Patent Application
20110200945
The present invention relates to a method of manufacturing a flat panel display such as a plasma display panel.
In recent years, among flat panel displays, a plasma display panel (hereinafter, referred to as “PDP”) which is easy to make a larger size has become widely used.
In a conventional PDP, a large number of discharge cells are formed between a front panel and a back panel facing each other. The front panel includes a glass substrate on the front side, one pair of display electrodes composed of a scan electrode and a sustain electrode, and a dielectric layer and a protective layer which cover the electrodes. The back panel includes a glass substrate on the back side, data electrodes formed on the glass substrate, a dielectric layer covering them, barrier ribs, and phosphor layers. The front panel and the back panel are placed to face each other such that the display electrode pairs and the data electrodes cross each other in a grade separated manner and is sealed, and a discharge gas is charged into and sealed in a discharge space inside thereof. Here, a discharge cell is formed at a position at which the display electrode pair and the data electrode face each other. In the discharge cell of the PDP having the structure, a gas discharge is performed and red, green, and blue phosphors are excited. Thus the phosphors emit light and a color display is performed.
The scan and sustain electrodes take a form in which a bus electrode having a narrow stripe shape is stacked on a transparent electrode having a broad stripe shape. The transparent electrode is formed by patterning an indium tin oxide (hereinafter, referred to as “ITO”) thin film, which is formed on the entire surface of the glass substrate by a sputtering method, with a photolithography method into the striped shape. Alignment marks for aligning positions of exposing masks which are used in a subsequent process (step) are also simultaneously formed during the patterning. The bus electrodes are formed by printing a conductive photosensitive paste on the glass substrate on which the transparent electrodes and the alignment marks are formed, then exposing the printed paste after position alignment, and finally etching the printed paste (see patent document 1).
However, a vacuum apparatus, which has a large size, and an ITO target material, which is expensive, are needed to form the ITO thin film by a sputtering method when forming the transparent electrodes. Furthermore, an exposing apparatus and an exposing mask are also needed to pattern the ITO thin film. That is, there is a problem in that not only is the manufacturing equipment large but also the productivity of the PDP is low.
For such a reason, a PDP manufactured by a method in which the scan electrodes and the sustain electrodes are formed with the conductive bus electrodes instead of the transparent electrodes is disclosed (for example, see patent document 2). However, the PDP without the transparent electrodes also has another problem such that the alignment marks must be formed in another way. As the method of forming the alignment marks, there are known examples. One is a method of forming the alignment marks by a printing method or a laser marking method (for example, see patent document 3). Another is a method of forming the alignment marks with the same material as the bus electrodes.
Position precision, shape precision, and visibility are important for the alignment marks of the flat panel display. In a high precision PDP which has been widely used in recent years, very high position and shape precision is especially required. However, in the case of manufacturing the PDP having an electrode structure and no transparent electrodes, there are problems such that the alignment marks must be formed in a different way, the manufacturing line must be modified, and the manufacturing man-hours increase.
For example, a method of forming the alignment marks using the conventional photosensitive paste is also disclosed, but the method also has a problem with a significant increase of manufacturing man-hours because the exposing and developing processes must be additionally incorporated in the previous stage of formation of the display electrode pairs.
Further, the alignment marks and the display electrode pairs can be simultaneously formed upon forming the display electrode pairs using the conventional conductive photosensitive paste. However, in the case of forming the display electrode pairs through a number of exposures, such methods cannot be used. In practice, when forming the display electrode pairs, two exposures are performed to suppress scratches on and dust adhesion to the exposing mask. In this case, as a minimum, an alignment mark for position alignment with an exposing mask for the second exposure is essential to prevent misalignment between a first exposure and a second exposure.
The invention is conceived in view of the above problems, and provides a manufacturing method of a flat panel display by which it is possible to simply form alignment marks having high precision and good visibility without modification of a manufacturing line or an increase in man hours and by which it is possible to manufacture a flat panel display at low cost and with high productivity.
A manufacturing method of the flat panel display of the invention includes a step of forming a photosensitive film on a substrate, a step of forming an alignment mark by exposing the photosensitive film, and a step of detecting a position of the substrate by recognizing the alignment mark in the state in which the photosensitive film is not yet developed.
According to the method, it is possible to simply form an alignment mark having high precision and good visibility without modification of a manufacturing line or an increase of man hours and to manufacture a flat panel display at low cost and with high productivity.
Hereinafter, a manufacturing method of a flat panel display according to the embodiment of the invention will be described with reference to the drawings, exemplifying a manufacturing method of a PDP.
Back panel 30 includes glass substrate 31 on the back side, data electrodes 32, dielectric layer 33, barrier ribs 34, and phosphor layers 35. A plurality of data electrodes 32 is formed in parallel on glass substrate 31. Dielectric layer 33 is formed so as to cover the data electrodes 32. Barrier ribs 34 composed of longitudinal barrier ribs 34a and lateral barrel ribs 34b are formed on dielectric layer 33 in a grid-like form. Red, green, and blue phosphor layers 35 are formed on the surface of dielectric layer 33 and the side walls of barrier ribs 34.
Front panel 20 and back panel 30 are placed to face each other such that display electrode pairs 24 and data electrodes 32 grade-separated cross each other. Discharge cells are formed at a place where display electrode pairs 24 and data electrode 32 face each other. Front panel 20 and back panel 30 are sealed to each other with low melting point glass at a position outside an image display region in which the discharge cells are formed, and a discharge space on the inner side is charged with a discharge gas.
Scan electrode 22 includes bus electrode 221 and bus electrode 222. Sustain electrode 23 also includes bus electrode 231 and bus electrode 232. Discharge gap MG is formed between bus electrodes 221 and bus electrodes 231.
Each of bus electrodes 221 and 222 is composed of black layer 221b, 222b and conductive layer 221c, 222c, and each of bus electrodes 231 and 232 is composed of black layer 231b, 232b and conductive layer 231c, 232c. Black layers 221b, 222b, 231b, and 232b are provided in order to make scan electrodes 22 and sustain electrodes 23 look black when they are viewed from the displaying surface side of PDP 10. For example, a black material such as ruthenium oxide is formed on glass substrate 21 in a stripe form having a small width. Conductive layers 221c, 222c, 231c, and 232c are formed in order to increase conductivity of scan electrodes 22 and sustain electrodes 23, and formed by stacking a conductive material containing silver on black layers 221b, 222b, 231b, and 232b.
In the embodiment, as various pastes used to specifically manufacture front panel 20, a photosensitive paste of a black color (hereinafter, referred to as “black photosensitive paste”), a photosensitive paste having conductivity (hereinafter, referred to as “conductive photosensitive paste”), and a dielectric paste are used. A method of preparing the pastes is described below.
Black Photosensitive Paste
The black photosensitive paste is a photosensitive paste provided in order to form black layers 221b, 222b, 231b, and 232b and the alignment marks. The black photosensitive paste is formed by forming a first photosensitive film (hereinafter, referred to as “black photosensitive film”) by coating a paste on glass substrate 21 and then drying it, and exposing the first photosensitive film. The black photosensitive paste is composed of an inorganic component containing a black color material and glass powder as solid content and an organic material component containing a photosensitive polymer, a photosensitive monomer, and a photo polymerization initiator. The particle size of the black color material is 1 μm or smaller.
The black photosensitive paste is prepared by blending an inorganic material composed of a black color material and glass powder, a photosensitive polymer such as photo-curable polymer, a photosensitive monomer, and various organic materials such as a photo polymerization initiator and a solvent so as to be a predetermined composition, and uniformly mixing and dispersing the mixture.
As the black material, at least one oxide selected from the group consisting of ruthenium oxide, ferric oxide, cobalt oxide, nickel oxide, copper oxide, and manganese dioxide can be used. The average particle size of the black pigment may be preferably set to 1 μm or smaller, and more preferably to the range of 0.01 to 0.5 μm in order to increase the precision of the alignment marks. By incorporating 5 to 40% by weight of the black color material into the paste, it is possible to form good black layers 221b, 222b, 231b, and 232b, and alignment marks. If the content of the black material is less than 5% by weight, the color becomes thinner and therefore there is a possibility that the contrast will deteriorate. Conversely, if the content of the black material is greater than 40% by weight, a softening point of the paste becomes higher and it is difficult to harmonize the thermal expansion coefficient with glass substrate 21. Furthermore, it is not desirable because there is a possibility that the UV rays cannot reach the bottom portion when the exposure is performed and thus formation failure of the black layer occurs.
As the glass powder, glass powder whose main component is bismuth oxide can be used. The average particle size of the glass powder is preferably 0.3 to 1.0 μm. If the average particle size of glass powder is greater than 1.0 μm, it influences the surface roughness of the black photosensitive film bx, resulting in deterioration of the recognition precision of the alignment marks as described above. On the other hand, if the average particle size of the glass powder is less than 0.3 μm, there is a likelihood that agglomeration of the glass powder will occur, resulting in an increase of the particle size of the agglomerates. That is, the surface roughness of the black photosensitive film bx is affected by the average particle size and therefore the recognition precision of the alignment marks deteriorates. Further, the maximum particle size may be preferably 2.0 μm or smaller. The composition of the glass powder preferably includes 30 to 85% by weight of oxide bismuth, 5 to 30% by weight of silicon oxide, 5 to 20% of boron oxide, 0.1 to 10% by weight of zirconium oxide, 2 to 20% by weight of zinc oxide, and 1 to 5% by weight of aluminum oxide. The content of the glass powder in the paste is preferably 25 to 40% by weight to enhance adhesion to the glass substrate.
Regarding the inorganic material for the black photosensitive paste, a conductive material may be preferably contained therein. As the conductive material, metal particulates, having an average particle size of preferably 1 μm or less and more preferably 0.01 to 0.5 μm, for example, silver, platinum, palladium, cobalt, nickel, manganese, molybdenum and ruthenium can be used.
As the organic material for the black photosensitive paste, as the photosensitive polymer, an oligomer or a polymer having a weight average molecular weight of 500 to 100000, containing a carboxyl group, and an unsaturated double bonding structure is preferably used. As the photosensitive monomer, a compound having a carbon-carbon unsaturated bonding structure can be used. By setting the content of the organic material components to 20 to 60% by weight, it is possible to prepare the black photosensitive paste having a good printing characteristic. As the organic material, additional additives such as a binder, an ultraviolet (UV) absorbing agent, a sensitizer, a sensitization aid, a polymerization inhibitor, a plasticizer, a thickener, an organic solvent, an antioxidant, a dispersant, a precipitation inhibitor, and a leveling agent may be added besides the photosensitive polymer, the photosensitive monomer, the photo polymerization initiator, and the solvent if needed.
The viscosity of the black photosensitive paste is preferably in the range of 2000 to 20000 cps. For example, the viscosity is preferably 50000 to 200000 cps in order to obtain the black photosensitive film having a thickness of 5 to 20 μm by a single coating of the paste by a screen printing method. When obtaining the black photosensitive film with a blade coating method or a die coater method, it is preferably 1500 to 20000 cps. The viscosity of the black photosensitive paste can be adjusted so as to fall into the range at the addition ratio of the inorganic powder, thickener, organic solvent, plasticizer, and precipitation inhibitor.
In the embodiment, in the composition, the content of ruthenium oxide having an average particle size of 0.1 μm and serving as the black material is 10% by weight, the content of cobalt tetroxide is 26% by weight, the content of commercially available glass frit containing bismuth oxide as glass powder is 12% by weight, the total content of organic materials including commercially available photo-curable polymer, photosensitive monomer, and polymerization initiator is 22% by weight, and the content of the solvent is 30% by weight. These components are uniformly mixed with three rollers and dispersed in order to prepare the black photosensitive paste.
Conductive Photosensitive Paste
The conductive photosensitive paste is a material for forming conductive layers 221c, 222c, 231c, and 232c. It is coated on the black photosensitive film and dried to form a second photosensitive film (hereinafter, referred to as “conductive photosensitive film”), and then the second photosensitive film is exposed to form the conductive layers. The conductive photosensitive paste is prepared by blending an inorganic material component composed of a conductive material whose main component is silver and glass powder, and an organic material component composed of a photosensitive polymer such as a photo-curable polymer, a photosensitive monomer, a photo polymerization initiator, and a solvent to become a predetermined composition, and then uniformly mixing and dispersing the mixture.
As the conductive material, silver powder having an average particle size of 0.1 to 2.0 μm is preferably used to finely form conductive layers 221c, 222c, 231c, and 232c. By having 45% by weight or more of silver powder contained in the paste, it is possible to form a pattern for desirable conductive layers.
As the glass powder, glass powder whose main component is bismuth oxide can be used. The average particle size of the glass powder is preferably 0.3 to 1.0 μm, and more preferably the maximum particle size is 2.0 μm or smaller. The composition of the glass powder preferably includes 30 to 85% by weight of bismuth oxide, 5 to 30% by weight of silicon oxide, 5 to 20% by weight of boron oxide, 0.1 to 10% by weight of zirconium oxide, 2 to 20% by weight of zinc oxide, and 1 to 5% by weight of aluminum oxide. Further, the paste preferably contains 0.5 to 5% by weight of glass powder to enhance adhesion to the glass substrate. By setting the content of the various organic materials to 20 to 45% by weight, it is possible to form the conductive photosensitive paste having a good printing characteristic.
In the embodiment, the conductive photosensitive paste is prepared by uniformly mixing and dispersing by the three rollers the combination of 69% by weight of silver powder having an average particle size of 0.8 μm, 3% by weight of glass frit which is commercially available and whose main component is bismuth oxide, 13% by weight of a mixture of a commercially available photo-curable polymer, a photosensitive monomer, and a photo polymerization initiator, and 15% by weight of a solvent with 3 rollers.
Dielectric Paste
The dielectric paste is a material for forming the dielectric layer 26. The dielectric paste is a paste containing dielectric glass having a softening point of 520 to 590° C. and containing one or more substances selected from the group consisting of boron oxide, silicon oxide, zinc oxide, alkaline earth oxide, alkaline metal oxide, bismuth oxide, aluminum oxide, molybdenum oxide, tungsten oxide, and cerium oxide.
For the dielectric layer 26 of the embodiment, a dielectric paste including dielectric glass containing 35% by weight of boron oxide, 1.4% by weight of silicon oxide, 27.2% by weight of zinc oxide, 3.3% by weight of barium oxide, 25% by weight of bismuth oxide, 1.1% by weight of aluminum oxide, 4.0% by weight of molybdenum oxide, and 3.0% by weight of tungsten oxide is prepared. The softening point of the dielectric glass prepared in the above way is 570° C.
A manufacturing method of PDP 10 will be described below.
First Step
In a first step, as a substrate, a glass substrate 21 is used for the front side substrate. A black photosensitive film bx serving as a first photosensitive film is formed by coating a black photosensitive paste on glass substrate 21 and drying it. Glass substrate 21 is cleaned with an alkali. Glass substrate 21 may be a glass substrate having a size of 980 mm×554 mm and a thickness of 1.8 mm in the case of a 42″ PDP.
Next, as shown in
Next, as shown in
Second Step
In a second step, the alignment marks are formed by exposing the black photosensitive film bx with a first exposing mask. First exposing mask 41 is provided with a pattern for bus electrodes 221, 222, 231, and 232 and a pattern for alignment marks 51.
As shown in
As described above, alignment marks 51 are formed by forming the black photosensitive film bx by coating the black photosensitive paste on glass substrate 21 and then drying it, and providing at least either the convexity or the concavity to the surface of the black photosensitive film bx.
In the embodiment, as shown in
There is a tendency for the degree of the concavity and convexity of the surface of the black photosensitive film bx to be relatively small right after the exposure and to become larger as time passes. For this reason, in the embodiment, 30 to 60 minutes of leaving time is provided after the first exposure.
The profile of the surface near alignment marks 51 in 60 minutes after the exposing is measured by the surface roughness meter by the inventors. As a result, as shown in
Although there is likelihood that only the convex portion or only the concave portion will be formed according to the degree of the diffusion and swelling, it can be recognized as the alignment marks if the amplitude of the difference reaches the above-mentioned degree.
When light is irradiated on the alignment marks, the contrast is generated to the reflected light according to the presence of the convex portion or the concave portion and imaged by a camera. Accordingly, it may be considered that a figure can be detected.
In addition to the above, the factor that the volume decreases by drying and the difference is created at the border between the unexposed region and the exposed region can be considered. In practice, it is possible to form the alignment marks in a short time by drying the glass substrate after the exposure.
Third Step
In a third step, as shown in
By repeating the exposure for forming bus electrodes 221, 222, 231, and 232 two times, it is possible to suppress the exposure failure attributable to scratches on or dust adhesion to exposing masks 41 and 42 substantially to zero. To prevent exposing misalignment between the first exposure and the second exposure, position alignment for second exposing mask 42 is performed by using the alignment mark formed during the first exposure. Furthermore, since the electrode pattern of second exposing mask 42 is designed so as to have a slightly smaller width than that of the electrode pattern of first exposing mask 41, although slight positioning misalignment occurs, a case in which the form of the formed electrode is significantly impaired does not occur.
Fourth Step
In a fourth step, scan electrodes 22 and sustain electrodes 23 are formed by developing the black photosensitive film bx. Specifically, as shown in
Next, as shown in
“Precursor” in the invention means a material obtained by heating a structure member paste in the state in which the structure member paste such as the black photosensitive paste is coated and then the organic component therein is removed, leaving the inorganic component which is not melted.
Fifth Step
In a fifth step, as shown in
Next, as shown in
In the above way, front panel 20 is completed.
Next, the manufacturing method of back panel 30 is described.
As shown in
Next, as shown in
Subsequently, as shown in
Subsequently, as shown in
As shown in
As the red phosphor, for example, (Y, Gd)BO3:Eu or (Y, V)PO4:Eu, or the like can be used. As the green phosphor, Zn2SiO4:Mn, (Y, Gd)BO3:Tb, (Y, Gd)Al3(BO3)4:Tb can be used. As the blue phosphor, for example, BaMgAl10O17:Eu or Sr3MgSi2O8:Eu can be used.
In the above way, back panel 30 is completed.
Front panel 20 and back panel 30 are placed to face each other such that display electrode pairs 24 and data electrodes 32 grade-separated cross each other, and are sealed to each other with low melting point glass at a position outside the image displaying region in which discharge cells are formed. After that, a discharge gas containing xenon is charged into and sealed in the discharge space, completing PDP 10.
As described above, the embodiment includes a first step of forming the black photosensitive film bx on glass substrate 21, a second step of forming alignment marks 51 by exposing the black photosensitive film bx, and a third step of detecting the position of glass substrate 21 by recognizing alignment marks 51 in the undeveloped state of the black photosensitive film bx.
With the method, it is possible to form the alignment marks having high precision and good visibility in a simple manner without modification of a manufacturing line or a significant increase of man hours, and to manufacture the PDP with high productivity at low cost.
Further, it is possible to simultaneously form alignment marks 51 with the first exposure in a way of only changing the pattern of first exposing mask 41 used in formation of display electrode pairs 24. Accordingly, it is possible to manufacture the PDP at low cost without the use of an additional exposing mask.
A structure of a PDP according to embodiment 2 is the same as the structure shown in
First Step
In a first step, a black photosensitive paste is applied and dried on glass substrate 21 of the front panel side, forming a black photosensitive film bx serving as a first photosensitive film.
Glass substrate 21 is cleaned with an alkali. Next, as shown in
In this instance, the black photosensitive paste is applied at a region of glass substrate 21 at which display electrode pairs 24 are not supposed to be formed but the alignment marks are supposed to be formed. In the embodiment, the region corresponds to four corner areas of glass substrate 21. This point is the same as embodiment 1.
Second Step
In a second step, as shown in
In detail, an exposure for forming first alignment mark 56 and second alignment mark 57 is performed using a first exposing mask 45 which is an exclusive exposing mask only for the alignment marks. In this instance, two alignment marks 56 and 57 are formed for every corner position of glass substrate 21 when forming the electrodes in consideration of a second exposure. First alignment mark 56 and second alignment mark 57 formed in the above way appear in the form of protrusions on the black photosensitive film bx. An exposure intensity of this instance is, for example, 300 mJ/cm2.
Next, as shown in
As described above, the convexity and concavity on the surface of the black photosensitive film bx is relatively small at the time right after the exposure of the alignment marks and a certain period of time must pass before they can be used as the alignment marks. However, in embodiment 2, since glass substrate 21 is dried when forming the conductive photosensitive film cx after performing an exposure for forming the alignment marks, the alignment marks can be formed in a short time.
Third Step
In a third step, as shown in
Next, as shown in
Fourth Step
In a fourth step, as shown in
Next, as shown in
Fifth Step
In a fifth step, as shown in
Next, as shown in
Subsequently, front panel 20 and back panel 30 prepared in the same manner as in embodiment 1 are placed to face each other such that display electrode pairs 24 and data electrodes 32 grade-separated cross each other, and are sealed to each other with low melting point glass at a position outside the image displaying region in which discharge cells are formed. After that, a discharge gas containing xenon is charged into the discharge space and sealed therein, and PDP 10 is completed.
As described above, in embodiment 2, the number of steps for forming first alignment mark 56 and second alignment mark 57 is increased. However, this method has an advantage of being capable of performing an exposure without additionally providing a leaving time. The manufacturing method of embodiment 2 is especially advantageous in the case of manufacturing the PDP in which a black stripe is provided between neighboring display electrode pairs 24. By incorporating a pattern of the alignment marks into the exposing mask used for forming the black stripe, it is possible to simultaneously perform an exposing for the black stripe and form the alignment marks. Accordingly, it is possible to manufacture the PDP without the increase of man hours.
In embodiment 1 or embodiment 2 of the invention, as shown in
By structuring scan electrode 62 and sustain electrode 63 in such a form, it is possible to decrease the resistance between bus electrode 621 and bus electrode 622 and the resistance between bus electrode 631 and bus electrode 632 and also generate a more stable discharge.
In embodiment 1 and embodiment 2 of the invention, manufacturing methods of the PDP in which one front panel 20 and one back panel 30 are manufactured for one PDP by using the glass substrate having a size corresponding to one PDP are exemplified, but the invention is not limited thereto. For example, a plurality of front panels 20 and a plurality of back panels 30 may be manufactured at the same time by using a glass substrate having a size corresponding to plural PDPs, for example, 4 or 6 PDPs. That is, the invention can be applied to a so-called multiple-sheet manufacturing method.
Specific values used in embodiment 1 and embodiment 2 are only exemplarily provided, so those may be appropriately set to the optimum values according to specification of the PDPs.
According to the manufacturing method of the flat panel display of the invention, it is possible to form the alignment mark having high precision and good visibility in a simple manner without modification of a manufacturing line or a great increase of man hours, and the invention is useful as a manufacturing method of a flat panel display such as a plasma display panel. That is, the invention is useful.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-292248 | Nov 2008 | JP | national |
| 2008-292249 | Nov 2008 | JP | national |
| 2008-292250 | Nov 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/006035 | 11/12/2009 | WO | 00 | 4/20/2010 |
