JP2004200109A - Cold cathode field electron emission display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold cathode electric field electron emission display device in which generation of optical crosstalk can be prevented surely without installing a focusing electrode. <P>SOLUTION: This cold cathode electric field electron emission display device is composed by such a way that a cathode panel provided with a plurality of the cold cathode electric field electron emitters and an anode panel in which a fluorescent material layer and an anode electrode are installed are joined at their peripheral parts. The cold cathode electric field electron emitters are composed of a cathode electrode, an insulating layer, a gate electrode, an opening part formed at the gate electrode and the insulating layer portions positioned at an overlapping region where the cathode electrode and the gate electrode are overlapped, and an electron emitting part positioned at the bottom part of the opening part. The value of the second order differential coefficient ϕ"=[d<SP>2</SP>ϕ/dz<SP>2</SP>]<SB>x=0, y=0</SB>of an equipotential surface formed by the anode electrode, the gate electrode, and the cathode electrode on the center axis line of the opening part satisfies -0.02<ϕ"<0.02. Here, d of [d<SP>2</SP>ϕ/dz<SP>2</SP>] of the equation means partial differential. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cold cathode field emission display.
[0002]
[Prior art]
In the field of display devices used for television receivers and information terminal equipment, flat-panel (flat panel) that can meet the demands for thinner, lighter, larger screen, and higher definition from the conventional mainstream cathode ray tube (CRT) (Type) display devices are being considered. Examples of such a flat display device include a liquid crystal display (LCD), an electroluminescence display (ELD), a plasma display (PDP), and a cold cathode field emission display (FED). Can be. Among them, the liquid crystal display device is widely used as a display device for information terminal equipment, but there is still a problem in high brightness and large size for application to a stationary television receiver. . On the other hand, a cold cathode field emission display device is a cold cathode field emission device (hereinafter, referred to as a field emission device) capable of emitting electrons from a solid into a vacuum based on a quantum tunnel effect without thermal excitation. (Which may be referred to as an element), and has attracted attention in terms of high luminance and low power consumption.
[0003]
FIG. 2 and FIG. 3 show an example of a cold cathode field emission display (hereinafter sometimes referred to as a display) using a field emission device. FIG. 2 is a schematic partial end view of the display device, and FIG. 3 is a schematic partial perspective view when the cathode panel CP and the anode panel AP are disassembled.
[0004]
The illustrated field emission device is a so-called flat type field emission device having a substantially planar electron emission portion. The field emission device includes a cathode electrode 11 formed on a support 10, an insulating layer 12 formed on the support 10 and the cathode electrode 11, a gate electrode 13 formed on the insulating layer 12, An opening 14 provided in the electrode 13 and the insulating layer 12 (a first opening 14A provided in the gate electrode 13 and a second opening 14B provided in the insulating layer 12) and a bottom of the opening 14 It comprises an electron emitting portion 15 formed on the located cathode electrode 11. In general, the cathode electrode 11 and the gate electrode 13 are formed such that projected images of these two electrodes are formed in stripes in directions orthogonal to each other, and an overlapping area (one sub-pixel) where the projected images of these two electrodes overlap. Is generally provided with a plurality of field emission devices. Further, such overlapping areas are usually arranged in a two-dimensional matrix in an effective area (area functioning as an actual display portion) of the cathode panel CP.
[0005]
On the other hand, the anode panel AP includes a substrate 30, a phosphor layer 31 (31R, 31B, 31G) formed on the substrate 30 and having a predetermined pattern, and an anode electrode 33 formed thereon. . One sub-pixel includes a group of field emission elements provided in an overlapping region of the cathode electrode 11 and the gate electrode 13 on the cathode panel side, and a phosphor layer 31 on the anode panel side facing the group of these field emission elements. It is constituted by. In the effective area, pixels composed of the three sub-pixels are arranged, for example, in the order of several hundred thousand to several million. A black matrix 32 is formed on the substrate 30 between the phosphor layers 31.
[0006]
The display device can be manufactured by arranging the anode panel AP and the cathode panel CP such that the overlap region and the phosphor layer 31 face each other and joining the peripheral panel with the frame 34 therebetween. The space surrounded by the anode panel AP, the cathode panel CP, and the frame 34 is a vacuum.
[0007]
A relatively negative voltage is applied to the cathode electrode 11 from the cathode electrode control circuit 40, a relatively positive voltage is applied to the gate electrode 13 from the gate electrode control circuit 41, and the anode electrode 33 has a higher voltage than the gate electrode 13. A higher positive voltage is applied from the anode electrode control circuit 42. Due to an electric field generated when a voltage is applied between the cathode electrode 11 and the gate electrode 13, electrons are emitted from the electron emitting portion 15 based on the quantum tunnel effect, and the electrons are attracted to the anode electrode 33, and the fluorescent layer 31 Collide with As a result, the phosphor layer 31 is excited to emit light, and a desired image can be obtained. That is, the operation of the display device is basically controlled by the voltage applied to the gate electrode 13 and the voltage applied to the electron emission unit 15 through the cathode electrode 11.
[0008]
As described above, when a voltage is applied to the cathode electrode 11, the gate electrode 13, and the anode electrode 33, an electrostatic field is formed in the space between the gate electrode 13 and the anode electrode 33 and in the opening 14, and the opening 14 A kind of electron lens is formed inside and in the space near the opening 14. It should be noted that whether this electron lens is a convex lens or a concave lens is determined by determining the secondary differential coefficient φ of the equipotential surface formed by the anode electrode 33, the gate electrode 13, and the cathode electrode 11 on the central axis CL of the opening 14. ”= [∂^Twoφ / ∂z^Two]_{x = 0, y = 0}Is defined as follows. In the following description, the direction in which the center axis CL of the opening 14 extends is the z direction, the direction in which the gate electrode 13 extends is the x direction for convenience, and the direction in which the cathode electrode 11 extends is the y direction for convenience. . The y direction corresponds to the direction perpendicular to the plane of the drawing of FIG. FIG. 10 schematically shows a state in which the electron lens of the convex lens is formed.
[0009]
φ "<0: concave lens
φ ″> 0 ・ ・ ・ convex lens
[0010]
By the way, the electrons emitted from the electron emitting portion 15 generally have kinetic energy components not only in the z direction but also in the x direction and the y direction. Therefore, the electrons are emitted from the electron emitting portion 15 with a certain width with a certain solid angle centered on the normal direction of the support 10.
[0011]
In the case of φ ″ ≪0, that is, when the above-mentioned electron lens corresponds to a concave lens having a short focal length, the spread of the emitted electrons is expanded by the concave lens, and as a result, the electrons collide with the phosphor layer 31 facing the electron-emitting portion 15. In some cases, the light may collide with the phosphor layer 31 adjacent to the phosphor layer 31. Such a state is schematically shown in FIG. A decrease in purity and optical crosstalk between adjacent pixels occur.
[0012]
On the other hand, when φ ″ ≫0, that is, when the above-mentioned electron lens corresponds to a convex lens having a short focal length, the electrons emitted from the electron emitting portion 15 are generated in the space between the gate electrode 13 and the anode electrode 33. As a result of being once converged and then diverging, there is a case where the light does not collide with the phosphor layer 31 facing the electron emitting portion 15 but collides with the phosphor layer 31 adjacent to the phosphor layer 31. Such a phenomenon. Occurs, a decrease in luminance, a decrease in color purity, and an optical crosstalk between adjacent pixels occur.
[0013]
FIG. 4 shows a schematic layout of the cathode electrode 11, the gate electrode 13, and the opening 14 in a part of the cathode panel CP. One pixel has three sub-pixels (SP_R, SP_G, SP_B). In FIG. 4, the cathode electrode 11 extends in the vertical direction (y direction) on the paper, and the gate electrode 13 extends in the horizontal direction (x direction) on the paper. For example, when the size of one pixel is 0.5 mm × 0.5 mm, the size of one sub-pixel (L₁× L_Two) Is 0.5 mm × 0.166 mm. Also, the width of the gate electrode 13 (W_GATE) Is 0.42 mm. Note that FIG. 4 shows a state in which five openings 14 are provided in one subpixel, but the number of openings 14 is not limited to this. Although the cathode electrode 11 is hatched to clearly show the cathode electrode 11, the cathode electrode 11 is actually covered with the insulating layer 12.
[0014]
In such an arrangement, the distance between the adjacent phosphor layers 31 in the x direction is shorter than the distance between the adjacent phosphor layers 31 in the y direction. The spread of electrons must be less in the x direction.
[0015]
In order to prevent the occurrence of optical crosstalk, a field emission device provided with a focusing electrode 113 as shown in a schematic partial end view in FIG. 12 has been proposed (for example, JP-A-2002-270099). reference). In this field emission device, a second insulating layer 112 is further provided on the gate electrode 13 and the insulating layer 12, and a focusing electrode 113 is provided on the second insulating layer 112. Here, the focusing electrode 113 has a sheet-like shape that covers the effective area. Reference numeral 314 denotes an opening provided in the focusing electrode 113 and the second insulating layer 112. A relatively negative voltage (for example, 0 volt) is applied to the focusing electrode 113 from a focusing electrode control circuit (not shown). By providing the focusing electrode 113 in this way, by forming an electron lens composed of a kind of convex lens, it is possible to converge the trajectory of the emitted electrons emitted from the second opening 314 toward the anode electrode 33. Have been.
[0016]
[Patent Document 1] JP-A-2002-270099
[Patent Document 2] JP-A-8-96703
[0017]
[Problems to be solved by the invention]
However, the provision of the focusing electrode 113 complicates the manufacturing process of the cathode panel, and causes a problem of increasing the manufacturing cost of the cold cathode field emission display.
[0018]
It should be noted that paragraph No. 0035 of Japanese Patent Application Laid-Open No. Hei 8-96703 discloses that a particle having a small work function in contact with a first electrode (corresponding to a cathode electrode) in a micropore for emitting energetic particles such as electrons. A technique in which a substance is provided on a thin film (corresponding to an electron-emitting portion) is disclosed. When a voltage is applied between the first electrode and the second electrode (corresponding to a gate electrode), an equipotential surface is formed flat along the thin film. Particles that travel orthogonally travel from the micropores to the object (eg, phosphor surface) with a fairly uniform direction, so that they can always reach the target object and greatly reduce mislanding. It is said that high definition can be achieved. However, this patent publication does not disclose any concept such as a second derivative φ ″ of an equipotential surface formed by the anode electrode, the gate electrode, and the cathode electrode on the central axis of the opening.
[0019]
Therefore, an object of the present invention is to provide a cold cathode field emission display device which can reliably prevent a decrease in luminance, a decrease in color purity, and the occurrence of optical crosstalk without providing a focusing electrode. .
[0020]
[Means for Solving the Problems]
The cold cathode field emission display of the present invention to achieve the above object,
A cold cathode field emission display device comprising: a cathode panel including a plurality of cold cathode field emission devices; and an anode panel provided with a phosphor layer and an anode electrode, which are joined at a peripheral portion thereof. ,
Cold cathode field emission devices
(A) a cathode electrode formed on a support and extending in a first direction;
(B) an insulating layer formed on the support and the cathode electrode;
(C) a gate electrode formed on the insulating layer and extending in a second direction different from the first direction;
(D) an opening formed in a portion of the gate electrode and the insulating layer located in an overlapping region where the cathode electrode and the gate electrode overlap;
(E) an electron-emitting portion located at the bottom of the opening;
Consisting of
On the central axis line CL of the opening, a second derivative of the equipotential surface formed by the anode electrode, the gate electrode, and the cathode electrode, φ ″ = [∂^Twoφ / ∂z^Two]_{x = 0, y = 0}Is the value of
−0.02 <φ ”<0.02
Is satisfied.
[0021]
Note that the secondary differential coefficient φ ″ = [∂^Twoφ / ∂z^Two]_{x = 0, y = 0}(The coordinate Z of the region along the z-direction)₀The area above the cathode electrode surface along the central axis of the opening with the cathode electrode surface as the origin) is 0.2t ≦ Z, where t is the thickness of the insulating layer.₀≦ 1.5t, preferably 0.2t ≦ Z₀It is desirable that ≦ 3t. In addition, the point (0, 0, Z) of the central axis line CL of the opening._PIf the value of the second derivative φ ″ of the equipotential surface along the direction orthogonal to the direction perpendicular to the above) is not the same value, the largest value of the second derivative φ ″ needs to satisfy the above range. Here, the point (0, 0, 0) is a point (origin) located at the center of the opening 14 and on the surface of the cathode electrode 11, and Z₀= 0 means the surface of the cathode electrode 11.
[0022]
The value of the secondary differential coefficient φ ″ of the equipotential surface can be obtained by calculation or simulation using the following numerical values as parameters.
[0023]
(1) Voltage applied to anode electrode
(2) Voltage applied to gate electrode
(3) Voltage applied to cathode electrode
(4) Distance from anode electrode to gate electrode
(5) Thickness of gate electrode
(6) Thickness of insulating layer
(7) Shape and size of opening provided in gate electrode and insulating layer
(8) Shape and size of electron-emitting portion
(9) Number of electron emission portions provided in one overlap region
(10) Measurement value obtained from the relationship between the electric field intensity and the amount of emitted electrons (emitted electron current) near the electron emission portion when electrons are emitted from the electron emission portion
(11) A solid angle at which electrons are emitted from the electron-emitting portion with a certain solid angle centered on the normal line of the support when the electrons are emitted from the electron-emitting portion (the size of the electron-emitting portion is smaller than the size of the opening portion). Is small enough, the contribution of this parameter is small, and in some cases this parameter need not be considered.)
[0024]
In the case of performing color display in a cold cathode field emission display device, one pixel having a regular square planar shape is generally configured by juxtaposing three rectangular sub-pixels. Therefore, the red light-emitting phosphor layer that emits red light, the green light-emitting phosphor layer that emits green light, and the blue light-emitting phosphor layer that emits blue light also occupy the rectangular area. The short side direction of the rectangular region occupied by each phosphor layer is called the x direction for convenience, and the long side direction is called the y direction.
[0025]
In the cold cathode field emission display according to the present invention, the plane shape of the overlapping region where the cathode electrode and the gate electrode overlap is rectangular (that is, the short side is parallel to the x direction, and the long side is y. A rectangular shape having a long side parallel to the long side of the overlapping area of the rectangle (that is, a short side is parallel to the x direction and a long side is y (Parallel to the direction). By forming the opening in such a planar shape, it is possible to more reliably prevent a decrease in luminance, a decrease in color purity, and an occurrence of optical crosstalk. When the planar shape of the opening is a rectangle, the corner of the rectangle may be rounded.
[0026]
In the cold cathode field emission display device of the present invention including the above-described embodiment, the cold cathode field emission device (hereinafter, abbreviated as a field emission device) may include:
(1) Flat field emission device (a field emission device in which a substantially flat electron emission portion is provided on a cathode electrode located at the bottom of an opening)
(2) Crown-type field emission device (a field emission device in which a crown-shaped electron emission portion is provided on a cathode electrode located at the bottom of an opening)
(3) A flat field emission device that emits electrons from a flat cathode electrode surface
(4) Crater-type field emission device that emits electrons from projections on the surface of the cathode electrode on which irregularities are formed
(5) Edge-type field emission device that emits electrons from the edge of the cathode electrode
(6) Spindt-type field emission device (a field emission device in which a conical electron emission portion is provided on a cathode electrode located at the bottom of an opening)
Among them, a flat field emission device composed of a carbon nanotube structure is preferable.
[0027]
In the flat-type field emission device, as the material forming the electron emitting portion, it is preferable to configure the material having a work function Φ smaller than the material forming the cathode electrode. What is necessary is just to determine based on the work function of the material which comprises a cathode electrode, the potential difference between a gate electrode and a cathode electrode, the magnitude | size of required emission electron current density, etc. Typical materials constituting the cathode electrode in the field emission device include tungsten (Φ = 4.55 eV), niobium (Φ = 4.02 to 4.87 eV), molybdenum (Φ = 4.53 to 4.95 eV), Aluminum (Φ = 4.28 eV), copper (Φ = 4.6 eV), tantalum (Φ = 4.3 eV), chromium (Φ = 4.5 eV), and silicon (Φ = 4.9 eV) can be exemplified. . The electron emitting portion preferably has a work function Φ smaller than these materials, and its value is preferably about 3 eV or less. Such materials include carbon (Φ <1 eV), cesium (Φ = 2.14 eV), LaB₆(Φ = 2.66 to 2.76 eV), BaO (Φ = 1.6 to 2.7 eV), SrO (Φ = 1.25 to 1.6 eV), Y_TwoO_Three(Φ = 2.0 eV), CaO (Φ = 1.6-1.86 eV), BaS (Φ = 2.05 eV), TiN (Φ = 2.92 eV), ZrN (Φ = 2.92 eV). be able to. It is more preferable that the electron-emitting portion is made of a material having a work function Φ of 2 eV or less. Note that the material forming the electron emitting portion does not necessarily need to have conductivity.
[0028]
Alternatively, in the flat-type field emission device, as a material constituting the electron emitting portion, a material such that the secondary electron gain δ of such a material is larger than the secondary electron gain δ of the conductive material constituting the cathode electrode. It may be selected appropriately. That is, silver (Ag), aluminum (Al), gold (Au), cobalt (Co), copper (Cu), molybdenum (Mo), niobium (Nb), nickel (Ni), platinum (Pt), and tantalum (Ta) ), Metals such as tungsten (W) and zirconium (Zr); semiconductors such as silicon (Si) and germanium (Ge); inorganic simple substances such as carbon and diamond; and aluminum oxide (Al_TwoO_Three), Barium oxide (BaO), beryllium oxide (BeO), calcium oxide (CaO), magnesium oxide (MgO), tin oxide (SnO)_Two), Barium fluoride (BaF_Two), Calcium fluoride (CaF_Two) And the like. Note that the material forming the electron emitting portion does not necessarily need to have conductivity.
[0029]
In the flat field emission device, as a particularly preferable constituent material of the electron emission portion, carbon, more specifically, diamond, graphite, or a carbon nanotube structure can be exemplified. When the electron-emitting portion is composed of these, 5 × 10⁷An emission electron current density required for a cold cathode field emission display can be obtained at an electric field strength of V / m or less. In addition, since diamond is an electric resistor, the emission electron current obtained from each electron-emitting portion can be made uniform, thereby suppressing luminance variations when incorporated in a cold cathode field emission display. It becomes. Furthermore, since these materials have extremely high resistance to the sputtering action of the residual gas ions in the cold cathode field emission display, the life of the field emission device can be extended.
[0030]
Specific examples of the carbon nanotube structure include carbon nanotubes and / or carbon nanofibers. More specifically, the electron emission portion may be composed of carbon nanotubes, the electron emission portion may be composed of carbon nanofibers, or the electron emission portion may be composed of a mixture of carbon nanotubes and carbon nanofibers. You may comprise a part. Macroscopically, carbon nanotubes and carbon nanofibers may be in the form of powder or thin film, and in some cases, the carbon nanotube structure has a conical shape. May be. Carbon nanotubes and carbon nanofibers are formed by various known CVD methods such as the well-known arc discharge method and laser ablation method such as PVD method, plasma CVD method, laser CVD method, thermal CVD method, vapor phase synthesis method and vapor phase growth method. Can be manufactured and formed.
[0031]
A method in which a flat field emission device is applied, for example, to a desired region of a cathode electrode by dispersing a carbon nanotube structure in a binder material, and then firing or curing the binder material (more specifically, epoxy After dispersing a carbon nanotube structure in an organic binder material such as an organic resin or an acrylic resin or an inorganic binder material such as water glass, for example, in a desired region of the cathode electrode, removing the solvent, removing the binder (A method of firing and curing the material). Note that such a method is referred to as a first method for forming a carbon nanotube structure. As an application method, a screen printing method can be exemplified.
[0032]
Alternatively, the flat field emission device can be manufactured by a method in which a metal compound solution in which a carbon nanotube structure is dispersed is applied on a cathode electrode, and then the metal compound is baked. The carbon nanotube structure is fixed to the surface of the cathode electrode by the matrix containing the constituent metal atoms. Note that such a method is referred to as a second method for forming a carbon nanotube structure. The matrix is preferably made of a conductive metal oxide, more specifically, tin oxide, indium oxide, indium-tin oxide, zinc oxide, antimony oxide, or antimony oxide-tin. preferable. After firing, a state in which a part of each carbon nanotube structure is embedded in the matrix can be obtained, or a state in which the entire carbon nanotube structure is entirely embedded in the matrix can be obtained. The volume resistivity of the matrix is 1 × 10^-9Ω · m to 5 × 10^-6Ω · m is desirable.
[0033]
Examples of the metal compound constituting the metal compound solution include an organic metal compound, an organic acid metal compound, and a metal salt (eg, chloride, nitrate, acetate). As an organic acid metal compound solution, an organic tin compound, an organic indium compound, an organic zinc compound, and an organic antimony compound are dissolved in an acid (eg, hydrochloric acid, nitric acid, or sulfuric acid), and this is dissolved in an organic solvent (eg, toluene, butyl acetate, Isopropyl alcohol). Examples of the organometallic compound solution include those in which an organic tin compound, an organic indium compound, an organic zinc compound, and an organic antimony compound are dissolved in an organic solvent (for example, toluene, butyl acetate, and isopropyl alcohol). When the solution is 100 parts by weight, the composition preferably contains 0.001 to 20 parts by weight of the carbon nanotube structure and 0.1 to 10 parts by weight of the metal compound. The solution may contain a dispersant and a surfactant. From the viewpoint of increasing the thickness of the matrix, an additive such as carbon black may be added to the metal compound solution. In some cases, water can be used as a solvent instead of an organic solvent.
[0034]
Examples of a method of applying a metal compound solution in which a carbon nanotube structure is dispersed on a cathode electrode include a spray method, a spin coating method, a dipping method, a die quarter method, and a screen printing method. Is preferred from the viewpoint of ease of application.
[0035]
After the metal compound solution in which the carbon nanotube structure was dispersed was applied on the cathode electrode, the metal compound solution was dried to form a metal compound layer, and then unnecessary portions of the metal compound layer on the cathode electrode were removed. Thereafter, the metal compound may be fired, or after firing the metal compound, an unnecessary portion on the cathode electrode may be removed, or the metal compound solution may be applied only on a desired region of the cathode electrode. Good.
[0036]
The calcination temperature of the metal compound is, for example, a temperature at which the metal salt is oxidized to form a conductive metal oxide, or the organometallic compound or the organic acid metal compound is decomposed to form the organic metal compound or the organic acid. The temperature may be a temperature at which a matrix (for example, a conductive metal oxide) containing metal atoms constituting the metal compound can be formed, and is preferably, for example, 300 ° C. or higher. The upper limit of the firing temperature may be a temperature at which no thermal damage or the like occurs to the components of the field emission device or the cathode panel.
[0037]
In the first method or the second method of forming the carbon nanotube structure, after the formation of the electron-emitting portion, a type of activation treatment (cleaning treatment) on the surface of the electron-emitting portion is performed. This is preferable from the viewpoint of further improving the efficiency of emitting electrons from the emitting portion. Examples of such treatment include plasma treatment in a gas atmosphere such as hydrogen gas, ammonia gas, helium gas, argon gas, neon gas, methane gas, ethylene gas, acetylene gas, and nitrogen gas.
[0038]
In the first method or the second method of forming the carbon nanotube structure, the electron emission portion may be formed on the surface of the portion of the cathode electrode located at the bottom of the opening. May be formed to extend from the portion of the cathode electrode located at the bottom of the opening to the surface of the portion of the cathode electrode other than the bottom of the opening. In addition, the electron emission portion may be formed on the entire surface of the portion of the cathode electrode located at the bottom of the opening, or may be formed partially.
[0039]
Materials constituting the cathode electrode in various field emission devices include tungsten (W), niobium (Nb), tantalum (Ta), titanium (Ti), molybdenum (Mo), chromium (Cr), aluminum (Al), and copper. Metals such as (Cu), gold (Au) and silver (Ag); alloys or compounds containing these metal elements (for example, nitrides such as TiN, WSi_Two, MoSi_Two, TiSi_Two, TaSi_TwoSemiconductors such as silicon (Si); carbon thin films such as diamond; and ITO (indium tin oxide). The thickness of the cathode electrode is desirably in the range of approximately 0.05 to 0.5 μm, preferably 0.1 to 0.3 μm, but is not limited to such a range.
[0040]
Tungsten (W), niobium (Nb), tantalum (Ta), titanium (Ti), molybdenum (Mo), chromium (Cr), aluminum (Al) are used as conductive materials for forming gate electrodes in various field emission devices. , Copper (Cu), gold (Au), silver (Ag), nickel (Ni), cobalt (Co), zirconium (Zr), iron (Fe), platinum (Pt) and zinc (Zn). At least one type of metal; alloys or compounds containing these metal elements (for example, nitrides such as TiN, WSi_Two, MoSi_Two, TiSi_Two, TaSi_TwoOr a semiconductor such as silicon (Si); and conductive metal oxides such as ITO (indium tin oxide), indium oxide, and zinc oxide.
[0041]
Examples of the method of forming the cathode electrode and the gate electrode include a vapor deposition method such as an electron beam vapor deposition method and a hot filament vapor deposition method, a sputtering method, a combination of a CVD method, an ion plating method and an etching method, a screen printing method, a plating method, and a lift-off method. And the like. According to the screen printing method or the plating method, it is possible to directly form, for example, a striped cathode electrode or a gate electrode.
[0042]
In the field emission device, depending on the structure of the field emission device, one opening (an opening provided in the gate electrode is referred to as a first opening, and an opening provided in the insulating layer is referred to as a second opening). ), A plurality of electron-emitting portions may exist in one opening, and a plurality of first openings may be provided in the gate electrode. One second opening communicating with the first opening may be provided in the insulating layer, and one or more electron-emitting portions may be present in one second opening provided in the insulating layer.
[0043]
The planar shape of the first opening (the opening formed in the gate electrode) or the second opening (the opening formed in the insulating layer) (shape when the opening is cut along a virtual plane parallel to the surface of the support) ) Can be any shape, such as a circle, an ellipse, a rectangle, a polygon, a rounded rectangle, a rounded polygon, etc., but most preferably has the above-described rectangular shape. The formation of the first opening can be performed by, for example, anisotropic etching, isotropic etching, a combination of anisotropic etching and isotropic etching, or depending on the method of forming the gate electrode, The first opening can also be formed directly. The second opening can also be formed by, for example, anisotropic etching, isotropic etching, or a combination of anisotropic etching and isotropic etching.
[0044]
In the field emission device, a resistor layer may be provided between the cathode electrode and the electron emission portion. Alternatively, when the surface of the cathode electrode corresponds to the electron emission portion, the cathode electrode may have a three-layer structure of a conductive material layer, a resistor layer, and an electron emission layer corresponding to the electron emission portion. By providing the resistor layer, the operation of the field emission device can be stabilized and the electron emission characteristics can be made uniform. Examples of the material forming the resistor layer include carbon-based materials such as silicon carbide (SiC) and SiCN, semiconductor materials such as SiN and amorphous silicon, and ruthenium oxide (RuO)._Two), High melting point metal oxides such as tantalum oxide and tantalum nitride. Examples of the method for forming the resistor layer include a sputtering method, a CVD method, and a screen printing method. The resistance value is approximately 1 × 10^Five~ 1 × 10⁷Ω, preferably several MΩ.
[0045]
SiO 2 as a constituent material of the insulating layer_Two, BPSG, PSG, BSG, AsSG, PbSG, SiN, SiON, SOG (spin on glass), low melting point glass, SiO such as glass paste_TwoAn insulating resin such as a system material, SiN, or polyimide can be used alone or in an appropriate combination. Known processes such as a CVD method, a coating method, a sputtering method, and a screen printing method can be used for forming the insulating layer.
[0046]
The constituent material of the anode electrode may be appropriately selected depending on the configuration of the cold cathode field emission display. That is, when the cold cathode field emission display is a transmission type (the anode panel corresponds to the display surface), and the anode electrode and the phosphor layer are laminated in this order on the substrate constituting the anode panel. In this case, the anode electrode itself must be transparent as well as the substrate, and a transparent conductive material such as ITO (indium tin oxide) is used. On the other hand, when the cold cathode field emission display is of a reflection type (a cathode panel corresponds to a display surface), and even of a transmission type, a phosphor layer and an anode electrode are laminated in this order on a substrate. In this case, aluminum (Al) or chromium (Cr) can be used in addition to ITO. When the anode electrode is made of aluminum (Al) or chromium (Cr), the thickness of the anode electrode is specifically 3 × 10^-8m (30 nm) to 1.5 × 10^-7m (150 nm), preferably 5 × 10^-8m (50 nm) to 1 × 10^-7m (100 nm). The anode electrode can be formed by an evaporation method or a sputtering method.
[0047]
Further, on the anode panel, electrons recoiled from the phosphor layer or secondary electrons emitted from the phosphor layer enter another phosphor layer, so-called optical crosstalk (color turbidity) occurs. To prevent this, or when the electrons recoiled from the phosphor layer or the secondary electrons emitted from the phosphor layer enter the other phosphor layer beyond the partition walls, these It is preferable that a plurality of partitions are provided to prevent electrons from colliding with other phosphor layers.
[0048]
Examples of the planar shape of the partition wall include a lattice shape (cross-girder shape), that is, a shape corresponding to one sub-pixel, for example, a shape surrounding a phosphor layer having a substantially rectangular (dot-like) planar shape, or A band shape or a stripe shape extending in parallel with two opposing sides of the substantially rectangular or striped phosphor layer can be given. When the partition has a lattice shape, the partition may have a shape that continuously surrounds four sides of one phosphor layer region or a shape that surrounds discontinuously. When the partition has a band shape or a stripe shape, the partition may have a continuous shape or a discontinuous shape. After the partition is formed, the partition may be polished to planarize the top surface of the partition.
[0049]
A black matrix that absorbs light from the phosphor layer is provided between the phosphor layer and the phosphor layer (when a partition is formed, between the phosphor layer and the phosphor layer, and between the phosphor layer and the substrate. Is preferable from the viewpoint of improving the contrast of the displayed image. As a material constituting the black matrix, it is preferable to select a material that absorbs 99% or more of light from the phosphor layer. Such materials include carbon, metal thin films (for example, chromium, nickel, aluminum, molybdenum, or alloys thereof), metal oxides (for example, chromium oxide), metal nitrides (for example, chromium nitride), and heat-resistant materials. Examples include materials such as a photosensitive organic resin, a glass paste, a glass paste containing conductive particles such as black pigment and silver, and a photosensitive polyimide resin, chromium oxide, and a chromium oxide / chrome laminated film. Can be exemplified. In the chromium oxide / chromium laminated film, the chromium film is in contact with the substrate.
[0050]
When joining the cathode panel and the anode panel at the peripheral portion, the joining may be performed using an adhesive layer, or using a frame made of an insulating rigid material such as glass or ceramics and the adhesive layer in combination. You may. When the frame and the adhesive layer are used together, by appropriately selecting the height of the frame, the facing distance between the cathode panel and the anode panel is set longer than when using only the adhesive layer. It is possible to As a constituent material of the adhesive layer, frit glass is generally used, but a so-called low melting point metal material having a melting point of about 120 to 400 ° C. may be used. Examples of such a low melting point metal material include In (indium: melting point: 157 ° C.); indium-gold based low melting point alloy; Sn₈₀Ag₂₀(Melting point 220-370 ° C), Sn₉₅Cu_Five(Sn) high temperature solder such as (melting point 227-370 ° C.); Pb_97.5Ag_2.5(Melting point 304 ° C), Pb_94.5Ag_5.5(Melting point 304-365 ° C), Pb_97.5Ag_1.5Sn_1.0(Pb) high temperature solder such as (melting point 309 ° C); Zn₉₅Al_Five(Melting point: 380 ° C) such as zinc (Zn) based high temperature solder; Sn_FivePb₉₅(Melting point 300-314 ° C), Sn_TwoPb₉₈(Melting point 316 to 322 ° C.) such as tin-lead standard solder; Au₈₈Ga₁₂(All the subscripts above represent atomic%) such as (melting point 381 ° C.).
[0051]
When joining the three members of the cathode panel, the anode panel, and the frame, the three may be joined at the same time, or, in the first stage, either the cathode panel or the anode panel and the frame are joined, In the second stage, the other of the cathode panel or the anode panel and the frame may be joined. If the three-member simultaneous bonding and the bonding in the second stage are performed in a high vacuum atmosphere, the space surrounded by the cathode panel, the anode panel, the frame, and the adhesive layer is evacuated simultaneously with the bonding. Alternatively, after the three members have been joined, the space surrounded by the cathode panel, the anode panel, the frame, and the adhesive layer can be evacuated to a vacuum. When evacuation is performed after the bonding, the pressure of the atmosphere at the time of the bonding may be either normal pressure or reduced pressure. The gas constituting the atmosphere may be air, nitrogen gas, or group 0 of the periodic table. May be an inert gas containing a gas belonging to (for example, Ar gas).
[0052]
When exhausting after bonding, the exhaust can be performed through a tip tube previously connected to the cathode panel and / or the anode panel. The tip tube is typically configured using a glass tube, and is bonded around a through portion provided in an inactive area of the cathode panel and / or the anode panel using frit glass or the above-described low melting point metal material. After the space reaches a predetermined degree of vacuum, it is sealed off by heat fusion. Note that if the entire cold cathode field emission display is once heated and cooled before sealing is performed, residual gas can be released into the space, and the residual gas can be removed to the outside by exhaust. This is preferable because
[0053]
The support constituting the cathode panel only needs to have at least the surface made of an insulating member.A glass substrate, a glass substrate having an insulating film formed on its surface, a quartz substrate, and a quartz substrate having an insulating film formed on its surface Although a semiconductor substrate having an insulating film formed on its surface can be used, a glass substrate or a glass substrate having an insulating film formed on its surface is preferably used from the viewpoint of manufacturing cost reduction. The substrate forming the anode panel can be configured similarly to the support.
[0054]
In the present invention, the second derivative φ ″ = [∂] of the equipotential surface formed by the anode electrode, the gate electrode, and the cathode electrode on the central axis of the opening.^Twoφ / ∂z^Two]_{x = 0, y = 0}Is defined as −0.02 <φ ″ <0.02, the electrons emitted from the electron-emitting portion do not collide with the phosphor layer facing the electron-emitting portion, and the phosphor layer Can reliably be prevented from colliding with the phosphor layer adjacent to the phosphor layer.
[0055]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on embodiments of the present invention (hereinafter, abbreviated as embodiments) with reference to the drawings.
[0056]
(Embodiment 1)
Embodiment 1 relates to a cold cathode field emission display (hereinafter simply referred to as a display) of the present invention. 2 and 3 show an example of the display device of Embodiment 1. FIG. FIG. 2 is a schematic partial end view of the display device, and FIG. 3 is a schematic partial perspective view when the cathode panel CP and the anode panel AP are disassembled.
[0057]
The display device includes a cathode panel CP having a plurality of cold cathode field emission devices (hereinafter, referred to as field emission devices) and an anode panel AP provided with a phosphor layer 31 and an anode electrode 33. Are joined at the periphery.
[0058]
Here, the field emission device is a flat field emission device in which a substantially planar electron emission portion is provided on a cathode electrode located at the bottom of an opening (more specifically, a field emission device formed of a carbon nanotube structure). Flat field emission device).
[0059]
That is, the cold cathode field emission device is
(A) a cathode electrode 11 formed on a support 10 and extending in a first direction (a y-direction which is a direction perpendicular to the plane of FIG. 2);
(B) an insulating layer 12 formed on the support 10 and the cathode electrode 11;
(C) a gate electrode 13 formed on the insulating layer 12 and extending in a second direction different from the first direction (the x direction which is a horizontal direction in FIG. 2);
(D) Opening 14 (first opening 14A provided in gate electrode 13 and insulating layer formed in a portion of gate electrode and insulating layer located in an overlapping region where cathode electrode 11 and gate electrode 13 overlap) 12, a second opening 14B) communicating with the first opening 14A);
(E) an electron-emitting portion 15 located at the bottom of the opening 14;
Consists of
[0060]
Then, on the central axis line CL of the opening 14, the secondary differential coefficient φ ″ = [∂ of the equipotential surface formed by the anode electrode, the gate electrode, and the cathode electrode.^Twoφ / ∂z^Two]_{x = 0, y = 0}Satisfies -0.02 <φ ″ <0.02.
[0061]
The cathode electrode 11 and the gate electrode 13 are formed such that projected images of these two electrodes are formed in a stripe shape in a direction orthogonal to each other, and an overlapping area (one subpixel) where the projected images of these two electrodes overlap. Are provided with a plurality of field emission devices. Further, such overlapping areas are usually arranged in a two-dimensional matrix in an effective area (area functioning as an actual display portion) of the cathode panel CP.
[0062]
On the other hand, the anode panel AP includes a substrate 30, a phosphor layer 31 (31R, 31B, 31G) formed on the substrate 30 and having a predetermined pattern, and an anode electrode 33 formed thereon. . One sub-pixel includes a group of field emission elements provided in an overlapping region of the cathode electrode 11 and the gate electrode 13 on the cathode panel side, and a phosphor layer 31 on the anode panel side facing the group of these field emission elements. It is constituted by. In the effective area, pixels composed of the three sub-pixels are arranged, for example, in the order of several hundred thousand to several million. A black matrix 32 is formed on the substrate 30 between the phosphor layers 31.
[0063]
The display device can be manufactured by arranging the anode panel AP and the cathode panel CP such that the overlap region and the phosphor layer 31 face each other and joining the peripheral panel with the frame 34 therebetween. A through hole 36 for evacuation is provided in an ineffective area (in the illustrated example, an ineffective area of the cathode panel CP) surrounding the effective area and in which a peripheral circuit for selecting a pixel is formed. The through-hole 36 is connected to a chip tube 37 that has been sealed off after evacuation. That is, the space surrounded by the anode panel AP, the cathode panel CP, and the frame 34 is in a vacuum.
[0064]
A relatively negative voltage is applied to the cathode electrode 11 from the cathode electrode control circuit 40, a relatively positive voltage is applied to the gate electrode 13 from the gate electrode control circuit 41, and the anode electrode 33 has a higher voltage than the gate electrode 13. A higher positive voltage is applied from the anode electrode control circuit 42. When displaying on such a display device, for example, a scanning signal is input to the cathode electrode 11 from the cathode electrode control circuit 40, and a video signal is input to the gate electrode 13 from the gate electrode control circuit 41. Alternatively, a video signal may be input to the cathode electrode 11 from the cathode electrode control circuit 40, and a scanning signal may be input to the gate electrode 13 from the gate electrode control circuit 41. Due to an electric field generated when a voltage is applied between the cathode electrode 11 and the gate electrode 13, electrons are emitted from the electron emitting portion 15 based on the quantum tunnel effect, and the electrons are attracted to the anode electrode 33, and the fluorescent layer 31 Collide with As a result, the phosphor layer 31 is excited to emit light, and a desired image can be obtained. That is, the operation of the display device is basically controlled by the voltage applied to the gate electrode 13 and the voltage applied to the electron emission unit 15 through the cathode electrode 11.
[0065]
FIG. 4 shows a schematic layout of the cathode electrode 11, the gate electrode 13, and the opening 14 in a part of the cathode panel CP. One pixel has three sub-pixels (SP_R, SP_G, SP_B). In FIG. 4, the cathode electrode 11 extends in the vertical direction (y direction) on the paper, and the gate electrode 13 extends in the horizontal direction (x direction) on the paper. The size of one pixel is 0.5 mm × 0.5 mm, and the size of one subpixel (overlap area) (L₁× L_Two) Is 0.5 mm × 0.166 mm, and the width of the gate electrode 13 (W_GATE) Is set to 0.42 mm, the voltage applied from the anode electrode control circuit 42 to the anode electrode 33 is 10 kilovolts, the voltage applied from the cathode electrode control circuit 40 to the cathode electrode 11 is 0 volt, The distance from the gate electrode 13 is 2.0 mm, the diameter of the opening 14 having a circular planar shape is 40 μm, and the electron emission having a circular planar shape provided on the cathode electrode 11 located at the center of the bottom of the opening 14. The diameter of the portion 15 is 20 μm, the number of the electron emission portions 15 provided in one overlap region is 5, and the electron emission portions 15 are spread from the electron emission portion 15 while having a certain solid angle around the normal of the support 10. Assuming that the solid angle at which the electrons are emitted is 60 degrees (the emission angle of the electrons emitted from the electron emission portion 15 with respect to the normal of the support 10 is ± 30 degrees), Electrons from part 15 is previously obtained by experiment the relationship between electric field intensity and the amount of emitted electrons in the vicinity of the electron emitting portion 15 when released (emitted electron current).
[0066]
Then, the thickness of the gate electrode 13 is changed from 0.3 μm to 15 μm, and the thickness of the insulating layer 12 is changed from 2 μm to 20 μm. Is applied to the gate electrode 13 so as to obtain 0.86 μA (0.86 × 5 = 4.3 μA in one overlapping region) as an emission electron current value based on_gAre calculated, and the voltages applied to the anode electrode 33, the gate electrode 13 and the cathode electrode 11 (10 kV, V_g, 0 volts), the space between the gate electrode 13 and the anode electrode 33 and the electrostatic field (equipotential surface) in the opening 14 are obtained by calculation. Second derivative φ ″ of this equipotential surface on CL = [＝^Twoφ / ∂z^Two]_{x = 0, y = 0}And the size (spot diameter V) of the phosphor layer 31 when the electrons emitted from the electron emission section 15 collide with the phosphor layer 31._ssmm). “Φ” and “V_ss1 is shown in FIG. It should be noted that the value of the secondary differential coefficient φ ″ of the equipotential surface is determined by the area on the central axis CL of the opening 14 (the coordinate Z of the area along the z direction)₀) Is 0 ≦ Z, where t is the thickness of the insulating layer and the origin is a point where the center axis CL of the opening 14 intersects the surface of the cathode electrode 11.₀This is the maximum value among the values in the range of ≦ 3t. Since the calculation was performed assuming that the surface of the electron emitting portion 15 was a plane, the value of the secondary differential coefficient φ ″ of the equipotential surface was set to 0 ≦ Z₀≤ 3t, but the maximum value among the values in the range of ≤ 3t. However, since the actual surface of the electron-emitting portion 15 has irregularities, when the thickness of the insulating layer is t, 0.2t ≤ Z₀≦ 1.5t, preferably 0.2t ≦ Z₀It is desirable to set the maximum value among the values in the range of ≦ 3t.
[0067]
Spot diameter V_ssIs a quadratic function of φ ″, and V_ss= F (φ ″) was as follows.
[0068]
V_ss= 6.2127φ "^Two-0.0571φ "+0.1665
[0069]
Spot diameter V_ssIs almost 0 when the value of the minimum spot diameter is minimum, and the value of the second order differential coefficient φ ″ when the allowable spot diameter is 1.05 times the minimum spot diameter is approximately ± 0. .02. Accordingly, the value of the secondary differential coefficient φ ″ of the equipotential surface formed by the electrode 33, the gate electrode 13, and the cathode electrode 11 on the central axis line CL of the opening 14 is −0.02 <φ ″ <0.02. Then, the allowable spot diameter can be set within 1.05 times the minimum spot diameter.
[0070]
Note that the allowable range of the second derivative φ ″ varies depending on the design of the entire display device, such as the width of the phosphor layer, and the size of the opening 14 that gives the allowable range of the second derivative φ ″ is also electronic. It changes according to the voltage-current characteristics of the emission part. However, as described above, when the thickness of the gate electrode 13 is 0.3 μm to 15 μm and the thickness of the insulating layer 12 is 2 μm to 20 μm, the value of the secondary differential coefficient φ ″ is −0.02 <φ ″ < It has been found from calculation that if 0.02, the allowable spot diameter can be set within 1.05 times the minimum spot diameter.
[0071]
In the above-described example, the plane shape of the opening 14 is circular. However, by adjusting the plane shape of the opening 14, the influence of the voltage applied to the anode electrode 33 on the equipotential surface can be controlled. The differential coefficient φ ″ may be set to −0.02 <φ ″ <0.02.
[0072]
When the threshold voltage (voltage at which electrons start to be emitted from the electron emission unit 15) in the voltage-current characteristics of the electron emission unit 15 is high, a predetermined emission electron current value based on the electrons emitted from the electron emission unit 15 is obtained. Gate voltage V_gIs higher, the secondary differential coefficient φ ″ <0, that is, a kind of concave lens is formed as an electron lens. In such a case, by increasing the size of the opening portion 14, the voltage applied to the anode electrode 33 can be increased. The influence on the potential surface can be increased, and the secondary differential coefficient φ ″ can approach 0. However, when the plane shape of the opening 14 is circular, the spot diameter V of the electron beam that collides with the phosphor layer 31 is increased by the increase in the opening diameter._ssAnd the effect of improving the secondary differential coefficient φ ″ is negated.
[0073]
As described above, the distance between the adjacent phosphor layers 31 in the x direction is shorter than the distance between the adjacent phosphor layers 31 in the y direction. Therefore, the planar shape of the overlapping region where the cathode electrode 11 and the gate electrode 13 overlap is rectangular, and the planar shape of the opening 14 is a rectangle having a long side parallel to the long side of the rectangular overlapping region. Thereby, the influence on the equipotential surface by the voltage applied to the anode electrode 33 is increased, the secondary differential coefficient φ ″ is set to −0.02 <φ ″ <0.02, and the electrons that collide with the phosphor layer 31 are set. The beam spot diameter (particularly, the spot diameter in the x direction) can be improved. The number of openings in the overlapping area may be one or two or more. FIG. 5 shows a schematic arrangement diagram of the cathode electrode 11, the gate electrode 13, and the opening 114 in a part of the cathode panel CP when the number of the openings 114 in the overlapping region is one. The size of the opening 114 (L_Three× L_Four) Is 270 μm × 20 μm. FIG. 6 is a schematic layout diagram of the cathode electrode 11, the gate electrode 13, and the opening 214 in a part of the cathode panel CP when the number of the openings 214 in the overlapping region is plural. The size of the opening 214 (L_Five× L₆) Is 70 μm × 10 μm, and the distance between the openings 214 along the longitudinal direction of the openings 214 (L₇) Is 30 μm, and the distance (L) between the openings 214 along the widthwise direction of the openings 214.₈) Is 5 μm. In FIGS. 5 and 6, the cathode electrode 11 is hatched to clearly show the cathode electrode 11, but the cathode electrode 11 is actually covered with the insulating layer 12. The cathode electrode 11 extends in the vertical direction (y direction) on the paper, and the gate electrode 13 extends in the horizontal direction (x direction) on the paper.
[0074]
Hereinafter, various field emission devices and methods of manufacturing the same will be described. 7 to 9, only one electron emitting portion is shown.
[0075]
[Flat field emission device (1)]
Flat field emission devices are
(A) a cathode electrode 11 provided on a support 10 and extending in a first direction;
(B) an insulating layer 12 formed on the support 10 and the cathode electrode 11,
(C) a gate electrode 13 provided on the insulating layer 12 and extending in a second direction different from the first direction;
(D) a first opening 14A provided in the gate electrode 13 and a second opening 14B provided in the insulating layer 12 and communicating with the first opening 14A;
(E) a flat electron-emitting portion 15 provided on the cathode electrode 11 located at the bottom of the second opening 14B;
Consisting of
It has a structure in which electrons are emitted from the electron emission portion 15 exposed at the bottom of the second opening 14B.
[0076]
The electron emission portion 15 is composed of a matrix 20 and a carbon nanotube structure (specifically, carbon nanotube 21) embedded in the matrix 20 with its tip protruding. (Specifically, indium-tin oxide, ITO).
[0077]
Hereinafter, a method for manufacturing the field emission device will be described with reference to FIGS. 7A and 7B and FIGS. 8A and 8B.
[0078]
[Step-100]
First, a stripe-shaped cathode electrode 11 made of a chromium (Cr) layer having a thickness of about 0.2 μm and formed by, for example, a sputtering method and an etching technique is formed on a support 10 made of, for example, a glass substrate.
[0079]
[Step-110]
Next, a metal compound solution composed of an organic acid metal compound in which the carbon nanotube structure is dispersed is applied on the cathode electrode 11 by, for example, a spray method. Specifically, a metal compound solution exemplified in Table 1 below is used. In the metal compound solution, the organic tin compound and the organic indium compound are in a state of being dissolved in an acid (for example, hydrochloric acid, nitric acid, or sulfuric acid). Carbon nanotubes are manufactured by an arc discharge method and have an average diameter of 30 nm and an average length of 1 μm. At the time of coating, the support is heated to 70 to 150 ° C. The coating atmosphere is an air atmosphere. After coating, the support is heated for 5 to 30 minutes to sufficiently evaporate butyl acetate. As described above, by heating the support at the time of coating, the coating solution starts drying before self-leveling in a direction in which the carbon nanotubes approach the surface of the cathode electrode horizontally. The carbon nanotubes can be arranged on the surface of the cathode electrode in a state where the carbon nanotubes do not come off. That is, it is possible to orient the carbon nanotubes in a state where the tips of the carbon nanotubes face the direction of the anode electrode, in other words, in a direction approaching the normal direction of the support. In addition, a metal compound solution having the composition shown in Table 1 may be prepared in advance, or a metal compound solution to which no carbon nanotube is added is prepared, and the carbon nanotube and the metal compound are added before coating. You may mix with a solution. In addition, ultrasonic waves may be applied during the preparation of the metal compound solution in order to improve the dispersibility of the carbon nanotubes.
[0080]
[Table 1]
Organic tin compound and organic indium compound: 0.1 to 10 parts by weight
Dispersant (sodium dodecyl sulfate): 0.1 to 5 parts by weight
Carbon nanotubes: 0.1 to 20 parts by weight
Butyl acetate: residue
[0081]
Incidentally, as the organic acid metal compound solution, if a solution obtained by dissolving an organic tin compound in an acid is used, tin oxide is obtained as a matrix.If a solution obtained by dissolving an organic indium compound in an acid is used, indium oxide is obtained as a matrix. If an organic zinc compound is dissolved in an acid, zinc oxide is obtained as a matrix.If an organic antimony compound is dissolved in an acid, antimony oxide is obtained as a matrix.The organic antimony compound and the organic tin compound are obtained. Is dissolved in an acid to obtain antimony-tin oxide as a matrix. In addition, when an organotin compound is used as an organometallic compound solution, tin oxide is obtained as a matrix.When an organic indium compound is used, indium oxide is obtained as a matrix.When an organic zinc compound is used, zinc oxide is used as a matrix. When an organic antimony compound is used, antimony oxide is obtained as a matrix, and when an organic antimony compound and an organic tin compound are used, antimony-tin oxide is obtained as a matrix. Alternatively, a solution of a metal chloride (eg, tin chloride, indium chloride) may be used.
[0082]
In some cases, significant irregularities are formed on the surface of the metal compound layer after drying the metal compound solution. In such a case, it is desirable to apply the metal compound solution again on the metal compound layer without heating the support.
[0083]
[Step-120]
After that, by firing the metal compound composed of the organic acid metal compound, a matrix (specifically, a metal oxide containing metal atoms (specifically, In and Sn)) constituting the organic acid metal compound, More specifically, the electron-emitting portion 15 in which the carbon nanotubes 21 are fixed to the surface of the cathode electrode 11 is obtained by ITO (20). The firing is performed in an air atmosphere at 350 ° C. for 20 minutes. Thus, the volume resistivity of the obtained matrix 20 is 5 × 10^-7Ω · m. By using an organic acid metal compound as a starting material, the matrix 20 made of ITO can be formed even at a low firing temperature of 350 ° C. In addition, instead of the organic acid metal compound solution, an organic metal compound solution may be used, or when a metal chloride solution (for example, tin chloride or indium chloride) is used, tin chloride or indium chloride is obtained by firing. While being oxidized, a matrix 20 of ITO is formed.
[0084]
[Step-130]
Next, a resist layer is formed on the entire surface, and a circular resist layer having a diameter of, for example, 20 μm is left above a desired region of the cathode electrode 11. Then, the matrix 20 is etched using hydrochloric acid at 10 to 60 ° C. for 1 to 30 minutes to remove an unnecessary portion of the electron emission portion. Further, if the carbon nanotubes still exist in regions other than the desired region, the carbon nanotubes are etched by oxygen plasma etching under the conditions exemplified in Table 2 below. Although the bias power may be 0 W, that is, it may be DC, it is desirable to add the bias power. Further, the support may be heated to, for example, about 80 ° C.
[0085]
[Table 2]
Equipment used: RIE equipment
Introduced gas: gas containing oxygen
Plasma excitation power: 500W
Bias power: 0-150W
Processing time: 10 seconds or more
[0086]
Alternatively, the carbon nanotubes may be etched by wet etching under the conditions exemplified in Table 3.
[0087]
[Table 3]
Working solution: KMnO_Four
Temperature: 20-120 ° C
Processing time: 10 seconds to 20 minutes
[0088]
After that, the structure shown in FIG. 7A can be obtained by removing the resist layer. Note that the present invention is not limited to leaving a circular electron emitting portion having a diameter of 20 μm. For example, the electron emission portion may be left on the cathode electrode 11.
[0089]
In addition, you may perform in order of [step-110], [step-130], and [step-120].
[0090]
[Step-140]
Next, the insulating layer 12 is formed on the electron-emitting portion 15, the support 10, and the cathode electrode 11. Specifically, the insulating layer 12 having a thickness of about 15 μm is formed on the entire surface by, for example, a CVD method using TEOS (tetraethoxysilane) as a source gas.
[0091]
[Step-150]
After that, a stripe-shaped gate electrode 13 is formed on the insulating layer 12, a mask layer 22 is further provided on the insulating layer 12 and the gate electrode 13, and a first opening 14A is formed in the gate electrode 13. Further, a second opening 14B communicating with the first opening 14A formed in the gate electrode 13 is formed in the insulating layer 12 (see FIG. 7B). When the matrix 20 is made of a metal oxide, for example, ITO, when the insulating layer 12 is etched, the matrix 20 is not etched. That is, the etching selectivity between the insulating layer 12 and the matrix 20 is almost infinite. Therefore, the carbon nanotubes 21 are not damaged by the etching of the insulating layer 12. The thickness of the gate electrode 13 was 10 μm, and the diameter of the first opening 14A and the second opening 14B was 40 μm.
[0092]
[Step-160]
Next, it is preferable to remove a part of the matrix 20 under the conditions exemplified in Table 4 below to obtain the carbon nanotubes 21 in a state where the tips protrude from the matrix 20. Thus, the electron-emitting portion 15 having the structure shown in FIG. 8A can be obtained.
[0093]
[Table 4]
Etching solution: hydrochloric acid
Etching time: 10-30 seconds
Etching temperature: 10-60 ° C
[0094]
In some cases, the surface state of some or all of the carbon nanotubes 21 changes due to etching of the matrix 20 (for example, oxygen atoms, oxygen molecules, and fluorine atoms are adsorbed on the surface), and the carbon nanotubes 21 are inactive with respect to field emission. is there. Therefore, after that, it is preferable to perform the plasma treatment on the electron emitting portion 15 in a hydrogen gas atmosphere, whereby the electron emitting portion 15 is activated, and the emission efficiency of the electron from the electron emitting portion 15 is further improved. Can be improved. Table 5 shows the conditions of the plasma processing.
[0095]
[Table 5]
Gas used: H_Two= 100sccm
Power supply power: 1000W
Support applied power: 50V
Reaction pressure: 0.1 Pa
Support temperature: 300 ° C
[0096]
After that, a heat treatment or various plasma treatments may be performed to release gas from the carbon nanotubes 21, or a substance to be adsorbed to intentionally adsorb adsorbed substances on the surface of the carbon nanotubes 21 may be used. The carbon nanotubes 21 may be exposed to a contained gas. In order to purify the carbon nanotubes 21, an oxygen plasma treatment or a fluorine plasma treatment may be performed.
[0097]
[Step-170]
Thereafter, it is preferable to retreat the side wall surface of the second opening 14B provided in the insulating layer 12 by isotropic etching from the viewpoint of exposing the opening end of the gate electrode 13. The isotropic etching can be performed by dry etching using radicals as a main etching species, such as chemical dry etching, or wet etching using an etchant. As the etchant, for example, a mixture of a 49% hydrofluoric acid aqueous solution and pure water at a ratio of 1: 100 (volume ratio) can be used. Next, the mask layer 22 is removed. Thus, the field emission device shown in FIG. 8B can be completed.
[0098]
After [Step-150], the steps may be executed in the order of [Step-170] and [Step-160].
[0099]
[Flat field emission device (No. 2)]
FIG. 9A is a schematic partial cross-sectional view of the flat field emission device. The flat field emission device includes a cathode electrode 11 formed on a support 10 made of, for example, glass, an insulating layer 12 formed on the support 10 and the cathode electrode 11, and a gate electrode formed on the insulating layer 12. 13, an opening 14 penetrating the gate electrode 13 and the insulating layer 12 (a first opening provided in the gate electrode 13 and a second opening provided in the insulating layer 12 and communicating with the first opening 14A) And a flat electron emission portion (electron emission layer 15A) provided on the portion of the cathode electrode 11 located at the bottom of the opening 14. Here, the electron emission layer 15A is formed on the striped cathode electrode 11 extending in the direction perpendicular to the plane of the drawing. Further, the gate electrode 13 extends in the horizontal direction of the drawing. The cathode electrode 11 and the gate electrode 13 are made of chromium. The electron emission layer 15A is specifically formed of a thin layer made of graphite powder. In the flat field emission device shown in FIG. 9A, the electron emission layer 15A is formed over the entire surface of the cathode electrode 11, but the invention is not limited to such a structure. In short, it is only necessary that the electron emission layer 15A is provided at least at the bottom of the opening 14.
[0100]
[Flat field emission device]
FIG. 9B is a schematic partial cross-sectional view of the flat field emission device. This planar type field emission device is formed on a striped cathode electrode 11 formed on a support 10 made of, for example, glass, an insulating layer 12 formed on the support 10 and the cathode electrode 11, and an insulating layer 12. And a first opening and a second opening (opening 14) penetrating the gate electrode 13 and the insulating layer 12. The cathode electrode 11 is exposed at the bottom of the opening 14. The cathode electrode 11 extends in a direction perpendicular to the plane of the drawing, and the gate electrode 13 extends in a horizontal direction of the drawing. The cathode electrode 11 and the gate electrode 13 are made of chromium (Cr), and the insulating layer 12 is made of SiO._TwoConsists of Here, the portion of the cathode electrode 11 exposed at the bottom of the opening 14 corresponds to the electron emitting portion 15B.
[0101]
As described above, the present invention has been described based on the embodiments of the present invention, but the present invention is not limited to these. The configurations and structures of the anode panel, the cathode panel, the display device, and the field emission device described in the embodiment of the invention are exemplifications, and can be appropriately changed. The anode panel, the cathode panel, the display device, and the field emission device Is also an example, and can be changed as appropriate. Further, various materials used in the production of the anode panel and the cathode panel are also examples, and can be appropriately changed. In the display device, color display has been described as an example, but a monochrome display may be used.
[0102]
In the embodiment, the configuration in which the cathode electrode 11 extends in the y direction and the gate electrode 13 extends in the x direction has been described, but the cathode electrode 11 extends in the x direction and the gate electrode 13 extends in the y direction. It can also be configured.
[0103]
The anode electrode may be a type in which the effective area is covered with one sheet of conductive material, or may be a type in which anode electrode units corresponding to one or a plurality of pixels are assembled. When the anode electrode has the former configuration, such an anode electrode may be connected to the anode electrode control circuit. When the anode electrode has the latter configuration, for example, each anode electrode unit may be connected to the anode electrode control circuit.
[0104]
In the field emission device, one electron emission portion corresponds to one opening portion. However, depending on the structure of the field emission device, a plurality of electron emission portions correspond to one opening portion. Or a form in which one electron-emitting portion corresponds to a plurality of openings. Alternatively, a plurality of first openings may be provided in the gate electrode, one second opening communicating with the plurality of first openings in the insulating layer may be provided, and one or a plurality of electron emission portions may be provided. You can also.
[0105]
The electron emission region can be constituted by a field emission element commonly called a surface conduction type field emission element. This surface conduction type field emission device is composed of, for example, tin oxide (SnO) on a support made of glass._Two), Gold (Au), indium oxide (In)_TwoO_Three) / Tin oxide (SnO)_Two), A conductive material such as carbon, palladium oxide (PdO), etc., having a small area, and a pair of electrodes arranged at a predetermined interval (gap) formed in a matrix. A carbon thin film is formed on each electrode. Then, a row-direction wiring is connected to one electrode of the pair of electrodes, and a column-direction wiring is connected to the other electrode of the pair of electrodes. By applying a voltage to the pair of electrodes, an electric field is applied to the carbon thin films facing each other across the gap, and electrons are emitted from the carbon thin films. By causing the electrons to collide with the phosphor layer on the anode panel, the phosphor layer is excited and emits light, and a desired image can be obtained.
[0106]
【The invention's effect】
In the present invention, the second derivative φ ″ of the equipotential surface formed by the anode electrode, the gate electrode, and the cathode electrode on the central axis of the opening is defined as −0.02 <φ ″ <0.02. Accordingly, it is possible to reliably prevent the electrons emitted from the electron emitting portion from colliding with the phosphor layer adjacent to the phosphor layer without colliding with the phosphor layer facing the electron emitting portion. . Therefore, it is possible to reliably prevent a decrease in luminance, a decrease in color purity, and an occurrence of optical crosstalk between adjacent pixels. Moreover, the structure of the cathode panel does not become complicated, and the manufacturing cost of the cold cathode field emission display does not increase.
[0107]
When the second derivative φ ″> 0, the electric field intensity at the electron emission portion located at the center of the opening becomes strong, and a large amount of electrons are emitted from the electron emission portion located at the center of the opening. On the other hand, when the second derivative φ ″ <0, the electric field intensity at the portion of the electron emission portion located at the periphery of the opening is increased, and the electron emission from the portion of the electron emission portion located at the periphery of the opening is increased. Is released in large quantities. However, in the present invention, by defining the secondary differential coefficient φ ″ as −0.02 <φ ″ <0.02, it is possible to make the electric field intensity uniform over the entire electron emission portion, and therefore, the electron emission As a result of the emission of electrons from the entire part, the emission site density can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a secondary differential coefficient φ ″ of an equipotential surface formed by an anode electrode, a gate electrode, and a cathode electrode on a central axis line of an opening; Spot diameter V, which is the size of the phosphor layer when colliding with the body layer_ss6 is a graph showing the relationship of.
FIG. 2 is a schematic partial end view of a cold cathode field emission display.
FIG. 3 is a schematic partial perspective view when the cathode panel CP and the anode panel AP are disassembled.
FIG. 4 is a schematic layout diagram of a cathode electrode, a gate electrode, and an opening in a part of the cathode panel.
FIG. 5 is a schematic layout diagram of a cathode electrode, a gate electrode, and an opening in a part of the cathode panel when the number of openings in the overlapping region is one;
FIG. 6 is a schematic layout diagram of a cathode electrode, a gate electrode, and an opening in a part of the cathode panel when the number of openings in the overlapping region is plural.
FIGS. 7A and 7B are schematic partial cross-sectional views of a support and the like for describing a method of manufacturing a flat cold cathode field emission device (No. 1).
FIGS. 8A and 8B are schematic diagrams of a support or the like for explaining a method of manufacturing a flat cold cathode field emission device (No. 1), following FIG. 7B. It is a typical partial sectional view.
FIGS. 9A and 9B are a schematic partial cross-sectional view of a flat cold cathode field emission device (No. 2), and a flat cold cathode field emission device, respectively. It is a schematic partial sectional view.
FIG. 10 is a diagram schematically showing a state in which an electron lens made of a kind of convex lens is formed in an opening and in a space near the opening.
FIG. 11 is a schematic diagram illustrating a state in which electrons emitted from an electron emitting portion collide with a phosphor layer adjacent to the phosphor layer without colliding with a phosphor layer facing the electron emitting portion. FIG.
FIG. 12 is a schematic partial end view of a cold cathode field emission device provided with a focusing electrode.
[Explanation of symbols]
CP: cathode panel, AP: anode panel, 10: support, 11: cathode electrode, 12: insulating layer, 13: gate electrode, 14, 114, 214 ... Opening, 14A: First opening, 14B: Second opening, 15, 15A, 15B: Electron emitting section, 20: Matrix, 21: Carbon nanotube, 30 ... -Substrate, 31, 31R, 31G, 31B ... phosphor layer, 32 ... black matrix, 33 ... anode electrode, 40 ... cathode electrode control circuit, 41 ... gate electrode control circuit, 42 ... Anode electrode control circuit

Claims (3)

A cold cathode field emission display device comprising: a cathode panel including a plurality of cold cathode field emission devices; and an anode panel provided with a phosphor layer and an anode electrode, which are joined at a peripheral portion thereof. ,
Cold cathode field emission devices
(A) a cathode electrode formed on a support and extending in a first direction;
(B) an insulating layer formed on the support and the cathode electrode;
(C) a gate electrode formed on the insulating layer and extending in a second direction different from the first direction;
(D) an opening formed in a portion of the gate electrode and the insulating layer located in an overlapping region where the cathode electrode and the gate electrode overlap;
(E) an electron-emitting portion located at the bottom of the opening;
Consisting of
A value of the second derivative φ ″ = [∂ ² φ / ∂z ² ] _{x = 0, y = 0} of the equipotential surface formed by the anode electrode, the gate electrode, and the cathode electrode on the central axis of the opening. But,
−0.02 <φ ”<0.02
A cold cathode field emission display device characterized by satisfying the following. The planar shape of the overlapping area is a rectangle,
2. The cold cathode field emission display according to claim 1, wherein a plane shape of the opening is a rectangle having a long side parallel to a long side of the rectangular overlapping region. 3. The cold cathode field emission display according to claim 1, wherein the electron emission portion is formed of a carbon nanotube structure.

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