Image recording method and inkjet recording medium

Abstract

An image recording method and inkjet recorded article, the method comprising the following steps: preparing at least two inks including a first ink and a second ink; heating a substrate; applying the at least two inks to the heated substrate using an inkjet recording method; and irradiating the at least two inks with active energy rays. In the step of applying the at least two inks, a mixed region in which the at least two inks are mixed is formed in at least a portion of the substrate by the application of active energy rays. The first ink contains a first polymerizable liquid crystal compound, and the second ink contains a second chiral compound.

Description

Technical Field

[0001] The present invention relates to an image recording method and an inkjet recorded material. Background Art

[0002] In recent years, image recording methods using inks containing liquid crystal compounds have been proposed. Cholesteric liquid crystals, produced by adding a chiral agent to a liquid crystal compound, exhibit exceptional light reflectivity and a characteristic in which the color tone changes depending on the viewing angle. Using inks containing liquid crystal compounds enables the recording of unique images not visible on other image recording materials, leading to promising applications for unique decoration of items such as packaging and in security printing.

[0003] For example, International Publication No. 2020 / 194831 discloses an image recording method, which includes: a base layer forming process, in which a base ink is applied to a substrate by an inkjet recording method to form a base layer; and an image recording process, in which an image recording ink containing a polymerizable liquid crystal compound and a chiral compound is applied to the base layer by an inkjet recording method to record an ink image. Summary of the Invention

[0004] Technical issues to be solved by the invention

[0005] However, International Publication No. 2020 / 194831 only discloses the case of applying a single image recording ink to a base layer, and does not describe focusing on reproducing multiple colors.

[0006] The present invention has been made in view of such circumstances, and according to one embodiment of the present invention, provides an image recording method and an inkjet recorded material capable of reproducing a plurality of colors with high color development properties.

[0007] Means for solving technical problems

[0008] The present invention includes the following aspects.

[0009] <1> An image recording method comprising the following steps: preparing at least two inks including a first ink and a second ink; heating a substrate; applying the at least two inks to the heated substrate using an inkjet recording method; and irradiating the at least two inks with active energy rays, wherein in the step of applying the at least two inks, a mixed region in which the at least two inks are mixed is formed in at least a portion of the substrate by the application, wherein the first ink contains a first polymerizable liquid crystal compound and the second ink contains a second chiral compound.

[0010] <2> The image recording method according to <1>, wherein the first ink contains a first polymerizable liquid crystal compound, a first chiral compound, and a first organic solvent, and the second ink contains a second polymerizable liquid crystal compound, a second chiral compound, and a second organic solvent, and the absolute value of the difference between the maximum reflection wavelength of the ink film formed by the first ink and the maximum reflection wavelength of the ink film formed by the second ink is greater than 100 nm.

[0011] <3> The image recording method according to <1> or <2>, wherein the maximum reflection wavelength of the ink film formed by the first ink is 380 nm to 490 nm, and the maximum reflection wavelength of the ink film formed by the second ink is 600 nm to 800 nm.

[0012] <4> The image recording method according to any one of <1> to <3>, wherein, in the step of preparing at least two inks, a third ink containing a third polymerizable liquid crystal compound, a third chiral compound and a third organic solvent is further prepared, and the absolute value of the difference between the maximum reflection wavelength of the ink film formed by the first ink and the maximum reflection wavelength of the ink film formed by the second ink and the maximum reflection wavelength of the ink film formed by the third ink is greater than 40 nm.

[0013] <5> The image recording method according to <4>, wherein the maximum reflection wavelength of the ink film formed by the first ink is 380 nm to 490 nm, the maximum reflection wavelength of the ink film formed by the second ink is 600 nm to 800 nm, and the maximum reflection wavelength of the ink film formed by the third ink is 500 nm to 590 nm.

[0014] <6> The image recording method according to any one of <1> to <5>, wherein in the step of applying at least two inks, the total amount of the at least two inks applied per unit area in the mixed region is set to 3 g / m 2 ~20g / m 2 range to be given.

[0015] <7> The image recording method according to any one of <2> to <6>, wherein in the step of applying at least two inks, the total amount of the polymerizable liquid crystal compound contained in the at least two inks applied per unit area in the mixed region is set to 1.5 g / m 2 ~8g / m 2 range to give.

[0016] <8> The image recording method according to any one of <2> to <7>, wherein in the step of applying at least two inks, the total amount of organic solvent contained in the at least two inks applied per unit area in the mixed region is set to 2.5 g / m 2 ~12.5g / m2 range to give.

[0017] <9> The image recording method according to any one of <1> to <8>, wherein the viscosity of at least two inks is 7 mPa·s or higher.

[0018] <10> The image recording method according to any one of <1> to <9>, wherein the maximum absolute value of the difference in surface tension between the at least two inks is 1 mN / m or less.

[0019] <11> The image recording method according to any one of <1> to <10>, wherein in the step of heating the substrate, the substrate is heated to 40° C. or higher.

[0020] <12> An inkjet recorded material comprising: a substrate; and an ink film containing a liquid crystal polymer disposed on the substrate, the ink film including a plurality of regions having mutually different maximum reflection wavelengths when viewed from above, wherein the orientation state of the liquid crystal polymer continuously changes between two adjacent regions.

[0021] Effects of the Invention

[0022] According to one embodiment of the present invention, there are provided an image recording method and an inkjet recorded material capable of reproducing a plurality of colors with high color development properties. DETAILED DESCRIPTION

[0023] Hereinafter, the image recording method of the present invention will be described in detail.

[0024] In this specification, the numerical range expressed using "to" indicates a range including the numerical values described before and after "to" as the minimum value and the maximum value, respectively.

[0025] In the numerical ranges described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced by the upper limit or lower limit of another numerical range described in another stage. In addition, in the numerical ranges described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced by the value shown in the Examples.

[0026] In this specification, when a plurality of substances corresponding to each component are present in a composition, the amount of each component in the composition refers to the total amount of the plurality of substances present in the composition unless otherwise specified.

[0027] Furthermore, in this specification, a combination of two or more preferred aspects is a more preferred aspect.

[0028] Furthermore, in this specification, the term "process" refers not only to an independent process but also to a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0029] In this specification, "(meth)acrylate" means acrylate or methacrylate.

[0030] [Image recording method]

[0031] The image recording method of the present invention includes the following steps: preparing at least two inks including a first ink and a second ink; heating a substrate; applying the at least two inks to the heated substrate using an inkjet recording method; and irradiating the at least two inks with active energy rays. In the step of applying the at least two inks, a mixed area in which the at least two inks are mixed is formed in at least a portion of the substrate by applying the at least two inks, wherein the first ink contains a first polymerizable liquid crystal compound and the second ink contains a second chiral compound, thereby enabling the reproduction of multiple colors with high color rendering properties.

[0032] According to the present invention, an ink image can be recorded by applying ink to a substrate. The ink image is a solidified product of the ink. In the image recording method of the present invention, in the process of applying at least two inks, a mixed region of at least two inks is formed in at least a portion of the substrate by applying. Because the first ink contains a first polymerizable liquid crystal compound and the second ink contains a second chiral compound, the first polymerizable liquid crystal compound is mixed with the second chiral compound, and the first polymerizable liquid crystal compound forms a helical structure through the second chiral compound, becoming a cholesteric liquid crystal. Cholesteric liquid crystals selectively reflect light of a wavelength corresponding to the pitch of the helical structure and display structural colors, so the ink image in the present invention displays structural colors. In addition, by controlling the ejection amount of the first ink and the ejection amount of the second ink, the mixing ratio of the first polymerizable liquid crystal compound contained in the first ink and the second chiral compound contained in the second ink in the mixed region can be adjusted. Therefore, by forming a mixed region of at least two inks, a variety of colors can be reproduced.

[0033] Furthermore, in the image recording method of the present invention, even when at least two inks are applied to a heated substrate using an inkjet recording method to form a mixed region of the at least two inks, the mixed region is unlikely to expand. Therefore, the polymerizable liquid crystal compound can be uniformly aligned by the chiral compound, enabling the reproduction of colors with high color rendering properties.

[0034] Hereinafter, each step in the image recording method of the present invention will be described in detail.

[0035] (Ink preparation process)

[0036] The image recording method of the present invention includes a step of preparing at least two inks including a first ink and a second ink (hereinafter also referred to as an "ink preparation step").

[0037] The first ink contains a first polymerizable liquid crystal compound, and the second ink contains a second chiral compound. That is, at least two inks contain a polymerizable liquid crystal compound and a chiral compound. By applying the ink to form a mixed region where the at least two inks are mixed, the polymerizable liquid crystal compound and the chiral compound can be mixed, and the polymerizable liquid crystal compound can be aligned by the chiral compound.

[0038] The first ink may contain components other than the first polymerizable liquid crystal compound. Furthermore, the second ink may contain components other than the second chiral compound. The combination of the first ink and the second ink in the image recording method of the present invention includes the following aspects.

[0039] (1) The first ink contains a first polymerizable liquid crystal compound, and the second ink contains a second polymerizable liquid crystal compound and a second chiral compound

[0040] (2) The first ink contains a first polymerizable liquid crystal compound and a first chiral compound, and the second ink contains a second polymerizable liquid crystal compound and a second chiral compound.

[0041] (3) The first ink contains a first polymerizable liquid crystal compound, a first chiral compound, and a first organic solvent, and the second ink contains a second polymerizable liquid crystal compound and a second chiral compound.

[0042] (4) The first ink contains a first polymerizable liquid crystal compound, a first chiral compound, and a first organic solvent, and the second ink contains a second polymerizable liquid crystal compound, a second chiral compound, and a second organic solvent.

[0043] (5) The first ink contains a first polymerizable liquid crystal compound and a first organic solvent, and the second ink contains a second chiral compound and a second organic solvent.

[0044] Furthermore, in the image recording method of the present invention, it is preferred that the first ink contain a first polymerizable liquid crystal compound, a first chiral compound, and a first organic solvent, and the second ink contain a second polymerizable liquid crystal compound, a second chiral compound, and a second organic solvent, and the absolute value of the difference between the maximum reflection wavelength of the ink film formed by the first ink and the maximum reflection wavelength of the ink film formed by the second ink is 100 nm or greater. In other words, it is preferred that both the first ink and the second ink contain a polymerizable liquid crystal compound, a chiral compound, and an organic solvent, and the ink film formed by the first ink and the ink film formed by the second ink have different hues.

[0045] The first polymerizable liquid crystal compound and the second polymerizable liquid crystal compound may be the same or different. The first chiral compound and the second chiral compound may be the same or different. The first organic solvent and the second organic solvent may be the same or different.

[0046] If the absolute value of the difference between the maximum reflection wavelength of the ink film formed by the first ink and the maximum reflection wavelength of the ink film formed by the second ink is 100 nm or greater, a large hue difference is achieved, enabling the reproduction of a wide range of colors. The absolute value of this difference is more preferably 130 nm or greater, and even more preferably 150 nm or greater. The upper limit of the absolute value of this difference is, for example, 400 nm.

[0047] For example, when the first polymerizable liquid crystal compound and the second polymerizable liquid crystal compound are the same, and the first chiral compound and the second chiral compound are the same, by adjusting the content of the polymerizable liquid crystal compound or the chiral compound, the absolute value of the difference between the maximum reflection wavelength of the ink film formed by the first ink and the maximum reflection wavelength of the ink film formed by the second ink can be made greater than 100 nm.

[0048] Specifically, from the perspective of reproducing multiple colors, the maximum reflection wavelength of the ink film formed by the first ink is preferably 380 nm to 490 nm, and the maximum reflection wavelength of the ink film formed by the second ink is preferably 600 nm to 800 nm. Furthermore, the maximum reflection wavelength of the ink film formed by the first ink is more preferably 390 nm to 420 nm, and the maximum reflection wavelength of the ink film formed by the second ink is more preferably 600 nm to 700 nm.

[0049] The maximum reflection wavelength of the ink film is calculated by the following method.

[0050] The ink was applied to a transparent polyethylene terephthalate substrate at a dot ratio of 100%, dried at 50°C for 5 minutes, and then dried at 80°C for another 5 minutes to completely remove the organic solvent contained in the ink. Subsequently, the ink was cured using a metal halide lamp (product name "CSOT-40, manufactured by GS Yuasa Corporation) to obtain an ink film. The maximum reflection wavelength was calculated by measuring the spectral reflectance of the ink film using a fluorescence spectrophotometer (product name "FD-7", manufactured by Konica Minolta, Inc.). During the measurement, black opacity measurement paper (standard: JIS K 5600 (ISO / FDIS 6504-3:1998), manufactured by TP Giken Co., Ltd.) was placed below the substrate, with the ink film as the outermost layer, and the color was measured.

[0051] From the perspective of reproducing a wider variety of colors, it is preferable to further prepare a third ink during the ink preparation step. The third ink contains a third polymerizable liquid crystal compound, a third chiral compound, and a third organic solvent. The absolute value of the difference between the maximum reflection wavelength of the ink film formed by the first ink and the maximum reflection wavelength of the ink film formed by the second ink and the maximum reflection wavelength of the ink film formed by the third ink is preferably 40 nm or greater. In other words, the absolute value of the difference between the maximum reflection wavelength of the ink film formed by the first ink and the maximum reflection wavelength of the ink film formed by the third ink, and the absolute value of the difference between the maximum reflection wavelength of the ink film formed by the second ink and the maximum reflection wavelength of the ink film formed by the third ink, are both preferably 40 nm or greater.

[0052] The third polymerizable liquid crystal compound may be the same as or different from the first and second polymerizable liquid crystal compounds. The third chiral compound may be the same as or different from the first and second chiral compounds. The third organic solvent may be the same as or different from the first and second organic solvents.

[0053] If the absolute value of the difference between the maximum reflection wavelength of the ink film formed by the first ink, the maximum reflection wavelength of the ink film formed by the second ink, and the maximum reflection wavelength of the ink film formed by the third ink is 40 nm or greater, a wider range of colors can be reproduced. The absolute value of this difference is more preferably 50 nm or greater, and even more preferably 70 nm or greater. The upper limit of the absolute value of this difference is, for example, 150 nm.

[0054] For example, when the first polymerizable liquid crystal compound, the second polymerizable liquid crystal compound, and the third polymerizable liquid crystal compound are the same, and the first chiral compound, the second chiral compound, and the third chiral compound are the same, by adjusting the content of the polymerizable liquid crystal compound or the chiral compound, the absolute value of the difference between the maximum reflection wavelength of the ink film formed by the first ink, the maximum reflection wavelength of the ink film formed by the second ink, and the maximum reflection wavelength of the ink film formed by the third ink can be made to be 40 nm or more.

[0055] Specifically, from the perspective of reproducing a wider variety of colors, the maximum reflection wavelength of the ink film formed by the first ink is preferably 380 nm to 490 nm, the maximum reflection wavelength of the ink film formed by the second ink is preferably 600 nm to 800 nm, and the maximum reflection wavelength of the ink film formed by the third ink is preferably 500 nm to 590 nm. Furthermore, the maximum reflection wavelength of the ink film formed by the first ink is more preferably 390 nm to 470 nm, the maximum reflection wavelength of the ink film formed by the second ink is more preferably 600 nm to 700 nm, and the maximum reflection wavelength of the ink film formed by the third ink is more preferably 500 nm to 550 nm.

[0056] The following describes the various components contained in the inks. The polymerizable liquid crystal compounds (e.g., the first to third polymerizable liquid crystal compounds) contained in the at least two inks prepared in the ink preparation process will be referred to simply as "polymerizable liquid crystal compounds" for this description. The chiral compounds (e.g., the first to third chiral compounds) contained in the at least two inks prepared in the ink preparation process will be referred to simply as "chiral compounds" for this description. The organic solvents (e.g., the first to third organic solvents) contained in the at least two inks prepared in the ink preparation process will be referred to simply as "organic solvents" for this description. Furthermore, the at least two inks prepared in the ink preparation process will be referred to simply as "inks" for this description.

[0057] <Polymerizable liquid crystal compound>

[0058] In the present invention, the polymerizable liquid crystal compound is a liquid crystal compound having a polymerizable group.

[0059] The liquid crystal compound may be a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound, and is preferably a rod-shaped liquid crystal compound.

[0060] Examples of rod-shaped liquid crystal compounds include rod-shaped nematic liquid crystal compounds. Preferred rod-shaped nematic liquid crystal compounds include azomethine compounds, azoxy compounds, cyanobiphenyl compounds, cyanophenyl ester compounds, benzoic acid esters, phenyl cyclohexanecarboxylate, cyanophenylcyclohexane compounds, cyano-substituted phenylpyrimidine compounds, alkoxy-substituted phenylpyrimidine compounds, phenyldioxane compounds, tolan compounds, and alkenylcyclohexylbenzonitrile compounds. Rod-shaped liquid crystal compounds include not only low-molecular-weight liquid crystal compounds but also high-molecular-weight liquid crystal compounds.

[0061] The polymerizable liquid crystal compound is obtained by introducing a polymerizable group into a liquid crystal compound. Examples of the polymerizable group include a polymerizable unsaturated group, an epoxy group, and an aziridine group. Among them, the polymerizable group is preferably a polymerizable unsaturated group, and particularly preferably an ethylenically unsaturated group. The number of polymerizable groups possessed by the polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3. From the perspective of the durability of the image obtained, the polymerizable liquid crystal compound further preferably has two polymerizable groups in the molecule.

[0062] Examples of polymerizable liquid crystal compounds include Makromol. Chem., Vol. 190, p. 2255 (1989), Advanced Materials, Vol. 5, p. 107 (1993), U.S. Pat. No. 4,683,327, U.S. Pat. No. 5,622,648, U.S. Pat. No. 5,770,107, International Publication No. 95 / 22586, International Publication No. 95 / 24455, International Publication No. 97 / 00600, International Publication No. 98 / 23580, International Publication No. 98 / 52905, Japanese Patent Application Publication No. 1-272551, Japanese Patent Application Publication No. 6-16616, Japanese Patent Application Publication No. 7-110469, Japanese Patent Application Publication No. 11-80081, and Japanese Patent Application Publication No. 2001-328973.

[0063] Specific examples of the polymerizable liquid crystal compound include the following compounds (1) to (17). The polymerizable liquid crystal compound is not limited to the following examples.

[0064] [Chemical Formula 1]

[0065]

[0066] [Chemical Formula 2]

[0067]

[0068] [Chemical Formula 3]

[0069]

[0070] In compound (12), X 1 Each independently represents an integer of 2 to 5.

[0071] [Chemical Formula 4]

[0072]

[0073] [Chemical Formula 5]

[0074]

[0075] Examples of polymerizable liquid crystal compounds other than those exemplified above include cyclic organopolysiloxane compounds disclosed in Japanese Patent Application Laid-Open No. 57-165480.

[0076] The ink may contain only one type of polymerizable liquid crystal compound, or may contain two or more types.

[0077] The ink preferably contains two or more different polymerizable liquid crystal compounds. By using two or more polymerizable liquid crystal compounds, color reproducibility can be further improved.

[0078] The content of the polymerizable liquid crystal compound is preferably 1% to 70% by mass, more preferably 5% to 60% by mass, and particularly preferably 15% to 45% by mass, relative to the total amount of the ink.

[0079] In the present invention, to improve color reproducibility, the first and second inks preferably differ in at least one of the type and content of the polymerizable liquid crystal compound. Furthermore, when a third ink is used along with the first and second inks, the first, second, and third inks preferably differ in at least one of the type and content of the polymerizable liquid crystal compound. Depending on the type of polymerizable liquid crystal compound, the pitch of the helical structure of the polymerizable liquid crystal compound when it forms a cholesteric liquid crystal varies, resulting in different wavelengths of light selectively reflected. By varying the type of polymerizable liquid crystal compound, ink films with different hues can be obtained. Furthermore, by varying the content of the polymerizable liquid crystal compound and the mixing ratio with the chiral compound, ink films with different hues can be obtained.

[0080] (Chiral Compound)

[0081] Chiral compounds, also known as optically active compounds, have the ability to induce a helical structure in polymerizable liquid crystal compounds. The twisting direction and pitch of the induced helical structure vary depending on the type and content of the chiral compound.

[0082] There are no particular limitations on the chiral compound, and known compounds can be used (for example, described in Handbook of Liquid Crystal Devices, Chapter 3, Item 4-3, Chiral Reagents for TN and STN, page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), for example, isosorbide derivatives and isomannide derivatives.

[0083] Chiral compounds generally contain an asymmetric carbon atom, but may also contain no asymmetric carbon atom as long as they contain chirality. Examples of chiral compounds include axial asymmetric compounds having a binaphthyl structure, helical asymmetric compounds having a helicene structure, and planar asymmetric compounds having a cycloaromatic structure.

[0084] The chiral compound may also have a polymerizable group. In the case where the chiral compound has a polymerizable group, a polymer having structural units derived from the polymerizable liquid crystal compound and structural units derived from the chiral compound is formed by the polymerization reaction of the chiral compound and the polymerizable liquid crystal compound. In the case where the chiral compound has a polymerizable group, the polymerizable group is preferably a group of the same type as the polymerizable group possessed by the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral compound is preferably a polymerizable unsaturated group, an epoxy group or an aziridine group, more preferably a polymerizable unsaturated group, and particularly preferably an ethylenically unsaturated group. Furthermore, the chiral compound itself may be a liquid crystal compound.

[0085] Specific examples of chiral compounds include the following compounds. The chiral compounds that can be used in the ink composition are not limited to the following examples. "Me" in the compound refers to a methyl group.

[0086] [Chemical Formula 6]

[0087]

[0088] [Chemical Formula 7]

[0089]

[0090] [Chemical Formula 8]

[0091]

[0092] In the above compounds, X each independently represents an integer of 2 to 5.

[0093] In the ink composition, the content of the chiral compound is preferably 1 to 15 parts by mass, and more preferably 1.5 to 5 parts by mass, relative to 100 parts by mass of the polymerizable liquid crystal compound.

[0094] The first and second inks preferably have different chiral compound contents. Furthermore, if a third ink is used, the chiral compound contents of the first, second, and third inks preferably differ. Depending on the chiral compound content, the pitch of the helical structure of the polymerizable liquid crystal compound when it forms a cholesteric liquid crystal varies, resulting in different wavelengths of light selectively reflected. By varying the chiral compound content, ink films with varying hues can be obtained. Increasing the chiral compound content shifts the reflected wavelength toward shorter wavelengths, while decreasing the chiral compound content shifts the reflected wavelength toward longer wavelengths.

[0095] Organic solvents

[0096] The type of the organic solvent is not particularly limited and can be appropriately selected depending on the intended purpose.

[0097] Examples of the organic solvent include ketone solvents, alkyl halide solvents, amide solvents, sulfoxide solvents, heterocyclic compounds, hydrocarbon solvents, ester solvents, and ether solvents.

[0098] The content of the organic solvent is preferably 20% by mass to 90% by mass, more preferably 40% by mass to 80% by mass, and more preferably 50% by mass to 80% by mass, relative to the total amount of the ink.

[0099] <Polymerization initiator>

[0100] The ink preferably further contains a polymerization initiator. The polymerization initiator is preferably a photopolymerization initiator, and more preferably a radical polymerization initiator having a function of generating radicals by irradiation with ultraviolet rays.

[0101] Examples of the polymerization initiator include alkylphenone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, intramolecular hydrogen abstraction-type photopolymerization initiators, oxime ester-based photopolymerization initiators, and cationic photopolymerization initiators. Among these, the polymerization initiator is preferably an acylphosphine oxide-based photopolymerization initiator, specifically (2,4,6-trimethylbenzoyl)diphenylphosphine oxide or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0102] The content of the polymerization initiator is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 12 parts by mass, relative to 100 parts by mass of the polymerizable liquid crystal compound.

[0103] <Additives>

[0104] The ink may contain additives as needed within a range that does not impair the effects of the present invention.

[0105] Examples of the additives include surfactants, cross-linking agents, and non-polymerizable polymers for improving ink ejection properties.

[0106] When the ink contains a surfactant, the polymerizable liquid crystal compound aligns horizontally on the air interface side during ink curing, and the helical axis direction is controlled to be more uniform. The surfactant is preferably a compound that functions as an alignment control agent that stably or rapidly forms a planar oriented cholesteric structure. Examples of the surfactant include silicone surfactants and fluorine-based surfactants, with fluorine-based surfactants being preferred.

[0107] The content of the surfactant is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and even more preferably 0.02 to 1 part by mass, relative to 100 parts by mass of the polymerizable liquid crystal compound.

[0108] <Physical Properties>

[0109] The viscosity of at least two inks is preferably 7 mPa·s or higher, more preferably 8 mPa·s or higher, and even more preferably 10 mPa·s or higher. From the perspective of ink ejection properties, the upper limit of the ink viscosity is, for example, 30 mPa·s.

[0110] If the viscosities of at least two inks are both 7 mPa·s or higher, ink droplets landed on the substrate are less likely to spread. In particular, when chiral compounds contained in the inks flow and mix with adjacent ink droplets, the boundaries between areas where images were originally recorded with different hues become blurred, tending to reduce image clarity. In contrast, if ink droplets are less likely to spread, high-definition images can be produced.

[0111] The viscosity of the ink is measured at 25° C. using a viscometer, for example, a viscometer (product name “RE-85L”, manufactured by Toki Sangyo Co., Ltd.).

[0112] The surface tension of at least two inks is preferably 20 mN / m to 40 mN / m, more preferably 23 mN / m to 35 mN / m.

[0113] The surface tension of the ink is measured at 25° C. using a surface tensiometer, for example, a surface tensiometer (product name “DY-700”, manufactured by Kyowa Interface Science Co., Ltd.).

[0114] The absolute value of the difference in surface tension between the at least two inks is preferably less than 1 mN / m, more preferably less than 0.7 mN / m. When the difference in surface tension between the inks is small and the absolute value of the difference is less than 1 mN / m, when a mixed area is formed in which at least two inks are mixed, the area where the inks are mixed in a desired ratio is easily fixed. If the area in which the inks are uniformly mixed can be properly controlled, an image can be obtained in which the polymerizable liquid crystal compound is uniformly oriented and has little color unevenness. Moreover, after the inks are landed on adjacent areas, if the surface tension difference is less than 1 mN / m, the occurrence of color bleeding can be suppressed.

[0115] In the ink preparation step, it is preferred to prepare at least two inks containing the same polymerizable liquid crystal compound and chiral compound for easier mixing. In this case, the chiral compound contents of the at least two inks are preferably different.

[0116] (Substrate Heating Process)

[0117] The image recording method of the present invention includes a step of heating the substrate (hereinafter also referred to as a "substrate heating step"). By preheating the substrate, the ink can be applied to the heated substrate.

[0118] The substrate is not particularly limited, and any substrate can be selected. The substrate may be any of an ink-absorbing substrate, a low-ink-absorbing substrate, and a non-ink-absorbing substrate. Examples of the substrate include paper, leather, cloth, and resin. From the perspective of color development, the substrate is preferably a non-ink-absorbing substrate, and more preferably a resin substrate.

[0119] Examples of the resin constituting the resin substrate include cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, acrylic resins, chlorinated polyolefin resins, polyethersulfone resins, polyethylene terephthalate (PET), polyethylene naphthalate, nylon, polyethylene, polystyrene, polypropylene, polycycloolefin resins, polyimide resins, polycarbonate resins, and polyvinyl acetal. The resin substrate may contain only one of these resins or a mixture of two or more of these resins.

[0120] The thickness of the substrate is not particularly limited, and is, for example, 1 μm to 10 mm.

[0121] In the substrate heating step, the method for heating the substrate is not particularly limited, and examples thereof include a heating drum, warm air, infrared lamp, oven, hot plate, and hot plate. The substrate heating temperature is preferably 40°C or higher, more preferably 50°C to 100°C, and even more preferably 55°C to 80°C.

[0122] (Ink application process)

[0123] The image recording method of the present invention includes a step of applying at least two inks to a heated substrate using an inkjet recording method (hereinafter also referred to as the "ink applying step"). In the ink applying step, a mixed region of the at least two inks is formed in at least a portion of the substrate by the application.

[0124] During the ink application process, a mixed area of at least two inks is formed on at least a portion of the substrate, enabling the reproduction of multiple colors with high color rendering properties. Furthermore, by applying the ink to the heated substrate, ink droplets that land on the substrate are less likely to spread. This prevents ink droplets from spreading and allows them to remain at their landing locations, resulting in high-definition images.

[0125] The mixed region, where at least two inks are mixed, only needs to be formed on at least a portion of the substrate. That is, the mixed region can be formed on the entire surface of the substrate. Furthermore, as long as the mixed region is formed on a portion of the substrate, the mixed region may not be formed on other portions of the substrate.

[0126] In the present invention, the mixed region refers to a region on a substrate where at least two types of ink are mixed. Specific methods for forming the mixed region include the following two methods.

[0127] When at least two inks are ejected continuously, the at least two inks are mixed by causing the subsequently ejected ink to land on the ink landing area formed by the previously ejected ink. When at least two inks are ejected simultaneously, the at least two inks are mixed by causing the ink landing areas formed by the at least two inks to land so that at least a portion of them overlap. The term "mixed area" as used in the present invention does not include an area where the ink landing areas partially overlap as the inks spread onto the substrate after the at least two inks are ejected so that the ink landing areas do not overlap.

[0128] The formation of the mixed region can be confirmed by the following method.

[0129] By measuring the reflection wavelength of the mixed area using a fluorescence spectrophotometer (product name "FD-7") or the like, it can be confirmed that the reflection wavelength is different from that of the unmixed area. Furthermore, since the color rendering properties of the mixed area are different from those of the unmixed area, this can also be easily confirmed visually.

[0130] In the image recording method of the present invention, the ink film (also referred to as "ink layer") formed by applying the ink on the substrate in the ink applying step is a single layer.

[0131] For example, methods for recording images on substrates involve stacking ink layers. However, the image recording method of the present invention reduces the number of steps by forming the ink layer as a single layer. Furthermore, the ink design only needs to consider the interaction between the substrate and the ink (e.g., wettability). Compared to stacking ink layers, there is no need to consider the interaction between the ink layers. Furthermore, because the ink is applied as a single layer in the image recording method of the present invention, images with higher color rendering properties can be obtained compared to stacking ink layers.

[0132] The inkjet recording method can use generally known methods, for example, a charge control method that utilizes electrostatic induction force to discharge the ink composition, a drop-on-demand inkjet method (pressure pulse method) that utilizes the vibration pressure of a piezoelectric element, an acoustic inkjet method that converts an electrical signal into an acoustic beam and irradiates the ink composition to discharge the ink composition using the radiation pressure, and a thermal inkjet method that heats the ink composition to form bubbles and utilizes the generated pressure.

[0133] Generally speaking, image recording methods based on inkjet recording devices include a shuttle scanning method (also called a "serial head method") that uses a short serial head to record images, and a single-pass method (also called a "line head method") that uses a line head in which recording elements are arranged across the entire width of the recording medium to record images. In the shuttle scanning method, image recording is performed while the serial head is scanned along the width of the recording medium. In contrast, in the single-pass method, the image can be recorded on the entire surface of the recording medium by scanning the recording medium in a direction perpendicular to the arrangement direction of the recording elements. Therefore, in the single-pass method, unlike the shuttle scanning method, a transport system such as a carriage for scanning the serial head is not required. In addition, in the single-pass method, there is no need for carriage movement and complex scanning control of the recording medium; only the recording medium moves, thereby increasing the recording speed compared to the shuttle scanning method.

[0134] In the ink application step, the total application amount of at least two inks per unit area in the mixed area is preferably set to 3 g / m 2 ~20g / m 2 The range of giving is preferably set to 3.5g / m 2 ~20g / m 2 The range of giving, more preferably set to 3.5g / m 2 ~18g / m 2 It is preferably given in the range of 3.5 g / m 2 ~16g / m 2 It is preferably given in the range of 3.5 g / m 2 ~13g / m 2 range to give.

[0135] In particular, since at least two types of ink are mixed in the mixed area, the amount of ink applied is increased compared to areas other than the mixed area. In the mixed area, the total amount of ink applied is set to 3.0 g / m2 to 20 g / m2. 2 The range of the ink droplets is given, the landed ink droplets are not easy to expand, and high-definition images can be obtained.

[0136] In addition, in the ink application step, it is also preferable to set the application amount of ink per unit area in one image recording to 3 g / m2 in the area other than the mixed area. 2 ~20g / m 2 The range of giving is preferably set to 3.5g / m 2 ~20g / m 2 The range of giving, more preferably set to 3.5g / m 2 ~18g / m 2 It is preferably given in the range of 3.5 g / m 2 ~16g / m 2 It is preferably given in the range of 3.5 g / m 2 ~13g / m 2 The area other than the mixed area refers to an area on the substrate where only one ink is applied without mixing at least two inks.

[0137] Furthermore, in the ink application step, in the mixed region, the total application amount per unit area of the polymerizable liquid crystal compound contained in at least two inks is preferably set to 1 g / m 2 ~8g / m 2 The range of the given, more preferably set to 1.5g / m 2 ~8g / m 2 The range of giving is preferably set to 1.5g / m 2 ~7.5g / m 2 The most preferred range is 1.5 g / m 2 ~7g / m 2 range to give.

[0138] If the total amount of the above is set to 1g / m 2 ~8g / m 2 If the range is provided, the polymerizable liquid crystal compound is more uniformly aligned, and an image with high color rendering properties can be obtained.

[0139] In addition, in the ink application step, it is also preferable to set the application amount per unit area of the polymerizable liquid crystal compound contained in the ink to 1 g / m2 in the area other than the mixed area. 2 ~8g / m 2 The range of the given, more preferably set to 1.5g / m 2 ~8g / m 2 The range of is preferably set to 1.5 g / m 2 ~7.5g / m 2 The most preferred range is 1.5 g / m 2 ~7g / m 2 range to give.

[0140] Furthermore, in the ink application step, in the mixed region, the total application amount per unit area of the organic solvent contained in at least two inks is preferably set to 1.5 g / m 2 ~12.5g / m 2 The range of the given, more preferably set to 2.5g / m 2 ~12.5g / m 2 It is preferably given in the range of 2.5 g / m 2 ~10g / m 2 range to give.

[0141] In particular, since at least two inks are mixed in the mixing area, the total amount of organic solvent contained in the ink increases compared to the area other than the mixing area. 2 ~12.5g / m 2 The range of the ink droplets is given, the landed ink droplets are not easy to expand, and high-definition images can be obtained.

[0142] In addition, in the ink application step, it is also preferable to set the application amount per unit area of the organic solvent contained in the ink to 1.5 g / m2 in the area other than the mixing area. 2 ~12.5g / m 2 The range of the given, more preferably set to 2.5g / m 2 ~12.5g / m 2 It is preferably given in the range of 2.5 g / m 2 The range of ~10g / m2 is given.

[0143] The ink application amount was calculated using the following method.

[0144] At the desired dot rate (the ratio of the portion of the recorded image to the total area calculated as a percentage), 1m 2 The image is recorded on an area of ​​the substrate. The weight of the substrate before and after image recording is measured, and the amount of ink applied is calculated based on the weight difference. The amount of ink applied can be arbitrarily changed by setting the dot ratio and adjusting the ink discharge rate of the device.

[0145] The amount of the polymerizable liquid crystal compound contained in the ink to be applied is calculated based on the amount of ink applied and the content of the polymerizable liquid crystal compound contained in the ink.

[0146] The amount of the organic solvent added to the ink is calculated based on the amount of ink added and the content of the organic solvent in the ink.

[0147] The total amount of ink applied in the mixed region is calculated as the total amount of each ink applied.

[0148] In the ink application process, the ink ejected from the inkjet head is preferably ejected at a volume of 1 pL (picoliter) to 30 pL, more preferably 2 pL to 10 pL. The ejection volume refers to the volume of ink ejected from a single nozzle in an inkjet recording process.

[0149] In the ink application step, the ink is applied at a resolution of preferably 100 dpi (dots per inch) x 100 dpi to 2400 dpi x 2400 dpi, more preferably 200 dpi x 200 dpi to 1200 dpi x 1200 dpi. "Dpi" refers to the number of dots per 25.4 mm.

[0150] Furthermore, in the ink application step, the ink film formed by the at least two inks is preferably applied in the mixed region so that the thickness of the ink film formed during a single image recording is 1 μm to 20 μm, more preferably 1 μm to 15 μm. Applying the ink film to a thickness of 1 μm to 20 μm facilitates drying of the applied ink, allows for more uniform alignment of the polymerizable liquid crystal compound, and enables the production of an image with high color rendering properties.

[0151] The image recording method of the present invention includes a step of irradiating at least two types of inks with active energy rays (hereinafter also referred to as “active energy ray irradiation step”).

[0152] In the active energy ray irradiation step, examples of the active energy ray include ultraviolet rays, visible rays, and electron beams, and ultraviolet rays (hereinafter also referred to as "UV") are preferred among them.

[0153] The peak wavelength of ultraviolet rays is preferably 200 nm to 405 nm, more preferably 220 nm to 390 nm, and even more preferably 220 nm to 380 nm.

[0154] The exposure dose of ultraviolet light is preferably 20 mJ / cm 2 ~5J / cm 2 , more preferably 100 mJ / cm 2 ~1,500mJ / cm 2 The irradiation conditions and basic irradiation method can be applied to those disclosed in Japanese Patent Application Laid-Open No. 60-132767. Specifically, the irradiation method is preferably a method in which light sources are provided on both sides of a head unit containing an ink ejection device, and the head unit and light sources are scanned in a so-called reciprocating manner, or a method in which another light source is not driven.

[0155] Mercury lamps, gas lasers, and solid-state lasers are the main sources of ultraviolet radiation. Mercury lamps, metal halide lamps, and ultraviolet fluorescent lamps are widely known. Furthermore, UV-LEDs (light-emitting diodes) and UV-LDs (laser diodes) are compact, have long lifespans, high efficiency, and are low-cost, making them promising sources of ultraviolet radiation. Preferred sources of ultraviolet radiation include metal halide lamps, high-pressure mercury lamps, medium-pressure mercury lamps, low-pressure mercury lamps, or UV-LEDs.

[0156] [Inkjet Recordings]

[0157] The inkjet recorded material of the present invention comprises: a substrate; and an ink film containing a liquid crystal polymer provided on the substrate, wherein the ink film includes a plurality of regions having mutually different maximum reflection wavelengths when viewed from above, and the orientation state of the liquid crystal polymer continuously changes between two adjacent regions.

[0158] The inkjet recorded article of the present invention is preferably an inkjet recorded article obtained by the above-mentioned image recording method. For example, after applying an ink containing a polymerizable liquid crystal compound to a substrate, the polymerizable liquid crystal compound is polymerized by irradiation with active energy rays to form an ink film containing a liquid crystal polymer.

[0159] The inkjet recorded matter of the present invention may have an ink film directly provided on a substrate, or may have another layer provided between the substrate and the ink film.

[0160] Since the ink film includes a plurality of regions having mutually different maximum reflection wavelengths when viewed from above, it is possible to reproduce a variety of colors with high color rendering properties.

[0161] The alignment state of the liquid crystal polymer between two adjacent regions can be confirmed by the following method.

[0162] First, the ink film was cut along its thickness to obtain a sample, so that the sample contained multiple regions with different maximum reflection wavelengths when viewed from above. Using a scanning electron microscope (S-4800, manufactured by Hitachi High-Technologies Corporation, observation magnification: 10,000x, accelerating voltage: 2.0 kV), the cross-sectional SEM image was observed to confirm the presence of a light-dark streak pattern caused by changes in the refractive index of the cholesteric liquid crystal phase. If a streak pattern was observed, the sample was determined to be a cholesteric liquid crystal phase.

[0163] In a cross-sectional SEM image, one cycle of dark and light areas in the fringe pattern corresponds to a 180-degree twist in the liquid crystal. Therefore, two cycles of dark, light, dark, light in the fringe pattern correspond to a 360-degree twist in the liquid crystal. In other words, the width of the two cycles representing the dark and light fringe patterns corresponds to the length of the helical pitch in the cholesteric liquid crystal phase.

[0164] Because the ink film contains multiple regions with different maximum reflection wavelengths, the maximum reflection wavelengths of two adjacent regions also differ. Therefore, the helical pitch lengths in the cholesteric liquid crystal phase differ between the two adjacent regions. In this case, if the helical pitch length continuously changes between the two adjacent regions, it is determined that the orientation state of the liquid crystal polymer is continuously changing.

[0165] Example

[0166] The present invention will be described in more detail below using examples. However, the present invention is not limited to the following examples unless the scope of the present invention deviates from the scope of the present invention. The viscosity of the ink is measured using a viscometer (product name "RE-85L", manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25°C. The surface tension of the ink is measured using a surface tensiometer (product name "DY-700", manufactured by Kyowa Interface Science Co., Ltd.).

[0167] <Example 1>

[0168] [Preparation of ink]

[0169] (Ink Bm1)

[0170] The following components were mixed to prepare ink Bm1. The viscosity of ink Bm1 (25° C.) was 11 mPa·s.

[0171] Diethylene glycol diethyl ether…61.27 parts by mass

[0172] ·Mixture A of polymerizable liquid crystal compounds 1…35 parts by mass

[0173] Polymerization initiator: 1.5 parts by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (product name "Omni rad819")

[0174] Chiral compound A...2.2 parts by mass

[0175] Fluorine-based surfactant (product name "Fergent 208G", manufactured by NEOS COMPANY) ... 0.03 parts by mass

[0176] The mixture of polymerizable liquid crystal compounds is a mixture in the following ratio.

[0177] Mixture A1 of polymerizable liquid crystal compounds: 50% by mass of compound (10), 50% by mass of compound (11)

[0178] Mixture A2 of polymerizable liquid crystal compounds: 50% by mass of compound (10), 50% by mass of compound (12)

[0179] Mixture A3 of polymerizable liquid crystal compounds: 33% by mass of compound (10), 34% by mass of compound (11), and 33% by mass of compound (12)

[0180] Compounds (10) to (12) are rod-shaped liquid crystal compounds. Compound (10), Compound (11), Compound (12) (X 1 =2) and the structures of chiral compound A are as follows.

[0181] (Compound (10), Compound (11) and Compound (12))

[0182] [Chemical Formula 9]

[0183]

[0184] (Chiral Compound A)

[0185] [Chemical Formula 10]

[0186]

[0187] The reflectance of the ink film formed from ink Bm1 in the visible light region was measured using a spectroscopic reflectometer (manufactured by Konica Minolta, Inc., product name "FD-7"). The results showed that ink Bm1 formed an ink film with a maximum reflection wavelength of 440 nm. Furthermore, polarization characteristics were measured using a left-handed circular polarizer, but no reflectance spectrum was obtained. In other words, ink composition Bm1 formed a right-polarized blue ink film. The surface tension of ink Bm1 was 28 mN / m. Measurements were performed using the same method as for ink Bm1 for the other inks, unless otherwise specified.

[0188] (Ink Rm1)

[0189] Ink Rm1 was prepared using the same method as Ink Bm1, except that the content of chiral compound A in Ink Bm1 was changed from 2.2 parts by mass to 1.6 parts by mass, and the content of diethylene glycol diethyl ether was adjusted to match the total content of Ink Bm1. Ink Rm1 had a viscosity (at 25°C) of 11 mPa·s. Ink Rm1 formed a right-polarized red ink film that reflected right-handed circularly polarized light with a maximum reflection wavelength of 620 nm. The surface tension of Ink Rm1 was 27.6 mN / m.

[0190] [Image Record]

[0191] As a substrate, a PET sheet (product name "Viewful UV TP-188", manufactured by Kimoto Co., Ltd.) was used. The substrate was placed on a hot plate made by attaching a rubber heater to a metal plate, and heated until the temperature of the substrate reached 60°C. Using an inkjet printer (product name "UJF3042HG", manufactured by MIMAK I ENGINEERING CO., LTD.), ink Bm1 and ink Rm1 were ejected onto the substrate heated to 60°C. Data was prepared with an image resolution of 600dpi×720dpi, and images of 7mm squares with the ratios of the applied amounts of ink Bm1 and ink Rm1 adjusted to 100:0, 83:17, 2:1, 50:50, 1:2, 17:83, and 0:100 were arranged in a vertical column without gaps. An image that was reversed up and down was arranged next to it. Using the prepared image data, the total applied amount of ink in each image area was 15g / m 2 The ink ejection amount was adjusted in such a manner that an image was recorded. After the image recording was completed, the substrate was held at 60°C for 1 minute, and then heated at 80°C for 5 minutes. Then, a metal halide lamp mounted on an ultraviolet irradiation device (product name "CSOT-40", manufactured by GS Yuasa Corporation) was used to irradiate the substrate with ultraviolet A waves (UV-A, wavelength 320-390 nm) at a rate of 350 mJ / cm 2 irradiation in a manner of , an image record 1 was obtained.

[0192] Image recorded material 2 was obtained by the same method as that for image recorded material 1 except that the 7 mm square image was changed to a 2 mm square image.

[0193] <Example 2>

[0194] [Preparation of ink]

[0195] (Ink Gm1)

[0196] Ink Gm1 was prepared using the same method as ink Bm1, except that the content of chiral compound A in ink Bm1 was changed from 2.2 parts by mass to 1.9 parts by mass, and the content of diethylene glycol diethyl ether was adjusted to match the total content of ink Bm1. Ink Rm1 had a viscosity (at 25°C) of 11 mPa·s. Ink Gm1 formed a right-polarized green ink film that reflected right-handed circularly polarized light with a maximum reflection wavelength of 510 nm. The surface tension of ink Gm1 was 28 mN / m.

[0197] [Image Record]

[0198] As a substrate, a PET sheet (product name "Viewful UV TP-188", manufactured by Kimoto Co., Ltd.) was used. The substrate was placed on a rubber heater and heated until the temperature of the substrate reached 60°C. Using an inkjet printer (product name "UJF3042HG", manufactured by MIMAKI ENGINEERING CO., LTD.), ink Bm1, ink Rm1, and ink Gm1 were ejected onto the substrate heated to 60°C. Image data was prepared with an image resolution of 600dpi×720dpi, and the ratios of the applied amounts of ink Bm1, ink Rm1, and ink Gm1 were adjusted to 1:0:0, 2:1:0, 1:2:0, 0:1:0, 0:2:1, 0:1:2, and 0:0:1, respectively. Using the prepared image data, the total applied amount of ink in each image area was 15g / m 2 The ink ejection amount was adjusted in such a manner that the same image as in Example 1 was recorded without gaps. After the image recording was completed, the substrate was kept at 60°C for 1 minute, and then heated at 80°C for 5 minutes. Then, a metal halide lamp mounted on an ultraviolet irradiation device (product name "CSOT-40", manufactured by GS Yuasa Corporation) was used to irradiate the substrate with ultraviolet A waves (UV-A, wavelength 320-390 nm) at a rate of 350 mJ / cm 2 irradiation in a manner of , image recorded matter 1 and image recorded matter 2 were obtained.

[0199] <Example 3>

[0200] In Example 1, the total amount of ink applied to each image area is 7 g / m 2 Image recorded matter 1 and image recorded matter 2 were obtained by the same method as in Example 1 except that the ink ejection amount was adjusted in the manner of .

[0201] <Example 4>

[0202] Image recorded matter 1 and image recorded matter 2 were obtained by the same method as in Example 3 except that the temperature of the substrate during ink ejection was changed to 50°C.

[0203] <Example 5>

[0204] Image recorded articles 1 and 2 were obtained by the same method as in Example 3, except that the substrate temperature during ink ejection was changed to 80°C and the substrate was held at 80°C for 5 minutes after image recording. That is, in Example 5, no additional heating of the substrate was performed.

[0205] <Example 6>

[0206] Image recorded articles 1 and 2 were obtained by the same method as in Example 5, except that the substrate temperature during ink ejection was changed to 90°C and the substrate was held at 90°C for 5 minutes after image recording. That is, in Example 6, no additional heating of the substrate was performed.

[0207] <Example 7>

[0208] In Example 2, the total amount of ink applied to each image area is 7 g / m 2 Image recorded matter 1 and image recorded matter 2 were obtained by the same method as in Example 2 except that the ink ejection amount was adjusted in the manner of .

[0209] <Example 8>

[0210] Image recorded matter 1 and image recorded matter 2 were obtained by the same method as in Example 7 except that the temperature of the substrate during ink ejection was changed to 50°C.

[0211] <Example 9>

[0212] Image recorded articles 1 and 2 were obtained by the same method as in Example 7, except that the substrate temperature during ink ejection was changed to 80°C and the substrate was held at 80°C for 5 minutes after image recording. That is, in Example 9, no additional heating of the substrate was performed.

[0213] <Example 10>

[0214] In Example 7, the total amount of ink applied to each image area is 3 g / m 2 Image recorded matter 1 and image recorded matter 2 were obtained by the same method as in Example 7 except that the ink ejection amount was adjusted in the manner of .

[0215] <Example 11>

[0216] In Example 7, the total amount of ink applied to each image area was 1.2 g / m 2 Image recorded matter 1 and image recorded matter 2 were obtained by the same method as in Example 7 except that the ink ejection amount was adjusted in the manner of .

[0217] <Example 12>

[0218] In Example 1, the total amount of ink applied to each image area is 21 g / m 2 Image recorded matter 1 and image recorded matter 2 were obtained by the same method as in Example 1 except that the ink ejection amount was adjusted in the manner of .

[0219] Comparative Example 1

[0220] Image recorded materials 1 and 2 were obtained by the same method as in Example 1, except that the substrate was kept at room temperature (25° C.) without being heated.

[0221] Comparative Example 2

[0222] Image recorded materials 1 and 2 were obtained in the same manner as in Example 2, except that the substrate was kept at room temperature (25° C.) without being heated.

[0223] <Example 13>

[0224] [Preparation of ink]

[0225] (Ink Bm2)

[0226] The following components were mixed to prepare ink Bm2. The viscosity of ink Bm2 (25° C.) was 6 mPa·s.

[0227] Diethylene glycol diethyl ether…68.27 parts by mass

[0228] ·Mixture A of polymerizable liquid crystal compounds 1…28 parts by mass

[0229] Polymerization initiator: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide

[0230] (Product name: "Omnirad 819, manufactured by IGM Resins BV") ... 1.5 parts by mass

[0231] Chiral compound A...2.2 parts by mass

[0232] Fluorine-based surfactant (product name "Fergent 208G", manufactured by NEOS COMPANY) ... 0.03 parts by mass

[0233] Ink Bm2 is an ink that forms a right-polarized blue ink film that reflects right-handed circularly polarized light with a maximum reflection wavelength of 430 nm. The surface tension of ink Bm2 is 27 mN / m.

[0234] (Ink Rm2)

[0235] Ink Rm2 was prepared using the same method as Ink Bm2, except that the content of chiral compound A in Ink Bm2 was changed from 2.2 parts by mass to 1.6 parts by mass, and the content of diethylene glycol diethyl ether was adjusted to match the total content of Ink Bm2. Ink Rm2 had a viscosity (at 25°C) of 6 mPa·s. Ink Rm2 formed a right-polarized red ink film that reflected right-handed circularly polarized light with a maximum reflection wavelength of 620 nm. The surface tension of Ink Rm2 was 27 mN / m.

[0236] [Image Record]

[0237] In Example 5, an image recorded material was obtained by the same method as in Example 5, except that the ink Bm2 was used instead of the ink Bm1, and the ink Rm2 was used instead of the ink Rm1.

[0238] <Example 14>

[0239] [Preparation of ink]

[0240] (Ink Rm3)

[0241] Ink Rm3 was prepared using the same method as ink Rm1, except that the fluorochemical surfactant content in ink Rm1 was changed from 0.03 parts by mass to 0.2 parts by mass and the diethylene glycol diethyl ether content was adjusted to match that of ink Rm1. The viscosity of ink Rm3 (at 25°C) was 11 mPa·s. Ink Rm3 forms a right-polarized red ink film that reflects right-handed circularly polarized light with a maximum reflection wavelength of 620 nm. The surface tension of ink Rm3 was 25 mN / m.

[0242] [Image Record]

[0243] In Example 5, an image recorded material was obtained by the same method as in Example 5, except that the ink Rm3 was used instead of the ink Rm1.

[0244] Table 1 shows the types of inks used in Examples and Comparative Examples; the amounts of ink, organic solvent, and polymerizable liquid crystal compound applied; the maximum absolute value of the difference in surface tension; and the temperature of the substrate when the ink was ejected.

[0245] The absolute value of the difference in surface tension between the inks is calculated, and the largest value among the calculated absolute values is defined as the maximum value of the absolute value of the difference in surface tension.

[0246] <Evaluation>

[0247] (1) Color rendering in multiple wavelength regions

[0248] The produced image record 1 was placed on the black surface of opacity measurement paper (JIS K 5600). Using a spectroscopic reflectometer (product name "FD-7", manufactured by Konica Minolta, Inc.), spectral reflectance spectra were measured in multiple wavelength regions to evaluate color rendering properties in multiple color ranges. Measurements were performed under reflectance measurement conditions, an observation field of view of 2°, an observation light source of D50, and no polarizing filter. Specifically, spectral reflectance spectra were measured in seven wavelength regions: 420nm to 460nm, 465nm to 475nm, 480nm to 520nm, 525nm to 550nm, 555nm to 565nm, 570nm to 605nm, and 610nm to 730nm. The presence of a reflection wavelength peak in each wavelength region was confirmed. Furthermore, for image record 2, it was confirmed whether the same color as image record 1 could be visually recognized. The evaluation criteria are as follows. The evaluation results are shown in Table 1.

[0249] <Evaluation Criteria>

[0250] 7: It is visually recognized that image recorded material 1 has a reflection wavelength peak with a reflectance of 1% or more in all wavelength regions, and that image recorded material 2 reproduces the same color as image recorded material 1 in all wavelength regions.

[0251] 6: Image recorded material 1 has a reflection wavelength peak with a reflectance of 1% or more in all wavelength regions, and image recorded material 2 has 4 to 6 regions in which the same color as image recorded material 1 is reproduced.

[0252] 5: Image recorded material 1 has six wavelength regions with reflection wavelength peaks having a reflectance of 1% or more, and image recorded material 2 reproduces the same color as image recorded material 1 in all wavelength regions.

[0253] 4: Image recorded material 1 has six wavelength regions with reflection wavelength peaks having a reflectance of 1% or more, and image recorded material 2 has four or five regions in which the same color as image recorded material 1 is reproduced.

[0254] 3: It is visually recognized that image recorded material 1 has five wavelength regions with reflection wavelength peaks having a reflectance of 1% or more, and image recorded material 2 reproduces the same color as image recorded material 1 in all wavelength regions.

[0255] 2: Image recorded material 1 has five wavelength regions with reflection wavelength peaks having a reflectance of 1% or more, and image recorded material 2 has four regions in which the same color as that of image recorded material 1 is reproduced.

[0256] 1: Image recorded material 1 has four or fewer wavelength regions with reflection wavelength peaks having a reflectance of 1% or higher, or image recorded material 2 has three or fewer regions in which the same color as image recorded material 1 is reproduced.

[0257] (2) Glossiness

[0258] The produced image record 1 was placed on the black side of a sheet of opacity measurement paper (standard: JIS K 5600, manufactured by TP Giken). The image was visually observed and the glossiness was evaluated. The evaluation criteria were as follows: 2 or higher was considered a level with no practical problems. The evaluation results are shown in Table 1.

[0259] <Evaluation Criteria>

[0260] 4: Excellent gloss.

[0261] 3: Glossy.

[0262] 2: A little glossy.

[0263] 1: There is no glossiness and the color looks cloudy.

[0264] (3) Uniformity

[0265] The produced image record 1 was placed on the black surface of a sheet of opacity measurement paper (JIS K 5600) and visually inspected for turbidity or unevenness in the observed area. The observed area was a mixed area containing at least two inks. If there was no turbidity or unevenness in the image, the image was considered to have high uniformity. The evaluation criteria were as follows: 2 or higher was considered a level with no practical problems. The evaluation results are shown in Table 1.

[0266] <Evaluation Criteria>

[0267] 4: No turbidity or unevenness.

[0268] 3: Very little turbidity or unevenness.

[0269] 2: Slightly turbid or uneven appearance that can be visually observed.

[0270] 1: Clearly cloudy or uneven, causing problems in practical use.

[0271] (4) Image quality (clarity)

[0272] The produced image record was placed on the black surface of a coverage measurement paper (JIS K 5600) and visually observed to see if color mixing was observed between adjacent image areas. The evaluation criteria were as follows. A rating of 2 or higher was considered to be a practically acceptable rating. The evaluation results are shown in Table 1.

[0273] <Evaluation Criteria>

[0274] 5: No color mixing is observed at all, or almost no color mixing is observed.

[0275] 4: Color mixing is rarely observed.

[0276] 3: Color mixing is slightly observed, but the color mixed portion is not noticeable.

[0277] 2: Color mixing is observed, and the color mixed portion is slightly conspicuous.

[0278] 1: The area of completely mixed colors is wide and noticeable.

[0279] [Table 1]

[0280]

[0281] As shown in Table 1, Examples 1 to 13 include the following steps: preparing at least two inks, including a first ink and a second ink; heating a substrate; applying the at least two inks to the heated substrate using an inkjet recording method; and irradiating the at least two inks with active energy rays. During the step of applying the at least two inks, the at least two inks are applied to form a mixed region of the at least two inks in at least a portion of the substrate. This demonstrates excellent color rendering properties across multiple wavelengths. Specifically, Examples 1 to 13 demonstrate the ability to reproduce a wide range of colors with high color rendering properties.

[0282] On the other hand, in Comparative Examples 1 and 2, the step of heating the substrate is not included, and at least two types of inks are not applied to the heated substrate. Therefore, multiple colors cannot be reproduced with high color development properties.

[0283] Furthermore, in Example 1, the total amount of at least two inks applied per unit area in the mixed region was set to 3 g / m 2 ~20g / m 2 Therefore, compared with Example 12, more colors can be reproduced with high color rendering, white turbidity and unevenness of the image are suppressed, and a more glossy image is obtained.

[0284] In Example 2, since a mixed region in which three types of inks are mixed is formed in a portion of the substrate, a wider range of colors can be reproduced with higher color development properties than in Example 1.

[0285] In Example 3, the total amount of at least two inks applied per unit area in the mixed region was set to 3.5 g / m 2 ~13g / m 2Therefore, compared with Example 1, more colors can be reproduced with high color rendering, white turbidity and unevenness of the image are suppressed, and a higher-definition and glossy image is obtained.

[0286] In Example 3, since the substrate temperature during ink ejection is 55° C. or higher, a wider range of colors can be reproduced with high color rendering compared to Example 4, white turbidity and unevenness of the image are suppressed, and a higher-resolution and glossy image is obtained.

[0287] In Example 5, since the temperature of the substrate during ink ejection was 80° C. or lower, the cloudiness and unevenness of the image were further suppressed compared to Example 6.

[0288] In Example 7, the total amount of at least two inks applied per unit area in the mixed region was set to 13 g / m 2 The following inks are applied, so compared with Example 2, a wider range of colors can be reproduced with high color rendering, white turbidity and unevenness of the image are suppressed, and a higher definition and glossy image is obtained. In addition, since three inks are used, the color rendering is excellent compared with Example 3. In Example 10, the total application amount of at least two inks per unit area in the mixed area is set to 3g / m 2 ~20g / m 2 range, thus reproducing more colors with high color rendering properties than in Example 11.

[0289] In Example 7, since the substrate temperature during ink ejection was 55° C. or higher, a wider range of colors could be reproduced with high color rendering compared to Example 8, white turbidity and unevenness of the image were suppressed, and a higher-resolution and glossy image was obtained.

[0290] In Example 5, since the viscosities of at least two inks are both 7 mPa·s or higher, a wider range of colors can be reproduced with high color development compared to Example 13, and white turbidity and unevenness of the image are suppressed.

[0291] In Example 5, the maximum absolute value of the difference in surface tension between the inks is less than 1 mN / m, so compared with Example 14, a wider range of colors can be reproduced with high color rendering, white turbidity and unevenness of the image are suppressed, and a higher-definition image is obtained.

[0292] <Example 101 to Example 103>

[0293] [Image Record]

[0294] Image recorded materials 1 and 2 were obtained by the same method as in Examples 1, 3, and 7, except that the inkjet recording apparatus was replaced with an inkjet printer (product name "SUJV-160", manufactured by Mimaki Engineering Co., Ltd.), the heater temperature was set to 70°C, and exposure was performed using an exposure device attached to the inkjet printer.

[0295] The same evaluation as in Example 1, Example 3, and Example 7 was performed. As a result, Examples 101 to 103 were also able to reproduce a variety of colors with high color rendering properties.

[0296] <Example 200>

[0297] [Preparation of ink]

[0298] (Ink Nm1)

[0299] The following components were mixed to prepare ink Nm1. The viscosity of ink Nm1 (25° C.) was 9 mPa·s.

[0300] Diethylene glycol diethyl ether…63.43 parts by mass

[0301] ·Mixture of polymerizable liquid crystal compounds…35 parts by mass

[0302] Polymerization initiator: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide

[0303] (Product name: "Omnirad 819, manufactured by IGM Resins BV") ... 1.5 parts by mass

[0304] Fluorine-based surfactant (product name "Fergent 208G", manufactured by NEOS COMPANY) ... 0.03 parts by mass

[0305] The mixture of polymerizable liquid crystal compounds contained 33.4% by mass of compound (10), 33.3% by mass of compound (11), and compound (12) (X 1 =2) 33.3% by mass. Compounds (10) to (12) are rod-shaped liquid crystal compounds.

[0306] (Ink Nm2)

[0307] The following components were mixed to prepare ink Nm2. The viscosity of ink Nm2 (25° C.) was 1.7 mPa·s.

[0308] Diethylene glycol diethyl ether…94.7 parts by mass

[0309] Polymerization initiator: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide

[0310] (Product name: "Omnirad 819, manufactured by IGM Resins BV") ... 1.5 parts by mass

[0311] Chiral compound A...4 parts by mass

[0312] Fluorine-based surfactant (product name "Fergent 208G", manufactured by NEOS COMPANY) ... 0.03 parts by mass

[0313] [Image Record]

[0314] As a substrate, a PET sheet (product name "Viewful UV TP-188", manufactured by Kimoto Co., Ltd.) was used. The substrate was placed on a rubber heater and heated until the temperature of the substrate reached 60°C. Using an inkjet printer (product name "UJF3042HG", manufactured by MIMAKI ENGINEERING CO., LTD.), ink Nm1 and ink Nm2 were ejected onto the substrate heated to 60°C. The amount of ink Nm2 applied was changed in various ways to form a mixed area in which ink Nm1 and ink Nm2 were mixed (with an image resolution of 600dpi×720dpi), thereby recording an ink image. After the image recording was completed, the substrate was kept at 60°C for 1 minute, and after further heating the substrate at 80°C for 5 minutes, a metal halide lamp mounted on an ultraviolet irradiation device (product name "CSOT-40", manufactured by GS Yuasa Corporation) was used to make an ultraviolet radiation of 350mJ / cm 2 The image recorded material 1 was obtained by irradiating ultraviolet A waves (UV-A, wavelength 320 to 390 nm) in a manner.

[0315] Image recorded material 2 was obtained by the same method as that for image recorded material 1 except that the 7 mm square image was changed to a 2 mm square image.

[0316] It can be seen that the hue of the obtained image recorded material differs depending on the amount of ink Nm2 applied.

[0317] That is, in Example 200 as well, a variety of colors can be reproduced with high color rendering properties.

[0318] <Example 15 to Example 28>

[0319] In Examples 1 to 14, image recorded materials 1 and 2 were obtained by the same methods as in Examples 1 to 14, except that the polymerizable liquid crystal compound mixture A1 was replaced with the polymerizable liquid crystal compound mixture A2. The same evaluations as in Examples 1 to 14 were performed, and similar results were obtained in Examples 15 to 28.

[0320] <Example 104 to Example 106>

[0321] In Examples 101 to 103, the same ink as in Examples 15, 17, and 21 was used, and the same evaluation as in Examples 15, 17, and 21 was performed. As a result, in Examples 104 to 106, a variety of colors could be reproduced with high color rendering properties.

[0322] <Example 29 to Example 42>

[0323] In Examples 1 to 14, image recorded materials 1 and 2 were obtained by the same methods as in Examples 1 to 14, except that the polymerizable liquid crystal compound mixture A1 was replaced with the polymerizable liquid crystal compound mixture A3. The same evaluations as in Examples 1 to 14 were performed, and similar results were obtained in Examples 29 to 42.

[0324] <Example 107 to Example 109>

[0325] In Examples 101 to 103, the same ink as in Examples 29, 31 and 35 was used, and the same evaluation as in Examples 29, 31 and 35 was performed. As a result, in Examples 107 to 109, multiple colors could also be reproduced with high color rendering properties.

[0326] In addition, the entire disclosure of Japanese Patent Application No. 2020-217654 filed on December 25, 2020 is incorporated herein by reference. Furthermore, all documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each document, patent application, or technical standard were specifically and individually described as being incorporated by reference.

Claims

1. An image recording method comprising the following steps: preparing at least two inks including a first ink and a second ink; heating the substrate; applying the at least two inks to the heated substrate using an inkjet recording method; and irradiating the at least two inks with active energy rays, In the step of applying at least two inks, a mixed region where the at least two inks are mixed is formed in at least a portion of the substrate by the applying. The first ink contains a first polymerizable liquid crystal compound, and the second ink contains a second chiral compound.

2. The image recording method according to claim 1, wherein: The first ink contains the first polymerizable liquid crystal compound, a first chiral compound, and a first organic solvent. The second ink contains a second polymerizable liquid crystal compound, the second chiral compound, and a second organic solvent. An absolute value of a difference between a maximum reflection wavelength of an ink film formed from the first ink and a maximum reflection wavelength of an ink film formed from the second ink is 100 nm to 400 nm.

3. The image recording method according to claim 1 or 2, wherein: The maximum reflection wavelength of the ink film formed by the first ink is 380 nm to 490 nm, and the maximum reflection wavelength of the ink film formed by the second ink is 600 nm to 800 nm.

4. The image recording method according to claim 1 or 2, wherein: In the step of preparing at least two inks, a third ink containing a third polymerizable liquid crystal compound, a third chiral compound, and a third organic solvent is further prepared. The absolute value of the difference between the maximum reflection wavelength of the ink film formed by the first ink and the maximum reflection wavelength of the ink film formed by the second ink and the maximum reflection wavelength of the ink film formed by the third ink is 40 nm to 150 nm.

5. The image recording method according to claim 4, wherein: The maximum reflection wavelength of the ink film formed by the first ink is 380 nm to 490 nm, the maximum reflection wavelength of the ink film formed by the second ink is 600 nm to 800 nm, and the maximum reflection wavelength of the ink film formed by the third ink is 500 nm to 590 nm.

6. The image recording method according to claim 1 or 2, wherein: In the step of applying at least two kinds of inks, the total amount of the at least two kinds of inks applied per unit area in the mixed region is set to 3 g / m 2 ~20g / m 2 range to give.

7. The image recording method according to claim 2, wherein: In the step of applying at least two inks, the total amount of the polymerizable liquid crystal compound contained in the at least two inks applied per unit area in the mixed region is set to 1.5 g / m 2 ~8g / m 2 range to be given.

8. The image recording method according to claim 2, wherein: In the step of applying at least two inks, the total amount of the organic solvent contained in the at least two inks applied per unit area in the mixed region is set to 2.5 g / m 2 ~12.5g / m 2 range to be given.

9. The image recording method according to claim 1 or 2, wherein: The viscosity of the at least two inks is 7 mPa·s to 30 mPa·s.

10. The image recording method according to claim 1 or 2, wherein: The maximum absolute value of the difference in surface tension between the at least two inks is 1 mN / m or less.

11. The image recording method according to claim 1 or 2, wherein: In the step of heating the substrate, the substrate is heated to 40°C to 100°C.

Images