JP2011152486A - Method for cleaning apparatus for discharging liquid droplet, and apparatus for discharging liquid droplet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for cleaning an apparatus for discharging liquid droplets, which favorably removes dirt in an ink flow path for forming conductor patterns in the apparatus for discharging the liquid droplet and also removes clogging of a head for discharging the liquid droplet, and also to provide the apparatus for discharging the liquid droplet. <P>SOLUTION: The method for cleaning the apparatus for discharging liquid droplets is an method for cleaning an apparatus for discharging ink for forming conductive patterns, wherein: the apparatus for discharging the liquid droplet includes a head for discharging the liquid droplet with a discharger which discharges the ink for forming conductive patterns and a path for carrying the ink for forming conductive patterns to the head for discharging the liquid droplet; and the head for discharging the liquid droplet includes a body of the head, a diaphragm, and a piezoelectric element. The ink for forming conductive patterns is sent into the head for discharging the liquid droplet through the path for carrying the ink. The ink for forming conductive patterns is suctioned from the discharger, and the suctioned ink is sent back to the head for discharging the liquid droplet while the piezoelectric element is driven by applied voltages with a frequency between 10 and 300 kHz. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cleaning method for a droplet discharge device and a droplet discharge device.

  For example, a photolithography method is used for manufacturing a wiring used for an electronic circuit or an integrated circuit. In this photolithography method, a photosensitive material called a resist is coated on a substrate coated with a conductive film in advance, a circuit pattern is irradiated and developed, and the conductive film is etched according to the resist pattern, thereby forming a wiring made of a conductor pattern. Is formed. This photolithography method requires large-scale equipment such as a vacuum apparatus and a complicated process, and the material use efficiency is about several percent, and most of it must be discarded, and the manufacturing cost is high.

  On the other hand, a method of forming a conductor pattern (wiring) by using a droplet discharge method in which a liquid material is discharged from a liquid discharge head in the form of droplets, a so-called inkjet method has been proposed (for example, see Patent Document 1). ). In this method, a conductive pattern forming ink in which conductive fine particles are dispersed is directly applied to a substrate, and then the solvent is removed to obtain a conductive pattern precursor, which is then converted into a conductive pattern by sintering. According to this method, there is an advantage that photolithography is not required, the process is greatly simplified, and the amount of raw materials used is reduced. Further, according to this method, it is possible to form a fine conductor pattern as compared with the conventional method, which is advantageous in improving the circuit density.

  By the way, a droplet discharge device (industrial use) used for forming a conductor pattern is completely different from that applied to a printer (consumer use). For example, a large number of droplets are long for mass production. It is required to discharge continuously over time. Also, the ink used for forming the conductor pattern (industrial) is generally poorer in liquid discharge during ejection than the ink used in printers (consumer use), and the ejection part (nozzle) of the inkjet head. Ink tends to remain on the discharge surface. As a result, when the ink is continuously discharged, the components contained in the ink adhere to the ink flow path of the droplet discharge device, and the supply of ink to the droplet discharge head becomes unstable. Also, the ink used for forming the conductor pattern (industrial) has more compositional restrictions than those used in printers (consumer use) and has sufficient characteristics such as drying and re-dissolvability. In other words, solid content such as metal particles precipitates or aggregates, and the discharge portion of the droplet discharge head is likely to be clogged, and the flight of the droplet frequently occurs. In such a case, it is difficult for the pattern formed on the substrate with the conductive pattern forming ink to have a sufficiently uniform thickness and width. As described above, when a pattern having a desired shape cannot be formed, disconnection is likely to occur in a part of the formed conductor pattern. In addition, since the conductor pattern does not have a desired shape, there is a problem that the conductor pattern has characteristics that deviate from the target frequency characteristics (Q value). In particular, the occurrence of such a problem has been remarkable with the recent increase in the density of circuit boards due to the miniaturization of wiring and the reduction in pitch.

  For this reason, for example, by a method (e.g., spitting) of ejecting droplets on a portion without a ceramic substrate of a droplet ejecting device, aggregates, deposits, etc. present in the droplet ejecting head or the ink flow path Remove and remove dirt and clogging with ink. However, such a method alone cannot sufficiently remove aggregates and deposits, and if droplets are discharged again, the droplet discharge amount becomes unstable or discharged in a relatively short period of time. There was a problem that the part was clogged again. In such a case, it is necessary to frequently replace the droplet discharge head and other members, and the productivity of the ceramic circuit board is extremely reduced.

JP 2007-84387 A

  An object of the present invention is applied to a cleaning method of a droplet discharge device and such a cleaning method that can suitably eliminate contamination in a flow path of ink for forming a conductor pattern of the droplet discharge device and clogging of a droplet discharge head. And providing a droplet discharge device.

Such an object is achieved by the present invention described below.
The method for cleaning a droplet discharge device of the present invention is used for forming a conductor pattern by a droplet discharge method, and is a cleaning method for cleaning a droplet discharge device that discharges a conductive pattern forming ink in which metal particles are dispersed in an aqueous dispersion medium. A method,
The droplet discharge device includes a droplet discharge head including a discharge unit that discharges the conductor pattern forming ink, and a transport path for transporting the conductor pattern forming ink to the droplet discharge head. ,
The droplet discharge head includes a head body, a diaphragm, and a piezo element,
The conductor pattern forming ink is fed into the droplet discharge head via the transport path, and the piezoelectric element is driven by the applied voltage having a frequency of 10 kHz or more and 300 kHz or less from the discharge unit to the conductor pattern. After sucking the forming ink, the sucked conductive pattern forming ink is returned to the droplet discharge head.
Accordingly, it is possible to provide a cleaning method for a droplet discharge device that can suitably eliminate contamination in the flow path of the conductor pattern forming ink of the droplet discharge device and clogging of the droplet discharge head.

In the cleaning method for a droplet discharge device of the present invention, it is preferable that the conductor pattern forming ink contains ceramic particles.
Thereby, contamination in the flow path of the conductor pattern forming ink of the droplet discharge device and clogging of the droplet discharge head can be more preferably eliminated.
In the method for cleaning a droplet discharge device of the present invention, the ceramic particles preferably include a metal oxide.
Such metal oxides are chemically stable and stably dispersed in the cleaning liquid. Moreover, since the hardness is relatively high, dirt in the droplet discharge device can be suitably removed.

In the method for cleaning a droplet discharge device of the present invention, the metal oxide is preferably silicon dioxide or aluminum oxide.
These compounds have high hardness and have relatively high detergency.
In the cleaning method for a droplet discharge device of the present invention, the ceramic particles preferably have an average particle diameter of 5 nm to 300 nm.
Thereby, metal particles (dirt) adhering to the ink flow path can be more effectively removed.

In the method for cleaning a droplet discharge device of the present invention, the content of the ceramic particles in the conductor pattern forming ink is preferably 0.1 wt% or more and 1.6 wt% or less.
Thereby, it is possible to prevent the metal particles from adhering to the ink flow path while preventing the ceramic particles from affecting the performance of the formed conductor pattern.
In the method for cleaning a droplet discharge device of the present invention, it is preferable that the sucked ink for forming a conductor pattern is returned to the droplet discharge head via a filter.
Thereby, it is possible to effectively prevent dirt such as silver once released from reattaching to the ink flow path or the like.

A droplet discharge device of the present invention is a droplet discharge device that is used for forming a conductor pattern by a droplet discharge method and discharges a conductive pattern forming ink in which metal particles are dispersed in an aqueous dispersion medium.
In order to clean the inside of the droplet discharge device, a droplet discharge head having a discharge portion for discharging the conductor pattern formation ink, a conveyance path for conveying the conductor pattern formation ink to the droplet discharge head And a cleaning mechanism
The droplet discharge head includes a head body, a diaphragm, and a piezo element,
The cleaning mechanism includes a suction unit that sucks the conductor pattern forming ink in the droplet discharge head, a collection tank that collects the conductor pattern forming ink sucked by the suction unit, and a suction unit. A suction ink transport path for transporting the sucked conductor pattern forming ink to the recovery tank, and a recovery ink transport for transporting the conductor pattern formation ink recovered to the recovery tank to the droplet discharge head side again And a road.
Accordingly, it is possible to provide a droplet discharge device that can suitably eliminate dirt in the flow path of the conductor pattern forming ink and clogging of the droplet discharge head.

It is a perspective view which shows schematic structure of a droplet discharge apparatus. FIG. 2 is a schematic diagram for explaining a schematic configuration of a droplet discharge head provided in the droplet discharge device of FIG. 1. It is the schematic diagram which showed an example of the whole structure of the washing | cleaning mechanism of a droplet discharge apparatus.

Hereinafter, preferred embodiments of the present invention will be described in detail.
<Droplet ejection device>
First, prior to the description of the cleaning method of the present invention, a preferred embodiment of a droplet discharge apparatus to which the present invention is applied will be described.
FIG. 1 is a perspective view illustrating an example of a preferred embodiment of a droplet discharge device (inkjet device), and FIG. 2 illustrates a schematic configuration of a droplet discharge head (inkjet head) included in the droplet discharge device of FIG. FIG. 3 is a schematic diagram showing an example of the overall configuration of the cleaning mechanism of the droplet discharge device.

As shown in FIGS. 1 and 3, the droplet discharge device 100 includes a droplet discharge head (inkjet head; hereinafter simply referred to as a head) 110, a base 130, a table 140, and an ink reservoir shown in FIG. 150, a table positioning unit 170, a head positioning unit 180, and a control device 190.
The droplet discharge device 100 is a device used to form a conductor pattern by discharging a conductor pattern forming ink in which genus particles are dispersed in an aqueous dispersion medium.

The base 130 is a table that supports each component of the droplet discharge device 100 such as the table 140, the table positioning unit 170, and the head positioning unit 180.
The table 140 is installed on the base 130 via the table positioning means 170. The table 140 is used for placing the substrate S (the ceramic molded body 15 in this embodiment).
A rubber heater (not shown) is disposed on the back surface of the table 140. The ceramic molded body 15 placed on the table 140 is heated to a predetermined temperature by a rubber heater over the entire upper surface thereof.

  At least a part of the aqueous dispersion medium evaporates from the surface side of the ink (conductor pattern forming ink described later) 1 landed on the ceramic molded body 15. At this time, since the ceramic molded body 15 is heated, evaporation of the aqueous dispersion medium is promoted. The ink 1 that has landed on the ceramic molded body 15 is thickened from the outer edge of the surface as it dries. That is, the solid content (particles) concentration at the outer peripheral portion is faster than the central portion and reaches the saturated concentration. Thicken from the outer edge. The thickened ink 1 on the outer edge stops its own wetting and spreading along the surface direction of the ceramic molded body 15, so that the line width can be easily controlled with respect to the landing diameter.

The heating temperature of the ceramic molded body 15 is preferably 40 ° C. or higher and 100 ° C. or lower, and more preferably 50 ° C. or higher and 70 ° C. or lower. By setting it as such conditions, when an aqueous dispersion medium evaporates, it can prevent more effectively that a crack generate | occur | produces.
The table positioning unit 170 includes a first moving unit 171 and a motor 172. The table positioning means 170 determines the position of the table 140 in the base 130, and thereby determines the position of the ceramic green sheet 15 in the base 130.

The first moving means 171 has two rails provided substantially parallel to the Y direction and a support base that moves on the rails. The support base of the first moving means 171 supports the table 140 via the motor 172. Then, as the support base moves on the rail, the table 140 on which the base material S is placed is moved and positioned in the Y direction.
The motor 172 supports the table 140 and swings and positions the table 140 in the θz direction.

The head positioning unit 180 includes a second moving unit 181, a linear motor 182, and motors 183, 184 and 185. The head positioning unit 180 determines the position of the head 110.
The second moving means 181 is provided with two support pillars standing from the base 130, a support base provided between the support pillars, the rail support having two rails, and the rails. And a support member (not shown) for supporting the head 110. Then, as the support member moves along the rail, the head 110 is moved and positioned in the X direction.

The linear motor 182 is provided in the vicinity of the support member, and can move and position the head 110 in the Z direction.
Motors 183, 184, and 185 swing and position the head 110 in the α, β, and γ directions, respectively.
By the table positioning unit 170 and the head positioning unit 180 as described above, the ink jet apparatus 100 accurately controls the relative position and posture of the ink ejection surface 115P of the head 110 and the base material S on the table 140. It can be done.

  As shown in FIG. 2, the head 110 ejects ink 1 from nozzles (protruding portions) 118 by an inkjet method (droplet ejection method). In the present embodiment, the head 110 uses a piezo method in which ink is ejected using a piezo element 113 as a piezoelectric element. The piezo method has the advantage that the composition of the material is not affected because heat is not applied to the ink 1.

The head 110 has a head body 111, a diaphragm 112, and a piezo element 113.
The head main body 111 has a main body 114 and a nozzle plate 115 on the lower end surface thereof. Then, the main body 114 is sandwiched between the plate-like nozzle plate 115 and the vibration plate 112, whereby a reservoir 116 as a space and a plurality of ink chambers 117 branched from the reservoir 116 are formed.

Ink 1 is supplied to the reservoir 116 from an ink storage tank 150 described later. The reservoir 116 forms a flow path for supplying the ink 1 to each ink chamber 117.
The nozzle plate 115 is attached to the lower end surface of the main body 114 and constitutes an ink ejection surface 115P. In the nozzle plate 115, a plurality of nozzles 118 that discharge ink 1 are opened corresponding to the ink chambers 117. An ink flow path is formed from each ink chamber 117 toward the corresponding nozzle (ejection unit) 118.

The diaphragm 112 is attached to the upper end surface of the head body 111 and constitutes the wall surface of each ink chamber 117. The diaphragm 112 can vibrate according to the vibration of the piezo element 113.
The piezo element 113 is provided corresponding to each ink chamber 117 on the opposite side of the vibration plate 112 from the head body 111. The piezoelectric element 113 is obtained by sandwiching a piezoelectric material such as quartz with a pair of electrodes (not shown). The pair of electrodes is connected to the drive circuit 191.

When an electric signal is input from the drive circuit 191 to the piezo element 113, the piezo element 113 is expanded or contracted. When the piezo element 113 contracts and deforms, the pressure in the ink chamber 117 decreases, and the ink 1 flows from the reservoir 116 into the ink chamber 117. Further, when the piezo element 113 expands and deforms, the pressure in the ink chamber 117 increases and the ink 1 is ejected from the nozzle 118. Note that the amount of deformation of the piezo element 113 can be controlled by changing the applied voltage. Further, the deformation speed of the piezo element 113 can be controlled by changing the frequency of the applied voltage. That is, by controlling the voltage applied to the piezo element 113, the ejection conditions of the ink 1 can be controlled.
The control device 190 controls each part of the inkjet device 100. For example, the discharge position of ink 1 on the substrate S is controlled by adjusting the waveform of the applied voltage generated by the drive circuit 191 to control the discharge condition of the ink 1 or by controlling the head positioning unit 170 and the table positioning unit 180. Control.

The ink storage tank 150 stores the ink 1.
As shown in FIG. 3, the ink storage tank 150 is connected to the head 110 (reservoir 116) via a conveyance path 151, and the ink 1 stored in the ink storage tank 150 is used when a droplet is discharged. It is supplied to the reservoir 116 as necessary.
Further, a cock 152 is provided in the middle of the transport path 151, and the cock 152 is connected to a recovered ink transport path 220 described later.
Further, as shown in FIG. 3, a self-sealing valve 153 is provided between the cock 152 and the head 110. The self-sealing valve 153 controls the liquid feeding of the ink 1 to the head 110 and prevents the ink 1 from flowing backward.
As shown in FIG. 3, the droplet discharge device 100 includes a cleaning mechanism.

The cleaning mechanism includes a suction unit 200 that sucks the ink 1 in the head 110, a collection tank 210 that collects the ink 1 sucked out by the suction unit 200, and a recovery tank 210 that collects the ink 1 sucked out by the suction unit 200. And a recovery ink transport path 220 for transporting the ink 1 recovered to the recovery tank 210 to the droplet discharge head 110 side again.
The suction unit 200 has a function of sucking the ink 1 in the head 110. The ink 1 sucked out by the suction means 200 is transported to the recovery tank 210 via the suction ink transport path 201 as shown in FIG.

As shown in FIG. 3, the ink 1 collected in the collection tank 210 is conveyed to the conveyance path 151 (droplet ejection head 110 side) via the collection ink conveyance path 220 and the cock 152.
Further, a filter 221 is provided in the collected ink conveyance path 220, and foreign matter in the collected ink 1 is removed by this filter.

<Dropping device cleaning method>
Next, a preferred embodiment of the method for cleaning a droplet discharge device of the present invention will be described.
In the present embodiment, a cleaning method for cleaning the droplet discharge device 100 as described above will be representatively described, but the present invention is not limited to the droplet discharge device 100 as described above.
In the present embodiment, first, the ink 1 is transported (injected) from the ink storage tank 150 to the head 110 via the transport path 151, the cock 152, and the self-sealing valve 153, and the ink 1 is put into the droplet discharge device 100. Fill.

Next, the piezo element 113 of the head 110 is driven (vibrated) with an applied voltage having a frequency of 10 kHz to 300 kHz. The ink 1 in the droplet discharge device 100 is sucked from the nozzle (discharge portion) 118 using the suction means 200 while vibrating the piezo element 113 in this way.
Next, the sucked ink 1 is transported to the recovery tank 210 via the suction ink transport path 201.

Thereafter, the ink 1 collected in the collection tank 210 is conveyed again to the conveyance path 151 (the droplet discharge head 110 side) through the collection ink conveyance path 220 while removing foreign matters by the filter 221.
The transported ink 1 is transported again to the droplet discharge head 110 and used for cleaning the ink flow path and the like.

  By the way, a droplet discharge device (industrial use) used for forming a conductor pattern is completely different from that applied to a printer (consumer use). For example, a large number of droplets are long for mass production. It is required to discharge continuously over time. Also, the ink used for forming the conductor pattern (industrial) is generally poorer in liquid discharge during ejection than the ink used in printers (consumer use), and the ejection part (nozzle) of the inkjet head. Ink tends to remain. As a result, when droplets are continuously discharged, components contained in the ink adhere to the ink flow path of the droplet discharge device, and the supply of ink to the droplet discharge head becomes unstable. Also, the ink used for forming the conductor pattern (industrial) has more compositional restrictions than those used in printers (consumer use) and has sufficient characteristics such as drying and re-dissolvability. In other words, solids such as metal particles are dried or aggregated, and the discharge part of the droplet discharge head is likely to be clogged. As a result, the droplet discharge device is inferior in uniformity and discharge property of the droplet amount at the time of discharging the droplet, the flying curve of the droplet occurs frequently, and the formed conductor pattern has low reliability. Become. In such a case, it is difficult for the pattern formed on the substrate with the conductive pattern forming ink to have a sufficiently uniform thickness and width. As described above, when a pattern having a desired shape cannot be formed, disconnection is likely to occur in a part of the formed conductor pattern. In particular, the occurrence of such a problem has been remarkable with the recent increase in the density of circuit boards due to the miniaturization of wiring and the reduction in pitch.

  For this reason, for example, by a method of ejecting droplets in a portion without a ceramic substrate of a droplet ejection device (e.g. spit), aggregates, deposits, etc. existing in the droplet ejection head and the ink flow path are removed, Removes dirt and clogging caused by ink. However, with only such a method, aggregates and deposits in the droplet discharge device cannot be sufficiently removed, and when the discharge is restarted, the droplet discharge amount can be reduced in a relatively short period of time. There has been a problem that it becomes unstable or the discharge part is clogged again. In such a case, it is necessary to frequently replace the droplet discharge head and other members, and the productivity of the ceramic circuit board is extremely reduced.

  In contrast, the method for cleaning a droplet discharge device according to the present invention fills a droplet discharge head with a conductor pattern forming ink and discharges the piezoelectric element while vibrating it by applying a voltage of a predetermined frequency. The conductive pattern forming ink is sucked and collected from the portion, and the collected conductive pattern forming ink is returned to the droplet discharge head side again. By having such a feature, in order to suck the conductor pattern forming ink in a state where dirt such as metal particles adhering to the vibration of the piezo element is floated, in the flow path of the conductor pattern forming ink of the droplet discharge device Dirt and clogging of the droplet discharge head can be reliably removed, and the inside of the droplet discharge device can be effectively cleaned.

In the present invention, the frequency of the voltage applied to the piezoelectric element is 10 kHz to 300 kHz, more preferably 50 kHz to 250 kHz, and still more preferably 100 kHz to 200 kHz. Thereby, the effect of this invention can be made more remarkable.
Further, the speed at which the conductor pattern forming ink 1 fed into the droplet discharge device 100 is sucked by the suction means is preferably 2 mL / min or more and 60 mL / min or less per droplet discharge head 110. More preferably, it is 5 mL / min or more and 30 mL / min or less. Thereby, the inside of the droplet discharge device 100 can be cleaned more effectively.

<Conductor pattern forming ink>
Next, a preferred embodiment of the conductive pattern forming ink that can be applied to the cleaning method of the present invention will be described.
The conductor pattern forming ink is an ink used for forming a conductor pattern on a substrate, and in particular, an ink used for forming a conductor pattern by a droplet discharge method.
In this embodiment, a case where a dispersion liquid in which silver particles are dispersed is used as a dispersion liquid in which metal particles are dispersed in an aqueous dispersion medium.

The substrate on which the conductor pattern is formed may be any substrate, but in the present embodiment, a ceramic substrate mainly composed of ceramics is used as the substrate. In the present embodiment, the description will be made assuming that the ink for forming a conductor pattern is applied to a sheet-like ceramic formed body (ceramic green sheet) made of a material containing ceramics and a binder. The ceramic molded body is sintered as described later to become a ceramic substrate.
Hereinafter, each component of the conductor pattern forming ink will be described in detail.

[Aqueous dispersion medium]
First, the aqueous dispersion medium will be described.
In the present invention, the “aqueous dispersion medium” refers to one composed of water and / or a liquid having excellent compatibility with water (for example, water at 25 ° C .: a liquid having a solubility in 100 g of 30 g or more). As described above, the aqueous dispersion medium is composed of water and / or a liquid having excellent compatibility with water, but is preferably composed mainly of water. It is preferably 70 wt% or more, more preferably 90 wt% or more.

Specific examples of the aqueous dispersion medium include, for example, water, methanol, ethanol, butanol, propanol, isopropanol and other alcohol solvents, 1,4-dioxane, tetrahydrofuran (THF) and other ether solvents, pyridine, pyrazine, pyrrole and the like. Aromatic heterocyclic compound solvents, amide solvents such as N, N-dimethylformamide (DMF) and N, N-dimethylacetamide (DMA), nitrile solvents such as acetonitrile, and aldehyde solvents such as acetaldehyde. Of these, one or a combination of two or more can be used.
Further, the content of the aqueous dispersion medium in the conductor pattern forming ink is preferably 25 wt% or more and 60 wt% or less, and more preferably 30 wt% or more and 50 wt% or less. Thereby, while making the viscosity of an ink suitable, the change of the viscosity by volatilization of a dispersion medium can be made small.

[Silver particles]
Next, silver particles (metal particles) will be described.
Silver particles are the main component of the conductor pattern to be formed, and are components that impart conductivity to the conductor pattern.
The silver particles are dispersed in the ink.

  The average particle diameter of the silver particles is preferably 1 nm or more and 100 nm or less, and more preferably 10 nm or more and 30 nm or less. As a result, the ink ejection stability can be further improved, and a fine conductor pattern can be easily formed. In the present specification, the “average particle size” means a volume-based average particle size unless otherwise specified.

Further, the content of silver particles (silver particles (metal particles) in which the dispersant is not adsorbed on the surface) contained in the ink is preferably 0.5 wt% or more and 60 wt% or less, and is preferably 10 wt% or more and 45 wt%. The following is more preferable. Thereby, disconnection of a conductor pattern can be prevented more effectively, and a more reliable conductor pattern can be provided.
The silver particles (metal particles) are preferably dispersed in an aqueous dispersion medium as silver colloid particles (metal colloid particles) having a dispersant attached to the surface thereof. Thereby, the dispersibility of the silver particles in the aqueous dispersion medium is particularly excellent, and the ink ejection stability is particularly excellent.

  The content of the silver colloid particles in the ink is preferably 1 wt% or more and 60 wt% or less, and more preferably 10 wt% or more and 50 wt% or less. When the content of the silver colloidal particles is less than the lower limit, the silver content is small, and when a conductive pattern is formed, it is necessary to apply a plurality of times when a relatively thick film is formed. On the other hand, when the content of the silver colloidal particles exceeds the upper limit, the silver content increases and the dispersibility decreases. To prevent this, the frequency of stirring increases.

  Further, the heat loss to 500 ° C. in the thermogravimetric analysis of the silver colloid particles is preferably 1 wt% or more and 25 wt% or less. When the colloidal particles (solid content) are heated to 500 ° C., the dispersant or the like attached to the surface is oxidized and decomposed, and most of them are gasified and disappear. The weight loss due to heating up to 500 ° C. is considered to substantially correspond to the amount of the dispersant in the silver colloid particles. When the loss on heating is less than 1 wt%, the amount of the dispersant with respect to the silver particles is small, and the sufficient dispersibility of the silver particles is lowered. On the other hand, when it exceeds 25 wt%, the amount of the residual dispersant with respect to the silver particles increases, and the specific resistance of the conductor pattern increases. However, the specific resistance can be improved to some extent by heating and sintering after formation of the conductor pattern to decompose and disappear organic components. Therefore, such an effect can be easily obtained when a ceramic molded body sintered at a higher temperature is used as the substrate.

[Ceramic particles]
In addition, it is preferable that the conductor pattern forming ink contains ceramic particles.
The ceramic particles have relatively high hardness and function as an abrasive for the flow path of the conductor pattern forming ink. As a result, when applied to the cleaning method of the present invention, dirt in the droplet discharge device 100 can be more easily removed, and dirt and droplet discharge in the flow path of the conductive pattern forming ink of the droplet discharge device can be obtained. The clogging of the head can be solved more suitably.

In addition, since the conductor pattern forming ink contains ceramic particles, the formed conductor pattern precursor becomes relatively hard, and as a result, the conductor pattern precursor is crushed and widened when a plurality of substrates are stacked. The phenomenon (wiring thickening) is prevented.
Then, the dimensional accuracy of the conductor pattern is increased and the thickness of the wiring is prevented, so that the frequency characteristic (Q value) of the formed conductor pattern is close to a desired one.

The ceramic material that can be used as the ceramic particles is not particularly limited. For example, aluminum oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, lanthanum oxide, zinc oxide, gallium oxide, indium oxide, titanium oxide, and oxide. Metal oxides such as germanium, tin oxide, titanium oxide and zirconium oxide, glass materials such as borosilicate glass, silicate and silicon dioxide, carbides such as silicon carbide, nitrides such as silicon nitride, halides such as fluorite , Antimony oxide, bismuth oxide and the like, or a mixture thereof, and the like can be used, and one or more of these can be used in combination.
Moreover, it is preferable that a ceramic particle contains a metal oxide among the above-mentioned. Such a compound is chemically stable even when it has been in the conductor pattern forming ink for a long time, and is stably dispersed in the ink. Moreover, since the hardness is relatively high, it is possible to suitably remove the dirt on the discharge port.

  In particular, when the ceramic particles contain silicon dioxide or aluminum oxide as the metal oxide, the following effects can be obtained. These compounds have high hardness, are particularly excellent in the cleaning effect, and can more effectively prevent the wiring from becoming thicker. Further, these compounds have a relatively high melting point, and do not melt when the conductor pattern precursor is sintered, but exist as particles. As a result, when the silver particles of the conductor pattern are melted, these ceramic particles are pushed out by the surface tension of the liquid silver, and the ceramic particles are excluded from the formed conductor pattern. As a result, the formed conductor pattern can exhibit the intended performance more reliably and has high reliability. In particular, silicon dioxide and aluminum oxide are generally used as constituent materials of a ceramic molded body to be a substrate, and have little influence on the ceramic substrate formed from the ceramic molded body.

  Moreover, among the above-mentioned ceramic particles, it is preferable to include a glass material, and it is more preferable to include silicon dioxide or silicate. Such a compound can contribute to improvement in the adhesion between the conductor pattern and the substrate by melting at least part of the compound during sintering, and can further increase the reliability of the conductor pattern. In particular, silicon dioxide and silicate are generally used as a constituent material of a ceramic molded body serving as a substrate. When the ceramic molded body contains silicon dioxide or silicate, ceramics formed from the ceramic molded body At the same time, the influence on the substrate is reduced, and at the same time, the adhesion between the conductor pattern and the ceramic substrate is further improved, and the reliability of the conductor pattern is further improved.

The average particle size of the ceramic particles is preferably 5 nm or more and 300 nm or less, and more preferably 30 nm or more and 60 nm or less. As a result, it is possible to more suitably remove dirt adhering to the ink flow path, and it is possible to increase the ink ejection stability by increasing the dispersion stability of the ceramic particles.
Further, the content of the ceramic particles in the conductive pattern forming ink (as will be described later, when the ceramic particles are present as a colloid) is 0.1 wt% or more and 1.6 wt% or less. It is preferably 0.8 wt% or more and 1.6 wt% or less. Thereby, it is possible to prevent the metal particles from adhering to the ink flow path while preventing the ceramic particles from affecting the performance of the formed conductor pattern.

The ceramic particles are preferably dispersed in an aqueous dispersion medium as ceramic colloidal particles having a dispersant attached to the surface thereof. As a result, the dispersibility of the ceramic colloid particles in the aqueous dispersion medium is particularly excellent, and the ink ejection stability is particularly excellent.
Moreover, the heating loss to 500 ° C. in the thermogravimetric analysis of the ceramic colloidal particles is preferably 1 wt% or more and 25 wt% or less. Thereby, it is possible to prevent the specific resistance of the formed conductor pattern from being increased while making the dispersion stability of the ceramic colloidal particles particularly excellent.

[Dispersant]
The conductor pattern forming ink preferably contains a dispersant.
The dispersant adheres to silver particles and ceramic particles to form silver colloid particles and ceramic colloid particles, respectively. Since such silver colloidal particles and ceramic colloidal particles are excellent in dispersion stability, the ejection stability of the droplets of the conductor pattern forming ink is more excellent.

Although it does not specifically limit as a dispersing agent, it has 3 or more of COOH groups and OH groups, and the number of COOH groups is the same as that of OH groups, or contains hydroxy acid or its salt more than it. Is preferred. These dispersants adsorb on the surface of silver particles and ceramic particles to form colloidal particles, and silver colloid particles and ceramic colloid particles are uniformly dispersed in an aqueous solution by the electric repulsive force of COOH groups present in the dispersant. Disperses and stabilizes the colloidal liquid. As described above, since the silver colloid particles and the ceramic colloid particles are stably present in the ink, a fine conductor pattern can be formed more easily. Further, silver particles are uniformly distributed in a pattern (conductor pattern precursor) formed with ink, and cracks, disconnections, and the like are less likely to occur. In contrast, if the number of COOH groups and OH groups in the dispersant is less than 3 or the number of COOH groups is less than the number of OH groups, the dispersibility of the silver colloid particles and ceramic colloid particles is sufficient. May not be obtained.
Examples of such a dispersing agent include citric acid, malic acid, trisodium citrate, tripotassium citrate, trilithium citrate, triammonium citrate, disodium malate, tannic acid, gallotannic acid, and pentaploid tannin. Of these, one or a combination of two or more can be used.

  Further, the dispersant may contain mercapto acid or a salt thereof having two or more COOH groups and SH groups. In these dispersants, mercapto groups are adsorbed on the surfaces of silver particles and ceramic particles to form colloidal particles, and the colloidal particles are uniformly dispersed in an aqueous solution by the electric repulsive force of COOH groups present in the dispersant. Has the function of stabilizing the colloidal liquid. As described above, since the silver colloid particles and the ceramic colloid particles are stably present in the ink, a fine conductor pattern can be formed more easily. Further, silver particles are uniformly distributed in a pattern (conductor pattern precursor) formed with ink, and cracks, disconnections, and the like are less likely to occur. On the other hand, when the number of COOH groups and SH groups in the dispersant is less than 2, that is, only one, the dispersibility of the silver colloid particles and ceramic colloid particles may not be sufficiently obtained.

  Examples of such dispersants include mercaptoacetic acid, mercaptopropionic acid, thiodipropionic acid, mercaptosuccinic acid, thioacetic acid, sodium mercaptoacetate, sodium mercaptopropionate, sodium thiodipropionate, disodium mercaptosuccinate, Examples include potassium mercaptoacetate, potassium mercaptopropionate, potassium thiodipropionate, dipotassium mercaptosuccinate, and the like, and one or more of these can be used in combination.

[Organic binder]
The conductive pattern forming ink may contain an organic binder. The organic binder prevents aggregation of silver particles in the conductor pattern precursor formed by the conductor pattern forming ink. That is, in the formed conductor pattern precursor, the organic binder is present between the silver particles, whereby the silver particles can be prevented from aggregating and cracking in a part of the pattern can be prevented. Further, at the time of sintering, the organic binder can be decomposed and removed, and the silver particles in the conductor pattern precursor are bonded to form a conductor pattern.

  Although it does not specifically limit as an organic binder, For example, polyethyleneglycol # 200 (weight average molecular weight 200), polyethyleneglycol # 300 (weight average molecular weight 300), polyethyleneglycol # 400 (average molecular weight 400), polyethyleneglycol # 600 ( Weight average molecular weight 600), polyethylene glycol # 1000 (weight average molecular weight 1000), polyethylene glycol # 1500 (weight average molecular weight 1500), polyethylene glycol # 1540 (weight average molecular weight 1540), polyethylene glycol # 2000 (weight average molecular weight 2000), etc. Polyethylene glycol, polyvinyl alcohol # 200 (weight average molecular weight: 200), polyvinyl alcohol # 300 (weight average molecular weight: 300), polyvinyl alcohol # 400 (average molecular weight: 400), polyvinyl alcohol # 600 (weight average molecular weight: 600), polyvinyl alcohol # 1000 (weight average molecular weight: 1000), polyvinyl alcohol # 1500 (weight average molecular weight: 1500), polyvinyl alcohol # Polyglycerin compounds having a polyglycerin skeleton such as polyvinyl alcohol such as 1540 (weight average molecular weight: 1540), polyvinyl alcohol # 2000 (weight average molecular weight: 2000), polyglycerin, polyglycerin ester, etc. Alternatively, two or more kinds can be used in combination. Examples of polyglycerol esters include polyglycerol monostearate, tristearate, tetrastearate, monooleate, pentaoleate, monolaurate, monocaprylate, polycinnolate, sesquistearate, decaoleate, and sesquioleate. Etc.

Among these, when a polyglycerin compound is used as the organic binder, the following effects can be obtained.
The polyglycerin compound can particularly suitably prevent the conductor pattern precursor from cracking when the conductor pattern precursor formed by the conductor pattern forming ink is dried (dedispersing medium). This is considered as follows. When the polyglycerin compound is contained in the conductive pattern forming ink, polymer chains exist between the silver particles (metal particles), and the polyglycerin compound makes the distance between the silver particles moderate. Can do. Furthermore, since the polyglycerin compound has a relatively high boiling point, it is not removed when the aqueous dispersion medium is removed, and adheres around the silver particles. As described above, at the time of removing the aqueous dispersion medium, the polyglycerin compound continuously encapsulates the silver particles, and as a result, rapid volume shrinkage due to volatilization of the aqueous dispersion medium is avoided and silver grain growth (aggregation) is hindered. It is considered that generation of cracks in the conductor pattern precursor is suppressed.

Further, the polyglycerin compound can more reliably prevent disconnection from occurring during sintering when forming the conductor pattern. This is considered as follows. Polyglycerin compounds have a relatively high boiling point or decomposition temperature. Therefore, in the process of forming the conductor pattern from the conductor pattern forming ink, the polyglycerol compound is not evaporated or thermally (oxidized) decomposed to a relatively high temperature after the aqueous dispersion medium evaporates. Can exist in the body. Therefore, until the polyglycerin compound evaporates or is thermally (oxidized) decomposed, the polyglycerin compound exists around the silver particles, and the approach and aggregation of the silver particles can be suppressed, and the polyglycerin compound is decomposed. Later, the silver particles can be joined more uniformly. Furthermore, a polymer chain (polyglycerin compound) exists between silver particles (metal particles) in the pattern during sintering, and the polyglycerin compound can keep the distance between the silver particles. Moreover, this polyglycerin compound has moderate fluidity | liquidity. For this reason, by including a polyglycerin compound, the conductor pattern precursor has excellent followability to expansion / contraction due to temperature change of the ceramic molded body.
From the above, it is considered that disconnection of the formed conductor pattern can be more reliably prevented.

  In addition, since the polyglycerin compound has a relatively large number of hydroxyl groups, it has excellent affinity with the above-described metal oxide. For this reason, when the conductive pattern forming ink contains a metal oxide as ceramic particles and a polyglycerin compound, the dispersion stability of the ceramic particles in the conductive pattern forming ink is particularly excellent, and the conductive pattern formation In particular, the ejection stability of the ink drops is excellent.

Moreover, by including such a polyglycerin compound, the viscosity of the ink can be made more appropriate, and the ejection stability from the ink jet head can be improved more effectively. In addition, film formability can be improved.
Among the above-mentioned polyglycerin compounds, polyglycerin is preferably used. Polyglycerin is a component that is particularly excellent in the ability to follow expansion and contraction due to temperature changes of the ceramic molded body, and can be more reliably removed from the conductor pattern after the ceramic molded body is sintered. As a result, the electrical characteristics of the conductor pattern can be made higher. Furthermore, since polyglycerin has high solubility in an aqueous dispersion medium, it can be suitably used.

  The organic binder preferably has a weight average molecular weight of 300 or more and 3000 or less, more preferably 400 or more and 1000 or less, and still more preferably 400 or more and 600 or less. Thereby, when the pattern formed with the conductor pattern forming ink is dried, the occurrence of cracks can be more reliably prevented. On the other hand, if the weight average molecular weight of the organic binder is less than the lower limit, depending on the composition of the organic binder, the organic binder tends to be decomposed when removing the aqueous dispersion medium, and breakage and cracks are generated. The effect to prevent becomes small. When the weight average molecular weight of the organic binder exceeds the upper limit, the solubility and dispersibility in the ink may be reduced depending on the composition of the organic binder due to the excluded volume effect or the like.

  Further, the content of the organic binder in the ink is preferably 1 wt% or more and 30 wt% or less, and more preferably 5 wt% or more and 20 wt% or less. This makes it possible to more effectively prevent the occurrence of cracks and disconnections while making the ink ejection stability particularly excellent. On the other hand, when the content of the organic binder is less than the lower limit, the effect of preventing disconnection or cracking may be reduced depending on the composition of the organic binder. If the content of the organic binder exceeds the upper limit, it may be difficult to make the viscosity of the ink sufficiently low depending on the composition of the organic binder.

[Drying inhibitor]
Further, the conductor pattern forming ink may contain a drying inhibitor. The drying inhibitor prevents unintended volatilization of the aqueous dispersion medium in the ink. As a result, the aqueous dispersion medium can be prevented from volatilizing in the vicinity of the ejection portion of the ink jet apparatus, and the increase in the viscosity and drying of the ink can be suppressed. As a result of including such a drying inhibitor, the conductive pattern forming ink has particularly excellent ink droplet ejection stability. That is, variation in the weight of ink droplets is small, and clogging, flight bending, and the like are small. In particular, even when the ink jet device is in a standby state without being operated for a long time (for example, 5 days) after the ink for forming the conductor pattern is filled in the ink jet device, the conductor pattern forming ink of the present invention is used. The ink can be accurately ejected to the target position in a uniform amount.

  Such a drying inhibitor is not particularly limited, and examples thereof include compounds represented by the following formula (I), sugar alcohols, alkanolamines, etc., and one or more of these may be used in combination. Can do. These compounds have a function of preventing volatilization of the aqueous dispersion medium as described above, and have a large number of polar groups such as hydroxyl groups and carbonyl groups. For this reason, the metal oxide is encapsulated in these conductors. Disperses stably in the pattern forming ink. For this reason, when the conductive pattern forming ink contains a metal oxide as the ceramic particles and the above compound, the dispersion stability of the ceramic particles in the conductive pattern forming ink is particularly excellent. In particular, the ejection stability of the ink drops is excellent.

（ただし、Ｒ、Ｒ’は、それぞれ、Ｈまたはアルキル基である。）

(However, R and R ′ are each H or an alkyl group.)

The compound represented by the above formula (I) is a component having a high hydrogen bonding property. For this reason, it has a high affinity with water, can retain an appropriate amount of water, and can prevent unintentional volatilization of the aqueous dispersion medium of the conductive pattern forming ink.
Moreover, the said compound is comparatively easy to burn, and when forming a conductor pattern, it can remove (oxidative decomposition) more easily from the inside of a conductor pattern.

  Further, when the pattern formed by the conductor pattern forming ink is dried (dedispersion medium), the concentration of the compound increases as the aqueous dispersion medium volatilizes. Thereby, since the viscosity of the conductor pattern precursor is increased, the ink constituting the conductor pattern precursor is more reliably prevented from flowing out to an unintended portion. As a result, the formed conductor pattern can be formed into a desired shape with higher accuracy.

  In addition, when the metal particles (silver particles) or ceramic particles are colloidal particles having a dispersant attached to the surface as described above, the compound as described above is bonded to the surface dispersant by hydrogen bonding, and the metal particles or It has the effect of improving the dispersion stability of ceramic particles. Accordingly, the ejection stability of the conductor pattern forming ink is excellent, and the storage stability is also excellent.

  As described above, R and R ′ in the compound represented by the above formula (I) used in the present invention are each hydrogen or an alkyl group, but R and R ′ are both hydrogen. preferable. That is, urea is preferable. As a result, the moisture retention as described above can be made particularly high, and particularly excellent ejection stability can be obtained. Further, when metal particles or ceramic particles are present as colloidal particles as described above, particularly excellent dispersion stability is exhibited.

  The content of the compound represented by the above formula (I) in the ink is preferably 5 wt% or more and 25 wt% or less, more preferably 8 wt% or more and 20 wt% or less, and 10 wt% or more and 18 wt% or less. % Or less is more preferable. Thereby, unintentional drying of the conductor pattern forming ink can be prevented more efficiently. As a result, the ink ejection stability can be made particularly excellent.

Alkanolamine is a highly moisturizing component, and when the metal particles and ceramic particles are colloidal particles as described above, the functional group of the dispersant on the surface of the colloidal particles can be activated. The dispersion stability of the ceramic particles can be made higher.
Examples of the alkanolamine include monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, and tripropanolamine.

The alkanolamine is preferably a tertiary amine. Tertiary amines have particularly high moisture retention among alkanolamines, and can make the above effects more remarkable.
Among tertiary amines, it is particularly preferable to use triethanolamine from the viewpoints of ease of handling, high moisture retention, and the like.

The content of alkanolamine in the conductor pattern forming ink is preferably 1 wt% or more and 10 wt% or less, and more preferably 3 wt% or more and 7 wt% or less. As a result, the moisture retention of the conductor pattern forming ink can be made sufficiently high, and the ejection stability of the conductor pattern forming ink can be made more excellent.
Sugar alcohol is obtained by reducing aldehyde groups and ketone groups of sugars.

  Sugar alcohol is a compound having high moisture retention. In addition, since sugar alcohol has a large number of oxygen per molecular weight, it is easily decomposed and removed when the atmosphere reaches the decomposition temperature of sugar alcohol. For this reason, when forming a conductor pattern, sugar alcohol can be reliably removed (oxidative decomposition) from the conductor pattern by making the temperature of the conductor pattern higher than the decomposition temperature of the sugar alcohol.

  Examples of sugar alcohols include threitol, erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, arabitol, ribitol, xylitol, sorbitol, mannitol, threitol, glycol, tallitol, galactitol, allitol, altritol, dolitol, iditol. Glycerin (glycerol), inositol, maltitol, isomaltitol, lactitol, tranitol and the like, and one or more of these can be used in combination.

  The content of the sugar alcohol in the conductive pattern forming ink as described above is preferably 3 wt% or more and 20 wt% or less, and more preferably 5 wt% or more and 15 wt% or less. Thereby, volatilization of the aqueous dispersion medium of the conductor pattern forming ink can be more reliably suppressed, and the conductor pattern forming ink has particularly excellent droplet discharge stability over a longer period of time.

[Surface tension modifier]
Further, the conductive pattern forming ink may contain a surface tension adjusting agent.
The surface tension adjusting agent is used to adjust the contact angle between the conductor pattern forming ink and the ceramic molded body to a predetermined angle.
As the surface tension adjusting agent, various surfactants can be used, and one or a combination of two or more types can be used, but it is preferable to include an acetylene glycol compound.

  The contact angle between the conductive pattern forming ink and the ceramic molded body can be adjusted within a predetermined range with a small addition amount of the acetylene glycol compound. Thus, a finer conductor pattern can be formed by adjusting the contact angle between the conductor pattern forming ink and the ceramic molded body within a predetermined range. Further, even when bubbles are mixed in the discharged droplets, the bubbles can be quickly removed. As a result, generation of cracks and disconnections in the formed conductor pattern can be more effectively prevented.

Examples of acetylene glycol compounds include Surfynol 104 series (104E, 104H, 104PG-50, 104PA, etc.), Surfynol 400 series (420, 465, 485, etc.), Olphine series (EXP4036, EXP4001, E1010, etc.). ("Surfinol" and "Orphine" are trade names of Nissin Chemical Industry Co., Ltd.) and the like, and one or more of these can be used in combination.
The ink preferably contains two or more acetylene glycol compounds having different HLB values. The contact angle between the conductor pattern forming ink and the ceramic molded body can be easily adjusted within a predetermined range.

In particular, the difference between the HLB value of the acetylene glycol compound having the highest HLB value and the HLB value of the acetylene glycol compound having the lowest HLB value among two or more kinds of acetylene glycol compounds contained in the ink is 4 It is preferably 12 or more and more preferably 5 or more and 10 or less. Accordingly, the contact angle between the conductor pattern forming ink and the ceramic molded body can be easily adjusted within a predetermined range with a smaller amount of the acetylene glycol compound.
When an ink containing two or more acetylene glycol compounds is used, the HLB value of the acetylene glycol compound having the highest HLB value is preferably 8 or more and 16 or less, and preferably 9 or more and 14 or less. More preferred.

Moreover, when using what contains 2 or more types of acetylene glycol type compounds in an ink, it is preferable that the HLB value of the acetylene glycol type compound with the lowest HLB value is 2-7, and it is 3-5. Is more preferable.
The content of the surface tension adjusting agent contained in the ink is preferably 0.001 wt% or more and 1 wt% or less, and more preferably 0.01 wt% or more and 0.5 wt% or less. As a result, the contact angle between the conductor pattern forming ink and the ceramic molded body can be more effectively adjusted to a predetermined range.

[Other ingredients]
The constituent components of the conductor pattern forming ink are not limited to the above components, and may include components other than those described above.
For example, the conductor pattern forming ink may contain 1,3-propanediol in addition to the above components. As a result, volatilization of the aqueous dispersion medium in the vicinity of the ejection portion of the inkjet head can be more effectively suppressed, the viscosity of the ink can be made more appropriate, and ejection stability is further improved.

When 1,3-propanediol is contained in the ink, the content is preferably 0.5 wt% or more and 20 wt% or less, and more preferably 2 wt% or more and 10 wt% or less. Thereby, the ejection stability of ink can be improved more effectively.
In addition, for example, the conductor pattern forming ink may contain a polyhydric alcohol such as ethylene glycol, 1,3-butylene glycol, and propylene glycol. The conductor pattern forming ink may contain thiourea in addition to the urea described above.

  The contact angle between the conductor pattern forming ink and the ceramic molded body is not particularly limited, but is preferably 40 ° or more and 80 ° or less, and more preferably 50 ° or more and 80 ° or less. If the contact angle is too small, it may be difficult to form a conductor pattern with a fine line width. On the other hand, if the contact angle is too large, it may be difficult to form a conductor pattern with a uniform line width depending on the discharge conditions and the like. In addition, the contact area between the landed droplet and the ceramic molded body may be too small, and the landed droplet may be displaced from the landing position.

  The viscosity of the conductor pattern forming ink is not particularly limited, but is preferably 2.0 mPa · s or more and 11.0 mPa · s or less, and more preferably 4.0 mPa · s or more and 6.0 mPa · s or less. preferable. As a result, the droplet discharge stability can be improved, and wetting and spreading of the ink that has landed on the ceramic molded body can be prevented, and a conductor pattern precursor having a fine line width can be formed. Can do.

<< Method for producing conductive pattern forming ink >>
Next, an example of a method for producing the above-described conductor pattern forming ink will be described.
In this embodiment, the conductor pattern forming ink will be described as a colloidal liquid in which silver colloidal particles are dispersed in an aqueous dispersion medium.
When manufacturing the ink of this embodiment, first, an aqueous solution in which the dispersant and the reducing agent are dissolved is prepared.

As a blending amount of the dispersing agent, it is preferable to blend so that a molar ratio of silver and the dispersing agent in a silver salt such as silver nitrate as a starting material is about 1: 1 to 1: 100. When the molar ratio of the dispersant to the silver salt is increased, the particle size of the silver particles is reduced and the contact points between the particles after the formation of the conductor pattern is increased, so that a film having a low volume resistance value can be obtained.
The reducing agent has a function of generating silver particles by reducing Ag ⁺ ions in a silver salt such as silver nitrate (Ag ⁺ NO ³⁻ ) which is a starting material.

  The reducing agent is not particularly limited, and examples thereof include amines such as hydrazine, dimethylaminoethanol, methyldiethanolamine, and triethanolamine; hydrogen compounds such as sodium borohydride, hydrogen gas, and hydrogen iodide; carbon monoxide, Oxides such as hyposulfite hypophosphorous acid, low valent metal salts such as Fe (II) compounds and Sn (II) compounds, saccharides such as D-glucose, organic compounds such as formaldehyde, or the above dispersions Citric acid and malic acid which are the hydroxy acids mentioned as agents, and trisodium citrate, tripotassium citrate, trilithium citrate, triammonium citrate, disodium malate and tannic acid which are hydroxy acid salts It is done. Among them, tannic acid and hydroxy acid can be suitably used because they function as a reducing agent and at the same time exert an effect as a dispersant. Alternatively, mercaptoacetic acid, mercaptopropionic acid, thiodipropionic acid, mercaptosuccinic acid, mercaptosuccinic acid, sodium mercaptoacetate, which is thioacetic acid or mercaptoate, listed above as a dispersant that forms a stable bond on the metal surface, Sodium mercaptopropionate, sodium thiodipropionate, sodium mercaptosuccinate, potassium mercaptoacetate, potassium mercaptopropionate, potassium thiodipropionate, potassium mercaptosuccinate and the like can be suitably used. These dispersants and reducing agents may be used alone or in combination of two or more. When these compounds are used, the reduction reaction may be promoted by applying light or heat.

In addition, the amount of the reducing agent is required to be an amount that can completely reduce the silver salt that is the starting material. However, the excessive reducing agent remains as impurities in the silver colloidal solution, and the film is formed after film formation. The necessary minimum amount is preferable because it causes deterioration of conductivity. Specifically, the molar ratio of the silver salt to the reducing agent is about 1: 1 to 1: 3.
In this embodiment, it is preferable to adjust the pH of the aqueous solution to 6 to 12 after dissolving the dispersant and the reducing agent to prepare the aqueous solution.

This is due to the following reasons. For example, when trisodium citrate, which is a dispersant, and ferrous sulfate, which is a reducing agent, are mixed, the pH is about 4 to 5 and lower than the above pH 6, although it depends on the overall concentration. The hydrogen ions present at this time move the equilibrium of the reaction represented by the following reaction formula (1) to the right side, and the amount of COOH increases. Therefore, thereafter, the electric repulsive force on the surface of the silver particles obtained by dropping the silver salt solution decreases, and the dispersibility of the silver particles (colloid particles) decreases.
−COO ⁻ + H ⁺ → −COOH (1)

Therefore, after dissolving the dispersant and the reducing agent to prepare an aqueous solution, an alkaline compound is added to the aqueous solution to reduce the hydrogen ion concentration.
It does not specifically limit as an alkaline compound to add, For example, sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia water, the alkanolamine mentioned above, etc. can be used. Among these, when alkanolamine is used, the pH can be easily adjusted and the dispersion stability of the formed silver colloidal particles can be further improved.
In addition, when there is too much addition amount of an alkaline compound and pH exceeds 12, precipitation of the hydroxide of the ion of the remaining reducing agent like iron ion will occur easily.

Next, in the ink manufacturing process of this embodiment, an aqueous solution containing a silver salt is dropped into an aqueous solution in which the prepared dispersant and reducing agent are dissolved.
The silver salt is not particularly limited, and for example, silver acetate, silver carbonate, silver oxide, silver sulfate, silver nitrite, silver chlorate, silver sulfide, silver chromate, silver nitrate, silver dichromate and the like can be used. . Among these, silver nitrate having a high solubility in water is preferable.
The amount of the silver salt is determined in consideration of the content of the desired colloidal particles and the ratio reduced by the reducing agent. For example, in the case of silver nitrate, 15 to 70 parts per 100 parts by weight of the aqueous solution. The amount is preferably about parts by weight.

The silver salt aqueous solution is prepared by dissolving the silver salt in pure water, and the prepared silver salt aqueous solution is gradually dropped into the aqueous solution in which the dispersing agent and reducing agent described above are dissolved.
In this step, the silver salt is reduced to silver particles by a reducing agent, and the dispersant is adsorbed on the surface of the silver particles to form silver colloidal particles. As a result, an aqueous solution in which silver colloidal particles are colloidally dispersed in the aqueous solution is obtained.

In the obtained solution, in addition to the colloidal particles, a reducing agent residue and a dispersing agent are present, and the ion concentration of the whole liquid is high. The liquid in such a state is likely to coagulate and precipitate easily. Therefore, it is desirable to perform cleaning in order to remove excess ions in such an aqueous solution and lower the ion concentration.
As a washing method, for example, the aqueous solution containing the obtained colloidal particles is allowed to stand for a certain period, and the resulting supernatant liquid is removed, and then pure water is added and stirred again, and further left to stand for a certain period. In addition, a method of repeating the step of removing the supernatant liquid several times, a method of performing centrifugation instead of the above-mentioned standing, a method of removing ions by ultrafiltration, and the like can be mentioned.

  Alternatively, cleaning may be performed by the following method. After the solution is prepared, the pH of the solution is adjusted to an acidic region of 5 or less, and the electric repulsive force on the surface of the silver particles is reduced by moving the equilibrium of the reaction of the above reaction formula (1) to the right side. It is possible to remove salts and solvents by washing in a state where metal colloidal particles are aggregated. In the case of a metal colloid particle having a low molecular weight sulfur compound such as mercapto acid on the particle surface as a dispersant, a stable bond is formed on the metal surface. Therefore, the aggregated metal colloid particle has an alkaline pH of 6 or more. By re-adjusting to this region, it is possible to obtain a metal colloid liquid that is easily redispersed and excellent in dispersion stability.

In the ink production process of the present embodiment, it is preferable to adjust the final pH to 6 to 11 by adding an aqueous alkali metal hydroxide solution to an aqueous solution in which silver colloidal particles are dispersed as necessary after the above step.
This is because the concentration of sodium, which is an electrolyte ion, may be decreased because washing is performed after reduction. In the solution in such a state, the equilibrium of the reaction represented by the following reaction formula (2) moves to the right side. To do. If this is the case, the electrical repulsive force of the silver colloid is reduced and the dispersibility of the silver particles is lowered. Therefore, by adding an appropriate amount of alkali hydroxide, the equilibrium of the reaction formula (2) is shifted to the left side, and silver It stabilizes the colloid.
—COO ^— Na ⁺ + H ₂ O → —COOH + Na ⁺ + OH ⁻ (2)

As said alkali metal hydroxide used at this time, the compound similar to the compound used when adjusting pH first can be mentioned, for example.
If the pH is less than 6, the equilibrium of the reaction formula (2) shifts to the right side, so that the colloidal particles become unstable. This is not preferable because precipitation of selenium tends to occur. However, if iron ions or the like are removed in advance, there is no major problem even if the pH exceeds 11.
Cations such as sodium ions are preferably added in the form of hydroxides. This is because the self-protolysis of water can be used, so that cations such as sodium ions can be added to the aqueous solution most effectively.
Moreover, in the said process of adjusting pH to 6-11, you may use an alkanolamine instead of an alkali metal hydroxide aqueous solution.

By adding other components such as a ceramic colloid liquid in which ceramic colloid particles are dispersed to the aqueous solution in which silver colloid particles are dispersed as described above, a conductive pattern forming ink (for forming a conductive pattern of the present invention) is added. Ink).
In addition, the addition time of other components, such as a ceramic colloid liquid, is not specifically limited, As long as it is after formation of a silver colloid particle, it may be anytime.
As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, in the above-described embodiment, the case where the colloidal liquid is used as the dispersion liquid in which the metal particles are dispersed in the solvent has been described.

  In the above-described embodiment, the conductor pattern forming ink is described as having silver particles dispersed therein, but may be other than silver. Examples of the metal contained in the metal particles include silver, copper, palladium, platinum, gold, and alloys thereof. One or more of these can be used in combination. When the metal particles are an alloy, the metal is mainly used, and an alloy containing another metal may be used. Moreover, the alloy which the said metals mixed with arbitrary ratios may be sufficient. Further, mixed particles (for example, particles in which silver particles, copper particles, and palladium particles are present in an arbitrary ratio) may be dispersed in a liquid. Since these metals have a low resistivity and are stable and are not oxidized by heat treatment, it is possible to form a stable conductor pattern with a low resistance by using these metals.

  For example, in the above-described embodiment, the ceramic molded body is used as the substrate on which the conductor pattern precursor is formed. However, the present invention is not limited to this. The substrate used for forming the conductor pattern precursor is not particularly limited, and examples thereof include a ceramic sintered body, an alumina sintered body, a substrate made of polyimide resin, phenol resin, glass epoxy resin, glass, and the like.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
[1] Preparation of Ink for Conductive Pattern Formation Ink for forming a conductive pattern was produced as follows.
(Ink 1-13)
17 mL of trisodium citrate dihydrate and 0.36 g of tannic acid were dissolved in 50 mL of water made alkaline by adding 3 mL of 10N-NaOH aqueous solution. To the obtained solution, 3 mL of 3.87 mol / L silver nitrate aqueous solution was added and stirred for 2 hours to obtain a silver colloid solution. The obtained silver colloid solution was desalted by dialysis until the electrical conductivity was 30 μS / cm or less. After dialysis, the coarse metal colloid particles were removed by centrifugation at 3000 rpm for 10 minutes.

  To this silver colloid liquid, aluminum oxide colloid liquid (NANOBYK-3600, manufactured by Big Chemie Japan Co., Ltd., average particle size: 40 nm, content of aluminum oxide of solid content: 50 wt%) as a ceramic particle, colloidal silica ( As a drying inhibitor, colloidal liquid of silicon dioxide, manufactured by Nissan Chemical Industries, Ltd., Snowtex series and MP series, average particle size: 4.0 to 450 nm, content of silicon dioxide out of solid content: 40 wt%) Alkanolamine, urea, xylitol, polyglycerol, Surfynol 104PG-50 (manufactured by Nissin Chemical Industry Co., Ltd.) and Olphine EXP4036 (manufactured by Nissin Chemical Industry Co., Ltd.) as a surface tension modifier Add ion exchange water for concentration adjustment and adjust And a conductive pattern forming ink.

(Ink 14)
A conductive pattern forming ink was produced in the same manner as the ink 1 except that the ceramic particles and the dispersant for ceramic particles were not added and the blending amounts of other components were as shown in Table 1.
Table 1 shows the composition of each conductor pattern forming ink. In Table, SiO ₂ and silicon dioxide, aluminum oxide _Al 2 _{O 3,} and triethanolamine TEA, monoethanolamine MEA, diethanolamine DEA, urea Ur, xylitol Xyl, and Sor sorbitol.

[Selection of ink for forming conductor pattern used for droplet discharge device]
(Examples 1-14)
A droplet ejection device as shown in FIGS. 1 and 2 installed in a clean room of room temperature 25 ° C., relative humidity 50%, class 100, is filled with the conductor pattern forming ink shown in Table 2, and the drive waveform of the piezo element In an optimized state, 150,000 (150,000 droplets) of droplets were continuously discharged from each nozzle of the droplet discharge head. Thereafter, the inside of the droplet discharge device such as the ink flow path was cleaned using the cleaning mechanism of the droplet discharge device. The cleaning was performed by sucking ink from the ink storage unit into the droplet discharge device for 300 seconds using a suction unit. The cleaning liquid was sucked at a rate of 30 mL / min per head. The suction was performed while driving the piezoelectric element with an applied voltage having a frequency of 150 kHz.
The sucked ink was passed through a membrane filter and then washed again through the recovered ink transport path.
(Comparative example)
Droplets were discharged in the same manner as in Example 1 except that no cleaning was performed.

[3] Stability evaluation of droplet discharge (Stable discharge evaluation)
After washing in the above example (after ejecting droplets in the comparative example), the same ink was filled again in the ink flow path of the droplet ejection device. Filling was performed by flowing the conductor pattern forming ink at a flow rate of 1.0 ml / min for 300 seconds into the ink flow path. Subsequently, 150,000 (150,000 drops) of droplets were continuously discharged from each nozzle of the droplet discharge head. For the 150,000 droplets ejected from the designated nozzle near the center of the inkjet head after filling with the conductor pattern forming ink, the amount of deviation d from the center aiming position of the center position of each landed droplet An average value was obtained and evaluated according to the following four criteria. It can be said that the smaller the value is, the more effectively the occurrence of flight bending is prevented.
A: The average value of the shift amounts d is less than 0.03 μm.
B: The average value of the shift amount d is 0.03 μm or more and less than 0.08 μm.
C: The average value of the shift amount d is 0.08 μm or more and less than 0.12 μm.
D: The average value of the shift amount d is 0.12 μm or more.

These results are also shown in Table 2.
As is clear from Table 2, the cleaning method of the present invention was excellent in cleaning properties. On the other hand, satisfactory results were not obtained in each comparative example in which the cleaning method of the present invention was not used.
Further, when the content of the silver colloid particles in the conductor pattern forming ink was changed to 20 wt% and 30 wt%, the same result as above was obtained.

  DESCRIPTION OF SYMBOLS 1 ... Conductor pattern formation ink (ink) 15 ... Ceramic molded body 100 ... Inkjet device (droplet ejection device) 110 ... Inkjet head (droplet ejection head, head) 111 ... Head body 112 ... Vibration plate 113 ... Piezo element 114 ... Main body 115 ... Nozzle plate 115P ... Ink discharge surface 116 ... Reservoir 117 ... Ink chamber 118 ... Nozzle (protruding portion) 130 ... Base 140 ... Table 150 ... Ink storage tank 151 ... Conveying path 152 ... Cock 153 ... Self-sealing valve 170 ... Table positioning means 171 ... First moving means 172 ... Motor 180 ... Head positioning means 181 ... Second moving means 182 ... Linear motors 183, 184, 185 ... Motor 190 ... Control device 191 ... Drive circuit 200 ... Suction means 201 Sucking ink conveying path 210 ... recovery tank 220 ... recovered ink conveying path 221 ... filter S ... substrate

Claims (8)

A cleaning method for cleaning a droplet discharge device that is used for forming a conductor pattern by a droplet discharge method and discharges a conductor pattern forming ink in which metal particles are dispersed in an aqueous dispersion medium,
The droplet discharge device includes a droplet discharge head including a discharge unit that discharges the conductor pattern forming ink, and a transport path for transporting the conductor pattern forming ink to the droplet discharge head. ,
The droplet discharge head includes a head body, a diaphragm, and a piezo element,
The conductor pattern forming ink is fed into the droplet discharge head via the transport path, and the piezoelectric element is driven by the applied voltage having a frequency of 10 kHz or more and 300 kHz or less from the discharge unit to the conductor pattern. A method for cleaning a droplet discharge device, comprising: sucking the ink for forming and then returning the sucked ink for forming a conductor pattern to the droplet discharge head.   The method for cleaning a droplet discharge device according to claim 1, wherein the conductive pattern forming ink includes ceramic particles.   The method for cleaning a droplet discharge device according to claim 2, wherein the ceramic particles include a metal oxide.   The method for cleaning a droplet discharge device according to claim 3, wherein the metal oxide is silicon dioxide or aluminum oxide.   The method for cleaning a droplet discharge device according to claim 2, wherein the ceramic particles have an average particle diameter of 5 nm to 300 nm.   The method for cleaning a droplet discharge device according to any one of claims 1 to 5, wherein the content of the ceramic particles in the conductive pattern forming ink is 0.1 wt% or more and 1.6 wt% or less.   The method for cleaning a droplet discharge device according to claim 1, wherein the suctioned conductor pattern forming ink is returned to the droplet discharge head via a filter. A droplet discharge device that is used for forming a conductor pattern by a droplet discharge method and discharges a conductor pattern forming ink in which metal particles are dispersed in an aqueous dispersion medium,
In order to clean the inside of the droplet discharge device, a droplet discharge head having a discharge portion for discharging the conductor pattern formation ink, a conveyance path for conveying the conductor pattern formation ink to the droplet discharge head And a cleaning mechanism
The droplet discharge head includes a head body, a diaphragm, and a piezo element,
The cleaning mechanism includes a suction unit that sucks the conductor pattern forming ink in the droplet discharge head, a collection tank that collects the conductor pattern forming ink sucked by the suction unit, and a suction unit. A suction ink transport path for transporting the sucked conductor pattern forming ink to the recovery tank, and a recovery ink transport for transporting the conductor pattern formation ink recovered to the recovery tank to the droplet discharge head side again A droplet discharge device comprising a path.

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