JPS59215383A - Cathode ray tube - Google Patents

Abstract

PURPOSE:To provide a cathode ray tube having excellent anode current (Ib)- luminance output (Bo) property and developing well-balanced color, prepd. by using a specified phosphor as blue illuminant. CONSTITUTION:A blue phosphor consisting of (A) zinc sulfide phosphor activated with silver and chlorine (ZnS:Ag, Cl) and (B) lanthanum oxychloride phosphor activated with thulium (LaOCl:Tm) is used as blue phosphor for a cathode ray tube for color image display which employs a combination of red, green and blue phosphors. Y2O3:Eu and LaOCl:Tb are used as red and green phosphors, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to cathode ray tubes, and more particularly to a blue-emitting fluorescent screen thereof.

[Background of the technical statement of the invention and its problems]

As cathode ray tubes for projecting color images, shadow mask type color picture tubes and cathode shrink tubes mainly for large screen projection are used. The fluorescent screens of such cathode ray tubes must include phosphors that emit at least red, blue, and green light. As for the color image as a whole, first of all, the color compatibility is good due to the combination of phosphors of 2 and 3 glazes.
High brightness is required. Therefore, luminous efficiency, current saturation characteristics, temperature quenching characteristics, etc. are important factors for each phosphor, but adjustments must be made based on the phosphor with the lowest overall characteristics.

Of these, regarding the anode current (Ib) and brightness output (Bo), when the anode voltage αb) is constant, Bo = k
(Ib) Expressed in %. Here, (k) is a number determined by the focusing characteristics of the electron beam incident on the phosphor surface, scanning speed, repetition rate, etc., and (γ) is a number determined by the characteristics and formation conditions specific to the phosphor phase opening. The slope angle when Ib and Bo are expressed as logarithms is generally referred to as the γ characteristic.

That is, if the inclination angle is 45°, γ is 1.

Figure 1 shows that when the red, evening and green emitting phosphors are operated in the NTSC standard scanning system at Eb = 28 KV, the I
The γ characteristics are shown in which BO is expressed as a double logarithm with b as the vertical axis.

In Fig. 1, the γ characteristic (R) is Y as a red-emitting phosphor.
2O3: Uses Eu, exhibits a gamma snout of 1, and exhibits weak extinction even when the face temperature of the cathode ray tube reaches 80°C. Moreover, the γ characteristic (G) is γ=097 to 1.
0 and the face temperature is 80° C., the quenching S is weak. In other words, it can be said that these red- and green-emitting phosphors respond correctly to increases and decreases in Ib and are less affected by temperature increases. On the other hand, Zn8:Ag and C1l, which are conventionally used as blue-emitting phosphors, are γ
As shown in characteristic (B), B for increasing Ib. It exhibits a so-called strong current saturation characteristic in which the current is saturated, and its average γ is extremely low at γ=0.46 to 0.50.

When such color-emitting phosphors are applied to a projection cathode ray tube, if the face effective surface is 1301 m horizontally and 100 m vertically, it is mounted on a tube of Eb-28 and 1, for example, the Ib peak of green (G) W. Assuming 1500μA, the peak white color temperature is approximately 9300'I (CCIE chromaticity tFjteX=0.2B□
, y'-P O, 309) To find out more about K's red (R) neck and blue (El)% husband, Ib
(R)” = 700 μA, Ib(B) = 3
330 μA was obtained. That is, (R), (G) and (B
) Comparing the Ib value of each tube between (G) tube and the ratio, Ib (R-)/Ib (G) = 0.47, Ib (
R)/Ib(B) =0.21 and Ib(B)/lb
(G) = 2.22, and it can be seen that the Ib balance is extremely poor in the 1% (B) tube and (0) tube.

This collapse of the Ib balance raises many problems. First, for the (B) tube, it is necessary to add a special γ correction circuit, and the amplitude of the peak drive signal (R
) and (G). For this reason, there is no margin between the cutoff setting value and the drive amplitude, resulting in the risk of overdrive, and the cathode load factor is also larger compared to (R) and (G). A high current load factor will also accelerate cathode emissions and phosphor surface deterioration.

Second, the current ratio between (R), (G) and CB) is (B)
Due to the unbalance concentrated in Peak luminance cannot be obtained, and the white luminance output efficiency is substantially reduced due to (B).

Therefore, it is extremely difficult to obtain a constant white color temperature over the entire drive range, and faithful color reproducibility is difficult due to errors corresponding to variations in white color temperature within the entire drive range. I can't get it. Figure 2 shows drive voltage ED as Ib (几)/
Ib(G) and Ib(几)/Ib(B), i.e. (
R), (G) and (B) Ib − shown in FIG. 1 of the tube.
It can be seen that the typical trend of the current ratio for obtaining a constant white color temperature over the entire drive range caused by the variation in γ in the BO characteristic is shown and has a large slope.

In addition, when operating for a long time with a stationary drive peak in conjunction with various video equipment, it is necessary to take into account the temperature rise of the refresher that receives peak input for a long time. For high (B) pipes, there is a risk of face cracking, and a powerful cooling system must be installed separately. The above problems are extremely serious and cannot be ignored in tubes that require high brightness.

[Purpose of the invention]

The present invention has been made in view of the above points (R).

Out of (G) and (B), a blue-emitting phosphor with the smallest γ value and a high loading rate is used to improve the γ value and Bo value, resulting in a blue-emitting phosphor with good color balance; The purpose is to introduce cathode ray tubes with

[Summary of the invention]

The present invention uses a blue-coloring phosphor made of silver and chlorine-activated zinc sulfide, which has good current saturation characteristics, and thulium-activated lanthanum oxychloride, which has excellent γ characteristics.
Overall, it is a tube with improved color balance and improved 1b-Bo%.

[Embodiments of the invention]

Examples of the present invention will be described below.

Red (R) and green (G) color source firefly 31/, body is Y, 0. : Eu and La0CJ : To are used. The B color emitting phosphor to be combined with the red and green emitting phosphors is required to have a large γ value, good current saturation characteristics, and high brightness. Among these characteristics, thulium-activated lanthanum oxychloride (La0C1,: Tm) is an example of a phosphor having a large γ value.

This La0C1l:Tm phosphor has a high γ value of about 0.9.

Its brightness is 20%~409g in the low current range and 40%~409g in the high current range compared to Zn8:Ag, C1l phosphor.
As low as 50%.

Therefore, the brightness is insufficient to use La ocl: 'J,'rn alone. On the other hand, ZnS: Ag, CI
Although the luminance is acceptable for practical use, the γ value is extremely low as shown in FIG. Figure 3 shows the γ characteristics similarly to Figure 1, and (G) in the figure shows La OC.
l: Tb.

(BI) is Y2O2: Eu, (Y is ZnS: A
g, C1 and (B,) are La0Cl: γ of Tin
The characteristics are shown respectively. Therefore, it is expected that the γ value and Bo value can be ensured comprehensively by matching the Ib Bo% properties of the blue light-emitting phosphor that is a mixture of the two. γ in Figure 3
Characteristics (B,) are based on the above points of view: ZnS: Ag
, Cl and La0C1:Tm are mixed at a quantitative ratio of 1:1. 1 of (B,): value indicates approximately 06, (
B) ZnS:Ag, C1 (7) r value also shows an h value about 1.3 times higher.

This blue-emitting phosphor (B2) is combined with the above (R) and (G).
In combination with, Eb: 28KV, 122X
When applied to a 911M2 NTSC projection cathode ray tube, the following values were obtained for the emission brightness factor. That is,
From the Ib-BO characteristics in Figure 1, Ib is 2ooμA and 120
Calculate the total emission brightness rate of unit μ per person at 0 μA, 2o(
) The ratio of the quotient n value at the 1200 μA point to the calculated value at the μA point was as shown in the table below.

That is, the (B2) phosphor is supported by the luminous efficiency of (B) in the low Ib region, and supported by (B1) in the high Ib region, so that overall, the surface properties as shown in FIG. 3 are obtained.

Also (B) phosphor (7) CIE chromaticity coordinates); i
'-0,147, Y # 0.073 j6 J,
(I3z) Fluorescent CIE Color: X”-o, 1
44.Y? 0.052 TQ However, the CIB chromaticity coordinates of the B2 phosphor also show an intermediate value between the two,
[Particularly regarding the Y coordinate, (B) the phosphor has also been improved.

40th is the drive voltage ED and Ib(R) as in FIG.
Characteristics showing the relationship between /Ib(G) and Ib(R)/Ib(B) For one animal, (几)/(G) =, (几), /(B
) = 1, the conventional example shown in FIG. The mixing ratio of both phosphors can be appropriately selected depending on the type of tube to be applied, for example, depending on whether emphasis is placed on brightness or whether the night-time gamma value is viewed as r.

Next, a specific example of the above (B2) phosphor will be described. As the ZnS:Ag,Cl phosphor, a commercially available phosphor having a particle size distribution of 2 to 20 μm and a center particle diameter of about 9.4 μm is used. In addition, the La0C/:Tm phosphor has a particle size distribution of 1
~25 μm, with a center particle size of about 10 μm.5 For example, lanthanum oxide 100 g, ammonium chloride 50 g, thulium oxide
．． Obtained by calcining 25 g of the mixture.

Next, both phosphors are thoroughly mixed, for example, in a quantitative ratio of 1:1, water glass and pure water are added, and suspension i is prepared by ball milling or thorough shaking. On the other hand, the cathode ray tube glass panel stores a cushion liquid in which pure water and barium nitrate are mixed after δL purification, and the suspension liquid is gently poured into the cathode ray tube glass panel.

Then, the phosphor is left to stand for a certain period of time to allow the phosphor to settle uniformly on the inner surface of the face portion, and then the upper part 71: The liquid is gently drained completely and dried. In addition, the ratio of water glass to barium nitrate is preferably in the range of 200,000 parts and 40 parts from the viewpoint of turbidity of the sediment and binding strength. ) to obtain a membrane.

In the above embodiments, an example was explained in which it is applied to a projection type cathode ray tube, but the present invention is not limited to this, and the present invention is applicable to other types of cathode ray tubes for projecting color images. Base! It goes without saying that this can also be applied to S'.

〔Effect of the invention〕

As described above, according to Honbakucho, the γ correction circuit of (B)'tg can be simplified, the risk of overdrive is eliminated, the concentration of drive peak phosphor surface input is alleviated, and the relative In terms of (G) and (R)%, it is possible to obtain a highly reliable shaded tube with concentrated Ib share, high brightness, white color temperature and color reproduction over the entire drive range. can.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the γ characteristics of a conventional phosphor due to Io Bo properties, and Figure 2 is a characteristic diagram showing the γ characteristics of a conventional phosphor as a function of drive voltage.
71j is a characteristic diagram showing the flow ratio] 1, 31g is a characteristic diagram showing the γl characteristic similar to Figure 1, and Figure 4 is a characteristic diagram showing the flow ratio of 1 to 1 for the drive voltage similar to Figure 2. It is 1gl of weight showing an example of II.U usage. Agent: Patent Attorney Nori Chika Namesuke (and 1 other person) No.
l Figure □lb Figure 2 →E. Figure 3 m-〉lb MS Figure 4 ED

Claims (1)

[Claims] A cathode ray tube characterized in that it has a fluorescent screen equipped with a blue-emitting phosphor composed of silver and chlorine-activated zinc sulfide and thulium-activated lanthanum oxychloride.