JP2007287370A - Backlight device using cold cathode electron source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight device using a cold cathode electron source, and a liquid crystal display device provided with the backlight device capable of efficiently extracting uniform light. <P>SOLUTION: The backlight device has a structure including the cold cathode electron source 310 having an electron emission layer 303 formed on a cathode substrate 301 through a cathode electrode 302, and an anode part 320 provided with a phosphor layer 307 formed on an anode substrate 305 through an anode electrode 306, wherein the cold cathode electron source 310 and the anode part 320 face with each other. The electron emission layer includes fiber and has visible light beam transmissivity more than 10% at a wavelength 550 nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backlight device using a cold cathode electron source, and to a liquid crystal display (LCD) equipped with the backlight device.

  Unlike a light emitting type such as a plasma display, the liquid crystal display device is a non-light emitting type, and therefore requires a backlight device as a light emitting source. Examples of the backlight device include CFL (Cathode Fluorescense Lamp) and LED (Light Emitting Diode). However, the former is a linear light source, so it is difficult to provide uniform light emission over a wide range. In addition, the latter is a point light source and has high directivity, so it is difficult to provide uniform light emission over a wide range. There are problems such as being big. Under such circumstances, a backlight device using a cold cathode electron source has attracted attention as a surface light source capable of supplying light emission with low power consumption and excellent brightness and uniformity.

  FIG. 1 shows an example of a backlight device using a cold cathode electron source. The backlight device includes a cold cathode electron source 110 having an electron emission layer 103 formed on a cathode substrate 101 via a cathode electrode 102 and a phosphor layer 107 formed on an anode substrate 105 via an anode electrode 106. The anode part 120 provided has a structure facing each other. When an electric field is generated between the cathode electrode 102 and the anode electrode 106, electrons are emitted from the electron emission layer 103 to cause the phosphor layer 107 to emit light. The anode substrate 105 and the anode electrode 106 are usually transparent, and light emission can be extracted from the anode substrate 105 side.

  As a material for forming the electron emission layer of the cold cathode electron source, various types of fibers have been attracting attention because they can emit electrons with a uniform intensity at a low electric field, and a typical example is a carbon nanotube. In forming the electron emission layer, a method of growing a fiber directly on the cathode electrode by CVD or the like, and a method of attaching a fiber on the cathode electrode using a paste containing the fiber are known.

  Among these methods, a method using a paste is attracting attention because an electron emission layer can be easily formed in a large area without requiring a special apparatus or the like unlike CVD. In general, a paste is used in which a fiber is mixed with a vehicle containing an organic resin and an organic solvent. This paste is applied and printed on the cathode electrode by means such as screen printing, and then heated to decompose and remove the vehicle component, thereby forming an electron emission layer of the fiber.

Recently, there has been proposed a technique for forming an electron-emitting layer having a high mechanical strength and good adhesion to a cathode electrode by using a paste further blended with silica powder (see, for example, Patent Document 1). ). However, in these techniques, graphite particles formulated to ensure electrical contact with the cathode electrode make the electron emitting layer opaque. When such an opaque electron emission layer is used in a backlight device, the electron emission layer absorbs light emitted from the phosphor layer in the cold cathode electron source direction, thereby deteriorating light extraction efficiency.
JP 2003-303539 A

  An object of the present invention is to provide a backlight device using a cold cathode electron source that can efficiently extract uniform light, and a liquid crystal display device including the backlight device.

  In the present invention, a cold cathode electron source having an electron emission layer formed on a cathode substrate via a cathode electrode and an anode portion having a phosphor layer formed on the anode substrate via an anode electrode face each other. The present invention relates to a backlight device having a structure, wherein the electron emission layer includes a fiber and has a visible light transmittance of 10% or more.

  The present invention also includes a cold cathode electron source having an electron emission layer formed on a cathode substrate via a cathode electrode, and an anode portion having a phosphor layer formed on the anode substrate via an anode electrode. A backlight device having an opposing structure, in which an electron emission layer is coated with a paste containing a fiber, an organic solvent, an organic resin and a glass precursor on the cathode electrode, optionally dried, and then heat-treated. The present invention relates to the above backlight device.

  The backlight device of the present invention can efficiently extract uniform light and is optimal as a light emission source of a liquid crystal display device.

  The electron emission layer in the backlight device of the present invention is formed by applying a specific paste on the cathode electrode by means of screen printing or the like and then heating to decompose and remove the vehicle component.

〔paste〕
The paste includes a fiber, an organic resin, an organic solvent, and a glass precursor.

  The type and form of the fiber are not particularly limited as long as electrons can be emitted. Examples of the type of fiber include carbon-based and boron nitride-based, but carbon-based is preferable.

  The fiber may be linear or cylindrical, and examples thereof include a tube shape, a fiber shape, and a ribbon shape. The fiber may be on the nanometer order or micrometer order. The fiber may be either multilayer or single layer.

  For example, examples of carbon-based materials include carbon nanotubes, carbon nanocoils, carbon nanofibers, and graphite ribbons.

  Among these, carbon nanotubes and carbon nanofibers are preferable because they have a high aspect ratio structure in which electric field concentration tends to occur. The carbon nanotube is usually a very elongated hollow tubular carbon material having a diameter of 0.5 to 100 nm and a length of 0.5 to 100 μm. The carbon nanofiber is usually an elongated fibrous carbon material having a diameter of 1 to 500 nm and a length of 0.5 to 100 μm. In the present invention, the diameter and length are not particularly limited, but are preferably 1 to 40 nm in diameter and 0.5 to 30 μm in length. The carbon nanotube may be either a multilayer or a single wall. Carbon nanotubes and carbon nanofibers must also be manufactured by any method such as arc discharge, laser evaporation, plasma synthesis, hydrocarbon catalytic decomposition, chemical vapor deposition, or thermal decomposition. Can do. One type or two or more types of fibers can be used.

  Examples of organic solvents include, but are not limited to, carbitols, cellosolves, alcohols, and the like. Examples of carbitols include butyl carbitol and butyl carbitol acetate. Examples of cellosolves include butyl cellosolve and butyl cellosolve acetate. Examples of the alcohol include terpineol and texanol. Among these, terpineol and butyl carbitol acetate are preferable from the viewpoint of compatibility with fibers and coating suitability. 1 type (s) or 2 or more types can be used for an organic solvent.

  Examples of organic resins include, but are not limited to, cellulose resins and (meth) acrylic resins. Cellulosic resins are, for example, ethyl cellulose, methyl cellulose, nitrocellulose, cellulose acetate and the like. Examples of the (meth) acrylic resin include polymethyl acrylate, polymethyl methacrylate, polybutyl acrylate, and polybutyl methacrylate. Among these, ethyl cellulose is preferable from the viewpoints of affinity with fibers and coating suitability. The organic resin can use 1 type (s) or 2 or more types.

  The glass precursor is blended in terms of adhesion and adhesion between the electron emission layer and the substrate on which the electron emission layer is formed, and constitutes a glass component by heat treatment for forming the electron emission layer. If it is a substance, it will not specifically limit. From the viewpoints of adhesion and adhesiveness, tetraalkoxysilane or its condensate, organoalkoxysilane or its condensate is preferable. 1 type (s) or 2 or more types can be used for a glass precursor.

  The glass precursor may be liquid or powdery, but in the case of powder, the glass precursor is preferably a fine powder having an average particle diameter of 1 to 100 nm, more preferably an average particle diameter of 1 to 30 nm. It is a fine powder. When using a fine powder, it is preferable to use the glass precursor dispersion liquid previously disperse | distributed to alcohol (for example, ethanol, isopropyl alcohol, n-butanol) etc. from the dispersibility point of a paste.

  Examples of glass precursors include silane compounds such as tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-styryltrimethoxy. Silane, 3- (meth) acryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyl Triethoxysilane, etc. and metal alkoxides such as titanium alkoxides (tetraisopropoxytitanium, etc.), zirconium alkoxides (tetra-n-butoxyzirconium, etc.), aluminum Kokishido (tri -s- butoxy aluminum), as well as condensates thereof. The condensate may be a condensate of a single compound or a complex condensate of a plurality of compounds.

  In general, the paste for forming the electron emission layer is mixed with silica powder of micron order, so that it becomes an obstacle for uniform dispersion of fibers in the paste, and the temperature is high to sufficiently melt the paste. It is necessary and can damage the fiber. On the other hand, the present invention uses the glass precursor to uniformly disperse the fiber in the paste, and suppresses damage to the fiber by vitrification at a lower temperature. At the same time, the electron emission layer and the electron emission layer It is intended to ensure adhesion and adhesion with the base material on which is formed.

  In addition to the above, the paste can contain optional components such as a dispersant, a leveling agent, a conductivity imparting agent, and a photosensitizing agent.

  The amount of the fiber in the paste is preferably 0.01 to 20% by weight, more preferably 0.05 to 10% by weight, and particularly preferably 0, from the viewpoint of fiber dispersibility and the transmittance of the electron emission layer. 0.08 to 5% by weight. The amount of the organic solvent (including the organic solvent in the dispersion when the glass precursor dispersion is used) is preferably 50 to 99% by weight, more preferably 60 to 95% by weight from the viewpoint of paste viscosity and leveling properties. %, Particularly preferably 70 to 92% by weight. The amount of the organic resin is preferably from 0.1 to 30% by weight, more preferably from 0.5 to 20% by weight, and particularly preferably from 1 to 15% by weight, from the viewpoint of the viscosity of the paste. The amount of the glass precursor is preferably 0.05 to 10% by weight, more preferably 0.1 to 9% by weight, particularly preferably 0.15 to 8% by weight from the viewpoint of adhesion and adhesiveness. is there.

[Preparation method of paste]
The paste can be prepared by mixing fibers, organic solvents, organic resins, glass precursors and optional components. The paste can be prepared by mixing all the components at once, or can be prepared by dissolving an organic resin in an organic solvent, adding a fiber or the like to this, and mixing them.

  In particular, the paste is preferably prepared through stepwise mixing. For example, an organic resin is dissolved in an organic solvent, a fiber is added thereto, and mixed well to obtain a dispersion. Then, an organic resin, an organic solvent, a glass precursor, and optional components are further added to the dispersion. It is a method of adding and mixing well to obtain a paste. By passing through such a stage, a paste in which the aggregates of fibers controlled to a relatively uniform and appropriate size are well dispersed can be easily obtained.

  In this case, the ratio of the organic resin to the organic solvent used in the dispersion is preferably smaller than the ratio of the organic resin to the organic solvent of the final paste. Also, the concentration of the fiber in the dispersion is preferably about 2 to 4 times the fiber concentration in the final paste. The mixing after the addition of the fiber can be carried out with an ultrasonic wave, a stirrer, a mixer, a homogenizer, a ball mill, a bead mill or the like. The organic resin and organic solvent used in the dispersion and the additional organic resin and organic solvent added to the dispersion may be the same or different. The mixing after the addition of the additional organic resin and organic solvent and other components can be performed by a mixer, a ball mill, a roll mill or the like.

  By using such a paste, when the electron emission layer is formed, it is possible to avoid a situation in which the existence density of the fiber is extremely different depending on the location, so that uniform light emission is possible. By using the fiber as an aggregate, electron emission can be improved while controlling the existence density of the fiber. This is presumably because the end portion and the bent portion, which are understood as electron emission points, can be used effectively. If the fiber density is low in the film thickness direction and can be arranged on the electrode surface at regular intervals, the electron emission layer becomes translucent to transparent, so that light is suppressed from being absorbed by the electron emission layer, and the backlight The light extraction efficiency in the apparatus can be improved.

  Specifically, in the backlight device of the present invention, the visible light transmittance at a wavelength of 550 nm is 10% or more, preferably 25% or more. In general, the wavelength of 550 nm is the wavelength having the strongest human visibility (the intensity of light felt by the human eye), and is the wavelength that most affects the luminance measurement. The visible light transmittance can be changed by adjusting the film thickness and the concentration of the fiber in the paste. When the film thickness is reduced and the fiber concentration is decreased, the visible light transmittance is generally increased. However, when the number of fibers in the electron emission layer is extremely small, electron emission is insufficient. Usually, the upper limit of the visible light transmittance is about 95%, but may be higher if the electron emission is sufficient. In addition, the film thickness of the electron emission layer in the backlight apparatus of this invention can be 0.01-3 micrometers, for example, Preferably it can be 0.02-1 micrometers.

[Backlight device]
Hereinafter, a backlight device according to an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  A backlight device usually includes a cold cathode electron source having an electron emission layer formed on a cathode substrate via a cathode electrode, and an anode portion having a phosphor layer formed on the anode substrate via an anode electrode. It has an opposing structure.

[Top emission type backlight device]
An example of the backlight device will be described with reference to FIG. In this backlight device, the anode substrate is the transparent substrate 205, and the anode electrode is the transparent electrode 206. The electrons emitted from the electron emission layer 203 cause the phosphor layer 207 to emit light, and this light is extracted from the transparent substrate 205 side of the anode part 220 to function as a light source. The backlight device that takes out light from the anode side located opposite to the cold cathode electron source is referred to as a top emission type for convenience.

  Examples of the cathode substrate 201 include a quartz substrate, an alumina substrate, a silicon substrate, a Mo substrate, a SUS substrate, a Ni—Fe substrate, a glass substrate such as a soda lime glass substrate, a Pyrex substrate, and the like. Examples of the electrode 202 include Cr, Al, Au, Ag, Cu, and Ni. As a method of forming the cathode electrode 202 on the substrate 201, a conventionally known method can be used. For example, after a desired metal film is formed on the cathode substrate 201 by sputtering or vapor deposition, a photolithography technique is used. And a patterning method.

  The electron emission layer 203 can be formed by applying the above paste to a desired position of the cathode electrode 202 and optionally drying it, followed by heat treatment. In order to reduce the contact resistance between the fiber of the electron emission layer 203 and the cathode electrode 202, a fine conductive material such as a metal colloid is disposed on the cathode electrode 202, and the electron emission layer 203 is formed thereon. It may be formed.

  The method for applying the paste is not particularly limited, and includes screen printing, dispensing, gravure printing, offset printing, inkjet printing, and the like, but screen printing is preferable from the viewpoint of easy adjustment of the film thickness. The film thickness after printing can be changed according to the desired film thickness of the electron emission layer.

  Thereafter, the paste is dried and subjected to heat treatment. The drying temperature and time can be appropriately selected depending on the type of the organic solvent and the like, but can usually be dried at 100 to 200 ° C. Moreover, the conditions of heat processing can also be selected suitably, 300-500 degreeC is preferable for heating temperature, More preferably, it is 350-450 degreeC, Heating time is 0.1 to 10 hours, More preferably, it can be 0.5 to 5 hours.

  In this way, an electron emission layer having a visible light transmittance of 10% or more, preferably 25% or more at a wavelength of 550 nm can be obtained.

  The anode unit 220 including the transparent substrate 205, the transparent electrode 206, and the phosphor layer 207, which is disposed to face the cold cathode electron source 210, can be laminated according to a known method using a conventionally known material. . The anode unit 220 may further include a black matrix, a phosphor protective layer, an antistatic layer, an external light reflection layer, a light diffusion layer, and the like as necessary. The transparent substrate 205 is typically a glass substrate, and the transparent electrode 206 is typically an ITO electrode.

  In this backlight device, since the electron emission layer 203 is translucent to transparent, the light emitted from the phosphor layer 207 and directed toward the cold cathode electron source 210 passes through the electron emission layer 203 and becomes the cathode electrode. Since the light is reflected at 202 and travels again toward the anode portion 220, light can be extracted efficiently.

  The point that light can be extracted efficiently will be described using numerical values for easy understanding. Generally, the phosphor layer is composed of n layers (usually n = 2 to 6), and the lowest layer closest to the electron emission layer emits light. If this light emission is 100%, 50% is directed upward and 50% is directed downward. In a conventional top emission type backlight device using an opaque electron emission layer, the downward light is absorbed by the electron emission layer and thus is not extracted. The upward light passes through the phosphor layer while being irregularly reflected, and is extracted from the transparent substrate side. At this time, a loss occurs in the (n−1) layer on the lowermost layer, but n = In the case of 2 to 6, it is known that the loss can be approximated as a% per layer (usually, a = 6 to 10%). As a result, the finally extracted light is represented by the formula (I).

  Formula (I) = 50 × [1- (n−1) × a / 100]%

  For example, if n = 3 and a = 8%, the extracted light is 42%. FIG. 3 shows a schematic diagram of light emission of a phosphor layer having three layers.

  On the other hand, in the backlight device, the downward light passes through the electron emission layer 203 (the visible light transmittance at a wavelength of 550 nm is b%), is reflected by the cathode electrode 202, and again passes through the electron emission layer 203. Pass through and head upward. This light passes through the phosphor layer 207 while being irregularly reflected, and is extracted from the transparent substrate 205 side. At this time, a loss of a% per layer occurs for the n layer. As a result, the light finally extracted together with the upward light from the beginning is represented by the formula (II).

Formula (II) =
50 x [1- (n-1) x (a / 100)]% + 50 x (b / 100) ² x [1-n x (a / 100)]%

  For example, if n = 3, a = 8%, and b = 70%, the extracted light is 61%. In this example, 1.45 times more light is extracted than when the electron emission layer is opaque (the light emission of the phosphor layer is the same).

[Bottom emission type backlight device]
Another embodiment of the backlight of the present invention will be described with reference to FIG. In this backlight device, the cathode substrate is the transparent substrate 301, and the cathode electrode is the transparent electrode 302. The electrons emitted from the electron emission layer 303 cause the phosphor layer 307 to emit light, and this light is extracted from the transparent substrate 301 side of the cold cathode electron source 310, thereby functioning as a light source. The backlight device that takes out light from the cold cathode electron source side is referred to as a bottom emission type for convenience.

  As the transparent substrate 301 constituting the cold cathode electron source, a glass substrate is typical, and as the transparent electrode 302, an ITO electrode is typical. The electron emission layer 303 is formed by applying the above paste to a desired position of the transparent electrode 302 and drying it in some cases, followed by heat treatment. The formation of the electron emission layer 303 is the same as in the top emission type.

  In the anode unit 320 including the anode substrate 305, the anode electrode 306, and the phosphor layer 307, which are disposed to face the cold cathode electron source 310, the substrate 305 is, for example, a quartz substrate, an alumina substrate, a silicon substrate, or a Mo substrate. SUS substrate, Ni—Fe substrate, glass substrate such as soda lime glass substrate, pyrex substrate and the like. Examples of the anode electrode 306 include Cr, Al, Au, Ag, Cu, and Ni. As a method for forming the anode electrode 306 on the anode substrate 305, a conventionally known method can be used. For example, after a desired metal film is formed on the anode substrate 305 by sputtering or vapor deposition, a photolithography technique is used. The method of using and patterning is mentioned. The phosphor layer 307 can be made of a conventionally known material and can be laminated on the anode electrode 306 by a known method. The anode unit 320 may further include a black matrix, a phosphor protective layer, an antistatic layer, and the like as necessary.

  In this backlight device, light emitted from the phosphor layer 307 and directed toward the cold cathode electron source 310 passes through the translucent to transparent electron emission layer 303 and the transparent electrode 302 and is transmitted from the transparent substrate 301 side. It is taken out. Furthermore, light emitted from the phosphor layer 307 and directed toward the anode electrode 306 is reflected by the anode electrode 306 and travels toward the cold cathode electron source 310, so that light can be extracted efficiently.

  The point that light can be extracted efficiently will be described using numerical values for easy understanding. As described above, the phosphor layer is generally composed of n layers, and the lowest layer closest to the electron emission layer emits light. If this light emission is 100%, 50% is directed upward and 50% is directed downward. The upward light passes through the phosphor layer, is reflected by the anode electrode, passes through the phosphor layer, and travels downward again. However, in the bottom emission type backlight device using the conventional opaque electron emission layer, the downward light is finally absorbed by the electron emission layer, so that the extracted light is 0%.

  On the other hand, in the present backlight device, downward light from the beginning passes through the electron emission layer 303 (the visible light transmittance at a wavelength of 550 nm is b%) and is extracted from the transparent substrate 301 side. On the other hand, the upward light is reflected by the anode electrode 306, travels downward again, passes through the electron emission layer 303, and is extracted from the transparent substrate side. Before this light is reflected by the anode electrode 306, a loss of a% per layer occurs in the (n-1) layer above the lowermost layer, and further, the light is reflected by the anode electrode 306 and becomes phosphor. When passing through the layer 307, a loss of a% per layer occurs for the n layer. As a result, the light finally extracted together with the downward light from the beginning is expressed by the formula (III).

Formula (III) =
50 x (b / 100)% + 50 x [1- (2n-1) x (a / 100)] x (b / 100)%

  For example, if n = 3, a = 8%, and b = 70%, the extracted light is 51%. As described above, 0% of light is extracted by the bottom emission type backlight in which the electron emission layer is opaque. Further, in this example, 1.21 times as much light as that of a top emission type backlight device in which the electron emission layer is opaque (assuming that the light emission of the phosphor layer is the same) is extracted.

  By combining the top emission type and the bottom emission type, backlight devices having various structures can be obtained, and uniform light can be obtained with high emission intensity. FIG. 5 relates to a backlight device in which top emission types are stacked. FIG. 6 relates to a backlight device in which bottom emission types are stacked.

  The backlight device of the present invention can be used for a backlight of a liquid crystal display device, an illumination device, a display lamp, and the like.

[Production of paste]
Each component was mixed with the dispersion liquid composition shown in Table 1 for 60 minutes with a planetary ball mill to obtain a dispersion liquid. Next, using this dispersion, each component was mixed by a three-roll mill with the formulation of the paste shown in Table 1 to obtain pastes of Examples 1 to 7. A comparative paste was prepared by mixing all ingredients of Example 1 together on a three roll mill.

[Production of cold cathode electron source]
Using the pastes of Examples 1 to 7 and Comparative Example, a cold cathode electron source 210 that can be used in the top emission type backlight device shown in FIG. 2 was prepared as follows.

  As the cathode substrate 201, a 0.7 mm thick glass substrate was used. As the cathode electrode 202, a Cr film having a thickness of 0.2 mm was formed on the substrate 201 by vapor deposition. About the paste of Examples 1-7 and a comparative example, it printed on the cathode electrode 202 by screen printing (325 mesh) with the film thickness of 23 micrometers after printing. After printing, the temperature was raised at 10 ° C./min in an air atmosphere, held at 400 ° C. for 60 minutes, and then cooled to obtain an electron emission layer. The visible light transmittance of the electron emission layer was measured in a wavelength range of 380 to 800 nm using an ultraviolet-visible spectrophotometer UV-2550 manufactured by Shimadzu Corporation. The measurement results are shown in FIGS. Table 1 shows the visible light transmittance at 550 nm. Further, regarding the luminous efficiency of the backlight device using these as the electron emission layer of the cold cathode electron source, calculated values based on the above-described formulas (II) and (III) are shown (n = 3, a = 8%). ).

[Manufacture of top emission type backlight devices]
Next, a top emission type backlight device was produced using the cold cathode electron source 210 obtained by using the pastes of Example 1 and Comparative Example.

  As the transparent substrate 205 of the anode part 220, a 0.7 mm thick glass substrate was used. As the transparent electrode 206, an ITO film having a thickness of 0.2 mm was formed on the transparent substrate 205 by vapor deposition. Further, a CRT green phosphor (P22) was screen-printed on the transparent electrode 206 as a phosphor layer 207 to form a 10 μm phosphor layer (corresponding to two layers).

  Next, the cold cathode electron source 210 and the anode part 220 obtained by using the paste of Example 4 and the comparative example are opposed so that the distance between the cathode substrate 201 and the transparent substrate 205 is 0.5 mm. A top-emission type backlight device was created.

Under a vacuum environment of 10 ⁻⁶ torr, a voltage of 2 kV is applied to the transparent electrode 206 to emit electrons from the electron emission layer 203 to cause the phosphor layer 207 to emit light. Used to measure the spectral radiance (cd / m ² ) from 380 nm to 780 nm. The results are shown in Table 2. In Example 4, when an image image of the light extraction surface was captured by a CCD camera, bright spots were distributed throughout the light emission area, and it was confirmed that the light emission was uniform.

[Bottom emission type backlight device]
Using the pastes of Example 7 and Comparative Example, a cold cathode electron source that can be used in the bottom emission type backlight device shown in FIG. 4 was prepared.

  The cold cathode electron source 310 was manufactured as follows. As the transparent electrode 302, an ITO film having a thickness of 0.2 mm was used. The ITO film was created using vapor deposition. The electron emission layer was formed in the same manner as the cold cathode electron source that can be used in the top emission type backlight device.

  The anode part 320 was manufactured as follows. As the anode substrate 305 of the anode part 320, a 0.7 mm thick glass substrate was used. As the anode electrode 306, an Al film having a thickness of 0.2 mm was formed on the anode substrate 305 by vapor deposition. Further, a green phosphor for CRT (P22) was screen-printed as a phosphor layer 307 on the anode electrode 306 to prepare a 10 μm phosphor layer (corresponding to two layers).

  Next, the cold cathode electron source 310 and the anode part 320 obtained by using the paste of Example 7 and the comparative example are opposed so that the distance between the transparent substrate 301 and the anode substrate 305 becomes 0.5 mm. A bottom emission type backlight device was created.

Under a vacuum environment of 10 ⁻⁶ torr, a voltage of 2 kV is applied to the transparent electrode 302 to emit electrons from the electron emission layer 303 to cause the phosphor layer 307 to emit light, and a spectral radiometer SR-3 manufactured by Topcon Engineering is used. Used to measure the spectral radiance (cd / m ² ) from 380 nm to 780 nm. The results are shown in Table 3. In Example 7, when an image image of the light extraction surface was captured by a CCD camera, bright spots were distributed throughout the light emitting area, and it was confirmed that the light emission was uniform.

  The backlight device of the present invention can efficiently extract uniform light and is excellent in luminance.

It is an example of the backlight apparatus using a cold cathode electron source. It is a schematic diagram of a top emission type backlight device. It is a schematic diagram about light emission of the fluorescent substance layer which has three layers. It is a schematic diagram of a bottom emission type backlight device. It is a schematic diagram of the backlight apparatus which laminated | stacked the top emission type | mold. It is a schematic diagram of the backlight apparatus which laminated | stacked the bottom emission type | mold. It is the transmittance | permeability with a wavelength of 380-800 nm of the electron emission layer obtained using the paste of Examples 1-4. It is the transmittance | permeability with a wavelength of 380-800 nm of the electron emission layer obtained using the paste of Examples 5-7. It is the transmittance | permeability with a wavelength of 380-800 nm of the electron emission layer obtained using the paste of a comparative example.

Explanation of symbols

101 cathode substrate 102 cathode electrode 103 electron emission layer 105 anode substrate 106 anode electrode 107 phosphor layer 110 cold cathode electron source 120 anode part 201 cathode substrate 202 cathode electrode 203 electron emission layer 205 transparent substrate 206 transparent electrode 207 phosphor layer 210 cold Cathode electron source 220 Anode portion 301 Transparent substrate 302 Transparent electrode 303 Electron emission layer 305 Anode substrate 306 Anode electrode 307 Phosphor layer 310 Cold cathode electron source 320 Anode portion

Claims (6)

A back having a structure in which a cold cathode electron source having an electron emission layer formed on a cathode substrate via a cathode electrode and an anode portion having a phosphor layer formed on the anode substrate via an anode electrode are opposed to each other. A light device,
A backlight device in which the electron emission layer includes a fiber and has a visible light transmittance of 10% or more at a wavelength of 550 nm. A back having a structure in which a cold cathode electron source having an electron emission layer formed on a cathode substrate via a cathode electrode and an anode portion having a phosphor layer formed on the anode substrate via an anode electrode are opposed to each other. A light device,
The electron-emitting layer is formed by applying a paste containing a fiber, an organic solvent, an organic resin, and a glass precursor on the cathode electrode, optionally drying, and then heat-treating. Backlight device.   The backlight device according to claim 1, wherein the fiber is a carbon nanotube and / or a carbon nanofiber.   The backlight device according to claim 1, wherein the anode substrate is a transparent substrate and the anode electrode is a transparent electrode.   The backlight device according to claim 1, wherein the cathode substrate is a transparent substrate and the cathode electrode is a transparent electrode.   A liquid crystal display device comprising the backlight device according to claim 1.