JP6303656B2 - Ink jet recording method using sol-gel phase transition type ink jet ink - Google Patents

Description

  The present invention relates to an ink jet recording method using a sol-gel phase transition ink jet ink. The present invention also relates to an inkjet recording apparatus using an inkjet recording method using a sol-gel phase transition inkjet ink.

  Conventionally, actinic ray curable compositions that are cured by active energy rays such as ultraviolet rays and electron beams include various paints such as plastic, paper, woodwork and inorganic materials, adhesives, printing inks, printed circuit boards, and electrical insulation. It has been put to practical use. In addition, as an inkjet ink system using a polymerizable composition, there is an ultraviolet curable inkjet ink that is cured by ultraviolet rays, and an inkjet method using this ultraviolet curable ink is high in a recording medium that does not absorb ink. In recent years, it has been attracting attention in terms of ensuring scratch resistance and adhesion.

  For example, in Patent Documents 1 to 3, a method of forming an image using an inkjet ink containing a gelling agent and a curable monomer is disclosed, and using an ink containing a substance that can be gelled at a low temperature, A method has been proposed in which the ink is ejected from a head at high temperature, cooled after landing on a substrate to gel the ink, and then photocured. In Patent Document 4, a similar proposal has been made for an ink that forms a thixotropic gel at a low temperature.

  Further, Patent Document 5 proposes a technique for obtaining a glossy image by controlling the surface temperature of a recording medium in a method of forming an image on a recording medium using a gelling agent-containing inkjet ink, In Patent Document 6, a water-based inkjet ink is used to suppress the narrowing of the color gamut when a multi-color image is formed on a recording medium to which a treatment liquid containing a component that aggregates the ink composition is applied. A method is disclosed.

US Patent Application Publication No. 2007/0123601 US Patent Application Publication No. 2009/0234041 JP 2010-115791 A Special table 2009-510184 gazette JP2012-40760 JP 2013-180423 A

  However, in the image forming method using an inkjet system using these ultraviolet curable inkjet inks, adjacent dots are combined in high-speed recording such as a single-pass recording method using a line recording head or a high-speed serial method using a small number of passes. There was a problem that the image quality was inferior. Further, when recording a color image, there is a problem that color mixing occurs between colors and the image quality is deteriorated. As a method for solving these problems, an actinic ray curable ink containing a gelling agent in an ink and having a characteristic of solid-liquid phase transition depending on temperature is used to solidify the ink droplet at the same time as the ink droplet lands. Therefore, it is necessary to prevent the ink droplets from being coalesced to prevent image quality deterioration.

  When a color image is to be formed using a plurality of ink-jet inks having different hues, dots are formed between colors particularly in a high-density image region where the ink discharge amount is large with respect to changes in ink viscosity due to temperature. However, in the image forming methods described in Patent Documents 1 to 5, there is no description about the image forming method when using a plurality of colors. Further, in the image forming method described in Patent Document 6, it is impossible to suppress the minimization of the color gamut by the image forming method in which the ink itself is solidified, such as an inkjet ink containing a gelling agent.

  In view of the above circumstances, the present invention can record a color image having a high definition and a wide color gamut on a recording medium, in particular, a non-absorbent recording medium and a slightly absorbent recording medium. An object of the present invention is to provide an ink jet recording method, and further to provide an ink jet recording method capable of recording a color image with high gloss and little color variation. The present invention also provides an inkjet recording using an inkjet recording method capable of recording a color image having high definition, a wide color gamut, high gloss, and little color variation. An object is to provide an apparatus.

  As a result of intensive studies to achieve the above object, the present inventor recorded a color image by sequentially laminating a plurality of colors of ink-jet ink containing gelling agents having different hues on a recording medium. By adjusting the hardness of the ink landed on the medium first to a specific range, the fluctuation of the dot area of the ink landed on the recording medium is suppressed later, and the high-definition and wide-range The inventors have found that a color image having a color gamut, high gloss, and little color variation can be obtained, and the present invention has been completed.

Specific means for achieving the above object are the following items (1) to (9).
(1) An inkjet recording method for recording a color image on a recording medium by sequentially applying each of a plurality of inkjet inks having different hues to a recording medium in a droplet amount of 0.5 to 15 pL, Each of the plurality of inkjet inks contains a gelling agent and a coloring material, has a phase transition point at 40 ° C. or more and less than 100 ° C., and undergoes a sol-gel phase transition according to temperature,
Of the plurality of ink-jet inks, the second ink is landed on the first ink within one second after the first ink is landed on the recording medium, and the first ink and the first ink A layering step of laminating the two inks, in which the dot area of the second ink formed on the first ink is landed on the first ink. An ink jet recording method comprising: 80% or more and 120% or less of the dot area of the second ink formed on the recording medium with the same amount of ink as that of the ink.
(2) The surface temperature of the recording medium is controlled to −5 to −15 ° C. of the gelation temperature (Tgel) defined below of the first ink. The average value of the complex viscosity defined by the formula (1) is 50 to 500 Pa · s, and the slope of the linear approximation of the viscoelastic curve defined below for the first ink is 5 to 50 in absolute value. The inkjet recording method according to item (1), wherein: (The gelation temperature (Tgel) is a complex viscosity in a viscoelastic curve obtained by changing the temperature at a cooling rate of 0.1 ° C./s, a strain of 5%, an angular frequency of 10 radian / s, and a cooling rate of 0.1 ° C./s. This represents the temperature at which the rate becomes 1 Pa. The average value of the complex viscosity represents the average of the values of the complex viscosity in the temperature range from the gelation temperature (Tgel) to −5 to −15 ° C. Linear approximation of the viscoelastic curve In the temperature range from the gelation temperature (Tgel) to -5 to -15 ° C, the temperature drop rate is 0.1 ° C / s, the strain is 5%, the angular frequency is 10 radian / s, and the temperature drop rate is 0.1 ° C / s. (Represents the slope of linear approximation of the viscoelastic curve obtained by changing the temperature.)
(3) Among the plurality of inkjet heads loaded with each of the plurality of inkjet inks, the viscosity of the inkjet ink present in at least one inkjet head is set to 3 mPa · s or more and less than 20 mPa · s, The inkjet recording method according to (1) or (2), wherein the inkjet ink is ejected onto the recording medium.
(4) Each of the plurality of inkjet inks further includes a photopolymerizable compound and a photopolymerization initiator, and irradiates the first ink and the second ink laminated in the laminating step with actinic rays. The inkjet recording method according to any one of items (1) to (3), further including a step of curing the first ink and the second ink. .
(5) After the first ink and the second ink are laminated in the laminating step, the actinic rays are emitted from the first ink and the second ink within 0.01 to 5.0 seconds. The ink jet recording method according to item (4), wherein the ink jet recording method is characterized in that:
(6) The inkjet according to any one of (1) to (5), wherein in the laminating step, a conveyance speed of the recording medium is 300 mm / sec to 1500 mm / sec. Recording method.
(7) The plurality of inkjet inks is an ink set including at least two types of ink selected from the group of yellow ink, cyan ink, magenta ink, and black ink. Item 6. The inkjet recording method according to any one of Items 6 to 6.
(8) The plurality of inkjet inks is an ink set including magenta ink and at least one kind of ink selected from the group of yellow ink, cyan ink, and black ink, and the color material of the magenta ink is , C.I. I. Pigment violet 19 and C.I. I. The inkjet recording method according to any one of Items (1) to (6), wherein the pigment is a mixed crystal pigment of CI Pigment Red 202.
(9) An inkjet recording apparatus using the inkjet recording method according to any one of items (1) to (8).

  According to the present invention, there is provided an inkjet recording method for recording a color image having a high definition and a wide color gamut on a recording medium, in particular, a non-absorbent recording medium and a slightly absorbent recording medium. . Furthermore, according to the present invention, there is provided an ink jet recording method for recording a color image having high gloss and little color variation. Further, according to the present invention, an inkjet recording method capable of recording a color image having high definition, a wide color gamut, high gloss, and little color variation is used. An ink jet recording apparatus is provided.

FIG. 1 is a side view showing an example of the configuration of the main part of a line recording type inkjet recording apparatus 10 which is a preferred embodiment of the inkjet recording apparatus according to the present invention. FIG. 2 is a top view illustrating an example of a configuration of a main part of the line recording type inkjet recording apparatus 10 which is a preferred embodiment of the inkjet recording apparatus according to the present invention. FIG. 3 is a diagram showing the relationship between the complex viscosity (Pa · S) and the temperature (° C.) of the magenta ink (M1) used in Example 1 and the magenta ink (M6) used in Comparative Example 3. is there.

  The present invention is described in detail below.

(1) Inkjet recording method In the inkjet recording method according to the present invention, each ink of a plurality of inkjet inks having different hues (hereinafter, the inkjet ink may be simply referred to as ink) has a droplet amount of 0.5 to 15 pL. In the inkjet recording method of sequentially applying to a recording medium and recording a color image on the recording medium, each ink of the plurality of inkjet inks includes a gelling agent and a coloring material, and is 40 ° C. or more and less than 100 ° C. It has a phase transition point, undergoes a sol-gel phase transition according to temperature, and lands a first ink (hereinafter sometimes referred to as a first inkjet ink) among a plurality of inkjet inks on a recording medium. Within one second from the second ink, the second ink (hereinafter sometimes referred to as the second inkjet ink) is used as the first ink. And the first ink and the second ink are stacked, and in the stacking process, the dot area of the second ink formed on the first ink is set on the first ink. Inkjet, characterized in that it is 80% or more and 120% or less of the dot area of the second ink formed on the recording medium with the same droplet amount as the droplet amount of the second ink landed on It is a recording method. By using the ink jet recording method according to the present invention, it is possible to record a color image with high definition, wide color gamut, high gloss, and little color variation. Here, the first ink means the ink that is landed and printed as the first color on the recording medium, and the second ink is landed and laminated on the first ink as the second color. Means ink. For example, when the second ink is stacked on the first ink, the first ink and the second ink are at least in contact with each other, and the second ink is placed on the first ink. That there is. In the present invention, the third ink-jet ink (hereinafter sometimes referred to as the third ink) is landed and printed as the third color, on the first ink and / or the second ink. It may be laminated on top. Further, the fourth and subsequent inkjet inks may be landed and printed as the fourth and subsequent colors, and may be laminated on one or more inkjet inks of the first to third inkjet inks.

  An inkjet recording method according to the present invention is a method of sequentially recording a color image on a recording medium by sequentially applying each of a plurality of inkjet inks having different hues to a recording medium with a droplet amount of 0.5 to 15 pL. It is. In the ink jet recording method according to the present invention, the second ink jet ink is landed on the first ink jet ink within one second after the first ink jet ink is landed on the recording medium. A second inkjet in which a dot area of the second inkjet ink formed on the first inkjet ink is landed on the first inkjet ink in the lamination step. 80% to 120% of the dot area of the second inkjet ink formed on the recording medium with the same droplet amount as the ink droplet amount.

A dot area of the second ink-jet ink formed on the first ink-jet ink and a droplet amount equal to the droplet amount of the second ink-jet ink landed on the first ink-jet ink on the recording medium The relational expression with the dot area of the formed second inkjet ink is as follows.
Di / Db = 0.8 to 1.2
Db: Dot area of the second inkjet ink formed on the recording medium Di: Dot area of the second inkjet ink formed on the first inkjet ink

  The first ink and the second ink are inks having different hues, and each of the first ink and the second ink is not limited to one kind, and is two or more kinds of inks having different hues. Alternatively, the ink that comes to the lower layer when a plurality of inks are stacked is the first ink, and the ink that comes to the upper layer is the second ink. In the present invention, in the case of n types of inks having different hues, an n-order color image is formed (n is an integer of 2 or more). In order to improve the discharge property of the ink droplets, it is preferable to set the temperature of the inkjet ink in the inkjet recording head to a temperature that is 10 to 30 ° C. higher than the gelation temperature of the ink. If the ink temperature in the ink jet recording head is less than the gelation temperature + 10 ° C., the ink gels in the ink jet recording head or on the nozzle surface, and ink droplet ejection properties tend to decrease. On the other hand, when the temperature of the ink in the ink jet recording head exceeds the gelation temperature + 30 ° C., the ink becomes too hot, so the head, the ink flow path connected to the ink jet recording head, or the ink tank connected to the ink flow path Heat with etc. The ink component ejected from each nozzle of the ink jet recording head may deteriorate.

  For each of a plurality of inkjet inks having different hues, the amount of droplets ejected from each nozzle of the inkjet recording head is 0.5 to 15 pL depending on the resolution of the image. Preferably, it is more preferably 0.5 to 5.0 pL in order to form a high-definition image. In order to form a high-definition image with such a droplet amount, it is necessary that the ink after landing does not coalesce, that is, the ink sufficiently undergoes sol-gel phase transition. Since the ink in the present invention undergoes a sol-gel phase transition promptly, a high-definition image can be stably formed even with such a droplet amount.

  In addition, in the case of an actinic ray curable inkjet ink that preferably contains a photopolymerizable compound, the smaller the droplet, the greater the influence of oxygen and the more markedly lowering the curing sensitivity. Since it gels quickly, it is difficult for oxygen to enter the droplets, so that sufficient curing sensitivity can be obtained even with such a droplet amount.

  In the ink jet recording method according to the present invention, the landing interval between the first ink and the second and subsequent inks on the recording medium is 1 second or less, thereby speeding up image formation. As the landing interval is shorter, it becomes more difficult to control the dot shape of the second and subsequent colors, and deterioration of color reproducibility and color variation are likely to occur, so that the effects of the present invention are remarkably exhibited.

  By using the ink jet recording method according to the present invention, at least two inks selected from the group of primary colors of yellow ink (Y), cyan ink (C), magenta ink (M), and black ink (K) When reproducing a secondary color or more using a combination of the above, it is possible to obtain the expected color development from the highlight portion to the shadow portion, and to obtain a wider color gamut. In particular, the smaller the droplet size, the greater the number of dots that are applied to the same area. Therefore, when a color image is formed by overlapping a plurality of inkjet inks having different hues, the upper layer (for example, the second layer) If the dots printed on the inkjet ink do not reach the desired area, the influence on the color reproducibility increases. Specifically, in an inkjet recording method including a step of laminating and laminating a plurality of inkjet inks having different hues, the dot area of the second inkjet ink is formed by landing on the first ink in the present invention. The dot area is 80% or more and 120% or less of the dot area formed by printing the same droplet amount directly on the recording medium.

  When the area of the dots landed after the second color on the first ink is 80% or more, it indicates that the area has spread to some extent, and when it is 120% or less, excessive wetting and spreading is suppressed. That is, it has color development as expected and has a wide color gamut. If the area of dots printed after the second color on the first ink is smaller than 80%, the color developability after the second color is impaired and the color gamut becomes narrow. On the other hand, if it exceeds 120%, the color developability of the ink in the lower layer is suppressed and the color gamut becomes narrow. In the present invention, the area of dots printed after the second color on the first ink is 80% or more and 120% or less, and preferably 90% or more and 110%. In the present invention, the dot area means the dot area when completed as a printed matter. When the ink contains a compound such as a solvent or an actinic ray curable composition, the printed matter such as drying or curing treatment is used. It means the area in a state where necessary processing for completing as follows is performed and the ink is fixed on the lower layer ink or the recording medium. Such an area can be measured using a digital microscope VHX-500 manufactured by Keyence Corporation.

  In the present invention, the second and subsequent inks are landed and printed as the second and subsequent colors on the first ink, and the second and subsequent inks (hereinafter referred to as the upper layer ink) are factors that determine the area of the dots to be formed. And the hardness of the first ink (also referred to as “lower layer ink”) when the ink is landed and printed. The ink according to the present invention contains a gelling agent and a coloring material, and is characterized in that it undergoes a sol-gel phase transition reversibly with temperature. The sol-gel phase transition referred to in the present invention is a solution state having fluidity at a high temperature, but by cooling to below the gelation temperature, the entire liquid is gelled and changed to a state in which the fluidity has been lost. Although it is in a state in which it loses fluidity, it refers to a phenomenon in which it returns to a liquid state with fluidity when heated to a temperature above the solation temperature. In the present invention, gelation refers to interactions such as a lamellar structure, a polymer network formed by non-covalent bonds or hydrogen bonds, a polymer network formed by a physical aggregation state, and an aggregate structure of fine particles. This refers to a structure in which substances lose their independent movement due to the interaction of microcrystals, etc., and indicate a solidified, semi-solidified, or thickened state with a sudden increase in viscosity or elasticity. The term “solification” refers to a state in which the interaction formed by the gelation is eliminated and the liquid state is changed to a fluid state. In the present invention, the gelation temperature refers to a temperature at which gelation occurs and fluidity is lowered when ink in a sol state is cooled.

  An inkjet ink that undergoes a sol-gel phase transition with temperature is in a liquid state at a high temperature, and thus can be ejected by an inkjet recording head. When recording is performed using this high-temperature ink, after the ink droplets have landed on the recording medium, the ink is quickly cooled by natural cooling due to the temperature difference, and as a result, the adjacent dots are prevented from coalescing. Can prevent image quality degradation. However, when the solidification force of the ink droplets is strong, the dots are isolated from each other, resulting in unevenness in the image area, which may lead to an uneven glossiness such as an extremely low glossiness or an unnatural sparkle. Here, by controlling the surface temperature of the recording medium to preferably the gelation temperature (Tgel) of the ink from −5 to −15 ° C., it is possible to prevent the ink droplets from being coalesced to prevent image quality deterioration. High and natural luster is obtained.

  When inkjet ink of the same hue is ejected from a plurality of nozzles of the same head, after ink droplets land on the recording medium and the ink solidifies before the adjacent ink droplets land, gloss reduction and image area Unnatural sparkle occurs. On the other hand, when the ink droplets adhering to each other and solidifying after a while, liquid drift occurs, leading to extreme image quality degradation.

  When a plurality of inks having different hues ejected from a plurality of different heads are printed in a superimposed manner, the dot shapes of the second and subsequent colors are controlled according to the surface state of the ink printed first (first ink). That is, when the first ink is weakly solidified, the tackiness of the surface becomes strong, so that the spread of the dots after the second color is suppressed, or because the surface is flexible, the sinking of the dots after the second color occurs and the color developability. Will be damaged. In addition, when the first ink is strongly solidified, the pinning is strong, so that the irregularities on the surface of the ink layer become large, the dot shape of the second and subsequent colors is distorted, and the gloss does not spread cleanly. , Color developability will be impaired.

  By setting the complex viscosity at -5 to -15 ° C. of the gelation temperature (Tgel) of the first ink within a preferable range of 50 to 500 Pa · s, the wetting and spreading of the dots after the second color is controlled, and more A wide color gamut and higher gloss can be obtained.

  Here, the gelation temperature Tgel and the complex viscosity are measured using various rheometers (for example, a stress control type rheometer using a cone plate, Physica MCR series, manufactured by Anton Paar), and the temperature change of the dynamic viscoelasticity of the ink is measured. Can be obtained. Since the gelation temperature has the property of changing depending on the temperature increase / decrease rate, it is defined as follows in the present invention.

  The gelation temperature (Tgel) and complex viscosity of the ink-jet ink used in the present invention were measured when the temperature change of dynamic viscoelasticity was measured at a cooling rate of 0.1 ° C./s, a strain of 5%, and an angular frequency of 10 radian / s. When the temperature change of dynamic viscoelasticity is measured at a cooling rate of 0.1 ° C./s, a strain of 5%, and an angular frequency of 10 radian / s, the gel viscosity Tgel is 1 Pa · The temperature is s or more. The complex viscosity at -5 to -15 ° C of the gelation temperature (Tgel) in the present invention is an average value of the complex viscosity in this temperature range.

  In addition, by making the slope of the linear approximation curve approximated from the temperature and complex viscosity in the above-mentioned temperature range in this viscoelastic curve within a preferable range of 5 to 50 in absolute value, color variation due to temperature variation is smaller. Become.

  That is, if the slope of the viscoelastic curve at the ink landing temperature is small (absolute value of 50 or less), the variation in the viscosity of the ink with respect to the substrate temperature at the time of landing is small, so the variation in dot shape after the second color is small. Color variation is also stable. On the other hand, if the inclination is large (absolute value exceeds 50), the viscosity variation with respect to the temperature at the time of landing is large, so that the variation in the dot shape of the second and subsequent colors increases, and the color variation increases. The complex viscosity of the first ink depends on the surface temperature of the recording medium, the structure of the gelling agent, and the amount of gelling agent added. That is, the first ink has a gel viscosity (Tgel) of −5 to −15 ° C. with a complex viscosity of 50 to 500 Pa · s, and the slope of the linear approximation curve is 5 to 50 in absolute value. By using ink, a wider color gamut, higher glossiness, and better robustness of color variation due to substrate temperature can be obtained.

  The reason is presumed as follows. For inks having a viscosity of less than 50 Pa · s at a gelation temperature (Tgel) of −5 to −15 ° C. of the first ink, solidification at the time of gelation in the above temperature range is not strong, so the dots after the second color The color gamut will be slightly narrowed without spreading. Further, in inks higher than 500 Pa · s, since solidification after gelation is somewhat strong, the surface unevenness is somewhat large, and it is not easy to control the shape of the dots for the second and subsequent colors, and the gloss is somewhat lowered. In addition, since the ink of the present invention becomes a viscous gel having an appropriate viscosity after gelation, it is possible to adjust the solidification force of dots more appropriately even when dots of secondary colors or more are combined. , Image quality with wider color gamut and natural gloss can be obtained. Further, in the case of the actinic ray type ink-jet ink in which the ink-jet ink in the present invention contains a radical polymerizable compound, if the complex viscosity of the ink in the above temperature range is less than 50 Pa · s, the ink is easily affected by oxygen during curing. Sensitivity tends to decrease slightly.

  In the inkjet recording method according to the present invention, the viscosity of the inkjet ink present in at least one inkjet head among a plurality of inkjet heads having different hues loaded with each of the plurality of inkjet inks is 3 mPa · s or more. Preferably, the inkjet ink is ejected onto a recording medium at less than 20 mPa · s, and the viscosity of the inkjet ink present in at least one inkjet head is set to be 5 mPa · s or more and less than 15 mPa · s, and the inkjet ink is recorded on the recording medium. More preferably, it is discharged.

  Each of the plurality of inkjet inks having different hues used in the inkjet recording method according to the present invention preferably contains a photopolymerizable compound and a photopolymerization initiator, and is laminated in the laminating step included in the inkjet recording method according to the present invention. It is preferable that the method further includes a step of irradiating the first ink and the second ink which have been subjected to actinic rays to cure the first ink and the second ink.

  By irradiating light from an LED light source to a plurality of ink-jet inks having different hues that are landed and stacked on a recording medium, each ink can be cured by crosslinking or polymerizing the photopolymerizable compound contained in the ink. it can. The light applied to the ink attached to the recording medium is preferably ultraviolet light from an LED light source. Specific examples include a 395 nm, water-cooled LED, etc. manufactured by Phoseon Technology. As a general ultraviolet light source, a metal halide lamp can be mentioned. By using an LED as a light source, ink droplets are melted by the radiant heat of the light source; that is, curing failure occurs on the cured film surface of the ink droplets. Can be suppressed. The LED light source is installed so that the peak illuminance on the image surface is from 0.5 to 10 W / cm <2>, and more preferably from 1 to 5 W / cm <2>. The amount of light applied to the image is set to be less than 500 mJ / cm 2. This is to prevent the radiant heat from being applied to the ink droplets.

  The time from when the first ink and the second ink are laminated in the laminating process to when the first ink and the second ink are irradiated with the actinic ray is arbitrary as long as the effect of the present invention is achieved. Although time may be sufficient, it is preferable that it is 0.01 second-5.0 second, and it is more preferable that it is "0.1 second-2 second".

(2) A plurality of inkjet inks having different hues Each ink of a plurality of inkjet inks having different hues used in the inkjet recording method according to the present invention includes a gelling agent and a coloring material, and has a phase of 40 ° C. or more and less than 100 ° C. It has a transition point and undergoes a sol-gel phase transition with temperature. Below, a gelatinizer and a coloring material are demonstrated in detail.

[Gelling agent]
In the present invention, gelation means interactions such as a lamellar structure, a polymer network formed by non-covalent bonds or hydrogen bonds, a polymer network formed by a physical aggregation state, and an aggregate structure of fine particles. This refers to a structure in which substances lose their independent motion due to crystal interactions, etc., and indicate a solidified, semi-solidified, or thickened state with a sudden increase in viscosity or elasticity. .

  In general, a gel becomes a fluid solution (sometimes called a sol) by heating, a thermoreversible gel that returns to the original gel when cooled, and once gelled, it can be reheated even if heated. There is a heat irreversible gel that does not return. The gel formed by the oil gelling agent according to the present invention is preferably a thermoreversible gel from the viewpoint of preventing clogging in the head.

  In each of a plurality of inkjet inks having different hues used in the present invention, the gelation temperature (phase transition temperature) of the ink is preferably 40 ° C. or higher and lower than 100 ° C., more preferably 45 ° C. or higher. 70 ° C. or lower. Considering the temperature in the summer environment, if the phase transition temperature of the ink is 40 ° C. or higher, when the recording head ink droplets are ejected, stable emission can be obtained without being affected by the printing environment temperature. If it is less than 100 ° C., it is not necessary to heat the inkjet recording apparatus to an excessively high temperature, and the load on the head of the inkjet recording apparatus and the members of the ink supply system can be reduced.

  The gelation temperature in the present invention refers to a temperature at which the viscosity suddenly changes from a fluid solution state to become a gel state. Gel transition temperature, gel dissolution temperature, phase transition temperature, sol-gel phase It is synonymous with terms called transition temperature and gel point. In the present invention, the method for measuring the gelation temperature of the ink is, for example, using various rheometers (for example, a stress control type rheometer using a cone plate, Physica MCR series, manufactured by Anton Paar) and using a high-temperature ink in a sol state. It can be determined from a viscosity curve obtained while changing the temperature at a low shear rate and a viscoelastic curve obtained by measuring the temperature change of dynamic viscoelasticity. The gelation temperature of the ink can be appropriately adjusted by changing the type of gelling agent used, the amount of gelling agent added, and the type of actinic ray curable monomer.

  In the plurality of ink-jet inks having different hues used in the present invention, the complex viscosity is from 50 to 500 Pa · s at −5 to −15 ° C. of the gelation temperature (Tgel) of the first ink, and the linear approximation curve The slope is preferably 5 to 30 in absolute value. If the first ink has a gel viscosity (Tgel) of −5 to −15 ° C. and a complex viscosity of 50 Pa · s or more, the second and subsequent dots can be held in a desired shape and good color developability. If it is 500 Pa · s or less, good leveling properties can be obtained, and high gloss without streaks can be obtained. The viscosity of the ink can be appropriately adjusted by changing the type of gelling agent used, the amount of gelling agent added, and the type of actinic ray curable monomer. The complex viscosity referred to in the present invention refers to a stress-controlled rheometer using a cone plate, Physica MCR series, manufactured by Anton Paar), a cooling rate of 0.1 ° C./s, a strain of 5%, and an angular frequency of 10 radian / s. It was measured by.

  The gelling agent contained in the ink-jet ink has a function of reversibly sol-gel phase transition with temperature. The gelling agent may be soluble in the photopolymerizable compound or non-polymerizable resin at a temperature higher than the gelation temperature, and may be crystallized in the ink at a temperature lower than the gelation temperature. When the gelling agent crystallizes in the ink, it is preferable to form a space three-dimensionally surrounded by plate crystals which are crystallized products of the gelling agent, and to enclose the photopolymerizable compound in the space. Thus, the structure in which the photopolymerizable compound is encapsulated in the space three-dimensionally surrounded by the plate crystal is sometimes referred to as “card house structure”. When the card house structure is formed, the liquid photopolymerizable compound can be held and ink droplets can be pinned. Thereby, coalescence of droplets can be suppressed. In order to form the card house structure, it is preferable that the photopolymerizable compound dissolved in the ink and the gelling agent are compatible. On the other hand, when the photopolymerizable compound dissolved in the ink and the gelling agent are phase-separated, it may be difficult to form a card house structure.

  In order to stably discharge ink droplets from an ink jet recording apparatus, it is necessary that the compatibility of the photopolymerizable compound and the gelling agent is good in the sol-like ink (at a high temperature). Furthermore, in order to stably suppress coalescence of droplets even during high-speed printing, after the ink droplets have landed on the recording medium, the gelling agent quickly crystallizes to form a strong card house structure. preferable.

Examples of such gelling agents include
An aliphatic ketone compound;
Aliphatic ester compounds;
Petroleum waxes such as paraffin wax, microcrystalline wax, petrolactam;
Plant waxes such as candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, jojoba solid wax, and jojoba ester;
Animal waxes such as beeswax, lanolin and whale wax;
Mineral waxes such as montan wax and hydrogenated wax;
Hydrogenated castor oil or hydrogenated castor oil derivative;
Modified waxes such as montan wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives or 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 acid 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, 12-hydroxystearic acid amide (for example, Nikka Amide series manufactured by Nippon Kasei Co., Ltd.) ITOWAX series manufactured by Ito Oil Co., Ltd., FATTYAMID series manufactured by Kao Corporation, etc.);
N-substituted fatty acid amides such as N-stearyl stearamide and N-oleyl palmitate amide;
Special fatty acid amides such as N, N′-ethylenebisstearylamide, N, N′-ethylenebis-12-hydroxystearylamide, and N, N′-xylylenebisstearylamide;
Higher amines such as dodecylamine, tetradecylamine or octadecylamine;
Stearyl stearic acid, oleyl palmitic acid, glycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, ethylene glycol fatty acid ester, polyoxyethylene fatty acid ester and other fatty acid ester compounds (for example, Emullex series manufactured by Nihon Emulsion Co., Ltd., Riken Vitamin Co., Ltd. Marl series, RIKEN VITAMIN POM series, etc.);
Esters of sucrose fatty acids such as sucrose stearic acid and sucrose palmitic acid (eg Ryoto Sugar Ester series manufactured by Mitsubishi Chemical Foods);
Synthetic waxes such as polyethylene wax and α-olefin maleic anhydride copolymer wax (such as UNILIN series manufactured by Baker-Petrolite);
Dimer acid;
Dimer diol (such as PRIDA series manufactured by CRODA);
Fatty acid inulins such as inulin stearate;
Fatty acid dextrins such as dextrin palmitate and dextrin myristate (such as Leopard series manufactured by Chiba Flour Mills);
Glyceryl behenate eicosane diacid;
Eicosane polyglyceryl behenate (Nomshin Eulio Co., Ltd. Nomucoat series, etc.);
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 (available from Gelol D Shin Nippon Chemical);
Low molecular oil gelling agents described in JP-A-2005-126507, JP-A-2005-255821, and JP-A-2010-1111790;
Etc. are included.

  The ink preferably contains a compound containing a linear alkyl group having 12 or more carbon atoms as a gelling agent. When the gelling agent contains a linear alkyl group having 12 or more carbon atoms, the aforementioned “card house structure” is easily formed. The structure of the gelling agent may have a branched chain.

Specific examples of the gelling agent containing a linear alkyl group having 12 or more carbon atoms include aliphatic ketone compounds, aliphatic ester compounds, higher fatty acids, higher alcohols having a linear alkyl group having 12 or more carbon atoms, Fatty acid amides and the like are included. However, a gelling agent having a polar group such as —OH or —COOH at the end of the alkyl chain has poor stability in a sol-like ink and may precipitate or phase-separate. In addition, the gelling agent may gradually bleed out with time from the cured film of the ink. Therefore, the gelling agent is preferably an aliphatic ketone compound or an aliphatic ester compound. That is, a compound represented by the following general formulas (G1) and (G2) is preferable.
General formula (G1): R1-CO-R2
General formula (G2): R3-COO-R4
In general formulas (G1) and (G2), R1 to R4 each independently represent a hydrocarbon group having a straight chain portion having 12 or more carbon atoms. R1 to R4 may have a branched portion.

  In General Formula (G1), the hydrocarbon groups represented by R1 and R2 are each preferably an aliphatic hydrocarbon group including a straight chain portion having 12 to 25 carbon atoms. If the number of carbon atoms in the straight chain portion contained in the aliphatic hydrocarbon group represented by R1 and R2 is less than 12, it does not function as a gelling agent because it does not have sufficient crystallinity, and the card described above In the house structure, there is a possibility that a sufficient space for encapsulating the photopolymerizable compound cannot be formed. On the other hand, if the number of carbon atoms in the straight chain portion contained in the aliphatic hydrocarbon group exceeds 25, the melting point becomes too high, so that the ink may not be dissolved in the ink unless the ink discharge temperature is increased.

  Examples of the aliphatic ketone compound represented by the general formula (G1) include dilignoceryl ketone (C24-C24), dibehenyl ketone (C22-C22, melting point 88 ° C.), distearyl ketone (C18-C18, 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.) , Lauryl 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), Valmityl behenyl ketone (C 6-C22), include stearyl and behenyl ketone (C18-C22) and the like.

Examples of commercially available compounds represented by the general formula (G1) include 18-Pentriacontanon (manufactured by Alfa Aeser), Hentriacontan-16-on (manufactured by Alfa Aeser), Kao wax T1 (manufactured by Kao Corporation), and the like. included.
The aliphatic ketone compound contained in the ink may be only one type or a mixture of two or more types.

In the general formula (G2), the hydrocarbon group represented by R3 and R4 is not particularly limited, but is preferably an aliphatic hydrocarbon group including a linear portion having 12 to 26 carbon atoms. When the number of carbon atoms in the straight chain portion contained in the aliphatic hydrocarbon group represented by R3 and R4 is 12 or more and 26 or less, it is necessary for the gelling agent as in the compound represented by the general formula (G1). The above-mentioned card house structure can be formed while having excellent crystallinity, and the melting point is not too high.
Examples of the aliphatic ester compound represented by the formula (2) include behenyl behenate (C21-C22, melting point 70 ° C.), icosyl icosanoate (C19-C20), stearyl stearate (C17-C18, melting point 60 ° C.). ), Palmitic acid stearate (C17-C16), lauryl stearate (C17-C12), cetyl palmitate (C15-C16, melting point 54 ° C.), stearyl palmitate (C15-C18), myristyl myristate (C13-C)
14, melting point 43 ° C), cetyl myristate (C13-C16, melting point 50 ° C), octyldodecyl myristate (C13-C20), stearyl oleate (C17-C18), stearyl erucate (C21-C18), linoleic acid Stearyl (C17-C18), behenyl oleate (C18-C22), myricyl serotate (C25-C16), stearyl montanate (C27-C18), behenyl montanate (C27-C22), arachidyl linoleate (C17-C20) ), Palmitic acid triacontanoate (C29-C16) and the like.

  Examples of commercially available products of the aliphatic ester compound represented by the formula (2) include Unistar M-2222SL (manufactured by NOF Corporation), EXCEPARL SS (manufactured by Kao Corporation, melting point 60 ° C.), EMALEXCC-18 (Japan) Emulsion Co., Ltd.), Amreps PC (manufactured by Higher Alcohol Industry Co., Ltd.), Exepal MY-M (Kao Co., Ltd.), Spalm Acechi (Nissho Co., Ltd.), EMALEX CC-10 (Nihon Emulsion Co., Ltd.) included. Since these commercial products are often a mixture of two or more types, they may be separated and purified as necessary.

  The aliphatic ester compound contained in the ink may be only one type or a mixture of two or more types.

  The total amount of the gelling agent contained in the ink is preferably 0.5 to 10.0% by mass, more preferably 1 to 7% by mass, and particularly preferably 1 to 4% by mass with respect to the total mass of the ink. . If it is less than 0.5% by mass, the ink droplets cannot be gelled (sol-gel phase transition due to temperature). On the other hand, when the amount of the gelling agent exceeds 10% by mass, the gelling agent is not sufficiently dissolved in the ink, and the discharge property of the ink droplets is lowered.

[Color material]
Each of the plurality of inkjet inks having different hues used in the inkjet recording method according to the present invention preferably contains at least one selected from various known dyes and pigments, and more preferably contains a pigment. .

The pigments that can be contained in each of a plurality of inkjet inks having different hues are listed below, but are not limited to these pigments.
C. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 109, 114, 120, 128, 129, 138, 150, 151, 154, 155, 180, 185, 213
C. I. Pigment Red 5, 7, 12, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 101, 112, 122, 123, 144, 146, 168, 184, 185, 202
C. I. Pigment Violet 19, 23
C. I. Pigment Blue 1, 2, 3, 15: 1, 15: 2, 15: 3, 15: 4, 18, 22, 27, 29, 60
C. I. Pigment Green 7,36
C. I. Pigment White 6, 18, 21
C. I. Pigment Black 7

  Examples of the magenta pigment of the magenta ink used in the present invention include C.I. I. It is preferable to use a mixed crystal pigment containing CI Pigment Violet 19, especially C.I. I. Pigment violet 19 and C.I. I. It is preferably a mixed crystal pigment consisting of CI Pigment Red 122 or 202, and C.I. I. Pigment violet 19 / C.I. I. Pigment Red 202 mixed crystal pigment is more preferable.

  C. I. Since a mixed crystal pigment containing Pigment Violet 19 is used, C.I. I. Compared to Pigment Violet 19 alone, a color reproduction range is wide, and a high density and a high color can be obtained even in a secondary color having a high image density.

  The volume average particle diameter of the pigment is preferably 0.08 to 0.5 μm, and the particle diameter of the pigment is 0.3 to 10 μm, preferably 0.3 to 3 μm. By adjusting the particle size of the pigment, clogging of the nozzles of the ink jet recording head can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.

  On the other hand, the dye that can be contained in each of the plurality of inkjet inks having different hues can be an oil-soluble dye or the like. Examples of oil-soluble dyes include the following various dyes. Examples of magenta dyes include MS Magenta VP, MS Magenta HM-1450, MS Magenta HSo-147 (manufactured by Mitsui Toatsu), AIZENSOT Red-1, AIZEN SOT Red-2, AIZEN SOTRed-3, and AIZEN SOT. Pink-1, SPIRON Red GEH SPECIAL (above, manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN Red FB 200%, MACROLEX Red Violet R, MACROLEX ROT5B (above, manufactured by Bayer Japan), KAYASET Red B, KAYASE RED 130, 802 (above, Nippon Kayaku Co., Ltd.), PHLOXIN, ROSE Bengal, ACID Red (above, Daiwa Kasei Co., Ltd.), H R-31, DIARESIN Red K (manufactured by Mitsubishi Kasei Corp.), include Oil Red (manufactured by BASF Japan Ltd.).

Examples of cyan dyes include MS Cyan HM-1238, MS Cyan HSo-16, Cyan HSo-144, MS Cyan VPG (manufactured by Mitsui Toatsu), AIZEN SOT Blue-4 (manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN BR. Blue BGLN 200%, MACROLEX Blue RR, CERES Blue GN, SIRIUS SUPRATURQ. Blue Z-BGL, SIRIUS SUTRA TURQ. Blue FB-LL 330% (above, Bayer Japan), KAYASET Blue FR, KAYASET Blue N, KAYASET Blue 814, Turq. Blue GL-5 200, Light Blue BGL-5 200 (above, Nippon Kayaku Co., Ltd.), DAIWA Blue 7000, Oleosol Fast Blue GL (above, Daiwa Kasei), DIARESIN Blue P (Mitsubishi Kasei), SUDAN Blue 670, NEOPEN Blue 808, ZAPON Blue 806 (above, manufactured by BASF Japan Ltd.) and the like are included.
Examples of yellow dyes include MS Yellow HSm-41, Yellow KX-7, Yellow EX-27 (Mitsui Toatsu), AIZEN SOT Yellow-1, AIZEN SOT Yellow W-3, AIZEN SOT Yellow-6 (above, Hodogaya) Chemical Co., Ltd.), MACROLEX Yellow 6G, MACROLEX FLUOR. Yellow 10GN (above, manufactured by Bayer Japan), KAYASET Yellow SF-G, KAYASET Yellow 2G, KAYASET Yellow AG, KAYASET Yellow EG (above, manufactured by Nippon Kayaku), DAIWA YELLOW 330H HSY-68 (manufactured by Mitsubishi Kasei Co., Ltd.), SUDAN Yellow 146, NEOPEN Yellow 075 (above, manufactured by BASF Japan Ltd.) and the like.

  Examples of black dyes include MS Black VPC (Mitsui Toatsu Co., Ltd.), AIZEN SOT Black-1, AIZEN SOT Black-5 (above, manufactured by Hodogaya Chemical Co., Ltd.), RESORIN Black GSN 200%, RESOLIN BlackBS (above, Bayer Japan), KAYASET Black A-N (Nippon Kayaku), DAIWA Black MSC (Daiwa Kasei), HSB-202 (Mitsubishi Kasei), NEPTUNE Black X60, NEOPEN Black X58 (above, BASF Japan product).

  The content of the pigment or dye is preferably 0.1 to 20% by mass, and more preferably 0.4 to 10% by mass with respect to the photocurable inkjet ink. This is because if the content of the pigment or dye is too small, the color of the resulting image is not sufficient, and if it is too large, the viscosity of the ink increases and the jetting property decreases. Moreover, the inkjet ink may contain a synergist corresponding to various pigments as a dispersion aid. The total amount of the dispersant and the dispersion aid is preferably 1 to 50% by mass with respect to the pigment.

  The pigment must be dispersed in the inkjet ink. Therefore, it is preferable to obtain an inkjet ink by preparing a pigment dispersion and further mixing the pigment dispersion and other ink components.

  The pigment dispersion is prepared by dispersing the pigment in a dispersion medium. The pigment may be dispersed using, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like. Further, a dispersing agent can be added when dispersing the pigment. As the dispersant, a polymer dispersant is preferably used, and examples of the polymer dispersant include Avecia's Solsperse series and Ajinomoto Fine-Techno's PB series.

  The dispersion medium of the pigment dispersion can be a solvent or a polymerizable compound; however, the ink-jet ink in the present invention is preferably gel-free immediately after landing on the recording medium, and is preferably solvent-free. Further, if the solvent remains in the cured image, solvent resistance is deteriorated and VOC of the remaining solvent is caused. Therefore, the solvent-free ink is preferable. Therefore, the dispersion medium of the pigment dispersion is preferably not a solvent but a polymerizable compound, particularly a monomer having the lowest viscosity, in view of dispersion suitability.

  Each of the plurality of inkjet inks having different hues used in the inkjet recording method according to the present invention preferably contains a photopolymerizable compound and a photopolymerization initiator, and thus the durability and abrasion resistance of the formed image are improved. And adhesion with a recording medium can be improved.

[Photopolymerizable compound]
The photopolymerizable compound is a compound that crosslinks or polymerizes when irradiated with actinic rays. The actinic rays are, for example, electron beams, ultraviolet rays, α rays, γ rays, and X-rays, and are preferably ultraviolet rays. The photopolymerizable compound can be a radical polymerizable compound or a cationic polymerizable compound. A radical polymerizable compound is preferred.

The radically polymerizable compound is a compound (monomer, oligomer, polymer or mixture thereof) having a radically polymerizable ethylenically unsaturated bond. Only one kind of radically polymerizable compound may be contained in the ink, or two or more kinds thereof may be contained.
Examples of the compound having an ethylenically unsaturated bond capable of radical polymerization include an unsaturated carboxylic acid and a salt thereof, an unsaturated carboxylic acid ester compound, an unsaturated carboxylic acid urethane compound, an unsaturated carboxylic acid amide compound and an anhydride thereof, Examples include acrylonitrile, styrene, unsaturated polyester, unsaturated polyether, unsaturated polyamide, and unsaturated urethane. Examples of the unsaturated carboxylic acid include (meth) acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid and the like.

Especially, it is preferable that a radically polymerizable compound is an unsaturated carboxylic acid ester compound, and it is more preferable that it is a (meth) acrylate compound. The (meth) acrylate compound may be not only a monomer described later, but also an oligomer, a mixture of a monomer and an oligomer, a modified product, an oligomer having a polymerizable functional group, and the like. Here, “(meth) acrylate” refers to both and / or “acrylate” and “methacrylate”, and “(meth) acryl” refers to both and / or “acryl” and “methacryl”.
Examples of (meth) acrylate compounds include isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, isomyristyl (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, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, phenoxyethyl ( Acrylate), tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2 -(Meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl-2-hydroxyethyl-phthalic acid, t-butylcyclohexyl (meth) acrylate, etc. Monofunctional monomers: triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, reethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene group Cold 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, bisphenol A PO adduct di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, and other bifunctional monomers Trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylol Trifunctional or higher polyfunctional monomers such as propanetetra (meth) acrylate, glycerinpropoxytri (meth) acrylate, pentaerythritol ethoxytetra (meth) acrylate, and the like are included.
Among them, from the viewpoint of photosensitivity, stearyl (meth) acrylate, lauryl (meth) acrylate, isostearyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, isobornyl (meth) acrylate, tetraethylene glycol di (meth) acrylate , Glycerin propoxytri (meth) acrylate and the like are preferable.

  The (meth) acrylate compound may be a modified product. Examples thereof include ethylene oxide-modified (meth) acrylate compounds such as ethylene oxide-modified trimethylolpropane tri (meth) acrylate and ethylene oxide-modified pentaerythritol tetraacrylate; Caprolactone-modified (meth) acrylate compounds such as caprolactone-modified trimethylolpropane tri (meth) acrylate; and caprolactam-modified (meth) acrylate compounds such as caprolactam-modified dipentaerythritol hexa (meth) acrylate and the like are included. Among these, an ethylene oxide-modified (meth) acrylate compound is preferable from the viewpoint of high photosensitivity and easy formation of a card house structure described later when gelling at a low temperature. In addition, the ethylene oxide-modified (meth) acrylate compound is easily dissolved in other ink components at high temperatures and has little curing shrinkage, so that curling of the printed matter hardly occurs.

Examples of ethylene oxide-modified (meth) acrylate compounds include 4EO-modified hexanediol diacrylate CD561 (molecular weight 358), 3EO-modified trimethylolpropane triacrylate SR454 (molecular weight 429), 6EO-modified trimethylolpropane triacrylate SR499 manufactured by Sartomer. (Molecular weight 560), 4EO-modified pentaerythritol tetraacrylate SR494 (molecular weight 528); polyethylene glycol diacrylate NK ester A-400 (molecular weight 508), polyethylene glycol diacrylate NK ester A-600 (molecular weight 742) manufactured by Shin-Nakamura Chemical Co., Ltd. , Polyethylene glycol dimethacrylate NK ester 9G (molecular weight 536), polyethylene glycol dimethacrylate NK ester 4G (molecular weight 770); Tetraethylene glycol diacrylate V # 335HP (molecular weight 302) manufactured by Osaka Organic Chemical Co .; 3PO-modified trimethylolpropane triacrylate Photomer 4072 (molecular weight 471) manufactured by Cognis; 1 manufactured by Shin-Nakamura Chemical Co., Ltd. , 10-decanediol dimethacrylate NK ester DOD-N (molecular weight 310), tricyclodecane dimethanol diacrylate NK ester A-DCP (molecular weight 304), tricyclodecane dimethanol dimethacrylate NK ester DCP (molecular weight 332), etc. included.
The (meth) acrylate compound may be a polymerizable oligomer. Examples of such polymerizable oligomers include epoxy (meth) acrylate oligomers, aliphatic urethane (meth) acrylate oligomers, aromatic urethane (meth) acrylate oligomers, polyester (meth) acrylate oligomers, and linear (meth) acrylic. Oligomers and the like are included.

  The content of the photopolymerizable compound is preferably 1 to 97% by mass and more preferably 30 to 95% by mass with respect to the total mass of the ink. When the amount of the photopolymerizable compound is too small, the coloring material cannot be sufficiently dispersed, and the ink dischargeability from the ink jet recording apparatus is lowered. On the other hand, when the amount of the photopolymerizable compound is excessive, the amount of the gelling agent and the photopolymerization initiator is relatively small, and the sol-gel phase transition may not be sufficiently performed or the curing is insufficient. there is a possibility.

[Photopolymerization initiator]
Photopolymerization initiators include an intramolecular bond cleavage type and an intramolecular hydrogen abstraction type. Examples of intramolecular bond cleavage type photopolymerization initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2. -Hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4 Acetophenones such as -thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone; benzoins such as benzoin, benzoin methyl ether, benzoin isopropyl ether; 2 Acylphosphine oxide systems such as 1,4,6-trimethylbenzoindiphenylphosphine oxide; benzyl and And methylphenylglyoxyester.
Examples of intramolecular hydrogen abstraction type photopolymerization initiators include benzophenone, methyl 4-phenylbenzophenone o-benzoylbenzoate, 4,4′-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4′-methyl-diphenyl. Benzophenones such as sulfide, acrylated benzophenone, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 3,3′-dimethyl-4-methoxybenzophenone; 2-isopropylthioxanthone, 2,4 -Thioxanthone series such as dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone; Aminobenzophenone series such as Michler ketone, 4,4'-diethylaminobenzophenone; 10-butyl-2-chloroacridone, 2-ethyl Anthraquinone, 9,10-phenanthrene Non camphorquinone, include triallyl phosphonium salts.

  When the photopolymerization initiator is acyl phosphine oxide or acyl phosphonate, the sensitivity is good. Specifically, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, and the like are preferable.

  The content of the photopolymerization initiator contained in each of the plurality of ink-jet inks having different hues depends on the light irradiated at the time of ink curing, the type of the photopolymerizable compound, and the like. It is preferable that it is 1 mass%-10 mass%, More preferably, it is 2-8 mass%.

  Each ink of the plurality of inkjet inks having different hues may further contain a photopolymerization initiator auxiliary agent, a polymerization inhibitor, or the like, if necessary. The photopolymerization initiator assistant may be a tertiary amine compound, preferably an aromatic tertiary amine compound. 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 and the like are included. Of these, N, N-dimethylamino-p-benzoic acid ethyl ester and N, N-dimethylamino-p-benzoic acid isoamyl ethyl ester are preferred. The ink may contain only one kind of these compounds, or may contain two or more kinds.

  Examples of polymerization inhibitors include (alkyl) phenol, hydroquinone, catechol, resorcin, 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, cuperone, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, N- (3-oxyanilino- 1,3-dimethylbutylidene) aniline oxide, dibutylcresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraloxime, methyl ethyl ketoxime, cyclohexanone oxime and the like.

[Other ingredients]
Each of the plurality of inkjet inks having different hues may further include other components as necessary. Other components may be various additives, other resins, and the like. Examples of the additive include a surfactant, a leveling additive, a matting agent, an ultraviolet absorber, an infrared absorber, an antibacterial agent, and a basic compound for enhancing the storage stability of the ink. Examples of the basic compound include basic alkali metal compounds, basic alkaline earth metal compounds, basic organic compounds such as amines, and the like. Examples of other resins include resins for adjusting the physical properties of the cured film, such as polyester resins, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes. It is.

(Method for preparing each of a plurality of inkjet inks having different hues)
A gelling agent and a coloring material contained in each of a plurality of inkjet inks having different hues, and a photopolymerizable compound and a photopolymerization initiator preferably contained therein are obtained by mixing under heating. For example, a pigment dispersion in which a color material (particularly a pigment) is dispersed in a part of the photopolymerizable compound is prepared and mixed with the pigment dispersion and other ink components. The obtained ink is preferably filtered through a predetermined filter. In order to improve the discharge property of each of a plurality of inkjet inks having different hues, it is preferable that the viscosity of the ink at a high temperature is not more than a certain level. Specifically, the actinic ray curable inkjet ink preferably has a viscosity at 80 ° C. of 3 to 20 mPa · s.

[recoding media]
The recording medium used in the ink jet recording method according to the present invention may be paper or a resin film. Examples of paper include coated paper for printing, coated paper B for printing, and the like. Examples of the resin film include a polyethylene terephthalate film and a vinyl chloride film.

  The surface temperature of the recording medium is preferably controlled to be −5 to −15 ° C., which is the gelation temperature (Tgel) of the first ink. If the temperature of the recording medium is too low, the ink droplets gel excessively and pinning, so that the ink droplets are not sufficiently leveled and the image gloss may be lowered. On the other hand, if the temperature of the recording medium is too high, the ink droplets are difficult to gel, adjacent dots of the ink droplets are mixed together, and the reproducibility of fine lines and gradations is deteriorated. By adjusting the surface temperature of the recording medium within the temperature range of the present invention, by using the ink of the present invention, adjacent dots ejected from the same head and inks having different hues ejected from different heads are laminated. Even when the ink is mixed, good color developability, appropriate leveling, and appropriate pinning capable of reproducing fine lines are realized.

  As the temperature control means of the recording medium, for example, a method of adjusting the temperature of the recording medium from the back by attaching a cooling device and a heating device in advance to a conveyance base for fixing the recording medium or a fixing drum, cold air or hot air The method of adjusting the temperature by spraying the recording medium, the method of attaching a refrigerant or heater on the upper surface of the recording medium fixing position on the apparatus and adjusting the temperature without contact, the method of adjusting the temperature by irradiating an IR laser, etc. The temperature of the recording medium may be adjusted in advance before ink jet recording, but it is necessary to make the in-plane temperature difference uniform and to improve the robustness against temperature changes. A heating method is preferred. As a temperature control method, for example, a method of attaching a Peltier element, a method of attaching a heater, a method of circulating refrigerant / cooling water, or the like is preferably used.

  In the ink jet recording method according to the present invention, in the laminating step, the recording medium conveyance speed is preferably 300 mm / sec to 1500 mm / sec. A higher conveying speed (for example, 700 mm / sec or more) is preferable because an image forming speed is increased and productivity is improved.

[Ink set]
The plurality of inkjet inks used in the inkjet recording method according to the present invention is preferably an ink set composed of at least two types of inks selected from the group of yellow ink, cyan ink, magenta ink, and black ink.

  The plurality of ink-jet inks used in the ink-jet recording method according to the present invention is an ink set composed of magenta ink and at least one ink selected from the group of yellow ink, cyan ink, and black ink. More preferably, the magenta ink color material is C.I. I. Pigment violet 19 and C.I. I. More preferably, it is a mixed crystal pigment of CI Pigment Red 202.

(3) Inkjet recording apparatus An inkjet recording apparatus according to the present invention is an inkjet recording apparatus using the inkjet recording method of the present invention.

  The ink jet recording apparatus according to the present invention is preferably a photocurable ink jet recording apparatus as long as the ink jet recording method of the present invention can be used. There are two types of photo-curing type ink jet recording apparatuses, a line recording method (single pass recording method) and a serial recording method, which may be selected according to the required image resolution and recording speed. However, the line recording method (single pass recording method) is more preferable from the viewpoint of high-speed recording.

  Hereinafter, an example of a line recording type ink jet recording apparatus which is a preferred embodiment of the ink jet recording apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing an example of the configuration of the main part of a line recording type inkjet recording apparatus 10 which is a preferred embodiment of the inkjet recording apparatus according to the present invention. FIG. 2 is a top view illustrating an example of a configuration of a main part of the line recording type inkjet recording apparatus 10 which is a preferred embodiment of the inkjet recording apparatus according to the present invention. As shown in FIGS. 1 and 2, the inkjet recording apparatus 10 accommodates a plurality of inkjet recording heads 121 to 124 (for yellow ink, magenta ink, cyan ink, and black ink, the same applies hereinafter). Ink flow paths 141 to 144 (for yellow ink, magenta ink) connected to the carriages 131 to 134 (for yellow ink, magenta ink, cyan ink, and black ink, respectively) and the head carriages 131 to 134 respectively. , For cyan ink and for black ink, the same applies hereinafter), ink tanks 151 to 154 for storing ink supplied through the ink flow paths 141 to 144, and the entire width of the recording medium 110 and the head carriages 131 to 134. On the downstream side of the recording medium It has a light irradiation unit 160 that is, a temperature control unit 170 which is disposed on the lower surface of the recording medium 110.

  The head carriages 131 to 134 are fixedly arranged so as to cover the entire width of the recording medium 110, and accommodate a plurality of ink jet recording heads 121 to 124 provided for each color. Ink is supplied to the ink jet recording heads 121 to 124. For example, the ink may be supplied directly or by an ink supply unit (not shown) from an ink cartridge (not shown) that is detachably attached to the inkjet recording apparatus 10.

  A plurality of ink jet recording heads 121 to 124 are arranged in the transport direction of the recording medium 110 for each color. The number of inkjet recording heads 121 to 124 arranged in the conveyance direction of the recording medium 110 is set according to the nozzle density of the inkjet recording heads 121 to 124 and the resolution of the print image. For example, when forming an image having a resolution of 1440 dpi using the inkjet recording heads 121 to 124 having a droplet amount of 2 pl and a nozzle density of 360 dpi, the four inkjet recording heads 121 to 124 are arranged in the transport direction of the recording medium 110. What is necessary is just to shift and arrange. Further, when forming an image with a resolution of 720 × 720 dpi using the ink jet recording heads 121 to 124 having a droplet amount of 6 pl and a nozzle density of 360 dpi, the two ink jet recording heads 121 to 124 may be arranged in a shifted manner. dpi represents the number of ink droplets (dots) per 2.54 cm.

  The ink tanks 151 to 154 are connected to the head carriages 131 to 134 via the ink flow path 30. The ink flow paths 141 to 144 are paths for supplying the ink in the ink tanks 151 to 154 to the head carriages 131 to 134. In order to discharge ink droplets stably, the ink tanks 151 to 154, the ink flow paths 141 to 144, the head carriages 131 to 134, and the ink jet recording heads 121 to 124 are heated to a predetermined temperature to change the gel state. maintain.

  The light irradiation unit 160 covers the entire width of the recording medium 110 and is disposed on the downstream side of the head carriages 131 to 134 in the recording medium conveyance direction. The light irradiation unit 160 irradiates the droplets ejected by the inkjet recording heads 121 to 124 and landed on the recording medium with light, thereby curing the droplets.

  The temperature control unit 170 is disposed on the lower surface of the recording medium 110 and maintains the recording medium 110 at a predetermined temperature. The temperature control unit 170 can be, for example, various heaters.

  Hereinafter, an ink jet recording method using the line recording type ink jet recording apparatus 10 will be described. The recording medium 110 is transported between the head carriages 131 to 134 and the temperature control unit 170 of the inkjet recording apparatus 10. On the other hand, the recording medium 110 is adjusted to a predetermined temperature by the temperature controller 170. Next, droplets of high-temperature ink are ejected from the ink jet recording heads 121 to 124 of the head carriages 131 to 134 and attached (landed) on the recording medium 110. Then, the light irradiating unit 160 irradiates the ink droplets attached on the recording medium 110 with light and cures them.

  The total ink droplet thickness after curing is preferably 2 to 25 μm. The “total ink droplet thickness” means the maximum value of the ink droplet thickness drawn on the recording medium, and the above-mentioned n-order color (primary color, secondary color, 3 The meaning of the total ink film thickness is the same in the image formed with the next color or the like.

  Hereinafter, the present invention will be specifically described with reference to examples, but the scope of the present invention is not limited thereto.

<Preparation of inkjet ink>
Inks of the examples and comparative examples were prepared using the following components.

[Preparation of pigment dispersion]
Each pigment dispersion was prepared by the following procedure. A dispersant and a dispersion medium are put into a stainless beaker, heated and stirred for 1 hour while being heated on a hot plate at 65 ° C., cooled to room temperature, a pigment is added thereto, and 200 g of zirconia beads having a diameter of 0.5 mm are added. Sealed in a glass jar. This was subjected to a dispersion treatment with a paint shaker until a desired particle size was obtained, and then zirconia beads were removed.

(Yellow pigment dispersion)
Dispersant 1: EFKA7701 (manufactured by BASF) 5.6 parts by mass Dispersant 2: Solsperse 22000 (manufactured by Nippon Lubrizol Co., Ltd.) 0.4 parts by mass Dispersion medium: tripropylene glycol diacrylate (containing 0.2% UV-10) 80.6 parts by mass Pigment: PY185 (manufactured by BASF, Paliotol Yellow D1155) 13.4 parts by mass (magenta pigment dispersion)
Dispersant: JET-9151 (manufactured by BYK) 11 parts by mass Dispersion medium: Tripropylene glycol diacrylate (containing 0.2% UV-10) 69 parts by mass Pigment: PV19 / PR202 (manufactured by BASF, D4500J) 20 parts by mass ( Cyan pigment dispersion)
Dispersant: JET-9151 (manufactured by BYK) 7 parts by weight Dispersion medium: tripropylene glycol diacrylate (containing 0.2% UV-10) 70 parts by weight Pigment: PB15: 4 (manufactured by Dainichi Seika, Chromofine Blue 6332JC) ) 23 parts by mass (black pigment dispersion)
Dispersant: JET-9151 (BYK) 7 parts by weight Dispersion medium: Tripropylene glycol diacrylate (containing 0.2% UV-10) 70 parts by weight Pigment: PB7 (Mitsubishi Chemical Corporation, MA-7) 23 parts by weight Part

[Photopolymerizable compound]
APG-200 (Tripropylene glycol diacrylate manufactured by Shin-Nakamura Chemical Co., Ltd.)
A-600 (manufactured by Shin-Nakamura Chemical Co., Ltd., polyethylene glycol # 600 diacrylate)
SR499 (Sartomer 6EO-modified trimethylolpropane triacrylate)
M360 (3PO modified trimethylolpropane triacrylate, manufactured by Mion)

[Curable oligomer]
Etcure 6361-100 (Hyperbranch polyester acrylate manufactured by Eternal Chemical)
CN2270 (aliphatic polyester acrylate manufactured by Sartomer)
[Photopolymerization initiator]
TPO (BASF)
819 (BASF)
ITX (made by LAMBSON)
[Gelling agent]
Kao Wax T1 (disoaryl ketone manufactured by Kao Corporation)
Unistar M-2222SL (behyl behenylate manufactured by NOF Corporation)
[Surfactant]
TSF-4442 (Toshiba Silicone)

  Each component and each pigment dispersion were mixed in accordance with the composition of the ink described in Table 1 below, and the mixture was heated to 80 ° C. and stirred. The obtained solution was filtered through a Teflon (registered trademark) 3 μm membrane filter manufactured by ADVATEC under heating. Then, the image was evaluated according to the evaluation criteria described later.

<Measurement of gel temperature, complex viscosity and slope of absolute value of linear approximation curve>
Co Npureto stress-controlled rheometer (PhysicaMCR series, Anton Paar Co., Ltd.) using using, respectively listed in Table 1 below ink (Y1~Y2, M1~M6, C1~C2 and Bk1～Bk2) The temperature change of dynamic viscoelasticity was measured at a temperature drop rate of 0.1 ° C./s, a strain of 5%, and an angular frequency of 10 radian / s. The gelation temperature Tgel is defined as the temperature at which the complex viscosity becomes 1 Pa · s or higher when the temperature change of dynamic viscoelasticity is measured at a temperature drop rate of 0.1 ° C./s, a strain of 5%, and an angular frequency of 10 radian / s. The complex viscosity was obtained as the average value of the complex viscosity values in the temperature range of −5 to −15 ° C. of the gelation temperature (Tgel). Regarding the slope of the absolute value of the linear approximation curve, the viscosity in the temperature range of −5 to −15 ° C. of the gelation temperature (Tgel) of each ink (Y1 to Y2, M1 to M6, C1 to C2, and Bk1 to Bk2). Obtained from a linear approximation of the shear curve. FIG. 3 is a diagram of a cohesive curve showing the relationship between the complex viscosity (Pa · S) and the temperature (° C.) of the magenta ink (M1) and the magenta ink (M6). As is clear from FIG. 3, for magenta ink (M1), the gelation temperature (Tgel) is 57 ° C., the slope of the absolute value of the linear approximation curve is 7.2, and for magenta ink (M6). The gelation temperature (Tgel) was 54 ° C., and the slope of the absolute value of the linear approximation curve was −1.5. Table 1 shows the results obtained for the gelation temperature, the complex viscosity, and the slope of the linear approximation curve for each of the inks (Y1-Y2, M1-M6, C1-C2, and Bk1-Bk2).

<Formation of inkjet image>
The prepared Y, M, C, and K ink compositions were loaded into an ink jet recording apparatus having an ink jet recording head equipped with a piezo ink jet nozzle. Using this apparatus, image recording was performed on half-size chrysanthemum coated paper (OK top coat, manufactured by Oji Paper Co., Ltd.). The conveyance speed of the recording medium was 1000 mm / sec.

  The ink supply system includes an ink tank, an ink flow path, a sub ink tank immediately before the ink jet recording head, a pipe with a metal filter, and a piezo head. The ink is heated to 90 ° C. from the ink tank to the head portion. A heater was also incorporated in the piezo head, and the ink temperature in the recording head was heated to 90 ° C. The piezo head has a nozzle diameter of 22 μm and a nozzle resolution of 600 dpi arranged in a staggered manner to form a 1200 dpi nozzle row. Using this ink jet device, a voltage is applied in the order of Y → M → C → K so that the amount of droplets becomes two size dots of 3.5 pl and 8.0 pl, and 1200 × 1200 dpi on the recording medium. The surface temperature of the substrate temperature is set to 42 ° C, 48 ° C, and 52 ° C for the secondary color patch with a dot rate of M100% + K80%, the gradation chart for YMCKBGR3C, and the chart for ISO 12642-2 (1617 colors). Each color image was formed. (Dpi represents the number of dots per 2.54 cm.) In this case, when Y is the first ink, M, C, and K are the second ink. Similarly, when M is the first ink, C and K are the second ink, and when C is the first ink, K is the second ink. The landing timing of the second ink for each first ink is shown in Table 2 below.

  Within 1 second after printing, an LED lamp (395 nm, 8 W / cm 2, water cooled unit) manufactured by Phoseon Technology was irradiated to cure the ink layer. The distance from the tube surface of the LED lamp to the recording medium was 50 mm (irradiation width 100 mm in the transport direction). The recording medium was conveyed by being adsorbed on a conveyance table. At this time, the temperature of the suction table was adjusted so that the temperature of the surface of the recording medium was constant when the ink droplet landed and during UV exposure.

<Evaluation of formed image>
The formed image was evaluated by the following method.

(Evaluation of dot area ratio)
Assuming that the first ink is M and the second ink is K, from the M100% + K80% secondary color patch and the K gradation chart, the dot area of K of 8.0 pl in the secondary color patch and the floor The dot area of K of 8.0 pl in the tone chart was measured, the area ratio was calculated, and evaluated according to the following criteria.
A: The area ratio is 90% or more and 110% or less.
○: The area ratio is 80% or more and 120% or less.
Δ: Area ratio is less than 70 to 80%.
X: The area ratio is less than 60%.

(Dot area ratio evaluation results)
As is clear from Table 3 below, Examples 3 and 4 are “「 ”having a dot area ratio of 90% or more and 110% or less, and very good results were obtained. The dot area ratio is 80% or more and 120% or less, and good results were obtained. On the other hand, for Comparative Examples 1 to 4, although Comparative Examples 1 and 4 gave good results of “◯”, Comparative Examples 2 and 3 were “x” with a dot area ratio of less than 60%. Was bad.

(Evaluation of color variation)
Using a spectrophotometer (X-rite's i1 iO Pro) and a colorimetry tool (X-rite's Measurement Tool and ProfileMaker) using a secondary color patch with substrate temperatures of 42 ° C and 52 ° C and M100% + K80% L * a * b * color measurement was performed, and the difference in color (ΔE) between 42 ° C. and 52 ° C. was calculated using the following formula, and evaluated according to the following criteria.
ΔE = SQRT ((ΔL *) ² + (Δa *) ² + (Δb *) ² )
A: ΔE = 2 or less B: ΔE = 2-4
Δ: ΔE = 4-6
×: ΔE = 6 or more

(Color variation evaluation results)
As is apparent from Table 3 below, Examples 1 to 4 have a color variation of “E” equal to or less than ΔE = 2, and very good results are obtained, while Comparative Examples 1 to 4 are comparative examples. In Example 1, a result of “Δ” was obtained, and in Comparative Example 4, a result of “◯” was obtained. In Comparative Examples 2 and 3, “X” having a color variation of ΔE = 6 or more was obtained. The result was poor.

(Evaluation of gloss (gloss value))
Using the ink shown in Table 3 below, the 60 degree gloss value of Blue (M → C) and 3C (Y → M → C) was measured by the method defined in JIS K 5600.
A: The solid surface has a surface gloss value of 30 or more at a substrate surface temperature of 48 ° C., high gloss, no streak, and a good image.
(Triangle | delta): The surface gloss value of a solid part in a base-material surface temperature of 48 degreeC is 20-30 or less, but a glossiness falls a little, but there exists an impact.
X: When the substrate surface temperature is 48 ° C., the surface gloss value of the solid part is 20 or less, the gloss is low, and impact is applied.

(Evaluation result of glossiness (gloss value))
As is clear from Table 3 below, Examples 1-4 have good gloss results as “◯”, while Comparative Examples 2 and 3 have good “◯” results. Although Comparative Example 1 and 4 were the results of “x”, glossiness was poor.

(Evaluation of gloss fluctuation)
Blue and 3C 60 degree gloss fluctuation values at substrate temperatures of 42 ° C. and 52 ° C. were measured.
◯: The surface gloss fluctuation value of the solid part when the substrate surface temperature is 42 ° C. to 52 ° C. is 10 or less.
(Triangle | delta): The surface gloss fluctuation value of a solid part is 10-15 when a base-material surface temperature is 42 to 52 degreeC.
X: The surface gloss fluctuation value of the solid part when the substrate surface temperature is 42 ° C. to 52 ° C. is 15 or more.

(Evaluation result of gloss fluctuation)
As is clear from Table 3 below, Examples 1 to 4 gave a result of “◯” with good gloss fluctuation, while Comparative Examples 2 and 3 showed a result of “△” for Comparatives 1 to 4. In Comparative Examples 1 and 4, the result of “x” was obtained, and the gloss fluctuation was poor.

(Evaluation of abrasion)
In accordance with the method described in “JIS Standard K5701-1-6.2.3 Friction Resistance Test” on a 5 cm × 5 cm solid image, a recording medium cut to an appropriate size is placed on the image, and a load is applied. And rubbed together. Thereafter, the degree of image density reduction was visually observed and evaluated according to the following criteria.
○: No change in image was observed even after rubbing 100 times or more. Δ: Image density decreased at the stage of rubbing 100 times, but practically acceptable. X: Visible with rubbing less than 50 times. The image density is noticeable, and the quality is unusable.

(Abrasion evaluation results)
As is apparent from Table 3 below, Examples 1 and 3 to 4 gave “◯” results with good scratching properties, and Example 2 gave “Δ” results. On the other hand, for Comparative Examples 1 to 4, Comparative Examples 1 and 4 gave a good result of “◯”, but Comparative Examples 2 and 3 were a result of “×”, and the fretting property was poor. .

(Evaluation of color gamut)
Using the chart of ISO 12642-2 (1617 colors) output using Example 1 (ink set 1) in Table 3 below, the color difference with respect to Japan Color 2011, which defined the standard color for commercial offset printing, was determined.

(Color gamut evaluation results)
A wide color gamut including Japan Color 2011 could be reproduced at any substrate temperature.

  By using the inkjet recording methods of Examples 1 to 4, it is possible to obtain an inkjet recording apparatus that can record a color image with high definition, wide color gamut, high gloss, and little color variation.

  The ink jet recording method of the present invention is suitable for forming a color image on a recording medium, particularly a non-absorbent recording medium and a slightly absorbent recording medium.

DESCRIPTION OF SYMBOLS 10 Inkjet recording apparatus 110 Recording medium 121 Inkjet recording head for yellow ink 122 Inkjet recording head for magenta ink 123 Inkjet recording head for cyan ink 124 Inkjet recording head for black ink 131 Head carriage for yellow ink 132 For magenta ink Head carriage 133 Cyan ink head carriage 134 Black ink head carriage 141 Yellow ink ink flow path 142 Magenta ink ink flow path 143 Cyan ink ink flow path 144 Black ink ink flow path 151 Ink tank for yellow ink 152 Ink tank for magenta ink 153 Ink tank for cyan ink 154 Black Ink tank 160 light irradiating unit 170 temperature controller for tank

Claims (8)

An ink jet recording method of sequentially applying each ink of a plurality of ink jet inks having different hues to a recording medium in a droplet amount of 0.5 to 15 pL and recording a color image on the recording medium,
Each of the plurality of ink-jet inks contains a gelling agent and a coloring material, has a phase transition point at 40 ° C. or more and less than 100 ° C., and undergoes a sol-gel phase transition according to temperature,
Of the plurality of ink-jet inks, the second ink is landed on the first ink within one second after the first ink is landed on the recording medium, and the first ink and the first ink Including a laminating step of laminating two inks,
The total amount of the gelling agent contained in each of the plurality of inkjet inks is 1 to 4% by mass with respect to the total mass of the ink,
In the stacking step, the dot area of the second ink formed on the first ink is the same as the droplet quantity of the second ink landed on the first ink. 80% to 120% of the dot area of the second ink formed on the recording medium.
The surface temperature of the recording medium is controlled to −5 to −15 ° C. of the gelation temperature (Tgel) defined below of the first ink,
The first ink has a complex viscosity average value defined below of 50 to 500 Pa · s , and the slope of the linear approximation of the viscoelastic curve defined below of the first ink. Is an absolute value of 5 to 50 , and an ink jet recording method.
(The average value of the complex viscosity represents the average of the values of the complex viscosity in the temperature range from −5 to −15 ° C. from the gelation temperature (Tgel), and the gelation temperature (Tgel) represents a temperature decrease rate of 0.1. ° C. / s, strain 5%, the angular frequency 10radian / s, in viscoelasticity curve obtained by a temperature change at a cooling rate of 0.1 ° C. / s, the linear. viscoelastic curves complex viscosity represents the temperature at which the 1Pa The approximate slope is as follows: temperature drop rate 0.1 ° C./s, strain 5%, angular frequency 10 radian / s, temperature drop rate 0.1 ° C./s in the temperature range from the gelation temperature (Tgel) to −5 to −15 ° C. Represents the slope of the linear approximation of the viscoelastic curve obtained by changing the temperature with. Among the plurality of inkjet heads loaded with each of the plurality of inkjet inks, the inkjet ink present in at least one inkjet head has a viscosity of 3 mPa · s or more and less than 20 mPa · s, 2. The ink jet recording method according to claim 1, wherein the ink jet recording is performed on the recording medium. Each of the plurality of inkjet inks further comprises a photopolymerizable compound and a photopolymerization initiator,
The method further includes the step of irradiating the first ink and the second ink laminated in the laminating step with an actinic ray to cure the first ink and the second ink. The ink jet recording method according to claim 1 or 2 . Irradiating the active light to the first ink and the second ink within 0.01 to 5.0 seconds after the first ink and the second ink are laminated in the laminating step. The inkjet recording method according to claim 3 , wherein: In the laminating step, wherein the conveying speed of the recording medium is 300mm / sec~1500mm / sec, inkjet recording method according to any one of claims 1-4. Said plurality of ink-jet inks, characterized in that the yellow ink, cyan ink, magenta ink, and an ink set composed of at least two inks selected from the group of black ink, one of the claims 1-5 The ink jet recording method according to claim 1. The plurality of inkjet inks is an ink set composed of magenta ink and at least one kind of ink selected from the group of yellow ink, cyan ink, and black ink,
The magenta ink color material is C.I. I. Pigment violet 19 and C.I. I. Characterized in that it is a mixed crystal pigment Pigment Red 202, an ink jet recording method according to any one of claims 1-5. Characterized by using the ink jet recording method according to any one of claims 1 to 7 the ink-jet recording apparatus.

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