US3340421A - Cathode ray tube having metallic layer of non-uniform thickness - Google Patents

Cathode ray tube having metallic layer of non-uniform thickness Download PDF

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Publication number
US3340421A
US3340421A US386349A US38634964A US3340421A US 3340421 A US3340421 A US 3340421A US 386349 A US386349 A US 386349A US 38634964 A US38634964 A US 38634964A US 3340421 A US3340421 A US 3340421A
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Prior art keywords
cathode ray
ray tube
metallic layer
thickness
screen
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US386349A
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Watanabe Yasumitsu
Inoue Takuji
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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
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
    • H01J31/20—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes for displaying images or patterns in two or more colours
    • H01J31/201—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes for displaying images or patterns in two or more colours using a colour-selection electrode
    • 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
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/18—Luminescent screens
    • H01J29/28—Luminescent screens with protective, conductive or reflective layers
    • 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
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/18—Luminescent screens
    • H01J29/30—Luminescent screens with luminescent material discontinuously arranged, e.g. in dots, in lines
    • H01J29/32—Luminescent screens with luminescent material discontinuously arranged, e.g. in dots, in lines with adjacent dots or lines of different luminescent material, e.g. for colour television

Definitions

  • a metallic layer which is over-laid -on a fluorescent screen is provided with a uniformity in its thickness.
  • brightness of the fluorescent screen is subtantially constant over the entire area thereof.
  • .cathode ray tubes such as a chromatrontype cathode ray tube having a grid for post deecting and focusing action disposed in spaced relation to the screen
  • some emitted electrons from the electron gun will impinge upon the grid structure causing emission of secondary electrons therefrom.
  • the probability that the emitted electrons will impinge upon the grid increases at .the peripheral portions Where incidence angles of electron beams are large with respect to the grid structures, and hence, secondary electrons from the grid inevitably increase greatly.
  • a so-called color running occurs at the peripheral portions of the screen. This effect is particularly noticeable at the two sides of a cathode ray tube forming vertical areas -of color running. This means that the contrast ratio is reduced which depends upon the primary electron, namely the scanning electron beam and the secondary electron.
  • a principal object of this invention is to provide a PDP-type cathode ray tube.
  • Another object of this invention is to provide a PDF- type cathode ray tube in which the aforementioned color-running or fog at the peripheral portions of the screen may effectively be avoided.
  • a further object of this invention is to provide an improved color cathode ray tube.
  • FIGURE 1 is a graph, illustrating the transmission factor through a metallic layer in relation to the electron energy and layer thickness;
  • FIGURE 2 is a sectional side elevational view schematically illustrating a preferred embodiment of a PDF- type cathode ray tube according to this invention.
  • FIGURE 3 is a partial sectional view of one corner portion of the cathode ray tube illustrated in FIGURE 1.
  • FIGURE 1 illustrates va family of curves of electron energy transmission factors, with a thickness d of a metal back layer, for example, an aluminum coating layer, as a parameter.
  • a thickness d of a metal back layer for example, an aluminum coating layer
  • the present invention is intended to utilize this influence to reduce the effects -due tosecondary electron emission at the peripheral portions of a screen.
  • a PDF-type cathode ray tube for example, a chromatrontype tube, generally designated with the reference numeral 1 includes a line grid 2 to which switching signals for color selecting are supplied as is well known in the art.
  • a phosphor screen 3 of the cathode ray tube 1 includes a repeating array of red, blue and green vertical stripes 4.
  • a metallic layer 5 such as aluminum or the like is coated on the inside surface of the screen.
  • A11 electron beam source such as for example an electron gun device 6 is disposed for emitting electrons therefrom. The emitted electrons are directed toward the line grid 2 as illustrated by the electron path generally designated With the reference numeral 7.
  • FIGURES 2 and 3 parts which have no direct relationship with respect to the explanation of the present invention, such as for example, an electron beam delecting device and the like, are omited for the sake of simplicity.
  • the thickness of the metallic layer 5 is different at a peripheral portion 5a than that at a central portion 5b thereof. That is, a thickness d1 of the peripheral portion 5a is made greater than a thickness d2 of the central portion 5b.
  • the thickness of the metal back layer 5 increases gradually o-r with offset toward the peripheral portion thereof from the center axis of the electron beam source l6. That is, the thickness increases directly with the radial distance from the center of the tube to the periphery of the tube.
  • the transmission factor at the peripheral portion 5a of the screen 3 is reduced to prevent the secondary electrons from passing through the metal back layer 5. It must be noted that the energy of the secondary electron is generally smaller than that of the primary electron.
  • the 'transmission factor of the metallic layer S corresponding to the peripheral portion of the grid 2 where the secondary electrons are produced at a high rate can be controlled by varying the thickness of the layer 5.
  • luminescence due to the secondary electron at the peripheral portion of the screen 3 is reduced, so that the contrast ratio of the primary electron, namely the scanning electron beam vs. the secondary electron at the peripheral portion may be made substantially equal to that at the central portion. Therefore, the color running, fog and the like at the peripheral portion of the screen can be avoided or greatly decreased.
  • the present invention has great advantages in providing higher quality picture representation.
  • One example -of the present invention includes operating the cathode ray tube with a voltage of approximately 25 kilovolts on the metallic layer and an operating point of the grid at 6 kilovolts.
  • a thickness of approximately 5,000 A. was employed for the dimension d2 and a Ithickness ⁇ of approximately 10,000 to 15,000 A. was employed for the dimension d1.
  • a cathode ray tube comprising an electron gun
  • the thickness of the metallic layer at a peripheral portion thereof being larger with respect to the thickness at a central portion thereof.
  • the cathode ray tube of claim 1 including an electron energy source of approximately 25 kilovolts connected to said metallic layer, and the thickness of the peripheral portion and the central portion of the metallic layer being in the range of approximately 10,000 A. to 15,000 A. and approximately 5,000' A. respectively.
  • a cathode ray tube comprising an electron gun
  • thethickness of the Imetallic layer at two edges 25 portion thereof being larger with respect to the thickness at a -central portion thereof.
  • a cathode ray tube comprising an electron gun

Landscapes

  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)

Description

, Sept? 1967 YAsLmansu WATANABE ETAL 3,340,421
CATHODI RAY TUBE HAVING METALLI-C LAYER OF' NON-UNIFORM THICKNESS Filed July 30, 1964 elecran en? r-gy fnzzsnT'mrfs. )zsu ml''SLL Wafalabe Taka. 'L'
/noue United States Patent O 3,340,421 CATHODE RAY TUBE HAVING METALLIC LAYER OF NON-UNIFORM THICKNESS Yasumitsu Watanabe and Takuji Inoue, Tokyo, Japan, assignors to Sony Corporation, Tokyo, Japan, a corporation of Japan Filed July 30, 1964, Ser. No. 386,349 Claims priority, application Japan, July 31, 1963, 38/41,203 Claims. (Cl. 315-14) ABSTRACT OF THE DISCLOSURE A cathode ray tube of the post deflecting and focus- This invention relates and more particularly to a post deflecting and focusing (PDF) type cathode ray tube. l
In ordinary cathode ray tubes a metallic layer which is over-laid -on a fluorescent screen is provided with a uniformity in its thickness. As a result of the thickness uniformity, brightness of the fluorescent screen is subtantially constant over the entire area thereof.
However, in .cathode ray tubes, such as a chromatrontype cathode ray tube having a grid for post deecting and focusing action disposed in spaced relation to the screen, some emitted electrons from the electron gun will impinge upon the grid structure causing emission of secondary electrons therefrom. The probability that the emitted electrons will impinge upon the grid increases at .the peripheral portions Where incidence angles of electron beams are large with respect to the grid structures, and hence, secondary electrons from the grid inevitably increase greatly. Accordingly, when the thickness of the metal back layer on the uorescent screen has been made uniform, a so-called color running occurs at the peripheral portions of the screen. This effect is particularly noticeable at the two sides of a cathode ray tube forming vertical areas -of color running. This means that the contrast ratio is reduced which depends upon the primary electron, namely the scanning electron beam and the secondary electron.
A principal object of this invention is to provide a PDP-type cathode ray tube.
Another object of this invention is to provide a PDF- type cathode ray tube in which the aforementioned color-running or fog at the peripheral portions of the screen may effectively be avoided.
A further object of this invention is to provide an improved color cathode ray tube.
Other objects, features and advantages of this invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:
FIGURE 1 is a graph, illustrating the transmission factor through a metallic layer in relation to the electron energy and layer thickness;
FIGURE 2 is a sectional side elevational view schematically illustrating a preferred embodiment of a PDF- type cathode ray tube according to this invention; and
FIGURE 3 is a partial sectional view of one corner portion of the cathode ray tube illustrated in FIGURE 1.
Like reference numerals throughout the various views of the drawings are intended to designate the same or similar structures.
generally to a cathode ray tube l FIGURE 1 illustrates va family of curves of electron energy transmission factors, with a thickness d of a metal back layer, for example, an aluminum coating layer, as a parameter. As is readily apparent from FIGURE 1, when the thickness d of the metallic layer is relatively large, the transmission factor is small and a small energy electron beam cannot be transmitted. The present invention is intended to utilize this influence to reduce the effects -due tosecondary electron emission at the peripheral portions of a screen.
With reference to FIGURES 2 and 3, there is shown one preferred embodiment of the present invention. A PDF-type cathode ray tube, for example, a chromatrontype tube, generally designated with the reference numeral 1 includes a line grid 2 to which switching signals for color selecting are supplied as is well known in the art. A phosphor screen 3 of the cathode ray tube 1 includes a repeating array of red, blue and green vertical stripes 4. A metallic layer 5 such as aluminum or the like is coated on the inside surface of the screen. A11 electron beam source such as for example an electron gun device 6 is disposed for emitting electrons therefrom. The emitted electrons are directed toward the line grid 2 as illustrated by the electron path generally designated With the reference numeral 7.
It is to be understood that in FIGURES 2 and 3, parts which have no direct relationship with respect to the explanation of the present invention, such as for example, an electron beam delecting device and the like, are omited for the sake of simplicity.
In the present invention, the thickness of the metallic layer 5 is different at a peripheral portion 5a than that at a central portion 5b thereof. That is, a thickness d1 of the peripheral portion 5a is made greater than a thickness d2 of the central portion 5b. The thickness of the metal back layer 5 increases gradually o-r with offset toward the peripheral portion thereof from the center axis of the electron beam source l6. That is, the thickness increases directly with the radial distance from the center of the tube to the periphery of the tube.
As a result of this change in thickness dimension, the transmission factor at the peripheral portion 5a of the screen 3 is reduced to prevent the secondary electrons from passing through the metal back layer 5. It must be noted that the energy of the secondary electron is generally smaller than that of the primary electron.
According to the present invention, the 'transmission factor of the metallic layer S corresponding to the peripheral portion of the grid 2 where the secondary electrons are produced at a high rate, can be controlled by varying the thickness of the layer 5. In this case, luminescence due to the secondary electron at the peripheral portion of the screen 3 is reduced, so that the contrast ratio of the primary electron, namely the scanning electron beam vs. the secondary electron at the peripheral portion may be made substantially equal to that at the central portion. Therefore, the color running, fog and the like at the peripheral portion of the screen can be avoided or greatly decreased. Thus, the present invention has great advantages in providing higher quality picture representation.
One example -of the present invention includes operating the cathode ray tube with a voltage of approximately 25 kilovolts on the metallic layer and an operating point of the grid at 6 kilovolts. A thickness of approximately 5,000 A. was employed for the dimension d2 and a Ithickness `of approximately 10,000 to 15,000 A. was employed for the dimension d1.
It will be apparent that many modifications and variations may be effected without departing from the scope of the novel concept of this invention.
What is claimed is:
1. A cathode ray tube comprising an electron gun,
a screen portion,
a lluorescent material on said screen portion,
a grid located adjacent to but spaced from said screen,
and
a metallic layer overlying said fluorescent material,
the thickness of the metallic layer at a peripheral portion thereof being larger with respect to the thickness at a central portion thereof.
2. The cathode ray tube of claim 1 including an electron energy source of approximately 25 kilovolts connected to said metallic layer, and the thickness of the peripheral portion and the central portion of the metallic layer being in the range of approximately 10,000 A. to 15,000 A. and approximately 5,000' A. respectively.
3. A cathode ray tube comprising an electron gun,
a screen portion,
a fluorescent material on said screen portion,
a grid located adjacent to but spaced from said screen,
and
a metallic layer overlying said uorescent material,
thethickness of the Imetallic layer at two edges 25 portion thereof being larger with respect to the thickness at a -central portion thereof.
4. A cathode ray tube comprising an electron gun,
a screen portion,
a fluorescent material on said screen portion,
a grid located adjacent to but spaced from said screen,
and
a metallic layer overlying said uorescent material,
and having a thickness increasing from a central portion to a peripheral portion thereof.
having a thickness increasing directly with the radial distance from the center thereof.
References Cited UNITED STATES PATENTS 11/1959 Evans 313-78 Assistant Examiners.

Claims (1)

1. A CATHODE RAY TUBE COMPRISING AN ELECTRON GUN, A SCREEN PORTION, A FLUORESCENT MATERIAL ON SAID SCREEN PORTION, A GRID LOCATED ADJACENT TO BUT SPACED FROM SAID SCREEN AND A METALLIC LAYER OVERLYING SAID FLUORESCENT MATERIAL, THE THICKNESS OF THE METALLIC LAYER AT A PERIPHERAL PORTION THEREOF BEING LARGER WITH RESPECT TO THE THICKNESS AT A CENTRAL PORTION THEREOF.
US386349A 1963-07-31 1964-07-30 Cathode ray tube having metallic layer of non-uniform thickness Expired - Lifetime US3340421A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3454808A (en) * 1965-09-30 1969-07-08 Victor Company Of Japan Color television picture tube having a fluorescent screen with a metal back of thickness to pass incident electrons and to limit the passage of secondary electrons
US4160187A (en) * 1975-11-05 1979-07-03 Gte Sylvania Incorporated Post-deflection acceleration crt system
US5639330A (en) * 1990-03-14 1997-06-17 Matsushita Electric Industrial Co., Ltd. Method of making an image display element

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0446878B1 (en) * 1990-03-14 1998-06-03 Matsushita Electric Industrial Co., Ltd. Image display element

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2914691A (en) * 1956-01-18 1959-11-24 Gen Electric Compensation of cathode ray post acceleration field distortion

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE25091E (en) * 1952-03-18 1961-11-28 Cathode-ray tubes of the lenticular grill variety

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2914691A (en) * 1956-01-18 1959-11-24 Gen Electric Compensation of cathode ray post acceleration field distortion

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3454808A (en) * 1965-09-30 1969-07-08 Victor Company Of Japan Color television picture tube having a fluorescent screen with a metal back of thickness to pass incident electrons and to limit the passage of secondary electrons
US4160187A (en) * 1975-11-05 1979-07-03 Gte Sylvania Incorporated Post-deflection acceleration crt system
US5639330A (en) * 1990-03-14 1997-06-17 Matsushita Electric Industrial Co., Ltd. Method of making an image display element

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