Abstract:
A method of manufacturing a luminescent screen assembly, having a light-absorbing matrix with a plurality of substantially equally-sized openings therein, on an inner surface of a faceplate panel of a cathode-ray tube (CRT) is provided. The tube has a color selection electrode spaced from the inner surface of the faceplate panel in which the color selection electrode has a plurality of strands interleaved with slots. The method includes the steps of providing a first photoresist layer, whose solubility is altered when exposed to light, such that greater dosages of light reduce the solubility thereof. The first photoresist layer is applied to the inner surface of the faceplate panel. The first photoresist layer is exposed to light from a light source, located relative to a central source position, as well as two symmetrical source positions relative to the central source position. The exposure selectively alters the solubility of the illuminated areas of the first photoresist layer to produce therein regions with greater solubility and regions of lesser solubility. The regions of greater solubility are subsequently removed to uncover areas of the inner surface of the faceplate panel, while retaining the regions of lesser solubility. The inner surface of the faceplate panel and the retained regions are then overcoated with a light-absorbing material. Thereafter, the retained regions of the first photoresist layer and the light-absorbing material thereon are removed, uncovering portions of the faceplate panel and defining first guardbands of light-absorbing material on the inner surface of the faceplate panel. This photolithographic process is repeated with a second photoresist layer and a third photoresist layer to define second guardbands of light-absorbing material and third guardbands of light-absorbing material, respectively. However, the light source positions for the second photoresist layer and the third photoresist layer are located at asymmetric positions relative to the central source position.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to a color cathode-ray tube (CRT) and, more particularly to a color CRT including a luminescent screen assembly.  
         BACKGROUND OF THE INVENTION  
         [0002]    A color cathode-ray tube (CRT) typically includes an electron gun, an aperture mask, and a screen. The aperture mask is interposed between the electron gun and the screen. The screen is located on an inner surface of a faceplate of the CRT tube. The aperture mask functions to direct electron beams generated in the electron gun toward appropriate color-emitting phosphors on the screen of the CRT tube.  
           [0003]    The screen may be a luminescent screen. Luminescent screens typically comprise an array of three different color-emitting phosphors (e.g., green, blue, and red). Each color-emitting phosphor is separated one from the other by a matrix line. The matrix lines are formed of a light-absorbing black inert material.  
           [0004]    The matrix lines may be deposited on the screen using aperture mask photolithographic processes, such as those described in U.S. Pat. No. 3,558,310. In aperture mask photolithographic processes, images of the aperture mask are formed in a layer of photoresist material coated on the screen, through exposure to actinic ultraviolet (UV) light and development in an appropriate developer, providing covered areas and uncovered areas on the screen surface. The covered areas on the screen surface are exposed to greater dosages of the actinic UV light, while the uncovered areas on the screen surface are exposed to lesser dosages of the actinic UV light.  
           [0005]    For aperture mask lithographic processes, the aperture mask is positioned a fixed distance from the screen such that shadows therefrom, projected onto the resist coated screen during exposure to actinic UV light, uncover matrix line openings in the photoresist having desired dimensions and positioned at appropriate locations on the screen. The covered areas define the matrix line openings, which will be filled with phosphor material. The uncovered areas define the black, light absorbing matrix lines.  
           [0006]    The matrix lines are formed by depositing the matrix material on both the covered and uncovered areas of the screen surface. After the matrix material, which typically comprises colloidal graphite, dries, an etchant is applied to solubilize the remaining photoresist that had been exposed to greater dosages of actinic UV light. The matrix line structure is completed by developing with high-pressure water such that the remaining photoresist and the matrix material coating it are released, thereby leaving behind on the surface of the screen only the matrix material that had coated the uncovered areas thereof.  
           [0007]    Conventional aperture masks typically have a transmission of about 18% to about 22%. Recently, in order to increase the brightness in a CRT tube without increasing the respective size of the matrix openings, aperture masks having transmissions of about 20% to about 80% have been incorporated into the color CRT tube. However, matrix line formation using aperture masks with transmissions of about 30% to about 80% cannot be achieved utilizing conventional matrix processes such as those described in U.S. Pat. No. 3,558,310, since the light images projected therefrom overlap each other causing the location of such matrix lines to be misaligned on the screen surface as well as have varying dimensions.  
           [0008]    Accordingly, a new method of manufacturing the matrix on a luminescent screen is required.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention relates to a method of manufacturing a luminescent screen assembly, having a light-absorbing matrix with a plurality of substantially equally-sized openings therein, on an inner surface of a faceplate panel of a cathode-ray tube (CRT). The tube has a color selection electrode or aperture mask spaced from the inner surface of the faceplate panel in which the color selection electrode has a plurality of slots.  
           [0010]    The method includes the steps of exposing a first photoresist layer to light from a light source, located relative to a central source position, as well as two symmetrical source positions relative to the central source position. The exposure selectively alters the solubility of the illuminated areas of the first photoresist layer to produce therein regions with greater solubility and regions of lesser solubility. The regions of greater solubility are subsequently removed to uncover areas of the inner surface of the faceplate panel, while retaining the regions of lesser solubility. The inner surface of the faceplate panel and the retained regions are then overcoated with a light-absorbing material. Thereafter, the retained regions of the first photoresist layer and the light-absorbing material thereon are removed, uncovering portions of the faceplate panel and defining first guardbands of light-absorbing material on the inner surface of the faceplate panel. This photolithographic process is repeated with a second photoresist layer and a third photoresist layer to define second guardbands of light-absorbing material and third guardbands of light-absorbing material, respectively. However, the light source positions for the second photoresist layer and the third photoresist layer are located at asymmetric positions relative to the central source position.  
           [0011]    The light-absorbing material applied to the interior surface of the faceplate panel preferably includes greater than about 5% by weight of solids. Additionally, an overcoat layer may be applied over the light absorbing material to seal such layer and reduce the porosity thereof. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The invention will now be described in greater detail, with relation to the accompanying drawings, in which:  
         [0013]    [0013]FIG. 1 is a plan view, partly in axial section, of a color cathode-ray tube (CRT) made according to the present invention;  
         [0014]    [0014]FIG. 2 is a section of a mask and a faceplate panel portion of the CRT of FIG. 1, showing a screen assembly;  
         [0015]    [0015]FIG. 3 is a plan view of a mask and frame used in the CRT of FIG. 1;  
         [0016]    [0016]FIGS. 4 a - 4   c  are block diagrams comprising flow charts of the RB, GR and GB guardband manufacturing processes for the screen assembly of FIG. 2;  
         [0017]    [0017]FIGS. 5 a - 5   e  depict views of the interior surface of the faceplate panel during RB guardband formation;  
         [0018]    [0018]FIG. 6 depicts the light source positions used to form the RB guardbands;  
         [0019]    [0019]FIGS. 7 a - 7   e  depict views of the interior surface of the faceplate panel during GR guardband formation;  
         [0020]    [0020]FIG. 8 depicts the light source positions used to form the GR guardbands;  
         [0021]    [0021]FIGS. 9 a - 9   e  depict views of the interior surface of the faceplate panel during GB guardband formation;  
         [0022]    [0022]FIG. 10 depicts the light source positions used to form the GB guardbands; and  
         [0023]    [0023]FIGS. 11 a - 11   c  illustrate different orientations of the faceplate panel at the onset of deposition of the photoresist and/or the light-absorbing material. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]    [0024]FIG. 1 shows a color cathode-ray tube (CRT)  10  having a glass envelope  11  comprising a faceplate panel  12  and a tubular neck  14  connected by a funnel  15 . The funnel  15  has an internal conductive coating (not shown) that is in contact with, and extends from, an anode button  16  to the neck  14 .  
         [0025]    The faceplate panel  12  comprises a viewing faceplate  18  and a peripheral flange or sidewall  20  that is sealed to the funnel  15  by a glass frit  21 . A three-color luminescent phosphor screen  22  is carried on the inner surface of the viewing faceplate  18 . The screen  22 , shown in cross-section in FIG. 2, is a line screen which includes a multiplicity of screen elements comprising red-emitting, green-emitting, and blue-emitting phosphor stripes R, G, and B, respectively, arranged in triads, each triad including a phosphor line of each of the three colors. The R, G, B, phosphor stripes are generally printed with a vertical orientation.  
         [0026]    A light absorbing matrix  23 , shown in FIG. 2, separates the phosphor lines. A thin conductive layer (not shown), preferably of aluminum, overlies the screen  22  and provides means for applying a uniform first anode potential to the screen  22 , as well as for reflecting light, emitted from the phosphor elements, through the faceplate  18 . The screen  22  and the overlying aluminum layer comprise a screen assembly.  
         [0027]    A multi-aperture color selection electrode, or mask  25 , is removably mounted, by conventional means, within the faceplate panel  12 , in predetermined spaced relation to the screen  22 . This space relation or distance of the mask  25  from the faceplate panel  12  is referred to as the “Q” spacing.  
         [0028]    An electron gun  26 , shown schematically by the dashed lines in FIG. 1, is centrally mounted within the neck  14 , to generate and direct three inline electron beams  28 , a center and two side or outer beams, along convergent paths through the mask  25  to the screen  22 . The inline direction of the center beam  28  is approximately normal to the plane of the paper.  
         [0029]    The CRT  10  of FIG. 1 is designed to be used with an external magnetic deflection yoke  30 , in the neighborhood of the funnel-to-neck junction. When activated, the yoke  30  subjects the three electron beams  28  to magnetic fields that cause the electron beams  28  to scan a horizontal and vertical rectangular raster across the screen  22 .  
         [0030]    As shown in FIG. 3, the mask  25  is formed, preferably, from a thin rectangular sheet of about 0.05 mm (2 mil) thick low carbon steel, that includes two horizontal sides and two vertical sides. The two horizontal sides of the mask  25  parallel the central major axis, X, of the mask and the two vertical sides parallel the central minor axis, Y, of the mask. With reference to FIGS. 2 and 3, the mask  25  includes an apertured portion that contains a plurality of elongated strands  32  separated by slots  33  that parallel the minor axis, Y, of the mask.  
         [0031]    In one configuration, the mask pitch, D m , defined as the transverse dimension of a strand  32  and an adjacent slot  33 , is 0.87 mm (37 mils). As shown in FIG. 2, each strand  32  can have a transverse dimension, or width, w, of about 0.38 mm (15 mils) and each slot  33  can have a width, a′, of about 0.53 mm (21 mils). The slots  33  extend from one horizontal side of the mask to the other horizontal side thereof. The pitch, D m  of the mask  25  can be varied. For example, in a second configuration, with a mask pitch of about 0.68 mm (27 mils) and a strand width of about 0.3 mm (12 mils), each matrix opening has a width, c, of about 0.13 mm (5 mils). Again with reference to FIG. 2, the screen  22 , formed on the viewing faceplate  18 , includes the light-absorbing matrix  23  with rectangular openings in which the color-emitting phosphor lines are disposed. The corresponding matrix openings have a width, c, of about 0.20 mm (8 mils). The width, d, of each matrix line is about 0.10 mm (4 mils) and each phosphor triad has a width or screen pitch, T, of about 0.96 mm (38 mils). For this embodiment, the mask  25  is spaced at a distance, Q, (hereinafter Q-spacing) of about 15.24 mm (600 mils) from the center of the interior surface of the faceplate panel  12 .  
         [0032]    The process for manufacturing the light-absorbing matrix according to the preferred embodiment begins with cleaning the interior surface of the faceplate  18  with an acid such as hydrofluoric acid (HF). The cleaning process, indicated as panel cleaning step  50  in FIG. 4 a,  is concluded by rinsing the faceplate  18  with copious quantities of water.  
         [0033]    A polymer precoat layer (not shown) may be applied to the interior surface of the faceplate  18 , as indicated by step  52  in FIG. 4 a.  The polymer precoat layer is a thin film that enhances the adhesion of the light absorbing material and promotes greater opacity of the matrix lines. The polymer precoat layer may comprise a material such as polyvinyl alcohol (PVA). The polymer precoat layer may be deposited by spin coating a 0.1 to 0.3% aqueous PVA solution thereon. The polymer precoat layer typically has a thickness no greater than about 0.25 μm.  
         [0034]    Referring to FIG. 5 a  and step  58  of FIG. 4 a,  a first photoresist layer  56  is applied, by spin coating, on the inner surface of the viewing faceplate  18 . The first photoresist layer  56  may comprise a polyvinyl pyrrolidone (PVP)-diazido stilbene system, a polyvinyl alcohol (PVA)-dichromate system, or other suitable negative photoresist systems.  
         [0035]    As shown in FIG. 5 b,  a mask  25  is secured near the faceplate panel  12  and the panel-mask assembly placed on a lighthouse (not shown). The mask  25  is positioned between the faceplate panel  12  and a movable light source  51 , shown in FIG. 6. The first photoresist layer  56  is exposed to light, through the slots  33  of the mask  25 , from the RB source positions (green source positions), as indicated by step  78  in FIG. 4 a.  The first color source position, +G, is located at a distance, ΔX, relative to a central source position or standard green location,  0 . The second color source position, −G, is located a distance, −ΔX, relative to the central source position,  0 . For a  68  cm mask, ΔX can be about 1.78 mm (70 mils). The third source position is preferably the central source position,  0 . However, this third source position can be from at least one position between −ΔX and ΔX The third source position ensures that regions  53  of the first photoresist layer  56  are entirely exposed thereby producing a desired level of lesser solubility therein.  
         [0036]    The Q-spacing between the mask  25  and the interior surface of the faceplate panel  12 , on which the first photoresist layer  56  is disposed is about 449 mils. The light emanating from the three source positions selectively alters the solubility of the illuminated areas of the first photoresist layer  56  thereby producing regions  53  of lesser solubility. The areas  54  and  54   a  of the first photoresist layer  56  that are shaded by the mask strands. Areas  54  and  54   a  are unchanged and constitute areas of greater solubility. The areas  54  define the matrix RB guardband where +G defines the red edge of guardband RB and −G defines the blue edge of guardband RB. Area  54   a  defines where the phosphor screen terminates.  
         [0037]    As shown in FIG. 5 c  and indicated by step  84  in FIG. 4 a,  the first photoresist layer  56  is developed by rinsing the panel  12  with a suitable solvent, such as for example water. This development step removes the regions  54  and  54   a  of greater solubility, thereby exposing areas  57  of the surface of the panel  12 , while leaving intact the illuminated areas  53  of layer  56  having lesser solubility.  
         [0038]    The matrix is formed, as shown in FIG. 5 d  and indicated in step  88  of FIG. 4 a,  by overcoating the exposed areas  57  of the surface of the panel  12  as well as the retained areas  53  of layer  56 , having lesser solubility, with a first layer of light absorbing material  59 . The first layer of the light absorbing material  59  adheres to the interior surface of the faceplate panel  12  in the uncovered areas  57  and  57   a.  The first layer of the light-absorbing material  59  is preferably made of a suitable graphite composition such as those commercially available from Acheson Colloids Company, Port Huron, Mich.  
         [0039]    The first layer of the light-absorbing material  59  preferably comprises a suspension of sub-micron graphite colloids. Additionally, the first layer of light-absorbing material may also include surface-active agents. It is believed that the surface-active agents in the light-absorbing material layer promotes improved wetting of the faceplate panel  12  for film-formation thereon.  
         [0040]    The graphite colloids in the suspension are optionally coated with an oxidation barrier. Suitable oxidation barriers may comprise oxides such as, for example, silicon dioxide (SiO 2 ), and aluminum oxide (Al 2 O 3 ). The oxidation barrier is believed to reduce the oxidation of the graphite during subsequent tube processing.  
         [0041]    A composition containing the light-absorbing material with a solids concentration between about 5.5% and about 8.0% is applied to the uncovered areas  57  and  57   a,  as well as the retained areas  53  of lesser solubility. As indicated by step  90  of FIG. 4 a,  the first layer of light-absorbing material is dried at temperatures within a range of about 40° C. to about 70° C. for a time period of about 3 minutes to about 5 minutes. The thickness of the first layer of light absorbing material is about 1 μm.  
         [0042]    Referring to FIG. 5 e  and step  92  of FIG. 4 a,  the light-absorbing matrix is developed by depositing a suitable solvent, such as aqueous periodic acid, or the equivalent, onto the matrix to soften and swell the underlying retained areas  53  of layer  56  having lesser solubility. The matrix is then flushed with water to remove the loosened, less soluble, retained areas  53  of layer  56 , forming openings therein, but leaving the RB guardbands and a border  62  of light-absorbing material attached to the exposed portions of the interior surface of the faceplate panel  12 .  
         [0043]    The above-described process is repeated two more times for the GR source positions (blue source positions) and GB source positions (red source positions). As such, a second photoresist layer  94  is applied on the interior surface of the faceplate panel  12 , as shown in FIG. 7 a  and indicated in step  95  of FIG. 4 b.  Referring to FIGS. 7 b  and  8  as well as step  96  of FIG. 4 b,  the second photoresist layer  94  is exposed to light, through the mask  25 , from the GR source positions  51 , within a lighthouse (not shown). For the GR source positions formed with the 68 cm mask, the color first source position, +B, is asymmetrically located a distance, 2X+ΔX, about 8.99 mm (354 mils) relative to the central source position,  0 . The position −X and 2X are known as the primary and secondary source positions for blue, respectively. The second color source position, −B, is asymmetrically located a distance, −X+ΔX, about −3.61 mm (−142 mils), relative to a central source position,  0 . The third position is the primary source position for blue, −X, −212 mils (or otherwise known as the standard blue position used in printing blue phosphors lines in a screening process and printing the blue matrix opening in a conventional matrix process. However, this third source position can be from at least one position between −X−ΔX and −X+ΔX.  
         [0044]    As shown in FIG. 7 b,  the Q-spacing between the mask  25  and the inner surface of the faceplate panel  12  is about 449 mils. The light emanating from the GR source positions selectively alters the solubility of the illuminate areas of the second photoresist layer  94 , thereby producing regions  150  of lesser solubility. The areas of the second photoresist layer  94  that are shaded by the mask strands  32  are unchanged and constitute regions  152  and  152   a  of greater solubility. (Start Here) Referring to FIG. 7 c  and step  98  of FIG. 4 b,  the photoresist is developed with water, removing regions  152  of greater solubility and uncovering areas  154  of the inner surface of the faceplate panel  12 . Regions  150  of the second photoresist layer  94  with lesser solubility are retained.  
         [0045]    The matrix is formed, as shown in FIG. 7 d  and indicated in step  100  of FIG. 4 b,  by overcoating the uncovered areas  154  and the retained regions  150  of lesser solubility on the inner surface of the faceplate panel  12  with a second layer of light-absorbing material  156 . The second layer of light-absorbing material  156  preferably has a similar composition, thickness, etc, as the first layer of light-absorbing material  59  and may be applied using a similar process.  
         [0046]    The second layer of the light-absorbing material  156  is dried, as indicated in step  102  of FIG. 4 b,  and retained regions  150  of the second photoresist layer  94  as well as the second layer of light-absorbing material  156  thereon, are removed. As shown in FIG. 7 e  and indicated by step  104  of FIG. 4 b,  the retained regions  150  of the second photoresist layer  94  are removed by rinsing the faceplate panel  12  using a suitable solvent, such as aqueous periodic acid, or the equivalent. After the retained regions  150  of the second photoresist layer  94  are removed GR guardbands, the previously formed RB guardbands, and a border  62  are retained on the inner surface of the faceplate panel  12 .  
         [0047]    The process is repeated for a third time when a third layer of photoresist material  210  is provided on the inner surface of the faceplate panel  12 , as shown in FIG. 9 a  and indicated in step  200  of FIG. 4 c.  Referring to FIGS. 9 b  and  10  as well as step  202  of FIG. 4 c,  the third photoresist layer  210  is exposed to light, through the mask  25 , from the GB source positions, within a lighthouse (not shown). For the GB source positions formed using the 68 cm mask, the first color source position, +R, is asymmetrically located a distance, X−ΔX, about 3.61 mm (142 mils) relative to the central source position,  0 . The second color source position, −R, is asymmetrically located a distance, −2X+ΔX, about −8.99 mm (−354 mils), relative to a central source position,  0 . The position X and −2X is also known as the primary and secondary source positions for red, respectively. The third source position is the primary source position red, X, 212 mils (or otherwise known as the standard red position used in printing blue phosphors lines in a screening process and printing the blue matrix opening in a conventional matrix process). However, this third source position can be from at least one position between X−ΔX and X+ΔX.  
         [0048]    As shown in FIG. 9 b,  the Q-spacing between the mask  25  and the inner surface of the faceplate panel  12 , on which the third photoresist layer  210  is disposed, remains at about 449 mils. The light emanating from the GB source positions selectively alters the solubility of the illuminated areas of the third photoresist layer  210 , thereby producing regions  506  of lesser solubility. The areas of the third photoresist layer  210  that are shaded by the mask strands  32  are unchanged and constitute regions  508  and  508   a  of greater solubility.  
         [0049]    Referring to FIG. 9 c  and step  204  of FIG. 4 c,  the third photoresist layer  210  is developed with water, thereby removing the regions of greater solubility  508  and  508   a,  thereby uncovering areas  510  of the inner surface of the faceplate panel  12 . Regions  506  of the third photoresist layer  210  with lesser solubility are retained.  
         [0050]    The matrix is formed, as shown in FIG. 9 d  and indicated in step  206  of FIG. 4 c,  by overcoating uncovered areas  510  as well as retained regions  506  of the third photoresist layer  210  on the faceplate panel  12  with a third layer of light-absorbing material  215 . The third layer of light-absorbing material  215  preferably has a similar composition, thickness, etc, as the first layer of light-absorbing material  59  and second layer of light-absorbing material  156 .  
         [0051]    The third layer of light-absorbing material is dried, as indicated in step  207  of FIG. 4 c,  and the retained regions  506  of the third photoresist layer  210  as well as the light-absorbing material  206  thereon, are removed. As shown in FIG. 9 e  and indicated in step  208  of FIG. 4 c,  the retained regions  506  of the third photoresist layer  210  are removed by rinsing the faceplate panel  12  using a suitable solvent, such as aqueous periodic acid, or the equivalent. After the retained regions  506  of the third photoresist layer  210  are removed GB guardbands, the previously formed GR and RB guardbands, and the border  62  are retained on the inner surface of the faceplate panel  12 .  
         [0052]    After forming the series of three guardbands, a potassium silicate coating (not shown) may be disposed atop the matrix. Prior to the application of the silicate, deionized water is applied to the first guardbands RB, second guardbands GB, and third guardbands GR, as well as the areas between the guardbands. These areas are otherwise known as matrix openings. The deionized water is preferably held a temperature of about 40° C. Excess deionized water is then spun off, and the potassium silicate solution, also at about 40° C., is applied. Preferably, the potassium silicate solution has a concentration of about 3.5% by weight in deionized water. Excess potassium silicate is spun off at a rate of about 130 rpm for a time period of about 30 seconds. The potassium silicate film is then dried at a temperature of about 40° C. to about 60° C. for a time period of about 5 minutes. Suitable potassium silicate compositions are commercially available such as KASIL® brand, available from the PQ Corporation, Valley Forge, Pa. The potassium silicate coating preferably has a thickness of about 0.5 μm to about 1.0 μm. The presence of the potassium silicate coating on the guardbands and the matrix openings prevents the deterioration of the guardbands during subsequent processing.  
         [0053]    Further improvements to the matrix process described in U.S. Pat. No. 6,013,400 are realized by intentionally altering the techniques used to apply the three photoresist layers. Specifically, the first photoresist layer  56 , the second photoresist layer  94 , and the third photoresist layer  210  may be applied using different orientations, &lt;A, &lt;B, and &lt;C, with respect to each other. For example, FIGS. 11 a - 11   c,  illustrate different orientations of the faceplate panel  12  at the onset of photoresist layer formation, wherein the major axis  13  of the faceplate panel  12  is oriented relative to the fixed X-axis of the spin coat machine.  
         [0054]    Alternatively, the first layer of light-absorbing material  59 , the second layer of light-absorbing material  156 , and the third layer of light-absorbing material  215  may also be applied using different orientations, &lt;D, &lt;E, and &lt;F, with respect to each other. For example, FIGS. 11 a - 11   c,  may also illustrate different orientations of the faceplate panel at the onset of light-absorbing material application, wherein the major axis  13  of the faceplate panel  12  is oriented relative to the fixed X-axis of the spin coat machine.  
         [0055]    Additionally, the first photoresist layer  56 , the second photoresist layer  94 , and the third photoresist layer  210  may also be applied on the faceplate panel  12  using different spin rates, A′, B′, and C′. Spin rates such as, for example, 90 rpm, 110 rpm, and 130 rpm, may be used for A′, B′, and C′, respectively. Similarly, the first light-absorbing material  59 , the second light-absorbing material  156 , and the third first light-absorbing material  215  may be applied on the faceplate panel  12  using different spin rates, D′, E′, and F′. Again, spin rates such as, for example, 90 rpm, 110 rpm, and 130 rpm, may also be used for D′, E′, F′.  
         [0056]    Modulating the orientation and/or spin rates of the photoresist layers and/or the light-absorbing materials, creates multiple streak patterns in the light-absorbing material that are mismatched with respect to one another. The result is the human eye has difficulty resolving any net streak pattern in the finished CRT faceplate panel. This “optical confusion” generated using the techniques described above reduces or eliminates the perception of unappealing patterns on the display screen.  
         [0057]    The exposure sequence of the current invention also represents an improvement over U.S. Pat. No. 6,013,400 in that, the third exposure (i.e., the central source position,  0  for guardband RB, B in guardband GR, and R in guardband GB) in the deposition sequence for each guardband is novel. The third exposure is novel in that this exposure prevents anomalous or extra guardbands from being printed, particularly at lower mask transmissions.  
         [0058]    For example, at mask transmission values of about 45% or less, anomalous guardbands may be printed. Referring to FIGS. 5 b,    7   b,  and  9   c,  at lower mask transmissions, for any given guardband printing sequence, it is possible that there is not sufficient overlap between the first exposure (i.e., −G, −B and −R) and the second exposure (i.e., +G, +B, and +R) to harden the photoresist in the central areas between the guardbands (i.e., region  53 , region  150 , and region  506 ). The result is that anomalous guardbands may be formed in these central areas, rendering the display screen non-functional. However, referring to FIGS. 6, 8, and  10 , the incorporation of the third exposure (i.e.,  0 , B, and R) provides sufficient exposure to harden the photoresist in all areas except in the location of the intended guardbands RG, GR, and GB, shown in FIGS. 5 e,    7   e  and  9   e,  respectively.