JP5891603B2 - Liquid ejecting apparatus and liquid ejecting method - Google Patents

Description

  The present invention relates to a liquid ejection device and a liquid ejection method.

  There is known a liquid ejecting apparatus that records an image or characters by ejecting a liquid such as ink from a nozzle and landing droplets (ink dots) on a medium. Some liquid ejecting apparatuses eject ultraviolet curable ink (UV ink) that cures when irradiated with ultraviolet (UV) light.

  When recording an image using such UV ink, first, colored ink is ejected onto a medium to form an image, and then clear ink (transparent ink) is ejected to form a clear ink layer on the image. A method for coating an image is known. At this time, by adjusting the ejection amount of clear ink and the amount of ultraviolet light to be irradiated, a method has been proposed in which fine irregularities are imparted to the clear ink layer to make the surface “matte (low glossiness)”. (For example, Patent Document 1).

JP 2008-213152 A

  According to the method of Patent Document 1, it is possible to record an image having a matte surface by the liquid ejecting apparatus. Here, in order to express a high-definition matte tone, it is preferable to make the clear ink dots forming the clear ink layer as small as possible so that adjacent clear ink dots do not contact each other. This is because when large clear ink dots are concentrated, light is easily reflected and gloss is easily generated on the image surface.

  However, when dots are formed using a general ultraviolet curable clear ink, the clear ink dot spreads immediately after landing on the surface of the image and the dot diameter increases. That is, it is difficult to form dots having a small diameter with a general ultraviolet curable clear ink, and it is difficult to form a sufficiently high-quality matte image.

  An object of the present invention is to form a sufficiently high-quality matte image when an image is formed using ultraviolet curable ink.

The main invention for achieving the above object is: A) a head unit for ejecting liquid from a nozzle; (B) an irradiation unit for irradiating light; and (C) control for controlling ejection of the liquid and irradiation of the light. And the control unit ejects a liquid that is cured by receiving light irradiation from the head unit to each pixel in a predetermined region of the medium , and then ejects the liquid from the irradiation unit to the ejected liquid. Irradiate light to form a dot having a curing rate of 70% or more and a diameter equal to or greater than the diagonal length of the pixel as a base layer , and light from the head portion to the base layer . A clear liquid that is cured by being irradiated with a clear dot is irradiated with light from the irradiating unit to the ejected clear liquid, and has a diameter smaller than the side length of the pixel on the base layer. forming a liquid jet equipment That.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

1 is a block diagram illustrating an overall configuration of a printer. FIG. 2 is a schematic side view illustrating a configuration of the printer 1. FIG. 3A is a diagram illustrating the arrangement of a plurality of short heads in the color ink head 31 of the head unit 30. FIG. 3B is a diagram illustrating the state of the nozzle rows arranged on the lower surface of each head. 4A to 4C are diagrams illustrating the concept of an image recording operation using the printer 1. 5A and 5B are diagrams for explaining the relationship between the dot size and the glossiness of the image. 6A to 6C are diagrams for explaining changes in the shape of the clear ink dot due to the difference in water repellency of the underlying layer. It is a figure showing the relationship between the cure rate of a base layer, and the diameter of the clear ink dot formed on a base layer. 2 is a block diagram illustrating an overall configuration of a printer. FIG. FIG. 9A is a bird's eye view showing the configuration of the printer 2, and FIG. 9B is a side view showing the configuration of the printer 2. FIG. 4 is a diagram illustrating a state of a nozzle row provided in a head. It is a figure explaining the image recording operation | movement in 2nd Embodiment.

  At least the following matters will become clear from the description of the present specification and the accompanying drawings.

(A) a head unit that ejects liquid from a nozzle; (B) an irradiation unit that irradiates light; and (C) a control unit that controls ejection of the liquid and irradiation of the light, and the control unit includes: Then, a liquid that is cured by being irradiated with light is ejected from the head unit to the medium, and light is irradiated from the irradiation unit to the ejected liquid to form dots having a curing rate of 70% or more. The diameter is smaller than the length of the side of the pixel by ejecting a clear liquid that is cured by being irradiated with light from the head unit to the dots and irradiating the clear liquid ejected from the irradiation unit. A liquid ejecting apparatus for forming clear dots having
According to such a liquid ejecting apparatus, a sufficiently high-definition matte image can be formed when an image is formed using ultraviolet curable ink.

In the liquid ejecting apparatus, the control unit may form the dot as a dot having a diameter equal to or larger than the diagonal length of the pixel at each pixel in the region where the dot is formed, and It is desirable to form an underlayer.
According to such a liquid ejecting apparatus, the clear ink dots are surely formed on the base layer, and the image can be matted. Further, it is possible to prevent a difference in matte tone depending on the position (pixel) where the clear ink dot lands.

In this liquid ejecting apparatus, it is desirable that the liquid forming the dots is a liquid having an irradiation energy required for curing of 300 mJ / cm ² or less.
According to such a liquid ejecting apparatus, even when the irradiation energy (UV) is small, a good matte image can be efficiently formed.

In such a liquid ejecting apparatus, the liquid forming the base layer is represented by the following general formula (1).
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (1)
(In the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a monovalent organic residue having 1 to 11 carbon atoms. .)
It is desirable to contain the component represented by these.
According to such a liquid ejecting apparatus, the base layer can be easily cured, so that a higher definition matte image can be formed.

In this liquid ejecting apparatus, it is preferable that the diameter of the clear dot is smaller than 80% of the length of the side of the pixel.
According to such a liquid ejecting apparatus, a higher-definition matte image can be formed.

In this liquid ejecting apparatus, it is preferable that the control unit causes the clear dots to be formed in each pixel in a region where the dots are formed.
According to such a liquid ejecting apparatus, it is possible to form a uniform matte tone image in which a difference in glossiness hardly occurs for each pixel.

In addition, a liquid that is cured by being irradiated with light is ejected from a nozzle to a medium, and the ejected liquid is irradiated with light from an irradiation unit to form dots having a curing rate of 70% or more. A clear liquid that cures when irradiated with light is ejected from the nozzle to the dots, and the clear liquid that is ejected is irradiated with light from the irradiation unit to have a diameter smaller than the side length of the pixel. Forming dots,
A liquid ejection method having

  And (A) a head unit that ejects liquid from the nozzle, (B) an irradiation unit that irradiates light, and (C) a control unit that controls ejection of the liquid and irradiation of the light. The unit ejects a liquid that is cured by receiving light from the head unit to the medium, and irradiates the ejected liquid with light from the irradiation unit to form dots that cure the liquid. Then, a clear liquid that is cured by being irradiated with light is ejected from the head unit to the dots, and light is emitted from the irradiation unit to the ejected clear liquid to form clear dots, and the clear liquid is formed. The diameter of the dot is a clear dot having a diameter smaller than the diameter of the clear dot when the clear liquid is ejected onto the medium and formed by irradiating the ejected clear liquid with light. Squirt Device is clear.

=== First Embodiment ===
In the first embodiment, a line printer (printer 1) will be described as an example of a liquid ejecting apparatus for carrying out the invention.

<Configuration of Printer 1>
The printer 1 is a liquid ejecting apparatus that records an image by ejecting a liquid such as ink toward a medium such as paper, cloth, or film sheet. In this embodiment, an image is recorded on a medium by ejecting ultraviolet curable ink (hereinafter, UV ink) that is cured by irradiating ultraviolet rays (hereinafter, UV). The UV ink is an ink containing an ultraviolet curable resin, and is cured by undergoing a photopolymerization reaction in the ultraviolet curable resin when irradiated with UV. Details of the UV ink will be described later. Note that the printer 1 according to the present embodiment uses four color inks of black (K), cyan (C), magenta (M), and yellow (Y) as a UV ink, and a colorless and transparent clear ink (CL ) To record an image.

  FIG. 1 is a block diagram showing the overall structure of the printer 1. The printer 1 includes a transport unit 20, a head unit 30, an irradiation unit 40, a detector group 50, and a controller 60. The controller 60 is a control unit that controls each unit such as the head unit 30 and the irradiation unit 40 based on print data received from the computer 110 that is an external device. The situation in the printer 1 is monitored by the detector group 50, and the detector group 50 outputs the detection result to the controller 60. The controller 60 controls each unit based on the detection result output from the detector group 50.

<Computer 110>
The printer 1 is communicably connected to a computer 110 that is an external device. A printer driver is installed in the computer 110. The printer driver is a program for causing a display device to display a user interface and converting image data output from an application program into print data. This printer driver is recorded on a recording medium (computer-readable recording medium) such as a flexible disk FD or a CD-ROM. Also, the printer driver can be downloaded to the computer 110 via the Internet. In addition, this program is comprised from the code | cord | chord for implement | achieving various functions.

  The computer 110 outputs print data corresponding to the image to be printed to the printer 1 in order to cause the printer 1 to print an image. The print data is data in a format that can be interpreted by the printer 1 and includes various command data and pixel data. The command data is data for instructing the printer 1 to execute a specific operation. The command data includes, for example, command data for instructing medium supply, command data indicating the transport amount of the medium, and command data for instructing medium ejection. The pixel data is data related to pixels of an image to be printed.

  Here, the pixel is a unit element constituting an image, and is a recording unit area defined by the recording resolution. For example, if the recording resolution is 720 × 720 dpi, the area is (1/720) × (1/720) inch, and the length of the side of the pixel is 1/720 inch. The size of the pixel is the size of the distance between adjacent dots when dots are formed in each pixel. An image is formed by two-dimensionally arranging the pixels. Pixel data in the print data is data (for example, gradation values) related to dots formed on a medium (for example, paper S). The pixel data is composed of, for example, 2-bit data for each pixel. The 2-bit pixel data is data that can express one pixel with four gradations.

<Transport unit 20>
FIG. 2 is a schematic side view showing the configuration of the printer 1 of the present embodiment.

  The transport unit 20 is for transporting a medium in a predetermined direction (hereinafter referred to as a transport direction). The transport unit 20 includes a transport roller 23A on the upstream side in the transport direction, a transport roller 23B on the downstream side in the transport direction, and a belt 24 (FIG. 2). When a transport motor (not shown) rotates, the upstream transport roller 23A and the downstream transport roller 23B rotate, and the belt 24 rotates. The medium supplied by the medium supply roller (not shown) is conveyed to a printable area (an area facing a head unit 30 described later) by the belt 24. The medium that has passed through the printable area is discharged to the outside by the belt 24. Note that the medium being conveyed is electrostatically attracted or vacuum attracted to the belt 24.

<Head unit 30>
The head unit 30 is for ejecting UV ink onto the medium. The head unit 30 forms dots by ejecting color (KCMY) and clear (CL) inks to the medium being transported, and records an image on the medium. The printer 1 of the present embodiment is a line printer, and each head of the head unit 30 can form dots for the medium width at a time.

  In FIG. 2, a color ink head 31 is provided on the upstream side in the transport direction. The color ink head is composed of a black ink head (K) 311, a cyan ink head (C) 312, a magenta ink head (M) 313, and a yellow ink head (Y) 314, and UV ink of each color of KCMY. Erupt. A clear ink head 32 that ejects clear (CL) UV ink is provided on the downstream side in the transport direction of the color ink head 31. Characters and images (color images) are recorded on the medium by these heads, and a base layer described later is formed. It should be noted that the nozzle for ejecting the color ink (KCMY) and the nozzle for ejecting the clear ink (CL) may be provided in the same head.

  Further, a clear ink head 35 for ejecting clear (CL) UV ink is provided on the downstream side in the transport direction of the clear ink head 32. By ejecting clear ink from the clear ink head 35 onto the image (underlying layer), a large number of clear ink dots are formed on the image surface. In this embodiment, the clear ink dots make the image matte. Details of the method for making the image matte will be described later.

  Each head is composed of a plurality of short heads, and each short head is provided with a plurality of nozzles that are ejection ports for ejecting UV ink.

  FIG. 3A is a diagram illustrating the arrangement of a plurality of short heads in the color ink head 31 of the head unit 30. FIG. 3B is a diagram illustrating the state of the nozzle rows arranged on the lower surface of each head. 3A and 3B are views of the nozzle virtually seen from above.

  Among the color ink heads 31, the black ink head (K) 311 has a plurality of short heads 311a to 311n arranged in a staggered pattern along the medium width direction. Similarly, in the cyan ink head (C) 312, a plurality of short heads 312 a to 312 n are arranged in a staggered pattern along the medium width direction (FIG. 3A). The same applies to the magenta ink head (M) 313 and the yellow ink head (Y) 314 (not shown).

  A plurality of nozzle rows are formed in each short head (FIG. 3B). Each nozzle row includes 180 nozzles that eject ink, and the nozzles are arranged at a constant nozzle pitch (for example, 360 dpi) from # 1 to # 180 along the paper width direction. The number of nozzles in one row is not limited to 180. For example, 360 nozzles may be provided in one row, or 90 nozzles may be provided. Each nozzle is provided with an ink chamber and a piezoelectric element (both not shown) which are piezoelectric elements. The piezo element is driven by a drive signal generated by the unit control circuit 64. Then, the ink chamber expands and contracts by driving the piezo element, and the ink filled in the ink chamber is ejected from the nozzle. The piezo element group includes a plurality of comb-like piezo elements PZT (drive elements), and is provided in a number corresponding to the nozzles Nz.

  Each nozzle can eject a plurality of types of ink droplets having different amounts by a pulse applied to the piezo element in accordance with a drive signal. For example, from each nozzle, three types of ink comprising a large ink droplet capable of forming a large dot, a medium ink droplet capable of forming a medium dot, and a small ink droplet empty capable of forming a small dot. Can be ejected. Then, ink droplets are intermittently ejected from each nozzle to the medium being transported, whereby each nozzle forms a dot line (raster line) along the medium transport direction.

  The clear ink heads 32 and 35 also include a plurality of short heads similar to the color ink head 31, and the nozzle array of each short head includes 180 nozzles Nz for ejecting ink.

<Irradiation unit 40>
The irradiation unit 40 irradiates UV toward the UV ink dots landed on the medium. The dots formed on the medium are cured by receiving UV irradiation from the irradiation unit 40. The irradiation unit 40 of this embodiment includes a first irradiation unit 41 and a second irradiation unit 45.

  The first irradiation unit 41 is provided on the downstream side in the transport direction of the clear ink head 32 (FIG. 2), and irradiates UV for curing the dots formed by the color ink head 31 and the clear ink head 32. To do. The length of the first irradiation unit 41 in the medium width direction is equal to or greater than the medium width.

In the present embodiment, the first irradiation unit 41 includes a light emitting diode (LED) as a light source for UV irradiation. An LED having a wavelength peak of 395 nm is used. The LED can easily change the irradiation energy by controlling the magnitude of the input current. In this embodiment, by changing the irradiation energy in the range of 150 to 300 mJ / cm ² , the UV irradiation intensity is controlled to adjust the curing rate of the UV ink dots.

  The color ink head 31, the clear ink head 32, and the first irradiation unit 41 are collectively referred to as a base layer forming unit (see FIG. 2).

The second irradiation unit 45 is provided on the downstream side in the transport direction of the clear ink head 35 (FIG. 2), and emits UV for curing the clear ink dots formed by the clear ink head 35. The length of the second irradiation unit 45 in the medium width direction is equal to or greater than the medium width. The 2nd irradiation part 45 is also provided with LED similar to the 1st irradiation part 41 as a light source, and can change irradiation energy.
The clear ink head 35 and the second irradiation unit 45 are also collectively referred to as a clear ink dot forming unit (see FIG. 2).

<Detector group>
The detector group 50 includes a rotary encoder (not shown), a medium detection sensor (not shown), and the like. The rotary encoder detects the rotation amount of the upstream side conveyance roller 23A and the downstream side conveyance roller 23B. The transport amount of the medium can be detected based on the detection result of the rotary encoder. The medium detection sensor detects the position of the front end of the medium being supplied.

<Controller>
The controller 60 is a control unit (control unit) for controlling the printer. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64.

  The interface unit 61 transmits and receives data between the computer 110 that is an external device and the printer 1. The CPU 62 is an arithmetic processing device for performing overall control of the printer 1. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and is configured by a storage element such as a RAM or an EEPROM. Then, the CPU 62 controls each unit such as the transport unit 20 via the unit control circuit 64 in accordance with a program stored in the memory 63.

<Image recording operation>
An image recording operation by the printer 1 will be briefly described. 4A to 4C are diagrams for explaining the concept of an image recording operation using the printer 1.

  When the printer 1 receives print data from the computer 110, the controller 60 first rotates a medium supply roller (not shown) by the transport unit 20 and sends the medium to be printed onto the belt 24.

  The medium is conveyed on the belt 24 without stopping at a constant speed, and passes under the base layer forming portion. During this time, color ink (KCMY) is intermittently ejected from each nozzle of the color ink head 31 to form characters and images consisting of color ink dots (hereinafter also simply referred to as dots) on the medium ( FIG. 4A). Further, the clear ink (CL) is intermittently ejected from each nozzle of the clear ink head 32, thereby forming a clear ink dot (hereinafter also simply referred to as a clear dot) in a pixel where no color ink dot is formed. . Then, the color ink dots and the clear ink dots are cured by irradiating UV from the first irradiation unit 41 of the irradiation unit 40. As a result, all the pixels on the medium are filled with the color ink dots or the clear ink dots, and the base layer is formed (FIG. 4B).

After the foundation layer is formed, the medium is conveyed on the belt 24 without stopping at a constant speed, and passes through the clear ink dot forming portion. During this time, clear ink (CL) is intermittently ejected from each nozzle of the clear ink head 35 to form small dots of clear ink on the underlying layer. Then, UV is emitted from the second irradiation unit 45 of the irradiation unit 40 to cure the clear dots. As a result, a large number of small clear dots are formed on the base layer (FIG. 4C).
Finally, the controller 60 discharges the medium on which image printing has been completed.

=== About liquid ===
In the present embodiment, a liquid that is used to form dots and clear dots for forming a base layer and is cured by receiving light irradiation will be described. The liquid is, for example, UV ink. The liquid contains a polymerizable compound, and may further contain a photopolymerization initiator and other additives. The liquid is preferably cured with an irradiation energy of 300 mJ / cm ² or less, more preferably with an irradiation energy of 250 mJ / cm ² or less. In that case, LED which has a peak wavelength in 360-420 nm can be used as an irradiation light source, and irradiation intensity | strength can be 500-2000 mW / cm < ² >.

  The liquid preferably has a viscosity at 20 ° C. of 7 mPa · S or higher, and more preferably 7 mPa · S or higher and 30 mPa · S or lower. The UV ink preferably has a surface tension of 35 mN / m or more, more preferably 35 to 45 mN / m. Within this range, it is possible to form dots with a uniform spread of dots, and to reduce heating for lowering the viscosity during ejection.

  The polymerizable compound contained in the liquid of the present invention is a compound having a polymerizable functional group. The polymerizable functional group is a functional group that can undergo a polymerization reaction when irradiated with light, and is preferably a functional group having an unsaturated carbon double bond, such as a vinyl group, a vinyl ether group, a (meth) acryl group, and the like. Raised. Specific examples of the polymerizable compound include various (meth) acrylate monomers, various (meth) acrylate oligomers, various vinyl monomers, various vinyl ether monomers, and the like. A polymerizable compound having plural kinds of polymerizable functional groups may be used. The polymerizable compound is preferably contained in the liquid in an amount of 60 to 95% by mass.

Although it does not restrict | limit especially as a polymeric compound contained in the liquid of this invention, It can be set as a liquid with good sclerosis | hardenability by using the monomer A represented by following General formula (1).
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (1)
(In the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms. Group.)

In the above general formula (1), the divalent organic residue having 2 to 20 carbon atoms represented by R ² is a linear, branched or cyclic substituted having 2 to 20 carbon atoms. An alkylene group that may be substituted, an alkylene group that has an oxygen atom by an ether bond and / or an ester bond in the structure, an optionally substituted alkylene group that has 2 to 20 carbon atoms, and an optionally substituted divalent that has 6 to 11 carbon atoms Aromatic groups are preferred. Among these, C2-C6 alkylene groups such as ethylene group, n-propylene group, isopropylene group, and butylene group, oxyethylene group, oxy n-propylene group, oxyisopropylene group, and oxybutylene group An alkylene group having 2 to 9 carbon atoms having an oxygen atom due to an ether bond in the structure is preferably used.

In the general formula (1), the monovalent organic residue having 1 to 11 carbon atoms represented by R ³ is a linear, branched or cyclic substituted having 1 to 10 carbon atoms. Suitable alkyl groups and optionally substituted aromatic groups having 6 to 11 carbon atoms are preferred. Among these, C6-C2 aromatic groups, such as a C1-C2 alkyl group which is a methyl group or an ethyl group, a phenyl group, and a benzyl group, are used suitably.

  When each of the organic residues is an optionally substituted group, the substituent is divided into a group containing a carbon atom and a group not containing a carbon atom. First, when the substituent is a group containing a carbon atom, the carbon atom is counted in the carbon number of the organic residue. Examples of the group containing a carbon atom include, but are not limited to, a carboxyl group and an alkoxy group. Next, examples of the group not containing a carbon atom include, but are not limited to, a hydroxyl group and a halo group. The content of the monomer A in the liquid is not particularly limited, but is preferably 10% by mass or more, more preferably 10% by mass to 70% by mass, and further preferably 10% by mass to 60% by mass.

  The liquid of the present invention may further contain a photopolymerization initiator. The photopolymerization initiator is a compound having a function of efficiently initiating polymerization of a polymerizable compound when irradiated with light. Specific examples of the photoinitiator include alkylphenone initiators, acylphosphine initiators, titanocene initiators, thioxanthone initiators, and the like. The photopolymerization initiator is preferably contained in the ink in an amount of 5 to 15% by mass.

  The liquid of the present invention may contain other additives as required. Examples of other additives include solvents, surfactants, polymerization inhibitors, polymerization accelerators, coloring materials such as pigments and dyes, and the like.

  Among the liquids used in the present invention, a clear liquid (clear liquid) used for forming clear dots is a liquid called a clear ink if the liquid is an ink. Adjustment of glossiness of a recorded matter, protective layer, and color ink This liquid is used for improving the color developability, and generally contains little or no colorant. Further, the liquid for forming the underlayer may be a color ink containing a color material, or may be a clear liquid. When the clear liquid is used, the formation of the underlayer without imparting color to the recording medium. It is possible to use the clear liquid used for forming the clear dots.

=== Matte Property of Image ===
In the present embodiment, the clear ink is superimposed on the image (underlayer) formed by dots and ejected to form a large number of clear dots on the image surface, thereby making the image matte (low gloss). . At that time, the glossiness of the image changes depending on the size (diameter) of the clear dots formed on the image surface.

  5A and 5B are diagrams for explaining the relationship between the dot size and the glossiness of the image. In the figure, one square of the area divided by a broken line in a square pattern represents one pixel of the image, and a circle indicated by a hatched portion indicates a clear dot formed on the pixel.

  FIG. 5A shows an example in which the diameter of the clear dots formed on the image surface is small. As shown in the figure, if the dot diameter is small, the gap between adjacent dots becomes large, so that a portion where the clear dot is formed and a portion where the clear dot is not formed are generated on the image surface. Then, as shown in the AA cross section of FIG. 5A, when the light incident on the formed image is reflected, the light reflected by the portion where the clear dot is formed and the portion where the clear dot is not formed (image The light reflected on the surface) is mixed, the reflected light of the image is easily scattered, and the glossiness is lowered. In other words, the smaller the size of the clear dots formed on the image surface, the lower the glossiness, resulting in a matte image.

  FIG. 5B shows an example where the diameter of the clear dots formed on the image surface is large. If the dot diameter is large, contrary to the case of FIG. 5A, the gap generated between adjacent dots is small, so that the entire image surface is covered with clear dots. Then, as shown in the BB cross section of FIG. 5B, the light incident on the formed image is almost reflected by the portion where the clear dots are formed, and the reflected light of the image tends to be uniform and glossy. The degree becomes higher. That is, the larger the clear dot size formed on the image surface, the higher the glossiness and the glossy image.

  Therefore, by making the size of the clear dots formed on the surface of the image (underlying layer) as small as possible, it becomes possible to form a matte (low gloss) image. Note that by forming the clear dots on all the pixels in the region where the base layer is formed, it is possible to obtain a uniform matte tone image that hardly causes a difference in glossiness between pixels. .

  Next, a change in dot size (diameter) will be described. After the clear dots land on the underlying layer, the dot diameter changes by spreading wet. The change in dot diameter is greatly affected by the water repellency of the underlayer. Note that the clear ink does not penetrate into the underlayer.

  FIGS. 6A to 6C are diagrams for explaining the change in the shape of the clear dot due to the difference in water repellency of the underlying layer. For comparison, in FIGS. 6A to 6C, the same amount of clear ink is ejected in the same amount to form dots. First, FIG. 6A shows an example of the shape of a clear dot when the water repellency of the underlayer is maximum. The clear ink landed on the medium becomes a spherical dot as shown in the figure. And since it does not spread wet and does not penetrate into the underlying layer, if it is cured by UV irradiation in this state, it maintains a spherical shape. The dot diameter (diameter) at this time is D1.

  Next, FIG. 6B shows an example of the shape of a clear dot when the water repellency of the underlayer is lower than that in FIG. 6A. The clear dots that have landed on the medium initially have the same spherical shape as in FIG. 6A, but gradually become wet and spread out, and become a slightly crushed dome shape as shown in FIG. 6B. The dot diameter is D2 (D2> D1).

  Next, FIG. 6C shows an example of the shape of the clear dots when the water repellency of the underlayer is lower than that in FIG. 6B. In this case, the clear dots are wet and spread more greatly than in FIG. 6B, resulting in a flat disk shape. The dot diameter is also maximum at D3 (D3> D2).

  Therefore, when the same amount of ink is ejected, the clearer dots formed on the underlying layer are more difficult to spread as the water repellency of the underlying layer increases. That is, since it becomes easy to form a clear dot having a small diameter, a gap between adjacent clear dots becomes large. As a result, the glossiness of the underlayer (image) can be lowered and a matte image can be formed. Here, in order to increase the water repellency of the underlying layer (image), the curing rate of the dots (color ink dots and clear ink dots) forming the underlying layer may be increased. The harder the surface of the underlying layer (image), the easier it is to clear the clear dots that land on it.

  Therefore, in this embodiment, by controlling the curing rate of the dots that form the underlying layer (image), the size of the clear dots formed thereon is adjusted, and a high-definition matte image is formed. To do.

=== Embodiment ===
<Composition of UV ink>
Table 1 shows the composition components of the four types of UV inks used in the description of this embodiment. Inks 1, 2, and 4 are clear inks, and only ink 3 is a color ink. The difference between the clear ink and the color ink in the table is whether or not a pigment component (cyan in Table 1) is included, and the ink curability at the time of UV irradiation is influenced by other components.

In Table 1, the polymerizable compound VEEA corresponds to the monomer A described above.

VEEA: 2- (2-vinyloxyethoxy) ethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.)
・ DEGDA: Diethylene glycol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.)
・ TMPTA: Trimethylolpropane triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
・ IBXA: Isobornyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.)
・ 819: IRGACURE 819 (BASF)
-TPO: DAROCUR TPO (BASF)
・ DETX-S: KAYACURE DETX-S (manufactured by Nippon Kayaku Co., Ltd.)
Pigment: PIGMENT BLUE 15: 4 (manufactured by DIC)
Leveling agent: BYK-UV3500 (manufactured by BYK)
-Polymerization inhibitor: MEHQ (manufactured by Kanto Chemical)

<Curing rate of UV ink>
The curing of the UV ink dots can be grasped by measuring the curing rate. The curing rate is a product indicating the ratio of the degree of polymerization when the degree of polymerization (degree of polymerization) in a state where the ink is completely cured is 100, and can be obtained, for example, by analysis of an infrared spectrum. That is, for a specific peak that changes due to the polymerization reaction, the difference in absorbance (maximum change) between the unreacted state and the time when sufficient energy and time are given to reach the steady state is measured, and the absorbance at a given timing is measured. Obtained as a ratio of the change amount to the maximum change amount. The curing rate can be measured, for example, by measuring a change with time after giving a predetermined amount of light using an infrared spectrophotometer capable of measuring in real time such as NEXUS470 manufactured by Thermo Nicolet. Here, the complete curing of the ink means, for example, a time point at which the change in absorbance at a certain time point is within 0.1 within 10 seconds thereafter.

<Irradiation energy necessary for curing UV ink>
A solid pattern of 720 × 720 dpi was applied to a PET film (Panasonic Lumirror 125E20) with a maximum film thickness of 10 μm, and an LED having a peak wavelength at 395 nm was irradiated at an irradiation intensity of 800 mW / cm ² , and the above complete Evaluate the irradiation energy required to reach cure. The evaluation criteria are as follows. The evaluation results are shown in Table 1.
A: 250mJ / cm ² or less B: 250 super 300 less mJ / cm ² or less C: 300mJ / cm ² than

<Evaluation of mat properties>
The matte property of an image is evaluated by measuring the glossiness of the image. The “glossiness” is an index representing the degree of glossiness and can be measured using a glossmeter. In a general gloss meter, light is emitted from a light source toward the measurement surface at a predetermined angle (incident angle), and light reflected from the measurement surface (reflected light) is detected by a light receiving unit installed in the regular reflection direction. To measure the glossiness.

  The gloss watch uses a gloss meter GM-60 manufactured by Konica Minolta. In addition, there is a method of measuring the light angle at 20 degrees, 45 degrees, 60 degrees, 75 degrees, and 85 degrees. In this embodiment, the measurement is performed with an incident angle / reflection angle of 20 degrees. In addition, since glossiness shows a value proportional to the magnitude | size of an angle, even if it does not measure all angles, the glossiness of another angle can be measured by measuring about 20 degree light. .

  With respect to the glossiness X measured in this way, the mat property AA when X ≦ 25, the mat property A when 25 <X ≦ 60, the mat property B when 85 <X ≦ 85, and 85 < When the case of X is mat property C, the mat property is evaluated. The images having the mat properties A and AA are high-definition mat images.

=== Reference Example ===
First, as a reference example, an example in which clear dots are formed with clear inks 1, 2, and 4 in the absence of a base layer is shown. That is, the mat property evaluation in the case where clear dots are directly formed on the medium will be described. In the following example, PET film (Panasonic Lumirror 125E20) is used as the medium.

Use an inkjet printer modified from an inkjet printer (Seiko Epson). The ink jet printer is provided with a mechanism for heating the ink in the head, performs heating according to the ink, and discharges the ink so that the viscosity of the ink is approximately 10 mPa · S. In addition, a light source is provided on the carriage, and irradiation is performed immediately after printing. As the light source, an LED having an emission peak wavelength of 395 nm and an irradiation intensity of 800 mW / cm ² is used. The test pattern has a recording resolution of 720 × 720 dpi and ejects a predetermined amount of ink to one pixel which is a recording unit area defined by the recording resolution.

Table 2 shows clear dot formation conditions and matte property evaluation data in the reference example.

In Reference Example 1, a predetermined amount of the above-described ink 1 (see Table 1) is ejected from a clear ink head 35 to a certain area on the medium, and UV of 300 mJ / cm ² is irradiated from the second irradiation unit 45. Clear dots are formed.

  In this reference example, since the image recording resolution is 720 × 720 dpi, if one pixel is square, the length of one side is about 35.3 μm. On the other hand, the diameter of the formed clear dot is 29 μm, which is 80% or more of the length of one side of the pixel. That is, a relatively large dot is formed with respect to the size of the pixel. Accordingly, since the gap between the clear dots is reduced in the area where the clear dots are formed, the glossiness (the glossiness of the medium) is increased as described above, and the mat property evaluation is B.

Similarly, in the reference example 2 and the reference example 3, the diameter of the formed clear dot is relatively large, and the mat property evaluation is B. In Reference Example 2 using ink 2 (see Table 1) whose evaluation of irradiation energy necessary for curing is C, a larger UV irradiation energy (350 mJ / cm ² ) is required to cure the dots. It can be confirmed.

=== Example ===
In the first embodiment, a base layer (image) is formed on a medium, and then clear dots are formed on the base layer. Then, how the mat property evaluation is affected by the difference in the formation conditions of the underlayer will be described. The ink ejection amount for forming the clear dots is the same as that in the reference example.

<When changing the curing rate of the underlayer>
Table 3 shows data of mat property evaluation when the curing rate of the underlayer is changed (Examples 1 to 5).

  In Table 3, a base layer and a clear dot thereon are formed using the above-described ink 1 (see Table 1). In any of the embodiments, the ink ejection amount is adjusted so that the diameter of the dots forming the base layer is 80 μm. And the hardening rate of a base layer is changed by changing the magnitude | size of UV energy irradiated from the 1st irradiation part 41 for every Example. In Table 3, the underlayer curing rate of Example 1 is the largest at 78%. The underlayer curing rate gradually decreases between Example 2 and Example 5, and in Example 5, the underlayer curing rate is 60%. In this way, the mat property is evaluated by paying attention to the size of the clear dots formed on the base layers having different curing rates.

  The reason why the diameter of the dots forming the base layer is set to 80 μm is that all the pixels to be printed are filled with the dots. When UV ink is ejected at a resolution of 720 × 720 dpi to form a base layer (image), if the pixel is square, the length of the diagonal line of one pixel is about 50 μm. Therefore, dots having a diameter (80 μm) equal to or longer than the length of the diagonal line (50 μm) of the pixel are formed in each pixel in the region where the base layer is formed. In the present embodiment, as described with reference to FIG. 4B, the base layer is formed by forming dots in all the pixels. Therefore, a base layer having a more uniform shape can be formed by filling the surface of the medium with dots having a size larger than a pixel without any gap. This ensures that clear dots are formed on the underlying layer. Also, a difference is prevented from occurring depending on the position (pixel) where the clear dot lands.

In the example of Table 3, the clear dots formed on the base layer are formed under the same conditions as in Reference Example 1 described above. That is, after forming the base layer, the same amount of ink 1 as that in Reference Example 1 is ejected from the clear ink head 35, and 300 mJ / cm ² of UV is irradiated from the second irradiation unit 45 to form clear dots. By making the clear dot formation conditions the same as those in the reference example, it becomes easier to compare with the case where there is no underlying layer.

  For example, the reference example 1 and the example 1 are compared. When clear dots are formed directly on the medium without a base layer (reference example 1), the clear dot diameter is 29 μm, which is 80% or more of the length of one side of the pixel (about 35 μm). Therefore, the mat property evaluation of the reference example 1 is B. In contrast, when a clear dot is formed on the ground layer under the same conditions as in Reference Example 1 after forming a ground layer with a curing rate of 78% (Example 1), the clear dot diameter is 22 μm, which is smaller than 80% of the length of one side of the pixel. Therefore, the mat property evaluation of Example 1 is A. In Example 1, since a base layer having a high curing rate and a large water repellency is formed, the clear dots are difficult to spread. For this reason, in Reference Example 1 and Example 1, the clear dot diameter formed in Example 1 is smaller in spite of ejecting the same amount of clear ink. As a result, a gap between adjacent clear dots is increased, and accordingly, a high matting property can be obtained.

  In this way, by forming the base layer having a high curing rate, the diameter of the clear dots formed thereon can be further reduced, so that a high-definition matte image can be formed.

  Further, the diameter of the clear dots formed on the underlayer is greatly influenced by the curing rate of the underlayer. As can be seen from Table 1, even when the same ink (ink 1) is ejected by the same amount, the clear dot diameter decreases as the curing rate of the underlying layer increases. FIG. 7 is a diagram showing the relationship between the curing rate of the underlayer and the diameter of the clear dots formed on the underlayer.

  When the curing rate of the underlayer is 70% or more (Examples 1 to 3), the clear dot diameter is 28 μm or less (less than 80% of the length of one side of the pixel), and the mat property evaluation is A. As described above, the higher the curing rate of the underlayer, the easier the clear dots formed thereon are repelled, and the clear dots are more likely to maintain a spherical shape as shown in FIG. 6A. Therefore, by forming a base layer having a high curing rate, the diameter of the clear dots can be reduced, and an image having a high matting property is formed.

  On the other hand, when the curing rate of the underlayer is 65% or less (Examples 4 to 5), the clear dot diameter is 31 μm or more (80% or more of the length of one side of the pixel), and the mat property evaluation is C. It becomes. That is, the mat property evaluation is worse than that of Reference Example 1 in which the underlayer is not formed. As the curing rate of the underlayer is lower, the clear dots formed thereon are more likely to spread and the clear dots are likely to have a disk shape as shown in FIG. 6C. As a result, the diameter of the clear dot becomes large, and an image with low matting property is easily formed.

  In this embodiment, when the underlayer curing rate is 70% or more, an image with a mat property evaluation of A can be formed. Therefore, when forming the underlayer, the curing rate is 70% or more. It is desirable to do. However, since wetting and spreading of the clear dots are affected by the component composition of the UV ink itself, the UV irradiation output, and the irradiation timing, even if the cured layer of the underlayer is less than 70%, a high-definition matte image It is not impossible to form.

<When changing the ink to be used>
Next, an example in which the UV ink for forming the base layer and the clear dots is changed will be described. Table 4 shows data of mat property evaluation when the ink to be used is changed (Examples 6 to 10).

  In any of the examples in Table 4, as in the case of Examples 1 to 5 (Table 3) described above, the diameter of the dots forming the base layer is adjusted to be 80 μm. In addition, the amount of UV ink ejected when forming the clear dots and the UV irradiation energy correspond to the reference examples 1 to 4, respectively, according to the ink numbers (ink numbers 1, 2, and 4) that form the clear dots. Same conditions as in 3.

  Example 6 is an example in which a base layer and clear dots thereon are formed using ink 4. Compared to Reference Example 3 in which no underlayer is formed, in Reference Example 3, the clear dot diameter is 29 μm, whereas in Example 6, the clear dot diameter is 23 μm, and the diameter of the formed clear dots is reduced. As described above, it can be seen that a good matte evaluation (A) can be obtained by forming the under layer and then forming clear dots thereon.

In Example 6, since the underlayer is formed with ink 4 (see Table 1) whose evaluation of irradiation energy necessary for curing is A, the underlayer is cured as compared with the case where the underlayer is formed with ink 1. It becomes easy to do. For example, in Example 3 of Table 3, the underlayer is formed using the ink 1 with a UV irradiation energy of 230 mJ / cm ² , and the underlayer curing rate at this time is 70%. On the other hand, in Example 6, the underlayer was formed using the ink 4 with the same UV irradiation energy 230 mJ / cm ² as in Example 3, but the underlayer curing rate at this time was 75% (Table 4). In other words, by forming the underlayer using an ink having good curability, the underlayer is easily cured, so that a higher-definition matte image can be easily formed.

  Examples 7 and 8 are examples in which an ink 2 is used to form a base layer and clear dots thereon. In Example 7, the diameter of the formed clear dots is smaller than that in Reference Example 2 in which the base layer is not formed. Like the above-mentioned example, favorable mat | matte evaluation (A) can be obtained by forming a base layer with a high hardening rate and forming a clear dot on it.

On the other hand, since the underlayer is formed with the ink 2 (see Table 1) whose evaluation of the irradiation energy necessary for curing is C, it is larger than the case where the ink 4 is used to sufficiently cure the underlayer. It is necessary to perform UV irradiation with energy. For example, Example 6 and Example 8 are compared. Curing ratio of Example relative to 6 in UV irradiation energy 230 mJ / cm ² to form a cured 75% of the base layer, the base layer formed in Example 8 the same UV irradiation energy 230 mJ / cm ² Is 65%. In Example 8, since the curing rate of the underlayer is insufficient, the diameter of the formed clear dot is as large as 30 μm and is 80% or more of the length of one side of the pixel. End up.

Therefore, by increasing the UV irradiation energy to 310 mJ / cm ² as in Example 7, a base layer with a curing rate of 72% is formed, and a high-definition matte image is formed. However, even in the case of Example 7, compared with Example 6, the efficiency of irradiation is inferior because the curing rate of the underlayer becomes lower for a larger UV irradiation energy.

  The same can be said for clear dots on the underlying layer. That is, in the ink 2, it is necessary to increase the UV irradiation energy for curing the ink dots as compared with the ink 1 and the ink 4 (Table 4). Therefore, in order to form a good matte tone image with small irradiation energy, it is preferable to use UV ink having good curability (low irradiation energy necessary for curing).

  Examples 9 and 10 are examples in which a base layer and clear dots thereon are formed using different inks.

In Example 9, a base layer is formed using ink 2, and clear dots are formed using ink 1 thereon. The underlayer curing rate and the clear dot diameter in Example 9 were almost the same as those in Example 7 in which the underlayer was formed with ink 2, and the mat property evaluation was A. (Underlayer curing rates are 72% and 73%, and clear dot diameter is 24 μm).
On the other hand, in Example 10, contrary to Example 9, a base layer is formed using ink 1 and clear dots are formed using ink 2 thereon. Compared to Example 2 in which the underlayer was formed with ink 1, both the underlayer cure rate was 73% and the clear dot diameters were 26 μm and 25 μm. is there.
That is, UV inks having different compositions can be combined as long as the curing rate of the underlayer can be 70% or more.

  Example 11 is an example in which a base layer is formed using ink 3 which is a color ink containing a pigment. Ink 3 has substantially the same composition as ink 1 except that it contains cyan as a pigment component (see Table 1). Therefore, compared with Example 2 which is a case where the underlayer is formed using the ink 1, there are some differences in the underlayer curing rate and clear dot diameter, but the mat property evaluation is A, which is sufficiently good. A matte tone image can be formed. That is, as the UV ink for forming the base layer, both clear ink (for example, ink 1) and color ink (for example, ink 3) can be used.

<About the characteristics of UV ink>
From the above examples, it is preferable to use UV ink having good curability for the underlayer because it can be efficiently cured with less irradiation energy. For example, it is preferable to use an ink whose evaluation of irradiation energy necessary for the above-mentioned curing is A or B. Specifically, it is preferable to use a UV ink whose irradiation energy required for curing is 300 mJ / cm ² or less, and it is more preferable to use a UV ink whose irradiation energy required for curing is 250 mJ / cm ² or less. Moreover, it is preferable to use the monomer A represented by Formula (1) as a polymerizable compound as UV ink with good curability. The content of the monomer A in the ink is not particularly limited, but is preferably 10% by mass or more, more preferably 10 to 70% by mass, and further preferably 10 to 60% by mass. It is possible to further increase the content of the monomer A, but the above range is preferable when other aspects are taken into consideration, such as film quality after curing. Further, any UV ink having good curability may be used, and the polymerizable compound to be used is not limited to the monomer A.

  The curing rate of the dots forming the underlayer is preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more. The ink for forming the base layer (dot) may be a clear ink or a color ink, and the ink for forming the base layer (dot) and the ink for forming the clear dot may be the same ink or different inks.

=== Second Embodiment ===
In the second embodiment, as a liquid ejecting apparatus for carrying out the invention, a serial printer (printer 2) that records an image by ejecting UV ink while reciprocating the head unit 30 in a direction perpendicular to the medium transport direction. Is used to form a high definition matte image. The UV ink used for forming an image is the same as that in the first embodiment.

<Configuration of Printer 2>
FIG. 8 is a block diagram showing the overall configuration of the printer 2.
The printer 2 includes a transport unit 20, a head unit 30, an irradiation unit 40, a detector group 50, a controller 60, and a carriage unit 70. The printer 2 is communicably connected to a computer 110 similar to that of the first embodiment. The controller 60 controls each unit such as the transport unit 20 and the carriage unit 70 based on the print data received from the computer 110, and records an image on a medium.

<Transport unit 20>
FIG. 9A is a bird's-eye view showing the configuration of the printer 2 of this embodiment, and FIG. 9B is a side view showing the configuration of the printer 2.

  The transport unit 20 is for transporting the medium in the transport direction. Here, the transport direction is a direction that intersects the moving direction of the carriage. The transport unit 20 includes a medium supply roller 25, a transport motor 26, a transport roller 27, a platen 28, and a medium discharge roller 29 (FIGS. 9A and 9B).

  The medium supply roller 25 is a roller for supplying the medium inserted into the medium insertion port into the printer. The conveyance roller 27 is a roller that conveys the medium supplied by the medium supply roller 25 to an area where an image can be recorded (hereinafter also referred to as a recording area), and is driven by the conveyance motor 26. The operation of the transport motor 26 is controlled by a controller 60 on the printer side. The platen 28 is a member that supports the medium during image recording from the back side of the medium. The medium discharge roller 29 is a roller for discharging the medium to the outside of the printer, and is provided on the downstream side in the transport direction with respect to the recording area.

<Head unit 30>
The head unit 30 is for ejecting UV ink onto the medium. The head unit 30 includes a head 38 having a plurality of nozzles. The head 38 is provided on the carriage 71. When the carriage 71 moves in the movement direction, the head 38 also moves in the movement direction. Then, by intermittently ejecting UV ink while the head 31 is moving in the moving direction, dot lines (raster lines) along the moving direction are formed on the medium.

  FIG. 10 is an explanatory diagram of the nozzles Nz provided in the head 38. As shown in FIG. 10, on the nozzle surface, each color ink nozzle row of KCMY is provided as a color ink ejection nozzle row that forms a main image. Next to the yellow nozzle row Y, a clear nozzle row CL that ejects clear ink is provided. In each nozzle row, nozzles Nz, which are ejection ports for ejecting ink of each color, are arranged at a predetermined interval D in the transport direction. Each nozzle row includes 360 nozzles Nz # 1 to # 360. In addition, the number of nozzles per row is arbitrary, and it is not necessarily required to be 360. For example, the number of nozzles per row may be 180 or 240.

<Irradiation unit 40>
The irradiation unit 40 of this embodiment has irradiation parts 48a and 48b. The irradiation units 48a and 48b are provided on the carriage 71 so as to be adjacent to the outer ends of both ends of the KCMY and CL nozzle rows arranged in the scanning direction (see FIG. 10). Accordingly, the carriage 71 described later can irradiate UV even with ink ejected while moving from one end side to the other end side or from the other end side to the one end side. It is configured.
The light source used for the irradiation unit 40 and the UV wavelength are the same as those of the irradiation unit 40 of the first embodiment.

<Detector group 50>
The detector group 50 is for monitoring the status of the printer 2. The detector group 50 includes a linear encoder 51, a rotary encoder 52, a medium detection sensor 53, an optical sensor 54, and the like (FIGS. 9A and 9B).

  The linear encoder 51 detects the position of the carriage 71 in the moving direction. The rotary encoder 52 detects the rotation amount of the transport roller 27. The medium detection sensor 53 detects the position of the front end of the medium being supplied. The optical sensor 54 detects the presence / absence of the medium at the opposed position by the light emitting unit and the light receiving unit attached to the carriage 71, for example, detects the position of the end of the medium while moving, and detects the width of the medium. can do. The optical sensor 54 can also detect the front end (the end on the downstream side in the transport direction, also referred to as the upper end) and the rear end (the end on the upstream side in the transport direction, also referred to as the lower end) depending on the situation. .

<Controller 60>
The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64 as in the first embodiment. However, in the present embodiment, the control of the carriage unit 70 in image forming characters, the method of ejecting UV ink from the head unit 30, and the method of UV irradiation from the irradiation unit 40 are different from those in the first embodiment.

<Carriage unit 70>
The carriage unit 70 is for moving (also referred to as “scanning”) a carriage 71 to which the head unit 30 is attached in a predetermined direction (hereinafter referred to as a moving direction). The carriage unit 70 includes a carriage 71 and a carriage motor 72 (also referred to as a CR motor) (FIGS. 9A and 9B).

  The carriage 71 can reciprocate in the moving direction and is driven by a carriage motor 72. The operation of the carriage motor 72 is controlled by the controller 60 on the printer side. The carriage 71 detachably holds an ink cartridge that stores UV ink.

<Image recording operation using printer 2>
Also in this embodiment, as in the first embodiment, first, a base layer (image) is formed using color ink and clear ink, and after UV irradiation is performed to set the curing rate of the base layer to 70% or more, A small dot of clear ink is formed on the base layer.

  FIG. 11 is a diagram for explaining an image recording operation in the second embodiment. In FIG. 11, for simplicity, the color ink nozzle row is represented by Co and the clear ink nozzle row is represented by CL. Of the nozzle rows of Co and CL, the nozzle Nz displayed in the hatched portion represents the nozzle that ejects ink in the scan (pass). In addition, among the irradiation units 48a and 48b, the irradiation unit displayed by the hatched portion represents the irradiation unit that irradiates UV in the scanning (pass).

  In the first pass (during forward movement), when the carriage 71 moves from one end side to the other end side, half of the nozzles Nz (# 1 to # 180) provided in the head 38 are used. Color ink dots and clear ink dots are ejected. In the same scan, UV is irradiated from the irradiation unit 48b to cure the ejected ink dots. Thereby, dot rows from the first to 180th raster lines are formed. This dot row becomes a base layer (image) formed in the first pass. In the figure on the right side of FIG. 11, large circles arranged in the movement direction represent the respective dot rows, and an image (underlayer) is formed by connecting these dot rows in the transport direction. At this time, the UV irradiation output from the irradiation unit 48b is adjusted so that the curing rate of the dots forming the base layer is 70% or more.

  After the first pass (forward movement) is completed, the medium is conveyed by the length of half of the nozzle row (for example, the length of 180D when the number of nozzles is 360 and the nozzle interval is D), and then A second pass (return) is performed.

  In the second pass (during backward movement), when the carriage 71 moves from the other end side to the one end side, the half nozzles Nz (# 181 to # 360) of the clear ink nozzle row provided in the head 38 are used. Clear ink. Then, in the same scanning, UV is irradiated from the irradiation unit 48b, and the formed clear dots are cured. Thereby, small dots of clear ink are formed on the base layer formed in the first pass (forward movement). In the diagram on the right side of FIG. 11, a small circle on each dot row (large circle) forming the base layer represents a small clear dot formed in the second pass.

  At the same time, UV ink is ejected from the nozzles Nz (# 1 to # 180) which are half of the color and clear ink nozzle rows, and new underlayers (181st to 360th raster lines) are formed in this portion.

  By repeating this operation, small dots of clear ink can be formed on the base layer (image), and a high-definition matte image can be formed.

  Note that the above-described printing operation represents a case where band-type printing is performed. In the case of performing interlaced printing, the dots formed until the base layer is completed are subjected to UV irradiation a plurality of times. Here, the interlace method is shorter than the distance in the medium conveyance direction of the nozzles used for printing the nozzle row (the distance between nozzles D of the head 38 × (the number of nozzles used for printing the nozzle row−1)). Is a printing method in which a dot row that is not recorded is sandwiched between dot rows that are recorded while moving once in the main scanning direction. It only has to be.

  Further, when it is necessary to change the UV irradiation energy between the formation of the base layer (dots) and the formation of the clear dots thereon, the irradiation units 48a and 48b are divided into upper and lower parts, and the upper half side It is better to make the irradiation energy variable on the lower half side.

<Summary of Second Embodiment>
In the second embodiment, a high-definition matte image can be obtained by forming a large number of clear dots on a base layer (dots) using a serial printer, as in the first embodiment. .

=== Other Embodiments ===
Although a printer or the like as one embodiment has been described, the above embodiment is for facilitating the understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About liquid ejection device>
In each of the above-described embodiments, the printer has been described as an example of the liquid ejection device, but the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional molding machine, liquid vaporizer, organic EL manufacturing apparatus (especially polymer EL manufacturing apparatus), display manufacturing apparatus, film formation You may apply the technique similar to this embodiment to the various liquid ejection apparatuses which applied inkjet technology, such as an apparatus and a DNA chip manufacturing apparatus.

<About ink>
In the above-described embodiment, ink (UV ink) that is cured by being irradiated with ultraviolet rays (UV) is ejected from the nozzle. However, the liquid to be ejected is not limited to such an ink, and may be cured by receiving irradiation of electromagnetic waves other than UV.

<About nozzle row>
In the above-described embodiment, an example in which an image (underlayer) is formed using four colors of KCMY and clear ink has been described. However, the present invention is not limited to this. For example, an image may be recorded using inks of colors other than KCMY and CL, such as light cyan, light magenta, and white.

  The order of arrangement of the nozzle rows in the head portion is also arbitrary. For example, the order of the nozzle rows for K and C may be switched, or the number of nozzle rows for K ink may be greater than the number of nozzle rows for other inks.

<About piezo elements>
In each of the above-described embodiments, the piezo element PZT is exemplified as the element that performs the operation for ejecting the liquid. However, other elements may be used. For example, a heating element or an electrostatic actuator may be used.

<About the printer driver>
In each of the above-described embodiments, it has been described that the printer driver processing is performed by the computer 110 (PC). However, the printer driver may be installed in the controller 60 and the printer driver processing may be performed by the printer itself.

<About pixel side length>
When the vertical and horizontal recording resolutions are different and the pixel shape is a rectangle, the size of the dots formed by the clear liquid with respect to the pixel side length is the length of the short side of the pixel. The size of the dots formed by the liquid forming the underlayer with respect to the length of the pixel side is the length of the long side of the pixel.

1 printer, 2 printer,
20 transport unit, 23A upstream transport roller, 23B downstream transport roller,
24 belt, 25 medium supply roller, 26 transport motor, 27 transport roller,
28 platen, 29 media discharge roller,
30 head unit, 31 color ink head, 32 clear ink head,
35 heads for clear ink, 38 heads,
40 irradiation unit, 41 1st irradiation part, 45 2nd irradiation part,
48a irradiation unit, 48b irradiation unit,
50 detector groups, 51 linear encoder, 52 rotary encoder,
53 medium detection sensor, 54 optical sensor,
60 controller, 61 interface, 62 CPU, 63 memory,
64 unit control circuit,
70 Carriage unit, 71 Carriage, 72 Carriage motor,
110 computer

Claims (9)

(A) a head portion for ejecting liquid from the nozzle;
(B) an irradiation unit that emits light;
(C) a control unit that controls ejection of the liquid and irradiation of the light, and
The control unit ejects a liquid that is cured by receiving light irradiation to each pixel in a predetermined region of the medium from the head unit, and irradiates the ejected liquid with light from the irradiation unit, Forming a dot having a curing rate of 70% or more and having a diameter not less than the length of the diagonal line of the pixel as an underlayer;
A clear liquid that is cured by being irradiated with light is ejected from the head unit to the base layer , and light is irradiated from the irradiation unit to the ejected clear liquid, and the pixel is formed on the base layer . Forming a clear dot having a diameter smaller than the length of the side,
Liquid jet equipment. The liquid ejection device according to claim 1 ,
The liquid forming apparatus is a liquid ejecting apparatus in which the liquid for forming the dots is a liquid having an irradiation energy required for curing of 300 mJ / cm ² or less.   The liquid ejection device according to claim 1 or 2,
  The liquid forming the underlayer is
  The following general formula (1)
CH ₂ = CR ¹ -COOR ² -O-CH = CH-R ^Three   ... (1)
(Wherein R ¹ Is a hydrogen atom or a methyl group, R ² Is a divalent organic residue having 2 to 20 carbon atoms, R ^Three Is a monovalent organic residue having 1 to 11 carbon atoms. )
The liquid ejection apparatus containing the component represented by these. The liquid ejection device according to any one of claims 1 to 3,
The clear liquid is
The following general formula (1)
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (1)
Wherein R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a monovalent organic residue having 1 to 11 carbon atoms. .)
The liquid ejection apparatus containing the component represented by these. The liquid ejection device according to any one of claims 1 to 4,
The diameter of the clear dot is
A liquid ejecting apparatus that is smaller than 80% of the length of a side of the pixel. The liquid ejection device according to any one of claims 1 to 5,
The controller is
A liquid ejecting apparatus that causes the clear dots to be formed at each pixel in a region where the dots are formed. The liquid which is cured by receiving irradiation of light ejected for each pixel in a predetermined region of the medium from the nozzle, the jetted by irradiating light from the irradiation portion to the liquid, curing rate is not more than 70% And forming a dot having a diameter equal to or longer than the diagonal length of the pixel as an underlayer ,
A clear liquid that is cured by being irradiated with light is ejected from the nozzle to the underlayer, the clear liquid that is ejected is irradiated with light from an irradiation unit, and the length of the side of the pixel on the underlayer Forming a clear dot having a smaller diameter,
Liquid ejection how with.   The liquid ejection method according to claim 7,
  The liquid forming the underlayer is
  The following general formula (1)
CH ₂ = CR ¹ -COOR ² -O-CH = CH-R ^Three   ... (1)
(Wherein R ¹ Is a hydrogen atom or a methyl group, R ² Is a divalent organic residue having 2 to 20 carbon atoms, R ^Three Is a monovalent organic residue having 1 to 11 carbon atoms. )
The liquid ejection method containing the component represented by these. A liquid ejection method according to claim 7 or 8 ,
The clear liquid is
The following general formula (1)
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (1)
Wherein R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a monovalent organic residue having 1 to 11 carbon atoms. .)
The liquid ejection method containing the component represented by these.

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