BE624850A - - Google Patents

Description

       

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  Luminescent screens *
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 Ik prisent * imtioa c5ncé * he, d'toe f * $ ô & idiirr, luminescent screens for elabfcrôiiiquèi tubes dd dw ttbftdîtîôh screen Illâ fii tappcfté pàmo, ëpdël "ëi ment to the very groin e 3 layers of pile 13m6t oblibtd "los odiïol qUOâ de $ processes of âbndâtîbü de tblîoi 4" tea, La t4târtece t4itt à ptitÀtabd de 4â attit twiiiïi dale Hw liai te in nothing dlaeii i6tt dot p i-ticulè k L '* pl' * l colloidal "toute tu 6 && tïM, used here in loti àtiâ plus îtï-gê designating a particle of such intortsion, â your proptii- Kt of jMï'ft <6! 0 predominate as compared to # pr6pft4tt * b di kàsse, by < UEispl in the and $ where forces surface i4 * iAtiefm * ïlt a suspended particle dtüb a liquid whose weight is 4, aitim qu ouf lower than that of the particle.



  ¯¯¯.Dn-d8ire7-JiSn some cases diippliô4t4îttî Obtain from 'extttâ phosphor layers have thin. üd type do tàibè to

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 'tayond "thôdielîtëâ, 11 1 fttftftfe de zure atrr screen luilhebdont eoapo * 4 de ôoüéhoîo âupërlwoéêâ de luageôph6rto dittlêrtbtg ëtt * each one * luaiéte dbunt otiuimtt during this deltobot 1,' ' ia4ï élootttte drtri épàiiaeuf di l tfdtftfn it eft 'r3ltt'ït i ".btVii there fltilit d # ub dbul e4todbiu 416aïk tropic, either in Usa pliit tlildâêâux Uymit dts wtx different from ustate dbitophetivetIV, 06 dbitophetIV in exûough ddl, 06d to exutat, dbitophetIV, to exûhoutrophet IV Ibôttet de pmwitê d L "geâ polydhroa * * Coma * the flow iuaineui in eb9lemr * if a tbnëtiott of 14 penetration dir é <5 ** an pat 16 fieu,

   100 êjotohêg do luainophoï1 mi | {âilifli must beteo ciiftcos #Ode quo 1 # jj (Jnétf * tiôn de, lbigeân dbübê ddubbe de lUAinophoî-e to the other 6to dÔüdd4U * ità 14 balëttibi Att 6 theiro can 0'fëoK 'ee de tension 6 <bîbt M tion i3 "t in practiced. LÎ9 doüdhëà dJâtMâ d'tui tol tubé 1106 growls must attrô alftboi # it 4M) t <ti * see an ipitiâïülë têt4ê.

   iibed and btre itêêht tiort ot4umet oû ci âthi queilléi d, wrt ttft th 6ubstAflc niantes d-bîùtdràtibdoâ do piqütto du dé bàet4oi In the presence of ihtersticis, of p, r '4 of âVtia tîtiol douho dmo * task ,, some electtona of the falacfc * UD # 4, # At ttkfêHët uno oUche t êxeltéf 141 sswtw # law * qüâëft done, $ <dA ne eeeteaït worse if liSis'I Le * couché do 5, nph'rw itineenit oôw hou téuëât iïït psuf t1 tubes at f-ayorn 'gathodi4ttâb earlyiotiohdâât uiY * Ht 16 pï-indipt due degree of Péiidttlti6a de lUcfan 4 the iffet diobtehie of the yews in ollêutf harmed Uë8i in other ciàfl dêtplibutiôn, by such places. are Useful * d'âne li t4o de ttprodtictionâ do fdë tiüëootà N0 dmoi les tûbloi image and some tubta d & cl'll & pMèS.



  It has been proposed, with the intention of obtaining * ± clear coulters from non-porous phosphors, dw the * to produce pêt 4ivaporaê tioa. 6 <tpend & Rt the layers of 'lu' hoppers deposited by 4, t & POratw tloa showed a ca luainous flow, Véttlt weak. Oïiutxe pâti, the (strains of phosphores with rehdeiieftt ilolativmont flêté iè

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 particle size component. a6. + were running #atr naked by deposition of particles on a surface 4th suppôt au tg4vero
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 of a liquid cushion, not suitable; * not for relief; layers
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 thin because of the relatively large dimensions of the phosphor 1. "e.

   These have, by te "i # b" \ Ut, dimension p3, u greater than the desired thickness e 1% Q9l; Ç4Ç1 44 outpe, do warm layers of sediment particles *? . * 'Q1f P "l.1t". of t \ Jh .. l. \ 8 'of the large interstices between the p "91400 qg 99 oggt 999 JBp 1ï -
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 neatly packed. :
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 The invention aims to ppecupee dea. #? * # * * rt9l- thin, new and pe; vt, 01; 9!. 'U \' J t.1o & 4 ", ... QpoW1!
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 of one or more layers of papttogop of # car tÓri8tSes by a relatively thickness, 4t. ',,' '3 dis, regular dimension * of surface 4 surface st by gne tt1M' 499 pQ'W''1 while having a yield l'J.! Un .t3,.,. q 'n. ,, "The invention. also ot' w1 do | f9S3Pip n el * qç4e4 new and improved from fabf4-Bft | ft # f4s) W 3W rim iHlJRiW fe Reposing of one or more 99,49iqe do | pfe | f} ABU | 1tl 4t fJ! 1o "strongly packed. ;

  e In short, according to a pJ '\. "" "dt r, f' 5 .o, luminescent ee composed of.a1.1! 9oAnw us * POUO ognètp #f W VA 4 several deposits of pJ.rUc '\ 4Ct 'de, Q1 t'q ",. 1; . | if4f 9 $ The particles are ren .... d1 \ 4l ".w, eftW # 4100 al V) * t support zee, by inserting PtUt.'1I u '' '. n ûnC", horn; gelatin pellets * 4P4a n, .t ma! 4t '#' at okffopt do etices having the m6M.e order of magnitude 9'4 trdBe 41 '¯lNpl1I "laughing to that of the phosphor particles * i 6ït \ * if, the parts cules being forteaep.t tasit6on and the layer 41p.tj "3d \ v (> 1IfA 'Mn porous. Moreover, as we used from $, PJ1.'t; l.cm: lI d9, t4 * f4 not a film deposited by évpqrf t \ m9 on pt; \! IA '\' the "4" 'I ment luminous.

   On the other hand, the use of "1Uf \ m" colloidal parules makes it possible to keep layers very rinsed, '' xa.ua;
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 of.
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 According to other pt \; "c1. \ L ... tc!: S of # vt40n .. 4 '.
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 Luminescent screens for use in cathode-ray tubes of the penetrating beam type may comprise several superimposed layers of such phosphor particles in the form either of an extended layer or of a set of,) particles coated with several layers.

   In the case of screens with extended layers, each of the superimposed phosphor layers completely covers the front face of the tube * In the case of coated particle screens, the superimposed coating layers are formed * of superimposed layers of phosphors coating a particle relatively large, for example glass, or other phosphor, these particles then being deposited in a layer on the front face of the tube.



   Another feature of the invention is a process for depositing a layer of phosphor particles with a view to obtaining a novel type luminescent screen by the use of adsorbent films attracting the phosphor particles and re-emitting them. holding by adhesion. Such a film is interposed between a support surface and phosphor particles which are to be deposited in a layer on the support surface. This can be constituted by the front face of the tube or by large base particles on which the layer of phosphor particles is to be formed.

   The method may consist, for example, either in forming such a film on the support surface which is then bathed in a liquid suspension containing the phosphor particles intended to form the layer, or in forming this film on the particles of phosphor themselves intended to form the layer and then to bathe the support surface with a liquid suspension containing the phosphor particles coated with the film. In both cases, the phosphor particles adhere to the S1 support surface. depositing in one layer.



     In one embodiment of the process of the present invention, a support surface, for example the glass front face of a tube, is covered with an adsorbent film. The film is then bathed in a liquid suspension of particles of

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 phosphor. Thus, the particles adhere to the film. The excess liquid suspension is then removed. These operations can be repeated as many times as necessary to obtain a layer of phosphor particles having any desired thickness;
In the accompanying drawings:
Figure 1 is a longitudinal section of a cathode ray tube having a luminescent screen.



   Figures 2 and 3 show large-scale cross-sections of single-layer and multi-layer screens, respectively, which may be used in the tube of Figure 1.



   Figure 4 is a sectional view, on a large scale, of a variant of the multi-layered screen of Figure 3.



   Figure 5 is a section of a particle) coated with several layers.



   Figure 6 is a variant of the coated particle of Figure 5.



   Figure 7 is a sectional view of a multi-layered luminescent screen composed of coated particles of Figure 6, and
Figure 8 is a sectional view, on a very large scale, of a phosphor layer.



   In Figure 1, a cathode ray tube 10 comprises a casing 11 composed of a neck 12, a front face 14 and an intermediate frustoconical portion 16. An electron gun 18, housed - in the neck 12, is intended to project a beam 20 of electrons towards the front face 14. The neck 12 is closed, at one end, by a tail 22 crossed by several sealed current supply conductors 24. Appropriate supply voltages are applied to the electronic gun 18 via the conclue-! current feeders 24.

   The inner part of the truncated portion 16 is covered with a conductive coating 26 which acts as an accelerating electrode. A suitable high voltage is applied to electrode 26 through a crack-sealed terminal of frustoconical portion 16 and shown schematically by arrow 28. For example, a magnetic deflection assembly 30 is used.

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   read to deflect the electron beam 20 so that it describes a frame on the front face 14.



   A luminescent screen 32 covering the inner surface of face 14 consists of one or more layers of phosphor particles * Luminescent screen 32 may, for example, consist of a single layer of particles intended to produce either light of a single color, or of: White light * Or, the screen can be composed of several superimposed layers of phosphor particles, preferably of colloidal dimensions, if we want to produce light of different colours.



   The present invention can be applied to the manufacture of luminescent screens of a variety of types, including white and black cathode ray tube screens as well as polychrome cathode ray tube screens.



   When a screen 32 with several layers is used, and this screen is bombarded by electrons having different speeds, it is possible to provide means for pocketing the dimensional deformations of the frame. These means may consist of a mesh 34 disposed across the frustoconical part 16, or any other suitable device. When electrode 34 is used, this is connected to electrode 26 and tube 10 operates according to post-acceleration principles. A separate current lead, shown schematically by arrow 36, serves to apply suitable electrical potentials to multi-layer screen 32 for color selection.

   In the case of a screen 32 with a single phosphor layer, the electrode 34 can be omitted or it can be maintained to obtain a post-acceleration, which has advantages.



   FIG. 2 shows a luminescent screen 38 consisting of a single layer 40 of phosphor particles and capable of drawing used in tube 10. Layer 40 is characterized in that its thickness is notably greater than the dimension of the particles, which makes it possible to obtain a layer having a thickness of several particles, free from holes. As, in the example considered

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 The particles have a colloid dimension, the layer 40 is very mined and has good light transmission properties.



   A metal layer 41 reflecting the light, made of aluminum for example, is deposited on the layer 40.



   Figure 3 shows a three-layer luminescent screen 48 which may be used in tube 10 to produce. polychrome images. The luminescent screen 48 consists of three superimposed layers 50, 52 and 54 of colloidal phosphor particles.



  The superimposed layers 50, 52 and 54 can touch each other or they can alternate, as shown, with internal (non-luminescent) separation layers 56 and 58. The separation layers 56 and 58 can be constituted, by for example, by powdered mica, vermiculite, colloidal silica, bentonite, kaolin, vanadium pentoxide or talc. These release layers can be deposited in various ways, for example, as used to deposit phosphor layers 50, 52, 54 which will be described below.

   The separation layers 56 and 58 serve, among other things, to reduce the mixtures of- color in the light produced * The screen 48 is also provided with a metallic base layer 59 reflecting the light, made of aluminum by example*
A variant of the screen 48 is shown in Figure 4.



  In Figures 3 and 4. the same elements of the ecuan 48 bear the same references * Figure 4 shows a luminescent screen 60 arranged on a support 14 and comprising one or more layers of relatively thin and non-porous colloidal particles 50 and 52 superimposed on a relatively thick powder phosphor layer 62 consisting of particles larger than colloidal, for example of sedimentary size. As in the case of screen 48 of FIG. 3, the continuous phosphor layers are separated by inert separating layers 56 and 58, while a light reflecting metallic layer 59 covers the phosphor layer 50.



   The screen 60 of figure 4 shows, next to other

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 the advantages of being able to choose different application techniques for the deposition of the first phosphor layer 62. For example, the well known sedimentation method can be used.



   Since, for the operation of the tube 10, the electron beam must not pass right through the phosphor layer closest to the front face of the tube, this layer must be neither extremely thin nor non-porous. The porosity of the coarse-grained layer 62 may be greater than that of the two layers 50 and 52 closer to the electron gun of the tube.



   In the case of a luminescent screen consisting of colloidal phosphor particles, a good light output can be obtained with thin layers of phosphors which, however, are non-porous. For example, a good light output has been obtained with a screen 48 with three layers having a total thickness of a few microns.



   When depositing a layer of phosphor particles, adsorbent films of polymeric materials having the protective properties of colloids are used. Examples of such materials which have been used successfully include gelatin, polyvinyl alcohol, and certain modified starches such as those sold under the trademark "Ceron-N" by the "Hercules Powder Company." Many other materials which have the protective properties of colloids and which can be used in the practice of the invention are known.



   When the protective colloid is applied, according to the process of the invention, either to the phosphor particles or to the support on which the particles are to be deposited (but not to both), the desired degree of affinity is obtained and adhesion between the particles and the support.



    CONTINUOUS LAYERS.



   A method of manufacturing a thin luminescent screen as shown in Figures 2, 3 or 4 will be described below.



   The adsorbent film can be inserted between the particles and their support surface either (1) by application of

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 the film on the support, the surface of which is thus covered with an adsorbent film in order to be subsequently bathed in a dispersion of particles not coated with film, either (2) by coating the particles with film, each particle being coated with an adsorbent film and a non-film carrier surface then being bathed in a dispersion of film coated particles.



  Support covered with film,
To obtain a single phosphor layer count: Layer 40 of Fig. 2 by the film-coated support method, an adsorbent film is first applied to which the phosphor particles contained in a liquid suspension will come out. attach, to a support surface, for example the glass front face 14 of a tube.

   The film can be obtained by introducing a certain amount of a suitable material having the protective properties of colloids, for example a solution of gelatin in water, inside the envelope 11, to bring it into contact with the film. inner surface of the front face 14 which is thus completely covered with a gelatin film. The excess liquid is then discharged from the casing by pouring it out.



  After that a very thin film of liquid remains on the front side 14.



   A solution of about 0.1% gelatin in water makes an excellent adsorbent film. Satisfactory results have been obtained with a gelatin concentration ranging from 0.01% to 10%. When the concentration is inside it. 0.01%, too large amounts of gelatin solution must be handled. On the other hand, gelatin concentrations greater than 10%: pose a problem of use, because of the stability and the viscosity of gelatin solutions.



   The pH of the aqueous gelatin solution is preferably adjusted to around 4 by the addition of an acid. Various acids can be used; glacial acetic acid has been found to be satisfactory. The degree of acidity, that is to say the pH, will not be critical, except that too strong an acidity, for example a

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 solution having a pH much lower than 3, can be harmful for certain phosphors. The acid appears to increase the affinity of the adsorbent gelatin film for the phosphor particles which are subsequently contacted with it.



   As a variant or as a supplement to the addition of an acid to the aqueous gelatin solution, the absorbent film can be given an acid bath when the latter has been deposited on the support surface (front face 14). The acid bath can be given by introducing a quantity of a suitable acid, for example acetic acid, into the casing 11 and running it over the adsorbent film covering the inner surface of the face. before 14. The excess acid is then drained off.



   With the acid bath or the application of acidified gelatin, as the case may be, a water bath is followed. Water is introduced into the casing 11 and it is carefully run over the entire film covering the front face 14. The water is then discharged.



  The water bath serves to remove excess gelatin which is not in actual adherent contact with the support surface. The bath also serves to remove excess acid remaining on the absorbent gelatin film. After evacuation of the water, a rotational movement is preferably imparted to the front face 14 so as to remove any excess water. The adsorbent film can be dried, if desired, to set the gelatin. However, this is not essential.



   After this wringing operation, a suspension of the desired phosphor particles in a suitable liquid such as water is introduced into the envelope 11, so as to bathe the support and its gelatin film. If desired, the suspension of phosphor particles can be acidified as described below. A sufficient quantity of the suspension is used to cover the surface of the film on the front face 14 well.



  When the gelatin film is completely embedded in this aqueous suspension of phosphor particles, the phosphor particles adhere to the film as a deposit believed to be substantially the thickness of a single part.

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 cule. Like the. sedimentation is not the main action by which the phosphor particles are deposited on their support, - one can, without inconvenience, stir the suspension of phosphor particles, and washing or bathing with a suspension of particles. of agitated phosphor may be the most efficient way to achieve the most even deposit possible, and therefore be the preferred process.

   The process of the present invention is distinguished from sedimentation techniques in that washing with a suspension of agitated or unstirred phosphor particles is normally carried out in a much shorter time than would be required for a useful number. phosphor particles precipitate even in the absence of any agitation.



   Suspending media other than water can be used, if desired. Applicants prefer to use an aqueous suspension of phosphor particles containing particles.
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 The phosphors of a size less than one micron at a concentration of about 10 to 30 milligrams of particles per cubic centimeter of water, to obtain adsorption. Lumino-
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 Phore greater or less than about 1.0 mg / CM3 can be used.

   In general, the more concentrated the phosphor suspension, the higher the adsorption rate.
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 Significantly less than 16 mg / cm3 phosphor concentrations give rise to abnormally slow adsorption rates, while phosphor concentrations well above 50 mg / cm3 give rise to difficulties in centrifugation / and. the r Usp4 'sion of the phosphor particles. Phosphor particles having dimensions of up to three microns and larger have been layered by the method of the present invention.
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  When the suspension of particles dd 3.uza.i.nophorb Wtë, brought into full contact with the absorbent gelatin film,
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 the excess is evacuated, ipres evacuation of the suspension of particles, of phosphor, the layer of phosphor adhering to the adsorbent gelatin can be bathed in water in order to dpenl; ever all ejtces of lmir "phrp h <h # j! 3f ? ' the adsorbent film.

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   The suspension of phosphor particles cannot contain an appreciable proportion of material constituting an adsorbent film, gelatin in the process described. If there was any. adsorbent material in the suspension, the phosphor particles would be covered with it. As a result, the phosphor particles and the support surface (front face 14) would be provided with the same coating and would have the same type of surface. There would therefore be no effect of attraction by adsorption.



   The operations described above give rise to the deposition of a thin film of gelatin which is itself covered with a deposit of phosphor particles in the form of a layer. The phosphor particle layer has substantially the thickness of a single particle and a little too low particle concentration or density to completely cover the support, unless the phosphor suspension has been acidified. When a sufficient number of phosphor particles adhere to the gelatin film to obtain a certain concentration of particles, the deposition of phosphor on the gelatin film substantially ceases. In certain cases of application, such a deposit of phosphor particles suffices.

   For other applications, however, it is preferable to have denser or thicker phosphor layers.



   The particle concentration can be increased by adding to the process described above a series of alternating washes with acid and the phosphor suspension. Substantially complete coating of the support can thus be obtained. Each acid wash renews the affinity of the gelatin film for additional phosphor particles, so that adsorption can continue.



   The acid baths forming part of the alternate washings can be done with acetic acid solutions having a pH of approximately 4. It has been found, moreover, that several, for example three or four, of this) additional alternate washings with acid

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 and at the. The phosphor suspension appears to give maximum density to the deposit of phosphor having the thickness of a particle on the gelatin film. A greater number of alternate washes with lucid and the phosphor suspension only results in the deposition of a few phosphor particles, if any, on the gelatin film.



   Instead of using the aforementioned alternate washes with acid and phosphor suspension, the particle density can be increased by acidifying the initial phosphor suspension, i.e. giving it a pH below 7, either before applying it to the support covered with its gelatin film, or when the suspension is already in contact with the support and the film which covers it * 11 has been found, for example, that a pH of about 5 is suitable. In the case of a suspension that is too acidic, for example a pH much lower than 3, the phosphor can undergo harmful effects.

   With this simplified process, it is possible to adsorb a sufficient number of luminophore particles with a single application of luminophore slurry to obtain a dense underlayer of luminophore particles having l. particle thickness and substantially the same density as that of a layer produced by a series of alternating washes with acid and the phosphor suspension.



   Thicker phosphor layers can be made using either of the following two methods.



   For example, the thickness of the layer can be increased by alternately repeating the washings with gelatin and with the phosphor suspension. Water washes and pH adjustment of the gelatin solution are carried out according to the above.



   Alternatively, the thickness of the phosphor particle layer can be increased by superimposing several particle sublayers. In the latter case, a dense sub-layer having the thickness of a particle is first deposited on a gelatin film using either alternate washes with acid and the phosphor suspension, or simplified process consis

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 so much to acidify the sus. phosphor ansion as described above -,% before.



   When a first sub-layer is thus deposited, a washing with water is carried out. A second gelatin film is then applied to the first underlayer and a second dense layer of phosphor particles is deposited on the second gelatin film. This process can be repeated as often as desired to overlay any desired number of underlayments. dense. of phosphor particles.



   Several means can be used to maintain good adhesion of the phosphor particles on the one hand between themselves and on the other hand between them and their support surface once the screen obtained is mounted in the finished state in a. cathode ray tube. For example, the deposited phosphor layer (s) can be given a final bath with a silicate solution, for example a 2% potassium silicate solution.



  It is useless and even dangerous to follow this bath with a washing with water, for fear of removing the silicate. Alternatively, the phosphor layers are washed with a gelatin hardener, for example a small amount of a 2% chromium alum solution or a 37% formaldehyde solution, after which the gel is washed. screen in the water. If desired, an additional gelatin coat can be applied immediately prior to the formaldehyde or chromium alum wash.



   The adhesion can also be increased by applying to the support, between washing with phosphor suspension and additional washing with gelatin solution, a suspension of extremely fine particles which are smaller than the deposited phosphor particles. The extremely fine particles are preferably but not exclusively luminescent and of the same phosphor material as the deposited phosphor layer.



  Experience shows that colloidal silica can be used successfully as extremely fine particles. These are adsorbed by the gelatin film between the phosphor particles and

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 gerveat to the liver to better fix the phosphor particles on the gelatin film and to increase the packing.

   This proeassu, of increasing adhesion is of particular interest when used in combination, with the process amplifies
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 described above to acidify the suspension of lumL'L- vphore ea to obtain dense sublayers of the thickness of a single parti-! cule. The Applicant has found that if a suspension is acidified
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 phosphor at 30 mg / = 38 substantially all of the phosphor particles separate from the suspension and are adsorbed by the gelatin film * A suspension of extremely
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 fines, for example colloidal silica,

   can be applied to the phosphor underlayer Thus obtained by leaving the support in contact with the suspension medium (water) of which the phosphor particles have been adsorbed and by suspending, in this medium, a certain quantity of colloidal silica so as to
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 obtain a suspension of extreme fine rat particles. This adhesion increase process can be used as a replacement for the aforementioned alternate washes with potassium silicate, chromium alum or formaldehyde, or in combination therewith.



   An example of the manufacture of a continuous layer type screen by the film coated support method is described below.



   Four gelatin cramates are added to 400 char of water *! This mixture is stirred, and then allowed to settle for thirty.
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 minutes, the Mu-gelatin solution is then heated to 60 ° C and bone & .. maintained at this temperature for fifteen minutes. The gelatin is thus completely dissolved. This 1% gelatin solution is used either as is, diluted, as specified above.
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 after. A layer of alpha-activated sine sulfide blue emitting phosphor (as used in the commercial color kihescope. 21CTP22) is coated as follows. on the front face of the tube.

   Twice 20 grams of blue phosphorus are washed in two different volumes of 20 milliliters of water.

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 At each wash, the phosphor is stirred in water, left to settle for a few minutes, then the water and the fine particles in suspension are removed and the deposited phosphor is recovered for later use * The phosphor recovered is suspended with 0.06 gram of sodium pyrophosphate in another volume of 250 cm3 of water. The sodium pyrophosphate is used to prevent the phosphor particles from clumping together during a subsequent grinding operation.



   The phosphor suspension is then ground in a ball mill for 72 minutes, to then be diluted in another 250 car volume of water; follows a cantrifugation at 1,800 revolutions / minute for 16 minutes. All particles less than about 0.4 microns in diameter as well as sodium pyrophosphate and excess water are discarded. All the particles of the centri material are recovered for later use. fugue having a diameter of between about 0.4 microns and 5 or 10 microns.



   Glacial acetic acid is added to a quantity of the 1% gelatin solution to adjust its pH to about 4. A 53 cm standard rectangular front face of a tube is then covered with a film. of this gelatin solution, covering the face with the solution and tilting and rotating it gently so that the solution flows over the entire surface. The gelatin-coated front face is then washed with water. The gelatin coating operation is then repeated to ensure that the front face is completely covered with gelatin. This does not, however, have the effect of covering the front face with a thicker layer of gelatin.



     The front face filled with gelatin is then covered with a water depth of about five centimeters. 5 grams of the centrifuge blue phosphor powder are suspended in 500 car of water and this solution is sprayed onto the surface of the water covering the front face.

   The solution is then allowed to settle for about 15 minutes and then most of the water is drained off. The remaining water is stirred and the.! left-'

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 phosphor cells by running the suspension over the entire
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 front face, by tilting and rotating gently a7,, e.w, When a layer of blue phosphor particles adhe "" re thus to the gelatin coated front face,

   we uve 11¯u there. phosphor layer so as to remove all loose particles and then bathed with 2% potassium silicate solution to increase Adhesion * The front face is placed vertically and allowed to dry at room temperature. local.



   The above operations are then repeated once
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 coating J. gelatin, phosphor and 4u silicate, so as to obtain, on the front face, a layer of particles of blue phosphor of the desired thickness.
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  A first release layer of vermiculite is then deposited on the layer of blue phosphor, in the following manner. Add 250 milliliters of extended commercial vermiculite (such as the Tonality Company of Trenton, New Jerney, which manufactures and sells under the Terra-Lite brand) to 250 cc of water, and the whole is mixed in a household mixer. "Waring" for thirty
 EMI17.4
 minutes * The mixture of vazaa, iaul, te and water is then centrifuged for ten minutes at 900 revolutions / minute. This gives a suspension of particles of vexn3, cuZite, the largest of which has a mass equivalent to that of a sphere of about one micron.

   In fact, however, the vermiculite particles are flakes, the largest dimension of which probably reaches around ten microns. This suspension is then made more concentrated by a further centrifugation at 1,800 rpm for one hour, in order to obtain a concentration of about 18 milligrams per cm3.



   The front face is then washed with a gela solution *
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 tine to 1 having a pH of about 4, and then rewashed at 1 "* tn as before. The front face is then covered with the vermiculite slurry and rotated at about 150 blasts / minute. so as to obtain a uniform height of the vermicult suspension above the surface. After 15 minutes, oh remove

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 EMI18.1
 the vermleulite suspension: l1te and the face is washed with water in order to detach all the particles of vermleulite which do not adhere perfectly to the gelatin film.

   Some vel'ln1cul1 particles, however, still adhere to the gelatin film covering the layer of blue phosphor. These washes are repeated at
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 gelatin solution, 1 water, worm slurry and water so as to obtain five applications of vemieulite particles giving, in total, a layer of worm weighing approximately . ron 0.17 milligrams per cm.



   Next, a layer of phosphor with green emission of zinc orthosilicate is deposited on the first separation layer.
 EMI18.3
 -active to manganese (as used in the current color kinescope 21CYP22), in the following manner 25 grams of green phosphor are added to x0 emm of water, * and the whole is ground for 74 hours in a ball mill * It is then left to deposit for 48 hours and the upper three quarters of the suspension are
 EMI18.4
 separated for later use. A suspension of green phosphor particles is thus obtained, the size of which does not exceed approximately half a micron.



   The front face is then washed with a gela solution *
 EMI18.5
 0 # 1% $ tine followed by washing with water to remove all excess gelatin, leaving only a thin film of gelatin. The front face is then dried so as to make the gelatin set, it is washed again with water and the front face is rotated, in order to wring out the excess water. The front face is then covered with the suspension of lumino phore green and stir by rotation in the same way as for the vermiculite layer,

     as described above. The excess green phosphor suspension is removed from the face and washed so as to remove non-adherent green phosphor particles.



   The washes are repeated with the gelatin solution, with water, with the suspension of green phosphor and with water, so as to make six applications of particles of green phosphor giving, -au

 <Desc / Clms Page number 19>

 
 EMI19.1
 total one coat weighing about 0.29 milligrams per C1A. 1.8 green phosphor layer is then washed with 2% potassium silicate sol.5cr and dried.



   A second layer 1 of separation is then applied by
 EMI19.2
 vemculi te to the layer of green phosphor, the same way that the first release layer was applied on the layer of
 EMI19.3
 Blue phosphor, except that a 0.1% solution of, é1 ...... tin is used here.

   As before, three applications of gelatin and varmulite particles are made, so as to obtain a separating layer having a weight of about 0.14 milligrams per.
 EMI19.4
 ci After the last application of particles of vex.ou7.its ,, the surface is 1.:1 1e -with a 2% potassium silicate solution ¯ # i ### - = ¯ "A layer of emission phosphor
 EMI19.5
 z1nc-magnes1u silicate red:

  u-cadmiUlU active with manganese on
 EMI19.6
 the second separating layer, as follows: 4 n mixture X3 * to 3 grams of phosphor rises to 273 water horn, the whole being ground for 70 hours in a ball mill. This mixture of water and phosphor is then left to settle for 96 hours and the upper three quarters are recovered for further use.
 EMI19.7
 tarieur. A suspension of red phosphor particles is thus obtained, the size of which does not exceed about half a micron. Six applications of gelatin and red phosphor are made on the second separation layer in Term1 (lUl: 1te, of The same way as for the green phosphor layer, we obtain a layer of about bzz milligram per caT.

   The red phosphor layer is then washed with a solution of potassium silicate. sium at 2% * The front side is then drained and se'Thee with the teatpe-! erasure of the premises.
 EMI19.8
 



  The front side bearing the superimposed layers of lwn1no-. blue, green and red phores are finally .s.uraiisa according to known techniques. A film of nitrocellulose is deposited on the layer of red phosphor by flotation on a water bath and
 EMI19.9
 then evacuates the water from below * It is then deposited by 'evaporation

 <Desc / Clms Page number 20>

 a layer of aluminum over the nitrocellulose film. The face ! Before completed is then shown with the other elements so as to constitute a cathode ray tube which is subjected to opera-! Usual cooking, draining and other tions well known in the industry.



    Film-coated particles.



   To obtain a single phosphor layer, such as layer 40 of Figure 2, by the method using film-coated particles *, an adsorbent coating having attraction for the phosphor is first applied to each phosphor particle. support surface, the front face 14 for example. The phosphor particles which are to be coated with film can be bathed in a solution of gelatin in said water. The gelatin solution can be similar to that used for the coating deposition of particles by the film coated carrier method.

   The phosphor particles are stirred in the gelatin solution for a short period of time, are then removed from the gelatin solution and washed thoroughly to remove any loose gelatin. In this way, each particle taken separately is coated with a thin film of gelatin.



   The gelatin coated phosphor particles can then be deposited on a support surface such as the front face 14, by first suspending the coated phosphor particles in water and then washing the front face 14 with this suspension. . Since the gelatin film covering the particles is adsorbent, the coated particles are attracted and adsorbed by the support surface to form a layer the thickness of a single particle. The coated particles are washed thoroughly, as above, in order to prevent excess loose gelatin from preventing subsequent deposition of the suspension.

   If this were not so, both the particles and the support surface would be covered with a gelatin film, which would prevent good attraction by adsorption.



   An example of the deposition of a layer formed of particles

 <Desc / Clms Page number 21>

 
 EMI21.1
 coated is given below. The pH of a solution of 11atine in water is adjusted to z to 4 by adding glacial acetic acid *! Its particles of phosphor to be coated with a film are introduced into a container with the gelatin solution, and stirred for 10 to 15 minutes. The suspension of phosphor particles is then allowed to settle in the gelatin solution, if particles are large enough. If the particles are too
 EMI21.2
 small to settle, the suspension is centrifuged.

   The excess gelatin solution is thus discharged. We then completely lare them? remaining particles by stirring the particles in four or five
 EMI21.3
 different amounts of wash water. The coated particles are shown to be free from loose gelatin by testing samples to determine whether the particles, suspended in clean water, can be adsorbed by a clean support surface.



   Each washing of the coated particles is carried out by
 EMI21.4
 suspending the particles in a quantity of water so as to obtain a concentration of about 50 milligrams of coated parts per cm3 of water. When a test kills one of these suspensions which indicates good adsorption, this suspension is applied to a support surface using the process of adsorption of the film coated particles! V., 1 (, s dea processes
Since a phosphor layer can consist of several sublayers of phosphor particles, it becomes inferior *!
 EMI21.5
 However, in order to obtain a layer of phosphor of relatively regular thickness, to produce sub-layers of a roofly regular thickness.

   If the phosphor particles constituting the sub-layers have very variable particle sizes,
 EMI21.6
 a given sub-layer may have a relatively t18i ... gular thickness. If a thick part, for example made up of a relatively large particle, of a sub-layer could cover exactly a part of a corresponding thickness of the neighboring sub-layer, we would obtain a smoothing of the air from liàal4ho *

 <Desc / Clms Page number 22>

 resistant phore. While statistically the probability of this happening is low, this probability can be minimized by using phosphor particles whose dimensions vary relatively little.

   With regard to irregular layer thicknesses, the size range includes large particles as well as small colloidal particles, because the range of particle sizes is larger than the absolute particle sizes. of phosphor must be kept between limits as narrow as possible in practice * The Applicant has discovered that layers of particles of a very regular thickness are obtained when a significant part of the smallest particles is not smaller in size. .one-quarter the size of the largest particles * The technique of limiting the range of particle sizes applies both when the support is film coated and when the particles

  are coated with film.



   According to a variant of the process, it is possible to improve both the regularity of thickness of the phosphors and their non-porosity. This variant involves a change only in the operations of washing the support surface with the phosphor suspension.



   The support surface is first bathed with a first suspension containing phosphor particles of given dimensions. This operation is carried out in the usual manner as described above. The support can be coated with film, or the particles can be coated with it. After washing with the first suspension, the support surface is washed with a second suspension containing phosphor particles smaller than said given dimensions. Acid washing can be used to increase the adhesion of the phosphor particles of the second suspension.

   This second washing with the suspension of smaller particles serves to fill in the gaps left between the large particles previously deposited, which has the effect of reducing

 <Desc / Clms Page number 23>

 porosity and increase the thickness regularity of the sub-
 EMI23.1
 layer, As no Adsorbent material is applied to 2 .- su. naar support between the first and second pensions, the small particles only adhere.t where. a large particle has not already adhered. There are essentially no small particles which cover the large ones.



   The aforementioned preferred use of a narrow range of particle sizes can be adopted for the first and second suspensions, in case this alternative two-dimensional particle treatment is applied,
 EMI23.2
 LAYERS OF PARTIMUµ 3fflROB ± ffg u TIMES.



  The screens which have been described so far are of the type
 EMI23.3
 xontlnu, that is to say consisting of a layer of phosphor covering without interruption the entire support had from the front face, 'In the case of multi-layered screens used in cathode ray tubes of the type at penetration, we superimpose several
 EMI23.4
 4th tan coats.

   However, instead of making multi-layered screens in this way, they cannot be made according to! other characteristics of 1- * Inv = tione by first coating basic particles (serving as nuclei), for example small
 EMI23.5
 glass beads or particles of 1.n3aacaphorus, separating layers and other phosphor layers to prevent depositing these multi-coated particles on the support in a continuous layer * Such screens, including phosphor layers are superimposed on each particle in particular, are preferable, from certain points of view,

   to multi-coated screens ** Such
 EMI23.6
 screens can be applied to multi-coated particle screens.



  The single screens of the penetrating typo kineseopes as described herein, whether of the continuous type OR of the coated particle type:., Can be considered / to consist of *
 EMI23.7
 a multiplicity of fragmentary surfaces of superimposed phosphor layers. In the case of coated particle screens, such a fragmentary surface may consist of one or more

 <Desc / Clms Page number 24>

 multi-coated particles.



     FIG. 5 represents a form of luminescent material using glass beads as a core on the various phosphor layers with which they are coated. The beads correspond to the support surface of the screens described above.



  The beads used may, for example, have a diameter of about 40 nacrons. For example, in Figure 5, a multi-coated particle consists of a glass bead 70 carrying, in the order cited a layer of a first phosphor 71, a first non-luminescent release layer 72, a layer of a second phosphor 73, a second non-luminescent release layer 74 and a layer of a third phosphor 75. The three phosphor layers each emit light of a different color from the others.

   An elementary screen with several layers is therefore formed on each bead. If desired, a third luminescent layer 76 can cover the outer phosphor layer 75 so as to protect its particles during the following handling and processing operations. mounting ¯ the screen.



     Instead of using a non-luminescent glass bead as the core and support surface for the different phosphor layers, a single phosphor particle can be used as the core. In this case, the core phosphor particle not only serves as a support surface, but is also chosen so as to be able to constitute the corresponding first phosphor layer. dant to layer 71 of Figure 5. This is shown in Figure 6.



   FIG. 6 shows a multi-coated phosphor particle comprising a particle 80 of a first phosphor coated, in the order cited: with a first layer of non-luminescent separator 81, with a layer 82 of non-luminescent separator. a second phosphor, a second non-luminescent release layer 83, a layer 84, a third phosphor, and a third non-luminescent layer 85 serving as a protective coating. The size of the particle 80 may, for example,

   be between 9 and 40 microns *

 <Desc / Clms Page number 25>

 Each of the three phosphors emits a different color
 EMI25.1
 Figure 7 shows a luminescent screen with .t, 14ht layers constructed by means of the phosphor particles with multiple coatings of figure 6. The small dimension of the figures does not allow to represent the different coatings of the particles that
 EMI25.2
 schematically. 1-The same general type of screen can be obtained - the glass beads coated with several phosphors of the figure The screen consists of a layer 91 of particles of
 EMI25.3
 Coated phosphor deposited on a support 92, by etëëplë the fc4 before a cathode ray tube.

   By way of example, the layer 91 shown has in substance the thickness of two particles **
 EMI25.4
 By having a screen thickness of two or more party croie1! with several coatings, the risk of luminescent dots on the screen is reduced * Each particle with several coatings Made up of
 EMI25.5
 in fact a tiny screen has several layers complete in IUââtà4 and forming an intimate fragment of the entire screen ,,
The coated particles are covered with a film 93 of heat decomposable organic material.
 EMI25.6
 for example, nitrocellulose or methylatht:

  .4'td deposits by evaporation a layer of aluminum 94 OR% - 34 9t ,,, r j4y, The film 93 is. then removed by dvàporatich during It it sound and evacuation of the tube. The operations of applying heat-decomposable film 93 and ilualniua 94 film may be similar to those used for tabildatlon of other kinds of cathode ray tubes *
 EMI25.7
 The multiple coatings * of glass crystals 69 or to the coated phosphor particles can be applied by following the general steps of the previously described methods. This means that coatings can consist of layers of particles
 EMI25.8
 applied by the principle of superficial adsorption # * aymt toim course to protective colloids to obtain the phenomenon d) tdeorption.

   In addition, the coating layers applied by t, 1 'on the core particles can be applied either by the

 <Desc / Clms Page number 26>

 The method using a film coated carrier (core particle) or the method uses film coated particles.



   Suspensions of phosphor particles and release material should contain particles significantly smaller than glass beads 70 or core phosphor particles 80. Preferably, the suspensions contain phosphor and release particles. colloidal dimensions, while glass beads or core phosphor particles are approximately 40 microns in size.



   The coating operations are essentially the same for the glass beads 70 and for the core phosphor particles 80. The only difference is that the glass beads 70 receive a first phosphor coating which is unnecessary when using particles. phosphor even as cores and as support surfaces for the various coating layers.



  The operations for applying the coatings are in substance the same as when depositing continuous layers directly on a front face, except that the adsorption operations, in the case of particles, are carried out in a container which is not the bulb of the cathode ray tube used as the tint product.



     As an example of the manufacture of a multi-coated partial screen, a detailed description of the manufacture of the coated phosphor particles of Figure 8 is given below. Although the invention is not limited to any determined order of application of the various phosphor layers, for ease of explanation, a structure will be described below consisting of a core particle of blue emission phosphor on which a layer of green phosphor * and a layer of red emission phosphor is superimposed in the order cited.



   In the case of such an embodiment, the core particles of the basic blue phosphor are first introduced into a container and bathed in a particle adsorption liquid, for example a solution of. gelatin in water. The mixture is stirred so as to wash the particles with the liquid,

 <Desc / Clms Page number 27>

 the excess liquid is then allowed to settle and evaluated so as to leave an adsorbent film on the particles of blue light.

   The absorbent film is treated with lucid comm. above. The core particles with their film coating are then bathed or washed in water. The 111-water wash can be repeated several times.



   The first release layer is then deposited to remove the blue phosphor core particles by a similar washing process. A suitable non-luminescent material, for example colloids of silica or mica suspended in water, with the blue phosphor core particles coated with the adsorbent film, is introduced into the container. container so as to cover the various core particles with colloidal separating particles.We then leave to deposit and evacuate,

   excess separation slurry. The average blue phosphor particles are then washed in water. Other applications of release particles can be made at will to increase the thickness of the release layer. This is done by bathing the blue phosphor particles again successively in the adsorbent liquid, in water, in: The separation slurry and in water.

   As explained above, it is possible to have recourse either to several alternating washes with acid and the phosphor suspension or to the simplified method of treating the phosphor suspension with acid in order to obtain phosphor deposits in us. dense layer.



   When the first release layer is of the desired thickness, the green phosphor coating layer is applied over the first release layer of the blue phosphor core particles. This is done in the same way as that used to apply the first release layer. The blue phosphor core particles were subjected to a series of shaking washes in baths of adsorbent liquid, water, a suspension of colloidal sized green phosphor particles and water.

   We

 <Desc / Clms Page number 28>

   makes a sufficient number of applications of green phosphor particles (and as desired, the above processes can be used to give dense undercoats) to obtain a green phosphor layer of the desired thickness. @
The green phosphor layer of the second separation layer is covered in the same manner as for the first separation layer. A layer of red phosphor is then deposited on each coated particle.

   The second layer of separator is covered with the red phosphor layer in the same way as the green phosphor layer was deposited on the first layer of separations. After complete application of the red phosphor particles, washing is carried out. Water the coated blue phosphor core particles * to remove any colloidal lumino particles. non-adherent red phore. This last wash can be repeated several times, if desired.



     After final application of the red phosphor, the coated particles can be given a final treatment to achieve good adhesion of the phosphor particle layers. This can be done by washing the coated particles with a formaldehyde solution, d chromium or potassium silicate alum, as above. Alternatively, the red phosphor layer can be covered with a final coating of a non-luminescent release material. The hardened gelatin layer or non-luminescent release material serves to prevent washout of the red phosphor layer upon application of the coated particles to the front side of the tube.

   Operations of enhancing the adhesion of the phosphor particles, as described above, may optionally be employed at various stages of the application of the coatings to the core particles.



   After the last coating, the multi-coated particles are deposited on the front face of a cathode ray tube, which can be done in various ways. For example, the

 <Desc / Clms Page number 29>

 
 EMI29.1
 deposition can be carried out by wine diluting or a pr <t <) G. sedimentation. The layer of particles & several coatings can then be covered with a film and be û \ 11drt; L 114, ¯or.
 EMI29.2
 represents in figure 7.
 EMI29.3
 



  The multi-coated particles can be stored either wet or dry until such time as
 EMI29.4
 Apply them to the front side of a tube. If the particles are
 EMI29.5
 stored wet, they are simply left in a part of Vêàà; from the last wash. If they are stored Dry, OR evacuates I AU and the particles are dried at the temperature of local 1 "emoe-pibd 'An example of preparation of imâihbpâbeï particles
 EMI29.6
 several coatings is described below *
 EMI29.7
 Lino .activa at .iJ.1.artÜ 'sulfide (sold under the trademark P7) is used as the blue-emitting phosphor * and the core particles on which the following douenës do: U. \ idII1i.f' are used. be applied. This blue phosphor. iâ an iëiâb of dimensions of about to 20 microns.

   In 1 & Vë ed dmâ * ëï hrt.,! of water and let settle. The water is removed from 1 ... 1 dt cuti foreign matter in suspension, from t.a90! 1 to ne 1a: tUtf l | iii Ui "tk .. desired cells having a dimension of $ d mioron <We then place these 50 graded of partial! di iteU1 blue nophore in a flask. with a cartaine quantity 4 * a '\' iu .. tion at 0; 1% gelatin in water, having a pS of 141 to tat41Mic. is Stir for 10 to 15 minutes, and then leave to stand for about 5 minutes, then pour in the solution ..41111: ± 111 leaving the phosphor particles bled together in a gelatin film.

   The particles are then washed three times i * Mb with their platinum film, in K fiâtitort,
 EMI29.8
 in order to remove non-adherent gelatin
 EMI29.9
 We then apply -a first ** Uëe tif ..t + jUIliI 46 .111cD 150 :): 0 'the particles ;; i.aux de luatinophart 11ft, thence "bib
 EMI29.10
 next.
 EMI29.11
 



  A suspension of silica d011illi is poured into the flask containing bed of their film.

 <Desc / Clms Page number 30>

 water the pH of which has been adjusted to 4 using SI * - cial acetic acid. The suspension of silica in water has a concentration of 33 milligrams of silica per cm3 of water. The container is placed for
10 to 15 minutes, ..and then left to deposit for about 5 minutes.

   The aqueous silica suspension is discharged and the blue particles are washed three times so as to remove any non-adherent silica. A deposit of colloidal silica particles remains adherent to the blue phosphor particles covered with their gelatin film. The successive washings of the blue phosphor particles in a gelatin solution, in water, in the silica suspension and in water are repeated six times so as to obtain a layer of colloidal silica particles of about 0 , 2 milligrams per cm2.



   The blue particles coated with silica are then covered with a layer of phosphor with green emission consisting of sine orthosilicate activated with magnesium, as follows **
A suspension of green phosphor, as described for the manufacture of continuous layer screens, is first centrifuged so as to leave suspended particles having a maximum size of 0.8 microns.

   What remains in suspension is repaid and is further centrifuged so as to obtain a concentration of about 20 milligrams of phosphor per car of water. Six applications of green phosphor particles are then made to the blue silica-coated particles, repeating a series of broad ones with the gelatin solution, water, green phosphor suspension and water, in a manner similar to what was done on z; deposition of the first silica separation layer. A layer of green phosphor particles is thus obtained having a weight of about 0.3 milligram per cm.



     A second separating layer of colloidal silica is then deposited on the green phosphor layer * The process is generally the same as for the deposition of the first separating silica layer on the blue core particles, except that the pH of the silica suspension in water is adjusted to and eight applications are made to obtain a layer of

 <Desc / Clms Page number 31>

 colloidal silica of about 0.2 milligram per cm2.



     A layer of red phosphor is then deposited on the second silica separation layer, using a zinc-magnesium-cadmium silicate suspension activated with manganese, as described for the manufacture of continuous layer screens.



   The core particles are subjected to successive washings by introducing into the flask, stirring and then removing a 0.1% gelatin solution having a pH of 4, water, and the suspension of red phosphor. and water. Six applications of red phosphor were made to obtain a coating of about 0.4 milligrams per cm 2.



     As a final coating, the core particles of blue phosphor are washed in a gelatin solution and then in a suspension of colloidal silica, to obtain a thin outer layer of silica.



   Multi-coated particle screens have many advantages. For example, the preparation of multiple layers of phosphors should not be done in the factory where the tubes are manufactured. As a result, the manufacture of the tubes in itself is greatly simplified. The coated particles can be made in advance and a quantity of these particles can be kept in stock for the manufacture of the tubes.

   Therefore! since the manufacture of the phosphor layers is separate from the manufacture of the tubes, a shutdown in one of the factories does not necessarily affect the other factory * In addition, these independent production * can be done simultaneously, which shortens the total manufacturing time of a finished tube. Furthermore, if desired, means existing in the manufacture of white and black cathode ray tubes can be used for the deposition of the coated particles.



   Another advantage of the multi-coated particle screens is the ease of obtaining uniform color emissions during tube operation. It is easy to make multi-coated particles having good evenness.

 <Desc / Clms Page number 32>

 thickness of the phosphor layers of one coated particle 1 the other. This regularity of thickness is communicated to the entire surface of the screen which is composed of particles with several coatings.



   In the case of the phosphor layers prepared by this process the particles are essentially in contact with each other * There are no significant amounts of binder between the particles * The adsorbent films are extremely thin, even in comparison with the phosphor particles colloidal, and constitute a negligible percentage of the total mass of the phosphor layer.



   Laboratory examination of an undercoat of colloidal phosphor particles and an adsorbent gelatin film shows that the thickness of the gelatin film constitutes a very small fraction by weight of the phosphor undercoat. The adsorbent films are believed to be less than about 100 angetroms thick.



   FIG. 8 represents, in whole or in part, a layer of phosphor formed by dense superimposed sub-layers.



    Each having the thickness of a particle. The phosphor layer can, for example, constitute all or part of the layer 40 of Figure 2 or of the layer 54 of Figure 3. As Figure 8 shows, the layer consists of three alternate adsorbent gelatin films. with three dense sublayers of phosphor particles of the same phosphor material which were deposited by the film-coated carrier method, using alternate washes of acid and the phosphor suspension.



   In constituting the layer of FIG. 8, an absorbent gelatin film A is first formed on the support 14, the latter being shown in FIG. 5 in the form of a front tube face. The adsorbent film A is then bathed in a suspension of phosphor particles, resulting in phosphor particles @ 1 adhering thereto. An acid wash followed by a second wash with the phosphor suspension as described above

 <Desc / Clms Page number 33>

 
 EMI33.1
 As a consequence, particles of J.UJn.1nophorè -a adhere to the gelatin film A.

   Similarly, particles of lumino-
 EMI33.2
 phore a3 are deposited on the gelatin film A by a three dome washing with the phosphor suspension, followed by a second
 EMI33.3
 acid wash. These alternating washes with lucid and with the phosphor suspension are repeated until in substance no additional phosphor material is deposited. This gives a relatively dense sub-layer having the thickness of a particle;
 EMI33.4
 composed of particles of phosphor .1-a3 'etc ... reetsuftant # in substance completely the gelatin film Mdsorbxfte At The gelatin film c & d.lSotbl1'ite is deposited in a similar manner:

  D on the. first sub-layer of phosphor particles a ,, "" '' '' 2 .- .. ,, 'such that a second sub-layer having the thickness of a particle and composed of the particles of phosphor b, , "'b2"' b3 adhered to 1'.1.



  Adsorbent swell B. These different operations 6, bftt to tW'tIl & \ 1 repeated! "For depostt1" lJ {p., UiëUie of gelatin aé110tt'Nt.11h 'b 4t. \ 8 third layer of phosphor particles next to2w * j # If one wishes to obtain a thicker phosphor layer 'titi. ptut overlay additional dense sublayers to the ssoeA c1-c2-0 "The evenness of thickness and degree of wttsnt # - particles of a layer of a given thickness can 't1". expressed as a function of the acceleration voltage or dc 14. 1 V'1tdl '.. at which the bombardment electrons begin to completely cross the layer under consideration.

   This speed can #rt t ', 11i as the threshold voltage of penetration speed *
Generally speaking, the way in which electrons can pass through a given shell depends on the mass thickness of the shell (i.e. the product of the average density-mass and the average thickness of a relatively large surface portion * of the layer). your density-mass (called hereafter simply density) of a layer is determined by the nature of the layer and by its settlement (the ratio between the volume of material and the volume of
 EMI33.5
 count: aënt).

   A layer without voids between particles can be said

 <Desc / Clms Page number 34>

 perfectly packed. Such a layer can be obtained, for example, by solidifying a molten mass of the material under consideration. Perfectly packed layers which are further characterized by substantially perfect regularity of thickness may be called layers having a mass thickness of substantially perfect regularity. The evaporative deposited, light-reflecting ordinary aluminum layer, which is commonly used in cathode ray tubes, can be considered as an example of a layer having a mass thickness of a regularity of. perfect substance; the same is true of gold or aluminum leaves.



   Considering the average characteristics of relatively large surfaces of two layers, a weakly packed layer of irregular thickness resists the penetration of electrons in the same way or absorbs the same amount of energy from the electrons therein. penetrate, that a strongly packed layer and of regular thickness, if the two layers have led average mass thickness. It is not the same if we consider elementary fragments of the layer. In the present specification, an elementary fragment is understood to mean a surface portion of a layer having, over its entire surface, a perfectly uniform mass thickness. In particle layers, an elementary fragment has the same order of magnitude as a particle, or even less.

   In perfectly packed layers, like gold leaf, the size of an elementary fragment approaches molecular dimensions.



   The loosely packed layers have an irregular density, some elementary fragments having a density greater than. the mean density of the layer and some elementary fragments having a density lower than the mean density of the layer. Likewise, in the case of layers of irregular thickness, some elementary fragments have a thickness greater than the average, and others have a thickness less than the average.

   These two types of irregularity contribute, when they are present, to the irregularity.

 <Desc / Clms Page number 35>

 gularity of the mass thickness of a layer * That is to say that certain elementary fragments of the layer have a mass thickness greater than the average mass thickness of the layer, while certain elementary fragments have a mass thickness. than less than the average mass thickness of the jug. When an electron strikes a layer at the height of an elementary fragment of lesser mass thickness, it can cross entirely with a layer - whereas an electron with the same speed may not pass through a layer of the same average mass thickness but regular.

   As the thickness of a particulate layer is increased, both the absolute value of its penetration threshold voltage and the ratio of its penetration threshold voltage to that of a layer having the penetration are increased. same mass thickness but perfectly regular.



   This is so because the unevenness of the layer due to imperfect settlement is compensated, by making the layer thicker, by a statistical distribution of void -miter phosphor particles. However, to obtain satisfactory performance from a multi-layered luminescent screen used in penetrating type cathode ray tubes, the different phosphor layers must be relatively thin in order to be able to select colors with the minimum possible difference. between the tensions, the mass thickness had to be at the same time sufficiently regular to reduce to a minimum the color washings.

   Experience shows that such phosphor layers are preferably thin enough to have a penetration threshold voltage not exceeding approximately 10 kilovolts while having a sufficiently regular mass thickness so that their penetration threshold voltage is at less equal to half that of a layer of the same average mass thickness but perfectly regular.

   It is possible, with the methods of the present invention, to deposit layers of phosphor particles having only penetration threshold voltages of about 5 kilovolts for example, this voltage being however equal to both.

 <Desc / Clms Page number 36>

 third or three quarters of that of a layer having a perfectly regular mass thickness.

   If we compare phosphor layers having the same mean mass thickness of a given value, we see that while a layer having a perfectly regular mass thickness can have a penetration threshold voltage of about 8.8 kilovolts, a layer according to the invention can have a penetration threshold voltage of about 6 kilovolts, a layer of known type obtained by sedimentation being able to have a penetration threshold voltage barely slightly above zero kilovolts.



   We have produced and successively put into use polychrome luminescent screens of the continuous layer type and of the particle type with several coatings, as well as monochrome screens of the continuous layer type. Both the coated particle process and the coated support process have been employed in the manufacture of such screens.

   In all cases, the Applicant has obtained screens exhibiting satisfactory adhesion, functioning satisfactorily, in cathode ray tubes which have been successfully subjected to the conventional treatments of the manufacture of tubes such as baking, sealing. - casing and aging, and having a good operation and a satisfactory light output.



   Although the invention has been described in terms of particular embodiments and examples, it goes without saying that various changes or modifications can be made to it without departing from the scope.



   Unless indicated! ' On the contrary, it goes without saying that the different stages of the process need not necessarily occur in the order cited.


    

Claims (1)

CLAIMS 1.- Luminescent screen composed of a support and a layer of phosphor particles, characterized in that: The said layer consists of several sublayers of these phosphor particles *, each sublayer having the single particle thickness * EMI37.1 2.- Luminescent screen 'following 3 # tevend1ce. 'tien jt. oa.c, j. triod in that the support is a particle of phosphor of sedimentary dimension and the particles of the layer are colloidal * lt..m1nophot "COr1.t1 'tIUIi'G EMI37.2 3. A luminescent screen according to claim 1, where the support is a 4motant phosphor particle of .la. light of one color and the layer is phosphor. emitting light of a different color. EMI37.3 4 - Luminescent screen according to claim Ij, '<Mtâ <! T "terized in that it comprises several superimposed layers of phosphors emitting lights of different colors. @ EMI37.4 ¯¯¯Ecan-Lu following r.ilter'1d1Óitn 3 .; oâtto-b 't & r1sé in that it comprises several superimposed layers of lmino * j phores emitting lights of d: 1terentate colors, \ i minus one of the layers comprising particles of phosphor and being EMI37.5 such that the velocity voltage at which a barely perceptible percentaëe of all the bombarding electrons begins to EMI37.6 completely crossing said layer is not $ \ iPet: 1éUtt \ 'on .. ron 5 kilovolts and is at least equal to about two-thirds of the velocity voltage at which a barely perceptible percentage of EMI37.7 the set of bombardment electrons begins at tfA².r1 "in '* t1èremen.t a layer whose mass thickness is the same J but is in substance perfectly uniform * 6. A luminescent screen according to claim 1, charac- EMI37.8 terized in that it has several * superimposed * layers of 1 \ 1- j adnophores emitting lights of different colors * One * of the layers consisting of phosphor particles of dimension <Desc / Clms Page number 38> sedimentary, another layer consisting of lumino, phore colloldales particles another layer having a thickness of less than about one micron. 7. Luminescent Earan according to claim 1, characterized in that it comprises, in the order cited, a support surface, a first phosphor layer having the thickness of several particles and consisting of cohesive phosphor particles, a first non-luminescent release layer, a second phosphor layer, a second non-luminescent release layer, and a third phosphor layer, each of the second and third phosphor layers consisting of colloidal phosphor particles and having a relatively thin thickness while being non-porous compared to the first phosphor layer. 8. A luminescent screen according to claim 1, characterized in that the layer is formed of a large number of coated cores, and the sublayers are coatings superimposed on the core particles. 9. A luminescent screen according to claim 1, characterized in that the support is a core particle of a first phosphor producing luminescence of a first color and carrying the following superimposed layers, cited in order: a first layer of non-luminescent colloidal particles, a layer of colloidal particles of a second phosphor producing luminescence of a second color, a second layer of non-luminescent colloidal particles and a layer of colloidal particles of a third phosphor producing luminescence of a third color 10.- A method of manufacturing a luminescent screen according to claim 1 comprising a support covered with a layer of phosphor particles, characterized in that the surface of the support is covered with an adhesive material, the layers are deposited. phosphor particles on the adhesive material, removing excess phosphor particles not adhering to the adhesive material, and we <Desc / Clms Page number 39> repeats the cycle of operations to obtain a layer of phosphor particles of the desired thickness. @ @ @ 11. - A method of manufacturing a luminescent screen according to claim 10, characterized in that a support surface is covered with a quantity of liquid forming a film of adsorption of the particles, the excess is removed of liquid in order to leave an adsorbent film on the surface, the film-coated surface is covered with a liquid suspension containing the phosphor particles, and the excess suspension is removed after a period of time shorter than that necessary for a useful number of phosphor particles to precipitate from the suspension. 12. A method of manufacturing a luminescent screen according to claim 10, characterized in that the support is bathed in an amount of liquid forming an adsorbent film so as to coat the surface of the support with. a film, the surface coated with the film is bathed in a liquid suspension containing particles of phosphor so as to deposit particles of phosphor on the film, and the film-coated surface is then washed alternately with an acid solution and a liquid suspension of phosphor particles a desired number of times to obtain a layer of a desired particle density on the support surface. manufacture of a light screen according to claim 10, characterized in that the surface of the support is coated with a film of an acid-treated protective colloid, the surface coated with the film is washed with water, washing the film-coated surface with a liquid suspension by stirring. containing phosphor particles so as to deposit phosphor particles on the film, the film-coated surface is washed with water, and the above operations are repeated so as to obtain a layer of the phosphor particles of desired thickness. 14.- Method of manufacturing a following light screen <Desc / Clms Page number 40> Claim 10 characterized in that a large number of core particles of a first luminescent phosphor producing luminescence of a first color are coated with films of a material selected from the group consisting of gelatin and alcohol. polyvinyl, the film-coated core particles are washed with a liquid suspension of particles of a second phosphor producing luminescence of a second color so as to deposit a layer of these particles of the second phosphor on the core particles, the size of the particles of the second phosphor being notably smaller than that of the core particles, the liquid suspension having a pH of about 5, and said coated core particles are then deposited in a layer on a support surface. 15.- A method of manufacturing a luminescent screen according to claim 10, characterized in that a quantity of core particles is washed with a suspension of protective colloids in order to coat the core particles with a first adsorbent film, the core particles are then washed with a liquid suspension containing colloidal particles of a first phosphor so as to cover the first adsorbent film with a layer of this first phosphor, then the base particles are washed with the first phosphor. suspension of protective colloids In order to cover the layer of colloidal particles of the first phosphor with a second adsorbent film, the core particles are washed with a liquid suspension containing non-luminescent colloidal particles so that a layer of these covers the second adsorbent film, the core particles are then washed with the suspension of protective colloids - in order to apply a third adsorbent film on the layer of luminescent lion particles, and the core particles are then washed with a liquid suspension containing colloidal particles of a second phosphor so that a layer thereof covers the third adsorbent film, and then deposited the coated particles thus obtained in a layer on a support. EMI40.1 'ca raa' l.v'e.cccx4f 'r aai''ri- <Desc / Clms Page number 41> se in that the core particles are lumino- phore particles of a larger size than the colloidal particles and in that the core phosphor particles produce luminescence of a different color from those of the colloidal particles of the first and second. second phosphors. 17.- Process of manufacturing a screen. luminous according to Claim 10, characterized in that a quantity of core particles of a first phosphor of given dimensions is bathed in an acid solution of protective colloids so as to cover the core particles with a first film of \ this protective colloid, the core particles are then bathed in water, the core particles are then bathed in a liquid suspension containing non-luminescent particles whose dimensions are many times greater than the said given dimensions, the core particles are then bathed in water, we ; then bathes the core particles in an acid solution of. protective colloid so as to cover the core particles with a second film of this protective colloid, the core particles are bathed in water, the core particles are bathed, with stirring, in an acidic liquid suspension containing. particles of a second phosphor whose dimensions are many times smaller than said given dimensions, the core particles are then bathed in water, the core particles are then bathed in an acidulated solution of protective colloid so as to cover the core particles with a third film of this protective colloid, the core particles are then bathed in water, the core particles are then bathed in a liquid suspension containing non-luminescent particles many times smaller than the said given dimensions, the core particles are then bathed in water, the core particles are then bathed in an acidulated solution of protective colloid so as to cover the core particles with a fourth film of this protective colloid, the core particles are then bathed in water, then bathed, shake it, <Desc / Clms Page number 42> the core particles in an acidulated liquid solution containing particles of a third phosphor whose dimensions are many times smaller than the said given dimensions, the core particles are then bathed in water, - then the core particles in a layer on a support, the layer is aluminized, and the aluminized layer is subjected to baking. @ 18.- A method of manufacturing a luminescent screen according to claim 17, characterized in that the protective colloid is a material selected from a group comprising gelatin and polyvinyl alcohol, and in that each -acidulated suspension of phosphor has a pH of around 5.