JP2008288003A - Dielectric formation glass paste for plasma display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric formation glass paste for a plasma display panel capable of providing a baked film hardly leaving a trace of a screen mesh even when dried and baked immediately after forming a coating film by a screen printing method, having a smooth and uniform film thickness, and hardly including remaining foam, and capable of forming a dielectric layer high in transparency and withstand voltage. <P>SOLUTION: This dielectric formation glass paste for a plasma display panel contains glass powder, a thermoplastic resin, fatty acid ester and a solvent, and is characterized in that 1-15 mass% of the fatty acid ester is included therein, and the maximum particle diameter D<SB>max</SB>and 50% particle diameter D<SB>50</SB>of the glass powder are not larger than 15 μm and 0.5-2.5 μm, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a dielectric-formed glass paste for a plasma display panel.

  A plasma display panel is a self-luminous flat panel display that has excellent characteristics such as light weight and thinness, a high viewing angle, etc., and can have a large screen. It is attracting attention as one.

  The plasma display panel has a structure in which a front glass substrate and a back glass substrate are opposed to each other at a constant interval, and the periphery thereof is hermetically sealed with sealing glass. The inside of the panel is filled with a rare gas such as Ne or Xe.

  A scanning electrode for plasma discharge is formed on the front glass substrate used for the above application, and a dielectric layer (transparent dielectric layer) having a film thickness of 30 to 40 μm is formed thereon to protect the scanning electrode. Is formed.

  In addition, an address electrode for determining the position of plasma discharge is formed on the rear glass substrate, and a dielectric layer (address protection dielectric layer) having a thickness of 10 to 20 μm is formed thereon to protect the address electrode. Is formed. Further, barrier ribs are formed on the address protection dielectric layer to partition discharge cells, and phosphors of red (R), green (G), and blue (B) are coated in the cells. The phosphor is stimulated to emit light by generating plasma discharge and generating ultraviolet rays.

  The address protection dielectric layer formed on the rear glass substrate has a high withstand voltage, and the transparent dielectric layer formed on the front glass substrate has a high withstand voltage and also has a high transparency. However, these characteristics greatly depend on the quality of the dielectric layer, that is, the surface smoothness and the state of bubbles in the layer.

Conventionally, as a method for forming such a dielectric layer, a paste-like dielectric material prepared by kneading a powder component such as glass powder and a vehicle (a solution obtained by dissolving a thermoplastic resin in a solvent) is screen printing. The method of apply | coating by this, drying and baking is known.
JP-A-11-292561

  However, in the screen printing method, the screen mesh marks remain on the surface of the coated film after printing, and it is difficult to obtain a fired film (dielectric layer) having a smooth and uniform film thickness, and a dielectric layer having a high withstand voltage. There was a problem that it was difficult to obtain. Furthermore, from the viewpoint of improving productivity in recent years, after printing, without drying the coating film, the coating film is immediately dried and fired, so it is difficult to obtain leveling properties of the coating film by standing, Increasingly, it is difficult to obtain a fired film having a smooth and uniform film thickness.

  As a method for obtaining a fired film having a smooth and uniform film thickness, a paste having a high boiling point solvent (plasticizer) such as phthalate such as dibutyl phthalate or dioctyl phthalate in an amount of 10% or more is applied. It is conceivable to improve the leveling property of the coated film by slowing the drying rate of the coating film.

  However, when a phthalate ester is included in the paste, combustion (debinding) of the thermoplastic resin contained in the paste is inhibited during drying and baking of the coated film, and bubbles are formed in the film after baking. As a result, there is a problem that it is difficult to obtain a dielectric layer having high transparency and high withstand voltage.

  The object of the present invention is to provide a smooth and uniform film thickness with little screen mesh traces even after drying and firing immediately after forming a coating film by screen printing, and most of the remaining bubbles It is an object to provide a dielectric-forming glass paste for a plasma display panel that can obtain a fired film having no transparency and can form a dielectric layer having high transparency and high withstand voltage.

  As a result of various experiments, the present inventors have found that the above object can be achieved by including a fatty acid ester and a glass powder having a controlled particle size distribution, and propose the present invention.

That is, the dielectric-forming glass paste for a plasma display panel according to the present invention is a dielectric-forming glass paste for a plasma display panel containing glass powder, a thermoplastic resin, a fatty acid ester and a solvent, and the fatty acid ester is 1 to 15% by mass. And the maximum particle diameter D _max of the glass powder is 15 μm or less, and the 50% particle diameter D ₅₀ is 0.5 to 2.5 μm.

  The dielectric-formed glass paste for a plasma display panel of the present invention has a smooth and uniform film thickness that hardly leaves traces of the screen mesh even if it is dried and fired immediately after forming a coating film by screen printing. Moreover, it is possible to obtain a fired film having almost no remaining bubbles. Therefore, it is suitable as a dielectric-forming glass paste for a plasma display panel capable of forming a dielectric layer having excellent transparency and high withstand voltage.

  The dielectric-forming glass paste for a plasma display panel of the present invention is a fatty acid that is a component that shows a flammability and prevents a decrease in debindering property in the firing process, although the drying speed is moderated in the coating film drying process. An ester and glass powder controlled to have a particle size distribution that is easy to flow are contained. Therefore, even if it is dried and fired immediately after forming the coating film by screen printing, the leveling property of the coating film can be improved, and the trace of the screen mesh hardly remains, and the film thickness is smooth and uniform. Moreover, it becomes a fired film having almost no remaining bubbles, and a dielectric layer having high transparency and high withstand voltage can be obtained.

  Since the fatty acid ester is liquid at about 200 ° C. and exhibits combustibility at a temperature of 200 ° C. or higher, the glass paste of the present invention is applied at a slow drying rate of the coating film in the drying step. The leveling property of the film can be improved, and the debinding property can be prevented from being lowered in the firing step. It is important that the content is 1 to 15% by mass. When the content of the fatty acid ester is reduced, the leveling property of the coating film is lowered, it becomes difficult to obtain a fired film having a smooth and uniform film thickness, and the dielectric strength of the dielectric layer is likely to be lowered. On the other hand, when the content is increased, compatibility with the thermoplastic resin is deteriorated, and separation or the like is likely to occur, and the paste is likely to be deteriorated. A preferable range of the fatty acid ester is 1 to 10% by mass.

  As the fatty acid ester, stearic acid ester, palmitic acid ester, oleic acid ester, linoleic acid ester, linolenic acid ester, sebacic acid ester, caprylic acid ester, and capric acid ester are preferably used alone or in combination. If it is a fatty acid ester, the leveling property of a coating film can be improved by reducing the drying speed of a coating film, without reducing a binder removal property.

Moreover, it is important to use a glass powder having a maximum particle diameter _Dmax of 15 μm or less and a 50% particle diameter D50 controlled to _0.5 to 2.5 μm. By restricting the particle size distribution of the glass powder in this way, the glass powder can easily flow, the leveling property of the coating film can be improved, and a fired film having a smooth and uniform film thickness can be obtained. A high dielectric layer can be obtained. Further, since the gaps between the glass powder particles are extremely small, the bubbles contained in the fired film are extremely reduced, the remaining bubbles are extremely small, and a highly transparent dielectric layer can be obtained. If either of the maximum particle diameter _Dmax and the 50% particle diameter exceeds the upper limit, the glass powder becomes difficult to flow, the leveling property of the coated film is lowered, or the interval between the particles becomes too large. Since many bubbles remain in the fired film and the bubble diameter becomes large, it becomes difficult to obtain a fired film having sufficient transparency and surface smoothness, and the transparency and withstand voltage of the dielectric layer are likely to decrease. Become. On the other hand, when the 50% particle diameter D ₅₀ decreases, there is a tendency that the viscosity of the glass paste is increased, the desired thickness is difficult to obtain. Maximum preferred range of particle diameter _{D max} is 5 to 10 [mu] m, the preferred range of 50% particle diameter _{D 50} is 0.5 to 2.0 [mu] m.

As the glass powder, in percent by mass, 5 to 50% ZnO (preferably _{10~45%), B 2 O 3} 10~40% ( preferably _{15~38%), SiO 2 2~30%} ( preferably 3 to 28%), BaO + CaO + Bi ₂ O ₃ 0-30% (preferably 2-25%), Li ₂ O + Na ₂ O + K ₂ O 1-16% (preferably 2-15%). It is preferable to use a glass within the composition range, since it exhibits good fluidity when fired at 500 to 600 ° C., and is excellent in transparency and insulating properties, and also has a wide vitrification range and is suitable. It is.

  The glass powder having the above characteristics is suitable for a dielectric layer forming paste, and is used after being made into a paste as described later.

  The dielectric-forming glass paste for a plasma display panel of the present invention comprises a thermoplastic resin and a solvent in addition to the above glass powder and fatty acid ester.

  Glass powder is a component for forming a dielectric layer having a high withstand voltage, and the content thereof is preferably in the range of 30 to 85% by mass, particularly 50 to 75% by mass.

  Fatty acid ester is a component which improves the leveling property of a coating film, without reducing a binder removal property, It is preferable that the content exists in the range of 1-15 mass%, especially 1-10 mass%. As the fatty acid ester, stearic acid ester, palmitic acid ester, oleic acid ester, linoleic acid ester, linolenic acid ester, sebacic acid ester, caprylic acid ester, and capric acid ester can be used alone or in combination.

  The thermoplastic resin is a component that increases the film strength after drying and imparts flexibility, and its content is preferably in the range of 0.1 to 25% by mass, particularly 1 to 20% by mass. As the thermoplastic resin, polybutyl methacrylate, polyvinyl butyral, polymethyl methacrylate, polyethyl methacrylate, ethyl cellulose and the like can be used, and these can be used alone or in combination.

  The solvent is a material for pasting the material, and the content thereof is preferably in the range of 5 to 60% by mass, particularly 15 to 50% by mass. As the solvent, for example, terpineol, diethylene glycol monobutyl ether acetate, 2,2,4-trimethyl-1,3-pentadiol monoisobutyrate or the like can be used alone or in combination.

  Moreover, a plasticizer, an inorganic filler powder, etc. can also be added as needed other than the said component.

  The plasticizer is a component that controls the drying speed of the coated film and imparts flexibility to the dried film, and can be added up to 10% by mass. However, when the content of the plasticizer is increased, the debinding property is remarkably lowered, and bubbles are likely to remain in the fired film. Therefore, it is particularly preferably in the range of 0 to 5% by mass. As the plasticizer, butylbenzyl phthalate, dioctyl phthalate, diisooctyl phthalate, dicapryl phthalate, dibutyl phthalate and the like can be used, and these are used alone or in combination.

  The inorganic filler powder is a component that adjusts the fluidity, sinterability, or thermal expansion coefficient of the paste, and can be added up to 40% by mass. However, if the content of the inorganic filler powder is increased, sintering cannot be performed sufficiently and it becomes difficult to form a dense film, and therefore it is particularly preferably in the range of 0 to 30% by mass. As the inorganic filler powder, for example, alumina, zirconia, zircon, titania, cordierite, mullite, silica, willemite, tin oxide, zinc oxide and the like can be used alone or in combination.

  The dielectric-formed glass paste for a plasma display panel of the present invention can be used for either front dielectric or rear dielectric. When used as a transparent dielectric material for a front glass substrate, the content of the inorganic filler powder can be 0 to 20% by mass (preferably 0 to 10% by mass). By setting the content of the inorganic filler powder in this way, it is possible to obtain a fired film having high transparency while suppressing the scattering of visible light due to the addition of the inorganic filler powder. Moreover, when using as an address protection dielectric material for back glass substrates, the inorganic filler powder is in the range of 0 to 40% by mass (more preferably 5 to 40% by mass, and still more preferably 10 to 30% by mass). It can be used by containing. By setting the content of the inorganic filler powder in this way, a fired film having high strength can be obtained.

  Next, a method for producing the dielectric-formed glass paste of the present invention will be described.

  First, glass powder, fatty acid ester, thermoplastic resin, solvent, and the like are prepared. It is important that the glass powder has a predetermined particle size distribution by pulverization using a ball mill, a fluid energy mill, or the like, and further classification by airflow classification or the like. Subsequently, a paste-like material can be obtained by kneading each component at a predetermined ratio.

  Next, a method for forming a dielectric layer using this material will be described.

  First, prepare a front glass substrate on which scanning electrodes are formed and a rear glass substrate on which address electrodes are formed, and apply the dielectric-forming glass paste of the present invention on these glass substrates using a screen printing method. Then, a coating layer having a predetermined film thickness (50 to 100 μm in the case of a transparent dielectric layer and 30 to 50 μm in the case of an address protection dielectric layer) is formed. Subsequently, the coated film is dried at a temperature of about 80 to 120 ° C. Then, a predetermined dielectric layer can be obtained by holding and baking at a temperature of 500 to 600 ° C. for 10 to 30 minutes. If the firing temperature is too low or the holding time is shortened, sufficient sintering cannot be performed, and it becomes difficult to form a dense film. On the other hand, if the firing temperature is too high or the holding time is long, the glass substrate is deformed or the electrode and the dielectric layer react to make it difficult to obtain a dielectric layer with excellent transparency.

  Hereinafter, the dielectric material of the plasma display of the present invention will be described in detail based on examples.

  Tables 1 and 2 show Examples (Sample Nos. 1 to 6) and Comparative Examples (Sample Nos. 7 to 9) of the present invention, respectively.

  Each sample in the table was prepared as follows.

First, by mass%, BaO 15%, ZnO 45%, B ₂ O ₃ 30%, SiO ₂ 6%, Li ₂ O 2%, Na ₂ O 2% (glass A softening point 564 ° C.) and BaO 8%, ZnO 47%, B ₂ O ₃ 29%, SiO ₂ 9%, Li ₂ O 2%, Na ₂ O 3%, Al ₂ O ₃ 1%, TiO ₂ 1% (glass B softening point 561 ° C.) The raw materials were prepared and mixed uniformly. Subsequently, after putting in a platinum crucible and melting at 1300 ° C. for 2 hours, the molten glass was formed into a thin plate shape. Subsequently, these were pulverized by a ball mill, and airflow classification was performed to obtain a glass powder having a particle size distribution shown in the table.

  Next, glass powder, a thermoplastic resin, a solvent, and a fatty acid ester were mixed at a ratio shown in the table, and kneaded uniformly with a three-roll mill. In addition, sample No. which is a comparative example. In No. 9, dioctyl phthalate (plasticizer) was used without using a fatty acid ester.

As the fatty acid ester, the following fatty acid esters a to d were used.
Fatty acid ester a: (oleic acid / linoleic acid / palmitic acid / stearic acid / linolenic acid (mass mixing ratio: 45/35/11/5/4))-2 ethylhexyl,
Fatty acid ester b: (oleic acid / linoleic acid / palmitic acid / stearic acid / linolenic acid (mass mixing ratio: 45/35/11/5/4))-ethylhexyl,
Fatty acid ester c: di (2-butyloctyl) sebacate
Fatty acid ester d: di-n-octyl sebacate Further, ethyl cellulose was used as the thermoplastic resin, and terpineol was used as the solvent.

  A dielectric layer was formed using the obtained dielectric-forming glass paste. First, each sample was screen-printed on the surface of a 1.7 mm thick soda lime glass plate, dried, and then fired at 570 ° C. for 30 minutes to form a fired film (dielectric layer) having a thickness of 10 μm. Then, about the obtained fired film, the condition of the screen mesh trace, the surface roughness, the state of foam, and the transmittance | permeability were evaluated. The results are shown in the table.

  As is apparent from the table, sample No. which is an example of the present invention is shown. About 1-6, the surface roughness of the fired film was as small as 0.24 μm or less, and no mesh marks were observed. Moreover, there were no bubbles exceeding 20 μm remaining in the fired film, and there were few bubbles of 20 μm or less. Furthermore, the transmittance of the fired film was as high as 90% or more.

  On the other hand, sample No. which is a comparative example. In Nos. 7 and 8, the surface roughness of the fired film was as large as 0.32 μm or more, and mesh marks were also observed. Further, the transmittance of the fired film was as low as 89.0% or less. Sample No. No. 9 had 3 bubbles exceeding 20 μm remaining in the fired film and 12 bubbles of 20 μm or less.

  These facts indicate that when the dielectric-formed glass paste of the present invention is used, it is possible to obtain a fired film having a smooth and uniform film thickness with hardly any remaining bubbles, with traces of the screen mesh hardly remaining. This shows that a dielectric layer having high withstand voltage and excellent transparency can be formed.

  In addition, about the softening point of glass, it measured using the macro-type differential thermal analyzer, and made the softening point the value of the 4th inflection point.

The maximum particle size D _max and 50% particle size D ₅₀ of the glass powder are confirmed using a laser diffraction particle size distribution analyzer SALD-2100J manufactured by Shimadzu Corporation, and the refractive index used for calculating the value of the particle size distribution is: The real part is 1.75 and the imaginary part is 0.05i.

  Regarding the screen mesh traces, the surface of the fired film obtained by firing was observed with a stereomicroscope, and “◯” indicates that the mesh trace was not observed, and “X” indicates that it was recognized.

  The surface roughness of the fired film was measured using a stylus type surface roughness meter.

The bubble state was evaluated using a stereomicroscope by counting the number of bubbles exceeding 20 μm and the number of bubbles of 20 μm or less present in the 10 cm ² range of the sample after firing.

  Regarding the transmittance, the diffuse transmittance at a wavelength of 550 nm was measured using a spectrophotometer equipped with an integrating sphere. In addition, the sample used for the transmittance | permeability measurement used what was used for the measurement of the number of bubbles, the measurement was performed by Shimadzu UV-3100, and the value after canceling the value of a glass plate was shown.

Claims (5)

A dielectric-forming glass paste for a plasma display panel comprising glass powder, a thermoplastic resin, a fatty acid ester and a solvent, comprising 1 to 15% by mass of a fatty acid ester, and the maximum particle size D _max of the glass powder is 15 μm or less. A dielectric-forming glass paste for a plasma display panel, wherein the 50% particle diameter D ₅₀ is 0.5 to 2.5 μm.   The fatty acid ester is composed of at least one selected from stearic acid ester, palmitic acid ester, oleic acid ester, linoleic acid ester, linolenic acid ester, sebacic acid ester, caprylic acid ester, and capric acid ester. The dielectric-forming glass paste for a plasma display panel according to claim 1. Glass powder, in percent by _{mass, 5~50% ZnO, B 2 O} 3 10~40%, SiO 2 2~30%, BaO + CaO + Bi 2 O 3 0~30%, Li 2 O + Na 2 O + K 2 O 1~16% The dielectric-forming glass paste for a plasma display panel according to claim 1, comprising a glass containing the composition of   By weight percentage, glass powder 35-80%, inorganic filler powder 0-40%, fatty acid ester 1-15%, thermoplastic resin 0.1-25%, solvent 5-60%, plasticizer 0-10% The dielectric-forming glass paste for a plasma display panel according to any one of claims 1 to 3, wherein   The dielectric-forming glass paste for a plasma display panel according to any one of claims 1 to 4, which is a glass paste for screen printing.