JP2008246718A - Method for detecting droplet size - Google Patents

Abstract

Disclosed is a method for detecting a droplet ejection point size which can be accurately and easily calculated.
An ink droplet is continuously ejected from an ejection portion, and an ink liquid is disposed at a position adjacent to and in contact with a droplet ejection point formed by ink droplets ejected from the same ejection portion. A droplet ejection line forming step for forming droplet ejection points by forming droplets by forming droplets and connecting droplet ejection points formed by one ejection unit, and formed on a recording medium Based on the droplet ejection line width detection step for detecting the droplet ejection line width from the read image and the droplet ejection line formation conditions, the droplet ejection lines corresponding to the formation conditions prepared in advance are used. Based on the calculated condition reading step for reading the relationship between the width of the droplet and the size of the droplet ejection point, and the relationship between the width of the read droplet ejection line and the size of the droplet ejection point, the droplet ejection point is calculated from the detected width of the droplet ejection line. The above-mentioned problem is solved by providing a calculation step for calculating the size.
[Selection] Figure 15

Description

  The present invention relates to a droplet ejection point size detection method for detecting a droplet ejection point size of an ink droplet ejected from an ejection unit of an image recording apparatus including an ejection unit that ejects ink droplets.

As a method for recording an image on a recording medium, there is an ink jet drawing method in which ink droplets are ejected in accordance with an image signal, landed on the recording medium, and an image is recorded.
As an image drawing apparatus using such an ink jet drawing method, an ejection unit (nozzle) for ejecting ink droplets is arranged in a line corresponding to the entire area of one side of a recording medium, and the recording medium is There is a full-line head type image drawing apparatus that records an image over the entire area of a recording medium by conveying in a direction orthogonal to the ejection unit.
The full line head type image drawing apparatus can draw an image on the entire area of the recording medium by transporting the recording medium without moving the ejection section, and can increase the recording speed.

Here, the image drawing apparatus recorded on the recording medium by causing variations in the size of the ejected droplets, that is, the size of the droplet ejection points to be formed due to variations in manufacturing of the ejection unit and changes over time. There is a problem that streaks and unevenness occur in the image.
As a method for detecting the size of a droplet ejection point for detecting a discharge portion that forms a droplet ejection point having a size different from a desired size that causes image streaks and unevenness, Patent Document 1 discloses. There is a way.

Patent Document 1 discloses a dot position detection device that detects a dot position of an ink jet printer, and predicts a dot position in an image formed by the ink jet printer, and is predicted by the dot position prediction means. A dot position calculation unit that calculates the position of the dot in the image based on the dot position, and an ideal position that calculates an ideal position where the dot should be formed based on the dot position calculated by the dot position calculation unit Calculating means, and dot position deviation calculating means for calculating a deviation amount between the dot position calculated by the dot position calculating means and the ideal position of the dot calculated by the ideal position calculating means. A dot position detection device is described.
In this patent document 1, in order to calculate the dot position, the outer edge of the dot (that is, the droplet ejection point) is detected by detecting the dot density along two straight lines that pass through the ideal position of the dot and are orthogonal to each other. That is, the calculation of size) is also described.

Patent Document 2 describes that the volume of ink droplets is changed by changing the magnitude and pulse width of a voltage pulse applied to a resistor of an ejection portion of an inkjet printer. It also describes that the drawn line width is measured, the volume of ink droplets is changed according to the result, and the printing density is kept constant.
This Patent Document 2 describes that the drawn line width is measured, but the specific method is not described, and the detection of the size of the droplet ejection point is also described. Absent.

  In addition, the line head type image drawing apparatus also has a problem that streaks and unevenness occur in an image recorded on a recording medium due to variations in manufacturing such as positional deviation of the ejection unit.

  As a method for reducing such streaks and unevenness, Patent Document 3 detects an abnormal nozzle whose droplet flying direction is deviated, and a part of dots ejected from a nozzle adjacent to the abnormal nozzle has a size. An image forming apparatus is described in which large compensation dots are ejected, a gap formed between the dot rows is filled with the compensation dots, and streaks and unevenness due to the gaps are reduced.

JP 2006-142546 A Japanese Patent No. 3368251 Japanese Patent Laid-Open No. 2005-70956

Here, for example, in an ink jet drawing apparatus that draws an image with a resolution of 300 dpi (dot per inch) to 650 dpi, the interval between ink droplet ejection positions is 85 to 42.5 μm. For this reason, that is, as the resolution of the ink jet drawing apparatus increases, the interval between the ink droplet ejection positions becomes shorter.
For this reason, in order to efficiently and accurately reduce streaks and unevenness, it is necessary to more accurately detect the size of the droplet ejection point formed by landing of the ink droplets ejected from the ejection unit.
Specifically, in order to detect the unevenness due to the size of the droplet ejection point, the size of the droplet ejection point, that is, the size of the landed ink droplet is different from the desired size, also causes the unevenness. It is necessary to accurately detect the size of the droplet ejection point.

In addition, when forming correction dots as in the image forming apparatus described in Patent Document 3, droplet ejection points having a plurality of sizes are formed from one ejection unit. Furthermore, there is also an image drawing apparatus that selectively forms a plurality of droplet ejection points from one ejection unit in order to draw an image with higher definition on a recording medium.
As described above, when a plurality of types of droplet ejection points are formed, in order to perform an appropriate correction even when streaks or unevenness occurs in the image, in particular, in order to form a high-quality image, the droplet ejection that is formed It is necessary to accurately detect the size of the points.

On the other hand, the dot position detection device described in Patent Document 1 can calculate the dot size by calculating the outer edge (outer shape, edge, and boundary line) of the dot. In order to accurately calculate the size of the dots, it is necessary to read the dot density distribution, that is, the histogram, with a high-resolution image reader. In addition, since the calculation is performed with one dot, there is a problem that the calculation accuracy is low.
In the method described in Patent Document 2, the line width is detected, but the size of the droplet ejection point cannot be detected.
Patent Document 3 describes a method for reducing streaks and unevenness at the time of recording, but does not particularly describe a method for calculating the size of dot ejection points.

An object of the present invention is to provide a droplet ejection point size detection method capable of solving the above-mentioned problems based on the prior art and calculating the droplet ejection spot size accurately and easily.
Further, in order to reduce streaks and unevenness, it is necessary to accurately detect the positional deviation of the ink droplet landing position (hereinafter also referred to as “droplet point”).
Therefore, another object of the present invention is to provide a droplet ejection point size detection method capable of accurately and easily calculating the interval between droplet ejection points and the deviation of the droplet ejection point position.

In order to solve the above-described problems, the present invention provides a droplet ejection point size of an ink droplet that is ejected from the ejection unit of a recording head including at least one ejection unit that ejects ink droplets and landed on a recording medium. A method for detecting a droplet ejection size for detecting
Ink droplets are continuously ejected from the ejection unit, and the ink droplets are disposed adjacent to and in contact with the droplet ejection point formed by the ink droplets ejected from the same ejection unit. A droplet ejection line forming step for forming a droplet ejection point by landing and forming a droplet ejection line formed by connecting the droplet ejection points formed by one of the ejection units;
A droplet ejection line width detecting step for reading the droplet ejection line formed on the recording medium by the droplet ejection line forming step and detecting the width of the droplet ejection line from the read image;
A calculation condition reading step for reading out the relationship between the width of the droplet ejection line and the size of the droplet ejection point in accordance with the formation condition prepared in advance based on the formation condition of the droplet ejection line in the droplet ejection line formation step When,
A droplet ejection point size comprising: a calculation step of calculating the size of the droplet ejection point from the width of the detected droplet ejection line based on the relationship between the width of the read droplet ejection line and the size of the droplet ejection point A detection method is provided.

Here, the droplet ejection point size detection method of the present invention measures the relationship between the droplet ejection line width and the droplet ejection point size for each droplet ejection line formation condition, and performs each droplet ejection line formation condition. Preferably, the method includes a step of calculating a relationship between the width of the droplet ejection line and the size of the droplet ejection point.
In addition, it is preferable that the formation condition of the droplet ejection line is the number of ink droplets ejected from the ejection unit in order to form one droplet ejection point.

The droplet ejection line width detecting step includes
An image reading step for reading an image composed of the droplet ejection lines formed on the recording medium as a read image with a direction substantially orthogonal to the droplet ejection lines formed by the ejection unit as a reference direction;
From the read image, for each of the droplet ejection lines, one end position and the other end position in the reference direction of the droplet ejection line are ejected at predetermined intervals in a direction orthogonal to the reference direction. A droplet ejection line end position information calculating step for calculating as end position information;
From the droplet ejection line end position information, an approximate straight line connecting a plurality of the one end position and an approximate straight line connecting the plurality of the other end positions, the inclination of the approximate straight line is a total droplet ejection line. An approximate straight line calculation step for calculating for each droplet ejection line as common,
A droplet ejection line width calculating step for calculating the width of the droplet ejection line formed by each of the ejection units from the calculated approximate line of one end and the approximate line of the other end for each ejection unit; It is preferable to have.
In the approximate line calculation step, the approximate line is preferably calculated by a least square method.

In the recording head, it is preferable that a plurality of ejection portions are arranged in a row, and the droplet ejection line is formed for each ejection portion.
In the droplet ejection line forming step, a plurality of ink droplets are ejected from each of the ejection units while relatively moving the recording medium and the ejection unit in a direction substantially perpendicular to the arrangement direction of the ejection units. It is preferable that a droplet ejection line in which a plurality of droplet ejection points are continuously arranged on the recording medium in a direction substantially orthogonal to the arrangement direction of the ejection units is formed for each ejection unit.
In the droplet ejection line forming step, the droplet ejection line is preferably formed in a non-contact manner with another adjacent droplet ejection line.
Further, in the droplet ejection line forming step, the droplet ejection lines formed on the recording medium may be formed at different positions in a direction orthogonal to the arrangement direction of the ejection units according to the arrangement position of the ejection units. preferable.
In the droplet ejection line forming step, after the ink droplets are ejected from every other ejection unit among the plurality of ejection units and the droplet ejection line is formed on the recording medium, the remaining droplet ejection lines are formed. It is preferable that ink droplets are ejected from the ejection part to form droplet ejection lines on the recording medium.
Moreover, it is preferable that the said droplet ejection line formation step forms the said droplet ejection line with the width | variety which does not contact an adjacent droplet ejection line.

  Further, the interval between the droplet ejection point of the ejection unit and the droplet ejection point of the other ejection unit is calculated from the approximate straight line at one end position calculated for each droplet ejection line and the approximate straight line at the other end position. It is preferable to have a step of calculating the interval between droplet ejection points.

According to the present invention, the size of the droplet ejection point can be detected more accurately by detecting the droplet ejection line size from the width of the droplet ejection line based on the formation conditions of the droplet ejection line. Moreover, by detecting from the droplet ejection line, it is possible to detect more accurately than when detecting from one droplet ejection point.
In addition, by detecting the positions of both ends of the droplet ejection line at predetermined intervals and calculating the size of the droplet ejection point, the size of the droplet ejection point can be accurately detected. Further, even when the image of the droplet ejection line is read at a low resolution, the size of the droplet ejection point can be accurately detected.
Furthermore, by forming a droplet ejection line for each discharge unit, detecting the position of the droplet ejection line at predetermined intervals, calculating an approximate straight line of each droplet ejection line, and calculating a positional deviation of the droplet ejection point interval The interval between the droplet ejection points can be accurately calculated, and the positional deviation of the droplet ejection points can also be accurately detected. Further, even when the image of the droplet ejection line is read at a low resolution, the positional deviation of the droplet ejection point can be accurately detected.

  A droplet ejection point size detection method according to the present invention will be described in detail based on an embodiment shown in the accompanying drawings.

First, an example in which the droplet ejection spot size detection method of the present invention is used in a digital label printing apparatus using an ink jet drawing apparatus will be described.
1 is a schematic configuration diagram showing an example of a digital label printing apparatus 100, FIG. 2 is a longitudinal sectional view of a recording medium for label printing used in the digital label printing apparatus 100 shown in FIG. 1, and FIG. FIG. 2 is an enlarged schematic perspective view showing a drawing unit 112 of the digital label printing apparatus 100 shown in FIG. 1. 4A is a front view showing an arrangement pattern of the ejection portions 60 of the recording head 136K, and FIG. 4B is an enlarged cross-sectional view showing one ejection portion 60 of the recording head 136K. FIG. 5 is a schematic diagram showing a configuration of an ink supply system and a head peripheral portion in the ink jet drawing apparatus 100, and FIG. 6A is a cross-sectional view showing a main part of a recording medium having an uneven surface. FIG. 6B is a cross-sectional view showing a main part of the recording medium pressed with foil without smoothing, and FIG. 6C shows the recording medium pressed with foil smoothed by the smoothing part. It is sectional drawing which shows the principal part.

The digital label printing apparatus 100 of the present embodiment is an ultraviolet curable inkjet digital label printing apparatus using an ultraviolet curable ink that is an active energy (active light) curable ink, and has a foil stamping unit and is capable of foil stamp printing. It is a label printing device.
Here, foil press printing is a method of pressing a foil such as a gold foil, a silver foil, a color foil, etc. on a book cover or spine against a mating member with a heated letterpress to heat-press (foil press) the foil. Also called a hot stamp.
Further, as shown in FIG. 2, the recording medium P of the present embodiment has a two-sheet structure in which an adhesive sheet 180 having a back surface coated with an adhesive 180a is superposed on a release paper 182 as a mount.

  As shown in FIG. 1, the digital label printing apparatus 100 basically includes a transport unit 110, an undercoat unit 111, a drawing unit 112, an image reading unit 114, a smoothing unit 116, a foil pressing unit 118, a label. A punching part 120 and a control part 121 are provided. The control unit 121 controls various operations of the transport unit 110, the undercoat unit 111, the drawing unit 112, the image reading unit 114, the smoothing unit 116, the foil pressing unit 118, and the label removing unit 120.

  Here, the transport unit 110 transports a continuous paper-like recording medium P for label printing (hereinafter referred to as “recording medium P”) in a certain direction (from left to right in FIG. 1). The undercoat unit 111, the drawing unit 112, the image reading unit 114, the smoothing unit 116, the foil pressing unit 118, and the label removing unit 120 are arranged in the order of the transport direction of the recording medium P, that is, from upstream to downstream. Part 112, image reading part 114, smoothing part 116, foil pressing part 118, and label removing part 120 are arranged in this order.

The conveyance unit 110 includes a supply roll 122, conveyance roller pairs 124, 126, 128, 130, and 132, and a product winding unit 134.
A continuous paper-like recording medium P for label printing is wound around the supply roll 122 in a roll shape. The conveyance roller pairs 124, 126, 128, 130, and 132 are driven to rotate by a conveyance motor (not shown), and the recording medium P is fed out from the supply roll 122, and the undercoat section 111. The drawing unit 112, the image reading unit 114, the smoothing unit 116, the foil pressing unit 118, and the label removing unit 120 are sequentially conveyed.
The product winding unit 134 is disposed on the most downstream side in the conveyance direction of the recording medium P, and is conveyed by the conveyance roll pairs 124, 126, 128, 130, 132, and the undercoat unit 111, the drawing unit 112, the image reading unit 114, The recording medium P that has passed through the smoothing unit 116, the foil pressing unit 118, and the label removing unit 120 is taken up.

  The undercoat unit 111 includes an application roll 202 that applies the undercoat liquid to the recording medium P, a driving unit 204 that rotates the application roll 202, a blade 206 that adjusts the amount of the undercoat liquid that adheres to the application roll 202, and an application roll. The undercoat liquid is irradiated by irradiating the recording medium P on which the undercoat liquid is applied with the positioning unit 210 that supports the record medium P so that the record medium P is in a predetermined position with respect to 202 and the undercoat layer is formed. An undercoat liquid semi-cured portion 216 that makes the (undercoat layer) semi-cured.

The coating roll 202 is disposed on the downstream side of the supply roll 122 in the conveyance path of the recording medium P and in contact with the surface of the recording medium P on which the image is formed.
The application roll 202 is a roll longer than the width of the recording medium P, and is a so-called gravure roller in which concave portions are uniformly formed on the surface (outer peripheral surface) at regular intervals.
Here, the shape of the recess formed in the coating roll 202 is not particularly limited, and may be various shapes such as a circle, a rectangle, a polygon, and a star. Moreover, you may form a recessed part in groove shape in the perimeter of an application | coating roll.

The drive unit 204 is connected to the application roll 202 and rotates the application roll 202 in a direction opposite to the conveyance direction of the recording medium P (clockwise in FIG. 1).
The driving method by the driving unit 204 is not particularly limited, and various methods such as gear driving, pulley driving, belt driving, direct driving, and the like can be used.

The blade 206 is disposed in contact with the surface of the coating roll 202 on the downstream side in the conveyance direction of the recording medium P.
In addition, an undercoat liquid is stored in a space (hereinafter referred to as “storage section 208”) formed in an upper portion of a contact portion (contact portion) between the coating roll 202 and the blade 206. The reservoir 208 is supplied with an undercoat liquid from a supply tank (not shown) as necessary.
Accordingly, the application roll 202 is immersed in the undercoat liquid in the storage unit 208 and is in contact with the recording medium P.
The blade 206 immerses the coating roll 202 in the storage unit 208 to scrape off the undercoating liquid adhering more than necessary from the adhering undercoating liquid, so that the amount of the undercoating liquid adhering to the coating roll 202 is fixed. . Specifically, the blade 206 scrapes off the undercoat liquid adhering to other parts of the application roll 202 except for the undercoat liquid held in the recesses formed on the surface of the application roll 202.
As a result, the undercoat liquid held in the portion of the coating roll 202 that contacts the recording medium P can be only the undercoat liquid held in the recess. That is, the amount of the undercoat liquid that comes into contact with the recording medium P can be made constant.

The positioning unit 210 includes positioning rolls 212 and 214, and supports the recording medium P so that the recording medium P at a position in contact with the coating roll 202 is at a predetermined position. That is, the positioning unit 210 sets the transport path of the recording medium P at a position where the coating roll 202 and the recording medium P are in contact with each other to a predetermined position.
The positioning roll 212 is on the side opposite to the surface on which the image of the recording medium P is formed (the surface on which the undercoat liquid is applied) and in the transport direction of the recording medium P, It is arranged between the coating roll 202.
The positioning roll is between the coating roll 202 and an undercoat liquid semi-curing portion 216 described later on the surface side opposite to the surface on which the image of the recording medium P is formed and in the transport direction of the recording medium P. Is arranged.
That is, the positioning rolls 212 and 214 are sandwiched between the coating roll 202 in the conveyance direction of the recording medium P on the opposite side of the coating roll 202 via the recording medium P, that is, upstream of the coating roll 202. And arranged on the downstream side.
The positioning rolls 212 and 214 support the recording medium P from the surface opposite to the surface on which the image of the recording medium P is formed.

The undercoat unit 111 has the above-described configuration, and the drive unit 204 rotates the application roll 202 in the direction opposite to the conveyance direction of the recording medium P. The surface of the rotating coating roll 202 is immersed in the undercoat liquid stored in the storage unit 208, and then comes into contact with the blade 206, so that the amount of the undercoat liquid held on the surface is made constant. Thereafter, the portion where the amount of the undercoat liquid of the application roll 202 is a constant amount is brought into contact with the recording medium P by rotating the application roll 202, and the undercoat liquid is applied onto the recording medium P. In this way, by applying the undercoat liquid to the recording medium P by rotating the coating roll 202 in the direction opposite to the conveyance direction of the recording medium P, the coating roll 202 is smoothed and has a good coated surface shape without unevenness. A layer of undercoat liquid (hereinafter also referred to as “undercoat layer”) can be formed on the recording medium P. The coating roll 202 that has come into contact with the recording medium P further rotates and is immersed again in the undercoat liquid of the storage unit 208.
In this way, the undercoat unit 111 rotates the application roll 202 to apply the undercoat liquid to the surface of the recording medium P, thereby forming an undercoat layer on the surface of the recording medium P.

  Here, the undercoat layer U with improved surface shape can be formed on the recording medium P by rotating the coating roll 202 in the direction opposite to the conveyance direction of the recording medium P. That is, an undercoat layer having a small surface roughness can be formed on the recording medium P, thereby forming a high-quality image.

The undercoat liquid semi-curing unit 216 includes a UV lamp and is disposed to face the conveyance path of the recording medium P. Here, the UV lamp is a light source that emits ultraviolet light, and various ultraviolet light sources such as a metal halide lamp and a high-pressure mercury lamp can be used.
The undercoat liquid semi-curing portion 216 irradiates the entire area in the width direction of the recording medium P passing through the opposing position with ultraviolet rays.

  The undercoat liquid semi-curing unit 216 irradiates the recording medium P with the undercoat liquid applied to the surface passing through the opposing position, and puts the undercoat liquid applied on the surface of the recording medium P into a semi-cured state. To do. That is, the undercoat liquid semi-curing unit 14 sets the undercoat liquid applied on the recording medium P to a semi-cured state. The state where the undercoat liquid is semi-cured will be described in detail later.

The drawing unit 112 includes a recording head unit 135, an ink storage / loading unit 137, and an ultraviolet irradiation unit 138.
The recording head unit 135 has recording heads (ink jet heads) 136W, 136C, 136M, 136Y, and 136K, similar to the recording head unit 136 described above, and is positioned at a position facing the conveyance path of the recording medium P, that is, ink ejection. The front end of the part is arranged to face the recording medium P.

The recording heads 136W, 136C, 136M, 136Y, and 136K are ink jet heads that discharge white (W), cyan (C), magenta (M), yellow (Y), and black (K) ink from the discharge unit, respectively. The recording head 136W, the recording head 136C, the recording head 136M, the recording head 136Y, and the recording head 136K are arranged in this order from upstream to downstream in the conveyance direction of the recording medium P. The recording heads 136 </ b> W, 136 </ b> C, 136 </ b> M, 136 </ b> Y, and 136 </ b> K are connected to the ink storage / loading unit 137 and the control unit 121.
As shown in FIG. 3, the recording heads 136W, 136C, 136M, 136Y, and 136K include a plurality of recording heads in a region where the width in the direction orthogonal to the conveyance direction of the recording medium P exceeds the maximum width of the recording medium P to be conveyed. This is a full-line type inkjet head in which ejection portions (nozzles) are arranged in a line. The structure of the inkjet head will be described in detail later together with the relationship with the ink storage / loading unit 137.

As in this embodiment, the recording head is a full-line type, so that the recording medium P and the drawing unit 112 are relatively 1 in the direction (sub-scanning direction) orthogonal to the extending direction of the ejection unit of the recording head. The image can be recorded on the entire surface of the recording medium P by being moved once (that is, by one scanning). Thereby, it is possible to perform high-speed printing as compared with the shuttle type head in which the recording head reciprocates in the main scanning direction, and productivity can be improved.
Further, a color image can be formed on the recording medium P by ejecting the color inks from the recording heads 136W, 136C, 136M, 136Y, and 136K while transporting the recording medium P.

The ink storage / loading unit 137 includes an ink supply tank that stores ink of a color corresponding to each of the recording heads 136W, 136C, 136M, 136Y, and 136K.
As the ink supply tank, for example, a system that replenishes ink into a tank from a replenishing port (not shown) or a cartridge system that replaces the entire tank when the ink remaining amount is low can be used.
Each ink supply tank of the ink storage / loading unit 137 communicates with each recording head 136W, 136C, 136M, 136Y, 136K via a pipe line (not shown), and each recording head 136W, 136C, 136M, 136Y, 136K. Ink is supplied.

  Next, the structure of the recording heads 136W, 136C, 136M, 136Y, and 136K will be described. Here, since the recording heads 136W, 136C, 136M, 136Y, and 136K have the same configuration except for the color of the ejected ink, the recording head 750K will be described below as a representative.

4A is a front view showing an arrangement pattern of the ejection portions 60 of the recording head 136K, and FIG. 4B is an enlarged cross-sectional view showing one ejection portion 60 of the recording head 136K.
As shown in FIG. 4A, in the recording head 136K, a plurality of ejection units 60 are arranged in a line at regular intervals.

  As shown in FIG. 4B, one ejection unit 60 includes an ink chamber unit 61 and an actuator 66. Further, the ink chamber unit 61 is connected to the common flow path 65. The common flow path 65 is connected to the ink chamber units 61 of the plurality of ejection units 60.

The ink chamber unit 61 has a nozzle 62, a pressure chamber 63, and a supply port 64.
The nozzle 62 is an opening for ejecting ink droplets, and has one end opened on a surface facing the recording medium P and the other end connected to the pressure chamber 63.
The pressure chamber 63 has a rectangular parallelepiped shape whose plane shape perpendicular to the direction in which the ink droplets are ejected, and both corners on the diagonal are connected to the nozzle 62 and the supply port 64.
The supply port 64 has one end connected to the pressure chamber 63 and the other end communicating with the common flow path 65.

The actuator 66 is disposed on a surface (top surface) opposite to the connection surface of the pressure chamber 63 with the nozzle 62 and the supply port 64, and includes a pressure plate 67 and an individual electrode 68.
The actuator 66 deforms the pressure plate 67 by applying a driving voltage to the individual electrode 68.

An ink discharge method of the discharge unit 60 will be described.
Ink is supplied from the common flow path 65 to the pressure chamber 63 and the nozzle 62 via the common port 64.
When a drive voltage is applied to the individual electrode 68 while the pressure chamber 63 and the nozzle 62 are filled with ink, the pressure plate 67 is deformed, the pressure chamber 63 is pressurized, and ink is ejected from the nozzle 62. The By driving the actuator 66 in this way, ink droplets can be ejected from the nozzle 62.
When ink is ejected, new ink is supplied from the common flow path 65 through the supply port 64 to the pressure chamber 63.

  In addition, the arrangement structure of the discharge part of this invention is not limited to the example of illustration. In this embodiment, a method of ejecting ink droplets by deformation of an actuator 66 typified by a piezo element (piezoelectric element) is adopted. However, the present invention is not limited to this, and a method of ejecting ink is particularly used. The present invention is not limited, and various methods such as a thermal jet method in which bubbles are generated by heating ink with a heating element such as a heater and ink droplets are ejected by the pressure can be applied instead of the piezo method.

Next, the relationship between the recording head unit 135 and the ink storage / loading unit 137 will be described in more detail.
FIG. 5 is a schematic diagram illustrating a configuration of an ink supply system and a head peripheral portion in the digital label printing apparatus 100. Since the relationship between the recording heads 136W, 136C, 136M, 136Y, and 136K and the ink storage / loading unit 137 is the same except for the type of ink, the recording head 136K and the ink storage will be described below. Only the relationship with the / loading unit 137 will be described, and the description of the relationship between the recording heads 136W, 136C, 136M, and 136Y and the ink storage / loading unit 137 will be omitted.

The ink supply tank 70 is a tank that stores a color corresponding to the recording head 136 </ b> K, that is, black ink, and is disposed inside the ink storage / loading unit 137. The recording head 136K and the ink supply head 70 are connected by a supply pipe.
A filter 72 is provided in the middle of the flow path connecting the ink supply tank 70 and the recording head 136K to remove foreign substances and bubbles. The filter mesh size of the filter 72 is preferably equal to or smaller than the nozzle diameter (generally about 20 μm).

  A sub tank is preferably provided in the vicinity of the recording head 136K or integrally with the recording head 136K. By providing the sub-tank, it is possible to obtain a damper effect that prevents fluctuations in the internal pressure of the head, and to improve refilling.

  Further, as shown in FIG. 5, the digital label printing apparatus 100 includes a cap 74, a suction pump 77 and a collection tank 78 as means for preventing the nozzle 62 from drying or preventing an increase in ink viscosity near the nozzle, and a recording. A cleaning blade 76 is provided as a cleaning means for the nozzle surface of the head 136K, that is, the surface where the opening of the nozzle 62 is formed.

  The maintenance unit including the cap 74 and the cleaning blade 76 can be moved relative to the recording head 50 by a moving mechanism (not shown), and is moved from a predetermined retracted position to a maintenance position below the recording head 136K as necessary. .

The cap 74 is disposed at a position facing the recording head 136K in the maintenance position, and is supported so as to be movable up and down relative to the recording head unit 135 by a lifting mechanism (not shown).
The cap 74 is raised to a predetermined ascending position by a lifting mechanism (not shown) when the power is turned off or during standby for printing, is in close contact with the recording head 136K, and covers the nozzle surface of the recording head 136K with the cap 74.
In this way, the cap 74 covers the nozzle surface of the recording head 136K and seals it, so that the ink in the nozzle is dried and fixed, and the ink solvent evaporates to increase the ink viscosity. Can be prevented.

Alternatively, the cap 74 may be attached to the recording head 136K at the time of maintenance or at regular intervals, and the actuator 66 may be driven to eject ink from the nozzles 62.
In the recording head 136K, when the specific nozzle 62 is used less frequently during drawing or standby, and ink is not ejected for a certain period of time, the ink solvent near the nozzle evaporates and the ink viscosity increases. As a result, the ink may not be ejected from the nozzle 62, but the ink is preliminarily ejected to the cap 74 (purge, idle ejection, spit) and the deteriorated ink in the nozzle 62 (near the nozzle whose viscosity has increased). Ink) can be discharged from the nozzle 62. Thereby, it is possible to prevent the nozzle 62 from being clogged with ink, and it is also possible to prevent the nozzle 62 from having a different ink viscosity and change in ejection characteristics. Thereby, ink droplets can be stably discharged.

The suction pump 77 has one end connected to the cap 74 and the other end connected to the recovery tank 78. The cap 74 is attached to the recording head 136K, and suction is performed by the suction pump 77 in a state where the cap 74 and the recording head 136K are in close contact with each other, whereby the ink in the nozzle 62 is sucked out. Further, the ink sucked by the suction pump 77 is sent to the collection tank 78.
Thus, by sucking ink by the suction pump 77, for example, bubbles are mixed into the ink (in the pressure chamber 63) in the recording head 136K, and the ink can be ejected from the nozzle even if the actuator 66 is operated. Even if it is not possible, the ink in the pressure chamber 63 (ink mixed with bubbles) can be removed by suction by sucking the ink with the suction pump 67. That is, the ink droplets can be ejected.
The suction by the suction pump 77 is preferably performed in order to suck out the deteriorated ink whose viscosity has been increased (solidified) even when the ink is initially loaded into the head or when the ink is used after being stopped for a long time.
Further, since the suction by the suction pump 77 is performed on the entire ink in the pressure chamber 63, the amount of ink consumption increases. Accordingly, when the increase in the viscosity of the ink is small, it is preferable to discharge the ink droplets (preliminary discharge) onto the cap 74 described above.

The cleaning blade 76 is formed of an elastic member such as rubber, and is arranged in contact with the nozzle surface of the recording head 136K during maintenance. The cleaning blade 76 is connected to a blade moving mechanism (wiper) (not shown), and is slid on the nozzle surface by the blade moving mechanism. As the cleaning blade 76 slides on the nozzle surface, ink droplets and foreign matter adhering to the nozzle surface are wiped off. That is, the nozzle surface can be cleaned.
In addition, it is preferable to perform preliminary ejection in order to prevent foreign matter from being mixed into the nozzle 62 by the blade when the dirt on the ink ejection surface is cleaned by the blade mechanism.

Returning to FIG. 1, another part of the digital label printing apparatus 100 will be described.
The ultraviolet irradiation unit 138 is an active energy irradiation light source, and is disposed on the downstream side of each recording head 136W, 136C, 136M, 136Y, 136K corresponding to each recording head 136W, 136C, 136M, 136Y, 136K. Yes. As the ultraviolet irradiation unit 138, various ultraviolet light sources such as a metal halide lamp, a high-pressure mercury lamp, a UV LED, and a fluorescent lamp can be used.
The ultraviolet irradiation unit 138 passes the recording heads 136W, 136C, 136M, 136Y, and 136K, and irradiates the recording medium P on which the image is formed with ultraviolet rays. That is, the ultraviolet irradiation unit 138 gives the ink on the recording medium the energy that the ink ejected from the recording head and placed on the recording medium P is immediately cured, and the ink on the recording medium P is semi-cured, or , Cure.

Here, the ultraviolet irradiation unit 138 irradiates the ink on the recording medium P with the emitted ultraviolet light and does not irradiate the ink ejection ports of the recording heads 136W, 136C, 136M, 136Y, and 136K. It is preferable that In this way, by preventing the ink ejection port from being irradiated with ultraviolet rays, it is possible to prevent the ink from being cured at the ejection port.
Further, it is preferable to perform a light reflection preventing treatment (for example, a matte black treatment) on each part in the vicinity of the ultraviolet irradiation unit 138.

  The image reading unit 114 is disposed on the downstream side of the ultraviolet irradiation unit 138 corresponding to the recording head 136K in the conveyance path of the recording medium P so as to face the recording medium P. The image reading unit 114 includes an image sensor (line sensor or the like) for capturing the droplet ejection result of the drawing unit 112, and sends droplet ejection image data read by the image sensor to the control unit 121. More specifically, in the control unit 121, an arithmetic device (not shown) of the control unit 121 detects the size of the droplet ejection point and the deviation of the droplet ejection point position from the image data sent from the image reading unit 114. The detection of the size of the droplet ejection point and the deviation of the droplet ejection point position will be described in detail later.

  The image reading unit 114 of the present embodiment is configured by a line sensor having a light receiving element array wider than the ink ejection width (image recording width) by the recording heads 136W, 136C, 136M, 136Y, and 136K. The line sensor includes an R sensor array in which photoelectric conversion elements (pixels) provided with a red (R) color filter are arranged in a line, a G sensor array provided with a green (G) color filter, And a color separation line CCD sensor including a B sensor array provided with a blue (B) color filter. Instead of the line sensor, an area sensor in which the light receiving elements are two-dimensionally arranged can be used.

  Next, the smoothing unit 116 is disposed on the downstream side of the drawing unit in the conveyance direction of the recording medium P, and is transparent on the surface of the recording medium P (ultraviolet in the present embodiment) curable liquid (hereinafter, “ The varnish coater 142, which is a transparent liquid supply means for supplying an “active energy curable transparent liquid” or simply “transparent liquid”), and a flat surface process for pressing and smoothing the foil supply range described later of the recording medium P. The pressure member 146 includes an ultraviolet irradiation unit 148 that is an active energy irradiation unit that irradiates and cures the transparent liquid with active energy.

The varnish coater 142 includes a pair of application rollers 144 and 145.
The coating rolls 144 and 145 have a transparent liquid attached (impregnated) on the surface, and are disposed at positions where the recording medium P conveyed by the conveying unit 110 is sandwiched. The application rolls 144 and 145 rotate in response to (synchronously with) the movement of the recording medium P while sandwiching the recording medium P, thereby passing through the drawing unit 112 and the recording medium on which an image is formed. A transparent liquid is applied to the surface of P (the surface on which the image is formed).

  Here, the transparent liquid applied by the varnish coater 142 is an active energy curable transparent liquid that can be cured by ultraviolet irradiation, and includes at least a polymerizable compound and a photoinitiator as main components, for example, a cationic polymerization composition. , Radical polymerization compositions, aqueous compositions and the like. Details will be described later.

The flat pressure member 146 is movable in the vertical direction (arrow direction shown in the figure) with the smooth surface 146a facing the recording medium P on the downstream side of the varnish coater 142 in the conveyance direction of the recording medium P. Is arranged in.
The flat pressure member 146 moves in the vertical direction, contacts the recording medium P, presses at least the surface (image surface) in the foil donation range of the recording medium P with the smooth surface 146a, and the recording medium P The ink that is ejected onto the surface of the ink and forms an image is smoothed.
The smooth surface 146a has at least an area larger than the foil donation range.

  The ultraviolet irradiation unit 148 is disposed on the downstream side of the flat pressure member 146 in the conveyance direction of the recording medium P. The ultraviolet irradiation unit 148 irradiates the recording medium P with active energy (ultraviolet rays in the present embodiment), and cures the smoothed transparent liquid applied to the surface of the recording medium P. As the ultraviolet irradiation unit 148, for example, a metal halide lamp, a high pressure mercury lamp, a UV-LED, or the like can be used.

  The varnish coater 142 and the ultraviolet irradiation unit 148 are not essential devices for smoothing the foil donation range of the recording medium P, but are installed because a smooth surface can be obtained by applying a transparent liquid. Is preferred.

The foil pressing unit 118 includes a foil supply roll 150, a foil winding roll 152, rollers 154 and 156, a foil 158, and a hot stamp plate 160, and the smoothing unit 116 in the conveyance direction of the recording medium P. It is arranged on the downstream side.
The foil supply roll 150 and the foil take-up roll 152 are arranged at a predetermined interval. Further, the roller 154 and the roller 156 are separated from each other by a predetermined distance, the surface connecting the roller 154 and the roller 156 is parallel to the surface of the recording medium P, and more than the foil supply roll 150 and the foil take-up roll 152. It is arranged at a position close to the recording medium P. The rollers 154 and 156 are arranged at positions very close to the recording medium P.
The foil 158 is supplied from the foil supply roll 150, wound around the roller 154 and the roller 156, and then stretched around the foil winding roll 152. Here, the foil 158 between the roller 154 and the roller 156 is parallel to the recording medium P.

The hot stamp plate (letter plate) 160 is disposed between the roller 154 and the roller 156 at a position facing the recording medium P via the foil 158. The hot stamp plate 160 is provided with a relief plate portion 160a that comes into contact with the foil 158 and presses the foil 158 on the surface of the recording medium P, and is formed of zinc, brass, or the like. Further, the hot stamp plate 160 has a heating device (not shown) for heating the relief plate portion 160a and a moving mechanism for moving the hot stamp plate 160 in a direction approaching or separating from the recording medium P.
The hot stamp plate 160 is heated and pressure-bonded on the recording medium P according to the shape of the relief plate portion 160a by bringing the heated relief plate portion 160a into contact with the recording medium P via the foil 158 and pressing it. To do.

Here, in the present embodiment, a transport buffer is provided between the smoothing unit 116 and the foil pressing unit 118.
By providing the transport buffer, it is possible to absorb the slack of the recording medium P for continuous paper-like label printing caused by the difference in transport speed between the smoothing unit 116 and the foil pressing unit 118, and efficiently manufacture labels. be able to.

  The label removing unit 120 is disposed on the downstream side of the ultraviolet irradiation unit 164 in the conveyance direction of the recording medium P, and an active energy curable transparent liquid (in this embodiment, an ultraviolet curable transparent liquid) is used on the image surface. A varnish coater 162 and an ultraviolet irradiation unit 164 for improving the gloss by coating, a die cutter 166 for making a label-shaped cut in the continuous paper-like recording medium P, and a residue removing unit 172 that is an unnecessary portion peeling unit. .

The varnish coater 162 is disposed on the downstream side of the foil pressing unit 118 in the conveyance direction of the recording medium P.
The varnish coater 162 has a pair of coating rolls (impregnated) with an ultraviolet curable transparent liquid attached to the surface thereof, and supports the movement of the recording medium P (synchronized) while sandwiching the recording medium P. By rotating, the ultraviolet curable transparent liquid is applied to the surface (the surface on which the image is formed) of the recording medium P pressed with foil.
The ultraviolet irradiation unit 164 is disposed on the downstream side of the varnish coater 162 in the conveyance direction of the recording medium P. The ultraviolet irradiation unit 164 irradiates the recording medium P with active energy (ultraviolet in the present embodiment), and cures the ultraviolet curable transparent liquid applied to the surface of the recording medium P.
By applying and curing an ultraviolet curable transparent liquid on the surface of the recording medium P, the image surface of the recording medium P can be given gloss, and the image quality can be improved.

As shown in FIG. 2, the die cutter 166 is provided with a desired label-shaped cut 180 b only in the adhesive sheet 180 of the recording medium P for printing a continuous paper-like label. , The cylinder cutter 168 disposed on the downstream side of the ultraviolet irradiation unit 164 and disposed on the image surface side of the recording medium P, and the cylinder cutter 168 disposed on the opposite side of the recording medium P. Receiving roller 170.
The cylinder cutter 168 includes a cylindrical cylinder 168a and a plurality of cutting blades 168b wound around the cylindrical surface of the cylinder 168a and formed in a label shape.

  The die cutter 166 oscillates and rotates intermittently in synchronization with the conveyance speed of the recording medium P while the recording medium P is sandwiched between the cylinder cutter 168 and the receiving roller 170, so that the cutting blade 168b is rotated. Only the P adhesive sheet 180 is cut into a label shape.

  Here, the reason why the die cutter 166 swings and rotates intermittently is to solve the problem caused by the discrepancy between the circumferential length of the cylindrical surface of the cylinder 168a and the required length of the cutting blade 168b. That is, when the die cutter 166 is continuously rotated to insert the label-shaped cut 180b, the recording medium P corresponding to the portion where the cutting blade 168b of the cylinder cutter 168 is not provided is also fed and the recording medium P is wasted. However, by rotating and rotating the die cutter 166, the cuts 180b can be formed continuously, and waste of the recording medium P can be eliminated.

The scrap removing part 172 peels off an unnecessary part (peripheral part of the label L) of the adhesive sheet 180 that does not become the label (product) L from the release paper 182 and winds it up.
The recording medium P in which the unnecessary portion is wound, that is, the recording medium P in which only the label L is attached to the release paper 182 is wound around the product winding section 134 to become a product.

Next, a method for creating a label by the digital label printing apparatus 100 will be described.
Here, FIG. 6A is a cross-sectional view showing the main part of the recording medium having irregularities on the image surface, and FIG. 6B shows the main part of the recording medium pressed without smoothing. FIG. 6C is a cross-sectional view showing the main part of the recording medium that has been smoothed by the smoothing part and pressed with a foil.
As shown in FIG. 1, the recording medium P sent out from a supply roll 122 wound in a roll shape is transported to the undercoat section 111 by a transport section 110 (specifically, a pair of transport rollers 124 and 126). The

The recording medium P transported to the undercoat part 111 by the transport part 110 comes into contact with the application roll 202 of the undercoat part 111, and an undercoat liquid is applied to the surface to form an undercoat layer U.
Here, the application roll 202 is rotated in the direction opposite to the conveyance direction of the recording medium P by the drive unit 204. That is, the drive unit 204 moves the coating roll 202 in a direction in which the moving direction of the surface of the coating roll 202 and the moving direction of the recording medium P are opposite to each other at the contact position between the coating roll 202 and the recording medium P. It is rotating.

The recording medium P on which the undercoat liquid has been applied and the undercoat layer U is formed is further transported by the transport roll pairs 124 and 126 of the transport section 110 and passes through a position facing the undercoat liquid semi-curing section 216.
The undercoat liquid semi-curing unit 216 irradiates the recording medium P coated with the undercoat liquid that passes through the opposing position, and semi-cures the undercoat layer U on the recording medium P. The semi-curing will be described in detail later.

  The recording medium P on which the undercoat layer is formed is transported to the drawing unit 112 by the transport roller pairs 124 and 126 of the transport unit 110.

The recording heads 136 </ b> Y, 136 </ b> C, 136 </ b> M, and 136 </ b> K eject ink droplets of ultraviolet curable ink to the recording medium P that passes through the opposing positions based on control by the control unit 121. The recording medium P on which the ink has been ejected is further conveyed, passes through a position facing the ultraviolet irradiation unit 138, is irradiated with ultraviolet rays, and the ink is semi-cured or cured.
That is, when the recording medium P passes through the positions facing the recording heads 136Y, 136C, and 136M, ink droplets are ejected from the recording heads 136Y, 136C, and 136M toward the recording medium P, and then the ultraviolet irradiation unit Ultraviolet rays are irradiated from 138, and each ink landed on the recording medium P is semi-cured. Further, when the recording medium P passes through a position facing the recording head 136K, ink droplets are ejected from the recording head 136K toward the recording medium P, and then ultraviolet rays are irradiated from the ultraviolet irradiation unit 138, All the ink and the undercoat liquid that have landed on the recording medium P are cured.
As a result, an image is formed on the surface of the recording medium P.

  The recording medium P on which the image has been recorded is transported to the smoothing unit 116 and is thickened by the varnish coater 142 so as to cover the entire image 184 formed on the recording medium P as shown in FIG. A transparent liquid 186 having a thickness of about 5 to 30 μm (dry film thickness) is applied.

  The recording medium P coated with the transparent liquid 186 is conveyed to a position facing the flat pressure member 146. The flat pressure member 146 moves in a direction approaching the recording medium P, and presses the recording medium P with a smooth surface 146a. By pressing the recording medium P with the smooth surface 146a, the ink on the recording medium P is crushed. Thereby, the ink (image) on the recording medium P becomes smooth. Here, the area of the smooth surface 146a of the flat pressure member 146 is larger than the foil supply range.

  The recording medium P with the smoothed image is conveyed to the foil pressing unit 118 via the conveyance buffer. The recording medium P conveyed to the foil pressing unit 118 is pressed by the hot stamp plate 160 through the foil 158. On the surface of the recording medium P pressed by the hot stamp plate 160, a foil 158 is heat-pressed on the surface according to the shape of the relief plate portion 160a of the hot stamp plate 160.

  The recording medium P to which the foil 158 has been heat-pressed, that is, pressed with foil, is conveyed to the label removing unit 120 and applied with an ultraviolet curable transparent liquid by the varnish coater 162, and then irradiated with ultraviolet rays by the ultraviolet irradiation unit 164. The applied UV curable transparent liquid is cured.

The recording medium P in which the ultraviolet curable transparent liquid is cured is conveyed to a die cutter 166, and a cut 180b is formed in the shape of the label L only on the adhesive sheet 180 by the cylinder cutter 168 and the receiving roller 170.
At this time, as described above, since the die cutter 166 makes the cut 180b having the shape of the label L while swinging intermittently, the cut 180b can be continuously formed, and the recording medium P is wasted. The part never occurs.
Thereafter, unnecessary portions other than the label L of the pressure-sensitive adhesive sheet 180 of the recording medium P are peeled off from the release paper 182 and taken up by the residue removing portion 172. The recording medium P in a state where only the label L is stuck on the release paper 182 is wound around the product winding unit 134 to become a product.
A label is created as described above.

  Here, as shown in FIG. 6A, the image surface of the recording medium P is three-dimensionally swelled by overlapping the cured inks 184 of a plurality of colors. The rise height of the ink varies depending on the ink absorbability of the recording medium P (the lower the absorbency, the higher the height), but it is about 10 μm per color, and when one multicolor ink is used. May be approximately 40 μm. The image surface of the recording medium P is uneven. This unevenness greatly affects the adhesion between the foil 158 and the recording medium P (more specifically, the ink 184 on the recording medium P) when foil-pressing the image surface of the recording medium P.

  That is, as shown in FIG. 6B, when foil pressing is performed on an image surface in which the foil donation range is not smoothed (in other words, the ultraviolet curable ink is discharged and cured in the drawing unit 112), The foil 158 is heated and pressure-bonded only on the concave and convex peak portions, and is not pressed on the valley portions. That is, the degree of adhesion between the foil 158 and the recording medium P is low, and is easily peeled off.

  In contrast, in the present embodiment, the foil donation range is smoothed in advance by the flat pressure member 146 and then pressed onto the recording medium P. As a result, as shown in FIG. 6C, the foil 158 can be heat-bonded to a smooth surface having a large area, and the foil pressing with high adhesion between the recording medium P and the foil 158 is difficult. it can.

That is, according to the digital label printing apparatus 100 of the present embodiment, smoothing is performed by using the flat pressure member 146 to smooth the ink 184 and the transparent liquid 186 in at least the foil donation range on the recording medium P upstream of the foil pressing unit 118. By disposing the portion 116, the foil 158 can be provided and pressed in the range smoothed by the smoothing portion 116.
Thereby, the adhesiveness of the recording medium P and the foil 158 can be improved, and favorable foil stamp printing can be performed. Moreover, since it is smoothed by the flat pressure member 146, it can be smoothed in a short time, and productivity can be improved.

  Further, a transparent liquid supply means (varnish coater) 142 for supplying the smoothing unit 116 with a transparent active energy curable liquid on the image surface on the recording medium P, and an active energy curable liquid (transparent liquid) after supply. Active energy irradiation means (ultraviolet irradiation unit) 148 for irradiating active energy is provided, and the image surface is covered and smoothed with a transparent active energy curable liquid so that the image surface has large irregularities. A foil donating range with good flatness can be formed.

  Furthermore, by using a varnish coater as the transparent liquid supply means, the transparent liquid 186 can be stably applied to the surface of the recording medium P on which the uneven image is formed with a simple and inexpensive mechanism.

  Here, the formation of the film of the ultraviolet curable transparent liquid by the varnish coater 162 and the ultraviolet irradiation unit 164 is not necessarily required because it is intended to give the image surface a gloss and obtain a high-quality image. When not required, it can be set not to form a film of an ultraviolet curable transparent liquid.

  In addition, by forming an undercoat layer on the recording medium, it is possible to prevent ink droplets that have landed on the recording medium from penetrating into the recording medium and causing blurring of the image, thereby forming a high-quality image. It becomes possible. It is also possible to use a recording medium that has low adhesion to ink droplets, that is, repels the landed ink droplets. In other words, it is possible to record images on various recording media.

Next, the semi-curing of the undercoat liquid and the ink liquid will be described.
In the present invention, “semi-cured” means partially cured (partial cured), and the undercoat liquid and / or the ink liquid (that is, the colored liquid) is partially cured, but completely cured. The state that is not cured. When the undercoat liquid applied on the recording medium (base material) P or the ink liquid ejected onto the undercoat liquid is semi-cured, the degree of curing may be uneven. It is preferable that the ink liquid is cured in the depth direction. Here, in this embodiment, the undercoat liquid to be semi-cured is an undercoat liquid forming an undercoat layer, and the ink liquid to be semi-cured is an ink liquid that lands on an undercoat layer or a recording medium to form an ink layer. It is a drop.

  For example, when a radical polymerizable undercoating liquid or ink liquid is cured in air or air partially substituted with an inert gas, the surface of the undercoating liquid or ink liquid is used to suppress the radical polymerization of oxygen. There is a tendency for radical polymerization to be inhibited. As a result, the semi-curing becomes non-uniform, the curing proceeds more inside the undercoat liquid or the ink liquid, and the surface curing tends to be delayed.

  In the present invention, a radical photopolymerizable undercoat liquid or ink liquid is used in the presence of radical polymerization-inhibiting oxygen and partially photocured, whereby the degree of cure of the undercoat liquid and / or ink liquid is The inside can be higher than the outside.

In addition, in the case of curing the cationic polymerizable undercoat liquid or ink liquid in the air having moisture, since the water has a cationic polymerization inhibiting action, the curing proceeds more inside the undercoat liquid or ink liquid, Surface hardening tends to be delayed.
Even if this cationically polymerizable undercoat liquid or ink liquid is partially photocured using humidity conditions having an inhibitory action on cationic polymerization, the degree of cure of the undercoat liquid and / or ink liquid is higher than that of the outside. Can be higher.

  In this way, the undercoat liquid or ink liquid is semi-cured, and the ink liquid is ejected onto the semi-cured undercoat liquid, or an ink liquid having a different hue is applied to the semi-cured ink liquid. When droplets are ejected, a technical effect favorable to the quality of the obtained printed matter can be obtained. Moreover, the action mechanism can be confirmed by observing the cross section of the printed matter.

Hereinafter, the semi-curing of the undercoat liquid (that is, the undercoat layer formed on the recording medium with the undercoat liquid) will be described in detail. In the following, when about 12 pL of ink liquid (that is, ink droplets) is deposited on the semi-cured undercoat liquid having a thickness of about 5 μm provided on the recording medium P. A high density portion will be described as an example.
FIG. 7 is a schematic cross-sectional view showing an example of a recording medium in which an ink liquid is ejected onto a semi-cured undercoat liquid. FIGS. 8A and 8B are uncured undercoat liquids, respectively. FIG. 8C is a schematic cross-sectional view showing an example of a recording medium on which ink liquid has been deposited, and FIG. 8C is a diagram of the recording medium on which ink liquid has been deposited on an undercoat liquid that has been completely cured. It is a typical sectional view showing an example.

According to the present invention, the undercoat liquid is semi-cured, so that the degree of cure on the recording medium P side becomes higher than the degree of cure of the surface layer. In this case, three features are observed. That is, as shown in FIG. 7, when the ink liquid d is ejected onto the semi-cured undercoat liquid U, (1) a part of the ink liquid d comes out on the surface of the undercoat liquid U. (2) Ink liquid A part of d is embedded in the undercoat liquid U, and (3) the undercoat liquid exists between the lower side of the ink liquid d and the recording medium P.
As described above, when the undercoat liquid and the ink liquid satisfy the above conditions (1), (2), and (3) when the ink liquid is ejected onto the undercoat liquid, the undercoat liquid is in a semi-cured state. It can be said that there is.
By semi-curing the undercoat liquid, that is, by curing the undercoat liquid so as to satisfy the above (1), (2), and (3), droplets of ink liquid that has been ejected at high density (that is, Ink droplets) are connected to each other to form an ink liquid film layer (that is, an ink liquid film or an ink layer), which gives a uniform and high color density.

On the other hand, when the ink liquid is ejected onto the uncured undercoat liquid, all of the ink liquid d enters the undercoat liquid U as shown in FIG. 8A and / or FIG. As shown in B), the undercoat liquid U does not exist below the ink liquid d.
In this case, even when the ink liquid is applied at a high density, the droplets are independent of each other, which causes a decrease in color density.

In addition, when the ink liquid is ejected onto the completely hardened undercoat liquid, the ink liquid d does not enter the undercoat liquid U as shown in FIG.
In this case, droplet ejection interference occurs, a uniform ink liquid film layer cannot be formed, and color reproducibility cannot be increased (that is, color reproducibility is reduced).

Here, when droplets of ink liquid are applied at high density, the droplets do not become independent, from the viewpoint of forming a uniform ink liquid film layer, and from the viewpoint of suppressing the occurrence of droplet ejection interference, The amount of the uncured portion of the undercoat liquid (that is, the undercoat layer) per unit area is preferably smaller than the maximum droplet amount of the ink liquid applied per unit area, and more preferably sufficiently small. That is, the weight M _u (also referred to as M (undercoat liquid)) per unit area of the uncured portion of the undercoat liquid layer and the maximum weight m _i (m (ink liquid)) of the ink liquid ejected per unit area. ) Preferably satisfies (m _i / 30) <M _u <m _i , more preferably satisfies (m _i / 20) <M _u <(m _i / 3), and (m _i / 10) It is particularly preferable that <M _u <(m _i / 5). Here, the maximum weight of the ink liquid ejected per unit area is the maximum weight per color.
By setting (m _i / 30) <M _u , the occurrence of droplet ejection interference can be prevented, and the dot size reproducibility can be increased. In addition, by setting M _u <m _i , the liquid layer of the ink liquid can be formed uniformly, and the decrease in density can be prevented.

Here, the weight of the uncured portion of the undercoat liquid per unit area is determined by a transfer test. Specifically, after completion of the semi-curing process (for example, after irradiation with active energy rays) and before ink droplets are ejected, a penetrating medium such as plain paper is pressed against the semi-cured undercoat liquid. Then, the amount of the undercoat liquid transferred to the permeation medium is measured by weight measurement, and the measured value is defined as the weight of the uncured portion of the undercoat liquid.
For example, the maximum amount of the second ink, in droplet deposition density of 600 × 600 dpi, is set to 12 picoliters per pixel, the maximum weight m _i of the ink ejected per unit area, and 0.04 g / cm ² (Note that the density of the ink liquid is about 1.1 g / cm ³ ). Therefore, in this case, the weight M _u uncured portions per unit area of the undercoat liquid is preferably to 0.0013 g / cm ² greater than 0.04 g / cm less than ^2, from 0.002 g / cm ² greater more preferably to less than 0.013 g / cm ^2, it is particularly preferable to increase the 0.008 g / cm ² than 0.004 g / cm ^2.

Next, the semi-curing of the ink liquid (that is, the ink droplet landed on the recording medium or the undercoat layer or the ink layer formed by the landed ink droplet) will be described.
Figure 9 is a schematic cross-sectional view on the semi-cured first ink d _a shows a recording medium which ink droplets have been deposited d _b, FIG 10 (A) and (B), is in an uncured state is a schematic sectional view showing an example of a recording medium having ink d _b is deposited as droplets onto the first ink d _a, FIG. 10 (C) hitting the ink on the ink liquid while being fully cured It is a typical sectional view showing an example of a recording medium dropped.
The ink d _a after ejected, when forming a secondary color by ink d _b is deposited as droplets onto the first ink d _a is the ink d _b onto the first ink d _a semi-cured It is preferable to give.
Here, the semi-cured state of the first ink d _a, the same as the semi-cured state of the undercoating liquid described above, as shown in FIG. 9, when the second ink d _b is deposited as droplets onto the first ink d _a , (1) a portion of the second ink d _b emerges at the surface of the first ink d _a, (2) a portion of the second ink d _b lies within the first ink d _a, and (3) ink d _b the lower is a condition where there is an ink d _a.
By thus semi-curing the ink, can be suitably superimposed cured film of the ink d _a a (colored film A) and an ink liquid d _b cured film (colored film B), good color reproduction Is possible.

In contrast, when ink d _b is deposited as droplets onto the first ink d _a uncured, or all of the ink d _b as shown in FIG. 10 (A) sinks into ink d _a, In addition, as shown in FIG. _10B , the ink liquid d _a does not exist in the lower layer of the ink liquid db. In this case, even if high density imparts ink d _b droplets, since the droplets are independent of each other, causing the color saturation of the secondary color to decrease.

Also, if ink d _b is deposited _as droplets completely cured ink on d _a, ink d _b as shown in FIG. 10 (C) does not sink into ink d _a. In this case, droplet ejection interference occurs, a uniform ink liquid film layer cannot be formed, and color reproducibility is reduced.

Here, the droplets are not independent of each other when applying droplets of a high density ink d _b, the viewpoint of forming a uniform film of the second ink d _b, and suppress the occurrence of fired droplet interference from the viewpoint of the amount of the uncured portion of the ink d _a per unit area is preferably less than the maximum droplet amount of the ink d _b applied per unit area, and more preferably substantially smaller. That is, (also referred to as M (ink liquid A).) Weight M _da per unit surface area of uncured regions of the first ink d _a layer and the maximum weight of the ink ejected per unit area m _db (m (ink liquid B It is preferable that (m _db / 30) <M _da <m _db is satisfied, and that (m _(db / 20) <M _da <(m _db / 3) is further satisfied. It is particularly preferable that (m _db / 10) <M _da <(m _db / 5) is satisfied.
By setting (m _db / 30) <M _da , it is possible to prevent the occurrence of droplet ejection interference and to further improve the dot size reproducibility. In addition, by setting M _da <m _db, can uniformly form a film of the first ink d _a, a decrease in density can be prevented.

Here, the weight of the uncured regions of the first ink d _a per unit area, as in the case of the undercoating liquid described above, is determined by a transfer test. Specifically, after completion of the semi-curing step (e.g. after irradiating with actinic radiation) before deposition of the droplets of the second ink d _b a, a permeable medium such as plain paper in a semi-cured state ink is pressed against the liquid d _a layer, the amount of _the first ink d _a that transfers to the permeable medium is determined by weight measurement. the measured value is defined as the weight of the uncured regions of the first ink.
For example, the maximum amount of the second ink d _b, in droplet deposition density of 600 × 600 dpi, is set to 12 picoliters per pixel, the maximum weight m _db of the second ink d _b ejected per unit surface area, 0.04 g / cm ² and becomes (assuming the density of the second ink d _b is about 1.1g / cm3.). Therefore, in this case, the weight M _da uncured portions per unit area of the first ink d _a layer is preferably set to 0.0013 g / cm ² greater than 0.04 g / cm less than ^2, 0.002 g / more preferably greater 0.013 g / cm less than ² than cm ^2, and particularly preferably a large 0.008 g / cm less than ² than 0.004 g / cm ^2.

  In the case where the semi-cured state of the undercoat liquid and / or ink liquid is realized by a polymerization reaction of a polymerizable compound initiated by irradiation with active energy rays or heating, the non-polymerization rate (that is, from the viewpoint of improving the scratching property of the printed matter) A (after polymerization) / A (before polymerization) is preferably from 0.2 to 0.9, more preferably from 0.3 to 0.9, and from 0.5 to 0.00. Particularly preferably, it is 9 or less.

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

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

  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 the ethylenically unsaturated group or the cyclic ether group.

  Moreover, as a method of semi-curing the undercoat liquid and / or the ink liquid, (1) a basic compound is imparted to the acidic polymer, or an acidic compound or a metal compound is imparted to the basic polymer. , A method using a so-called agglomeration phenomenon, (2) The undercoating liquid and / or the ink liquid is prepared to have a high viscosity in advance, and the viscosity is lowered by adding a low boiling organic solvent thereto, and the low boiling organic solvent is evaporated. (3) A method of returning to the original high viscosity by heating and cooling the undercoat liquid and / or ink liquid prepared to a high viscosity, and (4) a method of returning to the original high viscosity. There are known thickening methods such as a method in which an active energy ray or heat is applied to the ink liquid to cause a curing reaction. Among them, (4) a method in which an active energy ray or heat is applied to the undercoat liquid and / or the ink liquid to cause a curing reaction is preferable.

  The method of causing a semi-curing reaction by applying active energy rays or heat is a method in which the polymerization reaction of the polymerizable compound on the surface of the undercoat liquid and / or ink liquid applied to the recording medium is insufficient. is there. On the surface of the undercoat liquid and / or ink liquid, the polymerization reaction is more likely to be inhibited by the influence of oxygen in the air than in the interior thereof. Therefore, the semi-curing reaction of the undercoat liquid and / or the ink liquid can be caused by controlling the application conditions of the active energy ray or heat.

The amount of energy required for semi-curing the undercoat liquid and / or ink liquid varies depending on the type and content of the polymerization initiator, but generally 1 to 500 mJ / cm ² when energy is applied by active energy rays. The degree is preferred. 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.

As in the present embodiment, the undercoat liquid (that is, the undercoat layer) is semi-cured by the undercoat liquid semi-cured portion, so that even if the ink droplets overlap each other and land on the recording medium, the undercoat liquid And the ink droplets can be prevented from being coalesced between the adjacent ink droplets.
That is, by forming a semi-cured undercoat liquid layer on the recording medium, when the ink droplets ejected from the recording head land on the recording medium, for example, a single color ink droplet The ink droplets can be prevented from moving even when the ink droplets land on the recording medium with overlapping portions or when the ink droplets of different colors land on the recording medium with overlapping portions.
As a result, it is possible to effectively prevent the occurrence of blurring of the image, non-uniformity of the line width such as fine lines in the image and color unevenness of the colored surface, and sharp lines can be formed with a uniform width. For example, it is possible to record an inkjet image having a high droplet ejection density such as a fine line with good reproducibility. That is, a high-quality image can be formed on the recording medium.

In addition, an ultraviolet irradiation unit is arranged between the recording heads, and ink droplets that have landed on the recording medium by the recording heads, that is, images are semi-cured so that ink droplets of different colors landed at close positions. Can be prevented, and the landed ink droplets can be prevented from moving. Further, by semi-curing the ink liquid, a uniform ink layer can be formed, interference between ink droplets can be prevented, and a plurality of different ink layers can be suitably stacked.
The ultraviolet irradiation unit irradiates ultraviolet rays for several hundred milliseconds to five seconds after the ink droplets have landed on the recording medium by the recording head, so that the ink droplets that have landed on the recording medium are half cut. It is preferable to cure.
By semi-curing the ink droplets within a few hundred milliseconds to 5 seconds after the ink droplets have landed, the shape of the ink droplets on the recording medium can be prevented from collapsing, and high-quality images can be formed. can do.

Here, the viscosity (25 ° C.) of the semi-cured undercoat layer and / or the inner layer of the ink droplet is preferably 5000 mPa · s or more.
Further, the viscosity (25 ° C.) of the semi-cured undercoat layer and / or the surface layer of the ink droplet is preferably 100 mPa · s or more and 5000 mPa · s or less.
Further, the viscosity (25 ° C.) of the semi-cured undercoat layer and / or the inner layer of the ink droplet is 1.5 times or more of the viscosity (25 ° C.) of the semi-cured and / or ink droplet surface layer. Preferably, it is more preferably 2 times or more, and further preferably 3 times or more.
By setting it as the said range, an undercoat and / or an ink droplet can be semi-hardened suitably.

Further, the polymerization degree of the polymerizable compound on the surface of the internally cured undercoat liquid (that is, undercoat layer) and / or ink droplets is preferably 1% or more and 70% or less, and is preferably 5% or more and 60% or less. It is more preferable to set it to 10% or more and 50% or less. Here, the degree of polymerization can be measured by IR or the like.
By setting it as the said range, an undercoat can be semi-hardened suitably.

  Further, by applying the undercoat liquid onto the recording medium P by using the coating roll 202 and further rotating the coating roll 202 in the direction opposite to the conveying direction of the recording medium P, the surface of the recording medium P is covered. An undercoat layer U having an improved shape can be formed. That is, when the coating roll 202 is separated from the recording medium P after the coating roll 202 has applied the undercoat liquid to the recording medium P by rotating the coating roll 202 in the direction opposite to the conveyance direction of the recording medium P. The surface of the undercoat liquid applied onto the recording medium P can be prevented from being disturbed, and the undercoat layer U having a smooth surface, that is, a small surface roughness can be formed on the recording medium P.

Here, for example, as shown in FIGS. 11A and 11B, when the amount of ink droplets ejected from the ejection unit is smaller than a desired amount, the ejection unit number described later is A11. Like the droplet ejection point formed by the discharge unit 60, the size of the droplet ejection point becomes small. As described above, when the size of the droplet ejection point is different from the desired size, streaks and unevenness occur in the formed image.
Further, when the ink droplets ejected from the ejection unit at the time of image drawing by the recording head unit 135 are ejected in a different direction from the ink droplets ejected from the other ejection units, the ejection unit number described later is ejected with A5. Like the droplet ejection point formed by the unit 60, the position of the ink droplet ejection point is shifted, that is, the landing position of the ink droplet is shifted, and streaks and unevenness occur in the formed image.

  In the present invention, in order to prevent the occurrence of streaks and unevenness in such an image, and in order to correct the streaks and unevenness, the size of the droplet ejection point formed by each ejection unit becomes a desired size. Further, it is detected whether the position of the droplet ejection point is a desired position.

Hereinafter, a method for detecting a droplet ejection size for detecting the size of a droplet ejection point will be described.
Here, since the droplet ejection spot size is detected by the same method in any of the recording heads 136W, 136C, 136M, 136Y, and 136K, the recording head 136K will be described below as a representative.

First, an image used for detecting the droplet ejection point size is drawn on the recording medium P by the recording head 136K.
In the present embodiment, when the plurality of ejection units arranged in a row are defined as A1, A2, A3,..., An in order from one end to the other end (see FIGS. 11 and 12), A1, A3 , A5,..., Ink droplets are continuously ejected only from the odd-numbered ejection portions, and droplet ejection points are formed at positions where they contact adjacent droplet ejection points formed by the same ejection portion. In this manner, a droplet ejection line in which a plurality of droplet ejection points formed by the same ejection unit are connected is formed for each ejection unit. More specifically, while the recording medium P is transported in a direction orthogonal to the arrangement direction of the ejection sections, each ejection section continuously ejects a plurality of ink droplets to eject onto the recording medium P. A droplet ejection line in which a plurality of droplet ejection points are connected in a direction (conveying direction) substantially orthogonal to the arrangement direction of the portions is formed for each ejection unit.
At this time, the droplet ejection points of the ink droplets ejected by the ejection part A1 and the ejection part A3 do not contact each other. That is, the droplet ejection lines formed for each discharge unit do not contact each other.

  After ejecting ink droplets from odd-numbered ejection portions to form droplet ejection lines, similarly, ink droplets are continuously continuously ejected from even-numbered ejection portions A2, A4, A6,. By ejecting, droplet ejection lines are formed on the recording medium P for each ejection unit. Here, the droplet ejection lines formed by ejecting a predetermined number of ink droplets from the even-numbered ejection sections are also formed at positions where each droplet ejection line does not contact other droplet ejection lines.

FIG. 12 is a top view showing an example of an image (test pattern) used for droplet ejection point size detection.
In this way, an image is drawn on the recording medium P, that is, a droplet ejection line is formed for each ejection part, and an odd number of ejections are formed on one recording medium P as shown in FIG. a collection G _a droplet deposition lines formed by ejecting ink droplets from the part, forming the aggregate G _B in droplet lines formed by ejecting ink droplets from the ejection portion of the even-numbered. That is, the ink droplets are selectively ejected from a plurality of ejection units without ejecting the ink droplets simultaneously from all ejection units, and the direction orthogonal to the extending direction (arrangement direction) of the ejection units on the recording medium In FIG. 2, droplet ejection lines are formed at a plurality of different portions. That is, the droplet ejection lines formed on the recording medium are formed at different positions in the direction orthogonal to the arrangement direction of the ejection units, according to the arrangement positions of the ejection units. Here, the extending direction of the ejection part is the direction in which the plurality of ejection parts are arranged, that is, the direction in which the line connecting the ejection parts extends, in other words, the longitudinal direction of the recording head (inkjet head), In this embodiment, it is the width direction of the recording medium.

  Next, the image reading unit 114 reads an image formed on the recording medium P. That is, each droplet ejection line is read by the image reading unit 114. The read image data is sent to the control unit 121.

FIG. 13A is a schematic view showing a part of one droplet ejection line of an image (read image) read by the image reading unit 114, and FIG. 13B is shown in FIG. It is a schematic diagram which shows an example which binarized image data. Here, in each of FIGS. 13A and 13B, each square is one pixel. By increasing the reading pixel density, that is, the reading resolution, each cell can be made smaller, and the droplet ejection line can be read more finely.
An arithmetic unit (not shown) of the control unit 121 binarizes the droplet ejection line image (see FIG. 13A) read by the image reading unit 114 for each pixel as shown in FIG. 13B. . In other words, it is determined whether or not the ink density of each pixel, that is, the density of the read image is equal to or higher than a threshold value. The pixel has no ink component. In other words, each read pixel has only two values with or without an ink component.

  Next, only the pixels that are binarized to form the droplet ejection line, that is, only the pixels having an ink density within a certain level within the pixel are taken out, and in a direction (reference direction) orthogonal to the direction substantially parallel to the droplet ejection line. Pixels at one end of the droplet ejection line (hereinafter also simply referred to as “one end”) and the other end (hereinafter also simply referred to as “the other end”) in the reference direction of the droplet ejection line. Calculate the coordinates. Here, the coordinates of the pixels at one end of the droplet ejection line and the coordinates of the pixels at the other end are calculated at predetermined intervals in a direction orthogonal to the reference direction. That is, for each droplet ejection line, a plurality of points are calculated at predetermined intervals in the direction orthogonal to the reference direction for each of the coordinates of one end and the coordinates of the other end.

Here, the coordinate axis of the coordinates to be calculated is the direction in which the image reading unit 114 extends, that is, the direction substantially orthogonal to the conveyance direction of the recording medium P (the direction orthogonal to the direction substantially parallel to the droplet ejection line). A reference direction (X-axis direction) is defined as a direction perpendicular to the reference direction, that is, a direction substantially parallel to the transport direction of the recording medium P, and an arbitrary point is defined as an origin. This coordinate axis is a coordinate axis common to all droplet ejection lines, that is, all droplet ejection points forming the droplet ejection line.
Hereinafter, in the present embodiment, the coordinate axes are first formed so that all the droplet ejection lines, that is, all the droplet ejection points constituting the droplet ejection lines are located in the positive regions of the X axis and the Y axis. In the following description, it is assumed that the droplet ejection point (that is, the droplet ejection point formed on the most downstream side in the transport direction) is set closest to the X axis.

Specifically, the coordinates of the end of the droplet ejection line are detected as follows.
As shown in FIG. 14A, a pixel 190 at one end (left end in the drawing) in the reference direction of the droplet ejection line is detected, and the coordinates of the detected pixel 190 are converted into one end portion ( The coordinates of the left end in the figure). The detection of the pixel 190 at one end is performed at predetermined intervals α in the Y-axis direction for one droplet ejection line, and the coordinates of one end at a plurality of positions in the Y-axis direction are detected.
Similarly, the pixel 192 at the other end (right end in the drawing) is detected at the other end of the droplet ejection line, and each pixel is set as the coordinate of the other end (right end in the drawing). Similarly, the detection of the pixel 192 at the other end is performed at a predetermined interval α in the Y-axis direction for one droplet ejection line, and the coordinates of the other end at a plurality of positions in the Y-axis direction are detected. .
In this way, for each droplet ejection line, the coordinates of both ends of the droplet ejection line are detected at predetermined intervals in the Y-axis direction. Here, in this embodiment, since the coordinate axis is set as described above, one end portion (left end portion in FIG. 14) of the droplet ejection line becomes an end portion on the side close to the Y axis, and the other end. Is the end on the side far from the Y axis.

  The predetermined interval α in the Y-axis direction when detecting the positions of both ends of the droplet ejection line can take various values, but the droplet ejection points constituting one droplet ejection line It is preferable that the distance is smaller than the droplet ejection point interval in the Y-axis direction. By using an approximate straight line calculated for each of both ends of the droplet ejection line, which will be described later, by making the interval α smaller than the droplet ejection point interval in the Y-axis direction of the droplet ejection points constituting one droplet ejection line. Thus, it is possible to obtain sufficient droplet ejection line end position information for calculating the width of the droplet ejection line with higher accuracy.

As described above, in this embodiment, end position information at a plurality of points is calculated (detected) from an image composed of a plurality of droplet ejection lines arranged without contacting each other. Thereby, the pixel which comprises the droplet ejection line formed of one discharge part can be discriminate | determined easily. That is, the pixels constituting the droplet ejection line formed by the adjacent ejection units can be easily distinguished for each ejection unit, and the droplet ejection line is detected when detecting the droplet ejection line end position information. It is possible to easily distinguish by which discharge portion each pixel to be formed is drawn.
That is, in the present embodiment, since the ends of a plurality of droplet ejection lines formed for each ejection unit are detected, it is possible to easily determine the value obtained by detecting the ends of the same droplet ejection line. That is, since end portions at a plurality of positions are calculated from continuous droplet ejection lines, the calculated end position information can be easily classified for each ejection unit (droplet ejection line).

  In addition, by using a droplet ejection line extending continuously in one direction, both ends of the droplet ejection line formed by the same ejection unit can be used when detecting the position information of the droplet ejection line end. It can be easily distinguished from one end of the other and the other end.

Next, from the calculated coordinates of both ends of each droplet ejection line (droplet ejection line edge position information), the least square method is used for each of the one edge and the other edge for each droplet ejection line. As shown in FIG. 15, an approximate straight line connecting one end portion (in FIG. 15, the left end of the droplet ejection line) and the other end portion (in FIG. 15, in FIG. 15). The approximate straight line connecting the right ends of the drip lines is calculated.
Specifically, when the number of the ejection unit is m, the approximate straight line at one end of the droplet ejection point formed by the ejection unit _m is expressed as y = ax + b _m based on the coordinate axis described above. Furthermore, the approximate straight line at the other end is expressed as y = ax + _cm .
Here, a is the slope of the approximate straight line, b _m is the intercept of the approximate straight line at one end, and c _m is the intercept of the approximate straight line at the other end. The slope a of the approximate line is calculated as a slope common to all approximate lines. Accordingly, the approximate straight lines are all parallel to each other.
The inclination a, the intercept b _m and the intercept _cm are calculated by the following equations (1), (2), and (3).

Here, M is the total number of ejection parts, m is the number of the ejection part, and Nm is one end part (or the other end part) detected from the droplet ejection line drawn by the ejection part m. (Xl _mn , yl _mn ) are the coordinates of one end of the nth detected from the droplet ejection line drawn by the ejection part m, and (xr _mn , yr _mn ) It is the coordinate of the n-th other edge part detected from the drawn droplet ejection line.

Next, from the calculated approximate straight lines a, b _m , and c _m , the width of the droplet ejection line formed by the discharge unit m is calculated. When the width of the droplet ejection line formed by the discharge unit m is R _m , the following equation (4) is calculated from the approximate straight lines calculated for both ends of the droplet ejection line.

As described above, based on a plurality of coordinates of both ends of the droplet ejection wire made of droplet ejection points formed by the discharge portion m, a width R _m of droplet ejection lines of two approximated straight lines respectively calculated To detect.

Next, a method for calculating the size of the droplet ejection point formed by the ejection unit _m from the width Rm of the droplet ejection line will be described.
Here, FIGS. 16A to 16C are top views schematically showing the relationship between the droplet ejection point and the droplet ejection line, respectively. More specifically, FIG. 16A shows a case where one droplet ejection point is formed by one ink droplet ejected from the ejection unit, and FIG. FIG. 16C shows a droplet ejection point when one droplet ejection point is formed by three ink droplets ejected from the ejection unit. FIG. 6 is a top view showing droplet ejection lines formed by the droplet ejection points. Also shows droplet line l _a in FIG. 16 (A) ~ (C) , l b, l each droplet ejection point _c d _a, d _b, the size of d _c, i.e. the size a dotted line.
The present inventors show that the relationship between the size of the droplet ejection point and the width of the droplet ejection line changes according to the formation conditions of the droplet ejection point, as shown in FIGS. I found out. More specifically, even when the droplet ejection lines l _a , l _b and l _c have the same width, the ink droplets ejected to form one droplet ejection point d _a , d _b and d _c It was found that the size of the droplet ejection point (that is, the size of the droplet ejection point) differs depending on the number.

  Here, in the present invention, the relationship between the width of the droplet ejection line and the size of the droplet ejection point is calculated in advance for each condition for forming the droplet ejection line, and stored in the arithmetic unit of the control unit. Here, the formation condition in the present embodiment is the number of ink droplets ejected from the ejection unit in order to form one droplet ejection point.

Here, the relationship between the droplet ejection line width and the droplet ejection point size calculated for each droplet ejection line formation condition stored in advance is calculated as follows.
First, as shown in FIG. 16 (A), in the same forming conditions to form a Dashizukusen l _a and Dashizukuten d _a on the recording medium. Here, each of the droplet ejection point d _a, may be increased ejection interval than the case of forming a Dashizukusen l _a.
Then, detecting the size of the width and Dashizukuten d _a droplet deposition line l _a produced.
The width of Dashizukusen l _a is preferably detected by the same manner as described above. The size of Dashizukuten d _a is read by the image reading apparatus a plurality of droplet ejection points, and the average value and the size of the droplet ejection points. Here, the method of detecting the size of each droplet ejection point is not particularly limited. For example, even if the read image is enlarged and the operator visually determines, the outer edge is detected and the size is detected by approximating a circle. May be.
In this way, the same formation conditions, other conditions that can be adjusted are changed, and the size of the droplet ejection line and the width of the droplet ejection line are detected to detect the width of the droplet ejection line under a predetermined formation condition. And the size of the droplet ejection point are calculated.
The relationship between the size of the width and Dashizukuten d _b in droplet line l _b shown in FIG. 16 (B), the size of the width and Dashizukuten d _c in droplet line l _c shown in FIG. 16 (c) The relationship with is calculated in the same manner.
In this way, the relationship between the droplet ejection line width calculated for each droplet ejection line formation condition and the droplet ejection point size is calculated.

17A to 17C are graphs schematically showing the relationship between the width of the droplet ejection line and the size of the droplet ejection point according to the conditions for forming the droplet ejection line.
More specifically, FIG. 17A shows a case where one ink droplet is ejected from the ejection part, and FIG. FIG. 17C shows a droplet ejection point when one droplet ejection point is formed by three ink droplets ejected from the ejection unit. 5 is a graph showing the relationship between the size of the droplet and the width of the droplet ejection line formed by the droplet ejection point. Here, in the graphs of FIGS. 17A to 17C, the vertical axis represents the droplet ejection spot diameter, that is, the size of the droplet ejection spot, and the horizontal axis represents the droplet ejection line width.
In the arithmetic unit of the control unit 121, the width of the droplet ejection line and the droplet ejection point calculated for each droplet ejection line formation condition as shown in FIGS. The relationship with the size is stored.

In this way, by calculating the relationship between the width of the droplet ejection line and the size of the droplet ejection point for each formation condition, the relationship between the width of the droplet ejection line and the size of the droplet ejection point under the necessary formation conditions is calculated. can do.
Since the relationship between the width of the droplet ejection line and the size of the droplet ejection point is common to each ejection unit, the relationship between the width of the droplet ejection line calculated in one ejection unit and the size of the droplet ejection point is different from the other. It can also be used for the discharge part.
In addition, it is preferable to use a high-resolution image reading apparatus as the image reading apparatus used for reading the image of the droplet ejection point and the droplet ejection line. Specifically, it is preferable to use an image reading device having a higher resolution than the image reading device of the image reading unit used in the digital label printing device. By using a high-resolution image reader and accurately calculating the relationship between the width of the droplet ejection line and the size of the droplet ejection point, the size of the droplet ejection point can be calculated more accurately.

Computing device, in order to calculate the size of the droplet ejection point, reads the relationship between the size of the width and droplet deposition points in droplet line corresponding to the conditions for forming the droplet line width R _m as described above.
In the present embodiment, when one droplet ejection point is formed by one ink droplet, the relationship shown in FIG. 17A is formed by one ink droplet point by two ink droplets. In this case, the relationship shown in FIG. 17B is read. When one droplet ejection point is formed by three ink droplets, the relationship shown in FIG. 17C is read.

Next, using the relationship between the size of the width and droplet deposition points of the readout droplet ejection line, it detects the size of the droplet ejection points formed by the discharge portion m from the calculated width R _m.
Thereby, it is possible to calculate (detect) the size of the droplet ejection point of the ink droplet ejected from each ejection unit.

In the present embodiment, the interval between the droplet ejection lines is further calculated from the calculated approximate straight lines a, b _m , and _cm . When the distance between the droplet line with droplet ejection line of the discharge portion m + 1 of the discharge portion m was d _m, d _m is calculated by the following equation (5).

  Here, the interval between the droplet ejection lines is substantially the same value as the interval between the droplet ejection points. Accordingly, the interval between the droplet ejection points can be obtained by calculating the interval between the droplet ejection lines as described above. Thereby, it is possible to calculate (detect) the positional deviation of the ink droplet ejection points of the ink droplets ejected from each ejection unit.

  The control unit detects the abnormal ejection unit based on the size of the droplet ejection point detected by the droplet ejection point size detection method and the positional deviation of the droplet ejection point, and performs correction based on the detection result. A high-quality printed matter can be created.

As described above, according to the droplet ejection point size detection method of the present embodiment, the droplet ejection point size can be calculated in consideration of the droplet ejection line formation conditions, and the droplet ejection point size can be accurately detected. can do.
In this way, by accurately calculating the size of the droplet ejection point, the size of the droplet ejection point causing streaks, unevenness, etc. is different from the desired size, that is, an amount different from the desired amount. It is possible to accurately obtain information (ejection size abnormality information) of the ejection unit from which ink is ejected.

In addition, by detecting the relationship between the width of the droplet ejection line and the size of the droplet ejection point for each droplet ejection line formation condition in advance, it is not necessary to detect one droplet ejection point with high accuracy each time. Since the average value of a plurality of droplet ejection points can be calculated by using the droplet ejection line formed at the droplet ejection points, the measurement accuracy can be increased.
Further, it is not necessary to accurately calculate the outline of the droplet ejection point, and the size of the droplet ejection point can be accurately detected even when an image reading apparatus with low reading accuracy is used.
Further, as described above, the relationship between the width of the droplet ejection line and the size of the droplet ejection point for each droplet ejection line formation condition can be made common to each ejection unit. As a result, the relationship between the width of the droplet ejection line and the size of the droplet ejection point for each droplet ejection line formation condition can be easily calculated, the detection can be performed efficiently, and the cost associated with the apparatus is reduced. be able to.

  Further, as in the present embodiment, the droplet ejection line width is detected from the approximate straight line calculated based on the plurality of coordinates of the respective ends of the droplet ejection line, and the size of the droplet ejection point is calculated (detected). Thus, the size of the droplet ejection point can be calculated (detected) more accurately. As a result, it is possible to accurately obtain information on the ejection portion having an abnormal droplet ejection point size that causes streaks, unevenness, and the like.

  Moreover, the length of the droplet ejection line formed for each discharge part can be set to an arbitrary length. That is, the number of droplet ejection points constituting each droplet ejection line can be an arbitrary number, and depending on the required accuracy, the reading length of the droplet ejection line and the reading interval at the end of the droplet ejection line (predetermined interval α) ) Etc. can be set in various ways. Furthermore, even when a reading device with a low reading accuracy, that is, a low resolution is used for reading the droplet ejection line, the size of the droplet ejection point can be detected with high accuracy by increasing the number of droplet ejection points to be read.

  Also, by calculating the approximate straight line at both ends of each droplet ejection line, and calculating the size of the droplet ejection line based on the approximate lines at both ends, that is, two approximate lines, a more accurate droplet ejection point size can be calculated. can do. In addition, since the droplet ejection point interval can be calculated using only the coordinates of the end of the droplet ejection line, the calculation can be simplified.

  Moreover, in order to calculate the approximate straight line by detecting a plurality of ends of the continuous droplet ejection lines formed for each discharge unit, the detected end portions can be easily classified for each ejection unit (for each droplet ejection line). Can do. Further, the interval for detecting the end portion can be set to an arbitrary interval, and the position information of an arbitrary number of end portions can be detected by adjusting the interval. Therefore, even when droplet ejection lines having the same length are formed, the number of position information on the end can be adjusted as necessary.

  In addition, an approximate straight line is calculated from the droplet ejection lines formed for each discharge unit, the calculated approximate straight lines are compared to calculate the droplet ejection line interval, and the droplet ejection point interval is obtained from the droplet ejection line interval. This makes it possible to accurately calculate (detect) the position deviation of the droplet ejection point, and to accurately identify the information on the ejection part (droplet flight direction abnormality information) that causes the position of the droplet ejection point to cause streaks, unevenness, etc. Can get to.

  In addition, in the same way as the detection of the size of the droplet ejection point, the position shift can be detected by increasing the number of droplet ejection points and increasing the length of the droplet ejection line, and also shortening the reading interval at the end of the droplet ejection line. By doing so, it is possible to calculate with high accuracy. Further, a reading device having a low resolution can also be suitably used.

Also, if the droplet ejection lines are drawn on the same recording medium, the droplet ejection lines of all the ejection sections are not formed on the same straight line in the extending direction of the ejection section (the direction perpendicular to the transport direction of the recording medium). However, for example, even if the droplet ejection lines are formed in a plurality of different portions in the direction orthogonal to the extending direction of the ejection portion on the recording medium (the conveyance direction of the recording medium), the droplet ejection point size is preferably And the droplet ejection point interval can be calculated.
In addition, by shifting the position of the droplet ejection line in the direction parallel to the transport direction, even when the arrangement density of the ejection portions is high and adjacent droplet ejection lines (droplet ejection points) overlap, the width of the droplet ejection line is reduced. That is, the droplet ejection point size and the droplet ejection point interval can be calculated without reducing the droplet ejection point. Further, even when the formation conditions are changed as described above, the size of the droplet ejection point can be detected according to the formation condition, so that the size of the droplet ejection point can be accurately detected.

Here, in this embodiment, the relationship between the droplet ejection line width and the droplet ejection point size for each droplet ejection line formation condition is stored in the arithmetic device, but a storage device is provided separately from the arithmetic device. You may make it memorize | store in a memory | storage device and read the relationship between the width | variety of the corresponding droplet ejection line and the size of a droplet ejection point from a memory | storage device according to the formation conditions of a droplet ejection line.
Note that the relationship between the width of the droplet ejection line and the size of the droplet ejection point may be calculated and stored in the form of an equation or a table (ie, LUT), and the method is not particularly limited.

In the present embodiment, the number of ink droplets that form the droplet ejection point is used as the droplet ejection line formation condition. However, the present invention is not limited to this, and the ink type (color, etc.), the recording medium These types, nozzle types, and the like may be used as the formation conditions. That is, the relationship between the droplet ejection line width and the droplet ejection point size may be calculated for each ink type, each recording medium type, and each nozzle type.
Here, the formation condition is a condition in which the value is changed during normal operation (that is, during image recording), and at the time of ejection adjustment for finely adjusting the size of the ejected ink droplets to a desired size. This is a condition that does not change. Therefore, for example, when a piezo-type ink jet head is used, the applied voltage, applied time, applied voltage waveform, etc. applied to the piezoelectric element are values at the time of ejection adjustment in order to make the ink droplets to be ejected a desired size. However, conditions that do not change from the set value during normal operation are not formation conditions.
Further, the condition to be changed to calculate the relationship between the width of one droplet ejection line and the size of the droplet ejection point is not the formation condition.

Also, the number of one end (or the other end) of the droplet ejection line read for each ejection unit, the size of the droplet ejection point (resolution of the image drawn by the recording head), and the image reading unit The relationship between the image reading apparatus (line sensor) and the resolution is [the number of measurements at one end (or the other end) of the droplet ejection line drawn by one ejection unit] × [the number of droplet ejection points It is preferable that the resolution (resolution of the image drawn by the recording head, minimum interval)] / [reading resolution of image reading apparatus (minimum reading interval)]> 100 is satisfied.
By satisfying the above formula, the size of the droplet ejection point can be accurately calculated. Furthermore, the position of the droplet ejection point can be accurately calculated, and the positional deviation of the droplet ejection point can also be accurately calculated.

  Further, in this embodiment, as shown in FIGS. 14A and 14B, when detecting the coordinates of the end of the droplet ejection line, the y coordinate where one end is different from the other end is used. Although the point which has is detected, you may detect the point which has the same y coordinate.

  Also, as described above, depending on the position of the origin of the coordinate axis, one end of the droplet ejection line is the end near the Y axis, and the other end of the droplet ejection line is the end far from the Y axis. However, the present invention is not limited to this. One end of the droplet ejection line is an end on the side far from the Y axis, and the other end of the droplet ejection line is an end near the Y axis. Also good.

Further, in the present embodiment, the droplet ejection points formed on the recording medium P, a collection G _A droplet deposition line formed by the odd number of ejection portions, the droplet ejection line formed by the even number of ejection portions Although divided into aggregate G _B, the present invention is not limited thereto, be formed a row of droplet ejection lines in three, be formed a row of droplet ejection lines in four Good.

Further, a state in which adjacent droplet ejection lines do not contact on the recording medium, that is, a droplet ejection line formed by a certain ejection unit and a droplet ejection line formed by an adjacent ejection unit can be formed in a non-contact manner. preferable.
By not contacting the droplet ejection line and the adjacent droplet ejection line, both ends in the reference direction of each droplet ejection line can be accurately detected.
For example, if the size of the ejected ink droplet can be adjusted, that is, the size of the droplet ejection point (width of the droplet ejection line) can be adjusted, the ejected ink droplet can be made smaller and the droplet ejection point made smaller. It is preferable that the droplet ejection line and the adjacent droplet ejection line are formed in a non-contact manner.
Further, if the droplet ejection lines can be formed in a non-contact manner, the droplet ejection lines formed by all the discharge units may be formed at positions where the positions in the reference direction are the same.

In this embodiment, an image in which droplet ejection lines are formed only by odd-numbered ejection sections and droplet ejection lines are formed by only even-number ejection sections is formed. However, the present invention is not limited to this, and odd-number ejection nozzles are formed. Alternatively, an image may be formed in which a plurality of droplet ejection lines are formed alternately for each ejection unit by the number of ejection units and the even number of ejection units.
In this way, even when a plurality of droplet ejection lines are formed apart from each other, that is, in other words, in the direction orthogonal to the reference direction, another ejection unit is formed between two droplet ejection lines formed by the same ejection unit. Even when the droplet ejection line formed by the above is formed, an approximate straight line for each ejection unit can be calculated in the same manner, and the droplet ejection point size and the droplet ejection point interval can be calculated (detected).

  Further, in order to accurately calculate the droplet ejection point interval between all the ejection units, it is preferable to form all droplet ejection lines on one recording medium, but the present invention is not limited to this, and a plurality of droplet ejection lines are not limited to this. A droplet ejection line may be calculated by forming a droplet ejection line on the recording medium. In this case, ink droplets are always ejected from a part of the ejection units, that is, droplet ejection lines are formed on all of the plurality of recording media, and the reference droplet ejection lines are formed. By taking correspondence between the recording media, it is possible to detect the size of the droplet ejection point of all the ejection units and the position deviation of the droplet ejection point between all the ejection units.

  Further, the method of calculating the approximate line is not limited to the least square method, and various calculation methods can be used. For example, two adjacent points, that is, any one point of one end detected from the droplet ejection line formed by the same ejection unit, and the above arbitrary one point of one end of the same droplet ejection line The slope (α) and intercept (β) of the approximate line may be calculated by averaging the slope (a) and intercept (b) of a straight line (y = ax + b) calculated from another adjacent point. More specifically, the number of one end or the other end detected from the droplet ejection line formed by one ejection unit is N, and the x coordinate of the i-th one or other end is the x coordinate. An approximate straight line can also be calculated using the following equation (6), where xi is the y coordinate of one or the other end of the i th point of the droplet ejection point.

  Furthermore, in the present embodiment, the width of the droplet ejection line is detected using an approximate straight line, but the present invention is not limited to this, and a method for calculating the width of the droplet ejection line is a drawn droplet ejection line array. Various methods such as a method of calculating a line width based on a preset threshold value from an image density profile in a direction orthogonal to the droplet ejection line array on the data in which the image is captured can be used.

  Further, in this embodiment, in addition to the size of the droplet ejection point, the positional deviation of the droplet ejection point (interval of the droplet ejection point) is detected. However, the present invention is not limited to this, and only the size of the droplet ejection point is detected. May be.

  In this embodiment, the active energy curable ink is used as the ink, and the active energy curable ink is ejected from the recording head to form an image of the active energy curable ink on the recording medium P. Although described as a digital label printing apparatus that irradiates light, cures an image, and fixes an image on a recording medium, the present invention is not limited to this, and will be described in detail later with specific examples. It can also be used as a droplet ejection point size detection method for an ink jet drawing apparatus that fixes an image on the recording medium P by heating and pressurizing the image recorded on the recording medium P.

  In the above-described embodiment, the recording head of the drawing unit is a full-line head type in which the ejection units are arranged in a line in a line. However, the recording head is not limited to a single-line arrangement, and as shown in FIG. 640 may be arranged in a staggered manner by shifting a plurality of rows of ejection portions by a certain pitch. In this manner, by arranging the ejection units 60 in a staggered manner and forming one row of droplet ejection points with a plurality of rows of ejection units, it is possible to form an image with higher resolution.

  Here, in this embodiment, the image data detected by the image reading unit is sent to the control unit, the image data is processed by the arithmetic unit of the control unit, and the size of the droplet ejection point and the positional deviation of the droplet ejection point are detected. The present invention is not limited to this, and the image reading unit may be integrally provided with an arithmetic device. That is, a droplet ejection point size detection device in which the image reading unit and the arithmetic device are integrated may be used.

  In this embodiment, the image reading unit and the arithmetic unit are provided in the ink jet drawing apparatus. However, the present invention is not limited to this, and the ink jet drawing apparatus is not provided with the image reading unit in the ink jet drawing apparatus. It is also possible to use a droplet ejection point size detection device that reads a recording medium on which an image has been drawn with an image reading device and detects the size of the droplet ejection point in the same manner as described above.

As an example, as shown in FIG. 19, even if the digital label printing device 650, the arithmetic device 660, and the image reading device 670 are separate devices, the size of the droplet ejection point and the positional deviation of the droplet ejection point are detected. be able to.
The digital label printing apparatus 650 is an apparatus that forms an image on the recording medium P using a full-line head type ink jet head, and the arithmetic unit 660 is an ejection for forming an image on the recording medium from input image data. The image reading device 670 is a device that reads an image formed on the recording medium P by the digital label printing device 650. Here, the ejection signal refers to an ejection unit to be driven among a plurality of ejection units of the recording head according to the conveyance of the recording medium P, timing for ejecting ink droplets from the ejection unit, amount of ejected droplets, etc. For example, in the case of a piezo-type ink jet head, this is a signal for controlling the height, length, timing, etc. of the voltage applied to the actuator for each ejection unit.

In the case of such an apparatus configuration, first, the droplet ejection point size and the image data for detecting the positional deviation of the droplet ejection point are input to the arithmetic unit 660. Specifically, image data of an image as shown in FIG. 12 is input.
The arithmetic device 660 calculates an ejection signal from the input image data and sends it to the digital label printing device 650. The digital label printing device 650 forms an image on the recording medium P based on the ejection signal calculated by the arithmetic device 660. In this manner, an image for detecting the size of the droplet ejection point and the position deviation of the droplet ejection point is formed. Note that the droplet ejection point size and the droplet ejection point displacement detection image are formed for each ejection unit on a single recording medium as shown in FIG. 12, and are adjacent to the arrangement direction of the ejection units. It is an image formed at a position where the droplet ejection lines do not contact each other.

Next, the image reading device 670 reads an image for detecting the size of the droplet ejection point and the droplet ejection point position deviation. The image reading device 670 sends the read image to the arithmetic device 660.
The arithmetic device 660 calculates the size of the droplet ejection point and the positional deviation (interval) of the droplet ejection point based on the image data sent from the image reading device 670. The method for calculating the size of the droplet ejection point and the positional deviation of the droplet ejection point from the read image data is the same as described above.
Further, the arithmetic device 660 calculates a correction value based on the acquired droplet ejection point size and droplet ejection point positional deviation information.
Thereafter, when normal image data is input, the arithmetic device 660 calculates an ejection signal from the input image data while taking into account the calculated correction value.
The digital label printing apparatus 650 forms an image on the recording medium P based on the acquired ejection signal.
In this way, by calculating the ejection signal in consideration of the size of the droplet ejection point and the positional deviation of the droplet ejection point, and rendering the image with the digital label printing apparatus, it is possible to render an image without streaks or unevenness. .

Here, in the present embodiment, the calculation device, the digital label printing device, and the image reading device are divided into three, but the present invention is not limited to this, and the calculation device and the digital label printing device are used as one device. Also good. Further, the image reading device only reads the image for detecting the droplet ejection point position deviation and the droplet ejection point size, and the computing device calculates the droplet ejection point size and the droplet ejection point position from the read image data. Although the calculation of the positional deviation (interval) of the droplet ejection point and the correspondence between the droplet ejection point and the ejection portion of the recording head, etc., the present invention is not limited to this. Further, the droplet ejection point interval may be calculated, and the calculation result may be sent to the arithmetic device.
In this embodiment, the digital label printing apparatus is used. However, when the digital label printing apparatus is an ink jet drawing apparatus, each apparatus can be a separate apparatus in the same manner as described above.

Next, another example of the digital label printing apparatus will be described with reference to FIG.
The digital label printing apparatus 101 shown in FIG. 20 has the same configuration as the digital label printing apparatus 100 shown in FIG. 1 except for the position of the buffer. Accordingly, the same reference numerals are given to the same components in both, and the detailed description thereof will be omitted, and the points peculiar to the digital label printing apparatus 101 will be mainly described below.
In the digital label printing apparatus 101 illustrated in FIG. 20, a buffer is disposed between the drawing unit 112 and the smoothing unit 116. Thus, the position of the transport buffer is not particularly limited, and can be various positions. Similarly, in the following embodiments, the transfer buffer may be disposed between the drawing unit 112 and the smoothing unit 116.

In the above embodiment, the undercoat layer is formed on the recording medium. However, the present invention is not limited to this, and the undercoat layer is not necessarily provided. It can also be used for an image recording apparatus for forming a drop point.
In addition, when an undercoat layer is provided, a uniform undercoat layer can be formed, and therefore, it is preferable to apply by the above-described method. Also good.
Further, since an image with higher image quality can be formed as described above, the undercoat layer is preferably semi-cured, but the image may be formed without being semi-cured.

  In the above embodiment, the digital label printing apparatus has been described as an ultraviolet curable ink jet head label printing machine. However, the present invention is not limited to this, and can be applied to any type of printing apparatus capable of foil stamp printing. The effect of.

  In the above embodiment, an example in which the present invention is used in a digital label printing apparatus has been described. However, the present invention is not limited to this, and is not limited to a recording head using an active energy ray-curable ink. The present invention can be used in various types of ink jet drawing apparatuses using various inks.

FIG. 21 is a front view showing a schematic configuration of another example ink jet drawing apparatus 710 using the droplet ejection spot size detection method of the present invention, and FIG. 22 is a suction belt conveyance unit of the ink jet drawing apparatus 710 shown in FIG. 736 is a top view illustrating a recording head unit 750 and 736. FIG.
The inkjet drawing apparatus 710 basically includes a supply unit 712 that supplies the recording medium P, a conveyance unit 714 that conveys the recording medium P supplied from the supply unit 712 while maintaining flatness, and a conveyance unit. A drawing unit 716 disposed opposite to the recording medium 714 and having a recording head unit 750 for drawing an image on the recording medium P, an ink storage / loading unit 752 for storing ink to be supplied to the recording head unit 750, and the like. Is recorded on the recording medium P by the heating and pressing unit 718 that heats and presses the recording medium P on which the image is drawn, the discharge unit 720 that discharges the recording medium P on which the image is drawn, and the drawing unit 716. An image reading unit 724 that reads a scanned image, a calculation unit 726 that calculates the size of the droplet ejection point from the image data read by the image reading unit 724, and controls these from the image data That a control unit 722.

The supply unit 712 includes a magazine 730, a heating drum 732, and a cutter 734.
The magazine 730 stores a roll-shaped recording medium P. At the time of image drawing, the recording medium P is supplied from the magazine 730 to the heating drum 732.
The heating drum 732 is arranged on the downstream side of the magazine 730 in the conveyance path of the recording medium P, and the recording medium P sent out from the magazine 730 is bent in a direction opposite to the direction stored in the magazine 730. Heat in state.
By heating the recording medium P by the heating drum 732, the winding habit attached to the recording medium P is removed while being stored in the magazine 730. That is, the heating drum 732 performs a decurling process on the recording medium P.
At this time, it is preferable to control the heating temperature so that the recording medium P is curled outwardly on the printing surface.

The cutter 734 includes a fixed blade 734A having a length equal to or larger than the conveyance path width of the recording medium P and a round blade 734B that moves along the fixed blade 734A. The round blade 734b is disposed on the surface, and the fixed blade 734A is disposed on the opposite surface across the conveyance path.
The cutter 734 cuts the recording medium P supplied through the heating drum 732 into a desired size.

  Here, in this embodiment, the supply unit has one magazine. However, the present invention is not limited to this. For example, a plurality of magazines containing recording media having different paper width, paper quality, and type may be arranged. Also, a cassette in which a large number of recording media that have been cut in advance to a predetermined length can be used instead of or in addition to the magazine. When only the recording medium P that has been cut to a predetermined length is used as the recording medium P, the above-described heating roller and cutter are not necessarily provided.

  Further, when a plurality of magazines and / or cassettes are used and a plurality of types of recording paper can be used, an information recording body such as a bar code or a wireless tag in which the paper type information is recorded is used as the magazine and / or cassette. Attach and read the information of the information recording medium with a predetermined reader to automatically determine the type of paper to be used, and perform ink ejection control to realize appropriate ink ejection according to the type of paper Preferably it is done.

  The conveyance unit 714 includes an adsorption belt conveyance unit 736, an adsorption chamber 739, a fan 740, a belt cleaning unit 742, and a heating fan 744. The recording medium P that has been decurled by the supply unit 712 and cut to a predetermined length is provided. The drawing position is conveyed to a position where an image is drawn by a drawing unit 716 described later.

The suction belt conveyance unit 736 is disposed on the downstream side of the cutter 734 in the conveyance path of the recording medium P, and includes a roller 737a, a roller 737b, and a belt 738.
The belt 738 is an endless belt having a width that is wider than the width of the recording medium P, and is stretched between a roller 737a and a roller 737b. The belt 738 has a plurality of suction holes (not shown) formed on the belt surface.
Further, at least an image drawing (printing) position of the suction belt conveyance unit 736, that is, a nozzle surface of a recording head unit 750 described later of the drawing unit 716 and an image detection position, that is, a sensor surface of the image reading unit 724 described later. The facing portions are held horizontally (flat) with respect to the nozzle surface and the sensor surface.
At least one of the rollers 737a and 737b around which the belt 738 is wound is connected to a motor (not shown), and the power of the motor is transmitted to the belt 738 via at least one of the rollers 737a and 737b. Is driven in the clockwise direction in FIG. 21, and the recording medium P held on the belt 738 is conveyed from left to right in FIG.

  Here, the transport means for the recording medium P is not particularly limited, and a roller / nip transport mechanism can be used instead of the suction belt transport section 736. However, when the drawing area is conveyed by the roller / nip, the roller contacts the printing surface immediately after printing, so that there is a problem that the image is likely to spread. Therefore, the printing area does not contact the image surface as in the present embodiment. Adsorption belt conveyance is preferred.

The suction chamber 739 is provided inside the belt 738 at a position facing a nozzle surface of a recording head unit 750 (to be described later) of the drawing unit 716 and a sensor surface of the image reading unit 724. The fan 740 is connected to the adsorption chamber 739. By sucking the suction chamber 739 with the fan 740 and making it a negative pressure, the recording medium P on the belt 738 is sucked and held on the belt 738.
By adsorbing the recording medium P to the belt, the recording medium P can be stably held.

The belt cleaning unit 742 is disposed outside the belt 738, that is, on the side facing the ring-shaped outer peripheral surface, and at a position away from the conveyance path of the recording medium P. That is, the belt 738 passes through the drawing unit 716, discharges the recording medium P to a pressure roller 754 described later, and then passes through a position facing the belt cleaning unit 742.
The belt cleaning unit 742 removes ink attached on the belt 738 by performing borderless printing or the like. Examples of the belt cleaning unit 742 include a method of niping a brush / roll, a water absorbing roll, an air blow method of blowing clean air, or a combination thereof. In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.

The heating fan 744 is disposed outside the belt 738 and on the upstream side of a recording head unit 750 described later of the drawing unit 716 on the conveyance path of the recording medium P.
The heating fan 744 blows heated air on the recording medium P before drawing to heat the recording medium P. By heating the recording medium P immediately before drawing, the ink is easily dried after landing.

  The drawing unit 716 includes a recording head unit 750 that draws (prints) an image, and an ink storage / loading unit 752 that supplies ink to the recording head unit 750.

The recording head unit 750 includes recording heads 750C, 750M, 750Y, and 750K, and is disposed to face a surface of the belt 738 on which the recording medium P is placed.
The recording heads 750C, 750M, 750Y, and 750K are piezo-type inkjet heads that discharge cyan (C), magenta (M), yellow (Y), and black (K) ink from the discharge unit, respectively. The recording heads 750 </ b> C, 750 </ b> M, 750 </ b> Y, and 750 </ b> K are arranged in the order closer to the heating fan 744 on the downstream side in the transport direction of the recording medium P from the heating fan 744 facing the surface on which the recording medium P of 738 is placed. Arranged in order.
Further, as shown in FIG. 22, the recording heads 750C, 750M, 750Y, and 750K include a plurality of recording heads in a region where the width in the direction orthogonal to the conveyance direction of the recording medium P exceeds the maximum width of the recording medium P to be conveyed. This is a full-line type inkjet head in which ejection portions (nozzles) are arranged in a line. Since the configuration around the ejection section of the recording heads 750C, 750M, 750Y, and 750K is the same as that of the recording heads 136C, 136M, 136Y, and 136K described above, detailed description thereof is omitted.
Further, a color image can be formed on the recording medium P by ejecting the color inks from the recording heads 750C, 750M, 750Y, and 750K while conveying the recording medium P.

Here, in this embodiment, the recording head unit is configured to have CMYK standard colors (four colors), but the combination of ink colors and the number of colors is not limited to this embodiment, and for example, light ink, dark ink May be added. More specifically, it is possible to add a recording head that discharges light ink such as light cyan and light magenta.
Further, the recording head unit can be used only as a recording head that discharges K (black) ink, that is, a monochrome recording head unit, and can be used as an image drawing apparatus that draws a monochrome image.

The ink storage / loading unit 752 includes an ink supply tank that stores ink of a color corresponding to each of the recording heads 750C, 750M, 750Y, and 750K.
As the ink supply tank, for example, a system that replenishes ink into a tank from a replenishing port (not shown) or a cartridge system that replaces the entire tank when the ink remaining amount is low can be used.
Each ink supply tank of the ink storage / loading unit 752 communicates with each recording head 750C, 750M, 750Y, 750K via a pipe line (not shown), and supplies ink to each recording head 750C, 750M, 750Y, 750K. To do.

Here, the ink storage / loading unit 752 includes notifying means (display means, warning sound generating means, etc.) for notifying when the ink remaining amount is low, and a mechanism for preventing erroneous loading between colors. It is preferable to have.
Further, when the ink type is changed according to the intended use, it is preferable to use a cartridge system. In addition, it is preferable that the ink type information is identified by a barcode or the like, and ejection control is performed according to the ink type.

The heating / pressurizing unit 718 includes a post-drying unit 746 and a pressure roller pair 754, and heats and presses the recording medium P on which an image is drawn by the drawing unit 716, thereby drying and fixing the image portion. .
The post-drying unit 746 is disposed on the downstream side of the recording head unit 750 in the conveyance path of the recording medium P and at a position facing the belt 738. The post-drying unit 746 is a heating fan or the like, blows hot air on the image surface of the recording medium P, and dries the drawn image.
Here, the post-drying unit 746 is preferably blown with hot air using a heating fan.
By drying the ink in the image area on the recording medium with the heating fan, the ink can be dried without contacting the image area. Thereby, it is possible to prevent the image drawn on the recording medium P from causing image defects and image stains.

Further, the pressure roller pair 754 is disposed on the downstream side of the post-drying unit 746 in the conveyance path of the recording medium P. The pressure roller pair 754 sandwiches and conveys the recording medium P separated from the belt 738 after passing through the post-drying unit 746.
The pressure roller pair 754 is a means for controlling the glossiness of the image surface. The heating roller pair 754 has a predetermined surface uneven shape while heating the image surface of the recording medium P conveyed by the suction belt conveyance unit 736. Pressure is applied by the pressure roller 754 to transfer the uneven shape to the image surface.

  In addition, when printing on porous paper with dye-based ink, it is possible to prevent contact with things that cause destruction of dye molecules, such as ozone, by blocking the paper holes by pressurization. The weather resistance of can be improved.

Further, in the inkjet drawing apparatus 710, a cutter (second cutter) 756 is disposed on the downstream side of the heating / pressurizing unit 718 in the conveyance path of the recording medium P.
The cutter 756 includes a fixed blade 756A and a round blade 756B. When a normal image and an image for detecting displacement are formed on the recording medium P, a normal image portion and an image for detecting the droplet ejection point size are formed. Separate the part.

The discharge unit 720 includes a first discharge unit 758 </ b> A and a second discharge unit 758 </ b> B, and is disposed on the downstream side of the cutter 756 in the conveyance direction of the recording medium P. The discharge unit 720 discharges the recording medium P on which the image is fixed by the heating / pressurizing unit 718.
Here, in the present embodiment, according to the image recorded on the recording medium P, the sorting unit (not shown) switches the discharging unit that discharges the recording medium P, and a normal image is drawn on the first discharging unit 758A. The recorded medium is discharged, and the second discharged portion 758B is discharged with the recording medium on which the image used for detecting the misregistration is drawn or an unnecessary recorded medium.

  Further, it is preferable that the discharge unit 720 is provided with a sorter for collecting images according to orders.

  As in the present embodiment, it is preferable to provide two discharge units so that the discharge unit can be selected according to the purpose. However, the present invention is not limited to this. The medium may be discharged from one discharge unit. Moreover, you may provide three or more discharge parts.

  Next, the control unit 722 supplies the recording medium by the supply unit 712, the conveyance unit 714, the drawing unit 716, the heating / pressurizing unit 718, the discharge unit 720, and the image reading unit 724, heating, drawing, and the droplet ejection point. Control size detection. The configuration of the control unit 722 will be described in detail later.

  The image reading unit 724 is disposed at a position facing the outside (outer peripheral surface) of the belt 738 and between the recording head unit 750 and the post-drying unit 746. The image reading unit 724 includes an image sensor (line sensor or the like) for imaging the droplet ejection result of the drawing unit 716, and reads an image using the image sensor.

  The image reading unit 724 according to this embodiment includes a line sensor having a light receiving element array wider than the ink discharge width (image recording width) by the recording heads 750C, 750M, 750Y, and 750K. The line sensor includes an R sensor array in which photoelectric conversion elements (pixels) provided with a red (R) color filter are arranged in a line, a G sensor array provided with a green (G) color filter, And a color separation line CCD sensor including a B sensor array provided with a blue (B) color filter. Instead of the line sensor, an area sensor in which the light receiving elements are two-dimensionally arranged can be used.

The image reading unit 724 reads the test pattern drawn by the recording heads 750C, 750M, 750Y, and 750K for each color, and sends the read image data to the calculation unit 726.
The arithmetic device 726 detects the droplet ejection point size of each recording head and further the position deviation of the droplet ejection point based on the image data of the test pattern sent from the image reading unit.
The arrangement position of the calculation unit 726 is not particularly limited, and may be arranged in a part of the image reading unit or a part of the control unit.

FIG. 23 is a principal block diagram showing the system configuration of the control unit 722 of the ink jet drawing apparatus 710.
The control unit 722 includes a communication interface 780, a system controller 782, an image memory 784, a motor driver 786, a heater driver 788, a print control unit 790, an image buffer memory 792, a head driver 794, and the like, and as described above, the supply unit 712. , Transport unit 714, drawing unit 716, heating / pressurizing unit 718, discharge unit 720, image reading unit 724, operation unit 726, control of conveyance, heating, drawing, detection of droplet ejection point size, etc. To do.

  The system controller 782 is a control unit that controls the communication interface 780, the image memory 784, the motor driver 786, the heater driver 788, and the like. The system controller 782 includes a central processing unit (CPU) and its peripheral circuits, and performs communication control with the host computer 796, read / write control of the image memory 784, and the like, and a motor 798 and a heater 799 for the transport system. A control signal for controlling is generated.

  The communication interface 780 receives image data sent from the host computer 796 and sends it to the system controller 782. As the communication interface 780, a serial interface such as USB, IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be used. Furthermore, a buffer memory for speeding up communication may be installed.

The image memory 784 is a storage unit that temporarily stores an image input via the communication interface 780, and data is read and written through the system controller 782. The image memory 784 is not limited to a memory composed of semiconductor elements, and a magnetic medium such as a hard disk may be used.
Image data sent from the host computer 796 is taken into the inkjet drawing apparatus 710 via the communication interface 780 and stored in the image memory 784 via the system controller 782.

The motor driver 786 is a driver (drive circuit) that drives the motor 798 in accordance with an instruction from the system controller 782.
The heater driver 788 is a driver that drives the heater 799 such as the post-drying unit 746 in accordance with an instruction from the system controller 782.

  The print control unit 790 has a signal processing function for performing various processes such as processing and correction for generating a print control signal from image data in the image memory 784 under the control of the system controller 782, and the generated print The control unit supplies a control signal (print data) to the head driver 794. The print control unit 790 performs necessary signal processing, and controls the ejection amount and ejection timing of the ink droplets of the recording head 750 via the head driver 794 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 790 includes an image buffer memory 792, and image data, parameters, and other data are temporarily stored in the image buffer memory 792 when image data is processed in the print control unit 790. In FIG. 23, the image buffer memory 792 is shown in a mode associated with the print control unit 790, but it can also be used as the image memory 784. Also possible is an aspect in which the print control unit 790 and the system controller 782 are integrated to form a single processor.

  The head driver 794 drives the actuators of the ejection units of the recording heads 750C, 750M, 750Y, and 750K for each color based on the image (printing) data provided from the print control unit 790. The head driver 794 may include a feedback control system for keeping the head driving conditions constant.

Next, a method for creating a print or printed matter using the inkjet recording apparatus 710 will be described.
The recording medium P supplied from the magazine 730 of the supply unit 712 is decurled by the heating drum 732 and flattened. Thereafter, the sheet is cut into a predetermined length by the cutter 734 and then supplied to the transport unit 714.
The recording medium P supplied to the transport unit 714 is placed on the belt 738 of the suction belt transport unit 736 and transported along with the rotation of the belt 738.
The recording medium P transported by the suction belt transport unit 736 passes through a position facing the heating fan 744 and is heated to a predetermined temperature, and then passes through a position facing the recording head unit 750 and on the surface thereof. Each recording head ejects ink droplets in the order of C, M, Y, and K, and an image is formed on the recording medium P. When the recording medium P passes through a position facing the recording head unit 750, the recording medium P is sucked by the suction chamber 739, and the distance between the recording medium P and the recording head unit 750 is constant.
The recording medium P on which the image is formed by the recording head unit 750 is further conveyed by the belt 738, passes through a position facing the post-drying unit 746, and the image unit formed of ink is dried and pressurized. After being fixed by the roller 754, it is discharged from the first discharge portion 758A.

  The ink jet drawing apparatus 710 draws (records) an image on the recording medium P in this way, and produces a print or printed matter.

Further, since the ink jet drawing apparatus 710 of the present embodiment also uses a full line type ink jet head as a recording head, the ink droplet ejection points ejected from the respective ejection units are the same as in the digital label printing apparatus 100. If the size is different from the desired size, streaks and unevenness are caused.
On the other hand, in the ink jet drawing apparatus 710, by using the image reading unit 724 and detecting the droplet ejection point size in the same manner as the digital label printing apparatus 100 described above, the droplet ejection point can be accurately and easily determined. It is possible to detect the size and further detect the deviation of the droplet ejection point. By performing correction based on the detected size and position deviation of the droplet ejection point, a high-quality image free from streaks and unevenness can be formed.
The method for detecting the droplet ejection size, that is, the method for forming an image for detection, the method for detecting the droplet ejection point, the method for calculating the size of the droplet ejection point, and the method for calculating the interval are the same as those in the inkjet drawing apparatus according to the present embodiment. In this case, the method is the same as in the case of the digital label printing apparatus described above, and therefore the description thereof is omitted.

  Hereinafter, an example of a recording medium, an undercoat liquid, and ink that can be suitably used in an ink jet drawing apparatus and a digital label printing apparatus that can be used in the droplet ejection spot size detection method of the present invention will be described.

(Physical properties of ink and undercoat liquid)
Here, the physical properties of the ink (droplet) ejected onto the recording medium vary depending on the apparatus, but generally the viscosity at 25 ° C. is preferably 5 to 100 mPa · s, and 10 to 80 mPa · s. It is more preferable that The viscosity (25 ° C.) of the undercoat liquid before internal curing is preferably 10 to 500 mPa · s, and more preferably 50 to 300 mPa · s.

In the present invention, from the viewpoint of forming dots of a desired size on the recording medium, the undercoat liquid preferably contains a surfactant, and the following conditions (A), (B) and (C) It is more preferable to satisfy all of the above.
(A) The surface tension of the undercoat liquid is smaller than the surface tension of any ink ejected onto the recording medium.
(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) ^max ) / 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. γs (saturation) ^max is the maximum value of γs (saturation) determined for all surfactants satisfying the condition (B) among the surfactants contained in the undercoat liquid.

<Condition (A)>
In the present invention, as described above, in order to form an ink dot of a desired size on a recording medium, it is preferable to make the surface tension γs of the undercoat liquid smaller than the surface tension γk of any ink. .
Further, from the viewpoint of more effectively preventing the expansion of ink dots from landing to exposure, it is more preferable that γs <γk-3 (mN / m), and γs <γk-5 (mN / m). It is particularly preferred that
In the case of forming (printing or drawing) a full-color image, from the viewpoint of improving the sharpness of the image, the surface tension γs of the undercoat liquid is at least higher than the surface tension of the ink containing a colorant having high visibility. It is preferable to make it smaller, and it is more preferred to make it smaller than the surface tension of all inks. Examples of the colorant with high visibility include colorants exhibiting magenta, black, and cyan colors.
Further, from the viewpoint of proper discharge, the surface tension γk of the ink and the surface tension γs of the undercoat liquid satisfy the above-described relationship between the surface tension γk of the ink and the surface tension γs of the undercoat liquid, and each 15 mN / m. It is preferably in the range of 50 mN / m or less, more preferably 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.
By setting both values to 15 mN / m or more, it is possible to suitably form droplets at the time of droplet ejection by the inkjet head, and it is possible to prevent non-ejection. That is, ink droplets can be suitably discharged. Moreover, by setting it as 50 mN / m or less, wettability with an inkjet head can be made high and an ink droplet can be discharged suitably. That is, it is possible to prevent non-ejection of droplets. By setting both values within the range of 18 mN / m or more and 40 mN / m or less, and further within the range of 20 mN / m or more and 38 mN / m or less, the above effects can be obtained more suitably, and ink droplets can be obtained. Can be reliably discharged.
Here, in the present embodiment, 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). The value measured at 60% RH.

<Condition (B) and Condition (C)>
In the present invention, the undercoat liquid preferably contains at least one kind of surfactant. By containing at least one type of surfactant in the undercoat liquid, it is possible to more reliably form ink dots of a desired size on the recording medium. 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) ^max ) / 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. γs (saturation) ^max 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 (saturated), and γs (saturated) ^max will be specifically described.
For example, the components constituting the undercoat liquid (Example 1) are a high boiling point solvent (diethyl phthalate, manufactured by Wako Pure Chemical Industries, Ltd.), a polymerizable material (dipropylene glycol diacrylate, manufactured by Akcros), a polymerization initiator. (TPO, the following initiator-1), fluorosurfactant (Megafac F475, manufactured by Dainippon Ink & Chemicals, Inc.), hydrocarbon surfactant (di-2-ethylhexyl sodium sulfosuccinate) Γs (0), γs (saturated) ¹ (when a fluorosurfactant is added), γs (saturated) ² (when a hydrocarbon surfactant is added), γs (saturated), and γs (Saturation) ^max is as follows.

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

From the above results, the surface tension γs of the undercoat liquid in the above specific example is
γs <(γs (0) + γs (saturation) ^max ) /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) ^max } / 4
It is more preferable to satisfy the relationship
γs ≦ γs (saturation) ^max
It is particularly preferable to satisfy this relationship.

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

(Surfactant)
In the present invention, as the surfactant, hexane, cyclohexane, p-xylene, toluene, ethyl acetate, methyl ethyl ketone, butyl carbitol, cyclohexanone, triethylene glycol monobutyl ether, 1,2-hexanediol, propylene glycol monomethyl ether, isopropanol, Substance having strong surface activity against at least one solvent among methanol, water, isobornyl acrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, preferably hexane, toluene, propylene glycol monomethyl ether , Isobornyl acrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate More preferably, it has a strong surface activity against at least one solvent among propylene glycol monomethyl ether, isobornyl acrylate, 1,6-hexanediol diacrylate, and polyethylene glycol diacrylate. It is preferable to use a substance having a strong surface activity with respect to at least one kind of solvent among the substances having, particularly preferably isobonyl acrylate, 1,6-hexanediol diacrylate, and polyethylene glycol diacrylate.

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

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

(Curing sensitivity of ink and undercoat liquid)
In the present invention, the curing sensitivity of the ink is preferably equal to or higher than the curing sensitivity of the undercoat liquid. The curing sensitivity of the ink is more preferably set to be equal to or higher than the curing sensitivity of the undercoat liquid and 4 times or less of the curing sensitivity of the undercoat liquid, and is set to be equal to or higher than the curing sensitivity of the undercoat liquid and not more than twice the curing sensitivity of the undercoat liquid. Is more preferable.
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 (ultrahigh pressure, high pressure, medium pressure, etc., preferably an ultrahigh 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 required for complete curing is ½.
Further, the phrase “curing sensitivity is equivalent” means that the difference in curing sensitivity between the two compared is 2 times or less, more preferably 1.5 times or less.

(Recording medium)
In the ink jet recording apparatus of this embodiment, any of a permeable recording medium, a non-permeable recording medium, and a slowly permeable recording medium can be used as the recording medium. In particular, when a non-permeable or slowly permeable recording medium is used as the recording medium, the effects of the present invention can be obtained more remarkably. Here, the permeable recording medium is a recording medium in which, for example, when a 10 pL (picoliter) droplet is dropped on the recording medium, the time until the entire liquid amount permeates is 100 ms or less. Say. Further, the non-permeable recording medium refers to a recording medium in which liquid droplets do not substantially permeate. “Substantially does not penetrate” means, for example, that the penetration rate of a droplet after 1 minute is 5% or less. Further, the slow-penetrating recording medium refers to a recording medium in which when a 10 pL droplet is dropped on the recording medium, the time until the entire liquid amount 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 recording medium of 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, Examples include acrylonitrile-butadiene-styrene copolymer, diacetate, triacetate, polyimide, cellophane, celluloid and the like. 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.

  As the recording medium of this synthetic resin, it is also preferable to use various non-absorbing plastics in the form of films used for so-called soft packaging and films thereof. 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 recording medium for resin-coated paper include a transparent polyester film, an opaque polyester film, an opaque polyolefin resin film, and a paper support in which both sides of paper are laminated with a polyolefin resin. In particular, it is preferable to use a paper support in which both sides of paper are laminated with a polyolefin resin.

  The metal recording medium is not particularly limited, and for example, aluminum, iron, gold, silver, copper, nickel, titanium, chromium, molybdenum, silicon, lead, zinc, etc. and stainless steel, and composite materials thereof are suitable. Can be used.

  Furthermore, as a recording medium, 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, a rewritable optical disk, or the like can be used. In this case, it is preferable to record an image on the so-called label surface side.

(Ink and undercoat liquid)
Hereinafter, the ink and the undercoat liquid that can be suitably used in the present invention will be described in detail.

The ink has a composition that forms at least an image, includes at least one polymerizable or crosslinkable material, and uses a polymerization initiator, a lipophilic solvent, a colorant, and other components as necessary. Composed.
The undercoat liquid preferably contains at least one polymerizable or crosslinkable material, and is composed of a polymerization initiator, a lipophilic solvent, a colorant and other components as necessary. Further, the undercoat liquid is preferably configured to have a composition different from that of the ink.

The polymerization initiator is preferably capable of initiating a polymerization reaction or a crosslinking reaction by 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 and / or ink contain a radically polymerizable composition. In the present invention, the radical polymerizable composition is a composition containing at least one radical polymerizable material and at least one radical polymerization initiator. When the undercoat liquid and / or the ink contains the radical polymerizable composition, the curing reaction of the undercoat liquid and / or the ink can be performed with high sensitivity in a short time.
The ink preferably contains a colorant. In addition, the undercoat liquid used in combination with this ink is either a composition containing no colorant or having a colorant content of less than 1% by mass, or a composition in which the undercoat liquid contains a white pigment as a colorant. Preferably there is.
Hereinafter, each component constituting the ink and / or the undercoat liquid will be described in detail.

(Polymerizable or crosslinkable material)
The polymerizable or crosslinkable material has a function of causing a polymerization or crosslinking reaction by an initiating species such as a radical generated from a polymerization initiator described later, and curing a composition containing these.

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

As the polymerizable or crosslinkable material in the present invention, it is particularly preferable to use various known radically polymerizable monomers that cause a polymerization reaction with an initiating species generated from a radical initiator.
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, shear Ethyl (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, glycidyl (meth) acrylate, glycidyloxybutyl (meth) acrylate, glycidyloxyethyl (meth) acrylate, glycidyloxypropyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, hydroxyalkyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate,

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

  Specific examples of the bifunctional (meth) acrylate include 1,6-hexanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 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 (Meth) acrylate, 1,9-nonane di (meth) acrylate, propoxylated ethoxylated bisphenol A di (meth) acrylate, tricyclodecane di (meth) acrylate and the like.

  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, dipentaerythritol tri (meth) acrylate propionate, tris (( (Meth) acryloyloxyethyl) isocyanurate, hydroxypivalaldehyde-modified dimethylolpropane tri (meth) acrylate, sorbitol tri (meta) Acrylate, propoxylated trimethylolpropane tri (meth) acrylate, and the like ethoxylated glycerol triacrylate.

  Specific examples of tetrafunctional (meth) acrylates include pentaerythritol tetra (meth) acrylate, sorbitol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate propionate, ethoxylation Examples include pentaerythritol 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) acrylates include dipentaerythritol hexa (meth) acrylate, sorbitol hexa (meth) acrylate, phosphazene alkylene oxide modified hexa (meth) acrylate, captolactone modified dipentaerythritol hexa (meth) An acrylate etc. are mentioned.

  Examples of (meth) acrylamides include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, and 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- Examples include diethyl (meth) acrylamide, (meth) acryloylmorpholine, and the like.

  Specific examples of 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 benzoic acid. Methyl ester, 3-methylstyrene, 4-methylstyrene, 3-ethylstyrene, 4-ethylstyrene, 3-propylstyrene, 4-propylstyrene, 3-butylstyrene, 4-butylstyrene, 3-hexylstyrene, 4- Hexyl styrene, 3-octyl styrene, 4-octyl styrene, 3- (2-ethylhexyl) styrene, 4- (2-ethylhexyl) styrene, allyl styrene, isopropenyl styrene, butenyl styrene, octenyl Styrene, 4-t-butoxycarbonyl styrene, 4-methoxystyrene, and a 4-t-butoxystyrene.

  Specific examples of vinyl ethers include, as examples of monofunctional vinyl ethers, 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, Cyclohexylmethyl 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 , Methoxypolye Lenglycol 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. Divinyl ethers such as divinyl ether; trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexa Nyl 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 pentane And polyfunctional vinyl ethers such as erythritol tetravinyl ether, ethylene oxide-added dipentaerythritol hexavinyl ether, and propylene oxide-added dipentaerythritol hexavinyl ether.
The vinyl ether compound is preferably a di- or trivinyl ether compound, and more preferably a divinyl ether compound, particularly from the viewpoints of curability, adhesion to a recording medium, and surface hardness of the formed image. .

  In addition to the above, the radical polymerizable monomer 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, it is preferable to use (meth) acrylates and (meth) acrylamides from the viewpoint of curing speed, and particularly from the viewpoint of curing speed, tetrafunctional or higher functional (meth) acrylate is preferably used. It is preferable to use it. Furthermore, from the viewpoint of the viscosity of the ink composition, it is preferable to use a polyfunctional (meth) acrylate in combination with a monofunctional or bifunctional (meth) acrylate or (meth) acrylamide.

The content of the polymerizable or crosslinkable material in the ink and undercoat liquid is preferably in the range of 50 to 99.6% by mass with respect to the total solid content (mass) of each droplet, and is preferably 70 to 99. It is more preferable to set it as the range of 0.0 mass%, and it is further more preferable to set it as the range of 80-99.0 mass%.
Moreover, as content in a droplet, it is preferable to set it as the range of 20-98 mass% with respect to the total mass of each droplet, The range of 40-95 mass% is more preferable, 50-90 mass% It is particularly preferable to set the range.

(Polymerization initiator)
Moreover, it is preferable that at least the undercoat liquid, or the ink and the undercoat liquid contain at least one polymerization initiator. 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 preferably contains a polymerization initiator that causes radical polymerization, and more preferably a photopolymerization initiator.
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 compound group that undergoes 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.

  Here, as the (b) aromatic onium salt compound, elements of Group V, VI and VII of the periodic table, specifically N, P, As, Sb, Bi, O, S, Se, Te, Or an aromatic onium salt of I. 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. In addition, compounds described in JP-B Nos. 52-147277, 52-14278, and 52-14279 can be preferably used. Generates radicals and acids as active species.

  Further, (c) “organic peroxide” includes almost all organic compounds having one or more oxygen-oxygen bonds in the molecule. For example, 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- Peroxyesters such as isopropylcumylperoxycarbonyl) benzophenone and di-t-butyldiperoxyisophthalate It is preferably used.

  Examples of (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 '-Tetraphenylbiimidazole, 2,2'-bis (o-methylphenyl) -4,4', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o-trifluorophenyl) -4 , 4 ′, 5,5′-tetraphenylbiimidazole and the like.

  Examples of the (e) ketoxime ester include 3-benzoyloxyiminobutane-2-one, 3-acetoxyiminobutan-2-one, 3-propionyloxyiminobutan-2-one, and 2-acetoxyimino. Pentan-3-one, 2-acetoxyimino-1-phenylpropan-1-one, 2-benzoyloxyimino-1-phenylpropan-1-one, 3-p-toluenesulfonyloxyiminobutan-2-one, And 2-ethoxycarbonyloxyimino-1-phenylpropan-1-one.

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

  Examples of (h) metallocene compounds include JP-A-59-152396, JP-A-61-151197, JP-A-63-41484, JP-A-2-249, and JP-A-2-4705. Examples thereof include titanocene compounds described in the publication, and 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-bis 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 (cyclopentadienyl) ) Bis [2,6-difluoro-3- (N-butylbialoyl-amino) phenyl] titanium and the like.

  Examples of (i) active ester compounds 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 Patent Nos. 099672, 84515, 199672, 0441115, and 0101122, respectively. Specifications, 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. JP-B 62-6223, JP-B 63-14 No. 40, and compounds, and the like described in the JP-A-59-174831.

  Moreover, (j) As a preferable example of the compound which has a carbon halogen bond, 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. Further, 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.

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

  In addition, as a polymerization initiator, what is excellent in a sensitivity is preferable, However, From a viewpoint of storage stability, it is preferable to use the polymerization initiator which does not raise | generate thermal decomposition at the temperature to 80 degreeC.

  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.

  As content in the undercoat liquid of a polymerization initiator, it shall be in the range of 0.5-20 mass% with respect to the polymeric material in undercoat liquid from a viewpoint of temporal stability, sclerosis | hardenability, and a cure rate. Is preferable, it is more preferable to set it as 1-15 mass%, and it is especially preferable to set it as 3-10 mass%. By setting the content within the above range, it is possible to suppress the occurrence of precipitation or separation over time, or the deterioration of performance such as the strength and rubbing resistance of the ink after curing.

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

(Sensitizing dye)
In addition, a sensitizing dye is preferably added to the ink and / or undercoat liquid 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.

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

  Examples of more preferable sensitizing dyes include compounds represented by the following general formulas (IX) to (XIII).

In the formula (IX), A ¹ represents a sulfur atom or —NR ⁵⁰ —, R ⁵⁰ represents an alkyl group or an aryl group, and L ² represents a basic nucleus of the dye in combination with the adjacent A ¹ and the adjacent carbon atom. R ⁵¹ and R ⁵² each independently represents a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁵¹ and R ⁵² are bonded to each other to form an acidic nucleus of the dye. May be. W represents an oxygen atom or a sulfur atom.
In formula (X), Ar ¹ and Ar ² each independently represent an aryl group and are linked via a bond with —L ³ —. Here, L ³ represents —O— or —S—. W is synonymous with that shown in the general formula (IX).
In the formula (XI), A ² represents a sulfur atom or —NR ⁵⁹ —, L ⁴ represents a nonmetallic atomic group that forms a basic nucleus of the dye together with the adjacent A ² and carbon atom, and R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ and R ⁵⁸ each independently represents a monovalent nonmetallic 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 —, wherein R ⁶² and R ⁶³ each independently represent a substituted or unsubstituted alkyl group, substituted or represents an unsubstituted aryl group, L to ^5, L ⁶ are each independently, together with the adjacent a ^3, a ⁴ and adjacent carbon atoms represents a nonmetallic atom group necessary for forming a basic nucleus of a dye, R ⁶⁰ , R ⁶¹ each independently represents a hydrogen atom or a monovalent non-metallic 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.

  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, it is preferable to add a known compound as a co-sensitizer to the ink and / or undercoat liquid that has a function of further improving sensitivity or suppressing polymerization inhibition by oxygen.
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)
At least the ink or the ink and the undercoat liquid contain at least one colorant. 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. In particular, when the ink and the undercoat liquid are composed of a water-insoluble organic solvent system that can suitably obtain the effects of the present invention, the colorant is an oil-soluble material that is easily dispersed and dissolved in a water-insoluble medium. It is preferable to use dyes and pigments.

  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. When the undercoat liquid contains a white pigment as the colorant, the content of the colorant in the undercoat liquid is preferably 2 to 45% by mass, and more preferably 4 to 35% by mass.

Hereinafter, the pigment suitable for the present invention will be mainly described.
<Pigment>
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 248M. I. Pigment red 262, or C.I. I. Disazo condensation pigments such as CI Pigment Brown 23 (C.I. No. 20060),

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

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

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

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

(Other ingredients)
In addition to the above-described components, known additives and the like can be used in combination with the ink and / or undercoat liquid depending on the purpose.

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

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

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

<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, those having a property excellent in compatibility with the constituent materials, particularly with the monomers are preferable.
Specifically, tripropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monobenzyl ether, diethylene glycol monobenzyl ether should be used. Is preferred.

  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 should be 0 to 20% by mass in each liquid. It is more preferable to set it as 0-10 mass%, and it is especially preferable not to contain substantially. The ink and undercoat liquid according to the present invention contain substantially no water, thereby improving the stability over time such as non-uniformity over time, turbidity of the liquid due to precipitation of dyes, etc. The drying property when using a slow-penetrating recording medium can also be improved. In addition, it does not contain substantially means accepting presence of an inevitable impurity.

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

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

  As described above, the droplet ejection point size detection method according to the present invention has been described in detail. However, the present invention is not limited to the above embodiment, and various improvements and modifications can be made without departing from the gist of the present invention. May be performed.

  For example, as described above, the present invention is a line head type, particularly a full head, in which the ejection unit is fixed and the recording medium is scanned in one direction, or the recording medium is fixed and the ejection unit is scanned in one direction. Although it can be particularly suitably used for an image recording apparatus using a line head type ink jet head, the same method can be used for a serial head type ink jet head.

It is a front view which shows schematic structure of an example of the digital label printing apparatus which can use the droplet ejection spot size detection method of this invention. It is a longitudinal cross-sectional view which shows the layer structure of a recording medium. It is a schematic perspective view which expands and shows the drawing part of the digital label printing apparatus shown in FIG. (A) is a front view showing an arrangement pattern of ejection portions of the recording head, and (B) is an enlarged sectional view showing one ejection portion of the recording head shown in (A). It is a schematic diagram which shows the structure of the ink supply system and head peripheral part in an inkjet drawing apparatus. The foil pressing state is shown, (A) is a cross-sectional view of the main part of the recording medium having a large unevenness on the image surface, (B) is a cross-sectional view of the main part of the recording medium pressed without smoothing, (C) is It is principal part sectional drawing of the recording medium which smoothed the unevenness | corrugation by the smoothing means, and was foil-pressed. FIG. 6 is a schematic cross-sectional view showing an example of a recording medium in which an ink liquid is ejected onto a semi-cured undercoat liquid. (A) and (B) are schematic cross-sectional views showing an example of a recording medium in which an ink liquid is deposited on an uncured undercoat liquid, and (C) is a completely cured state. FIG. 3 is a schematic cross-sectional view showing an example of a recording medium in which an ink liquid is ejected onto an undercoat liquid. FIG. 5 is a schematic cross-sectional view illustrating an example of a recording medium in which an ink liquid is ejected onto a semi-cured ink liquid. (A) and (B) are schematic cross-sectional views showing an example of a recording medium in which an ink liquid is ejected onto an uncured ink liquid, respectively, and (C) is a completely cured state. FIG. 3 is a schematic cross-sectional view illustrating an example of a recording medium on which ink liquid is ejected onto the ink liquid. (A) is a side view showing the relationship between each ejection part of the recording head and the landing position of the ink droplet, and (B) is a top view of (A). It is a top view which shows an example of the image (test pattern) used for droplet ejection spot size detection. (A) is a schematic diagram showing an example of a part of one droplet ejection line of an image read by the image reading unit, and (B) is an example of binarizing the image data shown in (A). It is a schematic diagram shown. (A) And (B) is a schematic diagram explaining an example of the calculation method of the position of the both ends of a droplet ejection line, respectively. It is a schematic diagram which shows the approximate straight line computed for every discharge part. (A)-(C) are the top views which show typically the relationship between a droplet ejection point and a droplet ejection line, respectively. (A)-(C) is a graph which shows the relationship between the width of a droplet ejection line according to the formation conditions of a droplet ejection line, and the size of a droplet ejection point, respectively. FIG. 10 is a top view illustrating another example of the arrangement pattern of the ejection units of the recording head. It is a schematic block diagram which shows another example of the apparatus structure which can use the droplet ejection point size detection method of this invention. It is a schematic block diagram of the digital label printing apparatus of the modification of the digital label printing apparatus shown in FIG. It is a front view which shows schematic structure of an inkjet drawing apparatus. FIG. 22 is a top view showing the suction conveyance bell and the recording head unit of the ink jet drawing apparatus shown in FIG. 21. It is a principal part block diagram which shows the system configuration | structure of the control part shown in FIG.

Explanation of symbols

60 Discharge Unit 61 Ink Chamber Unit 62 Nozzle 63 Pressure Chamber 64 Supply Port 65 Common Channel 66 Actuator 67 Pressure Plate 68 Individual Electrode 70 Ink Supply Tank 72 Filter 74 Cap 76 Cleaning Blade 77 Suction Pump 78 Collection Tank 80 Communication Interface 82 System Controller 84 Image memory 86 Motor driver 88 Heat driver 90 Print control unit 92 Image buffer memory 94 Head driver 96 Host computer 98 Motor 99 Heater 100 Digital label printing device 110, 714 Conveying unit 112, 716 Drawing unit 114, 724 Image reading unit 116 Smoothing Forming section 118 foil pressing section 120 label removing section 121, 722 control section 122 supply roll 124, 126, 128, 130, 132 Feed roller pair 134 product roll 135,750 recording head unit 136W, 136C, 136Y, 136M, 136K, 750K, 750C, 750M, 750Y recording head (inkjet head)
137, 752 Ink storage / loading unit 138 UV irradiation unit 142 Varnish coater 144, 145 Coating roller 146 Flat pressure member 148 UV irradiation unit 150 Foil supply roll 152 Foil winding rolls 154, 156, 737b Roller 158 Foil 160 Hot stamp Plate 162 Varnish coater 164 Ultraviolet irradiation section 166 Die cutter 168 Cylinder cutter 170 Receiving roller 172 Waste removal section 710 Inkjet drawing device 712 Supply section 718 Heating / pressurizing section 720 Discharge section 726 Calculation section 730 Magazine 732 Heating drum 734, 756 Cutter 734 Fixed blades 734b and 756b Round blades 736 Adsorption belt transport unit 738 Belt 739 Adsorption chamber 740 Fan 742 Belt cleaning unit 744 Heating fan 74 A post-drying unit 754 the pressure roller 758 discharge portion P of the recording medium

Claims (12)

A droplet ejection point size detection method for detecting a droplet ejection point size of an ink droplet ejected from the ejection unit of a recording head including at least one ejection unit that ejects ink droplets and landing on a recording medium. ,
Ink droplets are continuously ejected from the ejection unit, and the ink droplets are disposed adjacent to and in contact with the droplet ejection point formed by the ink droplets ejected from the same ejection unit. A droplet ejection line forming step for forming a droplet ejection point by landing and forming a droplet ejection line formed by connecting the droplet ejection points formed by one of the ejection units;
A droplet ejection line width detecting step for reading the droplet ejection line formed on the recording medium by the droplet ejection line forming step and detecting the width of the droplet ejection line from the read image;
A calculation condition reading step for reading out the relationship between the width of the droplet ejection line and the size of the droplet ejection point in accordance with the formation condition prepared in advance based on the formation condition of the droplet ejection line in the droplet ejection line formation step When,
A droplet ejection point size comprising: a calculation step of calculating the size of the droplet ejection point from the width of the detected droplet ejection line based on the relationship between the width of the read droplet ejection line and the size of the droplet ejection point Detection method.   The relationship between the width of the droplet ejection line and the size of the droplet ejection point is measured for each formation condition of the droplet ejection line, and the width of the droplet ejection line and the size of the droplet ejection point are determined for each formation condition of the droplet ejection line. The droplet ejection point size detection method according to claim 1, further comprising a step of calculating a relationship.   3. The droplet ejection point size detection method according to claim 1, wherein the formation condition of the droplet ejection line is the number of ink droplets ejected from the ejection unit to form one droplet ejection point. 4. The droplet ejection line width detecting step includes:
An image reading step for reading an image composed of the droplet ejection lines formed on the recording medium as a read image with a direction substantially orthogonal to the droplet ejection lines formed by the ejection unit as a reference direction;
From the read image, for each of the droplet ejection lines, one end position and the other end position in the reference direction of the droplet ejection line are ejected at predetermined intervals in a direction orthogonal to the reference direction. A droplet ejection line end position information calculating step for calculating as end position information;
From the droplet ejection line end position information, an approximate straight line connecting a plurality of the one end position and an approximate straight line connecting the plurality of the other end positions, the inclination of the approximate straight line is a total droplet ejection line. An approximate straight line calculation step for calculating for each droplet ejection line as common,
A droplet ejection line width calculating step for calculating a width of the droplet ejection line formed by each of the ejection units from the calculated approximate line of one end and the approximate line of the other end for each ejection unit; The droplet ejection point size detection method according to any one of claims 1 to 3.   5. The droplet ejection spot size detection method according to claim 4, wherein the approximate line calculation step calculates the approximate line by a least square method.   The droplet ejection point size detection method according to claim 1, wherein the recording head includes a plurality of ejection units arranged in a line, and the droplet ejection line is formed for each ejection unit.   In the droplet ejection line forming step, a plurality of ink droplets are ejected from each of the ejection units while relatively moving the recording medium and the ejection unit in a direction substantially perpendicular to the arrangement direction of the ejection units. The droplet ejection line according to claim 6, wherein a droplet ejection line in which a plurality of droplet ejection points are continuously arranged on the recording medium in a direction substantially orthogonal to the arrangement direction of the ejection units is formed for each ejection unit. Droplet size detection method.   8. The droplet ejection point size detection method according to claim 6, wherein the droplet ejection line forming step forms the droplet ejection line in a non-contact manner with another adjacent droplet ejection line.   7. The droplet ejection line forming step forms droplet ejection lines to be formed on the recording medium at different positions in a direction orthogonal to the arrangement direction of the ejection units according to the arrangement position of the ejection units. 9. The droplet ejection point size detection method according to any one of 8 above.   In the droplet ejection line forming step, ink droplets are ejected from every other ejection unit among the plurality of ejection units to form the droplet ejection line on the recording medium, and then the remaining ejection units 10. A droplet ejection point size detection method according to any one of claims 6 to 9, wherein ink droplets are ejected from a nozzle to form droplet ejection lines on the recording medium.   The droplet ejection point size detection method according to any one of claims 6 to 10, wherein the droplet ejection line forming step forms the droplet ejection line with a width that does not contact with an adjacent droplet ejection line.   Further, the interval between the droplet ejection point of the ejection unit and the droplet ejection point of the other ejection unit is calculated from the approximate straight line at one end position calculated for each droplet ejection line and the approximate straight line at the other end position. The droplet ejection point size detection method according to claim 6, further comprising a droplet ejection point interval calculating step.

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