-emitting phosphor made of terbium-activated lanthanum oxybromide for use in projection tubes (
J, Electrechem, 8oc, E
x, AbstrNo., 153 (1981, April
Ll)). However, when a fluorescent film is formed on the inner surface of the face of a cathode ray tube by using a commonly used sedimentation method using Nacala and conoranthane oxybromide-based phosphors, this phosphor is chemically unstable, so the phosphor film does not flow easily. It has already been disclosed in Japanese Patent Application No. 57-201159 that this causes the problem of occurrence of.

From the above, it is necessary for a white light emitting screen within the JEDEC standard for projection tubes to fully satisfy the following conditions. In other words, a white image within the JBDEC standard can be obtained even under 0 strong electron beam energy, ■ No reduction in luminous efficiency occurs even at high temperatures (60°C or higher), ■ Superior chemical stability and formation of a precipitated film. Things like things that don't flow with time.

However, to date, a white luminescent screen for projection tubes that meets the JEDEC standards has not been developed that satisfies the above-mentioned conditions.

[Purpose of the invention]

The present invention is a new JED for projection tubes that satisfies the above conditions.
The purpose of the present invention is to provide a white luminescent screen that meets EC standards and a method for manufacturing the same.

[Summary of the invention]

The white luminescent screen within the J EDEC standard for projection tubes of the present invention has a terbium concentration of lanthanum oxychloride Zoo
A terbium-activated lanthanum oxychloride phosphor with a concentration of 0.2 to 1.5 parts by weight based on the M slide and a europium concentration of 0.5 to 20 parts by weight based on 100 parts by weight of lanthanum oxychloride.
It is characterized by being made of a phosphor mixed with an appropriate amount of europium-activated lanthanum oxychloride phosphor, which is a weight part of the phosphor. The present invention is characterized in that a sedimentation film of the above-mentioned phosphor is formed using a sedimentation liquid having a weight ratio of 20 to 4.0.

First, the mixed phosphor constituting the screen of the present invention is a terbium-activated lanthanum oxychloride phosphor (LaOCI).
It is a mixture of Tb) and europium-activated lanthanum oxychloride phosphor (LaOCj:Eu), and the emission color of both of these must be in the white range within the JBDEC standard.

In the LaOCj:Tb phosphor, if the Tb concentration is less than 0.2 parts by weight per 100 parts by weight of lanthanum oxychloride, the emission color shifts to the blue side and the brightness decreases,
Moreover, when the amount exceeds 1.5 parts by weight, the emitted light color shifts to the green side. Therefore, Tba degree is lanthanum oxychloride 100
It is set within the range of 0.2 to 1.5 parts by weight.

On the other hand; IL/10C1: In Eu phosphor, Eu
When the concentration is less than 0.5 parts by weight, the luminescent color shifts to yellow, and when it exceeds 20 parts by weight, the brightness decreases.

Therefore, the Eu concentration is set within the range of 0.5 to 20 parts by weight per 100 parts by weight of lanthanum oxychloride.

Further, the mixing ratio of the La0CJ:Tb phosphor and the La0CAI:Eu phosphor is set in a range of lO:1 to 1:1 in terms of weight ratio. Outside this range, the emitted color will change to J
It deviates significantly from the white area within the EDEC standard.

Such La0Cj:Tb and La0Cj:Eu phosphors can be prepared as follows. That is, L
a0(J:Tb is a lanthanum source such as lanthanum oxide (Latos) or an oxygen source, terbium oxide (Tb+Oy
), as well as a chlorine source such as ammonium chloride (NH,CJ), while LllOCj :Eu is europium oxide (EulO
A europium source or oxygen source such as s), a lanthanum source or oxygen source such as lanthanum oxide (La!On), and a chlorine source such as ammonium chloride (NH, Cg) are weighed in predetermined amounts, respectively. For example, after thorough mixing in a ball mill, the obtained mixed powder is placed in, for example, a quartz crucible.

In LIIOCJ:Tb, an appropriate amount of carbon powder is placed and then fired in air at a temperature of 800 to 1200°C for 30 minutes to 3 hours. If carbon powder is not used, the entire
The firing may be carried out in a reducing atmosphere such as a nitrogen atmosphere containing ~50% hydrogen. On the other hand, La0C1:Eu is fired in air at 800 to 1300 degrees Celsius for 30 minutes to 3 hours.

After the obtained fired body or fired powder is cooled, it is placed in a nylon mesh bag, rinsed thoroughly with water, and then dried by passing it through while replacing the water with alcohol, for example. Then, 2 for the screen of the present invention
Becomes a seed phosphor.

The screen of the present invention comprises La0C prepared by the above method.
J:Tb and La0Cj:Eu phosphors at a weight ratio of 10
This is a precipitated film formed by precipitating phosphors mixed at a ratio of 1:1 to 1:1 on the inner surfaces of the faces and frames of a cathode ray tube by a commonly used sedimentation method.

In the present invention, this sedimentation film is made of water glass (Kto
・3S i Ox ) and barium nitrate (B a (N
ot)t) or barium acetate (B a (CHs
(COO) , will be done.

If WG/Ba is less than 20, the sedimentation liquid becomes cloudy and the desired sedimentation film cannot be formed, and if it exceeds 40, the adhesion force of the sedimentation film to the inner surface of the cathode ray tube face is extremely reduced and the sedimentation film becomes cloudy. A peeling phenomenon occurs.

The thus formed screen is then sequentially subjected to lacquer filming, aluminum film deposition, and baking according to the conventional method.Finally, an electron gun is attached to produce a white light emitting projection tube that meets the JgDBc standard. is manufactured.

[Embodiments of the Invention] Examples 1 to 6 LaOCj:'rb is L aloB , NH, CI
, T b 40g of 6 powders respectively 5ON, 17g, 0
．． 35F were weighed and mixed well in a ball mill. The obtained mixed powder was placed in a quartz crucible, an appropriate amount of carbon was placed on the back, the crucible was covered, and the crucible was fired at 1200° C. for 2 hours. The obtained baked product was placed in a nylon mesh bag, rinsed with water, and thoroughly washed with pure water. After that, the bag was rinsed with ethanol without replacing the water.

Thereafter, it was dried at about 120° C. to obtain powder of LaQC:Tb phosphor. Tb 9 degrees is 0.35% by weight.

On the other hand, LaQCJ: Eu is La, Q, , NH, C
6 powders of I and Eu1O@ are 5i and 20.59, respectively.
．． 1# Weigh and mix them well in a ball mill,
The obtained mixed powder was placed in a quartz crucible and heated at 1200℃ for 2 hours.
Baked for an hour. The obtained baked product was placed in a nylon mesh bag, rinsed with water, thoroughly washed with pure water, and then passed through while replacing the water with ethanol. Thereafter, it was dried at about 120° C. to obtain La0Cj:Eu phosphor powder. Next, water glass with a concentration of 25% (K, 0・asto
) and pure water were mixed at various mixing ratios (volume ratios) to a total volume of 200 ml, and the above-mentioned La
0CITb and LsOCl: Eu weight ratio 13=6
A phosphor suspension was prepared by adding 0.8 # of mixed phosphor powder at a ratio of . Similarly, barium nitrate (B a (NOI)! ) or barium acetate (B
a (CHsCOO) and pure water were mixed at various mixing ratios (volume ratios) to give a total volume of 400 ml.

The latter solution was poured into a Finch cathode ray tube and left to stand, after which the former suspension was poured into it and heated for 30 minutes.
It was quiet for a minute. The phosphor precipitated and a precipitated film was formed.

Thereafter, the supernatant liquid was poured out to obtain a luminescent screen on the inner surface of the face of the cathode ray tube.

At this time, the transparency of the sedimentation liquid and the state of the sedimentation film were observed with the naked eye, and the amounts of the water glass stock solution, barium nitrate or barium acetate stock solution were determined, and the weight ratio of water glass and barium nitrate or barium acetate in the sedimentation liquid was determined. (WG/Ba)
The relationship between the two is shown together in the table. In the table, good results are indicated by ◯, those which cannot be formed into a film are indicated by X, and those in an intermediate state are indicated by Δ.

In addition, in order to measure the luminance of the luminescent screen, a cathode ray tube was manufactured using the following method.

That is, an organic film is formed on the obtained luminescent screen by a lacquer filming process, and an aluminum film is further deposited on this film.

After baking, a single gun was attached and the cathode ray tube was completed. The relative values of the brightness of these cathode ray tubes are also listed in the table.

Next, the cathode ray tube equipped with the white luminescent screen of Example 4 was caused to emit light under an operating condition (80° C.) with an accelerating voltage of 28 KV, and the current-luminance saturation characteristics (gamma characteristics) were measured.

The results are shown as song 11ia) in Figure 1. @1 Figure is based on the applied current of 200 μA.

For comparison, Zn8:AI and ZnCd8:Cu, AJ
As is clear from Figure 0 shown as curve 1b) in Figure @1 for the case of a white-emitting phosphor that is a mixed phosphor with Zn8:AJ and Zn8:
Cd5: Gamma characteristics are significantly better than that of a mixed white-emitting cathode ray tube with Cu and An; at 1200 μA, 2
．． It's twice as big.

Figure Ka2 shows the relationship between the temperature of the white luminescent screen and the surface of the cathode ray tube. In the figure, curve 1 represents the case of Example 4, and curve 1 represents the case of ZnS:AII and ZnCd5:Cu, An mixed phosphor. As is clear from the figure, the white luminescent screen of the present invention is composed of Zn8:AJ and ZnCd8:Cu,AJ
Compared to a mixed white luminescent screen, the temperature characteristics are better and are 7% higher under normal operating conditions (80° C.).

White luminescent screen of Example 4 + 2 bright cathode ray tubes
The color of the emitted light when operating at 8KV, 200μAa1200#A1' was measured, and the chromaticity points are shown in Wl-W in FIG. These luminescent colors have chromaticity coordinates Wl (x-0,270,y-0,290) on the CIB chromaticity diagram.

Wl (X-0,275, y"mo, ao 5), which is within the JFSDEC standard. For comparison, Z
28KV, 200μA and 1200μA of white light emitting cathode ray tube mixed with nS:AJ and ZnCd5:Cu,Aj
t'' (0 chromaticity point) is shown as Ws, W in the lG3 diagram.

These chromaticity coordinates are W.

(Xsao, 261, y wealth 0.295), w, (xm
o, 238. y-0,251) and is within the JBI) EC standard at a low current of 200 μA, but 1200
At a high current of μA, it shows a stomach-like white color, which is far outside the JEDEC standard. Na edict, I! The shape ABCDI in Figure 3 means the JEDFfC standard, and in terms of A body, the chromaticity coordinates of the CIB chromaticity diagram are AC! -0,286,y-0,329)
, B(X-0,290°yo, aoa), C(x-0
,265,7-0,270),D(xsan0.255.y
-0,270), F: (x-0,255, y=0.29
3) shows the area surrounded by the five points.

As is clear from the figure, the chromaticity point of the white luminescent screen of the present invention falls within the white region within the JBDEC standard under high electron beam energy. On the other hand, ZnS:AIi and ZnCd
8: The chromaticity point of a white luminescent screen mixed with Cu and AI is Jll! under high electron beam energy. It deviates significantly from the area within the 1DBc standard.

When this cathode ray tube conforming to the JEDEC standard was mounted on an actual white light emitting projection tube and visual perception was evaluated, the image was bright as a white light emitting image even in the high electron beam sleep current region.

Furthermore, since there was no 'fading' of the cathode ray tube or a decrease in brightness due to temperature rise, the white luminescence image did not change over time.

〔Effect of the invention〕

When the white luminescent screen of the present invention is mounted on a projection tube, 1) the phosphor used has excellent current-brightness saturation characteristics (gamma characteristics), so it has high brightness under high electron beam energy; It is especially useful because it has the characteristics that the luminous efficiency decreases little even when the temperature rises to <80'C), and the purity of the white color is also good as seen from the chromaticity diagram. .

Moreover, in its production, the phosphor used is chemically stable, and the effect of the sedimentation liquid allows for excellent productivity, which is of great industrial value.

[Brief explanation of drawings]

@1 Figure shows the white luminescent screen for projection tubes (curve a) within the JEDEC standard of the present invention, Zn8:Ay and Zncd8.
: White luminescent screen mixed with Cu, It (curve b
), FIG. 2 is a characteristic diagram showing the current-luminance saturation characteristics of the present invention, a white luminescent screen (curve a) within the JEDEC standard,
zrts:Characteristic diagram showing the relationship between the brightness of a cathode ray tube and the temperature of the cathode ray tube surface of a white luminescent screen (curve b) that is a mixture of Ay, ZnCd8:Cu, and AI, 禦3
The figure is a CIE chromaticity diagram, w% and w7 are J EDF of the present invention.
The chromaticity points, Ws, W, in the iC standard are Zn8:Ajl and Z
It is a characteristic diagram showing the chromaticity point when mixed with nCd5:Cu and AJ. Representative Patent Attorney Noriyuki Chika (and 1 other person) Figure 1 Electron line diagram (ytisA>- Figure 2)

Claims (2)

[Claims] (1) Terbium concentration is lanthanum oxychloride 100
A terbium-activated lanthanum oxychloride phosphor having a concentration of 0.2 to 1.5 parts by weight per part by weight and a europium-activated lanthanum having a europium concentration of 0.5 to 20 parts by weight per 100 parts by weight of lanthanum oxychloride. A white luminescent screen for a projection tube, characterized in that it is formed of a mixed phosphor with a mixing weight ratio of 10:1 to 1:1 with an oxychloride phosphor. (2) Terbium concentration is lanthanum oxychloride 100
A terbium-activated lanthanum oxychloride phosphor having a concentration of 0.2 to 1.5 parts by weight per part by weight and a europium concentration of 0.5 to 20 parts by weight per 100 parts by weight of lanthanum oxychloride.
A mixed phosphor with a weight ratio of 10:1 to 1:1 with europium-activated lanthanum oxychloride phosphor is placed on the inner face of the cathode ray tube, and a weight ratio of water glass with barium nitrate or barium acetate is 20. A method for manufacturing a white luminescent screen for a projection tube, comprising forming a sedimentation film using a sedimentation liquid having a molecular weight of 40 to 40.