JP4907447B2 - Undercoat liquid, ink jet recording method and ink jet recording apparatus - Google Patents

Description

  The present invention relates to an undercoat liquid, an ink jet recording method, and an ink jet recording apparatus, and more particularly to an undercoat liquid, an ink jet recording method, and an ink jet recording apparatus that are suitable for forming high-quality images at high speed.

  An ink jet system that ejects ink in droplets from an ink ejection port is used in many printers because it is small and inexpensive, and can form an image without contact with a recording medium. Among these ink jet methods, the piezo ink jet method that ejects ink using deformation of piezoelectric elements and the thermal ink jet method that ejects ink droplets by utilizing the boiling phenomenon of ink due to thermal energy achieve high resolution and high printability. It has the feature of being excellent.

  2. Description of the Related Art Currently, high speed and high image quality when ink is ejected onto a non-water-absorbing recording medium such as plain paper or plastic by an ink jet printer are important issues.

  Ink jet recording is a method in which ink droplets are ejected according to image data and lines are formed on the recording medium or images are formed. When recording is performed on the recording medium, it takes time to dry the droplets after droplet ejection or to penetrate into the recording medium, and the image tends to bleed, and between adjacent ink droplets on the recording medium. There was a problem in practical use such as mixing and hindering sharp image formation. When mixing between droplets, adjacent droplets that have been struck are united to cause movement of the droplets, so that they deviate from the landing position, and when drawing thin lines, the line width is uneven. When a colored surface is drawn, color unevenness or the like occurs. In addition, since the degree of non-uniform line width and color unevenness on the colored surface varies depending on the ink absorbability and wettability of the surface of the recording medium, various recording media can be used even if the ink used and its discharge conditions are constant. There was also a problem that the images were different.

  As a method for suppressing image bleeding, line width non-uniformity, and the like, there is a method of promoting droplet fixing. For example, in order to give high-definition drawing properties, there is a method that uses a reactive two-component ink and causes both to react on the recording medium. For example, a liquid having a basic polymer is attached. Then, after applying a method of recording an ink containing an anionic dye (see, for example, Patent Document 1) or a liquid composition containing a cationic substance, an ink containing an anionic compound and a coloring material is applied. A method (for example, refer to Patent Document 2) is disclosed.

In addition, UV curable ink is applied as the ink, and UV curable color ink dots ejected onto the recording medium are irradiated with ultraviolet rays in accordance with their respective ejection timings to increase the viscosity and adjacent dots do not mix with each other. There has been proposed an ink jet recording method in which pre-curing is carried out to a certain degree and then UV-irradiation is further performed to perform main curing (see, for example, Patent Document 3).
In addition, a radiation-curable white ink is uniformly applied as an undercoat layer on a transparent or translucent non-absorbable recording medium, solidified or thickened by irradiation, and then a radiation-curable color ink set is used. There has been proposed a technique (for example, refer to Patent Documents 4 and 5) for improving the problem of color ink visibility, bleeding, and the difference in image between various recording media. In addition, a technique for applying a substantially transparent actinic ray curable ink by an inkjet head instead of the radiation curable white ink has been proposed (for example, see Patent Document 6).
Japanese Unexamined Patent Publication No. 63-60783 JP-A-8-174997 JP 2004-42548 A JP 2003-145745 A JP 2004-42525 A JP 2005-96254 A

  However, in the method described in Patent Document 3, bleeding is suppressed, but there remains a problem that images differ between various recording media, and the line width is uneven due to mixing between droplets. Insufficient to eliminate color unevenness and the like. In addition, the methods described in Patent Documents 4 and 5 are insufficient for eliminating line width non-uniformity and color unevenness caused by mixing between droplets. Furthermore, the method described in Patent Document 6 still has problems such as non-uniform line width and color unevenness due to mixing between droplets.

  On the other hand, in the ink jet image forming method, in order to sequentially apply the color ink onto the base material at the time of image formation, the ink applied later is applied onto the previously applied color ink. And when applied to a portion to which color ink is not applied. If the dot diameter (and dot shape) differs in each case, there is also a problem that image degradation occurs.

  The present invention has been made in view of the above, and is excellent in image uniformity between various recording media irrespective of the recording medium, and can suppress the occurrence of ink bleeding, non-uniform line width, color unevenness, and the like. In addition, an object of the present invention is to provide an undercoat liquid, an ink jet recording method, and an ink jet recording apparatus capable of maintaining a uniform dot diameter even when ink droplets are deposited and recording with high density and high reproducibility regardless of the image form. And to achieve the purpose.

  The present invention provides a good image both in the case where the color ink is ejected on a portion where the color ink is not applied and in the case where the color ink is further ejected on a portion where the color ink is applied. The inventors have obtained knowledge that it is important to have drawability and that the dot diameter (and dot shape) does not change, and have been achieved based on such knowledge.

<1> An undercoat liquid for applying ink onto a recording medium in advance before ejecting ink onto the recording medium to record an image, which is a water-insoluble and oil-soluble acrylamide polymer; An undercoat liquid comprising a radically polymerizable compound having an acid group.
<2> The undercoat liquid according to <1>, further comprising a radical polymerization initiator .
<3> The undercoat liquid according to <1> or <2>, wherein the content of the radical polymerizable compound having a phosphate group is 1 to 50% by mass .
<4> The undercoat liquid according to any one of <1> to <3>, wherein the content of the acrylamide polymer is 1 to 50% by mass .

< 5 > An undercoat liquid applying step for applying an undercoat liquid containing a water-insoluble and oil-soluble acrylamide polymer and a radical polymerizable compound having a phosphate group on a recording medium, and the applied undercoat An ink jet recording method comprising: a curing step of semi-curing a liquid; and a recording step of recording an image on the semi-cured undercoat liquid by ejecting ink that can be cured by irradiation with active energy rays.

<6> The ink jet recording method according to <5>, wherein the undercoat liquid is semi-cured by irradiation with active energy rays.
<7> The ink jet recording method according to <5> or <6> , wherein the undercoat liquid further contains a radical polymerization initiator.

<8> The recording step includes a step of recording an image using an ink set including multicolor inks and a step of semi-curing the ejected at least one color ink. < 5 >- <7> The inkjet recording method according to any one of the above.
<9> The inkjet recording method according to any one of < 5 > to <8>, further comprising a step of further promoting the curing of the undercoat liquid and the discharged ink.
<10> The curing sensitivity of the ink is not less than the curing sensitivity of the undercoat liquid and not more than 4 times the curing sensitivity of the undercoat liquid, < 5 > to <9>, Inkjet recording method.

<11> Undercoat liquid applying means for applying an undercoat liquid containing a water-insoluble and oil-soluble acrylamide-type polymer and a radically polymerizable compound having a phosphate group on a recording medium; An undercoating liquid curing unit disposed downstream of the undercoating liquid application unit in the moving direction, applying an active energy ray to at least a part of the undercoating liquid, and semi-curing the undercoating liquid; and the moving medium in the moving direction of the recording medium An ink jet recording apparatus comprising: an image recording unit that is disposed downstream of an undercoat liquid curing unit and that discharges a curable ink by irradiation with an active energy ray and records an image on the semi-cured undercoat liquid. is there.

<12> A transport unit that transports the recording medium, and a recording medium that is disposed downstream of the image recording unit in the transport direction of the transported recording medium and on which an image is recorded by the image recording unit And an active energy ray irradiating means for further accelerating curing of the undercoat liquid and the ejected ink, wherein the image recording means is orthogonal to the transport direction of the recording medium. <11>, wherein the ink is ejected by using at least one line-type ink-jet head that is arranged in parallel with a direction and has a length corresponding to the entire recordable width of the recording medium. Inkjet recording apparatus.

According to the present invention, regardless of the recording medium, the image uniformity between various recording media is excellent, the occurrence of ink bleeding, line width non-uniformity, color unevenness, and the like can be suppressed, and ink is laid on top of each other. Even when the ink droplets are dropped, it is possible to provide an undercoat liquid, an ink jet recording method, and an ink jet recording apparatus that can maintain a uniform dot diameter and can be recorded with high density and high reproducibility regardless of the image form.
In addition, the dot diameter (and the dot shape) does not change between the case where the color ink is ejected on the portion where the color ink is not applied and the case where the color ink is further ejected on the portion where the color ink is applied. High quality images can be obtained.

  Hereinafter, the undercoat liquid, the ink jet recording method and the ink jet recording apparatus of the present invention will be described in detail.

The undercoat liquid of the present invention is used to pre-apply ink onto the recording medium before ejecting the ink when the ink is ejected onto the recording medium to record an image. And a radically polymerizable compound having a phosphoric acid group, which will be described later. The undercoat liquid preferably further contains a radical polymerization initiator described later. The undercoat liquid is preferably used in the inkjet recording method of the present invention described below.
The inkjet recording method of the present invention includes an undercoat liquid application step for applying an undercoat liquid containing a polymer and a radical polymerizable compound having a phosphate group on a recording medium, and the applied undercoat liquid is semi-treated. A curing process for curing and a recording process for recording an image by ejecting ink that can be cured by irradiation with active energy rays on the semi-cured undercoat liquid are provided. Further, if necessary, other steps such as a step of semi-curing the ink can be provided.

In general, in the ink jet recording method, adjacent ink droplets that are applied with overlapping portions to obtain a high image density stay on and contact the recording medium before drying. Are merged with each other to cause blurring of the image and non-uniformity of the line width of the thin line, and the sharp image formation is liable to be impaired. However, in the inkjet recording method of the present invention, by applying an undercoat liquid onto a recording medium and semi-curing the undercoat liquid, ink droplets overlap each other on the semi-cured undercoat liquid. Even if it is provided, it is possible to suppress coalescence between these adjacent ink droplets due to the interaction between the undercoat liquid and the ink droplets. This effectively prevents the occurrence of blurring of the image, non-uniform line widths such as fine lines in the image, and color unevenness on the colored surface.
In addition, the undercoat liquid in the present invention is composed of a polymer and a radical polymerizable compound having a phosphate group, so that the ink that has landed spreads appropriately and connects the dots, but the dot shape is impaired. The image area is low enough to prevent the image from being spread to such an extent that the image is disturbed or blurred. In the case of recording the image of (2), it is possible to suppress the occurrence of white spots and to keep the density of the entire image high in detail and to record an image clearly reproduced in detail.
Therefore, according to the ink jet recording method of the present invention, sharp lines can be formed with a uniform width even if recording is performed with a small amount of liquid and a low dot density. The reproducibility of a fine image such as a fine line in the image can be improved without causing a decrease in density.

  In addition, since the ink jet recording method of the present invention is configured using an undercoat liquid containing a polymer and a radical polymerizable compound having a phosphate group in the undercoat liquid, a multicolored color is formed on the undercoat liquid. A good image can be recorded even when ink is deposited and deposited. For example, even when an image is drawn on the undercoat liquid with the first color ink and dots or lines are drawn on the image with the second color ink, the spread of the dots and lines is suppressed, and the first color It is possible to draw the same dots and lines as in the case where there is no image of the ink. Similarly, for example, when an image is drawn with the first color ink on the undercoat liquid and a grid pattern composed of grid lines is drawn with the second color ink on the image, the grid line width of the second color itself As a result, it is possible to suppress the phenomenon that the area where the ink of the second color is not ejected between the two grid lines is narrowed, and there is no image of the ink of the first color. A lattice pattern similar to the case can be drawn.

  Here, the adjacent ink droplets are droplets that are ejected from the ink ejection port using a single color ink, and are ejected with overlapping portions, or inks of different colors are used. It means a droplet ejected from an ink ejection port and ejected with an overlapping portion. Adjacent ink droplets may be droplets that are ejected at the same time, or may be preceding droplets and subsequent droplets that have a relationship between preceding droplet ejection and subsequent droplet ejection.

In the present invention, at least one kind of ink and at least one kind of undercoat liquid are used as the liquid for forming an image. The undercoat liquid preferably has a composition different from that of the ink. The undercoat liquid is preferably applied to the same area as the image formed by ejecting ink droplets on the recording medium or an area wider than the image.
The ink in the present invention is preferably a multicolor ink set using a plurality of colors of ink. Further, when a multicolor ink set is used, it is preferable that the ink droplets are further semi-cured after each color ink is ejected.

  One specific configuration of the ink jet recording method of the present invention is that a plurality of color ink droplets to be ejected onto a recording medium contains a polymerizable or crosslinkable material for forming an image. In addition, an undercoat liquid having a composition different from that of the ink and containing a polymer and a radically polymerizable compound having a phosphate group is the same as or wider than the image formed by the ink droplets. A step of applying to the recording medium in advance, a step of applying an active energy ray or heat to the undercoating liquid applied on the recording medium to be semi-cured, and applying an active energy ray or heat to be semi-cured, And a step of ejecting ink droplets of a plurality of colors on the undercoat liquid.

  Further, after applying an undercoat liquid in advance as described above and then depositing at least all desired ink droplets (preferably multicolor ink droplets), excellent fixability to ink is obtained. From the viewpoint, it is preferable to provide a step (hereinafter referred to as a fixing step) for fixing the recorded image by further accelerating the curing of the undercoat liquid and the ejected ink by applying, for example, an active energy ray.

-Undercoat liquid application process, recording process-
In the undercoat liquid application step, an undercoat liquid is applied on the recording medium. The undercoat liquid contains at least a polymer and a radically polymerizable compound having a phosphate group, and can preferably be constituted using a radical polymerization initiator and a surfactant. Moreover, it can comprise using another component as needed. Details of each component constituting the undercoat layer and the recording medium will be described later.

  In the recording step, an image is recorded by ejecting ink that can be cured by irradiation of active energy rays onto the undercoat liquid semi-cured in the curing step described later. The ink is applied onto the undercoat liquid that has been semi-cured into droplets using an inkjet nozzle or the like.

  In the inkjet recording method of the present invention, the undercoat liquid can be applied to a recording medium using a coating apparatus or an inkjet nozzle.

(I) Coating using a coating device In the present invention, an image recording is performed by coating an undercoat liquid on a recording medium using a coating device and then ejecting ink droplets with an inkjet nozzle. preferable. The ink jet nozzle will be described later.

  The coating apparatus is not particularly limited and can be appropriately selected from known coating apparatuses according to the purpose, for example, an air doctor coater, a blade coater, a lot coater, a knife coater, a squeeze coater, and an impregnation coater. , Reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, extrusion coater and the like. For details, see Yuji Harasaki's “Coating Engineering”.

(Ii) Discharge by Inkjet Nozzle In the present invention, a mode in which an image is recorded by discharging an undercoat liquid by an inkjet nozzle and then ejecting ink droplets by an inkjet nozzle is also preferably used. The ink jet nozzle will be described later.
The condition for applying the undercoat liquid with the ink jet nozzle is that a head having a larger discharge droplet volume and a lower nozzle density than the head for ink drawing is arranged as a full line head unit in the width direction of the recording medium, and thereby the undercoat liquid. It is desirable to discharge. Such a head having a large amount of ejected droplets generally has a large ejection force, and therefore can easily cope with a highly viscous undercoat liquid, and is also advantageous for clogging the nozzle. Further, when a head with a large amount of ejected droplets is used, there is an advantage that an inexpensive head with a low driving frequency can be applied because the droplet resolving power of the undercoat liquid in the recording medium transport direction can be reduced.

  In any of the above embodiments, liquids other than the undercoat liquid and ink droplets can be further applied. The application of the other liquid may be applied to the recording medium by any method such as application by an application device or ejection by an ink jet nozzle, and the application timing is not particularly limited. When the other liquid contains a colorant, a method of discharging with an ink jet nozzle is preferable, and it is preferable to apply after applying the undercoat liquid.

Next, a discharge method (inkjet recording method) using an inkjet nozzle will be described.
In the present invention, for example, an electrostatic attraction method in which ink is ejected using electrostatic force, a drop-on-demand method (pressure pulse method) in which vibration pressure of a piezo element is used, an electric signal is converted into an acoustic beam, and ink is irradiated. A known method such as an acoustic ink jet method in which ink is ejected using radiation pressure, or a thermal ink jet method in which ink is heated to form bubbles and the generated pressure is used is suitable.
Inkjet recording methods include a method of ejecting a large number of low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different densities, and colorless and transparent inks. The method using is included.

  In the present invention, the ink ejected onto the semi-cured undercoat liquid is preferably ejected with a droplet size of 0.1 pL (picoliter; the same applies hereinafter) to 100 pL (preferably by an inkjet nozzle). . When the droplet size is within the above range, it is effective in that an image with high sharpness can be drawn with density. More preferably, it is 0.5 pL or more and 50 pL or less.

  Further, the application amount (mass ratio per unit area) of the undercoat liquid is preferably within a range of 0.05 to 5 when the ink droplet amount is 1, and is within a range of 0.07 to 4. Is more preferable, and the range of 0.1 to 3 is particularly preferable.

  It is preferable that the droplet ejection interval until the ink droplet is ejected after the undercoat liquid is semi-cured is in the range of 5 μs or more and 10 seconds or less. It is effective in that the effect of the present invention can be remarkably exhibited when the droplet ejection interval is within the above range. The droplet ejection interval of the ink droplets is more preferably 10 μs to 5 seconds, and particularly preferably 20 μs to 5 seconds.

  In the recording step, a multicolor image can be recorded using an ink set including multicolor inks. In this case, in terms of fine image reproduction and color reproduction, a step of semi-curing one color or two or more inks of a plurality of colors ejected onto the recording medium is provided, and one color or a predetermined color A configuration in which exposure (so-called pinning exposure) is performed every several inks is preferable.

An active energy ray is suitable for pinning exposure, and the details of the active energy ray are the same as those in the fixing step described later. Examples thereof include ultraviolet rays and visible rays, and α rays, γ rays, X rays, electron rays, and the like. From the viewpoint of cost and safety, ultraviolet rays and visible rays are preferable, and ultraviolet rays are particularly preferable.
The amount of energy necessary for semi-curing here varies depending on the type or content of the polymerization initiator, generally 1 to 500 mJ / cm ² about, more preferably from 1 to 200 mJ / cm ² or less, 1 100 mJ / cm ² or less is particularly preferable.

-Curing process-
In the present invention, a curing step is provided in which the applied undercoat liquid is semi-cured between the application of the undercoat liquid in the undercoat liquid application process and the deposition of at least one ink droplet in the recording process.

Here, the semi-curing of the undercoat liquid (undercoat layer) will be described.
In the present invention, “semi-cured” means partially cured (partially cured) and refers to a state where the undercoat layer is partially cured but not completely cured. When the undercoat layer applied on the recording medium (base material) is semi-cured, the degree of curing may be non-uniform. For example, the undercoat layer is preferably cured in the depth direction.

  When a radically polymerizable undercoat layer is used in air or air partially substituted with an inert gas, radical polymerization is inhibited on the surface of the undercoat layer because of the action of suppressing radical polymerization of oxygen. Tend. As a result, the curing becomes non-uniform, the curing progresses more inside the undercoat layer, and the surface curing tends to be delayed.

  Even when the cationic polymerizable undercoat layer is used in air with moisture, the water has a cationic polymerization inhibiting action, so that the curing proceeds more inside the undercoat layer and the surface tends to be delayed. .

  In the present invention, when a radical photopolymerizable undercoat layer is used in the presence of radical polymerization-inhibiting oxygen and partially photocured, the degree of cure of the undercoat layer is higher on the inside than on the outside.

  When ink (colored liquid) is ejected onto the semi-cured undercoat layer, a technical effect favorable to the quality of the image formed on the recording medium is brought about. Further, the action mechanism can be confirmed by observing a cross section of the recording medium on which an image is formed.

  An example of a high-density portion when about 12 pL of ink is deposited on a semi-cured undercoat layer having a thickness of about 5 μm provided on the substrate will be described as an example.

  According to the present invention, the undercoat layer is semi-cured, and the degree of cure is higher on the side closer to the substrate than on the side farther from the substrate. In this case, three features are observed. That is, as shown in FIG. 1, (1) a part of the ink 24 is exposed on the surface 22, (2) a part of the ink 24 is embedded in the undercoat layer 20, and (3) the ink 24 The undercoat liquid 20 exists between the base material 26. That is, the recording medium on which an image obtained by applying the ink 24 on the semi-cured undercoat layer 20 has a cross section as schematically shown in FIG. When the above conditions (1), (2), and (3) are satisfied, it can be said that the ink is applied to the semi-cured undercoat layer. In this case, the ink droplets ejected with high density are connected to each other to form a colored film, giving a uniform and high color density.

  On the other hand, when ink is ejected onto the uncured undercoat layer, all of the ink 24 sinks into the undercoat layer 20 as shown in FIG. 2A and / or FIG. Thus, the undercoat liquid 20 does not exist between the ink 24 and the base material 26. In this case, even when ink is applied at a high density, the droplets are independent of each other, which causes a decrease in color density. The recording medium on which the image obtained by applying the ink 24 on the uncured undercoat layer 20 is schematically shown in FIGS. 2 (a) and 2 (b). It has a cross section.

  In addition, when ink is ejected onto the completely cured undercoat layer, the ink 24 does not enter the undercoat layer 20 as shown in FIG. Such a state causes occurrence of droplet ejection interference, a uniform ink film cannot be formed, and color reproducibility is deteriorated. The recording medium on which an image obtained by applying ink onto the fully cured undercoat layer has a cross section as schematically shown in FIG.

From the viewpoint of forming a uniform ink liquid layer without causing ink droplets to become independent when ink droplets are applied at high density, and from the viewpoint of suppressing the occurrence of droplet ejection interference, an undercoat layer per unit area The amount of the uncured portion is preferably sufficiently smaller than the maximum amount of ink droplets applied per unit area. That is, the relationship between the mass M per unit area of the uncured portion of the undercoat layer (undercoat liquid) and the maximum mass m of ink ejected per unit area is “m (ink) / 30 <M (undercoat layer) <m (Ink) ”is preferable, and“ m (ink) / 20 <M (undercoat layer) <m (ink) / 3 ”is further preferable, and“ m (ink) / 10 <M (undercoat layer) ”. ) <M (ink) / 5 ”is particularly preferable. Here, the maximum mass of ink ejected per unit area is the maximum mass per color.
When m (ink) / 30 <M (undercoat layer), the occurrence of droplet ejection interference can be prevented, and the dot size reproducibility is excellent. Further, when M (undercoat liquid) <m (ink), a uniform ink liquid layer can be formed, and a high concentration can be obtained.

The mass of the uncured portion of the undercoat layer per unit area is determined by the transfer test described below. After the completion of the semi-curing process (for example, after irradiation with active energy rays) and before the ink droplets are ejected, the penetrating medium such as plain paper is pressed against the semi-cured undercoat layer to form the penetrating medium. It is calculated | required by the mass measurement of the liquid of the undercoat layer transcribe | transferred to.
For example, assuming that the maximum ink ejection amount is 12 picoliters per pixel at a droplet ejection density of 600 × 600 dpi, the maximum mass m of ink ejected per unit area is 0.74 mg / cm ^2. (Here, the ink density is assumed to be about 1.1 g / cm ³ ). Therefore, the mass of the uncured portion of the preferred subbing layer is 0.025 mg / cm ² or more per unit area 0.74 mg / cm ² or less, more preferably 0.037 mg / cm ² or more 0.25 mg / cm ² or less It is particularly preferably 0.074 mg / cm ² or more and 0.148 mg / cm ² or less.

  When forming a secondary color with two colors of ink (here, ink A and ink B), one of them is semi-cured, for example, ink B is applied onto the semi-cured ink A. be able to. When the ink B is ejected onto the semi-cured ink A, as shown in FIG. 3, a part of the ink B28 sinks into the ink A24, and the ink A24 exists below the ink B28. Become. That is, the recording medium on which the image obtained by applying the ink B28 on the semi-cured ink A24 has a cross section as schematically illustrated in FIG. Good color reproduction is possible by the state where the ink A cured film and the ink B cured film are laminated.

  On the other hand, when the ink B is ejected onto the uncured ink A, all of the ink B28 may sink into the ink A24 as shown in FIG. 4 (a) and / or as shown in FIG. 4 (b). Thus, the ink A24 does not exist in the lower layer of the ink B28. In this case, even if the ink B droplets are applied at a high density, the droplets are independent of each other, which causes a decrease in the saturation of the secondary color. The printed matter obtained by applying the ink B28 onto the uncured ink A24 has a cross section as schematically illustrated in FIGS. 4 (a) and 4 (b).

  Further, when the ink B is ejected onto the completely cured ink A, the ink B28 does not sink into the ink A24 as shown in FIG. 4C. Such a state causes occurrence of droplet ejection interference, a uniform ink layer cannot be formed, and color reproducibility is deteriorated. Thus, the recording medium on which the image obtained by applying the ink B28 on the fully cured ink A24 has a cross section as schematically illustrated in FIG.

From the viewpoint of forming a uniform ink B liquid layer and suppressing the occurrence of droplet ejection interference when the droplets of ink B are applied at high density, the droplets are not independent from each other. The amount of the uncured portion of the ink A is preferably sufficiently smaller than the maximum droplet amount of the ink B applied per unit area. That is, the relationship between the mass M (ink A) per unit area of the uncured portion of the ink A layer and the maximum mass m (ink B) of the ink B layer ejected per unit area is “m (ink B) / 30. <M (ink A) <m (ink B) ”is preferable, and“ m (ink B) / 20 <M (ink A) <m (ink B) / 3 ”is more preferable. It is particularly preferable that m (ink B) / 10 <M (ink A) <m (ink B) / 5 ”.
When m (ink B) / 30 <M (ink A), the occurrence of droplet ejection interference can be prevented, and the dot size reproducibility is excellent. Further, when M (ink A) <m (ink B), a uniform ink liquid layer can be formed, and a high density can be obtained.

The mass of the uncured portion of the ink A per unit area is determined by a transfer test described below. After completion of the semi-curing process (for example, after irradiation with active energy rays) and before droplets of ink B are ejected, a penetrating medium such as plain paper is pressed against the semi-cured ink A layer, It is calculated | required by the mass measurement of the liquid of the ink A layer transcribe | transferred to the osmosis | permeation medium.
For example, assuming that the maximum ejection amount of ink B is 12 picoliters per pixel at a droplet ejection density of 600 × 600 dpi, the maximum mass m (ink) of ink B ejected per unit area is 0.74 mg. / Cm ² (here, the density of the ink B is assumed to be about 1.1 g / cm ³ ). Therefore, the mass of the uncured portion of the preferred ink A layer is 0.025 mg / cm ² or more per unit area 0.74 mg / cm ² or less, more preferably 0.037 mg / cm ² or more 0.25 mg / cm ² Or less, particularly preferably 0.074 mg / cm ² or more and 0.148 mg / cm ² or less.

  In the case of a curing reaction based on an ethylenically unsaturated compound or a cyclic ether, the non-polymerization rate can be quantitatively measured by the reaction rate of an ethylenically unsaturated group or a cyclic ether group (described later).

  In the case where the semi-cured state of the undercoat liquid and / or ink is realized by a polymerization reaction of a polymerizable compound that is initiated by irradiation with active energy rays or heating, a non-polymerization rate (A ( After polymerization) / A (before polymerization)) is preferably 0.2 or more and 0.9 or less, more preferably 0.3 or more and 0.9 or less, and 0.5 or more and 0.9 or less. It is particularly preferred.

Here, A (after polymerization) is the absorbance of the infrared absorption peak due to the polymerizable group after the polymerization reaction, and A (before polymerization) is the absorbance of the infrared absorption peak due to the polymerizable group before the polymerization reaction. is there. For example, when the polymerizable compound contained in the undercoat liquid and / or the ink is an acrylate monomer or a methacrylate monomer, an absorption peak based on a polymerizable group (acrylate group or methacrylate group) can be observed in the vicinity of 810 cm ^−1. The non-polymerization rate is preferably defined by the absorbance of. When the polymerizable compound is an oxetane compound, an absorption peak based on a polymerizable group (oxetane ring) can be observed in the vicinity of 986 cm ⁻¹ , and it is preferable to define the non-polymerization rate based on the absorption light intensity of the peak. . When the polymerizable compound is an epoxy compound, an absorption peak based on a polymerizable group (epoxy group) can be observed in the vicinity of 750 cm ⁻¹ , and the non-polymerization rate is preferably defined by the absorption luminous intensity of the peak.

  In addition, as a means for measuring the infrared absorption spectrum, a commercially available infrared spectrophotometer can be used, which may be either a transmission type or a reflection type, and is preferably selected as appropriate in the form of a sample. For example, it can be measured using an infrared spectrophotometer FTS-6000 manufactured by BIO-RAD.

Furthermore, a preferable semi-cured state can be determined by observing a cross section of an ink droplet ejected onto a semi-cured undercoat layer.
The method for observing the cross section is not particularly limited. For example, a commercially available microtome (for example, Leica, Microtome RM2255) and a commercially available optical microscope (for example, Nikon optical microscope measuring microscope MM-40) are used. be able to. In addition, the size of the ink droplets deposited on the semi-cured undercoat layer is preferably in the range of 1 picoliter to 100 picoliters, and is further equal to the ink droplet size actually used. It is preferable. Moreover, it is preferable to solidify the semi-cured film by some method during cross-sectional observation. The method for solidifying is not particularly limited, but freezing or curing by polymerization can be used.

  As a method for semi-curing the undercoat layer, (1) a method using a so-called agglomeration phenomenon such as imparting a basic compound to an acidic polymer or imparting an acidic compound or a metal compound to a basic polymer. (2) A method in which an undercoat liquid is prepared in advance to have a high viscosity, and a low boiling point organic solvent is added thereto to reduce the viscosity, and the low boiling point organic solvent is evaporated to return to the original high viscosity, (3) A method in which the undercoat liquid prepared to have a high viscosity is heated to lower the viscosity and then returned to the original high viscosity by cooling. (4) A method in which an active energy ray or heat is applied to the undercoat liquid to cause a curing reaction, etc. And known thickening methods. Among these, (4) a method in which an active energy ray or heat is applied to the undercoat liquid to cause a curing reaction is preferable.

  The method of applying an active energy ray or heat to cause a curing reaction is a method of insufficiently carrying out the polymerization reaction of the polymerizable compound on the surface of the undercoat layer applied to the recording medium. On the surface of the undercoat layer, the polymerization reaction tends to be hindered by the influence of oxygen in the air as compared with the inside. Therefore, the semi-curing of the undercoat layer can be caused by controlling the active energy ray or heat application conditions.

The amount of energy required for the semi-curing of the undercoat liquid varies depending on the type and content of the polymerization initiator, but in the case where energy is applied by active energy rays, generally about 1 to 500 mJ / cm ² is preferable. In addition, when energy is applied by heating, it is preferable to heat for 0.1 to 1 second under the condition that the surface temperature of the recording medium is in a temperature range of 40 to 80 ° C.

Generation of active species due to decomposition of the polymerization initiator is promoted by application of active energy rays such as actinic light and heating, or heat, and polymerizability or cross-linkability caused by the active species is increased by increasing the active species or increasing the temperature. The curing reaction by polymerization or crosslinking of the material is accelerated.
Moreover, thickening (viscosity increase) can also be suitably performed by irradiation of actinic light or heating.

  The semi-curing of the undercoat liquid has been described above, but the same applies to the semi-curing of ink (hereinafter also referred to as “ink liquid”).

The viscosity (25 ° C.) of the undercoat liquid in the “semi-cured” state is preferably 5000 mPa · s or more. The viscosity (25 ° C.) of the undercoat liquid on the surface portion in the “semi-cured” state is preferably 100 mPa · s or more and less than 5000 mPa · s. The viscosity of the surface of the undercoat liquid and the internal viscosity were measured with a commercially available viscometer (for example, a hand-held digital viscometer for laboratories manufactured by Maruyasu Kogyo Co., Ltd.). can do.
Further, the viscosity (25 ° C.) of the internal undercoat liquid in the “semi-cured” state is “semi-cured” in that the interaction between the undercoat liquid and the ink droplets suppresses coalescence between adjacent ink droplets. It is preferably 1.5 times or more, preferably 2 times or more, more preferably 3 times or more of the viscosity (25 ° C.) of the undercoat liquid in the surface portion in the state.

  The standard of the degree of polymerization of the polymerizable compound on the surface of the semi-cured undercoat liquid is preferably 1% to 70%, more preferably 5% to 60%, and particularly preferably 10% to 50%. The degree of polymerization can be measured by IR or the like.

  Details of the active energy rays are the same as those in the fixing step described later, and examples include ultraviolet rays, visible rays, and α rays, γ rays, X rays, electron rays, etc., and cost and safety. Therefore, ultraviolet rays and visible rays are preferable, and ultraviolet rays are particularly preferable.

-Fixing process-
The fixing step is preferably provided after the undercoat liquid applying step, the curing step, and the recording step. In this fixing step, for example, by applying energy, the curing of the undercoat liquid and the discharged ink is further promoted, and the recorded image is fixed.

  When a polymerizable or crosslinkable material is included, by applying energy, a curing reaction by the polymerization or crosslinking can be promoted, and a stronger image can be formed more efficiently. For example, in a system containing a polymerization initiator, generation of active species due to decomposition of the polymerization initiator is promoted by application of active energy such as active energy rays and heating, and due to increase of active species and temperature rise, it is attributed to active species. The curing reaction due to polymerization or crosslinking of the polymerizable or crosslinkable material is accelerated.

The application of energy can be suitably performed by irradiation with active energy rays or heating.
The active energy ray can be the same as the active light for fixing the image described later, for example, ultraviolet rays, visible rays, etc., as well as α rays, γ rays, X rays, electron rays, etc. From the viewpoint of cost and safety, ultraviolet rays and visible rays are preferable, and ultraviolet rays are particularly preferable.
Moreover, heating can be performed using a non-contact type heating means, such as a heating means for passing through a heating furnace such as an oven, a heating means by full exposure of ultraviolet light to visible light to infrared light, etc. Is preferred. Examples of light sources suitable for exposure as the heating means include metal halide lamps, xenon lamps, tungsten lamps, carbon arc lamps, mercury lamps and the like.

When energy is applied by irradiation with actinic light, the amount of energy required for the curing reaction varies depending on the type and content of the polymerization initiator, but is generally preferably about 100 to 10,000 mJ / cm ² . In addition, when energy is applied by heating, it is preferable to heat for 0.1 to 1 second under the condition that the surface temperature of the recording medium is in a temperature range of 40 to 80 ° C.

(Curing sensitivity of ink and undercoat liquid)
In the present invention, the curing sensitivity of the ink is preferably equal to or higher than the curing sensitivity of the undercoat liquid. More preferably, the curing sensitivity of the ink is not less than the curing sensitivity of the undercoat liquid and not more than 4 times the curing sensitivity of the undercoat liquid. More preferably, the curing sensitivity of the ink is not less than the curing sensitivity of the undercoat liquid and not more than twice the curing sensitivity of the undercoat liquid.
By making the ink curing sensitivity the same or higher than that of the undercoat liquid, it was possible to strike on the undercoat liquid during multi-color printing and on the ink liquid that was previously deposited. In this case, the dot diameter and dot shape can be made uniform.

Here, the curing sensitivity is the amount of energy required for complete curing when the ink and / or undercoat liquid is cured using a mercury lamp (ultra-high pressure, high pressure, medium pressure, etc., preferably an ultra-high pressure mercury lamp). The smaller the amount of energy, the higher the sensitivity. Therefore, a curing sensitivity of 2 means that the amount of energy is ½.
Further, the phrase “curing sensitivity is equivalent” means that the difference in curing sensitivity between the two compared is twice or less.

(Physical properties of ink and undercoat liquid)
The physical properties of the ink (droplet) ejected onto the recording medium by the ink jet recording method differ depending on the apparatus, but in general, the viscosity at 25 ° C. is preferably in the range of 5 to 100 mPa · s. -80 mPa · s is more preferable. Further, the viscosity (25 ° C.) of the undercoat liquid before semi-curing is preferably in the range of 100 mPa · s to less than 5000 mPa · s, and more preferably 200 mPa · s to less than 3000 mPa · s.

In the present invention, from the viewpoint of forming dots of a desired size on the recording medium, the undercoat liquid preferably contains a surfactant, and the following conditions (A), (B) and (C) are satisfied. It is preferable to satisfy all.
(A) The surface tension of the undercoat liquid is smaller than the surface tension of any ink.
(B) At least one of the surfactants contained in the undercoat liquid is
γs (0) −γs (saturation)> 0 (mN / m)
Satisfy the relationship.
(C) The surface tension of the undercoat liquid is
γs <(γs (0) + γs (saturation) ^maximum ) / 2
Satisfy the relationship.

Here, γs is the value of the surface tension of the undercoat liquid. γs (0) is the value of the surface tension of the liquid excluding all surfactants in the composition of the undercoat liquid. γs (saturation) is obtained when one surfactant among the surfactants contained in the undercoat liquid is added to the “liquid excluding all surfactants” and the concentration of the surfactant is increased. The surface tension value of the liquid with the surface tension saturated. The γs (saturation) ^maximum is the maximum value of γs (saturation) obtained for all surfactants satisfying the condition (B) among the surfactants contained in the undercoat liquid.

<Condition (A)>
In the present invention, as described above, in order to form an ink dot of a desired size on a recording medium, it is preferable to make the surface tension γs of the undercoat liquid smaller than the surface tension γk of any ink. .
Further, from the viewpoint of more effectively preventing the expansion of ink dots from landing to exposure, γs <γk-3 (mN / m) is more preferable, and γs <γk-5 (mN / m). It is particularly preferred that
In the case of printing a full-color image, from the viewpoint of improving the sharpness of the image, it is preferable that the surface tension γs of the undercoat liquid is at least smaller than the surface tension of the ink containing a colorant having high visibility. It is more preferable that the surface tension of all the inks be smaller. Examples of the colorant having high visibility include colorants exhibiting magenta, black, and cyan colors.
Even if the surface tension γk of the ink and the surface tension γs of the undercoat liquid satisfy the above relationship, if both values are less than 15 mN / m, it is difficult to form droplets during ink jetting. Discharge may occur. On the other hand, if it exceeds 50 mN / m, the wettability with the ink jet head may be deteriorated, resulting in a problem of non-ejection. Therefore, from the viewpoint of proper ejection, the surface tension γk of the ink and the surface tension γs of the undercoat liquid are preferably in the range of 15 mN / m or more and 50 mN / m or less, respectively 18 mN / m or more and 40 mN / m or less. More preferably, it is in the range, and particularly preferably in the range of 20 mN / m to 38 mN / m.
Here, the surface tension is measured by a Wilhelmy method using a commonly used surface tension meter (for example, Kyowa Interface Science Co., Ltd., surface tension meter CBVP-Z, etc.) at a liquid temperature of 20 ° C. and 60% RH. It is the value measured by.

<Condition (B) and Condition (C)>
In the present invention, in order to form ink dots of a desired size on a recording medium, the undercoat liquid preferably contains at least one kind of surfactant. In this case, at least one of the surfactants contained in the undercoat liquid preferably satisfies the following condition (B).
γs (0) −γs (saturation)> 0 (mN / m) Condition (B)
Furthermore, the surface tension of the undercoat liquid preferably satisfies the relationship of the following condition (C).
γs <(γs (0) + γs (saturation) ^maximum ) / 2 ... condition (C)

As described above, γs is the value of the surface tension of the undercoat liquid. Γs (0) is the value of the surface tension of the liquid excluding all the surfactants in the composition of the undercoat liquid. γs (saturation) is obtained when one surfactant among the surfactants contained in the undercoat liquid is added to the “liquid excluding all surfactants” and the concentration of the surfactant is increased. The surface tension value of the liquid with the surface tension saturated. The γs (saturation) ^maximum is the maximum value of γs (saturation) obtained for all surfactants satisfying the condition (B) among the surfactants contained in the undercoat liquid.

  The γs (0) is obtained by measuring the surface tension value of the liquid excluding all surfactants in the composition of the undercoat liquid. The γs (saturation) is obtained by adding one surfactant among the surfactants contained in the undercoat liquid to the “liquid excluding all surfactants”, and adjusting the concentration of the surfactant. It is obtained by measuring the surface tension of the liquid when the amount of change in the surface tension with respect to the change in the surfactant concentration becomes 0.01 mN / m or less when it is increased by 0.01% by mass.

Hereinafter, the γs (0), γs (saturation), and γs (saturation) ^maximum will be specifically described.
For example, the components constituting the undercoat liquid (Example 1) are a high boiling point solvent (diethyl phthalate, manufactured by Wako Pure Chemical Industries, Ltd.), a polymerizable material (dipropylene glycol diacrylate, manufactured by Akcros), a polymerization initiator. (TPO, the following initiator-1), fluorosurfactant (Megafac F475, manufactured by Dainippon Ink & Chemicals, Inc.), hydrocarbon surfactant (di-2-ethylhexyl sodium sulfosuccinate) Γs (0), γs (saturated) ¹ (when a fluorosurfactant is added), γs (saturated) ² (when a hydrocarbon surfactant is added), γs (saturated), and γs The (saturation) ^maximum is as follows.

That is, γs (0) is the surface tension value of the liquid of the undercoat liquid excluding all the surfactants, and is 36.7 mN / m. Further, when the saturation value of the surface tension of the liquid when the concentration is increased by adding the fluorosurfactant to the liquid is γs (saturation) ¹ , the value is 20.2 mN / m. . Furthermore, when the hydrocarbon surfactant is added to the liquid and the concentration of the surface tension of the liquid is increased to γs (saturated) ² when the concentration is increased, the value is 30.5 mN / m.

Since the undercoat liquid (Example 1) contains two types of surfactants that satisfy the condition (B), γs (saturated) is carbonized when a fluorosurfactant is added (γs (saturated) ¹ ). When the hydrogen-based surfactant is added, two values (γs (saturated) ² ) can be taken. Here, since γs (saturation) ^maximum is the maximum value of γs (saturation) ¹ and γs (saturation) ² , it is a value of γs (saturation) ² .
From the above, they are summarized as follows.
γs (0) = 36.7 mN / m
γs (saturated) ¹ = 20.2 mN / m (when a fluorosurfactant is added)
γs (saturated) ² = 30.5 mN / m (when a hydrocarbon surfactant is added)
γs (saturation) ^maximum = 30.5 mN / m

From the above results, as the surface tension γs of the undercoat liquid,
γs <(γs (0) + γs (saturation) ^maximum ) /2=33.6 mN / m
It is preferable to satisfy the relationship.
As for the condition (C), from the viewpoint of more effectively preventing the expansion of ink droplets from landing to exposure, as the surface tension of the undercoat liquid,
γs <γs (0) −3 × {γs (0) −γs (saturation) ^maximum } / 4
It is more preferable to satisfy the relationship
γs ≦ γs (saturation) ^maximum
It is particularly preferable to satisfy this relationship.

  The composition of the ink and the undercoat liquid may be selected so as to obtain a desired surface tension, but these liquids preferably contain a surfactant. As described above, in order to form ink dots of a desired size on the recording medium, the undercoat liquid preferably contains at least one surfactant. The surfactant will be described below.

(Surfactant)
Surfactants in the present invention are hexane, cyclohexane, p-xylene, toluene, ethyl acetate, methyl ethyl ketone, butyl carbitol, cyclohexanone, triethylene glycol monobutyl ether, 1,2-hexanediol, propylene glycol monomethyl ether, isopropanol, methanol , Water, isobornyl acrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, a substance having strong surface activity against at least one solvent, preferably hexane, toluene, propylene glycol monomethyl ether , Isobornyl acrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate More preferably, the substance has a strong surface activity against at least one solvent among propylene glycol monomethyl ether, isobornyl acrylate, 1,6-hexanediol diacrylate, and polyethylene glycol diacrylate. The substance is particularly preferably a substance having a strong surface activity against at least one solvent among isobornyl acrylate, 1,6-hexanediol diacrylate, and polyethylene glycol diacrylate.

Whether or not a certain compound has a strong surface activity with respect to the solvents listed above can be determined by the following procedure.
(procedure)
One solvent is selected from the solvents listed above, and the surface tension γ _solvent (0) of the _solvent is measured. The compound is added to the same solution as the solvent for obtaining the γ _solvent (0), and the concentration of the compound is increased by 0.01% by mass. Measure the surface tension γ _solvent (saturation) of the solution when: The relationship between the γ _solvent (0) and the γ _solvent (saturated) is
γ _solvent (0) −γ _solvent (saturated)> 1 (mN / m)
If so, it can be determined that the compound is a substance having a strong surface activity with respect to the solvent.

  Specific examples of the surfactant contained in the undercoat liquid include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, Nonionic surfactants such as acetylene glycols and polyoxyethylene / polyoxypropylene block copolymers, cationic surfactants such as alkylamine salts and quaternary ammonium salts, and fluorosurfactants. In addition, examples of the surfactant include those described in JP-A Nos. 62-173463 and 62-183457.

-Recording medium-
In the inkjet recording method of the present invention, any of a permeable recording medium, a non-permeable recording medium, and a slowly permeable recording medium can be used as the recording medium. Among these, a non-permeable or slowly permeable recording medium is preferable from the viewpoint that the effects of the present invention are more remarkably exhibited. Here, the permeable recording medium is a recording medium in which, for example, when a 10 pL (picoliter) droplet is dropped on the recording medium, the time until the total liquid amount permeates is 100 ms or less. Say. Further, the non-permeable recording medium refers to a recording medium in which liquid droplets do not substantially permeate. “Substantially does not penetrate” means, for example, that the penetration rate of a droplet after 1 minute is 5% or less. Further, the slow-penetrating recording medium refers to a recording medium in which when a 10 pL droplet is dropped on the recording medium, the time until the entire liquid amount penetrates is 100 ms or more.

Examples of the permeable recording medium include plain paper, porous paper, and other recording media that can absorb liquid.
Examples of the non-permeable or slowly permeable recording medium include art paper, synthetic resin, rubber, resin-coated paper, glass, metal, earthenware, and wood. In the present invention, a recording medium obtained by combining a plurality of these materials can be used for the purpose of adding functions.

  As the synthetic resin, any synthetic resin can be used. For example, polyesters such as polyethylene terephthalate and polybutadiene terephthalate, polyolefins such as polyvinyl chloride, polystyrene, polyethylene, polyurethane, and polypropylene, acrylic resins, polycarbonates, and acrylonitrile-butadiene. -Styrene copolymer etc., Diacetate, Triacetate, Polyimide, Cellophane, Celluloid etc. are mentioned. The thickness and shape of the recording medium when using a synthetic resin are not particularly limited, and may be any of a film shape, a card shape, and a block shape, and may be transparent or opaque. Good.

  The synthetic resin is preferably used in the form of a film used for so-called soft packaging, and various non-absorbable plastics and films thereof can be used. Examples of the plastic film include a PET film, an OPS film, an OPP film, a PNy film, a PVC film, a PE film, a TAC film, and a PP film. Other plastics that can be used include polycarbonate, acrylic resin, ABS, polyacetal, PVA, and rubbers.

  Examples of the resin-coated paper include a transparent polyester film, an opaque polyester film, an opaque polyolefin resin film, and a paper support in which both surfaces of paper are laminated with a polyolefin resin. Particularly preferred is a paper support in which both sides of the paper are laminated with a polyolefin resin.

  There is no restriction | limiting in particular as said metal, For example, aluminum, iron, gold | metal | money, silver, copper, nickel, titanium, chromium, molybdenum, silicon, lead, zinc, stainless steel, etc., and these composite materials are suitable.

  Furthermore, a read-only optical disk such as a CD-ROM or DVD-ROM, a write-once optical disk such as a CD-R or DVD-R, or a rewritable optical disk can be used, and ink jet recording is performed on the label surface side. be able to.

-Ink and undercoat liquid-
Hereinafter, the ink and undercoat liquid used in the inkjet recording method of the present invention will be described in detail.

  The ink is configured to have at least a composition for forming an image. The ink preferably contains at least one selected from a polymerizable or crosslinkable material and a radically polymerizable compound having a phosphate group, and if necessary, contains a polymerization initiator, a lipophilic solvent, a colorant and other components. Constructed using.

  The undercoat liquid contains at least a polymer and a radical polymerizable compound having a phosphate group. With this configuration, it is possible to record a good image even when multicolor inks are deposited on the undercoat liquid. For example, even when an image is drawn on the undercoat liquid with the first color ink and dots or lines are drawn on the image with the second color ink, the spread of the dots and lines is suppressed, and the first color It is possible to draw the same dots and lines as in the case where there is no image of the ink. Similarly, for example, when an image is drawn with the first color ink on the undercoat liquid and a grid pattern composed of grid lines is drawn with the second color ink on the image, the grid line width of the second color itself As a result, it is possible to suppress the phenomenon that the area where the ink of the second color is not ejected between the two grid lines is narrowed, and there is no image of the ink of the first color. A lattice pattern similar to the case can be drawn.

The undercoat liquid is preferably configured to have a composition different from that of the ink. The undercoat liquid preferably contains at least one polymerizable or crosslinkable material, and can be suitably configured using a polymerization initiator, a lipophilic solvent, a colorant, and other components as necessary. .
The polymerization initiator is preferably capable of initiating a polymerization reaction or a crosslinking reaction with active energy rays. As a result, the undercoat liquid applied to the recording medium can be cured by irradiation with active energy rays.

The undercoat liquid preferably contains a radical polymerization initiator. It is more preferable that the undercoat liquid further contains a radical polymerizable material other than the phosphate group-containing radical polymerizable compound in addition to the radical polymerization initiator. Thereby, the curing reaction of the undercoat liquid can be performed with high sensitivity in a short time.
The ink in the present invention preferably contains a colorant. In addition, the undercoat liquid used in combination with this has either a constitution that does not contain a colorant or the content of the colorant is less than 1% by mass, or a constitution in which the undercoat liquid contains a white pigment as a colorant. It is preferable. Hereinafter, each component constituting each liquid will be described in detail.

(polymer)
The undercoat liquid in the present invention contains at least one polymer. By containing the polymer in the undercoat liquid, when ink is ejected onto the undercoat liquid, it is possible to have an action of suppressing the spreading of the ink that has been deposited by the semi-cured undercoat liquid.

  The mechanism of the above-mentioned effect in addition of the polymer is unknown, but is presumed as follows. In other words, since the viscosity of the undercoat liquid increases due to the addition of the polymer, when the droplet size of the ejected ink is very small, the ink does not reach below the undercoat liquid, and its dot shape is maintained as a particle. It is presumed that as the size increases, the ink overflows from where it stayed in the undercoat liquid portion and the ink droplets spread, resulting in the connection to adjacent ink droplets.

The polymer used in the present invention may be any polymer, but is preferably dissolved in an oil-soluble monomer and used in the present invention. Accordingly, the polymer used in the present invention is preferably water-insoluble and oil-soluble. The water-insoluble polymer used in the present invention is preferably a polymer described in WO88 / 00723 pamphlet and JP-A-63-44658. Among them, the polymers used in the present invention are particularly preferably vinyl polymers and polyester polymers in which the repeating unit has a — (C═O) — bond.
As the vinyl monomer preferably used for the synthesis of the vinyl polymer, two or more kinds of monomers can be used as comonomers according to various purposes (for example, improvement in solubility). In addition, a monomer having an acid group is also used as a comonomer so long as the copolymer does not become water-soluble in order to adjust color development and solubility. Further, a monomer having two or more ethylenically unsaturated components capable of crosslinking can be used. As such a monomer, for example, those described in JP-A-60-151636 can be preferably used.

  As long as the copolymer is not water-soluble when a hydrophilic monomer (here, a monomer that becomes water-soluble when made into a homopolymer) is used as a comonomer in the vinyl monomer used in the present invention. The ratio of the hydrophilic monomer in the copolymer is not particularly limited, but is preferably 40 mol% or less, more preferably 20 mol% or less, and still more preferably 10 mol% or less. Further, when the hydrophilic comonomer copolymerized with the monomer in the present invention has an acid group, the proportion of the comonomer having an acid group in the copolymer is usually 20 mol% or less, preferably from the viewpoint of image storability. Is 10 mol% or less, and most preferably does not contain such a comonomer. The monomers used for polymer synthesis are preferably methacrylate, acrylamide and methacrylamide. Particularly preferred are acrylamide and methacrylamide.

  The number average molecular weight of the methacrylate, acrylamide and methacrylamide polymers that can be used in the present invention is preferably 5000 or more and 150,000 or less, and more preferably 10,000 or more and 100,000 or less. The polymer used in the present invention is preferably composed of styrene, α-methylstyrene, β-methylstyrene or a monomer having a substituent in the benzene ring. In this case, the number average molecular weight of the polymer is preferable. The range is 500 or more and 5000 or less.

Examples of the polyester polymer used in the present invention include a polyester resin obtained by condensation of a polyhydric alcohol and a polybasic acid, or a polyester resin obtained by ring-opening polymerization. As the polyhydric alcohol used to make the former polyester, glycols having a structure of HO—R ₁ —OH (R ₁ is a hydrocarbon chain having 2 to 12 carbon atoms, particularly an aliphatic hydrocarbon chain), or Polyalkyl glycols are effective, and polybasic acids having HOOC-R ₂ —COOH (R ₂ represents a simple bond or a hydrocarbon chain having 1 to 12 carbon atoms) are effective. As the polyhydric alcohol or polybasic acid preferably used in the present invention, for example, those described in JP-A-6-250331 can be preferably used.

  The monomer used to make the latter polyester is preferably a 4- to 9-membered lactone, and β-propiolactone, ε-caprolactone, dimethylpropiolactone and the like are used. The polyester polymer can use two or more kinds of polyhydric alcohols, polybasic acids, or lactone monomers according to various purposes in the same manner as the vinyl polymer. In the case of a polyester polymer, a hydrophilic monomer (which becomes water-soluble when made into a homopolymer as described above) can be used as a comonomer in the same manner as the vinyl polymer. The ratio of the hydrophilic monomer in the polymer is preferably used in the amount described for the vinyl polymer. The water-insoluble polymer in the present invention is a polymer whose solubility in 100 g of distilled water (25 ° C.) is 3 g or less, preferably 1 g or less. Some specific examples of the polymer used in the present invention are described below, but the present invention is not limited thereto. The copolymerization ratio of the copolymer in the specific examples shown below is a molar ratio.

Among the polymers used in the present invention, an acrylamide type polymer is particularly preferably used because the image reproducibility is particularly excellent when multiple colors, which are the effects of the present invention, are superimposed.
The acrylamide type polymer is a polymer obtained by polymerizing monomers of acrylamide or methacrylamide (hereinafter also simply referred to as “acrylamide”).
It is presumed that the acrylamide polymer having an amide bond has a particularly strong effect of suppressing the spread of ink droplets by interaction with the undercoat liquid.
The acrylamide type polymer used in the present invention may be a homopolymer or a copolymer. When it is a copolymer, it may be a copolymer of two or more acrylamide monomers, or a copolymer of acrylamide monomers and other monomers. The ratio of the monomers can be arbitrarily selected, but in the case of a copolymer of an acrylamide monomer and another monomer, the content of the acrylamide monomer is preferably 20% or more, more preferably 50% or more, and more preferably 70% or more. Is particularly preferred. Further, 100% of acrylamide monomer is particularly preferable. From the viewpoint of ease of synthesis, a homopolymer is preferable. The acrylamide used in the present invention may be substituted with a substituent such as an alkyl group, an alkoxy group, an aryl group, an allyloxy group, a heterocyclic group, a heterocyclic oxy group, an acyl group, an acyloxy group, or a halogen atom.
In the present invention, an acrylamide type polymer is an average polymerization degree of acrylamide units from the viewpoint of suppressing the spread of viscosity characteristics, solubility, and droplet spreading when used in an undercoat liquid, and ease of coating. (Hereinafter, it is also simply referred to as “average degree of polymerization”) is preferably an acrylamide type polymer having 30 to 1000, preferably 40 to 800, and more preferably 50 to 600.
As a weight average molecular weight of an acrylamide type polymer, although a well-known compound called an acrylamide polymer can be selected arbitrarily, 5000-150,000 are preferable and 10,000-100,000 are more preferable.

As the acrylamide type polymer in the present invention, an alkyl group-substituted acrylamide type polymer and an aromatic group-substituted acrylamide type polymer are preferable, and an alkyl group-substituted acrylamide type polymer is preferable. Here, in the present invention, the alkyl group includes all of chain, branched, and cyclic.
Examples of the alkyl group-substituted acrylamide type polymer system include an acrylamide type polymer substituted with an alkyl group having 1 to 20 carbon atoms (preferably 1 to 12, more preferably 2 to 12, for example, polyethylacrylamide, Poly t-butylacrylamide, polyoctylacrylamide, polyt-octylacrylamide, polylaurylacrylamide, polycyclohexylacrylamide, polyt-butylmethacrylamide, polylaurylmethacrylamide and the like are suitable.

P-1) Polymethacrylate P-2) Polyethyl methacrylate P-3) Polyisopropyl methacrylate P-4) Polymethylchloroacrylate P-5) Poly (2-tert-butylphenyl acrylate)
P-6) Poly (4-tert-butylphenyl acrylate)
P-7) Ethyl methacrylate-n-butyl acrylate copolymer (70:30)
P-8) Methyl methacrylate-acrylonitrile copolymer (65:35)
P-9) Methyl methacrylate-styrene copolymer (90:10)
P-10) N-tert-butylmethacrylamide-methylmethacrylate-acrylic acid copolymer (60:30:10)
P-11) Methyl methacrylate-styrene-vinylsulfonamide copolymer (70:20:10)
P-12) Methyl methacrylate-cyclohexyl methacrylate copolymer (50:50)
P-13) Methyl methacrylate-acrylic acid copolymer (95: 5)

P-14) Methyl methacrylate-n-butyl methacrylate copolymer (65:35)
P-15) Methyl methacrylate-N-vinyl-2-pyrrolidone copolymer (90:10)
P-16) Poly (N-sec-butylacrylamide)
P-17) Poly (N-tert-butylacrylamide)
P-18) Polycyclohexylmethacrylate-methylmethacrylate copolymer (60:40)
P-19) n-butyl methacrylate-methyl methacrylate-acrylamide copolymer (20:70:10)
P-20) Diacetone acrylamide-methyl methacrylate copolymer (20:80)
P-21) N-tert-butylacrylamide-methyl methacrylate copolymer (40:60)
P-22) Poly (Nn-butylacrylamide)
P-23) tert-butyl methacrylate-N-tert-butylacrylamide copolymer (50:50)
P-24) tert-butyl methacrylate-methyl methacrylate copolymer (70:30)
P-25) Poly (N-tert-butylmethacrylamide)
P-26) N-tert-butylacrylamide-methyl methacrylate copolymer (60:40)
P-27) Methyl methacrylate-acrylonitrile copolymer (70:30)
P-28) Methyl methacrylate-styrene copolymer (75:25)
P-29) Methyl methacrylate-hexyl methacrylate copolymer (70:30)

P-30) Poly (4-biphenyl acrylate)
P-31) Poly (2-chlorophenyl acrylate)
P-32) Poly (4-chlorophenyl acrylate)
P-33) Poly (pentachlorophenyl acrylate)
P-34) Poly (4-ethoxycarbonylphenyl acrylate)
P-35) Poly (4-methoxycarbonylphenyl acrylate)
P-36) Poly (4-cyanophenyl acrylate)
P-37) Poly (4-methoxyphenyl acrylate)
P-38) Poly (3,5-dimethyladamantyl acrylate)
P-39) Poly (3-dimethylaminophenyl acrylate)
P-40) Poly (2-naphthyl acrylate)
P-41) Poly (phenyl acrylate)
P-42) Poly (N, N-dibutylacrylamide)
P-43) Poly (isohexylacrylamide)
P-44) Poly (isooctylacrylamide)
P-45) Poly (N-methyl-N-phenylacrylamide)
P-46) Poly (adamantyl methacrylate)
P-47) Poly (sec-butyl methacrylate)
P-48) N-tert-butylacrylamide-acrylic acid copolymer (97: 3)
P-49) Poly (2-chloroethyl methacrylate)

P-50) Poly (2-cyanoethyl methacrylate)
P-51) Poly (2-cyanomethylphenyl methacrylate)
P-52) Poly (4-cyanophenyl methacrylate)
P-53) Poly (cyclohexyl methacrylate)
P-54) Poly (2-hydroxypropyl methacrylate)
P-55) Poly (4-methoxycarbonylphenyl methacrylate)
P-56) Poly (3,5-dimethyladamantyl methacrylate)
P-57) Poly (phenyl methacrylate)
P-58) Poly (4-butoxycarbonylphenylmethacrylamide)
P-59) Poly (4-carboxyphenylmethacrylamide)
P-60) Poly (4-ethoxycarbonylphenylmethacrylamide)
P-61) Poly (4-methoxycarbonylphenylmethacrylamide)
P-62) Poly (cyclohexyl chloroacrylate)
P-63) Poly (ethyl chloroacrylate)
P-64) Poly (isobutylchloroacrylate)
P-65) Poly (isopropylchloroacrylate)
P-66) Poly (phenylacrylamide)
P-67) Poly (cyclohexylacrylamide)
P-68) Poly (phenylmethacrylamide)
P-69) Poly (cyclohexylmethacrylamide)
P-70) Poly (butylene adipate)
P-71) Polystyrene P-72) Poly (α-methylstyrene)
P-73) Poly (β-methylstyrene)
P-74) Poly (4-chlorostyrene)
P-75) Poly (4-methoxystyrene)
P-76) Poly (4-methylstyrene)
P-77) Poly (2,4-dimethylstyrene)
P-78) Poly (4-isopropylstyrene)
P-79) Poly (4-t-butylstyrene)
P-80) Poly (3,4-dichlorostyrene)
P-81) Poly (N-ethylacrylamide)
P-82) Poly (Nn-octylacrylamide)
P-83) Poly (Nt-octylacrylamide)
P-84) Poly (N-laurylacrylamide)
P-85) Poly (N-methoxyethylacrylamide)
P-86) Poly (N-lauryl methacrylamide)
P-87) Poly (t-butyl acrylate)
P-88) Poly (t-butyl methacrylate)

The polymer in this invention may be used individually by 1 type, or may use multiple types together.
As content in the undercoat liquid of the polymer in this invention, 1-50 mass% is preferable with respect to the total mass of undercoat liquid, 2-40 mass% is more preferable, 5-30 mass% is especially preferable.
When the polymer content is within the above range, the dot shape of the deposited ink and the connected state between the dots are secured while preventing the dot shape from being damaged or spreading to such an extent that the image is disturbed or blurred. It is more effective to do. Further, there is an advantage that the viscosity of the undercoat liquid can be kept low, and as a result, it can be applied more accurately with an inexpensive roll coater or the like.

(Radical polymerizable compound having a phosphate group)
The undercoat liquid of the present invention contains at least one radically polymerizable compound having a phosphate group (hereinafter also referred to as “phosphate group-containing radically polymerizable compound”).
Since the undercoat liquid of the present invention has the above-described configuration, the fine line drawing property and the bonding property of adjacent dots can be kept good. The cause of this is not clear, but the highly polar phosphate group-containing radical polymerizable compound diffuses into the undercoat liquid and the ink liquid applied thereon, and transmits the anti-diffusion effect of the polymer to the ink liquid. It is presumed that.
The phosphoric acid group-containing radical polymerizable compound may be contained as an optional component in the ink liquid.

The phosphoric acid group-containing radical polymerizable compound is a compound that cures itself by irradiation of active energy rays due to the action of a polymerization initiator described later, and this polymerization is more effective than a system containing only a polymer. It is possible to increase the adhesive force with the recording medium that comes into direct contact by the action of polymerization by the above. This is presumably because the polarity of the phosphate group affects the adhesion to the recording medium. As described above, according to the undercoat liquid of the present invention, it is possible to prevent the image recorded on the recording medium from being peeled off due to external force, and it is possible to form a robust image having excellent scratch resistance.
In addition, the undercoat liquid of the present invention uses a radically polymerizable compound having a phosphate group and another polymerizable or crosslinkable material in combination, so that the adhesion between the undercoat liquid of the present invention and the recording medium is improved. Can be further improved.
The undercoat liquid of the present invention has high adhesiveness to any recording medium such as metal, resin such as PET, and glass, but sufficiently exhibits its effect particularly on resin such as glass and PET. Can do.
Moreover, according to the undercoat liquid of the present invention, it is possible to suppress a decrease in the density of the ink after curing and to improve the printing density. Furthermore, the undercoat liquid of the present invention can also improve the resistance (light resistance, ozone resistance) to light and oxidizing gas (especially ozone) of an image recorded on an arbitrarily selected recording medium. It is also effective in improving the performance.

  The phosphate group-containing radical polymerizable compound is not particularly limited as long as it is a polymerizable compound having a phosphate group.

Moreover, when the said phosphate group containing radically polymerizable compound is used for an inkjet recording use, it is preferable that it does not increase the viscosity of undercoat liquid by addition. For this reason, the said phosphate group containing radically polymerizable compound has a preferable monomer. The molecular weight of the phosphate group-containing radical polymerizable compound is not particularly limited, and is preferably, for example, 150 to 2000, more preferably 180 to 1500, and particularly preferably 200 to 1200.
Further, the number of carbon atoms of the phosphate group-containing radical polymerizable compound is preferably 4 to 100, more preferably 5 to 60 in consideration of the polarity of the phosphate group-containing radical polymerizable compound.

  The number of phosphate groups in the phosphate group-containing radical polymerizable compound is not particularly limited as long as it is at least one.

  The phosphate group-containing radical polymerizable compound of the present invention is preferably a compound in which all hydroxyl groups of phosphoric acid are esterified from the viewpoint of compatibility with other polymerizable compounds and polymers. Further, from the viewpoint of high strength of the finally formed film and good adhesion to the substrate, a bifunctional or higher phosphate group-containing radical polymerizable compound is preferable, and a trifunctional or higher functional phosphoric acid is preferred. A group-containing radically polymerizable compound is more preferable.

  Specific examples of the phosphate group-containing radical polymerizable compound include the following compounds.

  In the above specific examples, R is an alkyl group having 1 to 12 carbon atoms or an aralkyl group.

  Moreover, a part of the said phosphate group containing radically polymerizable compound is also available as a commercial item. Examples of the commercially available products include Kayamar PM-1, Kayamar PM-2, Kayamar PM-21 manufactured by Nippon Kayaku Co., Ltd .; Light Ester P-1M, Light Ester P-2M manufactured by Kyoeisha Chemical Co., Ltd .; Examples include Biscoat # 3PA manufactured by Osaka Organic Chemical Industry Co., Ltd .; JPA514, JAMP514 manufactured by Johoku Chemical Industry Co., Ltd., and the like.

A phosphoric acid group-containing radical polymerizable compound may be used in combination of a plurality of types in addition to a single type.
As content in the undercoat liquid of a phosphate group containing radically polymerizable compound, 1-50 mass% is preferable with respect to the total mass of undercoat liquid, 2-30 mass% is more preferable, and 5-20 mass% is preferable. Particularly preferred. When the content of the phosphoric acid group-containing radical polymerizable compound is within the above range, the dot shape of the ink that has landed and the spread of the dots are suppressed while preventing the dot shape from being damaged or spreading to such an extent that the image is disturbed or blurred. This is effective for securing the connection state between dots.

The phosphoric acid group-containing radical polymerizable compound can exert the effects of the present invention even when added in a small amount, and therefore the influence on curability and sensitivity can be reduced.
When the undercoat liquid contains a polymerizable or crosslinkable material other than the phosphate group-containing radically polymerizable compound, the polymerizable or crosslinkable material (from the viewpoints of adhesion, curability, print density, sensitivity, etc. of the undercoat liquid) The mass ratio (y / (x + y) × 100) between x) and the phosphate group-containing radical polymerizable compound (y) is preferably 0.2 to 20%, and preferably 1 to 15%. More preferred is 2 to 10%.
When the undercoat liquid contains a polymerizable or crosslinkable material other than the phosphate group-containing radical polymerizable compound, the content of the phosphate group-containing radical polymerizable compound in the undercoat liquid is a polymerizable or crosslinkable material. It is preferable to be determined so as to satisfy the above mass ratio in relation to the content of.

  From the viewpoint of obtaining the effect of the present invention more effectively, a combination of a polymer and a radical polymerizable compound having a phosphate group is also important. From the above viewpoint, as a preferable combination thereof, a combination of methacrylate, acrylamide, or methacrylamide and a radical polymerizable compound having a phosphate group in which all hydroxyl groups of phosphoric acid are esterified is more preferable. , And a radical polymerizable compound having a phosphate group in which all hydroxyl groups of phosphoric acid are esterified, and particularly preferably a radical polymerizable compound having a phosphate group having two or more functional groups. And the combination.

  From the viewpoint of obtaining the effect of the present invention more effectively, the mass ratio between the polymer and the radically polymerizable compound having a phosphate group is also important. From the above viewpoint, the mass ratio (polymer: radical polymerizable compound having a phosphate group) is preferably 1:10 to 10: 1, more preferably 1: 7 to 7: 1. A ratio of 1: 5 to 5: 1 is particularly preferable.

  Further, the preferred range of the polymer, the radically polymerizable compound having a phosphate group, and the individual contents are as described above, but from the viewpoint of obtaining the effect of the present invention more effectively, the phosphate group The total content of radically polymerizable compounds and polymers with From the above viewpoint, the total content is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, and particularly preferably 15 to 40% by mass with respect to the total mass of the undercoat liquid.

(Polymerizable or crosslinkable material)
The ink and undercoat liquid in the present invention can be constituted using at least one polymerizable or crosslinkable material other than the polymerizable compound having a phosphate group.
The polymerizable or crosslinkable material has a function of causing a polymerization or crosslinking reaction by an initiating species such as a radical generated from a polymerization initiator described later, and curing a composition containing these.

As the polymerizable or crosslinkable material, a polymerizable or crosslinkable material that causes a known polymerization or crosslinking reaction such as radical polymerization reaction or dimerization reaction can be applied. For example, an addition polymerizable compound having at least one ethylenically unsaturated double bond, a polymer compound having a maleimide group in the side chain, a cinnamyl group having a photodimerizable unsaturated double bond adjacent to the aromatic nucleus, Examples thereof include a polymer compound having a cinnamylidene group or a chalcone group in the side chain. Among these, an addition polymerizable compound having at least one ethylenically unsaturated double bond is more preferable, and from a compound (monofunctional or polyfunctional compound) having at least one terminal ethylenically unsaturated bond, more preferably two or more. It is particularly preferred that it is selected. Specifically, it can be appropriately selected from those widely known in the industrial field according to the present invention. For example, monomers, prepolymers (that is, dimers, trimers, and oligomers) and mixtures thereof, and those Those having a chemical form such as a copolymer of
A polymeric or crosslinkable material may be used individually by 1 type, and may be used in combination of 2 or more type.

As the polymerizable or crosslinkable material in the present invention, various known radically polymerizable monomers that cause a polymerization reaction with an initiating species generated from a radical initiator are particularly preferable.
Examples of the radical polymerizable monomer include (meth) acrylates, (meth) acrylamides, aromatic vinyls, vinyl ethers, and compounds having an internal double bond (such as maleic acid). 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) acrylates include the following.
Specific examples of monofunctional (meth) acrylates include hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, tert-octyl (meth) acrylate, isoamyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) ) Acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, 4-n-butylcyclohexyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate 2-ethylhexyl diglycol (meth) acrylate, butoxyethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 4-bromobutyl (meth) acrylate, cyano Chill (meth) acrylate, benzyl (meth) acrylate, butoxymethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, alkoxymethyl (meth) acrylate, alkoxyethyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (Meth) acrylate, 2- (2-butoxyethoxy) ethyl (meth) acrylate, 2,2,2-trifluoroethyl (meth) acrylate, 1H, 1H, 2H, 2H-perfluorodecyl (meth) acrylate, 4 -Butylphenyl (meth) acrylate, phenyl (meth) acrylate, 2,4,5-tetramethylphenyl (meth) acrylate, 4-chlorophenyl (meth) acrylate, phenoxymethyl (meth) acrylate, phenoxyethyl (meth) acrylate Relate, glycidyl (meth) acrylate, glycidyloxybutyl (meth) acrylate, glycidyloxyethyl (meth) acrylate, glycidyloxypropyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, hydroxyalkyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate,

2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, Diethylaminopropyl (meth) acrylate, trimethoxysilylpropyl (meth) acrylate, trimethylsilylpropyl (meth) acrylate, polyethylene oxide monomethyl ether (meth) acrylate, oligoethylene oxide monomethyl ether (meth) acrylate, polyethylene oxide (meth) acrylate, oligoethylene oxide (Meth) acrylate, oligoethylene oxide monoalkyl ether (meth) acrylate, Reethylene oxide monoalkyl ether (meth) acrylate, dipropylene glycol (meth) acrylate, polypropylene oxide monoalkyl ether (meth) acrylate, oligopropylene oxide monoalkyl ether (meth) acrylate, 2-methacryloyloxytyl succinic acid, 2- Methacryloyloxyhexahydrophthalic acid, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, butoxydiethylene glycol (meth) acrylate, trifluoroethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, 2-hydroxy-3 -Phenoxypropyl (meth) acrylate, EO modified phenol (meth) acrylate, EO modified cresol (meth) acrylate, EO modified noni Phenol (meth) acrylate, PO-modified nonylphenol (meth) acrylate, EO-modified 2-ethylhexyl (meth) acrylate and the like.

  Specific examples of the bifunctional (meth) acrylate include 1,6-hexanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and 2,4-dimethyl. -1,5-pentanediol di (meth) acrylate, butylethylpropanediol (meth) acrylate, ethoxylated cyclohexanemethanol di (meth) acrylate, polyethylene glycol di (meth) acrylate, oligoethylene glycol di (meth) acrylate, Ethylene glycol di (meth) acrylate, 2-ethyl-2-butyl-butanediol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, EO-modified bisphenol A di (meth) acrylate Bisphenol F polyethoxydi (meth) acrylate, polypropylene glycol di (meth) acrylate, oligopropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 2-ethyl-2-butylpropanediol di ( Examples include meth) acrylate, 1,9-nonanedi (meth) acrylate, propoxylated ethoxylated bisphenol A di (meth) acrylate, and tricyclodecane di (meth) acrylate.

  Specific examples of trifunctional (meth) acrylates include trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, trimethylolpropane alkylene oxide-modified tri (meth) acrylate, pentaerythritol tri (meth) acrylate , Dipentaerythritol tri (meth) acrylate, trimethylolpropane tris ((meth) acryloyloxypropyl) ether, isocyanuric acid alkylene oxide modified tri (meth) acrylate, propionate dipentaerythritol tri (meth) acrylate, tris ((meta) ) Acryloyloxyethyl) isocyanurate, hydroxypivalaldehyde-modified dimethylolpropane tri (meth) acrylate, sorbitol tri (meth) Acrylate, propoxylated trimethylolpropane tri (meth) acrylate, and ethoxylated glycerin triacrylate.

  Specific examples of tetrafunctional (meth) acrylates include pentaerythritol tetra (meth) acrylate, sorbitol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, propionate dipentaerythritol tetra (meth) acrylate, ethoxylated penta Examples include erythritol tetra (meth) acrylate.

  Specific examples of the pentafunctional (meth) acrylate include sorbitol penta (meth) acrylate and dipentaerythritol penta (meth) acrylate.

  Specific examples of hexafunctional (meth) acrylate include dipentaerythritol hexa (meth) acrylate, sorbitol hexa (meth) acrylate, phosphazene alkylene oxide modified hexa (meth) acrylate, captolactone modified dipentaerythritol hexa (meth) acrylate Etc.

  Examples of the (meth) acrylamides include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, Nn-butyl (meth) acrylamide, N-t-butyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (Meth) acrylamide, (meth) acryloylmorpholine, etc. are mentioned.

  Specific examples of the aromatic vinyls include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, chloromethyl styrene, methoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, vinyl benzoate. Acid methyl ester, 3-methylstyrene, 4-methylstyrene, 3-ethylstyrene, 4-ethylstyrene, 3-propylstyrene, 4-propylstyrene, 3-butylstyrene, 4-butylstyrene, 3-hexylstyrene, 4 -Hexylstyrene, 3-octylstyrene, 4-octylstyrene, 3- (2-ethylhexyl) styrene, 4- (2-ethylhexyl) styrene, allylstyrene, isopropenylstyrene, butenylstyrene, octene Rusuchiren, 4-t-butoxycarbonyl styrene, 4-methoxystyrene, and a 4-t-butoxystyrene.

  Specific examples of the vinyl ethers include monofunctional vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether. , Cyclohexyl methyl vinyl ether, 4-methylcyclohexyl methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl Vinyl ether, methoxypo Ethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexyl methyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether Chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxypolyethylene glycol vinyl ether, and the like.

Examples of polyfunctional vinyl ethers include ethylene glycol divinyl ether, diethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, bisphenol A alkylene oxide divinyl ether, bisphenol F alkylene oxide di Divinyl ethers such as vinyl ether; trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexabi Ether, ethylene oxide-added trimethylolpropane trivinyl ether, propylene oxide-added trimethylolpropane trivinyl ether, ethylene oxide-added ditrimethylolpropane tetravinyl ether, propylene oxide-added ditrimethylolpropane tetravinyl ether, ethylene oxide-added pentaerythritol tetravinyl ether, propylene oxide-added penta And polyfunctional vinyl ethers such as erythritol tetravinyl ether, ethylene oxide-added dipentaerythritol hexavinyl ether, and propylene oxide-added dipentaerythritol hexavinyl ether.
As the vinyl ether compound, a di- or trivinyl ether compound is preferable from the viewpoints of curability, adhesion to a recording medium, surface hardness of the formed image, and the like, and a divinyl ether compound is particularly preferable.

  In addition to the above, the radical polymerizable monomer in the present invention further includes vinyl esters [vinyl acetate, vinyl propionate, vinyl versatate, etc.], allyl esters [allyl acetate, etc.], halogen-containing monomers [vinylidene chloride]. , Vinyl chloride, etc.], vinyl cyanide [(meth) acrylonitrile, etc.], olefins [ethylene, propylene, etc.] and the like.

  Among the above, as the radical polymerizable monomer, (meth) acrylates and (meth) acrylamides are preferable from the viewpoint of curing speed, and tetrafunctional or higher (meth) acrylate is particularly preferable from the viewpoint of curing speed. Furthermore, from the viewpoint of the viscosity of the ink composition, a combination of polyfunctional (meth) acrylate and monofunctional or bifunctional (meth) acrylate or (meth) acrylamide is preferable.

The content of the polymerizable or crosslinkable material in the ink and undercoat liquid is preferably in the range of 50 to 99.6% by mass with respect to the total solid content (mass) of each droplet, and is preferably 70 to 99.0. The range of mass% is more preferable, and the range of 80 to 99.0 mass% is more preferable.
Moreover, as content in a droplet, the range of 20-98 mass% is preferable with respect to the total mass of each droplet, The range of 40-95 mass% is more preferable, The range of 50-90 mass% is preferable. Particularly preferred.

(Polymerization initiator)
The ink and the undercoat liquid can be suitably configured using at least one kind of polymerization initiator, and are preferably configured using at least the undercoat liquid. This polymerization initiator generates radicals and other starting species by applying actinic light, heat, or both, and initiates, accelerates and cures the polymerization or crosslinking reaction of the polymerizable or crosslinkable material described above. A compound.

In the polymerizable embodiment, it is preferable to contain a polymerization initiator that causes radical polymerization (that is, a radical polymerization initiator), and it is particularly preferable that they are photopolymerization initiators.
A photopolymerization initiator is a compound that generates a chemical change by the action of light and interaction with the electronically excited state of a sensitizing dye to generate at least one of a radical, an acid, and a base. From the viewpoint that polymerization can be initiated by such simple means, a photo radical generator is preferred.

  As the photopolymerization initiator in the present invention, irradiated actinic rays, for example, ultraviolet rays of 400 to 200 nm, deep ultraviolet rays, g rays, h rays, i rays, KrF excimer laser rays, ArF excimer laser rays, electron rays, X Those having sensitivity to a beam, molecular beam, ion beam, or the like can be appropriately selected and used.

  Specific photopolymerization initiators known among those skilled in the art can be used without limitation. For example, Bruce M. et al. Monroe et al., Chemical Review, 93, 435 (1993). R. S. By Davidson, Journal of Photochemistry and biologic A: Chemistry, 73.81 (1993). J. P. Faussier “Photoinitiated Polymerization—Theory and Applications”: Rapra Review vol. 9, Report, Rapra Technology (1998). M. Tsunooka et al. , Prog. Polym. Sci. , 21, 1 (1996). Many are described. Further, F.I. D. Saeva, Topics in Current Chemistry, 156, 59 (1990). G. G. Maslak, Topics in Current Chemistry, 168, 1 (1993). H., et al. B. Shuster et al, JACS, 112, 6329 (1990). I. D. F. Eaton et al, JACS, 102, 3298 (1980). As described above, a group of compounds that undergo oxidative or reductive bond cleavage through interaction with the electronically excited state of the sensitizing dye can also be used.

  Preferred photopolymerization initiators include (a) aromatic ketones, (b) aromatic onium salt compounds, (c) organic peroxides, (d) hexaarylbiimidazole compounds, (e) ketoxime ester compounds, f) borate compounds, (g) azinium compounds, (h) metallocene compounds, (i) active ester compounds, (j) compounds having a carbon halogen bond, and the like.

  Preferable examples of the (a) aromatic ketones include “RADIATION CURING IN POLYMER SCIENCE AND TECHNOLOGY” P. FOUASSIER J.M. F. Examples include compounds having a benzophenone skeleton or a thioxanthone skeleton described in RABEK (1993), p77-117. More preferable examples of (a) aromatic ketones include α-thiobenzophenone compounds described in JP-B-47-6416, benzoin ether compounds described in JP-B-47-3981, and JP-B-47-22326. Α-substituted benzoin compounds, benzoin derivatives described in JP-B-47-23664, aroylphosphonic acid esters described in JP-A-57-30704, dialkoxybenzophenones described in JP-B-60-26483, Benzoin ethers described in JP-A-60-26403, JP-A-62-81345, JP-B-1-34242, US Pat. No. 4,318,791, and α-aminobenzophenones described in European Patent 0284561A1, P-di (dimethyla) described in JP-A-2-211452 Nobenzoyl) benzene, thio-substituted aromatic ketone described in JP-A-61-194062, acylphosphine sulfide described in JP-B-2-9597, acylphosphine described in JP-B-2-9596, JP-B-63- Examples thereof include thioxanthones described in Japanese Patent No. 61950, and coumarins described in Japanese Patent Publication No. 59-42864.

  Examples of the (b) aromatic onium salt compound include elements of groups V, VI and VII of the periodic table, specifically, N, P, As, Sb, Bi, O, S, Se, Te, or I. Of the aromatic onium salt. For example, iodonium salts described in European Patent No. 104143, US Pat. No. 4,837,124, Japanese Patent Laid-Open No. 2-150848, Japanese Patent Laid-Open No. 2-96514, European Patent Nos. 370693, 233567, and 297443 are disclosed. , 294442, 279210, and 422570, U.S. Pat. Nos. 3,902,144, 4,933,377, 4,760013, 4,734,344, and 2,833,827, sulfonium salts and diazonium salts (Such as benzenediazonium which may have a substituent), diazonium salt resins (formaldehyde resin of diazodiphenylamine, etc.), N-alkoxypyridinium salts, etc. (for example, US Pat. No. 4,743,528, JP 63-138345 JP-A-63-142345, JP-A-63-142346, and JP-B-46-42363, specifically 1-methoxy-4-phenylpyridinium tetrafluoroborate, etc. And compounds described in JP-B Nos. 52-147277, 52-14278, and 52-14279 are preferably used. Generates radicals and acids as active species.

  The (c) “organic peroxide” includes almost all organic compounds having one or more oxygen-oxygen bonds in the molecule. Examples thereof include 3,3 ′, 4,4′- Tetrakis (t-butylperoxycarbonyl) benzophenone, 3,3'4,4'-tetrakis (t-amylperoxycarbonyl) benzophenone, 3,3'4,4'-tetrakis (t-hexylperoxycarbonyl) benzophenone 3,3′4,4′-tetrakis (t-octylperoxycarbonyl) benzophenone, 3,3′4,4′-tetrakis (cumylperoxycarbonyl) benzophenone, 3,3′4,4′-tetrakis ( p-Isopropylcumylperoxycarbonyl) benzophenone, di-t-butyldiperoxyisophthalate, etc. Le systems are preferred.

  Examples of the (d) hexaarylbiimidazole include lophine dimers described in JP-B Nos. 45-37377 and 44-86516, such as 2,2′-bis (o-chlorophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-bromophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o, p-dichlorophenyl) ) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-chlorophenyl) -4,4 ′, 5,5′-tetrakis (m-methoxyphenyl) biimidazole, 2 , 2′-bis (o, o′-dichlorophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-nitrophenyl) -4,4 ′, 5,5 -Tetraphenylbiimidazole, 2,2'-bis (o-methylphenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o-trifluorophenyl) -4, Examples include 4 ', 5,5'-tetraphenylbiimidazole.

  Examples of the (e) ketoxime ester include 3-benzoyloxyiminobutan-2-one, 3-acetoxyiminobutan-2-one, 3-propionyloxyiminobutan-2-one, and 2-acetoxyiminopentane. -3-one, 2-acetoxyimino-1-phenylpropan-1-one, 2-benzoyloxyimino-1-phenylpropan-1-one, 3-p-toluenesulfonyloxyiminobutan-2-one, 2 -Ethoxycarbonyloxyimino-1-phenylpropan-1-one and the like.

Examples of the (f) borate compound include compounds described in US Pat. Nos. 3,567,453 and 4,343,891, European Patents 109,772 and 109,773.
Examples of the (g) azinium salt compound include JP-A-63-138345, JP-A-63-142345, JP-A-63-142346, JP-A-63-143537, and JP-B-46-42363. The compound group which has NO bond as described in each gazette of No. can be mentioned.

  Examples of the (h) metallocene compound include JP-A-59-152396, JP-A-61-151197, JP-A-63-41484, JP-A-2-249, and JP-A-2-4705. And the iron-arene complexes described in JP-A-1-304453 and JP-A-1-152109.

  Specific examples of the titanocene compound include di-cyclopentadienyl-Ti-di-chloride, di-cyclopentadienyl-Ti-bis-phenyl, and di-cyclopentadienyl-Ti-bis-2,3. 4,5,6-pentafluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,3,5,6-tetrafluorophen-1-yl, di-cyclopentadienyl-Ti- Bis-2,4,6-trifluorophen-1-yl, di-cyclopentadienyl-Ti-2,6-difluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,4 -Difluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophen-1-yl, di-methylcyclopentadienyl-Ti- -2,3,5,6-tetrafluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,4-difluorophen-1-yl, bis (cyclopentadienyl) -bis (2,6-difluoro-3- (pyridin-1-yl) phenyl) titanium, bis (cyclopentadienyl) bis [2,6-difluoro-3- (methylsulfonamido) phenyl] titanium, bis (cyclopenta And dienyl) bis [2,6-difluoro-3- (N-butylbialoyl-amino) phenyl] titanium.

  Examples of the (i) active ester compound include European Patent Nos. 0290750, 046083, 156153, 271851, and 0388343, U.S. Pat. Nitrobenzyl ester compounds described in JP-A-60-198538 and JP-A-53-133022, European Patents 099672, 84515, 199672, 0441115, and 0101122 , U.S. Pat. Nos. 4,618,564, 4,371,605 and 4,431,774, JP-A 64-18143, JP-A-2-245756, and JP-A-4-365048, respectively. Kosho 62-6223, Shoko 63-143 No. 0, and include compounds described in the JP-A-59-174831.

  Preferred examples of the compound (j) having a carbon halogen bond include those described in Wakabayashi et al., Bull. Chem. Soc. Examples include compounds described in Japan, 42, 2924 (1969), compounds described in British Patent 1388492, compounds described in JP-A-53-133428, compounds described in German Patent 3333724, and the like. .

  F.F. C. J. Schaefer et al. Org. Chem. 29, 1527 (1964), compounds described in JP-A-62-258241, compounds described in JP-A-5-281728, and the like. A compound as described in German Patent No. 2641100, a compound described in German Patent No. 3333450, a compound group described in German Patent No. 3021590, or a compound group described in German Patent No. 3021599, etc. Can be mentioned.

  As a photoinitiator in this invention, although the compound illustrated below can be mentioned, for example, It is not limited to these.

  The polymerization initiator is preferably excellent in sensitivity, but from the viewpoint of storage stability, it is preferable to select a polymerization initiator that does not cause thermal decomposition at temperatures up to 80 ° C.

  A polymerization initiator can be used 1 type or in combination of 2 or more types. Moreover, a well-known sensitizer can also be used together for the purpose of a sensitivity improvement in the range which does not impair the effect of this invention.

  The content of the polymerization initiator in the undercoat liquid is preferably in the range of 0.5 to 20% by mass with respect to the polymerizable material in the undercoat liquid, from the viewpoints of stability over time, curability, and curing speed. 1-15 mass% is still more preferable, and 3-10 mass% is especially preferable. In addition, it can suppress that performance, such as the intensity | strength of the ink after hardening, and abrasion resistance, deteriorates by making content into the said range and time-dependent.

  The polymerization initiator may be contained in the ink as well as in the undercoat liquid. In this case, the polymerization initiator may be appropriately selected and contained within a range in which the storage stability of the ink can be maintained at a desired level. In this case, the content in the ink droplet is preferably 0.5 to 20% by mass, and more preferably 1 to 15% by mass with respect to the polymerizable or crosslinkable compound in the ink.

(Sensitizing dye)
In the present invention, a sensitizing dye may be added for the purpose of improving the sensitivity of the photopolymerization initiator. Examples of preferred sensitizing dyes include those belonging to the following compounds and having an absorption wavelength in the 350 nm to 450 nm region.

  Polynuclear aromatics (eg, pyrene, perylene, triphenylene), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (eg, thiacarbocyanine, oxacarbocyanine), merocyanines ( For example, merocyanine, carbomerocyanine), thiazines (eg, thionine, methylene blue, toluidine blue), acridines (eg, acridine orange, chloroflavin, acriflavine), anthraquinones (eg, anthraquinone), squalium (eg, squalium) ), Coumarins (eg 7-diethylamino-4-methylcoumarin).

  More preferable examples of the sensitizing dye include compounds represented by the following general formulas (IX) to (XIII).

In the formula (IX), A ¹ represents a sulfur atom or —NR ⁵⁰ —, R ⁵⁰ represents an alkyl group or an aryl group, and L ² represents a basic nucleus of the dye in combination with the adjacent A ¹ and the adjacent carbon atom. R ⁵¹ and R ⁵² each independently represents a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁵¹ and R ⁵² are bonded to each other to form an acidic nucleus of the dye. May be. W represents an oxygen atom or a sulfur atom.
In formula (X), Ar ¹ and Ar ² each independently represent an aryl group and are linked via a bond with —L ³ —. Here, L ³ represents —O— or —S—. W is synonymous with that shown in the general formula (IX).
In the formula (XI), A ² represents a sulfur atom or —NR ⁵⁹ —, L ⁴ represents a nonmetallic atomic group that forms a basic nucleus of the dye together with the adjacent A ² and carbon atom, and R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ and R ⁵⁸ each independently represents a monovalent non-metallic atomic group, and R ⁵⁹ represents an alkyl group or an aryl group.

In formula (XII), A ³ and A ⁴ each independently represent —S— or —NR ⁶² — or —NR ⁶³ —, and R ⁶² and R ⁶³ each independently represent a substituted or unsubstituted alkyl group, substituted or Represents an unsubstituted aryl group, and L ⁵ and L ⁶ each independently represent a nonmetallic atomic group that forms a basic nucleus of a dye in cooperation with adjacent A ³ , A ^4, and adjacent carbon atoms, and R ⁶⁰ , R ⁶¹ each independently represents a hydrogen atom or a monovalent nonmetallic atomic group, or may be bonded to each other to form an aliphatic or aromatic ring.
In formula (XIII), R ⁶⁶ represents an aromatic ring or a hetero ring which may have a substituent, and A ⁵ represents an oxygen atom, a sulfur atom or —NR ⁶⁷ —. R ⁶⁴ , R ⁶⁵ and R ⁶⁷ each independently represent a hydrogen atom or a monovalent non-metallic atomic group, R ⁶⁷ and R ⁶⁴ , and R ⁶⁵ and R ⁶⁷ each represent an aliphatic or aromatic ring. Can be combined to form.

  Preferable specific examples of the compounds represented by the general formulas (IX) to (XIII) include the exemplified compounds (A-1) to (A-20) shown below.

(Co-sensitizer)
Furthermore, a known compound having a function of further improving sensitivity or suppressing polymerization inhibition by oxygen may be added as a co-sensitizer.
Examples of co-sensitizers include amines such as M.I. R. Sander et al., “Journal of Polymer Society”, Vol. 10, 3173 (1972), Japanese Patent Publication No. 44-20189, Japanese Patent Publication No. 51-82102, Japanese Patent Publication No. 52-134692, Japanese Patent Publication No. 59-138205. No. 60-84305, JP-A 62-18537, JP-A 64-33104, Research Disclosure 33825, and the like. Specific examples include triethanolamine. P-dimethylaminobenzoic acid ethyl ester, p-formyldimethylaniline, p-methylthiodimethylaniline and the like.

Other examples include thiols and sulfides, for example, thiol compounds described in JP-A-53-702, JP-B-55-500806, JP-A-5-142772, and JP-A-56-75643. Specific examples include 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzimidazole, 2-mercapto-4- (3H) -quinazoline, β-mercaptonaphthalene, and the like. It is done.
Other examples include amino acid compounds (eg, N-phenylglycine), organometallic compounds described in Japanese Patent Publication No. 48-42965 (eg, tributyltin acetate), and hydrogen described in Japanese Patent Publication No. 55-34414. Donors, sulfur compounds described in JP-A-6-308727 (eg, trithiane), phosphorus compounds described in JP-A-6-250387 (diethylphosphite, etc.), Si-- described in JP-A-8-65779 H, Ge-H compound, etc. are mentioned.

(Coloring agent)
The ink and the undercoat liquid can be suitably configured using at least one kind of colorant, and are preferably configured using at least the ink. In addition to the ink, the colorant may be contained in an undercoat liquid or other liquid.

  The colorant is not particularly limited, and can be appropriately selected from known water-soluble dyes, oil-soluble dyes, pigments, and the like. Among them, the ink and the undercoat liquid according to the present invention are preferably composed of a water-insoluble organic solvent system from the viewpoint of the effect of the present invention, and are oil-soluble dyes and pigments that are easily dispersed and dissolved in a water-insoluble medium. Is preferably used.

  The content of the colorant in the ink is preferably 1 to 30% by mass, more preferably 1.5 to 25% by mass, and particularly preferably 2 to 15% by mass. Moreover, when the undercoat liquid contains a white pigment, the content in the undercoat liquid is preferably 2 to 45% by mass, more preferably 4 to 35% by mass.

Hereinafter, the pigment suitable for the present invention will be mainly described.
<Pigment>
In the present invention, an embodiment using a pigment as the colorant is preferred. As the pigment, either an organic pigment or an inorganic pigment can be used, and as the black pigment, a carbon black pigment or the like is preferable. In general, pigments of three primary colors of black and cyan, magenta, and yellow are used, but other hues such as pigments having hues such as red, green, blue, brown, white, gold, silver, etc. Metal luster pigments, colorless or light extender pigments, and the like can also be used depending on the purpose.

  The organic pigment is not limited in hue, for example, perylene, perinone, quinacridone, quinacridonequinone, anthraquinone, anthanthrone, benzimidazolone, disazo condensation, disazo, azo, indanthrone, phthalocyanine, triaryl carbo Examples thereof include nium, dioxazine, aminoanthraquinone, diketopyrrolopyrrole, thioindigo, isoindoline, isoindolinone, pyranthrone, isoviolanthrone pigment, and mixtures thereof.

  More specifically, for example, C.I. I. Pigment red 190 (C.I. No. 71140), C.I. I. Pigment red 224 (C.I. No. 71127), C.I. I. Perylene pigments such as CI Pigment Violet 29 (C.I. No. 71129); I. Pigment orange 43 (C.I. No. 71105) or C.I. I. Perinone pigments such as CI Pigment Red 194 (C.I. No. 71100); I. Pigment violet 19 (C.I. No. 73900), C.I. I. Pigment violet 42, C.I. I. Pigment red 122 (C.I. No. 73915), C.I. I. Pigment red 192, C.I. I. Pigment red 202 (C.I. No. 73907), C.I. I. Pigment red 207 (C.I. No. 73900, 73906), or C.I. I. Pigment Red 209 (C.I. No. 73905), a quinacridone pigment, C.I. I. Pigment red 206 (C.I. No. 73900/73920), C.I. I. Pigment orange 48 (C.I. No. 73900/73920), or C.I. I. Quinacridone quinone pigments such as CI Pigment Orange 49 (C.I. No. 73900/73920); I. Anthraquinone pigments such as C.I. Pigment Yellow 147 (C.I. No. 60645); I. Anthanthrone pigments such as CI Pigment Red 168 (C.I. No. 59300); I. Pigment brown 25 (C.I. No. 12510), C.I. I. Pigment violet 32 (C.I. No. 12517), C.I. I. Pigment yellow 180 (C.I. No. 21290), C.I. I. Pigment yellow 181 (C.I. No. 11777), C.I. I. Pigment orange 62 (C.I. No. 11775), or C.I. I. Benzimidazolone pigments such as CI Pigment Red 185 (C.I. No. 12516); I. Pigment yellow 93 (C.I. No. 20710), C.I. I. Pigment yellow 94 (C.I. No. 20038), C.I. I. Pigment yellow 95 (C.I. No. 20034), C.I. I. Pigment yellow 128 (C.I. No. 20037), C.I. I. Pigment yellow 166 (C.I. No. 20003), C.I. I. Pigment orange 34 (C.I. No. 21115), C.I. I. Pigment orange 13 (C.I. No. 21110), C.I. I. Pigment orange 31 (C.I. No. 20050), C.I. I. Pigment red 144 (C.I. No. 20735), C.I. I. Pigment red 166 (C.I. No. 20730), C.I. I. Pigment red 220 (C.I. No. 20055), C.I. I. Pigment red 221 (C.I. No. 20065), C.I. I. Pigment red 242 (C.I. No. 20067), C.I. I. Pigment red 248, C.I. I. Pigment red 262, or C.I. I. Disazo condensation pigments such as CI Pigment Brown 23 (C.I. No. 20060),

C. I. Pigment yellow 13 (C.I. No. 21100), C.I. I. Pigment yellow 83 (C.I. No. 21108), or C.I. I. Disazo pigments such as CI Pigment Yellow 188 (C.I. No. 21094); I. Pigment red 187 (C.I. No. 12486), C.I. I. Pigment red 170 (C.I. No. 12475), C.I. I. Pigment yellow 74 (C.I. No. 11714), C.I. I. Pigment yellow 150 (C.I. No. 48545), C.I. I. Pigment red 48 (C.I. No. 15865), C.I. I. Pigment red 53 (C.I. No. 15585), C.I. I. Pigment orange 64 (C.I. No. 12760), or C.I. I. Azo pigments such as C.I. Pigment Red 247 (C.I. No. 15915), C.I. I. Indanthrone pigments such as CI Pigment Blue 60 (C.I. No. 69800); I. Pigment green 7 (C.I. No. 74260), C.I. I. Pigment Green 36 (C.I. No. 74265), Pigment Green 37 (C.I. No. 74255), Pigment Blue 16 (C.I. No. 74100), C.I. I. Phthalocyanine pigments such as CI Pigment Blue 75 (C.I. No. 74160: 2) or 15 (C.I. No. 74160); I. Pigment blue 56 (C.I. No. 42800) or C.I. I. Triarylcarbonium pigments such as C.I. Pigment Blue 61 (C.I. No. 42765: 1); I. Pigment violet 23 (C.I. No. 51319) or C.I. I. Dioxazine pigments such as CI Pigment Violet 37 (C.I. No. 51345); I. Aminoanthraquinone pigments such as C.I. Pigment Red 177 (C.I. No. 65300); I. Pigment red 254 (C.I. No. 56110), C.I. I. Pigment Red 255 (C.I. No. 561050), C.I. I. Pigment red 264, C.I. I. Pigment red 272 (C.I. No. 561150), C.I. I. Pigment orange 71, or C.I. I. Diketopyrrolopyrrole pigments such as C.I. Pigment Orange 73; I. Thioindigo pigments such as CI Pigment Red 88 (C.I. No. 7313), CI Pigment Yellow 139 (C.I. No. 56298), C.I. I. Pigment Orange 66 (C.I. No. 48210) and the like, isoindoline pigments such as C.I. I. Pigment yellow 109 (C.I. No. 56284), or C.I. Pigment Orange 61 (C.I. No. 11295) and the like, isoindolinone pigments such as C.I. I. Pigment Orange 40 (C.I. No. 59700), or C.I. I. Pyranthrone pigments such as CI Pigment Red 216 (C.I. No. 59710), or C.I. I. And isoviolanthrone pigments such as CI Pigment Violet 31 (60010).
In the present invention, two or more kinds of organic pigments or solid solutions of organic pigments can be used in combination.

  In addition, particles having silica, alumina, resin, or the like as a core material and having a dye or pigment fixed on the surface, an insoluble raked product of a dye, a colored emulsion, a colored latex, or the like can also be used as a pigment. Furthermore, resin-coated pigments can also be used. This is called a microcapsule pigment, and commercially available products such as those manufactured by Dainippon Ink and Chemicals and Toyo Ink are available.

  The volume average particle diameter of the pigment particles contained in the liquid is preferably in the range of 10 to 250 nm, more preferably 50 to 200 nm, from the viewpoint of balance between optical density and storage stability. Here, the volume average particle diameter of the pigment particles can be measured by a particle size distribution measuring device such as LB-500 (manufactured by HORIBA).

  The colorant may be used alone or in combination of two or more. Different colorants may be used for each droplet and liquid to be ejected, or the same colorant may be used.

(Other ingredients)
In addition to the components described above, known additives can be used in combination according to the purpose.

<Storage stabilizer>
A storage stabilizer can be added to the ink and the undercoat liquid (preferably ink) according to the present invention for the purpose of suppressing undesired polymerization during storage. The storage stabilizer is preferably used in combination with a polymerizable or crosslinkable material, and it is preferable to use a storage stabilizer that is soluble in the contained droplets or liquid or other coexisting components.

  Storage stabilizers include quaternary ammonium salts, hydroxylamines, cyclic amides, nitriles, substituted ureas, heterocyclic compounds, organic acids, hydroquinones, hydroquinone monoethers, organic phosphines, copper compounds, and the like. Specific examples include benzyltrimethylammonium chloride, diethylhydroxylamine, benzothiazole, 4-amino-2,2,6,6-tetramethylpiperidine, citric acid, hydroquinone monomethyl ether, hydroquinone monobutyl ether, and copper naphthenate. It is done.

  The amount of storage stabilizer added is preferably adjusted as appropriate based on the activity of the polymerization initiator, the polymerizability of the polymerisable or crosslinkable material, and the type of storage stabilizer, but the balance of storage stability and curability is balanced. In terms of solid content in the liquid, 0.005 to 1% by mass is preferable, 0.01 to 0.5% by mass is more preferable, and 0.01 to 0.2% by mass is even more preferable.

<Conductive salts>
Conductive salts are solid compounds that improve conductivity. In the present invention, it is preferable not to use it substantially because there is a great concern of precipitation during storage, but it is possible to increase the solubility of conductive salts or use a highly soluble liquid component. If it is good, an appropriate amount may be added.
Examples of the conductive salts include potassium thiocyanate, lithium nitrate, ammonium thiocyanate, dimethylamine hydrochloride and the like.

<solvent>
In the present invention, a known solvent can be used as necessary. The solvent can be used for the purpose of improving the polarity and viscosity of liquid (ink), surface tension, solubility and dispersibility of coloring materials, adjusting conductivity, and adjusting printing performance.
Since the solvent is a water-insoluble liquid and does not contain an aqueous solvent, it is preferable from the viewpoint of recording a high-quality image with quick drying and uniform line width. It is desirable to do.
As the high-boiling organic solvent in the present invention, those having a property excellent in compatibility with the constituent materials, particularly with the monomers are preferable.
Specifically, tripropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monobenzyl ether, and diethylene glycol monobenzyl ether are preferable.

  Known solvents include low boiling point organic solvents that are organic solvents at 100 ° C. or lower, but there is a concern of affecting the curability, and it is desirable not to use low boiling point organic solvents in consideration of environmental pollution. . When used, it is preferable to use a highly safe solvent, and a highly safe solvent is a solvent having a high management concentration (an index indicated by the work environment evaluation criteria), preferably 100 ppm or more, More preferably, it is 200 ppm or more. Specific examples include alcohols, ketones, esters, ethers, hydrocarbons, and the like, and specific examples include methanol, 2-butanol, acetone, methyl ethyl ketone, ethyl acetate, and tetrahydrofuran.

  Solvents can be used in combination other than one type alone, but when water and / or a low boiling point organic solvent is used, the amount of both used is preferably 0 to 20% by mass in each solution. 10 mass% is further more preferable, and it is preferable not to contain substantially. The ink and the undercoat liquid according to the present invention are substantially free of water, so that they are non-permeable or non-permeable, such as non-uniformity over time, liquid turbidity caused by precipitation of dyes, etc. This is suitable from the viewpoint of dryness when a recording medium with slow permeability is used. In addition, it does not contain substantially means accepting presence of an inevitable impurity.

<Other additives>
Furthermore, known additives such as polymers, surface tension adjusters, ultraviolet absorbers, antioxidants, anti-fading agents and pH adjusters can be used in combination.
Regarding the surface tension adjusting agent, ultraviolet absorber, antioxidant, anti-fading agent, and pH adjusting agent, known compounds may be appropriately selected and used. For example, JP-A-2001-181549 discloses a specific example. The additives described can be used.

In addition to the above, a set of compounds that react by mixing to generate aggregates or thicken can be separately contained in the ink and the undercoat liquid according to the present invention. The set of compounds has a feature of rapidly forming aggregates or rapidly thickening the liquid, thereby more effectively suppressing coalescence between adjacent droplets. Can do.
Examples of the reaction of the set of compounds include an acid / base reaction, a hydrogen bonding reaction with a carboxylic acid / amide group-containing compound, a crosslinking reaction represented by boronic acid / diol, and a reaction by electrostatic interaction with a cation / anion. Etc.

Next, the ink jet recording apparatus of the present invention will be described.
The ink jet recording apparatus of the present invention includes an undercoat liquid applying unit for applying an undercoat liquid containing a polymer and a radical polymerizable compound having a phosphate group on a recording medium, and an undercoat in the moving direction of the recording medium. An undercoat liquid curing means that is disposed downstream of the liquid application means, applies energy to at least a part of the undercoat liquid, and semi-cures the undercoat liquid; and is disposed downstream of the undercoat liquid curing means in the moving direction of the recording medium, On the semi-cured undercoat liquid, there is provided an image recording means for recording an image by ejecting ink curable by irradiation with active energy rays.

-Image recording principle and recording device-
Hereinafter, the principle of the present invention for reproducibly recording an image (particularly in the present invention, an image portion having a small liquid amount and a low dot density) on a recording medium while avoiding droplet ejection interference will be described with reference to FIG. An example will be specifically described.

  First, as shown in FIG. 5A, an undercoat liquid not containing a colorant is applied to the recording medium 16 to form a liquid film 81 made of the undercoat liquid on the surface of the recording medium 16. Such an undercoating liquid application mode is shown in the drawing as an application mode, but may be any mode such as droplet ejection (also referred to as “ejection”) by an ink jet head or spray coating.

  The thickness of the liquid film of the applied undercoat liquid is an average thickness obtained by dividing the volume of the applied undercoat liquid by the area of the portion to which the undercoat liquid has been applied. When the undercoat liquid is applied by droplet ejection, it can be determined from the volume of droplet ejection and the area of the portion where the undercoat liquid is deposited. The thickness of the liquid film of the undercoat liquid is desirably uniform and has no local difference in thickness. From this point of view, it is desirable that the physical property of the undercoat liquid that easily spreads on the recording medium, that is, the static surface tension is small, within a range that can be stably ejected from the inkjet head.

Next, as shown in FIG. 5B, after the undercoat liquid is semi-cured by irradiation of actinic rays from the light source W (semi-cured undercoat liquid (undercoat layer); 81a), ink droplets 82a are then formed. Drip. By this droplet ejection, as shown in FIG. 5C, the ink droplet 82a is landed on the undercoat layer 81a. At this time, since the degree of cure of the surface of the undercoat layer is lower than the degree of internal cure, it is easy to become familiar with the ink droplet 82a.
Further, as shown in FIG. 5D, in the region where the undercoat layer 81a exists on the recording medium 16 and in the vicinity of the landing position of the first droplet 82a that has been previously ejected, The droplet 82b is ejected. At this time, since the degree of cure of the surface of the undercoat layer is lower than the degree of cure inside, it is easy to become familiar with the ink droplet 82b. A force to try to unite the ink droplet 82a and the ink droplet 82b works, but the adhesion between the ink droplet and the surface of the undercoat layer is good, and the undercoat layer is in a cured state when trying to unite The inside becomes a resistance against the coalescence between the ink droplets, thereby suppressing the droplet ejection interference.

  Conventionally, in order to avoid droplet ejection interference, a substance that causes a chemical reaction that causes aggregation or insolubilization of the colorant contained in the ink has been included in the undercoat liquid. The droplet ejection interference can be avoided without the inclusion in the liquid.

  Further, as shown in FIG. 5D, while the droplet ejection interference is avoided and the shapes of the ink droplets 82a and 82b are maintained (in the case of the present invention, several hundred milliseconds to 5 seconds), that is, dots The ink droplets 82a and 82b are cured or semi-cured to such an extent that the shape does not collapse before the shape is deformed, and the color material in the ink droplets 82a and 82b is fixed to the recording medium 16. At least the ink contains an active energy ray-curable polymerizable compound, and is cured by a so-called polymerization reaction when irradiated with active energy rays such as ultraviolet rays. The undercoat liquid can also contain a polymerizable compound, and since the entire discharged liquid is cured, it is preferable in order to improve the adhesion.

Next, an overall configuration of an inline label printer as an example of an image recording apparatus including the inkjet recording apparatus of the present invention will be described with reference to the drawings.
FIG. 6 is an overall configuration diagram illustrating an example of an inline label printer (image recording apparatus) 100. The image recording apparatus 100 is a buffer unit between the inkjet recording unit 100A of the present invention, a post-processing unit 100B that performs post-processing on the drawn recording medium, and the inkjet recording unit 100A and the post-processing unit 100B. It consists of a buffer 104.
The ink jet recording apparatus of the present invention is applied to the ink jet recording unit 100A. The ink jet recording unit 100A includes an undercoat liquid film forming unit 100A1 for forming a semi-cured undercoat liquid film on a recording medium (label) 16 that does not contain a colorant, and four types of ink including a coloring material. The drawing unit 100 </ b> A <b> 2 forms a desired image on the recording medium 16 by being given to 16 predetermined positions.
As the recording medium, there is a recording medium that is not particularly permeable (for example, OPP (Oriented Polypropylene Film), CPP (Casted Polypropylene Film), PE (Polyethylene), PET (Polyethylene terephthalate), PP (Poly), PP (Poly). A good image can be formed when a low soft packaging material, laminated paper, coated paper, art paper, or the like is used.

In FIG. 6, the ink jet recording unit 100A includes a drawing unit 100A2 that applies an undercoat liquid with a roll coater 102P and applies ink to the recording medium 16 by ink jet droplets.
Further, the image recording apparatus 100 supplies a recording medium 16 and a light-shielded liquid storage / loading unit (not shown) that stores the undercoat liquid and ink supplied to the undercoat liquid film forming unit 100A1 and the drawing unit 100A2. The sheet feeding unit 101 includes an image detection unit 104c that reads an image as an ink droplet ejection result (in an ink droplet landing state) by the drawing unit 100A2, and a winding unit 109 that winds up a recorded recording medium. ing.

  In FIG. 6, as an example of the paper feeding unit 101, a paper that feeds roll paper (continuous paper) is shown, but a paper that feeds cut paper that has been cut in advance may be used.

  The ink jet recording unit 100A will be further described. The ink jet recording unit 100A is a drawing unit including ink droplet ejection heads 102Y, 102C, 102M, and 102K that eject ink onto the recording medium 16 in a single pass, pinning light sources 103Y, 103C, and 103M, and a final curing light source 103K. The undercoat liquid film forming unit 100A1 includes a roll coater 102P and a semi-curing light source 103P. More specifically, a so-called full-line type head in which a line-type head having a length corresponding to the entire recordable width of the recording medium 16 is arranged in a direction perpendicular to the medium conveyance direction (indicated by an arrow S in FIG. 6). It is a head. Further, in the figure, pinning light sources 103Y, 103C, and 103M are disposed downstream of the respective 102Y, 102C, and 102M to cure the dots ejected with the respective color inks so that at least the dot shape does not collapse.

The roll coater and each of the droplet ejection heads 102Y, 102C, 102M, and 102K include a coater and a plurality of nozzles (liquid ejection ports) over a length that exceeds at least one side of the recording medium 16 of the maximum size targeted by the ink jet recording unit 100A. It is arranged.
Further, along the medium transport direction S, from the upstream side (left side in FIG. 6), yellow ink (Y), cyan ink (C), magenta ink (M), and black ink (K). The droplet ejection heads 102Y, 102C, 102M, and 102K corresponding to the respective liquids are arranged in this order, and a color image can be formed on the recording medium 16.

  Specifically, first, the undercoat liquid is uniformly applied to the recording medium 16 by the roll coater (102P), and the undercoat liquid is semi-cured by the semi-curing ultraviolet light source 103P. Next, ink is ejected from the yellow ink droplet ejection head 102Y toward the recording medium 16, and the surface of the yellow ink on the recording medium is cured by the pinning light source 103Y disposed downstream of the head 102Y. It is semi-cured so that it does not collapse at least. Subsequently, the same process as the yellow ink is repeated in the heads 102C and 102M, and finally the undercoat liquid and all the inks are completely cured after the droplets are ejected by the black ink ejection head 102K. Curing is completed by a final curing light source 103K having Here, by causing the undercoat liquid and the ink to be semi-cured after being applied, the droplet ejection interference is avoided.

  Further, according to the drawing unit 100A2 composed of a full-line type droplet ejection head, the entire surface of the recording medium 16 can be obtained by performing only one operation of relatively moving the recording medium 16 and the drawing unit 100A2 in the medium transport direction. Can record images. Thereby, high-speed printing is possible and productivity can be improved as compared with a shuttle type head that reciprocates a droplet ejection head in a direction orthogonal to the medium conveyance direction while conveying a recording medium.

  In the present embodiment, the configuration of the standard colors (four colors) of YCMK has been exemplified. However, the number of ink colors and color combinations are not limited to the examples shown in the present embodiment. Ink, dark ink, white or other special color ink, transparent ink, or the like may be added. For example, a configuration in which a droplet ejection head that discharges light-colored ink such as light cyan or light magenta is added, a configuration in which a background is drawn with white ink, or a glossiness adjustment with transparent ink is possible.

The UV light sources 103P, 103Y, 103C, 103M, and 103K irradiate the recording medium 16 with ultraviolet rays in order to cure the ink containing the polymerizable compound. A known light source such as a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a metal halide lamp, a xenon lamp, a carbon arc lamp, an ultraviolet fluorescent lamp, an ultraviolet LED, an ultraviolet LD, etc. can be used as the ultraviolet light source. From the viewpoint of properties, it is preferable to use a high-pressure mercury lamp, an ultra-high pressure mercury lamp or a metal halide lamp. The UV light source preferably has a light intensity peak in the wavelength range of 200 nm to 400 nm, and preferably has an irradiation light intensity in the range of 1 to 500 mW / cm ^{2 at} the light intensity peak wavelength. The UV light source preferably uses a cold mirror for the reflector and an infrared cut glass for the cover glass to prevent a temperature rise of the recording medium due to heat ray irradiation. Although omitted in FIG. 6, in the ink containing the radical polymerizable compound, the polymerization atmosphere by the final curing light source 103 </ b> K is replaced with an inert gas (such as nitrogen) to suppress the inhibition of polymerization by oxygen. Good ink curing and fixing can be performed.

  Although not shown, an electron beam irradiation apparatus may be used as a means for curing the ink containing a polymerizable compound.

  In the above, examples of the UV light source and the electron beam irradiation apparatus are exemplified as means for curing the polymerizable compound, but these means are not limited to the examples shown here, and other radiation rays such as α Lines, γ-rays, X-rays, etc. may be used.

  The image detection unit 104c includes an image sensor (line sensor or the like) for imaging the droplet ejection result of the drawing unit 100A2, and functions as a unit that checks nozzle clogging and other ejection abnormalities from an image read by the image sensor. To do.

  There is a buffer 104 as a buffer section between the ink jet recording section 100A and the post-processing section 100B. A recording medium on which ink jet recording has been performed passes through a buffer 104 composed of several upper rollers 104a and several lower rollers 104b while moving up and down several times. The buffer 104 is an adjustment unit that absorbs the difference between the speeds of the upstream ink jet recording unit 100A and the downstream post-processing unit 100B (to be described later) (the transport speed of the recording medium 16).

A varnish coater 105 is downstream of the buffer 104. The varnish coater 105 is used to apply a thin varnish to the label surface to improve the scratch resistance of the label surface.
The label cutting unit 106 downstream of the varnish coater 105 includes a marking reader 106a, a die cutter driver 106b, a die cutter 106c equipped with a roll (plate) 106e having a blade, and a counter roller 106d.

  The label cut by the die cutter 106c of the label cutting unit 106 is wound downstream of the branch roller 107 as a product label by the label take-up unit 109, and the remaining debris is peeled off and discarded by the waste removing unit 108. Discard as waste.

* Structure of the droplet ejection head FIG. 7A shows a basic configuration of the droplet ejection head 50 by attaching a reference numeral 50 to the droplet ejection head representing the droplet ejection heads 102Y, 102C, 102M, and 102K shown in FIG. It is a plane perspective view which shows an example of a whole whole structure.
The droplet ejection head 50 shown as an example in FIG. 7A is a so-called full-line head, and is a direction (in the drawing) orthogonal to the transport direction of the recording medium 16 (the sub-scanning direction indicated by the arrow S in the drawing). In a main scanning direction indicated by an arrow M), two or more nozzles 51 (liquid ejection ports) that eject liquid toward the recording medium 16 are two-dimensionally formed over a length corresponding to the width Wm of the recording medium 16. It has an arrayed structure.

  The droplet ejection head 50 includes a nozzle 51, a pressure chamber 52 communicating with the nozzle 51, and a plurality of pressure chamber units 54 including a liquid supply port 53 with respect to the main scanning direction M and the main scanning direction M. They are arranged along two oblique directions forming an acute angle θ (0 degree <θ <90 degrees). In FIG. 7A, only a part of the pressure chamber units 54 is shown for convenience of illustration.

  Specifically, the nozzles 51 are arranged at a constant pitch d in an oblique direction that forms a predetermined acute angle θ with respect to the main scanning direction M, and thus, “on a straight line along the main scanning direction M” d × cos θ ”can be handled equivalently.

FIG. 7B shows a cross-sectional view taken along the line bb in FIG. 7A for the pressure chamber unit 54 described above as one ejection element constituting the droplet ejection head 50.
As shown in FIG. 7B, each pressure chamber 52 communicates with the common liquid chamber 55 through the liquid supply port 53. The common liquid chamber 55 communicates with a tank which is a liquid supply source (not shown), and the liquid supplied from the tank is distributed and supplied to each pressure chamber 52 via the common liquid chamber 55.

A piezoelectric body 58a is disposed on the diaphragm 56 constituting the top surface of the pressure chamber 52, and an individual electrode 57 is disposed on the piezoelectric body 58a. The diaphragm 56 is grounded and functions as a common electrode. These diaphragm 56, individual electrode 57 and piezoelectric body 58a constitute a piezoelectric actuator 58 as means for generating a liquid ejection force.
When a predetermined drive voltage is applied to the individual electrode 57 of the piezoelectric actuator 58, the piezoelectric body 58a is deformed to change the volume of the pressure chamber 52, and the pressure in the pressure chamber 52 is changed accordingly. Liquid is discharged. After the liquid is discharged, when the volume of the pressure chamber 52 is restored, a new liquid is supplied from the common liquid chamber 55 through the liquid supply port 53 to the pressure chamber 52.

  FIG. 7A shows an example in which a plurality of nozzles 51 are two-dimensionally arranged as a structure capable of forming a high-resolution image on the recording medium 16 at high speed. The droplet ejection head is not particularly limited to a structure in which a plurality of nozzles 51 are two-dimensionally arranged, and may have a structure in which a plurality of nozzles 51 are one-dimensionally arranged. Further, the pressure chamber unit 54 shown in FIG. 7B as an ejection element constituting the droplet ejection head is an example, and is not particularly limited to such a case. For example, instead of disposing the common liquid chamber 55 below the pressure chamber 52 (that is, the discharge surface 50a side than the pressure chamber 52), the common liquid is disposed above the pressure chamber 52 (that is, opposite to the discharge surface 50a). The chamber 55 may be disposed. Further, for example, instead of using the piezoelectric body 58a, a liquid discharge force may be generated using a heating element.

In the ink jet recording apparatus of the present invention, as means for applying the undercoat liquid onto the recording medium, other means such as ejection of the undercoat liquid from the nozzle may be used in addition to the application.
There is no restriction | limiting in particular as an apparatus used for the said application | coating, A well-known coating apparatus can be suitably selected according to the objective. Examples include air doctor coaters, blade coaters, lot coaters, knife coaters, squeeze coaters, impregnation coaters, reverse roll coaters, transfer roll coaters, gravure coaters, kiss roll coaters, cast coaters, spray coaters, curtain coaters, extrusion coaters, etc. It is done.

* Liquid Supply System FIG. 8 is a schematic diagram showing the configuration of the liquid supply system in the image recording apparatus 100.
The liquid tank 60 is a base tank for supplying liquid to the droplet ejection head 50. A liquid supply pump 62 that feeds liquid from the liquid tank 60 to the droplet ejection head 50 is provided in the middle of a pipe line that connects the liquid tank 60 and the droplet ejection head 50. It is preferable that the temperature of the liquid tank 60 and the droplet ejection head 50 and the pipe connecting the both are adjusted together with the ink inside by the temperature detection means and the heater. The ink temperature at this time is preferably adjusted to 40 ° C to 80 ° C.

  Also, the image recording apparatus 100 includes a cap 64 as a means for preventing the meniscus from drying out of the nozzle 51 or preventing an increase in viscosity in the vicinity of the meniscus during a long discharge suspension period, and a cleaning as a means for cleaning the discharge surface 50a. A blade 66 is provided. The maintenance unit including the cap 64 and the cleaning blade 66 can be moved relative to the droplet ejection head 50 by a moving mechanism (not shown), and if necessary, a maintenance position below the droplet ejection head 50 from a predetermined retraction position. To be moved to.

The cap 64 is moved up and down relatively with respect to the droplet ejection head 50 by a lifting mechanism (not shown). The elevating mechanism raises the cap 64 to a predetermined ascending position and contacts the droplet ejection head 50 to cover at least the nozzle region of the ejection surface 50a with the cap 64.
Preferably, the inside of the cap 64 is divided into a plurality of areas corresponding to the nozzle rows by a partition wall, and each of the partitioned areas can be selectively sucked by a selector or the like.

The cleaning blade 66 is made of an elastic member such as rubber, and can slide on the ejection surface 50a of the droplet ejection head 50 by a cleaning blade moving mechanism (not shown). When droplets or foreign matter adhere to the discharge surface 50a, the discharge surface 50a is wiped by sliding the cleaning blade 66 on the discharge surface 50a, and the discharge surface 50a is cleaned.
The suction pump 67 sucks the liquid from the nozzle 51 of the droplet ejection head 50 in a state where the discharge surface 50 a of the droplet ejection head 50 is covered with the cap 64, and sends the sucked liquid to the recovery tank 68.

Such a suction operation is stopped for a long time in addition to the case where the liquid tank 60 is loaded into the image recording apparatus 100 and the liquid is filled from the liquid tank 60 to the droplet ejection head 50 (at the time of initial filling), and the viscosity is increased by stopping for a long time. It is also performed when removing the liquid (when starting to use for a long time).
Here, if the discharge from the nozzle 51 is arranged, first, there is a normal discharge performed toward the recording medium in order to form an image on the recording medium such as paper, and second, the cap 64. Is purged toward the cap 64 as a liquid receiver (also referred to as idle discharge).

Further, if bubbles are mixed in the nozzle 51 or the pressure chamber 52 of the droplet ejection head 50 or if the viscosity increase in the nozzle 51 exceeds a certain level, the liquid cannot be discharged from the nozzle 51 by the above-described empty discharge. An operation in which the cap 64 is applied to the ejection surface 50 a of the droplet ejection head 50 and the liquid in which the bubbles in the pressure chamber 52 of the droplet ejection head 50 are mixed or the thickened liquid is sucked by the suction pump 67 is performed.
Here, the droplet ejection head 50, the liquid tank 60, the liquid supply pump 62, the cap 64, the cleaning blade 66, the suction pump 67, the recovery tank 68, the ink flow path connecting them, and other members and equipment that are directly touched by ink It preferably has dissolution resistance and swelling resistance. Moreover, it is preferable that these members and devices have light shielding properties.

* Control System FIG. 9 is a principal block diagram showing the system configuration of the image recording apparatus 100.
In FIG. 9, the image recording apparatus 100 mainly includes a drawing unit 102, an image detection unit 104c, a UV light source 103, a communication interface 110, a system controller 112, a memory 114, an image buffer memory 152, a transport motor 116, and a motor driver 118. , Heater 122, heater driver 124, medium type detection unit 132, ink type detection unit 134, illuminance detection unit 135, environmental temperature detection unit 136, environmental humidity detection unit 137, medium temperature detection unit 138, liquid supply unit 142, liquid supply The driver 144, the print controller 150, the head driver 154, and the light source driver 156 are configured.
The drawing unit 102 represents the droplet ejection heads 102Y, 102C, 102M, and 102K shown in FIG. 6, and the UV light source 103 represents the curing light sources 103P, 103Y, 103C, 103M, and 103K shown in FIG. Since the image detection unit 104c is the same as that described in FIG. 6 and has already been described, the description thereof is omitted here.

  The communication interface 110 is an image data input unit that receives image data transmitted from the host computer 300. The communication interface 110 may be a wired or wireless interface such as USB (Universal Serial Bus) or IEEE1394. The image data input to the image recording apparatus 100 via the communication interface 110 is temporarily stored in the first memory 114 for storing image data.

  The system controller 112 includes a central processing unit (CPU) and its peripheral circuits, and is main control means for controlling the entire image recording apparatus 100 according to a predetermined program stored in the first memory 114 in advance. That is, the system controller 112 controls each unit such as the communication interface 110, the motor driver 118, the heater driver 124, the medium type detection unit 132, the ink type detection unit 134, and the print control unit 150.

  A conveyance motor 116 applies power to a roller, a belt, or the like for conveying a recording medium. By this conveyance motor 116, the droplet ejection head 50 constituting the drawing unit 102 and the recording medium move relatively. The motor driver 118 is a circuit that drives the conveyance motor 116 in accordance with an instruction from the system controller 112.

  The heater 122 is a circuit that drives a heater (or cooling element) 122 (not shown), and maintains the temperature of the recording medium at a constant temperature. The heater driver 124 is a circuit that drives the heater 122 in accordance with an instruction from the system controller 112.

  The medium type detection unit 132 detects the type of the recording medium. There are various detection modes for the type of recording medium. For example, a mode in which a sensor is provided in a sheet feeding unit (not shown), a mode in which the sensor is input by a user operation, a mode in which the sensor is input from the host computer 300, and image data input from the host computer 300 There is a mode in which automatic detection is performed by analyzing (for example, resolution and color) or additional data of the image data.

  The ink type detection unit 134 detects the type of ink. There are various types of ink type detection modes. For example, a mode in which a sensor is provided in a liquid storage / loading unit (not shown), a mode in which input is performed by a user's operation, a mode in which data is input from the host computer 300, and a mode in which input is performed from the host computer 300 There is a mode in which image data (for example, resolution and color) or additional data of the image data is automatically detected by analysis.

The illuminance detection unit 135 detects the illuminance of ultraviolet rays emitted from the UV light source 103. As an illuminance detection mode, for example, an illuminance sensor is provided in the vicinity of the UV light source 103 in FIG. Based on the output of the illuminance sensor, the output of the UV light source is fed back.
The environmental temperature detection unit 136 detects the temperature of the outside air or the image recording apparatus. As an environmental temperature detection mode, for example, there is a mode of detection by providing a temperature sensor outside or inside the device.
The environmental humidity detector 137 detects the outside air or the humidity inside the image recording apparatus. As an environmental humidity detection mode, for example, there is a mode of detection by providing a humidity sensor outside or inside the device.
The medium temperature detection unit 138 detects the temperature at the time of image formation on the recording medium. There are various medium temperature detection modes. For example, there is a mode in which a contact type temperature sensor is provided for detection, and a mode in which a non-contact type temperature sensor is provided above the recording medium 16 for detection, and the temperature of the recording medium is kept constant by the heater 122 described above. .

The liquid supply unit 142 includes a conduit for flowing ink from the liquid tank 60 in FIG. 8 to the drawing unit 102, a liquid supply pump 62, and the like.
The liquid supply driver 144 is a circuit that drives the liquid supply pump 62 and the like constituting the liquid supply unit 142 so that the liquid is supplied to the drawing unit 102.

Based on the image data input to the image recording apparatus 100, the print control unit 150 is data necessary for each droplet ejection head 50 constituting the drawing unit 102 to eject (droplet ejection) toward the recording medium. (Droplet ejection data) is generated. That is, the print control unit 150 functions as an image processing unit that performs image processing such as various processes and corrections for generating droplet ejection data from image data in the first memory 114 under the control of the system controller 112. The generated droplet ejection data is supplied to the head driver 154.
The print controller 150 is accompanied by a second memory 152, and droplet ejection data and the like are temporarily stored in the second memory 152 during image processing in the print controller 150.

  In FIG. 9, the second memory 152 is shown as being attached to the print control unit 150, but it can also be used as the first memory 114. Also possible is an aspect in which the print controller 150 and the system controller 112 are integrated and configured with one processor.

  The head driver 154 applies the droplet ejection data provided from the print control unit 150 (actually, the droplet ejection data stored in the second memory 152) to each droplet ejection head 50 constituting the drawing unit 102. To output an ejection drive signal. The ejection drive signal output from the head driver 154 is applied to each droplet ejection head 50 (specifically, the actuator 58 shown in FIG. 7B), whereby the droplet ejection head 50 is directed toward the recording medium. Liquid (droplet) is discharged.

  The light source driver 156 detects an instruction from the print control unit 150, the illuminance detected by the illuminance detection unit 135, the environmental temperature detected by the environmental temperature detection unit 136, the environmental humidity detected by the environmental humidity detection unit 137, and the medium temperature detection. This is a circuit that controls the voltage, time, and timing input to the UV light source 103 based on the medium temperature detected by the unit 138 and drives the UV light source 103.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

[Example 1]
<Preparation of Cyan Pigment Dispersion P-1>
16 g of PB15: 3 (IRGALITE BLUE GLO; manufactured by Ciba Specialty Chemicals), 48 g of dipropylene glycol diacrylate (DPGDA; manufactured by Daicel Cytec Co., Ltd.), and 16 g of Solsperse 32000 (manufactured by Geneca Corporation) were mixed. The mixture was stirred with a stirrer for 1 hour. The mixture after stirring was dispersed with an Eiger mill to obtain a cyan pigment dispersion P-1.
Here, dispersion conditions were such that zirconia beads having a diameter of 0.65 mm were filled at a filling rate of 70%, the peripheral speed was 9 m / s, and the dispersion time was 1 hour.

<Preparation of Cyan Inkjet Recording Liquid I-1>
Components of the following composition were stirred, mixed and dissolved to prepare cyan ink jet recording liquid I-1 for cyan image recording. The surface tension (25 ° C.) of the cyan ink jet recording liquid I-1 was 27 mN / m, and the viscosity (25 ° C.) was 15 mPa · s.
<composition>
-Cyan pigment dispersion P-1 above 2.16 g
・ Dipropylene glycol diacrylate (polymerizable compound) ... 9.84 g
(DPGDA; manufactured by Daicel Cytec Co., Ltd.)
-The following polymerization initiator Irg907 ... 1.5g
(Ciba Specialty Chemicals)
・ The following sensitizer Darocur ITX: 0.75g
(Ciba Specialty Chemicals)
・ The following sensitizer Darocur EDB: 0.75g
(Ciba Specialty Chemicals)

<Preparation of magenta pigment dispersion P-2>
In the preparation of the cyan pigment dispersion P-1, the pigment PB15: 3 (IRGALITE BLUE GLO; manufactured by Ciba Specialty Chemicals) was replaced with PV19 (CINQUASIA MAGENTA RT-355D; manufactured by Ciba Specialty Chemicals). A magenta pigment dispersion P-2 was prepared in the same manner as the cyan pigment dispersion P-1, except that Solsperse 32000, which is a dispersant, was replaced with BYK168 (manufactured by Big Chemie).

<Preparation of yellow dispersion P-3>
In the preparation of the cyan pigment dispersion P-1, the pigment PB15: 3 (IRGALITE BLUE GLO; manufactured by Ciba Specialty Chemicals) was replaced with PY155 (NOVOPERM YELLOW 4G01; manufactured by Clariant) and Solsperse as a dispersant. A yellow pigment dispersion P-3 was prepared in the same manner as the cyan pigment dispersion P-1, except that 32000 was replaced with BYK168 (by Big Chemie).

<Preparation of Black Dispersion P-4>
In the preparation of the cyan pigment dispersion P-1, the pigment PB15: 3 (IRGALITE BLUE GLO; manufactured by Ciba Specialty Chemicals) was replaced with carbon black (SPECIAL BLACK 250; manufactured by Degussa) and used as a dispersant. Cyan Pigment Dispersion P-1 except that 16 g of Solsperse 32000 (manufactured by Zeneca) was replaced with 14 g of Solsperse 32000 (manufactured by Zeneca) and 2 g of Solsperse 5000 (manufactured by Zeneca). In the same manner as above, a black pigment dispersion P-4 was prepared.

<Preparation of magenta inkjet recording liquid I-2>
Components of the following composition were stirred, mixed and dissolved to prepare a magenta inkjet recording liquid I-2 for recording a magenta image. The magenta inkjet recording liquid I-2 had a surface tension (25 ° C.) of 27 mN / m and a viscosity (25 ° C.) of 16 mPa · s.
<composition>
・ Magenta pigment dispersion P-2 above 5.86 g
Dipropylene glycol diacrylate (polymerizable compound) ... 6.14 g
(DPGDA; manufactured by Daicel Cytec Co., Ltd.)
・ The polymerization initiator Irg907 ... 1.5g
(Ciba Specialty Chemicals)
・ Sensitizer Darocur ITX 0.75g
(Ciba Specialty Chemicals)
・ Sensitizer Darocur EDB 0.75g
(Ciba Specialty Chemicals)

<Preparation of Liquid I-3 for Yellow Inkjet Recording>
Components of the following composition were mixed with stirring and dissolved to prepare a yellow inkjet recording liquid I-3 for yellow image recording. The surface tension (25 ° C.) of the yellow inkjet recording liquid I-3 was 27 mN / m, and the viscosity (25 ° C.) was 16 mPa · s.
<composition>
・ Yellow pigment dispersion P-3: 4.68 g
・ Dipropylene glycol diacrylate (polymerizable compound): 7.32 g
(DPGDA; manufactured by Daicel Cytec Co., Ltd.)
・ The polymerization initiator Irg907 ... 1.5g
(Ciba Specialty Chemicals)
・ Sensitizer Darocur ITX 0.75g
(Ciba Specialty Chemicals)
・ Sensitizer Darocur EDB 0.75g
(Ciba Specialty Chemicals)

<Preparation of Liquid I-4 for Black Inkjet Recording>
Components of the following composition were mixed with stirring and dissolved to prepare a black inkjet recording liquid I-4 for black image recording. The black inkjet recording liquid I-4 had a surface tension (25 ° C.) of 27 mN / m and a viscosity (25 ° C.) of 15 mPa · s.
<composition>
・ The above black pigment dispersion P-4: 3.3 g
・ Dipropylene glycol diacrylate (polymerizable compound): 8.7 g
(DPGDA; manufactured by Daicel Cytec Co., Ltd.)
・ The polymerization initiator Irg907 ... 1.5g
(Ciba Specialty Chemicals)
・ Sensitizer Darocur ITX 0.75g
(Ciba Specialty Chemicals)
・ Sensitizer Darocur EDB 0.75g
(Ciba Specialty Chemicals)

<Preparation of undercoat liquid II-1>
A component of the following composition was stirred and mixed and dissolved to prepare a comparative undercoat liquid II-1 containing neither a polymer nor a phosphate group-containing radical polymerizable compound. The surface tension (25 ° C.) of the undercoat liquid II-1 was 22 mN / m, and the viscosity (25 ° C.) was 12 mPa · s.
<composition>
Dipropylene glycol diacrylate (polymerizable compound) ... 11.85 g
(DPGDA; manufactured by Daicel Cytec Co., Ltd.)
・ The polymerization initiator Irg907 ... 1.5g
(Ciba Specialty Chemicals)
・ Sensitizer Darocur ITX 0.75g
(Ciba Specialty Chemicals)
・ Sensitizer Darocur EDB 0.75g
(Ciba Specialty Chemicals)
・ BYK-307 (Bic Chemie) ・ ・ ・ 0.15g

<Preparation of undercoat liquids II-2 to II-21>
In the preparation of the undercoat liquid II-1, except that the polymer shown in Table 1 below and the phosphate group-containing radical polymerizable compound were further added in the addition amounts shown in Table 1 below, Undercoat liquids II-2 to II-21 were prepared in the same manner as in the preparation.
In the preparation of these undercoat liquids, the amount of DPGDA corresponding to the amount of the polymer and phosphate group-containing radical polymerizable compound added is reduced from the undercoat liquid II-1, and the polymer, phosphate group-containing radical polymerization is reduced. The total amount of the active compound and DPGDA was 15 g.

  The surface tension (25 ° C.) and viscosity (25 ° C.) of the undercoat liquids II-2 to II-21 were as shown in Table 2 below.

  In this example, the surface tension is measured using a surface tension meter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.), and the viscosity is measured using a viscometer TVE-22LT (Toki Sangyo Co., Ltd.). Made).

<Image recording and evaluation>
As an image recording apparatus, a conveyance mechanism that is a conveyance unit that rolls a recording medium by rotating a driving roller, a roll coater that is an undercoat liquid application unit for applying an undercoat liquid onto the recording medium, and a post-application A light source for undercoating that is an undercoating liquid curing means for semi-curing the undercoating liquid (in a direction orthogonal to the conveyance direction of the recording medium (that is, the main scanning direction (width direction) when recording on the recording medium)) A plurality of ultra-high pressure mercury lamps are arranged, and a head unit (manufactured by Toshiba Tec Corporation; droplet ejection frequency: 6.2 KHz, number of nozzles: 636, nozzle density: 300 npi (nozzle / inch, below) Same), drop size: 4 sets of 6 pl to 42 pl with 2 variable heads arranged in 7 stages and 600 npi full line array An inkjet printer equipped with the mounting being), was prepared an experimental machine equipped with a metal halide lamp, which is the active energy ray irradiating means to further cure the undercoat liquid and the recorded image on the recording medium.

  As shown in FIG. 6, a roll coater and a light source for undercoating semi-curing are arranged in this order from the upstream side to the downstream side, as shown in FIG. A head unit having discharge heads for yellow, cyan, magenta, and black (black) and a discharge head for each color are arranged on each conveyance direction side so that the recording medium can move directly under the head. An ultra-high pressure mercury lamp for semi-curing ink is also provided. The head is configured such that each of the yellow, cyan, magenta, and black (black) ejection heads is fixed to the machine body in order from the upstream side in the transport direction of the transport path of the recording medium. Further, a metal halide lamp is arranged further downstream in the recording medium conveyance direction of the black ejection head.

  In this embodiment, the undercoating liquid II-1 is loaded into the experimental machine, and the ink-jet printer unit is loaded with the four colors of ink-jet recording liquids I-1 to I-4 as follows. Thus, an image was recorded on the recording medium.

First, using the above experimental machine, the undercoat liquid was uniformly applied to a thickness of 5 μm by a roll coater (application speed: 400 mm / s). After application of the undercoat liquid, exposure was performed with a light source for undercoat semi-curing (light intensity 500 mW / cm ² ), and the applied undercoat liquid was semi-cured.

A transfer test was performed using plain paper (Fuji Xerox Co., Ltd., copy paper C2, product code V436) as the non-penetrable medium. The plain paper was pressed with a uniform force (500 mN / cm ² ) against the semi-cured undercoat liquid or semi-cured colored liquid on the recording medium that had been extracted, and allowed to stand for about 1 minute. Thereafter, the plain paper was gently peeled off, and the uncured liquid amount was determined by measuring the weight of the plain paper.
When an image is formed with 12 pL, the uncured liquid amount was ^{0.10mg / cm 2 ~0.12mg / cm 2} . In this embodiment, the maximum mass m of the ink discharged per unit area, the case of 600 dpi × 600 dpi, 12 ^pL, was ^{0.74mg / cm 2 ~0.87mg / cm 2} .
Therefore, the relationship between the weight M (undercoat liquid) per unit area of the uncured portion of the undercoat liquid and the maximum weight m (recording liquid) of the colored liquid discharged per unit area is “m (recording liquid) / 10. <M (undercoat liquid) <m (recording liquid) / 5 ”.

Thereafter, each of the inkjet recording liquids I-1 to I-4 is independently discharged onto the recording medium to which the undercoat liquid is applied by a head loaded with the inkjet recording liquids I-1 to I-4. The ultra-high pressure mercury lamp for semi-curing the ink was not irradiated), and ultraviolet light (wavelength 365 nm) was irradiated (cured) at a light intensity of 3000 mW / cm ² and fixed by a metal halide lamp.
At this time, the monochrome image drawn by ejecting each of the inkjet recording liquids I-1 to I-4 independently is a line drawn at 600 dpi in the main scanning direction and 150 dpi in the sub-scanning direction (use of 1 drop: 6 pL droplet ejection). is there.

In addition, after the undercoat liquid is applied and semi-cured in the same manner as described above, an ink jet recording liquid I-3 is applied onto the recording medium to which the undercoat liquid is applied, in the main scanning direction 600 dpi and the sub-scanning direction 600 dpi. The entire surface droplet ejection image (using 2 drops: 12 pL droplet ejection) was drawn and subjected to pinning exposure (light intensity 500 mW / cm ² ) with an ultra-high pressure mercury lamp for semi-curing ink. Further, using the ink jet recording liquids I-1, I-2, and I-4, respectively, on the entire surface droplet ejection image drawn by the ink jet recording liquid I-3 drawn on the recording medium, the width of 3 pixels. A grid image was formed with grid lines (the width of the region between the two grid lines where no grid line is drawn is also 3 pixels wide). Thereafter, ultraviolet rays (wavelength 365 nm) were irradiated with a metal halide lamp at a light intensity of 3000 mW / cm ² to fix the lattice image. This image formation was performed at 600 dpi in the main scanning direction and 600 dpi in the sub-scanning direction (2 drop specification, 12 pL droplet ejection).

Further, after the undercoat liquid is applied and semi-cured in the same manner as described above, ink jet recording is performed by a head in which the ink jet recording liquids I-1 to I-4 are loaded on the recording medium to which the undercoat liquid is applied. All of the recording liquids I-1 to I-4 were discharged, and a full color image (actual image) of a person (female) in the main scanning direction 600 dpi and the sub-operation direction 600 dpi was printed (recording medium conveyance speed 400 mm / s, 6 to 12 pL 3 gradation drawing (Anti-aliasing processing is performed). In this case, for each color, pinning exposure (light intensity 500 mW / cm ² ) was repeated with an ultra-high pressure mercury lamp for semi-curing the ink to cure the inside of the ink. Thereafter, ultraviolet rays (wavelength 365 nm) were irradiated with a metal halide lamp at a light intensity of 3000 mW / cm ² to fix a full-color image.

Maximum mass m of the ink discharged per unit area, the case of 600 dpi × 600 dpi 12 ^pL, was ^{0.74mg / cm 2 ~0.87mg / cm 2} .
Further, after each step, the amount of uncured liquid of yellow liquid after exposure to light source for pinning, the amount of uncured liquid of cyan liquid after exposure to light source for pinning, and the amount of uncured liquid of magenta liquid after exposure to light source for pinning Samples were withdrawn and measured by a transfer test. The amount of liquid also uncured for any liquid, when imaging at 12 pL, the uncured liquid weight was ^{0.10mg / cm 2 ~0.12mg / cm 2} .
Therefore, in the combination of liquids having different hues, the maximum mass per unit area M (liquid A) of the uncured portion of the liquid A applied to the recording medium first and the unit B of the liquid B applied later. The relationship of the weight m (liquid B) is “m (liquid B) / 10 <M (liquid A) <m (liquid B) / 5”.

In the above, the interval from the end of application of the undercoat liquid to the droplet ejection of the first color yellow ink jet recording liquid I-3 was 0.2 seconds.
Further, Lintec YUPO 80 (manufactured by Lintec Corporation) was used as a recording medium.

  After recording an image using the undercoat liquid II-1, an image was drawn in the same manner as described above, except that the undercoat liquid II-1 was replaced with the undercoat liquid II-2 to II-21.

  Here, the obtained monochromatic image was cut with a microtome and observed with an optical microscope (manufactured by Nikon, measuring microscope MM-40). A microtome (manufactured by Leica, Microtome RM2255) was used to obtain a section.

In the obtained image, as shown in FIG. 1, a part of the hardened material of the recording liquid protruded from the surface 22, and a part of the image part entered the undercoat layer 22. In addition, an undercoat layer 22 was observed below the cured product of the recording liquid. Furthermore, formation of a uniform cured layer of the recording liquid was confirmed.
Similarly, as shown in FIG. 3, in the full-color image portion, a part of the cured product of the recording liquid 28 is exposed on the surface, and a part of it is submerged in another recording liquid 24 layer. It was out. Further, a layer of the recording liquid 24 was observed below the recording liquid 28. Furthermore, formation of a uniform cured layer of the recording liquid 28 was confirmed.

  The following measurements and evaluations were performed on the images obtained from the above. The results of measurement and evaluation are shown in Tables 3 to 7 below.

-1. Measurement of [A (after polymerization) / A (before polymerization)]
After application of the undercoat liquid and before and after exposure with the light source for undercoat semi-curing, an infrared absorption spectrum of the undercoat liquid was measured to obtain [A (after polymerization) / A (before polymerization)].
The infrared absorption spectrum was measured using an infrared spectrophotometer FTS-6000 manufactured by BIO-RAD. A (after polymerization) is the absorbance of the infrared absorption peak due to the polymerizable group after the polymerization reaction, and A (before polymerization) is the absorbance of the infrared absorption peak due to the polymerizable group before the polymerization reaction. As the infrared absorption peak, an infrared absorption peak near 810 cm ⁻¹ was used.

-2. Line width evaluation
The line width of the image drawn in a line shape was measured using a dot analyzer DA6000 (manufactured by Oji Scientific Instruments).
The ideal line width is 42 to 43 μm at 600 dpi.

-3. Yellow Inkjet Recording Liquid I-3 Grid Image Evaluation Using Cyan, Magenta, and Black Inkjet Recording Liquids I-1, 2, and 4
Each grid image of cyan, magenta, and black drawn on the entire droplet ejection image with the yellow inkjet recording liquid I-3 was measured using a dot analyzer DA6000 (manufactured by Oji Scientific Instruments).
Specifically, the width of a region sandwiched between two grid lines where no grid line was drawn was measured, and the degree of narrowing with respect to a 3-pixel width (set value) was evaluated.
<Evaluation criteria>
A: Not narrowed (narrowing is less than 1%).
B: A narrowing of 1% or more and less than 10% was observed.
C: A narrowing of 10% or more was observed.

-4. Practical image evaluation-
A full-color person (woman) practical image was visually observed and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: A clear and clear image with sufficient density can be obtained.
B: High density portions such as hair portions are felt somewhat thin.
C: The color is generally felt light.
D: Blurred image.
E: Unevenness was observed.

As shown in the above Tables 3 to 6, regarding the evaluation of the line width, it can be seen that when both the polymer and the phosphate group-containing radical polymerizable compound are added, good fine line drawing properties can be obtained. .
On the other hand, in the evaluation of the lattice image, when neither a polymer nor a phosphate group-containing radical polymerizable compound was added, when the polymer was added alone, and when a phosphate group-containing radical polymerizable compound was added alone, the lattice However, when both the polymer and the phosphoric acid group-containing radical polymerizable compound are added, such a lattice narrowing is not observed, and it can be seen that a good image can be obtained.
In addition, in the practical images of Table 7, it can be seen that the present invention, in which both the polymer and the phosphate group-containing radical polymerizable compound are added, shows an extremely excellent effect as in the result of the lattice narrowing. .
The numerical values of “A (after polymerization) / A (before polymerization)” of the present invention in Tables 3 to 7 are in the range of 0.3 to 0.7, respectively, and a semi-cured state was confirmed (note that Quantitative accuracy is estimated to be about ± 20% due to uneven coating thickness, light source stability, etc.)

[Example 2]
In Example 1, when the cyan ink jet recording liquid I-1, the magenta ink jet recording liquid I-2, the yellow ink jet recording liquid I-3, and the undercoat liquid II-4 were respectively prepared, the addition amount of the initiator was changed. By changing, each inkjet recording liquid and undercoat liquid were prepared so that the curing sensitivity ratio Sc / Su of the sensitivity Sc of each inkjet recording liquid and the undercoat liquid Su would be the curing sensitivity ratio shown in Table 8 below. . Here, each ink-jet recording liquid was prepared to have the same curing sensitivity. Moreover, the increase / decrease amount of the initiator amount was compensated by increasing / decreasing dipropylene glycol diacrylate.
In the same manner as in the image recording in Example 1, an undercoat liquid is applied, exposure is performed with a light source for undercoating liquid semi-curing (light intensity 500 mW / cm ² ), and semi-curing is performed so as to be the same as the cured state in Example 1. I let you. Next, a black dot image (150 dpi × 1) is drawn by alternately drawing a portion in which no ink is ejected with 2 drops of each color and a 1 mm line formed by superposing droplets of yellow, magenta, and cyan in this order. An image with 150 dpi and 1 drop superimposed thereon was formed. After ejection of each color, exposure was performed so that each color ink was cured in the same state as in Example 1.
Using the evaluation apparatus (dot analyzer DA6000) used in Example 1, the dot diameter of the black ink of the prepared sample was measured. The dot diameter du of the black ink at a portion where no color ink was ejected and the dot diameter dc of the black ink at a portion where three color droplets were deposited were measured, and the ratio of dc to du was calculated. The relationship between the curing sensitivity ratio Sc / Su and dc / du is shown in Table 8 below.

  From Table 8, when the ratio Sc / Su of the curing sensitivity of the ink and the undercoat liquid is equal to or less than 5 times, the dot diameter of the black ink deposited on the undercoat liquid and the ink previously deposited It can be seen that the change in the dot diameter of the black ink deposited on the liquid is reduced.

It is a cross-sectional schematic diagram for demonstrating the mode of an ink droplet when an ink droplet is ejected on an undercoat layer. It is a cross-sectional schematic diagram for demonstrating the semi-hardened state in this invention, (a) And (b) is a figure which shows the case where an ink is applied to the undercoat layer of an unhardened state, (c) is complete hardening. It is a figure which shows the case where an ink is applied to the undercoat which was done. It is a cross-sectional schematic diagram for explaining the state of ink droplets when ink B is ejected onto the ink A layer. It is a cross-sectional schematic diagram for demonstrating the semi-hardened state in this invention, (a) And (b) is a figure which shows the case where the ink B is ejected to the uncured ink A, (c) is complete It is a figure which shows the case where the ink B is ejected to the cured ink A. FIG. (A)-(d) is process drawing for demonstrating the image formation principle. 1 is a schematic diagram illustrating an overall configuration of an image recording apparatus that records an image by an inkjet recording method of the present invention. (A) is a top view which shows the example of the fundamental whole structure of the droplet ejection head of FIG. 6, (b) is the bb sectional view taken on the line of (a). It is the schematic which shows the structural example of the liquid supply system which comprises an image recording device. It is a block diagram which shows the structural example of the control system which comprises an image recording device.

Explanation of symbols

16 Recording medium 20 Undercoat layer 22 Undercoat layer surface 24 Ink, ink A
28 Ink B
81 Undercoat liquid 81a Semi-cured undercoat liquid 82a, 82b Ink droplet 100 Image recording apparatus 100A Inkjet recording unit 100A1 Liquid film forming unit 100A2 Drawing unit 102P Roll coater 102Y, 102C, 102M, 102K Ink droplet ejection head 103P Undercoat liquid Curing light source 103Y, 103M, 103C Pinning light source 103K Final curing light source 104 Buffer 104a Upper roller 104b Lower roller 104c Image detection unit 100B Post-processing unit 105 Varnish coater 106 Label cutting unit 106a Marking reader 106b Die cutter driver 106c Die cutter 106d Opposing roller 106e Blade Attached plate 107 Branch roller 108 Scrap removal part 109 Label winding part 50 Droplet ejection head 50a Discharge surface 51 Nozzle 52 Pressure chamber 53 Liquid supply 54 Pressure chamber unit 55 Common liquid chamber 56 Diaphragm 57 Individual electrode 58a Piezoelectric body 58 Piezoelectric actuator 60 Liquid tank 64 Cap 66 Cleaning blade 67 Suction pump 68 Collection tank 102 Drawing unit 103 UV light source 110 Communication interface 112 System controller 114, 152 Memory 116 Motor for transportation 118 Motor driver 122 Heater 124 Heater driver 132 Medium type detection unit 134 Ink type detection unit 135 Illuminance detection unit 136 Environmental temperature detection unit 137 Environmental humidity detection unit 138 Medium temperature detection unit 142 Liquid supply unit 144 Liquid supply unit 144 Liquid supply driver 150 Print Control Unit 154 Head Driver 156 Light Source Driver

Claims (12)

An undercoat liquid for pre-applying ink onto a recording medium before recording an image, and comprising a water-insoluble and oil-soluble acrylamide polymer and a phosphate group And a radically polymerizable compound having an undercoat liquid. The undercoating liquid according to claim 1, further comprising a radical polymerization initiator. The undercoat liquid according to claim 1 or 2, wherein the content of the radical polymerizable compound having a phosphate group is 1 to 50% by mass . The undercoat liquid according to any one of claims 1 to 3, wherein the content of the acrylamide type polymer is 1 to 50% by mass . An undercoat liquid applying step for applying an undercoat liquid containing a water-insoluble and oil-soluble acrylamide type polymer and a radically polymerizable compound having a phosphate group on a recording medium;
A curing step of semi-curing the applied undercoat liquid;
A recording step of recording an image by ejecting ink that can be cured by irradiation of an active energy ray on the semi-cured undercoat liquid;
An inkjet recording method comprising: 6. The ink jet recording method according to claim 5 , wherein the undercoat liquid is semi-cured by irradiation with an active energy ray. The ink jet recording method according to claim 5 , wherein the undercoat liquid further contains a radical polymerization initiator. The recording process, as well for recording an image using an ink set including inks of multiple colors, any of at least one color ink ejected of claims 5-7, characterized in that it comprises a step of semi-curing The ink jet recording method according to claim 1. The inkjet recording method according to claim 5 , further comprising a step of further promoting the curing of the undercoat liquid and the discharged ink. The ink jet recording method according to any one of claims 5 to 9, wherein the ink has a curing sensitivity that is not less than the curing sensitivity of the undercoat liquid and not more than 4 times the curing sensitivity of the undercoat liquid . An undercoat liquid applying means for applying an undercoat liquid containing a water-insoluble and oil-soluble acrylamide type polymer and a radically polymerizable compound having a phosphate group on a recording medium;
An undercoat liquid curing means that is disposed downstream of the undercoat liquid application means in the moving direction of the recording medium, applies an active energy ray to at least a part of the undercoat liquid, and semi-cures the undercoat liquid;
Image recording means for recording an image by discharging ink curable by irradiation of active energy rays onto the semi-cured undercoat liquid disposed downstream of the undercoat liquid curing means in the moving direction of the recording medium. When,
An ink jet recording apparatus comprising: Conveying means for conveying the recording medium;
An active energy ray is applied to the recording medium that is disposed downstream of the image recording unit in the conveyance direction of the recording medium to be conveyed and on which an image is recorded by the image recording unit, and the undercoat liquid and the liquid are discharged. An active energy ray irradiation means for further promoting the curing of the ink,
The image recording means is arranged in parallel with a direction orthogonal to the conveyance direction of the recording medium, and uses at least one line type inkjet head having a length corresponding to the entire recordable width of the recording medium, The inkjet recording apparatus according to claim 11, wherein the ink is ejected.

Images