JP4722583B2 - Field emission display - Google Patents

Description

  The present invention relates to a field emission display using carbon nanotubes as an electron emission source.

Conventionally, a cathode ray tube (CRT) has been widely used as a display. However, with the recent progress of information processing equipment and higher image quality of TV broadcasting, there is an increasing expectation for thin displays that have characteristics such as high brightness and high definition, light weight, space saving, and low power consumption. Liquid crystal displays and plasma displays have already been put into practical use.
In addition, various types of thin displays such as a field emission display (FED) expected as a display capable of increasing the brightness, or an organic EL (Electro Luminescence) display characterized by low power consumption. Development is underway.

A field emission display, which is one of the above-mentioned thin displays, is constructed by bonding a cathode panel having an electron emission source and a cathode electrode and an anode panel having a phosphor and an anode electrode, and exhausting the internal gas. ing. Here, when a positive potential is applied to the anode electrode and a negative potential is applied to the cathode electrode, electrons are emitted from the electron emission source, for example, a field emission emitter toward the phosphor. The light emitted when the electrons collide with the phosphor is used as an image.
If necessary, a third electrode may be added between the anode panel and the cathode panel for the purpose of adjusting the electron beam.

  In recent years, research using carbon nanotubes (CNT) as an electron emission source has been performed. A carbon nanotube is a kind of carbon allotrope, is chemically and thermally stable, extremely thin, and has a high electron emission capability, and is expected to operate stably for a long period of time.

However, one of the problems in field emission displays using carbon nanotubes as an electron emission source is that brightness varies among pixels. Among many fine pixels, if there are pixels that do not emit light called black spots or pixels that are extremely brighter than surrounding pixels called bright spots, the entire display becomes very difficult to see.
Therefore, it is required to reduce variations in luminance between pixels including black spots and bright spots.

  As a method for suppressing variations in luminance between pixels, a method for improving electron emission characteristics is generally employed. That is, the light emission efficiency of each pixel is improved, thereby eliminating dark pixels and improving the luminance of all the pixels on the entire screen, with the result that luminance variations are suppressed.

  Here, as a method for improving the electron emission characteristics in each pixel, a method of increasing the number of electron emission portions in one pixel is employed. This is because, when the number of electron emission locations in one pixel is small, the difference in the number of electron emission locations between pixels causes a large difference in luminance of each pixel. When the number is large, even if there is a slight difference in the number of electron emission locations between pixels, there is no significant difference in the luminance of each pixel.

  In order to increase the number of electron emission locations in one pixel, for example, an electron-emitting device described in Patent Document 1 is arranged on a first electrode formed on a support member and the first electrode, and electron emission is performed. And a cold cathode member made of hybrid particles including first particles and second particles having different efficiencies. Here, the second particles are embedded in the surface of the first electrode. The first particles are rod-shaped, columnar, cylindrical, needle-shaped, tetrapot-shaped, or flat-plate-shaped, and a part of the first particles are inserted into the gaps between the second particles by the second particles. The posture is regulated at an angle rather than horizontal with respect to the electrodes.

  Further, for example, a flat panel display described in Patent Document 2 includes a front panel having an anode electrode and a phosphor layer, a cathode electrode provided for each pixel, and a grid disposed in proximity to and electrically insulating from the cathode electrode. 2. Description of the Related Art A flat panel display is known that includes a back panel having electrodes, and is configured such that the opposing peripheral edges of the front panel and the back panel are bonded and fixed with a sealing material so as to form a sealed space therein. Here, the cathode electrode is formed on the inner surface of the back panel, the adhesive layer made of a conductive material laminated on the cathode electrode, and at least a part of the cathode electrode is adhered to the sealed space to form a sealed space. A carbon nanotube aggregate including exposed carbon nanotubes is included.

Japanese Patent No. 3491578 JP 2002-343279 A

  In the devices described in Patent Document 1 and Patent Document 2, although the number of electron emission locations in one pixel can be increased, the potential distribution on the surfaces of the first electrode and the cathode electrode becomes uniform, and a specific There is a problem that electric field concentration is less likely to occur in the carbon nanotube, and as a result, electron emission is less likely to occur in the entire pixel.

  An object of the present invention is to solve the above-described problems, and the object of the present invention is to add carbon particles to the carbon nanotube-containing layer to determine the spacing between the carbon nanotubes. An object of the present invention is to provide a field emission display capable of arranging standing carbon nanotubes at appropriate intervals when raising the nanotubes.

A field emission display according to the present invention includes a cathode panel and an anode panel provided to face the cathode panel. The cathode panel includes a cathode substrate and a cathode electrode formed on the anode panel side of the cathode substrate; and a carbon nanotube-containing layer containing a beauty particle child Oyo carbon nanotubes provided on the anode panel side of the cathode electrode, the anode panel includes an anode substrate, an anode electrode for attracting the electrons provided to the anode substrate, electrostatic A phosphor that emits light by energy given from the child, the carbon nanotubes are raised by irradiating a predetermined laser beam, and the particles have a particle diameter of 0.5 μm to 20 μm and contain carbon nanotubes When the volume of the layer is 100%, the particle content is 10% by volume. Ri 70% der, when the carbon nanotubes are brushed, is shall be kept a clearance corresponding to the particle size by flowing between the carbon nanotubes particles were erected.

  According to the field emission display of the present invention, in order to determine the raising interval between the carbon nanotubes, the particle size is 0.5 μm to 20 μm and the volume of the carbon nanotube-containing layer is 100%. By adding particles having a volume ratio of 10% to 70% to the carbon nanotube-containing layer, when the carbon nanotubes are raised, the standing carbon nanotubes can be arranged uniformly at appropriate intervals. Therefore, sufficient electric field concentration can be caused for each standing carbon nanotube, and variation in luminance between pixels can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding members and parts will be described with the same reference numerals.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing a field emission display according to Embodiment 1 of the present invention.
In FIG. 1, the field emission display includes a cathode panel 1 and an anode panel 2.

The cathode panel 1 includes a cathode substrate 3 that is a glass plate, a cathode electrode 4 formed on the cathode substrate 3, a carbon nanotube-containing layer 7 formed so as to cover the cathode electrode 4, and a carbon nanotube-containing layer 7 And a gate electrode 9 formed on the insulating layer 8.
The carbon nanotube-containing layer 7 includes a carbon nanotube 5 whose tip is exposed to the anode panel 2 side and emits electrons, and glass particles 6 for defining a raised interval between the carbon nanotubes 5.

The anode panel 2 includes an anode substrate 10 that is a glass plate, an anode electrode 11 formed on the anode substrate 10, and a phosphor 12 formed on the anode electrode 11.
The cathode electrode 4, the gate electrode 9 and the anode electrode 11 are electrically connected to each other by a power supply 13.

The cathode electrode 4 is formed by the following procedure.
First, an aluminum thin film is formed on the entire surface of the cathode substrate 3 by sputtering. Next, a paste containing a photosensitive resin is applied over the entire surface, irradiated with laser light through a mask having a predetermined shape, and developed to form a photosensitive resin mask. Subsequently, unnecessary portions of the aluminum thin film are removed by chemical etching. The pattern of the aluminum thin film formed here applies a negative potential to the carbon nanotube 5.

The carbon nanotube-containing layer 7 is formed by the following procedure.
First, carbon nanotubes are contained by mixing and stirring the carbon nanotubes 5, ethyl cellulose for improving printability, glass particles 6 for determining the interval between the standing carbon nanotubes 5, and a solvent such as alcohol. Prepare paste. Next, this carbon nanotube-containing paste is printed on the cathode substrate 3 in a predetermined pattern. Subsequently, the cathode substrate 3 on which the carbon nanotube-containing paste is printed is placed in an electric furnace and heated to 200 ° C. to 600 ° C., thereby completely evaporating the solvent and decomposing ethyl cellulose.

The insulating layer 8 is formed by the following procedure.
First, a paste containing a photosensitive resin is applied over the entire surface, and the photosensitive resin is cured by irradiating only a portion to be masked with a laser beam through a mask having a predetermined shape. Next, baking is performed after removing the uncured photosensitive resin using a stripping solution.
The gate electrode 9 is formed in the same procedure as the cathode electrode 4 using chromium or the like.

The anode electrode 11 is formed in the same procedure as the cathode electrode 4.
In the phosphor 12, first, barriers (partitions, ribs) and address electrodes (not shown) are formed on the anode substrate 10, and then phosphor paste is formed on the anode substrate 10 in a predetermined pattern using a screen printing method. Form by printing.

  The cathode panel 1 and the anode panel 2 are welded to each other, and a vacuum is formed between the cathode panel 1 and the anode panel 2 to form a display.

  Here, at the stage where the carbon nanotube-containing layer 7 is formed, the individual carbon nanotubes 5 exist in the carbon nanotube-containing layer 7 in a state parallel to the substrate surface, that is, in a lying state. Even if a display is formed in this state and a voltage is applied, electron emission from the tip of the carbon nanotube 5 can hardly be expected. When the carbon nanotubes 5 existing in the vicinity of the surface of the carbon nanotube-containing layer 7 slightly protrude from the surface, it can serve as an electron emission source. However, since the number of such carbon nanotubes 5 is small, high luminous efficiency can be obtained. Absent.

  Therefore, raising of the carbon nanotubes 5 is necessary. Raising refers to raising the carbon nanotubes 5 lying in the carbon nanotube-containing layer 7 at some angle or perpendicular to the substrate surface by some method. Since the raised carbon nanotubes 5 have a very sharp tip, electric field concentration is likely to occur.

  As a method for raising the carbon nanotubes 5, in the first embodiment, a method of irradiating the carbon nanotube-containing layer 7 with a linear or circular laser beam is used. Since a black substance such as the carbon nanotube 5 easily absorbs a laser beam, a portion irradiated with the laser beam is rapidly heated. Therefore, some of the carbon nanotubes 5 are cut and stand up explosively. A part of the carbon nanotubes 5 present around the standing carbon nanotubes 5 is also dragged to stand up. This standing carbon nanotube 5 becomes an electron emission source of the field emission display.

The operation of the field emission display having the above configuration will be described below.
A positive potential is applied to the anode electrode 11 and the gate electrode 9, and a negative potential is applied to the cathode electrode 4. When a negative potential is applied to the cathode electrode 4, strong electric field concentration occurs at the tip portion of the carbon nanotube 5. As a result, electrons are emitted from the carbon nanotube 5 due to the potential difference between the gate electrode 9 and the cathode electrode 4.
The emitted electrons are attracted to the anode electrode 11 and collide with the phosphor 12. The phosphor 12 emits light according to the energy of electrons.

  Here, this inventor conducted experiment which measures a light emission rate, changing the particle size and particle content rate of the glass particle 6 added to the carbon nanotube content layer 7. FIG. As a method for obtaining the light emission rate, a method was adopted in which a small-scale cathode panel 1 and anode panel 2 were inserted into a vacuum vessel, and voltage was applied between the cathode electrode 4 and the anode electrode 11 to emit light.

FIG. 2 is an explanatory view showing a cathode panel of an apparatus for measuring the light emission rate of the field emission display of FIG.
In FIG. 2, a test pattern having a total of 100 pixels was created by arranging 10 square pixels of 100 μm square vertically and 10 horizontally. Of the 100 pixels, the number of emitted pixels is directly used as the light emission rate%.

Moreover, the conditions of the glass particle 6 to add are the case where a particle size is the range of 0.5 micrometer-20 micrometers, and the particle content is set to 100% of the volume of the carbon nanotube content layer 7 after baking about each particle size. Further, the volume ratio is in the range of 10% to 100%. In addition, the luminous rate was measured also about the case where the glass particle 6 is not added.
The measurement result of the light emission rate in this experiment is shown in FIG.

  From FIG. 3, by adding glass particles 6, when the particle size is 0.5 μm to 20 μm and the particle content is 10% to 70% by volume, compared to the case where glass particles 6 are not added. It can be seen that the light emission rate is improved.

  This is because when the glass particles 6 of 0.5 μm to 20 μm are added, the density of the standing carbon nanotubes 5 becomes smaller than when the glass particles 6 are not added, so that electric field concentration is likely to occur and light emission. It is thought that the effect of increasing the rate was obtained.

  On the other hand, when the glass particles 6 are not added, there are pixels that emit light, but the light emission rate does not show a sufficient value of 60%. This is presumably because the carbon nanotubes 5 were erected without gaps during raising, resulting in pixels that were less likely to cause electric field concentration.

For the glass particles 6 having a particle size of 20 μm or more, the inventor of the present application conducted an experiment to measure the light emission rate at a part of the particle content. At this time, although the luminous efficiency is improved by setting the interval between the standing carbon nanotubes 5 as compared with the case where the glass particles 6 are not added, the number of light emitting points in one pixel is reduced, resulting in a decrease in luminance. The result was obtained.
Therefore, it can be concluded that the appropriate particle size of the glass particles 6 added to the carbon nanotube-containing layer 7 is 0.5 μm to 20 μm.

  In addition, when glass particles 6 having a volume ratio of 10% to 70% are added, by distributing the carbon nanotubes 5 at an appropriate density, electric field concentration is likely to occur, and the effect of increasing the light emission rate can be obtained. it is conceivable that.

On the other hand, when the particle content is small, the carbon nanotubes 5 are erected at a high density in the entire pixel, and the erected carbon nanotubes 5 cannot be arranged at appropriate intervals. It is considered to be.
In addition, when the particle content exceeds 70%, it is considered that the carbon nanotube-containing layer 7 cannot secure conductivity, and thus does not emit light.
Therefore, it can be concluded that the particle content of the glass particles 6 added to the carbon nanotube-containing layer 7 is suitably 10% to 100% by volume.

Here, in FIG. 3, when the particle content is 30% by volume, FIG. 4 is a characteristic diagram showing the relationship between the particle size and the light emission rate when the particle size is changed from 0.5 μm to 20 μm. Shown in 3 is a characteristic diagram showing the relationship between the particle content and the light emission rate when the particle content is changed from 10% to 100% by volume when the particle size is 3 μm. Show.
From FIG. 3 to FIG. 5, when the particle size of the glass particles 6 is 3 μm to 7 μm and the particle content is 30% to 50% by volume, the light emission rate is 100%, which shows the best light emission rate. I understand that.

  This is because the particle size is in this range and the size is suitable for easily causing electric field concentration on the carbon nanotube 5 in which the glass particles 6 having the particle content in this range are erected, and within one pixel. This is considered to be because the number of light emitting points was in a very suitable range without decreasing.

  According to the field emission display according to Embodiment 1 of the present invention, in order to determine the raised spacing between the carbon nanotubes 5, the particle diameter is 0.5 μm to 20 μm, and the volume of the carbon nanotube-containing layer 7 is set to When the carbon nanotubes 5 are raised by adding glass particles 6 having a particle content of 10% to 70% by volume when the ratio is 100%, the upstanding carbon nanotubes 5 are arranged at appropriate intervals. can do. Therefore, since sufficient electric field concentration can be caused for each standing carbon nanotube 5, it is possible to reliably form electron emission points in a certain distribution state in one pixel. Variations can be reduced.

  Further, by adding the glass particles 6 to the carbon nanotube-containing layer 7, the carbon nanotubes 5 that are very thin, have a very large specific surface area, have high surface activity, and bring in a considerable amount of adsorbents. The amount of can be reduced. As a result, it is possible to suppress the deterioration of the degree of vacuum inside the display after completion.

  Further, by adding glass particles 6 to the carbon nanotube-containing layer 7, it is possible to reduce the amount of use of the thin, long, linear, and homogeneous carbon nanotubes 5 suitable as an electron emission source for a field emission display. As a result, costs can be reduced.

  In the first embodiment, the glass particles 6 are used as the particles for determining the interval between the carbon nanotubes 5. However, the present invention is of course not limited to this, and heat such as nitride, carbide, silicide, etc. Any material that is chemically and chemically stable may be used.

Embodiment 2. FIG.
In Embodiment 1 described above, the glass particles 6 are used as the particles to be added to the carbon nanotube-containing layer 7, but the particles to be added to the carbon nanotube-containing layer 7 are not limited to the glass particles 6.
In the present embodiment, the inventor adds metal particles such as solder particles, iron particles, copper particles, and gold particles having a particle diameter of 0.5 μm to 20 μm to the carbon nanotube-containing layer 7 instead of the glass particles 6. Then, an experiment for measuring the light emission rate was performed in the same manner as in the first embodiment.
Note that the structure and operating principle of the field emission display are the same as those in the first embodiment, and a description thereof will be omitted.

As a result of the measurement of the light emission rate, it was confirmed that the addition of these particles increased the light emission rate with the same tendency as in the first embodiment.
As in the first embodiment, it is considered that the electric field concentration is likely to occur and the luminous efficiency is increased by distributing the standing carbon nanotubes 5 at an appropriate density.

Furthermore, by adding metal particles in place of the glass particles 6, it was possible to confirm two improvements in electrical characteristics, that is, a decrease in extraction electric field and a decrease in electrical resistance during light emission. This effect is shown in FIG.
FIG. 6 shows a field extraction and electron emission when silver particles and glass particles having a particle diameter of 3 μm are added to a carbon nanotube-containing layer in a volume ratio of 30% in the field emission display according to Embodiment 2 of the present invention. It is a characteristic view which shows the relationship with an electric current.

  In FIG. 6, the extraction electric field is an electric field where current starts to flow between the anode and the cathode when the voltage between the gate electrode 9 and the cathode electrode 4 is gradually increased from 0 kV / mm. . The flow of current indicates that the electrons collide with the phosphor 12, that is, the phosphor 12 emits light.

  The electrical resistance corresponds to a slope of a straight line in a voltage region that is equal to or higher than the extraction electric field, and indicates that the electrical resistance decreases as the slope increases.

  It is considered that the effect of these electrical characteristics when the metal particles are added brings about the effect that these metal particles improve the conductivity between the carbon nanotube 5 and the cathode electrode 4.

  When metal particles are added, if the particle content exceeds 70% by volume, the light emission rate is significantly reduced. This is because the present invention raises the carbon nanotubes 5 by irradiating the laser, so that when the proportion of the metal particles increases, the heat for raising the carbon nanotubes 5 diffuses through the metal particles. This is considered to be because sufficient brushing is not performed.

  Although there is a possibility that the absolute amount of the raised carbon nanotubes 5 may be reduced with respect to this problem, by raising the carbon nanotubes 5 by a mechanical method that does not use heat, such as a tape peeling method or a scribing method, It is considered that the effect of adding can be reduced.

  According to the field emission display according to Embodiment 2 of the present invention, by adding metal particles to the carbon nanotube-containing layer 7, the metal particles have good conductivity between the carbon nanotubes 5 and the cathode electrode 4. Therefore, it is possible to realize a reduction in the extraction electric field and a reduction in the electrical resistance during light emission.

  In the second embodiment, the silver particles are used as the particles for determining the interval between the carbon nanotubes 5. However, the present invention is not limited to this, and evaporation, explosion, reaction, etc. are not limited to this. If not, other particles may be used.

Embodiment 3 FIG.
In Embodiment 1 described above, the glass particles 6 are used as the particles to be added to the carbon nanotube-containing layer 7, but the particles to be added to the carbon nanotube-containing layer 7 are not limited to the glass particles 6.
In this embodiment, the inventor of the present invention uses an oxide mainly composed of bismuth oxide having a particle diameter of 0.5 μm to 20 μm and a softening temperature of 300 ° C. to 400 ° C. instead of the glass particles 6 described above. An experiment was performed in which the low melting point glass particles as a mixture were added to the carbon nanotube-containing layer 7 and the light emission rate was measured in the same manner as in the first embodiment.
Note that the structure and operating principle of the field emission display are the same as those in the first embodiment, and a description thereof will be omitted.

As a result of the measurement of the light emission rate, it was confirmed that the light emission rate increased with the same tendency as in Embodiment 1 by adding the low melting point glass particles.
As in the first embodiment, it is considered that the electric field concentration is likely to occur and the luminous efficiency is increased by distributing the standing carbon nanotubes 5 at an appropriate density.

Further, by adding low melting point glass particles instead of the glass particles 6, another effect could be confirmed.
When the cathode panel 1 in which normal glass particles 6 were added to the carbon nanotube-containing layer 7 was formed and the long-term stability of the light emission characteristics was evaluated, pixels that suddenly did not emit light were found in the pixels. When the above pixel was examined, one carbon nanotube 5 was in contact with the cathode electrode 4. That is, the carbon nanotube 5 is broken for some reason or the carbon nanotube 5 that has come out of the carbon nanotube-containing layer 7 is moved by electrostatic force due to long-term use, and the carbon nanotube-containing layer 7, the cathode electrode 4, It was found that electrons could not be emitted by shorting the interval.

However, when the low-melting glass was added, no sudden light emission occurred in this way even when light was emitted continuously for a long time.
This is considered that the carbon nanotube 5 existing in the carbon nanotube-containing layer 7 is fixed by softening and deforming the low melting point glass when the carbon nanotube-containing layer 7 is fired.

  According to the field emission display according to Embodiment 3 of the present invention, by adding the low melting point glass to the carbon nanotube-containing layer 7, the low melting point glass is once melted when the carbon nanotube-containing layer 7 is fired, By curing again, the carbon nanotubes 5 can be reliably fixed, and when a voltage is applied between the cathode electrode 4 and the anode electrode 11, the carbon nanotubes 5 are prevented from being scattered by electrostatic force. Can do.

  In Embodiment 3 described above, glass particles 6 mainly composed of bismuth oxide have been described as an example of the low melting point glass, but of course not limited to this, and the softening temperature is 300 ° C. to 400 ° C. As long as it is a thing, another thing may be sufficient.

  The contents described in the above first to third embodiments are merely examples, as long as the elements described in the claims are included, and an actual field emission display includes a configuration, Various modifications can be made in the structure and specification materials.

It is sectional drawing which shows the field emission type display which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the cathode panel of the apparatus for measuring the light emission rate of the field emission display of FIG. It is a figure which shows the measurement result of the light emission rate in the relationship between the particle size and particle | grain content rate of the field emission display of FIG. FIG. 3 is a characteristic diagram showing the relationship between the particle size and the light emission rate when the particle size is changed from 0.5 μm to 20 μm when the particle content is 30% by volume. FIG. 3 is a characteristic diagram showing the relationship between the particle content and the light emission rate when the particle content is changed from 10% to 100% by volume when the particle size is 3 μm. In the field emission display according to Embodiment 2 of the present invention, the relationship between the extraction electric field and the electron emission current when silver particles and glass particles having a particle diameter of 3 μm are respectively added to the carbon nanotube-containing layer by 30% by volume. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Cathode panel, 2 Anode panel, 3 Cathode substrate, 4 Cathode electrode, 5 Carbon nanotube, 6 Glass particle, 7 Carbon nanotube content layer, 10 Anode substrate, 11 Anode electrode, 12 Phosphor

Claims (4)

A cathode panel and an anode panel provided facing the cathode panel;
The cathode panel is
A cathode substrate;
A cathode electrode formed on the anode panel side of the cathode substrate;
And a carbon nanotube-containing layer containing a beauty particle child Oyo carbon nanotubes provided on the anode panel side of the cathode electrode,
The anode panel is
An anode substrate;
An anode electrode provided on the anode substrate and attracting the electrons;
A phosphor that emits light by energy given from the electrons,
The carbon nanotubes are raised by irradiating a predetermined laser beam,
The particles had a particle size is 0.5Myuemu～20myuemu, and when the volume of the carbon nanotube-containing layer is 100%, Ri 10% to 70% der in volume particle content,
Wherein when the carbon nanotubes are brushed, field emission type display in which the particles are characterized that you hold the gap corresponding to the particle size by flowing between carbon nanotubes standing.   The field emission display according to claim 1, wherein the particles have a particle size of 3 μm to 7 μm.   The field emission display according to claim 1 or 2, wherein the particles have a particle content of 30% to 50% by volume.   The field emission display according to any one of claims 1 to 3, wherein the particles are particles of a low melting point glass that softens at a temperature lower than that of the cathode substrate and the anode substrate.

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