JP2022142730A - Photosensitive composition and use of the same - Google Patents

Abstract

To achieve stable supply of a low-resistant electronic component having a dense and thick conductive layer.SOLUTION: A photosensitive composition disclosed herein contains an inorganic component, an organic component and an organic-based dispersion medium. The inorganic component contains conductive powder, and the organic component contains an organic binder and a photocurable resin. A content of the conductive powder in the photosensitive composition disclosed herein is 74 mass% or more, and a content of the organic component is 7 mass% or more and 10 mass% or less. A weight average molecular weight Mw of th organic component is 10,000 or more and 32,000 or less, and the photocurable resin contains an urethane (meth)acrylate polymer having a weight average molecular weight of 6,000 or more and an urethane (meth)acrylate oligomer having a weight average molecular weight of less than 6,000. The photosensitive composition can dissolve the adverse effect by containing conductive powder having high concentration, and accordingly a low-resistant electronic component having a dense and thick conductive layer can be stably manufactured.SELECTED DRAWING: None

Description

The present invention relates to a photosensitive composition and its use.

Conventionally, a method of forming a conductive layer of an electronic component using a photosensitive composition containing a conductive powder and a photocurable resin is known (see Patent Documents 1 to 3). An example of such a technique is photolithography. In this photolithography method, first, a photosensitive composition is applied (printed) onto a substrate, and then the composition is dried to form a film (forming step). Next, the filmy body is covered with a photomask having openings of a predetermined pattern, and light is irradiated to a part of the filmy body exposed from the openings (exposure step). As a result, the exposed portion of the film is photocured to form a cured film. Next, the unexposed portion (uncured film-like body) shielded by the photomask is removed with a developer (development step). This leaves a cured film in the desired pattern on the substrate. Then, this cured film is baked together with the substrate (baking step). As a result, the organic components such as the photocurable resin are burned off and the conductive powder is sintered to form a conductive layer. According to such a method, an electronic component can be manufactured in which a conductive layer having a precise pattern is formed on a base material.

JP-A-2000-199954 JP 2019-168575 A Patent No. 6662491

By the way, in recent years, in order to realize further miniaturization and higher performance of electronic devices, there is an increasing demand for the performance of electronic components. For example, in recent years, in order to realize low-resistance electronic components, there is a demand for a technique for forming a dense and thick conductive layer. An example of a method for forming such a conductive layer is to increase the concentration of the conductive powder in the photosensitive composition. However, according to the study of the present inventors, a photosensitive composition containing a high concentration of conductive powder has a large decrease in light transmittance due to the light shielding property of the conductive powder. May not be fully photocured. In this case, an undercut may occur in which the exposed portion of the film is removed in the developing process. Furthermore, printing defects may occur due to an increase in the viscosity of the photosensitive composition due to the high concentration of the conductive powder contained therein. For this reason, it becomes difficult to stably supply electronic components in which a conductive layer having a desired pattern is accurately formed.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and an object thereof is to provide a technique for realizing a stable supply of low-resistance electronic components in which dense and thick conductive layers are accurately formed. is.

In order to achieve the above object, the technology disclosed herein provides a photosensitive composition having the following constitution.

The photosensitive composition disclosed herein contains an inorganic component, an organic component, and an organic dispersion medium, and is used to form a conductive layer. The inorganic component of the photosensitive composition contains a conductive powder, the organic component contains an organic binder and a photocurable resin, and the organic dispersion medium is a mixture of a glycol ether solvent and an alcohol solvent. Contains solvent. In the photosensitive composition disclosed herein, the content of the conductive powder is 74% by mass or more when the total weight of the photosensitive composition is 100% by mass, and the content of the organic component is It is 7 mass % or more and 10 mass % or less. Further, the weight average molecular weight Mw of the organic component is 10000 or more and 32000 or less, and the photocurable resin is a urethane (meth)acrylate polymer having a (meth)acryloyl group and a urethane bond and having a weight average molecular weight of 6000 or more. , and a urethane (meth)acrylate oligomer having a (meth)acryloyl group and a urethane bond and having a weight average molecular weight of less than 6,000.

The "average weight molecular weight Mw of the organic component" in the above configuration is the average weight molecular weight of the organic component contained in the photosensitive composition. Although details will be described later, the organic component of the photosensitive composition disclosed herein may contain an organic component other than an organic binder and a photocurable resin (excluding those that are liquid at room temperature). That is, the "average weight molecular weight Mw of the organic components" indicates the ratio of the total value of the molecular weights of the respective organic components to the total amount (weight) of these organic components. As an example, the “average weight molecular weight Mw of organic components” in a photosensitive composition containing n types of organic components is calculated by the following formula (1). “M ₁ to M _n ” in formula (1) indicate the weight average molecular weights of the first to n-th organic components. “W ₁ to W _n ” indicate the weight corresponding to each of the first organic component to the n-th organic component. The "weight average molecular weight" of each component is the weight-based average molecular weight measured by gel permeation chromatography (GPC) and converted using a standard polystyrene calibration curve.

First, the photosensitive composition having the above structure contains conductive powder at a high concentration of 74% by mass or more in order to form a dense and thick conductive layer. As described above, a photosensitive composition containing such a high-concentration conductive powder has very low light transmittance, making it difficult to accurately form a conductive layer with a desired pattern. In contrast, the photosensitive composition disclosed herein uses a urethane (meth)acrylate resin that exhibits high photocurability. Furthermore, for such urethane (meth)acrylate resin, a mixture of urethane (meth)acrylate polymer and urethane (meth)acrylate oligomer is used so that a network-like crosslinked structure with many reaction points is constructed after photocuring. ing. As a result, undercuts due to poor curing can be prevented even though the conductive powder is contained at a high concentration of 74% by mass or more, so that a conductive layer having a desired pattern can be accurately formed. On the other hand, a photocurable resin that is a mixture of a urethane (meth)acrylate polymer and a urethane (meth)acrylate oligomer cannot suppress the increase in viscosity due to the inclusion of a high concentration of conductive powder, and it is possible to improve printing defects. It was difficult. Therefore, as a result of further studies, it was found that the average weight molecular weight Mw of the organic component in the photosensitive composition having the above-mentioned structure can be reduced to 32000 or less. As a result, an increase in the viscosity of the photosensitive composition can be suppressed, and the occurrence of printing defects can be prevented. As described above, according to the photosensitive composition disclosed herein, although it contains a high concentration of conductive powder, it is possible to achieve both printability and photocurability at a high level. It is possible to realize a stable supply of low-resistance electronic components in which a thick conductive layer is accurately formed.

In a preferred embodiment of the photosensitive composition disclosed herein, the conductive powder contains silver-based particles. This makes it possible to form a conductive layer with an excellent balance between cost and electrical resistance.

In a preferred embodiment of the photosensitive composition disclosed herein, the content of the conductive powder is 79% by mass or more when the total weight of the photosensitive composition is 100% by mass. This makes it possible to obtain an electronic component with even lower resistance. According to the technology disclosed herein, even when a photosensitive composition containing 79% by mass or more of conductive powder is used, both printability and photocurability can be achieved at a high level.

In one preferred embodiment of the photosensitive composition disclosed herein, the organic component has a weight average molecular weight Mw of 25,000 or less. By this, the increase in the viscosity of the photosensitive composition can be suitably suppressed, and printing defects can be more suitably prevented.

In one preferred embodiment of the photosensitive composition disclosed herein, the organic binder contains a cellulosic compound. This can improve the fixability of the film-like body (photosensitive composition) to the substrate surface.

In a preferred embodiment of the photosensitive composition disclosed here, the average weight molecular weight Mw of the urethane (meth)acrylate oligomer is 500 or more and 5000 or less. This makes it possible to achieve both photocurability and printability at a higher level.

In a preferred embodiment of the photosensitive composition disclosed here, the average weight molecular weight of the organic binder is 20,000 or more and 60,000 or less. As a result, both fixability and printability of the film on the substrate surface can be achieved at a high level.

In one preferred embodiment of the photosensitive composition disclosed herein, the organic component further comprises a photoinitiator. As a result, the photocurability of the photocurable resin is favorably exhibited.

Also, as another aspect of the technology disclosed herein, a method for producing a photosensitive composition is provided. The manufacturing method disclosed herein comprises an inorganic component weighing step of weighing an inorganic component containing a conductive powder, an organic component weighing step of weighing an organic component containing an organic binder and a photocurable resin, an inorganic component and an organic A mixing step of mixing the components with an organic dispersion medium containing a mixed solvent of a glycol ether solvent and an alcohol solvent. In the manufacturing method disclosed herein, in the inorganic component weighing step, the conductive powder is added so that the content of the conductive powder is 74% by mass or more when the total weight of the photosensitive composition is 100% by mass. is weighed, and in the organic component weighing step, the content of the organic component is 7% by mass or more and 10% by mass or less when the total weight of the photosensitive composition is 100% by mass, and the weight average molecular weight Mw of the organic component is The organic component is weighed so as to be between 10,000 and 32,000. Further, in this organic component weighing step, a urethane (meth)acrylate polymer having a (meth)acryloyl group and a urethane bond and having a weight-average molecular weight Mw of 6000 or more and a (meth)acryloyl group are used as photocurable resins. A photocurable resin containing a urethane (meth)acrylate oligomer having a urethane bond and a weight average molecular weight Mw of less than 6,000 is used.

According to the manufacturing method having the above configuration, a photosensitive composition containing a high concentration (74% by mass or more) of conductive powder is manufactured. Such a photosensitive composition uses a photocurable resin containing a urethane (meth)acrylate polymer and a urethane (meth)acrylate oligomer. A conductive layer having a desired pattern can be accurately formed by exhibiting photocurability. Furthermore, since the weight-average molecular weight Mw of the organic component in the photosensitive composition having the above structure is reduced to 32000 or less, the increase in viscosity of the photosensitive composition can be suppressed and high printability can be maintained. Therefore, according to the manufacturing method having the above configuration, it is possible to manufacture a photosensitive composition that realizes a stable supply of low-resistance electronic components.

Further, according to the technology disclosed herein, a composite is provided that includes a green sheet and a cured film that is disposed on the green sheet and that is obtained by photocuring the photosensitive composition. Further, according to the technology disclosed herein, there is provided an electronic component having a conductive layer made of the fired body of the photosensitive composition. According to the above photosensitive composition, a dense and thick conductive layer can be stably formed, so that a stable supply of a low-resistance conductive layer can be achieved.

Also, as another aspect of the technology disclosed herein, a method for manufacturing an electronic component is provided. Such a method for producing an electronic component includes a step of applying the photosensitive composition onto a substrate, exposing, developing, and then baking to form a conductive layer composed of a baked body of the photosensitive composition. . This makes it possible to stably manufacture an electronic component having a dense and thick conductive layer.

1 is a cross-sectional view schematically showing the structure of a multilayer chip inductor according to one embodiment; FIG. It is an optical microscope image explaining the evaluation criteria of printability evaluation in a test example. It is an optical microscope image explaining the evaluation criteria of printability evaluation in a test example.

Preferred embodiments of the technology disclosed herein are described below. Matters other than those specifically mentioned in this specification, which are necessary for the implementation of the technology disclosed herein, are based on the technical content taught by this specification and those skilled in the art. can be understood based on general technical common sense. The technology disclosed herein can be implemented based on the content disclosed in this specification and common general technical knowledge in the field. In addition, the notation of "A to B" (A and B are arbitrary numbers) indicating the range in this specification means "preferably larger than A" and "preferably smaller than B" along with the meaning of A or more and B or less. shall include the meaning of

In this specification, the photosensitive composition dried at a temperature below the boiling point of the organic component (specifically, approximately 200° C. or below, for example, 100° C. or below) is referred to as a “film-like body”. Further, a film obtained by exposing and photocuring the filmy body is referred to as a “cured film”. A sintered body obtained by firing the "cured film" at a temperature equal to or higher than the sintering temperature of the conductive powder is called a "conductive layer". The shape of the conductive layer is not particularly limited, and may be linear or layered. Also, the term "paste" used herein is a term that includes ink and slurry.

<<Photosensitive composition>>
First, the composition of the photosensitive composition disclosed herein will be described. The photosensitive composition disclosed herein is a paste-like composition used for manufacturing electronic parts (forming a conductive layer). Such photosensitive compositions comprise (A) an inorganic component, (B) an organic component, and (C) an organic dispersion medium. Each component will be described below.

(A) Inorganic Component The inorganic component is a material that remains without being burned off during the firing treatment and becomes the main component of the conductive layer. This inorganic component contains at least (A-1) a conductive powder. Inorganic components that may be included in the photosensitive composition disclosed herein are described below.

(A-1) Conductive Powder The conductive powder is an inorganic component that imparts electrical conductivity to the conductive layer after firing. The type of the conductive powder is not particularly limited, and one of conventionally known metal materials can be used alone or two or more of them can be used in appropriate combination according to the application. Preferred examples of this conductive powder include gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), aluminum (Al), nickel (Ni), ruthenium (Ru), rhodium (Rh), tungsten (W), iridium (Ir), osmium (Os), and the like, as well as mixtures and alloys thereof. Among these preferred examples, silver-based particles are more preferred. The term “silver-based particles” encompasses all particulate materials containing elemental silver (Ag). Examples of such silver-based particles include simple silver particles, silver alloys, core-shell particles containing a silver component, and the like. Examples of silver alloys include silver-palladium (Ag-Pd), silver-platinum (Ag-Pt), silver-copper (Ag-Cu), and the like. Examples of the core-shell particles include silver-ceramic core-shell particles having a core particle containing elemental silver and a ceramic shell covering the core particle. Since these silver-based particles are relatively inexpensive and have high electrical conductivity, electronic components can be manufactured with an excellent balance between cost and low resistance.

Although not particularly limited, the _D50 particle size of the conductive powder is preferably 0.1 μm or more, more preferably 0.5 μm or more, and particularly preferably 1 μm or more. As a result, aggregation of the conductive powder in the paste can be suppressed, and printability onto the substrate can be improved. On the other hand, the upper limit of the _D50 particle size of the conductive powder is preferably 5 μm or less, more preferably 4.5 μm or less, and particularly preferably 4 μm or less. As a result, the conductive layer after sintering becomes even more dense, so that an electronic component with even lower resistance can be manufactured. In addition, the use of the conductive powder having a small particle size as described above can improve the resolution of the wiring pattern after printing, exposure and development on the surface of the base material, contributing to the formation of more precise patterns. The " _D50 particle size" in this specification is a particle size corresponding to an integrated value of 50% from the smaller particle size side in the volume-based particle size distribution based on the laser diffraction/scattering method.

Although not particularly limited, the entire conductive powder preferably has a lightness L ^* of 50 or more in the L ^* a ^* b ^* color system based on JIS Z 8781:2013. This makes it easier for the irradiation light to stably penetrate deep into the uncured film-like body. Therefore, it can contribute to stable formation of a thick conductive layer (thickness: 5 μm or more, further 10 μm or more). From the above viewpoint, the lightness L ^* of the conductive powder may be approximately 55 or more, for example 60 or more. The lightness L* can be adjusted, for example, by the type of the conductive powder and the _D50 particle size described above. The lightness L ^* can be measured with a spectrophotometer that complies with JIS Z 8722:2009, for example.

The photosensitive composition disclosed herein is characterized by containing a high concentration of conductive powder. Specifically, the photosensitive composition disclosed herein contains 74% by mass or more of the conductive powder when the total weight of the photosensitive composition is 100% by mass. As a result, a dense and thick conductive layer can be formed, and low-resistance electronic components can be manufactured. In addition, from the viewpoint of further reducing the resistance of the electronic component, the content of the conductive powder is preferably 78% by mass or more, more preferably 79% by mass or more, further preferably 80% by mass or more, and 81% by mass or more. Especially preferred. In addition, in general photosensitive compositions, as the content of the conductive powder is increased in this way, the printability and light transmittance decrease, so there is a tendency that stable supply of electronic parts tends to become difficult. However, according to the photosensitive composition disclosed herein, even when the content of the conductive powder is increased, sufficient printability can be ensured and appropriate photocurability can be exhibited. can be stably manufactured. On the other hand, the technique disclosed herein does not particularly limit the upper limit of the content of the conductive powder. For example, the content of the conductive powder may be 95% by mass or less, 90% by mass or less, or 85% by mass or less.

(A-2) Inorganic Additive The inorganic component of the photosensitive composition disclosed herein may be composed of only the conductive powder, or may contain inorganic additives other than the conductive powder. Inorganic additives other than such conductive powders that can be contained in a photosensitive composition for forming a conductive layer can be used without particular limitation as long as they do not significantly impair the effects of the technology disclosed herein. Examples of such inorganic additives include dielectric powders, sintering aids, and ceramic powders such as inorganic fillers.

(B) Organic component The organic component is a component added to maintain the shape of the film-like body (cured film) before firing, and is used in the firing process (for example, in an oxidizing atmosphere at approximately 250°C or higher, for example, 500°C or higher). heat treatment at a temperature of ). In other words, the "organic component" is an organic compound that burns out (vaporizes) at a temperature lower than the sintering temperature of the inorganic component and dissolves in an organic dispersion medium, which will be described later. The organic components of the photosensitive composition disclosed herein include at least (B-1) an organic binder and (B-2) a photocurable resin. In addition, the content of the organic component (total amount of the solid organic compound) can affect the viscosity of the photosensitive composition. Therefore, from the viewpoint of suppressing printing defects due to an increase in viscosity, the content of the organic component with respect to the total amount (100% by mass) of the photosensitive composition is 7% by mass or more and 10% by mass or less (preferably 8% by mass or more). 10% by mass or less, for example, 9% by mass).

Each component contained in the organic component will be described in detail below.

(B-1) Organic Binder The organic binder is an organic compound that enhances the adhesiveness (fixability to the substrate) between the film-like material before photocuring and the substrate. In addition, unlike the photocurable resin described later, the organic binder does not have photosensitivity (for example, photocurable). Also, the organic binder is preferably a water-soluble organic compound. As a result, the uncured film-like body can be easily removed in the developing step. Suitable examples of such organic binders include cellulosic compounds. Such cellulosic compounds have glucose rings, which are repeating units of cellulose. By adding the cellulose-based compound, the inorganic component and the photocurable resin become more compatible with each other, so that the storage stability of the photosensitive composition can be improved. In addition, cellulose-based compounds exhibit good water solubility due to the presence of a plurality of hydroxyl groups in the glucose ring. Since the photosensitive composition containing such a cellulose compound can be easily removed with an aqueous developer, the working efficiency of the developing process can be improved. Cellulose-based compounds include cellulose, cellulose derivatives, and salts thereof. As the cellulosic compound, one of conventionally known compounds can be used alone, or two or more of them can be used in appropriate combination. Preferred examples of cellulosic compounds include hydroxyalkylcelluloses such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose; alkylcelluloses such as methylcellulose and ethylcellulose; carboxyalkylcelluloses such as carboxymethylcellulose; Further, the acid value of the cellulose-based compound may be approximately 10 to 300 mgKOH/g, for example 20 to 200 mgKOH/g. The "acid value (mgKOH/g)" used herein is the content (mg) of potassium hydroxide (KOH) required to neutralize free fatty acids contained in a unit sample (1 g).

Further, the organic binder may be composed only of the cellulose-based compound described above, or may contain other organic compounds. Other examples of organic binders include (meth)acrylic resins, phenolic resins, epoxy resins, polyester resins, polyamide resins, polycarbonate resins, and the like.

Among the organic binders other than the cellulose compounds described above, (meth)acrylic resins having no photosensitivity are suitable. Examples of this (meth)acrylic resin include homopolymers of alkyl (meth)acrylates, copolymers containing alkyl (meth)acrylate as a main monomer and a sub-monomer having copolymerizability with the main monomer, and their Modified products are mentioned. The (meth)acrylic resin may have a highly alkali-soluble structural moiety such as a phenolic hydroxyl group, a carboxyl group, an ester bond group, a sulfo group, a phosphono group, and an acidic group such as a boronic acid group. By containing these highly alkali-soluble structural parts, the unexposed parts in the development process can be removed favorably with an alkaline aqueous developer. In addition, by including a (meth)acrylic resin, the flexibility of the conductive layer and followability to the base material can be improved, and the occurrence of peeling and disconnection can be better suppressed. Furthermore, the durability of the conductive layer can be improved.

ここで、上記式において、
Ｒ_１は、水素（Ｈ）原子またはメチル基（－ＣＨ_３）であり、
Ｒ_２は、水素（Ｈ）原子またはメチル基（－ＣＨ_３）であり、
Ｘは、水素（Ｈ）原子、または以下に示される有機官能基であり、
Ｙは、水素（Ｈ）原子、または以下に示される有機官能基であり、
ａおよびｂは、独立して０以上の整数である。 Specific examples of the (meth)acrylic resin include acrylic resins having the following structures.

Here, in the above formula,
R ₁ is a hydrogen (H) atom or a methyl group (--CH ₃ );
R ₂ is a hydrogen (H) atom or a methyl group (—CH ₃ );
X is a hydrogen (H) atom or an organic functional group shown below,
Y is a hydrogen (H) atom or an organic functional group shown below,
a and b are independently integers of 0 or greater.

および、

に示されるような環状アルキル基；フェニルメチル（－ＣＨ_２－Ｐｈ）、フェノキシエチル（－ＣＨ_２ＣＨ_２－Ｏ－Ｐｈ）等の芳香環含有基；等が挙げられる。なお、上記式（２）におけるＲ_１，Ｒ_２，ＸおよびＹを適宜設定することによって、（メタ）アクリル系樹脂のガラス転移点を調節することができる。そして、上記（メタ）アクリル系樹脂のガラス転移点は、５０℃以上１００℃以下が好ましく、５５℃以上８０℃以下が好ましく、５５℃以上７５℃以下が好ましく、５５℃以上７０℃以下が好ましい。これによって、感光性組成物の解像性を向上させ、現像マージンを長くすることができる。また、（メタ）アクリル樹脂の酸価は、（メタ）アクリル系樹脂中のカルボキシ基に応じて変動する。かかる（メタ）アクリル樹脂の酸価は、１０～３００ｍｇＫＯＨ／ｇでもよく、２０～２００ｍｇＫＯＨ／ｇでもよく、５０～１５０ｍｇＫＯＨ／ｇでもよい。また、本明細書において「ガラス転移点」とは、示差走査熱量分析（Ｄｉｆｆｅｒｅｎｔｉａｌ Ｓｃａｎｎｉｎｇ Ｃａｌｏｒｉｍｅｔｒｙ：ＤＳＣ）に基づくガラス転移温度（Ｔｇ）をいう。 Examples of the organic functional group for X or Y include methyl (--CH ₃ ), ethyl (--CH ₂ CH ₃ ), n-butyl (--CH ₂ CH ₂ CH ₂ CH ₃ ), iso-butyl (--CH ₂ CH (CH ₃ ) ₂ ), and alkyl groups such as tert-butyl (—C(CH ₃ ) ₃ ), hydroxyethyl group, 2-hydroxypropyl group; cyclohexyl,

and,

aromatic ring-containing groups such as phenylmethyl (--CH ₂ --Ph) and phenoxyethyl (--CH ₂ CH ₂ --O--Ph); and the like. By appropriately setting R ₁ , R ₂ , X and Y in the above formula (2), the glass transition point of the (meth)acrylic resin can be adjusted. The glass transition point of the (meth)acrylic resin is preferably 50° C. or higher and 100° C. or lower, preferably 55° C. or higher and 80° C. or lower, preferably 55° C. or higher and 75° C. or lower, and preferably 55° C. or higher and 70° C. or lower. . This can improve the resolution of the photosensitive composition and lengthen the development margin. Also, the acid value of the (meth)acrylic resin varies depending on the carboxy groups in the (meth)acrylic resin. The (meth)acrylic resin may have an acid value of 10 to 300 mgKOH/g, 20 to 200 mgKOH/g, or 50 to 150 mgKOH/g. In addition, the term "glass transition point" as used herein refers to the glass transition temperature (Tg) based on differential scanning calorimetry (DSC).

The weight average molecular weight of each component added as an organic component is not particularly limited as long as the "weight average molecular weight Mw of the organic component" satisfies a predetermined value. That is, when the weight-average molecular weight of the photocurable resin described later is increased, the weight-average molecular weight Mw of the organic component can be adjusted by decreasing the weight-average molecular weight of the organic binder. However, the weight average molecular weight of the organic binder is 5000 or more from the viewpoint of ensuring a certain or more adhesiveness (tackiness) of the film before photocuring and suppressing peeling of the film before photocuring. is preferred, 10,000 or more is more preferred, 15,000 or more is even more preferred, and 20,000 or more is particularly preferred. On the other hand, due to the configuration of the technique disclosed herein, if the weight average molecular weight of the organic binder is excessively increased, it is required that the weight average molecular weight of the photocurable resin is greatly reduced. Therefore, from the viewpoint of ensuring sufficient photocurability, the weight average molecular weight of the organic binder is preferably suppressed to 100,000 or less, more preferably 80,000 or less, and particularly preferably 60,000 or less.

Further, although not particularly limited, the content of the organic binder with respect to the total amount (100% by mass) of the photosensitive composition is generally 0.1 to 9% by mass, typically 1 to 7% by mass, for example It is preferably 2.5 to 5% by mass. By setting the content of the organic binder to a predetermined value or more, the uncured film-like body can be easily removed in the developing step, so that the developing time can be shortened. In addition, since the fixability of the filmy body to the base material before photocuring is enhanced, peeling and disconnection of the conductive layer can be more suitably suppressed. On the other hand, by setting the content of the organic binder to a predetermined value or less, the ratio of the photocurable resin described later is relatively improved, so that more suitable photocurability can be obtained.

(B-2) Photocurable resin A photocurable resin is an organic compound that is cured by a polymerization reaction, a cross-linking reaction, or the like when exposed to light. The "polymerization reaction" may be, for example, addition polymerization or ring-opening polymerization. Although not particularly limited, the content of the photocurable resin relative to the total amount of the photosensitive composition (100% by mass) is generally 0.1 to 9% by mass, typically 1 to 7% by mass. , for example, 3 to 6% by mass, preferably 3 to 5% by mass. By setting the ratio of the photocurable resin to a predetermined value or more, the film-like body can be hardened to a deep portion in the exposure process, so peeling and disconnection of the conductive layer can be suitably suppressed. On the other hand, by setting the ratio of the photocurable resin to a predetermined value or less, it is possible to suppress an increase in the viscosity of the photosensitive composition, thereby making it easier to maintain suitable printability.

The photocurable resin of the photosensitive composition disclosed herein contains (a) a urethane (meth)acrylate polymer and (b) a urethane (meth)acrylate oligomer. Each will be described below.

(a) Urethane (meth)acrylate polymer A urethane (meth)acrylate polymer is a urethane (meth)acrylate resin having a large weight average molecular weight. Here, the “urethane (meth)acrylate resin” in this specification is a (meth)acrylic photocurable resin having a (meth)acryloyl group, and a urethane bond (—NH—C (=O )-O-). Here, the above-mentioned "(meth)acryloyl group" means "methacryloyl group (-C(=O)-C(CH ₃ )=CH ₂ )" and "acryloyl group (-C(=O)-CH=CH ₂ )”. And "(meth)acrylate" is a term including "methacrylate" and "acrylate". Since such a urethane (meth)acrylate resin contains a (meth)acryloyl group, the flexibility of the cured film after photocuring and the followability to the base material are excellent, and peeling and disconnection of the cured film can be suitably suppressed. . Furthermore, since the urethane (meth)acrylate resin contains a urethane bond, it can exhibit high photocurability.

As described above, in this specification, a urethane (meth)acrylate resin having a large weight average molecular weight is referred to as a "urethane (meth)acrylate polymer". This urethane (meth)acrylate polymer is a urethane (meth)acrylate resin having a weight average molecular weight of 6000 or more. The term "urethane (meth)acrylate resin having a weight-average molecular weight of 6000 or more" is intended to indicate that the weight-average molecular weight measured by gel permeation chromatography is 6000 or more. It is not intended that all of the resin materials contained in the (meth)acrylate polymer have a molecular weight of 6000 or more. Although details will be described later, this urethane (meth)acrylate polymer functions as a trunk portion of a network-like crosslinked structure when the photosensitive composition (film-like body) is photocured. From the viewpoint of allowing photocurable monomers and oligomers to exist in a wide range in the film, the weight average molecular weight of the urethane (meth)acrylate polymer is preferably 7000 or more, more preferably 8000 or more, and particularly preferably 10000 or more. . On the other hand, as the weight-average molecular weight of the urethane (meth)acrylate polymer is decreased, the weight-average molecular weight of the organic binder relatively increases. From this point of view, the weight average molecular weight of the urethane (meth)acrylate polymer is preferably 60,000 or less, more preferably 50,000 or less, even more preferably 40,000 or less, and particularly preferably 30,000 or less.

Although not particularly limited, the content of the urethane (meth)acrylate polymer relative to the total amount (100% by mass) of the photosensitive composition is generally 0.1 to 8% by mass, typically 0.5%. It may be up to 5% by weight, for example 1 to 2% by weight. By setting the content of the urethane (meth)acrylate polymer to a predetermined value or more, the photocurability of the photosensitive composition can be further improved. On the other hand, by setting the ratio of the urethane (meth)acrylate polymer to a predetermined value or less, it is possible to suppress deterioration in printability due to an increase in the viscosity of the photosensitive composition.

(b) Urethane (meth)acrylate oligomer The urethane (meth)acrylate oligomer is a urethane (meth)acrylate-based resin having a small weight average molecular weight. This urethane (meth)acrylate oligomer is a urethane (meth)acrylate resin having a weight average molecular weight of less than 6,000. The term "urethane (meth)acrylate resin having a weight average molecular weight of less than 6,000" is intended to indicate that the weight average molecular weight measured by gel permeation chromatography is less than 6,000. It is not intended that all of the resin materials contained in the (meth)acrylate oligomer have a molecular weight of less than 6000. A photocurable resin obtained by mixing such a low-molecular-weight urethane (meth)acrylate oligomer and the above-described high-molecular-weight urethane (meth)acrylate polymer exhibits high photocurability. Even when the light transmittance of the photosensitive composition is lowered by the addition of, the occurrence of poor curing can be suitably prevented. The reason why such high photocurability is exhibited is that a network-like crosslinked structure is formed as a result of dendritic cross-linking of multiple urethane (meth) acrylate oligomers with a high-molecular urethane (meth) acrylate polymer as a backbone. presumed to be constructed. From the viewpoint of suitably constructing the network-like crosslinked structure described above, the weight average molecular weight of the urethane (meth)acrylate oligomer is preferably 4000 or less, more preferably 3500 or less, and particularly preferably 3000 or less. On the other hand, the lower limit of the weight average molecular weight of the urethane (meth)acrylate oligomer is not particularly limited, and may be 500 or more, 750 or more, 1000 or more, or 1500 or more. good too.

Further, the content of the urethane (meth)acrylate oligomer with respect to the total amount of the photosensitive composition is not particularly limited, and may be 0.1 to 8% by mass, 0.5 to 5% by mass, or 1 to 8% by mass. It may be 4% by mass, or 1.5 to 3.5% by mass. By setting the content of the urethane (meth)acrylate oligomer to a predetermined value or more, the photosensitive composition can be further strongly photocured. On the other hand, by setting the ratio of the urethane (meth)acrylate oligomer to a predetermined value or less, it is possible to suppress deterioration in printability due to an increase in the viscosity of the photosensitive composition.

Further, in the photosensitive composition disclosed herein, from the viewpoint of more preferably constructing the network-like crosslinked structure described above, the urethane (meth)acrylate polymer and the urethane (meth)acrylate oligomer in the photocurable resin It is preferable to adjust the mixing ratio with For example, the ratio of the content of the urethane (meth)acrylate oligomer to the content of the urethane (meth)acrylate polymer is suitably 0.5 times or more and 10 times or less, preferably 0.75 times or more and 8 times or less. 0.5 times or more and 3 times or less is more preferable, 1.6 times or more and 2.5 times or less is more preferable, and 1.7 times or more and 2.3 times or less is particularly preferable. Thereby, a network-like crosslinked structure can be constructed more preferably, and more suitable photocurability can be exhibited.

(c) Other photo-curing resins In addition, photo-curing resins other than urethane (meth)acrylate resins (other photo-curing resin) may be included. (Meth)acrylic resins can be mentioned as such photocurable resins. "(Meth)acrylic resin" in the present specification is a (meth)acrylic photocurable resin containing a monomer having a (meth)acryloyl group, and a urethane bond (-NH-C (=O)- O-). As such a (meth)acrylic resin, one of conventionally known resins can be used alone, or two or more of them can be used in appropriate combination. Preferred examples of (meth)acrylic resins include homopolymers of alkyl (meth)acrylates and copolymers containing alkyl (meth)acrylates as main monomers and copolymerizable sub-monomers in the main monomers. mentioned. Among them, a (meth)acrylic resin having a (meth)acryloyl group (preferably an acryloyl group) in a side chain is preferable from the viewpoint of improving photocurability. In addition, from the viewpoint of more preferably exhibiting the effect of the technology disclosed herein, the content of the above "other photocurable resin" when the total amount of the photocurable resin is 100% by mass is 10% by mass. % or less is preferable, 5 mass % or less is more preferable, 3 mass % or less is preferable, and 2 mass % or less is particularly preferable.

(B-3) Other Organic Components As described above, the organic components of the photosensitive composition disclosed herein include (B-1) an organic binder and (B-2) a photocurable resin. However, the organic components contained in the photosensitive composition are not limited to these. That is, the organic component may include an organic component (another organic component) that does not fall under either the organic binder or the photocurable resin, as long as the effects of the technology disclosed herein are not significantly impaired. Any organic compound that can be used in this type of photosensitive composition can be used as such other organic component without any particular limitation. For example, the organic component may include a photoinitiator. The photopolymerization initiator is a component that is decomposed by irradiation with light energy such as ultraviolet rays to generate active species such as radicals and cations, thereby initiating the polymerization reaction of the photocurable resin. As the photopolymerization initiator, one type can be used alone or two or more types can be used in appropriate combination from among conventionally known ones depending on the type of the photocurable resin and the like. Preferred examples of photopolymerization initiators include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morphol linophenyl)-butan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4-diethylthioxanthone, benzophenone and the like. be done.

Although not particularly limited, the content of the photopolymerization initiator is generally 0.01 to 5% by mass, typically 0.05 to 3% by mass, for example 0.1 to 2% by mass. Good. As a result, the photocurability of the photosensitive composition can be fully exhibited, and the conductive layer can be formed more stably. Further, the weight average molecular weight of the photopolymerization initiator is approximately 100-500, typically 100-300.

(B-4) Weight average molecular weight Mw of all organic components
In the photosensitive composition disclosed herein, the organic component has a weight-average molecular weight Mw of 32,000 or less. By keeping the weight average molecular weight Mw of the organic component low in this way, it is possible to suppress a rapid increase in viscosity even though the conductive powder is contained at a high concentration (for example, 74% by mass or more). Therefore, the photosensitive composition disclosed herein can maintain favorable printability. From the viewpoint of further improving the printability of the photosensitive composition, the upper limit of the weight average molecular weight Mw of the organic component is appropriately 31,500 or less, preferably 31,000 or less, more preferably 30,000 or less, and 29,000 or less. More preferably, 27,000 or less is particularly preferable, and for example, it can be set to 25,000 or less. On the other hand, even when the urethane (meth)acrylate resin described above is used, if the weight-average molecular weight Mw of the organic component is less than 10000, the fixability to the substrate surface is significantly impaired, resulting in insufficient printability. It may not be guaranteed. Therefore, in the photosensitive composition disclosed herein, the weight average molecular weight Mw of the organic component is specified to be 10,000 or more. From the viewpoint of ensuring sufficient printability more reliably, the lower limit of the weight-average molecular weight Mw of the organic component is preferably 11,000 or more, more preferably 13,000 or more, further preferably 16,000 or more, and particularly preferably 18,000 or more. .

(C) Organic Dispersion Medium The photosensitive composition disclosed herein contains an organic dispersion medium for dispersing the components described above. The organic dispersion medium is a liquid component that imparts appropriate viscosity and fluidity to the photosensitive composition and improves the handling properties of the photosensitive composition, workability during printing, and the like. As the organic dispersion medium, a mixed solvent obtained by mixing the following glycol ether solvent and alcohol solvent is used. Examples of glycol ether solvents include ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (cellosolve), diethylene glycol monobutyl ether (butyl carbitol), diethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether, and dipropylene glycol. Methyl ether acetate, propylene glycol phenyl ether, 3-methyl-3-methoxybutanol and the like. Examples of alcohol solvents include terpineol, dihydroterpineol, dihydroterpinylpropionate, and benzyl alcohol. Among the various solvents described above, a mixed solvent of dipropylene glycol methyl ether acetate and dihydroterpineol, a mixed solvent of propylene glycol phenyl ether and terpineol, and the like can be particularly suitably used. The mixing ratio of the glycol ether solvent and the alcohol solvent is preferably 95:5 to 50:50. In addition, the organic dispersion medium may contain a small amount of a solvent other than the mixed solvent of the glycol ether solvent and the alcohol solvent as long as the effect of the technology disclosed herein is not significantly impaired. For example, the content of the mixed solvent with respect to the total weight of the organic dispersion medium may be 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass. . Examples of solvents other than the mixed solvent include 1,7,7-trimethyl-2-acetoxy-bicyclo-[2,2,1]-heptane, 2,2,4-trimethyl-1,3-pentadiol mono ester solvents such as isobutyrate; hydrocarbon solvents such as toluene and xylene; glycol solvents such as ethylene glycol, propylene glycol and diethylene glycol; toluene, xylene, naphtha, solvent naphtha, mineral spirits, petroleum hydrocarbons petroleum-based solvents and the like. Although not particularly limited, the content of the organic dispersion medium in the entire photosensitive composition is generally 1 to 50% by mass, typically 3 to 30% by mass, for example 4 to 20% by mass. may be The molecular weights of these organic dispersion media are not added in the calculation of the "weight average molecular weight Mw of the organic component". This is because the organic dispersion medium is a liquid at room temperature (for example, 23° C.), and its molecular weight ensures sufficient printability of the photosensitive composition and accurately forms a dense and thick conductive layer. because it can be ignored for our purposes.

(D) Other additive components In addition to the components described above, the photosensitive composition may contain various additive components as necessary, as long as the effects of the technology disclosed herein are not significantly impaired. . As the additive component, one of conventionally known components can be used alone, or two or more can be used in appropriate combination. Examples of additive components include photosensitizers, polymerization inhibitors, radical scavengers, antioxidants, UV absorbers, plasticizers, surfactants, leveling agents, thickeners, dispersants, and antifoaming agents. , anti-gelling agents, stabilizers, preservatives, pigments and the like. Moreover, these additive components may be added in the paste of the photosensitive composition, or may adhere to the surface of the inorganic component. Specifically, the additive component here also includes a surface treatment agent or the like that is adhered to the surface of the inorganic component (conductive powder, etc.) in order to improve the dispersibility of the inorganic component. Although not particularly limited, the proportion of the additive component in the entire photosensitive composition is generally 5% by mass or less, typically 3% by mass or less, for example 2% by mass or less, preferably 1% by mass. It should be: Among the additive components described above, the molecular weight of the additive component, which is an organic compound that is solid at room temperature (for example, 23 ° C.), can affect the printability of the photosensitive composition. It is added when calculating the weight average molecular weight Mw of the component.

(E) Summary of photosensitive composition As described above, in order to form a dense and thick conductive layer in the production of electronic components, it is required to use a photosensitive composition containing a high concentration of conductive powder. . In contrast, the photosensitive composition disclosed herein uses a urethane (meth)acrylate resin in which a urethane (meth)acrylate polymer and a urethane (meth)acrylate oligomer are mixed. As a result, a network-like crosslinked structure having many reaction points is formed when irradiated with ultraviolet rays, so that high photocurability can be exhibited. As a result, a conductive layer having a precise pattern can be stably formed even though the light transmittance is lowered due to the addition of a large amount of conductive powder. Furthermore, in the technology disclosed herein, by suppressing the average weight molecular weight Mw of the organic component in the photosensitive composition having the above structure to 32000 or less, the viscosity is increased despite the use of a highly concentrated conductive powder. can be suppressed, and the occurrence of printing defects can be prevented. As described above, according to the photosensitive composition disclosed herein, it is possible to stably supply electronic components in which dense and thick conductive layers are accurately formed.

<<Method for producing photosensitive composition>>
Next, a method for producing the photosensitive composition disclosed herein will be described. The production method disclosed herein includes an inorganic component weighing step, an organic component weighing step, and a mixing step. Each step will be described below.

1. Inorganic Component Weighing Step First, in this step, the inorganic component including the conductive powder is weighed. In the manufacturing method disclosed herein, the content of the conductive powder is 74% by mass or more (preferably 78% by mass or more, more preferably 79% by mass or more, further preferably 80% by mass or more, particularly preferably is 81% by mass or more). This makes it possible to obtain a photosensitive composition capable of forming a dense and thick conductive layer. In addition, since it has already been described, redundant description is omitted, but the photosensitive composition disclosed herein contains inorganic additives (dielectric powder, sintering aid, inorganic filler, etc.) that are inorganic components other than the conductive powder. can contain In this step, these inorganic additives may be weighed. In this specification, for convenience of explanation, the name of this step is "inorganic component weighing step", but the name of this step is not intended to limit the weighing object in this step to inorganic components. do not have. For example, when using a conductive powder to which an organic surface treatment agent is attached, a part of the organic component is weighed in this step. In this case, the organic surface treatment agent is also regarded as part of the organic component, and the weight average molecular weight Mw of the organic component is adjusted in the next step.

2. Organic Component Weighing Step In this step, the organic components including the organic binder and the photocurable resin are weighed. In the production method disclosed herein, in this step, the content of the organic component is 7% by mass or more and 10% by mass or less, and the weight average molecular weight Mw of the organic component is 10000 or more and 32000 or less. Weigh the ingredients. Specifically, when n types of organic components are added, under the premise that the total amount of the organic components is within the range of 7 to 10% by mass, the first organic component to the nth organic component Based on each weight average molecular weight (M ₁ to M _n ) and the following formula (1), the weight of each organic component (W ₁ to W _n ) so that the weight average molecular weight Mw of the organic component satisfies the above range adjust the Thus, by suppressing the weight-average molecular weight Mw of the organic component to 32,000 or less, it is possible to suppress deterioration in printability due to a significant increase in viscosity of the photosensitive composition after production.

Furthermore, in the production method disclosed herein, a urethane (meth)acrylate resin obtained by mixing a urethane (meth)acrylate polymer and a urethane (meth)acrylate oligomer is used as the photocurable resin. As a result, the photocurability of the photosensitive composition can be sufficiently ensured even if the light transmittance is lowered due to the increase in the concentration of the conductive powder. As a result, undercutting of the film-like body (cured film) due to poor curing can be sufficiently prevented, and the conductive layer can be accurately formed in a desired pattern.

3. Mixing Step In the manufacturing method disclosed herein, the organic component and the inorganic component weighed in each step described above are mixed to prepare a photosensitive composition. The means for mixing each component is not particularly limited, and conventionally known means can be employed without particular limitations. For example, for mixing each component, a conventionally known stirring and mixing device such as a roll mill, magnetic stirrer, planetary mixer, disper, etc. can be used as appropriate. Alternatively, an organic vehicle in which an organic component is mixed with an organic dispersion medium may be prepared in advance, and the organic vehicle and the inorganic component may be mixed. In this case, various conventionally known stirring devices such as mixers and stirrers using stirring blades can be used. Also, in the preparation of the organic vehicle, a means of heating to 50° C. to 120° C. and mixing can be employed. Since the photosensitive composition prepared through the above steps contains a urethane (meth)acrylate resin obtained by mixing a urethane (meth)acrylate polymer and a urethane (meth)acrylate oligomer, it has a high concentration of conductivity. In spite of containing the powder, it is possible to suitably prevent the occurrence of undercuts in the film-like body (cured film) due to deterioration in photocurability. Furthermore, the weight-average molecular weight Mw of the organic component is controlled so as to prevent printing defects (exposed base material, steps on the surface of the conductive layer, etc.) due to rapid viscosity increase. That is, by using the photosensitive composition produced by the production method disclosed herein, low-resistance electronic components can be stably produced.

<<Use of photosensitive composition>>
As described above, according to the photosensitive composition disclosed herein, a dense and thick conductive layer can be stably formed, so that the performance of various electronic parts such as inductance parts, capacitor parts, and multilayer circuit boards can be improved. (lower resistance).

Electronic components for which the photosensitive composition disclosed herein is used may be of various mounting forms such as surface mounting type and through-hole mounting type. The electronic component may be a laminated type, a wound type, or a thin film type. Typical examples of inductance components include high frequency filters, common mode filters, inductors (coils) for high frequency circuits, inductors (coils) for general circuits, high frequency filters, choke coils, and transformers.

Ceramic electronic components are one example of electronic components. In this specification, the term "ceramic electronic component" refers to electronic components in general that use ceramic materials, and includes amorphous ceramic substrates (glass-ceramic substrates) or crystalline (i.e., non-glass) ceramics. It includes general electronic parts having a conductive layer formed on the surface of a base material. Typical examples of ceramic electronic components include high-frequency filters with ceramic substrates, ceramic inductors (coils), ceramic capacitors, low temperature co-fired ceramic substrates (LTCC substrates), and high-temperature fired multilayer ceramic substrates. material (High Temperature Co-fired Ceramics Substrate: HTCC base material) and the like.

The ceramic material constituting the substrate is not particularly limited, but examples include zirconium oxide (zirconia), magnesium oxide (magnesia), aluminum oxide (alumina), silicon oxide (silica), and titanium oxide. (titania), cerium oxide (ceria), yttrium oxide (yttria), barium titanate, and other oxide materials; cordierite, mullite, forsterite, steatite, sialon, zircon, ferrite, and other composite oxide materials nitride materials such as silicon nitride and aluminum nitride; carbide materials such as silicon carbide; hydroxide materials such as hydroxyapatite;

A procedure for manufacturing a multilayer chip inductor using the photosensitive composition disclosed herein will be described below. FIG. 1 is a cross-sectional view schematically showing the structure of a multilayer chip inductor. Note that the dimensional relationships (length, width, thickness, etc.) in FIG. 1 do not necessarily reflect the actual dimensional relationships. Further, the symbol X in the drawings indicates the "horizontal direction" and the symbol Y indicates the "vertical direction". However, these directions are determined for convenience of explanation, and are not intended to limit the manner of installation during manufacture or use of the multilayer chip inductor 1 .

As shown in FIG. 1, the multilayer chip inductor 1 includes a body portion 10 and external electrodes 20 provided on both lateral side portions of the body portion 10 in the horizontal direction X. As shown in FIG. Examples of the size of the multilayer chip inductor 1 include 0806 shape (0.8 mm×0.6 mm), 1608 shape (1.6 mm×0.8 mm), and 2520 shape (2.5 mm×2.0 mm). .

The body portion 10 has a structure in which a ceramic layer (dielectric layer) 12 and an internal electrode layer 14 are integrated. The ceramic layer 12 is made of a ceramic material. Internal electrode layers 14 are arranged between the ceramic layers 12 in the vertical direction Y. As shown in FIG. In the electronic component manufacturing method disclosed herein, the internal electrode layers 14 are formed using the photosensitive composition described above. The internal electrode layers 14 adjacent in the vertical direction Y with the ceramic layer 12 interposed therebetween are electrically connected through vias 16 penetrating the ceramic layer 12 . As a result, the internal electrode layers 14 are configured in a three-dimensional spiral shape (helical shape). Both ends of the internal electrode layer 14 are connected to the external electrodes 20 respectively.

Such a multilayer chip inductor 1 can be manufactured, for example, as follows. First, a paste containing a ceramic material, a binder resin and an organic solvent is prepared and supplied onto a carrier sheet to form a ceramic green sheet. Next, the ceramic green sheets are rolled and cut into desired sizes to obtain a plurality of ceramic layer-forming green sheets. Next, via holes are appropriately formed at predetermined positions of the plurality of ceramic layer forming green sheets using a drilling machine or the like.

Next, using the photosensitive composition described above, a cured film having a predetermined coil pattern is formed on predetermined positions of the plurality of ceramic layer-forming green sheets. As an example, a manufacturing method including the following steps is carried out. Thereby, a cured film having a predetermined pattern can be formed on the surface of the ceramic layer forming green sheet.
Forming step: The photosensitive composition is applied (printed) onto the ceramic layer-forming green sheet and dried to form a film-like body, which is a dried body of the photosensitive composition.
Exposure step: The filmy body is covered with a photomask having openings of a predetermined pattern, and the part of the filmy body exposed from the openings is exposed to form a cured film on the part of the filmy body.
Development step: The uncured film-like body is removed using a developer.

In forming the cured film, a conventionally known method can be appropriately used. For example, application of the photosensitive composition in the molding step can be performed using various printing methods such as screen printing, a bar coater, and the like. Moreover, drying of the photosensitive composition is preferably carried out at a temperature (typically 50 to 100° C.) below the boiling point of the organic binder and the photocurable resin. Next, in the exposure step, an exposure machine that emits light in a wavelength range of 10 to 500 nm, for example, an ultraviolet irradiation lamp such as a high-pressure mercury lamp, a metal halide lamp, or a xenon lamp can be used. An alkaline aqueous developer can be used as the developer in the development process. As an example of such an aqueous developer, an aqueous sodium hydroxide solution, an aqueous sodium carbonate solution, or the like can be used. The alkali concentration of these water-based developers may be adjusted to, for example, 0.01 to 0.5% by mass.

Next, in manufacturing the multilayer chip inductor 1, the baking process is performed after the developing process. Specifically, a laminate of ceramic green sheets is manufactured by laminating and pressing a plurality of green sheets for forming a ceramic layer on which a cured film is formed. Then, by collectively firing this laminate, the plurality of ceramic green sheets are integrally sintered. As a result, as shown in FIG. 1, the body portion 10 is formed in which the ceramic layer 12 and the conductive layer (the internal electrode layer 14) formed by sintering the cured film are integrated. The sintering temperature (maximum temperature in the sintering treatment) in this step is preferably about 600 to 1000° C., for example.

In manufacturing the multilayer chip inductor 1, the external electrode forming paste is applied to both ends in the left-right direction X of the fired main body 10, and then fired under predetermined conditions. As a result, the multilayer chip inductor 1 having the external electrodes 20 on both ends of the main body 10 is manufactured. In the manufacture of the multilayer chip inductor 1, the photosensitive composition having the structure described above is used to form the internal electrode layers 14, so that the dense and thick internal electrode layers 14 are appropriately formed. Therefore, the manufactured multilayer chip inductor 1 has a low electric resistance and can be suitably used for constructing a high-performance electronic device.

[Test example]
Test examples relating to the technology disclosed herein will be described below. It should be noted that the following description is not intended to limit the technology disclosed herein to those shown in the test examples.

<First test>
1. Preparation of photosensitive composition (1) Sample 1
For this sample, a photosensitive composition was prepared by mixing a conductive powder, an organic binder, a photocurable resin, and an organic dispersion medium. In this sample, a photopolymerization initiator was also added in addition to these main components. First, silver powder ( _D50 particle size: 2 μm) was prepared as a conductive powder.

As organic binders, a cellulose-based water-soluble resin and two types of acrylic water-soluble resins were prepared. The weight average molecular weight of the cellulose-based water-soluble resin is 110,000. The weight average molecular weight of the first acrylic water-soluble resin is 35,000, and the weight average molecular weight of the second acrylic water-soluble resin is 8,000. In addition, in this test, a cellulose-based water-soluble resin having a carboxy group was used. Further, the acrylic water-soluble resin having a weight average molecular weight of 35,000 is represented by the formula of Chemical Formula 1, and has a glass transition point of 90 ° C. and an acid value of 100 mgKOH / g. soft resin was used. On the other hand, for the acrylic water-soluble resin having a weight average molecular weight of 8000, an acrylic water-soluble resin having a glass transition point of 60° C. and an acid value of 95 mgKOH/g represented by the above formula 1 soft resin was used.

Moreover, a urethane acrylate polymer (weight average molecular weight: 9000) and a urethane acrylate oligomer (weight average molecular weight: 2000) were prepared as photocurable resins. In addition, 2-benzyl-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone and 2,4-diethylthioxanthone are used as the photopolymerization initiator so that the weight average molecular weight becomes 300. I used a mixture of A mixed solvent of dipropylene glycol methyl ether acetate and dihydroterpineol was used as the organic dispersion medium.

Then, a photosensitive composition of Sample 1 was prepared by weighing and then mixing the above components. Specifically, first, each organic component (cellulosic water-soluble resin, acrylic water-soluble resin, urethane acrylate polymer, urethane acrylate oligomer, photopolymerization initiator) is weighed so as to have the content ratio shown in Table 1. and dissolved in an organic dispersion medium to prepare a vehicle. Then, the silver powder prepared above and the vehicle prepared above were mixed at a mass ratio of 81:19. As a result, a photosensitive composition (Sample 1) containing 81 wt % silver powder and having a weight average molecular weight Mw of the organic component of 44,067 was prepared. In addition, the mass ratio shown in Table 1 is when the entire photosensitive composition is 100% by mass, and when the total mass ratio shown in Table 1 is less than 100% by mass, other additive components (For example, a polymerization inhibitor, a sensitizer, an anti-gelling agent, an ultraviolet absorber) is contained in a trace amount.

(2) Samples 2-9
A photosensitive composition was prepared under the same conditions as in Sample 1, except that the content of each organic component was adjusted while the total amount of the organic component was maintained at 9 wt%, and the weight average molecular weight Mw of the organic component was changed. prepared (samples 2-9). Table 1 shows the amount of each component added in each of Samples 2-9.

(3) Samples 10-12
A photosensitive composition was prepared by mixing each component under the same conditions as for sample 6 (samples 10 to 12), except that the amount of silver powder added was varied within the range of 79 wt % to 85 wt %. Table 1 or Table 2 shows the amount of each component added in each of Samples 10-12.

(4) Sample 13
A photosensitive composition was prepared under the same conditions as Sample 6, except that a urethane acrylate polymer with a different weight average molecular weight was used (Sample 13). Table 2 shows the amount of each component added in Sample 13. The weight average molecular weight of the urethane acrylate polymer used in Sample 13 is 30,000.

(5) Sample 14
A photosensitive composition was prepared under the same conditions as Sample 6, except that urethane acrylate polymers with different weight average molecular weights were used and the amount of urethane acrylate oligomer (weight average molecular weight: 2000) added was changed ( Sample 14). Table 2 shows the amount of each component added in Sample 14. The weight average molecular weight of the urethane acrylate polymer used in sample 14 is 60,000.

(6) Samples 15-24
Ten kinds of photosensitive compositions were prepared by adjusting the content of each organic component so that the total amount of the organic component varied in the range of 7 wt % to 10 wt % (Samples 15 to 24). Tables 2 and 3 show the amount of each component added in each of Samples 15-24.

2. Evaluation test In this test, composites in which a cured film was formed on a green sheet were produced using the photosensitive compositions of Samples 1 to 24, and printability evaluation, residue evaluation, and peelability evaluation were performed. The procedure for each evaluation will be described below.

(1) Fabrication of Composite First, the photosensitive compositions (Samples 1 to 24) were applied to commercially available ceramic green sheets in a size of 4 cm×4 cm using screen printing. Next, this was dried at 60° C. for 15 minutes to form a film-like body (solid film) on the green sheet (forming step). Next, after covering the filmy body with a photomask having openings in a predetermined pattern, light is irradiated with an exposure machine under the conditions of an illuminance of 50 mW/cm ² and an exposure amount of 200 mJ/cm ² to expose the exposed portion. was cured (exposure step). At this time, the pattern of openings formed in the photomask is such that linear openings are formed in parallel at predetermined intervals. A photomask in which the ratio L/S (line/space) of the width of the opening (the width of the cured film) and the width of the interval between the adjacent openings (the interval of the cured film) is set to 20 μm/20 μm. It was used.

Next, a 0.1% by mass alkaline Na ₂ CO ₃ aqueous solution (developer) was sprayed onto the surface of the ceramic green sheet until the breaking point (BP) +5 seconds was reached (development step). In addition, B. P. was the time until the unexposed film-like material was removed with a 0.1% by mass alkaline developer and the removal of the film-like material could be visually confirmed. Then, the ceramic green sheet from which the unexposed film-like body was removed was washed with pure water and dried at room temperature. As a result, a composite was obtained in which a cured film was formed on the ceramic green sheet with a wiring pattern of L/S=20 μm/20 μm.

(2) Printability Evaluation Visual observation of a total of 20 fields of view was performed with an optical microscope on the film-like body (solid film) formed in the molding process. Then, the printability of each sample was evaluated by examining whether or not there was a step on the film surface and whether or not the base material was exposed. In addition, the “step on the film surface” is a portion observed in white when observed with an optical microscope as shown in FIG. 2 . If the concave portion of the step is arranged in the cured film after photocuring, it may cause an increase in resistance or disconnection due to insufficient film thickness. Moreover, when a photosensitive composition having suitable printability is used, a filmy body having a uniform thickness is formed in all regions as shown in FIG. The results of such visual observation are shown in the column of "printability evaluation" in Table 1. In addition, the evaluation criteria in this evaluation are as follows.
"A": No step on the film surface or exposure of the base material was observed in any field of view.
"◯": Steps on the film surface were observed in one field of view.
“Δ”: Steps on the film surface were observed in two or more fields of view.
"X": Exposure of the substrate was confirmed in one or more fields of view.

(3) Evaluation of Residue After the development step, the intervals between the wiring patterns of the cured film formed were visually observed with an optical microscope for a total of 20 fields. Then, it was confirmed whether or not a part of the film-like body which was not removed remained (whether or not there was a residue). The results are shown in the column of "Residue evaluation" in Table 1. The evaluation criteria in this evaluation are as follows.
"A": No residue was observed in 20 visual fields.
"◯": A residue was confirmed in one field of view.
"Δ": Residues were observed in 2 or more and 4 or less visual fields.
"x": Residue was confirmed in five or less visual fields.

(4) Evaluation of Peelability Samples evaluated to be able to form a cured film to some extent in the evaluation of printability (samples with a printability evaluation of "O" or higher) were subjected to peelability evaluation. Specifically, three types of photomasks (L/S=15 μm/15 μm, 20 μm/20 μm, 25 μm/25 μm) with different wiring pattern L/S are prepared, and each photomask is used to obtain a predetermined A cured film having a wiring pattern was formed on the ceramic green sheet. In the development process in this evaluation, the development time was set to the break point (B.P.) + 5 seconds in consideration of the development margin. Except for this point, the composite was produced in the same procedure as in "(1) Preparation of composite" above.

Next, each wiring pattern prepared above was observed with an optical microscope for a total of 10 fields of view, and the presence or absence of peeling was confirmed from the obtained observation images. Then, the smallest L/S where peeling was not confirmed was examined. Moreover, based on this result, the following index evaluated. The results are shown in the column of "Peelability Evaluation" in Table 1. In addition, the evaluation criteria are as follows.
"A": The minimum L/S at which peeling was not confirmed was 15 µm/15 µm.
"◯": The minimum L/S at which peeling was not confirmed was 20 μm/20 μm.
"Poor": Peeling was confirmed even when L/S was 25 μm/25 μm.

As shown in the residue evaluation and peelability evaluation in Table 1, in Samples 3 to 8 and 10 to 24, the unexposed filmy material was properly removed, and the exposed filmy material was properly exposed to light. A precise pattern was formed effectively without peeling. Furthermore, as shown in the evaluation of printability, suitable printability was confirmed in all of Samples 3-8 and 10-24. From these experimental results, if a urethane acrylate resin obtained by mixing a urethane acrylate polymer and a urethane acrylate oligomer is used as a photocurable resin and the weight average molecular weight Mw of the organic component is adjusted to 10,000 or more and 32,000 or less, high It has been found that electronic parts can be stably produced even when a concentration of conductive powder is contained.

Moreover, among the samples 3 to 8 described above, samples 5 to 7 were confirmed to have particularly favorable printability. From this, it was found that the weight average molecular weight Mw of the organic component is preferably 18,000 or more and 25,000 or less from the viewpoint of improving printability. Moreover, as shown in samples 6 and 10 to 12, it was found that even when the concentration of the conductive powder was increased to 85% by mass, low-resistance electronic components could be sufficiently manufactured. However, from the viewpoint of ensuring more suitable printability, it was found that the concentration of the conductive powder is preferably 81% by mass or less. Furthermore, as shown in Sample 13, even when a high molecular weight urethane acrylate polymer having a weight average molecular weight of 30,000 is used, appropriate printability can be obtained by adjusting the weight average molecular weight Mw of the entire organic component to 32,000 or less. was found to be able to ensure

<Second test>
1. Preparation of Photosensitive Composition In this test, a photosensitive composition was prepared under the same conditions as for Sample 5 above, except that the components of the organic dispersion medium were changed. The organic dispersion medium used in each sample is described below.

(1) Sample 25
In this sample, a mixed solvent of dipropylene glycol methyl ether acetate (DPMA) and dihydroterpineol (DHT) was first prepared as in sample 5 above. Then, benzyl alcohol (alcohol-based solvent) was added to this mixed solvent to prepare an organic dispersion medium in which 10% of the organic dispersion medium used in sample 5 was replaced with benzyl alcohol.

(2) Sample 26
In this sample, an organic dispersion medium was prepared in the same manner as for sample 25, except that benzyl alcohol (alcohol-based solvent) was changed to propylene glycol phenyl ether (glycol ether-based solvent). That is, the organic dispersion medium used in sample 26 was obtained by substituting 10% of the organic dispersion medium used in sample 5 with propylene glycol phenyl ether.

(3) Sample 27
In this sample, an organic dispersion medium was prepared in the same manner as for sample 25, except that benzyl alcohol (alcohol-based solvent) was changed to solvent naphtha (petroleum-based solvent). That is, the organic dispersion medium used in sample 27 was obtained by substituting 10% of the organic dispersion medium used in sample 5 with solvent naphtha.

(4) Sample 28
In this sample, the procedure was the same as for sample 25, except that benzyl alcohol (alcohol solvent) was changed to 2,2,4-trimethyl-1,3-pentadiol monoisobutyrate (ester solvent). An organic dispersion medium was prepared. That is, the organic dispersion medium used in sample 27 was obtained by substituting 10% of the organic dispersion medium used in sample 5 with 2,2,4-trimethyl-1,3-pentadiol monoisobutyrate.

(5) Sample 29
In this sample, instead of the "mixed solvent of DPMA and DHT" used in sample 5, a "mixed solvent of propylene glycol phenyl ether and terpineol" was used as the organic dispersion medium.

Samples 25 to 29 are photosensitive compositions prepared in the same manner as Sample 5, except that the organic dispersion medium was changed.

2. Evaluation Test The photosensitive compositions of Samples 25 to 29 were subjected to printability evaluation, residue evaluation, and peelability evaluation according to the same procedures as in the first test. Table 4 lists the results of each evaluation test.

First, as shown in Table 4, it was confirmed that Samples 25 to 28, like Sample 5 (see Table 1), showed favorable results in each of printability evaluation, residue evaluation, and peelability evaluation. From this experimental result, the organic dispersion medium in the photosensitive composition disclosed herein is within a range of 10% by mass or less with respect to the total amount of the organic dispersion medium, glycol ether solvent and alcohol solvent. It was confirmed that a solvent other than the mixed solvent with may also be included. Moreover, as shown in Sample 29, even when a mixed solvent of propylene glycol phenyl ether and terpineol was used instead of a mixed solvent of DPMA and DHT, favorable results were obtained for each of printability evaluation, residue evaluation, and peelability evaluation. It was confirmed that From this, it was found that a mixed solvent of a glycol ether solvent and an alcohol solvent can be widely used as the organic dispersion medium in the photosensitive composition disclosed herein.

Although the present invention has been described in detail above, these are merely examples, and the present invention can be modified in various ways without departing from the scope of the invention.

REFERENCE SIGNS LIST 1 multilayer chip inductor 10 main body 12 ceramic layer 14 internal electrode layer 20 external electrode

Claims (12)

A photosensitive composition containing an inorganic component, an organic component and an organic dispersion medium and used for forming a conductive layer,
The inorganic component includes a conductive powder,
The organic component includes an organic binder and a photocurable resin,
The organic dispersion medium contains a mixed solvent of a glycol ether solvent and an alcohol solvent,
When the total weight of the photosensitive composition is 100% by mass, the content of the conductive powder is 74% by mass or more, and the content of the organic component is 7% by mass or more and 10% by mass or less. ,
The weight average molecular weight Mw of the organic component is 10000 or more and 32000 or less,
The photocurable resin is
A urethane (meth)acrylate polymer having a (meth)acryloyl group and a urethane bond and having a weight average molecular weight of 6000 or more, and a urethane (meth)acryloyl group and a urethane bond having a weight average molecular weight of less than 6000 ( and a meth)acrylate oligomer. 2. The photosensitive composition of claim 1, wherein said conductive powder comprises silver-based particles. 3. The photosensitive composition according to claim 1, wherein the content of said conductive powder is 79% by mass or more when the total weight of said photosensitive composition is 100% by mass. 4. The photosensitive composition according to any one of claims 1 to 3, wherein the organic component has a weight average molecular weight Mw of 25,000 or less. The photosensitive composition according to any one of claims 1 to 4, wherein the organic binder comprises a cellulosic compound. The photosensitive composition according to any one of claims 1 to 5, wherein the urethane (meth)acrylate oligomer has an average weight molecular weight Mw of 500 or more and 5000 or less. 7. The photosensitive composition according to any one of claims 1 to 6, wherein the organic binder has an average weight molecular weight Mw of 20,000 or more and 60,000 or less. The photosensitive composition according to any one of claims 1 to 7, wherein the organic component further comprises a photopolymerization initiator. A method for producing a photosensitive composition used to form a conductive layer, comprising:
an inorganic component weighing step of weighing an inorganic component containing a conductive powder;
an organic component weighing step of weighing an organic component including an organic binder and a photocurable resin;
A mixing step of mixing the inorganic component, the organic component, and an organic dispersion medium containing a mixed solvent of a glycol ether solvent and an alcohol solvent,
In the inorganic component weighing step, weighing the conductive powder so that the content of the conductive powder is 74% by mass or more when the total weight of the photosensitive composition is 100% by mass;
In the organic component weighing step, the content of the organic component is 7% by mass or more and 10% by mass or less when the total weight of the photosensitive composition is 100% by mass, and the weight average molecular weight Mw of the organic component is 10000 or more and 32000 or less, and the photocurable resin is a urethane (meth)acrylate polymer having a (meth)acryloyl group and a urethane bond and having a weight average molecular weight Mw of 6000 or more. and a photocurable resin containing a urethane (meth)acrylate oligomer having a (meth)acryloyl group and a urethane bond and having a weight average molecular weight Mw of less than 6,000. green sheet and
A cured film disposed on the green sheet and photocured from the photosensitive composition according to any one of claims 1 to 8;
A complex comprising: An electronic component comprising a conductive layer comprising a fired body of the photosensitive composition according to any one of claims 1 to 8. The photosensitive composition according to any one of claims 1 to 8 is applied onto a substrate, exposed, developed, and then baked to form a conductive layer composed of a baked body of the photosensitive composition. A method of manufacturing an electronic component, comprising the step of

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