JP2002208366A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diminish a discharge scale and prevent damage or degradation of an electron emission element and a fluorescent screen in a flat-screen image device using an electron emission element. SOLUTION: With the image display device provided with a face plate having a fluorescent screen containing a phosphor layer, and a rear plate having a plurality of electron emission elements and arranged opposite to the face plate, a resistive membrane is formed on the side the rear plate of the phosphor layer. Its sheet resistance is desired to be not less than 102 Ω/(square). Further, in an ordinary case, fluorescent screen resistance is to be not less than 102 Ω/(square).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device, and more particularly to a structure of a fluorescent screen of a flat type image display device using an electron-emitting device.

[0002]

2. Description of the Related Art In recent years, as a next-generation image display device, a flat-type image display device in which a large number of electron-emitting devices (hereinafter, referred to as emitters) are arranged and arranged to face a phosphor screen has been developed. There are various types of emitters, all of which basically use field emission. These display devices are generally known as FED (Field Emission).
Display). Among them, the display device using the surface conduction type emitter is distinguished from the FED by the SE.
D (Surface conductionselect)
(Emission Display), but in the present invention, FE is a general term including SED.
The term D is used.

FIG. 2 shows the basic structure of an FED. Substrate 21
A rear plate (hereinafter abbreviated as RP as appropriate) 23 on which an emitter layer 2 on which a number of emitters are arranged is formed.
A face plate (hereinafter, appropriately abbreviated as FP) 26 having a fluorescent screen 25 formed on a substrate 24 is disposed opposite to the substrate 24. The substrates 21 and 24 have a thickness of 1 to 3 m.
m glass plate. The rear plate 23 and the face plate 26 are joined at the peripheral edge by a frame-shaped side wall 27 to form a vacuum container. The inside of the vacuum vessel is maintained at a high vacuum having a degree of vacuum of about 10 ⁻⁴ Pa or less. A plurality of spacers (not shown) for withstanding atmospheric pressure are provided between the rear plate 23 and the face plate 26.
Are arranged to avoid the trajectory of the electron beam.

A matrix wiring (not shown) is connected to the emitter, and is driven by a video signal. When performing color display, pixels consisting of R, G, and B are formed on the phosphor screen so as to correspond to the emitters. An anode voltage is applied to the phosphor screen, and an electron beam emitted from the emitter is accelerated by the anode voltage and collides with the phosphor screen to emit light, thereby displaying an image.

[0005] There are a low voltage type and a high voltage type in the basic configuration of the FED. For low voltage type, gap between RP and FP (h)
Is about 0.1 to 0.5 mm, and the anode voltage (Va) applied to the phosphor screen is about 1 kV or less. In this configuration, the luminous efficiency and the life of the phosphor are regarded as major practical problems.

Therefore, a high voltage type uses a phosphor for CRT having high luminous efficiency and a phosphor screen on which a metal back is formed. Here, the metal back refers to a metal thin film formed on the back side (RP side) of the phosphor layer, reflects light from the phosphor, improves luminance, and secures conductivity of the phosphor screen. And a function of preventing deterioration of the phosphor due to ion collision, and preventing low energy electrons to improve contrast. The film thickness is preferably as small as possible from the point of the electron transmittance, but it is necessary to increase the film thickness to some extent from the viewpoint of light reflectance and film strength, and is appropriately selected in the range of 10 to 100 nm. .

In order to use such a phosphor screen, the anode voltage (Va) must be at least 4 kV or more.
Preferably, the voltage is set to 8 kV or more. for that reason,
The gap (h) between RP and FP needs to be a value that does not cause discharge at such a high voltage. However, since the electron beam spreads as h increases, there is a limit to increasing h in terms of resolution. Also,
Since the spacer needs to have a very small width of about 0.05 to 0.3 mm, when h becomes large, difficulty in production and strength increases. Further, there is a problem that the trajectory of the electron beam deviates from the original trajectory when the spacer is charged, but this also increases as h increases. Considering these constraints, the gap (h) between RP and FP is 2
mm or less is desired.

As described above, in the FED, it is desired to apply as high a voltage as possible between gaps as small as possible. Therefore, countermeasures against discharge (dielectric breakdown) are important issues. When a discharge occurs, a current of several tens of A or more may flow instantaneously, and destruction or deterioration of the emitter or the phosphor screen may occur. Further, a circuit for operating the FED may be broken. Hereinafter, these are collectively referred to as damage due to discharge. In order to put the FED into practical use as a product, it is necessary to at least prevent such a discharge that causes such damage.

For this purpose, there are roughly two approaches. The first is to prevent discharge from occurring. Generally, the discharge voltage of a vacuum discharge has a broad distribution, and below a certain threshold voltage, the probability of occurrence of the discharge becomes so small as to be negligible. To prevent the discharge from occurring is, in other words, to make the anode voltage smaller than this threshold value. Raising the threshold can be divided into raising the average discharge voltage and reducing the variation in the discharge voltage.Hereafter, these will be collectively referred to as simply increasing or improving the breakdown voltage. .

[0010] The breakdown voltage is determined by the structure, material, manufacturing process, and the like of the FP and RP. However, there is not much freedom to change these, and what can be done to increase the breakdown voltage is limited. In particular, with regard to FP, since a metal back having a low strength becomes the facing surface, peeling of the metal back is a great restriction on the withstand voltage. Further, the discharge may be triggered by the collision of the particles with the opposing surface, but it is difficult to completely eliminate the particles in a practical manufacturing process. Further, creeping discharge at the spacer for supporting the atmospheric pressure is also a problem.

As described above, several problems are involved in the breakdown voltage of the FED, and it is not easy to improve it.
Attempting to reduce the discharge probability to a practical level by lowering the anode voltage or increasing the gap at the current withstand voltage level sacrifices resolution, brightness, and the like, thereby deteriorating the practicality.

The second is to reduce the magnitude of the discharge so that, even if the discharge occurs, the emitter and the phosphor screen are not destroyed or deteriorated or the circuit is destroyed. As a technique therefor, a technique of inserting a resistance or an inductance between an anode power supply and an anode is well known. However, in the case of the FED, since the capacitance of the capacitor formed by the panel itself is considerably large at 10 ³ to 10 ⁴ pF, even if an external impedance is provided, the accumulated charge of these capacitors is prevented from becoming a discharge current. The effect of such a method cannot be expected very much.

[0013] In this connection, in CRTs, a technique for suppressing the magnitude of discharge called soft flash is widely used. On the inner and outer surfaces of the funnel of the CRT, conductive films called inner and outer dogs are formed, respectively. In a CRT, the discharge occurs between the electrodes of the electron gun, but the supply of the anode voltage to the electron gun is performed through the inner tag. Therefore, at the time of discharging, not only the accumulated charge between the electron gun and the electrode, but also the inner tag and the outer tag. The electric charge accumulated in the capacitor formed by the above can be a discharge current.

Therefore, the magnitude of the discharge is reduced by appropriately increasing the resistance value of the doug. In this case, when viewed from the electron gun electrode, the external resistance is included, but not only that, but the characteristic is that the resistance value of the facing surface of the capacitor related to discharge is increased. This is also a technique that can only be achieved with a CRT.
Not applicable to

As described above, it is very difficult to prevent a discharge from occurring in the FED, and measures to reduce the magnitude of the discharge are strongly desired. The method could not be applied.

[0016]

As described above, F
In the ED, a discharge countermeasure is important, but there is a limit to a countermeasure for preventing a discharge, and it is difficult to apply a countermeasure for reducing the scale of the discharge to eliminate the damage. If the anode voltage is lowered or the gap between FP and RP is widened, there is a possibility that discharge can be suppressed, but in that case, performance such as brightness and resolution must be sacrificed, and the performance desired as a product Was difficult to meet.

The present invention is intended to solve these problems. In the FED, the size of the discharge is reduced or the discharge itself is hardly caused, and the breakdown and deterioration of the emitter and the phosphor screen and the breakdown of the circuit are caused. The aim is to provide technology that will not.

Further, this technique makes it possible to increase the anode voltage and reduce the gap between the FP and the RP as compared with the conventional assumption, so that the performance such as brightness and resolution can be improved. Will be able to Further, when the anode voltage is low, the life of the phosphor, in which the luminance of the phosphor deteriorates with time, becomes a problem. By increasing the anode voltage, the life of the phosphor can be extended.

[0019]

In order to solve the above problems, the present invention provides a face plate having a phosphor screen including a phosphor layer, and a plurality of electron-emitting devices arranged to face the face plate. And a rear plate formed with a resistive film on the rear plate side of the phosphor layer. Its sheet resistance is 10 ²
Ω / □ or more is preferred. More generally, the phosphor screen resistance is set to 10 ² Ω / □ or more.

[0020]

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

FIG. 1 shows an FE according to an embodiment of the present invention.
The enlarged view of the fluorescent screen of D is shown. Figure 2 shows the basic structure of FED.
And the description is omitted.

On the inner surface of the glass translucent substrate 1, a black material layer 2 usually called a black matrix or a black stripe is formed in a predetermined arrangement.
The black material layer 2 absorbs external light to increase contrast,
It has a role of hiding the boundary of the phosphor and hiding the spacer. The phosphor layer 3 is formed between the black material layers 2. Phosphors of three colors of red, green and blue are arranged in the phosphor layer 3 in a predetermined arrangement. On the black material layer 2 and the phosphor layer 3, a resistive metal back layer 4 is formed. Although the term metal back layer is used,
In the present invention, the material is not limited to metal.
However, in the following description, this term, which is widely used for convenience, will be used even when a nonmetal is used.

Generally, aluminum is used for the metal back layer for the following reason. That is,
Since the metal back layer needs to reflect the light of the phosphor, it is necessary that the metal back layer has a reflectance as high as possible. Although it is necessary to transmit electrons as much as possible, the range of the electrons is almost proportional to the density, so that it is necessary to use a material having a low density. Even if a material having a high density is used, if the film thickness is reduced, the electron transmittance can be secured, but the film strength, the reflectance, the uniformity of the film, etc. are sacrificed, and the aluminum density (2.7 g / cm ³ ) It is difficult to use a material larger than the extent. In addition, since the phosphor is usually insulative, the metal back layer plays the role of passing the beam current and must be a conductor. Further, the cost must be low. Considering these conditions, it is considered inevitable to use aluminum, and in fact, in CRTs, aluminum is used in all products.

However, in the FED, measures against discharge are extremely important issues, and it is strongly desired to introduce measures to reduce the magnitude of discharge. The present inventors have paid attention to the fact that the metal back layer has a low resistance, and as a result of studying to overcome this limitation, it is possible to increase the resistance of the metal back layer. ,
As a result, it has been found that the discharge scale can be reduced and damage due to discharge can be eliminated.

Therefore, in the present embodiment, a resistive film is used for the metal back layer 4. Also,
Even if the metal back layer has a high resistance, if a low-resistance material is used for the black material layer 2, the resistance as the fluorescent screen will decrease. Therefore, a material having a high resistance value is also used for the black material layer 2. This makes the phosphor screen as a whole resistant. Here, the term “resistivity” means having a high resistance value that cannot be realized with an aluminum thin film.

As the resistive metal back layer, for example, a film in which a metal and an insulator are mixed can be used.
Such a film is sometimes referred to as a cermet, and a film using a specific material is used in a thin film resistor and various other fields. In the present invention, considering the reason why aluminum is conventionally used for the metal back layer, a material based on aluminum is also preferable. In addition, titanium having a density of 4.5 g / cm ³ can be used.

As a result of the experiment, it was confirmed that when a film in which these metals and various insulating materials were mixed at an appropriate ratio was formed, it was possible to increase the resistance value while securing a certain level of light reflectance. Was.

In the experiment, a flash evaporation method widely used for depositing a mixture was used. This is because when forming a deposited film of a mixture of substances having different melting points, simply placing multiple materials on a heating boat
Since it is difficult to control the mixing ratio, this is a well-known vapor deposition method in which the material is made into a powder and introduced little by little into the heating unit.

For film formation, an electron beam (EB)
Various known thin film forming techniques such as vapor deposition, various types of sputtering, and ion plating can be used.
Further, for example, oxides of aluminum (Al ₂ O ₃ ) and nitrides (AlN) are insulators. Therefore, if they are mixed films with these materials, oxygen or nitrogen is introduced as a gas instead of being supplied as a target. A method for forming a film can be used. Further, the configuration of the film is not limited to the mixture of the metal and the insulator, and it is needless to say that any other configuration may be used.

Now, whether the configuration in which the metal back layer is made to have a resistance actually has the effect of reducing the discharge scale,
Further, in order to clarify whether it is effective for the FED and to determine the appropriate resistance value, the following experiment was performed.

In the first experiment, the screen diagonal diameter was 25 cm.
A (10-inch) VGA-compatible SED was used. FP
Was formed as follows. First, after a black material layer was formed on a glass substrate, R, G, and B phosphor layers were formed by screen printing. The thickness of each of the black material layer and the phosphor layer was set to 15 ± 3 μm, and the roughness was made as small as possible so that a smooth metal back layer was formed. For the black substance layer, a material having a volume resistance of 10 ³ Ω · m was used. With such a value, the electric conduction by the black material layer becomes negligibly small with respect to the resistance value of the metal back layer in this experiment.

Next, after forming a lacquer film on the black material layer, a resistive metal back layer is formed.
Baking was performed at 0 ° C. For the formation of the metal back layer, an aluminum powder and an alumina (Al ₂ O ₃ ) powder were used, and a mixed film of both was formed by a flash evaporation method. The film thickness was controlled in the range of 50 ± 15 nm. By controlling the mixing ratio, a film was formed in which the sheet resistance ρs after firing was changed by a factor of 10 in the range of 1 to 10 ⁵ Ω / □.

The FP thus formed is sealed with the RP, and a prescribed process such as forming and activation is performed.
The ED panel was completed. The RP-FP gap (h) of this panel is 1.5 mm, and the assumed anode voltage (Va) is 7 kV. In contrast, the discharge was forcibly induced by increasing the anode voltage. Two panels were prepared for one resistance value, and five discharges were generated for one panel. In this way, data for ten times was obtained for one resistance value. Each time a discharge occurred, the damage of the emitter, the phosphor screen, and the circuit was confirmed. If none of them was damaged, it was determined that there was no damage, and the number of times was counted. This number was taken as the damage suppression index.
Table 1 shows the results.

In Table 1, the sheet resistance ρs is 1
Ω / □ is the case where the metal back layer is formed only of aluminum. The actual resistance value may have shifted from the target value in the range of 0.5 to 2 times,
Here, the order is a problem, so simply 10 ³
It is written as such.

[0035]

[Table 1]

From the results shown in Table 1, the sheet resistance ρs was 10 ²
Ω / □ or more has the effect of suppressing discharge damage,
It was found that the damage was almost completely suppressed when the resistance was set to 10 ³ Ω / □ or more.

In this experiment alone, there is a possibility that the difference in the physical property value of the film instead of the resistance value is related to discharge suppression.
Therefore, a resistive film was formed by another method, and the following experiment was performed.

In the second experiment, a transparent conductive film was formed ignoring light reflectivity. Others were common to the first experiment. ρs
Are 10 Ω / □ and 10 ² Ω / □, the ITO film formed by the sputtering method is 10 ³ Ω / □ and 1 Ω / □.
0 ⁴ Ω / □ for the ITO film formed by spin coating, 10 ⁵ Ω / □ for, using _SnO 2 + Sb film by sputtering. Table 2 shows the experimental results.

[0039]

[Table 2]

As shown in Table 2, almost the same results as in the first experiment were obtained. From this, it was found that the dependence on the material was small, and the sheet resistance was an important factor for determining the effect.

Next, in order to examine the size dependence, a third experiment was performed in the same manner as the second experiment on an SED panel having a screen diagonal diameter of 76 cm (30 inches). For this panel, the gap (h) is 1.8 mm. In this experiment, the number of panels was only one for each resistance value, and one panel induced 10 discharges.
The experiment was omitted when the sheet resistance ρs was 10 ⁵ Ω / □. Table 3 shows the experimental results.

[0042]

[Table 3]

As shown in Table 3, the same result as in the first and second experiments was obtained in the third experiment. From this, it was confirmed that the dependence on the screen size, that is, the capacity of the panel was small, and the sheet resistance was also an important factor.

From the above experiments, it is found that the discharge damage can be suppressed when the sheet resistance of the metal back layer is set to 10 ² Ω / □ or more, and the discharge damage can be almost completely suppressed when the sheet resistance is set to 10 ³ Ω / □ or more. all right.

These are the experimental results for a specific emitter and a specific dimension. Although the sheet resistance value of the metal back layer of 10 ² Ω / □ or more cannot be completely generalized, the resistance of the metal back layer, and It is clear that if the resistance value of the phosphor screen is set to a high value that cannot be realized by the aluminum thin film, the effect of suppressing the discharge damage and the effect of improving the discharge voltage can be expected. Also,
In proceeding with the above experiment, it was found that when the fluorescent screen was made resistant, the discharge voltage was slightly improved.

In the present embodiment, a configuration in which a resistive material is used for the metal back layer has been described. However, the present invention is not limited to this. For example, a configuration in which the metal back layer is divided into islands may be formed. Conceivable. In this case, from a macro perspective, the sheet resistance becomes infinite. In such a case, a portion where a beam current or a discharge current flows is a black material layer and a phosphor screen, and it is important to control these resistance values. Considering such a case, it is generally effective to set the sheet resistance of the phosphor screen viewed macroscopically (referred to as phosphor screen resistance) to 10 ² Ω / □ or more.

Although the upper limit of the sheet resistance ρs is actually restricted by the flow of a beam current, it is practically possible to set ρs to about 10 ⁵ Ω / □ under normal conditions. Furthermore, what actually relates to the characteristics is
The resistance value is a value in a vacuum after passing through a thermal process, but cannot be measured. Therefore, the resistance value is a value before assembling the panel or a value measured by opening the panel to the atmosphere.

As is clear from the above description, according to the present invention, the scale of the discharge can be reduced by making the metal back layer, generally the fluorescent screen, resistive, and the emitter by the discharge can be reduced. And the destruction and deterioration of the phosphor screen and the destruction of the circuit can be suppressed. Furthermore, it is possible to make the discharge itself difficult to occur, and it is possible to improve not only the measures against the discharge but also the basic performance of the display device.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an embodiment of an image display device of the present invention.

FIG. 2 is a cross-sectional view showing a schematic structure of a general FED.

[Explanation of symbols]

1 translucent substrate, 2 black material layer, 3 phosphor layer, 4 resistive metal back layer

Claims (3)

[Claims] 1. An image display apparatus comprising: a face plate having a phosphor screen including a phosphor layer; and a rear plate having a plurality of electron-emitting devices and disposed opposite to the face plate. An image display device, wherein a resistive film is formed on the rear plate side of a layer. 2. The sheet resistance of the resistive film is 10 ² Ω.
2. The image display device according to claim 1, wherein the value is not less than / □. 3. An image display apparatus comprising: a face plate having a phosphor screen including a phosphor layer; and a rear plate having a plurality of electron-emitting devices and disposed opposite to the face plate. An image display device characterized in that the phosphor screen resistance is 10 ² Ω / □ or more.