JPS5935948B2 - fluorescent material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phosphor for excitation with electron beams, and particularly to provide a phosphor for excitation with slow electron beams that emits green light with high purity.

Conventionally, a zinc-activated zinc oxide phosphor (ZnO
) Since this phosphor emits light at a voltage of 5V or more, it is used in fluorescent display tubes that operate with low-speed electron beams.Recently, in home appliances and many systems, it is used for purposes other than numerical display. Fluorescent display tubes are also used for various operation displays such as level display and graphic display, but in order to make various operation displays easier to understand, a luminescent color is used to replace the green-white light emitted by ZnO and Zn, which has poor color purity. It is desired to develop a phosphor for slow electron beam excitation having the following properties.

Zn2S is one of the green-emitting phosphors that can be excited by high-speed electron beams.
This phosphor has iO4:Mn, ZnS:Cu:A
Compared to other green-emitting phosphors such as Y2O2S:Tb, it emits green light with the highest degree of saturation. However, a low-speed electron beam of 100 V or less has low brightness and is not practical. The inventors coated the surface of electrically conductive zinc oxide (ZnO) with a manganese-activated zinc silicate phosphor (Zn2S1O4:Mn), thereby making the coating layer emit highly saturated green light when exposed to slow electron beams. Furthermore, it has been found that by using the phosphor according to the present invention, a fluorescent display tube with extremely high display performance can be formed.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross-sectional view for explaining a phosphor according to the present invention. As shown in the figure, a part or the entire surface of the ZnO particle 1 is coated with a layer 2 of Zn2S1O4:Mn to an appropriate thickness.
ZnO particles for general reagents, ZnO2Zn phosphor, or ZnO particles obtained by firing a zinc compound such as zinc carbonate, zinc hydroxide, or zinc sulfate in air are used. ZnO particles containing impurities that increase electrical conductivity, such as aluminum, potassium, and indium, are also used. Next, Zn2sio4■M covering the surface of ZnO particle 1
Explaining the method for forming the n-layer 2 Generally, Zn2s
io42Mn is made by mixing ZnO, Znco3, etc. and Si04 at a molar ratio of 2:1, and then adding Mn as an activator using MnCO3 at a weight ratio of 0.1 to 1.0.
%, mixed and fired in air at 1200 to 1300°C. In the present invention, Zn2SiO
4: To make the Mn coating layer thinner and strengthen its adhesion,
It was manufactured by the method described below. The manufacturing method can basically be divided into the following two types: (1) The surface part of the ZnO particles, which forms the center of the phosphor according to the present invention, is reacted at high temperature with SiO2 or a silicon compound that becomes SlO2 at high temperature. Zn
2slO4: temperature for forming Mn thin film
2SiO4:Mn thin layer is formed.

In production methods (1) and (2), the activator Mn is
It may be added at the same time during Zn2siO4 synthesis, or it may be added by re-firing after Zn2siO4 synthesis.The amount added is 0.1 to 1.0% by weight with respect to the Zn2slO4 thin layer to be synthesized. do. Specific examples of each manufacturing method will be described below.Example of manufacturing method (1)The surface area was determined from the average particle diameter of the ZnO particles that form the center of the phosphor, and Zn2siO4 of the desired thickness was formed. As described above, SiO2 or a silicon compound that becomes SiO2 at high temperature is attached to the ZnO surface.Si02 can be produced by ultrafine silicic anhydride (manufactured by Nippon Aerosil Co., Ltd.) with an average particle size of 5 to 100 mμ or by a precipitation method. For example, ZnO powder 5 with an average particle size of 4 μm is used.
0.15 g of silicic anhydride is added to each g of the mixture, and wet-mixed using a ball mill or the like.

A silicon compound that becomes SiO2 at high temperatures. For example, water glass can be used. For example, by adding ZnO powder 51 with an average particle size of 4 μm (7) and 20" of 1% water glass to 100" of pure water, gradually adding ammonium carbonate while stirring thoroughly, and filtering the precipitate. SiO2 and . A silicon compound can be attached. After drying these substances, 900 to 130
By firing at 0°C for 1 to 4 hours, the surface of the ZnO particles has an average thickness of 0.1 μm (hereinafter, average thickness refers to ZnO
The thickness is calculated from the surface area of the particles and the amount of SiO2 added. )・Mn, which is an activator capable of forming a Zn22iO4 layer, can be used to activate Zn22iO4 using manganese chloride, manganese nitrate, manganese carbonate, manganese hydroxide, etc.
The weight ratio of Mn to 2siO4 is 0.3% with Zn2s
It is added during the synthesis of the IO4 layer or by re-baking after synthesis.

Example using manufacturing method (2) (Part 1) Determine the surface area from the average particle size of the ZnO particles that form the center of the phosphor, and then sinter at a high temperature so that Zn2siO4 of the desired thickness is formed. A substance from which Zn2siO4 is synthesized is attached to the ZnO surface.

For example, ZnO with an average particle size of 4 μm (7) is added to 100" pure water.
Powder 59 and 20d of 1% water glass were added, and 0.1grm01/l of ZnsO4 aqueous solution was added with sufficient stirring.
0" is gradually added. After filtering and drying the material produced by such an operation, a Zn2siO4 layer with an average thickness of 0.1 μm is formed on the surface of the ZnO particles by baking it in air at 900 to 1300°C for 1 to 4 hours. Mn, which is an activator, is added by the method described in the example by manufacturing method U) above.Example by manufacturing method (2) (Part 2) .2N-H
Add Cl5O'' and collect the liquid after stirring thoroughly.Meanwhile, add 0.2N-(N
H4) Add 50" of 2C03 and gradually add the above filtrate while stirring thoroughly.

After filtering and drying this material, the material was baked in air at 900 to 1300°C for 1 to 4 hours to form a 0.1%
The Zn2SiO4:Mn-coated ZnO synthesized by the method described above, which can form a Zn2SiO4:Mn layer with an average thickness of .mu.m, exhibits high-intensity light emission even at low voltage. In Figure 2,
The average thickness of the formed Zn2SiO4:Mn layer and 50
As can be seen from Figure 3, which shows the relationship between the emission intensity and the electron acceleration voltage of V, and the relationship between the average thickness of the Zn2SiO4:Mn layer and the emission threshold voltage,
The average thickness of the 2SiO4:Mn layer is 0.005-2.0t
tm is appropriate. If it is less than 0.005 μm, the emission intensity will be weak, and if it is larger than 2.0 μm, the threshold voltage for light emission will be high, making it unsuitable as a phosphor for slow electron beam excitation.Next, Fig. 4A, B shows an example of a hot cathode fluorescent display tube using the phosphor according to the present invention.

In the figure, reference numeral 3 denotes a transparent glass container, in which a filament-shaped hot cathode 4 is arranged at the forefront, and a mesh-shaped control grid 5 is arranged behind the cathode 4. At the rear of the control grid 5, a plurality of character segment electrodes 7 whose surfaces are coated with phosphor 6 are insulated from each other and are hermetically passed through an interconnect container 3 disposed on a support substrate 8 to form a plurality of leads. A line 9 is provided and connected to each of the electrodes T in the container 3. Note that here, the phosphor 6
The above Zn2SiO4:Mn coated ZnO phosphor was used.

In the fluorescent display tube described above, a voltage of 3 to 5 V is applied to the cathode 4 to generate heat, and a voltage of 20 V, for example, is applied to the control grid 5.

By selectively applying voltage to the character segment electrodes 7, characters can be displayed. As a result of configuring the phosphor film with the Zn2SiO4:Mn-coated ZnO phosphor as described above, characters are displayed in green with higher color purity than in a fluorescent display tube using a conventional ZnO2Zn phosphor. This makes it possible to display characters clearly even under white ambient light. As described above, the phosphor according to the present invention emits green light with very high purity when irradiated with a slow electron beam, and has great practical value when used in a fluorescent display tube or the like.

Incidentally, light emission has long been observed at relatively low accelerating voltages by mixing Zn2slO4Mn with conductive fine powder, such as carbon, ZnO, or N2O3. Since the specific gravity and particle size of the powders are greatly different from each other, the luminescent properties vary depending on the mixing state and coating method, making it difficult to form display tubes with good reproducibility. Since it is made of structured particles, the phosphor can be easily applied with good reproducibility, and a fluorescent display tube with less variation in characteristics can be formed.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view for explaining one embodiment of the phosphor according to the present invention, and FIG.
Figure 3 is a curve diagram showing the relationship between the emission intensity when irradiated with an electron beam and the average thickness of the Zn2SiO4:Mn layer forming a part of the phosphor.
A curve diagram showing the relationship between the average thickness of the O4:Mn layer, and FIG. 4 shows the structure of an example of a fluorescent display tube using the phosphor according to the present invention, and FIG. A is a partially cutaway perspective view. Figure B is a cross-sectional view. 1... Zinc oxide particles, 2... Manganese activated zinc silicate layer, 4... Hot cathode, 5...
... Control grid, 6... Phosphor, 7...
...Character segment electrode.

Claims (1)

[Claims] 1 At least a part of the surface of zinc oxide (ZnO) is made of manganese-activated zinc silicate phosphor (Zn_2SiO_4:Mn)
A phosphor characterized by being coated with. 2 Zn_2SiO_4: The average thickness of the Mn coating layer is 0.
The phosphor according to claim 1, wherein the phosphor has a particle size in the range of 0.005 to 2.0 μm.