Kim, Young-nam (Buyoung Apt, Okgye-dong Gumi-si, Gyeongsangbuk-do 730-772, 202-1503, KR)
| 1. | ] [Claim 1 ] A rear plate for a plasma display panel, comprising: electrodes formed on a substrate; a dielectric layer formed on the substrate to cover the electrodes; a partition wall formed on the dielectric layer; and a phosphor layer formed on the partition wall and the dielectric layer, wherein the partition wall comprises 0.1 60 wt% Of B2O3 or SiO2; 1 50 wt% of one selected from the group consisting of P2O5, Bi2O3, V2O5 and mixtures thereof; 1 ~ 20 wt% of Al2O3; 5 ~ 55 wt% of ZnO; and glass powder comprising 5 ~ 30 wt% of one selected from an alkali oxide (R2O), an alkali earth metal oxide (RO), and an alkali fluoride (RF), the alkali oxide (R2O) being selected from the group consisting of Li2O, Na2O, K2O, Cs2O, Fr2O, Rb2O and mixtures thereof, the alkali earth metal oxide (RO) being selected from the group consisting of MgO, CaO, SrO, BaO, RaO, BeO, SnO and mixtures thereof, the alkali fluoride (RF) being selected from the group consisting of LiF, NaF, KF, CsF, FrF, RbF and mixtures thereof. [Claim 2] The rear plate according to claim 1, wherein the glass powder further comprises both 10 50 wt% Of B2O3 and 0.1 15 wt% of SiO2. [Claim 3] The rear plate according to claim 1, wherein the content Of P2O5 is in the range of 1 25 wt%. [Claim 4] The rear plate according to any one of claims 1 to 3, wherein the content Of Al2O3 is in the range of 5 10 wt%. [Claim 5] The rear plate according to any one of claims 1 to 3, wherein the glass powder further comprises 1 30 weight parts of one selected from the group consisting of ZrO2, Ti2O, Y2O3, Ga2O3, Nb2O5, WO3, CeO2 and mixtures thereof or the group consisting of CuO, MnO2, Fe2O3, CoO, NiO and mixtures thereof, with respect to 100 weight parts of the glass powder. [Claim 6] The rear plate according to any one of claims 1 to 3, wherein the glass powder further comprises one selected from the group consisting of TiO2, ZrO2, ZnO, Al2O3, BN, mullite, MgO, NiO, Fe2O3, CrO, MnO2, CuO and mixtures thereof as a filler, the content of the filler being in the range of 1 ~ 30 weight parts with respect to 100 weight parts of the glass powder. [Claim 7] The rear plate according to claim 6, wherein the glass powder has an average particle size of 1 ~ 10 //in, and a softening temperature of 530 °C or less. [Claim 8] The rear plate according to any one of claims 1 to 3, wherein the partition wall is etched at an etching rate of 10 μm/mm or more. [Claim 9] The rear plate according to any one of claims 1 to 3, wherein the partition wall has a thermal expansion coefficient of 60 ~ 87 x 10"7/°C . |
REAR PLATE FOR PLASMA DISPLAY PANEL
[Technical Field]
The present invention relates to a rear plate for a plasma display panel, and, more particularly, to a rear plate for a plasma display panel, which is formed of an environmentally friendly material, and comprises a partition wall layer capable of being processed by wet etching.
[Background Art]
A plasma display panel (which will hereinafter be referred to as "PDP") is a display device employing a principle whereby visible light is generated from a phosphor when ultraviolet rays generated via gas discharge excite the phosphor. The PDP has various advantages in terms of thinness, light weight, high performance, and large screen size in comparison with a cathode ray tube (CRT) which has been mainly used as the display device. The PDP comprises a number of discharge cells arranged in a matrix, in which each discharge cell constitutes a single pixel on a screen.
In a conventional triple-electrode surface-discharge type PDP, each discharge cell comprises a scan electrode and a sustain electrode of a pair of sustain electrodes formed on an upper substrate, an upper dielectric layer formed on the scan electrode and sustain electrode, an upper plate including a protective layer formed on the upper dielectric layer, an address electrode formed on a lower substrate to traverse the pair of sustain electrodes, a lower plate including a lower dielectric layer formed on the address electrode, a partition wall formed at a discharge space between the upper and lower plates, and a phosphor layer formed between the partition wall and the lower dielectric layer.
In such a PDP, after the discharge cells are selected by opposed discharge between the address electrode and the sustain electrode, discharge of the selected cells is sustained by surface discharge between the pair of the sustain electrodes. Visible light is emitted to an outside of the discharge cells from the phosphor layer via ultraviolet rays generated upon sustain discharge. As a result, the discharge cells realize grayscales by adjusting a period of sustaining the discharge, and are arranged in the matrix to display an image on the PDP.
The partition wall is generally composed of a glass material having a low melting point, and is required to have low baking temperature, sufficient voltage, low dielectric constant for reducing electric current consumption upon discharge, and the like.
As a conventional material for the partition wall, a PbO-based material, that is, a PbO-SiO 2 -B 2 O 3 based glass has been mainly used. However, as Pb is an ingredient of the PbO-based material that is extremely detrimental to human being and environment, a Pb-free glass for the partition wall is under continuous investigation. As for the Pb-free glass, P 2 O 5 -ZnO based glass, Bi 2 O 3 -SiO 2 based glass, ZnO-Bi 2 O 3 -SiO 2 based glass, BaO-Bi 2 O 3 -SiO 2 based glass, etc. have been suggested.
For example, Japanese Patent Laid-open Publication No. 2001-180972 discloses a P 2 O 5 -ZnO based glass composition as a Pb-free low melting point glass composition. However, since this composition comprises 55 wt% or more Of P 2 O 5 which is an excessive amount, the glass composition suffers from a deteriorated mechanical strength, an increased thermal expansion coefficient, and glass foaming, which is one of the disadvantages of the PbO-based glass. Korean Patent Laid-open Publication No. 2003-10416 discloses a transparent Pb-free, alkali-free dielectric material which comprises Bi 2 O 3 instead of PbO. In this regard, bismuth has problems in terms of its toxicity as well as rarity and expensiveness. In addition, since the transparent dielectric material comprises 60 wt% or more of Bi 2 O 3 which is an excessive amount, it inevitably suffers from yellow discoloration, and increase in thermal expansion coefficient.
In addition, Japanese Patent Laid-open Publication No. 2000-226231
discloses a Pb-free glass composition. The Pb-free glass composition has problems in that a baking temperature of a partition wall is increased due to its high softening temperature, making it difficult to control dimensions of a substrate.
Meanwhile, the conventional partition wall of the PDP is generally produced using a screen print process or a sand-blast process. With the screen print process, paste for the partition wall is applied in a predetermined pattern to a substrate, which has an address electrode and a lower dielectric layer sequentially formed thereon, in such a way of repetitiously printing/drying the paste thereon using a screen printer, and then baked, thereby forming a desired partition wall. With the sand-blast process, after printing paste for the partition wall over an entire surface of a substrate, which has an address electrode and a lower dielectric layer sequentially formed thereon, the paste for the partition wall is patterned using a photoresist pattern formed via exposure and development processes, and baked, thereby forming a desired partition wall. In the case of the screen print process, since the patterned partition wall is formed by repetitious printing, there is a problem in view of difficulty in precise adjustment of dimensions. On the other hand, in the case of the sand-blast process, since it is necessary to perform a secondary baking process after primarily baking the dielectric layer, and forming the partition wall on the dielectric layer, the sand- blast process has low process efficiency. In addition, since it is necessary to input an excessive amount of filler in order to prevent the partition wall from being demolished before baking, there are problems in that the baking temperature is increased, and that the content of the filler must be precisely determined.
In order to solve these problems, chemical etching has been suggested as a process for forming the partition wall. The chemical etching is a process which forms the partition wall in such a way of forming a predetermined pattern on a partition wall layer, followed by etching the partition wall layer using an acid-based liquid composition (etchant) through the pattern. When forming the partition wall via chemical etching, it is necessary for the partition wall to be etched at a high etching rate after baking, and to have a dense structure with low porosity. However, since the composition for the partition wall used in the conventional
screen print process and the sand-blast process has a significantly low etching rate for the acid-based liquid composition after baking, it provides a problem of low productivity.
[Disclosure] [Technical Problem]
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a rear plate for a plasma display panel, which is formed of an environmentally friendly material, and is capable of being baked at a lower temperature and etched at an etching rate that ensures satisfactory productivity, and comprises a dense partition wall which has excellent mechanical strength and does not suffer from yellow discoloration.
[Technical Solution]
In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a rear plate for a plasma display panel, comprising: electrodes formed on a substrate; a dielectric layer formed on the substrate to cover the electrodes; a partition wall formed on the dielectric layer; and a phosphor layer formed on the partition wall and the dielectric layer, wherein the partition wall comprises 0.1 - 60 wt% of B 2 O 3 or SiO 2 ; 1 ~ 50 wt% of one selected from the group consisting of P 2 O 5 , Bi 2 O 3 , V 2 O 5 and mixtures thereof; 1 ~ 20 wt% Of Al 2 O 3 ; 5 - 55 wt% of ZnO; and glass powder comprising 5 - 30 wt% of one selected from an alkali oxide, an alkali earth metal oxide, and an alkali fluoride, the alkali oxide being selected from the group consisting of Li 2 O, Na 2 O, K 2 O, Cs 2 O, Fr 2 O, Rb 2 O and mixtures thereof, the alkali earth metal oxide being selected from the group consisting of MgO, CaO, SrO, BaO, RaO, BeO, SnO and mixtures thereof, the alkali fluoride being selected from the group consisting of
LiF, NaF, KF, CsF, FrF, RbF and mixtures thereof.
Preferably, the glass powder further comprises both 10 - 50 wt% Of B 2 O 3
and 0.1 ~ 15 wt% of SiO 2 .
Preferably, the content Of P 2 O 5 is in the range of 1 ~ 25 wt%.
Preferably, the content Of Al 2 O 3 is in the range of 5 ~ 10 wt%.
Preferably, the glass powder further comprises 1 - 30 weight parts of one selected from the group consisting of ZrO 2 , Ti 2 O, Y 2 O 3 , Ga 2 O 3 , Nb 2 O 5 , WO 3 , CeO 2 and mixtures thereof or the group consisting of CuO, MnO 2 , Fe 2 O 3 , CoO, NiO and mixtures thereof, with respect to 100 weight parts of the glass powder.
Preferably, the glass powder further comprises one selected from the group consisting of TiO 2 , ZrO 2 , ZnO, Al 2 O 3 , BN, mullite, MgO, NiO, Fe 2 O 3 , CrO, MnO 2 , CuO and mixtures thereof as a filler, the content of the filler being in the range of 1 ~ 30 weight parts with respect to 1 OO weight parts of the glass powder.
Preferably, the glass powder has an average particle size of 1 ~ 10 /zm, and a softening temperature of 490 ~ 530 ° C .
Preferably, the partition wall is etched at an etching rate of 10 μm/min or more with respect to the acid-based liquid composition.
Preferably, the partition wall has a thermal expansion coefficient of 60 ~ 87 x 10 "7 / ° C.
The present invention will be described in detail with reference to Figs. 1 to 2f. Fig. 1 is a cross-sectional view illustrating a plasma display panel according to the present invention.
A discharge cell of a PDP according to the present invention shown in
Fig. 1 comprises a scan electrode Y and a sustain electrode Z formed on an upper substrate 60, and an address electrode X formed on a lower substrate 50. Each of the scan electrode Y and the sustain electrode Z comprises a transparent electrode 64Y or 64Z, and a bus electrode 66Y or 66Z, which is formed at one edge of the transparent electrode 64Y or 64Z and has a narrower line width than that of the transparent electrode 64Y or 64Z. The transparent electrodes 64Y and 64Z are typically composed of indium tin oxide (ITO), and formed on the upper substrate 60. The bus electrodes 66Y and 66Z are formed of metal having a high conductivity on the transparent electrodes 64Y and 64Z, and
serve to reduce voltage drop caused by the transparent electrodes 64Y and 64Z having high resistance.
An upper dielectric layer 68 and a protective layer 62 are stacked on the upper substrate 60 having the scan electrode Y and the sustain electrode Z formed side by side thereon. The upper dielectric layer 68 accumulates wall charges upon plasma discharge. The protective layer 62 prevents the upper dielectric layer 68 from being damaged due to sputtering during the plasma discharge while enhancing emission efficiency of secondary electrons. As for the protective layer 62, magnesium oxide (MgO) is typically used. The address electrode X is formed in a direction of traversing the scan electrode Y and the sustain electrode Z. A lower dielectric layer 54 and a partition wall 56 are formed on the lower substrate 50 having the address electrode X formed thereon, and are coated with a phosphor 58. The partition wall 56 is formed in parallel with the address electrode X to prevent ultraviolet rays and visible light generated via discharge from being leaked to an adjacent discharge cell. The phosphor 58 is excited by ultraviolet rays generated upon the plasma discharge, and emits visible light having one color among red, green and blue.
A discharge space is defined between the upper and lower substrates 60 and 50 and the partition wall 56, and has an inactive gas injected thereinto for gas discharge.
According to the present invention, since the glass powder used for forming the partition wall comprises appropriate components, which are environmentally friendly while reducing a softening temperature of the glass, instead of PbO, it is possible to form a dense partition wall, which can be baked at a low temperature, processed at an etching rate capable of ensuring satisfactory productivity, does not suffer from yellow discoloration, and has an excellent mechanical strength.
B 2 O 3 and SiO 2 constitute the glass powder, and serves to allow glass frit to have a stable glass state. If the contents of these components are less than 0.1 wt%, glass formation becomes unstable, and a thermal expansion rate is increased. On the other hand, if the contents of these components exceed 60 wt%, viscosity of
the glass is lowered, causing easy crystallization of the glass.
Meanwhile, since SiO 2 has a relatively low dielectric constant, it serves to lower an entire dielectric constant of the glass formed therewith. Preferably, the content of SiO 2 is in the range of 0.1 ~ 15 wt%. If the content of SiO 2 exceeds 15 wt%, the softening temperature is further increased, thereby possibly causing deficiency in sintering. Meanwhile, the content of B 2 O 3 is preferably in the range of 50 wt% or less. If the content Of B 2 O 3 exceeds 50 wt%, the expansion ratio is significantly lowered, thereby possibly causing convex bending of the substrate.
P 2 θ 5 , Bi 2 O 3 , and V 2 O 5 serve to lower the softening temperature of the glass, and are preferably added in the range of 1 ~ 50 wt%. If the content of the components exceeds 50 wt%, there is possibility of increase in thermal expansion coefficient or yellow discoloration. In particular, if the content of P 2 O 5 is excessive, there is possibility of deteriorating endurance of the glass. Thus, the content Of P 2 O 5 is preferably in the range of 1 - 25 wt%. Meanwhile, Bi 2 O 3 is used instead of PbO, and serves to lower the melting point of the glass. The content of
Bi 2 O 3 is preferably in the range of 30 wt% or less. If the content of Bi 2 O 3 exceeds 30 wt%, there is possibility of increase in thermal expansion coefficient and yellow discoloration along with an increase in dielectric constant, which may possibly cause a low response speed when driving the PDP. In addition, since an excessive content of V 2 O 5 causes yellow or brown discoloration, and lowers reflectivity, it is undesirable.
Al 2 O 3 serves to suppress crystallization of the glass upon reheating the glass powder. If the crystallization of the glass occurs in the partition wall, a plastic profile is changed according to size of crystallized particles, causing difficulty in process control, and variation in properties such as dielectric constant. If the content Of Al 2 O 3 is less than 1 wt%, addition effect thereof is insignificant, whereas the content of Al 2 O 3 exceeding 20 wt% causes an increase in softening temperature of the glass powder. The content Of Al 2 O 3 is preferably in the range of 5 ~ 10 wt%. ZnO serves to lower the softening temperature and the thermal expansion coefficient. If the content of ZnO exceeds 55 wt%, there is possibility of difficulty
in glassification of the glass powder.
According to the present invention, the composition for the partition wall comprises 5 - 30 wt% of the alkali earth metal oxide selected from the group consisting of MgO, CaO, SrO, BaO, RaO, BeO, SnO and mixtures thereof, the alkali oxide selected from the group consisting of Li 2 O, Na 2 O, K 2 O, Cs 2 O, Fr 2 O, Rb 2 O and mixtures thereof, or the alkali fluoride selected from the group consisting of LiF, NaF, KF, CsF, FrF, RbF and mixtures thereof. These components serve to lower the softening temperature of the glass powder while increasing fluidity thereof. In particular, F ions contained in the alkali fluoride serve to suppress deterioration of voltage resistance. Among these components, if the content of the alkali earth metal oxide is excessive, there is possibility of crystallization of the glass powder. On the other hand, if the alkali oxide and/or the alkali fluoride are excessively added above the contents as described above, deterioration in chemical resistance and electrical insulation properties occurs along with an increase in thermal expansion coefficient, causing easier crystallization of the glass powder than the alkali earth metal oxide.
According to the present invention, the glass powder may comprise 1 - 30 weight parts of one selected from the group consisting of ZrO 2 , Ti 2 O, Y 2 O 3 , Ga 2 O 3 , Nb 2 O 5 , WO 3 , CeO 2 and mixtures thereof or the group consisting of CuO, MnO 2 , Fe 2 O 3 , CoO, NiO and the mixtures thereof with respect to 100 weight parts of the glass powder. ZrO 2 , Ti 2 O, Y 2 O 3 , Ga 2 O 3 , Nb 2 O 5 , WO 3 , CeO 2 and mixtures thereof serve to prevent discoloration and softening of the electrodes, and to stabilize the glass. CuO, MnO 2 , Fe 2 O 3 , CoO, NiO and the mixtures thereof serve to allow the glass powder to have various colors. If the content of these components exceed 1 - 30 weight parts, there is a problem in that the softening temperature is rapidly increased, causing insufficient glassification.
According to the present invention, the glass powder for the partition wall may have a glass-softening temperature of 530 ° C or less. If the glass-softening temperature of the glass powder exceeds 530 ° C , there is a problem in that the baking temperature of the partition wall is increased, causing difficulty in controlling dimensions of the substrate.
In addition, the glass powder preferably has an average particle size of 1 ~ 10 /ziii. If the glass powder has an average particle size less than 1 μm, it is difficult to allow the partition wall to act as paste, whereas if the glass powder has an average particle size greater than 10 μm, it is difficult for the glass powder to become dense when baking the partition wall, which causes bubbles to be created in the partition wall.
According to the present invention, the glass powder for the partition wall may further comprise filler. The filler may comprise one selected from the group consisting of TiO 2 , ZrO 2 , ZnO, Al 2 O 3 , BN, mullite, MgO, NiO, Fe 2 O 3 , CrO, MnO 2 , CuO and mixtures thereof. The content of the filler is preferably in the range of 1 - 30 weight parts with respect to 100 weight parts of the glass powder. The filler is added to the glass powder in order to increase physical/chemical endurance, the dielectric constant of the glass powder, reflectivity and brightness of colors emitted from the phosphor. If the content of the filler is less than 1 weight part, effect achieved by adding the filler is insignificant. On the other hand, if the content of the filler is greater than 30 weight parts, an amount of non-reacted oxide in the glass powder is increased, thereby lowering the chemical endurance, and plastic strength as a supporter for the dielectric layer and the partition wall.
Meanwhile, according to the present invention, the partition wall is preferably etched at an etching rate of 10 /an/min or more with respect to the acid- based liquid composition. An etching rate less than 10 μm/min is undesirable since workability and productivity are deteriorated when wet etching the partition wall.
According to the present invention, the partition wall preferably has a thermal expansion coefficient of 60 ~ 87 x 10 "7 / ° C . If the partition wall has a thermal expansion coefficient less than 60 x 10 "7 / ° C, the substrate suffers from convex bending, and if the partition wall has a thermal expansion coefficient greater than 87 x 10 "7 / ° C, the substrate suffers from concave bending.
Figs. 2 to 7 are cross-sectional views illustrating a method for producing a rear plate of a plasma display panel according to the present invention. First, after forming an electrode material layer on a substrate 50, an electrode layer 52 is formed on the substrate 50 as shown in Fig. 2 by patterning
the electrode material layer using a photolithography process and an etching process.
Next, a dielectric material layer is formed by applying glass powder for forming a dielectric layer of the present invention to the surface of the substrate 50 which has the electrode layer 52 formed thereon, and is then baked independently or together with a paste layer for a partition wall or with a green tape-shaped partition wall which will be formed by a subsequent process, thereby forming a dielectric layer 54 as shown in Fig. 3.
When forming a partition wall material layer 86 by applying the paste for the partition wall to an upper surface of the substrate 50 having the dielectric material layer or the dielectric layer 54 formed thereon, the paste for the partition wall may comprise binder to impart strength, solvent to impart fluidity required for operation of melting, milling and casting the material for the partition wall, plasticizer to enhance workability, defoamer to reduce generation of bubbles, dispersants to help dispersion of inorganic materials, dyes, and lubricant oils, in addition to the glass powder. By repeating operation of applying and drying the paste layer for 5 ~ 20 minutes at a temperature of 20 ~ 180 ° C until the paste layer has a desired height, a partition wall material layer 86 is formed on the dielectric layer as shown in Fig. 4. The binder comprises one or more selected from the group consisting of polyvinyl butyral, polyvinyl alcohol, polyvinyl acetate, polymethyl methacrylate, polyethyl acrylate, poly acrylic acid, ethyl cellulose, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, acrylic ester, and ammonium polyacrylate. The solvent comprises one or more selected from the group consisting of ethyl alcohol, n-butyl alcohol, toluene, water, methyl alcohol, n- propyl alcohol, isopropyl alcohol, ethylene glycol, benzaldehyde, ethyl acetate, cyclohexane, isopropyl acetate, n-octyl alcohol, benzyl alcohol, glycerol, acetone, methyl ethyl ketone, propionic acid, n-octanoic acid, n-hexane, O-xylene, MIBK, xylene, and terpineol. The plasticizer comprises one or more selected from the group consisting of water, ethylene glycol, diethylene glycol, tetraethylene glycol, glycerine, dimethyl phthalate, dibutyl phthalate, benzyl butyl phthalate,
polypropylene glycol, and polyethylene glycol.
As for the additives described above, any kinds of available additives can be applied to the present invention.
Meanwhile, the partition wall may be formed using green tape-shaped slurries having viscosity of 500 ~ 40,000 cP, which are formed by mixing the binder, the plasticizer, the inorganic solvent, and a subsidiary solvent, for example, isopropyl alcohol, with the glass powder which forms the partition wall layer. The slurries may be formed into the green-tape shape by a doctor blade process and the like, for example, by coating the slurries onto a PET sheet to form a thin layer, followed by drying the solvent. The green tape-shaped partition wall layer is attached to an upper surface of the dielectric layer 54 by laminating the tapes, and baking, so that the dielectric layer 54 is baked simultaneously with the partition wall layer 54.
Then, a photoresist 78 is coated over an entire upper surface of the partition wall material layer 86, and then patterned by exposure and development processes using a photomask, thereby forming a photoresist pattern 88 as shown in Fig. 5. A partition wall 56 can be formed as shown in Fig. 6 by etching the partition wall material layer with the acid-based liquid composition by using the photoresist pattern 88 as a mask. Any kind of available acid-based liquid composition can be applied to the present invention. Preferably, the acid-based liquid composition comprises nitric acid. For example, it is possible to use an etchant used in Korean Patent Registration Nos. 300233 and 390347. Then, after stripping off the photoresist pattern remaining on the partition wall 56, and cleaning the partition wall with water, paste for the phosphors is printed on the substrate 50 which has the partition wall formed thereon, followed by drying/baking, thereby forming R, G and B phosphor layers 58 as shown in Fig. 7.
[Advantageous Effects]
As apparent from the above description, the rear plate of the plasma display panel according to the present invention is formed of an environmentally
friendly material, and is capable of being baked at a lower temperature and etched at an etching rate that ensures satisfactory productivity, and comprises a dense partition wall, which has an excellent mechanical strength and does not suffer from yellow discoloration, thereby providing a high performance PDP.
[Description of Drawings]
The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Fig. 1 is a cross-sectional view illustrating a plasma display panel according to the present invention; and
Figs. 2 to 7 are cross-sectional views illustrating a method for producing the rear plate of the plasma display panel shown in Fig. 1.
[Best Mode]
The present invention will be described in detail hereinafter with reference to preferred examples. However, it should be noted that the present invention is not limited to these examples.
Inventive Examples 1 ~ 8
After forming a patterned electrode layer on a soda lime glass substrate via a photolithography process and an etching process, a dielectric material layer was formed by applying a paste composition for a dielectric layer to the substrate, in which the paste composition comprises 43.5 wt% of PbO, 16 wt% of SiO 2 , 8 wt% of B 2 O 3 , 2.5 wt% of Al 2 O 3 , 29 wt% of ZnO, and 1 wt% of NaO. Respective batch raw materials were mixed to form a glass powder composition as shown in the following Table 1, and melted at a temperature of 1,100 ~ 1,200 °C, followed by quenching, thereby forming a flake glass. After grinding the glass using a ball mill, the ground glass was classified using an air classification device to provide glass
powder having an average particle size of 3 μm. Paste for a partition wall was produced by mixing the glass powder with an organic vehicle comprising Terfenol and ethyl cellulose. The paste for the partition wall was applied to an upper surface of the dielectric material layer, and baked at 550 ° C for 60 minutes, forming the partition wall material layer. After applying a photoresist to an upper surface of the partition wall material layer, the photoresist was exposed, developed, and then etched using an acid-based liquid composition comprising nitric acid, forming a partition wall. The remaining photoresist on the partition wall was stripped off by a thin film process, and the partition wall was cleaned using water. Finally, after printing paste for phosphor over the entire upper surface of the partition wall and the dielectric layer, the paste for phosphor was dried and baked to form R, G, and B phosphor layers 58, thereby forming PDP rear plates.
Comparative Examples (CE) 1 ~ 3 PDP rear plates of comparative examples (CE) were produced by the same method as that of Inventive Examples (IE) 1 to 4 except that paste for a partition wall having different contents as shown in the following Table 2 was used.
Table 1
Table 2
Test 1
Measurement of Softening Temperature
Respective batch raw materials were mixed to form glass powder compositions as shown in Inventive Examples (IE) 1 to 8 of Table 1 and Comparative Examples (CE) 1 ~ 3 of Table 2, and melted at a temperature of 1,100 ~ 1,200 ° C, followed by quenching, thereby forming a flake glass. Then, after grinding the glass using the ball mill, the ground glass was classified using the air classification device to provide glass powder having an average particle size of 3 /Λn. Softening temperatures of the glass powder were measured using a DSC thermo- analyzer, results of which are shown in the following Tables 3 and 4.
Test 2
Measurement of Thermal Expansion Coefficient Respective batch raw materials were mixed to form glass powder compositions as shown in Inventive Examples (IE) 1 to 8 of Table 1 and Comparative Examples (CE) 1 ~ 3 of Table 2, and melted at a temperature of 1,100 ~ 1,200 0 C, followed by quenching, thereby forming a flake glass. After processing the flake glass to have a rectangular shape of a predetermined size, changes in length per minute of the rectangular glass were measured while
increasing the temperature up to 350 ° C , thereby obtaining thermal expansion coefficients of the glass, results of which are shown in the following Table 3 and 4.
Test 3 Measurement of Etching Rate
Respective batch raw materials were mixed to form glass powder compositions as shown in Inventive Examples (IE) 1 to 8 of Table 1 and Comparative Examples (CE) 1 ~ 3 of Table 2, and melted at a temperature of 1,100 ~ 1 ,200 ° C , followed by quenching, thereby forming a flake glass. After grinding the glass using the ball mill, the ground glass was classified using the air classification device to provide glass powder having an average particle size of 3 im, and paste for a partition wall was produced by mixing the glass powder with an organic vehicle comprising Terfenol and ethyl cellulose. Next, the paste for the partition wall was screen-printed on an upper surface of a soda lime glass substrate, and baked at 550 ° C for 60 minutes. After cutting the completed samples to 2 x 4 cm, the cut samples were taped excluding a length of about 5 mm. When the samples were etched using an acid-based liquid composition comprising nitric acid, untapped portions of the samples were etched by the acid-based liquid composition. After measuring heights of the taped portions and the untapped portions, the heights were divided by etching minutes, thereby obtaining etching rates per minute of the samples, results of which are shown in Tables 3 and 4.
Test 4
Measurement of Yellow Discoloration Respective batch raw materials were mixed to form glass powder compositions as shown in Inventive Examples (IE) 1 to 8 of Table 1 and Comparative Examples (CE) 1 ~ 3 of Table 2, and melted at 1,100 ~ 1,200 ° C , followed by quenching, thereby forming a flake glass. After grinding the glass using the ball mill, the ground glass was classified using the air classification device to provide glass powder having an average particle size of 3 μm, and paste for a partition wall was produced by mixing the glass powder with an organic vehicle
comprising Terfenol and ethyl cellulose. The paste for the partition wall was screen-printed on an upper surface of a soda lime glass substrate, and baked at 550 ° C for 60 minutes. Yellow discoloration of the completed samples was evaluated with naked eyes, results of which are shown in Tables 3 and 4 in which, if the yellow discoloration was not observed with naked eyes on a certain sample, the sample was indicated by mark O, and if the yellow discoloration was observed with naked eyes on another sample, the sample was indicated by mark X.
Test 5 Measurement of Hardness
Respective batch raw materials were mixed to form glass powder compositions as shown in Inventive Examples (IE) 1 to 8 of Table 1 and Comparative Examples (CE) 1 ~ 3 of Table 2, and melted at a temperature of 1,100 ~ 1,200 ° C, followed by quenching, thereby forming a flake glass. After grinding the glass using the ball mill, the ground glass was classified using the air classification device to provide glass powder having an average particle size of 3 μm, and paste for a partition wall was produced by mixing the glass powder with an organic vehicle comprising Terfenol and ethyl cellulose. The paste for the partition wall was screen-printed on an upper surface of a soda lime glass substrate, and baked at 550 ° C for 60 minutes. Then, hardness of the completed samples was measured via an indentation length using a Vickers hardness tester, results of which are shown in Tables 3 and 4 in which, if the hardness is equal to or greater than 600 Hv, the sample was indicated by mark O, and if the hardness is less than 600 Hv, the sample was indicated by mark X. Table 3
Table 4
From the tests, it can be appreciated that, since both Comparative Examples 2 and 3 have slow etching rates below 10 /zm/min, the process efficiency thereof is low, and that Comparative Examples 1 and 3 have high softening temperatures. In addition, from the tests, it can be appreciated that Comparative Examples 2 and 3 have excessive thermal expansion coefficients. In particular, Comparative Example 2 suffers from yellow discoloration, and Comparative Example 1 has a low hardness.
On the contrary, the dielectric layer of the rear plate of the plasma display panel of the invention ensures chemical resistance against the etchant used when forming the partition wall, has a low thermal expansion coefficient thus not suffering from bending, allows low temperature baking below 550 ° C , and does not suffer from yellow discoloration, thereby allowing a high performance PDP.
[Industrial Applicability]
Since the rear plate of the plasma display panel according to the present invention is formed of an environmentally friendly material while allowing low temperature baking and an etching rate ensuring satisfactory productivity, and comprises a dense partition wall, which has excellent mechanical strength and does not suffer from yellow discoloration, so that, when the rear plate is applied to the plasma display panel, a high performance PDP can be manufactured.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
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