JP3898555B2 - Display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display device, and more particularly to a display device using a large number of electron-emitting devices.
[0002]
[Prior art]
In recent years, an image display device for high-definition broadcasting or a high-resolution image accompanying this has been desired, and the screen display performance is required to be more severe. In order to achieve these demands, it is essential to flatten the screen surface and increase the resolution, and at the same time, it is necessary to reduce the weight and thickness.
[0003]
Therefore, as a next-generation display device that satisfies the above demands, development of a display device in which a large number of electron-emitting devices (hereinafter referred to as emitters) are arranged and opposed to a phosphor screen is being promoted. As the emitter, a field emission type or surface conduction type element is assumed. In general, a display device using a field emission electron emission element as an emitter is a field emission display (hereinafter referred to as FED), and a display device using a surface conduction electron emission element as an emitter is a surface conduction electron emission display. (Hereinafter referred to as SED).
[0004]
For example, an FED generally has a front substrate and a rear substrate that are arranged to face each other with a predetermined gap, and these substrates are connected to each other through a rectangular frame-shaped side wall so that their peripheral portions are bonded to each other. It constitutes an envelope. A phosphor screen is formed on the inner surface of the front substrate, and a number of emitters are provided on the inner surface of the rear substrate as electron emission sources that excite the phosphor to emit light.
[0005]
In addition, a plate-like grid is disposed between the two substrates, and a number of apertures positioned in alignment with the emitter are formed in this grid. Further, in order to support an atmospheric pressure load applied to the rear substrate and the front substrate, a plurality of support members are disposed between these substrates. These grids and at least a part of the support member are bonded to either the back substrate or the front substrate.
[0006]
In the FED configured as described above, the electron beam emitted from each emitter is irradiated to the desired phosphor layer through the corresponding aperture of the grid, thereby causing the phosphor to emit light and displaying an image.
[0007]
In such an FED, the size of the emitter is on the order of micrometers, and the gap between the front substrate and the rear substrate can be set on the order of millimeters. For this reason, it is possible to achieve higher resolution, lighter weight, and thinner thickness as compared with a cathode ray tube (CRT) or the like currently used as a television or computer display.
[0008]
[Problems to be solved by the invention]
In the manufacturing process of the display device configured as described above, the rear substrate to which structures such as a grid and a supporting member are bonded in advance and the front substrate are baked at 300 ° C. or more to perform gas out, and the side wall is formed. When the back substrate and the front substrate are bonded to each other, the back substrate and the front substrate are heated from the outside by the heater. Therefore, in such a manufacturing process, the back substrate and the front substrate to which the structure such as the grid is fixed are at a higher temperature than these structures.
[0009]
Further, as described above, during operation of the display device, a number of emitters provided on the back substrate emit electrons toward the phosphor layer. At this time, the emitter generates heat, so that the temperature of the back substrate is reduced. It rises and tends to be hotter than the grid.
[0010]
As described above, during the manufacturing or operation of the display device, the back substrate and the front substrate have a higher temperature than the structures fixed to these substrates. For example, there is a temperature difference of several tens of degrees between the back substrate and the structure. It may also occur. When the difference in thermal expansion occurs between the back substrate and the structure fixed to the substrate due to such a temperature difference, in particular, the back substrate has a greater thermal expansion than the structure. In the case where the number increases, a tension acts on the structure, and there is a possibility that the connection between the structure and the rear substrate is released.
[0011]
Therefore, in this case, a manufacturing failure of the display device occurs, the manufacturing yield decreases, and the reliability during operation decreases.
[0012]
The present invention has been made in view of the above points, and an object of the present invention is to prevent a peeling and damage of a joint due to a temperature difference, and to reduce manufacturing defects and improve reliability. Is to provide.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a display device according to the present invention includes a vacuum envelope having a first substrate and a second substrate that are opposed to each other with a gap between the first substrate and the second substrate. A plate-like grid disposed in the vacuum envelope so as to face the first substrate and the second substrate, and joined to at least one of the first and second substrates; And a fluorescent screen provided on the inner surface of one of the second substrates, and a plurality of electron-emitting devices provided on the inner surface of the other of the first and second substrates and emitting electrons to the fluorescent screen. The grid has a thermal expansion coefficient of 1.02 to 1.2 times the thermal expansion coefficient of the at least one substrate to which the grid is bonded.
[0015]
According to the display device configured as described above, the structure has a larger coefficient of thermal expansion than the one substrate to which the structure is bonded. Even when the temperature of the substrate becomes higher than that of the structure, the thermal expansion amount of the one substrate does not become larger than the thermal expansion amount of the structure. Therefore, no tensile force is generated in the structure body, and peeling and damage of the joint portion of the structure body to the substrate can be prevented.
[0016]
According to the present invention, it is desirable that the structure has a thermal expansion characteristic in which the elongation rate is higher than that of the one substrate at any temperature.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the display device of the present invention is applied to an SED will be described in detail with reference to the drawings.
As shown in FIGS. 1 and 3, the SED includes an effective display area 3 having an aspect ratio of 4: 3 and a diagonal dimension of 36 inches. The SED includes a rectangular front substrate 10 and a rear substrate 20 which are arranged to face each other with a predetermined gap, and the front substrate 10 and the rear substrate 20 have a peripheral edge via a frame-shaped side wall 8 made of a glass material. The parts are joined together to form a vacuum envelope 4. The side wall 8 is joined to the front substrate 10 and the back substrate 20 by frit glass or a low melting point metal such as indium or an alloy. The internal space of the vacuum envelope 4 is maintained at a high vacuum of about 10 ⁻⁸ Torr, for example.
[0018]
A rectangular plate-like grid 18 connected to a predetermined potential is disposed between the front substrate 10 and the rear substrate 12 to prevent abnormal discharge between the substrates, and faces the effective display region 3. Is located. The front substrate 10 and the rear substrate 12 are supported against atmospheric pressure by a plurality of spacers 30 disposed between these substrates, and are maintained at a distance of 1.5 to 2.0 mm, for example.
[0019]
As shown in FIG. 3, the front substrate 10 functioning as the first substrate includes an insulating substrate 11 made of non-alkali glass and a phosphor screen 12 formed on the inner surface of the insulating substrate. The phosphor screen 12 functioning as an image display surface and a phosphor screen has stripe-shaped phosphor layers each having red (R), blue (B), and green (G) emission characteristics and arranged at a predetermined pitch. 13 and a band-shaped light shielding layer 14 disposed between the phosphor layers 13 for improving the contrast ratio.
[0020]
A conductive thin film 15 made of aluminum or an alloy thereof is formed on the phosphor screen 12, and a vapor deposition getter layer 16 made of barium (Ba) is formed on the conductive thin film 15. The conductive thin film 15 functions as an anode electrode. The vapor deposition getter layer 16 is formed by vapor-depositing a getter material in the vacuum chamber prior to bonding the front substrate 10 and the rear substrate 20 in the vacuum chamber when the SED is manufactured. By performing a series of processes from vapor deposition to sealing of the getter material in a vacuum atmosphere without exposure to the air, a high-performance vapor deposition getter layer 16 can be obtained.
[0021]
As shown in FIGS. 3 and 4, the back substrate 20 functioning as the second substrate includes an insulating substrate 22 made of non-alkali glass. A plurality of scanning electrodes 23 and signal electrodes 24 arranged in a matrix are provided on the inner surface of the insulating substrate 22. In the vicinity of the intersection between each scanning electrode 23 and signal electrode 24, a gate electrode 25 and an emitter electrode 26 extending from the scanning electrode and the signal electrode are provided. The gate electrode 25 and the emitter electrode 26 are opposed to each other with a predetermined interval. Further, although not shown, for example, a graphite film is disposed between these electrodes 25 and 26 with an interval of 5 mm, thereby constituting a surface conduction electron-emitting device 27. A protective film 28 is formed on each scanning electrode 23.
[0022]
The grid 18 disposed between the front substrate 10 and the rear substrate 20 having the above-described configuration is formed in a rectangular shape having a size substantially corresponding to the effective display area 3, and faces the front substrate 10 and the rear substrate 20. Yes. As shown in FIGS. 1 and 3, the four corners of the grid 18 are fixed to the back substrate 20 via pedestals 60, respectively.
[0023]
As shown in FIG. 2 and FIG. 3, each pedestal 60 is formed in a disc shape and is fixed on the insulating substrate 22 of the back substrate 20 via a conductive frit glass 62 and a silver paste 64. . The grid 18 is welded to the upper surface of the pedestal 60 at the corner side edges at two welding points 61, for example. In the insulating substrate 22, a through hole 66 is formed at a position facing one pedestal 60, and this pedestal 60 is electrically connected to a power supply terminal 67 formed on the outer surface of the insulating substrate 22 through the through hole 66. Connected. Therefore, a predetermined grid potential can be supplied to the grid 18 from the power supply terminal 67 through the through hole 66 and the pedestal 60.
[0024]
The grid 18 is made of a material having a larger coefficient of thermal expansion than the insulating substrate 22 of the back substrate 20 to which the grid is fixed. For example, the grid 18 is formed of an iron-nickel alloy having a thickness of 0.1 mm, and the surface thereof is oxidized. The thermal expansion coefficient of the glass constituting the insulating substrate 22 is 84 × 10 ⁻⁷ / K, whereas the thermal expansion coefficient of the grid 18 is 94 × 10 ⁻⁷ / K.
[0025]
FIG. 5 shows a comparison between the thermal expansion characteristic B of the grid 18 and the thermal expansion characteristic A of the glass constituting the insulating substrate 22, and the grid 18 has a higher elongation rate than the insulating substrate 22 at any temperature. It has the following thermal expansion characteristics.
[0026]
As shown in FIGS. 3 and 4, each grid 18 is formed with a rectangular opening 44 for transmitting an electron beam emitted from the electron emission element 27, and faces the electron emission element 27. The grid 18 is formed with a plurality of circular openings 46 for connecting first and second spacers described later.
[0027]
Each spacer 30 functioning as a support member is formed integrally with the grid 18. That is, the grid 18 has a first main surface facing the back substrate 20 and a second main surface facing the front substrate 10. A plurality of first spacers 48 are formed integrally with the grid 18 on the first main surface side, and a plurality of second spacers 50 are formed integrally with the grid 18 on the second main surface side. The first spacer 48 and the second spacer 50 are connected by a connecting portion 52 disposed in the opening 46 of the grid 18. In the present embodiment, two second spacers 50 are connected to one first spacer 48 via a connecting portion 52 to constitute the spacer 30.
[0028]
The first spacer 48 is disposed on the scanning electrode 23 via the protective film 28 and extends along the extending direction of the scanning electrode. Each of the first spacers 48 has an oval cross section and a height h1 of 0.5 mm.
[0029]
Two second spacers 50 provided for each first spacer 48 are formed in a columnar shape having a slight taper, and their heights h2 are each 1.0 mm. As a result, the second spacer 50 has a sufficiently large aspect ratio (ratio of the length in the major axis direction of the cross section at the grid 18 side end of the second spacer to the height of the second spacer) relative to the first spacer 48. Is formed. Two adjacent second spacers 50 are connected to one first spacer 48 via the opening 46 of the grid 18, that is, via the connecting portion 52, and are integrated with the first spacer 48 and the grid 18. It has become.
[0030]
In a state where the grid 18 integrally provided with the spacer 30 having the above-described configuration is disposed in the vacuum envelope 4, each first spacer 48 contacts the back substrate 10 through the protective film 28 and the scanning electrode 23, and The second spacer 50 is in contact with the front substrate 10 via the vapor deposition getter layer 16, the conductive thin film layer 15, and the phosphor screen 12. Thereby, the spacer 30 supports the front substrate 10 and the rear substrate 20 with respect to atmospheric pressure.
[0031]
According to the SED configured as described above, in the manufacturing process, after the structures such as the grid 18 and the spacer 30 are fixed and bonded to the back substrate 20 in advance, the back substrate 20 and the front substrate 10 are heated at 300 ° C. or higher. Bake out gas. In addition, after baking, when the back substrate 20 and the front substrate 10 are joined via the side wall 8 to form the vacuum envelope 4, the back substrate 20 and the front substrate 10 are heated from the outside by a heater. Therefore, in such a manufacturing process, the back substrate 20 and the front substrate 10 to which the structures such as the grid 18 are fixed are at a higher temperature than these structures.
[0032]
Further, during the operation of the SED, a large number of electron-emitting devices 27 provided on the back substrate 20 emit electrons toward the phosphor layer, but generate heat at that time. Therefore, the temperature of the back substrate 20 rises and becomes higher than the structures such as the grid 18 and the spacer 30.
[0033]
As described above, when the SED is manufactured or operated, the back substrate 20 is heated to a temperature higher than the structure fixed to the back substrate, for example, the grid 18, and a temperature difference of several tens of degrees may be generated between them. It is done. However, according to the SED according to the present embodiment, the grid 18 has a larger coefficient of thermal expansion than the insulating substrate 22 of the back substrate 20 to which the grid is bonded. Therefore, even when the temperature of the insulating substrate 22 becomes higher than that of the grid 18 during manufacturing or operation, the thermal expansion amount of the insulating substrate 22 does not become larger than the thermal expansion amount of the grid. Accordingly, no tensile force is generated in the grid 18, and peeling of the joint portion of the grid 18 to the insulating substrate 22, that is, the welded portion between the grid 18 and the pedestal 60, or the joint portion between the pedestal 60 and the insulating substrate 22. And damage can be reliably prevented. As a result, it is possible to prevent the occurrence of manufacturing defects and improve the manufacturing yield, and to obtain an SED with improved reliability.
[0034]
In the above-described embodiment, the description has been made centering on the grid 18 among the structures disposed between the front substrate 10 and the rear substrate 20 and bonded to at least one of these substrates. The structure is a concept including not only the grid 18 but also wirings and spacers such as scanning electrodes and signal electrodes.
[0035]
That is, in the above-described embodiment, the scanning electrode 23 and the signal electrode 24 are formed on the insulating substrate 22 of the back substrate 20, that is, bonded to the insulating substrate 22. Therefore, similarly to the grid 18 described above, the scan electrodes 23 and the signal electrodes 24 are formed of a material having a thermal expansion coefficient larger than that of the insulating substrate 22 and are insulated at any temperature. By providing a thermal expansion characteristic in which the elongation rate is higher than that of the substrate 22, there is no tensile force acting on the scan electrode and the signal electrode during manufacturing and operation, and the scan electrode and the signal electrode are peeled off and disconnected. Can be prevented.
[0036]
Similarly, the spacer is also formed of a material having a thermal expansion coefficient larger than that of the front substrate 10 or the rear substrate 20 and has the same thermal expansion characteristics as described above, whereby the spacer and the rear substrate are formed. Can be prevented from peeling off or damaging the joint between the spacer and the front substrate. In particular, for example, when a long spacer extending between two opposing sides of the vacuum envelope is used as the spacer, a remarkable effect can be obtained.
[0037]
Here, a preferable range of the difference in thermal expansion coefficient will be described. Now, let Tf be the temperature at which no tensile force is generated at the joint when the temperature of the structure and the substrate are equal. If the structure is fixed without applying a pulling force, Tf becomes the temperature at the time of fixing. Assuming that the thermal expansion coefficient and temperature of the structure are αs and Ts, respectively, and the thermal expansion coefficient and temperature of the substrate to which the structure is attached are αp and Tp, respectively, the conditions under which a tensile force is generated at the joint of the structure are as follows:
αs (Ts−Tf) ≦ αp (Tp−Tf)
Than,
αs / αp ≦ (Tp−Tf) / (Ts−Tf)
It becomes. If the left and right sides of this equation are k and Q, respectively,
k ≦ Q
It becomes.
[0038]
The number of Qs varies depending on manufacturing conditions and operating conditions. In practice, the temperature of the structure and the substrate is not uniform and has a distribution inside. Furthermore, whether or not the joint part is detached also relates to the fixing strength of the joint part.
[0039]
On the other hand, if k is too large, no tensile force will be generated, but there will be a problem such as deflection of the structure due to a difference in thermal expansion. Therefore, the allowable amount of k cannot be simply determined, but is determined by examining the display device designed in consideration of practicality in a manufacturing device that assumes mass production.
[0040]
After such an examination, about the grid,
1.07 ≦ k ≦ 1.15
The result that it was desirable to be obtained. When k is smaller than 1.05, it has been difficult to avoid the problem that the joint is disconnected due to a temperature difference that occurs at the manufacturing stage. Further, when k is larger than 1.15, it is difficult to avoid problems of the deflection and position accuracy of the grid when the temperature of the grid and the back substrate becomes high.
[0041]
Furthermore, when the range of k that can be tolerated is estimated with respect to the structure in general, apart from the inherent conditions of the above examination,
1.02 ≦ k ≦ 1.2
The result was obtained.
[0042]
The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. For example, the present invention is not limited to the SED, but can also be applied to an FED using a field emission type electron-emitting device and other flat display devices. Further, the grid is not limited to the rear substrate, and may be bonded to the front substrate. Furthermore, the dimensions, materials, and the like of each component are not limited to the numerical values and materials shown in the above-described embodiments, and can be variously selected as necessary.
[0043]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a display device that can prevent peeling and damage of a joint due to a temperature difference, reduce manufacturing defects, and improve reliability. .
[Brief description of the drawings]
FIG. 1 is a perspective view showing an SED according to an embodiment of the present invention.
FIG. 2 is an enlarged plan view showing a joint portion between a grid and a back substrate in the FED.
3 is a cross-sectional view taken along line AA in FIG.
FIG. 4 is an enlarged perspective view showing a main part of the SED.
FIG. 5 is a diagram showing a comparison of thermal expansion characteristics between a grid and a back substrate in the SED.
[Explanation of symbols]
4 ... Vacuum envelope 8 ... Side wall 10 ... Front substrate 12 ... Phosphor screen 18 ... Grid 20 ... Back substrate 23 ... Scan electrode 24 ... Signal electrode 27 ... Surface conduction electron-emitting device 30 ... Spacer 46 ... Opening 48 ... 1st spacer 50 ... 2nd spacer

Claims (6)

A vacuum envelope having a first substrate and a second substrate disposed opposite each other with a gap between them;
The first substrate and the second substrate are disposed in the vacuum envelope so as to face the first substrate and the second substrate, and are bonded to at least one of the first and second substrates. Plate-like grid ,
A fluorescent screen provided on the inner surface of one of the first and second substrates;
A plurality of electron-emitting devices provided on the other substrate inner surface of the first and second substrates and emitting electrons to the phosphor screen;
The grid, the thermal expansion coefficient of this grid are joined above at least one of the substrates with respect to the display device, characterized in that it has a 1.02 to 1.2 times the thermal expansion coefficient of the. 2. The display device according to claim 1, wherein the grid has a coefficient of thermal expansion of 1.07 to 1.15 times that of the one substrate. The grid, at any temperature, the display device according to claim 1 or 2, characterized in that it has a thermal expansion characteristic that elongation from the at least one substrate is increased. 2. The display device according to claim 1, wherein the grid includes a plurality of bonding portions bonded to a second substrate on which the plurality of electron-emitting devices are provided.   5. The plurality of electron-emitting devices are provided on the second substrate, and the grid includes a plurality of joint portions joined to the second substrate via pedestals, respectively. Display device. A power supply terminal provided on an outer surface of the second substrate; the grid is electrically conductive and electrically connected to the power supply terminal via at least one pedestal and a through hole formed in the second substrate. The display device according to claim 5 , wherein the display devices are connected to each other.

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