JP2008246837A - Inkjet recording method, and inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording method which is excellent in image uniformity among various kinds of mediums to be recorded regardless of the medium to be recorded and can suppress the generation of unevenness in a line width or a difference in color resulting from the bleeding of ink and the coalescence between liquid droplets as well as form an color image of a high picture quality on a white ink even when the white ink is imparted in advance. <P>SOLUTION: This inkjet recording method includes an undercoating liquid imparting process, a white ink imparting process, a hardening process, and a recording process. In this case, in the undercoating liquid imparting process, an undercoating liquid is imparted on the medium to be recorded. In the white ink imparting process, the white ink containing a white pigment is imparted. In the hardening process, the imparted undercoating liquid and the imparted white ink are semi-hardened. In the recording process, the image is recorded on the semi-hardened undercoating liquid and white ink by discharging an ink which is curable by the irradiation of an active energy beam. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink jet recording method and an ink jet recording apparatus suitable for recording a high quality image at high speed by an ink jet method.

  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 ejects ink droplets in accordance with image data and forms lines or images on the recording medium with these droplets. When recording on a recording medium, if it takes time to dry the droplets after droplet ejection or penetrate into the recording medium, the image tends to bleed, and the ink droplets adjacent on the recording medium There was a problem in practical use such as mixing between the two and hindering the formation of a sharp image. 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.

Further, when ink jet recording is performed on a recording medium for a seal label, a color image may be formed after white ink is applied on the recording medium. In this case, it has been difficult to form a color image with high image quality on white ink applied in advance. On the other hand, when the recording medium is transparent, a technique for forming a color image on the front surface with high image quality by applying white ink from the back surface of the recording medium is known. However, in the case of a recording medium for a seal label, an adhesive layer or the like is provided on the back surface, and it is virtually impossible to apply white ink from the back surface.
Further, in inkjet recording for seal labels, a single-pass method using a line head is desired for high productivity. In this case, the recording medium is mainly in the form of a roll. There is also a need for a short time to wind up the roll after recording, and a short ink drying (curing) time.

  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 performed to an extent, and then ultraviolet curing 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.

  The present invention has been made in view of the above, and is excellent in image uniformity between various recording media regardless of the recording medium, and non-uniform line width caused by ink bleeding and coalescence between droplets. It is an object of the present invention to provide an ink jet recording method and an ink jet recording apparatus that can suppress the occurrence of color unevenness and the like and can form a color image with high image quality even when white ink is applied in advance. The goal is to achieve this.

  In the present invention, when ink jet recording is performed after applying an undercoat liquid and a white ink containing a white pigment on a recording medium, droplet ejection interference prevention is performed on an undercoat layer containing the previously formed undercoat liquid and the white ink. It has been completed by finding that it is possible to form a high-quality color image even on the applied white ink by providing the function.

Specific means for achieving the above object are as follows.
<1> An undercoat liquid applying step for applying an undercoat liquid on a recording medium, a white ink applying step for applying a white ink containing a white pigment on the recording medium, and the applied undercoat liquid and the white ink. An ink jet recording method comprising: a curing step for semi-curing; and a recording step for ejecting ink that can be cured by irradiation of active energy rays onto the semi-cured undercoat liquid and the white ink to record an image. .
<2> The inkjet recording according to <1>, wherein the white ink application step is a step of applying a white ink on the applied undercoat liquid after the undercoat liquid application process. Is the method.
<3> The undercoat liquid applying step is a step of applying an undercoat liquid on the recording medium and / or the applied white ink after the white ink applying step. 1>. The inkjet recording method according to 1>.

<4> The inkjet recording method according to any one of <1> to <3>, wherein the undercoat liquid and / or the white ink is curable by irradiation with active energy rays.
<5> The ink jet recording method according to any one of <1> to <4>, wherein the undercoat liquid and / or the white ink further contains a radical polymerizable composition.
<6> The <1>, wherein the recording step includes a step of recording an image using an ink set including multicolored inks and semi-curing the ejected at least one color ink. It is an inkjet recording method of any one of-<5>.

<7> The inkjet recording method according to any one of <1> to <6>, further comprising a step of further promoting curing of the undercoat liquid, the white ink, and the ejected ink. It is.
<8> The inkjet recording method according to any one of <1> to <7>, wherein the curing sensitivity of the ink is equal to or higher than the curing sensitivity of the undercoat liquid and the white ink. .

<9> Undercoat liquid applying means for applying an undercoat liquid on the recording medium, white ink applying means for applying white ink containing a white pigment on the recording medium, and the undercoat liquid in the moving direction of the recording medium An undercoat liquid and a white ink curing means that are arranged downstream of the application means and the white ink application means, apply energy to at least a part of the undercoat liquid and the white ink, and semi-cure the undercoat liquid and the white ink; An image is formed by ejecting ink curable by irradiation of active energy rays onto the semi-cured undercoat liquid and white ink disposed downstream of the undercoat liquid and white ink curing means in the moving direction of the recording medium. And an image recording means for recording.
<10> The white ink applying unit is disposed downstream of the undercoat liquid applying unit in the moving direction of the recording medium, and applies white ink on the applied undercoat liquid. 9>.
<11> A recording medium on which an image is recorded by the image recording unit, which is disposed downstream of the image recording unit in a conveyance path of the recording medium and the image recording unit in a conveyance path of the recording medium to be conveyed. Active energy ray irradiating means for irradiating active energy rays to further accelerate curing of the undercoat liquid, white ink, and the ejected ink, and the image recording means includes a transport direction of the recording medium; <9>, wherein the ink is ejected by using at least one line-type ink-jet head that is arranged in parallel to a perpendicular direction and has a length corresponding to the full recordable width of the recording medium. Or it is an inkjet recording device as described in <10>.

  According to the present invention, regardless of the recording medium, the image uniformity between various recording media is excellent, and the occurrence of unevenness in line width, color unevenness, etc. due to ink bleeding and coalescence between droplets. It is possible to provide an ink jet recording method and an ink jet recording apparatus that can suppress the above and can form a color image with high image quality even when white ink is applied in advance.

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

  The inkjet recording method of the present invention includes an undercoat liquid application step for applying an undercoat liquid on a recording medium, a white ink application step for applying a white ink containing a white pigment on the recording medium, A curing step of semi-curing the undercoat liquid and the white ink, and a recording step of recording an image by ejecting ink that can be cured by irradiation of active energy rays onto the semi-cured undercoat liquid and the white ink. It is provided and configured. 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 fine lines, and the sharp image formation is liable to be impaired. However, in the ink jet recording method of the present invention, the undercoat liquid and the white ink are applied onto the recording medium, the undercoat liquid and the white ink are semi-cured, and the semi-cured undercoat containing the undercoat liquid and the white ink is obtained. By forming the layer, even if the ink droplets are provided on the semi-cured undercoat layer so as to overlap each other, these adjacent ink liquids are caused by the interaction between the undercoat layer and the ink droplets. The coalescence between drops can be suppressed. 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.

  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, at least one kind of undercoat liquid, and at least one kind of white ink are used as the liquid for forming an image. The ink preferably has a composition different from that of the undercoat liquid and the white ink. The undercoat liquid and the white ink are 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 of the specific configurations of the ink jet recording method of the present invention includes a polymerizable or crosslinkable material for forming an image in which a plurality of color ink droplets ejected onto a recording medium, In addition, a step of applying an undercoat liquid having a composition different from that of the ink and containing a polymerizable or crosslinkable material to a recording medium in advance in the same range as the image formed by the ink droplets or wider than the image. And a white recording medium having a composition different from that of the ink and containing a polymerizable or cross-linkable material and a white pigment in advance in the same or wider range than the image formed by the ink droplets. A step of applying an active energy ray or heat to the undercoat layer containing the undercoat liquid and white ink formed on the recording medium and semi-curing, and applying an active energy ray or heat to semi-curing After letting A step of droplet of ink droplets of a plurality of colors on this undercoat layer, a structure in which a.

  Further, after applying the undercoat liquid and the white ink in advance as described above, and then ejecting at least all of the desired ink droplets (preferably multicolor ink droplets), excellent fixing to the ink is achieved. From the standpoint of obtaining the desired properties, for example, by applying energy, a step of fixing the recorded image by further promoting the curing of the undercoat liquid, the white ink and the discharged ink (hereinafter referred to as a fixing step) is provided. preferable.

-Undercoat liquid application process, white ink application process, recording process-
In the undercoat liquid application step, an undercoat liquid is applied at least on the recording medium. The undercoat liquid is preferably cured by irradiation with active energy rays, and more preferably contains at least one radical polymerizable composition. Further, the undercoat liquid can be constituted by using other components (for example, a surfactant or the like) as necessary. Details of each component constituting the undercoat liquid and the recording medium will be described later.

  In the white ink application step, at least white ink is applied on the recording medium. The white ink contains at least one kind of white pigment, is preferably cured by irradiation with active energy rays, and more preferably contains at least one kind of radically polymerizable composition. Further, the white ink can be constituted by using other components (for example, a surfactant or the like) as necessary. Details of each component constituting the white ink will be described later.

In the present invention, after applying the undercoat liquid and the white ink on the recording medium, the undercoat liquid and the white ink are mixed to form an undercoat layer. By applying energy to the undercoat layer containing the undercoat liquid and the white ink, a semi-cured undercoat layer is formed. Therefore, the order of the undercoat liquid application process for applying the undercoat liquid and the white ink application process for applying the white ink on the recording medium is not particularly limited.
In the present invention, since the undercoat liquid does not need to be applied imagewise, it can be applied using a coating device such as a roll coater, whereas white ink may be applied imagewise by an inkjet nozzle. In addition, it is preferable to apply the white ink after applying the undercoat liquid on the recording medium, and when the undercoat liquid and the white ink are respectively applied by an inkjet nozzle, the white ink and the color ink applied later From the viewpoint of suppressing the mixing of the ink and the white ink, it is also preferable to apply the undercoat liquid on the recording medium and / or the applied white ink after applying the white ink on the recording medium.

  In the recording step, an image is recorded by ejecting ink that can be cured by irradiation with active energy rays onto the undercoat layer containing the undercoat liquid and the white ink that has been semi-cured in the later-described curing step. The ink is applied onto an undercoat layer 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 embodiment in which an undercoat liquid is coated on a recording medium using a coating device is preferable. 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, an embodiment in which the undercoat liquid is discharged by the inkjet nozzle is also preferably used. The ink jet nozzle will be described later.
The condition for applying the undercoat liquid by 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 with a large amount of ejected droplets generally has a large ejection force, so it can easily cope with a highly viscous undercoat liquid and is also advantageous for clogging of nozzles. 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 the ink jet recording method of the present invention, white ink can be applied to a recording medium using a coating device or an ink jet nozzle. The above matters can be applied as they are to the coating apparatus. The ink jet nozzle will be described later.
In this invention, the aspect which provides white ink using an inkjet nozzle is preferable. By applying white ink using an inkjet nozzle, it is possible to apply white ink in a desired shape.

  In any of the above embodiments, liquids other than the undercoat liquid, the white ink, and the 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 on the semi-cured undercoat layer 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.
The amount of white ink applied is preferably in the range of 0.05 to 5 when the ink droplet amount is 1, more preferably in the range of 0.07 to 4, A range of 3 is particularly preferable.

  It is preferable that the droplet ejection interval until the ink droplets are ejected after the undercoat liquid and the white ink are semi-cured is in the range of 5 μs or more and 10 seconds or less. When the droplet ejection interval is within the above range, it is effective in that the effect of the present invention can be remarkably exhibited. 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, after the formation of the undercoat layer containing the undercoat liquid and the white ink applied in the undercoat liquid application step and the white ink application step, and before the ejection of at least one ink droplet in the recording step. A curing step for semi-curing the applied undercoat layer is provided.

Here, the semi-curing of the 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.

  As an example, FIG. 1 shows a high concentration portion when about 12 pL of ink (hereinafter also referred to as “colored liquid”) is deposited on a semi-cured undercoat layer having a thickness of about 5 μm provided on a substrate. It demonstrates with reference to ~ 2.

  As shown in FIG. 1, the undercoat layer 20 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, (1) a part of the colored liquid 24 is exposed on the surface, (2) a part of the colored liquid 24 is embedded in the undercoat layer 20, and (3) the colored liquid 24 and the substrate 26 are There is an undercoat liquid in between. That is, the recording medium on which an image obtained by applying the colored liquid 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 colored liquid 24 is applied to the semi-cured undercoat layer 20. In this case, the colored droplets ejected at a high density are connected to each other to form a colored film, giving a uniform and high color density.

  On the other hand, as shown in FIG. 2, when the colored liquid 24 is deposited on the uncured undercoat layer 20, the entire colored liquid 24 is embedded in the undercoat layer 20 and / or the colored liquid 24 and Undercoat liquid is not present between the base material 26 and the base material 26. In this case, even if the coloring liquid is applied at a high density, the droplets are independent from each other, which causes a decrease in color density. A recording medium on which an image obtained by applying the colored liquid 24 onto the uncured undercoat layer 20 is schematically shown in FIGS. 2 (a) and 2 (b). It has a simple cross section.

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

From the viewpoint of forming a uniform colored liquid liquid layer and preventing the occurrence of droplet ejection interference without the liquid droplets becoming independent when the colored liquid droplets are applied at high density, The amount of the uncured portion of the undercoat layer is preferably sufficiently smaller than the maximum droplet amount of the colored liquid applied per unit area. That is, the relationship between the mass M (undercoat liquid) per unit area of the uncured portion of the undercoat layer and the maximum mass m (color liquid) of the colored liquid discharged per unit area is “m (colored liquid) / 30 <M (Undercoat layer) <m (colored liquid) ”is preferable, and“ m (colored liquid) / 20 <M (undercoat layer) <m (colored liquid) / 3 ”is further preferable, and“ m (colored liquid) / 3 ”. It is particularly preferable that “coloring liquid) / 10 <M (undercoat layer) <m (coloring liquid) / 5”. Here, the maximum mass of the colored liquid discharged per unit area is the maximum mass per color.
When m (colored liquid) / 30 <M (undercoat layer), the occurrence of droplet ejection interference can be prevented, and the dot size reproducibility is excellent. If M (undercoat liquid) <m (colored liquid), a uniform colored 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 completion of the semi-curing process (for example, after irradiation with active energy rays) and before droplets of colored liquid are deposited, the penetrating medium such as plain paper is pressed against the semi-cured undercoat layer to penetrate It is obtained by measuring the mass of the undercoat layer liquid transferred to the medium.
For example, if the maximum discharge amount of the colored liquid is 600 × 600 dpi and the droplet ejection density is 12 picoliters per pixel, the maximum mass m (colored liquid) discharged per unit area is 0. 04 g / cm ² (here, the density of the colored liquid is assumed to be about 1.1 g / cm ³ ). Therefore, the mass of the uncured portion of the preferred undercoat layer is greater than 0.04 g / cm ² than the unit area per 0.0013 g / cm ^2, more preferably greater than 0.002g / cm ² 0.013g / cm less than ^2, and particularly preferably greater 0.008 g / cm ² than 0.004 g / cm ^2.

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

  When the semi-cured state of the undercoat liquid and / or the colored liquid is realized by a polymerization reaction of a polymerizable compound that is initiated by irradiation with active energy rays or heating, the 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 that

Here, A (after polymerization (is the absorbance of the infrared absorption peak due to the polymerizable group after the polymerization reaction, A (before polymerization) is the absorbance of the infrared absorption peak due to the polymerizable group before the polymerization reaction) For example, when the polymerizable compound contained in the undercoat liquid and / or the coloring liquid is an acrylate monomer or a methacrylate monomer, an absorption peak based on a polymerizable group (acrylate group, methacrylate group) can be observed near 810 cm ^−1. The polymerization rate is preferably defined by the absorption light intensity of the peak, and 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. , of the absorbance of this peak, when defining the polymerization rate is preferred. polymerizable compound is an epoxy compound, 750 cm ¹ near the observable absorption peak based on polymerizable groups (epoxy group), with the absorbance of this peak is preferably defined by the rate of polymerization.

  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.

  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 the undercoat liquid and the white ink are prepared to have a high viscosity in advance, the viscosity is lowered by adding a low boiling point organic solvent thereto, and the low boiling point organic solvent is evaporated to return to the original high viscosity, (3) A method in which the undercoat liquid and white ink prepared to have a high viscosity are heated to reduce the viscosity, and then returned to the original high viscosity by cooling. (4) An active energy ray or heat is applied to the undercoat liquid and the white ink. A known thickening method such as a method of giving a curing reaction is given. Among these, (4) a method in which an active energy ray or heat is applied to the undercoat liquid and the white ink 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 semi-curing 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 crosslinkability due to the increase of active species or temperature rises. 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.

A more preferable semi-cured state can be determined by observing a cross section of an ink droplet ejected on the semi-cured undercoat layer.
The method for observing the cross section is not particularly limited. For example, a commercially available microtome and a commercially available optical microscope can be used. 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.

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

-Fixing process-
The fixing step is preferably provided after the undercoat liquid applying step, the white ink applying step, the curing step, and the recording step. In this fixing step, for example, by applying energy, curing of the undercoat liquid, the white ink, 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.
Further, 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, undercoat liquid and white ink)
In the present invention, the curing sensitivity of the ink is preferably equal to or higher than the curing sensitivity of the undercoat liquid and the white ink. More preferably, the curing sensitivity of the ink is not less than the curing sensitivity of the undercoat liquid and the white ink and not more than 4 times the curing sensitivity of the undercoat liquid and the white ink. More preferably, the curing sensitivity of the ink is not less than the curing sensitivity of the undercoat liquid and the white ink and not more than twice the curing sensitivity of the undercoat liquid and the white ink.
By making the ink curing sensitivity equal to or higher than the curing sensitivity of the undercoat liquid and the white ink, when printing on the undercoat liquid in multicolor printing, it is suitable for hitting 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 less than twice.

(Physical properties of ink, undercoat liquid and white ink)
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 or more and less than 5000 mPa · s, and more preferably 200 mPa · s or more and less than 3000 mPa · s.

In the present invention, from the viewpoint of forming the undercoat layer on the recording medium, the relationship between the surface tension of the undercoat liquid, the white ink, and the color ink satisfies all of the following conditions (A), (B), and (C). It is preferable. Further, from the viewpoint of forming dots of a desired size on the recording medium, the undercoat liquid and the white ink preferably each contain a surfactant, and the following conditions (A), (B) and (C) It is preferable to satisfy all of the above.
(A) The surface tension of the undercoat liquid is smaller than the surface tension of any of the white ink and the color 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 ink dots of a target size on the recording medium, it is preferable that the surface tension γs of the undercoat liquid is smaller than the surface tension γw of the white ink.
Further, from the viewpoint of more effectively preventing the expansion of ink dots from landing to exposure, it is more preferable that γs <γw-3 (mN / m), and γs <γw-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, the surface tension γs of the undercoat liquid may be at least smaller than the surface tension of the color ink containing a colorant having high visibility. Preferably, it is more preferable to make it smaller than the surface tension of all color inks. Examples of the colorant with high visibility include colorants exhibiting magenta, black, and cyan colors.
Similarly, the relationship between the surface tension γk of each color ink and the surface tension γs + w of the liquid in which the undercoat liquid and the white ink are mixed is preferably γs + w <γk (mN / m), and γs + w <γk−3 ( mN / m), and γs + w <γk-5 (mN / m) is particularly preferable.
In addition, even if the surface tension γk of each color ink, the surface tension γw of the white ink, and the surface tension γs of the undercoat liquid satisfy the above-described relationship, if these values are less than 15 mN / m, inkjet droplet ejection Sometimes, it becomes difficult to form droplets and non-ejection 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 discharge, the surface tension γk of each color ink, the surface tension γw of the white ink, and the surface tension γs of the undercoat liquid are preferably in the range of 15 mN / m to 50 mN / m, respectively. More preferably, it is in the range of 18 mN / m or more and 40 mN / m or less, and particularly preferably in the range of 20 mN / m or more and 38 mN / m or less.
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 the 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 the surfactants”, and adjusting the concentration of the surfactant. It can be obtained by measuring the surface tension of the liquid when the change amount of the surface tension with respect to the change of 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. (Irg907, manufactured by Ciba Specialty Chemicals Co., Ltd., the following polymerization initiator-1), fluorine-based surfactant (Megafac F475, manufactured by Dainippon Ink & Chemicals, Inc.), hydrocarbon-based surfactant (disulfosuccinic acid di) -2-ethylhexyl sodium), γs (0), γs (saturated) ¹ (when a fluorosurfactant is added), γs (saturated) ² (when a hydrocarbon surfactant is added), γs (saturation) and γs (saturation) ^maximum are 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 ). Two values (γs (saturated) ² ) can be taken when the hydrogen-based surfactant is added. 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 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 color ink, the white ink, and the undercoat liquid may be selected so that a desired surface tension can be obtained, 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)
The surfactant in the present invention is hexane, cyclohexane, p-xylene, toluene, ethyl acetate, methyl ethyl ketone, diethylene glycol monobutyl ether (butyl carbitol), cyclohexanone, triethylene glycol monobutyl ether, 1,2-hexanediol, propylene glycol monomethyl. A substance having strong surface activity against at least one solvent among ether, isopropanol, methanol, water, isobornyl acrylate, 1,6-hexane diacrylate, and polyethylene glycol diacrylate, preferably hexane, toluene , Propylene glycol monomethyl ether, isobornyl acrylate, 1,6-hexane diacrylate, polyethylene glycol diacrylate It is a substance having a strong surface activity for at least one kind of solvent, and more preferably at least one kind of propylene glycol monomethyl ether, isobornyl acrylate, 1,6-hexane diacrylate, polyethylene glycol diacrylate. A substance having a strong surface activity against a solvent, particularly preferably a substance having a strong surface activity against at least one kind of solvent among isobornyl acrylate, 1,6-hexane diacrylate and polyethylene glycol diacrylate It is.

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), the concentration of the compound is increased by 0.01% by mass, and the change in the surface tension with respect to the change in the compound concentration is 0.01 mN / m. 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 of more remarkable effects of the present invention. Here, the permeable recording medium is, for example, a recording medium having a time of 100 ms or less until the total liquid amount permeates when a 10 pL (picoliter) droplet is dropped on the recording medium. 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 permeates 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, undercoat liquid and white ink-
Hereinafter, the ink, undercoat liquid and white ink used in the ink jet 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 kind of a polymerizable or crosslinkable material, and is configured using a polymerization initiator, a lipophilic solvent, a colorant, and other components as necessary.

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.

  Moreover, it is preferable that undercoat liquid contains a radically polymerizable composition. The radical polymerizable composition in the present invention is a composition containing at least one radical polymerizable material and at least one radical polymerization initiator. Thereby, the curing reaction of the undercoat liquid can be performed with high sensitivity in a short time.

  The white ink in the present invention preferably contains at least one white pigment and has a composition different from that of the ink. For the constituent components other than the white pigment, the constituent components of the undercoat liquid can be suitably used.

  The ink in the present invention preferably contains a colorant. Moreover, it is preferable that the undercoat liquid used in combination with this does not contain a colorant or the content of the colorant is less than 1% by mass. Hereinafter, each component constituting each liquid will be described in detail.

(Polymerizable or crosslinkable material)
The polymerizable or crosslinkable material in the present invention 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 them.

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, polyethyleneoxy monomethyl ether (meth) acrylate, oligoethyleneoxy monomethyl ether (meth) acrylate, polyethyleneoxy (meth) acrylate, oligo Ethyleneoxy (meth) acrylate, oligoethyleneoxy monoalkyl ether (meth) acrylate, polyethylene Oxymonoalkyl ether (meth) acrylate, dipropylene glycol (meth) acrylate, polypropylene oxide monoalkyl ether (meth) acrylate, oligopropyleneoxy monoalkyl ether (meth) acrylate, 2-methacryloyloxytyl succinic acid, 2-methacrylic Leuoxyhexahydrophthalic 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 nonylphenol ( Data) 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, the undercoat liquid and the white ink is preferably in the range of 50 to 99.6% by mass with respect to the total solid content (mass) of each droplet, The range of 99.0% by mass is more preferable, and the range of 80 to 99.0% by 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, undercoat liquid, and white ink can be suitably configured using at least one 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, 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). A group of compounds that undergo oxidative or reductive bond cleavage through interaction with the electronically excited state of the sensitizing dye described in the above 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. Nos. 3,901,710 and 4,181,531, 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 undercoat liquid and may be contained in the ink and / or the white ink. In this case, the polymerization initiator is appropriately selected and contained within a range in which the storage stability of the ink can be maintained. be able to. 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 (for example, thionine, methylene blue, toluidine blue), acridines (for example, acridine orange, chloroflavin, acriflavine), anthraquinones (for example, anthraquinone), squalium (for example, 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 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 adjacent A ¹ and an 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 formula (XI), A ² represents a sulfur atom or —NR ⁵⁹ —, L ⁴ represents a nonmetallic atomic group that forms a basic nucleus of a dye in combination with adjacent A ² and a 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.

  Preferred 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 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, and includes, 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), C.I. I. 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. I. Pigment Orange 61 (C.I. No. 11295) and other isoindolinone pigments, 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 (C.I. No. 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.

(White pigment)
The white ink in the present invention contains at least one white pigment.
Examples of white pigments include calcium carbonate, kaolin, talc, clay, diatomaceous earth, synthetic amorphous silica, aluminum silicate, magnesium silicate, calcium silicate, aluminum hydroxide, alumina, lithopone, zeolite, barium sulfate, calcium sulfate, and oxidation. Inorganic white pigments such as titanium, zinc sulfide, zinc oxide, zinc carbonate, barium carbonate, silica antimony trioxide, titanium phosphate, magnesium oxide, magnesium hydroxide, styrene pigment, acrylic pigment, urea resin, melamine resin, etc. An organic pigment etc. are mentioned suitably. Among these white pigments, inorganic white pigments are preferable, and titanium oxide is particularly preferable. These pigments may be used alone or in combination of two or more.

  As the particle size of the white pigment, the volume average particle diameter is preferably 0.1 to 0.5 μm. By setting the particle size in the above range, it is possible to effectively avoid a decrease in whiteness or a decrease in glossiness.

  The titanium oxide may be a rutile type or an anatase type, and these may be used alone or in combination. Further, any of those manufactured by the sulfuric acid method and those manufactured by the chlorine method may be used. Examples of the titanium oxide include hydrous alumina treatment, hydrous silicon dioxide treatment, or surface coating treatment with an inorganic substance such as zinc oxide treatment, trimethylolmethane, trimethylolethane, trimethylolpropane, and 2,4-dihydroxy-2. -It can select suitably from what carried out surface coating processing by organic substances, such as methylpentane, or siloxane processing, such as polydimethylsiloxane.

The refractive index of the white pigment is preferably 1.5 or more. When a white pigment having a refractive index in this range is included, a high-quality image can be formed.
The white ink in the present invention can contain a white pigment in a dispersed state. It is preferable to use a dispersant for dispersing the white pigment. In the present invention, the dispersant can be used without any particular limitation, but a polymer dispersant is preferably used.

Examples of the polymer dispersing agent include a polymer dispersing agent such as 4000 series manufactured by efka, a Solsperse series manufactured by Nippon Lubrizol, and a dispersbyk series manufactured by BYK-chemie. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment.
For the dispersion of the pigment, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like can 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, the undercoat liquid and the white ink (preferably to the ink) according to the present invention for the purpose of suppressing undesirable 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 in terms 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 properties excellent in compatibility with constituent materials, particularly 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 still more preferable, and it is preferable not to contain substantially. The ink, the undercoat liquid and the white ink according to the present invention are substantially free of water, so that they are non-uniform over time, liquid turbidity is caused by dye precipitation, etc. This is suitable in terms of drying when a permeable or slow permeable recording medium 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 to produce aggregates or thicken may be separately contained in the ink according to the present invention and the undercoat liquid and / or the white ink. it can. 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 inkjet recording apparatus of the present invention includes an undercoat liquid applying unit for applying an undercoat liquid on a recording medium, a white ink applying unit for applying a white ink containing a white pigment on the recording medium, and movement of the recording medium An undercoat liquid and a white ink which are disposed downstream of the undercoat layer applying means and the white ink applying means in a direction and impart energy to at least a part of the undercoat liquid and the white ink, thereby semi-curing the undercoat liquid and the white ink. The curing means and the undercoat liquid and the white ink curing means in the moving direction of the recording medium are disposed downstream of the semi-cured undercoat liquid and the white ink, and ink that can be cured by irradiation of active energy rays is ejected onto the semi-cured undercoat liquid and the white ink. And an image recording means for recording an image.

  In the present invention, it is preferable that the white ink applying unit is disposed downstream of the undercoat liquid applying unit in the moving direction of the recording medium, and applies the white ink on the applied undercoat liquid. This facilitates preventing contamination of the undercoat liquid applying means.

The ink jet recording apparatus of the present invention is further disposed downstream of the conveying means for conveying the recording medium and the image recording means in the conveying path of the recording medium to be conveyed, and an image is recorded by the image recording means. An active energy ray irradiating means for irradiating the activated recording medium with the active energy ray to further accelerate the curing of the undercoat liquid, the white ink, and the discharged ink (that is, the image) can be provided.
Further, the image recording means uses at least one line-type inkjet head that is arranged in parallel with a direction orthogonal to the conveyance direction of the recording medium and has a length corresponding to the entire recordable width of the recording medium. In the case of discharging ink, it is preferable.

-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. 3A, 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, although not shown, white ink is applied onto the undercoat liquid by the white ink applying means. The means for applying the white ink is not particularly limited, and may be either application or droplet ejection by an inkjet head. The applied white ink is mixed with the undercoat liquid to form a single undercoat layer.

Next, as shown in FIG. 3B, after the undercoat layer is semi-cured by irradiation with actinic rays from the light source W (semi-cured undercoat layer (semi-cured undercoat layer) 81a), the ink droplet 82a is formed. Drip. By this droplet ejection, as shown in FIG. 3C, ink droplets 82a are landed on the semi-cured undercoat layer 81a. At this time, since the surface of the semi-cured undercoat layer is not cured or is in a semi-cured state, it is easily compatible with the ink droplet 82a.
Further, as shown in FIG. 3 (d), in the region where the semi-cured undercoat layer 81a exists on the recording medium 16 and in the vicinity of the landing position of the first droplet 82a hit before, An ink 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. Although the force to join the ink droplet 82a and the ink droplet 82b works, the adhesion between the ink droplet and the surface of the undercoat layer is good and the inside of the undercoat layer that is in a cured state when trying to join Is a resistance against coalescence between the ink droplets, thereby suppressing 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. 3D, 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. 4 is an overall configuration diagram illustrating an example of an inline label printing machine (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 records an undercoat liquid film forming unit 100A1 for forming an undercoat liquid film on a recording medium (label) 16 that does not contain a colorant, and five types of ink containing a white pigment or a colorant. The drawing unit 100 </ b> A <b> 2 is provided that forms a desired image on the recording medium 16 by giving it to a predetermined position of the medium 16.
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), and 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. 4, 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 jetting.
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. 4, 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 includes ink droplet ejection heads 102W, 102Y, 102C, 102M, and 102K that eject ink onto the recording medium 16 in a single pass, a semi-curing light source 103P, and pinning light sources 103Y, 103C, and 103M, and finally. The drawing unit 100A2 includes the curing light source 103K, and the undercoat liquid film forming unit 100A1 includes the roll coater 102P. 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 orthogonal to the medium conveying direction (indicated by an arrow S in FIG. 4). It is a head. Further, in the figure, a semi-curing light source 103P is arranged downstream of 102W, and further downstream of each of 102Y, 102C, and 102M is a dot ejected with each color ink, and at least their dot shape. Pinning light sources 103Y, 103C, and 103M that are cured to such an extent that they do not collapse are arranged.

The roll coater and each of the droplet ejection heads 102W, 102Y, 102C, 102M, and 102K are provided with a coater and a plurality of nozzles (liquid ejection ports) over a length exceeding at least one side of the maximum size recording medium 16 targeted by the inkjet recording unit 100A. ) Are arranged.
Further, along the medium transport direction S, from the upstream side (left side in FIG. 4), white ink (W), yellow ink (Y), cyan ink (C), magenta ink (M), The droplet ejection heads 102W, 102Y, 102C, 102M, and 102K corresponding to the respective liquids are arranged in the order of the black ink (K), 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). Next, white ink is ejected from the white ink droplet ejection head 102W toward the undercoat liquid to form an undercoat layer, and the undercoat layer 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. 4, in the ink containing the radical polymerizable compound, the polymerization atmosphere by the final curing light source 103K is replaced with an inert gas (such as nitrogen) to suppress polymerization inhibition due to 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. The recording material on which ink jet recording has been performed passes up and down several times through a buffer 104 composed of several upper rollers 104a and several lower rollers 104b. 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 applies 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 other debris is peeled off and discarded by the debris removal unit 108. Discard as waste.

* Structure of the droplet ejection head FIG. 5A shows a droplet ejection head representing the droplet ejection heads 102W, 102Y, 102C, 102M, and 102K shown in FIG. It is a plane perspective view which shows an example of a basic whole structure.
The droplet ejection head 50 shown as an example in FIG. 5A 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. 5A, only a part of the pressure chamber units 54 is illustrated 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. 5B is a cross-sectional view taken along the line bb in FIG. 5A with respect to the pressure chamber unit 54 described above as one ejection element constituting the droplet ejection head 50.
As shown in FIG. 5B, each pressure chamber 52 communicates with a common liquid chamber 55 through a 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.

  5A 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 a 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. The pressure chamber unit 54 shown in FIG. 5B 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. In addition to the droplet ejection by the droplet ejection head, other means such as coating may be used as the white ink application unit.
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. 6 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 detecting means and the heater. The ink temperature at this time is preferably adjusted to 40 ° C to 80 ° C.

  The image recording apparatus 100 also 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 pause 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. 7 is a principal block diagram showing the system configuration of the image recording apparatus 100.
In FIG. 7, an 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 102W, 102Y, 102C, 102M, and 102K shown in FIG. 4, and the UV light source 103 represents the curing light sources 103P, 103Y, 103C, and 103M shown in FIG. , 103K, and the image detection unit 104c is the same as that described in FIG. 4 and has already been described.

  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 are 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. 6 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. 7, the second memory 152 is shown as being attached to the print control unit 150, but 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 12. 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. 5B), so that 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 white pigment dispersion W-1>
Mixing 16g of titanium oxide (JR-805 manufactured by Teica Co., Ltd.), 60.8g of 1,6-hexanediol diacrylate (HDODA; manufactured by Daicel Cytec Co., Ltd.), and 3.2g of BYK-111 (manufactured by BYK Chemie) And stirred with a stirrer for 1 hour. The mixture after stirring was dispersed with an Eiger mill to obtain pigment dispersion W-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 Liquid W-1 for Inkjet Recording Containing White Pigment>
Components of the following composition were mixed with stirring and dissolved to prepare inkjet recording liquid W-1 (white ink). The surface tension (25 ° C.) of the liquid W-1 for inkjet recording was 23 mN / m, and the viscosity (25 ° C.) was 15 mPa · s.
・ Pigment dispersion W-1 ... 9g
・ 1,6 hexanediol diacrylate (polymerizable compound) 2.7g
(HDODA; manufactured by Daicel Cytec Co., Ltd.)
・ The following polymerization initiator-1
(Irg907, manufactured by Ciba Specialty Chemicals)… 1.5g
-The following sensitizer-1
(Darocur ITX, manufactured by Ciba Specialty Chemicals)… 0.75g
-The following sensitizer-2
(Darocur EDB, Ciba Specialty Chemicals) 0.75g
・ Megafac F475 (Dainippon Ink Chemical Co., Ltd.) ... 0.3g

<Preparation of Cyan Pigment Dispersion P-1>
PB15: 3 (IRGALITE BLUE GLO; manufactured by Ciba Specialty Chemicals) 16 g, dipropylene glycol diacrylate (DPGDA; manufactured by Daicel Cytec Co., Ltd.) 48 g, and Solsperse 32000 (manufactured by Nippon Lubrizol Co., Ltd.) 16 g And stirred with a stirrer for 1 hour. The mixture after stirring was dispersed with an Eiger mill to obtain 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 mixed with stirring and dissolved to prepare inkjet recording liquid I-1 for cyan image recording. The surface tension (25 ° C.) of the liquid I-1 for inkjet recording was 27 mN / m, and the viscosity (25 ° C.) was 15 mPa · s.
<Composition>
-Pigment dispersion P-1 ... 2.16 g
・ Dipropylene glycol diacrylate (polymerizable compound) ... 9.84 g
(DPGDA; manufactured by Daicel Cytec Co., Ltd.)
・ The above 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 magenta pigment dispersion P-2>
In the preparation of the cyan dispersion P-1, the pigment PB15: 3 (IRGALITE BLUE GLO; manufactured by Ciba Specialty Chemicals) was changed to PV19 (CINQUASIA MAGENTA RT-355D; manufactured by Ciba Specialty Chemicals). A magenta dispersion P-2 was prepared in the same manner as the cyan pigment dispersion P-1, except that Solsperse 32000 (manufactured by Nippon Lubrizol Co., Ltd.) as a dispersant was changed to BYK168 (manufactured by Big Chemie). .

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

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

<Preparation of magenta inkjet recording liquid I-2>
Ingredients having the following composition were stirred, mixed and dissolved to prepare 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>
-The above pigment dispersion P-2 ... 5.86 g
・ Dipropylene glycol diacrylate (polymerizable compound): 6.14 g
(DPGDA; manufactured by Daicel Cytec Co., Ltd.)
・ The above polymerization initiator Irg907 ... 1.5g
(Ciba Specialty Chemicals)
・ Top 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>
Ingredients having the following composition were stirred, mixed and dissolved to prepare 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>
-The above-mentioned pigment dispersion P-3 ... 4.68 g
・ Dipropylene glycol diacrylate (polymerizable compound): 7.32 g
(DPGDA; manufactured by Daicel Cytec Co., Ltd.)
・ The above 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 an 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>
-Pigment dispersion P-4 above 3.3 g
・ Dipropylene glycol diacrylate (polymerizable compound) 8.7g
(DPGDA; manufactured by Daicel Cytec Co., Ltd.)
・ The above 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>
Components under the following composition were mixed with stirring and dissolved to prepare an undercoat liquid II-1 containing no acrylamide type polymer. 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 above 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

  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 semi-curing, which is an undercoating liquid curing means for semi-curing the undercoating liquid (not shown; a direction perpendicular to the transport direction of the recording medium (that is, the main scanning direction (width direction) when recording on the recording medium) ) And a head unit which is an image recording means for white ink (manufactured by TOSHIBA TEC; droplet ejection frequency: 6.2 KHz, number of nozzles: 636, nozzle density) : 300 npi (nozzle / inch, the same applies below), drop size: 6 pl to 42 pl, two variable heads arranged in 7 stages to 600 npi, and a full line array Parallel to the light source for undercoating and white ink semi-curing (in the direction orthogonal to the transport 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 arranged on the head) and a head unit (produced by Toshiba Tec Corporation; droplet ejection frequency: 6.2 KHz, number of nozzles: 636, nozzle density: 300 npi (nozzle / inch; The same applies to the following), an inkjet printer unit equipped with a drop size: 4 headsets in which two variable heads of 6 pl to 42 pl are arranged in 7 stages and 600 npi are arranged in a full line) A metal halide lamp that is an active energy ray irradiation means for further curing the undercoat layer on the recording medium and the recorded image. It was.

[Image Forming Method I]
As shown in FIG. 4, a roll coater and a light source for semi-curing undercoat liquid (not shown) are arranged in this order from the upstream side to the downstream side in the conveyance path through which the recording medium is conveyed. A head unit having a white ink ejection head, an undercoat liquid, and a white ink semi-curing light source are arranged in order so that the recording medium can be moved immediately below the head. Further downstream, a head unit having discharge heads of yellow, cyan, magenta, and black (black), and an ultra-high pressure for semi-curing ink respectively disposed on the transport direction side of the discharge heads of each color There is a mercury lamp. The head has a configuration in which each of the discharge heads of yellow, cyan, magenta, and black (black) 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 the present embodiment, the undercoating liquid II-1 is loaded into the experimental machine, and the inkjet recording liquid W-1 is loaded into the head unit, which is an image recording means for white ink, and the inkjet printer unit is filled with the above-described liquid. The four colors of ink-jet recording liquids I-1 to I-4 were loaded, and the following images were formed on the recording medium as follows. Note that PET50 (manufactured by Lintec) was used as a 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).

Next, the undercoat liquid is applied by a head loaded with the ink jet recording liquids I-1 to I-4, and the ink jet recording liquids I-1 to I- are applied to the recording medium on which the undercoat liquid is not semi-cured. 4 were ejected independently (no irradiation with the super-high pressure mercury lamp for semi-curing the ink), and the following monochromatic image was drawn. Subsequently, ultraviolet light (wavelength 365 nm) was irradiated (cured) with a metal halide lamp at a light intensity of 3000 mW / cm ² to be fixed.
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.

The monochrome image was drawn by ejecting each of the inkjet recording liquids I-1 to I-4 independently. In this case, the drawn image is a line drawn at 600 dpi in the main scanning direction and 150 dpi in the sub-scanning direction (using 1 drop: 6 pL droplet ejection), and an entire surface droplet ejection image (using 2 drops: 600 dpi in the main scanning direction and 600 dpi in the sub-scanning direction). 12 pL droplet ejection).
This image forming method is referred to as an image forming method I.

[Image Forming Method I ′]
In the image forming method I, before discharging the ink-jet recording liquids I-1 to I-4, a full hit image having a main scanning direction of 600 dpi and a sub-scanning direction of 600 dpi by a head unit which is an image recording unit for white ink. Image formation was carried out in the same manner as in image formation method I, except that it was applied (using 2 drops: 12 pL droplet ejection).

[Image Forming Method II]
In image forming method I, the same as image forming method I, except that after application of the undercoat liquid, exposure (light intensity 500 mW / cm ² ) was performed with an undercoat liquid semi-curing light source, and the applied undercoat liquid was semi-cured. Thus, image formation was performed.

[Image Forming Method II ′]
In the image forming method II, after the undercoat liquid is semi-cured, the entire unit hitting image having a main scanning direction of 600 dpi and a sub-scanning direction of 600 dpi by a head unit which is an image recording unit for white ink (using 2 drops: 12 pL droplet ejection) Image formation was carried out in the same manner as in image formation method II except that it was applied in the above.

[Image Forming Method III ′]
In image forming method II ′, after applying white ink, exposure (light intensity 500 mW / cm ² ) was performed with an undercoat liquid and a white ink semi-curing light source, and the applied white ink was semi-cured. Image formation was performed in the same manner as II ′.

[Image Forming Method IV ′]
In the image forming method III ′, image formation was performed in the same manner as in the image forming method III ′ except that the exposure with the light source for undercoating liquid semi-curing was not performed.

  The above image forming methods are summarized in Table 1.

[Practical image drawing]
Next, in each of the image forming methods, instead of drawing the monochrome image, a full color image of a person (woman) in the main scanning direction 600 dpi and the sub-operation direction 600 dpi was printed using all the colors. In this case, pinning exposure (light intensity 500 mW / cm ² ) was repeated for each color with an ultra-high pressure mercury lamp for semi-curing ink to semi-cur the ink. (Recording medium conveyance speed of 400 mm / s, 6 to 12 pL three-tone drawing. Anti-aliasing processing is performed). Thereafter, ultraviolet light (wavelength 365 nm) was irradiated with a metal halide lamp at a light intensity of 3000 mW / cm ² to fix the image.

The following measurements and evaluations were performed on the monochromatic images and practical images of each color obtained above. The results are shown in Tables 2 to 6 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. Cross-sectional observation
The obtained monochromatic image was cut with a microtome and observed with an optical microscope (optical microscope measuring microscope MM-40 manufactured by Nikon). A microtome (Leica Microtome RM2255) was used to obtain the sections.

-3. Measurement of transfer amount of semi-cured undercoat layer-
After applying the undercoat liquid and the white ink, and after performing exposure with the light source for undercoating liquid and the white ink semi-curing, and before ejecting the colored ink, the plain paper (Fuji Xerox Co., Ltd. copy paper C2, The product code V436) is pressed against the undercoat liquid and white ink with a uniform force (500 mN / cm ² ), and the mass of the transferred undercoat liquid and white ink is measured. The amount of semi-cured undercoat layer transferred was determined as the mass of the uncured portion of the ink (the amount of uncured liquid).

-4. Line width evaluation
The line width of the monochromatic image drawn on the line was measured by a dot analyzer DA6000 (manufactured by Oji Scientific Instruments).
When a line is drawn under the above conditions, the ideal line width is 40 μm.

-5. Evaluation of 600 dpi x 600 dpi whole surface droplet ejection image-
The entire droplet ejection image was visually observed and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: There was no white spot on the entire surface.
B: Slight white spots (5 μm or less) were observed.
C: A white portion (5 μm or more) was clearly observed.

-6. 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: The outline portion is slightly blurred.
C: The color is generally felt light.
D: Blurred image.

As shown in Tables 2 to 6, the image forming method IV ′ according to the present invention is the same as in the case of II in which the undercoat liquid is semi-cured in the case where the white ink is not used but the white ink is used. It has image forming properties. On the other hand, it can be seen that the image forming methods I ′ and II ′, which are comparative examples, do not have sufficient image forming properties on the entire surface, and the image forming method III ′ has insufficient thin line drawing properties.
When a practical image is drawn, the image forming methods I and II do not use white ink, so the color is felt light. In the image forming methods I ′ and II ′, the white color is felt and the color is felt light. It was. In addition, the image forming method III ′ felt blurred at the contour portion and the like because the thin line drawing performance was not sufficient.
On the other hand, it can be seen that when the image forming method IV ′ is used, a good practical image can be obtained because it is excellent in fine line drawing property and overall image forming property.

  The numerical values of “A (after polymerization) / A (before polymerization)” of the present invention in Tables 2 to 6 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 coating thickness unevenness, light source stability, etc.)

  Of the image obtained by the embodiment of the present invention, as shown in FIG. 1, a portion of the colored liquid cured product is exposed on the surface, and a part thereof is an undercoat layer. Dive into. Further, an undercoat layer was observed at the lower part of the colored liquid cured product. Furthermore, it was confirmed that a uniform colored liquid cured layer was formed.

Further, in the embodiment of the present invention, the maximum application amount per unit area of the applied colored liquid, each color colored liquid ^was in the range of ^{0.74mg / cm 2 ~0.87mg / cm 2} .
Furthermore, the semi-cured undercoat layer transfer amount in the embodiment of the present invention (mass per unit area of the uncured part) ^{was 0.10mg / cm 2 ~0.12mg / cm 2} .
Therefore, the relationship between the mass M (undercoat liquid) per unit area of the uncured portion of the undercoat liquid layer and the maximum mass m (colored liquid) discharged per unit area is “m (colored liquid) / 10 < M (undercoat liquid)) <m (colored liquid) / 5 ".

(Example 2)
In Example 1, a cyan ink jet recording liquid (I-1), a magenta ink jet recording liquid (I-2), a yellow ink jet recording liquid (I-3), an undercoat liquid (II-1), and a white pigment When each of the inkjet recording liquids (W-1, white ink) to be prepared is changed, the curing sensitivity Sc of each inkjet recording liquid and the curing sensitivity Su of the undercoat liquid and the white ink are changed by changing the addition amount of the initiator. The ink-jet recording liquid, the undercoat liquid, and the white ink were prepared so that the curing sensitivity ratio Sc / Su was the same as the curing sensitivity ratio shown in Table 7 below. Here, each ink-jet recording liquid was prepared so as to have the same curing sensitivity, and the undercoat liquid and the white ink had 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 forming method IV ′, the undercoat liquid and the white ink are applied, and the undercoat liquid and the white ink semi-curing light source are exposed (light intensity 500 mW / cm ² ). Semi-cured so as to be. 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. 150 dpi, 1 drop) was created. 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 7 below.

  From Table 7, when the ratio Sc / Su of the curing sensitivity of the ink and the undercoat liquid and the white ink is equal to or less than 5 times, the dot diameter of the black ink deposited on the undercoat liquid and the white ink and the tip It can be seen that the change in the dot diameter of the black ink deposited on the ink liquid ejected on the ink is reduced.

It is a cross-sectional schematic diagram showing the state of ink droplets when ink droplets are deposited on the undercoat layer. It is a cross-sectional schematic diagram for demonstrating the semi-hardened state in this invention. It is process drawing for demonstrating the image formation principle. 1 is a schematic cross-sectional view 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. 4, (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

20 Undercoat layer 22 Undercoat layer surface 24 Ink droplet 26 Base material 16 Recording medium 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 102W, 102Y, 102C, 102M, 102K Ink ejection head 103P Undercoat liquid and white ink 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 Rear Processing unit 105 Varnish coater 106 Label cutting unit 106a Marking reader 106b Die cutter driver 106c Die cutter 106d Opposing roller 106e Bladed plate 107 Branch roller 108 Waste removal Label 109 Winding unit 50 Droplet ejection head 50a Discharge surface 51 Nozzle 52 Pressure chamber 53 Liquid supply port 54 Pressure chamber unit 55 Common liquid chamber 56 Vibration plate 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 Transport motor 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 detector 137 Environmental humidity detector 138 Medium temperature detector,
142 Liquid Supply Unit 144 Liquid Supply Driver 150 Print Control Unit 154 Head Driver 156 Light Source Driver

Claims (11)

An undercoat liquid applying step of applying an undercoat liquid onto the recording medium;
A white ink application step of applying a white ink containing a white pigment on a recording medium;
A curing step of semi-curing the applied undercoat liquid and the white ink;
And a recording step of recording an image on the semi-cured undercoat liquid and the white ink by ejecting ink that can be cured by irradiation with an active energy ray.   The inkjet recording method according to claim 1, wherein the white ink application step is a step of applying white ink on the applied undercoat liquid after the undercoat liquid application process.   2. The undercoat liquid applying step is a step of applying an undercoat liquid on the recording medium and / or the applied white ink after the white ink applying step. Inkjet recording method.   The ink jet recording method according to any one of claims 1 to 3, wherein the undercoat liquid and / or the white ink is curable by irradiation with an active energy ray.   The ink jet recording method according to any one of claims 1 to 4, wherein the undercoat liquid and / or the white ink further contains a radical polymerizable composition.   6. The recording process according to claim 1, wherein the recording step includes a step of recording an image using an ink set including multicolored inks and semi-curing at least one color of the ejected ink. The inkjet recording method according to any one of the above.   The inkjet recording method according to claim 1, further comprising a step of further accelerating curing of the undercoat liquid, the white ink, and the discharged ink.   The ink jet recording method according to claim 1, wherein the curing sensitivity of the ink is equal to or higher than the curing sensitivity of the undercoat liquid and the white ink. Undercoat liquid applying means for applying an undercoat liquid onto a recording medium;
A white ink applying means for applying a white ink containing a white pigment on a recording medium;
Arranged downstream of the undercoat liquid applying means and the white ink applying means in the moving direction of the recording medium, energy is applied to at least a part of the undercoat liquid and the white ink, and the undercoat liquid and the white ink are semi-cured. An undercoat liquid and a white ink curing means,
An image is formed by ejecting ink curable by irradiation of active energy rays onto the semi-cured undercoat liquid and white ink disposed downstream of the undercoat liquid and white ink curing means in the moving direction of the recording medium. And an image recording means for recording the image.   10. The white ink applying unit is disposed downstream of the undercoat liquid applying unit in the moving direction of the recording medium, and applies white ink on the applied undercoat liquid. Inkjet recording apparatus. Means for conveying the recording medium;
An active energy ray is applied to the recording medium that is disposed downstream in the conveyance direction of the image recording means in the conveyance path of the recording medium to be conveyed, and on which the image is recorded by the image recording means,
An active energy ray irradiation means for further promoting the curing of the undercoat liquid, the white ink and the discharged 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 ink jet recording apparatus according to claim 9, wherein the ink is ejected.

Images