TWI407485B - Method for treating surface of cold cathode - Google Patents

Abstract

The invention relates to a method for treating surface of cold cathode. The method includes the following steps: providing a cold cathode which includes a plurality of one-dimensional emitters; positioning a liquid glue on a surface of the cold cathode; solidifying the liquid glue; removing the solidified glue so as to erect the one-dimensional emitters.

Description

Surface treatment method for cold cathode

The present invention relates to a surface treatment method, and more particularly to a surface treatment method for a cold cathode.

The cold cathode electron source prepared by the screen printing thick film technology has the advantages of low cost and large area preparation, and can be applied to vacuum microelectronic devices such as field emission flat panel displays. The current printable cold cathode is basically composed of a mixture of a carbon nanotube and a common conductive paste, or a mixture of a carbon nanotube and a conductive silver powder, a plurality of solid binder materials, and an organic solvent. (NS Lee, et al., Diamond Relat. Master., 2001, 10: 265-270). The field-emitting cold cathode prepared by using the carbon nanotube-conductive silver paste slurry is subjected to high-temperature heat treatment to remove the organic solvent, and is mainly composed of a carbon nanotube, a conductive phase metal particle and a glassy solid binder material. The carbon nanotubes serve as the main field electron emission source.

The cold cathode slurry is subjected to high temperature heat treatment to obtain a cold cathode. The surface of the cold cathode is covered by the glassy solid binder and other impurities, and the number of carbon nanotube field emitters exposed on the surface of the cold cathode is small, and the electron emission stream is emitted. small. It is therefore necessary to introduce some surface treatment techniques to improve the field emission characteristics of the cold cathode.

The prior art discloses a method for treating a cold cathode using a carbon nanotube as a field emitter by using a tape, comprising the steps of: sticking a specific tape to a surface of a cold cathode; heating the tape at a specific temperature; The tape is peeled off at a specific temperature to erect the carbon nanotubes on the surface of the cold cathode.

However, the surface treatment method of the above cold cathode has the following disadvantages: one must be at a specific temperature The tape is heated down and the tape is removed to achieve the purpose of erecting the cold cathode surface carbon nanotubes. However, the control of the heating temperature in the method has a great influence on the surface treatment effect: too low heating temperature completely peels the carbon nanotube from the cold cathode to the surface treatment purpose; excessive heating temperature causes The glue of the tape remains on the surface of the cold cathode, which affects its emission performance and life. Second, when the tape is adhered to the surface of the cold cathode, it is difficult for the tape to uniformly contact the cold cathode due to the actual operation, thereby causing residual air between the tape and the cold cathode, which is represented by air bubbles on the tape. Moreover, since the tape is in a state of view, once the bubble is generated, it is difficult to discharge. The carbon nanotubes at the bubble are not in contact with the tape, so when the tape is removed, the carbon nanotubes at the bubble are still randomly distributed and cannot be erected, which reduces the uniformity of field emission of the carbon nanotubes.

In view of this, it is necessary to provide a simple and stable cold cathode surface treatment method to solve the above technical problems.

A surface treatment method for a cold cathode, comprising the steps of: providing a cold cathode comprising a plurality of one-dimensional field emitters and a binder; disposing a liquid glue on the surface of the cold cathode; and heating and curing the The liquid glue, the binder that simultaneously heats the cold cathode is in a semi-molten state; the solidified liquid glue on the surface of the cold cathode is removed to erect the one-dimensional field emitter on the surface of the cold cathode.

Compared with the prior art, the surface treatment method of the cold cathode provided by the invention has the following advantages: First, the surface treatment method of the cold cathode provided by the invention does not need to accurately control the temperature, and therefore, the method is simple, stable, reproducible and operable. Second, because of the fluidity of the liquid glue, even if there is part of the air between the surface of the cold cathode and the liquid glue, it can be discharged through the liquid glue, so that the one-dimensional field emitter exposed to the surface of the cold cathode is close to the liquid glue. Contact, no residual bubbles, so the efficiency of the one-dimensional field emitter erecting the surface of the cold cathode is higher; third, because the liquid glue has fluidity, it can handle the surface of various cold cathodes, especially the tape is difficult to handle or cannot be processed. Groove and / or side.

1 is a flow chart of a cold cathode surface treatment method provided by a specific embodiment of the present invention.

2 is a flow chart of a method for preparing a cold cathode used in a cold cathode surface treatment method according to an embodiment of the present invention.

The surface treatment method of the cold cathode provided by the embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

Referring to FIG. 1, a method for surface treatment of a cold cathode according to an embodiment of the present invention includes the following steps: step S101, providing a cold cathode; step S102, providing a liquid glue on the cold cathode surface; and step S103, curing The liquid glue is described; in step S104, the solidified liquid glue on the surface of the cold cathode is removed to erect the one-dimensional field emitter on the surface of the cold cathode.

In step S101, the cold cathode includes a plurality of one-dimensional field emitters. Since the one-dimensional field emitter has a high aspect ratio, electrons can be emitted at a lower electric field.

Alternatively, the cold cathode may further include one or more of a conductive phase, a binder, and getter particles. The one-dimensional field emitters are randomly distributed in the cold cathode and at least a portion of the one-dimensional field emitters are at least partially exposed to the cold cathode surface. In this embodiment, the cold cathode includes a plurality of one-dimensional field emitters, a conductive phase, and a binder.

The one-dimensional field emitter includes one or more of a nanotube, a nanowire, a nanofiber, a nanorod or a nanobelt having field emission characteristics. Wherein, the nanowire comprises an oxide nanowire, a nitride nanowire or a carbide nanowire. The oxide nanowire may include alumina (Al ₂ O ₃ ) nanowire, magnesium oxide (MgO) nanowire, zirconia (ZrO) nanowire, titanium dioxide (TiO ₂ ) nanowire or calcium oxide (CaO) nanowire and so on. The nitride nanowire may include an aluminum nitride (AlN) nanowire, a boron nitride (BN) nanowire, a tantalum nitride (SiN) nanowire, or a titanium nitride (TiN) nanowire. The carbide nanowire may include tantalum carbide (SiC) nanowire, titanium carbide (TiC) nanowire, tungsten carbide (WC) nanowire, zirconium carbide (ZrC) nanowire or niobium carbide (NbC) Nano line. The nanofibers include carbon fibers. The one-dimensional field emitter may also be a one-dimensional composite material, such as a surface modification material formed on the surface of the one-dimensional field emitter to improve the field emission characteristics of the one-dimensional field emitter. In this embodiment, the one-dimensional field emitter is a carbon nanotube. The carbon nanotubes may comprise single-walled carbon nanotubes, double-walled carbon nanotubes or multi-walled carbon nanotubes. The diameter of the single-walled carbon nanotube is preferably from 0.5 nm to 50 nm. The diameter of the double-walled carbon nanotubes is preferably from 1.0 nm to 50 nm. The diameter of the multi-walled carbon nanotubes is preferably from 1.5 nm to 50 nm.

The conductive phase includes metal fine particles, indium oxide (In ₂ O ₃ ) fine particles, tin oxide (SnO ₃ ) fine particles, or indium tin oxide (ITO) fine particles. The metal particles include nickel, cadmium, and the like. The conductive phase serves to enhance electrical connection between the one-dimensional field emitters, the one-dimensional field emitters, and the bottom electrode in the cold cathode. The bottom electrode is electrically connected to the cold cathode. The conductive phase in this embodiment is ITO microparticles.

The binder is a trapezoidal polyphenylsesquioxanes (PPSQ) or an inorganic material, and preferably the binder is glass powder or spin-on glass (SOG). At room temperature, SOG is a liquid phase insulating material equivalent to SiO ₂ . In this embodiment, the binder is glass frit.

As described above, the cold cathode in the present embodiment includes a carbon nanotube, a glass frit, and ITO fine particles. The cold cathode can be obtained by the preparation method of the cold cathode shown in FIG. 2. The method for preparing the cold cathode comprises the following steps: Step S201, the carbon nanotubes, the ITO particles, and the glass frit are thoroughly mixed in an organic vehicle to form a cold cathode slurry.

The components of the cold cathode slurry are prepared at a concentration ratio of 5% to 15% of carbon nanotubes, 10% to 20% of ITO particles, 5% of glass powder, and 60% to 80% of organic vehicle. The length of the carbon nanotubes is preferably in the range of 5 micrometers to 25 micrometers. Too short will weaken the field emission characteristics of the carbon nanotubes, and too long, the nanocarbon tubes may be entangled or broken.

The organic vehicle may include terpineol, ethanol, ethylene glycol, isopropanol, hydrocarbon, water, and a mixed solvent thereof as a solvent, a small amount of ortho-xylene dibutylate as a plasticizer, and as a stabilizer A small amount of ethylcellulose formed by a mixture of agents. In order to meet the requirements of the screen printing process, a plurality of organic solvents and organic auxiliaries such as tackifiers, dispersants and surfactants may be added to the cold cathode slurry to adjust the viscosity and fluidity of the slurry. And other physical properties. The organic solvent and organic auxiliary used are not particularly limited. The amount of the organic solvent and the organic auxiliary added is mainly determined according to the printing process. The organic vehicle in the present embodiment includes ethanol and terpineol as a solvent, ethyl cellulose as a stabilizer, and the like.

Step S202, the cold cathode slurry is treated by low temperature heating.

The cold cathode slurry is subjected to low-temperature heat treatment to volatilize the organic vehicle, the organic solvent, and the organic auxiliary component. After removing the organic carrier, the organic solvent and the organic auxiliary component, the glass powder, the carbon nanotubes and the ITO particles form a close bond by virtue of the van der Waals force. In this example, the cold cathode slurry was sintered at a temperature of 150 ° C, and terpineol and ethanol were volatilized. Glass powder, ITO particles and carbon nanotubes are combined by Van der Waals force.

In step S203, the cold cathode slurry is sintered to obtain a cold cathode.

The cold cathode slurry is sintered to completely melt or semi-melt the binder therein. The binder is cooled such that the conductive phase and the one-dimensional field emitter are consolidated in the binder. This sintering process can also volatilize a portion of the high melting organic vehicle in the cold cathode slurry. Preferably, the cold cathode slurry is sintered such that the binder therein is in a semi-molten state, and then the binder in a semi-molten state is cooled thereby The conductive phase and the one-dimensional field emitter are consolidated in a semi-molten binder. If the cold cathode is a glass frit, the sintering temperature is higher than the glass transition temperature. Preferably, the sintering temperature is between the transition temperature and the softening temperature of the glass frit. The sintering temperature is higher than the transition temperature of the glass frit, at which time the glass frit is in a completely molten state. The sintering temperature is between the transition temperature and the softening temperature of the glass frit, and the glass frit is in a semi-molten state. In this embodiment, the cold cathode slurry is sintered at a temperature of 400 ° C to make the glass powder in the cold cathode slurry into a semi-molten state, after which the glass frit is cooled, so that the carbon nanotubes and the ITO particles are Fixed in glass powder. Since the glass frit in the cold cathode is in a semi-molten state, there is a certain gap between the components of the cold cathode. During this sintering process, the ethyl cellulose in the cold cathode is volatilized. Through the above steps, a cold cathode suitable for the step S101 can be obtained.

Further, the cold cathode may include only a plurality of carbon nanotubes. The preparation method of the cold cathode including only the carbon nanotubes can be prepared by mixing the carbon nanotubes with the dimethylformamide solution and then volatilizing to remove dimethylformamide, or by chemical vapor deposition. (Chemical Vapor Deposition, CVD) method. The method for mixing a carbon nanotube and a dimethylformamide solution to volatilize and remove dimethylformamide to form a cold cathode comprises the following steps: first, mixing a carbon nanotube and a dimethylformamide solution And the nano carbon tube is further dispersed in the dimethylformamide solution by ultrasonic vibration to form a mixed solution; secondly, the dimethylformamide in the mixed liquid is removed by volatilization, thereby obtaining a A cold cathode of a carbon nanotube comprising a plurality of carbon nanotubes with a certain gap between the plurality of carbon nanotubes.

The cold cathode produced in accordance with the above method needs to be subjected to the treatment of step S102.

In step S102, the liquid glue is a glue that can be cured. The liquid glue may be a thermosetting glue, a thermoplastic glue or an ultraviolet curing glue. Specifically, the liquid glue may be a liquid silicone, a polyoxyalkylene ester liquid crystal (PMMS), an ultraviolet curing adhesive or the like. The liquid glue can be cured by a physical method such as heating, cooling, exposure, electron beam irradiation or magnetoelectric or a chemical method such as adding a curing agent. In this embodiment, the liquid glue is silicone.

The method for setting a liquid glue on a cold cathode surface comprises the steps of: first, pouring a liquid glue onto a surface of a cold cathode; secondly, leveling the liquid glue on a surface of the cold cathode to cause one-dimensional field emission exposed to the surface of the cold cathode; The body is in intimate contact with the liquid glue. Since the liquid glue has fluidity, even if there is a part of air between the cold cathode surface and the liquid glue, it can be discharged through the liquid glue, so that the one-dimensional field emitter exposed to the surface of the cold cathode is in close contact with the liquid glue.

The liquid glue can be leveled on the surface of the cold cathode by rotating the cold cathode, or the liquid glue can be naturally leveled on the surface of the cold cathode, and the liquid glue can be flattened by brushing after pouring the liquid glue onto the surface of the cold cathode. The liquid glue is used, or the liquid glue is placed on the surface of the cold cathode by a dispenser to level the liquid glue.

In this embodiment, the liquid silicone is disposed on the surface of the cold cathode in such a manner that the liquid silicone is naturally leveled on the surface of the cold cathode. Since the liquid glue has good fluidity, after the liquid glue is placed on the surface of the cold cathode, the liquid glue can be in full contact with the one-dimensional field emitter on the surface of the cold cathode without leaving bubbles. Since there is a certain gap between the components of the cold cathode used in this embodiment, the liquid glue will penetrate into the gap of the cold cathode after being laid on the surface of the cold cathode. After the liquid glue is leveled on the surface of the cold cathode, step S103 can be performed.

In step S103, the cured liquid glue forms a certain bonding force with the one-dimensional field emitter exposed to the surface of the cold cathode. The method of curing the liquid glue depends on the nature of the liquid glue itself.

For the thermosetting glue, it is cured by a stepwise heating method. The method of curing the thermosetting glue by heating is specifically: heating the liquid glue by a heating device until a solid state is formed. The temperature and time of curing of the thermosetting glue are determined by the nature and amount of the thermosetting glue. The heating device may be an oven, a heating furnace or the like.

The thermoplastic glue is cured by cooling. The thermoplastic glue is cured by natural cooling at room temperature or by cooling the liquid glue by a cooling device to form a solid. The cold However, the device may be one of a cooling device such as a circulating water cooler, a hydraulic oil cooler or a water-oil cooler.

The UV curable adhesive can be cured by ultraviolet light irradiation. The wavelength range and exposure time of the selected UV light is determined by the nature and amount of UV curable glue selected.

Alternatively, the method of curing the liquid glue may be any magnetic, electrical, optical, thermal, acoustic, etc., as long as the method can cure the selected liquid glue into a solid glue, which is within the scope of the present invention. .

In this embodiment, the method of curing the liquid silicone is to cure the liquid silicone by heating at a temperature of 150 ° C for 10 minutes. Since some of the liquid glue penetrates into the gap of the cold cathode, the binding force of the liquid glue after solidification to the cold cathode is strong.

In step S104, the method of removing the cured liquid glue may be directly removing the cured liquid glue or peeling off the cured liquid glue with tweezers or other tools. The cured liquid glue is removed, and the one-dimensional field body exposed to the surface of the cold cathode has a certain binding force with the liquid glue after curing, and the carbon nanotube surface of the cold cathode surface can be made by the bonding force. Was erected. If the binder in the cold cathode is in a semi-molten state, the binder particles in direct contact with the cured liquid glue adhere to the cured product while the process of curing the liquid glue is removed. The surface of the liquid gel is thus detached from the cold cathode so that the carbon nanotubes on the surface of the cold cathode are exposed and erected. Therefore, if the binder in the cold cathode is in a semi-molten state, the surface treatment of the cold cathode by the present invention is less likely to cause a gel retention phenomenon.

In the present embodiment, the cured liquid silicone is directly removed by hand to erect the carbon nanotubes on the surface of the cold cathode. Since the glass powder in the cold cathode in the embodiment is in a semi-molten state, the binding strength of the cured tantalum to the cold cathode is greater than the bonding force between the components in the cold cathode. Therefore, during the process of peeling off the silicone, part of the cold cathode that is in direct contact with the silicone adheres to the surface of the silicone and leaves the cold cathode. Thereby, the carbon nanotubes are exposed and erected, and it is difficult to leave residual glue on the surface of the cold cathode.

Alternatively, a surface modification layer may be formed on the surface of the erected carbon nanotube of the cold cathode, and the surface modification layer may be made of zirconium carbide or titanium carbide. The work function of the surface modification layer is lower than the work function of the carbon nanotubes. The surface modification layer on the surface of the carbon nanotube can effectively reduce the work function of the emission end of the carbon nanotube field emitter.

The surface treatment method of the cold cathode provided by the invention has the following advantages: First, the surface treatment method of the cold cathode provided by the invention does not need to accurately control the temperature, and therefore, the method is simple, stable, reproducible and operable; secondly, The liquid glue has fluidity, and even if there is a part of air between the surface of the cold cathode and the liquid glue, it can be discharged through the liquid glue, so that the one-dimensional field emitter exposed to the surface of the cold cathode is in close contact with the liquid glue, and no air bubbles remain. Therefore, the efficiency of the one-dimensional field emitter erecting the surface of the cold cathode is higher; thirdly, because the liquid glue has fluidity, it can handle the surface of various cold cathodes, especially the grooves which are difficult to handle or cannot be processed by the tape and/or Or side.

Claims (11)

A surface treatment method for a cold cathode, comprising the steps of: providing a cold cathode comprising a plurality of one-dimensional field emitters and a binder; disposing a liquid glue on the surface of the cold cathode; and heating and curing the The liquid glue, while the binder for heating the cold cathode is in a semi-molten state; the solidified liquid glue on the surface of the cold cathode is removed to erect the one-dimensional field emitter on the surface of the cold cathode. The surface treatment method of the cold cathode according to claim 1, wherein the one-dimensional field emitter comprises a nanotube having a field emission characteristic, a nanowire, a nanofiber, a nanorod, and a nanobelt. One or several. The surface treatment method of the cold cathode according to claim 2, wherein the nanowire comprises an oxide nanowire, a nitride nanowire or a carbide nanowire. The surface treatment method of the cold cathode according to claim 1, wherein the liquid glue is a thermosetting glue. The surface treatment method of the cold cathode according to claim 1, wherein the liquid glue is liquid silicone, and the one-dimensional field emitter is a carbon nanotube. The surface treatment method of the cold cathode according to claim 5, wherein the method of curing the liquid silicone is heated at a temperature of 150 ° C for 10 minutes. The surface treatment method of the cold cathode according to claim 1, wherein the method of disposing a liquid glue on the surface of the cold cathode comprises the steps of: pouring a liquid glue onto a surface of a cold cathode; and bonding the liquid to a surface of the cold cathode. Leveling. The surface treatment method of the cold cathode according to claim 7, wherein the method of leveling the liquid glue on the surface of the cold cathode is to cause the liquid glue to naturally level or rotate the cold cathode on the surface of the cold cathode. The liquid glue leveles on the surface of the cold cathode. The method for surface treatment of a cold cathode according to claim 1, wherein the method of removing the cured liquid glue is to directly remove the cured liquid glue or use the forceps to melt the liquid glue. Uncover it. The surface treatment method of the cold cathode according to claim 1, wherein the cold cathode further comprises one or more of a one-dimensional field emitter, a conductive phase, and a binder. The method of surface treatment of a cold cathode according to claim 10, wherein the plurality of one-dimensional field emitters are randomly distributed in the cold cathode, and at least a portion of the one-dimensional field emitter is at least partially exposed to the surface of the cold cathode.