Ceramic sheet and method of manufacturing the same

Abstract

The present application relates to a ceramic sheet manufacturing method, comprising: a primary sheet forming step of forming a composition containing a resin and a ceramic material into a sheet shape by pressing; a laminate forming step of laminating a plurality of primary sheets in a thickness direction or folding or winding the primary sheet to obtain a laminate; a sheeting step of sheeting the laminate at an angle of 45° or less with respect to a lamination direction to obtain a secondary sheet; and a firing step of firing the secondary sheet.

Description

Technical Field

[0001] This invention relates to ceramic sheets and methods for manufacturing the same. Background Technology

[0002] Ceramic sheets have long been used in a wide range of applications. It is known that various properties of ceramic sheets can be improved by controlling their structure. For example, Patent Document 1 proposes a method for manufacturing an oriented ceramic sintered body by dispersing a specified non-ferromagnetic powder in a solvent to obtain a slurry, solidifying the slurry in a magnetic field, and then sintering it; and an oriented alumina ceramic sintered body in which the (006) diffraction intensity of X-ray diffraction on the C-plane of the alumina crystal is more than 1.2 times that of the (110) diffraction intensity.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent document 1: Japanese Patent Application Publication No. 2002-193672. Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In recent years, there has been a demand for ceramic sheets with superior properties compared to those previously provided. Therefore, the object of this invention is to provide a ceramic sheet with a novel orientation structure.

[0008] Solution for solving the problem

[0009] To achieve the aforementioned objectives, the inventors conducted in-depth research. Furthermore, the inventors have discovered a novel method: molding a composition containing resin and ceramic materials into a sheet, stacking multiple primary sheets in the thickness direction to obtain a laminate, slicing the laminate to obtain a secondary sheet, and firing the secondary sheet yields a ceramic sheet with a novel orientation structure, thus completing the present invention.

[0010] That is, the object of the present invention is to advantageously solve the above-mentioned problems. The method for manufacturing ceramic sheets of the present invention is characterized by comprising: a primary sheet forming step, wherein a composition comprising resin and ceramic material is pressed and formed into a sheet to obtain a primary sheet; a laminate forming step, wherein multiple primary sheets are laminated in the thickness direction, or the primary sheets are folded or rolled to obtain a laminate; a slicing step, wherein the laminate is sliced ​​at an angle of 45° or less relative to the lamination direction to obtain a secondary sheet; and a firing step, wherein the secondary sheet is fired.

[0011] This manufacturing method can efficiently produce ceramic sheets with novel orientation structures.

[0012] Here, in the method for manufacturing ceramic sheets of the present invention, it is preferable to perform a degreasing process before the firing process, wherein the secondary sheet is heated in an environment of 300°C or higher for degreasing, and the firing process is performed in an environment of 1000°C or higher. According to this manufacturing method, ceramic sheets with novel orientation structures can be provided more efficiently.

[0013] In addition, the temperatures mentioned above in the degreasing and firing processes are at 1 atm.

[0014] Furthermore, in the method for manufacturing the ceramic sheet of the present invention, the thickness of the primary sheet is preferably 2.5 mm or less. According to this manufacturing method, ceramic sheets with novel orientation structures can be provided more efficiently.

[0015] Furthermore, in the method for manufacturing the ceramic sheet of the present invention, based on the total volume of the resin and the ceramic material, the volume fraction of the ceramic material in the primary sheet is preferably 50% by volume or more and 75% by volume or less. According to this manufacturing method, the quality of ceramic sheets with novel orientation structures can be improved.

[0016] The purpose of this invention is to advantageously solve the above-mentioned problems. The ceramic sheet of this invention is a ceramic sheet composed of a sintered ceramic body, characterized in that the a-axis value is positive when Lotgering analysis is performed on the ceramic sheet. This ceramic sheet has a novel orientation structure.

[0017] In addition, the Lothgreen analysis of the ceramic sheet can be performed according to the method described in the examples.

[0018] Here, the ceramic sheet of the present invention is preferably one in which the c-axis value is negative when the Lothgreen analysis is performed on the ceramic sheet. When the c-axis value is negative when the Lothgreen analysis is performed on the ceramic sheet, the orientation of the a-axis is relatively high, and thus suitable properties can be exhibited.

[0019] Furthermore, in the ceramic sheet of the present invention, the ceramic may also contain alumina. As a ceramic, the ceramic sheet containing alumina has excellent quality.

[0020] Furthermore, in the ceramic sheet of the present invention, the ceramic preferably comprises flake-shaped ceramic. If the ceramic sheet comprises flake-shaped ceramic, the thermal conductivity is excellent. Moreover, in the ceramic sheet of the present invention, the proportion of the flake-shaped ceramic in the ceramic is preferably 65% ​​by volume or less. If the proportion of the flake-shaped ceramic is 65% by volume or less of the total ceramic, the strength of the ceramic sheet can be improved.

[0021] Invention Effects

[0022] According to the present invention, it is possible to provide ceramic sheets with novel orientation structures. Detailed Implementation

[0023] The embodiments of the present invention will now be described in detail.

[0024] (Ceramic shard)

[0025] The ceramic sheet of the present invention is a ceramic sheet composed of a sintered ceramic body and has a novel orientation structure. More specifically, the a-axis value of the ceramic sheet of the present invention is positive when Lotgering analysis is performed, and the a-axis of the crystal axes of the ceramic constituting the ceramic sheet is oriented in the thickness direction of the ceramic sheet (the a-axis is parallel to the thickness direction). This ceramic sheet has excellent thermal conductivity in the thickness direction and exhibits anisotropy in thermal conductivity, meaning that the thermal conductivity in the thickness direction is higher than that in the direction of the main surface of the ceramic sheet. Here, "main surface of the ceramic sheet" means at least one side surface of the ceramic sheet.

[0026] In the ceramic sheet of the present invention, "the a-axis of the ceramic crystals is oriented in the thickness direction of the ceramic sheet" means that the ceramic crystals constituting the ceramic sheet are oriented in the a-axis direction, and this a-axis direction is approximately consistent with the thickness direction of the ceramic sheet. In the ceramic sheet, if the a-axis direction of the ceramic crystals is oriented in the thickness direction of the sheet, the ceramic sheet exhibits excellent thermal conductivity and can display anisotropy in thermal conductivity, such that the thermal conductivity in the thickness direction is higher than that in the main surface direction of the sheet.

[0027] In this specification, the ceramic crystal constituting the ceramic sheet is "oriented in the a-axis direction". In addition to the fact that the value of the a-axis is positive when Rothegreen analysis is performed, it can also be understood by the value obtained by dividing the scattering intensity in the plane corresponding to the a-axis direction of the crystal obtained by X-ray diffraction (XRD) by the scattering intensity in the plane corresponding to the c-axis direction (hereinafter, sometimes referred to as "a / c") as described in the examples.

[0028] Here, according to the method described in the embodiment, the value obtained by dividing the value of a / c when the a-axis direction is oriented in the thickness direction of the ceramic sheet by the value of a / c when the a-axis direction is not oriented in the thickness direction of the ceramic sheet (hereinafter, sometimes referred to as the "vertical orientation parameter of the ceramic") is preferably 1.50 or more, more preferably 1.55 or more, more preferably 3.00 or more, and even more preferably 3.60 or more. If the value of the vertical orientation parameter is above this lower limit, the a-axis direction of the ceramic crystal is more well oriented in the thickness direction of the ceramic sheet, and the thermal conductivity of the ceramic sheet is better.

[0029] When the ceramic sheet undergoes Lotgering analysis, the a-axis value (Lotgering factor) needs to be positive, more preferably 0.010 or higher, and even more preferably 0.020 or higher. This results in superior thermal conductivity in the thickness direction and high anisotropy of thermal conductivity. Furthermore, there is no particular upper limit to the a-axis value when Lotgering analysis is performed; for example, it can be 1.000 or lower. In the principle of Lotgering analysis, the Lotgering factor is 1.000 in the case of complete orientation and zero in the case of no orientation. Moreover, the closer the Lotgering factor is to 1, the higher the degree of orientation.

[0030] Furthermore, the value of the c-axis (Lotte Green factor) of the ceramic sheet when subjected to Lotte Green analysis is preferably negative, preferably -0.0001 or less, and more preferably -0.0010 or less. Since the a-axis of this ceramic sheet is relatively oriented, the thermal conductivity in the thickness direction is superior, and the anisotropy of thermal conductivity is high. Additionally, the lower limit of the c-axis value when subjected to Lotte Green analysis is not particularly limited, and for example, it can be -0.0030 or more. In the principle of Lotte Green analysis, a negative Lotte Green factor means that, compared to an unoriented sample, the proportion of grains oriented along the c-axis is low, i.e., the proportion of grains oriented along axes other than the c-axis is high.

[0031] Furthermore, the value obtained by dividing the thermal conductivity in the thickness direction of the ceramic sheet by the thermal conductivity in the main surface direction (hereinafter sometimes referred to as the "anisotropic parameter of thermal conductivity") is preferably 1.01 or higher, more preferably 1.05 or higher. This ceramic sheet exhibits anisotropy with respect to thermal conductivity. The upper limit of the anisotropic parameter of thermal conductivity is not particularly limited, and for example, it may be 3.0 or lower.

[0032] Furthermore, the ceramic material constituting the ceramic sheet is not particularly limited, and examples include alumina, barium titanate, boron nitride, silicon nitride, silicon carbide, and hydroxyapatite. Alumina is preferably included in the ceramic material constituting the ceramic sheet. When the ceramic material contains alumina, the ceramic sheet has a high quality.

[0033] Furthermore, the ceramic constituting the ceramic sheet preferably includes flake-shaped ceramic. Ceramic sheets containing flake-shaped ceramic have excellent thermal conductivity. In this case, the proportion of flake-shaped ceramic relative to the total volume of the ceramic is preferably 65% ​​by volume or less, more preferably 55% by volume or less, and even more preferably 40% by volume or less. If the proportion of flake-shaped ceramic relative to the total volume of the ceramic is below the above-mentioned upper limit, the quality of the ceramic sheet is high. More specifically, when manufacturing ceramic sheets according to the manufacturing method of the present invention described later, by using a composition in which the proportion of flake-shaped ceramic is below the above-mentioned upper limit, it is possible to suppress the peeling of flakes during the firing process and improve the quality of the obtained ceramic sheet. In addition, from the viewpoint of improving the orientation of the crystal axes of the ceramic, when the ceramic sheet contains flake-shaped ceramic, the proportion of flake-shaped ceramic relative to the total volume of the ceramic is preferably 15% by volume or more.

[0034] Here, the ceramics constituting the ceramic sheet may include granular ceramics in addition to, or instead of, the aforementioned flake-shaped ceramics. Furthermore, the ceramic sheet is composed of a sintered body of these ceramics. Therefore, in the ceramic sheet, the flake-shaped ceramics or granular ceramics do not exist independently, but rather form a dense structure composed of multiple individuals bonded together.

[0035] (Methods for manufacturing ceramic tiles)

[0036] The ceramic sheet of the present invention, possessing the above-described features, can be efficiently manufactured according to the manufacturing method of the ceramic sheet of the present invention. The manufacturing method of the ceramic sheet of the present invention is characterized by comprising: a primary sheet forming step, wherein a composition comprising resin and ceramic material is pressurized and formed into a sheet to obtain a primary sheet; a laminate forming step, wherein multiple primary sheets are laminated in the thickness direction, or the primary sheets are folded or rolled to obtain a laminate; a slicing step, wherein the laminate is sliced ​​at an angle of 45° or less relative to the lamination direction to obtain a secondary sheet; and a firing step, wherein the secondary sheet is fired. Furthermore, the manufacturing method of the present invention preferably includes a degreasing step before the firing step, wherein the secondary sheet is heated in an environment of 400° or higher to perform degreasing. Each step will be described below.

[0037] <One-time sheet forming process>

[0038] In the primary sheet forming process, a composition containing resin and ceramic materials is pressed and formed into a sheet to obtain a primary sheet.

[0039] [Composition]

[0040] Here, it is possible to mix resins, ceramic materials, and any other components to prepare a composition.

[0041] -Ceramic Materials-

[0042] As the ceramic material, any ceramic material composed of the various ceramics described above that can be included in the ceramic sheet of the present invention can be used. When the ceramic material is granular, there are no particular limitations; granular ceramic materials with a volume average particle size D50 of 0.4 μm or more and 10.0 μm or less can be used. Furthermore, when the ceramic material is flake-shaped, there are no particular limitations; flake-shaped ceramic materials with a volume average particle size D50 of 2 μm or more and 10 μm or less can be used. Additionally, "granular" means that the aspect ratio is 5 or less. Here, the ceramic material is observed using SEM (scanning electron microscope), and the maximum diameter (major diameter) and the particle size in the direction orthogonal to the maximum diameter (minor diameter) of any 50 ceramic materials are measured. The average value of the ratio of the major diameter to the minor diameter (major diameter / minor diameter) is calculated, thereby determining the aspect ratio. Additionally, in the above, for example, when using SEM to observe flake-like ceramic materials, "major axis" refers to the length of the major axis of the main surface of the flake-like ceramic material, and "minor axis" refers to the length of the major axis in the same plane as the main surface, in a direction orthogonal to the major axis of the main surface.

[0043] Furthermore, in ceramic materials, it is preferable that the c-axis of the grains has an orientation tendency in the thickness direction. Here, the "thickness" direction of granular ceramic materials refers to determining the longest axis when the granular ceramic material is approximated as a pseudo-ellipsoid, finding two axes orthogonal to this longest axis (which are also mutually orthogonal), and considering the direction of the shorter of these two axes as the thickness direction. In addition, in flake-like ceramic materials, the direction perpendicular to the main surface direction is considered the thickness direction. Here, "the c-axis of the grains has an orientation tendency" in ceramic materials means that the grains are regularly arranged within the secondary crystals (i.e., the ceramic material). Moreover, if such ceramic materials are oriented using the manufacturing method of the present invention, the orientation effect is more easily achieved.

[0044] -Resin-

[0045] There are no particular limitations on the resin used; various resins can be used. Examples of such resins include, for instance, polyethylene-based crystalline resins such as linear or branched high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene; polypropylene-based crystalline resins such as linear or branched high-density polypropylene and low-density polypropylene; polyolefin-based crystalline resins represented by polymethylpentene, polybutene, polymethylbutene, polymethylhexene, polyvinylnaphthalene, and polyxylene; polyester-based crystalline resins represented by polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate, and aromatic polyesters; and polyamide-based crystalline resins represented by nylon-6, nylon-66, nylon-12, and polyamide-imide. The resins include: fluorinated crystalline resins such as polyvinylidene fluoride and polytetrafluoroethylene; others include rosin-based resins, polyvinylidene chloride, polyacrylonitrile, syndiotactic polystyrene, polyoxymethylene, polyphenylene sulfide (PPS), polyether ether ketone (PEEK), cellulose, acetal resins, chlorinated polyethers, ethylene-vinyl acetate copolymers, liquid crystal polymers (aromatic polycyclic condensation polymers), and other crystalline resins; as well as elastomers such as acrylonitrile-butadiene rubber, styrene-butadiene-styrene block copolymers, styrene-ethylene-butene-styrene copolymers, styrene-isoprene-styrene block copolymers, styrene-ethylene-propylene-styrene copolymers, silicone rubber, and fluororubber. Acrylonitrile-butadiene rubber is preferred.

[0046] -Other ingredients-

[0047] As other components that can be arbitrarily incorporated into the composition, other components that can be used for molding the single-piece sheet can be further incorporated as needed. Moreover, there are no particular limitations on other components that can be incorporated into the composition, and examples include crosslinking agents; reaction initiators; flame retardants such as red phosphorus-based flame retardants and phosphate ester-based flame retardants; plasticizers such as fatty acid ester-based plasticizers; toughness modifiers such as polyurethane acrylates; hygroscopic agents such as calcium oxide and magnesium oxide; adhesion enhancers such as silane coupling agents, titanium coupling agents, and acid anhydrides; wettability enhancers such as nonionic surfactants and fluorinated surfactants; and ion scavenging agents such as inorganic ion exchangers.

[0048] Furthermore, there are no particular limitations on the mixing of the aforementioned components, and known mixing devices such as kneaders, Henschel mixers, Hobart mixers, high-speed mixers, twin-shaft mixers, and roller mixers can be used. Additionally, mixing can be carried out in the presence of a solvent. The resin can also be pre-dissolved or dispersed in a solvent as a resin solution and then mixed with the ceramic material and any other components. Moreover, the mixing time can be, for example, 5 minutes or more and 60 minutes or less. Furthermore, the mixing temperature can be, for example, 5°C or more and 160°C or less.

[0049] [Forming of the composition]

[0050] Furthermore, the composition prepared as described above can be degassed and pulverized in any way, and then pressurized to form a sheet. The sheet obtained by pressing the composition in this way can be used as a primary sheet. In addition, if a solvent is used during mixing, it is preferable to form the sheet after removing the solvent. For example, if vacuum degassing is used, the solvent can be removed simultaneously during degassing.

[0051] Here, there are no particular limitations on the molding method for the composition as long as it is a pressure-applied molding method, and it can be molded into a sheet using known molding methods such as compression molding, calendering, or extrusion molding.

[0052] [One-shot film]

[0053] Furthermore, in the primary sheet obtained by pressing the composition into a sheet shape, it is presumed that the ceramic material is mainly arranged neatly in the in-plane direction. In the primary sheet stage, the "ceramic material" neatly arranged in the in-plane direction is a polycrystalline aggregate of multiple grains. In the primary sheet, the polycrystalline aggregate is neatly arranged in the in-plane direction, but it is presumed that the crystal axes of the multiple grains constituting the polycrystalline aggregate remain essentially unchanged from the state of the polycrystalline raw material at this stage. Through the laminate formation process described later, followed by the slicing process, the a-axis orientation becomes more pronounced in the resulting ceramic sheet.

[0054] The thickness of the primary sheet is preferably 2.5 mm or less, more preferably 2.0 mm or less, and even more preferably 1.5 mm or less. If the thickness of the primary sheet is below the above-mentioned upper limit, it is possible to effectively suppress cracking or breakage of the sheet caused by shrinkage in subsequent firing processes, and ceramic sheets can be formed efficiently. In addition, the lower limit of the thickness of the primary sheet is not particularly limited, for example, it can be 0.1 mm or more.

[0055] Furthermore, based on the total volume of resin and ceramic materials, the volume fraction of ceramic material in the primary sheet is preferably 50% by volume or more, more preferably 55% by volume or more, even more preferably 60% by volume or more, preferably 75% by volume or less, and more preferably 70% by volume or less. If the volume fraction of ceramic material in the primary sheet is above the aforementioned lower limit, cracking or breakage of the ceramic sheet during the subsequent firing process can be effectively suppressed, or firing shrinkage can be reduced, thereby improving the quality of the obtained ceramic sheet. If the volume fraction of ceramic material in the primary sheet is below the aforementioned upper limit, the quality of the obtained ceramic sheet can be improved by preventing cracking and breakage of the primary sheet itself before firing.

[0056] <Laminated Body Forming Process>

[0057] In the laminate formation process, multiple primary sheets are stacked in the thickness direction, or primary sheets are folded or rolled to obtain a laminate. Here, there are no particular limitations on forming a laminate by folding primary sheets; it can be done by folding the primary sheets to a fixed width using a folding machine. Furthermore, there are no particular limitations on forming a laminate by rolling primary sheets; it can be done by rolling the primary sheets around an axis parallel to the short or long side direction of the primary sheets. Moreover, there are no particular limitations on forming a laminate by stacking primary sheets; it can be done using a lamination device. For example, if a sheet lamination device (manufactured by Nikkiso Co., Ltd., product name "Hi-Stacker") is used, air ingress between layers can be suppressed, thus efficiently obtaining a high-quality laminate.

[0058] Furthermore, in the lamination process, it is preferable to heat the resulting laminate while simultaneously applying pressure in the lamination direction (secondary pressure). By applying secondary pressure to the laminate while simultaneously heating it in the lamination direction, the welding between the primary sheets of the laminate can be promoted.

[0059] Here, the pressure applied to the laminate in the lamination direction can be 0.05 MPa or more and 0.50 MPa or less. Furthermore, the heating temperature of the laminate is not particularly limited, but is preferably 50°C or more and 170°C or less. Moreover, the heating time of the laminate can be, for example, 10 seconds or more and 30 minutes or less.

[0060] Furthermore, in a laminate obtained by stacking, folding, or rolling primary sheets, it is presumed that the ceramic material (polycrystalline) is oriented in a direction approximately orthogonal to the stacking direction. For example, if the ceramic material includes flake-like ceramics, it is presumed that the direction of the long axis of the main face of the flake-like ceramics is approximately orthogonal to the stacking direction.

[0061] <(iii) Slicing process>

[0062] In the slicing process, the laminate obtained in the above-described process is sliced ​​at an angle of 45° or less relative to the lamination direction to obtain a secondary slice. Here, the method for slicing the laminate is not particularly limited, and examples include multi-blade slicing, laser processing, water jet slicing, and blade slicing. Among these, blade slicing is preferred from the perspective of easily achieving uniform thickness in the secondary slice. Furthermore, the cutting tool for slicing the laminate is not particularly limited, and a slicing member having a smooth disc with a slit and a blade protruding from that slit (e.g., a planer with a sharp blade, a slicer) can be used.

[0063] Furthermore, from the viewpoint of improving the thermal conductivity of the obtained ceramic sheet in the thickness direction, the angle at which the laminate is sliced ​​is preferably 30° or less relative to the lamination direction, and more preferably 15° relative to the lamination direction.

[0064] Hereinafter, it is preferred that the angle is approximately 0° relative to the stacking direction (i.e., the direction along the stacking direction).

[0065] Moreover, in the secondary sheet obtained in this way, the ceramic material (polycrystalline) is well oriented in the thickness direction, and has excellent thermal conductivity in the thickness direction.

[0066] <Degreasing process>

[0067] In any of the degreasing processes, the secondary sheet is heated in an environment of 300°C or higher to perform degreasing. The ambient temperature in the degreasing process is more preferably 350°C or higher, and even more preferably 400°C or higher. The upper limit of the heating temperature in the degreasing process needs to be lower than the ambient temperature of the firing process, for example, it can be 600°C or lower. If the ambient temperature in the degreasing process is above or below the aforementioned lower limit, the degreasing process can be performed without leaving any resin contained in the primary sheet. Furthermore, if the ambient temperature in the degreasing process is below the aforementioned upper limit, the degreasing process can be performed without carbonizing the resin contained in the primary sheet.

[0068] Here, the degreasing process is preferably carried out in an inert gas environment (e.g., nitrogen and argon) at atmospheric pressure (1 atm).

[0069] <Firing Process>

[0070] In the firing process, secondary sheets are fired. The environment during the firing process is preferably 1000°C or higher, more preferably 1500°C or higher, and most preferably 2000°C or lower. If the temperature of the environment during the firing process is above the lower limit mentioned above, the ceramic can be sintered more densely.

[0071] Here, the firing process is the same as the degreasing process, and it is preferably carried out in an inert gas environment (e.g., nitrogen and argon) at atmospheric pressure (1 atm).

[0072] According to the manufacturing method of the present invention, which includes the above steps, the ceramic sheet of the present invention can be manufactured efficiently, that is, a ceramic sheet composed of a sintered body of ceramic, wherein the a-axis of the crystal axis of the ceramic constituting the ceramic sheet is oriented in the thickness direction of the ceramic sheet.

[0073] Example

[0074] The present invention will now be specifically described based on embodiments, but the present invention is not limited to these embodiments. Furthermore, in the following description, unless otherwise specified, "%" and "parts" are used to indicate quantities based on mass.

[0075] In each embodiment and comparative example, various attributes and evaluations were measured or evaluated according to the following methods.

[0076] Thermal conductivity

[0077] For the main surface of the ceramic chip, the thermal diffusivity α (m 2 / s), the specific heat at constant pressure Cp (J / g·K), and the specific gravity ρ (g / m 3 ) are measured respectively by the following methods.

[0078] [Thermal diffusivity α (m 2 / s)]

[0079] Using a thermal property measuring device (manufactured by BETHEL Co., Ltd., product name "Thermal Wave Analyzer TA35"), the thermal diffusivity in the X, Y, and Z directions is measured.

[0080] [Specific heat at constant pressure Cp (J / g·K)]

[0081] Using a differential scanning calorimeter (manufactured by Rigaku Corporation, product name "DSC8230"), the specific heat is measured under the heating condition of 10°C / min.

[0082] [Specific gravity ρ (g / m 3 )]

[0083] Using an automatic hydrometer (manufactured by Toyo Seiki Seisaku-sho, Ltd., trade name "DENSIMETER-H"), the specific gravity (density) (g / m 3 ) is measured.

[0084] Then, the measured values obtained are substituted into the following formula (I):

[0085] λ = α × Cp × ρ...(Ⅰ),

[0086] For the ceramic chip, the thermal conductivity λ (W / m·K) in the X, Y, and Z directions is obtained.

[0087] [Anisotropy of thermal conductivity]

[0088] Using the thermal conductivity λ in the X, Y, and Z directions of the ceramic chip obtained above, the thermal conductivity in the Z direction is divided by the larger value of the thermal conductivity in the X direction and the thermal conductivity in the Y direction to calculate the anisotropy of thermal conductivity.

[0089] [Measurement of XRD pattern]

[0090] For the ceramic sheets obtained in the Examples and Comparative Examples (but excluding Comparative Example 2) and the ceramic particles as non-oriented samples, XRD patterns were measured in the range of 2θ = 20 to 90° when irradiated with X-rays using an XRD apparatus (Rigaku Corporation, trade name "RINT2200"). The non-oriented ceramic particles were prepared by pulverizing the ceramic sheets obtained in each Example and Comparative Example into powder in a mortar. Specifically, CuKα rays were used, and the measurements were performed under conditions of 40 kV voltage and 400 mA current. Furthermore, for the ceramic sheets, XRD patterns were measured on the surface of the sheets.

[0091] The Lautergreen Analysis

[0092] Then, following the Lautergreen method, the orientation degrees of the a-axis and c-axis are calculated based on the obtained XRD patterns. Specifically, the Lautergreen factor f, which is associated with the orientation degree of each axis, is calculated according to the following steps.

[0093] The Lottling factor f is calculated using the peak intensity of X-rays diffracted from the crystal plane of the object, by the following equation (1).

[0094] f=(ρ-ρ0) / (1-ρ0) (1).

[0095] Here, ρ0 is calculated using the X-ray diffraction intensity (I0) of the unoriented sample. In the case of c-axis orientation, it is the ratio of the total diffraction intensity of all planes perpendicular to the c-axis (the planes perpendicular to the c-axis) to the sum of the total diffraction intensities (∑I0(hkl)), which is obtained by the following equation (2).

[0096] ρ0=∑I o (C-axis vertical plane) / ∑I0(hkI) (2).

[0097] ρ is calculated using the X-ray diffraction intensity (I) of the oriented sample. In the case of c-axis orientation, it is the ratio of the total diffraction intensity of the C-axis perpendicular plane to the sum of the total diffraction intensities (∑I(hkl)), which is the same as in equation (2) above, and is obtained by equation (3) below.

[0098] ρ=∑I(C-axis vertical plane) / ∑I(hkI) (3).

[0099] In the case of the a-axis orientation, the Lautergreen factor f is calculated in the same manner as described above.

[0100] Calculation of Scattering Intensity Ratio

[0101] For Examples 1-7 and Comparative Examples 1-2, which use alumina as the ceramic material, the scattering intensity of the (300) plane (2θ = 68°; the scattering intensity of the plane corresponding to the a-axis direction) in the XRD pattern was divided by the scattering intensity of the (006) plane (2θ = 37°; the scattering intensity of the plane corresponding to the c-axis direction) to evaluate the degree of orientation in the a-axis direction (a / c).

[0102] For Example 8 and Comparative Example 3, which used barium titanate as the ceramic material, the scattering intensity of the (200) plane (2θ = 44.8°; the scattering intensity of the plane corresponding to the a-axis direction) in the XRD pattern was divided by the scattering intensity of the (002) plane (2θ = 45.4°; the scattering intensity of the plane corresponding to the c-axis direction) to evaluate the degree of orientation in the a-axis direction (a / c).

[0103] <Vertical Orientation Parameters>

[0104] Regarding the vertical orientation parameter, for Examples 1 to 7 using alumina as the ceramic material, the a / c value calculated in these examples is used as the "a / c value when the a-axis direction is oriented in the thickness direction of the ceramic sheet", and the a / c value of Comparative Example 1 obtained as described above is used as the "a / c value when the a-axis direction is not oriented in the thickness direction of the ceramic sheet". The former is divided by the latter to calculate the vertical orientation parameter of the ceramic.

[0105] For Example 8, which uses barium titanate as the ceramic material, the vertical orientation parameter of the ceramic is calculated by dividing the a / c value calculated in Example 8 by the a / c value calculated in Comparative Example 3.

[0106] <Quality of Ceramic Tiles>

[0107] The quality of the ceramic sheets was assessed visually. In cases of significant shrinkage during the firing of secondary sheets, a defect was identified where the sheets separated during the firing process.

[0108] A: It is not peeled off in strips, but fired as a thin sheet.

[0109] B: Strips peel off at points 1 to 4, and the fired sheet separates into 2 to 5 pieces (partially).

[0110] C: There are more than 5 places where the strips peel off within a thin sheet, and the thin sheet after firing separates into more than 6 pieces.

[0111] (Example 1)

[0112] <One-time sheet forming process>

[0113] <<Preparation of the Composition>>

[0114] 62 parts of liquid nitrile rubber (NBR) (manufactured by Zeon Corporation, Japan, trade name "Nipol 1312", decomposition start temperature: 336°C), 62 parts of solid nitrile rubber (NBR) (manufactured by Zeon Corporation, Japan, trade name "Nipol 3350", decomposition start temperature: 375°C), and 700 parts of granular alumina material (manufactured by Light Metals Corporation, Japan, trade name "LS-711C", volume average particle size: 0.5 μm, aspect ratio: 1.2) were mixed using a pressure kneader (manufactured by Spindle Manufacturing Co., Ltd., Japan) at 150°C for 20 minutes.

[0115] <<The Forming of a Single Sheet>>

[0116] Next, 50g of the obtained composition was sandwiched between a 50μm thick PET film (protective film) that had undergone sandblasting treatment, and calendered (one-time pressing) under the conditions of 1000μm roller gap, 50℃ roller temperature, 50kg / cm roller linear pressure, and 1m / min roller speed to obtain a primary sheet with a thickness of 1.0mm.

[0117] <Laminated Body Forming Process>

[0118] Next, the primary sheet obtained above is cut into 150mm x 150mm x 0.8mm thickness pieces, and 188 pieces are stacked in the thickness direction of the primary sheet. Then, it is pressed (secondary pressurization) in the stacking direction at a temperature of 120℃ and a pressure of 0.1MPa for 3 minutes to obtain a laminate with a height of about 150mm.

[0119] <Slicing Process>

[0120] Then, while pressing the laminated side of the secondary pressurized body with a pressure of 0.3 MPa, a woodworking slicer (manufactured by Marunaka Tekko Co., Ltd., trade name "Seiko Planer SUPER MECA-S") is used to slice the laminate at an angle of 0 degrees relative to the lamination direction (in other words, in the normal direction of the main surface of the primary sheet), thereby obtaining a secondary sheet with a length of 150 mm × width of 150 mm × thickness of 0.30 mm.

[0121] <Degreasing process ~ Firing process>

[0122] The resulting secondary sheet is then heated at 400°C for 3 days under normal pressure and nitrogen to perform a degreasing process, which burns the resin components (degreasing process). Next, the temperature is increased to 1600°C at a rate of 10°C / minute under the same conditions for 1 day of firing (firing process).

[0123] The obtained ceramic plates were used for various measurements and evaluations. The results are shown in Table 1.

[0124] (Example 2)

[0125] When preparing the composition in the single-sheet forming process, the granular alumina material used as the ceramic material was changed to a larger diameter granular alumina material (manufactured by Nippon Light Metals Co., Ltd., trade name "LS-130F", volume average particle size: 3 μm, aspect ratio: 1.2). Otherwise, the process was the same as in Example 1, and ceramic sheets were obtained. Various measurements and evaluations were performed. The results are shown in Table 1.

[0126] (Example 3)

[0127] When preparing the composition in the single-sheet molding process, the proportions of various resins and the proportion of granular alumina material were changed as shown in Table 1. Furthermore, 158 parts of flake-shaped alumina material (manufactured by Kinsei Kogyo Co., Ltd., trade name "SERATH", volume average particle size: 10 μm, aspect ratio: 1.8) were added as the ceramic material. Otherwise, the process was the same as in Example 1 to obtain ceramic sheets, and various measurements and evaluations were performed. The results are shown in Table 1.

[0128] (Examples 4-5)

[0129] When preparing the composition in the single-piece molding process, the proportions of various resins and ceramic materials were changed as shown in Table 1. Otherwise, the process was the same as in Example 3 to obtain ceramic sheets, which were then subjected to various measurements and evaluations. The results are shown in Table 1.

[0130] (Example 6)

[0131] When preparing the composition in a single-piece molding process, the amounts of various resins and ceramic materials were changed as shown in Table 1. Otherwise, the process was the same as in Example 1 to obtain ceramic sheets, which were then subjected to various measurements and evaluations. The results are shown in Table 1.

[0132] (Example 7)

[0133] When forming the primary sheet in the primary sheet forming process, the thickness was changed to 2.0 mm. Otherwise, the process was the same as in Example 1 to obtain ceramic sheets, which were then subjected to various measurements and evaluations. The results are shown in Table 1.

[0134] (Example 8)

[0135] When preparing the composition in the single-piece molding process, the proportions of various resins were changed as shown in Table 1. Furthermore, 900 parts of barium titanate (manufactured by Nippon Chemical Industries, Ltd., trade name "BESPA", volume average particle size: 10 μm, aspect ratio: 1.1, specific gravity: 6.02) were added as a ceramic material. Otherwise, the process was the same as in Example 1 to obtain ceramic sheets, and various measurements and evaluations were performed. The results are shown in Table 1.

[0136] (Comparative Example 1)

[0137] The primary sheet obtained in the primary sheet forming process was cut into 50mm × 50mm pieces (1.0mm thick) and directly fed to the degreasing and firing processes without being sent to the slicing process. Otherwise, the process was carried out in the same manner as in Example 1 to obtain ceramic sheets. The obtained ceramic sheets underwent the same various measurements and evaluations as in Example 1. The results are shown in Table 1.

[0138] (Comparative Example 2)

[0139] The secondary sheet, which has undergone the same primary sheet forming process, laminate formation process, and slicing process as in Example 1, is not provided to the degreasing and firing process. For the obtained ceramic sheet, the thermal conductivity is measured in the same manner as in Example 1, and the anisotropic parameters of thermal conductivity are calculated.

[0140] (Comparative Example 3)

[0141] The primary sheet obtained in the primary sheet forming process was cut into 50mm × 50mm pieces (1.0mm thick) and directly fed to the degreasing and firing processes without being sent to the slicing process, as in Example 8, to obtain ceramic sheets. The obtained ceramic sheets underwent the same various measurements and evaluations as in Example 8. The results are shown in Table 1.

[0142] [Table 1]

[0143]

[0144] As shown in Table 1, the ceramic sheet composed of the sintered ceramic obtained in Examples 1 to 8 has a new orientation structure in which the a-axis value is positive when Lothgreen analysis is performed, and the a-axis orientation direction of the ceramic material in the ceramic sheet is perpendicular to the direction of the thickness of the ceramic sheet.

[0145] Industrial availability

[0146] According to the present invention, it is possible to provide ceramic sheets with novel orientation structures.

Claims

1. A method for manufacturing a ceramic sheet, comprising: The primary sheet forming process involves pressing a composition containing resin and ceramic materials into a sheet shape to obtain a primary sheet; In the laminate formation process, multiple sheets of the primary sheet are stacked in the thickness direction, or the primary sheet is folded or rolled up, and then pressure is applied in the stacking direction at a pressure of 0.05 MPa or more and 0.50 MPa or less to obtain a laminate. The slicing process involves slicing the laminate at an angle of less than 45° relative to the lamination direction to obtain secondary slices. as well as The firing process involves firing the secondary sheet. The ceramic is alumina or barium titanate, and based on the total volume of the resin and the ceramic material, the volume fraction of the ceramic material in the primary sheet is more than 50% and less than 75% by volume.

2. The manufacturing method according to claim 1, wherein, In the laminate formation process, the material is heated at a temperature of 50°C or higher and 170°C or lower while being pressurized in the lamination direction at a pressure of 0.05 MPa or higher and 0.50 MPa or lower.

3. The manufacturing method according to claim 1 or 2, wherein, Prior to the firing process, a degreasing process is performed by heating the secondary sheet in an environment above 300°C to degrease it. The firing process is carried out in an environment above 1000°C.

4. The manufacturing method according to claim 1 or 2, wherein, The thickness of the primary sheet is less than 2.5 mm.

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