JP3775367B2 - Cold cathode electron source and display device using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cold cathode electron source that emits electrons by the action of an electric field. Furthermore, the present invention relates to a flat panel display device using the cold cathode electron source.
[0002]
[Prior art]
Field electron emission in which electrons are emitted by the action of an electric field means that when an applied electric field on the surface of a metal or a semiconductor is set to about 10 ⁹ V / m, the electron is emitted into a vacuum even at room temperature through a barrier due to a tunnel effect. It is a phenomenon. This field electron emission electron source is called a cold cathode electron source, and has many excellent features such as energy saving and longer life compared to an electron source that emits thermal electrons using thermal energy (hot cathode electron source). Has a point.
[0003]
A carbon nanotube (hereinafter abbreviated as CNT) is known as an electron emission material applied to a cold cathode electron source. CNT is a material having a very high aspect ratio of 4 to 50 nm in diameter and 10 μm or more in length, so that an external electric field can be efficiently concentrated on the tip of the CNT. This indicates that even if the electric field applied from the outside is macroscopically low, the electric field is amplified greatly in the vicinity of the CNT, and a sufficient electric field strength can be generated to extract electrons. As a result, electrons can be emitted even if the extraction electrode potential applied to the electrode is relatively small, and there is an advantage that the voltage required for the control power supply can be reduced.
[0004]
FIG. 5 is a cross-sectional view of a main part of the display device disclosed in Japanese Patent Application Laid-Open No. 2001-155666. Reference numeral 109 denotes a display surface, 141 denotes a transparent anode, 142 denotes a phosphor film, and the light-emitting portion includes the transparent anode 141 and the phosphor film 142. Reference numeral 120 denotes an electron emission portion made of CNT, 121 denotes a substrate electrode, and 125 denotes an electron extraction electrode. The surface of the electron emission unit 120 is irradiated with a laser to expose the CNTs.
[0005]
When a positive potential is applied to the electron extraction electrode 125 and a negative potential is applied to the substrate electrode 121 to apply an electric field to the electron emission portion 120, electrons are emitted from the tip portion of the CNT. The electrons pass through the opening of the electron extraction electrode 125 and reach the light emitting portion, and light emission occurs when the electrons collide with the light emitting portion. An image is displayed on the display surface 109 using this light emission.
[0006]
[Problems to be solved by the invention]
However, there is a problem in that the image quality is non-uniform because the light emitting points are scattered in the form of dots on the display surface 109. This is because the CNT is exposed unevenly depending on the fine unevenness of the surface state of the electron emission portion 120, and the electron emission region is biased on the surface of the electron emission portion 120. Although the surface of the electron emission portion 120 has been flattened so far, it has been difficult to flatten the surface with an accuracy of 1 μm or less.
[0007]
The present invention has been made to solve the above-described problems, and provides a cold cathode electron source capable of ensuring the uniformity of electron emission. In addition, a flat panel display device using the electron source to improve image quality is provided.
[0008]
[Means for Solving the Problems]
The cold cathode electron source according to claim 1 includes an electron emission material that emits electrons by the action of an electric field, a substrate electrode and an electron extraction electrode for applying an electric field to the electron emission material, and a substrate electrode and an electron extraction electrode. A porous member made of continuous pores in between, the porous member contains an electron emission material, and the tip of the electron emission material protrudes from the hole wall of the porous member.
[0009]
The cold cathode electron source according to claim 2 is such that the electron emission material is a carbon nanotube.
[0010]
In the cold cathode electron source according to claim 3, the porous member is formed of a secondary electron multiplying material and has an uneven hole wall surface.
[0011]
According to a fourth aspect of the present invention, there is provided a cold cathode electron source comprising: an electron emission material that emits electrons by the action of an electric field; a substrate electrode and an electron extraction electrode for applying an electric field to the electron emission material; Ri Do from the interconnected pores between, formed by the secondary electron multiplication material, and a porous member having a hole wall surface having irregularities, the electron-emitting material in which is disposed on a surface of the substrate electrode is there.
[0012]
6. A display device according to claim 5, wherein the cold cathode electron source emits electrons by the action of an electric field in a display device that displays an image using light emission caused by collision of electrons emitted from the cold cathode electron source. A substrate electrode and an electron extraction electrode for applying an electric field to the electron emission material, and a porous member comprising continuous holes between the substrate electrode and the electron extraction electrode, and the porous member contains the electron emission material And the front-end | tip part of an electron emission material protrudes from the hole wall of a porous member.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a cross-sectional view of an essential part for explaining Embodiment 1 of a display device to which the present invention is applied. FIG. 2 is a cross-sectional view of a cold cathode electron source used in this display device. In the figure, 1 is a substrate glass, 2 is a cold cathode electron source, and 3 is a spacer. 4 is an aluminum back anode, 5 is a phosphor film, and both form a light emitting portion. 6 is a black matrix, 7 is a display surface, and 8 is an extraction electrode. In the cold cathode electron source 2, 21 is CNT as an electron emission source material, 22 is a substrate electrode, 23 is an electron extraction electrode, and 24 is a porous member comprising continuous holes.
[0014]
The porous member 24 is located between the substrate electrode 22 and the electron extraction electrode 23 and is formed from a high resistance glass layer. At this time, the glass layer is preferably a secondary electron multiplier material, and includes, for example, magnesium oxide. Only the hole wall surface of the continuous hole may be covered with the secondary electron multiplier material. Moreover, the hole wall surface of a continuous hole has an unevenness | corrugation, and a hole part shall be a magnitude | size about 2 micrometers in diameter in general. The tip of the CNT 21 protrudes from the hole wall of the porous member 24.
[0015]
Then, the formation method of the porous member 24 is demonstrated. First, CNT is mixed in the glass paste and spherical organic material is mixed. Examples of the spherical material include plastic particles such as polymethyl methacrylate (hereinafter abbreviated as PMMA). It is preferable that 10 to 20% by weight of CNT is mixed in the glass paste. PMMA particles having a diameter of 5 to 10 μm are preferable, and 5 to 10 wt% is preferably mixed in the glass paste. At this time, the CNT and PMMA are uniformly dispersed in the glass paste by sufficiently kneading the glass paste.
[0016]
A glass paste in which CNT and PMMA are mixed is printed on the substrate electrode 22 by screen printing. In this case, the glass paste pattern may be formed by a screen printing plate, or may be formed in a predetermined shape by blasting or the like after printing a certain area as a solid film. Control of the required thickness in the film thickness direction can be performed by adjusting the viscosity of the glass paste and the printing pressure of the screen plate, and multilayer coating may be performed. In addition to screen printing, flexographic printing and offset printing are also possible, and there may be an inkjet method.
[0017]
The glass paste pattern thus formed is fired after drying to become a porous member. Here, the PMMA particles and the organic solvent as the glass paste binder burn out at about 350 ° C. in an oxygen atmosphere. In general, the firing temperature required for the glass paste to be printed and transformed into a glass layer is in the range of 400 to 600 ° C. Under these firing conditions, the PMMA particles and the organic solvent are combusted. The porous member obtained after firing shrinks by 20-30% compared to before firing, and the combustion mark of PMMA particles becomes vacancies, and due to this dimensional shrinkage, vacancies are connected to form a large number of continuous holes. . In addition, most of the CNTs protrude from the hole wall at the time of dimensional shrinkage, and the amount of exposure of the CNT tip increases. Furthermore, since the CNT and PMMA are uniformly dispersed, the exposure uniformity of the CNT tip is also improved.
[0018]
Next, the operation will be described. When a positive potential is applied to the electron extraction electrode 23 and a negative potential is applied to the substrate electrode 22 to apply an electric field to the CNT 21 in the porous member 24, electrons are emitted from the tip of the CNT 21. The electrons pass through the opening of the electron extraction electrode 23 and reach the light emitting portion. When the electrons collide with the light emitting portion, an image is displayed on the display surface 7.
[0019]
When the thickness of the porous member 24 is 20 μm, a high electric field of 10 V / μm is generated at an applied voltage of 200 V. In general, since the dielectric strength of glass is about 20 V / μm, dielectric breakdown does not occur under such operating conditions. Since the electron emission electric field strength of the CNT 21 is about 3 V / μm, electrons are emitted from the tip of the CNT 21 protruding from the hole wall of the porous member 24 by the action of this electric field. Since the exposure uniformity of the tip of the CNT 21 is improved, the electron emission characteristics can be made uniform.
[0020]
Furthermore, since the porous member 24 is made of a secondary electron multiplying material, new electrons are emitted by the electrons colliding with the hole walls. FIG. 3 is a schematic diagram for explaining the locus of the emitted electrons from the electron emitting material in this embodiment. In the figure, arrows indicate the locus of emitted electrons. Since the hole wall surface of the continuous hole has irregular irregularities, the emitted electrons colliding with the hole wall surface are irregularly reflected, and further proceed to the electron extraction electrode 23 while emitting secondary electrons. Like the emitted electrons, the secondary electrons collide with the hole wall surface and diffusely reflect, and advance toward the electron extraction electrode 23 while emitting new secondary electrons. In this embodiment, irregular irregularities on the hole wall surface improve the collision frequency of emitted electrons or secondary electrons, and the secondary electron multiplication effect is great. Due to a synergistic effect with the increase in the exposure amount at the tip of the CNT, it is possible to significantly reduce the applied voltage when electrons are emitted from the electron extraction electrode toward the light emitting portion.
[0021]
Further, when electrons are emitted from the CNT, a positive charge remains in the CNT. As long as this positive charge does not disappear, the electric field in the vicinity of the CNT becomes small, and the next electron emission is unlikely to occur. Therefore, in this embodiment, all the CNTs are connected to the substrate electrode 22 through the high-resistance porous member 24. This positive charge flows into the substrate electrode 22 as a leakage current transmitted through the porous member 24 and disappears. When the positive charge disappears from the CNT, an electric field sufficient to emit electrons from the CNT again is applied in the vicinity of the CNT. Thus, if a high resistance body exists between the CNT and the substrate electrode, each CNT does not emit electrons one after another, and the electron emission current is limited both spatially and temporally. Therefore, the electron emission current can be stabilized in the entire cold cathode electron source.
[0022]
Therefore, the cold cathode electron source in this embodiment has the effect of reducing the applied voltage for electron emission and stabilizing the electron emission current, in addition to uniformizing the electron emission characteristics. If such a cold cathode electron source is used in a flat panel type display device, high image quality such as uniformity of light emission and smoothness of an image can be achieved. In FIG. 2, the electron extraction electrode 23 and the porous member 24 are in contact with each other, but in actuality, they may be separated from each other, and setting the distance appropriately is a design matter.
[0023]
Embodiment 2. FIG.
FIG. 4 is a cross-sectional view of a cold cathode electron source for explaining the second embodiment. This embodiment is different from the first embodiment in that CNTs are not contained in the porous member and are arranged on the surface of the substrate electrode. In the figure, the CNT 21 is bonded to the surface of the substrate electrode 22 with a silica-based binder.
[0024]
In this embodiment as well, since all the CNTs 21 are exposed, it goes without saying that the electron emission characteristics are made uniform. Further, the distance through which the emitted electrons pass through the continuous hole is longer than that of the first embodiment, and the secondary electron multiplication effect due to the improved collision frequency of the emitted electrons or secondary electrons is much greater. Therefore, the applied voltage at the time of electron emission can be significantly reduced by a synergistic effect with an increase in the exposure amount of the CNT tip. If such a cold cathode electron source is used in a flat panel type display device, high image quality such as uniformity of light emission and smoothness of an image can be achieved.
[0025]
【The invention's effect】
According to this invention, an electron emission material that emits electrons by the action of an electric field, a substrate electrode and an electron extraction electrode for applying an electric field to the electron emission material, and a continuous hole between the substrate electrode and the electron extraction electrode. A porous member containing an electron-emitting material, and the tip of the electron-emitting material protrudes from the hole wall of the porous member. It is easy to improve the uniformity, and a cold cathode electron source with uniform electron emission characteristics can be provided.
[0026]
Further, since the electron emission material is a carbon nanotube, the applied voltage when electrons are emitted can be reduced.
[0027]
In addition, because the porous member is made of a secondary electron multiplier material and has an uneven hole wall surface, the secondary electron multiplication effect by increasing the electron collision frequency is great, and it is applied when electrons are emitted. The voltage can be greatly reduced.
[0028]
According to this invention, an electron emission material that emits electrons by the action of an electric field, a substrate electrode and an electron extraction electrode for applying an electric field to the electron emission material, and a continuous hole between the substrate electrode and the electron extraction electrode. Do Ri, formed by the secondary electron multiplication material, and a porous member having a hole wall surface having irregularities, since the electron emission material is disposed on the surface of the substrate electrode, the electron emission materials of all This not only facilitates exposure and makes the electron emission characteristics uniform, but also increases the collision frequency of emitted electrons or secondary electrons because the distance through which the emitted electrons pass through the continuous hole is longer. Due to the synergistic effect of the double effect and the increase in the exposure amount at the tip of the CNT, it is possible to provide a cold cathode electron source that significantly reduces the applied voltage when emitting electrons.
[0029]
According to the present invention, in a display device that displays an image using light emission caused by collision of electrons emitted from a cold cathode electron source, the electron emission material from which the cold cathode electron source emits electrons by the action of an electric field, A substrate electrode and an electron extraction electrode for applying an electric field to the emission material, and a porous member comprising continuous holes between the substrate electrode and the electron extraction electrode, the porous member containing the electron emission material, and an electron Since the tip of the emission material protrudes from the hole wall of the porous member, it is possible to provide a display device with high image quality due to the uniformity of light emission.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of main parts of a display device for explaining Embodiment 1;
FIG. 2 is a cross-sectional view of a cold cathode electron source for explaining the first embodiment.
FIG. 3 is a schematic diagram for explaining the first embodiment;
FIG. 4 is a cross-sectional view of a cold cathode electron source for explaining the second embodiment.
FIG. 5 is a cross-sectional view of a main part of a display device for explaining a conventional technique.
[Explanation of symbols]
1 substrate glass, 2 cold cathode electron source, 21 CNT, 22 substrate electrode, 23 electron extraction electrode, 24 porous member, 3 spacer, 4 aluminum back anode, 5 phosphor film, 6 black matrix, 7 display surface, 8 extraction Electrode, 109 display surface, 120 electron emission part, 121 substrate electrode, 125 electron extraction electrode, 141 transparent anode, 142 phosphor film

Claims (5)

  Electron emission material that emits electrons by the action of an electric field, a substrate electrode and an electron extraction electrode for applying an electric field to the electron emission material, and a porosity formed of continuous holes between the substrate electrode and the electron extraction electrode A cold cathode electron source, wherein the porous member contains the electron emission material, and a tip portion of the electron emission material protrudes from a hole wall of the porous member.   2. The cold cathode electron source according to claim 1, wherein the electron emission material is a carbon nanotube.   3. The cold cathode electron source according to claim 2, wherein the porous member is made of a secondary electron multiplying material and has an uneven hole wall surface. An electron emitting material for emitting electrons by the action of an electric field, the electron-emitting material substrate electrode and the electron extraction for applying an electric field to the electrodes, Ri Do from the continuous pores between the substrate electrode and the electronic extraction electrode, A cold cathode electron comprising a porous member made of a secondary electron multiplying material and having an uneven pore wall surface , wherein the electron emission material is disposed on a surface of the substrate electrode source.   In a display device that displays an image using light emission caused by collision of electrons emitted from a cold cathode electron source, the cold cathode electron source includes an electron emitting material that emits electrons by the action of an electric field, and an electron emitting material. A substrate electrode and an electron extraction electrode for applying an electric field, and a porous member comprising continuous holes between the substrate electrode and the electron extraction electrode, the porous member contains the electron emission material, A display device, wherein a tip portion of the electron emission material protrudes from a hole wall of the porous member.

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