JPH02178386A - Blue luminous fluorescent substance - Google Patents

Abstract

PURPOSE:To obtain an oxide based low-speed electronic beam-excited blue luminous fluorescent substance containing no S component by blending a fluorescent substance matrix consisting of ZnO.Ga2O3 with zinc oxide (based electroconductive material) at a specific ratio. CONSTITUTION:The aimed fluorescent substance obtained by blending a zinc oxide or zinc oxide based electroconductive material with a fluorescent substance obtained by adding a lithium compound, preferably selected from lithium phosphate, lithium halide and lithium titanium to a matrix expressed by the composition formula ZnO.Ga2O3 at an amount of 0.1-20wt.% based on the fluorescent substance. Furthermore, when the above-mentioned fluorescent substance is used for fluorescent display tube, etc., excellent emission characteristics and long life are exhibited.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a phosphor that emits blue light when excited by an electron beam, and in particular does not contain a sulfur (S) component and is used, for example, in a fluorescent display tube. This invention relates to an oxide-based low-speed electron beam-excited phosphor that has excellent emissive properties and a long life when used as a phosphor.

[Conventional technology]

In general, electron beam-excited phosphors are used for cathode ray tubes, flat displays, and light-emitting units of large-screen display devices that emit light at an accelerating voltage of several tens of kilovolts, and those that emit light at an acceleration voltage of several volts to several tens of diameters. It is divided into low-speed electron beam-excited phosphors for use in fluorescent display tubes and fluorescent light emitting tubes that emit light using voltage.

The present invention relates to the latter type of low-speed electron beam excited phosphor (hereinafter simply referred to as phosphor), and a typical phosphor thereof is a green-emitting ZnO:Zn phosphor.

This ZnO: Zn phosphor has an emission threshold voltage of 1 to 2.
Since the anode voltage is extremely low, usually around 10 to 20 V, sufficient brightness can be obtained for display, making it suitable for home appliances,
It is used as a phosphor in various fluorescent display devices such as audio products, clocks, and automobile instrument panels.

However, recent fluorescent display devices have tended to display multicolor displays using red, blue, yellow, etc. instead of the conventional one-color green display.

Therefore, as an example of a conventional blue-emitting phosphor, ZnS
: [Zn] phosphor, ZnS: Ag phosphor, Zn
S: Single phosphor such as Ag or AQ phosphor, and ZnS
: Ag + In2O, phosphor.

Phosphors such as ZnS:Ag r AQ +In2ow1 phosphors are known, which are a mixture of a single phosphor and a conductive substance, In2O.

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

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

Therefore, the reason for the deterioration of the emission characteristics will be explained with reference to the plan view of the fluorescent display tube shown in FIG. 1 and the sectional view shown in FIG.

Reference numeral 1 designates an insulating substrate, and a box-shaped container portion 4 consisting of a side plate 2 standing upright around the substrate 1 and a front plate 3 facing the substrate is placed over the substrate 1 in the form of a flat box. It forms an envelope. The inside of the envelope is maintained in a high vacuum state, and the wiring conductor 5, anode conductor 6, and sulfide phosphor layer 7 are connected to the substrate 1.
Laminated on top. The anode conductor 6 and the sulfide phosphor 7 constitute an anode 8.

A mesh-like control fIi electrode 9 is disposed above the anode 8 as required, and a filament-like cathode 10 is stretched above it. The filamentary cathode 10 has a directly heated type and an indirectly heated type, but in both cases, the surface is made of an alkaline earth metal such as Da or Ca.

An electron emitting layer made of a solid solution of Sr oxide (+3a, Ca, 5r)O is formed.

Next, the function of the fluorescent display tube will be explained.

When a cathode voltage is applied to the filamentary cathode 10.

It is heated to cause electrons to be emitted from the electron-emitting layer on the surface.

These electrons are accelerated by the control electrode 9 and are allowed to pass through the anode 8, but control is performed as to whether they are cut or not. 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, resulting in one light emission display.

The electrons emitted from the filamentary cathode 10 in this manner are attracted by the control electrode 9 and the anode 8 and accelerated, so they have large energy. Therefore, when it hits the sulfide phosphor layer 7, it not only causes the phosphor layer 7 to emit light but also decomposes the phosphor layer 7 on the surface. As a result, the sulfide phosphor decomposes, and sulfide-based gases such as s, so, and so□ are scattered, and fine particles containing sulfur (S) are scattered. These sulfide-based gases and fine particles react with the oxide that is the electron emission layer of the filamentary cathode 10, poisoning or sintering the surface of the cathode 10, and thus deteriorating the emission characteristics of the filamentary cathode 10. I will let you do it.

Therefore, a blue-emitting phosphor other than a sulfide phosphor was required as a blue-emitting phosphor for use in fluorescent display tubes.

One of them is a gallate-based composite oxide phosphor, which is known from Japanese Patent Publication No. 31236/1983. The compositional formula of this phosphor is A(7,n)-z Mgx)O・Ga2O, (
However, 2O. 6≦A≦1.2 and 0≦X≦0.5.

).

However, this phosphor had problems in that the emission voltage was high and the emission brightness was low, so the inventors of the present invention developed the above phosphor with A=1. We developed a phosphor in which a lithium compound is added to a matrix of ZnO.Ga, o, in which X=O, as a matrix.

A phosphor in which the lithium compound is lithium halide is known from JP-A No. 62-243679, and a phosphor in which the lithium compound is lithium phosphate is known from JP-A No. 62-331358.

[Problem to be solved by the invention]

However, although ZnO-Ga,O, phosphors doped with lithium halide or lithium phosphate can be used for low-speed electron beams, they still have high resistance compared to conventional ZnO:Zn phosphors, and under certain conditions The brightness was low in the slow electron beam control. In particular, when the anode voltage and control voltage were 30 V or less, the brightness was low, and the brightness varied widely depending on the actual conditions of the fluorescent display tube, especially the thickness of the phosphor film.

Therefore, an object of the present invention is to further lower the resistance of the conventional phosphor based on the znO-Ga203 phosphor to provide a blue-emitting phosphor that does not contain sulfides and is capable of emitting high-intensity light even at low voltage. The purpose is to

[Means to solve the problem]

In order to achieve the above object, the present invention has one compositional formula of ZnO.
・0.1 to 20 wt% of zinc oxide or zinc oxide-based conductive material to the phosphor having a matrix represented by Ga, O,
It is characterized by mixing at a ratio of .

Further, the phosphor may be one in which a lithium compound is added to a matrix represented by ZnO-Ga2O3.

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

[For production]

A phosphor in which ZnO is mixed into a phosphor having a matrix represented by ZnO-Ga2O3 not only improves the conductivity of the phosphor itself due to ZnO, but also increases the number of luminescent centers by depriving the matrix of oxygen. Several volts to several tens of volts
It has the ability to emit light with high brightness even at low voltages.

[Example 1] First, a matrix of znO-Ga20. is formed as follows.

A matrix is formed by dissolving equimolar amounts of 2nO and Ga2O.

That is, 3.3 g of ZnO and 7.5 g of Ga2O3 were weighed, mixed thoroughly, and then placed in an alumina crucible, and the firing temperature was set at ttoo to 1300°C in a firing furnace in an atmospheric atmosphere.
The first firing was carried out for 3 hours at a temperature of
O.

A matrix was formed which was a solid solution of .

Next, 5X10-3 to 4X10-1 mol of 13PO is added to the Zn0-Ga, O base material per 1 mole of the base material. In this example, 0, which corresponds to 5X10' moles,
23 g of Li.

po4 was added.

The ZnO.Ga2O3 matrix is thoroughly ground using an agate ball mill to disperse the agglomerates. After pulverization, 0.23 g of the Li, PO, was added to the Zn0-Ga2O
．． After thoroughly mixing with the matrix, place it in an alumina boat and create a reducing atmosphere, such as a mixed atmosphere of N2 and N2, with H,/N2.
= 40/160 (m97 minutes) in a firing furnace, set the firing temperature to 1000°C, and fired for 1 hour.
ZnO-Ga2O3 whose matrix is doped with Li and P:
A Li,P phosphor was obtained.

In order to further lower the resistance of this ZnO.Gaz03:Li,P phosphor, indium oxide In2O, zinc oxide ZnO1, and tin oxide SnO2 were respectively added and mixed as conductive materials. The mixing amount is 1wt% based on the phosphor.
They were 3wt%, 5wt%, and 10wt%. The conductive material used had an average particle size of 1 μm.

In this way, the mixed conductive material and the phosphor mixed in different amounts are formed, mixed with an organic binder to form a phosphor paste, and then screen printed to form the fluorescent 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.

Furthermore, a mesh-like control electrode 9, a filament-like cathode lO
were arranged, the container part 4 was sealed so as to cover these electrodes, the inside was evacuated, and when a high vacuum state was achieved, the container was sealed to produce a fluorescent display tube.

For comparison, the same fluorescent display tube was similarly implemented using a phosphor without a conductive material mixed therein.

The completed fluorescent display tube was lit under the following driving conditions and compared.

A cathode voltage of 1.7 Vdc, a control voltage of 12 Vdc, and an anode voltage of 30 Vdc were applied to evaluate the brightness characteristics.

The results are shown in Table-1.

Luminous brightness and luminous efficiency are averages of 5 samples.

(Margins below) Table 1 From the above results, it was found that In, O, and SnO□ had lower brightness and luminous efficiency than conventional phosphors that did not contain conductive materials, and were found to be ineffective.6 As conductive materials, Z
ZnO-Ga2O mixed with nO: Li.

P+ZnO phosphor has an emission brightness of 160% without conductive material.
cd/rrr is 280-320cd/rrf, which is approximately 1.75-2 times, and the luminous efficiency is also 0.373Qm.
/w was improved by about 1.5 times to 0.441 to 0.564 Qrn/ν.

The reason why ZnO is superior to In, O, and SnO2 as a conductive material is as follows.

The phosphor mounted on the fluorescent display tube is exposed to 40°C several times during the manufacturing process.
It undergoes heat treatment at 0-450°C. So ZnO: Ga2
This is thought to be due to the exchange of oxygen between the phosphor and the conductive material due to heat treatment during the process when the above-mentioned In2O, SnO, or conductive material is mixed with the O3-based phosphor. For example, In2O3.

Since it is a material that easily creates oxygen defects, during heat treatment during the manufacturing process, ZnO, which is in contact with In2O3, is
Ga2O, by giving oxygen to the parent body, ZnO・G
It is thought that the brightness characteristics were not improved because the luminescent centers related to a2O and parent oxygen defects were destroyed.

However, in the case of ZnO in this application, in addition to improving the conductivity of the phosphor itself, it is also difficult to release oxygen compared to In, 03, etc., so ZnO is used in the heat treatment of the manufacturing process.
By depriving oxygen from the ZnO·Ga, 03 matrix that is in contact with the ZnO·Ga, 03 matrix, the number of luminescent centers associated with oxygen defects in the ZnO·Ga, 0, matrix increases, 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 and the resistance of the phosphor layer decreases.
The brightness characteristics have been improved.

Next, the amount of ZnO conductive material to be mixed will be explained.

FIG. 3 is a graph showing the relationship between the amount of ZnO conductive material mixed and relative luminance. In the case of the above-mentioned example, the average particle size was 1 μm, so the graph represented by the curve A was obtained. The brightness was measured at 1 μm and expressed as relative brightness with the highest value being 100.

The brightness is highest when the mixing amount of ZnO is around 3% to 11%, and if the relative brightness is in the excellent range of 50 or more, it is 0.1 to 11%.
10 wt% is the range where the brightness becomes high. If the amount of ZnO mixed is less than 0.1 wt%, the effect of lowering the resistance is not observed, and if it is more than IQwt%, the area of ZnO that does not emit light and blocks the light emission of the phosphor increases, and the light emitting area decreases. As a result, the brightness decreases.

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

As the particle size increases, the brightness generally tends to decrease. Furthermore, 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
There is a tendency for the upper limit to widen to 3 to 3.5 t%. this is,
This is because as the particle size increases, the number of particles decreases even with the same mixing amount, and the total area to be blocked becomes smaller.

However, the relative brightness peaks at 50 when the average particle size is 10 μm. Therefore, it was found that all particle sizes of 10 μm or more are undesirable because they are 50 or less.

Also, the upper limit of the mixing amount is 20wt when the peak is 10μm.
%, so it was found that if it is in a lower range, that is, 201% or less, the brightness will be high and it can be put to practical use as a phosphor for low-speed electron beams.

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

Figure 4 shows a ZnO conductive material with an average particle size of 1 μm.
-Ga2O. : Luminance when phosphors mixed with Li and P phosphors at 0t%, 1wt%, 5iit%, and 10wt% are mounted in a fluorescent display tube and emitted by changing the anode voltage. It is a graph showing the relationship between anode voltage Eb.

Compared to the conventional example with a mixture amount of Oυt%, the brightness of the present invention is higher at all mixture amounts.In particular, the fluorescent display tube with a 1wt% mixture has a brightness higher than that of other mixture amounts when the anode voltage is 25V or more. highest.

Similarly, a fluorescent display tube with a mixture of 5 wt% has the second highest brightness at about 25 V or higher than a mixture of 1 wt%.

In the fluorescent display tube containing 10wt% mixture, the conventional example (Qwt%
), but the brightness is high below 40V. The effect is particularly noticeable below 25V.

Furthermore, the light emission starting voltage is also lower than that of the conventional example.

In this way, the phosphor of the present invention can achieve higher luminance than the conventional example in a low voltage region.

Figure 5 shows a conventional example in which the ZnO-Ga, O, +ZnO phosphor has a mixed amount of Qwt% of ZnO with an average particle size of 1 μm, and a 3t
It is an emission spectrum diagram of a phosphor mixed with st% and a phosphor mixed with 10 wt%.

The conventional example with a mixing amount of 0 wt% has a peak at 415 nm, whereas when the mixing amount is 3 tit%, there is a peak at 425 nm, and when the mixing amount becomes 1 (ht%), it shifts further to the longer wavelength side, The peak appears at 435 nm.As the amount of mixture increases in this way, there is a tendency for the wavelength to shift to the longer wavelength side.In other words, the color changes from purple to bluer.

In any case, the emission spectrum of the phosphor of the present invention includes a blue component of 420r+m to 530nm, so the emission color is blue.

[Example 2] Zn0-Ga2O. The steps up to the formation of the matrix are the same as in Example 1, so the explanation will be omitted. Pulverized ZnO・Ga, 0
．． 0.0 lithium halide per 1 mole of base material
Add 5-15 mol% and mix thoroughly. In the case of this example, 3 mol% of lithium fluoride was added to the lithium halide.

The well-mixed phosphor material was mixed with N2 and N2 as in Example 1.
The reduction furnace is fed with a mixed reducing atmosphere under similar conditions.
Sintered at a firing temperature of 1000℃ for 1 hour to form ZnO・Ga2O
3: A phosphor having a composition formula of Li, F was obtained.

A zinc oxide-based conductive material such as ZnO doped with aluminum M is used as a conductive material in this phosphor.
: Ml was used.

This ZnO:M conductive material is prepared by adding ZnO to an aqueous solution of MCL 6H20 and evaporating it to dryness in a weak reducing atmosphere, that is, +1. /N, the ratio is 5/195 (+
nR/min) in a reducing furnace at a firing temperature of 1000° C. for 1 hour to dope the material.

The amount of ZnOCAQ added is ZnO・Ga2O3: Li
When mixed with 5 wt% of the F phosphor, mounted in a fluorescent display tube in the same manner as in Example 1, and lit under the same driving conditions, blue light emission was observed from around 15 V at the anode voltage, and approximately 200 Cd/rd at 30 V. was obtained, and the same effect as ZnO was obtained.

Note that the average particle size of ZnO: Afl of the conductive material is 1
μm ones were used.

In addition to ZnO:AQ, ZnO is used as a zinc oxide-based conductive material.
nO:B, ZnO:Ga+ ZnO:In, ZnO
:Tρ, ZnO:Zn, etc. have the same effect of lowering the resistance.

〔Effect of the invention〕

As explained above, the present invention can be applied to conventional ZnO:Ga,
Since 0.1 to 20 wt % of zinc oxide or zinc oxide-based conductive material is mixed with the phosphor based on O, the following effects are obtained.

(1) The phosphor of the present invention has higher brightness in a low voltage region than conventional phosphors that do not contain conductive materials, so it can be used satisfactorily as a phosphor for fluorescent display tubes.

(2) Since the phosphor composition of the present invention does not contain a sulfur S component, a non-sulfide-based blue-emitting phosphor that does not scatter sulfide-based gases, etc. and does not deteriorate the emission characteristics of the filament cathode can be used. can be provided.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a fluorescent display tube inside the shell, Fig. 2 is a cross-sectional view of the same, and Fig. 3 is a relation between the mixed view and relative brightness of conductive material ZnO according to particle size. FIG. 4 is a graph showing the relationship between the anode voltage and brightness of the conventional example of the present invention, and FIG. 5 is an emission spectrum diagram of the present invention and the conventional example.

Claims (3)

[Claims] (1) A blue-emitting phosphor characterized in that zinc oxide or a zinc oxide-based conductive material is mixed in a proportion of 0.1 to 20 wt% with respect to a phosphor having a matrix represented by the compositional formula ZnO.Ga_2O_3. (2) A blue color characterized by mixing zinc oxide or a zinc oxide-based conductive material at a ratio of 0.1 to 20 wt% to a phosphor whose composition formula is ZnO.Ga_2O_3 and which has a lithium compound added to the matrix. Luminescent phosphor. (3) The blue-emitting phosphor according to claim 2, wherein the lithium compound is one selected from lithium phosphate, lithium halide, and lithium titanate.