Patent Application
20080026320
These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.
Aspects of the present invention will now be described in more detail. Aspects of the present invention provide a photosensitive paste composition comprising a metal oxide sol and an inorganic compound, wherein the average optical refractive index (N1) of the metal oxide sol and the average light optical refractive index (N2) of the inorganic compound satisfy Equation 1 below:
−0.2≦N1−N2≦0.2 Equation 1
Unlike a conventional photosensitive paste composition, the photosensitive paste composition comprises a metal oxide sol. The metal oxide sol is a sol-state material in which a metal oxide having a diameter of several to tens of nm is dispersed in an organic mixture. The metal oxide is dispersed in the organic mixture in a stable state in which phenomena such as agglomeration or precipitation do not occur. The metal oxide sol can be used in combination with an inorganic compound. A barrier rib prepared using the photosensitive paste composition comprising a metal oxide sol has higher reflectivity than a conventional photosensitive barrier rib, and thus provides increased luminance, functions as a support in order that the shape of the barrier rib is not deformed in a sintering process, and provides increased compactness of the barrier rib, thereby reducing its surface roughness.
A metal component of the metal oxide sol can be, but is not limited to, at least one metal component selected from the group consisting of Si, Ti, Al, Zr, Ta, Ge, Y, Zn and the like. The metal oxide sol is generally prepared by preparing a metal oxide precursor from an alkoxide or halide compound using hydrolysis and condensation, and dispersing the prepared metal oxide precursor in an organic mixture. Herein, a surface modifier can be additionally introduced as desired in the process of preparing the metal oxide precursor.
In the preparation of the metal oxide precursor, an average particle diameter of the metal oxide is determined by the degree of the hydrolysis and condensation. As a non-limited example, the metal oxide may preferably have an average particle diameter of 1-60 nm. As a more specific, non-limiting example, the metal oxide may have an average particle diameter of 2-40 nm. As an even more specific, non-limiting example, the metal oxide may have an average particle diameter of 4-20 nm. When the average particle diameter of the metal oxide is less than 1 nm, its preparation is difficult and it is difficult for the metal oxide to be uniformly dispersed in an organic mixture. When the average particle diameter of the metal oxide is greater than 60 nm, the metal oxide scatters light when exposed to light, and thus interferes with light transmittance.
The average light refractive index of the metal oxide of the metal oxide precursor may be in the range of 1.3-3.0. The average light refractive index of a metal oxide sol prepared by dispersing the metal oxide precursor in an organic mixture may be in the range of 1.4-2.0. When the average light refractive indices of the metal oxide precursor and the metal oxide sol are not within these ranges, it is difficult to prepare a photosensitive paste composition having a refractive index within the refractive index range given in Equation 1 above.
The term “average light refractive index of the metal oxide sol” refers to the average light refractive index measured in the absence of a solvent. The light refractive index of the metal oxide sol is measured using a light refractive index measuring apparatus by coating the metal oxide sol onto a transparent film or a glass substrate, and then drying the coated metal oxide sol for several to tens of minutes at a temperature in the range of 80-100° C.
In addition, in the preparation of the metal oxide sol by dispersing the metal oxide precursor in an organic mixture, the amount of the metal oxide may be 5-50 parts by volume with respect to 100 parts by volume of the organic mixture. When the amount of the metal oxide is less than 5 parts by volume with respect to 100 parts by volume of the organic mixture, the increase in the reflective index of the barrier rib is not great. When the amount of the metal oxide is greater than 50 parts by volume with respect to 100 parts by volume of the organic mixture, a crosslinking reaction is insufficiently performed when the metal oxide sol is exposed to light, and thus the barrier rib can not have a desired shape.
When the metal oxide sol is mixed with an inorganic compound, two mixing ratios are taken into consideration. One is the mixing ratio of the refractive index of the metal oxide sol and the inorganic compound. In particular, the value of the refractive index of the metal oxide sol and the inorganic compound may, as a non-limiting example, satisfy Equation 1 given above. As a more specific, non-limiting example, the value of the refractive index of the metal oxide sol and the inorganic compound may satisfy Equation 2 below. a As an even more specific, non-limiting example, the value of the refractive index of the metal oxide sol and the inorganic compound may satisfy Equation 3 below.
−0.1≦N1−N2≦0.1 Equation 2
−0.05≦N1−N2≦0.05 Equation 3
where each of N1 and N2 is the same as defined in Equation 1.
When the relation between the refractive indices of the metal oxide sol and the inorganic compound is beyond the range given in Equation 1, transmittance of light irradiated during exposure to light is reduced so that a barrier rib can not be formed by a single exposure. When the relation between the refractive indices of the metal oxide sol and the inorganic compound is in the range of Equation 3 given above, light exposure sensitivity is excellent, and the scattering of irradiated light is reduced so that the straightness of the barrier rib pattern is also excellent.
The amount of the metal oxide in the metal oxide sol with respect to the inorganic compound in the photosensitive paste composition should also be taken into consideration, when the mixing ratio of metal oxide sol to the inorganic compound is determined. As a non-limiting example, the amount of the metal oxide may be 3-30 parts by volume with respect to 100 parts by volume of the inorganic compound. As a more specific, non-limiting example, the amount of the metal oxide may be 5-20 parts by volume with respect to 100 parts by volume of the inorganic compound. When the amount of the metal oxide is less than 3 parts by volume with respect to 100 parts by volume of the inorganic compound, the increase in the reflective index of a barrier rib is not great. When the amount of the metal oxide is greater than 30 parts by volume with respect to 100 parts by volume of the inorganic compound, the inorganic compound cannot be fully sintered, and thus the compactness of a barrier rib is reduced.
The average thermal expansion coefficient α of the metal oxide and the inorganic compound may satisfy Equation 4 below.
Substrate thermal expansion coefficient×0.9≦α≦Substrate thermal expansion coefficient Equation 4
When the average thermal expansion coefficient of the metal oxide and the inorganic compound is beyond the range of Equation 4, in the severe case, the substrate bends or breaks after sintering.
The inorganic compound of the photosensitive paste composition used according to aspects of the present invention may have an average light refractive index within the range of 1.5-1.8. When the average light refractive index of the inorganic compound is beyond this range, the difference between the light refractive index of the inorganic compound and the light refractive index of the metal oxide sol is so large that a barrier rib can not be formed by a single exposure to light.
The inorganic compound comprises a glass frit having a low melting point and a glass frit having a high melting point. The glass frit having a low melting point of the inorganic compound is sintered in a sintering process, thereby forming a compact barrier rib membrane, and the glass frit having a high melting point maintains the shape of the barrier rib membrane in the sintering process.
The particle shape of the glass frit having a low melting point is not particularly limited, but, as a non-limiting example, may be spherical or almost spherical. The nearer the particle shape of the glass frit having a low melting point is to being spherical, the more improved are the characteristics with respect to the packing ratio and ultraviolet ray transmittance. The average particle diameter of the glass frit having a low melting point may have a median value D50 of 2-5 μm, a minimum value Dmin of 0.1 μm and a maximum value Dmax of 20 μm. When the median value D50 is less than 2 μm, or the minimum value Dmin is less than 0.1 μm, the dispersibility of the glass frit having a low melting point is reduced so that the printing properties are worsened, and a contraction ratio thereof is high in a sintering process so that a barrier rib having a desired shape cannot be obtained. When the median value D50 is greater than 5 μm, or the maximum value Dmax is greater than 20 um, the compactness and straightness of the barrier rib are reduced.
The softening temperature Ts of the glass frit having a low melting point may satisfy Equation 5 below.
Sintering temperature−80° C.<Ts<sintering temperature Equation 5
When the softening temperature of the glass frit having a low melting point is less than the sintering temperature minus 80° C., the shape of a barrier rib is deformed in the sintering process. When the softening temperature of the glass frit having a low melting point is greater than the sintering temperature, sintering is not fully performed.
The amount of the glass frit having a low melting point may be 70-100 parts by volume with respect to 100 parts by volume of the inorganic compound. When the amount of the glass frit having a low melting point is less than 70 parts by volume with respect to 100 parts by volume of the inorganic compound, sintering is not fully performed.
Examples of the glass frit having a low melting point include, but are not limited to, a complex oxide comprising at least three oxides selected from oxides of Pb, Bi, Si, B, Al, Ba, Zn, Mg, Ca, P, V, Mo, Te and the like. The glass frit having a low melting point can be used alone or in combination with two complex oxides. More particularly, the glass frit having a low melting point may comprise a compound selected from a PbO—B2O3 based glass, a PbO—SiO2—B2O3 based glass, a Bi2O3—B2O3 based glass, a Bi2O3—SiO2—B2O3 based glass, a SiO2—B2O3—Al2O3 based glass, a SiO2—B2O3—BaO based glass, a SiO2—B2O3—CaO based glass, a ZnO—B2O3—Al2O3 based glass, a ZnO—SiO2—B2O3 based glass, a P2O5 based glass, a SnO—P2O5 based glass, a V2O5—P2O5 based glass, a V2O5—Mo2O3 based glass, and a V2O5—P2O5—TeO2 based glass.
The particle shape of the glass frit having a high melting point is not particularly limited, but, as a non-limiting example, may be spherical or almost spherical. The nearer the particle shape of the glass frit having a high melting point is to being spherical, the more improved are the characteristics with respect to the packing ratio and ultraviolet ray transmittance. The average particle diameter of the glass frit having a high melting point may have a median value of 1-4 μm, a minimum value of 0.1 μm and a maximum value of 20 μm. When the median value is less than 1 μm, or the minimum value is less than 0.1 μm, light exposure sensitivity is reduced and a contraction ratio is high in a sintering process so that a barrier rib having a desired shape cannot be obtained. When the median value is greater than 5 μm, or the maximum value is greater than 20 μm, the compactness and straightness of the barrier rib are reduced.
The softening temperature Ts of the glass frit having a high melting point may satisfy Equation 6 below.
T
s>sintering temperature+20° C. Equation 6
When the softening temperature of the glass frit having a high melting point is less than sintering temperature+20° C., the shape of the barrier rib is deformed in a sintering process.
The amount of the glass frit having a high melting point may be 0-30 parts by volume with respect to 100 parts by volume of the inorganic compound. When the amount of the glass frit having a high melting point is greater than 30 parts by volume with respect to 100 parts by volume of the inorganic compound, sintering is not fully performed.
Examples of the glass frit having a high melting point include, but are not limited to, a complex oxide comprising at least three oxides selected from the group consisting of Si oxide, B oxide, Al oxide, Ba oxide, Zn oxide, Mg oxide, Ca oxide, and the like. The glass frit having a high melting point can be used alone or in combination with two complex oxides. More particularly, the glass frit having a high melting point may comprise a compound selected from a SiO2—B2O3—BaO based glass, a SiO2—B2O3—CaO based glass, a SiO2—B2O3—MgO based glass, a SiO2—B2O3—CaO—BaO based glass, a SiO2—B2O3—CaO—MgO based glass, a SiO2—Al2O3—BaO based glass, a SiO2—Al2O3—CaO based glass, a SiO2—Al2O3—MgO based glass, a SiO2—Al2O3—BaO—CaO based glass, a SiO2—Al2O3—CaO—MgO based glass, and the like.
Average light refractive indices of the glass frit having a low melting point and the glass frit having a high melting point may be in the range of 1.5-1.8 as described above. In addition, a difference between a refractive index N3 of the glass frit having a low melting point and a refractive index N4 of the glass frit having a high melting point may satisfy Equation 7 below. As a specific, non-limiting example, the difference between the refractive index N3 of the glass frit having a low melting point and the refractive index N4 of the glass frit having a high melting point may satisfy Equation 8 below. As a specific, non-limiting example, the difference between the refractive index N3 of the glass frit having a low melting point and the refractive index N4 of the glass frit having a high melting point may satisfy Equation 9 below.
−0.2≦N3−N4≦0.2 Equation 7
−0.1≦N3−N4≦0.1 Equation 8
−0.05≦N3−N4≦0.05 Equation 9
When the difference between the light refractive indices of the glass frit having a low melting point and the glass frit having a high melting point is beyond the range of Equation 7, transmittance of light irradiated during exposure to light is reduced so that a barrier rib cannot be formed by a single exposure to light.
The organic mixture used according to aspects of the present invention comprises a binder, a photo initiator and a cross linking agent. In addition, the organic mixture may comprise a solvent for additives used to improve characteristics of a paste and to adjust viscosity or the like.
For the binder, an acryl-based resin having a carboxyl group is generally used, which makes developing possible in an alkali developing solution and makes a characteristic adjustment according to a change in composition of components easy. The acryl-based resin having a carboxyl group makes it possible for developing to be performed in an aqueous alkali solution, makes it easier for inorganic components to be dispersed in the photosensitive paste composition, and provides appropriate viscosity and elasticity. The acryl-based resin having a carboxyl group can be prepared by copolymerization of a monomer having a carboxyl group and a monomer having an ethylene unsaturated group.
As a non-limiting example, the monomer having a carboxyl group may be at least one selected from the group consisting of an acrylic acid, a methacrylic acid, a fumaric acid, a maleic acid, a vinylacetic acid, and an anhydride thereof. As specific non-limiting examples, the monomer having an ethylene unsaturated group may be at least one selected from the group consisting of methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, sec-butyl(meth)acrylate, isobutyl(meth)acrylate, tert-butyl(meth)acrylate, n-pentyl(meth)acrylate, aryl(meth)acrylate, phenyl(meth)acrylate, benzyl(meth)acrylate, butoxyethyl(meth)acrylate, butoxytriethyleneglycol(meth)acrylate, cyclohexyl(meth)acrylate, dicyclopentanyl(meth)acrylate, dicyclopentenyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, glycerol(meth)acrylate, glycidyl(meth)acrylate, isobornyl(meth)acrylate, isodexyl(meth)acrylate, isooctyl(meth)acrylate, lauryl(meth)acrylate, 2-methoxyethyl(meth)acrylate, methoxyethyleneglycol(meth)acrylate, methoxydiethyleneglycol(meth)acrylate, phenoxyethyl(meth)acrylate, stearyl(meth)acrylate, 1-naphthyl(meth)acrylate, 2-naphthyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, aminoethyl(meth)acrylate, styrene, α-methylstyrene, α-2-dimethylstyrene, 3-methylstyrene, 4-methylstyrene, and the like.
In addition, a cross-linkable group that can induce a cross-linking reaction between a monomer having a carboxyl group and an ethylenically unsaturated monomer may be further added to the binder. As non-limiting examples, the ethylenically unsaturated monomer may be selected from the group consisting of acryloylchloride, methacryloylchloride, allylchloride, glycidylacrylate, glycidylmethacrylate, 3,4-epoxycyclohexylmethylacrylate, and 3,4-epoxycyclohexylmethylmethacrylate, 3,4-epoxycyclohexylmethylacrylate, 3,4-epoxycyclohexylmethylmethacrylate and the like.
The copolymer can be used alone as the binder. However, for the purpose of enhancing the film leveling properties and/or thixotropic properties of the organic mixture, the copolymer may be mixed with an agent that enhances the film leveling properties and/or thixotropic properties. As a non-limiting example, the copolymer may be mixed with at least one selected from the group consisting of cellulose, methylcellulose, ethylcellulose, n-propylcellulose, hydroxyethylcellulose, 2-hydroxyethylcellulose, methyl-2-hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxybutylmethylcellulose, hydroxypropylmethylcellulose phthalate, cellulose nitrate, cellulose acetate, cellulose triacetate, cellulose acetate butylate, cellulose acetate hydrogenphthalate, cellulose acetate propionate, cellulose propionate, (acrylamidomethyl)cellulose acetate propionate, (acrylamidomethyl)cellulose acetate butylate, cyanoethylate cellulose, pectic acid, chitosan, chitin, carboxymethylcellulose, carboxymethylcellulose sodium salt, carboxyethylcellulose, and carboxyethylmethylcellulose.
The copolymer may have a weight average molecular weight in a range of 500-100,000 g/mol and an acid value of 50-300 mg KOH/g. If the weight average molecular weight of the copolymer is less than 500 g/mol, the dispersibility of the inorganic compound in the paste is reduced. If the weight average molecular weight of the copolymer is greater than 100,000 g/mol, the developing speed is too slow or the developing is not performed. In addition, if the acid value of the copolymer is less than 50 mg KOH/g, the developing property deteriorates. If the acid value of the copolymer is greater than 300 mg KOH/g, even an exposed region may be developed.
The amount of binder may be 30-80 parts by weight with respect to 100 parts by weight of the organic mixture. When the amount of the binder is less than 30 parts by weight with respect to 100 parts by weight of the organic mixture, the coating property and dispersibility of the paste are reduced. When the amount of the binder is greater than 80 parts by weight with respect to 100 parts by weight of the organic mixture, a cross-linking reaction is insufficiently performed during exposure to light, and thus a pattern having a desired shape cannot be obtained.
The photo initiator produces radicals upon exposure to light, such as, for example, light irradiated by an exposure apparatus, and the produced radicals induce a polymerization reaction of the crosslinking agent having an ethylene unsaturated group to create a product that is insoluble with respect to a developing solution. Since the photo initiator requires high sensitivity, at least two of the following photo initiators may be combined. Examples of the photo initiator include, but are not limited to, combinations of (i) an imidazole-based compound, (ii) a triazine-based compound, (iii) an aminoacetophenone-based compound, (iv) a benzophenone and acetophenone based compound, (v) a benzoin-based compound, (vi) a titanocene-based compound, (vii) an oxadiazole-based compound, (viii) a thioxanthone-based compound, (ix) a (bis)acylphosphineoxide-based compound, and (x) an organic boron salt compound.
As non-limiting examples, the imidazole-based compound may be 2,2′-bis(o-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole, 2,2′-bis(o-bromophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole, 2,2′-bis(o-chlorophenyl)-4,4′,5,5′-tetra(o,p-dichlorophenyl)-1,2′-biimidazole, 2,2′-bis(o,p-dichlorophenyl)-4,4′,5,5′-tetra(o,p-dichlorophenyl)-1,2′-biimidazole, 2,2′-bis(o-chlorophenyl)-4,4′,5,5′-tetra(m-methoxyphenyl)-1,2′-biimidazole, 2,2′-bis(o-methylphenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole or the like.
As non-limiting examples, the triazine-based compound may be 2,4,6-tris(trichloromethyl)-s-triazine, 2,4,6-tris(tribromomethyl)-s-triazine, 2-propyonyl-4,6-bis(trichloromethyl)-s-triazine, 2-benzoyl-4,6-bis(trichloromethyl)-s-triazine, 2-(4-chlorophenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-4-bis(4-methoxyphenyl)-6-trichloromethyl)-s-triazine, 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-chlorostyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-aminophenyl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(3-chlorophenyl)-6-trichloromethyl-s-triazine, 2-(4-aminostyryl)-4,6-bis(dichloromethyl)-s-triazine or the like.
As non-limiting examples, the aminoacetophenone compound may be 2-methyl-2-amino(4-morpholinophenyl)ethane-1-one, 2-ethyl-2-amino(4-morpholinophenyl)ethane-1-one, 2-propyl-2-amino(4-morpholinophenyl)ethane-1-one, 2-butyl-2-amino(4-morpholinophenyl)ethane-1-one, 2-methyl-2-amino(4-morpholinophenyl)propane-1-one, 2-methyl-2-amino(4-morpholinophenyl)butane-1-one, 2-ethyl-2-amino(4-morpholinophenyl)propane-1-one, 2-ethyl-2-amino(4-morpholinophenyl)butane-1-one, 2-methyl-2-methylamino(4-morpholinophenyl)propane-1-one, 2-methyl-2-dimethylamino(4-morpholinophenyl)propane-1-one, 2-methyl-2-diethylamino(4-morpholinophenyl)propane-1-one or the like.
As non-limiting examples, the benzophenone and acetophenone based compound may be benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 3,3′-dimethyl-4-methoxybenzophenone, 4-benzoyl-4′-methyldiphenylsulfide, 4,4′-bis(N,N-dimethylamino)benzophenone, 4,4′-bis(N,N-diethylamino)benzophenone, 3,3′,4,4′-tetra(tert-butylperoxycarbonyl)benzophenone, (2-acryloyloxy ethyl)(4-benzoylbenzyl)dimethylammonium bromide, 4-(3-dimethylamino-2-hydroxypropyl)benzophenone, (4-benzoylbenzyl)trimethylammonium chloride, methochloride monohydrate, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-(4-isopropylphenyl)-2-methylpropane-1-one, 1-hydroxycyclohexylphenylketone, 4-tert-butyl-trichloroacetophenone or the like.
As non-limiting examples, the benzoin-based compound may be benzoin, benzoinmethylether, benzomethylether, benzoinisopropylether, benzoinisobutylether or the like.
As non-limiting examples, the titanocene-based compound may be dicyclopentadienyl-Ti-dichloride, dicyclopentadienyl-Ti-diphenyl, dicyclopentadienyl-Ti-bis(2,3,4,5,6-pentafluorophenyl), dicyclopentadienyl-Ti-bis(2,3,5,6-tetrafluorophenyl), dicyclopentadienyl-Ti-bis(2,4,6-trifluorophenyl), dicyclopentadienyl-Ti-bis(2,6-difluorophenyl), dicyclopentadienyl-Ti-bis(2,4-difluorophenyl), bis(methylcyclopentadienyl)-Ti-bis(2,3,4,5,6-pentafluorophenyl), bis(methylcyclopentadienyl)-Ti-bis(2,3,5,6-tetrafluorophenyl), bis(methylcyclopentadienyl)-Ti-bis(2,4,6-trifluorophenyl), bis(methylcyclopentadienyl)-Ti-bis(2,6-difluorophenyl), bis(methylcyclopentadienyl)-Ti-bis(2,4-difluorophenyl) or the like.
As non-limiting examples, the oxadiazole-based compound may be 2-phenyl-5-trichloromethyl-1,3,4-oxadiazole, 2-(p-methylphenyl)-5-trichloromethyl-1,3,4-oxadiazole, 2-(p-methoxyphenyl)-5-trichloromethyl-1,3,4-oxadiazole, 2-styryl-5-trichloromethyl-1,3,4-oxadiazole, 2-(p-methoxystyryl)-5-trichloromethyl-1,3,4-oxadiazole, 2-(p-butoxystyryl)-5-trichloromethyl-1,3,4-oxadiazole or the like.
As non-limiting examples, the thioxanthone-based compound may be thioxanthone, 2,4-diethylthioxanthone, isopropyl thioxanthone, 2,4-diisopropylthioxanthone, 2-chlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2-(3-dimethylamino-2-hydroxypropoxy)-3,4-dimethyl-9H-thioxanthone-9-one methochloride or the like.
As non-limiting examples, the (bis)acylphosphineoxide-based compound may be 2,4,6-trimethylbenzoyldiphenylphosphineoxide; bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphineoxide, bis(2,6-dichlorobenzoyl)phenylphosphineoxide, bis(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphineoxide, bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide or the like.
As non-limiting examples, the organic boron salt compound may be a quaternary organic boron salt compound represented by Formula I below:
where each of R1, R2, R3, and R4 is independently an alkyl group, an aryl group, an aralkyl group, an alkenyl group, an alkynyl group, a silyl group, a heterocyclic group, or a halogen atom that can have substituents if needed, and Z+ represents an arbitrary positive ion.
The organic boron salt compound comprises a quaternary organic boron negative ion and a positive ion Z+. In Formula I, each of R1, R2, R3, and R4 is independently an alkyl group, an aryl group, an aralkyl group, an alkenyl group, an alkynyl group, a silyl group, a heterocyclic group, or a halogen atom, and these groups may have substituents if needed. As non-limiting examples, the substituents may be a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-octyl group, an n-dodecyl group, a cyclopentyl group, a cyclohexyl group, a phenyl group, a tolyl group, a xylyl group, an anisyl group, a biphenyl group, a diphenylmethyl group, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, an isobutoxy group, a tert-butoxy group, a methylenedioxy group, an ethylenedioxy group, a phenoxy group, a naphthoxy group, a benzyloxy group, a methylthio group, a phenylthio group, a 2-furyl group, a 2-thienyl group, a 2-pyridyl group, a boron group or the like.
As non-limiting examples, the quaternary organic boron negative ion of the organic boron salt compound may be methyltriphenylborate, n-butyltriphenylborate, n-octyltriphenylborate, n-dodecyltriphenylborate, sec-butyltriphenylborate, tert-butyltriphenylborate, benzyltriphenylborate, n-butyltri(p-anisyl)borate, n-octyltri(p-anisyl)borate, n-dodecyltri(p-anisyl)borate, n-butyltri(p-tolyl)borate, n-butyltri(o-tolyl)borate, n-butyltri(4-tert-butylphenyl)borate, n-butyltri(4-fluoro-2-methylphenyl)borate, n-butyltri(4-fluorophenyl)borate, n-butyltri(1-naphthyl)borate, ethyltri(1-naphthyl)borate, n-butyltri[1-(4-methylnaphthyl)]borate, methyltri[1-(4-methylnaphthyl)]borate, triphenylsilyltriphenylborate, trimethylsilyltriphenylborate, tetra-n-butylborate, di-n-butyldiphenylborate, tetrabenzylborate or the like. In R1, R2, R3, and R4 of the quaternary organic boron negative ion, it is preferred, but not necessary in all aspects, that R1 be an alkyl group, and R2, R3, and R4 be a naphthyl group in order to maintain balance of stability and photoreactivity of the organic boron salt compound.
As non-limiting examples, the positive ion Z+ of the organic boron salt compound may be tetramethylammonium, tetraethylammonium, tetra-n-butylammonium, tetraoctylammonium, N-methylquinolium, N-ethylquinolium, N-methylpyridinium, N-ethylpyridinium, tetramethylphosphonium, tetra-n-butylphosphonium, trimethylsulfonium, triphenylsulfonium, trimethylsulfoxonium, diphenyl]odonium, di(4-tert-butylphenyl)iodonium, Li positive ion, Na positive ion, K positive ion or the like.
The photo initiator may be used in combination with a sensitizer for obtaining a higher sensitivity. The selection of the sensitizer depends on the photo initiator, and some of the photo initiators described above may also function as a sensitizer of other photo initiators. For example, when an imidazole-based photo initiator is used, a benzophenone-based or thioxanthone-based compound functions as both a photo initiator and a sensitizer, and thus may be used in combination. A sensitizer that can be used in combination with the organic boron salt compound may be any material that can absorb light and decompose the organic boron salt compound. As non-limiting examples, compounds having such functions may be selected from a benzophenone-based compound, a thioxanthone-based compound, a quinone-based compound, and positive ionic dyes. The benzophenone-based compound and the thioxanthone-based compound may be selected from the compounds described above. The quinone-based compound may be quinhydrone, 2,5-dichloro-1,4-benzoquinone, 2,6-dichloro-1,4-benzoquinone, phenyl-1,4-benzoquinone, 2-methyl-1,4-naphthoquinone, 2,3-dichloro-1,4-naphthoquinone, 2-hydroxy-1,4-naphthoquinone, 5-hydroxy-1,4-naphthoquinone, 2-amino-3-chloro-1,4-naphthoquinone, 2-chloro-3-morpholino-1,4-naphthoquinone, anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2,3-dimethylanthraquinone, 1-chloroanthraquinone, 2-chloroanthraquinone, 1,4-dichloroanthraquinone, 2-(hydroxymethyl)anthraquinone, 9,10-phenanthrenquinone or the like. The positive ionic dyes may be a dye having a maximum absorption wavelength within the range of 300 nm to near-infrared wavelengths, and may be generally yellow, orange, red, green or blue. Examples of the positive ionic dyes may include Basic yellow 11, Astrazon orange G, Thioflavin T, Auramine O, Indocyanine green, 1,1′,3,3,3′,3′-hexamethylindocarbocyanine iodine, IR-786 perchlorate and the like.
The amount of the photo initiator may be 1-20 parts by weight with respect to 100 parts by weight of the organic mixture. When the amount of the photo initiator is less than 1 part by weight with respect to 100 parts by weight of the organic mixture, the light exposure sensitivity is reduced. When the amount of the photo initiator is greater than 20 parts by weight with respect to 100 parts by weight of the organic mixture, even a non-exposed region is not developed.
As non-limiting examples, the cross-linking agent can comprise monoacrylates and multi-functional acrylates. The mono(meth)acrylates may be, but are not limited to, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, allyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, butoxyethyl (meth)acrylate, butoxytriethyleneglycol (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, glycerol (meth)acrylate, glysidyl (meth)acrylate, isobornyl (meth)acrylate, isodexyl (meth)acrylate, isooctyl (meth)acrylate, lauryl (meth)acrylate, 2-methoxyethyl (meth)acrylate, methoxyethyleneglycol (meth)acrylate, methoxydiethyleneglycol (meth)acrylate, phenoxyethyl (meth)acrylate, stearyl (meth)acrylate, 1-naphthyl (meth)acrylate, 2-naphthyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, aminoethyl (meth)acrylate, and the like. The multi-functional acrylates may be, but are not limited to, di(meth)acrylates such as 1,6-hexanediol diacrylate, (ethoxylated) 1,6-hexanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanoldiol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tripropyleneglycol di(meth)acrylate, dipropyleneglycol di(meth)acrylate, tetraethyleneglycol di(meth)acrylate, (ethoxylated)n (n=2 to 8) bisphenol A di(meth)acrylate, or bisphenol A epoxy di(meth)acrylate; triacrylates such as trimethylolpropane tri(meth)acrylate, (ethoxylated) trimethylolpropane tri(meth)acrylate, propoxylated) glycerin tri(meth)acrylate, pentaeritritol tri(meth)acrylate, or (propoxylated) trimethylolpropane-3-tri(meth)acrylate; tetra(meth)acrylates such as ditrimethylolpropane tetra(meth)acrylate, tetramethylolpropane tetra(meth)acrylate, or pentaeritritol tetra(meth)acrylate; penta(meth)acrylates such as dipentaeritritol penta(meth)acrylate; hexa(meth)acrylates such as dipentaeritritol hexa(meth)acrylate, or the like. The cross-linking agent may be at least one selected from the group consisting of the mono and multi-functional acrylates described above.
The amount of the cross-linking agent may be 15-60 parts by weight with respect to 100 parts by weight of the organic mixture. When the amount of the cross-linking agent is less than 15 parts by weight with respect to 100 parts by weight of the organic mixture, the light exposure sensitivity is reduced. When the amount of the cross-linking agent is greater than 60 parts by weight with respect to 100 parts by weight of the organic mixture, the barrier rib may be detached or disconnected in a sintering process.
The photosensitive paste composition may further comprise additives. As non-limiting examples, the additives can be a polymerization inhibitor and antioxidant that improves the storage stability of the photosensitive paste compound, an ultraviolet absorbent that improves the resolution, an antifoaming agent that reduces air bubbles in the composition, a dispersant that improves dispersibility, a leveling agent that improves the smoothness of the membrane during printing, a plasticizer that improves the thermal decomposition characteristics, a thixotropic agent that provides the thixotropy characteristics, or the like.
The solvent may be a solvent that does not reduce the dispersibility of the metal oxide, dissolves the binder and the photo initiator, is satisfactorily mixed with the cross-linking agent and extra additives, and has a low boiling point of at least 150° C. When the boiling point of the solvent is less than 150° C., the possibility of volatilization is high in the process of preparing the photosensitive paste compound, particularly in a 3-roll mill process, and the solvent may be volatilized so quickly during printing that the print state is not good. The solvent that can satisfy the conditions described above may be, but is not limited to, at least one selected from the group consisting of ethyl carbitol, butyl carbitol, ethyl carbitol acetate, butyl carbitol acetate, texanol, terpine oil, diethylene glycol, dipropylene glycol, tripropylene glycol, dipropyleneglycol methylether, dipropyleneglycol ethylether, dipropyleneglycol monomethylether acetate, y-butyrolactone, cellosolve acetate and butyl cellosolve acetate.
The amount of the solvent is not particularly limited, but the solvent should be used in a sufficient amount to provide a viscosity of the paste suitable for printing or coating.
The photosensitive paste composition of the present invention can be prepared by using the following procedures.
First, a metal oxide sol is prepared. The metal oxide sol is prepared by preparing a metal oxide precursor and then dispersing it in an organic mixture. The organic mixture comprises a binder, a photo initiator, a cross-linking agent and additives, and may comprise a solvent if needed. The organic mixture is prepared as a uniform and transparent solution such that each component of the organic mixture is mixed and fully stirred.
The prepared metal oxide sol is mixed with an inorganic compound to prepare the paste. The paste may be mixed using a planetary mixer (PLM) or the like, and then mechanically mixed thoroughly by 3-roll milling. When the process of 3-roll milling is terminated, the resultant is filtered using, for example, a stainless steel (SUS) mesh #400 filter, and then degassed using a vacuum pump to prepare a photosensitive paste composition.
Aspects of the present invention provide a barrier rib of a plasma display panel (PDP), which is prepared using the photosensitive paste composition. A method of preparing the barrier rib of the PDP using the photosensitive paste composition is as follows. The photosensitive paste composition is coated onto a lower substrate of a PDP on which address electrodes and a dielectric layer have been formed, using screen printing or a table coater. The coated substrate is then dried in a dry oven or an IR oven at 80 to 120° C. for 5 to 60 minutes to remove most of the solvent from the photosensitive paste composition. Then, a light of a predetermined wavelength is irradiated onto the dried film using an ultraviolet exposure device in which a photomask is installed. A portion of the dried film onto which ultraviolet rays are irradiated becomes insoluble in a developing solution through cross-linking. Then, in a developing process, an appropriate alkaline developer such as a Na2CO3 solution, a KOH solution, a TMAH solution, a monoethanolamine solution or the like, which has been diluted in pure water, is used at a developing temperature of about 30° C. to remove an unexposed portion of the photosensitive paste. As a result, a pattern is obtained. The resultant is sintered in an electric furnace at 500 to 600° C. for 5 to 60 minutes to remove remaining organic mixtures and to sinter the glass frit having a low melting point. Accordingly, a patterned barrier rib can be obtained.
Aspects of the present invention also provide a PDP including the barrier rib.
The PDP includes a front panel 110 and a rear panel 120. The front panel 110 includes a front substrate 111; sustain electrode pairs (114 for each) formed on a rear surface 111a of the front substrate 111, each sustain electrode pair 114 including a Y electrode 112 and an X electrode 113; a front dielectric layer 115 covering the sustain electrode pairs; and a protective layer 116 covering the front dielectric layer 115. The Y electrode 112 and the X electrode 113 respectively include transparent electrodes 112b and 113b made of a transparent conductive material such as, for example, ITO, etc., and bus electrodes 112a and 113a each consisting of a black electrode (not shown) for contrast enhancement and a white electrode (not shown) for imparting conductivity. The bus electrodes 112a and 113a are connected to connection cables (not shown) disposed on the left and right sides of the PDP.
The rear panel 120 includes a rear substrate 121; address electrodes (122) formed on a front surface 121a of the rear substrate 121 so as to intersect with the sustain electrode pairs; a rear dielectric layer 123 covering the address electrodes; a barrier rib 124 formed on the rear dielectric layer 123 so as to partition discharge cells (126); and a phosphor layer 125 disposed in the discharge cells. The address electrodes 122 are connected to connection cables disposed on upper and lower sides of the PDP.
Hereinafter, aspects of the present invention will be described more specifically with reference to the following Examples. The following Examples are for illustrative purposes and are not intended to limit the scope of the invention.
Preparation of Metal Oxide Precursor
100 ml of n-BuOH and 100 ml of diethylene glycol were added to a reaction container equipped with a thermometer and a stirrer, and stirred. During stirring, 10 ml of 1.0 N HCl was slowly added to the mixture. After stirring for about 30 minutes, 10.0 g of tantalum ethoxide was slowly added to the mixture while stirring. Then, the resulting mixture was stirred at room temperature for 12 hours to complete hydrolysis and a condensation reaction, and then 0.1 g of bis(polyoxyethylene polycyclic phenylether) methacrylate sulfuric ester salt was added to the resulting mixture as a surface modifier and the resultant was stirred at room temperature for 6 hours. n-BuOH and pure water were removed using vacuum distillation to prepare a tantalum oxide precursor using diethylene glycol as a dispersion medium.
100 ml of n-BuOH and 100 ml of tripropylene glycol were added to a reaction container equipped with a thermometer and a stirrer, and stirred. During stirring, 10 ml of 28% ammonia water was slowly added to the mixture. After stirring for about 30 minutes, 10.0 g of titanium (VI) chloride was slowly added to the mixture while stirring. Then, the resulting mixture was stirred at room temperature for 6 hours to complete hydrolysis and a condensation reaction. n-BuOH and pure water were removed using vacuum distillation to prepare a titanium oxide precursor using tripropylene glycol as a dispersion medium.
100 ml of n-propanol and 100 ml of dipropylene glycol were added to a reaction container equipped with a thermometer and a stirrer, and stirred. During stirring, 5 ml of 1.0 N HCl was slowly added to the mixture. After stirring for about 30 minutes, 10.0 g of zirconium (VI) n-propoxide was slowly added to the mixture while stirring. Then, the resulting mixture was stirred at room temperature for 24 hours to complete hydrolysis and a condensation reaction. n-BuOH and pure water were removed using vacuum distillation to prepare a zirconium oxide precursor using dipropylene glycol as a dispersion medium.
100 ml of ethanol and 100 ml of dipropylene glycol were added to a reaction container equipped with a thermometer and a stirrer, and stirred. During stirring, 5 ml of 1.0 N HCl was slowly added to the mixture. After stirring for about 30 minutes, 10.0 g of tetraethoxy silane was slowly added to the mixture while stirring. Then, the resulting mixture was stirred at room temperature for 6 hours to complete hydrolysis and a condensation reaction. Ethanol and pure water were removed using vacuum distillation to prepare a silicone oxide precursor using dipropylene glycol as a dispersion medium.
100 ml of isopropanol and 100 ml of tripropylene glycol were added to a reaction container equipped with a thermometer and a stirrer, and stirred. During stirring, 5 ml of 1.0 N HCl was slowly added to the mixture. After stirring for about 30 minutes, 10.0 g of aluminum (III) isoproxide was slowly added to the mixture while stirring. Then, the resulting mixture was stirred at room temperature for 6 hours to complete hydrolysis and a condensation reaction. Isopropanol and pure water were removed using vacuum distillation to prepare an aluminum oxide precursor using dipropylene glycol as a dispersion medium.
100 ml of ethanol and 100 ml of diethylene glycol were added to a reaction container equipped with a thermometer and a stirrer, and stirred. During stirring, 5 ml of 1.0 N HCl was slowly added to the mixture. After stirring for about 30 minutes, 5.0 g of tantalum (V) ethoxide and 5.0 g of titanium (VI) chloride were slowly added to the mixture while stirring. Then, the resulting mixture was stirred at room temperature for 12 hours to complete hydrolysis and a condensation reaction. Ethanol and pure water were removed using vacuum distillation to prepare a tantalum-titanium oxide precursor using diethylene glycol as a dispersion medium.
100 ml of ethanol and 100 ml of diethylene glycol were added to a reaction container equipped with a thermometer and a stirrer, and stirred. During stirring, 10 ml of 28% ammonia water was slowly added to the mixture. After stirring for about 30 minutes, 5.0 g of tetraethoxy silane and 5.0 g of titanium (VI) chloride were slowly added to the mixture while stirring. Then, the resulting mixture was stirred at room temperature for 6 hours to complete hydrolysis and a condensation reaction, and then 0.1 g of bis(methacryloxyethyl)phosphate was added to the resulting mixture as a surface modifier and the resultant was stirred at room temperature for 6 hours. Ethanol and pure water were removed using vacuum distillation to prepare a silicone-titanium oxide precursor using diethylene glycol as a dispersion medium.
Measurement of Physical Properties of Metal Oxide Precursors
Results of measuring light refractive indices, specific gravities and average particle diameters of metal oxides of the metal oxide precursors prepared in Examples 1 through 7 are shown in Table 1 below. The values of the light refractive indices and specific gravities were measured at 20° C., and the average particle diameters were measured using photon correlation spectroscopy (PCS).
Preparation of Organic Mixture
An organic mixture to be used for preparing a metal oxide sol by dispersing the metal oxide precursor prepared as above in the organic mixture, was prepared as follows.
Organic mixture 1 was prepared by mixing 47.2% by weight of a poly(methylmethacrylate-co-n-butylmethacrylate-co-methylmethacrylic acid) copolymer having a weight average molecular weight of 5,000 g/mol and an acid value of 120 mg KOH/g as a binder, 3.5% by weight of 2-benzyl-2-dimethylamino-1-(4-morpolynophenyl)-1-butanone as a photo initiator, 46.8% by weight of trimethylolpropaneethoxylated triacrylate as a cross-linking agent, and 2.5% by weight of benzotriazol as a storage stabilizer.
Organic mixture 2 was prepared by mixing 44.1% by weight of a poly(styrene-co-methylmethacrylic acid) copolymer having a weight average molecular weight of 12,000 g/mol and an acid value of 210 mg KOH/g as a binder, 5.5% by weight of 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone as a photo initiator, 27.0% by weight of bisphenol A modified epoxy diacrylate as a cross-linking agent, and 19.0% by weight of tripropylene glycol as a solvent.
Measurement of Physical Properties of Organic Mixtures
Results of measuring light refractive indices and specific gravities of the organic mixtures prepared in Examples 8 and 9 are shown in Table 2 below.
Preparation of Metal Oxide Sol
The metal oxide precursors of Examples 1 through 7 were dispersed in the organic mixtures of Examples 8 and 9 to prepare metal oxide sols. Each metal oxide sol was prepared using the following procedure: first, the organic mixture was added to a stirring container and stirred, and a calculated amount of the metal oxide precursor was slowly added thereto during stirring, then the mixture was stirred for several hours to prepare a transparent metal oxide sol.
The tantalum oxide precursor of Example 1 and organic mixture 1 of Example 8 were mixed at a volume ratio of 20:80, wherein the volume of the tantalum oxide precursor was based only on the volume of tantalum oxide in the tantalum oxide precursor. The refractive index measured after mixing was 1.66.
The titanium oxide precursor of Example 2 and organic mixture 1 of Example 8 were mixed at a volume ratio of 15:85, wherein the volume of the titanium oxide precursor based only on the volume of titanium oxide in the titanium oxide precursor. The refractive index measured after mixing was 1.65.
The zirconium oxide precursor of Example 3 and organic mixture 2 of Example 9 were mixed at a volume ratio of 20:80, wherein the calculation of the volume of the zirconium oxide precursor was based only on the volume of zirconium oxide in the zirconium oxide precursor and the volume of organic mixture 2 was measured without the solvent. The refractive index measured after mixing was 1.66.
The silicone oxide precursor of Example 4 and organic mixture 2 of Example 9 were mixed at a volume ratio of 10:90, wherein the volume of the silicone oxide precursor was based only on the volume of silicone oxide in the silicone oxide precursor and the volume of organic mixture 2 was measured without the solvent. The refractive index measured after mixing was 1.54.
The aluminum oxide precursor of Example 5 and organic mixture 2 of Example 9 were mixed at a volume ratio of 20:80, wherein the volume of the aluminum oxide precursor was based only on the volume of aluminum oxide in the aluminum oxide precursor and the volume of organic mixture 2 was measured without the solvent. The refractive index measured after mixing was 1.60.
The tantalum-titanium oxide precursor of Example 6 and organic mixture 1 of Example 8 were mixed at a volume ratio of 15:85, wherein the volume of the tantalum-titanium oxide precursor was based only on the volume of tantalum-titanium oxide in the tantalum-titanium oxide precursor. The refractive index measured after mixing was 1.64.
The silicone-titanium oxide precursor of Example 7 and organic mixture 2 of Example 9 were mixed at a volume ratio of 20:80, wherein the volume of the silicone-titanium oxide precursor was based only on the volume of silicone-titanium oxide of the silicone-titanium oxide precursor and the volume of organic mixture 2 was measured without the solvent. The refractive index measured after mixing was 1.64.
Photosensitive paste compositions were prepared by mixing the metal oxide sols of Examples 10 through 16 with an inorganic compound comprising a glass frit having a low melting point and a glass frit having a high melting point as described below.
A photosensitive paste composition 1 was prepared by mixing 40% by weight of the metal oxide sol of Example 10, 55% by volume of a glass frit having a low melting point (ZnO—BaO-B2O3-based, amorphous, D50=3.2 μm, refractive index=1.68, specific gravity=3.86), and 5% by volume of a glass frit having a high melting point (SiO2—B2O3—Al2O3-based, amorphous, D50=2.5 μm, refractive index=1.67, specific gravity=3.67).
Photosensitive paste compositions 2 through 7, respectively, were prepared in the same manner as photosensitive paste composition 1, except that the metal oxide sols of Examples 11 through 16, respectively, were used instead of the metal oxide sol of Example 10.
A photosensitive paste composition comprising 40% by volume of the organic mixture of Example 9, 55% by volume of a glass frit having a low melting point (Li2O—SiO2—B2O3-based, amorphous, D50=3.2 μm, refractive index=1.56, specific gravity=2.56), and 5% by volume of a glass frit having a high melting point (SiO2—B2O3—Al2O3-based, amorphous, D50=3.0 μm, refractive index=1.55, specific gravity=2.52) was prepared as a control.
Evaluation and Result of Photosensitive Paste Compositions
The photosensitive paste compositions of Examples 17 through 23 and Comparative Example 1, respectively, were coated onto a glass substrate using a coater, and then dried in a dry oven at 100° C. for 30 minutes. Subsequently, 300-1500 mJ/cm2 of light was irradiated using a high voltage mercury lamp ultraviolet exposure device equipped with a photomask having a grating pattern (width: linewidth=40 μm (pitch=160 μm), length: linewidth=40 μm (pitch=560 μm). The light-irradiated glass substrate was developed by spraying 0.4% by weight of aqueous NaCO3 solution thereonto at 30° C. at a nozzle pressure of 1.2 kgf/cm2 for 180 seconds, and then rinsed by spraying pure water at room temperature at a nozzle pressure of 1.2 kgf/cm2 for 30 seconds. Subsequently, the developed glass substrate was dried using an air knife and then placed into an electric furnace and sintered at 560° C. for 20 minutes to form a barrier rib. Then, the formed barrier rib was evaluated using an optical microscope and scanning electron microscopy (SEM). The evaluation results are shown in Table 3 below. In Table 3, the term “optimum exposure amount” refers to a value that provides optimum pattern results. The terms “surface roughness” and “surface compactness” refer to qualities obtained by observation using SEM. The value for the surface compactness was obtained calculating an area of an empty space in an unit area of a cross-section of the barrier rib, and subtracting the calculated area of empty space from the unit area. That is, when the surface compactness is 100%, an empty space does not exist at all in the cross-section of the barrier rib, indicating that a compact barrier rib is formed.
From the results of Table 4, the photosensitive paste composition of Comparative Example 1, which did not contain a metal oxide, exhibited the best exposure sensitivity (optimum exposure amount). This is because if a photosensitive paste composition includes a metal oxide, the amount of an organic mixture involved in a photo reaction is relatively low, and the metal oxide absorbs irradiated ultraviolet rays. In particular, the titanium oxide exhibited much less exposure sensitivity. The photosensitive paste composition of Example 20 exhibited the least exposure sensitivity, and also had the lowest height, that is, 45 μm, of a barrier rib formed by a single exposure to light. This is assumed to be due to a relatively big difference between the light refractive index of the metal oxide sol and that of the inorganic compound. In addition, as shown in Table 4, the lower the exposure sensitivity, the larger the upper width and the narrower the lower width of the barrier rib. This is because the bigger the difference is between the refractive index of a metal oxide sol and that of an inorganic compound, the lower the transmittance of light irradiated in an exposure process, while reflection and scattering are increased. Since the photosensitive paste compound of Comparative Example 1 t does not contain a metal oxide, the exposure sensitivity is relatively excellent, while the surface roughness and compactness are low. This suggests that a metal oxide decomposes an organic mixture in a sintering process, and then the empty space is filled with a glass frit having a low melting point during sintering.
Manufacture of a PDP and Evaluation of Characteristics Thereof.
The photosensitive paste compositions of Examples 17 through 19 and Comparative Example 1, respectively, were used to manufacture a 6″ panel. The 6″ panel was manufactured in a pilot line to have specs for a 42″ HD type panel. The results of evaluating the luminances of the manufactured panels are shown in Table 4 below.
From the luminance results of Table 4, it can be seen that the photosensitive paste compositions of the present invention exhibit a luminance increasing effect compared with the photosensitive paste composition of Comparative Example 1. Without being bound to any particular theory, it is believed that this result occurs because when a metal oxide sol is used, the metal oxide formed in the barrier rib increases the reflective index of visible rays, and thus luminance is increased, the roughness of a barrier rib itself is reduced and compactness thereof becomes excellent.
According to aspects of the present invention, since a pattern of a barrier rib for a PDP having high resolution and high precision can be made by a process that includes only a single exposure to light, and a barrier rib having a higher reflective index than a conventional barrier rib can also be provided, a PDP including the barrier rib can have a high luminance.
Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-55410 | Jun 2006 | KR | national |
