US3254216A - Method of evaluating gettering techniques - Google Patents

Description

y 1956 V w. P. CLOSE ETAL 3,254,216

METHOD OF EVALUATING GETTERING TECHNIQUES Filed Oct. 2. 1961 2 Sheets-Sheet l INVENTORS Man-7M C7016 May 31, 1966 w. P. CLOSE ETAL METHOD OF EVALUATING. GETTERING TECHNIQUES 2 Sheets-Sheet 2 Filed Oct. 2. 1961 United States Patent 3,254,216 METHOD OF EVALUATING GETTERING TECHNIQUES William P. Close and Karel F. Sporek, both of Toledo,

Ohio, assignors to Owens-Illinois Glass Company, a corporation of Ohio Filed Oct. 2, 1961, Ser. No. 142,147

Claims. (Cl. 250-41) The present invention relates to methods and means employed in high vacuum techniques to obtain and maintain high vacuum in electron discharge devices and, more particularly, to methods and means utilized in gettering of such devices to evaluate the effects thereof. Further, the invention concerns a novel method of determining the distributive effects of various getter structures and materials in the art of gettering electron discharge devices.

In the manufacture of many types of electron discharge devices, a getter structure is utilized to direct the activation flash of getter material over prescribed internal surfaces of the device. The getter material serves as a clean-up and maintenance agent within an electron discharge device such as an electron tube. Normally, during the evacua tion of a tube envelope, the getter material is rapidly heated to a temperature considerably above its boiling point. The getter material volatilizes due to such rapid heating in a manner known as a getter flash to deposit the getter material in a prescribed pattern on surfaces within the tube.

Procedures have been employed heretofore to determine the physical and chemical effects of the gettering material on the surfaces where deposited. These methods are essentially analytical in character to determine the amount of gettering material deposited and the concentration thereof in prescribed areas. The getter material where deposited not only serves to collect and retain gases by absorption or adsorption, but also serves as a maintenance agent to eliminate impurities as they may be evolved by the' working elements of the tube during service.

In flash gettering chemically active metals essentially of the alkaline-earth group are volatilized within the tube by heating at or near the conclusion of the pumping process in evacuating such tubes. The metal vapor produced on volatilization diffuses around the vacuumized space and condenses in the tube. This vapor during and subsequent to condensation rapidly reacts with gaseous residues within the tube envelope and forms, normally on the cooler walls of the tube, a so-called getter mirror. Strontium, barhim, and calcium are commonly used as flash getters in high Vacuum electron tubes. Barium is the most commonly used single active'ingredient of'most flash getters.

In fabricating cathode-ray television picture tubes, for example, various techniques of flash gettering are employed by the different tube manufacturers. Due to process variations it has been observed that occasionally the gettering technique will deviate from optimum conditions and due to the minute amounts of getter material being deposited, getter effects may be less than desired. In any event an expeditious method of analyzing gettering procedures is required and the present invention is directed at fulfilling this need.

Accordingly, it is an object of this invention to provide ice.

a new and improved method of evaluating the flashing of I a getter material in an electron discharge device.

Another object of this invention isto provide a new and improved method of evaluating the distribution pattern of gettering material where deposited within the envelope of an electron discharge device.

Another object of the present invention is to provide a method of evaluating various getter structures, materials,

and techniquesby reacting the deposited material in situ to form fluorescent salts which can be viewed with ultraviolet light.

A further object of this invention is to provide a method of evaluating gettering methods and means in fabricating electron tubes whereby even minute amounts of getter material can be analyzed where deposited to correlate gettering effects with physical and chemical properties of tube elements which affect tube life.

A still further object of this invention is to provide an expeditious method of determining the effects obtained by various gettering techniques utilized in fabricating cathoderay television picture tubes by providing access into the interior of the tube envelope, reacting the getter material in sit-u where deposited on various component parts and envelope sidewalls to form fluorescent salts and scanning the fluorescent salts with ultraviolet light.

The specific nature of this invention, as well as other objects and advantages thereof, will become more apparent to those skilled in the art from the following detailed description, taken in conjunction with the annexed sheets of drawings on which, by way of preferred example only, are illustrated the preferred embodiments of this invention.

In the accompanying drawings:

FIG. 1 is a vertical sectional view of a cathode-ray television picture tube illustrating the results of one form of flash gettering technique;

FIG. 2 is a horizontal sectional view of the tube envelope taken along the line 22 of FIG. 1, illustrating disposition of getter material on the internal surface of the face plate;

FIG. 3 is a view similar to FIG. 1, illustrating the results of another form of gettering technique; and

FIG. 4 is a sectional view taken along the line 44 of FIG. 3 illustrating the second form of gettering technique. The present invention may be summarily described as a novel method of evaluating gettering techniques within electron discharge devices such as television picture tubes for, among other purposes, to correlate the results obtainable by certain gettering procedures to other characteristics such as tube life.

The present method is intended for use in measuring the effects obtainable by individual getter structures, methods, and materials to show variations in a given gettering technique to facilitate more precise control thereof. The invention is also applicable to qualitative chemical analysis of various common gettering materials where deposited in electron tubes whether on glass, ceramic, or metal parts to evaluate the particular gettering technique involved.

along a seal line 14. The small or apex end of frustopyramidal shaped funnel member 11 has a neck tubulation 15 sealed thereto. The opposite end of neck tubulation .15 is sealed with an end cap member 16 which supports an electron beam emitting gun member 17 of any conventional type disposed axially within the neck.

A getter structure 20 consisting of a ring-shaped hollow trough is shown disposed in the region of the tube envelope adjacent the intersection of the funnel apex end and the interconnecting end of neck tubulation 15. Getter structure 20 is mounted on beam gun 17 as a forwardly-projecting extension thereof coaxially aligned within the neck. Getter structure 20 is preferably fabricated of sheet metal and is circularly shaped to facilitate its rapid heating by induced radio frequency energy. The ring-shaped trough of getter structure 20 is formed having its wall portions disposed in closely adjacent proximity with its open side preferably facing forwardly. Getter structure 20 retains a getter material which may be fabricated in the'form of a wire of suflicient length to fit within the circular trough. After its disposition in the getter trough the wire may be enclosed by proper modification of the trough to retain the wire in the circular pattern.

The getter material may be comprised of barium or barium alloy having a protective coating of aluminum, for example, to prevent the barium which constitutes the core from reacting with the atmosphere. Normally, the aluminum coating is volatilized along with a considerable portion of the barium core during the activation flash.

The getter material is most commonly comprised of barium and aluminum although certain types of getters for special purposes may also be comprised of magnesium, strontium, calcium, titanium, zirconium or other materials in lesser amount. As stated, barium and aluminum are most commonly used.

After proper arrangement of the getter structure 20 within the tube envelope 11 and, during or immediately following the tipping ofl operation, the getter structure is directly heated by a heater coil 21, for example, as shown schematically in FIGS. 1 and 3. The getter structure may also be indirectly heated by radiation or by conduction from other heating components disposed within the envelope. After getter flashing the getter material 22 is deposited over prescribed areas of the tube sidewalls in a flared pattern such as shown in FIG. 1. In this case the getter structure and its arrangement within the tube envelope effect a rather narrow pattern of deposition of the getter material over internal side walls of the flaring tube apex area 18 of the tube funnel and the central region only of the face plate internal surface 12a. The portion of getter material disposed centrally on face plate surface 12a is designated by the numeral 22a while the portion deposited in the yoke area 18 is designated by the numeral 22b. The particular getter material 22 thus finally resides within the tube envelope in the areas marked 22a and 22b after the activation flash of getter structure 20.

In another form of gettering as shown in FIGS. 3 and 4, the getter material is deposited within the tube envelope with a much broader pattern of deposition as shown. In this embodiment the getter material 24 is shown as deposited from getter structure 20 disposed in slightly different arrangement. In this case the getter material 24b deposits in an annular band internally of the tube envelope on the yoke area 18 as well as on internal surfaces 12a of the face plate due to the lighthousing effect of the flashing. Where the distribution pattern has wider angles of divergence as shown in FIGS. 3 and 4, a greater annular area of the tube yoke portion 18 has getter material 24b deposited thereon. Concurrently, a greater area of the face plate internal surface 12a has getter material 24a deposited thereover which covers a substantial major portion of the face plate screen or target.

form fluorescent metallic salts.

The getter is usually deposited in the form of fine particles having a diameter of the order of about 1 to 10 microns which particles are adherent to the contacted surfaces.

In practicing the present method a fully completed electron discharge device is taken for examination following flashing of the getter material. The device may be a television picture tube as shown which has been subjected to life tests as well as other tests. Access is provided into the envelope interior either by removing the neck portion of the tube envelope or by effecting separation of face plate and funnel parts along seal line 14. Preferably with the major component parts of the tube envelope separated from one another, each of the individual parts is taken for examination.

An aqueous solution of a compound which is substantially non-fluorescent or slightly fluorescent per se, but which is capable of forming distinctive fluorescent salts, is prepared. S-hydroxyquinoline (oxine) is a preferred compound for reaction with conventional gettering materials in view of its sensitivity in reaction with barium and aluminum to form metal hydroxyquinolinates which are highly fluorescent. A dilute acetic acid solution of 8'hydroxyquinoline is preferred. The solution is prepared by dissolving 10 grams of 8-hydroxyquinoline (or S-quinolinal), C H NO, (mol. wt. 145.16, M.P. 74 C.) in 50 milliliters of glacial acetic acid and diluting the solution with 50 milliliters of water.

The prepared solution is sprayed over the glass and metal parts to be examined in the form of a finely atomized spray having a particle size of the order of about 1 to 10 microns to contact the extremely small particles of the deposited getter material. The reagent solution should be sprayed in the form of fine particles preferably not exceeding 10 microns. The S-hydroxyquinoline reacts with the deposited getter material to The glass surface bearing deposited barium in the form of oxide or carbonate is thus treated with the solution of S-hydroxyquinoline in dilute acetic acid. The barium hydroxyquinolinate which is formed is detected through its fluorescence in ultraviolet light. Minute quantities of barium in submilligram amounts are readily detectable. The fluorescence of the salts is readily perceptible when the reaction product is dried or exposed to an ammonium hydroxide solution and subjected to ultraviolet light. The first reagent produces a fluorescent compound with the metal while the ammonia retards the color fading of this compound under ultraviolet light.

After the fluorescent salts are formed in situ by reaction with the getter material, the reaction products are examined by scanning with ultraviolet light such as long wave ultraviolet light. An ultraviolet lamp such as a mineral light, Model SL-3660, manufactured by Ultraviolet Products Inc., San Gabriel, California, may be used. The fluorescence of the reaction products is readily detectable on glass surfaces as well as metal parts. The glass parts taken for examination may be coated with conventional phosphors in the form of a target screen on the face plate viewing area or aluminized coatings which do not interfere with detection of the getter material. 'By this method the material flashed in the getter structure is made visible and, in the case of television picture tubes, is seen as a large circle on the face plate and as a spotted deposit or ring in the neck and yoke areas.

Each of the common'getter materials has been found to form distinctive fluorescent salts which have individual identifying colors. The fluorescence of dried salts is relatively permanent without appreciable color variation from one test to the next to permit photographing the effects as well as to perform comparison tests over a considerable period of time. The fluorescence is different for each metal utilized as a getter due to the distinctive fluorescent colors of the S-hydroxyquinoline complexes which are formed. The following colorations under fluorescent light are obtainable utilizing this compound as the reagent: 7

Ba (barium) Blue.

Al (aluminum) Brilliant yellow. Mg (magnesium) Green.

Ca (calcium) Greenish-blue.

Other reagents which are capable of use to form fluorescent metallic salts are the following: 7 sulfo 8- hydroxyquinoline; 7 iodo 5 sulfo 8 hydroxyquinoline; rhodamine B; morin; quercetin; and eriochrome (blue black R, 6.1. 202). Each of these compounds is either non-fluorescent per se or produces a fluorescence distinct from its metallic compounds and readily distinguished from them. Further, each has been found applicable to forming fluorescent salts with conventional gettering materials. Each of these reagents is capable of forming salts having their own individual fluorescent colors which are slightly different from the colorations obtained by using S-hydroxyquinoline.

The following table indicates the fluorescence obtained with various metals tested after being deposited within cathode-ray picture tubes as getters using 8-hydroxyquinoline as the detecting reagent.

Blue. Blue. Briant yellow. None.

Greenish-blue. Greenish-blue- Very weak green None Ca (carbonate) Sr (nitrate) On (acetate) None None. Ni None None. Cr N one None. 00 None None.

It has been found that the metals iron, copper, nickel, chromium, and cobalt, which are not normally included in gettering materials, do not interfere with detection of the deposited getters. Also since these metals may be included in stainless steel working component parts of an electron tube such as in color television picture tubes, for example, getter materials can be detected on both glass and metal parts without interference by these metals. The distributive patterns of getter materials 22a, 22b, 24a and 24b shown in the drawings as well as widely varying other patterns are fully capable of determination after reaction to form the fluorescent salts. The individual parts of the tube envelope are scanned with ultraviolet light in the range of from about 200 to 4000 Angstrom units in wave length to study the distribution and concentration of the getter materials.

The subject method is utilized in establishing relationships between tube life and the position, design and flashing technique with its resultant distribution of getter materials on internal surface areas of television picture tubes.

Various modifications may be resorted to within the spirit and scope of the appended claims.

We claim:

1. A method of detecting and evaluating deposition of metallic getters 0n the inner surface of a hollow evacuated electrical discharge device, such as cathode: ray tubes and the like, said method comprising:

selecting a device for examination,

providing access to the interior of the device,

introducing thereto a reagent capable of reacting on contact with the metallic getter in said device to yield a metal salt of distinctive fluorescence upon excitation by ultraviolet light and scanning the device with ultraviolet light to generate said distinctive fluorescence.

2. The method as claimed in'claim 1, wherein said reagent is introduced dissolved in dilute acetic acid.

3. The method as claimed in claim 2, wherein the acetic acid solution of reagent is introduced onto interior surfaces of said device as a fine spray having a particle size of about 1-10 microns.

4. The method as claimed in claim 2, wherein said metal salt reaction product is contacted with an ammonium hydroxide solution to retard fading of the fluorescent coloration. 5. The method as claimed in claim 2, wherein said reagent is selected from the group consisting of 8-hydroxyquinoline, 7-sulfo-8-hydroxyquinoline, -7 iodo 5- sulfo-S-hydroxyquinoline, rhodamine B, morin, quercetin,

evacuated electrical discharge device, such as cathoderay tubes and the like, said method comprising:

selecting a device for examination, providing access to the interior of the device, introducing thereto an essentially non-fluorescent reagent capable of reacting on contact with the metallic getter in said device to yield a fluorescent metal salt product upon excitation by ultraviolet light and scanning the device with ultraviolet light to reveal the fluorescent salt.

8. In the method of determining gettering effects in the manufacture of cathode-ray television picture tubes by exhausting a fully-fabricated tube envelope, activating an electrode-associated getter comprised of at least barium spaced from the wall portions thereof so that such getter is deposited on prescribed wall portions of the envelope to effect purification of the internal atmosphere and to serve as a maintenance agent during the life of the picture tube, the method comprising the steps of providing access into the envelope interior, reacting said deposited metallic getter in situ with a solution of S-hydroxyquinoline sprayed over at least a portionof said envelope interior in fine particle form to form fluorescent salt, and scanning the wall portions with ultraviolet light to determine the distribution pattern of the fluorescent salts.

9. In the method of determining gettering effects in the manufacture of cathode-ray television picture tubes by exhausting a fully-fabricated tube envelope, activating an electrode-associated getter comprised of at least barium spaced from the wall portions thereof so that such getter is deposited on prescribed wall portions of the envelope to effect purification of the internal atmosphere and to serve as a maintenance agent during the life of the picture tube by eliminating impurities as they are evolved, the method comprising the steps of providing access into the envelope interior, reacting said deposited getter in si-tu with an acetic acid solution of 8-hydroxyquinoline sprayed over prescribed areas of said envelope interior in finely-atomized form to form fluorescent salts consisting essentially of barium hydroxyquinoline, drying the newly-formed fluorescent salts, and scanning at least the prescribed areas of said envelope with ultraviolet light to determine the distribution pattern of the fluorescent salts.

10. In the method of analyzing gettering effects in the manufacture of an electrical discharge device such as cathode-ray television picture tubes and the like by exhausting tube envelope, activating an electrode-associated getter comprised of at least barium and aluminum spaced from the wall portions thereof so that such getter is deposited on prescribed wall port-ions of the envelope to effect purification of the internal atmosphere and to serve as a maintenance agent during the life of the device by eliminating impurities as they are evolved, the improvement comprising the steps of providing access to the envelope interior, reacting said deposited getter in situ by spraying the same with a solution containing a compound selected from the group consisting of 8 -hydroxyquinoline, 7-sulfo-8-hydr0xyquinoline, 7 iodo 5- sulfo-8-hydroxyquino1ine, rhodamine B, morin,i-quercetin, and eriochrome (blue black R. Cl. 202), to form fluores: cent metallic salts, subjecting the said fluorescent salts to an ammonia solution, and scanning the wall portions with ultraviolet light to determine the distribution pattern of the fluorescent salts.

, References Cited by the Examiner UNITED STATES PATENTS 2,275,864 3/1942 ..Record 313181 X 5 2,898,475 8/1959 Larach.

3,021,448 2/1962 Daly 313-181 X FOREIGN PATENTS 729,917 5/ 1955 Great Britain.

10 GEORGE N. \iVESTBY, Primary Examiner.

RAPHL NILSSON, Examiner.

C. O. GARDNER, R. SEGAL, Assistant Examiners.

Claims (1)

1. A METHOD OF DETECTING AND EVALUATING DEPOSITION OF METALLIC GETTERS ON THE INNER SURFACE OF A HOLLOW EVACUATED ELECTRICAL DISCHARGE DEVICE, SUCH AS CATHODERAY TUBES AND THE LIKE, SAID METHOD COMPRISING: SELECTING A DEVICE FOR EXAMINATION, PROVIDING ACCESS TO THE INTERIOR OF THE DEVICE, INTRODUCING THERETO A REAGENT CAPABLE OF REACTING ON CONTACT WITH THE METALLIC GETTER IN SAID DEVICE TO YIELD A METAL SALT OF DISTINCTIVE FLURORSCENCE UPON EXCITATION BY ULTRAVIOLET LIGHT AND

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