JP4814023B2 - Driving method of electron emitter - Google Patents

Description

  The present invention relates to a method of driving an electron emitter having a number of nanometer-order fine protrusions having a shape suitable for field emission.

  Examples of the electron emitter include a spint type structure in which silicon or metal is formed in a minute conical shape on a substrate in Patent Document 1 or the like, or a structure in which carbon nanotubes are formed on a substrate in Patent Document 2 or the like. Others are known. One application of such an electron emitter is a field emission lamp in which the electron emitter is placed opposite to the anode in a vacuum sealed state in a glass tube and a phosphor is laminated on the anode.

  In this field emission lamp, an electric field is applied to the electron emitter, and electrons are emitted from the surface of fine projections such as carbon nanotubes. The emitted electrons collide with the phosphor and can emit light. .

When the aspect ratio of the fine protrusions is not uniform, electric field concentration occurs in specific fine protrusions with an aspect ratio, and electrons are emitted, and the fine protrusions are consumed by thermal evaporation earlier than other fine protrusions. Then, as the electric field concentration occurs in fine projections with different aspect ratios, the electron emission properties become unstable, causing problems such as flickering of light emission and unevenness of light emission, and the life characteristics become short and unstable. End up.
JP-A-10-223128 JP 2005-317415 A

  The problem to be solved by the present invention is to provide a driving method that stabilizes the electron emission physical properties and lifetime characteristics of an electron emitter.

An electron emitter driving method according to the first aspect of the present invention is a method of driving an electron emitter having a plurality of fine protrusions capable of field emission and applying an electric field to the anode to emit electrons from the fine protrusions toward the anode. , The driving voltage for applying the electric field between the anode and the electron emitter is a pulse voltage that is positive and periodically repeated , and this pulse voltage is at the initial stage of its rise. The waveform is shorter in time than the waveform of the other stage following the initial stage, the crest value is higher on the positive side than the waveform of the other stage following the initial stage , and the fine protrusions are evaporated. It is easily set to a voltage value that can stabilize the electron emission physical properties and lifetime characteristics of the electron emitter, and the peak value of the waveform after the initial stage is less likely to cause field evaporation of the fine protrusions. And it is characterized in that it is set below the voltage value that can be field electron emission. Here, field evaporation is a phenomenon in which atoms of a conductive substance are ionized from the surface under a high electric field of about several V / nm.

In the first aspect of the present invention , any one of a plurality of fine protrusions selected from among a plurality of fine protrusions at the initial rising stage of the waveform of the drive voltage applied between the anode and the electron emitter to emit electrons from the electron emitter by field emission. Since the lifetime of the electron emitter is stabilized by field evaporation, the lifetime of the electron emitter can be significantly extended. In this case, the drive voltage is a pulsed voltage that is positive and is periodically repeated, and this pulsed voltage has a peak value of the waveform at the initial stage of the rising of the other stage following the initial stage. Since it is higher than the waveform on the positive polarity side and is set to a voltage value above which the fine protrusions are easy to evaporate , the lifetime characteristics of the electron emitter can be stabilized periodically during driving, In particular, the electron emission properties of the electron emitter can be stabilized and the life characteristics can be improved.

An electron emitter driving method according to the second aspect of the present invention is a method of driving an electron emitter having a plurality of fine protrusions capable of field emission and applying an electric field to the anode to emit electrons from the fine protrusions toward the anode. in the drive voltage for applying the electric field between the anode and the electron emitter is a pulsed voltage are repeated periodic manner, the voltage of the pulse-shaped, the waveform of the rising early stage the It is shorter in time than the waveform of the other stage following the initial stage, the absolute value of the wave height is higher on the negative polarity side than the waveform of the positive polarity of the other stage following the initial stage, and the fine protrusion is It is set to a voltage value that can stabilize the electron emission physical properties and lifetime characteristics of the electron emitter, which is easy to evaporate, and the peak value of the waveform after the initial stage is fine on the positive electrode side. It is characterized in that Kiga is set below the voltage value that can be field evaporation difficult field emission.

In the second aspect of the present invention , any one of the selected fine protrusions among the plurality of fine protrusions at the initial rising stage of the waveform of the driving voltage applied between the anode and the electron emitter for emitting electrons from the electron emitter by field emission. Since the electron emission properties and lifetime characteristics of the electron emitter are stabilized by field evaporation, the electron emission of the electron emitter is improved and the lifetime can be greatly extended. In this case, a pulse voltage whose driving voltage is repeated periodic manner, positive other stages following the absolute value the initial stage of the peak of the pulse-shaped voltage waveform of the rising initial stage rather higher than the waveform on the negative polarity side, and since the fine projections is set to more than the electric field easily evaporated voltage value, remarkably to achieve improved stabilization and lifetime of the electron emission properties of the electron emitter than conventional Will be able to.

  According to the present invention, the electron emitter can be driven so as to stabilize the electron emission physical properties and life characteristics of the electron emitter.

  Hereinafter, an electron emitter driving method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Although the electronic device in which the electron emitter is incorporated is applied to a field emission lamp as an example, the electronic device to which the driving method of the embodiment is applied is not limited to the field emission lamp. Further, the field emission lamp is not limited to a tubular shape, and may include a flat panel type.

  FIG. 1 schematically shows the field emission lamp 10, in which an anode 12 is formed on the inner surface of a vacuum-sealed glass tube 12, and a phosphor 16 is laminated on the anode 12. A wire-shaped electron emitter 18 is disposed at a substantially center of the glass tube 12 in the longitudinal direction of the glass tube. The electron emitter 18 is configured by forming a fine protrusion 18b having a sharp end in the order of nm made of a carbon film on the surface of a conductor wire 18a. The fine protrusions 18 include carbon nanotubes, carbon nanowalls, acicular carbon films, and others. The fine protrusion 18b may be formed of a metal film.

  In this field emission lamp 10, when a power supply (not shown) is applied between the anode 12 and the electron emitter 18, the fine protrusion 18b of the electron emitter 18 emits electrons by field emission, and the phosphor 16 emits the electrons. Excited light is emitted upon irradiation with electrons.

  FIG. 2 shows the electron emitter 18 in an enlarged manner. FIG. 2 is schematically exaggerated for understanding the illustration. As shown in FIG. 2, the fine protrusions 18b on the conductor wire 18a in the embodiment are carbon nanotubes, carbon nanowalls, or other carbon films. The fine protrusions 18b shown in FIG. 2 are shown in a state where the aspect ratios are not uniform before the stabilization process. The fine protrusions are not limited to the carbon film but may be composed of a metal film.

  FIG. 3 shows a waveform of a drive voltage applied from the power source between the anode 14 and the electron emitter 18 to drive the electron emitter 18. In FIG. 3, the horizontal axis represents time (t) and the vertical axis represents voltage (V). This drive voltage waveform is pulse-like, and a drive period Ton that is a period for applying the drive voltage and a stop period Toff that is a period for stopping the application of the drive voltage are alternately and periodically repeated. Yes. The waveform of the drive voltage in the drive period Ton is a periodic voltage that is positive and periodically repeated. The rising initial stage is the stabilization process stage Ta, and the peak value Va is the stabilization process stage Ta. It is made higher on the positive polarity side than the peak value Vb of the driving stage Td, which is another stage that follows. As a result, a high electric field is applied to the fine protrusions 18b of the electron emitter 18 at an initial stage every time the drive voltage rises, and the fine protrusions 18b are selectively evaporated to have an aspect ratio as a whole. It is equalized.

  The crest value Va is preferably set to be equal to or higher than a voltage value at which the fine protrusions 18b of the electron emitter 18 are easily evaporated and can be equalized. The crest value Vb is preferably set to be equal to or less than a voltage value at which the fine protrusions 18b of the electron emitter 18 are less likely to evaporate in the field and emit field electrons.

  The driving period Ton is a combination of the stabilization processing stage Ta and the driving stage Tb. This stabilization process will be described. In the embodiment, the stabilization process Ta is performed in a very short time, and this stabilization is performed mainly by field evaporation. When the fine protrusions 18b are stabilized by electric field evaporation, the aspect ratio of the entire fine protrusions 18b is equalized, the unstable part with respect to the electric field is removed, and the electron emission physical properties are extremely stabilized.

  FIG. 4 shows the electron emitter 18 after stabilizing the electron emitter 18 shown in FIG. As a result of this stabilization treatment, the fine projections 18b on the surface of the electron emitter 18 are made uniform in overall aspect ratio by field evaporation, and the unstable portion with respect to the electric field is removed, and the electron emission physical properties and lifetime characteristics are stabilized. It has an electron emitter configuration.

  Here, the principle of the stabilization process by field evaporation will be described with reference to FIG. First, when the facing distance between the electrode (anode) 14 used for the stabilization process and the electron emitter 18 is d and the voltage of the DC power supply 20 is V, the average electric field E1 in the whole anode 14 and electron emitter 18 is V / d. Given in. In this case, the electric field required for causing the atoms constituting the fine protrusions 18b on the surface of the electron emitter 18 to jump out is required to be on the order of V / nm. In this case, since the aspect ratio of the fine protrusion 18b is not uniform, electric field concentration locally occurs in the specific fine protrusion 18b. In such a case, the local electric field E2 applied to each fine protrusion 18b is given by E1 · β using the electric field concentration factor β in the Fowler-Nordheim equation. The electric field concentration factor β increases as the tip of the fine protrusion 18b becomes sharper, but is about 1000 or more. Therefore, when the facing distance d between the anode 14 and the electron emitter 18 is set to the μm order, the electron emitter 18 By applying the high voltage to the surface of the fine projection 18b, a high electric field on the order of V / nm is applied to the surface of the fine projection 18b, and atoms are ejected from the surface of the fine projection 18b, causing the fine projection 18b to be evaporated. Is done. As a result, the aspect ratio of the fine protrusions 18b is equalized, and the life characteristics are improved.

  As described above, in the embodiment, the initial stage of the drive voltage rise is set as the stabilization process stage Ta, and the peak value of the drive voltage is set high to Va to stabilize the fine protrusions. Since the high value is set low to Vb and electrons are emitted from the fine protrusions of the electron emitter, the life characteristics are remarkably improved.

  FIG. 6 shows the lifetime characteristics of the electron emitter when stabilized according to the embodiment, and FIG. 7 shows the lifetime characteristics of the electron emitter when not stabilized.

  FIG. 6A shows the waveform of the drive voltage in the embodiment, and FIG. 6B shows the waveform of the current in the embodiment. In the embodiment, as shown in FIG. 6A, when the driving process is performed in the next period Tb after the stabilization process is performed in the initial period Ta as shown in FIG. Even if a slight current decrease is observed in the period Ta during the stabilization process, the current increases in the next period Tb, which indicates that the lifetime of the electron emitter is greatly extended.

  FIG. 7A shows a conventional driving voltage waveform, and FIG. 7B shows a conventional current waveform. Conventionally, as shown in FIG. 7 (a), the driving voltage is driven for the entire period Ton and is not stabilized. Therefore, as shown in FIG. 7 (b), every time the electron emitter is driven with the driving voltage. It is shown that the lifetime characteristics are decreasing due to the decrease in current.

  As shown in FIG. 8, the pulse waveform of the drive voltage may be a negative voltage during the initial period Ta, and may be subjected to stabilization by performing field evaporation with this negative voltage.

As a reference example of the waveform of the drive voltage, a sine wave may be used as shown in FIG. In the initial stage of rising of the drive voltage, the negative half wave side of both polarities of the sine wave is set as the stabilization processing stage Ta, the peak value is set high to Va, and the positive side half wave side is set as the drive stage Tb. be able to.

  As described above, in the embodiment, in order to emit electrons from the electron emitter 18 by field emission, the fine protrusions 18b are selectively evaporated in the initial stage of the rising of the waveform of the driving voltage applied between the anode 14 and the electron emitter 18. Therefore, the lifetime of the electron emitter 18 can be greatly extended.

FIG. 1 is a diagram showing the configuration of a field emission lamp. FIG. 2 is an enlarged view showing an electron emitter before stabilization processing in the field emission lamp of FIG. FIG. 3 is a diagram showing a waveform of a driving voltage applied between the anode and the electron emitter. FIG. 4 is an enlarged view showing the stabilized electron emitter. FIG. 5 is a diagram used to explain field evaporation. FIG. 6A is a diagram showing a waveform of a drive voltage including a stabilization processing waveform at the beginning of the rise of the drive voltage, and FIG. 6B is a graph showing the time of the electron emitter when driven by the drive voltage of FIG. It is a figure which shows an electric current characteristic. FIG. 7A is a diagram showing a waveform of a drive voltage that does not include a stabilization processing waveform at the beginning of the rise of the drive voltage, and FIG. 7B is a time of an electron emitter when driven by the drive voltage of FIG. It is a figure which shows the electric current characteristic with respect to. FIG. 8 is a diagram showing waveforms of other drive voltages. FIG. 9 is a diagram illustrating a waveform of the drive voltage according to the reference example .

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electron emitter 12 Glass tube 14 Anode 16 Phosphor 18 Electron emitter 18a Conductor wire 18b Fine protrusion

Claims (2)

In a method of driving an electron emitter having a plurality of fine projections capable of field emission and applying an electric field between the anode and emitting electrons from the fine projections toward the anode,
The driving voltage for applying the electric field between the anode and the electron emitter is a pulsed voltage that is positive and periodically repeated ,
This pulse-like voltage is such that the waveform of the initial stage of the rising is shorter in time than the waveform of the other stage that follows the initial stage, and the peak value is more positive than the waveform of the other stage that follows the initial stage. Is set to be higher than the voltage value that can stabilize the electron emission physical properties and life characteristics of the electron emitter, and the fine protrusions are easy to evaporate in the electric field,
An electron emitter driving method, characterized in that a peak value of a waveform at a stage after the initial stage is set to be equal to or less than a voltage value at which fine projections are hard to evaporate in a field and field electrons can be emitted . In a method of driving an electron emitter having a plurality of fine projections capable of field emission and applying an electric field between the anode and emitting electrons from the fine projections toward the anode,
Driving voltage for applying the electric field between the anode and the electron emitter is a pulsed voltage are repeated periodic manner,
This pulse-like voltage is such that the waveform at the initial stage of the rise is shorter in time than the waveform of the other stage that follows the initial stage, and the absolute value of the wave height of the other stage that follows the initial stage. Higher than the waveform of the positive polarity on the negative polarity side, and the fine protrusions are easy to evaporate in the electric field , and are set to a voltage value or more that can stabilize the electron emission physical properties and life characteristics of the electron emitter,
The driving method of the electron emitter, wherein the peak value of the waveform after the initial stage is set to be equal to or less than a voltage value at which the fine protrusions are difficult to evaporate in the field and can emit field electrons on the positive electrode side .

Images