JP2010209198A - Photocurable ink composition, inkjet recording method, record matter, ink set, ink cartridge and recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocurable ink composition which exhibits excellent photocurability even at a low PII (low skin irritativeness) and a low viscosity with low illuminance ultraviolet irradiation. <P>SOLUTION: The photocurable ink composition includes at least a polymerizable compound and a photopolymerization initiator and the polymerizable compound includes a resinous polymer and tripropylene glycol diacrylate and/or dipropylene glycol diacrylate, and the photopolymerization initiator includes 2,4-diethylthioxanthone and/or isopropylthioxanthone. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink composition that is cured by light such as ultraviolet rays, and more specifically, a photocurable ink that exhibits excellent photocurability even when irradiated with ultraviolet rays with low PII (low skin irritation), low viscosity, and low illuminance. It relates to a composition. The present invention also relates to an ink jet recording method using the photocurable ink composition and a recorded matter thereof. The present invention further relates to an ink set, an ink cartridge, and a recording apparatus provided with the photocurable ink composition.

The ink jet recording method is a printing method in which printing is performed by causing a droplet of an ink composition to fly and adhere to a recording medium such as paper. This ink jet recording method is characterized in that a high-resolution and high-quality image can be printed at high speed. The ink composition used in the ink jet recording method generally contains an aqueous solvent as a main component and contains a coloring component and a wetting agent such as glycerin for the purpose of preventing clogging.
On the other hand, paper or fabrics that are difficult to penetrate water-based ink compositions, or materials such as metals, plastics, and the like that do not penetrate, such as phenol, melamine, vinyl chloride, acrylic, polycarbonate, PET, PP, and PE When printing on a recording medium such as a film, the ink composition is required to contain a component capable of stably fixing the coloring material to the recording medium.

  In response to such a requirement, a photocurable inkjet ink containing a coloring material, a photocuring agent, a polymerization initiator and the like has been disclosed (for example, see Patent Document 1). According to this ink, it is said that the ink can be prevented from bleeding into the recording medium and the image quality can be improved.

In recent years, this photocurable ink composition has been developed from many viewpoints such as film quality, curability and ejection stability.
Patent Document 2 can form a cured image excellent in film quality and film strength (curability, chemical resistance, mechanical strength, adhesion) by adding a hyperbranched polymer to the ink composition. It is disclosed.
However, when other additives such as a photopolymerization initiator are added to the hyperbranched polymer, the increase in viscosity is large. Therefore, there is a demand for a formulation that increases the curability while maintaining a low viscosity.

On the other hand, with respect to monomers used in conventional UV curable ink compositions, generally, those having high curability tend to have high primary skin irritation (PII, Primary Irritation Index), and those having low PII also have curability. It is known that there is a characteristic that it tends to be low. Conventional UV curable ink compositions often use a material having a high PII as a raw material in order to increase the curability, and accordingly, handling is necessary in use.
In general, the curability of ultraviolet curing tends to be higher as the molecular weight of the monomer used is lower. That is, the lower the molecular weight of the monomer used, the higher the curability but the higher the PII. On the other hand, the higher the molecular weight of the monomer used, the lower the PII but the lower the curability and the higher the viscosity. When the viscosity of the ink composition is high, the handleability at the time of use, such as being ejected by an ink jet method, is lowered.

  Furthermore, as one of the factors for realizing miniaturization and price reduction of a printer, an ink composition that exhibits excellent curability even with a low illuminance light source is desired.

US Pat. No. 5,562,001 JP 2004-99796 A

  An object of the present invention is to provide a photocurable ink composition that exhibits excellent photocurability even when irradiated with ultraviolet rays of low PII (low skin irritation), low viscosity, and low illuminance.

  As a result of intensive studies, the inventors of the present invention have developed a specific polymerizable compound and a specific photopolymerization initiator in a photocurable ink composition that uses a dendritic polymer capable of forming a cured image having excellent film quality and film strength. It was found that the above-mentioned problems of the prior art can be solved by using the resin, and low PII (low skin irritation), low viscosity, and excellent photocurability can be achieved at a high level, and the present invention has been achieved. It was. That is, the present invention is as follows.

(1) A photocurable ink composition comprising at least a polymerizable compound and a photopolymerization initiator,
The polymerizable compound includes a resinous polymer and tripropylene glycol diacrylate and / or dipropylene glycol diacrylate,
A photocurable ink composition comprising 2,4-diethylthioxanthone and / or isopropylthioxanthone as a photopolymerization initiator.
(2) An inkjet recording method for forming an image using the photocurable ink composition described in (1) above.
(3) The inkjet recording method according to (2), wherein the photocurable ink composition is cured using an LED having an emission spectrum peak at a wavelength of 360 nm to 410 nm.
(4) A recorded matter in which an image is formed on a recording medium by the inkjet recording method described in (2) or (3) above.
(5) An ink set comprising a plurality of photocurable ink compositions, the ink set comprising at least the photocurable ink composition described in (1) above.
(6) An ink cartridge comprising the ink set described in (5) above.
(7) A recording apparatus including the ink cartridge according to (6).

  Since the photocurable ink composition according to the present invention has low PII (low skin irritation), it is excellent in handleability. Moreover, since it has a low viscosity, it is excellent in storage stability and can be preferably applied to a recording apparatus equipped with an inkjet system. Furthermore, since it exhibits excellent photocurability even when irradiated with low-intensity ultraviolet rays, a large-scale and expensive curing light source is not required, that is, a compact and low-cost recording apparatus can be realized.

  According to the ink jet recording method of the present invention, since the photocurable ink composition exhibiting excellent photocurability even when irradiated with ultraviolet rays having low PII (low skin irritation), low viscosity, and low illuminance is used, It is excellent in handleability and ejection stability, and can form a highly curable image even at low illuminance. In particular, since the photocurable ink composition of the present invention contains 2,4-diethylthioxanthone and / or isopropylthioxanthone as a photopolymerization initiator, the ink can be cured with an LED having an emission peak at a wavelength of 360 to 410 nm. . Therefore, the cost of the LED can be kept low. Moreover, the recorded matter obtained by such a method is excellent in curability.

  According to the ink set and the ink cartridge of the present invention, since the photocurable ink composition exhibiting excellent photocurability even when irradiated with ultraviolet rays having low PII (low skin irritation), low viscosity, and low illuminance, It is excellent in ink handling and ejection stability, and can form images with high curability even at low illuminance.

  According to the recording apparatus of the present invention, since the photocurable ink composition exhibiting excellent photocurability even when irradiated with ultraviolet rays with low PII (low skin irritation), low viscosity, and low illuminance is used, Images with excellent stability and ejection stability, and can form images with high curability even at low illuminance. In addition, as described above, the photocurable ink composition mounted on the recording apparatus exhibits excellent photocurability even when irradiated with low-illuminance ultraviolet rays, and thus does not require a large and expensive curing light source. Lower prices are possible.

Hereinafter, the photocurable ink composition of the present invention will be described in detail.
The photocurable ink composition of the present invention is a photocurable ink composition containing at least a polymerizable compound and a photopolymerization initiator, and includes, as the polymerizable compound, a resinous polymer, tripropylene glycol diacrylate and / or Dipropylene glycol diacrylate, and 2,4-diethylthioxanthone and / or isopropylthioxanthone as a photopolymerization initiator.

The photocurable ink composition of the present invention contains a dendritic polymer as a polymerizable compound. Dendritic polymers can be broadly classified into six structures as shown below ("dendritic macromolecules-a world of high functionality with multi-branched structures") supervised by Keigo Aoi / Masaaki Enomoto, NT Corporation・ See S).
I Dendrimer
II Linear dendritic polymer
III Dendrigraft polymer
IV Hyperbranched polymer
V star hyperbranched polymer
VI Hyper Graft Polymer

  Among these, I to III have a degree of branching (DB) of 1 and have a defect-free structure, whereas IV to VI have a random branch structure that may contain defects. is doing. In particular, dendrimers can be arranged with high density and concentration of reactive functional groups on the outermost surface compared to generally used linear polymers. Expectation is high. In addition, even if the hyperbranched polymer, dendrigraft polymer or hypergraft polymer is not as large as the dendrimer, it is possible to introduce many reactive functional groups on the outermost surface, and it is excellent in curability.

  Unlike conventional linear polymers and branched polymers, these dendritic polymers repeat highly branched structures in three dimensions and are highly branched. Therefore, it is possible to keep the viscosity low compared to a linear polymer having the same molecular weight.

  Examples of the method for synthesizing the dendrimer used in the present invention include a Divergent method for synthesizing from the center to the outside and a Convergent method for synthesizing from the outside to the center.

  The dendrimer, hyperbranched polymer, dendrigraft polymer and hypergraft polymer used in the present invention are preferably solid at room temperature and have a number average molecular weight in the range of 1,000 to 100,000, particularly in the range of 2000 to 50,000. Are preferably used. When it is not solid at room temperature, the maintainability of the formed image is deteriorated. In addition, when the molecular weight is lower than the above range, the fixed image becomes fragile, and when the molecular weight is higher than the above range, the viscosity of the ink becomes too high even if the addition amount is lowered, in terms of flight characteristics. It is no longer practical.

  The dendrimers, hyperbranched polymers, dendrigraft polymers and hypergraft polymers used in the present invention are dendrimers, hyperbranched polymers, dendrigraft polymers and hypergraft polymers having a radically polymerizable functional group on the outermost surface. Preferably there is. By adopting a structure capable of radical polymerization on the outermost surface, the polymerization reaction proceeds rapidly.

  Examples of the polymer having a dendrimer structure include amidoamine dendrimers (US Pat. Nos. 4,507,466, 4,558,120, 4,568,737, 4,587,329, and 4). 631,337, 4,694,064), phenyl ether dendrimers (US Pat. No. 5,041,516, Journal of American Chemistry 112 (1990, pages 7638-7647)) Etc. As for the amidoamine dendrimer, a dendrimer having a terminal amino group and a carboxylic acid methyl ester group is commercially available as “Starburst ™ (PAMAM)” from Aldrich. In addition, the terminal amino group of the amidoamine-based dendrimer can be reacted with various acrylic acid derivatives and methacrylic acid derivatives to synthesize amidoamine-based dendrimers having corresponding terminals, and then used.

  Examples of acrylic acid derivatives and methacrylic acid derivatives that can be used include acrylic acid such as methyl, ethyl, n-butyl, t-butyl, cyclohexyl, palmityl, and stearyl, or alkyl esters of methacrylic acid, acrylic acid such as acrylic acid amide, and isopropylamide. Alternatively, methacrylic acid alkylamides may be mentioned, but not limited thereto.

Various examples of the phenyl ether dendrimer are described in, for example, the above Journal of American Chemistry Vol. 112 (1990, pages 7638-7647). For example, 3,5-dihydroxybenzyl alcohol is used, A second-generation benzyl alcohol was synthesized by reacting with 5-diphenoxybenzyl bromide, the OH group was converted to Br using CBr ₄ and triphenylphosphine, and then reacted with 3,5-dihydroxybenzyl alcohol in the same manner. The next generation benzyl alcohol is synthesized, and the following reaction is repeated to synthesize the desired dendrimer. As for the phenyl ether dendrimer, the terminal can be substituted with one having various chemical structures instead of the terminal benzyl ether bond. For example, when synthesizing the dendrimer described in Journal of American Chemistry Vol. 112, various alkyl halides are used in place of the benzyl bromide, a phenyl ether dendrimer having a terminal structure having a corresponding alkyl group can be obtained. In addition, polyamine dendrimers (Macromol. Symp. 77, 21 (1994)) and derivatives obtained by modifying terminal groups thereof can be used.

  As the hyperbranched polymer, for example, hyperbranched polyethylene glycol can be used. A hyperbranched polymer uses a monomer that has two or more kinds of reaction points corresponding to a branched portion and one kind of another reaction point corresponding to a connecting portion in one molecule, and the target polymer in one step. It is obtained by synthesis (Macromolecules, 29 (1996), 3831-3838). For example, a 3,5-dihydroxybenzoic acid derivative is an example of a monomer for a hyperbranched polymer. An example of the production of hyperbranched polymer is 3,5-bis obtained from 1-bromo-8- (t-butyldiphenylsiloxy) -3,6-dioxaoctane and methyl 3,5-dihydroxybenzoate. 3,5-bis ((8'-hydroxy-3 ', 6) which is a hydrolyzate of methyl ((8'-(t-butyldiphenylsiloxy) -3 ', 6'-dioxaoctyl) oxy) benzoate The hyperbranched polymer poly [bis (triethyleneglycol) benzoate] can be synthesized by heating methyl '' -dioxaoctyl) oxy) benzoate with dibutyltin diacetate in a nitrogen atmosphere.

  When 3,5-dihydroxybenzoic acid is used, the hyperbranched polymer terminal group becomes a hydroxyl group, and therefore, hyperbranched polymers having various terminal groups are synthesized by using an appropriate alkyl halide for the hydroxyl group. be able to.

  The properties of monodisperse polymers or hyperbranched polymers with a dendrimer structure are governed by the chemical structure of the main chain and the chemical structure of the terminal group, but the characteristics are particularly dependent on the difference of the substituents in the terminal group and chemical structure. Are very different. Those having a polymerizable group at the terminal are particularly useful because of their reactivity, the gelation effect after photoreaction is great. A dendrimer having a polymerizable group can be obtained by chemically modifying a compound having a polymerizable group at the end of one having a basic atomic group such as an amino group, a substituted amino group, or a hydroxyl group at the end.

  For example, it is synthesized by adding, for example, an isocyanate group-containing vinyl compound to a polyfunctional compound obtained by Michael addition of an active hydrogen-containing (meth) acrylate compound to an amino dendrimer. Moreover, the dendrimer which has a polymerizable group at the terminal is obtained by making (meth) acrylic acid chloride etc. react with an amino dendrimer, for example. Examples of the vinyl compound providing such a polymerizable group include compounds having an ethylenically unsaturated bond capable of radical polymerization. Examples thereof include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, and isocrotonic acid. And compounds having ethylenically unsaturated bonds capable of various radical polymerization described later, such as unsaturated carboxylic acids such as maleic acid and salts thereof.

  In the present invention, the above dendrimer, hyperbranched polymer, dendrigraft polymer and hypergraft polymer may be used alone or in combination with other types of dendrimers and hyperbranched polymers.

In the photocurable ink composition of the present invention, the amount of the dendritic polymer added is preferably 5% by mass or more, more preferably 10 to 30% by mass, and still more preferably 10 to 20% by mass. If it is the said range, the suitability as a photocurable ink can be preferably maintained.
When the addition amount of the dendritic polymer is 5% by mass or more, good curability can be secured, and when the addition amount of the dendritic polymer is 30% by mass or less, the viscosity, dispersion stability, and storage stability of the ink composition There is no problem of sex.

The photocurable ink composition of the present invention contains tripropylene glycol diacrylate and / or dipropylene glycol diacrylate as the polymerizable compound.
Tripropylene glycol diacrylate and dipropylene glycol diacrylate are materials with low PII, with values of 1.6 and 2.8, respectively.
In the photocurable ink composition of the present invention, the total content of tripropylene glycol diacrylate and / or dipropylene glycol diacrylate is 20 to 80% by mass, preferably 50 to 80% by mass, based on the total amount of the ink composition. More preferably, it is contained in an amount of 50 to 75% by mass, and most preferably 60 to 75% by mass.
When the total content of tripropylene glycol diacrylate and / or dipropylene glycol diacrylate is less than 20% by mass, problems such as viscosity, dispersion stability, and storage stability of the ink composition occur, and when the total content exceeds 80% by mass. Curability as a photocurable ink composition may be insufficient.

Further, the photocurable ink composition of the present invention contains 2,4-diethylthioxanthone and / or isopropylthioxanthone as a photopolymerization initiator.
These are available under the trade names of Kayacure DETX-S (Nippon Kayaku Co., Ltd.) and DarocurITX (Ciba Specialty Chemicals Co., Ltd.), respectively.
In the photocurable ink composition of the present invention, the photopolymerization initiator is preferably contained in an amount of 0.5 to 5.0% by mass, and more preferably 1.0 to 3.0% by mass. When the content of the photopolymerization initiator is less than 0.5% by mass, the effect for improving the curability is low, and when it exceeds 5% by mass, there is a problem in film quality such as abrasion resistance and coloring by the color of the initiator itself.

The photocurable ink composition of the present invention may contain a photopolymerization initiator other than the above.
The photopolymerization initiator is preferably a radical photopolymerization initiator and is not particularly limited. For example, benzyl dimethyl ketal, α-hydroxyalkylphenone, α-aminoalkylphenone, acylphosphine oxide, oxime ester, α-dicarbonyl, Anthraquinone etc. are mentioned.

  Also, Vice 10, 30 (manufactured by Stauffer Chemical), Irgacure 127, 184, 500, 651, 2959, 907, 369, 379, 754, 1700, 1800, 1850, 1870, 819, OXE01, Darocur 1173, TPO (Ciba -Photopolymerization initiators available under the trade names of Specialty Chemicals and ESACURE KIP150 (Lamberti) can also be used.

  In the photocurable ink composition of the present invention, the total addition amount of the photopolymerization initiator is, for example, 1 to 20% by mass, preferably 3 to 15% by mass.

The photocurable ink composition of the present invention may contain a polymerization accelerator.
Although it does not specifically limit as a polymerization accelerator, Darocur EHA, EDB (made by Ciba Specialty Chemicals) etc. are mentioned.
The actinic ray curable ink composition of the present invention preferably contains a thermal radical polymerization inhibitor. Thereby, the storage stability of the ink composition is improved. Examples of the thermal radical polymerization inhibitor include Irgastab UV-10, UV-22 (manufactured by Ciba Specialty Chemicals) and the like.

  Furthermore, the actinic ray curable ink composition of the present invention can use a surfactant. For example, it is preferable to use a polyester-modified silicone or a polyether-modified silicone as a silicone-based surfactant. It is particularly preferable to use siloxane or polyester-modified polydimethylsiloxane. Specific examples include BYK-347, BYK-348, BYK-UV3500, 3510, 3530, and 3570 (manufactured by Big Chemie Japan Co., Ltd.).

Moreover, the photocurable ink composition of the present invention may contain a color material.
The coloring material used in this case may be either a dye or a pigment, but the pigment is more advantageous from the viewpoint of the durability of the printed matter.
As dyes used in the present invention, direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes, vat dyes, soluble vat dyes, reactive disperse dyes, etc. are usually used for inkjet recording. Various dyes can be used.

As the pigment used in the present invention, inorganic pigments and organic pigments can be used without any particular limitation.
As the inorganic pigment, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. Organic pigments include azo pigments (including azo lakes _, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines). Pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye chelates, acidic dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, and the like.

  Specific examples of the pigment include carbon black, No. manufactured by Mitsubishi Chemical Corporation. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, no. 2200B, etc. are Raven 5750, 5250, 5000, 3500, 1255, 700, etc. made by Columbia, and Regal 400R, 330R, 660R, Mogu L, 700, Monarch 800, 880, made by Cabot, 900, 1000, 1100, 1300, 1400, etc. are Color Black FW1, FW2, FW2V, FW18, FW200, ColorBlack S150, S160, S170, Printex 35, U, the same V, the same 140 U, the Special Black 6, the same 5, the same 4 A, the same 4, and the like.

Examples of pigments used in yellow ink include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 180, 185, 213 and the like.
Examples of pigments used for magenta ink include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, 209, C.I. I. Pigment violet 19 and the like.

Further, examples of pigments used for cyan ink include C.I. I. And CI Pigment Blue 1, 2, 3, 15: 3, 15: 4, 60, 16, and 22.
According to a preferred embodiment of the present invention, the pigment preferably has an average particle size in the range of 10 to 200 nm, more preferably about 50 to 150 nm.
The addition amount of the color material in the photocurable ink composition is preferably in the range of about 0.1 to 25% by mass, and more preferably in the range of about 0.5 to 15% by mass.

  The photocurable ink composition of the present invention can also be applied to inks such as varnish that do not contain a color material.

  According to a preferred embodiment of the present invention, these pigments can be made into a photocurable ink composition as a pigment dispersion obtained by dispersing in a medium with a dispersant or a surfactant. As a preferable dispersant, a dispersant conventionally used for preparing a pigment dispersion, for example, a polymer dispersant can be used.

  Moreover, when the photocurable ink composition contains a color material, the ink composition containing the color material may have a plurality for each color. For example, in addition to the basic four colors of yellow, magenta, cyan, and black, when adding the same series of dark and light colors for each color, in addition to light magenta, dark red, and cyan, in addition to magenta In addition to light light cyan, dark blue, and black, light gray, light black, and dark matte black can be used.

  In addition to this, surfactants, leveling additives, matting agents, polyester resins, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes are added to adjust film properties as necessary. I can do it.

  Further, the photocurable ink composition of the present invention may be a one-component type or a two-component type.

The photocurable ink composition of the present invention undergoes a curing reaction by light irradiation.
The irradiation light source is not particularly limited, but the irradiation light source preferably has a wavelength of 350 nm or more and 450 nm or less, and preferably has an emission peak at 360 to 410 nm.
The actinic ray species for curing the photocurable ink composition of the present invention is not particularly limited, but is preferably ultraviolet rays. The dose of ultraviolet rays, 10 mJ / cm ² or more and 10,000 / cm ² or less, and preferably 50 mJ / cm ² or more, 6,000 mJ / cm ² or less, more preferably 500 mJ / cm ² or more, 4000 mJ / Cm ² or less. If it is the ultraviolet irradiation amount (illuminance) within such a range, the curing reaction can be sufficiently performed.

Examples of the ultraviolet irradiation include lamps such as metal halide lamps, xenon lamps, carbon arc lamps, chemical lamps, low pressure mercury lamps, and high pressure mercury lamps. For example, a commercially available product such as an H lamp, D lamp, or V lamp manufactured by Fusion System can be used.
Further, ultraviolet irradiation can be performed by an ultraviolet light emitting semiconductor element such as an ultraviolet light emitting diode (ultraviolet LED) or an ultraviolet light emitting semiconductor laser.

The present invention can also provide an ink jet recording method in which an image is formed on a recording medium using the above-described photocurable ink composition.
As the ink jet recording method, any of the conventionally known methods can be used, and in particular, a method of ejecting droplets using vibration of a piezoelectric element (using an ink jet head that forms ink droplets by mechanical deformation of an electrostrictive element). Recording method) and a method using thermal energy, it is possible to perform excellent image recording.
According to the ink jet recording method of the present invention, since the photocurable ink composition exhibiting excellent photocurability even when irradiated with ultraviolet rays having low PII (low skin irritation), low viscosity, and low illuminance is used, It is excellent in handleability and ejection stability, and can form a highly curable image even at low illuminance. In particular, since the photocurable ink composition of the present invention contains 2,4-diethylthioxanthone and / or isopropylthioxanthone as a photopolymerization initiator, the ink can be cured with an LED having an emission peak at a wavelength of 360 to 410 nm. . Therefore, the cost of the LED can be kept low. Further, according to the present invention, it is possible to provide a recorded matter on which an image having excellent curability is recorded by the inkjet recording method.

  The present invention also provides an ink set comprising a plurality of photocurable ink compositions, comprising at least one photocurable ink composition of the present invention described above. Can do. According to the ink set of the present invention, since the photocurable ink composition exhibiting excellent photocurability even when irradiated with ultraviolet rays with low PII (low skin irritation), low viscosity, and low illuminance is used, Images with excellent stability and ejection stability, and can form images with high curability even at low illuminance.

  The present invention can also provide an ink cartridge comprising the above-described photocurable ink composition of the present invention. According to the ink cartridge of the present invention, since the photocurable ink composition exhibiting excellent photocurability even with low PII (low skin irritation), low viscosity, and low-illuminance ultraviolet irradiation is used, Images with excellent stability and ejection stability, and can form images with high curability even at low illuminance.

  The present invention can also provide a recording apparatus comprising the above-described ink cartridge of the present invention. According to the recording apparatus of the present invention, since the photocurable ink composition exhibiting excellent photocurability even when irradiated with ultraviolet rays with low PII (low skin irritation), low viscosity, and low illuminance is used, Images with excellent stability and ejection stability, and can form images with high curability even at low illuminance. Further, since it exhibits excellent photocurability even when irradiated with low-intensity ultraviolet rays, a large-scale and expensive curing light source is not required, that is, downsizing and cost reduction are possible.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

[Examples 1-8, Comparative Examples 1-6]
(Preparation of pigment dispersion)
In Examples and Comparative Examples, pigment dispersions were prepared by the method shown below.
As a coloring material, C.I. I. Pigment Black 7 (carbon black) 15% by mass, Discol N-509 (manufactured by Dainichi Seika Kogyo Co., Ltd.) 3.5% by mass as a dispersant, and monomers described in each Example and Comparative Example (for example, implementation) In Example 1, APG200 (manufactured by Shin-Nakamura Chemical Co., Ltd.) was added to make the whole 100% by mass, and the mixture was mixed and stirred to obtain a zirconia bead using a sand mill (Yaskawa Seisakusho). (A diameter of 1.5 mm) and a dispersion treatment were performed for 6 hours.
Thereafter, zirconia beads were separated by a separator to obtain a black pigment dispersion.

  In the same manner, pigment dispersions corresponding to the respective colors, that is, cyan pigment dispersion (CI Pigment Blue 15: 3), magenta pigment dispersion (CI Pigment Violet-19), yellow pigment dispersion (CI Pigment Yellow 155) was prepared.

(Preparation of ink composition)
In Examples and Comparative Examples, a polymerizable compound, a photopolymerization initiator, and a dispersant are mixed and completely dissolved to prepare an ink composition, and the pigment dispersion is gradually stirred into the ink solvent of the ink composition while stirring. It was dripped. After completion of the dropping, the mixture was stirred at room temperature for 1 hour to obtain an ink composition. Then, each ink composition was filtered with a 5-micrometer membrane filter, and it was set as the photocurable ink composition (Examples 1-8, Comparative Examples 1-6) shown in Table 1.
In addition, the numerical value in a table | surface shows "mass%."

The compounds used in Table 1 are as follows.
Tripropylene glycol diacrylate: APG200 (manufactured by Shin-Nakamura Chemical Co., Ltd.)
Dipropylene glycol diacrylate: APG100 (manufactured by Shin-Nakamura Chemical Co., Ltd.)
-2-hydroxyethyl acrylate: HEA (manufactured by Osaka Organic Chemical Industry Co., Ltd.)
Tetraethylene glycol diacrylate: V # 335HP (Osaka Organic Chemical Industry Co., Ltd.)
Biscoat # 1000: Dendritic polymer (hyperbranched polymer), manufactured by Osaka Organic Chemical Industry Co., Ltd. Irgacure 819: Photopolymerization initiator (acylphosphine oxide type), Ciba Specialty Chemicals Co., Ltd., Darocur TPO: Photopolymerization initiator (acylphosphine oxide), Ciba Specialty Chemicals Co., Ltd., Kayacure DETX-S: Photopolymerization initiator (2,4-diethylthioxanthone), Nippon Kayaku Co., Ltd., Darocur ITX: Photopolymerization initiator (isopropylthioxanthone), manufactured by Ciba Specialty Chemicals Co., Ltd.

(Film curability evaluation)
Using an inkjet printer PX-G920 (manufactured by Seiko Epson Corporation), the ink described in the examples and the ink described in the comparative example were filled in the RED nozzle row. Under normal pressure, a solid pattern of RED (printed with 720 × 720 dots per square inch by 1 ng) was printed on a PET film. (The actual print color is the ink color filled in the RED nozzle row). Thereafter, ultraviolet rays having a wavelength of 395 nm were irradiated using an ultraviolet irradiation device. Irradiation intensity was adjusted to 125 mW / cm ² and irradiated, and the point in time when the finger touch on the sample surface disappeared was judged to be cured. The curability was evaluated according to the following index at each irradiation intensity. The results are shown in Table 1.
A: required irradiation energy 625mJ / cm ² or less B: required irradiation energy 625mJ / cm ² greater, 950 mJ / cm ² or less C: required irradiation energy 950 mJ / cm ² than

(Ink viscosity)
The measurement was performed using an E-type viscometer (manufactured by Tokyo Keiki Co., Ltd .: EMD type conical plate type rotary type) (measurement temperature: 20 ° C.). The results are shown in Table 1. The viscosity was evaluated according to the following index.
A: Less than 40 mPa · s B: 40 mPa · s or more and less than 60 mPa · s C: 60 mPa · s or more

(Monomer PII value)
The PII value of the monomer is a value published by Shin Nakamura Chemical Co., Ltd. and Osaka Organic Chemical Industry Co., Ltd., which are manufacturers.

  From the results of Table 1, it can be seen that the photocurable ink compositions of Examples 1 to 8 have low PII and low viscosity, and exhibit excellent curability even under low illumination conditions.

  On the other hand, the comparative example 1 which does not use a hyperbranched polymer was inferior in curability although the viscosity was favorable. On the other hand, Comparative Example 6 using a large amount of the hyperbranched polymer had good curability without using 2,4-thioxanthone or isopropylthioxanthone, but had a high viscosity.

  Moreover, although the comparative example 3 contained a suitable amount of hyperbranched polymer, since it did not contain 2, 4- thioxanthone or isopropyl thioxanthone, it resulted in inferior curability. Thus, as Comparative Example 2, a photocurable ink composition was prepared by increasing the amount of the photopolymerizable initiator of the photocurable ink composition of Comparative Example 3, but the effect of increasing the amount of the photopolymerizable initiator was small. The effect similar to 1-8 was not acquired.

  In Comparative Example 4 using 2-hydroxyethyl acrylate instead of tripropylene glycol diacrylate or dipropylene glycol diacrylate, good curability and viscosity are obtained, but the PII value is high.

  In Comparative Example 5, tetraethylene glycol diacrylate was used instead of tripropylene glycol diacrylate or dipropylene glycol diacrylate, but the composition was hardened despite containing a hyperbranched polymer and 2,4-thioxanthone. It became inferior result.

(Film curability evaluation)
The ink described in Example 1 was filled in the RED nozzle array using an inkjet printer PX-G920 (manufactured by Seiko Epson Corporation). Under normal pressure, a solid pattern of RED (printed with 720 × 720 dots per square inch by 1 ng) was printed on a PET film. (The actual print color is the ink color filled in the RED nozzle row). Thereafter, ultraviolet rays having a wavelength of 355 nm, 365 nm, 395 nm, or 420 nm were irradiated using an ultraviolet irradiation device. Irradiation intensity was adjusted to 125 mW / cm ² and irradiated, and the point in time when the finger touch on the sample surface disappeared was judged to be cured. The curability was evaluated according to the following index at each irradiation intensity. The results are shown in Table 2.
A: required irradiation energy 625mJ / cm ² or less B: required irradiation energy 625mJ / cm ² greater, 950 mJ / cm ² or less C: required irradiation energy 950 mJ / cm ² than

  According to Table 2, it was found that good curability was exhibited particularly at a wavelength of 360 nm to 410 nm. The ink that cures at the wavelength can reduce the cost of the LED, and it is difficult to cure in the visible light region, so that it is excellent in handleability.

Claims (7)

A photocurable ink composition comprising at least a polymerizable compound and a photopolymerization initiator,
The polymerizable compound includes a resinous polymer and tripropylene glycol diacrylate and / or dipropylene glycol diacrylate,
A photocurable ink composition comprising 2,4-diethylthioxanthone and / or isopropylthioxanthone as a photopolymerization initiator.   An ink jet recording method for forming an image using the photocurable ink composition according to claim 1.   3. The ink jet recording method according to claim 2, wherein the photocurable ink composition is cured using an LED having an emission spectrum peak at a wavelength of 360 nm to 410 nm.   A recorded matter in which an image is formed on a recording medium by the ink jet recording method according to claim 2.   An ink set comprising a plurality of photocurable ink compositions, comprising at least the photocurable ink composition according to claim 1.   An ink cartridge comprising the ink set according to claim 5.   A recording apparatus comprising the ink cartridge according to claim 6.