JP2005148592A - Method for reusing inorganic powder, and photosensitive paste using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inexpensively manufacturing a photosensitive paste and a plasma display panel member. <P>SOLUTION: Inorganic powder is recovered from a developing solution of a photosensitive paste coating film, which containing inorganic powder and a photosensitive organic component. The recovered inorganic powder is cleaned, classified and then reused. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for recycling inorganic powder, a photosensitive paste using the recycled powder, and a method for manufacturing a member for a display panel such as a plasma display or a plasma address liquid crystal display.

  Plasma display panels (hereinafter referred to as PDPs) are capable of high-speed display as compared with liquid crystal panels, and are easy to increase in size, and thus have penetrated fields such as OA equipment and public information display devices. Furthermore, progress in the field of high-definition television is highly expected. Accompanying such expansion of applications, a fine color PDP having a large number of display cells has attracted attention.

  The PDP generates a plasma discharge between electrodes in a discharge space provided between a front glass substrate and a back glass substrate, and emits ultraviolet rays generated from the gas enclosed in the discharge space to fluoresce in the discharge space. The display is performed by touching the body. In this case, a barrier rib having a shape with a width of about 20 to 80 μm and a height of about 20 to 200 μm is used in order to suppress the spread of the discharge to a certain area and perform display in a prescribed cell, and at the same time to secure a uniform discharge space. Is provided.

  As a method of forming this partition wall, a glass paste is printed and dried by screen printing, this process is repeated a number of times to obtain a predetermined height and then fired, and a photosensitive glass paste is used to form by a photolithography technique. There are known methods for forming partition walls by sand blasting or liquid honing through a subtractive mask layer formed by a photolithography method. Among them, a method for forming by a photolithographic technique using a photosensitive glass paste. However, it is excellent in that the formation accuracy and the process are simple.

  However, the photosensitive glass paste is applied to the entire surface of the substrate, and then exposed and developed, whereby unnecessary portions are washed away by the developer, and the glass powder is deposited in the developer tank. If the glass in the developer tank is reusable, the production cost of the photosensitive paste and PDP can be reduced, and the environmental burden can be reduced by reducing waste.

  Conventionally, as a method for reusing the glass in the developer, a method has been proposed in which the inorganic powder is recovered by a wet method including a washing step with a washing solution and reused in a photosensitive paste (for example, Patent Document 1). 2).

However, in the method proposed in Patent Document 1, there is no description of a specific recovery method, and there is a glass powder of several hundred kg to several t in an actual developing basket, which is proposed in Patent Document 1. The method was insufficient for practical use. In Patent Document 1, the settled inorganic powder is washed, the supernatant liquid is discarded, and after drying at 100 ° C., it is used for pasting. However, drying at 100 ° C. does not sufficiently remove moisture, and the temperature is about 100 ° C. Drying has a problem that the viscosity change after pasting becomes large. Further, when the paste was made as it was after drying, there were problems that the kneading process at the time of making the paste was long, the problem that the pattern shape was changed, and the surface state of the pattern surface was rough due to the influence of the aggregate of inorganic powder. Furthermore, depending on the developer, the components of the inorganic powder are melted, and the physical properties of the inorganic powder are changed, which makes it impossible to reuse.
JP 2002-131927 (pages 2-9) JP 2000-56472 A (pages 1 to 8)

  Then, in view of the said prior art, this invention aims at providing the reuse method of the inorganic powder which can be used practically.

  Another object of the present invention is to provide a photosensitive paste using such recycled powder and a method for producing a member for a plasma display panel at a low cost.

  That is, the present invention is a method for reusing an inorganic powder, wherein the inorganic powder is recovered from the developer, processed and reused in the photosensitive paste.

  Moreover, this invention is a manufacturing method of the member for display panels including the process of apply | coating the photosensitive paste using the said recycle powder, and a photosensitive paste on a board | substrate, and drying.

  A method for producing a photosensitive paste and a member for a plasma display panel can be provided at low cost by recovering the inorganic powder from the developer, reusing it and then reusing it as the photosensitive paste.

  The present invention relates to an inorganic powder and an inorganic powder characterized in that the inorganic powder is recovered from the developer of the photosensitive paste coating film containing the photosensitive organic component, and the inorganic powder is reused after being washed and classified. This is a method of reusing powder.

  The photosensitive paste in the present invention is composed of an inorganic powder and a photosensitive organic component. The content of the inorganic powder is preferably 35 to 95% by weight, and more preferably 40 to 90% by weight because the shrinkage ratio during firing is small and the shape change due to firing is small. Examples of the inorganic powder in the paste include glass powder, metal powder, refractory filler, and the like.

The glass powder preferably has a thermal expansion coefficient of 50 × 10 ^{−7 to} 100 × 10 ⁻⁷ at 50 to 400 ° C. Moreover, it is required as a partition wall for electrical insulation, strength, coefficient of thermal expansion, denseness of insulating layer, etc. by blending silicon oxide in glass in the range of 3 to 60% by weight and boron oxide in the range of 5 to 50% by weight. Improved electrical, mechanical and thermal properties. The glass powder in the present invention is preferably mainly composed of a low-melting glass powder. The glass transition temperature of the low melting glass powder is preferably 430 to 500 ° C., and the glass softening point is preferably 470 to 620 ° C. When the glass transition temperature and the glass softening point are in this range, the distortion of the substrate is small during firing, and a dense partition layer is obtained. The particle diameter of the glass powder is selected in consideration of the line width and height of the partition wall to be produced. The center diameter of the volume-based distribution is 1 to 6 μm, the maximum particle size is 30 μm or less, the specific surface area is 1.5 to It is preferably 4 cm ² / g.

  As metal powder, what contains at least 1 sort (s) chosen from the group of Ag, Au, Pd, Ni, Cu, Al, and Pt can be used. These can be used independently, in an alloy state, or in a mixed powder state. As the particle diameter of the metal powder, the center diameter of the volume-based distribution is preferably 0.7 to 6 μm. More preferably, it is 1.3-4 micrometers. When the particle diameter is in this range, a fine fine pattern can be formed.

  The refractory filler is preferably added to stabilize the shape during firing. As the refractory filler, those that do not soften at a firing temperature of about 500 to 650 ° C. can be widely used, and high melting point glass and ceramic powders such as alumina, magnesia, calcia, cordierite, silica, mullite, zircon, zirconia are exemplified. it can. In order to reduce external light reflection of the PDP and increase the practical contrast, when the partition walls are dark, Co-Cr-Fe, Co-Mn-Fe, Co-Fe-Mn are used as refractory black pigments. -Al, Co-Ni-Cr-Fe, Co-Ni-Mn-Cr-Fe, Co-Ni-Al-Cr-Fe, Co-Mn-AL-Cr-Fe-Si pigments may be used. . On the other hand, when whitening the partition for the purpose of effectively guiding the light emission of the phosphor to the front surface of the panel, titania or the like may be used as a fire-resistant white pigment.

  Examples of the photosensitive organic component in the present invention include a binder resin, a photosensitive polymer, a photosensitive oligomer, a photosensitive monomer, a photopolymerization initiator, and an organic solvent. Furthermore, additive components such as a sensitizer, an ultraviolet absorber, a polymerization inhibitor, a plasticizer, an antioxidant, an antifoaming agent, and a thixotropic agent can be added.

  The binder resin is preferably oxidized or / and decomposed or / and vaporized at the time of firing so that the carbide does not remain in the inorganic substance. Ethyl cellulose, methyl cellulose, nitrocellulose, cellulose acetate, cellulose propionate, cellulose butyrate, hydroxypropyl cellulose Cellulose resin such as methyl (meth) acrylate, ethyl (meth) acrylate, normal butyl (meth) acrylate, isobutyl (meth) acrylate, isopropyl (meth) acrylate, 2-ethylmethyl (meth) acrylate, 2- An acrylic resin made of a polymer or copolymer such as hydroxylethyl (meth) acrylate, poly-α-methylsulfone, polyvinyl alcohol, polybutene and the like are preferably used. The content of the binder resin is in the range of 5 to 65% by weight, more preferably 10 to 60% by weight.

  Furthermore, in the present invention, it is preferable to use a photosensitive polymer or / and a photosensitive oligomer as the binder resin. The oligomer or polymer is obtained by polymerization or copolymerization of components selected from compounds having a carbon-carbon double bond.

  By copolymerizing an unsaturated acid such as an unsaturated carboxylic acid, the developability in an alkaline aqueous solution after exposure can be improved. Specific examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinyl acetic acid, and acid anhydrides thereof.

  The acid value of the polymer or oligomer having an acidic group such as a carboxyl group in the side chain thus obtained is preferably in the range of 50 to 180, more preferably 70 to 140.

  As the photosensitive monomer, a compound having an active carbon-carbon unsaturated double bond is often used. As the functional group, monofunctional and polyfunctional compounds having a vinyl group, an allyl group, an acrylate group, a methacrylate group, or an acrylamide group can be applied. Specifically, 2- (2-ethoxyethoxy) ethyl acrylate, 1,3-butanediol diacrylate, pentaerythritol triacrylate, ditrimethylolpropane tetraacrylate, cyclohexyl methacrylate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate And glycidyl methacrylate.

  The photopolymerization initiator is preferably added in the range of 0.005 to 5% by weight with respect to the photosensitive paste in terms of photosensitive characteristics.

  An organic solvent is used to adjust the viscosity when the paste is applied to the substrate in accordance with the application method. Examples of the organic solvent used at this time include diethylene glycol monobutyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol mono-2-ethylhexyl ether, 2,2,4-trimethyl-1,3- Pentanediol monoisobutyrate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, 2-ethyl-1,3-hexanediol, terpineol, benzyl alcohol, 1-butoxy-2-propane, 1 , 2-diacetoxypropane, 1-methoxy-2-propanol, 2-acetoxy-1-ethoxypropane, (1,2-methoxypropoxy) -2-propanol, (1,2-ethoxypropoxy) -2-pro 2-hydroxy-4-methyl-2-pentanone, 3-methoxy-3-methylbutyl acetate, 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethanol, 2-isopropoxyethanol, 2- Butoxyethanol, 2- (isopentyloxy) ethanol, 2- (hexyloxy) ethanol, 2-phenoxyethanol, 2- (benzyloxy) ethanol, benzyl alcohol, furfuryl alcohol, tetrafurfuryl alcohol, 2,2′-dihydroxy Diethyl ether, 2- (2-methoxyethoxy) ethanol, 2- [2- (2-methoxyethoxy) ethoxy] ethanol, 2-methyl-1-butanenor, 3-methyl-2-butanol, 2-methyl-1- Pentanol, 4-methyl 2-pentanol, 2-ethyl-1-butanol, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate, 2-phenoxyethyl acetate. In the present invention, the organic solvent is preferably contained in the paste in the range of 20 to 70 wt%, more preferably in the range of 30 to 65 wt%. If the organic solvent is less than 20 wt%, the viscosity of the paste increases and high-speed coating becomes difficult. On the other hand, when the organic solvent exceeds 70 wt%, the sedimentation of the dispersed particles is accelerated, and it becomes difficult to stabilize the composition of the paste, and there is a tendency that a great amount of energy and time are required for drying.

  The photosensitive paste of the present invention is prepared by blending various components so as to have a predetermined composition, and then pre-dispersed by a mixer such as a planetary mixer, and is uniformly produced by a dispersing and kneading means using a dispersing machine such as a three-roller. .

  Next, an example of performing pattern processing will be described. First, a photosensitive paste is applied over the entire surface or partially on the substrate. As a coating method, methods such as a screen printing method, a bar coater, a roll coater, a die coater, and a blade coater can be used. After the application, it is dried using a ventilation oven, a hot plate, an IR dryer or the like.

  After drying, irradiation with light through a photomask having a desired pattern selectively causes a difference in molecular weight and a difference in solubility in the developer. A proximity exposure machine or the like can be used as the exposure apparatus. Moreover, when performing exposure of a large area, after apply | coating the photosensitive paste on a board | substrate and exposing while conveying, a large area can be exposed with the exposure machine of a small exposure area.

  After the exposure, development is performed using the difference in solubility between the exposed portion and the non-exposed portion in the developer. In this case, the immersion method, the spray method, and the brush method are used. For the developer, an organic solvent that can dissolve the organic components in the photosensitive paste is used. Further, water may be added to the organic solvent as long as its dissolving power is not lost. When a compound having an acidic group such as a carboxyl group is present in the photosensitive paste, it can be developed with an alkaline aqueous solution. As the alkaline aqueous solution, sodium hydroxide, sodium carbonate, calcium hydroxide aqueous solution or the like can be used. However, it is preferable to use an organic alkaline aqueous solution because an alkaline component can be easily removed during firing. As the organic alkali, a general amine compound can be used. Specific examples include tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide, monoethanolamine, and diethanolamine. The concentration of the alkaline aqueous solution is usually 0.05 to 5% by weight, more preferably 0.1 to 1% by weight. If the alkali concentration is too low, the soluble portion is not removed, and if the alkali concentration is too high, the pattern portion may be peeled off and the non-soluble portion may be corroded. The development temperature during development is preferably 20 to 50 ° C. in terms of process control.

  In this development step, the portions other than the desired pattern portion are developed. In the development, the photosensitive component is eluted in the developer, but the inorganic powder does not dissolve and remains in the developer. In the PDP, a display of 32 to 60 inches diagonal is formed, and development on a large substrate is required. Further, for example, when the partition walls are formed, a coating film having a thickness of 200 to 300 μm is formed. Therefore, a large amount of inorganic powder remains in the developer every time one sheet is formed.

  A large amount of inorganic powder remaining in the developer is recovered. The collection method is not particularly limited, and a method of providing a filter in the developer circulation line, a method of collecting with a pantyhose mesh, a method of providing a sedimentation tank, a method of collecting with a centrifugal separation mechanism, and the like can be used. Among these methods, a method of collecting by a centrifugal separation mechanism is preferable.

  Centrifugation is a method of mechanically separating an inorganic powder from a developer by centrifugal force using a specific gravity difference between the inorganic powder present in the developer and the developer. Depending on the particle size, separation is possible if the specific gravity difference is inorganic powder-developer specific gravity / developer specific gravity is 0.2 or more. By utilizing this, the inorganic powder / developer can be separated.

  Centrifugation is mechanically separated, so there is no need to place a polymer flocculant in the liquid and separate the particles after making them larger as in the case of separation using a filter or filter paper. There is no chemical mixture. Therefore, there is no secondary influence on the development operation, and the developer after collecting the inorganic powder can be used for development as it is. Moreover, since the specific gravity difference is used, even a residue having a wide particle size distribution can be easily separated.

  The centrifugal separation mechanism is not particularly limited, but is preferably a decanter system because continuous processing of inorganic powder recovery is possible. As shown in FIG. 1, the decanter system is usually a bowl conveyor 1, a screw conveyor 3 that continuously discharges inorganic powder 2, a motor 4 that rotates them, and a speed reducer that gives a relative differential speed between the bowl 1 and the screw conveyor 3. It consists of five elements.

  When the developer 8 containing inorganic powder is inserted from the feed pipe 6 into the bowl portion 1 rotating at high speed, the inorganic powder precipitates on the outer periphery of the bowl portion 1 due to a centrifugal effect of 2,000 G or more. The inorganic powder is fed out by a screw conveyor 3 to which a differential speed is given, and only the dehydrated inorganic powder 2 is taken out and separated from the developer 7. This is a very effective method for the case where both the inorganic powder 2 and the developer 7 are continuously discharged and a large amount of inorganic powder is produced in a short time.

  The inside of the separator is preferably subjected to wear resistance processing. Since the photosensitive paste contains inorganic powder having a relatively high hardness such as glass or metal, the inside of the apparatus may be worn. By performing the wear resistance treatment, the mixing of the metal constituting the separator can be prevented. More preferably, the tip of the screw conveyor 3 that is most likely to be worn is subjected to wear resistance treatment. As a specific wear resistance treatment method, tungsten carbide (WC), Hastelloy B & WC, Hastelloy C-276, Stellite # 1, Stellite 1016, Utaroloy, Locoid C, Alumina, Meteco # 101 and the like are sprayed. Or it is preferable to perform an abrasion-resistant process by sticking as a chip | tip.

  It is also preferable to provide a separation zone (vane) 9 in the decanter because fine particles can be recovered. By having the separation plate 9 as shown in FIG. 2, the inorganic powder slides on the surface of the separation plate 9 and falls in the outer peripheral direction of the rotating body, so that not only the separation is promoted, but also fine particles that are easily raised in the liquid. Can be recovered. The material of the separation plate 9 is generally a plastic, stainless steel such as SUS306 or SUS314, but may be subjected to wear resistance treatment. However, if it becomes too heavy, it will be inconvenient to rotate, so it is better to select the material in consideration of that point.

  It is preferable because the collection rate can be improved by further passing the developer 7 separated by the centrifuge through a filter to collect fine particles. The filter mesh is preferably 1 μm or less, more preferably 0.5 μm or less.

  The inorganic powder recovery unit 10 that removes the inorganic powder from the developer is connected to the tank unit 12 in which the developer is agitated and temperature-controlled in parallel with the developer 11, and is configured to repeatedly recover the inorganic powder. It is preferable. The configuration is such that the liquid is taken out from the tank portion 12, the inorganic powder is recovered, and the developer is returned to the tank portion 12. Thus, the flow rate to the inorganic powder recovery portion 10 can be arbitrarily adjusted, and the optimum inorganic Powder recovery processing conditions can be selected.

  In many cases, the recovered inorganic powder is not dissolved in the developer on the surface of the inorganic powder, and the photosensitive organic components in a separated state are adhered to the surface of the inorganic powder. May cause problems. It must be reused after processing after collection. As the treatment after collection, washing, heating, classification and the like are preferable.

  As the cleaning liquid used for cleaning, an organic solvent and / or an acidic aqueous solution is preferable. The organic solvent is preferably a solvent that dissolves the photosensitive organic component of the photosensitive paste or a solvent that easily volatilizes the organic component after washing, but is not particularly limited. As the acidic aqueous solution, aqueous solutions of hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, acetic acid and the like can be used. It is preferable to wash with pure water after washing with an organic solvent and / or an acidic aqueous solution. As a cleaning method, a method of providing a precipitation tank can be applied. For example, the collected inorganic powder and cleaning liquid are placed in a precipitation tank and stirred for several hours. At this time, the amount of the cleaning liquid is preferably 3 times or more that of the inorganic powder by volume because the cleaning effect can be enhanced. After stirring, the mixture is allowed to stand for several hours to precipitate inorganic powder, and then the supernatant liquid is sucked up using an electric pump or the like and discarded. Next, pure water is added, and stirring, standing, and discarding the supernatant liquid are repeated several times for washing. In addition, depending on the cleaning liquid, components of the inorganic powder are eluted, and the properties of the inorganic powder change, so care must be taken when selecting the cleaning liquid.

  Heating is preferably performed after washing. The heating temperature is preferably 300 ° C. or higher. When the heating temperature is lower than 300 ° C., the viscosity of the photosensitive paste may increase. Although heating time changes with dryers, the range of 0.5 to 72 hours is preferable normally. As the dryer, known ones such as a ventilating oven, an IR dryer, and an electric furnace can be used.

  Classification is preferably performed after drying. For classification, an air classifier or a sieve of about 3.5 to 440 mesh can be used. In the case of sieving, it is preferable to use an electromagnetic sieving shaker to improve efficiency. If classification is not performed after drying, there may be problems such as a problem that the kneading process during paste formation becomes longer, a problem that the pattern shape changes, and a problem that the surface state of the pattern surface becomes rough due to the influence of the aggregate of inorganic powder. is there.

  The inorganic powder that has been processed after being collected from the developing tank is reused in the photosensitive paste. The photosensitive paste is prepared by mixing the above-described photosensitive organic component and inorganic powder that has been processed after being collected from the developing tank so as to have a predetermined composition, and is then pre-dispersed by a mixer such as a planetary mixer. It is produced homogeneously by a dispersing / kneading means with a dispersing machine such as. At this time, it is preferable to use a mixture of reused inorganic powder and unused inorganic powder because the quality of the photosensitive paste can be stabilized. In this case, the ratio of the reused inorganic powder / unused inorganic powder is preferably in the range of 1/99 to 80/20. More preferably, it is the range of 5/95-70/30.

  Next, the example which applies the photosensitive paste using the recycle powder of this invention to the member for display panels is demonstrated.

  A stripe-shaped electrode is formed on a substrate by a photolithography method using a photosensitive silver paste as a writing electrode, and a dielectric paste is applied to the substrate, followed by firing at 500 to 600 ° C. to form a dielectric layer. Form.

  Furthermore, using a photosensitive glass paste on the dielectric layer, after pattern formation by a photolithography method, baking is performed at 500 to 600 ° C. for 10 to 60 minutes to form a stripe-like partition wall pattern.

  The phosphor paste is formed on the barrier ribs thus formed. The method for forming the phosphor is not particularly limited, and examples include a screen printing method, a method for ejecting the phosphor paste from the die, and a photosensitive paste method. Among these, a method for ejecting the phosphor paste from the die, a screen Since the printing method is simple and a low-cost PDP can be obtained, it is preferable. After the phosphor paste is applied and dried, for example, it is baked at 500 ° C. for 30 minutes to form phosphor layers on the side and bottom portions of the partition walls.

  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to this. The concentration (%) in the examples is% by weight.

Example 1
First, a photosensitive silver paste was prepared. 3% glass powder having an average particle size of 0.8 μm obtained by pulverizing glass made of bismuth oxide, silicon oxide, boron oxide, zirconium oxide, zinc oxide, aluminum oxide, methyl methacrylate / methacrylic acid copolymer (weight composition ratio 60/40 , Weight average molecular weight 32000) 6%, dipentaerythritol hexaacrylate 3%, benzophenone 1%, silver powder 74% having an average particle size of 1.2 μm, and organic solvent (diethylene glycol monobutyl ether acetate) 13%, weighed and mixed, A photosensitive silver paste was obtained by kneading with three rollers.

  The obtained photosensitive silver paste was screen printed on a 50 inch substrate (Murakami Co., Ltd.), dried with an IR dryer (Chuo Riken Co., Ltd.), and then exposed through a mask on which a stripe pattern was formed. . After the exposure, development was performed using the following developing device (the exposure machine was manufactured by Hitachi Electronics Engineering).

  The developing device includes a developing unit 11 (not shown), a tank unit 12, and an inorganic powder collecting unit 10. The developing unit 11 is provided with nozzles facing downward at a pitch of 150 mm per shower tube. Under this, the developer moves at a constant speed, and after the developer is sprayed from the nozzle onto the developer, it is collected and guided to the tank unit 12.

  The tank unit 12 has a capacity of 300 L and is divided into three rooms by a partition plate 13. The capacities are 50L, 70L, and 180L in order, and the developer is led from the developing unit 11 to the 50L tank, and has a cascade structure that passes the partition plate 13 and flows in the order of the 70L tank and the 180L tank. The concentration of the developer is always controlled by an automatic titrator, and monoethanolamine, which is a developer stock solution, is injected at the set lower limit value to adjust the set value concentration (0.2 wt% monoethanolamine aqueous solution). A line extending from the 50 L tank to the inorganic powder collecting unit 10 is drawn, and after entering the inorganic powder collecting unit 10, the tank is returned to the 180 L tank. In the 180 L tank, the temperature is adjusted by a heater while stirring the developer, and is sucked up by a pump from here, guided to a shower tube, and sprayed to the developer again.

  The inorganic powder recovery unit 10 includes a decanter type centrifugal separator and a filter having a filter diameter of 0.5 μm connected in series. As a flow of the liquid, the liquid is introduced from the tank unit 50L by a pump, the clarified developer 8 is passed through the filter, and then the liquid is returned to the 180 L tank. The centrifuge device is a decanter type device having a separating plate 9 as shown in FIG. The main constituent material is SUS304, but the tip of the screw conveyor 3 that is heavily worn is subjected to wear resistance treatment with a WC chip attached.

  Development was performed using this developing device, and a striped silver electrode was formed with a thickness of 8 μm before firing. By development, 120 g of inorganic powder (glass powder and silver powder) per substrate is mixed into the developer. 200 sheets of this were developed, and inorganic powder was recovered. The inorganic powder after removing moisture was 23 kg.

  Subsequently, 23 kg of recovered inorganic powder and 120 L of butyl acetate were placed in a 200 L polyethylene container equipped with an air motor explosion-proof stirrer (manufactured by Chuo Rika Co., Ltd.), and stirred at 400 rpm for 5 hours. After stopping the stirring, the mixture was allowed to stand at room temperature for 18 hours. After removing the supernatant using an electric pump, 120 L of purified water was added and stirred at 400 rpm for 5 hours. After stopping the stirring, the mixture was allowed to stand at room temperature for 18 hours. Stirring with this purified water, standing, and supernatant removal operation were repeated 5 times.

  After the fifth supernatant removal operation, the inorganic powder in the container was transferred to a hollow bat and dried in a ventilated oven (manufactured by Koyo Lindberg Co., Ltd.) at 350 ° C. for 48 hours. After drying, crush the solidified part with a spatula and powder it, and then use a sieve shaker (manufactured by Tanaka Tech Co., Ltd.) set with a sieve of 16, 50, 100, 200, 440 mesh from the top. Classification was performed. The processing conditions were as follows: shaking number 250 rpm, hammer hit number 125 tpm.

After recovery, a photosensitive silver paste was prepared using the treated inorganic powder. Recovered / treated inorganic powder 77%, methyl methacrylate / methacrylic acid copolymer (weight composition ratio 60/40, weight average molecular weight 32000) 6%, dipentaerythritol hexaacrylate 3%, benzophenone 1%, organic solvent (diethylene glycol mono Butyl ether acetate) 13% was weighed, mixed, and kneaded with three rollers to obtain a photosensitive silver paste. At this time, the kneading state was the same as the state in which unused inorganic powder was used, and no problem was found. The viscosity of the obtained photosensitive silver paste was measured using a Brookfield viscometer (Brookfield, model DV-1). The viscosity at a shear rate of 1.2 s ⁻¹ was 41 Pa · s (25 ° C.).

  Next, a photosensitive barrier rib paste was prepared. Glass powder having an average particle diameter of 2 μm consisting of lithium oxide 10% by weight, silicon oxide 25% by weight, boron oxide 30% by weight, zinc oxide 15% by weight, aluminum oxide 5% by weight, calcium oxide 15% by weight is used. It was. Examples of the organic component including the photosensitive component include a carboxyl group-containing acrylic polymer (“cyclomer” P (ACA250, manufactured by Daicel Chemical Industries)) 30% by weight, dipentaerythritol hexaacrylate 30% by weight, and a photopolymerization initiator. A material comprising 10% by weight of benzophenone and 30% by weight of propylene glycol monomethyl ether acetate was used. The photosensitive partition paste was prepared by mixing the glass powder and the organic component containing the photosensitive component in a weight ratio of 70:30, and then kneading them with three rollers.

  The obtained photosensitive partition paste was applied to a 50-inch substrate using a die coater (manufactured by Toray Industries, Inc.), dried with an IR dryer, and then exposed through a mask on which a stripe pattern was formed. After the exposure, development was performed using a developing device having the same specifications as the photosensitive silver paste, and stripe-shaped partition walls were formed with a thickness of 200 μm before firing. By development, 300 g of glass powder per substrate is mixed into the developer. 100 sheets of this were developed, and glass powder was recovered. The glass powder after removing moisture was 29 kg.

After the collection, the same operation (washing, drying, classification) was performed under the same conditions as in the case of the photosensitive silver paste, and after the collection, a photosensitive partition paste was prepared using the treated glass powder. The recovered / processed glass powder and the organic component including the photosensitive component were mixed at a weight ratio of 70:30, respectively, and then kneaded with three rollers to prepare a photosensitive partition paste. At this time, the kneading state was the same as the state in which unused inorganic powder was used, and no problem was found. The viscosity of the obtained photosensitive partition paste was measured using a Brookfield type viscometer (Brookfield, model DV-1). The viscosity at a shear rate of 1.2 s ⁻¹ was 30 Pa · s (25 ° C.).

  Next, a back plate of an AC (alternating current) type plasma display panel was formed using a 50-inch glass substrate (PD-200; manufactured by Asahi Glass Co., Ltd.).

  A stripe-shaped electrode having a pitch of 140 μm, a line width of 60 μm, and a thickness of 4 μm after firing was formed on the substrate by photolithography using a photosensitive silver paste using the collected and treated inorganic powder as a writing electrode. There was no problem with pattern formation at this time. A dielectric paste was applied to the substrate and then fired at 550 ° C. to form a dielectric layer having a thickness of 10 μm.

  Further, a pattern is formed by photolithography using a photosensitive partition paste using glass powder collected / processed on the dielectric layer, and then baked at 570 ° C. for 15 minutes, with a pitch of 140 μm, a line width of 20 μm, and a height of 100 μm. A stripe-shaped partition wall pattern was formed. There was no problem with pattern formation at this time. Moreover, the surface roughness (Ra) of the partition walls was 0.8 μm.

  Each color phosphor paste was applied and fired (500 ° C., 30 minutes) using a screen printing method on the barrier ribs thus formed to form phosphor layers on the side and bottom portions of the barrier ribs.

  Next, the front plate was produced by the following steps. First, ITO was formed on the same glass substrate as the back plate by sputtering, and then a resist was applied thereon, and a transparent electrode having a thickness of 0.1 μm and a line width of 200 μm was formed by exposure / development processing and etching processing. Further, a bus electrode having a thickness of 10 μm after firing was formed by photolithography using a photosensitive silver paste made of black silver powder. Electrodes with a pitch of 140 μm and a line width of 60 μm were prepared.

  Furthermore, 20 μm of a transparent dielectric paste was applied on the electrode-formed front plate, and baked by holding at 430 ° C. for 20 minutes. Next, an MgO film having a thickness of 0.5 μm was formed by using an electron beam vapor deposition device so as to uniformly coat the formed transparent electrode, black electrode, and dielectric layer, thereby completing the front plate.

  The obtained front glass substrate was bonded and sealed to the rear glass substrate, and then a discharge gas was sealed, and a driving circuit was joined to produce a plasma display (PDP). When the display was observed by applying a voltage to this panel, the display state was good. In addition, 500 substrates were loaded, and the yield of PDP production was 89%. The defect rate of 11% was mainly caused by foreign matters and aggregates in the photosensitive paste.

Example 2
The same procedure as in Example 1 was performed except that 4-hydroxy-4-methyl-2-pentanone was used as the cleaning solution after recovery from the developer. No problem was found in the kneaded state when a photosensitive silver paste and a photosensitive barrier rib paste were prepared using the recovered / treated inorganic powder. When the viscosity of the obtained photosensitive silver paste and photosensitive partition paste was measured using a Brookfield viscometer (Brookfield, model DV-1), the viscosities were 40 and 31 Pa · s (25, respectively). ° C and shear rate of 1.2 s ^-1 ).

  Next, PDP was produced using this photosensitive silver paste and photosensitive partition paste. There was no problem with the pattern formation of the back plate electrodes and barrier ribs. When the voltage was applied to the panel and the display was observed, the display state was good. In addition, 500 substrates were loaded, and the yield of PDP production was 90%. The defect rate of 10% was mainly caused by foreign matters and aggregates in the photosensitive paste.

Example 3
The same procedure as in Example 1 was performed, except that 0.28N hydrochloric acid was used as the cleaning solution after recovery from the developer. No problem was found in the kneaded state when a photosensitive silver paste and a photosensitive barrier rib paste were prepared using the recovered / treated inorganic powder. When the viscosity of the obtained photosensitive silver paste and photosensitive partition paste was measured using a Brookfield viscometer (Brookfield, model DV-1), the viscosities were 39 and 31 Pa · s (25, respectively). ° C and shear rate of 1.2 s ^-1 ).

  Next, PDP was produced using this photosensitive silver paste and photosensitive partition paste. There was no problem with the pattern formation of the back plate electrodes and barrier ribs. When the voltage was applied to the panel and the display was observed, the display state was good. In addition, 500 substrates were loaded, and the yield of PDP production was 89%. The defect rate of 11% was mainly caused by foreign matters and aggregates in the photosensitive paste.

Example 4
The same procedure as in Example 1 was performed except that the drying temperature after recovery from the developer was 200 ° C. No problem was found in the kneaded state when a photosensitive silver paste and a photosensitive barrier rib paste were prepared using the recovered / treated inorganic powder. When the viscosity of the obtained photosensitive silver paste and photosensitive partition paste was measured using a Brookfield viscometer (Brookfield, model DV-1), the viscosities were 63 and 44 Pa · s (25, respectively). C. and shear rate of 1.2 s.sup.- ¹ ), which were slightly higher.

  Next, PDP was produced using this photosensitive silver paste and photosensitive partition paste. Although no problem was found in the pattern forming properties of the electrodes on the back plate and the barrier ribs, there were some portions where uneven coating was observed. When the voltage was applied to the panel and the display was observed, the display state was good. In addition, 500 substrates were loaded, and the yield of PDP production was 83%. The defective rate of 17% was mainly caused by foreign matters, aggregates and coating unevenness in the photosensitive paste.

Example 5
The same procedure as in Example 1 was performed except that the sieving treatment after drying was not performed. Using the recovered / treated inorganic powder, a photosensitive silver paste and a photosensitive partition paste were produced. As a result, there were many powder aggregates and the dispersion time was long. When the viscosity of the obtained photosensitive silver paste and the photosensitive partition paste was measured using a Brookfield viscometer (Brookfield, model DV-1), the viscosities were 42 and 34 Pa · s (25, respectively). ° C and shear rate of 1.2 s ^-1 ).

  Next, PDP was produced using this photosensitive silver paste and photosensitive partition paste. Although no problem was found in the patterning properties of the electrodes on the back plate and the barrier ribs, the surface roughness of the barrier ribs was slightly increased (Ra = 1.7 μm). When the voltage was applied to the panel and the display was observed, the display state was good. In addition, 500 substrates were loaded, and the yield of PDP production was 81%. The cause of the 19% defect rate was the absence of partition walls when the front glass substrate and the back glass substrate were bonded and sealed mainly due to foreign matters, aggregates and surface roughness of the partition walls in the photosensitive paste.

Example 6
The same procedure as in Example 1 was performed except that the powder collected / processed from the developer and the unused powder were mixed at a weight ratio of 70:30 to prepare a paste. There was no problem in the kneading state when the paste was produced. When the viscosity of the obtained photosensitive silver paste and photosensitive partition paste was measured using a Brookfield viscometer (Brookfield, model DV-1), the viscosities were 40 and 31 Pa · s (25, respectively). ° C and shear rate of 1.2 s ^-1 ).

  Next, PDP was produced using this photosensitive silver paste and photosensitive partition paste. There was no problem with the pattern formation of the back plate electrodes and barrier ribs. When the voltage was applied to the panel and the display was observed, the display state was good. In addition, 500 substrates were loaded, and the yield of PDP production was 91%. The cause of the 9% defect rate was mainly due to foreign matters and aggregates in the photosensitive paste.

Example 7
The same procedure as in Example 1 was performed except that the powder collected / processed from the developer and the unused powder were mixed at a weight ratio of 50:50 to prepare a paste. There was no problem in the kneading state when the paste was produced. When the viscosity of the obtained photosensitive silver paste and the photosensitive partition paste was measured using a Brookfield viscometer (Brookfield, model DV-1), the viscosity was 39 and 30 Pa · s (25, respectively). ° C and shear rate of 1.2 s ^-1 ).

  Next, PDP was produced using this photosensitive silver paste and photosensitive partition paste. There was no problem with the pattern formation of the back plate electrodes and barrier ribs. When the voltage was applied to the panel and the display was observed, the display state was good. In addition, 500 substrates were loaded, and the yield of PDP production was 91%. The cause of the 9% defect rate was mainly due to foreign matters and aggregates in the photosensitive paste.

Example 8
The same procedure as in Example 1 was performed except that the powder collected / processed from the developer and the unused powder were mixed at a weight ratio of 20:80 to prepare a paste. There was no problem in the kneading state when the paste was produced. When the viscosity of the obtained photosensitive silver paste and photosensitive partition paste was measured using a Brookfield viscometer (manufactured by Brookfield, model DV-1), the viscosity was 40 and 30 Pa · s (25, respectively). ° C and shear rate of 1.2 s ^-1 ).

  Next, PDP was produced using this photosensitive silver paste and photosensitive partition paste. There was no problem with the pattern formation of the back plate electrodes and barrier ribs. When the voltage was applied to the panel and the display was observed, the display state was good. In addition, 500 substrates were loaded, and the yield of PDP production was 93%. The cause of the defective rate of 7% was mainly due to foreign matters and aggregates in the photosensitive paste.

Example 9
The same procedure as in Example 1 was conducted except that the paste collected by mixing the powder recovered / processed from the developer and the unused powder at a weight ratio of 5:95, respectively. There was no problem in the kneading state when the paste was produced. When the viscosity of the obtained photosensitive silver paste and the photosensitive partition paste was measured using a Brookfield viscometer (Brookfield, model DV-1), the viscosity was 39 and 30 Pa · s (25, respectively). ° C and shear rate of 1.2 s ^-1 ).

  Next, PDP was produced using this photosensitive silver paste and photosensitive partition paste. There was no problem with the pattern formation of the back plate electrodes and barrier ribs. When the voltage was applied to the panel and the display was observed, the display state was good. In addition, 500 substrates were loaded, and the yield of PDP production was 96%. The cause of the defective rate of 4% was mainly due to foreign matters and aggregates in the photosensitive paste.

Comparative Example 1
The same procedure as in Example 1 was performed except that the paste was prepared using unused powder without collecting the powder. There was no problem in the kneading state when the paste was produced. When the viscosity of the obtained photosensitive silver paste and photosensitive partition paste was measured using a Brookfield viscometer (manufactured by Brookfield, model DV-1), the viscosity was 40 and 30 Pa · s (25, respectively). ° C and shear rate of 1.2 s ^-1 ).

  Next, PDP was produced using this photosensitive silver paste and photosensitive partition paste. There was no problem with the pattern formation of the back plate electrodes and barrier ribs. When the voltage was applied to the panel and the display was observed, the display state was good. In addition, 500 substrates were loaded, and the yield of PDP production was 96%. The cause of the defective rate of 4% was mainly due to foreign matters and aggregates in the photosensitive paste.

Comparative Example 2
The same procedure as in Example 1 was performed except that the powder recovered from the developer was not processed. When the paste was prepared, the kneading state was poor and a long dispersion time was required. When the viscosity of the obtained photosensitive silver paste and the photosensitive partition paste was measured using a Brookfield viscometer (Brookfield, model DV-1), the viscosities were 105 and 72 Pa · s (25, respectively). ° C and shear rate of 1.2 s ^-1 ).

  Next, an attempt was made to form a back plate electrode and barrier rib pattern using this photosensitive silver paste and photosensitive barrier rib paste. However, a good pattern could not be formed and a PDP could not be manufactured.

It is simple sectional drawing which shows an example of the centrifuge used for this invention. It is the simple schematic which shows an example of the centrifuge used for this invention. It is the simple schematic which shows an example of the tank part used for this invention. It is the simple schematic which shows an example of the tank part used for this invention.

Explanation of symbols

1: Bowl part 2: Inorganic powder 3: Screw conveyor 4: Motor 5: Reducer 6: Feed pipe 7: Developer separated by centrifuge 8: Developer 9: Separation plate 10: Inorganic powder recovery part 11: Developer Part 12: Tank part 13: Partition plate 14: Liquid flow

Claims (11)

Reuse of inorganic powder characterized in that inorganic powder is recovered from the developer of the photosensitive paste coating film containing the inorganic powder and the photosensitive organic component, and the inorganic powder is reused after being washed and classified. Method. The method for reusing an inorganic powder according to claim 1, wherein the inorganic powder is collected by a centrifugal separation mechanism. The method for reusing inorganic powder according to claim 2, wherein the centrifugal separation mechanism is a decanter system. The method for reusing an inorganic powder according to any one of claims 1 to 3, wherein the inorganic powder is washed with an organic solvent or / and an acidic aqueous solution. The method for reusing an inorganic powder according to any one of claims 1 to 4, wherein the inorganic powder is heat-treated between the cleaning treatment and the classification treatment of the inorganic powder. 6. The method for reusing an inorganic powder according to claim 5, wherein the inorganic powder is subjected to a heat treatment at 300 ° C. or higher after the washing treatment. A photosensitive paste using an inorganic powder recycled by the method according to claim 1. A photosensitive paste comprising a mixture of an inorganic powder reused by the method according to claim 1 and an unused inorganic powder. The photosensitive paste according to claim 8, wherein the ratio of the reused inorganic powder / unused inorganic powder is in the range of 1/99 to 80/20. The photosensitive paste according to claim 7, wherein the inorganic powder is at least one selected from the group consisting of glass, a refractory filler, a metal, and a metal oxide. It is a manufacturing method of the member for display panels including the process of apply | coating a photosensitive paste on a board | substrate, and drying, Comprising: The photosensitive paste in any one of Claims 7-10 is used for a photosensitive paste, A method for manufacturing a display panel member.

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