JP7607066B2 - Photosensitive composition and its use - Google Patents

Description

This disclosure relates to a photosensitive composition and its use.

For example, electronic materials such as multilayer chip inductors include a circuit board in which a conductive film (wiring conductor) of a predetermined pattern is formed on a substrate. For example, Patent Document 1 discloses a conductive composition containing a partial hydrolysis condensate of tetraalkoxysilane from the viewpoint of obtaining a conductive film with high heat resistance.

On the other hand, in recent years, there has been a demand for further thinning of the conductor film, and a method (typically a photolithography method) of producing a conductor film by utilizing a photochemical action using a composition containing a photopolymerizable compound and conductive particles (hereinafter referred to as a "photosensitive composition") is preferably used. In this method, a pre-prepared photosensitive composition is first applied to a substrate and dried. Next, the applied composition is exposed to light and cured (reacted). At this time, a wiring circuit of a desired pattern can be drawn by controlling the exposed area using a photomask or the like. Thereafter, the uncured part shielded by the photomask is removed by washing with a developer. Finally, the substrate is baked at a predetermined temperature to produce (baked) the cured part, i.e., a patterned photocured film, on the surface of the substrate. According to this method, a conductor film of a fine pattern can be produced relatively easily on the substrate. For example, Patent Document 2 discloses a photosensitive composition suitable for such an application.

Patent No. 4965232 Patent No. 4660991

However, according to the study by the present inventors, it has been found that, for example, when the photosensitive composition as described above is fired at a high temperature (for example, about 800°C to 900°C), the higher the firing temperature, the larger the volume of the resulting conductor film (hereinafter, such a phenomenon is also simply referred to as "inverted expansion"). In such cases, the conductivity of the conductor film may decrease, or cracks may occur in the conductor film during firing, which is undesirable from the viewpoint of the performance of electronic materials. There is also a demand for further reducing the resistance of such conductor films.

The present disclosure has been made in view of the above circumstances, and its main objective is to provide a photosensitive composition that can effectively suppress inversion expansion of a conductor film, for example, during high-temperature firing, and can effectively reduce the resistance of the conductor film and prevent cracks. Another objective is to provide such a conductor film and an electronic material that includes the conductor film.

（式Ｉ中のＲ^１～Ｒ^６は互いに独立し、それぞれ、アルキル基、フェニル基、ポリエーテル基、アラルキル基、フロロアルキル基、脂肪酸エステル基、または脂肪酸アミド基が挿入された基を表す。また、ｍ、ｎは互いに独立した０以上の整数を表す。）
で表され、上記シリコーン樹脂は、上記導電性粒子の全重量を１００％としたとき、０．０５％～１．０％含まれる、感光性組成物を提供する。詳細については後述するが、上記式（Ｉ）で表されるシリコーン樹脂を、上記範囲内で含有する感光性組成物によると、例えば高温焼成時における導体膜の反転膨張を好適に抑制することができ、かつ、導体膜の低抵抗化やクラックの防止を好適に実現することができる。 In order to achieve this object, the present disclosure provides a photosensitive composition comprising conductive particles, a photopolymerizable compound, and a silicone resin, the silicone resin being represented by the following formula (I):

(R ¹ to R ⁶ in formula I are each independently an alkyl group, a phenyl group, a polyether group, an aralkyl group, a fluoroalkyl group, a fatty acid ester group, or a group having a fatty acid amide group inserted therein. Furthermore, m and n are each independently an integer of 0 or more.)
and the silicone resin is contained in an amount of 0.05% to 1.0% when the total weight of the conductive particles is taken as 100%. Although details will be described later, a photosensitive composition containing the silicone resin represented by formula (I) within the above range can suitably suppress inversion expansion of a conductive film during high-temperature firing, for example, and can suitably achieve low resistance of the conductive film and prevention of cracks.

Preferred examples of the silicone resin include polydimethylsiloxane, poly(methylphenylsiloxane), and side-chain polyether-modified polysiloxane. In embodiments using these types of silicone resin as the silicone resin, the above-mentioned effects can be more favorably obtained.

In a preferred embodiment of the photosensitive composition disclosed herein, the weight average molecular weight of the silicone resin is 1,000 to 100,000. In an embodiment in which a silicone resin having a weight average molecular weight within the above range is used as the silicone resin, the above-mentioned effects can be more suitably obtained.

In a preferred embodiment of the photosensitive composition disclosed herein, the conductive particles have an average particle size of 1 μm to 5 μm. In an embodiment using conductive particles with an average particle size of 1 μm to 5 μm, in addition to the effects described above, thinning of the conductor film can be more suitably achieved.

In a preferred embodiment of the photosensitive composition disclosed herein, the conductive particles have a brightness L* of 50 or more in the L*a*b color system based on JIS Z 8781. In an embodiment containing conductive particles with a brightness L* of 50 or more, the irradiated light can stably reach deep into the conductive film before curing, so that the conductive film can be formed more stably.

The photosensitive composition disclosed herein can be used, for example, to form electrodes on ceramic green sheets.

The photosensitive composition disclosed herein can be used to form fine lines, for example lines with widths of 30 μm or less.

From another aspect, a conductor film made of a sintered body of any of the photosensitive compositions disclosed herein is provided. Furthermore, an electronic material is provided that includes a conductor film made of a sintered body of any of the photosensitive compositions disclosed herein. Such an electronic material can be said to be a high-quality electronic material because it includes a conductor film in which inversion expansion during high-temperature sintering is suitably suppressed and low resistance is suitably achieved, for example.

1 is a cross-sectional view showing a schematic structure of an electronic material (multilayer chip inductor) according to one embodiment. 11A to 11C are explanatory diagrams for explaining a method for manufacturing an electronic material (multilayer chip inductor) according to another embodiment. 13 is a SEM image showing the electrode surface at 900° C. for Example 14 of the Test Example. 1 is a SEM image showing the electrode surface at 900° C. sintering according to Example 3 of the Test Example. 13 is a SEM image showing the electrode surface at 900° C. sintering according to Example 4 of the Test Example. 13 is a SEM image showing the electrode surface at 900° C. for Example 6 of the Test Example. 13 is a SEM image showing the electrode surface at 900° C. sintering according to Example 8 of the Test Example.

The following describes preferred embodiments of the present disclosure. Matters other than those specifically mentioned in this specification that are necessary for implementing the present disclosure can be understood as design matters for a person skilled in the art based on the conventional technology in the field. The present disclosure can be implemented based on the contents disclosed in this specification and the technical common sense in the field. The following embodiments are not intended to limit the technology disclosed herein to such embodiments. In the following drawings, dimensional relationships (length, width, thickness, etc.) do not reflect actual dimensional relationships, and do not limit the present disclosure unless otherwise specified. In this specification and claims, when a certain numerical range is described as A to B (A and B are arbitrary numerical values), it means A or more and B or less. Therefore, it includes cases where it is greater than A and less than B.

In addition, when we say "conductive particles," we mean a group of many fine particles (i.e., particles), except when referring to a single particle. In Japanese, it is unclear whether to use the singular or plural form, so we have defined it as above to clarify the meaning of "conductive particles." In this specification, the term "paste" is a concept that includes slurry-like compositions and ink-like compositions.

（式Ｉ中のＲ^１～Ｒ^６は互いに独立し、それぞれ、アルキル基、フェニル基、ポリエーテル基、アラルキル基、フロロアルキル基、脂肪酸エステル基、または脂肪酸アミド基が挿入された基を表す。また、ｍ、ｎは互いに独立した０以上の整数を表す。）で表される。そして、上記シリコーン樹脂は、上記導電性粒子の全重量を１００％としたとき、０．０５％～１．０％含まれる。 <Photosensitive composition>
The photosensitive composition disclosed herein includes conductive particles, a photopolymerizable compound, and a silicone resin. The silicone resin is represented by the following formula (I):

(R ¹ to R ⁶ in formula I are each independent of one another and each independently represent an alkyl group, a phenyl group, a polyether group, an aralkyl group, a fluoroalkyl group, a fatty acid ester group, or a group having a fatty acid amide group inserted therein. Also, m and n are each independent of one another and each represent an integer of 0 or more.) The silicone resin is contained in an amount of 0.05% to 1.0% when the total weight of the conductive particles is taken as 100%.

As a result of intensive research by the present inventors, it was found that silicone resin functions as a sintering aid for conductive particles when sintering and grain growth between conductive particles progresses during high-temperature firing at, for example, 800°C to 900°C. Furthermore, it was found that when a silicone resin with low compatibility (in other words, low reactivity) with resins such as the photopolymerizable resins listed above is used, the opportunity for contact with conductive particles increases, so it functions favorably as a sintering aid for conductive particles. Furthermore, as a result of further examining various blending ratios of conductive particles and silicone resin, it was found that, from the viewpoint of favorably obtaining the above-mentioned effects, the silicone resin is preferably contained at a ratio of 0.05% to 1.0% when the total weight of the conductive particles is taken as 100%. In other words, it was found that a photosensitive composition containing the silicone resin represented by the above formula (I) within the above range can favorably realize low resistance and prevention of cracks in the obtained conductor film, because the conductive particles are sintered densely with few voids during high-temperature firing. In addition, it was also discovered that with this configuration, as the firing temperature increases, the conductive particles sinter and grow, so that the inversion expansion of the resulting conductor film is suitably suppressed. Note that the above explanation is the inventor's consideration based on experimental results, and the technology disclosed here should not be interpreted as being limited to the above mechanism. Each component will be described in detail below.

<Conductive particles>
The photosensitive composition disclosed herein contains conductive particles. The conductive particles are materials for mainly forming layers with high electrical conductivity (hereinafter simply referred to as "conductivity") such as electrodes, conductors, and conductive films in electronic materials. The type of conductive particles is not particularly limited, and one or more types of conductive particles may be used in appropriate combination from among those conventionally known. Examples of types of conductive particles include simple noble metals such as silver (Ag), platinum (Pt), gold (Au), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os), simple base metals such as nickel (Ni), aluminum (Al), copper (Cu), tungsten (W), and molybdenum (Mo), carbonaceous materials such as carbon black, and mixtures and alloys thereof. Among these, silver (silver particles) can be preferably used from the viewpoint of suitably obtaining an electronic material having a dense and low-resistance conductive film. Examples of the alloy include a silver-palladium (Ag-Pd) alloy, a silver-platinum (Ag-Pt) alloy, and a silver-copper (Ag-Cu) alloy. Core-shell particles having a core made of the above-mentioned metal and a shell covering the core can also be used. As the conductive particles described above, for example, commercially available particles can be used.

The average particle diameter of the conductive particles is not particularly limited as long as the effect of the technology disclosed herein can be obtained. The lower limit of the average particle diameter of the conductive particles is, for example, 0.1 μm or more, and from the viewpoint of suitably suppressing aggregation between conductive particles, it is preferably 0.5 μm or more, and more preferably 1 μm or more. The upper limit of the average particle diameter of the conductive particles is, for example, 10 μm or less, and from the viewpoint of suitably realizing thinning of the conductor film, it is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 2 μm or less. The average particle diameter of the conductive particles is preferably, for example, in the range of 1 μm to 5 μm. The "average particle diameter" of the conductive particles means a particle diameter (D50 particle diameter) equivalent to 50% of the cumulative value from the small particle diameter side in the volume-based particle size distribution based on the laser diffraction/scattering method. Such a measurement can be performed, for example, using a commercially available device, Microtrack MT3000II manufactured by Microtrack Bell Co., Ltd.

Although not particularly limited, the conductive particles as a whole may have a lightness L* of 50 or more in the L*a*b* color system based on JIS Z 8781:2013. This allows the irradiated light to reach deep into the conductive film before curing, and a thick conductive film, for example, with a film thickness of 5 μm or more, or even 10 μm or more, can be stably realized. From the above viewpoint, the lightness L* of the conductive particles may be approximately 55 or more, for example 60 or more. The lightness L* can be adjusted, for example, by the type and average particle diameter of the conductive particles. The lightness L* can be measured, for example, with a spectrophotometer conforming to JIS Z 8722:2009.

Although not particularly limited, the proportion of the conductive particles in the entire photosensitive composition (in other words, the proportion of the conductive particles when the entire photosensitive composition is taken as 100% by weight) is preferably approximately 50% by weight or more, typically 60 to 95% by weight, for example 70 to 90% by weight. By satisfying the above range, a conductive film with excellent density and electrical conductivity can be formed. In addition, the handleability of the photosensitive composition and the workability when forming the conductive film can be improved.

<Photopolymerizable Compound>
The photosensitive composition disclosed herein includes a photopolymerizable compound. The photopolymerizable compound is a photocurable component that undergoes a polymerization reaction, a crosslinking reaction, or the like, and hardens due to an active species generated by the decomposition of a photopolymerization initiator, which will be described later. The polymerization reaction may be, for example, addition polymerization or ring-opening polymerization. The photopolymerizable compound is not particularly limited, and one or more types may be appropriately selected from conventionally known compounds according to, for example, the purpose and the type of substrate, and used. The photopolymerizable compound typically has one or more unsaturated bonds and/or cyclic structures. Suitable examples of the photopolymerizable compound include radically polymerizable compounds having one or more ethylenically unsaturated bonds, such as (meth)acryloyl groups and vinyl groups, and cationic polymerizable compounds having a cyclic structure, such as epoxy groups. In this specification and claims, the term "photopolymerizable compound" includes photopolymerizable polymers, photopolymerizable oligomers, and photopolymerizable monomers.

The photosensitive composition disclosed herein may contain a photopolymerizable polymer as a photopolymerizable compound. The photopolymerizable polymer can be cured with a relatively small amount of exposure compared to monomers and oligomers. Therefore, it is possible to stably cure the deep part of the exposed part (the part close to the substrate). Therefore, by including a photopolymerizable polymer, the adhesion between the substrate and the conductive film is increased, and the occurrence of defects such as peeling and disconnection in the conductive film can be suitably suppressed. In addition, the water resistance and durability of the conductive film can be improved. In addition, when the photopolymerizable compound includes a photopolymerizable polymer, the adhesion (tackiness) to the substrate is increased, and the removability of the unexposed part in the development process is reduced. The weight average molecular weight of the photopolymerizable polymer is generally larger than 5,000, typically 10,000 or more, for example 15,000 or more, 20,000 or more, and may be generally 100,000 or less, for example 50,000 or less. It is preferable that the photopolymerizable compound further contains at least one of a photopolymerizable monomer and a photopolymerizable oligomer in addition to the photopolymerizable polymer. Although not particularly limited, the weight average molecular weight of the photopolymerizable monomer can be, for example, less than about 500, and the weight average molecular weight of the photopolymerizable oligomer can be, for example, about 500 to 5000. In this specification and claims, "weight average molecular weight" refers to the weight-based average molecular weight measured by gel permeation chromatography (GPC) and converted using a standard polystyrene calibration curve.

In a preferred embodiment, the photopolymerizable compound contains a (meth)acrylate having a (meth)acryloyl group. For example, the photopolymerizable compound may contain a (meth)acrylate polymer as the photopolymerizable polymer, a (meth)acrylate monomer as the photopolymerizable monomer, or a (meth)acrylate oligomer as the photopolymerizable oligomer. By containing a (meth)acrylate in the photopolymerizable compound, the flexibility of the conductor film and its conformity to the substrate can be improved. As a result, the occurrence of defects such as peeling and disconnection can be better suppressed. As a preferred example of the (meth)acrylate polymer, there is a homopolymer of an alkyl (meth)acrylate, or a copolymer containing a sub-monomer having copolymerizability with the main monomer, with an alkyl (meth)acrylate as the main monomer. In this specification, "(meth)acryloyl" includes "methacryloyl" and "acryloyl", and "(meth)acrylate" includes "methacrylate" and "acrylate".

In another preferred embodiment, the photopolymerizable compound contains a photopolymerizable compound (urethane bond-containing compound) having a urethane bond (-NH-C(=O)-O-). For example, the photopolymerizable compound may contain a urethane bond-containing polymer having a urethane bond as the photopolymerizable polymer, a urethane bond-containing monomer having a urethane bond as the photopolymerizable monomer, or a urethane bond-containing oligomer having a urethane bond as the photopolymerizable oligomer. By containing a urethane bond-containing compound in the photopolymerizable compound, the etching resistance of the exposed portion can be improved and a conductive film having even better flexibility and stretchability can be realized. Therefore, the adhesion between the substrate and the conductive film can be improved, and the occurrence of defects such as peeling and disconnection can be suppressed to a high level. Suitable examples of the urethane bond-containing compound include urethane-modified (meth)acrylate, urethane-modified epoxy, and polyfunctional urethane (meth)acrylate. In addition, as the (meth)acrylate-containing compound and the urethane bond-containing compound as described above, commercially available compounds can be used without any particular restrictions.

Although not particularly limited, when the photopolymerizable compound contains a photopolymerizable polymer, the ratio of the photopolymerizable polymer to the entire photopolymerizable compound may be, on a weight basis, approximately 10% by weight or more, typically 20% by weight or more, for example 30% by weight or more, and may be approximately 90% by weight or less, typically 80% by weight or less, for example 70% by weight or less. When the above range is satisfied, the effect of the technology disclosed herein is exerted at a high level. Also, although not particularly limited, when the photopolymerizable compound contains at least one of a photopolymerizable monomer and a photopolymerizable oligomer, the ratio of the photopolymerizable monomer and/or the photopolymerizable oligomer to the entire photopolymerizable compound may be, on a weight basis, approximately 10% by weight or more, typically 20% by weight or more, for example 50% by weight or more, and may be approximately 90% by weight or less, typically 80% by weight or less, for example 70% by weight or less.

Although not particularly limited, the ratio of the photopolymerizable compound to the entire photosensitive composition may be approximately 0.1 to 20% by weight, typically 0.5 to 10% by weight, for example 1 to 5% by weight. In addition, although not particularly limited, the content ratio of the photopolymerizable compound may be approximately 0.1 to 20 parts by weight, for example 0.5 to 10 parts by weight, per 100 parts by weight of the conductive particles. By satisfying the above range, the photocurability of the photosensitive composition is suitably exhibited, and a conductive film can be formed stably at a high level.

<Silicone resin>
The photosensitive composition disclosed herein contains a silicone resin represented by the following formula (I). In this case, R ¹ to R ⁶ in the following formula (I) are independent of each other and each represents a group having an alkyl group, a phenyl group, a polyether group, an aralkyl group, a fluoroalkyl group, a fatty acid ester group, or a fatty acid amide group inserted therein. Furthermore, m and n each represent an integer of 0 or more, which are independent of each other. The photosensitive composition disclosed herein may contain one or more silicone resins represented by the following formula (I). As the silicone resin, one having a main skeleton formed by a siloxane bond (Si—O—Si) can be preferably used.

Here, the alkyl group may be linear or branched. Although not particularly limited, the number of carbon atoms of such an alkyl group is, for example, 1 to 12, preferably 1 to 6, and more preferably 1 to 3. Furthermore, although not particularly limited, in a polyether group (typically represented as -R(C ₂ H ₄ O) _a (C ₃ H ₆ O) _b R', where a and b are integers of 0 or more independent of each other), a+b may be, for example, 1≦a+b≦80, 2≦a+b≦70, 3≦a+b≦60, or 5≦a+b≦50. Furthermore, the number of carbon atoms of R and R' may be, for example, 1 to 12, or may be 1 to 6 or 1 to 3. The number of carbon atoms of such R and R' may be the same or different. Although not particularly limited, in a fatty acid ester group (typically represented as -OCOR), the number of carbon atoms in R is, for example, 1 to 12, and may be 1 to 6 or 1 to 3. Furthermore, although not particularly limited, in a fatty acid amide group (typically represented as -RNHCOR'), the number of carbon atoms in R and R' is, for example, 1 to 12, and may be 1 to 6 or 1 to 3. The number of carbon atoms in R and R' may be the same or different. Furthermore, the combination of R ¹ to R ⁶ may be, for example, a combination of a polyether group, an alkyl group, and an aralkyl group, or a combination of an alkyl group and an aralkyl group.

Examples of the silicone resin include polydimethylsiloxane; side-chain phenyl-modified polysiloxanes such as poly(methylphenylsiloxane) (specifically, a polysiloxane in which R ¹ , R ³ , R ⁵ , and R ⁶ in the above formula (I) are methyl groups, and R ² and R ⁴ in the above formula (I) are phenyl groups), poly(dimethylsiloxane-co-diphenylsiloxane) (specifically, a polysiloxane in which R ¹ , R ² , R ⁵ , and R ⁶ in the above formula (I) are methyl groups, and R ³ and R ⁴ in the above formula (I) are phenyl groups), and poly(dimethylsiloxane-co-methylphenylsiloxane) (specifically, a polysiloxane in which R ¹ , R ² , R ³ , R ⁵ , and R ⁶ in the above formula (I) are methyl groups, and R ⁴ in the above formula (I) is a phenyl group); and side-chain polyether-modified polysiloxanes (specifically, a polysiloxane in which R ⁵ and R polysiloxanes in which R 5 and R ⁶ are methyl groups and at least one of R ¹ , R ² , R ³ and R ⁴ is substituted with a polyether group), side-chain fluoroalkyl-modified polysiloxanes (specifically, polysiloxanes in which R ⁵ and R ⁶ in the above formula (I) are methyl groups and at least one of R ¹ , R ² , R ³ and R ⁴ is substituted with a fluoroalkyl group), side-chain fatty acid ester-modified polysiloxanes (specifically, polysiloxanes in which R ⁵ and R ⁶ in the above formula (I) are methyl groups and at least one of R ¹ , R ² , R ³ and R ⁴ is substituted with a fatty acid ester group), side-chain fatty acid amide-modified polysiloxanes (specifically, polysiloxanes in which R ⁵ and R ⁶ in the above formula (I) are methyl groups and at least one of R ¹ , R ² , R ³ and R side-chain modified polysiloxanes in which at least one of R ¹ , R ² , R ³ , and R ⁴ is substituted with a fatty acid amide group); one-end polyether modified siloxanes (specifically, polysiloxanes in which R 1 , R 2 , R 3 , and R ⁴ in the above formula (I) are substituted with a methyl group, and one of R ⁵ and R ⁶ is substituted with a polyether group. The end on the unsubstituted side can be, for example, a substituent other than a polyether group among the substituents listed above); both-end polyether modified siloxanes (specifically, polysiloxanes in which R ¹ , R ² , R ³ , and R ⁴ in the above formula (I) are substituted with a methyl group, and R ⁵ and R ⁶ are substituted with a polyether group), and the like. Among these, from the viewpoint of more suitably realizing the suppression of inversion expansion and the reduction of resistance of the conductor film, polydimethylsiloxane, poly(methylphenylsiloxane), and side-chain polyether modified polysiloxanes can be preferably used. As described above, m and n in the formula (I) each represent an integer of 0 or more, independent of each other. m and n may be the same or different from each other. Although not particularly limited, m+m may be, for example, 1≦m+n≦2000, 1≦m+n≦1500, or 1≦m+n≦1000. As the silicone resin, for example, one that is not photocurable can be more preferably used. As the silicone resin, commercially available ones can be used without any particular restrictions. As the silicone resin, for example, one manufactured by Shin-Etsu Chemical Co., Ltd., Dow Toray Co., Ltd., BYK-Chemie, and Asahi Kasei Corporation can be used.

The weight average molecular weight of the silicone resin is not particularly limited as long as the effect of the technology disclosed herein is exhibited. The lower limit of the weight average molecular weight of the silicone resin is, for example, 500 or more, and from the viewpoint of suppressing the inversion expansion of the conductor film and reducing the resistance, it is preferably 1000 or more, and may be 5000 or more. The upper limit of the weight average molecular weight of the silicone resin is, for example, 200,000 or less, and from the viewpoint of obtaining the above-mentioned effect, it is preferably 100,000 or less, and may be, for example, 90,000 or less (less than 90,000), 50,000 or less, or 10,000 or less. The weight average molecular weight of the silicone resin is preferably, for example, in the range of 1,000 to 100,000. In addition to the above effect, from the viewpoint of resolution, it is preferably, for example, in the range of 1,000 to 10,000. In addition, from the viewpoint of increasing compatibility with the conductive particles and functioning suitably as a sintering aid for the conductive particles, it is preferable that the silicone resin is liquid or oily, for example, at room temperature (about 20±5°C) and at 1 atmospheric pressure. The silicone resin is preferably a liquid or oily composition that is uniformly dispersed or dissolved in the photosensitive composition. When the silicone resin is liquid or oily, it is preferred because it is more compatible with the conductive particles. Among silicone resins, for example, those that are mainly composed of a straight-chain structure with 2000 or less siloxane bonds are preferably used because they are oily.

In the photosensitive composition disclosed herein, the silicone resin is contained in an amount of 0.05% to 1.0% when the total weight of the conductive particles is taken as 100%. By containing the silicone resin within the above range, it is possible to preferably suppress the inversion expansion of the obtained conductor film and reduce the resistance. In addition, from the viewpoint of more preferably obtaining the above-mentioned effect, the silicone resin may be in the range of 0.1% to 1.0% when the total weight of the conductive particles is taken as 100%, and more preferably in the range of 0.15% to 1.0%, more preferably in the range of 0.15% to 0.8%, and even more preferably in the range of 0.15% to 0.6% when the total weight of the conductive particles is taken as 100%. In addition to the above-mentioned effect, from the viewpoint of preferably obtaining resolution, the silicone resin is preferably in the range of 0.05% to 0.8% when the total weight of the conductive particles is taken as 100%.

<Organic binder>
The photosensitive composition disclosed herein may contain an organic binder in addition to the above components. The organic binder is a component that enhances the adhesion between the substrate and the film-like body (uncured material) before photocuring. As the organic binder, one or more types can be appropriately selected and used from conventionally known ones depending on, for example, the type of substrate and the type of photopolymerizable compound. As the organic binder, one that can be easily removed with an aqueous developer in the development process is preferable. For example, when an alkaline aqueous developer is used in the development process, an alkali-soluble resin or the like can be preferably used. This makes it easier to remove the unexposed part in the development process.

The alkali-soluble resin may have a structural portion with high alkali solubility, for example, an acidic group (acidic functional group) such as a phenolic hydroxyl group, a carboxyl group, a sulfo group, a phosphono group, or a boronic acid group. Carboxyl groups are preferred. The acidic group is a substituent that has a dissociable proton and exhibits acidity in water. The acidic group may be partially esterified. The acidic group may be bonded to a carbon atom in the main chain (a carbon chain with the maximum number of carbon atoms; the same applies below) of the alkali-soluble resin, or may be bonded to a carbon atom in a side chain (a carbon chain branched from the main chain; the same applies below). By including a structural portion with high alkali solubility, the unexposed portion can be removed more quickly and without residue in an alkaline aqueous developer.

In a preferred embodiment, the alkali-soluble resin has an acid value. The acid value of the alkali-soluble resin is, for example, 10 mgKOH/g or more, preferably 20 mgKOH/g or more, more preferably 25 mgKOH/g or more, for example 30 mgKOH/g or more, and is typically smaller than the (meth)acrylic photocurable resin described later, and is approximately 150 mgKOH/g or less, preferably 100 mgKOH/g or less, for example 50 mgKOH/g or less. It is more preferable that the acid value of the entire organic binder is in the above range. In other words, it is preferable that the entire organic binder exhibits a predetermined acidity. When the acid value is a predetermined value or more, the removability of the unexposed portion in the development process is enhanced, and the developability can be improved. In addition, when the acid value is a predetermined value or less, the solubility in the aqueous developer is suppressed, and peeling and disconnection of the exposed portion in the development process can be better suppressed. Therefore, the effect of the technology disclosed herein can be exerted at a higher level. In this specification, "acid value" refers to the amount (mg) of potassium hydroxide (KOH) required to neutralize the free fatty acids contained in a unit sample (1 g). The unit is mgKOH/g.

Suitable examples of organic binders include cellulose-based resins such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and hydroxymethyl cellulose, (meth)acrylic resins, phenolic resins, alkyd resins, polyvinyl alcohol, and polyvinyl butyral. Among them, cellulose-based resins and acrylic resins can be preferably used from the viewpoint of ease of removal in the development process. As described above, these resins preferably have acidic groups and preferably have acid values within the above range. The weight average molecular weight of the organic binder is not particularly limited as long as the effects of the technology disclosed herein are exhibited, but is generally 5,000 to 500,000, and can be within the range of, for example, 7,000 to 200,000 or 10,000 to 150,000. As the organic binder as described above, commercially available ones can be used without any particular restrictions.

When the photosensitive composition contains an organic binder, the proportion of the organic binder in the entire photosensitive composition is not particularly limited, but may be approximately 0.1 to 20% by weight, typically 0.5 to 10% by weight, for example 1 to 5% by weight.

<Dispersion medium>
The photosensitive composition disclosed herein may contain, in addition to the above components, a dispersion medium (e.g., an organic dispersion medium) for dispersing these components. The dispersion medium is a component that imparts appropriate viscosity and fluidity to the photosensitive composition, thereby improving the handleability of the photosensitive composition and improving the workability when forming a conductor film. In addition, from the viewpoint of improving the workability when forming a conductor film, it is preferable that the photosensitive composition is prepared in a paste form using the dispersion medium. As the dispersion medium, one or more types can be appropriately selected from conventionally known ones depending on, for example, the type of photopolymerizable compound, and the like.

Suitable examples of dispersion media include alcohol-based solvents such as terpineol, dihydroterpineol, texanol, 3-methyl-3-methoxybutanol, and benzyl alcohol; glycol-based solvents such as ethylene glycol, propylene glycol, and diethylene glycol; ether-based solvents such as dipropylene glycol methyl ether, methyl cellosolve (ethylene glycol monomethyl ether), cellosolve (ethylene glycol monoethyl ether), ethylene glycol monobutyl ether, and butyl carbitol (diethylene glycol monobutyl ether); ester-based solvents such as diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, butyl glycol acetate, butyl diglycol acetate, butyl cellosolve acetate, butyl carbitol acetate (diethylene glycol monobutyl ether acetate), and isobornyl acetate; hydrocarbon-based solvents such as toluene, xylene, naphtha, and petroleum hydrocarbons; and mineral spirits. As the dispersion medium described above, any commercially available product can be used without any particular restrictions.

Among these, from the viewpoint of improving the storage stability of the photosensitive composition and the ease of handling during the formation of the conductive film, organic solvents with a boiling point of 150°C or higher, and even more preferably 170°C or higher, are preferred. As another preferred example, from the viewpoint of keeping the drying temperature low after printing the conductive film, organic solvents with a boiling point of 250°C or lower, and even more preferably 220°C or lower, are preferred. This makes it possible to improve productivity and reduce production costs.

When the photosensitive composition contains a dispersion medium, the proportion of the dispersion medium in the entire photosensitive composition may be, but is not limited to, approximately 1 to 50% by weight, typically 3 to 30% by weight, for example 5 to 20% by weight. When the photosensitive composition is prepared in the form of a paste containing a dispersion medium, the viscosity of the paste is not particularly limited, but is preferably approximately 10 to 100 mPa·s (for example, approximately 20 to 70 Pa·s). Such a viscosity can be measured, for example, by a commercially available viscometer.

<Photopolymerization initiator>
The photosensitive composition disclosed herein may contain a photopolymerization initiator in addition to the above components. As the photopolymerization initiator, one or more types can be appropriately selected from conventionally known ones depending on the type of photosensitive resin, etc., and can be used. The photopolymerization initiator is a component that decomposes when irradiated with active energy rays such as visible light, ultraviolet light, and electron beams, generates active species such as radicals and cations, and initiates the reaction of the photopolymerizable compound. Suitable examples include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4-diethylthioxanthone, benzophenone, and the like. As the photopolymerization initiator as described above, commercially available ones can be used without any particular restrictions.

Although not particularly limited, the ratio of the photopolymerization initiator to the entire photosensitive composition is generally 0.01 to 5% by weight, typically 0.1 to 4% by weight, for example 0.2 to 3% by weight or 0.3 to 2% by weight. This allows the photocuring properties of the photosensitive composition to be optimally exhibited, and allows the conductive film to be formed more stably.

<Other added ingredients>
The photosensitive composition disclosed herein may further contain various additive components as necessary in addition to the above components, as long as the effect of the technology disclosed herein is not significantly impaired. The additive components may be selected from one or more of conventionally known ones. Examples of additive components include inorganic fillers such as silica (SiO ₂ ) and alumina (Al ₂ O ₃ ), glass particles, photosensitizers, polymerization inhibitors, radical scavengers, antioxidants, ultraviolet absorbers, dispersants (e.g., anionic dispersants, cationic dispersants, nonionic dispersants, etc.), plasticizers, surfactants, leveling agents, thickeners, defoamers, gelling inhibitors, stabilizers, preservatives, pigments, etc. Although not particularly limited, the proportion of additive components in the entire photosensitive composition is generally 5% by weight or less, typically 3% by weight or less, for example 2% by weight or less, and preferably 1% by weight or less.

The photosensitive composition disclosed herein can be used, for example, to form an electrode on a ceramic green sheet (see <<Uses of the Photosensitive Composition>> below). One example of such a type of ceramic green sheet is a ceramic green sheet made of borosilicate glass. In addition, such a ceramic sheet may contain ceramic particles such as alumina or silica as appropriate from the viewpoint of improving heat resistance, etc.

The photosensitive composition disclosed herein can be used to form fine lines with a line width (in other words, line L) of 30 μm or less. Furthermore, it is possible to form a conductor film with a space S of 30 μm or less. In such a case, the film thickness is not particularly limited, but is generally 10 μm or less, and preferably 8 μm or less.

In addition, according to the photosensitive composition disclosed herein, the difference between the disk shrinkage rate A (%) when fired at 800°C and the disk shrinkage rate B (%) when fired at 900°C: B-A (%) can be adjusted to B-A≧-0.5. Here, the "disk shrinkage rate" is a parameter indicating the shrinkage rate of the conductor film, and is a value that can be calculated, for example, by the method described in the test example described later. Here, the volume of the conductor film made of the photosensitive composition can be equal to or reduced as the temperature increases from room temperature (for example, about 25°C) to a certain temperature (for example, about 800°C) due to resin burning out and sintering of the photosensitive composition. On the other hand, in a photosensitive composition with a relatively high resin content of 5% by weight or more or even 7% by weight or more, the volume of the conductor film when fired at about 900°C may be larger (i.e., the shrinkage rate may be smaller) than the volume of the conductor film when fired at about 800°C. This is undesirable because it may cause the conductivity of the conductive film to decrease, or cause a shrinkage difference between the conductive film and the substrate (e.g., a green sheet) which tends to shrink as the firing temperature increases, which may result in peeling of the conductive film from the substrate or cracks. In contrast, the photosensitive composition disclosed herein can suitably suppress such inverted expansion, and thus solve the above-mentioned problems. The more positive the value of B-A, the higher the firing temperature, and it is preferable that B-A>0, and more preferably B-A≧0.5 (e.g., B-A>0.5). The upper limit of the above B-A is not particularly limited as long as the effect of the technology disclosed herein can be obtained, but it may be, for example, B-A≦20, or B-A≦10.

<Uses of the photosensitive composition>
According to the photosensitive composition disclosed herein, a fine-line conductor film can be stably formed. Therefore, the photosensitive composition disclosed herein can be suitably used for forming a conductive film in various electronic materials such as inductance parts, capacitor parts, and multilayer circuit boards. In other words, the present disclosure can provide a conductor film made of a sintered body of the photosensitive composition disclosed herein, or an electronic material having a conductor film made of a sintered body of the photosensitive composition disclosed herein. Such an electronic material can be said to be a high-quality electronic material, since it has a conductor film in which, for example, inversion expansion during high-temperature sintering is suitably suppressed and low resistance is suitably realized.

The electronic materials may be of various mounting types, such as surface mount type and through-hole mount type. The electronic materials may be of laminated type, wire-wound type, or 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, transformers, etc.

An example of an electronic material is a ceramic electronic material. In this specification, the term "ceramic electronic material" refers to electronic materials made of ceramic materials in general, including electronic materials having an amorphous ceramic substrate (glass ceramic substrate) or a crystalline (i.e. non-glass) ceramic substrate in general. Typical examples of ceramic electronic materials include high-frequency filters having a ceramic substrate, ceramic inductors (coils), ceramic capacitors, low-temperature co-fired ceramic substrates (LTCC substrates), and high-temperature co-fired ceramic substrates (HTCC substrates). The ceramic material is not particularly limited, but examples include materials composed of the components listed above as ceramic components.

Figure 1 is a cross-sectional view showing a schematic structure of a multilayer chip inductor 1. Note that the dimensional relationships (length, width, thickness, etc.) in Figure 1 do not necessarily reflect the actual dimensional relationships. Also, the symbols X and Y in the drawing represent the left-right and up-down directions, respectively. However, these are merely directions for the convenience of explanation.

The laminated chip inductor 1 comprises a main body 10 and external electrodes 20 provided on both side surfaces of the main body 10 in the left-right direction X. The laminated chip inductor 1 is, for example, 0603 (0.6 mm x 0.3 mm), 0806 shape (0.8 mm x 0.6 mm), 1608 shape (1.6 mm x 0.8 mm), 2520 shape (2.5 mm x 2.0 mm), etc.

The main body 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. In the vertical direction Y, the internal electrode layer 14 is disposed between the ceramic layers 12. The internal electrode layer 14 is formed using the above-mentioned photosensitive composition. The internal electrode layers 14 adjacent to each other in the vertical direction Y across the ceramic layer 12 are electrically connected through vias 16 provided in the ceramic layer 12. As a result, the internal electrode layer 14 is configured in a three-dimensional spiral shape (spiral shape). Both ends of the internal electrode layer 14 are connected to external electrodes 20.

Such a multilayer chip inductor 1 can be manufactured, for example, by the following procedure. First, a paste containing raw ceramic material, binder resin, and organic solvent is prepared and supplied onto a carrier sheet to form a ceramic green sheet. Next, this ceramic green sheet is rolled and cut to the desired size to obtain multiple green sheets for forming ceramic layers. Next, via holes are appropriately formed at predetermined positions on the multiple green sheets for forming ceramic layers using a drilling machine or the like.

Next, the photosensitive composition is used to form a conductive film of a predetermined coil pattern at a predetermined position on a plurality of green sheets for forming a ceramic layer. As an example, a conductive film in an unfired state can be formed by a manufacturing method including the following steps: (Step S1: Film-like body forming step) A step of forming a conductive film consisting of a dried body of the photosensitive composition by applying the photosensitive composition onto a green sheet for forming a ceramic layer and drying it; (Step S2: Exposure step) A step of covering the conductive film with a photomask having a predetermined opening pattern, exposing the conductive film through the photomask, and partially photocuring the conductive film; (Step S3: Development step) A step of etching the conductive film after photocuring to remove the unexposed parts.

When forming a conductive film using the photosensitive composition, a conventionally known method can be appropriately used. For example, in (step S1), the photosensitive composition can be applied by various printing methods such as screen printing, or by using a bar coater. The photosensitive composition can be dried at a temperature below the boiling point of the photopolymerizable compound and the photopolymerization initiator, typically at 50 to 100°C. In (step S2), for exposure, an exposure machine that emits light in the 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. In (step S3), for etching, typically, an alkaline aqueous developer can be used. For example, an aqueous solution containing sodium hydroxide, sodium carbonate, or the like can be used. The concentration of the alkaline aqueous solution can be adjusted to, for example, 0.01 to 0.5% by weight.

Next, (Step S4: Firing process) a plurality of green sheets for forming ceramic layers, on which unfired conductive films are formed, are stacked and pressed together. This produces a laminate of unfired ceramic green sheets. The laminate is then cut to the desired chip size. The laminate cut to the chip size is then fired, for example, at 600 to 950°C. This causes the ceramic green sheets to be sintered together, forming a main body 10 having a ceramic layer 12 and an internal electrode layer 14 made of a fired photosensitive composition. Then, an appropriate paste for forming external electrodes is applied to both ends of the main body 10, and fired to form external electrodes 20. In this manner, the multilayer chip inductor 1 can be manufactured.

The photosensitive composition disclosed herein can be used, for example, in combination with a photosensitive glass composition to form electrodes and further to manufacture electronic materials. Here, FIG. 2 is an explanatory diagram for explaining the manufacture of a multilayer chip inductor having an electrode formed by combining such a photosensitive composition and a photosensitive glass composition. An example of a method for manufacturing such a multilayer chip inductor is described below.

First, a paste containing ceramic material, binder resin, and organic solvent is prepared and then applied onto a carrier sheet to form a ceramic green sheet.

Next, the above-mentioned photosensitive composition is used to form a cured film of a predetermined coil pattern at a predetermined position on the green sheet. As an example, the process includes the following steps: a first forming step in which the photosensitive glass composition is applied (printed) onto a green sheet as a substrate and dried to form a glass film body, which is a dried body of the photosensitive glass composition; a first exposure step in which a photomask having a predetermined pattern is placed on the glass film body, a part of the glass film body exposed from the opening is exposed to light, and a part of the glass film body is made into a cured glass film; a first development step in which the uncured glass film body is removed using a developing solution to form a cured glass film having a predetermined groove on the substrate; a second forming step in which a photosensitive composition is applied (printed) onto the groove of the formed cured glass film, and dried to form a conductive film body, which is a dried body of the photosensitive composition, in the groove of the glass film body; a second exposure step in which a photomask having a predetermined pattern is placed on the conductive film body, a part of the conductive film body exposed from the opening is exposed to light, and a part of the conductive film body is made into a cured conductive film; and a second development step in which the uncured conductive film body is removed using a developing solution. This allows an unfired glass cured film to be formed on the surface of the substrate, and a conductive cured film to be formed in the grooves of the glass cured film.

Here, the photosensitive glass composition is not particularly limited, and any conventionally known photosensitive glass composition that can be used in manufacturing electronic components can be used without any particular limitation. For example, the photosensitive composition may be a paste-like composition containing a glass powder, a photopolymerizable compound, a photopolymerization initiator, and an organic dispersion medium. As the glass powder, any one that can be used in this type of photosensitive glass composition can be used without any particular limitation. In addition, as the photopolymerizable compound, the photopolymerization initiator, and the organic dispersion medium, the same kind of ones as those in the above-mentioned photosensitive composition can be used without any particular limitation, so detailed explanations are omitted. In addition, the photosensitive glass composition may contain additional components other than the above-mentioned components. Such additional components are not particularly limited, and examples thereof include polymerization inhibitors, radical scavengers, antioxidants, plasticizers, surfactants, leveling agents, dispersants, defoamers, gelling inhibitors, stabilizers, preservatives, etc.

When forming the glass cured film and the conductive cured film using the photosensitive glass composition and the photosensitive composition, conventionally known methods can be used as appropriate. For example, in the first and second forming steps, the photosensitive glass composition and the photosensitive composition can be applied by various printing methods such as screen printing, or by using a bar coater, etc. These compositions are typically dried at 40 to 100°C.

Next, the first exposure step and the second exposure step are performed by placing a photomask having slits of a predetermined pattern on the glass film and exposing a portion of the glass film (or conductive film) exposed through the slits. In this exposure process, an exposure machine that emits light rays (typically ultraviolet light) in the wavelength range of, for example, 10 nm to 500 nm, such as an ultraviolet light irradiation lamp such as a high-pressure mercury lamp, a metal halide lamp, or a xenon lamp, can be used. The exposure amount of the exposure machine can be set to, for example, 100 mJ/cm ² to 3000 mJ/cm ² .

In the first and second development steps, an alkaline aqueous developer can be used as the developer. Examples of such aqueous developers include an aqueous sodium hydroxide solution and an aqueous sodium carbonate solution. The alkaline concentration of these developers can be adjusted to, for example, 0.01 to 0.5% by weight.

Figure 2 is a schematic diagram showing the laminate 100 before firing. As shown in Figure 2, by repeatedly carrying out the above-mentioned first forming step to second developing step, a laminate 100 having a plurality of layers (first layer L1 to fourth layer L4 in Figure 2) including a glass cured film 21 having a precise groove and a conductive cured film 22 formed in the groove on a ceramic substrate 50 can be produced. In addition, in this laminate 100, the conductive cured film 22 of each layer of the first layer L1 to the fourth layer L4 is connected through a via 26. The via 26 can be formed by, for example, forming a via hole in the glass cured film 21 forming the upper surface of the first layer L1 using a guide hole drilling machine, exposing a part of the upper surface of the conductive cured film 22, filling the via hole with a photosensitive composition, and then drying and exposing the via hole.

After applying the paste for forming the external electrodes to the laminate 100, a firing process is performed to manufacture a laminated chip inductor having a precise conductive layer 24. The firing temperature (maximum temperature in the firing process) is preferably, for example, about 600 to 950°C. In the manufacture of such a laminated chip inductor, the photosensitive glass composition of the above configuration is used to form the glass cured film 21, so precise patterning with high rectangularity is possible. By applying a photosensitive composition to the glass cured film 21 to form the conductive cured film 22, a conductive cured film 22 having a fine pattern can be formed. Then, by firing these, electronic components having a fine pattern with an L/S of 30 μm/30 μm or less can be manufactured with high precision. That is, according to this manufacturing method, even if the electronic component has a fine pattern, undercutting in which the exposed part of the film-like body is removed in the above-mentioned development process can be suppressed, and highly reliable electronic components can be manufactured. Furthermore, in the manufacture of such multilayer chip inductors, the density of the electrode layer, which is the sintered body of the conductor cured film, and the dielectric layer, which is the sintered body of the glass cured film, during the sintering process is extremely important, and the effects of the technology disclosed here are more pronounced.

Below, we will explain test examples related to the disclosed subject matter, but we are not intended to limit the disclosure to such test examples.

[Test Example]
In the following test examples, 18 types of photosensitive compositions were prepared as Examples 1 to 18, and the conductive films, which were fired products of each photosensitive composition, were evaluated. Note that the resolution evaluation described below was performed using conductive films in an unfired state.

<Preparation of photosensitive compositions according to each example>
(Photosensitive composition according to Example 1)
First, silver particles (average particle diameter (D50 particle diameter): 2 μm) were prepared as conductive particles. In addition, commercially available reactive polymers (urethane, weight average molecular weight: 9000) and reactive oligomers (urethane, weight average molecular weight: 2000) were prepared as photopolymerization compounds, and commercially available cellulose-based water-soluble resins and acrylic-based water-soluble resins were prepared as binder resins. In addition, commercially available polydimethylsiloxane (weight average molecular weight: 50000) was prepared as silicone resin. A mixture of commercially available 2-benzyl-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone and 2,4-diethylthioxanthone was prepared as a photopolymerization initiator, with the weight average molecular weight being 300. The silver particles, photopolymerizable compound, binder resin, silicone resin, and photopolymerization initiator prepared above were dispersed in a mixed solvent of commercially available dipropylene glycol methyl ether acetate and dihydroterpineol as a solvent to prepare a photosensitive composition according to Example 1. The blending ratio (wt%) of each material was as shown in Table 1. The viscosity of the photosensitive composition was about 20 to 70 Pa·s at 25° C.-100 rpm (measured using a Brookfield HB type viscometer, spindle: SC-4-14, small cup, and at a measurement temperature of 25° C.).

(Photosensitive compositions according to Examples 2 to 7 and 15)
Photosensitive compositions according to Examples 2 to 7 and 15 were prepared in the same manner as the photosensitive composition according to Example 1, except that the blending amount of silicone resin (polydimethylsiloxane) was as shown in Table 1.

(Photosensitive compositions according to Examples 8 to 10)
Photosensitive compositions according to Examples 8 to 10 were prepared in the same manner as in the photosensitive composition according to Example 4, except that the weight average molecular weight of the silicone resin (polydimethylsiloxane) was as shown in Table 1.

(Photosensitive compositions according to Examples 11, 12, 16 and 17)
Photosensitive compositions according to Examples 11, 12, 16, and 17 were prepared in the same manner as the photosensitive composition according to Example 1, except that the type of silicone resin was as shown in Table 1. In addition, the side chain fatty acid-modified polysiloxane in Table 1 means a polysiloxane in which R ¹ , R ² , R ³ , R ⁵ , and R ⁶ in the above formula (I) are methyl groups and R ⁴ is a fatty acid, and the side chain amine-modified polysiloxane means a polysiloxane in which R ¹ , R ² , R ³ , R ⁵ , and R ⁶ in the above formula (I) are methyl groups and R ⁴ is an amine. These were commercially available products.

(Photosensitive composition according to Example 13)
A photosensitive composition according to Example 13 was prepared in the same manner as in the photosensitive composition according to Example 4, except that a silane coupling agent (trimethoxymethylsilane) was added instead of the silicone resin.

(Photosensitive composition according to Example 14)
The photosensitive composition of Example 14 was prepared in the same manner as the photosensitive composition of Example 1, except that no silicone resin was added.

(Photosensitive composition according to Example 18)
A photosensitive composition according to Example 18 was prepared in the same manner as in the photosensitive composition according to Example 4, except that silica (SiO ₂ ) was added instead of the silicone resin.

(Evaluation test)
In this evaluation test, the photosensitive composition according to each example was used to evaluate the resolution, the shrinkage rate, and the resistance value. The procedures for each evaluation are described below.

(1) Evaluation of Resolution First, the photosensitive composition (Examples 1 to 18) was applied to a commercially available ceramic green sheet made of borosilicate glass and alumina in a size of 4 cm x 4 cm by screen printing (printing process). Next, this was dried at 60°C for 15 minutes to form a film-like body (solid film) on the green sheet (forming process). Next, a photomask having openings of a predetermined pattern was placed on the film-like body, and then light was irradiated by an exposure machine under conditions of illuminance of 50 mW/cm ² and exposure amount of 300 mJ/cm ² to harden the exposed parts (exposure process). At this time, the pattern of the openings formed on the photomask was formed by linear openings formed in parallel at a predetermined interval. A photomask was used in which the ratio L/S (line/space) of the width of the openings (width of the cured film) to the width of the space between adjacent openings (space between the cured film) was set to 30 μm/30 μm.

Next, a 0.1 wt% alkaline _{Na2CO3 aqueous} solution (developer) was sprayed onto the surface of the ceramic green sheet until the break point (B.P.) was reached for 1.1 times the time (developing step). The B.P. was the time until the unexposed film was removed by the 0.1 wt% alkaline developer and the removal of the film was visually confirmed. The ceramic green sheet after the unexposed film was removed was washed with pure water and dried at room temperature. This resulted in a composite in which a cured film was formed on the ceramic green sheet with a wiring pattern of L/S = 30 μm/30 μm and a film thickness of 8 μm.

The spacing of the wiring pattern of the cured film formed after the development step was visually observed with an optical microscope in a total of 20 fields of view. Then, it was confirmed whether or not a part of the film-like body that was not removed remained (presence or absence of residue). The results are shown in the corresponding columns in Table 1. The evaluation criteria in this evaluation are as follows.
"A": No residue was observed within 20 visual fields.
"◯": Residue was observed in one visual field.
"△": Residues were observed in two to four visual fields.
"X": Residues were observed in five or more visual fields.

(2) Evaluation of disk shrinkage First, the photosensitive composition according to each example was applied onto a PET film to form a coating film. The application was performed using an applicator with a gap of 150 μm. The coating film was then dried at 150° C. for 1 hour. Next, the dried coating film was punched out with a die of φ15 mm to obtain a disk-shaped dried film. Then, the dried film was baked on a ceramic plate. The baking conditions were as follows: the temperature was raised to 400° C. in 8 hours, then held for 30 minutes, cooled to room temperature (about 25° C., the same below), heated to 800° C. (or 900° C.) at 10° C./min, and then held for another 30 minutes, and then cooled to room temperature. The ratio of the diameter of the dried film before and after baking was calculated as the disk shrinkage. The results are shown in the corresponding columns of Table 1. In Table 1, the disk shrinkage rate at 800° C. is designated as A (%), and the disk shrinkage rate at 900° C. is designated as B (%). The evaluation criteria in this evaluation are as follows.
"Excellent": The difference in disk shrinkage rate: B-A (%) was more than 0.5.
"◯": The difference in disk shrinkage rate: B-A (%) was -0.5 or more and 0.5 or less.
"X": The difference in disk shrinkage rate: B-A (%) was less than -0.5.

(3) Evaluation of Electrical Resistivity First, the photosensitive composition according to each example was formed on an alumina substrate. The silver conductive film was formed by screen printing, and the screen pattern was 200 μm wide and 2 cm long. This was baked at 900° C. (held for 30 minutes) to form a silver line electrode. Next, the direct current resistance of each silver line electrode according to each example was measured based on a two-terminal measurement method, and the electrical resistivity was calculated from the cross-sectional area and length of the silver line electrode. A digital multimeter (SC-7401, manufactured by Iwasaki Electric Co., Ltd.) was used to measure the direct current resistance, and a laser microscope (VK-X1050, manufactured by Keyence Corporation) was used to measure the electrode cross-sectional area. The results are shown in the “Electrical Resistivity” column in Table 1. The evaluation criteria in this evaluation are as follows.
"Excellent": Electric resistivity was 2.5×10 ⁶ μΩcm or less.
"Good": The electrical resistivity was greater than 2.5 x 10 ⁶ μΩcm and less than 3.0 x 10 ⁶ μΩcm.
"X": The electrical resistivity was 3.0×10 ⁶ μΩcm or more.

Figures 3 to 7 are SEM images (magnification: 9000x) showing the electrode surfaces of Examples 14, 3, 4, 6, and 8, respectively, after firing at 900°C.

As shown in Table 1, in Examples 1 to 12, which are photosensitive compositions containing conductive particles (here, silver particles), a photopolymerizable compound, and a silicone resin, the silicone resin is represented by the above formula (I), and the silicone resin is contained in an amount of 0.05% to 1.0% when the total weight of the conductive particles is taken as 100%, it was confirmed that inversion and expansion of the conductive film during high-temperature firing (here, 800°C to 900°C) was suitably suppressed and low resistance of the conductive film was suitably achieved, compared to Example 13, in which a silane coupling agent was added, Example 14, in which no silicone resin was added, Examples 16 and 17, in which a silicone resin other than that of the above formula (I) (in other words, a silicone resin highly reactive with resins such as photopolymerizable compounds and organic binders) was added, Example 18, in which silica was added, and Example 15, in which a silicone resin represented by the above formula (I) was added outside the above range. Also, as can be seen from Figures 3 to 7, in Example 14, where no silicone resin was added, the sintering of the silver particles did not progress sufficiently, resulting in large voids, whereas in Examples 3, 4, 6, and 8, the sintering and grain growth of the silver particles progressed, resulting in higher conductivity of the conductor film (i.e., lower resistance).

As can be seen from the results of Examples 1 to 7, when the total weight of the conductive particles is taken as 100%, if the silicone resin is contained at 0.15% to 0.6%, it is possible to more suitably suppress the inversion expansion of the conductor film during high-temperature firing and reduce the resistance of the conductor film. And as can be seen from the results of Examples 8 to 10, from the viewpoint of more suitably improving the resolution in addition to suppressing the inversion expansion of the conductor film during high-temperature firing and reducing the resistance of the conductor film, it is more preferable for the weight-average molecular weight of the silicone resin to be 1,000 to 10,000.

Specific examples of the present disclosure have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples given above.

（式Ｉ中のＲ^１～Ｒ^６は互いに独立し、それぞれ、アルキル基、フェニル基、ポリエーテル基、アラルキル基、フロロアルキル基、脂肪酸エステル基、または脂肪酸アミド基が挿入された基を表す。また、ｍ、ｎは互いに独立した０以上の整数を表す。）
で表され、上記シリコーン樹脂は、上記導電性粒子の全重量を１００％としたとき、０．０５％～１．０％含まれる、感光性組成物。
項２：上記シリコーン樹脂は、ポリジメチルシロキサン、ポリ（メチルフェニルシロキサン）、および側鎖ポリエーテル変性ポリシロキサンからなる群から選択される少なくとも１種を含む、項１に記載の感光性組成物。
項３：上記シリコーン樹脂の重量平均分子量は、１０００～１０万である、項１または項２に記載の感光性組成物。
項４：上記導電性粒子の平均粒子径は、１μｍ～５μｍである、項１～項３のいずれか一つに記載の感光性組成物。
項５：上記導電性粒子の、ＪＩＳ Ｚ ８７８１に基づくＬ＊ａ＊ｂ表色系の明度Ｌ＊は５０以上である、項１～項４のいずれか一つに記載の感光性組成物。
項６：上記感光性組成物は、セラミックグリーンシート上に電極を形成するために用いられる、項１～項５のいずれか一つに記載の感光性組成物。
項７：上記感光性組成物は、線幅３０μｍ以下の細線の形成に用いられる、項１～項６のいずれか一つに記載の感光性組成物。
項８：項１～項７のいずれか一つに記載の感光性組成物の焼成体からなる、導体膜。
項９：項１～項７のいずれか一つに記載の感光性組成物の焼成体からなる導体膜を備えた、電子材料。 As described above, specific aspects of the technology disclosed herein include those described in the following items.
Item 1: A photosensitive composition comprising conductive particles, a photopolymerizable compound, and a silicone resin, the silicone resin being represented by the following formula (I):

(R ¹ to R ⁶ in formula I are each independently an alkyl group, a phenyl group, a polyether group, an aralkyl group, a fluoroalkyl group, a fatty acid ester group, or a group having a fatty acid amide group inserted therein. Furthermore, m and n are each independently an integer of 0 or more.)
and the silicone resin is contained in an amount of 0.05% to 1.0% when the total weight of the conductive particles is taken as 100%.
Item 2: The photosensitive composition according to item 1, wherein the silicone resin comprises at least one selected from the group consisting of polydimethylsiloxane, poly(methylphenylsiloxane), and side-chain polyether-modified polysiloxane.
Item 3: The photosensitive composition according to item 1 or 2, wherein the silicone resin has a weight average molecular weight of 1,000 to 100,000.
Item 4: The photosensitive composition according to any one of Items 1 to 3, wherein the conductive particles have an average particle size of 1 μm to 5 μm.
Item 5: The photosensitive composition according to any one of items 1 to 4, wherein the conductive particles have a lightness L* of 50 or more in the L*a*b color system based on JIS Z 8781.
Item 6: The photosensitive composition according to any one of Items 1 to 5, which is used for forming an electrode on a ceramic green sheet.
Item 7: The photosensitive composition according to any one of Items 1 to 6, which is used for forming a fine line having a line width of 30 μm or less.
Item 8: A conductor film comprising a fired product of the photosensitive composition according to any one of items 1 to 7.
Item 9: An electronic material having a conductor film made of a sintered product of the photosensitive composition according to any one of items 1 to 7.

Reference Signs List 1 Multilayer chip inductor 10 Main body 12 Ceramic layer 14 Internal electrode layer 16 Via 20 External electrode 21 Glass cured film 22 Conductive cured film 26 Via 50 Ceramic substrate 100 Laminate

Claims (9)

A photosensitive composition comprising conductive particles, a photopolymerizable compound, and a silicone resin,
The silicone resin has the following formula (I):

(R ¹ to R ⁶ in formula I are each independently an alkyl group, a phenyl group, a polyether group, an aralkyl group, a fluoroalkyl group, a fatty acid ester group, or a group having a fatty acid amide group inserted therein. Furthermore, m and n are each independently an integer of 0 or more.)
It is expressed as
the silicone resin is contained in an amount of 0.05% to 1.0% when the total weight of the conductive particles is taken as 100%,
Further, the organic binder contains both a water-soluble cellulose-based resin and a water-soluble acrylic resin having a substituent that is acidic in water,
A photosensitive composition , wherein the conductive particles contained in the composition are composed only of a simple substance of a precious metal, a mixture consisting only of a simple substance of a precious metal, or an alloy consisting only of a precious metal . The photosensitive composition according to claim 1, wherein the silicone resin comprises at least one selected from the group consisting of polydimethylsiloxane, poly(methylphenylsiloxane), and side-chain polyether-modified polysiloxane. The photosensitive composition according to claim 1 or 2, wherein the weight average molecular weight of the silicone resin is 1,000 to 100,000. The photosensitive composition according to claim 1 or 2, wherein the conductive particles have an average particle size, D50, of 1 μm to 5 μm in a volume-based particle size distribution based on a laser diffraction/scattering method. The photosensitive composition according to claim 1 or 2, wherein the conductive particles have a lightness L* of 50 or more in the L*a*b color system based on JIS Z 8781. The photosensitive composition according to claim 1 or 2, which is used to form an electrode on a ceramic green sheet. The photosensitive composition according to claim 1 or 2, which is used to form fine lines with a line width of 30 μm or less. A conductive film comprising a fired body of the photosensitive composition according to claim 1 or 2. 3. An electronic material comprising a conductor film made of a sintered product of the photosensitive composition according to claim 1.

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