US3925700A - Shadow mask for a black-stripe color picture tube having successively curved perforations - Google Patents

Shadow mask for a black-stripe color picture tube having successively curved perforations Download PDF

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Publication number
US3925700A
US3925700A US531414A US53141474A US3925700A US 3925700 A US3925700 A US 3925700A US 531414 A US531414 A US 531414A US 53141474 A US53141474 A US 53141474A US 3925700 A US3925700 A US 3925700A
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United States
Prior art keywords
shadow mask
perforations
mask
plane
curvature
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Expired - Lifetime
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US531414A
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English (en)
Inventor
Yuji Saito
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NEC Corp
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Nippon Electric Co Ltd
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    • 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

Definitions

  • This invention relates to a shadow mask for a color picture tube having color luminescent materials deposited in stripes on an inside surface of a glass face or viewing plate of the picture tube.
  • a color picture tube of the type described has black stripes between the respective color luminescent stripes.
  • a shadow mask according to this invention is therefore described herein with regard to a color picture tube of the so-called black-stripe type although the shadow mask is not restricted to that for use in a picture tube of the last-mentioned type.
  • each color picture tube includes a shadow mask at present.
  • the shadow mask does not only serve to reproduce a colored picture but also is resorted to on depositing the color luminescent materials on the face plate inside surface.
  • a conventional shadow mask for a color picture tube of the type described is of a general shape of a rectangle and has a plurality of perforations which are elongate in the direction of the minor or shorter sides of the rectangle and arranged in a regular array with respect to the minor sides and to major or longer sides of the rectangle. With this shadow mask, the color luminescent material stripes become distorted at peripheral portions of the mask to result in colored pictures of an unpleasing appearance. Although it has been proposed to resort to partial exposure in the manner later described with reference to the accompanying drawing, this reduces the productivity of color picture tubes.
  • a color picture tube of the type described has a generally rectangular glass face plate of a substantially spherical curvature.
  • a shadow mask for the color picture tube has a shape of a similar rectangle and an approximately equal spherical curvature so as to be positioned substantially parallel to an inside surface of the face plate and has a plurality of perforations formed therethrough.
  • the perforations are elongate in the direction of a predetermined pair of sides of the similar rectangle and arranged in a regular array with respect to the direction and another direction perpendicular to the first-mentioned direction.
  • the perforations are arranged, when the mask is extended to coincide with a plane, parallel to the above-mentioned pair of sides in an area adjacent to a center line bisecting the remaining pair of the sides and, in remaining areas of the mask, along a plurality of curves whose curvatures grow larger with an increase in the distance from the center line.
  • FIG. 1 is a fragmentary perspective view of a glass panel of a color picture tube, a shadow mask therefor, and a conventional device for projecting light rays onto an inside surface of the panel through perforations of a conventional shadow mask;
  • FIG. 2 is a perspective view of a conventional shadow mask
  • FIG. 3 shows a back view of the panel together with several stripes of light rays projected onto the inside or back surface of the panel through perforations of a conventional shadow mask;
  • FIG. 4 shows a back view of the panel and a restricted area for the light rays
  • FIG. 5 illustrates an arrangement of perforations of a shadow mask according to the instant invention
  • FIG. 6 is a schematic perspective view of a shadow mask for describing the arrangement of perforations with reference to an orthogonal coordinate system
  • FIG. 7 shows a projection of the perforations on the X-Y plane of the coordinate system
  • FIG. 8 again shows the coordinate system illustrated in FIG. 6 for describing an arrangement of the perforations of a prototype of the shadow masks according to this invention
  • FIG. 9 shows the prototype extended on a plane, together with the X and Y axes of the coordinate system projected onto the plane;
  • FIG. 10 shows another orthogonal coordinate system for describing a simplified arrangement of the perforations of the prototype.
  • FIG. 11 is an exploded schematic perspective view of an arrangement for manufacturing shadow masks according to this invention.
  • a color picture tube of the black-stripe type has a glass member generally called a glass panel in the art.
  • the panel consists of a generally rectangular glass face or viewing plate 20 of a substantially spherical curvature and a skirt portion extended from the periphery of the face plate 20 generally perpendicularly therof.
  • a shadow mask 21 for the color picture tube has a surface of a similar rectangle and an approximately equal spherical curvature so as to be positioned substantially parallel to an inside or back surface of the face plate 20 and has a plurality of perforations 22 formed through the mask surface.
  • the perforations 22 are elongate in the direction of minor or shorter sides of the rectangle and arranged in a regular array with respect to the minor sides and to major or longer sides of the rectangle.
  • the shadow mask 21 is flat.
  • the perforations 22 are formed through the flast mask plate parallel to the minor sides.
  • the slotted mask plate is subsequently pressed into a shadow mask 21 having a surface of a substantially spherical curvature.
  • the stripes of color luminescent materials are deposited on the face plate inside surface by coating at first the inside surface with a photosensitive film (not shown), on which a beam of light rays is projected through the perforations 22 from a light source 25 placed at a point where electron source means (not shown) of the color picture tube is subsequently positioned.
  • a photosensitive film not shown
  • the perforations 22 arranged along a line substantially parallel to the minor sides are partitioned by a plurality of bridges 26. It is therefore necessary that the light source 25 be elongate in the direction of the minor sides and that the length be longer than the perforations 22.
  • stripes S of the light projected on the face plate inside surface become distorted with an increase in the distance from the center point of the face plate 20.
  • stripes (not shown) of the color luminescent materials and black stripes (not shown) disposed between the respective color luminescent stripes are deposited on the face plate inside surface accordingly distorted.
  • the device 27 has a slotted plate 28 for moving an area 29 exposed to the light rays parallel to the minor sides in synchronism with the rocking movemento f the light source 25. It is, however, impossible with the partial exposure as called herein to utilize the whole rays emitted by the light source 25. This reduces the productivity of the color picture tubes.
  • a shadow mask 21 according to the present invention has perforations 22 formed, before the mask surface is pressed into a substantially spherical form, parallel to the minor sides in an area adjacent to a center line bisecting the major sides of the rectangle and, in remaining areas of the mask surface, along a plurality of curves whose. curvatures grow larger with an increase in the distance from the center line.
  • the shadow mask 21 has a spherical surface having its center of curvature at a point 30 and that the elongate light source 25 is placed at an origin of a right-handed orthogonal coordinate system having an X and a Y axis parallel to the major andminor sides of the mask 21 and a Z axis perpendicular to the X-Y plane.
  • the light beam emitted by the source 25 along a plane 31 that passes through the Y axis and makes an angle a with respect to the Z axis intersects the mask surface along a small circle .32.
  • the perforations 22 (not shown in FIG. 6) of a shadow mask 21 according to this invention are arranged along the small circle 32 and similar small circles.
  • the perforations 22 (not shown in FIG. 6) of a conventional shadow mask are arranged along great circles exemplified at 33 as an intersection of the mask surface and a plane 34 that is parallel to the Y axis and makes an angle [3 with respect to the Z axis. If the planes 31 and 34 have acornmon point 35 on the mask surface, the angles are given by:
  • an angle (b measured from a plane 36 parallel to the X-Z plane and passing through the common point 35 to that portion of the small circle 32 which is adjacent to the common point 35 is:
  • the device 27 rocks the light source 25 so that the plane along which the light rays are projected may make an angle (1) to the X-Z plane at a pointplaced in the moving area 29 for the partial exposure.
  • the perforations 22 of a shadow mask 21 according to this invention are arranged as described along the small circles, such as 32.
  • the stripe portions of the light rays projected on the face plate inside surface are therefore aligned, for example, on the small circle 32 if it is again surmised that the faace plate inside surface is in direct contact with the mask surface. It is consequently unnecessary to resort to the device 27 thus far described on depositing the color luminescent and black stripes. This not only raises the productivity of the color picture tubes of the type described but also raises the precision of the stripe arrangement.
  • this invention reduces the cost of installation for manufacture of the color picture tubes of the type described.
  • a shadow mask is generally manufactured by the use of a flat prototype of patterns for the perforations to be formed through the mask surface. It is therefore an important task to form a prototype for shadow masks according to this invention.
  • one of the small circles 32 along which the perforations should be aligned according to this invention intersects the X-Z plane at a point 36. Let the Z axis intersect the spherical surface of the shadow mask at a point 40 and the distance on the spherical surface between the point 36 and 40 be denoted by L.
  • the point 36 is a point which the point 36 illustrated with reference to FIG. 8 assumes on the flat or extended shadow mask surface.
  • the X and Y axes of FIg. 9 are orthogonal projections of the X and Y axes of FIG. 8 on the flat prototype surface.
  • That portion of the small circle 32 of alignment of the perforations according to this invention which is adjacent to the great circle 41 may approximately be represented by a curve of intersection 42 of a plane 43 (not shown in FIGS. 8 and 9) including the small circle 32 and a right cylindrical surface 44 (not shown in FIGS. 8 and 9) which is tangential to the spherical surface at the great circle 41, namely, which has the great circle 41 as the director curve.
  • the perfo- -rations are now-jaligned according to this invention along the curve or an ellipse of approximation 42 instead of the small circle 32.
  • the ellipse of approximation 42 becomes a curve 42', which may be specified by the distances, such as PP, from the straight line 41 and the ordinates of the line segments representative of the distances.
  • the X-Y plane includes the great circle 41, the origin being placed at the center of the great circle 41.
  • the point 36 is on the X axis in its positive region, the coordinates of the point 36 being given by (R, 0, 0).
  • the plane 43 of the small circle 32 and the ellipse of approximation 42 is depicted.
  • the cylindrical surface 44 and the distance PP are also illustrated In FIG. 8, let the coordinates of the point 36 be (X, 0, Z) although the values of X and Z may differ from those for the point 35 illustrated with reference to FIG. 6.
  • Equations (1) and (2) An angle (1) between these planes is given, in terms of X, by:
  • Equation (9) PP Rll cos( Y/Rlltanrb results from Equation (9). This applies also to the substantially vertically aligned perforations, two of which are placed contiguous to the horizontal center line,
  • the radius of curvature R of a shadow mask surface be 800 mm.
  • the distance m between the center of curvature 30 and the light source 25 be 535 mm.
  • the pitches H and V be 0.52 mm and 1.00 mm, respectively.
  • the small displacement PP for the (364,j)-th perforation is:
  • a shadow mask may often have different radii of curvature in the X-Z and Y-Z planes of FIG. 8. For example, let arcs of a first and a second circle of radii R and R be drawn on the X-Z and Y-Z planes, both having the centers on the Z axis and passing through the point or vertex 40, and let a plane on which the second arc is present be tilted from the Y-Z plane with the center of the first circle fixed and with the second arc guided by the first arc to generate a substantially spherical surface of a shadow mask. If the center of the first circle is placed at a point 30 whose coordinates are (0, 0, m), the angle 4) is given by:
  • Equation (10) and (11) become:
  • a shadow mask of the color picture tube of the type described generally has curved minor sides.
  • several lines of the perforation arrangement are cut short in longitudinal end portions of the mask. This results in an additionally unpleasing appearance of the colored pictures at the horizontal end portions.
  • a shadow mask naturally has rounded corners. Let a point of connection between the minor side and a rounded corner be placed at a point whose X and Y coordinates are (X Y,). The abscissa is:
  • X. (X .R..) M where R, and X represent the radius of curvature of the curved minor side and the abscissa of an intersection of the X axis and the curved minor side.
  • R, and X represent the radius of curvature of the curved minor side and the abscissa of an intersection of the X axis and the curved minor side.
  • a shadow mask according to this invention may be manufactured by the use of a flat prototype 50 through which substantially vertically running slits 51 are formed in the manner thus far described and a transparent screen 52 on which opaque line segments 53 are printed or otherwise formed so as to intersect the slits 51 at portions corresponding to the bridges 26 of a flat shadow mask.
  • the prototype 51 and screen 52 are superposed on a metal plate 55 coated with a photosensitive film, which is exposed to a light source exemplified by an incandescent lamp 56 through'the slits 51 cut at portions by the opaque line segments 53.
  • the slits 51 may be readily formed by the use ofa numerically controlled machine. In this connection, it should be mentioned that the precision for the line segments 53 is not serious because the color luminescent stripes and the black stripes, if any, are continuous along the curves mentioned above.
  • a shadow mask for a color picture tube having a generally rectangular glass face plate of a substantially spherical curvature, and mask having a shape of a similar rectangle and an approximately equal spherical curvature to be positioned substantially parallel to an inside surface of said face plate and having a'plurality of perforations formed therethrough, said perforations being elongate in a first direction parallel to a predetermined pair of sides of said similar rectangle and arranged in a regular array with respect to said direction and to a second direction perpendicular to said first direction, the improvement wherein said perforations are arranged, when said mask is extended to coincide with a plane, parallel to said first direction in an area adjacent to a center line bisecting the remaining pair of said sides and, in remaining areas of said mask, along a plurality of curves whose curvatures grow successively larger with an increase in the distance from said center line.
  • a shadow mask according to claim 1 wherein said predetermined side pair runs along those two of said curves which are disposed outermost as regards said second direction.
  • said picture tube including electron source means for projecting electrons onto said face plate inside surface through said mask, said approximately equal spherical curvature being R, in an X-Z plane and-R in a Y-Z plane, said X-Z and Y-Z planes being coordinate planes of an orthogonal XYZ coordinate system having an X and a Y axis in said second and first directions and a Z axis passing through a center point of said mask, centers of curvature for the curvatures R anad R being placed on said Z axis, wherein, when said mask is extended to coincide with a plane, said perforations are arranged with a pitch of H along said X-Z plane and a pitch of V in said first direction and said curves are specified by small displacements towards said center line from respective straight lines passing through points aligned along said X-Z plane at X-coordinate of iI-I (i being representative of 0 and positive and negative integers), said displacements at
  • m represents the distance between said electron source means and said center of curvature for the curvature R 4.

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US531414A 1973-12-10 1974-12-10 Shadow mask for a black-stripe color picture tube having successively curved perforations Expired - Lifetime US3925700A (en)

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JP48139463A JPS6024533B2 (ja) 1973-12-10 1973-12-10 シヤドウマスクの製造方法

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JP (1) JPS6024533B2 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
DE (1) DE2458427A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
GB (1) GB1442877A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4059834A (en) * 1974-03-13 1977-11-22 Matsushita Electronics Corporation Light exposing apparatus for forming a phosphor screen of a cathode ray tube
EP0001673A3 (en) * 1977-10-26 1979-05-16 N.V. Philips' Gloeilampenfabrieken Colour selection electrode with elongate apertures in a colour display tube
US4226513A (en) * 1976-12-11 1980-10-07 Tokyo Shibaura Electric Co., Ltd. Exposure device for making a stripe screen on a faceplate of a color cathode ray tube
DE3430395A1 (de) * 1983-08-19 1985-03-07 Rca Corp., New York, N.Y. Verfahren zur bildschirmherstellung bei schlitzmasken-farbbildroehren mit linienrasterschirm
US4568162A (en) * 1983-08-19 1986-02-04 Rca Corporation Method for screening line screen slit mask color picture tubes
FR2579018A1 (fr) * 1985-03-14 1986-09-19 Rca Corp Tube image couleur a masque d'ombre perfectionne
US4631441A (en) * 1985-03-14 1986-12-23 Rca Corporation Color picture tube having improved line screen
US4634247A (en) * 1985-12-19 1987-01-06 Rca Corporation Method for screening line screen slit mask color picture tubes
US4665339A (en) * 1984-05-25 1987-05-12 Rca Corporation Color picture tube having improved slit column pattern
US4677339A (en) * 1984-09-13 1987-06-30 Kabushiki Kaisha Toshiba Color cathode ray tube
US4691138A (en) * 1985-03-14 1987-09-01 Rca Corporation Color picture tube having shadow mask with varied aperture column spacing
US4697119A (en) * 1985-01-11 1987-09-29 Kabushiki Kaisha Toshiba Color cathode ray tube having a non-spherical curved mask
US20030132895A1 (en) * 2001-12-13 2003-07-17 International Bisiness Machines Corporation System and method for anti-moire display

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2656995C2 (de) * 1976-12-16 1983-12-01 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Rechteckförmige Farbwahlmaske für eine Farbbildkathodenstrahlröhre
JPS5998562U (ja) * 1982-12-23 1984-07-04 株式会社東芝 カラ−受像管
FR2589002B1 (fr) * 1985-10-22 1994-09-23 Videocolor Tube de television en couleurs du type a masque et son procede de fabrication

Citations (2)

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Publication number Priority date Publication date Assignee Title
US3721853A (en) * 1971-12-01 1973-03-20 Sony Corp Shadow mask having apertures at intersections of barrel-shaped and pincushion shaped lines
US3731129A (en) * 1969-11-04 1973-05-01 Tokyo Shibaura Electric Co Rectangular color tube with funnel section changing from rectangular to circular

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CA921540A (en) * 1968-11-21 1973-02-20 Fuse Yuzo Shadow mask
JPS5244511B2 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) * 1972-08-30 1977-11-08
NL7303077A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) * 1973-03-06 1974-09-10
JPS5244511A (en) * 1975-10-06 1977-04-07 Nippon Telegr & Teleph Corp <Ntt> Illumination light source for facsimile

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3731129A (en) * 1969-11-04 1973-05-01 Tokyo Shibaura Electric Co Rectangular color tube with funnel section changing from rectangular to circular
US3721853A (en) * 1971-12-01 1973-03-20 Sony Corp Shadow mask having apertures at intersections of barrel-shaped and pincushion shaped lines

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4059834A (en) * 1974-03-13 1977-11-22 Matsushita Electronics Corporation Light exposing apparatus for forming a phosphor screen of a cathode ray tube
US4226513A (en) * 1976-12-11 1980-10-07 Tokyo Shibaura Electric Co., Ltd. Exposure device for making a stripe screen on a faceplate of a color cathode ray tube
EP0001673A3 (en) * 1977-10-26 1979-05-16 N.V. Philips' Gloeilampenfabrieken Colour selection electrode with elongate apertures in a colour display tube
DE3430395A1 (de) * 1983-08-19 1985-03-07 Rca Corp., New York, N.Y. Verfahren zur bildschirmherstellung bei schlitzmasken-farbbildroehren mit linienrasterschirm
US4516841A (en) * 1983-08-19 1985-05-14 Rca Corporation Method for screening line screen slit mask color picture tubes
US4568162A (en) * 1983-08-19 1986-02-04 Rca Corporation Method for screening line screen slit mask color picture tubes
US4665339A (en) * 1984-05-25 1987-05-12 Rca Corporation Color picture tube having improved slit column pattern
US4677339A (en) * 1984-09-13 1987-06-30 Kabushiki Kaisha Toshiba Color cathode ray tube
US4697119A (en) * 1985-01-11 1987-09-29 Kabushiki Kaisha Toshiba Color cathode ray tube having a non-spherical curved mask
US4631441A (en) * 1985-03-14 1986-12-23 Rca Corporation Color picture tube having improved line screen
GB2175132A (en) * 1985-03-14 1986-11-19 Rca Corp Color picture tube shadow mask
FR2579018A1 (fr) * 1985-03-14 1986-09-19 Rca Corp Tube image couleur a masque d'ombre perfectionne
US4691138A (en) * 1985-03-14 1987-09-01 Rca Corporation Color picture tube having shadow mask with varied aperture column spacing
GB2175132B (en) * 1985-03-14 1989-06-21 Rca Corp Color picture tube having improved shadow mask
US4634247A (en) * 1985-12-19 1987-01-06 Rca Corporation Method for screening line screen slit mask color picture tubes
DE3643113A1 (de) * 1985-12-19 1987-06-25 Rca Corp Verfahren zur herstellung eines linienrasterschirms einer schlitzmasken-farbbildroehre
US20030132895A1 (en) * 2001-12-13 2003-07-17 International Bisiness Machines Corporation System and method for anti-moire display
US6784856B2 (en) * 2001-12-13 2004-08-31 International Business Machines Corp. System and method for anti-moire display

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GB1442877A (en) 1976-07-14
DE2458427A1 (de) 1975-06-19
JPS6024533B2 (ja) 1985-06-13
JPS5090284A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1975-07-19

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