Patent Application
20110146881
1. Field of the Invention
The present invention relates to a method of producing an image display apparatus having spacers between a front plate and a back plate.
2. Description of the Related Art
In a flat panel display, in order to achieve a uniform load on a spacer having uneven height disposed on a substrate, Japanese Patent Laid-Open No. 10-83778 discloses a technology of disposing a metal flexible member between the spacer and the substrate.
In the technology, the metal flexible member is made of gold or a gold-palladium alloy. Recently, a demand for a novel flexible member that can achieve a further uniform load on the spacer has been increasing, because that breakage of the spacer or breakage of the substrate on which the spacer is abutted, which is caused by the load, has not been sufficiently solved yet.
The present invention provides a method of producing an image display apparatus having a back plate, a front plate disposed so as to face the back plate, spacers disposed between the back plate and the front plate, a frame member joining the back plate and the front plate and forming an airtight space between the back plate and the front plate, and image display members arranged in the airtight space. The method includes the step of forming an abutting layer containing a metal or a metal oxide and having a porosity ranging from 20% to 50% on the back plate or the front plate at positions where the spacers are abutted and the step of abutting the spacers on the abutting layer.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
As shown in
A method of producing the image display apparatus according to the embodiment will be described below.
First, in the embodiment, a front plate 11 shown in
As shown in
The substrate 11a transmits at least light having the wavelength of light emitted by the light-emitting layers 17. For example, the substrate 11a transmits light having a wavelength ranging from 360 to 830 nm, that is, visible light. The substrate 11a is typically a glass substrate such as a silica glass or soda-lime glass substrate.
The light-shielding layer 18 having a plurality of openings arranged in a matrix form is formed on the substrate 11a by, for example, applying a photo paste containing a black inorganic pigment onto the entire surface of the substrate 11a, exposing and developing the photo paste using a photo mask having a pattern corresponding to the openings, and then firing the photo paste. The photo paste can be applied onto the substrate 11a by, for example, screen printing or slit coating.
The light-emitting layers 17 are formed in the plurality of the openings arranged in a matrix form of the light-shielding layer 18 by, for example, applying a photo paste containing phosphor powder onto the light-shielding layer 18 and into the openings, exposing and developing the photo paste using a photo mask, and then firing the photo paste remaining in the openings of the light-shielding layer 18. The application of the photo paste onto the light-shielding layer 18 and into the openings can be conducted by, for example, screen printing.
The light-reflecting layer 20 is formed on the light-shielding layer 18 and on the light-emitting layers 17 by forming a resin layer on the light-shielding layer 18 and the light-emitting layers 17, forming a metal layer on the resin layer by, for example, vapor deposition or sputtering, and then firing the resin layer. The light-reflecting layer 20 can be made of a material having metallic luster, such as aluminum, and can have a thickness in a range of from 10 nm to 1 μm.
Then, as shown in
In the embodiment, as shown in
The inorganic solid is a plurality of metal particles or a plurality of metal oxide particles, and the precursor 19′ can further contain a frit in addition to the metal particles or the metal oxide particles. Since the frit functions as an adhesive material of the metal particles or the metal oxide particles, generation of debris from the abutting layer when the spacers are abutted on the abutting layer is reduced. Examples of the metal particles or the metal oxide particles being the inorganic solid include zinc oxide particles, titanium oxide particles, silver particles, gold particles, and aluminum particles, and these types of particles may be used alone or in combination. The metal particles or the metal oxide particles may be powder like and have a median diameter ranging from 10 to 100 nm. The frit as an inorganic solid may be any so-called glassy powder. For example, a lead-glass frit or a bismuth-glass frit can be used.
The binder may be any material that can disperse the inorganic solid, and examples thereof include acrylic resins, melamine resins, urea resins, acryl-melamine copolymer resins, melamine-urea copolymer resins, polyurethane resins, polyester resins, epoxy resins, alkyd resins, polyamide resins, vinyl resins, and cellulose resins. These materials can be used alone or in combination.
The resin particles 19a can be obtained by pulverizing a resin mass. However, resin particles having a uniform shape are preferred to those having different shapes, and approximately spherical resin particles (hereinafter, referred to as resin spheres) can be used. The resin spheres can be formed by a known method, for example, by suspension polymerization. Thermoplastic resin spheres may be produced by spraying a thermoplastic resin in a melted state and granulating the resin by cooling. The raw material of the resin particles 19a may be an alkyl acrylate resin having a linear-chain structure or an olefin resin having a linear-chain structure, and examples thereof include polybutylmethacrylate, polymethylmethacrylate, polymethylmethacrylate, polyethylene, and polystyrene. Furthermore, the commercially available resin spheres can be used. For example, as butyl methacrylate-based acrylic resin spheres, FA series (trade name, products of Fuji Shikiso Co., Ltd.) and BMX series (trade name, products of Sekisui Plastics Co., Ltd.) can be used. As methyl methacrylate-based acrylic resin spheres, MBX series (trade name, products of Sekisui Plastics Co., Ltd.), Liosphere (trade name, a product of Toyo Ink Mfg. Co., Ltd.), and Epostar MA series (trade name, products of Nippon Shokubai Co., Ltd.) can be used. As formaldehyde-condensed resin spheres, Epostar series (trade name, products of Nippon Shokubai Co., Ltd.) can be used. As polyethylene resin spheres, LE series (trade name, products of Sumitomo Seika Chemicals Company) can be used. These resins can be used alone or in combination as the resin particles 19a. The resin particles 19a having a particle diameter larger than that of the metal particles or metal oxide particles can easily provide a predetermined porosity described below to the abutting layer. For example, the resin particles 19a have a median diameter ranging from 0.5 to 5.0 μm.
The abutting layer can be easily provided with a predetermined porosity described below when the final temperatures of thermal decomposition of the binder and the resin particles 19a are lower than the melting point of the metal particles or the metal oxide particles contained as the inorganic solid. The final temperature of thermal decomposition is defined as follows: The temperature at which the mass loss in thermogravimetric analysis of the binder or the resin particles reaches 70% is called “standard temperature”. More specifically, the standard temperature is the temperature at which the mass loss reaches 70%, when a material having a predetermined mass is heated in air at a temperature-increasing rate of 10±1° C./min. That is, the standard temperature is the temperature at which the mass of the remaining material is 30% of the initial mass of the material. When a material is heated, the temperature at which mass loss starts is called initial temperature of thermal decomposition, the temperature at which the mass loss reaches 50% is called midpoint temperature of thermal decomposition, and the temperature at which the mass loss is finished is called final temperature of thermal decomposition. The standard temperature and the midpoint temperature are determined by thermogravimetric analysis of each material of the binder and the resin particles. The initial temperature of thermal decomposition and the final temperature of thermal decomposition are determined from a mass loss curve drawn by the thermogravimetric analysis. The details of the thermogravimetric analysis can be referred to JIS K 7120-1987.
In the embodiment, the precursor 19′ of the abutting layer mentioned above is formed by applying a paste being a mixture of at least the inorganic solid, the binder, and the resin particles 19a on the light-shielding layer 18 among the plurality of light-emitting layers 17 on the front plate 11 shown in
Then, as shown in
The thickness of the abutting layer 19 can be suitably adjusted according to uneven height of the spacers to be abutted. The lower limit of the thickness is 130% or more of the maximum variation in height of the spacers for enhancing uniformizing the load on the spacers. The maximum variation is determined as follows: First, the heights at a plurality of points of one spacer are measured. This measurement is conducted for all spacers, and the maximum value and the minimum value of the heights are determined from the measurement results. A value obtained by subtracting the minimum value from the maximum value is the maximum variation. The height of a spacer is the thickness of the spacer in the direction perpendicular to the back plate or the front plate on which the spacer is abutted. The upper limit of the thickness of the abutting layer 19 is preferably 20 μm or less and more preferably 17 μm, by considering the possibility of partial breakage of the abutting layer due to compression stress when the spacers are abutted. Based on such a thickness of the abutting layer 19, in the spacers applied to the embodiment, the maximum variation in height is 15.4 μm (=20 μm/130×100) or less, particularly preferably 13.1 μm (=17 μm/130×100) or less. The thickness of the abutting layer 19 is defined as an arithmetic average roughness Ra of the surface of a base on which the abutting layer 19 is formed, that is, in the embodiment, the distance from the central line determining the arithmetic average roughness Ra of the surface of a light-reflecting layer 18 to the central line determining the arithmetic average roughness Ra of the surface of the abutting layer.
The porosity of the abutting layer 19 in the embodiment ranges 20% to 50%. Its technical meaning will be described below.
The present inventors have conducted the following experiments. First, a paste having a composition shown in Table 1 was prepared. Then, resin particles were added to the paste in an amount of 0, 10, 20, 30, or 40 wt % relative to the amount of the inorganic solid.
The five pastes were applied on glass substrates by printing, dried at 110° C., and fired at 500° C. to form five types of abutting layers each having a thickness of 14 μm, a length of 60 μm, and a width of 60 μm on the glass substrates.
The volume ratio of voids (hereinafter, referred to as porosity) of each abutting layer was evaluated. The porosity was determined as an area ratio of voids to solid layer determined by binarized image analysis of a cross-sectional SEM image of the abutting layer. The results are shown in
Furthermore, the present inventors have investigated a relationship between the amount of the deformation of the abutting layer and the porosity. The method for the evaluation is shown in
In order to ensure a predetermined amount of deformation at the entire positions where the spacers are abutted in an image display apparatus, it is desirable to control the porosity to a range where the change in the amount of deformation is small. It was revealed that the change in the amount of deformation is small when the porosity of the abutting layer is controlled to a range of 20% to 50% and that the amount of deformation in this range is 9 μm or more.
The experimental results above show that the porosity in the abutting layer can be controlled to the range of 20% to 50% by controlling the amount of the resin particles in a range of 20 to 30 wt % relative to the amount of the inorganic solid in the paste for forming the abutting layer or in the precursor of the abutting layer.
Then, a back plate 12 shown in
As shown in
Furthermore, a plurality of spacers 13 are fixed on the row wirings 14 on the back plate 12 in advance. The spacer 13 is fixed by bonding its both ends in the longitudinal direction to the row wiring 14 or to the back plate 12 with an adhesive. The spacer 13 can be made of glass or ceramics. Furthermore, the surface of the spacer 13 may be covered by a resistance film for preventing electrostatic charging. As the adhesive, for example, a glass frit or a reactive inorganic adhesive is used. Furthermore, a frame member 26 is fixed on the back plate 12. The frame member shown in
Then, the spacers 13 are abutted on the abutting layer.
First, an adhesive is applied to the frame member 26 on the back plate 12 shown in
Then, the inside of the vacuum chamber is deaerated, and the adhesive on the frame member 26 is heated. When the pressure in the vacuum chamber has reached to about 1.3×10−3 to 1.3×10−5 Pa, the spacers 13 are abutted on the abutting layer 19 by pressing the front plate 11 onto the frame member 26 on the back plate 12. The back plate 12 and the front plate 11 are joined through the frame member 26 by returning the inside of the vacuum chamber to ordinary temperature and ordinary pressure to form a depressurized airtight space between the back plate 12 and the front plate 11.
In the embodiment, the spacers 13 are abutted on the abutting layer 19 in a vacuum chamber, but the spacers 13 may be abutted on the abutting layer 19 under atmospheric pressure. In such a case, after the spacers 13 are abutted on the abutting layer 19, the back plate 12 and the front plate 11 are joined through the frame member 26, and a depressurized airtight space is formed between the back plate 12 and the front plate by exhausting from an exhaust pipe provided to the substrate 11a of the front plate 11 or the substrate 12a of the back plate 12.
As shown in
In the embodiment described above, the abutting layer is disposed on the front plate, but a configuration where the abutting layer is disposed on the back plate also can achieve similar effects. When the abutting layer is disposed on the back plate, the spacers are fixed to the front plate at regions excluding the light-emitting layers, and the abutting layer is formed on the back plate at regions excluding the electron-emitting devices. For example, the spacers are fixed to the light-shielding layer 18 excluding the light-emitting layers 17 shown in
In addition, in the embodiment, the spacers are a plate-like member as shown in
First, the front plate 11 shown in
Then, spacers were prepared, and the maximum variation in height of the spacers was determined. The spacer was a plate-like spacer 13 shown in
Then, as shown in
In the paste for forming the abutting layer in this Example, zinc oxide particles having a median diameter of 30 nm were used as the metal oxide, and butyl methacrylate-based acrylic resin spheres having a median diameter of 2 μm were used as the resin particles 19a. The butyl methacrylate-based acrylic resin spheres had an initial temperature of thermal decomposition of 250° C., a final temperature of thermal decomposition of 400° C., and a standard temperature of 330° C.
The median diameters of the metal oxide particles and the resin particles 19a were each measured in advance in their powder form before the preparation of the paste for forming the abutting layer. In the metal oxide particles or the resin particles 19a having a median diameter of 6 μm or less, the median diameters were determined by a dynamic light scattering method using Zetasizer Nano ZS (trade name, a product of Sysmex Corporation). In the metal oxide particles or the resin particles 19a having a median diameter larger than 6 μm, the median diameters were determined by a laser diffraction scattering method using Mastersizer 2000 (trade name, a product of Sysmex Corporation). The laser diffraction scattering method can be also applied to measurement of median diameters not larger than 6 μm. Note that no significant differences were observed as a whole in the shapes of the particles in the powder forms and in cut surfaces after application as a paste and drying of the metal oxide particles and the resin particles, when observed with an electron microscope. The sizes of the metal oxide particles and the resin particles observed with an electron microscope seemed to be near their median diameters.
Then, the precursor 19′ of the abutting layer shown in
Another front plate formed by the same method for testing was subjected to electron microscopic observation for a cut surface of the abutting layer 19 to confirm that the resin particles 19a were burned down to form voids 19b in the abutting layer 19. Furthermore, the porosity was estimated to be 20% from binarized image analysis of a cross-sectional FIB-SEM image. The front plate for testing was subjected to measurement of the amount of deformation in the abutting layer 19 at 100 points on the surface of the front plate 11 using an indenter with a bottom size of Φ 60 μm of a micro compression testing machine MCT-W500-J, a product of Shimadzu Corporation. The results were that the amount of deformation of the abutting layer 19 at a compression stress of 80 MPa was 9.5±0.5 μm.
Then, as shown in
The substrate 12a was a glass substrate (length: 600 mm, width: 1000 mm, thickness: 1.8 mm) called PD200. On the substrate 12a, a plurality of row wirings 14 and a plurality of column wirings 15 were formed using an Ag paste by screen printing. The electron-emitting devices 16 were surface-conduction electron-emitting devices and were arranged with the same pitch as that of the openings provided to the light-shielding layer 18 of the front plate. The twenty spacers 13 were fixed on the row wirings 14 on the back plate 12 with approximately equal spaces therebetween. The spacer 13 was fixed by bonding its both ends to the row wiring 14 with a heat-resistant inorganic adhesive, “Aron Ceramics W”, a product of Toagosei Co., Ltd. Furthermore, the frame member 26 made of glass was fixed to the back plate 12 by bonding with a glass frit applied to the periphery of the substrate 12a.
Then, as shown in
First, the frit glass was applied onto the frame member 26 and was heated to 200° C. for calcining the frit glass. The back plate 12 and the front plate 11 were placed with a tool (not shown) so that the abutting layer 19 and the spacers 13 face each other. The positions of the light-emitting layers 17 of the front plate 11 and the electron-emitting devices 16 of the back plate 12 were adjusted, and the relative positions of both substrates were fixed in a state that a distance was provided between both substrates. Both substrates were placed between a pair of hot plates of a vacuum chamber. The pair of hot plates was provided with a hoisting and lowering mechanism. The inside of the vacuum chamber was deaerated to 1.3×10−5 Pa, and then the hot plates were brought into contact with both substrates and heated the substrates to 400° C. Then, the front plate 11 was pressed against the back plate 12 with the hoisting and lowering mechanism. After both substrates were cooled to ordinary temperature, the pressure in the vacuum chamber was increased to ordinary pressure, and the substrates were taken out.
Thus, the spacers 13 were abutted on the abutting layer 19 to form an image display apparatus.
The substrate 11a of the front plate 11 of the image display apparatus produced in this example was perforated to make the pressure in the airtight space surrounded by the front plate 11, the back plate 12, and the frame member 26 to an atmospheric pressure. Then, the front plate 11 was separated from the image display apparatus by cutting the bonding portion between the front plate 11 and the frame member 26.
The abutting layer 19 of the separated front plate 11 and the spacers 13 of the back plate 12 were observed with an optical microscope. First, the abutting surfaces of all spacers 13 with the abutting layer 19 were investigated to confirm no breakage and chipping occurred. In addition, no breakage was observed in the abutting layer 19. Furthermore, evidence of abutting with the spacers 13 was observed in the entire abutting region of the abutting layer 19.
In the separated front plate 11, the cut surfaces of the abutting layer 19 at the regions being positioned among the spacers 13 and on which the spacers 13 were not abutted were observed with an electron microscope. The porosity was estimated to be 20% from binarized image analysis of a cross-sectional FIB-SEM image of the abutting layer.
In this example, an image display apparatus was produced as in Example 1 except that the composition of the paste for forming the abutting layer was changed so that the abutting layer 19 had a thickness of 14 μm and a porosity of 50%. The composition of the paste used in this example is shown in Table 3.
As in Example 1, a cut surface of the abutting layer 19 of the front plate for testing was observed with an electron microscope to confirm that the resin particles 19a were burned down to form voids 19b in the abutting layer 19. The porosity was estimated to be 50% from binarized image analysis of a cross-sectional FIB-SEM image. Furthermore, the front plate for testing was subjected to measurement of the amount of deformation in the abutting layer 19 at 100 points on the surface of the front plate 11 using an indenter with a bottom size of Φ 60 μm of a micro compression testing machine MCT-W500-J, a product of Shimadzu Corporation. The results were that the amount of deformation of the abutting layer 19 at a compression stress of 80 MPa was 10±0.5 μm.
As in Example 1, the abutting layer 19 of the separated front plate 11 and the spacers 13 of the back plate 12 were observed with an optical microscope. First, the abutting surfaces of all spacers 13 with the abutting layer 19 were investigated to confirm no breakage and chipping occurred. In addition, no breakage was observed in the abutting layers 19. Furthermore, evidence of abutting with the spacers 13 was observed in the entire abutting region of the abutting layer 19.
In the separated front plate 11, the cut surfaces of the abutting layer 19 at the regions being positioned among the spacers 13 and on which the spacers 13 were not abutted were observed with an electron microscope. The porosity was estimated to be 50% from binarized image analysis of a cross-sectional FIB-SEM image of the abutting layer.
In this Comparative Example, an image display apparatus was produced as in Example 1 except that the composition of the paste for forming the abutting layer 19 did not contain resin particles of Example 1.
As in Example 1, a cut surface of the abutting layer of the front plate for testing was observed with an electron microscope to confirm that very few voids were formed in the abutting layer. The porosity was estimated to be 2% from binarized image analysis of a cross-sectional FIB-SEM image. Furthermore, the front plate for testing was subjected to measurement of the amount of deformation in the abutting layer at 100 points on the surface of the front plate using an indenter with a bottom size of Φ 60 μm of a micro compression testing machine MCT-W500-J, a product of Shimadzu Corporation. The results were that the amount of deformation of the abutting layer at a compression stress of 80 MPa was 6±0.5 μm.
As in Example 1, the abutting layer of the separated front plate and the spacers of the back plate were observed with an optical microscope. First, the abutting surfaces of all spacers with the abutting layer were investigated to confirm obvious chipping occurred at several positions. In addition, no evidence of abutting with the spacers was observed in some positions in the abutting region of the abutting layer.
Image display apparatuses in Examples 3 and 4 were produced as in Examples 1 and 2, respectively, except that the resin particles contained in the pastes for forming the abutting layers were methyl methacrylate-based acrylic resin spheres having a median diameter of 2 μm.
The methyl methacrylate-based acrylic resin spheres had an initial temperature of thermal decomposition of 250° C., a final temperature of thermal decomposition of 410° C., and a standard temperature of 350° C.
Example 3 showed similar results to those in Example 1, and Example 4 showed similar results to those in Example 2.
Image display apparatuses in Examples 5 and 6 were produced as in Examples 1 and 2, respectively, except that the resin particles contained in the pastes for forming the abutting layers were polyformaldehyde resin spheres having a median diameter of 2 μm.
The polyformaldehyde resin spheres had an initial temperature of thermal decomposition of 300° C., a final temperature of thermal decomposition of 400° C., and a standard temperature of 370° C.
Example 5 showed similar results to those in Example 1, and Example 6 showed similar results to those in Example 2.
Image display apparatuses in Examples 7 and 8 were produced as in Examples 1 and 2, respectively, except that the pastes used for forming the abutting layers contained titanium oxide particles (median diameter: 30 nm) instead of the zinc oxide particles (median diameter: 30 nm).
Example 7 showed similar results to those in Example 1, and Example 8 showed similar results to those in Example 2.
Image display apparatuses in Examples 9 and 10 were produced as in Examples 1 and 2, respectively, except that the pastes used for forming the abutting layers contained silver particles (median diameter: 30 nm) instead of the zinc oxide particles (median diameter: 30 nm).
Example 9 showed similar results to those in Example 1, and Example 10 showed similar results to those in Example 2.
Image display apparatuses in Examples 11 and 12 were produced as in Examples 1 and 2, respectively, except that the pastes used for forming the abutting layers contained gold particles (median diameter: 30 nm) instead of the zinc oxide particles (median diameter: 30 nm).
Example 11 showed similar results to those in Example 1, and Example 12 showed similar results to those in Example 2.
Image display apparatuses in Examples 13 and 14 were produced as in Examples 1 and 2, respectively, except that the pastes used for forming the abutting layers contained aluminum particles (median diameter: 30 nm) instead of the zinc oxide particles (median diameter: 30 nm).
Example 13 showed similar results to those in Example 1, and Example 14 showed similar results to those in Example 2.
Image display apparatuses in Examples 15 and 16 were produced as in Examples 1 and 2, respectively, except that the pastes used for forming the abutting layers contained butyl methacrylate-based acrylic resin spheres having a median diameter of 0.5 μm instead of the resin particles.
The butyl methacrylate-based resin spheres had an initial temperature of thermal decomposition of 250° C., a final temperature of thermal decomposition of 400° C., and a standard temperature of 330° C.
Example 15 showed similar results to those in Example 1, and Example 16 showed similar results to those in Example 2.
Image display apparatuses in Examples 17 and 18 were produced as in Examples 1 and 2, respectively, except that the pastes used for forming the abutting layers contained butyl methacrylate-based acrylic resin spheres having a median diameter of 5 μm instead of the resin particles.
Example 17 showed similar results to those in Example 1, and Example 18 showed similar results to those in Example 2.
Image display apparatuses in Examples 19 and 20 were produced as in Examples 1 and 2, respectively, except that the pastes used for forming the abutting layers did not contain the Bi glass frit and the zinc oxide particles (median diameter: 30 nm) but did contain silver particles (median diameter: 30 nm) in an amount of the sum of the contents of the Bi glass frit and the zinc oxide particles in Examples 1 and 2.
Example 19 showed similar results to those in Example 1, and Example 20 showed similar results to those in Example 2.
The present invention can provide a method of producing an image display apparatus where the probability of occurrence of breakage of the spacers is significantly reduced.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the 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. 2009-289730 filed Dec. 21, 2009, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-289730 | Dec 2009 | JP | national |
