JPS5943076B2 - red luminescent material - Google Patents

Description

[Detailed description of the invention] The present invention relates to a luminescent material that emits red light.

More specifically, the present invention provides low-speed electron beam excitation, which is produced by mixing an appropriate amount of one or more red-emitting phosphors having a specific particle size distribution and one or more conductive metal oxides. The present invention relates to a red light-emitting composition for use. As is well known, a low-speed electron beam-excited fluorescent display tube (hereinafter abbreviated as "fluorescent display tube") consists of an anode plate having a fluorescent film on one side, and a cathode facing the fluorescent film. It essentially has a structure in which it is sealed in a vacuum container, and the fluorescent film on the anode plate is excited by the low-speed electron beam emitted from the cathode, causing it to emit light.

FIG. 1 is a side sectional view showing a typical example of such a fluorescent display tube, in which 1 is a windshield, 2 is
3a to 3n are glass substrates; 3a to 3n are anode groups formed by coating the glass substrate 2 with a phosphor; 4 are linear cathode filaments disposed opposite to these anode groups 3a to 3n; 5a to 5n;
is a mesh-like control grid group provided between each of the anode groups 3a to 3n and the cathode filament 4.

The transparent windshield 1 and the glass substrate 2 are sealed,
It forms a vacuum envelope. After the inside of the container is evacuated normally and tip-off is performed, a getter flash is applied inside the container to maintain a high vacuum.

The light emitting layers of the anode groups 3a to 3n are usually formed as follows. That is, the phosphor powder is thoroughly mixed with PVA and an organic solvent to form a paste, which is applied by screen printing, or the phosphor is dispersed in a suitable dispersion medium and applied by electrodeposition, and then air is applied. Bake at medium 500℃ for 30 minutes. In recent years, many phosphors using transition metal ions, rare earth element ions, etc. as activators have been developed.

It has long been known that when these metal ions in various solids or liquids are irradiated with electron beams, ultraviolet rays, near-infrared light, etc., they exhibit bright line-like emission spectra that are unique to each metal ion. In particular, it has attracted attention and research as a laser material. Among these studies, for example, YAG:Nd
While lasers were put into practical use, it was also discovered that cerium, europium, erbium, etc. can emit light with high efficiency when contained in various matrix materials, and since then, phosphors using rare earth element ions as activators have become popular. was studied. As a result, many products have been put into practical use, and among these, yttrium oxide activated with europium, yttrium oxysulfide, and yttrium vanadate are particularly important, and are used as red components in color televisions, high-pressure mercury lamps, etc. These phosphors emit light with high brightness when excited by high-speed electron beams of several kilovolts or more, ultraviolet rays, or the like. However, these phosphors hardly emit light under low-speed electron beam excitation of several IOV or less, and therefore cannot be used as phosphors for fluorescent display tubes. As a result, the use of fluorescent display tubes with a fringe color emitted by the self-activated zinc oxide phosphor described above is limited, and in order to expand the use of display tubes, it is necessary to develop luminescent materials that emit bright light other than the fringe color. has been strongly requested. Conventionally, ZnCdS:Ag has been used as a red-emitting phosphor for low-speed electron beam excitation.
It is known that low-resistance materials exhibit high brightness.

However, Cd contained in this phosphor is a causative substance of painful and painful diseases, and for industrial use, a large amount of equipment cost for pollution prevention soil is required. Furthermore, even if pollution control devices are installed, it cannot be said that there will be no impact on workers and surrounding residents, and it is not desirable to use such toxic substances industrially. Therefore, it has been desired to develop a Cd-free phosphor that emits red light as a phosphor for excitation with slow electron beams. Red-emitting phosphors that can replace ZnCdS:Ag include indium oxide (In2O3), eurobium-activated yttrium sulfide phosphor (Y2O2S:Eu), and eurobium-activated yttrium oxide phosphor (Y2O3:Eu).
and at least one of eurobium-activated yttrium vanadate phosphor (YVO4:Eu);
A luminescent composition and zinc oxide (ZnO) mixed in a weight ratio of 9 to 9:1 and a Y2O2S:EU phosphor, Y2
Luminescent compositions are known which are formed by mixing an O3:EU phosphor and at least one of a YVO4:Eu phosphor in a weight ratio of 1:9 to 9:1.

These luminescent compositions have an accelerating voltage of 1 K or less, especially 100
Although it exhibits high-brightness red light emission under slow electron beam excitation of V or less, it is desired to further improve the light-emission brightness from a practical standpoint. Based on these facts, the inventor has determined that LU2O2S:EU
As a result of our efforts to improve the brightness of system materials (where Lu is one or more of Y, Cd, and La) at low acceleration voltages, we found that the voltage at which the brightness begins to increase due to the atomization of LU2O2:EU particles was 20 or less, and at an acceleration voltage of 40 V, the present invention was achieved by obtaining a luminance comparable to ZnCdS:Ag-based materials.

An object of the present invention is to provide a red light-emitting material with improved fluorescence brightness under slow electron beam excitation at an accelerating voltage of IKV or less, particularly 50 or less. LU2O2S:
As already mentioned, the EU phosphor does not emit light at the accelerating voltage (100 V at most) applied in the fluorescent display tube.

LU2O2S: When a conductive material is mixed with EU, it emits light quite brightly even at an acceleration voltage of about 30V. This excitation process can be considered as follows. That is, when irradiated with an electron beam, LU2O2S:EU, which is an insulator, becomes electrically charged and no electrons enter it, so it does not emit light. However, by mixing a conductive material, the conductive powder clings to the LU2O2S:EU and conducts with the anode, thereby increasing the potential of the LU2O2S:EU in the vicinity of the contact with the conductive powder relative to electrons. Therefore, electrons are continuously incident in the vicinity, and light is emitted. The principle of light emission of a conventional mixed phosphor consisting of a red-emitting phosphor and a conductive material is as described above, but the present inventor has discovered that the following phenomenon occurs in a phosphor excited by a slow electron beam. I found it.

That is, if the LU2O2S:EU particle is spherical, the amount of charge at time t(s) after electron irradiation is given by the following equation.

However, TlC'1r~: The amount of charge g(t) increases with time t, and t
= final shift Q at 10τ.

It becomes 91% of O. Final charge amount Q. O is the particle dielectric constant ε
8. It is determined only by the electric field E and the grain size r. What greatly influences the QOO is the particle radius r, and as the radius r decreases, the QOO decreases rapidly. Therefore, the smaller the particle size, the more likely it will be excited even at a low accelerating voltage. Also, since it is necessary to mix conductive powder to absorb the electrostatic charges, LU
2O2S: The smaller the EU particles, the greater the relative area of the area into which the electric field from the conductive powder enters, and the more LU2
The O2S:EU particle surface will be excited by the incident electrons.

Therefore, brightness at low acceleration voltages is improved. For example, Y
FIG. 2 shows the relationship between the particle size and brightness of Y2O2S:EU particles obtained by mixing NO3 conductive powder with 2O2S:EU phosphor powder at an acceleration voltage of 40V. As mentioned above, LU2O
When using a 2S:EU phosphor in a fluorescent display tube excited by a slow electron beam, based on the inventor's findings, the smaller the particle size, the lower the amount of collision charge, and the larger particles are coated with conductive powder. Since a much larger proportion of the LU2O2S:EU particle surface can be excited by slow electrons than in the case of mixing, the brightness in the low acceleration voltage region is improved.

And, the fact that the smaller the LU2O2S:Eu particles are, the higher the brightness can be obtained, which means that in high-speed electron excitation such as T,
This is in contrast to the fact that higher brightness can be obtained if the particles are larger without impairing coating properties, and the reason for this is
This is because the energies of excited electrons are completely different, so the initial process of the excitation process is significantly different between the two. Next, examples of the present invention will be described.

Example 1 99.9999% pure Y2O3 and 99.999% pure
of EU2O3 was dissolved in nitric acid, and an aqueous oxalic acid solution was added to precipitate oxalate.

After washing the precipitate with water and drying it, it was heated in oxygen at 1000°C for 1
After time pyrolysis, Y2O3:EU phosphor powder was obtained. The molar ratio of Y2O3:EU, Na2cO3 and S is 1:1.
Dry mixed 5:4. This mixture was mixed in a N2 atmosphere for 1
The reaction was carried out at 000°C for 5 hours. The reaction product was treated with hydrochloric acid, washed with water, and dried to obtain a Y2O2S:EU phosphor powder having a particle size distribution with a median value of 0.5 μm and a standard deviation value of 0.5 or less. This phosphor powder has a median value of 0.05μ,
In2O3 conductive powder with a standard deviation value of 0.7 at a weight ratio of 15
% mixed. This mixed powder is sufficiently mixed with PVA and an organic solvent to form a paste, and the anode group 3a in FIG.
~3n by screen printing method and heated to 500℃ in air.
Baked in 30 minutes.

When a fluorescent display tube as shown in FIG. 1 is assembled and the voltage of the anodes 3a to 3n is set to 30V, the voltage of the grids 5a to 5n is set to 15V, the voltage of the filament 4 is set to 1.7V, and the fluorescent display tube is driven. , as shown in Figure 2, Y2O2S:
Approximately 100 Ft-L when the particle size of EU is 0.5μ, or approximately 150Ft-L when 0.1μ is created by changing the firing conditions.
brightness was obtained. Example 2 99.999% pure G (I2O3 and 99.99% pure
of EU2O3 was dissolved in nitric acid, and an aqueous oxalic acid solution was added to precipitate oxalate.

After washing the precipitate with water and drying it, it was heated at 10,000C in oxygen.
After pyrolysis for 1 hour, Gd2O3:Eu phosphor powder was obtained.
The molar ratio of Gd2O3:EU, Na2cO3 and S is 1
:1, 5:4. This mixture was reacted at 1000° C. for 5 hours in a N2 atmosphere. After treating the reaction product with hydrochloric acid, washing with water and drying, Gd2O2S:E has a particle size distribution with a median value of 0.5 μm and a standard deviation value of 0.5 or less.
U phosphor powder was obtained. This phosphor powder has a median value of 0.0.
N2O3 conductive powder having a diameter of 5μ and a standard deviation value of 0.7 was mixed at a weight ratio of 15%. This mixed powder was sufficiently mixed with PVA and an organic solvent to form a paste, which was then applied to the anode groups 3a to 3n in Fig. 1 using a screen printing method.
Baked at ℃ for 30 minutes.

After that, assemble the fluorescent display tube as shown in Fig. 1, set the voltage of the anodes 3a to 3n to 30V, set the voltage of the grids 5a to 5n to 15V, and set the voltage of the filament 4 to 1.7V to drive the fluorescent display tube once. As a result, a brightness of about 90 Ft-L was obtained.
In addition, Gd2 with a particle size of 0.1μ was created by changing the formation conditions for one day.
With O2S:Eu, a luminance of about 130 Ft-L was obtained.
Example 3 La2O2S:E was prepared in the same manner as in Examples 1 and 2.
When U was made and emitted light, the particle size of 0.5μ was 70
When the FtL1 particle size was 0.1μ, a brightness of 140Ft-L was obtained.

Example 4 Lu202S:Eu (Lu=Y, Gd, OrLa) fine particles and In2O3 fine particles at a weight mixing ratio of 19:1 to 1
:1 was mixed and placed on the anodes 3a to 3n of a fluorescent display tube as shown in FIG. 1, and emitted light under the same conditions as in Examples 1 to 3. The mixture ratio shown in FIG. 2 was obtained. Values of 70% to 100% of the maximum brightness obtained when the particle size was varied were obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the typical basic structure of a fluorescent display tube, in which 1 is a transparent windshield, 2 is a glass substrate, and 3a to 3
n is an anode group coated with a luminescent material, 4 is a cathode filament, and 5a to 5n are control grid groups. Figure 2 shows the relationship between the Y2O2S:EU particle size and brightness of EU (51n203 conductive powder) in the Y2O2S: mixed phosphor.
The V1 filament voltage is 1.7V.

Claims (1)

[Claims] 1 It has a particle size distribution with a median value of 0.1μ to 2μ and a standard deviation value of 0.7 or less, and the general formula is Lu_2O_2S
: A phosphor contained in a europium-activated rare earth oxysulfide phosphor represented by Eu (where Lu is one or more of Y, Gd, and La) and a conductive substance are combined into one
A red luminescent material mixed at a weight ratio of 9:1 to 1:1.