Actinic radiation curable ink, image forming method, and output

Abstract

To provide an active ray-curable ink having high antibacterial and antiviral properties, and an image formation method using the same and an output product thereof.SOLUTION: An active ray-curable ink contains at least a polymerizable compound and a photosensitizer, the photosensitizer having a singlet oxygen generating ability.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an actinic radiation curable ink, an image forming method, and an output product. More specifically, it relates to actinic radiation curable inks with high antibacterial and antiviral properties. [Background technology]

[0002] Actinic radiation-curable inks are widely used as inks that can form images with high abrasion resistance and adhesion even on non-absorbent media. Furthermore, with the recent spread of infectious diseases, there has been an increasing demand for printed materials with antibacterial and antiviral properties in the commercial and industrial printing fields. As one way to provide printed materials with antibacterial and antiviral properties, actinic radiation-curable inks are also required to have antibacterial and antiviral properties.

[0003] As a technology relating to actinic radiation-curable inks having antibacterial and antiviral properties, Patent Document 1 describes that an antibacterial composition comprising a silver-based antibacterial agent and a polymerizable compound can be used as a UV inkjet ink.

[0004] However, the silver-based antibacterial agent used in the invention described in Patent Document 1, as well as other commonly used antibacterial substances such as ionic compounds of copper, zinc, etc., and photocatalysts such as titanium oxide, have the drawback that they are not sufficiently effective in low-moisture, low-humidity environments. Furthermore, even if these antibacterial substances are contained in actinic radiation-curable ink, there is also the problem that the antibacterial and antiviral effects are only exerted in the area where the actinic radiation-curable ink is applied.

[0005] As mentioned above, there is room for improvement in conventional technology, and there has been a demand for actinic radiation-curable inks with stronger antibacterial and antiviral properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2019 / 172041 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above problems and circumstances, and its object is to provide an actinic radiation-curable ink with high antibacterial and antiviral properties, as well as an image forming method and output using the same. [Means for solving the problem]

[0008] In order to solve the above problems, the present inventors have investigated the causes of the above problems and have found that by incorporating a photosensitizer capable of generating singlet oxygen, it is possible to provide an actinic radiation-curable ink or the like that has high antibacterial and antiviral properties, which led to the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0009] An actinic radiation curable ink containing at least a polymerizable compound and a photosensitizer, The photosensitizer has singlet oxygen generating ability. death, The photosensitizer has a structure represented by the following general formula (1): do 1. An actinic radiation curable ink comprising: [ka] [In the above general formula (1), M represents a metal atom of Group 14. 1 and Q 2 Each independently represents a monovalent axial ligand. 1 and Q 2 It is not necessary to have either of the above. 1 ~A 4 each independently represents an atomic group forming an aromatic ring which may have a substituent.

[0010] 2. Contains a photopolymerization initiator, and The maximum absorption maximum wavelength of the photosensitizer in a monomolecular state is on the longer wavelength side than the absorption end of the absorption spectrum of the photopolymerization initiator. 2. The actinic radiation curable ink according to claim 1,

[0011] 3. The polymerizable compound is an actinic radiation polymerizable compound, and The maximum absorption maximum wavelength of the photosensitizer in a monomolecular state is on the longer wavelength side than the absorption end of the absorption spectrum of the actinic radiation-polymerizable compound. 2. The actinic radiation curable ink according to claim 1,

[0012] 4. The maximum absorption wavelength of the photosensitizer in a single molecule state is within the range of 360 to 800 nm. 4. The actinic radiation curable ink according to any one of items 1 to 3,

[0013] 5. Further contains a colorant 5. The actinic radiation curable ink according to any one of items 1 to 4,

[0015] 6 The coloring is due to the single molecule absorption spectrum of the photosensitizer. The first to second items are characterized by the 5 Item 1. The actinic radiation curable ink according to any one of items 1 to 5.

[0016] 7 An image forming method using actinic radiation curable ink, The actinic radiation curable ink is 6 The actinic radiation curable ink according to any one of the preceding items. An image forming method comprising:

[0017] 8 The difference between the maximum absorption wavelength of the photosensitizer in a monomolecular state and the maximum wavelength of the actinic ray irradiated when curing the actinic ray-curable ink is 100 nm or more. The first feature is 7 Item 1. An image forming method according to item 1.

[0018] 9 The actinic radiation curable ink is applied independently of the image area. The first feature is 7 Section or Article8 Item 1. An image forming method according to item 1.

[0019] 1 0 A foil is transferred onto the area where the actinic radiation curable ink is applied to form a decorative image. The first feature is 7 Section to section 9 Item 1. The image forming method according to any one of items 1 to 5.

[0020] 1 1 The actinic radiation curable ink is applied onto a recording medium by an inkjet method. The first feature is 7 Section 1 to 1 0 Item 1. The image forming method according to any one of items 1 to 5.

[0021] 1 2 An output formed using actinic radiation curable ink, The actinic radiation curable ink is 6 The actinic radiation curable ink according to any one of the preceding items. An output product characterized by the above. [Effects of the Invention]

[0022] The above-described means of the present invention can provide an actinic radiation-curable ink with high antibacterial and antiviral properties, as well as an image forming method and output using the same.

[0023] The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows.

[0024] The actinic radiation-curable ink of the present invention contains a photosensitizer capable of generating singlet oxygen, and generates singlet oxygen when exposed to room light. Singlet oxygen is known to have high antibacterial and antiviral properties even in low-humidity environments.

[0025] Furthermore, because singlet oxygen is a gas, it diffuses after it is generated, providing antibacterial and antiviral effects not only to the area where the actinic radiation-curable ink is applied, but also to the surrounding area.

[0026] It is believed that these mechanisms of expression or action can provide actinic radiation-curable inks and other products with high antibacterial and antiviral properties.

[0027] The antibacterial and antiviral effects of singlet oxygen generated by photosensitizers have been demonstrated by technology developed by a research institute at the University of Regensburg in Germany and TriOptoTec GmbH, as well as by a water-based varnish (Lock3) commercialized by Varcotec GmbH in Germany based on this technology (see, for example, https: / / www.sinsei-corp.co.jp / information / lock3.html). [Brief explanation of the drawings]

[0028] [Figure 1] Schematic diagram showing energy transfer between photosensitizer and oxygen [Figure 2] Diagram showing changes in absorption spectrum due to differences in the molecular aggregation state of photosensitizers [Figure 3] Schematic diagram of an inkjet image forming device 1 [Figure 4] Schematic diagram of inkjet image forming device 2 [Figure 5] 1 is a diagram showing each step of forming a decorative image; [Figure 6] FIG. 10 is a diagram illustrating a compression method for forming a decorative image. [Figure 7] Schematic diagram of decorative image forming device 1 [Figure 8] Schematic diagram of decorative image forming device 2 DETAILED DESCRIPTION OF THE INVENTION

[0029] The actinic radiation-curable ink of the present invention (hereinafter, the "actinic radiation-curable ink" may also be simply referred to as "ink") is an actinic radiation-curable ink containing at least a polymerizable compound and a photosensitizer, and is characterized in that the photosensitizer has the ability to generate singlet oxygen. This feature is a technical feature common to or corresponding to the following embodiments.

[0030] In an embodiment of the actinic radiation-curable ink of the present invention, it is preferred that the ink contains a photopolymerization initiator, and that the maximum absorption maximum wavelength of the photosensitizer in a monomolecular state is on the longer wavelength side than the absorption end of the absorption spectrum of the photopolymerization initiator. This allows the ink to be cured using actinic radiation that does not overlap with the absorption wavelength range of the photopolymerization initiator, and prevents the deactivation of the singlet oxygen generating ability of the photosensitizer.

[0031] In an embodiment of the actinic radiation-curable ink of the present invention, it is preferred that the polymerizable compound is an actinic radiation-polymerizable compound, and that the maximum absorption maximum wavelength of the photosensitizer in a monomolecular state is on the longer wavelength side than the absorption end of the absorption spectrum of the actinic radiation-polymerizable compound. This allows the ink to be cured using actinic radiation that does not overlap with the absorption wavelength range of the actinic radiation-polymerizable compound, and prevents deactivation of the singlet oxygen-generating ability of the photosensitizer.

[0032] In an embodiment of the actinic radiation-curable ink of the present invention, the maximum absorption maximum wavelength of the photosensitizer in a monomolecular state is preferably within the range of 360 to 800 nm, which can prevent the singlet oxygen generating ability of the photosensitizer from being deactivated when the ink is cured using ultraviolet light.

[0033] In an embodiment of the actinic radiation-curable ink of the present invention, a colorant may be further contained, which allows the color of the ink to be adjusted as desired.

[0034] In an embodiment of the actinic radiation-curable ink of the present invention, the photosensitizer preferably has a structure represented by the above general formula (1), which makes it easier for the photosensitizer to be contained in the ink in a monomolecular state with high singlet oxygen generating ability.

[0035] In an embodiment of the actinic radiation-curable ink of the present invention, it is preferable that the ink exhibits a color derived from the monomolecular absorption spectrum of the photosensitizer, which allows visual confirmation of whether or not the photosensitizer contained in the ink fixed on a recording medium has singlet oxygen generating ability.

[0036] The image forming method of the present invention is an image forming method using actinic radiation curable ink, characterized in that the actinic radiation curable ink is the actinic radiation curable ink of the present invention.

[0037] In an embodiment of the image forming method of the present invention, the difference between the maximum absorption wavelength of the photosensitizer in a monomolecular state and the maximum absorption wavelength of the actinic ray irradiated when curing the actinic ray-curable ink is preferably 100 nm or more, thereby preventing the loss of singlet oxygen generating ability due to absorption of the actinic ray irradiated when curing the ink.

[0038] In an embodiment of the image forming method of the present invention, it is preferable to apply the actinic radiation-curable ink independently of the image area, which allows the ink to be applied regardless of the image pattern, and can provide, for example, antibacterial and antiviral effects to the entire surface of the printed product.

[0039] In a preferred embodiment of the image forming method of the present invention, a decorative image is formed by transferring a foil onto the area where the actinic radiation-curable ink has been applied, thereby obtaining a decorative image and output product that are endowed with antibacterial and antiviral properties.

[0040] In a preferred embodiment of the image forming method of the present invention, the actinic radiation-curable ink is applied to a recording medium by an inkjet system, which makes it possible to form an image imparted with antibacterial and antiviral properties on demand.

[0041] The output product of the present invention is an output product formed using actinic radiation curable ink, characterized in that the actinic radiation curable ink is the actinic radiation curable ink of the present invention.

[0042] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0043] (1) Actinic radiation curable ink The actinic radiation curable ink of the present invention is an actinic radiation curable ink containing at least a polymerizable compound and a photosensitizer, and is characterized in that the photosensitizer has the ability to generate singlet oxygen.

[0044] (1.1) Photosensitizers The photosensitizer according to the present invention is characterized by having the ability to generate singlet oxygen.

[0045] The content of the photosensitizer is preferably in the range of 0.001 to 1% by mass, and more preferably in the range of 0.01 to 0.1% by mass, relative to the total mass of the ink.

[0046] (Singlet oxygen generation ability) "Singlet oxygen generating ability" refers to the property of being able to generate singlet oxygen by exciting triplet-state oxygen molecules present in the air, etc., to a singlet state. In other words, the photosensitizer according to the present invention needs to be contained in the ink in a state that allows it to generate singlet oxygen.

[0047] In the case of the photosensitizer according to the present invention, the photosensitizer PS(T1) that has been brought into a triplet excited state by photoexcitation and intersystem crossing transfers energy to the nearby triplet oxygen O2( 3 Σ g ) is excited to produce singlet oxygen O2 ( 1 Δ g ) is generated (see Figure 1).

[0048] The excitation energy in the triplet excited state T1 is triplet oxygen O2( 3 Σ g ), triplet oxygen O2 ( 3 Σ g ) energy transfer to singlet oxygen O2( 1 Δ g ) can be generated.

[0049] Common antibacterial substances such as ionic compounds of silver, copper, zinc, etc., and photocatalysts such as titanium oxide, are not sufficiently effective in low-humidity environments, but singlet oxygen is known to have sufficient antibacterial and antiviral effects even in low-humidity environments. Therefore, by using the ink of the present invention, it is possible to produce printed objects with high antibacterial and antiviral properties even in low-humidity environments where bacteria and viruses are likely to be a problem.

[0050] Furthermore, because singlet oxygen is a gas, it diffuses after generation, providing antibacterial and antiviral effects not only to the area where the ink is applied, but also to the surrounding area. Furthermore, the diffusion distance of singlet oxygen (the distance it diffuses before reverting to triplet oxygen and losing its antibacterial and antiviral effects) depends on humidity; the lower the humidity, the greater the diffusion distance. Therefore, the ink of the present invention is particularly effective in low-humidity environments.

[0051] The diffusion distance of singlet oxygen can be calculated by the following formula. Expression X 2 =2Dt X: Diffusion distance [m] D: Diffusion coefficient [m 2 / sec] t: Life [seconds]

[0052] Using the above formula, the diffusion distance X of singlet oxygen at a humidity of 50% can be calculated to be approximately 1.57 mm. Here, the diffusion coefficient D and the lifetime t are calculated as follows: the diffusion coefficient D at a humidity of 50% is 2 × 10 -5 m 2 / sec, and the lifetime t at 50% humidity is 62×10 -3 He cited a reported figure of seconds.

[0053] From the above calculation results, singlet oxygen can diffuse up to a range of approximately 1.57 mm in an environment with a humidity of 50%, so if the ink of the present invention is present on a printed object with a dot spacing of 3 mm, it is calculated that the generated singlet oxygen will diffuse over roughly the entire surface of the printed object.

[0054] If the dot spacing is 3 mm, adjusting the dot size to, for example, 30 μm makes it possible to apply an ink that exhibits a color derived from a photosensitizer so that it is invisible. Therefore, by applying the ink of the present invention to the entire surface of a recording medium with an invisible dot size and dot spacing, it is possible to impart antibacterial and antiviral effects to the entire surface of the printed material without degrading image quality.

[0055] (Confirmation of singlet oxygen generation ability) Whether or not the photosensitizer in the ink is in a state capable of generating singlet oxygen can be determined by detecting phosphorescence derived from singlet oxygen.

[0056] In this case, the ink is first applied to a recording medium and then photocured to fix the ink to the recording medium. When the recording medium on which the ink has been fixed is irradiated with monochromatic light corresponding to the maximum absorption wavelength of the photosensitizer in a single molecular state, if phosphorescence having a maximum emission wavelength attributable to singlet oxygen around 1270 nm is observed, it can be determined that the photosensitizer in the ink is in a state capable of generating singlet oxygen. Phosphorescence can be measured using, for example, a spectrofluorometer (EP-8700 manufactured by JASCO Corporation).

[0057] (Molecular aggregation state of photosensitizer) The molecular aggregation state of the photosensitizer in the ink is not particularly limited as long as it is in a state that allows singlet oxygen to be generated. For example, it may be in a monomolecular state or an aggregated state. However, since the photosensitizer can generate singlet oxygen more efficiently in a monomolecular state, it is preferable that the ink of the present invention contains the photosensitizer in a monomolecular state.

[0058] Whether or not the photosensitizer contained is in a monomolecular state can be determined by whether or not an absorption peak of the photosensitizer in a monomolecular state is present in the absorption spectrum of the ink. For example, in the case of a photosensitizer that has an absorption peak with a maximum absorption maximum at 680 nm in a monomolecular state, if an absorption peak at 680 nm is present in the absorption spectrum of the ink, it can be determined that the photosensitizer contained is in a monomolecular state. In the case of pigment-containing ink, this can be determined without being affected by the pigment by measuring the absorption spectrum of the ink after separating and removing the solid component consisting of the pigment using a centrifuge.

[0059] This determination is possible because the absorption spectrum of the compound used as the photosensitizer differs between the monomolecular state and the aggregated state. Figure 2 shows an example of the absorption spectrum of a phthalocyanine compound, which has an absorption peak with a maximum absorption maximum at 680 nm in the monomolecular state. Thus, while the absorption spectrum in the monomolecular state (Figure 2(a)) has an absorption peak at 680 nm, the absorption spectrum in the aggregated state (Figure 2(b)) broadens due to intermolecular interactions and other factors, and the absorption peak shifts to the long-wave or short-wave side depending on the molecular orientation. Because these differences in the absorption spectrum of the photosensitizer also affect the absorption spectrum of the ink, whether the photosensitizer contained is in a monomolecular state can be determined by whether the absorption peak of the monomolecular photosensitizer is present in the absorption spectrum of the ink.

[0060] In addition, if the ink does not contain a pigment, this determination method can be performed not only from the absorption spectrum of the liquid ink, but also from the absorption spectrum of the cured ink present on the printed material.

[0061] (Ink indicator properties) The ink of the present invention preferably exhibits a color derived from the monomolecular absorption spectrum of the photosensitizer as an indicator of the photosensitizer's ability to generate singlet oxygen, which makes it possible to visually confirm whether the photosensitizer contained in the ink fixed on a recording medium has singlet oxygen generating ability, without detecting phosphorescence derived from singlet oxygen as described above.

[0062] In inks that exhibit such indicator properties, when the photosensitizer has the ability to generate singlet oxygen, the ink must exhibit a color derived from the monomolecular absorption spectrum of the photosensitizer, and therefore the photosensitizer must be contained in a monomolecular state.

[0063] Ink that exhibits indicator properties has the property that when the molecular structure or molecular aggregation state of the photosensitizer changes due to deterioration over time or the like and it no longer exhibits the coloring derived from the monomolecular absorption spectrum, it also loses its singlet oxygen generating ability.

[0064] Therefore, for example, if an ink exhibiting indicator properties contains a photosensitizer that exhibits a blue color due to a monomolecular absorption spectrum, when the ink no longer exhibits the blue color, it can be determined that the ink has lost its singlet oxygen generating ability and the associated antibacterial effect.

[0065] (Absorption wavelength range of photosensitizer considering actinic rays) Since the ink of the present invention is actinic radiation-curable, it must be designed on the assumption that actinic radiation will be irradiated during image formation. The photosensitizer can generate singlet oxygen to a certain extent continuously, even though it will deteriorate over time due to light absorption, provided that the light intensity is comparable to that of indoor light. However, if the absorption wavelength range of the photosensitizer largely overlaps with the wavelength range of the actinic radiation irradiated during image formation, the photosensitizer may rapidly deteriorate upon irradiation with actinic radiation, and its singlet oxygen generating ability may be lost. Therefore, for the ink of the present invention, it is preferable to select a photosensitizer taking into account the wavelength range of the actinic radiation irradiated during image formation.

[0066] The wavelength of the actinic light irradiated during image formation is set to match the absorption wavelength of the photopolymerization initiator or actinic light-polymerizable compound contained in the ink. Therefore, when the ink contains a photopolymerization initiator, it is preferable that the maximum absorption maximum wavelength of the photosensitizer in a monomolecular state is longer than the absorption end of the absorption spectrum of the photopolymerization initiator. Alternatively, when the ink contains an actinic light-polymerizable compound, it is preferable that the maximum absorption maximum wavelength of the photosensitizer in a monomolecular state is longer than the absorption end of the absorption spectrum of the actinic light-polymerizable compound. This allows the ink to be cured using actinic light that does not overlap with the absorption wavelength range of the photosensitizer, thereby avoiding deactivation of the singlet oxygen-generating ability of the photosensitizer.

[0067] In the present invention, the "absorption end of the absorption spectrum" refers to the point that appears on the longest wavelength side among the points at which the absorption intensity curve on the side where the light absorption intensity decreases from the maximum point of absorbance at the light absorption peak (also referred to as "light absorption band") reaches a value equivalent to the baseline (a baseline obtained by correcting with an absorption spectrum measured excluding the object to be measured) in an optical spectrum obtained by absorbance measurement with an ultraviolet-visible spectrophotometer.

[0068] Furthermore, assuming that commonly used ultraviolet rays are used as actinic rays, the maximum absorption wavelength of the photosensitizer in a monomolecular state is preferably within the range of 360 to 800 nm, and more preferably within the range of 500 to 800 nm, which can prevent the singlet oxygen generating ability of the photosensitizer from being deactivated when the ink is cured using ultraviolet rays.

[0069] (Compounds that can be used as photosensitizers) The compound that can be used as the photosensitizer according to the present invention is not particularly limited as long as it can be contained in the ink in a state that allows it to generate singlet oxygen. For example, conventionally known compounds that can be used as photosensitizers capable of generating singlet oxygen include phthalocyanine compounds, naphthalocyanine compounds, phenalene compounds, and rose bengal compounds.

[0070] Among these compounds, phthalocyanine compounds are preferred, and those having a structure represented by the following general formula (1) are particularly preferred because they are easily contained in the ink in a monomolecular state with high singlet oxygen generating ability.

[0071] [ka]

[0072] [In the above general formula (1), M represents a metal atom of Group 14. Q1 and Q2 each independently represent a monovalent axial ligand. Note that the above general formula (1) may not have either Q1 or Q2. A1 to A4 each independently represent an atomic group forming an aromatic ring which may have a substituent.]

[0073] The central metal atom M is a metal atom of Group 14, and thus can take multiple axial ligands in the vertical direction of the conjugated plane. In the present invention, the metal atom of Group 14 also includes Si, and specific examples thereof include Si, Ge, Sn, and Pb. Among these, the silicon atom Si is preferred.

[0074] In compounds having a structure represented by general formula (1), the axial ligands (Q1, Q2) suppress the π-π stacking interactions of the conjugated plane, making it difficult for the photosensitizers to aggregate, and therefore making them more likely to form monomolecular structures.

[0075] In the present invention, the term "axial ligand" refers to a ligand that is coordinated from above and below the plane that constitutes the phthalocyanine ring.

[0076] Examples of substituents that the atomic groups A1 to A4 may have include electron-withdrawing groups such as a chlorine atom, a methyl chloride halide group (-CClX2) (where X is a halogen atom), a fluoromethyl group (-CH2F), a trifluoromethyl group (-CF3), and a nitro group (-NO2), as well as alkyl and alkoxy groups. In particular, alkyl or alkoxy groups having 4 to 18 carbon atoms are preferred from the viewpoint of solubility in polymerizable compounds. The alkyl or alkoxy groups may further have a substituent.

[0077] Furthermore, the solubility of the photosensitizer in the polymerizable compound can be improved by adopting a molecular structure that allows the introduction of a soluble group into the aromatic rings (A1 to A4) or the axial ligands (Q1 and Q2). In particular, introducing a soluble group into the axial ligands (Q1 and Q2) is preferable because it effectively suppresses the π-π stacking interaction of the conjugated planes of the molecules due to steric hindrance.

[0078] Among the compounds having a structure represented by general formula (1), compounds having a structure represented by the following general formula (1F) or (1G) are more preferred.

[0079] [ka]

[0080] [ka]

[0081] [In general formula (1F) and general formula (1G), M, Q1, and Q2 have the same meanings as M, Q1, and Q2 in general formula (1), respectively. R1 to R4 each independently represent a hydrogen atom or a substituent.]

[0082] Examples of the substituents R1 to R4 include electron-withdrawing groups such as a chlorine atom, a methyl chloride halide group (-CClX2) (where X is a halogen atom), a fluoromethyl group (-CH2F), a trifluoromethyl group (-CF3), and a nitro group (-NO2), as well as alkyl and alkoxy groups. In particular, alkyl or alkoxy groups having 4 to 18 carbon atoms are preferred from the viewpoint of solubility in the polymerizable compound. The alkyl or alkoxy group may further have a substituent.

[0083] Preferred specific examples of compounds having a structure represented by general formula (1F) or general formula (1G) are exemplified in Table I. Note that * in Q1 and Q2 indicates the bonding site with M.

[0084] [Table 1]

[0085] [ka]

[0086] Next, a compound having a structure represented by general formula (H) will be described as a compound that does not have a structure represented by general formula (1) but can be used as a photosensitizer according to the present invention.

[0087] [ka]

[0088] [In general formula (H), M' represents a metal atom other than that of Group 14 or two hydrogen atoms (2H). Q1' represents a monovalent or divalent axial ligand. R1 to R4 each independently represent a hydrogen atom or a substituent.]

[0089] Examples of the substituents R1 to R4 include electron-withdrawing groups such as a chlorine atom, a methyl chloride halide group (-CClX2) (where X is a halogen atom), a fluoromethyl group (-CH2F), a trifluoromethyl group (-CF3), and a nitro group (-NO2), as well as alkyl and alkoxy groups. In particular, alkyl or alkoxy groups having 4 to 18 carbon atoms are preferred from the viewpoint of solubility in the polymerizable compound. The alkyl or alkoxy group may further have a substituent.

[0090] Preferred examples of compounds having a structure represented by general formula (H) are shown in Table II. Note that the * in Q1′ represents the bonding site with M.

[0091] [Table 2]

[0092] Next, examples of compounds that can be used as the photosensitizer according to the present invention other than the compounds listed above are given below. However, the compounds that can be used as the photosensitizer according to the present invention are not limited to these.

[0093] [ka]

[0094] (1.2) Polymerizable compound The ink of the present invention is characterized by containing a polymerizable compound.

[0095] The content of the polymerizable compound is preferably within a range from 1 to 97% by mass, and more preferably within a range from 30 to 90% by mass, relative to the total mass of the ink.

[0096] The polymerizable compound is not particularly limited as long as it can be used in an actinic radiation-curable ink, and can be a compound that initiates a polymerization reaction upon irradiation with actinic radiation in the presence or absence of a photopolymerization initiator and cures through polymerization and crosslinking. The polymerizable compound may be any of a monomer, a polymerizable oligomer, a prepolymer, and a mixture thereof.

[0097] Among polymerizable compounds, a polymerizable compound that can initiate a polymerization reaction by itself upon irradiation with actinic rays (e.g., electron beams) even in the absence of a photopolymerization initiator and can be sufficiently cured is referred to in the present invention as an "actinic ray-polymerizable compound."

[0098] Examples of the polymerizable compound include a cationically polymerizable compound, a radically polymerizable compound, or a mixture thereof. In particular, from the viewpoint of the polymerization rate and degree of polymerization, a radically polymerizable compound is preferred.

[0099] The term "radical polymerizable compound" refers to a compound having an ethylenically unsaturated double bond in the molecule. The radical polymerizable compound may be either a monofunctional or polyfunctional compound. An example of the radical polymerizable compound is (meth)acrylate, which is an unsaturated carboxylic acid ester compound. In the present invention, "(meth)acrylate" refers to acrylate or methacrylate, "(meth)acryloyl group" refers to acryloyl group or methacryloyl group, and "(meth)acrylic" refers to acrylic or methacrylic.

[0100] Examples of monofunctional (meth)acrylates include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomylstyryl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypoly Examples include ethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl-phthalate, and t-butylcyclohexyl (meth)acrylate.

[0101] Examples of polyfunctional (meth)acrylates include triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, PO adduct di(meth)acrylate of bisphenol A, hydroxypivalic acid neopentyl glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, Examples of the acrylate include bifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate, polyethylene glycol diacrylate, and tripropylene glycol diacrylate; trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; tri- or higher functional (meth)acrylates such as pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin propoxy tri(meth)acrylate, and pentaerythritol ethoxy tetra(meth)acrylate; oligomers having (meth)acryloyl groups, including polyester acrylate oligomers, and modified products thereof. Examples of the modified products include ethylene oxide-modified (EO-modified) acrylates in which ethylene oxide groups are inserted, and propylene oxide-modified (PO-modified) acrylates in which propylene oxide is inserted.

[0102] The term "cationically polymerizable compound" refers to a compound having a cationically polymerizable group in the molecule. Examples of the cationically polymerizable compound include epoxy compounds, vinyl ether compounds, and oxetane compounds.

[0103] Examples of the epoxy compound include alicyclic epoxy resins such as 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene monoepoxide, ε-caprolactone-modified 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate, 1-methyl-4-(2-methyloxiranyl)-7-oxabicyclo[4,1,0]heptane, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexanone-meta-dioxane, and bis(2,3-epoxycyclopentyl)ether, diglycidyl ether of 1,4-butanediol, diglycidyl ether of 1,6-hexanediol, and glycerin. Examples of the epoxy compounds include aliphatic epoxy compounds including triglycidyl ethers of bisphenol A, triglycidyl ethers of trimethylolpropane, diglycidyl ethers of polyethylene glycol, diglycidyl ethers of propylene glycol, and polyglycidyl ethers of polyether polyols obtained by adding one or more alkylene oxides (ethylene oxide, propylene oxide, etc.) to aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, and glycerin; and aromatic epoxy compounds including di- or polyglycidyl ethers of bisphenol A or its alkylene oxide adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or its alkylene oxide adducts, and novolac-type epoxy resins.

[0104] Examples of the vinyl ether compound include monovinyl ether compounds such as ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-o-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether; and di- or trivinyl ether compounds such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, and trimethylolpropane trivinyl ether.

[0105] Examples of the oxetane compound include 3-hydroxymethyl-3-methyloxetane, 3-hydroxymethyl-3-ethyloxetane, 3-hydroxymethyl-3-propyloxetane, 3-hydroxymethyl-3-n-butyloxetane, 3-hydroxymethyl-3-phenyloxetane, 3-hydroxymethyl-3-benzyloxetane, 3-hydroxyethyl-3-methyloxetane, 3-hydroxyethyl-3-ethyloxetane, 3-hydroxyethyl-3-propyloxetane, 3-hydroxyethyl butyl-3-phenyloxetane, 3-hydroxypropyl-3-methyloxetane, 3-hydroxypropyl-3-ethyloxetane, 3-hydroxypropyl-3-propyloxetane, 3-hydroxypropyl-3-phenyloxetane, 3-hydroxybutyl-3-methyloxetane, 1,4 bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and di[1-ethyl(3-oxetanyl)]methyl ether.

[0106] (1.3) Photopolymerization initiator The ink of the present invention preferably further contains a photopolymerization initiator as needed.

[0107] The content of the photopolymerization initiator can be set arbitrarily as long as the ink is sufficiently cured by irradiation with actinic rays and the ink jet ejection stability of the ink is not impaired. For example, the content of the photopolymerization initiator is preferably in the range of 0.1 to 20% by mass, and more preferably in the range of 1.0 to 12% by mass, relative to the total mass of the ink.

[0108] The photopolymerization initiator may be any photopolymerization initiator capable of initiating polymerization of the polymerizable compound. For example, when the ink contains a radically polymerizable compound, the photopolymerization initiator is a radical-based photopolymerization initiator, and when the ink contains a cationic polymerizable compound, the photopolymerization initiator is a cationic-based photopolymerization initiator.

[0109] The photopolymerization initiator may be used alone or in combination of two or more kinds. Also, both a radical photopolymerization initiator and a cationic photopolymerization initiator may be used in combination.

[0110] Radical photopolymerization initiators include intramolecular bond cleavage type and intramolecular hydrogen abstraction type.

[0111] Examples of the intramolecular bond cleavage type radical photopolymerization initiator include acetophenone-based initiators such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-methylthiophenyl)propan-1-one, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone; benzoin-based initiators such as benzoin, benzoin methyl ether, and benzoin isopropyl ether; acylphosphine oxide-based initiators; and benzyl and methylphenyl glyoxyesters.

[0112] Among these, acylphosphine oxide-based polymerization initiators are preferred from the viewpoint of further improving the curability of the polymerizable compound, particularly the curability in a curing process using UV-LED light.

[0113] The acylphosphine oxide polymerization initiator is not particularly limited, and examples thereof include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0114] Furthermore, examples of commercially available acylphosphine oxide polymerization initiators include IRGACURE (registered trademark) 819 (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide), IRGACURE (registered trademark) 1800 (a mixture of bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and 1-hydroxy-cyclohexyl-phenyl ketone in a mass ratio of 25:75), and IRGACURE (registered trademark) TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide).

[0115] Examples of the intramolecular hydrogen abstraction type radical photopolymerization initiator include benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated benzophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone initiators including 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone; Michler's ketone; aminobenzophenone initiators including 4,4'-diethylaminobenzophenone; 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone.

[0116] Examples of cationic photopolymerization initiators include photoacid generators, such as aromatic onium compounds B(C6F5)4, including diazonium, ammonium, iodonium, sulfonium, and phosphonium. - , PF6 - , AsF6 - , SbF6 - , CF3SO3 -These include salts, sulfonates that generate sulfonic acid, halides that photogenerate hydrogen halide, and iron-allene complexes.

[0117] (1.4) Colorants The ink of the present invention may further contain a colorant as needed, which allows it to be used as a colored ink with high antibacterial and antiviral properties.

[0118] The content of the colorant is preferably in the range of 0.1 to 20% by mass, and more preferably in the range of 0.4 to 10% by mass, relative to the total mass of the ink. When the content of the pigment or dye is 0.1% by mass or more, good color development is obtained, and when it is 20% by mass or less, the ink has an appropriate viscosity.

[0119] In the present invention, the term "colorant" refers to a component that is contained mainly for the purpose of coloring, separately from a component capable of generating singlet oxygen, such as the photosensitizer.

[0120] The colorant is not particularly limited, and examples thereof include pigments and dyes. From the viewpoint of obtaining dispersion stability and weather resistance of the ink, the colorant is preferably a pigment. From the viewpoint of not reducing the sensitivity of the curing reaction due to irradiation with actinic rays, it is preferable to select a compound that does not function as a polymerization inhibitor.

[0121] The pigment is not particularly limited, and examples thereof include known organic pigments and inorganic pigments, as well as resin particles dyed with dyes, commercially available pigment dispersions, and surface-treated pigments (for example, pigments dispersed in an insoluble resin as a dispersion medium, or pigments with a resin grafted onto the surface). Examples of the pigments include those described in "Dictionary of Pigments" edited by Seijiro Ito (published in 2000), "Industrial Organic Pigments" by W. Herbst and K. Hunger, and JP-A Nos. 2002-12607, 2002-188025, 2003-26978, and 2003-342503.

[0122] Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 53:1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 88, 104, 108, 112, 122, 123, 144, 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, and 257; Pigment Violet 3, 19, 23, 29, 30, 37, 50, and 88; and Pigment Orange. 13, 16, 20, 36 or a mixture thereof.

[0123] Examples of blue or cyan pigments include pigments selected from Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17-1, 22, 27, 28, 29, 36, and 60, or mixtures thereof.

[0124] Examples of green pigments include pigments selected from Pigment Green 7, 26, 36, and 50, or mixtures thereof.

[0125] Examples of yellow pigments include pigments selected from Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, and 193, or mixtures thereof.

[0126] Examples of black pigments include pigments selected from Pigment Black 7, 26, and 28, and mixtures thereof.

[0127] Examples of the white pigment include titanium oxide and hollow particles.

[0128] Examples of commercially available pigments include Chromofine Yellow 2080, 5900, 5930, AF-1300, 2700L, Chromofine Orange 3700L, 6730, Chromofine Scarlet 6750, Chromofine Magenta 6880, 6886, 6891N, 6790, 6887, Chromofine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, Chrome Fine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Chrome Fine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400(B), 2500, 2600, ZAY-260, 2700(B), 2770, Seikafast Red 8040, C405(F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seikafast Carmine 6B 1476T-7, 1483LT, 3840, 3870, Seikafast Bordeaux 10B-430, Seikalite Rose R40, Seikalite Violet B 800, 7805, Seikafast Maroon 460N, Seikafast Orange 900, 2900, Seikalite Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (all manufactured by Dainichiseika Color & Chemicals); KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (all manufactured by Dainippon Ink & Chemicals);Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pigment Yellow1705, Colortex Orange 202, Colortex Red101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, USN, Colortex Maroon601, Colortex BrownB610N, Colortex Violet600, Pigment Red 122, Colortex Blue516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403, Colortex Black 702, U905 (all manufactured by Sanyo Dyes); Lionol Yellow 1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (all manufactured by Toyo Ink); Toner Magenta E02, Permanent Rubin F6B, Toner Yellow HG, Permanent Yellow GG-02, Hostapearm Blue B2G (all manufactured by Hoechst Industrie); Novoperm P-HG, Hostaperm Pink E, Hostaperm Blue B2G (all manufactured by Clariant); carbon black #2600, #2400, #2350, #2200, #1000, #990, #980, #970, #960, #950, #850, MCF88, #750, #650, MA600, MA7, MA8, MA11, MA100, MA100R, MA77, #52, #50, #47, #45, #45L, #40, #33, #32, #30, #25, #20, #10, #5, #44, and CF9 (all manufactured by Mitsubishi Chemical Corporation) are examples.

[0129] The average particle size of the pigment is not particularly limited, but since the finer the particle size, the better the color development, it is preferably in the range of 0.01 to 0.4 μm, and more preferably in the range of 0.02 to 0.2 μm. The maximum particle size of the pigment is preferably about 3 μm, and more preferably about 1 μm. The particle size of the pigment can be adjusted by selecting the type of pigment, dispersant, dispersion medium, dispersion conditions, filtration conditions, etc. Controlling the particle size of the pigment can prevent clogging of the head nozzle and maintain the storage stability, transparency, and curing sensitivity of the ink.

[0130] The particle size of the pigment can be measured by a known measurement method, specifically, a centrifugal sedimentation light transmission method, an X-ray transmission method, a laser diffraction scattering method, or a dynamic light scattering method.

[0131] The colorant may be used alone or in combination of two or more kinds.

[0132] (1.5) Gelling agent The ink of the present invention preferably further contains a gelling agent, if necessary.

[0133] The content of the gelling agent is 0.5 to 10% by mass, preferably 1 to 7% by mass, based on the total mass of the ink. When the content is 0.5% by mass or more, the ink droplets can be sufficiently gelled (sol-gel phase transition due to temperature). When the content is 10% by mass or less, the gelling agent can be sufficiently dissolved in the ink, and the inkjet ejection stability of the ink will not be reduced.

[0134] The gelling agent has the function of imparting sol-gel phase transition properties to the ink, which will be described later. Such a gelling agent must be able to dissolve in polymerizable compounds at least at temperatures higher than the sol-gel phase transition temperature, and must be able to crystallize at temperatures below the sol-gel phase transition temperature.

[0135] While the type of gelling agent is not particularly limited, it is preferable that, when crystallized in the ink, a space is formed three-dimensionally surrounded by plate-like crystals, which are crystallized products of the gelling agent, and that the polymerizable compound is encapsulated in this space. This structure, in which the polymerizable compound is encapsulated in the space three-dimensionally surrounded by the plate-like crystals, is sometimes referred to as a "house of card structure." When the house of card structure is formed, the polymerizable compound is retained within the house of card structure, and the ink droplets are pinned. In other words, the ink droplets are less likely to spread after landing on the recording medium, making it possible to form images with fine patterns. For the ink droplets to form a house of card structure after landing on the recording medium, it is preferable that the polymerizable compound dissolved in the ink and the gelling agent are compatible. Furthermore, when forming images using an inkjet system, it is important that the polymerizable compound and the gelling agent have good compatibility in the ink in a sol state (at high temperatures) in order to stably eject ink droplets from an inkjet recording device.

[0136] Examples of such gelling agents include: Aliphatic ketone compounds; Aliphatic ester compounds; Petroleum-based waxes such as paraffin wax, microcrystalline wax, and petrolactam; vegetable waxes such as candelilla wax, carnauba wax, rice wax, Japan wax, jojoba oil, jojoba solid wax, and jojoba esters; Animal-based waxes such as beeswax, lanolin, and spermaceti; Mineral waxes such as montan wax and hydrogenated wax; hydrogenated castor oil or hydrogenated castor oil derivatives; Modified waxes such as montan wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives, and polyethylene wax derivatives; Higher fatty acids such as behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, and erucic acid; higher alcohols such as stearyl alcohol and behenyl alcohol; hydroxystearic acids such as 12-hydroxystearic acid; 12-hydroxystearic acid derivatives; fatty acid amides such as lauric acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, and 12-hydroxystearic acid amide (e.g., the Nikkaamide series manufactured by Nippon Kasei Co., Ltd., the ITOWAX series manufactured by Ito Oil Mills, and the FATTYAMID series manufactured by Kao Corporation); N-substituted fatty acid amides such as N-stearyl stearic acid amide and N-oleyl palmitic acid amide; Special fatty acids such as N,N'-ethylenebisstearylamide, N,N'-ethylenebis-12-hydroxystearylamide, and N,N'-xylylenebisstearylamide amide; higher amines such as dodecylamine, tetradecylamine, and octadecylamine; Fatty acid ester compounds such as stearyl stearic acid, oleyl palmitic acid, glycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, ethylene glycol fatty acid esters, and polyoxyethylene fatty acid esters (e.g., the EMALLEX series manufactured by Nippon Emulsion Co., Ltd., the Rikemal series manufactured by Riken Vitamin Co., Ltd., and the Poem series manufactured by Riken Vitamin Co., Ltd.); Sucrose fatty acid esters such as sucrose stearic acid and sucrose palmitic acid (e.g., Ryoto Sugar Ester series, manufactured by Mitsubishi Chemical Foods Corporation); Synthetic waxes such as polyethylene wax and α-olefin maleic anhydride copolymer wax (Baker-Petrolite's UNILIN series, etc.); Dimer acid; Dimer diol (CRODA PRIPOR series, etc.); fatty acid inulins such as stearate inulin; Fatty acid dextrins such as dextrin palmitate and dextrin myristate (e.g., the Leo Pearl series manufactured by Chiba Flour Milling Co., Ltd.); Glyceryl Behenate Eicosandioate; Eicosanepolyglyceryl behenate (such as the Nomcoat series manufactured by Nisshin Oillio Co., Ltd.); Amide compounds such as N-lauroyl-L-glutamic acid dibutylamide and N-(2-ethylhexanoyl)-L-glutamic acid dibutylamide (available from Ajinomoto Fine-Techno); dibenzylidene sorbitols such as 1,3:2,4-bis-O-benzylidene-D-glucitol (Gelol D available from Shin-Nippon Rika); low molecular weight oil gelling agents described in JP 2005-126507 A, JP 2005-255821 A, and JP 2010-111790 A; etc. are included.

[0137] The gelling agent molecule preferably contains a linear alkyl structure having 12 or more carbon atoms. A linear alkyl structure having 12 or more carbon atoms refers to a structure consisting of a linear alkyl group, the linear portion of which contains 12 or more carbon atoms. When the gelling agent molecule contains a linear alkyl structure having 12 or more carbon atoms, the aforementioned house-of-cards structure is more likely to be formed.

[0138] Specific examples of gelling agents having such a structure include aliphatic ketone compounds, aliphatic ester compounds, higher fatty acids, higher alcohols, fatty acid amides, etc., each having a linear alkyl group having 12 or more carbon atoms.

[0139] Among these, from the viewpoint of easily increasing the hydrophobicity of the adhesive layer made of the cured ink, it is preferable that the gelling agent is an aliphatic ketone represented by the following general formula (2), or a fatty acid or aliphatic ester represented by the general formula (3).

[0140] R1-CO-R2...General formula (2) [In general formula (2), R1 and R2 each independently represent a linear or branched hydrocarbon group having 1 to 24 carbon atoms, provided that at least one of R1 and R2 contains a linear alkyl structure having 12 or more carbon atoms.]

[0141] R1 and R2 are each independently more preferably a straight-chain hydrocarbon group having 1 to 24 carbon atoms, and even more preferably a straight-chain hydrocarbon group having 8 to 22 carbon atoms. Preferably, both R1 and R2 contain a straight-chain alkyl structure having 12 or more carbon atoms.

[0142] In the aliphatic ketone represented by the general formula (2), the linear alkyl structure preferably has 12 to 24 carbon atoms. When the linear alkyl structure has 12 or more carbon atoms, the crystallinity of the gelling agent is likely to be increased. Furthermore, in the house-of-card structure, the polymerizable compound is likely to be sufficiently encapsulated, making it easier to form a dense image. On the other hand, when the linear alkyl structure has 24 or less carbon atoms, the melting point of the gelling agent is not excessively high, and the gelling agent is sufficiently soluble in the ink.

[0143] Examples of aliphatic ketones represented by the general formula (2) include dilignoceryl ketone (C24-C24), dibehenyl ketone (C22-C22, melting point 88°C), distearyl ketone (C18-C18, melting point 84°C), dieicosyl ketone (C20-C20), dipalmityl ketone (C16-C16, melting point 80°C), dimyristyl ketone (C14-C14), dilauryl ketone (C12-C12, melting point 68°C), lauric acid ketone (C16-C16, melting point 80°C), and lauric acid ketone (C16-C16, melting point 80°C). Myristyl myristyl ketone (C12-C14), lauryl palmityl ketone (C12-C16), myristyl palmityl ketone (C14-C16), myristyl stearyl ketone (C14-C18), myristyl behenyl ketone (C14-C22), palmityl stearyl ketone (C16-C18), palmityl behenyl ketone (C16-C22), stearyl behenyl ketone (C18-C22), and the like.

[0144] Examples of commercially available products of the compound represented by general formula (2) include 18-Pentatriacontanone (manufactured by Alfa Aeser), Hentriacontan-16-one (manufactured by Alfa Aeser), Kaowax T1 (manufactured by Kao Corporation), and the like.

[0145] The ink of the present invention may contain only one type of aliphatic ketone represented by the above general formula (2), or may contain two or more types.

[0146] R3-COO-R4...General formula (3) [In general formula (3), R3 represents a linear or branched hydrocarbon group having 1 to 24 carbon atoms. R4 represents a hydrogen atom or a linear or branched hydrocarbon group having 1 to 24 carbon atoms. However, at least one of R3 and R4 contains a linear alkyl structure having 12 or more carbon atoms.]

[0147] R3 and R4 are each independently more preferably a straight-chain hydrocarbon group having 1 to 24 carbon atoms, and even more preferably a straight-chain hydrocarbon group having 8 to 22 carbon atoms. Preferably, both R3 and R4 contain a straight-chain alkyl structure having 12 or more carbon atoms.

[0148] In general formula (3), the linear alkyl structure preferably has 12 to 24 carbon atoms. When the linear alkyl structure has 12 or more carbon atoms, the crystallinity of the gelling agent is likely to be increased. Furthermore, in the house-of-card structure, the polymerizable compound is easily encapsulated, making it easier to form an image in a dense pattern. On the other hand, when the linear alkyl structure has 24 or less carbon atoms, the melting point of the gelling agent does not increase excessively, and the gelling agent dissolves sufficiently in the ink.

[0149] Examples of fatty acids or aliphatic esters represented by general formula (3) include behenic acid, behenyl behenate (C21-C22, melting point 70°C), icosanoic acid icosyl (C19-C20), stearyl stearate (C17-C18, melting point 60°C), palmityl stearate (C17-C16), lauryl stearate (C17-C12), cetyl palmitate (C15-C16, melting point 54°C), stearyl palmitate (C15-C18), myristyl myristate (C13-C14, melting point 43°C), and cetyl myristate. Examples of oleic acid fatty acids include octyl myristate (C13-C16, melting point 50°C), octyldodecyl myristate (C13-C20), stearyl oleate (C17-C18), stearyl erucate (C21-C18), stearyl linoleate (C17-C18), behenyl oleate (C18-C22), myricyl ceramide (C25-C16), stearyl montanate (C27-C18), behenyl montanate (C27-C22), arachidyl linoleate (C17-C20), and palmityl triacontanoate (C29-C16).

[0150] Examples of commercially available aliphatic esters represented by general formula (3) include Unistar M-2222SL (manufactured by NOF Corporation), Exepar SS (manufactured by Kao Corporation, melting point 60°C), EMALEX CC-18 (manufactured by Nippon Emulsion Co., Ltd.), Amleps PC (manufactured by Kokyu Alcohol Kogyo Co., Ltd.), Exepar MY-M (manufactured by Kao Corporation), Sperm Acetate (manufactured by NOF Corporation), and EMALEX CC-10 (manufactured by Nippon Emulsion Co., Ltd.). These commercially available products are often mixtures of two or more types, and therefore may be separated and purified as necessary.

[0151] The ink of the present invention may contain only one type of fatty acid or aliphatic ester compound represented by the above general formula (2), or may contain two or more types.

[0152] (1.6) Non-polymerizable resin The ink of the present invention may further contain a non-polymerizable resin as needed, and it is particularly preferable for inks containing a gelling agent and having sol-gel phase transition properties to further contain a non-polymerizable resin.

[0153] In the present invention, the term "non-polymerizable resin" refers to a resin that does not have a group that crosslinks or polymerizes upon irradiation with actinic rays (photopolymerizable group).

[0154] Examples of non-polymerizable resins include polyester resins and ketone resins, each of which has at least one polar functional group in its molecule. When such polyester resins or ketone resins are included in ink, the polar functional groups facilitate precipitation of the gelling agent on the droplet surface after the ink lands on a recording medium. Meanwhile, the relatively weakly polar moieties (ester moieties and ketone moieties) of the polyester resin or ketone resin have affinity for the gelling agent. This means that the gelling agent is more easily mixed uniformly into the ink in a sol state. Furthermore, the polar functional groups of the polyester resin or ketone resin bond with functional groups on the recording medium surface, enhancing adhesion between the cured ink and the recording medium.

[0155] The polar functional group possessed by the polyester resin or ketone resin is preferably a group selected from the group consisting of -OH, -COOH, -NH, -NO, and -CN. When the polyester resin or ketone resin has these polar functional groups, the gelling agent is more likely to precipitate on the surface of the ink after it has landed on the recording medium. In particular, it is preferable that the polyester resin or ketone resin has both -OH and -COOH groups. When the polyester resin or ketone resin has these groups, adhesion is likely to be improved regardless of the functional group present on the surface of the recording medium.

[0156] The amount of polar functional groups in the polyester resin or ketone resin is not particularly limited, but the acid value or base value of the polyester resin or ketone resin is preferably in the range of 10 to 350 mgKOH / g. The acid value or base value of the polyester resin or ketone resin is more preferably 10 to 65 mgKOH / g. If the acid value or base value of the polyester resin or ketone resin is 10 mgKOH / g, the adhesion between the cured ink and the recording medium is not sufficiently improved, and the ink does not undergo a sufficient sol-gel phase transition. On the other hand, if the acid value or base value of the polyester resin or ketone resin exceeds 350 mgKOH / g, it is difficult to introduce polar functional groups into the polyester resin or ketone resin. Furthermore, excessive polar functional groups may reduce the compatibility of the gelling agent in the ink sol. The acid value and base value are measured in accordance with the neutralization value test method described in JIS K2501.

[0157] The number-average molecular weight of the polyester resin or ketone resin having a polar functional group is preferably 1,000 to 5,000, and more preferably 1,200 to 3,000. If the number-average molecular weight of the polyester resin or ketone resin is less than 1,000, the compatibility with the gelling agent increases, making it difficult for the gelling agent to precipitate. On the other hand, if the number-average molecular weight of the polyester resin or ketone resin is greater than 5,000, the viscosity of the ink increases, and in the case of image formation using an inkjet system, the ejection stability of the ink from the inkjet recording device decreases. The number-average molecular weight is a value measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0158] Specific examples of polyester resins having hydroxy groups include special ester resins manufactured by EVONIK INDUSTRIES (TEGOAddBond series (LTH, LTW, 1270, 2440, 3350UV), all of which have an average molecular weight of 1500 to 3000, an acid value of 15 to 65 mgKOH / g, and a base value of 10 to 50 mgKOH / g).

[0159] Specific examples of ketone resins having a hydroxy group include ketone resins manufactured by Degussa (TEGO VARIPLUS SK (average molecular weight 1000 to 2000, acid value approximately 0 mgKOH / g, base value approximately 300 mgKOH / g)).

[0160] Specific examples of ketone resins having urethane groups include ketone resin (TEGO VARIPLUS PZZ-1201) manufactured by Degussa.

[0161] The amount of polyester resin or ketone resin having a polar functional group contained in the ink is preferably in the range of 1.0 to 15.0% by mass, more preferably 3.0 to 10.0% by mass, based on the total mass of the ink. When two or more types of polyester resin or ketone resin having a polar functional group are contained, it is preferable that the total amount of these is within the above range. If the amount of polyester resin or ketone resin having a polar functional group is less than 1.0% by mass, the gelling agent may not sufficiently precipitate (crystallize) in the ink after it has landed. On the other hand, if the amount of polyester resin or ketone resin having a polar functional group exceeds 15.0% by mass, not only will the viscosity of the ink in a sol state increase, but the solubility of the gelling agent in the ink in a sol state will also decrease.

[0162] The method for preparing the polyester resin having a polar functional group is not particularly limited. For example, the polyester resin can be obtained by preparing the polyester resin from a polyhydric alcohol, a polycarboxylic acid, a cyclic lactone, or the like having a polar functional group. Specifically, the polyester resin having a polar functional group can be prepared by carrying out the following reaction. (i) Direct esterification reaction of di- or higher functional polyhydric alcohols and di- or higher functional polycarboxylic acids (ii) Transesterification of di- or higher functional polyesters and di- or higher functional polyhydric alcohols (iii) Esterification reaction of di- or higher functional polyhydric alcohols and acid anhydrides (iv) Direct esterification of hydroxycarboxylic acids containing one or more hydroxy groups and one or more carboxy groups per molecule (v) Ring-opening polymerization of cyclic lactones with polar functional groups attached to the ring

[0163] The acid value and base value of the polyester resin are adjusted by the number of functional groups in the raw materials such as polyhydric alcohol, polycarboxylic acid, hydroxycarboxylic acid, and polar group-containing cyclic lactone.

[0164] A ketone resin having a polar functional group can be prepared by reacting an aromatic ketone compound such as acetophenone with a compound having a polar functional group. For example, a ketone resin having an -OH group can be prepared by reacting an aromatic ketone compound such as acetophenone with an aldehyde compound such as formaldehyde, and then hydrogenating the resulting ketone resin.

[0165] The acid value and base value of the ketone resin are adjusted by the amount of the compound reacted with the ketone compound, the type of compound, and the like.

[0166] (1.7) Photopolymerization initiator assistant The ink of the present invention may further contain a photopolymerization initiator aid, if necessary.

[0167] The photopolymerization initiator aid may be a tertiary amine compound, and an aromatic tertiary amine compound is preferred. Examples of aromatic tertiary amine compounds include N,N-dimethylaniline, N,N-diethylaniline, N,N-dimethyl-p-toluidine, N,N-dimethylamino-p-benzoic acid ethyl ester, N,N-dimethylamino-p-benzoic acid isoamyl ethyl ester, N,N-dihydroxyethylaniline, triethylamine, N,N-dimethylhexylamine, etc. Among these, N,N-dimethylamino-p-benzoic acid ethyl ester or N,N-dimethylamino-p-benzoic acid isoamyl ethyl ester is preferred.

[0168] (1.8) Polymerization inhibitor The ink of the present invention may further contain a polymerization inhibitor, if necessary.

[0169] Examples of the polymerization inhibitor include (alkyl)phenols, hydroquinone, catechol, resorcinol, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone, nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cupferron, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, N-(3-oxyanilino-1,3-dimethylbutylidene)aniline oxide, dibutyl cresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxime, cyclohexanone oxime, and the like.

[0170] (1.9) Other ingredients The ink of the present invention may further contain other components as needed, such as various additives and other resins.

[0171] Examples of the additives include dispersing aids, surfactants, leveling additives, matting agents, ultraviolet absorbers, infrared absorbers, antibacterial agents, and basic compounds for improving the storage stability of the ink.

[0172] Examples of the basic compound include basic alkali metal compounds, basic alkaline earth metal compounds, and basic organic compounds such as amines.

[0173] Examples of other resins include resins for adjusting the physical properties of the cured ink, such as polyester-based resins, polyurethane-based resins, vinyl-based resins, acrylic-based resins, rubber-based resins, and waxes.

[0174] (1.10) Sol-gel phase transition of ink The ink of the present invention preferably has sol-gel phase transition properties. In the present invention, "sol-gel phase transition properties" refers to the property of reversibly changing between a fluid sol state and a non-fluid gel state, with the sol-gel phase transition temperature being the boundary between a sol state at high temperatures and a gel state at low temperatures.

[0175] The ink's sol-gel phase transition property allows it to be in a sol state when ejected, improving ejection stability when forming images using the inkjet method, and to be in a gel state after impact, preventing liquid segregation.

[0176] The sol-gel phase transition temperature is preferably in the range of 40 to 70°C, and more preferably in the range of 50 to 65°C. When the ejection temperature from the inkjet device is around 80°C, if the sol-gel phase transition temperature of the ink is 70°C or less, the ink will easily change to a sol state during ejection, resulting in good ejection stability. Furthermore, if the sol-gel phase transition temperature is 40°C or higher, the temperature of the recording medium, which is preferably set at least 30°C lower than the sol-gel phase transition temperature of the ink, can be set at 10°C or higher, thereby avoiding the complexity of the image formation process.

[0177] Furthermore, from the viewpoint of improving the ejection stability of ink droplets from an inkjet device, it is preferable that the viscosity of the ink at high temperatures (sol state) be below a certain level. Specifically, the viscosity of the ink at 80°C is preferably 3 to 20 mPa·s. On the other hand, from the viewpoint of forming images with fine patterns, it is preferable that the viscosity of the ink after landing on the recording medium (gel state) be above a certain level. Specifically, it is preferable that the viscosity of the ink at 25°C be 1000 mPa·s or higher.

[0178] The ink's viscosity at 80°C, viscosity at 25°C, and sol-gel phase transition temperature can be determined by measuring the temperature change of the ink's dynamic viscoelasticity using a rheometer. Specifically, the ink is heated to 100°C and cooled to 20°C at a shear rate of 11.7 ( / s) and a cooling rate of 0.1°C / s, and a viscosity temperature curve is obtained. The viscosities at 80°C and 25°C can then be determined by reading the viscosities at 80°C and 25°C, respectively, on the viscosity temperature curve. The sol-gel phase transition temperature can be determined as the temperature at which the viscosity reaches 200 mPa·s on the viscosity temperature curve.

[0179] The rheometer used can be a stress-controlled rheometer from the Physica MCR series manufactured by Anton Paar. The diameter of the cone plate can be set to 75 mm and the cone angle to 1.0°.

[0180] (1.11) Ink preparation method The ink of the present invention can be prepared by mixing the above-mentioned photosensitizer, polymerizable compound, photopolymerization initiator, colorant, etc., while heating using a known method.

[0181] (2) Image forming method The image forming method of the present invention is characterized by using the actinic radiation-curable ink of the present invention. Specifically, the ink of the present invention described above is applied to a recording medium, and the ink is cured by irradiating with actinic radiation to form an image. This makes it possible to form an image that is imparted with antibacterial and antiviral properties.

[0182] The image forming method will be described in detail below. Note that "applying ink independently of the image area" and "formation of a decorative image", which are embodiments of the image forming method of the present invention, will be described later.

[0183] (2.1) Recording Media The recording medium that can be used is not particularly limited and may be appropriately selected depending on the application, and may be, for example, various plastic substrates, metal substrates, glass substrates, stone substrates, cloth substrates, natural pulp substrates, fleece substrates made of a mixture of natural pulp and synthetic fibers, Japanese paper substrates, etc.

[0184] The recording medium may be a sheet in the form of a single sheet, a long sheet wound into a roll, or a molded body made of various resins.

[0185] When using ink with sol-gel phase transition properties, the temperature of the recording medium is preferably set to a temperature at least 30°C lower than the sol-gel phase transition temperature of the ink. In this case, the temperature of the recording medium is preferably 30 to 70°C lower, and more preferably 30 to 50°C lower, than the sol-gel phase transition temperature of the ink. This allows ink droplets that land on the recording medium to quickly gel, forming an image in the desired pattern. Here, the temperature of the recording medium refers to the surface temperature of the recording medium on which the ink lands, and the entire recording medium does not necessarily have to be at the above temperature. The surface temperature of the recording medium is measured using an infrared radiation thermometer or the like.

[0186] The temperature of the recording medium is adjusted by heating or cooling the recording medium by a known method. The heating or cooling method is not particularly limited, and can be performed using various heaters, chillers, Peltier elements, etc.

[0187] (2.2) Ink application The ink application method is not particularly limited, and the ink can be applied by an inkjet method or an offset method. The inkjet method is preferred when forming an image on demand, and the offset method is preferred when forming the same image in large quantities.

[0188] In the case of an inkjet system, the amount of liquid ejected from each nozzle of the inkjet recording head is preferably 0.5 to 10 pL, depending on the image resolution, and more preferably 0.5 to 2.5 pL in order to form a high-resolution image.

[0189] When using ink with sol-gel phase transition properties in an inkjet system, it is preferable to set the temperature of the ink inside the inkjet recording head 10 to 30°C higher than the ink's sol-gel phase transition temperature in order to improve the ejection stability of the ink droplets. If the ink temperature inside the inkjet recording head is 10°C above the sol-gel phase transition temperature, the ink is less likely to gel inside the inkjet recording head or on the nozzle surface, resulting in good ejection stability of the ink droplets. On the other hand, if the ink temperature inside the inkjet recording head is 30°C above the sol-gel phase transition temperature, the ink does not become too hot, preventing the ink components from deteriorating.

[0190] (2.3) Irradiation with actinic rays After the ink is applied onto the recording medium, it is irradiated with actinic rays to crosslink or polymerize the polymerizable compound contained in the ink and harden it, thereby fixing the ink onto the recording medium.

[0191] The actinic rays to be irradiated are not particularly limited and are appropriately selected depending on the type of photopolymerization initiator or actinic radiation-polymerizable compound contained in the ink, taking into account its absorption wavelength range. Examples include electron beams, ultraviolet rays, α rays, γ rays, and X-rays. Ultraviolet rays are preferred, and ultraviolet rays from an LED light source are particularly preferred. Examples of LED devices capable of irradiating ultraviolet rays include a 395 nm water-cooled LED manufactured by Phoseon Technology.

[0192] Metal halide lamps are commonly used as ultraviolet light sources, but LEDs can reduce the amount of radiant heat emitted from the light source, which reduces the viscosity of the ink and prevents deformation of the image.

[0193] Here, from the viewpoint of suppressing radiation heat irradiation and sufficiently curing the ink, the peak irradiance of the actinic rays on the ink surface is set to 0.5 to 10 W / cm. 2 It is preferable that the range is 1 to 5 W / cm 2 It is more preferable that the range is within the range of

[0194] The energy of the actinic rays irradiated is 200 to 1000 mJ / cm 2 It is preferable that the energy is in the range of 200 mJ / cm. 2 By setting the energy to 1000 mJ / cm or more, the polymerizable compound can be sufficiently polymerized and crosslinked, and the energy is 1000 mJ / cm or more. 2 When the energy of the irradiated actinic rays is 300 to 800 mJ / cm or less, the pinning property is less likely to be reduced due to a decrease in the viscosity of the ink caused by the heat of the irradiated actinic rays. 2 More preferably, it is in the range of 350 to 500 mJ / cm 2 It is more preferable that the range is within the range of

[0195] Furthermore, the singlet oxygen generating ability of the photosensitizer contained in the ink of the present invention may be inactivated by absorption of actinic light irradiated during curing of the ink. From the viewpoint of preventing this, the difference between the maximum absorption maximum wavelength of the photosensitizer in a monomolecular state and the maximum maximum wavelength of the actinic light irradiated to the ink is preferably 100 nm or more, and more preferably 200 nm or more.

[0196] (2.4) Inkjet image forming device An image forming apparatus (also called an "inkjet image forming apparatus") that can be used in an inkjet image forming method will be described.

[0197] Inkjet image forming apparatuses are generally classified into on-demand and continuous types depending on the ink ejection method. The inkjet image forming apparatus that can be used in the image forming method of the present invention may be of either type. Examples of on-demand inkjet image forming apparatuses include electro-mechanical conversion types, including single-cavity, double-cavity, bender, piston, shear-mode, and shared-wall types, and electro-thermal conversion types, including thermal inkjet and bubble-jet (Bubble Jet is a registered trademark of Canon Inc.) types.

[0198] Inkjet image forming apparatuses are classified into scan type and line type (also called "single pass type") depending on the scanning method of the head. The inkjet image forming apparatus that can be used in the image forming method of the present invention may be of either type, but from the viewpoint of high-speed image formation, the line type is preferred.

[0199] The line-type inkjet image forming apparatus will be described below with reference to FIG.

[0200] 3 is a schematic diagram showing an exemplary configuration of a line-type inkjet image forming apparatus 100. The inkjet image forming apparatus 100 shown in FIG.

[0201] The ink ejection unit 104 includes an inkjet recording means 113 and a temperature control means 119 .

[0202] The inkjet recording means 113 has a head carriage 116 that houses a plurality of inkjet recording heads 114 , an ink flow path 117 connected to the head carriage 116 , and an ink tank 118 that stores ink to be supplied through the ink flow path 117 .

[0203] The ink tank 118 is connected to the head carriage via an ink flow path 117. The ink flow path 117 is a path that supplies ink in the ink tank 118 to the head carriage .

[0204] The head carriage 116 is fixedly disposed so as to cover the entire width of the recording medium 1, and houses a plurality of inkjet recording heads 114. In the example shown in Fig. 3, each head carriage 116 houses an inkjet recording head 114 for each color of yellow (Y), magenta (M), cyan (C), and black (K).

[0205] A plurality of inkjet recording heads 114 are arranged in the transport direction of the recording medium 1, and the number of inkjet recording heads 114 arranged in the transport direction of the recording medium 1 is determined by the nozzle density of the inkjet recording heads 114 and the resolution of the print image. For example, when forming an image with a resolution of 1440 dpi using inkjet recording heads 114 with a droplet volume of 2 pL and a nozzle density of 360 dpi, four inkjet recording heads 114 are arranged with a staggered arrangement in the transport direction of the recording medium 1. When forming an image with a resolution of 720 x 720 dpi using inkjet recording heads 114 with a droplet volume of 6 pL and a nozzle density of 360 dpi, two inkjet recording heads 114 are arranged with a staggered arrangement. dpi represents the number of ink droplets (dots) per 2.54 cm.

[0206] The ink tank 118, the ink flow path 117, the head carriage 116, and the inkjet recording head 114 may be provided with a temperature adjustment means (not shown), and the temperature inside these can be controlled so that the ink is in a sol state, for example.

[0207] The temperature control means 119 is disposed so as to cover the entire width of the recording medium 1. When the ink discharge unit 104 and the actinic ray irradiation unit 103 are continuous as shown in Fig. 3, the temperature control means 119 may be disposed continuously from the ink discharge unit 104 to the actinic ray irradiation unit 103.

[0208] The temperature control means 119 includes a temperature detection unit (not shown) for detecting the surface temperature of the recording medium 1, and a temperature adjustment unit (not shown) such as a heater or chiller. In the inkjet image forming apparatus 100 shown in Fig. 3, the temperature control means 119 is disposed on the lower surface of the recording medium 1, but the temperature control means 119 may be disposed at any position depending on the thickness, shape, etc. of the recording medium 1.

[0209] The actinic ray irradiation unit 103 has an actinic ray irradiation section 131. The actinic ray irradiation section 131 is installed so as to cover the entire width of the recording medium 1. In the actinic ray irradiation unit 103, the ink applied on the recording medium is irradiated with the above-mentioned actinic ray to cure the ink.

[0210] (3) Ink application independent from the image area In one embodiment of the image forming method of the present invention, the ink of the present invention can be applied independently of the image area.

[0211] "Image area" refers to the area where an image (visible letters, figures, patterns, etc. formed on a recording medium by the cured ink or foil transferred thereon) is formed or has been formed. "Non-image area" refers to the area that is not an image area.

[0212] "Applying ink independently of the image area" means applying ink to the recording medium in invisible dot sizes and dot spacing, regardless of whether it is an image area or a non-image area, for the purpose of imparting antibacterial and antiviral properties to the output.

[0213] As mentioned above, the singlet oxygen generated by the photosensitizer contained in the ink of the present invention is a gas, and therefore diffuses into the surroundings after generation. For example, at 50% humidity, the diffusion distance is approximately 1.57 mm. Therefore, for example, by applying the ink of the present invention to the entire surface of a recording medium, independently of the image area, with a dot size of 30 μm and a dot spacing of 3 mm, it is possible to impart antibacterial and antiviral effects to the entire surface of the printed material without degrading image quality.

[0214] It is preferable that the ink applied independently of the image portion in this way is not visible, and therefore it is preferable that the ink does not contain a colorant (hereinafter also referred to as "clear ink").

[0215] From the viewpoint of balancing antibacterial and antiviral effects with maintaining image quality, the coverage rate of ink applied independently of the image area is preferably within the range of 0.001 to 0.5%, and more preferably within the range of 0.01 to 0.3%. As mentioned above, when ink is applied to the entire surface of a recording medium with a dot size of 30 μm and dot spacing of 3 mm, the coverage rate of ink applied independently of the image area is approximately 0.01%. Note that "coverage rate" refers to the percentage of the area to which ink is applied relative to the total area of ​​the recording medium or printed matter.

[0216] When the ink of the present invention is applied independently of the image area in this manner, it is preferable that the ink forming the image area is also the ink of the present invention, but it does not necessarily have to be the ink of the present invention and may be another ink.

[0217] The step of applying ink independently of the image area can be carried out simultaneously with the step of applying ink to form the image area, but it can also be carried out separately before or after the step of applying ink to form the image area. Furthermore, the timing of curing the ink applied independently of the image area and the timing of curing the ink to form the image area may be simultaneous or different. That is, after one ink application step, the ink is cured by irradiation with actinic rays, and then the other ink application step is carried out, and the ink is cured by irradiation with actinic rays again, so that each ink application step can be carried out separately.

[0218] In the inkjet method, when the process of applying ink that does not contain a colorant independently of the image area and the process of applying ink that forms the image area are carried out simultaneously, the respective processes can be carried out simultaneously by adding a head carriage 116 for the ink that does not contain a colorant (N), for example, as shown in Figure 4.

[0219] In the offset method, when a process of applying an ink that does not contain a colorant independently of the image area and a process of applying an ink that forms the image area are carried out simultaneously, each process can be carried out simultaneously by applying each ink using a different plate.

[0220] (4) Decorative image formation In one embodiment of the image forming method of the present invention, a decorative image (also called a "foil image") can be formed by transferring foil onto an area where the ink of the present invention has been applied. This makes it possible to obtain a decorative image that has been imparted with antibacterial and antiviral properties.

[0221] In the present invention, the term "decorative image" refers to an image formed by adhering a foil such as a metal foil in a desired shape to a recording medium.

[0222] In forming a decorative image, before the ink applied to the recording medium is cured, a foil is transferred onto the ink, and then the ink is cured by irradiating it with actinic rays.

[0223] In the image forming method for forming a decorative image, it is preferable to use an ink that has sol-gel phase transition properties. This makes it difficult for ink droplets to wet and spread after landing on the recording medium, making it possible to form a decorative image that includes a fine pattern. In addition, because ink droplets are less likely to penetrate into the unevenness of the recording medium after landing on the recording medium, the thickness of the uncured image (an image made of ink before curing) tends to be uniform, making it less likely for defects to occur in the resulting decorative image.

[0224] Hereinafter, an example of each step of forming a decorative image will be described with reference to FIG.

[0225] First, as shown in FIG. 5(a), ink is ejected in a pattern onto a recording medium 1 to form an uncured image 2.

[0226] The average thickness of the uncured image 2 is preferably about 0.1 to 1000 μm, and more preferably about 1 to 300 μm. When the thickness of the uncured image is 1 μm or more, the adhesive strength between the foil layer 5 of the transfer foil 3 and the uncured image 2 tends to be sufficiently high. The average thickness can be measured by observing the cross section of the uncured image 2 with an SEM.

[0227] Next, as shown in FIG. 5(b), a transfer foil 3 including a support material 4 and a foil layer 5 is pressed onto the uncured image 2 with the foil layer 5 facing downward.

[0228] The transfer foil 3 may be a sheet in the form of individual leaves, or a long sheet wound into a roll. The transfer foil 3 includes at least a support material 4 and a foil layer 5, and for example, a release layer or a colored layer may be formed between the support material 4 and the foil layer 5. If a colored layer is formed, the colored layer is also transferred onto the uncured image 2 together with the foil layer 5. In addition, an adhesive layer may be formed on the transfer surface of the transfer foil 3.

[0229] The foil layer 5 is a layer for imparting metallic or glossy characters or patterns, which are difficult to achieve by conventional printing, or transparent watermark characters or patterns, to the recording medium. The foil layer 5 can be, for example, a metal foil, a metal-deposited film, a hologram film, a pearlescent film, an iridescent film, a black / white film, a color film, or a clear film. The foil layer 5 can also be a layer made of a composite material of a plastic film and a metal for the purpose of improving strength. The foil layer 5 can also be a layer in which a regular pattern is imparted to a metal film by known processing methods such as water-washed seelite processing, etching, or laser processing. The thickness of the foil layer 5 is selected appropriately depending on the type, but is typically about 10 to 100 nm.

[0230] The support material 4 is not particularly limited as long as it is a member capable of supporting the foil layer 5, and may be, for example, a film or sheet made of a flexible resin or the like, or a paper sheet. Examples of resins that may be used to form the support material 4 include known resins such as polyethylene terephthalate (PET) resin, polyethylene naphthalate (PEN) resin, polypropylene (PP) resin, polyethersulfone resin, and polyimide resin. The support material 4 may have a single-layer structure or a multi-layer structure.

[0231] As described above, a release layer (not shown) may be formed on the transfer foil 3. The release layer is a layer that ensures the peelability of the foil layer 5 from the support material 4. The release layer may be, for example, a layer made of a thermosetting resin using melamine or isocyanate as a curing agent, or a layer containing a known wax such as a fluorine-based or silicon-based monomer or polymer.

[0232] As described above, an adhesive layer (not shown) may be formed on the transfer foil 3. The adhesive layer may be a layer that exhibits adhesiveness to an uncured image when heated. The adhesive layer may be, for example, a layer made of a heat-sensitive adhesive known as a hot-melt type. Examples of heat-sensitive adhesives include adhesives containing acrylic resin, vinyl chloride-vinyl acetate copolymer, epoxy resin, and ethylene-vinyl alcohol copolymer.

[0233] The force (pressure) for pressing the uncured image 2 and the transfer foil 3 together is preferably 100 to 800 kPa, more preferably 200 to 600 kPa, in terms of nip surface pressure, and the pressure-bonding time is preferably 0.1 to 30 seconds, more preferably 0.5 to 10 seconds.

[0234] The method of crimping is not particularly limited, and crimping can be performed by the method shown in Figs. 6(a) to 6(c), for example.

[0235] In the pressure bonding method shown in FIG. 6(a), the recording medium 6 on which the uncured image has been formed and the transfer foil 3 are pressed against a plate 41 in a flat plate shape or a desired shape to bond them together.

[0236] In the pressure bonding method shown in FIG. 6(b), the recording medium 6 on which the uncured image has been formed and the transfer foil 3 are passed through a pair of transfer rollers 42a and 42b to be pressure bonded together.

[0237] The pressure bonding method shown in FIG. 6(c) is a method in which the recording medium 6 on which the uncured image has been formed and the transfer foil 3 are pressure-bonded together by applying pressure with a transfer roller 43.

[0238] Here, the recording medium 6 on which the uncured image has been formed and the transfer foil 3 may be pressed together while being heated. Heating can be performed, for example, by heating a transfer roller or plate. The heating temperature is preferably 30 to 90°C, and more preferably 40 to 60°C. Heating makes it easier to peel the foil layer 5 from the transfer foil 3, allowing the foil layer 5 to be transferred in a short time. However, if the heating temperature is excessively high, the ink constituting the uncured image 2 may soften, causing the pattern to collapse. Therefore, it is preferable to set the heating temperature within the above range.

[0239] Next, as shown in Figure 5(c), the transfer foil 3 is removed. At this time, the foil layer 7 that has been pressed onto the uncured image 2 remains on the uncured image 2. Meanwhile, the foil layer 5 that has not been pressed onto the uncured image 2 is removed together with the support material 4. In other words, the foil layer 7 remains on the recording medium 1 in the pattern of the uncured image 2, and this becomes the decorative image.

[0240] Finally, as shown in FIG. 5( d ), the uncured image 2 is irradiated with actinic rays from the actinic ray irradiation unit 131 to cure the ink and fix the foil layer 7 onto the recording medium 1 .

[0241] At this time, the actinic ray may be irradiated from above the foil layer 7, or if the recording medium 1 is transparent to the actinic ray, the actinic ray may be irradiated from below the recording medium 1.

[0242] FIG. 7 shows an example of an image forming apparatus (decorative image forming apparatus) that can be used to form a decorative image.

[0243] The decorative image forming apparatus 200 shown in FIG. 7 includes an adhesive ink ejection unit 101, a foil transfer unit 102, and an actinic ray irradiation unit 103.

[0244] The adhesive ink ejection unit 101 is an ejection unit for adhesive ink for adhering a foil onto a recording medium. The adhesive ink ejection unit 101 shown in Fig. 7 has an inkjet recording means 113 and a temperature control means 119. The details of each component are the same as those shown in Fig. 3.

[0245] The foil transfer unit 102 has a pair of transfer rollers 42a and 42b that sandwich the recording medium 1, a foil delivery spool 121 that supplies the transfer foil 3 between the pair of transfer rollers 42a and 42b, and a take-up spool 122 that collects the transfer foil 3 after the foil layer has been transferred.

[0246] In the foil transfer unit 102, the uncured image formed by the adhesive ink discharge unit 101 and the transfer surface of the transfer foil are pressed together by a pair of transfer rollers 42a and 42b. As a result, the foil layer of the transfer foil is transferred onto the uncured image, forming a decorative image. Meanwhile, the transfer foil 3 after pressing is collected by a take-up spool 122.

[0247] The actinic ray irradiation unit 103 has an actinic ray irradiation section 131. The actinic ray irradiation section 131 is installed so as to cover the entire width of the recording medium 1. In the actinic ray irradiation unit 103, the actinic ray irradiation section 131 irradiates the uncured image with actinic rays to cure the ink and fix the foil layer on the recording medium.

[0248] In the image forming method of the present invention, for example, a decorative image forming apparatus as shown in Fig. 8 can be used to form a decorative image, and then ink can be applied from above. This makes it possible to form an image composed of a combination of foil and colorant-containing ink, or a decorative image to which ink is applied independently of the image area. In this case, the irradiation of actinic rays to fix the foil layer and the irradiation of actinic rays to cure the colorant-containing ink, etc., can be performed together, or can be performed separately.

[0249] Alternatively, a decorative image can be formed by applying a colorant-containing ink or an ink separate from the image area, curing the ink by irradiating it with actinic rays once, and then applying another ink.

[0250] (5) Printed materials The output of the present invention is characterized by being formed using the actinic radiation curable ink of the present invention.

[0251] In the present invention, the term "output" refers to an image (including a decorative image) formed on a recording medium. By using the actinic radiation-curable ink of the present invention, it is possible to form an output having high antibacterial and antiviral properties. [Example]

[0252] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass."

[0253] 1. Preparation of Colorant Dispersion A cyan pigment dispersion and a black pigment dispersion were prepared as colorant dispersions by the following procedure.

[0254] (cyan pigment dispersion) A cyan pigment dispersion was prepared by placing 20 parts by mass of Lionol Blue FG-7400-G (manufactured by Toyocolor Co., Ltd.), 6.5 parts by mass of BYKJET-9151 dispersant (manufactured by BYK, "BYKJET" is a registered trademark of the company), 73.2 parts by mass of polyethylene glycol #400 diacrylate, 0.3 parts by mass of Irgastab UV10 photopolymerization inhibitor (manufactured by BASF, "Irgastab" is a registered trademark of the company), and 0.3 mm YTZ ball zirconia beads (manufactured by Nikkato Corporation) in a 100 mL plastic container and dispersing the mixture for 3 hours using a paint shaker. The zirconia beads were then removed, and the resulting mixture was used to prepare a cyan pigment dispersion.

[0255] (Black pigment dispersion) A black pigment dispersion was prepared in the same manner as the cyan pigment dispersion, except that the cyan pigment was changed to a black pigment, "Pigment Black 7" (carbon black, manufactured by Mitsubishi Chemical Corporation).

[0256] 2. Ink Preparation Inks No. 1 to 17 were prepared according to the following procedure. The maximum absorption maximum wavelength of each photosensitizer in the monomolecular state is shown in Table III. The maximum absorption maximum wavelength in the monomolecular state was determined from the absorption spectrum of a solution in which the photosensitizer was dissolved in THF (tetrahydrofuran). However, in the case of photosensitizer B-1, the maximum absorption maximum wavelength was determined from the absorption spectrum of a solution in which the photosensitizer was dissolved in THF:methanol = 1:1. The solution concentration was adjusted so that the absorbance at the maximum absorption maximum wavelength in the absorption spectrum of the solution was 1.0 Abs. The absorption spectra were measured using a UV-Vis-Infrared Spectrophotometer V-750 (manufactured by JASCO Corporation).

[0257] (Ink No. 1) Polyethylene glycol #400 diacrylate (25.0 parts by mass), 4EO-modified pentaerythritol tetraacrylate (20.0 parts by mass), 3PO-modified trimethylolpropane triacrylate (15.0 parts by mass), phenoxyethyl acrylate (40 parts by mass), photopolymerization initiator "IRGACURE 819" (manufactured by BASF, "IRGACURE" is a registered trademark of the company) (5.0 parts by mass), photosensitizer F-13 (0.08 parts by mass), and photopolymerization inhibitor "Irgastab UV10" (0.1 parts by mass) were added, stirred at 105°C for 45 minutes, and then filtered through a 3 μm membrane filter (Teflon (registered trademark) manufactured by ADVANTEC) to prepare Ink No. 1.

[0258] The absorption spectrum of the photopolymerization initiator "IRGACURE819" has an absorption end point of 450 nm.

[0259] (Ink No. 2) Ink No. 2 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to F-13 (0.008 parts by mass).

[0260] (Ink No. 3) Ink No. 3 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to F-13 (0.8 parts by mass).

[0261] (Ink No. 4) Ink No. 4 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to E-1 (0.08 parts by mass).

[0262] (Ink No. 5) Ink No. 5 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to F-7 (0.08 parts by mass).

[0263] (Ink No. 6) Ink No. 6 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to F-10 (0.08 parts by mass).

[0264] (Ink No. 7) Ink No. 7 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to H-5 (0.08 parts by mass).

[0265] (Ink No. 8) Ink No. 8 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to H-2 (0.08 parts by mass).

[0266] (Ink No. 9) Ink No. 9 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to G-6 (0.08 parts by mass).

[0267] (Ink No. 10) Ink No. 10 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to F-10 (0.08 parts by mass) and a cyan pigment dispersion (10 parts by mass, 2 parts by mass in terms of pigment) was added.

[0268] (Ink No. 11) Ink No. 11 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to B-1 (0.08 parts by mass) and a cyan pigment dispersion (10 parts by mass, 2 parts by mass in terms of pigment) was added.

[0269] (Ink No. 12) Ink No. 12 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to F-13 (0.16 parts by mass) and a black pigment dispersion (10 parts by mass, 2 parts by mass in terms of pigment) was added.

[0270] (Ink No. 13) Ink No. 13 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to F-13 (0.16 parts by mass) and a cyan pigment dispersion (10 parts by mass, 2 parts by mass in terms of pigment) was added.

[0271] (Ink No. 14) Ink No. 14 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to I-2 (0.08 parts by mass).

[0272] (Ink No. 15) Ink No. 15 was prepared in the same manner as Ink No. 1, except that the photosensitizer was changed to F-10 (0.08 parts by mass), and a cyan pigment dispersion (10 parts by mass, 2 parts by mass in terms of pigment) and behenyl behenate (8 parts by mass) were added as a gelling agent.

[0273] (Ink No. 16) Ink No. 16 was prepared in the same manner as Ink No. 1, except that no photosensitizer was added.

[0274] (Ink No. 17) Ink No. 17 was prepared in the same manner as Ink No. 1, except that no photosensitizer was added and a cyan pigment dispersion (10 parts by mass, 2 parts by mass in terms of pigment) was added.

[0275] 3. Confirmation of the molecular aggregation state of the photosensitizer in the ink The absorption spectra of inks No. 1 to 15 were measured using a V-750 UV-Vis-Infrared Spectrophotometer (manufactured by JASCO Corporation). For inks No. 10 to 13 and 15, the absorption spectra were measured after separating and removing the solid pigment components from each ink using a centrifuge. The measured absorption spectra showed that each ink had an absorption peak that matched the maximum absorption wavelength of the photosensitizer contained in each ink in a monomolecular state (see Table III). These results confirmed that the photosensitizer contained in inks No. 1 to 15 was in a monomolecular state.

[0276] 4. Image Formation Using each of the inks described above, images were formed by the following image forming methods Nos. 1 to 3, and output products were obtained.

[0277] (Image formation method No. 1) A piezoelectric ink jet recording head filled with the ink shown in Table III was installed in an ink jet recording apparatus (KM512MHX, manufactured by Konica Minolta).

[0278] Using this device, a printing coated paper (OK top coat, basis weight 128 g / m) was printed at a resolution of 720 x 720 dpi. 2 The ink was applied to a paper (manufactured by Oji Paper Co., Ltd.) at a printing rate of 100% so as to form a solid image area of ​​5 cm square.

[0279] Then, actinic rays with a maximum wavelength of 395 nm were applied at a cumulative total of 350 mJ / cm 2 The photoresist was irradiated with light at 1000 W and subjected to a curing treatment to obtain an output product.

[0280] (Image formation method No. 2) A piezoelectric inkjet recording head 1 filled with ink No. 13 (cyan ink) and a piezoelectric inkjet recording head 2 filled with ink No. 1 (clear ink) were introduced in series into an inkjet recording apparatus (KM512MHX, manufactured by Konica Minolta).

[0281] The piezoelectric inkjet recording head 1 of the device was used to print coated paper (OK top coat, basis weight 128 g / m) at a resolution of 720 × 720 dpi. 2 Ink No. 13 (cyan ink) was applied to a printing press (manufactured by Oji Paper Co., Ltd.) at a printing rate of 100% to form a 5 cm square solid image. At the same time, ink No. 1 (clear ink) was applied to the entire surface of printing coated paper at a printing rate of 0.1% using piezo-type inkjet recording head 2.

[0282] Then, actinic rays with a maximum wavelength of 395 nm were applied at a cumulative total of 350 mJ / cm 2 The photoresist was irradiated with light at 1000 W and subjected to a curing treatment to obtain an output product.

[0283] In the image formed by image forming method No. 2, the area where a solid image area was formed is the "image area," and the area where no solid image area was formed and only Ink No. 1 (clear ink) was applied at a printing rate of 0.1% is the "non-image area."

[0284] (Image formation method No. 3) A piezoelectric inkjet recording head filled with ink No. 15 (gelling agent-containing cyan ink) was installed in an inkjet recording apparatus (KM512MHX, manufactured by Konica Minolta).

[0285] Using this device, while maintaining the head temperature (discharge temperature) at 80°C, printing was performed on coated printing paper (OK top coat, basis weight 128 g / m) heated to 50°C under the condition of a resolution of 720 x 720 dpi. 2 Ink No. 15 (gelling agent-containing cyan ink) was applied to a paper (manufactured by Oji Paper Co., Ltd.) at a printing rate of 100% so as to form a solid image area of ​​5 cm square.

[0286] Then, actinic rays with a maximum wavelength of 395 nm were applied at a cumulative total of 350 mJ / cm 2 The photoresist was irradiated with light at 1000 W and subjected to a curing treatment to obtain an output product.

[0287] 5. Evaluation of singlet oxygen generation ability by phosphorescence detection Using the printouts in which images were formed using inks No. 1 to 17 and image forming methods No. 1 to 3 in the combinations shown in Table III, the presence or absence of the singlet oxygen generating ability of the photosensitizer was evaluated by detecting phosphorescence derived from singlet oxygen.

[0288] The image area or non-image area shown in Table III was used as an evaluation area, and the output was cut into a 5 cm square to prepare an image sample.

[0289] The phosphorescence spectrum of the ink on the image sample was measured under the following conditions. Measurement system EP-8700 (JASCO Corporation) Measurement mode: Fluorescence (monochromatic light monitor ratio calculation method) Measurement interval 5nm Measurement wavelength range: 1200~1350nm Data capture interval: 2nm

[0290] The excitation wavelength during measurement was adjusted to the maximum absorption wavelength (see Table III) of the photosensitizer contained in the ink used to form each image sample in a single molecule state.

[0291] For inks Nos. 1 to 15, an emission peak was confirmed in the vicinity of 1270 nm, which is the emission peak of singlet oxygen, from the phosphorescence spectrum obtained, and phosphorescence derived from singlet oxygen was detected.

[0292] From these results, it was confirmed that the photosensitizer contained in the ink of the present invention is a sensitizer for oxygen and has the ability to generate singlet oxygen.

[0293] 6. Evaluation of singlet oxygen generation ability by rubrene bleaching test Using the printouts in which images were formed by applying inks Nos. 1 to 17 and image forming methods Nos. 1 to 3 in the combinations shown in Table III, the singlet oxygen generating ability of the photosensitizers was relatively evaluated by a rubrene discoloration test.

[0294] The image area or non-image area shown in Table III was used as an evaluation area, and the output was cut into a 5 cm square to prepare an image sample.

[0295] A 5 mm square piece of filter paper was soaked in 0.1% rubrene-alcohol solution, and the dye concentration of the filter paper was then measured.

[0296] The image sample was placed in a transparent petri dish, and the filter paper was placed on top of it and sealed. In this state, it was left at room temperature under a fluorescent light of 1000 (lx) for 24 hours.

[0297] The filter paper was removed from the petri dish, and the dye concentration was measured again. The dye concentration remaining rate was calculated from the dye concentration before and after standing, and the rubrene fading effect was evaluated according to the following criteria.

[0298] ◎ Pigment concentration remaining rate less than 10% ○ Pigment concentration remaining rate: 10% or more but less than 30% △ Pigment concentration remaining rate: 30% or more but less than 90% × Dye concentration residual rate 90% or more

[0299] The results of this evaluation are shown in Table 3. Since the rubrene fading effect is thought to be due to singlet oxygen, it was possible to relatively evaluate the singlet oxygen generating ability of the photosensitizer contained in the ink of the present invention.

[0300] Furthermore, from these results, it was confirmed that the photosensitizer contained in the ink of the present invention can generate singlet oxygen from oxygen in the air even under weak light such as indoor illumination. In Table III, the word "present invention" in the remarks column for Examples Nos. 4, 7, 8, 11 and 15 should be read as "Reference Example."

[0301] [Table 3]

[0302] 7. Evaluation of indicator properties of singlet oxygen generation ability Ink No. 1, which was confirmed to have singlet oxygen generating ability, was evaluated for its indicator properties for singlet oxygen generating ability according to the following procedure.

[0303] From the output on which an image was formed using Ink No. 1 and Image Forming Method No. 1, a 5 cm square solid image portion was cut out to serve as an image sample.

[0304] The ink No. 1 applied to the image sample exhibited a blue color due to the monomolecular absorption spectrum of the photosensitizer F-13 it contained. As mentioned above, ink No. 1 had an emission peak around 1270 nm, confirming its ability to generate singlet oxygen.

[0305] The ink No. 1 applied to the image sample was illuminated with a xenon lamp at 1 SUN (100 mW / cm 2 ) and irradiated for 8 hours and 30 days.

[0306] After 8 hours of light irradiation, the ink No. 1 applied to the image sample exhibited the same blue color as before light irradiation. When the phosphorescence spectrum of this ink No. 1 after 8 hours of light irradiation was measured under the same conditions as above, it was confirmed that it had an emission peak near 1270 nm, and that it had the ability to generate singlet oxygen, just like before light irradiation.

[0307] After 30 days of light irradiation, Ink No. 1 applied to the image sample had not faded to a blue color, unlike before light irradiation. When the phosphorescence spectrum of Ink No. 1 after 30 days of light irradiation was measured under the same conditions as above, there was no emission peak near 1270 nm, confirming that the singlet oxygen generating ability had disappeared due to 30 days of light irradiation.

[0308] From the above results, it was confirmed that the ink of the present invention exhibits coloration derived from the monomolecular absorption spectrum of the photosensitizer, and can be used as an indicator of singlet oxygen generating ability.

[0309] 8. Evaluation of antibacterial and antiviral properties using film adhesion method Ink No. 1, which was confirmed to have singlet oxygen generating ability, was evaluated for antibacterial and antiviral properties using the following procedure.

[0310] From the output on which an image was formed using Ink No. 1 and Image Forming Method No. 1, a 5 cm square solid image portion was cut out to serve as an image sample.

[0311] The image sample was subjected to an antibacterial test using the film adhesion method in accordance with JIS Z 2801:2010 (antibacterial processed products - antibacterial test method, antibacterial effect) using the following procedure.

[0312] 5g of meat extract, 10g of peptone, and 5g of sodium chloride were dissolved in 1L of distilled water to prepare a normal bouillon solution. This normal bouillon solution was further diluted 500 times. Escherichia coli (ISO3301) was added to the diluted solution to a bacterial concentration of 1.0 x 10 6 The test bacteria solution was prepared by adding and suspending the bacteria so that the concentration was 1 / mL.

[0313] The image sample was filled with 0.5 mL of test bacterial solution (equivalent to 0.5 x 10 6 A coating film (polyethylene film) was then attached to the mixture, and the mixture was left at 35°C for 24 hours.

[0314] Bacteria adhering to the image sample and the coating film were washed out into a sterile petri dish using 9.5 mL of SCDLP medium (manufactured by Nippon Pharmaceutical Co., Ltd.). The number of viable bacteria in 1 mL of this washed-out liquid was measured by the agar plate dilution method using standard agar medium for measuring bacterial counts (manufactured by Nissui Co., Ltd.). The sterilization rate calculated from the measured viable bacteria count was 99.99%.

[0315] Based on the film adhesion method standard, which defines good antibacterial properties as a reduction in the number of live bacteria to less than one thousandth (i.e., a sterilization rate of 99.9% or more), it was confirmed that Ink No. 1 has high antibacterial properties.

[0316] Furthermore, as is generally known, singlet oxygen has antiviral as well as antibacterial properties, so Ink No. 1 is also thought to have high antiviral properties.

[0317] Furthermore, it is assumed that other inks that have been confirmed to have the same singlet oxygen generating ability as Ink No. 1 also have antibacterial and antiviral properties as Ink No. 1. [Explanation of symbols]

[0318] 1. Recording media 2 Uncured image 3 Transfer foil 4 Support material 5 foil layer 6. Recording medium on which an uncured image is formed 7 Bonded foil layers 41st edition 42a, 42b Pair of transfer rollers 43 Transfer roller 100 Inkjet image forming device 101 Adhesive ink ejection unit 102 Foil transfer unit 103 Actinic Ray Irradiation Unit 104 Ink ejection unit 113 Inkjet recording means 114 Inkjet recording head 116 Head carriage 117 Ink flow path 118 Ink Tank 119 Temperature control means 121 Foil delivery spool 122 Take-up spool 131 Active ray irradiation section 200 Decorative image forming device

Claims

1. An actinic radiation curable ink containing at least a polymerizable compound and a photosensitizer, the photosensitizer has singlet oxygen generating ability, The photosensitizer has a structure represented by the following general formula (1):

1. An actinic radiation curable ink comprising: 【Chemistry 1】 [In the above general formula (1), M represents a metal atom of Group 14. Q 1 and Q 2 each independently represent a monovalent axial ligand. Note that the above general formula (1) may not have either Q 1 or Q 2 . A 1 to A 4 each independently represent an atomic group forming an aromatic ring which may have a substituent.]

2. Contains a photopolymerization initiator, and The maximum absorption maximum wavelength of the photosensitizer in a monomolecular state is on the longer wavelength side than the absorption end of the absorption spectrum of the photopolymerization initiator.

2. The actinic radiation curable ink according to claim 1.

3. the polymerizable compound is an actinic radiation-polymerizable compound, and The maximum absorption maximum wavelength of the photosensitizer in a monomolecular state is on the longer wavelength side than the absorption end of the absorption spectrum of the actinic radiation-polymerizable compound.

2. The actinic radiation curable ink according to claim 1.

4. The maximum absorption wavelength of the photosensitizer in a single molecule state is within the range of 360 to 800 nm.

4. The actinic radiation curable ink according to claim 1.

5. Further contains a colorant 5. The actinic radiation curable ink according to claim 1.

6. The coloring is due to the single molecule absorption spectrum of the photosensitizer.

6. The actinic radiation curable ink according to claim 1.

7. An image forming method using actinic radiation curable ink, comprising: The actinic radiation curable ink is the actinic radiation curable ink according to any one of claims 1 to 6. An image forming method comprising:

8. The difference between the maximum absorption wavelength of the photosensitizer in a monomolecular state and the maximum absorption wavelength of the actinic ray irradiated when curing the actinic ray-curable ink is 100 nm or more.

8. The image forming method according to claim 7.

9. The actinic ray curable ink is applied independently of the image area.

9. The image forming method according to claim 7 or 8.

10. A foil is transferred onto the area where the actinic radiation curable ink is applied to form a decorative image.

10. The image forming method according to claim 7, wherein the image forming method is a method for forming an image on a recording medium.

11. The actinic radiation curable ink is applied onto a recording medium by an inkjet method.

11. The image forming method according to claim 7, wherein the image forming method is a method for forming an image on a recording medium.

12. An output formed using actinic radiation curable ink, The actinic radiation curable ink is the actinic radiation curable ink according to any one of claims 1 to 6. An output product characterized by the above.

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