JP3207842B2 - Method of manufacturing AC type plasma display panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention relates to the production how the AC type plasma display panel (PDP), in particular characterized by a method of forming the protective film of the dielectric layer.

In an AC type PDP, a pair of electrodes for discharge are covered with a dielectric layer such as a low-melting glass, and a heat-resistant protection is provided on the surface to protect the dielectric layer from ion bombardment during discharge. A membrane is provided.

[0003] Since the protective film is in contact with the discharge space, it greatly affects the discharge characteristics. Therefore, improvement of the protective film is regarded as one of important matters for stabilizing display, facilitating driving, and extending the life.

[0004]

2. Description of the Related Art In general, a PDP is provided with a thin film having a thickness of about several thousand of magnesium oxide (MgO) as a protective film for a dielectric layer.

[0005] Magnesium oxide is a metal oxide having a large secondary electron emission coefficient, and by using this, the firing voltage can be reduced, so that driving can be facilitated.

[0006] Such a magnesium oxide film is formed by a technique of evaporating a film material by, for example, electron beam heating and depositing it on the surface of a dielectric layer in the form of crystal growth, that is, a vapor deposition method.

[0007]

In the conventional PDP, there is a problem that the change in discharge characteristics with time is relatively remarkable.

It is considered that the change with time is caused by the incorporation of impurities such as carbon compounds and hydroxyl groups into the magnesium oxide film during and after the formation of the protective film.
That is, when an organic solvent (carbon compound) is mixed in from the sealing material around the discharge space, magnesium carbonate (MgCO ₃ ) is generated in the magnesium oxide film. Magnesium carbonate undergoes a chemical change due to discharge energy, and carbon monoxide (CO) or carbon dioxide (CO ₂ ) generated by the change is adsorbed on the surface of the magnesium oxide film. The discharge start voltage rises and the display operation becomes unstable.

Further, since CO and CO ₂ tend to collect on discharge cells which do not emit light on the surface of the protective film, the discharge starting voltage of discharge cells having low light emission frequency rises more than others (so-called burn-in). ) Occurs, and the life of the PDP is shortened.

The present invention has been made in view of the above-described problems, and has as its object to suppress a temporal change in discharge characteristics due to a magnesium oxide film for protecting a dielectric layer, thereby stabilizing a display and extending the life. .

[0011]

According to a first aspect of the present invention, there is provided a method of manufacturing an AC type plasma display panel, wherein the oxygen partial pressure is 5 × 10 ^-5 to 1 × 10 ^-4 [Torr].
In a deposition atmosphere mainly composed of oxygen , oxygen
A protective film composed of a <111> oriented film of magnesium oxide is formed on a dielectric layer by an ion assisted vapor deposition method of irradiating an ion beam of a mixed gas of oxygen and argon, mainly comprising

[0012]

According to a second aspect of the present invention, in the ion assisted vapor deposition, the irradiation gas ion current value is set to 5 to 20.
It is set to a value within the range of [mA].

The <111> oriented film of magnesium oxide constituting the protective film of the dielectric layer is a <111> oriented crystal (crystal orientation in the film thickness direction is <111> and a plane parallel to the film plane is {111}. (A crystal on the surface) is a magnesium oxide film that is dominant over other crystals in number, and is formed by ion-assisted vapor deposition with an appropriate ion irradiation amount.

[0015] Such a <111> orientation film is different from a magnesium oxide film of other film quality, that is, a specific crystal orientation does not become dominant over other crystal orientations, and each crystal has an irregular orientation. It is superior in terms of display stabilization and long life as compared with a film in a state of crystal growth and an <200> orientation film which is relatively easy to form.

That is, after examining the film structures of various magnesium oxide films formed by changing the deposition conditions by X-ray diffraction, the seizure voltage of the PDP provided with each magnesium oxide film was measured. As shown in FIG. 7, it was found that the more the <111> oriented crystal was included in the film, the smaller the value of the image sticking voltage.

Here, the image sticking voltage is a value indicating the degree of image sticking described above. That is, as a test for confirming the change over time in the discharge characteristics, a part of the discharge cells of the PDP are continuously lit (discharged) for, for example, about 500 hours (seizure test time), and then each discharge cell is discharged. The difference in the measured value between the lit discharge cell and the non-lit discharge cell in the vicinity when the discharge start voltage was measured for the sample was shown as the image sticking voltage. The smaller the value of the seizure voltage, the less the seizure, and the better the quality of the magnesium oxide film in terms of discharge characteristics.

[0018]

FIG. 1 is a sectional view showing the structure of a main part of a PDP 1 according to the present invention. The PDP 1 is a matrix discharge type surface discharge type PDP, and includes a pair of glass substrates 11 and 21 and a display electrode 1 disposed adjacent to and parallel to each other.
3, 14; a dielectric layer 15 for AC driving; a partition wall 19 for dividing an internal discharge space 30 into unit light emitting regions;
It is composed of a protective film 16, which will be described later, a partition wall 29 in contact with the partition wall 19 to define a gap size of the discharge space 30, an address electrode 22 for selectively emitting light in a unit light emitting region, and a phosphor 28 of a predetermined emission color. ing.

The discharge space 30 is filled with a penning gas composed of, for example, neon and xenon as a discharge gas. The dielectric layer 15 and the partitions 19 and 29 are formed by printing a low-melting glass paste in a predetermined shape and firing the paste.

When a predetermined drive voltage (alternating pulse) is applied to the pair of display electrodes 13 and 14 so that the relative potential between them is alternately inverted, the dielectric layer 15 is applied each time.
(Surface discharge) occurs in the surface direction of the phosphor, and the ultraviolet light generated by the discharge excites the phosphor 28 to emit light. At this time, wall charges of the opposite polarity to the drive voltage accumulate in the dielectric layer 15 for each discharge, whereby the drive voltage can be made lower than the discharge start voltage by the amount of the wall charges.

The protective film 16 is provided at a stage after the formation of the partition wall 19 in the manufacture of the PDP 1, and covers the surface of the dielectric layer 15 including the partition wall 19 with respect to the discharge space 30.
Deterioration of the dielectric layer 15 is prevented.

In the PDP 1, as the protective film 16,
Among the magnesium oxide films that are advantageous in lowering the discharge starting voltage, the <111> orientation film that is less likely to seize than the other magnesium oxide films is provided, as described above.

The PDP 1 having the above structure is composed of the glass substrates 1
Providing predetermined components separately for 1, 21;
It is manufactured through a process of sealing the periphery by arranging the glass substrates 11 and 21 facing each other and a process of sealing a discharge gas. At this time, on the glass substrate 11 side, the protective film 16 is formed by vapor deposition.

FIG. 2 is a diagram showing a schematic configuration of the vapor deposition apparatus 2 according to the present invention. The vapor deposition device 2 includes a chamber 40,
An electron beam heating type evaporation source 41 provided therein,
It comprises a heater 45, a partial pressure vacuum gauge 46 and the like.

The evaporation source 41 includes a filament 42 that emits thermoelectrons, a heat-resistant container (crucible) 43 that stores magnesium oxide (MgO) 16a as an evaporation material (target) of a film material, and a deflection of the thermoelectron stream EB. The magnetic flux generating unit 44 guides to the target, and heats and evaporates the magnesium oxide 16a by the energy of the thermionic current EB.

Next, the protective film 16 performed by using the vapor deposition device 2
Will be described. First, a predetermined number of glass substrates 11 after the dielectric 15 and the not-shown partition 19 are provided,
The dielectric layer 15 is fixed at a predetermined position in the chamber 40 so as to face the evaporation source 41.

Subsequently, the chamber 40 is evacuated by a vacuum pump (not shown), so that the inside of the chamber 40 is 1 × 10
^-6 [Torr] vacuum. The glass substrate 11 is heated by the heat radiation of the heater 45 in parallel with the formation of the vacuum state or after the formation of the vacuum state.

When the surface temperature of the dielectric layer 15 reaches about 150.degree.
6a is evaporated. The evaporated magnesium oxide 16a reaches the glass substrate 11 as a vapor stream MB, and is deposited on the surface (film formation surface) 15a of the dielectric layer 15 in the form of crystal growth. At this time, the evaporation source 41 is controlled so that the deposition rate is, for example, 20 ° per second.

At the same time, oxygen gas 16b is supplied from the gas cylinder 50 into the chamber 40, and crystal growth proceeds in an oxygen atmosphere. At this time, the supply amount of oxygen is adjusted by the mass flow controller 51, and the partial pressure of oxygen in the chamber 40 is maintained at a predetermined value.

After a predetermined time elapses, 4000 to 5000
When the formation of the protective film 15 having a thickness of about Å is completed, the operations of the evaporation source 41 and the heater 45 are stopped, and the chamber 40 is waited until the temperature of the glass substrate 11 decreases to some extent.
The inside is returned to the atmospheric pressure, and the glass substrate 11 is taken out. Then, the removed glass substrate 11 is sent to a subsequent process.

FIG. 3 is a graph showing the relationship between the oxygen partial pressure and the crystal orientation of the magnesium oxide film. In FIG.
The left vertical axis shows <11 in the magnesium oxide crystals in the film.
1> The ratio occupied by the oriented crystals, and corresponds to the ratio of the peak intensity of the <111> crystal orientation to the sum of the peak intensities of the respective crystal orientations in X-ray diffraction. The peak intensity referred to here usually indicates the area of the peak waveform (that is, the integrated intensity), and the peak intensity corresponds to a predetermined number of crystals (this definition will be the same hereinafter). ).

As shown by the solid line in the figure, as the oxygen partial pressure increases, the ratio of the <111> -oriented crystals in the film increases, and the increase becomes remarkable from around 5 × 10 ⁻⁵ [Torr], and becomes 7 ×. In the vicinity of 10 ^-5 [Torr], the ratio exceeds 50%.

However, as shown by the broken line in the figure, when the oxygen partial pressure becomes about 1 × 10 ⁻⁴ [Torr] or more, the crystallinity of the whole film rapidly deteriorates. That is, the magnesium oxide film becomes amorphous. Therefore, the absolute amount of the <111> -oriented crystals in the film decreases as the oxygen partial pressure exceeds about 8 × 10 ⁻⁵ [Torr], as indicated by the chain line in the figure.

FIG. 4 is a graph showing the relationship between the seizure test time and the seizure voltage using the oxygen partial pressure as a parameter. In FIG. 4, the oxygen partial pressure is 5 × 10 ⁻⁵ or 8 × 10 ⁻⁵ [T
[orr], the magnesium oxide film deposited in an oxygen atmosphere hardly causes seizure even when continuously discharged for 1000 hours. On the other hand, in a magnesium oxide film deposited in an oxygen atmosphere having an oxygen partial pressure of 2 × 10 ⁻⁵ [Torr], seizure becomes remarkable as the discharge time becomes longer, and the seizure voltage exceeds 5 V in 1000 hours. Reach

That is, referring to FIGS. 3 and 4, when forming the protective film 16 by vapor deposition in an oxygen atmosphere, the value of the oxygen partial pressure is 5 × 10 ⁻⁵ to 1 × 10 ⁻⁴ [Torr
r] is preferable.

FIG. 5 is a diagram showing a schematic configuration of another vapor deposition apparatus 3 according to the present invention. 5, components having the same functions as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

The vapor deposition device 3 is provided with a cold cathode type ion gun 48 for so-called ion assisted vapor deposition. The ion gun 48 ionizes an oxygen-based mixed gas 55 supplied from a gas cylinder 50B via a mass flow controller 51, and emits an oxygen ion beam IB. The mixed gas 55 of this embodiment is a gas obtained by mixing oxygen and argon at a ratio of 5: 1.

At the time of depositing the protective film 16 using the vapor deposition device 3, the mixed gas 55 is supplied to the ion gun 48 at a constant flow rate and the irradiation gas ion An ion beam IB having an energy of 500 to 1500 [eV] is applied to the surface 15a of the dielectric layer 15 while keeping the current value constant.

As a result, the magnesium oxide 16a reaching the glass substrate 11 as the vapor stream MB and the oxygen ions incident as the ion beam IB are appropriately combined,
In combination with the surface cleaning by the ion beam IB, a magnesium oxide film having a substantially uniform composition is formed on the surface 15a of the dielectric layer 15 in the form of crystal growth.

FIG. 6 is a graph showing the relationship between the irradiation gas ion current for ion-assisted deposition and the crystal orientation of the magnesium oxide film. As shown by the solid line in the figure, in the range where the irradiation gas ion current value is larger than about 5 [mA],
The ratio of <111> oriented crystals in the film is almost uniformly large.
However, the crystallinity of the entire film is such that the irradiation gas ion current value is 1
It becomes maximum (best) at about 0 [mA], and decreases as the irradiation gas ion current value increases. Note that when the irradiation gas ion current value was 100 mA or more, the magnesium oxide film became an amorphous film (amorphous film) due to the incorporation of argon.

Therefore, when forming the protective film 16 by ion-assisted vapor deposition, the irradiation gas ion current value is preferably in the range of, for example, 5 to 20 [mA]. According to the embodiment of FIG. 5, since oxygen is supplied to the film formation surface by ion irradiation, the film formation surface is compared with the case where oxygen gas 16b is introduced to compensate for the lack of oxygen on the composition of the magnesium oxide film. It is easy to stabilize the oxygen density in the vicinity of. That is, the composition of the protective film 16 formed by the ion-assisted vapor deposition method becomes uniform.

In the above embodiment, the surface discharge type PD
Although P1 is illustrated, the present invention can be applied to a facing discharge type PDP. In the above embodiment, the evaporation source 4
Type 1, the structure of the chamber 40, and the control conditions for evaporation are as follows:
It can be changed appropriately within a range where a <111> orientation film of magnesium oxide can be obtained.

[0043]

According to the first or second aspect of the present invention, a change over time in the discharge characteristics caused by the magnesium oxide film for protecting the dielectric layer (particularly, a partial increase in the discharge starting voltage due to image sticking). Can be suppressed, and the display can be stabilized and the life can be extended.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a main part of a PDP according to the present invention.

FIG. 2 is a diagram showing a schematic configuration of a vapor deposition apparatus according to the present invention.

FIG. 3 is a graph showing a relationship between oxygen partial pressure and crystal orientation of a magnesium oxide film.

FIG. 4 is a graph showing the relationship between the seizure test time and the seizure voltage using oxygen partial pressure as a parameter.

FIG. 5 is a diagram showing a schematic configuration of another vapor deposition apparatus according to the present invention.

FIG. 6 is a graph showing a relationship between an irradiation gas ion current and a crystal orientation of a magnesium oxide film according to the ion assisted deposition.

FIG. 7 is a graph showing the relationship between the amount of <111> oriented crystals in the magnesium oxide film and the seizure voltage related to discharge characteristics.

[Explanation of symbols]

 Reference Signs List 1 PDP (AC plasma display panel) 30 Discharge space 15 Dielectric layer 16 Protective film (<111> oriented film of magnesium oxide)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-188604 (JP, A) Kenji Machida et al., “STM Observation of Vacuum Evaporated MgO Films in AC Plasma Displays”, Institute of Electronics, Information and Communication Engineers. Report, The Institute of Electronics, Information and Communication Engineers, issued October 31, 1991, Vol. 91, No. 309, p. 57-61 (58) Field surveyed (Int.Cl. ⁷ , DB name) H01J 9/02 H01J 11/00-11/02

Claims (2)

(57) [Claims] An oxygen partial pressure of 5 × 10 ^-5 to 1 × 10 ^-4 [To
rr] in an atmosphere of vapor deposition mainly composed of oxygen, by an ion-assisted vapor deposition method of irradiating an ion beam of a mixed gas of oxygen mainly composed of oxygen and argon to a deposition surface.
AC including a step of forming a protective film made of a <111> oriented film of magnesium oxide on a dielectric layer.
Of manufacturing a plasma display panel. 2. The method of manufacturing an AC type plasma display panel according to claim 1, wherein the irradiation gas ion current value during ion assisted deposition is set to a value within a range of 5 to 20 [mA].