JPH0715096B2 - Afterglow fluorescent - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention mainly relates to an afterglow phosphor used for a display tube of a computer terminal.

[Prior art]

A display tube such as a computer terminal whose main purpose is to display characters and figures is required to have high resolution in order to clearly display small characters. High-resolution monitor televisions have a method of slowing down the scanning speed of the electron beam irradiating the phosphor coating film on the face plate of the display tube as a means for increasing the resolution by narrowing the frequency bandwidth of the video signal amplifier circuit. Has been adopted. If the scanning speed of the electron beam is kept constant and the resolution of the display tube is increased, it is necessary to design the frequency band of the video signal amplifier circuit of the monitor television to be wide in proportion to the resolution.
Therefore, monitor TVs with high-resolution display tubes have an amplification band of several tens of MHz to 100 MHz, which is several times to several tens of times wider than that of ordinary home TVs. This complicates the video signal amplifier circuit, restricts the arrangement of parts, requires a high-speed semiconductor, requires extremely advanced design and assembly technology, and makes the monitor TV extremely expensive. I have to. Also, there are restrictions on the frequency band of the video signal amplifier circuit,
A high-resolution display tube for displaying ultra-fine characters cannot be put into practical use unless the scanning speed of the electron beam is reduced. If the frequency band of the video signal amplifier circuit is narrowed and the scanning speed of the electron beam is slowed down, flicker occurs on the screen. Therefore,
In order to put a high resolution display tube into practical use, a 10% afterglow time (the time required for the emission brightness to drop to 10% of that after excitation after the excitation is stopped) is a normal display in order to prevent flicker. Dozens more than phosphors used in tubes
Phosphors that are hundreds of times longer are required. Conventionally, as phosphors that can be used for the high-resolution display tube, manganese- and 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-emitting phosphor [Cd ₅ Cl (P
O ₄ ) ₃ : Mn] and the like are known. As is well known, a display tube whose emission color is white,
In order to obtain a color display tube, a red light emitting phosphor, a blue light emitting phosphor and a green light emitting phosphor are indispensable,
In order to obtain the high-resolution display tube, development of a viable long-afterglow blue-emitting phosphor is desired. The fact that a blue-emitting phosphor having sufficient afterglow characteristics and emission brightness has not been put into practical use impedes the transition of the ultra-high-resolution display tube from monochrome to color. A phosphor that emits blue light when stimulated by an electron beam and emits yellow light afterglow has been developed. This phosphor is a silver-activated zinc sulfide phosphor (Zn
S: Ag), a long afterglow green phosphor Zn ₂ SiO ₄ : Mn, As,
Zn ₃ (PO ₄ ) ₂ : Mn, which is a long-afterglow red phosphor, is mixed, and the blue-emitting phosphor is made to have afterglow properties with red and green phosphors. Therefore, this phosphor has a drawback that the emission color is blue, but the afterglow color is yellow, which lowers the color purity of all emission colors. 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 (JP-A-58).
-79814, JP-A-58-83084, JP-A-58-83
085, JP-A-58-120521, JP-A-58-12908
No. 3 bulletin). 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. These phosphors are based on zinc sulfide ZnS, the phosphor of this composition has a blue emission color, and has a blue afterglow color, but the emission brightness is lower than that of conventional short afterglow blue phosphors. Is extremely low, and the burning characteristics, which are important for long-afterglow phosphors, are poor, and the linearity of the emission brightness with respect to the electron beam current is poor, and there is a drawback that emission brightness proportional to the DC density cannot be realized. It has not been put to practical use.

[Problems to be Solved by the Invention]

As described above, the long-afterglow phosphor is used for high-resolution display tubes to clearly display characters and figures on the screen, but the phosphor for this type of application is a phosphor coating film. A certain position of a specific portion is strongly irradiated with an electron beam, and therefore deterioration (burning) easily causes local brightness reduction, which causes a uniform display capability of the display tube and shortens the life. . The colors used for normal, home television,
Alternatively, in a CRT for a monochrome television, the entire surface of the fluorescent film is irradiated with the electron beam on average, so that the burning occurs uniformly and is not a serious problem. However, in the high-resolution display tube for this kind of application, the local current density of a specific portion is high, the scanning speed of the electron beam is slow, and the irradiation time of the electron beam is long, so that the burning characteristic is particularly important. Furthermore, as another important condition, even a long afterglow phosphor is required to have high emission brightness. However, in principle, the long afterglow phosphor has lower emission luminance than the short afterglow phosphor. This is because the long afterglow phosphor 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. That is, when light is emitted for a short time like a short-afterglow phosphor, the amount of light emitted per unit time is large, and as a result, the emission brightness is high. With a photoluminescent material, the amount of light emitted per unit time is small,
As a result, the emission brightness becomes low. Furthermore, the problem is that a phosphor with a low emission brightness increases the electron beam current density in order to increase the emission brightness, but the current density is increased to increase the electron beam stimulation of the phosphor. The higher the level, the more likely it is to cause burning. That is, when the emission brightness is low, the burning characteristics are also deteriorated and the characteristics of the entire phosphor are significantly deteriorated. From this, it goes without saying that the afterglow phosphor has a long afterglow time, and high emission brightness is also a very important condition. Another condition is current characteristics. The current characteristic is the linearity of the emission brightness with respect to the current density passed through the phosphor. An ideal phosphor has a current density of 10
If the brightness is increased to 100 times or 100 times, the emission brightness also increases linearly to 10 times or 100 times in proportion to the current density. In this state, the current characteristic of luminous efficiency is said to be 100%. However, in the existing phosphor, the luminance characteristic with respect to the current does not change linearly accurately, and the luminance characteristic 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. In order to improve the linearity of emission brightness, a afterglow phosphor has been developed which has (Zn, Cd) S as a matrix and is activated with at least one of Ag and Ga or In and halogen or Al. (JP-A-59-203350 and JP-A-59-2022).
No. 84). The afterglow phosphors described in these publications can improve the linearity of the emission brightness by specifying the activator. However, this phosphor also has a drawback that it cannot realize excellent burning characteristics and its life is shortened. It is desired that the phosphor used in the high-resolution display tube has good burning characteristics in addition to favorable afterglow characteristics, current characteristics, and emission brightness. An important object of the present invention is to provide a afterglow phosphor which is blue in both emission color and afterglow color and has excellent afterglow characteristics, emission luminance, burning characteristics, and current characteristics.

[Means for Solving the Problems]

The phosphor of the present invention is zinc cadmium sulfide [(Zn, Cd)
S] as a matrix, Ag as an activator, Ga as a first coactivator, and Cl as a second coactivator. The afterglow time, emission color, and emission brightness change according to the CdS content in the host material. If the amount of CdS is too large or too small, the afterglow time will decrease. From this, CdS is
It is determined to be 0.1 to 20% by weight, preferably 1 to 15% by weight. The emission brightness and emission color change depending on the content of the activator Ag. The luminescent brightness decreases when the amount of activator is too large or too small. The addition amount of the activator is determined to be an optimum value in consideration of the emission brightness required for the phosphor, the emission color and the raw material cost.
Usually, it is determined to be 1 × 10 ^-5 to 1 × 10 ^-1 % by weight, preferably 5 × 10 ^{-4 to} 5 × 10 ^-2 % by weight, based on the matrix. Ga, which is the first co-inactivating agent, is contained in the sulfide matrix to adjust the afterglow time. These first coactivators have the effect of further increasing the afterglow due to the inclusion of CdS at a specific content within a preferred use range. In addition, although the afterglow time increases as the content increases, the emission luminance decreases. Furthermore, if the type of material contained changes, the afterglow time, emission brightness, and emission color also change. Therefore, the content of these first co-activators to be used is selected according to the afterglow time, the emission brightness, and the emission color required for the phosphor, and the content of the first co-activator depends on the sulfide of the base material. for,
Usually, it is determined to be 1 × 10 ^{−5 to} 5 × 10 ⁻² % by weight. Further, Cl, which is the second co-activator, changes the emission brightness and emission color depending on the type and content of the material, and the emission brightness decreases if the content is too large or too small from the optimum value. . Therefore, the optimum value of these materials is determined from the required emission brightness and emission color. Cl is based on maternal sulfide
Usually 5 × 10 ^-5 to 1 × 10 ^-1 % by weight, preferably 5 × 10 ^-4 to
It is contained in an amount of 5 × 10 ^-2 % by weight. Furthermore, in the afterglow phosphor of the present invention, a boron compound is added as a flux to improve the burning property. The boron _{compound, H 3 BO 3, BCl 3} , BF 3 and the like can be used. When orthoboric acid is used as the flux, the addition amount is appropriately 5 × 10 ^{−4 to} 5 × 10 ⁻² % by weight based on the base material.

【Example】

The phosphor of the present invention is manufactured by the method described below. As a phosphor material, (a) as a host material, both ZnS and CdS, (b) as an activator, Ag, and (c) when using the first co-activator, Ga chloride is used. . (D) The ammonium salt and sodium salt of Cl are used as the second coactivator. Further, H ₃ BO ₃ , BCl ₃ , BF _3, etc. are added as a flux. The amount of orthoboric acid added is 5 × 10 ^{−4 to} 5 × 10 5 relative to the mother body.
^-2 % by weight. The phosphor of the present invention is prepared by kneading the above-mentioned raw materials in an optimum amount, drying the mixture, and filling the obtained phosphor raw material mixture in a heat-resistant container such as a quartz crucible or a quartz tube for firing. Firing is a hydrogen sulfide atmosphere,
Perform in a sulfur atmosphere such as a sulfur vapor atmosphere or a carbon disulfide 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., but 1 to 8 hours is suitable. After firing, the obtained fired product is thoroughly washed with water, dried and sieved to obtain the phosphor of the present invention. Example 1. Zinc sulfide ZnS 900g Cadmium sulfide CdS 100g Silver nitrate AgNO ₃ 0.13g Gallium chloride GaCl ₃ 0.8g Sodium sulfide NaCl 10g Orthoboric acid H ₃ BO ₃ 18g Quartz crucibles were filled with appropriate amounts of sulfur and activated carbon added to the phosphor raw material mixture. After covering the quartz crucible,
It was put in an electric furnace and fired at a temperature of 950 ° C. for 3 hours. After firing, the obtained fired product was thoroughly washed with water, dried and sieved. In this way, a (Zn, Cd) S: Ag, Ga, Cl phosphor was obtained. This phosphor is 8 × 1 with respect to the matrix (Zn, Cd) S
0 ^-3 wt% silver, 1.6 x 10 ^-2 wt% gallium, 5 x 10 ^-3
It contained% by weight chlorine. As shown in Table 1, the above phosphors emit blue light with high color purity of x = 0.147, y = 0.067 in the x and y values of CIE chromaticity display, and the long-lasting light emission of the conventional phosphors. The emission brightness is extremely high at 63.5% compared to the relative emission brightness (30.5%) of the photoluminescent blue-emitting phosphor (ZnS: Ag, Ga, Cl), and the 10% afterglow time after stopping electron beam excitation is 56 It showed an excellent value of milliseconds. In Table 1, the conventional short afterglow blue-emitting phosphor (ZnS:
Ag, Cl) was produced on a trial basis under the same conditions as in Example 1 except that CdS and GaCl ₃ were removed from the raw materials of Example 1. In addition, conventional long afterglow blue-emitting phosphor (ZnS: Ag, Ga, Cl)
Used a phosphor of 1 × 10 ⁻² wt% Ag, 1.1 × 10 ⁻² wt% Ga, and 1 × 10 ⁻⁴ wt% Cl having favorable characteristics as a conventional product with respect to the matrix. In this manufacturing process, the relative emission luminance and the afterglow time of the phosphor were measured by adjusting the amount of GaCl ₃ that is the raw material of the first coactivator in the manufacturing process. The results are shown in FIGS. 1 and 2. As is apparent from FIG. 1, the emission brightness decreases as the Ga content increases, but the afterglow time is
More than 20 milliseconds in the range of 2.5 × 10 ^{-4 to} 1.4 × 10 ^-1 % by weight,
It was 40 milliseconds or more in the range of 2.2 × 10 ⁻³ to 8 × 10 ⁻² wt%. By the way, in FIG. 1 and FIG. 2, the relative emission luminance with respect to the content of the first coactivator is shown with the phosphor containing no first coactivator as 100%. The second co-activator is the same as the Cl used in the above examples.
Not only Br but also I, F, Al, etc. can be used. Cl, Br, I,
Similar to the first coactivator, F and Al can be used not only alone but also in a plurality of kinds in the matrix. When plural kinds of the first and second co-activators are contained together in the matrix, the content with respect to the matrix ZnS is adjusted by the total amount of the total content of the first and second co-activators. It

【The invention's effect】

It is described in Table 1 that the phosphor of the present invention has excellent emission brightness, afterglow time, and preferable emission color, as compared with the conventional long afterglow blue light emitting phosphor. That is, the long afterglow blue-emitting phosphor of the present invention has a relative emission brightness of about 2 times and about 3 times that of the conventional long afterglow blue-emitting phosphor (ZnS: Ag, Ga, Cl, etc.). It had an extremely excellent characteristic of having an afterglow time. 3 to 5 show afterglow characteristics, burning characteristics, and current characteristics of the phosphor of the present invention prototyped in Example 1. Third
In FIG. 4, FIG. 5 and FIG. 5, the curve a shows the characteristics of the ZnS: Ag, Cl phosphor shown in Table 1 as the conventional short afterglow blue light-emitting phosphor (a), and the curve b shows the characteristics. Table 1 shows the characteristics of the ZnS: Ag, Ga, Cl phosphor represented by the conventional long-afterglow blue-emitting phosphor (b), and the curve c shows the phosphor of the present invention (Zn manufactured in Example 1 as a prototype. , Cd) S: Ag, Ga, Cl shows the characteristics of the phosphor. The burning characteristics shown in FIG. 4 were measured under the following conditions.
Pyrex glass is coated with a measuring phosphor by precipitation, acrylic lacquer filming and metal back are applied, and a phosphor brightness measuring device is used to measure a current density of 20 μA / cm ² at a voltage of 27 kV.
The phosphor coating film was scanned with the electron beam of No. 2 for a specific time to obtain a phosphor coating film that was forcibly deteriorated. The phosphor coating film that was not scanned with an electron beam was stimulated with an electron beam with a voltage of 27 kV and a current density of 0.5 μA / cm ² , and the emission brightness at this time was set to 100%, and it was forcibly deteriorated at the same voltage and current density. The emission brightness of the phosphor coating film was measured, and the relative emission brightness was expressed as a percentage. This was made into the burning characteristic of specific time. The current characteristics shown in FIG. 5 were measured under the following conditions. When the current density is 0.05 μA / cm ² , the emission brightness is 100%,
Assuming an ideal phosphor, the emission brightness will be 10 times and 100 times as it is when the current density is 10 times and 100 times,
The ideal phosphor has an emission brightness of 10 at each current density.
The relative emission brightness when 0% is defined as the current characteristic,
It was measured. As is clear from the afterglow characteristics of FIG. 3, the phosphor of the present invention has excellent emission brightness as compared with the conventional long afterglow phosphor,
It is clear that afterglow characteristics are exhibited, and from FIG.
It is also clear that it has excellent burning properties. In actual use, phosphors with low emission brightness
It is used by increasing the current density to raise the emission brightness. The phosphor of the present invention having a high emission brightness can be used at a lower current density to obtain a desired brightness of a display tube as compared with a conventional afterglow phosphor having a low emission brightness. This is synergistic,
The burning properties of the phosphors of the present invention are superior to conventional phosphors. FIG. 5 shows the characteristic of the current characteristic, and the curve b is the characteristic of the conventional afterglow blue light emitting phosphor. From this, it is clear that the phosphor of the present invention has excellent current characteristics as compared with the conventional long afterglow blue light emitting phosphor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 are graphs showing relative emission brightness and afterglow time of the phosphor of the present invention with respect to gallium amount, and FIG. 3 is a graph of emission brightness with respect to afterglow time of the phosphor. FIG. 4 is a graph of the burning characteristic in which the relative emission brightness is reduced with respect to the electron excitation time, and FIG. 5 is a graph of the relative emission brightness with respect to the current density.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Keisho Yamashita 491-1, Oka, Kaminaka-cho, Anan City, Tokushima Prefecture Nichia Kagaku Kogyo Co., Ltd. Within Nichia Kagaku Kogyo Co., Ltd. (72) Inventor Akio Fujii 491-1 Oka, Kaminaka-cho, Anan City, Tokushima Prefecture Within Nichia Kagaku Kogyo Co., Ltd. (56) Reference JP-A-59-203350 (JP, A) Kaisho 59-202284 (JP, A)

Claims (5)

[Claims] 1. A (Zn, Cd) S (zinc cadmium sulfide) base material, Ag (silver) activator, and a first co-activator is Ga
(Gallium), the second coactivator is Cl (chlorine), and a boron compound is added as a flux at the time of firing. 2. The afterglow phosphor according to claim 1, wherein the content of cadmium sulfide is 0.1 to 20% by weight based on the sulfide matrix. 3. The afterglow fluorescence according to claim 1, wherein the content of silver in the activator is 1 × 10 ^-5 to 1 × 10 ^-1 % by weight based on the sulfide matrix. body. 4. The balance according to claim 1, wherein the content of the first coactivator is 1 × 10 ^{−5 to} 5 × 10 ⁻² % by weight based on the sulfide matrix. Photoluminescent phosphor. 5. The content of Cl, which is the second co-activator, is 5 × 10 ⁻⁵ to 1 × 10 ⁻¹ wt% with respect to the sulfide base material. The afterglow fluorescent substance described.