JPH0747733B2 - Blue light emitting phosphor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a phosphor that emits blue light when excited by an electron beam, and does not particularly contain a sulfur (S) component and is used for, for example, a fluorescent display tube. The present invention relates to an oxide-based low-speed electron beam-excited phosphor having excellent emission characteristics and long life when used as a phosphor.

[Conventional technology]

Generally, an electron beam excitation phosphor is a phosphor for a cathode ray tube, a flat panel display, a light emitting unit of a large-screen display device or the like that emits light at an accelerating voltage of about several tens of KV and several V to several V.
It is classified into a fluorescent display tube that emits light at a low accelerating voltage of about several tens of volts, and a low-speed electron beam excitation phosphor for a fluorescent light emitting tube.

The present invention relates to the latter slow electron beam excitation phosphor (hereinafter simply referred to as a phosphor), and a typical phosphor thereof is a green light emitting ZnO: Zn phosphor. This ZnO: Zn phosphor has an extremely low emission threshold voltage of 1 to 2 V, usually 10 to 20 V.
Since it is possible to obtain sufficient brightness to obtain a display with a certain level of anode voltage, it is used as a phosphor for various fluorescent display devices such as home appliances, audio products, clocks, and instrument panels of automobiles.

However, recent fluorescent display devices tend to have a multicolor display using red, blue, yellow, etc. instead of the conventional green color.

Therefore, as an example of a conventional blue light emitting phosphor, ZnS: [Z
n] Phosphors, ZnS: Ag phosphors, ZnS: Ag, Al phosphors and other phosphors alone, and phosphors such as ZnS: Ag + In ₂ O ₃ phosphors and ZnS: Ag, Al + In ₂ O ₃ phosphors A phosphor in which In ₂ O ₃ which is a conductive substance is mixed with a simple substance is known.

Since the composition of the phosphor contains a sulfur (S) component, these phosphors are generically referred to as sulfide phosphors and are generally used for blue color display.

However, it is well known that the sulfide phosphor has a problem that the sulfur (S) component in the composition adversely affects the filament cathode during the operation of the fluorescent display tube and deteriorates the emission characteristics of the filament cathode. is there.

Therefore, the reason for the emission characteristic deterioration will be described with reference to the plan view of the fluorescent display tube of FIG. 1 and the sectional view of FIG.

Reference numeral 1 denotes a substrate having an insulating property, which is a flat box-shaped container part 4 formed of a side plate 2 standing upright around the substrate 1 and a front plate 3 facing the substrate so as to cover the substrate 1. It forms the envelope. The inside of the envelope is kept in a high vacuum state, and the wiring conductor 5, the anode conductor 6 and the sulfide phosphor layer 7 are laminated on the substrate 1. The anode conductor 6 and the sulfide phosphor 7 constitute the anode 8.

A mesh-shaped control electrode 9 is provided above the anode 8 as required, and a filament cathode 10 is stretched above the control electrode 9. This filamentary cathode 10 has a direct heating type and an indirectly heating type, and the surface of each is a solid solution of an oxide of an alkaline earth metal such as Ba, Ca, Sr (Ba, Ca, Br).
An electron emission layer made of O is formed.

Next, the operation of the fluorescent display tube will be described.

When a cathode voltage is applied to the filament cathode 10, the filament cathode 10 is heated and emits electrons from the electron emission layer on the surface. The electrons are accelerated by the control electrode 9 and the electrons are passed through the anode 8 or cut. The electrons that have passed through the anode 8 impinge on the sulfide phosphor layer 7 of the anode 8 to which the anode electrode is applied, and emit light.

Thus, the electrons emitted from the filamentary cathode 10 are attracted by the control electrode 9 and the anode 8 and accelerated, and thus have a large energy. Therefore, in addition to the function of causing the phosphor layer 7 to emit light when impinging on the sulfide phosphor layer 7, the phosphor layer 7 on the surface is decomposed. As a result, the sulfide phosphor is decomposed, and a sulfide-based gas such as S, SO, and SO ₂ scatters, or fine particles containing sulfur (S) scatter. These sulfide-based gas and fine particles react with the oxide that is the electron emission layer of the filamentary cathode 10, and the cathode 10
Since the surface of the cathode is poisoned or sintered, the emission characteristics of the filamentary cathode 10 are deteriorated.

Therefore, a blue light emitting phosphor other than a sulfide phosphor is required as a blue light emitting phosphor used for a fluorescent display tube.

One of them is known as a gallate complex oxide phosphor in Japanese Patent Publication No. 60-31236. The composition formula of this phosphor is
A (Zn _1-X Mgx) O ・ Ga ₂ O ₃ (provided that 0.6 ≦ A ≦ 1.2 and 0
≦ X ≦ 0.5. ).

However, since this phosphor has a problem that the emission voltage is high and the emission brightness is low, the present inventors have found that ZnO.Ga ₂ O in which A = 1 and X = 0 of the above phosphor is used. We have developed a phosphor in which a lithium compound is added to this matrix, with _three phosphors as a matrix.

A phosphor in the case where the lithium compound is a lithium halide is known in JP-A-62-243679, and a case in which the lithium compound is lithium phosphate is in Japanese Patent Application No. 62-331358, which is related to the prior application of the present application.

[Problems to be Solved by the Invention]

However, ZnO / Ga ₂ O ₃ phosphors containing lithium halide or lithium phosphate can be used for low-speed electron beams, but have higher resistance than conventional ZnO: Zn phosphors, and under certain conditions. The brightness was low when illuminated by a slow electron beam.
In particular, the brightness was low when the anode voltage and the control voltage were 30 V or less, and the brightness varied greatly depending on the actual conditions of the fluorescent display tube, particularly the phosphor film thickness.

Therefore, the present invention further reduces the resistance of the conventional phosphor having a ZnO / Ga ₂ O ₃ phosphor as a base material, and is capable of emitting light with high brightness even at a low voltage, a blue-emitting phosphor containing no sulfide. It is intended to be provided.

[Means for Solving the Problems]

ZnO and Ga ₂ O ₃ are solid-solved in equimolar proportions and the composition formula is ZnO ・ Ga ₂ O ₃
After the lithium oxide is added to the matrix represented by and the phosphor is baked, zinc oxide having an average particle size of 3 μm or less or zinc oxide doped with a metal element is mixed at a ratio of 0.1 to 10 wt%, and then 400 to 450 ° C. It is characterized by undergoing the heating step of.

Further, as the lithium compound, lithium phosphate and lithium halide are preferable.

[Action]

A phosphor in which ZnO is mixed with a phosphor having a matrix represented by ZnO / Ga ₂ O ₃ has a feature that ZnO improves the conductivity of the phosphor itself, and in addition to the emission center by depriving the matrix of oxygen. Therefore, even if the voltage is as low as several V to several tens of V, it has the effect of emitting light with high brightness.

Example 1 First, ZnO.Ga ₂ O ₃ as a base material is formed as follows.

ZnO and Ga ₂ O ₃ are equimolarly dissolved to form a matrix.

That is, 3.3 g of ZnO and 7.5 g of Ga ₂ O ₃ are weighed, mixed well and put in an alumina crucible, and the firing temperature is 1100-1300 ° C. for 3 hours in a firing furnace in the atmosphere. The second firing was performed to form a matrix that was a solid solution of ZnO and Ga ₂ O ₃ .

Next, 5 × 10 ⁻³ to 4 × 10 ⁻¹ mol of Li ₃ PO ₄ is added to the ZnO · Ga ₂ O ₃ matrix, relative to 1 mole of the matrix. In the case of this example, 0.23 g of Li ₃ PO ₄ corresponding to 5 × 10 ⁻² mol was added.

The ZnO.Ga ₂ O ₃ matrix is sufficiently crushed using an agate ball mill to disperse the agglomerates. After grinding, said Li ₃ PO ₄
Put the 0.23g alumina boat was thoroughly mixed in the base of the ZnO · Ga ₂ O _3, a reducing atmosphere, for example, a mixed atmosphere of H ₂ and _{N 2 H 2 / N 2 =} 40/160 (ml / min In the firing furnace sent under the conditions of (1), the firing temperature is set to 1000 ° C and firing is performed for 1 hour.
A ZnO.Ga ₂ O ₃ : Li, P phosphor having a matrix doped with Li and P was obtained.

In order to further reduce the resistance of this ZnO / Ga ₂ O ₃ : Li, P phosphor, indium oxide In ₂ O ₃ and zinc oxide Zn are used as conductive materials.
O and tin oxide SnO ₂ were added and mixed. The mixing amounts were 1 wt%, 3 wt%, 5 wt% and 10 wt% with respect to the phosphor. The conductive material used had an average particle diameter of 1 μm.

In this way, mixed conductive materials and phosphors with different mixing amounts are formed, mixed with an organic binder to form a phosphor paste, and screen-printed to produce the phosphor display tube shown in FIGS. 1 and 2. A phosphor layer 7 is formed on the surface of the anode conductor 6 on the substrate 1.
Was deposited. Further, a mesh-shaped control electrode 9 and a filament cathode 10 are arranged, the container portion 4 is sealed so as to cover these electrodes, the inside is evacuated, and when the high vacuum state is reached, the fluorescent display tube is sealed. I made it.

For comparison, the same fluorescent display tube was mounted in the same manner by using a phosphor in which a conductive material was not mixed.

The completed fluorescent display tube was lit under the following driving conditions for comparison.
A cathode voltage of 1.7 Vdc, a control voltage of 12 Vdc, and an anode voltage of 30 Vdc were applied, and the characteristics of the brightness were evaluated. The results are shown in Table-1.

Luminous intensity and luminous efficiency are averages of 5 samples.

From the above results, it was found that In ₂ O ₃ and SnO ₂ were ineffective because the luminance and the luminous efficiency were worse than the conventional phosphor in which the conductive material was not mixed.

The ZnO / Ga ₂ O ₃ : Li, P + ZnO phosphor mixed with ZnO as the conductive material has an emission brightness of 280 vs. 160 cd / m ² without the conductive material.
~ 320cd / m ^{2, which} is about 1.75 to ² times, and the luminous efficiency is 0.37
It was improved from 0.441 to 0.564 lm / w, which is about 1.5 times that of 3 lm / w.

The reason why ZnO is superior to In ₂ O ₃ and SnO ₂ as the conductive material is as follows.

The fluorescent material mounted on the fluorescent display tube is
Heat treatment at ~ 450 ℃. Therefore, when ZnO: Ga ₂ O ₃ as a host phosphor is mixed with the above-mentioned In ₂ O ₃ or SnO ₃ conductive material, heat treatment during the process causes oxygen to be generated between the phosphor and the conductive material. It is considered that the exchange occurred. For example, since In ₂ O ₃ is a material that easily creates oxygen defects, Z that is in contact with In ₂ O ₃ during heat treatment during the manufacturing process
By supplying oxygen to the nO ・ Ga ₂ O ₃ matrix, ZnO ・ Ga ₂ O ₃
It is considered that the luminance characteristics were not improved because the luminescent centers related to the oxygen defects of the base were destroyed.

However, in the case of ZnO of the present application, in addition to improving the conductivity of the phosphor itself, it is more difficult to release oxygen than In ₂ O _3, etc., so in the heat treatment of the manufacturing process, ZnO ・ Ga _{2 in} contact with ZnO By depriving oxygen of the O ₃ matrix, ZnO ・ Ga ₂
The number of luminescence centers related to oxygen defects in the O ₃ matrix is increased, and the conductivity of the matrix itself is improved. Therefore, when this ZnO conductive material is mixed, the anode current in the low voltage region increases, the resistance of the phosphor layer is lowered, and the brightness characteristics are improved.

Next, the mixing amount of the ZnO conductive material will be described.

FIG. 3 is a graph showing the relationship between the amount of ZnO conductive material mixed and the relative emission brightness. In the case of the above-mentioned examples, the average particle size is 1 μm, and therefore the graph of the curve indicated by A is obtained. The brightness was 1 μm and expressed as relative brightness with the maximum value being 100.

The highest brightness is obtained when the mixing amount of ZnO is around 3 wt%, and the relative brightness is
When 50 or more is considered as an excellent range, 0.1 to 10 wt% is a range where the brightness is high. When the content of ZnO is 0.1 wt% or less, the effect of lowering the resistance is not recognized, and when it is 10 wt% or more, the area of ZnO that does not emit light and blocks the emission of the phosphor increases, and the light emitting area decreases. Therefore, the brightness is reduced.

Next, when a ZnO conductive material having an average particle diameter of 3 μm is mixed, a curve graph B is obtained.

The larger the particle size, the lower the brightness as a whole. The maximum mixing amount (peak value) also tends to increase.
With this average particle size of 3 μm, the range where the relative brightness is 50 or more is:
The upper limit tends to widen to 3 to 13.5 wt%. This is because the larger the particle size, the smaller the number of particles even with the same mixing amount, and the smaller the total area to be blocked.

However, when the average particle size is 10 μm, the relative brightness reaches a peak of 50. Therefore, it was found that particle diameters of 10 μm or more are all less than 50, which is not preferable.

It was also found that the upper limit of the mixing amount is 20 wt% at 10 μm, so that the luminance is high in the range below that, that is, 20 wt% or less, and it can be put to practical use as a phosphor for low-speed electron beams.

However, preferably, the average particle size is 3 μm or less, and the optimum amount of the mixture is 0.1 to 10 wt%.

Fig. 4 shows the ZnO conductive material with an average particle size of 1 μm as ZnO ・ Ga ₂ O.
₃ : For Li, P phosphor, mixing amount is 0wt%, 1wt%, 5wt%, 1
7 is a graph showing the relationship between the luminance L and the anode voltage Eb when a fluorescent substance mixed with 0 wt% is mounted on a fluorescent display tube and the anode voltage is changed to emit light.

Compared with the conventional example in which the mixing amount is 0 wt%, the brightness is higher in all the mixing amounts of the present invention, and particularly, the fluorescent display tube mixed with 1 wt% has an anode voltage of 25 V or more and the brightness is higher than that of other mixing amounts. highest.

Fluorescent display tube mixed with 5wt% is also 1wt above 25V.
The brightness is the second highest after the mixed amount of%.

The fluorescent display tube mixed with 10 wt% has a value close to that of the conventional example (0 wt%), but the brightness is high at 40 V or less. Especially 2
The effect is remarkable when the voltage is 5 V or less.

The light emission start voltage is also lower than that of the conventional example. As described above, the phosphor of the present invention can have higher brightness than the conventional example in the low voltage region.

Figure 5 shows ZnO / Ga ₂ O ₃ + ZnO phosphor with average particle size of 1μm.
A phosphor mixed with a conventional example in which the amount of nO mixed is 0 wt% and 3 wt%,
It is an emission spectrum figure of the fluorescent substance which mixed 10 wt%.

The peak of the conventional example with a mixing amount of 0 wt% is at 415 nm, whereas there is a peak at 425 nm when the mixing amount is 3 wt%, and when the mixing amount is 10 wt%, it shifts to the longer wavelength side, and 435 n
There is a peak at m. When the mixing amount increases in this way, there is a tendency to shift to the long wavelength side. That is, it changes from purple to blue.

In any case, since the emission spectrum of the phosphor of the present invention contains a blue component of 420 nm to 530 nm, the emission color is blue.

[Example 2] The description is omitted since it is the same as in Example 1 until the ZnO.Ga ₂ O ₃ matrix is formed. Lithium halide is added to the crushed ZnO.Ga ₂ O ₃ matrix in an amount of 0.05 to 15 mol% with respect to 1 mol of the matrix, and they are mixed sufficiently. In the case of the present embodiment, 3 mol% of lithium fluoride was added to the lithium halide.

A well-mixed phosphor material was fired in a reducing furnace in which the same mixed reducing atmosphere of H ₂ and N ₂ as in Example 1 was fed under the same conditions as above, and was fired at a firing temperature of 1000 ° C. for 1 hour to obtain ZnO / Ga ₂ O ₃ :. A phosphor having a composition formula of Li and F was obtained.

Zinc oxide doped with a metal element, for example, ZnO doped with aluminum Al, that is, ZnO: Al was used as a conductive material for this phosphor.

The ZnO: Al conductive material, an aqueous solution prepared by dissolving AlCl ₃ · 6H ₂ O
After adding ZnO and evaporating it to dryness, it was calcined for 1 hour at a firing temperature of 1000 ° C in a reducing furnace with a weak reducing atmosphere, that is, a H ₂ / N ₂ ratio of 5/195 (ml / min), to remove Al. Made dope

The amount of ZnO: Al added is 5 wt% based on the ZnO / Ga ₂ O ₃ : Li, F phosphor.
When mixed and mounted on a fluorescent display tube in the same manner as in Example 1 and turned on under the same driving conditions, blue light emission was observed from around 15 V of the anode voltage, and about 200 cd / m ² was obtained at 30 V, which was similar to ZnO. The effect was obtained.

The conductive material used had an average particle size of ZnO: Al of 1 μm.

In addition to ZnO: Al as zinc oxide doped with metallic elements,
ZnO: B, ZnO: Ga, ZnO: In, ZnO: Tl, ZnO: Zn, etc. have the same effect of reducing the resistance.

〔The invention's effect〕

The present invention, As described above, the conventional ZnO · Ga ₂ O ₃ with respect to the phosphor as a matrix, since the zinc oxide doped with zinc oxide or metal mixed 0.1-10% following effects Have.

(1) Since the phosphor of the present invention has improved conductivity of the phosphor coating film as compared with the conventional phosphor containing no conductive material, it has high brightness in a low voltage region, and thus is sufficient as a phosphor for a fluorescent display tube. Can be used.

(2) Since the phosphor composition of the present invention does not contain a sulfur S component, a non-sulfide type blue light emitting phosphor that does not scatter sulfide type gas or the like and does not deteriorate the emission characteristics of the filamentary cathode is obtained. Can be provided.

[Brief description of drawings]

FIG. 1 is a plan view of a general fluorescent display tube, FIG. 2 is a cross-sectional view of the same, and FIG. 3 shows the relationship between the mixing amount and the relative brightness of ZnO particles of a conductive material by particle size. The graph shown in Fig. 4 is
A graph showing the relationship between the anode voltage and the brightness of the conventional example of the present invention,
FIG. 5 is an emission spectrum diagram of the present invention and a conventional example.

Claims (2)

[Claims] The average particle size relative to 1. A ZnO and Ga ₂ O ₃ phosphor having a composition formula by solid solution equimolar increments were calcined by adding a lithium compound to the mother represented by ZnO · Ga ₂ O ₃ is 0.1-10wt% of zinc oxide less than 3μm or zinc oxide doped with metal element
%, Followed by a heating step at 400 to 450 ° C., which is a blue light emitting phosphor. 2. The blue light-emitting phosphor according to claim 1, wherein the lithium compound is one selected from lithium phosphate, lithium halide and lithium titanate.