DE2014511A1 - Vieia luminescent fluorescent screen for a cathode ray tube - Google Patents

Description

RCA 61516

US-PA.811,532 _.'.- ■■

Piled March 28,1969

EGA Corporation, üfew York, U ^- * Υ «," V.St.A *

White lum ines ornamental he Leuch tstoffach i rm for a Katho dens tralilr eyelets "

The present invention relates to a phosphor screen for a cathode ray tube with a white ruminescent fluorescent mixture, which essentially consists of a "blue luminescent, silver-activated zinc sulfide phosphor and a yellow luminescent zinc cadmium sulfide phosphor " ο

Picture tubes for black and white television receivers usually contain a white luminescent phosphor screen which consists of a two-component mixture of a "blue luminescent and a yellow luminescent phosphor". A fluorescent screen of this type is referred to as a P4 screen. "A mixture that has been used commercially on a large scale for many years consists of blue-luminescent, silver-activated zinc sulfide and yellow-emitting silver-activating! tem zinc cadmium sulfide (RCA Review 1947 S "554 to 563) β ^:

Ι A disadvantage of the known phosphor screens of this type is similar, which reduces their sensitivity to poisoning by copper itself in such small quantities, as it exists in the atmosphere the Lumnineszenzwirkungsgrad. Phosphor materials of this type must also be used in the manufacturing

i conditions of the tube be stable, you should have a white j.

Have body color, enable high luminance levels and have little ■ cost ■ ·

The present invention is accordingly intended to Object to be achieved, a fluorescent screen with a white luminescent Specify phosphor mixture that is insensitive

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against foreign substances and the above-mentioned desired properties Has" ;

According to the invention, this object is achieved with a phosphor4

Screen of the type mentioned above is achieved in that the yellow luminescent phosphor is activated with copper and aluminum Zinc cadmium sulfide is phosphor in which the weight ratio of GdS to ZnS is between 18/88 and 17/83 lies. The mixture preferably contains about 54 to 58 percent by weight of the blue luminescent phosphor and 46 up to 42 percent by weight of the yellow luminescent phosphor

A fluorescent screen made of this white luminescent Compared to the known fluorescent screens, mixture is distinguished by its sensitivity to poisoning and stability in the manufacturing process, white body color, high light intensity and low material costs from «

The invention is illustrated in conjunction with examples explained in more detail with the drawing, which is a television picture tube with a white luminescent Leuohtstoffschirm shows according to the invention.

The picture tube shown contains an evacuated glass bulb 21, which consists of a neck 23> a funnel-shaped part 25 and a front plate 27 consists. Located in the throat an electron gun 29 »on the inside of the Front plate 27 is a phosphor layer 31 is arranged, the is deposited with a reflective aluminum layer 33 and with this forms the fluorescent screen of the tube.

In one embodiment of the invention, the phosphor layer consists of a two-component mixture which about 56 percent by weight of a blue luminescent silver activated Zinc sulfide phosphor at about 0.020 weight percent Silver as an actuator, and about 44 percent by weight yellow luminescent zinc cadmium sulfide phosphor activated with copper and aluminum with about 0.007 weight percent Copper as an activator and 0.007 percent by weight aluminum as

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Contains coactivator. The weight ratio of CdS / ZnS is approx. 15/85 β The composition of the screen can be indicated by the following abbreviation: 56% ZnS: Ag (0.020) + 44 £ 0 * 85 2nS 0.15 GdSiOu (0.007), Al (0.007)

Any known blue-emitting silver-activated zinc sulfide phosphor can be used as the blue luminescent phosphor Blue luminescent are preferred Phosphors containing 0.010 to 0.030 percent by weight silver as an activator. The yellow luminescent phosphor will is selected from a composition range as follows can be defined:

m ZnS «η GdS: Cu (χ), Al (y). lie there

m between 0.83 and 0.88 parts by weight, η between 0.12 and 0.17 parts by weight, χ between 0.005 and 0.009 percent by weight, 'y between 0.005 and 0.009 percent by weight and m + η = 1.00.

The phosphors are partially shaped, with the individual particles in the size range between about 3 and 15 µm. The j Particles may have a thin coating of a translucent material such as silica or zinc silicate around them To facilitate the manufacture of the fluorescent screen.

The present luminescent screen can be used in a television picture tube or a display tube for another electronic device be used. In both cases the screen contains a coherent layer of the phosphor mixture. at In other embodiments, the luminescent screen may be separate white luminescent areas alone or in combination with separate areas that have different emission properties, · The fluorescent screen can also be used for tubes that are not used to display or reproduce information to serve.

The phosphor layer can be in the cathode ray tube can be made by any screen forming process. A cohesive layer of fluorescent material, as found in TV picture tubes and the like is preferably made by settling from a liquid. At a preferred processes are the phosphor components with one another mixed in an aqueous medium. The mixture is then poured into the open envelope of the cathode ray tube. When a layer of the desired thickness of the phosphor mixture forms on the inside of the front plate of the bulb has set, the excess liquid is carefully removed without disturbing the separated umbrella »The umbrella will then dried, coated with an organic film and evaporated with an aluminum layer. After steaming it will the screen baked out in air at about 440 ° G to organic and to remove other volatile components. The tube is then completed in the usual manner.

The phosphor layer consists essentially of one Mixture of 54 to 58 percent by weight of the blue luminescent! the phosphor with 46 to 42 percent by weight of the yellow lumi-! nescent phosphor. The ratio can be the one you want Tint of the emitted white light can be selected accordingly. A higher proportion of blue luminescent phosphor naturally results in a more bluish white, while higher proportions of yellow luminescent phosphor produce a more yellowish one Deliver white. Outside the specified range, the emitted light has an excessive blue or yellow cast than that it could still be called white in the narrower sense.

The novelty of the present fluorescent screen exists in that the two-component phosphor mixture as the one component contains a yellow luminescent phosphor which consists essentially of zinc cadmium sulfide, the activated with copper and aluminum. The differences in the compositions of this yellow luminescent phosphor activated with copper and aluminum and the one currently in

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silver-activated ones used extensively in P4 fluorescent screens Zinc cadmium sulphide phosphor can be found in the following list:

yellow lumineszo

ZnGdS fluorescent J ₀ ZnS $> OdS $> Activator firing temp.

Ou-Al activated 83-88 17-12 0.005-0.009 1200-100 ⁰ C Ag activated. 45-55 55-45 0.010-0.030 900 ± 100 ° C tubes with the present phosphor screen have compared to tubes with the above-mentioned silver-activated yellow luminescent phosphor the gate part that they are less sensitive to impurities, have a higher stability during processing, a whiter body color have, enable greater light intensities and can be produced with lower material costs. The following should be noted in detail: j

Insensitivity to poisoning: One has already | seeks to "develop yellow luminescent phosphors that are insensitive to contamination by copper ₉ but this could only be achieved with a certain loss of luminescence efficiency * The yellow luminescent phosphor activated with copper and aluminum according to the invention is so highly insensitive to contamination, so that it can practically be described as contamination-proof.This advantage is achieved without any loss of efficiency;

Stability during processing; ng: phosphors sulfide-based are known to their luminescence efficiency suffers during tube production as a result of interaction with the environment. Targeted experiments have shown that the present; The yellow luminescent phosphors activated with copper and aluminum are less sensitive to a reduction in the efficiency of handling. This is shown in the following table, in which the efficiency of white luminescent P4 phosphor mixtures is listed, which are produced with an ordinary blue luminescent phosphor and various yellow luminescent zinc cadmium sulfide

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phosphors were produced:

Gel luminescent. Initial efficiency Relative us phosphor the P4 of the yellow luminescence degree of the P4 misohung the fluorescent luminescent screen

Ag activated with

high efficiency $ 112 114 #

Ag activated
insensitive to contamination 100 100

Ou-Al activated 114 125

Body color; Phosphors with a glass material made from solid solutions of zinc cadmium sulfide usually have a yellow to orange body color, the tint of which is essentially proportional to the cadmium content. The yellow body color looks also as an optical filter for blue light, thereby reducing the achievable with the blue luminescent component of the mixture luminance significantly · The lower 30 i "cadmium content of this! yellow luminescent phosphor activated with copper and aluminum results in a considerably lighter body color than the known silver-activated yellow luminescent phosphor. The lighter body color contributes both to an improvement in the appearance of the non-excited luminescent screen and to an increase in the luminescence efficiency.

Light intensity ; P4 phosphor mixtures, which contain a yellow-emitting phosphor activated with copper and aluminum, have a significantly higher luminous intensity than comparable P4 phosphor screens which are made with contamination-resistant, silver-activated, yellow-luminescent phosphors or such high-efficiency phosphors. The lighter body color and the higher stability during processing together result in P4 fluorescent screens with significantly greater brightness, as the following comparison shows »

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20 14 5 "Tl

«7-

Ag activated, A <
high efficiency
grd. sj-enabled,
contaminate
gung sunemp-
sensitive Cu-Al-acti
fourth Attempt. A.
Light intensity 229 201 252 Attempt B
(Foot lambert) 204 - 224 Attempt C 196 . 216 Material costs: The main part of the material cost of zinc

The cadmium part contains cadmium sulphide. The current cost of raw cadmium oxide, as used for phosphor production, "is nearly three times the cost of zinc oxide. Since the present Gu-Al-activated yellow-emitting phosphors require less cadmium, costs in the proportion of yellow emittieren- j vw the phosphor about 20 # to be reduced. Because of the higher effective efficiency of the Cu-Al-activated yellow luminescent phosphor!, the proportion of yellow-emitting phosphor in combination with the blue luminescent phosphor for the Production of a white luminescent screen needs to be reduced by about $ 5 (from about 49 to about 44%.) On the whole, the present phosphor mixture is about 14 "4" cheaper than the known mixtures which contain a silver-activated yellow luminescent phosphor · . - '

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Claims (1)

20H511 Claims. \\ J Fluorescent screen for a cathode ray tube with a white luminescent phosphor mixture which consists essentially of a blue luminescent, silver-activated zinc sulfide phosphor and a yellow luminescent zinc cadmium sulfide phosphor, characterized in that the yellow luminescent zinc cadmium sulfide phosphor is activated in a weight ratio of copper and aluminum and is OdSnS phosphorus contains from 18/88 to 17/83, 2 ο fluorescent screen according to claim 1, characterized in that the substantially 54 to 58 percent by weight blue luminescent phosphor and 46 to 42 percent by weight yellow luminescent phosphor consists. 3. Luminous screen according to claim 1 or 2 _9, characterized in that the blue luminescent phosphor is a zinc sulfide activated with 0.01 to 0.03 weight percent / oil silver and that the yellow luminescent phosphor with 0.005 to 0.009 weight percent copper and 0.005 to 0.009 weight percent Aluminum is activated, 4 ο fluorescent screen according to claim 3 »thereby characterized in that the blue luminescent phosphor made of zinc sulfide, with 0.020 percent by weight Silver is activated, and that the yellow luminescent phosphor is zinc cadmium sulfide, which contains CdS and ZnS in a weight ratio of 15/85 and 0.007 percent by weight copper and 0.007 percent by weight aluminum as an activator.