US3406251A

US3406251A - Color tv tube structure

Info

Publication number: US3406251A
Application number: US518136A
Authority: US
Inventors: Morton E Jones
Original assignee: Texas Instruments Inc
Current assignee: Texas Instruments Inc
Priority date: 1966-01-03
Filing date: 1966-01-03
Publication date: 1968-10-15
Anticipated expiration: 1985-10-15
Also published as: DE1487746A1; SE325050B; FR1507097A; NL6700034A; GB1163096A

Description

Oct. 15, 1968 M. E JONES COLOR TV TUBE STRUCTURE 2 Sheets-Sheet 1 Filed Jan. 3, 1966 L Y E l R H U I M 0 W V GAD. GT H [UP 5 l C HOU SE vs an DD A) N 3 5 OS 3 nw U w m 7 E C 4 h N 91 m 3 T R ox D G Tm E RAT. Du O A v E U T 0 00 M m E W N v D E E S V DA R .r G R/ Y MB W V m m mm 6 re H Oct. 15, 1968 Filed Jan. 5, 1966 E. JONES coLon TV TUBE STRUCTURE ALL PHOSPHORS ACTIVATED (BLUISH WHITE) R AND CYAN A CTIVATED (WARM WH'TE) ONLY RED PHOSPHORS ACTIVATED (RED) 2 Sheets-Sheet 2 WJiZl/ United States Patent 3,406,251 COLOR TV TUBE STRUCTURE Morton E. Jones, Richardson, Tex., assignor to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Filed Jan. 3, 1966, Ser. No. 518,136 6 Claims. (Cl. 178--5.4)

ABSTRACT OF THE DISCLOSURE There is disclosed, for use in a two color television display, a homogeneous screen containing two phosphors the first emitting light when scanned by a beam of one energy level and the second emitting light at a higher energy level. Superposed over the screen are indexing strips which when scanned by a beam at the higher energy level generate indexing pulses and lower the beam energy level reaching the screen, obviating the need for high voltage switching to produce the two color display.

This invention relates to color display systems and more particularly to such a system including a screen which is responsive to a beam of electrons at a single energy level for producing a display in a plurality of different colors.

It has previously been proposed to provide a multicolor television image display by providing a kinescope screen in which different color phosphors are arranged in successive narrow vertical stripes across the face of the kinescope. As a beam of electrons is then scanned horizontally across the face, the different phosphors are excited successively. By modulating the beam current successively in accordance with corresponding different color records in synchronism with the rate at which the different stripes are scanned, component images in the different colors may then be produced which combine to provide a full color display. This method, however, is relatively expensive in that it involves the precision deposition of different phosphors in closely spaced stripes.

-It has also been proposed to obtain the necessary different colors in a full color display by providing a mixture of phosphors of different colors which have different electron energy thresholds or responses so that the selec tion of color may be obtained by the selection beam electron energy. However, to obtain electrons at different energies these known systems used multiple electron guns or switched electron voltages relative to a single gun at a rapid rate. Further, the use of multiple accelerating voltages introduces a need for compensating deflection forces since the electrons accelerated by the higher voltage are not as easily deflected as those accelerated by relative low voltages.

Among the several objects of the invention may be noted the provision of a multicolor image display system; the provision of such a system which does not require selective precision deposition of different color phosphors; the provision of such a system which does not require the acceleration of electrons to several different energies; the provision of such a system which yields a natural and pleasant color rendition; the provision of such a system which is simple, inexpensive and reliable; and the provision of a novel color display screen for use in such a system. Further objects include the provision of simple and economical methods of making color display screens. Other objects and features will be in part apparent and in part pointed out hereinafter.

Briefly, a color display screen according to the invention includes a phosphor layer having in each scannable domain thereof both a first and a second phosphor. The first phosphor when energized by electrons having an energy greater than a first preselected level emits light 3,406,251 Patented Oct. 15, 1968 of a first color while the second phosphor when energized by electrons having an energy greater than a second preselected level emits light of a second color, the second energy level being above the first energy level. A layer of energy absorbing material overlies selected portions of the phosphor layer for reducing the energy of impinging electrons from a predetermined energy level above the aforesaid second level to an energy level intermediate the first and second levels. Thus the impingement of a beam of electrons at that predetermined energy level on the portions of the phosphor layer which are overlaid by the energy absorbing material will energize only the first phosphor to produce light of the first color while impingement of the beam on the uncovered portions of the phosphor layer will energize both of the phosphors to produce light of a different color, the different color being a composite of said first and second colors.

A display system according to the invention incorporates a screen such as described above and further includes means for scanning the screen with a beam of electrons at an energy level above the aforesaid first and second energy levels. An important feature of the invention is the use of the overlaid energy absorbing material for the purpose of generating indexing signals whereby the beam intensity is modulated alternately in accordance with respective first and second color records as the beam scans from covered to uncovered areas of the screen. The overlaid energy absorbing material is arranged in stripes transverse to the scanning direction of the electron beam.

The invention accordingly comprises the apparatus and methods hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, in which several of various possible embodiments of the invention are illustrated,

FIGURE 1 is a greatly enlarged perspective view partially in section, of a portion of a color display kinescope screen;

FIGURE 2 is a schematic block diagram illustrating the operation of a color display system including a kinescope having a color display screen such as that shown in FIGURE 1; and

FIGURE 3 is a greatly enlarged sectional view of another embodiment of a color display screen according to the present invention.

Corresponding reference characters indicate corresponding parts throughout the drawings.

Referring now to the drawings, FIGURE 1 illustrates a color display kinescope screen 11 which is suitable for use in a television receiver. Screen 11 includes a glass face plate 15 which constitutes a substrate upon which is deposited a phosphor layer 17. Layer 17 is constituted by a random mixture of discrete red light emitting phosphor particles 19 and cyan light emitting particles 21. Instead of a phosphor material which emits cyan light, it is understood of course that a combination of two phosphors, one emitting blue and the other green, may be used together to provide cyan. Each domain of layer 17 which may be scanned by an electron beam includes both kinds of particles.

The red light emitting phosphor particles 19 and the cyan light emitting particles 21 respond differently to impinging electrons having different energies or velocities. Particles 19 have a low energization threshold and are energized even when struck by electrons which have been accelerated by a relatively low voltage. The particles 21, however, emit cyan light only when struck by electrons which have been accelerated by a relatively high voltage. Low energy electrons will thus energize only the particles 19 so that a red light is emitted while electrons having energies above the threshold of the particles 21 will energize both the red and the cyan light emitting particles 3 so that light of a different color, substantially white, will be emitted.

The difference in the sensitivities of the phosphors to electrons of different energies may be produced, for example, by providing a barrier layer on the cyan light emitting particles. The barrier produces a raised energy threshold which must be exceeded before the particle is energized to emit light. Alternatively, both types of particles 19 and 21 are provided with barriers, the cyan light emitting particles being given a thicker barrier to pro duce the desired differential between the energy thresholds of the two different kinds of particles. Preferably, the barrier is provided by subjecting the phosphor particles to an oxidizing atmosphere to convert the outer surface of the particles to an inert, non-light-emitting oxide which functions as the barrier. Another suitable barrier layer is a coating of silicon dioxide deposited on individual particles. This coating is deposited, for example, by the cracking of a tetraethoxysilane atmosphere within which the phosphor particles are suspended.

Phosphor layer 17 is coated with an electron permeable aluminum film 23 by means of which an electron beam accelerating voltage may be applied to the screen. Aluminum film 23 is in turn covered by an insulating layer 25. This layer 25 may, for example, be formed by anodizing the aluminum film 23. The aluminum film 23 and the insulating layer 25 are relatively thin so that the energies of impinging electrons are not substantially reduced by passing through these layers.

On top of the insulating layer 25 are a series of parallel aluminum stripes 29 which extend across the screen leaving uncovered portions or areas 30 therebetween. The aluminum which constitutes the stripes 29 may be deposited through a mask to leave the uncovered areas 30 or may be deposited as a continuous layer, the aluminum in the areas 30 being later etched away. The aluminum which constitutes the stripes 29 is of appreciable thickness so that the energies of electrons impinging upon the areas covered by the stripes are appreciably reduced. Thus, the stripes 29 constiutte a layer of energy absorbing material overlying selected portions of the phosphor layer 17.

The particular thickness of the stripes 29 is chosen such that electrons impinging with a predetermined energy which is above the threshold level of the cyan light emitting particles 21 will be reduced in energy to a level which is below the energization threshold of the particles 21 and yet which is still high enough to effect energization of the particles 19. Accordingly, a. beam of such electrons such as that indicated at 31 will, as it is scanned across screen 11, energize both kinds of phosphor particles 19 and 21 to produce white light when it does not encounter one of the stripes 29 but will, when impeded by a stripe 29, energize only the particles 19 to produce red light.

In the receiver illustrated in FIGURE 2, screen 11 is incorporated into a color television kinescope 33. Kinescope 33 includes an envelope 35 having a neck portion 37. Within neck portion 37 is mounted a conventional electron beam gun 39 having an electron emissive cathode 41 and a grid 43 operative to control the intensity of the beam emitted by the gun. Electrons emitted by gun 39 are accelerated towards screen 11 by a fixed high potential applied to screen 11 by a high voltage supply HV. Around the neck portion 37 of kinescope 33 is mounted a conventional magnetic deflection yoke 47.

The receiver shown in FIGURE 2 is constructed for operation in conjunction with signals transmitted in accordance with the presently standard NTSC system of television broadcasting. It is to be understood however that signals derived according to other transmission systems, e.g., PAL or SECAM, may also be employed in the practice of the invention. The receiver includes suitable radio frequency circuits RF for obtaining the synchronization signals and the video signal which includes the luminance information and the chrominance subcarrier. Such radio frequency circuits are conventional and form no part of the present invention.

The receiver also includes suitable deflection circuits DF which, under control of the synchronization signals, energize yoke 47 for generating magnetic fields in the neck portion of the kinescope 33 to deflect the electron beam emitted from gun 39 in a conventional scanning raster. Screen 11 is oriented with the stripes 29 extending vertically so that the rapid horizontal scanning causes the electron beam to move generally perpendicular to the stripes and to traverse the stripes 29 and the areas 30 in rapid succession.

The stripes 29 are connected together and also to a terminal 51 on kinescope 33. As the electron beam is scanned across the stripes 29 and the intervening areas 30, the beam current intermittently absorbed by the stripes 29 generates a high frequency signal at terminal 51. This signal is amplified by a sensitive detector NX for use as an index signal as described in greater detail hereinafter.

The video signal obtained from the radio frequency circuits RF is applied to a color demodulator and matrix MX to obtain a pair of signals which constitute the red and green records of the transmitted picture information. These signals are applied alternately to the grid 43 by a high frequency electronic switch or gate GT which is operated in synchronism with the index signal provided by the detector NX. This alternate and synchronous application of the color signals causes the intensity of the electron beam emitted from gun 39 to be modulated in accordance with the red record when the electron beam falls on the areas of screen 11 which are overlaid by the stripes 29 and to be modulated in accordance with the green record when the beam falls on the intervening areas 30. Since the beam produces red light when it strikes the portions of screen 11 which are covered by the stripes 29 as described previously, it can be seen that the red record creates an image in red light. The cyan record on the other hand creates an image in white or substantially achromatic light, the white image being interlaced with the. red image. The red and white images produced on screen 11 combine to form a composite image which subjectively appears to include a full range of hues, including those which are not actually present in the colorimetric sense. This general two color system of presenting color images is known in the art and provides an image of pleasing appearance wherein the hues appear more saturated than they really are.

An alternative method of obtaining a signal for synchronizing the alternation of modulation between the two records with the progression of the electron beam from stripes 29 to areas 30 is to detect the fluctuations in secondary emission radiation which the electron beam produces by its impingement upon the screen. The differences in the materials of the stripes 29 and the areas 30 will cause significant variations in the kind and intensity of the secondary emissions and these fluctuations are inherently synchronized with the progress of the beam across the screen. Included among the secondary emissions which may be so utilized are those which occur in the ultra-violet and X-ray spectrums.

FIGURE 3 illustrates another embodiment of a color display screen according to the invention, which embodiment provides a three color display. The screen 61 includes a glass face plate 63 upon which is supported a phosphor layer 65. Phosphor layer 65 is constituted by a random mixture of three types of phosphor particles; red light emitting particles 67 which can be energized by electrons of relatively low energy level; cyan light emitting particles 69 which can be energized by electrons having an energy greater than a second preselected threshold or level; and blue light emitting phosphor particles 71 which can be energized by electrons having energies greater than a third energy level; the third energy level being greater than the second energy level. Over the phosphor layer 65 is deposited an electron permeable aluminum film 73 by means of which an electron beam accelerating volt-age can be applied to the screen. On top of the aluminum film 73 are a series of parallel stripes 75 of an insulating material such as silicon dioxide. The insulating stripes 75 are separated by areas 76 which are half as wide as the adjacent insulating stripes 75. The thickness of the insulation material is chosen in relation to its energy absorbing properties so that the stripes will reduce the energy level of an electron beam from a predetermined level above the thresholds of all three phosphors to a level intermediate the thresholds of the cyan phosphor particles 69 and the blue phosphor particles 71. It can thus be seen that, while an electron beam of that predetermined level which impinges upon an area 76 will energize all of the different phosphor particles, such as electron beam which impinges upon and penetrates the insulating stripe 75 will energize only the red and cyan phosphor particles.

Over one-half of the width of each of the insulating stripes 75 is a narrower stripe 7 9 of aluminum. The thicknesses of the aluminum stripes 79 are chosen such that they will reduce the energy of an impinging electron beam from the level intermediate the thresholds of the cyan phosphor particles 69 and the blue phosphor particles 71 to a level which is intermediate the thresholds of the red phosphor particles 67 and the cyan phosphor particles 69. It can thus be seen that an electron beam of the single predetermined energy level described previously which impinges upon the portions of screen 61 overlaid by both the aluminum stripe 79 and the insulating stripe 75 will energize only the red phosphor particles 67. It is noted also that it makes no difference in the energy absorption required of each of the stripes whether the aluminum stripe is on top of the insulating stripe or vice versa. The portions of the phosphor layer 65 which underlie stripes 79 are covered by sufficient energy absorbing material in total to reduce the energy of impinging electrons from the predetermined level to a level intermediate the thresholds of the particles 67 and the particles 69.

It can be seen that the screen 61 shown in FIGURE 3 is capable of producing light of three colors in response to an electron beam of but a single energy level. Red is produced when only the phosphor particles 67 are energized. A warm white is produced when both the red light emitting phosphor particles 67 and the cyan light emitting phosphor particles 69 are simultaneously energized and a cool or bluish white is produced when all three phosphors are energized. Screen 61 can be utilized in a three color television display in a manner similar or analogous to the two color display illustrated in FIG- URE 2 which uses the screen 11. In the three color display a three state gate is used for applying the three color signals to the electron beam gun sequentially, the signal available from the aluminum stripes 79 being used to synchronize a three step function generator which controls the gate. The characteristics and advantages of this three color presentation wherein the different phosphors have different energy thresholds and are cumulatively energized by electrons of increasing energies are described in greater detail in copending, coassigned application Ser. No. 450,705.

While discrete particles with deposited barrier layers for obtaining a raised encrgization threshold have been described by way of an example, differences in sensitivity to electrons of different energies may also be obtained by treating the phosphor itself as by leaching out the activator components near the surface or even by choosing phosphors having inherently different energization characteristics. Also, one phosphor may act as a barrier for another so that random mixes of discrete particles are not required. Other variations may also be used such as different materials or distribution for the various energy absorbing layers.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above apparatus and methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a color display system, a color display screen which is responsive to a scanned beam of electrons at a single predetermined energy level for producing images in light of a plurality of different colors, said screen comprising:

a phosphor layer including in each scannable domain thereof both first and second phosphors, said first phosphor when energized by electrons having an energy greater than a first preselected level emitting light of a first color, said second phosphor when energized by electrons having an energy greater than a second preselected level emitting light of a second color, said second energy level being above said first energy level;

a layer of energy absorbing material overlying selected portions of said phosphor layer for reducing the energy of impinging electrons from a single predetermined energy level above said second level to an energy level intermediate said first and second levels whereby the impingement of a beam of electrons at said predetermined energy level on the portions of said phosphor layer which are overlaid by said energy absorbing material will energize only said first phosphor to produce light of said first color while the impingement of the same said beam on the uncovered portions of said phosphor layer will energize both of said phosphors to produce light of a different color which is a composite of said first and second colors, the layer of energy absorbing material being arranged in a pattern of generally parallel stripes on said screen with the stripes being generally perpendicular to the direction of scanning of said beam of electrons; and

means including said layer of energy absorbing material for detecting the position of said beam on said screen and for altering the electrical signal content of said electron beam in response to the detected position thereof.

2. A color display screen as set forth in claim 1 wherein said phosphor layer comprises a random mixture of phosphor particles which emit light of different colors, the particles constituting said second phosphor including a barrier layer which causes the particles to respond only to electrons having an energy greater than said second preselected level.

3. A color display screen as set forth in claim 1 wherein said phosphor layer includes a third phosphor which emits light of a third color when energized by electrons having an energy greater than a third preselected level, said third preselected level being above said second preselected level, and wherein other portions of said phosphor layer are overlaid by energy absorbing material for reducing the energy of impinging electrons from said pre determined energy level to a level between said second and third levels whereby a beam of electrons at said predetermined energy level will energize all three phosphors in uncovered portions of said phosphor layer to produce light of a color which is a composite of all three said colors, and whereby said electron beam will energize only said first phosphor in the first said overlaid portions of said phosphor layer to produce light of said first color, and whereby said electron beam will energize said first and second phosphors in said other portions to produce light of a color which is a composite of said first and second colors.

7 4. A color display system for producing light of a plurality of difierent colors, said system comprising:

a viewing screen having a phosphor layer which includes in each scannable domain thereof both first and second phosphors, said first phosphor when energized by electrons having an energy greater than a first preselected level emitting light of a first color, said second phosphor when energized by electrons having an energy greater than a second preselected level emitting light of a second color, said second energy level being above said first energy level, said viewing screen including also a layer of energy absorbing material overlying selected portions of said phosphor layer for reducing the energy of impinging electrons from a predetermined energy level above said second level to an energy level intermediate said first and second levels, the layer of energy absorbing material being arranged in a pattern of generally parallel stripes on said screen;

means for scanning said screen in a direction generally perpendicular to said stripes with a beam of electrons at said predetermined energy level whereby when said beam of electrons impinges on the portions of said phosphor layer which are overlaid by said energy absorbing material only said first phosphor is energized to produce light of said first color and when said beam impinges on the uncovered portions of said phosphor layer both of said phosphors are energized to produce light of a different color which is a composite of said first and second colors; and

means including said layer of energy absorbing material for detecting the position of said beam and for altering the electrical signal content of said electron beam in response thereto.

5' A color display system which is responsive to first and second color records for producing images in light of at least two different colors, said system comprising:

a viewing screen having a phosphor layer which includes in each scannable domain thereof both first and second phosphors, said first phosphor when energized by electrons having an energy greater than a first preselected level emitting light of a first color, said second phosphor when energized by electrons having an energy greater than a second preselected level emitting light of a second color, said second energy level being above said first energy level, said viewing screen including also a layer of energy absorbing material overlying selected portions of said phosphor layer in a pattern of generally parallel stripes for reducing the energy of impinging electrons from a predetermined energy level above said second level to an energy level intermediate said first and second levels;

means for scanning said screen with a beam of electrons at said predetermined energy level is a direction generally normal to said stripes;

means for detecting the position of said beam in relation to said stripes to produce an indexing signal; and

means responsive to said indexing signal for modulating the intensity of said beam in accordance with said first record when said beam impinges upon portions of said screen overlaid with said absorbing layer and for modulating the intensity of said beam in accordance with said second record when it impinges upon uncovered portions of said screen whereby an image in light of said first color is produced in accordance with said first record and an image in light of a different color is produced in accordance with said second record.

6. A color display system which is responsive to first,

second and third color records for producing images in light of three different colors, said system comprising:

a viewing screen having a phosphor layer which includes in each scannable domain thereof first, second and third phosphors, said first phosphor when energized by electrons having an energy greater than a first preselected level emitting light of a first color, said second phosphor when energized by electrons having an energy greater than a second preselected level emitting light of a second color, said second energy level being above said first energy level, said third phosphor when energized by electrons having an energy greater than a third preselected level emitting light of a third color, said third energy level being above said second energy level, said viewing screen including also a layer of insulating, energy absorbing material disposed in parallel stripes overlying portions of said phosphor layer for reducing the energy of impinging electrons from a predetermined energy level above said third level to an energy level intermediate said second and third levels, said viewing screen further including a layer of conductive, energy absorbing material disposed in parallel stripes overlying portions only of said stripes of insulating material for reducing the energy of electrons from said intermediate energy level to a level between said first and second preselected levels;

means for scanning said screen with a beam of electrons at said predetermined energy level;

gating means for modulating the intensity of said beam in accordance with said three records in predetermined order corresponding to the distribution of said stripes; and

means responsive to variations in the quantity of beam electrons absorbed by said stripes of conductive material for synchronizing said gating means with the scanning of said beam across Said screen.

No references cited.

55 ROBERT L. GRIFFIN, Primary Examiner.

RICHARD R. MURRAY, Assistant Examiner.