JP2002090346A - Ceramic sheet through hole inspection method and ceramic sheet inspected by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a through hole inspection method for accurately inspecting the existence/absence of a minute through hole causing a ventilation defect in an insulating ceramic sheet such as a solid electrolyte film for a flat solid electrolyte type fuel cell. SOLUTION: In this through hole inspection method for the insulating ceramic sheet, both faces of the sheet are clamped between two electrode plates arranged in parallel to each other, and when an electric discharge current generated by impression of a direct current high voltage between the electrodes is detected, the existence/absence of the through hole possibly formed in the ceramic sheet and provided with a minimum length of 2 Å or more is inspected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ceramic sheet,
In particular, a through-hole inspection method capable of accurately inspecting the presence or absence of fine through-holes that cause ventilation defects in an insulating ceramic sheet such as a solid electrolyte membrane for a plate-shaped solid oxide fuel cell, and a ventilation method using the method. The present invention relates to a ceramic sheet with high product reliability, which has been confirmed to be free from defects.

[0002]

2. Description of the Related Art The structure of a flat solid electrolyte fuel cell is as follows.
A cell stack is basically a cell stack in which an anode electrode and a cathode electrode are attached to both sides of a solid electrolyte membrane, or a cell stack in which a large number of cells having an electrolyte and a counter electrode attached on the surface of the electrode are vertically stacked. Separators (interconnectors) are arranged between the cells so that the fuel gas and air are not mixed with each other, and the electrolyte membrane and the periphery of the cells and the separators are sealed.
Fixed. In addition, when a manifold is provided inside the battery cell, it is sealed and fixed at the peripheral portion thereof.

[0003] Dense ceramic sheets used for such solid electrolyte membranes include electrical properties such as insulation and dielectric strength, mechanical properties such as bending strength and Young's modulus, and the like.
In addition to requiring surface workability such as printability, hydrogen as fuel, natural gas, air and oxygen as oxidizers,
It is required to have a gas isolation property against water vapor as a generated gas.

In particular, thin sheets expected to be put to practical use for fuel cells, for example, having a thickness of 500 μm or less,
Further, when a thin sheet having a thickness of 200 μm or less, especially 100 μm or less is formed, a pinhole in which a scratch, a dent, a void, etc. of the sheet surface reaches near the back surface, and further, a through hole in which the sheet surface reaches the back surface is present. And the power generation performance expected as a fuel cell system cannot be obtained.

[0005] Therefore, the presence or absence of through-holes in a ceramic sheet used for a solid electrolyte membrane is related to the reliability as a fuel cell component.
The sampling inspection generally performed is insufficient, and it is necessary to confirm that there is no through-hole by 100% inspection.

As a method for inspecting pinholes present in a sheet material, for example, Japanese Patent Application Laid-Open Nos. 3-226604 and 4-274390 are known, but an industrial inspection method for through holes is not yet available. Not established, and usually employs a permeation test method or a water test method in accordance with JIS R2115, or a color check method in which an alcohol solution such as fuchsin is soaked into a sheet to be inspected and detected by the dyeing state of both sides of the sheet. Have been. Although these methods can obtain considerable reliability even for the inspection of through holes in dense ceramic sheets, the inspection is complicated and takes a long time, and it is versatile as an inspection method in industrial production lines. Lacks.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide, for example, a dense ceramic sheet used as a flat solid electrolyte membrane for a fuel cell. In addition to establishing an inspection method that can easily and accurately detect the presence or absence of a through hole in an industrial production line in a short time, and by applying the inspection method, it is confirmed that there is no through hole. And to provide a highly reliable ceramic sheet.

[0008]

According to the present invention, there is provided an inspection method for inspecting a through hole of an insulating ceramic sheet, wherein both sides of the sheet are arranged in parallel. By detecting the discharge current generated when a high DC voltage is applied between the two electrode plates, the presence or absence of a through hole having a minimum length of 2 mm or more in the ceramic sheet is detected. It has a gist where it is inspected.

As a ceramic sheet applied to this inspection method, an insulating ceramic sheet having a volume resistivity of 10 ⁸ Ωcm or more is used, and a high DC voltage to be applied is in a range of 0.2 to 20 kV. This is preferable because the presence or absence of the through hole can be more reliably detected. When the above method is applied to an insulating ceramic sheet having a thickness of 10 to 500 μm, a conductive polymer sheet having the same size as the electrode plate is disposed between the ceramic sheet and the electrode plate. By applying a DC high voltage, the detection accuracy can be further increased, which is preferable.

In carrying out this method, the insulating ceramic sheet and the electrode plate may have a congruent shape or a similar shape in which at least the electrode plate does not protrude from the periphery of the insulating ceramic sheet. In the latter case, by setting the length of the peripheral edge of the insulating ceramic sheet protruding from the peripheral edge of the electrode plate to 3 mm or less, particularly denseness except for a small part of the peripheral edge is regarded as important. This is preferable because the presence or absence of a through hole in the entire internal region can be reliably detected.

It is desirable that this inspection method be continuously performed in a ceramic sheet production line. In order to continuously perform inspection even in such a production line or not in a production line, the following steps are required. At least in part,
It is desirable to employ a continuous inspection system that can automatically perform the entire process.

(1) a step of placing an insulating ceramic sheet on one of the electrode plates A; (2) a step of confirming that the sheet is at a predetermined position on the electrode plate A; Placing the other electrode plate B on (4) checking the placement position of the other electrode plate B, (5) applying a high DC voltage between the electrode plates A and B, and generating a discharge. A step of inspecting the presence or absence of a through hole in the ceramic sheet by detecting a current, (6) a step of detaching the electrode plate B from above the ceramic sheet after the inspection, (7) the ceramic sheet,
A step of separating from the electrode plate A;

The ceramic sheet which has been inspected by the method of the present invention and in which it is confirmed that the through-hole does not exist has a minimum length of the through-hole which can be present in the sheet is 2 mm.
A high quality and reliable ceramic sheet free from defects less than Å is included in the scope of the present invention. In particular,
The ceramic sheet is composed mainly of zirconium oxide stabilized with an oxide of at least one element selected from the group consisting of Y, Ce, Pr, Sm, Sc, or a composite oxide having a perovskite crystal structure Is mainly composed of
The solid electrolyte membrane for a fuel cell has stable quality.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The above-mentioned through hole defined in the present invention refers to a hole or a flaw extending from one surface of a ceramic sheet to the other surface, and the shape on the surface of the sheet is not specified. Since the size of the through-hole does not appear as long as it does not allow the permeation of hydrogen gas whose molecular cross-sectional area is substantially minimum, the through-hole does not appear. The minimum length is specified as 2 mm or more.

[0015] The through-holes are rarely 1 mm ² or more in a ceramic sheet manufactured by an ordinary method. Even if the through holes are large, the cross-sectional area is 0.8 mm ² or less, and if the cross-sectional shape is circular, the diameter is 1 mm 2. Below, the area is preferably 0.03 mm ² or less, and the diameter is 0.2 mm or less, assuming that the shape is circular.

The basic configuration of the apparatus used for detecting the through-hole in the present invention is a DC stabilized power supply and a detector composed of two electrode plates kept in parallel. Has an output voltage of 0 to 20 kV and an output current of 0 to 2 mA
And the output polarity can be switched between positive polarity and negative polarity.

The principle of detecting a through-hole using such a detecting device is as follows. When a ceramic sheet as an object is sandwiched between two electrode plates, and a voltage is applied between the electrodes and the voltage is maintained at a constant voltage, a ceramic sheet is formed. If a through-hole as described above is present, a current flows through the through-hole regardless of the shape and directionality of the through-hole, so that the discharge current is detected as an overcurrent, and it is determined that there is a through-hole. .

That is, if this detector is used, the presence or absence of the through hole can be reliably detected by detecting the discharge current, and the inspection operation can be performed easily, quickly and with high reliability. Therefore, it is possible to realize a continuous manufacturing process or a continuous inspection process on an industrial scale.

The detector preferably has a maximum applied voltage of about 20 kV, and the applied voltage at the time of the measurement of the through hole is set to be equal to or lower than the dielectric breakdown voltage of the material of the ceramic sheet to be measured. It is preferable to use an optimum applied voltage according to the shape and thickness, noise at the time of measurement, and the like, but usually, a range of 0.2 to 10 kV is used.

In general, it is desirable to reduce the applied voltage as the ceramic sheet becomes thinner and the noise becomes larger. However, if the ceramic sheet is too small, the detection limit of the through-hole becomes narrow, and there is a possibility that the fine through-hole may be missed. Therefore, the lower limit of the applied voltage should be about 0.2 kV, more preferably about 0.5 kV.

The size and shape of the electrode plate used are the same as the size and shape of the ceramic sheet or a similar shape slightly smaller than the ceramic sheet. In the latter case,
The peripheral edge of the ceramic sheet is at most 3 from the peripheral edge of the electrode plate.
It is preferable that the entire area of the ceramic sheet except for the peripheral seal portion can be inspected by forming a similar shape and size not exceeding mm or more.

In the actual inspection of the through hole, an electrode plate made of a conductive polymer material having flexibility is used as the electrode plate, or a substantially same size and shape as the electrode plate is provided between the ceramic sheet and the electrode plate. It is desirable to apply a voltage by arranging a conductive polymer sheet material having flexibility.
However, in the case of a hard electrode plate, the detection accuracy may be reduced due to insufficient adhesion with the ceramic sheet. However, the electrode plate itself is given flexibility, or a flexible sheet material is provided between the electrode plate and the ceramic sheet material. This is because not only the problem described above due to insufficient adhesion can be avoided, but also problems such as scratching and cracking of the ceramic sheet due to contact with the electrode plate can be avoided.

The conductive polymer material used above is not particularly limited as long as it has conductivity and moderate flexibility. Polyacetylene, polypyrrole, polythiophene, polyaniline, poly-p-phenylene, polyphenylenevinylene , Conductive polymers such as polyphenylene sulfide, poly (3-methylthiophene) and polyoxadiazole, silicone rubber, urethane rubber, nitrile rubber, PEDM (ethylene-propylene rubber),
SEP (polystyrene-poly (ethylene-propylene)
A composite conductive material in which conductive fillers such as carbon black powder, Ag powder, Ag alloy powder, and Ni powder are dispersed and blended in a polymer matrix such as a thermoplastic elastomer) can be used. And a conductive rubber material such as conductive silicone in which carbon black is dispersed, in that the sheet can be in close contact with the electrode.

The greatest advantage of applying the above-described inspection method according to the present invention is that an extremely fine through hole (minimum length of a hole is 2 mm or more) in an insulating ceramic sheet is arranged with the ceramic sheet interposed therebetween. The detection of such fine through-holes is carried out when the through-holes are present in the ceramic sheet. Utilizing a phenomenon in which a DC high voltage applied therebetween causes a discharge in the through-hole portion, a defect, that is, a through-hole can be reliably and promptly detected by detecting a discharge current. Since such a discharge current does not occur in an insulating ceramic sheet having no defect, it can be quickly confirmed that the sheet is a good quality sheet having no defect.

That is, according to the present invention, the presence or absence of a through-hole defect in an insulating ceramic sheet can be quickly detected, so that this detector can be provided separately from a continuous production line of insulating ceramic sheets or a production line. If the ceramic sheet in which the defect is detected is taken out as a defective product in the continuous inspection line provided in the above, the defective product can be completely prevented from being mixed into the product.

In order to enable the present invention to be carried out in such a continuous operation line, it is necessary to automate discharge of a ceramic sheet to be inspected, detection of a discharge current, and further removal of a ceramic sheet after inspection. For this purpose, it is desirable to set up an automation system that can automatically perform at least a part of the following steps, preferably, the entire process.

(1) a step of placing an insulating ceramic sheet on one of the electrode plates A; (2) a step of confirming that the sheet is at a predetermined position on the electrode plate A; Placing the other electrode plate B on (4) checking the placement position of the other electrode plate B, (5) applying a high DC voltage between the electrode plates A and B, and generating a discharge. A step of inspecting the presence or absence of a through hole in the ceramic sheet by detecting a current, (6) a step of detaching the electrode plate B from above the ceramic sheet after the inspection, (7) the ceramic sheet,
A step of separating from the electrode plate A;

If an automatic extracting means for extracting a defective product in which the presence of a through hole is confirmed by a discharge current is provided in or at the downstream side of the detaching process (6), defective products can be removed from the inspected product. Mixing can be reliably prevented, and the reliability as a product can be significantly improved. Note that a robot hand designed in consideration of the shape and thickness of the ceramic sheet may be used for attaching and detaching the ceramic sheet employed in the above steps.

Further, with regard to specific devices, parts design and operation mechanisms for automating each process including the above-mentioned attachment and detachment, devices, parts and operation mechanisms used for known automatic control are appropriately changed. What is necessary is just to design and embody, and an example is as shown in FIG.

That is, FIG. 1 is a conceptual explanatory view exemplifying a continuous inspection equipment employed when fully automating the present invention. In FIG. 1, reference numeral 1 denotes a ceramic sheet to be inspected, 2a and 2b denote electrode plates, Reference numerals 3a and 3b denote conductive polymer sheets to be attached as necessary, 4 denotes a DC high-voltage power supply, and 5 denotes a discharge current detector.

In detecting a through hole using this device, the ceramic sheet 1 is positioned and placed on the electrode plate 2a attached to the main body of the detection device using the robot hand 6. And from above the electrode plate 2
b is lowered and brought into close contact with the upper surface of the ceramic sheet 1. At this time, the electrode plates 2a and 2b
Or a size whose peripheral edge does not protrude from the peripheral edge of the ceramic sheet 1, preferably the electrode plates 2a and 2b.
The amount of protrusion of the peripheral edge of the ceramic sheet 1 from the peripheral edge is 3
The dimensions of the electrode plates 2a and 2b are adjusted according to the dimensions and shape of the ceramic sheet 1 so that the dimensions are within the range of mm.

Next, a high DC voltage is applied between the electrode plates 2a and 2b from the high voltage power supply 4, and a discharge current generated between the electrodes is detected by the detector 5, and the current value is displayed on a display. When there is no through-hole defect in the ceramic sheet 1 as an object, no current flows between the electrode plates 2a and 2b because the sheet 1 is insulative, but if a through-hole exists in the ceramic sheet 1, Discharge occurs between the electrode plates 2a and 2b through the through hole, and the current flowing by the discharge is immediately detected by the detector 5, and the existence of the through hole is confirmed.

After the presence or absence of the through-hole is confirmed in this way, the electrode plate 2b is raised, and then the ceramic sheet is gripped by the robot hand 6 (not shown) and detached from the electrode plate 2a. The normal sheet 1A determined to be absent is returned to the product line, and the defective product 1B determined to have the through hole by the discharge current is transferred to a defective line different from the regular line. The ceramic sheet returned to the product line after the completion of this inspection is confirmed to have no through-hole by the complete inspection.

Next, the insulating ceramic sheet to which the present invention is applied refers to alumina used for an insulating substrate of an electronic material or the like obtained by adding MgO or SiO ₂ to alumina.
2% alumina and 96% alumina, zirconia, aluminum nitride, mullite, cordierite, steatite,
Solids for fuel cells such as forsterite, zircon, alumina / borosilicate glass, cordierite / borosilicate glass, or various ceramics in which oxides such as alkaline earth metals and rare earth elements are added to these ceramic materials All ceramic sheet materials used as electrolyte membranes are included.

Above all, it is used for a solid electrolyte membrane.
Zirconia is used as an insulating ceramic sheet.
Alkaline earth metal acids such as O, CaO, SrO, BaO
Compound, Y_TwoO_Three, La_TwoO_Three, Ce_TwoO_Three, Pr_TwoO_Three, Nd_Two
O_Three, Sm_TwoO_Three, Eu_TwoO_Three, Gd _TwoO_Three, Tb_TwoO_Three, Dy_Two
O_Three, Ho_TwoO_Three, Er_TwoO_Three, Yb_TwoO_ThreeRare earth metal
Oxides and even Sc_TwoO_Three, Bi_TwoO_Three, In_TwoO_ThreeSuch as cheap
Zirconia-based cells containing one or more stabilizing agents
And other additives, such as lamic.
SiO_Two, Al_TwoO_Three, SnO_Two, Ta_TwoO_Five, Nb_TwoO_FiveSuch
May be included.

In addition, CeO_TwoOr Bi_TwoO_ThreeMg
Alkaline earth metal acids such as O, CaO, SrO, BaO
Compound, Y_TwoO_Three, La_TwoO_Three, Ce_TwoO_Three, Pr_TwoO_Three, Nd_Two
O_Three, Sm_TwoO_Three, Eu_TwoO_Three, Gd_TwoO_Three, Tb_TwoO_Three, Dy_Two
O_Three, Ho_TwoO_Three, Er_TwoO_Three, Yb _TwoO_ThreeRare earth metal
Oxide, Sc_TwoO_Three, In_TwoO_Three, PbO, WO_Three, Mo
O_Three, V_TwoO_FiveSeri with one or more kinds of
A-based or bismuth-based ceramics, and LaGaO_Three
System and SmCeO_ThreeHas a perovskite crystal structure like a system
Ceramic sheets containing a composite oxide as the main component are also preferred.
This is exemplified as a new insulating ceramic sheet. Further
Is based on SiO 2_Two, Al_TwoO_Three, Ge_TwoO_Three, SnO_Two,
Ta_TwoO_Five, Nd_TwoO_FiveEtc. may be included.

Among these, particularly preferred for solid electrolyte membranes are composite oxides having a zirconia or perovskite crystal structure stabilized by an oxide of at least one element of Y, Ce, Pr, Sm and Sc. Is a ceramic sheet mainly composed of

It is indispensable that the ceramic sheet applied to the inspection of the present invention is insulative. As a standard of the insulative property, the volume resistivity is 10 ⁸ Ωcm or more, preferably 10 ¹⁰ Ωcm or more, and more preferably 10 ¹⁰ Ωcm or more. Preferably 10 ¹² Ωcm
As described above, when the volume resistivity is less than 10 ⁸ Ωcm, current may flow through the sheet even if there is no through hole when a voltage is applied, and may be detected as a discharge voltage,
Test reliability is reduced.

It is desirable that the dielectric constant of the sheet is 6 or more at 1 MHz, preferably 8 or more. If it is less than 6, when a direct current is applied, if a small voltage is applied, the sheet satisfies Ohm's law. As the voltage increases, the current increases in a non-linear manner, and eventually a tendency to cause dielectric breakdown appears.

Further, the thickness of the ceramic sheet applied to the present invention is preferably in the range of 10 to 500 μm. If the thickness is less than 10 μm, the strength becomes insufficient. Occasionally, cracking or chipping may occur, and if the thickness exceeds 500 μm, the applied voltage must be excessively increased, resulting in increased noise and the possibility of misidentifying the through-hole. From these viewpoints, the preferred thickness of the ceramic sheet applied to the present invention is 2
The range is from 0 to 200 μm, and more preferably from 30 to 100 μm.

In the present invention, the object to be inspected is specified as a ceramic sheet. However, if the above-described principle of detecting through holes is used, the volume specific resistance value is not less than 10 ⁸ Ωcm as in a glass epoxy sheet or a polyimide sheet. The same can be applied to a certain ceramic composite sheet or polymer sheet.

The shape of the sheet is not particularly limited, and may be any of a circle, an ellipse, a polygon such as a square and a hexagon, a polygon having a radius, and the like. One or two or more holes having an arbitrary shape such as an ellipse, a polygon, and a polygon having a radius may be formed.

According to the present invention, a normal product group having no defective products can be obtained by detecting the presence or absence of fine through holes in the insulating ceramic sheet as described above and extracting defective products by the above-described means. Can be. Therefore, all of the products that have been subjected to the inspection are highly reliable products in which no through-holes having a hole size of more than 2 mm exist. For example, after being incorporated in a fuel cell system, the performance derived from the solid electrolyte membrane as a component is reduced. Since a situation in which a defect is found can be prevented beforehand, a highly reliable ceramic sheet that has been confirmed to have no through-hole defect by the inspection is also an object of the present invention.

In order to effectively utilize the features of the present invention in practice, it is necessary to manufacture an insulating ceramic sheet having as few as possible through-hole defects. From this point of view, as a result of examining the preferable manufacturing conditions for manufacturing an insulating ceramic sheet having no through-hole defect, particularly the green density and debinding conditions of the ceramic green sheet before sintering, the following points are noted. For example, it was confirmed that an insulating ceramic sheet having few through-hole defects could be manufactured with a high yield.

First, in the production of the green sheet, the pore diameter in the green sheet before sintering is increased by increasing the packing density of the raw material powder by using the fine particle diameter of the ceramic raw material powder and narrowing the particle size distribution as much as possible. The binder in the green sheet is decomposed by thermal decomposition and the binder is completely removed in the debinding temperature range. By smoothly progressing the mass transfer accompanying the shrinkage of the ceramic component, it is possible to obtain a ceramic sheet having no through-hole defect at a high yield.

The method of producing such a ceramic sheet itself is not particularly limited, and a slurry containing ceramic powder, an organic binder, a dispersion medium (solvent), a dispersion medium and a plasticizer, if necessary, is used according to a conventional method by a doctor blade method. A green sheet is obtained by applying a suitable thickness to a smooth sheet, for example, a polyester sheet, by a calender roll method, an extrusion method, or the like, and then drying and volatilizing and removing the dispersion medium.

The type of ceramic powder used here is as described above. The preferred particle size is laser diffraction type particle size distribution in order to enhance the punching workability of the green sheet and to minimize burrs generated on the punched end face. The average particle diameter measured with a measuring device (trade name “SALD-1100” manufactured by Shimadzu Corporation) is 0.1 to 0.8 μm, and 9
It is desirable to use one having a 0 volume% diameter in the range of 1 to 5 μm.

The kind of the binder used in the present invention is not particularly limited, and a conventionally known organic or inorganic binder can be appropriately selected and used. Examples of the organic binder include ethylene copolymers, styrene copolymers, acrylate and methacrylate copolymers, vinyl acetate copolymers, maleic acid copolymers, vinyl butyral resins, and vinyl acetal resins. And vinyl formal resins, vinyl alcohol resins, waxes, and celluloses such as ethyl cellulose.

Among them, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl are preferred from the viewpoints of green sheet moldability, punching workability, strength, and thermal decomposition property during firing. Alkyl acrylates having an alkyl group having 10 or less carbon atoms such as acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, octyl methacrylate, 2
-Ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, etc., alkyl methacrylates having an alkyl group having 20 or less carbon atoms, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, etc. And hydroxyalkyl acrylates or hydroxyalkyl methacrylates, dimethylaminoethyl acrylate, aminoalkyl methacrylates such as dimethylaminoethyl methacrylate, and maleic acid half-esters such as (meth) acrylic acid, maleic acid and monoisopropyl maleate Such as carboxyl group-containing Obtained by polymerizing or copolymerizing at least one mer, the number average molecular weight of 2,000 to 200,000, more preferably 5,00
0-100,000 (meth) acrylate copolymers are recommended as preferred. These organic binders can be used alone or in combination of two or more as needed. Among them, particularly preferred is a copolymer of a monomer containing 60% by mass or more of isobutyl methacrylate and / or 2-ethylhexyl methacrylate.

As the inorganic binder, zirconia sol, silica sol, alumina sol, titania sol and the like can be used alone or in combination of two or more.

The use ratio of the ceramic raw material powder and the binder is 5 to 30 parts by mass with respect to 100 parts by mass of the former.
More preferably, the range of 10 to 20 parts by mass is suitable,
When the amount of the binder used is insufficient, the strength and flexibility of the green sheet become insufficient.On the contrary, when the amount is too large, not only the viscosity of the slurry becomes difficult to adjust, but also the amount of decomposition and release of the binder component during firing is reduced. Many and intense, it is difficult to obtain a homogeneous and dense green sheet.

Examples of the dispersion medium used for producing the green sheet include water, alcohols such as methanol, ethanol, 2-propanol, 1-butanol and 1-hexanol, ketones such as acetone and 2-butanone, and pentane. And aliphatic hydrocarbons such as hexane, heptane and the like, aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, and acetates such as methyl acetate, ethyl acetate and butyl acetate. These dispersion media can be used alone, or two or more of them can be used by being appropriately mixed. The amount of the dispersing medium to be used is preferably adjusted appropriately in consideration of the viscosity of the slurry at the time of forming the green sheet.
It is good to adjust so as to be in the range of ~ 200 poise, more preferably 10 ~ 50 poise.

In preparing the slurry, a polymer electrolyte such as polyacrylic acid and polyammonium polyacrylate is used to promote peptization and dispersion of the ceramic raw material powder.
A dispersant comprising an organic acid such as citric acid or tartaric acid, a copolymer of isobutylene or styrene with maleic anhydride and its ammonium salt or amine salt, a copolymer of butadiene with maleic anhydride and its ammonium salt, etc .; green Plasticizers such as dibutyl phthalate and dioctyl phthalate to provide flexibility to the sheet, glycols such as propylene glycol, and glycol ethers; and surfactants and defoamers. It can be added as needed.

Thus, according to the present invention, it is possible to quickly and reliably detect a through-hole in which an extremely fine through-hole rarely exists in an insulating ceramic sheet, which is a serious product defect, by a simple method. . Then, by automating a series of operations, this inspection is performed on all sheets on a continuous production line or an individual continuous inspection line to extract defective products, thereby completely preventing defective products having ventilation defects from being mixed. Thus, it is possible to provide an insulating ceramic sheet having extremely high reliability and excellent airtightness.

[0055]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples, and the scope of the present invention can be adapted to the above and following points. It is also possible to carry out the present invention with appropriate modifications, all of which are included in the technical scope of the present invention.

Example 1 3 mol% yttria-stabilized zirconia powder (trade name “HSY-3.0”, manufactured by Daiichi Kagaku Kagaku KK), average particle size: 0.1%
A binder composed of a methacrylate copolymer (average molecular weight: 40,000, glass transition temperature: -8) with respect to 100 parts by mass of 53 μm, 90% by volume diameter: 1.78 μm.
C., solid content concentration: 50% by mass), 14 parts by mass of solid content, 2 parts by mass of dibutyl phthalate as a plasticizer, and toluene / isopropyl alcohol (mass ratio = 3) as a dispersion medium.
50 parts by mass of the mixed solvent of (2) was put into a nylon pot into which a zirconia ball having a diameter of 5 mm was charged, and kneaded at about 60 rpm at a critical speed of 70% for 40 hours to prepare a slurry.

The slurry is concentrated and defoamed to a viscosity of 3 Pa.
After adjusting to s (23 ° C.) and finally passing through a 200-mesh filter, a green sheet was obtained by coating on a polyethylene terephthalate film by a doctor blade method.

After drying the green sheet at 100 ° C. for 30 minutes, the green sheet is cut into a disk shape using a Thomson blade and fired at 1425 ° C. for 3 hours to obtain a green sheet of 100 mm diameter.
A zirconia sheet (A) having a thickness of 80 μm and a thickness of 80 μm was obtained.

The volume resistivity (room temperature) of the obtained sheet (A) was measured with an insulation resistance meter (trade name “HP-4775”) manufactured by Hewlett-Packard Company, and was found to be 10 ¹⁵ Ωcm.

Example 2 LaGaO ₃ -based powder having a perovskite crystal structure doped with Sr and Mg (PRAXAIR SPECIA)
Product name "CP-LSGM" manufactured by LTY CERAMICS
8282 ") Average particle size: 0.72 μm, 90% by volume
(Mass: 2.14 μm) 100 parts by mass of a binder composed of a methacrylate-based copolymer (average molecular weight: 70,
000, glass transition temperature: -15 ° C, solid content concentration: 45
% By mass), 2 parts by mass of dibutyl phthalate as a plasticizer, 50 parts by mass of a mixed solvent of toluene / isopropyl alcohol (mass ratio = 3/2) as a dispersion medium, and a zirconia ball having a diameter of 5 mm is mounted. About 60% of the critical speed at about 60 rpm
For 40 hours to prepare a slurry.

The slurry is concentrated and defoamed to a viscosity of 5 Pa.
After adjusting to s (23 ° C.) and finally passing through a 200-mesh filter, a green sheet was obtained by coating on a polyethylene terephthalate film by a doctor blade method.

After drying the green sheet at 100 ° C. for 30 minutes, the green sheet is cut into a disk shape using a Thomson blade and fired at 1380 ° C. for 3 hours to obtain a green sheet having a diameter of 100 mm.
A ceramic sheet (B) made of lanthanum gallate having a thickness of 200 mm and a thickness of 200 μm was obtained.

[0063] The volume resistivity of the sheet (B) (at room temperature) was measured in the same manner as in Example 1, 10 ¹³
Ωcm.

Comparative Example 1 A green sheet obtained in the same manner as in Example 1 was cut into a circle using a Thomson blade, and then cut 10 mm from the outer peripheral edge.
A hole was made with a needle at the position of, and similarly baked at 1425 ° C. for 3 hours to obtain a zirconia sheet (C) having a diameter of 100 mm and a thickness of 80 μm.

The obtained disk-shaped zirconia sheet (C)
Has a substantially circular diameter of 0.2 mm at a position about 8 mm from the periphery.
mm and a through-hole having an area of 0.03 mm ² .

[Through Hole Inspection Test] The ceramic sheets (A) and (B) obtained in Examples 1 and 2 and the ceramic sheet (C) obtained in Comparative Example 1 were placed in parallel as illustrated in FIG. The discharge current detector 5 detects a discharge current generated when a high DC voltage is applied between the two electrode plates 2a and 2b and detects the presence or absence of a through hole. Done.

The electrode plates 2a and 2b have a diameter of 98.
mm stainless steel conductive plate is used, and the outer peripheral edge of each ceramic sheet is arranged so as to protrude 1 mm from the electrode plates 2a and 2b. The DC high voltage applied between the electrode plates is a ceramic sheet (A), ( In the case of C), 1 kV,
In the case of the ceramic sheet (B), the voltage was set to 5 kV. Also,
When the ceramic sheet (C) is used, the electrode plates 2a,
A high DC voltage was applied between the sample 2b and the test ceramic sheet 1 with a conductive rubber sheet (1 mm thick) having the same dimensions as the electrode plate.

Also, 3 of the 997 test sheets (A)
Insert the test sheets (C) at any positions, for a total of 10 sheets.
The inspection for the presence or absence of the above-mentioned through-hole was performed on 00 test sheets.

As an inspection method, the test sheet 1 is placed on a predetermined position of the electrode plate 2a by using a detachable robot hand that sandwiches the test sheet 1 between the electrode plates 2a and 2b by a suction method, and the other side is placed on the test sheet 1 The operation of lowering the electrode plate 2b and bringing the electrode plate 2b into close contact with the test sheet 1 and then detecting the discharge current generated when a high DC voltage is applied between the electrode plates 2a and 2b by the detector 5 is referred to as one test sheet. The discharge current was detected as having a through-hole, and the discharge current was not determined as having no through-hole. During this time, the required inspection time per sheet was 10 seconds.

The results are as shown in Table 1. In the test sheets (A) and (B) consisting of only normal sheets, the discharge current could not be detected and the through-hole defect could not be confirmed. In the opened test sheet (C), a clear discharge current due to the through hole is detected. In addition, as a result of mixing the test sheet (C) having a through hole with the normal test sheet (A) and conducting a continuous inspection, only three test sheets (C) having a through hole were discharged. Thus, it can be understood that the through hole defective sheet can be reliably detected by this method.

[0071]

[Table 1]

[0072]

The present invention is constituted as described above. Particularly, the presence or absence of such a through hole defect in an insulating ceramic sheet in which an extremely fine through hole becomes a serious product defect such as a solid electrolyte membrane for a fuel cell. Can be detected easily and reliably in a short time, the detection work can be automated, and through-holes can be continuously inspected on a continuous production line for ceramic sheets or on an inspection line provided separately from the production line. A sheet having a defect can be reliably detected and extracted. As a result, all the sheet materials that have passed the inspection can be supplied to the market as extremely reliable products having no through-hole defects.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a through-hole inspection test device used in an experiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic sheet 1A Normal sheet 1B Defective sheet 2a, 2b Electrode plate 3a, 3b Conductive insulating sheet 4 DC high voltage power supply 5 Discharge current detector 6 Robot hand

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Teruhisa Nagashima 992, Nishioki, Okihama-shi, Abashi-ku, Himeji-shi, Hyogo Japan Nippon Shokubai Co., Ltd. F-term in Nippon Shokubai (reference) 4G031 AA07 AA08 AA12 BA03 CA08 5H026 AA06 BB00 CX04 EE12 HH03 HH04

Claims (6)

[Claims] 1. A method for inspecting a through hole of an insulating ceramic sheet, wherein both surfaces of the sheet are sandwiched between two electrode plates arranged in parallel, and a high DC voltage is applied between the electrode plates. A method for inspecting a through hole in a ceramic sheet, comprising detecting the presence or absence of a through hole having a minimum length of 2 mm or more in the ceramic sheet by detecting a discharge current generated at that time. 2. The insulating ceramic sheet having a thickness of 1
The inspection method according to claim 1, wherein a conductive high-molecular sheet having a flexibility of the same size as the electrode plate is applied between the ceramic sheet and the electrode plate, and a high DC voltage is applied between the ceramic sheet and the electrode plate. . 3. The inspection method according to claim 1, wherein at least a part of the following steps is automatically performed. (1) a step of placing an insulating ceramic sheet on one electrode plate A, (2) a step of confirming that the sheet is placed at a predetermined position on the electrode plate A, and (3) a step of placing the sheet on the ceramic sheet. A step of mounting the other electrode plate B, (4) a step of confirming a mounting position of the other electrode plate B, and (5) applying a high DC voltage between the electrode plates A and B to generate a discharge current. (6) removing the electrode plate B from above the ceramic sheet after the inspection, (7) the ceramic sheet, Step of separating from the electrode plate A. 4. A ceramic sheet having undergone the inspection method according to claim 1, wherein a shortest length of a through hole that can be present in the sheet is less than 2 mm. Ceramic sheet. 5. The method according to claim 1, wherein the ceramic sheet is made of Y, Ce, Pr, Sm, S
5. A material mainly composed of zirconium oxide stabilized with an oxide of at least one element selected from the group consisting of c or a composite oxide having a perovskite crystal structure as a main component. Sheet. 6. The sheet according to claim 4, which is used as a solid electrolyte membrane of a fuel cell.