JP2003242911A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device capable of reducing a damage caused by a discharge. <P>SOLUTION: A front substrate 2 of the image display device has a phosphor surface 6 including a phosphor layer and a light shielding layer 22, and a metal back layer 7 composed of a conductive film superposed on the phosphor layer. A plurality of electron emitting elements emitting electron against the phosphor layer are arranged to a back base plate arranged so as to face the front base plate. The metal back layer is divided into a plurality of regions of which, the sheet resistance is not less than 10 Ω/square. <P>COPYRIGHT: (C)2003,JPO

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 flat image display device using electron-emitting devices.

[0002]

2. Description of the Related Art In recent years, as a next-generation image display device, development of a flat image display device in which a large number of electron-emitting devices (hereinafter referred to as "emitters") are arranged and arranged so as to face a phosphor screen has been under way. Although there are various types of emitters, all of them basically use field emission, and a display device using these emitters is generally called a field emission display (hereinafter, referred to as FED). ing. A display device using a surface conduction type emitter among FEDs is a surface conduction type electron emission display (hereinafter referred to as SED).
SED is also referred to as “SED” in the present application.
The term "FED" is used as a general term including ".

The FED generally has a front substrate and a rear substrate which are arranged to face each other with a predetermined gap therebetween, and these substrates are vacuumized by bonding their peripheral portions to each other via a rectangular frame-shaped side wall. It constitutes the envelope. The inside of the vacuum container is maintained at a high vacuum with a degree of vacuum of about 10 ⁻⁴ Pa or less. Further, in order to support the atmospheric pressure load applied to the back substrate and the front substrate, a plurality of support members are arranged between these substrates.

A phosphor screen including red, blue and green phosphor layers is formed on the inner surface of the front substrate, and a large number of emitters for emitting electrons to excite the phosphors to emit light are provided on the inner surface of the rear substrate. Has been. Also, a large number of scanning lines and signal lines are formed in a matrix and connected to each emitter.

An anode voltage is applied to the phosphor screen, and the electron beam emitted from the emitter is accelerated by the anode voltage and collides with the phosphor screen, whereby the phosphor emits light and an image is displayed.

In such an FED, the gap between the front substrate and the rear substrate can be set to several millimeters or less, and compared with a cathode ray tube (CRT) currently used as a display of a television or a computer at present, It is possible to achieve weight reduction and thickness reduction.

[0007]

In order to obtain practical display characteristics in the FED constructed as described above,
It is necessary to use the same phosphor as in a normal cathode ray tube, and further to use a phosphor screen on which an aluminum thin film called a metal back is formed. In this case, the anode voltage applied to the phosphor screen is at least several kV, and preferably 10 kV.
It is desirable to do the above.

However, the gap between the front substrate and the rear substrate cannot be increased so much from the viewpoint of resolution and characteristics of the supporting member, and it is necessary to set the gap to about 1 to 2 mm.

Therefore, in the FED, it is unavoidable that a strong electric field is formed in the small gap between the front substrate and the rear substrate, and discharge (dielectric breakdown) between both substrates becomes a problem.

When discharge occurs, a current of 100 A or more may momentarily flow, which may cause destruction or deterioration of the emitter or phosphor screen, or even destruction of the drive circuit. These are collectively referred to as discharge damage. The discharge that leads to the occurrence of such a defect is not allowed as a product. Therefore, in order to put the FED into practical use, it must be constructed so that damage due to discharge does not occur over a long period of time. However, it is very difficult to completely suppress the discharge over a long period of time.

On the other hand, instead of preventing the discharge from occurring, it is possible to consider a measure to suppress the scale of the discharge so that the influence on the emitter can be ignored even if the discharge occurs. As a technique related to such an idea, for example, Japanese Patent Laid-Open No.
Japanese Patent Application Laid-Open No. 000-311642 discloses a technique in which a metal back provided on the phosphor screen is provided with a notch to form a pattern such as a zigzag pattern to increase the effective inductance / resistance of the phosphor screen. However, as a result of various studies, this technology can reduce the discharge scale, but its effect is limited, and it is difficult to completely suppress discharge damage over a long period of time. I understood it.

Further, Japanese Patent Laid-Open No. 10-326583 discloses a technique for dividing a metal back, and further, Japanese Patent Laid-Open No. 2000-2000.
Japanese Patent Publication No. 251797 discloses a technique in which a coating of a conductive material is provided on a divided portion in order to suppress creeping discharge at the divided portion. However, it is difficult to sufficiently suppress the discharge damage even by these techniques.

The present invention is intended to solve such a problem, and an object thereof is to sufficiently reduce the scale of discharge and prevent the destruction and deterioration of the emitter and the fluorescent screen and the destruction of the circuit. It is to provide a possible image display device.

[0014]

In order to solve the above-mentioned problems, an image display device according to an aspect of the present invention is a conductive thin film provided so as to overlap a fluorescent screen including a fluorescent layer and a light-shielding layer and the fluorescent screen. A front substrate having a metal back layer made of, and being arranged to face the front substrate,
A rear substrate on which a plurality of electron-emitting devices that emit electrons toward the phosphor screen are arranged, the metal back layer is divided into a plurality of regions, and a sheet resistance is formed to 10 Ω / □ or more. .

An image display device according to another aspect of the present invention has a phosphor screen including a phosphor layer and a light-shielding layer, and a metal back layer formed of a conductive thin film provided on the phosphor screen. A front substrate; and a rear substrate that is arranged to face the front substrate and on which a plurality of electron-emitting devices that emit electrons toward the phosphor screen are arranged. Formed in a zigzag pattern having a plurality of linear portions arranged with a gap of, and a plurality of folded portions connecting ends of adjacent linear portions,
The sheet resistance of the metal back layer is 10 Ω / □ or more.

According to the image display device having the above structure, the anode voltage can be increased and the gap between the front substrate and the rear substrate can be reduced, and the image display with improved display characteristics such as brightness and resolution can be achieved. The device can be obtained. Further, as the anode voltage is lower, the deterioration of the phosphor becomes more problematic. However, since the anode voltage can be set higher as described above, the deterioration of the phosphor can be alleviated and the life of the product can be extended.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an FED to which the present invention is applied will be described below in detail with reference to the drawings. As shown in FIGS. 1 and 2, this FED includes a front substrate 2 and a rear substrate 1 each made of rectangular glass, and these substrates are arranged facing each other with a gap of 1 to 2 mm. The front substrate 2 and the rear substrate 1 are joined together at their peripheral edge portions via the rectangular frame-shaped side walls 3, and the inside thereof is a flat rectangular vacuum envelope maintained at a high vacuum of about 10 ⁻⁴ Pa or less. It constitutes the container 4.

A fluorescent screen 6 is formed on the inner surface of the front substrate 2. As will be described later, the phosphor screen 6 is composed of a phosphor layer that emits red, green, and blue lights and a matrix-shaped black light-shielding layer. The phosphor layer is formed in a stripe shape or a dot shape. A metal back layer 7 that functions as an anode electrode is formed on the phosphor screen 6. During the display operation, a predetermined anode voltage is applied to the metal back layer 7.

On the inner surface of the rear substrate 1, a large number of electron emitting elements 8 for emitting an electron beam for exciting the phosphor layer are provided. These electron-emitting devices 8 are arranged in a plurality of columns and a plurality of rows corresponding to each pixel. The electron-emitting device is driven by matrix wiring (not shown).

Between the rear substrate 1 and the front substrate 2, a large number of plate-like or columnar spacers 10 are arranged for atmospheric pressure resistance. An anode voltage is applied to the phosphor screen 6 via the metal back layer 7, and the electron beam emitted from the electron-emitting device 8 is accelerated by the anode voltage and collides with the phosphor screen 6. As a result, the corresponding phosphor layer emits light and an image is displayed.

Next, the phosphor screen 6 and the metal back layer 7 in the FED will be described in detail. As shown in FIGS. 3 and 4, the phosphor screen 6 provided on the inner surface of the front substrate 2 has a black light shielding layer 22. The black light shielding layer 22 is formed of, for example, a large number of stripe portions 22 a arranged in parallel with a predetermined gap and a rectangular frame portion 22 b extending along the peripheral edge of the phosphor screen 6. Also, the fluorescent screen 6
Are a large number of phosphor layers R each of which is formed between the stripe portions 22a of the black light shielding layer 22 and emits red, blue, and green.
It has G and B.

The metal back layer 7 formed on the phosphor screen 6 is formed as a resistive split metal back layer. That is, the metal back layer 7 is the black light shielding layer 22.
Is divided into a large number of divided regions 7a at positions facing the striped portions 22a, and each divided region 7a is formed in an elongated stripe shape corresponding to the black light shielding layer 22. And
These divided regions 7a functioning as high resistance regions are provided on the phosphor screen 6 so as to overlap the phosphor layers R, G, B, and extend in parallel to each other with a predetermined gap. As a result, a region of the metal back layer 7 that overlaps the black light shielding layer 22 becomes a gap, and most of the black light shielding layer is exposed. If necessary, another material layer may be formed in the gap 7b between the divided areas 7a. The metal back layer 7 is formed to include a terminal portion 30 for energizing the metal back layer.

The metal back layer 7 is formed by a thin film process such as vapor deposition. At this time, since the phosphor screen 6 has irregularities, if the metal back layer 7 is directly formed on the phosphor screen 6, a mirror surface cannot be formed. Therefore, a method of performing vapor deposition after performing smoothing treatment with a lacquer or the like is well known. As another method, a method in which a sheet on which aluminum is vapor-deposited is transferred by heating can be used. The thickness of the metal back layer 7 is preferably about 50 to 200 nm in consideration of electron beam transmissivity and film strength.

To form the dividing pattern, a method of masking at the time of film formation, a method of forming an undivided film and then dividing with a laser can be used.

Although the term metal back layer is used, in the present invention, the material is a simple metal.
It is not limited to. However, in the description of this embodiment, the term metal back layer is used for convenience.

In the present embodiment, metal back layer 7 is formed of a conductive film made of a material having a higher resistance than aluminum. Sheet resistance is 1 for aluminum
Ω / □ or less, but 10 in the present embodiment
Set to Ω / □ or higher. As a material for this purpose, a metal having high resistance such as nichrome is a candidate. 10
Compared with the volume resistivity at 0 ° C., aluminum is 3.
55E-8Ω ・ m, whereas Nichrome has 108E
It is −8 Ω · m, which is about 30 times. Therefore, a metal back having a sheet resistance of 10Ω / □ or more can be realized.

However, when used as a metal back, if a material having a high density such as nichrome is used, the amount of electrons transmitted is reduced, resulting in a large loss of brightness.
In addition, the heavier atoms have a larger amount of scattered electrons, which lowers the contrast. Therefore, practically, there are many problems in using a metal such as nichrome. As a result of examination, an alloy having a low density and a high resistance could not be found.

Then, as a result of further study on the material which meets such purpose, the possibility of using a film in which a metal and an insulating material are mixed is found. Such a film is well known as a cermet and is also used industrially as a resistance material, but it is limited to a specific metal such as Cr-SiO. No match was found. For the purpose of this time, it is preferable to use aluminum as a base from the viewpoint of density. Therefore, as a result of conducting experiments on a mixed film of aluminum and Al ₂ O ₃ , the sheet resistance was 1E3Ω / □.
It was found that a metal back layer up to a certain degree can be formed. If it is made higher than this, the resistance suddenly rises and becomes insulating, so it seems that a film having the same resistance cannot be stably formed.

Since it is difficult to theoretically derive the sheet resistance required to enhance the discharge effect, the following experiments were conducted. The experiment has a diagonal size of 36
Performed using an inch SED. By using a metal mask when depositing the metal back layer, the pitch is about 1.2.
A metal back layer divided by mm was formed. By controlling the resistance value of the black light shielding layer 22, the resistance between the divided metal backs was set to 10 kΩ. Sheet resistance of metal back layer is 1, 3, 10, 30, 100Ω /
The SEDs were changed to □ and 300Ω / □, discharge was caused by increasing the high voltage above a predetermined voltage, and the presence or absence of discharge damage at that time was evaluated. Since the same discharge does not occur every time, discharge was generated 10 times, and the number of discharge damages to the electron-emitting device was defined as the discharge damage index. The results are shown in Table 1. Regarding the damage to the phosphor screen and the damage to the circuit, neither was observed because the discharge scale was already made considerably smaller by dividing the metal back layer.

[0030]

[Table 1]

As described above, with aluminum, the discharge damage could not be completely suppressed, but it was confirmed that the discharge suppression effect was enhanced by increasing the sheet resistance to 10 Ω / □ or more. The reason why the sheet resistance is not effective when it is less than 10 Ω / □ has not been completely explained, but it is considered as follows. When the metal back layer is divided,
The resistance RS of the divided strip-shaped metal back is expressed by RS = ρs · L / d. Here, ρs, L, and d are the sheet resistance, length, and width of the metal back, respectively. In this experiment,
L / d = 2E3. Therefore, when ρs = 10Ω, RS = 20 kΩ.

According to the electric circuit simulation,
When RS is about 10 kΩ or less, the divided metal back can be treated as having substantially the same potential on the discharge time scale, and the potential distribution in the length direction is very small. When RS increases, a potential distribution also occurs in the length direction of the metal back at the time of discharging, and the function of suppressing the discharge current can be expected. The result of this experiment corresponds to such a simple study, and the sheet resistance is 10Ω /
□ The above can be judged to be the required sheet resistance from the viewpoint of the effect of suppressing discharge.

In this experiment, aluminum and A
Although a mixed film of l ₂ O ₃ was used, the insulating material was Al.
_In addition to ₂ O ₃ , various materials such as SiO ₂ and TiO ₂ can be used. For metals, from the point of view of density,
Aluminum is preferred, but other metals such as titanium or other metals can be used.

According to the second embodiment shown in FIG. 5, the metal back layer 7 is formed as a resistive patterned metal back layer. That is, the metal back layer 7 is
It is formed in a zigzag pattern formed by folding a long and thin strip-shaped conductive thin film into a bellows shape. This zigzag pattern has a large number of elongated striped linear portions 7c that extend in parallel with each other with a predetermined gap, and a plurality of folded portions 7d that connect the ends of adjacent linear portions.

The linear portion 7c and the folded portion 7d functioning as the high resistance region are provided on the phosphor screen 6 with the phosphor layer R,
It is provided so as to overlap G and B. A region of the metal back layer 7 that overlaps with the black light shielding layer 22 is a gap, and most of the black light shielding layer is exposed.

In the present embodiment, the metal back layer 7
Is formed of a conductive film made of a material having a higher resistance than aluminum. Sheet resistance is 1 for aluminum
Ω / □ or less, but 10 in the present embodiment
Set to Ω / □ or higher. As a material for this, a mixed film of metal and an insulating material can be used as in the first embodiment.

Also in the present embodiment, since it is difficult to theoretically derive the sheet resistance required to enhance the discharge effect, the following experiments were conducted.

The experiment was carried out by using an SED having a diagonal size of 36 inches.
Was performed using. By using a metal mask when depositing the metal back layer, a metal back layer formed in a zigzag pattern with a pitch of about 1.2 mm was formed. By controlling the resistance value of the black light shielding layer 22, the resistance between the divided metal backs was set to 20 kΩ. Sheet resistance of the metal back layer is 1, 3, 10, 30, 100Ω / □,
An SED having a value of 300Ω / □ was manufactured, and discharge was caused by increasing the high voltage above a predetermined voltage, and the presence or absence of discharge damage at that time was evaluated. Since the same discharge does not occur every time, the discharge was generated 10 times, and the number of times the emitter was damaged by discharge was defined as the discharge damage index. The results are shown in Table 2. Regarding the damage to the fluorescent screen and the damage to the circuit, neither of them was observed because the discharge scale had already been considerably reduced by dividing the metal back layer.

[0039]

[Table 2]

As described above, with aluminum, the discharge damage could not be suppressed, but it was confirmed that the discharge suppression effect was enhanced by increasing the sheet resistance to 10 Ω / □ or more.

Besides, the present invention is not limited to the above-mentioned embodiments, but can be variously modified within the scope of the present invention. For example, the dimensions and materials of each component are not limited to the numerical values and materials shown in the above-mentioned embodiment,
Various selections can be made as necessary.

[0042]

As described above, according to the present invention,
Even when discharge occurs between the front substrate and the rear substrate, the discharge current at that time can be sufficiently suppressed, so that it is possible to provide an image display device in which damage due to discharge does not occur.

[Brief description of drawings]

FIG. 1 is a perspective view showing an FED according to an embodiment of the present invention.

2 is a cross-sectional view of the FED taken along line AA of FIG.

FIG. 3 is a plan view showing a phosphor screen and a metal back layer of a front substrate in the FED.

FIG. 4 is a cross-sectional view taken along the line BB in FIG.

FIG. 5 is a plan view showing a phosphor screen and a metal back layer of a front substrate in an FED according to a second embodiment of the present invention.

[Explanation of symbols]

1 ... Rear substrate 2 ... Front substrate 3 ... Side wall 4 ... Vacuum envelope 6 ... Phosphor screen 7. Metal back 7a ... divided area 7b ... Gap 7c ... Straight part 7d ... Folding part 8 ... Electron emitting device 22 ... Black light shielding layer 22a ... Stripe section 22b ... frame-shaped portion

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yuji Haraguchi             2 shares, 1-9-1 Harara-cho, Fukaya City, Saitama Prefecture             Company Toshiba Fukaya Factory F term (reference) 5C036 BB04 EE09 EG36 EH08 EH09

Claims (3)

[Claims] 1. A front substrate having a phosphor screen including a phosphor layer and a light-shielding layer, and a metal back layer made of a conductive thin film, which is provided so as to overlap the phosphor screen, and is arranged to face the front substrate. And a rear substrate on which a plurality of electron-emitting devices that emit electrons toward the phosphor screen are arranged, the metal back layer is divided into a plurality of regions, and the sheet resistance of the metal back layer is An image display device having a resistance of 10 Ω / □ or more. 2. A front substrate having a phosphor screen including a phosphor layer and a light-shielding layer and a metal back layer made of a conductive thin film, which is provided so as to overlap the phosphor screen, and is arranged to face the front substrate. And a rear substrate on which a plurality of electron-emitting devices that emit electrons toward the phosphor screen are arranged, and the metal back layer has a plurality of linear portions arranged with a predetermined gap, An image display device, which is formed in a zigzag pattern having a plurality of folded portions in which ends of adjacent straight portions are connected to each other, and in which the sheet resistance of the metal back layer is 10 Ω / □ or more. 3. The image display device according to claim 1, wherein the metal back layer is formed of a mixed film of metal and an insulator.