JP4224225B2 - Display element, display device, and display device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display device, and more particularly to a display device capable of high-definition display capable of displaying a stereoscopic image.
[0002]
[Prior art]
For flat display devices, there have been PDP (Plasma Display Panel), PALC (Plasma Address Liquid Crystal), LCD (Liquid Crystal Display), EL (Electro Luminescent) display, FED (Field Emission Display), LED (Light Emitting). Diode) displays have been developed, and some of these have already been put into practical use.
[0003]
In the technology for performing stereoscopic display such as holography, a high-definition display device having a resolution about the wavelength of the light to be used is required to control the wavefront of light, but at present, the wavelength of visible light to be used is required. A display device having a resolution of the order (several hundred nm to 1 μm) has not been realized.
[0004]
[Problems to be solved by the invention]
The plasma display panel (PDP) described above excites a mixed gas such as xenon, neon, and helium confined in a limited space in a pixel cell by discharge. Then, the display device uses the principle that the phosphor applied to the inner surface of the pixel cell absorbs ultraviolet rays emitted when the excited gas returns to the ground state, and the absorbed phosphor emits visible light.
[0005]
In order to achieve a resolution of about the wavelength of light (several hundred nm) using this plasma display panel (PDP), it is necessary to make the pixel cell 1 μm or less in size.
[0006]
However, when the size of the pixel cell is reduced, the energy loss on the inner wall of the pixel cell is relatively increased, so that there is a problem in that the ultraviolet radiation efficiency due to the mixed gas inside decreases.
[0007]
Further, since the discharge start voltage increases when the size of the pixel cell is reduced, it is necessary to increase the pressure of the internal mixed gas in order to obtain the same discharge start voltage as before the size reduction.
[0008]
Therefore, with the current technology, there is a problem that it is difficult to configure a pixel cell having a size of 1 μm or less.
[0009]
For the same reason, it is difficult to construct a pixel cell with a size of 1 μm or less for a plasma addressed liquid crystal (PALC) that uses a discharge similar to that of a plasma display panel (PDP) and uses an ON / OFF switch of the pixel cell. was there.
[0010]
A liquid crystal display (LCD) sandwiches liquid crystal between transparent substrates on which transparent electrodes are formed. Then, by applying a voltage between the transparent electrodes and changing the orientation direction of the sandwiched liquid crystal molecules, light modulation is performed by controlling the light transmittance.
[0011]
Since the liquid crystal display configured as described above cannot sufficiently modulate light if the thickness of the liquid crystal layer is thin, a liquid crystal layer having a thickness of about 1 to 2 μm is currently required. Since the electric field generated by the voltage applied to the transparent electrodes on both sides of the liquid crystal layer spreads in the thickness direction of the liquid crystal layer, there is a problem that light modulation by the liquid crystal layer of 1 μm or less is difficult.
[0012]
Next, in the case of a display device using electroluminescence (EL), the display elements are all suitable for miniaturization of pixel cells because they use a solid thin film. Until now, a basic device having a pixel pitch of about 20 μm has been prototyped. In the display element using EL, the thickness of the light emitting layer is required to be about 1 μm, and furthermore, since it is necessary to provide insulating layers having substantially the same thickness on both sides of the light emitting layer, the electric field distribution in the light emitting layer is widened, There is a problem that it is difficult to realize a display device having a resolution of 1 μm or less.
[0013]
Further, in a light emitting diode or a laser diode made of a compound semiconductor, a microfabrication technique of a semiconductor manufacturing technique can be used. Therefore, although each light emitting layer can be miniaturized to nano-size, it is difficult to create three primary colors necessary for a full-color display by monolithic (integration), and a material that emits each light is selected. There is a need. And there existed a problem that it was difficult to produce the light emitting layer which consists of a different material on the same board | substrate.
[0014]
As described above, with the current display technology, it is difficult to realize a display device having a resolution of about the wavelength of visible light (several hundred nm to 1 μm) necessary for stereoscopic display such as holography and integral photography. was there.
[0015]
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a display device having a resolution of about the wavelength of visible light (several hundred nm to 1 μm). is there.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, a display element according to the present invention includes a phosphor, emits electrons when an electric field is applied from the outside, and has a cold cathode whose tip shape is sharpened, and is opposed to the cold cathode. An anode disposed, and when electrons are emitted from the cold cathode by applying a voltage between the cold cathode and the anode, a tip region of the cold cathode emits light. With such a configuration, a display element having a resolution of about the wavelength of visible light (several hundred nm to 1 μm) can be provided.
Further, by sharpening the shape of the tip of the cold cathode, the region for emitting electrons can be concentrated on the tip of the cold cathode.
[0017]
Further, the display device according to the present invention is a display device including a plurality of display elements that emit light, wherein the light-emitting element includes a phosphor, emits electrons when an electric field is applied from the outside, and has a sharpened tip shape. A cold cathode, and an anode disposed opposite to the cold cathode, and when electrons are emitted from the cold cathode by applying a voltage between the cold cathode and the anode, the cold cathode The tip region of the light emitting element is characterized in that it emits light.
[0018]
With such a configuration, it is possible to provide a display device having a resolution of about the wavelength of visible light (several hundred nm to 1 μm) and capable of high-definition display.
[0019]
The display device includes a red light cold cathode that emits red light, a green light cold cathode that emits green light, and a blue light cold cathode that emits blue light. With this configuration, color display can be performed.
[0021]
The phosphor is characterized by containing a II-VI group semiconductor as a main component.
[0022]
The phosphor has a rare earth oxide as a main component.
[0023]
Further, the display device further serves as a base for forming the cold cathode, and includes regularly arranged cathode buses, and the anodes are regularly arranged while being substantially orthogonal to the cathode buses. And
[0024]
The cold cathodes are arranged in a matrix, and the display device selectively applies a voltage to the cold cathodes arranged in a matrix. With this configuration, the anode can be configured as a single flat planar electrode.
[0025]
The display device is a stereoscopic video display device that displays a stereoscopic video. With this configuration, it is possible to display a stereoscopic image by taking advantage of the resolution of about the wavelength of visible light (several hundred nm to 1 μm).
[0026]
In addition, a display device manufacturing method according to the present invention is a display device manufacturing method for manufacturing a display device, on a transparent substrate on which a cathode matrix is formed that forms a cold cathode that emits electrons when an electric field is applied from the outside. And a phosphor forming step for forming a cold cathode containing the phosphor, and a sharpening step for sharpening the tip of the cold cathode formed in the phosphor forming step. By comprising in this way, the display apparatus which has the resolution | decomposability about the wavelength of visible light (several hundred nm-1 micrometer) can be manufactured.
[0027]
The cold cathode forming step includes a phosphor deposition step of depositing a phosphor substantially only on the cathode matrix. By comprising in this way, the display apparatus which has the resolution | decomposability about the wavelength of visible light (several hundred nm-1 micrometer) can be manufactured.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a display element used in a display device according to the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing a schematic configuration of the display element in the first embodiment. In FIG. 1, the display element according to the first embodiment includes a glass substrate 1 a, a glass substrate 1 b, a cathode bus 2 (an example of a cathode host), an anode bus 3 (an example of an anode), and a phosphor cold cathode 4. .
[0029]
Further, a rare gas is filled between the glass substrate 1a (an example of a transparent substrate) on which the anode bus 3 is formed and the glass substrate 1b on which the phosphor cold cathode 4 is formed. By filling the rare gas in this way, there is an advantage that it is not necessary to make a high vacuum unlike a normal FED (Field Emission Display). Note that a vacuum may be used without filling the rare gas. Although the cathode bus 2 is used as an example of the cathode matrix, a dot-like cathode matrix may be used and arranged in a matrix.
[0030]
The cathode bus 2 serves as a host for forming the phosphor cold cathode 4, and is regularly arranged on the glass substrate 1b. Moreover, the cathode bus 2 is configured to be able to apply a voltage.
[0031]
The anode bus 3 is transparent and is regularly formed on the glass substrate 1 a so as to be substantially perpendicular to the cathode bus 2. The anode bus 3 is configured to be able to apply a voltage in the same manner as the cathode bus 2.
[0032]
The phosphor cold cathode 4 is made of a phosphor and has a tip that is sharpened.
[0033]
Examples of the phosphor include II-VI group semiconductors such as ZnS and ZnO, and rare earth oxides.
[0034]
The display element in Embodiment 1 is configured as described above, and the operation and action will be described below.
[0035]
When a voltage is applied between the cathode bus 2 and the anode bus 3, a potential difference is generated between the phosphor cold cathode 4 and the anode bus 3 based on the applied voltage. For this reason, an electric field is generated between the phosphor cold cathode 4 and the anode bus 3. The generated electric field is concentrated on the tip of the phosphor cold cathode 4.
[0036]
When the generated electric field exceeds a predetermined magnitude, electrons flow from the cathode bus 2 to the phosphor cold cathode 4 and electrons are emitted from the tip region of the phosphor cold cathode 4 by the field emission effect. When electrons pass through the phosphor cold cathode 4, the emission center of the phosphor is excited. Light is emitted when the excited emission center returns to the ground state. Since light emission occurs in a place where electrons flow, the light emitting region of the phosphor cold cathode 4 can be concentrated on the tip region of the phosphor cold cathode 4 from which electrons are emitted.
[0037]
Therefore, the light emitting region can be reduced by the shape of the tip of the phosphor cold cathode 4. For this reason, a display element having a resolution of about the wavelength of visible light (several hundred nm to 1 μm) can be realized. In other words, by using this display element, it is possible to provide a high-definition display device having a resolution of about the wavelength of light.
[0038]
Hereinafter, the operation principle for explaining the above-described operation will be described with reference to FIGS.
[0039]
FIG. 2 shows the band structure of the cathode bus 2, the phosphor cold cathode 4, and the anode bus 3 when a voltage that does not cause electron emission from the phosphor cold cathode 4 is applied between the cathode bus 2 and the anode bus 3. FIG.
[0040]
FIG. 3 is a diagram showing the band structure of the cathode bus 2, the phosphor cold cathode 4, and the anode bus 3 when electrons are emitted from the phosphor cold cathode 4.
[0041]
In the case shown in FIG. 2, there is no electron emission from the phosphor cold cathode 4, and the band structure of the phosphor cold cathode 4 is almost the same as when no voltage is applied. In this case, since no electrons move in the phosphor cold cathode 4, no light is emitted.
[0042]
In contrast, when the voltage is higher than a predetermined voltage (electron emission start voltage) between the phosphor cold cathode 4 and the anode bus 3, electrons are emitted from the tip of the phosphor cold cathode 4. The mechanism by which electrons are emitted is not clearly understood at present, but is thought to be due to the mechanism described below.
[0043]
That is, the electrons in the vicinity of the Fermi energy of the metal constituting the cathode bus 2 pass through the barrier of the metal (metal constituting the cathode bus 2) / phosphor (phosphor constituting the phosphor cold cathode) by the tunnel effect and fluoresce. Injected into the body's conduction band.
[0044]
Electrons injected into the conduction band of the phosphor travel through the conduction band of the phosphor, pass through the phosphor / gas layer barrier by the tunnel effect, and are emitted to the gas layer.
[0045]
Further, when electrons are emitted in the vicinity of the boundary surface between the phosphor cold cathode 4 and the gas layer, and the electron injection frequency in the vicinity of the boundary surface between the cathode bus 2 and the phosphor cold cathode 4 is low, space charges are generated in the phosphor. And the band bends as shown in FIG. The greater the difference between the emission of electrons near the boundary between the phosphor cold cathode 4 and the gas layer and the injection of electrons near the boundary between the cathode bus 2 and the phosphor cold cathode 4, the greater the bending of the band.
[0046]
Electrons that move in the phosphor under an electric field generated by the bending of the band are accelerated. Therefore, if an impurity serving as a light emission center is added to the phosphor cold cathode 4, the electrons that are accelerated and move at high speed are added. Colliding and exciting impurities that become the emission center. Then, electroluminescence (EL) occurs in which the excited impurity emits light when returning to the ground state.
[0047]
FIG. 3 shows the case where the inner core electrons of the impurity serving as the emission center are excited, but the principle is the same in the case of light emission due to donor-acceptor recombination due to electron-hole pair formation in the phosphor.
[0048]
If the bending of the band is increased, the electrons are further accelerated, so that the emission intensity can be increased. For this purpose, it is desirable to increase the difference between the electron emission near the boundary surface between the phosphor cold cathode 4 and the gas layer and the electron injection near the boundary surface between the cathode bus 2 and the phosphor cold cathode 4.
[0049]
Therefore, it is desirable to select a combination of the cathode bus material and the phosphor so that the Schottky barrier between the cathode matrix 2 and the phosphor cold cathode 4 is increased.
[0050]
In this manner, in the structure of the display element shown in FIG. 1, the electric field is concentrated on the tip region of the phosphor cold cathode 4, so that the light emitting region can be reduced according to the processing level of the tip.
[0051]
Further, when a nano-sized crystal of a II-VI group semiconductor or a rare earth oxide is used as the phosphor cold cathode 4, a display device having nano-sized pixels can be realized. That is, the light emitting region can be determined by the size of the phosphor cold cathode 4.
[0052]
Embodiment 2. FIG.
In Embodiment 2, a method for manufacturing a display device using the display element described in Embodiment 1 will be described.
[0053]
FIG. 4 is a diagram schematically showing main steps of a method for manufacturing a display device. First, as shown in FIG. 4A, the cathode bus 2 is formed on the glass substrate 1b. As a technique for forming the cathode bus 2, for example, a photolithography technique used when manufacturing a semiconductor can be used. According to this photolithography technique, the line width of the cathode bus 2 formed on the glass substrate 1b can be several tens of nm.
[0054]
Next, as shown in FIG. 4B, for example, a host crystal of a phosphor made of a II-VI group semiconductor such as ZnS or ZnO is deposited on the glass substrate 1b on which the cathode bus 2 is formed. As a deposition method, for example, a CVD (Chemical Vapor Deposition) method or an MBE (Molecular Beam Epitaxy) method is used. The thickness of the II-VI group semiconductor to be deposited is determined in consideration of the voltage applied to the cathode bus 2.
[0055]
The material to be deposited may be a phosphor made of rare earth oxide, for example.
[0056]
Next, as shown in FIG. 4C, an impurity serving as a light emission center is implanted into a region corresponding to the cathode bus 2 with respect to the deposited mother crystal. Impurities to be injected are a red light impurity for emitting red light, a green light impurity for emitting green light, and a blue light impurity for emitting blue light.
[0057]
For the implantation, an ion implantation method or the like can be used. In this manner, the red light cold cathode 41 that emits red light, the green light cold cathode 42 that emits green light, and the blue light cold cathode 43 that emits blue light can be formed.
[0058]
As the impurity emitting red light, for example, Ag or Al is used when the mother crystal is ZnS. Examples of the green light emitting impurity include Cu, Al, and Zn when the mother crystal is ZnS. Examples of impurities that emit blue light include Ag, Al, and Zn. In addition, the step in FIG.4 (b) and FIG.4 (c) is an example of a cold cathode formation step.
[0059]
After the impurity is implanted, an annealing process is performed for solid solution of the implanted impurity at the lattice position and recovery of crystallinity damaged by the impurity implantation.
[0060]
Subsequently, as shown in FIG. 4D, the shapes of the tips of the red light cold cathode 41, the green light cold cathode 42, and the blue light cold cathode 43 are sharpened.
[0061]
As a sharpening method, for example, etching can be performed. This step is an example of a sharpening step.
[0062]
In this way, with respect to the glass substrate 1b on which the phosphor cold cathode 4 is formed, as shown in FIG. 4 (e), the glass substrate 1a having the anode bus 3 arranged in a direction substantially orthogonal to the cathode bus 2. Are arranged to face each other as a display device.
[0063]
In this manner, a display device using the display element in Embodiment Mode 1 can be manufactured.
[0064]
As shown in FIG. 4A, there is no need to form the cathode bus 2 on the glass substrate 1b. That is, you may use the glass substrate 1b which formed the cathode bus-bar 2 previously.
[0065]
FIG. 5 shows a modification of the method for manufacturing the display device described in FIG. In the step shown in FIG. 4B, the host crystal of the phosphor is deposited, but as shown in FIG. 5B, the phosphor made of II-VI group semiconductor or the phosphor made of rare earth oxide is used. Nano-sized (1 μm or less) crystals may be formed only on the cathode bus 2 (phosphor deposition step). In this case, it is desirable to deposit on the cathode bus 2 under the condition that crystals selectively grow.
[0066]
Alternatively, the phosphor cold cathodes may be arranged in a matrix, and the display device may be configured to selectively apply a voltage to the phosphor cold cathodes arranged in a matrix. In this case, since the anode can be configured as a single flat planar electrode, the anode need not have a busbar structure. Moreover, since the position of the anode can be set to a position suitable for electron emission from the cold cathode, the degree of freedom in device design can be increased. For this reason, when a vacuum is applied between the phosphor cold cathode and the anode, vacuum packaging can be easily performed.
[0067]
【The invention's effect】
The display element according to the present invention can provide a display element having a resolution of about the wavelength of visible light (several hundred nm to 1 μm).
[0068]
Further, according to the display device of the present invention, it is possible to provide a display device having a resolution of about the wavelength of visible light (several hundred nm to 1 μm).
[0069]
Further, according to the display device manufacturing method according to the present invention, a display device having a resolution of about the wavelength of visible light (several hundred nm to 1 μm) can be manufactured.
[0070]
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a schematic structure of a display element in Embodiment 1. FIG.
FIG. 2 is a diagram showing a band structure when electrons are not emitted.
FIG. 3 is a diagram showing a band structure when electrons are emitted.
4 is a diagram schematically showing a part of the manufacturing method of the display device using the display element in the first embodiment. FIG.
FIG. 5 shows a modification of the method for manufacturing the display device described in FIG.
[Explanation of symbols]
1a glass substrate 1b glass substrate 2 cathode bus 3 anode bus 4 phosphor cold cathode 5 mother crystal 41 red light cold cathode 42 green light cold cathode 43 blue light cold cathode

Claims (10)

A cold cathode containing a phosphor, emitting electrons when an electric field is applied from the outside, and having a sharpened tip shape ;
An anode disposed opposite to the cold cathode,
A display element, wherein when a voltage is applied between the cold cathode and the anode, electrons are emitted from the cold cathode, and a tip region of the cold cathode emits light. In a display device including a plurality of display elements that emit light,
The light emitting element includes a phosphor, emits electrons when an electric field is applied from the outside, and a cold cathode whose tip shape is sharpened ;
An anode disposed opposite to the cold cathode,
A display device, wherein when a voltage is applied between the cold cathode and the anode, electrons are emitted from the cold cathode, and a tip region of the cold cathode emits light.   The display device according to claim 2, further comprising a red light cold cathode that emits red light, a green light cold cathode that emits green light, and a blue light cold cathode that emits blue light. The phosphor A display device according to claim 2 or 3, characterized in that a main component group II-VI semiconductor. The phosphor A display device according to claim 2 or 3, characterized in that a main component a rare earth oxide. The display device further serves as a base for forming the cold cathode, and includes regularly arranged cathode bus bars,
The display device according to claim 2, wherein the anode is regularly arranged while being substantially orthogonal to the cathode bus. The cold cathode is arranged in a matrix,
The display device according to claim 2, wherein the display device selectively applies a voltage to the cold cathodes arranged in a matrix. The display device, a display device according to any one of claims 2, characterized in that a stereoscopic image display device for displaying a stereoscopic image 7. A display device manufacturing method for manufacturing the display device according to claim 2 ,
A cold cathode forming step of forming a cold cathode containing a phosphor on a cathode matrix that forms a cold cathode that emits electrons when an electric field is applied from the outside;
A sharpening step for sharpening the tip of the cold cathode formed in the cold cathode forming step. The display device manufacturing method according to claim 9 , wherein the cold cathode forming step includes a phosphor deposition step of depositing a phosphor substantially only on the cathode matrix.

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