JPH075885B2 - Color cathode ray tube for display - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a color cathode ray tube for a display.

[Prior art]

It is generally known that a color cathode ray tube used for a display device of characters or figures is used with a screen scanning speed slower than that of a general color television in order to increase resolution. Therefore, when a general cathode ray tube for a color television is used for a display device, the afterglow of the light emitting screen after the excitation by the cathode ray is stopped is short, so that the screen flickers to the viewer. Therefore, the color cathode ray tube used for the display device needs to be provided with a light emitting screen having a longer afterglow than the cathode ray tube for color television. In other words, when the afterglow length is normally expressed as the time until the brightness becomes 1/10 of the brightness after the stimulus is stopped, that is, the 10% afterglow time, the 10% afterglow on the light-emitting screen for color television While the time is 1 millisecond or less, the display device requires a long afterglow time of tens to hundreds of times. Phosphors constituting a light-emitting screen that can meet such requirements include manganese-arsenic activated zinc green silicate phosphor (Zn ₂ SiO ₄ : Mn, As), manganese activated zinc orthophosphate red light-emitting phosphor. [Zn ₃ (PO ₄ ) ₂ : Mn), manganese-activated cadmium chloride orthophosphate, white luminescent phosphor [Cd ₅ C
l (PO ₄ ) ₃ : Mn] and the like are known. However, none of these phosphors emit blue light, and a blue long afterglow phosphor is disclosed in Japanese Patent Publication No. 57-37098. That is, in this publication, a relatively long afterglow is imparted to a blue light emitting element of a light emitting screen by mixing a long afterglow green and red phosphor with a short afterglow blue phosphor. Is disclosed. This phosphor is prepared by mixing a manganese-arsenic-activated zinc silicate green light-emitting phosphor and a manganese-activated zinc magnesium orthophosphate red-light-emitting phosphor at a predetermined ratio, and adding silver-activated zinc sulfide blue-light-emitting phosphor to this mixture. A blue light emitting element is formed by mixing the body. The emission color of this blue light emitting element is CI
It is close to the white point in the chromaticity coordinates of the E display system and is generally called a light blue phosphor. However, the light emitting device using the light blue phosphor described above has a shortcoming in that the afterglow color changes from yellow to orange after cathodic ray stimulation because the 10% afterglow time of the blue phosphor is short. In contrast to the red, blue, and green mixed phosphors, a phosphor having a blue emission color and an afterglow color alone has been proposed (Japanese Patent Laid-Open No. Sho 61-187).
58-79814, JP-A-58-83084, JP-A-58-
83085, JP58-120521A, JP58-129
083). These phosphors have zinc sulfide ZnS as a base material, silver as an activator, and one of Ga and In as a first co-activator,
Either Au or Cu is used as the second co-activator, and halogen, Al, or the like is used as the third co-activator. The blue light-emitting device using these phosphors emits blue light, and has a blue afterglow color, but the emission brightness is significantly lower than that of the conventional short afterglow blue phosphor (ZnS: Ag). Moreover, the burning characteristics, which are important for a long-afterglow light-emitting element, are poor, and the linearity of the emission brightness with respect to the current of the electron beam is poor, so that there is a drawback that the emission brightness proportional to the current density cannot be realized. It has not been done.

[Problems to be Solved by the Present Invention]

The long-afterglow luminescent screen has a lower emission brightness in principle than the short-afterglow luminescent screen. This is because the long afterglow luminescent screen emits light even after the electron beam stimulation is stopped, so that the energy given from the electron beam is emitted and emitted for a long time. Further, in order to increase the resolution of the screen, the degree of focus of the electron beam is increased to increase the current density. However, the higher the current density, the more easily the burnin occurs. Further, the long afterglow light emitting screen is used for a high-resolution display tube as described above to clearly display characters and figures on the screen, but the light emitting screen for this type of application is a phosphor-coated film. A certain position of a specific part of the display is strongly irradiated with an electron beam, and deterioration (burning) is likely to cause local brightness reduction, which causes a uniform display capability of the display tube and shortens the life. There is. Another condition is current characteristics. The current characteristic is the linearity of light emission luminance with respect to the current density passed through the light emitting element. The luminance characteristic of an existing light emitting element does not change linearly with respect to current, and is lower than that. The main cause of the deterioration of the current characteristics is that the emission color shifts when the current density is increased or decreased. The emission brightness is obtained by multiplying the emission energy by the color matching function of the standard observer and integrating it in the visible region wavelength. Therefore, when the emission color changes, the expected brightness cannot be obtained. If the color shift occurs due to the increase or decrease of the current density, the color reproducibility with respect to the brightness of the screen of the display tube is reduced, which is also not preferable. As described above, the luminescent screen used for the high-resolution display tube is desired to have high emission brightness, good burning characteristics and good current characteristics, in addition to preferable afterglow characteristics. An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a color cathode ray tube for a display, which can obtain a clear and flicker-free image by increasing the purity of blue color. Another important object of the present invention is to provide a color cathode ray tube for a display, which has a blue light emitting element that emits both blue light and an afterglow color and has excellent burning characteristics and current characteristics.

[Means for Solving the Problems]

An object of the present invention is to provide a blue phosphor with zinc sulfide (ZnS) as a base material, zinc (Zn) or europium (Eu) as an activator, and gallium introduced into the base material as a halide added during firing. At least one of Ga), indium (In), and thallium (Tl) is used as the first coactivator,
Chlorine (Cl), bromine (Br), fluorine (F), iodine (I)
And at least one of aluminum (Al) as a second co-activator, which is solved by a color cathode ray tube for a display including a light emitting element formed of this blue phosphor. The emission brightness and emission color of the blue light emitting element change depending on the contents of Zn and Eu which are activators of the blue light emitting phosphor. The luminescent brightness decreases when the amount of activator is too large or too small. When Eu is used as an activator in addition to self-activation of Zn, the emission brightness of the phosphor can be increased. Z, which is a self-activator for matrix ZnS
Although n cannot be analyzed from the obtained phosphor, it is adjusted to an optimum value depending on the firing temperature and the like. Ga, In, and Tl, which are the first co-inactivating agent, are contained in the ZnS phosphor to adjust the afterglow time. In the preferred range of use, these first coactivators have the longest afterglow time at a specific content.
Moreover, the emission brightness decreases as the content increases.
Furthermore, if the type of material contained changes, the afterglow time, emission brightness, and emission color also change. Therefore, these coactivator is required decay time, emission brightness, the material used in accordance with the light emission color is selected, the content thereof is, with respect to ZnS maternal, usually 1 × 10 ^{- 4 to} 3 × 10 ^-1 % by weight, preferably
It is determined to be 3 × 10 ^-3 to 1 × 10 ^-1 % by weight. Further, the second co-activator Cl, Br, I, F, Al changes the emission brightness and emission color depending on the type and content of the material,
If the content is too large or too small from the optimum value, the emission brightness is lowered. Therefore, the optimum value of these materials is determined from the required emission brightness and emission color. Cl, Br, I, and F are usually 5 × 10 ^{−4 with} respect to the matrix ZnS.
˜1 × 10 ⁻¹ wt%, preferably 5 × 10 ^-3 ˜5 × 10 ⁻² wt%, Al is 5 × 10 ^-4 ˜5 × 10 ⁻¹ wt%, preferably 5 based on the ZnS of the matrix. The content of x10 ^-3 to 1 x 10 ^-1 is contained.

【Example】

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 shows a CIE display chromaticity diagram of three types of light emitting elements in a light emitting screen of a general color display cathode ray tube. The three types of light emitting elements are composed of red, green and blue.
As shown in FIGS. 2A and 2B, these light emitting elements are formed in a dot shape or a stripe shape on the light emitting screen by a known optical printing method. Among these light emitting elements, the green light emitting element G and the red light emitting element R are each a manganese-arsenic activated zinc silicate phosphor Zn ₂ SiO ₄ : M.
n, As and manganese activated zinc calcium orthophosphate phosphor (Zn, Ca) ₃ (PO ₄ ) ₂ : Mn. The blue light emitting element B is formed of a zinc sulfide phosphor described in detail below. An outline of an improved zinc self-activated halogen-containing zinc sulfide phosphor will be described as an example of a preferable blue light emitting phosphor forming a blue light emitting element. This blue phosphor is 1 × 10 ^{−4 with} respect to ZnS: Zn matrix ZnS.
To 3 × 10 ^-1 wt% gallium (Ga) and 5 × 10 ^-4 to 1 × 10 ^-1 wt% halogen. That is, this blue phosphor has zinc sulfide ZnS as a matrix,
It uses self-activation with zinc, and is accompanied by co-activation with gallium Ga and halogen. Here, this blue phosphor is used as an activator in addition to self-activated zinc and europium.
Eu may be used. As the activation amount of gallium Ga is increased with respect to the host ZnS, the emission brightness and emission color purity gradually decrease.
As shown by the solid line in the figure, the afterglow time is 10%, and it becomes longer in the range of the activation amount of 1 × 10 ^-4 to 3 × 10 ^-1 wt% with respect to the host ZnS, especially 3 × 10 ^-1 wt% It becomes approximately 30 ms or more in the area of activation amount of 1 to 10 ^-1 . As shown by the dotted line and the alternate long and short dash line in FIG. 3, instead of gallium Ga as the first coactivator, either indium In or thallium Tl was added to the host ZnS at a concentration of 1 × 10. ^-4 to 3 × 10 ^-1 % by weight in the activation area, and the first coactivator contains both gallium Ga and indium In or thallium Tl. Good. Furthermore, although not shown,
The first coactivator may contain any one of tin Sn, lead Pb, arsenic As, antimony Sb and bismuth Bi. Further, the emission brightness and the emission color change depending on the halogen activation amount with respect to the host ZnS.
5 × 10 ^-4 to 1 × 10 ^-1 % by weight of S, preferably 5
It is contained in an amount of about ^{x10 -3} to ^{5x10 -2} wt%. Instead of halogen, aluminum Al may be used in the above-mentioned proportion, and, of course, the second coactivator may contain both halogen and aluminum Al. The blue phosphor thus formed has the following characteristics. That is, x value is 0.1 in CIE chromaticity display.
45-0.149, y value is 0.131-0.141, relative luminance Y (%) = 51.5 with the luminosity factor corrected based on the silver-activated zinc sulfide blue phosphor ZnS: Ag (x = 0.146, y = 0.138). ~ 66.0%
Z (%) = 52.1 to 65.3% as a blue component, and the 10% afterglow time is 48 to 92 milliseconds. FIG. 4 shows the afterglow characteristics of this blue phosphor in comparison with the silver-activated zinc sulfide blue phosphor ZnS: Ag and the gallium-chlorine co-activated silver-activated zinc sulfide phosphor. . In FIG. 4, the vertical axis represents relative luminance (%) on a logarithmic scale, and the horizontal axis represents the afterglow time, so that the blue fluorescence forming the blue light emitting element used in the cathode ray tube of the present invention is represented by the curve a. Body, curve c
Shows the afterglow characteristics of a conventional silver-activated zinc sulfide blue short afterglow phosphor, and curve b shows a conventional silver- and gallium co-activated zinc sulfide phosphor. As is clear from FIG. 4, the blue phosphor forming the blue light emitting element used in the color cathode ray tube of the present invention has sufficient afterglow characteristics and maintains high emission brightness. For example, the brightness between this single blue phosphor and a conventional light blue phosphor, that is, a mixed phosphor in which a short afterglow blue phosphor is mixed with long afterglow red and green phosphors. Comparing the two, the composition formula ZnS: Ag ＋ (Zn, Mg) ₃ (PO ₄ ) ₂ : Mn
+ Zn ₂ SiO ₄ : Mn, As phosphor, when x = 0.140, y = 0.150 and afterglow of 60 milliseconds, the luminance value Y with corrected luminosity is 80
%, On the other hand, in the phosphor of the composition formula ZnS: Zn, Ca, Cl, x =
When 0.143, y = 0.151 and afterglow 62 ms, the brightness value Y is
110%. That is, the brightness of the single blue phosphor is about 37% brighter than that of the conventional mixed phosphor when compared with the same afterglow time at almost the same chromaticity point. Further, this blue phosphor is excellent in burning characteristics and current characteristics when applied to a light emitting screen. The display color cathode ray tube including the blue light emitting element B formed of such a blue phosphor will be described below. As shown in FIG. 1, the chromaticity points r, g, b of these red, green and blue light emitting elements R, G, B are represented.
Here, for comparison, m represents the chromaticity point of the blue light emitting element using the conventional light blue phosphor. As is clear from FIG. 1, a blue light emitting device B comprising zinc self-activated gallium and halogen co-activated zinc sulfide phosphor.
In the color image display cathode ray tube using, no screen flicker occurs. Since the brightness of the blue light emitting element B is greatly improved, the screen can be made clearer. Furthermore,
As is clear from the fact that the chromaticity point b of the blue light emitting element in the CIE display system is far from the white point w as compared with the chromaticity point m of the conventional light blue blue light emitting element, the blue stimulus of the blue light emitting element is clear. At times, the purity of blue can be increased. Note that this blue color is not close to purple-blue,
As shown by the chromaticity point b of blue in the figure, a deep blue color that approaches the green color that contributes to the visual sensitivity and is farther than the white point w,
That is, it is a highly pure blue color. Therefore, the chromaticity range obtained by connecting the points r, g and b in FIG. 1 has excellent color reproducibility. The blue light-emitting element described above is formed of a single long-afterglow blue phosphor, but in the present invention, the blue light-emitting element is a known blue light-emitting element and a known emission color different from that of the blue phosphor. It may be formed of at least one phosphor having a long afterglow. That is, this blue phosphor and, for example, known manganese-
Arsenic Activated Zinc Silicate Green Phosphor Zn ₂ SiO ₄ : Mn, As (10
% Afterglow time 80 ms) and manganese activated zinc calcium orthophosphate red light-emitting phosphor (10% afterglow time 120 ms)
A mixed phosphor may be formed by mixing (Zn, Ca) ₃ (PO ₄ ) ₂ : Mn, and a light blue or white fluorescent element may be formed from this mixed phosphor. In addition, since the blue phosphor alone has a sufficiently long afterglow time, the blue light emitting element changes the emission color, so that the blue light emitting element has at least one of the blue phosphor and an emission color different from that of the blue phosphor. It may be composed of a short afterglow phosphor. In the color cathode ray tube for a display of the present invention, all the long afterglow phosphors which have been already used or have been developed can be used for the red and green light emitting elements of the light emitting screen. The phosphor forming the blue light emitting device can be manufactured by the following method. As a phosphor material, (a) as a base material, ZnS (zinc sulfide raw powder) (b) As an activator material, either ZnS or EuCl ₃ is used, and (c) as a first co-activator. , Ga, In, Tl, Sn, Pb, S
b, a halide of Bi, or As ₂ O ₃ is used, and (d) an ammonium salt of Cl, Br, I, F, or a chloride salt of aluminum or sulfuric acid is used as the second coactivator. At least one of salt and nitrate is used. For the phosphor, the above raw materials are kneaded and dried in an optimum amount, and the obtained phosphor raw material mixture is filled in a heat-resistant container such as a quartz crucible or a quartz tube and baked. Firing is performed in a sulfide atmosphere such as a hydrogen sulfide atmosphere, a sulfur vapor atmosphere, and a carbon sulfide atmosphere. A firing temperature of 800 ° C to 1100 ° C is suitable. The firing time varies depending on the firing temperature, the amount of the phosphor raw material mixture, etc.
Time is appropriate. After firing, the obtained fired product is thoroughly washed with water, dried and sieved to obtain a phosphor. Hereinafter, a specific method for manufacturing a phosphor for forming a blue light emitting element will be described in more detail. [Specific Example 1] Zinc sulfide ZnS 1000g Sodium chloride NaCl 18g Gallium chloride GaCl ₃ 0.1g The above raw materials were made into a water slurry and thoroughly kneaded to 100 ° C to 110 ° C.
After drying at 0 ° C., an appropriate amount of sulfur was added to the obtained phosphor raw material mixture and the mixture was filled in a quartz crucible. After covering the quartz crucible with a lid, the quartz crucible was placed in an electric furnace and baked in a reducing atmosphere at a temperature of 940 ° C. for 3 hours. After firing, the obtained fired product was thoroughly washed with water, dried at 100 ° C to 110 ° C, and sieved. Thus, a ZnS: Zn, Ga, Cl phosphor was obtained. This phosphor contained 3.2 × 10 ⁻³ wt% gallium and 1 × 10 ⁻² wt% chlorine with respect to the host ZnS. The above-mentioned phosphor exhibits blue emission with high color purity of x = 0.148 and y = 0.131 in the x and y values of CIE chromaticity display, and the conventional long-afterglow blue-emitting phosphor. (ZnS: Ag, Ga, Cl)
The emission brightness is higher than that of the
The% afterglow time was 58 milliseconds, which was a preferable value. [Specific Example 2] Zinc sulfide ZnS 1000g Gallium bromide GaBr ₃ 0.23g Magnesium bromide MgBr ₂ .6H ₂ O 15g Sodium bromide NaBr 10g The above raw materials were treated in the same manner as in Example 1 to obtain ZnS: Zn, Eu, A Ga phosphor was obtained. This phosphor is 5 × 10 ^-3 % by weight with respect to the host ZnS.
Of Ga, 1 × 10 ^-2 wt% Br. The above phosphor has excellent characteristics as a long afterglow blue light emitting phosphor as shown in Table 1. However, in Table 1, Y (%) indicates the relative luminance corrected for the visibility, and Z (%)
Indicates relative luminance as a blue component. By the way, as described above, the halogen and Al added to the zinc sulfide phosphor of the color cathode ray tube of the present invention as the second coactivator are the phosphors used in the cathode ray tube of the present invention. It does not affect the afterglow characteristics, which are the most important for the fluorescent material, but changes the emission color and brightness of the phosphor. Furthermore, in addition to self-activating Zn, the use of Eu as an activator does not affect the important afterglow characteristics of the phosphor used in the cathode ray tube of the present invention, and does not affect the emission brightness. To improve. Therefore, as shown in the following specific examples, Al is used instead of halogen, and Zn is used to increase the emission brightness.
In addition to the self-activation of, using Eu as an activator,
A zinc sulfide phosphor can be manufactured in the same manner as in Example 1 except that I and F are used instead of Na as the second coactivator. Specific Example 3 A halogenated zinc sulfide phosphor was obtained in the same manner as in Specific Example 1 except that a small amount of Eu was added as an activator. This phosphor is
The 10% afterglow time after the electron beam excitation was stopped showed almost the same preferable characteristics as in Example 1. Furthermore, this phosphor can be adjusted to have an optimum Eu addition amount to have higher emission brightness than the zinc self-activated halogen zinc sulfide phosphor of Example 1. [Specific Example 4] Instead of sodium chloride, an aluminum compound is added and baked so that the content of aluminum is 5 × 10 ^-3 to 1 × 10 ^-1 wt% with respect to ZnS of the mother pair. Other than the above, when a ZnS: Zn, Ga, Al phosphor was obtained in the same manner as in Example 1,
The 10% afterglow time after the electron beam excitation was stopped showed almost the same preferable characteristics as in Example 1. Since this halogen zinc sulfide phosphor uses Al instead of Na as the second co-activator, it is possible to change the emission color and the emission brightness with respect to the phosphor of Example 1. Specific Example 5 Specific Example 1 except that an iodine compound or a fluorine compound is used instead of sodium chloride as the second coactivator.
A halogen zinc sulfide phosphor was obtained in the same manner as in. This phosphor showed preferable characteristics, which were almost the same as in Example 1 after the 10% afterglow time after the electron beam excitation was stopped. Furthermore, this phosphor has the same amount of iodine compound or fluorine compound as that of the matrix.
The emission color and the brightness can be adjusted by adjusting the range of 5 × 10 ^{−3 to} 5 × 10 ⁻² wt% with respect to ZnS. In order to compare the characteristics of the blue light emitting element formed of the phosphors prototyped in the above specific examples, the short afterglow blue light emitting phosphor with high emission brightness that has been conventionally used, the emission color and the afterglow color The long-afterglow blue-emitting phosphor described in JP-A-58-79814 was manufactured as a prototype. A ZnS: Ag phosphor was used as the short afterglow blue phosphor. In addition, a ZnS: Ag, Ga, Cl phosphor is used for the long-afterglow blue light emitting phosphor, and the content of Ag as an activator is 1 × 1 with respect to ZnS.
0 ^-2% by weight, the content of Ga 1 × 10 ^-2 wt%, the content of Cl and 1 × 10 ^-2 wt%. The blue light emitting element forming the light emitting screen of the color cathode ray tube for a display of the present invention shows blue light emission of high color purity comparable to the conventional short afterglow phosphor in both x value and y value.
After the electron beam excitation was stopped, the afterglow time of 10% was longer than that of the conventional long-afterglow blue phosphor (ZnS: Ag, Ga, Cl), which was more than twice as long. Furthermore, the relative emission brightness was also dramatically improved compared to the conventional long-afterglow blue-emitting phosphor (ZnS: Ag, Ga, Cl). From this, the blue light emitting element forming the light emitting screen of the color cathode ray tube for a display of the present invention exhibits blue emission with high color purity and exhibits ideal characteristics superior to conventional products along with afterglow time and emission brightness. Practical application of high quality color cathode ray tubes for displays. Furthermore, as shown in FIG. 5, the blue light emitting element of the color cathode ray tube for display of the present invention showed excellent characteristics even in forced burning characteristics, which were not comparable to those of the conventional products. That is, in FIG. 5, a curve a shows the characteristics of the blue light emitting element formed of the phosphor used in the cathode ray tube of the present invention and manufactured as a prototype in the specific example, and the curve b.
Is a conventional long-afterglow blue-emitting phosphor, namely ZnS: Ag, G
The characteristics of a blue light emitting element formed of a, Cl phosphor are shown. However, the following method was used to measure the forced burning characteristics of the blue light emitting device. Pyrex glass is coated with phosphor, acrylic lacquer filming, and metal back is applied to form a blue light-emitting element, and a phosphor brightness measuring device is used to apply an electron beam of ²⁰ μA / cm ² at 27 kV for a specified time on the phosphor coating film. Scan to obtain the surface that was forcibly deteriorated. The emission brightness of the part of the blue light emitting element that was not scanned with an electron beam was measured at 27 kV at 0.5 μA / cm ² as 100%, and under the same conditions, the emission brightness of the surface that was forcibly deteriorated was measured.
The relative brightness was expressed as a percentage. This is the burning characteristic at a specific time. As is apparent from FIG. 5, the blue light emitting device used in the color cathode ray tube for display of the present invention showed a decrease in emission brightness of only 2.5% after 1 hour in the forced burning test. On the other hand, the blue light emitting element using the conventional ZnS: Ag, Ga, Cl long afterglow phosphor is
The emission luminance was reduced by 8%, which was about 3 times lower than that of the blue light emitting element of the color cathode ray tube for display of the present invention. From this, it is clear that the blue light emitting element used in the color cathode ray tube for a display of the present invention has remarkably excellent burning characteristics as compared with the blue light emitting element using the conventional long afterglow blue light emitting phosphor. Is. In an actual use state, a light emitting screen with low light emission brightness is used by increasing the current density to increase the brightness. The luminous screen with high emission brightness is the same as the conventional Zn with low emission brightness.
It can be used at a lower current density to obtain the desired brightness of the display tube as compared with the light emitting device using the S: Ag, Ga, Cl phosphor. Synergistically, the burning characteristics of the color cathode ray tube for display of the present invention are superior to those of conventional products. Further, FIG. 6 shows the measurement results of the current characteristics of the blue light emitting phosphor forming the light emitting screen of the color cathode ray tube for display of the present invention. The current measurement shown in FIG. 6 was performed under the following conditions. Assuming an ideal phosphor that has an emission luminance of 100 and a current density of 0.05 μA / cm ² and a current density of 10 and 100 times, respectively. However, the ideal phosphor has an emission brightness at each current density.
The relative emission luminance when 100% was defined as the current characteristic and measured. In the figure, a curve a shows the characteristics of a blue light emitting phosphor forming a light emitting screen of a color cathode ray tube for a display of the present invention, which is a prototype manufactured in a specific example, and a curve b shows a conventional long afterglow blue color. It is a characteristic of the light emitting phosphor (ZnS: Ag, Ga, Cl). From this, it is clear that the blue light emitting phosphor used in the color cathode ray tube for display of the present invention is superior in current characteristics to the conventional long afterglow blue light emitting phosphor. As described above, the light-emitting screen was formed by the blue light-emitting element which has excellent emission brightness and emission color, has a long 10% afterglow time characteristic, and further has good burning characteristics and current characteristics. The color cathode ray tube for a display of the present invention can realize a color cathode ray tube for a display of a high-quality image that is clear and does not flicker by using only the excellent characteristics of the red and green light emitting elements.

【The invention's effect】

The color cathode ray tube for a display of the present invention is provided with an afterglow phosphor having excellent emission brightness and a long afterglow time in a light emitting element. As shown in Table 1, the afterglow phosphor used in the color cathode ray tube of the present invention emits light when compared with the conventional long afterglow blue light-emitting phosphor (ZnS: Ag, Ga, Cl) phosphor. The brightness is about twice as high, the afterglow time is about three times as long, and the emission color with high blue purity is extremely excellent. The color cathode-ray tube for a display of the present invention using the afterglow phosphor having such excellent light emitting characteristics has a feature that the purity of blue color is increased and a clear and flicker-free image can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing CIE chromaticity of red, green and blue light emitting elements of a color cathode ray tube for a display of the present invention,
2 (a) and 2 (b) are partial views showing an example of the light emitting screen, and FIG. 3 is a first view of a blue phosphor forming a blue light emitting element used in the color cathode ray tube of the present invention. FIG. 4 is a diagram showing relative luminance with respect to a coactivator content, FIG. 4 is a diagram showing afterglow characteristics of a blue phosphor forming a blue light emitting element used in the color cathode ray tube of the present invention, and FIG. FIG. 6 is a graph showing a decrease in emission luminance (burning characteristic) with respect to electron beam excitation time, and FIG. 6 is a graph showing a decrease in emission luminance from an ideal phosphor (current characteristic) with respect to current density.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Keisho Yamashita 491-1, Oka, Kaminaka-cho, Anan City, Tokushima Prefecture Nichia Kagaku Kogyo Co., Ltd. Nichia Kagaku Kogyo Co., Ltd. (72) Inventor Akio Fujii 491-1 Oka, Kaminaka-cho, Anan City, Tokushima Prefecture Nichia Kagaku Kogyo Co., Ltd. (56) Reference JP-A-58-222180 (JP, A)

Claims (2)

[Claims] 1. Zinc sulfide (ZnS) as a base material, zinc (Zn)
Alternatively, europium (Eu) is used as an activator, and at least one of gallium (Ga), indium (In), and thallium (Tl) that is added as a halide at the time of firing and introduced into the mother body is used as a first co-activator. As the agent, at least one of chlorine (Cl), bromine (Br), fluorine (F), iodine (I) and aluminum (Al) is used as the second co-activator, and the first co-activator is 1 × 10 ^{−4 to} 3 × with respect to the phosphor matrix
A color cathode ray tube for a display, comprising a light emitting element formed of an afterglow blue phosphor adjusted to 10 ^-1 % by weight. 2. The light emitting device has the afterglow blue phosphor, and an emission color different from that of the afterglow blue phosphor.
%. A color cathode ray tube for a display as claimed in claim 1, characterized in that it is composed of a mixture with at least one phosphor having an afterglow time of 30 ms or more.