JPH03258868A - Ink composition - Google Patents

Abstract

PURPOSE:To obtain a colored ink composition of ultraviolet rays-curing type for ink-jet recording having excellent ultraviolet rays-curing property and preserving stability containing ultraviolet rays-transmissible resin particles having a particle diameter smaller than a specific value. CONSTITUTION:The aimed composition contains ultraviolet rays-transmissible resin particles having <=3mum particle diameter and preferably acylphosphine oxide compound (e.g. 2,2-dimethylpropyloyl diphenylphosphine oxide) as a photoreaction initiator in an ink composition containing colorant.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an ultraviolet curable colored ink composition for inkjet recording that contains a colorant and has excellent ultraviolet curability and storage stability.

<Prior Art and Problems to be Solved> The inkjet recording method is a non-impact recording method that generates almost no noise during recording, and has become widely used in recent years because it is capable of high-speed recording.

This inkjet recording method is also being applied to printing on electronic parts, etc., but in such fields, it is necessary to wash with solvent after printing, so it is not only fast drying (quick curing) but also durable. Solvent properties are also required. Therefore, recently, ultraviolet curable inks with excellent solvent resistance have been developed as inkjet recording inks.

These ultraviolet curable inks usually consist of an ultraviolet polymerizable vehicle, a photoreaction initiator, and a colorant as essential components, and further include an organic solvent and additives as necessary.

However, conventional UV-curable inks contain colorants and therefore have poor UV-curability, and when insoluble colorants such as colored pigments are used as colorants, they tend to cause secondary agglomeration and precipitation. The aggregates are difficult to redisperse;
Therefore, there is a problem that nozzle clogging is likely to occur during printing.

In view of the current situation, the inventors of the present invention have made extensive studies and have developed an ultraviolet curable colored ink for inkjet recording that has good ultraviolet curability, good storage stability, and good redispersibility even if a precipitate is formed. The present invention was achieved by discovering a composition.

Means for Solving the Problems> That is, the present invention relates to an ultraviolet-curable colored ink composition for inkjet recording, which contains ultraviolet-transparent resin particles with a particle size of 3 μm or less in an ink composition containing a colorant. It is something.

The present invention will be explained in detail below.

The ultraviolet curable colored ink composition for inkjet recording of the present invention contains an ultraviolet polymerizable vehicle, a photoreaction initiator, a colorant, and ultraviolet transparent resin particles as essential components, and further contains an organic solvent, additives, etc. as necessary. It was forced upon me.

As the vehicle component, a compound having an unsaturated double bond capable of radical polymerization in the molecule can be used. Specifically, unsaturated polyester resins, unsaturated acrylic resins, unsaturated urethane resins, unsaturated epoxy resins, unsaturated polyamide resins, or these resins and ethylenic resins are used in ordinary ultraviolet curable inks. A typical example is a mixture with a reactive diluent having an unsaturated group. In particular, the following vehicles having excellent weather resistance, adhesion, etc. are suitable.

The vehicle has an acrylic urethane oligomer as a main component, and the acrylic urethane oligomer has a urethane bond in the molecule and an unsaturated double bond capable of radical polymerization, and has an average molecular weight of about several hundred to several hundred. It includes a wide range of words that are tone-like at room temperature.

For example, polyisocyanate and hydroxyl group-containing (meth)
In addition to oligomers obtained by reaction with acrylic esters, polyether-based acrylic urethane oligomers,
Also included are polyester-based acrylic urethane oligomers, polybutadiene-based acrylic urethane oligomers, and the like.

Specifically, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, their isomers or excess polyisocyanate and polyester polyol, polyoxymethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, A combination of a polyisocyanate (preferably a non-yellowing type polyisocyanate), such as a compound having an isocyanate end, which is a reaction product of caprolactone polyol, trimethylolpropane, or pentaerythritol with a polyhydric alcohol, and a compound having a hydroxyl group and an unsaturated group. Examples include reaction products. The compounds having a hydroxyl group and an unsaturated group include hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyethyl (meth)acrylate,
Typical examples include glycidyl (meth)acrylate.

The vehicle consists of these acrylic urethane oligomers and a reactive diluent. Reactive diluents include 2-ethylhexyl (meth)acrylate, 2hydroxyethyl (meth)acrylate, isobornyl (meth)acrylate, tripropylene glycol diacrylate, 1.6-
Hexanediol diacrylate, tetraethylene glycol diacrylate, trimethylolpropane tri(
Representative examples include meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane pentaacrylate, dipentaerythritol hexaacrylate, vinyl acetate, N-vinylpyrrolidone, dimethyl(meth)acrylamide, vinyltoluene, divinylbenzene, etc. These reaction diluents are listed as 1% by weight per 100 parts by weight of the acrylic urethane oligomer.
It is suitable to mix 0 to 300 parts by weight.

In addition, these vehicles may be present in an amount of 2 to 50% by weight in the ink composition.
It is appropriate to mix them.

Examples of the photoreaction initiator include benzophenone, acetophenone, jetoxyacetophenone, chloroacetophenone, and 2,2-dimethoxy-
2-phenylacetophenone, propiophenone, thioxanthone, benzoin, benzyl, anthraquinone,
Typical examples include benzyl ketal, benzoin ethyl ether, benzoin isopropyl ether, dimethoxyphenylacetophenone, and 2-hydroxy-2-methyl-1-phenylpropan-1-one. Excellent and less likely to thicken during ink storage for several months.
Particularly preferred are acylphosphine oxide compounds or mixtures thereof with the conventional photoinitiators mentioned above.

This acylphosphine oxide compound is a compound represented by the following general formula (I).

In the formula c, R1 is a linear or branched alkyl group having 1 to 6 carbon atoms, cyclohexyl having a total of 6 to 2 carbon atoms,
cyclopentyl-, aryl-halogen-, alkyl-
1 or alkoxy-substituted aryl group, or S- or N-
represents a 5- or 6-membered heterocyclic group (containing other carbon atoms); R2 has the same meaning as R1, and R1 and R2 may be the same or different, or 1~
represents an alkoxy group having 6 or an aryloxy group or arylalkoxy group having a total of 6 to 12 carbon atoms,
Or R' and R2 together with the phosphorus atom have 2 to 2 carbon atoms.
and R3 has 2 to 12 carbon atoms;
linear or branched alkyl group having 18 carbon atoms, 3 to 10 carbon atoms
alicyclic group, phenyl group or naphthyl group, or S
-1○-1 or N-containing 5- or 6-membered heterocyclic group (containing other carbon atoms), R3 group is one or more substituents or groups: (wherein R1 and R2 are as defined above), X represents a phenylene group or an aliphatic or alicyclic divalent group having 2 to 6 carbon atoms, and one or more of R1 to R3 is an olefinic inorganic group. It may be saturated.] Specifically, 2,2-dimethylpropioyldiphenylphosphine oxide, 2,2-dimethylpentanoyldiphenylphosphine oxide, 2,2-dimethyloctanoyldiphenylphosphine oxide, methyl 2. 2-dimethyloctanoyl phenyl phosphinate, 2-methyl-2-ethylhexanoyl diphenyl phosphine oxide, 2,6-dimethylbenzoyl diphenyl phosphine oxide, 2,6-simethoxybenzoyl diphenyl phosphine oxide, 2
．． 6-cyclobenzoyldiphenylphosphine oxide, 2.4.6-) lyntylbenzoyldiphenylphosphine oxide, methyl 2.4.6-) lyntylbenzoyl phenylphosphinate, 2,3.6-
) lyntylbenzoyldiphenylphosphine oxide, 2゜4.6-trimethoxybenzoyldiphenylphosphine oxide, 2.4.6-trichlorobenzoyldiphenylphosphine oxide, 2゜4, 6
-) Typical examples include lyntylbenzoylnaphthyl phosphonate.

The photoreaction initiator is used in an amount of 100 parts by weight of the vehicle component,
It is appropriate to add 0.1 to 30 parts by weight, preferably 0.2 to 20 parts by weight.

The coloring agent is 5olvent Black 22.
．． 27.28.29.5olvent Red 83's 1.125.132.5olvent B1ue48.
Soluble dyes such as 47.5olvent Yellow88.89, titanium oxide, carbon black, zinc sulfide,
Typical examples include inorganic or organic pigments such as oil smoke, yellow lead, red iron, phthalocyanine blue, phthalocyanine green, brilliant carmino 6B, Lake Red C1 Watching Red, and disazo yellow.

In the case of insoluble pigments, the particle size is desirably 3 μm or less, preferably 1 μm or less to prevent nozzle clogging.

It is appropriate that the colorant be added in an amount of about 0.5 to 20% by weight in the ink composition.

The ultraviolet-transparent resin particles are insoluble in organic solvents, are interposed between colorants in the ink composition, and have the function of propagating light energy into the coating and improving ultraviolet curability;
It is also included because it has the function of improving the dispersion stability of colorants (particularly pigments) and improving the redispersibility of colorant precipitates even if they occur.

It is desirable that the resin particles be substantially transparent in order to have the above-mentioned functions, but translucent or colored resin particles can also be used as long as they have UV transmittance. Further, the particle diameter is suitably 3 μm or less, preferably 0.05 to 0.5 μm. In addition, if the particle size exceeds 3 μm, it is not preferable because it may cause nozzle clogging or the effect on the dispersibility of the colorant will be reduced. Further, the shape of the resin particles is preferably spherical or close to spherical. Typical resin particles include polystyrene resin, acrylic resin, polyester resin, silicone resin, polyolefin resin, polyurethane resin, vinyl chloride resin, epoxy resin, etc. These resin particles can be used to improve dispersibility as necessary. Therefore, those whose surface has been modified with a silane coupling agent etc. can also be used.

Further, in the present invention, inorganic particles preferably having a specific gravity of 2 or less, such as glass balloons or shirasu balloons, which have ultraviolet transmittance, can be used in combination with resin particles or alone.

It is appropriate that the resin particles be blended in an amount of about 1 to 20% by weight in the ink composition.

The organic solvent is used to appropriately adjust the viscosity of the ink, and includes ketones such as acetone, methyl ethyl ketone, and cyclohexanone, alcohols such as methanol, ethanol, and isopropanol, and ethers such as cellosolve and butyl cellosolve. is cited as a representative example.

The organic solvent is blended in an amount that satisfies the properties of the inkjet recording ink composition such as viscosity, which will be described later, but it is usually blended in an amount of 0 to 90% by weight in the ink composition. Appropriate.

Typical examples of the additives include conductivity regulators, surfactants, and antioxidants.

Although the ink composition of the present invention is composed of the components described above, it is naturally necessary to have properties suitable for inkjet printing, and therefore the viscosity of the ink composition is 1 to 20CP.
S (20℃), specific resistance is 200-3000Ω'Cm,
Surface tension is 20-60 dynes/cm, specific gravity is 0.8-2
．． The one adjusted to 0 should be used.

The ink composition of the present invention having such a composition and properties is mixed and stirred, and then filtered and purified using a filter having a pore size of 115 or less relative to the nozzle diameter of an inkjet printer, usually a pore size filter of 5 μm, for use in inkjet recording. It is provided as an ink composition.

Note that conventionally known printers can be used as the inkjet printer, and typical examples include a charge control method, an ink-on-demant method, and a method in which the ink composition is ejected using a thermal head.

As a light source used for irradiating ultraviolet rays, a low pressure mercury lamp, a high pressure mercury lamp, a metal halide lamp, a carbon arc lamp, a xenon lamp, a chemical lamp, etc. are used.

As printing materials, non-ink-adsorbing materials such as metal, plastic, glass, and ceramics can also be applied to ink-adsorbing materials such as heat, wood, paper, and concrete.

<Effects of the Invention> As described above, since the ultraviolet curable colored ink composition for inkjet recording of the present invention uses ultraviolet-transparent resin particles, it is possible to achieve effects that are considered impossible with conventional ultraviolet ray-curable colored ink compositions. The resulting ink composition has improved ultraviolet curability and improved dispersibility of the colorant, and therefore has good storage stability.

In addition, when an acylphosphine oxide compound is used as a photoreaction initiator, the ultraviolet curability is further improved,
Furthermore, an ink that does not easily thicken during storage can be obtained, and can be said to be an innovative ink composition.

<Examples> Hereinafter, the present invention will be explained in more detail with reference to Examples. In the examples, "parts" and "%" are expressed on a weight basis.

[Preparation of Acrylic Urethane Oligomer (I) 1 mol of coisophorone diisocyanate and 2 mol of 2-hydroxyethyl acrylate were subjected to an addition reaction in a conventional manner to prepare an acrylic urethane oligomer (I) having an average molecular weight of about 500.

[Preparation of acrylic urethane oligomer (n)] 1.6-
2.1 moles of hexanediol, 1 mole of ethylene glycol, and 2.4 moles of adipic acid were subjected to a condensation reaction to produce a polyester having a molecular weight of 1000. The polyester 1
mol, 2 mol of isophorone diisocyanate, and 2 mol of 2-hydroxyethyl acrylate in a conventional manner to prepare a polyester type acrylic urethane oligomer (II) having an average molecular weight of about 1,700.

[Preparation of acrylic epoxy oligomer (I [I)] Bisphenol A type jepoxy compound (trade name "Epicor" manufactured by Yuka Shell Epoxy Co., Ltd.) 828J Molecular weight approximately 380:]
An acrylic epoxy oligomer (III) having an acid value of 20 was prepared by addition reaction of 1 mole and 2 moles of acrylic acid using a conventional method.

Examples 1 to 8 and Comparative Examples 1 to 3 The formulations shown in Table 1 had an ink viscosity of 2.5.
After mixing methyl ethyl ketone to achieve CPS (20° C.), the mixture was filtered and purified using a 5.0 μm pore size filter to prepare an ultraviolet curable colored ink for inkjet recording.

The resulting ink was stored in a dark room at 20° C. for 1 month to perform a dispersibility test, and was stored at 20° C. in a dark room for 6 months with occasional stirring to perform a thickening test.

In addition, 6 pieces of polyethylene terephthalate plates are conveyed on a conveyor.
While moving at a speed of 0 m/sec, each ink was ejected using an inkjet printer to print in a dot shape, and then immediately irradiated with ultraviolet rays from a distance of 13 cm using a 120 W/cm high pressure mercury lamp to harden the film. The results are shown in Table 2.

As is clear from Table 2, the ink composition of the present invention had good dispersibility and good solvent resistance due to its good UV curability.

On the other hand, in Comparative Examples 1 to 3, which did not contain resin particles, the UV curability was poor, and in Comparative Examples 1 and 3, in which pigments were used as colorants, the precipitates did not redisperse and the dispersibility was poor. Ta.

hand Continued Supplementary Positive book

Claims (2)

[Claims] (1) An ultraviolet-curable colored ink composition for inkjet recording, which contains ultraviolet-transparent resin particles having a particle size of 3 μm or less in an ink composition containing a colorant. (2) The ink composition according to claim (1), which contains an acylphosphine oxide compound as a photoreaction initiator.