Patent Grant
8821677
1. Field of the Invention
The present invention relates to a manufacturing method of a hermetic container and, more particularly, to a manufacturing method of a hermetic container for an image display apparatus having electron-emitting devices in each of which an inside is held in a vacuum state and a phosphor film.
2. Description of the Related Art
Image display apparatuses of a flat panel type such as organic LED display (OLED), field emission display (FED), plasma display panel (PDP), and the like are well known. Each of those image display apparatuses is manufactured by forming an internal space by sealing glass substrates which face each other and has a container in which the internal space is partitioned to an external space. To manufacture such a hermetic container, a spacing distance defining member, a local adhesive, and the like are arranged between the facing glass substrates as necessary, a sealing material is arranged in a frame shape to peripheral portions of the glass substrates, and a heat sealing process is executed. As a heating method of the sealing material, a method whereby the whole glass substrates are baked by a furnace and a method whereby the sealing material is selectively heated and molten by local heating have been known. The local heating is more advantageous than the whole heating from viewpoints of a time which is required to heat and cool, an energy which is required to heat, productivity, a prevention of thermal deformation of the hermetic container, a prevention of thermal deterioration of a function device arranged in the hermetic container, and the like. Particularly, a unit using a laser beam has been known as a unit for performing the local heating (local heating unit). Such a manufacturing method of the hermetic container can be also applied as a manufacturing method of a hermetic container (vacuum insulated grazing glass) which does not have a function device therein.
A seal-sealing method of a container which is used for an FED, a fluorescent electron tube (VFD), and the like has been disclosed in Japanese Patent Application Laid-Open No. H08-022767. First, a first glass substrate and a second glass substrate are position-matched through a sealing material (seal glass). Subsequently, the circumferential sealing material (seal glass) is locally heated by the local heating unit and the first glass substrate and the second glass substrate are temporarily fixed in at least two positions. After that, by heating them in a seal-sealing furnace, the first glass substrate and the second glass substrate are seal-sealed.
A manufacturing method of a container of an FED has been disclosed in U.S. Pat. No. 6,109,994. First, a frame member and a sealing material (frit) are arranged in circumferential edge portions of the first glass substrate and the second glass substrate arranged so as to face each other. The sealing material has venting slots for exhaustion. Subsequently, a laser beam is intermittently irradiated along the extending direction of the sealing material, the sealing material is discretely heated, and discrete portions are sealed. Subsequently, the laser beam is continuously irradiated to the whole circumference of the sealing material including partially sealed regions, and while embedding the venting slots between both of the glass substrates by thermally expanding the sealing material, the internal space is airtightly sealed.
A manufacturing method of a hermetic container has been disclosed in Japanese Patent Application Laid-Open No. 2009-070687. A sealing material is arranged in a gap portion between a first glass substrate and a second glass substrate and the sealing material is partially heated by a heating apparatus along the extending direction of the sealing material and is also pressurized. A pressurizing force of the sealing material is changed based on a height of sealing material at a heating position.
According to the methods in the related arts, there is a case where adherence between the sealing material and the glass substrate when the laser beam is irradiated is difficult to be assured due to an influence of the rough surfaces of the sealing material and the glass substrates or an influence of the rough surfaces which are caused by structures such as wirings and the like provided for the glass substrates. When the adherence deteriorates, there is a case where airtightness of the hermetic container deteriorates and the reliability is deteriorated.
It is an object of the present invention to provide a manufacturing method of a hermetic container whereby adherence between a sealing material and glass substrates is assured and airtightness is improved.
A manufacturing method of a hermetic container according to the present invention has an assembling step and a sealing step. In the assembling step, a first glass substrate and a second glass substrate are aligned through a circumferential sealing material having plural straight line portions and plural coupling portions which connect the plural straight line portions so as to define an internal space between the first glass substrate and the second glass substrate. In the sealing step which is executed after the assembling step, the internal space is maintained to a negative pressure to an outside, such local force as to compress the coupling portions of the circumferential sealing material in a thickness direction of the sealing material is applied, and the sealing material is heated and molten by irradiating local heating light to the sealing material, thereby sealing the first glass substrate and the second glass substrate.
Further, a manufacturing method of a hermetic container according to the present invention has an assembling step, a step of setting an internal space to a negative pressure, and a sealing step. In the assembling step, while a circumferential sealing material constituted by plural straight line portions and plural coupling portions is sandwiched between a frame member and a first glass substrate, the first glass substrate and a second glass substrate are arranged so as to face each other through the frame member, and an internal space is defined between the first glass substrate and the second glass substrate. In the sealing step which is executed after the assembling step, the internal space is maintained to a negative pressure to an external space. In the sealing step, local force is applied in a thickness direction of the sealing material so as to decrease a distance increased between the sealing material and the first glass substrate by the step of maintaining the internal space to the negative pressure to the external space, and the sealing material is molten by moving a local heating unit along the sealing material, thereby sealing the first glass substrate and the second glass substrate.
Furthermore, according to a hermetic container of the present invention, an internal space is defined by glass substrates which face each other and a circumferential sealing material which is sandwiched between the glass substrate pair, fixes the glass substrate pair, and is constituted by plural straight line portions and plural coupling portions, the internal space is set to a negative pressure than that of an external space, and the container has a second sealing material which exists in the external space, is surrounded by the intersecting straight line portions of the sealing material, and fixes the glass substrate pair in a region including an extension line of a diagonal line connecting the two coupling portions having a diagonal positional relation.
According to the present invention, adherence between the sealing material and the glass substrates is assured, and airtightness of the hermetic container can be improved.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
An embodiment of the present invention will be described hereinbelow with reference to the drawings. Although a container which is used as a hermetic container in image display apparatuses such as FED, OLED, PDP and the like will be described hereinbelow, the hermetic container of the present invention is not limited to them but can be applied to all containers which are airtightly sealed. There is a vacuum insulated grazing glass container as an example of such a hermetic container.
In particular, a manufacturing method of the hermetic container according to the present invention can be desirably applied to a manufacturing method of a container having a pressure-reduced internal space. In the image display apparatus such as an FED or the like having the pressure-reduced internal space, a joining strength which can cope with an atmospheric pressure caused by a negative pressure of the internal space is required. However, according to the manufacturing method of the hermetic container according to the present invention, both an assurance of the joining strength and an airtightness of the internal space can be accomplished.
A number of electron-emitting devices 727 for emitting electrons in response to an image signal are provided on the rear plate 713. Matrix wirings (X-directional wirings 728, Y-directional wirings 729) for making each electron-emitting device 727 operative in response to the image signal are formed on the rear plate 713. A phosphor film 734 made of phosphor which receives an irradiation of the electrons emitted from the electron-emitting devices 727, emits light, and displays an image is provided on the face plate 712 located so as to face the rear plate 713. Black stripes 735 are further provided on the face plate 712. The phosphor film 734 and the black stripes 735 are alternately arranged. A metal back 736 made of an aluminum (Al) thin film is formed on the phosphor film 734. The metal back 736 has a function as an electrode for attracting the electron and receives a supply of an electric potential from a high voltage terminal Hv provided for the container 710. A non-evaporable getter 737 made of a titanium (Ti) thin film is formed on the metal back 736.
It is sufficient that the face plate 712, rear plate 713, and frame member 714 are transparent and have translucency. Soda-lime glass, glass having a high strain point, no-alkali glass, or the like can be used. It is desirable that at a wavelength of local heating light and in an absorption wavelength band of the sealing material, which will be described hereinbelow, it is desirable that those members 712, 713 and 714 have a good translucency. The rear plate 713 is desirable from a viewpoint of suppressing a residual stress to the hermetic container so long as it is a material whose linear expansion coefficient coincides with that of each of the frame member 714 and the face plate 712.
Subsequently, the manufacturing method of the hermetic container according to the present invention will be described with reference to
A first glass substrate and a second glass substrate constituting the hermetic container are prepared as a preparation stage.
A specific example of each component member constituting the hermetic container will be described hereinbelow. First, the face plate 712 having phosphor (not illustrated), the black stripes, and the metal back, the frame member 714, and the rear plate 713 are prepared. A glass frit (not illustrated) is formed onto the phosphor-formed surface of the face plate 712 by a printing and a baking. The glass frit and the frame member 714 come into contact with each other, are temporarily assembled by a pressurizing member (not illustrated), and are airtightly sealed and integrated in an atmospheric firing furnace. The first glass substrate in which the frame member 714 and the face plate 712 have been integrated in this manner is prepared. A sealing material 701 made of the glass frit is formed in the portion of the frame member 714 of the face plate (first glass substrate) 712 integrated with the frame member 714 by the printing and the baking.
The sealing material 701 which seals the first glass substrate with a second glass substrate, which will be described hereinafter, is a circumferential sealing material having plural straight line portions 701a and curved coupling portions 701b for connecting the straight line portions 701a (refer to
The straight line portion 701a indicates a rectangular region surrounded by both rectilinearly extending edge sides of the sealing material. The coupling portion 701b indicates a transition region adapted to shift from one straight line portion to another straight line portion (refer to
The matrix wirings constituted by the plural X-directional wirings 728 and the plural Y-directional wirings 729 illustrated in
The frame member 714, the sealing material 701, and the like may be formed on the face plate 712 in arbitrary order. It is not always necessary to previously integrate those members but the frame member 714 and the face plate 712 may be sealed after or during a sealing step, which will be described hereinafter. In the above example, a matter in which the frame member 714 and the face plate 712 were integrated has been used as a first glass substrate, and the rear plate 713 has been used as a second glass substrate. However, the face plate 712 may be used as a first glass substrate and a matter in which the frame member 714 and the rear plate 713 were integrated may be used as a second glass substrate.
Although the sealing material 701 has been printed and formed onto the frame member 714, a sheet frit or the like serving as a sealing material 701 can be also arranged between the frame member 714 and the rear plate 713 in place of such a method. As for the sealing material 701, it is desirable that its viscosity has a negative temperature coefficient (temperature dependency), the material is softened at a high temperature, and its softening point is lower than that of each of the face plate 712, rear plate 713, and frame member 714. As an example of the sealing material 701, a glass frit, an inorganic adhesive, an organic adhesive, or the like can be mentioned. It is desirable that the sealing material 701 shows high absorbability to a wavelength of the local heating light, which will be described hereinafter. In the case where the hermetic container 710 is used as a container or the like for an FED in which it is required to maintain a vacuum degree of the internal space 717, a glass frit, an inorganic adhesive, or the like which can suppress a decomposition of residual hydrocarbon is desirably used as a sealing material 701.
In the assembling step, as illustrated in
There is a case where the members (the first glass substrate, the second glass substrate, and the whole sealing material) which define the internal space 717 in the state where the foregoing component elements have been assembled in the assembling step are called “assembly structure” hereinbelow.
In the sealing step after the assembling step, such local force as to set the internal space 717 to the negative pressure to the outside and to compress the coupling portions 701b of the circumferential sealing material 701 in the thickness direction of the sealing material is applied. At the same time, the sealing material 701 is heated and molten by irradiating the local heating light to the sealing material 701, thereby sealing the first glass substrate and the second glass substrate.
In order to set the internal space 717 to the negative pressure to the outside, for example, as illustrated in
Although an air volume displacement of the internal space 717 by the evacuating apparatus 68 can be set according to the expected pressurizing force, by setting the pressure in the internal space 717 to 0.5 atmospheric pressure or less, much desirably, 0.1 atmospheric pressure or less, the sufficient pressurizing force can be assured. As an evacuating apparatus 68 for exhausting the internal space 717, an arbitrary apparatus such as dry scroll pump, rotary pump, thermal diffusion pump, turbo-molecular pump, or the like can be used. If it is demanded to prevent contamination of the internal space 717 of the hermetic container, the dry scroll pump or the turbo-molecular pump can be desirably used.
In the foregoing embodiment, in the sealing step, by reducing the pressure in the internal space 717, the internal space 717 is maintained to the negative pressure to the outside. However, the internal space 717 may be set to the negative pressure by increasing the outside atmospheric pressure. Such examples are illustrated in
A specific example of a method of applying such local force to compress the coupling portions 701b of the circumferential sealing material 701 in the thickness direction of the sealing material will be described hereinbelow with reference to
The position where the local force is applied is not limited to the positions on both sides which sandwich the sealing material as illustrated in
As illustrated in
As illustrated in
The inventors of the present invention have found out that by applying the local force to the coupling portions 701b of the sealing material as mentioned above, an effect which will be described hereinbelow is obtained. The force which is applied to the assembly structure from the outside thereof is applied to the sealing material 701.
An example of the assembly structure in the case where the pressurizing force to the region near the coupling portion 701b is insufficient is illustrated in
As mentioned above, since the strength of the region near the coupling portion 701b of the sealing material is larger than the that near the straight line portion 701a, there is a case where if the coupling portion 701b of the sealing material is not pressurized by the force larger than that to the straight line portion 701a of the sealing material, the defective junction occurs near the coupling portion 701b of the sealing material. According to the present invention, since such local force as to compress the coupling portions 701b of the circumferential sealing material in the thickness direction of the sealing material is applied, the adherence between the first glass substrate and the second glass substrate can be improved.
From a viewpoint of improvement of the adherence, it is desirable to apply such local force as to compress all of the coupling portions 701b of the sealing material in the sealing step.
Subsequently, in the sealing step, a region where the local force is applied (pressurizing region) will be described with reference to
In
Even if the coupling portion of the sealing material has vertically been bent as illustrated in
As described above, by setting the internal space 717 to the negative pressure to the outside and by applying such local force as to compress the coupling portions 701b of the circumferential sealing material in the thickness direction of the sealing material, the lack of the pressurizing force in the region near the coupling portion 701b of the sealing material can be supplemented. Thus, the adherence between the whole circumference of the sealing material 701 and the glass substrate can be improved.
As for the timing for setting the internal space 717 to the negative pressure to the outside and the timing for starting to apply such local force as to compress the coupling portions 701b of the circumferential sealing material, those operations may be executed in arbitrary order or may be simultaneously started. In brief, it is sufficient that the negative pressure of the internal space 717 and the application of the local force are maintained during the sealing step, which will be described hereafter. However, in the case where it is difficult to set the internal space 717 to the negative pressure because of the lack of the adherence of the coupling portion 701b of the sealing material, it is much desirable that after such local force as to compress the coupling portions 701b of the circumferential sealing material was applied, the internal space 717 is set to the negative pressure.
In the sealing step, as for the state of the negative pressure of the internal space 717 and the application of such local force as to compress the coupling portions 701b of the sealing material, the local heating light is irradiated to the sealing material 701 and maintained for a period of time during which the first glass substrate and the second glass substrate are sealed. Desirably, the local heating light is scanned along the sealing material 701 and the sealing material 701 is sequentially heated and molten in the glass substrate surface.
The scanning of the local heating light will be described hereinbelow with reference to
Subsequently, the local force applied to the coupling portions 701b of the sealing material is cancelled. After that, as illustrated in
In the case where the internal space 717 of the hermetic container is maintained in a vacuum state, it is sufficient that after the sealing step, the pressure reduction of the internal space of the hermetic container is cancelled, subsequently, a step of exhausting the gas in the internal space 717 is again executed, and thereafter, the exhaust hole 69 is sealed. In place of the foregoing method, the exhaust hole 69 may be sealed while maintaining the negative pressure of the internal space 717 during the sealing step.
As an example of a method whereby the exhaust hole 69 is sealed by the cover member 70 while maintaining the internal space 717 in the vacuum state, a cover sealing apparatus may be used as illustrated in
As another method of sealing the exhaust hole 69 while maintaining the internal space 717 in the vacuum state, as illustrated in
Hereinafter, concrete examples of the above-described embodiment will be described in detail.
In this example, the foregoing manufacturing method of the hermetic container is applied, an integrated matter of the frame member and the face plate and the rear plate are airtightly sealed, further, the pressurization is cancelled, and after that, while the internal space is again exhausted from the exhaust hole, the exhaust hole is sealed by the cover member. In this manner, a vacuum hermetic container which can be applied as a container for the FED is manufactured.
First, a face plate is prepared. The face plate is formed by cutting a high strain point glass substrate having a thickness of 1.8 mm (PD200: made by Asahi Glass Co., Ltd.) into a plate glass shape having an external shape of 980 mm×570 mm×1.8 mm by a cutting work. Subsequently, the surface of the face plate is degreased by an organic solvent cleaning, a pure water rinsing, and a UV-ozone cleaning. Then, by forming phosphor, a black matrix, and an anode as a pattern onto the face plate, an image forming region is formed onto one surface of the face plate. Subsequently, a non-evaporable getter made of metal Ti is formed onto the anode by a sputtering method. Then, a sealing material made of a glass frit is formed in the outside of the image forming region on the face plate by a screen printing and an atmosphere heating. In this manner, the face plate with the sealing material is prepared.
Subsequently, a frame member is prepared. Concretely, a high strain point glass substrate having a thickness of 1.5 mm (PD200) is cut into a size having an external shape of 980 mm×580 mm×1.5 mm. A region of 970 mm×560 mm×1.5 mm of a center region of the glass substrate having such a size is cut out by the cutting work, thereby forming the almost quadrangular frame member in which a straight line portion has a width of 5 mm and a height of 1.5 mm. Then, in a manner similar to the face plate, the surface of the frame member is degreased by the organic solvent cleaning, pure water rinsing, and UV-ozone cleaning.
Subsequently, the surface (having the phosphor pattern) of the prepared face plate with the sealing material and the frame member are come into contact with each other, are temporarily assembled by a pressurizing tool (not illustrated), and are sealed and integrated without gaps by an atmospheric firing furnace, thereby preparing the face plate (first glass substrate) with the integrated frame member.
Subsequently, the sealing material is formed on the frame member. In this example, a glass frit is used as a sealing material. The glass frit used is such a paste that a Bi system lead-free glass frit (BAS115: made by Asahi Glass Co., Ltd.) having a thermal expansion coefficient of α=79×10−7/° C., a transition point of 357° C., and a softening point of 420° C. is used as a base material, and an organic substance is dispersed and mixed as a binder. Subsequently, a sealing material having a width of 1 mm and a thickness of 7 μm is formed along the circumferential length on the frame member by the screen printing. Each face plate with the integrated frame member serving as a first glass substrate is dried at 120° C. In order to burn out the organic substance, it is heated and baked at 460° C., thereby forming the sealing material. In this manner, an integrated matter of the sealing material, frame member, and face plate serving as a first glass substrate is prepared.
Subsequently, as a rear plate, a glass substrate having a size of 990 mm×580 mm×1.8 mm and made of high strain point glass (PD200: made by Asahi Glass Co., Ltd.) is prepared. Then, an exhaust hole having a diameter of 2 mm is formed in a region out of the image forming region of the rear plate by the cutting work. Subsequently, in a manner similar to the face plate and the frame member, after the rear plate was cleaned, the electron-emitting devices and the matrix wirings for driving (not illustrated) are formed. The non-evaporable getter made of a metal (Ti) (not illustrated) is formed on the matrix wirings for driving by the sputtering method. Subsequently, the spacers (not illustrated) are arranged on scanning signal wirings.
Subsequently, the prepared integrated matter of the sealing material, frame member serving as a first glass substrate, and face plate and the electron-emitting device plate are arranged in such a manner that the surface formed with the phosphor pattern and the surface formed with the electron-emitting device face each other. Thus, the assembly structure which defines the internal space 717 is formed as illustrated in
Subsequently, the evacuating apparatus comprising the scroll pump and the turbo-molecular pump is connected to the exhaust hole 69 through the exhaust pipe, thereby exhausting until the atmospheric pressure of the internal space 717 reaches 1×104 Pa as illustrated in
Subsequently, as illustrated in
Subsequently, while maintaining the pressurizing state to the assembly structure, as illustrated in
At this time, as for the local heating light 15, two semiconductor laser apparatuses for working (not illustrated) are prepared and arranged in such a manner that irradiation spots of a first laser light source and a second laser light source are aligned on a straight line.
As a first laser light source, a laser beam having a wavelength of 980 nm, a laser power of 212 W, and an effective diameter of 2 mm is used and scanned at a speed of 1000 mm/sec. The second laser light source is arranged behind the first laser light source in the scanning direction with a delay time of 0.05 seconds, that is, by a distance of 50 mm as an irradiation spot, and this spacing distance is also maintained during the scanning operation. At this time, as a laser beam from the second laser light source, a laser beam having a wavelength of 980 nm, a laser power of 212 W, and an effective diameter of 2 mm is used.
Subsequently, the pressurization of the pressurizing tool is released, the evacuating apparatus and the exhaust pipe are removed from the exhaust hole, and the pressure reduction of the internal space is cancelled. After that, while the internal space 717 is exhausted from the exhaust hole 69, the whole hermetic container is heated in a cart type furnace having a cover sealing apparatus as illustrated in
The hermetic container is manufactured in this manner, a driving circuit and the like are further attached by an ordinary method, and an FED apparatus having the hermetic container is completed. The completed FED was made operative, so that it has been confirmed that the stable electron emission and image display for a long time can be performed and such stable airtightness that can be applied to the FED is assured.
In the second example, as illustrated in
In the third example, processes are executed in a manner similar to the first example except that in place of pressurizing by the pressurizing tool 14 in the first example, as illustrated in
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the present invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2010-075067, filed Mar. 29, 2010, which is hereby incorporated by reference herein in its entirety.
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