US3705322A - Shadow mask having apertures at intersections of barrel-shaped horizontal and pin-cushion-shaped vertical lines - Google Patents

Shadow mask having apertures at intersections of barrel-shaped horizontal and pin-cushion-shaped vertical lines Download PDF

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Publication number
US3705322A
US3705322A US40868A US3705322DA US3705322A US 3705322 A US3705322 A US 3705322A US 40868 A US40868 A US 40868A US 3705322D A US3705322D A US 3705322DA US 3705322 A US3705322 A US 3705322A
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United States
Prior art keywords
apertures
shadow mask
barrel
mask
curved lines
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Expired - Lifetime
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US40868A
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English (en)
Inventor
Yohsuke Naruse
Ryosuke Ashiya
Takehiko Nii
Yuzo Fuse
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Sony Corp
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Sony Corp
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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

  • ABSTRACT In a cathode ray tube having a curved'phosphor screen, a shadow mask having apertures therein and electron beam generating means for generating three in-line electron beams aligned in a horizontal direction, the apertures of the shadow mask are aligned in the form of barrel-shaped lines extending in ahorizontal direction and are aligned in the form of pin-cushioned lines extending in a vertical direction.
  • the apertures are circular at the central portion of the mask but become gradually elliptic as the peripheral portion of the mask is approached from its center, and
  • the longer axis of .the elliptic apertures are inclined at predetermined angles to a horizontal direction corresponding to their particular locationo'ns.
  • This invention relates to an improved shadow mask, and more particularly to a .color cathode ray tube in which an improved shadow mask is used to ensure that the electron beam strikes exactly on a color dot of the tube.
  • color cathode ray tubes comprise an electron gun for emitting an electron beam, a colorsc reen and a shadow mask or aperture grill for beam selection, in which each of the apertures perforated in the mask or grill is supposed to correspond exactly to each of the color dotsto cause the beams to strike precisely on predetermined .color dots for reproducing exerciser picture.
  • the beam does not strike thedots accuratelydue to certain causes that introduce improper masking and or misconvergence. This effect is worse in the peripheral areas of the screen than at the center.
  • the present invention is directed to a shadow-mask type color cathode ray tube in which a plurality of electron beams originally aligned in one plane, are deflected horizontally and vertically while being kept aligned in a common plane and are caused to scan an outwardly projecting screen having spherical or cylindrical curvature or the like.
  • the beams pass through a shadow mask to reach thescreen and the transmission factor of the shadow mask is increased to provide for enhanced brightness in the reproduced picture.
  • one'object of this invention is to provide an improved shadow mask.
  • Another object of this invention is to provide a color cathode ray tube which employs an in-line gun.
  • Still another object of this invention is to provide a color cathode ray tube employing an improved shadow mask having a plurality of apertures in a particular pattern and in which color dots on the screen are closely packed in its peripheral portion.
  • FIG. 1 is a perspective view, partlycut away, showing certain geometric relations in a cathode ray tube
  • FIGS. 3A and 3B are schematic diagrams showing the relative arrangement of Phosphor dots on the screen perpendicular to the central axis of a cathode ray tube employing the shadow mask depicted in FIG.
  • FIG. 4 is a schematic diagramshowing the relative arrangement of the Phosphor dots on a spherical screen of a cathode ray tube using the shadow mask shown in FIG. 2;
  • FIGS. 5A, 5B and 5C show, onenlarged scale the relative arrangement of the Phosphor dots on a screen in accordance with this invention
  • FIG. 6 is a schematic diagram illustrating one example of a shadow-mask for explaining this invention.
  • FIG. 8 is a schematic diagram illustrating another example of a shadow mask for explaining this invention.
  • FIG. 10 is an enlarged schematic diagram showing the relative arrangement of the Phosphor dots on the screen.
  • FIG. 11 shows geometrical relations for explaining the shape of the apertures of the mask of this invention.
  • FIG. 12 is a schematic diagram, for explaining the orientation of apertures in this invention.
  • the relationship between mask apertures and screen dots will be described first in connection with a conventional type of shadow mask 1 depicted in FIG. 2, in which assumed horizontal and vertical lines X X X1, 0 1 X2, 3- and a Y2, Y1, 0 Y1, Y2, Y are drawn on the shadow mask 1 as viewed from the z-axis direction.
  • the shadow mask 1 is of the type having apertures 2 located at intersections of evennumber horizontal and vertical lines X X X and Y Y Y and at intersections of oddnumber horizontal and vertical lines X X X and Y3, Y1, Y3
  • the first assumption is that the phosphor screen 3 is a surface perpendicular to the central axis of the tube and that red, green and blue phosphor dots D D and D,, on
  • oeooa 001 l with the screen 3 are formed by a well-known light or electron beam printing method employing a light or electron beam passing through the horizontal and vertical deflection center of the beam.
  • the phosphor dots D D and D have a diameter and form triplets of picture elements for each aperture 2 of the mask 1. These triplets are sequentially arranged on the horizontal lines.
  • the pitch Lx of adjacent vertical columns of apertures of the shadow mask 1 is selected to be V3 times the pitch Ly of adjacent horizontal rows of apertures.
  • the beam triplets passing through individual apertures 19 are tilted relative to the original alignment of the three beams as shown in FIG. 4.
  • This phenomenon is referred to as the twist of in-line beam triplets.
  • the twist phenomenon is a purely geometrical effect caused by the combination of in-line alignment of three beams and a spherical screen.
  • the three beams l2, l3 and 14 passing through the aperture 19 of the shadow mask 17 define the flat plane 16 which is parallel to the x-axis of the tube and which makes an angle of (i /(the angle of vertical deflection) to the 1-2 plane.
  • This flat plane 16 intersects the spherical screen 18 which has the center 0 on the zaxis.
  • the in-line beam triplet 10 thus falls on an intersection line 1, which is an elliptical arc as viewed from the z-axis direction and is expressed as follows.
  • the present inventors have previously proposed in the copending United States patent application Ser. No. 877,183, filed Nov. 17, 1969, now abandoned, a shadow mask of the type in which the horizontal alignment lines of the apertures are barrel-shaped; and the vertical alignment lines of the apertures are pincushioned. These horizontal and vertical alignment lines are orthogonal to each other, and the apertures are located at the intersections of the horizontal and vertical alignment lines.
  • the primary object of the prior invention was to compensate the twist phenomenon completely. This object was met by providing an appropriate aperture pattern on the shadow mask.
  • yo is a parameter which is the intercept of the y-axis by the curve.
  • the group of arcs of ellipses (Eq. 4) form a barrelshaped group of curves X X X,, X X,, X X as shown in FIG. 6.
  • the vertical alignment lines of the apertures must be made pin-cushioned" so as to be orthogonal to the horizontal alignment lines throughout the shadow mask plane.
  • the vertical alignment lines can be obtained by solving the following differential equation, which is the inverse and has the opposite sign of the equation of geometrical twist (Eq. 2).
  • the phosphor screen 3 is spherical but the same approach can be followed in the case in which the screen is a cylindrical surface extending in a vertical direction.
  • the relationship of the inclination angle of the horizontal row of the triplet of the phosphor dots D D and D for each aperture 2 of the mask 1 to the horizontal line is as follows.
  • the horizontal alignment lines of the apertures are made barrel-shaped; and the vertical alignment lines are made pin-cushioned" so as to be orthogonal to the horizontal alignment lines throughout the shadow mask plane.
  • the apertures are positioned at the intersections of the horizontal and vertical alignment lines, as described above.
  • the curve of the horizontal alignment lines is obtained by solving the differential equation (Eq. 8) to obtain an equation corresponding to equation (4) and by satisfying the resulting equation.
  • the curve of the vertical alignment lines is obtained by solving the following differential equation, which is the inverse, and has the opposite sign, of equation (8):
  • the pitches of the apertures 2 on the horizontal and vertical alignment lines X and Y on the mask 1 are respectively x and I' (x 3 y peculiar to the xand y-axis.
  • the apertures on each line are arranged at regular intervals and the pitches of the apertures 2 of the vertical alignment lines are gradually increased according to the distance from the center of the mask 1, while the pitches of the apertures 2 of the horizontal alignment lines are gradually decreased according to the distance from the center of the'mask 1.
  • the horizontal rows of triplets of phosphor dots D D and D laid down on the screen 3 at places remote from the center of mask 1 are angularly displaced relative to the horizontal lines and do not overlap adjacent dots, as depicted in FIG. 7.
  • the vertical spacings of the phosphor dots are reduced as compared with the vertical spacing at the center of the screen, and the horizontal spacings of the dots are enlarged as compared with the horizontal spacing at the center.
  • this spacing does not fully satisfy the requirement for closely packed hexagonal arrays of phosphor dots and introduces the possibility of deterioration of color purity resulting from overlapping of the phosphor dots of adjacent horizontal rows of the triplets, as shown in FIG. 5c.
  • the present invention has as one of its objects the improvement of the shadow mask of the construction depicted in FIG. 6 for use with a shadow mask color cathode ray tube of the type in which the red, green and blue electron beams, aligned in a common horizontal plane, are deflected by deflection means horizontally and vertically while in a common plane and are thereby caused to scan an outwardly curved spherical screen through a shadow mask.
  • the shadow mask of this invention is arranged so that the pitches of the vertical alignment lines of the apertures are enlarged toward both ends of the vertical alignment lines of the apertures, and the pitches of the horizontal alignment lines of the apertures are reduced toward both ends of the horizontal alignment lines so that the this differential equation and by satisfying the resulting pitches of the horizontal and vertical alignment lines of equation, the same results as mentioned previously canbe obtained.
  • the process of solving the simultaneous equations derived from the equations (4) and (6) produces a power series of variables such as x /R y /R xy/R x RL, y /RL, xy/RL RL whose numerators are terms of second order with respect to a length on the shadow mask plane and whose denominators are terms of second order with respect to the length of the radius of curvature R of the spherical screen or the distance from the deflection center of the bean to the center of the screen or both of them.
  • the higher order terms are neglected in the approximation for obtaining the equations l0) and (l l since the aforementioned variables are less than 0.2 in practice.
  • (x,,-x,, l) is the pitch of the vertical alignment lines on the x-axis (X and may be expressed by P (n, 0)
  • (y,,,-y,,, 1) is the pitch of the horizontal alignment lines on the y-axis (Y and may be expressed by P (0, m).
  • equations l8) and 19) are respectively expressed as including y and x,,.
  • equation (22) is substituted into the aforementioned equations (10) and (l l) and an approximation similar to that for obtaining equations (10) and (l l) is used
  • equation (18) can be expressed as including only x
  • equation (19) can be expressed including only ym
  • P,,(n, 0) and P (O, m) are given by the following
  • the apertures of the mask described above are formed elliptic so as to eliminate the possibility of deterioration of the color purity.
  • the apertureat the center of the mask is circular and the longer and shorter axes of the elliptic apertures at other positions are selected to be in predetermined ratios to avoid the possibility of deterioration of the color purity.
  • the predetermined ratios of the longer and shorter axes of the elliptic apertures can be obtained by the following method.
  • the aperture 2 of the mask 1 at any point, namely at the point P is formed with an elliptic shape as depicted in FIG. 11 and if the ratio of its longer and shorter axes is selected to be (1 (x, y,,, )/2RL) in the equation (46), a closely packed array of phosphor dots is obtained and the phosphor dots do not overlap, as can be seen in FIG. 10.
  • the present invention is characterized by the improvements in shadow masks disclosed in the aforementioned co-pending application.
  • Equation (50) corresponds to the equation (2).
  • the horizontal alignment lines are made barrel-shaped; and the vertical alignment lines of the apertures are made pin-cushioned" so as to be orthogonal to the horizontal alignment lines throughout the shadow mask plane. Apertures are positioned at the intersections of the horizontal and vertical alignment lines.
  • the curve of the horizontal alignment lines is obtained by solving the differential equation (10) to obtain an equation corresponding to the equation (2) and by satisfying the resulting equation.
  • the curve of the vertical alignment lines is obtained by solving the following differential equation, which is the inverse of the equation l0) and is of the opposite sign:
  • the present invention has been described in connection with the case where the electron beams respectively corresponding to red, green and blue colors enter the position of the horizontal and vertical deflection means while aligned in a common horizontal plane, the invention is also applicable to the case in which these electron beams enter the position of the deflection means while aligned in a common vertical plane. In this case, however, it is necessary, of course, to use a shadow mask having apertures formed at intersections of the horizontal alignment lines made pincushioned and the vertical alignment lines made barrel-shaped and to exchange the curves of the horizontal and vertical alignment lines.
  • a color cathode ray tube comprising: means for generating multiple electron beams in a common plane and converging toward a common point; a fluorescent screen defining a first concave surface facing said beam generating means and having deposited thereon ,a plurality of phosphor dot triplets for emitting light in a plurality of colors when impinged uponby the respective electron beams, each of said triplets having the phosphor dots thereof arrayed generally parallel to said common plane of the beams; and a shadow mask located between said screen and the beam-generating means and comprising a metal plate with a plurality of apertures therein for the passage of said beams and being located at the intersecting points of barrelshaped curved lines extending generally parallel to said plane and pin-cushioned curved lines substantially orthogonal to said barrel-shaped curved lines, and said apertures being substantially circular at said central part of said shadow mask and elliptic at other areas thereof and having a ratio of longer diameter to shorter diameter which is a function of the distance from said central

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US40868A 1969-05-31 1970-05-27 Shadow mask having apertures at intersections of barrel-shaped horizontal and pin-cushion-shaped vertical lines Expired - Lifetime US3705322A (en)

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JP44042143A JPS4831373B1 (enrdf_load_stackoverflow) 1969-05-31 1969-05-31

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US (1) US3705322A (enrdf_load_stackoverflow)
JP (1) JPS4831373B1 (enrdf_load_stackoverflow)
CA (1) CA946907A (enrdf_load_stackoverflow)
DE (1) DE2026413A1 (enrdf_load_stackoverflow)
FR (1) FR2063883A5 (enrdf_load_stackoverflow)
GB (1) GB1316624A (enrdf_load_stackoverflow)
NL (1) NL7007877A (enrdf_load_stackoverflow)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4139797A (en) * 1977-07-01 1979-02-13 Zenith Radio Corporation Color television screen and shadow mask assembly having increased tolerance to radial registration errors
US4370591A (en) * 1979-09-14 1983-01-25 Hitachi, Ltd. Color picture tube shadow mask
US4623818A (en) 1983-12-23 1986-11-18 Hitachi, Ltd. Shadow mask type color picture tube
EP0707335A1 (en) 1994-10-14 1996-04-17 Thomson Consumer Electronics, Inc. Display apparatus having an enhanced resolution shadow mask and method of making same
US5534746A (en) * 1995-06-06 1996-07-09 Thomson Consumer Electronics, Inc. Color picture tube having shadow mask with improved aperture spacing
US20030111950A1 (en) * 2001-12-19 2003-06-19 Lg. Philips Displays Korea Co., Ltd. Flat type color cathode ray tube
US20030132895A1 (en) * 2001-12-13 2003-07-17 International Bisiness Machines Corporation System and method for anti-moire display
US6650071B2 (en) * 2001-08-23 2003-11-18 Koninklijke Philips Electronics N.V. Color display tube with improved shadow mask
US6664724B2 (en) 2001-11-10 2003-12-16 Lg. Philips Display Korea Co., Ltd. Shadow mask for color CRT

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU1461377A3 (ru) * 1984-05-25 1989-02-23 Рка Корпорейшн (Фирма) Цветной кинескоп
US4631441A (en) * 1985-03-14 1986-12-23 Rca Corporation Color picture tube having improved line screen

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4139797A (en) * 1977-07-01 1979-02-13 Zenith Radio Corporation Color television screen and shadow mask assembly having increased tolerance to radial registration errors
US4370591A (en) * 1979-09-14 1983-01-25 Hitachi, Ltd. Color picture tube shadow mask
US4623818A (en) 1983-12-23 1986-11-18 Hitachi, Ltd. Shadow mask type color picture tube
EP0707335A1 (en) 1994-10-14 1996-04-17 Thomson Consumer Electronics, Inc. Display apparatus having an enhanced resolution shadow mask and method of making same
US5730887A (en) * 1994-10-14 1998-03-24 Thomson Consumer Electronics, Inc. Display apparatus having enhanced resolution shadow mask and method of making same
US5534746A (en) * 1995-06-06 1996-07-09 Thomson Consumer Electronics, Inc. Color picture tube having shadow mask with improved aperture spacing
US6650071B2 (en) * 2001-08-23 2003-11-18 Koninklijke Philips Electronics N.V. Color display tube with improved shadow mask
US6664724B2 (en) 2001-11-10 2003-12-16 Lg. Philips Display Korea Co., Ltd. Shadow mask for color CRT
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
US20030111950A1 (en) * 2001-12-19 2003-06-19 Lg. Philips Displays Korea Co., Ltd. Flat type color cathode ray tube
US6972515B2 (en) 2001-12-19 2005-12-06 Lg. Philips Displays Korea Co., Ltd. Flat type color cathode ray tube

Also Published As

Publication number Publication date
FR2063883A5 (enrdf_load_stackoverflow) 1971-07-09
DE2026413A1 (de) 1970-12-03
NL7007877A (enrdf_load_stackoverflow) 1970-12-02
CA946907A (en) 1974-05-07
JPS4831373B1 (enrdf_load_stackoverflow) 1973-09-28
GB1316624A (en) 1973-05-09

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