KR100918633B1 - Process and device for upgrading current emission - Google Patents

Abstract

The invention is a process applied to a current-emitting device consisting of a material comprising carbon, which can work well on a display screen, in particular a display on a mobile device or a small device, or on a device with a power supply limited to a low voltage level or low capacity. To provide.

Display screen, display, low voltage level, low capacity, power, current dissipation device

Description

PROCESS AND DEVICE FOR UPGRADING CURRENT EMISSION

1 is a view showing an image of two carbon nanotubes taken with a transmission electron microscope (TEM).

2 shows an image of carbon oxide nanotubes taken with a transmission electron microscope, oxidized according to the present invention.

3 shows another image of carbon oxide nanotubes taken with a transmission electron microscope, oxidized according to the present invention.

4 shows another image of carbon oxide nanotubes taken with a transmission electron microscope, oxidized according to the present invention.

5 is a diagram showing the (emission current-emission voltage) relationship of the original carbon nanotube array oxidized according to the present invention.

FIG. 6 shows the relationship of In (J / E ² ) to I / E according to the Fowler-Nordheim field emission theory for the original carbon nanotube array oxidized according to the present invention.

FIG. 7 is a diagram showing the (emission current-emission voltage) relationship of the original carbon nanotube arrays oxidized by O ₃ and BR ₂ according to the present invention.

The present invention relates generally to current emitting devices, more specifically to carbon nanotubes and emission processes used for electron emission.

A great deal of effort has been made by various people to explore or discover new ways of emitting electrons to drive display screens or other devices. This is particularly important when the application of a display to a mobile device is generalized and expectations for miniaturization of the device including the display are high. One of the most important new approaches explored or discovered for this purpose is to present a compact, electron-emitting display of the current-emitting device without the need for a high onset or low onset emission voltage to minimize voltage source capacity. You want to make it easy to drive the screen. It is evident that both small current dissipating devices and voltage sources of low capacitance and / or low voltage levels have a significant effect on the dimensional miniaturization of devices including display screens. Devices requiring a low operating voltage (due to a low starting emission voltage that emits electrons to drive the display screen) consume less energy and can therefore be operated for a long time based on the same battery capacity. This is particularly important for mobile devices with displays.                         

In order to have the above-mentioned features in the current dissipating device, various kinds of means have been tried, among which a carbon nanotube array or film (for example, an array consisting of a plurality of carbon nanotubes, or a plurality of carbon nanotubes) Film containing) was noticeably noticed. However, it is preferable to use carbon nanotubes as a current emitting device, but there is a problem that it is not possible to emit enough electrons to drive the display screen with a feasible starting emission voltage. Accordingly, it will be appreciated that for carbon nanotubes to be used as a current emitting device for driving a display screen, it is an important condition that it is possible to emit enough electrons to drive the display screen with a feasible starting emission voltage.

To date, many scientists believe that carbon nanotubes are considered the most potent current-emitting devices that drive display screens (especially where the display is as small as possible, or where the voltage-level of the capacity and / or power supply is limited). Attempts have been made to allow the tube to emit more electrons at a more feasible starting emission voltage. Among these trials, a carbon nanotube array was grown on an iron / silica substrate, then peeled off and inverted so that the bottom (the side in contact with the original substrate) faced upwards, resulting in open carbon nanotubes with 0.6-1.0 It was a strong impression that reaching a very low turn-on voltage of V / μm (a conventional starting emission voltage of vertically aligned carbon nanotubes formed by the CVD method is known to be in the range of 4-0.9 V / μm). While the low onset emission voltage is achieved in this approach, the process of stripping and inverting the nanotube array or film is required, requiring skill in the art, and it is difficult to implement this process, especially when trying to commercialize a product. This is the reason why numerous attempts have been made to achieve a current emitting device that can be easily produced to emit sufficient electrons to drive a display screen at an economically feasible starting emission voltage. Of these attempts, it is most desirable to have carbon nanotubes that are easily formed and can be well adapted to actual products.

Accordingly, it is an object of the present invention to provide a current dissipating device consisting of a material comprising carbon, which can work well on display screens, in particular on displays on mobile devices or small devices, or on devices with power supplies limited to low voltage levels or low capacities. To provide a process that applies to.

Accordingly, another object of the present invention is to provide a process applied to an object made of a material comprising carbon, which works well for a display.

Accordingly, another object of the present invention includes carbon, which can emit more electrons (i.e., increase current dissipation), or can emit electrons at lower onset emission voltages (i.e., less applied electric fields). It is to provide a process that is applied to an object composed of a material.

It is a further object of the present invention to provide a current dissipating device which is readily manufactured to work well on a display, in particular on a mobile device or a small device, or on a device with a power supply limited to a low voltage level or low capacity.                         

Other features, advantages, and objects will be apparent from the following detailed description with reference to the accompanying drawings.

In the present specification, "start emission voltage for current discharge" means an electric field required for current discharge, and "turn-on voltage" means a minimum electric field for any current discharge.

One aspect of the present invention may be represented by a process applied to a current dissipation device that is composed of a material having a distal end and comprising a carbon, and that works well for a display or any device in which emission of electronic current from an object is desired. The process includes oxidizing the current dissipating device at an operating temperature higher than ambient temperature until at least the shape of a portion of the distal end is changed. The current dissipating device here may be in the form of tubes or nanotubes or small-sized balls (such as spherical balls or elliptical balls), or semi-elliptical, extending (or growing) from the substrate or carrier and extending out of the substrate (or carrier). It may have a distal end. For example, the distal end may be a surface facing the display screen on which electrons emitted from the current emitting device are driven (ie, collided). The current dissipation device may be considered to have other ends on or connect them to the substrate (or carrier), or may be considered to be grown from the substrate.

Another aspect of the invention is a process that is applied to a current dissipation device, comprised of a material comprising carbon, that works well for a display or any device in which emission of electronic current is desired. Here, the current dissipating device does not have a portion that is considered as a distal end. For example, the current dissipating device may be ball-shaped, or ball-like, or half-ball shaped with a flat surface on a substrate or carrier. The direction in which the current emitting device emits electrons need not be limited to a particular direction or to a specific area, and electrons need not be emitted from the distal end of the device.

When a current dissipating device composed of a material containing carbon is oxidized by a fluid containing O ₃ , the operating temperature required for oxidation (or high density current dissipation) to obtain a current dissipating device that can work well on the display screen is only It can be as low as minus 50 degrees Celsius, minus 50 degrees Celsius in the real world. Accordingly, another aspect of the present invention provides a current release that can oxidize the current release device to any temperature in the real world using a fluid comprising O ₃ to release high density currents at the same or lower onset release voltage. The process of obtaining a device.

After being oxidized in accordance with the present invention, current-emitting devices composed of carbon-containing materials always surface carboxylic acid groups (-COOH), and / or hydroxyl groups (-OH), and / or ketone groups (> C = O). On at least a portion of the. Thus, another aspect of the present invention includes carbon, having a carboxylic acid group (-COOH), and / or a hydroxyl group (-OH), and / or a ketone group (> C = O) on at least a portion of the surface. It is to provide a current dissipation device composed of a material.

In current-emitting devices composed of carbon-containing materials, the cause of the shape change to release high-density electrons at the same or lower onset emission temperatures is that some C = C double bonds in the carbon therein break up. . The process according to the invention comprises C = C double bonds in a current dissipating device which consists of a material comprising carbon and which works well on a display or which is capable of dissipating many currents at the same or lower onset emission voltage. Splitting is a unique technique. Thus, another aspect of the present invention improves the current dissipation of the current dissipating device by breaking the C = C double bond of the current dissipating device, i.e., the current dissipating device emits a high density of current at the same or lower starting discharge voltage. To provide a process that can be applied to the current-emitting device consisting of a material containing carbon that can be.

Obviously, the current dissipation device treated according to the invention is not necessarily used exclusively for displays. In practice the device can be used in any case where the current emitted from the object plays a role.

The present invention will be fully understood from the following detailed description disclosed with reference to the accompanying drawings.

1, the carbon nanotube 11 has a distal end 12 and can be used as a current emitting device for emitting electrons. For example, an array of carbon nanotubes 11 can be used to emit electrons driving a display screen (not shown), ie the emitted electrons collide with the display screen to form an image on the display screen. The carbon nanotubes 11 may be considered to have other end portions 13 on or in connection with or on a substrate or carrier (not shown), or may be considered to be grown from a substrate.                     

2 is a view of the carbon nanotubes 21 oxidized in accordance with the present invention to change their distal end 22 shape. For example, at least a portion 23 of the distal end 22 is recessed and at least a portion 24 of the distal end is modified in tip shape or similar to the tip shape, thereby improving the current dissipation of the carbon nanotubes and initiating emission voltage. Will descend.

3 is a view of carbon nanotubes 31 that have been oxidized in accordance with the present invention to change their distal end 32 shapes. For example, at least a portion 33 of the distal end 32 is recessed and at least a portion 34, 35 of the distal end is modified in tip shape or similar to the tip shape, thereby improving and initiating current dissipation of the carbon nanotubes. The emission voltage goes down.

FIG. 4 is a view of the carbon nanotubes 41 in which the current emission of the carbon nanotubes is improved and the starting emission voltage is lowered by oxidizing according to the present invention and recessing at least a portion (denoted by three white arrows 43). to be.

FIG. 5 is a diagram showing the (emission current-emission voltage) relationship between carbon nanotubes oxidized according to the present invention using an original carbon nanotube array and a gaseous fluid comprising oxygen. The Y axis represents the emission current density J (unit: dB / cm ² ), and the X axis represents the applied electric field E (unit: V / µm). The curves shown as open circles ○ are for the original carbon nanotubes (not nanotubes oxidized according to the invention). The closed triangle ▲ curve shows carbon nanoparticles that oxidize for 10 minutes at 400 ° C. using a gaseous fluid containing oxygen, or oxidize for 10 minutes using a gaseous fluid containing oxygen and have a temperature of 400 ° C. For tube arrays. The curves shown as open triangles Δ are carbon nanoparticles oxidized for 20 minutes at 400 ° C. using a gaseous fluid containing oxygen, or carbon nanoparticles for 20 minutes using a gaseous fluid containing oxygen and 400 ° C. For tube arrays. The open star curves are carbon nanoparticles that oxidize for 25 minutes at 400 ° C. using a gaseous fluid containing oxygen or oxidize for 25 minutes using a gaseous fluid containing oxygen and have a temperature of 400 ° C. For tube arrays.

Referring to FIG. 5, when the nanotubes are oxidized for 10 minutes at 400 ° C. using a gaseous fluid containing oxygen, the nanotubes are not significantly different from the original nanotubes in terms of current emission. Comparing the two curves indicated by o), the nanotubes were oxidized for 20 to 25 minutes at an operating temperature of 400 ° C. using a gaseous fluid containing oxygen (△, ☆, And three curves, each denoted by (circle) and o). For condition E (applied electric field) = 4.5 V / μm, the J (emitted current density) of the original nanotubes (see the curves indicated by ○) is about 9 mA / cm ² , whereas the gaseous fluid containing oxygen J of the nanotubes oxidized for 25 minutes or more at an operating temperature of 400 ° C. can reach 72 μs / cm ² , which is eight times the original amount of nanotubes. As can be seen from the relationship of ln (J / E ² ) to l / E in FIG. 6 according to the Fowler-Nordheim field emission theory, the turn-on voltage for field emission (or current emission) is 0.8 V. / M to 0.5 V / m. The carbon nanotubes can be grown on a p-Si substrate.

FIG. 6 shows the relationship between ln (J / E ² ) versus l / E according to the Fowler-Nordheim field emission theory. In FIG. 6, the Y axis represents ln (J / E ² ) and the X axis represents l / E, where J is the emitted current density in ㎂ / cm ² and E is the applied electric field in V / μm. )to be. What is meant by the curves (actually lines) represented by o, o, o, and ☆ in FIG. 6 is similar to the meaning for the symbol in FIG. Arrow 7 represents the turn-on voltage region of the field emission (or current emission). The turn-on voltage of the field emission of the original nanotubes (see line marked ○) is about 0.8 V / μm, whereas the nanotubes oxidized for at least 25 minutes at 400 ° C using a gaseous fluid containing oxygen It will be appreciated that the turn-on voltage of the field emission (or current emission) (see lines denoted by Δ and ☆) can be as low as 0.5 V / μm. If nanotubes are used to drive the display screen (i.e., emit electrons colliding with the screen to display an image on the screen), and the spacer thickness between the screen and the emitter of the nanotube is 200 μm, field emission ( Or a decrease in the turn-on voltage of the current release from 0.8 V / μm to 0.5 V / μm means that the required 60 V field is reduced, which in particular limits the capacity and / or voltage level of the display or power supply on the mobile device. Or use of nanotubes in any device where the convenience of accommodating high voltage levels is limited.

Although the curves of FIGS. 5 and 6 were tested at an operating temperature of 400 ° C., in order to achieve the object of the present invention, it can actually be oxidized for a suitable time at any temperature above ambient temperature, preferably at 70 ° C. or higher.

FIG. 7 is a diagram showing the (emission current-emission voltage) relationship between an original carbon nanotube array and nanotubes oxidized according to the present invention using a gaseous fluid comprising ozone (O ₃ ) or bromine (Br ₂ ). . The Y axis represents the emission current density J (unit: dB / cm ² ), and the X axis represents the applied electric field E (unit: V / µm). The curves shown as open circles ○ are for the original carbon nanotube arrays (not oxidized according to the invention). The curve denoted by the symbol x is for a carbon nanotube array oxidized for 20 minutes at room temperature using a gaseous fluid containing bromine. The curve denoted by the symbol ▽ is for a carbon nanotube array oxidized for one minute at room temperature using a gaseous fluid containing ozone. The curve denoted by the symbol □ is for a carbon nanotube array oxidized for 3 minutes at room temperature using a gaseous fluid containing ozone. The curve represented by the symbol Δ is for an array of carbon nanotubes oxidized for 5 minutes at room temperature using a gaseous fluid containing ozone. The curve marked with the symbol ★ is for a carbon nanotube array oxidized for 7 minutes at room temperature using a gaseous fluid containing ozone. The curve represented by the symbol + is for an array of carbon nanotubes oxidized for 9 minutes at room temperature using a gaseous fluid containing ozone.

Referring to FIG. 7, the carbon nanotubes are oxidized for 1 minute at room temperature using a gaseous fluid containing ozone or 20 minutes at room temperature using a gaseous fluid containing bromine in terms of current emission of the carbon nanotubes. Oxidation does not differ significantly from the original nanotubes (compare three curves, respectively, denoted by ▽, ×, and ○), but if the nanotubes are oxidized for three minutes at room temperature using a gaseous fluid containing ozone, It can be seen that there is a significant difference from the nanotubes of (compare the five curves, respectively, indicated by?,?, ★, +, and?). It should be noted that oxidizing nanotubes at room temperature using a gaseous fluid containing ozone does not necessarily result in good electron emission. For example, the gaseous fluid containing ozone can be known from four curves represented by □, Δ, ★, and + while oxidizing carbon nanotubes at room temperature for 3 minutes, 5 minutes, 7 minutes, and 9 minutes, respectively. As can be seen, the shorter the time the carbon nanotubes are oxidized, the better the carbon nanotubes emit electrons. Oxidation of carbon nanotubes at room temperature with ozone for extended periods of time causes oxidation damage along the walls of the nanotubes, thus reducing current dissipation.

In experiments, when the ambient temperature is above 50 ° C. (ie −50 ° C.), the carbon nanotube arrays have significantly improved their electron current emission (i.e., high density electron current) with the same or lower onset emission voltage. It can be seen that it can be oxidized using ozone.

Changing shape so that the carbon nanotubes can emit high density electrons at the same or lower onset emission voltage (existing tips become sharper, or new tips or depressions are formed, for example) in the carbon nanotubes This is because some C = C double bonds in carbon are cleaved, where C represents carbon. The process according to the invention allows the carbon nanotubes to behave better in displays due to the cleavage of C = C double bonds in the carbon nanotubes, or they can emit high density currents at the same or lower onset emission voltage. This is a unique technology at this point.

Although the experiments on the curves of FIGS. 5 and 7 are mainly based on the oxides of oxygen and ozone, the process according to the invention is not necessarily limited to the use of oxygen and ozone as oxides, in practice O ₂ , O ₃ , CO Oxides selected from ₂ , NO ₂ , SO ₂ and SO ₃ , or mixtures of at least two of them can be used, and either can cleave some C = C double bonds of carbon in the carbon nanotubes, where O , C, N, S is oxygen, carbon. Nitrogen and sulfur are respectively shown.

Experiments have shown that the sharper the tip of the carbon nanotube, the lower the starting emission voltage for the current to be emitted from the nanotube and more current can be released from the nanotube.

Oxides in liquid fluid form can be used for the oxidation according to the invention, but gas oxides are preferred.

Obviously, to achieve the object of the present invention, it is not necessary to expose the entire carbon nanotube to the oxide in the process according to the present invention. For example, when only electron terminals emit electron current, the terminal portions need only be exposed to oxides.

The process of oxidizing a nanotube array by an oxide (or a fluid comprising an oxide) to an operating temperature higher than ambient temperature, heats the oxide (or fluid) until the oxide (or fluid) reaches the operating temperature. It will be appreciated that the method may comprise the steps of exposing and exposing at least a portion (eg, a distal end) of the nanotube to the oxide (or fluid) until the shape of at least a portion of the nanotube changes. .

While the invention has been described with reference to the most practical and preferred embodiments, it will be understood that the invention is not limited to the above embodiments. On the contrary, any modification or similar device is considered to be included in the spirit of the present invention.

The process according to the invention allows the carbon nanotubes to function better in the display due to the cleavage of C = C double bonds in the carbon nanotubes, or to emit high density currents at the same or lower onset emission voltage.

Claims (35)

In a process applied to a current dissipating device having a distal end and composed of a material comprising carbon, Oxidizing the current dissipating device at an operating temperature of at least 70 ° C. and at most 400 ° C. until at least a portion of the distal end is tip shaped or recessed. Process comprising. delete delete The method of claim 1, And wherein said current dissipating device is a carbon nanotube. delete The method of claim 1, At least a portion of said distal end is exposed to a fluid comprised of a material comprising oxygen. The method of claim 6, Said fluid is a gaseous substance. delete delete delete delete delete In a process applied to a current dissipating device composed of a material comprising carbon, Oxidizing the current discharging device at an operating temperature of at least 70 ° C. and no more than 400 ° C. until at least a portion of the current discharging device is tip-shaped or recessed. Process comprising. delete delete The method of claim 13, And the current dissipating device is carbon nanotubes. delete delete delete delete delete delete delete In a process applied to a current dissipating device composed of a material comprising carbon, Oxidizing the current discharging device with a fluid comprising O ₃ until at least a portion of the current discharging device is tip-shaped or recessed. Process comprising. delete delete The method of claim 24, Wherein said current dissipating device is oxidized at a temperature of at least minus 50 degrees Celsius. delete delete delete A surface having at least one of a carboxyl group (-COOH), a hydroxyl group (-OH), and a ketone group (> C = O) on its upper side, and A body portion enclosed by the surface and composed of a material comprising carbon Current discharge device comprising a. The method of claim 31, wherein And the surface has a tip shape at least a portion thereof. The method of claim 31, wherein And the surface is recessed at least a portion thereof. In a process applied to a current dissipating device composed of a material comprising carbon, Separating some C = C double bonds of carbon in the current-emitting device until at least a portion of the current-emitting device is tip-shaped or recessed Process comprising. The method of claim 34, wherein And wherein said current dissipating device is comprised of nanotubes.

Images