JP2021056199A - Method for evaluating organic vehicle for functional paste and method for evaluating functional paste - Google Patents

Abstract

To provide a method for evaluating an organic vehicle for a functional paste or a method for evaluating, on a microscopic level, a functional paste that can examine a compatible state of resin when the resin is forming a coating film.SOLUTION: The present invention relates to a method for evaluating an organic vehicle for a functional paste, the organic vehicle including an organic solvent and at least two types of resins. The method includes the steps of: manufacturing a coating film by applying the organic vehicle on a base material and drying the base material; processing the coating film to expose a processing surface; and analyzing the surface characteristics of the coating film in the processing surface by using an atomic force microscope.SELECTED DRAWING: Figure 8

Description

The present invention relates to an evaluation method for an organic vehicle for a functional paste and an evaluation method for a functional paste.

With the miniaturization and high performance of electronic devices such as mobile phones and digital devices, there is a demand for miniaturization and high performance of parts such as electronic parts. Many of such components are provided with functional layers such as an electrode layer (conductive layer), an electrical resistance layer, a magnetic layer, a heat conductive layer and / or a heat shielding layer. This functional layer is produced by applying, drying and firing a functional paste in which a functional powder such as a conductive powder is dispersed in an organic vehicle on a base material.

For example, a multilayer ceramic capacitor (MLCC) for which miniaturization and high capacity are desired is manufactured as follows. First, a ceramic powder such as barium titanate (BaTIO ₃ ), a binder resin, an organic solvent and the like are mixed to prepare a dielectric paste. The obtained dielectric paste is applied on a substrate such as a polyethylene terephthalate (PET) film and dried to prepare a dielectric green sheet. A pattern of the conductive paste is printed on the surface of the dielectric green sheet to obtain a printed dielectric green sheet. A plurality of printed dielectric green sheets are laminated and crimped to prepare a crimped body (laminated body), which is cut into individual pieces. The obtained individual pieces are subjected to a debinder treatment and a firing treatment to prepare a firing chip. Finally, external electrodes are provided at both ends of the fired chip to form a multilayer ceramic capacitor.

The conductive paste used for forming the internal electrode layer is a kind of functional paste, and is produced by dispersing the conductive powder and, if necessary, a co-material in an organic vehicle. The organic vehicle is mainly produced by mixing and dissolving a binder resin in an organic solvent. As the conductive powder, metal powders such as silver (Ag), palladium (Pd) and / or nickel (Ni) are used, and in recent years, nickel (Ni) powder, which is an inexpensive base metal, has been widely used. The common material is _{a ceramic powder such as barium titanate (BaTIO 3} ), which is used for the purpose of suppressing shrinkage of the internal electrode layer during firing. Cellulose-based resin or the like is used as the binder resin, and tarpineol or the like is used as the organic solvent.

In recent years, it has been proposed to combine a plurality of resins as a binder resin for a functional paste (conductive paste or the like) or an organic vehicle as a precursor thereof. For example, as disclosed in Patent Documents 1 to 3 below, a combination of a cellulosic resin and an acetal resin has been proposed as a binder resin for a conductive paste for a laminated ceramic capacitor.

Patent Document 1 describes a conductive paste containing at least conductive metal particles, a common material, a resin, an organic solvent, and an organic additive for forming an internal electrode layer on a green sheet which is a dielectric layer of a multilayer ceramic capacitor. , The common material consists of the main constituent material of the green sheet, contains at least polyvinyl butyral as a resin, and the organic additive shows a compound having a functional group showing an acid value and a functional group showing an amine value, and / and showing an acid value. A conductive paste for an internal electrode of a laminated ceramic capacitor is disclosed, which is a mixture of a compound having a functional group and a compound having a functional group exhibiting an amine value (claim 1 of Patent Document 1). Further, in Patent Document 1, the binder resin may be polyvinyl butyral alone, or may be used in combination with other resins such as ethyl cellulose, nitrocellulose, acrylic, etc., in order to improve compatibility with an organic solvent. It is described that it is a preferable method (Patent Document 1 [0020]).

Patent Document 2 is a paste for an internal electrode containing a nickel powder, a ceramic powder, an ethyl cellulose resin, a polyvinyl butyral resin, an organic solvent and an anionic surfactant, and the polyvinyl butyral resin is used with respect to the total amount of the paste. The anionic surfactant is contained in an amount of 1% by mass or more and 2.5% by mass or less, has at least one carboxyl group (COOH group), and is 0.1% by mass based on 100 parts by mass of the nickel powder. Disclosed is a paste for an internal electrode, which contains at least 6.5 parts by mass and contains water in a range of 0.8 mol times or more and 2 mol times or less with respect to the carboxyl group (COOH group) of the anionic surfactant. (Claim 1 of Patent Document 2). Further, in Patent Document 2, when the content of the polyvinyl butyral resin is within the above range (1% by mass or more and 2.5% by mass or less), the adhesion strength between the green sheet and the dry film of the internal electrode paste can be increased. It is described that it can be done (Patent Document 2 [[0024]).

Patent Document 3 describes a preparatory step of preparing a cellulose derivative, a polyvinyl acetal, and a binder having two or more functional groups in the molecule capable of reacting with the cellulose derivative and the hydroxyl group of the polyvinyl acetal in the reaction step. A reaction step in which the cellulose derivative and the binder in a amount of twice the molar amount or more of the polyvinyl acetal having a larger number of moles are mixed to bond the hydroxyl group and the functional group. A method for producing a binder resin having the above is disclosed (claim 1 of Patent Document 3). Further, in Patent Document 3, since the binder resin of the present invention has high homogeneity, the coating film formed from a paste such as a conductive paste produced by using the binder resin has a dispersibility of inorganic particles such as metal particles. Since it is high and the viscosity ratio is small, the smoothness of the coating film is excellent, and fine holes (defects) are unlikely to occur. Therefore, the smoothness and denseness of the coating film (metal film, etc.) after firing, etc. It is described that the film quality can be greatly improved (Patent Document 3 [0031]).

Japanese Unexamined Patent Publication No. 2004-200450 JP-A-2017-143202 International Publication No. 2015/107811

As described above, it has been proposed to combine a plurality of resins as a resin binder for a functional paste (conductive paste or the like) or an organic vehicle. When using a plurality of resins, their compatibility is important. If the compatibility is low, unevenness (phase separation) occurs in the distribution of the resin in the organic solvent. In addition, the functional powder (conductive powder, etc.) is unevenly distributed due to the phase separation of the resin. On the other hand, by using a combination of highly compatible resins, it is possible to uniformly dissolve the resins at the molecular level in an organic solvent. Therefore, when selecting a resin, studies have been conventionally conducted from the viewpoint of compatibility of the resin in a functional paste or an organic vehicle.

However, as a result of investigation by the present inventor, it was found that even if a combination of a functional paste or a resin having high compatibility in an organic vehicle is used, the functional powder and the co-material may be unevenly distributed in the coating film. .. Then, in the process of investigating the cause, it was hypothesized that the distribution of the resin in the coating film is different from the state in the paste or vehicle. That is, even if the resin was uniformly dissolved in the organic solvent, the resin was phase-separated in the drying step, which may cause uneven distribution of the functional powder and the co-material in the coating film.

The distribution of functional powders and co-materials in the coating film is important for obtaining the desired properties of the functional layer (electrode layer, etc.). Therefore, it is desired to appropriately control the distribution of the resin in the coating film, which affects the distribution of the functional powder and the common material. Therefore, it is not enough to examine the compatibility of the resin in the paste or vehicle, and it is necessary to investigate the compatibility of the resin in the coating film. However, conventionally, attention has not been paid to the compatible state of the resin in the coating film, much less a method for examining the compatible state of the resin in the coating film at a microscopic level has not been known.

In order to evaluate a functional paste and an organic vehicle that is a precursor thereof, it is important for the present inventor to investigate the compatibility state of the resin in the coating film, and the surface characteristics of the coating film processed surface are atomic. By analyzing with an atomic force microscope, it was found that the compatibility state of the resin in the coating film can be examined at a microscopic level.

The present invention has been completed based on such findings, and is a method for evaluating an organic vehicle for a functional paste or a functional paste, and microscopically shows the compatible state of the resin in a coated state. The challenge is to provide a method that can be investigated at various levels.

The present invention includes the following aspects (1) to (10). In addition, in this specification, the expression "~" includes the numerical values at both ends thereof. That is, "X to Y" is synonymous with "X or more and Y or less".

(1) An evaluation method for organic vehicles for functional pastes.
The organic vehicle contains an organic solvent and two or more kinds of resins, and the method is described in the following steps;
A step of applying the organic vehicle onto a substrate and drying it to prepare a coating film.
A step of processing the coating film to expose the processed surface, and a step of analyzing the surface characteristics of the coating film on the processed surface using an atomic force microscope.
The method.

(2) This is an evaluation method for functional paste.
The functional paste contains an organic vehicle containing an organic solvent and two or more kinds of resins, and a functional powder, and the method is described in the following steps;
A step of applying the functional paste onto a substrate and drying it to prepare a coating film.
A step of processing the coating film to expose the processed surface, and a step of analyzing the surface characteristics of the coating film on the processed surface using an atomic force microscope.
The method.

(3) The method according to (2) above, wherein the functional powder contains a conductive powder and the functional paste is a conductive paste.

(4) At least the conductive powder selected from the group consisting of nickel (Ni), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), copper (Cu) and alloys thereof. The method (3) above, which is a kind of metal powder.

(5) The method according to (2) above, wherein the functional powder contains aluminum nitride (AlN) powder and the functional paste is a heat conductive paste.

(6) The method according to any one of (1) to (5) above, wherein the resin contains a cellulosic resin and an acetal resin.

(7) The method according to any one of (1) to (6) above, wherein the processed surface is a cross section of a coating film.

(8) The method according to any one of (1) to (7) above, wherein the processing is performed using a microtome.

(9) The method according to any one of (1) to (8) above, wherein the surface property is an elastic modulus.

(10) In the step of analyzing the surface characteristics of the coating film, a mapping image or frequency distribution of the surface characteristics is created, and the compatibility state of the resin is evaluated based on the mapping image or frequency distribution. Any method of (9).

According to the present invention, there is provided a method for evaluating an organic vehicle for a functional paste or a functional paste, which can examine the compatibility state of a resin in a coating film state at a microscopic level. Will be done.

The height mapping image and frequency distribution of the cross section of the organic vehicle coating film (Example 1) are shown. The height mapping image and frequency distribution of the cross section of the organic vehicle coating film (Example 2) are shown. The height mapping image and frequency distribution of the cross section of the organic vehicle coating film (Example 3) are shown. The elastic modulus mapping image and frequency distribution of the organic vehicle coating film cross section (Example 1) are shown. The elastic modulus mapping image and frequency distribution of the cross section of the organic vehicle coating film (Example 2) are shown. The elastic modulus mapping image and frequency distribution of the organic vehicle coating film cross section (Example 3) are shown. The height mapping image and frequency distribution of the cross section of the conductive paste coating film (Example 4) are shown. The elastic modulus mapping image and frequency distribution of the cross section of the conductive paste coating film (Example 4) are shown. The infrared absorption spectra of polyvinyl butyral (PVB) and ethyl cellulose (EC) are shown. A mapping image of ^{the infrared absorption intensity (wave number 1742 cm -1} ) of the cross section of the conductive paste coating film (Example 4) is shown. The infrared absorption spectrum of the cross section of the conductive paste coating film (Example 4) is shown.

A specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”) will be described. The present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention.

Evaluation of Organic Vehicle for Functional Paste The evaluation method for the organic vehicle for functional paste of the present embodiment is as follows: a step of applying the organic vehicle on a substrate and drying it to prepare a coating film (coating film preparation step). ), A step of processing the obtained coating film to expose the processed surface (processing step), and a step of analyzing the surface characteristics of the coating film on the exposed processed surface using an atomic force microscope (analysis step). .. Details of each step will be described below.

<Coating film manufacturing process>
In the coating film preparation step, an organic vehicle for a functional paste is applied and dried on a substrate to prepare a coating film (vehicle dry film). The organic vehicle is a precursor of the functional paste, and the functional powder is mixed and kneaded with the organic vehicle to obtain a functional paste. The organic vehicle contains an organic solvent and two or more kinds of resins (binder resins). A known solvent used for the coating paste may be used as the organic solvent. Examples of such a solvent include terpene-based solvents such as tarpineol and dihydroterpineol, and higher alcohols such as octanol, decanol or tridecanol.

Two types of resins are used in combination as the binder resin. As the resin, a known resin used for the coating paste may be used. Examples of such resins include cellulose resins such as ethyl cellulose, ethyl hydroxyethyl cellulose, nitrocellulose, methyl cellulose, propyl cellulose and acetyl cellulose, acetal resins such as polyvinyl butyral, and acrylic resins such as butyl methacrylate and methyl methacrylate. .. Of these, the resin preferably contains a cellulosic resin and an acetal resin. This is because the combination of these resins provides an internal electrode having excellent adhesion to the dielectric layer when the organic vehicle is applied to the conductive paste for a multilayer ceramic capacitor. In addition, the organic vehicle may contain an additive that is soluble in an organic solvent. Dispersants and binders are exemplified as such additives. Further, the organic vehicle may be produced by a known method. For example, a resin and, if necessary, an additive may be mixed and dissolved in an organic solvent.

The base material is not particularly limited as long as it can be coated with an organic vehicle and can withstand heating in the drying step. For example, a support film such as a polyethylene terephthalate (PET) film can be mentioned. The coating may be performed by a known means such as screen printing, a doctor blade or an applicator. In addition, drying may be performed by a known method, and the conditions may be determined according to the type of organic solvent and resin used. The drying temperature may be, for example, 50 to 300 ° C. and may be 80 to 150 ° C.

<Processing process>
In the processing process, the obtained coating film is processed to expose the processed surface. By exposing the processed surface, it is possible to accurately analyze the compatibility state of the resin inside the coating film in the subsequent analysis step. The processing is preferably performed by a method in which heat is not applied to the film. If heat is applied during processing, the resin in the coating film may melt, making it difficult to accurately check the compatibility state of the resin. The method of processing is not limited as long as heat is not applied. However, it is preferable to perform the processing using a microtome. A microtome is an instrument that cuts out ultrathin pieces from a sample and is used to prepare a sample for microscopic observation. By using a microtome, it is possible to uniformly cut out flakes with a thickness on the order of micrometers to several tens of nanometers. Further, in the processing using the microtome, unlike the processing using the focused ion beam (FIB), heat is not applied. Therefore, flakes can be cut out without melting the coating film. The surface of this flakes is smooth.

The processed surface is preferably a cross section of the coating film. The surface of the coating film is wrinkled, making accurate analysis difficult. In addition, some resins and additives may be segregated on the surface. On the other hand, by analyzing the cross section, the state inside the coating film can be investigated and the state change in the thickness direction can be known.

<Analysis process>
In the analysis step, the surface characteristics of the coating film on the exposed processed surface are analyzed using an atomic force microscope. Atomic Force Microscope (AFM) detects the displacement induced in the cantilever holding the probe by the force acting between the sample surface and the probe, and uses it to evaluate the surface shape. It is a microscope. Specifically, the atomic force microscope detects the interaction force acting between the cantilever having a sharp probe at the tip and the sample. The cantilever warps when the probe comes into contact with the sample. The amount of warpage of the cantilever is the load applied to the evaluation sample based on Hooke's law. The atomic force microscope is equipped with an optical means for detecting the amount of warpage of the cantilever and a piezo element for detecting the relative distance relationship between the evaluation sample and the cantilever in the direction in which the probe is pushed. The signal to be detected is converted into the amount of displacement of the evaluation sample. The optical means for detecting the amount of warpage irradiates the cantilever with a laser beam, and detects the reflection angle of the laser that changes due to the warp of the cantilever by changing the detection position of the reflected laser beam. The amount of displacement of the evaluation sample differs depending on the device used, but the amount of displacement can also be known by moving the evaluation sample with a piezo element with respect to a fixed probe, fixing the evaluation sample, and moving the cantilever. Can also be known by the method of controlling with a piezo element. Atomic force microscopes can detect the interaction force by bringing the probe at the tip of the cantilever into contact with the sample surface and directly detecting its displacement (contact mode), or by vibrating the cantilever near the resonance frequency and vibrating it. It is roughly classified into a method (dynamic mode) for detecting changes in characteristics.

By using an atomic force microscope, it is possible to obtain the surface characteristics of the coated surface on the order of several tens of nanometers, and by scanning the probe parallel to the sample surface, the surface characteristics are two-dimensional. It is possible to obtain a mapping image. Therefore, if phase separation occurs in the resin in the coating film according to the compatibility state, the distribution can be examined at a microscopic level.

The surface characteristics to be measured are not particularly limited as long as they can be obtained by using an atomic force microscope. For example, there are mechanical properties such as surface texture such as height from the machined surface, elastic modulus, hardness and friction coefficient. Further, by providing a heating mechanism on the probe, it is possible to measure the coefficient of thermal expansion and rubbing. Appropriate surface properties may be selected from the viewpoint of ease of analysis of the resin compatibility state. For example, the surface property may be elastic modulus. The elastic modulus varies depending on the type of resin. Therefore, it is possible to easily check the resin compatibility state by measuring the elastic modulus.

It is preferable to prepare a mapping image or frequency distribution of surface characteristics in the analysis step and evaluate the compatibility state of the resin based on the mapping image or frequency distribution. In the mapping image, the magnitude of the surface characteristic can be indicated by the shade of color. Therefore, it is possible to visually grasp the positional distribution of the surface characteristics on the machined surface. In addition, the frequency distribution can indicate the frequency of surface properties on the machined surface. For example, when elastic modulus is selected as the surface property, the elastic modulus differs depending on the type of resin. Therefore, by creating a mapping image of elastic modulus, it is possible to know the distribution of the resin on the machined surface. If the resin is completely compatible in the coating film, the elastic modulus mapping image will be a uniform image with no shade of color. On the other hand, if the resin is phase-separated in the coating film, the elastic modulus mapping image becomes a non-uniform image, for example, an image showing a sea-island structure. Further, by analyzing the mapping image, it becomes possible to investigate the state of phase separation of the resin. Therefore, when the mapping image shows the sea-island structure, the diameter of the island-shaped part and its distribution can be investigated.

In determining the surface characteristics, an atomic force microscope is used for analysis, and the obtained analytical data is analyzed to calculate the surface characteristics. The analysis data may be analyzed by a known method. For example, as a method for analyzing the elastic modulus, a method based on Hertz theory, DMT theory, or JKR theory is known. Here, the Hertz theory is a theory based on the contact mechanics when the axisymmetric probe is press-fitted into the elastic body, and is used for a system in which the probe does not adhere to the sample surface. On the other hand, the DMT theory and the JKR theory are theories that take into account the adhesion contact. The DMT theory is valid for hard materials and the JKR theory is valid for soft materials. Resins used in conductive pastes and organic vehicles are generally not very hard. Therefore, it is preferable to obtain the elastic modulus by analysis based on the JKR theory.

The analysis method using an atomic force microscope may be determined according to the type of coating film and surface characteristics, and is not particularly limited. The measurement modes of the atomic force microscope include a contact mode, a tapping mode, a non-contact mode, a force modulation mode, and a force volume mode. The measurement mode may be determined according to the type of surface characteristics to be obtained, but the force module mode is preferable. In the force module mode, it is possible to obtain the mechanical properties of each minute region on the sample surface. Therefore, for example, a mapping image of elastic modulus and a frequency distribution can be obtained.

It is desirable to use a cantilever or probe of an atomic force microscope that does not break due to the force generated when the probe is pushed in within the range that gives elastic deformation to the evaluation sample. Although it is not uniquely determined, a cantilever or probe that does not break during analysis may be selected in consideration of various conditions such as the pushing force and the elastic modulus of the evaluation sample.

Evaluation of Functional Paste The evaluation method of the functional paste of the present embodiment is obtained by the following steps; a step of applying the functional paste on a substrate and drying it to prepare a coating film (coating film preparation step). It has a step of processing the coating film to expose the processed surface (processing step) and a step of analyzing the surface characteristics of the coating film on the exposed processed surface using an atomic force microscope (analysis step). Details of each step will be described below.

<Coating film manufacturing process>
In the coating film production step, a coating film (paste drying film) is produced by applying and drying a functional paste on a substrate. The functional paste is a precursor of the functional layer, and the functional paste is applied, dried and fired to prepare the functional layer. The functional layer has electrical, magnetic, thermal and / or mechanical functions, and is an element element that positively utilizes these functions. Examples of such a functional layer include an electrode layer (conductive layer), an electric resistance layer, a magnetic layer, a heat conductive layer, and a heat shielding layer.

Functional pastes include functional powders and organic vehicles. The functional powder is used for expressing the function of the functional layer, and examples thereof include a conductive powder, an electric resistance powder, a magnetic powder, a heat conductive powder, and a heat shielding powder. The organic vehicle is as described above. The functional paste may contain other components in addition to the functional powder and the organic vehicle. Examples of such a component include a common material such as ceramic powder.

The functional paste may be a conductive paste. In this case, the functional powder contains a conductive powder. The conductive powder is at least one metal powder selected from the group consisting of nickel (Ni), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), copper (Cu) and alloys thereof. Is preferably included. This is because these metal powders have excellent conductivity. In particular, a conductive paste containing nickel (Ni) powder as a functional powder is suitably used for producing an internal electrode layer of a laminated ceramic capacitor (MLCC). Further, the functional paste may be a heat conductive paste. In this case, the functional powder preferably contains aluminum nitride (AlN) powder. This is because aluminum nitride (AlN) has excellent thermal conductivity.

The base material, coating and drying method may be the same as in the evaluation of the organic vehicle for functional paste.

<Processing process>
In the processing process, the obtained coating film is processed to expose the processed surface. This step may be performed in the same manner as in the case of evaluating the organic vehicle for functional paste.

<Analysis process>
In the analysis step, the surface characteristics of the coating film on the exposed processed surface are analyzed using an atomic force microscope. This step may be performed in the same manner as in the case of evaluating the organic vehicle for functional paste.

As described above, according to the method for evaluating the organic vehicle for functional paste or the functional paste of the present embodiment, it is possible to investigate the compatibility state of the resin in the state of being coated at a microscopic level. .. For example, in the mapping image of surface characteristics (elastic modulus, etc.), if the contrast of the sea-island structure of about several tens of nanometers to several micrometers is observed, it can be determined that the phases are separated, that is, they are not compatible. This is because if the phases are separated, the contrast of the surface characteristics can be seen by the difference between the average values of the surface characteristics of each resin.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples.

[Experimental Example 1]
(1) Preparation and evaluation of organic vehicle In Experimental Example 1, an organic vehicle was prepared and evaluated.

Example 1
<Making organic vehicles>
The organic vehicle was prepared as follows. Ethyl cellulose (EC; Nissin Kasei Co., Ltd., ETHOCEL300) was prepared as a cellulosic resin, polyvinyl butyral (PVB; Sekisui Chemical Co., Ltd., BM-SZ) was prepared as an acetal resin, and tarpineol (TPO) was prepared as an organic solvent.

Ethyl cellulose was dissolved in tarpineol so that its content was 10.5% by mass to prepare an EC / TPO solution. Separately, polyvinyl butyral was dissolved in tarpineol so that its content was 15.0% by mass to prepare a PVB / TPO solution. 10.01 g of EC / TPO solution and 5.00 g of PVB / TPO solution were placed in a vessel (content volume 100 mL) of a rotation / revolution mixer (Shinky Co., Ltd., Rentaro Awatori). Further, two alumina balls (φ1 cm) were placed in the vessel. After mixing for 4 minutes at a rotation speed of 2000 rpm, defoaming was performed for 1 minute at a rotation speed of 2200 rpm to prepare an organic vehicle.

<Coating film manufacturing process>
The obtained organic vehicle was applied onto a PET film using an applicator. The post-coating film thickness (wet film thickness) was 254 μm. The applied organic vehicle was dried in a heat convection oven to prepare a coating film. Drying was carried out under the condition of holding at 120 ° C. for 40 minutes.

<Processing process>
The dry coating on the PET film was mounted on a fixing jig and cut using a microtome (Leica Microsystems, Leica EM FC6), thereby exposing a smooth cross section of the coating.

<Analysis process>
The cross section of the coating film was analyzed using an atomic force microscope (AFM), and the height from the measurement surface (cross section of the coating film) and the elastic modulus of the measurement surface were determined. The analysis was performed in force volume mode using an atomic force microscope (Bruker, MultiMode8) equipped with a cantilever (Olympus Corporation, OMCL-C200TS). In addition, an analysis based on the JKR theory was performed when calculating the elastic modulus. Then, a mapping image and frequency distribution of height and elastic modulus on the measurement surface were created.

Example 2
When preparing the organic vehicle, two types of low molecular weight additives were added to 10.01 g of the EC / TPO solution and 5.00 g of the PVB / TPO solution in the addition amounts of 0.03 g and 0.12 g. Other than that, an organic vehicle was prepared and evaluated in the same manner as in Example 1.

Example 3
When preparing the organic vehicle, two types of low molecular weight additives were added to 10.01 g of the EC / TPO solution and 5.00 g of the PVB / TPO solution in the addition amounts of 0.09 g and 0.12 g. Other than that, an organic vehicle was prepared and evaluated in the same manner as in Example 1.

(2) Evaluation Results of Organic Vehicles For each of Examples 1 to 3, the mapping image and frequency distribution of height data are shown in FIGS. 1 to 3. Further, the mapping image and frequency distribution of the elastic modulus data are shown in FIGS. 4 to 6. In FIGS. 1 to 6, (a) is a mapping image and (b) is a frequency distribution.

As shown in FIGS. 1, 2, 4 and 5, in the coating films of the organic vehicles of Examples 1 and 2, a sea-island structure was observed in the mapping image. There was also a gap between the phases. From this, it was found that the two types of resins (ethyl cellulose and polyvinyl butyral) used for producing the organic vehicle were phase-separated in the coating film. On the other hand, as shown in FIGS. 3 and 6, no sea-island structure was observed in the mapping image of Example 3, but a columnar structure was observed.

[Experimental Example 2]
(1) Preparation and Evaluation of Conductive Paste In Experimental Example 2, a conductive paste was prepared and evaluated.

Example 4
The EC / TPO solution, PVB / TPO solution and low molecular weight additive were blended in the same proportions as in Example 2, and 1.00 g of nickel (Ni) powder was further added. Then, mixing and defoaming were carried out in the same manner as in Example 2 to prepare a conductive paste. Then, using the obtained conductive paste, a coating film was prepared, processed and analyzed in the same manner as in Example 2.

(2) Evaluation result of conductive paste For Example 4, the mapping image and frequency distribution of the height data are shown in FIG. The mapping image and frequency distribution of the elastic modulus data are shown in FIG. In FIGS. 7 and 8, (a) is a mapping image and (b) is a frequency distribution. As shown in FIGS. 7 and 8, in the coating film of the conductive paste of Example 4, a sea-island structure was observed in the mapping image. By examining the elastic modulus mapping image prepared by using the atomic force microscope in this way, the distribution of the components (EC, PVD and Ni powder) in the coating film could be determined.

In order to examine the validity of the evaluation of the elastic modulus mapping image, the cross section of the coating film of Example 4 was analyzed by infrared spectroscopy (IR absorption). In the analysis, first, the infrared (IR) absorption spectra of pure polyvinyl butyral (PVB) and ethyl cellulose (EC) were obtained individually, and based on the results, a mapping image of the infrared absorption intensity of the cross section of the coating film of Example 4 was created. did. The analysis by infrared spectroscopy was performed under the following conditions.

-Analyzer: Submicron Infrared Spectroscopy System (Photothermal Spectroscopy, MILrage)
-Excitation light: QCL laser (output: 0.1-10%)
-Detection light: Visible light laser (wavelength: 532 nm)

When creating a mapping image of infrared absorption intensity, the sample surface was irradiated with ^{pulsed infrared light (wave number 1742 cm -1).} When irradiated with pulsed infrared light, the irradiated area expands according to the amplitude of the pulse. By detecting the expanding part with a visible light laser, the part absorbing infrared light was mapped.

The infrared absorption spectra of pure PVD and EC are shown in FIGS. 9 (a) and 9 (b), respectively. In pure PVB, absorption characteristic of wave number 1742 cm- ¹ is observed (Fig. 9 (a)). In contrast, pure EC had no absorption at ^{wavenumbers of 1742 cm-1.}

Based on this result, in order to confirm the distribution of PVB in the coating film, a mapping image of the absorption intensity at a ^{wave number of 1742 cm-1 was prepared for the coating film cross section of Example 4.} The absorption intensity mapping image is shown in FIG. As shown in FIG. 10, there was a remarkable difference in the absorption intensity of PVB with the linearly distributed metal particles as a boundary. That is, the PVB absorption intensity was high in the region surrounded by the linearly distributed metal particles, and the PVB absorption intensity was low in the region not surrounded by the metal particles. When the infrared absorption spectrum was examined at a portion surrounded by metal particles (marked with ● in the figure), a ^{peak was observed at 1742 cm -1,} and it was found that the PVD concentration was high at this location (Fig. 11 (a)). ). On the other hand, the PVD concentration was low in the portion not surrounded by the metal particles (▲ mark in the figure) (FIG. 11 (b)). These results suggest that PVB forms a marine structure in the coating.

Infrared spectroscopy also confirmed that a resin sea-island structure was formed in the cross section of the coating film. Therefore, it can be said that the elastic modulus mapping image created by using the atomic force microscope accurately represents the distribution of the coating film components.

From the evaluation results of Experimental Example 1 and Experimental Example 2, it was found that the compatibility state of the resin in the coating film prepared from the conductive paste (functional paste) and the organic vehicle can be evaluated by using the atomic force microscope. ..

Claims (10)

This is an evaluation method for organic vehicles for functional pastes.
The organic vehicle contains an organic solvent and two or more kinds of resins, and the method is described in the following steps;
A step of applying the organic vehicle onto a substrate and drying it to prepare a coating film.
A step of processing the coating film to expose the processed surface, and a step of analyzing the surface characteristics of the coating film on the processed surface using an atomic force microscope.
The method. It is an evaluation method of functional paste.
The functional paste contains an organic vehicle containing an organic solvent and two or more kinds of resins, and a functional powder, and the method is described in the following steps;
A step of applying the functional paste onto a substrate and drying it to prepare a coating film.
A step of processing the coating film to expose the processed surface, and a step of analyzing the surface characteristics of the coating film on the processed surface using an atomic force microscope.
The method. The method according to claim 2, wherein the functional powder contains a conductive powder and the functional paste is a conductive paste. The conductive powder is at least one metal selected from the group consisting of nickel (Ni), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), copper (Cu) and alloys thereof. The method according to claim 3, which is a powder. The method according to claim 2, wherein the functional powder contains aluminum nitride (AlN) powder, and the functional paste is a heat conductive paste. The method according to any one of claims 1 to 5, wherein the resin contains a cellulosic resin and an acetal resin. The method according to any one of claims 1 to 6, wherein the processed surface is a cross section of a coating film. The method according to any one of claims 1 to 7, wherein the processing is performed using a microtome. The method according to any one of claims 1 to 8, wherein the surface property is elastic modulus. Any of claims 1 to 9, wherein in the step of analyzing the surface characteristics of the coating film, a mapping image or frequency distribution of the surface characteristics is created, and the compatibility state of the resin is evaluated based on the mapping image or frequency distribution. The method described in paragraph 1.

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