CA1142570A - Color picture tube having improved slit type shadow mask and method of making same - Google Patents
Color picture tube having improved slit type shadow mask and method of making sameInfo
- Publication number
- CA1142570A CA1142570A CA000351855A CA351855A CA1142570A CA 1142570 A CA1142570 A CA 1142570A CA 000351855 A CA000351855 A CA 000351855A CA 351855 A CA351855 A CA 351855A CA 1142570 A CA1142570 A CA 1142570A
- Authority
- CA
- Canada
- Prior art keywords
- apertures
- color picture
- mask
- picture tube
- photomaster
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000004519 manufacturing process Methods 0.000 title claims description 3
- 238000000034 method Methods 0.000 claims abstract description 4
- 239000002184 metal Substances 0.000 claims description 7
- 238000005530 etching Methods 0.000 claims description 5
- 239000000463 material Substances 0.000 claims description 4
- 239000011248 coating agent Substances 0.000 claims description 2
- 238000000576 coating method Methods 0.000 claims description 2
- 238000010894 electron beam technology Methods 0.000 description 10
- 230000005540 biological transmission Effects 0.000 description 7
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 5
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- SQEHCNOBYLQFTG-UHFFFAOYSA-M lithium;thiophene-2-carboxylate Chemical compound [Li+].[O-]C(=O)C1=CC=CS1 SQEHCNOBYLQFTG-UHFFFAOYSA-M 0.000 description 1
- 230000000873 masking effect Effects 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/14—Manufacture of electrodes or electrode systems of non-emitting electrodes
- H01J9/142—Manufacture of electrodes or electrode systems of non-emitting electrodes of shadow-masks for colour television tubes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
- H01J29/06—Screens for shielding; Masks interposed in the electron stream
- H01J29/07—Shadow masks for colour television tubes
- H01J29/076—Shadow masks for colour television tubes characterised by the shape or distribution of beam-passing apertures
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Electrodes For Cathode-Ray Tubes (AREA)
Abstract
RCA 73,919 Abstract A color picture tube having a slit type apertured mask, wherein the slit apertures are arranged in columns and the apertures in each column are separated by webs is improved by increasing the radius of curvature of the ends of the apertures at the webs to substantially greater than half the width of the central portions of the respective apertures. Such aperture shape may be achieved by a method wherein the aperture image elements of a photomaster used in fabricating the mask have greater width at the ends than at the centers thereof.
Description
11'~2570 -1- RCA 73, 919 COLOR PICTURE TUBE HAVING IMPROVED SLIT
TYPE SHADOW MASK AND METHOD OF MAKING SAME
This invention relates to color picture tubes and particularly to such tubes having a slit type apertured mask.
Shadow mask type color picture tubes usually include a screen of red, green and blue emitting phosphor lines or dots, electron gun means for exciting the screen and a shadow mask interposed between the ~un means and the screen. The shadow mask is a thin multiapertured sheet of metal precisely disposed adjacent the screen so that the mask or apertures are systematically related to the phosphor lines or dots.
Color picture tubes having shadowmasks with slit shaped apertures have received relatively recent commercial acceptance. One of the reasons for this acceptance is that the percentage of electron beam transmission through the mask can be made higher for a slit-mask, line-screen type of tube than for a circular-apertured-mask, dot-screen type tube. Even though the use of a slit mask provides a definite advantage in electron beam transmission, the percentage of electron beam transmission through a slit mask can be increased even further than is practiced in the present art.
In one type of slit shadow mask, the mask has vertically extending slit apertures which are interrupted by a plurality of spaced bridges or webs which provide mechanical rigidity. The presence of these webs, however, has an effect on electron beam transmission and thus on luminescent brightness.
FIGURE 1 shows a portion of a prior art shadow mask 10 having slit shaped apertures 12 arranged in columns, the apertures in each column being separated by webs 14. Each aperture 12 has an elongated shape with curved ends. Generally, the curvature of each end has a radius approximately equal to half the width of an aperture measured in the center of the aperture. Such curved aperture shape at the webs occurs because of the etching process. Apertured masks are formed 40 by first coating a metal sheet with a photosensitive O
1 -2- RCA 73,919 material, exposiny the photosensitive material through a photomaster having a desired aperture pattern thereon, and thereafter etching the metal sheet to open the apertures.
5 Most prior art photomasters have rectangularly shaped ele-ments at the locations of the intended apertures. Unfortun-ately, during etching, the apertures become rounded at their ends instead of being formed as rectangles. Because of this rounding, some electron beam transmission is lost in the 10 corners of the apertures as illustrated by the shaded areas 16 of FIGURE 2, which shows the shape of a photomaster element 18 superimposed on its resultant aperture 20. It is, therefore, desirable to develop an aperture pattern which, when etched, will form more nearly rectangular apertures 15 thereby permitting increased electron beam transmission.
In accordance with the invention, a color picture tube having a slit type apertured mask, wherein the slit apertures are arranged in columns and the apertures in each column are separated by webs, is improved by increasing the 20 radius of curvature of the ends of the apertures at the webs to substantially greater than half the width of the central portions of the respective apertures. Such aperture shape may be achieved by a method wherein the aperture image elements of a photomaster used in fabricating the mask have
TYPE SHADOW MASK AND METHOD OF MAKING SAME
This invention relates to color picture tubes and particularly to such tubes having a slit type apertured mask.
Shadow mask type color picture tubes usually include a screen of red, green and blue emitting phosphor lines or dots, electron gun means for exciting the screen and a shadow mask interposed between the ~un means and the screen. The shadow mask is a thin multiapertured sheet of metal precisely disposed adjacent the screen so that the mask or apertures are systematically related to the phosphor lines or dots.
Color picture tubes having shadowmasks with slit shaped apertures have received relatively recent commercial acceptance. One of the reasons for this acceptance is that the percentage of electron beam transmission through the mask can be made higher for a slit-mask, line-screen type of tube than for a circular-apertured-mask, dot-screen type tube. Even though the use of a slit mask provides a definite advantage in electron beam transmission, the percentage of electron beam transmission through a slit mask can be increased even further than is practiced in the present art.
In one type of slit shadow mask, the mask has vertically extending slit apertures which are interrupted by a plurality of spaced bridges or webs which provide mechanical rigidity. The presence of these webs, however, has an effect on electron beam transmission and thus on luminescent brightness.
FIGURE 1 shows a portion of a prior art shadow mask 10 having slit shaped apertures 12 arranged in columns, the apertures in each column being separated by webs 14. Each aperture 12 has an elongated shape with curved ends. Generally, the curvature of each end has a radius approximately equal to half the width of an aperture measured in the center of the aperture. Such curved aperture shape at the webs occurs because of the etching process. Apertured masks are formed 40 by first coating a metal sheet with a photosensitive O
1 -2- RCA 73,919 material, exposiny the photosensitive material through a photomaster having a desired aperture pattern thereon, and thereafter etching the metal sheet to open the apertures.
5 Most prior art photomasters have rectangularly shaped ele-ments at the locations of the intended apertures. Unfortun-ately, during etching, the apertures become rounded at their ends instead of being formed as rectangles. Because of this rounding, some electron beam transmission is lost in the 10 corners of the apertures as illustrated by the shaded areas 16 of FIGURE 2, which shows the shape of a photomaster element 18 superimposed on its resultant aperture 20. It is, therefore, desirable to develop an aperture pattern which, when etched, will form more nearly rectangular apertures 15 thereby permitting increased electron beam transmission.
In accordance with the invention, a color picture tube having a slit type apertured mask, wherein the slit apertures are arranged in columns and the apertures in each column are separated by webs, is improved by increasing the 20 radius of curvature of the ends of the apertures at the webs to substantially greater than half the width of the central portions of the respective apertures. Such aperture shape may be achieved by a method wherein the aperture image elements of a photomaster used in fabricating the mask have
2~ greater widths at the ends than at the centers thereof.
In the drawings:
FIGURE 1 (Sheet 1) is a plan view of a portion of a prior art shadow mask.
FIGURE 2 (Sheet 1) is a plan view of a prior art 30 photomaster element overlaying a resultant prior art aperture.
FIGURE 3 (Sheet 2) is a plan view, partly in axial section, of a shadow mask type color picture tube in accord-ance with the invention.
FIGURE 4 (Sheet 2) is a rear view, partly cut away, 35 of a tube faceplate assembly taken at line 4-4 of FIGURE 3.
FIGURE 5 (Sheet 1) is a plan view of a portion of a shadow mask having novel shaped apertures therein in accord-ance with the invention.
FIGURE 6 (Sheet 1) is a plan view of a novel photo-40 master element overlaying a resultant novel aperture also inaccordance with the invention.
il'~2S70 1 -3- RCA 73,919 FIGURES 7-12 (Sheet 3) are plan views of other novel photomaster elements used in generating slit apertures in accordance with the invention.
FIGURES 3 and 4 illustrate a rectangular color picture tube having a glass envelope 30 _omprising a rectangular faceplate panel or cap 32 and a tubular neck 34 connected by a rectangular funnel 36. The panel comprises a viewing faceplate 38 and a peripheral flange or sidewall 40 ~o which is sealed to the funnel 36. A mosaic three-color phosphor screen 42 is carried by the inner surface of the faceplate 38. The screen 42 is a line screen with the phosphor lines extending substantially parallel to the central vertical axis of the tube (normal to the plane of FIGURE 3). An improved domed multi-apertured color selection electrode or shadow mask 44 is removably mounted within the panel 32 by four springs 45 in predetermined spaced relation to the screen 42. An inline electron gun 46, shown schematically by dotted lines in FIGURE 1, is centrally 20 mounted within the neck 34 to generate and direct three electron beams 48 along coplanar convergent paths through the mask 44 to the screen 42. The mask 44 serves a color selection function by shadowing, or masking, each electron beam from the nonassociated color emitting phosphor lines, 25 while permitting it to strike its associated lines. A
magnetic deflection yoke 50 is positioned on the envelope 30 near the intersection of the funnel 36 and the neck 34. When suitably energized, the yoke 50 causes the electron beams 48 to scan the screen 42 in a rectangular raster.
Details of a portion of the shadow mask 44, which includes apertures 52 having a novel shape, are shown in FIGURE 5. The apertures 52 are elongated rectangular slits vertically aligned in columns. The columns are substantially parallel to each other, although they can also bow outwardly 35 at the left and right sides of the mask as is known in the art. The slits 52 in each column are separated from each other by bridges or webs 54 which connect the unapertured portions of the mask to provide the structural integrity required to maintain the domed contour of the mask.
The slit apertures 52 of the mask 44 appear to 1 -4- RCA 73,919 have a dogbone or dumbbell shape.being slightly wider at their ends than in the middle sections. The ends of the slit apertures 52 at the webs 54 are curved with a radius of curvature much larger than at the ends of the prior art apertures shown in FIGURE 1. In the prior art apertures, this radius of curvature is approximately equal to half the width of the aperture,whereas with the present novel slit aperture 52 the end radius is substantially greater than half the width of the central portions c)f the apertures. Because of this larger radius at the ends of the apertures 52, the apertures are more nearly rectangular, whereby much of the shaded areas 16 of the FIGURE 2 prior art aperture shape are open, thereby permitting increased electron beam transmission at the webs.
Aperture shapes, such as the foregoing dogbone shape, are generated by varying the shape of a photomaster element to resemble an I-shape,wherein the top and bottom of each element is made wider than the remainder of the element. FIGURE 6 shows the shape of an I-shaped photomaster element 56 overlaying a resultant aperture 58.
Variations may be made in the basic I-shape of the photomaster elements to modify the resultant aperture shapes. Some of these variations are shown in FIGURES 7-12.
In the photomaster element 60 of FIGURE 7, the top and bottom ends 62 and 64 of the I-shape are notched to further reduce the amount of rounding at the top and bottom of a resultant aperture. The photomaster element 66, shown in FIGURE 8, includes beveled ends, 68 and 70, of the cross 30 portions of the I-shape to reduce the width of the apertures at their ends. FIGURES 9 and 10 represent the inclusion of minor corrections that can be made to either or both of the embodiments of FIGURES 7 and 8, to fine tune the photomaster element shapes to obtain a more nearly rectangular aperture shape. In the photomaster element 72 of FIGURE 9, the ends 74 and 76 are concavely curved rather than notched~ and in the photomaster element 78 of FIGURE 10, the beveled ends, 8Q and 82, of the cross portions are slightly concavely curved. In each of these two embodiments, the slight curvature 40 permits a fine tuning of the resultant aperture shape to at il ~2570 1 -5- RCA 73,919 least approach a rectangular shape.
The photomaster element shapes, 84 and 86,of FIGURES 11 and 12, respectively, provide two ways in which to further reduce the outward bowing of the apertures at the ends of the apertures. In FIGURE 11, the angle of the bevel at the ends, 88 and 90, of the cross portions of the I-shapes are reversed;and in FIGURE 12,notches, 92 and 94, are placed in the photomaster element next to the cross portions.
In the drawings:
FIGURE 1 (Sheet 1) is a plan view of a portion of a prior art shadow mask.
FIGURE 2 (Sheet 1) is a plan view of a prior art 30 photomaster element overlaying a resultant prior art aperture.
FIGURE 3 (Sheet 2) is a plan view, partly in axial section, of a shadow mask type color picture tube in accord-ance with the invention.
FIGURE 4 (Sheet 2) is a rear view, partly cut away, 35 of a tube faceplate assembly taken at line 4-4 of FIGURE 3.
FIGURE 5 (Sheet 1) is a plan view of a portion of a shadow mask having novel shaped apertures therein in accord-ance with the invention.
FIGURE 6 (Sheet 1) is a plan view of a novel photo-40 master element overlaying a resultant novel aperture also inaccordance with the invention.
il'~2S70 1 -3- RCA 73,919 FIGURES 7-12 (Sheet 3) are plan views of other novel photomaster elements used in generating slit apertures in accordance with the invention.
FIGURES 3 and 4 illustrate a rectangular color picture tube having a glass envelope 30 _omprising a rectangular faceplate panel or cap 32 and a tubular neck 34 connected by a rectangular funnel 36. The panel comprises a viewing faceplate 38 and a peripheral flange or sidewall 40 ~o which is sealed to the funnel 36. A mosaic three-color phosphor screen 42 is carried by the inner surface of the faceplate 38. The screen 42 is a line screen with the phosphor lines extending substantially parallel to the central vertical axis of the tube (normal to the plane of FIGURE 3). An improved domed multi-apertured color selection electrode or shadow mask 44 is removably mounted within the panel 32 by four springs 45 in predetermined spaced relation to the screen 42. An inline electron gun 46, shown schematically by dotted lines in FIGURE 1, is centrally 20 mounted within the neck 34 to generate and direct three electron beams 48 along coplanar convergent paths through the mask 44 to the screen 42. The mask 44 serves a color selection function by shadowing, or masking, each electron beam from the nonassociated color emitting phosphor lines, 25 while permitting it to strike its associated lines. A
magnetic deflection yoke 50 is positioned on the envelope 30 near the intersection of the funnel 36 and the neck 34. When suitably energized, the yoke 50 causes the electron beams 48 to scan the screen 42 in a rectangular raster.
Details of a portion of the shadow mask 44, which includes apertures 52 having a novel shape, are shown in FIGURE 5. The apertures 52 are elongated rectangular slits vertically aligned in columns. The columns are substantially parallel to each other, although they can also bow outwardly 35 at the left and right sides of the mask as is known in the art. The slits 52 in each column are separated from each other by bridges or webs 54 which connect the unapertured portions of the mask to provide the structural integrity required to maintain the domed contour of the mask.
The slit apertures 52 of the mask 44 appear to 1 -4- RCA 73,919 have a dogbone or dumbbell shape.being slightly wider at their ends than in the middle sections. The ends of the slit apertures 52 at the webs 54 are curved with a radius of curvature much larger than at the ends of the prior art apertures shown in FIGURE 1. In the prior art apertures, this radius of curvature is approximately equal to half the width of the aperture,whereas with the present novel slit aperture 52 the end radius is substantially greater than half the width of the central portions c)f the apertures. Because of this larger radius at the ends of the apertures 52, the apertures are more nearly rectangular, whereby much of the shaded areas 16 of the FIGURE 2 prior art aperture shape are open, thereby permitting increased electron beam transmission at the webs.
Aperture shapes, such as the foregoing dogbone shape, are generated by varying the shape of a photomaster element to resemble an I-shape,wherein the top and bottom of each element is made wider than the remainder of the element. FIGURE 6 shows the shape of an I-shaped photomaster element 56 overlaying a resultant aperture 58.
Variations may be made in the basic I-shape of the photomaster elements to modify the resultant aperture shapes. Some of these variations are shown in FIGURES 7-12.
In the photomaster element 60 of FIGURE 7, the top and bottom ends 62 and 64 of the I-shape are notched to further reduce the amount of rounding at the top and bottom of a resultant aperture. The photomaster element 66, shown in FIGURE 8, includes beveled ends, 68 and 70, of the cross 30 portions of the I-shape to reduce the width of the apertures at their ends. FIGURES 9 and 10 represent the inclusion of minor corrections that can be made to either or both of the embodiments of FIGURES 7 and 8, to fine tune the photomaster element shapes to obtain a more nearly rectangular aperture shape. In the photomaster element 72 of FIGURE 9, the ends 74 and 76 are concavely curved rather than notched~ and in the photomaster element 78 of FIGURE 10, the beveled ends, 8Q and 82, of the cross portions are slightly concavely curved. In each of these two embodiments, the slight curvature 40 permits a fine tuning of the resultant aperture shape to at il ~2570 1 -5- RCA 73,919 least approach a rectangular shape.
The photomaster element shapes, 84 and 86,of FIGURES 11 and 12, respectively, provide two ways in which to further reduce the outward bowing of the apertures at the ends of the apertures. In FIGURE 11, the angle of the bevel at the ends, 88 and 90, of the cross portions of the I-shapes are reversed;and in FIGURE 12,notches, 92 and 94, are placed in the photomaster element next to the cross portions.
Claims (6)
1. A color picture tube having a slit type apertured mask, wherein the slit apertures are arranged in columns and he apertures in each column are separated by webs, the ends of each aperture at the webs being curved; wherein the radius of curvature of the ends of the apertures at the webs is substantially greater than half the width of central portions of the respective apertures.
2. A color picture tube according to claim 1, wherein said apertures are wider at the ends than at the center thereof.
3. A color picture tube according to claim 2, wherein said apertures have a dogbone configuration.
4. A color picture tube according to claim 1, wherein said apertures have shapes at the ends thereof which are more nearly square than semicircular.
5. A method of making a color picture tube having a slit type apertured mask, wherein the slit apertures are arranged in columns and the apertures in each column are separated by webs, said mask being formed by coating a metal sheet with a photosensitive material, exposing the photosensi-tive material through a photomaster having an apertured pattern thereon and thereafter etching the metal sheet to form aper-tures therein; comprising exposing said metal sheet through a photomaster having aperture image elements which have greater width at the ends than at the central portions of the elements, whereby upon etching said metal sheet apertures are generated therein which are more nearly rectangular than are apertures formed in a mask which was exposed by a photomaster having rectangular aperture image elements.
6. The method according to claim 5, wherein the aperture image elements in said photomaster have an I-shaped configuration.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US4199879A | 1979-05-24 | 1979-05-24 | |
| US041,998 | 1979-05-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1142570A true CA1142570A (en) | 1983-03-08 |
Family
ID=21919501
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000351855A Expired CA1142570A (en) | 1979-05-24 | 1980-05-13 | Color picture tube having improved slit type shadow mask and method of making same |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS55159545A (en) |
| CA (1) | CA1142570A (en) |
| DD (1) | DD153023A5 (en) |
| DE (1) | DE3019816A1 (en) |
| FR (1) | FR2457561A1 (en) |
| IT (1) | IT1131155B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2741036B2 (en) * | 1988-07-30 | 1998-04-15 | 大日本スクリーン製造株式会社 | Shadow mask for color picture tube |
| DE69132527T2 (en) * | 1990-11-22 | 2001-08-23 | Toshiba Kawasaki Kk | Negative plate for producing a shadow mask and method for producing the negative plate |
| KR20060109100A (en) | 2005-04-15 | 2006-10-19 | 삼성에스디아이 주식회사 | Shadow mask for cathode ray tube |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL203836A (en) * | 1956-01-21 | |||
| DE1951304A1 (en) * | 1968-10-30 | 1970-05-21 | Sanyo Electric Co | Color cathode ray tubes |
| GB1430864A (en) * | 1973-04-06 | 1976-04-07 | Woollenweber W E | Rotatable assembly including two vaned wheels mounted on a common shaft |
| US3834905A (en) * | 1973-05-23 | 1974-09-10 | Rca Corp | Method of making elliptically or rectangularly graded photoprinting masters |
| US3955980A (en) * | 1974-11-04 | 1976-05-11 | Zenith Radio Corporation | Method for making a color selection mask for a color cathode ray tube |
| JPS5158065A (en) * | 1974-11-18 | 1976-05-21 | Hitachi Ltd | KARAAJUZOKAN |
| JPS5320853A (en) * | 1976-08-11 | 1978-02-25 | Hitachi Ltd | Rear-stage convergence type color picture tube |
| JPS5376741A (en) * | 1976-12-20 | 1978-07-07 | Toshiba Corp | Shadow mask its fabrication |
-
1980
- 1980-05-06 IT IT21829/80A patent/IT1131155B/en active
- 1980-05-13 CA CA000351855A patent/CA1142570A/en not_active Expired
- 1980-05-13 FR FR8010701A patent/FR2457561A1/en not_active Withdrawn
- 1980-05-19 JP JP6705080A patent/JPS55159545A/en active Pending
- 1980-05-22 DD DD80221313A patent/DD153023A5/en unknown
- 1980-05-23 DE DE19803019816 patent/DE3019816A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| IT1131155B (en) | 1986-06-18 |
| JPS55159545A (en) | 1980-12-11 |
| FR2457561A1 (en) | 1980-12-19 |
| DE3019816A1 (en) | 1980-11-27 |
| IT8021829A0 (en) | 1980-05-06 |
| DD153023A5 (en) | 1981-12-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |