JP2012086511A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus and method using an electromagnetic curable ink that is hardly affected by oxygen inhibition.SOLUTION: The image forming apparatus includes: a liquid droplet jetting device for jetting a liquid droplet consisting of the electromagnetic curable ink containing a magnetic component on a medium to be recorded; an electromagnetic wave irradiation device for radiating an electromagnetic wave to the medium to be recorded; and a magnetic device for applying a magnetic field in the direction vertical to the surface of the medium to be recorded. The magnetic device applies the magnetic field when the liquid droplet lands on the medium to be recorded.

Description

  The present invention relates to an image forming apparatus.

Among printers (printing apparatuses) that are image forming apparatuses, there are printers that use electromagnetic wave curable ink when cured when irradiated with electromagnetic waves such as ultraviolet rays, electron beams, X-rays, microwaves, and visible rays. In such a printer, an irradiation unit that irradiates electromagnetic waves is provided on the downstream side of the head that discharges the electromagnetic wave curable ink.
Patent Document 1 has a gist of forming a three-dimensional printed matter by using a magnetism-containing pigment and a magnet, but does not disclose a forming method using an ink jet method.

JP 2009-90624 A

It is already known that the electromagnetic wave curable ink has a property that the curing is inhibited by the influence of oxygen contained in the atmosphere (oxygen inhibition). The oxygen inhibition of the electromagnetic wave curable ink tends to become remarkable when the surface area of the electromagnetic wave curable ink liquid is larger than the volume. When the electromagnetic wave curable ink is ejected by the ink jet method, since the droplets are minute, they are easily affected by oxygen inhibition, and it may be difficult to form a better image.

Accordingly, an object of the present invention is to provide an image forming method and an image forming apparatus using an electromagnetic wave curable ink which is not easily affected by oxygen inhibition.

The present invention can be realized as the following forms or application examples so as to solve at least one of the above-described problems.

Application Example 1 An image forming apparatus according to this application example includes a droplet discharge unit that discharges a droplet made of an electromagnetic wave curable ink containing a magnetic component to a recording medium, and an electromagnetic wave irradiation that irradiates the recording medium with an electromagnetic wave. And magnetic means for applying a magnetic field in a direction perpendicular to the surface of the recording medium, wherein the magnetic means applies a magnetic field when the droplets land on the recording medium. .

According to the above application example, the electromagnetic wave curable ink containing the magnetic component ejected by the droplet ejecting unit spreads on the recording medium by the action of the magnetic field applied in the direction perpendicular to the recording medium by the magnetic unit. Can not be. As a result, the influence of oxygen inhibition can be reduced. Then, a favorable image can be formed by irradiating electromagnetic waves with an irradiation means.

Application Example 2 In the application example described above, the magnetic unit is characterized in that a magnetic field is not applied until a droplet is landed on a recording medium after being ejected by the droplet ejection unit.

According to the application example described above, when the electromagnetic wave curable ink containing the magnetic component ejected by the droplet ejecting unit is flying, the magnetic field is not applied by the magnetic unit, so that the droplet landing position is shifted due to the influence of the magnetic field. Therefore, a good image can be formed.

Application Example 3 In the application example described above, the magnetic unit is characterized in that a magnetic field is not applied during a period until 0.11 milliseconds elapse after a droplet is ejected by the droplet ejection unit. .

According to the application example described above, it is possible to reliably apply the magnetic field when the electromagnetic wave curable ink containing the magnetic component ejected by the droplet ejecting means has landed on the medium. Further, the influence of the magnetic field applied by the electromagnetic wave curable ink during the flight can be minimized.

[Application Example 4] In the above application example, the magnetic means follows the drive signal of the droplet discharge means.
A magnetic field is applied to the magnetic means.

According to the application example described above, it is possible to prevent the magnetic field from being applied more accurately during the flight of the electromagnetic wave curable ink by applying the magnetic field to the magnetic unit according to the drive signal of the droplet discharge unit. Further, the configuration for synchronizing with the droplet discharge means can be simplified.

Application Example 5 In the application example described above, the magnetic means further includes an ink mist collecting means.

According to the above application example, even when the electromagnetic wave curable ink containing the magnetic component is scattered during the flight and the ink mist is generated, the ink can be recovered by the ink mist recovery means provided in the magnetic means. As a result, the ink mist does not contaminate the image forming apparatus, and the maintainability can be improved.

Application Example 6 In the application example described above, the magnetic means and the irradiation means are arranged so as to overlap in the main scanning direction.

According to the application example described above, since the magnetic means can quickly irradiate the liquid droplets that have landed on the recording medium while applying a magnetic field in a direction perpendicular to the surface of the non-recording medium, it has landed effectively. The electromagnetic wave curable ink can be cured.

1 is a block diagram showing a configuration of a printing system. FIG. 3 is a top view schematically showing the periphery of the head. Explanatory drawing regarding the contact angle of electromagnetic wave curable ink. FIG. 3 is a flowchart showing the operation of the printing system. FIG. 3 is a block diagram showing an electrical configuration of the head. The perspective view which shows the outline of an ink mist collection | recovery means. The schematic sectional drawing which shows the example of arrangement | positioning of a temporary irradiation part. The schematic sectional drawing which shows a 2nd Example.

Hereinafter, an embodiment will be described by taking an example of a printing system in which an image forming apparatus is an inkjet printer (hereinafter referred to as a printer) and a printer and a computer are connected.
A. B. Overall configuration of printing system Head unit C.I. Driving waveform Ink composition Example of printing operation Ink mist collection means G. Arrangement example of provisional irradiation unit Second embodiment

A. FIG. 1 is a block diagram showing the overall configuration of the printing system, and the printer 1 according to the present embodiment.
Is an apparatus that forms an image on a medium by ejecting ultraviolet curable ink (corresponding to “electromagnetic wave curable ink”) that is cured by irradiation of ultraviolet rays toward a medium such as paper, cloth, or film. The ultraviolet curable ink (hereinafter referred to as UV ink) is an ink containing an ultraviolet curable resin, and is cured by a radical polymerization reaction in the ultraviolet curable resin when irradiated with ultraviolet rays. The UV ink is an ink containing a magnetic pigment. For example, the UV ink is obtained by blending the predetermined magnetic pigment of the present invention with a normal UV ink.

The computer 80 is communicably connected to the printer 1 and outputs print data for causing the printer 1 to print an image to the printer 1. Computer 80 contains
A program (printer driver) for converting image data output from the application program into print data is installed.
The printer driver may be stored in a storage medium (a computer-readable storage medium) such as a CD-ROM or downloaded to a computer via the Internet.

The printer 1 that has received the print data from the computer 80 controls each unit by the controller 10 and prints an image on a medium. The detector group 60 monitors the situation in the printer 1, and the controller 10 controls each unit based on the detection result. The interface unit 11 in the controller 10 is for transmitting and receiving data between the computer 80 as an external device and the printer 1. The CPU 12 is an arithmetic processing unit for controlling the entire printer 1. The memory 13 is for securing an area for storing a program of the CPU 12, a work area, and the like. The CPU 12 controls each unit of the transport unit 20, the carriage unit 30, the head unit 40 as the droplet discharge unit, the irradiation unit 50, and the magnetic unit 70 as the magnetic unit by the unit control circuit 14.

The transport unit 20 is for transporting the medium from the upstream side to the downstream side in the transport direction.
The carriage unit 30 is for moving a head 41, which will be described later, in a moving direction that is a direction intersecting the medium transport direction.

B. Head Unit Next, the head unit 40 will be described with reference to FIG. FIG. 2 is a schematic top view of the periphery of the head.
The head unit 40 includes a head 41 that discharges UV ink from a nozzle to a medium. The printer 1 of the present embodiment ejects six colors of UV ink, and the head 41 has U of each color.
A nozzle row for discharging V ink is formed. In each nozzle row, a large number of nozzles are arranged at predetermined intervals in the transport direction. FIG. 2 is a view of the nozzle row virtually viewed from the upper surface of the head 41. From the left side in the moving direction, the dark cyan nozzle row Dc that discharges dark cyan ink and the light cyan nozzle row Lc that discharges light cyan ink. A black nozzle row K for discharging black ink, a dark magenta nozzle row Dm for discharging dark magenta ink, a light magenta nozzle row Lm for discharging light magenta ink, and a yellow nozzle row Y for discharging yellow ink, Are lined up. That is, for cyan and magenta, dark ink and light ink having the same hue and different densities are ejected from the head 41.

The head 41 ejects UV ink from the nozzles while moving in the movement direction together with the carriage 31. The ink discharge method from the nozzle may be a piezo method in which a voltage is applied to the drive element to expand and contract the pressure chamber filled with the ink, or a heating element is used in the nozzle. A thermal method in which bubbles are generated and ink is ejected by the bubbles may be used.

The magnetic unit 70 (corresponding to the magnetic means) applies a magnetic field to the UV ink that has landed on the medium. The printer 1 of this embodiment has two magnetic portions 71 in the magnetic unit 70 and landed on the medium. The UV ink is held so as not to be crushed and spread on the medium by the action of the magnetic field.

The magnetic part 71 is provided on the carriage 31, and the length of the magnetic part 71 in the transport direction is approximately the same as the length of the nozzle row in the transport direction. Therefore, the magnetic part 71 can suppress the spread of the dots of the UV ink that has landed on the medium by applying a magnetic field perpendicular to the medium surface to the UV ink that has just landed on the medium. Two magnetic portions 71 are provided on the carriage 31 with the head 41 interposed therebetween. Therefore, a magnetic field is applied to the UV ink immediately after landing on the medium by the magnetic unit 71 during the forward path in which the head 41 moves to one side in the movement direction and during the return path in which the head 41 moves to the other side in the movement direction. Is done. An example of the magnetic part 71 is an electromagnet.

The irradiation unit 50 (corresponding to an irradiation unit) irradiates ultraviolet rays toward the UV ink that has landed on the medium, and cures the UV ink. The printer 1 according to the present embodiment includes two preliminary irradiation units 51 and a main irradiation unit 52 in the irradiation unit 50, and the UV ink is cured in two stages.

The provisional irradiation unit 51 is provided on the carriage 31, and the length of the provisional irradiation unit 51 in the conveyance direction is approximately the same as the length of the nozzle row in the conveyance direction. Therefore, the provisional irradiation unit 51 irradiates the UV ink held on the medium so as not to be spread by the magnetic unit 71 to the extent that the UV ink is not completely cured. By doing so, it is possible to suppress the flow (spreading of dots) of the UV ink that has landed on the medium. Further, two provisional irradiation portions 51 are provided on the carriage 31 so as to sandwich the head 41 therebetween. Therefore, even when the head 41 moves to one side of the moving direction and when the head 41 moves to the other side of the moving direction, the provisional irradiation unit 51 applies ultraviolet rays to the UV ink immediately after landing on the medium. Irradiated. As a light source for ultraviolet irradiation of the provisional irradiation unit 51, for example, a light emitting diode (LED) is cited.

The main irradiation unit 52 is provided downstream of the carriage 31 in the transport direction, and the length of the main irradiation unit 52 in the moving direction is approximately the same as the length of the medium in the moving direction (width length). Therefore, the main irradiation unit 5
2 represents the UV ink on the medium transported under the main irradiator 52 by the transport operation.
Irradiate ultraviolet rays so that the V ink is completely cured. A lamp (for example, a metal halide lamp, a mercury lamp, etc.) is mentioned as a light source for ultraviolet irradiation of the main irradiation unit 52.

The provisional irradiation unit 51 does not completely cure the UV ink, and the main irradiation unit 52 completely cures the UV ink. Therefore, the main irradiation unit 52 has higher irradiation energy (mJ / cm ² ) of ultraviolet rays per unit area than the provisional irradiation unit 51. The irradiation energy amount per unit area is determined by the product of ultraviolet irradiation intensity (mW / cm ² ) and irradiation time (s). Also, FIG.
As shown in B, the length in the width direction of the provisional irradiation unit 51 and the main irradiation unit 52 is approximately the same as the length of the head 41 in the width direction. By doing so, the UV ink that has landed on the medium S can be irradiated with ultraviolet rays over the entire region in the width direction.

In such a printer 1, an image forming process in which UV light is irradiated by the provisional irradiation unit 51 while intermittently ejecting UV ink from the head 41 moving in the moving direction, and a medium downstream of the head 41 in the transport direction. The conveying process of conveying to the side is repeated. By doing so, dots are formed in a later image forming process at a position on the medium different from the positions of the dots formed by the previous image forming process, and a two-dimensional image is printed on the medium. The head 41 is U
The operation of moving once in the moving direction while discharging V ink (one image forming process) is “pass”.
Call it.

By the way, the UV ink used by the printer 1 of the present embodiment is cured by causing a radical polymerization reaction when irradiated with ultraviolet rays, but when the UV ink comes into contact with the atmosphere, oxygen inhibits the polymerization reaction (oxygen inhibition). If it does so, it will become difficult to harden UV ink (it will not harden | cure). In particular, when the amount of ink constituting the dot is small (when the thickness of the ink droplet is thin)
The contact area (surface area) with the atmosphere becomes larger than the amount of ink, which is easily affected by oxygen inhibition, and the UV ink is not cured. If the UV ink is not cured, problems such as peeling of the UV ink from the medium occur.

As shown in FIG. 3, the contact angle θ between the landed UV ink droplet and the medium surface has a sufficiently high wettability depending on the components of the UV ink and the material of the medium, and the contact angle is very high. In some cases, it becomes smaller (FIG. 3B). At this time, the surface area of the UV ink droplet becomes larger than the volume, and there is a problem that the UV ink droplet does not cure due to the influence of oxygen in the atmosphere. Further, if the wettability is to be reduced, it is necessary to select the component of the UV ink and the material of the medium, which causes a problem that the degree of freedom in design is limited.

Therefore, in this embodiment, a magnetic field is applied to the UV ink that has landed on the medium in a direction perpendicular to the medium surface so that the landed UV ink does not spread on the medium (FIG. 3 (
c)). Then, the UV ink is temporarily cured by the ultraviolet irradiation by the temporary irradiation unit 51 that has moved together with the carriage 31 while being held so as not to spread on the medium. By temporary curing, the flow of the UV ink that has landed on the medium S (spreading of dots) can be fixed while the magnetic field is applied. Since the UV ink droplet does not spread after the temporary curing, the magnetic unit 70 may stop the action of the magnetic field.
Note that it is sufficient for the purpose of the present invention that the magnetic field vector applied by the magnetic unit 70 has a component perpendicular to the medium surface, and whether or not the magnetic field vector has a component other than the medium surface perpendicular direction. Does not matter.

C. Drive Waveform FIG. 5 is a block diagram showing an electrical configuration of the head 41. As shown in FIG. The head 41 includes a plurality of shift registers 151A to 151N corresponding to the number of nozzles and a plurality of latch circuits 152A.
To 152N, a plurality of level shifters 153A to 153N, and a plurality of switch circuits 154
A to 154N and a plurality of piezo elements 155A to 155N. Print signal SI
Is synchronized with a clock signal CLK from an oscillation circuit (not shown).
To 151N. The latch circuits 152A to 152A1 are synchronized with the latch signal LAT.
52N is latched. The latched print signal SI is output from the level shifters 153A to 153.
N is amplified to a voltage that can drive the switch circuits 154A to 154N, and is supplied to the switch circuits 154A to 154N. A drive signal COM from a well-known drive waveform generation circuit (not shown) is input to the input side of the switch circuits 154A to 154N, and piezo elements 155A to 155N are connected to the output side.

For example, when the print signal SI is “1”, the switch circuits 154A to 154N operate by supplying the drive signal COM to the piezo elements 155A to 155N, and when the print signal SI is “0”, the switch circuits 154A to 154N do not operate.

As is well known, a piezo element is an element that transforms an electro-mechanical energy at a very high speed because its crystal structure is distorted by application of a voltage. Although not shown, the drive signal COM is the piezo element 1.
When supplied to 55A to 155N, the piezo elements 155A to 155N are deformed accordingly, and the walls of the ink chambers are also deformed. This controls the ejection of ink droplets from the nozzles. Printing is performed by the ejected ink droplets adhering to the print medium.

D. Ink Composition The printer 1 of the present embodiment ejects four types of UV ink (ink A, ink B, ink C, and ink D). The composition of each ink A to D is obtained by blending the following magnetic pigments with the following inks A ′ to D ′.

Various known pigments can be appropriately employed as the magnetic pigment, and in general, a fine flake-like magnetic material, particularly a thin plate-like magnetic material, is preferably used. The material is
In addition to ferromagnetic materials such as iron, nickel, cobalt, or alloys thereof, semi-magnetic materials such as bismuth, antimony, copper, and zinc can be used. Furthermore, metal oxide powders such as iron oxide can also be used. In addition to being able to be used effectively, those obtained by coating flaky particles with these magnetic materials, or those obtained by plating or coloring these magnetic materials with paints can also be used. Such a magnetic pigment generally has a size in the longitudinal direction of about 0.5 to 100 μm and an average thickness of about 30 to 500 nm.

Such a magnetic pigment is dispersed and contained in the UV ink, but the blending amount thereof is generally about 1/3 to 2/3 of the resin weight in the ink. . This is because if the blending amount is less than 1/3 of the resin weight in the ink, the concealing property becomes poor and the influence of the background color is greatly affected, and more than 2/3 of the resin weight. If it increases, it may become difficult to obtain a predetermined quality in the clarity or visibility of the printed matter after curing.

Ink A ′ (yellow ink) contains 19 pigment dispersions (described later) with respect to 100 parts by mass.
. 16.1 parts by mass of tripropylene glycol diacrylate (trade name: NK ester APG-200, manufactured by Shin-Nakamura Chemical Co., Ltd.) as a photopolymerizable monomer, dipropylene glycol diacrylate (trade name: NK ester) APG-100 (manufactured by Shin-Nakamura Chemical Co., Ltd.) 15.5 parts by mass, phenoxyethyl acrylate (trade name: Biscote # 192, manufactured by Osaka Organic Chemical Industry) 27.1 parts by mass, and dimethylol tricyclodecane diacrylate (Trade name: NK ester A-DCP, manufactured by Shin-Nakamura Chemical Co., Ltd.) 5.5 parts by mass, amino acrylate (trade name: EBECRYL7100, manufactured by Daicel Cytec Co., Ltd.), 3.5 parts by mass, and p as a polymerization inhibitor -0.2 parts by mass of methoxyphenol (trade name, manufactured by Kanto Chemical) and UV-10 (trade name) 0.1 part by weight of Ciba Specialty Chemicals),
As the surfactant, BYK UV-3500 (trade name, manufactured by Big Chemie Japan)
2 parts by mass, 5.5 parts by mass of IRGACURE 819 (trade name, manufactured by Ciba Specialty Chemicals), 4.5 parts by mass of DAROCURE TPO (trade name, manufactured by Ciba Specialty Chemicals), and KAYACURE DETX as photoinitiators -S (trade name, manufactured by Nippon Kayaku Co., Ltd.) is mixed with 2.8 parts by mass. The ink A ′ is produced by sufficiently stirring and dissolving the mixture.

The pigment dispersion of ink A ′ is prepared as follows. As a colorant with respect to 100 parts by mass, C.I. I. 15 parts by weight of Pigment Yellow 180, 5 parts by weight of Discol N-509 (trade name, manufactured by Dainichi Seika Kogyo Co., Ltd.) and phenoxyethyl acrylate (trade name: Biscote # 192, Osaka Organic Chemical Industry) 80 parts by mass of the product (manufactured) is sufficiently mixed, and dispersion treatment is performed for 10 hours with zirconia beads (diameter 1.5 mm) using a sand mill (manufactured by Yaskawa Seisakusho). Thereafter, the zirconia beads are separated with a separator.

Ink B ′ (black ink) is 14.0 parts by mass of the pigment dispersion, 19.6 parts by mass of tripropylene glycol diacrylate, 19.1 parts by mass of dipropylene glycol diacrylate, with respect to 100 parts by mass. 23.0 parts by mass of phenoxyethyl acrylate,
7.5 parts by mass of dimethylol tricyclodecane diacrylate and 3 amino acrylates
. 5 parts by mass, 0.2 parts by mass of p-methoxyphenol, 0.1 parts by mass of UV-10, BY
0.2 parts by mass of K UV-3500, 5.5 parts by mass of IRGACURE 819, DARO
CURE TPO is mixed in an amount of 4.5 parts by mass, and KAYACURE DETX-S in an amount of 2.8 parts by mass. By sufficiently stirring and dissolving this mixture, ink B ′ is produced.

The composition of the pigment dispersion of ink B ′ is 100% by mass with respect to C.I. I. The pigment black 7 is 15 parts by mass, the discol N-509 is 5 parts by mass, and the phenoxyethyl acrylate is 80 parts by mass.

Ink C ′ (magenta ink) is 26.5 parts by mass of the pigment dispersion, 10.5 parts by mass of tripropylene glycol diacrylate, 10.6 parts by mass of dipropylene glycol diacrylate, with respect to 100 parts by mass, 32.0 parts by mass of phenoxyethyl acrylate,
4.5 parts by mass of dimethylol tricyclodecane diacrylate and 3 amino acrylates
. 5 parts by mass, 0.2 parts by mass of p-methoxyphenol, 0.1 parts by mass of UV-10, BY
0.2 parts by mass of K UV-3500, 5.0 parts by mass of IRGACURE 819, DARO
CURE TPO is mixed in an amount of 4.5 parts by mass, and KAYACURE DETX-S is mixed in a ratio of 2.4 parts by mass. By sufficiently stirring and dissolving the mixture, ink C ′ is produced.

The composition of the pigment dispersion of ink B ′ is 100% by mass with respect to C.I. I. The pigment red 122 is 15 parts by mass, the disc N-509 is 5 parts by mass, and the phenoxyethyl acrylate is 80 parts by mass.

Ink D ′ (green ink) is 17.5 parts by mass of the pigment dispersion, 17.5 parts by mass of tripropylene glycol diacrylate, and 17.0 parts by mass of dipropylene glycol diacrylate, with respect to 100 parts by mass. 26.6 parts by mass of phenoxyethyl acrylate,
5.5 parts by mass of dimethylol tricyclodecane diacrylate and 3 amino acrylates
. 5 parts by mass, 0.2 parts by mass of p-methoxyphenol, 0.1 parts by mass of UV-10, BY
0.2 parts by mass of K UV-3500, 5.0 parts by mass of IRGACURE 819, DARO
CURE TPO is mixed in an amount of 4.5 parts by mass, and KAYACURE DETX-S is mixed in a ratio of 2.4 parts by mass. By sufficiently stirring and dissolving the mixture, ink D ′ is produced.

The composition of the pigment dispersion of ink D ′ is C.I. I. The pigment green 36 is 15 parts by mass, the disc N-509 is 5 parts by mass, and the phenoxyethyl acrylate is 80 parts by mass.

Usually, in color printing, four colors of ink (yellow, magenta, cyan, black) are used as basic inks. In order to improve color reproducibility, green ink or orange ink is used. However, in this embodiment, for the sake of simplicity, an example in which the printer 1 uses four types of ink (yellow, black, magenta, and green) having different characteristics will be described.

E. Example of Printing Operation First, the printer driver converts image data output from the application program into print resolution, and converts image data that is RGB data into CMYK data corresponding to the ink color of the printer 1. Next, the printer driver performs halftone processing using a predetermined mask. The halftone process is a process of converting multi-tone data into tone number data that can be expressed by the printer 1.
The image data that has undergone these processes is finally converted into a command such as “0” or “1” of the print signal SI for each piezo element in the head 41 and applied to the piezo element in accordance with the print signal SI. UV ink is ejected from the nozzles in accordance with the drive signal. For simplicity, the case where there is one piezo element will be described here. However, in the case where there are a plurality of piezo elements, the logical sum of the print signals SI for the respective piezo elements may be considered as the print signal SI described here.

FIG. 4 illustrates the operation of the printing apparatus after the print signal SI is input to the head 41.
First, it is determined whether or not the input print signal SI is “1” (S01), and it is determined whether or not the piezo element is driven.
Next, when the input print signal SI is “1”, a timer (not shown) is reset to 0 seconds (S02).
Next, it is determined whether 0.11 milliseconds have elapsed (S03). In the case of an ink jet printer using a general piezo element, the speed of ejected liquid droplets is 7-1.
It is known to be 0 m / sec, and the paper gap from the nozzle surface to the medium surface is about 1.1 mm to 1.5 mm, so the UV ink ejected according to the drive signal reaches the medium surface. 1.1 [mm] / 10 [m / sec] = 0.11 mse
c Required.
If the magnetic field is applied after 0.11 milliseconds, the UV ink may have already reached the medium surface and spread, and the effects of the present invention cannot be obtained.
On the other hand, if a magnetic field is applied significantly earlier than 0.11 milliseconds after the driving of the piezo element, the UV ink in flight containing the magnetic component is bent due to the magnetic field of the magnetic part 71, so that the magnetic field The application is desirably performed immediately before the UV ink reaches the medium surface.

Next, the provisional irradiation unit 51 performs provisional irradiation on the medium landed with the UV ink (S05) so that the ink does not flow.

After the provisional irradiation, the application of the magnetic field of the magnetic part 71 is stopped (S06). This is because the ink fluidity has already disappeared due to the provisional irradiation, so that even if the application of the magnetic field is stopped, there is no fear that the UV ink spreads on the medium surface.

Next, it is determined whether or not there is a print signal. If there is no print signal, the process ends (S0).
7). If there is a print signal, the processing from S01 is repeated.

F. Ink Mist Collection Unit FIG. 6 is a perspective view schematically showing the ink mist collection unit.
The ink mist collecting means 73 is arranged at the lower part in the vertical direction with respect to the magnetic part 71 provided on the carriage 31. Since the magnetic part 71 applies a magnetic field in a direction perpendicular to the medium as described above, the mist made of the electromagnetic wave curable ink ejected from the nozzles but scattered during the flight is applied to the magnetic field. And is guided to the lower part of the magnetic part 71 in the vertical direction (indicated by an arrow in the figure). The ink mist guided by the magnetic field is collected by the ink mist collecting means 73.
As a specific material of the ink mist collecting means, a well-known waste liquid pad material or the like can be used. By collecting the ink mist by the ink mist collecting means, it is possible to prevent the entire image forming apparatus from being contaminated by the ink mist.
In particular, when an electromagnetic wave curable ink containing a magnetic component is used as in the present invention, the periphery of the magnetic part 71 is contaminated by ink mist, so it is desirable to provide an ink mist collecting means.

G. Arrangement Example of Provisional Irradiation Unit FIG. 7 is a cross-sectional view schematically showing an arrangement example of the provisional irradiation unit 51. In this arrangement example, the provisional irradiation unit 5
1 is arranged in a magnetic part 71 provided in the carriage 31, and the magnetic part 71 and the provisional irradiation part 51 are arranged so as to overlap in the main scanning direction of the carriage.
By disposing in this way, the electromagnetic wave curable ink held so as not to spread by the magnetic part 71 can be quickly temporarily cured. As already described, since the electromagnetic wave curable ink is affected by oxygen inhibition by contact with the atmosphere, the influence of oxygen inhibition can be further reduced by arranging in this way.

H. Second Embodiment FIG. 8 is a schematic view of a second embodiment according to the present invention. Printer 100 of the second embodiment
The heads 131 (1) to 131 (4) of each color are fixedly arranged independently, and the nozzle surface of each color head is moved to the medium S by the transport unit 120 including the transport rollers 121 a and 121 b and the transport belt 122. Passes through to form an image. In this embodiment, the same number of magnetic portions 152 (1) to 152 (4) as the number of heads are used for the respective heads 131 (1) to 131 (4) and provisional irradiation portions 141 (1) to 141 (4). Between. Further, a main irradiation unit 142 is arranged on the downstream side in the transport direction, and the UV ink is completely cured by the ultraviolet irradiation of the main irradiation unit 142.
The UV ink containing the magnetic pigment ejected by the heads 131 (1) to 131 (4) is
The magnetic portions 152 (1) to 152 (4) are held so as not to spread by the action of the magnetic field applied by the magnetic portions 152 (1) to 152 (4), and are then quickly cured by temporary irradiation by the temporary irradiation portion.

DESCRIPTION OF SYMBOLS 1 Printer as an image forming apparatus, 10 Controller, 11 Interface part, 12 CPU, 13 Memory, 14 Unit control circuit, 20 Conveyance unit,
30 Carriage unit, 31 Carriage, 40 head unit as droplet discharge means, 41 head, 50 Irradiation unit as electromagnetic wave irradiation means, 51 Temporary irradiation section, 52
Main irradiation unit, 60 detector group, 70 magnetic unit as magnetic means, 80 computer.

Claims (6)

Droplet ejection means for ejecting droplets made of electromagnetic wave curable ink containing a magnetic component onto a recording medium;
Electromagnetic wave irradiation means for irradiating the recording medium with electromagnetic waves;
Magnetic means for applying a magnetic field in a direction perpendicular to the recording medium surface;
With
The magnetic means applies a magnetic field when the droplets land on the recording medium,
Image forming apparatus. The magnetic means does not apply a magnetic field until the droplets land on the recording medium after the droplets are ejected by the droplet ejecting means.
The image forming apparatus according to claim 1. The magnetic means does not apply a magnetic field for a period until 0.11 milliseconds elapse after the droplet is ejected by the droplet ejecting means.
The image forming apparatus according to claim 1. The magnetic means applies a magnetic field to the magnetic means in accordance with a drive signal of the droplet discharge means;
The image forming apparatus according to claim 2. The magnetic means further includes an ink mist collecting means,
The image forming apparatus according to claim 1. The magnetic means and the irradiation means are arranged so as to overlap in the main scanning direction,
The image forming apparatus according to claim 1.

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