JPS6145347B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial application field The low-speed electron beam phosphor of the present invention is used in fluorescent display tubes. In addition, fluorescent display tubes have high brightness and clarity, and are used as display elements in handheld calculators, clocks, cash registers, audio equipment, home appliances, automobiles, and measuring instruments.
A wide range of colors such as orange and red can be displayed. In addition, it operates at low voltage, consumes little power, and has a fast response speed, so it can be driven directly by an LSI. Furthermore, since display patterns can be produced using thin film technology, precise and free patterns can be displayed. Furthermore, since everything other than the terminals is housed in a vacuum, it has features such as high reliability and long life, so it is used as a display element in various electronic devices as mentioned above. (b) Prior art It is known that phosphors for slow electron beams have appropriate conductivity, as shown on pages 42 to 48 of Electroceramics Vol. 11, published January 1, 1980. It is classified into the following three types depending on the method of imparting conductivity. (a) Low-resistance matrix phosphor A typical example is ZnO:Zn phosphor, which uses a conductive material as the matrix of the phosphor. In addition, SnO ₂ :Eu phosphor and (Zn _1-x Cd _x )
S: There is an Ag phosphor. (b) Mixed phosphor For example, ZnS:Ag+In ₂ O ₃ phosphor, high resistance phosphor, ZnS:Ag, ZnS:Cu, Al,
Y ₂ O ₂ S: A phosphor containing Eu and other conductive substances such as SnO ₂ , In ₂ O ₃ , and ZnO to reduce the overall resistance. (c) Doped phosphors Examples include ZnS:Ag, Zn, and Al phosphors.
This ZnS:Ag phosphor is normally close to an insulator, but this phosphor has impurities such as Zn and Al doped into its crystal to fill the Zn vacancies and give it conductivity. The low-speed electron beam phosphor of the present invention, in which ZnO:Zn is coated with a conductive material, belongs to the (a) low-resistance matrix-type phosphor according to the aforementioned classification. However, it is known that even the ZnO:Zn phosphor layer, which is known as a low-resistance phosphor, has an apparent resistivity of about 1×10 ⁴ Ωcm to 1×10 ⁶ Ωcm. In addition, as a conventional example of a fluorescent display tube using the above-mentioned phosphor for low-speed electron beams,
There is a publication No. 54-133874. This fluorescent display tube has a phosphor coated on an anode having a group of small light-transmitting gaps on a light-transmitting substrate, and the electrons emitted from the cathode placed opposite to the anode collide. In this type, the light emitted from the phosphor is transmitted through the gaps between the anodes and observed through the substrate. FIG. 1 is an enlarged sectional view showing the relationship between the anode conductor and the phosphor layer on the substrate of this conventional example. A plurality of anode conductors 2 made of Al, Ag, etc. are arranged on a glass substrate 1, gaps 3 are formed between the anode conductors, and a ZnO:Zn phosphor layer 4 is deposited on the anode conductors 2 and gaps 3. was used to form the anode substrate. Therefore, electrons emitted from the cathode (not shown) impinge on the surface of the phosphor, and as described above, the electrons are 1×10 ⁴
It flows to the anode conductor through a phosphor having a resistivity of Ωcm to 1×10 ⁶ Ωcm. Further, the anode current flows in the opposite direction to the flow of electrons, but since there is resistance due to the phosphor layer on the way, the potential on the surface of the phosphor layer is lower than the potential on the anode conductor. In other words, a phenomenon called voltage drop occurs. The rate at which the surface potential of the phosphor layer decreases is determined by the distance between the anode conductor and the surface of the phosphor layer. That is, the larger the distance, the greater the voltage drop and the lower the surface potential, resulting in a lower anode current. When this surface potential becomes less than a predetermined value, the luminance of light emission decreases or no light is emitted. Therefore, the luminescence of the phosphor 4 shines best right above the anode conductor 2, and the brightness decreases above the gap 3 away from the anode conductor 2. However, there is a contradiction in that the light emitted from the phosphor 4 directly above the anode conductor 2, which has the highest brightness, cannot be observed through the substrate 1 if the anode conductor 2 is not a transparent electrode. Therefore, in order to emit light uniformly and with excellent brightness, it is better to narrow the gap width, but this creates a contradiction in that the aperture ratio decreases and the amount of light that can be seen through the substrate decreases. That is, on an anode conductor with a conventional gap,
ZnO: Fluorescent display tubes that are coated with Zn phosphor and viewed through the substrate have the above-mentioned problems such that the brightness does not increase, and although the brightness is high near the anode conductor, it is difficult to see through the gap. There was a problem in that near the middle of , the brightness was low, the segments could not emit uniform light, and the display quality was poor. (c) Purpose of the Invention The present invention has been made in view of the above-mentioned circumstances, and has an anode structure with a gap, and even when used in a so-called front-emitting fluorescent display tube in which observation is made through a substrate, the segments are uniform. It is an object of the present invention to provide a fluorescent display tube using a phosphor for low-speed electron beams, which emits light, has excellent display quality, and can increase luminance. (d) Structure of the invention In order to achieve the above object, the structure of the present invention is as follows:
Electrons emitted from the hot cathode are made to strike an anode provided on one surface of a translucent insulating substrate, the upper surface of which is coated with a phosphor layer, to excite the phosphor layer and emit light, thereby making the phosphor layer transparent. In a fluorescent display tube that obtains a display through a substrate, a low-speed electron beam impinges on the anode conductor, which is a conductive thin film and is deposited on the transparent substrate with gaps such as a mesh, comb, or stripe shape. A phosphor for low-speed electron beams, which is coated with 0.01% to 5% by weight of a conductive material based on the ZnO:Zn phosphor, is deposited on the anode conductor and the gap to conduct electricity in the gap. This fluorescent display tube is constructed so that a voltage drop does not occur in the phosphor layer deposited in the gap due to the presence of a large amount of a chemical substance. (E) Description of Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 2 shows an enlarged view of the low-speed electron beam phosphor of the present invention, and 5 is a conventionally known ZnO:Zn
This is the phosphor 5. The ZnO:Zn phosphor 5 having a particle size of about 0.5 to 15 μm can be used, but in this example, one with an average particle size of 7.2 μm was used. A conductive substance 6 is added to and mixed with this ZnO:Zn phosphor 5.
In ₂ O ₃ , In ₂ O ₃ −SnO ₂ (ITO), SnO ₂ , SnO ₂ −
Examples include Sb ₂ O ₅ and TiO ₂ , but in this example,
In ₂ O ₃ was used as the conductive material 6. The average particle size of the In ₂ O ₃ conductive material 6 is 0.3 to 0.4 μm, which is very small compared to the particle size of the ZnO:Zn phosphor 5 and is preferably ultrafine. In ₂ O ₃ conductive material 6 is added to the ZnO:Zn phosphor 5 and stirred for a long time. The amount of the In ₂ O ₃ conductive substance 6 to be added is preferably 0.01% to 5% by weight relative to the ZnO:Zn phosphor 5, as shown in Figure 2.
ZnO: An In ₂ O ₃ conductive material 6 is deposited on the surface of the Zn phosphor 5 . ZnO:Zn with In ₂ O ₃ formed as described above
In order to investigate the effect of the phosphor, a fluorescent display tube was manufactured under the following conditions and its characteristics were investigated. ZnO: As a conductive material added to Zn phosphor
In ₂ O ₃ amount 0 wt%, 0.05 wt%, 0.1 wt%, 0.5
A cellulose-based vehicle (a cellulose-based binder such as methyl cellulose or ethyl elulose, to which a binder solvent is added) is added to the phosphor at 1.0 and 5.0 parts by weight for each 10 parts of the phosphor. After adding 3 to 10 parts of the system vehicle, the mixture is thoroughly stirred and mixed to form a paste-like phosphor. The average particle size of this ZnO:Zn phosphor is
The average particle size of In ₂ O ₃ is 0.3 μm. The anode conductor is made by depositing a thin film of Al on the entire surface of the glass substrate 1 by a physical method such as vapor deposition, sputtering, or ion plating, and then by photoetching the anode conductor 2 and the like as shown in FIG. A pattern of wiring conductor 7 is formed. The anode conductor 2 had a rectangular mesh structure with vertical and horizontal lines perpendicular to each other. The line width of Al in this case is 10
The width of the gap between the lines was 90 μm.
For comparison, a solid Al anode conductor 2 with no gap was formed on the Al anode as shown in FIG. 3B. It should be noted that the shape of the mesh may, of course, be composed of polygons such as hexagons and octagons in addition to rectangles. As shown in FIGS. 3A and 3B, a phosphor 5 paste coated with the conductive material 6 was deposited on each anode conductor having a mesh structure and a solid structure by a thick film printing method to form an anode substrate. A control electrode 8 and a cathode 9 are disposed above facing the anode consisting of the anode conductor 2 and the phosphor layer 4, and a rear container consisting of a side plate 10 and a back plate 11 is placed on the anode substrate so as to maintain a high vacuum state. After sealing, a fluorescent display tube as shown in FIGS. 5 and 6 was formed, and the characteristics of the phosphor were examined. Measure the anode voltage Eb when an anode current Ib (0.1 mA with an area of 0.18 cm ² corresponding to one digit of 7 segments flows through these fluorescent display tubes), and calculate the value of Eb/Ib as a number representing the ease with which electrons flow. As a result, the values shown in Table 1 were obtained.

[Table] As can be seen from this table, the ideal light-emitting state is the conventional type where the Al anode is solid and the distance from the phosphor is small, and the amount of In ₂ O ₃ that lowers the resistance of the phosphor layer is 0%. Yes, and Eb/Ib in this state is 1.4×10 ⁴ . In order to create a state in which electrons can easily flow to the same degree as the ideal type by depositing In ₂ O ₃ on the phosphor using an Al mesh type in such a light-emitting state,
For Al mesh type, _In2O3 is 0.05% by weight and 0.1% by weight _.
If a certain amount between weight% is added, Eb/Ib becomes 1.4×10 ⁴
It can be seen that this results in an ideal light emitting condition. That is, in general, the electrical conductivity increases as the amount of In ₂ O ₃ is added, but it is known that the luminous efficiency η peaks at a certain amount of conductive material and then decreases. The relationship between the electrical conductivity ρ and the luminous efficiency η is shown in FIG. 7 in a graph. This is because if a certain amount of conductive material is added, the conductive material only allows current to flow but does not emit light, which in turn reduces the number of electrons that contribute to the excitation of the phosphor, thereby inhibiting light emission. FIG. 8 is a graph showing the relationship between the anode voltage Eb and the relative brightness L of the anode when the above-mentioned fluorescent display tube emits light. In this graph, the anode conductor is an Al mesh electrode with graphs A, B, and C for phosphor layers containing 0.05, 0.5, and 5% by weight of In ₂ O ₃ , respectively, and graphs for phosphor layers with 0% In ₂ O ₃ . Comparing D, we see that with only ZnO:Zn phosphor without In ₂ O ₃ in the mesh type anode conductor, the anode voltage will be high, but In ₂ O ₃
By adding , the threshold voltage becomes lower and at a certain operating voltage, for example 12V,
It can be seen that when In ₂ O ₃ is 0%, the relative brightness L is around 40, but when In ₂ O ₃ is added, the relative brightness is higher than 70. Figure 9 shows ZnO:Zn phosphor (average particle size 7.2μ).
m) is a conductive material In ₂ O ₃ (average particle size 0.3 μm)
2 is a graph of the relationship between the amount of addition of In ₂ O ₃ and the relative brightness L of the In 2 O 3-doped Zn ₂ O:Zn phosphor. When about 0.01% of In ₂ O ₃ is added, the relative luminance L is about 50th, _which is about 50 _% .
If it is less than 0.01%, it has no effect of imparting conductivity and In ₂ O ₃
As the amount of In 2 O 3 added increases, the relative brightness L gradually increases, and the relative brightness L peaks when the amount of In ₂ O ₃ added is around 0.5%, and when the amount of In ₂ O ₃ added is 0.5% or more,
In ₂ O ₃ inhibits the light emission of the ZnO:Zn phosphor, and the relative brightness L gradually decreases. When the additive amount is 5.0%, the relative brightness L is approximately 50, and if the relative brightness L is 50 or more, it can withstand normal use. In the above embodiment, In ₂ O ₃ was used as the conductive material, but In ₂ O ₃ − was used instead of In ₂ O ₃ .
Even when a conductive substance such as SnO ₂ , SnO ₂ , SnO ₂ -Sb ₂ O ₅ is added, the same effect can be obtained by adding 0.01% to 5% by weight according to the example of In ₂ O ₃ described above. was discovered through experiments. An embodiment of a front-emitting type fluorescent display tube of the present invention using the phosphor formed as described above will be described below with reference to FIGS. 3A and 4 to 6. The substrate 1 is required to have insulating properties such as glass or ceramics, and also to have translucency. For example, porosity can be explained using the example of glass substrates, such as clear plain glass, ground glass that has a physically uneven surface on one side, etched glass that has an uneven surface that has been chemically etched, etc. Also includes translucent glass. In this embodiment, a case will be explained in which etching glass is used. Cut the etching glass into a rectangle and make the substrate 1.
shall be. The substrate 1 is coated with Al, Ag, Ag, A conductive thin film of Cr, Au, Ni, etc. is deposited and molded. and anode conductor 2 wiring conductor 7
The remaining conductive thin film is removed by photoetching to form a pattern of the conductive thin film as shown in FIG. 4, for example. In this pattern, an anode conductor 2 made of Al is arranged for each segment, and a wiring conductor 7 connected to the anode conductor 2 is arranged. The anode conductor 2 is
The anode conductor is formed by arranging fine lines (line width 10 μm) of Al thin film vertically and horizontally to create many gaps in the square mesh. Furthermore, a frame portion of an Al thin film is provided around the outer periphery of the mesh. On the upper surface of this anode conductor 2, a conductive substance-containing phosphor 4 is applied to the anode conductor 2 and the gap 3 by a thick film printing method, as shown in FIG. 3A. Further, since the phosphor layer 4 may be applied onto the frame portion slightly protruding from the mesh, the phosphor layer 4 can be easily applied even if the printing accuracy is somewhat poor. As shown in FIGS. 5 and 6, a control electrode 8 and a filament-shaped cathode 9 are disposed on the substrate 1 at a position facing the phosphor layer 4. As shown in FIGS. An insulating layer 12 may be provided on the substrate 1 if necessary. After a back container consisting of a side plate 10 and a back plate 11 is sealed to this substrate 1, the container is evacuated through an exhaust pipe 13, sealed, and the inside is maintained at a high vacuum, thereby completing the fluorescent display tube of the present invention. Note that the present invention is not limited to the embodiments shown in the drawings and described above, but can be implemented with various changes without changing the gist of the present invention.
For example, although a static drive pattern is shown in the embodiment, the present invention can also be practiced with a dynamic drive pattern. (F) Effects of the Invention As explained above, in the present invention, a phosphor obtained by adding a conductive substance to a ZnO:Zn phosphor is deposited on an anode segment having a gap, so that an anode current is not applied to the anode. When emitting light, current flows through the phosphor layer deposited in the gap without causing a voltage drop, so it is possible to emit light in the same way as the phosphor layer on the anode conductor. Therefore, in a front-emission display tube that displays only the light emitted from the gaps, it is possible for each gap to emit light uniformly, so that the entire segment can also emit light uniformly, resulting in an effect that the display quality is excellent. Furthermore, since the resistance is small, it is possible to pass a large amount of anode current, which has the effect of emitting light with higher brightness than conventional fluorescent display tubes using ZnO:Zn phosphors. Furthermore, since the resistance of the phosphor is reduced, even if the gap width of the mesh is increased, the light can be emitted uniformly. Since the aperture ratio of the anode conductor of each segment of the front-emitting fluorescent display tube can be increased, the amount of light emitted toward the viewer increases, and from this point of view as well, there is an effect that high brightness is possible.

[Brief explanation of the drawing]

FIG. 1 is an enlarged vertical cross-sectional view of the main part of a conventional front-emission type anode substrate, FIG. 2 is an enlarged view of the low-speed electron beam phosphor of the present invention, and FIG. 3A is a fluorescent display of the present invention. An explanatory diagram of the anode substrate used in the tube, FIG. 3B, is
For comparison, an explanatory diagram of an example of an anode substrate provided with an anode conductor on the entire surface, FIG. 4 is a plan view of the main part of the anode substrate of the present invention, and FIG. 5 is a diagram showing a part of the fluorescent display tube of the present invention. FIG. 6 is a broken plan view, and FIG. 6 is a vertical cross-sectional view taken along line X-X in FIG. 5. FIG. FIG. 8 is a graph showing the relationship between the anode voltage and relative brightness of the phosphor of the present invention, and FIG. 9 is a graph showing the relationship between the amount of In ₂ O ₃ and relative brightness of the phosphor of the present invention. 1...Substrate, 2...Anode conductor, 3...Gap part,
4...phosphor layer, 5...ZnO:Zn phosphor, 6...
conductive material.

Claims (1)

[Claims] 1. Electrons emitted from the hot cathode are made to strike an anode provided on one surface of a light-transmitting insulating substrate and having a phosphor layer adhered to the upper surface, thereby exciting the phosphor layer to emit light and transmitting light. In fluorescent display tubes that obtain display through a conductive substrate, conductive thin films are formed into mesh-like, comb-like,
0.01 for the ZnO:Zn phosphor that is excited to emit light by impacting the anode conductor on the light-transmitting substrate with gaps such as stripes and a low-velocity electron beam.
A phosphor for low-speed electron beams, in which fine particles of a conductive substance are added in an amount of 5% by weight to 5% by weight, and a conductive substance is coated on the surface of the ZnO:Zn phosphor, is deposited on the anode conductor and the gap. A fluorescent display tube characterized in that: