JPH03258867A - Ink composition - Google Patents

Abstract

PURPOSE:To obtain a colored ink composition of ultraviolet rays-curing type for ink-jet recording simultaneously satisfying both of ultraviolet rays-curing property and a long time preserving stability containing an acylphosphine oxide compound as a photoreaction initiator and dye. CONSTITUTION:The aimed composition contains an acylphosphine oxide compound expressed by the formula (R<1> is 1-6C alkyl, 6-12C cyclohexylsubstituted aryl, etc.; R<2> is R<1> ; R<3> is 2-18C alkyl, 3-10C alicyclic phenyl or naphthyl, etc.) as a photoreaction initiator (e.g. 2,2-dimethylpropyloyl diphenylphosphine oxide) and dye [preferably having >=0.8 absorbance ratio (absorbance to light having 500nm wavelength)/(absorbance to light having 360nm wavelength)].

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 colored dye and has excellent ultraviolet curability and storage stability.

<Conventional technology and its problems to be solved> The inkjet recording method is a non-impact recording method that generates almost no noise during recording, and it has become widely used in recent years because it is capable of high-speed recording. It's here.

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 colored dye as essential components, and further include an organic solvent and additives as necessary.

However, conventional UV-curable inks have poor UV-curability because they contain dyes, and also have poor storage stability as the ink thickens and precipitates during storage. There was a point.

In view of the current situation, the inventors of the present invention have made extensive studies and have found an ultraviolet curable colored ink composition for inkjet recording that has good ultraviolet curability and good storage stability.
This has led to the present invention.

<Means for Solving the Problems> That is, the present invention relates to an ultraviolet curable colored ink composition for inkjet recording containing an acylphosphine oxide compound as a photoreaction initiator and a dye.

The present invention utilizes many common photoinitiators such as benzophenone, acetophenone, jetoxyacetophenone,
Chloroacetophenone, 2,2-dimethoxy-2-phenylacetophenone, propiophenone, thioxanthone, 2-hydroxy 2-methyl-1-phenylpropan-1-one, benzine, pensinobeanthraquinone,
Representative examples include benzyl ketal, benzoin ethyl ether, benzoin isopropyl ether, dimethoxyphenylacetophenone, and 1-hydroxyethylhexylphenyl ketone; however, when used in colored inks containing dyes, However, unexpectedly, when an acylphosphine oxide compound was used as a photoreaction initiator, UV curability and/or storage stability were poor. The present invention was completed by discovering an ink with good curability and good storage stability.

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, and a dye as essential components, and further contains an organic solvent, additives, etc. as necessary.

As the vehicle component, a compound having an unsaturated double bond capable of radical polymerization in the molecule can be used. Specifically, ordinary ultraviolet curable ink: unsaturated polyester resin, unsaturated acrylic tlllK, unsaturated urethane resin, unsaturated epoxy resin, unsaturated polyamide resin, or these resins and ethylene. A typical example is a mixture with a reactive diluent having a sexually unsaturated group. In particular, the following vehicles with 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 several hundred to several hundred. It includes a wide range of tone-like words at room temperature.

For example, polyisocyanate and hydroxyl group-containing (meth)
Oligomer obtained by reaction with acrylic ester〇In addition, polyether-based acrylic urethane oligomer,
Also included are polyester-based acrylic urethane oligomers, polybutadiene-based acrylic urethane oligomers, and the like.

Specifically, toluene diisonanate, hexamethylene diisocyanate, isophorone diisonanate, diphenylmethane diisonanate, xylene diisocyanate, their isomers or excess polyisocyanate, polyester polyol, polyoxymethylene glycol, polyoxine ethylene glycol A polyisocyanate (preferably a non-yellowing type polyisocyanate) such as a compound having an isocyanate end, which is a reaction product of a polyol, polyoxypropylene glyconepecabrolactone polyol, trimethylolpropane, or pentaerythritol with a polyhydric alcohol, and a hydroxyl group. and reaction products with compounds having unsaturated groups. 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. As reactive diluents, 2-ethylhexyl (meth)acrylate, 2-hydroquinethyl (
meth)acrylate, inbornyl(meth)acrylate, tripropylene glycol diacrylate, 1.6
-Hexanediol diacrylate, tetraethylene glycol diacrylate, trimethylolpronochloride tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane pentaacrylate, dipentaerythritol hexaacrylate, vinyl acetate, N-vinylpyrrolidone , dimethyl (meth)acrylamide, vinyltoluene, divinylbenzene, etc. are listed as typical examples, and it is preferable to mix 10 to 300 parts by weight of these reaction diluents with respect to 100 parts by weight of the acrylic urethane oligomer. Further, it is appropriate that these vehicles be blended in an amount of 2 to 90% by weight in the ink composition.

As a photoreaction initiator, an acylphosphine oxide compound is used. This acylphosphine oxide compound is a compound represented by the following general formula (I).

[In the formula, R1 is a linear or branched alkyl group having 1 to 6 carbon atoms, cyclohexyl having a total of 6 to 12 carbon atoms,
cyclopentyl-71J -halogen-, alkyl-1 or alkoxy-substituted aryl group, or S- or N
- represents a 5- or 6-membered multi-S cyclic group (containing other carbon atoms): R2 has the same meaning as R1, and R' and R2 may be the same or different, or carbon number 1
represents an alkoxy group having ~6 carbon atoms, an aryloxy group or an arylalkoxy group having a total carbon number of 6 to 12, or R1 and R2 together with the phosphorus atom represent an alkoxy group having a total carbon number of 6 to 12;
and R3 has 2 carbon atoms.
Linear or branched alkyl group having ~18 carbon atoms, 3 to 1 carbon atoms
represents an alicyclic group, a phenyl group or a naphthyl group having 0, or an S-1○-1 or X-containing 5- or 6-membered heterocyclic group (containing other carbon atoms); has the above substituent or group: (wherein R1 and R2 are as defined above), and X is a phenylene group or has 2 carbon atoms.
represents an aliphatic or alicyclic divalent group having ~6, Rl
, one or more of R3 may be olefinically unsaturated. ] Specifically, 2,2-dimethylpropioyldiphenylphosphine oxide, 2,2-dimethylpentanoyldiphenylphosphine oxide, 2,2-dimethyloctanoyldiphenylphosphine oxide, methyl 2,2-dimethyloctanoylphenyl Phosphinate, 2-methyl-2-ethylhexanoyldiphenylphosphine oxide, 2,6-dimethylbenzoyldiphenylphosphine oxide, 2,6-simethoxybenzoyldiphenylphosphine oxide, 2.
6-cyclobenzoyldiphenylphosphine oxide, 2,4.6-trimethylbenzoyldiphenylphosphine oxide, methyl 2,4.6-trimethylbenzoylphenylphosphine), 2,3.6-)
lyntylbenzoyldiphenylphosphine oxide, 2゜4.6-)rimethoxybenzoyldiphenylphosphine oxide, 2,4.6-trichlorobenzoyldiphenylphosphine oxide, 2゜4.6-)
Limethylbenzoylnaphthylphosphonate and the like are representative examples.

The acylphosphine oxide compound is suitably blended in an amount of 0.1 to 15 parts by weight, preferably 0.2 to IO parts by weight, per 100 parts by weight of the vehicle. Furthermore, the acylphosphine oxide compound can also be used in combination with the photoreaction initiator that has been commonly used in the past.

As the dye, ordinary dyes conventionally used in inkjet recording inks can be used without particular restrictions, as long as they are stably dissolved in the ink. Specifically, for example, 5olvent Black 22.27.2
8.29 etc. black dye 1.5olvent Red83
red dye such as 125.132, 301VentB
blue dye such as lue 48.67, 5olvent Y
Yellow dye such as yellow88.89? ; These are representative examples.

In particular, in the present invention, dyes with an absorbance ratio [(absorbance for light with a wavelength of 500 nm)/(absorbance for light with a wavelength of 360 nm)] of 0.8 or more are preferably used because the ink has particularly excellent curing properties. .

The appropriate amount of dye to be blended in the ink composition is 0.5 to 20% by weight.

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 impropatol, and ethers such as cellosolve and butyl cellosol. 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 appropriate to blend it in an amount of 10 to 70% by weight in the ink composition. It is.

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

Although the ink composition of the present invention is composed of the above-mentioned ingredients, it is naturally necessary to have properties suitable for inkjet printing, and therefore the viscosity of the ink composition is 1 to 10CP.
S (20℃), specific resistance is 200-3000Ω・Cm,
Surface tension is 20-60 dynes/am, specific gravity is 0.8-1
．． You should use one adjusted to 2.

The ink composition of the present invention having such a composition and properties is mixed and stirred, and then passed through a pore size LOμ membrane filter.
By filtration and purification, it is provided as an ink composition for inkjet recording.

As an inkjet printer, any conventional printer can be used, such as a charge control method, an ink-on-demant method, or a method in which ink is ejected using a thermal head. ; Listed as a thing.

5) As a light source used for irradiating ultraviolet rays, a low-pressure mercury lamp, a high-pressure mercury lamp, a metallolide 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 the above-mentioned specific photoreaction initiator, it is possible to overcome the effects that conventional ultraviolet curable colored ink compositions cannot. It can be said to be a revolutionary ink composition, as it simultaneously satisfies both ultraviolet curability and storage stability over several months.

<Example> Hereinafter, the present invention will be explained in more detail from Example 2. In the examples, "part" and -% are expressed on a weight basis.

[Preparation of Acrylic Urethane Oligomer CI) Acrylic urethane oligomer (I) having an average molecular weight line of 500 was prepared by addition reaction of 1 mole of bimodal inphorone diisonate and 2 moles of 2-hydroxyethyl acrylate by a conventional method. .

[Preparation of acrylic urethane oligomer (II)] 1.6
- 2.1 mol of hexanediol, 1 mol of ethylene glycol
mol and 2.4 mol of adipic acid were subjected to a condensation reaction to produce a polyester having a molecular weight of 1000. 1 mole of the polyester, 2 moles of inphorone diisocyanate, and 2 moles of 2-hydroxyethyl acrylate were subjected to an addition reaction in a conventional manner to prepare a polyester type acrylic urethane oligomer (II) having an average molecular weight of 1700.

Preparation of this acrylic epoxy oligomer (III): Bisphenol A type jepoxy compound (manufactured by Yuka NEL Epoxy Co., Ltd., trade name "Epicote 828", molecular weight approximately 380 21
mol and 2 moles of acrylic acid are subjected to an addition reaction using a conventional method,
An acrylic epoxy oligomer (III) having an acid value of 20 was prepared.

Examples 1 to 5 and Comparative Examples 1 to 4 The ink viscosity obtained with the formulations shown in Table 1 is 3CPS.
(20℃)? After mixing methyl ethyl ketone as shown in FIG.

The obtained ink was stored at 20° C. in a dark room for 6 months, and the storage stability of the ink was tested.

Furthermore, while moving the aluminum plate at a speed of 7 cm/sec on a conveyor, each of the above inks was ejected using an inkjet printer to print dots, and then immediately from a distance of 12c+n using a 120w/cm high pressure mercury lamp. The coating was cured by irradiation with ultraviolet rays, and tested for solvent resistance. The results are shown in Table 2.

As is clear from Table 2, the ink of the present invention had good storage stability with a small increase in viscosity, and also had good UV curability and good solvent resistance.

On the other hand, in Comparative Examples 1 to 4, in which a conventional general photoreaction initiator was used without using an anlphosphine oxide compound as a photoreaction initiator, those with good storage stability had poor UV curability. Those with good external radiation curability had poor storage stability, and either storage stability or ultraviolet ray curability was poor, and there was no material that satisfied both.

The following parts of the specification are corrected as follows.

*MW′″E IF2.5.10 Heisei Year Month Day 1.Display of the incident 1990 Patent Application No. 56245 2. Name of the invention stomach hmm composition 3. Person who makes corrections Relationship with the incident Out wish Man given name name (332) Dainippon Paint Co., Ltd. 4, generation Reason Man 5. Date of amendment order Self Departure 6. Subject of correction Detailed description of the invention in the specification

Claims (2)

[Claims] (1) An ultraviolet curable colored ink composition for inkjet recording containing an acylphosphine oxide compound as a photoreaction initiator and a dye. (2) The ink composition according to claim (1), wherein the dye has an absorbance ratio [(absorbance to light with a wavelength of 500 nm)/(absorbance to light with a wavelength of 360 nm)] of 0.8 or more.