JP2011152504A - Method for cleaning 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 without making any adverse impact on a head for discharging the liquid droplet of the apparatus. <P>SOLUTION: The method for cleaning the apparatus for discharging liquid droplets is a method for cleaning the apparatus which discharges ink whose metal particles are dispersed in an aqueous dispersion medium, wherein the apparatus includes: an reservoir which reserves ink; a head for discharging the liquid droplet with a discharger which discharges the ink; a path for carrying the ink from the reservoir to the head; a self-sealing valve which is arranged on the path and prevents the ink from flowing back; and a filter which is arranged closer to the reservoir side than to the self-sealing valve on the path. The apparatus flows a cleaning solution used for cleaning the apparatus in the path to the direction opposite to that to which the ink flows. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cleaning method for 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

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for cleaning a droplet discharge device that can suitably eliminate contamination in the flow path of the conductor pattern forming ink of the droplet discharge device without affecting the droplet discharge head of the droplet discharge device. It is to provide.

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: an ink storage layer that stores the conductive pattern forming ink; a droplet discharge head that includes a discharge unit that discharges the conductive pattern forming ink; and the droplet discharge from the ink storage unit. A transport path for transporting the conductor pattern forming ink toward the head; a self-sealing valve provided in the transport path to prevent backflow of the conductor pattern forming ink; and the self-sealing valve of the transport path More than the filter provided on the ink storage part side,
A cleaning liquid used for cleaning the droplet discharge device is caused to flow in the transport path in a direction opposite to a direction in which the conductor pattern forming ink flows.
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 without affecting the droplet discharge head of the droplet discharge device.

In the method for cleaning a droplet discharge device of the present invention, it is preferable that the cleaning liquid that has flowed into the transport path is recovered after passing through the self-sealing valve and the filter.
Thus, the self-sealing valve and the filter can be easily cleaned without affecting the droplet discharge head of the droplet discharge device.
In the method for cleaning a droplet discharge device of the present invention, it is preferable that the cleaning liquid includes ceramic particles and an aqueous dispersion medium in which the ceramic particles are dispersed.
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, it is possible to suitably remove dirt in the flow path of the conductor pattern forming ink.

In the method for cleaning a droplet discharge device of the present invention, the metal oxide is preferably aluminum oxide, zinc oxide, or titanium oxide.
These compounds have a higher hardness than metal particles having electrical conductivity, and have a relatively high detergency.
In the method for cleaning a droplet discharge device of the present invention, the ceramic particles preferably include a glass material.
The glass material has a function of adsorbing dirt adhering to the inside of the droplet discharge device such as a flow path of the ink for forming the conductor pattern. Can be washed.

In the cleaning method for a droplet discharge device of the present invention, the ceramic particles preferably have an average particle size of 10 nm to 300 nm.
Thereby, the cleaning effect of ceramic particles can be made particularly excellent.
In the cleaning method of the droplet discharge device of the present invention, the content of the ceramic particles in the cleaning liquid is preferably 1 wt% or more and 30 wt% or less.
Accordingly, it is possible to prevent the metal particles from adhering to the droplet discharge device and to prevent the ceramic particles from remaining in the droplet discharge device after cleaning.

In the method for cleaning a droplet discharge device of the present invention, both the cleaning liquid and the conductor pattern forming ink include a dispersant,
It is preferable that the dispersant contained in the cleaning liquid contains at least a part of components constituting the dispersant contained in the conductor pattern forming ink.
Thereby, the cleaning liquid becomes more excellent in cleaning properties. Further, after cleaning, the cleaning liquid in the ink flow path and the conductor pattern forming ink can be quickly replaced.

In the cleaning method for a droplet discharge device of the present invention, the cleaning liquid has three or more COOH groups and OH groups as a dispersant, and the number of COOH groups is equal to the number of OH groups or COOH. It is preferable to include a hydroxy acid or a salt thereof having a larger number of groups than the number of OH groups.
As a result, the cleaning effect of the ceramic particles is sufficiently exerted, and the once-separated dirt such as silver is hardly reattached to the ink flow path or the like.
In the droplet discharge device cleaning method of the present invention, it is preferable that the droplet discharge device has a cleaning liquid storage tank for storing the cleaning liquid.
As a result, the inside of the droplet discharge device can be cleaned more easily.

It is a perspective view which shows an example of suitable embodiment of a droplet discharge apparatus (inkjet 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 Discharge Device and Cleaning Method for Droplet Discharge 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 cleaning liquid storage tank 160, 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 metal 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 molded body (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 is controlled by adjusting the waveform of the applied voltage generated by the drive circuit 191, or the discharge position of the ink 1 onto the substrate S is controlled by controlling the head positioning unit 180 and the table positioning unit 170. 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.
In the transport path 151, in order from the ink storage tank 150 toward the head 110, a cock (branch) 152, a filter 154 for removing impurities of the ink 1, and a self-sealing for preventing backflow of the ink 1 are provided. A stop valve 153 and a cock (branch) 155 are provided.
The ink 1 stored in the ink storage tank 150 is sent to the transport path 151 as necessary when droplets are ejected, and the reservoir 116 is passed through the cock 152, the filter 154, the self-sealing valve 153, and the cock 155. To be supplied.

The cleaning liquid storage tank 160 stores the cleaning liquid 2.
The cleaning liquid 2 in the cleaning liquid storage tank 160 is transported to the ink flow path by the cleaning liquid transport path 161 and cleans the ink flow path.
The cleaning liquid conveyance path 161 is connected to the conveyance path 151 at the cock 155, and a cock (branch) 162 is provided in the middle.
Further, a cleaning liquid conveyance path 163 branches from the cock 162, and the cleaning liquid conveyance path 163 is connected to the conveyance path 151 at the cock 152.

A cock (branch) 164 is provided in the middle of the cleaning liquid transport path 163, and a cleaning liquid recovery path 165 branches from the cock 164.
The cleaning liquid recovery path 165 is connected at a cock 202 to a suction ink transport path 201 described later.
In the cleaning method of the droplet discharge device of the present embodiment, the cleaning liquid 2 is introduced into the transport path 151 via the cleaning liquid transport path 161, and the input cleaning liquid 2 is in the direction opposite to the transport direction of the ink 1 (FIG. 3). (In the direction of the arrow in the middle) and further conveyed to the cleaning liquid conveyance path 163 by the cock 152. Thereafter, the cleaning liquid 2 subjected to the cleaning is recovered through the cock 164 and the cleaning liquid recovery path 165.

  As described above, the present invention is characterized in that the cleaning liquid used for cleaning the droplet discharge device is caused to flow in the ink transport path in the direction opposite to the direction in which the ink flows. Thereby, the stain | pollution | contamination adhering to the flow path of an ink can be removed easily. Further, since the cleaning liquid can be passed without passing through the head, the cleaning liquid can be flowed into the ink flow path with a relatively high pressure, and a high cleaning effect can be obtained. Further, since the cleaning liquid is allowed to flow without passing through the head, the ink flow path can be cleaned without damaging (influencing) the head.

In particular, the stain of the ink 1 accumulated in the state of being caught by the filter 154 can be easily removed by causing the cleaning liquid 2 to flow backward, and the life (replacement time) of the filter 154 can be extended. In general, a filter is provided for each of a large number of heads, and it takes time to replace the filter. However, according to the present invention, it is possible to extend the replacement time of the filter and increase the production efficiency. is there.
The liquid feed speed at which the cleaning liquid 2 flows backward is preferably 20 mL / min or more and 200 mL / min or less, and more preferably 50 mL / min or more and 150 mL / min or less. This makes it possible to more effectively clean the ink flow path.

The cleaning liquid 2 subjected to the cleaning is not recovered through the cleaning liquid recovery path 165 but is transported as it is to the cleaning liquid transport path 161 through the cock 162, so that the cleaning liquid transport path 161, the transport path 151, and the cleaning liquid transport path are The cleaning liquid 2 may be circulated in the order of 163.
Further, the cleaning liquid 2 may be sent to the head 110 via the cock 155 and the conveyance path 151. As a result, the inside of the head 110 can be cleaned.
As shown in FIG. 3, the droplet discharge device 100 includes a cleaning mechanism for cleaning the head 110.

The cleaning mechanism includes a suction unit 200 that sucks the ink 1 (or cleaning liquid 2) in the head 110, a recovery tank 210 that collects the ink 1 sucked by the suction unit 200, and the ink sucked by the suction unit 200. And a suction ink transport path 201 for transporting 1 to the recovery tank 210.
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 201 and the cock 152.
A cock 202 is provided in the suction ink transport path 201, and the suction ink transport path 201 and the cleaning liquid recovery path 165 described above are connected in the cock 202.

<Cleaning liquid>
Next, a cleaning liquid that can be suitably applied to the cleaning method of the present invention will be described.
The cleaning liquid (cleaning ink) applied to the present invention is for cleaning a droplet discharge device used for forming a conductor pattern, and in particular, a conductor pattern forming ink (hereinafter also simply referred to as ink) as described later. Therefore, it is possible to suitably eliminate contamination, clogging, and the like of the droplet discharge device.

The cleaning liquid that can be applied to the cleaning method of the present invention is not particularly limited, but it is preferable to use a liquid containing ceramic particles and a dispersion medium for dispersing the ceramic particles.
These ceramic particles have relatively high hardness and function as an abrasive for the flow path of the conductor pattern forming ink. As a result, even when metal particles are deposited in the vicinity of the discharge part of the droplet discharge head, the metal particles on which the ceramic particles are deposited are quickly scraped off and accumulated in the vicinity of the discharge port of the droplet discharge head. Is prevented. For this reason, when the flow path of the conductor pattern forming ink is washed with the cleaning liquid, the flying of the conductor pattern forming ink and the instability of the droplet discharge amount are prevented, and the droplet discharge stability is improved. It will be excellent. And when the flow path of the conductor pattern forming ink is cleaned using the cleaning liquid, a fine pattern can be accurately drawn with the conductor pattern forming ink, and the formed conductor pattern is highly reliable in which disconnection is prevented. It will be a thing.

[Ceramic particles]
As described above, the cleaning liquid contains ceramic particles.
The ceramic particles are dispersed in an aqueous dispersion medium to be described later.
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 and stably dispersed in the cleaning liquid. In addition, since the hardness is relatively high, dirt on the discharge port is preferably removed, and as a result, the discharge stability of the ink for forming the conductor pattern can be made particularly excellent.
In particular, when the ceramic particles contain aluminum oxide or titanium oxide as the metal oxide, the following effects can be obtained. These compounds have high hardness and have relatively high detergency. In addition, since these compounds have a relatively high melting point, the conductor pattern precursor in the conductor pattern formed by the conductor pattern forming ink is used even when the cleaning liquid remains in the ink flow path. When sintered, it does not melt and exists 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, aluminum oxide and titanium oxide are generally used as a constituent material of a ceramic molded body to be a substrate, and have little influence on a 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. The glass material has a function of adsorbing dirt adhering to the ink flow path, and the ink flow path can be suitably washed by adsorbing the dirt once scraped off. Further, even when the cleaning liquid remains in the ink flow path, in the conductor pattern formed by the conductor pattern forming ink, such a compound is melted at least partially during sintering, This can contribute to improvement in the adhesion between the conductor pattern and the substrate, 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 diameter of the ceramic particles is preferably 10 nm or more and 300 nm or less, and more preferably 20 nm or more and 200 nm or less. Thereby, the metal particles adhering to the ink flow path can be removed. That is, the cleaning effect of the ceramic particles can be made particularly excellent. As a result, a fine conductor pattern precursor can be easily and accurately formed using the cleaned droplet discharge device.
In the present specification, the “average particle size” means a volume-based average particle size unless otherwise specified.

  The content of ceramic particles (ceramic colloid particles when ceramic particles are present as a colloid) in the cleaning liquid is preferably 1 wt% or more and 30 wt% or less, and preferably 3 wt% or more and 25 wt% or less. More preferred. Accordingly, it is possible to prevent the metal particles from adhering to the ink flow path and to prevent the ceramic particles from remaining in the ink flow path after the cleaning.

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 cleaning performance of the ceramic particles is suitably exhibited, and the ceramic particles hardly remain in the ink flow path.
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, the dispersion stability stability of the ceramic colloid particles can be made particularly excellent, and the cleaning effect by the ceramic particles can be made more remarkable.

[Dispersant]
The cleaning liquid preferably contains a dispersant.
The dispersant adheres to the free silver particles to form silver colloidal particles when the ceramic particles scrape off the silver particles adhering to the ink flow path. For this reason, once dispersed silver particles can be prevented from adhering again to the ink flow path, and the cleaning effect of the cleaning liquid can be enhanced.
Moreover, a dispersing agent adheres to a ceramic particle and each forms a ceramic colloid particle. Since such ceramic colloidal particles are excellent in dispersion stability, the cleaning performance is suitably exhibited, and the ceramic colloid particles hardly remain in the ink flow path after cleaning.

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 a result, the cleaning effect of the ceramic particles is sufficiently exhibited, and dirt such as silver once released is hardly reattached to the ink flow path. 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. Thereby, the same effect as the hydroxy acid or the salt thereof as described above can be obtained. 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.

  The dispersant contained in the cleaning liquid preferably contains at least a part of the components constituting the dispersant contained in the conductor pattern forming ink, and the composition of the dispersant and the constituent contained in the conductor pattern forming ink is almost the same. More preferably, they are the same. Since the deposited deposit is considered to have adhered to the original dispersant for the conductor pattern forming ink, the deposited deposit is the same as the dispersant contained in the conductor pattern forming ink. By adhering the dispersing agent in the cleaning liquid, the easily released deposit can be dispersed in the cleaning liquid as colloidal particles. For this reason, the cleaning liquid is more excellent in cleaning properties. Further, after cleaning, the cleaning liquid in the ink flow path and the conductor pattern forming ink can be quickly replaced.

  The content of the dispersant in the cleaning liquid is not particularly limited, but is preferably 0.1 wt% or more and 20 wt% or less, and more preferably 0.3 wt% or more and 10 wt% or less. As a result, the dispersion effect of the ceramic particles and silver particles as described above can be remarkably exhibited, and there are too many dispersants, so that the dispersant remains after cleaning, and it takes time to replace the cleaning liquid with the conductor pattern forming ink. Can be prevented.

[Aqueous dispersion medium]
Next, the aqueous dispersion medium will be described.
In the present invention, the “aqueous dispersion medium” refers to a liquid composed of water and / or a liquid having excellent compatibility with water (for example, a liquid having a solubility in 100 g of water at 25 ° C. 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.
Moreover, it is preferable that the aqueous dispersion medium contained in the cleaning liquid has substantially the same composition as the aqueous dispersion medium constituting the conductor pattern forming ink described later. As a result, the replaceability with the ink is particularly excellent, and the remaining ink can be quickly mixed and replaced.

Specific examples of the aqueous dispersion medium include, for example, water, methanol, ethanol, butanol, propanol, isopropanol, ethylene glycol, an alcohol solvent such as propanediol, an ether solvent such as 1,4-dioxane, tetrahydrofuran (THF), Aromatic heterocyclic compound solvents such as pyridine, pyrazine and pyrrole, amide solvents such as N, N-dimethylformamide (DMF) and N, N-dimethylacetamide (DMA), nitrile solvents such as acetonitrile, acetaldehyde and the like Examples of the solvent include aldehyde solvents, and one or more of these can be used in combination.
Further, the content of the aqueous dispersion medium in the cleaning liquid is preferably 95 to 65 wt%, and more preferably 85 to 75 wt%. Thereby, the viscosity of the cleaning liquid can be made suitable, and the characteristics as the cleaning liquid can be made higher.

[Drying inhibitor]
Moreover, it is preferable that a washing | cleaning liquid contains a drying inhibitor. The drying inhibitor has a function of preventing the ink flow path from being dried after washing. Thereby, when ink is refilled after cleaning, mixing of bubbles can be prevented, and ink can be easily refilled.

  Examples of such a drying inhibitor include compounds represented by the following formula (I), sugar alcohols, alkanolamines, and the like, and one or more of them can be used in combination. These compounds have a function of preventing volatilization of the aqueous dispersion medium as described above, and also have a large number of polar groups such as hydroxyl groups and carbonyl groups. Disperses stably in. For this reason, when the conductor pattern forming ink contains a metal oxide as ceramic particles and contains the above-mentioned compound, the dispersion stability of the ceramic particles in the cleaning liquid is particularly excellent, and the cleaning performance of the cleaning liquid is particularly excellent. It will be.

（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 in the ink flow path.
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. Thereby, the moisture retention as described above can be made particularly high. Further, when the ceramic particles are present as colloidal particles as described above, particularly excellent dispersion stability is exhibited, and the cleaning property of the cleaning liquid is 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. Dispersion stability 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.

Sugar alcohol is obtained by reducing aldehyde groups and ketone groups of sugars.
Sugar alcohol is a compound having high moisture retention.
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.

In addition, when the conductor pattern forming ink contains a drying inhibitor, the drying inhibitor contained in the cleaning liquid contains at least a part of the components constituting the dispersant contained in the conductor pattern forming ink. However, it is preferable. Thereby, after cleaning, the cleaning liquid in the ink flow path and the conductor pattern forming ink can be quickly replaced.
The content of the drying inhibitor as described above in the cleaning liquid is preferably 3 wt% or more and 20 wt% or less, and more preferably 5 wt% or more and 15 wt% or less. Thereby, the unintentional volatilization of the aqueous dispersion medium in the ink flow path can be more effectively prevented.

[Other ingredients]
The cleaning liquid may contain other components.
Examples of such components include components used in conductor pattern forming inks to be described later. Specifically, surface tension adjusters, organic binders, ethylene glycol, 1,3-propanediol, 1,3- Examples thereof include polyhydric alcohols such as butylene glycol and propylene glycol, and thiourea.

The cleaning liquid as described above preferably has a lower surface tension at 25 ° C. than the conductor pattern forming ink described below. Thereby, at the time of washing | cleaning, a washing | cleaning liquid can spread suitably in the washing | cleaning site | part of a droplet discharge apparatus. For this reason, the amount of dirt remaining on the cleaned portion after cleaning is particularly small.
The surface tension of the cleaning liquid at 25 ° C. is not particularly limited, but is preferably 15 to 45 dyn / cm, and more preferably 20 to 40 dyn / cm. Thereby, at the time of washing | cleaning, a washing | cleaning liquid can spread suitably on the washing | cleaning site | part of a droplet discharge apparatus, and it can make the washing | cleaning property of the washing | cleaning liquid excellent. Even if the cleaning liquid remains in a very small amount, the influence on the surface tension of the ink described later can be made extremely small. In addition, in this specification, the value measured based on JISK3362 can be employ | adopted for surface tension.

  The cleaning liquid preferably has a viscosity at 25 ° C. lower than that of the conductor pattern forming ink described later. Thereby, at the time of washing | cleaning, a washing | cleaning liquid can spread suitably in the washing | cleaning site | part of a droplet discharge apparatus. Further, at the time of cleaning, the cleaning liquid can increase the flow velocity in the ink flow path. For this reason, the amount of dirt remaining on the cleaned portion after cleaning is particularly small.

  The viscosity of the cleaning liquid at 25 ° C. is not particularly limited. For example, it is preferably 20 mPa · s or less, and more preferably 10 mPa · s or less. Thereby, at the time of washing | cleaning, a washing | cleaning liquid can spread suitably on the washing | cleaning site | part of a droplet discharge apparatus, and it can make the washing | cleaning property of the washing | cleaning liquid excellent. Further, even when a minute amount of the cleaning liquid remains, the influence on the viscosity of the ink described later can be made extremely small. In the present specification, as the value of the viscosity, a value obtained by measurement at 25 ° C. using a vibration viscometer can be adopted, and in particular, the viscosity is measured at 25 ° C. in accordance with JIS Z8809. The required value can be adopted.

Hereinafter, the conductive pattern forming ink in which the above-described cleaning liquid is preferably used will be described.
<Conductor pattern forming ink>
Next, the conductor pattern forming ink that can be ejected from the droplet ejection apparatus applied to the cleaning method of the present invention will be described.

Conductive pattern forming ink (hereinafter, also simply referred to as ink) is ink used to form a conductive pattern on a substrate, and in particular, ink used to form a conductive 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]
As the aqueous dispersion medium, the same liquid as the cleaning liquid described above can be used.
In particular, it is preferable to use an aqueous dispersion medium having a composition substantially equivalent to that of the aqueous dispersion medium constituting the cleaning liquid described above. Thereby, the replaceability of the ink when refilling the ink after washing can be made higher.
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.

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. In addition, since the silver colloid particles are stably present in the ink as described above, 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.

Although it does not specifically limit as a dispersing agent, For example, the dispersing agent which can be used for a washing | cleaning liquid as mentioned above can be used.
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 colloidal 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 obtained when a ceramic molded body that is sintered at a higher temperature is used as the substrate.

[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.
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, when 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, thereby preventing the occurrence of cracks. The effect is reduced. 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 the occurrence of cracks 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 filling the ink jet device with the conductor pattern forming ink, A uniform amount can be accurately discharged to a target position.

Although it does not specifically limit as such a drying inhibitor, For example, the drying inhibitor which can be used for a washing | cleaning liquid as mentioned above can be used.
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) are colloidal particles having a dispersant attached to the surface as described above, the compound represented by the above formula (I) is bonded to the surface dispersant by hydrogen bonding, It has the effect of improving the dispersion stability of the particles. Accordingly, the ejection stability of the conductor pattern forming ink is excellent, and the storage stability is also excellent.
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.

As described above, alkanolamine is a highly moisturizing component, and when the metal 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 particles can be made higher.
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. Thereby, the discharge stability of the conductor pattern forming ink can be further improved.

  As described above, the 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.

  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 3 mPa · s or more and 20 mPa · s or less, and more preferably 4 mPa · s or more and 15 mPa · s or less. 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.

  The conductive pattern forming ink is preferably applied onto a substrate configured to include at least one of the components included in the ceramic particles in the cleaning liquid. Thereby, even if the ceramic particles remain in the ink flow path of the droplet discharge device, the influence on the conductor pattern on which the ceramic particles are formed is small. Further, when the conductive pattern forming ink and the substrate contain the same component, the adhesiveness of the conductive pattern to the substrate becomes excellent, and the conductive pattern becomes highly reliable.

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 Cleaning Liquid and Conductive Pattern Forming Ink Cleaning liquid and conductive pattern forming ink in each Example and each Comparative Example were manufactured as follows.

[Preparation of cleaning solution]
(Cleaning liquid 1)
Ion-exchanged water, colloidal silica as ceramic particles as ceramic particles (silicon dioxide colloidal liquid, average particle size: 30 nm solid content, content of silicon dioxide: 30 wt%), and drying inhibitor shown in Table 1 A cleaning liquid 1 was obtained by mixing trisodium citrate dihydrate and tannic acid as dispersants in the blending amounts shown in Table 1.
(Cleaning liquid 2-13)
Cleaning liquids 2 to 13 were obtained in the same manner as in the cleaning liquid 1 except that the types and amounts of the cleaning liquid materials were changed as shown in Table 1.

Table 1 shows the composition of each manufactured cleaning solution. In the table, silicon dioxide is SiO ₂ and aluminum oxide (aluminum oxide colloidal solution, NANOBYK-3600, manufactured by Big Chemie Japan, average particle size: 40 nm, solid content of aluminum oxide content: 91 wt%). Al ₂ O ₃ , titanium oxide TiO ₂ , zinc oxide (average particle size: 20 nm) ZnO 20, zinc oxide (average particle size: 40 nm) ZnO 40, zinc oxide (average particle size: 60 nm) ZnO 60, triethanolamine Was TEA, urea was Ur, xylitol was Xyl, tannic acid was TA, trisodium citrate dihydrate was CNa, and mercaptoacetic acid was TGA. In addition, about hydrates, such as trisodium citrate dihydrate, the hydrated water was described as content of water. Further, as the titanium oxide, a titanium oxide colloid liquid (average particle size: 100 nm, content of titanium oxide in solid content: 85 wt%) was used. In addition, as zinc oxide (average particle size: 20 nm), zinc oxide colloidal liquid (NANOBYK-3820, manufactured by Big Chemie Japan Co., Ltd., zinc oxide content: 89 wt% in solid content) is changed to zinc oxide (average particle size). As the zinc oxide colloidal liquid (NANOBYK-3840, manufactured by Big Chemie Japan Co., Ltd., solid content of zinc oxide content: 91 wt%) as zinc oxide (average particle diameter: 60 nm), A zinc oxide colloidal solution (NANOBYK-3860, manufactured by Big Chemie Japan Co., Ltd., containing zinc oxide in the solid content: 91 wt%) was used. The content of the ceramic colloid particles in the table is the solid content.

[Preparation of conductive pattern forming ink]
(Conductor pattern forming ink 1)
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.

  In this silver colloid liquid, the drying inhibitor shown in Table 2, polyglycerin, Surfynol 104PG-50 (manufactured by Nissin Chemical Industry Co., Ltd.) and Olphine EXP4036 (manufactured by Nissin Chemical Industry Co., Ltd.) as surface tension modifiers, Was added, and ion-exchanged water for concentration adjustment was further added for adjustment to obtain a conductor pattern forming ink 1. When the pH of the silver colloid solution at this time was not in the range of 6 to 11, the pH of the silver colloid solution was adjusted to 6 to 11 using a 1N-NaOH aqueous solution. Furthermore, the ion-exchange water for density | concentration adjustment was added and adjusted, and it was set as the conductor pattern formation ink 1 (ink 1).

(Conductor pattern forming inks 2 to 6)
Conductor pattern forming inks 2 to 6 (ink 2 to ink 6) are the same as the conductor pattern forming ink 1 except that the types and blending amounts of the respective materials of the conductor pattern forming ink are changed as shown in Table 1. )

(Conductor pattern forming ink 7)
A cleaning solution and a conductor pattern forming ink were prepared in the same manner as in Example 1 except that the conductor pattern forming ink was prepared as follows.
While stirring a silver nitrate aqueous solution having a concentration of 50 mmol / L: 1000 mL, 3.0 g of mercaptoacetic acid as a low molecular weight sulfur compound was added, and then the pH of the aqueous solution was adjusted to 10.0 with 26 wt% aqueous ammonia. At room temperature, the aqueous solution of sodium borohydride having a concentration of 400 mmol / L as a reducing agent: 50 mL was rapidly added to the aqueous solution to carry out a reduction reaction to produce silver colloid particles having mercaptoacetic acid on the particle surface in the solution. .

The colloidal solution thus obtained was adjusted to pH 3.0 using 20 wt% nitric acid, and silver colloid particles were allowed to settle, followed by filtration with a vacuum filter. The electric conductivity of the filtrate was 10.0 μS / cm. It washed with water until it became below, and obtained the wet cake of the silver colloid particle.
The silver colloid particle wet cake is added to water so that the concentration becomes 10 wt%, and the pH is adjusted to 9.0 with 26 wt% ammonia water while stirring and redispersed. A liquid was obtained.

Thereafter, a conductive pattern forming ink 7 (ink 7) was prepared in the same manner as the conductive pattern forming ink 1.
Table 2 shows the composition of each conductor pattern forming ink produced. In the table, triethanolamine is TEA, monoethanolamine is MEA, diethanolamine is DEA, urea is Ur, xylitol is Xyl, and sorbitol is Sor.

[Selection of cleaning liquid and conductor pattern forming ink used in droplet discharge device]
(Examples 1 to 19)
Among the cleaning liquids and the conductor pattern forming inks manufactured as described above, the cleaning liquid and the conductor pattern forming inks were selected as shown in Table 3, and the cleaning liquids and the conductor pattern forming inks in the respective examples were used.

(Comparative example)
Among the cleaning liquids and the conductor pattern forming inks manufactured as described above, the cleaning liquid and the conductor pattern forming inks were selected as shown in Table 3, and used as the cleaning liquid and the conductor pattern forming ink in the comparative example.

[3] Stability evaluation of droplet discharge (Stable discharge evaluation)
[3.1] Evaluation of Landing Position Accuracy Conductor patterns of the above-described embodiments and comparative examples were applied to an ink jet apparatus 100 as shown in FIGS. 1 and 2 installed in a clean room of class 100, room temperature 25 ° C., relative humidity 50%. In the state where the forming ink was filled and the drive waveform of the piezo element was optimized, 150,000 (150,000 droplets) of droplets were continuously discharged from each nozzle of the inkjet head. Thereafter, the ink flow path was washed with the cleaning liquid of each of the above examples. For cleaning, the cleaning liquid is supplied from the cleaning liquid storage tank 160 to the transport path 151 via the cleaning liquid transport path 161, and the cleaning liquid is allowed to flow at the speed shown in Table 3 in the direction opposite to the ink transport direction. The cleaning liquid used for cleaning was recovered via the cleaning liquid transport path 163, the cock 164, and the cleaning liquid recovery path 165. Washing was performed for 300 seconds.

After washing, the same ink was filled again in the ink flow path of the inkjet apparatus. 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 inkjet 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. In the comparative example, cleaning was performed by flowing the cleaning liquid in the same direction as the ink conveyance direction at the same speed as above for the same time. That is, the path of the cleaning liquid in the comparative example is the same as that of the conductive pattern forming ink. (In FIG. 3, 150 → 151 → 152 → 154 → 153 → 155 → 110 → 200 → 201 → 202 → 210)
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 3.
As is clear from Table 3, the cleaning method of the present invention was excellent in cleaning properties. On the other hand, a satisfactory result was not obtained in the 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) 2 ... Cleaning liquid 100 ... Inkjet apparatus (droplet discharge apparatus) 110 ... Inkjet head (droplet discharge head, head) 111 ... Head main body 112 ... Diaphragm 113 ... Piezo element 114 ... Main body DESCRIPTION OF SYMBOLS 115 ... Nozzle plate 115P ... Ink discharge surface 116 ... Reservoir 117 ... Ink chamber 118 ... Nozzle (protrusion part) 130 ... Base 140 ... Table 15 ... Ceramic molded body 150 ... Ink storage tank 151 ... Conveyance path 152 ... Cock 153 ... Self-sealing Stop valve 154 ... Filter 155 ... Cock 160 ... Cleaning liquid storage tank 161 ... Cleaning liquid transport path 162 ... Cock 163 ... Cleaning liquid transport path 164 ... Cock 165 ... Cleaning liquid recovery path 170 ... Table positioning means 171 ... First moving means 172 ... MO 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 ... suction ink transport path 202 ... cock 210 ... collection tank S ... base Material

Claims (11)

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: an ink storage layer that stores the conductive pattern forming ink; a droplet discharge head that includes a discharge unit that discharges the conductive pattern forming ink; and the droplet discharge from the ink storage unit. A transport path for transporting the conductor pattern forming ink toward the head; a self-sealing valve provided in the transport path to prevent backflow of the conductor pattern forming ink; and the self-sealing valve of the transport path More than the filter provided on the ink storage part side,
A cleaning method for a droplet discharge device, wherein a cleaning liquid used for cleaning the droplet discharge device is caused to flow in the transport path in a direction opposite to a direction in which the conductor pattern forming ink flows.   The method for cleaning a droplet discharge device according to claim 1, wherein the cleaning liquid that has flowed into the transport path is recovered after passing through the self-sealing valve and the filter.   The method for cleaning a droplet discharge device according to claim 1, wherein the cleaning liquid includes ceramic particles and an aqueous dispersion medium in which the ceramic particles are dispersed.   The method for cleaning a droplet discharge device according to claim 3, wherein the ceramic particles include a metal oxide.   The method for cleaning a droplet discharge device according to claim 4, wherein the metal oxide is aluminum oxide, zinc oxide, or titanium oxide.   The method for cleaning a droplet discharge device according to claim 1, wherein the ceramic particles include a glass material.   The method for cleaning a droplet discharge device according to claim 1, wherein the ceramic particles have an average particle size of 10 nm to 300 nm.   The method for cleaning a droplet discharge device according to claim 1, wherein a content of the ceramic particles in the cleaning liquid is 1 wt% or more and 30 wt% or less. Both the cleaning liquid and the conductor pattern forming ink include a dispersant,
The liquid droplet ejection apparatus cleaning according to any one of claims 1 to 8, wherein the dispersant contained in the cleaning liquid contains at least a part of components constituting the dispersant contained in the conductive pattern forming ink. Method.   The cleaning liquid has 3 or more COOH groups and OH groups as a dispersant, and the number of COOH groups is the same as the number of OH groups or the number of COOH groups is larger than the number of OH groups. The method for cleaning a droplet discharge device according to claim 1, comprising an acid or a salt thereof.   The method for cleaning a droplet discharge device according to claim 1, wherein the droplet discharge device includes a cleaning liquid storage tank for storing the cleaning liquid.

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