JP2004012373A - Evaluation method of slurry and preparation method of slurry - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mixed-state evaluation method of slurry capable of evaluating highly accurately the mixed state of the slurry, and a preparation method of the slurry capable of performing inline control of the mixing state of the slurry exerting a direct influence on a sheet density in the middle of mixing by using the evaluation method, to thereby always keep the sheet density constant. <P>SOLUTION: In this evaluation method of the slurry at the preparation time of the slurry by a powder mixer, concerning the slurry containing at least inorganic powder, a binder, a dispersion medium and a plasticizer, each particle size distribution of a first slurry sample acquired by only diluting by the dispersion medium the slurry collected as the sample in the middle of preparation and a second slurry sample acquired by dispersion by a strong dispersion means after diluting by the dispersion medium the slurry collected as the sample in the middle of preparation, is measured, and the mixing state of the powder in the slurry is evaluated from a relative value of the measured particle size distributions of the first and second slurry samples. <P>COPYRIGHT: (C)2004,JPO

Description

【００７１】
表１より、試料１と試料２とを比較すると、試料１は全てのロットでシート密度の讃定値１．７５ｇ／ｃｍ^３をほぼ満足しており、ばらつきも小さい。それに対して試料２では各ロットのシート密度のばらつきは極めて大きくなる。
【００７２】
（実施例２）
粉体混合工程終了後からシート塗工までの間以外に関しては、実施例１における試料１の場合と同様とした。混合終了６０時間後に、ダイコーティング方式で乾燥後の膜厚が２０μｍとなるように膜庫を制御し、毎分５ｍの塗工速度で塗工、乾燥炉温度８０℃で乾燥し、シートを作成した。作成したシートのうち、連続する１００ｍを試料とした。上記試料を以下の３通りのスラリー調製方法にて１０ロット作製した。
【００７３】
（試料３）塗工機で塗工するまでの期間中、１０００Ｗで６０分おきに超音波盆敷を開始したさらに、超音波分散を行いながら、上記実施例１と同様の方法で、粒度分布の累積平均径Ｄ_５０の差ΔＤ_５０を測定することにより、相対値が一定の値となるように超音波分散を制御した。
【００７４】
（試料４）比較例として、塗工機で塗工するまでの期間中、５０ｒｐｍでプロペラ攪拌を行った。
【００７５】
上記のように作成したセラミックグリーンシート試料に対して、各ロットにおけるシート密度を５０点測定した。これをもとに、測定したシート密度５０点の平均値、ロット間のばらつきを標準備差で評価した。結果を表２に示した。
【００７６】
【表２】

【００７７】
表２より、試料３と試料４とを比較すると、試料３は全てのロットでシート密度の設定値１．７５ｇ／ｃｍ^３をほぼ満足しており、ばらつきも小さい。それに対して試料４ではシート密度のばらつきは大きくなる。
【００７８】
【発明の効果】
以上説明したとおり、本発明によれば、スラリーの混合状態を高精度に評価することができるため、スラリーの混合をインラインで制御し、スラリー混合状態を常に一定に調製でき、スラリー混合状態と相関のあるシート密度を一定にすることができる。このため、塗工機の膜厚管理のみでシートのロット内及びロット間の塗着量ばらつきは抑えられる。
【００７９】
また、本発明の方法で調整されたスラリーを用いて作製したシートを、コンデンサやインダクタ、あるいはこれらを含む積層複合部品等の積層デバイスの積層シートに用いることにより、ロット振れの少ない安定した品質の積層部品を、効率よく生産することができる。
【図面の簡単な説明】
【図１】本発明によるスラリーの調製方法の実施形態２を示す説明図
【図２】混合が十分に進んでいない粉体より作成したシートを示す断面図
【図３】混合が十分に進んだ粉体より作成したシートを示す断面図
【図４】混合時間と粒度分布の相対値の関係を示すグラフ
【図５】混合が十分に進んでいないときのスラリーの混合状態を示す図
【図６】混合が進んだときのスラリーの混合状態を示す図
【図７】粉体同士の再凝集が現れたときのスラリーの混合状態を示す図
【図８】粒度分布の相対値とシート密度の関係を示すグラフ
【図９】本発明によるスラリーの調製方法の実施形態３を示す説明図
【図１０】調製中のスラリー中の粒体の累積粒度分布を示すグラフ
【図１１】調製中のスラリー中の粒体の粒径に対応する存在頻度を示すグラフ
【符号の説明】
１　　スラリー
２　　スラリー混合制御装置
３　　スラリー混合装置
４　　塗工機にスラリーを誘導する経路
５　　スラリー混合状態測定装置
６　　スラリー混合状態測定装置に誘導する経路
７　　分散媒供給装置
８　　希釈されたスラリー
９　　シート密度変換装置
１０　　スラリー供給装置
２０１　　フィルム
２０２　　シート
２０３　　見かけの粉体
２０４　　粉体間の隙間
２０５　　粉体の内部の空隙
３０１　　フィルム
３０２　　シート
３０３　　見かけの粉体
５０１　　スラリー
５０２　　粉体
５０３　　凝集粉体
９０１　　混合を終了したスラリー
９０３　　スラリー保存装置
９０４　　超音波発振子[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ceramic green sheet used for manufacturing a capacitor, an inductor, or the like, or a laminated composite part including such a part, which has a laminated structure, wherein a ceramic slurry as a material of the ceramic green sheet is dispersed by powder. The present invention relates to a method for evaluating a mixed state of ceramic slurry at the time of preparation, and a method for preparing a ceramic slurry using the evaluation method.
[0002]
[Prior art]
2. Description of the Related Art In recent years, multilayer devices such as capacitors and inductors having a multilayer structure, and multilayer composite parts including these have been actively employed for the purpose of miniaturizing electronic components and enhancing their functions.
[0003]
Hereinafter, a conventional method for manufacturing a laminated device will be described. By mixing a predetermined amount of an inorganic powder containing a ceramic material as a raw material, an organic binder, a plasticizer, a dispersion medium, and the like, and performing mixing and dispersion under a predetermined condition using a ball mill or a medium stirring mill, a ceramic slurry is obtained. can get. In order to evaluate the mixing state of the slurry, viscosity measurement of the slurry, particle size distribution measurement of the slurry sample diluted with the dispersion medium, and particle size distribution measurement of the slurry sample without dilution are generally performed.
[0004]
Next, this ceramic slurry is coated on the film by a doctor blade method, a roll coating method or a die coating method while controlling the film thickness. Thereafter, the ceramic slurry is dried to obtain a ceramic green sheet.
[0005]
Next, punching or laser drilling is performed on the ceramic green sheet as necessary, and then a conductive paste is printed on the punched portion by screen printing. The hole is filled with the conductive paste. Thereafter, the designed circuit pattern is screen-printed on the sheet surface with a conductive paste to form electrodes. Next, a stacked body is formed by stacking a plurality of these sheets with high positional accuracy so that the electrode patterns formed on each sheet are electrically connected. As a method for manufacturing a laminated ceramic capacitor capable of obtaining a desired capacitance with high accuracy, the number of laminated layers is conventionally determined based on a measured value of a ceramic green sheet as disclosed in JP-A-08-09074. Such a method is adopted.
[0006]
Then, the obtained laminate is pressed in the direction perpendicular to the sheet surface, and the laminate is pressed. Thereafter, the laminate is subjected to binder removal and firing at a predetermined temperature to obtain a laminate device.
[0007]
By the way, in order to secure the characteristics of the laminated device, it is necessary to make the thickness of the fired sheet constant at a predetermined thickness. This is because, for example, the capacitance value when a capacitor is formed by forming electrodes at both ends of the sheet and firing the sheet is directly affected by the thickness of the sheet. The thickness of the fired sheet is determined by the amount of powder per unit volume contained in the sheet.
[0008]
For this reason, the amount of the powder contained in the sheet per unit area must be kept constant. That is, it is necessary that the amount of the powder per unit area contained in the sheet is constant within the production lot and between lots. Therefore, as an evaluation of the created sheet, it is required to keep the coating amount, which is a product of the density and the film thickness of the sheet and an index indicating the weight per unit area of the sheet, constant. That is, if the coating amount is not constant within a lot or between lots, the characteristics when a plurality of sheets are made into a device by laminating, pressing, firing, etc. are not stable within a lot or between lots, and a desired specification is obtained. Many devices that do not satisfy the above will be produced.
[0009]
It is also necessary to individually control the sheet density and the sheet thickness together with the coating amount. Because of the variation of the raw material among lots including the particle size of the powder, in a uniform slurry preparation method with the same compounding ratio, the mixing state of the slurry fluctuates within and between lots, and the sheet density Is fluctuated within a lot and between lots. In this case, the amount of coating cannot be controlled only by controlling the thickness of the sheet.
[0010]
[Problems to be solved by the invention]
However, in the conventional slurry evaluation method, since the slurry is unstable due to a decrease in dispersibility caused by containing the plasticizer, the slurry viscosity and the particle size distribution measurement of the slurry in a state without dilution are performed. There is a problem that the evaluation of the mixed state cannot be performed accurately. Therefore, the particle size distribution measurement of a diluted system in which a slurry is diluted with a dispersion medium has been conventionally performed. There is a problem that the correlation of the sheet density reflecting the state is hard to be obtained well, and the mixing state of the slurry cannot be evaluated with high accuracy.
[0011]
In the conventional slurry preparation step and sheet preparation step, only the thickness is controlled in the sheet preparation step or the number of laminated sheets is controlled by measuring the film thickness. However, only a uniform preparation method, such as making the concentration constant, has been employed. For this reason, uniform slurry preparation methods using the same compounding ratio may cause, for example, the primary particles to agglomerate despite the fact that the actual particle size of the primary particles is small, due to variations in the lots of the raw materials including the particle size of the powder. The mixed state of the slurry fluctuates, for example, because the apparent particle size is measured in a state where the particles are aggregated as one particle, and it is sufficient to ensure that the sheet density varies between lots and between lots. It could not be suppressed.
[0012]
That is, in such a conventional slurry preparation step and sheet preparation step, the preparation of the slurry is not performed by accurately predicting the density of the sheet until the sheet is actually prepared. Therefore, there is a problem that the mixing state of the slurry cannot be controlled in-line during the preparation and mixing of the slurry.
[0013]
Further, during the period from the end of the powder mixing step of preparing the slurry to the application of the green sheet, in the conventional slurry preparation step, if left for a certain period or more, the mixing state of the slurry changes over time, so that the sheet density within the lot -There is a problem that it causes a lot-to-lot variation. Therefore, during the period from the end of the powder mixing step to the green sheet coating, a method of suppressing the temporal change of the slurry mixing state by propeller stirring or a roller mill is used. Since the roller mill must be continuously performed, the energy efficiency is remarkably deteriorated, and the change with time is not sufficiently suppressed due to, for example, heat generation of the slurry.
[0014]
Therefore, in order to solve the above-mentioned problems, the present invention provides a method for evaluating the mixed state of a slurry that can evaluate the mixed state of the slurry with high accuracy, and the method for controlling the mixed state of the slurry in-line during mixing by using the method. It is an object of the present invention to provide a method for preparing a slurry that can always make the slurry constant.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the first method for evaluating a slurry in the present invention is to prepare a slurry containing at least an inorganic powder, a binder, and a plasticizer by a powder mixing means while preparing the slurry. A sample collecting step of collecting a part of the sample, a measuring step of measuring a particle size distribution in a slurry sample obtained by diluting the collected sample with a dispersion medium, and a particle size of the slurry sample measured in the measuring step An evaluation step of evaluating the mixing state of the powder in the slurry based on the distribution.
[0016]
That is, by measuring the particle size distribution of the sample slurry, it becomes possible to evaluate the mixing state of the powder in the slurry containing the plasticizer with high accuracy. Therefore, it is possible to evaluate with high accuracy a change in the mixing state of the slurry with time during the mixing of the powder and a difference in the mixing state due to the variation between the lots of the raw materials such as the particle diameter of the powder.
[0017]
The method for evaluating a slurry according to the second aspect of the present invention includes the steps of: preparing a slurry containing at least an inorganic powder, a binder, a dispersion medium, and a plasticizer by a powder mixing means; A first slurry sample obtained by only diluting the collected sample with a dispersion medium, and diluting the sample with a dispersion medium, and then performing dispersion by a strong dispersion means. Measuring a particle size distribution in each of the second slurry sample and a relative value corresponding to the degree of approximation of the particle size distribution of the first and second slurry samples measured in the measuring step. Evaluating the mixing state of the powder in the slurry from the values.
[0018]
In other words, by diluting the sample slurry with a dispersion medium and dispersing it using a strong dispersing means, the powder in the slurry containing the plasticizer can be broken down to primary particles without aggregation or to a state close to primary particles. . By measuring the relative value between the particle size distribution in this state and the particle size distribution of a sample obtained by only diluting the slurry with a dispersion medium, the degree of approximation of the slurry of the sample to primary particles without coagulation or a state close to primary particles It will be clear that it has been done. For this reason, it becomes possible to evaluate the mixing state of the powder in the slurry containing the plasticizer, which has been impossible in the past, with high accuracy. Therefore, it is possible to evaluate with high accuracy a change in the mixing state of the slurry with time during the mixing of the powder and a difference in the mixing state due to the variation between the lots of the raw materials such as the particle diameter of the powder.
[0019]
The method for evaluating a slurry according to a third aspect of the present invention is characterized in that, in the second aspect of the present invention, the strong dispersion means is means for performing dispersion by ultrasonic waves.
[0020]
In other words, by diluting the slurry with a dispersion medium and dispersing using a dispersing means by ultrasonic waves, without pulverizing the powder in the slurry containing the plasticizer, a state close to primary particles or primary particles without aggregation is obtained. Can be solved. By measuring the relative value of the particle size distribution in this state and the particle size distribution obtained by only diluting the slurry with a dispersion medium, the mixing state of the powder in the slurry containing the plasticizer, which was conventionally impossible, can be accurately determined. It becomes possible to evaluate. For this reason, it is possible to evaluate with high accuracy a change in the mixing state of the slurry with time during the mixing of the powder and a difference in the mixing state due to the variation between the lots of the raw materials such as the particle diameter of the powder. In addition, if the powder in the slurry is pulverized more than necessary and finely divided, agglomeration of particles having a small particle diameter tends to be promoted, and the apparent particle diameter of the aggregated particles is also measured. Thereby, although the particle size measurement accuracy may be reduced, unnecessary fragmentation of such powder can be avoided.
[0021]
The method for evaluating a slurry according to the fourth aspect of the present invention is the method for evaluating a slurry according to the second or third aspect of the present invention, wherein the first slurry sample after the measurement of the particle size distribution in the measuring step is completed. This is a slurry evaluation method, characterized in that the second slurry sample is obtained by performing dispersion by a dispersion means.
[0022]
In this case, since the particle size distribution of the same sample is measured, the measurement accuracy is further improved.
[0023]
According to a fifth aspect of the present invention, there is provided a method of preparing a slurry, wherein at least a powder mixing step of mixing an inorganic powder, a binder, a dispersion medium, and a plasticizer, and a part of the slurry as a sample during the powder mixing step. A sample collection step, a first slurry sample obtained by diluting the sample collected only with a dispersion medium, and a second slurry sample obtained by diluting the sample with a dispersion medium and then performing dispersion by a strong dispersion means. A measuring step of measuring the particle size distribution in each of the slurry sample and a relative value calculating step of obtaining a relative value corresponding to the degree of approximation of the particle size distribution of the first and second slurry samples measured in the measuring step; A controlling step of controlling a mixing state of the slurry based on the relative value of the particle size distribution obtained in the relative value calculating step.
[0024]
That is, instead of preparing the slurry by a uniform method, by using the first to fourth methods for evaluating the mixing state of the powder in the slurry containing the plasticizer according to the present invention, the mixing state of the slurry prepared by the lot is adjusted. It can be prepared by performing control in accordance with the fluctuation of. This makes it possible to control the mixing state of the powder in-line with respect to the slurry in the middle of the mixing, not after the end of the powder mixing step.
[0025]
The method for preparing a slurry according to the sixth aspect of the present invention includes a powder mixing step of mixing at least an inorganic powder, a binder, a dispersion medium, and a plasticizer, and sampling a part of the slurry as a sample during the powder mixing step. A sample collection step, a first slurry sample obtained by diluting the sample collected only with a dispersion medium, and a second slurry sample obtained by diluting the sample with a dispersion medium and then performing dispersion by a strong dispersion means. A measuring step of measuring the particle size distribution in each of the slurry sample and a relative value calculating step of obtaining a relative value corresponding to the degree of approximation of the particle size distribution of the first and second slurry samples measured in the measuring step; A sheet density calculating step of calculating a sheet density when the slurry is formed into a film and dried to obtain a sheet based on the relative value of the particle size distribution obtained in the relative value calculating step; Based on the sheet density calculated by the calculating step is a process for the preparation of the slurry, characterized in that and a control step of controlling the mixing state of the slurry as desired the sheet density.
[0026]
That is, instead of preparing the slurry by a uniform method, by using the first to fourth methods for evaluating the mixing state of the powder in the slurry containing the plasticizer according to the present invention, the mixing state of the slurry prepared by the lot is adjusted. Can be prepared according to the variation of This makes it possible to control the mixing state of the powder in-line to the mixing state corresponding to the desired sheet density for the slurry during mixing, which was not possible before, rather than after the powder mixing step. become. For this reason, the density variation within the sheet lot and between the lots is suppressed, and the coating amount variation within the sheet lot and between the lots is suppressed only by controlling the film thickness of the coating machine.
[0027]
According to a seventh aspect of the present invention, in the method for preparing a slurry, in the fifth or sixth method for preparing a slurry, the strong dispersion means is means for performing dispersion by ultrasonic waves.
[0028]
In other words, instead of preparing the slurry in a uniform manner, in the third or fourth method for adjusting the slurry, the method for evaluating the mixing state of the powder in the slurry to be dispersed by ultrasonic waves is used to prepare the slurry. It can be prepared according to the variation of the mixing state depending on the lot. This makes it possible to control the mixing state of the powder in-line with the slurry in the middle of the mixing, up to the mixing state corresponding to the desired sheet density, rather than after the powder mixing step. For this reason, the density variation within the sheet lot and between the lots is suppressed, and the coating amount variation within the sheet lot and between the lots is suppressed only by controlling the film thickness of the coating machine.
[0029]
The method for preparing a slurry according to an eighth aspect of the present invention is the method for preparing a slurry according to the seventh slurry adjustment method, wherein a change in the slurry mixing state with time is suppressed at required time intervals during a period from the end of the powder mixing step to the sheet coating. A method for preparing a slurry, wherein ultrasonic dispersion is performed on the slurry.
[0030]
By knowing in advance the time at which the mixing state of the slurry begins to change significantly with time, less ultrasonic dispersion can be achieved by repeating ultrasonic dispersion multiple times within the time interval at which the mixing state of the slurry begins to change significantly with time. In a short period of time, changes in the mixing state of the slurry after the end of the powder mixing step are efficiently suppressed, and the heat generation of the slurry is small, so that it is possible to form a sheet reflecting the mixing state of the slurry immediately after the end of the powder mixing step. Become. For this reason, the variation in sheet density between lots and between lots due to the change over time of the mixing state of the slurry is suppressed, and the variation in the coating amount within lots and between lots of sheets is suppressed only by the film smoke management of the coating machine. You.
[0031]
The method for preparing a slurry according to the ninth aspect of the present invention includes a powder mixing step of mixing at least an inorganic powder, a binder, a dispersion medium, and a plasticizer, and sampling a part of the slurry as a sample during the powder mixing step. A sample collection step, a first slurry sample obtained by diluting the sample collected only with a dispersion medium, and a second slurry sample obtained by diluting the sample with a dispersion medium and then performing dispersion by a strong dispersion means. A measuring step of measuring the particle size distribution in each of the slurry sample and a relative value calculating step of obtaining a relative value corresponding to the degree of approximation of the particle size distribution of the first and second slurry samples measured in the measuring step; A time-dependent change suppression control step of performing control to suppress a time-dependent change in the slurry mixing state based on the relative value of the particle size distribution obtained in the relative value calculation step. It is the Lee method of preparation.
[0032]
Thereby, since the mixing state of the slurry after the powder mixing step can be controlled in-line, the ultrasonic mixing time can be reduced, the change over time in the mixing state of the slurry can be efficiently suppressed, and the heat generation of the slurry is small, so that A sheet can be formed that reflects the mixing state of the slurry immediately after the end of the body mixing step. For this reason, the variation in the sheet density between lots and between lots due to the change over time of the mixing state of the slurry is suppressed, and even if only the film thickness control of the coating machine is performed, the amount of coating within the sheet lot and between lots can be reduced. Variation is suppressed.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail. In each of the following embodiments, a case will be described as an example in which a ceramic green sheet having a laminated structure and used for a capacitor, an inductor, or a laminated composite part including these is manufactured.
[0034]
(Embodiment 1)
A first embodiment of the invention according to claims 1 to 4 will be described. First, the relationship between the degree of dispersion and aggregation of the powder in the ceramic slurry and the particle size distribution, and the sheet density when a thin ceramic green sheet is formed on a film will be described.
[0035]
In the preparation of ceramic slurries, the apparent particle size changes depending on the degree of dispersion and agglomeration of the powder, and the frequency of voids between the powders varies, so that the sheet density when a thin sheet is made is strongly affected. . This will be described with reference to FIGS.
[0036]
In the preparation of the ceramic slurry, when the mixing is insufficient, the powders agglomerate, the apparent powder diameter is large, and the relative value to the primary particle diameter is large. Here, the primary particles refer to substantially individual particles, that is, original particles that are not aggregated and regarded as pseudo one particle. Further, the apparent powder in which the powder is agglomerated contains many voids. When a sheet 202 is formed on the film 201 as shown in FIG. 2 in such a state, the apparent diameter of the powder 203 is large, the gap 204 between the powders is wide, and there are many voids 205 inside the powder. Sheet density is also reduced.
[0037]
When the mixing is sufficiently performed, the agglomeration of the powders contained in the slurry is broken, the apparent powder diameter is small, and the relative value to the primary particle diameter is also small. When the sheet 302 is formed on the film 301 as shown in FIG. 3 in such a state, the apparent diameter of the powder 303 is reduced, so that the gap between the powders is narrowed, and the voids inside the powder are also reduced. Therefore, the sheet density also increases.
[0038]
Based on the above relationship, a slurry evaluation method and a preparation method of the present embodiment will be described.
[0039]
This will be described more specifically. First, 1 to 20 parts by weight of an organic binder, 10 to 120 parts by weight of a dispersion medium, and a plasticizer are added to 100 parts by weight of an inorganic powder mainly composed of alumina having an average particle diameter of 0.1 to 10 μm as a raw material. 1 to 20 parts by weight were blended. This was mixed with a ball mill using zirconia with a cobblestone of φ5 mm. The slurry was sampled at regular intervals to prepare a plurality of types of slurries with different mixing times. A part of each slurry is collected as a sample, and in the same kind of sample, the particle size of a first slurry sample diluted with a dispersion medium and a second slurry sample diluted with a dispersion medium and dispersed by a strong dispersion means The respective distributions are measured and the cumulative average diameter D of the particle size distribution is measured. ₅₀ Relative value ΔD of ₅₀ Was calculated. Further, the film thickness of these slurries was controlled by a die coating method, applied under uniform conditions, dried, and then a sheet was prepared, and its density was measured. Cumulative average diameter D of this particle size distribution ₅₀ Measure the diameter of a predetermined number of particles in each sample, accumulate the number in order from the smallest diameter among the measured particles, and calculate the intermediate value of the predetermined number until the total number is accumulated. It is a value of the particle diameter. An example is shown in the graph of FIG. In FIG. 10, the horizontal axis corresponds to the measured particle size, and the vertical axis corresponds to the cumulative number of particles in which the total number of measured particles corresponds to 100 percent of the percentage. In FIG. 10, the solid line graph indicates the particle size distribution of the second slurry sample, and the dashed line graph indicates the particle size distribution of the first slurry sample. FIG. 11 shows a graph of the frequency of each particle diameter of the measured particles corresponding to FIG. In FIG. 11, the horizontal axis corresponds to the measured particle size, and the vertical axis corresponds to the measured frequency of the particles. In FIG. 11, the solid line graph indicates the particle size distribution of the second slurry sample, and the dashed line graph indicates the particle size distribution of the first slurry sample.
[0040]
Here, the relative value ΔD ₅₀ Is the cumulative average diameter D of the first slurry sample. ₅₀ 'And the cumulative average diameter D of the second slurry sample ₅₀ Is the value of the difference from That is, it is a relative value corresponding to the degree of approximation of the particle size distribution of the first and second slurry samples. This relative value is an index indicating how similar the particle size distributions of the first and second slurry samples are. When it is determined that the particle size distributions of the first and second slurry samples are more than a predetermined value, it is determined that the slurry has been adjusted to a desired state. Therefore, in the case of the first embodiment, the value ΔD ₅₀ Is smaller than or equal to a predetermined value, it is determined that the slurry has been adjusted to a desired state.
[0041]
FIG. 11 shows a graph of the frequency of each particle diameter of the measured particles corresponding to FIG. In FIG. 11, the horizontal axis corresponds to the measured particle size, and the vertical axis corresponds to the measured frequency of the particles. In FIG. 11, the solid line graph indicates the particle size distribution of the second slurry sample, and the dashed line graph indicates the particle size distribution of the first slurry sample.
[0042]
FIG. 4 shows the relationship between the mixing time and the relative value of the slurry particle size distribution. FIG. 4 shows that there are three tendencies. This will be described with reference to FIGS. First, when the dispersion is insufficient as shown in FIG. 4A, the powder 502 is aggregated in the slurry 501 to form an aggregated powder 503 as shown in FIG. Since the apparent particle size of the agglomerated powder 503 is large, the relative value ΔD with the primary particle size is ₅₀ Becomes larger. As the dispersion progresses as shown in FIG. 4 (b), the agglomeration of the powders in the slurry is broken as shown in FIG. 6, and the apparent powder diameter is small, and therefore, the relative value ΔD with the primary particle diameter is reduced. ₅₀ Is also smaller. When the dispersion further progresses as shown in FIG. 4 (c), reagglomeration of the powders occurs due to the pulverization of the powder contained in the slurry as shown in FIG. 7, and the apparent diameter of the powder decreases. Becomes slower with respect to time, or the apparent powder diameter becomes larger, so that the relative value ΔD to the primary powder diameter becomes larger than that in FIG. ₅₀ Is somewhat larger. This is because, in the case of the ceramic slurry, when the particle diameter of the powder becomes smaller than a predetermined diameter, the powder tends to be easily aggregated.
[0043]
FIG. 8 shows the relationship between the relative value of the particle size distribution of the slurry and the density of the prepared sheet. (A), (b) and (c) in the figure correspond to (a), (b) and (c) in FIG. It can be seen that there is a correlation between the relative value of the particle size distribution of the slurry and the sheet density if the conditions for preparing the sheets of the prepared slurry are constant when the mixing conditions of the powder are fixed. That is, the higher the sheet density, the smaller the abundance ratio of the agglomerated powder, and the relative value ΔD based on the measured particle distribution ₅₀ And the sheet density have a one-to-one correspondence. Thereby, the relative value ΔD of the particle size distribution of the slurry is obtained. ₅₀ Is measured, the sheet density can be calculated.
[0044]
Cumulative average diameter D of powder ₅₀ Is 10 μm or less, or lot variation in powder particle size distribution is D ₅₀ If the average value is ± 1% or more, the mixing state of the slurry may not be stable. Therefore, employing the evaluation method of the present invention is particularly effective in maintaining the mixing state of the slurry at a predetermined level. is there.
[0045]
(Embodiment 2)
A second embodiment according to claims 5, 6 and 7 will be described. FIG. 1 is an explanatory view showing, by a cross section, a block, or the like, an apparatus for performing a slurry evaluation method of the present invention and a slurry preparation method using the same. The slurry 1 is mixed by a slurry mixing device 3 using a medium stirring mill under the control of a slurry mixing control device 2. A route 4 for guiding the slurry 1 from the slurry mixing device 3 to the coating machine and a route 6 for guiding to the slurry mixing state measuring device 5 are branched. The slurry mixing state measuring device 5 can simultaneously measure the particle size distribution and ultrasonic dispersion of the slurry 8 diluted by the dispersion medium supply device 7. Reference numeral 9 denotes a sheet density conversion device, and reference numeral 10 denotes a slurry supply device.
[0046]
The flow up to sheet creation will be described below. First, 1 to 20 parts by weight of an organic binder, 10 to 120 parts by weight of a dispersion medium, and 1 to 20 parts by weight is blended to form slurry 1.
[0047]
The slurry 1 pre-dispersed at the above mixing ratio is charged into a container of a slurry mixing device 3 using a medium stirring mill and mixed. In a part of the mixing vessel, a path 6 for guiding the slurry during mixing to the slurry mixing state measuring device 5 is provided separately from the path 4 toward the coating machine used for mass production. Until the mixing is completed, the slurry is prevented from flowing in the path 4 toward the coating machine used for mass production.
[0048]
In order to evaluate the mixing state of the slurry during mixing, the slurry 1 is supplied from the path 6 for guiding the slurry during mixing to the slurry mixing state measuring device 5 at regular time intervals to the slurry mixing state measuring device 5 by the slurry supply device 10. Supply. The slurry may be supplied using a pump such as a gear pump or a tube pump or using compressed air.
[0049]
The slurry supplied to the slurry mixing state measuring device 5 is subjected to required dilution with the dispersion medium supplied by the dispersion medium supply device 7. Then, the particle size distribution of the slurry 8 diluted with the dispersion medium is measured. Next, the diluted slurry 8 is subjected to strong dispersion of 30 W or more by ultrasonic dispersion. Then, the particle size distribution of the slurry is measured. The measured value data is transmitted to the sheet density converter 9. Then, as shown in FIG. 8, the relative value ΔD of the particle size distribution obtained by measurement in advance. ₅₀ In the sheet density conversion device 9 in which the relationship between the particle size distribution and the sheet density is input, the cumulative average diameter D of the particle size distribution is obtained from the data of the particle size distribution received and input. ₅₀ Relative value ΔD of ₅₀ Is calculated and converted into the density of the sheet. The converted data of the sheet density is transmitted to the slurry mixing control device 2. From the sheet density data received by the slurry mixing control device 2, it is determined whether the powder mixing should be further promoted, and the mixing state of the slurry is controlled to a mixing state corresponding to a desired sheet density. The mixing state control can be performed, for example, by adjusting and controlling the stirring speed and the stirring time of a stirring device such as a medium stirring mill. From the viewpoint of preparing a slurry in a stable mixed state, the mixing time is controlled. The method is desirable.
[0050]
When the dispersion of the slurry has progressed to the desired sheet density, the dispersion of the slurry is completed, and the slurry is completed. The slurry prepared in this way is passed through a path 3 toward a coating machine used for mass production, the film thickness is controlled by a die coating method, and after coating and drying, a sheet is completed.
[0051]
(Embodiment 3)
A third embodiment of the present invention will be described with reference to FIG. The slurry 901 that has been mixed in the same manner as in the second embodiment is stored in the slurry storage device 903 shown in FIG. An ultrasonic oscillator 904 is provided on the wall surface of the slurry storage device 903, and can perform ultrasonic dispersion. Using this apparatus, ultrasonic dispersion is performed for a certain time at certain time intervals within a time interval within which the mixing state of the slurry starts to change significantly with time, until the coating is performed by the coating machine.
[0052]
By performing ultrasonic dispersion at regular time intervals within the time interval at which the mixing state of the slurry begins to significantly change over time, with less ultrasonic dispersion time, less heat generation of the slurry, and The change with time of the mixed state can be efficiently suppressed.
[0053]
(Embodiment 4)
A fourth embodiment of the present invention will be described with reference to FIG. The slurry 901 that has been mixed in the same manner as in the second embodiment is stored in the slurry storage device 903 shown in FIG. An ultrasonic oscillator 904 is provided on the wall surface of the slurry storage device 903, and can perform ultrasonic dispersion. Using this apparatus, ultrasonic dispersion is started at regular time intervals until the coating is performed by the coating machine.
[0054]
Further, the relative value ΔD of the particle size distribution is obtained in the same manner as in Embodiment 2 while performing ultrasonic dispersion. ₅₀ By measuring the relative value ΔD of the particle size distribution. ₅₀ Is controlled so as to have a predetermined constant value.
[0055]
When the dispersion of the slurry has progressed to the mixed state corresponding to the desired sheet density, the ultrasonic dispersion of the slurry is terminated, and this operation is repeated at regular time intervals, from the end of powder mixing to coating. During the period, a stable slurry with less heat generation of the slurry can be efficiently prepared with less ultrasonic dispersion time. For this reason, it is possible to form a sheet reflecting the mixing state of the slurry immediately after the end of the powder mixing step.
[0056]
In the third and fourth embodiments, as a method of ultrasonic dispersion, an oscillator capable of performing ultrasonic dispersion is provided on the wall surface of the slurry storage device. However, the slurry storage device and the ultrasonic oscillator are separated. Then, a system in which the slurry circulates between them may be adopted.
[0057]
The embodiment described above is an example that embodies the present invention, and does not limit the technical scope of the present invention.
[0058]
In the above embodiments, the constituent material of the slurry is as described above. However, in the present invention, the constituent material of the slurry may be any as long as it includes at least a powder, a binder, and a dispersion medium. The powder contains at least one of a metal such as iron, stainless steel, and aluminum, a ceramic such as alumina, silica, zirconia, barium titanate, and ferrite, and a silicate-based and borate-based glass. As the binder, polyvinyl butyral, polyvinyl alcohol, acrylic ester, methacrylic ester, engineered cellulose, polyurethane or the like is used.
[0059]
Examples of the dispersion medium include ketones such as acetone and methyl ethyl ketone, aromatics such as toluene and xylene, esters such as ethyl acetate and butyl acetate, alcohols such as methanol and ethanol, and water. Examples of the plasticizer include glycols such as glycerin and polyethylene glycol, and phthalic acids such as dibutyl phthalate and benzyl butyl phthalate. In addition, a chopping agent and the like can be used as appropriate.
[0060]
Further, in the above embodiment, the powder mixing means is a medium stirring mill, but other dispersing means such as a ball mill, a high-speed stirring mill, a sand mill, and a vibration mill may be used.
[0061]
Further, as a sheet forming method, besides coating by a die coating method, a roll coating method or a doctor blade method can be used. Further, the temperature of the drying furnace varies depending on the type of powder and dispersion medium to be used and the mixing ratio, but it is generally preferable to dry at 10 to 120 ° C, preferably 60 to 100 ° C.
[0062]
Further, as a relative value of the particle size distribution, a cumulative average diameter D ₅₀ It is preferred to use the difference ₁₀ And D ₉₀ For example, a difference in the cumulative value of the particle size distribution may be used. It is also possible to use a volume average diameter, an area average diameter, and a number average diameter. It is also possible to use the difference in the distribution width of the particle size distribution.
[0063]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.
[0064]
(Example 1)
Based on 100 parts by weight of an inorganic powder mainly composed of alumina having an average particle diameter of 1 ± 0.1 μm as a raw material, 10% by weight of polyvinyl butyral as an organic binder, 80% by weight of ethyl acetate as a dispersion medium, A slurry was prepared by mixing 8% by weight of dibutyl phthalate as a plasticizer. The total amount of slurry was 10 kg per lot.
[0065]
The slurry was premixed at 2,000 rpm for 1 hour with a stirrer, and then charged into a slurry mixing device using a medium stirring mill, mixed at 3,000 rpm, and the sheet density after drying was 1.75 g / cm. ³ A slurry was prepared such that
[0066]
Immediately after the completion of the mixing, the film thickness was controlled by a die coating method so that the film thickness after drying was 20 μm, coating was performed at a coating speed of 5 m / min, and drying was performed at a drying furnace temperature of 80 ° C. to form a sheet. . Of the sheets thus prepared, a continuous 100 m was used as a sample. Ten lots of the above sample were prepared by the following three slurry preparation methods.
[0067]
(Sample 1) The slurry adjusting method according to the second embodiment was used. The particle size distribution of the slurry diluted with the dispersion medium was measured by Microtrac HRA (manufactured by Honeywell), and then the diluted slurry was subjected to strong dispersion at 400 W for 60 seconds by ultrasonic waves. Then, the particle size distribution of the slurry subjected to the strong dispersion was measured. Cumulative average diameter D of these particle size distributions ₅₀ Difference △ D ₅₀ Was calculated, and when the mixing of the slurry had progressed to a difference corresponding to the desired sheet density, the mixing of the slurry was terminated.
[0068]
(Sample 2) As a comparative example, the mixing time was fixed. When the mixing of the slurry had progressed to a time corresponding to the desired sheet density, the mixing of the slurry was terminated.
[0069]
With respect to the ceramic green sheet sample prepared as described above, the sheet density in each lot was measured at 50 points. Based on this, the average value of the measured 50 sheet densities and the variation between lots were evaluated based on the standard deviation. The results are shown in Table 1.
[0070]
[Table 1]

[0071]
From Table 1, when comparing Sample 1 with Sample 2, Sample 1 had a sheet density of 1.75 g / cm in all lots. ³ And the variation is small. On the other hand, in the sample 2, the variation in the sheet density of each lot is extremely large.
[0072]
(Example 2)
Except for the period from the end of the powder mixing step to the time of sheet coating, it was the same as in the case of Sample 1 in Example 1. 60 hours after the end of mixing, the film storage is controlled by a die coating method so that the film thickness after drying is 20 μm, coating is performed at a coating speed of 5 m per minute, and drying is performed at a drying furnace temperature of 80 ° C. to prepare a sheet. did. Of the sheets thus prepared, a continuous 100 m was used as a sample. Ten lots of the above sample were prepared by the following three slurry preparation methods.
[0073]
(Sample 3) During the period before coating with the coating machine, ultrasonic bonsai was started at 1000 W every 60 minutes. Further, while performing ultrasonic dispersion, the particle size distribution was measured in the same manner as in Example 1 above. Cumulative average diameter D of ₅₀ Difference ΔD ₅₀ Was measured to control the ultrasonic dispersion so that the relative value became a constant value.
[0074]
(Sample 4) As a comparative example, propeller agitation was performed at 50 rpm during the period until coating with a coating machine.
[0075]
The sheet density in each lot was measured at 50 points on the ceramic green sheet sample prepared as described above. Based on this, the average value of the measured 50 sheet densities and the variation between lots were evaluated using standard deviations. The results are shown in Table 2.
[0076]
[Table 2]

[0077]
From Table 2, when Sample 3 and Sample 4 are compared, Sample 3 has a sheet density set value of 1.75 g / cm in all lots. ³ And the variation is small. On the other hand, in Sample 4, the sheet density varies greatly.
[0078]
【The invention's effect】
As described above, according to the present invention, the mixing state of the slurry can be evaluated with high precision, so that the mixing of the slurry can be controlled in-line, and the mixing state of the slurry can be constantly adjusted, and the correlation with the mixing state of the slurry can be maintained. Sheet density with a certain level can be kept constant. For this reason, variations in the coating amount within and between lots of sheets can be suppressed only by controlling the film thickness of the coating machine.
[0079]
Further, by using a sheet prepared using the slurry prepared by the method of the present invention as a laminated sheet of a laminated device such as a capacitor, an inductor, or a laminated composite part including these, a stable quality with less lot runout can be obtained. Laminated parts can be efficiently produced.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing Embodiment 2 of a slurry preparation method according to the present invention.
FIG. 2 is a cross-sectional view showing a sheet made from powder that has not sufficiently mixed.
FIG. 3 is a cross-sectional view showing a sheet made from a sufficiently mixed powder.
FIG. 4 is a graph showing the relationship between the mixing time and the relative value of the particle size distribution.
FIG. 5 is a diagram showing a slurry mixing state when mixing is not sufficiently advanced.
FIG. 6 is a view showing a mixing state of a slurry when mixing is advanced.
FIG. 7 is a diagram showing a mixing state of a slurry when powder re-agglomeration appears.
FIG. 8 is a graph showing the relationship between the relative value of the particle size distribution and the sheet density.
FIG. 9 is an explanatory view showing Embodiment 3 of the slurry preparation method according to the present invention.
FIG. 10 is a graph showing the cumulative particle size distribution of granules in a slurry during preparation.
FIG. 11 is a graph showing the frequency of occurrence corresponding to the particle size of the granules in the slurry being prepared.
[Explanation of symbols]
1 slurry
2 Slurry mixing control device
3 slurry mixing equipment
4 Route to guide slurry to coating machine
5 Slurry mixing state measuring device
6 Route to the slurry mixing state measuring device
7 Dispersion medium supply device
8 diluted slurry
9 Sheet density converter
10 Slurry supply device
201 film
202 sheets
203 Apparent powder
204 Gap between powders
205 Void inside powder
301 film
302 sheet
303 Apparent powder
501 slurry
502 powder
503 agglomerated powder
901 Slurry after mixing
903 Slurry storage device
904 ultrasonic oscillator

Claims (9)

At least an inorganic powder, a binder, while preparing a slurry containing a plasticizer by powder mixing means, a sampling step of sampling a part of the slurry being prepared as a sample,
A measurement step of measuring the particle size distribution of the slurry sample obtained by diluting the sample collected with a dispersion medium,
Based on the particle size distribution of the slurry sample measured in the measurement step, an evaluation step of evaluating the mixing state of the powder in the slurry,
A method for evaluating a slurry, comprising: At least an inorganic powder, a binder, while preparing a slurry containing a plasticizer by powder mixing means, a sampling step of sampling a part of the slurry being prepared as a sample,
A first slurry sample obtained by diluting the collected sample only with a dispersion medium, and a second slurry sample obtained by diluting the sample with a dispersion medium and then performing dispersion by strong dispersing means. A measuring step of measuring the particle size distribution in,
An evaluation step of obtaining a relative value corresponding to the degree of approximation of the particle size distribution of the first and second slurry samples measured in the measurement step, and evaluating the mixing state of the powder in the slurry from the relative value,
A method for evaluating a slurry, comprising: In the method for evaluating a slurry according to claim 2,
2. The method for evaluating a slurry according to claim 1, wherein said strong dispersion means is a means for performing dispersion by ultrasonic waves. The method for evaluating a slurry according to claim 2 or 3,
A method for evaluating a slurry, comprising: dispersing the first slurry sample after the measurement of the particle size distribution in the measurement step by a strong dispersing unit to obtain a second slurry sample. A powder mixing step of mixing at least an inorganic powder, a binder, a dispersion medium, and a plasticizer,
A sampling step of sampling a part of the slurry as a sample during the powder mixing step,
A first slurry sample obtained by diluting the collected sample only with a dispersion medium, and a second slurry sample obtained by diluting the sample with a dispersion medium and then performing dispersion by strong dispersing means. A measuring step of measuring the particle size distribution in,
A relative value calculation step of obtaining a relative value corresponding to the degree of approximation of the particle size distribution of the first and second slurry samples measured in the measurement step,
A control step of controlling the mixing state of the slurry based on the relative value of the particle size distribution obtained in the relative value calculation step,
A method for preparing a slurry, comprising: A powder mixing step of mixing at least an inorganic powder, a binder, a dispersion medium, and a plasticizer,
A sampling step of sampling a part of the slurry as a sample during the powder mixing step,
A first slurry sample obtained by diluting the collected sample only with a dispersion medium, and a second slurry sample obtained by diluting the sample with a dispersion medium and then performing dispersion by strong dispersing means. A measuring step of measuring the particle size distribution in,
A relative value calculation step of obtaining a relative value corresponding to the degree of approximation of the particle size distribution of the first and second slurry samples measured in the measurement step,
Based on the relative value of the particle size distribution determined in the relative value calculation step, the slurry is formed into a film, dried, and a sheet density calculation step of calculating the sheet density when the sheet is obtained,
Based on the sheet density calculated in the sheet density calculation step, a control step of controlling the mixing state of the slurry so that the desired sheet density is obtained,
A method for preparing a slurry, comprising: The slurry preparation method according to claim 5 or 6,
A method for preparing a slurry, wherein the strong dispersion means is a means for performing dispersion by ultrasonic waves. The method for preparing a slurry according to claim 7,
A method for preparing a slurry, comprising: performing ultrasonic dispersion on a slurry at a required time interval during a period from the end of a powder mixing step to sheet coating, so as to suppress a change with time of the slurry mixing state. A powder mixing step of mixing at least an inorganic powder, a binder, a dispersion medium, and a plasticizer,
A sampling step of sampling a part of the slurry as a sample during the powder mixing step,
A first slurry sample obtained by diluting the collected sample only with a dispersion medium, and a second slurry sample obtained by diluting the sample with a dispersion medium and then performing dispersion by strong dispersing means. A measuring step of measuring the particle size distribution in,
A relative value calculation step of obtaining a relative value corresponding to the degree of approximation of the particle size distribution of the first and second slurry samples measured in the measurement step,
Based on the relative value of the particle size distribution obtained in the relative value calculation step, a temporal change suppression control step of performing control to suppress a temporal change of the slurry mixing state,
A method for preparing a slurry, comprising:

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