JP2000298261A - Plasma address liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress reduction in the service life of a display device due to sputtering of a cathode material, even when mercury is not sealed by using a material essentially comprising hafnium carbide for at least one of a cathode and an anode. SOLUTION: Discharge electrodes of the cathode and the anode are formed by a thick-film printing method or the like on a glass substrate, where the discharge electrodes are to be formed. In this process, hafnium carbide(HfC) is used for the cathode. Thick film paste used is a black one so as to suppress reflection or scattering of light. The thick film paste consists of a powder of low-melting point glass, a ceramic filler, an org. binder or the like. When a gas is to be sealed, after a plasma channel is evacuated through tan evacuation tube called as a 'tip pipe', a discharge gas is injected into the channel. Since the HfC is used as the cathode material, He, Ne, Ar, Kr or a mixture of these which does not cause adsorption is used as the discharge gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma addressed liquid crystal display device using a specific electrode material and a method of manufacturing the same.

[0002]

2. Description of the Related Art The basic structure of a plasma addressed liquid crystal (PALC) display device will be described. Discharge electrodes (cathode, anode) and barrier ribs are provided on a glass substrate, a liquid crystal layer is present across the thin glass, and a discharge gas mainly composed of a rare gas is filled between the thin glass and the glass substrate. .

The principle of operation of the plasma addressed liquid crystal will be described below.

When a voltage is applied between the cathode and the anode to generate plasma (discharge), a conduction state is established between the thin glass and the anode. At this time, a voltage is applied to the ITO electrode on the liquid crystal side. Write charge on the back of the thin glass. The written charge is retained during the frame period when the discharge is turned off to make the thin glass and the anode insulated.

As described above, the plasma channel (the space where the discharge gas is filled and the plasma is generated) plays the same role as the TFT (thin film transistor) used in the active matrix liquid crystal display device.

In a PALC display device, a thick film paste such as Ni formed by a screen printing method is used as a discharge electrode, and a black glass paste formed by a screen printing method is used as a partition for separating a plasma channel. As TN (Twisted Nematic)
ASM (Axially Sy) mode and wide viewing angle
mmtricalized Microcellmo
de) is used, and a rare gas or a gas mainly composed of a rare gas is used as a discharge gas in the plasma channel.

On the other hand, a DC type plasma display (hereinafter referred to as D)
For C-PDP, the same electrode material as that of PALC is used. In the case of a monochrome PDP, a gas such as Ne-Ar can be used, but in the case of a color PDP, a discharge gas is mainly composed of a Xe gas for exciting a phosphor to emit light.
It is essential to use a nning effect gas (He / Xe, Ne / Xe).

An example in which HfC is used as a heat-resistant ohmic resistor is described in JP-A-6-275554.

[0009]

In a plasma addressed liquid crystal display device, a thick film Ni is conventionally used as an electrode material. Since the sputtering rate of Ni alone (the number of atoms of the cathode material jumping out when one discharge gas ion collides) is large, it is easy to be sputtered, and the sputtered Ni
Atoms contaminate the surface of the glass substrate and the back surface of the thin glass to lower the transmittance and cause a short circuit between the cathode and the anode. Therefore, measures have been taken to prolong the service life by enclosing mercury in the plasma channel. The mechanism by which mercury contributes to the prevention of cathode sputtering has not been elucidated yet, but the mercury gas cloud covers the Ni surface, thereby absorbing the kinetic energy of the discharge gas ions and discharging even if Ni is sputtered. It is speculated that Ni atoms may be returned to the cathode surface again by collision with the gas. The density of the mercury gas cloud is considered to be highly correlated with the saturated vapor pressure, and the life characteristic greatly changes with temperature due to the logarithmic (according to Rankine-Duplet equation) temperature dependence of the saturated vapor pressure. Particularly in a low temperature region, the sputtering effect of mercury may not be sufficiently exhibited.

[0010]

According to a first aspect of the present invention, there is provided a plasma liquid crystal display device having a structure in which a discharge electrode composed of a cathode and an anode is formed on a substrate, and a liquid crystal layer is arranged separated by a thin plate. And at least one of the cathode and the anode is made of a material mainly containing hafnium carbide.

The invention according to claim 2 is characterized in that thick film printing is used for forming hafnium carbide.

The invention according to claim 3 is characterized in that electrodeposition is used for forming hafnium carbide.

The invention according to claim 4 is characterized in that plasma spraying is used for forming hafnium carbide.

The invention according to claim 5 is characterized in that EB vapor deposition is used for forming hafnium carbide.

According to a sixth aspect of the present invention, a sputtering method is used for forming hafnium carbide.

The operation of the present invention will be described below.

Since hafnium carbide (HfC) is a material having a high melting point (about 4,000 ° C.) and a low work function (about 2.0 eV), it is used in a display device utilizing gas discharge represented by PALC or DC-PDP. Can be a suitable electrode material. It is generally known that the higher the melting point, the lower the sputtering rate.
Can suppress a reduction in life due to sputtering of a cathode material even if mercury is not sealed. Also, the lower the work function, the higher the secondary electron emission efficiency (the number of secondary electrons emitted when one discharge gas ion collides with the cathode), and the Paschen rule Vf = Bpd / (ln (Apd) -lnln) (1 + 1 /
γ)) p: gas pressure, d: electrode spacing, γ: secondary electron emission efficiency,
A, B: The discharge starting voltage can be reduced in accordance with the constant. If the discharge starting voltage can be lowered, the withstand voltage of the driver can be lowered and the cost can be reduced.

In the case of DC-PDP, the Journal of the Institute of Television Engineers of Japan, Vo
l. 48, no. 3, pp. As described in 295-300, HfC has been studied as a cathode material. In order to realize color display, Xe is contained as a sealing gas to excite the phosphor (He-Xe or Ne-
It is essential that the Xe penning system is the mainstream), but Xe atoms are trapped in the HfC film, and the partial pressure of Xe in the discharge gas is reduced, thereby lowering the luminance. The trapping mechanism is not disclosed, but probably Hf and X
It is considered that e invades by a chemical bond such as substitution of e.

In the case of PALC, the plasma portion is used for switching the liquid crystal and does not require light emission, and color display is performed by a color filter.
It is not necessary to use other rare gases (He, Ne, Ar, K
r) can be applied.

Therefore, by using HfC as the cathode material of the PALC display device, it is possible to realize a PALC display device which has a long life even in a low temperature region, can be driven at a low voltage, and can perform color display without enclosing mercury. .

According to the second aspect of the present invention, the productivity is high, the vacuum equipment is unnecessary, the capital investment is low, and the cost can be reduced.

According to the third aspect of the present invention, since HfC can be formed after the partition walls are fired, the surface oxidation of the HfC particles can be suppressed, and the original HfC (close to bulk) discharge characteristics can be obtained.

According to the fourth aspect of the present invention, the productivity is high and the screen can be easily enlarged. Further, a pure HfC film containing no binder or the like can be formed, and good plasma characteristics can be expected.

According to the fifth and sixth aspects of the present invention, HfC that is pure and has good crystallinity can be formed, and a stable discharge state can be provided.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A process for forming a PALC display device according to this embodiment will be described below. FIG. 1 shows a sectional view of a PALC display device.

(1) Forming a discharge electrode on a glass substrate A cathode and an anode discharge electrodes are formed on a glass substrate by a thick film printing method.
It is formed by an electrodeposition method, a plasma spraying method, and an EB vapor deposition / sputtering method. HfC is used as a cathode material.

(2) Forming Partitions Screen multilayer printing of a thick film paste, which is a general method of forming barriers, will be described. A thick paste is used to suppress reflection and scattering of light. The composition of the thick-film paste is a low-melting glass powder, a filler made of ceramic, a binder made of an organic substance (such as ethyl cellulose), a solvent such as BCA (diethylene glycol mono-n-butyl ether) or terpineol, and a black pigment.

Screen printing is a method in which a squeegee is used to extrude a paste from the opening to form a pattern on glass using a plate in which an opening is cut with a resin on a mesh in which stainless steel is woven. The process of drying (100-150 ° C.)-Screen printing-drying is repeated about 10 times to obtain a height of about 200.
It is formed to a thickness of μm.

(3) Baking the partition paste The binder paste is baked at a temperature of about 600 ° C. to remove the binder (removing the organic binder).
The low-melting glass particles are fused and bonded to each other to secure rigidity as a partition.

(4) Laminating Thin Glass with Frit A partition for filling gas is made with a frit material (component: low melting point glass, ceramic filler, organic binder, solvent) (not shown). The process includes frit dispensing-frit drying (~ 100 ° C)-frit temporary firing (~ 400 ° C) for removing organic binder-placing a thin plate-main firing (~ 500 ° C). The bonding of the glass substrate and the thin glass using the frit material is called a frit seal.

(5) Gas Injection and Sealing A plasma chamber is evacuated from a vacuum tube called a chip tube.
Vacuum inside the flannel (~ 10 ^-7Torr) and then discharge gas
Is injected inside. Since HfC is used as a cathode material,
He, Ne, Ar, which do not cause adsorption as a discharge gas,
Kr or a mixture of these gases is used. To gas pressure
For example, in the case of He, about 100 Torr,
In the case of Kr, it is desirable to set to 20 to 50 Torr.
No.

The sealing step is performed by heating and melting the chip tube as in the process in the CRT.

(6) Forming an alignment film An alignment material made of polyimide or the like is applied to the surface of the thin glass opposite to the surface on which the plasma channel is formed, and the film is formed at 200 ° C.
After baking at a temperature in the vicinity, a rubbing treatment is performed.

At this time, an alignment film is similarly formed on the glass substrate (the liquid crystal side) on which the ITO electrode serving as the data electrode is formed.

(7) The glass substrate (liquid crystal side) on which the sealing material is formed and the thin glass are bonded after dispersing the spacers. After applying the sealing material (thermosetting resin or ultraviolet effect resin, or a mixture thereof), calcining is performed. And bonded to the glass substrate (liquid crystal side).

(8) Liquid crystal injection / sealing treatment Nematic liquid crystal is injected between the thin glass and the glass substrate (liquid crystal side), and the injection port is sealed with a resin or the like.

Through the above steps, a PALC display device is manufactured.

Next, a method for forming an electrode made of HfC will be described.

(I) Example using thick film printing A thick film paste containing HfC (comprising HfC powder, low melting point glass, organic binder, solvent, etc.) is screen printed. Depending on the line resistance, both the cathode and the anode can be formed of only HfC as shown in FIG.
As shown in FIG.
It is desirable to form the base electrode with a paste containing a conductor such as l. In this case, it is not necessary to coat the HfC paste on the anode side which is not subjected to ion bombardment, but it is necessary to completely cover the steps on the cathode side in order to prevent the sputtering of the edge.

In screen printing, the line width is limited due to the influence of paste dripping. Therefore, in order to improve the accuracy, after solid printing on the entire surface of the glass, a pattern is formed by DFR (dry film resist having a thickness of about 30 μm). After that, the electrode pattern may be removed by sandblasting.

According to this method, the productivity is high, a vacuum device is unnecessary, the capital investment is low, and the cost can be reduced.

(Ii) Example of using electrodeposition A substrate on which a bus electrode made of a conductive thin film (or thick film) such as Al is formed is placed in a solvent such as water or an organic solvent by HfC
Powder, low-melting glass (lead borosilicate glass, etc.) powder, and electrolytes (nitrate, phosphate, etc.) dispersed in a suspension (hereinafter referred to as electrodeposition liquid), and by applying a voltage from the outside, A coating is formed on the bus electrode (FIGS. 3a and 3b).
Here, in order to make the concentration ratio between HfC and the low-melting glass in the electrodeposition liquid equal to the weight ratio in the electrodeposition film, it is desirable that the particle diameters of the two are approximately the same and the electrophoretic mobility is the same. .

The electrodeposition rate varies depending on the composition of the electrodeposition solution. According to experiments, the average particle size of HfC and the low-melting glass powder is set to 2 μm, and the conductivity in the solution is adjusted for about 2 minutes by adjusting the electrolyte concentration. To a thickness of 6 μm. Thereafter, the low-melting-point glass contained therein is melted at a temperature of about 500 ° C. so that HfC particles and HfC
The connection between / Al is taken.

According to this method, since HfC can be formed after the baking of the partition walls, the surface oxidation of the HfC particles can be suppressed,
The original (close to bulk) discharge characteristics of fC are obtained.

(Iii) Example using plasma spraying A substrate on which a bus electrode (thick film or thin film may be formed) is coated with H
It is formed by fC plasma spraying. Plasma spraying is a method in which powder is fed into a plasma jet (as high as 10,000 to 15,000 ° C) and adhered to the substrate in a state where the particles themselves are melted. Unlike thick film printing and electrodeposition, particles are sprayed. No binder is needed to connect them. For patterning, create an opening only in the area where you want to form a sprayed film in advance with DFR (dry film resist), etc.
After HfC is buried as shown in FIG. 4A, a method of removing the resist as shown in FIG. 4B is employed. In order to improve the adhesion by the mechanical anchoring effect, the opening may be subjected to a pretreatment such as sandblasting with alumina abrasive grains.

In the actual process, the average particle size of the HfC powder was set to 10 μm, the opening was set to 100 μm, and the thickness of the deposited film was 3 μm.
It was formed to 0 μm.

According to this method, the productivity is high and the screen can be easily enlarged. Further, a pure HfC film containing no binder or the like can be formed, and good plasma characteristics can be expected.

(Iv) Example using EB evaporation / sputtering As shown in FIG. 5A, a HfC thin film and a low-resistance material to be a bus electrode such as Al are sequentially formed by EB evaporation or sputtering to form an HfC film and patterned. . The thickness of the bus electrode is about 2 μm and the thickness of HfC is about 1 μm. However, regarding the patterning, HfC is excellent in chemical resistance, but has a drawback that etching is difficult, and therefore, like in the case of plasma spraying, HfC must be performed by a lift-off method. In order to extend the life, the structure shown in FIG.
After patterning the bus electrode, it is desirable to form an HfC thin film and pattern the HfC thin film so as to completely cover the bus electrode as shown in FIG.

According to this method, pure HfC having good crystallinity can be formed, and a stable discharge state can be provided.

[0050]

According to the present invention, even if mercury is not sealed, a reduction in life due to sputtering of the cathode material can be suppressed. In addition, the discharge starting voltage can be reduced, and the withstand voltage of the driver can be reduced, so that the cost can be reduced.

According to the second aspect of the present invention, the productivity is high, the vacuum equipment is unnecessary, the amount of capital investment is low, and the cost can be reduced.

According to the third aspect of the present invention, since HfC can be formed after the partition walls are fired, the surface oxidation of the HfC particles can be suppressed, and the original HfC (close to bulk) discharge characteristics can be obtained.

According to the fourth aspect of the present invention, the productivity is high and the screen can be easily enlarged. Further, a pure HfC film containing no binder or the like can be formed, and good plasma characteristics can be expected.

According to the fifth and sixth aspects of the present invention, HfC that is pure and has good crystallinity can be formed, and a stable discharge state can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a PALC display device.

FIG. 2 is a diagram illustrating electrode formation using thick film printing.

FIG. 3 is a diagram illustrating electrode formation using electrodeposition.

FIG. 4 is a diagram illustrating electrode formation using plasma spraying.

FIG. 5 is a diagram illustrating electrode formation using EB evaporation / sputtering.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H089 HA36 QA16 5C027 AA02 AA03 5C040 FA02 FA09 GB08 GB09 GC18 GC19 JA07 JA08 JA12 JA16 KA03 KB17 MA03 MA10 MA12 MA17 5C094 AA07 BA31 BA43 EA10 FB12 GB01

Claims (6)

[Claims] 1. A plasma liquid crystal display device having a structure in which a discharge electrode composed of a cathode and an anode is formed on a substrate and a liquid crystal layer is disposed separated by a thin plate, wherein at least one of the cathode and the anode mainly comprises hafnium carbide. A plasma-addressed liquid crystal display device characterized by using a prepared material. 2. The plasma addressed liquid crystal display device according to claim 1, wherein thick film printing is used for forming hafnium carbide. 3. The plasma addressed liquid crystal display device according to claim 1, wherein electrodeposition is used for forming hafnium carbide. 4. The plasma addressed liquid crystal display according to claim 1, wherein plasma spraying is used for forming hafnium carbide. 5. The plasma addressed liquid crystal display according to claim 1, wherein EB deposition is used for forming hafnium carbide. 6. The plasma addressed liquid crystal display device according to claim 1, wherein a sputtering method is used for forming hafnium carbide.