Ceramic member

Abstract: A ceramic member includes a thin plate (13) having a plurality of minute throughholes (4) and a rigid plate (9) supporting the thin plate. The area of the thin plate both ends of which are supported by the rigid plate has a part (14) bent toward the rigid plate so that a line along the apex of the bent part is a straight line, and the minute throughholes are formed in the vicinity of the apex of the bent part. Good contact or adhesion between minute throughholes formed on the line connecting the apexes of the bent part and a drum or other body is obtained. The member is used for example in an ion flow control head.

Description: Background of the Invention and Related Art Statement The present invention relates to a ceramic member, in particular a ceramic member to be used in ion flow control heads, encoders, scales, high-precision minute electric field shutters, etc. A ceramic member comprising a thin plate having a plurality of minute throughholes and supported by a rigid plate has been used in location detecting devices or recording devices as the parts of ion flow control heads, encoders, scales, and high-precision minute electric field shutters. In the applications mentioned above, the minute throughholes are used for detecting or recording locations by passing or not passing a gas, liquid, solid particles or light. For example, when the ceramic member is used as the part of an ion flow control head, as Fig. 3 shows an electrode 1 is provided on a surface, a dielectric drum 6 is installed on the side where a rigid plate 9 is present, and an ion source 5 is installed on the other side, so that the discharge of ions 2 through the minute throughholes 4 is inhibited by making the electrode 1 carry a charge of the same sign as the ions carry, or ions are allowed to discharge by making the electrode 1 carry a charge of the opposite sign from that which the ions 2 carry. In either use, it is preferred that the drum 3 or the dielectric drum 6 contacts tightly with the opening of the minute throughholes from the point of view of fluid discharge, fluid control, or transfer properties. However, when conventional ceramic members are used in a high-precision electric field shutters and the like, the presence of a rigid plate 9 interferes with the access of a drum and the like to the minute throughholes 4, causing a problem that the drum and the like cannot be contacted with the opening. If the drum is made to contact with the opening from the thin plate side, the electrode wiring contacts with the drum causing problems of the wear of the electrode, and the electric field cannot be applied to ions effectively because the electrode is apart from the ion source. Although it is preferred that the thickness of the thin plate 13 is small from the point of view of decreasing the resistance for passing particles and of drum shape followability, the strength of the thin plate 13 is reduced, the adhesion of the drum to the minute throughholes deteriorates due to the deformation of the thin plate 13 to the opposite direction when the drum is approached, or the thin plate 13 is broken when the drum is contacted. Therefore, it is the object of the present invention to provide a ceramic member which is well adhered with the drum and the like, and does not break due to the contact with the drum and the like. Summary of the Invention According to the present invention, there is provided a ceramic member as set out in claim 1. In the ceramic member of the invention, it is preferred that the thickness of the thin plate portion is 1 µm or more and 50 µm or less, and the thickness of the rigid plate is 50 µm or more, and the distance between a straight line connecting the two opposed edges of the thin plate and the straight line along the surface of the most protuberant portion of the bent part is 3 µm or more and not more than 10 times the thickness of the rigid plate. In the above ceramic member, it is preferred that the surface roughness Ra in the vicinity of the most protuberant portion of the bent part is 1 µm or less, and that the curvature in the vicinity of the most protuberant portion of the bent part is smaller than the curvature of the other parts of the bent part. The ceramic member may have a rectangular window providing the gap in the rigid plate, with the thin plate portion closing the window so that a further pair of opposed edges thereof are connected to the rigid plate, and parts of the thin plate portion connecting between the two ends most protuberant portion of the bent part and the further pair of opposed edges being also bent into the gap. Brief Description of the Drawings Fig. 1 is a perspective view illustrating an embodiment of the ceramic member according to the present invention. Fig. 2 is a diagram illustrating the concept of the curvature in the present invention. Fig. 3 is a sectional view illustrating a prior unpublished purposal of an ion flow controlling head using a ceramic member. Fig. 4 is a perspective view illustrating another embodiment of the ceramic member according to the present invention. Fig. 5 is a diagram illustrating the concept of the amount of bending. Fig. 6 is a perspective view illustrating another embodiment of the ceramic member according to the present invention. Fig. 7 is a sectional view illustrating an embodiment of the electric field shutter head using the ceramic member according to the present invention. Fig. 8 is a perspective view illustrating an embodiment of the ion flow controlling head using the ceramic member according to the present invention. Fig. 9 (a) is a top view, Fig. 9 (b) is a sectional view along the line A-A', and Fig. 9 (c) is a sectional view along the line B-B', all illustrating another embodiment of the ceramic member according to the present invention. Fig. 10 is a perspective view illustrating further embodiment of the ceramic member according to the present invention. Fig. 11 is an explanatory view showing a direction of filtration in a bent part of a ceramic member. Preferred Embodiments of the Invention In a ceramic member of the present invention shown in Fig. 1, a thin plate 13 has two ends supported by a rigid plate 9 and has a part 14 bent toward the rigid plate 9 so that a line along the most protuberant portion of the bent part 14 is a straight line, and the minute throughholes 4 are formed in the vicinity of the most protuberant portion of the bent part 14. Therefore, resilience and rigidity can be given to the thin plate 13, and even if the thickness of the thin plate 13 is decreased, the thin plate 13 follows the shape of the drum without escaping to the opposite direction when the drum is approached, thus enabling the drum to adhere with the openings of the minute throughholes 4. The damage of the thin plate 13 due to contact with the drum can also be prevented. This is because since deformation in the vicinity of the apex is small, cracks do not develop from the minute throughholes. Furthermore, since the thin plate 13 protrudes against the drum, the presence of the rigid plate 9 does not interfere with the access of the drum to the minute throughholes 4. The width of the thin plate portion supported by the rigid plate at the two ends is preferably 0.1-10 mm, and more preferably 2-5 mm from the point of view of rigidity, adhesion with the drum and followability to the shape of the drum. In the ceramic member of the present invention, the thickness of the thin plate is preferably 1 µm or more and 50 µm or less, more preferably 5 µm or more and 40 µm or less. If the thickness is less than 1 µm, the mechanical strength of the thin plate decreases leading to damage, and if the thickness exceeds 50 µm, rigidity increases but resilience cannot be given causing poor adhesion and high resistance for passing particles. Although the thin plate may be composed of a plurality of thin plates, its total thickness must meet the above requirements. The thickness of the rigid plate is preferably 50 µm or more and 500 µm or less. If the thickness is less than 50 µ m, the mechanical strength of the ceramic member decreases, and if the thickness exceeds 500 µm, the member becomes difficult to install onto equipment. The rigid plate may not only increase the rigidity of the member, but have other functions. In the ceramic member of the present invention, the distance between the straight line connecting the two ends of the thin plate supported by the rigid plate and the straight line along the most protuberant portion of the bent part (amount of bending) is preferably 3 µm or more and 10 times the thickness of the rigid plate or less. As Fig. 5 shows, "the distance between the line 15 connecting the two ends of the thin plate 13 supported by the rigid plate 9 and the line 16 along the most protuberant portion of the bent part 14" means the length of a segment 17 drawn between and perpendicularly to lines 15 and 16. If the length of the segments are not uniform, the largest length is taken as this distance. If the amount of bending is less than 3 µm, sufficient rigidity and resilience cannot be given to the thin plate. If the amount of bending exceeds 10 times the thickness of the rigid plate, the curvature of the bent part becomes excessively large, the rigidity and resilience of the thin plate become unsuitable, and the electrode becomes difficult to form in the vicinity of the minute throughholes. It is preferred, from the point of view of rigidity and resilience to improve adhesion, that the relationship between the thickness of the thin plate tu (µm), the amount of bending T (µm), and the width of the both end areas of the thin plate supported by the rigid plate W (µm) is that represented by the following equation. 0.0003 µm ≦ [T (µm) × tu (µm)]/ W (µm) ≦ 125 µm In the ceramic member of the present invention, as Fig. 6 shows, the curvature of the bent part 14 in the vicinity of the apex 18 (most protuberant portion) is preferably smaller than that of the bent part 14 in other parts. This is more concretely shown by a ceramic member in Fig. 10. If the curvature of the bent part 14 is increased, the rigidity and resilience of the thin plate 13 increase, but adhesion between the drum and the openings decreases significantly only by the small deviation of the location of the minute throughholes 4 from the straight line along the most protuberant portion of the bent part 14. Therefore, by decreasing the curvature in the vicinity of the straight line 18 along the most protuberant portion of the bent part 14, significant decrease in adhesion can be prevented even if the location where the minute throughholes 4 are formed is a little deviated, and by maintaining the curvature of the other parts large, the resilience and rigidity of the thin plate 13 can be kept high. The term of curvature used herein is the curvature of the most approximate circle when considering a circle a part of which conforms to the respective part of the bent part 14 as Fig. 2 shows. The surface roughness Ra (average roughness at the center line), measured using a Surfcom (manufactured by Tokyo Seimitsu Co. Ltd.) with the radius of the probe of 5 µm under the conditions of the cutoff of 0.08 mm, is preferably 1 µm or less, and more preferably 0.2 µm or less. When the surface roughness Ra is within the above range, adhesion is further improved. As Fig. 4 shows, the ceramic member of the present invention may have more than one bent part 14. In this case, each bent part must meet the requirements of the amount of bending and the like. As Fig. 9 shows, the ceramic member of the present invention may have a rigid plate 9 having a rectangular window 21, and the thin plate 13 may be installed to close the window under the condition that four sides of the thin plate 13 are supported by the rigid plate 9, and the part 24 of the thin plate 13 connecting between the two ends 22 of the bent part 14 of the thin plate 13 and the edge 23 of the window 21 of the rigid plate 9 may have a part 25 bent into the window of the rigid plate 9. By surrounding the circumference of the binding thin plate portion with the rigid plate, strength against the external force such as torsion can be increased, and the damage of the thin plate can be prevented. Although the materials of the ceramic member of the present invention are not limited to specific ones, and alumina, partially stabilized zirconia, completely stabilized zirconia, or the mixture thereof may be used, it is preferred, from the point of view of improving the strength and wear resistance of the ceramic member, and of giving adequate Young's modulus and deformability, that the ceramic member is based on partially stabilized zirconia containing 2-6 mole percent, preferably 2.5-4.0 mole percent of yttrium oxide, and that the average grain diameter of its crystals is 2 µm or less, and preferably 1 µm or less. Incidentally, the thin plate desirably has the same ceramic composition as the rigid plate as a main constituents, in ceramic members of the present invention, in view of reliability. Further, the thin plate is fired simultaneously with the rigid plate so as to obtain a unitary body in view of reliability. In the ceramic member of the present invention, the shape of the openings of the minute through holes provided on the thin plate is not limited to a specific shape, but may be circular, oval, rectangular, polygonal, or the combination thereof. The throughhole diameter of the openings is preferably 150 µm or less, and preferably 100 µm or less. The term of throughhole diameter used herein is the diameter when the shape of the minute throughholes is circular, the length of the major axis when it is oval, the length of the longer side when it is rectangular, and the length of the longest diagonal line when it is polygonal. Distance between the minute throughholes is preferably 150 µm or less, and more preferably 80 µm or less. The terms of distance between the minute throughholes used herein is the shortest distance between the edges of openings of adjacent minute throughholes. The ceramic member of the present invention can be produced for example using the following method. Ceramic green sheets for the thin plate and the rigid plate each having a desired thickness are formed using slurry or paste prepared by combining a suitable binder, plasticizer, dispersing agent, sintering additive, and organic solvent to ceramic powder, by a known method such as doctor blade, calendar, printing, and reverse roll coater methods. The green sheets are then processed by cutting, machining, punching, and the formation of minute throughholes to fabricate formed articles having desired shapes and dimensions. The minute throughholes are formed by methods such as die/NC punching and excimer laser processing. After the formed article for the thin plate and the formed article for the rigid plate are joined by heating and compressing and the like, the system is sintered at a temperature between about 1200 and 1700 °C, preferably between about 1300 and 1600 °C, and then the electrode is formed by screen printing, sputtering, or photolithography. The bent part is formed by controlling the shrinkage of the thin plate and the rigid plate during sintering. Alternatively, the bent part can be formed by forming a bent configuration in the condition of a laminate before firing and then firing the laminate. Although it is preferred that no local protrusions are present from the point of view of adhesion, such protrusions may preferably be removed by etching, grinding, or machining. Fig. 8 shows an embodiment of an ion flow controlling head using the ceramic member of the present invention. In the ion flow controlling head 10 shown in Fig. 8, an ion source 5 is provided through the ceramic substrate 19 on the side of the ceramic member 7 where the electrode 1 is installed, and a dielectric drum 6 is provided on the other side. The thin plate 13 is bent toward the rigid plate 9, and minute throughholes 4 are provided in the vicinity of the apex (most protuberant portion) of the bent part 14. Incidentally, a ceramic member of the present invention can be used for a filter, a screen, a filtering member, or the like, since it has the aforementioned constitution. Advantages of the use of a ceramic member of the present invention for a filter, a screen, or a filtering member are as follows: 1) A member of the present invention is excellent in abrasion resistance since it is made of ceramic. 2) Since a thin plate having minute throughholes has a very thin thickness of 1 - 50 µm, a filtration resistance can be decreased. 3) It is hardly broken because of the structure that a rigid plate supports a thin plate. 4) An efficiency of filter area can be increased because a density of opennings (minute throughholes) can be increased. 5) Since a portion of a thin plate is adequately bent, a filtration pressure resistance or a reverse wash pressure resistance can be made high even if a filter portion is thin. That is, the direction in which a particle to be filtered is passed can be either of the two directions will respect to the bent portion. Accordingly, as shown in Fig. 11, for example, when filtration is performed from the side X to the side Y, a filtration pressure resistance can be increased, and on the other hand, when filtration is performed from the side Y to the side X, a reverse wash pressure resistance can be increased. Although the present invention will be described in further detail based on a preferred example, the present invention is not limited to this example. A ceramic member in which a thin plate is bent toward a rigid plate, and minute throughholes are formed in the vicinity of the apex (most protuberant portion) of the bent part of the thin plate was fabricated, and an ion flow controlling head was produced using this ceramic member. The thickness of the thin plate was 30 µm, and the thickness of the rigid plate was 80 µm. The width of the two end areas of the thin plate supported by the rigid plate was 3.2 mm. The throughhole diameter of the minute throughholes was 75 µm, the distance between the minute throughholes 4 was 80 µm, and the amount of bending was 10 µm. The curvature in the vicinity of the straight line along the most protuberant portion of the bent part (i.e. along the apex of the bent part) was smaller than that of the other areas of the bent part, and the surface roughness, measured using a Surfcom (manufactured by Tokyo Seimitsu Co. Ltd.) with the radius of the probe of 5 µm under the conditions of the cutoff of 0.08 mm, was 0.1 µm. A partially stabilized zirconia-based ceramic was used as the material for the ceramic member. The result of ion transfer to the dielectric drum performed using this ion flow controlling head showed that good adhesion was obtained between the dielectric drum and the openings of the minute throughholes, and that images of better transfer properties were obtained compared with the case where the thin plate was not bent. Also, the thin plate is not damaged. According to the ceramic member of the present invention, since the area of the thin plate both ends of which are supported by the rigid plate is bent toward the rigid plate, good adhesion between minute throughholes formed on the line along the most protuberant portion of the bent part and the drum and the like is obtained, and defective transfer can be prevented. Also, since adequate rigidity and resilience can be given to the thin plate, the thin plate is not damaged due to contact with the drum, rollers, and the like even if the thickness of the thin plate is decreased.

Claims: A ceramic member comprising a thin plate portion (13) having a plurality of minute throughholes (4) and a pair of opposed edges, and a rigid plate (9) supporting said thin plate portion at said opposed edges so that the thin plate portion bridges a gap in the rigid plate (9), wherein said thin plate portion (13) is bent between said opposed edges to that a bent part (14) thereof lies in said gap of the rigid plate (9) and a line along the most protuberant portion of said bent part is a straight line, and said minute throughholes (4) are formed in the vicinity of the most protuberant portion of the bent part. A ceramic member as claimed in claim 1, wherein the thickness of said thin plate portion is in the range 1 µm to 50 µm, and the thickness of said rigid plate (9) is 50 µm or more, and the distance between a straight line connecting said opposed edges of said thin plate portion and said straight line along the surface of the most protuberant portion of said bent part is at least 3 µm and not more than 10 times the thickness of said rigid plate (9). A ceramic member as claimed in claim 1 or 2, wherein the curvature in the vicinity of the most protuberant portion of said bent part (14) is smaller than the curvature of the other parts of said bent part (14). A ceramic member as claimed in any one of claims 1 to 3, wherein the surface roughness Ra in the vicinity of the most protuberant portion of said bent part is 1 µm or less. A ceramic member as claimed in any one of claims 1 to 4, wherein said rigid plate (9) has a rectangular window providing said gap, said thin plate portion closing said window so that a further part of opposed edges thereof are connected to said rigid plate, and parts of said thin plate portion connecting between the two ends of the said most protuberant portion of said bent part and said further pair of opposed edges are also bent into said gap.

Inventors: NANATAKI TSUTOMU, OGUCHI TAKASHI, TAKEUCHI YUKIHISA, YAMAMOTO HISANORI, NANATAKI, TSUTOMU, OGUCHI, TAKASHI, TAKEUCHI, YUKIHISA, YAMAMOTO, HISANORI
Applicants: NGK INSULATORS LTD, NGK INSULATORS, LTD.
Application year: 1997
Main classification: B32B18
IPC codes: B32B18