Cleaning agent for conductive paste and cleaning method for conductive paste

Abstract

The present invention provides an alkaline cleaning agent that does not tend to affect screen plates, the cleaning agent permitting easy removal by filtration by detaching and precipitating the electroconductive paste adhered to the screen plate. One embodiment of the present invention relates to a cleaning agent composition for electroconductive paste, the cleaning agent composition containing a compound (component (A)) represented by formula (1) and an aliphatic alcohol (component (B)) having 2-6 (inclusive) carbon atoms and a molecular weight of 40-120 (inclusive). The pH of the cleaning agent composition is 11.0 or more and less than 14.0. Relative to the total mass of the cleaning agent composition, the content of the component (A) is 0.1-5 mass% (inclusive) and the content of the component (B) is 5-40 mass% (inclusive).　R1-O-(C2H4O)a-H … Formula (1) (In formula (1), R1 represents a C6-18 branched alkyl group and a, which is the average number of added mol of C2H4O groups, is a number 2-10 (inclusive).)

Description

[Technical Field]

[0001] The present invention relates to a cleaning composition for conductive paste and a method for cleaning conductive paste. [Background technology]

[0002] In recent years, the development of thinner and more miniaturized electronic circuits and electronic substrates has progressed in line with the trend toward smaller and lighter electronic devices. Printed electronics, a technology that meets the demand for thinner and more miniaturized electronic devices, has recently been put into practical use. Screen printing is commonly used in this technology, where electronic circuits are formed by printing a conductive paste, a mixture of conductive particles and resin, onto the surface of a substrate using a screen.

[0003] Conventionally, CFC- or chlorine-based organic solvents have been the mainstream for cleaning equipment and screens that use these conductive pastes. However, from the perspective of improving the natural and working environment, there is a growing demand for a reduction in VOCs, and there is a trend toward semi-aqueous or aqueous cleaners that use non-CFC hydrocarbon or glycol-based organic solvents.

[0004] For example, Patent Document 1 describes a cleaner composition for screen printing plates, which contains a glycol ether organic solvent and water.

[0005] Furthermore, for example, Patent Document 2 describes a cleaning composition for metal nanoink, which contains hydrogen peroxide, acid, water, and a hydrocarbon-based or glycol-based organic solvent.

[0006] Furthermore, for example, Patent Document 3 describes a semi-aqueous cleaner composition for screen printing plates, which contains an amine, an acid, and a glycol ether organic solvent. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 10-77426 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-165830 [Patent Document 3] Japanese Patent Application Publication No. 2018-21093 Summary of the Invention [Problem to be solved by the invention]

[0008] Conductive paste cleaners remove conductive paste from screens by dissolving it, raising concerns about re-adhesion and contamination of the screen due to conductive paste residue dissolved in the waste liquid. For example, the cleaner composition described in Patent Document 1 contains more than 70% glycol ether-based organic solvents, which dissolve and remove the conductive paste, raising concerns about re-adhesion and contamination of the screen. Furthermore, the cleaner composition described in Patent Document 2 is characterized by dissolving and removing metal components, raising concerns about the dissolution of the conductive paste and the re-adhesion and contamination of the screen. Furthermore, the cleaner contains 5 wt% sulfuric acid or hydrochloric acid, which may cause corrosion of the screen.

[0009] Furthermore, the waste liquid after washing is recycled and reused by distillation or the like, but distillation takes a long time and requires a large amount of energy in some cases.

[0010] Therefore, there is a need for semi-aqueous or aqueous cleaners that can remove the conductive paste and precipitate it, allowing the paste residue in the wastewater to be easily removed by filtration in a short time. On the other hand, there is also a need for high cleaning power to accommodate increasingly fine circuit wiring. In this regard, the cleaning composition described in Patent Document 3 has a high cleaning effect on flux. However, there is a risk that the cleaning power will be insufficient for conductive paste containing metal components with particle sizes smaller than those of flux.

[0011] Thus, there has been no cleaning agent that can remove precipitates and has good cleaning power at the same time.

[0012] The present invention has been made in view of the above circumstances, and aims to provide an alkaline cleaning agent that does not have a significant effect on the screen stencil, and that can be easily removed by filtration by peeling off and precipitating the conductive paste adhering to the screen stencil. [Means for solving the problem]

[0013] In one embodiment of the present invention to solve the above-mentioned problems, the cleaner for conductive paste is a cleaning composition for conductive paste, which contains a compound represented by formula (1) (component (A)) and an aliphatic alcohol (component (B)) having 2 to 6 carbon atoms and a molecular weight of 40 to 120, wherein the pH of the cleaning composition is 11.0 or higher and lower than 14.0, and the content of component (A) is 0.1 to 5 mass% and the content of component (B) is 5 to 40 mass% relative to the total mass of the cleaning composition. R 1 -O-(C2H4O)aH Formula (1) (In formula (1), R 1 represents a branched alkyl group having 6 to 18 carbon atoms, and a, which is the average number of moles of C2H4O groups added, is a number of 2 to 10.)

[0014] In order to solve the above problems, a method for cleaning a conductive paste according to one aspect of the present invention includes the steps of: preparing a screen plate having a conductive paste attached to its surface; and bringing the cleaning composition according to claim 1 into contact with the surface of the screen plate to which the conductive paste is attached. [Effects of the Invention]

[0015] The cleaning agent for conductive paste of the present invention has sufficient cleaning power to remove the conductive paste, and the conductive paste adhering to the screen is separated and precipitated, allowing it to be easily removed by filtration. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described.

[0017] A cleaning composition for conductive paste (hereinafter simply referred to as "cleaner") according to one embodiment of the present invention contains a compound represented by formula (1) (component (A)) and an aliphatic alcohol (component (B)) having 2 to 6 carbon atoms and a molecular weight of 40 to 120. The pH of the cleaning agent is 11.0 or higher and lower than 14.0, and the content of component (A) is 0.1 to 5% by mass, and the content of component (B) is 5 to 40% by mass, relative to the total mass of the cleaning agent. R 1 -O-(C2H4O)aH Formula (1) (In formula (1), R 1 represents a branched alkyl group having 6 to 18 carbon atoms, and a, which is the average number of moles of C2H4O groups added, is a number of 2 to 10.)

[0018] Each component contained in the detergent will be described below.

[0019] [Component (A)] Component (A) is a compound (polyalkylene glycol) represented by formula (1). The cleaning agent may contain only one type of component (A), or may contain multiple types. R 1 -O-(C2H4O)aH Formula (1)

[0020] In formula (1), R 1 R represents a branched alkyl group having 6 to 18 carbon atoms. 1 R is preferably a branched alkyl group having 8 to 10 carbon atoms. 1 If the alkyl group is a branched alkyl group having 8 to 10 carbon atoms, the paste can be easily peeled off due to its high penetration power.

[0021] In particular, component (A) is R 1 Since R is a branched alkyl group, it can be removed without solubilizing the conductive paste.1 The branched chain contained in is preferably an alkyl group having 1 to 3 carbon atoms, and is preferably a methyl branch or an ethyl branch.

[0022] R 1 Specific examples of R include an isooctyl group, a 2-ethylhexyl group, an isononyl group, a 3,5,5-trimethylhexyl group, and an isodecyl group. 1 may contain only one type or multiple types.

[0023] In formula (1), a is the average number of moles of oxyethylene groups (C2H4O) added, and is a number of 2 or more and 10 or less. a is preferably a number of 4 or more and 8 or less.

[0024] The HLB (Hydrophilic-Lipophilic Balance) value of component (A) is preferably 10 or more and 15 or less. If the HLB value of component (A) is 10 or more, component (A) does not tend to be too oil-soluble, making it difficult for the cleaner to separate into layers. If the HLB value of component (A) is 15 or less, component (A) does not tend to be too hydrophilic, making it difficult for the cleaner to solubilize paste residues.

[0025] The content of component (A) relative to the total mass of the cleaner is 0.1 to 5% by mass, preferably 0.5 to 4% by mass, and more preferably 1 to 3% by mass. When the content of component (A) is 0.1% by mass or more, the penetration of the cleaner is improved, allowing the paste to be peeled and precipitated. When the content of component (A) is 5% or less, the conductive paste is not easily solubilized, making it less likely for redeposition contamination to occur on the screen.

[0026] [Component (B)] Component (B) is an aliphatic alcohol having a carbon number of 2 or more and a molecular weight of 40 or more and 120 or less. Component (B) can improve the cleaning properties of the conductive paste. The effects of the present invention can be achieved by using an aliphatic alcohol having a carbon number and molecular weight within the above ranges. An aliphatic alcohol having a molecular weight of 120 or less can improve permeability and recovery properties and shorten filtration time. The cleaning agent may contain only one type of component (B), or may contain multiple types.

[0027] Component (B) has a Fedors SP value of 10 (cal / cm 3 ) 1 / 2 More than 14(cal / cm 3 ) 1 / 2 The SP value of component (B) is preferably 10 (cal / cm 3 ) 1 / 2 If the SP value of component (B) is 14 (cal / cm 3 ) 1 / 2 When the content is equal to or less than this, the compatibility between the detergent and the paste becomes good, and the detergency tends to be improved.

[0028] Component (B) is preferably a water-soluble alcohol. Component (B) may have an alicyclic structure or a non-alicyclic (straight-chain or branched-chain) structure. Component (B) may have an ether structure in the molecule. Component (B) may have one to two hydroxyl groups in the molecule.

[0029] Examples of component (B) include ethanol, isopropyl alcohol, 1,2-pentanediol, 2,4-pentanediol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, 3-methoxy-1-butanol, 3-methoxy-3-methyl-1-butanol, and tetrahydrofurfuryl alcohol.

[0030] Of these, 3-methoxy-3-methyl-1-butanol, ethanol, isopropyl alcohol and tetrahydrofurfuryl alcohol are preferred, and 3-methoxy-3-methyl-1-butanol is more preferred.

[0031] The content of component (B) relative to the total mass of the cleaning agent is 5% by mass or more and 40% by mass or less, preferably 10% by mass or more and 35% by mass or less, and more preferably 15% by mass or more and 30% by mass or less. When the content of component (B) is 5% by mass or more, the penetration of the cleaning agent is improved, allowing the paste to be removed and the filtration time to be shortened. When the content of component (B) is 40% by mass or less, not only is permeability and recoverability sufficiently improved and the filtration time to be shortened, but the cleaning agent is less likely to separate into layers and tends to have good storage stability.

[0032] [pH and alkaline components (component (C))] The pH of the cleaning agent is 11.0 or more and 14.0 or less, preferably 11.5 or more and 13.9 or less. When the pH is in the above range, the cleaning performance is sufficiently improved. The pH of the cleaning agent can be adjusted to the above range by adding a known alkaline component (component (C)). The cleaning agent may contain only one type of component (C) for adjusting the pH, or may contain multiple types.

[0033] Component (C) is a compound that is water-soluble and makes the aqueous solution alkaline when dissolved in water. Component (C) may be an organic alkaline component or an inorganic alkaline component.

[0034] Examples of organic alkali components in component (C) include monoethanolamine, diethanolamine, triethanolamine, pyridine, etc. Examples of inorganic alkali components in component (C) include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, sodium silicate, potassium silicate, etc.

[0035] From the viewpoint of further enhancing cleaning properties, component (C) is preferably monoethanolamine, diethanolamine, sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate, and more preferably sodium hydroxide or potassium hydroxide. Component (C) hydrolyzes the resin contained in the conductive paste, thereby peeling the paste from the screen.

[0036] [Acid component (component (D))] The cleaning agent may contain an acid component (component D) for adjusting the pH. Component (D) may contain only one type, or multiple types. Furthermore, in addition to component (C), component (D) may further be contained for fine adjustment of the pH. For example, an organic acid component can be used as component (D). Examples of organic acid components include propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, and lactic acid. Of these, citric acid and 2-ethylhexanoic acid are preferred.

[0037] [Other ingredients] In addition to the above-mentioned components, the cleaner may contain other components that are commonly used in conventional cleaners for conductive pastes, such as preservatives, thickeners, and colorants.

[0038] [Preparation of cleaning agent] The cleaning agent can be prepared by diluting the above components with water to an appropriate concentration to prepare an aqueous solution using a known method. The water used for dilution can be ion-exchanged water, distilled water, RO water, tap water, industrial water, etc.

[0039] The content of water relative to the total mass of the detergent is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 65% ​​by mass or more. The content of water is not particularly limited, but is preferably 90% by mass or less.

[0040] [Use of cleaning agents] The cleaning agent is used to remove the conductive paste that has temporarily adhered to the surface of the screen.

[0041] It is believed that the cleaning agent penetrates into the paste at the interface between the screen and the paste, reducing adhesion at the interface between the screen and the paste, thereby peeling off the paste. To fully exert these effects, it is preferable to allow the cleaning agent to fully penetrate into the paste so that a sufficient amount of cleaning agent reaches the interface between the screen and the conductive paste. Furthermore, it is believed that this penetration of the cleaning agent peels off the paste and makes it more likely to precipitate.

[0042] The temperature of the cleaning agent when it is brought into contact with the conductive paste is preferably about 30 to 70°C.

[0043] Conductive paste is a general term for materials in which conductive particles are dispersed in synthetic resin. Synthetic resins include thermoplastic resins such as acrylic resin and polyester, and thermosetting resins such as phenolic resin and epoxy resin. Conductive particles include carbon black, metal particles (silver, copper, nickel, etc.), and tin oxide, ranging in size from submicrons to 100 microns. [Example]

[0044] The present invention will be described below using examples and comparative examples, but the present invention is not limited to the following examples in any way.

[0045] 1. Prepare the cleaning agent 1-1.Materials 1-1-1. Component (A) Compound A1, compound A2, and compound A1′ shown in Table 1 were prepared. Compound A1 and compound A2 are compounds (component (A)) represented by formula (1), and compound A1′ has the structure represented by formula (1), but contains R 1 Since the above formula is different, it is not component (A). R 1 -O-(C2H4O)aH Formula (1)

[0046] Table 1 shows the R in formula (1) of Compound A1, Compound A2, and Compound A1′. 1 Structure (functional group name), R 1 The numbers indicate the number of carbon atoms, the number of a's in the oxyethylene group (C2H4O), and the HLB value.

[0047] [Table 1]

[0048] 1-1-2. Ingredient (B) Compounds B1 to B4 and compound B1' were prepared as shown in Table 2. Compounds B1 to B5 are aliphatic alcohols (component (B)) having 2 to 6 carbon atoms and a molecular weight of 40 to 120, and compound B1' is an organic solvent that is not component (B).

[0049] Table 2 shows the compound names, molecular weights, carbon numbers, hydroxyl group numbers, and SP values ​​of Compounds B1 to B4 and Compound B1'.

[0050] [Table 2]

[0051] 1-1-3. Ingredient (C) Compounds C1 to C3 shown in Table 3 were prepared. Compounds C1 to C3 are all component (C).

[0052] Table 3 shows the compound names of Compounds C1 to C3.

[0053] [Table 3]

[0054] 1-1-4. Ingredient (D) Compound D1 and compound D2 were prepared as shown in Table 4. Both compound D1 and compound D2 are component (D).

[0055] Table 4 shows the compound names of Compound D1 and Compound D2.

[0056] [Table 4]

[0057] 1-2. Preparation of cleaning agent The above components were dissolved in water, and water was further added so that the total amount became 100% by mass, thereby preparing the cleaning compositions of Examples 1 to 9 and Comparative Examples 1 to 6.

[0058] 2. pH Measurement The pH of the cleaning compositions of Examples 1 to 9 and Comparative Examples 1 to 6 was measured using a pH meter (LAQUA F-72, manufactured by Horiba, Ltd.) at 25°C, and the measurement was performed while stirring each cleaning composition in a thermostatic bath at 25°C.

[0059] 3. Evaluation of cleaning agents The cleaning compositions of Examples 1 to 9 and Comparative Examples 1 to 6 prepared above were evaluated according to the following criteria.

[0060] 3-1. Cleaning test 3-1-1. Preparation of cleaning test pieces (cleaning evaluation, transmittance evaluation) The weight of a 30 mm x 15 mm metal mesh (100 mesh) was recorded in advance. Then, conductive paste (DY-150H-30, manufactured by Toyobo Co., Ltd., resin: thermosetting resin, conductive particles: carbon black) was applied to the lower half (10 mm), and the excess paste was removed to form the test specimen. The weight of the test specimen with the paste applied was then reweighed, and the amount of paste applied was recorded.

[0061] 3-1-2. Cleaning test 10 g of the prepared cleaning agent was added to a 20 mL screw tube and kept at 60°C. The test piece prepared above was completely immersed and heated to 60°C while being irradiated with 125 W ultrasonic waves for 10 minutes using an ultrasonic cleaner (BRANSON B-220, manufactured by Emerson Electric Co.). The test piece was then rinsed with ion-exchanged water, thoroughly dried, and weighed. The cleaning rate was calculated from the change in weight of the test piece before and after cleaning. The cleaning rate was calculated as follows. This test was performed twice, and the average value was used as the measurement result.

[0062]

number

[0063] Based on the cleaning rate measured above, each cleaning solution was evaluated according to the following criteria.

[0064] <(1) Cleaning evaluation> ◎: Cleaning rate is 90% or more. ○: The cleaning rate is 80% or more but less than 90%. ×: The cleaning rate is less than 80%.

[0065] 3-2. Transmittance measurement The cleaning solution obtained in the above cleaning test was filtered through a filter cloth (2 μm, made of nylon). At this time, co-washing was carried out with 1 g of ion-exchanged water. The transmittance of the filtrate was measured using a spectrophotometer ("U-3010", manufactured by Hitachi, Ltd.). The transmittance was measured at a wavelength of 660 nm and calculated as a percentage by comparing it with the transmittance of ion-exchanged water. This test was carried out twice, and the average value was used as the measurement result of this test.

[0066] Based on the transmittance measured above, each cleaning solution was evaluated according to the following criteria.

[0067] <(2) Permeability evaluation> ◎: Transmittance is 80% or more. ◯: The transmittance is 70% or more and less than 80%. ×: The transmittance is less than 70%.

[0068] 3-3. Filtration test A pre-weighed filter paper for the Kiriyama funnel (No. 5B, manufactured by Kiriyama Seisakusho Co., Ltd., retention particle size 4 μm) was placed in the Kiriyama funnel. A cleaning test similar to that described above was carried out, and the resulting cleaning solution was filtered through the prepared Kiriyama funnel. After filtration, the filter paper was dried in an oven at 70°C for 1 hour. The weight of the dried filter paper was measured, and the recovery rate of the paste was calculated from the change in weight before and after filtration. The recovery rate was calculated as follows:

[0069]

number

[0070] Based on the recovery rates measured above, each cleaning solution was evaluated according to the following criteria.

[0071] <(3) Filtration recovery evaluation> ○: Recovery rate is 80% or more. ×: Recovery rate is less than 80%.

[0072] 3-4. Filtration time measurement test A funnel was created by sandwiching a membrane filter (ADVANTEC MEMBRANE FILTER, manufactured by ADVANTEC, pore size 0.1 μm, material PTFE) between the glass filter base and the funnel. A cleaning test similar to that described above was carried out, and the resulting cleaning liquid was poured into the prepared funnel and evaporated under reduced pressure (approximately -0.1 MPa) using an aspirator. The time from when the cleaning liquid was poured into the funnel until the entire amount of cleaning liquid was filtered was measured.

[0073] Based on the filtration times measured above, each cleaning solution was evaluated according to the following criteria.

[0074] <(4) Filtration time evaluation> ○: Within 100 seconds. ×: 100 seconds or more.

[0075] The contents of the above-mentioned components contained in the cleaning compositions of Examples 1 to 9 and Comparative Examples 1 to 6, the pH of each cleaning solution, and the results of the above-mentioned evaluations for each cleaning solution are shown in Tables 5 and 6. The numerical values ​​for the components in Tables 5 and 6 indicate the proportion (unit: mass %) to the total mass of the cleaning agent.

[0076] [Table 5]

[0077] [Table 6]

[0078] As shown in Tables 5 and 6, the cleaning agents containing components (A), (B) and (C), or components (A), (B), (C) and (D), had sufficient cleaning power to remove the conductive paste, and furthermore, the conductive paste adhering to the screen stencil was peeled off and precipitated, allowing it to be easily removed by filtration.

[0079] This application claims priority based on Japanese Application No. 2021-130581, filed on August 10, 2021, and the claims and specification of that application are incorporated herein by reference. [Industrial Applicability]

[0080] According to the present invention, the cleaning composition can be used for the conductive paste adhered to the screen printing plate, and the waste liquid treatment after cleaning is simple, which contributes to reducing the energy and time required for recycling.

Claims

1. A compound represented by formula (1) (component (A)), and A cleaning composition for conductive paste, comprising an aliphatic alcohol (component (B)) having 2 to 6 carbon atoms and a molecular weight of 40 to 120, The pH of the cleaning composition is 11.0 or more and less than 14.0, a content of the component (A) in the cleaning agent composition is 0.1% by mass or more and 5% by mass or less, and a content of the component (B) in the cleaning agent composition is 5% by mass or more and 40% by mass or less, based on the total mass of the cleaning agent composition. R １ -O-(C) ２ H ４ O)a-H ・・・Form (1) (In formula (1), R １ represents a branched alkyl group having 6 to 18 carbon atoms, ２ H ４ a, the average number of moles of O groups added, is a number of 2 or more and 10 or less.

2. preparing a screen having a conductive paste attached to its surface; A step of contacting the cleaning composition according to claim 1 with the surface of the screen plate to which the conductive paste is attached; The conductive paste cleaning method includes the steps of:

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