JP2004022189A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device preventing the generation of creep in a sealing part, and having high airtightness and high reliability. <P>SOLUTION: This image display device is equipped with an envelope 10 having a rear substrate 12 and a front substrate 11 facing the rear substrate. The front substrate and the rear substrate are sealed at their peripheries through a sealing layer 33, and the sealing layer is formed by mixing a first metal material which is main component and at least one second material having different hardness from the first metal material. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image display device provided with an envelope having a pair of substrates arranged opposite to each other.
[0002]
[Prior art]
2. Description of the Related Art In recent years, various image display devices have been developed as next-generation lightweight and thin display devices that replace cathode ray tubes (hereinafter, referred to as CRTs). Such an image display device includes a liquid crystal display (hereinafter, referred to as an LCD) that controls the intensity of light using the orientation of a liquid crystal, and a plasma display panel (hereinafter, referred to as a PDP) that emits a phosphor by ultraviolet rays of plasma discharge. ), A field emission display (hereinafter, referred to as FED) in which a phosphor is emitted by an electron beam emitted from a field emission type electron-emitting device, and surface conduction in which a phosphor is emitted by an electron beam of a surface conduction electron-emitting device. There is an electron emission display (hereinafter, referred to as SED).
[0003]
For example, FEDs and SEDs generally have a front substrate and a rear substrate which are opposed to each other with a predetermined gap therebetween. Of the envelope. A phosphor screen is formed on the inner surface of the front substrate, and a number of electron-emitting devices (hereinafter, referred to as emitters) are provided on the inner surface of the rear substrate as electron emission sources for exciting the phosphor to emit light.
[0004]
Further, in order to support the atmospheric pressure load applied to the rear substrate and the front substrate, a plurality of support members are disposed between these substrates. The potential on the back substrate side is almost the ground potential, and the anode voltage Va is applied to the phosphor screen. Then, an image is displayed by irradiating the red, green, and blue phosphors constituting the phosphor screen with an electron beam emitted from the emitter to cause the phosphors to emit light.
[0005]
In such FEDs and SEDs, the thickness of the display device can be reduced to about several millimeters, and the weight and thickness have been reduced compared to CRTs currently used as displays for televisions and computers. can do.
[0006]
[Problems to be solved by the invention]
In the FED and SED as described above, it is necessary to make the inside of the envelope high vacuum. Also, in the case of a PDP, it is necessary to fill the discharge gas after the inside of the envelope is once evacuated.
[0007]
As a method of evacuating the envelope, first, the front substrate, the rear substrate, and the side walls, which are components of the envelope, are joined by heating in an atmosphere with a suitable sealing material, and then the front substrate or After exhausting the inside of the envelope through an exhaust pipe provided on the rear substrate, there is a method of vacuum-sealing the exhaust pipe. However, in the case of a flat type envelope, the exhaust speed through the exhaust pipe is extremely low, and the achievable vacuum degree is also poor, so that there are problems in mass productivity and characteristics.
[0008]
As a method for solving this problem, for example, Japanese Patent Application Laid-Open No. 2000-229825 discloses a method in which the final assembly of a front substrate and a rear substrate constituting an envelope is performed in a vacuum chamber.
[0009]
In this method, first, the front substrate and the rear substrate brought into the vacuum chamber are sufficiently heated. This is to reduce the gas emission from the inner wall of the envelope, which is a main cause of deteriorating the degree of vacuum of the envelope. Next, when the front substrate and the rear substrate have cooled and the degree of vacuum in the vacuum chamber has been sufficiently improved, a getter film for improving and maintaining the degree of vacuum in the envelope is formed on the phosphor screen. Thereafter, the front substrate and the rear substrate are heated again to a temperature at which the sealing material dissolves, and the front substrate and the rear substrate are combined with each other at a predetermined position and cooled until the sealing material is solidified.
[0010]
The vacuum envelope produced by such a method serves both as a sealing step and a vacuum sealing step, does not require much time for evacuation, and can obtain an extremely good degree of vacuum. As the sealing material, it is desirable to use a low melting point metal material suitable for sealing and sealing batch processing.
[0011]
On the other hand, in a flat-type image display device, if the positional relationship between the front substrate and the rear substrate is not kept constant after sealing, a color shift occurs in the image area. As a cause of such a displacement, creep of the sealing portion can be considered. In order to obtain a high yield in mass production of a large-sized image display device, it is necessary to prevent creep from occurring.
[0012]
The present invention has been made in view of the above points, and an object of the present invention is to provide an image display device which prevents the occurrence of creep in a sealing portion and has improved airtightness and reliability.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, an image display device according to an aspect of the present invention includes a back substrate, and an envelope having a front substrate opposed to the back substrate, wherein the front substrate and the back substrate are sealed. The peripheral portion is sealed via the adhesion layer, and the sealing layer is formed by mixing a first metal material as a main component and at least one second material having higher creep resistance than the first metal material. Have been.
[0014]
According to the image display device configured as described above, by including a material having higher creep resistance than the main component in the sealing layer, it is possible to suppress creep or plastic deformation of the sealing layer, and to achieve airtightness. Thus, it is possible to realize a high-quality image display device with improved performance and reliability and no color shift.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment in which an image display device of the present invention is applied to an FED will be described in detail with reference to the drawings.
As shown in FIGS. 1 to 3, this FED includes a front substrate 11 and a rear substrate 12 each made of rectangular glass as an insulating substrate, and these substrates have a gap of about 1.5 to 3.0 mm. They are placed facing each other. The front substrate 11 and the rear substrate 12 are joined to each other via a rectangular frame-shaped side wall 18 to form a flat rectangular vacuum envelope 10 whose inside is maintained in a vacuum state. .
[0016]
A plurality of plate-shaped support members 14 are provided inside the vacuum envelope 10 to support the atmospheric pressure load applied to the rear substrate 12 and the front substrate 11. These support members 14 extend in a direction parallel to the short side of the vacuum envelope 10 and are arranged at predetermined intervals along a direction parallel to the long side. Note that the shape of the support member 14 is not particularly limited to this, and a columnar support member may be used.
[0017]
As shown in FIG. 4, a phosphor screen 16 is formed on the inner surface of the front substrate 11. The phosphor screen 16 has striped phosphor layers R, G, and B that emit light of three colors, red, blue, and green, and a striped black light absorption as a non-light-emitting portion located between these phosphor layers. The layers 20 are arranged side by side. The phosphor layers R, G, and B extend in a direction parallel to the short side of the vacuum envelope 10 and are arranged at predetermined intervals along a direction parallel to the long side. An aluminum layer (not shown) is deposited on the phosphor screen 16 as a metal back.
[0018]
As shown in FIG. 3, on the inner surface of the rear substrate 12, a large number of field emission electron-emitting devices 22 each emitting an electron beam are provided as electron emission sources for exciting the phosphor layers R, G, and B. Have been. These electron-emitting devices 22 are arranged in a plurality of columns and a plurality of rows corresponding to each pixel.
[0019]
More specifically, a conductive cathode layer 24 is formed on the inner surface of the back substrate 12, and a silicon dioxide film 26 having a number of cavities 25 is formed on the conductive cathode layer. On the silicon dioxide film 26, a gate electrode 28 made of molybdenum, niobium or the like is formed. A cone-shaped electron-emitting device 22 made of molybdenum or the like is provided in each cavity 25 on the inner surface of the back substrate 12. In addition, on the back substrate 12, a matrix-like wiring (not shown) connected to the electron-emitting device 22 is formed.
[0020]
In the FED configured as described above, a video signal is input to the electron-emitting device 22 and the gate electrode 28. When the electron emission element 22 is used as a reference, a gate voltage of +100 V is applied when the luminance is the highest. Further, +10 kV is applied to the phosphor screen 16. The size of the electron beam emitted from the electron-emitting device 22 is modulated by the voltage of the gate electrode 28, and the electron beam excites the phosphor layer of the phosphor screen 16 to emit light, thereby displaying an image. .
[0021]
Since a high voltage is applied to the phosphor screen 16 in this manner, a high strain point glass is used for the front glass 11, the rear substrate 12, the side wall 18, and the plate glass for the support member 14. As will be described later, the space between the rear substrate 12 and the side wall 18 is sealed with a low-melting glass 30 such as frit glass, and the space between the front substrate 11 and the side wall 18 is formed on a sealing surface. An underlayer 31 and an indium layer 32 formed on the underlayer 31 are sealed by a sealing layer 33 which is fused.
[0022]
Next, a method of manufacturing the FED configured as described above will be described in detail.
First, the phosphor screen 16 is formed on a plate glass to be the front substrate 11. In this method, a glass sheet having the same size as the front substrate 11 is prepared, and a stripe pattern of the phosphor layer is formed on the glass sheet by a plotter machine. The plate glass on which the phosphor stripe pattern is formed and the plate glass for the front substrate are placed on a positioning jig, set on an exposure table, exposed and developed, and a phosphor screen 16 is generated.
[0023]
Subsequently, the electron-emitting devices 22 are formed on the glass plate for the rear substrate. In this case, a matrix-shaped conductive cathode layer is formed on a sheet glass, and an insulating film of a silicon dioxide film is formed on the conductive cathode layer by, for example, a thermal oxidation method, a CVD method, or a sputtering method.
[0024]
Thereafter, a metal film for forming a gate electrode such as molybdenum or niobium is formed on the insulating film by, for example, a sputtering method or an electron beam evaporation method. Next, a resist pattern having a shape corresponding to the gate electrode to be formed is formed on the metal film by lithography. Using the resist pattern as a mask, the metal film is etched by a wet etching method or a dry etching method to form a gate electrode 28.
[0025]
Next, the insulating film is etched by wet etching or dry etching using the resist pattern and the gate electrode as a mask to form the cavity 25. After removing the resist pattern, a release layer made of, for example, aluminum or nickel is formed on the gate electrode 28 by performing electron beam evaporation from a direction inclined at a predetermined angle with respect to the rear substrate surface. Thereafter, for example, molybdenum as a material for forming a cathode is vapor-deposited from a direction perpendicular to the surface of the rear substrate by an electron beam vapor deposition method. Thus, the electron-emitting device 22 is formed inside each cavity 25. Subsequently, the release layer together with the metal film formed thereon is removed by a lift-off method.
[0026]
Next, the space between the peripheral edge of the rear substrate 12 on which the electron-emitting devices 22 are formed and the rectangular frame-shaped side wall 18 is sealed to each other with low-melting glass 30 in the atmosphere. After that, the rear substrate 12 and the front substrate 11 are sealed to each other via the side wall 18. In this case, as shown in FIG. 5, first, the underlayer 31 is formed to have a predetermined width over the entire circumference on the upper surface of the side wall 18 serving as the sealing surface and on the inner peripheral edge of the front substrate 11. Subsequently, indium as a metal sealing material is applied on each underlayer 31 to form an indium layer 32 extending over the entire circumference of each underlayer.
[0027]
In addition, as a metal sealing material, it is desirable to use a low melting point metal material having a melting point of about 350 ° C. or less and excellent adhesion and bonding properties. Indium (In) used in this embodiment has not only a low melting point of 156.7 ° C. but also excellent characteristics such as a low vapor pressure, a soft and strong impact, and a low brittleness even at a low temperature. Moreover, it can be directly bonded to glass depending on conditions.
[0028]
The base layer 31 is made of a material having good wettability and airtightness with respect to the metal sealing material, that is, a material having high affinity with the metal sealing material. As the base layer 31, a metal paste such as Ni, Co, Au, Cu, or Al can be used in addition to the silver paste.
[0029]
Next, the side wall 18 is sealed to the front substrate 11 having the base layer 31 and the indium layer 32 formed on the sealing surface, and the base layer 31 and the indium layer 32 are formed on the upper surface of the side wall. As shown in FIG. 6, the back side assembly is held by a jig or the like in a state where the sealing surfaces face each other and at a predetermined distance, and is put into a vacuum processing apparatus. .
[0030]
As shown in FIG. 7, the vacuum processing apparatus 100 includes a load chamber 101, a baking chamber, an electron beam cleaning chamber 102, a cooling chamber 103, a getter film deposition chamber 104, an assembling chamber 105, and a cooling chamber 106 provided in this order. , And an unloading chamber 107. Each of these chambers is configured as a processing chamber capable of performing vacuum processing, and all the chambers are evacuated during the manufacture of the FED. Adjacent processing chambers are connected by a gate valve or the like.
[0031]
The rear-side assembly and the front substrate 11 facing each other at a predetermined interval are put into the load chamber 101, and after the inside of the load chamber 101 is evacuated to a vacuum atmosphere, they are sent to the baking and electron beam cleaning chamber 102. In the baking and electron beam cleaning chamber 102, when a high degree of vacuum of about 10 ⁻⁵ Pa is reached, the back assembly and the front substrate 11 are heated to a temperature of about 300 ° C. and baked, and the surface of each member is baked. Sufficiently release the adsorbed gas.
[0032]
At this temperature, the indium layer (melting point: about 156 ° C.) 32 melts. However, since the indium layer 32 is formed on the base layer 31 having a high affinity, the indium is held on the base layer 31 without flowing, and the indium is kept on the electron emission element 22 side, the outside of the back substrate 12, or the phosphor. Outflow to the screen 16 side is prevented.
[0033]
In the baking / electron beam cleaning chamber 102, simultaneously with the heating, the electron emission device (not shown) attached to the baking / electron beam cleaning chamber 102 emits electrons from the phosphor screen surface of the front substrate 11 and the back surface substrate 12. The element surface is irradiated with an electron beam. Since this electron beam is deflected and scanned by a deflecting device mounted outside the electron beam generator, it is possible to clean the entire surface of the phosphor screen surface and the electron emission element surface with the electron beam.
[0034]
After the heating and the electron beam cleaning, the rear substrate side assembly and the front substrate 11 are sent to the cooling chamber 103 and cooled to a temperature of, for example, about 100 ° C. Subsequently, the back-side assembly and the front substrate 11 are sent to a deposition chamber 104 for forming a getter film, where a Ba film is deposited as a getter film outside the phosphor screen. The surface of the Ba film is prevented from being contaminated with oxygen, carbon, or the like, and can maintain an active state.
[0035]
Next, the rear-side assembly and the front substrate 11 are sent to the assembly chamber 105, where they are heated to 200 ° C., and the indium layer 32 is again melted or softened into a liquid state. In this state, after the front substrate 11 and the side wall 18 are joined and pressurized at a predetermined pressure, indium is cooled and solidified. Thus, the front substrate 11 and the side wall 18 are sealed by the sealing layer 33 in which the indium layer 32 and the base layer 31 are fused, and the vacuum envelope 10 is formed.
[0036]
The vacuum envelope 10 thus formed is cooled to room temperature in the cooling chamber 106 and then taken out of the unloading chamber 107. Through the above steps, the FED is completed.
[0037]
According to the FED configured as described above and the method of manufacturing the same, by sealing the front substrate 11 and the rear substrate 12 in a vacuum atmosphere, the surface adsorbed gas on the substrate can be reduced by using both baking and electron beam cleaning. The gas can be sufficiently released, and the getter film is not oxidized, so that a sufficient gas adsorption effect can be obtained. Thereby, an FED that can maintain a high degree of vacuum can be obtained.
[0038]
Further, by using indium as a sealing material, it is possible to obtain an FED panel having high airtightness and sealing strength without foaming in a vacuum as in the case of sealing with frit glass. At the same time, by providing the underlayer 31 below the indium layer 32, even when indium is melted in the sealing step, inflow of indium can be prevented and the indium can be held at a predetermined position. By manufacturing the FED in this manner, a highly airtight vacuum envelope 10 can be obtained.
[0039]
On the other hand, in the FED configured as described above, as shown in the TEM image shown in FIG. 8, the sealing layer 33 has elliptical portions 50 having a size of several μ order scattered therein substantially uniformly. Structure. The particle size of the elliptical portion 50 is about 0.1 to 10 μm. 9 to 11 show EDX analysis data at analysis points b1, b3, and b4 of the TEM image shown in FIG. 8, respectively. From these figures, it can be seen that the composition of the elliptical portion 50 (analysis points b3, b4) is an InAg alloy composed of about 70% indium and about 30% silver. Also, it can be seen that the composition of the analysis point b1 is about 99.7% indium and about 0.3% silver. The silver in the sealing layer 33 is supplied by being diffused into indium from the silver paste of the base layer during vacuum heating.
[0040]
The hardness of the InAg alloy increases as the Ag content increases. Therefore, the elliptical portion 50 made of an InAg alloy containing about 30% of silver has a higher hardness than other regions of the sealing layer 33. Therefore, even when some stress acts on the sealing layer 33, it is possible to prevent the occurrence of creep between the front substrate 11 and the rear substrate 12. At the same time, the viscosity when the material of the sealing layer 33 is melted is higher than the viscosity when only indium is melted at the same temperature, so that the flow of the melted sealing material can be more reliably prevented.
[0041]
As described above, the sealing layer 33 is obtained by dispersing the second material having a higher hardness and melting point than the first metal material, that is, InAg, in the first metal material, that is, indium, which is a main component of the sealing layer. It has a structure. Here, the main component indicates a component whose weight% in the sealing material is 50% or more.
[0042]
As the second material, a material having a different composition from the first metal material or a material having the same composition but a different component ratio is used. The second material is a precipitated phase containing a metal having a higher melting point than the first metal material. As such a second material, a material containing any metal or glass powder of Sn, Bi, Ag, Cu, Fe, Ni, Cr, or Co can be used. Aluminum, zirconia oxide, titania oxide, or the like can be used.
[0043]
InAg as the second material in the above-described embodiment contains the main metal In forming the first metal material, and the content ratio of this metal is lower than that of the first metal material. InAg contains 15% or more of Ag. As described above, the sealing material forming the sealing layer 33 of the vacuum envelope 10 contains a high-hardness material to prevent the occurrence of creep, and is airtight even in a large size of 50 inches or more. It is possible to realize an FED with improved image quality and reliability and high image quality without color misregistration.
[0044]
The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention. For example, in the above-described embodiment, the second material containing silver is deposited on the sealing layer by providing the base layer made of silver paste, but a sealing material in which indium contains silver in advance is used. It is good also as composition which seals. Further, the underlayer may be provided on one of the front substrate and the side wall. Further, the second material has a configuration in which the first metal material has an elliptical shape in the first metal material. However, the configuration is not limited to this, and the second material may have a circular or needle shape.
[0045]
In addition, in the above-described embodiment, a field emission type electron emitting device is used as the electron emitting device, but the present invention is not limited to this, and other electron emitting devices such as a pn type cold cathode device or a surface conduction type electron emitting device may be used. An element may be used. The present invention is also applicable to other image display devices such as a plasma display panel (PDP) and electroluminescence (EL).
[0046]
【The invention's effect】
As described in detail above, according to the present invention, it is possible to obtain a high-quality image display device that suppresses the occurrence of creep, improves airtightness and reliability, and has no color shift.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an FED according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a state where a front substrate of the FED is removed.
FIG. 3 is a sectional view taken along the line AA in FIG. 1;
FIG. 4 is a plan view showing a phosphor screen of the FED.
FIG. 5 is a perspective view showing a state in which a base layer and an indium layer are formed on a sealing surface of a side wall and a sealing surface of a front substrate constituting the vacuum envelope of the FED.
FIG. 6 is a cross-sectional view showing a state in which a rear-side assembly in which a base layer and an indium layer are formed in the sealing portion and a front substrate are opposed to each other.
FIG. 7 is a view schematically showing a vacuum processing apparatus used for manufacturing the FED.
FIG. 8 is a TEM observation image of the sealing layer of the FED by an ion milling method.
FIG. 9 is a view showing EDX analysis data at an analysis point b1 of the sealing layer in FIG. 8;
FIG. 10 is a view showing EDX analysis data of an analysis point b3 near the sealing layer boundary.
FIG. 11 is a diagram showing EDX analysis data at an analysis point b4 near the sealing layer boundary.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Vacuum envelope 11 ... Front substrate 12 ... Back substrate 14 ... Support member 16 ... Phosphor screen 18 ... Side wall 22 ... Electron emission element 30 ... Low melting glass 31 ... Underlayer 32 ... Indium layer 33 ... Sealing layer 50 ... elliptical shaped part 100 ... vacuum processing device

Claims (13)

A back substrate, and comprising an envelope having a front substrate disposed opposite to the back substrate,
The front substrate and the rear substrate are sealed at a peripheral portion via a sealing layer, and the sealing layer includes a first metal material as a main component, and at least one of the first metal material and the at least one having higher creep resistance than the first metal material. An image display device characterized by being formed by mixing a second material. The image display device according to claim 1, wherein the first metal material has a different composition from the second material or a different component ratio with the same composition. The image display device according to claim 1, wherein the first metal material is made of substantially one kind of metal. The image display device according to claim 1, wherein the first metal material contains In as a main component. The image display device according to claim 1, wherein the second material is a precipitated phase containing a metal having a higher melting point than the first metal material. The image display device according to claim 1, wherein the second material includes at least one of Sn, Bi, Ag, Cu, Fe, Ni, Cr, and Co. 2. The method according to claim 1, wherein the second material includes one of an SiO ₂ based inorganic material, aluminum oxide, zirconia oxide, and titanium oxide, and has a higher melting point than the first metal material. 3. The image display device as described in the above. The image display device according to claim 1, wherein the viscosity when the sealing layer is melted is higher than the viscosity when only the first metal material is melted at the same temperature. 2. The image display device according to claim 1, wherein the second material includes a main metal that forms the first metal material, and a content ratio of the metal is lower than the first metal material. 3. The image display device according to claim 1, wherein the second material contains 15% or more of Ag. The image display device according to claim 1, wherein the second material has a circular or elliptical shape in the first metal material. The image display device according to claim 1, wherein the second material has a needle shape in the first metal material. 13. The image display device according to claim 12, wherein the particle diameter of the second material is 0.1 to 10 [mu] m.

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