JP2005307199A - Active energy ray-curable aqueous ink composition, inkjet recording method, ink cartridge, recording unit, and inkjet recording apparatus using the composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an active energy ray-curable aqueous ink composition having excellent curing property due to containing a highly-reactive aqueous polymerizable substance and an aqueous polymerization initiator having excellent initiation efficiency, and also to provide an inkjet recording method, an ink cartridge, a recording unit and an inkjet recording apparatus using the ink composition. <P>SOLUTION: The active energy ray-curable aqueous ink composition contains at least water and a polymerizable substance which undergoes radical polymerization by active energy ray. The active energy ray-curable ink composition is characterized in that the polymerizable substance is an aqueous compound having two to six (meth)acrylic groups and the polymerization initiator is an aqueous acylphosphine oxide compound. The inkjet recording method, the ink cartridge, the recording unit and the inkjet recording apparatus using this ink composition are also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a highly reactive water-soluble polymerizable substance that radically polymerizes with active energy rays and a water-initiating polymerization initiator with high initiation efficiency that generates radicals with active energy rays. The present invention relates to an active energy ray curable aqueous ink composition, an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus using the active energy ray curable aqueous ink composition.

  The water-based active energy ray-curable ink can be suitably used for image printing, pretreatment for imparting printability to a recording medium, protection of printed images, post-treatment for decoration, etc., and strengthening VOC regulations This technology has many excellent features and possibilities, such as being applicable to high-density inkjet recording heads due to its low viscosity and low viscosity.

  A basic constituent material of an aqueous active energy ray-curable ink, a polymerizable substance that radically polymerizes with active energy rays (hereinafter referred to as a polymerizable substance) and a polymerization initiator that generates radicals with active energy rays (hereinafter referred to as a polymerization initiator). Was initially prepared in an emulsion in an aqueous solvent, but in terms of film-forming properties in polymerization and ejection stability when applied to an ink jet method, it should be uniform. Therefore, it has become necessary for the polymerizable substance and the polymerization initiator itself to be water-soluble or hydrophilic.

  As a water-soluble and hydrophilic polymerizable substance, as an example, an ester of succinic anhydride and 2-hydroxyethyl (meth) acrylate having both an acidic group and a (meth) acryloyl group or vinyl group in the molecule. In addition, esters of phthalic anhydride and 2-hydroxyethyl (meth) acrylate, vinyl naphthalene sulfonic acid, and the like are in practical use.

  Further, as a second example, industrially produced compounds having two or more polymerizable functional groups include polyhydric alcohols imparted with hydrophilicity by polyethylene oxide chains, such as tetraethylene glycol di (meth) acrylate. (Meth) acrylic acid ester and the like.

  Moreover, in patent document 1, the (meth) acrylic acid ester of the hydrophilic polyepoxide derived from polyhydric alcohols, such as glycerol, is illustrated.

  Examples of water-soluble and hydrophilic polymerization initiators include hydroxyphenyl ketone-based polymerization initiators that have been given water-solubility by adding a polyethylene oxide chain to Patent Document 2, and Patent Document 3 has a polyethylene oxide chain or an anionic functional group. A thioxanthone-based polymerization initiator imparted with water solubility by adding is disclosed. Further, Patent Document 4 discloses that an acylphosphine oxide-based polymerization having an ionic group is initiated as a polymerization initiator useful for the polymerization of an aqueous polymerizable composition such as a coating material, printing ink, unsaturated polyester molding material or recording material. The invention of the agent has been made.

Patent Document 5 discloses an invention in which the water-soluble acylphosphine oxide polymerization initiator described in Patent Document 4 is used in a dental polymerizable composition.
JP 2000-117960 A JP 2002-186242 A JP 2002-187918 A JP 57-197289 A JP 2000-159621 A

  The active energy ray-curable water-based ink has the excellent characteristics as described above, but on the other hand, it may be pointed out that the curing performance is lowered by dilution with water. Curing performance is improved by increasing the content of the polymerizable substance and the polymerization initiator, but is restricted by viscosity and the like when the active energy ray-curable water-based ink is applied to the ink jet system. As a result, the curing performance is highly dependent on the properties of the individual materials.

  In order to construct an active energy ray-curable water-based ink suitable for an ink jet system, it is a water-soluble polymerizable material with a low viscosity and good flow characteristics that can be used for high-density nozzles. It is necessary to have a cured ink film having excellent hardness and adhesion to a recording medium. The water-soluble polymerization initiator is required to have a high responsiveness to irradiation with an active energy ray for a short time and to generate many radicals and to have excellent initiation efficiency.

  With respect to the polymerizable substance of the first example, since the number of polymerizable functional groups is one in one molecule, the polymerization rate is slow and the degree of crosslinking of the cured product is extremely low. It cannot be a material.

  The polymerizable substance of the second example is not water-soluble when the length of the ethylene oxide chain is short. On the other hand, when the length of the ethylene oxide chain is long, the water-solubility is obtained, but when the polymerized or cured There arises a problem that solid physical properties are often insufficient in performance required for paints and inks such as hardness and adhesiveness.

  Further, the polymerizable substance of Patent Document 1 has high water solubility, a high polymerization rate by active energy rays, and excellent properties of the cured product. However, since it has a large number of hydroxyl groups, it has a characteristic that the viscosity is slightly high. Therefore, the amount that can be added to the ink may be reduced.

  The polymerization initiator of Patent Document 2 is in a liquid state and excellent in compatibility with water and a polymerizable substance, but is somewhat insufficient in terms of initiation efficiency. Since the polymerization initiator of Patent Document 3 is a hydrogen abstraction type, a hydrogen donor such as a tertiary amine is separately required. Also, because of the coloring, it is not suitable for a clear ink. The polymerization initiator of Patent Document 4 is characterized by a high quantum yield of radical generation, a high reactivity of radicals having unpaired electrons on the phosphorus atom, and a substantial lifetime of the generated radicals. The starting efficiency is high. Moreover, water solubility is also favorable.

  The water-soluble polymerization initiator of Patent Document 4 has such excellent characteristics, but the actual application is limited to the dental material described in Patent Document 5. In this application, there is no particular limitation on the irradiation time of the active energy ray, so the starting efficiency is not an essential item.

  The high starting efficiency is utilized in applications that require a curing speed such as printing ink, but such applications are not made because of the reactivity of the combined water-soluble polymerizable substances. This is thought to be because of insufficient.

  On the contrary, the performance of the aqueous polymerizable composition as a whole may be significantly reduced due to insufficient initiation efficiency of the combined water-soluble polymerization initiator for highly reactive water-soluble polymerizable substances. possible.

  From the above, in order to ensure sufficient curing performance as an active energy ray-curable water-based ink composition and to obtain adaptability to a wide range of uses, the reactivity of the water-soluble polymerizable substance and the water-soluble polymerization initiator It became clear again that it was necessary to focus on the combination of two factors, starting efficiency.

  Accordingly, a first object of the present invention is to provide an active energy ray-curable aqueous ink composition that has excellent curing performance by containing a water-soluble polymerizable substance exhibiting high reactivity and a water-soluble polymerization initiator exhibiting high initiation efficiency. It is to provide.

  The second object of the present invention is to provide an active energy ray having excellent curing performance and suitability for an ink jet system by containing a water-soluble polymerizable substance exhibiting high reactivity and a water-soluble polymerization initiator exhibiting high initiation efficiency. The object is to provide a curable aqueous ink composition.

  A third object of the present invention is to provide an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus using such an aqueous ink composition.

  The above object is achieved by the present invention described below. That is, the present invention relates to an active energy ray-curable aqueous ink composition containing at least water, a polymerizable substance that undergoes radical polymerization with active energy rays, and a polymerization initiator that generates radicals with active energy rays. An active energy ray-curable aqueous ink, wherein the polymerizable substance is a water-soluble compound having 2 to 6 (meth) acrylic groups, and the polymerization initiator is a water-soluble acylphosphine oxide compound. It is a composition.

  The present invention also includes a step of discharging the aqueous ink composition onto a recording medium, and a step of irradiating the recording medium to which the aqueous ink has been applied with active energy rays to cure the aqueous ink composition. It is an inkjet recording method characterized by having.

  According to another aspect of the present invention, there is provided an ink cartridge comprising an ink containing portion containing the aqueous ink composition.

  According to another aspect of the present invention, there is provided a recording unit comprising an ink storage portion storing the water-based ink composition and a recording head for discharging the water-based ink composition.

  The present invention further comprises means for applying such a water-based ink composition onto a recording medium, and means for irradiating the aqueous ink composition applied onto the recording medium with active energy rays. This is an ink jet recording apparatus.

  According to the embodiment of the present invention, an aqueous active energy ray-curable ink composition having excellent curing performance is provided. That is, an active energy ray curable type having excellent curability by containing a water-soluble polyfunctional acrylic compound showing high reactivity as a polymerizable substance and a water-soluble acylphosphine oxide compound showing high starting efficiency as a polymerization initiator. An aqueous ink composition is provided.

  According to another embodiment of the present invention, an active energy ray-curable aqueous ink composition having excellent curability and suitability for an ink jet system, and the active energy ray-curable aqueous ink composition are provided. There is provided a recording method including a step of applying an ink jet method onto a recording medium and then immediately irradiating and curing with an active energy ray. Thereby, it is possible to form an image having high quality and fastness even on a recording medium having high absorbency such as plain paper.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. In view of the above object, the present inventors have at least an active energy ray-curable aqueous solution containing water, a polymerizable substance that undergoes radical polymerization by active energy rays, and a polymerization initiator that generates radicals by active energy rays. In the ink composition, the polymerizable substance is a water-soluble compound having 2 to 6 (meth) acryl groups, and the polymerization initiator is a water-soluble acylphosphine oxide compound. An active energy ray-curable ink composition was prepared and evaluated by irradiation with active energy rays. As a result, the active energy ray-curable water-based ink composition having such a configuration has been found to exhibit excellent curing performance, leading to the present invention.

  That is, in the active energy ray-curable water-based ink composition according to the present invention, as a polymerizable substance that exhibits high reactivity with a small number of functional groups, a small acrylic equivalent, or a hydrogen bond formed between hydroxyl groups. High initiation efficiency due to high water-soluble polyfunctional acrylic compounds, high quantum yield of radical generation, high reactivity of radicals with unpaired electrons on phosphorus atoms, and substantial lifetime of the generated radicals By simultaneously containing a water-soluble acylphosphine oxide compound as a polymerization initiator, it is considered that excellent curing performance is exhibited even when diluted with water.

  The action and effect of printing by the water-based inkjet method, which is a main application example of the water-based active energy ray-curable ink composition according to the present invention, will be described below.

  In addition, examples of active energy rays that can be used in the present invention include ultraviolet rays and electron beams. Hereinafter, when a description is given with a water-based ultraviolet curable ink composition using a particularly preferable ultraviolet ray as a representative example. There is. However, this does not mean that the active energy ray is limited to ultraviolet rays.

The main purpose of using the aqueous active energy ray-curable ink composition according to the present invention for image formation using the water-based inkjet method is, for example, in the following points.
1) The ink can be dried to improve the printing speed.
2) By allowing a water-soluble polymerizable substance to act as a binder for a color material, it is possible to form images having excellent scratch properties on various recording media.
3) The scattering from the pigment particles is reduced, and a transparent ink layer can be formed.
4) The color reproduction range of the process color is expanded, and it is possible to form an image with high density, excellent saturation and lightness.
5) Further, it is possible to protect the color material from active light, gas components in the air, moisture, and the like.

  The active energy ray-curable water-based ink composition according to the present invention is an ink-absorbing material such as plain paper, but it is difficult to improve the color of a coloring material and the scratch resistance. On the other hand, it has a remarkable effect of improving it. Furthermore, the active energy ray-curable water-based ink composition according to the present invention enables printing with a water-based ink on a non-absorbable recording medium.

  In order to use the active energy ray-curable water-based ink composition according to the present invention in an ink jet system, the viscosity is of course within an appropriate range, but the surface tension is also high quality and high density especially on plain paper. It is more preferable to optimize from the viewpoint of balance between curing and penetration so that an image can be formed.

  Next, each of the constituent materials of the aqueous active energy ray-curable ink composition according to the present invention having the excellent actions and effects described above, and an ink jet recording method using the aqueous active energy ray-curable ink composition Will be described in detail.

≪Active energy ray-curable water-based ink composition≫
The active energy ray-curable aqueous ink composition according to the present invention includes at least water, a water-soluble compound having 2 to 6 (meth) acryl groups as a polymerizable substance that undergoes radical polymerization by active energy rays, and active energy. It contains a water-soluble acylphosphine oxide compound as a polymerization initiator that generates radicals by lines. Further, it may contain an aqueous coloring material, other water-soluble polymerization initiator, an aqueous solvent, an optional additive, and the like.

<Water-soluble polymerizable substance>
The polymerizable substance suitably used in the present invention will be described. Such a polymerizable substance is a water-soluble compound having 2 to 6 (meth) acrylic groups, and is preferably a water-soluble (meth) acrylic acid ester compound represented by the following general formula (1).

（式中、Ｚは水酸基を（ｘ１＋ｙ１）個有するポリオールの残基またはポリオールのエポキシエステルの残基を表し、ｘ１は０〜２の整数、ｙ１は２〜６の整数であって、ｘ１＋ｙ１は２〜６の整数である。Ｒ_１は各々独立して、水素原子またはメチル基を表す。Ｒ_２は各々独立して、下記式で示される原子団Ａを表す。

(In the formula, Z represents a residue of a polyol having (x1 + y1) hydroxyl groups or a residue of an epoxy ester of a polyol, x1 is an integer of 0 to 2, y1 is an integer of 2 to 6, and x1 + y1 is 2) And R ₁ each independently represents a hydrogen atom or a methyl group, and R ₂ each independently represents an atomic group A represented by the following formula.

（式中、Ｒ_３は各々独立して、水素原子またはメチル基を表す。ｍ１は１〜５の整数、ｎ１は０または１を表す。）

(In the formula, each R ₃ independently represents a hydrogen atom or a methyl group. M1 represents an integer of 1 to 5, and n1 represents 0 or 1.)

  The number of polymerizable functional groups in the water-soluble polymerizable substance suitably used in the present invention is preferably in the range of 2 to 6, more preferably in the range of 3 to 6. The greater the number of polymerizable functional groups, the faster the cure speed, but the larger the molecule and the higher the viscosity. In this case, particularly for the active energy ray-curable aqueous ink composition used in the ink jet system, the amount of addition is limited, so that improvement in curing performance cannot be expected so much. In addition, since the curing rate is high, it is necessary to keep in mind that molecular diffusion is suppressed at an early stage of polymerization, and unreacted polymerizable functional groups are likely to remain. On the other hand, when the number of polymerizable functional groups of the water-soluble polymerizable substance is 1, the curing rate is slow and the crosslinking degree is extremely low, which is not suitable. The polymerizable functional group preferably has a (meth) acryl group, and more preferably an acrylic group from the viewpoint of curing performance.

  In addition, the number of ethylene oxide chains and propylene oxide chains for imparting water solubility to the polymerizable substance is preferably in the range of 1 to 5, more preferably in the range of 1 to 3. When the ethylene oxide chain and the propylene oxide chain are long, water solubility is obtained, but the hardness of the film when cured and the adhesion to the recording medium are insufficient. In order to achieve both water solubility and curing performance, it is preferable that a glycidyl group is further contained. Viscosity increases due to the hydrogen bond generated between the hydroxyl groups of the glycidyl group, and therefore the amount added may be limited. However, the combination with the water-soluble polymerization initiator exhibiting excellent initiation efficiency according to the present invention is effective. Curing performance as an energy ray curable aqueous ink composition is sufficiently ensured.

  The polyol residue represented by Z is obtained by removing two or more hydroxyl groups from a polyol. Preferred polyols include, for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3. -Butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol, glycerin, 1,2,4-butanetriol, 1,2, 6-hexanetriol, 1,2,5-pe Phytantriol, thiodiglycol, trimethylol propane, ditrimethylolpropane, trimethylolethane, di-trimethylolpropane, neopentyl glycol, pentaerythritol, dipentaerythritol and their condensates. Other polyols include low molecular weight polyvinyl alcohol, triose, tetrose (erythritol, threitol), pentose (ribitol, arabinitol, xylitol), hexose (allitol, alitolitol, glucitol, mannitol, iditol, galactitol, inositol). , Heptose, octose, nonose, decose, and the like, and deoxy sugars, aldonic acids, aldaric acid derivatives, and the like, but are not limited thereto. Among these polyols, particularly preferred polyols include glycerin, 1,2,4-butanetriol, 1,2,6-hexanetriol, 1,2,5-pentanetriol, trimethylolpropane, trimethylolethane, Neopentyl glycol and pentaerythritol are mentioned.

  Specific preferred specific examples of the water-soluble polymerizable substance include, for example, water-soluble compounds having the structures shown below, but the water-soluble polymerizable substance used in the present invention is not limited thereto.

  Exemplary Compound 1

  Exemplary Compound 2

  Exemplary Compound 3

  Exemplary Compound 4

  Among these, Exemplified Compounds 2, 3 and 4 are particularly preferable.

<Water-soluble polymerization initiator>
The polymerization initiator suitably used in the present invention will be described. Such a polymerization initiator is a water-soluble acylphosphine oxide compound, preferably a nonionic or anionic water-soluble acylphosphine oxide compound represented by the following general formula (2).

｛式中、Ｒ_４はアルキル基またはフェニル基を表す。Ｒ_５はアルキルオキシ基またはフェニル基を表す。Ｒ_６は下記式で示される原子団Ｂを表す。

{In the formula, R ₄ represents an alkyl group or a phenyl group. R ₅ represents an alkyloxy group or a phenyl group. R ₆ represents an atomic group B represented by the following formula.

（式中、Ｒ_７は−［ＣＨ_２］ｘ_２−（ｘ２は０または１）またはフェニレン基を表す。ｍ２は０〜１０の整数を表す。ｎ２は０または１を表す。Ｒ_８は水素原子、スルホン基、カルボキシル基、ヒドロキシル基及びこれらの塩を表す。）｝

(In the formula, R ₇ represents — [CH ₂ ] x ₂ — (x2 is 0 or 1) or a phenylene group. M2 represents an integer of 0 to 10. n2 represents 0 or 1. R ₈ represents hydrogen. Represents an atom, a sulfone group, a carboxyl group, a hydroxyl group and a salt thereof)}

In addition, the alkyl group and phenyl group of R ₄ may have a substituent, such as halogen, a lower alkyl group having 1 to 5 carbon atoms, a lower alkyloxy group having 1 to 5 carbon atoms, The atomic group B, a sulfone group, a carboxyl group, a hydroxyl group and a sulfone group, a carboxyl group, and a salt of a hydroxyl group (—SO ₃ M, —CO ₂ M, —OM) may be mentioned. Such M is each independently a hydrogen atom, an alkali metal, an alkaline earth metal or ammonium represented by HNR ₉ R ₁₀ R ₁₁ (R ₉ , R ₁₀ , R ₁₁ are each independently a hydrogen atom, 5 represents a lower alkyl group, a monohydroxyl-substituted lower alkyl group having 1 to 5 carbon atoms, or a phenyl group.).

Particularly preferred R ₄ is a phenyl group having a lower alkyl group having 1 to 5 carbon atoms as a substituent.

In addition, the phenylene group of R ₇ may have a substituent, such as halogen, a lower alkyl group having 1 to 5 carbon atoms, a lower alkyloxy group having 1 to 5 carbon atoms, a sulfone group, Examples thereof include carboxyl groups, hydroxyl groups and sulfone groups, carboxyl groups, and salts of hydroxyl groups (—SO ₃ M, —CO ₂ M, —OM). Such M is each independently a hydrogen atom, an alkali metal, an alkaline earth metal or ammonium represented by HNR ₉ R ₁₀ R ₁₁ (R ₉ , R ₁₀ , R ₁₁ are each independently a hydrogen atom, 5 represents a lower alkyl group, a monohydroxyl-substituted lower alkyl group having 1 to 5 carbon atoms, or a phenyl group.).

Examples of the salt of R ₈ include —SO ₃ M, —CO ₂ M, and —OM. Such M is each independently a hydrogen atom, an alkali metal, an alkaline earth metal or ammonium represented by HNR ₉ R ₁₀ R ₁₁ (R ₉ , R ₁₀ , R ₁₁ are each independently a hydrogen atom, 5 represents a lower alkyl group, a monohydroxyl-substituted lower alkyl group having 1 to 5 carbon atoms, or a phenyl group.).

  These acylphosphine oxide polymerization initiators absorb in the longer wavelength region than conventional polymerization initiators, have excellent light transmission, and are cleaved by irradiation with active energy rays to produce acyl radicals and phosphorus atoms. Since the phosphinoyl radical having high reactivity is generated by having an unpaired electron on the top, the initiation efficiency is said to be high. Further, the amount of light absorption is reduced or the light is lost due to the cleavage, and it is possible to suppress coloring and apply to thick film curing.

The acylphosphine oxide compound preferably used in the present invention is one that imparts water solubility through a nonionic functional group and / or an anionic functional group. Examples of the nonionic functional group include a polyethylene oxide chain and a polypropylene oxide chain, and examples of the anionic functional group include a sulfone group, a carboxyl group, a hydroxyl group, and salts thereof (—SO ₃ M, —CO ₂ M, -OM (M is more preferably a hydrogen atom, an alkali metal such as lithium, sodium or potassium, or an ammonium such as ammonium, dimethylethanolammonium, methyldiethanolammonium, triethanolammonium, anilinium)). It is not limited to these.

  Specific examples of particularly preferred water-soluble polymerization initiators include water-soluble compounds having the structure shown below, but the water-soluble polymerization initiator used in the present invention is not limited to these.

  Exemplary Compound 5

  Exemplary Compound 6

  Exemplary Compound 7

<Color material>
In the present invention, a colored aqueous active energy ray-curable ink composition that can be cured can be obtained by adding a coloring material, and various image formations can be achieved by applying it to an inkjet system that supports multi-color. Can be done. The basic element of the colorant that can be suitably used in the aqueous active energy ray-curable ink composition according to the present invention is the above-mentioned water-solubility essential for making the ink active energy ray-curable. It is necessary that the compatibility with the polymerizable substance and the water-soluble polymerization initiator is satisfied. Specifically, an aqueous pigment dispersion or aqueous dye having an anionic dissociative group is more preferably used.

(Anionic aqueous pigment dispersion)
Examples of the black pigment include carbon black. The carbon black is, for example, a carbon black produced by a furnace method or a channel method, and has a primary particle diameter of 15 to 40 μm, a specific surface area by the BET method of 50 to 300 m ² / g, and a DBP oil absorption of 40 to 150 ml. / 100 g, a volatile component of 0.5 to 10%, a pH value of 2 to 9 and the like are preferably used. Examples of commercially available products having such characteristics include No. 2300, no. 900, MCF88, No. 33, no. 40, no. 52, MA7, MA8, no. 2200B (Mitsubishi Chemical), RAVEN 1255 (Columbia), REGAL400R, REGAL330R, REGAL 660R, MOGUL L (Cabot), Color Black FW1, Color Black FW18, Color Black S170, Color Black S170, Color Black P170 Printex U (manufactured by Degussa) and the like can be used preferably.

  Examples of the yellow pigment include Pigment Yellow 1, Pigment Yellow 2, Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 16, Pigment Yellow 17, Pigment Yellow 55, Pigment Yellow 73, and Pigment Yellow 74. Pigment Yellow 75, Pigment Yellow 83, Pigment Yellow 93, Pigment Yellow 95, Pigment Yellow 97, Pigment Yellow 98, Pigment Yellow 109, Pigment Yellow 110, Pigment Yellow 114, Pigment Yellow 128, Pigment Yellow 138, Pigment Yellow 139, Pigment Yellow 150, pigment yellow 151, pigment yellow 154, Pigment Yellow 155 and Pigment Yellow 180, and the like.

  Examples of magenta pigments include, for example, Pigment Red 5, Pigment Red 7, Pigment Red 12, Pigment Red 48 (Ca), Pigment Red 48 (Mn), Pigment Red 57: 1, Pigment Red 57 (Sr), and Pigment Red 57: 2, Pigment Red 122, Pigment Red 123, Pigment Red 168, Pigment Red 184, Pigment Red 202, Pigment Red 238, and the like.

  Examples of cyan pigments include Pigment Blue 1, Pigment Blue 2, Pigment Blue 3, Pigment Blue 16, Pigment Blue 22, Pigment Blue 60, Pigment Blue 15: 2, Pigment Blue 15: 3, Bat Blue 4 and Bat Blue 60. Etc.

  The average particle diameter of the pigment particles is preferably in the range of about 25 nm to 200 nm. Although this range depends on the use of the printed matter, it is sufficiently smaller than the wavelength of visible light, so that a printed matter that can be said to be sufficiently transparent is provided if the scattering is small.

(Anionic aqueous dye)
When a dye is used as a coloring material, unlike the case of using the above-mentioned pigment, it is difficult to use the dye without any fading due to irradiation with active energy rays, and there is some fading. For this reason, when a dye is applied as the coloring material of the ink, it is preferable to use a so-called azo metal-containing dye in which a complex is formed with metal ions because discoloration is small. However, if the level of fading is not a problem, even a general water-soluble dye can be used at least as an ink composition.

  Examples of the black dye include monoazo complexes, disazo complexes coordinated with polyvalent metals such as Cr, Cu, Mn, Al, Zn, and Fe, and non-complex azo black dyes such as direct black 17, direct black 19, Direct black 51, direct black 154, direct black 174, direct black 195, and the like can be suitably used.

  Examples of the yellow dye include Acid Yellow 11, Acid Yellow 17, Acid Yellow 23, Acid Yellow 25, Acid Yellow 29, Acid Yellow 42, Acid Yellow 49, Acid Yellow 61, Acid Yellow 71, Direct Yellow 12, Direct Yellow 24 Direct Yellow 26, Direct Yellow 44, Direct Yellow 86, Direct Yellow 87, Direct Yellow 98, Direct Yellow 100, Direct Yellow 130, Direct Yellow 132, Direct Yellow 142, and the like.

  Examples of the magenta dye include Acid Red 1, Acid Red 6, Acid Red 8, Acid Red 32, Acid Red 35, Acid Red 37, Acid Red 51, Acid Red 52, Acid Red 80, Acid Red 85, and Acid Red 87. Acid Red 92, Acid Red 94, Acid Red 115, Acid Red 180, Acid Red 254, Acid Red 256, Acid Red 289, Acid Red 315, Acid Red 317, Direct Red 1, Direct Red 4, Direct Red 13, Direct Red 17, Direct Red 23, Direct Red 28, Direct Red 31, Direct Red 62, Direct Red 79, Direct Red 81, Direct Red De 83, Direct Red 89, Direct Red 227, Direct Red 240, such as Direct Red 242 and Direct Red 243, and the like.

  Examples of cyan dyes include Acid Blue 9, Acid Blue 22, Acid Blue 40, Acid Blue 59, Acid Blue 93, Acid Blue 102, Acid Blue 104, Acid Blue 113, Acid Blue 117, Acid Blue 120, and Acid Blue 167. Acid Blue 229, Acid Blue 234, Acid Blue 254, Direct Blue 6, Direct Blue 22, Direct Blue 22, Direct Blue 25, Direct Blue 71, Direct Blue 78, Direct Blue 86, Direct Blue 90, Direct Blue 106 and Direct Blue 199 etc. Can be mentioned.

  A preferable concentration of the dye in the ink is in a range of 0.1 to 10% on the mass basis with respect to the total amount of the ink. When the density is low, for example, it is preferably applied to so-called light-color ink of density-modulated ink.

<Other water-soluble polymerization initiators>
In the present invention, other water-soluble polymerization initiators can be used in combination with the water-soluble acylphosphine oxide polymerization initiator. Preferable examples of such a polymerization initiator include at least one compound selected from the group of water-soluble compounds represented by the following general formulas (3) to (5).

（式中、ｍ３は１以上の整数を表し、ｎ３は０以上の整数を表し、ｍ３＋ｎ３は１〜８の整数を表す。）

(In the formula, m3 represents an integer of 1 or more, n3 represents an integer of 0 or more, and m3 + n3 represents an integer of 1 to 8.)

（式中、Ｒ_１２及びＲ_１３は各々独立に、水素原子またはアルキル基を表す。ｍ４は５〜１０の整数を表す。）

(Wherein R ₁₂ and R ₁₃ each independently represents a hydrogen atom or an alkyl group. M4 represents an integer of 5 to 10)

（式中、Ｒ_１２及びＲ_１３は各々独立に、水素原子またはアルキル基を表す。Ｒ_１４は、−［ＣＨ_２］ｘ３−（ｘ３は０または１）、−Ｏ−［ＣＨ_２］ｙ３−（ｙ３は１または２）、または置換もしくは未置換のフェニレン基を表す。Ｍは水素原子またはアルカリ金属を表す。

(Wherein R ₁₂ and R ₁₃ each independently represents a hydrogen atom or an alkyl group. R ₁₄ represents — [CH ₂ ] x 3 (x3 is 0 or 1), —O— [CH ₂ ] y 3 —. (Y3 represents 1 or 2), or a substituted or unsubstituted phenylene group, and M represents a hydrogen atom or an alkali metal.

  Although the absorption region of the acylphosphine oxide polymerization initiator extends to a long wavelength region of 400 nm or more, light in this long wavelength region is likely to penetrate into the inside. Therefore, it is excellent in internal curability in a system containing a pigment. However, since acylphosphine oxide polymerization initiators (especially phosphinoyl radicals formed on phosphorus atoms) are susceptible to oxygen inhibition, surface curability may be insufficient. On the other hand, it becomes possible to supplement the hardening of the surface layer by adding the above other polymerization initiator having an absorption region in a short wavelength region.

  When the thioxanthone polymerization initiator represented by the general formulas (4) and (5) is used, it is preferable to add, for example, triethanolamine as a hydrogen donor.

  Preferable specific examples of other water-soluble polymerization initiators that can be used in combination with the acylphosphine oxide polymerization initiator include, for example, water-soluble compounds having the following structures, but other water-soluble polymerizations used in the present invention. The initiator is not limited to these.

  Exemplary Compound 8

  Exemplary Compound 9

  Exemplary Compound 10

<Solvent component>
It is more preferable to add a slight amount of a solvent component to the aqueous active energy ray-curable ink composition according to the present invention. The solvent component imparts non-volatility to the ink, lowers the viscosity, imparts wettability to the recording medium, or suppresses sticking of the ink to the nozzle by maintaining the dispersion stability of the pigment. In addition to the conventional purpose, a polymerizable substance having a high reactivity and a high density between cross-linking points, and a polymerization initiator having a high initiation efficiency, such as the aqueous active energy ray-curable ink composition according to the present invention, It also includes the purpose of alleviating cure shrinkage in a high polymerization rate system used in combination. Furthermore, if polymerization proceeds to some extent in such a system, the diffusion of the polymerizable substance and the polymerization initiator is suppressed, and the final curing rate may not increase, but this is also effective as a countermeasure.

  Ink-jet printed materials are often viewed and viewed by the hands of an unspecified number of people, and a hardened film with sufficient strength and flexibility is formed so that it does not peel off from the recording medium. It is important to have sex.

  The solvent type is preferably selected from glycerin, ethylene glycol, diethylene glycol or a mixture thereof having a proven track record in ink jet recording suitability. Usually, the ink composition is contained in an amount of 0.5 to 5% based on the mass.

<Reactive diluent component>
As a solvent for diluting the water-soluble polymerizable substance and the water-soluble polymerization initiator according to the present invention, water is mainly used, but water-soluble and polymerization-reactive low-viscosity monomers can be used in addition thereto. The advantage of using such substances rather than ordinary solvents is that these substances do not remain as plasticizers in the solid after being cured with active energy rays, so that the influence on the solid physical properties is reduced. is there.

  Examples of reactive diluent solvent components selected for such purposes include acryloylmorpholine, N-vinyl-2-pyrrolidone, N-vinylformamide, acrylamide, methylenebisacrylamide, monosaccharide monoacrylate, oligoethylene oxide, and the like. Examples thereof include compounds such as monoacrylic acid esters and dibasic acid monoacrylic acid esters.

<Additives>
In the present invention, the aqueous active energy ray-curable ink composition may contain an optional additive in addition to the above substances. Examples of such additives include pH adjusters, leveling agents, viscosity adjusters, antioxidants, hindered amine light stabilizers (HALS), preservatives, fungicides and the like. When used, it is usually contained in an amount of 0.1 to 5% by mass based on the entire ink composition.

<Prescription for clear ink>
The aqueous active energy ray-curable ink composition according to the present invention is an undercoat for imparting suitability for image printing to a recording medium by providing a transparent form without containing a colorant as described above. Alternatively, it can be used for applications such as overcoating for the purpose of surface protection of images formed with ordinary inks, and further decoration and gloss. In the clear ink, colorless pigments or fine particles that are not intended for coloring can be dispersed and contained according to these applications. By adding these, it is possible to improve various properties such as image quality, fastness, and workability (handling property) of the printed matter in both the undercoat and the overcoat.

  When applied to such a clear ink, it is preferable that the content of the water-soluble polymerizable substance is 10 to 70% on a mass basis with respect to the total amount of the ink. Further, the polymerization initiator is contained in an amount of 1 to 10 parts by mass with respect to 100 parts by mass of the polymerizable substance, and at the same time, at least 0.5 part of the polymerization initiator is contained with respect to 100 parts of the ink composition. It is preferable to prepare.

<Material structure and physical properties of colorant-containing ink composition>
When a coloring material such as a pigment is used in the aqueous active energy ray-curable ink composition according to the present invention, the concentration of the pure pigment in the ink is generally 0.3 on a mass basis with respect to the total amount of the ink. It is preferable to be in the range of -10%. The coloring power of the pigment also depends on the dispersion state of the pigment particles, but if it is in the range of about 0.3 to 1%, it becomes a range used as a light-colored ink. On the other hand, if it is more than that, it gives a concentration used for general color coloring.

  As other blending amounts, the amount of water is preferably in the range of 40 to 90%, particularly in the range of 60 to 75%, based on the mass, with respect to the total amount of ink. Further, the content of the polymerizable substance in the ink is preferably in the range of 1% to 30%, particularly preferably in the range of 5 to 20%, based on the total mass of the ink. Although the polymerization initiator also depends on the content of the polymerizable substance, it is generally preferably 0.1 to 7% on a mass basis, particularly in the range of 0.3 to 5%, based on the total amount of the ink. It is preferable that

  When the active energy ray-curable aqueous ink composition of the present invention is applied to an ink jet system, the viscosity has no nonlinearity in a wide range, and the upper limit is 15 mPa · s. In the case of an ink jet system provided with fine high density and high driving frequency nozzles, the upper limit is preferably 10 mPa · s.

  Further, the surface tension is preferably 35 mN / m (dyne / cm) or more in consideration of printing on plain paper. In a normal aqueous inkjet ink, the bleed phenomenon is suppressed by adjusting the surface tension to a low value of about 30 mN / m and allowing the surface tension to permeate within a short time. In this case, however, the image density is lowered. On the other hand, in the active energy ray-curable aqueous ink composition according to the present invention, since the flow of ink can be suppressed by curing, if surface tension is increased and ink droplets are retained in the surface layer of the recording medium as much as possible, Both bleed and image density can be satisfied.

  Further, in order to ensure the image density, it is necessary that the ink droplets are wet to some extent with respect to the recording medium at the time of irradiation with the active energy ray. Therefore, the upper limit of the surface tension is more preferably about 50 mN / m.

≪Inkjet recording method≫
Next, an ink jet recording method for applying the active energy ray-curable aqueous ink composition as described above onto a recording medium by an ink jet method and irradiating and curing the active energy ray will be described.

<Printer system>
The active energy ray-curable water-based ink composition according to the present invention described above is suitably used for an inkjet discharge type head, and can also be used as an ink storage container in which the ink composition is stored, or a filling thereof. It is also effective as a printing ink. In particular, the present invention provides an excellent effect in a bubble jet (registered trademark) type recording head and recording apparatus among ink jet recording methods.

  As for the typical configuration and principle, for example, those performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 are preferable. . This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, the electric circuit arranged corresponding to the sheet or liquid path holding the ink is used. By applying at least one drive signal corresponding to the recording information and giving a rapid temperature rise exceeding nucleate boiling to the heat conversion body, heat energy is generated in the electrothermal conversion body, and the heat acting surface of the recording head This is effective because the film can be boiled, and as a result, the drive signals can be made to correspond one-to-one and bubbles in the ink can be formed. By the growth and contraction of the bubbles, ink is ejected through the ejection openings to form at least one droplet. It is more preferable that the drive signal has a pulse shape, because the bubble growth and contraction is performed immediately and appropriately, and thus ink discharge with particularly excellent responsiveness can be achieved. As this pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by employing the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate of the heat acting surface.

  As the configuration of the recording head, in addition to the combination configuration (straight liquid channel or right-angle liquid channel) of the discharge port, the liquid channel, and the electrothermal transducer as disclosed in each of the above-mentioned specifications, the heat acting part Is disclosed in US Pat. No. 4,558,333, US Pat. No. 4,459,600, or US Pat. No. 2,962,880, which discloses a configuration in which the lens is disposed in a bent region. The present invention is also effective for the discharge method of the atmospheric communication method described in Japanese Patent No. 3246949, and further, JP-A-11-188870. In addition, the present invention is also effective for a configuration (Japanese Patent Laid-Open No. 59-123670, etc.) in which a discharge hole is used as a discharge portion of the electrothermal transducer when common to a plurality of electrothermal transducers. . Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length is set by combining a plurality of recording heads as disclosed in the above specification. Either a satisfying configuration or a single integrated recording head configuration may be used, but the present invention can exhibit the above-described effects more effectively.

  In addition, it is mounted on the main body of the device so that it can be electrically connected to the main body of the device and supplied with ink from the main body of the device. The present invention is also effective when a cartridge type recording head is used. In the present invention, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc. provided as the configuration of the recording apparatus to be applied, because the effects of the present invention can be further stabilized. . Specific examples thereof include a capping unit for the recording head, a cleaning unit, a pressure or suction unit, an electrothermal converter, a heating element different from this, or a preheating unit using a combination thereof, This is a preliminary ejection mode in which ejection different from recording is performed.

  As shown in the schematic diagram of the front of the printer in FIG. 1, the recording apparatus for carrying out the recording method of the present invention includes an ink tank unit 1 containing the active energy ray-curable aqueous ink composition of the present invention, and recording. The head unit 2 to be actually used (a multi-head in which a large number of heads are arranged here is used), the lamp unit 3 that performs ultraviolet irradiation for curing, the head unit and the drive unit 4 that drives the lamp unit, and the recording target to be recorded The recording apparatus includes a paper discharge unit 5 that conveys a recording medium. In addition to these, a wiping unit (not shown), a capping unit, a paper feeding unit, and a drive motor unit are also provided.

  In FIG. 1, a nozzle unit for discharging an active energy ray-curable water-based ink composition is arranged symmetrically for each color in a head unit 2, and the head unit 2 and the lamp unit 3 are integrally scanned left and right. Then, after applying the active energy ray-curable aqueous ink composition to the recording medium, ultraviolet irradiation is performed immediately (details of the lamp will be described later). Therefore, when this recording apparatus is used, an ink jet recording method that effectively suppresses bleeding of ink droplets, bleeding between colors, and the like in ordinary paper recording and realizes an image having excellent fastness can be obtained.

  The ink tank unit 1 is arranged with four colors of black (Bk), cyan (C), magenta (M), and yellow (Y), but light cyan (LC) is used to record a higher-definition image. ) Or light magenta (LM). Further, since the reactivity of black is inferior to that of other colors, a three-color arrangement that forms a process black combining cyan, magenta, and yellow may be used. In the present invention, a tank that can block light is used.

  In the present invention, in addition to the recording system described above, a lamp is disposed on the front surface of the paper discharge unit, a paper supply / discharge process is performed around a rotating drum, and a drying unit is provided separately. Can be selected as appropriate.

<Ultraviolet irradiation lamp>
Hereinafter, an ultraviolet irradiation lamp that is particularly preferably used in curing the active energy ray-curable aqueous ink composition according to the present invention will be described. The ultraviolet irradiation lamp is preferably a so-called low-pressure mercury lamp, high-pressure mercury lamp, mercury lamp coated with a phosphor, or the like whose mercury vapor pressure is 1 to 10 Pa during lighting. The emission spectrum of these mercury lamps in the ultraviolet region is 450 nm or less, particularly in the range of 184 nm to 450 nm, and is suitable for efficiently reacting a polymerizable substance in black or colored ink. Also, it is suitable for mounting a power supply in a printer because a small power supply can be used. As mercury lamps, for example, metal halide lamps, high-pressure mercury lamps, ultrahigh-pressure mercury lamps, xenon flash lamps, deep UV lamps, lamps that excite mercury lamps from the outside using microwaves, UV lasers, and the like are in practical use. Since the wavelength range includes the above range, it is basically applicable if the power source size, input intensity, lamp shape, etc. are allowed. The light source is selected in accordance with the sensitivity of the polymerization initiator used.

The necessary ultraviolet intensity is preferably 500 to 5000 mW / cm ² in a wavelength region effective for curing. If the integrated intensity is weak, formation of an image having high quality and fastness cannot be achieved. On the other hand, if the irradiation intensity is too high, the recording medium may be damaged or the color material may be faded.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited by the following examples unless it exceeds the gist. In the text, “part” or “%” is based on mass unless otherwise specified.

(Synthesis Example 1) Synthesis of Sodium 2,4,6-Trimethylbenzoylphenylphosphinate (Exemplary Compound 5) The synthesis of the intended Exemplified Compound 5 is disclosed in Patent Document 4. However, according to the method of this document, alkyl iodide is produced as a by-product, and mutagenicity is suspected particularly for the methyl compound shown as a suitable example in the document. It is not preferable in terms of safety that such a substance may be contained as an impurity. Therefore, in the present invention, an attempt was made to synthesize Exemplified Compound 5 by decomposing a commercially available bisacylphosphine oxide compound under acidic conditions.

  Pyridine sulfate was prepared according to a conventional method by reacting pyridine which was dried and not containing water with sulfuric anhydride in chloroform. Next, 250 g of a 15% pyridine solution of phenyl-bis (2,4,6-trimethylbenzoyl) -phosphine oxide (trade name Irgacure 819: manufactured by Ciba Specialty Chemicals) was prepared and sufficiently dehydrated for dehydration. The pyridine sulfate 50g was added to this, and it boiled for 5 hours under recirculation | reflux. The reaction mixture was poured onto about 500 g of ice and neutralized by adding a 20% aqueous sodium hydroxide solution little by little. The filtrate obtained by filtering the obtained suspension was distilled to remove residual pyridine. The remaining aqueous layer was neutralized by adding 1N HClaq little by little, and then water was distilled off and vacuum dried. The residue was recrystallized from a small amount of ethanol and vacuum-dried to obtain about 20 g of 2,4,6-trimethylphenylphosphinic acid. This was dissolved in an excess amount of ethanol, and this solution was added in small portions to an ethanol solution of sodium hydroxide. The precipitate was separated by filtration, washed with cold ethanol, and vacuum dried to obtain about 15 g of sodium 2,4,6-trimethylbenzoylphenylphosphinate (Exemplary Compound 5).

  Synthesis Example 2 Synthesis of 2,4,6-trimethylbenzoylphenylphosphinic acid octaethylene glycol ester (Exemplary Compound 6)

  20 g of phenyl-bis (2,4,6-trimethylbenzoyl) -phosphine oxide (trade name Irgacure 819: manufactured by Ciba Specialty Chemicals), 45 g of potassium permanganate, 600 ml of pyridine, and 300 ml of water are mixed and heated and stirred at 85 ° C. for 6 hours. did. After the reaction solution was cooled to room temperature, the precipitated crystals were filtered off and washed with water. The filtrate was concentrated, 150 ml of 10% HClaq was added to the residue, and the mixture was extracted three times with 200 ml of ethyl acetate. The organic layers were combined, washed twice with 200 ml of saturated brine, and dried over anhydrous magnesium sulfate. This solution was concentrated and dried to obtain 21 g of a pale yellow solid.

  Next, 20 g of this solid, 600 g of polyethylene glycol 400, and 500 ml of chloroform were mixed, and the mixture was heated and stirred at 50 ° C. for 1 hour. After cooling the reaction solution to room temperature, water was added for liquid separation, and the aqueous layer was extracted with 1200 ml of chloroform. The organic layers were combined, washed with 1000 ml of saturated brine, and dried over anhydrous magnesium sulfate. The solvent was distilled off under reduced pressure, and the residue was purified by silica gel chromatography to obtain about 10 g of 2,4,6-trimethylbenzoylphenylphosphinic acid octaethylene glycol ester (Exemplary Compound 6).

(Examples 1 to 10)
The components described in Table 1 below were mixed, sufficiently stirred and dissolved, and then pressure filtered through a 0.50 μm filter to prepare inks of Examples 1 to 10, respectively. Further, the pH of the ink was adjusted with an aqueous sodium hydroxide solution so that the pH was finally 8.5.

(Comparative Examples 1-2)
The components described in Table 1 below were mixed, sufficiently stirred and dissolved, and then pressure filtered through a 0.50 μm filter to prepare inks of Comparative Examples 1 and 2, respectively. Further, the pH of the ink was adjusted with an aqueous sodium hydroxide solution so that the pH was finally 8.5.

  As the water-soluble polymerization initiator of Comparative Example 1, the exemplified compound 8 was used alone. As the water-soluble polymerizable substance of Comparative Example 2, Exemplified Compound 11 shown below was used.

  Exemplary Compound 11

<Evaluation of curing performance>
The active energy ray-curable water-based ink composition according to the present invention contains a highly reactive water-soluble polyfunctional acrylic compound as a polymerizable substance, and a water-soluble acylphosphine oxide compound with high initiation efficiency as a polymerization initiator. Even in a system to which a pigment is added, the curing performance is high, and it is possible to cope with high-speed printing on plain paper. This curing performance was evaluated using a Photo-DSC (light-differential scanning thermal analysis) apparatus and a bubble jet (registered trademark) printer remodeling machine equipped with an ultraviolet irradiation lamp.

(1) Photo-DSC Measurement About each of the active energy ray-curable aqueous ink compositions of Examples 1 to 10 and Comparative Examples 1 and 2 according to the present invention, about 1.5 mg was weighed into an aluminum pan, and used for reference. A photo-DSC apparatus (manufactured by METTLER TOLEDO) was loaded together with an empty aluminum pan. After standing for 10 minutes in an atmosphere at 25 ° C. in the air, ultraviolet rays having an intensity at 365 nm of 400 mW / cm ² were irradiated for 0.1 seconds. About the obtained DSC curve, after normalizing per unit weight, the gradient of the calorific value / time (W / g · s) from the rise of the exothermic peak to the top was measured and evaluated. This compares the responsiveness of curing to a certain irradiation energy. The larger the value, the better the curing performance. Table 2 summarizes the evaluation results. (Numerical values indicate relative values when the case of Example 2 is 1.0.)

(2) Print evaluation 1
For each of the active energy ray-curable water-based ink compositions of Examples 1 to 10 and Comparative Examples 1 and 2 according to the present invention, an on-demand type in which ink is ejected by applying thermal energy corresponding to the recording signal to the ink A bubble jet (registered trademark) printer PIXUS550i (manufactured by Canon Inc.) having a multi-recording head is exposed to an ultraviolet irradiation lamp (maximum irradiation intensity in the region of 300 to 400 nm is 1500 mW in the form adjacent to the recording head portion as shown in FIG. / Cm ² ) was used and evaluated according to the following methods and standards. Table 2 summarizes the evaluation results.

(2-1) Fixability A sample prepared by printing a 12-point character pattern on PPC paper (manufactured by Canon) with a predetermined ink using the modified machine and irradiating with ultraviolet rays. When the sillbon paper is placed and the sillbon paper is pulled with an overweight of 40 g / cm ² on the recording surface, the non-printing part (white background part) of the recording medium and the sylbon paper are smudged by the rubbing of the printing part. Whether or not it occurred was visually observed and evaluated according to the following criteria.
A: Dirt due to rubbing is hardly seen B: Dirt due to rubbing is slightly seen C: Dirt due to rubbing is conspicuous

(2-2) Marker resistance A sample prepared by printing a 12-point character pattern on PPC paper (manufactured by Canon) with a predetermined ink using the modified machine and irradiating with ultraviolet rays, and after 1 minute of printing, Using a yellow pen (BEAMLINER-S; manufactured by Zebra), the character part was marked once with normal writing pressure, and the presence or absence of disorder of the character was visually observed and evaluated according to the following criteria.
A: Character disorder due to the marker hardly occurs B: Character disorder due to the marker slightly occurs C: Character disorder due to the marker significantly occurs

<Evaluation of film performance>
The active energy ray-curable water-based ink composition according to the present invention exhibits high curing performance for the reasons described above, but the flexibility decreases due to curing shrinkage and becomes brittle, or the adhesion of the cured film to the recording medium. There is also a possibility that it will be easily peeled off. According to the present invention, it is also possible to add a small amount of an aqueous solvent component for the purpose of easing relaxation shrinkage or promoting the final curing rate. The film performance was evaluated using a Bubble Jet (registered trademark) printer modification machine equipped with an ultraviolet irradiation lamp.

(3) Print evaluation 2
For each of the active energy ray-curable water-based ink compositions of Examples 1 to 10 and Comparative Examples 1 and 2 according to the present invention, an on-demand type in which ink is ejected by applying thermal energy corresponding to the recording signal to the ink A bubble jet (registered trademark) printer PIXUS550i (manufactured by Canon Inc.) having a multi-recording head is exposed to an ultraviolet irradiation lamp (maximum irradiation intensity in the region of 300 to 400 nm is 1500 mW in the form adjacent to the recording head portion as shown in FIG. / Cm ² ) was used and evaluated according to the following methods and standards. Table 3 summarizes the evaluation results.

(3-1) Strength / Flexibility Using the modified machine, with a predetermined ink, a 300% solid pattern is printed on a white polyethylene terephthalate film with a uniform and clean surface, and the sample is created by ultraviolet irradiation. Ten minutes after printing, the state of the film when the sample was bent was visually observed and evaluated according to the following criteria.
A: Almost no change in the film B: Cracks and peeling occur slightly in the film C: Cracks and peeling occur significantly in the film

(3-2) Adhesiveness A sample prepared by printing a 300% solid pattern on a white polyethylene terephthalate film having a uniform and clean surface with a predetermined ink and irradiating with ultraviolet rays using the above-mentioned remodeling machine. After the time, the printed portion was cut in a lattice shape and covered with a tape, and then peeled off, and the proportion (residual rate) of the portion remaining in close contact was visually observed and evaluated according to the following criteria.
AA: Residual rate 90% or more A: Residual rate 80% to less than 90% B: Residual rate 70% to less than 80% C: Residual rate less than 70%

<Evaluation of image performance>
The active energy ray-curable aqueous ink composition according to the present invention exhibits high curing performance as described above. Therefore, even in a state where the surface tension is high and stays on the surface of the recording medium, suppression of character bleeding and bleeding and high image density are simultaneously achieved. This image performance was evaluated using a bubble jet printer remodeler equipped with an ultraviolet irradiation lamp.

(4) Print evaluation 3
For each of the active energy ray-curable water-based ink compositions of Examples 1 to 10 and Comparative Examples 1 and 2 according to the present invention, an on-demand type in which ink is ejected by applying thermal energy corresponding to the recording signal to the ink A bubble jet (registered trademark) printer PIXUS550i (manufactured by Canon Inc.) having a multi-recording head is exposed to an ultraviolet irradiation lamp (maximum irradiation intensity in the region of 300 to 400 nm is 1500 mW in the form adjacent to the recording head portion as shown in FIG. / Cm ² ) was used and evaluated according to the following methods and standards. Table 4 summarizes the evaluation results.

(4-1) Image Density For a sample prepared by printing a 100% solid pattern on PPC paper (made by Canon) using the modified machine and irradiating with ultraviolet rays, the reflection density was measured 24 hours after printing. Measurement was performed using a reflection densitometer Macbeth RD-918 (manufactured by Macbeth). The obtained results were evaluated according to the following criteria.
A: Reflection density is 1.3 or more B: Reflection density is 1.0 or more and less than 1.3 C: Reflection density is less than 1.0

(4-2) Character quality Using the modified machine, a sample printed and exposed with 16-point character patterns on PPC paper (manufactured by Canon) with predetermined ink was visually observed 24 hours after printing. The bleeding was evaluated according to the following criteria.
A: Almost no bleeding B: Some blurring characters can be seen C: Many blurring characters

(4-3) Bleed With respect to each of Examples 1 to 10 and Comparative Examples 1 and 2, an aqueous active energy ray-curable ink composition in which the pigment type of the pigment dispersion is Pigment Red 122 and Pigment Yellow 138 is also used. The ink set was prepared as cyan, magenta, and yellow.

Using the modified machine, a sample prepared by printing 100% solid parts of cyan, magenta, and yellow adjacent to each other on a PPC paper (Canon) with a predetermined ink set and irradiating with ultraviolet rays, 24 hours after printing The degree of bleeding at the boundary of each color was visually observed and evaluated according to the following criteria.
A: Bleed is almost inconspicuous B: Slightly bleed, but no problem level C: Bleed so that the color boundary line is not clear

1 is a schematic front view of a printer suitably used in an ink jet recording method according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ink tank part which accommodates the aqueous | water-based active energy ray hardening-type ink composition of this invention 2 The head part which an ink tank is attached and which actually records 3 Lamp part which performs ultraviolet irradiation for hardening 4 Head part and lamp part Drive unit for driving 5 Paper discharge unit for conveying a recording medium to be recorded

Claims (15)

  In the active energy ray-curable water-based ink composition containing at least water, a polymerizable substance that undergoes radical polymerization with active energy rays, and a polymerization initiator that generates radicals with active energy rays, the polymerizable substance comprises: An active energy ray-curable aqueous ink composition, which is a water-soluble compound having 2 to 6 meth) acrylic groups, and the polymerization initiator is a water-soluble acylphosphine oxide compound. The active energy ray-curable aqueous ink composition according to claim 1, wherein the polymerizable substance is a water-soluble (meth) acrylic acid ester compound represented by the following general formula (1).

(In the formula, Z represents a residue of a polyol having (x1 + y1) hydroxyl groups or a residue of an epoxy ester of a polyol, x1 is an integer of 0 to 2, y1 is an integer of 2 to 6, and x1 + y1 is 2) And R ₁ each independently represents a hydrogen atom or a methyl group, and R ₂ each independently represents an atomic group A represented by the following formula.

(In the formula, each R ₃ independently represents a hydrogen atom or a methyl group. M1 represents an integer of 1 to 5, and n1 represents 0 or 1.) The active energy ray-curable aqueous ink composition according to claim 1 or 2, wherein the polymerization initiator is a nonionic or anionic water-soluble acylphosphine oxide compound represented by the following general formula (2).

{In the formula, R ₄ represents an alkyl group or a phenyl group. R ₅ represents an alkyloxy group or a phenyl group. R ₆ represents an atomic group B represented by the following formula.

(In the formula, R ₇ represents — [CH ₂ ] x ₂ — (x2 is 0 or 1) or a phenylene group. M2 represents an integer of 0 to 10. n2 represents 0 or 1. R ₈ represents hydrogen. Represents an atom, a sulfone group, a carboxyl group, a hydroxyl group and a salt thereof)}   The active energy ray-curable water-based ink composition according to claim 1, wherein the water-based ink further contains a color material. The active energy according to any one of claims 1 to 4, wherein the water-based ink further contains, as another polymerization initiator, at least one compound selected from the group consisting of the following general formulas (3) to (5). A linear curable aqueous ink composition.

(In the formula, m3 represents an integer of 1 or more, n3 represents an integer of 0 or more, and m3 + n3 represents an integer of 1 to 8.)

(Wherein R ₁₂ and R ₁₃ each independently represents a hydrogen atom or an alkyl group. M4 represents an integer of 5 to 10)

(Wherein R ₁₂ and R ₁₃ each independently represents a hydrogen atom or an alkyl group. R ₁₄ represents — [CH ₂ ] x 3 (x3 is 0 or 1), —O— [CH ₂ ] y 3 —. (Y3 represents 1 or 2), or a substituted or unsubstituted phenylene group, and M represents a hydrogen atom or an alkali metal.   The active energy ray-curable water-based ink composition according to claim 1, wherein the water-based ink further contains at least one solvent selected from glycerin, ethylene glycol, and diethylene glycol.   The active energy ray-curable water-based ink composition according to claim 1, wherein the water-based ink is for inkjet recording.   The active energy ray-curable water-based ink composition according to claim 7, having a viscosity at 25 ° C. of 10 mPa · s or less.   9. The active energy ray-curable aqueous ink composition according to claim 7, wherein the surface tension at 25 ° C. is 35 mN / m (dyne / cm) or more.   A step of applying the active energy ray-curable aqueous ink composition according to any one of claims 7 to 9 onto a recording medium by an inkjet method, and an active energy ray to the recording medium provided with the aqueous ink composition An inkjet recording method comprising the step of curing the active energy ray-curable aqueous ink composition by irradiation of   The inkjet recording method according to claim 10, wherein the aqueous ink composition is applied onto a recording medium by applying thermal energy to the aqueous ink composition.   An ink cartridge comprising an ink containing portion containing the water-based ink composition according to claim 7.   A recording unit comprising: an ink storage unit storing the water-based ink composition according to claim 7; and a recording head for discharging the water-based ink composition.   Means for applying the aqueous ink composition according to any one of claims 7 to 9 onto a recording medium, and means for irradiating the aqueous ink composition applied onto the recording medium with active energy rays An ink jet recording apparatus comprising the ink jet recording apparatus. The inkjet recording according to claim 14, wherein the means for irradiating the active energy ray is an ultraviolet irradiation lamp having a light source having a wavelength of 450 nm or less, and an irradiation intensity of the ultraviolet portion is in a range of 500 to 5,000 mW / cm ^2. apparatus.

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