US2745773A

US2745773A - Apparatus and method for forming juxtaposed as well as superimposed coatings

Info

Publication number: US2745773A
Application number: US344498A
Authority: US
Inventors: Paul K Weimer
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1953-03-25
Filing date: 1953-03-25
Publication date: 1956-05-15
Anticipated expiration: 1973-05-15

Description

May 15, 1956 P. K. WEIMER 2,745,773

APPARATUS AND METHOD FOR FORMING JUXTAPOSED AS WELL AS SUPERIMPOSED commas 5 Sheets-Sheet 1 Filed March 25, 1956 a a a j M M M WW 0F 3 a r 0 u 1 3 s n.

4 a 3 F y INVENIOR. Pau/ K. We/mer ATTORNEY May 15, 1956 P K. WEIMER 2,745,773

APPARATUS AND METHOD FOR FORMING JUXTAPOSED AS WELL AS SUPERIMPOSED COATINGS Filed March 25, 1953 5 Sheets-Sheet 2 mumuum J/ I INVENTOR.

Pau/ Kv We/mer 11 TTOR NE 1 May 15, 1956 R WEEMER 2,745,773

APPARATUS AND METHOD FOR FORMING JUXTAPOSED AS WELL AS SUPERIMPOSED COATINGS Filed March 25, 1953 5 Sheets-Sheet 3 INIE .\'TOR.

Pau/ K. We/m 9/ TTORNEY P. K. WEIMER May 15, 1956 APPARATUS AND METHOD FOR FORMING JUXTAPOSED AS WELL AS SUPERIMPOSED COATINGS 5 Sheets-Sheet 4 Filed March 25, 1953 M e W k m P y 5, 1956 P. K. WEIMER 2,745,773

APPARATUS AND METHOD FOR FORMING JUXTAPOSED As WELL AS SUPERIMPOSED COATINGS Filed March 25, 1953 5 Sheets-Sheet 5 INVENTOR.

Pau/ K. We/mer Baal/1 United States Patent APPARATUS AND METHGD FOR FBRMING 3U;- TAPOSED AS WELL AS SUPERIMPOSED CGAT- INGS Paul K. Weimer, Princeton, N. 3., assignor to Radio Cor poration of America, a corporation oi Delaware Application March 25, 1953, Serial No. 344,498

18 Claims. (Cl. 117-212) This invention relates to a method and apparatus for making fine, juxtaposed lines or strips of materials particularly useful in making ray sensitive targets for cathode ray color television tubes. More particularly this invention relates to a method and apparatus for evaporating materials to form targets having signal strips and/ or color filter strips especially useful in simultaneous color television pickup tubes.

The methods and apparatus heretofore proposed for making fine, juxtaposed strips which are extremely thin in cross section have required repeated handling of the work by highly skilled operators as well as being time consuming without attaining the high degree of precision desired.

it is, therefore, a principal object of my invention to provide an improved method and apparatus for making fine juxtaposed as well as superimposed strips which are extremely thin.

Another object is to provide a highly advantageous method and apparatus for making an article such as a target for a color television pickup tube and having juxtaposed strips made up of one or more layers of extremely thin precisely determined cross sectional thickness.

Yet another object is to provide an improved method for making color filter strips each composed of a plurality of layers and having a desired eificiency.

Still another object is the provision of apparatus for readily making narrow, thin strips in accurate juxtaposed relation which strips are formed in a controlled atmosphere and each may differ from the strip adjacent thereto.

A further object is to provide apparatus which facilitates the making of narrow, thin strips in accurate juxtaposed relation whereby adjacent strips are formed successively without requiring removal of the work from the apparatus or manual handling thereof.

In accordance with my invention 1 provide a movable workpiece holder which permits ready precise location of the workpiece on one side of a fixed mask having alined apertures. The holder is readily displaced in a given direction to expose difierent portions of the workpiece to the apertures of the fixed mask. On the other side of the fixed mask, a movable mask is mounted which determines the length of the apertures in the fixed mask in a transverse direction to the aforementioned given direction as well as effectively shifting the apertures of the fixed mask in the transverse direction with respect to the workpiece. A controlled atmosphere may be provided in a chamber in which the apparatus is mounted and the various movements of the work iece and movable mask are effected by controls mounted externally of the chamber; thus eliminating the necessity for disturbing the atmosphere of the chamber. Various materials to be evaporated onto the surface of the workpiece to form the strips are each located in the chamber so that the desired material and in the proper sequence may be evaporated through the masks onto the workpiece. The workpiece being transparent, the thickness of the various layers is accurately 2,745,773 Patented May 15, 1956 controlled by passing light through the workpiece and measuring the light transmitted.

Further objects as well as advantages of my invention will be apparent from the following description and the accompanying drawing in which Figure l is an elevational view, partly in section of apparatus constructed in accordance with my invention;

Figure 2 is a plan View, broken away and on an exaggerated scale, of one type of article particularly suited for manufacture in accordance with my invention;

Figure 3 is a sectional view along the line 3-3 of Figure 2 on an enlarged scale;

Figure 4 is an enlarged fragmentary sectional view of one of the color filter strips not drawn to scale and showing the various layers;

Figure 5 is a perspective view, partially broken away for convenience of illustration, of a jig constructed in accordance with my invention;

Figure 6 is a sectional view along the line 6-6 of Figure 5;

Figure 7 is an exploded view of various parts of the jig and a workpiece;

Figure 8 is a fragmentary sectional view along the line fi$ of Figure 5;

Figure 9 is a fragmentary sectional view of another portion of the jig;

Figure 10 is a sectional view of one type of mask; and

Figure 11 is a perspective view of another type of mask.

Referring now to the drawing and to Figure l in particular it is seen that the apparatus includes a jig 10 supported in abell 11 above an evaporator 12. The interior of bell i1 is connected, in the present instance, to a vacuum pump (not shown).

it may be well to state here that in the present illustrative disclosure, the apparatus is shown as employed for making one form of target for a color television pickup tube. While my invention finds particular applicability to this use, it is to be understood that the present disclosure is by way of exemplification only. In the present instance, the apparatus is constructed for making such targets which will presently be more fully described. it is, of course, obvious that the apparatus as well as the method to be described herein may be employed to make articles other than the type here described.

It is believed that my invention will be most readily understood by first referring to one form of target for a simultaneous color television pickup tube in connection with which my invention is particularly useful. Such a target is described in detail in my application, Serial No. 344,497, filed simultaneously herewith and assigned to the assignee of this application. Referring then to Figures 2, 3 and 4, target 20 is shown with the dimensions thereof grossly exaggerated to facilitate this description. Target 29 comprises a support or workpiece 21 of clear glass having three spaced conductive lines or bus bars 22 adjacent opposite ends thereof. Extending across the surface of workpiece 21 are a plurality of juxtaposed color filter strips 23. As will be more fully described the filters are of the interference type and may include filters for the primary colors red, green and blue. Color filter strips 23 are in practice quite narrow as for example about .002 inch wide. Strips 23 are shown in side by side abutting relation, however, as will be apparent, they may be readily made so as to be juxtaposed in close spaced apart relation. The color filters 23 of the same color are alined with respect to each other but ofiset longitudinally with respect to the filters of the other colors as shown.

Transparent conductive signal strips 24 are formed one on each of the filter strips 23. Signal strips 24 are each somewhat longer than filter strips 23 and are oflset with respect to each other as described in connection with the filter strips. When filter strips 23 are in abutting relation, as shown, signal strips 23 are somewhat narrower than the filter strips and, as for example, are .0015 inch wide. Signal strips 24 on the red filters are connected adjacent each end thereof to red bus oars 22 and thus form a set of red signal strips. Similarly, signal strips 24 on the green and blue filter strips are each connected respectively to the green and blue bus bars. It is apparent then that three mutually independent sets of signal strips each interlaced with the other are provided.

As most clearly shown in Figure 3, filter strips 23, which are of insulating material, serve to insulate signal strips 24 from the bus bars 22 of the other colors at the points Where the signal strips for one color cross the bus bars for another color. For example at the points where a red signal strip crosses over the blue and green has bars. When desired, additional material, such one of the materials forming filter strips 23, be previously applied at those crossover points, shown as a separate layer 23' for convenience of illustration, to provide added insulation. Where signal strips 24* make electrical connection to their respective bus bars an intermediate conductive layer or finger strip 25 may be formed (Figure 3) when additional capacitance is desired. Such finger strips are described in detail in the application Serial No. 344,616 of S. Gray filed simultaneously herewith and assigned to the assignee of this application.

Each of the color filter strips is made up of a number of successively superimposed layers. Red and blue filters are made from eleven successive layers of zinc sulfide and cryolite as shown in Figure 4. Similarly, successive superimposed layers of zinc selenide and cryolite ar ut ized, but only nine in number, to form green filters.

Referring now to Figures 5, 6 and 7, jig ll? is conveniently supported in bell 11 on platform 3% having an opening 31 formed therethrough. Fig ll comprises two major subassernblies which are readily disconnected and connected again in accurately alined relation. The base or mask subassembly includes fixed mask 32 and movable mask 33 mounted on base 34. The workpiece subassembly includes a supporting framework 69 having workpiece holder 61 movably mounted therein. Means for accurately locating workpiece holder 61 with respect to

masks

32 and 33 are provided.

On the upwardly presented surface of base 34-, a pair of oppositely disposed guide rails 28, 29 (Figure 5) form a guideway which movable mask 33 is slideably mounted. Means for accurately and adiustably positioning movable mask 33 are provided by means of which both a large and fine adiustment of movable mask 33 may be readily made. Movable mask 33 may be reciprocated in the guideway on base 34 by rotatably mounted arm 35, a finger portion 35 of which engages movable mask 33. in the present instance finger portion 35' conveniently extends into slot 36 formed in movable mask 33 adjacent to one end thereof. As shown in Figure 5, arm 35 is supported on and is rotatable with rod 37. As will be hereinafter more fully described, rod 37 is connected through a suitable seal and gear train to a control knob located externally of bell it thus permitting ready adjustment thereof without disturbing bell 11 or its contents. A precise, micrometer adjustment for movable mask 33 is provided in the form of rod 38 rotatably mounted in base 34. One end portion of rod 38 is threaded into base 34 as at 39 while a beveled gear 40 is mounted on the opposite end portion thereof. Rod 38 is rotatable with gear 40 which is in turn driven by bevel gear ll rotatable with and supported on rod 42. To permit relative movement of rod 33 with respect to gear 40, rod 38 is slideable in the hub of gear 43 and is keyed thereto by spline 43 (Figure 6). Stops in the form of

collars

44, 45 are mounted in spaced rela tion on rod 38 and are engaged by a downwardly extending projection or lug 46 on movable mask 33. Thus, the throw of arm 35 slides movable mask 33 in its guideway to position projection 46 either against stop 44 or stop Rotation of rod 38 permits selective positioning of mask 33 in either position as a result of the movement of

collar

44 or 45 as the case may be. in view of the sliding engagement of gear ll) with rod 33, resilient finger 47, conveniently mounted on platform 30, urges gear i li toward rod 33 and against drive gear 41.

Mounted on base 34 and positioned over movable 33 is fixed mask 32. Fixed mask 32 is shown in the form or a wire masking gril having a plurality of fine closely spaced wires roughly indicated at 4-3 and supported by two spaced

cylinders

49, 50. The wire liv d rray be of any suitable material. However, wire stretched under tension such as wire formed y of: 85% nickel and 15% chromium is particc'arly advantageous. The wire is wound on cylinders 59 in any convenient manner well known in the grid ing art. Cylinders 45, Eli, with wires 48 connected thereoctween, are each mounted on a frame 51 in spaced relation by bolts Bolts are in threaded engagemeet with the cylinders 49, 5d and are rotatably mounted in posts on frame 51. Thus, adjustment of bolts serves to draw the associated cylinder away from its posts and thereby tension and stretch wires 43. This serves to remove any kinks or bends remaining in the wires after their attachment to the cylinders. Since the spaces formed between the wires define narrow apertures through which materials are to be evaporated the emoval of such kinks and bends prevents the formation of uude red irregularities in the coatings formed on the workpiece.

it should be noted that the movement of movable 33 previously described permits the positioning of a esired portion thereof under the wire masking grill or fixed mask 32. Movable mask 33 serves to define the length of the apertures formed between the wires 43. This is accomplished by the relatively large movement thereof when projection 45 is moved from engage ment with stop 4% into engagement with stop 45. Movable mask 33 may be provided with such apertures as will facilitate the manufacture of the articles in any given instance. As shown in Figure 7, movable mask is provided with an aperture 54 used in forming filter strips 23 and slots 55 used in forming the conductive finger strips 25. Another movable mask having an aperture 54- (see Fig. 11), which, larger than aperture 54 in the direction of arrow 55, is used in forming signal strips 2 Furthermore, in either position of mask 33 rotation of rod 33 and the consequent movement of stops d4, 45 serves to displace either ape ture 54 or slots 55 with respect to the workpiece and thereby effectively moves the evaporation apertures formed by

masks

32 and 33 with respect to the surface of the workpiece in the direction of arrow As will be seen, aperture 54 is positioned under workpiece 21 when filter strips 23 are being formed. 'When the longer signal strips are be ing formed a movable mask with a larger aperture 54' is place. Oiisetting of the different sets of color filters and the sets of signal strips is accomplished by means of stops 4-4 and 35 as the case may be.

As indicated above workpiece holder 61 is mounted in framework 6%. An aperture is provided in which workpiece 21 is readily removably seated. It should be noted that the spacing of the workpiece from the fixed mask 32 is shown exaggerated in the drawing. In practice the spacing is made as close as possible and just short of actual contact of the mask elements with the coatings to be formed so as to avoid damage thereto. Resilient fingers 62 together with spring loaded plungers 63 firmly maintain workpiece 21 in position. Holder 21 is mounted in a guideway formed in framework 6t? and is slideable in the direction indicated by arrow 64. Spring loaded plunger 65 (Figure 8) mounted in framework bears against one end of holder 61 and urges the same against one end of micrometer screw 66 (Figure 9) supported in framework 60 opposite to plunger 65. Micrometer screw 66 carries on its other end gear 67 (Figure which is driven by bevel gear 68. Gear 68 is mounted on rod 69 which is rotatably mounted in a manner similar to that previously described in connection with

rods

37 and 42. This arrangement permits accurate positioning of holder 61 to within a fraction of a mil from the outside of bell 11. Graduated scales shown in Figure 5 permit visual inspection from the outside of bell 11.

Means are also provided for alining the surface of workpiece 21 exposed to the apertures formed by the masks to insure a parallel relationship between the workpiece surface and wires 48 of the fixed mask. Such means include set screws 70 threaded into framework 60 and having bearing surfaces abutting the under surface of holder 61. Spring loaded plungers 71, also mounted in framework 60 are each apposed to one of the set screws 70 and urge holder 61 thereagainst. Acting transversely of plungers 71, plungers 72, one of which is indicated, urge holder 61 against the opposite wall of the guideway in which it is mounted.

Bolts 73, of which there may be four, extend through framework 60 and thread into base 34 thereby serving to rigidly connect and aline the workpiece holder subassembly to the mask or base subassembly. The proper adjustment of set screws 70 having been made, framework 60 carrying the workpiece may be removed from and then replaced on the base 34 in parallel alined relationship with fixed mask 32. Means are provided for accurately alining wires 48 one to the other in precise parallel relationship and with set screws 70 serve to provide predetermined spacing between the workpiece 21 and mask 32. As described in detail in my joint application with H. C. Thompson Serial No. 344,499 filed simultaneously herewith and assigned to the assignee of this application, such means may include a pair of spaced cylindrical members adjustably mounted on framework 60. Each of the cylindrical members 74 is precision threaded so as to have a precisely formed thread thereon with the turns thereof per inch being equal in number to the number of wires per inch carried by the fixed mask 32. Cylinders 74 are each mounted in a yoke 75. Screws 76, threaded into yoke 75, together with thumbscrews 77 which bear against yoke 75, permit accurate adjustment of cylinders 74 with respect to workpiece 21 in holder 61. When framework 60 is mounted on base 34, cylinders 74 each with their threads engage wires 48. Wires 48 are thus spaced in a predetermined manner from each other and from the surface of workpiece 21.

As previously indicated herein, evaporator 12 is mounted in bell 11 below jig 10. Evaporator 12 is rotatably mounted on platform 80 by its spindle 81. Spindle 81 has an elongated keyway 81 formed therein and is slideable through the hub of gear 82 which has a key formed therein. Gear 82 is rotatably mounted on platform 80 and meshes with idler gear 33. Idler gear 83, in turn, meshes with drive gear 84 mounted on and rotatable with rod 85. As shown, a rod 86 having a bifurcated end is rotatably mounted with the bifurcated end positioned between two spaced collars on spindle 81. Thus rotation of rod 86 serves to raise and lower evaporator 12.

Evaporator 12 is divided into compartments 12 for the various materials to be successively evaporated. Positioned so as to overhang evaporator 12 is a heating element 87 that has leads 88 sealed through bell supporting base 13 as shown for one of the leads at 89. Leads 88 are connected across a source of electrical power (not shown) through any arrangement permitting control of the heat generated at element 87.

Means are provided which are also operable from outside of bell 11 for readily starting and stopping the evaporation of material onto the workpiece 21. One

convenient arrangement is in the form of a swingably' mounted flap 104 mounted on and rotatable with rod 106. When flap 104 is in position between jig 10 and evaporator 12 the material being evaporated is deposited on the undersurface of the flap and does not reach the workpiece. In practice the material in the evaporator is heated until it is being evaporated at the desired rate and then flap 104 is swung out of the way. Evaporation of material onto the workpiece is stopped instantly by swinging flap 104 into its shielding position. The materials may thus be subjected to prolonged heating and outgassing without any material being deposited on the workpiece.

One advantageous arrangement for effecting the desired movements within bell 11 through

rods

37, 42, 69, 85, 86 and 106 will now be described in detail in connection with rod 42. Each of the rods, and with particular reference to rod 42 as shown in Figure l, is rotatably sealed through base 13. Bushing 90 is threaded into base 13 against O-ring gasket 91 and compresses the same. Such seals are well known and permit rotation of rod 42 which is connected to driven gear 92. Drive gear 93 carried on rod 94 meshes with gear 92. Rotation of rod 94, as by means of control knob 95 connected thereto, thus effects the desired movement of

stops

44, 45.

Means for monitoring or controlling the formation of the various coatings includes a light source partially indicated at 96 which may be any suitable projector of white light. The light is projected through the wall of hell 11, which may be of clear glass, through tunnel 97 onto mirror 98 mounted in chimney or shield 99. Chimney 99 is provided to minimize the deposit of evaporated materials onto mirror 98. The light is reflected by mirror 98 up through the masking apertures and workpiece 21 to collimator 100. From collimator 100, the light travels to the photocathode of phototube 101 indicated schematically. Phototube 101 may be any suitable phototube but preferably a photomultiplier tube is utilized. The photocathode is connected to the negative side of a source electricity, indicated generally by a battery while the anode or collector is connected through a microamrneter 102 to the positive side.

My method as well as the operation of the apparatus for the purpose of illustrating the same will now be described in connection with target 20 shown in Figure 2. In this connection then, workpiece 21 is a sheet of maferial having suitable dielectric and optical properties such as glass. Bus bars 22 are formed by evaporating thereon narrow conductive films through a mask 105 shown in Figure 10. Bus bars 22 may be about 500 angstrom units thick with the outside bus bars about ten mils wide and the inner ones about three mils wide. The bus bars in each of the two groups shown are spaced from each other about sixty mils. Gold is a material Zvhlch may be advantageously used in forming the bus ars.

Workpiece 21 is then positioned in holder 61 with the surface thereof carrying bus bars 22 presented toward the wire masking grill 32. Holder 61 is adjusted to expose only the areas on which red filter strips are to be formed to the apertures of fixed mask 32 while movable mask 33 is positioned against stop 44 with slots 55 which are about 40 mils wide in registration with the red bus bars 22. Bell 11 is placed in position on base 13 and evacuated to a pressure of about 10- mm. of mercury or less. When desired, conductive finger strips of gold, silver or other suitable material are formed by evaporating said material; the material being positioned under heating element 87 which is energized as previously indicated. When finger strips of a thickness of about 500 angstrom units have been formed further evaporation is stopped.

Without disturbing bell 11, movable mask 33 is shifted by adjusting the appropriate control knob to bring aperture 54 in registration with workpiece 21 for the formation of red color filter strips 23. Evaporator 12 is rotated by its knob to bring the appropriate material under heating element 87. A suitable monitoring filter 103 is mounted in front of collimator 100 and evaporation of the first layer of the red filter strips is started. Suitable monitoring filters are substantially monochromatic, narrow pass interference filters of the type commonly known as Fabry-Perot filters. For monitoring the red filter strips a filter 193 is utilized having its pass band peaked in the blue portion of the spectrum as for example, 4,500 angstrorn units. The layers, of which there may be eleven as indicated in Figure -l, are now successively formed one on the other; each having an optical thickness of one quarter of the wavelength of the monitoring filter. Light from projector 95 passes through each of the layers as they are being deposited and on through collimator 109 to the photocathode of tube 3101. Microammeter 102, by its fluctuation, indicates when a quarter wavelength optical thickness of a given layer has been deposited. For example, during the formation of the first zinc sulfide layer the meter reading decreases indicating that less light of 4500 angstroms in wavelength is reaching monitoring ter 103 to be passed on to tube it'll. It is to be understood that only light passing through the workpiece may reach tube 101; measures being taken to attain that end as for example the inclination of collimator 1% which thereby excludes light from heater element 87. When the current reading on meter 15?. reaches a minimum value, the layer has an optical thickness or" one quarter of 4500 angstroms and further deposit of zinc sulfide is prevented by swinging flap 104 into place between the work piece and the evaporator. Evaporator 12 is rotated to bring suitable material of a low index of refraction such as cryolite into position under the heating element by adjustment of the proper control knob. When the cryolite is sutficiently heated to be evaporating at the desired rate flap 164 is swung out of the way and formation of the second layer proceeds. This time the current reading on meter res increases and reaches a maximum when the optical thickness of the layer is one quarter of 4500 angstroms. Then another layer of zinc sulfide is formed with the minimum reading on the meter new lower than that for the first layer. The process is continued with each layer of zinc sulfide bringing to a new and lower minimum the amount of light of 4500 angstroms passed. Eleven layers of zinc sulfide and cryolite formed as above provide a suitable red passing filter.

By making the appropriate adjustments of the various control knobs, holder 61, movable mask 33, and evaporator 12 are successively positioned to form the conductive finger strips on the green bus bars, flse green filter strips, the conductive finger strips on the blue bus bars and the blue filter strips. In the case of green color filter strips 23 a monitoring filter having a narrow pass band peaked in the red portion of the spectrum at about 6500 angstroms is utilized. In place of zinc sulfide, zinc selenide is used and layers having an optical thickness of three quarters of 6500 angstroms are formed as described in connection with zinc sulfide. For blue filter strips 23 sulfide and cryolite are used as described for the red filter strips but a monitoring filter 103 is used having a narrow pass band peaked in the yellow-green portion of the spectrum as for example a wavelength of of 5,730 angstrom units.

When the sets of interlaced color filter strips have been formed, the interior of hell 11 is brought to atmospheric pressure and opened. The four bolts 73 securing the workpiece subassernbly to the mask subassernbly are un- -wed and the workpiece subassembly removed. The \VZI'C masking grill 32 used in forming the filter strips is by a similar grill having wires slightly larger in diameter so as to form the conducting signal strips narrower than the abutting color filter strips and thus space the signal strips so adjacent ones are sufficiently insulated one from the other. The movable mask is also replaced 3 with one having an aperture 54' longer than aperture 54 to form the signal strips longer than the filter strips. The workpiece subassernbly is then carefully bolted in place once again. Bell 11 is put in place.

The conductive signal strips are formed by successively evaporating suitable material such as gold onto each of the color filter strips. As most clearly shown in Figures 2 and 3, the color filter strips of each set are alined and extend from just short of the bus bar for that color on one side to just short of the other bus bar for that color on the other side. The filter strips extend over the intervening bus bars of the other color sets. When the signal strips are being formed, as for example, the red, only the filter strips and bus bars of that color are exposed through the apertures of the masks. As previously pointed out the signal strips are about 1.5 mils in width. They are separated from each other about .5 mil and are estimated to range in thickness from 50 to about 100 angstrom units. To form the green signal strips holder e3 is shifted to expose the green color filter strips and the movable mask is shifted to expose the green bus bars. Similar adjustments permit the formation of the blue signal strips thus completing three sets of interlaced signal strips with the signal strips of a given set connected in parallel by their bus bars and insulated from the signal strips and bus bars of the other colors. While the signal strips sets are formed they are each monitored with the same monitoring filter 103 in place as was described in connection with the respective color filter strips. This provides a convenient arrangement for determining the thickness of the signal strips while at the same time an undesired shift in the pass band of the color filter strips is also detected.

A coating of photosensitive material 26 is formed on the signal strips 24. At the present time photoconductive material is used having a broad spectral response similar to that of the human eye. One such mat rial is porous red antimony sulphide which is evaporated in poor vacuum, from .1 to about 10 mm. of mercury, and has a mat surface. Such a material may be laid down as a continuous coating over all of the signal strips confined to the area between the sets of bus bars by a suitably apertured mask; the wire masking grill having been removed. This or other materials may also be evaporated through the wire masking grill so as to form the photoconductive coating in strips one on each of the signal strips 24, as in the case where selectively color responsive photosensitive materials are utilized.

Numerous variations may be made in the foregoing method and apparatus as well as such as may be dictated by the article being produced. Where the color filter strips are not sufiiciently insulating they may be formed in spaced relation and evaporated through the same wire masking grill as is used in forming the signal strips In that case insulating layers 23' are formed at the cross over points of each of the signal strips with the bus bars of the other colors. Apertures such as slots 55 are conveniently utilized as was described in connection with the formation of conductive finger strips 2. insulating layers 23 may be conveniently formed at the cross over points even when the color filter strips are insulating and in abutting relation (Figure 2) to minimize coupling between the signal strips of one color and bus bars of the other colors.

In view of the precise manner in which the workpiece may be readily alined with the masks, precisely formed strips in accurate relation may be made even though, during the preparation, the workpiece subassembly is removed from the mask subassernbly. Thus, the usefulness of the apparatus is not impaired when as described one wire masking grill is changed for another having wires of different diameter. Furthermore the ease with which the various adjustments are carried out in a precisely accurate manner facilitates the following of any desired pattern or sequence of steps. For example, the

conductive finger strips 25 may be all formed before any of the color filter strips 23. All of the color filter strips 23 may be formed before any of the transparent conductive signal strips 24. While the apparatus minimizes the necessity of opening bell 11 to the atmosphere during the process, the number and quantity of the materials in evaporator 12 may be varied as desired. For example, an evaporator having therein only the material, such as silver, for conductive fingers 25 may be used or heated during the formation of all the finger strips. Then an other evaporator containing the material for the red and blue filter strips 23 may be shifted into position by operation of external controls and heat applied. On completion of the red and blue filters an evaporator containing the material for the green filter strips may be mounted followed in turn by an evaporator containing material for signal strips 24. Finally, an evaporator containing the photoconductive material may be mounted for forming photoconductive coating 26. The separate evaporators may be readily mounted on a turret or turntable and actuated from outside bell 11. Furthermore, when desired, conduction heating of the material to be evaporated may be utilized as in the case of such material as gold.

When it is not necessary to change fixed mask 32, as where all the superimposed layers are of the same width, a movable mask 58 may be used having apertures 54, 54' and slots 55 formed therein. Mask 58 is slideably mounted in the guideway of base 34. The various adjustments of mask 58 are effected by arm 35.

In accordance with well known techniques the various materials are outgassed prior to their being evaporated to form the target. Conveniently, such outgassing is carried out in situs by prolonged heating in the evaporator at a temperature at which the material just begins to evaporate. During such outgassing fiap 104 is in its shielding position.

Such a workpiece as target 20 may be subjected to such further processing as may be desired to enhance the properties thereof. For example baking at moderate temperatures has proven beneficial. In the case of the gold signal strips described hereinabove baking for about an hour at a temperature ranging from about 130 C. to about 200 C. may be used.

From the foregoing it is apparent that I have provided a highly useful apparatus and method. While I have described the same in connection with the apparatus shown, it is believed obvious that changes and variations may be made therein without departing from my invention. It is intended that all such changes and variations as come within the scope of the appended claims be included in my invention.

What is claimed is:

1. Apparatus for forming juxtaposed coatings on a surface of a workpiece, said apparatus comprising an enclosure, means for evaporating coating forming materials mounted in said enclosure, support means movably mounted within said enclosure for holding a workpiece in position to receive said materials on a surface of said workpiece, means for moving said workpiece support means at least in one given direction, a mask defining a plurality of juxtaposed apertures supported intermediate said evaporating means and said workpiece support means, a movably mounted mask supported intermediate said evaporator and said workpiece support means and having at least one aperture formed therein, at least one aperture in said movably mounted mask being in registry with an aperture in said first mentioned mask and with said means for evaporating coating forming materials whereby the position of said workpiece and said movable mask defines the portion of said surface to be exposed to said materials through said first mentioned mask, and means extending into said enclosure for efiecting movement of said workpiece support means and said movable mask.

2. Apparatus for successively forming juxtaposed as Well as superimposed layers of difierent materials on a surface of a workpiece, said apparatus comprising an enclosure, means for successively evaporating at least two difierent coating forming materials mounted in said enclosure, movable support means for holding said workpiece in position to receive said materials on said surface of said workpiece, a mask defining a plurality of juxtaposed apertures supported intermediate said evaporating means and said workpiece, means for successively registering different portions of said workpiece with said apertures, whereby juxtaposed coatings may be successively formed on said workpiece, and means sealed through said enclosure for selectively effecting registration of difierent portions of said workpiece with said apertures.

33. Apparatus for successively forming juxtaposed as well as superimposed layers of difierent materials on a surface of a workpiece, said apparatus comprising an enclosure, means for successively evaporating at least two diflerent coating forming materials mounted in said enclosure, movable supporting means holding a workpiece in position to receive said materials on the surface thereof, a mask defining a plurality of juxtaposed apertures sup ported intermediate said evaporating means and said workpiece, means for successively registering different portions of said workpiece with said apertures and including a movable mask having at least one aperture formed therein supported intermediate said work iece and said evaporating means whereby juxtaposed coatings may be successively formed on said workpiece, and means sealed through said enclosure for selectively effecting registration of diiferent portions of said workpiece with said apertures and for selectively positioning said movable mask.

4. Apparatus for successively forming juxtaposed as well as superimposed layers of difierent materials on a surface of a workpiece, said apparatus comprising an enclosure, means for successively evaporating at least two different coating forming materials mounted in said enclosure, a base supported above said evaporating means, a mask defining a plurality of juxtaposed apertures sup ported on said base, a second mask having at least one aperture formed therein and supported on said base, means for selectively moving one of said masks with respect to the other, a framework supported on said base on the side of said masks away from said evaporating means, said framework having a guideway formed therein, a workpiece holder for receiving a workpiece slideable in said guideway and supported by said framework, means for selectively moving said holder in said guideway and successively registering different portions of said workpiece with said apertures, and means sealed through said enclosure for effecting successive relative movement of said masks and said workpiece holder, whereby diiferent portions of a workpiece mounted in said holder may be successively registered with said apertures.

5. Apparatus for successively forming juxtaposed as well as superimposed layers of difierent materials on a surface of a workpiece, said apparatus comprising an enclosure, means for successively evaporating at least two difierent coating forming materials mounted in said enclosure, a base supported above said evaporating means. a mask comprising a plurality of closely spaced parallel wires defining a plurality of juxtaposed apertures and supported on said base, a framework supported on said base and having a guideway formed therein, a workpiece holder for receiving a workpiece and movably mounted in said guideway, said mask being positioned intermediate said workpiece holder and said evaporating means, a second mask intermediate said workpiece holder and said evaporating means, said second mask having at least one aperture formed therein and being movably mounted on said base, adjustable means on said framework for adjusting the spacing between said holder and said masks and for successively registering different portions of said workpiece with said apertures, and means sealed through said enclosure for selectively positioning said movable mask and said workpiece holder.

6. Apparatus for successively forming juxtaposed as well as superimposed layers of different materials on a surface of a workpiece, said apparatus comprising an enclosure, means for successively evaporating at least two different coating forming materials mounted in said enclosure, a base supported above said evaporating means, a mask comprising a plurality of closely spaced parallel wires defining a plurality of juxtaposed apertures and supported on said base, a framework supported on said base and having a guideway formed therein, said guideway extending transversely of said wires, a workpiece holder for receiving a workpiece and movably mounted in said guideway, said mask being positioned intermediate said workpiece holder and said evaporating means, a second mask intermediate said workpiece holder and said evaporating means, said second mask having at least one aperture formed therein and being movably mounted on said base for movement transversely of said guideway, adjustable means on said framework for adjusting the spacing between said holder and said masks and for successively registering different portions of said workpiece with said apertures, and means sealed through said enclosure for selectively positioning said movable mask and said workpiece holder.

7. The combination of apparatus for successively forming juxtaposed as well as superimposed light permeable layers of different materials on a light permeable workpiece with means for determining the thickness of said layers, said means comprising means for projecting a beam of light through an aperture in an apertured mask and through portions of said workpiece while a layer is being formed through said aperture and on said portions, and means responsive to the amount of light falling thereon positioned to receive light transmitted through said workpiece, the amount of light falling on said last mentioned means being a function of the thickness of said layers.

8. The combination of apparatus for successively forming juxtaposed as well as superimposed light permeable layers of different materials on a light permeable workpiece, the amount of light transmitted through said layers being a function of the thickness of said layers; said means including means for projecting a beam of light through an aperture in an apertured mask only through those portions of said workpiece on which a layer is being formed through said aperture, light sensitive means for measuring the amount of light received thereat and positioned to receive light transmitted through said portions of the workpiece, and means interposed between said workpiece and said light sensitive means for restricting the light received by said light sensitive means to that of a predetermined wavelength or band of wavelengths.

9. Apparatus for successively forming juxtaposed as well as superimposed layers of different materials on a surface of a workpiece, said apparatus comprising an enclosure, means for successively evaporating at least two different coating forming materials mounted in said enclosure, means including a guideway for movably supporting a workpiece in position to receive said materials on the surface thereof, a mask defining a plurality of juxtaposed apertures supported intermediate said evaporating means and said workpiece, means for successively registering different portions of said workpiece with said apertures, whereby juxtaposed coatings may be successively formed on said workpiece, means sealed through said enclosure for selectively effecting registrationvof different portions of said workpiece with said apertures, means for projecting light through said portions of the workpiece in registration with said apertures, light sensitive means for measuring the amount of light received thereat and positioned to receive light transmitted through said portions of the workpiece, whereby the amount of light received at said light sensitive means is a function of the thickness of the layers being formed.

10. Apparatus for successively forming juxtaposed as well as superimposed layers of different materials on a surface of a workpiece, said apparatus comprising an enclosure, means for successively evaporating at least two different coating forming materials mounted in said enclosure, means including a guideway for movably supporting a workpiece in position to receive said materials on the surface thereof, a mask defining a plurality of juxtaposed apertures supported intermediate said evaporating means and said workpiece, means for successively registering different portions of said workpiece with said apertures, whereby juxtaposed coatings may be successively formed on said workpiece, means sealed through said enclosure for selectively etfecting registration of different portions of said workpiece with said apertures, means for projecting light through said portions of the workpiece in registration with said apertures, light sensitive means for measuring the amount of light received thereat and positioned to receive light transmitted through said portions of the workpiece, whereby the amount of light received at said light sensitive means is a function of the thickness of the layers being formed, and means interposed between said workpiece and said light sensitive means for restricting the light received by said light sensitive means to that of a predetermined wavelength or band of Wavelengths.

11. Apparatus for forming juxtaposed as well as superimposed coatings on a surface of a workpiece, said apparatus comprising a base, a framework removably mounted on said base, at least one mask on said base and including elements defining apertures through which material may travel to form layers on said surface, a holder movably mounted on said framework said holder supporting said workpiece in registration with said apertures, and adjustable means for selectively positioning said holder in close spaced relation with said mask.

12. Apparatus for forming juxtaposed as well as superimposed coatings on a surface of a workpiece, said apparatus comprising a base, a mask connected to said base, a plurality of elements on said mask and defining a plurality of juxtaposed apertures, a movable mask having at least one aperture formed therein and movably mounted on said base, a framework removably mounted on said base, a workpiece holder movably mounted on said framework and supporting the workpiece in registration with said apertures, and adjustable positioning means for selectively moving said holder in close spaced relation with said first mentioned mask and for selectively positioning said movable mask.

13. Apparatus for forming juxtaposed as well as superimposed coatings on a surface of a workpiece, said apparatus comprising a base, a pair of spaced apart members connected to said base, a plurality of alined wires stretched between and connected to said members, said wires defining a plurality of apertures, said'base having a guideway formed therein, a movable mask slideably mounted in said guideway and having at least one aperture formed therein, a framework removably mounted on said base and having a guideway formed therein, a holder slideably mounted in the guideway of said framework and for supporting a workpiece in registration with said apertures, adjustable means for selectively positioning said holder in close space relation with said wires, and means for selectively positioning said movable mask in registration with said holder and said wires.

14. The method of forming juxtaposed interference color filters on a light permeable workpiece with a set of filters of one color interlaced with a set of another color and each capable of transmitting a different predetermined spectral bandwidth, said method including the steps of masking all but those spaced apart portions of the work piece on which the set of filters of one color are to be 13 formed, then forming on said portions successive superimposed layers of high and low index of refraction material each of a thickness determined by exposing said portions only to light and measuring the amount of light of a given wavelength transmitted through said portions to form said interference color filter set.

15. The method of forming juxtaposed interference color filters on a light permeable workpiece with a set of filters of one color interlaced with a set of another color and each capable of transmitting a different predetermined spectral bandwidth, said method comprising the steps of masking all but those spaced apart portions of the workpiece on which the set of filters of one color are to be formed, then forming on said portions successive superimposed layers of high and low index of refraction material each of a thickness determined by exposing said portions only to light and measuring the amount of light of a given wavelength transmitted through said portions to form said color filter set, then masking all but other portions of the workpiece on which another set of interference filters of a different color are to be formed, and then forming on said portions successive superimposed layers of high and low index of refraction material each of a thickness determined by exposing said other portions only to light and measuring the amount of light of a different g'ven wavelength transmitted through said other portions to form another set of interference filters.

16. The method of forming juxtaposed interference color filters on a light permeable workpiece with a set of filters of one color interlaced with a set of another color and each capable of transmitting a different predetermined spectral bandwidth, said method comprising the steps of masking all but those spaced apart portions of the workpiece on which the set of filters of one color are to be formed, then forming on said portions successive superimposed layers of high and low index of refraction material each of an optical thickness of substantially or an odd multiple of a A wavelength of light of a given wavelength, said thickness being determined by exposing said portions only to light and measuring the amount of light of said given wavelength transmitted through said portions to form said color filter set, then masking all but other portions of the workpiece on which another set of interference filters of a different color are to be formed, and then forming on said portions successive superimposed layers of high and low index of refraction material each of an optical thickness of substantially or an odd multiple of wavelength of light of a different given wavelength, said thickness being determined by exposing said other portions only to light and measuring the amount of light of said different wavelength transmitted through said other portions to form another set of interference filters.

17. The method of manufacturing a ray sensitive target for a cathode ray tube having juxtaposed color filters with a set of filters of one color interlaced with a set of another color and each capable of transmitting a difierent predetermined spectral bandwidth and having for each filter a transparent conductive signal strip which is electrically coupled to the ray sensitive material, said method including the steps of masking all but those spaced apart portions of the target on which the set of filters of one color are to be formed, evaporating onto said portions material to form one set of color filters capable of transmitting a predetermined spectral bandwidth, and evaporating onto said portions material to form transparent conductive signal strips.

18. The method of manufacturing a ray sensitive target for a cathode ray tube having juxtaposed interference color filters with a set of filters of one color interlaced with a set of another color and each capable of transmitting a different predetermined spectral bandwidth and having for each filter a transparent conductive signal strip which is electrically coupled to the ray sensitive material, said method including the steps of masking all but those spaced apart portions of the workpiece on which the set of filters of one color are to be formed, then forming on said portions successive superimposed layers of high and low index of refraction material each of a thickness determined by exposing said portions only to light and measuring the amount of light of a given wavelength transmitted through said portions to form said interference color set, and forming on each of said thus formed filters a layer of transparent conductive material.

References Cited in the file of this patent UNITED STATES PATENTS 2,418,627 Dimmick Apr. 8, 1947 2,432,950 Turner et al. Dec. 16, 1947 2,433,635 Sukumlyn Dec. 30, 1947 2,472,605 McRae et a1 June 7, 1949 2,545,576 Godley Mar. 20, 1951 2,600,579 Ruedy et al June 17, 1952

Claims

14. THE METHOD OF FORMING JUXTAPOSED INTERFERENCE COLOR FILTERS ON A LIGHT PERMEABLE WORKPIECE A SET OF FILTERS OF ONE COLOR INTERLACED WITH A SET OF ANOTHER COLOR AND EACH CAPABLE OF TRANSMITTING A DIFFERENT PREDETERMINED SPECTRAL BANDWIDTH, SAID METHOD INCLUDING THE STEPS OF MASKING ALL BUT THOSE SPACED APART PORTIONS OF THE WORKPIECE ON WHICH THE SET OF FILTERS OF ONE COLOR ARE TO BE FORMED, THEN FORMING ON SAID PORTIONS SUCCESSIVE SUPER-