JP2013080581A - Dielectric paste for plasma display panel, and plasma display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a plasma display panel reduced in power consumption, the plasma display panel being useful for a large screen display device or the like.SOLUTION: A dielectric paste of the present invention includes dielectric glass, a solvent and a resin. The solvent contains texanol and a surfactant, the texanol has a content of 40 wt.% or more and 99 wt.% or less in the organic solvent, and the surfactant is polyacrylate and has a content of 0.2 wt.% or more and 1.0 wt.% or less in the organic solvent. The resin contains 40 wt.% or more and 80 wt.% or less of an ethyl cellulose resin and 20 wt.% or more and 80 wt.% or less of an acrylic resin in the resin. A molar ratio of the dielectric glass is 25% or more and 38% or less, and a BET value of the dielectric glass is 2.5 m/g or more and 3.2 m/g or less.

Description

  The technology disclosed herein relates to an electrode paste for a plasma display panel used for a display device or the like and a method for manufacturing the plasma display panel.

  Silver electrodes for ensuring conductivity are used as bus electrodes constituting display electrodes of a plasma display panel (hereinafter referred to as PDP). Low-melting glass is used for the dielectric layer covering the bus electrode.

  For example, Patent Document 1 discloses a technique for reducing voids in a dielectric layer by using a screen printing method and a die coating method in combination.

JP 2002-25433 A

  However, since the dielectric layer plays a role of holding electric charge, it tends to cause a breakdown voltage failure depending on a defect of the dielectric layer. The present invention solves this problem and provides a high-quality dielectric layer and PDP.

The electrode paste for PDP includes dielectric glass, a solvent, and a resin, and the solvent includes texanol and a surfactant. The texanol is 40 wt% or more and 99 wt% or less in the organic solvent. The surfactant is a polyacrylate, and is 0.2% by weight or more and 1.0% by weight or less in the organic solvent. The resin is 40% by weight or more and 80% by weight or less of the ethyl cellulose resin and 20% by weight or more and 80% by weight or less of the acrylic resin in the resin. The dielectric glass has a molar ratio of 25% to 38%. The dielectric glass has a BET value of 2.5 m ² / g or more and 3.2 m ² / g or less.

  ADVANTAGE OF THE INVENTION According to this invention, the withstand voltage defect of a dielectric material layer can be suppressed and a high quality PDP can be provided.

The perspective view which shows the structure of PDP concerning this Embodiment Sectional view showing the structure of the PDP front plate

[1. Structure of PDP]
The PDP 1 of the present embodiment is an AC surface discharge type PDP. As shown in FIGS. 1 and 2, the PDP 1 includes a front plate 2 made of a front glass substrate 3 and a back plate 10 made of a back glass substrate 11 and the like. The front plate 2 and the back plate 10 are hermetically sealed with a sealing material whose outer peripheral portion is made of glass frit or the like. The discharge space 16 inside the sealed PDP 1 is filled with discharge gas such as neon (Ne) and xenon (Xe) at a pressure of 55 kPa (400 Torr) to 80 kPa (600 Torr).

  On the front glass substrate 3, a pair of strip-like display electrodes 6 composed of scanning electrodes 4 and sustain electrodes 5 and black stripes (light shielding layers) 7 are arranged in a plurality of rows in parallel with each other. A dielectric layer 8 that functions as a capacitor is formed on the front glass substrate 3 so as to cover the display electrodes 6 and the black stripes 7. Further, a protective layer 9 made of magnesium oxide (MgO) or the like is formed on the surface of the dielectric layer 8.

Scan electrode 4 and sustain electrode 5 are each formed by laminating a bus electrode made of Ag on a transparent electrode made of a conductive metal oxide such as indium tin oxide (ITO), tin oxide (SnO ₂ ), and zinc oxide (ZnO). Has been.

  On the rear glass substrate 11, a plurality of address electrodes 12 made of a conductive material mainly composed of silver (Ag) are arranged in parallel to each other in a direction orthogonal to the display electrodes 6. The address electrode 12 is covered with a base dielectric layer 13. Further, a partition wall 14 having a predetermined height is formed on the base dielectric layer 13 between the address electrodes 12 to divide the discharge space 16. In each groove between the barrier ribs 14, a phosphor layer 15 that emits red light by ultraviolet rays, a phosphor layer 15 that emits green light, and a phosphor layer 15 that emits blue light are sequentially applied to each address electrode 12. Yes. A discharge cell is formed at a position where the display electrode 6 and the address electrode 12 intersect. Discharge cells having red, green, and blue phosphor layers 15 arranged in the direction of the display electrode 6 serve as pixels for color display.

  In the present embodiment, the discharge gas sealed in the discharge space 16 contains 10% by volume or more and 30% by volume or less of Xe.

On the front glass substrate 3 manufactured by the float method or the like, the display electrodes 6 and the black stripes 7 made of the scanning electrodes 4 and the sustain electrodes 5 are formed in a pattern. Scan electrode 4 and sustain electrode 5 are made of transparent electrodes 4a and 5a made of indium tin oxide (ITO) or tin oxide (SnO ₂ ), respectively, and metal bus electrodes 4b and 5b formed on transparent electrodes 4a and 5a. It is comprised by. The metal bus electrodes 4b and 5b are used for the purpose of imparting conductivity in the longitudinal direction of the transparent electrodes 4a and 5a, and are formed of a conductive material whose main component is a silver (Ag) material.

[2. Manufacturing method of PDP1]
[2-1. Manufacturing method of front plate 2]
Scan electrode 4 and sustain electrode 5 and black stripe 7 are formed on front glass substrate 3. The transparent electrodes 4a and 5a and the metal bus electrodes 4b and 5b are formed by photolithography. As a material for the metal bus electrodes 4b and 5b, an electrode paste containing silver (Ag), a glass frit for binding silver, a photosensitive resin, a solvent, and the like is used. First, an electrode paste is applied to the front glass substrate 3 by a screen printing method or the like. Next, the solvent in the electrode paste is removed by a drying furnace. Next, the electrode paste is exposed through a photomask having a predetermined pattern.

  Next, the electrode paste is developed to form a bus electrode pattern. Finally, the bus electrode pattern is fired at a predetermined temperature in a firing furnace. That is, the photosensitive resin in the electrode pattern is removed. Further, the glass frit in the electrode pattern is melted and re-solidified. Similarly, a black stripe 7 is formed. As a material for the black stripe 7, a paste containing a black pigment is used.

  Next, the dielectric layer 8 is formed. As a material of the dielectric layer 8, a dielectric paste containing dielectric glass and a binder component (resin, solvent, etc.) is used. First, a dielectric paste is applied on the front glass substrate 3 by a die coating method or the like so as to cover the scan electrodes 4, the sustain electrodes 5 and the black stripes 7 with a predetermined thickness. Next, the solvent in the dielectric paste is removed by a drying furnace. Finally, the dielectric paste is fired at a temperature of about 450 ° C. to 600 ° C. in a firing furnace. That is, the resin in the dielectric paste is removed. In addition, the dielectric glass melts and resolidifies. Through the above steps, the dielectric layer 8 is formed. That is, the dielectric paste contains a resin and a solvent in addition to the dielectric glass, but components other than the dielectric glass are removed by drying and firing. Therefore, the dielectric layer 8 is substantially composed of a component of dielectric glass.

  Here, besides the method of die coating the dielectric paste, a screen printing method, a spin coating method, or the like can be used. Alternatively, a film that becomes the dielectric layer 8 can be formed by a CVD (Chemical Vapor Deposition) method or the like without using the dielectric paste.

  Next, a protective layer 9 made of magnesium oxide (MgO) or the like is formed on the dielectric layer 8.

  Through the above steps, the scanning electrode 4, the sustain electrode 5, the black stripe 7, the dielectric layer 8, and the protective layer 9 are formed on the front glass substrate 3, and the front plate 2 is completed.

[2-2. Manufacturing method of back plate 10]
Address electrodes 12 are formed on the rear glass substrate 11 by photolithography. As an address electrode material, silver (Ag) for securing conductivity, glass frit for binding silver, a photosensitive resin, a solvent, and the like are used. First, the address electrode paste is applied on the rear glass substrate 11 with a predetermined thickness by screen printing or the like. Next, the solvent in the address electrode paste is removed by a drying furnace. Next, the address electrode paste is exposed through a photomask having a predetermined pattern. Next, the address electrode paste is developed to form an address electrode pattern. Finally, the address electrode pattern is fired at a predetermined temperature in a firing furnace. That is, the photosensitive resin in the address electrode pattern is removed. Further, the glass frit in the address electrode pattern is melted and re-solidified. The address electrode 12 is formed by the above process. Here, besides the method of screen printing the address electrode paste, a sputtering method, a vapor deposition method, or the like can be used.

  Next, the base dielectric layer 13 is formed. As a material for the base dielectric layer 13, a base dielectric paste containing a dielectric glass frit, a resin, a solvent, and the like is used. First, a base dielectric paste is applied by a screen printing method or the like so as to cover the address electrodes 12 on the rear glass substrate 11 on which the address electrodes 12 are formed with a predetermined thickness. Next, the solvent in the base dielectric paste is removed by a drying furnace. Finally, the base dielectric paste is fired at a predetermined temperature in a firing furnace. That is, the resin in the base dielectric paste is removed. In addition, the dielectric glass frit melts and resolidifies. Through the above steps, the base dielectric layer 13 is formed. Here, other than the method of screen printing the base dielectric paste, a die coating method, a spin coating method, or the like can be used. Further, a film to be the base dielectric layer 13 can be formed by CVD (Chemical Vapor Deposition) method or the like without using the base dielectric paste.

  Next, the partition wall 14 is formed by photolithography. As a material for the partition wall 14, a partition paste containing a filler, a glass frit for binding the filler, a photosensitive resin, a solvent, and the like is used. First, the barrier rib paste is applied on the underlying dielectric layer 13 with a predetermined thickness by a die coating method or the like. Next, the solvent in the partition wall paste is removed by a drying furnace. Next, the barrier rib paste is exposed through a photomask having a predetermined pattern. Next, the barrier rib paste is developed to form a barrier rib pattern. Finally, the partition pattern is fired at a predetermined temperature in a firing furnace. That is, the photosensitive resin in the partition pattern is removed. Further, the glass frit in the partition wall pattern is melted and re-solidified. The partition wall 14 is formed by the above process. Here, in addition to the photolithography method, a sandblast method or the like can be used.

  Next, the phosphor layer 15 is formed. As the material of the phosphor layer 15, a phosphor paste containing phosphor particles, a binder, a solvent, and the like is used. First, a phosphor paste is applied on the base dielectric layer 13 between adjacent barrier ribs 14 and on the side surfaces of the barrier ribs 14 by a dispensing method or the like. Next, the solvent in the phosphor paste is removed by a drying furnace. Finally, the phosphor paste is fired at a predetermined temperature in a firing furnace. That is, the resin in the phosphor paste is removed. The phosphor layer 15 is formed by the above steps. Here, in addition to the dispensing method, a screen printing method or the like can be used.

  Through the above steps, the back plate 10 having predetermined components on the back glass substrate 11 is completed.

[2-3. Assembly method of front plate 2 and rear plate 10]
First, the front plate 2 and the back plate 10 are arranged to face each other so that the display electrodes 6 and the address electrodes 12 are orthogonal to each other. Next, the periphery of the front plate 2 and the back plate 10 is sealed with glass frit. Next, a discharge gas containing Ne, Xe or the like is sealed in the discharge space 16 to complete the PDP 1.

[3. Details of Dielectric Layer 8]
In recent years, PDPs are required to have higher definition. In the high definition PDP, the number of scanning lines increases and the number of display electrodes increases. That is, the display electrode interval is reduced. Therefore, the diffusion of silver ions from the silver electrode constituting the display electrode to the dielectric layer and the glass substrate increases. When silver ions diffuse into the dielectric layer or the glass substrate, they are reduced by alkali metal ions in the dielectric layer or divalent tin ions contained in the glass substrate to form silver colloids. As a result, the dielectric layer and the glass substrate are strongly colored yellow or brown, and the silver oxide is subjected to a reducing action to generate oxygen and generate bubbles in the dielectric layer.

  Therefore, as the number of scanning lines increases, yellowing of the glass substrate and generation of bubbles in the dielectric layer become more prominent, which significantly deteriorates image quality and causes insulation failure of the dielectric layer.

  However, the conventional dielectric layer that does not contain a lead component proposed for environmental considerations has a problem that it cannot satisfy both the suppression of yellowing phenomenon and the suppression of insulation failure of the dielectric layer. It was.

  The technology disclosed in this embodiment can solve the above-described problems, and can realize a PDP that ensures high luminance and high reliability even in high-definition display and further considers environmental issues.

  The dielectric layer 8 is required to have a high withstand voltage and a high light transmittance. These characteristics greatly depend on the composition of the dielectric layer 8.

Conventionally, in order to sinter the dielectric paste at about 450 ° C. to 600 ° C., the dielectric glass contains 20% by weight or more of lead oxide. However, in consideration of the environment, the dielectric glass contains substantially 0.5 to 40% by weight of bismuth oxide (Bi ₂ O ₃ ) without substantially containing a lead component.

When the content of Bi ₂ O _{3 in} the dielectric glass increases, the softening point of the dielectric glass decreases. Lowering the softening point of the dielectric glass has various advantages in the manufacturing process. However, since bismuth (Bi) -based materials are expensive, increasing the amount of Bi ₂ O ₃ added causes an increase in the cost of the raw materials used. Therefore, there is a technique using an alkali metal oxide selected from lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and the like as an alternative material for the Bi-based material. The atomic weight of Bi is 209. The greater the atomic weight, the greater the density. Therefore, it becomes difficult to realize a low dielectric constant glass required for improving the characteristics of future PDPs. Therefore, it is necessary to reduce the content of the glass material having a large atomic weight.

[3-1. Alkali metal oxide]
In the present embodiment, the dielectric glass contains potassium oxide (K ₂ O). Further, in the present embodiment, the dielectric glass may contain K ₂ O, and at least one of lithium oxide (Li ₂ O) and sodium oxide (Na ₂ O). This is based on the following reason. A front glass substrate 3 of a general PDP contains a large amount of K ₂ O and Na ₂ O. And if firing the dielectric layer 8 at a high temperature of 550 ° C. or higher, K ₂ O contained in the dielectric glass, Li ₂ O and alkali metal in the Na ₂ O contained in front glass substrate 3 ions (Li ^+, Exchange of Na ⁺ , K ⁺ ) occurs. However, Li ⁺ , Na ⁺ and K ⁺ have different contributions to the thermal expansion coefficient of the glass substrate. Therefore, when ion exchange occurs during firing of the dielectric layer 8, the amount of heat shrinkage in the vicinity of the dielectric layer 8 of the front glass substrate 3 and the amount of heat shrinkage in the portion other than the vicinity of the dielectric layer 8 of the front glass substrate 3. As a result, the front glass substrate 3 on which the dielectric layer 8 is formed is greatly warped.

On the other hand, when the dielectric glass contains K ₂ O as in the present embodiment, even if the above ion exchange occurs, the difference in heat shrinkage hardly occurs, and the warp of the front glass substrate 3 is caused. Can be reduced. As a result, the content of Bi ₂ O ₃ contained in the dielectric glass can be reduced to 5 mol% or less. Moreover, the curvature of the front glass substrate 3 can also be reduced. In the following description, unless otherwise specified, the content indicates the content in dielectric glass expressed in mol%. That is, the content is the content in the dielectric layer 8.

Further, the content of K ₂ O is preferably not more than 10 mol% 6 mol% or more. When the content of K ₂ O is 6 mol% or more, it becomes easy to lower the softening point of the dielectric glass. On the other hand, when the content of K ₂ O exceeds 10 mol%, the strength of the dielectric layer decreases and the dielectric constant increases.

Further, when the dielectric glass contains K ₂ O and at least one of Li ₂ O and Na ₂ O, in addition to reducing the warp of the front glass substrate 3, the softening point of the dielectric glass It becomes easy to lower.

Further, the content of Na ₂ O is preferably at most 0.5 mol% to 3 mol%. When the content of Na ₂ O increases, yellowing easily occurs in the front glass substrate 3 and the dielectric layer 8. As a result of evaluation by the inventors, it was found that yellowing is suppressed when the content of Na ₂ O is 3 mol% or less. On the other hand, it was found that when the content of Na ₂ O is 0.5 mol% or more, the warpage of the front glass substrate 3 can be reduced.

Furthermore, it is more preferable that the content of K ₂ O is larger than the total content of Li ₂ O and Na ₂ O. According to this structure, the change of the thermal expansion coefficient of the front glass substrate 3 can be suppressed, and the front glass substrate 3 can be prevented from greatly warping.

[3-2. MgO]
As described above, K ₂ O, Li ₂ O and Na ₂ O can lower the softening point of the dielectric glass. On the other hand, the alkali metal oxides represented by K ₂ O, Li ₂ O and Na ₂ O promote the reduction action of silver ions diffused from the metal bus electrodes 4b and 5b. That is, more silver colloid is formed. Therefore, phenomena such as coloring of the dielectric layer and generation of bubbles occur. As a result, there is a problem that image quality degradation of the PDP and insulation failure of the dielectric layer occur.

  In view of such a problem, the present embodiment contains 0.3 mol% or more and 1.0 mol% or less of MgO. MgO can suppress the generation of bubbles due to the binder component contained in the dielectric paste. In addition, the insulation of the dielectric layer is improved, and coloring of the metal bus electrodes 4b and 5b can be reduced. If the content of MgO is less than 0.3 mol%, the above effect cannot be obtained. Further, if the content of MgO is more than 1.0 mol%, the total light transmittance of the dielectric layer 8 is deteriorated (hereinafter referred to as devitrification).

The inventors investigated the relationship between the result of measuring the number of protrusions of the dielectric layer relative to the content of MgO and the result of measuring the degree of yellowing. Three kinds of dielectrics having different MgO contents were produced on a small-sized substrate on which a metal bus electrode was formed by the same method as the above production method. The following measurements were taken. The number of protrusions is measured by measuring the number of protrusions having a diameter equal to or larger than a certain diameter in a certain area after firing the dielectric layer. The degree of yellowing is determined by the degree of yellowing caused by silver (Ag). B ^* value was measured by CR-300). As a result, it has been found that as the MgO content increases, the number of protrusions of the dielectric layer changes, and the b * value indicating the degree of yellowing also decreases.

  If molybdenum (Mo), tungsten (W), or the like is added to suppress the generation of bubbles, the dielectric layer may be devitrified.

  However, when adding MgO, the total light transmittance does not fall below 78.5% until the MgO content exceeds 1.0 mol%. The total light transmittance of the dielectric layer 8 in the PDP is preferably 78.5% or more. When the total light transmittance is less than 78.5%, the brightness of the PDP decreases. Therefore, devitrification is reduced if the content of MgO is 1.0 mol% or less. In addition, HM-150 (made by Murakami Color Research Laboratory Co., Ltd.) was used for the measurement of the total light transmittance. In the present embodiment, the total light transmittance is a transmittance of light having a wavelength of 550 nm incident from a direction orthogonal to the front glass substrate 3 on which the dielectric layer 8 is formed.

  In the dielectric layer 8 used for this study, the composition of the dielectric layer 8 was adjusted so that the total amount of MgO and ZnO, which is the same divalent metal oxide as MgO, was equal. Furthermore, the composition other than MgO and ZnO has not changed. Therefore, the above result is considered to be based on the change in the content of MgO.

  When the dielectric layer 8 does not contain a Ca component, the oxidizing power as the dielectric layer is reduced. This may result in insufficient combustion of organic materials such as binder components contained in the dielectric paste. In this case, bubbles are generated during firing of the dielectric layer and remain as protrusions. However, since the present embodiment contains 0.3 mol% or more and 1.0 mol% or less of MgO, insulation failure of the dielectric layer is suppressed.

[3-3. SiO ₂ ]
This embodiment contains 35 mol% or more and 50 mol% or less of SiO ₂ . As the content of SiO ₂ increases, the breaking strength of the dielectric layer 8 increases. Therefore, the reliability of the PDP is improved. Further, when the content of SiO ₂ is increased, the softening speed of the dielectric glass is decreased. As a result, the growth of bubbles generated in the dielectric layer 8 is suppressed. Therefore, the quality of the dielectric layer 8 is further improved. The above effect can not be obtained when the content of SiO ₂ is less than 35 mol%. On the other hand, if the content of SiO ₂ exceeds 50 mol%, the firing temperature of the dielectric layer 8 increases excessively, which is not preferable.

  The breaking strength was evaluated by the iron ball dropping method. The breaking strength is the strength of the dielectric layer 8 and the front glass substrate 3 due to the collision between the dielectric layer 8 and the partition wall 14. First, the PDP 1 is horizontally arranged so that the front plate 2 is on the top. Next, an iron ball having a diameter of 10 mm is arranged at a predetermined height on the PDP 1. Next, an iron ball falls on the PDP 1. If the front plate 2 is not damaged even if the iron ball falls, the height at which the iron ball is arranged increases. Further, an iron ball falls on the PDP 1. If the front plate 2 is damaged as a result of the fall of the iron ball, the height at which the iron ball is disposed at this time is the breaking height. The higher the breaking height, the greater the breaking strength.

[4. Dielectric paste]
The dielectric paste for forming the dielectric layer is composed of a powder of glass material and binder components such as a vehicle and a solvent.

[4-1. Glass material powder]
Regarding the components other than the above components, the component ratio of the dielectric glass material is adjusted so that the softening point is lower than the firing temperature T (° C.) of the dielectric layer 8. In the present embodiment, the softening point of the glass material is 600 ° C. or less. The glass material of this composition component is pulverized by a wet jet mill, a ball mill, or the like so that the average particle size is 0.5 μm to 3.0 μm.

  Here, the specific surface area of the glass material will be described.

<BET value>
In the prior art, the yield of the glass material can be improved by broadening the particle size distribution during pulverization / classification of the dielectric glass material from the viewpoint of cost reduction. However, when the particle size distribution is broad, fine powder having a finer particle diameter than before or coarse powder having a larger particle diameter is contained.

  When coarse powder is mixed, in the step of filtering the dielectric paste, clogging occurs in the filtration unit, and the replacement frequency of the filtration filter increases, leading to an increase in cost. Further, when fine powder is mixed, cracks in the dry film after applying the dielectric paste are likely to occur. The cracks generated in the dried film may not be completely repaired even if the glass is softened in the dielectric layer firing step. In this case, the insulation resistance of the dielectric layer is lowered, and the yield is reduced. In particular, it is difficult to measure fine powder easily with high accuracy using a particle size distribution measuring device.

Therefore, in the present embodiment, in the step of forming the dielectric layer 8, the BET value of the dielectric glass material used for the dielectric paste is set to 2.5 m ² / g or more and 3.2 m ² / g or less.

  Thus, mixing of fine powder can be managed by setting the BET value of the dielectric glass material used for the dielectric paste within the above range. This is because the BET value measured from the measurement of the amount of gas adsorbed on the surface has a correlation with the particle size distribution, and the BET value increases when a large amount of fine powder is present. Therefore, it is effective to manage the fine powder content by the BET value.

When the BET value of the dielectric glass material is higher than 3.2 m ² / g, a lot of fine powder is present in the dielectric glass material, and as described above, cracks occur in the dry film after the dielectric paste is applied, The insulation resistance of the dielectric layer is deteriorated. On the other hand, when the BET value of the dielectric glass material is lower than 2.5 m ² / g or more, glass particles having a relatively large particle size increase, so that the portion where the dielectric paste is filtered is clogged, and the production running Cost increases.

  The BET value was measured by the BET flow method (specific surface area measurement method), and an apparatus manufactured by MACSORB (HM series) was used.

[4-2. Dielectric paste]
A dielectric paste is produced by kneading the dielectric glass material and the binder component. A three roll or the like is used for kneading. The binder component is composed of an organic resin and an organic solvent.

<Ratio of solid content>
In the present embodiment, the dielectric glass material occupies 25% to 38%, the organic resin 4% to 10%, and the organic solvent 50% to 70% in a molar ratio in the dielectric paste. As described above, in the present embodiment, the solid content ratio (the ratio of the dielectric glass material in the dielectric paste) is set to 25% to 38% in terms of molar ratio. This is based on the following reason.

  From the viewpoint of cost reduction of reducing the amount of dielectric paste used, increasing the solid content ratio in the dielectric paste is an effective means. However, when the solid content ratio is increased, the amount of variation (shrinkage) from the film thickness after applying the dielectric paste to the film thickness after passing through the drying process and the firing process becomes very small. For this reason, in order to keep the film thickness of the dielectric layer after firing uniform in the surface, it is necessary to control the film thickness after applying the dielectric paste very strictly. That is, when the solid content ratio is increased, the variation in the film thickness after firing becomes large, and it becomes difficult to obtain a good in-plane film thickness distribution. As a result of investigations by the inventors, it has been found that this phenomenon occurs when the solid content ratio in the dielectric paste is greater than 38% in terms of molar ratio.

  On the other hand, when the solid content ratio is lowered, the amount of dielectric paste used increases as described above, resulting in an increase in cost. Furthermore, in this case, the ratio of the organic resin and the organic solvent is increased, so that the dielectric glass material is not sufficiently dispersed in the dielectric paste, and the viscosity of the dielectric paste is low, so the shape of the paste coating film is stable. The phenomenon that coating property deteriorated, such as not performing, will arise. Similarly, from the inventors' investigation, this defect occurred when the solid content ratio in the dielectric paste was made smaller than 25% in terms of molar ratio. For this reason, in the present embodiment, the solid content ratio is in the above range in terms of molar ratio.

<Acrylic ratio>
In the present embodiment, the organic resin is composed of an ethyl cellulose resin and an acrylic resin. In the organic resin, the ethyl cellulose resin accounts for 40% to 80% and the acrylic resin accounts for 20% to 80% by weight. Desirably, the acrylic resin ratio is 35% to 45%. This is based on the following reason.

  In general, an ethyl cellulose resin has a large molecular weight and a long cellulose chain and tends to aggregate (this aggregated resin is called a resin gel).

  However, it is considered that this resin gel is generated at the time of the solvent and resin dispersion process in the initial stage of the paste preparation process. Since the resin gel once generated is small in size and soft, the subsequent dispersion process such as three rolls can also be used. It is difficult to loosen the agglomeration and obtain a uniform dispersion. Moreover, the filter in a filtration process may slip through and is difficult to remove.

  When a dielectric layer is formed using a paste containing such a resin gel, since the thermal decomposition of the resin is poor in the baking process, the dielectric glass starts to soften before the thermal decomposition of all the resins is completed. Bubble defects remain in the dielectric layer due to the gas generated from the resin.

  From the viewpoint of cost reduction, application of thinning of the dielectric layer is progressing. When such bubbles are generated, insulation failure is caused and yield is reduced.

  The above problem can be solved by sharpening the shape of the molecular weight distribution of the resin or by moving to a lower molecular weight, but since ethyl cellulose resin is a naturally derived component, the molecular weight distribution can be changed at low cost. It is difficult.

  On the other hand, since the acrylic resin is a synthetic resin, the molecular weight distribution can be controlled sharply rather than broadly, and the decomposability is good. However, when used as a binder resin, since the paste viscosity is low, the shear force is reduced in the paste dispersion step, and a sufficient dispersion state cannot be obtained. Furthermore, the accuracy of the film shape after coating is not stable due to this decrease in viscosity.

  On the other hand, in the present embodiment, these problems can be solved by setting the resin range of the dielectric paste forming the dielectric layer 8 to the above range. That is, in this embodiment, since both the ethyl cellulose resin and the acrylic resin are included, the generation of resin gel derived from the aggregation of the ethyl cellulose resin is reduced by the acrylic resin, and the viscosity of the dielectric paste is reduced by the ethyl cellulose resin. It is possible to improve the stability of the coating film shape.

<Surfactant and texanol>
In the present embodiment, the organic solvent includes a first solvent, a second solvent, and a surfactant. The first solvent is texanol and occupies 40% to 99% by weight in the organic solvent. Examples of the second solvent include terpineol and a high boiling point solvent.

  The reason for containing texanol as the first solvent is based on the following. As described above, in the present embodiment, an ethyl cellulose resin is contained as a resin component. However, the problem of the resin gel resulting from aggregation of an ethyl cellulose resin arises.

  In order to reduce this resin gel, it is effective to use a solvent having a high solubility of ethyl cellulose in the initial stage of paste preparation and a resin dispersion step.

  As a result of investigations by the inventors, it was confirmed that the solubility of ethyl cellulose resin was improved and the resin gel was reduced by substituting texanol for butyl carbitol acetate, which has been used conventionally. Therefore, in the present embodiment, texanol is contained in the above range. When the texanol is lower than 40%, the solubility of the ethylcellulose resin is not sufficiently obtained. When the texanol is higher than 99%, the viscosity in the solvent (vehicle) after dissolving the resin is increased, and the filterability is increased. Decreases, which is detrimental to paste preparation.

  Further, in the present embodiment, as described above, the organic solvent contains a surfactant. This is based on the following reason. As described above, when the solid content ratio in the dielectric paste is increased, the variation in the film thickness after baking becomes larger with respect to the variation in film thickness (variation, etc.) of the coating film. When such a portion exists as the dielectric layer of the PDP 1, the voltage required for the image display discharge changes in the portion, so that a large luminance difference occurs locally during lighting, resulting in a failure.

  As described above, this defect is caused by a steep local film thickness fluctuation gradient after applying the dielectric paste, so that the leveling property during drying of the coated film is improved to reduce the film thickness fluctuation gradient. Mitigating is effective.

  Therefore, in the present embodiment, a surfactant is contained in the organic solvent in the dielectric paste. A surface tension acts on the surface of the coating film at the time of drying, but the presence of this surfactant can reduce the surface tension and improve the leveling property at the time of drying the coating film. As a result, the gradient of the film thickness variation of the dielectric layer can be reduced.

  In the present embodiment, polyacrylate (acrylic modified product) is used as the surfactant. By selecting polyacrylate, in this embodiment, since an acrylic resin is contained as a resin component, the compatibility between the surfactant and the resin component is increased, and the dielectric paste is less likely to cause problems such as aggregation.

  Moreover, in this Embodiment, content of the said surfactant is 0.2 weight% or more and 1.0 weight% or less. When the content is lower than 0.2% by weight, the above effect cannot be obtained sufficiently. On the other hand, when the content is higher than 1.0% by weight, the viscosity of the dielectric paste is remarkably lowered, the paste is smeared at the edge of the coating region, and it is difficult to sufficiently control the dielectric layer forming region.

  In addition, dioctyl phthalate, dibutyl phthalate, triphenyl phosphate, tributyl phosphate and the like may be added to the organic solvent as a plasticizer. Further, glycerol monooleate, sorbitan sesquioleate, homogenol (product name of Kao Corporation), phosphate ester of alkylallyl group or the like may be added as a dispersant. This is because the printability of the dielectric paste is improved. In addition, you may match | combine a binder component with the solvent used for the grinding | pulverization of glass material.

[4-3. Method for Forming Dielectric Layer 8]
As a method for forming the dielectric layer 8, a screen printing method, a die coating method, or the like is used. First, a dielectric paste is applied on the front glass substrate 3 on which the display electrodes are formed, and then dried in a temperature range of 100 ° C. to 200 ° C. As a drying means, an infrared drying furnace, an electric furnace or the like is used. Air or an inert gas is used as an atmosphere for drying.

  Next, baking is performed. The firing temperature is in the temperature range of 450 ° C to 650 ° C. More preferably, the temperature range is 550 ° C to 600 ° C.

  In addition, the brightness | luminance of PDP1 improves, so that the film thickness of the dielectric material layer 8 is small. Further, the discharge voltage of the PDP 1 decreases as the thickness of the dielectric layer 8 decreases. Therefore, it is preferable that the film thickness of the dielectric layer 8 is as small as possible within a range where the withstand voltage does not decrease. In the present embodiment, as an example, the film thickness of the dielectric layer 8 is not less than 10 μm and not more than 30 μm from both the viewpoint of dielectric strength and the viewpoint of visible light transmittance.

  As described above, the present embodiment realizes a PDP electrode paste and a PDP manufacturing method that can significantly reduce production costs while maintaining high quality and high reliability of the PDP.

  As described above, the technology disclosed in the present embodiment realizes a low power consumption PDP and is useful for a large-screen display device or the like.

1 PDP
2 Front plate 3 Front glass substrate 4 Scan electrode 5 Sustain electrode 6 Display electrode 7 Black stripe (light shielding layer)
8 Dielectric layer 9 Protective layer 10 Back plate 11 Rear glass substrate 12 Address electrode 13 Base dielectric layer 14 Partition 15 Phosphor layer 16 Discharge space

Claims (2)

A dielectric glass, a solvent, and a resin are provided.
The solvent includes texanol and a surfactant,
The resin includes ethyl cellulose resin and acrylic resin,
A dielectric paste for a plasma display panel, wherein the dielectric glass has a molar ratio of 25% or more and 38% or less. A front plate on which a dielectric layer is formed, and a back plate,
A plasma display panel, wherein the dielectric layer is formed by the dielectric paste according to claim 1.

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