Barrier rib composition for plasma display panel

A barrier rib composition for a plasma display panel that is adapted to have a high molding property at a low pressure. In the barrier rib composition, a weight ratio of a plasticizer to a binder is less than 1. Accordingly, the barrier rib composition prevents a deformation of a substrate upon molding of the barrier rib and forms a high detailed barrier rib having a high aspect ratio.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This invention relates to a barrier rib composition for a plasma display
 panel and more particularly to a barrier rib composition for a plasma
 display panel that is adapted to have a high molding property at a low
 pressure.
 2. Description of the Related Art
 As shown in FIG. 1, a conventional plasma display panel of alternating
 current driving system (hereinafter, AC-system PDP) includes a lower glass
 substrate 10 mounted with an address electrode 12, and an upper glass
 substrate 20 mounted with a transparent electrode pair 22. A desired
 thickness of lower dielectric thick film 14 for forming a wall charge and
 a barrier rib 16 for dividing discharge cells are sequentially formed on
 the lower glass substrate 10 mounted with the address electrode 12. A
 desired thickness of fluorescent film 18 is coated on the surface of the
 lower dielectric thick film 14 and the wall surface of the barrier rib 16.
 This fluorescent film 18 is radiated by an ultraviolet ray generated
 during the plasma discharge to generate a visible light. Meanwhile, an
 upper dielectric thick film 24 and a protective film 26 are sequentially
 formed on the bottom surface of the upper glass substrate 20 mounted with
 the transparent electrode pair 22. The upper dielectric thick film 24
 forms a wall charge like the lower dielectric thick film 14, and the
 protective film 26 protects the upper dielectric thick film 24 from an
 impact of a gas ion during the plasma discharge. Such an AC-system PDP has
 discharge cells formed by isolating the lower and upper glass substrates
 14 and 16 through the barrier rib 8. He+Xe mixture gas or Ne+Xe mixture
 gas is sealed into the discharge cells.
 The barrier rib has more and more made into a high detailed shape in
 accordance with a tendency to apply a PDP to a high-resolution display. In
 other words, since a space become smaller as a resolution of the panel
 increases, it is necessary to form the barrier rib at a high level so as
 to improve the efficiency. Accordingly, the barrier rib requires a high
 aspect ratio having a narrow width and a great height. In order to meet
 such a requirement, there has been suggested the low temperature co-fired
 ceramic on metal(LTCCM) system that is capable of simplifying the process
 as well as fabricating a high detailed barrier rib having a high aspect
 ratio.
 Referring to FIGS. 2A to 2F, there is shown a method of fabricating a
 barrier rib according to the conventional LTCCM system step by step.
 First, a green sheet 30 is formed. Barrier rib material slurry is prepared
 in the first process. The barrier rib material slurry is prepared by
 mixing a barrier rib composition at a component ratio as indicated in the
 following Table:
 TABLE 1
 Barrier Rib Composition and Component Ratio
 Composition Component Ratio (weight %)
 Glass Powder 70
 Solvent 24
 Plasticizer 2
 Binder 3
 Additive 1
 wherein the component ratio is calculated assuming that a weight of glass
 be 100 weight %. As seen from the Table 1, the conventional barrier rib
 composition contains 70 weight % glass powder, 24 weight % solvent, 2
 weight % plasticizer, 3 weight % binder and 1 weight % additive. The
 barrier rib material slurry is prepared by mixing the barrier rib
 composition at a component ratio in the Table 1. The barrier rib
 composition keeps a liquid state and is used for a tape casting.
 Such a barrier rib composition is largely divided into an inorganic
 substance and an organic substance. The glass powder corresponds to the
 inorganic substance while the solvent, the plasticizer, the binder and the
 additive correspond to the organic substance. A function of the organic
 substance will be described in detail. The binder binds the glass powder
 and keeps a viscosity of the glass powder. Poly-Vinyl-Butyral(PVB) is used
 as the binder. The plasticizer prevents the green sheet 30 from being
 hardened easily to give certain flexibility to the green sheet 30.
 Butyl-Benzyl-Pthalate(BBP) is used as the plasticizer. The solvent is
 responsible for melting the binder and the plasticizer. Ethanol or
 Methyl-Ethyl-Ketone(MEK) is used as the solvent. The additive includes a
 dispersant and a surfactant so as to prevent a conglomeration of the
 powder. Fish oil is used as the additive.
 Meanwhile, an organic substance component ratio of the barrier rib is
 indicated in the following Table:
 TABLE 2
 Organic Substance Component Ratio of Barrier Rib
 Composition Component Ratio (weight %)
 Solvent 82
 Plasticizer 6
 Binder 9
 Additive 3
 wherein the component ratio is calculated assuming that a weight of the
 organic substance be 100 weight %. As seen from the Table 2, the organic
 substance of the conventional barrier rib contains 82 weight % solvent, 6
 weight % plasticizer, 9 weight % binder and 3 weight % additive.
 In the second process, a desired thickness of green sheet 30 is prepared by
 putting the barrier rib material slurry into a tape casting device(not
 shown). The green sheet 30 prepared by such a process is shown in FIG. 2A.
 Next, the green sheet 30 is disposed on a substrate 32. The green sheet 30
 is deposited on the upper part of the substrate 32 having a desired
 thickness(e.g., 0.5 mm). The substrate 32 is made from glass,
 glass-ceramic, ceramic and metal, etc. Particularly, Titanium having a
 thickness of 0.5 mm to 1 mm is mainly used as the metal. The green sheet
 30 disposed on the upper part of the substrate 32 is shown in FIG. 2B.
 Subsequently, an electrode 36 is formed on the green sheet 30. The
 electrode 36 is formed by putting the green sheet 30 deposited on the
 substrate 32 into a printer(not shown). The electrode 36 formed on the
 upper part of the green sheet 30 is shown in FIG. 2C.
 Next, an electrode protective layer 34 is formed on the upper part of the
 electrode 36. The electrode protective layer 34 protects the electrode 36
 from a sputtering caused by the discharge, and accumulates an electric
 charge produced by the discharge to lower a driving voltage. The electrode
 protective layer 34 formed on the upper part of the electrode 36 is shown
 in FIG. 2D.
 Finally, a barrier rib 40 is formed by positioning a mold 38 with a shape
 of barrier rib on the upper part of the substrate 32 and then applying a
 desired pressure thereto. The barrier rib 40 is molded at the green sheet
 30 by positioning the mold 38 having a hole 38a in a shape of barrier rib
 on the upper part of the substrate 32 and then applying a desired pressure
 thereto. In this case, a pressing is made between the mold 38 and the
 substrate 32, or a desired pressure is applied by means of a roller and
 the like. At this time, the green sheet 30 is moved into the hole 38a for
 a formation of the barrier rib by a pressure applied to the mold 38 and is
 molded into a shape of barrier rib. For instance, a pressure of 130
 kgf/cm.sup.2 is applied in the molding process. This results from a fact
 that a barrier rib having a size intended by a manufacturer can not be
 made until a hardening is rapidly progressed by a component ratio of the
 green sheet 30 so as to apply a high pressure. The process of molding the
 barrier rib is shown in FIG. 2E. Also, the barrier rib 40 in which a
 molding is completed is plasticized at a desired temperature. The barrier
 rib 40 formed by the plasticization is shown in FIG. 2F.
 As described above, the prior art has a problem in that, since a
 deformation of the substrate is caused when a high pressure is applied to
 form the barrier rib, a performance of the PDP is deteriorated. Thus, it
 is necessary to provide a barrier rib composition having an excellent
 molding property at a low pressure.
 SUMMARY OF THE INVENTION
 Accordingly, it is an object of the present invention to provide a barrier
 rib composition for a plasma display panel that is adapted to have a high
 molding property at a low pressure.
 In order to achieve these and other objects of the invention, a barrier rib
 composition for a high-brightness plasma display panel according to the
 present invention has a weight ratio of a plasticizer to a binder less
 than 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 A barrier rib composition for a high-brightness plasma display panel
 according to the present invention preferably includes 60 weight % glass
 powder, 3 weight % organic binder, 5 weight % plasticizer, 31 weight %
 solvent and 1 weight % additive.
 A method of fabricating the barrier rib will be described below. First,
 barrier rib material slurry is prepared by mixing a solvent, a
 plasticizer, an organic binder and an additive with glass powder.
 Subsequently, a green sheet is formed by putting the barrier rib slurry
 into a tape casting device (not shown). A high detailed barrier rib having
 a high aspect ratio at a low pressure is obtained by treating the green
 sheet made in this manner in similarity to the process as shown in FIGS.
 2A to 2F.
 Hereinafter, an embodiment of the barrier rib composition for a plasma
 display panel according to the present invention will be described. A
 composition and a component ratio of the barrier rib according to an
 embodiment of the present invention is indicated in the following Table:
 TABLE 3
 Barrier Rib Composition and Component ratio
 Composition Component Ratio (weight %)
 Glass Powder 60
 Solvent 31
 Plasticizer 5
 Binder 3
 Additive 1
 wherein the component ratio is calculated assuming that a weight of glass
 be 100 weight %.
 Meanwhile, an organic substance component ratio of the barrier rib is
 indicated in FIG. 3. An organic substance of the barrier rib according to
 the present invention contains 50 to 90 weight % solvent, 1 to 30 weight %
 plasticizer, 0.5 to 30 weight % binder and 0.1 to 10 weight % additive.
 Herein, an organic substance component ratio of the barrier rib was
 calculated assuming that a weight of the organic substance be 100 weight
 %. Functions of the plasticizer, the binder, the additive and the solvent
 will be omitted because they have been explained sufficiently with
 reference to FIG. 2A earlier. In this case, as shown in FIG. 3, it is
 preferable to allow a weight ratio of the plasticizer to the binder to be
 less than 1 so as to form a slurry. Particularly, it is desirable to keep
 a weight ratio of the plasticizer to the binder at a range of 0.3 to 1 for
 the purpose of fabricating a barrier rib having an excellent molding
 property. Accordingly, a green sheet satisfying the barrier rib component
 ratio according to the present invention has a good molding property at a
 low pressure.
 Meanwhile, at a designer's intent, the organic substance according to the
 present invention has a component ratio as indicated in the following
 Table:
 TABLE 4
 Organic Substance Component Ratio of Barrier Rib
 Composition Component Ratio (weight %)
 Solvent 75-85
 Plasticizer 5-10
 Binder 3-7
 Additive 1-5
 As seen from the Table 4, an organic substance of the barrier rib according
 to the present invention contains 75 to 85 weight % solvent, 5 to 10
 weight % plasticizer, 3 to 7 weight % binder and 1 to 5 weight % additive.
 In the case of the organic substance component ratio as indicated in the
 Table 4, the barrier rib has an improved molding property.
 Hereinafter, a method of fabricating a barrier rib using the barrier rib
 composition for a plasma display panel according to the present invention
 will be described. First, a green sheet 30 is formed. A barrier rib
 material slurry is prepared in the first process. The barrier rib material
 slurry is prepared by mixing a barrier rib composition at a component
 ratio as indicated in the Table 3. In this case, it is desirable that the
 organic substance composition of the barrier rib be kept at a range
 satisfying a component ratio as shown in FIG. 3. It is preferable to allow
 a weight ratio of the plasticizer to the binder to be less than 1 so as to
 form a slurry. Particularly, it is desirable to keep a weight ratio of the
 plasticizer to the binder at a range of 0.3 to 1 for the purpose of
 fabricating a barrier rib having an excellent molding property. In the
 second process, a desired thickness of green sheet is formed by putting
 the barrier rib material slurry into a tape casting device(not shown).
 Meanwhile, the organic component ratio as indicated in the Table 4 may be
 used at a designer's intent so that a molding property of the barrier rib
 can be improved. The barrier rib material slurry keeps a liquid state and
 is used for the tape casting. The barrier rib material slurry is put into
 the tape casting device to form the green she et.
 Subsequently, a barrier rib formation method using the green sheet will be
 omitted because it has the process similar to FIGS. 2B to 2F. Accordingly,
 a barrier rib for a PDP formed by utilizing the green sheet having the
 barrier rib composition according to the present invention has an improved
 molding property in comparison to the prior art.
 For instance, a pressure of 100 kgf/cm.sup.2 is applied to the mold in the
 molding process. This reduces 30% the pressure in comparison to a molding
 using the conventional barrier rib composition to thereby prevent a
 deformation of the substrate generated by a pressure applied in the
 molding process. Also, the barrier rib composition according to the
 present invention has an excellent molding property to form a barrier rib
 having a high detailed shape and a high aspect ratio. As described above,
 a barrier rib composition for a plasma display device according to the
 present invention applies a low pressure to form a barrier rib, so that it
 prevents a deformation of the substrate and forms a high detailed barrier
 rib having a high aspect ratio.
 Although the present invention has been explained by the embodiments shown
 in the drawings described above, it should be understood to the ordinary
 skilled person in the art that the invention is not limited to the
 embodiments, but rather that various changes or modifications thereof are
 possible without departing from the spirit of the invention. Accordingly,
 the scope of the invention shall be determined only by the appended claims
 and their equivalents.