JP2012185914A - Manufacturing method of plasma display and ink for plasma display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem in a process of coating a PDP protective film with MgO powder in the form of ink by means of a slit coater that the MgO powder dispersed on the PDP protective film is flicked (flick without nucleus), and to provide a manufacturing method which suppresses occurrence of flick without nucleus, and to provide an ink.SOLUTION: In the manufacturing method and the ink, the ink is composed of an MgO powder, a solvent A, a solvent B and a solvent C. The solvent A evaporates at first, and then the solvents B and C evaporate substantially simultaneously. Surface tension is smallest in the solvent A, largest in the solvent B, and substantially equal in the solvent C and A.

Description

  The present invention relates to a plasma display manufacturing method and a plasma display ink.

  At present, there is an increasing expectation for a display device using a plasma display panel (hereinafter also referred to as PDP) as a display device for displaying a high-definition television image on a large screen.

  In a PDP (for example, a three-electrode surface discharge type PDP), a front plate on the front side and a back plate on the back side are arranged opposite to each other as viewed from the viewer, and their peripheral portions are sealed with a sealing member. It has a structure. A discharge gas such as neon and xenon is enclosed in a discharge space formed between the front plate and the back plate. The front plate includes a display electrode formed of a scan electrode and a sustain electrode formed on one surface of the glass substrate, and a dielectric layer and a protective layer that cover these electrodes. The back plate includes a plurality of address electrodes formed in a stripe shape in a direction orthogonal to the display electrodes on the glass substrate, a base dielectric layer that covers these address electrodes, and a partition that partitions the discharge space for each address electrode And red, green, and blue phosphor layers formed on the side surfaces of the barrier ribs and the underlying dielectric layer.

  The display electrodes and the address electrodes are orthogonal to each other, and the intersections form discharge cells. These discharge cells are arranged in a matrix, and three discharge cells having red, green, and blue phosphor layers are pixels for color display. In such a PDP, a predetermined voltage is sequentially applied between the scan electrode and the address electrode and between the scan electrode and the sustain electrode to generate gas discharge. A phosphor layer is excited by ultraviolet rays generated by such gas discharge to emit visible light, thereby realizing color image display.

  As a protective layer of such a PDP, in order to protect the dielectric layer from ion collisions caused by discharge and to promote phosphor emission by secondary electron emission, a “thin film layer having a wall charge holding function” and “initial stage” In some cases, a protective layer having a two-layer structure of “a crystal layer having an electron emission function” is employed. As a raw material for such a protective layer, generally, magnesium oxide (MgO) having excellent sputtering resistance and a high secondary electron emission coefficient is used.

  In such a background, Patent Document 1 uses a vapor deposition method or the like for forming the MgO thin film layer, while using a slit coater method for forming the MgO crystal layer. In particular, in the first embodiment of Patent Document 1, MgO single crystal powder having a diameter of 0.5 to 10 μm is dispersed in a mixed solvent composed of 3-methoxy-3-methyl-1-butanol and α-terpineol. Therefore, the slit coater ink is prepared.

  When forming the MgO crystal layer using the slit coater method with the ink created in the first embodiment of Patent Document 1, as shown in FIG. 11, “MgO crystal powder is formed on the MgO thin film layer. There may occur a phenomenon in which a “non-existing region” or a “region in which the coverage of the MgO crystal powder is lower than the surrounding region” is formed (hereinafter referred to as “repelling phenomenon”). FIG. 11 is a perspective view schematically showing a conventional “repelling phenomenon”.

  The “repellency phenomenon” is considered to be caused by the convex portion 51 of the MgO thin film layer. The convex portion 51 of the MgO thin film layer is formed by vapor deposition of (A) dielectric protrusions and (B) MgO thin film layer. MgO foreign matter caused by MgO splash generated in the film, (C) environmental foreign matters mixed in the MgO thin film layer forming process, and the like are accidentally or inevitably generated in the process of manufacturing the PDP front plate.

JP 2009-295372 A

  As a conventional method, when an MgO crystal layer is formed using the slit coater method with the ink produced in the first embodiment of Patent Document 1, as shown in FIG. A region where the MgO crystal powder is not present "or a region where the coverage of the MgO crystal powder is lower than that of the surrounding region" (hereinafter referred to as "nuclear repellency phenomenon") occurs. Sometimes. When this phenomenon occurs, there is a problem that the uniformity of the coverage of the MgO crystal powder on the MgO thin film layer is reduced, and it becomes difficult to suppress the discharge delay and make the discharge probability uniform. The “repellent phenomenon” and “nuclear-free repellent phenomenon” described in Patent Document 1 are similar, but are different. The “nuclear repellency phenomenon” occurs even without the presence of the convex portion 51 of the MgO thin film layer.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a plasma display manufacturing method and a plasma display ink that suppress the “nuclear-free repelling phenomenon” in the slit coater method.

In order to solve the above problems, the present invention is a method and an ink for manufacturing a front panel of a plasma display panel in which an electrode, a dielectric layer, and a protective layer are formed on a substrate,
The formation of the protective layer
(I) forming a first protective layer on the dielectric layer formed on the substrate by sputtering or vapor deposition;
(Ii) applying an MgO raw material on the first protective layer to form an MgO raw material layer; and
(Iii) subjecting the MgO raw material layer to drying to obtain a second protective layer from the MgO raw material layer,
The MgO raw material used for forming the second protective layer comprises MgO powder and three types of solvents, and the difference in surface tension at 20 ° C. between the solvents is 10 mN / m or less.

  The three types of solvents include solvent A, solvent B, and solvent C. The ratio of the sum of solvent B and solvent C to the total solvent is 3.5% by mass or more, the vapor pressure of solvent A at 20 ° C. is 50 Pa or more, and the vapor pressure of solvent B at 20 ° C. is 10 Pa or more and 20 Pa or less. The vapor pressure of solvent C at 20 ° C. is 5 Pa or more and less than 15 Pa. The manufacturing method and ink characterized by the above are provided.

  In the manufacturing method of the present invention, the “nuclear-free repelling phenomenon” of the MgO raw material can be suppressed when forming the second protective layer. In other words, an MgO crystal layer having a uniform in-plane coverage can be formed, and the discharge delay can be suppressed and the discharge probability can be made uniform. As a result, it is possible to obtain a plasma display having good discharge characteristics with no selection failure.

The perspective view which shows the structure of PDP typically Sectional drawing which represented the front plate of PDP obtained with the manufacturing method of this invention typically Perspective view schematically showing the "nuclear repellency" mode The figure which shows the external appearance photograph of the board | substrate in an effect confirmation test (1) The figure which shows the relationship between the ultimate pressure and the evaporation of a solvent in an effect confirmation test (1) The figure which shows the relationship between the surface tension and solvent mixing ratio in an effect confirmation test (1) Diagram showing “dama” generation mechanism The figure which shows the external appearance photograph of the board | substrate in an effect confirmation test (2) The figure which shows the relationship between the ultimate pressure and the evaporation of a solvent in an effect confirmation test (2) The figure which shows the relationship between the surface tension and the solvent mixing ratio in the effect confirmation test (2) Perspective view schematically showing the mode of “repellency”

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Hereinafter, the manufacturing method of the plasma display panel of the present invention will be described in detail.

[Configuration of plasma display panel]
First, a plasma display panel (PDP) finally obtained through the manufacturing method of the present invention will be briefly described. FIG. 1 is a diagram schematically showing a configuration of a PDP by a cross-sectional perspective view.

  In the front plate 1 of the PDP 100, a plurality of display electrodes 11 including scan electrodes 12 and sustain electrodes 13 are formed on a smooth, transparent and insulating substrate 10 (for example, a glass substrate) on the front plate side. A dielectric layer 15 on the front plate side is formed so as to cover the electrode 11. Further, a protective layer 16 is formed on the dielectric layer 15 on the front plate side. Scan electrode 12 and sustain electrode 13 are each composed of a transparent electrode and a bus electrode made of Ag or the like electrically connected to the transparent electrode. A light shielding layer 14 can also be formed on the substrate 10 on the front plate side.

  In the back plate 2 disposed opposite to the front plate 1, a plurality of address electrodes 21 are formed on a substrate 20 on the insulating back plate side, and a dielectric layer 22 on the back plate side is formed so as to cover the address electrodes 21. Is formed. A partition wall 23 is provided at a position corresponding to the space between the address electrodes 21 on the dielectric layer 22 on the back plate side, and red, green, blue between the adjacent partition walls 23 on the surface of the dielectric layer 22 is provided. Each color phosphor layer 25 is provided.

  The front plate 1 and the back plate 2 are arranged to face each other with the partition wall 23 interposed therebetween so that the display electrode 11 and the address electrode 21 are orthogonal to each other and the discharge space 30 is formed. The discharge space 30 is filled with a rare gas such as helium, neon, argon or xenon as a discharge gas. In the PDP 100 having such a configuration, the discharge space 30 that is partitioned by the partition wall 23 and intersects the display electrode 11 and the address electrode 21 functions as the discharge cell 32.

[General manufacturing method of PDP]
Next, a typical manufacturing method of such a PDP 100 will be briefly described.

  The manufacture of the PDP 100 is divided into a front plate 1 forming step and a back plate 2 forming step. First, in the step of forming the front plate 1, the display electrode 11 is formed on the glass substrate 10 by forming a transparent electrode by, for example, a sputtering method and forming a bus electrode by a firing method or the like. Next, a dielectric material is applied on the glass substrate 10 so as to cover the display electrodes 11 and heat-treated to form the dielectric layer 15. Next, a protective layer 16 is formed on the dielectric layer 15 by forming a film made of MgO or the like by the method described above or later, and the front plate 1 is obtained.

  In the step of forming the back plate 2, the address electrode 21 is formed on a glass substrate by, for example, a firing method, and a dielectric material is applied thereon to form the dielectric layer 22. Next, the barrier ribs 23 made of low melting point glass are formed in a predetermined pattern, and the phosphor layer 25 is formed by applying a phosphor material between the barrier ribs 23 and baking it. Next, for example, a low melting point frit glass material is applied to the peripheral portion of the substrate and baked to form a sealing member (not shown in FIG. 1), whereby the back plate 2 is obtained.

  The obtained front plate 1 and back plate 2 are aligned so as to face each other, and the front plate 1 and the back plate 2 are joined in an airtight manner by heating in a fixed state and softening the sealing member. A so-called panel sealing step is performed. Subsequently, after performing a so-called exhaust baking process in which the gas in the discharge space 30 is exhausted while being heated, the discharge gas is enclosed in the discharge space 30 to complete the PDP 100.

[Production method of the present invention]
The method of the present invention relates to the production of a front plate, particularly the production of a protective layer formed on the front plate in the production of the above-mentioned PDP.

  An embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 2 is a cross-sectional view schematically showing a front plate of a PDP obtained by the manufacturing method of the present invention.

  First, in carrying out the present invention, a substrate on which an electrode and a dielectric layer are formed is prepared. More specifically, a “glass substrate on which a display electrode and a dielectric layer are formed” is prepared. Therefore, first, a substrate in which the display electrode 11 including the scan electrode 12 and the sustain electrode 13 is formed on the substrate 10 is prepared. The substrate 10 is preferably an insulating substrate made of soda lime glass, high strain point glass, or various ceramics, and preferably has a thickness of about 1.0 mm to 3 mm.

  Transparent electrodes 12a and 13a (thickness of about 50 nm to 500 nm) made of ITO or the like are formed on the scanning electrode 12 and the sustain electrode 13 of the display electrode 11, respectively, and the resistance value of the display electrode is formed on the transparent electrode. The bus electrodes 12b and 13b (thickness of about 1 μm to 8 μm) containing silver are formed (see FIG. 2). Therefore, after forming the transparent electrode by a thin film process or the like, the transparent electrode is formed through a bus electrode firing process or the like. In particular, when forming the bus electrode, first, a conductive paste mainly composed of silver is formed in a stripe shape by a screen printing method.

  In addition, the bus electrode is formed in a stripe shape by applying a photosensitive paste mainly composed of silver by a die coating method or a printing method, drying at 100 ° C. to 200 ° C., and then patterning by a photolithography method that exposes and develops. You may form in. Further, it may be formed by a dispensing method or an ink jet method. And finally, after subjecting to drying, a bus electrode is obtained by subjecting to baking at 400 ° C. to 600 ° C. On the transparent electrode, a metal electrode made of a metal such as Al, Cu or Cr or a laminate such as Cr / Cu / Cr may be formed.

Subsequent to the formation of the display electrode 11, a dielectric layer 15 is formed. The dielectric layer 15 can be obtained by a firing method or a sol-gel method used in general production of a PDP front plate. For example, a dielectric raw material paste formed by mixing glass powder containing SiO ₂ , B ₂ O ₃ , ZnO, Bi ₂ O ₃ , an organic solvent, and a binder resin is applied by screen printing, and then subjected to heat treatment. Thus, a dielectric layer can be formed. The thickness of the dielectric layer 15 is preferably about 5 to 30 μm, more preferably about 10 to 20 μm. Examples of the organic solvent include alcohols (for example, isopropyl alcohol) and ketones (for example, methyl isobutyl ketone), and examples of the binder resin include cellulose resins and acrylic resins.

  Subsequent to the formation of the dielectric layer 15, a protective layer is formed. Therefore, step (i) of the manufacturing method of the present invention is performed. In other words, the first protective layer is formed on the dielectric layer by sputtering (sputtering) or vapor deposition. Preferably, a first protective layer (that is, an MgO thin film layer) containing magnesium oxide (MgO) is formed. The thickness of the first protective layer to be formed is preferably about 0.1 to 2 [mu] m, more preferably about 0.5 to 1 [mu] m. As the vapor deposition method, CVD or PVD may be used. Note that the present invention is not limited to the sputtering method or the vapor deposition method, and other methods may be used as necessary as long as a desired MgO thin film layer can be formed.

  Next, step (ii) of the production method of the present invention is performed. That is, the MgO raw material layer is formed by applying the MgO raw material on the first protective layer (preferably the MgO thin film layer). The MgO raw material used comprises MgO powder, solvent A, solvent B, and solvent C. The MgO powder is preferably MgO crystal powder (MgO microcrystal powder), more preferably MgO single crystal powder. The particle diameter of the MgO crystal powder or MgO single crystal powder is preferably about 0.2 to 20 μm, more preferably about 0.5 to 10 μm. The amount of the MgO powder contained in the MgO raw material is preferably 0.3 to 20% by mass (based on MgO raw material), more preferably 0.3 to 10% by mass (based on MgO raw material), and still more preferably 0.8. 3 to 5% by mass (based on MgO raw material), for example, about 1% by mass (based on MgO raw material).

  Solvents contained in the MgO raw material are solvent A, solvent B, and solvent C. From the viewpoint of “convection during drying”, which will be described later, their vapor pressures must be separated to some extent and the difference in surface tension should be as small as possible. is there. The difference in surface tension between solvent A, solvent B, and solvent C at 20 ° C. is 10 mN / m or less, and the ratio of the sum of solvent B and solvent C to the total solvent is 3.5% by mass or more. The vapor pressure at 20 ° C. of A is 50 Pa or more, the vapor pressure at 20 ° C. of solvent B is 10 Pa or more and 20 Pa or less, and the vapor pressure of 20 ° C. of solvent C is 5 Pa or more and less than 15 Pa.

  And the surface tension at 20 ° C. of the solvent C in the production method is 5 mN / m or less from the surface tension at 20 ° C. of the previous solvent A, and the surface tension at 20 ° C. of the solvent B is The difference between the surface tension of A at 20 ° C. is 5 mN / m or more and 10 mN / m or less, and the surface tension of solvents B and C is larger than that of solvent A.

  The ratio of the sum of the solvent B and the solvent C to the total solvent contained in the MgO raw material (that is, the content ratio of the solvent B and the solvent C) is 3.5% by mass or more. Here, “total solvent” as used in the present specification substantially means “solvent A, solvent B, and solvent C” when the solvent is composed of solvent A, solvent B, and solvent C. In the case where the solvent additionally contains another solvent (that is, at least one other solvent), it means “solvent A, solvent B and other solvent” substantially.

  In addition, the ratio of the solvent B with respect to the total solvent becomes like this. Preferably it is 3.5 to 20 mass%, More preferably, it is 3.5 to 12 mass%. Examples of the solvent A include organic solvents such as 3-methoxy-3-methyl-1-butanol, n-heptyl alcohol, 2-ethoxyethanol, 2-methoxyethanol, n-hexyl alcohol, and 2-methyl-1-propanol. I can give you.

  The solvent B is preferably a hydrophilic solvent containing a hydrophilic group, and examples thereof include glycol organic solvents such as propylene glycol, 1,3-butylene glycol, and 1,5-pentanediol. However, since the glycol solvent has two —OH groups, the surface tension tends to be strong. Therefore, solvent C plays the role of reducing the surface tension of solvent B, diethylene glycol monoethyl ether 2- (2-ethoxyethoxy) ethanol, diethylene glycol monoethyl ether acetate 2- (2-ethoxyethoxy) ethyl acetate, diethylene glycol monomethyl ether, Examples thereof include organic solvents such as 1,3-butanediol-3-methyl-1-acetate.

  A slit coater method is preferably used for coating the MgO raw material. The “slit coater method” is a method in which a pasty raw material is applied to a predetermined surface by pumping and discharging a pasty raw material from a wide nozzle. When such a slit coater method is used, the MgO raw material preferably has a viscosity of about 7 mPa · s or less from the viewpoint of preventing aggregation of the MgO powder.

  Here, it should be noted that the viscosity used herein substantially means “viscosity at a shear rate of 100 s −1 and a temperature of 25 ° C.” since MgO raw materials can generally be non-Newtonian fluids. The viscosity of the MgO raw material is preferably 3 mPa · s or more and 7 mPa · s or less, more preferably 4 mPa · s or more and 7 mPa · s or less. This is because a raw material viscosity of 7 mPa · s or less is required from the slit coater, and 3 mPa · s or more is desirable from the viewpoint of suppressing sedimentation of the Mgo powder, depending on the particle size of the Mgo powder, but 4 mPa · s. The above is because the effect of suppressing the sedimentation of the Mgo powder is greater.

  The thickness of the MgO material layer formed by application of the MgO material (hereinafter also referred to as “Wet film thickness”) is preferably about 5 μm to about 13 μm when the slit coater method is used.

  When the formation of the MgO raw material layer is completed, step (iii) of the manufacturing method of the present invention is then performed. That is, the MgO raw material layer is subjected to drying to obtain a second protective layer (ie, MgO crystal layer) from the MgO raw material layer. Here, “drying” substantially means that the solvent (more specifically, solvent A, solvent B, solvent C) contained in the MgO raw material layer is vaporized and removed from the MgO raw material layer. is doing. For example, the MgO raw material layer may be placed under a reduced pressure of 7 to 0.1 Pa or under vacuum, or may be subjected to a heat treatment at about 100 to 400 ° C. under atmospheric pressure. If necessary, “under reduced pressure or under vacuum” and “heat treatment” may be combined. The thickness of the second protective layer obtained after drying is reduced from the thickness of the MgO raw material layer due to the removal of the solvent, and can be about 0.1 to 5 μm.

  Through the above steps (i) to (iii), a protective layer having a two-layer structure including a first protective layer (preferably a MgO thin film layer) and a second protective layer (MgO crystal layer) is formed, and the front plate 1 Will be completed.

  In contrast to the production of the front plate 1, the back plate 2 is produced as follows. First, a method of screen-printing a paste containing silver (Ag) material on a substrate (20) which is a glass substrate, or a photolithography method of exposing and developing after forming a metal film mainly composed of silver on the entire surface A precursor layer is formed by a method such as patterning using, and the address electrode 21 is formed by baking it at a desired temperature (for example, about 400 to about 700 ° C.). Next, a dielectric layer 22 serving as a base dielectric layer is formed on the substrate 20 on which the address electrodes 21 are formed.

First, a dielectric paste layer is formed by applying a “dielectric material paste mainly composed of glass components (material formed from SiO ₂ , B ₂ O _3, etc.) and vehicle components” by a die coating method or the like. To do. Thereafter, the dielectric layer 22 can be formed by firing the dielectric paste layer. Next, the partition walls 23 are formed at a predetermined pitch.

  Specifically, a partition wall forming raw material paste is applied on the dielectric layer 22 and patterned into a predetermined shape to form a partition wall material layer, which is then baked to form the partition wall 23. . For example, by a photolithography method in which a raw material paste mainly composed of a low melting point glass material, a vehicle component and a filler is applied by a die coating method or a printing method, dried at about 100 ° C. to 200 ° C., and then exposed and developed. The partition wall 23 is formed by patterning and then baking at about 400 ° C. to about 700 ° C.

The partition wall 23 is formed by screen printing to form a partition wall film, and then dried, and after patterning by exposure / development processing using a dry film containing a photosensitive resin, excavation is performed by sandblasting, and the dry film is peeled off. It can also be formed by firing. Next, the phosphor layer 25 is formed. A phosphor raw material paste containing a phosphor material is applied on the dielectric layer 22 between the adjacent barrier ribs 23 and on the side surfaces of the barrier ribs 23 and fired to form the phosphor layer 25. More specifically, the phosphor layer 25 is formed by applying a raw material paste mainly composed of phosphor powder and a vehicle component by a nozzle discharge method or the like, and then subjecting to drying at about 100 ° C. [YBO3: Eu ³⁺ ] is used as the red phosphor powder, [Zn ₂ SiO ₄ : Mn] is used as the green phosphor powder, and [BaMgAl10O17: Eu ²⁺ ] is used as the blue phosphor powder. Can do.

  Through the above steps, the address electrode 21, dielectric layer 22, partition wall 23, and phosphor layer 25, which are predetermined constituent members, are formed on the substrate 20, and the back plate 2 is completed.

  In this way, the front plate 1 and the back plate 2 provided with predetermined constituent members are arranged to face each other so that the display electrodes 11 and the address electrodes 21 are orthogonal to each other. Next, the periphery of the front plate 1 and the back plate 2 is sealed with glass frit. Then, after evacuating the discharge space 30 to be formed, the PDP 100 is finally completed by enclosing a discharge gas (such as helium, neon and / or xenon) preferably at a pressure of 55 kPa to 80 kPa.

  Although the embodiments of the present invention have been described above, those skilled in the art will readily understand that the present invention is not limited thereto and various modifications can be made. For example, the “two-layer structure” of the protective layer composed of the first protective layer and the second protective layer is not limited to the mode in which the first protective layer and the second protective layer can be clearly distinguished, but also the first protective layer. And a mode in which the second protective layer cannot be clearly distinguished (for example, a mode in which the interface between the first protective layer and the second protective layer is unclear) may be used.

(Example)
A test was conducted to investigate the desirable composition and physical properties of the MgO raw material used for forming the second protective layer. In the tests described below, the MgO raw material is called “ink” for convenience.
[Ink solvent component effect confirmation test (1)]
An MgO ink containing the following materials was used.
MgO crystal powder: 0.5-10 μm MgO single crystal powder Solvent A: 3-methoxy-3-methyl-1-butanol Solvent B: Propylene glycol Solvent C: Diethylene glycol monoethyl ether acetate 2-acetate (2-Ethoxyethoxy) ethyl In order to confirm the effect of the solvent C, inks containing only the solvent A and the solvent B were also prepared. Table 1 shows the solvent composition of the inks tested.

  The MgO powder concentration was all 0.7% by mass.

  In preparing the MgO ink, 2000 g of the mixture composed of the above materials was sonicated for 30 minutes with an amplitude of 20 μm so as not to cause lattice defects such as chipping on the surface of the MgO crystal powder. Dispersed.

  The obtained MgO ink was applied on a MgO thin film layer (thickness of about 0.7 μm) formed by a vapor deposition method. Specifically, MgO ink was applied by a slit coater method so that the wet film thickness was 12 μm (use of slit coater equipment manufactured by the applicant). Next, the atmosphere was reduced in pressure to 1 Pa and subjected to vacuum drying, whereby the solvent was vaporized and an MgO crystal layer (thickness of about 1.0 μm) was formed.

  The substrate used was a substrate left in a clean room for about 2 months in order to promote water absorption after the first protective film was deposited. FIG. 3 is a perspective view schematically showing an embodiment of the “nuclear-free repelling phenomenon”. When the MgO crystal layer is formed by the slit coater method, as shown in FIG. 3, the “region 53 in which no MgO crystal powder is present in the MgO thin film layer” or “the region 53 having a lower coverage than the surrounding region 52”. It should be noted that “nuclear-free repelling phenomenon” can generally occur. However, in the ink used in this experiment, “nuclear-free repelling” was hardly observed. However, different phenomena such as “dama” and “bias”, which will be described later, were confirmed as side effects.

  FIG. 4 is an appearance photograph of the substrate in the effect confirmation test (1). Images were taken at 150x using a scanning electron microscope. FIG. 4 shows the appearance of the substrates created in Experiment 1-1, Experiment 1-2, and Experiment 1-3. In the photograph, the white one is MgO powder. Further, an electrode (display electrode) 11 on the front plate side exists in the horizontal direction with respect to the photograph. Looking at these, in Experiment 1-3, the occurrence of “dama” having a diameter of about 10 μm, which is an aggregate of MgO powder, is remarkable. Further, in Experiment 1-2 in which the concentration of the solvent B was decreased, a phenomenon that the MgO powder on the electrode decreases was observed. Here, this phenomenon is called “bias”. In Experiment 1-1, the MgO powder is also present on the electrode and dispersed in a well-balanced manner.

  In order to derive these results, the following verification was performed. Table 2 shows typical physical properties of the solvent used this time.

  The common concept of the inks in Experiments 1-1, 1-2, and 1-3 is as follows. In the process of vacuum drying, it is presumed that most of the solvent A evaporates first, and then the solvent B or the mixture of the solvent C evaporates.

  In order to evaluate the evaporability of solvent B and solvent C, the following experiment was performed. About 30 mg of a simple solvent was put in a small cup having a diameter of 5 mm, dried under reduced pressure, and the mass of the evaporated solvent was measured for each ultimate pressure in the chamber (use of reduced pressure drying equipment manufactured by the applicant). FIG. 5 is a graph showing the relationship between ultimate pressure and solvent evaporation in the effect confirmation test (1).

  The horizontal axis represents the ultimate pressure in the chamber, and the vertical axis represents the mass ratio after evaporation relative to the initial solvent mass. In the solvent B and the solvent C, the mass ratio of the solvent with respect to the initial value rapidly decreases at an ultimate pressure of 10 to 11 Pa. From these, it is surmised that solvent B and solvent C evaporate almost simultaneously.

  Next, in order to estimate the surface tension during drying, the surface tension of the mixed solution of the solvent B and the solvent C was measured. FIG. 6 shows the relationship between the surface tension and the solvent mixing ratio in the effect confirmation test (1). The surface tension was measured five times for each condition by the pendant drop method. The measured value of surface tension is shown on the vertical axis, and the mixing ratio of solvent B and solvent C is shown on the horizontal axis. Each plot shows the measured average value, and the maximum and minimum values are indicated by upper and lower error bars for each plot. From this result, when the mixing ratio of the solvent B and the solvent C is 1: 1 (50% by mass), it is predicted that the surface tension of the mixed solvent can be reduced to 31.5 mN / m.

It is considered that reducing the surface tension of these mixed solvents has an effect of suppressing the occurrence of “dama”. FIG. 7 illustrates the “dama” generation mechanism. Here, for reference, an estimation generation mechanism of “dama” is shown in FIG. 7 by taking Experiment 1-3 as an example.
(1) Immediately after coating A homogeneous film composed of a mixed solvent of particles, solvent A and solvent B is formed.
(2) Initial stage of drying Evaporation of the solvent containing solvent A as a main component starts by drying under reduced pressure. Solvent A has a lower surface tension than solvent B. Since the solvent remaining after the solvent A evaporates increases in the content of the solvent B, the surface tension increases in the portion where the drying has progressed. As a result, surface tension variation occurs in the solvent, and convection occurs from a low surface tension to a high surface tension.
(3) Mid-drying period The effect of convection increases, and as a result of particle convection, cells called Benard cells are generated.
(4) End of drying Most of the solvent A evaporates, and the remaining solvent is mainly composed of the solvent B, and the convection due to the difference in surface tension converges. However, since the amount of the solvent B left almost simultaneously is small, the particles are fixed on the MgO thin film layer formed by the evaporation method while being influenced by convection. At this time, the shape of the cell collapses a little, and as a result, the particle becomes “dama” and is fixed.

  Convection caused by the difference in surface tension is considered to be stronger as the difference in surface tension is larger, and it is considered effective to reduce the difference in surface tension in order to suppress “dama”. Therefore, it was found that mixing with the solvent C as a means for reducing the surface tension of the solvent B is extremely effective.

From the above results, it was found that aggregation and aggregation of MgO powder can be prevented, and a PDP with uniform brightness and good scanning characteristics can be obtained.
[Ink solvent component effect confirmation test (2)]
An MgO ink containing the following materials was used.
MgO crystal powder: 0.5-10 μm MgO single crystal powder Solvent A: 3-methoxy-3-methyl-1-butanol Solvent B: Propylene glycol Solvent D: Diethylene glycol monoethyl ether 2- (2 -Ethoxyethoxy) ethanol In order to confirm the effect of solvent D, inks of only solvent A and solvent B were also prepared. Table 3 shows the solvent composition of the inks tested.

  The MgO powder concentration was all 0.7% by mass.

  In preparing the MgO ink, 2000 g of the mixture composed of the above materials was sonicated for 30 minutes with an amplitude of 20 μm so as not to cause lattice defects such as chipping on the surface of the MgO crystal powder. Dispersed.

  The obtained MgO ink was applied on a MgO thin film layer (thickness of about 0.7 μm) formed by a vapor deposition method. Specifically, MgO ink was applied by a slit coater method so that the wet film thickness was 12 μm (use of slit coater equipment manufactured by the applicant). Next, the atmosphere was reduced in pressure to 1 Pa and subjected to vacuum drying, whereby the solvent was vaporized and an MgO crystal layer (thickness of about 1.0 μm) was formed.

  In addition, it is considered that the used substrate partially absorbs water. Therefore, when the MgO crystal layer is formed by the slit coater method, “MgO crystal powder does not exist in the MgO thin film layer as shown in FIG. It should be noted that a “nuclear repellency phenomenon” such as “region 53” or “region 53 with a lower coverage than surrounding region 52” may generally occur. However, in the ink used in this experiment, “nuclear-free repelling” was hardly observed. However, different phenomena such as “dama” and “bias” described later were confirmed as side effects.

  FIG. 8 is a photograph of the appearance of the substrate in the effect confirmation test (2). Images were taken at 150x using a scanning electron microscope. FIG. 8 shows the appearance of the substrates created in Experiment 2-1, Experiment 1-2, and Experiment 1-3. In the photograph, the white one is MgO powder. Further, an electrode (display electrode) 11 on the front plate side exists in the horizontal direction with respect to the photograph. Looking at these, in Experiment 1-3, the occurrence of “dama” having a diameter of about 10 μm, which is an aggregate of MgO powder, is remarkable. Further, in Experiment 1-2 in which the concentration of the solvent B was decreased, a phenomenon that the MgO powder on the electrode decreases was observed. Here, this phenomenon is called “bias”. In Experiment 2-1, the MgO powder is also present on the electrode and dispersed in a balanced manner.

  In order to derive these results, the following verification was performed. Table 4 shows typical physical properties of the solvent used this time.

  The common concept of the inks in Experiments 2-1, 1-2, and 1-3 is as follows. In the process of vacuum drying, it is presumed that first, most of the solvent A evaporates, and then the solvent B or the mixture of the solvent D evaporates.

  In order to evaluate the evaporability of solvent B and solvent D, the following experiment was carried out (using a vacuum drying facility manufactured by the applicant). FIG. 9 is a graph showing the relationship between ultimate pressure and solvent evaporation in the effect confirmation test (2). About 30 mg of a simple solvent was put in a small cup having a diameter of 5 mm, dried under reduced pressure, and the mass of the solvent evaporated was measured for each ultimate pressure in the chamber.

  The horizontal axis represents the ultimate pressure in the chamber, and the vertical axis represents the mass ratio after evaporation relative to the initial solvent mass. From these, the solvent D evaporates first at an ultimate pressure of about 20 Pa in the chamber, and the solvent B evaporates together. As expected, as far as the evaporation of the mixed solvent is observed, the solvent B remains at the end and evaporates. Is considered to progress.

  Next, in order to estimate the surface tension during drying, the surface tension of the mixed solution of the solvent B and the solvent D was measured. FIG. 10 is a graph showing the relationship between the surface tension and the solvent mixing ratio in the effect confirmation test (2). The surface tension was measured five times for each condition by the pendant drop method. The measured value of surface tension is shown on the vertical axis, and the mixing ratio of solvent B and solvent D is shown on the horizontal axis. Each plot shows a measured average value, and the maximum value and the minimum value of the measured value are shown by upper and lower error bars for each plot. From this result, when the mixing ratio of the solvent B and the solvent D is 1: 1 (50% by mass), it is predicted that the surface tension of the mixed solvent can be reduced to 32.6 mN / m.

  Convection caused by the difference in surface tension is considered to be stronger as the difference in surface tension is larger, and it is considered effective to reduce the difference in surface tension in order to suppress “dama”. Therefore, it was found that mixing with the solvent D as a means for reducing the surface tension of the solvent B is extremely effective.

  From the above results, it was found that aggregation and aggregation of MgO powder can be prevented, and a PDP with uniform brightness and good scanning characteristics can be obtained.

  Since the PDP finally obtained through the manufacturing method of the present invention has good discharge characteristics, it can be suitably used as a plasma television for commercial use and a commercial plasma television, and also suitable as various other display devices. Can be used. Moreover, the manufacturing method of this invention is not limited to PDP, It can utilize also in another product field. For example, in the field of batteries, electronic components, etc., the ink containing no polymer / dispersant is applied to an uneven substrate by a slit coater method to form a powder layer with a very uniform coverage. Applicable.

11 Front panel electrode (display electrode)
12 Scan electrode 12a Transparent electrode 12b Bus electrode 13 Sustain electrode 14 Black stripe (light shielding layer)
21 Back plate electrode (address electrode)
23 partition 25 phosphor layer 30 discharge space 32 discharge cell 51 convex portion of MgO thin film layer

Claims (10)

In a method of manufacturing a front panel of a plasma display panel in which an electrode, a dielectric layer, and a protective layer are formed on a substrate,
Forming the protective layer,
(I) forming a first protective layer on the dielectric layer formed on the substrate by sputtering or vapor deposition;
(Ii) applying an MgO raw material on the first protective layer to form an MgO raw material layer; and
(Iii) subjecting the MgO raw material layer to drying to obtain a second protective layer from the MgO raw material layer,
The MgO raw material contains MgO powder and two or more solvents, and the difference in surface tension at 20 ° C. between the solvents is 10 mN / m or less,
A method of manufacturing a plasma display. The MgO raw material is composed of three types of solvent A, solvent B, and solvent C,
The plasma display manufacturing method according to claim 1, wherein a ratio of the sum of the solvent B and the solvent C to the total solvent is 3.5% by mass or more.   The plasma according to claim 2, wherein the vapor pressure of the solvent A at 20 ° C is 50 Pa or more, the vapor pressure of the solvent B at 20 ° C is 10 Pa or more and 20 Pa or less, and the vapor pressure of the solvent C at 20 ° C is 5 Pa or more and less than 15 Pa. Display manufacturing method.   4. The plasma display according to claim 2, wherein the surface tension of the solvent C at 20 ° C. is different from the surface tension of the solvent A at 20 ° C. by 5 mN / m or less and larger than the surface tension of the solvent A. 5. Production method.   5. The surface tension of the solvent B at 20 ° C. is a difference between the surface tension of the solvent A at 20 ° C. of 10 mN / m or less and larger than the surface tension of the solvent A. The plasma display manufacturing method as described in any one of. An ink used for a front plate of a plasma display panel in which an electrode, a dielectric layer, and a protective layer are formed on a substrate,
The formation of the protective layer is as follows:
(I) forming a first protective layer on the dielectric layer formed on the substrate by sputtering or vapor deposition;
(Ii) applying an MgO raw material on the first protective layer to form an MgO raw material layer; and
(Iii) subjecting the MgO raw material layer to drying to obtain a second protective layer from the MgO raw material layer,
The MgO raw material comprises MgO powder and two or more solvents, and the difference in surface tension of each solvent at 20 ° C. is 10 mN / m or less,
Ink for plasma display characterized by. The MgO raw material is composed of three types of solvent A, solvent B, and solvent C,
The ink for plasma display according to claim 6, wherein a ratio of the sum of the solvent B and the solvent C to the total solvent is 3.5% by mass or more.   The plasma display according to claim 7, wherein the vapor pressure of the solvent A at 20 ° C is 50 Pa or more, the vapor pressure of the solvent B at 20 ° C is 10 Pa or more and 20 Pa or less, and the vapor pressure of the solvent C at 20 ° C is 5 Pa or more and less than 15 Pa. For ink.   9. The plasma display according to claim 7, wherein the surface tension of the solvent C at 20 ° C. is different from the surface tension of the solvent A at 20 ° C. by 5 mN / m or less and larger than the surface tension of the solvent A. For ink.   10. The surface tension of the solvent B at 20 ° C. is a difference between the surface tension of the solvent A at 20 ° C. of 10 mN / m or less and larger than the surface tension of the solvent A. 2. Ink for plasma display.

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