JP6375643B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming method.

  As an image forming apparatus, for example, an ink jet recording apparatus is known as an image forming apparatus of a liquid discharge recording method using a recording head composed of a liquid discharge head (droplet discharge head) for discharging droplets.

  As such an image forming apparatus, there is an apparatus that forms an image using an active energy ray curable liquid such as an ultraviolet curable ink.

  2. Description of the Related Art Conventionally, an irradiation unit that irradiates actinic rays and an image forming unit that forms an image by ejecting ink cured by actinic rays with a head are provided on both sides of the image forming unit in the scanning direction of the carriage. A provisional curing irradiation means provided and a curing irradiation means provided on the downstream side in the conveyance direction of the recording medium. There is one in which the temporary curing irradiation means on the side is extinguished and droplets are ejected (Patent Document 1).

JP 2013-193349 A

  By the way, in general, when an image is formed by the liquid ejection method, there are a portion (for example, a solid portion) where there is no problem even if dots are blurred on the medium, and a portion (for example, a character or a fine line) that is not.

  Here, for example, in the case of forming an image using ultraviolet curable ink, if the whole is cured at the same level, it may spread without being cured at a portion where the image quality is deteriorated when it blurs like a contour portion. is there. On the contrary, if the characteristics are adjusted so as to be cured at the contour portion, the solid image may not be sufficiently blurred and a sufficient density may not be obtained.

  However, in the configuration disclosed in Patent Document 1 described above, the actinic ray irradiation units provided on both sides of the carriage are merely temporary curing irradiation units, and the main curing irradiation unit is provided on the downstream side in the medium transport direction. Therefore, actinic ray irradiation under the same conditions is performed on all the inks in the same image.

  As a result, it is possible to obtain the difference in functions that the original image quality as a whole, such as the part that wants to form beautiful dots for high image quality like the outline part, and the part that you want to level to fill the solid image. Therefore, there is a problem that a high-quality image cannot be obtained.

  The present invention has been made in view of the above problems, and an object thereof is to improve image quality.

In order to solve the above problems, an image forming apparatus according to claim 1 of the present invention provides:
One or a plurality of liquid ejection means for ejecting at least first and second active energy ray-curable liquid droplets having different curing characteristics;
The first on the medium ejected by said liquid ejecting means, that for the second droplet of the active energy ray curable liquid refers to the active energy rays respectively corresponding to the curing characteristics of each droplet irradiation 1 Or a plurality of active energy ray irradiation means,
A carriage that is reciprocated and mounted with the liquid ejection means and the active energy ray irradiation means,
The active energy ray irradiating means hardens the second active energy ray curable liquid after curing the first active energy ray curable liquid,
The first active energy ray-curable liquid contains a polymerization initiator having a curing reaction peak at a single wavelength,
The second active energy ray curable liquid contains a polymerization initiator having a curing reaction peak in a plurality of types of wavelength regions .

  According to the present invention, image quality can be improved.

1 is a schematic explanatory diagram of an example of an image forming apparatus according to a first embodiment of the present invention. It is the plane explanatory view which looked at an example of the head unit from the nozzle surface side. It is explanatory drawing with which it uses for description of an example of the relationship between the wavelength of a polymerization initiator, and an absorption characteristic. It is explanatory drawing with which it uses for description of the light emission wavelength in an ultraviolet irradiation device. It is explanatory drawing which shows the finishing state of the barcode image used for operation | movement description of the embodiment. It is typical explanatory drawing which similarly shows the difference in the structure dot of each bar. It is explanatory drawing with which it uses for description of the dot shape of the outline part and inner side part on a medium. It is explanatory drawing which shows the example of an image pattern other than a barcode image. It is explanatory drawing of the dot formation pattern of the image with which it uses for description of 2nd Embodiment of this invention. It is explanatory drawing explaining the example of a pattern of the color filter formed in 3rd Embodiment of this invention. It is explanatory drawing of the example of the dot formation pattern in a normal mask with which it uses for description of 4th Embodiment of this invention. It is explanatory drawing of the example of the dot formation pattern in a random mask similarly.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an image forming apparatus according to the present invention will be described with reference to FIG. FIG. 1 is a schematic explanatory view of the image forming apparatus.

  The image forming apparatus 1 includes a carriage 11 that reciprocates in the forward direction and the backward direction. The carriage 11 is mounted with a head unit 12 that is a liquid ejection unit having a plurality of liquid ejection heads, and first and second ultraviolet irradiation units 13A and 13B that are active energy ray irradiation units.

  The head unit 12 includes one or a plurality of liquid ejection heads that eject droplets of active energy ray-curable liquid having different curing characteristics. For example, a plurality of liquids that discharges droplets of first and second ultraviolet curable inks that are cured by irradiating ultraviolet rays and are different from each other in the first and second active energy ray curable liquids. A discharge head is provided. It is also possible to discharge active energy ray-curable liquids having different curing characteristics from a plurality of nozzle rows of one liquid discharge head.

  The ultraviolet irradiation unit 13A is a first active energy ray irradiation unit that irradiates the head unit 12 with ultraviolet light having a wavelength that cures the first ultraviolet curable ink ejected from the head unit 12. It is arranged on the rear side.

  The ultraviolet irradiation unit 13B is a second active energy ray irradiation unit that irradiates the head unit 12 with ultraviolet light having a wavelength that cures the second ultraviolet curable ink ejected from the head unit 12. It is arranged on the rear side.

  A transport stage 15 is disposed below the movement area of the carriage 11. The medium 10 is placed on the transport stage 15.

  Therefore, a desired image can be formed on the medium 10 by moving the carriage 11 and discharging droplets of ultraviolet curable ink from the head unit 12 onto the medium 10.

  Here, when an image is formed on a medium with an active energy ray curable ink, the material of the medium is not selected as compared with a normal water-based ink, and the non-permeable medium such as a plastic material (polypropylene, polyethylene, etc.) is used. It is also possible to form images. Therefore, in the following description, it is assumed that the medium 10 is an impermeable medium.

  Next, an example of the head unit 12 will be described with reference to FIG. FIG. 2 is a schematic plan view of the carriage unit.

  The head unit 12 includes liquid discharge heads (hereinafter simply referred to as “heads”) 101 to 112. The “head unit” is simply a general term for the entire heads 101 to 112 and does not mean that they are independent as a unit.

  Here, the heads 101 to 106 belonging to the first head group 100A eject droplets of the first ultraviolet curable ink having the first curing characteristics.

  The heads 107 to 112 belonging to the second head group 100B eject droplets of a second ultraviolet curable ink having a second curing characteristic different from the first curing characteristic.

  For example, black, cyan, magenta, yellow, clear, and white ink droplets of a total of six colors are ejected by the heads 101 to 106 of the first head group 100A.

  Similarly, a total of six ink droplets, for example, black, cyan, magenta, yellow, clear, and white are ejected by the heads 107 to 112 of the second head group 100B.

  Note that the number of colors is not limited to six. For example, four colors of black, cyan, magenta, and yellow may be used, or other numbers may be used.

  In this case, the first head group 100A and the second head group 100B eject inks having the same color and different curing characteristics. In addition, the nozzle rows of each of the heads 101 to 112 have a resolution of 300 dpi (= 150 dpi per row) with one set of two rows, and in this embodiment, one head has a two-color configuration.

  For example, as the black ink, the first ultraviolet curable ink is ejected from the two nozzle rows of the heads 101 and 102 of the first head group 100A, and the two rows of the heads 107 and 108 of the second head group 100B are ejected. The second ultraviolet curable ink is ejected from the nozzle row.

  As a result, a print width of two heads (two nozzle rows) can be secured in a direction intersecting the carriage movement direction in one scan of the carriage 11.

  The same applies to other colors.

  Here, referring to FIG. 3, an example of the curing reaction wavelength as the first curing characteristic and the second curing characteristic of the first and second ultraviolet curable inks ejected from the first head group 100A and the second head group 100B will be described. I will explain.

  In FIG. 3, ink A and ink B are inks that are cured by reacting with ultraviolet light having a wavelength in the range of 200 nm to 350 nm (this is referred to as “broad wavelength region reactive ink”). Ink C is an ink that cures in response to ultraviolet light having a wavelength of 395 nm (this is referred to as “395 nm wavelength region reactive ink”).

  Therefore, for example, the ink ejected from each of the heads 101 to 106 of the first head group 100A (hereinafter simply referred to as “ejection from the first head group 100A”) is 395 nm wavelength region reactive ink. On the other hand, the ink ejected from the second head group is a wide wavelength region reactive ink.

  Next, returning to FIG. 1, the first and second ultraviolet irradiation units 13A and 13B will be described.

  The first ultraviolet irradiation unit 13A located on the rear side of the head unit 12 in the outward direction emits ultraviolet light having a peak illuminance near 395 nm for curing the 395 nm wavelength region reactive ink ejected from the first head group 100A. Irradiate.

  Accordingly, the liquid droplets ejected from the first head group 100A can be cured by irradiating the ultraviolet light with the first ultraviolet radiation unit 13A, but the liquid droplets ejected from the second head group 100B are cured. do not do.

  The second ultraviolet irradiation unit 13B, which is located behind the head unit 12 in the backward direction, emits ultraviolet light having a wavelength with a peak illuminance in the wavelength region that cures the wide wavelength region reactive ink ejected from the second head group 100B. Irradiate.

  Accordingly, the liquid droplets ejected from the second head group 100B can be cured by irradiating the ultraviolet light with the second ultraviolet irradiation unit 13B.

  Here, the emission wavelength in a general ultraviolet irradiation apparatus will be described with reference to FIG.

  As an example of the light source of the ultraviolet irradiation unit, each ultraviolet region such as UV-A, UV-B, and UV-C is output as an emission spectrum, and a high-pressure mercury lamp, a metal halide lamp, an electrodeless UV lamp, a UV laser, a xenon lamp, An LED lamp, a sterilization lamp, etc. can be mentioned.

  In addition, there is an LED type ultraviolet irradiation device that narrows the emission wavelength to a specific narrow wavelength region, and further has high luminous efficiency with high peak wavelength emission efficiency, low power consumption and long life. .

  Here, the relationship between the emission wavelength and the illuminance distribution of an electroded lamp (metal halide lamp) and various LED lamps is as shown in FIG.

The number of typical 365nm of peak irradiance of electroded lamp whereas the number W / cm ^2, 395nmLED irradiation device, peak irradiance of 405nmLED irradiation device is ten W / cm ² and normal electroded lamp Double strength is obtained.

  The lamp used in these ultraviolet irradiation devices is preferably selected by the photopolymerization initiator in the ink composition and having an emission peak wavelength matched with the absorption characteristics of the photopolymerization initiator.

  For example, when a normal electroded lamp is used, if the reaction peak wavelength of the photopolymerization initiator in the ink composition is 365 nm, a lamp having a strong wavelength region of 300 to 450 nm, specifically a metal halide lamp is used. . If the reaction peak wavelength of the photopolymerization initiator in the ink composition is 240 nm, a high pressure mercury lamp is used.

  Thus, while an ordinary electroded lamp exhibits an emission spectrum in a wide wavelength range, an LED irradiation device is characterized in that it exhibits a narrow emission spectrum around each central wavelength as described above.

  Therefore, image formation is performed using two or more kinds of ultraviolet irradiation lamps having different emission wavelengths and an ink containing a polymerization initiator that reacts to the emission wavelength of each lamp. In addition to this, if the irradiation conditions (emission wavelength, leveling time, irradiation intensity, etc.) are controlled, it is possible to partially secure arbitrary image quality.

  In the present embodiment, an LED type ultraviolet irradiation device is used for the first ultraviolet irradiation unit 13A. By using an LED lamp, it is possible to cure only ink using a polymerization initiator that reacts only to that wavelength by single wavelength emission (here, 395 nm).

  Further, a metal halide lamp type ultraviolet irradiation device is used for the second ultraviolet irradiation unit 13B. By using a metal halide lamp, it is possible to cure ink using a polymerization initiator having reaction peaks in several wavelength regions by wide-range wavelength light emission (200 to 400 nm).

  The operation of the present embodiment configured as described above will be described.

  For example, when an image is formed with black ink (other colors may be used), the heads 101 and 102 of the first head group 100A and the second head group 100B are moved while moving the carriage 11 in the forward direction (moving forward). The first and second ultraviolet curable ink droplets are ejected from the heads 107 and 108, respectively, to form an image. That is, all images are formed by the movement of the carriage 11 in the forward direction.

  At this time, the contour portion of the image is formed by the first ultraviolet curable ink ejected from the first head group 100A, and the portion inside the contour portion of the image is the second ultraviolet curable ink ejected from the second head group 100B. Form with ink.

  In other words, the image data is divided into a first region formed with the first ultraviolet curable ink and a second region formed with the second ultraviolet curable ink, and the images are formed with liquids having different curing characteristics. Form.

  When the carriage 11 is moving in the forward direction, ultraviolet light that cures the first ultraviolet curable ink is irradiated from the first ultraviolet irradiation unit 13A while forming an image.

  As a result, the contour portion of the image is hardened in a state where droplets are standing on the non-permeable medium 10, and there is no bleeding of the contour portion, thereby improving the image quality.

  At this time, since the second ultraviolet curable ink forming the inner portion of the image is not cured, it spreads (levels) on the non-permeable medium 10. As a result, the liquid spreads sufficiently in the solid portion and there is no missing portion, and the concentration can be secured.

  Therefore, when the carriage 11 is moved in the backward direction after the forward path is completed (during the backward movement), the second ultraviolet irradiation unit 13B irradiates ultraviolet light that cures the second ultraviolet curable ink.

  As a result, the second ultraviolet curable ink spreading in the inner portion of the image is cured, so that the image quality is improved.

  In other words, it takes time to harden the part that needs to be leveled to form a solid part, and the edge part (contour part) whose quality deteriorates due to bleeding etc. when leveling is done, is hardened quickly after landing, resulting in high image quality. Can be realized.

  In this way, the finished image quality can be arbitrarily changed by changing the curing process while forming an image in a simultaneous process with ultraviolet curable inks having different curing characteristics.

  In this embodiment, an example in which an image is formed in the forward direction has been described. However, the present invention can also be applied to a case where bidirectional printing is performed.

  In this case, active energy ray irradiating means for irradiating active energy rays is provided on both sides of the head unit 12 of the carriage 11, both of which are the first and second active energy ray curable liquids. It is possible to irradiate an active energy ray that cures and to control the irradiation timing. Thereby, productivity can be improved.

  Further, in the above embodiment, the active energy ray irradiating means for curing in the return path direction can also be arranged on the front side of the head unit in the return path direction. For example, the second ultraviolet irradiation unit 13B of the above embodiment can also be arranged on the same side as the first ultraviolet irradiation unit 13A.

  In this embodiment, two types of inks having different curing characteristics are used. However, three or more types of inks having different curing characteristics can be used.

Moreover, in the said embodiment, although it has divided by the outline part of an image, and other than an outline part, it is not restricted to this. In short, the first active energy ray-curable liquid is used to form a portion to be formed while maintaining the dot shape in the image, and the second active energy ray-curable liquid is used to maintain the dot shape in the image. What is necessary is just to form parts other than the part formed in a state.

  Next, the configuration and operational effects of the above-described first embodiment will be specifically described with reference to FIGS.

The emission wavelength [nm] of ultraviolet rays used for curing the ink, the irradiation intensity (peak illuminance) [mW / cm ² ], and the integrated light quantity [mJ / cm ² ] are the adhesion to the substrate or the adhesion between the ink layers. This greatly affects the characteristics of the formed film.

  Specifically, film strength, glossiness, and film surface state can be controlled by changing each irradiation condition.

The first and second ultraviolet irradiation units 13A and 13B described above have a power change control function of the total output of the emission spectrum of each output region, and are necessary for ink curing from 0% output to 100% output. In addition, the irradiation intensity (peak illuminance) [mW / cm ² ] and the integrated light quantity [mJ / cm ² ] necessary to obtain the target film characteristics can be arbitrarily changed.

  When the film thickness is small, or when the film thickness of the lowermost layer and the film thickness are large in the multilayer structure, or when the film thickness of the uppermost layer in the multilayer structure is cured with the same control output, the composition of the ink is naturally If they are the same, there will be a difference in the finished film properties.

  In addition to the mechanical and electrical irradiation control as described above, the control of the ultraviolet irradiation timing after image formation with the ink discharged from the liquid discharge head is also an important parameter in determining the image quality. .

Optimum irradiation can be performed by arbitrarily changing the peak illuminance [mW / cm ² ] and the integrated light quantity [mJ / cm ² ] under irradiation conditions suitable for each purpose for each printing.

In this case, when it is desired to keep the integrated light quantity [mJ / cm ² ] constant, both means for irradiating strong light [mW / cm ² ] for a short time and means for irradiating weak light [mW / cm ² ] for a long time include Conceivable. However, when it is desired to secure the integrated light quantity, it is necessary to change the transport speed, which affects the productivity. Therefore, it is difficult to secure the target film characteristics only by these measures.

  Here, FIG. 5 shows the finished state of the barcode image, and FIG. 6 schematically shows the difference between the constituent dots of each bar.

  As described above, all the images themselves are formed during the movement of the carriage 11 in the forward direction. Then, the edge portion (thick line portion: image edge portion (contour portion)) 21 of the bar shown in FIG. 5 is cured by ultraviolet irradiation in the forward path, and the inner portion (hatched portion: inner portion) 22 of the edge portion is irradiated by ultraviolet irradiation in the return path. Harden.

  In this case, as described above, the ink used for image formation of each of the contour portion 21 and the inner portion 22 is an ink that reacts to the wavelength region irradiated from the respective ultraviolet irradiation units 13A and 13B.

  As a result, the contour portion (image edge portion) 21 can realize image formation with high image quality with ink droplets peculiar to inkjet, as shown in FIG. 7A, by an instantaneous curing action after image formation. .

  On the other hand, since the inner portion (inside the edge) 22 where the solid density is required as an image is cured by the ultraviolet irradiation in the return path, the leveling proceeds until the curing after the droplet discharge, as shown in FIG. 7B. As described above, a solid image having no gap after the dot coalescence is promoted is formed.

  As an image formed by the present invention, examples of the image pattern other than the barcode include a ring shape shown in FIG. 8A and a star-shaped image shown in FIG. 8B. Of course, the image formed by the present invention is not limited to such a bar code or graphic pattern.

  As described above, the second ultraviolet irradiation unit 13B is mounted on the rear side of the head unit 12 in the return direction, and at least one ultraviolet irradiation lamp uses a metal halide lamp.

  Thereby, it is possible to cure the ink using the polymerization initiator having reaction peaks in several kinds of wavelength regions by wide-range wavelength light emission (200 to 400 nm).

  As described above, the second ultraviolet irradiation unit 13B located on the rear side in the backward direction can cure the ink in a state where the leveling has progressed on the medium after ejection, and by combining the dots of the ink droplets In particular, a solid image can be formed, such as filling a gap, and a high transmission density image can be obtained. It is also effective for coating applications.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 9 is an explanatory diagram illustrating a dot formation pattern of an image formed in the embodiment.

  This embodiment is an example of forming an image by forming a multilayer film. In this case, since it is necessary to stack dots to increase the film thickness, it is necessary to stack the same image on the finished image.

  Therefore, as shown in FIG. 9, the base material in the lowermost layer is the surface of the medium 10, but the base material of the formation layer above it is the ink layer itself. That is, the first layer 31 is formed on the medium 10, and the second layer 32 is formed on the first layer 31. In this case, when each layer is imaged by the same image forming process, the quality is deteriorated.

For example, although not shown, in the case of a three-layer configuration, as a specification example required for each layer,
1st layer: Adhesiveness with substrate 2nd layer: Adhesiveness with lower ink layer (1st layer) 3rd layer: Formation of ideal dots for high image quality.

  Therefore, the first layer improves the adhesion with the base material in the pretreatment + leveling as described in the first embodiment. About the 2nd layer, the adhesiveness with the ink layer by leveling is improved. The third layer forms dot droplets for high image quality by ultraviolet irradiation immediately after image formation in the forward path operation.

  As a result, it is possible to obtain a good printed matter satisfying all required functions and specifications.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 10 is an explanatory diagram illustrating a pattern example of the color filter formed in the embodiment.

  As described in the first embodiment, the entire image itself is formed during the movement of the carriage in the forward direction.

  The vertical line wall image portion (black matrix portion) 41 in FIG. 10 is cured by irradiating with ultraviolet rays while moving in the forward direction, and the inside (RGB lines) 42 is irradiated with ultraviolet rays while moving in the backward direction. And let it harden.

  At this time, each portion performs image formation with ink that reacts with the wavelength region irradiated from each ultraviolet irradiation unit.

  As a result, the black matrix portion 41 forms an image with high image quality with droplets peculiar to the ink jet by an instantaneous curing action after image formation. On the other hand, for the RGB line portion 42 that requires a solid density as an image, a solid image without gaps is formed after leveling progresses and dot coalescence is promoted to cure by ultraviolet irradiation in the backward direction. The product can be completed in the same process.

  Next, a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 11 shows an example of a dot formation pattern with a normal mask, and FIG. 12 shows an example of a dot formation pattern with a random mask.

  In the present embodiment, an ultraviolet curable ink containing a surfactant is used. Here, a surfactant may be contained in the ultraviolet curable ink ejected from at least one head of the first embodiment.

  By containing a surfactant, when forming an image with a multilayer film, the drops on the upper layer are tightened, and an image can be formed with beautiful dot droplets, resulting in a high-quality image with a matte feeling. Can be obtained.

  In addition, when an image is directly formed on a substrate such as the first layer, inclusion of a surfactant improves the wetting and spreading, and improves the wettability, leveling property, or coating property to the substrate.

  That is, the dot shape formed on the medium varies greatly depending on the image forming process including the surface treatment of the medium and the ultraviolet irradiation conditions, and also varies greatly depending on the composition of the ink used. In the case of using UV curable ink, in addition to a polymerization initiator for accelerating curing by irradiating UV light, a pigment for producing the color of each color ink, an interface for adjusting the tightness of the landing droplet itself, etc. An activator is used.

  By using this surface active material, the ink droplets that have landed on the medium are wet and spread, and the ink droplets that have landed on the ink layer can be formed in a clean standing state. .

  By using a combination of the surfactant contained in the ink, a mask for determining image formation (dot landing order) used in the image forming process, and image processing, a completely different finished image can be obtained even when the same image forming apparatus is used. .

  That is, as described in the first embodiment, a dot formation pattern with a normal mask as shown in FIG. 11 is preferable for a portion where a high image quality of a formed image such as a border portion is required.

  On the other hand, a dot formation pattern with a random mask as shown in FIG. 12 is preferable for an image pattern that causes dot coalescence such as solid formation and needs to fill a gap.

  In the present application, the “image” is not limited to a planar image, but includes an image given to a three-dimensionally formed image and an image formed by three-dimensionally modeling a solid itself.

  The active energy ray curable liquid is not limited to the ultraviolet ray curable liquid, and may be other active energy ray curable liquid.

DESCRIPTION OF SYMBOLS 10 Medium 11 Carriage 12 Head unit 13A 1st ultraviolet irradiation unit 13B 2nd ultraviolet irradiation unit 100A 1st head group 100B 2nd head group

Claims (7)

One or a plurality of liquid ejection means for ejecting at least first and second active energy ray-curable liquid droplets having different curing characteristics;
Irradiating the first and second active energy ray-curable liquid droplets on the medium ejected by the liquid ejecting means with the active energy rays corresponding to the curing characteristics of the respective droplets 1 or A plurality of active energy ray irradiation means;
A carriage that is reciprocated and mounted with the liquid ejection means and the active energy ray irradiation means,
The active energy ray irradiating means hardens the second active energy ray curable liquid after curing the first active energy ray curable liquid,
The first active energy ray-curable liquid contains a polymerization initiator having a curing reaction peak at a single wavelength,
The image forming apparatus, wherein the second active energy ray-curable liquid contains a polymerization initiator having a curing reaction peak in a plurality of types of wavelength regions. The image forming apparatus according to claim 1, wherein the active energy ray-curable liquid is ink. All images are formed during the forward movement of the carriage,
During the forward movement of the carriage, the first active energy ray-curable liquid of the droplets forming the image is cured,
3. The image forming apparatus according to claim 1, wherein the second active energy ray-curable liquid of the droplets forming the image is cured during the backward movement of the carriage. Forming a portion to be formed in a state of maintaining the dot shape in the image with the first active energy ray-curable liquid;

4. The image forming apparatus according to claim 3 , wherein the second active energy ray-curable liquid forms a portion of the image other than a portion formed while maintaining the dot shape. 5. First active energy ray irradiating means for curing the droplets of the first active energy ray curable liquid;
Second active energy ray irradiating means for curing the droplets of the second active energy ray curable liquid,
The image forming apparatus according to any one of claims 1 to 4, characterized in that are arranged at mutually distant position from the first active-energy ray irradiation means and said second active energy ray irradiating means. The first active energy ray irradiating means is disposed in a region on the rear side of the carriage when the carriage moves in the forward direction.
The image forming apparatus according to claim 5 , wherein the second active energy ray irradiating unit is disposed in a region on the rear side of the carriage when the carriage moves in the backward direction. . Forming at least one first and second active energy ray-curable liquid droplets having different curing characteristics to form an image on a medium; and
Irradiating the active energy ray to cure the first active energy ray-curable liquid first to cure the first active energy ray-curable liquid;
Irradiating the active energy ray to cure the second active energy ray-curable liquid later to cure the second active energy ray-curable liquid, and
The first active energy ray-curable liquid contains a polymerization initiator having a curing reaction peak at a single wavelength,
The second active energy ray-curable liquid contains a polymerization initiator having a curing reaction peak in a plurality of types of wavelength regions.

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