JP2020037645A - Inkjet ink for resist - Google Patents

Abstract

To provide an inkjet ink for a resist that has good dissolution stability of a gelling agent and good pigment dispersibility and is excellent in injection stability of an ink, fine line reproducibility, etching resistance of a resist film to an acid, alkali solubility/removability and adhesion to a substrate (oxide film).SOLUTION: The inkjet ink for a resist contains a photopolymerizable compound having no acidic group, a photopolymerizable compound having an acidic group, a gelling agent having no acidic group and a photopolymerization initiator and undergoes a sol-gel phase transition depending on temperature.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ink jet ink for a resist, and in particular, has good dissolution stability of a gelling agent and good dispersibility of a pigment, and also has ejection stability of ink, fine line reproducibility, durability of a resist film, and dissolution and releasability to alkali. And an inkjet ink for resist having excellent adhesion to a substrate.

  In manufacturing a printed circuit board (PCB), for example, as shown in FIG. 1A, conventionally, an oxide film 2 made of a conductive material is formed on a substrate 1 and a mask pattern is formed on the oxide film 2. A resist is applied to print the resist film 3 to form a resist film 3 (see FIG. 1B), and the resist film 3 is irradiated with light (ultraviolet light) to transfer and expose the pattern of the mask 4 (see FIG. 1). 1 (c)). Thereafter, the exposed portion is developed (see FIG. 1D), and the portion of the oxide film 2 not covered with the resist film 3 is removed with an acid etching solution (see FIG. 1E). . Thereafter, the PCB is obtained by removing the resist film 3 covering the oxide film 2 with an alkali (see FIG. 1F).

On the other hand, it is known that the resist film is applied by patterning with an ink jet. As an inkjet ink used for such a resist film, for example, a hot melt ink containing an acid wax, an acrylate containing no acid group, and a radical initiator is disclosed (for example, see Patent Document 1).
However, the hot melt ink is 100% solid at room temperature, and the amount of the acid wax is 0.5 to 40% by mass, so that the amount of the wax is relatively large. Therefore, there is a problem that the load of dissolving in the monomer during ink supply and injection in the apparatus is large, and that an injection failure is likely to occur due to a temperature change at the time of injection. Further, since the amount of wax is large, it is difficult to obtain adhesion to an oxide film, and the removal of the resist film by alkali is poor. Further, since an acid wax is used, dispersion is destabilized when used in combination with a pigment due to the acid value of the wax.
In addition, for example, a resist inkjet ink using a normal UV ink as disclosed in Patent Document 2 has poor pinning properties at the time of inkjet drawing. Cannot be suppressed, resulting in non-uniformity of fine lines or difficulty in reproducing fine lines. Further, when the ink droplets are overprinted in order to increase the ink film thickness, the ink droplets spread laterally, so that it is difficult to achieve both the line width and the film thickness.

Japanese Patent No. 5731746 Japanese Patent No. 5255307

  The present invention has been made in view of the above-mentioned problems and circumstances, and the problem to be solved is that the dissolution stability of the gelling agent and the pigment dispersibility are good, and the ejection stability of ink, fine line reproducibility, acidity, etc. It is to provide an inkjet ink for resist excellent in etching resistance of a resist film, dissolution and peeling property to alkali and adhesion to a substrate (oxide film).

In order to solve the above-mentioned problems, the present inventor, in the course of examining the cause of the above-mentioned problems and the like, a photopolymerizable compound having no acidic group, a photopolymerizable compound having an acidic group, and a gel having no acidic group It has been found that a resist film suitable for an ink-jet method can be formed by adding an agent and a photopolymerization initiator, and the present invention has been accomplished.
That is, the above object according to the present invention is solved by the following means.

  1. It contains a photopolymerizable compound having no acidic group, a photopolymerizable compound having an acidic group, a gelling agent having no acidic group, and a photopolymerization initiator, and undergoes a sol-gel phase transition depending on temperature. An inkjet ink for a resist, comprising:

The viscosity at 2.25 ° C. is in the range of 1 to 1 × 10 ⁴ Pa · s, and has a phase transition point in the range of 40 ° C. or more and less than 100 ° C., as described in item 1 above. Inkjet ink for resist.

3. The resist according to claim 1 or 2, wherein the gelling agent contains at least one compound selected from compounds having a structure represented by the following general formulas (G1) and (G2). Inkjet ink.
General formula (G1): R ₁ —CO—R ₂
General formula (G2): R ₃ —COO—R ₄
[In the formula, R _{1 to} R ₄ each independently represent an alkyl chain having a straight-chain portion having 12 or more carbon atoms and optionally having a branch. ]

  4. 4. The resist inkjet according to claim 1, wherein the gelling agent is contained in a range of 0.5 to 5% by mass based on the whole ink. 5. ink.

5. As the photopolymerizable compound having an acidic group, a (meth) acrylate compound having an acidic group selected from a carboxy group, a phosphoric acid group, a sulfonic acid group, or a hydroxy group, and
5. The resist inkjet according to any one of items 1 to 4, wherein the (meth) acrylate compound is contained in a range of 1 to 30% by mass based on the whole ink. ink.

6. As the photopolymerizable compound having no acidic group, a (meth) acrylate compound having a molecular weight in the range of 300 to 1500 and a ClogP value in the range of 4.0 to 7.0 is contained, and
6. The resist inkjet according to any one of items 1 to 5, wherein the (meth) acrylate compound is contained within a range of 10 to 40% by mass based on the whole ink. ink.

7. As the photopolymerizable compound having no acidic group, a compound having 3 to 14 unit structures represented by (—CH ₂ —CH ₂ —O—) in a molecule within a molecular weight range of 300 to 1500. Further containing a (meth) acrylate compound, and
7. The resist ink jet ink according to claim 6, wherein the (meth) acrylate compound is contained within a range of 30 to 70% by mass based on the whole ink.

  8. Item 8. The inkjet ink for resist according to any one of Items 1 to 7, further comprising a colorant.

By the above means of the present invention, the dissolution stability of the gelling agent and the dispersibility of the pigment are good, the ejection stability of the ink, the reproducibility of fine lines, the etching resistance of the resist film by an acid, the dissolution and releasability to an alkali, and It is possible to provide a resist inkjet ink having excellent adhesion to (oxide film).
Although the mechanism of expression or action of the effect of the present invention has not been clarified, it is speculated as follows.
Although the inkjet ink for resist of the present invention is characterized by having a pinning property, it is preferable to increase the sol-gel phase transition rate in order to enhance the pinning property of the ink. By using a photopolymerizable compound that does not have a polymer and a gelling agent that does not have an acidic group, it has been found that a small amount of the gelling agent can exhibit high pinning properties, and at the same time, dissolution stability, injection stability, and fine line reproducibility. I think that is kept. It is also believed that the addition of a photopolymerizable compound having an acidic group improves alkali solubility and substrate adhesion.

Diagram for showing a conventional printed circuit board manufacturing process The figure for showing the manufacturing process of the printed circuit board using the inkjet ink for resist of the present invention

The inkjet ink for resist of the present invention contains a photopolymerizable compound having no acidic group, a photopolymerizable compound having an acidic group, a gelling agent having no acidic group, and a photopolymerization initiator, and Sol-gel phase transition depending on temperature.
This feature is a technical feature common or corresponding to each of the following embodiments.

As an embodiment of the present invention, it is preferable that the viscosity at 25 ° C. is in the range of 1 to 1 × 10 ⁴ Pa · s and the phase transition point is in the range of 40 ° C. or more and less than 100 ° C. This is preferable in that it has good reproducibility, enables drawing with both fine lines and film thickness, and is excellent in reproducibility of fine lines.

When the gelling agent contains at least one compound among the compounds having the structures represented by the general formulas (G1) and (G2), the pinning properties are good, and the fine wire and the film thickness are compatible. This is preferable because drawing can be performed and fine line reproducibility is excellent.
It is preferable that the gelling agent is contained in the range of 0.5 to 5% by mass based on the whole ink in terms of excellent ejection stability.

  As the photopolymerizable compound having an acidic group, a (meth) acrylate compound having an acidic group selected from a carboxy group, a phosphoric acid group, a sulfonic acid group, or a hydroxy group, and the (meth) acrylate compound, It is preferred that it is contained in the range of 1 to 30% by mass with respect to the whole ink, in that the durability of the resist film and the adhesion to the base material are excellent, and the dissolution and releasability to alkali are excellent.

  As the photopolymerizable compound having no acidic group, a (meth) acrylate compound having a molecular weight in the range of 300 to 1500 and a ClogP value in the range of 4.0 to 7.0 is contained, and It is preferable that the (meth) acrylate compound is contained in the range of 10 to 40% by mass based on the whole ink in view of the dissolution stability of the gelling agent.

As the photopolymerizable compound having no acidic group, a compound having 3 to 14 unit structures represented by (—CH ₂ —CH ₂ —O—) in a molecule within a molecular weight range of 300 to 1500. That the (meth) acrylate compound is further contained, and that the (meth) acrylate compound is contained within the range of 30 to 70% by mass based on the whole ink, the curing by the (meth) acrylate compound This is preferable in that the suppression of shrinkage is good and the adhesion to the substrate (oxide film) is excellent.

  Further, it is preferable to contain a coloring agent from the viewpoint of image quality evaluation because the visibility of the drawing pattern is improved.

  Hereinafter, the present invention, its components, and embodiments and modes for carrying out the present invention will be described. In addition, in this application, "-" is used in the meaning including the numerical value described before and after it as a lower limit and an upper limit.

[Inkjet ink for resist]
The inkjet ink for resist of the present invention (hereinafter, also simply referred to as ink) includes a photopolymerizable compound having no acidic group, a photopolymerizable compound having an acidic group, a gelling agent having no acidic group, It contains a photopolymerization initiator and undergoes a sol-gel phase transition depending on temperature.
The inkjet ink for resist of the present invention, for example, in various fields such as metal processing, electronic circuits, printed boards, plate making, semiconductor fields, color filters, and the like, functions as a resist used when forming an etching pattern on a substrate. is there.
Specifically, a resist film is formed by patterning with an ink of the present invention by inkjet printing on a conductive oxide film such as copper or zinc formed on a substrate. Next, a fine circuit or pattern is formed by removing the portion of the oxide film that is not covered with the resist film with an etching solution using an acid and further removing the resist film that has covered the oxide film with an alkali.

The ink of the present invention is an ink composition curable by actinic rays.
The “actinic ray” is a ray capable of imparting energy for generating a starting species in the ink composition by irradiation, and includes α rays, γ rays, X rays, ultraviolet rays, electron rays and the like. Above all, ultraviolet rays and electron beams are preferable from the viewpoint of curing sensitivity and availability of an apparatus, and ultraviolet rays are more preferable.

<Photopolymerizable compound having no acidic group>
The photopolymerizable compound having no acidic group according to the present invention is preferably an unsaturated carboxylic acid ester, and more preferably a (meth) acrylate compound (hereinafter, also simply referred to as (meth) acrylate).

  In the present invention, “(meth) acrylate” means acrylate or methacrylate, “(meth) acryloyl group” means acryloyl group or methacryloyl group, and “(meth) acryl” means acrylic Or methacrylic.

  Examples of the (meth) acrylate include isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, isomyristyl (meth) acrylate, and isostearyl (meth). Acrylate, 2-ethylhexyl-diglycol (meth) acrylate, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, Phenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, and t Monofunctional acrylates including -butylcyclohexyl (meth) acrylate, and triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate Acrylate, polypropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (Meth) acrylate, dimethylol-tricyclodecanedi (meth) acrylate, PO adduct of bisphenol A di (meth) acrylate, neopentyl glycol hydroxypivalate di (meth) acryle Difunctional acrylates, including polytetramethylene glycol di (meth) acrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, and tricyclodecane dimethanol diacrylate, and trimethylolpropane tri (meth) acrylate; Pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylolpropanetetra (meth) acrylate, glycerin propoxytri (meth) acrylate, and pentaerythritol ethoxytetra (meth) Polyfunctional acrylates including trifunctional or higher acrylates such as acrylates are included.

From the viewpoint of photosensitivity and the like, (meth) acrylate is stearyl (meth) acrylate, lauryl (meth) acrylate, isostearyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, isobornyl (meth) acrylate, tetraethylene glycol di ( (Meth) acrylate, glycerin propoxy tri (meth) acrylate and the like are preferred.
The (meth) acrylate may be a modified product. Examples of the modified (meth) acrylate include ethylene oxide-modified trimethylolpropane tri (meth) acrylate, ethylene oxide-modified pentaerythritol tetraacrylate, and other ethylene oxide-modified (meth) acrylates, and caprolactone-modified trimethylolpropane tri ( Examples include caprolactone-modified (meth) acrylate containing (meth) acrylate and the like, and caprolactam-modified (meth) acrylate containing caprolactam-modified dipentaerythritol hexa (meth) acrylate and the like.

  The (meth) acrylate may be a polymerizable oligomer. Examples of the polymerizable oligomer (meth) acrylate include an epoxy (meth) acrylate oligomer, an aliphatic urethane (meth) acrylate oligomer, an aromatic urethane (meth) acrylate oligomer, a polyester (meth) acrylate oligomer, and a linear ( (Meth) acrylic oligomers and the like.

As the photopolymerizable compound having no acidic group according to the present invention, among the (meth) acrylates, the molecular weight is in the range of 300 to 1500, and the ClogP value is in the range of 4.0 to 7.0 (meth). ) It is preferable to contain acrylate from the viewpoint of injection stability and dissolution stability of the gelling agent.
Examples of the (meth) acrylate having a molecular weight in the range of 300 to 1500 and a ClogP value in the range of 4.0 to 7.0 include, for example, propoxylated (2) neopentyl glycol diacrylate (molecular weight 471, ClogP 4.9), 1,10-decanediol dimethacrylate (molecular weight 310, ClogP 5.75), tricyclodecanedimethanol diacrylate (molecular weight 304, ClogP 4.69) and tricyclodecanedimethanol dimethacrylate (molecular weight 332, ClogP 5.12) and the like.
The (meth) acrylate having a molecular weight in the range of 300 to 1500 and a ClogP value in the range of 4.0 to 7.0 is contained in the range of 10 to 40% by mass based on the whole ink. Is preferable in terms of injection stability and dissolution stability of the gelling agent.

Here, the “logP value” in the present application is a coefficient indicating the affinity of an organic compound for water and 1-octanol.
The 1-octanol / water partition coefficient P is a distribution equilibrium when a trace amount of a compound is dissolved as a solute in a solvent in a two-liquid phase of 1-octanol and water, and is a ratio of the equilibrium concentrations of the compounds in the respective solvents. Indicated by their log logP relative to the base 10. That is, the “log P value” is a logarithmic value of the partition coefficient of 1-octanol / water, and is known as an important parameter indicating the hydrophilic / hydrophobic property of the molecule.

“ClogP value” is a logP value calculated by calculation. The ClogP value can be calculated by a fragment method, an atom approach method, or the like. More specifically, to calculate the ClogP value, reference can be made to a literature (C. Hansch and A. Leo, "Substitute Constants for Correlation Analysis in Chemistry and Biology" (Fragment, John Wiley & Sons, John Wiley & Sons, John Wiley & Sons, 1992). Or the following commercially available software package 1 or 2.
Software Package 1: MedChem Software (Release 3.54, August 1991, Medicinal Chemistry Project, Pomona College, Claremont, CA),
Software Package 2: Chem Draw Ultra ver. 8.0. (April 2003, CambridgeSoft Corporation, USA)
The numerical value of the ClogP value described in the present specification and the like is a “ClogP value” calculated using the software package 2.

In addition to the (meth) acrylate having a molecular weight in the range of 300 to 1500 and a ClogP value in the range of 4.0 to 7.0 as the photopolymerizable compound having no acidic group according to the present invention, Containing a (meth) acrylate having a molecular weight in the range of 300 to 1500 and having 3 to 14 unit structures represented by (—CH ₂ —CH ₂ —O—) in the molecule; It is preferable in terms of injection stability, dissolution stability of the gelling agent, and curing shrinkage.
As the (meth) acrylate having a molecular weight in the range of 300 to 1500 and having 3 to 14 unit structures represented by (—CH ₂ —CH ₂ —O—) in the molecule, for example, polyethylene Glycol diacrylate (molecular weight 508, ClogP 0.5), 4EO-modified hexanediol diacrylate (molecular weight 358, ClogP 2.5), 6EO-modified trimethylolpropane triacrylate (molecular weight 560, ClogP 3.6), 4EO-modified pentaerythritol Tetraacrylate (molecular weight 528, ClogP 2.3) and the like.
(Meth) acrylate having a molecular weight in the range of 300 to 1500 and having 3 to 14 unit structures represented by (—CH ₂ —CH ₂ —O—) in the molecule is used for the entire ink. On the other hand, it is preferable that it is contained in the range of 30 to 70% by mass from the viewpoint of curing shrinkage of the cured film.

<Photopolymerizable compound having acidic group>
The polymerizable compound having an acidic group according to the present invention has, in its molecule, an acidic group such as a carboxy group, a phosphate group (also referred to as a phospho group), a sulfonic acid group (also referred to as a sulfo group), or a hydroxy group. (Meth) acrylate compounds having the formula:

  Examples of the (meth) acrylate compound having a carboxy group include a (meth) acrylate compound having a hydroxy group and a (meth) acrylate obtained by adding an acid anhydride to an oligomer composed of the (meth) acrylate compound. As the acid anhydride, for example, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, hymic anhydride, maleic anhydride, trimellitic anhydride Acids, methylcyclohexentricarboxylic anhydride, and pyromellitic anhydride, such as 2-carboxyethyl acrylate, 4- (meth) acryloyloxyethoxycarbonyl phthalic acid, 4- (meth) acryloyloxybutoxycarbonyl phthalic acid, 4- ( (Meth) acryloyloxyalkoxycarbonylphthalates such as (meth) acryloyloxyhexyloxycarbonylphthalic acid and 4- (meth) acryloyloxydecyloxycarbonylphthalic acid, 4- (meth) acryloyloxye (Meth) acryloyloxyalkoxyalkoxycarbonylphthalic acids such as xyethoxycarbonylphthalic acid, mono-2- (acryloyloxy) ethyl succinate, 2,2-bis (acryloylamide) acetic acid, 2- (meth) acryloyloxyethyl Succinic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl-2-hydroxyethyl-phthalic acid, and 2- (meth) acryloyloxyethyl hexahydrophthalic acid.

  Examples of the (meth) acrylate compound having a phosphate group include bis (2- (meth) acryloyloxyethyl) phosphate, 2-hydroxyethyl (meth) acrylate acid phosphate, ethyl (meth) acrylate acid phosphate, -Chloro-2-acid phosphoxypropyl (meth) acrylate, polyoxyethylene glycol (meth) acrylate acid phosphate, 2- (meth) acryloyloxyethyl caproate acid phosphate, mono-2- (methacryloyloxy) ethyl phosphate Is mentioned. Further, 2- (meth) acryloyloxyethyl phosphate (meaning 2-acryloyloxyethyl phosphate or 2-methacryloyloxyethyl phosphate, hereinafter abbreviated), 2- or 3- (meth) Acryloyloxypropyl phosphate, 4- (meth) acryloyloxybutyl phosphate, 6- (meth) acryloyloxyhexyl phosphate, 8- (meth) acryloyloxyoctyl phosphate, 10- (meth) acryloyloxy Decyl phosphate, 12- (meth) acryloyloxylauryl phosphate, 16- (meth) acryloyloxycetyl phosphate, 18- (meth) acryloyloxystearyl phosphate, 20- (meth) acryloyloxyeico (Meth) acryloyloxyalkyl phosphates such as phosphoric acid ester; di (meth) acryloyloxyalkyl phosphates such as 1,3-di (meth) acryloyloxypropyl-2-phosphate; 2- ( (Meth) acryloyloxyalkylaryl phosphoric esters such as (meth) acryloyloxyethyl phenyl phosphate, 2- (meth) acryloyloxyethylanisyl phosphate, 2- (meth) acryloyloxyethyltolyl phosphate; (Meth) acryloyloxyalkylarylphosphonic acids such as 2- (meth) acryloyloxyethylphenylphosphonic acid; 2- (meth) acryloyloxyethylthiophosphoric acid ester, 2- or 3- (meth) acryloyloxypropylthiol ester Acid ester, 4- (meth) acryloyloxybutylthiophosphate, 6- (meth) acryloyloxyhexylthiophosphate, 8- (meth) acryloyloxyoctylthiophosphate, 10- (meth) acryloyloxydecylthiophosphate , 12- (meth) acryloyloxylauryl thiophosphate, 16- (meth) acryloyloxycetyl thiophosphate, 18- (meth) acryloyloxystearyl thiophosphate, 20- (meth) acryloyloxyeicosyl thiophosphate, etc. (Meth) acryloyloxyalkylthiophosphates; di (meth) acryloyloxyalkylthiophosphates such as 1,3-di (meth) acryloyloxypropyl-2-thiophosphate Stels; (meth) acryloyloxyalkyl such as 2- (meth) acryloyloxyethylphenylthiophosphate, 2- (meth) acryloyloxyethylanisylthiophosphate, 2- (meth) acryloyloxyethyltolylthiophosphate, etc. Arylthiophosphoric acid esters; and (meth) acryloyloxyalkylarylthiophosphonic acids such as 2- (meth) acryloyloxyethylphenylthiophosphonic acid.

  Examples of the (meth) acrylate compound having a sulfonic acid group include methallyl sulfonic acid, bis (3-sulfopropyl) itaconic acid, 2- (sulfoxy) ethyl methacrylic acid, and 2-acrylamide-2-methyl-1-methyl. Examples thereof include propanesulfonic acid, 3-sulfopropylacrylic acid, 3-sulfopropylmethacrylic acid, and acrylamido-2-methyl-2-propanesulfonic acid.

  Examples of the (meth) acrylate compound having a monofunctional hydroxy group include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 1-methyl-2-hydroxyethyl (meth) acrylate. 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 4-hydroxycyclohexyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate 4-hydroxymethylcyclohexylmethyl (meth) acrylate, p-hydroxymethylphenylmethyl (meth) acrylate, 2- (hydroxyethoxy) ethyl (meth) acrylate, 2- (hydroxyethoxyethoxy) (meth) acrylate Ethyl, (meth) acrylic acid 2 (Hydroxyethoxyethoxyethoxy) ethyl, α-hydroxymethyl acrylate, α-hydroxymethyl acrylate, hydroxyalkyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-methacryloyloxyethyl-2-hydroxy Propyl phthalate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and the like.

  Examples of the (meth) acrylate compound having a polyfunctional hydroxy group include 2-hydroxy-3-acryloyloxypropyl methacrylate, dipentaerythritol penta (meth) acrylate, ethylene oxide-added pentaerythritol tetra (meth) acrylate, Methylol propane diacrylate, glycerin di (meth) acrylate, glycerin acrylate methacrylate, pentaerythritol di (meth) acrylate, neopentyl glycol hydroxypivalate di (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol propionate Tri (meth) acrylate, hydroxypivalaldehyde-modified dimethylolpropane tri (meth) acrylate, sorbitol Tri (meth) acrylate, sorbitol tetra (meth) acrylate, sorbitol penta (meth) acrylate, sorbitol hexa (meth) acrylate, pentaerythritol tri (meth) acrylate.

Examples of the photopolymerizable compound having an acidic group include, among the (meth) acrylates, 2-acryloyloxyethyl-succinic acid, 2-acryloyloxyethylhexahydrophthalic acid, 2-methacryloyloxyethylsuccinic acid, -Methacryloxyethyl acid phosphate, 2-hydroxyethyl methacrylate acid phosphate, mono-2- (acryloyloxy) ethyl succinate, 2-methacryloyloxyethyl succinate, 2-methacryloyloxyethyl phthalate, and the like are preferable. .
Further, it is preferable that the (meth) acrylate is contained in the range of 1 to 30% by mass with respect to the whole ink in terms of excellent durability of the resist film and excellent dissolution and releasability to alkali. .

<Gelling agent having no acidic group>
The gelling agent having no acidic group according to the present invention can temporarily fix (pin) ink droplets that have landed on an oxide film in a gel state. When the ink is pinned in the gel state, the spread of the ink is suppressed and the adjacent dots are less likely to unite, so that a higher definition image can be formed. As the gelling agent, only one kind may be contained in the inkjet ink of the present invention, or two or more kinds may be contained.

  Examples of the gelling agent having no acidic group according to the present invention include a dialkyl ketone, a fatty acid ester, a fatty acid amide, an oil gelling agent, and the like. It has no acidic group such as -OH and -COOH. That is, the above-mentioned gelling agent having no acidic group is not limited to a gelling agent having a purity of 100% consisting only of those having no acidic group. The acid value may be 10 mgKOH / g or less, including the case where the gelling agent contained therein is contained as an impurity.

Particularly preferred gelling agents include at least one compound having a structure represented by the following general formulas (G1) and (G2).
General formula (G1): R ₁ —CO—R ₂
General formula (G2): R ₃ —COO—R ₄
[In the formula, R _{1 to} R ₄ each independently represent an alkyl chain having a straight-chain portion having 12 or more carbon atoms and optionally having a branch. ]

The ketone wax represented by the general formula (G1) or the ester wax represented by the general formula (G2) has a linear or branched hydrocarbon group (alkyl chain) having 12 or more carbon atoms. Therefore, the crystallinity of the gelling agent is further increased, and more sufficient space is generated in the following card house structure. Therefore, an ink medium such as a solvent and a photopolymerizable compound is easily sufficiently included in the space, and the pinning property of the ink is further improved.
Further, the carbon number of the linear or branched hydrocarbon group (alkyl chain) is preferably 26 or less, and if it is 26 or less, the melting point of the gelling agent does not become excessively high, so that the ink is ejected. There is no need to heat the ink excessively when doing so.
From the above viewpoint, it is particularly preferable that R ₁ and R ₂ , or R ₃ and R _{4 be} a linear hydrocarbon group having 12 to 23 carbon atoms.
In addition, from the viewpoint of increasing the gelling temperature of the ink and gelling the ink more rapidly after landing, carbon from which either R ₁ or R ₂ or R ₃ or R ₄ is saturated is used. It is preferably a hydrocarbon group having 12 to 23 atoms.
From the above viewpoint, it is more preferable that both R ₁ and R ₂ or both R ₃ and R ₄ are saturated hydrocarbon groups having 11 to 23 carbon atoms.

  Examples of the ketone wax represented by the general formula (G1) include dilignoceryl ketone (C24-C24), dibehenyl ketone (C22-C22), distearyl ketone (C18-C18), and dieicosyl ketone ( C20-C20), dipalmityl ketone (C16-C16), dimyristyl ketone (C14-C14), dilauryl ketone (C12-C12), lauryl myristyl ketone (C12-C14), lauryl palmityl ketone (C12-C16) ), Myristyl palmityl ketone (C14-C16), myristyl stearyl ketone (C14-C18), myristyl behenyl ketone (C14-C22), palmityl stearyl ketone (C16-C18), valmityl behenyl ketone (C16-C22), Stearyl behenyl ketone (C18-C 2) are included. The number of carbons in the parentheses indicates the number of carbons of each of the two hydrocarbon groups separated by the carbonyl group.

  Examples of commercially available ketone waxes represented by the general formula (G1) include Stearone (manufactured by Alfa Aeser; Stearon), 18-Pentriacontanon (manufactured by Alfa Aeser), and Hentriacontan-16-on (manufactured by Alfa Aeser). And Kaowax T-1 (manufactured by Kao Corporation).

  Examples of the fatty acid or ester wax represented by the general formula (G2) include behenyl behenate (C21-C22), icosyl icosanoate (C19-C20), stearyl stearate (C17-C18), and palmityl stearate (C17). -C16), lauryl stearate (C17-C12), cetyl palmitate (C15-C16), stearyl palmitate (C15-C18), myristyl myristate (C13-C14), cetyl myristate (C13-C16), myristine Octyldodecyl acid (C13-C20), stearyl oleate (C17-C18), stearyl erucate (C21-C18), stearyl linoleate (C17-C18), behenyl oleate (C18-C22) arachidyl linoleate (C17-C18) C20) included That. In addition, the carbon number in the parenthesis represents the carbon number of each of the two hydrocarbon groups separated by the ester group.

Examples of commercially available ester waxes represented by the general formula (G2) include Unistar M-2222SL and Sperm Aceti, manufactured by NOF Corporation (“UNISTAR” is a registered trademark of the company), Exepar SS and Exepal MY-M, Kao EMALEX CC-18 and EMALEX CC-10 (manufactured by Nippon Emulsion Co., Ltd.), and AMLEPS PC (manufactured by Nippon Emulsion Co., Ltd.) Is the company's registered trademark).
Since these commercially available products are often a mixture of two or more kinds, they may be separated and purified as necessary to be contained in the ink. Among these gelling agents, ketone waxes, ester waxes, higher fatty acids, higher alcohols and fatty acid amides are preferred from the viewpoint of further improving pinning properties.

  The content of the gelling agent is preferably in the range of 0.5 to 5.0% by mass based on the total mass of the ink. By setting the content of the gelling agent within the above range, the solubility and the pinning effect of the gelling agent with respect to the solvent component are improved. From the above viewpoint, the content of the gelling agent in the inkjet ink is more preferably in the range of 0.5 to 2.5% by mass.

  Further, from the following viewpoints, the gelling agent is preferably crystallized in the ink at a temperature equal to or lower than the gelation temperature of the ink. The gelling temperature refers to a temperature at which the viscosity of the ink rapidly changes when the gelling agent undergoes a phase transition from a sol to a gel when the sol or liquid ink is cooled by heating. Specifically, the sol or liquid ink is cooled while measuring the viscosity with a viscoelasticity measuring device (for example, MCR300, manufactured by Physica), and the temperature at which the viscosity sharply rises is determined by the temperature of the ink. It can be a gelling temperature.

When the gelling agent crystallizes in the ink, a structure may be formed in which the ink medium such as a solvent or a photopolymerizable compound is included in the three-dimensional space formed by the gelling agent crystallized in a plate shape. (Such a structure is hereinafter referred to as a “card house structure”).
When the card house structure is formed, the liquid ink medium is held in the space, so that the ink droplets are less likely to spread and spread, and the pinning property of the ink is further improved. When the ink pinning property is enhanced, the ink droplets that have landed on the recording medium are less likely to coalesce, and a higher definition image can be formed.
In order to form a card house structure, it is preferable that a solvent in the ink, an ink medium such as a photopolymerizable compound, and the gelling agent are compatible with each other. On the other hand, if the solvent and the ink medium such as the photopolymerizable compound in the ink and the gelling agent are phase-separated, it may be difficult to form a card house structure.

<Photopolymerization initiator>
The photopolymerization initiator uses a photoradical initiator when the photopolymerizable compound is a radical polymerizable compound, and uses a photoacid generator when the photopolymerizable compound is a cationic polymerizable compound. Is preferred.
The ink of the present invention may contain only one type of photopolymerization initiator or two or more types thereof. The photopolymerization initiator may be a combination of both a photoradical initiator and a photoacid generator.
The photo radical initiator includes a cleavage type radical initiator and a hydrogen abstraction type radical initiator.

Examples of the cleavage type radical initiator include an acetophenone-based initiator, a benzoin-based initiator, an acylphosphine oxide-based initiator, benzyl and methylphenylglyoxyester.
Examples of acetophenone-based initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethylketal, 1- (4-isopropylphenyl) -2-hydroxy-2-. Methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4-thiomethylphenyl) Includes propan-1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone.
Examples of benzoin-based initiators include benzoin, benzoin methyl ether and benzoin isopropyl ether.
Examples of the acylphosphine oxide-based initiator include 2,4,6-trimethylbenzoindiphenylphosphine oxide.

Examples of the hydrogen abstraction type radical initiator include a benzophenone-based initiator, a thioxanthone-based initiator, an aminobenzophenone-based initiator, 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10- Includes phenanthrenequinone and camphorquinone.
Examples of benzophenone-based initiators include benzophenone, methyl 4-phenylbenzophenone o-benzoylbenzoate, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenylsulfide, acrylated benzophenone , 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone and 3,3'-dimethyl-4-methoxybenzophenone.
Examples of the thioxanthone-based initiator include 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone.
Examples of aminobenzophenone-based initiators include Michler's ketone and 4,4'-diethylaminobenzophenone.

Examples of the photoacid generator include compounds described in “Organic Materials for Imaging”, edited by Society of Organic Electronics Materials, published by Bunshin Publishing (1993), pp. 187-192.
The content of the photopolymerization initiator may be any range as long as the ink can be sufficiently cured, and for example, may be in the range of 0.01 to 10% by mass based on the total mass of the ink of the present invention.
Examples of commercially available photopolymerization initiators include Irgacure TPO (manufactured by BASF), 819 (manufactured by BASF), Irgacure 379 (manufactured by BASF), Genocure ITX (manufactured by Rahn AG) Genocure EPD (Rahn) A.G.) and the like.

The ink of the present invention may further contain a photopolymerization initiator auxiliary agent, a polymerization inhibitor, and the like, if necessary.
The photopolymerization initiator assistant may be a tertiary amine compound, and is preferably an aromatic tertiary amine compound.
Examples of aromatic tertiary amine compounds include N, N-dimethylaniline, N, N-diethylaniline, N, N-dimethyl-p-toluidine, N, N-dimethylamino-p-benzoic acid ethyl ester, N, N-dimethylamino-p-benzoic acid isoamylethyl ester, N, N-dihydroxyethylaniline, triethylamine and N, N-dimethylhexylamine are included. Among them, N, N-dimethylamino-p-benzoic acid ethyl ester and N, N-dimethylamino-p-benzoic acid isoamylethyl ester are preferred. These compounds may be used alone or in combination of two or more.

<Colorant>
The ink of the present invention may further contain a colorant as necessary.
The colorant may be a dye or a pigment, but is preferably a pigment because it has good dispersibility in the components of the ink and has excellent weather resistance. The pigment is not particularly limited, and examples thereof include organic pigments and inorganic pigments having the following numbers described in the color index.

  Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, 53 : 1, 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144 , 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13, 16, 20, 36 or a mixture thereof.

  Examples of blue or cyan pigments include Pigment Blue 1, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17-1, 22, 27, 28, 29, 36. , 60 or a mixture thereof.

Examples of the green pigment include a pigment selected from Pigment Green 7, 26, 36, 50 or a mixture thereof.
Examples of yellow pigments include Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, and 137. 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193 or a mixture thereof.
Examples of black pigments include pigments selected from Pigment Black 7, 28, 26, and mixtures thereof.

  Examples of commercially available pigments include Black Pigment (manufactured by Mikuni), Chromofine Yellow 2080, 5900, 5930, AF-1300, 2700L, Chromofine Orange 3700L, 6730, Chromofine Scarlet 6750, Chromofine Magenta 6880, 6886. , 6891N, 6790, 6887, Chromofine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, Chromofine Green 2GN, 2GO, 2G-550 D, 5310, 5370, 6830, Chromofine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400 (B), 2500, 2600, ZAY-260, 2700 (B ), 2770, Seika Fast Red 8040, C405 (F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmin 6B1476T. -7, 1483 LT, 3840, 3870, Seika Fast Bordeaux 10B-430, Seika Light Rose R40, Seika Light Violet B800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 00, 2900, Seika Light Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (manufactured by Dainichi Seika Kogyo); KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118 , 124, KET Green 201 (manufactured by DIC); Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Y llow T-13, T-05, Pigment Yellow 1705, Colortex Orange 202, Colortex Red 101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN. , UG276, U456, U457, 105C, USN, Colortex Maroon601, Colortex BrownB610N, Colortex Violet600, Pigment Red 122, ColortexBlue 516, 517, 518, 519, Aol, Bol90, A8, P-90 (Manufactured by Sanyo Dyeing Co., Ltd.); Lionol Y llow1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (manufactured by Toyo Ink Co., Ltd.), Toner Magenta E02, Permanent Rubin F6B, Toner Yellow HG, PermanentGermany G Novoperm P-HG, Hostaperm Pink E, Hostaperm Blue B2G (manufactured by Clariant); carbon black # 2600, # 2400, # 2350, # 2200, # 1000, # 990, # 980, # 970, # 960, # 950, # 850, MCF88, # 750, # 650, MA600, MA7, MA8, M 11, MA100, MA100R, MA77, # 52, # 50, # 47, # 45, # 45L, # 40, # 33, # 32, # 30, # 25, # 20, # 10, # 5, # 44, CF9 (manufactured by Mitsubishi Chemical Corporation) and the like.

The pigment can be dispersed by, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker.
For the dispersion of the pigment, the volume average particle diameter of the pigment particles is preferably in the range of 0.08 to 0.5 μm, the maximum particle diameter is preferably in the range of 0.3 to 10 μm, and more preferably 0.3 to 3 μm. Is preferably performed within the range.
The dispersion of the pigment is adjusted by the selection of the pigment, the dispersant, and the dispersion medium, the dispersion conditions, the filtration conditions, and the like.

The ink of the present invention may further contain a dispersant to enhance the dispersibility of the pigment.
Examples of dispersants include carboxylic acid esters having a hydroxy group, salts of long-chain polyaminoamides and high-molecular-weight acid esters, salts of high-molecular-weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, and high-molecular-weight unsaturated salts Acid esters, polymer copolymers, modified polyurethanes, modified polyacrylates, polyetherester-type anionic activators, naphthalenesulfonic acid formalin condensate salts, aromatic sulfonic acid formalin condensate salts, polyoxyethylene alkyl phosphates, Polyoxyethylene nonyl phenyl ether, stearylamine acetate and the like are included. Examples of commercially available dispersants include Solsperse series of Avecia, PB series of Ajinomoto Fine Techno, and the like.

  The ink of the present invention may further contain a dispersing aid as needed. The dispersing aid may be selected according to the pigment.

  The total amount of the dispersant and the dispersing aid is preferably in the range of 1 to 50% by mass based on the pigment.

  The ink of the present invention may further include a dispersion medium for dispersing the pigment, if necessary. A solvent may be included in the ink as a dispersion medium, but in order to suppress the solvent from remaining in the formed image, use of the above-described photopolymerizable compound (particularly, a monomer having a low viscosity) as the dispersion medium. Is preferred.

Examples of the dye include an oil-soluble dye.
The oil-soluble dyes include the following various dyes. Examples of magenta dyes include MS Magenta VP, MS Magenta HM-1450, MS Magenta HSo-147 (all manufactured by Mitsui Toatsu), AIZENSOT Red-1, AIZEN SOT Red-2, AIZEN SOTRed-3, AIZEN SOT Pink-1, SPIRON Red GEH SPECIAL (all made by Hodogaya Chemical Co., Ltd.), RESOLIN Red FB 200%, MACROLEX Red Violet R, MACROLEX ROT5B (all made by Bayer Japan), KAYASET RedB, KAYASET REDA 802 (above, manufactured by Nippon Kayaku), PHLOXIN, ROSE BENGAL, ACID Red (above, manufactured by Daiwa Kasei), HSR-31, DIAR SIN Red K (manufactured by Mitsubishi Kasei Co., Ltd.), is included Oil Red (manufactured by BASF Japan Co., Ltd.).

  Examples of cyan dyes include MS Cyan HM-1238, MS Cyan HSo-16, Cyan HSo-144, MS Cyan VPG (all made by Mitsui Toatsu), AIZEN SOT Blue-4 (made by Hodogaya Chemical), RESOLIN BR. Blue BGLN 200%, MACROLEX Blue RR, CERES Blue GN, SIRIUS SUPRATURQ. Blue Z-BGL, SIRIUS SUPRA TURQ. Blue FB-LL 330% (manufactured by Bayer Japan KK), KAYASET Blue FR, KAYASET Blue N, KAYASET Blue 814, Turq. Blue GL-5200, Light Blue BGL-5200 (all manufactured by Nippon Kayaku Co., Ltd.), DAIWA Blue 7000, Oleosol Fast Blue GL (all manufactured by Daiwa Kasei Co., Ltd.), DIAREIN Blue P (Mitsubishi Chemical Co., Ltd.) , NEOPEN Blue 808, and ZAPON Blue 806 (all manufactured by BASF Japan).

  Examples of the yellow dye include MS Yellow HSm-41, Yellow KX-7, Yellow EX-27 (manufactured by Mitsui Toatsu Co., Ltd.), AIZEN SOT Yellow-1, AIZEN SOT YellowW-3, AIZEN SOT Yellow-6 (or more, Hodogaya Chemical Co., Ltd.), MACROLEX Yellow 6G, MACROLEX FLUOR. Yellow 10GN (manufactured by Bayer Japan), KAYASET Yellow SF-G, KAYASET Yellow 2G, KAYASET Yellow A-G, KAYASET Yellow EG (manufactured by Nippon Kayaku), DAIWA HYLO , HSY-68 (manufactured by Mitsubishi Kasei Corporation), SUDAN Yellow 146, NEOPEN Yellow 075 (all manufactured by BASF Japan) and the like.

  Examples of black dyes include MS Black VPC (manufactured by Mitsui Toatsu Co., Ltd.), AIZEN SOT Black-1, AIZEN SOT Black-5 (manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN Black GSN 200%, RESOLIN BlackBS (manufactured by: Bayer Japan), KAYASET Black AN (Nippon Kayaku), DAIWA Black MSC (Daiwa Kasei), HSB-202 (Mitsubishi Kasei), NEPTUNE Black X60, NEOPEN Black X58 (above, BASF) Japan Co., Ltd.).

  The content of the colorant is preferably in the range of 0.1 to 20% by mass, more preferably in the range of 0.4 to 10% by mass, based on the total amount of the ink.

<Other ingredients>
The ink of the present invention may further include other components including a polymerization inhibitor and a surfactant as long as the effects of the present invention are obtained. Only one of these components may be contained in the ink of the present invention, or two or more thereof may be contained.

(Polymerization inhibitor)
Examples of the polymerization inhibitor include (alkyl) phenol, hydroquinone, catechol, resorcin, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone , Nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cuperon, aluminum N-nitrosophenylhydroxyamine, tri-p-nitrophenylmethyl, N- (3-oxyanilino- 1,3-dimethylbutylidene) aniline oxide, dibutyl cresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxime and cyclohexanone oxime Murrell.
Examples of commercially available polymerization inhibitors include Irgastab UV10 (manufactured by BASF), Genorad 18 (manufactured by Rahn AG), and the like.

The amount of the polymerization inhibitor can be arbitrarily set as long as the effects of the present invention can be obtained.
The amount of the polymerization inhibitor can be, for example, 0.001% by mass or more and less than 1.0% by mass based on the total mass of the ink.

(Surfactant)
Examples of surfactants include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates and fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols and polyoxy Nonionic surfactants such as ethylene-polyoxypropylene block copolymers, cationic surfactants such as alkylamine salts and quaternary ammonium salts, and silicone-based and fluorine-based surfactants are included.

  Examples of the silicone-based surfactant include a polyether-modified polysiloxane compound, specifically, Tego rad 2250, manufactured by Evonik, KF-351A, KF-352A, KF-642, and X-22-4272, Shin-Etsu Chemical Industries, BYK307, BYK345, BYK347 and BYK348, Big Chemie (“BYK” is a registered trademark), and TSF4452, Momentive Performance Materials.

The fluorine-based surfactant means a surfactant obtained by substituting a part or the whole of fluorine instead of hydrogen bonded to carbon of a hydrophobic group of a normal surfactant.
Examples of fluorine-based surfactants include Megafac F, manufactured by DIC (“Megafac” is a registered trademark of the company), Surflon, AGC Seika Chemical (“Sulflon” is a registered trademark of the company), Fluorad FC, 3M (“Fluorad” is a registered trademark of the company), Monflor, manufactured by Imperial Chemical Industries, Zonyls, manufactured by E.I. Dupont Nemelas and Company, Licowet VPF, manufactured by Rubeberke Hoechst, and FTERGENT. And Neos (“FTERGENT” is a registered trademark of the company).

  The amount of the surfactant can be arbitrarily set as long as the effects of the present invention can be obtained. The amount of the surfactant can be, for example, 0.001% by mass or more and less than 1.0% by mass based on the total mass of the ink.

(Physical properties)
The viscosity at 25 ° C. of the ink of the present invention is preferably in the range of 1 to 1 × 10 ⁴ Pa · s, and when the ink has landed and cooled to room temperature, the ink is sufficiently gelled, and the pinning property is good. This is preferred.
Further, from the viewpoint of further improving the dischargeability from the inkjet head, the viscosity of the ink of the present invention at 80 ° C. is preferably in the range of 3 to 20 mPa · s, and is in the range of 7 to 9 mPa · s. Is more preferable.

The ink of the present invention preferably has a phase transition point in the range of 40 ° C. or more and less than 100 ° C. When the phase transition point is 40 ° C. or higher, the ink quickly gels after landing on the recording medium, so that the pinning property is further improved. Further, when the phase transition point is less than 100 ° C., the ink handling properties are good and the ejection stability is high.
From the viewpoint of enabling the ink to be ejected at a lower temperature and reducing the load on the image forming apparatus, the phase transition point of the ink of the present invention is more preferably in the range of 40 to 60 ° C.

The viscosity at 80 ° C., the viscosity at 25 ° C., and the phase transition point of the ink of the present invention can be determined by measuring the temperature change of the dynamic viscoelasticity of the ink with a rheometer.
In the present invention, the viscosity and the phase transition point are values obtained by the following method.
The ink of the present invention is heated to 100 ° C., and the shear rate is 11.7 while measuring the viscosity by a stress control type rheometer Physica MCR301 (cone plate diameter: 75 mm, cone angle: 1.0 °) manufactured by Anton Paar. (1 / s), the ink is cooled to 20 ° C. under the condition of a temperature decreasing rate of 0.1 ° C./s to obtain a temperature change curve of viscosity.
The viscosity at 80 ° C. and the viscosity at 25 ° C. can be determined by reading the viscosity at 80 ° C. and 25 ° C. in a temperature change curve of the viscosity, respectively. The phase transition point can be determined as a temperature at which the viscosity becomes 200 mPa · s in a temperature change curve of the viscosity.

From the viewpoint of further improving the dischargeability from the inkjet head, the average dispersed particle diameter of the pigment particles according to the present invention is in the range of 50 to 150 nm, and the maximum particle diameter is preferably in the range of 300 to 1000 nm. . A more preferred average dispersed particle size is in the range of 80 to 130 nm.
The average dispersed particle diameter of the pigment particles in the present invention means a value obtained by a dynamic light scattering method using Datasizer Nano ZSP manufactured by Malvern. Since the ink containing the colorant has a high concentration and does not transmit light with this measuring instrument, the measurement is performed after diluting the ink by 200 times. The measurement temperature is normal temperature (25 ° C.).

[Method of forming resist film]
The method of forming a resist film using the ink of the present invention includes: (1) a step of discharging the ink of the present invention from a nozzle of an inkjet head to land on an oxide film on a substrate; and (2) landing on the oxide film. Irradiating the ink with actinic light to cure the ink.

<Step (1)>
In the step (1), as shown in FIG. 2 (b), ink droplets are ejected from the inkjet head 5, and the ink droplets on the conductive oxide film 2 formed on the substrate 1 as a recording medium are formed. Then, it is landed at a position corresponding to the resist film 3 to be formed, and is patterned.
The discharge method from the inkjet head may be either an on-demand method or a continuous method.
On-demand type inkjet heads include electro-mechanical conversion types such as single-cavity type, double-cavity type, bender type, piston type, shared mode type and shared wall type, as well as thermal inkjet type and bubble jet (registered trademark). (Bubble jet is a registered trademark of Canon Inc.) or any other type of electric-heat conversion method.

  By ejecting the ink droplets from the inkjet head in a heated state, the ejection stability can be improved. The temperature of the ink at the time of ejection is preferably in the range of 40 to 100 ° C., and more preferably in the range of 40 to 90 ° C. in order to further enhance ejection stability. In particular, it is preferable to perform ejection at an ink temperature such that the viscosity of the ink is in the range of 7 to 15 mPa · s, more preferably in the range of 8 to 13 mPa · s.

  The sol-gel phase transition type ink has a temperature of (gelation temperature + 10) ° C. to (gelation temperature) of the ink when the ink is filled in the inkjet head in order to enhance the ejection property of the ink from the inkjet head. The temperature is preferably set to +30) ° C. If the temperature of the ink in the inkjet head is lower than (gelling temperature + 10) ° C., the ink is gelled in the inkjet head or on the nozzle surface, and the ink ejection property is likely to be reduced. On the other hand, if the temperature of the ink in the inkjet head exceeds (gelling temperature + 30) ° C., the temperature of the ink becomes too high, and the ink components may deteriorate.

The method of heating the ink is not particularly limited. For example, at least one of an ink tank constituting a head carriage, an ink supply system such as a supply pipe and a front chamber ink tank immediately before the head, a pipe with a filter, and a piezo head is heated by a panel heater, a ribbon heater, or warm water. be able to.
The amount of ink droplets when ejected is preferably in the range of 2 to 20 pL from the viewpoint of recording speed and image quality.

The substrate is not particularly limited. For example, paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / non-woven cloth epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, fluorine / polyethylene / PPO / cyanate ester, etc. All grades (FR-4, etc.) of copper-clad laminates, and other polyimide films, PET films, glass substrates, ceramic substrates, wafer plates, stainless steel plates, using materials such as the used copper-clad laminated plates for high-frequency circuits And the like.
Examples of the conductive oxide film include copper, gold, silver, aluminum, nickel, and ITO.

<Step (2)>
In the step (2), the ink that has landed on the oxide film in the step (1) is irradiated with actinic rays to form a resist film formed by curing the ink.
The actinic ray can be selected from, for example, electron beams, ultraviolet rays, α-rays, γ-rays, and X-rays, but is preferably ultraviolet rays.
Irradiation with ultraviolet rays can be performed, for example, using a water-cooled LED manufactured by Phoseon Technology under the condition of a wavelength of 395 nm. By using an LED as a light source, it is possible to suppress poor curing of the ink due to melting of the ink by radiant heat of the light source.

Irradiation with ultraviolet rays has a peak illuminance of ultraviolet rays having a wavelength in the range of 370 to 410 nm on the resist film surface, preferably in the range of 0.5 to ¹⁰ W / cm ² , more preferably in the range of 1 to 5 W / cm ² . Perform so that it is within. From the viewpoint of suppressing irradiation of the ink with radiant heat, it is preferable that the amount of light irradiated on the resist film is less than 350 mJ / cm ² .
Irradiation with actinic rays is preferably performed between 0.001 and 1.0 second after the ink has landed, and between 0.001 and 0.5 second to form a high-definition resist film. Is more preferred.

Irradiation with actinic light may be performed in two stages.
First, after the ink has landed, the ink is temporarily cured by irradiating with actinic rays for 0.001 to 2.0 seconds, and after all printing is completed, the ink may be further cured by irradiating with actinic rays. . By dividing the irradiation of the actinic ray into two stages, the contraction of the recording material that occurs during the curing of the ink is less likely to occur.

The oxide film 2 not covered with the resist film 3 formed by the ink-jet method as described above was removed with an acid etching solution (see FIG. 2C), and the oxide film 2 was covered with an alkali solution. By removing the resist film 3, fine and accurate line drawings such as circuits, patterns, characters, and images can be obtained (see FIG. 2D). Note that the resist film may be used for an application that does not etch.
Examples of the etching solution include ferric chloride aqueous solution, cupric chloride aqueous solution, ammonia copper aqueous solution, high-concentration sodium hydroxide aqueous solution, high-concentration hydrochloric acid, hydrogen fluoride water, ferric nitrate aqueous solution, and the like. Examples thereof include aqueous potassium hydroxide, aqueous tetramethylammonium hydroxide, and aqueous sodium (meth) silicate.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.
[Inkjet ink material]
The following were used as the inkjet ink materials.
<Photopolymerizable compound>
The compounds shown in the following table were used as the photopolymerizable compounds.

<Gelling agent>
As the gelling agent, those shown in the following table were used.

<Surfactant>
・ KF-352A (Shin-Etsu Chemical Co., Ltd.)

<Photopolymerization initiator>
・ IRGACURE TPO (BASF)
・ 819 (manufactured by BASF)

<Sensitization aid>
・ ITX (2-isopropylthioxanthone)

<Polymerization inhibitor>
・ Irgastab UV10 (manufactured by BASF)

<Pigment dispersion>
(Preparation of Pigment Dispersion 1)
The following dispersant and dispersion medium were placed in a stainless steel beaker and dissolved by heating and stirring for 1 hour while heating on a hot plate at 65 ° C. After cooling to room temperature, the following pigment was added thereto, and zirconia beads having a diameter of 0.5 mm were added. 200g together with the glass bottle was sealed. This was subjected to a dispersion treatment using a paint shaker until a desired particle size was reached, and then the zirconia beads were removed.
Dispersant: BYKJET-9151 (manufactured by BYK) 7 parts by mass Dispersion medium: tripropylene glycol diacrylate (0.2% in the dispersion medium containing Irgastab UV10 as a thermal polymerization inhibitor)
70 parts by mass Pigment: Pigment Blue 15: 4 (Chromium Fine Blue 6332JC, manufactured by Dainichi Seika)
23 parts by mass

(Preparation of Pigment Dispersion Liquid 2)
In the preparation of the pigment dispersion 1, instead of tripropylene glycol diacrylate as a dispersion medium, NK ester A-400 (manufactured by Shin-Nakamura Chemical Co., Ltd.) (photopolymerizable compound having no acidic group: having a molecular weight of 300 to 1500) Within the range, a pigment dispersion liquid was prepared in the same manner except that a (meth) acrylate compound having 3 to 14 unit structures represented by (—CH ₂ —CH ₂ —O—) in the molecule was used. 2 was prepared.

[Preparation of ink]
Ink components (photopolymerizable compounds, photopolymerization initiators, gelling agents, surfactants, photopolymerization initiators, sensitization aids, polymerization inhibitors and pigments described in Tables III-1 to III-3 below The mixture was filtered according to a Teflon (registered trademark) 3 μm membrane filter manufactured by ADVANTEC while heating the mixture to 80 ° C. to obtain Inks 1 to 25.
Further, the viscosity at 25 ° C. and the sol-gel phase transition temperature of each ink were measured using a viscoelasticity measuring device MCR300 manufactured by Physica, and a shear rate of 11 (1 / s). The measurement results are shown in the following table.

<Pattern formation by inkjet>
The prepared ink was loaded in an inkjet recording apparatus having an inkjet recording head equipped with a piezo type inkjet nozzle. Using this apparatus, a pattern was formed on a copper-clad laminate for printed wiring boards (FR-4 thickness 1.6 mm, size 150 mm × 95 mm).
The ink supply system includes an ink tank, an ink flow path, a sub-ink tank immediately before an inkjet recording head, a pipe with a metal filter, and a piezo head. The ink is heated to 90 ° C. from the ink tank to the head. A heater was also built in the piezo head, and the ink temperature in the recording head was heated to 90 ° C. The piezo head has a nozzle diameter of 22 μm and heads having a nozzle resolution of 600 dpi are staggered to form a 1200 dpi nozzle row. Using this ink jet recording apparatus, a voltage is applied so that the amount of droplets becomes 8.0 pl dots, and a 20 mm × 50 mm solid pattern and a 100 μm line & space comb pattern are formed on the substrate, respectively. Is printed so as to have a thickness of 20 μm, and then an LED lamp (395 nm, 8 W / cm ² , water cooled unit) manufactured by Phoseon Technology is irradiated to 500 mJ / cm ² to cure the ink layer to obtain a cured film. Was.

[Evaluation]
<Solubility of gelling agent>
After preparing the ink, the state of dissolution after standing at 100 ° C. for 4 hours was visually observed.
A: No separation or precipitation.
：: Two or less oil droplets of 1 mm or less were precipitated after standing for 4 hours, but disappeared by stirring.
Δ: Five or less oil droplets of 1 mm or less were precipitated after standing for 4 hours, but disappeared by stirring.
X: Oil balls gathered on the surface and remained (separated) even after stirring.

<Pigment dispersion stability>
With respect to the pigment particles contained in the ink, the average particle size in each ink was measured by a dynamic light scattering method using Datasizer Nano ZSP (manufactured by Malvern). Each ink was collected in a heat-resistant tube and stored in a thermostat at 60 ° C. for one month. The average particle size of the pigment particles in each of the inks after storage was measured in the same manner, and the difference (PA-PB) between the average particle size before storage (PA) and the average particle size after storage (PB) was calculated.
：: Difference in average particle size is less than 7 nm.
Δ: Difference in average particle size is 7 nm or more and less than 15 nm.
X: The difference of average particle diameter is 15 nm or more.

<Ink ejection stability>
Using the piezo head, the liquid is continuously discharged (driven) under the conditions of a droplet amount of 3.5 pl, a droplet speed of 7 m / sec, an ejection frequency of 40 kHz, and a printing rate of 100%, and 1 minute and 5 minutes after the start of driving. After 10 minutes, the number of nozzles not ejected was counted.
A: The number of missing nozzles is less than 2.
：: The number of missing nozzles is 2 or more and less than 10.
Δ: The number of missing nozzles is 10 or more and less than 50.
X: The number of missing nozzles is 50 or more.

<Fine line reproducibility>
The print sample of the comb pattern was observed at a magnification of 500 times using a microscope (VHX-5000 manufactured by KEYENCE).
：: A sharp line, 100 μm line & space is reproduced with an error of ± 10 μm or less, and no scattering of satellites or the like occurs.
Δ: The line is slightly thick and thin, but the line and space of 100 μm is reproduced with an error of more than ± 10 μm and within ± 20 μm.
×: The lines are uneven and lines and spaces are crushed.

<Substrate adhesion>
The printed sample of the solid pattern was cut into a cross-cut in the cured film according to the cross-cut method of JIS K5600, an adhesive tape was applied, and the peeled-off state of the cured film was observed.
A: Adhesion residual ratio is 100%.
：: Adhesion residual ratio is 80% or more and less than 100%.
Δ: Adhesion residue rate is 60% or more and less than 80%.
X: Adhesion residual rate is less than 60%.

<Etching resistance>
The printed sample of the solid pattern was immersed in an aqueous ferric chloride solution at 60 ° C. for 30 minutes, washed with water, dried, and then adhered with an adhesive tape and peeled off to observe the peeled state of the cured film.
A: No peeling occurred.
：: No peeling occurred, but some discoloration was observed.
Δ: Partial peeling occurred.
×: Peeling occurred on the entire surface.

<Alkali peelability>
The printed sample of the solid pattern was immersed in a 2.5% aqueous solution of sodium hydroxide at 40 ° C. for 1 minute, and the cured film was visually observed for dissolution and peelability.
：: Completely dissolved and peeled.
Δ: Not completely dissolved, but peeled.
X: It did not peel.

  From the above results, the ink of the present invention is more soluble in the gelling agent, the pigment dispersion stability, the ejection stability of the ink, the fine line reproducibility, the substrate adhesion, the etching resistance and the alkali peeling compared to the ink of the comparative example. It is recognized that the properties are good.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Oxide film 3 Resist film 4 Mask 5 Ink jet head

Claims (8)

  It contains a photopolymerizable compound having no acidic group, a photopolymerizable compound having an acidic group, a gelling agent having no acidic group, and a photopolymerization initiator, and undergoes a sol-gel phase transition depending on temperature. An inkjet ink for a resist, comprising: The resist according to claim 1, wherein the viscosity at 25 ° C. is in the range of 1 to 1 × 10 ⁴ Pa · s, and the phase transition point is in the range of 40 ° C. or more and less than 100 ° C. 3. Inkjet ink. The resist according to claim 1, wherein the gelling agent contains at least one compound having a structure represented by the following general formulas (G1) and (G2). 4. Inkjet ink.
General formula (G1): R ₁ —CO—R ₂
General formula (G2): R ₃ —COO—R ₄
[In the formula, R _{1 to} R ₄ each independently represent an alkyl chain having a straight-chain portion having 12 or more carbon atoms and optionally having a branch. ]   The resist ink jet according to any one of claims 1 to 3, wherein the gelling agent is contained in a range of 0.5 to 5% by mass based on the whole ink. ink. As the photopolymerizable compound having an acidic group, a (meth) acrylate compound having an acidic group selected from a carboxy group, a phosphoric acid group, a sulfonic acid group, or a hydroxy group, and
The resist inkjet according to any one of claims 1 to 4, wherein the (meth) acrylate compound is contained within a range of 1 to 30% by mass based on the whole ink. ink. As the photopolymerizable compound having no acidic group, a (meth) acrylate compound having a molecular weight in the range of 300 to 1500 and a ClogP value in the range of 4.0 to 7.0 is contained, and
The resist inkjet according to any one of claims 1 to 5, wherein the (meth) acrylate compound is contained within a range of 10 to 40% by mass based on the whole ink. ink. As the photopolymerizable compound having no acidic group, a compound having 3 to 14 unit structures represented by (—CH ₂ —CH ₂ —O—) in a molecule within a molecular weight range of 300 to 1500. Further containing a (meth) acrylate compound, and
The inkjet ink for resist according to claim 6, wherein the (meth) acrylate compound is contained within a range of 30 to 70% by mass based on the whole ink.   The inkjet ink for resist according to any one of claims 1 to 7, further comprising a coloring agent.

Images