Patent Grant
8164245
The present invention relates to a plasma display panel and a field emission display that each have an anti-reflection function.
In various displays (a plasma display panel (hereinafter referred to as a PDP), a field emission display (hereinafter referred to as an FED), and the like), there may be a case where it becomes difficult to see an image of a display screen due to reflection of its surroundings by surface reflection of incident light from external so that visibility is decreased. This is a considerable problem, particularly in regards to an increase in the size of the display device or outdoor use thereof.
In order to prevent such reflection of incident light from external, a method for providing display screens of a PDP and an FED each having an anti-reflection film has been employed. For example, there is a method for providing an anti-reflective film that has a multilayer structure of stacked layers having different refractive indexes so as to be effective for a wide wavelength range of visible light (see, for example, Reference 1: Japanese Published Patent Application No. 2003-248102). With a multilayer structure, incident lights from external reflected at each interface between the stacked layers interfere with canceling each other out, which provides an anti-reflection effect.
As an anti-reflection structure, minute cone-shaped or pyramid-shaped protrusions are arranged over a substrate and reflectance of the surface of the substrate is decreased (see, for example, Reference 2: Japanese Published Patent Application No. 2004-85831).
However, with the above-described multilayer structure, lights which cannot be cancelled in the lights from external reflected at interfaces are emitted to the viewer side as reflected light. In order to achieve mutual cancellation of incident lights from external, it has been necessary to precisely control optical characteristics of materials, thicknesses, and the like of films stacked, and it has been difficult to perform anti-reflection treatment for all incident lights from external which are incident from various angles. In addition, a cone-shaped or pyramid-shaped anti-reflection structure has not had a sufficient anti-reflection function.
In view of the foregoing, a conventional anti-reflection film has a functional limitation, and a PDP and an FED that each have a higher anti-reflection function have been demanded.
It is an object of the present invention to provide a PDP and an FED that each have high visibility and an anti-reflection function that can further reduce reflection of incident light from external.
The present invention provides a PDP and an FED that each have an anti-reflection layer which can prevent reflection of light by geometrically including a plurality of adjacent projections having a pyramid shape (hereinafter referred to as pyramidal projections). One feature of the present invention is to change a refractive index for incident light from external by a physical shape which is a pyramidal projection protruded toward the outside (an air side) from a surface of a substrate that is to serve as a display screen. In addition, another feature is to provide a protective layer formed of a material having a lower refractive index than a refractive index of the pyramidal projection so as to fill a space among a plurality of pyramidal projections. The space among the plurality of pyramidal projections refers to a depression formed by arrangement of pyramidal projections.
As the pyramidal projection, a projection having a pyramidal shape with a hexagonal base (hereinafter also referred to a hexagonal pyramidal projection) is preferable. A plurality of hexagonal pyramidal projections can be packed together without any spaces and light can be diffused in many directions efficiently because six side surfaces of a pyramidal projection face different directions with respect to a base. The periphery of one pyramidal projection is surrounded by other pyramidal projections, and each side of the base forming a pyramidal shape in one pyramidal projection is shared with the base forming a pyramidal projection in another adjacent pyramidal projection.
A projection having a pyramidal shape with a hexagonal base in an anti-reflection layer of the present invention can have a close-packed structure without any spaces and light can be diffused in many directions efficiently because a pyramidal projection with such a shape has the largest number of side surfaces of a pyramidal projection. Therefore, the projection having a pyramidal shape with a hexagonal base in an anti-reflection layer of the present invention has a high antireflection function.
As for the anti-reflection layer of the present invention, it is preferable that the distance between apexes of a plurality of pyramidal projections be 350 nm or less and the height of the plurality of pyramidal projections be 800 nm or higher. Further, the filling factor (a filling (occupying) percentage over a substrate that is to serve as a display screen) of bases of the plurality of pyramidal projections per unit area over a substrate that is to serve as a display screen is preferably 80% or more, and more preferably, 90% or more. The filling factor is the percentage of the total area that is covered by the formation region of the hexagonal pyramidal projection in the substrate to serve as the display screen. When the filling factor is 80% or more, a ratio of a planar portion where a hexagonal pyramidal projection is not formed over the substrate that is to serve as a display screen is 20% or less. In addition, it is preferable that the ratio between the height and the width of a base of a pyramidal projection be 5 or more to 1.
In the present invention, the thickness of the protective layer, which is provided to fill a space among a plurality of pyramidal projections, may be equivalent to the height of the pyramidal projection or may be higher than the height of the pyramidal projection to cover the pyramidal projection. In this case, surface unevenness due to the pyramidal projections is planarized by the protective layer. Alternatively, the thickness of the protective layer may be less than the height of the pyramidal projection, and in this case, the portion of the pyramidal projection closer to the side of the base is selectively covered and the portion of the projection closer to the apex is exposed on the surface.
The pyramidal projection can further reduce reflection of incident light from external because of its shape. However, when there is a foreign substance such as dirt or dust in the air among the pyramidal projections, the foreign substance causes reflection of incident light from external, and accordingly, there is a case where a sufficient anti-reflection effect for incident light from external cannot be obtained. Since the protective layer is formed in the space among the pyramidal projections in the present invention, the entry of a contaminant such as dust into the space among the pyramidal projections can be prevented. Therefore, a decrease in anti-reflection function due to the entry of dust or the like can be prevented, and physical strength of the anti-reflection film can be increased by filling a space among the pyramidal projections. Accordingly, reliability can be improved.
Since the protective layer filling the space among the pyramidal projections is formed using a material having a lower refractive index than a material used for the pyramidal projections, the difference between the refractive index of the air and that of the protective layer is lower than the difference between the refractive index of the air and that of the material used for the pyramidal projections, and reflection at interfaces can be further suppressed.
The present invention can provide a PDP and an FED that each have an anti-reflection layer including a plurality of adjacent pyramidal projections, and as a result, the present invention can provide a high anti-reflection function.
In the present invention, the PDP includes a main body of a display panel having a discharge cell and a display device to which a flexible printed circuit (FPC) and/or a printed wiring board (PWB) that are/is provided with one or more of an IC, a resistor, a capacitor, an inductor, and a transistor is attached. In addition, an optical filter having an electromagnetic field shielding function or a near infrared ray shielding function may be included.
The FED includes a main body of a display panel having a light-emitting cell and a display device to which a flexible printed circuit (FPC) and/or a printed wiring board (PWB) that are/is provided with one or more of an IC, a resistor, a capacitor, an inductor, and a transistor is attached. In addition, an optical filter having an electromagnetic field shielding function or a near infrared ray shielding function may be included.
The PDP and the FED of the present invention are each provided with an anti-reflection layer having a plurality of pyramidal projections arranged without any spaces on a surface. Since a side surface of a pyramidal projection is not parallel to a display screen, incident light from external is not reflected to a viewer side but is reflected to another adjacent pyramidal projection or travels among the pyramidal projections. In addition, hexagonal pyramidal projections have a close-packed structure without any spaces and have an optimal shape having the largest number of side surfaces of a pyramidal projection among such shapes and a high anti-reflection function that can diffuse light in many directions efficiently. One part of incident light enters pyramidal projections, and the other part of the incident light is then incident on an adjacent pyramidal projection as reflected light. In this manner, incident light from external reflected at the surface of the side of a pyramidal projection is repeatedly incident on adjacent pyramidal projections.
In other words, of the incident light from external that is incident on the anti-reflection layer, the number of times that the light is incident on the pyramidal projections of the anti-reflection layer is increased; therefore, the amount of incident light from external entering the pyramidal projection of the anti-reflection layer is increased. Thus, the amount of incident light from external reflected to a viewer side can be reduced, and the cause of reduction in visibility such as reflection can be prevented.
Furthermore, since the protective layer is formed in the space among the pyramidal projections in the present invention, the entry of a contaminant such as dust into the space among the pyramidal projections can be prevented. Therefore, a decrease in an anti-reflection function due to the entry of dust or the like can be prevented, and physical strength of the PDP and the FED can be increased by filling the space among the pyramidal projections. Accordingly, reliability can be improved.
Accordingly, a PDP and an FED that each have higher quality and higher performance can be manufactured.
Hereinafter, embodiment modes of the present invention will be described with reference to the accompanying drawings. However, the present invention can be implemented in various modes. As can be easily understood by those skilled in the art, the modes and details of the present invention can be changed in various ways without departing from the spirit and scope of the present invention. Thus, the present invention should not be interpreted as being limited to the following description of the embodiment modes. Note that the same reference numeral may be used to denote the same portions or portions having similar functions in different diagrams for explaining the structure of the embodiment modes with reference to drawings, and repetitive explanation thereof is omitted.
In this embodiment mode, an example of an anti-reflection layer for the purpose of having an anti-reflection function that can further reduce reflection of incident light from external and increasing visibility will be described.
As for the anti-reflection layer, incident light from external is reflected to a viewer side when there is a planar portion (a surface parallel to a display screen) with respect to incident light from external; therefore, a small planar portion has a higher anti-reflection function. In addition, it is preferable that a surface of the anti-reflection layer be formed of a plurality of side surfaces of pyramidal projections which face in different directions for further diffusing incident light from external.
The hexagonal pyramidal projections in this embodiment mode can have a close-packed structure without any spaces and each of the hexagonal pyramidal projections has an optimal shape among such shapes, having the largest number of side surfaces of a pyramidal projection and a high anti-reflection function that can diffuse light in many directions efficiently.
The plurality of pyramidal projections all come into contact with each other so as to be geometrically continuous, and each side of the base of one pyramidal projection comes into contact with one side of the base of another adjacent pyramidal projection. Therefore, as shown in
Furthermore, the hexagonal pyramidal projection comes into contact with vertexes of bases of the plurality of hexagonal pyramidal projections at the vertexes of the base, and is surrounded by a plurality of side surfaces of pyramidal projections which face in different directions with respect to a base; therefore, light can be easily reflected in many directions. Accordingly, the hexagonal pyramidal projection having many vertexes on the base achieves a high anti-reflection function.
Since all of the plurality of pyramidal projections 451 of this embodiment mode are provided at equal distances from the vertexes of the adjacent plurality of pyramidal projections, a cross section having the same shape as that shown in
As comparative examples,
In
As for the conical projection, the quadrangular pyramidal projection, and the hexagonal pyramidal projection of this embodiment mode, the results of optical calculations are shown hereinafter. Note that as for the conical projection, the quadrangular pyramidal projection, and the hexagonal pyramidal projection of this embodiment mode, a depression formed by providing pyramidal projections is filled by a protective layer. The calculation in this embodiment mode is made by using Diffract MOD (made by RSoft Design Group, Inc.), an optical calculation simulator for optical devices. The calculation of reflectance is made by performing optical calculation in three-dimensions.
In
When the filling factor of the bases of a plurality of hexagonal pyramidal projections per unit area in a surface of a display screen (that is, the surface of the substrate that is to serve as a display screen) is 80% or more, preferably 90% or more, since the ratio of incident light from external which is incident on a planar portion is reduced, incident light from external can be prevented from being reflected to a viewer side, which is preferable. The filling factor is the percentage of the total area of the substrate that is to serve as the display screen that is covered by the formation region of the hexagonal pyramidal projection. When the filling factor is 80% or more, the ratio of the planar portion where the hexagonal pyramidal projection is not formed over the substrate that is to serve as a display screen is 20% or less.
Similarly, in the model in which the hexagonal pyramidal projections are packed together, the calculation results for changes, caused by changing the width a and the height b of the hexagonal pyramidal projection, in the reflectance with respect to each wavelength is shown hereinafter. In
Furthermore,
As described above, the distance between the apexes of the plurality of adjacent pyramidal projections is preferably 350 nm or less (more preferably, greater than or equal to 100 nm and less than or equal to 300 nm), and the height of each of the plurality of pyramidal projections is preferably 800 nm or more (more preferably, 1000 nm or more, and even more preferably, greater than or equal to 1600 nm and less than or equal to 2000 nm).
In the pyramidal projection of this embodiment mode, it is preferable that the ratio of the height b to the width a of the base of the pyramidal projection be 5 or more to 1.
As a substrate (that is, a substrate that is to serve as a display screen) provided with a pyramidal projection, a glass substrate, a quartz substrate, or the like can be used. In addition, a flexible substrate may be used. The flexible substrate means a (flexible) substrate that is capable of being bent; for example, a plastic substrate formed of polyethylene terephthalate, polyethersulfone, polystyrene, polyethylene naphthalate, polycarbonate, polyimide, polyalylate, or the like; an elastomer which is a material that has a high molecular weight, or the like, with a property of being flexible at high temperature to be shaped similarly to plastic and a property of being an elastic body like a rubber at room temperature can be given. In addition, a film (formed of polypropylene, polyester, vinyl, polyvinyl fluoride, vinyl chloride, an inorganic vapor deposition film, or the like) can be used.
In the present invention, there are no limitations on the shape of the protective layer as long as it is provided in the space among the pyramidal projections.
Alternatively, the thickness of the protective layer may be less than the height of the pyramidal projection, and in this case, a portion of the pyramidal projection closer to the side of the base is selectively covered and an apical portion of the pyramidal projection closer to the apex is exposed on the surface.
Depending on a formation method of the protective layer, a protective layer 495 formed in the space among the pyramidal projections 491 over the substrate 490 that is to serve as a display screen may have a shape in which the thickness is decreased as with a depression formed in the space among the pyramidal projections, as shown in
Any material is acceptable as long as the protective layer is formed using at least a material having a lower refractive index than a material used for the pyramidal projection having the anti-reflection function. Accordingly, the material used for the protective layer can be set as appropriate because it is determined relative to materials of a substrate forming a display screen of the PDP and the FED and the pyramidal projections formed over the substrate.
The pyramidal projection can further reduce reflection of incident light from external by its shape. However, when there is a foreign substance such as dirt or dust in the air in the space among the pyramidal projections, the foreign substance causes reflection of incident light from external, and accordingly, there is a case where a sufficient anti-reflection effect for incident light from external cannot be obtained. Since the protective layer is formed in the space among the pyramidal projections in the present invention, the entry of a contaminant, such as dust, into the space among the pyramidal projections can be prevented. Therefore, a decrease in anti-reflection function due to the entry of dust or the like can be prevented, and the physical strength of the anti-reflection film can be increased by filling the space among the pyramidal projections. Accordingly, reliability can be improved.
Since the protective layer filling the space among the pyramidal projections is formed using a material having a lower refractive index than a material used for the pyramidal projection, the difference between the refractive index of the air and that of the material used for the protective layer is lower than the difference between the refractive index of the air and that of the material used for the pyramidal projection, and reflection at interfaces can be further suppressed.
The pyramidal projection and the protective layer can be each formed not of a material with a uniform refractive index but of a material whose refractive index changes in the direction from an apical portion of the pyramidal projection to a portion closer to a substrate that is to serve as a display screen. For example, a structure in which a portion closer to the apical portion of each pyramidal projection is formed of a material having a refractive index equivalent to that of the air or the protective layer to reduce reflection of incident light from external which is incident on each pyramidal projection from the air on the surface of each pyramidal projection can be used. Meanwhile, the plurality of pyramidal projections may be formed of a material whose refractive index gets closer to that of the substrate that is to serve as the display screen so that reflection of light which propagates inside each pyramidal projection and is incident on the substrate is further reduced at the interface between the pyramidal projections and the substrate. When a glass substrate is used for the substrate, the refractive index of the air or the protective layer is lower than that of the glass substrate. Therefore, each pyramidal projection may have a structure which is formed in such a manner that a portion closer to an apical portion of each pyramidal projection is formed of a material having a lower refractive index and a portion closer to a base of each pyramidal projection is formed of a material having a higher refractive index, that is, the refractive index increases in the direction from the apical portion to the base of each pyramidal projection.
The composition of a material used for forming the pyramidal projection, such as silicon, nitrogen, fluorine, oxide, nitride, or fluoride, may be appropriately selected in accordance with a material of the substrate forming a surface of a display screen. The oxide may be silicon oxide, boric oxide, sodium oxide, magnesium oxide, aluminum oxide (alumina), potassium oxide, calcium oxide, diarsenic trioxide (arsenious oxide), strontium oxide, antimony oxide, barium oxide, indium tin oxide (ITO), zinc oxide, indium zinc oxide (IZO) in which indium oxide is mixed with zinc oxide, a conductive material in which indium oxide is mixed with silicon oxide, organic indium, organotin, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, or the like. The nitride may be aluminum nitride, silicon nitride, or the like. The fluoride may be lithium fluoride, sodium fluoride, magnesium fluoride, calcium fluoride, lanthanum fluoride, or the like. The composition of a material used for forming the pyramidal projection may include one or more kinds of the above-mentioned silicon, nitrogen, fluorine, oxide, nitride, and fluoride. A mixing ratio thereof may be appropriately set in accordance with a ratio of components (a composition ratio) of each substrate.
The pyramidal projection can be formed by forming a thin film by a sputtering method, a vacuum evaporation method, a PVD (physical vapor deposition) method, or a CVD (chemical vapor deposition) method such as a low-pressure CVD (LPCVD) method or a plasma CVD method and then etching the thin film into a desired shape. Alternatively, a droplet discharge method by which a pattern can be formed selectively, a printing method by which a pattern can be transferred or drawn (a method for forming a pattern such as screen printing or offset printing), a coating method such as a spin coating method, a dipping method, a dispenser method, a brush application method, a spray method, a flow coating method, or the like can be employed. Still alternatively, an imprinting technique or a nanoimprinting technique by which a nanoscale three-dimensional structure can be formed by a transfer technology can be employed. Imprinting and nanoimprinting are techniques by which a minute three-dimensional structure can be formed without using a photolithography process.
The protective layer can be formed using a material for forming the pyramidal projection, or the like. As a material having a lower refractive index, silica, alumina, aerogel containing carbon, or the like can be used. A manufacturing method thereof is preferably a wet process, and a droplet discharge method by which a pattern can be formed selectively, a printing method by which a pattern can be transferred or drawn (a method for forming a pattern such as screen printing or offset printing), a coating method such as a spin coating method, a dipping method, a dispenser method, a brush application method, a spray method, a flow coating method, or the like can be employed.
An anti-reflection function of the anti-reflection layer having a plurality of pyramidal projections of this embodiment mode is described with reference to
In this manner, the anti-reflection layer of this embodiment mode includes a plurality of pyramidal projections. Incident light from external is reflected not to a viewer side but to another adjacent pyramidal projection because the side surface of each pyramidal projection is not parallel to the display screen. Alternatively, incident light propagates between the pyramidal projections. One part of incident light enters an adjacent pyramidal projection, and the other part of the incident light is then incident on an adjacent pyramidal projection as reflected light. In this manner, incident light from external reflected at a side surface of a pyramidal projection is repeatedly incident on another adjacent pyramidal projection.
In other words, of the incident light from external that is incident on the anti-reflection layer, the number of times that the light is incident on the pyramidal projection of the anti-reflection layer is increased; therefore, the amount of incident light from external entering the anti-reflection layer is increased. Thus, the amount of incident light from external reflected to a viewer side can be reduced, and the cause of reduction in visibility such as reflection can be prevented.
Furthermore, since the protective layer is formed in the space among the pyramidal projections in this embodiment mode, the entry of a contaminant such as dust into the space among the pyramidal projections can be prevented. Therefore, a decrease in an anti-reflection function due to the entry of dust or the like can be prevented, and physical strength of the anti-reflection film (substrate) and the display device can be increased by filling the space among the pyramidal projections. Accordingly, reliability can be improved.
This embodiment mode can provide a PDP and an FED that each have high visibility and a high anti-reflection function that can further reduce reflection of incident light from external by providing the anti-reflection layer having a plurality of adjacent pyramidal projections to its surface and the protective layer in the space among the pyramidal projections. Accordingly, a PDP and an FED that each have higher quality and higher performance can be manufactured.
In this embodiment mode, an example of a PDP for the purpose of having an anti-reflection function that can further reduce reflection of incident light from external and increasing visibility will be described. That is, a structure of a PDP including a pair of substrates, a pair of electrodes provided between the pair of substrates, a phosphor layer provided between the pair of electrodes, and an anti-reflection layer provided on an outer side of one substrate of the pair of substrates will be described in detail.
In this embodiment mode, a surface emission PDP of an alternating current discharge type (an AC type) is shown. As shown in
Discharge cells of a display portion are arranged in matrix, and each discharge cell is provided at an intersection of a display electrode on the front substrate 110 and an address electrode on the back substrate 120.
The front substrate 110 is formed such that a display electrode extending in a first direction is formed on one surface of a first light-transmitting substrate 111. The display electrode is formed of light-transmitting conductive layers 112a and 112b, a scan electrode 113a, and a sustain electrode 113b. A light-transmitting insulating layer 114 which covers the first light-transmitting substrate 111, the light-transmitting conductive layers 112a and 112b, the scan electrode 113a, and the sustain electrode 113b is formed. Further, a protective layer 115 is formed on the light-transmitting insulating layer 114.
On the other surface of the first light-transmitting substrate 111, an anti-reflection layer 100 is formed. The anti-reflection layer 100 includes a pyramidal projection 101 and a protective layer 102. For the pyramidal projection 101 and the protective layer 102 included in the anti-reflection layer 100, the pyramidal projection and the protective layer described in Embodiment Mode 1 can be used, respectively.
The back substrate 120 is formed such that a data electrode 122 extending in a second direction intersecting with the first direction is formed over one surface of a second light-transmitting substrate 121. A dielectric layer 123 which covers the second light-transmitting substrate 121 and the data electrode 122 is formed. Partitions (ribs) 124 for dividing each discharge cell are formed over the dielectric layer 123. A phosphor layer 125 is formed in a region surrounded by the partitions (ribs) 124 and the dielectric layer 123.
A space surrounded by the phosphor layer 125 and the protective layer 115 is filled in with a discharge gas.
The first light-transmitting substrate 111 and the second light-transmitting substrate 121 can be formed using a glass substrate that has a high strain point or a soda lime glass substrate which can withstand a baking process performed at a temperature that exceeds 500° C., or the like.
The light-transmitting conductive layers 112a and 112b formed on the first light-transmitting substrate 111 preferably each have a light-transmitting property to transmit light emitted from a phosphor and are formed using ITO or tin oxide. In addition, the light-transmitting conductive layers 112a and 112b may be rectangular or T-shaped. The light-transmitting conductive layers 112a and 112b can be formed in such a way that a conductive layer is formed on the first light-transmitting substrate 111 by a sputtering method, a coating method, or the like and then selectively etched. Alternatively, the light-transmitting conductive layers 112a and 112b can be formed in such a way that a composition is selectively applied by a droplet discharge method, a printing method, or the like and then baked. Further alternatively, the Light-transmitting conductive layers 112a and 112b can be formed by a lift-off method.
The scan electrode 113a and the sustain electrode 113b are preferably formed of a conductive layer with a low resistance value and can be formed using chromium, copper, silver, aluminum, gold, or the like. In addition, a stack of copper, chromium, and copper or a stack of chromium, aluminum, and chromium can be used. As a method for forming the scan electrode 113a and the sustain electrode 113b, a similar method to that for forming the light-transmitting conductive layers 112a and 112b can be used, as appropriate.
The light-transmitting insulating layer 114 can be formed using glass with a low melting point containing lead or zinc. As a method for forming the light-transmitting insulating layer 114, a printing method, a coating method, a green sheet laminating method, or the like can be used.
The protective layer 115 is provided to protect from discharge plasma of the dielectric layer and to facilitate the emission of secondary electrons. Therefore, a material having a low ion sputtering rate, a high secondary electron emission coefficient, a low discharge starting voltage, and a high surface insulating property is preferably used. A typical example of such a material is magnesium oxide. As a method for forming the protective layer 115, an electron beam evaporation method, a sputtering method, an ion plating method, an evaporation method, or the like can be used.
Note that a color filter and a black matrix may be provided at an interface between the first light-transmitting substrate 111 and the light-transmitting conductive layers 112a and 112b, at an interface between the light-transmitting conductive layers 112a and 112b and the light-transmitting insulating layer 114, in the light-transmitting insulating layer 114, at an interface between the light-transmitting insulating layer 114 and the protective layer 115, or the like. Providing the color filter and the black matrix makes it possible to improve contrast between light and dark and the color purity of emission color of a phosphor can be improved. A colored layer corresponding to an emission spectrum of a light-emission cell is provided for the color filter.
As the material of the color filter, there are a material in which an inorganic pigment is dispersed throughout light-transmitting glass having a low melting point, colored glass of which a colored component is a metal or metal oxide, and the like. For the inorganic pigment, an iron oxide-based material (red), a chromium-based material (green), a vanadium-chromium-based material (green), a cobalt aluminate-based material (blue), or a vanadium-zirconium-based material (blue) can be used. Moreover, for the inorganic pigment of the black matrix, an iron-cobalt-chromium-based material can be used. In addition to the inorganic pigment, colorants can be mixed as appropriate to be used as a desired color tone of RGB or a desired black matrix.
The data electrode 122 can be formed in a manner similar to that of the scan electrode 113a and the sustain electrode 113b.
The dielectric layer 123 is preferably white having a high reflectance so as to efficiently extract light emitted from a phosphor to the front substrate side. The dielectric layer 123 can be formed using glass with a low melting point containing lead, alumina, titania, or the like. As a method for forming the dielectric layer 123, a similar method to that for forming the light-transmitting insulating layer 114 can be used, as appropriate.
The partitions (ribs) 124 are formed using glass with a low melting point containing lead and a ceramic. The partitions (ribs) can prevent color mixture of emitted light between adjacent discharge cells and improve color purity when the partitions (ribs) are formed in a criss-cross shape. As a method for forming the partitions (ribs) 124, a screen printing method, a sandblast method, an additive method, a photosensitive paste method, a pressure forming method, or the like can be used. Although the partitions (ribs) 124 are formed in a crisscross shape in
The phosphor layer 125 can be formed using various fluorescent materials which can emit light by ultraviolet irradiation. For example, there are BaMgApl14O23:Eu as a fluorescent material for blue, (Y.Ga)BO3:Eu as a fluorescent material for red, and Zn2SiO4:Mn as a fluorescent material for green; however, other fluorescent materials can be used, as appropriate. The phosphor layer 125 can be formed by a printing method, a dispenser method, an optical adhesive method, a phosphor dry film method by which a dry film resist in which phosphor powder is dispersed is laminated, or the like.
For a discharge gas, a mixed gas of neon and argon; a mixed gas of helium, neon and xenon; a mixed gas of helium, xenon, and krypton; or the like can be used.
Next, a method for forming a PDP is shown hereinafter.
In the periphery of the back substrate 120, glass for sealing is printed by a printing method and then pre-baked. Next, the front substrate 110 and the back substrate 120 are aligned, temporally fixed to each other, and then heated. As a result, the glass for sealing is melted and cooled, whereby the front substrate 110 and the back substrate 120 are attached together so that a panel is made. Next, the inside of the panel is drawn down to vacuum while the panel is being heated. Next, after a discharge gas is introduced inside the panel from a vent pipe provided in the back substrate 120, an open end of the vent pipe is blocked and the inside of the panel is sealed airtight by heating the vent pipe provided in the back substrate 120. Then, a cell of the panel is discharged, and aging during which discharging is continued until luminescence properties and electric discharge characteristics become stable is performed. Thus, the panel can be completed.
As a PDP of this embodiment mode, as shown in
When plasma is generated inside of the PDP, electromagnetic waves, infrared rays, and the like are released outside of the PDP. Electromagnetic waves are harmful to human bodies. In addition, infrared rays cause malfunction of a remote controlled For this reason, the optical filter 130 is preferably used to shield from electromagnetic waves and infrared rays.
The anti-reflection layer 100 may be formed over the light-transmitting substrate 131 by the manufacturing method described in Embodiment Mode 1. Alternatively, the surface of the light-transmitting substrate 131 may be an anti-reflection layer. Further alternatively, the anti-reflection layer 100 may be attached to the light-transmitting substrate 131 using a UV curing adhesive or the like.
As a typical example of the electromagnetic wave shield layer 133, there are metal mesh, metal fiber mesh, mesh in which an organic resin fiber is coated with a metal layer, and the like. The metal mesh and the metal fiber mesh are formed of gold, silver, platinum, palladium, copper, titanium, chromium, molybdenum, nickel, zirconium, or the like. The metal mesh can be formed by a plating method, an electroless plating method, or the like after a resist mask is formed over the light-transmitting substrate 131. Alternatively, the metal mesh can be formed in such a way that a conductive layer is formed over the light-transmitting substrate 131, and then, the conductive layer is selectively etched by using a resist mask formed by a photolithography process. In addition, the metal mesh can be formed by using a printing method, a droplet discharge method, or the like, as appropriate. Note that the surface of each of the metal mesh, the metal fiber mesh, and the metal layer formed on a surface of the resin fiber is preferably processed to be black in order to reduce reflectance of visible light.
An organic resin fiber whose surface is covered with a metal layer can be formed of polyester, nylon, vinylidene chloride, aramid, vinylon, cellulose, or the like. In addition, the metal layer on the surface of the organic resin fiber can be formed using any one of the materials used for the metal mesh.
For the electromagnetic wave shield layer 133, a light-transmitting conductive layer having a surface resistance of 10Ω/or less, preferably, 4Ω/or less, and more preferably, 2.5Ω/or less can be used. For the light-transmitting conductive layer, a light-transmitting conductive layer formed of ITO, tin oxide, zinc oxide, or the like can be used. The thickness of the light-transmitting conductive layer is preferably greater than or equal to 100 nm and less than or equal to 5 μm considering surface resistance and a light-transmitting property.
In addition, as the electromagnetic wave shield layer 133, a light-transmitting conductive film can be used. As the light-transmitting conductive film, a plastic film throughout which conductive particles are dispersed can be used. For the conductive particles, there are particles of carbon, gold, silver, platinum, palladium, copper, titanium, chromium, molybdenum, nickel, zirconium, and the like.
Further, as the electromagnetic wave shield layer 133, a plurality of electromagnetic wave absorbers 135 having a pyramidal shape as shown in
Note that the electromagnetic wave shield layer 133 may be attached to the near-infrared ray shielding layer 132 using an adhesive such as an acrylic-based adhesive, a silicone-based adhesive, or a urethane-based adhesive.
Note that an end portion of the electromagnetic wave shield layer 133 is grounded to an earth ground terminal.
The near-infrared ray shielding layer 132 is a layer in which one or more kinds of dyes having a maximum absorption wavelength in a wavelength range of 800 nm to 1000 nm is dissolved into an organic resin. As the dyes, there are a cyanine-based compound, a phthalocyanine-based compound, a naphthalocyanine-based compound, a naphthoquinone-based compound, an anthraquinone-based compound, a dithiol-based complex, and the like.
As an organic resin which can be used for the near-infrared ray shielding layer 132, a polyester resin, a polyurethane resin, an acrylic resin, or the like can be used, as appropriate. In addition, a solvent can be used, as appropriate, to dissolve the dye.
As the near-infrared ray shielding layer 132, a light-transmitting conductive layer formed of a copper-based material, a phthalocyanine-based compound, zinc oxide, silver, ITO, or the like; or a nickel complex layer may be formed on the surface of the light-transmitting substrate 131. Note that, in the case of forming the near-infrared ray shielding layer 132 with the material, the near-infrared ray shielding layer 132 has a light-transmitting property and is formed at a thickness at which near-infrared rays are blocked.
As a method for forming the near-infrared ray shielding layer 132, a composition can be applied by a printing method, a coating method, or the like and cured by heat or light irradiation.
For the light-transmitting substrate 131, a glass substrate, a quartz substrate, or the like can be used. In addition, a flexible substrate may be used as well. A flexible substrate is a (flexible) substrate that is capable of being bent, and for example, a plastic substrate and the like formed of polyethylene terephthalate, polyethersulfone, polystyrene, polyethylene naphthalate, polycarbonate, polyimide, polyarylate, and the like are given. Alternatively, a film (formed of polypropylene, polyester, vinyl, polyvinyl fluoride, vinyl chloride, polyamide, an inorganic vapor deposition film, or the like) can be used.
Note that in
In particular, when a plastic is used for the light-transmitting substrate 131 and the optical filter 130 is provided on the surface of the front substrate 110 by use of the adhesive 136, reductions in thickness and weight of a plasma display can be achieved.
Note that the electromagnetic wave shield layer 133 and the near-infrared ray shielding layer 132 are formed using different layers here; however, the electromagnetic wave shield layer 133 and the near-infrared ray shielding layer 132 may be formed of one functional layer that has an electromagnetic wave shield function and a near-infrared ray shielding function instead. In this way, the thickness of the optical filter 130 can be reduced, and reductions in weight and thickness of the PDP can be achieved.
Next, a PDP module and a driving method thereof are described with reference to
As shown in
A data electrode driver circuit 144 that drives a data electrode is provided over the second light-transmitting substrate which is part of the back substrate 120 and is connected to the data electrode. Here, the data electrode driver circuit 144 is provided over a wiring board 146 and connected to the data electrode through an FPC 147. Although not shown, a control circuit which controls the scan electrode driver circuit 142, the sustain electrode driver circuit 143, and the data electrode driver circuit 144 is provided over the first light-transmitting substrate 111 or the second light-transmitting substrate 121.
As shown in
Note that, because there is not need for the sustain electrode 113b to scan the inside of the display portion 145, the sustain electrode 113b can serve as a common electrode. In addition, with the sustain electrode serving as a common electrode, the number of driver ICs can be reduced.
As a PDP in this embodiment mode, an AC type reflection type surface emission PDP is described; however, the present invention is not limited thereto. In an AC discharge type transmissive emission PDP, the anti-reflection layer 100 can be provided. Further, in a direct current (DC) discharge type PDP, the anti-reflection layer 100 can be provided.
The PDP described in this embodiment mode includes the anti-reflection layer on its surface. The anti-reflection layer includes a plurality of pyramidal projections, and incident light from external is reflected not to a viewer side but to another adjacent pyramidal projection because the side of each pyramidal projection is not perpendicular to the direction of incidence of incident light from external. Alternatively, reflected light of incident light from external propagates between the adjacent pyramidal projections. One part of incident light enters an adjacent pyramidal projection, and the other part of the incident light is then incident on an adjacent pyramidal projection as reflected light. In this manner, incident light from external reflected at the surface of the side of a pyramidal projection is repeatedly incident on adjacent pyramidal projections.
In other words, the number of times which is incident on the pyramidal projections of the PDP of incidence of incident light from external is increased; therefore, the amount of incident light from external entering the pyramidal projection is increased. Thus, the amount of incident light from external reflected to a viewer side is reduced, and a cause of the reduction in visibility such as reflection can be prevented.
In a display screen, since incident light from external is reflected to a viewer side when there is a planar portion (a surface parallel to the display screen) with respect to incident light from external, a smaller planar region has a high antireflection function. In addition, it is preferable that a pyramidal projection with a plurality of side surfaces of a pyramidal projection which face in different directions with respect to a base be formed on a surface of a substrate that is to serve as a display screen for diffusing incident light from external.
The hexagonal pyramidal projection in this embodiment mode can have a close-packed structure without any spaces and has an optimal shape from among such shapes, having the largest number of sides of a pyramidal projection and a high anti-reflection function that can diffuse light in many directions efficiently.
The distance between apexes of the plurality of adjacent pyramidal projections is preferably 350 nm or less, and the height of the plurality of pyramidal projections is preferably 800 nm or higher. In addition, when the filling factor of a base of the plurality of pyramidal projections per unit area over the surface of the substrate that is to serve as a display screen is 80% or more, preferably, 90% or more, since the ratio of incident light from external which is incident on a planar portion is reduced, light can be prevented from being reflected to a viewer side, which is preferable.
The pyramidal projection can be formed not of a material with a uniform refractive index but of a material whose refractive index changes from an apical portion of the pyramidal projection to a portion closer to a substrate that is to serve as a display screen. For example, in each of the plurality of pyramidal projections, a structure is used in which a portion closer to the apical portion of each pyramidal projection can be formed of a material having a refractive index equivalent to that of the air or the protective layer to further reduce reflection of incident light from external which is incident on the surface of each pyramidal projection from the air. Meanwhile, the plurality of pyramidal projections is formed of a material having a refractive index equivalent to that of the substrate as a portion closer to the substrate that is to serve as the display screen so that reflection of light which propagates inside each pyramidal projection and is incident on the substrate is reduced at the interface between each pyramidal projection and the substrate. When a glass substrate is used for the substrate, the refractive index of the air or the protective layer is lower than that of the glass substrate. Therefore, each pyramidal projection may have a structure which is formed in such a manner that a portion closer to an apical portion of each pyramidal projection is formed of a material having a lower refractive index and a portion closer to a base of each pyramidal projection is formed of a material having a higher refractive index, that is, the refractive index increases from the apical portion to the base of each pyramidal projection.
Furthermore, since the protective layer is formed in the space among the pyramidal projections in the present invention, the entry of a contaminant, such as dust, into the space among the pyramidal projections can be prevented. Therefore, a decrease in anti-reflection function due to the entry of dust or the like can be prevented, and the physical strength of the PDP can be increased by filling the space among the pyramidal projections. Accordingly, reliability can be improved.
The PDP described in this embodiment mode includes a high anti-reflection function that can further reduce reflection of incident light from external by providing the anti-reflection layer having a plurality of adjacent pyramidal projections to its surface and the protective layer in the space among the pyramidal projections. Therefore, a PDP having high visibility can be provided. Accordingly, a PDP having higher quality and higher performance can be manufactured.
In this embodiment mode, an FED for the purpose of having an anti-reflection function that can further reduce reflection of incident light from external and increasing visibility will be described. That is, a structure of an FED including a pair of substrates, a field emission element provided on one substrate of the pair of substrates, an electrode provided on the other substrate of the pair of substrates, a phosphor layer which comes into contact with the electrode, and an anti-reflection layer provided on an outer side of the other substrate will be described in detail.
The FED is a display device in which a phosphor is exited by an electron beam to emit light. The FED can be classified into a diode FED, a triode FED, and a tetrode FED according to the configuration of electrodes.
The diode FED has a structure where a rectangular cathode electrode is formed on a surface of a first substrate while a rectangular anode electrode is formed on a surface of a second substrate, and the cathode electrode and the anode electrode cross each other with a distance of several μm to several mm interposed therebetween. An electron beam is emitted between the electrodes at an intersection in a vacuum space between the cathode electrode and the anode electrode by setting a potential difference of 10 kV or lower. These electrons reach the phosphor layer provided to the cathode electrode to excite the phosphor and emit light, whereby an image can be displayed.
The triode FED has a structure where a gate electrode crossing a cathode electrode with an insulating film interposed therebetween is formed over a first substrate provided with the cathode electrode. The cathode electrode and the gate electrode are arranged in rectangular or in matrix, and an electron-emission element is formed in an intersection portion, which includes the insulating film, of the cathode electrode and the gate electrode. By applying a voltage to the cathode electrode and the gate electrode, an electron beam is emitted from the electron-emission element. This electron beam is pulled toward the anode electrode of the second substrate to which a voltage higher than the voltage applied to the gate electrode is applied, whereby the phosphor layer provided to the anode electrode is excited, so that an image can be displayed by light emission.
The tetrode FED has a structure where a placoid or thin film focusing electrode having an opening is formed in each pixel between a gate electrode and an anode electrode of the triode FED. By focusing electron beams emitted from an electron-emission element in each pixel by the focusing electrode, the phosphor layer provided to the anode electrode can be excited, and thus, an image can be displayed by light emission.
The discharge cells of a display portion are arranged in matrix.
In the front substrate 210, the phosphor layer 232 is farmed on one surface of a first light-transmitting substrate 211. A metal back 234 is formed on the phosphor layer 232. Note that an anode electrode may be formed between the first light-transmitting substrate 211 and the phosphor layer 232. For the anode electrode, a rectangular conductive layer which extends in the first direction can be formed.
An anti-reflection layer 200 is formed on the other surface of the first light-transmitting substrate 211. The anti-reflection layer 200 includes a pyramidal projection 201 and the protective layer 102. As the pyramidal projection 201 and the protective layer 102, the pyramidal projection and the protective layer described in Embodiment Mode 1 can be used, respectively.
In the back substrate 220, an electron-emission element 226 is formed on one surface of a second light-transmitting substrate 221. As the electron-emission element, various structures are proposed. Specifically, there are a Spindt-type electron-emission element, a surface-conduction electron-emission element, a ballistic-electron plane-emission-type electron-emission element, a metal-insulator-metal (MIM) element, a carbon nanotube, graphite nanofiber, diamond-like carbon (DLC), and the like.
Here, a typical electron-emission element is shown with reference to
A cathode electrode 222 and cone-shaped electron sources 225 formed over the cathode electrode 222 are included in a Spindt-type electron-emission element 230. The cone-shaped electron sources 225 are formed of a metal or a semiconductor. A gate electrode 224 is arranged in the periphery of the cone-shaped electron sources 225. Note that the gate electrode 224 and the cathode electrode 222 are insulated from each other with an interlayer insulating layer 223.
When a voltage is applied between the gate electrode 224 and the cathode electrode 222 formed in the back substrate 220, an electric field concentrates on each apical portion of the cone-shaped electron sources 225 to increase the intensity of the electric field, so that electrons are emitted into a vacuum from a metal or a semiconductor which forms the cone-shaped electron sources 225 by tunneling. On the other hand, the front substrate 210 is provided with the metal back 234 (or an anode electrode) and the phosphor layer 232. By applying a voltage to the metal back 234 (or the anode electrode), an electron beam 235 emitted from the cone-shaped electron sources 225 is guided to the phosphor layer 232, and a phosphor is exited, so that light emission can be obtained. Therefore, the cone-shaped electron sources 225 surrounded by the gate electrode 224 can be arranged in matrix, and light emission of each cell can be controlled by selectively applying a voltage to the cathode electrode, the metal back (or the anode electrode), and the gate electrode.
The Spindt-type electron-emission element has advantages in that (1) an electron extraction efficiency is high since it has a structure where an electron-emission element is arranged in a central region of a gate electrode with the largest concentration of the electric field, (2) in-plane uniformity of an extraction current of an electron-emission element is high since patterns having the arrangement of electron-emission elements can be accurately drawn to set suitable arrangement for electric field distribution, and the like.
Next, a structure of the cell having the Spindt-type electron-emission element is described. The front substrate 210 includes the first light-transmitting substrate 211, the phosphor layer 232 and a black matrix 233 formed on the first light-transmitting substrate 211, and the metal back 234 formed on the phosphor layer 232 and the black matrix 233.
As the first light-transmitting substrate 211, a substrate similar to the first light-transmitting substrate 111 described in Embodiment Mode 2 can be used.
For the phosphor layer 232, a fluorescent material to be excited by the electron beam 235 can be used. Further, as the phosphor layer 232, phosphor layers of RGB can be provided with rectangular arrangement, lattice arrangement, or delta arrangement, so that color display is possible. As a typical example, Y2O2S:Eu (red), Zn2SiO4:Mn (green), ZnS:Ag,Al (blue), and the like can be given. Other than these, a fluorescent material which is excited by a known electron beam can also be used.
The black matrix 233 is formed between the respective phosphor layers 232. By providing the black matrix, discrepancy in emission color due to misalignment of an irradiated position of the electron beam 235 can be prevented. Further, by providing conductivity to the black matrix 233, the charge-up of the phosphor layer 232 due to an electron beam can be prevented. For the black matrix 233, carbon particles can be used. Note that a known black matrix material for an FED can also be used.
The phosphor layer 232 and the black matrix 233 can be formed using a slurry process or a printing method. In the slurry process, a composition in which the fluorescent material or carbon particles are mixed into a photosensitive material, a solvent, or the like is applied by spin coating and dried, and then exposed and developed.
The metal back 234 can be formed using a conductive thin film of aluminum or the like having a thickness of 10 nm to 200 nm, preferably a thickness of 50 nm to 150 nm. By providing the metal back 234, light which is emitted from the phosphor layer 232 and goes to the back substrate 220 side can be reflected toward the first light-transmitting substrate 211, so that luminance can be improved. In addition, the metal back 234 can prevent the phosphor layer 232 from being damaged by shock of ions which are generated in such a way that a gas which remains in a cell is ionized by the electron beam 235. The metal back 234 can guide the electron beam 235 to the phosphor layer 232 because the metal back 234 plays a role as an anode electrode with respect to the electron-emission element 230. The metal back 234 can be formed in such a way that a conductive layer is formed by a sputtering method and then selectively etched.
The back substrate 220 is formed of the second light-transmitting substrate 221, the cathode electrode 222 formed over the second light-transmitting substrate 221, the cone-shaped electron sources 225 formed over the cathode electrode 222, the interlayer insulating layer 223 which separates the electron sources 225 into each cell, and the gate electrode 224 formed over the interlayer insulating layer 223.
As the second light-transmitting substrate 221, a substrate similar to the second light-transmitting substrate 121 described in Embodiment Mode 2 can be used.
The cathode electrode 222 can be formed using tungsten, molybdenum, niobium, tantalum, titanium, chromium, aluminum, copper, or ITO. As a method for forming the cathode electrode 222, an electron beam evaporation method, a thermal evaporation method, a printing method, a plating method, or the like can be used. Further, a conductive layer is formed by a sputtering method, a CVD method, an ion plating method, or the like over an entire surface, and then, the conductive layer is selectively etched by using a resist mask or the like, so that the cathode electrode 222 can be formed. When an anode electrode is formed, the cathode electrode can be formed of a rectangular conductive layer which extends in the first direction parallel to the anode electrode.
The electron sources 225 can be formed using tungsten, a tungsten alloy, molybdenum, a molybdenum alloy, niobium, a niobium alloy, tantalum, a tantalum alloy, titanium, a titanium alloy, chromium, a chromium alloy, silicon which imparts n-type conductivity (doped with phosphorus), or the like.
The interlayer insulating layer 223 can be formed using the following: an inorganic siloxane polymer including a Si—O—Si bond among compounds including silicon, oxygen, and hydrogen formed by using a siloxane polymer-based material as a starting material, which is typified by silica glass; or an organic siloxane polymer in which hydrogen bonded to silicon is substituted by an organic group such as methyl or phenyl, which is typified by an alkylsiloxane polymer, an alkylsilsesquioxane polymer, a silsesquioxane hydride polymer, or an alkylsilsesquioxane hydride polymer. When the interlayer insulating layer 223 is formed using the above material, a coating method, a printing method, or the like is used. Alternatively, as the interlayer insulating layer 223, a silicon oxide layer may be formed by a sputtering method, a CVD method, or the like. Note that, in regions where the electron sources 225 are formed, the interlayer insulating layer 223 is provided with openings.
The gate electrode 224 can be formed using tungsten, molybdenum, niobium, tantalum, chromium, aluminum, copper, or the like. As a method for forming the gate electrode 224, the method for forming the cathode electrode 222 can be used, as appropriate. The gate electrode 224 can be formed of a rectangular conductive layer which extends in the second direction that intersects with the first direction at 90°. Note that, in the regions where the electron sources 225 are formed, the gate electrode is provided with openings.
Note that, in a space between the gate electrode 224 and the metal back 234, that is, in a space between the front substrate 210 and the back substrate 220, a focusing electrode may be formed. The focusing electrode is provided in order to focus an electron beam emitted from the electron-emission element. By providing the focusing electrode, light emission luminance of the light-emission cell can be improved, reduction in contrast due to color mixture of adjacent cells can be suppressed, or the like. A negative voltage is preferably applied to the focusing electrode, compared with the metal back (or the anode electrode).
Next, a structure of a cell of an FED having a surface-conduction electron-emission element is described.
A surface-conduction electron-emission element 250 is formed of element electrodes 255 and 256 which are opposed to each other, and conductive layers 258 and 259 which come into contact with the element electrodes 255 and 256, respectively. The conductive layers 258 and 259 have a space portion. When a voltage is applied to the element electrodes 255 and 256, an intense electric field is generated in the space portion, and electrons are emitted from one of the conductive layers to the other thereof due to a tunnel effect. By applying a positive voltage to the metal back 234 (or the anode electrode) provided in the front substrate 210, the electrons emitted from one of the conductive layers to the other thereof is guided to the phosphor layer 232. When this electron beam 260 excites a phosphor, light emission can be obtained.
Therefore, the surface-conduction electron-emission elements are arranged in matrix, and a voltage is selectively applied to the element electrodes 255 and 256 and the metal back (or the anode electrode), so that light emission of each cell can be controlled.
Because a drive voltage of the surface-conduction electron-emission element is low, compared with other electron-emission elements, power consumption of the FED can be lowered.
Next, a structure of a cell having a surface-conduction electron-emission element is described. The front substrate 210 includes the first light-transmitting substrate 211, the phosphor layer 232 and the black matrix 233 formed on the first light-transmitting substrate 211, and the metal back 234 formed on the phosphor layer 232 and the black matrix 233. Note that an anode electrode may be formed between the first light-transmitting substrate 211 and the phosphor layer 232. For the anode electrode, a rectangular conductive layer which extends in the first direction can be formed.
The back substrate 220 is formed of the second light-transmitting substrate 221, a row direction wiring 252 formed over the second light-transmitting substrate 221, an interlayer insulating layer 253 formed over the row direction wiring 252 and the second light-transmitting substrate 221, a connection wiring 254 connected to the row direction wiring 252 with the interlayer insulating layer 253 interposed therebetween, the element electrode 255 which is connected to the connection wiring 254 and formed over the interlayer insulating layer 253, the element electrode 256 formed over the interlayer insulating layer 253, a column direction wiring 257 connected to the element electrode 256, the conductive layer 258 which comes into contact with the element electrode 255, and the conductive layer 259 which comes into contact with the element electrode 256. Note that the electron-emission element 250 shown in
The row direction wiring 252 can be formed using a metal such as titanium, nickel, gold, silver, copper, aluminum, or platinum; or an alloy of these. As a method for forming the row direction wiring 252, a droplet discharge method, a vacuum evaporation method, a printing method, or the like can be used. Alternatively, the row direction wiring 252 can be formed in such a way that a conductive layer formed by a sputtering method, a CVD method, or the like is selectively etched. The thickness of each of the element electrodes 255 and 256 is preferably 20 nm to 500 nm.
As the interlayer insulating layer 253, a material and a formation method similar to those of the interlayer insulating layer 223 shown in
As the connection wiring 254, a material and a formation method similar to those of the row direction wiring 252 can be used, as appropriate.
The pair of the element electrodes 255 and 256 can be formed using a metal such as chromium, copper, iridium, molybdenum, palladium, platinum, titanium, tantalum, tungsten, or zirconium; or an alloy of these. As a method for forming the element electrodes 255 and 256, a droplet discharge method, a vacuum evaporation method, a printing method, or the like can be used. The element electrodes 255 and 256 can be formed in such a way that a conductive layer formed by a sputtering method, a CVD method, or the like is selectively etched. The thickness of each of the element electrodes 255 and 256 is preferably 20 nm to 500 nm.
As the column direction wiring 257, a material and a formation method similar to those of the row direction wiring 252 can be used, as appropriate.
As a material of the pair of the conductive layers 258 and 259, a metal such as palladium, platinum, chromium, titanium, copper, tantalum, or tungsten; oxide such as palladium oxide, tin oxide, a mixture of indium oxide and antimony oxide; silicon; carbon; or the like can be used, as appropriate. Further, a stack using a plurality of the above materials may be used. In addition, the conductive layers 258 and 259 can be formed using particles of any of the above materials. Note that an oxide layer may be formed around the particles of any of the above materials. By using the particles having an oxide layer, electrons can be accelerated and easily emitted. As a method for forming the conductive layers 258 and 259, a droplet discharge method, a vacuum evaporation method, a printing method, or the like can be used. The thickness of each of the conductive layers 258 and 259 is preferably 0.1 nm to 50 nm.
A distance of the space portion formed between the pair of the conductive layers 258 and 259 is preferably 100 nm or less, more preferably, 50 nm or less. The space portion can be formed by cleavage by application of a voltage to the conductive layers 258 and 259 or cleavage by using a focused ion beam. Alternatively, the space portion can be formed by performing selective etching by wet etching or dry etching with the use of a resist mask.
Note that a focusing electrode may be formed in the space between the front substrate 210 and the back substrate 220. By providing the focusing electrode, an electron beam emitted from the electron-emission element can be focused, light emission luminance of the cell can be improved, reduction in contrast due to color mixture of adjacent cells can be suppressed, or the like. A negative voltage is preferably applied to the focusing electrode, compared with the metal back 234 (or the anode electrode).
Next, a method for forming an FED panel is described hereinafter
In the periphery of the back substrate 220, glass for sealing is printed by a printing method and then pre-baked. Next, the front substrate 210 and the back substrate 220 are aligned, temporally fixed to each other, and then heated. As a result, the glass for sealing is melted and cooled, whereby the front substrate 210 and the back substrate 220 are attached together so that a panel is made. Next, the inside of the panel is drawn down to vacuum while the panel is being heated. Next, by heating a vent pipe provided for the back substrate 220, an open end of the vent pipe is blocked and the inside of the panel is vacuum locked. Accordingly, the FED panel can be completed.
As an FED, as shown in
Note that in
In particular, when a plastic is used for the light-transmitting substrate 131 and the optical filter 130 is provided on the surface of the front substrate 210 by use of the adhesive 136, reductions in thickness and weight of the FED can be achieved.
Note that here, the structure in which the optical filter 130 is provided with the electromagnetic wave shield layer 133 and the anti-reflection layer 200 is described; however, a near-infrared ray shielding layer may be provided as well as the electromagnetic wave shield layer 133 in a manner similar to Embodiment Mode 2. Furthermore, one functional layer that has an electromagnetic wave shield function and a near-infrared ray shielding function may be formed.
Next, an FED module having the Spindt-type electron-emission element and a driving method thereof are described with reference to
As shown in
Over the second light-transmitting substrate which is part of the back substrate 220, a driver circuit 263 which applies a voltage to a metal back (or an anode electrode) is provided and connected to the metal back (or the anode electrode). Here, the driver circuit 263 which applies a voltage to the metal back (or the anode electrode) is provided over a wiring board 264, and the driver circuit 263 and the metal back (or the anode electrode) are connected through an FPC 265. Further, although not shown, a control circuit which controls the driver circuits 261 to 263 is provided over the first light-transmitting substrate 211 or the second light-transmitting substrate 221.
As shown in
Next, an FED module having the surface-conduction electron-emission element and a driving method thereof are described with reference to
As shown in
Over the second light-transmitting substrate which is part of the back substrate 220, the driver circuit 263 which applies a voltage to the metal back (or the anode electrode) is provided and connected to the metal back (or the anode electrode). Although not shown, a control circuit which controls the driver circuits 261 to 263 is provided over the first light-transmitting substrate or the second light-transmitting substrate.
As shown in
The FED described in this embodiment mode includes the anti-reflection layer on its surface. The anti-reflection layer includes a plurality of pyramidal projections, and incident light from external is reflected not to a viewer side but to another adjacent pyramidal projection because the side of each pyramidal projection is not perpendicular to the direction of incidence of incident light from external. Alternatively, reflected light of incident light from external propagates between the adjacent pyramidal projections. One part of incident light enters an adjacent pyramidal projection, and the other part of the incident light is then incident on an adjacent pyramidal projection as reflected light. In this manner, incident light from external reflected at the surface of the side of a pyramidal projection is repeatedly incident on adjacent pyramidal projections.
In other words, the number of times which is incident on the pyramidal projections of the FED of incidence of incident light from external is increased; therefore, the amount of incident light from external entering the pyramidal projection is increased. Thus, the amount of incident light from external reflected to a viewer side is reduced, and a cause of the reduction in visibility such as reflection can be prevented.
In a display screen, since incident light from external is reflected to a viewer side when there is a planar portion (a surface parallel to the display screen) with respect to incident light from external, a smaller planar region has a high antireflection function. In addition, it is preferable that a surface of a display screen be formed of a plurality of side surfaces of a pyramidal projection which face in different directions with respect to a base for diffusing incident light from external.
The hexagonal pyramidal projection in this embodiment mode can have a close-packed structure without any spaces and has an optimal shape from among such shapes, having the largest number of sides of a pyramidal projection and a high anti-reflection function that can diffuse light in many directions efficiently.
The distance between apexes of the plurality of adjacent pyramidal projections is preferably 350 nm or less, and the height of the plurality of pyramidal projections is preferably 800 nm or higher. In addition, the filling factor of a base of the plurality of pyramidal projections per unit area over the surface of the substrate that is to serve as a display screen is preferably 80% or more, more preferably, 90% or more. Under the above conditions, since the ratio of incident light from external, which is incident on a planar portion is reduced, light can be prevented from being reflected to a viewer side, which is preferable.
The pyramidal projection can be formed not of a material with a uniform refractive index but of a material whose refractive index changes from an apical portion of the pyramidal projection to a portion closer to a substrate that is to serve as a display screen. For example, in each of the plurality of pyramidal projections, a structure is used in which a portion closer to the apical portion of each pyramidal projection can be formed of a material having a refractive index equivalent to that of the air or the protective layer to further reduce reflection of incident light from external which is incident on the surface of each pyramidal projection from the air. Meanwhile, a structure is used in which a portion closer to the substrate that is to serve as the display screen is formed of a material having a refractive index equivalent to that of the substrate so that reflection of light which propagates inside each pyramidal projection and is incident on the substrate is reduced at the interface between each pyramidal projection and the substrate. When a glass substrate is used for the substrate, the refractive index of the air or the protective layer is lower than that of the glass substrate. Therefore, each pyramidal projection may have a structure which is formed in such a manner that a portion closer to an apical portion of each pyramidal projection is formed of a material having a lower refractive index and a portion closer to a base of each pyramidal projection is formed of a material having a higher refractive index, that is, the refractive index increases from the apical portion to the base of each pyramidal projection.
Furthermore, since the protective layer is formed in the space among the pyramidal projections in the present invention, the entry of a contaminant, such as dust, into the space among the pyramidal projections can be prevented. Therefore, a decrease in anti-reflection function due to the entry of dust or the like can be prevented, and the physical strength of the FED can be increased by filling the space among the pyramidal projections. Accordingly, reliability can be improved.
The FED described in this embodiment mode includes a high anti-reflection function that can further reduce reflection of incident light from external by providing the anti-reflection layer having a plurality of adjacent pyramidal projections to its surface and the anti-reflection layer provided with the protective layer in the space among the pyramidal projections. Therefore, an FED having high visibility can be provided. Accordingly, an FED having higher quality and higher performance can be manufactured.
With the PDP and the FED of the present invention, a television device (also simply referred to as a television, or a television receiver) can be completed.
A driver IC 2751 may be mounted on the substrate 2700 by a chip on glass (COG) method as shown in
As another structure of an external circuit in
Among signals received by the tuner 904, an audio signal is transmitted to an audio signal amplifier circuit 909, and an output thereof is supplied to a speaker 913 through an audio signal processing circuit 910. A control circuit 911 receives control information of a receiving station (reception frequency) or sound volume from an input portion 912 and transmits signals to the tuner 904 and the audio signal processing circuit 910.
A television device can be completed by incorporating the display module into a chassis as shown in
A display panel 2002 is incorporated in a chassis 2001, and general TV broadcast can be received by a receiver 2005. When the display device is connected to a communication network by wired or wireless connections via a modem 2004, one-way (from a sender to a receiver) or two-way (between a sender and a receiver or between receivers) information communication can be performed. The television device can be operated by a switch built in the chassis 2001 or a remote control unit 2006. A display portion 2007 for displaying output information may also be provided in the remote control device 2006.
Further, the television device may include a sub screen 2008 formed using a second display panel so as to display channels, volume, or the like, as well as the main screen 2003.
Naturally, the present invention is not limited to the television device, and can be applied to various use applications, as a large-sized display medium such as an information display board at a train station, an airport, or the like, or an advertisement display board on the street, as well as a monitor of a personal computer.
This embodiment mode can be combined with any of Embodiment Modes 1 to 3, as appropriate.
Examples of electronic devices using a PDP and an FED in accordance with the present invention are as follows: a television device (also simply referred to as a television, or a television receiver), a camera such as a digital camera or a digital video camera, a cellular telephone device (also simply referred to as a cellular phone or a cell-phone), a portable information terminal such as a PDA, a portable game machine, a computer monitor, a computer, a sound reproducing device such as a car audio system, an image reproducing device including a recording medium, such as a home-use game machine, and the like. In addition, the present invention can be applied to any game machine having a display device, such as a pachinko machine, a slot machine, a pinball machine, or a large-sized game machine. Specific examples of them are described with reference to
A portable information terminal device shown in
A digital video camera shown in
A cellular phone shown in
A portable television device shown in
A portable computer shown in
A slot machine shown in
As described above, using the display device of the present invention makes it possible to provide a high-performance electronic device which can display a high-quality image superior in visibility.
This embodiment mode can be combined with any of Embodiment Modes 1 to 4.
This application is based on Japanese Patent Application serial No. 2006-328213 filed in Japan Patent Office on Dec. 5, 2006, the entire contents of which are hereby incorporated by reference.
100: anti-reflection layer, 101: pyramidal projection, 102: protective layer, 110: front substrate, 111: light-transmitting substrate, 114: light-transmitting insulating layer, 115: protective layer, 116: plasma, 117: ultraviolet rays, 118: light emission, 120: back substrate, 121: light-transmitting substrate, 122: data electrode, 123: dielectric layer, 124: partition (rib), 125: phosphor layer, 130: optical filter, 131: light-transmitting substrate, 132: near-infrared ray shielding layer, 133: electromagnetic wave shield layer, 134: space, 135: electromagnetic wave absorber, 136: adhesive, 141: glass for sealing, 142: scan electrode driver circuit, 143: sustain electrode driver circuit, 144: data electrode driver circuit, 145: display portion, 146: wiring board, 147: FPC, 150: discharge cell, 200: anti-reflection layer, 201: pyramidal projection, 210: front substrate, 211: light-transmitting substrate, 213: spacer, 220: back substrate, 221: light-transmitting substrate, 222: cathode electrode, 223: interlayer insulating layer, 224: gate electrode, 225: electron source, 226: electron-emission element, 230: electron-emission element, 232: phosphor layer, 233: black matrix, 234: metal back, 235: electron beam, 250: electron-emission element, 252: row direction wiring, 253: interlayer insulating layer, 254: connection wiring, 255: element electrode, 256: element electrode, 257: column direction wiring, 258: conductive layer, 259: conductive layer, 260: electron beam, 261: driver circuit, 262: driver circuit, 263: driver circuit, 264: wiring board, 265: FPC, 266: display portion, 267: light-emission cell, 410: substrate, 414: incident light from external, 415: reflected light ray, 416: protective layer, 450: FED, 451: pyramidal projection, 452: protective layer, 470: substrate, 471: pyramidal projection, 480: substrate, 481: pyramidal projection, 486: film, 490: substrate, 491: pyramidal projection, 492: protective layer, 493: protective layer, 494: protective layer, 495: protective layer, 800: wavelength, 904: tuner, 905: video signal amplifier circuit, 906: video signal processing circuit, 907: control circuit, 908: signal dividing circuit, 909: audio signal amplifier circuit, 910: audio signal processing circuit, 911: control circuit, 912: input portion, 913: speaker, 112a: light-transmitting conductive layer, 112b: light-transmitting conductive layer, 113a: scan electrode, 113b: sustain electrode, 2001: chassis, 2002: display panel, 2003: main screen, 2004: modem, 2005: receiver, 2006: remote control device, 2007: display portion, 2008: sub screen, 2009: speaker portion, 2010: chassis, 2011: display portion, 2012: remote control device, 2013: speaker portion, 2700: substrate, 2701: pixel portion, 2702: pixel, 2703: input terminal, 2750: FPC (flexible printed circuit), 2751: driver IC, 411a: pyramidal projection, 411b: pyramidal projection, 411c: pyramidal projection, 411d: pyramidal projection, 412a: transmitted light ray, 412b: reflected light ray, 412c: reflected light ray, 412d: reflected light ray, 413a: transmitted light ray, 413b: transmitted light ray, 413c: transmitted light ray, 413d: transmitted light ray, 5000: pyramidal projection, 5100: apex, 5200: conical projection, 5230: quadrangular pyramidal projection, 5250: triangular pyramidal projection, 5300: pyramidal projection, 5301: pyramidal projection, 9101: main body, 9102: display portion, 9201: main body, 9202: display portion, 9301: main body, 9302: display portion, 9401: main body, 9402: display portion, 9501: main body, 9502: display portion, 9701: display portion, 9702: display portion, 5001a: pyramidal projection, 5001f: pyramidal projection, 5101a: apex, 5101f: apex, 5201a: conical projection, 5201f: conical projection, 5231a: quadrangular pyramidal projection, 5231h: quadrangular pyramidal projection, 5251a: triangular pyramidal projection, and 51511: triangular pyramidal projection
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