JP6653362B2 - Ink for ink jet - Google Patents

Description

  The present invention relates to an ink-jet ink used for an ink-jet printer.

In general, as a recording method on plastic, glass, metal, or the like, an ink jet printer that can easily print variable information without contact is widely used. As an ink jet ink used in such an ink jet printer, those in which an oily dye, a vinyl chloride resin, a vinyl acetate resin, an acrylic resin, a butyral resin, or the like is dissolved in a solvent such as methyl ethyl ketone or alcohol are known. .
However, the inks using these resins are designed to provide sufficient stability and re-dissolvability when ejected using an inkjet printer, so that the stability in the printer is extremely improved. However, there is a problem in the solvent resistance of the printed body formed on the surface of the printing medium, and the ink easily melts even if the ink is sufficiently dried.

Thus, in order to obtain solvent resistance, there is a method of using a component that becomes insoluble after drying as an ink component.
For example, a so-called UV (ultraviolet ray) curable ink or an EB (electron beam irradiation) curable ink that irradiates ultraviolet rays or an electron beam to crosslink a monomer is known.
However, with respect to UV-curable ink, a UV irradiation device is relatively expensive, and ozone is generated at the time of UV irradiation, so that a complicated and expensive printing environment is required. On the other hand, the EB curing type ink has the disadvantage that the EB apparatus becomes more expensive, and adjustment in a vacuum system or a nitrogen atmosphere is required, and it is not easy to introduce the ink.

As another method for imparting solvent resistance, a method of imparting solvent resistance or the like by using a curing agent and causing a resin to react by the action of a catalyst or heat is also performed.
However, in the method using such a curing agent, even if the curability after printing is good, it is easy to cause gelation of the ink due to a temperature change in the ink jet printer, and it is not possible to obtain a stable ink. There was a problem that it was not easy.

In view of the above background, the present applicant has proposed an ink for an ink jet printer comprising a ketone solvent and a colorant, wherein the ink further comprises a blocked isocyanate. (See Patent Document 1).
The ink described in Patent Literature 1 is excellent in adhesion of a printed body, and also excellent in ejection stability and resolubility of the ink because the isocyanate is blocked. Further, it has excellent solvent resistance due to heat curing.

JP 2013-18939 A

The present invention seeks to achieve the object of the invention of Patent Document 1 at a higher level.
Specifically, for example, in Examples of Patent Document 1, ethanol resistance is evaluated with respect to solvent resistance, but there is still room for improvement when examining acetone resistance.
Also, regarding the evaluation of the ejection stability, when the nozzle diameter was reduced and verified, there was still room for improvement. As long as the ejection stability is excellent even when the nozzle diameter is reduced, the printing area can be reduced and high resolution can be realized.

  As described above, an object of the present invention is to provide an ink jet ink that is excellent in ejection stability in an ink jet printer, and has excellent adhesion to a surface of a print substrate, and excellent washing resistance and solvent resistance after printing. .

The present invention has the following configuration in order to solve the above-mentioned problems.
That is, the ink jet ink according to the present invention, viewed contains a solvent comprising a ketone solvent in a ratio of more than 50 wt% solvent based on the total amount of a colorant, a poly-para vinylphenol resin, a blocked isocyanate, and a conductive agent The blending ratio of the colorant is 2 to 15 wt%, the blending ratio of the polyparavinylphenol resin is 1 to 20 wt%, and the blending ratio of the blocked isocyanate is 0.1 to 10 wt% based on the total weight of the ink. %, And the mixing ratio of the conductive agent is 0.3 to 2.5% by weight .

The ink-jet ink of the present invention has excellent ejection stability in an ink-jet printer, as well as excellent adhesiveness to the surface of a printing substrate, washing resistance after printing, and solvent resistance.
In particular, it is excellent in ejection stability and solvent resistance. Regarding ejection stability, it shows stable ejection performance even when using an ink jet printer with a small nozzle diameter. It also exhibits good solvent resistance to other solvents such as acetone and acetone.

4 is a photograph of a data matrix in an ejection stability test (40 μm) of Example 1. 4 is a photograph of a data matrix in an ejection stability test (40 μm) of Comparative Example 1.

  Hereinafter, the ink-jet ink according to the present invention will be described in detail, but the scope of the present invention is not limited to these descriptions, and other than the following examples, appropriately changed and implemented without impairing the spirit of the present invention. I can do it.

(Inkjet ink)
The inkjet ink of the present invention (hereinafter may be simply referred to as “ink”) contains a ketone-based solvent, a colorant, a polyparavinylphenol resin, and a blocked isocyanate.

<Colorant>
Examples of the colorant used in the present invention include pigments and dyes, and these may be used as a mixture.

When a pigment is used, both an inorganic pigment and an organic pigment can be used.
Examples of the inorganic pigment include titanium oxide, calcium carbonate, iron oxide, and cobalt blue.
Examples of the organic pigment include quinacridone, phthalocyanine, benzimidazolone, isoindolinone, quinophthalone, condensed azo, isoindoline, and diketopyrrolopyrrole.
Since the pigments described above have good light fastness, they are particularly preferable for applications requiring light fastness. For titanium oxide, those obtained by treating the surface of a pigment with an aluminum-based, zinc-based, or silica-based surface treatment agent are described below with respect to dispersibility, sedimentation prevention, thickening over time, aggregation prevention, and the like. Preferred for stability with resins and blocked isocyanates.

  Specific examples of the above-mentioned organic pigments include insoluble azo pigments such as toluidine red, toluidine maroon, hansa yellow, benzidine yellow, and pyrazolone red; lithol red, helio bordeaux, pigment scarlet, and soluble azo pigments such as permanent red 2B; Indanthrone, derivatives from vat dyes such as thioindigo maroon, phthalocyanine blue, phthalocyanine based such as phthalocyanine green, quinacridone red, quinacridone based such as quinacridone magenta, perylene red, perylene based such as perylene scarlet, isoindolinone yellow, Isoindolinones such as isoindolinone orange, pyranthrone reds, pyranthrones such as pyranthrone orange, thioindigos, condensed azos, benzimidazolones And other pigments such as flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet, diketopyrrolopyrrole and the like. .

  When the above-mentioned pigments are represented by a color index (CI) number, C.I. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 109, 110, 117, 125, 128, 129, 137, 138, 139, 147, 148, 151, 153, 154 181, 166, 168, 185, C.I. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, C.I. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 177, 180, 192, 202, 206, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, C.I. I. Pigment Violet 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, C.I. I. Pigment Green 7, 36, C.I. I. Pigment Brown 23, 25, 26, and the like.

When a pigment is used, it is preferable to disperse the pigment so that the average particle diameter (median diameter (D50) of the cumulative distribution) measured by a particle size distribution meter is in the range of 10 to 300 nm and the maximum particle diameter is 1 μm or less. The average particle size of these pigments is preferably 0.3 μm or less.
If the average particle size is larger than 0.3 μm, the dispersion stability of the ink is poor, and the generation of sediment increases. In particular, when the maximum particle size is 1 μm or more, sedimentation of the pigment becomes remarkable, and the stability of printing may be impaired. On the other hand, when the average particle size is 10 nm or less, there is no particular problem. However, since the particle size is too small, there is a possibility that light resistance is likely to deteriorate.
As described above, the pigment used in the present invention is preferably fine pigment particles, but in order to obtain an ink for inkjet, it is necessary to further add a dispersant and perform high-speed stirring with a disperser to form a stable dispersion. preferable.
The pigment is desirably contained in an amount of 0.5 to 20% by weight based on the total weight of the inkjet ink in order to obtain a sufficient density of an image and a sufficient light resistance after recording.

In the present invention, as described above, a dye can be used.
The dye is not particularly limited as long as it can be dissolved in a ketone solvent. However, from the viewpoint of solvent resistance, if the solvent to be contacted after the printed material is cured is alcohol, a solvent insoluble in alcohol is preferable.
Specifically, for example, Solvent Yellow 2, 14, 16, 19, 21, 34, 48, 56, 79, 88, 89, 93, 95, 98, 133, 137, 147, and Solvent Orange in color index numbers 5, 6, 45, 60, 63, Solvent Red 1, 3, 7, 8, 9, 18, 23, 24, 27, 49, 83, 100, 111, 122, 125, 130, 132, 135, 195, 202, 212, Solvent Blue 2, 3, 4, 5, 7, 18, 25, 26, 35, 36, 37, 38, 43, 44, 45, 47, 48, 51, 58, 59, 59: 1, 63, 64, 67, 68, 69, 70, 78, 79, 83, 94, 97, 98, 99, 100, 101, 102, 104, 105, 111, 112, 122, 124, 128, 12 , 132, 136, 137, 138, 139, 143, Solvent Green 5, 7, 14, 15, 20, 35, 66, 122, 125, 131, Solvent Black 1, 3, 6, 22, 27, 28, 29 , Solvent Violet 13, Solvent Brown 1, 53, etc., and these can be used alone or in combination of two or more.
It is also possible to use a basic oil dye.
Examples of such basic oil-based dyes include C.I. I. Basic Violet 3, C.I. I. Basic Red 1, 8, C.I. I. Basic Black 2 and the like.

<Blocked isocyanate>
The ink of the present invention contains a blocked isocyanate.
Blocked isocyanate is a compound having a protected isocyanate group, and can be obtained by reacting an isocyanate compound with a protected compound (blocking agent).
The blocked isocyanate is inactive at room temperature, but has the property that the protective group is dissociated by heating to regenerate the isocyanate group. For this reason, it is possible to mix the compound having an active hydrogen group with the compound having an active hydrogen group in advance under a condition not heated.

  As the compound having an isocyanate group, one or more isocyanate groups may be contained in one molecule, and examples thereof include aliphatic, aromatic or alicyclic mono-, di-, and triisocyanate compounds.

  Examples of the blocking agent for protecting the isocyanate group include alcohol compounds, phenol compounds, lactam compounds, oxime compounds, alkyl acetoacetate compounds, alkyl malonate compounds, phthalimide compounds, and imidazole compounds.

In the ink state, the blocked isocyanate used in the present invention is sufficiently soluble in a ketone solvent which is a main solvent component of the ink and is stable. Then, this blocked isocyanate, after the printing step of drying after printing, in the subsequent heating step, when given any heat, together with the resin component described later, or reacts with a part of the resin component, Alternatively, it reacts with a part of the printing material to make the printed ink film stronger.
Because general isocyanates are highly reactive, the reaction can easily proceed without the application of heat.However, blocked isocyanates can react by exceeding a certain temperature. Problems such as thickening and gelling can be prevented.

As such a blocked isocyanate, one in which dimethylpyrazole, diethylmalonate, methylethylketone oxime, caprolactam, or the like is incorporated as a blocking agent in the isocyanate molecular structure is known.
These blocking agents can adjust the temperature at which the block dissociates depending on the type, but in consideration of the temperature in the inkjet printer, suitability for storage temperature, or the actual post-treatment process, etc. The conditions for dissociation and dissociation at 250 ° C. or lower from the viewpoint of energy efficiency are preferred.

In order to impart suitability to such conditions, it is preferable to use, for example, dimethylpyrazole, diethylmalonate, methylethylketone oxime, or caprolactam as the blocking agent. It is preferred to select Diethyl malonate tends to crystallize a cured coating film, and may not be preferred as a part of the characteristics of the coating film. Since methyl ethyl ketone oxime dissociates at a relatively high temperature, it requires slightly more energy for curing. Further, the caprolactam-based has a drawback that deposits (dusts) are easily generated in a curing treatment facility.
In addition, dimethylpyrazole, block isocyanate of a type obtained by mixing one or two or more of diethylmalonate, methylethylketone oxime, and caprolactam are preferable because appropriate curability of dimethylpyrazole and characteristics at the time of curing can be desirably adjusted.
It is desirable to make adjustments in accordance with the long-term circulation in the printer and the heat treatment environment after printing. Further, when the substrate of the printing material is previously coated with a thermosetting material, it is necessary to set a category that does not deviate from the curing conditions. By using dimethylpyrazole as the main component, the allowable value can be set broadly, so that it is easy to adjust to meet the above requirements.

The larger the amount of the above-mentioned blocked isocyanate added to the ink, the higher the solvent resistance and the hardness of the coating film to be described later. Not only does this easily occur, but also because of the presence of excess blocked isocyanate that has not reacted with the resin, the strength of the coating film is reduced, and the thermosetting property is rather reduced. On the other hand, if the amount is too small, the thermosetting property is reduced, and no improvement in film strength, which can be judged from solvent resistance and the like, is not observed.
From such a viewpoint, it is preferably used in the range of 0.1 to 10% by weight, more preferably in the range of 3 to 9% by weight, based on the total weight of the ink.

<Resin>
The ink of the present invention contains a polyparavinylphenol resin as a resin component.
Polyparavinylphenol resin is a polymer having paravinylphenol as a monomer unit. A copolymer having a monomer unit other than paravinylphenol may be used as long as the effects of the present invention are not impaired.

  Polyparavinyl phenol resin has high solubility in ketone solvents, so it provides excellent ejection stability and resolubility, and also has high solvent resistance by being thermally cured in combination with blocked isocyanate. Bring.

  Although the molecular weight of the polyparavinylphenol resin is not particularly limited, for example, the weight average molecular weight is preferably in the range of 1,000 to 30,000, and more preferably in the range of 1500 to 15,000. If the weight average molecular weight is too large, the ink may gel and the storage stability may be impaired, or the ink may not be ejected properly by a printer.If the weight average molecular weight is too small, sufficient coating strength may not be obtained. There is.

<Solvent>
As a solvent used in the present invention, a ketone solvent is used as a main component of the solvent.
Examples of the ketone solvent include acetone, methyl ethyl ketone, dipropyl ketone, methyl isobutyl ketone, methyl isopropyl ketone, cyclopentanone and the like. Above all, methyl ethyl ketone can be preferably used for ink for a continuous ink jet printer because of its solubility in resin, dispersibility of pigment, conductivity, and drying property of ink.

  In the above description, "the main component of the solvent" means that the solvent may include only a ketone-based solvent and may include other solvents as long as the effects of the present invention are not impaired. Usually, it refers to a case where a ketone solvent is used in a proportion of 50% by weight or more of the total amount of the solvent. More preferably, the ketone solvent is used in a proportion of at least 60% by weight, more preferably at least 70% by weight, even more preferably at least 80% by weight, more preferably at least 90% by weight of the total amount of the solvent. Is particularly preferable, and it is most preferable to use only a ketone solvent as a solvent.

  Examples of solvents other than ketone solvents include ethyl acetate, n-propyl acetate, butyl acetate, toluene, xylene, isopropyl alcohol, butanol, dioxane, 2- (methoxymethoxy) ethanol, 2-butoxyethanol, and 2- ( Isopentyloxy) ethanol, 2- (hexyloxy) ethanol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, liquid polyethylene glycol, 1-methoxy-2-propanol , 1-ethoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol mono Chirueteru, dipropylene glycol monoethyl ether, low molecular weight polypropylene glycol.

  The amount of the ketone-based solvent with respect to the total weight of the ink is not particularly limited, but from the viewpoint of the solubility of the resin, the dispersibility of the pigment, the conductivity, the drying property of the ink, etc. Is preferably 60% by weight or more. In particular, it is preferable to use methyl ethyl ketone at a rate of 55% by weight or more based on the total weight of the ink.

<Other components>
The ink of the present invention can be suitably used for an ink jet printer, particularly a continuous ink jet printer of a continuous ejection type of charged dots. In this case, a conductive agent is used to adjust the amount of deflection of the ink droplets ejected from the printer by the electric field.
Examples of such a conductive agent include ammonium thiocyanate, potassium thiocyanate, sodium thiocyanate, lithium nitrate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium bromide, and quaternary ammonium salt of tetraphenylboron. Among them, when the stability of the ink is evaluated from the viewpoint of compatibility with the blocked isocyanate, organic conductive agents such as tetrabutylammonium hexafluorophosphate and quaternary ammonium tetraphenylboron are stable for a long time. It is preferable because it exhibits the following characteristics.

  The conductive agent is preferably used in a range of 0.5 to 2.5% by weight based on the total weight of the ink. If the content of the conductive agent is less than 0.5% by weight, sufficient conductivity may not be obtained, and the deflection in the printer may not be stably maintained. On the other hand, if the content of the conductive agent is more than 2.5% by weight, the compatibility with each material cannot be maintained sufficiently, and the stability over time is reduced, and the unstable printing state in the printer is reduced. May be invited. Care should be taken when adding conductive agents other than those described above, because they may cause poor dispersion or aggregation of the pigment.

In the ink of the present invention, a dispersant may be used in order to improve the dispersibility of the pigment.
Examples of such a pigment dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long-chain polyaminoamide and a high-molecular-weight acid ester, a salt of a high-molecular-weight polycarboxylic acid, a salt of a long-chain polyaminoamide and a polar acid ester, and a salt thereof. Molecular weight unsaturated acid ester, high molecular weight copolymer, modified polyurethane, modified polyacrylate, polyetherester type anionic activator, naphthalene sulfonate formalin condensate, special aromatic sulfonate formalin condensate, polyoxyethylene alkyl Phosphoric acid esters, polyoxyethylene nonylphenyl ether, stearylamine acetate and the like can be mentioned.
Specifically, Anti-Terra-U, Anti-Terra-203 / 204, and Disperbyk-101, 107, 110, 130, 161, 162, 163, 164, 165, 166, 170, 400, manufactured by BYK Chemie. Bykumen, BYK-P104, P105, P104S, 240S, Lactimon, Efka 44, 46, 47, 48, 49, 54, 63, 64, 65, 66, 71, 701, 764, 766, Efka polymer 100 manufactured by Efka Chemicals. , 150, 400, 401, 402, 403, 450, 451, 452, 453, 745, Floren TG-710, Flownon SH-290, SP-1000, Polyflow No. 50E, No. 300, Ajisper PB821 manufactured by Ajinomoto Finetech, Dispalon KS-860, 873SN, 874, # 2150, # 7004 manufactured by Kusumoto Kasei Co., Ltd., Demol RN, N, MS, C, SN-B, EP, manufactured by Kao Corporation. Homogenol L-18, Emulgen 920,930,931,935,950,985, Acetamine 24,86, Lusizol Solsperse 5000,7000,13240,13940,17000,22,000,24000,28000,32000,38500, Nikko Chemical Nikkor T106, MYS-IEX, Hexagline 4a-U and the like can be exemplified.

  Furthermore, it is also possible to use a silicon-based surfactant or a fluorine-based surfactant as an adjusting agent for forming dots. When an inorganic pigment having a large specific gravity, such as titanium oxide or iron oxide, is used, an unsaturated carboxylic acid-based hard cake inhibitor can be used to prevent the hard cake from being caused by sedimentation.

<Blend of each component>
The mixing ratio of each component is not particularly limited. For example, the mixing ratio of the coloring agent is 2 to 15% by weight, and the mixing ratio of the polyparavinylphenol resin is 1 to 1 based on the total weight of the ink. 20% by weight, the compounding ratio of the blocked isocyanate is 0.1 to 10% by weight, the compounding ratio of the conductive agent is 0.3 to 2.5% by weight, and the remainder is a solvent containing a ketone-based solvent. preferable.
In addition, when the optimum range of the mutual ratio between the polyparavinylphenol resin and the blocked isocyanate is exemplified, for example, it is preferable that polyparavinylphenol resin: blocked isocyanate = 1: 1 to 3: 1 on a weight basis. More preferably, the ratio is 5: 1 to 2.5: 1. If the amount of the polyparavinylphenol resin is too large (if the amount of the blocked isocyanate is too small), the strength of the coating film may be reduced due to the presence of an excessive amount of unreacted polyparavinylphenol resin with the blocked isocyanate. When the amount is too small (when the amount of the blocked isocyanate is too large), the strength of the coating film may be reduced due to the presence of the excess blocked isocyanate that has not reacted with the polyparavinylphenol resin.

[Use of ink]
Examples of the substrate to be printed with the ink of the present invention include metal, glass, and plastics, and a coating material coated on the surface of these materials. For heat curing, the heat-resistant temperature of the printing material is preferably 100 ° C. or higher.
The above-described ink is sprayed onto such a printing material by an ink-jet printer to form printing (printed material) of various codes such as characters, bar codes, and data matrix codes. Is passed over 10 to 60 minutes. The preferred heating temperature is from 130 to 250 ° C, more preferably from 150 to 210 ° C. The preferred heating time is about 15 to 30 minutes. Such heating conditions are preferable from the viewpoint of solvent resistance, adhesion, and washing resistance with a surfactant aqueous solution, and sufficiently exhibit the accuracy of a reading rate with a reader that reads a barcode, a data matrix, and the like. Can be.

  The viscosity of the ink of the present invention is preferably adjusted within a range of, for example, 3.2 to 5.5 mPa · s (20 ° C.) in order to widen an appropriate printable area in an inkjet printer. When the viscosity of the ink falls below 3.2 mPa · s, the formation of dots of the ink on the surface of the printing substrate becomes poor, and the density (printing density) of the formed printed material becomes low. On the other hand, if the viscosity of the ink exceeds 5.5 mPa · s, problems such as poor ejection of ink droplets and poor drying after printing are likely to occur.

  Hereinafter, the ink according to the present invention will be described in detail using examples, but the present invention is not limited to these examples.

[Example 1]
15 parts by weight of a polyparavinylphenol resin (weight average molecular weight Mw = 11000) and 3 parts by weight of Solsperse 38500 (dispersant: manufactured by Lubrizol Co.) are dissolved in 58.5 parts by weight of methyl ethyl ketone and 5 parts by weight of cyclopentanone. 10 parts by weight of titanium oxide (Al / Si treatment, rutile type TiO ₂ , average particle size 0.24 μm) was added to the solution, and the mixture was stirred and mixed. The mixture was supplied to a horizontal sand mill to remove the titanium oxide. Dispersed.
To this dispersion, 7 parts by weight of a blocked isocyanate using dimethylpyrazole as a blocking agent was added and mixed, and 1.5 parts by weight of tetrabutylammonium hexafluorophosphate was further added, followed by high-speed stirring and mixing.
Thereafter, the mixed dispersion was filtered with a filter having an opening of 1.0 μm to obtain an ink for an inkjet printer.
In the trial production of the ink, it is possible to put all the components constituting the ink in one container and disperse them all at once.However, only a part of the pigment, the dispersant, the resin and the solvent is used to prepare the pigment. It is preferable to perform dispersion as a concentration system and to add a blocked isocyanate and a conductive agent to mix and dissolve after the dispersion in order to obtain a stable ink.

[Examples 2 to 10, Comparative Examples 1 and 2]
The inks of Examples 2 to 10 and Comparative Examples 1 and 2 were prepared in the same manner as in Example 1 except that the various raw materials were changed as shown in Table 1 below. Table 1 also shows the prescription of Example 1.
In addition, in Table 1, the numerical values shown in the prescription column represent weight% with respect to the total weight of the ink.

[Evaluation of physical properties of ink]
The physical properties of the ink were evaluated and are shown in Table 1 above.
Details of the evaluation items are as follows.

<Viscosity>
It was measured at 20 ° C. using an EH type viscometer.

<Conductivity>
It was measured at 20 ° C. using a conductivity meter. In a continuous ink jet printer, a conductivity of 0.5 mS / cm or more is preferable for performing accurate dot deflection control.

<Dispersibility>
When the resin liquid of the pigment was dispersed by a horizontal sand mill, it was evaluated whether or not there was little residual lumps and coarse particles and the state was fluid. A sample in which the dispersion state including the average particle size was very good was marked with “◎”, and a surface state of the draw-down coating film and one in which the fluidity during dispersion was good was marked with “○”.

<Average particle size>
It was shown by the particle diameter (nm) of D50 measured with a laser detection type particle size distribution meter (UPA-150 manufactured by Nikkiso Co., Ltd.).

<Discharge stability>
The ink shown in each example was printed on the resin-coated surface of the glass substrate surface using a continuous ink-jet printer (CCS3000P manufactured by Kishu Giken Kogyo Co., Ltd.) using a 50 μm nozzle and a 40 μm nozzle, and the state of the printed material was visually evaluated. Things. The ejection characteristics were also evaluated by adjusting the ejection state of the nozzles during continuous printing according to the state of the obtained printed material.
"X" indicates that no dot was lost in the middle of continuous printing, or each printed dot was not printed at a predetermined position. Further, the printed two-dimensional barcode was read by a reader to confirm the accuracy of the reading, and the reading was abnormal when the reading was abnormal. When each of the printed dots was accurately and continuously printed at a predetermined position, and the printed two-dimensional barcode was normally read by the reader, it was marked as “○”.
For Example 1 and Comparative Example 1, photographs when the data matrix was printed with a 40 μm nozzle are shown in FIGS. 1 and 2, respectively.

<Storage stability>
The ink was sealed in a sealed container and stored at 45 ° C., and the appearance and viscosity change of the ink were confirmed after 2 months. The sample whose appearance and viscosity did not change more than a predetermined value (thickness of 8% or more) was marked with “○”, and the sample whose viscosity changed more than a predetermined value was marked “x”.

<Thermosetting>
As the conditions for thermally curing the printed body after printing, the curability at 170 ° C. for 30 minutes and the curability at 200 ° C. for 15 minutes were respectively confirmed. This thermosetting property is obtained by applying alcohol to a cured surface cured by heat and confirming whether or not the thermally cured printed material is dissolved. Those that did not dissolve were marked with “○”, and those that partially dissolved were marked with “x”.

<Alcohol resistance>
The surface of the print material after the print was thermally cured was rubbed with a cotton swab soaked with alcohol to confirm the dissolution and peeling of print dots on the print material surface. Those that did not peel off after 50 or more rubs were marked with “◎”, those that did not peel off after 20 to 50 rubs were marked with “○”, and those that did peel off were marked with “x”.

<Acetone resistance>
The surface of the print material after the print was thermally cured was rubbed with a cotton swab soaked in acetone to confirm the dissolution and peeling of print dots on the print material surface. The sample that did not peel off after 20 to 30 rubs was marked with “◎”, the sample that did not peel off after 10 to 20 rubs was marked with “○”, and the sample that peeled off was marked with “X”.

<Washability>
The printed material on which the two-dimensional barcode or data matrix is printed is immersed in a 0.25% nonionic surfactant aqueous solution, and a cleaning test is performed by ultrasonic irradiation for 15 minutes, and the printed two-dimensional barcode or data matrix is read. This is to evaluate whether the data can be read by a machine. A sample with no reading error was marked with “○”, and a sample with reading error was marked with “x”.

<Adhesion>
Adheres cellophane tape to the surface of the printed material on which the data matrix is printed, and evaluates whether or not the printed dots (printed material) constituting the data matrix are peeled off when the cellophane tape is peeled off. It is. The sample that did not have the printed dots peeled was marked with “、”, and the sample that did peeled was marked with “x”.

[Consideration of results]
From the results of Examples 1 to 10 shown in Table 1 and FIG. 1, the inks of the present invention showed all of the dispersibility, ejection stability, storage stability, thermosetting properties, solvent resistance, cleaning properties, and adhesion. It can be seen that the evaluation items have excellent physical properties.
From the results shown in Table 1 and FIG. 2, it can be said that the ink of Comparative Example 1 is basically an ink having excellent physical properties, but the ejection stability with a 40 μm nozzle is not sufficient, and the acetone resistance is high. Was inferior to the inks of Examples 1 to 10. Comparative Example 1 does not contain a polyparavinylphenol resin as a resin and does not satisfy the conditions of the present invention in that it is an ink using a butyral resin and a rosin-modified maleic resin. It was found that the use of the polyparavinylphenol resin led to the improvement of the ejection stability (40 μm) and the solvent resistance.
In addition, the ink of Comparative Example 2 had insufficient ejection stability (40 μm) and storage stability, and was inferior in acetone resistance to the inks of Examples 1 to 10. Comparative Example 2 did not use a ketone-based solvent as a main component of the solvent, and did not satisfy the conditions of the present invention. From these results, it was found that it is necessary to use a ketone-based solvent as a main component of the solvent in order to obtain the effects of the present invention.
In addition, in the white ink (Examples 1 to 8), when a reading test was performed on the two-dimensional barcode after being immersed in ethanol, the reading confirmation speed was high. Similarly, when a reading test was performed on the two-dimensional barcode after immersion in acetone in the white ink (Examples 1 to 8), the reading confirmation speed was also high. These results also confirm the high solvent resistance of the ink of the present invention.

Claims (5)

A solvent containing a ketone solvent in a ratio of more than 50 wt% solvent based on the total amount of a colorant, a poly-para vinylphenol resin, seen containing a blocked isocyanate, and a conductive agent, relative to the total ink weight, the colorant Is 2 to 15% by weight, the compounding ratio of the polyparavinylphenol resin is 1 to 20% by weight, the compounding ratio of the blocked isocyanate is 0.1 to 10% by weight, and the compounding ratio of the conductive agent is 0.1 to 10% by weight. 3 to 2.5% by weight of an inkjet ink. The inkjet ink according to claim 1, wherein the blocking agent incorporated in the blocked isocyanate includes one or more selected from the group consisting of dimethylpyrazole, diethylmalonate, methylethylketone oxime, and caprolactam. 3. The inkjet ink according to claim 2 , wherein the blocking agent incorporated in the blocked isocyanate includes dimethylpyrazole, and further includes one or more selected from the group consisting of diethyl malonate, methyl ethyl ketone oxime, and caprolactam. 4. ink. The inkjet ink according to any one of claims 1 to 3 , wherein the polyparavinylphenol resin has a weight average molecular weight in a range of 1,000 to 30,000. The inkjet ink according to any one of claims 1 to 4 , wherein the conductive agent is at least one of tetrabutylammonium hexafluorophosphate and quaternary ammonium tetraphenylboron.