JPH0830185B2 - Slow electron beam excited phosphor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a color phosphor capable of obtaining various luminescent colors from blue to red excited by a slow electron beam, and particularly to a part of a luminescent composition. Sulfide phosphor is mixed, but scatter of sulfide-containing gas is extremely small during light emission,
The present invention relates to a low-speed electron beam excited phosphor that can be used in a light emitting device such as a fluorescent display tube or various light sources to which the principle of the fluorescent display tube is applied.

[Prior Art and its Problems] Generally, electron-beam-excited phosphors used in light-emitting devices include phosphors for high-speed electron beams for cathode ray tubes that are excited by high-speed electron beams with an accelerating voltage of about several tens of kV. It is divided into low-speed electron beam phosphors for fluorescent display tubes that are excited by electron beams having a low acceleration voltage of about 10V.

Currently, phosphors used in fluorescent display tubes are slow electron beam excitation phosphors (hereinafter simply referred to as phosphors), and their emission colors can be obtained from blue on the short wavelength side to red on the long wave side. It is designed to be used. However, the green emission
In addition to ZnO: Zn, sulfide phosphors containing S component in the composition formula are often used. Examples of sulfide-based phosphors include:
ZnS: [Zn] (blue), ZnS: Mn (orange), ZnS: Ag (blue),
ZnS: Au, Al (orange), ZnS: Ag, Al (blue), ZnS: Cu, A
l (green), (Zn, Cd) S: Ag, Cl (lemon), (Zn _0.9 Cd
_0.1 ) S: Au, Al (yellow), (Zn _0.8 Cd _0.2 ) S: Au, Al (orange), Y ₂ O ₂ S: Eu (red), etc., but all have high resistance and are slow electron beams as they are. It was not possible to use it for business. Therefore, conventionally, In ₂ O ₃ or ZnO or Sn is added to the sulfide phosphor.
It is used by mixing 10 to 20 wt% of a conductive material such as O ₂ .
However, since the conductive material is not a light emitting substance, it blocks the light emission of the light emitting body, resulting in a problem that the light emitting efficiency is not good.

Further, when the sulfided phosphor mixed with the conductive material is made to emit light, the initial luminance is lower than that of ZnO: Zn phosphor, but higher than that of a sulfide-based phosphor, which is practically in a range that is acceptable. . However, when it is lit for a long time, there is a problem that the capability of the filament-shaped cathode which is the electron emission source, that is, the pulse emission characteristic is deteriorated and the brightness is lowered. The light emission mechanism of the fluorescent display tube can be considered as a cause of this decrease in brightness. In the light emitting mechanism, an electron beam having thermal energy is emitted from the filament cathode, is accelerated by being attracted to the control electrode and the anode, and is accelerated to impinge on the phosphor layer of the anode to excite the phosphor by the energy of the electron beam. It makes them emit light. However, when the electrons are accelerated and impinge on the phosphor in this way, part of the energy of the electron beam decomposes the phosphor, and the sulfur component, which is the component of the sulfide phosphor, is converted into S, SO, SO ₂ , Scatter in the form of sulfides such as H ₂ S. It is considered that when the sulfide-based scattered material adheres to the filamentary cathode, it reacts with the oxide of the alkaline earth metal on the surface and poisons the surface (poison), which deteriorates the pulse emission characteristics.

Further, it is known that this development further deteriorates the emission characteristics when the density of the electron beam exciting the sulfide phosphor is high. Therefore, as a measure against this emission deterioration, a non-sulfide type phosphor has been developed, but a phosphor capable of satisfying all of the emission color, the emission effect, the life characteristics, etc. has not yet appeared.

As another measure, it is conceivable to increase the luminous efficiency of the phosphor itself so that light may be emitted even if the density of the electron beam irradiated is low. That is, the sulfide phosphor may be bombarded with an electron beam having a low density to reduce the energy of the electron beam and prevent the phosphor from being decomposed.

However, the current sulfide-based phosphor is mixed with a large amount of 10 to 20 wt% of a conductive material that does not contribute to light emission, so that a part of the electron beam flows through the conductive material to the anode conductor. That is, since a part of the electron beam flows as an ineffective current, the light emission efficiency is poor, and when the electron beam density is reduced, the number of electrons that excite the phosphor is reduced and the brightness is lowered, which is not preferable.

[Object of the Invention] In order to solve the above-mentioned problems, the present invention is to excite a sulfide phosphor with ultraviolet light to emit light, and in the case of ultraviolet excitation, light directly excites an emission center. Focusing on making the phosphor emit light without decomposing it, by mixing a phosphor that emits ultraviolet rays by a low-speed electron beam with a sulfide-based phosphor to reduce the conductive material, it is possible to use sulfide in a fluorescent display tube. An object of the present invention is to provide a novel phosphor that reduces generation of system gas and is excellent in emission characteristics, life, brightness and the like.

[Structure of the Invention] In order to achieve the above-mentioned object, the structure of the phosphor for low-speed electron beams according to the present invention is such that ZnO.Ga ₂ which mainly emits ultraviolet rays when excited by low-speed electron beams or ultraviolet rays having an anode voltage of 100 V or less. An O ₃ : Cd UV-emitting phosphor and a sulfide phosphor obtained by adding 3% or less of a conductive substance to a phosphor that emits visible light when excited by the low-speed electron beam and the ultraviolet light and scatters sulfide. It is characterized by being mixed.

[Operation] In general, when a phosphor absorbs energy from the outside to excite the phosphor itself and releases the absorbed energy to become stable, a part of the emitted energy is generated as light. The absorption energy is called excitation energy, and the excitation energy has various energy forms such as light, electron beam, X-ray, and heat, but in the case of light, its wavelength is generally known to be on the short-wave side of the emission wavelength. Has been. Therefore, it is possible to excite the phosphor by the ultraviolet rays on the short-wave side of visible light.

The ZnO.Ga ₂ O ₃ : Cd phosphor, which is an ultraviolet-emitting phosphor that is one component of the phosphor of the present invention, has a peak at 365 nm as shown in the emission spectrum of FIG. 1 and has a spectrum in the ultraviolet region. It emits ultraviolet light when excited by a low-speed electron beam and also emits visible light. The ultraviolet rays have a function of exciting the visible light emitting phosphor, which is another mixed component of the present invention, to emit light. Further, since the ultraviolet ray emitting phosphor has conductivity, it has an action of lowering the resistance of the phosphor layer by mixing with the sulfide phosphor.

Therefore, in the phosphor of the present invention, ultraviolet rays are emitted from the ultraviolet-emitting phosphor by the excitation of the low-speed electron beam, and some of the low-speed electron beams are low due to ZnO.Ga ₂ O ₃ : Cd and a small amount of a conductive substance. Visible light is emitted by irradiating the resistant visible light emitting phosphor. The ultraviolet light emitted from the ultraviolet phosphor further excites the visible light emitting phosphor to generate visible light, which has the effect of emitting visible light.

Therefore, since the luminous efficiency is high, it is possible to emit the light of the target brightness from the electron beam of low energy, and a part of the low-speed electron beam is irradiated to the ultraviolet-emitting phosphor and the conductive substance to emit the sulfide fluorescence. Since the amount of irradiation on the body is reduced, the action of decomposing the phosphor is reduced.

[Example 1] The phosphor of the present invention is a light-emitting composition obtained by mixing an ultraviolet-emitting phosphor and a visible light-emitting phosphor, and an experiment described below for determining the mixing ratio of both phosphors. I went.

First, ZnO.Ga ₂ O ₃ : Cd phosphor was selected as the UV emitting phosphor.

Next, since sulfide-based phosphors as visible light emitting phosphors generally have high resistance, the resistance as a phosphor coating film is lowered, and conductive materials such as In ₂ O ₃ are used for the purpose of preventing charge-up of electrons. It is an example using a phosphor in which a small amount of substances are mixed.

A ZnO.Ga ₂ O ₃ : Cd phosphor was used as the ultraviolet light emitting phosphor. The ZnO.Ga ₂ O ₃ : Cd phosphor manufacturing method is a ZnO.Ga ₂ O ₃ : Cd phosphor with a Cd doping amount of 0.1 mol.
Weigh 1g, CdCO ₃ 0.17g and Ga ₂ O ₃ 1.87g, mix well with a ball mill, mixer, mortar, etc., put the mixture in a heat-resistant container such as an alumina boat, and in an air atmosphere at 1300 ° C for 5
It was obtained by firing for an hour. A well-known ZnS: Cu, Al sulfide phosphor was mixed with 2 wt% of In ₂ O ₃ as a conductive material.

The mixture of both is ZnO: Ga ₂ O ₃ : Cd phosphor 25wt%, ZnS: C
u, Al + In ₂ O ₃ (2 wt%) phosphor was mixed at a ratio of 75 wt% to synthesize phosphor A. For comparison, as a conventional example, a conventional phosphor B in which ZnS: Cu, Al was added as much as 20 wt% of In ₂ O ₃ without mixing the ultraviolet-emitting phosphor was synthesized.

The phosphor A synthesized in this example is mounted on a fluorescent display tube,
A voltage was applied to the anode electrode to cause it to emit light, and the emission color was measured. FIG. 2 shows an emission spectrum diagram of the phosphors synthesized in each example of the present invention. The curve indicated by a in the figure is a spectrum diagram of the phosphor A of this example, and green light emission having a peak near 540 nm was obtained.

Next, in order to compare with the phosphor A of the present example to examine the emission brightness, the conventional phosphor B, ZnS: Cu, Al + In ₂ O ₃ (20 wt%)
The mixed one is mounted on a fluorescent display tube, and the anode voltage is 0 to
The luminescence brightness when applying up to 50 V was measured. FIG. 3 is a graph showing the anode voltage and the emission luminance, the solid line is the phosphor A of this embodiment, and the dotted line is the conventional sulfide phosphor containing a conductive substance. In both cases, the emission threshold voltage was 5 to 6V. However, when the anode voltage was raised to 30 V, the conventional ZnS: Cu, Al + In ₂ O ₃ (20 wt%) was 500 ft-L, whereas the phosphor A of the present invention was 750 ft-L. The brightness of the phosphor of the present invention was superior even at other voltages.

Further, FIG. 6 shows the relationship between the lighting time and the residual brightness ratio, in which the above-mentioned phosphor was made to emit light at the same initial brightness and a continuous lighting life test was conducted under the conditions. As can be seen from this figure, the residual brightness rate after lighting for 5000 hours was as low as 95% for the phosphor A of the present invention and 55% for the conventional phosphor B. This difference is due to the difference in the anode current caused by the difference in the electron emission capability of the filament cathode. That is, the conventional phosphor B can obtain a brightness of 750 ft-L at an anode voltage of 42 V, whereas the phosphor of the present invention has an anode voltage of 30 V.
A brightness of 750ft-L can be obtained at V. Therefore, the required brightness can be obtained even if the amount of energy is small, and the phosphor is efficient. Therefore, the rate at which the electron beam energy decomposes the phosphor is smaller in the present invention, less sulfide is scattered, and the probability of poisoning the filamentary cathode is also reduced. Therefore, it is shown that the rate at which the electron emission capability (emission characteristic) of the filamentary cathode is lowered is smaller than that of the conventional phosphor.

[Example 2] This example, as a phosphor UV-emitting phosphor which is a component of the present invention, in the same manner as in Example 1 ZnO · Ga ₂ O _3: Cd phosphor and 30 wt% of the visible light emitting As an example of a sulfide phosphor as a phosphor, 70% by weight of a phosphor obtained by mixing ZnS: [Zn] with 3 wt% of In ₂ O ₃ was mixed to synthesize phosphor C.

The ZnO.Ga ₂ O ₃ : Cd phosphor is the same as in Example 1, and therefore its explanation is omitted. As the sulfided phosphor ZnS: [Zn], a commercially available known phosphor in which 3 wt% of In ₂ O ₃ particles were mixed with the phosphor was used.

The phosphor C synthesized in this example was mounted on a fluorescent display tube to emit light, and the emission color was measured. The curve indicated by c in FIG. 2 is a spectrum diagram of phosphor C, and blue light emission having a peak near 450 nm was obtained.

Next, in order to examine the emission brightness, ZnS: [Zn] of In ₂ O ₃ of 20 wt% was used as a conventional phosphor D for comparison with the phosphor C of this example.
% Mixture is mounted on a fluorescent display and the anode voltage is set to 0.
The luminescence brightness was measured when a voltage of up to 70 V was applied. FIG. 4 is a graph showing the anode voltage and the emission luminance, the solid line shows the phosphor C of the present invention, and the dotted line shows that of the conventional phosphor D.
ZnS: [Zn] + In ₂ O ₃ (20 wt%).

The threshold voltage is 10V or less, but the phosphor of the present invention has higher brightness when the anode voltage is higher,
At 40 V, the phosphor C of the present invention was at 220 ft-L position, whereas the conventional phosphor D was at 150 ft-L position, which was lower than that of the phosphor of the present invention. Next, the aforementioned phosphor C of the present invention and the conventional phosphor D
FIG. 7 shows the relationship between the lighting time and the residual brightness rate, in which the LED was made to emit light at the same initial brightness, and a continuous lighting life test was performed under the light emitting conditions. As can be seen from this figure, the residual ratio of the luminance after 5000 hours was as high as 92% for the phosphor C of the present invention, and as low as 50% for the conventional phosphor D. .

From this result, as in Example 1, the phosphor of the present invention was
Since the brightness can be increased at a low voltage, the rate of decomposing the phosphor is small, and therefore the scattering of sulfide-based gas is also small,
This shows that the deterioration of the fimento-shaped cathode is small, which proves that the reliability is improved when the phosphor of the present invention is used.

Example 3 In this example, 10 wt% ZnO.Ga ₂ O ₃ : Cd phosphor similar to the previous example was used as an ultraviolet light emitting phosphor, and a sulfide phosphor as a visible light emitting phosphor (Zn _0.2 Cd _0.8 ) S: Ag, Cl In ₂ O ₃
The phosphor E of this example was synthesized by mixing 90 wt% of the mixture containing 1 wt% of

For comparison, a conventional phosphor (Zn _0.2 Cd _0.8 ) S:
Phosphor F was prepared by mixing 10% by weight of In ₂ O ₃ with AgCl.

Next, the phosphor E of the present invention, namely ZnO.Ga ₂ O ₃ : Cd + (Zn
_When the emission spectrum of _0.2 Cd _0.8 ) S: Ag, Cl was examined, red emission having a peak near 660 nm was obtained as shown in FIG.

Next, the phosphor E of the present invention and the conventional phosphor F were mounted on a fluorescent display tube, respectively, and an anode voltage of 0 to 60 V was applied to emit light. FIG. 5 is a graph showing the measured luminance for each anode voltage.

Similar to Examples 1 and 2, the phosphor E of the present invention has higher luminance than the conventional phosphor F, and the phosphor E of the present invention is 275 ft-L at an anode voltage of 40 V. Conventional phosphor F
Was a low value of 175 ft-L.

Furthermore, when the above-mentioned phosphors E and F were mounted and a continuous lighting life test was conducted at the same initial brightness, the residual rate of the brightness after 5000 hours was 98% for the phosphor E of the present invention as shown in FIG.
%, The conventional phosphor F had a low value of 60%.

These results also show that the phosphor of the present invention causes less scattering of the sulfide-based gas when the phosphor emits light and less deteriorates the filament cathode.

[Effects of the Invention] The slow-electron-beam-excited phosphor of the present invention is an ultraviolet-emitting phosphor that emits ultraviolet light when excited by an electron beam, and a phosphor that emits visible light and scatters sulfides when excited by an electron beam. Since it is a phosphor mixed with a sulfide phosphor to which a conductive material is added, it has the following effects when it is mounted on a fluorescent display tube to emit light.

(1) The ultraviolet ray-emitting phosphor, which is a component of the phosphor of the present invention, has conductivity and therefore has a high resistance. For example, even a sulfide-based phosphor is obtained by adding a small amount of a conductive substance. However, the resistance can be lowered and the required brightness can be obtained even with an anode voltage of 100 V or less as a phosphor for low-speed electron beams.

(2) The ultraviolet ray emitting phosphor emits ultraviolet rays by excitation of an electron beam, and the ultraviolet rays impinge on and excite the sulfide fluorescent substance to emit light. Therefore, the sulfided phosphor emits light in the phase of excitation by electron beam and excitation by ultraviolet ray, and thus has excellent emission efficiency.

(3) The sulfide phosphor can obtain the required brightness even if the amount of energy of the electron beam is small, so that the rate of decomposing the sulfide phosphor is small, so that the scattering of the sulfide-based gas is small. Become. Therefore, poisoning of the filamentary cathode is almost eliminated, and a phosphor having high brightness and long life can be provided.

(4) When the ultraviolet light emitting phosphor is a phosphor represented by the composition formula ZnO.Ga ₂ O ₃ : Cd, it emits blue visible light as well as ultraviolet light, and therefore the visible light emitting phosphor emits blue light. In this case, the luminous efficiency is particularly excellent, and the color purity of the emission color of blue is also excellent.

[Brief description of drawings]

FIG. 1 is an emission spectrum diagram of a ZnO.Ga ₂ O ₃ : Cd phosphor which is an example of an ultraviolet light emitting phosphor which is one component of the phosphor of the present invention, and FIG. 2 was obtained in each example. Spectral distribution diagrams of phosphors A, C and E of the present invention, FIGS. 3 to 5 are graphs showing the relationship between the anode voltage and the brightness of the phosphor of the present invention and conventional phosphors, and FIGS. FIG. 8 is a diagram showing the relationship between the continuous lighting time and the residual brightness rate of the phosphor of the present invention and the conventional phosphor.

Claims (2)

[Claims] 1. A ZnO.Ga ₂ O ₃ : Cd phosphor that mainly emits ultraviolet rays when excited with a low-speed electron beam having an anode voltage of 100 V or less, and emits visible light when excited by the low-speed electron beam and the ultraviolet rays. A low-electron-beam-excited phosphor obtained by mixing a sulfide-scattering phosphor with a sulfide phosphor containing 3% or less of a conductive substance. 2. The phosphor according to claim 1, wherein the ultraviolet emitting phosphor is mixed in an amount of 10 to 30 wt% with respect to the sulfide phosphor.