JPH0260707B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a new phosphor that is excited by electron beams or ultraviolet rays and has an emission spectrum in both the ultraviolet region and the visible region. The present invention relates to a long-life oxide-based electron beam-excited phosphor that has excellent emission characteristics as a phosphor for display tubes, and a phosphor that can be used in ultraviolet generating equipment. [Prior art and problems] Conventionally, electron beam excited phosphors include cathode ray tube phosphors that emit light at accelerating voltages of several tens of kilovolts, and
There was a phosphor for fluorescent display tubes that emitted light at a low acceleration voltage. ZnS:Ag, Al phosphor and ZnS:Ag phosphor are known as blue-emitting phosphors for cathode ray tubes. When using the above phosphor for a fluorescent display tube, it is generally known that a conductive substance such as In ₂ O ₃ or SnO ₂ is mixed into the phosphor to lower the resistance. Since all of the phosphors contain a sulfur S component, the phosphors are collectively referred to as sulfide phosphors. This sulfide phosphor is often used as a color phosphor in fluorescent display tubes. When this sulfide phosphor is applied to the anode conductor of a fluorescent display tube and the electrons emitted from the cathode are made to collide with it to emit light, the electrons with high energy collide with the phosphor layer. When the phosphor is partially decomposed, sulfide-based gases such as S, SO, and SO ₂ are scattered. When this sulfide-based gas adheres to the filament-shaped cathode, it reacts with the alkaline earth metal oxide layer that is the electron-emitting layer deposited on the surface of the filament-shaped cathode, poisoning the surface of the filament-shaped cathode and damaging the cathode. It has problems such as deteriorating the emission characteristics, shortening the life of the cathode, and lowering the brightness of the fluorescent display tube. Therefore, color phosphors other than sulfide phosphors have become required. One of the color phosphors other than sulfide phosphors was a gallate-based complex oxide phosphor.
-31236. The compositional formula of this phosphor is
A(Zn _1-x , Mgx)O・Ga ₂ O ₃ (However, 0.6≦A≦1.2
and O≦x≦0.5. ). Luminous color x
=O, the color is blue, and by making x larger than O, the color shifts to the longer wavelength side and becomes closer to green, but the emission threshold voltage becomes higher. Further, the A(Zn _1-x , Mgx)O.Ga ₂ O ₃ phosphor had low luminance and had room for improvement. For example, in a ZnO.Ga ₂ O ₃ phosphor in which A=1 and x=O, when an anode voltage of 80 V and a cathode voltage of 0.6 V were applied, the luminance was about 4 ft-L. Also,
If we use (Zn _0.7 , Mg _0.3 ) O.Ga ₂ O ₃ phosphor mixed with MgO so that A = 1 and x = 0.3, the emission wavelength will shift to the longer wavelength side, and even if the brightness increases somewhat, the driving conditions will remain the same. When the same anode voltage was applied to 80 V and cathode voltage was applied to 0.6 V, the voltage was 8 ft-L, which was still too low for practical use and had the problem that it could not be used for fluorescent display tubes. [Object of the invention] The present invention utilizes the above-mentioned known phosphors (Zn _1-x ,
Focusing on a phosphor of ZnO/Ga ₂ O ₃ where x=O (Mgx) O/Ga ₂ O ₃ , by doping this phosphor with Cd, it was possible to emit blue light when excited by a slow electron beam. The object of the present invention is to provide a gallate-based complex oxide phosphor that not only has high luminance and can be used for fluorescent display tubes, but also emits ultraviolet rays and can be used as an ultraviolet radiation source. . [Structure of the Invention] In order to achieve the above-mentioned object, the phosphor of the present invention is characterized in that the general formula is represented by ZnO.Ga ₂ O ₃ :Cd. In addition, 1 mol of the base Ga ₂ O ₃
It is preferable that 0.5 to 4.0 mol of ZnO is dissolved in the solid solution, and the amount of Cd doped is 5 × 10 ^-4 to 3 ×
Preferably it is 10 ^-1 mol. [Function] The ZnO.Ga ₂ O ₃ :Cd phosphor of the present invention emits ultraviolet light having a peak around 365 nm and a spectrum in the ultraviolet region when excited by an electron beam, and a part of the spectrum is Since it extends into the visible range, it also has the effect of emitting light in the blue visible range. Further, since the phosphor has conductivity and low resistance, it has the effect of emitting light when excited by a slow electron beam. Furthermore, since the phosphor does not contain a sulfur S component, even if this phosphor is used in a fluorescent display tube, it does not have the effect of scattering sulfide gases. Furthermore, the phosphor has the effect of emitting light when excited by electron beams other than low-speed electron beams and also by ultraviolet rays. Example 1 To synthesize the ZnO・Ga ₂ O ₃ :Cd phosphor of the present invention, the ratio of ZnO to 1 mol of Ga ₂ O ₃ is preferably in the range of 0.5 to 4.0 mol, but in this example,
The case where ZnO is 1 mol will be explained. Specifically, gallium oxide Ga ₂ O ₃ was fixed at 1.87 g, ZnO as the Zn component was fixed at 0.81 g, and the Cd component was fixed at 1.87 g.
Phosphors were synthesized by changing CdCO ₃ in various ways. The specific amount of CdCO ₃ is determined by the Cd in the composition formula of the phosphor.
The doping amount was determined as shown in the following table.

[Table] Instead of Ga ₂ O ₃ , compounds such as Ga nitrates, carbonates, sulfates, etc. that can be easily converted into Ga ₂ O ₃ by firing in air may be used. In addition, when converting compounds that easily convert into ZnO and CdO when fired in air using nitrates, carbonates, sulfates, etc. of Zn and Cd instead of ZnO and CdCO ₃ into oxides, They may be mixed as desired. The mixing method involves thoroughly mixing the above-mentioned materials using a ball mill, mixer, mortar, or the like. Place the mixture in a heat-resistant container such as an alumina boat.
The phosphor was synthesized by baking in air at 1300°C for 2 hours. Since the synthesized phosphor is an aggregate of phosphor crystals, a phosphor in a better crystalline state can be obtained by pulverizing the phosphor and then baking it in air at 1000° C. for about 3 hours. Next, each phosphor synthesized under conditions with different doping amounts of Cd as shown in the previous table is made into a paste using an organic binder and applied to the anode conductor on the glass substrate using a printing method, controlling it above the phosphor. The electrodes and filament cathode were arranged in a stretched structure, covered with a container section consisting of a side plate and a front plate, and the inside was evacuated to a vacuum state to form a fluorescent display tube. By changing the amount of Cd doping as shown in the previous table,
A fluorescent display tube equipped with seven types of phosphors ranging from 0.0005mol to 0.5mol and a fluorescent display tube equipped with a conventional ZnO・Ga ₂ O ₃ phosphor prepared for comparison were simultaneously made to emit light, and the brightness was measured. Characteristics were measured. Figure 1 shows the luminance of these various phosphors when applied to a fluorescent display tube, with the cathode voltage fixed at 1.7V, the control voltage fixed at 12V, and the anode voltage varied from 0 to 200V. become that way. As can be seen from this graph, from the perspective of luminance, when the amount of Cd doped is 0.0005 mol or less,
The effect of Cd does not appear, and it remains the same as the conventional ZnO・Ga ₂ O ₃ phosphor without the amount of Cd doped. In addition, if the amount of Cd doped is 0.2 mol or more, for example
At 0.5 mol%, it is the same as conventional Cd without doping,
There are some parts where the brightness is lower than that. Therefore, the preferred doping amount of Cd is in the range of 5×10 ⁻⁴ to 3×10 ⁻¹ mol based on the above results. Figure 3 shows a ZnO/Ga ₂ O ₃ :Cd phosphor of the present invention doped with 0.1 mol of Cd and a conventional ZnO/Ga ₂ O ₃ phosphor mounted in a fluorescent display tube for comparison. The light is emitted and the color of the emitted light is shown in an emission spectrum diagram. This spectrum diagram shows that the peak wavelength of the phosphor of the present invention is around 365 nm, and it has a peak in the ultraviolet region, but it also includes wavelengths around 400 nm on the longer wavelength side of the peak value. Therefore, in the visible region, this phosphor is a blue-emitting phosphor. Compared to the conventional ZnO・Ga ₂ O ₃ phosphor, it is shifted to the shorter wavelength side. Furthermore, Fig. 4 shows the CIE chromaticity coordinates, and the above-mentioned
A phosphor doped with 0.1 mol of Cd using ZnO.Ga ₂ O ₃ :Cd is plotted at the chromaticity point of x=0.171, y=0.105, and has a good color purity of 80.0%. Traditional
The ZnO.Ga ₂ O ₃ phosphor has a chromaticity point of x=0.170, y=0.130, and has a color purity of 76.5%. Therefore, it is clear that the ZnO.Ga ₂ O ₃ phosphor of the present invention can be used as a blue-emitting phosphor with good color purity. By the way, in order to obtain the brightness characteristics of the phosphor of the present invention, it was mounted in a fluorescent display tube and the anode voltage was varied from 0 to 200V to obtain the characteristics shown in FIG. However, in general, fluorescent display tubes are often driven with an anode voltage of 100V or less. Therefore, in order to examine whether the phosphor of the present invention can be used as a phosphor for slow electron beam excitation in a fluorescent display tube, we drove it with an anode voltage of 90 V, a cathode voltage of 1.7 V, and a control electrode voltage of 12 V. Made it emit light. As a result, the Cd doping amount
0.1mol had the highest brightness, at 50ft-L. The next phosphor was a phosphor doped with 0.02 mol of Cd and had a brightness of 47 ft-L. Next, the amount of Cd doped is 0.01mol
The luminance was 20 ft-L using phosphors. Since the conventional ZnO.Ga ₂ O ₃ phosphor is used for high-speed electron beams, its brightness was low at 1 ft-L under the same conditions.
As is clear from these results, it can be seen that the phosphor of the present invention is fully usable as a phosphor for low-speed electron beams for fluorescent display tubes. Figure 5 shows the ZnO・Ga ₂ O ₃ :Cd phosphor of the present invention and a conventional sulfide-based phosphor for comparison.
ZnS: Each of the [Zn] phosphors is mounted on a fluorescent display tube with an anode voltage of 90V, a control voltage of 12V, and a cathode voltage of 1.7V.
FIG. 3 is a diagram showing the life characteristics when the light is lit for 5000 hours. The extent to which the brightness decreases when the initial brightness is set to 100 is plotted in terms of brightness retention rate. As can be seen from this figure, the ZnO of the present invention
Since the Ga ₂ O ₃ :Cd phosphor does not contain an S component, it does not poison the filament cathode. Therefore, compared to conventional sulfide-based phosphors, the luminance retention rate is higher even after the lighting time has elapsed, and 5000
Even after time passed, the value remained high at 95%. Traditional
ZnS: [Zn] phosphor has a survival rate of less than 50% after 5000 hours. From this result, the ZnO.Ga ₂ O ₃ :Cd phosphor of the present invention has excellent emission characteristics when used in a fluorescent display tube, and has the effect of providing a long-life fluorescent display tube. Example 2 In the above-mentioned example, the molar ratio of ZnO mixed with 1 mol of Ga ₂ O ₃ was fixed at 1 and the optimum range of the amount of Cd doped was determined.
Let's consider the optimal value of ZnO in ZnO・Ga ₂ O ₃ phosphor. As is clear from FIG. 1, the above-mentioned Example 1
The best brightness specification was obtained when the Cd doping amount was 0.1 mol. Therefore, here, the doping amount of Cd was fixed at 0.1 mol per 1 mol of Ga ₂ O ₃ and each material was weighed so that the value of ZnO was 0.1 to 5 mol to create seven types of phosphors. The weighing values of each material are as shown in the table below.

〔effect〕

As described above, the present invention focuses on ZnO.Ga ₂ O ₃ phosphor, and by doping it with Cd, a novel ZnO.Ga ₂ O ₃ :Cd phosphor can be obtained.
It has the following effects. (1) The ZnO・Ga ₂ O ₃ :Cd phosphor of the present invention is doped with Cd to lower the resistance, so it has a brightness of 50 ft-L even at an anode voltage of 100 V or less, and is a blue phosphor for fluorescent display tubes. It can be used satisfactorily as a color fluorescent display tube, leading to expanded use of color fluorescent display tubes. (2) Since the ZnO・Ga ₂ O ₃ :Cd phosphor of the present invention is an oxide-based phosphor that does not contain sulfide, it does not contain sulfide-based gas even if it is mounted in a fluorescent display tube and emitted light. The scattering phenomenon does not occur, and there is no deterioration of the emission characteristics, which has the effect of providing a long-life and highly reliable phosphor. (3) The ZnO/Ga ₂ O ₃ :Cd phosphor of the present invention emits only safe ultraviolet light of 3650 Å when excited by an electron beam, so it can be used in devices that use ultraviolet light to create safe ultraviolet devices. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between anode voltage and brightness when the Cd content of the ZnO・Ga ₂ O ₃ :Cd phosphor of the present invention is changed, and FIG.
ZnO・Ga ₂ O ₃ : Figure 3 is a graph showing the relationship between the number of moles of ZnO in a Cd phosphor and the relative intensity.
ZnO・Ga ₂ O ₃ : Emission spectrum diagram of Cd phosphor and conventional ZnO・Ga ₂ O ₃ phosphor. Figure 4 shows CIE of the phosphor of the present invention and conventional ZnO・Ga ₂ O ₃ phosphor. Figure 5 shows the chromaticity coordinates of the ZnO Ga ₂ O ₃ :Cd phosphor of the present invention and the conventional sulfide phosphor ZnS: [Zn] phosphor mounted and lit for 5000 hours. It is a graph showing the residual rate of brightness.

Claims (1)

[Claims] 1. A phosphor having the general formula ZnO.Ga ₂ O ₃ :Cd and having an emission spectrum in the ultraviolet and visible regions when excited by electron beams or ultraviolet rays. 2 ZnO is 0.5 for 1 mol of Ga ₂ O ₃ of the above-mentioned base material.
The phosphor according to claim 1, in which the phosphor is dissolved in a solid solution of ~4.0 mol. 3. The phosphor according to claim 1, wherein the doping amount of Cd is 5 x 10 ^-4 to 3 x 10 ^-1 mol.