JPH11307020A - Field emission type display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a FED(field emission type display element) provided with a phosphor hard to decompose and scatter even under the driving conditions of low-voltage and high-current, and suppressing deterioration of an emitter. SOLUTION: A phosphor GaN: Zn is obtained by nitriding Ga2 S3 and ZnS in an air flow of NH3 at a temperature of 1000 deg.C. A FED using the phosphor is formed. The relationship between calcination temperature of the phosphor and initial luminance when it emits a light in the FED is shown. Here, the driving condition is 400 V, 1/240 Duty, 75 mA/cm<2> (average current 300 Α/cm<2> ). The phosphor GaN in this case is suitable for the FED as the phosphor having a luminescent peak at approximately 410 nm if the calcination temperature is in the range of 450 deg.C-550 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a field emission cathode (F
An object of the present invention is to provide a phosphor which is useful as a phosphor of a light emitting display section of a field emission display device (Field Emission Display, FED) using an electron emission cathode (FEC) as an electron source.

[0002]

2. Description of the Related Art At present, research and development of a field emission display (FED) combining a field emission cathode and a phosphor are being conducted. The driving voltage is 1 kv or less, and a reduction in thickness and weight is expected.

[0003] The portion of the FED that emits electrons is an emitter, and an emitter using a metal such as Mo or an emitter using diamond-like carbon has been studied. On the other hand, ZnO: Zn phosphor has been widely studied as a phosphor. In addition, various phosphors, mainly oxides, are being studied for full color.

If a graphic FED is constructed based on the performance of the current phosphor used in a CRT or the like and a graphic display is performed, the driving voltage is 1 kV.
Hereinafter, the duty ratio is 1/240, and the driving current is 100 m.
A condition such as A / cm ² or less (400 μA / cm ^{2 in} average current) is required.

In a normal CRT or the like, the average current value is at most 0.
Several to several μA, and FED is 100 to 1
A current density of 000 times is required. As described above, since a large current density is required in the FED, the usual phosphors are decomposed and scattered, and the efficiency of the phosphor itself is reduced, and the emitters are contaminated by the scattered matters.

As described above, the acceleration voltage of electrons in the CRT is much higher than that of the FED. Therefore, if the energy at the time of light emission is the same, the current density of the FED must be much higher than that of the CRT. Therefore, FED
This is a low voltage and large current driving condition with low energy conversion efficiency, and there has been a problem that energy loss becomes heat and the phosphor is decomposed and scattered.

It is also reported that particularly in the case of a metal cone-shaped emitter, contamination with highly reactive sulfur or oxygen causes fatal deterioration. For these reasons, there has been a problem that the current phosphor has poor life characteristics even when used for an FED.

An object of the present invention is to provide an FED having a phosphor which is hardly decomposed and scattered even under driving conditions of a low voltage and a large current and whose emitter is hardly deteriorated.

[0009]

According to a first aspect of the present invention, there is provided a field emission display device comprising a cathode substrate having a field emission cathode formed on an inner surface thereof and an anode having a phosphor surface made of a phosphor on the inner surface. In the field emission display device in which the anode substrate is faced at a predetermined interval and the gaps between the outer peripheral portions of the cathode substrate and the anode substrate are sealed, the gallium nitride-based phosphor is used as the phosphor. It is characterized by:

According to a second aspect of the present invention, in the field emission display device of the first aspect, the phosphor screen is a thin film of the phosphor.

According to a third aspect of the present invention, in the field emission display device according to the first aspect, the phosphor screen is a phosphor layer composed of an aggregate of the phosphor particles. It is characterized by having.

According to a fourth aspect of the present invention, in the field emission display device of the first aspect, the gallium nitride-based phosphor is a phosphor represented by the following formula. And Ga _1-x In _x N: A, B where 0 ≦ x ≦ 0.9, where A is Zn and M
g is selected from the group consisting of g, and B is selected from nothing and Si and Ge.

According to a fifth aspect of the present invention, in the field emission type display device of the first aspect, the anode is used at a voltage of 1 kV or less and an anode current of 20 μA / cm ² or more. Features.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have made intensive efforts to develop a phosphor for an FED which can be driven at a low voltage and a large current and has no adverse effect on an emitter, in order to achieve the above object. The condition that such a phosphor should have is that, even if the phosphor is decomposed, it does not produce scattered substances that adversely affect the emitter, and that it has appropriate conductivity for driving a large current and a low voltage. And a relatively high melting point. That is, since the phosphor for FED is used under the driving conditions of low voltage and high current density, it is difficult to be decomposed even by the impact of electrons, and even if decomposed, the decomposed substance does not harm the cathode. Preferably, there is.

As a candidate for a material satisfying these conditions, a phosphor containing, as components, an element such as N which does not easily react with the cathode and a metal such as Ga which has a low vapor pressure and is difficult to decompose can be considered. The present inventors have examined whether Ga _1-x In _x N: A, B can be used as a phosphor for FED as an example of such a phosphor. It is already known that this phosphor emits blue and green light with high efficiency in LED. This material is also known to become oxide at 900 ° C. in air.

However, when this material is applied to an FED, the slurry is applied at 450 ° C. to 550 ° C. in air.
It is necessary to bake at ° C., and it is necessary to take measures to prevent surface oxidation at this point. Hereinafter, Ga _1-x I
n _x N: A, concrete examples of the B phosphor will be described.

(1) Example 1 (GaN: Zn phosphor) A GaN: Zn phosphor is made of, for example, Ga ₂ S ₃ as a base material, and ZnS as a raw material for supplying Zn as a dopant. It can be obtained by nitriding at 1000 ° C. in an NH ₃ stream.

An FED using this phosphor is manufactured. F
The structure of the ED will be described with reference to FIG. An FEC 2 is formed on the inner surface of the cathode substrate 1. First, the FEC 2 has a cathode conductor 3. On the cathode conductor 3 is an insulating layer 4. On the insulating layer 4 is a gate electrode 5. Holes 6 are formed in the gate electrode 5 and the insulating layer 4. Vacancy 6
On the cathode conductor 3 inside, a cone-shaped emitter 7 is formed.

An anode 11 is formed on the inner surface of the transparent anode substrate 10. The anode 11 includes a translucent anode conductor 12 such as an ITO film formed on the inner surface of the anode substrate 10 and a phosphor layer 13 formed thereon. The phosphor is applied to the anode conductor 12 by a slurry method, and then fired to remove the binder of the slurry constituent material.

The cathode substrate 1 and the anode substrate 10 are arranged so as to face each other so that the FEC 2 and the anode 11 face each other at a predetermined interval, and the gap between the outer peripheral portions of the two substrates 1 and 10 is sealed by a spacer member. An envelope is configured. The interior of the envelope is evacuated to a high vacuum.

According to the FED having such a configuration, the FEC
The electrons emitted from the emitter 7 strike the phosphor layer 13 of the anode 11 to emit light. Light emission of the phosphor layer 13 is observed from outside the envelope through the translucent anode conductor 12 and the transparent anode substrate 10.

In this embodiment, for comparison, an FED using Y ₂ SiO ₅ : Ce as a blue phosphor was also experimentally manufactured. Further, the firing temperature at the time of firing after the application of GaN was changed in the range of 400 ° C. to 600 ° C., and the change in characteristics was examined.

FIG. 2 shows the relationship between the firing temperature and the initial luminance.
The driving conditions were 400V, 1/240 Duty, 75mA /
cm ² (the same average current of 300 μA / cm ² ). Thus, the GaN phosphor of this example has a firing temperature of 450 ° C. to 5 ° C.
In the range of 50 ° C., it was found that the phosphor can be used as a blue-emitting phosphor having a peak at about 410 nm.

FIG. 3 shows the results of the life test. Ga of this example
The N phosphor had a luminance remaining ratio of 70% or more even after lapse of 5000 hours when the firing temperature was in the range of 450 ° C. to 550 ° C., which proved to be good as a phosphor for FED.
This is considered to indicate that the decrease in the emission amount is small, and that the luminous efficiency, which indicates the deterioration of the phosphor itself, hardly deteriorates.

Table 1 shows the AE of the surface of the GaN phosphor of this example.
The results of S analysis are shown for each firing temperature. From this result, 55
It can be seen that if the temperature is 0 ° C. or lower, the oxidation of the phosphor surface can be suppressed. This temperature is a value within the effective firing temperature range.

[0026]

[Table 1]

Table 2 shows the AES of the cathode surface after the life test.
The results of the analysis are shown. "No Life" indicates that the sample is after the life test. According to this, when the Y ₂ SiO ₅ : Ce phosphor is used as the oxide phosphor as a comparative example, it is found that oxygen increases after the life test.
On the other hand, in the GaN phosphor of this example, an increase in harmful oxygen is small even at the firing temperature of 600 ° C., and no increase is observed at 500 ° C. which is a value within the effective firing temperature range.

[0028]

[Table 2]

When the GaN phosphor of this example was mounted on a VFD having a filament cathode and evaluated in the same manner, a luminance remaining ratio of 70% was obtained in about 10,000 hours.

With respect to the Y ₂ SiO ₅ : Ce phosphor for comparison and the GaN phosphor of this example, the emission and residual ratio of the luminous efficiency after 1000 hours were measured, and Tables 3 and 4 were obtained.
It was shown to. Here, the current density at the time of driving is not a value under practical driving conditions, but is 0.4 μm lower than that under normal use.
It was changed from A / cm ² to 400 μA / cm ² which was higher. As is evident from the results, the GaN phosphor of this example shows little degradation even at a high current density, and is particularly excellent in use at a current density of 5 mA / cm ² or more. It is possible to realize. When a display is performed with a drive voltage of 1 kV or less, sufficient brightness cannot be obtained based on the brightness of the room when the current density is 1 mA / cm ² or less.

[0031]

[Table 3]

[0032]

[Table 4]

(2) Example 2 (GaInN: Mg phosphor) In the same manner as in Example 1, Ga_TwoS_Three0.7 mol,
In_TwoS_Three0.3 mol as the base material,
MgCl as a raw material for supplying Mg _TwoFor
These are NH_ThreeNitting at 1000 ° C in an air stream
And can be obtained by

In the same manner as in Example 1, a prototype FED was manufactured to evaluate the light emitting state of the phosphor. As a result, blue-green light was emitted. In addition, the same experiment as in Table 3 of Example 1 was performed on the GaInN: Mg phosphor of this example and the Y ₃ Al ₅ O ₁₂ : Tb phosphor produced as a trial for comparison. As in Example 1,
The phosphor of this example is also less deteriorated at a high current density, and is particularly excellent in use at a current density of 5 mA / cm ² or more. By using this, a highly reliable FED can be realized. .

(3) Example 3 (GaInN: Zn, Si phosphor) TMGa, NH ₃ and TMIn (trimethylindium) as raw materials, DEZn (diethyl zinc) and silane (SiH ₄ ) as dopants, and serve as nuclei. AlN having an average particle size of 0.5 μm was used as a powder, and a phosphor was grown on this surface. The growth method is as follows. A Si wafer on which AlN is placed is set in a vacuum chamber to 800 ° C. at a temperature of the Si wafer by lamp heating, and the inside of the vacuum chamber is set to 40 torr.
r, TMG is 5 μmol / min, TMIn
Is 20 μmol / min and NH ₃ is 0.08 mol / m
Inflow, each of the above materials as a dopant is 0.5 μm
ol / min and GaIn is applied to the surface of the AlN particles.
_0.6 N: Zn, Si was grown. Put this in nitrogen 6
Annealing was performed at 50 ° C. to produce a phosphor.

Evaluation was made in the same manner as in each of the above Examples. As a result, yellow luminescence was obtained, and no deterioration was observed even after a life test of 1,000 hours.

(3) Example 4 (Ga _0.2 In _0.8 N: Z
n, a Ga ₂ S ₃ 0.2 mol of the Si phosphor) In ₂ S ₃ 0.8mol the raw material KataHiroshi, ZnCl ₂ and polysilazane (Si, N,
H) as a dopant, nitrided and Ga
_{A 0.2} In _0.8 N: Zn, Si phosphor was produced.

Evaluation was made in the same manner as in each of the above Examples, and red light emission was obtained. Also, 400V, 1/24
0 Duty, 75 mA / cm ² (same average current 300 μA
/ Cm ² ) and no deterioration was observed in the life evaluation of 500 hours.

In the first to fourth embodiments described above, F
The phosphor screen of the ED was constituted by a phosphor layer which was an aggregate of phosphor particles. However, in the case of a thin film of a phosphor, that is, a film in which the phosphor is bonded at the atomic or molecular level, the surface area of the FED is smaller than that of a simple phosphor layer. And the amount of gas adsorbed on the surface is reduced.

(5) Embodiment 5 (Ga _{1 -x} In _x N: A, B
5 is an example of a color graphic FED having three emission colors of RGB using phosphors. However, 0 ≦ x ≦ 0.9,
A is selected from the group consisting of Zn and Mg, and B is selected from nothing and Si and Ge. )

The substrate shown in FIG. 4 is a MgAl ₂ O ₄ substrate,
It is on a sapphire substrate or a SiO ₂ / Si substrate. On this substrate, Ga _1-x In _x N: A, B phosphor is formed. At this time, thin films of three phosphors having different compositions are formed in a certain order in a strip shape by periodically changing the value of X. By changing the value of X, Ga _1-X In _X N:
The emission colors of the A and B phosphors also change. For example, blue at X = 0,
Green at X = 0.4 and red at X = 0.8-0.9. Thus, a color graphic FED composed of repetitions of three beautiful patterns of R (red), G (green), and B (blue)
Phosphor screen (thin film) can be formed.

In order to form the above-mentioned phosphor thin film, the amount of In is adjusted to three levels by using a mask vapor deposition method. The substrate on which the phosphor thin film is formed is directly mounted in a vacuum-tight container. Alternatively, the substrate is fixed on the inner surface of the anode substrate constituting the envelope of the display element, connected to the external terminal electrodes, and mounted in a vacuum-tight container.

As a method of growing a phosphor thin film on a substrate, there is a selective MOCVD method or the like. MOCVD
The GaN film grown by the method can be obtained by implanting a necessary amount of a doping material in a required pattern by a mask ion implantation method in a required pattern.

In each of the embodiments described above, the phosphor of the present invention is applied to the FED having the cone-shaped emitter made of Mo. However, the phosphor of the present invention can be applied to a light emitting element having another configuration. is there. For example, surface conduction type FEC, SC
The present invention is also applicable to a cold cathode electron source such as an E element and a MIM (metal ice rate metal) element.

Further, in addition to a cold cathode electron source such as an FED, the phosphor of the present invention can be applied to a tungsten filament, an oxide filament, an oxide-coated electron gun, and the like.

[0046]

According to the FED of the present invention, the light emitting portion has a phosphor containing, as components, Ga, which has a low vapor pressure and is hardly decomposed, and N, which is hard to react with the cathode. Therefore, even in a display device having a low voltage and a high current density, such as an FED, a phosphor is less likely to be decomposed than a CRT. Is obtained.

In particular, the phosphor is preferably made of Ga _1-x In
_xN : A, B (where 0 ≦ x ≦ 0.9, where A is Zn and Mg
Is selected from the group consisting of
e. ), An FED that emits light of each color from blue to red can be made by changing the composition of Ga and In by changing X.

[Brief description of the drawings]

FIG. 1 is a sectional view of an FED in each example of the present invention.

FIG. 2 shows the relationship between the firing temperature of the phosphor and the initial luminance in Example 1.

FIG. 3 shows the results of a life test at different firing temperatures of the phosphor in Example 1.

FIG. 4 shows three types of Ga _{1 -X} In _X N having different values of _X :
FIG. 13 is a perspective view of a substrate of Example 5 in which A and B phosphors are formed in a thin-film strip shape.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cathode substrate 2 Field emission cathode (FEC) 10 Anode substrate 11 Anode 12 Anode conductor 13 Phosphor layer

Claims (5)

[Claims] 1. A cathode substrate having a field emission cathode formed on an inner surface thereof and an anode substrate having an anode having a phosphor screen made of a phosphor formed on an inner surface thereof at a predetermined interval. A field emission display device in which gaps at respective outer peripheral portions of the anode substrate are sealed, wherein the phosphor is a gallium nitride-based phosphor. 2. The field emission display device according to claim 1, wherein said phosphor screen is a thin film of said phosphor. 3. The field emission display device according to claim 1, wherein the phosphor screen is a phosphor layer composed of an aggregate of the phosphor particles. 4. The field emission display device according to claim 1, wherein the gallium nitride-based phosphor is represented by the following formula. Ga _1-x In _x N: A, B where 0 ≦ x ≦ 0.9, A is selected from the group consisting of Zn and Mg, B is selected from nothing and Si and Ge. 5. An anode having a voltage of 1 kV or less and an anode current of 2 kV.
^2. The field emission display device according to claim 1, wherein the device is used at 0 μA / cm ² or more.