CA1178639A - Current-sensitive color cathode ray tube - Google Patents
Current-sensitive color cathode ray tubeInfo
- Publication number
- CA1178639A CA1178639A CA000404160A CA404160A CA1178639A CA 1178639 A CA1178639 A CA 1178639A CA 000404160 A CA000404160 A CA 000404160A CA 404160 A CA404160 A CA 404160A CA 1178639 A CA1178639 A CA 1178639A
- Authority
- CA
- Canada
- Prior art keywords
- emitting phosphor
- red
- phosphor
- ray tube
- cathode ray
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
- C09K11/7783—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals one of which being europium
- C09K11/7784—Chalcogenides
- C09K11/7787—Oxides
- C09K11/7789—Oxysulfides
-
- 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
- H01J29/187—Luminescent screens screens with more than one luminescent material (as mixtures for the treatment of the screens)
-
- 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
- H01J29/26—Luminescent screens with superimposed luminescent layers
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Luminescent Compositions (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A current-sensitive color cathode ray tube having a phosphor screen scanned by an electron beam from an electron-source, with the current density in said beam varied at substantially constant accelerating voltage is disclosed. In this case, the screen comprises a red-emitting phosphor having a sublinear characteristic in the intensity-current density relationship and a different color-emitting phosphor other than red having a linear or superlinear characteristic in the intensity-current density relationship, in which the red emitting phosphor has a following formula:
(Ln1-xEux)2O2S
wherein Ln is a material selected from the group consisting of Y, La, Gd and Lu, and x ranges from 0.05 to 0.10 and further, concentration of a rare earth impurity such as terbium Tb and praseodymium Pr is less than 10 ppm.
A current-sensitive color cathode ray tube having a phosphor screen scanned by an electron beam from an electron-source, with the current density in said beam varied at substantially constant accelerating voltage is disclosed. In this case, the screen comprises a red-emitting phosphor having a sublinear characteristic in the intensity-current density relationship and a different color-emitting phosphor other than red having a linear or superlinear characteristic in the intensity-current density relationship, in which the red emitting phosphor has a following formula:
(Ln1-xEux)2O2S
wherein Ln is a material selected from the group consisting of Y, La, Gd and Lu, and x ranges from 0.05 to 0.10 and further, concentration of a rare earth impurity such as terbium Tb and praseodymium Pr is less than 10 ppm.
Description
'78~i39 BACKGROUND OF THE INVENTION
- Field of the Invention -The present invention relates generally to a color cathode ray tube and more particularly to a current-sensitive color cathode ray tube.
Description of the Prior Art In a color cathode ray tube used in an ordinary color television receiver and so on, in opposed relation to its phosphor screen, located is a means such as a shadow `;
mask, aperture grill or the like which functions to determine the landing position of an electron beam on the phosphor screen, whereby the electron beams corresponding to the respective colors are landed on the respective color phosphor dots or stripes of the phosphor screen to thereby provide respective color emissions and h'ence reproduce a color - picture on the phosphor screen.
On the contrary, in a current-sensitive color cathode ray tube, there is provide no means to determine the landing position of the electron beam but itc phosphor screen is formed of more than two color phosphors, which are mixed and then coated, and emits necessary color light or lights within a predetermined limited color gamut in response to the beam current density.
Since such the current-sensitive color cathode ray tube has no means to determine the electron beam landing position, it performs such an advantage that its weight becomes light, its assembling or manufacturing process becomes simpli~ied and its resoLution is improved and also _ 2 - ~
.
, .
~ 1~7~3~3~ :
such an advantage to avoid various problems, ~or example, mislanding caused by the relative positional displacement between the ph~sphor screens and the means to de~ermine the electron beam landing position.
BRIEF DESCRIPTION OF THE DR~WINGS
Fig. 1 is a graph showing the current density versus luminance characteristic used to explain a prior art current-sensitive color cathode ray tube;
Fig~ 2 is a schematic diagram showing an example of the current-sensit ~e color ca~hode ray tube according to the present inv~ntion;
Figs. 3, 5, 9, 10 and 11 are respectively graphs showing the beam current density versus luminance characæ~istics;
Fig. 4, ap~¢ing with~Figs. 1 and 2, ~s a ch~ticity diagram;
Fig. 6 is a graph showing a measured ourve repre-senting the selation between Eu amount in red-emitting phosphor and luminance thereof;
Fig. 7 is a graph showing the simil~r Eu amount and chromaticity value; and Fig. 8 is a cross-sectional view of the phosphor screen used in the cathode ray tube shown in Fig. 2.
: A prior art curren~-sensi~ive colox cath~de xay '! tube, mentioned just above, includes a phosphor screen made of mixed color phosphors of-a green phosphor showing a so-called sub-linear characteristic represented by a curve 1 in the graph of Fig~ 1 which shows the luminanee character-.~ istic of the phosph~r to the electron beam ~urrent density, - --3~
, , ..
: ~ :
~ 7~ ~ 3 ~
with a red phosphor showing a 50- called super-linear characteristic xepre~entea by a ~urve 2 in the graph of Fig.
1. In this case, within a range where the beam current density is small, the light emission of green is dominant, while within a range where the beam current density is large, the light emission of red is dominant, whereby a color image having a color gamut of synthesized two colors in response to tha beam current density is produced.
As the green-emitting phosphor whose current density versus luminance characteristic is the above sub-linear characteristic, phosphor of Zn2SiO~: Mn is generally used, while as the xed-emitting phosphor showing the super-linear characteris~ic, ~CdZn)S: Ag, Ni is usually employed. In this case, for making the green-emitting phosphor Zn2SiO4 :
Mn represent th~ sub~linear characteristic, it is necessary to select t~e adding amount of Mn small. When the adding amount of Mn is selected small, a problem of burn by the beam irradiatio~ occurs. On the other hand, if the super -linear char~cteri~tic i8 pr~sented by the red-emitting phosphor (ZnCd)5: Ag, N$, the amount of Cd must be increased. When, howe~er, the amount of Cd i~ increased, the luminance thereof becomes low and its color purity becomes also low. This low color purity of the above prior art color cathode ray tube xesults in tha~ its color gamut, which can be re~roducedt becomes relatively narrow.
OBJECTS AND SI~ RY OF THE INVENTIO~
.
Accordingly, it is an object of the present ,:
'~
, ~L7~3~3~
, invention ~o provide a curren~-sensitive color cathode ray tube in which color purity is improved to thereby widen light emission color gamut.
Acc~rding to an aspect of this invention there is provided a current-sensitive color cathode ray tube having a phosphor screen scanned by an electron beam from an electron-source, with the current density in said beam varied at substantially constant accelerating voltage, said screen comprising a red-~mitting phosphor having a sublinear characteristic in the intensity-current density relationship and a different color-emitting phosphor other than red having a linear or superlinear characteristic in the intensity-current density relationship, characterized in that said red emitting phosphor has a following formula:
(Lnl_xEux)2O2s wherein Ln is a material selected from the group consisting of Y, La, Gd and Lu, and x ranges from 0.05 to 0.10 and further, concentration of a rare earth impurity such as terbium Tb and praseodymium Pr is less than 10 ppm.
The other objects, eatures and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings through which the like references designate the : same elements and part~.
DESCRIPTION OF THE PR~FE~RED ~ODIMEnTS
: The present invention will be hereinbelow described with reference to the attached drawings.
In general, according to the present invention, by using the combination of one color-~mitting phosphor, which has its current density versus luminance characteristic .
representing the sub-linear characteristic, with another color-emitting phosphor whose current density versus luminance characteristic represents the super-linear or linear characteristic, there is generated light emission with hue or color gamut represented by the synthesized color of the lights emitted from both color phosphors by controlling the current density, for example, modulating the cathode :
current.
~ . - In this invention, especially, as the phosphor which shows the above sub-linear characteristic a red-emitting p~osphor, which is high in color purity and has the compo-sition formula of (Lnl xEux)2O2S is used. In this formula Ln is formed of at least one kind in the group consisting of yttrium Y, lanthanum La, gadolinium Gd and luletium Lu, and x is selected to satisfy the condition of 0.05 - ~ - 0.10.
Further, in this red-emitting phosphor rare-earth impurities such as terbium Tb, praseodymium Pr and so on are selected less than 10 ppm.
The phosphor screen used in the current-sensitive color cathode ray tube of this invention is made by such a manner that the above red-emitting phosphor with sub-linear characteristic is mixed with another color, for example, green-emitting phosphor or blue-green-emitting phosphor with the super-linear or linear characteristic and the mixed phosphor is laminated as a layer, or each phosphor is re-spectively and sequentially laminated as a plurality of layers.
The reason why the value of x in the red-emitting phospnor (Lnl_xEux)2O2s is selected to satisfy 0.05 ~ x _ 0.10 in the invention is that such a fact was noted that if x was less than 0.05 the color pu:ity was lowered and ycllowish ~7~39 light emission is caused, while if x exceeded 0.10 the luminance became low. Further, the reason why the rare-earth impurity concentration of Tb, Pr and so on is selected less than 10 ppm is that it was ascertained that when the rare-earth impurity concentration of Tb, Pr and so on exceeded 10 ppm, the luminance was difficult to be saturated upon high beam current density and hence the sub-linear characteristic was not presented.
Now, the examples of this invention will be explained as follows:
Example 1 The red-emitting phosphor is made as follows:
Rare-earth oxide Ln203 is added with europium oxide Eu203 at a predetermined amount and then they are mixed to prepare a mixed rare-earth oxide; the mixed rare-earth oxide is further added with sulphur S at 30 to 80 weight %~ sodium carbonate Na2C03 at 30 to 80 weight %~ which serves as flux, and so on and they are mixed; and the mixture is burned in air at 900 to 1300C in 0.5 to 5 hours to provide phosphor represented by the composition fQrmula of (Lnl xEux)202S.
By hydraulic elutriation method, small size particles are removed from the above phosphor and, by use of a sieve large size particles are removed from this phosphor. While, green -emitting phosphor (ZnO 64Cdo 36)S: Ag,Ni which contains 50 ppm of Ag and 10 ppm of Ni is prepared. Then, the red-emitting phosphor and green-emitting phosphor are respectively weighted to be 35 weight % and 65 weight % and then mixed.
Then, the phosphor thus mixed is coated on the inner surface of a panel 3a of a cathode ray tube envelope 3 by the sedimentation method to form a phosphor screen 4 as . , , ~ ,~
shown in Fig. 2. In Fig. 2, reference numeral 5 designates an electron gun which will emit an electron beam to the phosphor screen 4 and reference numeral 6 denotes its horizontal and vertical deflection means. This current-S sensitive color cathode ray tube is provided with no means to determine the landing position of the electron beam on the phosphor screen 4j for-example, no shadow mask or ~~
aperture grill and so on and hence this color cathode ra~
~ tube can take the similar construction to that of an ordinary monochromatic cathode Yay tube.
Fig. 3 is a graph showing measured current density versus luminance characteristics of the phosphor screen 4 of the invention for such a case where in the Example 1 the red-emission phosphor is Y202S: Eu. In the graph o Fig. 1, a broken line curve 11 represents the current density to luminance characteristic of the red light emission by the red-emitting phosphor Y202S: Eu, a -- solid line curve 12 shows that of the green light emission by the green-emitting phosphor ~ZnO.64CdO.36) g a one-dot chain line curve 13 represents the current density to luminance characteristic of this phosphor screen, namely the total luminance versus current density characteristic of respective color lights of the color cathode ray tube.
As will be apparent from the graph of Fig. 3, the red-emitting phosphor Y202S: Eu shows the sub-linear characteristic while the green-emitting phosphor (ZnO 64Cdo 36)S Ag, Ni shows the super-linear characteristic, respectively.
Now, the color gamut of the light emission by the red and green-emitting phosphors will he considered with reference to the graph of Fig. 4 which is a MacAdam's u,v .
1~78G39 chromaticity diagram. In the graph of Fig. 4, reference letters R, G and B respectively shows the chromaticities of red, green and blue. In this case, the line RlGl from a point Rl to a point Gl shows a color gamut within which the light emission of the color cathode ray tube with the phosphor screen made by the mixture of the red-emitting phosphor Y202S: Eu with the g~een-emitting phosphor (ZnO 6~ ;
Cdo 36)S: Ag, Ni according to Example 1 is possible. In ~ - this case, in accordance with the beam current density, namely as the beam current density becomes large, such light emission with hue is generated in which the hue goes to the point Gl in the line RlGl, while as the beam current density becomes low the hue of light emission goes to the point Rl.
In the graph of Fig: 4, letters Rl' and Gl' respectively designate chromaticity points of red and green colors of a prior art current-sensitive color cathode ray tube mentioned previously. In this case, the color gamut which can be .. . .
reproduced rests on the line connecting the points Rl' and G '. As will be apparent from the comparison of both lines RlGl and Rl'Gl', it is understood that the color gamut of this invention which can be reproduced is wider than that of the prior art since the line RlGl is longer than that Rl'Gl' and hence the color purity of, especially red color is improved.
In the graph of Fig. 5, a solid line curve 21 shows the current density to lumir,ance characteristic of Y202S: Eu which corresponds to the broken line curve 11 in the graph of Fig. 3, and a solid line curve 22 in the graph of Fig. 5 shows the similar characteristic of Y202S: Eu, Tb from which it will be clear that when Tb is added to the -. :
' ~.
~1~7~3639 :: `
phosphor, it beco~es di~ficult to present the sub-linear characteristic.
The graph of Fig. 6 shows reIative values of the luminance for the amount of Eu ~n the Y2O2S: Eu phosphor Cnamely the value x in the Composit~on formula (Lnl xEux)202S) which were measured, and curVes 31 and 32 in the~ graph of F~gO 7 respectively show values of x and y in the x-y chromaticit~ diagram of the amoun~ of Eu in similar phosphors.
In the x y chromaticity value, when the Eu amount is less 10 than 5 mole %, the p~osphor represents yellow. Thereforè, it will ~e easily understood that the Eu amount is selected more than 5 mole % and less than 10 mole ~ so as to select the relative value of the luminance more than 50 ~ in view of the luminance characteristic in the graph of Fig. 6, 15 namel~ the x ~alue in t~e above composition is selected to satisfy 0.05 _ x _ 0.10.
- In the above Example 1, although the red and green phosphors are mixed to form the phosphor screen 4, it is possible that the res~ective color phosphors are r~spectively 20 laminated as layers to form the phosphor screen 4. ~ow, an example of such case will be described.
Example 2 90 weight % of the gr~en-emittin~ phosphor used in Example 1 is first coated on the inner surface of the panel 25 3a of the cathode ray tube envelope 3 by the sedimentation method and the phosphor layer thus formed is dried sufficiently.
~17~3~3~
Thereafter, 10 weight % of the red-emitting phosphor used in ~xample 1 is coated on the above green-emit~ing phosphor layer by the similar sedimentation method. Thus, the phosphor - --- screen 4 consisting of green and red phosphor layers 4G and .
-lOa~
.
.. . . ..
, .
~ ~7~3t;35~
4b laminated in this order on the inner surface of the panel 3a is provided as shown in Fig. 8 and hence a current -sensitive color cathode ray tube similar to that explained in connection with Fig. 2 is provided.
The current density to luminance characteristics of the red and green colors in Example 2 become as indicated by broken line and solid line curves'!41 and'42 in t'he'graph ' '''-~
of Fig. 9 and the total characteristic thereof is shown by a one-dot chain line curve 43 in the same graph. In this , case, as will be apparent from the comparison of the curve 12 in the graph of Fig. 3 with that 42 in the graph of Fig.
9, in case of the laminated phosphor screen o~ Example 2, the current density versus luminance characteristic of the lower layer, namely the green-emitting phosphor layer 4G
located on the side opposite to the electron beam impinging side represents lower luminance at the low current range so that the purity of t~e red can be enhanced much.
~' It is needless to say that the present invention is not limited to the combination of the~red-emitting phosphor having sub-linear characteristic with the green-emitting phosphor having the super-linear or linear characteristic, but the invention can be applied to the combination of the red-emitting phosphor having the sub-linear characteristic with another color phosphor having the super-linear or linear characteristic such as blue-green -emitting phosphor. An example o~ this case will be now described.
Example 3 Similar to Example 1 but in place of the green -emitting phosphor, a blue-green-emitting phosphor .
_ ~1 7~ ~ 3 ~
(ZnO 82Cdo l8)S: Ag, Ni is used. The current density versus luminance characteristics of xed light emission, blue-green light emission and total light emission of this case are respectively measured as shown by broken, solid ::
and one-dot chain line curves 51, 52 and 53 in the graph of Fig. lO.
Example ~
Similar to the laminated structure as in Example
- Field of the Invention -The present invention relates generally to a color cathode ray tube and more particularly to a current-sensitive color cathode ray tube.
Description of the Prior Art In a color cathode ray tube used in an ordinary color television receiver and so on, in opposed relation to its phosphor screen, located is a means such as a shadow `;
mask, aperture grill or the like which functions to determine the landing position of an electron beam on the phosphor screen, whereby the electron beams corresponding to the respective colors are landed on the respective color phosphor dots or stripes of the phosphor screen to thereby provide respective color emissions and h'ence reproduce a color - picture on the phosphor screen.
On the contrary, in a current-sensitive color cathode ray tube, there is provide no means to determine the landing position of the electron beam but itc phosphor screen is formed of more than two color phosphors, which are mixed and then coated, and emits necessary color light or lights within a predetermined limited color gamut in response to the beam current density.
Since such the current-sensitive color cathode ray tube has no means to determine the electron beam landing position, it performs such an advantage that its weight becomes light, its assembling or manufacturing process becomes simpli~ied and its resoLution is improved and also _ 2 - ~
.
, .
~ 1~7~3~3~ :
such an advantage to avoid various problems, ~or example, mislanding caused by the relative positional displacement between the ph~sphor screens and the means to de~ermine the electron beam landing position.
BRIEF DESCRIPTION OF THE DR~WINGS
Fig. 1 is a graph showing the current density versus luminance characteristic used to explain a prior art current-sensitive color cathode ray tube;
Fig~ 2 is a schematic diagram showing an example of the current-sensit ~e color ca~hode ray tube according to the present inv~ntion;
Figs. 3, 5, 9, 10 and 11 are respectively graphs showing the beam current density versus luminance characæ~istics;
Fig. 4, ap~¢ing with~Figs. 1 and 2, ~s a ch~ticity diagram;
Fig. 6 is a graph showing a measured ourve repre-senting the selation between Eu amount in red-emitting phosphor and luminance thereof;
Fig. 7 is a graph showing the simil~r Eu amount and chromaticity value; and Fig. 8 is a cross-sectional view of the phosphor screen used in the cathode ray tube shown in Fig. 2.
: A prior art curren~-sensi~ive colox cath~de xay '! tube, mentioned just above, includes a phosphor screen made of mixed color phosphors of-a green phosphor showing a so-called sub-linear characteristic represented by a curve 1 in the graph of Fig~ 1 which shows the luminanee character-.~ istic of the phosph~r to the electron beam ~urrent density, - --3~
, , ..
: ~ :
~ 7~ ~ 3 ~
with a red phosphor showing a 50- called super-linear characteristic xepre~entea by a ~urve 2 in the graph of Fig.
1. In this case, within a range where the beam current density is small, the light emission of green is dominant, while within a range where the beam current density is large, the light emission of red is dominant, whereby a color image having a color gamut of synthesized two colors in response to tha beam current density is produced.
As the green-emitting phosphor whose current density versus luminance characteristic is the above sub-linear characteristic, phosphor of Zn2SiO~: Mn is generally used, while as the xed-emitting phosphor showing the super-linear characteris~ic, ~CdZn)S: Ag, Ni is usually employed. In this case, for making the green-emitting phosphor Zn2SiO4 :
Mn represent th~ sub~linear characteristic, it is necessary to select t~e adding amount of Mn small. When the adding amount of Mn is selected small, a problem of burn by the beam irradiatio~ occurs. On the other hand, if the super -linear char~cteri~tic i8 pr~sented by the red-emitting phosphor (ZnCd)5: Ag, N$, the amount of Cd must be increased. When, howe~er, the amount of Cd i~ increased, the luminance thereof becomes low and its color purity becomes also low. This low color purity of the above prior art color cathode ray tube xesults in tha~ its color gamut, which can be re~roducedt becomes relatively narrow.
OBJECTS AND SI~ RY OF THE INVENTIO~
.
Accordingly, it is an object of the present ,:
'~
, ~L7~3~3~
, invention ~o provide a curren~-sensitive color cathode ray tube in which color purity is improved to thereby widen light emission color gamut.
Acc~rding to an aspect of this invention there is provided a current-sensitive color cathode ray tube having a phosphor screen scanned by an electron beam from an electron-source, with the current density in said beam varied at substantially constant accelerating voltage, said screen comprising a red-~mitting phosphor having a sublinear characteristic in the intensity-current density relationship and a different color-emitting phosphor other than red having a linear or superlinear characteristic in the intensity-current density relationship, characterized in that said red emitting phosphor has a following formula:
(Lnl_xEux)2O2s wherein Ln is a material selected from the group consisting of Y, La, Gd and Lu, and x ranges from 0.05 to 0.10 and further, concentration of a rare earth impurity such as terbium Tb and praseodymium Pr is less than 10 ppm.
The other objects, eatures and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings through which the like references designate the : same elements and part~.
DESCRIPTION OF THE PR~FE~RED ~ODIMEnTS
: The present invention will be hereinbelow described with reference to the attached drawings.
In general, according to the present invention, by using the combination of one color-~mitting phosphor, which has its current density versus luminance characteristic .
representing the sub-linear characteristic, with another color-emitting phosphor whose current density versus luminance characteristic represents the super-linear or linear characteristic, there is generated light emission with hue or color gamut represented by the synthesized color of the lights emitted from both color phosphors by controlling the current density, for example, modulating the cathode :
current.
~ . - In this invention, especially, as the phosphor which shows the above sub-linear characteristic a red-emitting p~osphor, which is high in color purity and has the compo-sition formula of (Lnl xEux)2O2S is used. In this formula Ln is formed of at least one kind in the group consisting of yttrium Y, lanthanum La, gadolinium Gd and luletium Lu, and x is selected to satisfy the condition of 0.05 - ~ - 0.10.
Further, in this red-emitting phosphor rare-earth impurities such as terbium Tb, praseodymium Pr and so on are selected less than 10 ppm.
The phosphor screen used in the current-sensitive color cathode ray tube of this invention is made by such a manner that the above red-emitting phosphor with sub-linear characteristic is mixed with another color, for example, green-emitting phosphor or blue-green-emitting phosphor with the super-linear or linear characteristic and the mixed phosphor is laminated as a layer, or each phosphor is re-spectively and sequentially laminated as a plurality of layers.
The reason why the value of x in the red-emitting phospnor (Lnl_xEux)2O2s is selected to satisfy 0.05 ~ x _ 0.10 in the invention is that such a fact was noted that if x was less than 0.05 the color pu:ity was lowered and ycllowish ~7~39 light emission is caused, while if x exceeded 0.10 the luminance became low. Further, the reason why the rare-earth impurity concentration of Tb, Pr and so on is selected less than 10 ppm is that it was ascertained that when the rare-earth impurity concentration of Tb, Pr and so on exceeded 10 ppm, the luminance was difficult to be saturated upon high beam current density and hence the sub-linear characteristic was not presented.
Now, the examples of this invention will be explained as follows:
Example 1 The red-emitting phosphor is made as follows:
Rare-earth oxide Ln203 is added with europium oxide Eu203 at a predetermined amount and then they are mixed to prepare a mixed rare-earth oxide; the mixed rare-earth oxide is further added with sulphur S at 30 to 80 weight %~ sodium carbonate Na2C03 at 30 to 80 weight %~ which serves as flux, and so on and they are mixed; and the mixture is burned in air at 900 to 1300C in 0.5 to 5 hours to provide phosphor represented by the composition fQrmula of (Lnl xEux)202S.
By hydraulic elutriation method, small size particles are removed from the above phosphor and, by use of a sieve large size particles are removed from this phosphor. While, green -emitting phosphor (ZnO 64Cdo 36)S: Ag,Ni which contains 50 ppm of Ag and 10 ppm of Ni is prepared. Then, the red-emitting phosphor and green-emitting phosphor are respectively weighted to be 35 weight % and 65 weight % and then mixed.
Then, the phosphor thus mixed is coated on the inner surface of a panel 3a of a cathode ray tube envelope 3 by the sedimentation method to form a phosphor screen 4 as . , , ~ ,~
shown in Fig. 2. In Fig. 2, reference numeral 5 designates an electron gun which will emit an electron beam to the phosphor screen 4 and reference numeral 6 denotes its horizontal and vertical deflection means. This current-S sensitive color cathode ray tube is provided with no means to determine the landing position of the electron beam on the phosphor screen 4j for-example, no shadow mask or ~~
aperture grill and so on and hence this color cathode ra~
~ tube can take the similar construction to that of an ordinary monochromatic cathode Yay tube.
Fig. 3 is a graph showing measured current density versus luminance characteristics of the phosphor screen 4 of the invention for such a case where in the Example 1 the red-emission phosphor is Y202S: Eu. In the graph o Fig. 1, a broken line curve 11 represents the current density to luminance characteristic of the red light emission by the red-emitting phosphor Y202S: Eu, a -- solid line curve 12 shows that of the green light emission by the green-emitting phosphor ~ZnO.64CdO.36) g a one-dot chain line curve 13 represents the current density to luminance characteristic of this phosphor screen, namely the total luminance versus current density characteristic of respective color lights of the color cathode ray tube.
As will be apparent from the graph of Fig. 3, the red-emitting phosphor Y202S: Eu shows the sub-linear characteristic while the green-emitting phosphor (ZnO 64Cdo 36)S Ag, Ni shows the super-linear characteristic, respectively.
Now, the color gamut of the light emission by the red and green-emitting phosphors will he considered with reference to the graph of Fig. 4 which is a MacAdam's u,v .
1~78G39 chromaticity diagram. In the graph of Fig. 4, reference letters R, G and B respectively shows the chromaticities of red, green and blue. In this case, the line RlGl from a point Rl to a point Gl shows a color gamut within which the light emission of the color cathode ray tube with the phosphor screen made by the mixture of the red-emitting phosphor Y202S: Eu with the g~een-emitting phosphor (ZnO 6~ ;
Cdo 36)S: Ag, Ni according to Example 1 is possible. In ~ - this case, in accordance with the beam current density, namely as the beam current density becomes large, such light emission with hue is generated in which the hue goes to the point Gl in the line RlGl, while as the beam current density becomes low the hue of light emission goes to the point Rl.
In the graph of Fig: 4, letters Rl' and Gl' respectively designate chromaticity points of red and green colors of a prior art current-sensitive color cathode ray tube mentioned previously. In this case, the color gamut which can be .. . .
reproduced rests on the line connecting the points Rl' and G '. As will be apparent from the comparison of both lines RlGl and Rl'Gl', it is understood that the color gamut of this invention which can be reproduced is wider than that of the prior art since the line RlGl is longer than that Rl'Gl' and hence the color purity of, especially red color is improved.
In the graph of Fig. 5, a solid line curve 21 shows the current density to lumir,ance characteristic of Y202S: Eu which corresponds to the broken line curve 11 in the graph of Fig. 3, and a solid line curve 22 in the graph of Fig. 5 shows the similar characteristic of Y202S: Eu, Tb from which it will be clear that when Tb is added to the -. :
' ~.
~1~7~3639 :: `
phosphor, it beco~es di~ficult to present the sub-linear characteristic.
The graph of Fig. 6 shows reIative values of the luminance for the amount of Eu ~n the Y2O2S: Eu phosphor Cnamely the value x in the Composit~on formula (Lnl xEux)202S) which were measured, and curVes 31 and 32 in the~ graph of F~gO 7 respectively show values of x and y in the x-y chromaticit~ diagram of the amoun~ of Eu in similar phosphors.
In the x y chromaticity value, when the Eu amount is less 10 than 5 mole %, the p~osphor represents yellow. Thereforè, it will ~e easily understood that the Eu amount is selected more than 5 mole % and less than 10 mole ~ so as to select the relative value of the luminance more than 50 ~ in view of the luminance characteristic in the graph of Fig. 6, 15 namel~ the x ~alue in t~e above composition is selected to satisfy 0.05 _ x _ 0.10.
- In the above Example 1, although the red and green phosphors are mixed to form the phosphor screen 4, it is possible that the res~ective color phosphors are r~spectively 20 laminated as layers to form the phosphor screen 4. ~ow, an example of such case will be described.
Example 2 90 weight % of the gr~en-emittin~ phosphor used in Example 1 is first coated on the inner surface of the panel 25 3a of the cathode ray tube envelope 3 by the sedimentation method and the phosphor layer thus formed is dried sufficiently.
~17~3~3~
Thereafter, 10 weight % of the red-emitting phosphor used in ~xample 1 is coated on the above green-emit~ing phosphor layer by the similar sedimentation method. Thus, the phosphor - --- screen 4 consisting of green and red phosphor layers 4G and .
-lOa~
.
.. . . ..
, .
~ ~7~3t;35~
4b laminated in this order on the inner surface of the panel 3a is provided as shown in Fig. 8 and hence a current -sensitive color cathode ray tube similar to that explained in connection with Fig. 2 is provided.
The current density to luminance characteristics of the red and green colors in Example 2 become as indicated by broken line and solid line curves'!41 and'42 in t'he'graph ' '''-~
of Fig. 9 and the total characteristic thereof is shown by a one-dot chain line curve 43 in the same graph. In this , case, as will be apparent from the comparison of the curve 12 in the graph of Fig. 3 with that 42 in the graph of Fig.
9, in case of the laminated phosphor screen o~ Example 2, the current density versus luminance characteristic of the lower layer, namely the green-emitting phosphor layer 4G
located on the side opposite to the electron beam impinging side represents lower luminance at the low current range so that the purity of t~e red can be enhanced much.
~' It is needless to say that the present invention is not limited to the combination of the~red-emitting phosphor having sub-linear characteristic with the green-emitting phosphor having the super-linear or linear characteristic, but the invention can be applied to the combination of the red-emitting phosphor having the sub-linear characteristic with another color phosphor having the super-linear or linear characteristic such as blue-green -emitting phosphor. An example o~ this case will be now described.
Example 3 Similar to Example 1 but in place of the green -emitting phosphor, a blue-green-emitting phosphor .
_ ~1 7~ ~ 3 ~
(ZnO 82Cdo l8)S: Ag, Ni is used. The current density versus luminance characteristics of xed light emission, blue-green light emission and total light emission of this case are respectively measured as shown by broken, solid ::
and one-dot chain line curves 51, 52 and 53 in the graph of Fig. lO.
Example ~
Similar to the laminated structure as in Example
2, but in place of the green-emitting phosphor, a blue-emitting phosphor (ZnO 82Cdo l8)S: Ag, Ni is used. The current density versus luminance characteristics of red light emission, bluish. green light emission and total light emission of this case are respectively measured as indicated by broken, solid and one-dot chain line curves 61, 62 and 63 in the graph of Fig. 11.
As will be apparent from the oregoing explanation, according to the current-sensitive color cathode ray tube of ~` the present invention, its color purity is Pnhanced as compared with the conventional color cathode ray tube of this kind and accordingly, light emission colox gamut can be widened.
The above description is given on the preferred embodiments of the invention, but it will be apparent that many modifications and variations could be effected by one skilled in the art without departing from the spirits or scope of the novel concepts of the invention, so that the scope of the invèntion should be determined by the appended claims only.
, :,
As will be apparent from the oregoing explanation, according to the current-sensitive color cathode ray tube of ~` the present invention, its color purity is Pnhanced as compared with the conventional color cathode ray tube of this kind and accordingly, light emission colox gamut can be widened.
The above description is given on the preferred embodiments of the invention, but it will be apparent that many modifications and variations could be effected by one skilled in the art without departing from the spirits or scope of the novel concepts of the invention, so that the scope of the invèntion should be determined by the appended claims only.
, :,
Claims (5)
1. A current-sensitive color cathode ray tube having a phosphor screen scanned by an electron beam from an electron-source, with the current density in said beam varied at substantially constant accelerating voltage, said screen comprising a red-emitting phosphor having a sublinear characteristic in the intensity-current density relationship and a different color-emitting phosphor other than red having a linear or superlinear characteristic in the intensity-current density relationship, characterized in that said red emitting phosphor has a following formula:
(Ln1-xEux)2O2S
wherein Ln is a material selected from the group consisting of Y, La, Gd and Lu, and x ranges from 0.05 to 0.10 and further, concentration of a rare earth impurity such as terbium Tb and praseodymium Pr is less than 10 ppm.
(Ln1-xEux)2O2S
wherein Ln is a material selected from the group consisting of Y, La, Gd and Lu, and x ranges from 0.05 to 0.10 and further, concentration of a rare earth impurity such as terbium Tb and praseodymium Pr is less than 10 ppm.
2. A current-sensitive color cathode ray tube according to claim 1, wherein said different color-emitting phosphor is green.
3. A current-sensitive color cathode ray tube according to claim 1, wherein said different color-emitting phosphor is blue-green.
4. A current-sensitive color cathode ray tube according to claim 1, wherein said different color-emitting phosphor and said red-emitting phosphor are sequentially coated onto the inner surface of said cathode ray tube to provide a plurality of layers.
5. A current-sensitive color cathode ray tube according to claim 1, wherein said red-emitting phosphor and said different color-emitting phosphor are mixed to provide a single layer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56090471A JPS57205946A (en) | 1981-06-12 | 1981-06-12 | Current-dependent color cathode-ray tube |
| JP90471/81 | 1981-06-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1178639A true CA1178639A (en) | 1984-11-27 |
Family
ID=13999502
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000404160A Expired CA1178639A (en) | 1981-06-12 | 1982-05-31 | Current-sensitive color cathode ray tube |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS57205946A (en) |
| KR (1) | KR900002077B1 (en) |
| CA (1) | CA1178639A (en) |
| GB (1) | GB2102197B (en) |
-
1981
- 1981-06-12 JP JP56090471A patent/JPS57205946A/en active Pending
-
1982
- 1982-05-31 CA CA000404160A patent/CA1178639A/en not_active Expired
- 1982-06-10 GB GB08216897A patent/GB2102197B/en not_active Expired
- 1982-06-11 KR KR8202606A patent/KR900002077B1/en active
Also Published As
| Publication number | Publication date |
|---|---|
| JPS57205946A (en) | 1982-12-17 |
| KR900002077B1 (en) | 1990-03-31 |
| KR840000976A (en) | 1984-03-26 |
| GB2102197B (en) | 1985-06-05 |
| GB2102197A (en) | 1983-01-26 |
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